JP3653264B2 - Torque sensor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a torque sensor, and more particularly to a non-contact type magnetostrictive torque sensor.
[0002]
[Prior art]
A non-contact type magnetostrictive torque sensor generally includes a magnetic metal thin film that is fixed to a torque transmission shaft and has uniaxial magnetic anisotropy, and an excitation coil and a detection coil that are arranged close to the magnetic metal thin film. The applied torque is detected by taking out the increase / decrease of the magnetic permeability generated in the magnetostrictive film by the torque as the potential difference of the detection coil.
[0003]
As an example of this type of non-contact type magnetostrictive torque sensor, the one proposed in Patent Document 1 below can be cited. The torque sensor according to the prior art is used to detect a steering torque input from a driver via a steering wheel in an electric power steering apparatus that assists the steering torque of the vehicle with an electric motor.
[0004]
Specifically, the steering torque detected by the torque sensor (70) is sent to the control means (81) of the electric power steering apparatus, and the control means (81) controls the electric motor (82) based on the inputted steering torque. Configured to do.
[0005]
[Patent Document 1]
JP 2001-133337 A (paragraph 0027, FIG. 2)
[0006]
[Problems to be solved by the invention]
A torque sensor generally uses a sine wave generated from an analog oscillation circuit typified by Hartley, Colpitts, etc. as an excitation signal, so that it is not affected by disturbances such as temperature changes and power supply voltage fluctuations. Easy to receive. For this reason, in the torque sensor according to the prior art, a stable excitation signal (sine wave) cannot be obtained, and the torque detection accuracy may be reduced.
[0007]
Further, in a torque sensor, in particular, a sensor used for torque detection of a torque transmission shaft of a vehicle, such as the torque sensor according to the prior art described above, a control means comprising a microcomputer or the like for abnormality in the output of the torque sensor It is desirable that the torque sensor can be monitored as soon as possible (timely). However, in the torque sensor according to the prior art, the torque sensor and the control means such as a microcomputer for monitoring the abnormality are separated into separate systems (analog signal system and digital signal system) and operate independently at different frequencies. Therefore, there is a disadvantage that a time delay occurs between the time when the torque sensor generates an output and the time when the microcomputer detects a failure based on the output.
[0008]
Therefore, an object of the present invention is to improve the torque detection accuracy by supplying a stable excitation signal and to delay the time from when the torque sensor generates an output until failure detection is performed by the microcomputer. It is an object of the present invention to provide a torque sensor that can eliminate the problem.
[0009]
On the other hand, if there is an individual difference (manufacturing variation) in the characteristics of an analog circuit that generates an excitation signal (especially, a band secondary filter (bandpass filter) that passes only a predetermined frequency), the excitation signal contains noise. There is a disadvantage that the accuracy of torque detection is lowered.
[0010]
Therefore, a second object of the present invention is to generate an excitation signal that does not include noise even when individual differences (manufacturing variation) occur in the characteristics of the analog circuit that generates the excitation signal. It is an object of the present invention to provide a torque sensor that can further improve accuracy.
[0011]
[Means for Solving the Problems]
  In order to achieve the above object, in claim 1,In the torque sensor for detecting the torque applied to the torque transmission shaft,Arranged close to the magnetostrictive film fixed to the torque transmission shaftPrimary sideExcitation coilAnd the secondary side that generates an output when the primary side excitation coil is excited.A detection coil;A tertiary detection coil that produces an output when the primary excitation coil is excited;SaidSecondary detection coil and tertiary detection coilThat detects the torque applied to the torque transmission shaft from the input valueWhen,Clock frequency of the microcomputerFrom the rectangular wave obtained by dividingGenerate excitation signalAn excitation signal generation unit that supplies the primary side excitation coil and a failure detection unit that detects a failure of the torque sensor based on outputs of the secondary detection coil and the tertiary detection coil.It was configured as follows.
[0012]
  The excitation signal supplied to the excitation coil is the microcomputer clock frequency (operating frequency).From the rectangular wave obtained by dividingSince it is configured to generate an excitation signal from a digital signal, it is possible to supply a stable excitation signal that is not easily affected by temperature changes and power supply voltage fluctuations, thus improving torque detection accuracy. be able to. Further, since the operations of the microcomputer and the torque sensor are synchronized, it is possible to eliminate a time delay from when the torque sensor generates an output until failure detection is performed by the microcomputer.Furthermore, since the two detection coils on the secondary side and the tertiary side are provided and the failure of the torque sensor is detected based on their outputs, the failure of the torque sensor can be detected more accurately. .
[0013]
  Further, in the present invention, the excitation signal generator isNoriA sine wave having a predetermined frequency is generated from the waveform wave via an analog circuit, and the excitation signal is generated from the generated sine wave.
[0014]
Since the sine wave of a predetermined frequency is generated from the rectangular wave obtained by dividing the clock frequency of the microcomputer through an analog circuit, the excitation signal is generated from the sine wave. The frequency of the rectangular wave input to the analog circuit by changing can be adjusted. Specifically, the frequency of the rectangular wave input to the analog circuit is changed by changing the division ratio by changing the setting value (count value) of the counter that counts the clock frequency, and the characteristics of the analog circuit (particularly, It can be set to a value corresponding to a band secondary filter (bandpass filter characteristic) that passes only a predetermined frequency. For this reason, even when individual differences occur in the characteristics of the analog circuit, an excitation signal (sine wave) that does not include noise can be generated, and thus the torque detection accuracy can be further improved.
[0017]
  Claims3In the above configuration, the torque sensor is configured to be a torque sensor that detects the steering torque of an electric power steering apparatus that assists the steering torque of the vehicle with an electric motor.
[0018]
  From claim 12Since the torque sensor according to the above item has the above-described effect, it is possible to accurately detect the steering torque applied from the driver via the steering wheel even when mounted on the electric power steering device mounted on the vehicle. The steering feeling of the power steering can be improved, and a time delay from when the torque sensor generates an output until failure detection is performed by the microcomputer can be eliminated. Furthermore, when the torque sensor according to claim 2 is used, an excitation signal that does not include noise can be obtained by optimally setting a frequency division ratio according to individual differences of analog circuits that generate the excitation signal before shipping the product. Therefore, the torque detection accuracy can be further improved.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
A torque sensor according to an embodiment of the present invention will be described below with reference to the attached drawings.
[0020]
FIG. 1 is a principle diagram schematically showing a torque sensor according to one embodiment of the present invention.
[0021]
As shown in the figure, the torque sensor 10 is fixed to a torque transmission shaft (rotating shaft) 12 and has a magnetostrictive film (magnetic metal thin film) 14 having magnetic anisotropy, and an excitation coil disposed close to the magnetostrictive film 14. (Indicated as the primary side) 16 and two detection coils 20 and 22 on the secondary side and the tertiary side, which are similarly arranged close to the magnetostrictive film 14. Hereinafter, the secondary detection coil 20 is referred to as a “secondary detection coil”, and the tertiary detection coil 22 is referred to as a “tertiary detection coil”.
[0022]
The torque transmission shaft 12 is made of chromium molybdenum steel (JIS-G-4105, symbol SCM) or the like that hardly contains Ni. The magnetostrictive film 14 includes a first magnetostrictive film 14a and a second magnetostrictive film 14b to which magnetic anisotropy is given.
[0023]
Specifically, the first magnetostrictive film 14a and the second magnetostrictive film 14b have uniaxial magnetic anisotropy in a direction of ± 45 degrees with respect to the axis 12a of the torque transmission shaft 12 as indicated by an arrow in the figure. In addition, the torque transmission shaft 12 is fixed (applied) over a predetermined width to the entire circumference. More specifically, each of the magnetostrictive films 14a and 14b is a metal film made of a material having a large permeability change with respect to strain stress (compressive stress and tensile stress). For example, the outer periphery of the torque transmission shaft 12 is wet plated. It consists of a formed Ni—Fe alloy film. In the Ni—Fe-based alloy film, for example, Ni is 50 to 60 in weight%, and the balance is Fe.
[0024]
The magnetostrictive film 14 may be provided directly on the outer surface of the torque transmission shaft 12 as described above, or may be fixed on the torque transmission shaft 12 together with another member after being formed on another pipe-shaped member. . Needless to say, the materials of the magnetostrictive film 14 and the torque transmission shaft 12 are not limited to those described above.
[0025]
The exciting coil 16 includes a first exciting coil 16a and a second exciting coil 16b. The first excitation coil 16a and the second excitation coil 16b are close to the first magnetostrictive film 14a and the second magnetostrictive film 14b (and the torque transmission shaft 12), respectively, and more specifically 0.4 to 0. It is wound around a magnetic core (not shown) arranged with a gap of about 6 mm, and excited by being supplied with an alternating current from the excitation power supply 26.
[0026]
The secondary detection coil 20 includes a first secondary detection coil 20a and a second secondary detection coil 20b. Similar to the exciting coil 16, the first secondary detection coil 20a and the second secondary detection coil 20b are respectively connected to the first magnetostrictive film 14a and the second magnetostrictive film 14b (and the torque transmission shaft 12). In close proximity, more specifically, it is arranged with a gap of about 0.4 to 0.6 mm. The magnetic core of the excitation coil 16 and the magnetic core of the detection coil 20 are arranged to face each other while being close to the magnetostrictive film 14 (and the torque transmission shaft 12). Further, the first secondary detection coil 20a and the second secondary detection coil 20b are wound in opposite directions, and are differentially coupled, specifically, differential coupling between the negative voltage sides.
[0027]
Further, the tertiary detection coil 22 includes a first tertiary detection coil 22a and a second tertiary detection coil 22b, and the first tertiary detection coil 22a and the second tertiary detection. The coils 22b are arranged close to the first magnetostrictive film 14a and the second magnetostrictive film 14b (and the torque transmission shaft 12), respectively, and more specifically with a gap of about 0.4 to 0.6 mm. In addition, the first tertiary detection coil 22a and the second tertiary detection coil 22b are also wound in opposite directions, and are differentially coupled, specifically, differential coupling between the positive voltage sides.
[0028]
The first tertiary detection coil 22a has a polarity opposite to that of the first secondary detection coil 20a, and the second tertiary detection coil 22b has a second polarity. The winding direction of the secondary side detection coil 20b is reversed and the polarity is made different.
[0029]
Thus, in the torque sensor 10 according to this embodiment, while including a total of four detection coils, connected coils, and coils arranged close to the same magnetostrictive film, They are arranged so that the winding direction is opposite (inverse).
[0030]
A magnetic circuit is formed between the torque transmission shaft 12 (and the magnetostrictive film 14) and the magnetic core. When the excitation coil 16 is excited in the magnetic circuit, the torque transmission shaft 12 is applied to the torque transmission shaft 12 according to the torque applied from the outside. The permeability increases or decreases in proportion to the generated stress strain, and the induced voltage is output to the output terminals of the detection coils 20 and 22 as a minute voltage value change.
[0031]
Outputs from the secondary detection coil 20 and the tertiary detection coil 22 are input to the processing circuit 28. The processing circuit 28 detects the direction and magnitude of the applied torque, as will be described later, and generates an output indicating them.
[0032]
Hereinafter, the case where the torque sensor 10 according to this embodiment is mounted on an electric power steering device that assists the steering torque of the vehicle and is used as a torque sensor that detects the steering torque input from the driver will be described in detail as an example. .
[0033]
FIG. 2 is an explanatory diagram showing a case where the torque sensor 10 is used as a torque sensor for detecting the steering torque of the electric power steering apparatus.
[0034]
As shown in the figure, the steering wheel 34 disposed at the driver's seat in the vehicle 30 is connected to a steering shaft 36, and the steering shaft 36 is connected to a connecting shaft 42 via universal joints 38 and 40.
[0035]
The connecting shaft 42 is connected to a pinion 46 of the rack and pinion type steering gear 44. The pinion 46 meshes with the rack 48, so that the rotational motion input from the steering wheel 34 is converted into the reciprocating motion of the rack 48 via the pinion 46, and tie rods (steering rods) 50 disposed at both ends of the front axle and Two front wheels (steering wheels) 52 are steered in a desired direction via a kingpin (not shown).
[0036]
An electric motor (electric motor) 54 and a ball screw mechanism 56 are coaxially arranged on the rack 48, and the electric motor output is converted into a reciprocating motion of the rack 48 via the ball screw mechanism 56 and input via the steering wheel 34. The rack 48 is driven in a direction to assist (decrease) the steering torque (steering force).
[0037]
Here, the torque sensor 10 described above is provided at an appropriate position of the steering shaft 36, and outputs a signal corresponding to the direction and magnitude of the steering force (steering torque) input by the driver.
[0038]
The output of the torque sensor 10 is input to an ECU (electronic control unit) 60 for the electric power steering apparatus. The ECU 60 is composed of a microcomputer, and is supplied with driving power from an in-vehicle battery (12V single power source) 62 and operates at a predetermined clock frequency (operating frequency).
[0039]
The ECU 60 determines the assist amount and direction of the steering torque based on the direction and magnitude of the steering torque detected by the torque sensor 10 and a signal representing the vehicle speed supplied from another ECU (not shown). ) And the drive of the motor 54 is controlled via the motor drive circuit 64. For this reason, the detection accuracy of the steering torque of the torque sensor 10 affects the steering feeling of the electric power steering.
[0040]
Further, the ECU 60 detects a failure of the torque sensor 10 based on the output of the torque sensor 10, and when a failure is detected, turns on a warning lamp 66 arranged near the driver's seat and reports it to the driver.
[0041]
FIG. 3 is a block diagram showing the configuration of the torque sensor 10 in detail.
[0042]
As shown in the drawing, the vehicle-mounted battery 62 is connected to the ECU 60 via a constant voltage regulator 68 of 5V, and an operating voltage of 5V is supplied. Here, the clock frequency (operating frequency, more specifically, the internal frequency of the CPU constituting the microcomputer) of the ECU 60 is obtained by multiplying the oscillation frequency (external frequency) of the crystal oscillator 70 by a predetermined value internally. The frequency. In this embodiment, the oscillation frequency of the crystal oscillator 70 is set to 10 MHz, and the magnification inside the ECU 60 is set to 4 times. Therefore, in the ECU 60, from the supplied operating voltage of 5 V, the amplitude is 5 V and the frequency is 40 MHz. Assume that a square wave is generated.
[0043]
The ECU 60 includes a frequency divider (circuit) 60a therein. The frequency divider 60a includes a counter (not shown) that counts the clock frequency of the ECU 60, and sets the frequency division ratio to an arbitrary value by changing the set value (count value) of the counter by external programming. can do. In this embodiment, the frequency division ratio is set to 1/1600 by setting the count value of the counter to 1600, and a rectangular wave of 25 kHz (amplitude 5 V) is output from the frequency divider 60a.
[0044]
The output of the frequency divider 60 a is input to the reference voltage generation unit 72. In this specification, “reference voltage” means a voltage value indicating the midpoint (midpoint of amplitude) of an AC signal generated inside the processing circuit 28. The reference voltage generation unit 72 outputs a voltage corresponding to a duty ratio of 50% of a rectangular wave with an amplitude of 5V output from the frequency divider 60a, that is, a constant voltage of 2.5V as a reference voltage.
[0045]
On the other hand, the 25 kHz rectangular wave output from the frequency divider 60 a is also input to the band second-order filter (bandpass filter) 74 where harmonic components other than 25 kHz constituting the rectangular wave are removed (attenuated). The reference voltage generated by the reference voltage generation unit 72 is input, and thus a sine wave (sin wave) having an amplitude of 5 V and a frequency of 25 kHz with a midpoint of 2.5 V is generated.
[0046]
The sine wave generated by the band second-order filter 74 is subjected to waveform inversion and amplitude amplification processing by an inverting amplification unit (op-amp) 76 (the midpoint of the processed waveform is also set as the reference voltage described above. ) And an RC filter (low-pass filter) 78, and supplied as an excitation signal to the excitation coil 16 (specifically, the first excitation coil 16 a and the second excitation coil 16 b connected thereto). When an excitation signal is supplied to the excitation coil 16, the direction and the magnitude of the steering torque applied to the steering shaft 36 (not shown in FIG. 3) are applied to the secondary detection coil 20 and the tertiary detection coil 22. A phase output (voltage waveform) corresponding to
[0047]
In this embodiment, as described above, the sine wave as the excitation signal is generated from the waveform obtained by dividing the rectangular wave output from the ECU 60, that is, the excitation signal is generated from the digital signal. Thus, it is possible to supply a stable excitation signal that is hardly affected by temperature changes and power supply voltage fluctuations. Accordingly, the waveforms output from the secondary side detection coil 20 and the tertiary side detection coil 22 are also stabilized, so that the torque detection accuracy can be improved. For this reason, the steering torque applied from the driver via the steering wheel 34 can be detected with high accuracy, and thus the steering feeling of the electric power steering can be improved.
[0048]
Further, when individual differences (manufacturing variations) occur in the characteristics of analog circuits for generating excitation signals such as the band secondary filter 74, the inverting amplifier 76, and the RC filter 78, the counter is set by programming from the outside. By changing the value (count value) and changing the frequency division ratio of the frequency divider 60a, the frequency of the rectangular wave input to the analog circuit corresponds to the characteristics of the analog circuit, particularly the time constant of the band secondary filter 74. Value can be set. For this reason, even when individual differences occur in the characteristics of the analog circuit, an excitation signal (sine wave) that does not include noise can be generated, and the torque detection accuracy can be further improved.
[0049]
Further, since the reference voltage indicating the midpoint of the sine wave (excitation signal) is set to a voltage corresponding to a duty ratio of 50% of the rectangular wave, the voltage Vcc supplied from the excitation power supply varies as shown in FIG. Even if the amplitude of the sine wave changes, the reference voltage Vref indicating the midpoint of the amplitude also changes following the change. For example, when the voltage Vcc of the excitation power supply indicates 5.2V, the reference voltage Vref is 50%, that is, 2.6V.
[0050]
For this reason, even when the excitation signal is generated using a single power source (single power source) such as the in-vehicle battery 62, the upper and lower amplitudes (specifically, the upper amplitude and the lower when the reference voltage Vref is set to the middle point). It is possible to generate an excitation signal having a large amplitude that does not cause a difference in (side amplitude). In other words, the excitation signal can be generated using the maximum voltage supplied from the excitation power supply. In the configuration shown in FIG. 3, the excitation power source refers to each configuration from the on-vehicle battery 62 to the frequency divider 60a, that is, the on-vehicle battery 62, the constant voltage regulator 68, the ECU 60, and the frequency divider 60a.
[0051]
Next, the secondary detection coil 20 and the tertiary detection coil 22 will be described in detail with reference to FIG. FIG. 5 is an enlarged view of the sensing unit indicated by a symbol S in FIG. The sensing unit S includes an exciting coil 16, a secondary side detection coil 20, a tertiary side detection coil 22, and a steering shaft 36 (and a magnetostrictive film 14 fixed thereto) (not shown).
[0052]
As shown in FIG. 5, a first secondary detection coil 20a and a first tertiary coil 22a are arranged at a position close to the first excitation coil 16a. As described above, the first secondary side detection coil 20a and the first tertiary side coil 22a have the winding directions reversed (reversely) to make the polarities different. Specifically, the first excitation coil 16a and the first secondary detection coil 20a have the same polarity, and the first excitation coil 16a and the first tertiary coil 22a have different polarities. It is done.
[0053]
In addition, a second secondary detection coil 20b and a second tertiary coil 22b are provided at a position close to the second excitation coil 16b. As described above, the second secondary side detection coil 20b and the second tertiary side coil 22b are similarly reversed in the winding direction (reversely) to have different polarities. Specifically, the second excitation coil 16b and the second secondary detection coil 20b have different polarities, and the second excitation coil 16b and the first tertiary coil 22b have the same polarity. The
[0054]
As shown in the figure, the first excitation coil 16a and the second excitation coil 16b are connected in series on the negative voltage side and the positive voltage side, respectively. On the other hand, the first secondary detection coil 20a and the second secondary detection coil 20b are differentially coupled with their negative voltage sides connected in series. The first tertiary detection coil 22a and the second tertiary detection coil 22b are differentially coupled with their positive voltage sides connected in series.
[0055]
Here, the induced voltage generated in each coil will be described. In the figure, an arrow (black) indicates a self-induced voltage, and an arrow (white) indicates a mutual induction voltage. The subscripts of the arrows indicate that 1 is an exciting coil, 2 is a secondary detection coil, and 3 is an induced voltage generated by an electromotive force of a tertiary detection coil.
[0056]
The first coil (16a, 20a, 22a) to which the symbol a is attached will be described as an example. When an excitation signal is supplied to the first excitation coil 16a and a voltage is applied, the first excitation coil 16a is applied to the first excitation coil 16a. Causes a current i1 to flow and a self-induced voltage opposite to the flow direction. At this time, a mutual induction voltage is generated in the first secondary detection coil 20a and the first tertiary detection coil 22a.
[0057]
When an induced voltage is generated in the first secondary detection coil 20a and the first tertiary detection coil 22a, currents (inductive currents) i2 and i3 are generated in the respective coils, and the directions opposite to the generated currents are generated. Self-induced voltage is generated. When a self induction voltage is generated in the first secondary detection coil 20a and the first tertiary detection coil 22a, a mutual induction voltage is generated in the first excitation coil 16a. The apparent inductance of 16a changes (the flowing current changes).
[0058]
However, in this embodiment, since the winding directions of the first secondary detection coil 20a and the first tertiary detection coil 22a are reversed (reversely), Since the phases of the currents flowing through the coils are shifted by 180 degrees, the self-induced voltages generated in them are also opposed. Therefore, if i2 = i3, the self-induced voltages generated in the first secondary detection coil 20a and the first tertiary detection coil 22a cancel each other and become zero, and the first generated due to them. The mutual induction voltage of the exciting coil 16a is also canceled and becomes zero.
[0059]
Therefore, as shown in the second coil (16b, 20b, 22b) to which the reference symbol b is given as an example, the induced voltage generated in each coil is the self-induced voltage of the exciting coil 16 and the secondary voltage resulting therefrom. Only the mutual induction voltage of the side detection coil 20 and the tertiary detection coil 22 is obtained. That is, the inductance of the exciting coil 16 is not changed due to the self-induced voltage of the detection coils 20 and 22, and the output of the detection coils 20 and 22 reflects only the applied torque.
[0060]
Thus, since the winding directions of the secondary detection coil 20 and the tertiary detection coil 22 are reversed (reversely), the self-induced voltage of the detection coils 20 and 22 and the excitation generated due to the self-induced voltage are generated. The mutual induction voltage of the coil 16 is canceled and the inductance of the exciting coil 16 does not change. For this reason, the relationship between the output of the detection coils 20 and 22 and the applied torque becomes a proportional relationship, so that the accuracy of torque detection can be improved.
[0061]
Next, the change in inductance caused by the temperature change will be described. As described above, since the first secondary detection coil 20a and the second secondary detection coil 20b are differentially coupled with the negative voltage sides connected in series, the inductance caused by the temperature change is reduced. Even if the change occurs in each of the first and second secondary detection coils 20a and 20b, the change in inductance of the secondary detection coil 20 as a whole is canceled and becomes zero. Also in the tertiary detection coil 22, since the first tertiary detection coil 22a and the second tertiary detection coil 22b are differentially coupled to each other on the positive voltage side, the change in inductance is similarly Canceled to zero.
[0062]
The first secondary detection coil 20a and the second secondary detection coil 20b are differentially coupled to each other on the negative voltage side, and the first tertiary detection coil 22a and the second tertiary side Since the detection coil 22b is a differential coupling between the positive voltage sides, even when the torque sensor 10 is mounted on the electric power steering device and exposed to a large temperature change, the inductance change caused by the temperature change is canceled out. The influence can be eliminated, and thus stable detection characteristics can be obtained. For this reason, the steering torque applied from the driver via the steering wheel 34 can be detected with high accuracy, and the steering feeling of the electric power steering can be further improved.
[0063]
Returning to the description of FIG. 3, the excitation signal output from the RC filter 78, more specifically, the voltage waveform actually supplied to the excitation coil 16 is also input to the secondary side bias voltage generation unit 80, Therefore, a secondary cosine wave whose phase is advanced by 90 degrees is generated. The excitation signal (the voltage waveform that is actually input to the excitation coil 16) is also input to the tertiary bias voltage generator 82, where the phase is delayed by 90 degrees (advanced by -90 degrees). A side cos wave is generated.
[0064]
The secondary side cos wave is added to the output (voltage waveform) of the secondary side detection coil 20 by the secondary side adder 84 to generate a secondary side addition waveform. Further, the output (voltage waveform) of the tertiary side detection coil 22 is added with the above-mentioned tertiary side cosine wave by the tertiary side addition unit 86 to generate a tertiary side addition waveform. That is, the secondary side cosine wave and the tertiary side cosine wave mean a bias voltage added to the voltage waveform output from each detection coil.
[0065]
FIG. 6 is an explanatory graph showing each waveform such as a secondary addition waveform when torque is not applied to the steering shaft 36. FIG. 7 is an explanatory graph showing each waveform such as a tertiary addition waveform when no torque is applied to the steering shaft 36 in the same manner.
[0066]
As shown in FIG. 6, when no torque is applied to the steering shaft 36, the outputs of the first secondary detection coil 20a and the second secondary detection coil 20b cancel each other, and the secondary indicated by V2 The output of the entire side detection coil 20 (hereinafter referred to as “secondary side output”) matches the reference voltage Vref (becomes zero). Therefore, the secondary side addition waveform indicated by Vplus2 matches the secondary side cosine wave indicated by Vcos2. An excitation signal (sine wave) actually supplied to the excitation coil 16 is indicated by Vsin.
[0067]
Further, as shown in FIG. 7, when no torque is applied to the steering shaft 36, the outputs of the first tertiary detection coil 22a and the second tertiary detection coil 22b are also canceled out and indicated by V3. The output of the tertiary detection coil 22 as a whole (hereinafter referred to as “tertiary output”) matches the reference voltage Vref (becomes zero). Accordingly, the tertiary side addition waveform indicated by Vplus3 matches the tertiary side cosine wave indicated by Vcos3.
[0068]
On the other hand, when torque in the clockwise direction is applied to the steering shaft 36, the balance of the inductances of the first secondary detection coil 20a and the second secondary detection coil 20b is lost, and as shown in FIG. A secondary output V2 having the same phase as the excitation signal Vsin is generated. For this reason, the phase of the secondary side addition waveform Vplus2 is shifted in the delay direction from the secondary side cosine wave Vcos2. A phase difference (second phase difference when both indicate the reference voltage Vref) of the secondary side added waveform Vplus2 with respect to the secondary side cos wave Vcos2 when a torque in the clockwise direction is applied to the steering shaft 36 is indicated by “R2”.
[0069]
Also in the tertiary side detection coil 22, since the balance of the inductances of the first tertiary side detection coil 22a and the second tertiary side detection coil 22b is lost, as shown in FIG. A tertiary output V3 having the same phase is generated. For this reason, the phase of the tertiary side addition waveform Vplus3 is shifted in the advance direction from the tertiary side cosine wave Vcos3. The phase difference of the tertiary side added waveform Vplus3 with respect to the tertiary side cos wave Vcos3 when the torque in the clockwise direction is applied to the steering shaft 36 (phase difference when both indicate the reference voltage Vref) is indicated by “R3”.
[0070]
Each waveform such as the secondary side addition waveform when torque in the left rotation direction is applied to the steering shaft 36 is shown in FIG. 10, and each waveform such as the tertiary side addition waveform is shown in FIG.
[0071]
As shown in FIG. 10, the secondary output V2 has a waveform that is 180 degrees out of phase with that when the torque in the clockwise direction is applied. Accordingly, the phase difference between the secondary side cosine wave Vcos2 and the secondary side addition waveform Vplus2 (both phase differences when the reference voltage Vref is indicated; indicated by “L2”) is also 180 degrees opposite, and the phase difference from the secondary side cosine wave Vcos2 Shifts in the direction of travel. Further, as shown in FIG. 11, the tertiary output V3 also has a waveform that is 180 degrees out of phase with that when the torque in the clockwise direction is applied, and the tertiary cosine wave Vcos3 and the tertiary addition The phase difference of the waveform Vplus3 (both phase differences when indicating the reference voltage Vref, indicated by “L3”) is also opposite by 180 degrees. That is, the phase is shifted in the delay direction from the tertiary cos wave Vcos3.
[0072]
FIG. 12 shows the relationship between the secondary output V2 and the tertiary output V3 with respect to the applied torque. As described above, since the secondary detection coil 20 is differentially coupled to the negative voltage side, the secondary detection coil 22 is differentially coupled to the positive voltage side. The secondary output V3 has characteristics that are contradictory to the applied torque.
[0073]
For this reason, a bias voltage is applied to each of the secondary side output V2 and the tertiary side output V3, and the resulting waveforms (ie, the secondary side addition waveform Vplus2 and the tertiary side addition waveform Vplus3) and the bias voltage (ie, By detecting the direction and magnitude of the phase difference between the secondary side cosine wave Vcos2 and the tertiary side cosine wave Vcos3), it is possible to accurately detect the direction and magnitude of the applied torque.
[0074]
Here, since the self-induced voltage generated in the excitation coil 16 becomes an electromotive force in the opposite direction to the applied voltage, it has a phase difference of 90 degrees from the excitation signal Vsin actually supplied to the excitation coil 16. . Therefore, the phase difference is maximized by using a waveform obtained by shifting the phase of the excitation signal Vsin by 90 degrees as the bias voltage, and the same phase difference can be obtained for the left and right torques. In other words, torque detection sensitivity is maximized, and the same sensitivity can be obtained for the left and right torques.
[0075]
This will be described with reference to FIG. 13 and FIG. FIG. 13 is an explanatory diagram (phasor diagram) illustrating vector synthesis when the secondary side cosine wave Vcos2 is added to the secondary side output V2. FIG. 14 is an explanatory diagram (phasor diagram) showing vector synthesis when a bias voltage shifted by 60 degrees with respect to the excitation signal Vsin is applied to the secondary output V2. In both figures, V2 (+) indicates the secondary output V2 when the torque in the right rotation direction is applied to the steering shaft 36, and V2 (-) indicates the secondary output when the torque in the left rotation direction is applied. Side output V2 is shown.
[0076]
13 and 14, θR is a phase difference caused by a DC resistance component from when the excitation signal is generated to when it is actually supplied to the excitation coil 16. Since this θR is generated, the secondary side and tertiary side bias voltage generators 80 and 82 described above shift the phase of the excitation signal Vsin actually supplied to the excitation coil 16 by a predetermined amount to shift the secondary side and the tertiary side. Side cos waves Vcos2 and Vcos3 were obtained.
[0077]
As shown in FIG. 13, the addition of the secondary side is performed by adding the vector indicating the secondary side cos wave Vcos2 to the vector indicating the secondary side output V2 when the torque in the clockwise direction is applied, and combining them. The angle formed by the vector indicating the waveform Vplus2 (Vplus2 (+)) and the vector indicating the secondary cosine wave Vcos2, that is, the phase difference can be maximized. In addition, as shown in the figure, as the voltage value of the secondary output V2 increases and the vector increases, the angle formed by the vector indicating the secondary addition waveform Vplus2 and the vector indicating the secondary cos wave Vcos2 increases. It can be seen that the phase difference increases. In other words, it is possible to detect the increase or decrease in the magnetic permeability generated by applying the torque by the voltage value, and further describe the change of the voltage value by the change of the phase.
[0078]
As shown in FIG. 14, the secondary voltage V2 can also be applied by adding a bias voltage other than 90 degrees, for example, a bias voltage of 60 degrees, to the vector indicating the secondary output V2 when the torque in the clockwise direction is applied. The angle formed by the vector indicating the side addition waveform Vplus2 and the vector indicating the bias voltage, that is, the phase difference increases, but the increase is smaller than when the 90 ° secondary side cosine wave Vcos2 is added. .
[0079]
Further, when the same bias voltage of 60 degrees is added to the vector (V2 (−)) indicating the secondary output V2 when the torque in the counterclockwise direction is applied, the vector (Vplus2) indicating the secondary addition waveform Vplus2 There is a problem in that the angle formed by (−)) and the vector indicating the secondary cos wave Vcos2 is different from that when the torque in the clockwise direction is applied. That is, even if the magnitude of the input torque is the same, the amount of phase change (deviation amount) differs depending on the input direction, so that the detection sensitivity does not match between the torque in the right rotation direction and the torque in the left rotation direction. .
[0080]
On the other hand, as shown in FIG. 13, by adding the +90 degree secondary cosine wave Vcos2, the amount of change in the left and right angles (the absolute value of the amount of phase change (deviation)) can be matched. Therefore, the detection sensitivity of the torque in the right rotation direction and the torque in the left rotation direction can be matched.
[0081]
As for the vector synthesis of the tertiary output V3 and the tertiary cos wave Vcos3, + and − described in parentheses in FIGS. 13 and 14 are reversed, and instead of the vector indicating +90 degrees, The above description is valid as it is except that a vector indicating −90 degrees in the reverse direction is used.
[0082]
Thus, the bias voltage obtained by shifting the phase of the excitation signal Vsin supplied to the excitation coil 16 by a predetermined amount and the outputs V2 and V3 of the secondary side and tertiary side detection coils 20 and 22 are added. The phase shift between the secondary side and tertiary side addition waveforms Vplus2 and Vplus3 that are the addition values and the bias voltage that is the comparison target (that is, the secondary side and tertiary side cosine waves Vcos2 and Vcos3) is increased. Thus, the detection sensitivity can be improved, so that the torque detection accuracy can be improved.
[0083]
Further, the bias voltage is set to a secondary side cosine wave Vcos2 generated by advancing the phase of the excitation signal Vsin by 90 degrees, and a tertiary side cosine wave Vcos3 generated by delaying the phase of the excitation signal Vsin by 90 degrees. The phase shift between the secondary side and tertiary side added waveforms Vplus2 and Vplus3 and the secondary side and tertiary side cosine waves Vcos2 and Vcos3 is maximized, and the detection sensitivity can be further improved and the left and right torque can be increased. In contrast, since the detection sensitivity is the same, the detection accuracy can be further improved. For this reason, the steering torque applied from the driver via the steering wheel 34 can be detected with high accuracy, and the steering feeling of the electric power steering can be further improved.
[0084]
Note that the phase of the secondary side cosine wave Vcos2 and the tertiary side cosine wave Vcos3 are set to be shifted by 180 degrees (to 90 degrees and -90 degrees) as shown in FIG. Even if the phases of the secondary side cosine wave Vcos2 and the tertiary side cosine wave Vcos3 vary due to the influence of the above, etc., the respective vectors move in the same rotational direction, so the secondary side and the tertiary side This is because the effect is offset.
[0085]
Returning to the description of FIG. 3, the phase comparator 90 detects the phase difference (deviation) between the secondary side added waveform Vplus2 and the secondary side cosine wave Vcos2. Specifically, the excitation signal Vsin and the secondary addition waveform Vplus2 are input to an AND circuit (element), more specifically, an AND circuit (secondary AND circuit, not shown), and the magnitude of the applied torque is calculated. A rectangular wave corresponding to the direction (in other words, the phase difference between the secondary addition waveform Vplus2 and the secondary cos wave Vcos2) is obtained. This is the secondary side detection torque Vt2.
[0086]
Further, the phase comparison unit 90 inverts the waveform obtained by inverting the tertiary side added waveform Vplus3 with an inverter (not shown) (hereinafter referred to as “the inverted third side added waveform Vplus3inv”) and the phase difference between the tertiary side cosine wave Vcos3. (Displacement) is detected. Specifically, the excitation signal Vsin and the inverted third-side added waveform Vplus3inv are input to an AND circuit (element), more specifically, an AND circuit (third-order AND circuit, not shown), and the applied torque A rectangular wave corresponding to the magnitude and direction (in other words, the phase difference between the inverted third-side added waveform Vplus3inv and the tertiary-side cosine wave Vcos3) is obtained. This is the tertiary detection torque Vt3. Each rectangular wave showing the inverted third-side added waveform Vplus3inv, the secondary-side detected torque Vt2, the tertiary-side detected torque Vt3, etc. is shown in the lower part of FIGS.
[0087]
As shown in FIG. 6 to FIG. 11, the secondary detection torque Vt2 is made an H (High) signal (level) when both the secondary addition waveform Vplus2 and the excitation signal Vsin are equal to or higher than the reference voltage Vref. When either one falls below the reference voltage Vref, the signal is set to an L (Low) signal (level). Further, the tertiary side detection torque Vt3 is an H signal when both the inverted tertiary side addition waveform Vplus3inv and the excitation signal Vsin are equal to or higher than the reference voltage Vref, and when either one is lower than the reference voltage Vref. L signal. For convenience of understanding, the output period of the H signal is indicated by hatching in FIGS.
[0088]
As can be seen by comparing FIG. 6 and FIG. 7, when the applied torque is zero, the secondary detection torque Vt2 and the tertiary detection torque Vt3 always show the same output. On the other hand, when the torque in the clockwise direction is applied as shown in FIGS. 8 and 9, the output time of the H signal of the secondary detection torque Vt2 is extended in proportion to the magnitude of the applied torque, while 3 The output time of the H signal of the secondary detection torque Vt3 is shortened. Also, as shown in FIGS. 10 and 11, when the torque in the counterclockwise direction is applied, the output time of the H signal of the secondary detection torque Vt2 is shortened in proportion to the magnitude of the applied torque, The output time of the H signal of the tertiary detection torque Vt3 is extended.
[0089]
As described above, the output time of the H signal increases or decreases according to the phase difference between the secondary addition waveform Vplus2 and the secondary cosine wave Vcos2, that is, the magnitude and direction of the applied torque. In addition, the output time of the H signal also increases or decreases in the tertiary detection torque Vt3 according to the phase difference between the inverted tertiary addition waveform Vplus3inv and the tertiary cos wave Vcos3, that is, the magnitude and direction of the applied torque. Since the secondary side detection torque Vt2 and the tertiary side detection torque Vt3 indicate outputs that are opposite to the direction of the applied torque, the difference between them indicates the direction of the torque applied to the steering shaft 36. The size can be detected with high sensitivity.
[0090]
6 to 11, since the reference voltage Vref accurately indicates the midpoint of the excitation signal as described above, the secondary side cosine waves Vcos2 and 3 obtained by phase-shifting the excitation signal Vsin by a predetermined amount are used. The midpoint of the secondary cosine wave Vcos3, and the midpoint of the secondary output V2 and the tertiary output V3 are also shown accurately. Therefore, the midpoint of the secondary side addition waveform Vplus2 and the tertiary side addition waveform Vplus3 (and the inverted tertiary side addition waveform Vplus3inv) is also accurately shown.
[0091]
Therefore, the phase difference between the secondary side cosine wave Vcos2 and the secondary side addition waveform Vplus2 and the phase difference between the tertiary side cosine wave Vcos3 and the inverted tertiary side addition waveform Vplus3inv can be accurately detected, and torque can be detected. Accuracy can be improved. Therefore, the steering torque applied from the driver via the steering wheel 34 can be detected with high accuracy, and the steering feeling of the electric power steering can be further improved. In this embodiment, the magnitude of the amplitude of the detected waveform is not detected, but as described above, the torque sensor 10 according to this embodiment accurately knows the midpoint of the amplitude of the detected waveform. Therefore, it is possible to detect the magnitude of the amplitude with high accuracy.
[0092]
Returning to the explanation of FIG. 3, the secondary side detection torque Vt2 and the tertiary side detection torque Vt3 output from the phase comparison unit 90 are smoothed through CR filters (smoothing circuits) 92 and 94, respectively. The difference is input to the ECU 60 and input to the differential amplifier 96 to amplify the difference. The output of the differential amplifier 96 is input to the ECU 60 as the final detected torque Vtf.
[0093]
The ECU 60 detects the direction and magnitude of the torque (steering torque) input to the steering shaft 36 based on the input final detection torque Vtf (and the secondary detection torque Vt2 and the tertiary detection torque Vt3). To do.
[0094]
In this way, the bias voltage obtained by shifting the phase of the excitation signal by a predetermined amount is added to each of the secondary side output V2 and the tertiary side output V3, and the secondary side addition waveform Vplus2 and the tertiary side addition waveform thus obtained are obtained. Each of Vplus3 (specifically, the inverted third-side added waveform Vplus3inv obtained by inverting it) is compared with the bias voltage and the phase, and the torque is detected based on the phase difference, that is, the application of torque Increase / decrease in permeability caused by the change in voltage value is detected and the change in voltage value is detected in phase, so detection sensitivity is higher than when detecting torque only by change in voltage value. In addition, even if the detection voltage is weak, it is difficult to be affected by noise from the energizing current of the electric motor 54 and the like, so that the torque detection accuracy can be improved.
[0095]
Further, based on each of the secondary side output V2 and the tertiary side output V3 (specifically, the secondary side detection torque Vt2 and the tertiary side detection torque Vt3 obtained from them) having opposite characteristics, Since the phase difference is detected and the difference is amplified to detect the torque, the detection sensitivity can be further improved, the amplification factor by the differential amplifier 96 can be reduced, and noise from other electric devices can be reduced. (That is, since the noise is not amplified, the S / N ratio can be increased), and the torque detection accuracy can be further improved. In addition, since the change in inductance caused by the temperature change and the change in amplification factor of the differential amplifier 96 can be canceled by two outputs (phase differences), the influence can be eliminated and stable detection characteristics can be obtained. Can do.
[0096]
In addition, since the bias voltage added to the secondary side output V2 and the tertiary side output V3 is generated by shifting the phase of the excitation signal by 90 degrees or -90 degrees, respectively, the bias voltage (secondary side cosine wave Vcos2 and Phase difference of the addition waveform (secondary addition waveform Vplus2 and tertiary addition waveform Vplus3 (specifically, the inverted third addition waveform Vplus3inv obtained by inverting it) with respect to the tertiary cosine wave Vcos3) The detection sensitivity can be further improved and the detection sensitivity can be improved even if the input direction of the torque is different, so that the detection accuracy can be further improved.
[0097]
If the explanation of FIG. 3 is continued, the secondary side addition waveform Vplus2 and the tertiary side addition waveform Vplus3 (waveform before being inverted by the inverter) are further input to the failure detection unit 98.
[0098]
Here, when the torque sensor 10 is in a normal state, the secondary addition waveform Vplus2 is the voltage value of the excitation signal Vsin regardless of whether or not torque is applied, as shown in FIGS. H always indicates the H signal at the moment when the voltage exceeds the reference voltage Vref (the moment when the lower amplitude shifts to the upper amplitude), and the moment when the voltage value of the excitation signal Vsin falls below the reference voltage Vref (from the upper amplitude to the lower amplitude). L signal is always shown at the moment of transition to amplitude). Further, as shown in FIGS. 7, 9, and 11, the tertiary side addition waveform Vplus3 always outputs the L signal at the moment when the voltage value of the excitation signal Vsin exceeds the reference voltage Vref regardless of whether torque is applied. In addition, the H signal is always indicated at the moment when the voltage value of the excitation signal Vsin falls below the reference voltage Vref. However, when a failure occurs in the torque sensor 10, the above output relationship may be disrupted.
[0099]
Therefore, the failure detection unit 98 detects the outputs of the secondary side addition waveform Vplus2 and the tertiary side addition waveform Vplus3 at the rising and falling timings of the excitation signal Vsin, and when the detected value does not have the above relationship, the torque sensor A signal indicating 10 failures is generated and output to the ECU 60.
[0100]
When a signal indicating a failure of the torque sensor 10 is output from the failure detection unit 98, the ECU 60 turns on the warning lamp 66 to alert the driver.
[0101]
Here, as described above, since the excitation signal Vsin is generated based on the clock frequency (operation frequency) of the ECU 60, the secondary side added waveform Vplus2 and the tertiary side at the rising and falling timings of the excitation signal Vsin. The addition waveform Vplus3 can be detected in synchronization with the processing of the ECU 60. That is, it is possible to eliminate a time delay from when the torque sensor 10 generates an output until the ECU 60 detects a failure. For this reason, in the torque sensor 10 according to this embodiment, it is possible to sufficiently satisfy the requirement for the sensor mounted on the vehicle that the failure detection needs to be performed as soon as possible (timely). .
[0102]
In addition, since two detection coils (secondary side and tertiary side) are provided and a failure of the torque sensor 10 is detected based on their outputs, the failure of the torque sensor 10 can be detected more accurately. it can.
[0103]
As described above, in the torque sensor according to this embodiment, the excitation coil 16 and the detection coil (disposed in proximity to the magnetostrictive film 14 fixed to the torque transmission shaft 12 (and the steering shaft 36)) ( Secondary detection coil 20 and tertiary detection coil 22), and an excitation signal generator (band secondary filter 74, inverting amplifier 76, RC filter 78) that generates the excitation signal Vsin and supplies it to the excitation coil 16. And the output (secondary output V2 and tertiary output V3) of the detection coil when the excitation coil is excited, and the torque (secondary side) applied to the torque transmission shaft 12 from the input value. In the torque sensor 10 including a microcomputer (ECU 60) for detecting the detected torque Vt2, the tertiary detected torque Vt3, and the final detected torque Vtf) It said excitation signal generating unit configured to generate the excitation signal based on the clock frequency of the microcomputer.
[0104]
Further, the excitation signal generation unit generates an analog circuit (band secondary filter 74, inverting amplification unit 76, RC filter 78) from a rectangular wave obtained by dividing the clock frequency of the microcomputer (by the frequency divider 60a). A sine wave having a predetermined frequency is generated via the sine wave, and the excitation signal Vsin is generated from the generated sine wave.
[0105]
The torque sensor 10 includes a plurality of detection coils (secondary detection coil 20 and tertiary detection coil 22), and each of the plurality of detection coils when the excitation coil is excited. It is provided with a failure detection unit 98 for detecting a failure of the torque sensor 10 based on the outputs V2 and V3, more specifically, the secondary addition waveform Vplus2 and the tertiary addition waveform Vplus3 generated based on the outputs V2 and V3. Configured.
[0106]
The torque sensor 10 is configured to be a torque sensor that detects the steering torque of an electric power steering device that assists the steering torque of the vehicle 30 by an electric motor (electric motor) 64.
[0107]
In the above description, the torque sensor 10 according to the present invention has been described by taking as an example the case where the steering torque input to the electric power steering apparatus is detected. However, the application of the torque sensor 10 is not limited thereto. Needless to say.
[0108]
【The invention's effect】
  According to the first aspect of the present invention, the excitation signal supplied to the excitation coil is the microcomputer clock frequency (operating frequency).From the rectangular wave obtained by dividingSince it is configured to generate an excitation signal from a digital signal, it is possible to supply a stable excitation signal that is not easily affected by temperature changes and power supply voltage fluctuations, thus improving torque detection accuracy. be able to. Further, since the operations of the microcomputer and the torque sensor are synchronized, it is possible to eliminate a time delay from when the torque sensor generates an output until failure detection is performed by the microcomputer.Furthermore, since the two detection coils on the secondary side and the tertiary side are provided and the failure of the torque sensor is detected based on their outputs, the failure of the torque sensor can be detected more accurately. .
[0109]
According to a second aspect of the present invention, a sine wave having a predetermined frequency is generated from a rectangular wave obtained by dividing the clock frequency of the microcomputer via an analog circuit, and an excitation signal is generated from the sine wave. Since it is configured, it is possible to adjust the frequency of the rectangular wave input to the analog circuit by changing the programming of the microcomputer. Specifically, the frequency of the rectangular wave input to the analog circuit is changed by changing the division ratio by changing the setting value (count value) of the counter that counts the clock frequency, and the characteristics of the analog circuit (particularly, It can be set to a value corresponding to a band secondary filter (bandpass filter characteristic) that passes only a predetermined frequency. For this reason, even when individual differences occur in the characteristics of the analog circuit, an excitation signal (sine wave) that does not include noise can be generated, and thus the torque detection accuracy can be further improved.
[0111]
  Claim3In the paragraph, from claim 12Since the torque sensor according to the above item has the above-described effect, it is possible to accurately detect the steering torque applied from the driver via the steering wheel even when mounted on the electric power steering device mounted on the vehicle. The steering feeling of the power steering can be improved, and a time delay from when the torque sensor generates an output until failure detection is performed by the microcomputer can be eliminated. Furthermore, when the torque sensor according to claim 2 is used, an excitation signal that does not include noise can be obtained by optimally setting a frequency division ratio according to individual differences of analog circuits that generate the excitation signal before shipping the product. Therefore, the torque detection accuracy can be further improved.
[Brief description of the drawings]
FIG. 1 is a principle view schematically showing a torque sensor according to one embodiment of the present invention.
FIG. 2 is an explanatory diagram showing a case where the torque sensor shown in FIG. 1 is used as a torque sensor for detecting a steering torque of an electric power steering apparatus.
FIG. 3 is a block diagram showing the structure of the torque sensor shown in FIG. 1 in more detail.
4 is an explanatory diagram showing a reference voltage of the torque sensor shown in FIG. 1. FIG.
FIG. 5 is an explanatory diagram showing an enlarged sensing unit in the torque sensor shown in FIG. 1;
6 is an explanatory graph showing the output (voltage waveform) of the secondary detection coil and the like when no torque is applied to the torque transmission shaft in the torque sensor shown in FIG. 1;
7 is an explanatory graph showing an output (voltage waveform) of a tertiary detection coil and the like when no torque is applied to the torque transmission shaft in the torque sensor shown in FIG. 1;
8 is an explanatory graph showing an output (voltage waveform) of a secondary detection coil or the like when a clockwise applied torque is inputted to the torque transmission shaft in the torque sensor shown in FIG. 1;
9 is an explanatory graph showing an output (voltage waveform) of a tertiary detection coil and the like when a clockwise applied torque is inputted to the torque transmission shaft in the torque sensor shown in FIG. 1;
10 is an explanatory graph showing an output (voltage waveform) of a secondary side detection coil and the like when applied torque in the left rotation direction is input to the torque transmission shaft in the torque sensor shown in FIG. 1;
11 is an explanatory graph showing an output (voltage waveform) of a tertiary detection coil and the like when an applied torque in the left rotation direction is input to the torque transmission shaft in the torque sensor shown in FIG.
12 is a graph showing output characteristics with respect to applied torque of the secondary side detection coil and the tertiary side detection coil of the torque sensor shown in FIG. 1; FIG.
13 is an explanatory diagram (phasor diagram) showing vector synthesis when a secondary cosine wave is added to the output of the secondary detection coil of the torque sensor shown in FIG. 1; FIG.
14 is an explanatory diagram (phasor diagram) illustrating vector synthesis when a bias voltage shifted by 60 degrees from the excitation signal is applied to the output of the secondary side detection coil of the torque sensor shown in FIG. 1; FIG.
15 is an explanatory diagram (phasor diagram) showing vector synthesis when a secondary cosine wave and a tertiary cosine wave are added to the output of the secondary side detection coil of the torque sensor shown in FIG. 1; FIG.
[Explanation of symbols]
10 Torque sensor
12 Torque transmission shaft
14 Magnetostrictive film
14a First magnetostrictive film
14b Second magnetostrictive film
16 Excitation coil
16a First exciting coil
16b Second exciting coil
20 Secondary detection coil (detection coil)
20a First secondary detection coil
20b Second secondary detection coil
22 Tertiary detection coil (detection coil)
22a First tertiary detection coil
22b Second tertiary detection coil
30 vehicles
36 Steering shaft (torque transmission shaft)
54 Electric motor
60 ECU (microcomputer)
60a divider
74 Band secondary filter (Excitation signal generator)
76 Inversion amplifier (excitation signal generator)
78 RC filter (excitation signal generator)
98 Failure detection unit

Claims (3)

In the torque sensor for detecting the torque applied to the torque transmission shaft, when the primary side excitation coil disposed close to the magnetostrictive film fixed to the torque transmission shaft and the primary side excitation coil are excited The outputs of the secondary side detection coil generating the output, the tertiary side detection coil generating the output when the primary side excitation coil is excited, and the outputs of the secondary side detection coil and the tertiary side detection coil are input. detecting a torque applied to the torque transmission shaft from the input value each and a microcomputer, supplied to the microcomputer of the primary excitation coil to generate the excitation signal a clock frequency from the rectangular wave obtained by dividing to an excitation signal generator, torque, characterized in that it comprises a failure detecting section detecting a failure of the torque sensor based on an output of the secondary detector coil and tertiary detector coil Sensor. Said excitation signal generating section, the front through the analog circuit to generate a sine wave of a predetermined frequency from Kinori square wave, claim 1, wherein said generating said excitation signal from the sine wave said generated Torque sensor. The torque sensor, the torque sensor of claim 1 wherein or 2 wherein wherein the a torque sensor that detects the steering torque of the electric power steering device for assisting the steering torque of the vehicle by the electric motor.

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