JP2944067B2 - Electric steering device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric steering apparatus for directly applying the power of an electric motor to a steering system.

[0002]

2. Description of the Related Art In a conventional electric power steering apparatus, a steering torque signal detected by a steering torque detecting means is converted into a corresponding target current signal, and a motor current detection signal detected by the motor current detecting means is negatively fed back. Controlling the motor based on a deviation signal between the target current signal and the motor current detection signal, quickly converging the deviation signal to 0, driving the motor with a motor current equal to the target current, 2. Description of the Related Art There is known a configuration in which an auxiliary steering force is applied to a steering system by assisting a steering torque of a driver.

An outline of the configuration and operation of a conventional electric power steering device will be described. FIG. 9 shows a block diagram of a main part of a conventional electric power steering apparatus. In FIG. 9, a control means 41 of a conventional electric power steering apparatus 40 includes a steering torque signal TD obtained by converting the steering torque T detected by the steering torque detection means 48 into a digital signal.
And a steering torque signal (TD) -target current based on a vehicle speed signal VD (VL, VM, VH) shown in FIG. 10 based on a vehicle speed signal VD obtained by converting the vehicle speed V detected by the vehicle speed detecting means 49 into a digital signal. A target current setting means 42 for converting the signal (ISD) characteristic data into a target current signal ISD; a target current signal ISD; and a motor current detection signal IMD converted to a digital signal of the motor current IM detected by the motor current detection means 46. Determining means 43 for calculating the deviation signal ΔI (= ISD-IMD) of the above-mentioned, the characteristic of the deviation signal ΔI is improved through a PID controller, and the motor 47 is driven through the motor driving means 45 by the PWM with the driving signal having the improved characteristic.
A drive control means 44 for generating a drive control voltage signal VO for controlling the drive so that the deviation signal ΔI quickly converges to 0.
Is provided.

The control means 41 is based on a microprocessor and has a sequence function of software program control and a digital processing / arithmetic function. The control means 41 reads a steering torque signal TD and a motor current detection signal IMD at predetermined timings and sets them in advance. The deviation signal ΔI (= I
SD-IMD) calculation and control, and calculation and processing of a drive control voltage signal VO based on the calculation result of ΔI, and the motor voltage VM is supplied to the motor 47 via the motor driving means 45. The current IM is controlled to be equal to the target current ISD corresponding to the steering torque T.

As shown in FIG. 10, a conventional electric power steering device 40 outputs a large target current signal ISD in a low vehicle speed region (VL) even if the steering torque signal TD is small, while the vehicle speed V is at a middle vehicle speed. By setting the target current signal ISD to be small even when the steering torque signal TD is large as the vehicle speed changes from the region (VM) to the high vehicle speed region (VH), a sufficient steering assist force is provided to the steering system in a low speed region of the vehicle. The steering performance is improved by assisting, and in a high vehicle speed region, the vehicle behavior can be stabilized by suppressing the steering assist force and suppressing the excessive steering operation of the driver.

As described above, the conventional electric power steering apparatus 40 drives the electric motor 47 with the electric motor current IM corresponding to the steering torque T steered by the driver.
The steering torque T of the driver is assisted to the steering torque T of the driver to act on the steering system to reduce the steering force of the driver.

[0007]

The conventional electric power steering apparatus, when mounted on a vehicle having a small front shaft load, such as a light car or a midship sports car, provides sufficient steering assist force in a high vehicle speed region. Even if it is small, there is a problem that steering response is small, steering feeling is deteriorated, and vehicle behavior cannot be stabilized.

Further, when the vehicle speed becomes higher, even if the steering assist force is set to 0 and only the manual steering torque is used, there is a problem that the feeling of steering response is small, and the steering assist force in the opposite direction to the manual torque is applied. It is desired to increase the feeling of steering response.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and an object of the present invention is to apply a steering assist force in a low vehicle speed region and to provide a motor torque in a direction opposite to a manual torque in a high vehicle speed region, thereby providing a low vehicle speed. It is an object of the present invention to provide an electric steering device that improves steering feeling in a vehicle region and increases steering response in a high vehicle speed region to stabilize vehicle behavior.

[0010]

According to a first aspect of the present invention, there is provided an electric motor control device for an electric steering apparatus, wherein electric motor power acts in a direction opposite to a direction in which a steering torque acts in a high vehicle speed range . And a signal conversion means for performing such control.

Further, the electric steering device according to a second aspect of the present invention, wherein the signal converting means includes a vehicle speed coefficient generating means for generating a negative coefficient signal when the vehicle speed signal detected by the vehicle speed sensor exceeds a predetermined value. It is characterized by having.

Further, in the electric steering apparatus according to a third aspect, the electric motor control means includes a steering state determination means for determining whether the steering is going or returning based on the steering torque signal and the steering rotation speed signal from the steering rotation speed sensor. And a vehicle speed coefficient generating means for generating a coefficient signal for steering forward or backward corresponding to the vehicle speed signal is provided in the signal conversion means.

Further, the electric steering apparatus according to a fourth aspect of the present invention provides the electric steering device, wherein the signal conversion means includes a forward vehicle speed coefficient generating means for generating a negative coefficient signal when the vehicle speed signal exceeds a predetermined value;
A returning vehicle speed coefficient generating means for generating a positive coefficient signal corresponding to the vehicle speed, and a switching means, wherein when the steering state determining means determines the steering state, the selecting means selects the going vehicle speed coefficient generating means, and A negative coefficient signal is generated only when the vehicle speed signal exceeds a predetermined value.

[0014]

According to the first aspect of the present invention, the electric motor control means of the electric steering device includes signal conversion means for controlling the electric motor power to act in the direction opposite to the direction in which the steering torque acts, so that the steering force acting on the steering system is reduced. It can be smaller than the manual steering force.

Further, the electric steering apparatus according to a second aspect of the present invention includes a vehicle speed coefficient generating means for generating a negative coefficient signal when the vehicle speed signal detected by the vehicle speed sensor exceeds a predetermined value. Therefore, when the steering force acting on the steering system exceeds a predetermined vehicle speed, it can be made smaller than the manual steering force.

Further, in the electric steering apparatus according to a third aspect, the electric motor control means includes a steering state determining means for determining whether the steering is going or returning based on the steering torque signal and the steering rotation speed signal from the steering rotation speed sensor. And the signal conversion means is provided with a vehicle speed coefficient generating means for generating a coefficient signal for steering forward or backward corresponding to the vehicle speed signal, so that the steering force acting on the steering system according to the steering situation can be reduced. Can be set.

Further, the electric steering apparatus according to a fourth aspect of the present invention provides the electric vehicle steering apparatus, wherein the signal converting means includes a forward vehicle speed coefficient generating means for generating a negative coefficient signal when the vehicle speed signal exceeds a predetermined value;
Since the return vehicle speed coefficient generating means for generating a positive coefficient signal corresponding to the vehicle speed and the switching means are provided, when the steering state determining means determines the steering state, the vehicle speed coefficient generating means is selected. A negative coefficient signal is generated only when the vehicle speed signal exceeds a predetermined value, and the steering force acting on the steering system can be made smaller than the manual steering force.

[0018]

Embodiments of the present invention will be described below with reference to the accompanying drawings. The following embodiment is one in which the electric steering device of the present invention is applied to an electric power steering device.
These are expressed as target current setting means and target current signal, respectively. FIG. 1 is an overall configuration diagram of an electric power steering device to which the present invention is applied. In FIG. 1, an electric power steering device 1 includes a universal joint 3 a, a universal joint 3 a, a steering shaft 2 provided integrally with a steering wheel 17.
The manual steering force generating means 6 is constituted by being connected to a pinion 5a of a rack & pinion mechanism 5 provided in the steering gear box 4 via a connecting shaft 3 provided with the steering gear box b.

The rack shaft 7 is provided with rack teeth 7a meshing with the pinion 5a, and reciprocates by the meshing.
The left and right front wheels 9 as rolling wheels are connected to both ends thereof via tie rods 8. In this manner, when the steering wheel 17 is steered, the direction of the vehicle is changed by rolling the front wheels 9 via the normal rack and pinion type steering.

In order to reduce the steering force by the manual steering force generating means 6, a motor 10 for supplying power to the motor is disposed coaxially with the rack shaft 7, and a ball screw mechanism 11 provided substantially parallel to the rack shaft 7. The power of the electric motor is converted into thrust through the motor and act on the rack shaft 7.

The rotor of the motor 10 has a helical drive side on the drive side.
A gear 10a is provided integrally, and the drive-side helical gear 10a is meshed with a driven-side helical gear 11a provided integrally at the shaft end of the screw shaft of the ball screw mechanism 11. The nut of the ball screw mechanism 11 is connected to the rack shaft 7.

The steering gear box 4 has a steering torque sensor 12 for detecting a manual torque acting on the pinion 5a, and the steering shaft 2 has a steering rotational speed N corresponding to the rotational speed of the steering shaft 2. And a steering torque signal T and a steering rotation speed signal N are provided to the motor control means 15. A vehicle speed sensor 14 for detecting a vehicle speed signal V corresponding to the vehicle speed is also provided.
Is provided to the motor control means 15.

In this embodiment, the steering wheel 1 and a front wheel 9 as a steered wheel are mechanically connected to each other, and a manual steering force generating means 6 for applying a driver's steering force to a steering system and a steering torque sensor 12 detect the steering wheel. A target current signal IMS corresponding to the steering torque signal T and a vehicle speed coefficient KV corresponding to the vehicle speed signal V detected by the vehicle speed sensor 14.
A forward or return state of the steering system is determined from the steering torque signal T and the steering rotation speed signal N detected by the steering rotation speed sensor 13, and the product of the target current signal IMS and the vehicle speed coefficient KV is determined based on the steering state and the vehicle speed V. A motor control means 15 for generating a corresponding motor control signal VO (for example, a PWM signal); a motor drive means 16 for outputting a motor voltage VM based on the motor control signal VO to drive the motor 10; The electric power steering device 1 is constituted by the electric motor 10 acting on the power. The steering rotation speed signal N may be obtained by using the function of the motor 10 itself as a generator, for example, in the case of a DC motor, by calculating from the motor voltage VM and the motor current IM.

FIG. 2 is a block diagram of a main part of an electric power steering apparatus to which the invention of claim 1 is applied. FIG.
, The electric power steering device 1 includes a steering torque sensor 12 for detecting a driver's steering torque T, an electric motor control means 15 for generating an electric motor control signal VO based on the steering torque T detected by the steering torque sensor 12,
A motor driving means 16 for driving the motor 10 at the motor voltage VM;
The motor 10 is provided so as to act on the rack shaft 7 by assisting the electric motor torque TM to the manual steering torque T to reduce the steering force of the driver.

The steering torque sensor 12 is constituted by, for example, a differential transformer or the like, and converts the steering torque T into a steering torque signal T (for example, an absolute value T, a direction, an electric signal) corresponding to the steering rotation direction and the magnitude of the torque force. F vector quantity), and supplies it to the motor control means 15.

The motor control means 15 is based on a microprocessor and is composed of various arithmetic functions, memories and processing functions operated by a command execution program of a software program. The target current signal setting means 21, the deviation determination means 22, the drive control means 23, a signal conversion means 24, and a multiplication means 25.

The target current signal setting means 21 has a memory such as a ROM, and converts a steering torque signal T of an analog electric signal detected by the steering torque sensor 12 into a digital steering torque signal TD by A / D conversion means (not shown). The target current signal IMS corresponding to the steering torque signal TD is read from the characteristic data of the steering torque signal TD and the target current signal IMS shown in FIG.

The signal conversion means 24 includes a memory such as a ROM, and has coefficients set in advance based on design values or experimental values.
For example, a vehicle speed coefficient KV corresponding to the vehicle speed V is stored,
A vehicle speed coefficient KV corresponding to a predetermined condition of the vehicle is selected, and a vehicle speed coefficient signal KV is provided to the multiplying means 25.

The signal conversion means 24 sets positive and negative vehicle speed coefficient KV data in a memory in advance and responds to vehicle conditions, for example, vehicle speed V and steering state (going state and return state). A positive vehicle speed coefficient signal KV in the same direction as the driver's steering torque T, or the vehicle speed is in a high vehicle speed region
A vehicle speed coefficient generating means for outputting a negative vehicle speed coefficient signal KV in a direction opposite to the steering torque T of the driver is provided.

The multiplying means 25 is composed of a multiplier and a software-controlled multiplying function, and supplies to the deviation determining means 22 a target current signal (KV * IMS) obtained by multiplying the target current signal IMS by the vehicle speed coefficient signal KV.

The deviation determining means 22 is constituted by a subtractor or a subtraction function of software control. The deviation determining means 22 calculates a deviation between the target current signal (KV * IMS) and the motor current detection signal IMD supplied from the motor current detection means 18, and calculates the deviation. Signal ΔI (= KV * IMS−IM
D) to the drive control means 23.

The drive control means 23 outputs the deviation signal ΔI (= K
V * IMS-IMD), a PID controller that calculates and processes proportional (P), integral (I) and derivative (D) to improve the characteristics to quickly and stably control the deviation signal ΔI to 0. From the signal of the PID controller, the motor 10
Signal or PWM depending on the direction and magnitude of the generated torque
(Pulse width modulation) The motor control signal VO includes a signal generator for generating a motor control signal VO which is a hybrid signal of the signals.
Is supplied to the motor driving means 16.

The motor driving means 16 is a switching element,
For example, a bridge circuit composed of four FETs (field-effect transistors) is used. The FETs (field-effect transistors) are driven and controlled by a motor control signal VO of an ON signal or a PWM (pulse width modulation) signal, and the driving direction and size are controlled. The motor 10 is driven by supplying the motor voltage VM having the following.

The motor 10 is composed of, for example, a DC motor, a brushless motor, etc., and is driven by a motor voltage VM.
The motor torque TM corresponding to the direction and magnitude of the motor voltage VM is applied to the rack shaft 7 shown in FIG.

As described above, the electric power steering apparatus 1 to which the invention of claim 1 is applied provides a positive vehicle speed coefficient signal KV in the same direction as the driver's steering torque T in accordance with vehicle conditions such as vehicle speed and steering state. Or the vehicle speed is high
In the region, the signal conversion means 24 for outputting a negative vehicle speed coefficient signal KV in a direction opposite to the steering torque T of the driver is provided, so that the steering torque T and the electric motor torque TM act on the rack shaft 7 and the signal conversion means 24 If the vehicle speed coefficient signal KV is positive, the motor torque TM in the same direction as the steering torque T
To act on the steering system to reduce the steering force of the driver. On the other hand, when the vehicle speed coefficient signal KV from the signal conversion means 24 is negative, the steering torque T is suppressed by the motor torque TM in the opposite direction. By acting on the steering system, the steering force of the driver can be increased to increase the feeling of steering response.

FIG. 3 is a block diagram showing an essential part of one embodiment of the signal conversion means of the electric power steering apparatus to which the invention of claim 2 is applied. In FIG. 3, the signal conversion means 24
Is a vehicle speed coefficient generating means 24A comprising a reference vehicle speed value storing means 26, a vehicle speed comparing means 27A, and a vehicle speed coefficient storing means 27B.
Is provided.

The reference vehicle speed value storage means 26 is composed of a memory such as a ROM, in which a reference vehicle speed value VR is set in advance, and a vehicle speed signal V of a pulse having a cycle proportional to the vehicle speed detected by the vehicle speed sensor 14 is stored in parallel. Digitally converted vehicle speed signal VD
Generates a reference vehicle speed signal VR in synchronization with a predetermined sampling time supplied to the vehicle speed comparing means 27A.
7A.

The vehicle speed comparison means 27A has a comparison function of software control, and compares the vehicle speed signal VD with the reference vehicle speed value signal VR.
When the vehicle speed signal VD is equal to or less than the reference vehicle speed value signal VR (VD ≦ VR), a positive vehicle speed coefficient KV corresponding to the vehicle speed signal VD is set in advance in the vehicle speed coefficient storage means 27B, and the vehicle speed coefficient signal KV is read. On the other hand, the vehicle speed signal VD is the reference vehicle speed value signal VR.
(VD> VR), the negative vehicle speed corresponding to the deviation Δ (= VD−VR) from the vehicle speed deviation Δ (= VD−VR) −vehicle speed coefficient KV−characteristic shown in FIG. The coefficient KV- is read out and the vehicle speed coefficient signal KV- is output to the multiplication means 25 in FIG.

As described above, when the vehicle speed signal VD exceeds the reference vehicle speed value VR (high vehicle speed region) , the signal conversion means 24 outputs the negative vehicle speed coefficient signal KV- corresponding to the deviation Δ (= VD−VR).
Is provided, the motor torque TM acting on the steering system in a direction opposite to the direction of the driver's steering torque T (manual torque) can be generated.

FIG. 4 is a block diagram showing a main part of another embodiment of the signal conversion means of the electric power steering apparatus to which the invention of claim 2 is applied. Referring to FIG.
Are vehicle speed coefficient output means 29A, vehicle speed coefficient storage means 29B
The vehicle speed coefficient output unit 29A receives a vehicle speed signal VD obtained by parallel-to-digital conversion of the pulse speed signal V detected by the vehicle speed sensor 14, and outputs a vehicle speed coefficient KV corresponding to the vehicle speed signal VD. The vehicle speed coefficient signal KV is read out from the vehicle speed coefficient storage means 29B and output to the multiplication means 25 in FIG.

The vehicle speed coefficient storage means 29B is constituted by a memory such as a ROM, and sets in advance the vehicle speed VD-vehicle speed coefficient KV characteristic data shown in FIG. A vehicle speed coefficient KV corresponding to the vehicle speed signal VD is provided to the vehicle speed coefficient output means 29A based on the vehicle speed signal VD.

As shown in FIG. 5B, the vehicle speed VD-
The vehicle speed coefficient KV characteristic data has a positive vehicle speed coefficient KV + of 1 or less when the vehicle speed signal VD is equal to or less than a predetermined value VR, and a negative vehicle speed coefficient of -1 or more when the vehicle speed signal VD exceeds the predetermined value VR. The vehicle speed coefficient KV is set to have KV-. When the vehicle speed signal VD is equal to the predetermined value VR (VD = VR), the vehicle speed coefficient KV is set to 0, and the change from the positive vehicle speed coefficient KV + to the negative vehicle speed coefficient KV- is made continuous. Thus, the steering feeling at the time of switching from the positive vehicle speed coefficient KV + to the negative vehicle speed coefficient KV- is naturally maintained.

As described above, the signal conversion means 28 outputs a positive vehicle speed coefficient KV + of 1 or less when the vehicle speed signal VD is equal to or less than the reference vehicle speed value VR (VD≤VR), and the vehicle speed signal VD is When the vehicle speed exceeds VR (VD> VR), a vehicle speed coefficient generating means 28A for outputting a negative vehicle speed coefficient KV- of -1 or more is provided.
(VD> VR), the driver's steering torque T
It is possible to generate an electric motor torque TM acting in a direction opposite to the direction in which the (manual torque) acts.

FIG. 6 is a block diagram of a main part of an electric power steering apparatus to which the inventions of claims 3 and 4 are applied. In FIG. 6, the motor control means 30 includes a vehicle speed VD-vehicle speed coefficient generating means 32 which sets characteristic data of vehicle speed VD-vehicle speed coefficient KV1 corresponding to a steering state and a vehicle speed VD-vehicle speed coefficient KV2 corresponding to a steering return state. The return vehicle speed coefficient generating means 33 having the characteristics set therein, the signal converting means 31 including the switching means 34, the direction code F of the steering torque signal T detected by the steering torque sensor 12, and the steering rotation detected by the steering rotational speed sensor 13. The difference from the electric motor control means 15 in FIG. 2 is that a steering state judgment means 35 for judging the going or returning state of the steering based on the direction code G of the speed signal is provided.

The outgoing vehicle speed coefficient generating means 32 has a memory such as a ROM, and is based on a preset vehicle speed signal VD-vehicle speed coefficient KV1 characteristic data corresponding to a steering going state as shown in FIG. 7A. The vehicle speed coefficient KV1 is read out, and a vehicle speed coefficient signal KV1 corresponding to the vehicle speed signal VD is output to one terminal of the switching means 34. In the memory, as the vehicle speed signal VD increases, the positive vehicle speed coefficient KV1 is decreased from 1 by a straight line having a predetermined gradient, and the vehicle speed signal VD is changed to a predetermined value VR.
(VD = VR), the vehicle speed coefficient KV1 is set to 0, and in a region where the vehicle speed signal VD exceeds a predetermined value VR (VD> VR), the negative vehicle speed coefficient KV1 is reduced by a straight line having a predetermined gradient (the vehicle speed coefficient KV1 ≧ −1). Range) is set.

The return vehicle speed coefficient generating means 33 includes a memory such as a ROM, and is based on a vehicle speed signal VD-vehicle speed coefficient KV2 characteristic data corresponding to a preset steering return state as shown in FIG. 7B. Then, a vehicle speed coefficient KV2 is read out, and a vehicle speed coefficient signal KV2 corresponding to the vehicle speed signal VD is output to the other terminal of the switching means 34. The memory stores a positive vehicle speed coefficient KV2 as the vehicle speed signal VD increases.
The vehicle speed coefficient KV2 is set so as to decrease with a straight line having a predetermined gradient within the range from 0 to 0.

The switching means 34 comprises an electronic switch or a switch function of software control.
5 based on the steering state signal ST supplied from
When the steering state signal ST detects the going state, for example, at the H level, the vehicle speed coefficient signal KV1 from the going vehicle speed coefficient generating means 32 is selected and provided to the multiplying means 25 as the vehicle speed coefficient signal KV.

On the other hand, the switching means 34 detects the return state of the steering state signal ST. For example, when the steering state signal ST is at L level, the vehicle speed coefficient signal K
V2 is selected and provided to the multiplication means 25 as a vehicle speed coefficient signal KV.

The steering state judging means 35 is constituted by a comparison function of software control. The direction code F of the steering torque signal T supplied from the steering torque sensor 12 and the steering rotational speed signal N supplied from the steering rotational speed sensor 13 are used. Is determined based on the direction signal G, the direction code F and the direction signal G are matched (the forward state if F = G, the return state if F ≠ G), and the steering state signal ST is supplied to the switching means 34. Speed coefficient signal K for steering going
The selection of V1 or the vehicle speed coefficient signal KV2 in the steering return state is controlled.

As described above, the motor control means 30 includes the outgoing vehicle speed coefficient generating means 32, the returning vehicle speed coefficient generating means 33, and the switching means 34 in the signal converting means 31, and the steering state determining means 35. Vehicle speed coefficient signal K corresponding to the going state or the returning state
Since V is generated, it is possible to output a motor control signal VO corresponding to the steering and control the driving of the motor 10.

When the vehicle speed signal VD exceeds a predetermined value VK, the going vehicle speed coefficient generating means 32 outputs a negative vehicle speed coefficient signal K.
Since V1 is generated, only when the vehicle goes beyond the predetermined value in the steering going state and the vehicle speed exceeds a predetermined value,
, A motor torque TM acting in the opposite direction to the driver's manual torque T can be generated.

[0052]

As described above, the electric motor control means of the electric steering apparatus according to the first aspect of the present invention has a high vehicle speed.
In the area, signal conversion means for controlling the auxiliary steering force to act in the direction opposite to the direction of the steering torque is provided, and the steering force acting on the steering system can be made smaller than the manual steering force. The responsiveness of manual steering of a vehicle with a small load, such as a minicar or a midship sports car, can be kept good.

Further, the electric steering apparatus according to the second aspect of the present invention includes the vehicle speed coefficient generating means for generating a negative coefficient signal when the vehicle speed signal detected by the vehicle speed sensor exceeds a predetermined value. When the steering force acting on the steering system exceeds a predetermined vehicle speed, the steering force can be made smaller than the manual steering force, so that the responsiveness of the manual steering in the high vehicle speed region can be kept good.

Further, in the electric steering apparatus according to the third aspect, the electric motor control means includes a steering state determining means for determining whether the steering is going or returning based on the steering torque signal and the steering rotation speed signal from the steering rotation speed sensor. In addition, the signal conversion means is provided with a vehicle speed coefficient generating means for generating a coefficient signal of a steering going or returning state corresponding to the vehicle speed signal, and a steering force acting on a steering system is set according to a steering situation. Therefore, it is possible to obtain an optimum steering feeling in the forward and backward steering states.

Further, the electric steering apparatus according to claim 4, wherein the signal converting means includes a forward vehicle speed coefficient generating means for generating a negative coefficient signal when the vehicle speed signal exceeds a predetermined value;
A returning vehicle speed coefficient generating means for generating a positive coefficient signal corresponding to the vehicle speed, and a switching means, wherein when the steering state determining means determines the steering state, the selecting means selects the going vehicle speed coefficient generating means, and A negative coefficient signal is generated only when the vehicle speed signal exceeds a predetermined value, and the steering force acting on the steering system can be made smaller than the manual steering force. In the case where the steering is returned, the driver's manual steering torque can be assisted by the electric motor torque in the same direction as the driver's manual steering torque so that a light steering feeling can be obtained. Thus, the steering torque in the high vehicle speed region can be increased by assisting the motor torque in the reverse direction to the manual steering torque of the driver. When the steering state determination means determines the return state of the steering, the vehicle speed coefficient generation means at the time of return is selected, and since the negative coefficient signal is not generated even if the vehicle speed signal exceeds a predetermined value, the return of the steering is performed. Therefore, a sense of response can be given when turning the steering wheel, and a slow return can be given when returning the steering wheel, and an excessive operation of the steering wheel can be suppressed.

Accordingly, it is possible to provide an electric steering apparatus which improves the steering feeling in a low vehicle speed region and increases the response to steering in a high vehicle speed region to stabilize the vehicle behavior.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an electric power steering device to which the present invention is applied.

FIG. 2 is a block diagram of a main part of an electric power steering apparatus to which the invention of claim 1 is applied.

FIG. 3 is a block diagram of a main part of an embodiment of a signal conversion means of an electric power steering apparatus to which the invention of claim 2 is applied.

FIG. 4 is a block diagram of a main part of another embodiment of the signal conversion means of the electric power steering apparatus to which the invention of claim 2 is applied.

FIG. 5 shows vehicle speed VD-vehicle speed coefficient KV characteristics corresponding to FIGS. 3 and 4.

FIG. 6 is a block diagram of a main part of an electric power steering apparatus to which the inventions of claims 3 and 4 are applied;

FIG. 7 is a characteristic diagram of a vehicle speed VD-vehicle speed coefficient KV corresponding to a steering going or returning state.

FIG. 8 is a characteristic diagram of the steering torque signal TD-target current signal IMS.

FIG. 9 is a block diagram of a main part of a conventional electric power steering device.

FIG. 10: Steering torque signal (TD) -target current signal (ISD) using vehicle speed signal VD (VL, VM, VH) as a parameter
Characteristic diagram

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electric power steering device, 2 ... Steering shaft, 3 ... Connection shaft, 3a, 3b ... Universal joint, 4 ... Steering gear box, 5 ... Rack & pinion mechanism, 5
a: pinion, 6: manual steering force generating means, 7: rack shaft, 7a: rack teeth, 8: tie rod, 9: front wheel, 10
... electric motor, 11 ... ball screw mechanism, 12 ... steering torque sensor, 13 ... steering rotation speed sensor, 14 ... vehicle speed sensor,
15, 30 ... motor control means, 16 ... motor drive means,
17 steering wheel, 21 target current setting means, 22 deviation calculation means, 23 drive control means, 24,
28, 31: signal conversion means, 24A, 28A: vehicle speed coefficient generation means, 25: multiplication means, 26: reference vehicle speed value storage means, 27A: vehicle speed comparison means, 29A: vehicle speed coefficient output means, 29B: vehicle speed coefficient storage means, 32: forward vehicle speed coefficient generating means, 33: returning vehicle speed coefficient generating means, 34: switching means, 35: steering state determining means, F, G: direction sign, ΔI: deviation signal, IMD: motor current detection signal, I
M: Target current signal, KV, KV +, KV-, KV1, KV2: Vehicle speed coefficient, N: Steering rotation speed signal, ST: Steering state signal, T, TD: Steering torque signal, TM: Motor torque,
V, VD: vehicle speed signal, VM: motor drive signal, VO: drive control voltage signal, VR: reference vehicle speed value.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-219311 (JP, A) JP-A-2-6271 (JP, A) JP-A-62-291769 (JP, A) JP-A-63-291769 291771 (JP, A) JP-A-2-127168 (JP, A) JP-A-2-290777 (JP, A) JP-A-59-195470 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B62D 6/00 B62D 5/04

Claims (4)

(57) [Claims] 1. A steering torque sensor for detecting a steering torque of a steering system, target drive signal generating means for generating a target drive signal corresponding to a steering torque signal from the steering torque sensor, and driving based on the target drive signal. A motor control means having a drive control means for outputting a control signal,
A motor driving means for driving the motor based on the drive control signal, is driven by the electric motor drive unit, the electric steering apparatus comprising a motor acting the motor power to the steering system, the motor control means, the vehicle speed is high An electric steering apparatus comprising: a signal conversion unit that controls the electric motor power to act in a direction opposite to the direction in which the steering torque acts in a vehicle speed region . 2. The vehicle according to claim 1, wherein said signal converting means includes a vehicle speed coefficient generating means for generating a negative coefficient signal when a vehicle speed signal detected by a vehicle speed sensor exceeds a predetermined value. An electric steering device as described in the above. 3. The motor control means further includes a steering state determination means for determining a forward or a return state of steering based on the steering torque signal and a steering rotation speed signal from a steering rotation speed sensor, and the signal conversion means. 2. The electric steering apparatus according to claim 1, further comprising a vehicle speed coefficient generating means for generating a coefficient signal indicating a forward or backward state of steering in response to the vehicle speed signal. 4. A forward vehicle speed coefficient generating means for generating a negative coefficient signal when the vehicle speed signal exceeds a predetermined value, and a return for generating a positive coefficient signal corresponding to the vehicle speed. Hour vehicle speed coefficient generating means, and switching means,
When the steering state determining means determines the steering state of the steering, selecting a going vehicle speed coefficient generating means,
The electric steering apparatus according to claim 3, wherein a negative coefficient signal is generated only when the vehicle speed signal exceeds a predetermined value.