JP2010173376A - Electric power steering device - Google Patents

Abstract

[PROBLEMS] To detect an ambient temperature of an EPS ECU without adding a thermistor to the EPS ECU and appropriately limit a current supplied to a motor in accordance with the ambient temperature, so that the motor control device of the EPS ECU is moderately protected from overheating. To protect.
An electric power steering apparatus having an electric power steering electronic control unit 30 disposed in a vehicle interior, wherein the electric power steering electronic control unit includes a current flowing in a motor 10 detected by the motor current detection apparatus 32; Based on the temperature in the passenger compartment detected by the passenger compartment thermometer 51, motor target current suppression processing means 45 for limiting the current supplied to the motor 10 is provided.
[Selection] Figure 3

Description

  The present invention relates to an electric power steering apparatus.

  Conventionally, as an electric power steering device, a steering wheel is steered by sliding of a rack shaft that meshes with a steering pinion connected to a steering side, and an electric power steering electronic control unit (EPS) according to steering torque on the steering side. In the electric power steering apparatus in which the power (assist force) of the motor driven and controlled by the ECU (ECU) is transmitted to the sliding of the rack shaft via the transmission mechanism to assist the steering, a part of the steering gear box or the steering There is one in which a motor is installed in an adjacent portion of a rack case adjacent to a gear box, and various functional element parts are mounted on a control board constituting a motor control device of the EPS ECU.

  In the electric power steering device described in Patent Document 1, the current supplied to the motor (assist current) is based on the current flowing through the motor detected by the motor current detection device and the substrate temperature detected by the thermistor mounted on the control board of the EPS ECU. ) Is limited to a constant target current, and as a result, overheating due to the assist current of the control board including the various functional elements of the motor control device, and thus thermal destruction, is prevented.

JP2006-62574

The prior art has the following problems.
(1) It is necessary to add a thermistor for detecting the substrate temperature to the control board of the EPS ECU, which increases the cost.

  (2) The mounting parts including the thermistor and the mounting area on the control board of the EPS ECU increase, and the heat capacity and dimensions of the EPS ECU increase.

  (3) If the thermistor is not mounted on the control board of the EPS ECU, the atmosphere temperature of the EPS ECU cannot be recognized. Therefore, it is necessary to provide a margin for overheating protection of the control board of the EPS ECU. There is a risk that the assist current will be excessively suppressed and the assist force will be reduced.

  An object of the present invention is to detect the ambient temperature of the EPS ECU without adding a thermistor to the EPS ECU and appropriately limit the current supplied to the motor in accordance with the ambient temperature. There is a moderate protection from overheating.

  The invention of claim 1 has an electric power steering electronic control unit disposed in the vehicle interior, and the steering wheel is steered by sliding of a rack shaft meshing with a steering pinion connected to the steering side, and the steering In the electric power steering device in which the power of the motor driven and controlled by the electric power steering electronic control unit according to the steering torque on the side is transmitted to the sliding of the rack shaft via the transmission mechanism to assist the steering, the steering side A torque sensor for detecting the steering torque of the steering gear box is disposed in the steering gear box, and the motor is disposed in a part of the steering gear box or in an adjacent portion of the rack case adjacent to the steering gear box. A motor current detection device that detects a flowing current and a vehicle interior The electric power steering electronic control unit includes a vehicle interior thermometer that detects a temperature, and the electric power steering electronic control unit is configured to provide a motor based on a current flowing through the motor detected by the motor current detector and a vehicle interior temperature detected by the vehicle interior thermometer. Motor target current suppression processing means for limiting the supply current to the motor.

  According to a second aspect of the present invention, in the first aspect of the invention, the motor target current suppression processing unit further integrates the current flowing through the motor detected by the motor current detecting device, and based on the integrated value, Current limiting processing for limiting the supply current is performed.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the detected temperature of the vehicle interior thermometer is input to the motor target current suppression processing means in the electric power steering electronic control unit via the in-vehicle network. It is what I did.

  According to a fourth aspect of the present invention, there is provided the engine control according to any one of the first to third aspects, further comprising a torque detection circuit that outputs a detection signal of the torque sensor as a torque detection voltage, and detects a temperature in the engine room. And a correction means for correcting the torque detection voltage based on the temperature in the engine room detected by the service temperature detection means.

(Claim 1)
(a) The motor target current suppression processing means of the EPS ECU is a current supplied to the motor (assist current) based on the current flowing through the motor detected by the motor current detection device and the temperature in the vehicle interior detected by the vehicle interior thermometer. As a result, overheating due to the assist current of the control board including various functional elements of the motor control device of the EPS ECU, and thus thermal destruction, is prevented.

  (b) The temperature of the passenger compartment detected by an existing passenger compartment thermometer used in the control of the air conditioner in the passenger compartment is used as the atmosphere temperature of the EPS ECU, and is used for detecting the substrate temperature on the control board of the EPS ECU. Because it is not necessary to add a dedicated thermistor, the cost can be reduced.

  (c) The mounting capacity and the mounting area including the thermistor on the control board of the EPS ECU do not increase, and the heat capacity and dimensions of the EPS ECU can be reduced.

  (d) Since the atmospheric temperature of the EPS ECU disposed in the vehicle interior can be correctly recognized from the detection result of the vehicle interior thermometer installed in the same vehicle interior, the overheat protection of the control board of the EPS ECU can be appropriately performed. . Therefore, the assist current to the motor is moderately suppressed, and when the ambient temperature is low (the assist current need not be excessively suppressed), the assist current suppression effect is delayed, and when the ambient temperature is high, the assist current is reduced. It is possible to generate a moderate assist force by suppressing the effect early.

(Claim 2)
(e) The main loss during the operation of the motor is copper loss, which is the square of the armature current value multiplied by the armature resistance. Can be converted into a quantity. Therefore, the motor target current suppression processing means integrates the current flowing through the motor detected by the motor current detection device, and the current supplied to the motor is limited based on the integrated value, thereby effectively generating heat from the motor. The motor control device of the EPS ECU can be appropriately protected from overheating by moderately limiting the current supplied to the motor.

(Claim 3)
(f) The detected temperature of the vehicle interior thermometer is input to the motor target current suppression processing means in the EPS ECU via the in-vehicle network such as CAN, so that the detected temperature of the vehicle interior thermometer is not dependent on the dedicated harness. It can be input to the motor target current suppression processing means. Further, the detected temperature of the vehicle interior thermometer can be input to the motor target current suppression processing means as a digital signal.

(Claim 4)
(g) The torque detection voltage detected by the torque sensor is corrected based on the temperature in the engine room detected by the engine control temperature detection means. The temperature in the engine room detected by the existing engine control temperature detecting means used for engine control is used as temperature compensation for the torque sensor, and the cost can be reduced.

FIG. 1 is an overall view showing an electric power steering apparatus. FIG. 2 is a schematic diagram showing an electric power steering apparatus. FIG. 3 is a block diagram showing a motor control device of the electric power steering device. FIG. 4 is a block diagram showing a modification of the motor control device of the electric power steering device.

Hereinafter, embodiments of the present invention will be described in detail.
As shown in FIG. 1, the electric power steering apparatus 1 is disposed in an engine room, and a rack shaft 3 is accommodated in a rack case 2 disposed along the left-right direction of the vehicle so as to be linearly movable. Tie rods 5 and 5 are provided at both ends of the rack shaft 3 protruding from both ends of the rack case 2 so that the left and right steered wheels of the vehicle can be steered.

  A steering gear box 6 is provided near one end of the rack case 2. An input shaft 7 connected to a steering shaft to which a steering wheel (not shown) is attached is rotatably supported on the steering gear box 6, and the input shaft 7 is torsion bar (not shown) in the steering gear box 6. ) To a steering pinion shaft (not shown). The pinion teeth of the steering pinion shaft and the rack teeth of the rack shaft 3 mesh with each other to constitute a rack and pinion mechanism.

  Therefore, the steering force transmitted to the input shaft 7 by the turning operation of the steering wheel rotates the steering pinion shaft via the torsion bar and linearly moves the rack shaft 3 by meshing the pinion teeth of the steering pinion shaft and the rack teeth. Move.

  In the electric power steering apparatus 1, the central part of the rack case 2 whose diameter is enlarged is a motor case 2 </ b> A, and the motor 10 is accommodated. In the motor 10, an annular inner rotor 11 rotates on the outer periphery of the rack shaft 3 on which the ball screw 3A is engraved, and an outer stator 12 is provided on the outer side along the inner peripheral surface of the motor case 2A. A connection sleeve 13 press-fitted into the inner peripheral surface of the annular inner rotor 11 extends around the rack shaft 3, and the sleeve 13 is rotatably supported on the inner periphery of the rack case 2 via a bearing 15. And united together. The ball nut 14 is screwed to the ball screw 3A of the rack shaft 3 via a ball.

  Therefore, when the motor 10 is driven and the inner rotor 11 rotates, the ball nut 14 integrated therewith rotates, and the rack shaft 3 screwed through the ball nut 14 and the ball is linearly moved to assist the steering force.

  In the electric power steering apparatus 1, a torque sensor 20 for detecting steering torque on the steering side is disposed around a torsion bar in the steering gear box 6. The torque sensor 20 detects a relative rotation angle generated between the input shaft 7 and the steering pinion shaft due to elastic torsional deformation of the torsion bar caused by the steering force applied to the steering wheel.

  As shown in FIG. 2, the electric power steering device 1 includes an electric power steering electronic control unit (EPS ECU) 30 for controlling the drive of the motor 10 in the vehicle interior, and controls the motor control device 30 </ b> A of the EPS ECU 30. Various functional element components are mounted on the substrate 30B.

  As shown in FIG. 3, the torque sensor 20 includes a steering torque detection circuit 21 and a torque sensor temperature detection device 22.

  The motor control device 30A of the EPS ECU 30 includes a motor drive device 31, a motor current detection device 32, and a CPU 40 on a control board 30B as shown in FIG. The CPU 40 includes control torque calculation processing means 41, torque sensor temperature correction value calculation means 42, target current calculation processing means 43, current feedback control unit 44, and motor target current suppression processing means 45. The motor control device 30 </ b> A of the EPS ECU 30 may include a steering torque detection circuit 21.

  The steering torque detection circuit 21 detects the steering torque on the steering side based on the detection result of the torque sensor 20 (the amount of relative rotational displacement generated between the input shaft 7 and the steering pinion shaft). The steering torque detection circuit 21 outputs the detected torque detection voltage Vt to the control torque calculation processing means 41 of the CPU 40. The CPU 40 outputs a motor control signal corresponding to the steering torque to the motor driving device 31 based on the torque detection voltage Vt, and drives the motor 10 by the motor driving device 31 to assist steering. The motor drive device 31 is a device in which, for example, four switching elements such as FETs (field effect transistors) are assembled in a bridge so that a pulse width modulation type DC chopper-controlled current can be supplied to the motor 10 in both forward and reverse directions. It is. The motor current detecting device 32 detects an armature current value Im supplied to the motor 10 and flowing through the armature, and the detected current value Im is fed back to the CPU 40 and the motor 10 generates heat based on the detected current value Im. It is suppressed.

  The torque sensor temperature detection device 22 detects the temperature of the torque sensor 20 and outputs this temperature detection signal Vth to the torque sensor temperature correction value calculation means 42 of the CPU 40. The torque sensor temperature correction value calculation means 42 calculates a temperature correction value ΔV of the torque sensor 20 corresponding to the temperature detection signal Vth of the torque sensor temperature detection device 22 and outputs the calculation result to the control torque calculation processing means 41 of the CPU 40. . The control torque calculation processing means 41 performs temperature compensation of the torque sensor 20 by adding the temperature correction value ΔV to the torque detection voltage Vt. The control torque calculation processing means 41 calculates an accurate steering torque with temperature compensation of the torque sensor 20, and calculates the calculated steering torque according to the relationship between the predetermined control torque and the optimum target current I0 with respect to the vehicle speed. , The target current I 0 is extracted, and the extraction result is output to the target current calculation processing means 43. The torque sensor temperature detection device 22 directly detects the temperature of the torque sensor board disposed in the vicinity of the torque sensor 20 in the steering gear box 6 with a thermistor, and corrects the torque sensor temperature in the CPU 40 as the temperature detection signal Vth. This is output to the value calculating means 42.

  The target current calculation processing unit 43 multiplies the target current I0 input from the control torque calculation processing unit 41 by a target current suppression value p transmitted from the target current suppression processing unit 45 as will be described later, to obtain a final target current. Ic is calculated. The final target current Ic calculated by the target current calculation processing means 43 is input to the current feedback control unit 44. The current feedback control unit 44 receives the feedback of the armature current value Im from the motor current detection device 32, and receives the final target current. A control signal is output to the motor drive device 31 so that the difference from Ic is zero, and the motor 10 is feedback controlled.

  However, the electric power steering device 1 detects the ambient temperature of the EPS ECU 30 without adding a new dedicated thermistor to the EPS ECU 30, limits the supply current Ic to the motor 10 and suppresses the heat generation of the motor 10, and the EPS. In order to protect the motor control device 30A of the ECU 30 from overheating and thermal destruction, the following configuration is provided.

  In the electric power steering apparatus 1, the detected temperature T of the vehicle interior thermometer 51 that is used in the air conditioner unit 50 or the like and detects the temperature in the vehicle interior is supplied to the motor target current in the EPS ECU 30 via the in-vehicle network 70 such as CAN. Input to the processing means 45.

  Then, in the motor control device 30A of the EPS ECU 30, the target current suppression processing means 45 sets the current value Im flowing through the motor 10 detected by the motor current detection device 32 and the vehicle interior temperature T detected by the vehicle interior thermometer 51. Based on this, a current limiting process for limiting the supply current Ic to the motor 10 is performed. When the target current calculation processing unit 43 outputs the target current I0 input from the control torque calculation processing unit 41 to the current feedback control unit 44 as the final target current Ic, the target current suppression processing unit 45 outputs the final target current. In order to limit Ic, a target current suppression value p to be multiplied by the target current I0 is extracted, and this target current suppression value p is output to the target current calculation processing means 43.

  The target current suppression processing means 45 drives the motor 10 so as to suppress a temperature rise above a predetermined temperature so that the control board 30B disposed in the EPS ECU 30 disposed in the passenger compartment is not thermally destroyed. A predetermined correspondence relationship between the target current suppression value p for suppressing the target current I0 and the ambient temperature T of the EPS ECU 30 is stored in the memory. Until the atmospheric temperature T reaches a predetermined suppression start temperature t, the target current suppression value p is 1.0. When the atmospheric temperature T exceeds the suppression start temperature t, the target current suppression value p gradually decreases from 1.0.

  The target current suppression value p extracted by the target current suppression processing means 45 based on the detected temperature T of the vehicle interior thermometer 51 is input to the target current calculation processing means 43 as described above, and the target current calculation processing means 43. Is multiplied by the target current I0 input from the control torque calculation processing means 41 to calculate the final target current Ic (= I0 × p). The final target current Ic output from the target current calculation processing unit 43 is input to the current feedback control unit 44, and the current feedback control unit 44 receives the feedback of the armature current value Im from the current detection device 34, and finally An instruction signal is output to the motor drive device 31 so that the difference from the target current Ic is zero, and the motor 10 is feedback-controlled.

  Accordingly, the vehicle interior temperature T detected by the vehicle interior thermometer 51 (also the ambient temperature of the EPS ECU 30 (motor control device 30A, control board 30B) disposed in the vehicle interior) has a predetermined suppression start temperature t. If it exceeds, the target current I0 is suppressed and the drive of the motor 10 is limited. If the ambient temperature T is high, the degree of inhibition of the target current I0 can be increased, and if the atmosphere temperature T is low, the degree of inhibition of the target current I0 can be reduced. Thereby, the heat generation of the motor 10 is suppressed and the thermal destruction of the control board 30B is prevented.

According to the present embodiment, the following operational effects can be obtained.
(a) The motor target current suppression processing means 45 of the EPS ECU 30 is supplied to the motor 10 based on the current flowing in the motor 10 detected by the motor current detection device 32 and the temperature in the vehicle interior detected by the vehicle interior thermometer 51. The current (assist current) is appropriately limited, and as a result, overheating due to the assist current of the control board 30B including various functional elements of the motor control device 30A of the EPS ECU 30 is prevented, and as a result, thermal destruction thereof is prevented.

  (b) The temperature of the passenger compartment detected by the existing passenger compartment thermometer 51 used in the control of the air conditioner unit 50 or the like in the passenger compartment is used as the atmospheric temperature of the EPS ECU 30, and is applied to the control board 30B of the EPS ECU 30. Since it is not necessary to add a dedicated thermistor for detecting the substrate temperature, the cost can be reduced.

  (c) The mounting capacity including the thermistor and the mounting area on the control board 30B of the EPS ECU 30 are not increased, and the heat capacity and dimensions of the EPS ECU 30 can be reduced.

  (d) Since the atmospheric temperature of the EPS ECU 30 disposed in the vehicle interior can be correctly recognized from the detection result of the vehicle interior thermometer 51 installed in the same vehicle interior, the overheat protection of the control board 30B of the EPS ECU 30 is appropriately performed. Can do. Therefore, the assist current to the motor 10 is moderately suppressed, and when the ambient temperature is low (the assist current need not be excessively suppressed), the assist current suppression effect is delayed, and when the ambient temperature is high, the assist current is assisted. The current can be suppressed early and a moderate assist force can be generated.

  (e) The main loss during the operation of the motor 10 is copper loss. The copper loss is obtained by multiplying the square of the armature current value by the armature resistance, and dividing it by the thermal resistance specific to the motor 10. Can be converted into calorific value. Accordingly, the motor target current suppression processing means 45 performs integration processing on the current flowing through the motor 10 detected by the motor current detection device 32, and limits the supply current to the motor 10 based on the integration value, thereby the motor 10 Can be effectively suppressed, the current supplied to the motor 10 can be appropriately limited, and the motor control device 30A of the EPS ECU 30 can be appropriately protected from overheating.

  (f) When the detected temperature of the vehicle interior thermometer 51 is input to the motor target current suppression processing means 45 in the EPS ECU 30 via the in-vehicle network 70 such as CAN, the detected temperature of the vehicle interior thermometer 51 is dedicated. It can be input to the motor target current suppression processing means 45 regardless of the harness. Further, the detected temperature of the vehicle interior thermometer 51 can be input to the motor target current suppression processing means 45 as a digital signal.

  FIG. 4 shows a modification of the electric power steering apparatus 1. This modification is different from the embodiment of FIGS. 1 to 3 in that the torque sensor temperature detection device 22 is removed, and the detected temperature θ of the engine control temperature detection means 61 input to the engine ECU 60 is in the vehicle such as CAN. That is, the torque sensor temperature correction value calculation means 42 in the EPS ECU 30 is input to the EPS ECU 30 via the network 70. The engine control temperature detecting means 61 detects the temperature θ in the engine room (which is also the atmospheric temperature of the torque sensor 20 arranged in the engine room). For example, the water temperature sensor 61A, the oil temperature sensor 61B, An intake air temperature sensor 61C or the like can be employed.

  According to this modification, the thermistor is not disposed in the vicinity of the torque sensor 20 in the steering gear box 6 disposed in the engine room, but based on the temperature in the engine room detected by the engine control temperature detecting means 61. Further, temperature compensation of the torque sensor 20 can be performed, and the following operational effects can be obtained.

  The torque detection voltage detected by the torque sensor 20 is corrected based on the temperature in the engine room detected by the engine control temperature detection means 61. The temperature in the engine room detected by the existing engine control temperature detecting means 61 used for engine control is used as temperature compensation for the torque sensor 20, and the cost can be reduced.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration of the present invention is not limited to this embodiment, and even if there is a design change or the like without departing from the gist of the present invention. It is included in the present invention. For example, the temperature T detected by the in-vehicle thermometer 51 of the present invention or the temperature θ detected by the engine control temperature detecting means 61 does not pass through the air conditioner unit 50 or the in-vehicle network 70 such as the engine ECU 60 or CAN. The power steering EPS ECU 30 may input the target current suppression processing unit 45 and the torque sensor temperature correction value calculation unit 42.

  The present invention detects the ambient temperature of the EPS ECU without adding a thermistor to the EPS ECU, appropriately limits the current supplied to the motor according to the ambient temperature, and prevents the EPS ECU motor control device from overheating. It can be protected moderately.

DESCRIPTION OF SYMBOLS 1 Electric power steering apparatus 2 Rack case 3 Rack shaft 6 Steering gear box 10 Motor 20 Torque sensor 21 Torque detection circuit 30 Electric power steering control electronic control unit (EPS ECU)
30A Motor control device 30B Control board 31 Motor drive device 32 Motor current detection device 41 Torque calculation processing means 42 for control Torque sensor temperature correction value calculation means 43 Target current calculation processing means 45 Target current suppression processing means 50 Air conditioner unit 51 Car interior temperature Total 60 engine electronic control unit 61 temperature detection means for engine control (engine ECU)
70 In-car network

Claims (4)

An electric power steering electronic control unit disposed in the passenger compartment;
The steering wheel is steered by sliding the rack shaft meshing with the steering pinion connected to the steering side, and the power of the motor driven and controlled by the electric power steering electronic control unit is transmitted according to the steering torque on the steering side. In the electric power steering device that is transmitted to the sliding of the rack shaft through a mechanism to assist the steering,
A torque sensor for detecting steering torque on the steering side is disposed in the steering gear box,
The motor is disposed in a part of the steering gear box or an adjacent part of the rack case adjacent to the steering gear box,
With a motor current detection device that detects the current flowing through the motor,
Equipped with a vehicle interior thermometer that detects the temperature in the vehicle interior,
The electric power steering electronic control unit is configured to suppress a motor target current that limits a supply current to the motor based on a current flowing through the motor detected by the motor current detection device and a temperature in the vehicle interior detected by the vehicle interior thermometer. An electric power steering apparatus comprising processing means.   2. The motor target current suppression processing means performs an integration process on a current flowing through the motor detected by the motor current detection device, and performs a current limiting process for limiting a supply current to the motor based on the integrated value. The electric power steering apparatus as described.   The electric power steering apparatus according to claim 1 or 2, wherein the temperature detected by the vehicle interior thermometer is input to a motor target current suppression processing means in the electric power steering electronic control unit via an in-vehicle network. A torque detection circuit that outputs a detection signal of the torque sensor as a torque detection voltage;
The electric power steering according to any one of claims 1 to 3, further comprising correction means for correcting the torque detection voltage based on the temperature in the engine room detected by the engine control temperature detection means for detecting the temperature in the engine room. apparatus.

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