JP2002059859A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric power steering device capable of accurately estimating a motor rotation speed regardless of a temperature change of the motor. SOLUTION: A motor control device 12 outputting a control signal to a motor 10 adding steering assist torque on steering system for a vehicle is provided with a motor rotation speed estimation part 12F estimating a rotation speed of the motor 10 based on drive voltage, drive current and an intrinsic resistance of the motor 10. The motor rotation speed estimation part 12F is provided with a resistance thermal correction part performing a thermal correction of a resistance of the motor 10 according to a detection signal of a temperature sensor 16 as a motor temperature detection means detecting the temperature of the motor 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power steering apparatus for adding a steering assist torque by an electric motor to a steering system of a vehicle, and more particularly, to an electric power steering apparatus capable of accurately estimating a rotational speed of an electric motor regardless of a temperature change of the electric motor. The present invention relates to a steering device.

[0002]

2. Description of the Related Art As a vehicle steering system, a so-called electric power steering system, which reduces the steering force of a driver by adding a steering assist torque by an electric motor to a steering system during steering of a steering wheel, has been widely used in recent years. This type of electric power steering device basically detects a steering torque of a steering system generated along with steering of a steering wheel, and generates a steering assist torque by the electric motor according to the direction and magnitude of the detected torque. It is configured to control. That is, a target value of the drive current flowing through the electric motor is set according to the steering torque detected by the steering torque sensor, and the electric motor is controlled such that the drive current of the electric motor detected by the current sensor converges to the target value. The motor control device includes a motor control device that outputs a control signal, and a motor drive circuit that drives the motor with a predetermined drive current in accordance with the control signal output from the motor control device.

In the above-mentioned electric power steering apparatus, when the steering wheel is steered suddenly, the steering torque of the steering system suddenly increases, and accordingly, the steering assist torque by the electric motor suddenly increases, thereby impairing the stability of the steering operation. There is fear. Therefore, as this kind of electric power steering apparatus, there is an electric power steering apparatus that employs damping control for preventing a sudden increase in steering assist torque accompanying sudden steering of a steering wheel in order to secure stability of steering operation.

[0004] The damping control is for reducing and correcting a target value of a drive current flowing through the motor at least according to the rotation speed of the motor. The rotation speed of the motor is usually estimated by a predetermined arithmetic expression. That is, the driving current of the motor is IM, the driving voltage of the motor is VM, the intrinsic resistance value such as the winding resistance of the motor is RM, and the induced voltage constant of the motor is K.
, The rotation speed NM of the electric motor is expressed as ｛NM = (VM
−IM · RM) / K｝ (see Japanese Patent Application Laid-Open No. 8-34359).

[0005]

The specific resistance value RM of the motor is a value that increases as the temperature of the motor increases and decreases as the temperature of the motor decreases. The resistance value RM is treated as a constant. Therefore, when the drive current IM and the drive voltage VM of the motor do not change and only the temperature of the motor increases, the specific resistance value RM actually increases, so that the rotation speed NM of the motor decreases. Regardless, according to the above equation, the rotation speed NM remains unchanged.

That is, the damping control at the time of high temperature of the motor is performed based on the rotation speed NM higher than the actual rotation speed of the motor, so that the target value of the drive current to be supplied to the motor is excessively reduced and corrected. The phenomenon that the control is too effective occurs. Conversely, since the damping control at the time of low temperature of the motor is performed based on the rotation speed NM lower than the actual rotation speed of the motor, the reduction correction of the target value is insufficient, and the phenomenon of insufficient damping control occurs. I do.

Further, the estimated offset value of the motor rotational speed changes due to an error in the specific resistance value RM. At this time, if the value of the estimated motor rotation speed is near 0, the sign of the motor rotation speed may be erroneously estimated. In this case, there is a problem that the damping control is performed based on the motor rotation speed in the reverse direction.

Accordingly, an object of the present invention is to provide an electric power steering apparatus capable of accurately estimating the rotational speed of a motor irrespective of a change in the temperature of the motor, and thereby enabling accurate and accurate damping control at all times. And

[0009]

In order to solve the above-mentioned problems, the present invention provides a steering torque sensor for detecting a steering torque of a steering system of a vehicle, an electric motor for applying a steering assist torque to the steering system, and A current sensor that detects a drive current of the motor, a voltage sensor that detects a drive voltage of the motor, and a target value of a drive current that flows through the motor according to at least a steering torque detected by the steering torque sensor; A motor control device for outputting a control signal for driving the motor, the motor control device including a drive current detected by the current sensor, a drive voltage detected by the voltage sensor, and a specific resistance of the motor. The electric power steering device is provided with a motor rotation speed estimating unit that estimates the rotation speed of the motor based on the value. And a motor temperature detecting means for directly or indirectly detecting the temperature of the motor, and a temperature correction means for correcting the specific resistance value of the motor in accordance with the temperature of the motor detected by the motor temperature detecting means. A section provided in the motor rotation speed estimation section.

[0010] In the electric power steering apparatus according to the present invention, the steering torque sensor detects the steering torque of the steering system as the steering wheel is steered. And
The electric motor control device sets a target value of the drive current to be supplied to the electric motor in accordance with the steering torque detected by the steering torque sensor.

Here, in the motor control device, the motor rotation speed estimating unit determines the rotation speed of the motor based on the drive current detected by the current sensor, the drive voltage detected by the voltage sensor, and the specific resistance value of the motor. presume. For example, when a damping correction unit is provided, the target value of the drive current flowing through the motor is reduced and corrected according to the rotation speed of the motor estimated by the motor rotation speed estimation unit. At that time, the motor temperature detecting means directly or indirectly detects the temperature of the motor, and the resistance value temperature correction unit temperature-corrects the specific resistance value of the motor according to the temperature of the motor detected by the motor temperature detecting means. . as a result,
The motor rotation speed estimation unit accurately estimates the rotation speed of the motor based on the specific resistance value of the motor temperature corrected by the resistance value temperature correction unit. The damping correction unit corrects and reduces the target value of the drive current flowing through the motor in accordance with the rotation speed of the motor accurately estimated by the motor rotation speed estimation unit.

In the electric power steering apparatus according to the present invention, the electric motor temperature detecting means may be constituted by a novel temperature sensor attached to the electric motor. In this case, the temperature of the electric motor can be accurately detected.

The motor temperature detecting means may include an existing temperature sensor separately provided in an engine room of the vehicle and a motor control device for estimating the temperature of the motor based on a temperature signal output from the temperature sensor. It may be constituted by a temperature correction unit. In this case, it is possible to accurately detect the temperature of the electric motor without providing a new temperature sensor.

Further, the motor temperature detecting means comprises a temperature estimating section of the motor control device for estimating the temperature of the motor based on the drive current detected by the current sensor and a control signal output from the motor control device. May be. In this case, no new hardware such as a temperature sensor is required in addition to the normally used current sensor, and the electric power steering device can be made compact.

Further, the motor temperature detecting means may be constituted by a temperature conversion section of a motor control device for converting the temperature of the motor based on a pulse transient response voltage output from the torque sensor. In this case, the temperature of the electric motor can be detected without providing a new temperature sensor. In addition, since the torque sensor is usually disposed near the electric motor, the temperature of the electric motor can be accurately detected.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an electric power steering apparatus according to the present invention will be described below with reference to the drawings. In the drawings to be referred to, FIG. 1 is a configuration diagram of a steering system to which an electric power steering device of one embodiment is applied, and FIG. 2 is a block configuration diagram of the electric power steering device of one embodiment.

In describing an electric power steering apparatus according to one embodiment, first, the structure of a steering system to which the electric power steering apparatus is applied will be described with reference to FIG. The steering system is a so-called rack and pinion type steering system. A lower end of a steering shaft 2 integrally connected to a steering wheel 1 is connected to a pair of universal joints 4 connected to each other via a connection shaft 3. 4 is connected to an input shaft 5 </ b> A of the steering torque sensor 5. The pinion 6A of the rack and pinion mechanism 6 is formed integrally with the output shaft of the steering torque sensor 5.

The rack and pinion mechanism 6 has a rack shaft 6C on which rack teeth 6B meshing with the pinion 6A are formed.
A knuckle arm (not shown) attached to the left and right front wheels 7, 7 of the vehicle is connected to both ends of the rack shaft 6C via tie rods 8, 8, respectively. A ball screw portion 9A of the ball screw mechanism 9 is formed coaxially with the rack shaft 6C. The ball nut 9B meshing with the ball screw portion 9A is
0 of the motor 10
Are arranged around the rack shaft 6C in a state where the rack shaft 6C passes therethrough.

Here, as shown in FIG. 1 and FIG. 2, the electric power steering apparatus according to one embodiment includes the steering torque sensor 5 and the later-described motor as means for feedback-controlling the drive current flowing through the electric motor 10 to a target value. A motor control device 12 for inputting a detection signal of a vehicle speed sensor 11 to output a control signal of the motor 10 and driving the motor 10 with a predetermined drive current in accordance with a control signal output from the motor control device 12 Motor drive circuit 1
3 is provided. Also, a current sensor 14 for detecting a drive current supplied from the motor drive circuit 13 to the motor 10 and outputting a detection signal to the motor control device 12, and a drive voltage for the motor 10 for detecting the drive current. Voltage sensor 1 for outputting a signal to the motor control device 12
5 and a temperature sensor 16 attached to the electric motor 10 as electric motor temperature detecting means.

First, each of the sensors will be described. The steering torque sensor 5 is described in, for example,
And a mechanism for converting the torsion angle of a not-shown torsion bar interposed between the input shaft 5A and the pinion 6A as an output shaft into a displacement of the core. And an LR integration circuit that outputs a detection voltage corresponding to the displacement of the core. Then, based on the voltage output from the LR integration circuit,
Steering torque signal T indicating the direction and magnitude of steering torque
S is configured to be output to the motor control device 12. The vehicle speed sensor 11 outputs a vehicle speed signal VP corresponding to the rotation speed of a transmission output shaft (not shown) to the motor control device 12 as a digital signal. Further, the temperature sensor 16 detects the temperature of the electric motor 10 and outputs a temperature signal TM to the electric motor control device 12.

On the other hand, the current sensor 14 includes a resistor or a Hall element connected in series to the electric motor 10 composed of a DC motor, and a driving current signal corresponding to the direction and magnitude of the driving current flowing through the electric motor 10. The IM is output to the motor control device 12. The voltage sensor 15
Outputs a drive voltage signal VM corresponding to the voltage applied to the electric motor 10 to the electric motor control device 12 by being connected to the electric motor 10 in parallel.

Next, the motor control device 12 and the motor drive circuit 13 will be sequentially described. First, the motor control device 12 includes the steering torque sensor 5, the vehicle speed sensor 11, the current sensor 14, the voltage sensor 15, and the temperature sensor 1.
6 input / output interface I / O, and
In addition to an A / D converter that converts an analog signal input from these sensors into a digital signal, a ROM (Read Only Memory) that stores various data and programs.
y), RAM (Random Ac) for temporarily storing various data, etc.
cess Memory), CPU (Central
Processing Unit) is provided as hardware.

As shown in FIG. 2, the motor control device 12 has a target current setting section 12A, a damping correction section 12B, a deviation calculation section 12C, and a basic software configuration for outputting a control signal of the motor 10. PID (Prop
ortional Integral Differential) control unit 12D, PW
An M (Pulse Width Modulation) signal generation unit 12E and a motor rotation speed estimation unit 12F are provided.

The steering torque signal TS output from the steering torque sensor 5 is converted into a digital signal and input to the target current setting section 12A of the motor control device 12, and is output from the vehicle speed sensor 11. Vehicle speed signal VP is input. The target current setting unit 12A increases with an increase in the steering torque of the steering system, and
A target current signal IT for causing the electric motor 10 to generate a steering assist torque having a basic characteristic that decreases as the vehicle speed increases,
An instantaneous search is made from a data area having the steering torque signal TS and the vehicle speed signal VP as addresses, and the searched target current signal IT is output to the damping correction unit 12B.

The damping correction unit 12B receives the target current signal IT from the target current setting unit 12A and the vehicle speed signal VP output from the vehicle speed sensor 11.
Also, the rotation speed signal NM of the motor 10 output from the motor rotation speed estimation unit 12F is input. The damping correction unit 12B performs a reduction correction on the target current signal IT as described later,
T ′ is output to the deviation calculator 12C.

The deviation calculating section 12C receives the correction target current signal IT 'from the damping correction section 12B and the driving current signal I' output from the current sensor 14.
M is converted into a digital signal and input. The deviation calculator 12C calculates a deviation between the correction target current signal IT 'and the drive current signal IM, and outputs the deviation signal ΔI to the PID controller 12D.

[0027] The PID control unit 12D receives the deviation signal ΔI
Are processed by proportional (P), integral (I), derivative (D), etc., to add the P, I, and D values to quickly converge the deviation of the deviation signal ΔI to zero. The PID operation signal IC is output to the PWM signal generator 12E. The PWM signal generator 12E is configured to output the PID operation signal IC
And generates a PWM control signal IP based on pulse width modulation for feedback-controlling the current flowing through the motor 10 based on the above, and outputs the PWM control signal IP to the motor drive circuit 13 as a control signal for the motor 10.

The motor rotation speed estimating section 12F receives a drive current signal IM output from the current sensor 14, a drive voltage signal VM output from the voltage sensor 15, and a temperature signal TM output from the temperature sensor 16. Each is converted into a digital signal and input. The motor rotation speed estimating unit 12F outputs the rotation speed signal NM of the electric motor 10 to the damping correction unit 12B in order to cause the damping correction unit 12B to execute the correction correction of the target current signal IT.

On the other hand, the motor drive circuit 13 is composed of a gate drive circuit 13A and a bridge circuit 13B. The gate drive circuit 13A includes the motor control device 1
The bridge circuit 13B is switched based on the PWM control signal IP input from the second PWM signal generation unit 12E. As shown in FIG. 3, the bridge circuit 13B includes four power FETs (Field Effect Transistor / Field Effect Transistor) forming a bridge circuit between a DC 12V power supply (vehicle battery and generator) and the motor 10. ) T1, T2, T3, and T4.

The gate drive circuit 13A outputs a drive signal to one of the gates G1 and G2 of the power FET (T1, T2) in accordance with the polarity of the PID operation signal IC, and outputs an off signal to the other. . At that time, the power FET (T
3, T4) to output an ON signal to one of the gates G3, G4 and an OFF signal to the other. For example, when a drive signal is output to the gate G1 of the power FET (T1), an ON signal is output to the gate G4 of the power FET (T4), and the gates G of the other power FETs (T2, T3) are output.
An off signal is output to G2 and G3.

Here, the damping correction unit 12B of the motor control unit 12 determines the target from the target current setting unit 12A according to the rotation speed signal NM from the motor rotation speed estimation unit 12F and the vehicle speed signal VP from the vehicle speed sensor 11. It has a function of adding a reduction correction to the current signal IT. The damping correction unit 12B has a large rotation speed signal NM,
As the rotation speed of 0 is higher, the amount of reduction correction of the target current signal IT is increased, and as the vehicle speed signal VP is larger and the vehicle speed is higher, the reduction correction amount is further increased.

As shown in FIG. 4, the damping correction section 12B includes a correction amount setting section 12B1 and a subtraction processing section 12B.
B2. The correction amount setting unit 12B1
The correction amount α is stored in a data area having the rotation speed signal NM and the vehicle speed signal VP as addresses, and the correction amount α is instantly searched according to the input of the rotation speed signal NM and the vehicle speed signal VP. The characteristic of the correction amount α is the rotation speed signal NM.
Is larger, the larger the vehicle speed signal VP is, the larger the vehicle speed signal VP is.

The subtraction processing section 12B2 receives the target current signal IT output from the target current setting section 12A and the correction amount α signal output from the correction amount setting section 12B1. Then, a value obtained by subtracting the correction amount α from the target current signal IT is output as the corrected target current signal IT ′ to the deviation calculator 12C.

The motor rotation speed estimation unit 12F
Is composed of a rotation speed calculation unit 12F1 and a resistance value temperature correction unit 12F2, as shown in FIG. The rotation speed calculation unit 12F1 includes a drive current signal IM from the current sensor 14 and a drive voltage signal VM from the voltage sensor 15.
And a correction resistance signal RM ′ from the resistance temperature correction unit 12F2. When the drive voltage of the motor 10 is VM, the drive current is IM, the specific resistance value is RM, and the induced voltage coefficient is K, the rotation speed calculation unit 12F1 calculates the correction resistance value RM ′ in RM of the following equation (1). To calculate the rotation speed NM of the electric motor 10 and obtain the rotation speed signal NM.
Is output to the damping correction unit 12B. NM = (VM−IM · RM) / K (1)

The resistance temperature correction section 12F2 has a function of correcting the specific resistance value RM of the electric motor 10 according to the temperature of the electric motor 10. This resistance temperature correction unit 12F2
The correction resistance value RM 'is stored in a data area having the temperature signal TM input from the temperature sensor 16 as an address, and the correction resistance value RM' is instantaneously searched according to the input of the temperature signal TM, and the correction resistance RM 'is retrieved. The value RM 'is converted into the rotation speed calculation unit 1
Output to 2F1. The correction resistance value RM ′ is set based on experimentally obtained data as the value of the specific resistance value RM that changes according to the temperature of the electric motor 10.

In the electric power steering apparatus according to the embodiment configured as described above, the steering torque sensor 5 is operated in accordance with the operation of the steering wheel 1 shown in FIG.
Detects the direction and magnitude of the steering torque generated in the steering system, and outputs the detected steering torque signal TS in FIG.
To the target current setting section 12A of the motor control device 12 shown in FIG. The vehicle speed sensor 11 detects the speed of the vehicle,
The detected vehicle speed signal VP is output to the target current setting unit 12A and the damping correction unit 12B of the motor control device 12.

In the motor control device 12, a target current setting unit 12 to which the steering torque signal TS from the steering torque sensor 5 and the vehicle speed signal VP from the vehicle speed sensor 11 are input.
A instantly searches for a target current signal IT for causing the electric motor 10 to generate a steering assist torque having a basic characteristic that increases as the steering torque of the steering system increases and decreases as the vehicle speed increases, The target current signal IT is output to the damping correction unit 12B.

The damping correction unit 12B includes a target current signal IT from the target current setting unit 12A, a rotation speed signal NM from the motor rotation speed estimation unit 12F, and the vehicle speed sensor 11.
, The reduction correction amount increases as the rotation speed signal NM increases, and the vehicle speed signal VP is increased.
Is larger, the target current signal IT is reduced and corrected so that the reduced correction amount is further increased, and the corrected target current signal I
T ′ is output to the deviation calculator 12C.

Thereafter, in the motor control unit 12, the deviation calculation unit 12C sends a deviation signal ΔI between the correction target current signal IT ′ from the damping correction unit 12B and the drive current signal IM from the current sensor 14 to the PID control unit 12D. Output. Subsequently, the PID control unit 12D sends a PID operation signal IC for causing the deviation to converge to zero to the PWM signal generation unit 1.
2E, and the PWM signal generation unit 12E outputs a PWM control signal IP corresponding to the PID operation signal IC to the motor drive circuit 1.
Output to 3. The motor drive circuit 13 responds to the PWM control signal IP from the motor control device 12 to
0 is rotationally driven by a predetermined drive current.

Accordingly, in the electric power steering apparatus of one embodiment, the electric motor 10 shown in FIG. 1 applies the auxiliary steering torque to the rack shaft 6C of the steering system via the ball screw mechanism 9, and the steering of the steering wheel 1 is performed. The torque is reduced.

At this time, the auxiliary steering torque by the electric motor 10 basically increases as the steering torque of the steering wheel 1 increases and the vehicle speed increases according to the target current signal IT output from the target current setting section 12A. Decrease. In response to the correction target current signal IT ′ output from the damping correction unit 12B, the auxiliary steering torque of the electric motor 10 is reduced and corrected as the steering speed of the steering wheel 1 increases and the rotation speed of the electric motor 10 increases. The higher the is, the lower the correction is. By performing the damping control in this way, the steering stability of the steering wheel 1 is ensured.

Here, in the electric power steering apparatus of one embodiment, a temperature sensor 16 attached to the electric motor 10 as electric motor temperature detecting means directly detects the temperature of the electric motor 10, and outputs a temperature signal TM of the electric signal to the electric motor control device 12. Is output to the resistance value temperature correcting section 12F2 of the motor rotation speed estimating section 12F. Therefore, the resistance temperature correction unit 12F
2 instantaneously retrieves an accurate correction resistance value RM 'corresponding to the temperature as the specific resistance value RM of the electric motor 10, and outputs the corrected resistance value RM' to the rotation speed calculation unit 12F1. Then, the rotation speed calculation unit 12F1 accurately calculates the rotation speed NM of the electric motor 10 by substituting the correction resistance value RM 'into RM of the above equation (1), and converts the rotation speed signal NM into the damping correction unit. It outputs to the correction amount setting unit 12B1 of 12B.

On the other hand, the correction amount setting section 12B1 of the damping correction section 12B includes the motor rotation speed estimation section 12F.
Speed signal NM of electric motor 10 estimated more accurately
By inputting the vehicle speed signal VP from the vehicle speed sensor 11, an accurate correction amount α corresponding to the rotation speed and the vehicle speed of the electric motor 10 without excess or deficiency is instantly retrieved and output to the subtraction processing unit 12B2. As a result, the subtraction processing unit 12B
2 is a motor 10 that outputs a target current signal IT flowing through the motor 10
Correction is made according to the rotational speed and vehicle speed of the vehicle.
Therefore, according to the electric power steering apparatus of one embodiment, it is possible to always perform accurate and accurate damping control regardless of the temperature change of the electric motor 10.

In the electric power steering apparatus according to the present invention, other means for detecting the temperature of the electric motor 10 can be employed in place of the temperature sensor 16. For example, a water temperature sensor of the cooling system, the current sensor 14, or the steering torque sensor 5 provided in the engine room of the vehicle can be used as a part of the motor temperature detecting means.

FIG. 6 shows an example in which a water temperature sensor 17 for a vehicle cooling system is used as the motor temperature detecting means.
In this case, the water temperature T detected by the water temperature sensor 17 is different from the temperature of the electric motor 10, but is affected by the ambient temperature in the engine room in which the electric motor 10 is disposed. Is there. Therefore, when the water temperature sensor 17 is used, the water temperature T is corrected and the electric motor 1 is used.
A temperature correction unit 12G for setting the temperature to 0 is provided in the motor control device 12. The temperature correction unit 12G multiplies the water temperature T input from the water temperature sensor 17 by a predetermined correction coefficient, adds a predetermined correction constant, or searches for a relation map between the water temperature T and the temperature of the electric motor 10 by searching. , Electric motor 1
Estimate the temperature of 0 and output the temperature signal TM to the motor rotation speed estimating unit 12F of the motor control device 12.

As described above, when the motor temperature detecting means is constituted by the water temperature sensor 17 and the temperature correction unit 12G, the temperature of the motor can be accurately detected without providing a new sensor such as the temperature sensor 16. Can.

FIG. 7 shows an example in which a control signal for driving the motor 10 output from the current sensor 14 and the motor control device 12 is used as the motor temperature detecting means. It is known that the temperature of the motor 10 has a correlation with the drive current flowing through the motor 10 and the duty value of the PWM drive signal IP output from the PWM signal generation unit 12E. Therefore, in this case, the drive current signal IM from the current sensor 14 and the PWM signal generation unit 1
The temperature estimating unit 12H for estimating the temperature of the motor 10 by inputting the PWM drive signal IP from the motor control device 12E
To be provided. The temperature estimating unit 12 </ b> H actually outputs the electric motor 1 to the PWM drive signal IP for driving the electric motor 10.
The temperature of the electric motor 10 is estimated by searching a relation map between the magnitude of the driving current flowing to 0 and the temperature of the electric motor 10, and the temperature signal TM is output to the electric motor rotation speed estimating unit 12 F of the electric motor control device 12.

As described above, when the motor temperature detecting means is constituted by the current sensor 14 and the temperature estimating section 12H, the temperature of the motor can be accurately detected without providing a new sensor such as the temperature sensor 16. .
Moreover, no new hardware is required in addition to the normally provided current sensor, and the electric power steering device can be made compact.

FIG. 8 shows an example in which the steering torque sensor 5 is used as a motor temperature detecting means. The steering torque sensor 5 is disclosed in, for example, Japanese Patent Laid-Open No. 7-332910.
As disclosed in Japanese Patent Application Laid-Open Publication No. H10-209, the system includes an LR integration circuit 5A built in the main body, and a pulse generation circuit 5B for supplying a pulse voltage to the LR integration circuit 5A. Low-pass filters 5C and 5D for inputting a pulse transient response voltage output from the LR integration circuit 5A according to a pulse voltage supplied from the pulse generation circuit 5B and removing high-frequency switching noise included in the voltage; Bottom hold circuits 5E and 5F are provided to hold and output the bottom voltages VT1 and VT2 of the pulse transient response voltages input via the low-pass filters 5C and 5D. Further, an operation amplifier 5G that calculates a deviation between the bottom voltages output from the bottom hold circuits 5E and 5F and outputs a deviation voltage amplified by a predetermined gain, and inverts the deviation voltage output from the operation amplifier 5G. And an inverting amplifier 5 that outputs a torque detection voltage VT3 (steering torque signal TS) shifted by, for example, a reference voltage of 2.5 V.
H is provided.

Of the bottom voltages VT1, VT2 and the torque detection voltage VT3 (steering torque signal TS) of the pulse transient response voltage output from the steering torque sensor 5 shown in FIG. 8, the bottom voltages VT1, VT2 are shown in FIG. like,
It changes uniformly like VT1 'and VT2' with the temperature change. This is because when the temperature of the LR integration circuit 5A built in the main body of the steering torque sensor 5 shown in FIG.
This is due to a change in the internal resistance of the coil, which is the L component. Therefore, in this case, the motor control device 12 is provided with a temperature conversion unit 12I that inputs the bottom voltages VT1 and VT2 output from the bottom hold circuits 5E and 5F of the steering torque sensor 5 and estimates the temperature of the motor 10. The temperature conversion unit 12I converts a temperature of the electric motor 10 by searching a relation map between the bottom voltages VT1 and VT2 and the temperature when the torque is 0 shown in FIG. 9 and converts the temperature signal TM into the electric motor control. It outputs to the motor rotation speed estimation unit 12F of the device 12.

As described above, when the motor temperature detecting means is constituted by the steering torque sensor 5 and the temperature conversion section 12I, the temperature of the motor can be accurately detected without providing a new sensor such as the temperature sensor 16. it can. Moreover, since the torque sensor is usually provided in the steering gear box and arranged near the electric motor, it is possible to accurately detect the temperature of the electric motor.

[0052]

As described above, in the electric power steering apparatus according to the present invention, the motor rotational speed estimating section of the motor control device uses the drive current detected by the current sensor, the drive voltage detected by the voltage sensor, and the drive voltage of the motor. The rotation speed of the motor is estimated based on the specific resistance value. In such a device, for example, when a damping correction unit is provided, the target value of the drive current flowing through the motor is reduced and corrected according to the rotation speed of the motor estimated by the motor rotation speed estimation unit. At that time, the motor temperature detecting means directly or indirectly detects the temperature of the motor, and the resistance value temperature correction unit temperature-corrects the specific resistance value of the motor according to the temperature of the motor detected by the motor temperature detecting means. . As a result, the motor rotation speed estimation unit accurately estimates the rotation speed of the motor based on the specific resistance value of the motor temperature corrected by the resistance temperature correction unit. The damping correction unit corrects and reduces the target value of the drive current flowing through the motor in accordance with the rotation speed of the motor accurately estimated by the motor rotation speed estimation unit. Therefore, according to the electric power steering apparatus of the present invention, it is possible to always perform accurate damping control without excess or deficiency regardless of the temperature change of the electric motor.

In the electric power steering apparatus according to the present invention, when the electric motor temperature detecting means is constituted by a novel temperature sensor attached to the electric motor, the temperature of the electric motor can be accurately detected.

Further, the motor is provided by an existing temperature sensor separately provided in the engine room of the vehicle, and a temperature correction unit of a motor control device for estimating the temperature of the motor based on a temperature signal output from the temperature sensor. When the temperature detecting means is configured, it is possible to accurately detect the temperature of the electric motor without providing a new temperature sensor.

Further, the motor temperature detecting means is constituted by a temperature estimating section of the motor control device for estimating the temperature of the motor based on the drive current detected by the current sensor and the control signal output from the motor control device. In such a case, hardware such as a temperature sensor is not required in addition to the normally used current sensor, and the electric power steering apparatus can be compactly configured.

In the electric power steering apparatus according to the present invention, the motor temperature detecting means is constituted by a temperature conversion section of the motor control device for converting the temperature of the motor based on the pulse transient response voltage output from the torque sensor. In this case, the temperature of the electric motor can be detected without providing a new temperature sensor. In addition, since the torque sensor is usually disposed near the electric motor, the temperature of the electric motor can be accurately detected.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a steering system to which an electric power steering device according to an embodiment of the present invention is applied.

FIG. 2 is a block diagram of a motor control device of the electric power steering device according to one embodiment.

FIG. 3 is a circuit diagram of a bridge circuit constituting a motor drive circuit of the electric power steering device according to one embodiment.

FIG. 4 is a block configuration diagram of a damping correction unit included in the electric motor control device of the electric power steering device according to the embodiment.

FIG. 5 is a block diagram of a motor rotation speed estimating unit included in the motor control device of the electric power steering device according to the embodiment.

FIG. 6 is a block diagram showing an example in which a water temperature sensor is used as an electric motor temperature detecting means included in the electric power steering device according to the embodiment.

FIG. 7 is a block diagram illustrating an example in which a current sensor is used as a motor temperature detecting unit included in the electric power steering apparatus according to the embodiment;

FIG. 8 is a block diagram showing an example in which a steering torque sensor is used as an electric motor temperature detecting unit included in the electric power steering apparatus according to the embodiment.

9 is a graph showing a characteristic of an output voltage of the steering torque sensor shown in FIG.

[Explanation of symbols]

 1: Steering wheel 5: Steering torque sensor 5A: LR integration circuit 5E, 5F: Bottom hold circuit 10: Motor 11: Vehicle speed sensor 12: Motor controller 12A: Target current setting unit 12B: Damping correction unit 12C: Deviation calculation unit 12D : PID control unit 12E: PWM signal generation unit 12F: Motor rotation speed estimation unit 12G: Temperature correction unit 12H: Temperature estimation unit 12I: Temperature conversion unit 13: Motor drive circuit 13A: Gate drive circuit 13B: Bridge circuit 14: Current sensor 15: Voltage sensor 16: Temperature sensor 17: Water temperature sensor

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) // B62D 101: 00 B62D 101: 00 107: 00 107: 00 119: 00 119: 00 F term (reference) 3D032 CC34 DA15 DA23 DA64 DA65 DA67 DC01 DC02 DC03 DD10 DD17 EA01 EC23 GG01 3D033 CA03 CA04 CA13 CA16 CA20 CA21 5H571 AA03 BB09 CC04 DD01 FF10 GG04 HA09 HC01 HD02 JJ04 JJ22 JJ23 JJ24 JJ25 JJ26 LL14 LL15 LL22 LL23

Claims (5)

[Claims] 1. A steering torque sensor for detecting a steering torque of a steering system of a vehicle, a motor for applying a steering assist torque to the steering system, a current sensor for detecting a drive current of the motor, and a drive voltage of the motor. And a motor control device that sets a target value of a drive current flowing through the motor according to at least the steering torque detected by the steering torque sensor, and outputs a control signal for driving the motor. The motor control device further includes a motor rotation speed estimation unit configured to estimate a rotation speed of the motor based on a drive current detected by the current sensor, a drive voltage detected by the voltage sensor, and a specific resistance value of the motor. The temperature of the electric motor is detected directly or indirectly in the electric power steering device provided with The motor rotation speed estimating unit is provided with a motor temperature detecting unit, and a resistance temperature correcting unit for correcting the specific resistance value of the motor in accordance with the temperature of the motor detected by the motor temperature detecting unit. Electric power steering device. 2. The electric power steering apparatus according to claim 1, wherein said electric motor temperature detecting means comprises a temperature sensor attached to said electric motor. 3. The electric power steering apparatus according to claim 1, wherein the electric motor temperature detecting means includes a temperature sensor provided separately in an engine room of the vehicle, and a temperature signal output from the temperature sensor. An electric power steering apparatus comprising: a temperature correction unit of a motor control device that estimates a temperature of the motor based on the temperature of the motor. 4. The electric power steering apparatus according to claim 1, wherein the electric motor temperature detecting means is configured to detect the electric motor based on a drive current detected by the current sensor and a control signal output from the electric motor control device. An electric power steering device, comprising: a temperature estimating unit of a motor control device for estimating a temperature of a vehicle. 5. The electric power steering apparatus according to claim 1, wherein the electric motor temperature detecting means converts an electric motor temperature based on a pulse transient response voltage output from the steering torque sensor. An electric power steering device comprising a temperature conversion unit of the device.