JP2002029440A - Electric power steering - Google Patents

Abstract

PROBLEM TO BE SOLVED: To continue to drive a motor for applying auxiliary steering force even after switching off an ignition switch during the travel of a vehicle. SOLUTION: A protecting means 24 in a control means 12 has a false vehicle speed setting means 31. The false vehicle speed setting means 31 generates a false vehicle speed signal RVs gradually decreasing, with time, the value of an actual vehicle speed signal V when an ignition signal IG from an ignition operation sensor IGS becomes an ignition off signal, The false vehicle speed signal RVs is outputted to a target current setting means 21. The drive of the motor 8 is stopped after the false vehicle speed signal RVs becomes 0.

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 reducing the steering force of a driver by directly applying the power of an electric motor to a steering system.

[0002]

2. Description of the Related Art An electric power steering apparatus assists a driver's steering force by directly using the driving force of an electric motor. 2. Description of the Related Art Vehicles equipped with an electric power steering device have become widespread, and the electric power steering device makes the steering movement light and eliminates the need for the driver to operate the steering with a strong force.

As such an electric power steering device, the present applicant discloses in Japanese Patent Publication No. 7-94227 a configuration in which when the electric power steering device is turned off, the electric motor control signal is gradually reduced and turned off. are doing. When the electric power steering device is turned off, the driving of the electric motor is stopped suddenly and the auxiliary steering force does not disappear, so that it is possible to prevent the steering from becoming heavy suddenly, so that the steering feeling is improved. Can be.

[0004] In this type of electric power steering apparatus, when an ignition-off signal from an ignition operation sensor for detecting an operation state of an ignition switch is detected, a drive stop operation of the electric motor is performed. However, in this electric power steering device, if the ignition operation sensor is turned off during the running of the vehicle (a fault that always outputs an ignition off signal, for example, a fuse blown), the vehicle is running, The drive of the motor stops. For this reason, there is a problem that the driver feels strange. Accordingly, the present applicant has disclosed in Japanese Patent Application Laid-Open No. H11-5944.
In Japanese Patent Application Publication No. 5 (JP-A-5), there is disclosed an electric power steering device that does not stop driving of an electric motor when an engine speed or a vehicle speed signal is a predetermined value or more even when an ignition off signal is output from an ignition operation sensor. are doing.

[0005]

SUMMARY OF THE INVENTION The above-mentioned Japanese Patent Application Laid-Open No. 11-59 / 1999
The conventional electric power steering device disclosed in Japanese Patent No. 445 can cope with a case where the ignition operation sensor is turned off. However, if the driver's foot hits the ignition switch while the vehicle is running and the ignition switch is turned off by mistake, an engine speed sensor that detects the engine speed, a vehicle speed sensor, or another sensor is used. Kind of output signal is also 0
Therefore, the driving of the electric motor is stopped, and it becomes impossible to continue to apply the auxiliary steering force. Therefore, for example, since the ignition switch has been turned off, even if the vehicle is guided to the shoulder of the road to stop it, an excessive load is imposed on the driving of the driver because no auxiliary steering force is applied. Was something.

Accordingly, an object of the present invention is to enable the auxiliary steering force of the electric power steering apparatus to be continuously applied to the steering system even when the ignition switch is turned off by mistake while the vehicle is running. For example, even when a vehicle is guided to a shoulder of a road, an excessive load is not applied to a driver.

[0007]

According to a first aspect of the present invention, there is provided an electric motor for applying an auxiliary steering force to a steering system, a steering torque signal from at least a torque sensor, and a vehicle speed sensor. Control means for generating a motor control signal based on an actual vehicle speed signal from the vehicle, motor drive means for driving the motor based on the motor control signal from the control means, and operation detection means for detecting an operation state of an ignition switch And a protection means for stopping driving of the electric motor based on an ignition off signal from the operation detection means, wherein the protection means comprises an ignition off signal from the operation detection means. The value of the actual vehicle speed signal at the time when is detected is stored, and the value of this actual vehicle speed signal is gradually reduced with time. A pseudo vehicle speed setting means for generating a vehicle speed signal, and when an ignition off signal from the operation detecting means is detected, a pseudo vehicle speed signal from the pseudo vehicle speed setting means is used instead of the actual vehicle speed signal from the vehicle speed sensor. An electric power steering apparatus, wherein the electric motor is driven based on the electric vehicle, and the driving of the electric motor is stopped after the pseudo vehicle speed signal becomes zero.

According to the first aspect of the present invention, the driving control of the electric motor for applying the auxiliary steering force to the steering system, which has been performed using the actual vehicle speed signal, is performed by using the pseudo vehicle speed signal when the ignition off signal is detected. To do it. According to such a configuration, even if the driver accidentally hits the foot with the ignition switch during running of the vehicle and turns off the ignition switch, for example, the driving of the electric motor is continued and the auxiliary steering force is continuously applied. be able to. Therefore, for example, even when the driver tries to stop the vehicle by guiding the vehicle to the shoulder of the road, it is possible to prevent a problem that an excessive burden is imposed on the driver.

According to a second aspect of the present invention, the protection means includes:
The electric power steering apparatus according to claim 1, further comprising: a signal gradual decrease unit that gradually reduces the electric motor control signal with time from when the pseudo vehicle speed signal becomes zero.

According to the second aspect of the present invention, after the pseudo vehicle speed signal becomes 0, the motor control signal is gradually reduced with time. For this reason, when the steering wheel is turned after the vehicle is stopped, the electric motor stops suddenly and the force is not suddenly applied to the steering system, and the steering force is suddenly reduced due to the reaction force caused by the return of the tire twist. It is possible to prevent a problem such as a sudden but slight movement.

[0011]

Embodiments of the present invention will be specifically described below with reference to the drawings.

The electric power steering apparatus according to the present embodiment is designed to assist a driver's manual steering torque.
An auxiliary steering torque (auxiliary steering force) is generated by the driving force of the electric motor. Therefore, the electric power steering device
The vehicle includes a steering torque sensor for detecting a driver's manual steering torque (steering force) and a control unit for outputting a control signal (motor control signal) for controlling the electric motor.

Hereinafter, an electric power steering apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings. First, the overall configuration of the electric power steering device 1 will be described with reference to FIGS. Here, FIG. 1 is an overall configuration diagram of the electric power steering device, and FIG. 2 is a block diagram of an electric system of the electric power steering device.

As shown in FIG. 1, an electric power steering apparatus 1 is configured such that when a driver steers a steering wheel 3, a manual steering force generating means (steering system) 2 causes front wheels W, W to be rolled by manual steering to thereby control the vehicle. Change direction. Furthermore, the electric power steering apparatus 1, the motor voltage V _M generated by the motor drive unit 13 based on the motor control signal V _O from the control unit 12, the auxiliary steering torque by driving the motor 8 in this motor voltage V _M (Auxiliary steering force) to reduce the manual steering force by the manual steering force generation means 2.

The manual steering force generating means 2 is connected to a steering shaft 4 provided integrally with the steering wheel 3 via a connecting shaft 5 to a pinion 7a of a rack & pinion mechanism 7 provided in a steering gear box 6. You. The connecting shaft 5 has universal joints 5a and 5b at both ends. The rack and pinion mechanism 7 has a rack shaft 9 formed with rack teeth 7b meshing with the pinion 7a.
The rotation of the pinion 7a is defined as the reciprocating movement of the rack shaft 9 in the lateral direction due to the engagement between the rack shaft 7 and the rack teeth 7b. Further, left and right front wheels W, W as rolling wheels are connected to both ends of the rack shaft 9 via tie rods 10, 10, respectively.

In the electric power steering apparatus 1, an electric motor 8 is driven by a rack shaft 9 to generate an auxiliary steering torque.
And coaxially arranged. Then, the rotation of the electric motor 8 is converted into thrust through a ball screw mechanism 11 provided coaxially with the rack shaft 9, and this thrust acts on the rack shaft 9 (ball screw shaft 11a).

The control means 12 includes a steering torque sensor T
S, the detection signal T of the vehicle speed sensor VS, and a current sensor in which the motor current detecting means 14, V, I _MO is entered.
The control means 12 determines the magnitude of the target current flowing through the motor 8 based on the detection signals T, V, and _IMO , and outputs a motor control signal V _O (control signal) based on the target current to the motor driving means 13. I do. The control unit 12 includes an arithmetic unit that performs various calculations and processes, an input signal conversion unit, a signal generation unit, a storage unit, and the like. Details of these points will be described later.

The steering torque sensor TS includes a steering torque sensor TS.
It is arranged in the gearbox 6 and detects the magnitude and direction of the manual steering torque (steering force) by the driver. And
The steering torque sensor TS transmits a manual steering torque signal T corresponding to the detected manual steering torque to the control means 12.

The vehicle speed sensor VS is provided on the output shaft of the transmission and detects an actual vehicle speed corresponding to the magnitude of the rotation speed of the output shaft of the transmission. Then, the vehicle speed sensor VS transmits an actual vehicle speed signal V corresponding to the detected actual vehicle speed to the control means 12.

The ignition operation sensor IGS detects whether the ignition switch 20 is on or off, and outputs an ignition signal IG to the control means 12. The control means 12 detects the ignition signal IG as an ignition-on signal when the ignition signal IG has an upper specified voltage value (for example, 8 V), and detects the ignition signal as an ignition off signal when the ignition signal IG has a lower specified voltage value (for example, 3 V). If the value is an intermediate value (for example, 3 to 8 V) between the upper specified voltage value and the lower specified voltage value, it is determined that the state is before the value. This ignition operation sensor IGS constitutes the operation detection means of the present invention.

The motor drive unit 13, the motor voltage V _M based on the motor control signal V _O which control unit 12 has output supplied to the electric motor 8 to drive the motor 8. The motor driving means 13 is composed of, for example, a bridge circuit composed of switching elements of four field effect transistors and a gate driving circuit. 4 when the motor control signal V _O to the gates of the field effect transistor is input, the motor voltage V _M is supplied to the electric motor 8 based on the motor control signal V _O. Then, the electric motor 8 flows the motor current I _M, the electric motor 8 generates assist steering torque proportional to the motor current I _M, to assist the steering operation of the driver.

The motor current detecting means 14 includes a resistor or a Hall element connected in series with the motor 8,
Actually flowing through the motor 8 to detect the magnitude and direction of the motor current I _M. Then, the motor current detecting means 14, controlling the motor current signal I _MO corresponding to the motor current I _M means 1
Feedback to 2 (negative feedback).

From the battery 15, fuse circuits 16, 1
7 is supplied with current. The current supplied to the fuse circuit 16 is supplied to the motor driving means 13 and the constant voltage circuit 19 via the relay circuit 18. Further, the current supplied to the fuse 17 depends on the ignition switch 2
0 is supplied to the constant voltage circuit 19. Constant voltage circuit 1
9 is a relay circuit 18 and an ignition switch 2
The current supplied from 0 is adjusted to a predetermined voltage, for example, 5 V, and supplied to the control means 12.

Next, the configuration of the control means 12 will be described with reference to FIG.
This will be further described with reference to FIG. The control means 12 includes a target current setting means 21, a deviation calculation means 22, a drive control means 23,
And protection means 24.

The target current setting means 21 has a table lookup function (not shown), and is set in advance based on the steering torque signal T output from the steering torque sensor TS and the actual vehicle speed signal V output from the vehicle speed sensor VS. from the steering torque T- vehicle speed V- target current I _M tables are those for reading a target current signal I _MS. Further, when the pseudo vehicle speed signal RV _S from the pseudo vehicle speed setting means 31 is output, the pseudo vehicle speed signal RV _S instead of the actual vehicle speed signal V is used. Further, the correction signal C output from the signal gradually decreasing unit 32
If _{the S} is input, in order to gradually decrease the motor control signal V _O, fade-out process of gradually decreasing the read target current signal I _MS is performed. Then, the target current setting means 21 outputs the read target current signal _IMS to the deviation calculating means 22.

The deviation calculation unit 22 includes a subtraction function of the subtractor or the software control, the target current target current signal outputted from the setting means 21 I _MS and the motor current outputted from the detection means 14 a motor current signal I _MO is Is entered. The target current signal I _MS from the motor current signal I _MO subtracted to calculate a deviation signal _{ΔI M (= I MS -I MO} ). Then, it outputs the calculated deviation signal [Delta] I _M to the drive control unit 23.

The drive control means 23 includes a PID controller, a PWM signal generation means, a logic circuit and the like, receives the deviation signal ΔI _M from the deviation calculation means 22, and outputs a motor control signal V _O to the motor drive means 13. . Drive control means 23 first deviation signal [Delta] I _M to P (proportional), I
(Integral) and D (differential) control, and further generates a PWM signal V _PWM , an ON signal V _ON , and an OFF signal V _OFF corresponding to the magnitude and polarity of the control result, and generates the motor as a motor control signal V _O. Output to the driving means 13. The motor voltage V _M output by the motor drive unit 13 is supplied to the electric motor 8, the motor 8 is driven.

The protection means 24 includes a pseudo vehicle speed setting means 31,
It is configured to include a signal gradual decrease unit 32 and a determination unit 33. When an ignition switch OFF signal is output from the ignition operation sensor IGS, control is performed based on the actual vehicle speed of the vehicle immediately before the ignition switch 20 is turned off. The pseudo vehicle speed setting means 31 has a storage means (not shown) and a signal gradual decrease function. Further, the pseudo vehicle speed setting means 31 detects an ignition signal from the ignition operation sensor IGS and an actual vehicle speed signal V from the vehicle speed sensor VS.

The storage means stores the actual vehicle speed signal V output from the vehicle speed sensor VS in the storage means while detecting the ignition-on signal as the ignition signal. Also, while the ignition signal is an ignition-on signal, a new actual vehicle speed signal V
Is output, the stored actual vehicle speed signal V is updated to a new actual vehicle speed signal V.

FIG. 3 is a graph showing the change with time of the pseudo vehicle speed signal and
Shows the relationship with the chronological change of the NISCHON switch on / off.
This is a graph. The pseudo vehicle speed setting means 31 is a signal gradually decreasing machine.
Depending on the function, as shown in FIG.
The input vehicle speed signal when the
The actual vehicle speed signal input from the vehicle VS and stored in the storage means
V, the value of the actual vehicle speed signal V gradually decreases with time.
And the pseudo vehicle speed signal RV _SAnd Such a pseudo vehicle speed setting
Setting means 31 outputs the ignition operation signal IG
When the NIS-OFF signal is detected, the signal
And the value of the actual vehicle speed signal V stored in the storage means as time
The pseudo vehicle speed signal RV_SAnd At this time,
The actual vehicle speed signal V stored in the storage means is an ignition signal.
The actual vehicle speed signal V when the switch off signal is detected.
is there.

Here, as shown by the broken line in FIG. 3, the simulated vehicle speed signal RV _S is the actual vehicle speed signal V when the ignition switch off signal is detected as the initial value of the simulated vehicle speed signal RV _S , and the value changes with time. For example, it is set so as to gradually decrease at a constant rate. Reduction ratio of the pseudo vehicle speed signal RV _S is set to be smaller than the decrease rate of the actual vehicle speed when the vehicle shown in FIG. 3 by a chain line is traveling by inertia. This is because the driving of the electric motor 8 is continued and the auxiliary steering force is added at least until the vehicle that has actually turned off the ignition switch 20 decelerates and stops. The reduction rate of the actual vehicle speed when the vehicle is running by inertia varies depending on the weight, performance, and the like of the vehicle. For example, the reduction rate can be obtained by an experiment performed in advance. If the actual vehicle speed signal V immediately before turning off the ignition switch 20 is 0 km / h, it means that the ignition switch 20 was turned off after the vehicle stopped.

Further, the pseudo vehicle speed setting means 31 detects the ignition off signal, and outputs a pseudo vehicle speed signal RV _S to the target current setting means 21. When the time from the start of outputting a pseudo vehicle speed signal RV _S to the pseudo vehicle speed signal RV _S becomes 0 and the pseudo vehicle speed signal fade out period (see pseudo vehicle speed fade-out period of 3 to be described later), a pseudo vehicle speed setting means 31 after a lapse of pseudo vehicle speed signal fade-out period, and stops the output of the pseudo vehicle speed signal RV _S.
On stopping the output of the pseudo vehicle speed signal RV _S, from the pseudo vehicle speed setting means 31, and outputs the pseudo vehicle speed stop signal RV _ST to the signal decreasing unit 32.

The signal gradual decrease section 32 outputs a pseudo vehicle speed stop signal RV.
Upon detection of _ST, in order to gradually decrease the motor control signal V _O to drive the motor 8, generating a correction signal C _S for fade-out process a target current signal I _MS. Further, the signal gradually decreasing unit 32 outputs the generated correction signal C _S to the target current setting unit 21. When the target current signal I _MS becomes 0 from the signal gradually decreasing portion 32 begins to output a correction signal C _S, i.e. Upon completion of the fade-out processing of the target current signal I _{M S} (see EPS fade-out period of 3 to be described later), The signal gradual decrease unit 32 sends the stop signal S to the determination unit 33.
Output _S. Thus, the target current setting means 21
It is gradually decreased to the target current signal I _MS from the motor control signal V
By gradually decreasing _O , fade-out control of driving of the electric motor 8 is performed.

The determination means 33 determines whether or not the stop signal S _S has been output from the signal gradually decreasing section 32. Then, the stop signal S _S is output from the signal gradually decreasing unit 32, and when the stop signal S _S is detected, the relay circuit off signal R _OFF is output to the relay circuit 18.

The relay circuit 18 turns off the relay when the judgment circuit 33 outputs the relay circuit off signal R _OFF , whereby the driving of the motor 8 is finally stopped.

Next, the operation and operation of the electric power steering apparatus according to this embodiment will be described. When the ignition switch 20 shown in FIG. 1 is turned on, for example, while the vehicle is running, an ignition signal IG from the ignition operation sensor IGS is output to the control means 12. When the driver starts to turn the steering wheel 3, the control means 12 shown in FIG. 2 outputs the manual steering torque signal T from the steering torque sensor TS and the actual vehicle speed signal V from the vehicle speed sensor VS to the target current setting means 21. Is read in.

Further, the motor current detector 14 detects the motor current I _M of the electric motor 8. Motor current detecting means 14, motor current from the detected motor current I _M signal I
_MO is generated, and this motor current signal _IMO is
Output to 2.

[0038] The target current setting means 21, a normal state, calculates the target current signal I _MS on the basis of the actual vehicle speed signal V outputted from the steering torque signal T and the vehicle speed sensor VS outputted from the steering torque sensor TS. Then, the target current signal _IMS is outputted to the deviation calculating means 22.

The deviation calculating means 22 includes a target current setting means.
21 is the target current signal I output from _MSFrom the motor current
Motor current signal I output from detection means 14_MOSubtract
And the deviation signal ΔI_MIs calculated. Then this deviation
Signal ΔI_MIs output to the drive control means 23. Drive control hand
In stage 23, the output deviation signal ΔI_MBased on
And the motor control signal V_OIs output to the motor driving means 13.
You.

[0040] Then, the electric motor driving unit 13 outputs a motor voltage V _M to the motor 8. Thereby, the electric motor 8
Generates assist steering torque as usual to assist the driver in steering operation.

The ignition signal IG from the ignition operation sensor IGS and the actual vehicle speed signal V from the vehicle speed sensor VS are output to the pseudo vehicle speed setting means 31 in the protection means 24. Normally, the ignition switch 20 is connected while the vehicle is running, so that the ignition operation sensor IGS outputs an ignition-on signal as the ignition operation signal IG. The pseudo vehicle speed setting means 31 stores the actual vehicle speed signal V in the storage means when detecting the ignition-on signal, and sequentially rewrites the actual vehicle speed signal V with the new actual vehicle speed signal V when detecting the new actual vehicle speed signal V. Has been updated.

Here, the driver may accidentally turn off the ignition switch 20 by, for example, suddenly hitting the foot with the ignition switch 20.
In this case, the ignition operation sensor IGS outputs an ignition off signal as the ignition signal IG. In addition, the ignition switch 20
Is cut off, the power from the battery 15 is no longer supplied to the vehicle speed sensor VS, and the actual vehicle speed signal V from the vehicle speed sensor VS becomes zero. Further, since the torque sensor TS operates mechanically, the torque is detected while the control means 12 is supplied with electricity. Even when the ignition switch 20 is turned off, the control means 12 is still supplied with electricity from the battery 15 through the relay circuit 18 and outputs a relay circuit off signal R _OFF to the relay circuit 18 to disconnect itself. It works unless it is.

While the vehicle is running, the ignition switch 2
0 is turned off, and when the ignition switch signal becomes the ignition off signal, the protection means 24 of the control means 12
The ignition-off signal is output to the pseudo vehicle speed setting means 31 at. In the pseudo vehicle speed setting means 31, when the ignition off signal is output, the pseudo vehicle speed signal RV _S based on the actual vehicle speed signal V that is stored in the storage means
Is output. Pseudo vehicle speed signal RV _S that is output here,
The actual vehicle speed signal V at the time when the ignition off signal is output is set as an initial value and is set so as to gradually decrease with time. For example, when the ignition off signal is outputted, when the actual vehicle speed signal V storage means stores was 130 km / h is, 130 km / h is set as the initial value of the pseudo vehicle speed signal RV _S . Also, 60k
If it is m / h, 60 km / h is set as the initial value.

[0044] Thus the pseudo vehicle speed signal RV When _S is read, the pseudo vehicle speed signal RV _S a target current setting unit 21
Output to At this time, since the vehicle speed sensor VS is stopped, the actual vehicle speed signal V output from the vehicle speed sensor VS to the target current setting means 21 is zero. Target current setting means 21
In the case where the pseudo vehicle speed signal RV _S from the pseudo vehicle speed setting means 31 is output, the pseudo vehicle speed signal RV _S and the steering torque output from the pseudo vehicle speed setting means 31 instead of the actual vehicle speed signal V from the vehicle speed sensor VS based on the T from the steering torque T- vehicle speed V- target current I _M table reads the target current signal I _MS. Thus, even when the ignition switch 20 is turned off, the driving of the electric motor 8 is continued, and the assist of the steering wheel steering force is continued.

[0045] In addition, the driver had turned off the ignition switch 20 is usually because you try to stop the vehicle, gradually decreases the pseudo vehicle speed signal RV _S. Ratio of decreasing of the pseudo vehicle speed signal RV _S is what is set in advance depending on the performance of a vehicle are as defined above.

[0046] Then, when the pseudo vehicle speed signal RV _S becomes zero after the lapse of the pseudo vehicle speed signal fade-out period shown in FIG. 3, the vehicle is also considered to be stopped, in order to reduce the power consumption of the battery, the electric motor 8 is performed. When the driving of the electric motor 8 is stopped, the steering wheel 3 is prevented from moving rapidly (slightly but abruptly) by the reaction force due to the twisting of the tire due to the disappearance of the auxiliary steering force, and the driver feels discomfort. In order to prevent this, a fade-out process (EPS fade-out process) is performed when the driving of the electric motor 8 is stopped. That is, as the turned pseudo vehicle speed signal RV _S 0 has elapsed pseudo vehicle speed signal fade-out period shown in FIG. 3, stops the output of the pseudo vehicle speed signal RV _S relative to the target current setting means 21, to the signal decreasing portion 32 outputting a pseudo vehicle speed stop signal RV _ST Te.

When detecting the pseudo vehicle speed stop signal RV _ST , the signal gradually decreasing section 32 controls the target current setting means 21 to perform fade-out control for driving the electric motor 8 (see the EPS fade-out period in FIG. 3). Correction signal C
Output _S. In the target current setting means 21, the correction signal C _S
Upon detection of the tapers of the target current signal I _MS read from the steering torque T- vehicle speed V- target current I _M table.
Thus, by decreasing the target current signal I _MS,
The motor control signal V _O for driving the motor 8 is faded out, and the driving of the motor is finally stopped. Therefore, it is possible to prevent the above-described problem from occurring when the driver stops the vehicle.
This fade-out time (EPS fade-out period) is set to several seconds, for example, about 1 to 2 seconds.

The preferred embodiment of the present invention has been described above, but the present invention is not limited to the above embodiment. For example, a mode in which the signal gradual decrease unit 32 for fading out the motor control signal V _O is not provided may be provided. In this case, after the pseudo vehicle speed fade-out period has elapsed, may output a stop signal S _S with respect to the determination means 33 from the pseudo vehicle speed setting means 31.

In order for the signal control section 32 to gradually reduce the motor control signal V _O , the correction signal C _S is not output to the target current setting means, but the correction signal is output to the drive control means 23, for example. It is also possible to adopt a mode in which

[0050]

As described above, claim 1 of the present invention
According to the invention according to the present invention, even if the driver accidentally hits the foot with the ignition switch while the vehicle is running and turns off the ignition switch, for example,
The driving of the electric motor can be continued, and the auxiliary steering force can be continuously applied to the steering system. Therefore, for example, even when the driver guides the vehicle to the road shoulder to stop the vehicle, it is possible to prevent the driver from being excessively burdened.

According to the second aspect of the present invention, when the electric motor is stopped, the auxiliary steering force of the power steering device gradually decreases. There is no such a problem that it moves suddenly, albeit a little. Further, when stopping the electric motor, the driver holding the steering wheel does not feel uncomfortable.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an electric power steering device according to an embodiment.

FIG. 2 is a block diagram of an electric system of the electric power steering device.

FIG. 3 is a graph showing a relationship between a temporal change of a pseudo vehicle speed signal and a temporal change of an ignition switch on / off.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 electric power steering device 2 manual steering force generating means (steering system) 8 electric motor 12 control means 13 electric motor driving means 14 electric motor current detecting means 20 ignition switch 24 protection means 31 pseudo vehicle speed setting means 32 signal decreasing section IGS ignition operation sensor (operation Detection means) RV _S pseudo vehicle speed signal C _S correction signal V _O Motor control signal

Claims (2)

[Claims] An electric motor for applying an auxiliary steering force to a steering system; a control unit for generating an electric motor control signal based on at least a steering torque signal from a torque sensor and an actual vehicle speed signal from a vehicle speed sensor; Motor driving means for driving the electric motor based on the electric motor control signal, operation detecting means for detecting an operation state of an ignition switch, and stopping the driving of the electric motor based on an ignition off signal from the operation detecting means. An electric power steering apparatus comprising: a protection unit, wherein the protection unit stores a value of an actual vehicle speed signal when an ignition off signal from the operation detection unit is detected, and stores the value of the actual vehicle speed signal. A pseudo vehicle speed setting means for generating a pseudo vehicle speed signal gradually decreasing with time; When a niche-off signal is detected, the electric motor is driven based on the pseudo vehicle speed signal from the pseudo vehicle speed setting means instead of the actual vehicle speed signal from the vehicle speed sensor, and after the pseudo vehicle speed signal becomes 0, the electric motor is driven. An electric power steering device, which stops driving. 2. The protection means according to claim 1, wherein said pseudo vehicle speed signal is zero.
2. The electric power steering apparatus according to claim 1, further comprising a signal gradually decreasing unit that gradually reduces the electric motor control signal with time from the time when the electric power steering signal is reduced.