JP2003072575A - Power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power steering device allowing the driver to know any failure in it certainly and capable of eliminating uncomfortable feeling in steering resulting from a quick increase of the steering resistance. SOLUTION: The power steering device includes an electronic control unit 30 which controls a motor 27 on the basis of the steering angle signal, current signal, and car speed signal given by a steering angle sensor 11, current sensing circuit 12, and car speed sensor 13. If any failure is detected in the power steering device, the target revolving speed of the motor 27 is decreased gradually on the condition that steering is taking place, and the motor 27 is put in standstill.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power steering device that applies a steering assist force to a steering mechanism by the hydraulic pressure generated by a pump driven by an electric motor.

[0002]

2. Description of the Related Art A power steering device is known that assists the operation of a steering wheel by supplying hydraulic oil from an oil pump to a power cylinder connected to a steering mechanism. The oil pump is driven by an electric motor, and a steering assist force corresponding to the rotation speed of the oil pump is generated from the power cylinder. On the steering shaft, there are a torsion bar that twists according to the direction and magnitude of the steering torque applied to the steering wheel, and a hydraulic control valve whose opening changes according to the direction and magnitude of the torsion of the torsion bar. It has been incorporated.
The hydraulic control valve is interposed in a hydraulic system between the oil pump and the power cylinder, and the steering assist force corresponding to the steering torque is generated from the power cylinder.

Drive control of the electric motor is performed, for example, based on the steering angular velocity of the steering wheel. That is, the steering angular velocity is obtained based on the output of the steering angle sensor provided in association with the steering wheel, and the target rotation speed of the electric motor is set based on the steering angular velocity. A voltage is supplied to the electric motor so that the target rotation speed is achieved. More specifically, when the steering angular velocity is small, the operation of the steering wheel is slight, so the electric motor is decelerated to the standby rotational speed that is the lower limit value of the target rotational speed. On the other hand, if the steering angular velocity is high, it is considered that the steering wheel is largely operated, the electric motor is driven according to the steering angular velocity at that time, and steering assist force is generated.

An electronic control unit for controlling the power steering device executes an abnormality monitoring process for detecting a failure of a sensor line or the like. When any abnormality (failure) is detected by this abnormality monitoring processing, the electronic control unit gradually decreases the rotation speed of the electric motor and stops the electric motor by fail-safe processing.

[0005]

However, in the current power steering device, the rotation speed of the electric motor is gradually reduced in response to the occurrence of an abnormality, and even if steering is not performed, The electric motor is brought to a stopped state. That is, for example, while the vehicle is traveling on a straight road and the steering wheel is held at the steering angle midpoint, the rotation speed of the electric motor decreases. Therefore, the driver is less likely to notice the abnormality of the power steering device, and the steering resistance increases sharply during the next steering,
You will feel uncomfortable steering.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above-mentioned technical problems, to make a driver surely recognize an abnormality of a power steering device, and to eliminate a feeling of strangeness in steering due to a sudden increase in steering resistance. A steering device is provided.

[0007]

In order to achieve the above object, the invention according to claim 1 provides a steering assist force by the hydraulic pressure generated by a pump (26) driven by an electric motor (27). A power steering device for generating a steering angular velocity detecting means (11, 31, S4) for detecting a steering angular velocity which is a speed of steering by an operation member (2) for steering a vehicle, and the power steering device. The abnormality detecting means (31, S1) for detecting an abnormality, the steering detecting means (11, 31, S9, S21, S22) for detecting the presence or absence of steering by the operating member, and the abnormality detecting means detect the abnormality. When there is not, the normal drive target value setting means (S5) that determines the drive target value of the electric motor based on the output of the steering angular velocity detection means and the abnormality detection means detect an abnormality. At this time, the abnormal drive target value setting means (31, S10, S10, which gradually decreases the drive target value of the electric motor to a predetermined abnormal drive target value on condition that the steering detection means detects steering. S11, S2
3, S31) and motor drive means (28, 31, S6) for driving the electric motor based on the drive target value set by the normal drive target value setting means or the abnormal drive target value setting means. It is a power steering device characterized by including.

The alphanumeric characters in parentheses indicate corresponding components in the embodiments described later. The same applies in this section below. According to the above configuration, the drive target value of the electric motor is set based on the output of the steering angular velocity detection means in the normal state. When an abnormality of the power steering device is detected, the drive target value setting means for abnormality drives the drive target value of the electric motor to a predetermined drive target value for abnormality (for example, zero). At this time, the abnormal drive target value setting means is
On condition that the steering detection means detects the presence of steering,
The drive target value is reduced.

Therefore, even when an abnormality occurs in the power steering device, the drive target value of the electric motor becomes equal to the drive target value at the time of abnormality during a period when steering by the operating member is not performed, that is, during a straight traveling period. There is no decrease. That is, since the drive target value is reduced only when the driver is steering, the driver can reliably recognize the gradual increase in steering resistance as the drive target value gradually decreases. As a result, the driver can be made sure to recognize the abnormality of the power steering device, and the uncomfortable feeling due to the sudden increase in the steering resistance can be eliminated.

The steering angle velocity detecting means is a steering angle sensor (11) for detecting the steering angle of the operating member, and means (31, S for differentiating the steering angle detected by the steering angle sensor).
4) and may be included. Further, the steering detecting means may detect whether there is a change in the steering angle detected by the steering angle sensor, or whether the steering angular velocity detecting means detects a steering angular velocity exceeding a predetermined value (for example, zero). The presence or absence of steering may be detected based on whether or not the steering is performed.

The rudder angle sensor may be configured to generate a detection signal (for example, a pulse signal) for each constant rudder angle change. Can be detected. According to a second aspect of the present invention, the abnormal drive target value setting means gradually increases the drive target value to the predetermined value when the drive target value at the time when the abnormality detecting means detects the abnormality is less than the predetermined value. The power steering device according to claim 1, wherein the power steering device includes (31, S7, S8).

If the drive target value at the time when the power steering device is abnormal is a small value close to the abnormal drive target value, the drive target value is promptly led to the abnormal drive target value. Therefore, the driver may not be able to feel the gradual increase in steering resistance and may not be able to recognize the occurrence of an abnormality. Therefore, in the present invention, when the drive target value at the time of abnormality detection is less than the predetermined value, the drive target value is gradually increased to the predetermined value. As a result, in the process in which the drive target value is gradually reduced from the predetermined value to the abnormal drive target value, the driver can be made aware of the gradual increase of the steering resistance and the abnormality can be surely recognized. In addition,
After the drive target value reaches the predetermined value, the drive target value is gradually decreased toward the drive target value, and as long as the abnormal state continues, the drive target value is not increased again.

According to a third aspect of the present invention, there is further provided a steering angle sensor (11) for detecting a steering angle change due to the operation of the operating member and outputting a detection signal for each constant steering angle change. Is for detecting the presence / absence of a detection signal from the steering angle sensor, and the abnormal drive target value setting means drives the drive target value by a constant value every time the detection signal from the steering angle sensor is input. The power steering device according to claim 1 or 2, wherein the power steering device reduces the power consumption.

In this configuration, the presence / absence of steering is detected by the presence / absence of a detection signal from a steering angle sensor that outputs a detection signal (for example, a detection pulse) for each constant steering angle change. Then, by a simple process of decreasing the drive target value by a constant value each time the steering angle sensor outputs a detection signal,
The driver can be made aware of the occurrence of the abnormality. Claim 4
In the invention described above, the steering detecting means detects whether the steering angular velocity detected by the steering angular velocity detecting means exceeds a predetermined value, and the abnormal drive target value setting means detects the steering angular velocity. When the steering angular velocity detected by the means exceeds the predetermined value, the drive target value is reduced at a rate of time change according to the steering angular velocity detected by the steering angular velocity detection means. Item 1 or 2
It is the described power steering apparatus.

With this configuration, the presence or absence of steering is detected based on whether the steering angular velocity is a value exceeding a predetermined value (for example, zero). Then, if the steering angular velocity exceeds a predetermined value,
The drive target value is gradually reduced at a rate of change with time according to the steering angular velocity. As a result, the manner in which the drive target value is reduced can be optimized, so that it is possible to surely recognize the occurrence of an abnormality without giving the driver a feeling of strangeness in steering. For example, it is preferable to gradually reduce the drive target value at a time change rate that is proportional to the reciprocal of the steering angular velocity. As a result, when the steering angular velocity is high as in the case of emergency steering, the steering resistance does not increase so much, and the steering resistance increases more rapidly as the slow steering is performed. Therefore, while improving safety, the driver can surely be made aware of the occurrence of the abnormality.

According to a fifth aspect of the present invention, the steering detecting means detects whether or not the steering angular velocity output by the steering angular velocity detecting means exceeds a predetermined value, and the abnormal drive target value setting means. When the steering angular velocity detected by the steering angular velocity detecting means is a value exceeding the predetermined value, the drive target value is decreased at a predetermined constant time change rate. It is the power steering device described in 2.

In this configuration, the presence or absence of steering is detected based on whether or not the steering angular velocity exceeds a predetermined value (for example, zero). Then, if the steering angular velocity exceeds a predetermined value,
The drive target value is reduced at a constant rate of change with time. As a result, the drive target value can be gradually reduced to the abnormal drive target value by a simple process that does not require complicated calculation, and the driver can be surely aware of the occurrence of the abnormality.

[0018]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is an illustrative view showing a basic configuration of a power steering device according to an embodiment of the present invention. The power steering device is provided in association with the steering mechanism 1 of the vehicle and is for applying a steering assist force to the steering mechanism 1.

The steering mechanism 1 includes a steering wheel 2 operated by a driver, a steering shaft 3 connected to the steering wheel 2, a pinion gear 4 provided at the tip of the steering shaft 3, and a pinion gear 4. It has a rack gear portion 5a that meshes with the rack shaft 5 that extends in the left-right direction of the vehicle. Rack shaft 5
Tie rods 6 are respectively connected to both ends of the tie rods 6, and the tie rods 6 are respectively connected to knuckle arms 7 that support front left and right wheels FL and FR as steering wheels. The knuckle arm 7 is provided rotatably around the kingpin 8.

With this configuration, the steering wheel 2
Is operated to rotate the steering shaft 3, this rotation is converted into a linear motion along the left-right direction of the vehicle by the pinion gear 4 and the rack shaft 5. This linear motion is
The knuckle arm 7 is converted into a rotation around the king pin 8, whereby steering of the front left and right wheels FL and FR is achieved. The steering wheel 2 is attached to the steering shaft 3.
The torsion bar 9 that causes a twist in accordance with the direction and the magnitude of the steering torque applied thereto and the hydraulic control valve 23 whose opening changes according to the direction and the magnitude of the torsion of the torsion bar 9 are incorporated. . The hydraulic control valve 23 is
It is connected to a power cylinder 20 that gives a steering assist force to the steering mechanism 1. The power cylinder 20 includes a piston 21 provided integrally with the rack shaft 5 and a pair of cylinder chambers 20 a, 20 partitioned by the piston 21.
b, the cylinder chambers 20a, 20b are connected to the hydraulic control valve 23 via oil supply / return paths 22a, 22b, respectively.

The hydraulic control valve 23 further includes an oil circulation path 24 passing through a reservoir tank 25 and an oil pump 26.
Is installed in the middle of the. The oil pump 26 is driven by the electric motor 27, pumps out the hydraulic oil stored in the reservoir tank 25, and supplies the hydraulic oil to the hydraulic control valve 23. The surplus hydraulic oil is returned from the hydraulic control valve 23 to the reservoir tank 25 via the oil circulation path 24. When the torsion bar 9 is twisted in one direction, the hydraulic control valve 23 is provided with oil supply / return paths 22a, 22.
The hydraulic oil is supplied to one of the cylinder chambers 20a and 20b of the power cylinder 20 through one of the b. When the torsion bar 9 is twisted in the other direction, hydraulic oil is supplied to the other of the cylinder chambers 20a, 20b via the other of the oil supply / return paths 22a, 22b. When the torsion bar 9 is hardly twisted, the hydraulic control valve 23 is in a so-called equilibrium state, and the hydraulic oil circulates in the oil circulation path 24 without being supplied to the power cylinder 20.

When hydraulic oil is supplied to one of the cylinder chambers of the power cylinder 20, the piston 21 moves in the vehicle width direction. As a result, the steering assist force acts on the rack shaft 5. An example of the configuration related to the hydraulic control valve 23 is disclosed in detail in Japanese Patent Laid-Open No. 59-18577. The electric motor 27 is, for example, a brushless motor, and is controlled by the electronic control unit 30 via the drive circuit 28. The drive circuit 28 is
For example, it is composed of a bridge circuit of power transistors, and supplies electric power from the vehicle-mounted battery 40 as a power source to the electric motor 27 according to a control signal given from the electronic control unit 30.

The electronic control unit 30 includes a vehicle-mounted battery 4
0 includes a microcomputer that operates by receiving a power supply from 0, and this microcomputer includes a CPU 31
And a RAM 3 that provides a work area for the CPU 31
2, a ROM 33 storing an operation program of the CPU 31, data for control, etc., a CPU 31, a RAM 32
And a bus 34 interconnecting the ROM 33. The steering angle signal output from the steering angle sensor 11 is given to the electronic control unit 30, and the steering angular velocity corresponding to the time differential value is calculated based on the steering angle signal. The steering angle sensor 11 may output, for example, a pulse signal as a detection signal for each constant steering angle change. In this case, the steering wheel 2
Is held at a constant angle position, the steering angle sensor 11 does not output a detection signal. Further, when the steering wheel 2 is operated quickly, the steering angle sensor 11 outputs a detection signal in a short cycle, and when the steering wheel 2 is operated slowly, the steering angle sensor 11 outputs a detection signal in a long cycle. . Therefore, the steering angular velocity, which is the speed of steering by the steering wheel 2, can be calculated based on the time interval of the detection signal.

The electronic control unit 30 further includes a current detection signal from the current detection circuit 12 that detects the current flowing through the electric motor 27 and a signal from the rotation sensor 15 that detects the rotational position of the rotor of the electric motor 27. Is given. Further, the electronic control unit 30 is provided with a vehicle speed signal output from the vehicle speed sensor 13. The vehicle speed sensor 13 may directly detect the vehicle speed, or may calculate the vehicle speed based on the output pulse of the wheel speed sensor provided in association with the wheel.

The electronic control unit 30 includes the steering angle sensor 1
1, the drive of the electric motor 27 is controlled based on the steering angle signal, the current signal, and the vehicle speed signal provided from the current detection circuit 12 and the vehicle speed sensor 13, respectively. FIG. 2 is a characteristic diagram showing a correspondence relationship between the steering angular velocity Vθ calculated based on the output of the steering angle sensor 11 and the target rotation speed R of the electric motor 27. The target rotation speed R is the first threshold value VT1 and the second threshold value VT set for the steering angular speed Vθ.
It is set between the lower limit value R1 and the upper limit value R2 so as to increase between two. The lower limit value R1 is the standby rotation speed, and for the steering angular speed less than the first threshold value VT1, the electric motor 27 is rotationally driven at the standby rotation speed R1.

As shown in FIG. 2, the CPU 31 variably sets the inclination of the target rotation speed R with respect to the steering angular speed Vθ, based on the vehicle speed. That is, the second threshold value VT2 is variably set according to the vehicle speed range. More specifically, the second threshold value VT2 is set to a larger value as the vehicle speed increases. As a result, the target rotation speed R is set smaller as the vehicle speed increases, and the steering assist force decreases.
In this way, vehicle speed responsive control for generating an appropriate steering assist force according to the vehicle speed is performed.

On the other hand, the CPU 31 repeatedly executes an abnormality monitoring routine for monitoring the abnormality of each part of the apparatus every control cycle. When an abnormality occurs, the fail safe process is executed to stop the electric motor 27. , Prevent undesired steering assistance. FIG. 3 is a flowchart illustrating a control process of the electric motor 27 that the CPU 31 repeatedly executes at each predetermined control cycle.

The CPU 31 determines whether or not there is an abnormality by executing an abnormality monitoring routine (step S).
1). If there is no abnormality (NO in step S1), CPU
31 reads the vehicle speed from the vehicle speed sensor 13 (step S2). Next, the CPU 31 reads the steering angle signal from the steering angle sensor 11 (step S3), and calculates the steering angular velocity as a time differential value of the steering angle based on this (step S3).
4). Based on the obtained steering angular velocity and the read vehicle speed, the CPU 31 sets the target rotation speed R of the electric motor 27 according to the characteristics shown in FIG. 2 (step S5). Then, the electric motor 27 is driven so as to reach the set target rotation speed R (step S
6). As a result, a steering assist force corresponding to the rotation speed of the electric motor 27 is generated. After that, if no abnormality is monitored by the abnormality monitoring routine of the CPU 31, step S
The processes of 1 to S6 are repeated.

When an abnormality is detected (Y in step S1)
ES), CPU31, after the target rotation speed R has occurred abnormal,
It is determined whether or not the rotation speed is once more than the predetermined rotation speed Z (eg 2000 rpm) (step S7). When the target rotation speed R is not equal to or higher than the predetermined rotation speed Z (Y in step S7)
ES), the CPU 31 sets a new target rotation speed R by adding a constant K (for example, K = 4) to the current target rotation speed R (step S8). Then, the electric motor 27 is driven based on the new target rotation speed R (step S6). After that, if the abnormal state continues (YES in step S1), steps S1, S7,
The process of S8 is repeated every control cycle. This allows
When an abnormality occurs, the target rotation speed R is gradually increased to the predetermined rotation speed Z at a constant time change rate.

If the target rotation speed R is equal to or higher than the predetermined rotation speed Z even once after the occurrence of the abnormality (NO in step S7), C
The PU 31 checks whether there is an output signal from the steering angle sensor 11 (step S9). When the pulse signal output from the steering angle sensor 11 is not confirmed (NO in step S9), the CPU 31 drives the electric motor 27 at the previous target rotation speed R (step S6). Rudder angle sensor 11
When a pulse signal is output from (YE in step S9
S), the CPU 31 determines the constant x from the current target rotation speed R.
(For example, x = 1) is subtracted to set a new target rotation speed R (step S10). If the newly set target rotation speed R is not zero (N in step S11)
O), the CPU 31 drives the electric motor 27 based on the target rotation speed R (step S6).

If the abnormal state continues (Y in step S1)
ES) and steps S7, S9, S10, S11 and S6 are repeated for each control cycle. As a result, the target rotation speed R is reduced by a constant value x each time the steering angle sensor 11 outputs a pulse signal, that is, every time there is a constant change in the steering angle. When the target rotation speed R is gradually reduced to zero in this way (YES in step S11), the CPU 31 stops the electric motor 27 (step S12).

FIG. 4 is a diagram showing an example of the change over time of the target rotation speed R. When an abnormality of the power steering device is detected at time F (YE in step S1 in FIG. 3).
S), after the abnormal occurrence of the target rotation speed R of the electric motor 27,
If the rotation speed is not equal to or higher than the predetermined rotation speed Z (YES in step S7 of FIG. 3), the CPU 31 gradually increases the target rotation speed R by the constant K for each control cycle to the predetermined rotation speed Z ( Step S8 of FIG. 3). After the target rotation speed R has become equal to or higher than the predetermined rotation speed Z once (NO in step S7 of FIG. 3), during the period T1 in which the steering angular speed Vθ is large, the pulse signal of the steering angle sensor 11 Since the cycle is short, the target rotation speed R decreases rapidly.

There is no change in the steering angle (that is, the steering angular velocity Vθ =
0) In the period T2, no pulse signal is generated from the steering angle sensor 11 (NO in step S9 in FIG. 3). Therefore, the CPU 31 determines that the steering is not performed, and the target rotation speed R is kept unchanged. In the period T3 in which the steering angular velocity Vθ is small, the pulse signal generated from the steering angle sensor 11 has a long cycle. Therefore, the target rotation speed R gradually decreases. Then, when the target rotation speed R becomes zero (step S11 in FIG. 3), the electric motor 27 stops (step S12 in FIG. 3).

As described above, according to this embodiment, when an abnormality occurs, the target rotation speed R is reduced by a constant x each time the steering angle sensor 11 outputs a pulse signal, and the electric motor 27 is stopped. Be led to. That is, the target rotation speed R does not decrease in a situation where there is no change in the steering angle such as when traveling straight ahead, and the target rotation speed R decreases and steering resistance increases only when substantial steering is performed. Become. With this, when an abnormality occurs, the driver can be surely made to recognize the abnormality occurrence by a simple process through the gradual increase of the steering resistance, and further, there is no fear that the steering resistance will be uncomfortable due to the sudden increase of the steering resistance.

Further, in this embodiment, when the target rotation speed R at the time of occurrence of an abnormality is less than the predetermined rotation speed Z, the target rotation speed R is gradually increased to the predetermined rotation speed Z in advance (increased by a constant K for each control cycle). Then, the target rotation speed R
Is gradually reduced to zero. This allows
Since it is possible for the driver to feel the gradual increase in steering resistance, it is possible to reliably notify the driver of the occurrence of an abnormality. FIG. 5 is a flow chart for explaining the processing by the power steering device according to the second embodiment of the present invention. In the description of this second embodiment, reference is again made to FIGS. 1 and 2 above. Further, in FIG. 5, the electric motor 2
Although the processing that the CPU 31 repeatedly executes for each control cycle for the control of FIG. 7 is shown, the steps similar to the steps shown in FIG. The same reference numerals as those in the case are attached.

In this embodiment, when it is determined in step S7 that the target rotation speed R is equal to or higher than the predetermined rotation speed Z, the CPU 31 differentiates the steering angle signal read from the steering angle sensor 11 with respect to time and steers the steering angle signal. The angular velocity Vθ is calculated (step S21). If the obtained steering angular velocity Vθ is zero (YES in step S22), the CPU 31 drives the electric motor 27 based on the previous target rotation speed R (step S6). If the calculated steering angular velocity Vθ is not zero (NO in step S22), the CPU 31 sets the variable A / which is proportional to the reciprocal of the current target rotation speed R to the steering angular velocity Vθ.
Vθ (where A is a positive proportional constant) is subtracted to set a new target rotation speed R (step S23).

If the newly set target rotation speed R is greater than zero (NO in step S11), the CPU 31
Drives the electric motor 27 based on the target rotation speed R (step S6). If the abnormal state continues (YES in step S1), steps S7, S21, S22,
The processing of S23, S11, and S6 is repeated every control cycle. As a result, when the calculated steering angle speed is not zero, that is, when there is a change in the steering angle, the target rotation speed R
The numerical value A / Vθ proportional to the reciprocal of the steering angular velocity Vθ is subtracted from.

When the target rotation speed R gradually decreases to zero in this way (YES in step S11), the CPU 31 stops the electric motor 27 (step S12). FIG. 6 is a diagram showing an example of a temporal change of the target rotation speed R in this embodiment. When an abnormality is detected in the power steering device at time F (YES in step S1 in FIG. 5),
If the target rotation speed R of the electric motor 27 has not exceeded the predetermined rotation speed Z even after the occurrence of the abnormality (YES in step S7 of FIG. 5), the CPU 31 sets the target rotation speed R by a constant K for each control cycle. By increasing it, the specified rotation speed Z
(Step S8 in FIG. 5).

The target rotation speed R is 1 degree and the predetermined rotation speed Z.
After that (NO in step S7 of FIG. 5), during the period T5 in which the steering angular velocity Vθ is zero (step S22 of FIG. 5).
YES), the target rotation speed R is kept unchanged. When the steering angular velocity Vθ is not zero (N in step S22 in FIG. 5)
In (O), the value A / Vθ proportional to the reciprocal of the steering angular velocity Vθ is subtracted from the target rotation speed R to obtain a new target rotation speed R (step S23 in FIG. 5). That is, the target rotation speed R gradually decreases in the period T4 where the steering angular speed Vθ is large, and the target rotation speed R rapidly decreases in the period T6 where the steering angular speed Vθ is small. Then, when the target rotation speed R becomes zero (step S11 in FIG. 5), the electric motor 27 stops (step S12 in FIG. 5).

As described above, the target rotation speed R of the electric motor 27 is reduced under the condition that the steering angular speed Vθ is not zero when an abnormality occurs. At this time, since the numerical value A / Vθ proportional to the reciprocal of the steering angular velocity Vθ is subtracted from the target rotation speed R, when the steering angular velocity Vθ is large, the reduction amount of the steering assist force is small, and when the steering angular velocity Vθ is small. Therefore, the amount of decrease in the steering assist force becomes large. That is, as in the case of emergency steering, the steering resistance increases less as the steering angular velocity Vθ increases, and the steering resistance increases rapidly when slow steering is performed. Therefore, while improving safety,
In addition, it is possible to make the driver surely recognize the occurrence of abnormality.

Besides, the same effects as in the case of the above-described first embodiment can be achieved together. FIG. 7 is a flow chart for explaining the processing by the power steering device according to the third embodiment of the present invention. In the description of this third embodiment, reference is again made to FIGS. 1 and 2 above. Further, FIG. 7 shows C for controlling the electric motor 27.
Although the processing that the PU 31 repeatedly executes for each control cycle is shown, the same reference numerals as those in FIG. 5 are used for the steps in which the same processing as that shown in FIG. Is attached.

In this embodiment, if it is determined in step S22 that the steering angular velocity Vθ is not zero, the CPU 3
1 is a constant y (for example, y =
4) is subtracted to set a new target rotation speed R (step S31). If the newly set target rotation speed R is greater than zero (NO in step S11), the CPU 3
1 drives the electric motor 27 based on the target rotation speed R (step S6).

If the abnormal state continues (Y in step S1)
ES), steps S7, S21, S22, S31, S1
The processes of 1 and S6 are repeated for each control cycle. Thus, on condition that the steering angular velocity Vθ is not zero, that is, in the situation where the steering change is detected, the target rotation speed R is gradually decreased by a constant y for each control cycle (that is, at a constant time change rate). To be done. When the target rotation speed R is gradually reduced to zero in this way (YES in step S11), the CPU 31 stops the electric motor 27 (step S12).

FIG. 8 is a diagram showing an example of the change over time of the target rotation speed R in this embodiment. At time F, if an abnormality is detected in the power steering device (YES in step S1 in FIG. 7), the target rotation speed R of the electric motor 27 has not exceeded the predetermined rotation speed Z even once after the abnormality has occurred (FIG. 7). 7, step S7 YES), CPU31
Causes the target rotation speed R to be gradually increased to a predetermined rotation speed Z by increasing the target rotation speed R by a constant K for each control cycle (FIG. 7).
Step S8).

The target rotation speed R is 1 degree, the predetermined rotation speed Z
After that (NO in step S7 in FIG. 7), the target rotation speed R is maintained unchanged during the period T8 in which the steering angular velocity Vθ is zero (YES in step S22 in FIG. 7). During periods T7 and T9 in which the steering angular velocity Vθ is not zero (NO in step S22 in FIG. 7), the target rotational speed R is reduced by a constant y for each control cycle regardless of the magnitude of the steering angular velocity Vθ (see FIG. 7). Step S31). Therefore, the target rotation speed R decreases at a constant time change rate only when steering is being performed. Then, when the target rotation speed R becomes zero (see FIG. 7).
Step S11), the electric motor 27 is stopped (FIG. 7).
Step S12).

According to this embodiment, the same effect as that of the above-described second embodiment can be achieved. Moreover, the steering angular velocity Vθ
Since it is not necessary to calculate the value A / Vθ that is proportional to the reciprocal of the above, it is possible to gradually reduce the drive target value to the drive target value at the time of abnormality by a simple process that does not require complicated calculation, and the driver can be sure that the abnormality is Can be recognized. Although the three embodiments of the present invention have been described above, the present invention can be implemented in other forms.

For example, in the above three embodiments, the target rotation speed R is used as the drive target value of the electric motor 27, but the drive target voltage (or current) of the electric motor 27 is used as the drive target value. May be. Further, in the above embodiment, the presence or absence of steering is detected based on the output of the steering angle sensor 11. However, for example, the presence or absence of steering is detected based on the output of a torque sensor that detects the steering torque applied to the steering wheel 2. It may be detected.

Further, in the second and third embodiments described above, it is determined that steering is present when the steering angular velocity Vθ is not zero, but the steering angular velocity Vθ exceeds a positive threshold value. It may be determined that steering is performed under the condition. In addition, various design changes can be made within the scope of the matters described in the claims.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing a basic configuration of a power steering device according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a relationship between a steering angular velocity and a target rotation speed of an electric motor.

FIG. 3 is a flow chart for explaining a control process of the electric motor that the CPU repeatedly executes for each predetermined control cycle.

FIG. 4 is a diagram showing an example of a change over time of a target rotation speed.

FIG. 5 is a flowchart for explaining control processing of an electric motor target rotation speed in the power steering device according to the second embodiment of the present invention.

FIG. 6 is a diagram showing an example of a temporal change of a target rotation speed of an electric motor by a control process according to the second embodiment.

FIG. 7 is a flow chart for explaining a control process of the electric motor in the power steering device according to the third embodiment of the present invention.

FIG. 8 is a diagram showing an example of a change over time of a target rotation speed of an electric motor by a control process according to the third embodiment.

[Explanation of symbols]

1 Steering mechanism 2 steering wheel 9 torsion bar 11 Rudder angle sensor 12 Current detection circuit 13 vehicle speed sensor 20 power cylinder 23 Hydraulic control valve 26 Oil pump 27 electric motor 28 Drive circuit 30 electronic control unit 31 CPU 33 ROM

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kazuhiko Fujita             3-5-8 Minamisenba, Chuo-ku, Osaka Koyo             Within Seiko Co., Ltd. F term (reference) 3D032 CC32 DA03 DA23 DE02 EC03                       EC22 GG01                 3D033 EB04

Claims (5)

[Claims] 1. A power steering device for generating a steering assist force by hydraulic pressure generated by a pump driven by an electric motor, the rudder detecting a steering angular velocity which is a speed of steering by an operation member for steering a vehicle. Angular velocity detecting means, abnormality detecting means for detecting an abnormality of the power steering device, steering detecting means for detecting the presence / absence of steering by the operating member, and the steering wheel when the abnormality detecting means detects no abnormality. The normal drive target value setting means for determining the drive target value of the electric motor based on the output of the angular velocity detecting means, and the steering detecting means detecting steering when the abnormality detecting means detects an abnormality. Under the condition, the drive target value of the electric motor is gradually reduced to a predetermined drive target value at the time of abnormality, Power steering apparatus comprising a motor driving means for driving the electric motor on the basis of the driving target value set by the constant section or abnormal driving target value setting means. 2. The abnormal drive target value setting means includes means for gradually increasing the drive target value to the predetermined value when the drive target value at the time when the abnormality detecting means detects an abnormality is less than the predetermined value. The power steering device according to claim 1, wherein 3. A steering angle sensor that detects a steering angle change due to an operation of the operation member and outputs a detection signal for each constant steering angle change, wherein the steering detection means detects the steering angle sensor. The presence or absence of a signal is detected, and the abnormal drive target value setting means decreases the drive target value by a constant value every time the detection signal from the steering angle sensor is input. The power steering device according to claim 1 or 2. 4. The steering detecting means detects whether or not the steering angular velocity detected by the steering angular velocity detecting means exceeds a predetermined value, and the abnormal drive target value setting means detects the steering angular velocity. When the steering angular velocity detected by the means exceeds the predetermined value, the drive target value is reduced at a rate of time change according to the steering angular velocity detected by the steering angular velocity detection means. Item 3. The power steering device according to item 1 or 2. 5. The steering detecting means detects whether the steering angular velocity output by the steering angular velocity detecting means exceeds a predetermined value, and the abnormal drive target value setting means detects the steering angular velocity. The power steering apparatus according to claim 1 or 2, wherein when the steering angular velocity detected by the means is a value exceeding the predetermined value, the drive target value is decreased at a predetermined constant time change rate. .