JP3099105B2 - Power steering device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a power steering apparatus for assisting a steering force according to a vehicle speed detected by a vehicle speed sensor.

[0002]

2. Description of the Related Art Conventionally, a power steering device for assisting a steering force not only is based on a torque detected by a torque sensor but also responds to a vehicle speed detected by a vehicle speed sensor to provide a steering assist force for assisting the steering force. It is moderate. That is, when the vehicle is stopped or running at a low speed, a large steering assist force is generated (steered wheels are lightened), while only a small steering assist force is generated at a high speed running (steered wheels are heavy),
Abrupt steering wheel operation during high-speed running is prevented.

In such a power steering device,
Even when the vehicle speed signal is rapidly decreased due to a failure of the vehicle speed sensor, noise superimposed on the vehicle speed signal from the vehicle speed sensor, disconnection, or the like during high-speed running, the steered wheels are not suddenly lightened. As a means, when the vehicle speed signal drops rapidly, the clutch in the transmission mechanism between the steered wheels and the power steering device is turned off, and then, when the vehicle speed is detected even a little, the clutch is turned on and normal operation is performed. Some will return. Further, when the vehicle speed signal rapidly decreases, the assisting force based on the vehicle speed immediately before the decrease is continuously generated (Japanese Patent Laid-Open No. 62-191271), and when the vehicle speed returns to a predetermined value or more, the assistance based on the vehicle speed is reduced. Some of them generate power and return to normal operation.

[0004]

However, when the vehicle speed sensor fails, the vehicle speed signal from the vehicle speed sensor does not always become zero immediately. In the case of a poor contact of the connector, the vehicle speed signal drops while fluctuating. Is also conceivable. In such a case, in the former, even if the vehicle speed signal suddenly drops, even if the vehicle speed is slightly detected due to the irregularity of the vehicle speed signal, and if the return condition is satisfied even temporarily, the vehicle may return to the normal operation. There is. Also, when the tire is locked by sudden braking and the fail-safe is activated, the latter does not return to the normal operation until the vehicle speed signal returns to a predetermined value or more, so the steering force is not assisted despite the failure. There is a problem that becomes longer.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and the steering assist force does not become unstable even when the vehicle speed drops sharply. It is an object of the present invention to provide a highly safe power steering device that quickly returns to a normal operation without a sudden change in force.

[0006]

According to a first aspect of the present invention, there is provided a power steering apparatus for controlling a steering assist force based on a torque detected by a torque sensor and a vehicle speed detected in time series by a vehicle speed sensor. A deviation detecting means for detecting a deviation between a vehicle speed detected by the vehicle speed sensor and a vehicle speed detected earlier by the vehicle speed sensor; and a control vehicle speed for steering assist force control based on the deviation detected by the deviation detecting means. Control vehicle speed correction means for correcting the vehicle speed, wherein the control vehicle speed correction means compares the deviation detected by the deviation detection means with a first predetermined value indicating a decrease in vehicle speed,
When the deviation detected by the deviation detecting means indicates a decrease in vehicle speed that is equal to or greater than the first predetermined value, means for setting a vehicle speed detected earlier as a control vehicle speed, and a vehicle speed detected by a vehicle speed sensor and a second predetermined value Means for comparing the vehicle speed with the second
Means for gradually bringing the control vehicle speed closer to the vehicle speed detected by the vehicle speed sensor when the vehicle speed returns to a predetermined value or more.

[0007] In the power steering apparatus according to the second invention, the control vehicle speed correction means further compares a deviation between the control vehicle speed and the vehicle speed detected by the vehicle speed sensor with a third predetermined value.
And a means for setting the vehicle speed detected by the vehicle speed sensor to a control vehicle speed when the deviation becomes smaller than a third predetermined value .

A power steering apparatus according to a third aspect of the present invention is a power steering apparatus for controlling a current of a motor for assisting a steering force based on a torque detected by a torque sensor and a vehicle speed detected in time series by a vehicle speed sensor. A deviation detecting means for detecting a deviation between the vehicle speed detected by the vehicle speed sensor and the vehicle speed detected by the vehicle speed sensor preceding the vehicle speed, and a control vehicle speed for steering assist force control based on the deviation detected by the deviation detecting means. Control vehicle speed correction means for correcting;
Motor maximum current limiting means for increasing or decreasing a maximum current limit value of the motor based on the deviation detected by the deviation detecting means, wherein the control vehicle speed correcting means comprises: Means for comparing the vehicle speed with a first predetermined value indicating the vehicle speed, and when the deviation detected by the deviation detecting means indicates a decrease in vehicle speed that is equal to or greater than the first predetermined value, setting the vehicle speed detected earlier as a control vehicle speed. Wherein the motor maximum current limiting means detects the motor maximum current limit value in advance when the deviation detected by the deviation detecting means indicates a decrease in vehicle speed equal to or greater than the first predetermined value. Means for setting the motor maximum current value at the vehicle speed; means for comparing the vehicle speed detected by the vehicle speed sensor with a second predetermined value; and when the vehicle speed returns to or above the second predetermined value, the motor is gradually turned off. Characterized in that it comprises a means for increasing the maximum current limit.

In the power steering apparatus according to a fourth aspect of the present invention, the motor maximum current limiting means further includes a deviation between the control vehicle speed and the vehicle speed detected by the vehicle speed sensor as a third predetermined value.
Means for comparing, said deviation being less than a third predetermined value
Was sometimes characterized by comprising a means for returning the maximum motor current limit value to the maximum motor current value at the time of vehicle stop.

In the power steering apparatus according to a fifth aspect, the control vehicle speed correction means further compares a deviation between the control vehicle speed and the vehicle speed detected by the vehicle speed sensor with a third predetermined value.
Means for setting the vehicle speed detected by the vehicle speed sensor to the control vehicle speed when the deviation becomes smaller than a third predetermined value .

[0011]

In the power steering device according to the first invention,
The deviation detecting means detects a deviation between the vehicle speed detected by the vehicle speed sensor and the vehicle speed detected earlier by the vehicle speed sensor, and the control vehicle speed correcting means detects the deviation detected by the deviation detecting means and a decrease in vehicle speed. And when the deviation detected by the deviation detecting means indicates a decrease in vehicle speed that is equal to or greater than the first predetermined value, the vehicle speed detected earlier is set as the control vehicle speed, and the vehicle speed detected by the vehicle speed sensor is compared with the second vehicle speed. When the vehicle speed returns to the second predetermined value or more, the control vehicle speed gradually approaches the vehicle speed detected by the vehicle speed sensor.

[0012] In the power steering apparatus according to the second aspect of the present invention, the deviation between the control vehicle speed and the vehicle speed detected by the vehicle speed sensor is determined by the second method.
3, and this deviation is smaller than the third predetermined value.
Since sometimes, a vehicle speed the vehicle speed Sesensa detects the control vehicle speed.

In the power steering apparatus according to the third invention, the deviation detecting means detects a deviation between the vehicle speed detected by the vehicle speed sensor and the vehicle speed detected earlier by the vehicle speed sensor, and the control vehicle speed correcting means detects the deviation. The deviation detected by the means is compared with a first predetermined value indicating a decrease in vehicle speed. When the deviation detected by the deviation detection means indicates a decrease in vehicle speed equal to or greater than the first predetermined value, the vehicle speed detected earlier is determined. In addition to the control vehicle speed, when the motor maximum current limiting means indicates a decrease in vehicle speed that is equal to or greater than the first predetermined value, the maximum current limit value of the motor assisting the steering force is set in advance. The motor maximum current value at the detected vehicle speed, the vehicle speed detected by the vehicle speed sensor is compared with a second predetermined value,
When the vehicle speed returns to or above the second predetermined value, the motor maximum current limit value is gradually increased.

In the power steering apparatus according to the fourth invention, the motor maximum current limiting means compares a deviation between the control vehicle speed and the vehicle speed detected by the vehicle speed sensor with a third predetermined value.
When the deviation becomes smaller than the third predetermined value , the motor maximum current limit value is returned to the motor maximum current value at the time of stopping.

[0015] In the power steering apparatus according to the fifth aspect of the invention, the control vehicle speed correction means compares a deviation between the control vehicle speed and the vehicle speed detected by the vehicle speed sensor with a third predetermined value.
When the vehicle speed becomes smaller than the third predetermined value , the vehicle speed detected by the vehicle speed sensor is set as the control vehicle speed.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a power steering apparatus according to the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a block diagram showing a schematic configuration of an embodiment of the power steering apparatus according to the first and second inventions. The output of the torque sensor 2 provided on the steering shaft (not shown) is input to the microcomputer 1 via the interface 3 and is A / D converted by the A / D converter 11 in the microcomputer 1, and then the phase compensator 12 compensates the phase.

The output of the vehicle speed sensor 7 is also input to the microcomputer 1. The vehicle speed signal output from the vehicle speed sensor 7 is calculated by a deviation detecting unit 20 to calculate a deviation from a previous vehicle speed signal detected last time in a detection cycle of the vehicle speed sensor and held by a previous value holding unit 19. Based on the vehicle speed, a control vehicle speed for steering assist force control is output from the control vehicle speed correction means 21 to the target current table 13. The microcomputer 1 stores the relationship between the detected torque and control vehicle speed and the drive current target value of the motor 5 in a target current table 13 in a memory, and reads and outputs a target current based on the detected torque and control vehicle speed. On the other hand, the output from the A / D conversion means 11 is differentiated by the differentiation means 18 and this is
Is added to the target current. This differential value is added for inertia compensation of the motor 5.

The difference between the above-mentioned addition result and the feedback value of the drive current of the motor 5 (detected by the drive current detection circuit 6 and A / D converted by the A / D conversion means 11a) is obtained by the subtraction means 15. , PI calculation means 1
According to 6, the deviation (proportional element) and the integral value of the deviation (integral element) are added to the previous control amount to become the current control amount. This control amount is a PWM (Pulse Width Moduration)
The means 17 converts the signal into a PWM wave signal and a signal indicating the rotation direction of the motor 5 and supplies the signal to the drive circuit 4 and the motor 5 configured as an H-type bridge with four switch transistors.

The operation of determining the control vehicle speed for controlling the steering assist force of the power steering device will be described below.
The operation will be described with reference to a flowchart (FIG. 2) showing the operation. A timer (not shown) that measures a predetermined time that is a detection cycle of the vehicle speed sensor 7 has started counting (FIG. 2S
9) Thereafter, the current vehicle speed is detected by the vehicle speed sensor 7, and the current vehicle speed signal is input to the deviation detecting means 20 (FIG. 2S).
10). The deviation detecting means 20 calculates the deviation between the previous vehicle speed signal held by the previous value holding means 19 and the current vehicle speed signal (S11 in FIG. 2). The control vehicle speed correction means 21 determines that the deviation corresponds to, for example, 20 km / h or more (FIG. 2).
S12, S13), the fail safe flag is set (S14 in FIG. 2).

Next, the control vehicle speed correcting means 21 determines that the current vehicle speed signal corresponds to, for example, 5 km / h or more (S1 in FIG. 2).
5), a vehicle speed signal corresponding to a predetermined vkm / h is subtracted from the previous vehicle speed signal (S16 in FIG. 2), and the previous vehicle speed signal after the subtraction is replaced with the current vehicle speed signal (S1 in FIG. 2).
7), and outputs the replaced current vehicle speed signal (previous vehicle speed signal) as a vehicle speed signal of the control vehicle speed (S18 in FIG. 2). When the current vehicle speed signal is less than 5 km / h (S15 in FIG. 2), the control vehicle speed correcting means 21 replaces the previous vehicle speed signal with the current vehicle speed signal (S17 in FIG. 2), and replaces the current vehicle speed signal (previous vehicle speed signal). Is output as a vehicle speed signal of the control vehicle speed.

The control vehicle speed correcting means 21 includes a deviation detecting means 2
When the fail-safe flag has already been set (S20 in FIG. 2), the above-mentioned deviation corresponds to, for example, 10 km / h or more (FIG. 2). 2S21), and when the current vehicle speed signal corresponds to, for example, 5 km / h or more (FIG. 2)
S15), a vehicle speed signal corresponding to a predetermined vkm / h is subtracted from the previous vehicle speed signal (FIG. 2S16), and the previous vehicle speed signal after the subtraction is replaced with the current vehicle speed signal (FIG. 2S).
17). Next, the replaced current vehicle speed signal is output as a vehicle speed signal of the control vehicle speed. On the other hand, the control vehicle speed correction means 21 corresponds to the above-mentioned deviation of 10 km / h or more (FIG. 2).
S21) When the current vehicle speed signal is less than 5 km / h (S15 in FIG. 2), the previous vehicle speed signal is replaced with the current vehicle speed signal (S17 in FIG. 2), and the replaced current vehicle speed signal (previous vehicle speed signal) is controlled. The signal is output as a vehicle speed signal (S18 in FIG. 2).

The control vehicle speed correcting means 21 includes the deviation detecting means 2
0 corresponds to a deviation of less than 20 km / h (S1 in FIG. 2).
2, S13), when the fail-safe flag is not set (S20 in FIG. 2), or when the fail-safe flag is set and the above-described deviation is less than 10 km / h (S21 in FIG. 2), the current vehicle speed signal is The value is held by the value holding means 19 (S22 in FIG. 2), the fail-safe flag is cleared (S23 in FIG. 2), and the current vehicle speed signal is output as a vehicle speed signal of the control vehicle speed (S18 in FIG. 2).

The control vehicle speed correcting means 21 includes the deviation detecting means 2
When the calculated deviation is less than 0 km / h (see FIG. 2)
S12), the current vehicle speed signal is held in the previous value holding means 19 (S22 in FIG. 2), the failsafe flag is cleared (S23 in FIG. 2), and the current vehicle speed signal is output as a vehicle speed signal of the control vehicle speed (S18 in FIG. 2). Next, after a predetermined time (detection cycle of the vehicle speed sensor 7) has elapsed from the start of the timer (S9 in FIG. 2) (S19 in FIG. 2), the flow returns to the next operation for detecting the current vehicle speed.

Accordingly, when the deviation between the previous vehicle speed and the current vehicle speed is, for example, 20 km / h or more and the current vehicle speed is less than 5 km / h, the control vehicle speed correcting means 21
The previous vehicle speed is set as the control vehicle speed. Thereafter, when the current vehicle speed detected by the vehicle speed sensor 7 returns to, for example, 5 km / h or more, each time the vehicle speed sensor 7 detects the vehicle speed, vkm / h
Only, the control vehicle speed is approached to the current vehicle speed detected by the vehicle speed sensor 7 (by appropriately setting v, the rate of change in which the control vehicle speed approaches the current vehicle speed can be adjusted). The detected current vehicle speed is, for example, 10
When it is within km / h, the current vehicle speed is set to the control vehicle speed (return to normal operation).

FIG. 3 is a block diagram showing a schematic configuration of one embodiment of the power steering apparatus according to the third to fifth inventions. FIG. 5 is a diagram showing one embodiment of the vehicle speed vs. motor maximum current characteristic of the power steering apparatus according to the third to fifth inventions. The output of the torque sensor 2 provided on the steering shaft (not shown) is input to the microcomputer 1a via the interface 3, and the A / D in the microcomputer 1a
A / D conversion is performed by the conversion unit 11 and then phase compensation is performed by the phase compensation unit 12.

The output of the vehicle speed sensor 7 is also input to the microcomputer 1a. The deviation of the vehicle speed signal output from the vehicle speed sensor 7 from the previous vehicle speed signal detected by the vehicle speed sensor in the detection cycle and held by the previous value holding unit 19 is calculated by the deviation detection unit 20. In accordance with the vehicle speed, a control vehicle speed for steering assist force control is output from the control vehicle speed correction means 22 to a target current table 13 and a motor maximum current limit means 23 described later. The vehicle speed signal output from the vehicle speed sensor 7 is also provided to the motor maximum current limiting means 23, and a motor maximum current limit value signal is output to the target current table 13 according to the deviation and the vehicle speed. When the above-mentioned deviation indicates a sharp decrease in the vehicle speed, information indicating a sharp decrease in the vehicle speed is provided from the control vehicle speed correcting means 22 to the motor maximum current limiting means 23.

The microcomputer 1a stores the relationship between the detected torque and the control vehicle speed and the drive current target value of the motor 5 in a memory as a target current table 13, and reads out a target current corresponding to the input torque and the control vehicle speed. Output. On the other hand, the output from the A / D converter 11 is differentiated by the differentiator 18, and this is added to the target current by the adder 14. This differential value is added for inertia compensation of the motor 5.

The difference between the above-described addition result and the feedback value of the drive current of the motor 5 (detected by the drive current detection circuit 6 and A / D converted by the A / D conversion means 11a) is obtained by the subtraction means 15. , PI calculation means 1
According to 6, the deviation (proportional element) and the integral value of the deviation (integral element) are added to the previous control amount to become the current control amount. This control amount is a PWM (Pulse Width Moduration)
The means 17 converts the signal into a PWM wave signal and a signal indicating the rotation direction of the motor 5 and supplies the signal to the drive circuit 4 and the motor 5 configured as an H-type bridge with four switch transistors.

The operation of determining the control vehicle speed for controlling the steering assist force of the power steering apparatus will be described below.
The operation will be described with reference to a flowchart (FIG. 4) showing the operation. A timer (not shown) that measures a predetermined time that is a detection cycle of the vehicle speed sensor 7 starts counting (S2 in FIG. 4).
9) Thereafter, the current vehicle speed is detected by the vehicle speed sensor 7, and the current vehicle speed signal is input to the deviation detecting means 20 (FIG. 4S).
30). The deviation detecting means 20 calculates the deviation between the previous vehicle speed signal held by the previous value holding means 19 and the current vehicle speed signal (S31 in FIG. 4). The deviation is, for example, 20 km /
h (S32, S33 in FIG. 4), and when the fail-safe flag is not set (S34 in FIG. 4), the control vehicle speed correcting means 22 sets the fail-safe flag (S35 in FIG. 4) and sets the motor maximum current limiting means 23. Sets the motor maximum current value at the previous vehicle speed as the motor maximum current limit value (S36 in FIG. 4).

Next, when the current vehicle speed signal corresponds to, for example, 5 km / h or more (S37 in FIG. 4), the motor maximum current limiting means 23 converts the signal corresponding to the motor maximum current limit value to a predetermined iA motor current value. The corresponding signals are added (FIG. 4
S38), the added value is set as the motor maximum current limit value, and a signal corresponding to the value is output. Next, the control vehicle speed correction means 22 replaces the previous vehicle speed signal with the current vehicle speed signal (S39 in FIG. 4) and outputs the replaced current vehicle speed signal (previous vehicle speed signal) as a vehicle speed signal of the control vehicle speed (S40 in FIG. 4). On the other hand, when the current vehicle speed signal is less than 5 km / h (S37 in FIG. 4),
Replace the previous vehicle speed signal with the current vehicle speed signal (S3 in FIG. 4).
9), and outputs the replaced current vehicle speed signal (previous vehicle speed signal) as the vehicle speed signal of the control vehicle speed (S40 in FIG. 4).

The motor maximum current limiting means 23 determines that the deviation obtained by the deviation detecting means 20 is, for example, 20 km / h or more (S32, S33 in FIG. 4), the fail-safe flag is already set (S34 in FIG. 4), and the current vehicle speed signal is For example, 5k
m / h or more (S37 in FIG. 4), a signal corresponding to the motor current value of a predetermined iA is added to the signal corresponding to the motor maximum current limit value (S38 in FIG. 4), and the added value is used as the motor maximum current. A signal corresponding to the limit value (S38 in FIG. 4) is output. Next, the control vehicle speed correction means 22 replaces the previous vehicle speed signal with the current vehicle speed signal (S39 in FIG. 4), and outputs the replaced current vehicle speed signal (previous vehicle speed signal) as a vehicle speed signal of the control vehicle speed (FIG. 4S4).
0). On the other hand, when the current vehicle speed signal is less than 5 km / h (S37 in FIG. 4), the control vehicle speed correction means 22 replaces the previous vehicle speed signal with the current vehicle speed signal (S39 in FIG. 4), and replaces the replaced current vehicle speed signal (previous vehicle speed). Signal) is output as a vehicle speed signal of the control vehicle speed (S40 in FIG. 4).

The motor maximum current limiting means 23 determines that the deviation obtained by the deviation detecting means 20 is, for example, less than 20 km / h (S32, S33 in FIG. 4), the fail-safe flag has already been set (S42 in FIG. 4), Is 10km /
When the current vehicle speed signal corresponds to, for example, 5 km / h or more (S37 in FIG. 4), the signal corresponding to the motor maximum current limit value corresponds to the signal corresponding to the motor current value of a predetermined iA. (S38 in FIG. 4), and the added value is used as the motor maximum current limit value (S3 in FIG. 4).
8) Output a signal corresponding thereto. Next, the control vehicle speed correction means 22 replaces the previous vehicle speed signal with the current vehicle speed signal (S39 in FIG. 4) and outputs the replaced current vehicle speed signal (previous vehicle speed signal) as a vehicle speed signal of the control vehicle speed (S40 in FIG. 4). On the other hand, the control vehicle speed correction means 22 determines that the current vehicle speed signal is less than 5 km / h (S3 in FIG. 4).
7), replacing the previous vehicle speed signal with the current vehicle speed signal (FIG. 4)
S39), and outputs the replaced current vehicle speed signal (previous vehicle speed signal) as a vehicle speed signal of the control vehicle speed (S4 in FIG. 4).
0).

The deviation obtained by the deviation detecting means 20 is 20 km
/ H (S32, S33 in FIG. 4), and when the fail-safe flag is not set (S42 in FIG. 4),
Alternatively, the fail-safe flag is set (S4 in FIG. 4).
2), when the above-mentioned deviation is less than 10 km / h (S43 in FIG. 4), the control vehicle speed correcting means 22 causes the previous value holding means 19 to hold the current vehicle speed signal (S44 in FIG. 4), and clears the fail-safe flag. Along with (S45 in FIG. 4), the motor maximum current limiter 23 outputs a signal corresponding to the motor maximum current limit value as the motor maximum current value when the vehicle speed is 0 km / h (FIG. 4S46). Next, the control vehicle speed correction means 22 outputs the current vehicle speed signal as a vehicle speed signal of the control vehicle speed (S40 in FIG. 4).

The deviation found by the deviation detecting means 20 is 0 km /
h (S32 in FIG. 4), the control vehicle speed correction means 22 causes the current vehicle speed signal to be held in the previous value holding means 19 (S44 in FIG. 4), clears the fail-safe flag (S45 in FIG. 4), and sets the motor maximum current. Limiting means 23
Outputs a signal corresponding to the motor maximum current limit value as the motor maximum current limit value when the vehicle speed is 0 km / h (FIG. 4S46). Next, the control vehicle speed correction means 22
Outputs the current vehicle speed signal as the vehicle speed signal of the control vehicle speed (S40 in FIG. 4). Next, after a predetermined time (detection cycle of the vehicle speed sensor 7) has elapsed from the start of the timer (S29 in FIG. 4) (S41 in FIG. 4), the process returns to the next operation for detecting the current vehicle speed.

Accordingly, the deviation between the previous vehicle speed and the current vehicle speed is, for example, 20 km / h or more, and the current vehicle speed is, for example, 5 km.
/ H, the motor maximum current limiting means 23
Once, the motor maximum current value at the previous vehicle speed is set as the motor maximum current limit value, and the control vehicle speed correction means 22 sets the previous vehicle speed as the control vehicle speed. Thereafter, when the current vehicle speed detected by the vehicle speed sensor 7 returns to, for example, 5 km / h or more, the motor maximum current limiting means 23 increases the motor maximum current limit value by iA each time the vehicle speed sensor 7 detects the vehicle speed. (By appropriately determining i, the rate of increase of the motor maximum current limit value can be adjusted).

When the deviation between the control vehicle speed and the current vehicle speed detected by the vehicle speed sensor 7 falls within, for example, 10 km / h, the motor maximum current limiting means 23 sets the motor maximum current limit value to the motor maximum current value when the vehicle is stopped. At the same time, the control vehicle speed correction means 22 sets the current vehicle speed as the control vehicle speed (returns to normal operation). In each of the above embodiments, the deviation detecting means obtains a deviation between the vehicle speed detected by the vehicle speed sensor 7 (current vehicle speed) and the vehicle speed detected immediately before by the vehicle speed sensor 7 (previous vehicle speed). But
The average value of the vehicle speed (current vehicle speed) detected by the vehicle speed sensor 7 and some vehicle speeds detected before (not necessarily immediately before), and some average values detected earlier than this The same can be achieved by calculating the deviation of the vehicle speed from the average value. The same can be achieved by calculating the deviation between the vehicle speed detected by the vehicle speed sensor 7 (current vehicle speed) and the vehicle speed detected preceding (not necessarily immediately before).

[0037]

According to the power steering apparatus of the first invention, the steering assist force does not become unstable even when the vehicle speed drops sharply, and there is no sudden change in the steering force even when the fail-safe is activated. Thus, it is possible to realize a highly safe power steering device that quickly returns to normal operation.

According to the power steering apparatus of the second aspect, when the deviation between the control vehicle speed and the vehicle speed detected by the vehicle speed sensor becomes smaller than a predetermined value, the vehicle speed detected by the vehicle speed sensor is set as the control vehicle speed, and the vehicle operates normally. The steering assist force does not become unstable even if the vehicle speed suddenly drops, and even if the fail-safe is activated, there is high safety to return to normal operation promptly without a sudden change in the steering force. A power steering device can be realized.

According to the power steering apparatus of the third aspect, the steering assist force does not become unstable even when the vehicle speed drops rapidly, and the steering force does not change suddenly even when the fail-safe is activated. A highly safe power steering device that quickly returns to normal operation can be realized.

According to the power steering apparatus of the fourth aspect, when the deviation between the control vehicle speed and the vehicle speed detected by the vehicle speed sensor is smaller than a predetermined value, the motor maximum current limit value is set to the motor maximum current when the vehicle is stopped. To the value,
Since the vehicle returns to normal operation, the steering assist force does not become unstable even if the vehicle speed drops suddenly, and even if the fail-safe is activated, the safety returns to normal operation immediately without a sudden change in the steering force. Power steering device with high performance can be realized.

According to the power steering system of the fifth aspect, when the deviation between the control vehicle speed and the vehicle speed detected by the vehicle speed sensor is smaller than a predetermined value, the vehicle speed detected by the vehicle speed sensor is set as the control vehicle speed, and the vehicle operates normally. The steering assist force does not become unstable even if the vehicle speed suddenly drops, and even if the fail-safe is activated, there is high safety to return to normal operation promptly without a sudden change in the steering force. A power steering device can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of one embodiment of a power steering device according to first and second inventions.

FIG. 2 is a flowchart showing an operation for determining a control vehicle speed for steering assist force control of the power steering apparatus according to the first and second inventions.

FIG. 3 is a block diagram showing a schematic configuration of an embodiment of the power steering apparatus according to the third to fifth inventions.

FIG. 4 is a flowchart showing an operation of determining a control vehicle speed and a motor maximum current limit value for controlling a steering assist force of the power steering apparatus according to the third to fifth inventions.

FIG. 5 is a characteristic diagram showing one example of a vehicle speed vs. motor maximum current characteristic of the power steering apparatus according to the third to fifth inventions.

[Explanation of symbols]

 1, 1a microcomputer 2 torque sensor 4 drive circuit 5 motor 7 vehicle speed sensor 19 previous value holding means 20 deviation detecting means 21, 22 control vehicle speed correcting means 23 motor maximum current limiting means

Claims (5)

(57) [Claims] 1. A power steering device for controlling a steering assist force based on a torque detected by a torque sensor and a vehicle speed detected in time series by a vehicle speed sensor, wherein the vehicle speed detected by the vehicle speed sensor and the vehicle speed sensor precede it. Deviation detection means for detecting a deviation from the detected vehicle speed, and control vehicle speed correction means for correcting a control vehicle speed for steering assist force control based on the deviation detected by the deviation detection means,
The control vehicle speed correction means includes means for comparing the deviation detected by the deviation detection means with a first predetermined value indicating a decrease in vehicle speed, and wherein the deviation detected by the deviation detection means is greater than or equal to the first predetermined value. Means for setting the vehicle speed detected in advance as a control vehicle speed, means for comparing the vehicle speed detected by the vehicle speed sensor with a second predetermined value, indicating that the vehicle speed is equal to or higher than the second predetermined value. Means for gradually bringing the control vehicle speed closer to the vehicle speed detected by the vehicle speed sensor when the vehicle is returned to the power steering device. 2. The control vehicle speed correction means further calculates a deviation between the control vehicle speed and a vehicle speed detected by a vehicle speed sensor as a third predetermined value.
Means for comparing with a value, the deviation being smaller than a third predetermined value.
2. The power steering apparatus according to claim 1, further comprising: means for setting a vehicle speed detected by the vehicle speed sensor to a control vehicle speed when the vehicle speed is changed. 3. A power steering device for controlling a current of a motor for assisting a steering force based on a torque detected by a torque sensor and a vehicle speed detected in time series by a vehicle speed sensor. Deviation detecting means for detecting a deviation from a vehicle speed detected by a vehicle speed sensor preceding the vehicle; control vehicle speed correcting means for correcting a control vehicle speed for steering assist force control based on the deviation detected by the deviation detecting means; Motor maximum current limiting means for increasing or decreasing a maximum current limit value of the motor based on the deviation detected by the deviation detecting means, wherein the control vehicle speed correcting means comprises: Means for comparing the first detection value with a first predetermined value indicating that the deviation detected by the deviation detection means is equal to the first predetermined value.
Means for setting a vehicle speed detected in advance as a control vehicle speed when the vehicle speed decreases by a predetermined value or more. When indicating a decrease in vehicle speed above the value,
Means for setting the maximum current limit value of the motor to a motor maximum current value at a vehicle speed detected in advance, means for comparing a vehicle speed detected by a vehicle speed sensor with a second predetermined value, Means for gradually increasing the motor maximum current limit value when the power steering device returns to a predetermined value or more. 4. The motor maximum current limiting means further calculates a deviation between the control vehicle speed and a vehicle speed detected by a vehicle speed sensor .
Means for comparing with a third predetermined value, and wherein the deviation is a third predetermined value.
4. The power steering apparatus according to claim 3, further comprising: means for returning the motor maximum current limit value to the motor maximum current value when the vehicle is stopped when the value becomes smaller . 5. The control vehicle speed correcting means further calculates a deviation between the control vehicle speed and a vehicle speed detected by a vehicle speed sensor as a third predetermined value.
Means for comparing with a value, the deviation being smaller than a third predetermined value.
Since sometimes, claim 3 or 4, characterized in that it comprises a means for the vehicle speed the vehicle speed sensor detects a control vehicle speed
A power steering device as described.