JP2006044505A - Power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power steering device capable of reducing a steering load when making a vehicle traveling in a straight line on a road with crossing gradient. <P>SOLUTION: The power steering device is equipped with a motor generating assist steering torque, and composed of a control amount setting portion 8 setting control amount Ic for controlling the motor according to steering torque of a driver, a crossing gradient detecting portion 1 detecting the crossing gradient of the road on which the vehicle is traveling, a correction control amount setting portion 4 setting a correction control amount Is for controlling the motor according to the detected crossing gradient, an adder 7 adding the control amount Ic and correction control amount Is' with gain corrected, and a controlling portion 9 drive-controlling the motor by the addition value. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a power steering device mounted on a vehicle.

Generally, the power steering apparatus is configured to assist the driver's steering by generating an auxiliary steering torque according to the steering torque at the time of steering.
When the vehicle travels straight, for example, if there is a crossing slope on the traveling road, the vehicle tends to flow toward the lower side of the road. At this time, if the steering wheel is kept at the neutral position, the vehicle cannot travel straight ahead stably. That is, in order to maintain a straight traveling state of a vehicle on a road having a cross slope, the steering wheel must be steered from the neutral position to the higher side of the road.
For example, Patent Document 1 discloses a method for detecting a crossing gradient of a traveling path.
Patent No. 3440765 (Claims, Claim 1)

However, the conventional power steering device is not provided with a function for detecting the crossing gradient and a function for assisting the steering of the driver. For this reason, when the vehicle is going straight on a road with a cross slope, the driver must steer while running straight ahead. On roads where the crossing gradient is continuous, the driver must continue to drive the vehicle while maintaining a steered state for a long time. In particular, when the vehicle speed is high, the generation of auxiliary steering torque is usually limited to stabilize the running. Therefore, a large steering torque must be generated to maintain the steered state, and the steering burden on the driver is large. There was a problem.
Patent Document 1 discloses a method for detecting a cross slope, but does not particularly indicate that the driver's steering is assisted by using the detection result. Although it is conceivable that the detection result of the cross slope is displayed on the monitor and displayed to the driver, for example, the steering burden itself cannot be reduced.
SUMMARY OF THE INVENTION In view of the above-described conventional problems, the present invention has an object to provide a power steering device that enables a vehicle to travel stably on a road with a cross slope and can reduce a driver's steering burden. Yes.

  For this reason, the invention according to claim 1 is a power steering device mounted on a vehicle, and includes an actuator for generating auxiliary steering torque and a control for controlling the actuator in accordance with a steering torque of a driver. A control amount setting means for setting the amount, a cross slope detecting means for detecting the cross slope of the road on which the vehicle is traveling, and a correction control amount for controlling the actuator according to the detected cross slope are set. Correction control amount setting means for controlling, and control means for driving and controlling the actuator by the set control amount and the correction control amount.

  According to a second aspect of the present invention, there is provided offset amount setting means for setting an offset amount for setting an insensitive region for the vehicle speed of the cross slope according to the vehicle speed of the vehicle, and the correction control amount setting means includes: The correction control amount is set based on the detected cross slope and the set offset amount.

  According to a third aspect of the present invention, there is provided gain setting means for setting a gain of the correction control amount in accordance with a vehicle speed of the vehicle, and the control means multiplies the control amount by the set gain. The actuator is driven and controlled according to the control amount.

  According to a fourth aspect of the present invention, the cross slope detecting means is based on the steering torque when the vehicle is in a straight traveling state and the steering torque continues for a predetermined time or more and is a predetermined value or more. The cross slope was calculated.

  According to the first aspect of the invention, the power steering apparatus sets the control amount based on the steering torque, detects the crossing gradient of the road that is running, sets the correction control amount based on the crossing gradient, and performs control. Since the auxiliary steering torque is generated by controlling the actuator by the amount and the correction control amount, the auxiliary steering torque corresponding to the driver's steering torque can be generated on a road having no cross slope. On a road having a cross slope, an auxiliary steering torque corresponding to the cross slope can be generated in addition to the steering torque. Therefore, for example, when a vehicle goes straight on a road with a cross slope, by generating an auxiliary steering torque according to the cross slope, the driver can maintain a steered state with a slight steering torque and maintain a straight running. it can.

  According to the second aspect of the invention, the cross slope offset amount is set according to the vehicle speed, and the correction control amount is set based on the cross slope offset amount and the detected cross slope. When generating the steering torque, the insensitive region of the cross gradient can be adjusted according to the vehicle speed.

  According to the third aspect of the present invention, the gain of the correction control amount is set according to the vehicle speed, and the control means drives and controls the actuator by the correction control amount and the control amount multiplied by the set gain. When generating the auxiliary steering torque according to the cross gradient, the generation amount, that is, the sensitivity of the auxiliary steering torque can be adjusted according to the vehicle speed.

  According to the fourth aspect of the present invention, the cross slope detecting means calculates the cross slope based on the steering torque when the vehicle is traveling straight and the steering torque of a predetermined value or more continues for a certain period of time. The transverse gradient can be calculated by using a torque sensor as the sensor.

Hereinafter, embodiments of the present invention will be described. FIG. 1 is a diagram showing a configuration of a steering system to which a power steering apparatus according to the present invention is applied.
The power steering apparatus shown in FIG. 1 includes a pinion rack mechanism 25, and a steering wheel 21 is coupled to the pinion side of the pinion rack mechanism 25 via a steering shaft 22. When the steering wheel 21 is rotated, the pinion connected thereto is rotated, and the steered wheels 24R and 24L are turned by moving the rack in the left-right direction.
A torque sensor 16 is provided on the steering shaft 22, and the torque sensor 16 detects a steering torque during steering, that is, when the steering wheel 21 is rotated. The detected steering torque is output to an ECU (electronic control unit) 20.
A motor 23 is provided on the pinion side of the pinion rack, and the ECU 20 determines the auxiliary steering torque based on the steering torque from the torque sensor 16 and outputs a drive current Ic ′ corresponding thereto to drive the motor 23. Therefore, at the time of steering, auxiliary steering torque by the motor is applied to the pinion rack mechanism 25 in addition to the steering torque from the driver, so that the driver can perform steering without generating a large steering torque.

  The ECU 20 has a function of detecting a crossing gradient from a running road. When the cross gradient is detected, the ECU 20 outputs the total current of the drive current corresponding to the steering torque and the drive current corresponding to the cross gradient to the motor 23 as the drive current Ic '. As a result, when a crossing gradient is detected, an auxiliary steering torque corresponding to the crossing gradient is generated in the pinion rack mechanism 25. Note that the generation of the drive current corresponding to the cross gradient is limited when the vehicle is traveling straight. Therefore, when the vehicle goes straight on a road with a cross slope, the driver can maintain the steered state only by generating a slight steering torque, and the vehicle can keep the straight traveling state. Next, generation of drive current in the ECU 20 will be described.

FIG. 2 is a block diagram showing functions of the ECU.
The ECU 20 includes a cross gradient detecting unit 1, an offset amount setting unit 2, a subtracter 3, a correction control amount setting unit 4, a gain setting unit 5, a multiplier 6, an adder 7, a control amount setting unit 8 and a control unit 9. is doing.

  The control amount setting unit 8 to which the torque sensor 16 is connected sets an auxiliary steering torque corresponding to the steering torque as a basic operation of the power steering device, so that the motor 23 is controlled based on the steering torque TR detected by the torque sensor 16. A control amount Ic is set. The set control amount Ic is output to the adder 7.

The cross gradient detector 1 detects a cross gradient SLT based on the steering torque TR detected by the torque sensor 16. Details of the detection will be described later. The detected cross slope SLT is output to the positive terminal of the subtractor 3. When the cross gradient SLT is detected, the vehicle speed V and the yaw rate YR are input from the vehicle speed sensor 17 and the yaw rate sensor 18 on the vehicle side, the running state of the vehicle is determined by the steering torque TR, and the vehicle goes straight. When traveling, it is also possible to detect a cross slope.
The offset amount setting unit 2 sets an offset amount SLTo for setting a dead area for the vehicle speed of the cross gradient according to the vehicle speed. The set offset amount SLTo is output to the negative terminal of the subtractor 3.
The subtractor 3 performs subtraction between the cross slope SLT and the offset amount SLTo, and the subtraction value is output to the correction control amount setting unit 4.
The correction control amount setting unit 4 sets the correction control amount Is based on the subtraction value between the cross slope SLT and the offset amount SLTo. The set correction control amount Is is output to the multiplier 6.
The gain setting unit 5 sets the gain SLTr of the correction control amount Is according to the vehicle speed V. This is for adjusting the sensitivity when the auxiliary steering torque is generated according to the cross gradient. The set gain SLTr is output to the multiplier 6.
The multiplier 6 performs a multiplication operation of the gain SLTr and the correction control amount Is. A correction control amount Is ′ that is gain-adjusted for the calculated multiplication value, that is, the correction control amount Is based on the cross gradient, is output to the adder 7.

In the adder 7, the control amount Ic set by the control amount setting unit 8 and the correction control amount Is ′ from the multiplier 6 are added, and the added value is output to the control unit 9.
In the control unit 9, the drive current Ic ′ corresponding to the added value of the correction control amount Is ′ and the control amount Ic is output to the motor 23.

Next, the flow of control in the ECU 20 will be described. FIG. 3 is a flowchart showing a control flow in the ECU.
First, the control amount setting unit 8 reads the steering torque TR from the torque sensor 16 (S1), and sets the control amount Ic of the motor 23 so as to generate a predetermined auxiliary steering torque according to the read steering torque (S2). ). The set control amount Ic is output to the adder 7.
The cross gradient detector 1 reads the vehicle speed V detected by the vehicle speed sensor 17 (S3), reads the steering torque TR from the torque sensor 16 (S4), and reads the yaw rate YR of the vehicle from the yaw rate sensor 18 (S5).
Based on the read vehicle speed V, steering torque TR, and yaw rate YR, the cross slope detector 1 calculates the cross slope SLT of the travel path (S6). The calculation method will be described later.
The offset amount setting unit 2 sets the offset amount SLTo according to the vehicle speed V (S7). For example, as shown in FIG. 4, the offset amount setting unit 2 owns a table storing the relationship between the preset vehicle speed V and the offset amount SLTo, and can be set by searching this table. In FIG. 4, the offset amount decreases as the vehicle speed V increases. Thus, when the auxiliary steering torque is generated according to the crossing gradient, the insensitive region of the crossing gradient becomes smaller as the vehicle speed V increases.

The subtracter 3 performs a subtraction operation between the transverse gradient SLT calculated in step S6 and the offset amount SLTo set in step S7 (S8). The subtraction value is output to the correction control amount setting unit 4.
The correction control amount setting unit 4 determines whether or not the subtraction value is greater than zero (S9). If it is larger, it is determined that the crossing gradient SLT is outside the insensitive region, and the process proceeds to step S10 so as to generate an auxiliary steering torque corresponding to the crossing gradient. Otherwise, it is determined that the crossing gradient SLT is in the dead zone, and the process proceeds to step S14 so as not to generate auxiliary steering torque according to the crossing gradient.

In step 10, the correction control amount setting unit 4 sets the correction control amount Is according to the subtraction value between the cross slope SLT and the offset amount SLTo. For example, as shown in FIG. 5, the correction control amount setting unit 4 has a table storing the relationship between the correction control amount Is and the cross gradient, and can be set by searching this table. The set correction control amount Is is output to the multiplier 6.
The gain setting unit 5 sets the gain SLTr of the correction control amount Is based on the vehicle speed V (S11). For example, as shown in FIG. 6, the gain setting unit 5 owns a table storing the relationship between the vehicle speed V and the gain SLTr, and can be set by searching this table. The set gain SLTr is output to the multiplier 6.

The multiplier 6 multiplies the correction control amount Is set in step s10 and the gain SLTr (S12). The calculated multiplication value, that is, the correction control amount Is ′ obtained by adjusting the gain of the correction control amount Is is output to the adder 7.
The adder 7 adds the control amount Ic set in step S2 and the corrected control amount Is ′ calculated in step S12 (S13). The added value is output to the control unit 9.
The controller 9 outputs to the motor 23 a drive current Ic ′ corresponding to the output of the adder 7, that is, the added value of the correction control amount Is ′ and the control amount Ic, and controls the motor 23 (S14).
If it is determined in step S9 that the crossing gradient SLT is in the dead zone, the auxiliary control torque corresponding to the crossing gradient is not generated, and thus a value of zero is output from the correction control amount 4. At this time, the gain setting unit 5 does not perform gain setting. Therefore, only the control amount Ic set in step 2 is input to the control unit 9, and the drive current Ic ′ corresponding to the control amount Ic is output to the motor 23 (S14).

  As described above, when the vehicle travels, the driver's steering torque TR is detected, the control amount Ic for controlling the motor 23 is set according to the steering torque TR, and the cross gradient SLT is detected. A correction control amount Is ′ for correcting the control amount Ic in accordance with the cross gradient SLT is set, and a drive current Ic ′ is output to the motor 23 by the addition value of the control amount Ic and the correction control amount Is ′. 23 is driven. For this reason, when a crossing gradient is detected, an auxiliary steering torque corresponding to the crossing gradient can be generated. For example, when the vehicle goes straight on a road with a cross slope, the turning state can be automatically held after the driver turns the vehicle so as to keep the vehicle traveling straight. As a result, the vehicle can travel straight ahead stably, and the driver's steering burden can be reduced.

In addition, when generating the auxiliary steering torque according to the cross gradient SLT, when the cross gradient insensitive area is set according to the vehicle speed and it is determined that the cross gradient SLT is in the non-sensitive area, the auxiliary according to the cross gradient is used. Since the steering torque is not generated, the vehicle can be driven stably.
Further, when the cross gradient SLT is detected, the gain is calculated according to the vehicle speed and the gain is adjusted to generate the auxiliary steering torque according to the cross gradient. Therefore, the sensitivity depends on the vehicle speed V. Adjusted. If the sensitivity is low, the vehicle may not be able to maintain the straight traveling state with the auxiliary steering torque corresponding to the cross slope SLT. In this case, the driver may increase the steering torque to compensate for it.

  In the above configuration, since the detection of the cross gradient SLT is based on the steering torque TR detected by the torque sensor 16, when the cross gradient SLT is detected and an auxiliary steering torque corresponding to the cross gradient SLT is generated, the driving is performed. As a result, the steering gradient cannot be detected correctly. In order to prevent this, for example, in the cross slope detecting section 1 shown in FIG. The generated auxiliary steering torque is estimated, and the cross gradient SLT may be detected based on the total value of the estimated value and the steering torque detected by the torque sensor 16.

Next, the detection of the cross gradient in the cross gradient detecting unit 1 will be described.
FIG. 7 is a block diagram showing the configuration of the cross slope detector.
As shown in the figure, the cross gradient detecting unit 1 includes a cross gradient amount calculating unit 11, a multiplier 14, a cross gradient correction ratio calculating unit 12, a cross gradient calculating condition determining unit 13, an output unit 15, and a reference value holding unit 19. Is done.

The cross gradient amount calculation unit 11 calculates a cross gradient amount SLTB of the road surface based on the steering torque TR detected by the torque sensor 16. For example, as shown in FIG. 8, a table storing a correspondence relationship between the road surface cross slope amount SLTB and the steering torque TR is provided, and the cross slope amount SLTB is calculated by searching the table based on the steering torque TR. Although this cross slope amount SLTB can be used as a detected value of the cross slope, in this embodiment, it is detected as a base value that is corrected by the vehicle speed in preparation for detection during high-speed driving. For this reason, the table of FIG. 8 shows the relationship between the steering torque TR at a certain vehicle speed and the cross slope SLTB of the road surface.
The cross slope correction ratio calculator 12 calculates a cross slope correction ratio SLTR for performing correction according to the vehicle speed with respect to the calculated base value of the cross slope SLTB. For example, a table storing the correspondence relationship between the road surface cross slope correction ratio SLTR and the vehicle speed V shown in FIG. 9 is provided, and the cross slope correction ratio SLTR is calculated by searching the table based on the detected vehicle speed V. .

The multiplier 14 multiplies the base value of the calculated cross slope amount SLTB by the calculated cross slope correction ratio SLTR to calculate the cross slope amount SLTB from which the influence of the self-aligning torque component is removed. . Incidentally, the self-aligning torque increases as the vehicle speed increases. Therefore, in the table of FIG. 9, the crossing slope correction ratio SLTR of the road surface is reduced as the vehicle speed V increases. Thereby, it is possible to prevent the determination that the gradient increases as the vehicle speed increases even though the crossing gradient is the same.
The cross slope calculation condition determination unit 13 performs a logical operation based on the steering torque TR, the vehicle speed V, and the yaw rate YR detected by the torque sensor 16, the vehicle speed sensor 17, and the yaw rate sensor 18, and calculates the cross slope based on the steering torque. (Logical operation will be described later with reference to FIG. 10). In other words, the cross gradient calculation condition determination unit 13 causes the output unit 15 to select whether the result multiplied by the multiplier 14 is a gradient or the reference value held in the reference value holding unit 19 is a gradient. Is.
The output unit 15 selects the cross gradient amount SLT calculated from the multiplier 14 based on the determination result of the cross gradient calculation condition determination unit 13 or the reference value zero held in the reference value holding unit 19 to detect the cross gradient. This is output as the value SLT. The detected value SLT of the cross slope is output to the positive terminal of the subtractor 3.

Next, the flow of detecting the cross gradient in the cross gradient detecting apparatus will be described. FIG. 10 is a flowchart showing the flow of detecting the cross gradient.
First. In order to determine whether or not the calculation condition of the crossing gradient based on the steering torque TR is satisfied, in step S21, the crossing gradient calculation condition determination unit 13 reads the vehicle speed V detected by the vehicle speed sensor 17, and a predetermined speed threshold value VEL. And compare. When the vehicle speed V is equal to or higher than the speed threshold VEL (YES), it is determined that the vehicle is traveling at a predetermined speed or higher, and the process proceeds to step S22. Otherwise (NO), the process proceeds to step S30.
In step S22, the cross slope calculation condition determination unit 13 reads the vehicle yaw rate YR detected by the yaw rate sensor 18, and compares the absolute value of the yaw rate YR with the yaw threshold YRD. If the absolute value of the yaw rate YR is equal to or greater than the yaw threshold YRD (YES), it is determined that the yaw rate of the vehicle is near neutral, and the process proceeds to step S23. Otherwise (NO), the process proceeds to step S30.
In step S23, the cross slope calculation condition determination unit 13 reads the steering torque TR detected by the torque sensor 16, and compares the absolute value of the steering torque TR with a predetermined torque threshold value TRQ. If the absolute value of the steering torque TR is equal to or greater than the torque threshold value TRQ (YES), it is determined that the steering torque TR greater than the predetermined value has occurred, and the process proceeds to step S24. If not (NO), the process proceeds to step S30.

In step S24, the cross slope calculation condition determination unit 13 increments a built-in timer, for example. That is, the timer value is added.
In step S25, the cross slope calculation condition determination unit 13 compares the timer value of the timer with the set value S. If the timer value exceeds the set value S, the vehicle travels straight ahead at a predetermined speed or more, and it is determined that a predetermined time has elapsed since the detection of the occurrence of steering torque exceeding the predetermined value. It is determined that the gradient calculation condition is satisfied, and the process proceeds to step S26. When that is not right (NO), it returns to step S1 and the said determination is repeated (return-> start). The reason for considering the timer value in this way is to stably detect the cross gradient.

In step S26, based on the steering torque TR detected by the torque sensor 16, the table for storing the relationship between the road surface gradient SLTB and the steering torque TR shown in FIG. The base value of the cross slope amount SLTB is calculated by searching.
When the auxiliary steering torque corresponding to the crossing gradient is generated, the straight traveling state of the vehicle is maintained by both the auxiliary steering torque by the motor 23 and the steering torque of the driver, so the auxiliary steering torque is estimated as described above. Alternatively, it is directly detected, and the base value of the cross gradient amount SLTB is calculated based on the total value of the auxiliary steering torque and the steering torque. The base value of the calculated cross slope amount SLTB is output to the multiplier 14.
In step S27, the cross slope correction ratio calculation unit 12 searches, for example, a table storing the relationship between the road cross slope correction ratio SLTR and the vehicle speed V shown in FIG. 9 based on the vehicle speed V detected by the vehicle speed sensor 17. Then, the cross slope correction ratio SLTR is calculated. The calculated cross slope correction ratio SLTR is output to the multiplier 14.

In step S28, the multiplier 14 multiplies the base value of the cross gradient amount SLTB from the cross gradient amount calculation unit 11 by the cross gradient correction ratio SLTR to calculate the cross gradient amount SLTB from which the self-aligning torque component has been removed. The calculated cross slope amount SLTB is output to the output unit 15.
In step S29, the output unit 15 selects the cross gradient amount SLTB from the multiplier 14 based on the determination result in the cross gradient calculation condition determination unit 13, and outputs it to the steering control unit 10 as the detected value SLT of the cross gradient. .

  On the other hand, if any of Step S21, Step S22, and Step S23 is determined as “NO”, the process proceeds to Step S30, where the timer value is set to zero. As a result, the cross slope calculation condition determination unit 13 determines that the cross gradient calculation condition based on the steering torque TR is not satisfied, and the output unit 15 steers the reference value zero held in the reference value holding unit 19 in step S11. Output to the control unit 10.

  The crossing gradient is detected as described above, and when the vehicle travels straight at a predetermined speed or higher and the vehicle travels for a predetermined time or longer with the steering torque TR exceeding a predetermined value, the crossing gradient is based on the steering torque TR. Since the cross gradient is calculated and detected, it can be detected without adding a new sensor. Usually, since the power steering apparatus is provided with a high-accuracy torque sensor, it is possible to detect the cross gradient with extremely high accuracy.

It is a figure which shows the structure of the steering system with which the power steering apparatus which concerns on this invention was applied. It is a block diagram which shows the function of ECU. It is a flowchart which shows the flow of control in ECU. It is a figure which shows the relationship between the vehicle speed V and offset amount SLTo. It is a figure which shows the relationship between correction | amendment control amount and a crossing gradient. It is a figure which shows the vehicle speed V and the gain SLTr. It is a block diagram which shows the structure of a cross slope detection part. It is a figure which shows the relationship between the amount of cross gradients of a road surface, and steering torque. It is a figure which shows the relationship between the cross slope correction ratio of a road surface, and a vehicle speed. It is a flowchart which shows the flow of detection of a cross gradient.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cross slope detection part 2 Offset amount setting part 3 Subtractor 4 Correction control amount setting part 5 Gain setting part 6 Multiplier 7 Adder 8 Control amount setting part 9 Control part 16 Torque sensor 17 Vehicle speed sensor 18 Yaw rate sensor 20 ECU
21 Steering wheel 22 Steering shaft 23 Motor (actuator)
24 steered wheels 11 crossing gradient amount calculation unit 12 crossing gradient correction ratio calculation unit 13 crossing gradient calculation condition determination unit 14 multiplier 15 output unit

Claims (4)

A power steering device mounted on a vehicle,
An actuator for generating auxiliary steering torque;
A control amount setting means for setting a control amount for controlling the actuator according to the steering torque of the driver;
Cross slope detecting means for detecting a cross slope of a road on which the vehicle is running;
A correction control amount setting means for setting a correction control amount for controlling the actuator according to the detected transverse gradient;
A power steering apparatus comprising: a control unit that drives and controls the actuator with a set control amount and a correction control amount. In accordance with the vehicle speed of the vehicle, provided an offset amount setting means for setting an offset amount for setting a dead zone for the vehicle speed of the cross slope,
The power steering apparatus according to claim 1, wherein the correction control amount setting means sets the correction control amount based on the detected cross slope and the set offset amount. A gain setting means for setting a gain of the correction control amount according to a vehicle speed of the vehicle is provided,
The power steering apparatus according to claim 1, wherein the control unit drives and controls the actuator based on the control amount and the correction control amount multiplied by a set gain.   The crossing gradient detecting means calculates the crossing gradient based on the steering torque when the vehicle is running straight and the steering torque continues for a predetermined time or more and is a predetermined value or more. The power steering apparatus according to any one of claims 1 to 3.

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