JPH06166377A - Vehicle steering system - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a proper steering feeling in cornering even if the cornering power of the wheels is somewhat unbalanced. According to signals from a steering angle sensor 25 as a steering angle detecting means and a behavior detecting means 37, a cornering power determining means 38 determines presence / absence of an abnormal wheel and its mounting position, and a turning ratio correcting means 39 determines the determination result. The steering ratio is corrected in accordance with the above, and the servo motor 20 executes the steering control according to the corrected steering ratio.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle steering system that detects vehicle behavior and controls the steering system accordingly.

[0002]

2. Description of the Related Art Conventionally, for example, JP-A-60-193771.
As disclosed in the publication, the steering angle of the front wheel that is steered according to the operation of the steering wheel and the steering angle of the rear wheel are set according to the preset steering characteristics, and the rear wheel is set accordingly. There is known a rear wheel steering device of a vehicle configured to steer the vehicle. The steering characteristics are generally stored as a graph corresponding to the vehicle speed, and the rear wheels are steered in a phase opposite to the front wheels during low speed traveling to improve the turning performance of the vehicle, and the rear wheels are operated during high speed traveling. It is set so that the vehicle can be steered in the same phase as the front wheels to improve the running stability of the vehicle.

[0003]

By the way, in the conventional vehicle as described above, for example, the air pressure is insufficient, the wheels are worn, or immediately after the spare tire (temper tire) is replaced. In case of
In other words, when the cornering power is in an unbalanced state, and when it is necessary to continue driving in that state, it will run with wheels that are unbalanced with other things, and it will be a normal driving for the driver. Had a different feeling, and a reduction in steering feeling was unavoidable. In view of the above circumstances, the present invention provides a driver with a steering feeling similar to the case where all the wheels are in a normal balance state with respect to cornering even when the abnormal wheels are mounted.

[0004]

According to a first aspect of the present invention, there is provided a vehicle steering system including a steering mechanism for steering wheels of a vehicle and a control unit for controlling the steering mechanism. The steering angle detecting means, the behavior detecting means for detecting the behavior of the vehicle at the time of turning, and the signals from the steering angle detecting means and the behavior detecting means indicating whether or not there is an abnormality in the cornering power acting on each wheel. According to the cornering power determining means for determining according to this, and if it is confirmed by this cornering power determining means that there is an abnormality in the cornering power of a specific wheel, a turning ratio correcting means for correcting the turning ratio characteristic is provided. is there.

According to a second aspect of the present invention, there is provided a vehicle steering system including a front wheel steering mechanism for steering the front wheels and a rear wheel steering mechanism for steering the rear wheels in conjunction with the front wheel steering mechanism by the front wheel steering mechanism. When the cornering power determination means determines that there is an abnormal wheel with cornering power on the front wheel side, reverse phase correction is performed, and when it is determined that there is an abnormal wheel on the rear wheel side, in-phase correction is performed. It is composed.

According to a third aspect of the present invention, there is provided operating speed changing means for changing the operating speed of the steering mechanism when the cornering power determining means determines that there is an abnormal wheel.

According to the present invention, the yaw rate sensor is provided in the behavior detecting means when the vehicle is steered.

[0008]

According to the invention as set forth in claim 1, in a steering device having a steering mechanism for steering wheels of a vehicle and a control unit for controlling the steering mechanism, a steering angle for detecting a steering angle of the vehicle. The cornering power determination means for determining whether or not the cornering power acting on each wheel is abnormal by the signal from the detection means and the behavior detection means for detecting the behavior of the vehicle at the time of turning, cornering the specific wheel. When it is confirmed that the power is abnormal, the steering ratio correction means for correcting the steering ratio characteristic performs the correction so that the cornering power value due to the specific wheel approaches the normal value.

According to the second aspect of the present invention, the cornering power determining means determines an abnormal wheel with respect to the cornering power, and when it is determined that there is an abnormal wheel on the front wheel side, the rear wheel with respect to the front wheel is detected. By performing the anti-phase correction for correcting the wheel turning angle to the anti-phase side, the understeer characteristic is corrected. Further, when it is determined that there is an abnormal wheel on the rear wheel side, the in-steering characteristic can be corrected by performing the in-phase correction for correcting the steering angle to the in-phase side.

According to the third aspect of the present invention, when the cornering power determining means determines that the abnormal wheels are present, the operating speed changing means sets the maximum operating speed of the drive section of the steering mechanism to a value smaller than the normal value. Change to regulate the operating speed of the steering mechanism.

According to the fourth aspect of the invention, the behavior of the vehicle is detected by detecting the angular velocity about the vertical axis of the vehicle body when the vehicle is steered.

[0012]

FIG. 1 shows an embodiment of a vehicle steering system according to the present invention. This vehicle has a front wheel steering mechanism 3 that steers the left and right front wheels 1 and 2, and a rear wheel steering mechanism 6 that steers rear wheels 4 and 5 in accordance with the steering of the front wheels 1 and 2. .

The front wheel steering mechanism 3 includes a pair of knuckle arm mechanisms 7, 8 and tie rods 9, 10 and a relay rod 11 for connecting the tie rods 9, 10 to each other, and a rack formed on the relay rod 11 (see FIG. A steering mechanism 14 having a steering shaft 13 having a pinion 12 meshing with a steering shaft 13 provided at a lower end portion thereof is provided. Then, the front wheel steering mechanism 3 steers the left and right front wheels 1 and 2 by slidingly displacing the relay rod 11 in the vehicle width direction according to the operation displacement amount of the steering wheel, that is, the steering wheel steering angle. Is configured.

The rear wheel steering mechanism 6 has a pair of knuckle arms 15 and 16 and tie rods 17 and 18, and a relay rod 19 connecting the tie rods 17 and 18 to each other.
And a reduction gear mechanism 21 that transmits the driving force of the servo motor 20 to the relay rod 19 and a servo motor 20 that serves as a drive unit that steers the left and right rear wheels 4 and 5. Then, the rear wheel steering mechanism 6 slides and displaces the relay rod 19 in the vehicle width direction in accordance with the driving force of the servo motor 20, whereby the left and right rear wheels 4, 5 are formed.
Is configured to steer.

Further, the rear wheel steering mechanism 6 is provided with a clutch 22 provided in the reduction gear mechanism 21 and a neutral biasing means including a spring 23 for biasing the relay rod 19 to a neutral position. A safety mechanism 24 is provided. The fail-safe mechanism 24 sets the clutch 22 in the disengaged state to interrupt the transmission of the driving force from the servo motor 20 to the relay rod 11 at the time of a failure in the case where the servo motor 20 or the like fails, so that the spring is stopped. The relay rod 19 is held in the neutral position by the urging force of 23 to bring the rear wheels 4 and 5 into the fail-safe state.

The above-mentioned vehicle has a steering angle sensor 25 as a steering angle detecting means for detecting a steering angle, a vehicle speed sensor 26 for detecting a vehicle speed, and a behavior detecting means 37 for detecting a behavior of the vehicle at the time of steering. Lateral acceleration sensor (lateral G sensor) 30 and yaw rate sensor 31, an encoder 27 that detects the rotational position of the servomotor 20, and a rear wheel steering angle sensor 2 that detects the amount of displacement of the rear wheel relay rod 19.
8 and a controller 29 that outputs a control signal for controlling the rotation of the servomotor 20 according to these detection signals.

The controller 29 sets the steering ratios of the rear wheels 4 and 5 to the front wheels 1 and 2 in accordance with the preset steering characteristics and the vehicle speed detected by the vehicle speed sensor 26, and The target turning angle of the rear wheels 4 and 5 is set based on the rear wheel turning ratio and the steering angle of the steering wheel detected by the rudder angle sensor 25, and a control signal corresponding to the target turning angle is set to the servo motor 20. It has a function to output to. The encoder 27 detects the rotational position of the servo motor 20, and the rear wheel steering angle sensor 28 detects the displacement amount of the relay rod 19 while steering the rear wheels 4, 5. There is.

As shown in FIG. 3, the steering characteristics are set such that the steering ratios .THETA.R / .THETA.F of the rear wheels 4 and 5 to the front wheels 1 and 2 are set to negative values in order to enhance the turning performance of the vehicle at low speed running. Is
The rear wheels 4 and 5 are steered in the opposite phase direction to the front wheels 1 and 2. In addition, as the vehicle speed increases, the steering ratio Θ
R / ΘF changes to a positive value and the rear wheels 4, 5
Are set to be steered in the same phase as the front wheels 1 and 2.

Further, the controller 29 receives signals from steering angle detecting means for detecting the steering angle of the steering wheel and behavior detecting means 37 for detecting the behavior of the vehicle at the time of turning, as shown in FIG. The cornering power determining means 38 for determining whether or not there is an abnormality in the cornering power acting on the wheel and specifying the wheel position, and the result of this determination,
There is also provided a turning ratio correction means 39 for correcting the turning ratio when it is determined that the vehicle is in an abnormal state. Then, by the output of the steering ratio correction means 39, the servo motor 20
The encoder 27, the reduction gear mechanism 21, and the like control the rear wheel steering mechanism 6 to the corrected steering ratio.

The cornering power determination means 38 is
Rudder angle sensor 25 and behavior detection means 3 as rudder angle detection means
By the signal from the lateral G sensor 30 as 7, the integrated value of the output of the lateral G sensor 30 during traveling is stored as a value corresponding to the cornering power for each left and right steering angles, and then the value is compared left and right. And compare. If the cornering powers of all the wheels are in a good balance state, the absolute values of the integrated values at the same steering angle on the left and right are the same, but if the wheels have different cornering powers as compared to other wheels for some reason. If so, there is a difference in the absolute value of the integrated values at the same left and right steering angles, and it is possible to confirm the existence of abnormal wheels having different cornering powers.

In the above case, the difference in cornering power was directly compared with the absolute value of the integrated value at the same steering angle on the left and right, but since there is no data of the lateral G sensor 30 at the desired steering angle, the above absolute value is obtained. If the value cannot be obtained, the difference between the left and right sides can be determined by calculating the absolute value of the integrated value at the desired steering angle value from the neighboring data by calculation and comparing the calculated absolute value. it can.

Generally, when turning, the cornering power of the turning outer wheel is mainly dominant. Therefore, for example, when a wheel with a small cornering power is mounted, the mounting position of the wheel and the turning direction are shown in FIG. Since it is known that such a characteristic is obtained, the absolute value of the cornering power is verified in the controller 29 in the state of various combinations of the stored data described above such as the turning direction and the magnitude of the absolute value. By comparing the result with FIG. 5, the abnormal wheel can be specified.

As described above, the cornering power determining means 38 functions by the signals from the steering angle sensor 25 and the lateral G sensor 30, but even if the yaw rate sensor 31 is used as the behavior detecting means 37, the lateral G sensor 30 is detected. It is possible to determine the presence / absence of abnormal wheels in the same way as when used.
It is also possible to specify the abnormal wheels as shown in FIG.

Therefore, in the practice of the present invention, one or both of the two sensors, the yaw rate sensor 31 and the lateral G sensor 30, may be selected depending on the type of the target vehicle and the situation in which the vehicle is used. Can be implemented using.

As described above, when the presence of the abnormal wheels is confirmed, the operation speed changing means for changing the operation speed of the steering mechanism according to the condition of the vehicle allows the servo motor 20 to further improve the steering feeling. The maximum operating speed VMAX of
The normal maximum operating speed VA is changed to the maximum operating speed VB when there are abnormal wheels. However, the two maximum operating speeds (VA and VB) have a relationship represented by the following equation (1).

VA> VB (1) On the other hand, the turning ratio correcting means 39 which functions in response to the judgment result of the cornering power judging means 38, as shown in FIG.
The final turning ratio K is determined by multiplying the turning ratio ΘR / ΘF determined in step 1 by the correction coefficient α. That is, the final turning ratio K is obtained by the following equation (2).

K = .THETA.R / .THETA.F.times..alpha. (2) This correction coefficient .alpha. Is set so as to correct an imbalanced state due to the fact that wheels having different cornering powers are mounted. The correction is required when traveling at a relatively high speed, and in FIG. 3, the correction is performed in the range where the rear wheel steering ratio ΘR / ΘF is greater than zero, that is, a positive value. More specifically, when the steering ratio is selected in the in-phase direction during high-speed traveling, if correction on the opposite phase side is necessary to correct the imbalance of the cornering power, for example, the correction coefficient α is set to 0. By setting the steering ratio to 0.8, the final steering ratio K becomes 20 in the in-phase direction.
%, On the other hand, when correction is required on the in-phase side, the correction coefficient α is set to 1.2 to further increase the final turning ratio K by 20% in the in-phase direction. Note that normally, this correction coefficient α is prepared in advance with several numerical values for various situations such as the mounting position of the abnormal wheels and the turning direction, and when correction is necessary, the correction coefficient α suitable for the situation is prepared. However, if the correction is unnecessary, the correction can be canceled by setting the correction coefficient α = 1.

In this embodiment, the cornering power value, which is different from the normal value generated when there are abnormal wheels, is corrected so as to approach the normal value. That is, to be more specific with reference to the table shown in FIG. 5, for example, the left wheel A of the front wheel
When there is something abnormal, the cornering power value by the lateral G sensor becomes smaller when turning right and understeer (U / S)
Therefore, in the present embodiment, when the vehicle is making a right turn, the rear wheels are steered to the opposite phase side to the normal phase to increase the cornering power value and correct it so that it approaches the same value when making a left turn, that is, a normal value. Is to do. Further, when the left wheel C of the rear wheels is abnormal, the cornering power value increases during right turn and oversteer (O / S) occurs. Therefore, during this right turn, the rear wheel is steered to the in-phase side than normal. By doing so, the cornering power value is reduced and correction is performed so as to approach the normal value when turning left.

As another method, the method of controlling the normal values in the above table by operating the normal values to some extent to reduce the difference from the non-normal values and the method of this embodiment are used in combination. There are methods, and any method can be implemented in the present invention.

The control operation of the embodiment of the present invention having the above-described functions and configurations will be described with reference to the flow chart shown in FIG. 6. When the power supply of the vehicle is turned on and the function of this flow chart is started, first, The steering angle is read from the steering angle sensor 25 (step S1), the lateral acceleration (lateral G) is then read from the lateral G sensor 30 (step S2), and the yaw rate is further read from the yaw rate sensor 31 (step S3). ) The reading of the data value from each sensor unit for the first time is completed. Then, step S which is a part of the cornering power determination means 38.
The data value of the lateral G sensor 30 already read in 4 is classified and stored for each of the left and right steering angles while performing the processing such as integration as described above, and the data is stored in step S5 as described above. The presence or absence of abnormal wheels having different cornering powers is determined by comparing the left and right steering angles.

If it is determined in step S5 that there is an abnormal wheel, step S6 as the operating speed changing means is performed.
Then, the maximum operating speed VMAX suitable for driving when there are wheels with different cornering powers is set to VB, and then in step S7, using the preset steering ratio characteristics as shown in FIG. The steering ratio is determined according to the signals from the vehicle speed sensor 26 and the steering angle sensor 25. After that, in step S8, under what circumstances the data value that reached the determination that there is an abnormal wheel in step S5 occurred is extracted from the stored data, and the result is displayed as described above. It is determined whether or not the abnormal wheel is the A wheel by collating with the location A column of the abnormal wheel in the table shown in FIG. As a result, if the abnormal wheel is determined to be the A wheel in step S8, step S12 as a part of the turning ratio correction means 39 is performed.
The correction coefficient for correcting when the wheel A is abnormal, that is, for correcting in the opposite phase direction when turning right,
The final steering ratio K is multiplied by the steering ratio determined in step S7.
To decide.

On the other hand, if it is determined in step S8 that the abnormal wheel is not the A wheel, the process proceeds to step S9, and the abnormal wheel is checked against the location B column of the table shown in FIG. Or not. If step S
If it is determined in 9 that the abnormal wheel is the B wheel, the process proceeds to step 13, and the correction coefficient is corrected in step S7 for correction when the B wheel is abnormal, that is, in the opposite phase direction when turning left. The final turning ratio K is determined by multiplying the turning ratio determined in. If it is determined in step S9 that the abnormal wheel is not the B wheel, it is determined in step S10 whether the abnormal wheel is the C wheel. If the abnormal wheel is the C wheel, the same calculation is performed in step S14. When the vehicle is making a right turn, the correction is performed to the in-phase side, and if the result of the determination in step S10 is that it is not the C wheel, it is determined in step S11 that the abnormal wheel is the D wheel, and step S15 In the same manner as above, correction is executed on the in-phase side when turning left.

As a result of the above, when the correction is completed, step S
At 16, the control is executed to the corrected turning ratio,
It provides a well-balanced steering with respect to cornering power.

If it is determined in step S5 that there are no abnormal wheels, the maximum operating speed VMAX is the same as the normal value VA.
On the other hand, as for the turning ratio, on the other hand, the normal turning ratio is determined in step S17 having the same function as step S7, and the correction cancellation calculation process, that is, the correction coefficient α = 1, is multiplied in step S18. Similar to the above, steering control is executed in step S16.

[0035]

As described above, according to the present invention, it is determined whether or not the cornering power acting on each wheel is abnormal, and the steering angle detection means for detecting the steering angle and the behavior detection for detecting the behavior of the vehicle. It is possible to determine the presence or absence of an abnormal wheel related to the cornering power and to specify the position of the wheel by the cornering power determination means that determines in accordance with the signal from the means. Therefore, even if wheels with slightly different cornering powers are mounted, it is possible to provide the driver with a steering feeling similar to driving when all the wheels are in a normal balance state.

Further, in the vehicle in which the present invention is implemented,
Since the unbalanced cornering power of the wheels is eliminated, the frequency of wheel rotation due to uneven wear is reduced, and the variation in the driving characteristics of each vehicle is reduced. The driver can easily and comfortably drive the vehicle even if he / she drives the vehicle, and by having the operating speed changing means for changing the operating speed of the drive part of the steering mechanism, Since the speed is changed, the steering ratio is smoothly controlled and the drive feeling is further improved.

When a yaw rate sensor is used as the behavior detecting means, the detecting means can be realized with a simple structure, and the detection signal is stable and accurate, which is very effective in the practice of the present invention.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view showing an embodiment of a vehicle steering system according to the present invention.

FIG. 2 is a block diagram showing a configuration of a controller of the steering device.

FIG. 3 is a graph showing steering characteristics of rear wheels.

FIG. 4 is a diagram showing wheel positions of a vehicle.

FIG. 5 is an explanatory diagram showing the relationship between the position of the abnormal wheels and the turning direction with respect to the value of cornering power.

FIG. 6 is a flowchart showing a control operation of the controller.

[Explanation of symbols]

 1, 2 front wheels 4, 5 rear wheels 3 front wheel steering mechanism 6 rear wheel steering mechanism 20 servo motor (driving unit) 25 steering angle sensor (steering angle detection means) 37 behavior detection means 38 cornering power determination means 39 steering ratio correction means

Claims (4)

[Claims] 1. A steering apparatus having a steering mechanism for steering wheels of a vehicle and a control unit for controlling the steering mechanism,
The steering angle detecting means for detecting the steering angle of the wheels, the behavior detecting means for detecting the behavior of the vehicle at the time of steering, and the steering angle detecting means for determining whether or not the cornering power acting on each wheel is abnormal. And a cornering power judging means for judging based on a signal from the behavior detecting means, and a steering wheel for correcting the steering ratio characteristic when it is confirmed by this cornering power judging means that there is an abnormality in the cornering power of a specific wheel. A vehicle steering system comprising a ratio correction means. 2. A steering system for a vehicle, comprising: a front wheel steering mechanism for steering front wheels; and a rear wheel steering mechanism for steering rear wheels in conjunction with front wheel steering by the front wheel steering mechanism. The power determination means is configured to perform reverse phase correction when it is determined that there is an abnormal wheel with cornering power on the front wheel side, and to perform in-phase correction when it is determined that there is an abnormal wheel on the rear wheel side. The steering apparatus for a vehicle according to claim 1, wherein: 3. The vehicle according to claim 1, further comprising operation speed changing means for changing the operation speed of the drive portion of the steering mechanism when the cornering power determination means determines that there is an abnormal wheel. Steering device. 4. The vehicle steering system according to claim 1, wherein the behavior detecting means including a yaw rate sensor detects the behavior of the vehicle during steering.