JPH1149010A - Steering device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steering device for a vehicle whereby steering reaction force given to a steering wheel is smoothly decreased, an extreme decrease in the steering reaction force due to abnormality of a torque sensor can be avoided, in the steering device for the vehicle with a steering mechanism and steering means mechanically in non-connection. SOLUTION: This constitution is provided with two torque sensors 23, 24 detecting steering torque applied to a steering wheel 2, reaction force motor 25 imparting steering reaction force to the steering wheel 2 in accordance with a detection value of one torque sensor 23, and a reaction force control part 4, in case of the detection value of the torque sensor 23 exceeding a prescribed value, in accordance with a detection value of the other torque sensor 24, driving the reaction force motor 25, also gradually decreasing an upper limit value of an output to the reaction force motor 25.

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 in which steering means and a steering mechanism are mechanically disconnected.

[0002]

2. Description of the Related Art A steering apparatus for a vehicle in which a steering means and a steering mechanism are not mechanically connected to each other is similar to an actuator for assisting steering in a power steering apparatus. An electric motor is provided, and the electric motor is driven based on a detected value of a steering angle of a steering wheel serving as a steering means, thereby performing steering according to steering of the steering wheel.

[0003] The steering wheel has a steering shaft provided on the lower side thereof rotatably held by an appropriate part of the vehicle body. In the middle of the steering shaft, for example, a motion converting mechanism combining a worm gear and a pinion gear is provided. A reaction force motor using an electric motor is connected thereto via an electromagnetic clutch. The reaction force motor acts to apply a force (reaction force) in a direction opposite to the steering direction, which is large or small, to the steering shaft according to the vehicle state such as the reaction force from the road surface to the wheels and the vehicle speed. The steering operation can be performed with a feeling similar to that of a vehicle steering system in which steering means and a steering mechanism are mechanically connected.

Therefore, it is necessary to apply a steering torque against the reaction torque generated by the reaction motor to the rotational steering of the steering wheel, and the steering torque applied to the steering wheel is provided adjacent to the reaction motor. The detected steering torque is used by the detected torque sensor, and is used for failure determination of the torque sensor.

A lower end of the steering shaft is coaxially connected with a torsion spring having one end fixed to an appropriate portion of the vehicle body.
When the rotary steering is stopped, the elasticity rotates the steering shaft to return the steering wheel to the neutral position. This return is necessary for returning the steering wheel in accordance with the return operation of the wheels in the straight traveling direction that occurs on the mechanically unconnected steering mechanism side.

[0006]

In the above-described conventional configuration, when an abnormality is detected in the detected value of the torque sensor, the electromagnetic clutch is disengaged and an abnormal reaction force of the reaction motor is not applied to the steering wheel. It is like that. However, since the electromagnetic clutch is disengaged, there is a problem that the steering reaction force is only the reaction force of the instantaneous twisting and the driver excessively turns the steering wheel.

If the detected value of the torque sensor at the time of detecting the abnormality is, for example, a disturbance and there is no abnormality in the torque sensor, the detected value of the torque sensor is monitored for a predetermined time, and the detected value is determined. When the steering reaction force is within the predetermined range, the steering reaction force is restored by the operation opposite to the above, but this time, the steering reaction force increases instantaneously, so the driver turns the steering wheel. There was a problem that it became difficult.

The present invention has been made in view of such circumstances, and when the detected value of the torque sensor exceeds a predetermined value, it is determined that the torque sensor is abnormal, and the upper limit of the drive current to the reaction motor is set. To provide a vehicle steering device capable of smoothly reducing a reaction force applied to a steering wheel by gradually decreasing a value thereof, thereby avoiding an extreme decrease in a steering reaction force due to an abnormality in a torque sensor. Aim.

Another object of the present invention is that the above-described abnormality detection is abrupt due to disturbance or the like, and when no abnormality is recognized in the torque sensor, the upper limit value of the drive current to the reaction motor is gradually increased. In this case, the reaction force applied to the steering wheel is smoothly increased by returning to the normal reaction force control state to avoid an extreme increase in the steering reaction force when the reaction force control is restored. .

[0010]

According to a first aspect of the present invention, there is provided a steering apparatus for a vehicle, wherein the steering mechanism is mechanically disconnected from the steering mechanism, and the steering mechanism is steered according to a steering amount of the steering means. Steering control means to be performed, and a steering device for a vehicle comprising means for urging the steering means in a neutral direction, wherein two steering torque detecting means for detecting a steering torque applied to the steering means, A reaction force actuator that applies a force in a direction opposite to steering to the steering means in accordance with a detection value of the steering torque detection means, and a detection value of the one steering torque detection means or a value related thereto exceeds a predetermined value In case,
And a reaction force control means for driving the reaction force actuator in accordance with a detection value of the other steering torque detection means and for gradually decreasing an upper limit value of an output to the reaction force actuator.

A vehicle steering system according to a second aspect of the present invention is the vehicle steering system according to the first aspect, wherein the reaction force control means determines whether the value detected by the one steering torque detection means or a value related thereto is a predetermined value. When the time is within a predetermined range, the upper limit value of the output to the reaction force actuator, which is gradually decreased, is gradually increased.

According to the vehicle steering system of the first invention,
Two steering torque detecting means are provided, and when the detected value of one of the steering torque detecting means or a value related thereto exceeds a predetermined value, it is determined that the steering torque detecting means is abnormal, and the other steering torque detecting means is detected. An extreme decrease in the steering reaction force can be suppressed by gradually decreasing the upper limit of the output to the reaction force actuator while driving the reaction force actuator according to the detection value of the means.

According to the vehicle steering system of the second aspect,
In the vehicle steering system according to the first invention, when the detected value of the one steering torque detecting means or a value related thereto is within a predetermined range for a predetermined time, abnormal detection from the steering torque detecting means is performed. The value is abrupt due to a disturbance or the like, and it is determined that there is no abnormality in the steering torque detecting means. Can be suppressed.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings showing the embodiments. FIG. 1 is a block diagram showing a configuration of a main part of a vehicle steering system according to the present invention.

In the vehicle steering system according to the present invention, a steering mechanism 1 for causing a pair of steering wheels 10, 10 arranged on the left and right sides of a vehicle body to perform a steering operation, and the steering mechanism 1 Steering wheel 2 as mechanically uncoupled steering means
And a steering control unit 3 and a reaction force control unit 4 using different microprocessors.
In response to the steering, the steering control unit 3 drives a steering motor 17 as an actuator disposed on the steering mechanism 1 to operate the steering mechanism 1 and to control the reaction force according to the steering and the state of the vehicle. The unit 4 drives a reaction motor 25 composed of an electric motor disposed on the steering wheel 2 side, and applies a steering reaction force to the steering wheel 2.

The steering mechanism 1 is provided in the left-right direction of the vehicle body, and has both ends of a steering shaft 11 which moves in the axial direction, and knuckle arms 12, 12 for supporting the left and right wheels 10, 10.
Are connected by separate tie rods 13, 13, and by moving the steering shaft 11 in both the left and right directions, the tie rods 13, 13 are moved.
Push and pull the knuckle arms 12, 12 through 13,
The steering wheel 10 is steered left and right, and the steering is performed by a steering motor 17 provided in the middle of the steering shaft 11.
Is converted into the axial motion of the steering shaft 11 by a motion converting mechanism comprising a combination of a gear and a ball screw.

A tie rod 13 composed of a linear sliding potentiometer spans a connecting portion between the one tie rod 13 and the steering shaft 11 and a steering shaft housing 14 which supports the steering shaft 11 movably in the axial direction. A displacement sensor 15 is provided, and a tie rod 1 for the steering shaft housing 14 is provided.
3 is detected in the axial direction. The detection result is given to the steering control unit 3 and is converted into a steering angle by performing a predetermined calculation.

In the middle part of the tie rods 13 on both the left and right sides, an axial force sensor 16 using a strain gauge,
16 is attached, and the axial force (tensile force or compressive force acting in the axial direction) of the tie rods 13, which changes due to the reaction force of the road surface, is detected. The detection result is given to the steering control unit 3. Note that the axial force sensors 16 and 16 are used when one of the wheels 10 is riding on a curb or when one of the wheels 10
The tie rods 13 are provided on the left and right sides in order to detect a state in which the reaction force between the left and right wheels 10 and the road surface is different from each other, for example, when the vehicle is in a groove.

The steering wheel 2 is provided with a steering shaft 20 protruding below the steering wheel 2, and the steering shaft 20 is rotatably supported by an appropriate portion of the vehicle body via a steering shaft housing (not shown). At the lower end of the steering shaft 20, a torsion bar 21 whose one end is fixed to an appropriate part of the vehicle body is coaxially connected.
By rotating 0, the steering wheel 2 is returned to the neutral position.

In the middle of the steering shaft 20, there is provided a motion converting mechanism comprising a combination of a worm gear and a pinion gear, and a reaction motor 25 comprising an electric motor.
Are connected via an electromagnetic clutch 26 at the output shaft. The reaction force motor 25 mainly includes the axial force sensors 16 and 1
6, a force (reaction force) in a direction opposite to the steering direction, which becomes large or small in accordance with the level of the road surface reaction force based on the output of the vehicle 6 or the level of the traveling speed (vehicle speed) of the vehicle, is included in Accordingly, the operation is applied to the steering wheel 2 so that the driver can simulate the road surface reaction force. The electromagnetic clutch 26 is provided for separating the driving force of the reaction force motor 25 from the steering wheel 2 when the reaction force motor 25 or its drive circuit is abnormal.

Therefore, it is necessary to apply a steering torque against the reaction force generated by the reaction force motor 25 to the rotational steering of the steering wheel 2, and this steering torque is applied to the steering shaft 2.
0, a torque sensor 23 using a potentiometer provided adjacent to the motion converting mechanism of the reaction force motor 25,
24. The torque sensors 23, 24
Are two systems, one of the torque sensors 23 is a main sensor that is usually used, and the other is a main sensor.
Reference numeral 4 is used as a backup when the torque sensor 23 fails, and the detection results of the torque sensors 23 and 24 are given to the steering control unit 3 via the reaction force control unit 4.
Note that the detected steering torque is transmitted to the torque sensors 23 and 2.
4 is used for failure determination.

The steering angle of the steering wheel 2 is detected by a steering angle sensor 22 using a potentiometer attached to a steering shaft 20, and the detection result is given to a steering control unit 3.

As described above, the steering control unit 3 is provided with the steering state actually occurring on the steering mechanism 1 side as inputs from the displacement sensor 15 and the axial force sensors 16, 16. The steering state of the steering wheel 2 is given as an input from the steering angle sensor 22, and the magnitude and direction of the reaction force applied in accordance with the steering of the steering wheel 2 are determined by the torque sensor 23, 24 from the reaction force control unit. 4 is provided.

Further, a vehicle speed sensor 5 for detecting the running speed of the vehicle, a yaw rate sensor 6 for detecting an angular velocity around an axis perpendicular to the vehicle body, ie, a yaw rate, generated when the vehicle turns, A lateral acceleration sensor 7 for detecting a lateral acceleration and a longitudinal acceleration sensor 8 for detecting a longitudinal acceleration with respect to the vehicle body are respectively provided at appropriate portions of the vehicle body. Input terminal.

The steering control unit 3 calculates a target steering angle according to the steering angle given from the steering angle sensor 22, and outputs a vehicle speed given from the vehicle speed sensor 5, a yaw rate given from the yaw rate sensor 6, and a lateral acceleration sensor. The target steering angle is corrected in accordance with the lateral acceleration given by the sensor 7 and the longitudinal acceleration given by the longitudinal acceleration sensor 8.
The steering motor 17 is driven such that the actual steering angle given by the controller is equal to the corrected target steering angle.

Further, the steering control unit 3 calculates a target reaction force in accordance with a detection value of an axial force sensor 16, 16 for detecting a road surface reaction force actually applied to the steering wheels 10, 10 during steering. After the calculation, the target reaction force is corrected according to the detection values of the vehicle speed sensor 5, the yaw rate sensor 6, the lateral acceleration sensor 7, and the longitudinal acceleration sensor 8, and the corrected target reaction force is given to the reaction force control unit 4.

The reaction force control unit 4 drives the reaction force motor 25 in accordance with the target reaction force given by the steering control unit 3 and simulates the road surface reaction force to the steering wheel 2 to thereby control the steering wheel 2. In addition, steering can be performed with a feeling similar to that of a general steering device (connected steering device) in which the steering mechanism 1 is mechanically connected.

FIG. 2 is a flow chart showing the control contents of the reaction force control unit 4 accompanying the control of the steering reaction force according to the present invention. FIG. 3 is a graph showing a change in the upper limit value of the motor current to the reaction force motor 25 due to this control, in which the vertical axis represents the motor current upper limit value of the reaction force motor 25, and the horizontal axis represents time. I have.

First, the detected value of the main-side torque sensor 23 is fetched (step 1), and it is confirmed whether or not the detected value exceeds a predetermined range (step 2). If it is within the predetermined range, the torque sensor 23 on the main side
Is determined to be "normal", the reaction motor 25 is driven based on the detected value (step 3), and the process ends (normal control period).

If it exceeds the predetermined range in step 2, it is determined that the torque sensor 23 on the main side is "abnormal", and the detection value of the torque sensor 24 on the sub side is taken in this time (step 4). ). Then, a motor current is applied to the reaction force motor 25 based on the detected value to drive the reaction force motor 25 (step 5), and the preset upper limit value of the motor current is reduced by a predetermined amount (step 6) (control stop preparation period). .
Next, it is confirmed whether or not the reduced upper limit has reached a predetermined value (step 7). When the upper limit has reached the predetermined value, the electromagnetic clutch 26 is turned off and the driving force of the reaction motor 25 is reduced by the steering wheel. 2 (step 8) (control suspension period). If the predetermined value is not reached in step 7, the operations of steps 6 and 7 are repeated.

In the return operation, after the abnormality detection operation up to step 8, the acquisition of the detection value of the torque sensor 23 on the main side is started again (step 9), and this detection value is determined by the number of sampling times corresponding to a predetermined time. In the meantime, it is confirmed whether or not a predetermined range is exceeded (step 10). If it is within the predetermined range, it is determined that the torque sensor 23 on the main side is "abnormal (normal)", and the upper limit value of the motor current is increased by a predetermined amount (step 11) (control return period). ). If it is determined in step 10 that the value exceeds the predetermined range, it is determined to be “abnormal” and the operations in steps 9 and 10 are repeated.

Next, it is confirmed whether or not the upper limit value has reached the predetermined value in the original normal control as described above (step 1).
2) If the value has reached the predetermined value, the process ends (normal control period). If not, the operations of steps 11 and 12 are repeated.

The detected value of the steering torque is preliminarily obtained from both the main-side torque sensor 23 and the sub-side torque sensor 24, and the detected value of the main-side torque sensor 23 is not limited to the above configuration. May be determined by comparing with the detection value of the torque sensor 24 on the sub side. In the case of such a configuration, when it is determined that the detection values of both the torque sensors 23 and 24 are abnormal, or when it is not possible to determine whether the detection value of either of the torque sensors 23 and 24 is abnormal. , Reaction motor 25
It is preferable to reduce the motor current to a predetermined rate.

Further, if the reaction force control unit 4 fails, a problem that an appropriate motor current cannot be given to the reaction force motor 25 may occur. In such a case, FIG. By configuring the inside of the reaction force control unit 4 as shown, a failure of the reaction force control unit 4 can be accurately diagnosed, and an operation such as stopping the driving of the reaction force motor 25 can be performed. .

FIG. 4 is a block diagram showing the structure of the reaction force control unit 4. The reaction force control unit 4 determines the magnitude (current value) of a motor current applied to the reaction force motor 25 based on the target reaction force given from the steering control unit 3, and the reaction force motor 25 is driven by the motor current. CPU 41 for calculating the direction (drive direction), the reaction motor drive circuit 42 for energizing the reaction motor 25 according to the current value and the drive direction calculated by the CPU 41, and the actual output of the reaction motor drive circuit 42. Motor current detection circuit 43 for detecting the current value and the driving direction of the motor,
CPU 41 based on the current value and driving direction detected by
And a CPU monitoring unit 44 that monitors the CPU.

The CPU 41 controls the reaction motor 2 including the driving direction based on the target reaction force given by the steering control unit 3.
5 is calculated, and the actual current value provided from the motor current detection circuit 43 is used as a feedback value to correct the target current value and output it to the reaction force motor drive circuit 42.

The reaction motor driving circuit 42 energizes the reaction motor 25 in accordance with the corrected target current value supplied from the CPU 41 and its driving direction. In addition, the reaction force motor drive circuit 42 can forcibly stop energization of the reaction force motor 25 when the CPU 41 is abnormal, based on a control stop signal from the CPU monitoring unit 44.

The motor current detecting circuit 43 detects an actual current value and a driving direction which are outputs from the reaction force motor driving circuit 42, and outputs a detection result to the CPU monitoring section 44 and the CPU 41.

The CPU monitoring unit 44 determines the actual current value and the driving direction given from the motor current detection circuit 43,
It is determined whether or not the CPU 41 is operating normally based on a target reaction force given from the steering control unit 3 as an input to the U41, and a current value and a driving direction output from the CPU41.

FIG. 5 is a flowchart showing the control contents of the CPU monitoring unit 44 accompanying the monitoring of the CPU 41. Starting with the input of the target reaction force from the steering control unit 3, first, the input target reaction force is fetched (step 1), and it is confirmed whether or not the fetched target reaction force is equal to or more than a predetermined value. (Step 2) If the value is equal to or more than the predetermined value, the actual driving direction provided by the motor current detection circuit 43 is taken (Step 3). Then, it is confirmed whether or not the driving direction of the reaction force motor 25 according to the target reaction force taken in Step 1 is opposite to the actual driving direction taken in Step 3 (Step 4). Are the same,
When the CPU 41 determines that the state is “normal”, the process ends. If the driving direction is reversed in step 4, CP
When U41 is determined to be "abnormal", a control stop signal is output to the reaction force motor drive circuit 42 (step 5), and the supply of power to the reaction force motor 25 by the reaction force motor drive circuit 42 is stopped.

On the other hand, if the current value is lower than the predetermined value in step 2, the actual current value supplied from the motor current detection circuit 43 is taken in (step 6), and it is confirmed whether or not the current value is higher than the predetermined value. (Step 7) If the value is equal to or more than the predetermined value, the operation of Step 5 is performed, and if the value is less than the predetermined value, the operation is ended.

With the above configuration, when the target reaction force from the steering control unit 3 is less than the predetermined value, when the actual current value is equal to or more than the predetermined value, or when the target reaction force from the steering control unit 3 When the force is equal to or greater than a predetermined value, the driving direction based on the target reaction force is
When any one of the conditions in the case where the driving direction is opposite to the actual driving direction is satisfied, the CPU 41 determines that there is an abnormality and diagnoses that the reaction force control unit 4 cannot perform normal reaction force control. it can. Then, based on the diagnosis result, the energization of the reaction force motor 25 by the reaction force motor drive circuit 42 is stopped, or the drive control of the reaction force motor 25 by the steering control unit 3 instead of the reaction force control unit 4 is performed. By taking a safety process such as starting, a safer vehicle steering system can be configured.

[0043]

As described above in detail, the vehicle steering system according to the present invention includes two steering torque detecting means, and the detected value of one of the steering torque detecting means or a value related thereto is a predetermined value. If it exceeds, it is determined that the steering torque detecting means is abnormal, and the upper limit of the output to the reaction force actuator is gradually reduced while driving the reaction force actuator according to the detection value of the other steering torque detection means. By doing so, an extreme decrease in the steering reaction force can be suppressed.

If the detected value of the one steering torque detecting means or a value related thereto is within a predetermined range for a predetermined time, an abnormal detected value from the steering torque detecting means is determined by disturbance or the like. It is sudden, it is determined that there is no abnormality in the torque sensor, and by gradually increasing the upper limit value of the output to the reaction force actuator that is gradually decreased, it is possible to suppress an extreme increase in the steering reaction force, etc. The present invention has excellent effects.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a main part of a vehicle steering system according to the present invention.

FIG. 2 is a flowchart showing control contents of a reaction force control unit accompanying control of a steering reaction force according to the present invention.

FIG. 3 is a graph showing a change in an upper limit value of a motor current to a reaction motor according to the control of FIG. 2;

FIG. 4 is a block diagram illustrating a configuration of a reaction force control unit.

FIG. 5 is a flowchart showing the control contents of a CPU monitoring unit when monitoring the CPU.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 steering mechanism 2 steering wheel 3 steering control unit 4 reaction force control unit 5 vehicle speed sensor 6 yaw rate sensor 7 lateral acceleration sensor 8 longitudinal acceleration sensor 11 steering shaft 12 knuckle arm 13 tie rod 14 steering shaft housing 15 displacement sensor 16 axis Force sensor 17 Steering motor 20 Steering shaft 21 Torsion 22 Steering angle sensor 23, 24 Torque sensor 25 Reaction motor 26 Electromagnetic clutch

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Akio Hayama 3-8-8 Minamisenba, Chuo-ku, Osaka City, Osaka Prefecture Inside Koyo Seiko Co., Ltd. (72) Inventor Yutaka Kawaguchi 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Inside the company

Claims (2)

[Claims] A steering mechanism mechanically disconnected from the steering mechanism; a steering control means for causing the steering mechanism to perform steering according to a steering amount of the steering means; A steering device for a vehicle, comprising: two steering torque detecting means for detecting a steering torque applied to the steering means; and a steering value corresponding to a detection value of one of the steering torque detecting means. A reaction force actuator that applies a force in the direction opposite to the steering, and a detection value of the one steering torque detection means or a value related thereto, when a detection value exceeds a predetermined value, according to a detection value of the other steering torque detection means. And a reaction force control means for driving the reaction force actuator and gradually reducing an upper limit value of an output to the reaction force actuator. 2. The reaction force control means according to claim 1, wherein the detection value of said one steering torque detection means or a value related thereto is within a predetermined range for a predetermined period of time, and said reaction force control means is adapted to gradually reduce said reaction force actuator. 2. The vehicle steering system according to claim 1, wherein the upper limit of the output of the vehicle is gradually increased.