JPH0523988B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an electric motor-driven rear wheel steering device that controls the steering angle of the rear wheels according to the steering angle of the front wheels.

(Prior Art) As a device of this type, the invention shown in FIG. 7 is conventionally known.

This conventional device detects the steering angle of the front wheels 1 with a steering sensor 2 and inputs the signal to a controller 3, which also receives a vehicle speed signal from a vehicle speed sensor 4. .
Then, the controller 3 calculates based on the output signals from the steering sensor 2 and the vehicle speed sensor 4, and operates the drive motor 6 of the hydraulic pump 5 and drives the pulse motor 7 according to the calculated values. The switching valve 8 is switched to drive the power cylinder 9 in a predetermined direction to control its steering direction.

(Problems to be Solved by the Present Invention) As described above, this conventional device uses a hydraulic cylinder as a steering actuator for the rear wheels, so there are problems with the complexity and responsiveness of the hydraulic piping. Furthermore, since the control method determines the steering angle of the rear wheels depending on the vehicle speed and the steering angle of the front wheels, it is not possible to change the steering angle of the rear wheels depending on the driving conditions of the vehicle.

To solve this problem, a device is known that detects the yaw angular velocity of the vehicle and controls the steering angle of the rear wheels according to the yaw angular velocity. The drawback was that the equipment was expensive and complicated.

This invention eliminates the hydraulic equipment for the rear wheels, adopts an electric motor as the steering drive actuator for the rear wheels, and employs means for detecting the axial load of the rack to detect the running conditions of the vehicle, To provide a device which has a simple mechanism and can easily detect accurate running conditions to control the drive of an electric motor.

(Means for Solving Problems) In order to achieve the above object, the present invention specifies the steering angle of the front wheels by moving the side rods of the front wheel steering mechanism in its axial direction, and also specifies the steering angle of the front wheels. The present invention assumes a rear wheel steering system that controls the steering angle of the rear wheels according to the following conditions.

Assuming this device, the axial load acting on the side rod of the front wheel steering mechanism is detected by each sensor such as a strain sensor, pressure sensor, or current sensor, and a signal from any of these sensors or a signal from any of these sensors is detected. a calculation unit that detects the control turning angle of the rear wheels according to a composite signal of the signal and the vehicle speed signal, and a control turning angle signal from the calculation unit and an actual turning angle signal from the actual turning angle sensor. A differential section that detects and outputs the difference between The structure is equipped with a motor drive unit that does this.

(Operation of the present invention) Since the present invention is configured as described above, the load sensor detects the axial load of the rack for switching the front wheels. In this way, the axial load of the rack can be determined as a composite value using factors such as the steering angle, yaw angular velocity, sideslip angle, and vehicle speed. This is detected as an alternative value for the angle.

(Effects of the present invention) As described above, the configuration is such that the yaw angular velocity and front wheel steering angle of the vehicle can be approximately detected by alternatively detecting the axial load using the load sensor. It is not necessary to use a device that separately detects the yaw angular velocity and the front wheel steering angle, which simplifies the configuration, and it is also possible to accurately grasp the driving conditions of the vehicle and use it to control the rear wheel steering angle. Available.

(Embodiment of the Invention) In the first embodiment shown in FIGS. 1 to 4, a rack 12 is provided on the side rod 11 of the front wheel 10, and a pinion 13 is engaged with the rack 12. Since this pinion 13 is connected to a handle 15 via a front wheel steering input shaft 14, when the handle 15 is rotated, the rack 12 moves in a predetermined direction, thereby specifying the steering direction of the front wheels.

When the rack 12 is moved by turning the handle 15 as described above, strain is generated in the axial direction of the rack 12 due to the turning resistance of the front wheel 10 at that time. It is detected by the strain sensor 16 that constitutes the sensor.

Furthermore, this strain sensor 16 is connected to the controller 1.
In addition to the strain sensor 16, this controller 17 is also connected to a vehicle speed sensor 18 and an actual steering angle sensor 20 for the rear wheels 19.

A pinion 22 is connected to the electric motor 21 controlled by the output signal of the controller 17, and the pinion 22 is engaged with a rack 24 provided on a side rod 23 of the rear wheel 19.

Then, the electric motor 21 is driven in accordance with the output signal of the controller 17 to specify the steering direction of the rear wheels 19, and the specific configuration of the controller 17 is as shown in FIG. 2.

That is, the strain sensor 16 and the vehicle speed sensor 1
The output signal from 8 is converted by the vehicle speed signal processing section 25 and the distortion signal processing section 26 into voltages V1 and V2 proportional to the vehicle speed and the axial load of the rack 12, and these signals V1 and V2 are calculated. 27.

This calculation unit 27 calculates the control turning angle of the rear wheels 19 based on both signals V1 and V2, and generates a control turning angle signal.
V5 is output, and the signal V5 is transmitted to the differential amplifier section 28.

Since this differential amplification section 28 is connected to the actual steering angle sensor 20 via the rear wheel actual steering angle signal processing section 29, a voltage proportional to the actual steering angle is applied to the differential amplification section 28.
V4 is input to this differential amplifier section 28.

Then, in the differential amplification section 28, both the signals V5
and V4, and outputs a signal V6 representing the difference and transmits it to the motor drive unit 30, and drives the electric motor 21 until the signal V7 output from the motor drive unit 30 becomes zero.

Therefore, the above-mentioned axial load F of the rack 12
can be approximated by the following equation at vehicle speeds above a certain level where the influence of road resistance becomes small, except when the car is stationary.

F=C1αf−{C2(ψ・/V)}−C3β In the above formula, αf is the steering angle, ψ・ is the yaw angular velocity, β is the sideslip angle, and C1, C2, and C3 are the various aspects of the vehicle. It is a constant determined by the element.

As is clear from the above formula, the above easy 1
If the axial load in step 2 is detected, the yaw angular velocity ψ is fed back, so the yaw angular velocity sensor becomes unnecessary, and since the front wheel steering angle αf is included, the front wheel steering angle sensor is also unnecessary. .

While the vehicle is running, the motor drive unit 30 is driven based on the vehicle speed, the axial load on the rack 12, and the actual steering angle of the rear wheels 19 until V7 becomes zero. For example, the motor 21 is driven until the controlled steering angle and the actual steering angle match, and the rear wheels 19
Determine the steering angle.

At this time, if the load torque is the same, the rotation speed N of the electric motor 21 is proportional to the terminal voltage V7, as shown in FIG.
The larger the difference between V5 and the actual steering angle V4, the more force acts to move the rear wheels 19 to the control position faster.

Then, when the rear wheel 19 moves to the control position and the terminal voltage V7 becomes near zero, the electric motor 21
The brakes will be applied, and a resistance force will always act against the external force from the road surface to maintain the control position.

In addition, in Fig. 3, the vertical axis shows the controlled steering angle V5, and the horizontal axis shows the vehicle speed V1. In addition to showing the characteristics, the relationship z<y<x is established.

In this device, when the vehicle speed is below a certain speed, the rear wheel steering angle is always set to zero and the rear wheels 19 are fixed; I'm trying to make the corners bigger. The reason why the vehicle speed is detected by the vehicle speed sensor 18 is to perform the vehicle speed dependent control described above.

In the second embodiment shown in FIG. 5, the steering mechanism for the front wheels 10 is hydraulic, and the power cylinder 31
A pressure sensor 32 is configured to detect the internal pressure. This pressure sensor 32 constitutes the load sensor of the present invention, and its substantial mechanism is the same as that of the first embodiment.

Further, in the third embodiment shown in FIG.
The steering mechanism is electrically driven, and a current sensor 34 that detects the current flowing through the motor 33 is used as a load sensor. Also in this embodiment, the other configurations are the same as in the first embodiment.

[Brief explanation of the drawing]

Figures 1 to 4 show a first embodiment of the present invention, in which Figure 1 is a control system diagram of the entire vehicle, Figure 2 is a control circuit diagram, and Figure 3 shows control steering angle, vehicle speed,
FIG. 4 is a graph showing the relationship between the rotational speed of the electric motor and the output torque, FIG. 5 is a control system diagram of the second embodiment, and FIG.
The figure is a control system diagram of the third embodiment, and FIG. 7 is a conventional control system diagram. 10...Front wheel, 11...Side rod, 16,
32, 34... Strain sensor as a load sensor, pressure sensor, current sensor, 19... Rear wheel, 20... Actual steering angle sensor, 21... Electric motor, 27... Calculation unit, 28... Differential Amplification section.

Claims (1)

[Claims] 1. In a rear wheel steering device that moves a side rod of the front wheel steering mechanism in its axial direction to specify the steering angle of the front wheels, and controls the steering angle of the rear wheels according to the steering angle of the front wheels, the front wheel The axial load acting on the side rod of the steering mechanism is detected by a sensor such as a strain sensor, pressure sensor, or current sensor, and a signal from any of these sensors or a composite signal of any of these signals and a vehicle speed signal is generated. a calculation unit that detects the control steering angle of the rear wheels according to the calculation unit, and detects and outputs the difference between the control steering angle signal from this calculation unit and the actual steering angle signal from the actual steering angle sensor. and a motor drive section that operates according to the output signal from the differential section and drives the electric motor until the difference between the controlled turning angle and the actual turning angle becomes zero. Features a rear wheel steering device.