JPS6177570A - Four-wheel steering device for car - Google Patents

Abstract

PURPOSE:To ensure required torque independently of the temperature change of a stepping motor that change the steering ratio of front and rear wheels by detecting the temperature of the stepping motor and changing the driving pulse frequency of the stepping motor. CONSTITUTION:A steering ratio sensing means 29 that detects the steering ratio is mounted on a steering ratio change mechanism 22 and a thermosensor 6 that detects the temperature is mounted on a stepping motor 5 that varies the steering ratio. The steering ratio signal and the temperature signal obtained from the sensing means 29 and the motor 6 are input to a control circuit 24. The control circuit 24 receives these signals and performs the correction control of the steering ratio and the control of the driving pulse frequency issued to the stepping motor 5.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a seven-wheel steering system for a vehicle.

(Prior art) Regarding a wheel steering device that controls the steering of the rear wheels in accordance with the steering of the front wheels of a vehicle, for example, Japanese Patent Application Laid-open Sho, f5P-♂
As described in Publication No. 27', a ring gear of a differential gear is engaged with a pinion of a steering shaft that steers the front wheels, and one side gear of the differential gear is connected to a motor, and the other side gear is connected to a motor. Techniques are known in which a motor is connected to a rear wheel steering shaft and controlled with respect to the steering direction and angle of the front wheels to change the steering phase and steering ratio of the front and rear wheels.

By the way, as a motor that changes the steering ratio as mentioned above,
Using a stepping motor allows highly accurate steering ratio control. However, when the motor temperature of this stepping motor increases due to an increase in outside temperature, etc., its dynamic torque decreases, making it impossible to obtain the necessary torque for variable steering ratio, resulting in a decrease in control accuracy. There is.

(Object of the Invention) The present invention provides a wheel steering system in which the steering ratio of the front and rear wheels is changed using a stepping motor, in which the output torque of the stepping motor is required to control the steering ratio regardless of changes in motor temperature. to ensure that you are able to do so without
This aims to improve the reliability of steering ratio control.

(Structure of the Invention) As shown in FIG. 1, in the vehicle 1, the rear wheels 6 are steered in accordance with the steering of the front wheels 2, and the steering ratio is determined by a stepping motor 5 based on a signal from the control unit 4 according to the driving state. The operation changes between opposite phases and the same phase. and,
The control section 4 includes a drive pulse frequency generation section 7 that receives an output from a thermosensor 6 that detects the temperature of the stepping motor 5 and varies the frequency of drive pulses for the stepping motor 5.

(Example) Hereinafter, an example of the present invention will be described based on FIGS. Note that the same reference numerals are used for components in the embodiment that correspond to those shown in FIG.

One embodiment/example is shown in FIGS. 2 to 7, and is an example in which the steering of the front wheels 2 is mechanically transmitted to the rear wheels 3.

First, the left and right front wheels 2, 2 are connected to both ends of a relay rod 11 via a knuckle arm 9.9 and a tie rod 10.10. A shaft 13 from a handle 12 is connected to the relay rod 11 by meshing with a rack 14 and a pinion 15, and when the handle 12 is rotated, the relay rod 11 moves left and right, and the left and right front wheels 2 are steered. It is supposed to be done.

On the other hand, the left and right rear wheels 6 and 3 also have knuckle arms of 16°16,
It is connected to both ends of a relay rod 18 via tie rods 17, 17, and is steered by shifting the relay rod 18 from side to side.

This relay rod 18 moves in conjunction with the movement of the front wheel side relay rod 11, and the movement is still assisted by hydraulic pressure.

Specifically, the front end of an operating rod 19 extending in the front-rear direction is connected to the relay rod 11 on the front wheel side by engaging a rack 20 and a pinion 21, and the rear end of this operating rod 19 is connected to the relay rod 11 on the front wheel side. Steering ratio changing mechanism 2 that changes the steering ratio
The relay rod 18 on the rear wheel side is connected to the control rod 23 via the relay rod 2. The control rod 23 slides left and right with a determined steering ratio, so that the rear wheels 6 are steered.

The steering ratio is changed by operating the stepping motor 5, and the operation of the stepping motor 5 is controlled by a control circuit 24 that outputs a control signal in accordance with the output from a vehicle speed sensor 8 that detects the vehicle speed. It is now possible to do so. Furthermore, a steering ratio detection means 29 for detecting the steering ratio is attached to the steering ratio changing mechanism 22, and a thermosensor 6 for detecting the stepping motor 5 (7) and motor temperature is attached.
A steering ratio signal and a temperature signal are respectively output to the control circuit 24, and the control circuit 24 receives these signals to correct the steering ratio and adjust the drive pulse frequency to be sent to the stepping motor 5. I'm trying to keep it under control. The control circuit 24 also includes an ignition switch 25.
A power source 26 is connected via the power source 26.

The relay rod 18 on the rear wheel side passes through a power cylinder 27 fixed to the vehicle body, and the inside of the power cylinder 27 is divided into two hydraulic chambers 3Qa and 30b by a piston 28 fixed to the relay rod 18. Both hydraulic chambers 30
a and 30b are connected to a control valve 66 via oil pipes 31 and 32, and an oil supply pipe 65 and an oil return pipe 66 from the reservoir/reservoir 34 are connected to the control valve 66. The control valve 66 detects the direction of movement of the control rod 23 and connects the oil supply pipe 35 to the hydraulic chamber 30a according to the direction of movement.

An oil return pipe 66 is connected to one side of the hydraulic chamber 60a.

30b, and controls the hydraulic pressure from the oil pump 67 installed in the oil supply pipe 35 to a pressure corresponding to the transfer force of the control rod 23. The shifting force of the relay rod 18 and the tabs assist the steering force of the rear wheels 3, 3.

The oil pump 37 is driven by an engine, and a relay rod 18 is installed in the hydraulic chambers 3Qa and 30b.
Springs 38 and 38 are interposed to bias the rear wheels to a neutral position, that is, a position where rear wheel steering is zero.

The specific configuration of the steering ratio changing mechanism 22 will be explained based on FIG. , orthogonal line ℃2 perpendicular to 1
A holder 4 rotatably supported on the vehicle body 39 about
0, and a swinging arm 41 is swingably held in this holder 40 by a swinging shaft 42. The swing shaft 42 is located at the intersection of the movement axis 21 and the orthogonal line 22, and its swing axis 3 extends in a direction perpendicular to the orthogonal line 22.

A connecting rod 4 is connected to the control rod 23.
One end of 6 is connected by a ball joint 44, and
The other end of this connecting rod 46 is connected to the tip of the swing arm 41 by a ball joint 45. The tip of a rotation imparting arm 47 having a rotation shaft 46 on the movement axis 21 is connected to this connecting rod 43 via a ball joint 48, and an operating rod 19 extending from the front wheel side relay rod 11 is connected to the connecting rod 43. is the bevel gear 49°5 with respect to the rotating shaft 46.
They are connected by 0 mesh. The rotation imparting arm 47 is fitted into a cylinder 51 that is integrated with the rotation shaft 46, and is allowed to move forward and backward in a direction perpendicular to the rotation shaft 46.

Then, the stepping motor 5 of the steering ratio changing mechanism 22
A worm 52 is provided on the output shaft of the holder 40, and this worm 52 meshes with a worm wheel 56 provided on the rotating shaft of the holder 40, and the υ steering ratio is changed by the operation of the stepping motor 5. Further, the steering ratio is detected from the rotation angle of the holder 40 by a steering ratio detection means 29 attached to the holder 40.

That is, in the steering ratio changing mechanism 22, the front wheels 2
The steering is transmitted to the swing arm 41 via the actuating rod 19, the rotation imparting arm 47, and the connecting rod 46, and the swing arm 41 swings (rotates) about the swing axis 25.

When the rotation angle of the holder 40 is set by the stepping motor 5, this swing axis g3 is set to the controller 1 and 2.
When it is aligned with the movement axis 2↑ of 6, the swing arm 4
1 is in a plane perpendicular to the movement axis 21, and even if the front wheel 2 is steered, no force is generated to move the control rod 23 via the connecting rod 46, so the rear wheel 6 Not steered (steering ratio is zero).

On the other hand, due to the operation of the stepping motor 5, the swing axis 23
As shown in FIG. 7, when the lower right side is tilted toward the axis of movement λ1, the swing locus of the tip of the swinging arm 41 is aligned with the axis of movement λ1.
The swinging arm 41 is tilted relative to the
Due to the rocking, a force is generated that moves the connecting rod 43 and the center control rod 26 from side to side.
The vehicle is steered in the same phase as the vehicle. If the swing axis 23 is still tilted in the opposite direction, the rear wheels 3 are steered in the opposite phase. In other words, the stepping motor 5 rotates the holder 40 along the swing axis! ;
By changing the inclination angle of V and 5, the swing locus of the swing arm 41 is changed, and the turning angle of the rear wheels 6 relative to the turning angle of the front wheels 2 is changed.
This means changing the steering ratio between negative (opposite phase) and positive (same phase).

In the case of this example, the holder 40 has arms 54 and 54 that support both ends of the swing shaft 42 and are connected in a U-shape, and the arms 54 and 54 abut the base ends of the arms 54 and 54 on the vehicle body side. A stopper 55,55 is provided to restrict the rotation angle of the swing shaft 42.

The configuration of the control system that controls and corrects the steering ratio change and controls the frequency of the stepping motor drive pulse is shown in FIG.

In the same control button, the control unit 4 includes a characteristic switching means 56 that receives a signal from the vehicle speed sensor 8 and outputs a steering ratio characteristic switching signal (vehicle speed signal), and a characteristic switching means 56 that receives a signal from the vehicle speed sensor 8 and outputs a steering ratio characteristic switching signal (vehicle speed signal), and receives this characteristic switching signal and outputs a control signal for rear wheel steering. A turning amount calculating section 57 outputs the output, a motor temperature calculating section 58 calculates the temperature of the stepping motor 5 from the output of the thermosensor B, and a stepping motor receives the outputs of the turning amount calculating section 57 and the motor temperature calculating section 58. Drive pulse frequency generator 7 that outputs a control signal to the drive unit 59
It is equipped with

That is, the steering amount calculating section 57 selects and calculates one of the steering ratio characteristic lines shown in FIG. A control signal regarding the rotational direction of the stepping motor 5 and the number of drive pulses is output to the section 7. The drive pulse frequency generator 7 calculates the frequency of the drive pulse to be output to the stepping motor 5 based on the motor temperature signal, and outputs the drive pulse at that frequency together with the rotation direction signal. That is, as shown in FIG. 7, the dynamic torque of the stepping motor 5 has a characteristic that it decreases as the drive pulse frequency increases, and further has a characteristic that it decreases as the motor temperature increases.

Then, the stepping motor 5 is connected to the steering ratio changing mechanism 22.
It is necessary to output a torque T that can rotate the swing shaft 42, and in order to speed up the responsiveness of changing the steering ratio, the drive pulse is driven with the highest frequency drive pulse that can obtain this required torque T. is preferable. The drive pulse frequency generating section 7 generates the required torque T at that temperature from the motor temperature signal.
Calculate the highest drive pulse frequency to obtain .

Specifically, the highest frequency at which the required torque can be obtained is set and calculated as a function of the motor temperature, and for example, as the motor temperature increases from 0°C to 0°C to ZO°C, the frequency is changed to fl, f2, and so on. Lower it to f3.

Further, the steering amount calculation unit 57 receives the steering ratio signal from the steering ratio detection means 29, compares the actual steering ratio with the steering ratio obtained from the above-mentioned steering ratio characteristic line, and calculates the actual steering ratio. A correction means is provided for outputting a correction control signal to the drive pulse frequency generator 7 so that the steering ratio matches the calculated steering ratio. This correction means does not operate all the time, but normally changes the steering ratio using open-loose control, and performs feedback control by the correction means at a set vehicle speed, for example, when the vehicle speed is zero, the steering ratio becomes zero. .

Therefore, in this embodiment, as the temperature of the stepping motor 5 increases, the frequency of the drive pulse decreases to ensure the necessary torque to rotate the swing shaft 42, so that the stepping motor 5 can be removed. This prevents
The accuracy of steering ratio change control can be maintained at a high level, and since the frequency of the drive pulse is set to the highest value that allows the required torque T to be obtained at the relevant motor temperature, the responsiveness of steering ratio changes can be improved. It does not cause a large decrease.

This example is shown in FIG. 2, and is an example in which the steering control of the rear wheels 6 in conjunction with the steering of the front wheels 2 is electrically performed.

That is, the seven-wheel steering device of this example is provided with a steering shaft 13, and receives a steering wheel angle signal from the steering wheel angle sensor 71, a steering wheel steering angle signal from the steering wheel angle sensor 71, and a vehicle speed signal from the vehicle speed sensor 8 to drive a stepping motor. A controller 72 outputs a control signal to the stepping motor drive section 59, and a stepping motor 5 steers the rear wheels 6 based on the drive signal from the stepping motor drive section 59.

In the case of this example, the stepping motor 5 is linked to a pinion 75 that meshes with a rack 74 of the rear wheel side relay rod 18 via a transmission mechanism 73 consisting of a pair of bevel gears, and the hydraulic control palflow 3 is connected to a pinion 750 that meshes with a rack 74 of the rear wheel side relay rod 18. The oil passage and oil pressure are changed by detecting the rotational direction and rotational force.

The stepping motor 5 also includes a rear wheel steering angle sensor 76.
and a thermosensor 6 are attached to the controller 72 to output a rear wheel steering angle signal and a motor temperature signal to the controller 72. The controller 72 also includes a display means 77 for graphically displaying the steering modes of the front wheels 2 and rear wheels 3, a control mode changeover switch 78 for setting the steering mode of the rear wheels 6,
An energizing wire 79 for operation that conducts electricity from the battery through the ignition switch 1 and an energizing wire 8 for storing the steering angle of the steering wheel.
0 is connected.

Then, the controller 72 includes a steering amount calculating section 81 that calculates a rear wheel turning amount from the front wheel turning amount calculated from the steering wheel steering angle signal and the steering ratio calculated from the vehicle speed signal and outputs a control signal. , receives this control signal and the motor temperature signal, calculates the highest frequency of drive pulses that can obtain the required torque T (example/reference) at the motor temperature, and sends a rotation direction signal of the stepping motor 5 to the stepping motor drive section 59. and outputs a driving pulse signal. Drive pulse frequency generator 7
and a steering ratio detection means 82 that detects the steering ratio from the steering wheel steering angle signal and the rear wheel steering angle signal and outputs a detection signal for steering ratio feedback correction to the steering amount calculation section 81. .

Therefore, in the case of this example, the steering amount calculation unit 81 of the controller 72 performs steering control of the rear wheels 6 including steering ratio change control, and the stepping motor 5 not only changes the steering ratio but also controls the actual steering. Now steer the rear wheels 6.

The control mode changeover switch 78 is still set to auto mode, in which the rear wheels 3 are steered in the opposite phase to the front wheels 2, and club mode, in which the rear wheels 3 are steered in the same phase as the front wheels 2, in low vehicle speed ranges. This is a switch for the driver to select and manually set the mode, and the steering ratio changes depending on the vehicle speed in each mode.

In each of the above embodiments, the steering ratio is changed depending on the vehicle speed and the vehicle speed and setting mode, but the steering ratio can be changed by combining these factors with other factors such as lateral acceleration acting on the vehicle body. Change control may also be performed. Furthermore, the steering ratio may be changed by controlling only one of the lateral acceleration, the control mode changeover switch 78, and the steering wheel angle, or by a combination of these.

(Effects of the Invention) According to the present invention, there is provided means for detecting the temperature of the steering motor that changes the steering ratio of the front and rear wheels and changing the driving pulse frequency of the stepping motor. Regardless, it is possible to secure the output torque of the stepping motor necessary for steering ratio change control, and the reliability of steering ratio change control can be improved.

[Brief explanation of drawings]

Figure 1 is a configuration diagram of the present invention, and Figures 2 to 7 are examples/
Fig. 2 is an overall configuration diagram of the wheel steering system;
Figure 3 is a partially sectional plan view of the steering ratio changing mechanism;
Fig. 5 is a sectional view taken along the line A-A in Fig. 3, Fig. 5 is a control system diagram, Fig. 4 is a steering ratio characteristic diagram, Fig. 7 is a characteristic diagram of the output torque of the stepping motor, and Fig. 2 FIG. 2 is an overall configuration diagram of a wheel steering device according to a second embodiment. 1...Vehicle, 2...Front wheel, 3...
・・Rear wheel, 4・・Control unit, 5・・Stepping motor, 6・・Thermo centimeter, 7・・・・
... Drive pulse frequency generation section, 8...Vehicle speed sensor Fig. 2 4b Fig. 5 Fig. 7 Fig. 6 Tomoe

Claims (1)

[Claims] (1) In a vehicle that steers the rear wheels in response to the steering of the front wheels, and the steering ratio of the rear wheels to the front wheels is variable between the opposite phase and the same phase depending on the driving condition, the above steering ratio is variable. a stepping motor, a control unit that outputs a control signal to change the steering ratio to the stepping motor, and a thermosensor that detects the temperature of the stepping motor, and the control unit receives the output signal from the thermosensor. A four-wheel steering system for a vehicle, comprising a drive pulse frequency generator that varies the frequency of drive pulses of the stepping motor.