JPH05583U - 4-wheel steering system - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a four-wheel steering device capable of restricting a rear wheel steering angle range according to a front wheel steering angle. [Structure] The motor 22 is rotationally controlled according to the steering angle of the front wheels 10, and the rear wheels 20 are steered. At this time, the drum 33 also rotates in response to the steering of the front wheels 10, and the width of the electrode plate 43 on the surface thereof changes. On the other hand, as the motor 22 rotates, the brush 44 fixedly mounted on the interlocking rack 31 also moves in the axial direction of the drum 33. When the motor 22 rotates excessively, the contact between the electrode plate 43 and the brush 44 disappears, and the motor 22
Further rotation of the is prevented.

Description

[Detailed description of the device]

[0001]

[Industrial application]

 The present invention relates to a four-wheel steering system capable of steering not only front wheels but also rear wheels.

[0002]

[Prior Art]

 Conventionally, in a four-wheel steering system in which the front wheels and the rear wheels are steered in the same phase or in the opposite phase, it is known that the actuator of the rear wheel steering system is controlled by a control valve operated by a pulse motor. This has the advantage that the rear wheel steering characteristics can be set freely according to the driving conditions.

In this type of four-wheel steering system, the controller calculates a target rear-wheel steering angle according to the front-wheel steering angle detected by the front-wheel steering angle sensor, and based on this, the pulse motor is rotationally controlled. However, the rear wheel is steered by the actuator by the target steering angle.

In such a four-wheel steering system, if the pulse motor is excessively rotated due to a failure of the control system or the like, the rear wheels may be largely steered. As a countermeasure against this, conventionally, the front wheel steering system is interlocked with the motion. The cam member that moves according to the steering angle of the front wheels is provided with a cam part that regulates the limit range of the steering angle of the rear wheels according to the steering angle of the front wheels. A device which is connected to a device is known (see Japanese Patent Laid-Open No. 63-199179).

[0005]

[Problems to be solved by the device]

 However, in such a conventional one, since the rear wheel steering angle range is regulated by a mechanical cam mechanism according to the front wheel steering angle, the rear wheel steering section is not operated due to a failure of the motor or the like. When locked, there is a problem that a large force acts on the stopper by steering the front wheels.

An object of the present invention is to provide a four-wheel steering system which solves the above-mentioned conventional problems and enables regulation of the rear wheel steering angle range according to the front wheel steering angle.

[0007]

[Means for Solving the Problems]

 In order to achieve the above object, the present invention provides a four-wheel steering system including a front-wheel steering system for steering front wheels based on a steering wheel operation and a rear-wheel steering system for steering rear wheels based on rotation of a motor. And a means for moving in response to the steering angle of the front wheels in conjunction with the movement of the front wheel steering device and for limiting the limit range of the steering angle of the rear wheels corresponding to the steering angle of the front wheels, and the rear wheel steering device. And means for controlling the energization range to the control motor in cooperation with the regulation means.

[0008]

[Action]

 According to the present invention, the rotation of the motor is controlled according to the steering angle of the front wheels, and the rear wheels are steered. Then, at this time, the means for moving the steering wheel according to the steering of the front wheels and regulating the limit of the steering angle of the rear wheels corresponding to the steering angle controls the energization range to the motor in conjunction with the rear wheel steering device. Work synergistically with the means. Therefore, when the rear wheel steering device tries to exceed the limit of the rear wheel steering angle, the power supply to the control motor is stopped, and no further steering is performed. On the other hand, even if the motor is locked, the front wheel steering system can handle smoothly.

[0009]

【Example】

 Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In FIG. 1, 10 is a front wheel, 11 is a front wheel steering device that steers the front wheel 10, 20 is a rear wheel, and 21 is a rear wheel steering device that steers the rear wheel 20. The front wheel steering device 11 includes a handle 12, a front wheel steering shaft 13 connected to the handle 12, a pinion shaft 14, a rack shaft 15 that meshes with the pinion shaft 14, and a pin provided on the rack shaft 15. A power cylinder 17 having a ton 16 and a cylinder chamber divided into left and right by the piston 16, and the piston 16 is operated based on relative rotation between the front wheel steering shaft 13 and the pinion shaft 14. The control valve 18 controls the supply and discharge of pressure oil.

Both ends of the rack shaft 15 are connected to the front wheels 10 via known tie rods, knuckle arms, etc., and the front wheels 10 are steered by the axial movement of the rack shaft 15. A front wheel steering angle sensor 19 for detecting a front wheel steering angle θ is provided on the front wheel steering shaft 13.

The rear wheel steering device 21 includes a stepping motor 22, a rear wheel steering shaft 23 that is rotated by the rotation of the stepping motor 22, a pinion shaft 24, and a rack shaft that meshes with the pinion shaft 24. 25, and a piston 26 provided on the rack shaft 25. The piston 27 divides the cylinder chamber into the left and right, and the relative rotation between the rear wheel steering shaft 23 and the pinion shaft 24. And a control valve 28 that controls the supply and discharge of pressure oil to and from the actuator 27.

Both ends of the rack shaft 25 are connected to the rear wheel 20 via known tie rods, knuckle arms, etc., and the rear wheel 20 is steered by the axial movement of the rack shaft 25. Springs 29 and 29 are respectively inserted in the left and right cylinder chambers of the actuator 27 in a resilient state to urge the rack shaft 25 to a neutral position at all times.

Reference numeral 31 denotes an interlocking rack rod slidably held in a direction parallel to the rack shaft 25 of the rear wheel steering device 21, and the rack rod 31 is provided on the rear wheel steering shaft 23. It is meshed with the union 32 and is axially moved in association with the rotation of the rear wheel steering shaft 23. In the vicinity of the interlocking rack rod 31, a drum 33 is rotatably supported around a vertical axis with the rack rod 31, and a screw gear 34 is formed at one end of the drum 33. A screw gear 36 formed at one end of 35 intersects at a right angle and is meshed.

On the other hand, a pinion 38 formed at one end of an interlocking shaft 37 is meshed with the rack shaft 15 of the front wheel steering device 11. The front wheel side interlocking shaft 37 and the rear wheel side interlocking shaft 35 are connected to each other by a connecting shaft 41 via universal joints 39 and 40. As a result, when the rack shaft 15 is axially moved based on the operation of the handle 12, the drum 33 is rotated via the interlocking shaft 37, the intermediate shaft 41 and the interlocking shaft 35. In this case, the rotation amount of the drum 33 is set such that when the front wheels 10 are turned leftward or rightward from the neutral position to the maximum steering angle, the rotation amounts are within 180 ° in the forward rotation direction and the reverse rotation direction, respectively. ..

In the figure, P1 and P2 indicate pumps for supplying pressure oil to the control valves 18 and 28 on the front and rear wheels, respectively.

An electrode plate 43 having a predetermined shape for setting a limit range of a rear wheel steering angle is attached to the drum 33, and a brush 44 fixed to the interlocking rack rod 31 is attached to the electrode plate 43. It is arranged to be accessible.

Therefore, the electrode plate 43 and the brush 44 are connected to a pulse generating circuit 57 described later, and the control motor 22 can be driven only when both are in a conductive state. Below, the electrode plate shape when the rear wheels 20 are steered in the same phase as the front wheel steering angle θf increases at medium and high speeds, and the rear wheels 20 in the opposite phase within the large steering angle range of the front wheels 10 at low speeds An example will be described based on the development view of FIG.

The electrode plate shape is set to have a degree of freedom with reference to the width of the target rear wheel steering characteristic with respect to the front wheel steering angle, which will be described later.

That is, it is located in the central portion of the electrode plate 43, which allows a slight axial movement of the interlocking rack rod 31, but when the width of the electrode plate 43 is exceeded, the energization is stopped, and the stepping motor 22 is in effect. The rotation of the drum 33 is restricted by the forward rotation and the reverse rotation of the drum 33 due to the steering of the front wheels 10, and the axial movement range of the interlocking lever rod 31 (the stepping motor 22 The rotation range) is increased.

In FIG. 1, reference numeral 50 denotes an electronic control unit, which includes a microprocessor 51, a writable memory (RAM) 52, and a read-only memory (ROM) 53 as main constituent elements. A vehicle speed sensor 54 for detecting the vehicle speed V 1 and the front wheel steering angle sensor 19 are connected to the microprocessor 51 via an interface. Further, the microprocessor 51 is connected with the pulse generation circuit 57 for applying a pulse to the above-mentioned stepping motor 22 through an interface.

When the front wheels 10 are steered, the drum 33 is rotated via the interlocking shafts 37 and 35, and the maximum contactable range of the brush 44 is set according to the front wheel steering angle θf. The brush 44 is movable within the width of the electrode plate 43 of the drum 33 together with the continuous rack rod 31 driven by the rotation of the stepping motor 22.

Therefore, even if the stepping motor 22 is abnormally rotated due to a failure of the control system or the like, and the rear wheels 20 are operated so as to greatly exceed the target steering angle, the movement amount of the brush 44 varies with the width of the electrode plate 43. It will be possible to prevent unforeseen circumstances due to control system failures, etc.

3 and 4 show a modification of the electrode plate shape. FIG. 3 shows the electrode plate shape in the same phase only in the small steering angle range of the front wheels 10 and in the large steering angle range during low speed traveling. The steering of the rear wheels 10 is allowed only in the reverse phase. That is, since the steering wheel is steered in a small steering angle range during high speed traveling, the rear wheels 20 can be controlled only in the same phase during high speed traveling, and the control in the opposite phase is disabled. Further, FIG. 4 shows the shape of the electrode plate in the case where the antiphase control is exclusively performed in the large steering angle range.

According to such a cam shape, there is an advantage that not only the rear wheel steering is quantitatively limited as in the above-described embodiment, but also an abnormality in the steering direction can be prevented.

Further, FIG. 5 shows another embodiment of the present invention. Instead of the power assist device or the interlocking rack rod 31 of the previous embodiment, the motor directly drives the rack shaft 25. It was done.

Therefore, the DC motor 22A is used together with the driver 57A, the pinion 24 is driven via the non-reversible reduction gear 100 such as a worm gear mechanism, and the brush 44 moves integrally with the rack shaft 25. Installed on.

Since other configurations are the same as those of the previous embodiment, the same functional parts are designated by the same reference numerals to avoid redundant description.

Also in this embodiment, even if the DC motor 22A abnormally rotates and the rear wheels 20 are steered far beyond the target steering angle, the brush 44 moves to the electrode plate 43 as the rack shaft 25 moves. It is possible to prevent the rear wheel 20 from being steered abnormally greatly by being deviated from the width and stopping the power supply to the motor 22A. Further, even in this rear wheel control abnormal state, the steering of the front wheels 10 can be performed normally.

Next, still another embodiment of the present invention will be described with reference to FIG.

In this embodiment, unlike the previous embodiment, in which the electrode plate 43 is attached to the surface of the drum 33 and the switch is configured with the brush 44, the cam surface 43A is formed on the surface of the drum 33. However, the switch mechanism 103 is directly turned on and off by the cam surface 43A.

That is, the casing 103A of the switch mechanism 103 is fixed to the above-mentioned interlocking rack rod 31, and is provided with a fixed contact 103B and a movable contact 103C. The movable contact 103C is capable of projecting and retracting in the casing 103A, and is in contact with the drum 33 and the follower 103F biased by the spring 103D toward the cam surface 43A. The shape of the cam surface 43A is set to be the same as that of the electrode plate 43 as described above with reference to FIGS.

Then, in the state where the follower rod 103E is in contact with the cam surface 43A of the drum 33, the follower rod 103F presses the movable contact 103C and is brought into conduction with the fixed contact 103B, and the motor 22 and 22A Wheel steering is possible. On the other hand, when the follower rod 103F is disengaged from the cam surface 43A due to excessive movement of the interlocking rack rod 31, the follower rod 103F abuts the surface of the drum 33 by the action of the spring 103D, and the movable contact 103C and the fixed contact 103B are electrically connected. Is released.

According to this embodiment, the drum 33 and the cam surface 43A can be integrally molded with resin, and the cost can be reduced.

Further, another embodiment of the present invention will be described with reference to FIGS. 7 and 8. This embodiment is an improvement of the embodiment shown in FIG. 6, in which another cam surface 43B is further added to the surface of the drum 33 and the three contact switches 104 are used to stop the motors 22 and 22A. The steering direction of the rear wheel 20 at the time can be detected and can be returned to the neutral side.

That is, on the drum 33, a cam surface 43B having a step difference is formed adjacent to the above-mentioned cam surface 43A. The cam follower 105 that comes into contact with the cam surface is L-shaped, and is rotatable about a pin 105A provided on a casing (not shown) of the switch 104. The end of the cam follower 105 is a movable contact 104A, which is slidably contactable with three fixed contacts 104B, 104C, 104D arranged in an arc shape. Then, each of these contacts is arranged in the motor drive circuit as shown in FIG.

Thus, as in the previous embodiment, when the cam follower 105 is in contact with the cam surface 43A as the interlocking rack rod 31 moves, the movable contact 104A is in conduction with the fixed contact 104C, and 22A is normally driven and controlled by the driver 57A.

By the way, when the cam follower 105 is disengaged from the cam surface 43A, the movable contact 104A disengages from the fixed contact 104C and is electrically connected to the fixed contact 104B or 104D, so that the driver 57A of the motor 22A can drive the steering angle increasing direction. Be stopped. Then, the rear wheel steering angle is returned to the neutral side by causing a current to flow in the direction opposite to the rotation direction of the motor 22A so far at the fixed contact 104B or 104D at which conduction is newly started.

[0038]

[Effect of the device]

 As is clear from the above description, according to the present invention, the maximum allowable range of the rear wheel steering angle is electrically limited, so that even if the control motor malfunctions due to a failure of the control system or the like, The steering of the rear wheels is electrically limited, and the rear wheels are prevented from being steered beyond the maximum allowable range, and the front wheels can be smoothly steered.

[Brief description of drawings]

FIG. 1 is a schematic view showing an entire four-wheel steering system according to an embodiment of the present invention.

FIG. 2 is a development view showing the shape of an electrode plate of a drum.

FIG. 3 is a diagram showing a modification of the electrode plate shape.

FIG. 4 is a schematic view showing a modification of the shape of an electrode plate.

FIG. 5 is a view showing another embodiment of the present invention.

FIG. 6 is a side view of essential parts showing another embodiment of the present invention.

FIG. 7 is a side view of an essential part showing still another embodiment of the present invention.

FIG. 8 is a circuit diagram of still another embodiment of the present invention.

[Explanation of symbols]

 11 Front Wheel Steering Device 21 Rear Wheel Steering Device 22, 22A Motor 33 Drum 43 Electrode Plate 43A Cam Surface 44 Brush

Claims (1)

Claims for utility model registration: 1. A four-wheel steering system comprising: a front wheel steering system for steering front wheels based on steering wheel operation; and a rear wheel steering system for steering rear wheels based on rotation of a motor. In the above, the means for moving the front wheel steering device in accordance with the steering angle of the front wheels in conjunction with the movement of the front wheel steering device, and for controlling the limit range of the steering angle of the rear wheels corresponding to the steering angle of the front wheels, and the rear wheel steering device. A four-wheel steering system comprising: a unit that is interlocked with the control unit to control an energization range to the control motor.