JPH0518227Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a front and rear wheel steering system for a vehicle, and in particular, a front wheel steering mechanism and a rear wheel steering mechanism are mechanically connected to each other by a connecting shaft. and a pinion that is rotatably supported by the housing and meshes with the rack teeth of the rack shaft. The present invention relates to a front and rear wheel steering system for a vehicle, which includes a pinion shaft integrally connected to the connecting shaft.

[Prior art]

Various devices of this type have been proposed in the past, such as Japanese Patent Laid-Open No. 59-26363,
This is proposed in Publication No. 61-163063. However, in the devices proposed in these publications, the front wheels are steered unless the steering angle ratio between the front wheels and the rear wheels is set to zero by the steering angle ratio setting device attached to the rear wheel steering mechanism. As a result, the rear wheels are always steered.

[Problem that the invention attempts to solve]

Therefore, if an abnormality occurs in the rear wheel steering mechanism and the rear wheel steering load increases abnormally when the steering angle ratio is set to the set value, even if the front wheel steering mechanism is normal, Steering becomes difficult.

In addition, if an abnormality occurs in the steering angle ratio setting device or the control device that controls these operations and the steering angle ratio between the front wheels and the rear wheels is not set to a normal value, the rear wheels may change as the front wheels turn. The vehicle is steered abnormally and the steering stability of the vehicle deteriorates.

In order to solve this problem, the applicant disclosed in Japanese Patent Application No. 61-3158 and Japanese Unexamined Patent Publication No. 62-163870 that when an abnormality occurs in the system, a clutch installed in the connecting shaft is actuated to disable power transmission. We proposed a device to do this. However, since this device requires a clutch to be interposed in the middle of the connecting shaft, there are problems in that the device is large and expensive.

This idea was created in view of the problems mentioned above.
The purpose of this is to enable the front wheel steering mechanism to operate normally when there is an abnormality in the steering system, and to maintain the steering angle of the rear wheels at zero even when the front wheels are turned. An object of the present invention is to provide a wheel steering device at a low cost.

[Means for solving problems]

In order to achieve the above-mentioned object, the present invention includes a front wheel steering mechanism and a rear wheel steering mechanism that are mechanically connected by a connecting shaft, and the front wheel steering mechanism or the rear wheel steering mechanism is supported by a housing. and a pinion shaft connected to the connecting shaft, the pinion shaft being rotatably supported by the housing and integrally having a pinion that meshes with the rack teeth of the rack shaft. In the front and rear wheel steering device for a vehicle, a return spring mechanism is provided on the rear wheel side from the meshing portion of the pinion and the rack teeth toward a position where the steering angle of the rear wheels is zero, and the housing and the pinion shaft, an eccentric cam is interposed between the pinion shaft and the pinion shaft to release the mesh between the pinion and the rack teeth by a predetermined amount of rotation, and the eccentric cam is used to receive an abnormality detection signal from an abnormality detection means for detecting an abnormality in the steering system. The construction is characterized by the fact that it is rotated by a predetermined amount by a drive device that operates in response.

[Effect of invention]

In the present invention configured as described above, if the steering system is normal, the abnormality detection means does not issue an abnormality detection signal and the drive device does not rotate the eccentric cam. Therefore, the engagement between the pinion and the rack teeth is maintained, and power (steering force) can be transmitted between the pinion shaft and the rack shaft. Therefore,
The front wheel steering mechanism and the rear wheel steering mechanism are linked via a connecting shaft, providing maneuverability through front and rear wheel steering.

By the way, in the present invention, when an abnormality occurs in the steering system, an abnormality detection signal is issued from the abnormality detection means, the driving device is activated, and the eccentric cam is rotated by a predetermined amount by the operation of the driving device. For this reason,
The pinion and rack teeth are disengaged, and power transmission between the pinion shaft and the rack shaft is disabled. Further, at this time, the return spring mechanism acts so that the steering angle of the rear wheels becomes zero, so that the rear wheels are brought into a straight-ahead state. Therefore, at this time, maneuverability can be obtained by steering only the front wheels.

[Effect of idea]

As can be understood from the above description of the operation, in the present invention, when there is an abnormality in the steering system, the meshing between the pinion and the rack teeth is released, and the power (steering force) from the front wheel steering mechanism is transferred from the meshing portion to the rear wheel side. ) is not transmitted, and the return spring mechanism sets the rear wheel steering angle to zero, so even if the rear wheel steering load abnormally increases due to the above abnormality, each device attached to the rear wheel steering mechanism ( For example, even if an abnormality occurs in the steering angle ratio setting device or the control device that controls these operations, the front wheel steering mechanism can be steered normally and easily, and the steering angle of the rear wheels can be maintained at zero. This makes it possible to maintain good drivability of the vehicle.

In addition, in the present invention, the means adopted to prevent the power (steering force) from the front wheel steering mechanism from being transmitted to the rear wheels in the event of an abnormality in the steering system is a means interposed between the housing and the pinion shaft. This is an eccentric cam and a drive device that rotates the eccentric cam. It can be integrally assembled into the housing together with the rack shaft, pinion shaft, etc., and the meshing part between the rack teeth of the rack shaft and the pinion of the pinion shaft is effectively Since the device is used in the following, the device can be constructed compactly and at low cost.

〔Example〕

An embodiment of the present invention will be described below based on the drawings.

FIG. 1 schematically shows a front and rear wheel steering device for a vehicle according to the present invention, and this front and rear wheel steering device includes a front wheel steering mechanism A, a rear wheel steering mechanism B, and an electric control device C.

The front wheel steering mechanism A includes a steering wheel 11
As the left and right front wheels FW1 and FW2 are rotated,
The steering wheel 11 steers the main shaft 12, the control valve device V,
It is connected to the left and right front wheels FW1 and FW2 via a rack and pinion mechanism D, a rack shaft (relay rod) 13, left and right tie rods 14a and 14b, and left and right knuckle arms 15a and 15b. The control valve device V supplies and discharges hydraulic oil supplied from the hydraulic pump P to the power cylinder E according to the steering torque acting on the main shaft 12, and the power cylinder E is connected to a housing 16 assembled to the vehicle body.
A part of the rack shaft 1 is configured as a cylinder body, and the rack shaft 13 is a piston rod.
3. Supports left and right movement (axial movement).

As shown in FIG. 2, the rack and pinion mechanism D includes a pinion shaft 21 that is rotatably assembled to the housing 16 via bearings 17 and 18 and connected to the main shaft 12 via a control valve device V. , a first gear that constantly meshes with a pinion 21a provided integrally with this pinion shaft 21.
This first rack tooth 13 consists of a rack tooth 13a.
a is provided integrally with the rack shaft 13. Further, a second rack tooth 13b is integrally provided on the rack shaft 13, and the second rack tooth 13b is removably meshed with a pinion 22a that is integrally provided on the pinion shaft 22. The rack shaft 13 is a rack guide biased by a compression spring 23 (the resiliency can be adjusted by screwing forward and backward a cap 26 that is screwed onto the housing 16 and fixed by a lock nut 25). 24, it is elastically biased toward the meshing portion of both pinions 21a, 22a and both rack teeth 13a, 13b, and is supported so as to be slidable in the axial direction.

The pinion shaft 22 transmits the horizontal movement of the rack shaft 13 to the connecting shaft S as rotation, and is connected to the connecting shaft S via a universal joint 27 at the rear end protruding from the housing 16 (first (see figure). In addition, the pinion shaft 22
is assembled to the housing 16 via bearings 31, 32, eccentric cam 33, and bearings 34, 35 so as to be rotatable, movable in the radial direction, and immovable in the axial direction. The bearings 31 and 32 are assembled between the pinion shaft 22 and the eccentric cam 33, and their movement in the axial direction is restricted by a stepped portion of the pinion shaft 22 and a nut 36 screwed onto the pinion shaft 22. On the other hand, the bearing 34,
35 is assembled between the eccentric cam 33 and the housing 16, and its movement in the axial direction is regulated by a stepped portion of the housing 16 and a sleeve 37 screwed onto the housing 16 and fixed by a lock nut 38. There is.

The eccentric cam 33 is formed such that its axis 01 is offset by a predetermined amount l from the axis 02 of the pinion shaft 22, and a wheel 33a that engages with the worm 41a is integrally provided on its outer periphery. ing. The worm 41a has a bearing 42 in the housing 16, as shown in FIG.
The wormshaft 41 is provided integrally with the wormshaft 41 which is rotatably but immovably assembled in the axial direction via the housing 16. It is composed of In addition, in FIG. 3, the eccentric cam 33 has been rotated 180 degrees from the state shown in FIG. 2, and the pinion 22a of the pinion shaft 22 has come off and separated from the second rack tooth 13b of the rack shaft. , power cannot be transmitted between the rack shaft 13 and the pinion shaft 22.

Next, the configuration of the rear wheel steering mechanism B will be explained.
As shown in FIG. 1, the rear wheel steering mechanism B is mechanically connected to the front wheel steering mechanism A by a connecting shaft S and includes a relay rod 51, left and right tie rods 52a, 52b, and knuckle arms 53a, 5.
3b, the link mechanism F steers the left and right rear wheels RW1 and RW2 by the left and right movement of the relay rod 51.
The rotation of the connecting shaft S, which rotates in response to the left-right movement of the rack shaft 13 in the front wheel steering mechanism A, is converted into the left-right movement of the relay rod 51 in accordance with the vehicle speed (in other words, the front wheels FW1, FW2 and the rear wheels RW1,
The steering angle ratio of RW2 is set according to the vehicle speed). The coupling mechanism G is proposed in Japanese Patent Application Laid-Open No. 163064/1982, and includes a step motor 54 (a housing 55 assembled to the vehicle body) controlled by an electric control device C.
), and the same motor 5
4 rotates the relay rod 51 around its axis to rotate the front wheels FW1, FW2 and the rear wheel RW.
1. It is now possible to change the rudder angle ratio of RW2. Note that a detailed configuration explanation of the coupling mechanism G will be omitted.

In addition, the rear wheel steering mechanism B includes a relay rod 51.
A return spring mechanism H is provided that biases the rear wheels RW1 and RW2 toward a neutral position, that is, a position where the steering angle of the rear wheels RW1 and RW2 is zero. As shown in FIG. 4, the return spring mechanism H includes a pair of retainers 6 slidably fitted onto the relay rod 51.
1, 62, a compression coil spring 63 (to which a predetermined preload is applied) stretched between both retainers 61, 62, and a stopper 6 fixed on the relay rod 51 using rings 64, 65.
6, 67, and stoppers 168, 69 that are immovably disposed within the cylindrical portion of the housing 55. In the position shown in FIG. The retainer 62 is in contact with both stoppers 67 and 69.

The electric control device C, as shown in FIG.
It has a front wheel steering angle sensor 71, a vehicle speed sensor 72, an oil pressure sensor 73, and a rear wheel steering angle sensor 74. The front wheel steering angle sensor 71 is attached to the main shaft 12 and detects the rotation angle of the main shaft 12 to output a front wheel steering angle signal representing the steering angle of the left and right front wheels FW1 and FW2, and is used to determine abnormality. It is connected to circuit 77. The vehicle speed sensor 72 is provided in a transmission (not shown) and outputs a vehicle speed signal representing the vehicle speed by detecting the rotation speed of the output shaft of the transmission.
5 and an abnormality determination circuit 77. The oil pressure sensor 73 detects the oil pressure discharged from the hydraulic pump P and supplied to the control valve device V, and outputs an oil pressure signal representing the oil pressure, and is connected to the abnormality determination circuit 77. Rear wheel steering angle sensor 74
is assembled into the housing 55 of the rear wheel steering mechanism B, and detects the amount of displacement in the axial direction of the relay rod 51, thereby outputting a rear wheel turning angle signal representing the turning angle of the left and right rear wheels RW1, RW2. Yes, and connected to the abnormality determination circuit 77.

The front and rear wheel steering angle ratio setting circuit 75 is constituted by an electric circuit such as a microcomputer, and has a memory that stores in the form of a table a target front and rear steering angle ratio that gradually changes from negative to positive as the vehicle speed increases. and,
It is equipped with a circuit that reads out a target front and rear wheel steering angle ratio from the memory according to the vehicle speed, and outputs a control signal representing the target front and rear wheel steering angle ratio. It is connected. Based on the control signal from the front and rear wheel steering angle ratio setting circuit 75, the drive circuit 76 sends a drive pulse train signal to the step motor 54 to rotate the step motor 54 so that the front and rear wheel steering angle ratio becomes the target front and rear steering angle ratio. The step motor 54 and the abnormality determination circuit 7
7 is connected. Note that the front and rear wheels steering angle ratio is negative, which means that when front wheels FW1 and FW2 are steered to the left (or right), rear wheels RW1 and RW2 are steered to the right (or left). This means that if the front and rear wheel steering angle ratio is positive, the front wheel FW
1. This means that when FW2 is steered to the left (or right), the rear wheels RW1 and RW2 are steered to the left (or right).

The abnormality determination circuit 77 is connected to each sensor 71, 72, 7.
3, 74, which detects an abnormality in the steering system based on signals from the front and rear wheel steering angle ratio setting circuit 75 and the drive circuit 76 as shown in (a) to (g) below, and outputs an abnormality detection signal. and is connected to a drive circuit 78 and a warning device 79.

(a) Whether there is a front wheel steering angle signal from the front wheel steering angle sensor 71 and whether the front wheel steering angle represented by the signal is greater than or equal to a mechanically impossible steering angle of the front wheel steering mechanism A. Based on this determination, an abnormality is detected in the sensor 71 and the conductor wire that guides the front wheel turning angle signal.

(b) By determining the presence or absence of a vehicle speed signal from the vehicle speed sensor 72 and whether the vehicle speed indicated by the signal is higher than a speed that is impossible in terms of vehicle performance, abnormalities in the sensor 72 and the conductor leading to the vehicle speed signal are detected. To detect.

(c) Whether there is a rear wheel steering angle signal from the rear wheel steering angle sensor 74 and whether the rear wheel steering angle indicated by the signal is greater than or equal to a mechanically impossible steering angle of the rear wheel steering mechanism B. Based on this determination, an abnormality in the sensor 74 and the conductor wire that guides the rear wheel turning angle signal is detected.

(d) Whether or not the relationship between the front wheel steering angle, vehicle speed, and rear wheel steering angle detected by the front wheel steering angle sensor 71, vehicle speed sensor 72, and rear wheel steering angle sensor 74 is a relationship that can occur when the vehicle is running. Based on this determination, an abnormality in any one of the sensors 71, 72, and 74 is detected.

(e) Abnormalities in the hydraulic system, such as the hydraulic pump P and the control valve device V, are detected by determining whether the hydraulic pressure detected by the hydraulic pressure sensor 73 is equal to or higher than the pressure required to operate the steering system.

(f) Runaway of the microcomputer configuring the front and rear wheel steering angle ratio setting circuit 75, rear wheel steering angle sensor 74
By determining that the front and rear wheel steering angle ratio obtained from the rear wheel steering angle detected by the front wheel steering angle and the front wheel steering angle detected by the front wheel steering angle sensor 71 does not approach the target front and rear wheel steering angle ratio even after an appropriate period of time. , an abnormality in the front and rear wheel steering angle ratio setting circuit 75, the drive circuit 76, the step motor 54, etc. is detected.

(g) The drive circuit 76
detect abnormalities.

Based on the abnormality detection signal from the abnormality detection circuit 77, the drive circuit 78 supplies the step motor 44 with a drive pulse train signal for rotating the step motor 44 so that the eccentric cam 33 is in the state shown in FIG. and is connected to the step motor 44. The warning device 79 is provided near the driver's seat and has a warning lamp or a warning buzzer that responds to the abnormality detection signal. Further, the abnormality detection signal from the abnormality determination circuit 77 is also guided to the drive circuit 76, and the circuit 76 stops outputting the drive pulse train signal to the step motor 54 in response to this abnormality detection signal. .

In this embodiment configured as described above, when the vehicle is driven with no abnormality occurring in the steering system, the abnormality determination circuit 77 does not issue an abnormality detection signal, so the eccentric cam 33 is Since it is not rotated by the motor 44, it is held in the state shown in FIG. Therefore, the engagement between the pinion 22a and the second rack tooth 13b is maintained, and power (steering force) can be transmitted between the pinion shaft 22 and the rack shaft 13. Therefore, the front wheel steering mechanism A and the rear wheel steering mechanism B are interlocked via the connecting shaft S. At this time, the front and rear wheel steering angle ratio setting circuit 75 inputs a vehicle speed signal representing the current vehicle speed from the vehicle speed sensor 72 and outputs a control signal representing the target front and rear wheel steering angle ratio to the drive circuit 76. Therefore, the drive circuit 76 outputs a drive pulse train signal corresponding to the target front and rear wheel steering angle ratio to the step motor 54 based on the supplied control signal.
Controls the rotation of 4. Therefore, the front and rear wheel steering angle ratio set in the coupling mechanism G is set as the target value,
The left and right rear wheels RW1 and RW2 are steered according to the front wheel steering angle and vehicle speed, and maneuverability is obtained by front and rear wheel steering. Note that at this time, the relay rod 51
According to the movement of the spring 63 of the return spring mechanism H is compressed.

By the way, in this embodiment, when an abnormality like the above-mentioned (a) to (g) occurs in the steering system, the abnormality determination circuit 77 detects the abnormality and outputs an abnormality detection signal. 78 supplies a drive pulse train signal to step motor 44. Therefore, the step motor 44 rotates to rotate the eccentric cam 33 from the state shown in FIG. 2 to the state shown in FIG. Therefore, the engagement between the pinion 22a and the second rack teeth 13b is released, and the pinion shaft 22
Power transmission between the rack shaft 13 and the rack shaft 13 is disabled. Further, at this time, the return spring mechanism H acts so that the steering angles of the rear wheels RW1 and RW2 become zero, so that the rear wheels RW1 and RW2 are brought into a straight-ahead state. Therefore, at this time, only the front wheel steering mechanism A is operated by the rotation of the steering wheel 11, and appropriate maneuverability is obtained by steering only the front wheels FW1 and FW2. At this time, since the drive circuit 76 stops the drive control of the step motor 54 in response to the abnormality detection signal from the abnormality determination circuit 77, unnecessary driving of the step motor 54 can be eliminated. Furthermore, since the warning device 79 also responds to the detection signal to warn the driver of the occurrence of the abnormality, the driver can notice the occurrence of the abnormality and take the vehicle to a repair shop. Also,
In this embodiment, the means adopted to prevent the power (steering force) from the front wheel steering mechanism A from being transmitted to the rear wheels when the steering system is abnormal is the housing 16 and the pinion shaft 22.
This is a drive device that rotates the eccentric cam 33 interposed between the eccentric cam 33 and the eccentric cam 33, and can be assembled integrally with the housing 16 together with the rack shaft 13, pinion shaft 22, etc. Teeth 13b and pinion shaft 22
Since the meshing portion with the pinion 22 is effectively utilized, the device can be constructed compactly and at low cost.

In the above embodiment, the wormshaft 41 that rotates the eccentric cam 33 is connected to the step motor 44.
However, as shown in FIG. 5, the piston rod 46a of the hydraulic cylinder 46 whose operation is controlled by the electromagnetic switching valve 45
The rack teeth 46b provided on the worm shaft 4
It is also possible to implement the present invention by meshing with a pinion 41b provided integrally with the worm shaft 41 and rotating the worm shaft 41 by the hydraulic cylinder 46 in the same manner as in the above embodiment.

Furthermore, in the above embodiment, the present invention was applied to a device in which the connecting portion between the front wheel steering mechanism A and the connecting shaft S had a meshing portion between the pinion and the rack teeth. The engagement portion between the pinion and the rack teeth in the connecting portion can be implemented in a certain device in the same manner or with appropriate modifications.

[Brief explanation of drawings]

Fig. 1 is a diagram schematically showing a front and rear wheel steering system for a vehicle according to the present invention, Fig. 2 is an enlarged partially cutaway side view showing the part shown in Fig. 1, and Fig. 3 is a diagram showing -
4 is an enlarged sectional view of the return spring mechanism shown in FIG. 1, and FIG. 5 is a diagram showing a modification of the drive device for rotating the eccentric cam. Explanation of symbols, A...Front wheel steering mechanism, B...Rear wheel steering mechanism, C...Electric control device, FW1, FW2
...Front wheel, RW1, RW2...Rear wheel, S...Connection shaft, H...Return spring mechanism, 13...
Rack shaft, 13b...Rack tooth, 16...Housing, 22...Pinion shaft, 22a...Pinion, 33...Eccentric cam, 44...Step motor, 46...Hydraulic cylinder.

Claims (1)

[Scope of utility model registration request] A front wheel steering mechanism and a rear wheel steering mechanism are mechanically connected by a connecting shaft, and the front wheel steering mechanism or the rear wheel steering mechanism is supported by a housing and has a rack shaft for steering the wheels when moving in an axial direction. A front and rear wheel steering system for a vehicle, comprising: a pinion shaft that is rotatably supported by the housing and integrally includes a pinion that meshes with the rack teeth of the rack shaft; and a pinion shaft that is connected to the connection shaft; A return spring mechanism is provided on the rear wheel side from the meshing portion of the lock teeth to a position where the steering angle of the rear wheels is zero, and a return spring mechanism is provided that biases the rear wheels toward a position where the steering angle is zero, and a predetermined amount of rotation is applied between the housing and the pinion shaft. An eccentric cam is interposed to release the engagement between the pinion and the rack teeth, and the eccentric cam is rotated by a predetermined amount by a drive device activated in response to an abnormality detection signal from an abnormality detection means for detecting an abnormality in the steering system. A vehicle front and rear wheel steering device characterized by: