JPS62160966A - Failsafe device for four wheel steering vehicle - Google Patents

Abstract

PURPOSE:To ensure the safety of a four wheel steering vehicle by returning the rear wheel to the neutral through a power steering device when a motor is brought into an uncontrollable condition. CONSTITUTION:When an uncontrollable condition of a motor 12 is detected through detection of the steering position of the rear wheel, for example, the first and second valve units 29, 30 are switched respectively to the second position. Here, the pressure oil from a pump is fed directly to a first conduit 18 or a second conduit 19 while detouring a control valve section 13. When a third valve unit 31 is switched in accordance with the steering direction of the rear wheel, the rear wheel is returned hydraulically to the neutral position by utilizing the power cylinder section in a power steering mechanism 14.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a fail-safe device for a four-wheel steering vehicle, and more particularly, the present invention relates to a fail-safe device for a four-wheel steering vehicle. In a four-wheel steering vehicle, in which the rear wheels are steered in a predetermined direction by human input to the power steering mechanism, even if the motor becomes uncontrollable, it is returned to the rear wheel power mediating position and the vehicle continues to move. Regarding things that ensure safety.

[Conventional technology]

2. Description of the Related Art Four-wheel steering vehicles are already known that are configured to steer not only the front wheels but also the rear wheels in order to achieve optimal vehicle steering performance in accordance with various situations. Among these, one that has already been proposed and filed by the applicant is a system that combines a stepping motor whose rotation is controlled by a control device and a known power steering mechanism into which the rotation of this stepping motor is input, to steer the rear wheels. There is a device which is configured as a device (Japanese Patent Application No. 59-257156). Since the amount of rotation of a stepping motor is proportional to the number of control pulses, digital control is easy, making it easy to steer the rear wheels to the optimal steering angle set according to the vehicle speed or front wheel steering angle. can. Further, since the power steering device has established technology as a front wheel steering mechanism, it is possible to construct a rear wheel steering device with a high degree of completeness at a relatively low cost.

[Problems to be solved by the invention]

By the way, when configuring the rear wheel steering device as described above,
If the motor that is input to the power steering mechanism is burnt out, or the vehicle speed information or front wheel steering angle information that should be input to the control device is no longer accurately input, and the motor becomes uncontrollable, the rear The wheels may become locked while being steered in an unintended direction, or the rear wheels may be steered freely in an unintended direction, making it impossible for the vehicle to drive normally straight ahead. This invention was conceived under the above circumstances,
The objective is to solve the above problem and provide a fail-safe device that can automatically return the rear wheels to the neutral position and put the vehicle into a front wheel steering state when the motor becomes uncontrollable. Take it as a challenge.

[Means to solve the problem]

In order to solve the above problem, the present invention takes the following technical measures. That is, the four-wheel steering system includes a front wheel steering mechanism operated by a steering device, a rear wheel steering device configured with a motor whose rotation is controlled by a control device, and a power steering mechanism into which the rotation of this motor is input. A vehicle smeller installs a first auxiliary pipe between the feed pipe of the control valve section λ of the power steering device and the first pipe on the output side of the control valve section, and a first auxiliary pipe between the return pipe from the control valve section and the output side of the control valve section. A second auxiliary pipe is provided between the second pipes, and the feed pipe has a first position where the pressure oil is sent to the control valve section, and a second position where the pressure oil is sent to the first auxiliary pipe. A first valve device that can select the return oil from the control valve section, and a second valve that can select the return oil from the second auxiliary pipe to the return pipe. Further, the first pipe line and the second pipe line are provided in the middle part of the first pipe line and the second pipe line on the side of the power cylinder from the connection part with the first auxiliary pipe line and the second auxiliary pipe line. A third valve device capable of selectively sending pressure oil to the two pipes is provided, and when the control device becomes unable to control the motor, the first valve device and the second valve device are respectively set to a second position. At the same time, the third valve device is switched so as to return the rear wheels to the neutral position.

[Effect]

In normal times, the first valve device and the second valve device are each in the first position, and pressure oil from the pump is sent only to the control valve section of the power steering device. Also, the third valve device is held in place. When the motor is rotated by a command from the control device, the input shaft of the control valve section is thereby rotated, and the control valve section supports the movement of the power piston in the direction of rotation of the input shaft. , sending pressure oil to the first pipe line or the second pipe line. On the other hand, when it is detected that the motor cannot be controlled by verifying the steering position of the rear wheels, the first valve device and the second valve device are respectively switched to the second position. It will be done. At this time, the pressure oil from the pump bypasses the control valve section and is directly sent to the first pipe line or the second pipe line. Further, by switching the third valve device in accordance with the steering direction of the rear wheels, the rear wheels can be returned to the neutral position purely hydraulically using the power cylinder section of the power steering mechanism.

【effect〕

As described above, according to the present invention, in a four-wheel steering vehicle in which a rear wheel steering device is configured by combining a motor whose rotation is controlled by a control device and a power steering mechanism into which the output of this motor is input, Even if the motor becomes uncontrollable, the rear wheels can be returned to the neutral position using the power cylinder section of the power steering device, ensuring safe driving. [Description of Embodiments] Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. FIG. 1 is an overall configuration diagram of a four-wheel steering vehicle to which the present invention is applied. Here, a conventionally known front wheel steering mechanism 1 is used. In other words, in the case of a two-rank and pinion steering mechanism, the rotation of the steering shaft 3 that rotates along with the steering wheel 2 is converted into a reciprocating motion of the rack rod 5 in the gear box 4, and then the reciprocating motion of the rack rod 5 is converted into a reciprocating motion of the rack rod 5. is converted into a rotation about the axis 8.8 of the knuckle arm through the tie rods 6.6 at both ends, and this rotation of the knuckle arm 7.7 causes the front wheels 9, 9 to rotate around the axis 8.8.
The ship is now steered around the center. On the other hand, the rear wheel steering device IO includes a stepping motor 12 controlled by a control device 11 composed of a microcomputer, and a known rack-and-binion type power steering device 14 to which the rotational output of the stepping motor 1 is input. Consisted of. That is, the output shaft of the stepping motor 12 is connected to the shaft 20 of an input pinion (not shown), and the control valve section 13 is arranged to hold the input pinion shaft.
A pressure oil feed pipe 15 and a return pipe 16 are connected to. On the output side of this control valve section 13, a double acting power cylinder section 1 formed within the gear box 21 is provided.
A first conduit 18 and a second conduit 19 to the second conduit 7 are connected. The power cylinder fa17 is driven by pressure oil selectively sent to the first pipe line 18 or the second pipe line 19 by the control valve section 13, and supports the movement of the rack rod 22. The movement of the rack rod 22 is transmitted to the knuckle arm 24.24 by tie rods 23.23 connected to both ends thereof.
is rotated about the axis 25.25, whereby the rear wheels 26.26 are steered in a predetermined direction about the axis 25.25. Further, a first auxiliary conduit 27 is provided between the feed pipe 15 and the first conduit 18, and a second auxiliary conduit 28 is provided between the return pipe 16 and the second conduit 19. are respectively arranged, and at the branch part of the first auxiliary pipe 27, a first position for sending the pressure oil to the control valve section 13 and a second position for sending the pressure oil to the first auxiliary pipe 27 can be selected. A first valve device 29 consisting of a boat two-position switching valve has a first position for returning oil from the control valve section 13 to the return pipe 16 and a second position for returning oil from the control valve section 13 to the return pipe 16 at a branch part of the second auxiliary pipe line 28. A second valve device 30 is provided, each consisting of a three-boat two-position switching valve capable of selecting a second position for returning oil from the auxiliary pipe 28. Further, in the intermediate portion of the first pipe FIlr18 and the second pipe line 19 on the power cylinder side from the connection part with the first auxiliary pipe line 27 and the second auxiliary pipe line 28, the first pipe line 18 and the second pipe line 19 are provided. A third valve device 31 that can selectively send pressure oil to the two pipes 19 is interposed. In FIG. 1, the first valve device 29 and the second valve device 30 are each in the first position. The microcomputer 11 is configured to receive information from a front wheel steering angle sensor 32, a vehicle speed sensor 33, and a rear wheel steering angle sensor 34 as inputs for control, and from this microcomputer 11, Control lines extend toward the drive circuit 12a of the stepping motor 12 and the respective valve devices 29, 30, and 31, respectively. Note that the rear wheel steering angle sensor 34 can be easily achieved by A/D converting the output voltage of a rotary potentiometer attached to the rotating shaft of the stepping motor 12 and inputting the converted signal to a microcomputer. The base end of the pressure oil feed pipe 15 is connected to a hydraulic pump 35 driven by an engine, and the return pipe 16 is connected to a hydraulic pump 35 driven by an engine.
The returned oil is returned to the reservoir tank 36. In the above configuration, under normal conditions, the target rear wheel steering angle Orr is determined from the vehicle speed information (1) from the vehicle speed sensor 33 and the front wheel steering angle information of from the front wheel steering angle sensor 32, and the rear wheel steering angle is Stepping motor 1 so that it forms a corner
A pulse signal is sent to 2. More specifically, the steering ratio k according to the vehicle speed V is expressed in a data table 3 as shown in FIG.
The target rear wheel steering angle θrr is determined based on the steering ratio read from 7 and determined thereby, and the front wheel steering angle information θr, and based on this, the direction and amount in which the stepping motor 12 should be rotated. is calculated, and a predetermined control pulse signal is sent to the drive circuit 12a of the stepping motor 12.
sent to. As a result, the rear wheels 26, 26 are steered in a predetermined direction so as to obtain the best steering performance at any vehicle speed. In other words, in Fig. 2, the region where the steering ratio k is positive indicates that the rear wheels are steered in the opposite direction to the front wheels, so-called anti-phase, and the region where the steering ratio k is negative indicates that the rear wheels are steered in the same direction as the front wheels. This indicates that the rear wheels are steered in the same phase. According to this, at low speeds, the rear wheels are steered in the opposite phase, so the center of vehicle turning moves forward and approaches the vehicle width direction line passing through the center of the vehicle, and as a result, the slip angle of the vehicle approaches 0 and the turning radius is smaller than when only the front wheels are steered. At high speeds, centrifugal force causes slippage between the front wheels and the road surface, which tends to shift the turning center forward, but this tendency can be offset by steering the rear wheels in the same direction as the front wheels. This allows the turning center to be brought closer to the vehicle width direction line passing through the center of the vehicle body. On the other hand, when it is detected by the signal from the rear wheel steering angle sensor 34 that the stepping motor 12 is in an uncontrollable state, the first valve device 29 and the second valve device 30
While being switched to the second position, the steering motor 12 is de-energized, the third valve device 31 is switched, and the power cylinder 17 forces the rear wheels 26, 26 back to the neutral position. Detecting that the stepping motor 12 is in an uncontrollable state based on the signal from the rear wheel steering angle sensor 34.
This is done, for example, by processing the signal as follows. That is, the rear wheel steering angle information θr from the rear wheel steering angle sensor 34 is compared with the rear wheel steering angle limit θr according to the vehicle speed read out from a data table 38 as shown in FIG. If the wheel steering angle information θr is larger than this rear wheel steering angle limit θrJLk, the stepping motor 1
2 is judged to be out of control. The data table in Fig. 3 corresponds to the data table in Fig. 2, and in Fig. 2, at vehicle speeds where the absolute value of the steering ratio is large, the rear wheel steering angle limit θr/, t becomes large. There is. Further, the reason why the steering angle limit θrA71 width becomes narrower as the speed increases is that the front wheels are steered significantly at high speeds, and it is impossible for the rear wheels to be steered significantly accordingly. If the rear wheel steering angle θr from the rear wheel steering angle sensor 34 exceeds the rear wheel steering angle limit θrμ shown in FIG. This suggests that the stepping motor 12 is in an uncontrollable state. In the present invention, in such a case, the power cylinder section 17 is changed from the switching drive by the control valve section 13 to the first valve device 29 and the second valve device 30.
and switching to switching drive by the third valve device 31,
The hydraulic pressure input to the power steering device 14 is used to forcibly return the rear wheels to the neutral position. Hereinafter, the control procedure by the control device for the four-wheel steered vehicle of this example will be further explained with reference to the flowchart shown in FIG. 4. First, vehicle speed information V from the vehicle speed sensor 33 (S101) is read, and based on this, the steering ratio k is read from the data table shown in FIG. 2 (S102). At this time, front wheel steering angle information θf from the front wheel steering angle sensor 32 is also read (5103). Then, it is verified whether the steering angle information θr from the rear wheel steering angle sensor 34 exceeds a preset rear wheel steering angle limit value θr (3104 to S106). That is, the rear wheel steering angle limit value θrLA< according to the current vehicle speed V is read from the data table 38 in FIG. 3, and this is compared with the rear wheel steering angle information θr. The rear wheel steering angle information θr is the rear wheel steering angle limit value θ.
If r& is not exceeded (NO in S106), the target rear wheel steering angle θrr is determined using the above steering ratio and the front wheel steering angle information θf (S107), and based on this, the stepping motor The direction and amount to rotate stepper motor 12 is determined, and control pulses are thereby sent to drive circuit 12a of stepping motor 12. On the other hand, if in the above 5106, the rear wheel steering angle information θr
is larger than the rear wheel steering angle limit value θrb (YES in S106), the stepping motor 1
2 is turned off (S109), and the first valve device 29 and the second valve device 30 are switched to the second position (S110). At the same time, the third valve device 31 is switched so that the rear wheels 26, 26 face in the neutral direction (Sllll). When the rear wheel steering angle information θr reaches the value θrm corresponding to the neutral position of the rear wheels, the third valve device 31 is switched to the hold position (S11
4) The first valve device 29 and the second valve device 30 are returned to the first position (3115), and the rear wheel steering control is stopped (3116). As described above, according to the present invention, the stepping motor 1
2 becomes uncontrollable, the hydraulic pressure of the power steering device and the power cylinder section 17 are used to purely hydraulically return the rear wheels 26, 26 to the neutral position, and the vehicle is returned to the front wheel steering state similar to that of a normal vehicle. This ensures safety. Of course, the scope of the invention is not limited to the embodiments described above. For example, although a stepping motor is used in the embodiment as the motor to be input to the power steering mechanism, this motor may also be a DC motor. In this case, the signal from the rear wheel steering angle sensor 34 can be used as a feed bank signal for the DC motor.

[Brief explanation of drawings]

Fig. 1 is an overall configuration diagram of a four-wheel steering vehicle to which the present invention is applied, Fig. 2 is a graph showing an example of the relationship between vehicle speed and steering ratio that should be used for four-wheel steering control, and Fig. 3 is a graph showing an example of the relationship between vehicle speed and steering ratio. FIG. 4 is a graph showing an example of the relationship between the vehicle speed and the rear wheel steering angle limit, which should be used to detect an uncontrollable state of the motor. FIG. 4 is a flowchart showing an example of the flow of control by the control device. 1... Front wheel steering mechanism, 2... Steering, 10.
... Rear wheel steering device, 11... Control device, 12... Motor, 13... Control valve section, 14... Power steering mechanism, 15... Feed pipe, 16...
Return pipe, 1st...First pipe line, 19...Second pipe line, 2
7... First auxiliary conduit, 30... Second auxiliary conduit, 29
...First valve device, 30...Second valve device, 31...
Third valve device.

Claims (1)

[Claims] (1) Four wheels equipped with a front wheel steering mechanism operated by a steering device, a rear wheel steering device configured with a motor whose rotation is controlled by a control device, and a power steering mechanism into which the rotation of this motor is input. In a steered vehicle, a first auxiliary pipe is provided between the feed pipe to the control valve section of the power steering device and the first pipe on the output side of the control valve section, and a first auxiliary pipe is provided between the return pipe from the control valve section and the output side of the control valve section. A second auxiliary pipe is provided between the second pipes, and the feed pipe is provided with a second position in which pressurized oil can be selected from a first position for sending pressure oil to the control valve section and a second position for sending pressure oil to the first auxiliary pipe. a second valve device that can select a first position for returning return oil from the control valve section and a second position for returning return oil from the second auxiliary pipe to the return pipe; further provided in the intermediate portion of the first conduit and the second conduit on the side of the power cylinder from the connection part with the first auxiliary conduit and the second auxiliary conduit, and in the first conduit and the second conduit. A third valve device capable of selectively sending pressure oil is provided, and when the control device cannot control the motor, the first valve device and the second valve device are each switched to a second position, and A fail-safe device for a four-wheel steering vehicle, characterized in that the third valve device is switched so as to return the rear wheels to a neutral position.