JPH0358948B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a four-wheel steering system for a vehicle that controls the steering of both the front wheels and the rear wheels through steering operation, particularly in a low vehicle speed region. This invention relates to an improvement in which the rear wheel steering angle characteristics are in opposite phase to the front wheel steering angle.

(Prior Art) In general, in this type of four-wheel steering system, in order to easily turn the vehicle around, park the vehicle, etc.
In order to reduce the minimum turning radius of the vehicle, in a low vehicle speed range below a set speed, the rear wheels are controlled to be steered in the opposite direction (opposite phase) to the steering direction of the front wheels. However, when a vehicle is stored in a garage close to a side wall, etc., when the vehicle is taken out of the garage, the rear part of the vehicle body juts out laterally due to the anti-phase steering of the rear wheels.
A situation may occur in which the vehicle comes into contact with the side wall of the garage or the like.

Therefore, conventionally, as disclosed in Japanese Patent Application Laid-Open No. 56-167562, a setting speed (for example, 40
Km/h or 20 Km/h) or less, the rear wheel steering angle is controlled to zero regardless of front wheel steering, and by positioning the rear wheels in the longitudinal direction of the vehicle body, lateral movement of the rear of the vehicle body is achieved. A device has been proposed that prevents contact accidents from occurring.

(Problem to be solved by the invention) However, it is usually difficult to enter or exit the garage after 10
This is done at extremely low speeds of less than Km/h, and the range of vehicle speed changes is small. For this reason, in the above-mentioned proposal that controls the rear wheel turning angle to zero based on the vehicle speed, there is a strong tendency that the rear wheel turning angle is not controlled in a timely manner, and as a result, it is difficult to reduce the minimum turning radius. The rear wheel steering angle may remain controlled to zero even when it is necessary, resulting in
The disadvantage was that the wheel steering system could not be used effectively.

The present invention has been made in view of the above, and is a four-wheel steering system that steers the rear wheels in opposite phases in a low vehicle speed region. When the vehicle is started, it is detected based on the starting state of the vehicle, and when starting, the rear wheel steering angle is always controlled to zero for a predetermined period of time. The purpose of this system is to make it possible to steer the rear wheels reliably and largely in the opposite phase at low vehicle speeds, while also reliably preventing collisions with the side walls of the garage when leaving the garage. be.

(Means for Solving the Problems) In order to achieve this object, the solving means of the present invention provides steering wheels that are substantially synchronized with the steering of the front wheels in a low vehicle speed region, and that the rear wheels and front wheels are steered in opposite directions and in opposite phases. This assumes a four-wheel steering system for a vehicle that is being steered. A start detecting means for detecting the start state of the vehicle, and a signal from the start detecting means are input, and when the signal from the start detecting means is input, the rear wheels are steered in opposite phase for a predetermined period of time. and control means for controlling so as to impose regulations.

(Function) As a result, in the present invention, when the vehicle starts to leave the garage or the like, for a predetermined period of time, the control means restricts the steering of the rear wheels in the opposite phase, regardless of the steering of the front wheels. For example, it will be forcibly controlled to zero.

(Example) Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 1 shows the overall configuration of a four-wheel steering system according to a first embodiment of the present invention, in which 1 indicates left and right front wheels 2a, 2b.
The steering device 1 includes a steering wheel 3, a rack and pinion mechanism 4, left and right tie rods 5, 5, and left and right knuckle arms 6, 6.

Reference numeral 7 denotes a rear wheel steering device for steering left and right rear wheels 8a, 8b.
and a hydraulic actuator 11 having a rod 11a extending in the lateral direction of the vehicle body and connected via tie rods 10,10. The hydraulic actuator 11 includes a left-turn hydraulic chamber 11c and a right-turn hydraulic chamber 11d, which are partitioned in the lateral direction of the vehicle body by a piston 11b fixed to a rod 11a, and each hydraulic chamber 11c, 11d is provided with a return spring 11e, 11f, respectively. has been reduced. Also,
The rear wheel steering device 7 includes a hydraulic pump 13 that absorbs oil in an oil reservoir 12 and supplies it to the hydraulic actuator 11, and an electric motor 1 that drives the hydraulic pump 13.
4, and a switching valve 15 that switches the direction of pressure oil supply from the hydraulic pump 13 to the hydraulic actuator 11. The switching valve 15 has a spool 15a.
and pilot chambers 15b, 15c formed at both left and right ends of the spool 15a, each of which is fitted with a return spring 15d, 15e, respectively.
a is positioned at the neutral position shown. moreover,
The rear wheel steering device 7 sucks oil in the oil reservoir 16 and supplies it to each pilot chamber 15b, 15 of the switching valve 15.
Pilot hydraulic pump 17 that supplies pressure oil to c.
and from the hydraulic pump 17 to each of the pilot chambers 1
A pilot switching valve 18 for switching the direction of pressure oil supply to 5b and 15c is provided. The pilot switching valve 18 has two positions: a forward position 18a that allows pressure oil to be supplied to the right pilot chamber 15c, and a reverse position 18b that allows pressure oil to be supplied to the left pilot chamber 15b. When the pilot switching valve 18 is in the forward direction position 18a, the hydraulic actuator 11 is moved by moving the spool 15a of the switching valve 15 to the left by an amount corresponding to the hydraulic pressure by supplying pressure oil to the right pilot chamber 15c.
By generating a pressure difference between the oil pressures acting on the two hydraulic chambers 11c and 11d according to the amount of spool movement and increasing the hydraulic pressure to the right diversion hydraulic chamber 11d,
The rod 11a of the hydraulic actuator 11 is moved to the right by an amount corresponding to the differential pressure, and the rear wheels 8a,
Turn 8b to the right (clockwise). On the other hand, when the pilot switching valve 18 is in the reverse position 18b, the rod 11a of the hydraulic actuator 11 is similarly steered to the left (counterclockwise).

Furthermore, 19 is a controller for controlling the operation of the rear wheel steering device 7, and the controller 19
As shown in FIG. 2, there is a steering angle sensor 20 for detecting each steering operation of the steering wheel 3.
Detection signals from a vehicle speed sensor 21 that detects the vehicle speed, and a rear wheel steering sensor 22 that detects the amount of left-right movement of the rod 11a of the hydraulic actuator 11 are input. The controller 19 also includes a pilot motor 23 that drives the pilot hydraulic pump 17, and an excitation coil 1 that attracts and moves the spool 18c of the pilot switching valve 18.
8d is connected. Furthermore, the controller 19 has a characteristic of the rod movement amount _S A of the hydraulic actuator 11 with respect to the steering angle _{θ S} as shown in FIG _. A characteristic storage section 24 is provided in which characteristics of are inputted and stored in advance. As can be seen from the figure, the characteristics of the above rear wheel turning angle θ _R are as follows:
In the speed range below V _O , the phase is opposite, and the vehicle speed is
The characteristics change according to the vehicle speed so that they are in the same phase in the speed range higher than _VO . Inside the controller 19, a hydraulic actuator 11 is further provided in response to both detection signals from the steering angle sensor 20 and vehicle speed sensor 21.
A target steering angle calculation section 25 calculates a target rod movement amount (target rear wheel turning angle) based on the characteristics of the characteristic storage section 24, and a target rod movement amount signal from the calculation section 25 is sent to a rear wheel steering sensor. a first comparator 26 that compares the actual rod movement amount signal from 22 and generates a difference signal according to the difference; and a triangular wave generator 27 that generates a triangular wave as shown in FIG.
The triangular wave signal from the triangular wave generator 27 is
It is equipped with a second comparator 28 that discriminates the magnitude based on the difference signal from the comparator 26, and a first transistor 29 that is turned on in response to the output signal from the second comparator 28, and when the first transistor 29 is turned on, the first transistor 29 is turned on. It is configured to drive and control the pilot motor 23. Therefore, when the difference between the target rod movement amount and the actual movement amount is large, the difference signal value of the first comparator 26 also increases accordingly, as shown by the broken line in FIG. becomes a signal with a high conduction rate as shown in FIG.
This increases the discharge pressure of the pilot hydraulic pump 17 and increases the amount of spool movement of the switching valve 15. On the other hand, when the difference between the target rod movement amount and the actual rod movement amount is small, the first comparator 2
6 also becomes smaller (shown by the dashed line in A of the same figure), and the output signal of the second comparator 28 becomes a signal with a low conduction rate as shown in C of the figure. 23 is lowered and the discharge pressure of the pilot hydraulic pump 17 is lowered to cause the switching valve 15 to reduce the amount of spool movement.

Inside the controller 19, there is a start operation detection section 30 as a start detection means for detecting a start operation by detecting the depression of the accelerator, the setting of a gear in a low position, etc., and an output signal from the detection section 30. Timer 31 that starts operating when received
and the output signal from the timer 31 (a signal that remains at "H" level for T seconds as shown in FIG. 5).
a second transistor 32 that operates ON while inputting the output signal from the timer 31;
A relay 33 that is turned on when the second transistor 32 is turned on, and a normally closed contact 33a of the relay 33 is connected to the power supply circuit 3 of the pilot motor 23.
4 is interposed. Therefore, when starting the vehicle, the pilot electric motor 23 and the pilot hydraulic pump 17 are deactivated for the time period T set by the timer 31 after the starting operation is detected, so that the switching valve 15 and the hydraulic actuator 11 are inactivated.
A control means is configured to set the rear wheel steering angle to a neutral state and to control the rear wheel steering angle to zero in order to restrict steering with a phase opposite to backward rotation. Although not shown, the controller 19 positions the pilot switching valve 18 at the forward position 18a when the steering wheel 3 is steered clockwise, and positions it at the reverse position 18b when the steering wheel 3 is steered counterclockwise. It is composed of Note that 35 is an on-vehicle battery.

Next, to explain the operation of the above embodiment,
When the vehicle starts, the start operation detection section 30 of the controller 19 generates an output signal, and the timer 31 generates an output signal that goes to the "H" level for a set time T. Therefore, during the above set time T,
The second transistor 32 is turned on, and then the relay 33 is also turned on, opening its normally closed contact 33a and opening the power supply circuit 34 of the pilot motor 23. As a result, the pilot motor 23 becomes inactive, the discharge pressure of the pilot hydraulic pump 17 becomes zero, and the switching valve 15 is positioned at the neutral position by the biasing force of the return springs 15a and 15e. In addition, along with this, the hydraulic pressures to the respective hydraulic chambers 11c and 11d of the hydraulic actuator 11 become equal, and the hydraulic actuator 11 is positioned at the neutral position by the biasing force of the return springs 11e and 11f. As a result, the steering angles of the rear wheels 8a and 8b are controlled to zero and become parallel to the longitudinal direction of the vehicle body. Therefore, even if the vehicle is stored in the garage close to the side wall, etc., the rear part of the vehicle will not protrude laterally when the vehicle is taken out of the garage, and accidents such as collisions between the vehicle and the garage side wall can be prevented. can.

Then, when the set time T of the timer 31 has elapsed, the vehicle has almost left the garage, and it is desired that the minimum turning radius becomes small in order to enter the predetermined road. At this time, the relay 33 of the controller 19 is turned off by the "L" level output of the timer 31, and the power supply circuit 34 of the pilot motor 23 is closed by opening the normally closed contact 33a. Therefore, the rotational speed of the pilot motor 23 increases or decreases depending on the flow rate of the output signal from the second comparator 28, and the discharge pressure of the pilot hydraulic pump 17 also changes accordingly. As a result, the spool movement amount of the switching valve 15 changes accordingly, and eventually the rod 11a of the hydraulic actuator 11 converges to the target rod movement amount in the characteristic storage section 24. As a result, the rear wheels 8a, 8b are steered to the target steering angle of the opposite phase based on the characteristics of the characteristic storage unit 24 (see FIG. This reduces the minimum turning radius.

Therefore, at the time of starting, it is possible to reliably prevent an accident of contact with the garage side wall, etc. at the rear of the vehicle when leaving the garage by initially controlling the rear wheel steering angle to zero, and after that, after the set time has elapsed. When it is required to reduce the minimum turning radius, the rear wheels 8a and 8b can be steered in opposite phases, so the requirement can be reliably met.
The wheel steering device can be used effectively.

FIG. 6 shows a second embodiment of the present invention, in which a link mechanism interlocked with the steering device 1 is used instead of the rear wheel steering device 7 of the hydraulically controlled type in the first embodiment. (In addition,
The same parts as in the first embodiment are given the same reference numerals, and the explanation thereof will be omitted).

That is, in FIG. 6, a first I-shaped link 37 arranged in the longitudinal direction of the vehicle body is connected to the rack 4a of the rack and pinion mechanism 4 via an L-shaped link 36, and the rack 4a of the rack 4a is connected in the lateral direction of the vehicle body. By rotating the L-shaped link 36 about its fulcrum 36a in accordance with the movement, the I-shaped link 37 is moved in the longitudinal direction of the vehicle body. Further, one end 38a of a variable lever ratio link 38 disposed in the lateral direction of the vehicle body is connected to the rear end portion of the I-shaped link 37. The variable lever ratio link 38 is provided with a movable fulcrum 39 that is slidable along the variable link 38, and one end 3 of the variable lever ratio link 38 is positioned at the movable fulcrum 39 as a fulcrum.
8a is moved in the longitudinal direction of the vehicle body in accordance with the movement of the first I-shaped link 37. Further, a second I-shaped link 40 disposed in the longitudinal direction of the vehicle body is provided at the center portion 38b of the variable lever ratio link 38.
A rod 42 in the lateral direction of the vehicle body is connected to the rear end of the I-shaped link 40 via an L-shaped link 41. By moving the I-shaped link 40 in the longitudinal direction of the vehicle body, the L-shaped link 41 is rotated about its fulcrum 41a, thereby moving the rod 42 in the lateral direction of the vehicle body, thereby steering the left and right rear wheels 8a, 8b. I try to do that. The above constitutes the rear wheel steering device 7'.

The movable fulcrum 39 of the variable lever ratio link 38 is connected to a threaded member 45 that threads onto a threaded rod 44 in the lateral direction of the vehicle body which is rotationally driven by an electric motor 43. stick 4
By moving the threaded member 45 in the lateral direction of the vehicle body by the rotation of 4, the movable fulcrum 39 is slid in the lateral direction of the vehicle body along the variable lever ratio link 38, and the movable fulcrum 39 is moved to the central portion 38b as shown in the figure. When positioned further to the right, the center portion 38b of the variable link 38 moves in the same direction as the one end 38a interlocking with the first I-shaped link 37, thereby moving the second I-shaped link 40 to the first Move the rear wheels 8a and 8b in the same direction as the I-shaped link 37 to connect the front wheels 2
It is steered in the same phase as a and 2b. On the other hand, movable fulcrum 3
9 to one end 38a and center portion 38b of the variable link 38
When the center portion 38b is positioned between the rear wheels 8a, the second I-shaped link 40 is moved in the opposite direction to the first I-shaped link 37 by interlocking with the end 38a in the opposite direction. 8b to front wheels 2a, 2
It is steered in the opposite phase to b. Furthermore, when the movable fulcrum 39 is positioned to match the central portion 38b,
Regardless of the movement of the one end 38a in the vehicle body longitudinal direction, the second I
By stopping the movement of the shaped link 40, the steering angle of the rear wheels 8a, 8b becomes zero regardless of the steering of the front wheels 2a, 2b, that is, the rear wheels 8a, 8b are turned in a direction parallel to the longitudinal direction of the vehicle body. I'm trying to change direction.

Further, inside the controller 19, the rear wheel turning angle characteristic with respect to the front wheel turning angle, that is, the fulcrum position characteristic of the movable fulcrum 39 with respect to the front wheel turning angle is input and stored in advance, and the controller 19 has a variable lever ratio link. A detection signal from a rear wheel steering sensor 22' that detects the position of a movable fulcrum 39 on a wheel 38 is input. As shown in FIG. 7, the controller 19' is equipped with a zero command signal generator 46 that commands the target rear wheel turning angle to be zero, and the contact 33b of the relay 33 is Zero command signal generation unit 46 and target turning angle calculation unit 25
is selectively connected to the first comparator 26, and when the relay 33 is turned OFF, the target turning angle calculation section 25 is selected, while the relay 33 is connected to the first comparator 26.
At the time of ON operation, the zero command signal generating section 46 is selected. The other configurations are the same as those of the first embodiment.

Therefore, during the set time T when starting, the zero signal generator 46 is selected by the ON operation of the relay 33, and the controller 19' moves the movable fulcrum 39 to the center of the variable lever ratio link 38 by controlling the operation of the electric motor 43. Since the rear wheel steering angle is located at the portion 38b, the rear wheel steering angle is forcibly controlled to zero. Also, the setting time T
After the elapse of , the target steering angle calculating section 25 is selected by the OFF operation of the relay 33, and the position of the movable fulcrum 39 is controlled based on the rear wheel steering angle characteristics of the characteristic storage section 24, so that the rear wheels 8a, 8b are Based on the above characteristics, the front wheels 2a and 2b are steered in a phase opposite to that of the front wheels 2a and 2b.

Therefore, similarly to the above embodiment, it is possible to reliably prevent collisions when leaving the garage, and at normal low vehicle speeds, the rear wheels 8a, 8b
are reliably steered to opposite phases, allowing effective use of the four-wheel steering device.

In addition, in the above explanation, the set time T at the time of starting is measured by the timer 31, but this set time T
Of course, the measurement may be performed by other means. For example, as shown in FIG. 8, a mileage accumulating section 47 is provided to calculate the mileage after starting, and the actual mileage signal from the accumulation section 47 is compared with a reference value corresponding to the set mileage using a comparator 48. By doing so, it is possible to measure the set time T.

(Effects of the Invention) As explained above, according to the present invention, the rear wheels are steered in the opposite phase to the front wheels in the low vehicle speed region.
In the wheel steering system, when the vehicle starts, for a predetermined period of time, the rear wheels are restricted from being steered in the opposite phase, regardless of whether the front wheels are being steered. While it is possible to significantly steer the front wheels in the opposite direction and in the opposite phase, it is possible to reliably prevent collisions with the side walls of the garage when leaving the garage. It is possible to improve the safety of

[Brief explanation of drawings]

The drawings show embodiments of the present invention, FIG. 1 is a general schematic diagram showing the first embodiment, FIG. 2 is a diagram showing the internal configuration of the controller in FIG. 1, and FIG. 3 is a diagram showing input to the characteristic storage section. A diagram showing the characteristics of the rear wheel steering angle with respect to the front wheel steering angle that is stored. FIGS. 4A to 4C are diagrams showing the output waveform of the triangular wave generator and the output waveform of the second comparator. FIG. FIG. 6 is an overall schematic configuration diagram showing the second embodiment, FIG. 7 is a diagram showing the internal configuration of the controller in FIG. 6, and FIG. 8 is a diagram showing a modification of the timer. 1... Steering device, 2a, 2b... Front wheels, 7, 7'... Rear wheel steering device, 8a, 8b...
Rear wheel, 11...Hydraulic actuator, 13...Hydraulic pump, 15...Switching valve, 17...Pilot hydraulic pump, 18...Pilot switching valve, 19,
19'...Controller, 20...Steering angle sensor, 21...Vehicle speed sensor, 22,2
2'...Rear wheel steering sensor, 23...Pilot electric motor, 24...Characteristic storage section, 25...Target steering angle calculation section, 26...First comparator, 27...Triangular wave generation section, 28...Th 2 comparators, 29...
...First transistor, 30... Vehicle start operation detection section,
31...Timer, 32...Second transistor, 3
3... Relay, 38... Lever ratio variable link, 3
8a...one end, 38b...center portion, 39...movable fulcrum, 46...zero command signal generation section, 47...mileage distance integration section, 48...comparator.

Claims (1)

[Scope of Claims] 1. In a four-wheel steering system for a vehicle that steers the rear wheels in the opposite direction and phase to the front wheels substantially in synchronization with the steering of the front wheels in a low vehicle speed region, the starting state of the vehicle is detected. a start detecting means to input a signal from the start detecting means, and control to restrict reverse phase steering of the rear wheels for a predetermined period of time when the signal from the start detecting means is input. A four-wheel steering device for a vehicle, characterized by comprising: means.