JPS638076A - Rear wheel steering device - Google Patents

Abstract

PURPOSE:To prevent the steering direction of a rear wheel from becoming reverse to the direction intended by a driver midway while operating by enabling switching from the same phase to the opposite phase or vice versa only when a lateral acceleration less than a set value continued for a defined period of time. CONSTITUTION:A powder cylinder S2 for steering rear wheels 10 is connected to a control valve 3 via an electromagnetic direction selector valve 11 and passages 12, 13. A solenoid 17 is provided in the electromagnetic direction selector valve 11 and its switching direction is controlled according to the exciting current for the solenoid 17. A solenoid 18 is also provided on a throttle valve 16, and the exciting currents for the solenoids 17, 18 are controlled by a controller C. A vehicle speed sensor 19, a lateral acceleration sensor 20, a steering angle sensor 21, and a rack shaft force sensor 22 are connected to the controller C and, when a lateral acceleration is larger than a set value, the phases of front and rear wheels are not varied even if the vehicle speed is changed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a rear wheel steering device that steers rear wheels using the driving force of a power cylinder.

(Prior Art) Conventionally, the rear wheels were steered in a predetermined direction depending on the vehicle speed. For example, when driving at high speeds, the wheels were placed in the same phase as the front wheels to improve maneuverability, while when driving at low speeds, the wheels were placed in the opposite phase to the front wheels to improve turning ability. While the vehicle is running, when the speed changes from high speed to low speed or from low speed to high speed, the system automatically switches from in-phase to anti-phase or from anti-phase to in-phase.

(Problems to be Solved by the Present Invention) In the conventional device as described above, if there is a change in speed, the phases of the front and rear wheels automatically change. Then, during the operation, the steering direction of the rear wheels becomes opposite to the direction intended by the driver, which is extremely dangerous.

An object of the present invention is to detect the lateral acceleration of the vehicle and switch the steering direction of the rear wheels only after the lateral acceleration has continued for a predetermined period of time, thereby eliminating the danger of switching direction. The goal is to provide the following.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides an electromagnetic directional switching valve that controls the power cylinder on the rear wheel side, and uses an electric directional switching valve controller to control the power cylinder on the rear wheel side. In the front and rear wheel steering device, the front and rear wheel steering devices control the front and rear wheels in the same phase or in opposite phases depending on the driving conditions of the vehicle, and are equipped with a lateral acceleration sensor and a vehicle speed sensor,
Both of these sensors are connected to the above controller, and only when the vehicle speed switches to either above or below the set speed and the lateral acceleration below the set value continues for a predetermined period of time, the in-phase to out-of-phase or out-of-phase The configuration is such that switching from in-phase to in-phase.

(Operation of the present invention) With the above configuration, the magnitude of the lateral acceleration G generated in the vehicle is determined, and if the lateral acceleration is greater than the set G, even if the vehicle speed changes, the Do not change the phase of the ring.

(Effects of the present invention) As described above, the phase of the front and rear wheels is changed only when the lateral acceleration remains smaller than the set G for a predetermined period of time, so even if the vehicle speed changes while the steering wheel is being operated, However, the phase of the front and rear wheels does not change. Therefore, when the driver starts operating the steering wheel, the rear wheels are steered in the direction that the driver intends.

(Embodiment of the present invention) The first embodiment shown in FIG. It engages with a rack 7 formed on the side rod 6 of 5. This side rod 6 transmits the driving force of the power cylinder S1 to the front wheel 5,
The steering force for the front wheels 5 is power assisted.

The control valve 3 is the power cylinder S! Depending on the switching direction, one cylinder chamber 8 of the power cylinder Sl is switched to the pump P or the tank T.
The other cylinder chamber 9 is connected to the tank T or the pump P.

Further, the power cylinder S2 for steering the rear wheel IO is communicated with the control valve 3 via the electromagnetic directional control valve 11 and the passage 12.13. And the above passage 12.13
is provided with a fixed throttle 14.15, and is connected to a passage 12.13 downstream of the fixed throttle 14.15 via a throttle valve 16.

The electromagnetic directional switching valve 11 is provided with a thread/id 17, and the switching direction thereof is controlled in accordance with the excitation current applied to the solenoid 17.

Further, the throttle valve 16 is also provided with a solenoid 18, and the throttle valve
The opening degree of 6 is controlled.

The excitation current for the solenoids 17 and 18 is controlled by the controller C.
, a vehicle speed sensor 19, a lateral acceleration sensor 20, a steering angle sensor 21. A rack axial force sensor 22, etc. is connected to it. The electromagnetic directional control valve 11 and throttle valve 16 connected to this controller C are operated according to the driving conditions of the vehicle.
The switching direction and opening degree are controlled.

When the handle 1 is turned, the pinion 4 first rolls on the rack 7, and the control valve 3 is switched by the rocking of the input shaft 2 at this time. As a result, one cylinder chamber 8 communicates with the pump P, and the other cylinder chamber 9 communicates with the tank T, for example. Therefore, the power cylinder S+ is driven to assist the steering force of the front wheels 5.

At this time, one passage 1 connected to the electromagnetic directional control valve 11
2 communicates with the pump P, and the other passage 13 communicates with the tank T.

Therefore, a part of the oil discharged from the pump P is supplied to the electromagnetic directional switching valve 11 via the one passage 12, and the supply flow rate is determined according to the opening degree of the throttle valve 16. The larger the opening degree of the throttle valve 16, the more the one passage 1
Since the second pressure oil escapes to the other passage 13 side via this throttle valve 16, the flow rate supplied to the electromagnetic directional control valve 11 decreases. Conversely, the smaller the opening degree of the throttle valve 16, the smaller the amount of escape, and therefore the larger the flow rate supplied to the electromagnetic directional switching valve 11.

Then, the electromagnetic directional switching valve 11 switches between the cylinder chambers 23 and 24 of the power cylinder S2 according to its switching position.
One of the chambers is communicated with one of the passages 12, and the other chamber is communicated with the other passage 13.

The electromagnetic directional control valve 11 and the throttle valve 1B are controlled according to the output signal of the controller C as described above. For example, the faster the vehicle speed is, the larger the opening degree of the throttle valve 16 is, The flow rate supplied to cylinder S2 is reduced to reduce its power assist force.

Further, the switching direction of the electromagnetic directional switching valve 11 is also controlled according to the driving conditions of the vehicle. As mentioned above, one cylinder chamber 8 of the power cylinder S1 on the front wheel side
When the front wheels 5 are being steered to the left as shown by the chain line, the electromagnetic directional control valve 11 is switched.
If pressure oil is supplied to one cylinder chamber 23 of the power cylinder S2 on the rear wheel side, the rear wheel 10 is also steered in the same direction as the front wheel 5, as shown by the chain line, so the rotation of the front and rear wheels at this time is The phases in the rudder direction are in phase.

When the front wheel side is steered to the left as described above, when the electromagnetic directional control valve 11 is switched to the opposite direction to supply pressure oil to the other cylinder chamber 24, the rear wheel lO is turned to the first
Since the vehicle is steered to the right, which is the opposite direction to the chain line in the diagram, the phases of the steering direction of the front and rear wheels at this time are opposite to each other.

If the phases of the steering direction of the front and rear wheels are made to be in the same phase at high speeds, the steering stability is improved, and if the phases of the steering direction of the front and rear wheels are made to be in opposite phases at low speeds, the turning ability is improved.

However, when the vehicle speed changes while operating the steering wheel 1, if the phase of the steering direction of the front and rear wheels is switched unconditionally, the rear wheels will be switched in a direction that the driver did not intend. Therefore, we have improved this point. In order to do this, the switching timing is shown in the timing chart of FIG.

In other words, when the lateral acceleration G of the vehicle traveling below the set speed becomes below the set value at the sexgon I and continues for a predetermined time, that is, when the /\handle l is hardly operated. When the vehicle speed exceeds the set speed in section (2) which continues for a predetermined period of time, the electromagnetic direction switching valve 11 starts to operate so that the phases of the steering directions of the front and rear wheels are in the same phase.

In other words, when the lateral acceleration G exceeds the set value in section ■ while continuing this running state, and the lateral acceleration G is maintained at or above the set value, in other words, when the lateral acceleration G exceeds the set value, When the vehicle is being steered, even if the vehicle speed becomes lower than the set speed in section (2), the phase of the steering direction of the front and rear wheels is not changed, that is, the same phase is maintained in section (2).

However, if the vehicle continues to travel at a speed below the set speed and the lateral acceleration G becomes below the set value in section V, and this continues for a predetermined period of time up to section ■, then , the electromagnetic directional switching valve 11 operates to switch so that the phases of the steering directions of the front and rear wheels are opposite to each other.

In other words, according to the signal from the lateral acceleration sensor 20,
The determination circuit 25 determines whether the lateral acceleration G is below the set value, and if it exceeds the set value, no matter how the vehicle speed changes, the controller C does not operate and the front and rear wheels are The phase of the steering direction is not changed, and even if the lateral acceleration G is below a set value, the phase is not changed until after this continues for a predetermined period of time. In other words, the phase is changed after a delay time has elapsed after the lateral acceleration G changes.

The second embodiment shown in FIG. 3 is similar to the throttle valve 18 of the first embodiment.
is omitted, and the electromagnetic directional switching valve 11 is provided with the flow rate control function performed by the throttle valve 18.

That is, in the electromagnetic directional switching valve 11 of the second embodiment, the switching direction and switching amount are controlled by the controller C described above.

The other configurations are the same as those of the first embodiment, and furthermore,
The control timing is also as shown in the chart of FIG.

In the third embodiment shown in FIG. 4, a pump P1 that supplies pressure oil to the power cylinder S1 on the front wheel 5 side and a pump P2 that supplies pressure oil to the power cylinder S2 on the rear wheel 10 side are separated. At the same time, a flow control valve 26 and a rear wheel control valve 27 having an opening/closing function are connected in the process from the pump P2 to the electromagnetic directional switching valve 11. The rear wheel control valve 27 is switched using the pressure in the passage 12.13 connected to the power cylinder S1 on the front wheel side as a pilot pressure. Therefore, when the front wheels are being steered, the control valve 27 is always kept open.

Note that the flow rate control valve 26 is controlled by an output signal from the controller C.

The rest of the configuration and its control form are the same as those of the first embodiment.

[Brief explanation of drawings]

Figure 1 is a circuit diagram of the first embodiment of the invention, Figure 2 is a chart of its control timing, and Figures 3.4 and 2.
FIG. 3 is a circuit diagram of a third embodiment. St, S2...power cylinder, 11...electromagnetic directional control valve, C...controller, 19...vehicle speed sensor. 20... Lateral acceleration sensor.

Claims (1)

[Claims] An electromagnetic directional switching valve is provided to control the power cylinder on the rear wheel side, and this electromagnetic directional switching valve is electrically controlled by a controller to set the steering direction of the front and rear wheels in the same phase according to the driving conditions of the vehicle. In a front and rear wheel steering system that uses a front and rear wheel steering system, it is equipped with a lateral acceleration sensor and a vehicle speed sensor, and these sensors are connected to the controller described above. A rear wheel steering device configured to switch from in-phase to anti-phase or from anti-phase to in-phase only when lateral acceleration below a value continues for a predetermined period of time.