JPH031346Y2 - - Google Patents

Description

[Detailed explanation of the invention] (Field of industrial application) This invention can be used for four-wheel steering vehicles that can steer the front and rear wheels. The present invention relates to a rear wheel steering device for a vehicle that makes it possible to prevent unnecessary rear wheel steering during driving.

(Prior Art) Conventionally, as shown in, for example, Japanese Unexamined Patent Publication No. 58-97566, a device has been proposed that uses a mechanical link to steer the front and rear wheels in response to the steering of a steering wheel. The applicant had also previously filed a patent application in 1982.
No. 15335 (see Japanese Unexamined Patent Application Publication No. 161259/1983) proposes a device that allows front and rear wheels to be steered.

The apparatus proposed by the applicant has a configuration as shown in FIG. This is the front wheel (not shown)
This is mounted on a vehicle that is steered by a power steering device, and the power cylinder 5 is used during steering.
The purpose is to simultaneously steer the rear wheels 34a and 34b by using the hydraulic pressure difference generated between the two wheels.

That is, in the cylinder 35 of the hydraulic actuator 31 having two left and right pressure chambers 37 and 38,
A piston rod 32 to which two pistons 45, 46 are fixed is inserted, and both ends of the piston rod 32 are connected to knuckle arms 33a, 33b of rear wheels 34a, 34b.

The left and right pressure chambers 37 and 38 are connected to the left and right pressure chambers 5c and 5c of the power cylinder 5 through oil passages 8 and 9, respectively.
I am contacting 5d. Here, the oil passages 8 and 9 intersect in the middle and form the left pressure chamber 5 of the power cylinder 5.
c shows the pressure chamber 3 on the right side of the hydraulic actuator 31.
8 is in the right pressure chamber 5d of the power cylinder 5,
The left pressure chamber 37 of the hydraulic actuator 31 is in communication. As a result, the rear wheels 34a, 34b
The front wheels are steered in the opposite direction (this is called "reverse phase steering"), making it possible to shorten the turning radius.

In the power cylinder 5, a piston rod 5b fixed to a piston 5a is connected to a knuckle arm of the front wheel, and a control valve 2 operates in response to the steering angle of the steering handle 1, communicating with left and right pressure chambers 5c and 5d. Oil lines 6, 7
The piston rod 5b is moved by adjusting the flow rate of the hydraulic oil. Further, the hydraulic oil is discharged from the oil pump 3 and returned to the tank 4.

Further, within the central chamber 36 of the hydraulic actuator 31, repulsion plates 40, 41 biased in the left-right direction by a spring 42 are accommodated in a loosely fitted state on the piston rod 32.

This is a structure to prevent the rear wheels from being steered when the steering torque of the steering handle 1 is less than a predetermined value. For example, when moving the piston rod 32 in the direction of arrow A in the figure, the left pressure chamber 37 Even if the hydraulic pressure increases, the piston 45
Since it receives the reaction force P _R of the repulsion plate 40, it will not move until a hydraulic pressure exceeding the reaction force of the spring 42 is applied to the piston 45 (this characteristic is shown in FIG. 8).

As a result, when driving at high speed, even if the steering wheel is slightly turned, the rear wheels 34a,
34b is not steered, it is possible to suppress the rocking of the rear part of the vehicle body, and it is possible to improve the steering stability during high-speed driving.

(Problem to be solved by the invention) However, in the rear wheel steering device using the hydraulic actuator 31 as described above, when the steering torque of the steering handle 1 is equal to or higher than a predetermined value, the rear wheels are always steered. For example, when driving at high speed, if you suddenly turn the steering wheel to avoid an emergency, the steering torque is large, so there is a risk that the rear wheels will be steered and the vehicle will turn sharply. There is.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides a system in which when the front wheels are steered by steering the steering wheel, the rear wheels are steered by an actuator supplied with pressure from a pressure source. a vehicle speed sensor that detects the running speed of the vehicle; and a vehicle that drains the pressure from the pressure source so that the rear wheels cannot be steered when the vehicle speed detected by the vehicle speed sensor exceeds a predetermined value. This configuration is provided with a variable throttle valve that lowers the value to a certain value.

(Function) When driving at high speeds, the pressure supplied from the pressure source to the actuator by the variable throttle valve is reduced to a pressure that makes it impossible to steer the rear wheels, so even if the steering wheel is turned significantly, the rear wheels are not steered and the vehicle body This eliminates inconveniences such as sudden turns.

(Embodiment) The configuration of a first embodiment of the present invention is shown in FIG. In this figure, the same components as those of the device according to the prior application shown in FIG. 7 are given the same reference numerals, and the explanation thereof will be omitted.

The device of this embodiment includes a vehicle speed sensor 62, a valve controller 63, and a variable throttle valve 154 in addition to the configuration of the device of the prior application shown in FIG.

The variable throttle valve 154 is provided between the discharge port of the oil pump 3 as a pressure source and the tank 4, and adjusts the drain amount of discharged oil.

This variable throttle valve 154 is driven by a valve controller 63, and this valve controller 63 increases or decreases the opening area of the variable throttle valve 54 in response to an increase or decrease in the vehicle speed detected by the vehicle speed sensor 62.

The other configurations are the same as the device of the prior application shown in FIG.

With such a configuration, the maximum value of the working oil pressure applied to the hydraulic actuator 31 as the actuator for steering the rear wheels changes depending on the vehicle speed. That is, as shown in Fig. 2, when the vehicle speed is low, the hydraulic pressure has the characteristic _P1 ,
Steering torque of steering handle 1 is a predetermined value
When T _S is exceeded, the reaction force of the repulsion plates 40 and 41 is exceeded, and the rear wheels are steered.

As the vehicle speed increases, the hydraulic pressure change characteristics change as shown in P ₂ to _{P 4} , and when driving at medium speeds, as shown in characteristic P ₂ , the change characteristics of the hydraulic pressure change at the point when the rear wheels start turning. The steering torque of _T1 becomes slightly higher.

In a high-speed running state where the vehicle speed exceeds a predetermined value, as shown in characteristics P ₃ and P ₄ , even if the steering torque increases, the hydraulic pressure is reduced by the reaction force of the repulsion plates 40 and 41.
P _R will no longer be exceeded, and no matter how much the steering wheel 1 is turned, the rear wheels will not be steered.

In this state, the piston rod 32 is held in the neutral position by the action of the repulsion plates 40, 41, so the rear wheels 34a, 34b are also fixed in the neutral position, and steering is also prevented by applying external force to the rear wheels. can.

Furthermore, since the variable throttle valve 154 can also vary the supply hydraulic pressure of the control valve 2, the rate of increase in the output of the power cylinder 5 for front wheel steering decreases as the vehicle speed increases, as shown in FIG. However, the steering wheel becomes harder to operate, improving steering stability. The characteristic P ₀ in the figure is the change characteristic of the steering force when the front wheels are steered without using the power steering device. Note that similar characteristics can be obtained for the rear wheels as well.

Next, FIG. 4 shows the configuration of a second embodiment of the present invention.

This embodiment shows an example in which the front wheels 52a, 52b are steered by a mechanical link type steering device 53, and the rear wheels 34a, 34b are
Hydraulic actuator 31 same as the first embodiment
The steering is carried out by

The hydraulic actuator 31 has left and right pressure chambers 37,
Oil passages 57 and 58 that supply hydraulic oil to the oil pump 38 are communicated with a discharge oil passage 55 of the oil pump 3 and a drain oil passage 56 to the tank 4 via a solenoid valve 60.

The direction of the solenoid valve 60 is changed by a controller 61, and the solenoid valve 60 is a parallel two-way valve 60a.
When the valve is switched to the two-way valve 60b, hydraulic pressure is supplied to the right pressure chamber 38, and the rear wheels 34a and 34b are turned to the right. Conversely, when the valve is switched to the two-way valve 60b, the rear wheels 34a and 34b are turned to the left.

Further, a variable throttle valve 154 is provided between the discharge oil passage 55 and the drain oil passage 56 to adjust the drain amount of the discharge oil. controller 6
1 switches the solenoid valve 60 in response to the positive or negative output of the steering torque sensor 54 that detects the steering torque of the steering handle 1, and is variable in response to the magnitude of the absolute value of the output of the steering torque sensor 54. The opening area of the throttle valve 154 is changed.
This operation causes the rear wheels 34a, 34b to turn to the left in accordance with the steering direction of the steering handle 1.
The right steering is switched, and the steering angle of the rear wheels is controlled in accordance with the steering angle of the steering handle 1.

At this time, as in the case of the first embodiment, due to the action of the repulsion plates 40 and 41 within the hydraulic actuator 31, the hydraulic pressure supplied to the pressure chambers 37 and 38 exceeds the reaction force of the repulsion plates 40 and 41. If this is not the case, the rear wheels will not be able to steer the vehicle.

That is, as shown in FIG. _5A0 , when the steering torque reaches a value _T0 that is slightly smaller than the predetermined value _Ts , the opening area of the variable throttle valve 154 starts to be reduced. Then, as shown in FIG. 6 P _L , the hydraulic pressure supplied to the hydraulic actuator 31 begins to increase, and when the steering torque exceeds a predetermined value T _S , the hydraulic pressure exceeds the reaction force P _R of the repulsion plate, and the rear Wheel steering takes place.

Further, the controller 61 operates to reduce the rate of increase in the opening area of the variable throttle valve 154 in response to an increase in the vehicle speed detected by the vehicle speed sensor 62.

As a result, when the vehicle speed exceeds a predetermined value, the variable throttle valve opening area becomes relatively large after the steering torque exceeds T _o , as shown in Figure _5A1 , and as shown in Figure 6P. As shown in _H , the working oil pressure supplied to the hydraulic actuator 31 is at most less than the reaction force P _R of the repulsion plate. Therefore, when the vehicle is running at high speed, the rear wheels will not be steered no matter how much the steering wheel 1 is turned.

In each of the above embodiments, an example is shown in which rear wheel steering is disabled by reducing the hydraulic pressure below the reaction force of the repulsion plates 40, 41 in the hydraulic actuator 31, but in addition to this, For example, when using a hydraulic actuator that does not include the repulsion plates 40, 41, the same effect can be obtained by reducing the working oil pressure to zero during high-speed travel.

(Effects of the invention) As explained in detail above, the invention prevents the rear wheels from being steered and prevents the vehicle from making sharp turns even when the steering wheel is turned significantly while driving at high speed. , safety can be improved.

Further, since it can be constructed by adding a cheap and simple member such as a variable throttle valve, it is advantageous in terms of manufacturing cost and workability.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the first embodiment of the present invention, Figs. 2 and 3 are operational characteristic diagrams of the same embodiment, Fig. 4 is a block diagram of the second embodiment of the present invention, and Figs. 6th
FIG. 7 is a diagram showing the operating characteristics of the same embodiment, FIG. 7 is a block diagram of the device according to the earlier application, and FIG. 8 is a diagram showing the operating characteristics of the device according to the earlier application. 1... Steering handle, 3... Oil pump (pressure source), 5... Power cylinder, 31...
... Hydraulic actuator (rear wheel steering actuator), 32 ... Piston rod, 34a, 34b
...Rear wheel, 37, 38...Pressure chamber, 45, 46...
...Piston, 52a, 52b...Front wheel, 154...
...Variable throttle valve, 61...Controller (valve controller), 62...Vehicle speed sensor, 63...Valve controller.

Claims (1)

[Scope of Claim for Utility Model Registration] In a vehicle in which the rear wheels are steered by an actuator supplied with pressure from a pressure source when the front wheels are steered by turning the steering wheel, a vehicle speed sensor that detects the running speed of the vehicle; and a variable throttle valve that drains the pressure from the pressure source to reduce the pressure to a value at which the rear wheels cannot be steered when the vehicle speed detected by the vehicle speed sensor exceeds a predetermined value. Rear wheel steering device for vehicles.