JPS6127771A - Rear-wheel steering gear - Google Patents

Abstract

PURPOSE:To miniaturize a steering gear so compact in size, by letting a set load of a spring act on a power piston via a free piston so as to resist the operation of the power piston, while making oil pressure act on the free piston so as to weaken the energizing force of the spring. CONSTITUTION:When a steering wheel 12 is steered to the right, a selector valve 15 operates via a steering sensor 13 and a controller 14 and takes a selecting position 15c, while a variable throttle 22 is properly throttled. Therefore, oil pressure in an oil pump 17 is led into an oil chamber 1a inside a power cylinder 1. Likewise, this oil pressure also acts on an outer end face 5a of a free piston via an oil passage 31. In consequence, a total thrust of each of a power piston 2 and the free piston 5 overcomes the set load of a spring 8, making a piston rod 3 move to the right, thus rear wheels are steered. Therefore, owing to the said total thrust, even if the set load of the spring 8 is made larger, the power cylinder 1 is in no case required to make it larger at all. When the steering wheel 12 is steered to left, it is quite same.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a rear wheel steering device for a vehicle that is capable of steering the rear wheels as well.

(Prior Art) An example of a rear wheel steering device that allows the rear wheels to be steered and also has a neutral maintenance function is disclosed in Japanese Patent Application No. 15335/1987, which was previously filed by the present applicant.

(Problem to be Solved by the Invention) However, in a vehicle having a rear wheel steering device as described above, even when a large external force is applied to the wheels when driving on a rough road, the external force overcomes the action of the neutral holding mechanism. There is a need to prevent the rear wheels from shaking and the running stability of the vehicle to deteriorate.

In order to reduce disturbances caused by external forces on the rear wheel, it is possible to increase the set load of the coil spring inserted between the two free pistons in the cylinder of the neutral holding mechanism, but if the set load becomes large, the rear Since the output of the power cylinder for steering the wheels must also be increased, there is a problem in that the power cylinder must be made large if the oil pressure is constant. However, since it is desirable to make the rear wheel steering device as small as possible, the present invention aims to provide a rear wheel steering device that does not make the rear wheel steering device too large and has a high resistance to external disturbances. It is something.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a pair of free pistons in the cylinder, a neutral holding mechanism in which a spring is inserted between these free pistons, and an oil pump. In the rear wheel steering device, the rear wheel steering device is connected to a power cylinder that supplies hydraulic pressure from the front wheel through a throttle that responds to the steering of the front wheels and steers the rear wheels against the spring. It is configured to apply hydraulic pressure.

(Function) As described above, in the present invention, the force generated by the piston of the power cylinder is affected by the force generated by applying hydraulic pressure to both end surfaces of the two free pistons of the neutral holding mechanism. Since the force generated by the hydraulic pressure acting on the outer end surface of the free piston is added, a sufficiently large force can be generated without increasing the diameter of the power cylinder. Therefore, it is possible to increase the set load of the spring inserted between the two free screws 1 to 1 of the neutral holding mechanism, so that the rear wheel steering device of the present invention is small and has a high resistance to external disturbances. becomes.

(Example) Hereinafter, the present invention will be described in detail with reference to the drawings.

In the figure, 1 is a power cylinder for steering the rear wheels, 2 is its piston, 3 is a piston rod, 3a is a small diameter part provided in the middle of the piston rod 3, 3b is a stepped part on one side, and 3G is a small diameter part of the small diameter part 3a. This is the flange provided on the other side. 4 is a neutral holding mechanism cylinder connected to the power cylinder 1 so as to enclose the small diameter portion 3a, 4a is an air hole, and 5 and 6 are provided within the cylinder 4 so as to be slidably fitted to the small diameter portion 3a. A pair of free pistons 8 is a spring (coil spring) inserted between the two free pistons 5°6.

Note that 9 is a case that closes the opening of the power cylinder 1;
10 is a case connected to the outer end of the cylinder 4, and 11 is its adapter.

FIG. 1 shows a first embodiment of the present invention, in which 11 is a front wheel, 12 is a steering wheel, 13 is a steering torque sensor provided on the column of the steering wheel 2, and 14 is electrically connected to this steering torque sensor 13. The controller 15 is a switching valve having three types of patterns 15a +' 15b, 15c, which operates based on commands from the controller 14. Further, 16 is an engine of the vehicle, 17 is an oil pump, 18 is an oil tank, 19 is an oil passage connecting the discharge port of the oil pump 17 and the switching valve 15, and 20 is the switching valve 15.
An oil passage 21 connects the oil tank 18 to the oil passage 19.
．． A bypass oil passage 22 provided between the bypass oil passages 20 and 20 is a variable throttle inserted in the bypass oil passage 21, and is controlled by the controller 14. These configurations are the same as those described in Japanese Patent Application No. 59-15335@, which is the earlier application, so detailed explanation will be omitted.

In this embodiment, openings 2 are provided on both sides of the power cylinder 1.
3.24.25.26 and an opening 27 communicating with the outer end surface 5a of the free piston 5,
0, an opening 2 communicating with the outer end surface 6a of the free piston 6
8 is installed, and the switching valve 15 and the frontage 23.24 are connected to the oil passage 29.
．． 30, the openings 25 and 27 are connected through an oil passage 31, and the openings 26 and 28 are connected through an oil passage 31.
are communicated with each other through an oil passage 32. In addition to this, the set load of the spring 8 is set to be large.

Next, the operation of this embodiment configured as described above will be explained. In FIG. 1, the switching position 15b of the switching valve 15 is at the oil path 19.2.
0.29.30, and in this case, the oil passages 29 and 30 are in communication, so the piston 2 of the power cylinder 1 for steering the rear wheels is in a neutral state due to the action of the neutral holding mechanism. Therefore, the rear wheels (not shown) are held in a straight forward state, but since the set load of the spring 8 is set to be higher than that of the conventional one, the rear wheels are disturbed by the external force that is applied to the rear wheels while the vehicle is running. is smaller than the previous one.

Furthermore, when the steering wheel 12 is steered to the right or left, the switching valve 1 is activated via the steering sensor 13 d5 and the controller 14.
5 is activated to select either the switching position 15a or 15c, and the variable diaphragm 22 is appropriately narrowed down. Therefore, the oil pressure of the oil pump 17 is introduced into the oil 11a or 1b in the power cylinder 1, and is also introduced into the outer end surface 5a or ζ of the free piston 5 via the oil passage 31 or 32.
Since hydraulic pressure acts on the outer end surface 6a of the free piston 6, this total thrust overcomes the set load of the spring 8 and moves the piston rod 3 to the right or left, thereby steering the rear wheels. According to the present invention, the thrust of the piston rod 3 is obtained by the total thrust acting on the piston 2 and the free piston 5 or 6. Therefore, even if the set load of the spring 8 is increased, the power cylinder 1 can be made larger. do not have to.

FIG. 2 shows a second embodiment of the present invention, in which the same reference numerals as those described above indicate equivalent parts. In this case 3
3 is a control valve for power steering connected to the handle 12, and 34 is a power cylinder for steering the front wheels connected to this control valve 33 via oil passages 35 and 36. Note that the oil passages 29 and 30 are connected to the power cylinder 34 in this case, and the other configurations are the same as in the first embodiment.

In this embodiment, when the handle 12 is steered, the hydraulic pressure generated in the oil pump 7 enters the front wheel steering power cylinder 34 via the oil passage 35 or 36 due to the action of the control valve 33, thereby steering the front wheels. Further, the oil pressure acts on the outer end surface 5a or 6a of the free piston 5 or 6 in the power cylinder 1 for steering the rear wheels and the cylinder 4 of the neutral holding mechanism to steer the rear wheels. That is, the control valve 33 also performs the same function as the variable throttle 22 shown in FIG. 1 described above.

In the case of this embodiment as well, since the set load of the spring 8 is large, disturbance to the rear wheel can be prevented, and the thrust of the piston rod 3 is obtained as the total thrust of the piston 2 and the free piston 5 or 6, so the rear There is no need to make the power cylinder for wheel steering larger than the conventional one, and the effect can be obtained that it can be made sufficiently small.

Further, FIG. 3 shows a third embodiment of the present invention, and the same reference numerals as those mentioned above in the figure indicate equivalent parts. In this case, instead of the oil passages 31, 32 of the previous embodiment, the opening 27.
28 is provided, and the other configurations are the same as in the previous embodiment.

Therefore, in this embodiment, by steering the handle 12, the hydraulic pressure generated upstream of the control valve 33 by the throttling action of the control valve 33 acts on either the oil chamber 1a or 1b of the power cylinder 1, and
The hydraulic pressure between the oil pump 17 and the control valve 33 also acts directly on the outer end surfaces 5a, 5a of the free pistons 5, 6 in the cylinder 4 of the neutral holding mechanism. For this reason, for example, when hydraulic pressure acts on the oil chamber 1a, the thrust force that pushes the piston 2 to the right in the figure due to this hydraulic pressure is combined with the thrust force that acts on the outer end surface 5a of the free piston 5, causing the piston rod 3 to spring. 8 and move it to the right. At this time, the outer end surface 6a of the free piston 6 is connected to the case 1.
0, and the hydraulic pressure acting on this outer end surface 6a only supports a part of the reaction force.

Therefore, in this embodiment as well, the same effects as in the previous embodiment can be obtained.

(Effects of the Invention) Since the device of the present invention is as described above, according to this, the load of the spring Cera 1 to be inserted between the two free pistons of the neutral holding mechanism of the rear wheel steering device is sufficiently increased. , it is possible to prevent the rear wheels from being disturbed by external forces while the vehicle is running. Moreover, in the device of the present invention, the thrust force generated by the piston of the power cylinder and the thrust force generated by the free piston are combined, so that the rear wheel steering device can be miniaturized, which is an excellent effect.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a first embodiment of the present invention, FIG. 2 is an explanatory diagram showing a second embodiment, and FIG. 3 is an explanatory diagram showing a third embodiment. 1... Power cylinder for rear wheel steering 2... Piston 3... Piston rod 4.
... Cylinder 5.6 of neutral holding mechanism ... Free piston 5a, 6a ... Outer end surface 8 ... Spring (coil spring) 12 ... Handle 13 ... Steering sensor 1
4...Controller 15...Switching valve 17...
Oil pump 22...Variable throttle 23, 24.25
．． 26.27.28...Opening 33...Control valve 34...Power cylinder for front wheel steering.

Claims (1)

[Claims] 1. A pair of free pistons is provided in the cylinder, and a neutral holding mechanism includes a spring inserted between these free pistons, and fluid pressure from an oil pump is supplied by a throttle that responds to the steering of the front wheels. A rear wheel steering device connected to a power cylinder that steers the rear wheels against the spring, characterized in that hydraulic pressure is also applied to both outer end surfaces of the two free pistons. Steering device. 2. A rear wheel steering system according to claim 1, wherein hydraulic pressure is introduced from a power cylinder to act on both outer end surfaces of two free pistons. 3. The rear wheel steering device according to claim 1, wherein hydraulic pressure acting on both outer end surfaces of the two free pistons is directly introduced through an oil pump and a throttle that responds to the steering of the front wheels.