JPS6210871B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power steering system for a vehicle, mainly an automobile, and more particularly to a steering wheel having a pinion shaft connected to a steering wheel and a pinion of the pinion shaft in a gear box. It consists of a series of rack rods, a power cylinder that can hydraulically drive the rack rods, and a switching valve that can selectively connect the left and right oil chambers of the power cylinder to a hydraulic power source and an oil reservoir, respectively. is supported on a rocking cage that is rotatably supported on the gear box with a certain amount of eccentricity with respect to its axis, and responds to the rotation of the rocking cage that occurs when a steering torque is applied to the pinion shaft. The invention relates to a power steering system in which the swing cage and the switching valve are interlocked with each other so that the switching valve performs a switching operation.

Power steering devices of this type are known in the art, for example as disclosed in US Pat. No. 3,897,845. However, in order to support the rocking cage on the gear box, the conventional type uses a pivot pin that is spaced apart from and parallel to the pinion shaft, so a relatively large space is required to install the pivot pin. However, there is a disadvantage that the device, especially the gear box, becomes larger.

Therefore, the present invention provides a simple and small-sized device that allows the rocking cage to be supported on the gear box while maintaining a predetermined eccentric relationship with the pinion shaft without using such a pivot pin. Its characteristics are that the outer circumferential surface of the rocking cage is supported by the gear box via an outer bearing, and an inner bearing that supports the pinion shaft is placed inside the rocking cage, and the outer peripheral surface of the rocking cage is The bearing is installed with a certain amount of eccentricity relative to the bearing.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings. Reference numeral 1 denotes a gear box fixed to a vehicle body (not shown), through which a rack rod 2 that is linked to a knuckle arm of a steering wheel (not shown) is slidably penetrated. A pinion 3a of a pinion shaft 3 connected to a steering handle (not shown) meshes with the rack 2a of the rack rod 2.

The pinion shaft 3 has a pair of upper and lower inner bearings 5, 5' on the inner peripheral surface of a rocking cage 4 that encloses the pinion 3a.
Further, the rocking cage 4 is rotatably supported via the gear box 1, and the outer peripheral surface of the rocking cage 4 is supported by a pair of upper and lower outer bearings 6,
6', in particular at least one inner bearing 5 is mounted in the gear box 1 inside the outer bearing 6. The above pinion shaft 3 and rocking cage 4
have different axes from each other due to the eccentric arrangement of the inner bearings 5, 5' and the outer bearings 6, 6', that is, the axis O3 of the rocking cage 4 is the axis _O3 of the pinion shaft 3.
It is shifted by a predetermined eccentric amount ε from O ₃ toward the meshing point of the rack 2a and pinion 3a, and when the switching valve 9 is in the neutral state, which will be described later, connects the axis O ₃ of the pinion shaft 3 and the meshing point of the rack 2a and pinion 3a. It is set to occupy a position on straight line A.

A window 7 is provided on one side of the swinging cage 4 to avoid interference with the rack 2a, and the rack 2a and pinion 3a are meshed through the window 7. Further, an operating rod 8 for a switching valve 9 is integrally provided on the upper end surface of the swinging cage 4 at a distance from its axis O ₄ by a distance l exceeding the eccentricity ε.

The switching valve 9 can be of any type as long as it is a four-way switching valve, but in the example shown, it is a valve box 10 fixed to the gear box 1 and a spool valve 12 that slides into the valve hole 11 of the valve box 10.
The spool valve 1 is configured in a spool type.
The tip of the operating rod 8 is engaged with a long hole 13 extending in the radial direction of the swinging cage 4 provided at one end of the swinging cage 2, so that the swinging cage 4 rotates around its axis _O4 . The spool valve 12 can be operated from side to side via the operating rod 8.

The spool valve 12 has three annular grooves 14, 15, and 16 on its outer circumferential surface, and the central groove 15 is connected to a hydraulic source 18 such as a hydraulic pump through a supply oil passage 17 that opens to the valve hole 11. Also, groove 1 on both sides
4 and 16 are in communication with the oil reservoir 20 via return oil passages 19 connected to the hollow portion 12a of the spool valve 12, respectively. On the other hand, the valve case 10 is provided with two annular grooves 21 and 22 arranged on the inner peripheral surface of the valve hole 11 so as to sandwich the open end of the supply oil passage 17, and these grooves are arranged on the rack rod 2. It communicates with the left and right oil chambers of a conventional power cylinder 23 (part of which is shown in FIG. 1) via output communication passages 24 and 25.

Therefore, if the spool valve 12 is displaced to the right or left from the neutral position shown in the figure, one of the left and right oil chambers of the power cylinder 23 will be connected to the supply oil path 17 and the other will be connected to the return oil path 19 as usual. As a result, pressure oil from the hydraulic source 18 is supplied to the oil chamber connected to the supply oil path 17, and the hydraulic pressure drives the rack rod 2 to the right or left for operation. The direction wheels can be turned.

A reaction mechanism 26 is attached to the switching valve 9 to normally hold the spool valve 12 in the neutral position shown. The mechanism 26 includes a cylinder hole 27 provided in the valve case 10 parallel to the valve hole 11, a pair of pressure receiving pistons 29 and 29' that slide into the cylinder hole 27 and define a reaction chamber 28 therein, and both pressure receiving pistons 29. , 29' outwardly, and a pair of contact pins 31, 3 that protrude from one side of the spool valve 12 and sandwich both pressure receiving pistons 29, 29'.
1', both pressure receiving pistons 2
9 and 29' are regulated in their outward movement by the inner surfaces of the left and right lids 10a and 10b of the valve case 10, and the reaction chamber 28 is connected to the annular groove 15 in the center of the spool valve 12, and thus to the supply oil path. It communicates with 17. Further, relief grooves 32, 32' are provided in the portions of the valve case 10 facing the abutment pins 31, 31' to avoid interference with the pins 31, 31' when the spool valve 12 is operated. .

In the illustrated example, the reaction mechanism 26 is connected to the spool valve 12.
Although it is provided only on one side, if a pair of these is provided symmetrically with the spool valve 12 in between, the bending forces applied to the spool valve 12 of each reaction mechanism will be balanced with each other, and the sliding performance of the spool valve 12 will be improved. It is effective in keeping the

The base 8a of the operating rod 8 is formed to have a large diameter so as to have sufficient strength, and the through hole 33 of the lid body 10a provided corresponding to the base 8a is formed to have an even larger diameter. , the operating rod 8 moves ±1 mm in the axial direction of the spool valve 12 from the neutral position shown.
A gap is ensured that allows for sufficient swing. The large-diameter base 8a of the operating rod 8 and the lid 10a having the through hole 33 constitute a fail-safe mechanism in the event of a hydraulic system failure.

The gear box 1 includes a guide piston 3 that slidably supports one side of the rack rod 2 on the opposite side from the pinion 3a.
4 is fitted, and a cap 36 is further screwed on with the spring 35 in between, and the elastic force of the spring 35 presses the rack rod 2 toward the pinion shaft 3 via the guide piston 34, and the rack 2a and pinion 3a It is designed to eliminate the crushing of the meshing part.

Next, to explain the operation of this embodiment, when no steering torque is applied to the pinion shaft 3, the neutral return spring 30 is activated by the pressure receiving piston 29,
29' is held in contact with the lids 10a and 10b, the spool valve 12 is held in the neutral position by these pistons via the pair of abutment pins 31 and 31', and the two grooves of the valve hole 11 are held in the neutral position. annular groove 21, 2
2 are connected to the supply oil passage 17 and the return oil passage 19 at the same time, so that the power cylinder 2
3 remains inactive. When the spool valve 12 is in the neutral state, the axis _O3 of the pinion shaft 3 is located on the extension line A of the straight line connecting the axis O4 of the rocking cage ₄ and the meshing point of the rack 2a and pinion 3a.

Therefore, if you try to drive the rack 2a in the axial direction from the pinion 3a by applying steering torque to the pinion shaft 3 via the steering handle, a reaction force will be generated from the rack 2a to the pinion 3a depending on the magnitude and direction of the driving force. This reaction force causes the pinion shaft 3 to rotate together with the swing cage 4 around the axis O ₄ of the swing cage. When this turning moment exceeds the opposing moment due to the set load of the neutral return spring 30, the above-mentioned turning starts, and the angular displacement of the pinion shaft 3 around the axis _O4 is expanded by the lever ratio l/ε. As a result, the operating rod 8 gives sufficient axial displacement to the spool valve 12 to reliably cause the switching operation, so that the power cylinder 23 operates to assist the pinion shaft 3 in driving the rack rod 2.

On the other hand, due to the switching operation of the switching valve 9, the reaction mechanism 26
The working pressure of pressure oil supplied from the supply oil path 17 to the power cylinder 23 is introduced into the reaction chamber 28,
This pushes the pressure receiving pistons 29, 29' outward and applies a reaction force to the spool valve 12 via the contact pins 31, 31' to return it to the neutral position. Excessive switching operation is suppressed.

In this case, as a result of expanding the movement of the operating rod 8 by the lever ratio l/ε, the force acting on the spool valve 12 from the operating rod 8 is conversely reduced by the ratio ε/l, so the effective pressure receiving area of the reaction chamber 28 In addition, the strength of the neutral return spring 30 can be set to a correspondingly small value, so that the reaction mechanism 26 can be configured to be extremely compact, and as a result, the entire device can be made compact.

During steering, the axis O 3 of the pinion shaft ₃ moves from its neutral position to the axis O ₄ of the rocking cage 4 in either the left or right direction.
, the pinion shaft 3 is pressed against the rack rod 2 due to the above-mentioned eccentric relationship between the pinion shaft 3 and the rocking cage 4, that is, it has a movement component in the direction toward the rack 2a. . Therefore, when the rack rod 2 is pressed against the pinion shaft 3 due to road resistance, the road resistance acts as a force to push the axis O 3 of the pinion shaft ₃ back to the neutral position shown in the figure, and is applied to the elastic force of the neutral return spring 30. If the rack rod 2 is pulled away from the pinion shaft 3 due to road resistance, the bearings 6, 6' of the rocking cage 4
The load on them is reduced and the frictional resistance on them is reduced. Therefore, in either case, the return of the swing cage 4 to neutrality is facilitated.

According to steering in an emergency when pressure oil cannot be supplied to the oil supply line 17 due to damage to the transmission member that drives the hydraulic power source 18 or failure of the engine, the rotation of the swing cage 4 causes the movement of the oil from the operating rod 8. Even if the spool valve 12 is moved, the power cylinder 23 cannot be operated, but when the rotation of the operating rod 8 reaches a certain amount, it collides with the side wall of the through hole 33 of the lid body 10b and stops.
Therefore, since the swinging cage 4 is immediately prevented from rotating, the steering torque applied to the pinion shaft 3 directly drives the rack rod 2, enabling manual steering and safely changing the course of the vehicle. I can do it. Even in this case, the reaction force acting on the pinion 3a from the rack 2a is reduced by the lever ratio ε/l and acts on the operating rod 8, so the strength of the operating rod 8, the surface pressure strength of the through hole 33, etc. are set significantly lower. can do.

As described above, according to the present invention, the outer peripheral surface of the swinging cage 4 is supported by the gear box 1 via the outer bearing 6, and the inner bearing 5 supporting the pinion shaft 3 is provided inside the swinging cage 4.
is mounted inside the outer bearing 6 with a certain amount of eccentricity relative to the bearing 6, so the swing cage 4 can be moved while maintaining a predetermined eccentric relationship with the pinion shaft 3 without using a special pivot pin. It can be supported on the gear box 1 without any inconvenience, and the number of parts is reduced compared to conventional ones, which not only simplifies the structure, but also
In particular, it can contribute to downsizing of gear boxes. Moreover, since the outer bearing 6 that supports the rocking cage 4 is arranged so as to surround the pinion shaft 3, it is possible to use a large diameter type with a large load capacity without any interference with the pinion shaft 3. Therefore, it can sufficiently withstand large steering torques and contribute to improved durability.

[Brief explanation of the drawing]

The drawings show one embodiment of the device of the present invention, and FIG. 1 is a front view of the main part, FIG.
The figure is a cross-sectional view taken along lines - and - in FIG. 1. 1... Gear box, 2... Rack rod, 2a... Rack, 3... Pinion shaft, 3a... Pinion, 4...
...Swinging basket, 5...Inner bearing, 6...Outer bearing, 8
...Operating rod, 9...Switching valve, 18...Hydraulic power source, 2
0...Oil sump, 23...Power cylinder, O ₃ ...
Axial center of pinion shaft, O ₄ ...Axis center of rocking cage, ε...
...Eccentricity.

Claims (1)

[Claims] 1 A pinion shaft 3 connected to the steering wheel; and a rack rod 2 connected to the steering wheel, with a rack 2a meshing with the pinion 3a of the pinion shaft 3 in the gear box 1.
It consists of a power cylinder 23 that can hydraulically drive the rack rod 2, and a switching valve 9 that can selectively connect the left and right oil chambers of the power cylinder 23 to the hydraulic power source 18 and the oil sump 20, respectively. The pinion shaft 3 is supported by a rocking cage 4 which is rotatably supported by the gear box 1 with a certain amount of eccentricity ε with respect to its axis, and the above-mentioned phenomenon occurs when a steering torque is applied to the pinion shaft 3. The switching valve 9 changes depending on the rotation of the swinging basket 4.
In a power steering system for a vehicle in which the swinging cage 4 and the switching valve 9 are interlocked with each other so as to perform switching operations, the outer peripheral surface of the swinging cage 4 is supported by the gear box 1 via an outer bearing 6. and an inner bearing 5 for supporting the pinion shaft 3 is mounted inside the outer bearing 6 in a state eccentric by the predetermined amount ε with respect to the bearing 6. Vehicle power steering system.