JPS6140585B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention includes a servo pump, a working piston that partitions a steering mechanism casing into two pressure chambers, and a steering nut rotatably supported within the working piston. a control valve having teeth such that the Pitman arm shaft is swung, the steering nut being eccentrically disposed transversely within the working piston via a companion pin to which the steering nut is attached; The present invention relates to a power steering device, especially for automobiles, which drives a motor vehicle.

A known power steering device of such construction (cf. German Patent Application No. 1817940) has two spring-loaded stopper pins in the transverse holes of a trailing pin connected to the steering nut. These stop pins are held without play by two adjusting bolts with conical tips which are screwed into the working piston and held by locking nuts. With such a centering device,
The steering nut position and control valve position are maintained in a neutral steering position. However, after a certain period of operation of such an auxiliary steering device, wear occurs between the adjusting bolt and the spring-loaded stop pin, so that accurate centering of the control valve is no longer possible. Furthermore, when the direction of rotation is reversed, as wear progresses, one of the stopper pins will no longer connect, resulting in a chattering noise. Apart from the reduced functional accuracy, the production of this known centering device is relatively expensive. That is, for example, each stop pin must be ground and its hole must be polished smooth for easy operation. Furthermore, there is a hole point where the characteristics of the control valve vary depending on two criteria: spring pressure and spring constant. Therefore, a linear characteristic curve determined by two points has been chosen.

On the other hand, Japanese Unexamined Patent Publication No. 120530/1989 describes an elastic return device that biases the inner and outer valve members of a power steering oil control valve to take a neutral position. The device cannot freely correct the neutral position of the control valve. In other words, even if it is discovered after the power steering device is assembled that the given neutral position of the steering nut does not correspond to the neutral position of the control valve due to hydraulic pressure, it cannot be corrected immediately. Furthermore, the characteristics of the control valve cannot be easily changed after assembly.

The present invention has been made in view of the above-mentioned problems in the prior art, and its object is to enable the centering device of a power steering device to accurately center a control valve without producing any chattering noise even after long-term operation. The goal is to form the structure in such a way that it can be released. Also,
SUMMARY OF THE INVENTION An object of the present invention is to provide a power steering device that can be manufactured at low cost, is easy to install, and allows the neutral position and characteristics of the control valve to be freely corrected afterwards.

This object is achieved according to the invention by installing one of the two recesses of the opposing valve members of the control valve in a device for centering the working piston and the steering nut in a neutral position between the working piston and the steering nut. This is achieved by forming the recesses in an elastic intermediate member and interposing rolling elements between both recesses.

In the present invention, with such a configuration, the centering position can be easily corrected by changing the prestress of the elastic intermediate member or by changing the shape of the recess. This correction is possible due to the ease of converting the entire elastic intermediate member. The elastic intermediate member can be formed from a structurally simple plate spring or the like, and can be installed in a position adjustable manner by means such as screwing, so that it is possible to correct the centering position and change the characteristics of the control valve due to centering. can be done freely. For example, the characteristics of the increase in steering oil pressure at the start of steering can be easily changed, and repair in the event of damage is also easy.

The invention will now be explained in detail based on two embodiments shown in the drawings.

In FIG. 1, a steering shaft 4 is supported by radial bearings 2 and 3 within a steering mechanism casing 1. As shown in FIG. steering shaft 4
The lower end portion of is formed as a steering worm 5. The working piston 6 divides the steering mechanism casing 1 into two pressure chambers 7 , 8 , a segment gear 9 arranged in one pressure chamber 8 meshing with the teeth of the working piston 6 . The segment gear 9 is connected via a pitman arm shaft 10 to a steering rod (not shown). Inside the working piston 6, a steering nut 13 with a companion pin 14 is arranged between two thrust bearings 11, 12 so as to be rotatable within a predetermined range. The companion pin 14 includes pin 1.
5 is provided, the pin 15 of which engages a control valve 17 through a stop bore 16 of the actuating piston 6. This control valve 17, which introduces pressure oil into one of the pressure chambers 7, 8, is arranged in the working piston 6 at right angles to the longitudinal axis of the working piston 6 and eccentrically.

The rotational movement of the steering shaft 4 generates a hydraulic adjustment movement of the actuating piston 6 via the steering worm 5, the ball row 18 and the steering nut 13. Ball circulation pipe 19 allows continuous ball circulation in a known manner. The thrust bearings 11, 12 are held without play on the working piston 6 by means of a threaded ring 20 with a bore 21.

The control valve 17 consists of a piston 23 introduced into a bush 22. This piston 23 can be moved from its neutral position by a predetermined control play, which is limited by the stop bore 16 of the companion pin 14. Control valve 17 with control groove and control flow path
Details of the structure of West German Patent Application No. 1817940
This is known from the publication No. 1, and is not important for the understanding of the centering device according to the invention.

The centering device of the present invention shown in FIGS. 2 to 5 is constructed by attaching a leaf spring 26 to an inclined hole 25 machined in the operating piston 6 by an end mill. The leaf spring 26 has a recess 27,
The steering nut 13 is provided with recesses 28 (see FIG. 3), into which recesses 27, 28 rolling elements, such as balls 29, are introduced in a prestressed state. The recess 28 is pressed into the steering nut 13 before tempering. The leaf spring 26 is made as a press-formed part and is attached to the hole 25 with two bolts, for example. Both recesses 27, 28 have the same size and shape.

When the steering nut 13 is rotated relative to the working piston 6, the rolling elements 29 move into the recesses 27, 2.
It rolls on a slope of 8. In this case, the leaf spring 26
is lifted, thereby increasing the spring pressure. As soon as the rotational force ceases to act, the steering nut 13 is returned via the rolling elements 29. That is, it is centered with respect to the working piston 6.
This means that the control valve 17 is returned to the neutral position via the companion pin 14.

Depending on the size and shape of the recesses 27, 28, the centering force is limited to a large portion of the total stroke of the control valve 17.

The embodiment in FIG. 6 shows a U-shaped spring 31 which, together with a companion pin 32, is preferably screwed into a steering nut 33.
A bolt 36 with a recess 37 is screwed into the actuating piston 34 and is held by a locking nut 35. This recess 37 and the opposite recess 38 in the U-shaped spring 31 guide the rolling elements 39 in a prestressed manner.

As described above, in the present invention, one of the pair of recesses to be engaged by the centering rolling member provided between the operating piston of the hydraulic control valve of the power steering device and the steering nut is formed in the elastic intermediate member. Therefore, by replacing the elastic intermediate member, adjusting the mounting position, etc., it is possible to easily correct the neutral position, modify the hydraulic characteristics of the control valve, and reduce manufacturing costs.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a power steering device incorporating a centering device according to the present invention, FIG. 2 is a sectional view taken along the - line in FIG. 1, and FIG. 3 is an enlarged detailed sectional view of the centering device. , FIG. 4 is a sectional view taken along the - line in FIG. 2, FIG. 5 is a plan view seen from the X direction in FIG. 4, and FIG. 6 is a partial sectional view of different implementation rows based on the present invention. 1...Power steering mechanism casing, 4
... Steering shaft, 6 ... Operating piston, 7, 8 ... Pressure chamber, 9 ... Segment gear,
13... Steering nut, 25... Inclined hole,
26... leaf spring, 27, 28... recess, 30...
...Rolling element, 31...U-shaped spring, 32...Following pin, 33...Steering nut, 34...Working piston, 36...Bolt, 37, 38...Indentation.

Claims (1)

[Claims] 1. A servo pump and an operating piston that divides the steering mechanism casing into two pressure chambers, the operating piston having teeth, through which the Pittman arm shaft is swung. Inside the actuating piston, there is provided a steering nut which is rotatable within a limited range and is elastically biased toward the neutral position. The control valve spool for applying a pressure medium to the piston is configured to be moved, and the two opposing recesses and the recesses between these recesses serve as a device for centering the working piston and the steering nut to a relative neutral position. In particular, in a power steering device for a motor vehicle, the power steering device is provided with a return member interposed therebetween.
The return member is constituted by a rolling element 29, and one of the recesses is formed by an elastic intermediate member 26, 3 installed between the working piston 6 and the steering nut 13.
1. A power steering device, especially for a motor vehicle, characterized in that it is formed as: 1. 2. The power steering device according to claim 1, wherein the elastic intermediate member comprises a U-shaped spring 31, and a recess 38 is formed on the outer surface of one leg thereof. 3 The other side 37 of the recess is formed in the bolt 36 screwed into the actuating piston 34 and the U-shaped spring 31
The power steering device according to claim 2, wherein the steering nut (33) is fixed to the steering nut (33). 4. Power steering device according to claim 3, in which a U-shaped spring 31 is screwed to a steering nut 33 together with a companion pin 32 for actuation of a control valve located inside the actuating piston. 5. A plate serving as an elastic intermediate member is installed in the portion left on the inner side of the inclined hole 25, which is bored obliquely from the outer surface of the actuating piston 6 toward the inner surface, and has only a portion of its cross section penetrating to the inner surface. A recess 27 is formed in the portion where the base end of the spring 26 is attached and the leaf spring is exposed when facing inward at the penetrating portion of the inclined hole.
The power steering device according to claim 1, wherein the other recess (28) is formed in the steering nut (13). 6. The power steering device according to any one of claims 1 to 5, wherein the rolling elements are balls 29.