JPS6225974Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rack-and-pinion power steering device mainly used in automobiles.

A rack-and-pinion power steering device is known as a device that uses hydraulic power to assist steering wheel operations.

In this case, a rack that connects to the steering arm of the wheel via a tie rod and a pinion that engages with the rack and rotates together with the steering handle are generally housed inside the gear housing. In order to eliminate play in the engagement between the rack and the pinion, a pressure pad housed in a cylinder formed in a part of the gear housing is slidably brought into elastic contact with the opposite side of the rack that engages with the pinion. There is.

By the way, in pressing the rack from the back to maintain proper engagement with the pinion, it is possible to maintain the pressure pad in the cylinder so that it can always slide reliably without becoming stuck, and also to prevent the rack from running at low speeds on rough roads. Various proposals have been made to prevent the occurrence of hitting sounds (commonly known as rattle sounds).

For example, in U.S. Pat. No. 3,844,181, the pressure pad is made of synthetic resin, and a plurality of radial protrusions (four in the example) and relief portions are provided on the outer periphery of the pad to reduce the sliding friction of the pressure pad. While machining is difficult and requires high precision, the thermal expansion of the protruding portion causes distortion, impairing the uniform contact of the smooth sliding surface.

In addition, British Patent No. 946501 utilizes the cylinder chamber housing the spring that biases the pressure pad as a back pressure chamber, but high precision is required for fitting the outer periphery of the pressure pad, and the pad is made of synthetic resin. It is necessary to take thermal expansion and contraction into account when setting the gap with the cylinder, and if the gap is made too small, the pad will tend to stick during thermal expansion, impairing followability.

Also, please refer to Utility Model Publication No. 56-18270 or Japanese Patent Application Publication No. 55
As shown in Japanese Patent No. 68472, there is also a device in which an annular element made of a wavy annular leaf spring or a rubber-like elastic body is interposed between the pressure pad and the cylinder.

Both of these absorb the thermal expansion mentioned above and prevent the pad from sticking, and the former in particular has less sliding resistance and good followability;
The wavy annular leaf spring has problems in processing accuracy and concentricity, and the easy sliding surface is uneven, and the latter has a problem in that the pad and cylinder cover the entire circumference, resulting in large sliding resistance and lack of followability.

The present invention was developed to solve the above-mentioned problems, and it maintains an appropriate tension margin at the fitting part between the synthetic resin presser pad and the cylinder, and also allows thermal expansion and contraction of the pad to reduce the slack caused by thermal distortion. To provide a rack-and-pinion type power steering device which avoids sticking of pads and generation of hitting sounds by preventing deviation of sliding surfaces.

Hereinafter, embodiments of the present invention will be described based on the drawings. In FIG. 1, 1 is a gear housing of a power steering device, and gear housing 1
Inside the pinion 3, a pinion 3 provided at the tip of an input shaft 2 connected to a steering handle (not shown) is rotatably supported by bearings 4 and 5 provided at both ends thereof. A rack 6, which is also supported by the gear housing 1 so as to be slidable in its axial direction, is engaged with the pinion 3 at its teeth 7, and when the input shaft 2 rotates, the rack 6 is slidably supported in the axial direction by the gear housing 1. 6 is driven in its axial direction. A piston-shaped pressure pad 9 housed in a cylinder 8 formed in the gear housing 1 is slidably disposed on the side surface of the rack 6 opposite to the rack teeth 7, that is, the back surface thereof, via its pressing portion 9A formed in an arc shape. The other end of the pressure pad 9 is elastically supported by a coil spring 11 interposed between it and a cover 10 that closes the outer end of the cylinder 8.

A gap δ is formed between the outer periphery of the pressure pad 9 and the inner periphery of the cylinder 8, which is large enough to allow the thermal expansion of the pressure pad 9. is provided. An elastic ring 13 made of an elastic material such as rubber is attached to this annular groove 12.

As shown in detail in FIG. 2, the elastic ring 13 has four inner circumferential restraining parts 14 that protrude so as to come into contact with the pressure pads 9 (the bottom of the annular groove 12), and a gap 16 between them. At the same time, the outer periphery is formed into an outer periphery contact portion 15 that contacts the inner periphery of the cylinder 8 all around. Note that the direction of easy sliding contact is with respect to the inner peripheral restraining portion 14 as shown by the arrow.
It is desirable that the direction includes

Next, the effect will be explained.

When the vehicle is running at low speed on a rough road, when an impact force that causes a relative displacement in the radial direction is applied between the cylinder 8 and the pressure pad 9, this causes the pressure pad 9 to impact against the cylinder 8 in the radial direction. However, such impactful displacement is absorbed by the elastic ring 13, and impactful contact between the inner circumferential surface of the cylinder 8 and the outer circumferential surface of the pressure pad 9 is prevented.

Furthermore, even if the pressure pad 9 thermally expands, the inner peripheral restraining portion 14 of the elastic ring 13
The pressure pad 9 expands toward absorb thermal distortion of the pad 9, and when it contracts, the inner circumferential restraint part 14 follows the shrinking pressure pad 9 to prevent rattling. 9 is held in the cylinder 8 via the tension of the elastic ring 13. Therefore, the outer periphery of the pressure pad 9 does not come into solid contact with the inner periphery of the cylinder 8, the sliding resistance is small, and thermal strain is released, so that no deviation occurs in the smooth sliding surface.

FIG. 3 shows another embodiment of the invention.

This is because outer circumferential restraining portions 17 protrude from three locations on the outer circumference of the elastic ring 13 so as to come into contact with the cylinder 8.
, and the inner periphery is a pressure pad 9.
An inner circumferential contact portion 1 that completely fits into the inner circumference of the annular groove 12 of
8. In this case, the thermal expansion is absorbed by the follow-up deformation of the outer circumferential restraining portion 17.

As explained above, according to the present invention, an elastic ring is interposed between the synthetic resin pressure pad and the cylinder, and the elastic ring is provided with a partial restraint part for one of the two and a full circumferential contact part for the other. Therefore, it is possible to reduce sliding resistance and absorb thermal distortion with a simple structure, and as a result, it is possible to prevent unevenness of the easy sliding surface, and also to prevent the pad from sticking and hitting noise.

[Brief explanation of the drawing]

Fig. 1 is a vertical sectional view showing an embodiment of the present invention;
The figure is a cross-sectional view taken along the line A--A in FIG. 1, and FIG. 3 is a cross-sectional view taken along the line A--A, similar to FIG. 2, showing another embodiment of the present invention. 1... Gear housing, 3... Pinion, 6...
... Rack, 8 ... Cylinder, 9 ... Pressure pad, 11 ... Coil spring, 12 ... Annular groove, 1
3...Elastic ring, 14...Inner peripheral restraint part, 15...
...Outer circumference contact portion, 17...Outer circumference restraint portion, 18...Inner circumference contact portion.

Claims (1)

[Scope of utility model registration request] A rack connected to the steering arm of the wheel via a tie rod and a pinion that engages with the rack and rotates together with the steering handle are housed inside the gear housing. In a rack-and-pinion power steering device in which a pressure pad housed in a cylinder formed in the gear housing is slidably and elastically contacted, a gap is provided between a synthetic resin pressure pad and the cylinder to allow thermal expansion of the pressure pad. An elastic ring is interposed in an annular groove formed on the outer periphery of the pressure pad, and the elastic ring has an inner periphery or outer periphery restraining part that partially contacts the outer periphery of the pressure pad or the inner periphery of the cylinder, and an inner periphery of the cylinder. Alternatively, a rack-and-pinion type power steering device is characterized in that an inner circumference or an outer circumference contact portion is formed that fits around the outer circumference of the brake pad.