JPS6230836Y2 - - 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. .

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 getting 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 (four in the example) radial protrusions and relief portions are provided on the outer periphery of the pressure pad to reduce the sliding friction of the pressure pad. While machining requires high precision and is difficult, the thermal expansion of the protrusion causes distortion,
This impairs 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 liquid 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 with machining 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, an embodiment of the present invention will be described with reference to the drawings. In FIG. 1, reference numeral 1 denotes a gear housing of a power steering device.
Inside the gear housing 1, 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, 5 provided at both ends. A rack 6, similarly supported by the gear housing 1 so as to be slidable in its axial direction, engages with the pinion 3 at its rack teeth 7, and the rack 6 is driven in its axial direction by the rotation of the input shaft 2. A piston-shaped pressure pad 9 housed in a cylinder 8 formed in the gear housing 1 is in sliding contact with the side of the rack 6 opposite the rack teeth 7, i.e., the back surface, via its arc-shaped pressing portion 9A, while the other end of the pressure pad 9 is elastically supported by a coil spring 11 interposed between the rack 6 and a cover 10 closing the outer end of the cylinder 8.

As shown in FIG. 2, this pressure pad 9 is formed into a perfect circle with an outer diameter d ₀ by, for example, injection molding.

On the other hand, as shown in FIG. 3, in the cylinder 8, four relief portions (relief grooves) 12 having an outer diameter of D are formed at equal intervals on the machined inner periphery of the inner circumference having an inner diameter of d.
This relief portion 12 is not formed by machining, but is integrally formed by, for example, casting.

Furthermore, there is a relationship of D>d ₀ >d, and as shown in FIG. A certain tightening allowance (d−d ₀ ) is given. Note that the direction of easy sliding contact is preferably a direction that includes the portion 13 where the pad 9 is provided with the interference, as shown by the arrow.

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 acts 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 an impactful displacement is absorbed while being accompanied by elastic deformation of the contact portion 13 that fits into the cylinder 8 of the pressure pad 9 with interference.

Furthermore, even if the pressure pad 9 expands thermally, the expansion is absorbed by the relief part 12 of the cylinder 8, and when it thermally contracts, it follows the pad 9 so that the strain absorbed by the relief part 12 is restored. The pressure pad 9 prevents rattling, so the pressure pad 9 has a partial contact area 13 during both thermal expansion and thermal contraction.
It is held in the cylinder 8 by this. Therefore,
The outer periphery of the pressure pad 9 does not come into solid contact with the entire inner periphery of the cylinder 8, the sliding resistance is small, and thermal strain is released, so that no unevenness occurs on the smooth sliding surface.

As explained above, according to the present invention, relief portions extending in the axial direction are formed at approximately equal intervals on the inner periphery of the cylinder, and the pressure pads made of synthetic resin housed in the cylinder are partially tightened. Since the pad is given a clearance, it is possible to reduce sliding resistance and absorb thermal distortion with a simple structure, and as a result, it prevents unevenness of the sliding surface and prevents the pad from sticking and hitting noise. effective.

[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 of the pressure pad in Figure 1,
The figure is a cross-sectional view of the cylinder in Figure 1, and Figure 4 is a cross-sectional view of the cylinder in Figure 1.
It is a sectional view taken along the line A-A in the figure. 1... Gear housing, 3... Pinion, 6...
... Rack, 8 ... Cylinder, 9 ... Pressure pad, 11 ... Coil spring, 12 ... Relief part.

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, synthetic resin pressure pads are arranged at approximately equal intervals on the inner periphery of the cylinder in sliding contact. A rack-and-pinion power steering device characterized by forming a plurality of relief portions extending in the axial direction.