JPH0331935B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rack guide for a rack and pinion steering system for a motor vehicle.

A rack and pinion steering device for an automobile has a pinion that is rotationally driven by a steering shaft and a rack that meshes with the pinion. Fitted and retained. The end of the rack extends from the end of the rack housing and is connected to the end of a tie rod, which in turn is connected to a knuckle arm that pivots the wheel. When the pinion is rotationally driven by rotation of the steering wheel, the rack inside the rack housing slides in the axial direction, and an operating motion is applied to the wheel via the tie rod.

In such a rack and pinion type steering device, the rack housing is supported on the vehicle body side, and the end of the rack that slides inside the rack housing is supported by a bush provided inside the end of the rack housing. . Conventional bushes used in this type of steering device are generally made of sintered metal and have a cylindrical shape, resulting in the following problems.

That is, in the case of such a bush made of sintered metal, variations in dimensional tolerance inevitably occur during molding. If the clearance between the bushing and the rack becomes larger than the allowable value due to variations in dimensional tolerances, vibrations and shocks from the outside will easily be transmitted, causing the rack to vibrate, and as a result, the rack and the bushing will A problem arises in that a hitting sound is generated between the inner surface and the noise is increased.

On the other hand, if the clearance between the bushing and the rack becomes smaller than the allowable value, the friction between the rack and the bushing will increase, and since external force will be applied to the rack, the sliding resistance during running will increase. However, a problem arises in that the steering operation becomes heavy.

In order to solve the above-mentioned problems, a synthetic resin bushing has been used to elastically hold rod members such as racks, but in the case of synthetic resin bushings, the variation in dimensional tolerance during molding is even greater. Therefore, the friction between the rack and the bush tends to increase, and especially when a rod member such as a rack is tilted due to external vibration, the sliding resistance becomes large, causing a problem that steering operation becomes heavy.

In view of the above-mentioned problems, the present invention has been developed in a rod guide for a rack and pinion type automobile steering system, which can reliably prevent an increase in sliding resistance due to variations in dimensional tolerances during molding or tilting vibrations of the rack member, and moreover, has a shape The purpose is to provide a bushing that is simple and easy to mold.

In order to achieve this object, the present invention includes a cylindrical rack housing, a rack that is loosely fitted into the rack housing and is slidably held in the axial direction,
A cylindrical bushing as a rack guide is interposed between the rack housing and the rack, and the bushing gradually increases the inner diameter of the cylindrical body from both axial ends of the bushing body toward the center. and the wall thickness of the center portion is smaller than the wall thickness of the center of both ends in the axial direction, and the inner diameter of the center portion is the same as or slightly smaller than the outer diameter of the rack, and the outer periphery of the center portion and the A gap is formed between the inner circumference of the rack housing and
Further, a plurality of holes opening to the inner and outer surfaces are formed at intervals in the circumferential direction in the central portion of the bush main body, and a plurality of holes extending in the axial direction through the inner openings of the holes are formed in the inner surface of the bush main body. A rod guide for a rack and pinion type automobile steering device is provided, characterized in that a plurality of grooves are formed on both end faces of a main body.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

Figures 1 and 2 show an embodiment of the rod guide of the rack and pinion steering system for automobiles according to the present invention. First, the schematic structure of the steering system will be explained. The rack 1 consists of a rod with a circular cross section. Teeth 2 are formed over a certain section in the axially intermediate portion of the rack 1. The rack 1 is loosely fitted into a cylindrical rack housing 3 and is held slidably in the axial direction within the rack housing 3. The teeth 2 of the rack 1 mesh with a pinion 4 such as spur teeth or helical teeth, and the pinion 4 is connected to a steering wheel via a steering shaft (not shown). Both ends of the rack 1 are connected via tie rods to a knuckle arm that pivots a wheel (not shown), and when the steering wheel is rotated, the rack 1, which engages with the pinion 4, slides back and forth in the axial direction, and the tie rod and the knuckle arm are connected to each other. The wheels are made to perform a steering operation through the steering wheel.

An enlarged portion 3a having a large diameter is formed at one end of the rack housing 3. One end of the rack 1 extends outward from this enlarged portion 3a by a suitable amount,
A bush 10 as a rack guide is inserted between the inner periphery of the enlarged portion 3a and the rack 1. Further, a mount rubber 5 is fitted to the outer periphery of the enlarged portion 3a of the rack housing 3, and the mount rubber 5 is semi-fitted into a concave receiving portion 7 provided on the vehicle body 6 side, and is fixed to the vehicle body 6 with bolts or the like. The end of the rack housing 3 is held with the mount rubber 5 interposed therebetween by a semicircular arc-shaped stopper 8. A dust boot 9 made of rubber or the like is installed between the mount rubber 5 and the tie rod.

A gearbox section (not shown) surrounding the pinion 4 is provided at the other end of the rack housing 3, and is supported by the vehicle body through a mount rubber (not shown). The other end of the rack 1 extends from the gearbox and is connected to the other wheel via a tie rod, and a dust boot is installed between the tie rod and the mount rubber.

The bush 10 is made by molding synthetic resin. As the synthetic resin, it is preferable to select a material that has a small coefficient of friction, sufficient strength and rigidity, and sufficient elasticity depending on the molded shape. Synthetic resin or not only synthetic resin but also a material with a copper-based or aluminum-based sliding material may be used.

As shown in FIGS. 3 to 5, the bush 10 has a substantially cylindrical bush main body 11. As shown in FIGS. Both axial end portions 11a of the bush main body 11,
The inner diameter D ₁ of the bushing body 11b is larger than the outer diameter of the rack 1, and the inner circumference _D2 of the central portion 11c of the bush body 11 is the same as or slightly smaller than the outer diameter of the rack 1. The inner circumference of the bush main body 11 gradually becomes smaller from the axially opposite end portions 11a, 11b toward the center portion 11c. That is, the inner surface of the bush main body 11 has a convex shape.

On the other hand, the outer diameter D ₄ of the central portion 11c of the bush main body 11 is the outer diameter D ₃ of the axially opposite end portions 11a and 11b.
It's getting smaller than that. Then, the wall thickness of the central portion 11c of the bushing body 11 is t ₂ (t ₂ = 1/2 (D ₄ −
D ₂ )) is the wall thickness t ₁ of both axial end portions 11a and 11b
(t ₁ = 1/2 (D ₃ − D ₁ )),
The wall thickness of the bush main body 11 is 11 at both ends in the axial direction.
The outer inclined surfaces 11d and 11e are gradually reduced in size between the outer inclined surfaces 11d and 11e between the outer slopes 11d and 11c.

A plurality of holes 12 opening on the inner and outer surfaces are formed at equal intervals in the circumferential direction in the central portion 11c of the bush main body 11, and a shaft is formed on the inner surface of the bush main body 11 through the inner opening of the hole 12. A plurality of grooves 13 are formed extending in the direction. The diameter of the circle connecting the bottoms of each groove 13 is the axially opposite end portions 11a and 11b.
The groove 13 is larger than the inner circumference D ₁ of the groove 13, and each groove 13 opens at the end surfaces of the axially opposite end portions 11a and 11b.

A protrusion 14 is formed on the outer periphery of one axial end portion (here end 11a) of the bush main body 11, and this protrusion 14 can be fitted into a hole 15 formed in the rack housing 3. .

The bush 10 with the above configuration is installed in the rack housing 3.
When the bush main body 11 is elastically deformed and inserted into the enlarged part 3a, the protrusion 14 is fitted into the hole 15. This prevents the bush 10 from coming off.

Since the central portion of the bushing 10 is thinner than both end portions, there is a gap between the outer periphery of the central portion of the bushing 10 and the inner periphery of the rack housing 3.
is formed.

Thereafter, when the rack 1 is inserted into the bush 10, the central portion 11c of the bush main body 11 is elastically deformed to fit around the outer periphery of the rack 1 and lightly hold the rack 1. Since the wall thickness of the central portion 11c has become smaller, even if the negative clearance between its inner diameter D ₂ and the outer diameter of the rack 1 becomes large due to variations in dimensional tolerance during molding, the central portion 11c is easily elastically deformed and fits into the rack 1 without difficulty. Therefore, the friction between the bush 10 and the rack 1 does not increase excessively.

During use, if vertical or horizontal vibration or impact is applied to the rack 1, the thickness of the central portion 11c of the bushing body 11 is thin, and the relationship between the central portion 11c and the rack housing 3 is Together with the fact that the gap is formed between them, the central portion 11c of the main body 11 easily elastically deforms to absorb and alleviate vibrations and shocks. Therefore, no noise such as tapping noise is generated.

On the other hand, when the rack 1 is tilted as shown by the dashed line in FIG. Since the tilting of the rack 1 is absorbed by the bushing body 11, no excessive compressive force is applied to the bush body 11, and therefore the sliding resistance of the rack 1 does not increase excessively.

Note that the hole 12 formed in the central portion 11c of the bush body 11 serves to further facilitate elastic deformation of the central portion 11c, and also serves as a supply and reservoir for lubricant such as grease.

Further, the groove 13 formed on the inner surface of the bush main body 11 serves as a reservoir for lubricant such as grease, and also serves to allow air to freely circulate in the axial direction of the bush main body 11.
Therefore, there is no need to separately provide a transfer tube or the like for ensuring air circulation between the closed spaces formed in the rack housing 3 with the bush 10 as a boundary.

Although one embodiment has been described above, the present invention is not limited to the aspect of the above embodiment. You may also do so.

As explained above, the present invention gradually reduces the inner diameter of the substantially cylindrical bushing body from both ends of the bushing body in the axial direction toward the central part, and also reduces the wall thickness of the central part of the bushing body. The wall thickness is made smaller than the wall thickness of both ends in the axial direction of the main body, and a gap is formed between the outer periphery of the central part of the bushing main body and the inner periphery of the rack housing, and the inner diameter of this central part is the same as the outer diameter of the rack. In addition, a plurality of holes opening to the inner and outer surfaces are formed at intervals in the circumferential direction in the central part of the bush main body, and furthermore, the inner surface side openings of the holes are formed on the inner surface of the bush main body. The bushing body is characterized by a plurality of grooves extending in the axial direction and opening at both end faces of the bushing body, so that the sliding movement due to the rocking of the rack member held at the central portion of the bushing body is prevented. It is possible to prevent an increase in resistance, the clearance between the bush and the rack does not become excessive, and the central portion can be easily elastically deformed, thereby easily absorbing dimensional tolerances, vibrations of the rack member, etc. Be able to do things.

In addition, the hole formed in the central part of the bushing body not only facilitates the elastic deformation of this central part, but also serves as a supply and reservoir for lubricants such as grease. The grooves formed in the bushing serve as a reservoir for lubricants such as grease, and also allow air to freely circulate in the axial direction of the bushing body. There is no need to separately provide a transfer tube or the like to ensure air circulation between the sealed spaces formed inside.

Moreover, since it has a simple shape, it can be manufactured easily and provided at low cost.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view showing an embodiment of a rod guide of a rack and pinion type automobile steering device using a bush according to the present invention; FIG. 2 is a sectional view of the vicinity of the bush of the steering device shown in FIG. 1; Figure 3 is a side view of the bush shown in Figure 1, Figure 4 is an end view of the bush shown in Figure 1, and Figure 5 is a sectional view of the bush shown in Figure 1 taken along the - line in Figure 4. be. 1...Rack, 3...Rack housing, 10
...button, 11...button body, 11a,
11b...Both end portions in the axial direction, 11c...Center portion.

Claims (1)

[Claims] 1. A cylindrical rack housing, a rack loosely fitted into the rack housing and slidably held in the axial direction, and a cylindrical bush as a rack guide interposed between the rack housing and the rack. The bush has a cylindrical body whose inner diameter gradually decreases from both ends of the bush main body in the axial direction toward a central part, and the wall thickness of the central part is smaller than the wall thickness of both end parts of the bush main body in the axial direction. The inner diameter of the central portion is the same as or slightly smaller than the outer diameter of the rack, and a gap is formed between the outer periphery of the central portion and the inner periphery of the rack housing. A plurality of holes opening to the inner and outer surfaces are formed in the central portion at intervals in the circumferential direction, and further, a plurality of holes are formed in the inner surface of the bushing body at intervals in the circumferential direction, and the holes extend in the axial direction through the inner openings of the holes and are formed on both end surfaces of the bushing main body. A rod guide for a rack and pinion type automobile steering device, characterized in that a plurality of open grooves are formed.