JPS62175261A - Manufacture of elastic plunger made of synthetic resin - Google Patents

Abstract

PURPOSE:To improve abrasion resistance by molding a plunger main body with synthetic resin having high compression rigidity then coating and molding the main body in a mold with synthetic resin having a low friction coefficient in the said plunger used for a rack pinion type steering device. CONSTITUTION:An elastic plunger 5 in a rack pinion type steering device is slidably inserted in the inner hole 4 of a gear box 1 and is slidingly brought into contact with the back of a rack 3 engaged with a pinion 2. The elastic plunger 5 elastically engages the rack 3 with the pinion 2 via a spring 6 on its back, thus removing the backlash of the engaged section between the rack 3 and the pinion 2. In this case, the main body 8 is molded with synthetic resin mixed and reinforced with glass fibers in advance and having high compression rigidity then is coated and molded in a mold with oily plastic to form a synthetic resin layer 9 on the surface of the elastic plunger 5.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a resilient plunger for use in a rack and pinion type steering device for vehicles such as automobiles, and in particular to a method for manufacturing a synthetic resin resilient plunger. It is.

[Prior art and its problems] Fig. 1 shows an example of the use of an explosive plunger. In the drawing, the resilient plunger 5 is slidably inserted into the inner bore 4 of the gearbox 1 and is in sliding contact behind the rack 3 that meshes with the pinion 2.

The resilient plunger 5 elastically engages the rack 3 with the pinion 2 by a spring 6 behind the resilient plunger 5, thereby eliminating backlash at the meshing portion between the rack 3 and the pinion 2.

This resilient plunger was generally obtained by molding a sintered alloy for bearings. However, in response to the desire to reduce the impact noise caused by the collision between the trigger plunger and the lid body due to vibrations during driving, and to reduce the weight of the device, attempts have been made to obtain a trigger plunger by molding synthetic resin. There is. However, manufacturing an elastic plunger made of synthetic resin has the following problems to be solved. First, the trigger plunger is in sliding contact with the rack, and if the sliding resistance is large, it will cause discomfort to the driver when operating the steering wheel, so smooth, low-friction sliding with the rack is desired. Therefore, it is desired that the rack has sufficient rigidity to resist backing up during vibrations during driving.

However, it is extremely difficult to satisfy both sliding properties and rigidity with synthetic resins. In the case of synthetic resin elastic plungers, a reduction in dimensional accuracy due to shrinkage during molding becomes a major problem.Due to variations in the dimensional accuracy of the outer diameter, an increase in sliding resistance with the inner hole of the gearbox is a major problem. Japanese Utility Model Application Publication No. 53-47222 discloses a method in which a notch is provided on the outer periphery of the resilient plunger, but it cannot be said to be perfect.

Therefore, shrinkage may occur during molding on the concave surface that receives the rack.
The concave surface becomes narrow and cannot accurately support the rack, resulting in problems in meshing the rack and pinion. Therefore, it has been difficult to put synthetic resin explosive plungers into practical use.

The present invention was made in view of these points, and it is possible to easily obtain a resilient plunger that has both smooth sliding with the rack and rigidity to resist the retreat of the rack. It is an object of the present invention to provide a method for manufacturing a synthetic resin explosive plunger that does not cause a decrease in accuracy.

□3□ [Means for solving the problem] The present invention has a gear box that is slidably inserted into an inner hole of a gear box,
In the manufacturing method of a synthetic resin elastic plunger in which a rack is elastically engaged with a pinion, the main body of the elastic plunger is first molded from a synthetic resin with high compression rigidity, and then the main body is molded with low friction in a mold. 9 [Function] Since the present invention is as described in 1 above, the body is made of a synthetic resin with a high compression rigidity and a different synthetic resin with a low coefficient of friction is used. The layers provide a resilient plunger that slides smoothly against the rack. The main body that is pre-molded may be deformed due to shrinkage during molding, or the synthetic resin layer that covers and molds the main body in the mold is thin, so the amount of shrinkage during molding is extremely small. Improved dimensional accuracy of explosive plunger
L.

[Embodiment Figure 2 shows the present embodiment, and in the drawing,
The main body 8 of the explosive plunger 5 is molded in advance from a synthetic resin with high compression rigidity reinforced by mixing glass fibers. Then, the main body 8 is coated and molded with oil-impregnated plastic in a mold to form a synthetic resin layer 9. As mentioned above, since the main body 8 made of synthetic resin with high compression rigidity is coated and molded with synthetic resin R9 with a low coefficient of friction, the main body 8 will shrink by 1 to 2% of its dimensions during molding. Since the molded synthetic resin layer 9 is thin, it shrinks only slightly.

In other words, the wall thickness and shrinkage rate of synthetic resins are approximately proportional, and by molding thinner, the shrinkage rate during molding becomes extremely small.
The dimensional accuracy of the explosive plunger 5 is significantly improved.

[Effects of the Invention] The present invention uses the above-described method of manufacturing a synthetic resin resilient plunger, which has sufficient slidability and abrasion resistance with respect to the rack, and is also resistant to rack backtracking due to vibrations during running. It is very easy to obtain a bombardment plunger with sufficient resistance.

In addition, the dimensional accuracy of the explosive plunger can be significantly improved, resulting in a synthetic resin explosive plunger that can slide smoothly with the gear box and accurately support the rack. It is possible to solve the problem as a starter plunger.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing an example of the use of a resilient plunger, and FIG. 2 is a sectional view of a synthetic resin resilient plunger according to an embodiment of the present invention. Explanation of symbols 1... Gear box 2... Pinion 3.
...Rack 4...Inner hole 5...Bullet plunger 8...Body 9...Synthetic resin layer? First mouth bud 2 diagram

Claims (1)

[Claims] In the manufacturing method of a synthetic resin elastic plunger that is slidably inserted into the inner hole of a gear box and elastically engages a rack with a pinion, the main body of the elastic plunger is first made of a synthetic resin with high compression rigidity. 1. A method for manufacturing a synthetic resin explosive plunger, comprising: molding the plunger, and then wrapping the main body in a mold with another synthetic resin having a low coefficient of friction for cover molding.