JPH074805U - Push valve structure of engine valve system - Google Patents

Abstract

(57) [Summary] [Purpose] The object of the present invention is to make a push rod of a valve train in an engine lightweight while maintaining sufficient strength against bending stress. [Structure] A push rod (10) is formed with a large diameter in an axial intermediate portion (10a) where a large bending stress is applied to the rod and both ends (10b) are formed in a small diameter, and the large diameter portion and the small diameter portion are made smooth without a step. I tried to connect them.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a push rod structure for an engine valve system, and more particularly to a technique for improving the strength and the like of the push rod.

[0002]

[Prior art]

 Conventionally, as shown in FIG. 2, an overbed valve (OHV) type engine in which a valve 1 is arranged in a cylinder head 2 is known. In this engine, the rotation of a crankshaft (not shown) is transmitted to the camshaft 3 by a chain or a gear, and as the cam 4 of the camshaft 3 rotates, the valve lifter 5 and the push rod 6 are pushed up and the camshaft 3 The rotational motion of is converted into up and down reciprocating motion.

The rocker arm 7 is swung by the reciprocating movement up and down, and the valve 1 is pushed up. The valve lifter 5 is interposed between the cam 4 of the cam shaft 3 and the push rod 6, and moves up and down by slidingly contacting the inner wall surface of the guide hole 9 of the cylinder block 8 in response to the rotation of the cam 4.

[0004]

[Problems to be solved by the device]

 Here, the push rod 6, which is also disclosed in Japanese Utility Model Laid-Open No. 2-19833, Japanese Utility Model Laid-Open No. 60-57711, Japanese Utility Model Laid-Open No. 52-98013, etc., has a constant rod diameter. In order to secure the strength, it is customary to increase the diameter of the rod to deal with it. .

In this case, the rod diameter D ₁ of the push rod is determined by the bending load bearing strength of the axially intermediate portion where the bending stress is maximized as shown in FIG. However, in the conventional push rod 6 as described above, when the strength is secured as described above, the diameter of the rod is increased to cope with it. It is not unthinkable because the weight increases and the weight of the valve train itself increases, resulting in poor followability of the engine at high speed.

Conventionally, as a technique for reducing the weight of a push rod while improving its strength, a central shaft portion of the push rod is formed of ceramics, and a steel pipe fixed by shrink fitting is provided on the outer periphery thereof. There is one (see Japanese Utility Model Publication No. 3-119504). The present invention has been made in view of the above, and it is an object of the present invention to form the push rod in a light weight while sufficiently maintaining the strength against bending stress.

[0007]

[Means for Solving the Problems]

 Therefore, according to the present invention, the push rod of the valve train in the engine is formed with a large diameter at the intermediate portion in the axial direction where the bending stress applied to the rod is large and at both ends with a small diameter, The small diameter part is smoothly connected without any step.

[0008]

[Action]

 In such a structure, the rod intermediate portion where the bending stress applied to the push rod is large is formed to have a large diameter, and both end portions of the rod are formed to have a small diameter, whereby the strength against bending stress can be sufficiently maintained and the weight can be reduced.

[0009]

【Example】

 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows the configuration of a push rod 10 that is pushed up as the cam of an overbed valve (OHV) type engine rotates and converts the rotational movement of the cam shaft into vertical reciprocating movement.

That is, in this figure, the push rod 10 has a large diameter (rod diameter D ₂ ) in the axial middle portion 10 a having a large bending force applied to the rod 10 and a small diameter (rod diameter) in both end portions 10 b. The diameter d) is formed and the large diameter portion and the small diameter portion are smoothly connected without a step. In this case, the rod diameter D ₂ is determined by the bending withstand strength of the intermediate portion in the axial direction where the bending stress becomes maximum as shown in the figure, and is equivalent to the conventional rod diameter D ₁ . Also, there is a relationship of D ₂ > d.

According to the structure of the push rod 10 having such a structure, the rod diameter of the axially intermediate portion where the bending stress is maximum is increased, and the rod diameters of both end portions where the bending stress does not act so much are reduced. Therefore, it is possible to achieve weight reduction while maintaining sufficient strength against bending stress. Further, as a result of the smooth connection of the large diameter portion and the small diameter portion without a step, excessive stress concentration does not occur at the connecting portion, and the strength at the connecting portion can be improved.

As described above, the present invention has been described with reference to the specific embodiments, but the present invention is not limited thereto, and is attached to the present invention by a person skilled in the art. It should be noted that various changes and modifications can be made without departing from the scope of the utility model registration claim.

[0013]

[Effect of device]

 As described above, according to the present invention, the push rod of the valve train in the engine is formed with a large diameter in the middle portion where the bending stress applied to the rod is large and small diameters at both ends, and a large diameter portion and a small diameter portion. Since the parts are connected smoothly without any step, it is a practical effect that the weight can be reduced while maintaining sufficient strength against bending stress.

[Brief description of drawings]

FIG. 1 is a plan view showing an embodiment of a push rod of a valve train in an engine according to the present invention.

FIG. 2 is a vertical sectional view of an internal combustion engine equipped with a conventional push rod.

FIG. 3 is a diagram showing a conventional push rod and a distribution of bending stress values applied to the push rod.

[Explanation of symbols]

 10 Push rod 10a Intermediate part 10b End part

Claims (1)

[Scope of utility model registration request] 1. A push rod for a valve train of an engine, wherein a large axial portion is formed at an axially intermediate portion where a large bending stress is applied to the rod and both end portions are formed at a small diameter, and a large diameter portion and a small diameter portion are formed. The push rod structure of the engine valve system is characterized by smoothly connecting the two without steps.