JP2001082111A - Cam shaft for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the weight of a cam shaft and lessen the driving force thereof by setting the width of a sliding contact surface in a base circle region smaller than the width of a sliding contact surface in a nose circle region in a cam lobe part of a cam shaft for driving a suction and exhaust valve of an internal combustion engine. SOLUTION: A cam lobe part 10 of a cam shaft 1 is formed of a base circle part S with a radius R3 and a cam nose part N with a radius R4, and provided with a sliding contact surface 11, a side surface 12 and a chamfered part 13. In this case, an N1 portion of the sliding contact surface 11 has the width L1 set to the maximum for receiving large force. In a region extending from B to A of a N2 portion and a region extending from C to D of an N3 portion, the width is made smaller, and the width L2 of the base circle part S is set to the minimum. According to the width of each region in the sliding surface 11, the chamfered part 13 is disposed to form a cam lobe 10. Thus, the weight and inertia moment of the cam shaft 1 are reduced to lessen the driving force.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a camshaft used for a valve train of an internal combustion engine.

[0002]

2. Description of the Related Art A valve mechanism for opening and closing an intake / exhaust valve of an internal combustion engine used in an automobile or the like has a camshaft position, the number of camshafts, and a type of a cam follower, as shown in FIG.
Although classified into HV type, OHC type, DOHC type, DOHC type, etc., the profile of the cam 2 of the camshaft 1 is determined in accordance with the lift characteristic of the intake / exhaust valve 5 in any type of the valve train. The rotation of the camshaft 1 is converted into a linear movement of the valve lift of the intake / exhaust valve 4 via the push rod 6, the cam follower 8, the rocker arm 7, and the lifter 9.

In FIG. 10, a valve spring for biasing the intake / exhaust valve 5 to a valve seat is not shown.

[0004] The valve lift is affected by two factors: system distortion due to insufficient rigidity of components interposed between the cam 2 and the valve 4 and inertia force due to mass. However, since this effect is increased, it is important to have a light weight and a high rigidity. In particular, the contact surface pressure of the cam surface greatly affects the durability of the cam.

Therefore, in the prior art, FIGS.
As shown in FIG. 14, the cam lobe portion of the camshaft 3
The cross-sectional shape of the 30 camshafts 3 perpendicular to the axis, that is, the profile is determined mainly by the relationship with the valve lift characteristics, and has a cam nose portion N and a base circular portion S.

In the width direction as shown in FIG. 11, the portion where the load is most severe, usually the portion of the tip portion M of the cam lobe portion 30, is the maximum stress generated in this portion and the surface of the cam lobe. The width Lc is determined so that the maximum surface pressure during sliding falls within the allowable value for design.
The cam lobe portion 30 is formed with a constant width c.

[0007]

The stress generated in the cam lobe and the surface pressure during sliding are not constant depending on the circumferential portion of the cam lobe. For example, as shown in FIG. In a large part (N1: BC), the repulsive force of the valve spring in the valve mechanism is received, so that the stress and the surface pressure generated in the cam lobe part are large, but the part with a small valve lift (N2: A−C). B, N3: CD),
In the base circle portion (S), both the stress and the surface pressure are reduced.

For this reason, the portions of N2, N2, and S of the cam lobe have unnecessarily high rigidity.

However, since the moment of inertia of the camshaft having the cam is directly related to the driving force of the valve train, any unnecessary weight increases the moment of inertia. In addition to the need for force, each component of the valve mechanism requires rigidity commensurate with this driving force, and the overall weight of the valve mechanism increases, and this increase in weight causes an increase in driving force. become.

Therefore, a slight weight reduction of the camshaft, that is, a reduction in the moment of inertia, has a ripple effect, leading to a reduction in the weight and the driving force of the entire valve train.

The present invention has been made on the basis of the above-mentioned findings, and an object of the present invention is to provide a camshaft having a cam lobe portion having a more appropriate shape to reduce the weight and reduce the driving force. An engine camshaft is provided.

[0012]

SUMMARY OF THE INVENTION A camshaft for an internal combustion engine for achieving the above object is constituted as follows. 1) In the cam lobe portion of the camshaft that moves the intake / exhaust valve of the internal combustion engine, the width of the sliding contact surface at the base circular portion is formed smaller than the width of the sliding contact surface at the nose portion.

With this configuration, when the force acting on the sliding contact surface when the camshaft slides is large, the force is received by the sliding contact surface of the wide nose portion, and when the force acting on the sliding contact surface is small, the nose portion has a small width. Since the force can be received at the sliding contact surface of the nose portion, sufficient rigidity can be maintained in terms of strength, and the weight of the camshaft can be reduced by narrowing the width of the sliding contact surface at the base circular portion. The drive force required for the valve train can be reduced by reducing the moment of inertia.

Therefore, the driving torque during rotation of the camshaft can be reduced without impairing the durability of the valve train. 2) The width of the sliding contact surface is formed so that the maximum stress generated on the sliding contact surface of the nose portion of the cam lobe portion and the maximum stress generated on the sliding contact surface of the base circular portion are substantially the same. I do.

In other words, the maximum width is set in accordance with the maximum stress and the maximum surface pressure generated at the time of valve lift, and the other widths are set to be substantially equal according to the force generated in that portion. Change the width of the cam lobe so that

In other words, the width of the cam lobe portion of the camshaft of the internal combustion engine is determined to be a width corresponding to the stress generated at each portion of the cam lobe portion and the surface pressure at the time of sliding. Without compromising the durability of the valve train,
This is a camshaft that can reduce the driving torque during rotation of the camshaft.

In this case, the width of the sliding contact surface of the nose portion is formed to be constant, and the width of the sliding contact surface of the base circular portion is formed to be constant, and the width of the sliding contact surface between the two is continuously adjusted. It may be formed by changing, and in this case, processing becomes easy.

Alternatively, the nose portion may be formed so that the width of the sliding surface of each portion of the base circle portion is continuously changed so as to increase the amount of weight reduction even a little.

The width of the cam lobe portion may be continuously changed so as to match the generated stress and surface pressure. The width of the cam lobe portion is formed in several widths so that it can be easily processed. A discontinuous portion may be provided. 3) By forming a chamfered portion on the side of the sliding surface of the base circular portion of the cam lobe portion, the width of the sliding surface of the base circular portion is formed smaller than the width of the sliding surface of the nose portion. In the case of forming a chamfered portion as shown in FIGS. 1 to 4, simple processing is relatively simple.

In addition to the chamfering method, as a method for changing the width of the sliding contact surface, as shown in FIGS. May be formed.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A camshaft for an internal combustion engine according to an embodiment of the present invention will be described below with reference to the drawings.

A camshaft 1 for an internal combustion engine according to an embodiment of the present invention is formed to have a cam lobe portion 10 as shown in FIGS.

The cam lobe portion 10 has a base circle portion S having a radius R3 and a cam nose portion N (= N1 + N2 +) having a maximum radius R4.
N3), and has a sliding contact surface 11, a side surface 12, and a chamfered portion 13.

The N1 portion of the sliding contact surface 11 receives a large force because the valve lift is large and the urging force of the valve spring is large. Therefore, the width is set to the maximum width L1. Further, the portion of N2 from B to A and the portion of N3 from C to D are narrowed to form the base circle S with a minimum width L2 smaller than the maximum width L1.

The maximum width L1 and the minimum width L2 are determined according to the magnitude of the force applied to each of the portions N1 to N3, S so that the generated stress and surface pressure are properly within the allowable values for design. .

In the first embodiment, as shown in FIGS. 1 to 4, the cam lobe 10 is formed by forming the chamfered portion 13 in accordance with the width L of each portion of the sliding contact surface 11. .

In the second embodiment, as shown in FIGS. 5 to 8, the side surface 12A has the same width as the axial direction of the camshaft 1A in accordance with the width L of each part of the sliding contact surface 11A. By forming vertically, the camshaft 1A is formed.

In this case, a step formed by the side surface 14A and the circumferential surface 15A is formed at the root of the cam lobe portion 10A.

With the above configuration, the following effects can be obtained.

Since the camshafts 1 and 1A are formed by continuously changing the width L1 of the cam lobe portions 10 and 10A so as to match the generated stress and surface pressure, the load applied to the sliding surfaces 11 and 11A is reduced. The portion N1 near the tip portion M of the large cam nose portion N has a maximum width L1, and the base circle portion S of the cam lobe portions 10, 10A with a small load applied to the sliding surface 11 has a minimum width L2.
Since the side surfaces of the portions N2, N3, and S with a small load are cut off, the mass of the cut-off portions is reduced, and the weight and moment of inertia of the camshafts 1 and 1A can be reduced, and the camshafts 1 and 1A The driving force required for driving the motor can be reduced.

As a ripple effect, the rigidity of related valve train components can be reduced.
These parts can also be reduced in weight, and the overall valve train can be reduced in weight and driving force.

[0032]

As described above, according to the camshaft of the internal combustion engine according to the present invention, when the force acting on the sliding contact surface during sliding of the camshaft is large, the sliding contact surface of the nose portion having a wide width is used. When the force acting on the sliding contact surface is small, the force can be received on the sliding contact surface of the nose part with a narrow width, so that sufficient rigidity and durability can be maintained in terms of strength, and the base circle The weight of the camshaft can be reduced by reducing the width of the sliding contact surface of the portion, and furthermore, the moment of inertia can be reduced, and the driving force required for the valve train can be reduced.

Further, by changing the width of the cam lobe portion continuously or discontinuously so as to match the generated stress and surface pressure, the width of the portion other than the portion where a large load is applied is reduced, so that the cam can be efficiently formed. The weight and moment of inertia of the shaft can be reduced, and as a result, the driving force required for driving the camshaft can be reduced.

As a ripple effect, the rigidity of related valve train components can be reduced.
These parts can also be reduced in weight, and the overall valve train can be reduced in weight and driving force.

[Brief description of the drawings]

FIG. 1 is a front view of a camshaft for an internal combustion engine according to the present invention.

FIG. 2 is a partial side view of the camshaft for the internal combustion engine of FIG. 1;

FIG. 3 is a sectional view taken along line EE of FIG. 1;

FIG. 4 is a sectional view taken along line FF of FIG. 1;

FIG. 5 is a front view of a camshaft for an internal combustion engine according to another embodiment of the present invention.

6 is a partial side view of the internal combustion engine camshaft of FIG. 5;

FIG. 7 is a sectional view taken along the line EE of FIG. 5;

FIG. 8 is a sectional view taken along line FF of FIG. 5;

FIG. 9 is a valve lift characteristic curve diagram.

FIG. 10 is a schematic front view showing an example of a valve train;
(A) is OHV type, (b) is OHC type, (c) is DOHC type of valve lifter type, (d) is D of rocker arm type
Indicates the OHC type.

FIG. 11 is a front view of a conventional camshaft for an internal combustion engine.

FIG. 12 is a partial side view of the internal combustion engine camshaft of FIG. 11;

FIG. 13 is a sectional view taken along the line EE of FIG. 11;

FIG. 14 is a sectional view taken along line FF of FIG. 11;

[Explanation of symbols]

 1,1A camshaft 5 intake / exhaust valve 10,10A cam lobe 11,11A sliding surface 12,12A sliding surface 13 chamfer N nose S base circle L1 maximum width L2 minimum width

Claims (3)

[Claims] In a cam lobe portion of a cam shaft for moving an intake / exhaust valve of an internal combustion engine, a width of a sliding contact surface at a base circular portion is formed smaller than a width of a sliding contact surface at a nose portion. Camshaft for internal combustion engine. 2. The sliding surface according to claim 1, wherein the maximum stress generated on the sliding surface of the nose portion of the cam lobe portion and the maximum stress generated on the sliding surface of the base circular portion are substantially the same. The camshaft for an internal combustion engine according to claim 1, wherein a width is formed. 3. The width of the sliding contact surface of the base circular portion is smaller than the width of the sliding contact surface of the nose portion by forming a chamfered portion on the side of the sliding contact surface of the base circular portion of the cam lobe portion. The camshaft for an internal combustion engine according to claim 1 or 2, wherein: