JP2001329807A - Cam follower device for valve gear of engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of pitching of the outer peripheral surface of a cam 3, prevent the occurrence of peeling of the outer peripheral surface of an outer ring 5, and simultaneously reduce abrasion of the outer peripheral surface of the cam 3. SOLUTION: The outer peripheral surface of the cam 3 is subjected to heat treatment so that the hardness thereof is Hv 613 or higher, and the roughness is 0.5 μmRa or lower. The outer peripheral surface of the outer ring 5 has a hardness higher than that of the outer peripheral surface of the cam 3, and has a difference of Hv 220 or less in hardness from the outer peripheral surface of the cam 3. The roughness of the outer peripheral surface of the outer ring 5 is 0.1 μmRa or lower.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION A cam follower device for an engine valve operating mechanism according to the present invention is used, for example, in a state where it is incorporated in a valve operating mechanism of an automobile engine.

[0002]

2. Description of the Related Art There are various types of engine for automobiles.
Except for the cycle engine, all are provided with an intake valve and an exhaust valve that open and close in synchronization with the rotation of the crankshaft. There are various types of valve operating mechanisms for driving these intake valves and exhaust valves. For example, the general OHC type shown in FIG. 1 will be described.

This valve mechanism converts the rotational motion of the camshaft 1 into a reciprocating motion of a valve body 2 which is an intake valve or an exhaust valve. For this purpose, the outer peripheral surface of the cam 3 fixed to the camshaft 1 is brought into contact with the outer peripheral surface of the outer ring 5 rotatably supported on the end of the rocker arm 4. The outer ring 5 is rotatably supported by a pivot 6 at one end (the right end in FIG. 1) of the rocker arm 4. To this end, a pair of support walls are formed at one end of the rocker arm 4 at a distance from each other, and the periphery of the pivot 6 provided in a state of being bridged between the two support walls. The outer ring 5 is rotatably supported by a needle bearing or the like. Further, the rocker arm 4 pivotally supports an intermediate portion thereof by a second pivot 7 so as to be swingable. Further, the distal end (the lower end in FIG. 1) of the adjusting screw 8 screwed to the other end (the left end in FIG. 1) of the rocker arm 4 is connected to the base end surface of the valve body 2 (the upper end in FIG. 1). Is hitting. still,
The valve body 2 is provided with an elastic force in a direction (upward in FIG. 1) for closing the intake port or the exhaust port by the compression spring 9.

[0004] During operation of the engine, the camshaft 1 rotates in synchronization with the crankshaft of the engine (at a half speed of the crankshaft in the case of a four-cycle engine). With this rotation, the rocker arm 4 is reciprocally oscillated about the second pivot 7 to press the valve 2 intermittently. As a result, the valve body 2 reciprocates in the axial direction by the pressing force of the rocker arm 4 and the elastic force of the compression spring 9.

As described above, the outer ring 5 that transmits the rotation of the cam 3 to the rocker arm 4 by the valve operating mechanism of the engine that reciprocates the valve body 2 based on the rotation of the camshaft 1 It is provided to reduce the frictional force of the engaging portion between the locker 3 and the rocker arm 4 and to reduce the fuel consumption rate during engine operation. That is, the cam 3
The outer ring 5 is rotated about the pivot 6 with the rotation of the cam 3. By changing the friction between the cam 3 and the member facing the cam 3 from sliding friction to rolling friction, the fuel consumption rate is reduced. Has been reduced.

When the above-described cam follower device is incorporated into a valve train of an engine, the outer peripheral surface of the cam 3 and the outer peripheral surface of the outer ring 5 come into rolling contact with the contact portion with a large contact surface pressure. Moreover, the contact surface pressure constantly fluctuates. Therefore, as it is, damage such as pitching is likely to occur on the outer peripheral surface of the cam 3 due to the variable load applied to the outer peripheral surface of the cam 3 by the outer peripheral surface of the outer ring 5. For this reason, conventionally, the camshaft 1 including the cam 3 is made of a high-strength and high-hardness metal such as quenched cast iron, chill cast iron, quenched steel, or a sintered alloy having excellent pitching resistance. It is made with materials.

On the other hand, Japanese Patent Application Laid-Open No. 3-117723-5 discloses that a number of dents are randomly formed on the surface by barrel processing so that the hardness of the surface layer is higher than the hardness of the inside and the surface layer is compressed. Inventions that produce residual stress are described.

[0008]

However, only the cam 3
When the camshaft 1 including the above is made of a high-strength and high-hardness metal material such as quenched cast iron, peeling is likely to occur on the outer peripheral surface of the outer ring 5 which comes into contact with the outer peripheral surface of the cam 3. Regarding this point, JP-A-6-129433
This is described in detail in Japanese Patent Publication No. On the other hand, on the outer peripheral surface of the outer race 5, the above-mentioned Japanese Patent Application Laid-Open No.
By performing the treatment described in Japanese Patent Application Laid-Open No. 5-205, increasing the hardness of the surface layer on the outer peripheral surface of the outer ring 5 and generating a compressive residual stress in the surface layer, the above-described peeling can be prevented.

However, the outer ring 5 whose outer peripheral surface is reinforced in this way has a problem in that the outer peripheral surface of the cam 3 is strongly aggressive against the outer peripheral surface of the cam 3 and significantly wears the outer peripheral surface of the cam 3. In view of such circumstances, the present invention prevents the occurrence of pitching on the outer peripheral surface of the cam 3 and the occurrence of peeling on the outer peripheral surface of the outer race 5 and at the same time reduces the wear on the outer peripheral surface of the cam 3. The present invention has been invented to realize a cam follower device for a valve operating mechanism of an engine.

[0010]

A cam follower device for a valve operating mechanism of an engine according to the present invention is, for example, shown in FIG.
As shown in FIG. 1, a steel cam 3 fixed to a camshaft 1 that rotates in synchronization with a crankshaft of an engine, is provided to face the cam 3, and is displaced by the movement of the cam 3. A steel outer ring 5 rotatably supported around a pivot 6 spanned between a pair of support walls provided at intervals on a driven member such as the rocker arm 4. The outer peripheral surface of the outer ring 5 is brought into contact with the outer peripheral surface of the cam 3 so that the movement of the cam 3 can be transmitted to a driven member such as the rocker arm 4.

In particular, in the cam follower device for an engine valve train of the present invention, the outer peripheral surface of the cam 3 has a hardness of Hv 613 or more by heat treatment and a roughness of 0.5 μm Ra or less. ing. The outer peripheral surface of the outer ring 5 has a hardness higher than that of the outer peripheral surface of the cam 3, but the difference from the hardness of the outer peripheral surface of the cam 3 is Hv220 or less, and the outer peripheral surface of the outer ring 5 Has a roughness of 0.1 μm
The finish is applied to a property uniformly distributed in the generatrix direction of the outer ring 5 below Ra.

[0012]

In the cam follower device for an engine valve operating mechanism according to the present invention, the occurrence of pitching on the outer peripheral surface of the cam 3 and the occurrence of peeling on the outer peripheral surface of the outer ring 5 are prevented, and at the same time, the outer peripheral surface of the cam 3 is prevented. Abrasion can be reduced. First, the outer peripheral surface of the cam 3 has a fine martensitic structure and a roughness of 0.5 μmRa or less by heat treatment for setting the hardness to Hv 613 or more. Therefore, the aggressiveness of the outer peripheral surface of the cam 3 on the outer peripheral surface of the outer ring 5 is reduced. On the other hand, the hardness of the outer peripheral surface of the outer race 5 is at most Hv220 higher than the hardness of the outer peripheral surface of the cam 3. Therefore, it is possible to effectively prevent peeling from occurring on the outer peripheral surface of the outer ring 5.

Although the hardness of the outer peripheral surface of the outer race 5 is higher than the hardness of the outer peripheral surface of the cam 3, the difference is Hv2.
Since it is limited to 20 or less, the aggressiveness of the outer peripheral surface of the outer ring 5 against the outer peripheral surface of the cam 3 is low. Moreover, since the outer peripheral surface of the outer ring 5 is finished to have a roughness of 0.1 μm Ra or less and is uniformly distributed in the generatrix direction of the outer ring 5, aggressiveness to the outer peripheral surface of the cam 3 is provided. Can be kept lower. The condition that the roughness is not more than 0.1 μmRa and is uniformly distributed in the generatrix direction of the outer ring is necessary to prevent abrasion in a part of the generatrix direction. On the other hand, regarding the properties of the outer peripheral surface of the cam 3 itself,
Since the hardness is Hv 613 or more, it is possible to prevent the occurrence of pitching on the outer peripheral surface of the cam 3 and to suppress the wear of the outer peripheral surface of the cam 3 in contact with the outer peripheral surface of the outer ring 5. it can.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One example of a method for processing the outer peripheral surface of a cam 3 and the outer peripheral surface of an outer ring 5 constituting a cam follower device for an engine valve operating mechanism of the present invention into predetermined properties and the effect of the present invention are confirmed. Next, an experiment performed by the present inventors will be described.
First, the cam 3 is made of bearing steel such as SUJ2 or S48.
It is made of medium carbon steel such as C and S53C. By subjecting the bearing steel or medium carbon steel to heat treatment including quenching and tempering, such as induction quenching and tempering, the hardness of the outer peripheral surface of the cam 3 is set to Hv 613 or more. Also, the cam 3
To SCM415, SCM420, SCr415, SC
It can also be made of carburized steel such as r420. In this case, the outer peripheral surface of the cam 3 is subjected to carburizing and quenching, which is a heat treatment for surface hardening, so that the hardness of the outer peripheral surface of the cam 3 is Hv 613 or more. The outer peripheral surface of the cam 3 whose surface is hardened by the heat treatment in this way is subjected to finish processing by grinding so that the roughness becomes 0.5 μmRa or less. This finishing method is not particularly limited as long as a desired surface roughness can be obtained. For example, after a normal grinding process, the cam 3 is finished by lapping.
Can have a roughness of 0.5 μm Ra or less.

On the other hand, the outer race 5 is made of bearing steel. This bearing steel can be quenched by induction hardening or tempering.
By performing a heat treatment including tempering, the hardness of the outer peripheral surface of the outer ring 5 is made higher than the hardness of the outer peripheral surface of the cam 3. However, the hardness of the outer peripheral surface of the cam 3 should not be higher than Hv220. The outer surface of the outer ring 5 whose surface is hardened in this way is subjected to surface finishing such as barreling after grinding on the outer surface of the outer ring 5 so that the outer surface of the outer ring 5 has a roughness of 0.1 μm Ra or less. Thus, the outer ring 5 is uniformly distributed in the generatrix direction. The finishing performed in this case is preferably a normal barrel processing. Shot peening or special barrel processing excessively hardens the surface of the outer ring 5 including its outer peripheral surface, and the outer ring 5
The hardness of the outer peripheral surface of the cam 3 is higher than the hardness of the outer peripheral surface of the cam 3 by Hv.
It is not preferable because it may be higher than 220.

The cam 3 and the outer ring 5 manufactured as described above were assembled in an experimental apparatus as shown in FIG. 2, and the durability of the cam 3 and the outer ring 5 was measured. This experimental apparatus includes an engine head 10 incorporating the cam 3 and the outer ring 5.
Is driven by the electric motor 11 via the coupling 12. The experimental conditions are shown in Table 1 below, the properties of the cam 3 and the outer ring 5 used in the experiment are shown in Table 2 below, and the experimental results are shown in Table 3 below. Each of the cams 3 was made of bearing steel, and was subjected to induction hardening and tempering as heat treatment for surface hardening. Each of the outer rings 5 was also made of bearing steel, quenched and tempered as a heat treatment for surface hardening, and then subjected to a surface treatment as shown in Table 2. In addition, the diesel engine degraded oil shown in Table 1 refers to engine oil that has been degraded due to long-term use while being injected into an actual diesel engine.

[0017]

[Table 1]

[0018]

[Table 2]

[0019]

[Table 3]

As is clear from Table 3 showing the results of such an experiment, no occurrence of pitching was observed on the outer peripheral surface of the cam 3 in any of the samples. The reason for this is that the properties of the outer peripheral surface of the cam 3 are all within the range of the present invention (the hardness is Hv 613 or more and the roughness is 0.5 μm Ra or less). Is considered to be due to the formation of a fine martensite structure due to the heat treatment for surface hardening. Also, no peeling was observed on the outer peripheral surface of the outer ring 5 in any of the samples. It is considered that the reason for this is that the hardness of the outer peripheral surface of the outer ring 5 is sufficiently high for all the samples.

On the other hand, it can be seen that the wear of the outer peripheral surface of the cam 3 becomes remarkable when the hardness of the outer peripheral surface of the outer ring 5 is too high or the value of the surface roughness is large. That is, the difference between the hardness of the outer peripheral surface of the outer race 5 and the hardness of the outer peripheral surface of the cam 3 is Hv220 or less, and the roughness of the outer peripheral surface of the outer race 5 is 0.1 μmRa or less. In this case, the amount of wear on the outer peripheral surface of the cam 3 is small. On the other hand, the difference between the hardness of the outer peripheral surface of the outer race 5 and the hardness of the outer peripheral surface of the cam 3 exceeds Hv220, and the roughness of the outer peripheral surface of the outer race 5 exceeds 0.1 μmRa. In the cases of (1) to (2), the amount of wear on the outer peripheral surface of the cam 3 becomes significant.

As described above, the difference between the hardness of the outer peripheral surface of the outer race 5 and the hardness of the outer peripheral surface of the cam 3 exceeds Hv220, or the roughness of the outer peripheral surface of the outer race 5 exceeds 0.1 μmRa. In any case, the aggressiveness of the outer peripheral surface of the outer race 5 against the outer peripheral surface of the cam 3 is increased, and the outer peripheral surface of the cam 3 is significantly worn. From the results of such an experiment,
The outer peripheral surface has a hardness of Hv 613 or more and a roughness of 0.5 μm Ra.
The hardness of the outer peripheral surface of the outer ring 5 is higher than the hardness of the outer peripheral surface of the cam 3, but the difference from the hardness of the outer peripheral surface of the cam 3 is Hv220 or less, and the roughness is 0.1 μmRa or less. Thus, it can be seen that the occurrence of pitching on the outer peripheral surface of the cam 3 and the occurrence of peeling on the outer peripheral surface of the outer race 5 can be prevented, and at the same time, the wear on the outer peripheral surface of the cam 3 can be reduced.

[0023]

The cam follower device for an engine valve train according to the present invention is constructed and operates as described above.
The durability of the engine incorporating the cam follower device can be improved.

[Brief description of the drawings]

FIG. 1 is a side view of a cam follower device for a valve train of an engine to which the present invention is applied.

FIG. 2 is a schematic side view of an experimental device used for confirming the effect of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 camshaft 2 valve element 3 cam 4 rocker arm 5 outer ring 6 pivot 7 second pivot 8 adjusting screw 9 compression spring 10 engine head 11 electric motor 12 coupling

Continued on the front page (72) Inventor Satoshi Kadokawa 1-5-50 Kumeinuma Shinmei, Fujisawa-shi, Kanagawa F-term in NSK Ltd. (reference) 3G016 AA06 AA19 BA34 BB22 EA03 EA24 FA12 FA17 FA19 GA02 3J030 EB01 EB07 EC04 EC07

Claims (1)

[Claims] 1. A steel cam fixed to a camshaft that rotates in synchronization with a crankshaft of an engine, and a driven member provided opposite to the cam and displaced by the movement of the cam. And a steel outer ring rotatably supported around a pivot spanned between a pair of support wall portions provided with a gap between the outer wall surface and the outer peripheral surface of the cam. In the cam follower device for the valve operating mechanism of the engine in which the movement of the cam is freely transmitted to the driven member, the outer peripheral surface of the cam has a hardness of Hv 613 or more by heat treatment. , Roughness is 0.
The hardness of the outer peripheral surface of the outer ring is higher than the hardness of the outer peripheral surface of the cam, but the difference from the hardness of the outer peripheral surface of the cam is Hv220 or less, and the outer peripheral surface of the outer ring is not more than 5 μmRa. A cam follower device for a valve train of an engine, characterized in that the surface has a finish of a roughness of 0.1 μm Ra or less and is uniformly distributed in a generatrix direction of the outer race.