JP2000161025A - Valve train of internal combustion engine - Google Patents

Abstract

(57) Abstract: An object of the present invention is to provide a valve operating mechanism of an internal combustion engine that can realize weight reduction and cost reduction. A minute valve clearance is provided between an end portion (14a) of a rocker arm (12) and a valve stem (20) to release thermal expansion of a valve (28) and to make the valve (28) securely adhere to a valve seat in a cylinder head (30) when closed. Is formed. In addition, one end 14b of the rocker arm 12 has a protrusion 2
2 are provided. The projection 22 is formed by welding a high-precision bearing steel ball. On the other hand, cylinder head 3
A pivot end 44 that supports the convex portion 22 is fitted in the mounting hole 42 provided in the “0”. Adjustment of the valve clearance is performed by a pivot end 44 fitted in the mounting hole 42.
Is exchanged for one having a different height.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve operating mechanism for an internal combustion engine, and more particularly, to a valve operating mechanism that converts a rotational motion of a cam into a reciprocating motion and transmits the reciprocating motion to an intake valve or an exhaust valve in the internal combustion engine. .

[0002]

2. Description of the Related Art Conventionally, in an internal combustion engine, a valve mechanism using a cam drive has been generally used to drive an intake valve and an exhaust valve. In such a mechanism, a rocker arm is widely used as a member that converts the rotational motion of the cam into a reciprocating motion. One end of the rocker arm is supported, for example, by a pivot end, and the other end is disposed at the upper end of the valve stem. During operation of the internal combustion engine, the rocker arm is pressed by the cam drive, and the rocker arm swings around the pivot end. When the rocker arm swings, the valve stem reciprocates in the axial direction, and the valve is opened and closed in the cylinder head.

Here, when the valve is closed, a minute valve clearance is formed between one end of the rocker arm and the valve stem. The valve clearance is for releasing the thermal expansion of the valve and ensuring that the valve is in close contact with the valve seat in the cylinder head when the valve is closed. The valve clearance changes due to expansion, contraction, wear, and the like of the valve train components accompanying the operation of the internal combustion engine.

If the valve clearance is too large, tappet noise, which is the sound of the rocker arm striking the valve, will be generated. On the other hand, if the valve clearance is too small, the valve cannot be in close contact with the valve seat in the closed state, and the valve is slightly opened. In this case, the compressibility of the combustion gas in the combustion chamber is reduced, and problems such as unstable idling of the internal combustion engine occur.
Therefore, various methods have conventionally been used to optimally adjust the valve clearance.

For example, Japanese Utility Model Laid-Open No. 2-127705 discloses that
A valve operating mechanism is disclosed in which a valve clearance is adjusted by an amount of protrusion of a pivot screw shaft screwed into a cylinder head. One end of the pivot screw shaft of this valve mechanism is screwed into the cylinder head, and the other end is provided with a spherical receiving portion. An engagement portion for engaging a rotary operation tool such as a hexagon wrench is provided at the top of the receiving portion. The pivot screw shaft is fixed to the cylinder head with a lock nut. On the other hand, a spherical concave seat is provided at one end of the rocker arm provided in the valve operating mechanism, and a receiving portion of the pivot screw shaft is slidably fitted therein. Further, a through hole penetrating through the front and back of the rocker arm is provided substantially at the center of the seat. For this reason, the engaging part of the receiving part fitted in the receiving seat of the rocker arm can be seen through the through hole.

In the above valve operating mechanism, when adjusting the valve clearance, first, the lock nut is loosened, and then an appropriate rotary operating tool is engaged with the engaging portion of the receiving portion. Then, the rotary operation tool engaged with the receiving portion is rotated. By rotating the rotary operation tool, the pivot screw shaft rotates and the amount of protrusion of the pivot screw shaft changes, so that the valve clearance can be adjusted.

In addition to the above example, there is also a valve operating mechanism in which a valve clearance is adjusted by an adjusting screw, a valve lash adjuster, or the like provided on the rocker arm side. For example, in the case of a valve mechanism having an adjusting screw on the rocker arm side, by loosening a lock nut for fixing the adjusting screw to the rocker arm and then rotating the adjusting screw, changing the amount of protrusion of the screw from the rocker arm. The valve clearance can be adjusted.

[0008]

However, the above-described conventional valve train requires a large number of components such as a pivot screw shaft and a lock nut. For this reason, the production cost and weight have been increased. Further, in the above conventional example, it is necessary to provide a high-precision spherical receiving portion at one end of the pivot screw shaft, and to provide a through hole at one end of the rocker arm. Therefore, it is necessary to perform complicated and precise processing on the pivot screw shaft and the rocker arm. Further, in the above-described conventional example, when adjusting the valve clearance, it is necessary to use a rocker arm having a long arm length in order to secure a space for using a rotating operation tool and a lock nut rotating tool.

In a case where an adjusting screw is provided on a sheet metal rocker arm and the valve clearance is adjusted by the amount of protrusion of the adjusting screw, a nut for screwing the adjusting screw to the rocker arm is welded to the rocker arm. It is necessary to keep. Further, in the case where a valve lash adjuster for automatically adjusting the valve clearance is arranged in the valve operating mechanism, the cost of the valve operating mechanism is increased due to the expensive valve lash adjuster. Further, when the valve lash adjuster is disposed in the valve operating mechanism, the friction increases by the oil pressure of the valve lash adjuster.

[0010] The present invention has been made in view of the above points, and has as its object to provide a valve train for an internal combustion engine that can be reduced in weight and cost.

[0011]

The above object is achieved by the present invention.
A rocker arm that has a convex portion at one end and swings about the convex portion to reciprocate a valve stem to open and close a valve; A valve end of the internal combustion engine having a pivot end supporting the pivot end, wherein the pivot end is configured to be replaceable, and a valve clearance between the rocker arm and the valve stem is determined based on a height of the pivot end. The adjustment is achieved by the valve train of the internal combustion engine.

In such a valve operating mechanism, the valve clearance can be easily adjusted only by changing the pivot end disposed on the cylinder head. Further, since the pivot portion can be formed only by the convex portion and the pivot end, the weight and cost of the valve operating mechanism can be reduced. Further, the above object is as described in claim 2.
2. The valve operating mechanism for an internal combustion engine according to claim 1, wherein the convex portion is achieved by a valve operating mechanism for an internal combustion engine, which is a bearing steel ball welded to one end of the rocker arm.

[0013] Mass-produced bearing steel balls are inexpensive.
And it is processed with high precision. For this reason, the cost reduction of the valve train is realized by welding the bearing steel ball to the end to form a projection. Further, by applying a high-precision bearing steel ball to the projection, friction at the time of rocking of the rocker arm is reduced.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the valve train according to the present invention will be described below. FIG. 1 shows a valve train 10 according to the present invention.
3 is a configuration diagram of a main part of FIG. As shown in FIG.
0 has a rocker arm 12. This rocker arm 1
2 has an arm body 14 and a roller 16 provided at the center of the arm body 14. The roller 16 is rotatable around a support shaft 18 passing through the arm body 14. The rocker arm 12 is formed using, for example, carbon steel.

A valve stem 20 is disposed at an end 14a of the arm body 14. Further, a convex portion 22 is provided at an end portion 14 b of the arm body 14. The protrusion 22 is formed by welding a high-precision bearing steel ball to the end 14b. Convex part 22 made of steel ball for bearing
Has high abrasion resistance. The valve stem 20 penetrates a valve guide 26, and has a valve 28 at its distal end. The valve stem 20 is formed of heat-resistant steel, and its surface is subjected to a surface treatment such as chrome plating for wear resistance.

The valve guide 26 has a cylinder head 30.
Press-fit. For this reason, the valve stem 20 can slide in the axial direction along the valve guide 26.
A rubber valve seal 32 having excellent oil resistance at high temperatures is provided above the valve guide 26. The valve seal 32 seals the valve guide 26 to prevent the lubricating oil from leaking into the cylinder. There is a small gap between the valve stem 20 and the valve seal 32, and lubricating oil required for lubrication between the valve stem 20 and the valve guide 26 is supplied through this gap.

A spring retainer 24 is fixed to the valve stem 20 via a valve cotter 34.
A valve spring 36 is provided between the spring retainer 24 and the cylinder head 30. The valve spring 36 is made of, for example, carbon steel for spring, and its surface is subjected to a surface treatment such as shot peening to improve fatigue strength. The valve spring 36 always urges the spring retainer 24 upward in FIG. For this reason, the spring retainer 24
The valve stem 20 and the valve 28 integrated with the valve spring are also urged upward by the valve spring 36.

The valve 28 is made of heat-resistant steel because it operates under high temperature and high pressure. In the valve 28, a portion to be seated on the valve seat is subjected to a surface treatment for improving abrasion resistance. The rocker arm 12
The material of the valve and the valve 28 is not limited to the above example. For example,
Rocker arm 12 may be formed of cast iron or an aluminum alloy.

A cam 38 is provided above the roller 16 so as to be in contact with the roller 16. During operation of the internal combustion engine, the cam 38
When the roller rotates while pressing the roller 16, the rocker arm 12 performs a swinging motion synchronized with the rotation of the cam 38 with the convex portion 22 as a fulcrum. When the end 14a of the rocker arm 12 moves downward during the rocking movement of the rocker arm 12, the end 14a presses the valve stem 20 downward against the restoring force of the valve spring 36. At this time, the valve 28
Is separated from the valve seat and is opened. On the other hand, when the end 14a of the rocker arm 12 moves upward, the valve stem 20 also moves upward due to the restoring force of the valve spring 36. When the valve stem 20 moves upward by a predetermined value, the valve 28 comes into close contact with the valve seat and is closed.

The cylinder head 30 has a mounting hole 42. A substantially cylindrical pivot end 44 is fitted in the mounting hole 42. The mounting hole 42 has a depth equal to its diameter. For this reason, the pivot end 44 fitted in the mounting hole 42 is securely held by the cylinder head 30. The mounting hole 42 is formed such that its diameter is slightly larger than the diameter of the pivot end 44. For this reason, the pivot end 44 is detachable from the cylinder head 30.

When the valve 28 is closed, the end 14a of the rocker arm 12 and the valve stem 20 are closed.
A minute valve clearance is formed between them. This valve clearance is for releasing the thermal expansion of the valve 28 and for ensuring that the valve 28 is in close contact with the valve seat in the cylinder head 30 in the closed state. The valve clearance changes due to expansion, contraction, wear, and the like of the valve train components accompanying the operation of the internal combustion engine. If the valve clearance exceeds an appropriate value, tappet noise occurs. Also,
If the valve clearance is smaller than the appropriate value, the valve 28 cannot be in close contact with the valve seat in the closed state, and the valve 28 is slightly opened. In this case, problems such as a decrease in the compressibility of the combustion gas in the combustion chamber occur.

Therefore, in the valve operating mechanism 10 of the present embodiment, a plurality of types of pivot ends 44 having different heights are prepared, and the pivot end 44 having an optimum height is attached to the cylinder head 30 to increase the valve clearance. The structure can be adjusted easily. This pivot end 4
The four types are determined in consideration of the size of the valve clearance, the manufacturing cost of the pivot end 44, and the like.

The pivot end 44 is formed of a steel alloy, and its surface is subjected to a surface treatment for improving abrasion resistance. Further, the pivot end 44 has a concave portion 46 which is spherically processed with high precision. This recess 46
The rocker arm 12 is supported by the engagement of the protrusion 22 provided on the rocker arm 12 with the rocker arm 12. The concave portion 46 is formed so that its radius of curvature is slightly smaller than the radius of curvature of the convex portion 22. For this reason, it is prevented that the convex part 22 and the concave part 46 contact only in one part, and the convex part 22 and the concave
The wear resistance of No. 6 is further improved. Further, since the surfaces of the convex portion 22 and the concave portion 46 are both processed with high precision, friction at the time of the rocking movement of the rocker arm 12 is reduced.

The pivot end 44 has a through hole 48 penetrating from the bottom to the concave portion 46. The through hole 48 is provided in the oil supply hole 5 of the cylinder head 30.
Communicates with 0. During operation of the internal combustion engine, the recess 4
6 is supplied with lubricating oil from an oil supply hole 50 through a through hole 48. Therefore, a lubricating oil film is formed on the concave portion 46, and the space between the convex portion 22 and the concave portion 46 is fluid-lubricated. Therefore,
The convex part 22 and the concave part 46 accompanying the rocking movement of the rocker arm 12
The sliding friction between them is reduced. Further, the through hole 48 also serves to release air when the pivot end 44 is attached.

As described above, the pivot portion of the valve mechanism 10 of the present embodiment is formed only by the convex portion 22 and the pivot end 44, and the pivot screw shaft, the lock nut, and the like, which are the components of the conventional example, are not provided. Since it is necessary, the weight reduction of the valve train 10 is achieved. Also, since there is no need to consider the space for using a tool for adjusting the valve clearance, the horizontal distance between the cam 38 and the pivot end 44 can be reduced. In this case, the overall length of the rocker arm 12 can be reduced while maintaining the rocker ratio. Then, as the rocker arm 12 is shortened, the rocker arm 1
Since the rigidity of the rocker arm 2 is improved, the rocker arm 12 can be made thinner and lighter. Further, since the convex portion 22 of the rocker arm 12 is obtained by welding a steel ball mass-produced for a bearing to the end portion 14b, it can be easily formed at low cost. The realization of such a lightweight and low-cost rocker arm 12 contributes to the weight reduction and cost reduction of the valve train 10.

[0026]

As described above, according to the first aspect of the present invention, the weight and cost of the valve train can be reduced. According to the second aspect of the present invention, cost reduction of the valve train is achieved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a main part of a valve train according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Valve operating mechanism 12 Rocker arm 14 Arm body 14a, 14b End 16 Roller 20 Valve stem 22 Convex part 24 Spring retainer 26 Valve guide 28 Valve 30 Cylinder head 36 Valve spring 38 Cam 42 Mounting hole 44 Pivot end 46 Depression 48 Through hole 50 Oil supply Hole

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Seiji Tsuda 10 Hamadashita, Nakahata-cho, Nishio-shi, Aichi F-term in Otics Co., Ltd. (reference) 3G016 AA06 AA19 BA45 BB11 BB18 BB22 BB23 CA04 CA05 CA11 CA12 CA13 CA16 CA51 CA52 CA57 DA11 EA02 FA22 FA30 GA00 GA01 GA02

Claims (2)

[Claims] A rocker arm having a convex portion at one end and reciprocating a valve stem to open and close a valve by performing a swinging movement about the convex portion, and a convex portion disposed on a cylinder head; A pivot end that supports the valve end, wherein the pivot end is configured to be replaceable, and a valve clearance between the rocker arm and the valve stem is determined based on a height of the pivot end. A valve train for an internal combustion engine, wherein the adjustment is performed. 2. The valve operating mechanism for an internal combustion engine according to claim 1, wherein the projection is a bearing steel ball welded to one end of the rocker arm.