JPH108921A - Engine valve gear - Google Patents

Abstract

(57) [Abstract] [Purpose] To realize a small and lightweight structure that contributes to high performance of an engine at low cost. [Structure] A valve lifter 9 is provided at a base end of a valve stem 4.
Are connected via a cotter 8. A valve spring 10 is provided between the valve lifter 9 and the cylinder head 1. A shim member 15 is provided between the base end surface of the valve stem 4 and the outer peripheral surface of the cam 17, and the movement of the cam 17 is transmitted to the valve body 3 without passing through the valve lifter 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION A valve train for an engine according to the present invention is provided with a valve for opening and closing an intake port or an exhaust port of an engine used for traveling of an automobile or the like in synchronization with rotation of a crankshaft. Move back and forth.

[0002]

2. Description of the Related Art An intake valve and an exhaust valve of an engine reciprocate in synchronization with the rotation of a crankshaft and must open and close an intake port or an exhaust port. Such a valve operating device for reciprocating the intake valve and the exhaust valve includes a camshaft that rotates in synchronization with the rotation of the crankshaft, and a camshaft that is supported by an intermediate portion of the camshaft and rotates together with the camshaft. And a valve lifter that reciprocates the intake valve or the exhaust valve based on the displacement of the outer peripheral surface of the cam. In the case of a structure in which two camshafts are provided so as to face the base ends of the intake valve and the exhaust valve, respectively, like a DOHC type engine,
The movement of the cam is directly transmitted to the valve lifter supported at the base end of the intake valve and the exhaust valve without going through the rocker arm.

[0003] A known valve train of an engine having such a structure is disclosed in, for example, Japanese Utility Model Laid-Open Publication No.
Japanese Patent Application Laid-Open Nos. 8305 and 64-34405 are known. In either case,
A valve body, which is an intake valve or an exhaust valve, is formed by fixing a flange-shaped valve portion at the tip of a rod-shaped valve stem, and reciprocatingly moves in the axial direction of the valve stem, thereby producing a combustion chamber of an engine. The intake port or the exhaust port, which is a port leading to the port, is opened and closed. A valve lifter is mounted on the outer peripheral surface of the base end of the valve stem, and the valve lifter is fitted to a guide portion provided on a cylinder head of the engine so as to be reciprocally movable in the axial direction of the valve stem. . A valve spring, which is a compression coil spring, is provided between the member engaged with the valve stem and a part of the cylinder head, and the intake port or the exhaust port is provided on the valve body by the valve portion. The elasticity in the closing direction is given. Further, a cam supported by an outer peripheral surface of an intermediate portion of a camshaft of the engine and rotating together with the camshaft is arranged to face the valve lifter. With the rotation of the cam, the valve body displaces against the elasticity of the valve spring, opens the intake port or the exhaust port, or displaces based on the elasticity of the valve spring, The intake port or the exhaust port is closed.

Among the valve gears of the engines described in the above publications, FIG. 2 of Japanese Utility Model Laid-Open No. 62-8305 and FIGS. In the prior art, a spring seat is coupled to a base end of a valve stem via a coupling member called a cotter, and one end of the valve spring is abutted against the spring seat (first example of a conventional structure). 62-
8305 and FIGS. 1, 2, and 4 of Japanese Utility Model Application Laid-Open No. 64-34405, the spring seat is omitted, a valve lifter is provided at the base end of a valve stem, a cotter and a cotter. The valve lifter can be connected to the base of the valve stem by connecting via a snap ring (second example of the conventional structure) or by screwing a screw hole formed in the cotter and a male screw formed in the base end of the valve stem. It is connected to the end (third example of the conventional structure).

[0005]

In the case of the first example of the conventional structure described in the above publications, a spring seat is provided at the base end of the valve stem in addition to the valve lifter.
In addition to increasing costs due to the increase in the number of parts,
The mass of the member reciprocating with the valve increases. In order to improve the performance of the engine (increase the rotation speed), it is necessary to reduce this mass as much as possible, and this increase in mass is not preferable.

On the other hand, the second and third examples of the conventional structure described in the above publications are troublesome in the processing of the component parts and cause an increase in cost. For example, in the case of the second example of the conventional structure, a locking groove is formed on the outer peripheral surface of the base end portion of the valve stem to prevent the cotter from loosening when the cam presses the valve stem, and the locking groove is snapped to the locking groove. Wearing a ring. As a result, the operation of forming the locking groove and the operation of attaching the snap ring to the locking groove are required, and the cost is increased. Further, in the case of the third example of the conventional structure, a screw working operation and a screw fixing operation are required, which also increases the cost. In view of such circumstances, the engine valve gear of the present invention has been invented to realize a lightweight and inexpensive structure.

[0007]

An engine valve gear according to the present invention has a valve body, a valve lifter, a valve spring, and a valve spring similar to a conventionally known engine valve gear.
And a cam. The valve body is formed by fixing a flange-shaped valve portion at the tip of a rod-shaped valve stem, and is a port that communicates with the combustion chamber of the engine by reciprocating in the axial direction of the valve stem. , Opening and closing the intake port or the exhaust port.
The valve lifter is supported by a cotter on an outer peripheral surface of a base end portion of the valve stem via a cotter, and is fitted to a guide portion provided on a cylinder head of the engine so as to be reciprocally movable in the axial direction of the valve stem. I have. The valve spring is provided between one surface of the valve lifter and a part of the cylinder head, and gives the valve body resilience in a direction of closing a port communicating with the combustion chamber by the valve portion. . Further, the cam is arranged to face the valve lifter, is supported on an outer peripheral surface of an intermediate portion of an engine camshaft, and rotates together with the camshaft. In particular, in the engine valve gear of the present invention, the base end surface of the valve stem and the outer peripheral surface of the cam are opposed to each other, and a shim member is sandwiched between the base end surface and the outer peripheral surface. . The movement of the cam is freely transmitted to the valve body without passing through the valve lifter.

[0008]

According to the valve train of an engine of the present invention configured as described above, it is possible to achieve both a reduction in weight, which leads to an improvement in engine performance, and a reduction in cost. That is, since one end of the valve spring abuts against one surface of the valve lifter, there is no need to provide an independent spring seat as in the first example of the conventional structure, and the weight and cost can be reduced by reducing the number of parts. The elasticity applied to the valve lifter by the valve spring always acts in the direction of tightening the cotter connecting the valve lifter and the valve stem. This action does not change when the valve body is moved against the elasticity of the valve spring. For this reason, even if a snap ring is not provided, the cotter does not loosen. Therefore, the snap ring and the locking groove for mounting the snap ring are omitted, and the cost of the engine valve gear can be reduced.

[0009]

FIG. 1 shows a first embodiment of the present invention.
An example is shown. For example, a cylinder guide 1 made of a harder metal is inserted into a cylinder head 1 of an engine made of an aluminum alloy.
A valve stem 4 constituting the valve body 3 is slidably inserted in the valve guide 2 in the axial direction (vertical direction in FIG. 1). The valve element 3 is a so-called mushroom valve. The valve element 5 is provided at the distal end (the lower end in FIG. 1) of the valve stem 4 based on the reciprocating movement of the valve stem 4, and the intake port (exhaust port) is provided. Mouth) 6 is opened and closed. A valve guide seal 7 is provided at a base end (upper end in FIG. 1) of the valve guide 2, and passes through a gap between an inner peripheral surface of the valve guide 2 and an outer peripheral surface of the valve stem 4. The mixture (exhaust) flowing through the intake (exhaust) 6 is prevented from leaking outside. Further, a valve lifter 9 is supported at the base end of the valve stem 4 via a cotter 8, and a valve spring 10 as a compression coil spring is provided between the valve lifter 9 and the cylinder head 1. Therefore, the valve section 5 of the valve body 3 keeps the air supply port (exhaust port) 6 closed as long as no external force acts.
The valve lifter 9 is fitted in a guide hole 18 provided in the cylinder head 11 as a guide portion so as to be freely displaceable in the axial direction.

As is well known, in order to connect the base end of the valve stem 4 and the valve lifter 9 by the cotter 8, an engagement groove 11 is formed on the outer peripheral surface of the base end of the valve stem 4, and the valve lifter 9 is provided. Are each provided with a tapered hole 12 at the center thereof. The diameter of the cotter 8 can be freely expanded or reduced by being formed in a partially cylindrical shape or divided into a plurality of pieces in the circumferential direction. On the inner peripheral surface of the cotter 8, an engagement ridge 13 is formed to be fitted with the engagement groove 11. The outer peripheral surface of the cotter 8 is a conical tapered surface that is in close contact with the tapered hole 12.
The inner diameter of these tapered holes 12 and the outer diameter of the cotter 8 are:
It becomes larger toward the base end surface (the upper end surface in FIG. 1) of the valve stem 4. Therefore, the cotter 8 is pressed against the outer peripheral surface of the valve stem 4 based on the elasticity applied to the valve lifter 9 from the valve spring 10.

Further, in the case of the engine valve gear of the present invention, a holding recess 14 is formed at the center of the base end surface (the upper end surface in FIG. 1) of the valve lifter 9, and a shim member 15 is formed in the holding recess 14. keeping. The shim member 15 is made of a material having excellent wear resistance, such as a hard metal. The camshaft 16 which rotates in synchronization with the crankshaft of the engine is arranged at a portion facing the shim member 15. An outer peripheral surface of a cam 17 fixed to an intermediate portion of the cam shaft 16 is in contact with the surface of the shim member 15. The thickness of the shim member 15 is set so that the shim member 15 is sandwiched between the base end surface of the valve stem 4 and the outer peripheral surface of the cam 17 over the entire stroke range of the valve body 3 without any gap. Regulating.

The engine valve gear of the present invention configured as described above operates and opens and closes the intake port (exhaust port) 6 in the following manner. First, as shown in FIG. 1, when the shim member 15 is in contact with the small diameter portion of the cam 17, the valve body 3 is displaced to the proximal side by the elastic force of the valve spring 10, The intake port (exhaust port) 6 is closed by the valve portion 5 provided in the above. On the other hand, the cam 17 together with the camshaft 16 is moved from the state of FIG.
When the shim member 15 comes into contact with the large diameter portion of the cam 17, the valve body 3
And the valve 5 provided at the distal end opens the intake port (exhaust port) 6.

During the reciprocating movement of the valve body 3 with the rotation of the cam 17, the valve lifter 9 is kept pressed toward the base end of the valve stem 4. The force for displacing the valve stem 4 against the elasticity of the valve spring 10 is first transmitted from the cam 17 to the valve stem 4 via the shim member 15. Next, the power is transmitted from the valve stem 4 to the valve lifter 9 via the cotter 8. Therefore, the force for displacing the valve stem 4 against the elasticity of the valve spring 10 is applied to the cotter 8.
It does not act in the direction of loosening. In other words, the cotter 8 always receives the force in the tightening direction due to the elasticity of the valve spring 10. Therefore, unlike the above-described second example of the conventional structure, the cotter 8 is not loosened even without providing a snap ring. Therefore, the snap ring and the locking groove for mounting the snap ring are omitted, and the cost of the engine valve gear can be reduced.

[0014]

The engine valve train of the present invention is constructed and operates as described above, so that a small and lightweight structure that contributes to high performance of the engine can be realized at low cost.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylinder head 2 Valve guide 3 Valve body 4 Valve stem 5 Valve part 6 Inlet (exhaust port) 7 Valve guide seal 8 Cotta 9 Valve lifter 10 Valve spring 11 Engagement groove 12 Tapered hole 13 Engagement ridge 14 Holding recess 15 Shim Member 16 Camshaft 17 Cam 18 Guide hole

Claims (1)

[Claims] 1. A valve body comprising a rod-shaped valve stem and a flange-shaped valve portion fixedly provided at a tip end thereof, and reciprocating in the axial direction of the valve stem to open and close a port communicating with a combustion chamber of an engine. A valve lifter coupled and supported on a base end outer peripheral surface of the valve stem via a cotter, and reciprocally fitted in a guide portion provided on an engine cylinder head in the axial direction of the valve stem; A valve spring that is provided between one surface of a valve lifter and a part of the cylinder head, and that provides the valve body with elasticity in a direction that closes an opening communicating with the combustion chamber by the valve portion; And a cam supported on the outer peripheral surface of the intermediate portion of the camshaft of the engine and rotating together with the camshaft.
The base end surface of the valve stem and the outer peripheral surface of the cam are opposed to each other, and a shim member is sandwiched between the base end surface and the outer peripheral surface, so that the movement of the cam is performed on the valve body without passing through the valve lifter. A valve train for an engine that can be transmitted freely.