JPH07332041A - Intake/exhaust valve structure of engine - Google Patents

Abstract

PURPOSE:To enlarge a valve opening area during intake/exhaust processing as well as to reduce the leakage of intake/exhaust gas. CONSTITUTION:A valve face 13 whose cross sectional shape is a circular arc is formed by rounding on the edge part of the outer circumference part of a valve head 10. A seat face 14 whose cross sectional shape is a circular arc is formed to the valve seat part of a valve seat 9 for the purpose of fitting the shape of the valve face 13. A valve opening area becomes small enough in a range where valve lift quantity is small, and rapidly becomes large accompanying the increment of the lift quantity because a contact surface between the valve head 10 and the valve seat 9 is formed in a circular arc shape. Therefore, in case that valve timing is set with due regrad to the buffer curve part of the cam of a valve system, the valve opening area in the buffer curve part is enough reduced so that the leakage of an intake/exhaust can be reduced, and the valve opening area is rapidly enlarged accompanying the increment of the lift quantity so that the enough valve opening area can be retained during intake/exhaust processing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvements in intake / exhaust valve structures for engines of automobiles, motorcycles and the like.

[0002]

2. Description of the Related Art In a conventional engine intake / exhaust valve structure, as shown in FIG. 4, a valve head 2 of a valve 1 is formed with a tapered valve face 3 and a valve seat portion of a valve seat 4 is formed. Further, the seat face 5 is formed so as to match the taper angle of the valve face 3. And valve 1
Is normally closed by bringing the valve face 3 into contact with the seat face 5 by the urging force of a valve spring (not shown) to shut off the combustion chamber from the intake / exhaust ports. Combined valve mechanism cam (not shown)
The valve is lifted and opened by the rotation of.

In the valve seat portion of the valve seat 4, the seat face 5 and the inner peripheral edge portion 7 and the outer peripheral edge portion 8 are multi-faced at a predetermined angle so as to reduce the intake / exhaust resistance. Has become.

In the above-described conventional air supply / exhaust valve structure, since the seat faces of the valve face 3 and the seat face 5 are flat faces, the valve opening area is small in the region where the lift amount is small as shown in FIG. It is determined by the distance between the face 3 and the seat face 5, that is, it is linearly proportional to the lift amount. Then, the lift amount is a predetermined value C
If it becomes above, it will depend on the distance between the inner peripheral edge A of the valve face 3 and the outer peripheral edge B of the seat face 5, and the inclination of increase will become large.

[0005]

By the way, in general, the cam of the valve mechanism has a valve clearance provided between it and the valve stem 6 (cam follower) to collide with the cam follower at the time of valve opening and the valve at the time of valve closing. In order to buffer the collision between the valve 1 and the valve seat 4, a buffer curve portion with a gentle profile is provided to reduce the speed of the valve 1 at the time of collision.

For this reason, the moving speed of the valve 1 at the time of starting the lift and at the time of seating becomes small. Therefore, in order to secure a sufficient valve area during the intake / exhaust stroke, the timing of opening the valve 1 is advanced accordingly. , It is necessary to delay the closing timing. In such a case, the valve opening area at the buffer curve portion of the cam can be made as small as possible to reduce the leakage of intake / exhaust gas and improve the combustion efficiency.

However, in the conventional intake / exhaust valve structure shown in FIG. 4, the valve opening area is linearly proportional to the lift amount in the region where the lift amount due to the buffer curve portion of the cam is small. At times, it was difficult to secure a sufficient valve opening area and to sufficiently reduce the valve opening area in the buffer curve portion of the cam.

In view of this, there has been a demand for an intake / exhaust valve structure in which the valve opening area is sufficiently small in the region where the lift amount is small, and the valve opening area increases rapidly as the lift amount increases.

As a prior art relating to such an intake / exhaust valve structure, Japanese Patent Laid-Open No. 57-59016 discloses that a valve seat is provided with a fitting portion for fitting a valve head, so that a suction amount is reduced in a small region. -The engine air supply / exhaust port that blocks the flow of exhaust gas is disclosed.

The present invention has been made in view of the above points, and the valve opening area is sufficiently small in a region where the lift amount is small, and the intake / exhaust is designed to increase rapidly as the lift amount increases. It is intended to provide a valve structure.

[0011]

In order to solve the above problems, in the intake / exhaust valve structure of the present invention, the contact surface between the valve seat and the valve head is formed to have an arc-shaped cross section. Characterize.

[0012]

With this configuration, the valve opening area is small in the region where the valve lift amount is small, and the valve opening area rapidly increases due to the subsequent increase in the lift amount. In addition, the rounded contact surface between the valve seat and the valve head reduces the intake and exhaust resistance when the valve is open,
The sealing property is improved when the valve is closed.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

As shown in FIG. 1, the intake / exhaust valve structure for an engine according to the present embodiment has a cylindrical valve seat 9 mounted on an opening (not shown) of an intake / exhaust port communicating with a combustion chamber. And a valve head 10 that is seated on and off the valve seat 9 and a valve 12 formed at one end of a valve stem 11. The valve stem 11 is inserted through the valve seat 9, and the other end side is engaged with a valve spring and a cam (not shown) of the valve gear.

As in the conventional valve 12, the valve head 10 is normally seated on the valve seat 9 by the urging force of the valve spring to close the intake / exhaust ports, and the cam of the valve operating device rotates. The valve stem 11 moves and the valve head 10 lifts from the valve seat 9 to open the intake / exhaust ports.

On the outer peripheral portion of the valve head 10, a contact surface with the valve seat 9, that is, an edge portion facing the valve seat 9, is provided with a rounded shape, and a valve face 13 having an arc-shaped cross section is formed. Has been done. A seat face 14 having a circular arc-shaped cross section is formed on the valve seat portion of the valve seat 9 in contact with the valve head 10 so as to match the shape of the valve face 13.

When the valve 12 is seated on the valve seat 9 by the urging force of the valve spring, the valve face 13 engages with the seat face 14 to close the intake / exhaust ports. In addition, seat face
The connection portion 15 between 14 and the inner peripheral surface of the valve seat 9 is formed by a smooth curved surface in order to reduce the intake / exhaust resistance.

The operation of the present embodiment configured as above will be described below.

Since the valve face 13 and the valve face 14, which are the contact surfaces between the valve 12 and the valve seat 9, are formed in an arc shape in cross section, as shown in FIG. In a region where the lift amount is small, the distance l is determined by the distance l between the outer peripheral end D of the seat face 14 and the valve face 13, that is, the radius r of the arc-shaped cross section of the valve face 14 is constant, so the distance l is the outer peripheral end D.
Is determined by the distance L between the center of the arc and the center O of the arc, and as shown by the solid line in FIG. 3, increases with an increase in the lift amount along a downwardly convex curve in the upper right direction. The valve opening area is sufficiently small in a region where the lift amount is small, and has a characteristic of rapidly increasing as the lift amount increases, as compared with the conventional valve shown in FIG. 4 (see the broken line in FIG. 3). .

Therefore, when the valve timing is set in consideration of the buffer curve portion of the cam of the valve mechanism, it is possible to sufficiently reduce the valve opening area at the buffer curve portion of the cam to reduce intake / exhaust leakage. In addition, the valve opening area increases rapidly with an increase in the lift amount, and a sufficient valve opening area can be secured during the intake and exhaust strokes. As a result, combustion efficiency can be improved, engine output and fuel consumption can be improved, and exhaust gas purification can be promoted.

Further, since the valve face 13 and the seat face 14 are constituted by smooth curved surfaces, the intake / exhaust resistance is reduced and the intake / exhaust can be smoothly performed. Furthermore, since the valve face 13 and the valve face 14 which are the contact surfaces between the valve 12 and the valve seat 9 are formed in an arc shape in cross section, the misalignment of the valve 12 can be aligned and the intake / exhaust can be performed. The sealability of the valve can be improved.

[0022]

As described above in detail, in the intake / exhaust valve structure of the present invention, the contact surface between the valve seat and the valve head is rounded so that the cross-sectional shape is arcuate. In a region where the valve lift amount is small, the valve opening area is small, and the valve opening area rapidly increases due to the subsequent increase in the lift amount. As a result, the valve opening area in the buffer curve portion of the cam can be made sufficiently small to reduce the intake / exhaust leakage, and the valve opening area can be increased rapidly as the lift amount increases. Since a sufficient valve opening area can be secured during the exhaust stroke, combustion efficiency can be improved, engine output and fuel consumption can be improved, and exhaust gas purification can be promoted. Further, due to the rounded contact surfaces of the valve seat and the valve head, the intake / exhaust resistance is reduced when the valve is open, and the sealing performance is improved when the valve is closed.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a valve opening area of the device of FIG.

3 is a diagram showing a relationship between a valve lift amount and a valve opening area of the device of FIG.

FIG. 4 is a vertical cross-sectional view of a conventional engine intake / exhaust valve structure.

5 is a diagram showing a relationship between a valve lift amount and a valve opening area of the device shown in FIG.

[Explanation of symbols]

 9 Valve seat 10 Valve head 12 Valve 13 Valve face 14 Seat face

Claims (1)

[Claims] 1. An intake / exhaust valve structure for an engine, wherein a contact surface between a valve seat and a valve head is formed so as to have an arc-shaped cross section.