JPH094423A - Valve driving mechanism for engine - Google Patents

Abstract

PURPOSE: To improve mechanical efficiency by removing a spring which is a cause of energy loss from a valve driving mechanism. CONSTITUTION: A positive cam (groove cam) 12 has a cam groove 14 at its side surface, which groove 14 has an inner wall 14a on its center side agreed with an outer peripheral surface of a conventional cam and an inner side wall 14b on an outer peripheral side similar to a cam surface of the inner side wall 14a. An intake valve 8 has a follower 15 at its end of a stem 8a. The follower 15 is engaged with the cam groove 14 for forcibly pushing the intake valve 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine valve drive mechanism for directly opening and closing a valve on a cam surface in a four-cycle engine.

[0002]

2. Description of the Related Art A four-cycle engine rotates by repeating four steps of intake, compression, explosion, and exhaust, but it is necessary to open and close each valve for intake and exhaust during intake and exhaust. . A cam is effectively used as the opening / closing means, and in the case of a recent automobile engine, a valve urged in a closing direction by a spring is used to push a rod, a rocker arm, etc. From the structure that pushes open indirectly through the structure, the cam shaft is arranged in the cylinder head, and the valve opens the valve with or without the rocker arm. Engines that have a cam shaft and open the valve directly on the cam surface have become mainstream. A typical example thereof is a cross-flow type DOHC engine, which has excellent valve followability and is convenient for high speed rotation.

[0003]

Even if the valve is directly pushed open by the cam surface, the spring force is still used for the closing operation, so that the valve is forcedly pushed open against the spring force. Energy loss occurs. This energy loss causes a reduction in output and also affects fuel consumption. It may be possible to add a separate independent cam for the closing operation, but two shafts for the opening operation and the closing operation are required, and the space for installing the shafts is secured to make the cylinder head huge. And the mountability deteriorates.

[0004]

SUMMARY OF THE INVENTION The present invention provides a valve mechanism for removing energy from the valve mechanism to reduce energy loss, and the valve mechanism has a follower at the end of the stem. A valve and a cam shaft are provided so as to be rotatable integrally with each other, and a side surface has a cam groove for engaging the follower,
A cam surface for pressing at least the valve in the opening operation direction is formed on the inner wall on the center side of the cam groove, and a cam surface for pressing at least the valve in the closing operation direction on the follower is formed on the inner wall on the outer peripheral side. And a front groove cam formed with. The front groove cam can be of a positive-acting type in which the width of the cam groove is equal to the diameter of the follower and the cam surfaces are provided on both inner walls of the cam groove.

[0005]

When the front cam rotates, the follower engaged with the cam groove is moved in the direction of opening the valve by the cam surface formed on the inner wall on the center side, and is moved to the inner wall on the outer peripheral side. The formed cam surface moves the valve in a direction to close it, whereby the valve is reliably opened and closed. Further, in the positive-acting type flat cam, the follower is sandwiched between both inner walls of the cam groove and does not bounce in the axial direction, and the movement is faithful to the cam curve.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a valve mechanism according to the present invention will be described with reference to the drawings. In FIG. 1, reference numeral 1 denotes a vertically open cylinder formed in a cylinder block 2, in which a piston 3 is reciprocally incorporated in the cylinder 1 and a cylinder head 4 having a roof-shaped recess is provided above the cylinder. By closing the end surface, the combustion chamber 5 is formed between the upper surface of the piston 3 and the cylinder head 4 at the top dead center position of the piston 3. The cylinder head 4 has an intake port 6 and an exhaust port 7 opened to the combustion chamber 5.
Valve seats 6a and 7a are provided around the openings of the intake and exhaust ports 6 and 7, respectively. An intake valve 8 and an exhaust valve 9 are installed in the cylinder head 4 so that the stems 8a and 9a are orthogonal to the opening surfaces of the intake and exhaust ports 6 and 7, respectively, and the stems 8a and 9a are extended. Camshafts 10 and 11 are respectively arranged on the upper side, and the cams 12 and 13 provided on the camshafts 10 and 11 respectively move the valves 8 and 9 forward and backward, and the umbrella portions of the valves 8 and 9 are moved. 8
The ports 6 and 7 can be opened and closed by bringing b and 9b into close contact with the valve seats 6a and 7a, respectively, or separating them from the valve seats 6a and 7a.

Since the basic structure of each drive mechanism of the intake valve 8 and the exhaust valve 9 is common, only the intake valve 8 side will be described below. In FIG.
Is a front groove cam that is integrally rotatable with the cam shaft 10, and the cam groove 14 formed on the side surface matches the inner wall 14a, which is the cam surface on the center side, with the outer peripheral surface of the existing cam, Inner wall 14b that is the cam surface on the outer peripheral side
Is similar to the cam surface of the inner wall 14a,
This is a positive acting type that secures a certain groove width. on the other hand,
A follower 15 engageable with the cam groove 14 is attached to the base end portion of the stem 8a of the intake valve 8, and the follower 15 is engaged with the cam groove 14 of the cam 12. It can be assembled. The follower 15 is provided with a roller.

In the valve drive mechanism constructed as described above, the side walls 14a, 14a,
The follower 15 sandwiched by 14b is guided to the cam groove 14,
Since the stem 8a moves back and forth in the axial direction, the intake valve 8
Forcibly and surely opens and closes the intake port 6 (a and b in FIG. 3). Since this valve drive mechanism has no spring for urging the valve in the closing operation direction,
One factor of energy loss is reduced and the camshaft can rotate without resistance. It goes without saying that the same applies to the exhaust valve.

In the above-mentioned embodiment, the positive movement type in which the cam groove of the front groove cam is formed over the entire circumference has been described. However, the cam groove is provided at least on the inner wall on the center side with respect to the follower. It is sufficient if a cam surface for pressing the valve downward, that is, in the opening operation direction, and a cam surface for pressing the valve with respect to the follower in the closing operation direction, are formed on the inner wall on the outer peripheral side. Therefore, although not shown, the diameter of the follower is made smaller than the groove width of the cam groove, and the follower is pressed in the direction of the valve opening operation only by the inner wall surface on the center side, and only the inner wall surface on the outer peripheral side is pressed. So that the follower presses the valve in the closing direction, or
In order to omit an unnecessary cam surface for pressing the intake valve 8 in the opening operation direction on the inner wall 14b on the outer peripheral side, a in FIG.
As shown in b, when the outer peripheral side of the cam groove 14 is partially opened and the opening operation is performed, the follower 15 is changed so as to be pressed only by the inner wall 14a on the center side, whereby the cam can be downsized.

It is desirable that a roller be attached to the follower 15 to reduce frictional resistance to the cam surface as shown in the embodiment, but the follower may be formed integrally with the stem to be rollerless, or As illustrated in FIG. 5, the stems 8a are separated from each other in the axial direction, and followers 15 'and 15' each having a small diameter are provided exclusively for each inner wall surface of the cam groove 14, or as illustrated in FIG. A pair of cams 12, 12 are arranged so as to sandwich the stem 8a, and followers 15, 15 are attached to both sides of the stem 8a.
It is also possible to engage 15 with the cam grooves 14, 14 provided on the facing surfaces of the cams 12, 12 to drive one valve with two cams.

Further, as shown in FIG. 7, in addition to the follower 15 to be engaged in the cam groove 14, a sub-follower 16 for tracing the outer peripheral surface of the cam 12 is provided to ensure the operation. Further, as shown in FIGS. 8A and 8B, a stepped shape is formed in which the center side of the cam groove forming surface sandwiching the cam groove 14 is raised, and the inner side wall 14a on the center side directly presses the tip of the stem. , The inner wall wall 14b pulls up the follower 15 for reciprocating drive, and although not shown,
In the case of the valve type, cam grooves are provided on both sides of the cam arranged between the stems, and followers provided on each stem are engaged with these cam grooves to drive two valves at the same time with one cam. The number and shape of the front groove cams, the number, size and shape of the cam grooves and the followers may be appropriately changed within the range where the above object of the present invention is achieved. still,
The valve drive mechanism of the present invention is suitable for a DOHC engine, but is provided with, for example, a wedge-shaped combustion chamber, both intake and exhaust valves are arranged on the same side, and a cam provided on one camshaft is used. It can also be adopted in an OHC engine of a type that can directly drive both valves.

[0012]

As described above, according to the present invention, the opening and closing of the valve can be forcibly driven only by the cam, so that the spring, which is a factor of energy loss, can be eliminated from the drive mechanism. Even the valve works reliably. Further, if the front groove cam is a positive-acting type, the bouncing phenomenon of the valve bouncing can be suppressed even at high rotation speeds. Further, the valve drive mechanism of the present invention can be dealt with by partially changing the design of the cylinder head in the existing engine, and the drive system of the camshaft or the like can be used.

[Brief description of drawings]

FIG. 1 is a partial explanatory view of an engine including a valve mechanism according to the present invention.

FIG. 2 is an explanatory diagram showing a relationship between a cam and a valve.

3A and 3B are explanatory views of valve operation.

4A and 4B are explanatory diagrams of a modification example.

FIG. 5 is an explanatory diagram of a modified example.

FIG. 6 is an explanatory diagram of a modification example.

FIG. 7 is an explanatory diagram of a modified example.

8A and 8B are explanatory diagrams of a modification example.

[Explanation of symbols]

1, cylinder, 2 cylinder block, 3 piston, 4 cylinder head, 5 combustion chamber, 6 intake port, 7 exhaust port, 8 intake valve, 8a
..Stem, 8b ·· Umbrella part, 9 ·· Exhaust valve, 9a ·
・ Stem, 9b ・ ・ Umbrella part, 10,11 ・ ・ Camshaft, 12,13 ・ ・ Cam, 14 ・ ・ Cam groove, 15 ・ ・ Follower, 15 '・ ・ Small diameter follower, 16 ・ ・ Sub-driven Child.

Claims (2)

[Claims] 1. A valve provided with a follower at an end of a stem, and a cam groove provided integrally rotatably with a cam shaft. The cam groove engages with the follower on a side surface thereof. A front surface in which a cam surface for pressing at least the valve in the opening operation direction is formed on the inner wall, and a cam surface for pressing the valve in the closing operation direction at least on the follower is formed on the inner wall on the outer peripheral side. An engine valve drive mechanism with a groove cam. 2. The cam for an engine according to claim 1, wherein the front groove cam is a positive-acting type in which the width of the cam groove is made equal to the diameter of the follower, and the cam surfaces are provided on both inner walls of the cam groove. Drive mechanism.