JPS6336009A - Valve operating device for internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent a valve from uneven wear by disposing a cam so that the action point of cam on a lifter is deviated from the valve axis axially of the cam shaft and interposing a thrust bearing between a spring for urging the valve in the closing direction and a spring support portion. CONSTITUTION:An intake-exhaust valve 3 reciprocated vertically through a lifter 11 provided on the upper surface with a shim 10 by a cam 1 on a cam shaft 2 rotated synchronously with engine rotation is fitted in a valve guide 5, press fitted into an engine head, slidably in the direction of valve axis 15 and rotatably around the valve axis 15. Also, a retainer 6 is fixed to a recess 3c on the circumference of shaft provided on the upper portion of valve 3 by a cotter 4. In this case, the lower surface 6a of retainer 6 smoothly finished abuts against a thrust bearing 12 by which is supported the upper end of spring 7. Also, the center point of action of cam 1 on the valve 3 and lifter 11 provided on the same axis is provided deviated by delta.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a valve operating mechanism in an internal combustion engine, and particularly to a so-called direct-acting valve operating device in which intake and exhaust valves are directly driven by a cam.

[Conventional technology]

The intake and exhaust valves of internal combustion engines open and close frequently during engine operation, so manufacturing and assembly errors in these valves can cause uneven wear between them and the valve seat in the cylinder head. This may occur. If such uneven wear is left untreated, it will eventually become difficult to completely seal the inside of the cylinder. In addition, especially regarding the exhaust valve, this exhaust valve traps combustion products between the valve seat of the cylinder head, worsening the sealing of the exhaust valve, and causing high-temperature combustion gas in the cylinder to flow out from the poorly sealed part, which is the worst case scenario. In this case, the exhaust valve seal may melt. As a preventive measure against these problems, it has been generally known for some time that it is sufficient to rotate the intake and exhaust valves. As a method for rotating this valve, in pulp systems that use a rocker arm, there is a known method in which the valve is rotated around its axis in conjunction with the operation of the rocker arm that contacts the upper end of the valve shaft of the valve and opens it. (Tokuko 1987)
-44803, Japanese Patent Publication No. 5B-55323).

However, recently, in order to increase the engine speed and make it maintenance-free, the rocker arm has been abolished and the cam is used to directly suck the air.
An increasing number of engines are adopting direct-acting valve train systems that drive exhaust valves. In this direct-acting valve train, since the cam cannot directly drive the upper end of the valve shaft of the intake/exhaust valve, a lifter is provided between the cam and the upper end of the valve shaft. In order to prevent uneven wear of the shim provided on the contact surface of the valve, a method is adopted in which the center of action of the cam is offset from the center of the valve shaft to rotate the lifter.

[Problem that the invention seeks to solve]

In the above-mentioned lifter rotation method in a direct-acting valve actuating device, the spring that biases the intake and exhaust valves twists when expanding and contracting, and the intake and exhaust valves try to rotate, but both ends of the spring and the spring Since the IT friction force between the support parts is large, this friction force obstructs the rotation of the intake and exhaust valves around the valve shaft,
Therefore, there is a problem in that the rotation of the intake and exhaust valves cannot be obtained as expected, especially when the engine speed is low.

The present invention provides a direct-acting valve actuator that can rotate the valve stably even when the engine is at low speed, and that can prevent excessive wear by preventing the valve from rotating when the valve is seated. It is intended to provide a device made by the manufacturer.

[Means for solving problems]

In order to solve the above problems, the configuration of the present invention is such that the intake and exhaust valves, which are biased in the closing direction by a spring, are directly driven by a cam attached to a camshaft via a lifter provided at the upper end of the valve shaft. In a valve operating device for an internal combustion engine that opens and closes with The feature is that a thrust bearing is interposed between the support part and the support part.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. 1st
The figure shows a first embodiment of the invention.

In FIG. 1, a camshaft 2 to which a cam 1 is fixed is rotatably attached to a cam case of an internal combustion engine (not shown), and rotates in accordance with the rotation of the internal combustion engine. 3 is the intake and exhaust valve, and the valve guide 5 is press-fitted into the engine head.
It is engaged within the valve axis 15 so as to be able to slide freely in the direction of the valve axis 15 and to rotate freely around the valve axis 15. A concave portion 3c provided in the -L portion of the intake/exhaust valve 3 on the axial circumference is engaged with a clasp 4 which can be divided into two parts, and the retainer 6 is fixed by the clasp 4. The lower surface 6a of the retainer 6 is finished smoothly, and is in contact with a thrust bearing 12 as a T friction reduction mechanism. The thrust bearing 12 (a thrust needle hair ring is used in this embodiment) is guided by the cylindrical portion 6b of the retainer and is engaged approximately concentrically with the valve axis 15 of the intake and exhaust valve 3.

A spring 7 is provided between the thrust bearing 12 and the engine head, and the intake and exhaust valves 3 are connected to the thrust bearing 12. It is constantly biased upward in the figure via the retainer 6 and the lever 4. A lifter 11 is provided between the cam 1 and the intake/exhaust valve 3, and slides two rotations within a guide portion 3a provided concentrically with the valve axis 15 of the intake/exhaust valve 3 provided in the engine head 13. freely engaged. The lifter 11 is in contact with the intake/exhaust valve 3 at the shaft end 3b, and transmits the movement of the lifter 11 to the intake/exhaust valve 3. A shim 10 is provided on the upper surface of the lifter 11 between it and the cam 1, and the inside of the base of the cam 1 is different from the inside of the base of the cam 1 when the cam 1 does not drive the lifter 11, that is, when the inside of the base of the cam 1 and the lifter 11 are engaged. The shim 10 plays a role in adjusting the clearance when the shim 10 is engaged with the lifter 11, that is, the generally called valve clearance. Reference numeral 14 denotes an intake/exhaust boat, which includes a valve seat 8 press-fitted into the boat wall 9 and a seat portion 3a of the intake/exhaust valve 3.
The connection between the combustion chamber and the combustion chamber is opened and closed. - An important aspect of the Rikishiki structure is the intake and exhaust valves 3. The center of action of the cam 1 is offset by δ with respect to the lifter 11. Therefore, as the cam 1 rotates, rotational torque from the cam 1 acts on the lifter 11. On the other hand, the rotational torque acts on the intake and exhaust valve 3 via the shaft end 3b. In this embodiment, the direction of the bias δ is defined as the direction of the rotational torque generated by the rotation of the cam 1.
The spring 7 is twisted in the same direction as the spring 7 when it is compressed, that is, the direction in which the spring 7 is unwound.
It is biased in a direction that helps the torsion.

5 and 6 show the thrust needle bearing 12 used in this embodiment. The thrust 1-needle bearing is the same as one commonly used, and has cylindrical rollers 12 and 13 installed on the same plane in cages 12b and 12C.

The operation in the above configuration will be explained. When camshaft 2 and cam 1 rotate in synchronization with the rotation of the internal combustion engine, shim 1
0. The intake and exhaust valves 3 are driven downward in the figure by compressing the spring 7 via the lifter 11, but the center of action of the cam 1 is located at the shim 10. Lifter 11 and the valve shaft of the intake and exhaust valves'! tp'A
Since the camshaft 15 is offset by δ in the axial direction of the camshaft 2, the frictional force between the cam 1 and the shim 10 causes the rotational force around the valve axis 15 to be shifted from the cam 1 to the shim 1.
Acts on 0.

The rotational force of the shim 10 is transmitted to the lifter 11 and then to the intake/exhaust valve 3 through the shaft end surface 3b of the intake/exhaust valve 3. On the other hand, when the intake and exhaust valves 3 are moved downward in the figure by the cam 1 via the lifter 11, the spring 7 is compressed.
The spring 7 is twisted in the direction in which the spring is unwound. On the other hand, since the rotational force acting on the intake and exhaust valves 3 from the cam 1 is the same as the direction in which the spring 7 is twisted (unwound) when compressed, the cam 1 begins to push the lifter II, that is, the intake and exhaust valves 3 are 1, the intake/exhaust valve 3 is driven downward in the figure by the cam 10 around the valve axis 15.
Start rotating in the direction of action.

After the cam 1 rotates further and the intake and exhaust valves 3 reach the maximum refractive index l-1°, the intake and exhaust valves 3 begin to close, that is, the springs 7 begin to expand, and the springs 7 move in the opposite direction to when they are compressed (direction that helps in winding). Although the twisting is tightened, the rotational force acting on the intake and exhaust valves 3 from the cam 1 remains the same, so that the retainer 6 fixed to the intake and exhaust valves 3 and the spring 7 become disengaged. However, in this embodiment, a thrust hair ring 12 is provided between the retainer 6 and the spring 7, and the F715 force between the retainer 6 and the spring 7 is very small. The rotation of the intake and exhaust valves 3 will continue to rotate about the valve axis 15 in the same direction because the resistance encountered by the rotation is small. In this way, the intake and exhaust valves 3 rotate sequentially, and the contact position between the valve seats 1-8 and the seat 1 part 3a of the intake and exhaust valve 3 changes, and the deviation between the valve seat 8 and the seat 1 part 3a changes. Abrasion 1 Local overheating and foreign matter getting caught can be prevented, and durability, reliability, and head protection can be improved.

Furthermore, when the engine rotates at high speeds, a strong torsional movement occurs due to the surging of the spring 7, but in this embodiment, since the thrust bearing 12 is interposed between the intake and exhaust valves 3 and the spring 7, this tearing movement of the spring 7 is prevented. is not transmitted to the intake/exhaust valve 3, and therefore the intake/exhaust valve 3 is prevented from rotating when seated, so the durability of the intake/exhaust valve 3 and the valve seat 8 is greatly improved. Further, since the rotational resistance between the intake and exhaust valves 3 and the spring 7 is reduced by the intervention of the thrust bearing 12, the intake and exhaust valves 3 can be rotated smoothly even when the engine rotates at low speed.

In this embodiment, the direction of the deviation δ between the valve axis 15 and the center of action of the cam 1 is determined by the direction of the rotational force acting from the cam 1 on the intake and exhaust valves 3, and the direction of the rotational force acting on the intake and exhaust valves 3 when the spring 7 is compressed. The direction in which the spring 7 twists in the direction in which it unravels, that is, the direction in which the spring 7 twists during compression, is the same, but if the direction in which the center of action of the cam 1 is deflected from the valve axis 15 is reversed from that in the above embodiment, When the intake and exhaust valve 3 is lifted, the spring 7
Since the direction of the force that rotates the intake and exhaust valves 3 by the cam 1 and the direction of the force that rotates the intake and exhaust valves 3 by the cam 1 are opposite, the intake and exhaust valves 3 are difficult to rotate around the valve axis 15. Compared to this, the starting engine speed and rotational characteristics are inferior, but since the thrust bearing 12 is provided, the rotational resistance is low, and it goes without saying that the characteristics are greatly improved compared to the case where the thrust bearing 12 is not provided. .

FIG. 2 shows a second embodiment of the invention. In the first embodiment, the thrust bearing 12 is provided between the retainer 6 and the upper end of the spring 7, but in the second embodiment, the thrust bearing 112 is provided between the lower end of the spring 107 and the engine head. It is provided between spring seats 1090. Since the engine head is usually made of aluminum, in this example, the thrust bearing 11
A thrust bearing ring 116 is provided between the spring seat 109 and the spring seat 109. A similar washer 117 is also provided between the spring 107 and the thrust bearing 112. The other configurations are the same as in the first embodiment. The operation is similar to that of the first embodiment, and the thrust bearing 11 provided between the spring 107 and the spring seat 109
2, rotational resistance can be reduced and the intake and exhaust valves 103 can be rotated smoothly. In the embodiment of Paintbrush 2, since the thrust bearing 112 is provided on the lower surface of the spring 107, the impact of the valve train driven by the cam 101 is reduced, and the follow-up of the valve train when the internal combustion engine rotates at speeds j and 7i is reduced. You will get the benefit of improved sexual performance.

FIG. 3 shows a third embodiment of the invention. In the first embodiment, the upper surface 1, Oa of the shim 10 that contacts the cam 1 is a flat surface, but in the third embodiment, the upper surface 210a of the shim 210 that contacts the cam 201 has four parts at the center. 210b
Because of the bias δ of the cam 201, the cam 201
The rotational force generated by the rotation of the lifter 211 is increased.
, which allows the intake and exhaust valves 203 to rotate more efficiently.

Other configurations and operations are similar to those of the first embodiment.

FIG. 4 shows a fourth embodiment of the invention. In the first embodiment, the cam 1 is connected to the cam shirt 1-2 by I+' (which has the same shape and dimension in any cross section, that is, the cam 1 is a flat surface, and the upper surface 10a of the shim 10 that contacts the cam 1 is flat. Although the cam 1 and the upper surface 10a of the shim 10 were configured to make line and surface contact, in the fourth embodiment, the cam 301 was set at an angle of θ. At the same time, the upper surface 310a of the shim 310 that contacts the cam 301 is configured to be a spherical convex surface.
The point a comes into contact with the valve axis 315 of the intake/exhaust valve 303 at a point offset by δ in the axial direction of the camshaft 302 . Since the contact point between the cam 301 and the upper surface 310a of the shim 310 is a point contact, the rotational force acting on the shim 310 from the cam 301 is very strong, and the lifter 311
The rotational force acting on the intake and exhaust valves 303 is also strong, and rotational resistance is reduced by the thrust bearing 312 provided between the retainer 306 and the spring 307, so the intake and exhaust valves 303 can rotate more easily. be. The other operations of the configuration 1 are the same as those of the first embodiment. Note that in this embodiment as well, the thrust bearing 3
12 may be provided between the lower end of the spring 307 and the spring seat on the engine head side.

〔Effect of the invention〕

As described above, according to the present invention, the rotation around the valve shaft of the intake/exhaust valve given by the biased cam in a direct-acting valve actuating device is caused by the expansion and contraction of the biasing spring attached to the intake/exhaust valve. It is less affected by twisting and can rotate smoothly even when the engine is rotating at low speeds.
Uneven wear between the valve seat and the valve seat can be prevented, local overheating and foreign matter can be prevented from getting caught, and the durability and reliability of the intake and exhaust valves can be improved. In addition, the influence of the strong torsional movement of the spring when the engine rotates at high speed is reduced, thereby preventing rotation of the intake and exhaust valves when they are seated, improving the durability of the intake and exhaust valves and valve seats.

[Brief explanation of drawings]

Fig. 1 is a vertical sectional view of the first embodiment of the present invention, Fig. 2 is a longitudinal sectional view of the second embodiment of the invention, Fig. 3 is a longitudinal sectional view of the third embodiment of the invention, and Fig. 4 is the longitudinal sectional view of the third embodiment of the invention. FIG. 5 is a plan view of the thrust bearing in the fourth embodiment; FIG. 6 is a side view of the thrust bearing in the fourth embodiment. 1...Cam, 2...Camshaft, 3.
...Intake and exhaust valve, 6...Retainer, 7, 107.2
07.307...Spring, 13, 109.209
...Engine head, 10, 110.210.310
...Shim, LL 111.211.311...Lifter, 12, 112.212.312...Thrust bearing. 3...1ifJFj eight sho 11°
Rikku to Sufust 112... Thrust bearing 212... Thrust bearing 302... Cam/Naft 303-0. Intake and exhaust valve 307... Spring 310... /mu 311... Lifter

Claims (1)

[Claims] 1. A valve for an internal combustion engine in which an intake and exhaust valve biased in the closing direction by a spring is opened and closed by being driven directly by a cam attached to a camshaft via a lifter provided at the upper end of the valve shaft. In the actuating device, the cam is disposed so that a point of action of the cam on the lifter is offset from the valve axis of the intake and exhaust valve in the axial direction of the camshaft, and a thrust force is provided between the spring and the support portion of the spring. A valve operating device for an internal combustion engine, characterized in that a bearing is interposed. 2. The valve operating device according to claim 1, wherein the thrust bearing is provided between the upper end of the spring and the spring seat on the intake/exhaust valve side. 3. The valve operating device according to claim 1, wherein the thrust bearing is provided between the lower end of the spring and a spring seat provided on the engine head. 4. The valve operating device according to claim 1, wherein a thrust needle bearing is used as the thrust bearing. 5. A patent in which the direction of deviation of the point of action of the cam from the valve axis of the intake and exhaust valve is such that the direction of the rotational force generated in the lifter by the rotation of the cam is the same direction as the direction of twisting of the spring when it is compressed. A valve operating device according to claim 1. 6. A hole or a recess is provided in the center of the upper surface of the shim placed on the lifter that comes into contact with the cam, so that the center of the shim does not come into contact with the contact surface of the cam. The valve actuation device according to item 1. 7. The valve operating device according to claim 1, wherein the cam is a tapered cam, and the upper surface of the shim mounted on the lifter, which comes into contact with the contact surface of the cam, is a spherical convex surface.