JPS6221684Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a variable valve timing engine.
More specifically, the present invention relates to a variable valve timing engine in which the opening/closing conditions of intake valves, exhaust valves, etc. of the engine are made variable in accordance with the operating characteristics of the engine.

In such a variable valve timing engine, a rocker arm is swingably supported on a rocker shaft, and a plurality of cams with different cam profiles are parked adjacent to each other on a camshaft that is parallel to the rocker shaft and rotates in time with the crankshaft. There is a variable valve timing engine in which the rocker arm is connected to a rocker arm movement shaft by a connecting spring. In such a variable valve timing engine, the rocker arm must be moved in a short period of time in the common base circle of adjacent cams to prevent wear and damage to the cams and rocker arms. For this purpose, attempts have been made to provide a mechanism that does not allow the rocker arm to move until a predetermined amount of energy is stored in the connection spring, but allows the rocker arm to move when a predetermined amount of movement energy is stored in the connection spring.

In an attempt to do this, circumferential grooves were formed on the rocker shaft at intervals corresponding to the cam spacing, and a small ball mounted in a small hole formed in the rocker arm was biased against the circumferential groove by a spring. There is.

However, this product has many parts and is difficult to assemble to the Rotsuker arm. Furthermore, since small steel balls are used, the small balls and the circumferential groove come into point contact, and a large load is applied locally to the corners of the grooves that are the contact points, causing the corners to wear or deform. As a countermeasure to this problem, using high-grade materials or performing special hardening to increase the hardness of the groove surface will increase the product cost. Furthermore, since the structure is subject to large local loads, operation tends to become unstable. In addition, since the small steel ball is pressed and biased from one direction, the rocker shaft is biased in one direction, which tends to cause uneven wear.

The object of the present invention is to provide a mechanism that is easy to assemble, is not subjected to large local loads, and does not suffer from the above-mentioned problems. In the present invention, an annular groove extending in the circumferential direction is bored in the engagement surface of the rocker arm and the rocker shaft, and a ring spring with a part of an arc cut out is attached to the annular groove, so that a predetermined movement energy is accumulated in the connecting spring. Then, the ring spring is retracted from the annular groove of the rocker shaft to allow movement of the rocker arm along the rocker shaft.

This will be explained below with reference to the drawings. In FIG. 1, a cylinder head 3 has a combustion chamber wall 3a formed in a cylinder block 1 having a cylinder bore 1a.
Place and fix the piston 5 in the cylinder bore 1a.
The combustion chamber 7 is formed by slidingly and sealingly fitting the two. An intake manifold 9 and an exhaust manifold (not shown) formed in the cylinder head 3 are respectively connected to an intake valve 11 that controls the intake of the air-fuel mixture into the combustion chamber and an exhaust valve (not shown) that controls the discharge of exhaust gas from the combustion chamber 7. (not shown) to the combustion chamber 7.

Since the structures of the intake valve 11 and the exhaust valve are similar, the intake valve 11 will be explained below. Intake valve 1
1 includes a valve body 11a and a valve rod 11b cooperating with a valve seat 9a. The valve rod 11b is slidably and sealingly fitted into the cylinder head 3, and a retainer 13 is fixedly attached to the rear end projecting from the cylinder head 3. A compression spring 15 is installed between the retainer 13 and the cylinder head 3 to bias the intake valve 11 upward. A cylindrical valve lifter 17 is attached to the head of the valve rod 11b, and the valve lifter 17
By pressing the upper surface of the intake valve 11 downward,
It is possible to open the valve.

A rocker arm 19 is swingably supported around a rocker shaft 21. A lock 25 whose length can be adjusted with a lock nut 22 is screwed onto the tip 19a of the locker arm 19.
The pad 19b at the other end is in contact with a cam 27, and when the cam 27 rotates in the direction of arrow a, the knocker 25 presses the valve lifter 17 downward to open the intake valve 11.

As shown in FIG. 2, the cam 27 is connected to the rocker shaft 2.
Two cams 27 with different cam profiles are provided adjacent to a cam shaft 29 installed parallel to the cam 1.
Contains a and 27b. Here, for example, the cam 27a has a cam profile for low engine speeds, and the cam 27b has a cam profile for high engine speeds, and the base circular portions of both cams 27a and 27b substantially match. The camshaft 29 rotates in the direction of arrow a (FIG. 1) in synchronization with the engine crankshaft (not shown).

The rocker shaft 21 is a hollow cylinder, and the rocker arm 19 is fitted to the outside of the hollow cylinder so as to be swingable and axially movable. Further, a rocker arm moving shaft 23 extending along the rocker shaft 21 is loosely fitted into the hollow portion of the rocker shaft 21. The end 23a of the Rocker arm moving shaft 23 is connected to the hydraulic cylinder 24.
The rocker shaft 21 is connected to a drive source such as (Fig. 2).
It is possible to move along the In FIG. 2, there are two annular plates 31 on the rocker arm movement shaft 23,
33 are fixed at intervals in the axial direction, and both plates 31,
Two annular movable plates 35 and 37 are loosely fitted to the rocker arm moving shaft 23 with a small interval between them. Compression connection springs 39 and 41 are installed between plates 31 and 35 and between plates 33 and 37.

A long hole 21a in the axial direction is bored in the rocker shaft 21 as shown in FIG.
It penetrates between 5 and 37. Thereby, the rocker arm 19 can be moved in the axial direction together with the plates 35 and 37.

Two circumferential annular grooves 21b, 21 are provided on the outer periphery of the rocker shaft 21 at positions corresponding to the cams 27a, 27b.
I'm wearing c. Further, a circumferential annular groove 19c is bored in the inner surface of the rocker arm 19. A ring spring 45 is attached to the annular groove 21b or 21c of the rocker shaft 21 and the annular groove 19c of the rocker arm 19. As shown in FIG. 4, the ring spring 45 has a C-shape with a part of the arc cut out.
The upper and lower parts 45a and 45b of the letter have a semicircular or trapezoidal cross section as shown in FIG. As shown in the figure, it is preferable to have a rectangular cross section and to have an appropriate spring action. The annular groove 21 of the rocker shaft 21 described above
b, 21c preferably have a cross-sectional shape corresponding to the cross-section of the upper and lower portions 45a, 45b of the ring spring shown in FIG.

A stopper 55 is provided between adjacent cams 27a and 27b (FIG. 2). That is, as shown in FIG. 1, one end of the stopper 55 is planted on the cam shaft 29 at an intermediate position between the base circles of the cams 27a, 27b, and the other end of the stopper 55 is attached to the cam 27a, 27b.
The cams 27a, 2
It is designed to slightly protrude from the base circle of 7b. The material of the stopper 55 is spring steel, and it has rigidity against the force applied to its side surface, but can be easily bent by the force applied to its surface.

When the Rocker arm moving shaft 23 is moved to the left from the state shown in FIG.
1 is pressed by the plate 33 and pushes the plate 37 to the left. However, the upper and lower parts 4 of the ring-shaped spring 45
5a and 45b are fitted into the groove 21b of the rocker shaft 21, the plate 37 does not move. As a result, the compression connection spring 41 is compressed and movement energy is stored. When the movement energy exceeds a predetermined amount, the ring-shaped spring 45 expands due to the pressing force of the connecting spring 41, and its upper and lower portions 45a, 45b are removed from the groove 21b.

If the rocker arm 19 starts to move while the pad 19b at the end of the rocker arm is in contact with the part of the base circle of the cams 27a, 27b without the stopper 55, the rocker arm 19 will move due to the movement energy accumulated in the connection spring 41. Cam 27a
It is reliably moved from the cam 27b to the cam 27b in a short time. Even if the pad 19b of the rocker arm 19 rides on the stopper 55 during movement, the stopper is bent by the pressing force and the stopper 55 sinks below the base circle, so the movement of the rocker arm is not impaired in any way.

On the other hand, when the pad 19b at the tip of the rocker arm is in contact with the lift part of the cams 27a, 27b other than the base circle part, when the cams 27a, 27b push the intake valve 11 open, the pressing force of the compression connection springs 39, 41 is applied. By setting the friction force to be smaller than the friction force between the cams 27a, 27b and the pad 19b of the rocker arm 19, the rocker arm 19 can be prevented from moving.

Also, the pad 19b at the tip of the rocker arm 19
When the rocker arm 19 is in contact with the latter half of the base circle of the cams 27a, 27b, that is, the portion where the stopper 55 protrudes from the base circle, movement of the rocker arm 19 is prevented by the protrusion of the stopper 55. This prevents the rocker arm 19 from moving and vibrating in the non-base circle portion of the cam, that is, the lift portion, and prevents the cams 27a, 27b or the rocker arm 19 from being worn out or damaged. In this case, the rocker arm 19 is moved when the cams 27a, 27b next reach the base circle portion.

In this invention, a C-shaped ring spring with a part of the arc cut out is attached to an annular groove bored on the outer peripheral surface of the Rocker shaft and the inner peripheral surface of the Rocker arm, so that a predetermined amount of movement energy is stored in the connecting spring. , simple structure and easy assembly. Also, compared to the conventional case where a small ball is pressed into an annular groove, a line or surface contact is obtained instead of a point contact.
This prevents the corners of the annular groove from being worn or deformed, and its operation becomes extremely stable. In addition C
Since the letter-shaped ring spring is biased against the rocker shaft from both opposing directions, there is no problem of the rocker shaft being worn out on one side. Therefore, according to the present invention, a variable valve timing engine can be obtained in which the cam and rocker arm are free from wear and damage.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional front view of one embodiment of the present invention;
The figure is a sectional view of FIG. 1, FIG. 3 is a sectional view of FIG. 1, FIG. 4 is a sectional front view of the ring spring in FIG. 1, and FIGS. FIG. 19...Rotzker arm, 19c...annular groove,
21... Rocker shaft, 21b, 21c... Annular groove, 23... Rocker arm movement axis, 27, 27
a, 27b...Cam, 39, 41...Connection spring,
45...Ring spring, 55...Stopper.

Claims (1)

[Scope of utility model registration request] A rocker arm is swingably and axially movably supported on a rocker shaft, and a plurality of cams with different cam profiles are fixed adjacent to each other on a cam shaft that is parallel to the rocker shaft and rotates in time with the crankshaft, A rocker arm movement shaft that is reciprocated according to the operating state of the internal combustion engine is provided along the rocker shaft,
The rocker arm is connected to the rocker arm moving shaft by a connecting spring, and an annular groove extending in the circumferential direction is bored in the engagement surface of the rocker arm and the rocker shaft corresponding to the plurality of cams, and a circular groove is formed in one of the annular grooves. When a ring spring with a cut-out section is attached and a predetermined movement energy is accumulated in the connecting spring, the ring spring moves from one annular groove of the rocker shaft to another annular groove, and thus moves along the rocker shaft of the rocker arm. A variable valve timing engine characterized by allowing movement.