JPH0133773Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial usage distribution] This invention is an internal combustion engine that variably controls the opening/closing timing of intake and exhaust valves and the amount of valve lift according to operating conditions.
In particular, it relates to an intake/exhaust valve drive device for an automobile internal combustion engine.

[Prior art]

Normally, in an internal combustion engine, the timing of opening and closing the intake and exhaust valves (valve timing) is fixed to achieve the best efficiency under certain operating conditions that are frequently used. Demonstrate efficiency. Therefore, in order to always obtain optimal valve overlap and fresh air charging efficiency, the opening/closing timing of the intake and exhaust valves (intake valve, exhaust valve, or both) and the amount of valve lift are adjusted according to the engine operating conditions. Various types of intake/exhaust valve driving devices that perform variable control have been proposed in the past. The main ones among these will be explained below.

That is, the other end of the rocker arm that contacts the valve drive cam is engaged with the valve stem end, and the back surface of the rocker arm is brought into fulcrum contact with a lever that can be changed depending on the operating conditions, and the rocker arm is swung to a predetermined value. A cam or a hydraulic mechanism is used to obtain the amount of lift, and when the inclination of the lever is varied to obtain the swing angle of the rocker arm, that is, the change in lift. U.S. patents are representative of these.
341396 and Japanese Patent Application Laid-open No. 188717/1983.

However, in the structure of U.S. Patent No. 341396, the rocker arm is fitted to the valve stem end, so when the cam is driven, the rocker arm receives thrust from the cam, which creates a strong bending moment on the valve stem. This causes problems such as wear and breakage of the valve stem.

On the other hand, the latter, disclosed in Japanese Patent Application Laid-open No. 57-188717, solves the problem of the former because the rocker arm is held by an intermediate support shaft. A locking guide with parallel surfaces supporting the support shaft is bolted to the lever, and this bolted structure poses a problem in that the positioning accuracy of the lever and rocker arm becomes difficult.

[Purpose of invention]

This invention is a further improvement on the latter, that is, the one disclosed in Japanese Patent Application Laid-open No. 57-188717, and instead of using the method of attaching the rocker guide for the intermediate support shaft of the rocker arm to the lever with bolts, it is possible to form a curved surface on the fulcrum contact surface. The object of this invention is to enable accurate positioning of the rocker arm relative to the lever.

〔composition〕

In order to achieve the above object, the present invention includes a valve drive cam that rotates in synchronization with engine rotation, one end of which contacts the drive cam, the other end of which is linked to a valve stem, and a support shaft provided at an intermediate portion. a locker arm, a lever disposed along the back surface of the locker arm and having a support surface with which the back surface comes into contact with a fulcrum and rotatably supported at one end on the valve stem side; an arm whose end is connected to a shaft on the valve stem side;
The gist of the invention is to include a control means for regulating the inclination of the lever.

[Effect]

While the support shaft of the rocker arm is held by the arm, the rocker arm makes contact with the lever on its back surface as a fulcrum and swings to transmit the movement of the drive cam to the valve stem and lift the valve. Change the opening/closing timing. At this time, in order to obtain a buffer during startup and a predetermined amount of lift, and to further reduce the contact surface pressure between the lever support surface and the rear surface of the rocker arm, the support surface of the lever is a curved surface of a predetermined shape, and the support surface and the rear surface are positioned. However, since the lever is formed separately from the arm, the supporting surface can be machined with high precision, and
Since both the lever and the arm are connected to the shaft on the valve stem side, the above positioning can be performed with high precision.

〔Example〕

First, the configuration will be explained with reference to FIGS. 1 and 2. 1 is a valve drive cam that rotates in synchronization with engine rotation, 2 is a rocker arm, 3 is an intake and exhaust valve, 4 is a support shaft, 5 is a lever, and 6 is a A pair of linked arms, 7, is a control cam.

The rocker arm 2 is provided with a support shaft 4 in the middle, and has a contact convex curved surface with a large radius of curvature and a small radius of curvature on the back surface 8, and is formed in a dogleg shape. and,
When one end 9 comes into contact with the drive cam 1, the other end 10 cooperates with the valve stem 11 to transmit the movement of the drive cam to the intake and exhaust valves. The intake and exhaust valves 3 are strongly pressed against the seat 13 of the cylinder head by a valve spring 12 to keep the combustion chamber airtight at zero lift.

The lever 5 has one end 15 rotatably supported by a shaft 14 fixed substantially on an extension of the valve stem 11, and a flat support surface 16a that is disposed close to the back surface 8 of the rocker arm and comes into contact with it as a fulcrum.
and a concavely curved support surface 16b connected thereto. The other end 17 is in contact with the eccentric cam surface of the control cam 7, and is a coil-shaped coil whose one end is fixed to the arm 6 and the other end to the lever 5 so that its inclination and therefore the contact position with the back surface of the rocker arm can be changed. It has a lever spring 18.

Reference numeral 19 denotes an adjusting screw that maintains the valve gap, ie, the gap between the valve stem 11 and the other end 10 of the rocker arm, at a predetermined amount to prevent the valve from opening due to expansion when the temperature rises. Although the above-mentioned gap is small and is not shown, when the rocker arm 2 is in contact with the base circle 20 of the drive cam, the lever spring 18 creates a gap between the rear surface 8 of the rocker arm and the support surfaces 16a and 16b of the lever. It is something that occurs in between.

Next, the support shaft 4 is provided at the middle portion of the rocker arm 2 so as to pass therethrough, and both ends of the support shaft 4 are rotatably connected to one end 21 of the pair of arms 6. The other end 22 of arm 6 is similarly connected to shaft 14 . This allows both arms 6 to swing about the axis 14, and guide the rocker arm 2 by means of their counter-tension and compression forces.

Next, the operation of the above embodiment will be explained.

(1) In the case of a large lift amount As shown in FIG. be.

When the drive cam 1 is in contact with its base circle 20 and one end 9 of the rocker arm, the valve lift is zero, as shown by the solid line. When the drive cam 1 rotates and its nose lifts one end 9 of the rocker arm, the valve lift becomes maximum, as shown by the dashed line. During this time, the locking arm has a large arc portion and a small arc portion on the back surface 8 of the lever support surfaces 16a, 16.
b using this as a fulcrum, and the fulcrum or contact point moves from point P to P', and as shown in Fig. 4, the buffer part A
and obtain the maximum lift part B. Therefore, smooth start-up of the lift and the required maximum valve lift can be achieved.

In the above, the rocker arm 2 has its support shaft 4
Since the lever 5 is supported by the shaft 14 at one end on the valve stem side, the locker arm 2 can swing while the small arc portion of the locker arm 2 is in contact with the concave curved surface of the lever 5. Even when the lift is controlled to a large extent, it is possible to reduce the surface pressure on the contact surface and prevent wear.

(2) When the lift amount is small In this case, as shown in Figure 3, the control cam 7
This is the case when the eccentric part of is directed upward. When the rocker arm is in contact with the base circle 20, the control cam 7 and one end 17 of the lever 5 approach each other, and the back surface 8 of the rocker arm 2 and the support surface 16b of the lever 5 are separated from each other, as shown by the solid line. are doing. Therefore, the drive cam 1 rotates and the above-mentioned spacing disappears in the middle of its nose. Then, when the drive cam 1 further rotates, the rocker arm 2
moves in contact with the support surface 16b of the lever 5 on its back surface 8 as a fulcrum, transmitting driving force to the valve stem. Therefore, as shown in FIG.
A small lift curve consisting of and a lift portion D can be obtained, and a valve opening/closing period can also be changed quickly.

In this embodiment, the arm 6 is used to hold the support shaft 4 of the rocker arm, and the rotation axis of this arm is shared with the shaft 14 for supporting rotation of the lever, so that the rocker arm 2 can be positioned with respect to the lever 5 with high precision. can. That is, the positioning of the rocker arm 2 and the lever 5 can be performed with high accuracy simply by increasing the accuracy of the distance between the holes at both ends of the arm 6 and the hole diameter.

Therefore, the lower surface of the lever 5, particularly the supporting surface 16b, and the upper surface of the rocker arm 2, that is, the convex curved surface R portion of the back surface 8, particularly the small radius portion, can come into contact without deviation.

Therefore, it is possible to very effectively prevent the occurrence of abrasion caused by the abutting surface pressure between the two being increased and the lubricating oil film on the abutting surface being liable to run out, which is a problem when the valve is lifted large.

Additionally, compared to the conventional method, it has the advantage of being easier to process, requiring fewer parts, and being lighter.

That is, since the lever 5 is separate from the arm 6,
The lower surface, that is, the support surface 16, can be processed with sufficient precision, and the difficult processing precision of conventional fork-shaped grooves, mounting holes, etc. is not required.

Next, FIGS. 5 and 6 show other embodiments. In this case, one end 15 of the lever 5 is supported by a lash adjuster 23 provided on the shaft 14. The latch adjuster 23 is connected to the oil passage 24 inside the shaft 14.
The oil chamber of the plunger 25 communicates with the oil chamber of the plunger 25, from which oil is supplied through a check valve 26 to push out the cylinder 27, thereby maintaining the valve gap at zero lash. Therefore, in this case, the lever spring 18 shown in FIG. 1 may be omitted.

Note that the other parts are the same as in FIG. 1, and the operation is also almost the same.

[Effect of idea]

As explained above, this invention is based on a rocker arm that transmits the movement of the drive cam to the valve stem by swinging the back surface of the drive cam in fulcrum contact with the lever support surface, which is supported around its rotation support shaft. Since the rocker arm is guided by the swinging movement of the link type arm, the lever does not need the aforementioned guide of the support shaft, and the machining of the support surface is extremely simple. The effect of being able to process complex, high-precision curved surfaces with no difficulty can be obtained. As a result, wear on the contact surface between the lever and rocker arm can be effectively prevented by reducing the surface pressure on the contact surface and preventing the lubricating oil film from running out.

[Brief explanation of the drawing]

Fig. 1 is a front view of an embodiment of this invention, Fig. 2 is a top view of Fig. 1, Fig. 3 is a front view of the same showing a small lift state, and Fig. 4 is a diagram showing the valve lift amount relative to the crank angle. 5 is a partial front view showing an example of the use of the lash adjuster, and FIG. 6 is a top view of FIG. 5. Explanation of symbols appearing in the drawings: 1; drive cam;
2; Rocker arm, 3; Intake and exhaust valve, 4; Support shaft,
5; lever, 6; arm, 7; control cam, 8; back surface, 11; valve stem, 14; shaft, 16; support surface (curved surface), 16a; flat support surface, 16b; concave curved support surface, 18 ;Lever spring, 19;
Adjustment screw, 20; base circle, 23; lash adjuster.

Claims (1)

[Scope of utility model registration request] A valve drive cam that rotates in synchronization with engine rotation, a rocker arm that has one end in contact with the drive cam and the other end that is linked to the valve stem and has a support shaft in the middle, and a rocker arm that is arranged along the back surface of the rocker arm. a lever that is arranged and has a support surface with which the back surface contacts the fulcrum and is rotatably supported at one end on the valve stem side; one end is connected to the support shaft and the other end is connected to the shaft on the valve stem side; An intake/exhaust valve drive device for an internal combustion engine, comprising: an arm with a fixed angle, and a control means for regulating the inclination of the lever.