JPS6228284B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a variable valve mechanism, and more particularly to a variable valve mechanism in which the opening and closing conditions of on-off valves such as intake valves and exhaust valves of an internal combustion engine are made variable in accordance with engine operating characteristics.

Generally, in conventional engines, engine characteristics are influenced by cam characteristics. For example, if the cam shape is selected to produce high torque in the low rotation range, torque in the high rotation range will be sacrificed. Conversely, if the cam shape is selected to obtain high torque in the high rotation range, the torque in the low rotation range will decrease. Therefore, it is impossible to always obtain high torque over the entire rotation range of the engine.

In view of the above, an object of the present invention is to provide a variable valve mechanism with a simple structure in which the opening and closing conditions of an on-off valve can be easily varied. That is, in the present invention, a rocker arm for opening and closing an on-off valve of an engine is pivotally mounted around a rocker shaft so as to be movable along the rocker shaft, and is attached to the crankshaft of the engine in parallel to the rocker shaft. A camshaft that rotates in time is provided, and a cam having a width that does not come off when the rocker arm moves is fixed to the camshaft, and one end of the rocker arm is brought into contact with the rocker arm, so that the rocker is inserted between the valve stem and the fulcrum of the opening/closing valve. This is a variable valve mechanism in which a lifter extending in the axial direction is installed, the other end of the rocker arm is brought into contact with the lifter, and the opening/closing valve is opened and closed with a predetermined valve lift depending on the rocker arm position.

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a plan view of a valve operating system for a one-cylinder open/close valve (intake valve or exhaust valve) of an internal combustion engine that employs a variable valve mechanism according to the present invention. The on-off valve main body has a structure similar to that of a conventional on-off valve, and a detailed explanation thereof will be omitted, and only the retainer 1 is shown in FIG. 1. As shown in FIG. 2, the retainer 1 is fixed to a valve rod 3 of an on-off valve, and is biased upward by a compression spring 5 installed between it and a cylinder head (not shown). A lifter 11 is stretched between a valve stem 7 formed at the top of the valve rod 3 and a fulcrum 9. As shown in FIG. 3, guide edges 11a are formed on both sides of the valve stem 7 abutting portion of the lifter 11 to prevent the lifter 11 from coming off the valve stem 7. In addition, as shown by the chain line in FIG.
The lifter 11 may be prevented from coming off from the fulcrum 9 by pressing with the support 9. As shown in FIG. 7, the end of the lifter 11 is pivoted to the bracket 14 by a pin 12 so that it can rotate about the pin 12 as a fulcrum, thereby preventing the lifter 11 from shifting laterally and coming off the fulcrum. Part 11a and lifter presser bar 15
may be omitted.

A rocker shaft 17 is provided substantially parallel to the lifter 11, and a rocker arm 19 is attached to the rocker shaft 17 so as to be swingable around it and movable in its axial direction. The rocker shaft 17 is hollow and has a long hole 17a extending in the axial direction. As shown in FIG. 4, a bolt 21 screwed onto the rocker arm 19 is made to protrude from the elongated hole 17a, penetrate into the hollow rocker shaft 17, and engage with the protrusion 23a of the rocker arm moving shaft 23. Thus, the end of the rocker arm moving shaft 23 is connected to the piston rod 25a of the hydraulic cylinder 25,
The hydraulic cylinder 25 communicates with a hydraulic pump 27 and has on-off switching valves 29a, 29b, 29c.
By operating the switching valves 29a, 29b, 29c, the piston and piston rod 25a can be placed in appropriate positions, and the rocker arm 19 can be placed in a predetermined position. 33 is an atmospheric communication hole. The return movement of the rocker arm 19 is performed by a return compression spring 35 attached to the rocker shaft 17.

A knocker 37 is screwed onto one end of the rocker arm 19 with a lock nut 39 so that its length can be adjusted, and the tip of the knocker 37 is brought into contact with the lifter 11 (see FIGS. 2 and 3). Also, Rotsuker Arm 19
As shown in FIG. 1, the other end is in contact with a cam 43 fixed to a camshaft 41 that is parallel to the rocker shaft 17 and rotates in time with the engine crankshaft (not shown). The width of the cam 43 is set so that the rocker arm 19 does not come off the cam when the rocker arm 19 moves. Further, the cam 43 may have the same shape in the width direction, or may be a three-dimensional cam that changes in the width direction.

In the above embodiment, the hydraulic cylinder 25, the rocker arm moving shaft 23, and the return spring 35
The lock 37 of the rocker arm 19 is changed by changing the position of the rocker arm 19 by the action of
moves on the lifter 11, thereby changing the valve lift of the on-off valve. Therefore, the opening and closing conditions of the on-off valve are optimized according to the engine operating conditions, for example, at low speeds and low loads, a low valve lift is used to increase the intake air flow rate, or the opening and closing timing of the on-off valve is narrowed to achieve valve timing with less overlap. This ensures stable combustion, and also increases the valve lift at high speeds and high loads, widens the opening/closing timing of the on-off valve, and uses valve timing with a certain amount of overlap to ensure sufficient intake air to achieve the desired result. Can be done with high output.

Another rocker arm moving mechanism will be described with reference to FIGS. 5 and 6. In FIG. 5, the rocker arm moving shaft 23 is provided outside the rocker shaft 17 rather than in the hollow part thereof, and the protrusion 19a of the rocker arm 19 is pressed and moved by the protrusion 23a. In addition, in FIG. 6, the rocker shaft 17 is made movable in the axial direction, and the snap spring 2 is fixed to the rocker shaft 17.
The rocker arm movement axis is omitted so that the rocker arm 19 is pressed by the rocker arm 19.

[Brief explanation of the drawing]

FIG. 1 is a plan view of an embodiment of the present invention, FIG. 2 is a view in the direction of the - arrow in FIG. 1, FIG. 3 is a view in the direction of the - arrow in FIG. 1, and FIG. 4 is a view in the direction of the - arrow in FIG. 5 and 6 are cross-sectional views of other embodiments of the invention, and FIG. 7 is a perspective view of another embodiment of the invention. 7... Valve stem, 9... Fulcrum, 11... Lifter, 11a... Guide edge, 19... Rocker arm, 37... Locker, 17... Rocker shaft, 41... Cam shaft, 43... Cam.

Claims (1)

[Scope of Claims] 1. A rocker arm for opening and closing an on-off valve of the engine is pivotably mounted around a rocker shaft and movable along the rocker shaft, and the engine crank is moved in parallel to the rocker shaft. A camshaft that rotates in synchronization with the shaft is provided, and a cam having a width that does not come off when the rocker arm moves is fixed to the camshaft, and one end of the rocker arm is brought into contact with the shaft, and a cam shaft is provided between the valve stem and the fulcrum of the opening/closing valve. A lifter extending in the axial direction of the rocker is installed in the rocker, and the other end of the rocker arm is brought into contact with the lifter, so that the opening/closing valve is opened and closed with a predetermined valve lift depending on the rocker arm position. Valve mechanism. 2. The variable valve mechanism according to claim 1, wherein the cam is a three-dimensional cam that changes in the cam axis direction and around the cam axis. 3. The variable valve mechanism according to claim 1, wherein the lifter is provided with guide edges located on both sides of the valve stem to prevent the lifter from separating from the valve stem. 4. The variable valve mechanism according to claim 1, wherein the rocker arm is moved by a rocker arm moving shaft provided parallel to the rocker shaft and a rocker arm return spring. 5. The variable valve mechanism according to claim 4, wherein the rocker shaft is hollow and the rocker arm movement shaft is provided inside the rocker shaft. 6. The variable valve mechanism according to claim 1, wherein the rocker shaft is movable in the axial direction and the rocker arm is moved by a return spring.