JPS6129925Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a variable valve timing mechanism.
More specifically, the present invention provides, for example, two intake cams per cylinder, and at low speeds, a low speed intake cam,
The present invention also relates to a variable valve timing mechanism that improves fuel efficiency and output by switching to a high-speed intake cam at high speeds.

In conventionally known variable valve timing mechanisms, the rocker arm switching mechanism is housed in a hollow rocker shaft, and a hydraulic cylinder is attached to the rear end of the rocker shaft, resulting in a long overall length.

Furthermore, a variable valve timing mechanism has been proposed in which each cylinder is provided with two intake cams and the valve timing is changed by moving the two intake cams relative to a rocker arm that drives the intake valve. However, in this cam-moving variable valve timing mechanism, it is structurally impossible to accommodate the switching mechanism within the camshaft, and it is also impossible to attach a hydraulic cylinder to the rear end of the camshaft.

Therefore, it is an object of the present invention to provide a variable valve timing mechanism that does not increase the overall length of the engine and is easy to mount on a vehicle. More specifically, the cam switching device is not housed within the camshaft, and the cam movement shaft is arranged parallel to the camshaft within the cam case. The hydraulic cylinder is not disposed at the rear end of the cam movement shaft, but a hydraulic cylinder for operating the cam movement shaft is installed parallel to the cam movement shaft and either integrally with the cam case or separately.

Such a configuration provides a variable valve timing mechanism with a compact cylinder head and head cover without substantially increasing the overall length of the engine from that of conventional engines. In addition, in this invention, the hydraulic cylinder that moves the cam movement axis has a tandem structure, so it is possible to generate the desired force using a piston with a smaller diameter under constant hydraulic pressure, and the hydraulic cylinder is compact. It can be done.

Embodiments of the present invention will be described below with reference to the accompanying drawings.

In FIG. 1, a cylinder block 1 is provided with a cylinder bore 1a, into which a piston 3 is hermetically fitted for reciprocating movement. A cylinder head 5 having a combustion chamber wall 5a bored therein is mounted and fixed on the cylinder block 1, and a combustion chamber 7 is formed by a space surrounded by the upper surface of the piston 3, the cylinder bore 1a, and the combustion chamber wall 5a.

The combustion chamber 7 is connected to the intake port 1 via the intake valve 9.
0, a valve retainer 11 is fixed to the valve rod 9a of the intake valve 9, and the valve retainer 1
A valve spring 13 is installed between the intake valve 1 and the cylinder head 3 to bias the intake valve 9 upward. A swing arm 17 is provided between the hydraulic lifter 15 and the valve rod 9a, and the swing arm 17 collides with the intake cam 19 to press the valve rod 9a.

Similarly, the combustion chamber 7 communicates with an exhaust port (not shown) via an exhaust valve (not shown), and as shown in FIG. 27 is provided so that the swing arm 27 collides with the exhaust cam 29 and presses the valve rod 21a.

The camshaft 31 rotates in synchronization with the rotation of the engine crankshaft (not shown), and the exhaust cam 29 is fixed to the camshaft 31, while the intake cam 19 cannot rotate relative to the camshaft 31. However, it is supported via a linear slide bearing 33 so as to be movable in the axial direction. That is, the axial groove 3 is formed on the camshaft 31.
1a and insert the slide bearing 33 into the groove 31a.
A ball 33a is fitted therein, and the circumferential position of the ball 33a is held by a retainer 33b. More specifically, in a four-cylinder internal combustion engine, there are four
The sets of grooves are spaced evenly apart by 90 degrees. Therefore, four cams 19 manufactured in the same shape,
In other words, it is only necessary to change the orientation of the cams for cylinders No. 1 to No. 4 and install them, making manufacturing and assembly easy.

As shown in FIG. 2, the intake cam 19 includes a low-speed cam 19a and a high-speed cam 19b, and a circular flange 19d is formed on the side surface of the high-speed cam 19b.

A fork 43 engaged with a collar 19d is loosely fitted onto a cam moving shaft 41 installed parallel to the cam shaft 31, and connecting springs 49, 51 are installed between plates 45, 47 fixed to the cam moving shaft 41 and the fork 43. ing.
A long hole 53a in the axial direction is bored in the surface of the hollow cylinder 53 facing the camshaft 31, and the fork 43 passes through the long hole 53a as shown in FIG.
9d. Two circumferential grooves 53b and 53c are bored in the inner surface of the long hole 53a of the hollow cylinder 53, as shown in FIG. This groove 5
The spacing between 3b and 53c is for both high and low speed cams 19 as described above.
It is equal to the a, 19b interval. A small hole 43a (the fifth
Attach the spring 55 and the indenter 57 to the spring 5
5, the indenter 57 presses the two circumferential grooves 1.
9a and 19b are engaged alternately.
In FIGS. 3 and 4, reference numeral 59 is a U-shaped stopper that comes into contact with the fork 43 to restrict its movement and position it.

Referring again to FIG. 2, a cam moving hydraulic cylinder 61 is provided parallel to the cam moving shaft 41. Here, the hydraulic cylinder 61 has two cylinder chambers 63a, 6 which are spaced apart in the axial direction and are fixed to the cam case 67 or formed integrally with the cam case.
3b, two pistons 65 that are hermetically fitted into the two cylinder chambers 63a and 63b and are slidable in the axial direction;
a, 65b and a piston rod 67 that connects the two pistons. The intermediate portion of the piston rod 67 and the cam movement shaft 41 are connected by a tie rod 69.

The chambers A and B divided by the pistons 65a and 65b of the hydraulic cylinder 61 are connected to the ports 81a and 8 of the hydraulic switching valve device 81 through conduits 71 and 73, respectively.
It communicates with 1b. Here is the hydraulic switching valve device 81
The oil inlet 81c communicates with an oil pump (not shown), while the oil outlet 81d communicates with an oil pan (not shown). The spool 83 is rotated manually or automatically according to engine characteristics to switch the flow path. Therefore, the pressure oil supplied from the oil pump is introduced into one of the upper and lower chambers of the cylinder 61 by the hydraulic switching valve device 81, and the pistons 65a, 65b are introduced into one of the upper and lower chambers of the cylinder 61.
is pushed up or down, and the oil discharged from the opposite chamber is returned to the oil pan.

Thus, when the cam movement shaft 41 is moved, the movement energy generated by compressing the connecting spring 49 or 51 is accumulated. The common base circle of the low-speed intake cam 19a and the high-speed intake cam 19b is the swing arm 1.
When the indenter 57 is positioned at position 7, the indenter 57, which is spring-biased by the accumulated movement energy, moves into the groove 53b or 53c.
The cam 19 is moved along the camshaft 31 at high speed. When the fork 43 comes into contact with another stopper 59, the indenter 57 (FIG. 4) moves into the groove 53c or 53.
b and is positioned. Note that the cam 19a, 1
The lift part of 9b is the swing arm 17 (Fig. 1)
When the cam 19 is in contact with the cam 19, the movement of the cam 19 is hindered by the frictional force acting therebetween.

In this invention, the hydraulic cylinder for cam movement is
Rather than installing it on the extension of the end of the cam movement shaft,
Since it is installed parallel to the cam movement axis, the overall length of the engine will not be excessive. Furthermore, since the hydraulic cylinder has a tandem structure, its piston diameter can be reduced. These synergistic effects result in a compact variable valve timing mechanism that is easy to mount on engines.

[Brief explanation of the drawing]

FIG. 1 is a sectional front view of an embodiment of the present invention, FIG. 2 is a plan view thereof, and FIG. 3 is a cross-sectional view of FIG.
Figure 4 is a side view showing the part in Figure 2 in detail;
The figure is a partially enlarged view of FIG. 4. 19, 19a, 19b...cam, 31...cam shaft, 41...cam movement axis, 43...fork, 6
1... Hydraulic cylinder, 63a, 63b... Cylinder, 65a, 65b... Piston, 67... Piston rod, 69... Tie rod.

Claims (1)

[Scope of utility model registration request] In a variable valve timing mechanism, two drive cams per opening/closing valve are mounted on a camshaft so as to be movable in the axial direction, and the drive cams are moved in the axial direction by a fork attached to the cam movement shaft. Pistons are slidably and sealingly fitted into two hydraulic cylinder chambers, respectively, and the two pistons are connected by a piston rod, and the piston rod is positioned parallel to the cam movement axis, and the tie rod is connected to the middle part of the cam movement axis. A variable valve timing mechanism characterized by being connected to.