JPS6133202Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an intake/exhaust valve drive device for an internal combustion engine that variably controls the opening/closing timing and valve lift amount of intake/exhaust valves according to operating conditions.

Various intake and exhaust valve drive devices have been proposed in the past, which variably control the opening/closing timing of the intake and exhaust valves and the amount of valve lift according to the engine operating conditions so that valve overlap, fresh air filling efficiency, etc. are always optimally achieved. One example is the U.S. Patent No. 1 shown in Figure 1.
No. 3413965 is known.

This valve drive device has a rocker arm 3 whose one end abuts the valve drive cam 1 and whose other end is fitted and supported by the stem end of the intake/exhaust valve 2. The back surface 4 of the rocker arm 3 is curved, and the back surface 4 is connected to the lever 5. By swinging the left and right sides of the rocker arm 3 while contacting the fulcrum,
The lift of the cam 1 is transmitted to the intake and exhaust valves 2, and in particular, the lever 5 is pivotably supported at one end thereof, and its inclination is regulated by a control cam 6. ing. The control cam 6 is rotationally driven in an appropriate phase according to engine operating conditions by a drive mechanism such as a hydraulic actuator, thereby variably controlling the opening/closing timing and lift amount of the intake/exhaust valve 2. That is, for example, if the lever 5 is pushed down by a large amount by the control cam 6, the free end of the lever 5 and the rocker arm 3 are close to each other in the base circle state of the valve drive cam 1, and therefore the intake and exhaust valves 2 are pushed down by a large amount. As the valve opening timing becomes earlier, the valve lift amount increases, and if the amount of depression by the control cam 6 is small, the free end of the lever 5 and the rocker arm 3 will move even if the valve drive cam 1 is in the same base circle state.
Therefore, the opening timing of the intake and exhaust valves is delayed and the amount of valve lift becomes small.

However, in this conventional valve drive device, since the rocker arm 3 receives a thrust force from the drive cam 1 in the longitudinal direction, a strong bending moment acts on the valve stem 2a of the intake and exhaust valve 2. For this reason, it is necessary to increase the diameter of the valve stem 2a or install a valve tappet 2b as shown in Fig. 2, but this results in an increase in the inertial mass of the moving parts, which is disadvantageous in high-speed operation, etc. When a valve tappet is provided, side thrust acts on the tappet cylinder wall 2c, increasing friction loss. Furthermore, since the relative sliding speed at the contact surface between the lever 5 and the rocker arm 3 is high, there are problems such as increased wear on the contact surface.

Furthermore, in this conventional configuration, the lever 5
Since the relative movement between the lever 5 and the locker arm 3 is complicated, it is difficult to provide a spring circle for returning the locker arm 3 between the lever 5 and the locker arm 3.
For example, when the rocker arm 3 is pushed down only slightly by the control cam 6, the followability of the rocker arm 3 with respect to the valve drive cam 1 deteriorates, and jumps or bounces of the rocker arm occur. These become a cause of noise vibration and abnormal wear. In addition, the rocker arm 3 is not regulated to be displaced in the axial direction of the camshaft, and there is a risk that it may come off the lever 5 during operation.

This invention aims to eliminate the above-mentioned conventional drawbacks, and one embodiment thereof will be described in detail below with reference to the drawings. In the following embodiments, the same parts as in the conventional example described above are denoted by the same reference numerals, and important explanations will be omitted.

In FIG. 3, 3 is a rocker arm for transmitting the lift of the valve drive cam 1 to the intake and exhaust valves 2 as described above, one end 3a is connected to the valve drive cam 1, and the other end 3b is connected to the valve stem 2a. Although each stem end 2a is in contact with the stem end 2a, a support shaft 11 is particularly fitted into the substantially central portion thereof. On the other hand, a rocker guide 13 is fixedly installed on the upper surface of the cylinder head 12 to support the rocker arm 3.
The rocker guide 13 has a guide groove 14 at its upper end that is substantially parallel to the axial direction of the valve stem 2a, and slidably holds both ends of the support shaft 11 from both sides of the rocker arm 3, as shown in FIG. are doing. Furthermore, the pin 1 at the lower end of the rocker guide 13
5 and both ends of the support shaft 11, a coil spring 16 is stretched, and the spring force urges the rocker arm 3 toward the valve drive cam 1 and the valve stem 2a. .

In addition, since the rocker arm 3 swings around the support shaft 11, the abutting portion 3b has an appropriate radius with respect to the stem end 2a of the valve stem 2a.
They are designed to come into contact in the form of sliding or rolling contact.

Next, its operation will be explained with reference to FIGS. 5 and 6.

First, if the amount of depression of the lever 5 by the control cam 6 is large depending on the engine operating conditions, the lever 5 is
and the back of ROTSUKA ARM 3 are close to each other. Therefore, when the valve driving cam 1 starts to lift from this state, the rocker arm 3 swings clockwise about the support shaft 11 while gradually moving the fulcrum of contact with the lever 5 to the left. As a result, the intake and exhaust valves 2 are opened and closed at substantially the same timing as the rise and fall of the valve drive cam 1, and as shown in FIG. 5, the maximum lift amount becomes large.

On the other hand, if the amount by which the lever 5 is pushed down by the control cam 6 is small depending on the engine operating conditions, the lever 5 may
There is a large distance between the front side and the back side of Rotsuka Arm 3.
Therefore, even if the lift amount of the valve drive cam 1 starts from this state, the intake and exhaust valves 2 will not open while the cam lift amount is small. Therefore, the valve opening timing is delayed for a certain period from the rise of the valve drive cam 1,
Similarly, the valve closing timing is earlier than the fall of the cam 1 by a certain period of time. Also, as shown in Figure 6,
The maximum lift amount is small (substantially 0 in the illustrated example).

In this way, the opening/closing timing and valve lift amount of the intake/exhaust valve 2 can be variably controlled as appropriate. Therefore, the thrust force generated along the longitudinal direction of the rocker arm 3 is supported by the above-mentioned engagement, and no bending force is applied to the valve stem 2a of the intake/exhaust valve 2. Further, since the rocker arm 3 swings about the support shaft 11, relative slippage between the back surface 4 of the rocker arm 3 and the support surface of the lever 5 is reduced. Furthermore,
The locker guide 13 prevents the locker arm 3 from falling off the lever 5, and the urging force of the coil spring 16 allows the locker arm 3 to reliably follow the valve drive cam 1.

The rocker guide 13 provided on the top surface of the cylinder head 12 may be cast integrally with the cylinder head 12, or may be a separate piece fixed with bolts, etc., but it is also possible to cast the rocker guide 13 integrally with the cylinder head 12, for example, from an aluminum alloy or the like. In this case, the wear resistance of the guide groove 14 portion is insufficient, so as shown in FIG. It is preferable to dispose a guide member 17 having the following structure.

As explained in detail above, according to this invention, a strong bending moment does not act on the valve stem of the intake and exhaust valve, and the bending deformation of the valve stem can be prevented without particularly strengthening the valve stem. This restricts the irregular movement of the rocker arm and improves its ability to follow the valve drive cam.
It has the following effects.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a conventional intake/exhaust valve drive device, Fig. 2 is a sectional view of a main part of a different conventional example, Fig. 3 is a sectional view of an intake/exhaust valve drive device according to this invention, and Fig. 4 is its sectional view. 5 is an explanatory diagram of the operation when the amount of depression by the control cam is increased, and FIG. 6 is an explanatory diagram of the operation when the amount of depression by the control cam is decreased, FIG. 7 is a sectional view showing a different embodiment of this invention. 1... Valve drive cam, 2... Intake and exhaust valve, 3...
...Rotsuka arm, 5...Lever, 6...Control cam, 11...Support shaft, 13...Rotsuka guide, 1
6...Coil spring, 17...Guide member.

Claims (1)

[Scope of utility model registration request] A valve drive cam rotates in synchronization with engine rotation, a rocker arm whose one end is linked to the valve drive cam and the other end is linked to the valve stem, and a support shaft is provided in the middle, and which is fixed to the cylinder head. a rocker guide which is arranged to slidably hold the support shaft; and a lever which is arranged substantially along the back surface of the rocker arm, makes fulcrum contact with the back surface, and is rotatably supported at one end on the valve stem side. and a control means for regulating the inclination of the lever.