JPS6132090Y2 - - 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 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, adjustment of valve clearance is not particularly considered, and the configuration is such that a certain valve clearance is given in advance, which causes problems such as increased noise and vibration. A cushioning curve is required on the profile of the back surface 4 of the rocker arm 3 as a countermeasure against shocks when standing up and sitting down, which has the drawback that the design and processing of the profile becomes complicated.

In view of these conventional drawbacks, this invention aims to solve the above-mentioned conventional drawbacks by providing a zero lash mechanism using an eccentric collar in the bearing portion of the lever where the back surface of the rocker arm makes fulcrum contact.

Hereinafter, one embodiment of this invention will be described in detail based on the drawings.

FIGS. 2 and 3 show an embodiment of this invention, and the basic structure of this embodiment is not particularly different from the conventional one shown in FIG. 1 except for the zero lash mechanism provided on the lever 5. The same parts are denoted by the same reference numerals, and redundant explanations will be omitted.

In the figure, reference numeral 11 indicates a lever shaft disposed approximately on an extension line of the valve stem 2a to support the lever 5, and reference numeral 12 indicates a cylindrical bearing portion formed at one end of the lever 5. A cylindrical eccentric collar 13 that can rotate smoothly is interposed between the lever shaft 11 and the lever shaft 11, and as the eccentric collar 13 rotates, the rotation center of the lever 5 changes.
O ₁ is configured to move up and down with respect to the center O ₂ of the lever shaft 11. A torsion coil spring 14 is wound around the outer periphery of the lever shaft 11, one end of which is fitted and locked in the groove of the eccentric collar 13, and the other end of which is fitted and locked in the groove of the lever shaft 11. The torsion coil spring 14 biases the eccentric collar 13 in the counterclockwise direction in FIG.

On the other hand, the lever shaft 11 is formed in a circular shape, and the inside thereof serves as a lubricating oil passage 15, and oil holes 16, 17 are formed on the outer circumferential surface of the lever shaft 11 and the outer circumferential surface of the eccentric collar 13, respectively.
Oil grooves 18 and 19 are cut in such a way as to sufficiently lubricate the contact surfaces between the lever shaft 11 and the eccentric collar 13, and the contact surfaces between the eccentric collar 13 and the bearing portion 12, respectively. It's getting old. Further, the lever 5 is provided with an oil hole 20 whose one end faces the oil groove 19 and whose other end opens in the rocker arm support surface 5a on the lower surface, causing relative slippage between the lever 5 and the rocker arm. It lubricates between 3 and 3.

Further, as mentioned above, 6 is a control cam that restricts the inclination of the lever 5 by coming into contact with the back surface of the lever 5. Within the movement range of the fulcrum (shown as symbols in Figure 2),
The contact point A is located at this point.

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

First, when the intake and exhaust valves 2 are not lifted,
That is, when the cam contact portion 3a of the rocker arm 3 is on the base circle of the valve drive cam 1, the eccentric collar 13 is urged to rotate counterclockwise in FIG. Since the center of motion _O1 is displaced downward, the lever 5
and Rotsuka Arm 3 or Rotsuka Arm 3
The valve clearance between the valve stem 2a and the valve stem 2a is maintained at zero.

Further, even if the valve stem 2a is in an elevated position due to thermal expansion of the valve stem 2a or wear of the valve seat, the valve clearance is similarly maintained at zero, and the torsion coil spring 14
Since the urging force is sufficiently smaller than the spring force of the valve spring 21, it is possible to ensure that the intake and exhaust valves 2 are completely closed.

Next, when the valve drive cam 1 rotates and the intake and exhaust valves 2 are lifted via the rocker arm 3, the rocker arm 3 is lifted by the reaction force of the valve spring 21.
tries to push the lever 5 upward with its back surface 4. FIG. 4 shows the force acting in the vertical direction on the bearing part 12 at the rotation center O1 of the lever _5. As shown in the figure, the contact fulcrum between the rocker arm 3 and the lever 5 is the contact fulcrum between the lever 5 and the control cam 6. At the start of the valve lift, which is in range ₁ on the right side of the figure from the contact point A with the rocker arm 3, a large upward force a acts in a pulse-like manner, and the contact fulcrum with the rocker arm 3 is on the left side of the figure ₂ with the contact point A. Conversely, a downward force b acts near a certain peak lift, and a large upward force c acts in a pulsed manner when the valve is seated, and the contact fulcrum with the rocker arm 3 twists from the contact point A to the range ₁ to the right in the figure. Incidentally, the dotted line B in FIG. 4 indicates the mounting load of the valve spring 21 (usually about 30 kg). Therefore, when the intake/exhaust valve 2 starts to be lifted, the eccentric collar 13 is rotated a few thousand times clockwise by the upward force a. However, since this upward force a is generated in a pulse form only for a very short period of time, it is inhibited by the inertia effect due to the mass of the eccentric collar 13 itself and the sliding resistance with the lever shaft 11, etc., and the rotation is not as large as it is to the left. Can not. Then, due to the downward force b that occurs subsequently, the eccentric collar 13 immediately returns to rotation in the counterclockwise direction, and eventually by appropriately setting the ratio of ₁ and ₂ , the rotation center of the lever 5 O ₁ is maintained approximately at the position set before the start of the valve lift.

In addition, the eccentric collar 13 is also rotated a few thousand times clockwise by the upward force c that acts when the valve is seated, but similarly, this amount of rotation is relatively small, and the torsion coil is Since it is quickly twisted counterclockwise by the biasing force of the spring 14, the valve clearance is adjusted to zero again.

The above-described process is repeated every revolution of the valve drive cam 1, and the valve clearance can be kept at zero regardless of thermal expansion of the valve stem 2a or wear of the valve seat.

In this manner, the intake/exhaust valve drive device having the above structure can always adjust the valve clearance to zero without using a complicated hydraulic actuator, and the structure is extremely simple. Moreover, since force is applied upward and downward to the bearing part 12 of the lever 5 every time the valve drive cam 1 lifts, a good lubricating oil film is formed between the eccentric collar 13 and the bearing part 12, and the oil film is broken. It is possible to prevent the stuck phenomenon due to

In addition, in order to suppress the amount of rotation of the eccentric collar 13 due to the above-mentioned bulge-like upward forces a and c,
It is preferable that the inertial mass of the eccentric collar 13 is large. For example, as shown by imaginary lines in FIGS. 2 and 3, a weight portion 22 is integrally formed at one end of the eccentric collar 13 to increase the inertial mass. Also good.

As explained above in detail, according to this invention, it is possible to always maintain the valve clearance at zero with an extremely simple configuration that does not use a hydraulic actuator, etc., and it is possible to significantly reduce engine noise and vibration. It is no longer necessary to provide a buffer curve on the profile of the back surface of the rocker arm that makes fulcrum contact with the lever, and the design and processing of the rocker arm is facilitated.

[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 the intake/exhaust valve drive device according to this invention, Fig. 3 is a plan view of the same, and Fig. 4 is a sectional view of a lever bearing part. FIG. 3 is a characteristic diagram showing the relationship between force and valve lift. 1... Valve drive cam, 2... Intake and exhaust valve, 3...
... Locker arm, 5 ... Lever, 6 ... Control cam, 11 ... Lever shaft, 12 ... Bearing section,
13... Eccentric collar, 14... Torsion coil spring.

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 valve drive cam and the other end that is linked to the valve stem; A lever that contacts the fulcrum and is rotatably supported at one end on the valve stem side, and a control that contacts the back surface of the lever within the movement range of the contact fulcrum and restricts the inclination of the lever. A cylindrical eccentric collar that is interposed between the cam, the support shaft and the bearing part of the lever, and whose rotation moves the lever rotation center up and down with respect to the support shaft center; An intake/exhaust drive device for an internal combustion engine, comprising a spring member that biases rotation.