JPH0332730Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a structure of a rocker arm in which the position of a rocker arm pad is changed.

[Conventional technology]

The rocker arm is located between the cam and the valve stem and transmits the movement of the cam to the valve stem.
The specifications of the rocker arm and cam affect the opening characteristics of the intake and exhaust valves, that is, the valve lift and cam operating angle. These factors determine the rotational range in which the engine operates efficiently. That is, in order to obtain high torque in the high engine speed range, it is preferable to increase the valve lift and cam operating angle. Conversely, if the valve lift and cam operating angle are reduced, the torque in the low engine speed range increases.

[Problem that the invention attempts to solve]

Regarding the rocker arm, the location of the rocker arm pad where the cam nose contacts the rocker arm affects the valve lift and cam operating angle.
In the structure of a conventional valve train, the rocker arm pad that forms the contact point between the cam nose and the rocker arm is fixed, and the valve lift and cam operating angle are determined entirely by the specifications of the rocker arm.
Therefore, the Rotsuka arm was designed according to the purpose of the engine. In other words, for engines that emphasize high revolutions, the specifications of the rocker arm are designed so that high torque can be obtained at high revolutions, and conversely, for engines that emphasize low revolutions, the specifications of the rocker arm are designed so that high torque can be obtained at low revolutions. design. Furthermore, in order to obtain moderate performance over the entire rotation range, the design must gradually sacrifice torque in the high and low rotation ranges. Therefore, with the conventional technology, there was a problem in that it was not possible to achieve high performance over the entire rotation range of the engine.

In JP-A-59-51117, a rocker arm is driven by a cam via a roller-shaped rocker arm pad, and the rocker arm pad is provided so as to be movable on the upper surface of the rocker arm in a direction perpendicular to the rocker shaft axis. , and the arm padded,
A rocker arm structure for an internal combustion engine has been proposed that changes the lift characteristics of a valve by controlling the position in a direction perpendicular to the rocker shaft axis.

With this rocker arm structure, the operating angle of the cam is changed by changing the position of the rocker arm pad using a hydraulic mechanism that responds to the engine speed.
Valve lift characteristics can be changed according to engine speed.

[Problem that the invention attempts to solve]

However, in this prior art, the rocker arm pad moves on the side of the cam that is closer to the rocker shaft. Therefore, in order to increase the operating angle, the rocker arm pad is moved away from the rocker shaft. However, since the effective arm length becomes longer when moving away from the rocker shaft, the amount of pushdown applied to the rocker arm by the cam becomes so small that a large working angle is required.As a result, changes in the lift of the cam can be effectively controlled.
This results in an inconvenient result in that it cannot be made larger.

The object of this invention is to provide a structure that allows for a large change in lift characteristics due to changes in the operating angle of the cam due to movement of the rocker arm pad.

[Means to solve the problem]

According to this invention, the rocker arm is driven by a cam via the rocker arm pad, and the rocker arm pad is provided so as to be movable on the upper surface of the rocker arm in a direction perpendicular to the rocker shaft axis.
and in a valve train structure for an internal combustion engine in which lift characteristics of a valve are changed by controlling the position of a rocker arm pad in a direction perpendicular to a rocker shaft axis, movement of the rocker arm pad in the direction by the position control means. A rocker arm structure is provided in which the range is set with respect to the cam on the side away from the rocker shaft in the aforementioned direction, and the operating angle of the cam increases as the rocker arm pad moves closer to the rocker shaft.

[Effect]

The position of the rocker arm pad is controlled by the control means to a predetermined position in a direction perpendicular to the axis of the rocker shaft.

When increasing the cam operating angle, the pad position is controlled so that it is close to the cam, and when decreasing the cam operating angle, the pad position is controlled so that it is located away from the cam. .

[Example] In FIG. 2, 10 is a rock arm,
One end thereof is connected to the rocker shaft 12, and an adjuster screw 14 is fixed to the other end by a nut 16. The lower end of the adjusting screw 14 is in contact with the upper end of the valve stem 20 of the intake/exhaust valve 18. A retainer 22 is fixedly attached to the upper end of the valve stem 20, and a valve spring 25 is disposed between the retainer 22 and the bottom surface 24 of the cylinder head, and biases the umbrella portion 19 of the intake and exhaust valve 18 to seat on the valve seat 27. are doing. The locker arm 10 has a locker arm pad 26 on its upper surface, and a cam 28 above the locker arm pad 26.
is placed. Cam 28 is a lock arm pad 2
When rotated so as to contact 6, the locking arm 10
rotates counterclockwise around the shaft 12, the valve stem 20 moves downward against the valve spring 25 by the adjuster screw 14, and the umbrella portion 19 of the intake/exhaust valve 18 moves toward the valve seat 27.
The further apart the intake and exhaust valves open.

FIG. 1 shows an enlarged cross-section of the rocker arm 10. As shown in FIG. An integral guide member 32 extends from the bottom surface of the rocker arm pad 26 into a guide groove 33 formed in the rocker arm 10. Therefore, the rocker arm pad 26 is movable on the rocker arm 10 in its longitudinal direction (that is, in the direction perpendicular to the axis of the rocker shaft 12). A lower end of the guide member 32 is connected to a piston 34 . piston 34
is slidably disposed within a cylinder 35 formed in the rocker arm 10. One end of the cylinder 35 is closed off from the outside by a plug 36. Opposite the bung 36 is a spring 38 which urges the piston 34 against the bung 36 to the left in the figure. The piston 34 has a cup shape that is open on the side of the stopper 36, and has a notch 40 formed in its side surface. On the other hand, an oil passage 42 is formed within the rocker arm 10, and one end of this oil passage 42 communicates with an oil hole 44. The oil passage 42 and the oil hole 44 are closed off from the outside by plugs 36, 46 and 48, respectively. piston 34
When the notch 40 of the piston 34 is in the leftmost position contacting the stopper 36 as shown in FIG. Oil from passage 42 is adapted to be supplied to piston 34. The other end of the oil passage 42 opens into an oil groove 50 formed on the inner surface of a hole 48 at the end of the rocker arm 10 through which the rocker shaft 12 is inserted.
2 is hollow, and there is an oil supply hole 56 that opens this hollow portion 52 into the oil groove 50. The hollow portion 52 is communicated with a hydraulic power source such as an engine oil pump (not shown).

Lubricating oil from the oil pump is introduced into the piston 34 through the hollow portion 52, the oil supply hole 56, the oil groove 50, the oil passage 42, and the oil hole 44.
As a result, the piston 34 is pushed to the right in FIG. 1 against the force of the spring 38. Therefore, the piston 34 moves in the same direction within the cylinder 35 to a position where the oil pressure and the load of the spring 38 are balanced, and in conjunction with this, the rocker arm pad 26 slides on the upper surface of the rocker arm as shown by the dashed line 26'. . As the rocker arm pad 26 moves to the right in FIG. As the distance becomes smaller, the vertical movement of the rocker arm 10, that is, the valve lift becomes larger due to the principle of the lever, and the cam operating angle also becomes larger. As a result, a valve lift and a cam operating angle that continuously and steplessly change depending on the position of the rocker arm pad 26 are obtained.

Now, if we control the discharge pressure of the lubricating oil pump so that it changes in proportion to the engine speed, the piston 34 will be located at the far left in Figure 1 because the oil pressure is small at low engine speeds, and the rocker arm pad 26 is also located on the leftmost side as shown by the solid line. At this time, in FIG. 3, if 28A is the base circle of the cam 28 and 28B is the nose circle, the position of the rocker arm pad 26 at the base circle 28A at low engine speed is represented by 26-1. At this time, there is a gap of X between the cam 28 and the rocker arm pad 26. Cam nose 28'
When the cam 28' rotates and the tip of the nose 28' reaches position P, the gap X between the cam 28 and the rocker arm pad 26 is eliminated, and the rocker arm pad begins to move downward, that is, to open the valve. When the nose 28' reaches the point x, the rocker arm pad assumes the lowest position as shown in 26-2. At this time, the rocker arm 10 is tilted at the fulcrum P (the center of the rocker shaft 12).
If the position of the rocker arm 10 at rest is represented by a straight line m, the maximum swing angle of the rocker arm 10 is θ. The lift of the intake and exhaust valves obtained at this time is the minimum, as shown in FIG. 4A. When the tip of the nose 28' reaches position q in FIG. 3, the cam separates from the rocker arm pad and the valve closes. Therefore, the cam operating angle at low engine speed is expressed by Θ. In this way, by positioning the rocker arm pad away from the fulcrum of the rocker shaft during low rotations, the valve lift θ and cam operating angle Θ are reduced, making it suitable for low rotational speed operation and achieving high torque during such operation. be able to.

When the engine rotates at a high speed, the oil pressure becomes high, so the piston 34 is pushed against the spring 38, and the rocker arm pad 26 is located at the far right side. In FIG. 3, 26'-1 is the position of the rocker arm pad on the base circle. At this time, there is a gap X'(<X) between the cam and the rocker arm pad. When the tip of the nose 28' comes to position p' due to the rotation of the cam,
The cam and the rocker arm pad begin to make contact, the rocker arm pad begins to descend, and the intake and exhaust valves begin to open. When the tip of nose 28' reaches point x', the rocker arm pad assumes the maximum lowered position indicated by 26'-2. The inclination of the rocker arm 10 at this time is represented by a straight line l' with respect to the fulcrum P, and the maximum swing angle of the rocker arm at that time is θ',
The lift of the intake and exhaust valves is maximum, as shown in Figure 4B. When the tip of the nose 28' reaches point q', the cam separates from the rocker arm pad and the valve closes. Therefore, the cam operating angle at high engine speed is expressed by Θ'. In this manner, the valve lift θ' and the cam operating angle Θ' are larger at high rotations than at low rotations, making it possible to obtain high torque. In FIG. 3, the range of movement of the rocker arm pad 26 (ie, the range of movement of the contact point between the cam and the rocker arm pad) is on the side of the cam 28 remote from the rocker shaft 12. Therefore, as the rocker arm pad 26 approaches the rocker shaft 12, the working angle becomes larger and at the same time the arm length becomes shorter, so that the amount of depression by the cam 28 becomes larger. As a result, the change in operating angle due to movement of the rocker arm pad 26 can be effectively increased.

[Effect of idea]

In the present invention, the movement range of the rocker arm pad is selected on the side away from the rocker shaft, and when a large working angle is required, the arm length is short, and when a small working angle is required, the arm length is large. By changing the operating angle in the structure, the lift can be changed more widely and efficiently within the limited movement range of the rocker arm pad, and larger engine torque can be obtained over a wide engine speed range. The effect that can be achieved is demonstrated.

[Brief explanation of the drawing]

Figure 1 is a sectional view of the rocker arm of this invention. Figure 2 is an overall view of the valve train system equipped with the rocker arm of this invention. FIG. 3 is a diagram illustrating the relative positional relationship between the cam and the rocker arm pad in this invention at high engine speed and low engine speed, respectively. FIG. 4 is a diagram showing the positional relationship of the cam, rocker arm, and valve stem at maximum lift for low rotation (A) and high operation (B). 10...Rotsuka arm, 12...Rotsuka shaft, 20...Valve stem, 26...Rotsuka arm pad, 28...Cam, 28'...Nose, 3
4... Piston.

Claims (1)

[Scope of utility model registration request] The rocker arm is driven by a cam via the rocker arm pad, and the rocker arm pad is provided so as to be movable on the upper surface of the rocker arm in a direction perpendicular to the rocker shaft axis, and the rocker arm pad is moved perpendicularly to the rocker shaft axis. In a valve train structure for an internal combustion engine in which lift characteristics of a valve are changed by controlling a position in a direction, the range of movement of the rocker arm pad in the direction by the position control means is such that the movement range of the rocker arm pad in the direction is spaced apart from the rocker shaft in the direction with respect to the cam. Rotsuka arm structure characterized by being set on the side.