JPS61201803A - Valve mechanism of internal-combustion engine - Google Patents

Abstract

PURPOSE:To obtain a lift curve of a valve optimum for engine speed by providing a cam to a cam shaft swingably by a predetermined angle or fixably and changing over to either swingable or fixable way, according to engine speed. CONSTITUTION:A cam is swingably provided to a cam shaft 1 and put in contact with a tappet mechanism of a rocker arm 3 etc. The cam 2 is provided with a groove 13 on its inner face in contact with the cam shaft 1 and a plunger 10 going in and out from the cam shaft 1 is engaged in the groove 13. When the projecting amount of the plunger is changed according to the oil pressure applied to the rear end of the plunger 10 from a hydraulic introduction hole 8 and the plunger 10 is projected largely, the cam 2 is fixed to the cam shaft 1 to realize lift characteristic of a valve whose opening time is long, and when the projecting amount is small, the cam 2 becomes swingable to the cam shaft 1 by a predetermined angle and the valve opening time becomes shorter. Then lift curve appropriate to engine speed can be obtained by control of oil pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a valve mechanism for an internal combustion engine that is capable of switching the opening angle of a valve between high speed and low speed.

[Prior Art] This type of valve mechanism is described in Japanese Patent Publication No. 44-26485. In this valve mechanism, a plurality of high-speed and low-speed cams with different profiles are provided on the camshaft, a valve operating member is provided to selectively engage with any one of these cams, and
The engagement is appropriately switched by a switching mechanism according to the rotational speed of the engine.

[Problems to be Solved by the Invention] In the above valve mechanism, the engagement of the valve actuating member) is switched between a plurality of cams. There is a risk that the switching will not be carried out smoothly due to hitting the step between the cams.

In view of the above-mentioned circumstances, the present invention has been devised so that the opening angle of the valve can be smoothly switched between high speed and low speed.
The purpose of the present invention is to provide a valve mechanism for an internal combustion engine.

[Means for Solving the Problems] The present invention solves the above problems, and provides a valve for an internal combustion engine that opens and closes the valve through a valve operating member that is in pressure contact with the cam by the rotation of the cam shaft. In the mechanism, the cam is attached to the camshaft so that it can swing freely in the circumferential direction, and there is also a mode in which the cam can swing freely within a predetermined angular range, and a mode in which the cam is fixed to the camshaft so that it cannot swing. The configuration includes a switching mechanism for switching to either mode.

[Operation] In the valve mechanism configured as described above, when the switching mechanism is set to a mode in which the cam is fixed to the camshaft in a non-swingable manner, the valve lifts according to the original cam profile formed on the cam.

On the other hand, when the switching mechanism is set to a mode in which the cam can freely swing within a predetermined angular range, the cam and the valve operating member operate as follows in response to the rotation of the camshaft.

That is, at the stage where the cam surface in contact with the valve operating member shifts from the base circle of the cam to the lift curve, the cam is swung by the pressing force of the valve operating member and is displaced toward the -blade side. Then, by rotating the camshaft in this state, the valve actuating member is displaced according to the lift curve of the cam, and the valve is lifted. When the point of contact with the valve operating member passes through the cam top, the cam is then rapidly swung in the opposite direction to the camshaft due to the pressing force of the valve operating member. . Then, the cam is displaced to the other side opposite to the above. Therefore, due to the oscillating displacement of the cam during valve lift, the valve is lifted according to a virtual cam profile different from the original cam profile, that is, a cam profile with a smaller opening angle than the original cam profile. .

Therefore, if you set the former fixed mode to the high-speed mode and the latter swing mode to the low-speed mode, and set the cam profile to the high-speed profile, you can change the mode at high speeds or low speeds by switching the modes. Each valve can be lifted at the optimal opening angle.

[Example code] Embodiments of the present invention will be described below with reference to the drawings.

First, a first embodiment will be described with reference to FIGS. 1 to 6. 1 and 2 show the structure of the valve mechanism, and reference numeral 1 indicates a camshaft. Kamun Yaft
A cam 2 is fitted to be able to swing freely in the circumferential direction. As usual, a slipper 4 of a rocker arm (valve operating member) 3 is pressed into contact with the cam surface of the cam 2 by the urging force of a valve spring 5. The profile of Cam 2 is
It is set to match the valve lift curve for high speeds. 6 is a valve.

To describe the relationship between the cam 2 and the camshaft l in detail, a plunger insertion hole 7 is formed in the cam fitting portion of the camshaft 1 in the radial direction. A hydraulic pressure introduction path 8 provided inside the camshaft 1 communicates with the bottom of the plunger insertion hole 7 .

A cylindrical plunger guide 9 with a bottom is inserted into the plunger insertion hole 7 so as to slide on the inner peripheral surface of the insertion hole 7 . This plunger guide 9 has a height such that its upper end sinks into the insertion hole 7, and by introducing hydraulic pressure from the hydraulic pressure introduction path 8 to the bottom of the insertion hole 7, the upper end becomes the upper edge of the insertion hole 7. It protrudes upward from.

Further, a plunger 10 having a spherical head is slidably inserted into the plunger guide 9. This plunger IO is urged to protrude upward from inside the plunger guide 9 by a spring 11 housed inside. Further, a small hole 12 communicating with the plunger internal cavity is provided at the center of the head of the plunger IO.

On the other hand, a groove 13 is formed on the inner peripheral surface of the fitting hole of the cam 2, located just inside the cam top P. This groove 13 has a bottom surface formed in the shape of an arc with a curvature larger than the curvature of the head of the plunger 10, and both side surfaces are formed in parallel. Larger than the diameter, just plunger guide 9
It is large enough to fit the outer circumference of the This groove 13 is formed by passing through the base from inside.

The cam 2 formed in this way is a groove on the inner peripheral surface of the fitting hole. 3, the plunger 10 attached to the camshaft 1 side is fitted into the camshaft 1. Note that the cam 2 is fixed with a snap ring or the like 14 so as not to move in the axial direction on the camshaft l.

Next, the operation of the valve mechanism configured as above will be explained.

When no hydraulic pressure is applied to the hydraulic pressure introduction path 8, the plunger guide 9 is sunk into the plunger insertion hole 7, and the plunger 10 is in contact with the bottom surface of the groove 13 of the cam 2. In this case, since the bottom of the groove 13 and the head of the plunger 10 are cylindrical and spherical with different curvatures, the cam top P is located on the center line of the plunger IO. This is because the pushing up force of the plunger 10 causes an alignment effect. In this state, the positions of the plunger guides 9 and 113 are aligned.

Apply hydraulic pressure to hydraulic pressure introduction path 8 at high speed. Then, the plunger guide 9 is pushed upward in the figure, and its upper end is fitted into the groove 13 of the cam 2, so that the cam 2 is fixed to the camshaft 1 so as not to be able to swing.

Therefore, in this state, the cam 2 rotates integrally with the camshaft l, and the valve 6 lifts according to the original cam profile. The valve lift curve at that time is shown by a solid line in FIG.

Next, we will discuss the case at low speed.

At low speeds, hydraulic pressure is removed from the hydraulic pressure introduction path 8. Then, the plunger guide 9 sinks into the plunger insertion hole 7,
The cam 2 pushes the plunger 1 due to the action of a force along the circumferential direction.
0 can be freely swung within a range until the head hits the side surface of the groove 13.

When the camshaft 1 rotates in this state, the cam 2 and the rocker arm 3 operate as follows.

3 to 5 show the relationship of each component according to the rotation of the camshaft 1. The white arrow in the figure indicates the rotation direction of the camshaft l.

As shown in FIG. 3, when the cam surface of the rocker arm 3 in contact with the slipper 4 approaches the lift curve from the base circle, the cam 2 is swung in the direction of arrow (A) in the figure by the pressing force of the rocker arm 3. , thereby causing plunger IO
is pushed and sinks.

When the head of the plunger io hits one side of the groove 13 of the cam 2, the cam 2 stops swinging, and the camshaft 1 rotates in this displaced state, causing the rocker arm 3 to move as indicated by the arrow. The valve 6 starts to lift when pressed as shown in a).

Figure 4 shows that the contact point with the rocker arm 3 is the cam top P.
It shows the state at the moment of passing through.

At the moment when the cam 2 passes through the cam top P, the cam 2 operates as shown in FIG. That is, when the camshaft 1 rotates further, the cam 2 suddenly swings relative to the camshaft 1 in the direction of the arrow opposite to the above due to the pressing force of the rocker arm 3, and the head of the plunger IO falls into the groove. 13 until it hits the other side.

Then, the valve 6 completes its lift according to the lift curve.

During such operation, the small hole 12 in the head of the plunger 10
The air vent functions as a hole through which the air in the plunger guide can escape.

As the cam 2 swings and displaces as described above, the valve 6 is lifted according to a virtual cam profile different from the original cam profile, that is, a cam profile with a smaller opening angle than the original cam profile. The curve shown by the broken line in FIG. 6 is the valve lift curve at that time.

In this way, by switching to the fixed mode in which the cam 2 is fixed, a valve lift curve for high speeds can be obtained, and by switching to the swing mode in which the cam 2 is free to swing, the valve lift curve for low speeds can be obtained. It is possible to obtain a curve and lift the valve at the optimal opening angle. However, since this switching is performed on the circumferential surface of one cam, smooth switching is required.

Next, a second example will be described.

Since FIG. 7 shows the relationship between the cam shaft 21 and the cam 22 in this embodiment, the same components as in the first embodiment are given the same reference numerals and their explanations are as follows: There is a hole 24 on the bottom,
A notebook 26 having a small hole 25 in the center is housed in the inner bottom of the plant guide 23 with its lower end fitted into the hole 2.1. A check pole 27 is provided in the notebook 26 so as to close the small hole 25. A cage 28 is provided above the check hole 27 and fixed to the inner surface of the plunger guide 23 so that the check pole 27 does not fall off.

On the other hand, a small groove 30 is provided in the center of the bottom surface of the groove 29 of the cam 22 so as to extend along the axial direction of the cam. The other configurations are the same as those of the first embodiment.

The mechanism of this second embodiment operates as follows when high-pressure oil is supplied to the hydraulic pressure introduction path 8 at high speed.

The oil passes through the small hole 25 of the notebook 26, presses the check pole 27, and enters the plunger 10. Therefore, when the cam 22 is oscillated and is blocked by the small hole I2 in the head of the plunger IO or the bottom of the groove 29, the pressure horn of the oil in the plunger IO causes the plunger guide 23 to move upward. do not. When the plant gear 10 returns to the illustrated position, the small hole 12 and the small groove 3 of the cam 22
0 or match, the oil in Planotsuya 10 is in that small groove 3.
Zero flows out. Then, the plunger guide 23 overcomes the force of the oil inside the plunger 10, and its upper end fits into the groove 29 of the cam 22, thereby locking the cam 22. Since the oil is continuously supplied, the plunger guide 23 remains in the upper bound state. When the camshaft 21 is rotated in this mode, a high-speed valve lift curve is obtained.

On the other hand, at low speeds, low-pressure oil is constantly supplied to the hydraulic pressure introduction path 8. In this case, the oil pressure is the spring 11
The plunger guide 23 is set to a size that does not push up the plunger guide 23 against the force of the above.
The cam 22 can now swing freely.

In this state, when the camshaft 21 rotates and the lift curve of the cam 22 is applied to the slipper of the rocker arm, the force applied to the cam 22 causes the cam 22 to swing, pushing the plunger 10 and sinking the valve. The open timing is delayed from the original timing obtained from the cam profile.

At this time, the head of the blunter 10 slides on the inner surface of the groove 29 of the cam 22, so that the small hole 12 in the head of the plunger 10 is closed, and there is no escape route for the oil in the plunger IO. As a result, the small hole 25 of the notebook 26 is closed by the check pole 27, and the oil is trapped within the plano gloss 10. This trapped oil exerts a damper effect on the operation of the blunt gloss 10.

Further, when the point of contact with the rocker arm 3 passes through the cam top P, the cam 2 swings to the opposite side at the moment of passing. As a result, the valve close timing is earlier than the original timing obtained from the cam profile.

Note that while the plunger 10 swings toward the other side, the small hole I2 in the head of the plunger 10 passes through the small groove 30 in the cam 22, but at this time, the oil supplied inside the plunger 10 flows out to the outside. , lubricate the head sliding surface of the plunger IO.

In this way, by switching to the fixed mode in which the cam 22 is fixed, a valve lift curve for high speeds can be obtained, and by switching to the swing mode in which the cam 22 is free to swing, the valve timing can be adjusted for high speeds. In comparison, it is possible to obtain a valve lift curve for low speeds with a late valve open timing and an early valve close timing.

Therefore, the valves can be lifted at their respective optimal opening angles.

Next, a third embodiment will be described.

Figures 8 and 9 show the camunyaft 4 in this embodiment.
This figure shows the relationship between cam 1 and cam 2, and the same components as in the first embodiment are given the same reference numerals and their explanations will be omitted.

The camshaft 41 is provided with another oil introduction passage 42, the tip of which communicates with a ring-shaped shallow groove 43 formed in the middle inner peripheral surface of the planter insertion hole 7.

The body of the plunger guide 44 includes a plunger guide 4
4 is sunk into the insertion hole 7, an oil passage 4 is formed at a plurality of locations on the circumference at a position corresponding to the ring-shaped groove 43.
5 is formed. Further, a ring-shaped shallow groove 46 is formed on the inner peripheral surface of the plunger guide 44 at a position where the oil passage 45 is located. Furthermore, an oil passage 48 corresponding to the oil passage 45 of the plunger guide 44 is provided in the body of the plunger 47 . Unlike the previous two embodiments, the head of the plunger guide 44 has
Two small holes 49, 49 are formed in a V-shape with openings offset from the center of the head. Further, the groove 13 formed on the inner circumferential surface of the cam 2 is formed by punching out from the lateral direction along the axial direction of the cam 2. The other configurations are the same as in the first embodiment.

In the mechanism of this embodiment, by supplying high pressure oil from the oil introduction path 8 at high speed, the plano gloss guide 44
is pushed up and cam 2 is locked. As a result, a valve lift curve for high speeds is obtained.

In addition, at low speeds, the oil supply is switched to the oil introduction path 42.
Switch to . When low pressure oil is supplied from the oil introduction passage 42, the oil passage 45 of the plunger guide 1111
, oil is guided into the plunger 47 via the oil passage 48 of the plunger 47. At this time, the plunger guide 44 sinks into the plunger insertion hole 7 as shown in the figure, and the cam 2 becomes able to swing freely.

In this state, camshaft 4! rotates, and when the lift curve of the cam 42 approaches the slipper of the rocker arm, the force applied to the cam 2 causes the cam 2 to swing, pushing the plunger 47 and sinking, so that the valve open timing can be determined from the cam profile. later than the original timing.

At this time, the oil in the plunger 47
It exerts a damper effect on the movement of 7. Further, oil flows out from a small hole 49 in the head of the plunger 47, and lubricates the sliding surface by swinging.

Further, when the contact point with the rocker arm passes through the cam top P, the cam 2 swings to the opposite side at the moment of passing. As a result, the valve close timing becomes earlier than the original timing obtained from the cam profile.

In this way, by switching the oil supply passage, it is possible to switch between fixed mode and swing mode, and the valve can be lifted at the optimal opening angle at high speed and low speed. .

In addition, in the above embodiment, the mode switching mechanism is
Both are hydraulic types using plungers and plunger guides, but any mechanism that can be switched between a swing mode that allows swinging within a predetermined angle range and a fixed mode can be used. do not have.

Further, although the number of modes to be switched is two in the above embodiment, it may be more than that.

[Effects of the Invention] The valve mechanism of the present invention has a mode in which the cam is attached to the camshaft so that it can swing freely in the circumferential direction, and a switching mechanism allows the cam to swing freely within a predetermined angular range. Since the cam is configured to be switched to a mode in which the cam is fixed to the camshaft in a non-swiveling manner, when the fixed mode is selected, the valve lifts according to the original cam profile formed on the cam.

In addition, when the oscillation mode is selected, the cam oscillates as appropriate in accordance with the rotation of the camshaft, and the valve creates a virtual cam profile that is different from the original cam profile, that is, the valve opens more than the original cam profile. It will be lifted according to the narrow cam profile. Therefore, if you set the former fixed mode to the high-speed mode and the latter swing mode to the low-speed mode, and set the cam profile to the high-speed profile, you can change the speed at high speed or low speed by switching the mote. Each valve can be lifted at the optimal opening angle.

Therefore, since the switching between high speed and low speed is performed depending on whether or not one cam is swung in the circumferential direction, the switching can be performed extremely smoothly.

[Brief explanation of the drawing]

1 to 6 are diagrams for explaining a first embodiment of the present invention, in which FIG. 1 is a longitudinal cross-sectional view showing the configuration of the main part of the valve mechanism, and FIG. 2 is a diagram similar to that of FIG. Cross-sectional view along the n-■ line, Figure 3~
FIG. 5 is a diagram for explaining the operation of each valve mechanism, and FIG. 6 is a diagram showing valve lift curves at high speed and low speed obtained in each switching mode. 7 and 8 are cross-sectional views showing the relationship between the cam and the camshaft in the second and third embodiments of the present invention, respectively, and FIG. 9 is a cross-sectional view taken along the line IX-IX in FIG. 8. It is. 1.21.41...Camshaft 2.22.・
・・・Pujmu 3・・・Rocker arm (valve operation/members) 4
...Slipper 5 ...Valve spring 6 ...Valve 7 ...Plunger insertion hole 8 ...Hydraulic pressure introduction path 9.23.44・・・・・・Plunger guide 10.4
7... Plunger 11... Spring 12... Small hole 13.29... Groove 24... Hole 25... Small hole 26...Seat 27...Check ball 28...Cage 30...Small groove 42...Oil introduction path 43.46... ...Ring groove 45.48 ...Oil passage 49 ...Small hole P ...Cam top procedure amendment (voluntary)

Claims (1)

[Claims] In a valve mechanism for an internal combustion engine that opens and closes a valve through a valve operating member that presses against the cam as the camshaft rotates, the cam is attached to the camshaft so that it can swing freely in the circumferential direction, and the cam is moved within a predetermined angular range. A valve mechanism for an internal combustion engine, characterized in that a switching mechanism is provided for switching between a mode in which the cam can swing freely within the camshaft and a mode in which the cam is fixed to the camshaft so that it cannot swing.