JPH0688509A - Variable valve timing lift device for four cycle engine - Google Patents

Abstract

PURPOSE:To make either a push plate or push pieces abut on an intake/exhaust valve so as to change over lift and a timing by providing an intermediate low speed cam and a high speed cam, and also providing an intermediate low speed slider provided with the push plate and a high speed slider provided with the push piece. CONSTITUTION:An intermediate/low speed cam 20 and high speed cams 21, 22 are provided on a cam shaft 23, and also an intermediate/low speed slider 24 provided with a push plate 25 and high speed sliders 26 enclosing slider lifts 27 and push pieces 28 are arranged. The push pieces 28 are advanced from the high speed sliders 26 by operation of an oil pressure switching valve at the time of high speed rotation so as to abut on lift plates 42 and operate intake/exhaust valves 11, 12 through the sliders 26 by the high speed cams 21, 22. At the time of intermediate/low speed, the push pieces 28 retreat so as to operate the intake/exhaust valves 11, 12 through the sliders 24 by the intermediate/low speed cam 20. Thus, valve lift and a timing is changed according to the number of revolution.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable valve timing lift device for a direct hit type DOHC (double overhead camshaft) 4-cycle engine which changes valve lift and valve timing according to the engine speed.

[0002]

2. Description of the Related Art In a four-cycle engine, a valve operating device capable of improving engine output characteristics by changing valve lift and valve lift timing of intake / exhaust valves in accordance with engine speed, is disclosed in Japanese Utility Model Publication No. 11
The devices described in Japanese Patent No. 8205 and the like have been proposed.

Such a valve operating device is called a variable valve timing lift device, and is a medium-low speed rocker arm directly fitted to the rocker shaft and operated by a low-speed cam, and an eccentric large rocker shaft. A high-speed rocker arm that is fitted to the diameter part and is operated by a high-speed cam, and a rocker shaft that is connected to the rocker shaft to rotate the rocker shaft. And a rocker shaft rotation drive source for selectively switching the operation of the high-speed rocker arm by the cam according to the engine speed.

[0004]

The variable valve timing lift device described above, however, is a rocker arm type DO.
It is applied to the HC four-cycle engine, and the rocker shaft and the rocker arm are essential components for switching the cam. Therefore, the above conventional variable valve timing lift device cannot be applied to a direct hit type DOHC four-cycle engine having no rocker arm or rocker shaft.

The present invention has been made in consideration of the above circumstances, and in a direct-acting DOHC four-cycle engine, the valve lift and valve timing of intake and exhaust valves are changed according to the engine speed, An object of the present invention is to provide a variable valve timing lift device for a 4-cycle engine that can improve output characteristics.

[0006]

According to the present invention, there is provided a camshaft which is arranged directly above an intake / exhaust valve, and which has a cam profile for different speeds, in which a cam for medium and low speeds and a cam for high speeds are adjacently arranged. A slider for medium and low speeds, which is arranged between the low speed cam and the intake / exhaust valve, is in contact with the medium / low speed cam, and has a push plate on the intake / exhaust valve side that can be in contact with the head of the valve; , The high-speed cam and the intake / exhaust valve are arranged to contact the high-speed cam, the push piece contacts the cam surface of the slide cam lifter housed slidably in the forward and reverse directions,
This push piece moves back and forth toward the intake / exhaust valve by the cam surface, and a high-speed slider is provided so as to be able to contact the head of this valve, and the slide cam lifter forward / reverse depending on the engine speed. Slide in the direction, and push either one of the push plate of the medium / low speed slider and the push piece of the high speed slider.
And an operation switching circuit that is brought into contact with the head portion of the exhaust valve.

[0007]

Therefore, in the variable valve timing lift device for a four-cycle engine according to the present invention, the operation switching circuit causes the slide cam lift of the high-speed slider to slide in the forward direction at the time of high engine rotation, thereby pushing the push piece of the high-speed slider. And pushes the push piece into contact with the head of the intake / exhaust valve, so that the intake / exhaust valve is operated by the high-speed cam via the high-speed slider. When the engine is running at low speed, the operating circuit is
Slide the slide cam lifter of the high-speed slider in the opposite direction to retract the push piece of the high-speed slider and bring the push plate of the medium-low speed slider into contact with the head of the intake / exhaust valve. Is operated by a medium-low speed cam via a medium-low speed slider. Thus, even in the direct hit type DOHC 4-cycle engine, the valve lift and valve timing of the intake / exhaust valves can be changed according to the engine speed,
The output characteristics of the engine can be improved.

[0008]

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

FIG. 1 is a sectional view showing an embodiment of a variable valve timing lift device for a 4-cycle engine according to the present invention. 2 and 3 are cross-sectional views taken along lines II-II and III-III of FIG. 1, respectively.

A four-cycle engine 1 partially shown in FIG.
Includes a cylinder block 2, a cylinder head 3, and a head cover (not shown) on a crank case (not shown).
Are sequentially assembled and configured. One or a plurality of cylinders 4 are formed in the cylinder block 2, and a piston 5 is reciprocally housed in each cylinder 4.

In the cylinder head 3, one or a plurality of combustion chambers 6 are formed corresponding to the cylinders 4, and each combustion chamber 6
Two intake ports 7 and two exhaust ports 8 are opened. In the cylinder head 3, an intake passage 9 is formed for each combustion chamber 6 and connected to the two intake ports 7. The air-fuel mixture is supplied from the intake passage 9 into the combustion chamber 6. Also,
In the cylinder head 3, one exhaust passage 10 is formed for each combustion chamber 6 and is connected to the two exhaust ports 8, and the combustion exhaust in the combustion chamber 6 is exhausted to the outside of the engine 1 from this exhaust passage 10.

The intake port 7 and the exhaust port 8 are opened and closed by an intake valve 11 and an exhaust valve 12, respectively.
The intake valve 11 and the exhaust valve 12 are slidably inserted in a valve guide 13 installed in the cylinder head 3. A spring retainer 15 is attached to the heads (stem heads) of the intake valve 11 and the exhaust valve 12 by a cotter 14, and a valve spring 16 is interposed between the spring retainer 15 and the cylinder head 3. With this valve spring 16,
The intake valve 11 and the exhaust valve 12 are constantly urged in the direction of closing the intake port 7 and the exhaust port 8. The variable valve timing lift device 17 controls opening / closing of the intake valve 11 and the exhaust valve 12.

This variable valve timing lift device 17
1, is rotatably supported between the cam shaft journal portion 18 and the cam shaft journal housing 19 of the cylinder head 3 located immediately above the intake valve 11 and the exhaust valve 12, and the middle and low speed cams 2 are
0 and a cam shaft 23 having high speed cams 21 and 22, a medium speed cam 20 and an intake valve 11 and an exhaust valve 12, and the push plate 2
5, a slider 24 for medium and low speed, a slider 26 for high speed, which is arranged between the cams 21 and 22 for high speed, the intake valve 11 and the exhaust valve 12, and has a slide cam lifter 27 and a push piece 28 built therein, and a slide cam slider. The lid 27 and the push piece 28 are moved, and an operation switching circuit 29 for switching the operations of the middle and low speed cams 20 and the high speed cams 21 and 22 is provided.

The camshaft 23, as shown in FIG.
Two cylinder heads, one each in front of and behind the vehicle, are arranged to extend in the vehicle width direction. The front camshaft 23 is used to drive the exhaust valve 12, and the rear camshaft 23 is used to drive the intake valve 11. is there. Each camshaft 23 has
As shown in FIG. 1, one set of cam units in which high-speed cams 21 and 22 are arranged adjacently on both sides of the medium-low speed cam 23 are formed by the number of cylinders 4, that is, the number of combustion chambers 6. ing. Each camshaft 23 is rotationally driven by a crankshaft (not shown) housed in the crankcase of the 4-cycle engine 1 via a cam chain (not shown).

The high speed cams 21 and 22 have the same cam profile. In addition, the middle and low speed cam 20
The cam profile is different from that of the high speed cams 21 and 22. That is, the cam profile for the medium- and low-speed cam 20 is formed so that the valve lift and the valve timing suitable for the operation of the engine in the medium-low speed rotation range can be obtained. Also,
The cam profiles of the high speed cams 21 and 22 are formed so that a suitable valve lift and valve timing can be obtained when the engine is operating in a high speed rotation range.

As shown in FIG. 4, the medium-speed slider 24 has guide holes 30 penetrating both sides in the longitudinal direction, and the guide shaft 31 shown in FIG. 3 is inserted into the guide holes 30. . The guide shaft 31 is screwed on the cylinder head 3 and is erected. A slider spring 33 is inserted between the flange 32 of the guide shaft 31 and the lower surface of the slider 24 for medium and low speeds while being inserted into the guide shaft 31. As shown in FIG. 6, the high speed slider 26 has guide grooves 34 formed on both sides in the longitudinal direction, and guide shafts 35 are fitted into the guide grooves 34. The guide shaft 35 is press-fitted into the cylinder head 3 to stand upright as shown in FIG. A spring receiving recess 36 shown in FIGS. 2 and 10 is formed on the lower surface of the high speed slider 26, and a slider spring 37 is interposed between the spring receiving recess 36 and the cylinder head 3.

As shown in FIG. 3, the medium-low speed slider 24 is urged upward by the slider spring 33 so that a piston shim 45 described later can come into contact with the medium-low speed cam 20. As shown in FIG. 2, the high-speed slider 26 is biased upward by the slider spring 37 so that a shim 57, which will be described later, can come into contact with the high-speed cams 21 and 22. The upper end positions of the sliders for medium and low speed 24 and the slider for high speed 26 that are moved by these slider springs 33 and 37 are regulated by a stopper plate 38.

The stopper plate 38 is formed in a substantially ring shape as shown in FIG. 14, and is provided so as to be able to come in contact with both upper surface side portions of the medium speed slider 24 and the high speed slider 26. The stopper plate 38 is fixedly supported in the bolt hole 39 of the cylinder head 3 shown in FIG. 13 with the bolt 40 shown in FIG. Further, the stopper plate 38 is mounted on the stopper plate 38 by using bolts 41 for high speed slider 2
The upper end of the guide shaft 35 of 6 is fixed, and the upper end of the guide shaft 35 is supported by the cylinder head 3 via the stopper plate 38.

The medium and low speed slider 2 shown in FIGS.
The push plate 25 is press-fitted and fixed to the lower part of the center of the longitudinal direction 4. The push plate 25 extends at right angles to the longitudinal direction of the medium- and low-speed slider 24, and reaches the position directly above the head of the intake valve 11 and the exhaust valve 12, as shown in FIG. Here, a lift plate 42 is capped on the heads of the intake valve 11 and the exhaust valve 12. Lift plate receiving portions 43 (FIGS. 4 and 5) that can come into contact with the lift plate 42 are formed below the front end portions of the push plate 25. Further, notches 25 </ b> A for avoiding interference with the push piece 28 of the high speed slider 26 are formed at both ends of the push plate 25.

Further, as shown in FIG. 3, a cylinder hole 44 opening upward is formed in the central portion in the longitudinal direction of the medium and low speed slider 24. A piston shim 45 capable of contacting the middle and low speed cam 20 is slidably fitted into the opening of the cylinder hole 44. A high-pressure oil chamber 46 is formed by being surrounded by the cylinder hole 44 and the piston shim 45. A guide shaft oil passage 47 is formed on one side of the guide shaft 31, and the guide shaft oil passage 47 communicates with the high pressure oil chamber 46 via the slider oil passage 48 and the piston shim oil passage 49. The guide shaft oil passage 47 is supplied with high-pressure oil (hydraulic pressure of ^{2 to 4} kg / cm ² ) from the main gallery 51 shown in FIG. 2 via the lash adjust oil passage 50 formed in the cylinder head 3. Is guided into the high pressure oil chamber 46 through the slider oil passage 48 and the piston shim oil passage 49 shown in FIG. A check valve 53, which is biased by a check valve spring 52 so as to allow only the supply of high pressure oil from the piston shim oil passage 49, is arranged in the high pressure oil chamber 46. Therefore, the piston shim 45 is constantly pressed against the medium / low speed cam 20 by the high pressure oil in the high pressure oil chamber 46, and the medium / low speed cam 20 and the piston shim 45 are automatically adjusted to zero rush (rush adjustment).

As shown in FIGS. 2, 7, and 8, a cylinder hole 54 extending in the longitudinal direction is penetrated through the high-speed slider 26. The slide cam lifter 27 is housed in the cylinder hole 54 so as to be slidable in the forward and reverse directions. Inside the slide hole 54 is the slide cam lifter 2 described above.
A high speed side oil chamber A and a low speed side oil chamber B are partitioned by 7. The high speed side oil chamber A communicates with a high speed side switching oil passage 56A formed in the cylinder head 3 via a high speed side oil passage 55A formed in one of the guide shafts 35. Also,
The low speed side oil chamber 50B is connected to the cylinder head 3 through the medium and low speed side oil passage 55B formed in the other guide shaft 35.
Is connected to the medium-low speed side switching oil passage 56B formed in the above.

A shim 57 that can contact the high speed cams 21 and 22 is mounted on the upper center of the high speed slider 26. The lower end of the shim 57 reaches the inside of the cylinder hole 54,
It is fitted into the slide groove 58 of the slide cam lifter 27. As shown in FIG. 11, the slide groove 58 is formed on a plane parallel to the axis of the slide cam lifter 27, and both ends of the slide groove 58 function as stoppers 59. By fitting the lower ends of the shims 57 and the slide grooves 58, the slide cam lifter 27 is restricted from rotating around its axis when the slide cam lifter 27 slides, and the lower end of the shim 57 contacts the stopper 59. The slide position of the slide cam lifter 27 is restricted.

As shown in FIGS. 7 and 8, the slide cam lifter 27 is provided with a cam surface 60 at its lower portion. The cam surface 60 is formed along the longitudinal direction of the slide cam lifter 27 such that the high speed side cam surface 61A is shallow on the high speed side oil chamber A side, and the middle and low speed side cam surface 61B is deep on the middle and low speed side oil chamber B side. An inclined surface 62 is continuously formed between the high-speed side cam surface 61A and the medium-low speed side cam surface 61B. The high speed side cam surface 61A and the medium and low speed side cam surface 61B
Are parallel to the axis of the slide cam lifter 27 and are formed in a plane as shown in FIG.

In the high speed slider 26, a stepped hole 63 is formed at the lower center of the longitudinal direction facing the shim 57, and a cylinder hole 54 is formed.
Is drilled in communication with. The push piece 28 is slidably accommodated in the stepped hole 63. The push piece 28 has a large-diameter hemispherical head portion 64, and a push piece spring 66 is interposed between the push piece head portion 64 and the step portion 65 of the stepped hole 63. Due to the urging force of the push piece spring 64, the push piece head 64 always contacts the cam surface 60 of the slide cam lifter 27. As a result, the slide cam lifter 2
When the slide piece 7 slides, the push piece 28 moves to the cam surface 6
The push piece 28 is configured to be capable of advancing and retracting in correspondence with 0.
At the time of advancing, the tip end portion of the push piece 28 is provided so as to be able to contact the lift plate 42 as shown in FIG.

The operation switching circuit 29 includes the high speed side switching oil passage 56A, the medium and low speed side switching oil passage 56B, and the switching valve 67.
And a switching oil passage 68. Switching oil passage 68
Is connected to the main gallery 51 and the switching valve 6
7 is also connected to the inlet 69. High speed side switching oil passage 56A
Is connected to the high-speed side discharge port 70A of the switching valve 67, and the medium-low speed side switching oil passage 56B is connected to the medium-low speed side discharge port 70B of the switching valve 67. The switching valve 67 is for operating the electromagnetic solenoid 71 to be turned on and off by a control circuit (not shown) to move the spool 72 forward and backward. That is, when the electromagnetic solenoid 71 is turned on, the spool 72 is retracted so that the introduction port 69 and the high speed side discharge port 70A communicate with each other.
Further, the spool 72 advances by the OFF operation of the electromagnetic solenoid 71, and the introduction port 69 and the medium-low speed side discharge port 70B communicate with each other.

Reference numeral 73A in FIGS. 7, 8 and 12
Is formed in the guide groove 34 of the high speed slider 26,
It is a high speed side oil groove that connects the high speed side oil chamber A and the high speed side oil passage 55A. Similarly, reference numeral 73B is similarly formed in the guide groove 34 of the high-speed slider 26, so that the medium-low speed side oil chamber B is formed.
And an intermediate-low speed side oil passage 55 </ b> B. Further, the slide cam lifter 27 of the high-speed slider 26, the push piece 28 and the shim 57, and the piston shim 45 of the medium-low speed slider 24 are made of high hardness material.

Next, the operation and effect will be described.

When the engine is rotating at a low speed, the control circuit (not shown) causes the electromagnetic solenoid 7 of the switching valve 67 shown in FIG.
Turn 1 OFF. Then, the high-pressure oil in the main gallery 51 is guided to the medium / low speed side switching oil passage 56B, passes through the medium / low speed side oil passage 55B and the medium / low speed side oil groove 73B, and reaches the low speed side oil chamber B in the high speed slider 26. . Therefore, the slide cam lifter 27 slides in the direction shown in FIG. 7, and the push piece 28 moves the slide cam lifter 27.
Of the push piece 28 does not come into contact with the lift plate 42. At this time, the push plate 25 of the medium-low speed slider 24 shown in FIG. 1 contacts the lift plate 42. As a result, the medium / low speed cam 20 operates the intake valve 11 and the exhaust valve 12 via the medium / low speed slider 24 at a valve lift and valve timing suitable for the medium / low speed rotation range of the engine.

When the engine rotates at a high speed, the control circuit turns on the electromagnetic solenoid 71 of the switching valve 67 shown in FIG. Then, the high-pressure oil in the main gallery 51 is guided to the high-speed side switching oil passage 56A, reaches the high-speed side oil chamber A of the high-speed slider 26 through the high-speed side oil passage 55A and the high-speed side oil groove 73A. Therefore, the slide cam lifter 27 slides in the direction shown in FIG. 8, and the push piece 28 moves the high-speed side cam surface 61A of the slide cam lifter 27.
And pushes out from the high speed slider 26, and the tip of the push piece 28 contacts the lift plate 42. As a result, the high-speed cams 21 and 22 shown in FIG. 2 pass through the high-speed slider 26 and the intake valve 1 at a valve lift and valve timing suitable for the high-speed rotation range of the engine.
1 and the exhaust valve 12 are operated. At this time,
Push plate 2 of slider 24 for medium and low speed shown in FIG.
5 does not come into contact with the lift plate 42, and the middle / low speed slider 24 is idle.

According to the above-described embodiment, the medium and low speed cams 20 and the high speed cams 21 and 22 are arranged on the cam shaft 23, and the medium and low speed slider 24 and the high speed cam 21 are provided directly below the medium and low speed cam 20. High speed sliders 26 are arranged directly under the high speed sliders 22 and 22, respectively, and the forward / backward operation of the push piece 28 in the high speed sliders 26 causes the medium / low speed sliders 24 to contact the intake valve 11 and the exhaust valve 12, or high speed sliders. Since the contact between the slider 26 and the intake valve 11 and the exhaust valve 12 is selectively switched to switch the operation of the medium-low speed cam 20 and the high-speed cams 21 and 22, the direct hit type DOHC four-cycle engine. In the intake valve 11 and the exhaust valve 12
It is possible to improve the output characteristic of the engine by changing the valve lift and the valve timing of the above according to the engine speed.

The medium-low speed slider 24 is used when the engine is running at a low speed, and the high-speed slider 2 is used when the engine is running at a high speed.
6 operate individually, and further, the slider spring 33 of the medium-low speed slider 24 and the high-speed slider 2 are operated.
The slider spring 37 of 6 functions as an auxiliary spring for the valve springs 16 of the intake valve 11 and the exhaust valve 12. From these, the variable valve timing lift device 17 capable of high rotation can be provided.

Further, the intake valve 11 and the exhaust valve 12, the medium and low speed cams 20 and the high speed cams 21 and 2
Since the slider 24 for medium and low speeds and the slider 26 for high speeds are only disposed between the variable valve timing lift device 17 and the control unit 2, the space for the variable valve timing lift device 17 can be made compact. Therefore, it is not necessary to significantly change the design of the cylinder head 3 and the head cover of the 4-cycle engine 1, and the increase in cost can be suppressed.

Also, the slide cam lifter 27 of the high speed slider 26 slides, and the slide cam lifter 27 slides.
Since the forward / backward state of the push piece 28 can be maintained by the solid contact between the cam surface 60 and the push piece 28, a highly accurate and highly reliable variable valve timing lift device can be obtained.

[0034]

As described above, according to the variable valve timing lift device for a four-cycle engine according to the present invention, the medium and low speed cams which are arranged directly above the intake and exhaust valves and have different cam profiles, and It is placed between the camshaft where the high speed cam is arranged adjacent to the middle and low speed cam and the intake / exhaust valve, and abuts the middle / low speed cam. A slider for a medium / low speed provided with a push plate capable of abutting, and a slide cam which is disposed between the high speed cam and the intake / exhaust valve and abuts against the high speed cam and is slidably housed in the forward and reverse directions. Provided so that the push piece comes into contact with the cam surface of the lid, and this push piece advances and retreats toward the intake / exhaust valve by the cam surface and can come into contact with the head of this valve. The high-speed slider and the slide cam lifter in the forward and reverse directions according to the engine speed, and either the push plate of the medium-low speed slider or the push piece of the high-speed slider is sucked or exhausted. In the direct hit type DOHC four-cycle engine, the valve lift and the valve lift timing of the intake / exhaust valve are changed according to the engine speed. The output characteristics of can be improved.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a variable valve timing lift device for a 4-cycle engine according to the present invention.

FIG. 2 is a sectional view taken along line II-II in FIG.

FIG. 3 is a sectional view taken along line III-III in FIG.

FIG. 4 is a perspective view showing the medium-low speed slider of FIG.

5 is a cross-sectional view taken along the line VV of FIG.

6 is a perspective view showing the high-speed slider of FIG.

FIG. 7 is an enlarged cross-sectional view of a high speed slider showing an operating state of a slide cam lifter of the high speed slider in an engine low speed rotation range.

FIG. 8 is an enlarged cross-sectional view of the high-speed slider showing the operating state of the slide cam lifter of the high-speed slider when the engine rotates at high speed.

FIG. 9 is a view on arrow IX in FIG. 7.

FIG. 10 is a view on arrow X in FIG. 7.

11 is a cross-sectional view taken along the line XI-XI of FIG.

FIG. 12 is a view on arrow XII in FIG.

FIG. 13 is an XIII arrow view showing the stopper plate in FIG.

14 is an XIV arrow view of FIG. 1. FIG.

[Explanation of symbols]

 1 4-cycle engine 11 intake valve 12 exhaust valve 17 variable valve timing lift device 20 low speed cam 21, 22 high speed cam 23 camshaft 24 medium and low speed slider 25 push plate 26 high speed slider 27 slide cam lifter 28 push piece 29 actuation Switching circuit 42 Lift plate 56A High speed side switching oil passage 56B Medium / low speed side switching oil passage 60 Cam surface 67 Switching valve 68 Switching oil passage A High speed side oil chamber B Medium / low speed side oil chamber

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] April 14, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Change

[Correction content]

Further, as shown in FIG. 3, a cylinder hole 44 opening upward is formed in the central portion in the longitudinal direction of the medium and low speed slider 24. A piston shim 45 capable of contacting the middle and low speed cam 20 is slidably fitted into the opening of the cylinder hole 44. A high-pressure oil chamber 46 is formed by being surrounded by the cylinder hole 44 and the piston shim 45. A guide shaft oil passage 47 is formed on one side of the guide shaft 31, and the guide shaft oil passage 47 communicates with the high pressure oil chamber 46 via the slider oil passage 48 and the piston shim oil passage 49. Pressure oil (hydraulic pressure of ^{2 to 4} kg / cm ² ) from the main gallery 51 shown in FIG. 2 is supplied to the guide shaft oil passage 47 through the lash adjust oil passage 50 formed in the cylinder head 3, and this pressure oil is supplied. But,
The slider oil passage 48 and the piston shim oil passage 4 shown in FIG.
9 is introduced into the high pressure oil chamber 46. In the high-pressure oil chamber 46, a check valve 53 urged by a check valve spring 52 to allow only the supply of pressure oil from the piston shim oil passage 49 is arranged. Therefore, the piston shim 45 is constantly pressed against the medium-low speed cam 20 by the pressure oil introduced into the high-pressure oil chamber 46, and the medium-low speed cam 20 and the piston shim 45 are automatically adjusted to zero rush (rush time). Adjust). Then, when the cam 20 for medium and low speeds is operated and the repulsive force of the valve spring 16 tries to push back the medium and low speed sliders 24, the high pressure oil chamber 46.
High pressure oil (50-100kg / cm ² )
Is generated and the intake and exhaust valves 11 and 12 are pushed down.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0021

[Correction method] Change

[Correction content]

As shown in FIGS. 7 and 8, a cylinder hole 54 extending in the longitudinal direction is passed through the high speed slider 26. The slide cam lifter 27 is housed in the cylinder hole 54 so as to be slidable in the forward and reverse directions.
The inside of the slide hole 54 is divided into a high speed side oil chamber A and a low speed side oil chamber B by the slide cam lifter 27. The high speed side oil chamber A communicates with a high speed side switching oil passage 56A formed in the cylinder head 3 via a high speed side oil passage 55A formed in one of the guide shafts 35. Further, the low speed side oil chamber B is communicated with a medium / low speed side switching oil path 56B formed in the cylinder head 3 via a medium / low speed side oil passage 55B formed in the other guide shaft 35.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0028

[Correction method] Change

[Correction content]

When the engine is rotating at a low speed, the control circuit (not shown) causes the electromagnetic solenoid 7 of the switching valve 67 shown in FIG.
Turn 1 OFF. Then, the pressure oil in the main gallery 51 is guided to the medium / low speed side switching oil passage 56B, passes through the medium / low speed side oil passage 55B and the medium / low speed side oil groove 73B, and reaches the low speed side oil chamber B in the high speed slider 26. . Therefore,
The slide cam lifter 27 slides in the direction shown in FIG. 7, the push piece 28 comes into contact with the low speed side cam surface 61B of the slide cam lifter 27 and retracts into the high speed slider 26, and the tip end portion of the push piece 28 lifts. It does not contact the plate 42. At this time, the push plate 25 of the medium-low speed slider 24 shown in FIG. 1 contacts the lift plate 42. As a result, the medium / low speed cam 20 operates the intake valve 11 and the exhaust valve 12 via the medium / low speed slider 24 at a valve lift and valve timing suitable for the medium / low speed rotation range of the engine.

[Procedure amendment 4]

[Document name to be amended] Statement

[Name of item to be corrected] 0029

[Correction method] Change

[Correction content]

When the engine rotates at a high speed, the control circuit turns on the electromagnetic solenoid 71 of the switching valve 67 shown in FIG. Then, the pressure oil in the main gallery 51 is guided to the high speed side switching oil passage 56A, passes through the high speed side oil passage 55A and the high speed side oil groove 73A, and reaches the high speed side oil chamber A in the high speed slider 26. Therefore, the slide cam lifter 27 slides in the direction shown in FIG.
8 contacts the high speed side cam surface 61A of the slide cam lifter 27 and advances from the high speed slider 26, and the tip end of the push piece 28 contacts the lift plate 42. As a result, the high-speed cams 21 and 22 shown in FIG. 2 pass through the high-speed slider 26 and the intake valve 11 with the valve lift and valve timing suitable for the high-speed rotation range of the engine.
And the exhaust valve 12 is operated. At this time, the push plate 25 of the medium-low speed slider 24 shown in FIG.
Does not contact the lift plate 42, and the slider 2 for medium and low speeds
No. 4 operates empty.

Claims (1)

[Claims] 1. A camshaft, which is arranged directly above an intake / exhaust valve, and in which a medium speed cam and a high speed cam having different cam profiles are adjacently arranged, said medium speed cam and said intake / exhaust gas. A slider for medium and low speeds, which is arranged between the valves and abuts on the cam for the medium and low speeds, and which has a push plate on the intake / exhaust valve side capable of abutting on the head of the valve; The push piece abuts on the cam surface of the slide cam lifter which is arranged between the exhaust valves and abuts on the high speed cam, and is slidably housed in the forward and reverse directions. A high-speed slider provided so that it can move forward and backward toward the exhaust valve and come into contact with the head of this valve, and the slide cam lifter can be slid forward and backward depending on the engine speed. A four-cycle engine including: an operation switching circuit that brings one of the push plate of the medium-low speed slider and the push piece of the high-speed slider into contact with the head of the intake / exhaust valve. Variable valve timing lift device.