JP2003106120A - Valve system of engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a whirl-stop of a tappet in the valve system of an engine having the tappet provided with a lift variable mechanism, by a simple constitution where machining is performed easily. SOLUTION: The cylindrical tappet 50 is divided into a center tappet 51 and a side tappet 52, enabling them to couple together and uncouple by a locking means. The locking means is constituted so that the base circle parts of cams 70a, 70b and 70c abutting on the tappet 50 are communicated in a straight line by through-holes 56, 61a and 61b, where a hydraulic plunger 71, a lock pin 72, a pressing spring 73, etc., are disposed. A fitting hole 77c is provided on the outer peripheral side of a bush 77 fitted and fixed to the end part of one of the through-hole 61a of the side tappet 52. A spherical member 86 is disposed in the fitting hole 77c and held by a holding member 87 having a bending claw part 87a, regulating the rotation of the tappet 50 in cooperation with a groove 88 on the inner periphery of a tappet guide hole 25.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine valve operating system, and more particularly to a direct type valve operating system in which a valve is directly driven by a cam via a tappet.

[0002]

2. Description of the Related Art In a direct type valve operating system in which an intake valve and an exhaust valve of an engine for an automobile or the like are directly driven by a cam via a tappet, a split tappet type variable lift mechanism is constructed to operate at high speed and at low speed. It is conventionally known that the operation of a variable lift mechanism is switched by hydraulic pressure during operation to change the operating lift characteristics of a valve between a large lift state and a small lift state, or a lift state and a non-lift state. Then, since the working hydraulic pressure is supplied to the lift variable mechanism from the oil passage on the cylinder head side through the oil passage on the tappet side, it is necessary to prevent the cylindrical tappet from rotating with respect to the cylinder head. For example, as described in German Patent Application Publication No. 19721208A1,
It has been practiced to arrange detent pins, balls, etc. between the outer circumference of the tappet and the cylinder head.

[0003]

However, in the conventional rotation-stopping structure in which the pins, balls, etc. are arranged between the outer circumference of the tappet and the cylinder head, a holding portion for holding the pins, balls, etc. is separately processed in the tappet body. This complicates the tappet processing process and structure.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a valve operating system for an engine having a tappet equipped with a split tappet type variable lift mechanism, so that the detent of the tappet can be achieved by a simple and easy processing structure.

[0005]

SUMMARY OF THE INVENTION An engine valve operating system according to the present invention comprises a cylindrical tappet which abuts a cam and slides in a tappet guide hole of a cylinder head side member in a valve opening / closing direction to lift a valve. The tappet is divided into a center tappet in the center of the cam axis and side tappets on both sides of the cam axis so that the center tappet and the side tappet can move relative to each other in the sliding direction of the tappet, and they can be mutually locked by a locking means. The cams are two types of cams having different cam profiles, the center tappet is in contact with one cam and the side tappet is in contact with the other cam, and the locking means is the center tappet. A center tappet that penetrates through the side tappet and extends in the cam axis direction and is slidably fitted in the through hole and driven by hydraulic pressure. A lock pin that couples with the side tappet and controls relative movement in the sliding direction of the tappet, and a spring that urges the lock pin to a position where the center tappet and the side tappet are disengaged from each other and can move relative to each other in the sliding direction of the tappet. In the valve operating device of the engine, which is configured by means of the locking means, and in which the drive characteristics of the valve can be changed by connecting and disconnecting the center tappet and the side tappet, the lock pin is connected to one end of the through hole of the tappet in the connecting direction of the lock pin. Fit a bush with a stopper that restricts movement,
A groove extending in the tappet sliding direction is provided on the inner periphery of the tappet guide hole, and the tappet rotation is regulated at the end of the bush on the outer peripheral side of the tappet in cooperation with the groove on the inner periphery of the tappet guide hole. The present invention is characterized in that the stopper member is supported.

In this case, a valve operating device of a split tappet type which is capable of changing the drive characteristics of the valve by switching the lock means by hydraulic pressure is constructed, and the through hole of the tappet is formed to regulate the movement of the lock pin of the lock means. With the configuration using the bush fitted and fixed to one end, the through-hole can be retained as a simple hole and the detent member can be securely held. Therefore, the tappet body does not need to be separately processed for holding the rotation stopping member, and the tappet structure is simple and the processing is easy.

This valve operating device has two types of cams, a high-speed cam having a large lift amount cam profile and a low-speed cam having a small lift amount cam profile. Aside from the contact, the side tappet is arranged to contact the low speed cam, and the valve is switched between the low speed cam drive mode and the high speed cam drive mode by connecting and disconnecting the center tappet and the side tappet by the locking means. May be

Further, the bush has a partition wall as the stopper portion at an axially central portion, a fitting hole for fitting a lock pin at one end across the partition wall, and a rotation hole at the other end. It is preferable to have a fitting hole for fitting the stopper member and a through hole for communicating both fitting holes in the partition wall, whereby the through hole of the partition wall acts as a breath hole and the lock pin Moves smoothly. Moreover, the processing is easy.

Further, in this valve operating device, the tappet stop member is preferably spherical, and the spherical tappet stop member is fitted to the bush by the holding member having the bent claw portion. It is preferable to hold it in a fitting hole. In this case, the tappet rotation stopping member can be held only by bending the bending claw portion of the holding member, and the assembling can be performed by a simple operation.

Further, in this valve operating device, the tappet has a substantially rectangular shape in which the center tappet is long in the cam sliding contact direction when viewed from the cam side in the tappet axial direction, and the side tappets are arranged on both sides of the tappet so that the entire tappet is substantially circular. The hydraulic plunger is slidably fitted into the through hole portion that penetrates one of the side tappets of the through hole that extends through the center tappet and the side tappet and extends in the cam axis direction, and operates on the back surface of the hydraulic plunger. An oil passage is formed in the one side tappet, which forms a hydraulic chamber and supplies hydraulic oil to the operating hydraulic chamber, and the lock pin is a portion that penetrates the center tappet of the through hole so as to be driven by a hydraulic plunger. The bush and the detent member may be attached to a portion of the through hole that penetrates the other side tappet, whereby the split taper Locking means capable of coupling and separating the door with a simple structure is obtained.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

1 to 3 show structures of a tappet and a tappet guide hole portion in an engine valve operating system according to an example of an embodiment of the present invention. This example is DOHC
(Double overhead cam) series multi-cylinder engine,
Equipped with a direct type valve operating device that directly drives the intake valve and exhaust valve by cams via tappets, and the valve operating device is a variable lift that can change the valve lift during high speed operation and low speed operation of the engine. Equipped with means.

The cam carrier 11 at the upper part of the cylinder head of this engine is provided with a tappet guide portion 27 forming a cylindrical tappet guide hole 25. In the tappet guide hole 25, a tappet 50 is provided with a cam 70a,
It is slidably accommodated so as to reciprocate the intake valve and the exhaust valve by being driven by 70b and 70c. In the case of an engine having no cam carrier, the tappet guide portion 25 is provided on the cylinder head body.

The tappet 50 has a cylindrical shape as a whole, and constitutes a center cam contact surface of a substantially rectangular planar shape which is long in the cam sliding contact direction, and is arranged on both sides of the cam contact surface of the center tappet 51. The center tappet 51 and the side tappet 52 are divided into a side tappet 52 that constitutes a side cam abutment surface having a substantially circular flat shape together with the center cam abutment surface of the center tappet 51. It is movable and can be coupled and disengaged from each other by a lock mechanism described later.

The side tappet 52 has a structure in which a pair of left and right tubular portions 52a and 52b having side cam contact surfaces are integrally connected by a lower connecting portion 52c which constitutes an abutting portion with a stem end of a valve. A tappet spring 53 is installed on the lower connecting portion 52c, and a center tappet 51 is incorporated between the tappet spring 53 and the left and right cylindrical portions 52a and 52b. In the tappet 50, the lower surface of the lower connecting portion 52c contacts the stem ends of the intake valve and the exhaust valve via a shim (not shown).

The center tappet 51 is a tappet parallel to the cam sliding contact direction and the tappet sliding direction that extend vertically downward from the edges of both long sides along the cam sliding contact direction of the above-mentioned substantially rectangular flat center cam contact surface. It has a pair of side end surfaces 54a, 54b which are symmetrical with respect to the axis, and has a circular arc-shaped cross section which is vertically downward from the edges of both short sides and is parallel to the tappet sliding direction and symmetrical with respect to the tappet axis. A pair of outer peripheral surfaces 55a, 55b
Have.

Further, the center tappet 51 is formed with a through hole 56 which is parallel to the cam axis direction and which is concentric with the tappet axis and penetrates from one side end surface to the other side end surface.

Further, the center tappet 51 has an outer peripheral surface 55a, 55b on the side of the side tappet 52 which is continuous with the outer peripheral surfaces 55a, 55b at the outer peripheral surfaces 55a, 55b. Overhangs and the inside is lateral end faces 54a, 54b
Is formed so as to extend in the direction of the cam axis at a substantially right angle from the above, and overhangs 57a to 57d that form a sliding contact surface with the side tappet 52 are formed over substantially the entire length in the direction of the tappet axis.

The side tappet 52 extends vertically downward from the inner edges of the pair of left and right cylindrical portions 52a and 52b, which face each other along the cam sliding contact direction of the side cam contact surfaces, and tappet sliding. The inner end surfaces 58a and 58b are parallel to each other and symmetrical with respect to the tappet axis, and the inner end surfaces 58a and 58b are provided with predetermined side end surfaces 54a and 54b of the center tappet 51 at both ends in the cam sliding contact direction. Projection portions 59a facing each other in a non-sliding contact state at intervals of
59d, which extends vertically downward from the edge of the side cam contact surface on the cam shaft outer end side, is parallel to the tappet sliding direction, and is symmetrical with respect to the tappet axis.
0a and 60b.

The tubular portion 52 of the side tappet 52
a and 52b are parallel to the cam axis direction and concentric with the tappet axis from the inner end surfaces 58a and 58b to the outer peripheral surface 60a.
The through holes 61a, 61b penetrating the 60b are in direct communication with the through hole 56 of the center tappet 51 when the center cam sliding contact surface of the center tappet 51 and the side cam sliding contact surface of the side tappet 52 are flush with each other. Has been formed.

The tubular portion 52 of the side tappet 52
The end portions of the inner end surfaces 58a, 58b of the a, 52b in the cam sliding contact direction are in sliding contact with the sliding contact surfaces of the overhanging portions 57a to 57d formed at the edges of the center tappet 51 in the cam sliding contact direction. The sliding contact portions 62a to 62d are formed in a rib shape over substantially the entire length in the axial direction of the tappet.

Center tappet 51 and side tappet 52
Is the side end surfaces 54a, 54b of the center tappet 51.
And projecting portions 59a-5 located at both ends of the inner end surfaces 58a, 58b of the tubular portions 52a, 52b of the side tappet 52.
9d face each other at a predetermined interval in a non-sliding contact state, and also the protruding portions 57a to 57d of the center tappet 51 and the sliding contact portions 62 of the tubular portions 52a and 52b of the side tappet 52.
Sliding contact with a to 62d is possible.

The camshaft 7 includes two side cams 70a and 70b (low speed cams) having the same cam profile with a low lift amount for each tappet 50.
Between the two side cams 70a, 70b,
It is provided with one high-speed center cam 70c (high-speed cam) having a high lift amount cam profile.

Center tappet 51 and side tappet 52
Of the center tappet 51 with the center cam sliding contact surface of the center tappet 51 contacting the base circle portion of the center cam 70c and the side cam sliding contact surface of the side tappet 52 contacting the base circle portions of the side cams 7oa and 70b. The center cam sliding contact surface and the side cam sliding contact surface of the side tappet 52 are substantially flush with each other, and in this state, the through hole 56 of the center tappet 51 and the through holes 61a and 61b of the side tappet 52 are in straight line communication.

The side tappet 52 has an outer peripheral surface 60.
The a and 60b substantially contact the inner peripheral surface of the tappet guide hole 25 in the cam axis direction. A predetermined gap is maintained between the protrusions 59a to 59d of the side tappet 52 and the center tappet 51, and this gap allows the side tappet 52 and the center tappet 51 of the tappet 50 to be inside the tappet guide holes 25 and 26. Machining error is allowed.

As for the through hole 56 (through hole portion) of the center tappet 51 and the through holes 61a and 61b (through hole portion) of the side tappet 52 of the tappet 50, the center cam sliding contact surface of the center tappet 51 is the center cam as described above. A series of through holes are formed by abutting on the base circle portion of 70c, and in a state where the side cam sliding contact surface of the side tappet 52 abuts on the base circle portion of the side cams 70a and 70b, communicate in a straight line in the cam axis direction. Then, in this through hole, it is possible to project to a through hole portion (through hole 61b) that penetrates one tubular portion 52b of the side tappet 52 and a through hole portion (through hole 56) that penetrates the center tappet 51 by hydraulic pressure. As described above, the hydraulic plunger 71 is built into the through hole portion (through hole 56) penetrating the center tappet 51, and the side tappet 52 is hydraulically driven through the hydraulic plunger 71.
Through hole portion (through hole 6
1a) has a lock pin 72 built therein so that it can be projected, and the lock pin 72 is pressed so as to urge the center tappet 51 and the side tappet 52 away from each other so that they can move relative to each other in the sliding direction of the tappet. The spring 73 is built in.

The center tappet 51 and the side tappet 5 are formed by the through holes 56, 61a and 61b, the hydraulic plunger 71, the lock pin 72, the pressing spring 73 and the like.
Locking means for connecting and disconnecting the two with each other is configured.

In the through-hole portion (through-hole 56) on the side of the center tappet 51, bushes 74 are provided at both ends of the divided portion with the side tappet 52 so as to be flush with the side end surfaces 54a and 54b of the center tappet 51. 75 are inserted and fixed. Among them, the bush 75 fixed to the end portion on the hydraulic plunger 71 side is a collar portion 76 on the outer periphery of the lock pin 72.
To restrict the movement of the lock pin 72 to the hydraulic plunger 71 side. The bush 74 fixed to the other end holds the pressing spring 73 in a compressed state between the bush 74 and the collar portion 76 on the outer periphery of the lock pin 72.

Further, bushes 77, 78 are provided in the through hole portions (through holes 61a, 61b) on the side tappet 52 side.
Are inserted and fixed. Of which, the hydraulic plunger 71
Through-hole portion (through-hole 61
The bush 78 inserted and fixed in b) has a fitting hole 78b, which is closed on the outer peripheral side of the tappet by an end wall 78a, and in which the hydraulic plunger 71 is slidably fitted.

The bush 77 inserted into and fixed to the through hole portion (through hole 61a) of the other tubular portion 52a has a partition wall 77a as a stopper portion for restricting the movement of the lock pin 72 in the central portion in the axial direction. Then, the fitting hole 77b for fitting the end of the lock pin 72 inward with the partition wall 77a sandwiched therebetween.
Has a fitting hole 77c on the outer peripheral side of the tappet for fitting a later-described locking member, and the partition wall 77a has both fitting holes 7c.
There is a through hole 77d that connects 7b and 77c.

The bushes 77, 78 on the side tappet 52 side have their end portions on the side of the center tappet 51 projected from the through hole portions (through holes 61a, 61b) by a predetermined dimension so that the through hole portions (through holes) of the center tappet 51 The bushes 74, 75 inserted and fixed in the holes 56) face each other at predetermined intervals.

In the locking means having such a structure, the hydraulic plunger 71 is provided with a lock pin 72 when hydraulic pressure is applied.
The lock pin 72 is moved to the side and the end portion is inserted into the through hole portion (through hole 56) on the side of the center tappet 51, and the lock pin 72 is moved against the pressing spring 73 to move the lock pin 72.
End portion of the side tappet 52 through hole portion (through hole 61
Introduce a). At this time, the hydraulic plunger 71 straddles the split portion of the center tappet 51 and the tubular portion 52b of the side tappet 52, and the lock pin 72
Straddles the divided portion of the center tappet 51 and the other tubular portion 52a of the side tappet 52, and they cooperate to join the center tappet 51 and the side tappet 52 into a locked state. When the hydraulic pressure is released, the pressing spring 73 moves the lock pin 72 to the hydraulic plunger 71 side, and the hydraulic plunger 71 returns to the original position,
Both end surfaces of the lock pin 72 are flush with the split portion of the center tappet 51 and the side tappet 52 in the through hole 56 of the center tappet 51, and the center tappet 51 is disengaged from the side tappet 52 and is unlocked (locked). It will be released).

As described above, the locking means can be switched between the locked state and the unlocked state by the hydraulic pressure. In the locked state, the side tappet 52 and the center tappet 51 are locked.
And the side tappet 52 and the center tappet 51 driven by the center cam 70c cooperate to lift the intake valve and the exhaust valve in a high speed manner, and the center tappet 51 is separated from the side tappet 52 in the unlocked state. And slide relatively, and the side cams 70a, 70b
Driven to lift the intake valve and the exhaust valve in a low speed manner.

The tappet 50 has a cylindrical portion 52a having a through hole 61b for accommodating the hydraulic plunger 71 of the side tappet 52, and an oil passage consisting of three processing holes for supplying working hydraulic pressure to the lock mechanism. 81, 82, 83 are provided. The first oil passage 81 is formed by a processed hole formed from the side of the side tappet 52 opposite to the cam side, and extends in the tappet sliding direction at a position offset from the cam axis direction center plane. In addition, the second oil passage 82 is formed by a processing hole that is vertically formed from the outer peripheral surface of the side tappet 52 toward the first oil passage 81. It can communicate with the hydraulic oil supply passage 93. The third oil passage 83 is connected to the side tappet 5
The through hole 61b of the second through hole 61b is formed from a hole on the outer peripheral side of the tappet toward the cam side end of the hole for forming the first oil passage 81. The tappet outer peripheral side end of the through hole 61b is communicated with the first oil passage 81.

One tubular portion 52b of the side tappet 52
The bush 78, which is inserted and fixed in the through hole 61b containing the hydraulic plunger 71, has an opening 84 for communicating the third oil passage 83 with the working hydraulic chamber at the back of the hydraulic plunger 71.
Are formed.

Further, in the tappet 50, a fitting hole 77c on the outer peripheral side of the tappet of a bush 77 fixed to the through hole 61a of the tubular portion 52a which does not include the hydraulic plunger 71.
A spherical member 86 as a tappet stopping member is rotatably held in a state of partially protruding from the outer circumference of the tappet.
The spherical member 86 has a ring-shaped holding member 87 having a bent claw portion 87a inserted from the outside along the inner circumference of the through hole 61a, and has a reduced diameter portion provided on the outer surface of the end portion of the bush 77. It is rotatably held by being fitted and fixed in between.

A spherical member 86, which serves as a tappet stopping member and is held on the tappet 50 side, is engaged with the inner circumference of the tappet guide hole 25 provided in the cam carrier 11 so as to move only in the sliding direction of the tappet. To make it possible
A groove 88 extending in the tappet sliding direction is provided. The spherical member 86 is the groove 8 on the inner circumference of the tappet guide hole 25.
The rotation of the tappet 50 is regulated in cooperation with 8.

The side end faces 5 of the center tappet 51 facing the tubular portions 52a and 52b of the side tappet 52 are opposite to each other.
4a and 54b project toward the inner end surfaces 58a and 58b of the tubular portions 52a and 52b of the side tappet 52 in the cam axis direction below the through hole 56, and the side tappet 5
Locking portions 89a and 89b that are locked to the ends of the bushes 77 and 78 that protrude inward from the through holes 61a and 61b of the two tubular portions 52a and 52b are formed. By locking the locking portions 89a and 89b on both sides to the bushes 77 and 78 on the side tappet 52 side, the center tappet 51 is restricted from moving upward in the tappet sliding direction.

The cam carrier 11 is provided with an oil gallery 91 that extends in the cylinder head longitudinal direction (cam axis direction) in the vicinity of the tappet guide hole portion 27 of each cylinder, and the oil pressure from the oil gallery 91 is applied to each tappet. A hydraulic oil supply passage 93 that branches from the oil gallery 91 and opens to the inner peripheral surface of the tappet guide hole 25 is provided so as to supply the variable lift mechanism 50.

The hydraulic oil supply passage 93 is provided in the cam carrier 11
Of the tappet guide hole 25. The tappet guide hole 25 is opened in the oil gallery 91 at a position offset from the center of the cylinder column direction by a predetermined amount in the column direction with respect to the tappet guide hole 25. It is opened at a position offset from the center plane in the cam shaft direction with respect to the inner peripheral surface of the.

At the opening of the inner peripheral surface of the tappet guide hole 25 of the hydraulic oil supply passage 93, the side cam sliding contact surface of the side tappet 52 has side cams 70a, 7ob.
The second oil passage 8 provided in the one tubular portion 52b of the side tappet 25 in a state of being in contact with the base circle portion of
Communicate with two.

The hydraulic pressure for actuating the hydraulic plunger 71 of the locking means of the tappet 50 is controlled by a hydraulic control valve (not shown), and the operating hydraulic pressure is supplied via the hydraulic pressure supply passage 93 at a high speed when the locking means of the tappet 50 is locked. Supplied to the chamber. At that time, the hydraulic pressure from the oil pump (hydraulic pressure source) is guided to the oil gallery 91 via the hydraulic control valve, the side cam sliding contact surface of the side tappet 52 contacts the base circle portions of the side cams 70a and 70b, and the hydraulic oil is supplied. The opening in the inner peripheral surface of the tappet guide hole 25 of the passage 93 is introduced into the second oil passage 82 via the hydraulic oil supply passage 93 in a state where the opening of the tappet guide hole 25 communicates with the second oil passage 82 of the side tappet 25. Oil passage 82 to first oil passage 81, third
It is introduced into the through hole 61b through the oil passage 83 and is supplied to the working hydraulic chamber behind the hydraulic plunger 71.

[0043]

As is apparent from the above description, according to the present invention, in a valve operating system of an engine having a tappet provided with a split tappet type variable lift mechanism, the detent of the tappet can be easily and easily machined. Can be achieved by configuration.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional plan view of a tappet and a tappet guide hole portion in an example of an embodiment of the present invention.

FIG. 2 is a vertical cross-sectional view of a tappet and a tappet guide hole portion in a cam axis direction according to an example of an embodiment of the present invention.

FIG. 3 is a partial vertical cross-sectional view of the tappet and the tappet guide hole portion of the embodiment of the present invention, which is orthogonal to the cam axis direction.

[Explanation of symbols]

11 cam carrier 25 Tappet Guide Hall 27 Tappet guide 50 tappets 51 Center Tappet 52 Side Tappet 56 through hole 61a, 61b Through hole 70a, 70b Side cam 70c Center cam 71 Hydraulic plunger 72 Lock pin 73 Pressing spring 74,74,77,78 Bush 77a bulkhead 77b, 77c Fitting part 77d through hole 81 First oil passage 82 Second oil passage 83rd oil passage 86 Spherical member 87 holding member 87a Bending claw part 88 groove 91, 92 Oil Gallery 93, 94 hydraulic oil supply passage

Continued front page    F term (reference) 3G016 AA02 AA06 AA19 BA37 BB01                       BB04 BB30 BB31 BB37 BB40                       CA02 CA04 CA12 CA16 CA19                       CA20 CA29 CA31 CA43 CA52                       DA01 DA22 EA01 FA35 FA37                       FA38 GA01 GA02                 3G018 AB02 AB17 BA21 BA22 CA19                       DA17 DA18 DA29 DA51 DA52                       DA83 EA05 EA06 EA07 EA31                       FA02 FA03 FA06 GA14 GA17                       GA18

Claims (5)

[Claims] 1. A cylindrical tappet that abuts on a cam and slides in a tappet guide hole of a cylinder head side member in a valve opening / closing direction to lift a valve, wherein the tappet is a center tappet in a center in a cam axis direction. The center tappet and the side tappet are movable relative to each other in the sliding direction of the tappet and can be coupled and disengaged from each other by a locking means by dividing into side tappets on both sides in the cam axis direction, and the cam has a cam profile. As the two different types of cams, the center tappet contacts one cam and the side tappet contacts the other cam, and the locking means penetrates the center tappet and the side tappets in the cam axial direction. And a side tappet that is slidably fitted into the through hole and driven by hydraulic pressure to connect the center tappet and the side tappet. And a spring for urging the lock pin to a position where the center tappet and the side tappet are disengaged from each other and relatively movable in the sliding direction of the tappet. In the valve operating device of the engine, in which the drive characteristics of the valve can be changed by connecting / disconnecting the center tappet and the side tappet by the locking means, in the connecting direction of the lock pin at one end of the through hole of the tappet. A bush having a stopper portion that restricts the movement of the tappet guide hole is provided, a groove extending in the tappet sliding direction is provided on the inner circumference of the tappet guide hole, and the tappet guide is provided on the tappet outer peripheral side end portion of the bush. It is characterized in that the tappet stop member is supported so as to regulate the rotation of the tappet in cooperation with the groove on the inner circumference of the hole. Engine valve system. 2. The cam includes two types of cams, a high speed cam having a large lift amount cam profile and a low speed cam having a small lift amount cam profile. The center tappet contacts the high speed cam, and A structure in which the side tappet is arranged to abut on a low speed cam, and the valve is switched between a low speed cam drive mode and a high speed cam drive mode by connecting and disconnecting the center tappet and the side tappet by the locking means. 1. The engine valve operating system according to 1. 3. The bush has a partition wall serving as the stopper portion at a central portion in the axial direction, has a fitting hole for fitting the lock pin at one end portion with the partition wall sandwiched between the bushing, and the other end portion. The engine valve operating system according to claim 1, further comprising a fitting hole into which the rotation stopping member is fitted, and a through hole communicating with the fitting hole in the partition wall. 4. A configuration in which the tappet detent member is spherical, and the spherical tappet detent member is held in a fitting hole for fitting the detent member of the bush by a holding member having a bent claw portion. The valve operating system for the engine according to claim 3. 5. The tappet is configured such that the center tappet is a substantially rectangular shape that is long in the cam sliding contact direction when viewed from the cam side in the tappet axial direction, and side tappets are arranged on both sides of the center tappet so that the entire tappet is substantially circular. A hydraulic plunger is slidably fitted in a through hole portion penetrating one of the side tappets, which penetrates the center tappet and the side tappet and extends in the cam axis direction, and an operating hydraulic chamber is formed on the back surface of the hydraulic plunger. In addition, an oil passage for supplying hydraulic oil to the working hydraulic chamber is formed in the one side tappet, and the lock pin is arranged in a portion of the through hole that penetrates the center tappet so as to be driven by the hydraulic plunger. The engine valve operating system according to claim 3, wherein the bush and the rotation stopping member are attached to a portion of the through hole that penetrates the other side tappet.