JPH10280930A - Valve system for internal combustion engine with multiple cylinder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify the structure by decreasing the number of parts of a valve system used for internal combustion engines with multiple cylinders. SOLUTION: There are juxtaposed lower lift cams 41 (42, 43, 44) and higher lift cams 51 (52, 53, 54) for each cylinder on a camshaft 11 for internal combustion engines having a plurality of cylinders disposed in parallel with each of their axes. The higher lift cam is made movable in the radial direction of the camshaft 11. There are further provided a piston 70A for a first and a second cylinders which switches the high lift cam 51 to the operating condition or the non-operating condition, depending on the the operating condition of the internal combustion engines and a piston 70B for a third and fourth cylinders; which makes it possible to change over the operating condition of the higher lift and the lower lift cams. Thus, the rotating motion of the cams is transmitted as an opening and closing motions of an intake valve 7 of respective cylinder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve gear for opening and closing an intake / exhaust valve of an internal combustion engine by rotation of a cam, and more particularly to a valve gear having a mechanism for switching a cam according to an operation state of the internal combustion engine. Things.

[0002]

2. Description of the Related Art In order to improve fuel efficiency characteristics and output characteristics (torque characteristics) in the entire rotation speed range of an engine, a camshaft has a low lift cam for a low speed rotation range and a low lift cam for a high speed rotation range. High lift cams in parallel, and
There is a type in which a high lift cam is provided so as to be movable in a radial direction of a camshaft with respect to a low lift cam, and can be switched between a high lift cam operation state and a low lift cam operation state according to an operation state of the internal combustion engine.

[0003] Japanese Patent Application Laid-Open No. 7-133708 discloses an example of the seed valve apparatus. In this valve gear, a pin that pushes the high lift cam against the low lift cam in the radial direction of the cam shaft is provided on the cam shaft so as to be movable in the radial direction, and the pin moves in the cam shaft in the axial direction. It is engaged with the inclined surface of the piston which can be stored. This piston is urged in one direction by a return spring, and by supplying a predetermined amount of hydraulic pressure to a hydraulic chamber provided on the side opposite to the return spring, the piston is made elastic by the return spring. Then, the cam nose of the high lift cam is made to protrude more than the cam nose of the low lift cam to bring the high lift cam into operation. Then, by releasing the hydraulic pressure in the hydraulic chamber, the piston is pushed back to the hydraulic chamber side by the reaction force of the return spring, and the cam nose of the high lift cam and the cam nose of the low lift cam coincide with each other, so that the low lift cam operates.

[0004]

In the variable lift valve operating mechanism disclosed in the above publication, a high lift cam moving mechanism including a piston and a return spring is provided for each valve operating group, and the structure is complicated. In addition, there is a problem that the number of parts increases and the manufacturing cost increases.

Further, since there are many hydraulic chambers for introducing hydraulic pressure for moving the piston from the oil pump, a large amount of hydraulic oil is required, and the required capacity of the oil pump increases. For example, in the case of a DOHC inline four-cylinder engine, eight pistons are required only on the intake side, and an oil amount of (8 × piston area × piston stroke amount) must be supplied to the camshaft.

Further, since the operating oil also serves to lubricate the piston, oil leakage is inevitable, which also contributes to an increase in the amount of oil and increases the required capacity of the oil pump.
When the oil pump is driven by the output of the internal combustion engine, the increase in the capacity of these oil pumps is disadvantageous because it increases the mechanical loss of the internal combustion engine.

Further, a large amount of hydraulic oil is required, which adversely affects the responsiveness of the valve train. SUMMARY OF THE INVENTION The present invention has been made in view of such problems of the related art, and a problem to be solved by the present invention is to provide a valve operating device by providing a common cam operation switching unit for a plurality of cylinders. The aim is to simplify the structure, reduce costs, and improve responsiveness.

[0008]

The present invention has the following features to attain the object mentioned above. According to the present invention, a low lift cam and a high lift cam are provided side by side on a camshaft of an internal combustion engine having a plurality of cylinders so that the phases of their nose portions are substantially the same as each other, and the high lift cam is connected to a camshaft. A cam operation switching means for movably providing the low lift cam in the radial direction of the internal combustion engine and for switching the high lift cam to an operation state or a non-operation state according to an operation state of the internal combustion engine; In a valve operating device of a multi-cylinder internal combustion engine that enables the state to be switched and transmits the rotational movement of the cam as the opening and closing movement of a valve that opens and closes a gas flow path connected to the combustion chamber of each cylinder, the two cylinders adjacent to each other A valve operating device for a multi-cylinder internal combustion engine, characterized in that cam operation switching means is shared.

The number of cam operation switching means can be reduced as compared with the number of cylinders, the number of parts of the valve gear can be reduced, the structure is simplified, and the driving means of the cam operation switching means is reduced. Can be simplified, and the cost can be reduced.

In the present invention, examples of the multi-cylinder internal combustion engine include a gasoline engine and a diesel engine. Further, the valve train of the present invention can be applied to a four-stroke engine and a two-stroke engine, and can be applied to an arrangement of cylinders in series and a V-type arrangement. Examples of the valve train in the present invention include an intake valve and an exhaust valve.

In the present invention, the cam operation switching means includes a slider capable of reciprocating in a camshaft in an axial direction,
And driving means for driving the slider. In this case, the high lift cam is switched between an operating state and a non-operating state depending on the position of the slider. Examples of the driving unit include a hydraulic drive and an electromagnetic drive.

The slider has a switching portion corresponding to each of two adjacent cylinders that share cam operation switching means, and connects the two switching portions with a connecting portion having a smaller diameter than the switching portion. Can be configured. By doing so, the sliding resistance of the slider can be reduced, and the response is improved.

Further, the present invention comprises a plurality of the cam operation switching means which are shared, and the driving means for driving the cam operation switching means is such that the respective cam operation switching means are shifted in phase from each other in the direction of rotation of the cam shaft. It can be configured to include drive switching means for switching to be driven. With this configuration, the driving force of one driving unit can be switched by the driving switching unit and transmitted to the plurality of cam operation switching units, and the structure can be simplified.

[0014]

FIG. 1 is a block diagram showing an embodiment of the present invention.
17 will be described with reference to FIG. [First Embodiment] First, a first embodiment of the valve train of the present invention will be described.
The embodiment will be described with reference to FIGS. 1 to 8.

[0015] The valve train 10 is a four-wheel drive as an internal combustion engine.
This is an embodiment applied to a cycle in-line four-cylinder gasoline engine, and FIGS. 2A and 2B are a plan view of a cylinder and a basic mechanism diagram of one cylinder of the gasoline engine.

As is well known, in an inline four-cylinder gasoline engine, a first cylinder (indicated by # 1 in FIG. 2; the same applies hereinafter), a second cylinder (# 2), a third cylinder (# 3), and a fourth cylinder All the cylinders (# 4) are arranged in a line with their axis Q parallel to each other.

In the present embodiment, the ignition order is changed from the first cylinder (# 1) to the third cylinder (# 3) to the fourth cylinder (#
4) Suppose that it is set to the second cylinder (# 2).

FIG. 3 is a schematic configuration diagram of a gasoline engine. In this engine, a piston 2 is slidably provided in a cylinder 1 of each cylinder, and a combustion chamber 3 is formed between the cylinder 1 and the piston 2. A spark plug 4 is provided facing the combustion chamber 3, and an intake port 5 and an exhaust port 6 provided in the cylinder 1 open to the combustion chamber 3, respectively, and a pair of intake valves 7 and an exhaust port for opening and closing the intake port 5. A pair of exhaust valves 8 for opening and closing the fuel injection valve 6 are provided, and a fuel injection nozzle 9 is installed so that fuel can be injected into the intake port 5.

The valve train 10 of this embodiment employs a direct drive type DOHC. The intake valve 7 of each cylinder is opened and closed by an intake side high / low speed switching cam mechanism 12 provided on an intake camshaft 11. The exhaust valve 8 of each cylinder is driven to open and close by an exhaust-side high / low speed switching cam mechanism 14 provided on the exhaust camshaft 13.

A pair of intake valves 7 in each cylinder is connected to an intake side high / low speed switching cam mechanism 12 via one valve lifter 20.
To be lifted. That is, as shown in an example of the third cylinder (# 3) in FIG. 1, between the valve spring retainer 21 connected to the upper end of the valve stem 7a of each intake valve 7 and the spring receiving portion of the cylinder block (not shown). The intake valve 7 is urged in the valve closing direction by the provided valve spring 22, and the upper ends of the valve stems 7 a of the two intake valves 7 are respectively connected to one common valve lifter 20 via the inner shim 23. I have. The valve lifter 20 is pressed against the cam of the intake-side high / low speed switching cam mechanism 12 by the urging force of the valve spring 22. Note that the same applies to the pair of exhaust valves 8 in each cylinder, which is lifted by the exhaust-side high / low speed switching cam mechanism 14 via one valve lifter 20.

Hereinafter, the valve train of the intake valve 7 of the valve train 10 will be described, and the valve train of the exhaust valve 8 has the same configuration, and the description thereof will be omitted. In the following description,
When simply referred to as the high-low speed switching cam mechanism, it means the intake-side high-low speed cam mechanism 12, and when simply referred to the left side, it indicates the left side in FIG. 1, and when simply referred to the right side, it indicates the right side in FIG.

As shown in FIG. 1, the intake camshaft 11
Are the first camshaft 31, the second camshaft 32, and the third camshaft 3 in order from the left end to the right end.
The third and fourth camshafts 34 and the fifth camshaft 35 are connected to each other, and a high-low speed switching cam mechanism 12 corresponding to each cylinder is provided at a connecting portion of each camshaft.

More specifically, a cylindrical second camshaft 32 is externally fitted and fixed to a substantially central portion of the first camshaft 31 so as not to rotate relatively and to move in the relative axial direction. Low lift cams 41 for low-speed rotation for lifting the intake valve 7 of the first cylinder (# 1) are respectively provided on the outer periphery of the middle part of the first camshaft 31 and the outer periphery of the left end of the second camshaft 32. High lift cams 51 for high-speed rotation, which are formed between the low lift cams 41 and 41 and have a cylindrical shape and the first camshaft 31 is inserted therebetween.
Are held so as to contact both low lift cams 41.

The right end of the first camshaft 31 penetrates through the second camshaft 32 and protrudes rightward. The left end of the third camshaft 33 cannot be relatively rotated and cannot move in the relative axial direction. Is fixed to the outside.

The outer periphery of the right end of the second camshaft 32 and the third
Low-lift cams 42 for low-speed rotation for lifting the intake valve 7 of the second cylinder (# 2) are formed on the outer periphery of the left end portion of the camshaft 33 so as to face each other. , 42, a high-speed rotation high lift cam 52 having a cylindrical shape and through which the first camshaft 31 is inserted is sandwiched between the two low lift cams 42.

At a substantially central portion of the third camshaft 33, a cylindrical fourth camshaft 34 is externally fitted and fixed so that it cannot rotate relatively and cannot move in the relative axial direction. The low-lift cams 43 for low-speed rotation for lifting the intake valve 7 of the third cylinder (# 3) are respectively provided on the outer periphery of the middle part of the third cam shaft 33 and the outer periphery of the left end of the fourth cam shaft 34.
Are formed so as to face each other, and between the low lift cams 43, 43, a high-speed rotation high lift cam 53 having a cylindrical shape and through which the third cam shaft 33 is inserted comes into contact with both low lift cams 43. It is sandwiched.

The right end portion of the third camshaft 33 projects rightward through the fourth camshaft 34, and the cylindrical fifth camshaft 35 having the right end portion closed by this protruding portion cannot be relatively rotated. In addition, it is externally fitted and fixed so as not to move in the relative axial direction.

The outer periphery of the right end of the fourth camshaft 34 and the fifth camshaft 34
Low-lift cams 44 for low-speed rotation for lifting the intake valve 7 of the fourth cylinder (# 4) are formed on the outer periphery of the left end of the camshaft 35 so as to face each other. , 44, a high-lift cam 54 for high-speed rotation having a cylindrical shape and through which the third camshaft 33 is inserted is sandwiched so as to contact both low-lift cams 44.

As described above, the first camshaft 3
The first camshaft 32, the third camshaft 33, the fourth camshaft 34, and the fifth camshaft 35 are integrally connected to each other so as not to rotate relative to each other and to move relative to each other in the axial direction. Is composed.

The intake camshaft 11 has a substantially central portion of the second camshaft 32, a substantially central portion of the third camshaft 33, a substantially central portion of the fourth camshaft 34, and a right end of the fifth camshaft 35. Bearing portions 61, 62, 63, 64, 6 near the left end portion of the first camshaft 31 and near the left end portion of the first cam shaft 31.
The rotation of the crankshaft (not shown) of the engine is transmitted through a cam pulley 15 fixed to the left end of the first camshaft 31, a pulley belt (not shown), and the like. The timing drive is performed at a half rotation speed of the shaft.

The bearings 61, 62, 63, 64, 65 are provided with oil supply holes 61a, 62a, 63a, 64a, 65a, and the oil supplied from the oil pump under pressure is supplied to these oil supply holes 61a, 62a, 63a. , 64a, 65a and the intake camshaft 11 and the bearings 61, 62, 6
3, 64, and 65 are supplied as lubricating oil.

Further, inside the intake camshaft 11,
A cylinder 3 that reaches from the left end surface of the first camshaft 31 to the vicinity of the right end of the fifth camshaft 35 along the center of rotation.
6, two pistons 70A and 70B as sliders are inserted into the cylinder 36 so as to be slidable in the axial direction.

One piston 70A is the first cylinder (# 1)
And low / high speed switching cam mechanism 12 for the cylinder and the second cylinder (# 2)
A and 12B, and the other piston 70B is located at a position corresponding to the high / low speed switching cam mechanisms 12C and 12D for the third cylinder (# 3) and the fourth cylinder (# 4). Thus, a hydraulic chamber 37 is formed in the cylinder 36 between the pistons 70A and 70B.

The pistons 70A and 70B are formed at both ends in the axial direction and have a switching portion 71 having an outer diameter substantially the same as the inner diameter of the cylinder 36, and a switching portion 71 having an outer diameter smaller than that of the switching portion 71. And a connecting portion 72 for connecting the portions 71, 71. By providing the small-diameter connecting portions 72 on the pistons 70A and 70B, the sliding resistance when the pistons 70A and 70B slide in the cylinder 36 in the axial direction can be reduced.

The piston 70A is connected to the first camshaft 31
The return spring 79A provided between the right end face of the cam pulley fixing bolt 15a screwed to the left and the switching portion 71 on the left side of the piston 70A urges the piston 70B in the direction approaching the hydraulic chamber 37. Is a return spring 79 provided between the right end closing portion of the third camshaft 33 and the right switching portion 71 of the piston 70B.
B is urged in a direction approaching the hydraulic chamber 37.

The outer peripheral surface near the right edge of the piston 70A and the outer peripheral surface near the left edge of the piston 70B are liquid-tightly sealed between the outer peripheral surface of the piston 70A or the piston 70B and the inner peripheral surface of the cylinder 36, respectively. Seal ring 7
The seal ring 73 slides in the cylinder 36 in the axial direction together with the pistons 70A and 70B to keep the hydraulic chamber 37 a closed space.

An elongated groove 74 is provided on the outer peripheral surface of each switching portion 71 of the pistons 70A and 70B in the axial direction. In the piston 70A, as shown in FIG. 4, both the grooves 74 have a deep groove 74a with a deeper depth on the left side and a shallow groove 74b with a depth smaller than the deep groove 74a on the right side. On the other hand, in the piston 70B, both the grooves 74 have a deep groove 74a with a greater depth on the right side, and a shallow groove 74b with a depth smaller than the deep groove 74a on the left side.

The four grooves 74 formed in the pistons 70A and 70B are arranged around the rotation center of the intake camshaft 11 with a phase shifted by 90 degrees, which will be described later in detail.

An annular groove 33a is formed on the sliding surface of the third camshaft 33 which slides and rotates by the bearing 62. The annular groove 33a extends around the outer peripheral surface of the third camshaft 33. From this groove 33a, the third camshaft 3
Two through holes 38 penetrating the third and first camshafts 31 in the radial direction and communicating with the cylinder 36 are provided 180 degrees apart from each other. The annular groove 33a communicates with the oil supply hole 62a of the bearing 62, so that the oil of the oil pump can always be supplied to the hydraulic chamber 37 even when the intake camshaft 11 is rotating. .

Next, the high / low speed switching cam mechanism 12 will be described in detail. The high / low speed switching cam mechanism 12A for the first cylinder (# 1) will be described as an example.
2A has a low lift cam 41 and a high lift cam 51 as main components, and as shown in FIGS.
A base circle portion 41a and a cam nose portion 41b are formed in series on the outer periphery of the high lift cam 51, and the base circle portion 51a and the nose portion 51b are also connected to each other via a step portion 51c. Here, the radius of curvature of the base circle portion 41a of the low lift cam 41 and the base circle portion 5 of the high lift cam 51
The radius of curvature of 1a is set to the same dimension.

An imaginary center line C1 connecting the apex of the nose portion 51b of the high lift cam 51 and the rotation center of the intake camshaft 11, and an imaginary connection line between the apex of the cam nose portion 41b of the low lift cam 41 and the rotation center of the intake camshaft 11. The center line C2 is arranged on the same plane, and the two imaginary center lines C1 and C2 coincide in phase around the rotation center of the intake camshaft 11.

The inner peripheral shape of the cylindrical high lift cam 51 has a substantially elliptical shape symmetrical with respect to the virtual center line C1, and the virtual center lines are formed on both inner side surfaces of the high lift cam 51 sandwiching the virtual center line. A guide surface 53 formed in a plane parallel to C1 is formed. A flat guide surface 39 which is parallel to each other is also formed on the outer peripheral surface of the first camshaft 31 of the intake camshaft 11.
9 in sliding contact with both guide surfaces 53 of the high lift cam 51,
The first camshaft 31 supports the high lift cam 51. The high lift cam 51 is movable in the radial direction perpendicular to the rotation center of the intake camshaft 11 along the virtual center line with respect to the low lift cam 41.

The tip of a pin 55 that passes through a through hole 31a provided in the first camshaft 31 is connected to the inner peripheral surface of the high lift cam 51 on the nose 51b side.
The high lift cam 51 is urged radially outward of the first camshaft 31 by a spring 56 provided between the tip portion 55a of the pin 55 and the first camshaft 31.

The base end of the pin 55 is inserted into the groove 74 of the switching portion 71 on the left end side of the piston 70A. Then, when the high lift cam 51 moves to the maximum in the radially outward direction,
As shown in FIGS. 5A and 5B, the nose portion 51b of the high lift cam 51 projects outward beyond the nose portion 41b of the low lift cam 41. At this time, the proximal end of the pin 55 The portion 55b is provided in the groove 7 in the piston 70A.
4 can ride on the shallow groove 74b, and can relatively move along the axial direction of the intake camshaft 11 in the groove 74.

The base end 55b of the pin 55 is set so that it does not come off the groove 74 even when the high lift cam 51 moves to the maximum in the radially outward direction. Will always rotate in synchronization with the first camshaft 31.

Further, when the high lift cam 51 moves to the maximum in the radially outward direction, the cam lobe of the high lift cam 51 is smoothly connected to the base circle portion 41a of the low lift cam 41.

When the pin 55 is located on the side of the deep groove 74a of the groove 74, the base end portion 55b of the pin 55 can enter into the deep groove 74a, and the high lift cam 51 is moved inward in the radial direction. 6B, the distal end of the nose portion 51b of the high lift cam 51 and the distal end of the nose portion 41b of the low lift cam 41 overlap, as shown in FIG. The base circle portion 51 a of 51 overlaps the base circle portion 41 a of the low lift cam 41.

The high / low speed switching cam mechanism 12B for the second cylinder (# 2), the high / low speed switching cam mechanism 12C for the third cylinder (# 3), and the high / low speed switching cam mechanism 12D for the fourth cylinder (# 4). The configuration is also the first cylinder (# 1)
Therefore, the description of the same aspects will be omitted, and only the differences will be described below.

In the high / low speed switching cam mechanism 12B for the second cylinder (# 2), the base end 55b of the pin 55 is
A, the high / low speed switching cam mechanism 12 is inserted into the groove 74 of the switching portion 71 on the right end side and is connected to the third cylinder (# 3).
In C, the base end portion 55b of the pin 55 is inserted into the groove 74 of the switching portion 71 on the left end side of the piston 70B.
In the high / low speed switching cam mechanism 12D for the cylinder (# 4), the base end portion 55b of the pin 55 is inserted into the groove 74 of the switching portion 71 on the right end side of the piston 70B.

As shown in FIG. 7, the rotation direction of the intake camshaft 11 is clockwise as indicated by the arrow in FIG.
The ignition order of the cylinders is changed from the first cylinder (# 1) to the third cylinder (# 3)
If the fourth cylinder (# 4) is the second cylinder (# 2), the rotation direction of the intake camshaft 11 is 90 degrees with respect to the high / low speed switching cam mechanism 12A of the first cylinder (# 1). Each time, a high / low speed switching cam mechanism 12B of the second cylinder (# 2), a high / low speed switching cam mechanism 12D of the fourth cylinder (# 4), and a high / low speed switching cam mechanism 12C of the third cylinder (# 3) are arranged. . Therefore, the grooves 74 provided in the pistons 70A and 70B described above.
Are also arranged at the same phase difference.

Next, the operation of the valve train 10 will be described. In this valve train 10, a predetermined threshold value is set for the rotation speed and shaft output of the engine crankshaft,
An oil passage switching means is provided in a hydraulic circuit (not shown) connected to the oil supply hole 62a of the bearing 62, and when the pressure is equal to or less than the threshold value, the hydraulic chamber 37 communicates with a low-pressure oil passage returning to an oil pan (not shown).
When the threshold value is exceeded, the oil path switching means is controlled so that the hydraulic chamber 37 communicates with the high pressure oil path connected to the discharge side of the oil pump.

The hydraulic pressure in the hydraulic chamber 37 when the hydraulic chamber 37 is in communication with the low-pressure oil passage is the piston 70A, 7A.
0B cannot be pushed against the elasticity of the return springs 79A, 79B, and when the hydraulic chamber 37 is communicated with the high pressure oil passage, the pistons 70A, 7
The spring constants of the return springs 79A and 79B and the initial mounting load are set in advance so that 0B can be pushed against the elasticity of the return springs 79A and 79B.

<Low Lift Cam Operation State> When the rotation speed and the shaft output of the engine crankshaft are equal to or lower than the threshold values, the hydraulic chamber 37 communicates with the low-pressure oil passage. Maintained at low pressure.

At this time, the hydraulic pressure in the hydraulic chamber 37 causes the pistons 70A and 70B to move through the intake camshaft 11 respectively.
Return spring 7 than the force pushing toward the end of
The force by which 9A and 79B urge pistons 70A and 70B toward each other is greater, and therefore, pistons 70A and 70B are held at positions closest to each other. Here, the position where the pistons 70A and 70B are closest to each other means that each pin 55 connected to each of the high lift cams 51, 52, 53 and 54 has a groove 7 in the pistons 70A and 70B.
4 and the pistons 70A, 70A
This is the position where B stops, and is hereinafter referred to as the low lift cam operating position.

The operation of the high / low speed switching cam mechanism 12A for the first cylinder (# 1) when the piston 70A is stopped at the low lift cam operating position will be described with reference to FIGS. The linked pin 55 is located such that its base end 55b can be immersed in the deep groove 74a of the switching portion 71 on the left end side of the piston 70A.

As shown in FIG. 6A, the first cylinder (#
1) The valve lifter 20 of the intake valve 7 is a low lift cam 41
When the high lift cam 51 is in sliding contact with the base circular portion 41a and the base circular portion 51a of the high lift cam 51, the high lift cam 51 projects its nose portion 51b radially outward from the nose portion 41b of the low lift cam 41 due to the elasticity of the spring 56. In this state, it rotates synchronously with the intake camshaft 11 and the low lift cam 41.

The nose portion 51 of the high lift cam 51
a starts to contact the valve lifter 20, the valve spring 22 moves through the valve lifter 20 to the high lift cam 51.
Is higher than the force by which the spring 56 pushes down the high lift cam 51, the high lift cam 51 is pushed up toward the rotation center of the intake camshaft 11 against the elasticity of the spring 56.
At that time, since the base 55b of the pin 55 is immersed in the deep groove 74a, the upward movement of the high lift cam 51 is not hindered.

In this way, the high lift cam 51 is raised with the rotation of the intake camshaft 11, and when the intake valve 7 is at the maximum lift, the tip of the nose portion 51b of the high lift cam 51 as shown in FIG. And low lift cam 41
The tips of b will coincide.

That is, in this case, the intake valve 7 lifts and opens and closes according to the cam profile of the low lift cam 41, and the high lift cam 51 does not participate in the lift of the intake valve 7 at all. This is the low lift cam operation state of the valve train 10.

<High lift cam operation state> On the other hand, when the rotation speed of the crankshaft or the shaft output of the engine exceeds the threshold value, the hydraulic chamber 37 communicates with the high-pressure oil passage. The oil pressure is maintained at a high pressure.

At this time, the return spring 79A,
The hydraulic pressure in the hydraulic chamber 37 is less than the force of the piston 79B for urging the pistons 70A and 70B toward each other.
The force that pushes 0A and 70B toward the end of the intake camshaft 11 is greater. Therefore, when the high / low speed switching cam mechanism 12A is in the low lift cam operating state until immediately before, when the communication with the hydraulic chamber 37 is switched from the low pressure oil passage to the high pressure oil passage, the pistons 70A,
70B moves in a direction approaching the end of the intake camshaft 11, in other words, the pistons 70A and 70B move in a direction away from each other. And each high lift cam 5
The pins 55 connected to 1, 52, 53, 54 are engaged with the edges of the pistons 70A, 70B on the side of the shallow groove 74b of the groove 74, and the pistons 70A, 70B stop. Less than,
This is called a high lift cam operation position.

However, the fact that the pistons 70A and 70B can actually move in the direction away from each other is the intake valve 7
Is not lifted and cannot move during lift. This is because when the intake valve 7 is lifted in the low lift cam operating state, the pin 5
5, the base 55a is immersed in the deep groove 74a, during which the pistons 70A, 70B are formed between the deep groove 74a and the shallow groove 74b in the groove 74 even if the pistons 70A, 70B try to move toward the end of the intake camshaft 11. This is because the pin 55 hits the step and cannot move.

On the other hand, when the intake valve 7 is not lifted, the pistons 70A and 70B return to the position where the base end 55b of the pin 55 can ride on the shallow groove 74b as described above. Spring 7
It can move toward the end of the intake camshaft 11 against the elasticity of 9A and 79B.

The operation of the high / low speed switching cam mechanism 12A after the pistons 70A and 70B have moved to the end portions of the intake camshaft 11, respectively, will be described with reference to FIGS. 1 and 5. FIGS. Pin 5 as shown in B)
5, the high-lift cam 51 is always in the radial direction of the intake camshaft 11 while the intake camshaft 11 is rotating. And is held in a state protruding in a direction away from the center of rotation.

As a result, the low lift cam 41 is used when the lift is not performed.
The base circular portion 41a slides on the valve lifter 20 of the intake valve 7, and at the start of the lift, the sliding contact portion with the valve lifter 20 shifts from the base circular portion 41a of the low lift cam 41 to the cam lobe of the high lift cam 51. After the sliding position with the valve lifter 20 moves to the cam lobe of the high lift cam 51, the intake valve 7 is lifted and opened and closed according to the profile of the nose portion 51b of the high lift cam 51. This is the high lift cam operating state of the valve train 10.

In order to switch the valve train 10 from the high-lift operation state to the low-lift operation state, the oil passage switching means is switched to connect the hydraulic chamber 37 from the high-pressure oil passage to the low-pressure oil passage. 70A and 70B can be spring-backed to the above-described low lift cam operating position by the elasticity of the return springs 79A and 79B.

However, also in this case, the piston 70
A and 70B can be moved to the low lift cam operation position only when the intake valve 7 is not lifted, and cannot be moved during lift. That is, when the intake valve 7 is lifted in the high lift cam operating state, the valve spring 22 is connected to the high lift cam 5 via the valve lifter 20.
1 is extremely large, and the resistance caused by the frictional force generated between the base end surface of the pin 55 and the bottom surface of the shallow groove 74b is larger than that of the first embodiment. This is because the return springs 79A, 79B cannot move the pistons 70A, 70B because the return springs 79A, 79B are superior to the force of pushing the pistons 70A, 70B toward each other (that is, the direction returning to the low lift cam operation state).

Therefore, in this valve operating device 10, FIG.
As shown in the torque characteristic diagram, when the rotation speed and the shaft output of the crankshaft are equal to or less than a predetermined threshold value, the high / low speed switching cam mechanism 12 is in a low lift cam operation state, and when the rotation speed exceeds the threshold value, the high lift cam operation is performed. State.

While the high / low speed switching cam mechanism 12A for the first cylinder (# 1) has been described above, the same applies to the remaining three high / low speed switching cam mechanisms 12B, C and D.
The high / low speed switching cam mechanism 12A, 12B can be switched between a high lift cam operating state and a low lift cam operating state by one piston 70A.
2C and 12D can be switched between a high lift cam operation state and a low lift cam operation state by one piston 70B.

Further, as a result of this configuration, the period during which the cam operation positions of the high / low speed switching cam mechanisms 12A and 12B can be switched is as shown in FIG. 7 for the first cylinder (# 1).
Of the low lift cam 41 and the second cylinder (#
2) The period α1 in which the low lift cam 42 and the base circle portion 42a overlap is the period α1, and the high / low speed switching cam mechanisms 12C, 12D
The period during which the cam operation position can be switched is the third cylinder (#
The period α2 in which the base circle portion 43a of the low lift cam 43 of 3) overlaps with the base circle portion 44a of the low lift cam 44 of the fourth cylinder (# 4).

In FIG. 1, the left piston 70A is located at the low lift cam operating position and the first cylinder (# 1) and the second cylinder
High / low speed switching cam mechanism 12A, 1 corresponding to cylinder (# 2)
2B is in a low lift cam operation state, while the right and left piston 70B is located at a high lift cam operation position and a high / low speed switching cam mechanism 12C corresponding to the third cylinder (# 3) and the fourth cylinder (# 4). , 12D are in the high lift cam operating state, but this is for convenience of explanation only.

That is, in this embodiment, the piston 70
A, 70B are supplied from one common hydraulic chamber 37, and the hydraulic pressure is
Since the oil pressure in the oil supply hole 62a is always applied to the intake camshaft 11 through the annular groove 33a provided on the outer peripheral surface of the third camshaft 33, the pistons 70A, 70B Are always in the same cam operating state.

That is, when the piston 70A is located at the low lift cam operating position, the piston 70B is also located at the low lift cam operating position, so that the high / low speed switching cam mechanisms 12A, 12B, 12C, 12D are all in the low lift cam operating state. On the other hand, when the piston 70A is located at the high lift cam operating position, the piston 70B is also located at the high lift cam operating position, so that the high / low speed switching cam mechanisms 12A, 12B, 12C, 12D are all in the high lift cam operating state. It is.

As described above, in the case of a DOHC type valve train in an in-line four-cylinder four-cycle gasoline engine, for example, in the case of an intake system, conventionally, eight intake valves each have one piston and return spring as switching means. In this embodiment, a total of eight pistons are required. However, in this embodiment, the two pistons 70A, 70
B and two return springs 79A and 79B are required, so that the number of parts can be reduced and cost can be reduced.

As a modification of this embodiment, even if the intake valve 7 and the valve lifter 20 are provided in one-to-one correspondence, only four pistons and four return springs are required. Can be reduced.

As disclosed in Japanese Patent Application Laid-Open No. 7-133708, conventionally, at least four hydraulic chambers serving as driving sources for the pistons are required for each pair of intake valves, that is, at least four in total. However, in this embodiment, there is only one between the pistons 70A and 70B,
The structure of the valve train 10 can be simplified.

Further, since the number of hydraulic chambers is reduced and the number of pistons moved by hydraulic pressure is reduced, the amount of oil required for driving the pistons can be reduced, and the number of locations where oil leaks is reduced. Oil leakage is also reduced. As a result, the capacity of the oil pump can be reduced, the mechanical loss of the engine can be reduced, and the responsiveness when switching between the low lift cam operating state and the high lift cam operating state is also improved.

Further, in this embodiment, the pair of intake valves 7 are shared by one valve lifter 20, so that
The total number of the low lift cams (41, 42, 43, 44) and the high lift cams (51, 52, 53, 54) can be halved as compared with the conventional one, further simplifying the structure, reducing the number of parts, Cost can be reduced.

In the first embodiment, the hydraulic chamber 37 and the return springs 79A, 79B constitute driving means in the cam operation switching means, and the pistons 70A, 70B constitute sliders in the cam operation switching means.

[Second Embodiment] A case where the valve train 10 according to the present invention is applied to an in-line six-cylinder four-cycle gasoline engine will be described with reference to FIGS.

FIG. 9 is a plan view showing the cylinder arrangement of an in-line six-cylinder gasoline engine and the camshaft 1 of the valve train 10.
1 is a plan view of a piston and a hydraulic chamber in FIG.

As is well known, in an in-line six-cylinder gasoline engine, the first to sixth cylinders (# 1 to # 1 in FIG. 9)
6) are arranged in a line with their axes parallel to each other.

Now, in this embodiment, the ignition order is set to the first
Cylinder (# 1) → fifth cylinder (# 5) → third cylinder (# 3) →
Sixth cylinder (# 6) → second cylinder (# 2) → fourth cylinder (#
It is assumed that 4) is set.

In that case, the first cylinder (# 1) to the sixth cylinder (# 1)
(# 6) high / low speed switching cam mechanism 12A-12F of cylinder
10, as shown in FIG. 10, the rotation speed of the camshaft is 60 degrees with respect to the high / low speed switching cam mechanism 12A for the first cylinder.
Each time, the high / low speed switching cam mechanism 12D for the fourth cylinder, the second
A high / low speed switching cam mechanism 12B for the cylinder, a high / low speed switching cam mechanism 12F for the sixth cylinder, a high / low speed switching cam mechanism 12C for the third cylinder, and a high / low speed switching cam mechanism 12E for the fifth cylinder are arranged in this order.

In this in-line six-cylinder gasoline engine, as shown in FIG. 9, the second cylinder (# 2) and the third cylinder (# 3)
High and low speed switching cam mechanism for one piston 70A
, The two high and low speed switching cam mechanisms for the fourth cylinder (# 4) and the fifth cylinder (# 5) are switched by another piston 70B. When a common hydraulic chamber 37a is provided between the pistons 70A and 70B, both pistons 70A and 70B can be driven simultaneously by supplying hydraulic pressure to the hydraulic chamber 37a, and the number of pistons and hydraulic chambers can be minimized. Can be

In this in-line six-cylinder gasoline engine, the cam operation switching period of the high / low speed switching cam mechanism for the second cylinder (# 2) and the third cylinder (# 3) is based on the base circular portions of the low lift cams of both cylinders. Are polymerized, that is, α3 in FIG.
, The fourth cylinder (# 4) and the fifth cylinder (#
The cam operation switching period of the high / low speed switching cam mechanism for 5) is a period in which the base circle portions of the low lift cams of both cylinders overlap,
That is, the period indicated by α4 in FIG.

The first cylinder (# 1) and the sixth cylinder (# 6)
For each of the high and low speed switching cam mechanisms, separate pistons 70C and 70D and hydraulic chambers 37b and 37c are provided to switch the cam operation.

Also in this embodiment, the number of pistons, return springs, hydraulic chambers and the like can be reduced. Therefore, as in the first embodiment, the structure is simplified, the number of parts is reduced, and the cost is reduced. Can be achieved.

Third Embodiment A case where the valve train 10 according to the present invention is applied to a V-type 6-cylinder 4-cycle gasoline engine will be described with reference to FIGS. 11 and 12.

FIG. 11 (A) shows a plan view of a cylinder in a V-type 6-cylinder gasoline engine and a plan view of pistons and hydraulic chambers in camshafts 11A and 11B of the valve train 10. FIG. 11B is a basic mechanism diagram for one cylinder of each bank. As is well known, in a V-type six-cylinder gasoline engine, the first cylinder (#
1), the third cylinder (# 3) and the fifth cylinder (# 5) are arranged in a row with their axis Q1 arranged in parallel with each other to form one bank A, and the second cylinder ( # 2), the fourth cylinder (# 4), and the sixth cylinder (# 6),
2 are arranged in parallel with each other and arranged in a row, and the other bank B
Is composed.

Now, in this embodiment, the ignition order is set to the first
Cylinder (# 1) → second cylinder (# 2) → third cylinder (# 3) →
4th cylinder (# 4) → 5th cylinder (# 5) → 6th cylinder (#
It is assumed that 6) is set.

In this case, the ignition in one bank A is performed in the order of the first cylinder (# 1) → the third cylinder (# 3) → the fifth cylinder (# 5) at intervals of 120 degrees in the rotation direction of the camshaft. Therefore, as shown in FIG. 12 (A), the high / low speed switching cam mechanisms 12A, 12C, 12E for these cylinders are shifted by 120 degrees in the rotation direction of the camshaft with respect to the first cylinder high / low speed switching cam mechanism 12A. Each time, the high / low speed switching cam mechanism 12E for the fifth cylinder and the high / low speed switching cam mechanism 12C for the third cylinder are arranged in this order.

The ignition in the other bank B is performed from the second cylinder (# 2) → the fourth cylinder (# 4) → the sixth cylinder (# 6).
Are performed at intervals of 120 degrees in the direction of rotation of the camshaft, so that the high / low speed switching cam mechanism 12B,
12D and 12F, as shown in FIG. 12 (B), the high / low speed switching cam mechanism for the sixth cylinder every 120 degrees of the rotation direction of the camshaft with respect to the high / low speed switching cam mechanism 12B for the second cylinder. 12F, high / low speed switching cam mechanism 12 for fourth cylinder
Arrange in the order of D.

In this V-type six-cylinder gasoline engine, as shown in FIG. 11A, in bank A, two high / low speed switching cams for the first cylinder (# 1) and the third cylinder (# 3) are provided. The cam mechanism is switched by one piston 70A, and the high / low speed switching cam mechanism for the fifth cylinder (# 5) is switched by another piston 70B. Shared hydraulic chamber 37 during
When a is provided, both pistons 70A and 70B can be driven simultaneously by supplying hydraulic pressure to the hydraulic chamber 37a, and the number of pistons and hydraulic chambers can be minimized.

In the other bank B, two high and low speed switching cam mechanisms for the second cylinder (# 2) and the fourth cylinder (# 4) are switched by one piston 70C to perform cam operation. The high / low speed switching cam mechanism for the sixth cylinder (# 6) performs cam operation switching with another piston 70D,
When the common hydraulic chamber 37b is provided between the pistons 70C and 70D, the pistons 70C and 70D can be driven simultaneously by supplying hydraulic pressure to the hydraulic chamber 37b, and the number of pistons and hydraulic chambers can be minimized. Can be limited.

The first cylinder (# 1) and the third cylinder (# 3)
The cam operation switching period of the high / low speed switching cam mechanism is a period in which the base circle portions of the low lift cams of both cylinders overlap, that is, a period indicated by α5 in FIG. On the other hand, the cam operation switching period of the high / low speed switching cam mechanism for the second cylinder (# 2) and the fourth cylinder (# 4) is a period during which the base circle portions of the low lift cams of both cylinders overlap, that is, FIG. The period indicated by α6 in B).

In the V-type six-cylinder gasoline engine, for bank A, two high / low speed switching cam mechanisms for the third cylinder (# 3) and the fifth cylinder (# 5) are cam operated by one piston. It is also possible to perform switching,
For bank B, the fourth cylinder (# 4) and the sixth cylinder (#
It is also possible to switch the cam operation between the two high / low speed switching cam mechanisms for 6) using one piston.

Also in this embodiment, the number of pistons, return springs and hydraulic chambers can be reduced.
Therefore, similar to the first embodiment, simplification of the structure,
The number of parts and cost can be reduced.

In the case of a V-type 8-cylinder 4-cycle gasoline engine, the piston arrangement in the valve train similar to that of the in-line 4-cylinder 4-cycle gasoline engine in the first embodiment is possible when considering one bank. .

[Fourth Embodiment] Next, a fourth embodiment of the valve train 10 of the present invention will be described with reference to FIGS.
7 will be described.

The valve train 10 in the fourth embodiment
Since the basic configuration is the same as that of the first embodiment, the same parts as those of the first embodiment are denoted by the same reference numerals in the drawings, and description thereof will be omitted. This will be described below.

In the first embodiment, the piston 70
A driving oil pressure for the A and 70B is applied from a common oil pressure chamber 37. In addition, the oil pressure chamber 37 is provided with an annular groove 3 surrounding the outer peripheral surface of the third camshaft 33.
The oil pressure of the oil supply hole 62a is always applied via 3a. On the other hand, as described above, the period during which the cam operation can be switched is limited to the period during which the piston 70A or 70B can move.

Therefore, in the first embodiment, as long as the hydraulic chamber 37 is in communication with the high-pressure oil passage through the oil supply hole 62a, the pistons 70A and 70B are not connected to each other even during the period in which the cam operation cannot be switched. The oil pressure in the oil pressure chamber 37 is applied in the separating direction.

Therefore, for example, in the high / low speed switching cam mechanism 12A for the first cylinder (# 1), in the low lift cam operating state immediately before switching to the high lift cam operating state, the outer peripheral surface of the pin 55 and the inside of the deep groove 74a in the piston 70A. The friction force generated between the high lift cam 51 and the peripheral surface is extremely large, and the high lift cam 51 moves in the radial direction of the intake camshaft 11 while overcoming this friction force. This increases the friction of the valve train 10 and is disadvantageous in that the pins 55 and the grooves 74 are worn.

The fourth embodiment has solved this disadvantage. In the valve train 10 according to the fourth embodiment, a shut-off plate 80 that divides the hydraulic chamber 37 into two right and left hydraulic chambers 37a and 37b is mounted substantially at the center of the third camshaft 33.

The inner peripheral surface of the bearing 62 for supporting the second camshaft 32 and the third camshaft 33 has the structure shown in FIG.
As shown in FIGS. 5 to 17, an arc-shaped oil supply groove 62b communicating with the oil supply hole 62a is formed to a predetermined length in the circumferential direction.

The third camshaft 33 has a communication hole 33b for allowing communication between the oil supply groove 62b of the bearing portion 62 and the hydraulic chamber 37a, and a communication hole for enabling communication between the oil supply hole 62b and the hydraulic chamber 37b. 33c are provided 180 degrees apart from each other in the circumferential direction.

The oil supply groove 62b is provided between the high and low speed switching cam mechanisms 12A and 12B of the first cylinder (# 1) and the second cylinder (# 2).
(This is the same as the cam operation switchable period of the high and low speed switching cam mechanisms 12C and 12D of the third and fourth cylinders), and the oil supply groove 62b is The communication hole 33b (33c) is shut off immediately before the start of the cam operation switching period (see FIG. 15), and communicates with the communication hole 33b (33c) during the cam operation switching period (FIG. 1).
6) at the end of the cam operation switching period.
3b (33c) is arranged (see FIG. 17). In the fourth embodiment, the annular groove 33a is not provided on the outer peripheral surface of the third camshaft 33.

Therefore, in the fourth embodiment, the oil pressure of the oil supply hole 62a is reduced only when the oil supply groove 62b is in communication with the communication hole 33b (or 33c).
Through the communication hole 33b (or 33c) and the hydraulic chamber 37
a (or the hydraulic chamber 37b) and the oil supply groove 62b
During the period in which the communication hole 33b (or 33c) is shut off, the oil pressure in the oil supply hole 62a is not supplied to the hydraulic chamber 37a (or the hydraulic chamber 37b).

In the fourth embodiment thus configured, when the engine rotation speed or the shaft output exceeds the threshold value, the hydraulic chamber 37 is switched by the oil passage switching means (not shown).
Even when a and 37b communicate with the high-pressure oil passage via the oil supply hole 62a, the oil pressure in the oil supply hole 62a is supplied to the oil pressure chambers 37a and 37b only during a period during which the cam operation can be switched.

Therefore, when the cam operation cannot be switched, the frictional force between the pin 55 and the groove 74 becomes extremely small, and the friction of the valve train 10 can be reduced. Wear can be extremely reduced.

In the fourth embodiment, the communication holes 33b, 3
The drive switching means is constituted by 3c, the oil supply groove 62b, and the blocking plate 80. The fourth embodiment can be combined with the second or third embodiment.

[0113]

As described above, according to the present invention,
On a camshaft of an internal combustion engine having a plurality of cylinders, a low-lift cam and a high-lift cam are arranged side by side with the phases of their nose portions being substantially the same as each other for each cylinder, and the high-lift cam is arranged in the radial direction of the camshaft. A cam operation switching means is provided movably provided with respect to the low lift cam and switches the high lift cam to an operation state or a non-operation state according to an operation state of the internal combustion engine, and can switch between a high lift cam operation state and a low lift cam operation state. In a valve operating device for a multi-cylinder internal combustion engine that transmits the rotational motion of a cam as an opening and closing motion of a valve that opens and closes a gas flow path connected to a combustion chamber of each cylinder, cam operation switching means in two cylinders adjacent to each other , The number of cam operation switching means can be reduced, and the number of parts of the valve train can be reduced. As well as the structure is simplified, the drive means of the cam actuating the switching means can also be simplified, the cost is also achieved an excellent effect of being able to inexpensively.

Further, the cam operation switching means includes a slider which can reciprocate in the camshaft in the axial direction, and a driving means for driving the slider, and the slider uses a common cam operation switching means. A switching portion corresponding to each of two adjacent cylinders, and a configuration in which both switching portions are connected by a connecting portion having a smaller diameter than the switching portion, to reduce the sliding resistance of the slider. The responsiveness at the time of switching between the high lift cam operation state and the low lift cam operation state is improved.

Further, a plurality of the cam operation switching means are provided in common, and the driving means for driving the cam operation switching means are driven such that the respective cam operation switching means are shifted in phase from each other in the cam shaft rotation direction. In the case where the drive switching means is provided to switch the driving force to the plurality of cam operation switching means, the driving force of one drive means can be switched by the drive switching means and transmitted to the plurality of cam operation switching means. .

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a camshaft and a cam mechanism in a first embodiment of a valve train for a multi-cylinder internal combustion engine according to the present invention.

FIG. 2A is a plan layout view of a cylinder according to the first embodiment, and FIG. 2B is a basic configuration diagram of one cylinder.

FIG. 3 is a schematic configuration diagram of a gasoline engine according to the first embodiment of the present invention.

FIG. 4 is a partially cutaway front view of a main part of a piston as a cam operation switching unit according to the first embodiment of the present invention.

FIG. 5 is a longitudinal sectional view of the cam in a high lift cam operating state according to the first embodiment of the present invention.

FIG. 6 is a longitudinal sectional view of the cam in a state where the high lift cam is not operated according to the first embodiment of the present invention.

FIG. 7 is a diagram illustrating a cam arrangement and a switching section according to the first embodiment of the present invention.

FIG. 8 is a diagram illustrating a relationship between an engine torque characteristic and a cam operation region according to the first embodiment of the present invention.

FIG. 9 is a diagram showing both a plan layout of cylinders and a layout of main components of a valve train in a multi-cylinder internal combustion engine according to a second embodiment of the present invention.

FIG. 10 is a diagram showing a cam arrangement and a switching section according to a second embodiment of the present invention.

FIG. 11A is a diagram showing both a plan layout of cylinders and a layout of main components of a valve train in a multi-cylinder internal combustion engine according to a third embodiment of the present invention.
(B) is a basic configuration diagram of a V-type engine.

FIG. 12 is a diagram showing a cam arrangement and a switching section according to a third embodiment of the present invention.

FIG. 13 is a longitudinal sectional view of a camshaft and a cam mechanism in a fourth embodiment of the valve train for a multi-cylinder internal combustion engine according to the present invention.

FIG. 14 is an enlarged longitudinal sectional view of a main part of a cam shaft and a cam mechanism according to a fourth embodiment of the present invention.

FIG. 15 is a longitudinal sectional view around a drive switching unit according to a fourth embodiment of the present invention.

FIG. 16 is a longitudinal sectional view around a drive switching unit according to a fourth embodiment of the present invention.

FIG. 17 is a longitudinal sectional view around a drive switching unit according to a fourth embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Cylinder (cylinder) 10 Valve train 11 Intake camshaft (camshaft) 33b, 33c Communication hole (drive switching means) 37, 37a, 37b Hydraulic chamber (cam operation switching means, driving means) 41, 42, 43, 44 Low lift cam 41b Nose part of low lift cam 51, 52, 53, 54 High lift cam 51b Nose part of high lift cam 62b Oil supply groove (drive switching means) 70A, 70B Piston (cam operation switching means, slider) 71 Switching part 72 Connecting part 79A , 79B Return spring (cam operation switching means, driving means) 80 Cut-off plate (drive switching means)

Claims (4)

[Claims] A low-lift cam and a high-lift cam are provided side by side on a camshaft of an internal combustion engine having a plurality of cylinders so that the phases of their nose portions are substantially the same as each other. A cam operation switching means is provided movably with respect to the low lift cam in the radial direction of the shaft, and switches the high lift cam between an operation state and a non-operation state according to an operation state of the internal combustion engine. In a valve operating device for a multi-cylinder internal combustion engine, the operating state is switchable, and a cam rotational movement is transmitted as an opening and closing movement of a valve that opens and closes a gas flow path connected to a combustion chamber of each cylinder. A valve operating device for a multi-cylinder internal combustion engine, characterized in that cam operation switching means is shared. 2. The multi-cylinder internal combustion engine according to claim 1, wherein said cam operation switching means includes a slider capable of reciprocating in a camshaft in an axial direction, and a driving means for driving said slider. Engine valve gear. 3. The slider according to claim 2, further comprising a switching unit corresponding to each of the two adjacent cylinders, wherein the switching unit is connected by a connecting portion having a smaller diameter than the switching unit. 3. The valve train for a multi-cylinder internal combustion engine according to 2. 4. A driving device for driving a plurality of the cam operation switching units, wherein the plurality of cam operation switching units are driven in such a manner that the respective cam operation switching units are out of phase with each other in the camshaft rotation direction. 2. The valve operating apparatus for a multi-cylinder internal combustion engine according to claim 1, further comprising a drive switching unit that switches the operation mode to the operation mode.