JP2003027910A - Valve system and internal combustion engine provided therewith - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a valve system capable of ensuring the smooth and adequate operation, and improving the performance, and an internal combustion engine having the valve system. SOLUTION: The valve system comprises a cam 13 which is formed so that the cam height and the cam operational angle are continuously changed, integrally rotated with a cam shaft 11, and relatively movable in the axial direction, and a valve lifter which is pressed by a cam surface of the cam 13 to advance/ retract valves 41. The cam 13 is provided on each of the plurality of valves 41, and the cam shaft 11 integrally rotated with each cam 13 is disposed in the direction orthogonal to the axial direction of a crank shaft. The valve lifter includes a roller tappet 31 with a contact part with the cam 13 formed in an arc, and is disposed so that the diameter direction of the roller tappet 31 agrees in the axial direction of the crank shaft.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve operating system for variably controlling a lift amount, a lift timing and a working angle of a valve in an internal combustion engine of a motorcycle, an automobile or the like according to an accelerator opening.

[0002]

2. Description of the Related Art In this type of internal combustion engine, various ideas and proposals have been made to improve the combustion efficiency. Beginning with the variable phase method that shifts the opening and closing timing of the valve, variable control of valve lift by cam switching and valve suspension have been adopted. In this cam switching system, two cams for low speed and high speed are prepared and the cam having a smaller working angle is switched to the one having a larger working angle according to the engine output.

More recently, a combination of variable phase and cam switching has begun to appear, and thereafter, a system using a three-dimensional cam for continuously varying the working angle and the lift amount has been proposed. For example, in the variable valve mechanism disclosed in Japanese Unexamined Patent Publication No. 9-296714, a cam shaft is provided in the cylinder arranging direction, and the cam profile changes axially in the cam shaft.
A three-dimensional cam (three-dimensional cam) is provided.

[0004]

However, in such a conventional example, for example, in the valve mechanism disclosed in the above-mentioned publication, if it is attempted to control each valve individually, the axial length of the cam becomes short due to the space. In that case, the inclination angle of the cam nose portion becomes steep, and if it is left as it is, the resistance load in the thrust direction accompanying the movement of the cam becomes large. Then, it becomes difficult to realize a smooth switching operation. Also, the output change due to cam thrust movement becomes large,
Subtle accelerator control becomes virtually impossible.

In view of the above situation, it is an object of the present invention to provide a valve gear that ensures smooth and proper operation and improves performance, and an internal combustion engine equipped with the valve gear.

[0006]

The valve gear of the present invention is formed so that the cam height and the cam working angle are continuously changed, and is configured to rotate integrally with the cam shaft and relatively move in the axial direction thereof. And a valve lifter for advancing and retracting the valve by being pressed by the cam surface of the cam, wherein each valve has a cam, and a cam shaft that rotates integrally with each cam is a crank. It is characterized in that it is arranged in a direction orthogonal to the axial direction of the shaft.

Further, in the valve gear of the present invention, the valve lifter includes a roller tappet whose contact portion with the cam is formed in an arc shape, and a central axis direction of the roller tappet is an axial direction of the crankshaft. It is characterized in that they are arranged orthogonally.

Further, in the valve gear of the present invention, the angle formed by the inclined surface of the cam portion of the cam and the tappet stroke axis of the tappet is set to be substantially right angle.

Further, in the valve gear of the present invention, the cam shaft is set on a mating surface of the cylinder head and the cylinder head cover.

Further, in the valve operating system of the present invention, the valve stem of the valve is arranged so as to be inclined by a predetermined angle in the central axis direction of the cylinder.

Further, in the valve gear of the present invention, the arrangement pitch of the cam shafts is set to 1/2 of the cylinder pitch between the cylinders.

Further, the internal combustion engine of the present invention is an internal combustion engine in which intake and exhaust are controlled by an intake valve and an exhaust valve, and at least the intake side is equipped with any one of the above valve operating devices. To do.

Further, the internal combustion engine of the present invention includes a steering head pipe pivotally supporting a front fork, a fuel tank mounted on a vehicle body frame connected to the steering head pipe, and a rear portion of the fuel tank. In a motorcycle having a seat continuously connected to the air cleaner, and an air cleaner arranged below the seat and the fuel tank, an intake pipe mounted in front of the air cleaner and connecting the rear part and the air cleaner to the intake pipe An internal combustion engine having an exhaust pipe connected to the opposite side to the connected one, wherein the cam height and the cam working angle are formed to continuously change, and the cam shaft rotates integrally with the cam shaft and A plurality of cams are provided, each of which includes a cam configured to be relatively movable, and a valve lifter that is pressed by a cam surface of the cam to advance and retract the valve. Has a cam for each blanking, the cam and cam shaft integrally rotating and having a valve operating device disposed in the direction perpendicular to the axial direction of the crankshaft.

According to the present invention, the camshaft is arranged for each valve in the direction orthogonal to the axial direction of the crankshaft. A large slide stroke of the cam can be secured, frictional resistance of the cam can be reduced, and mechanical loss can be effectively reduced. Further, since the sliding stroke of the cam is increased, a fine three-dimensional map of the cam portion can be realized and the valve lift amount can be finely and delicately controlled.

Further, the workability and assembling of the components are improved by devising the arrangement relationship of the camshafts.
A very advantageous and simple structure can be realized in manufacturing, assembly, and the like.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. The valve gear according to the present invention can be effectively applied to various gasoline engines mounted on a motorcycle or a four-wheeled vehicle. In this embodiment, for example, a motorcycle engine as shown in FIG. To do.

First, the overall structure of the motorcycle 100 according to this embodiment will be described. In FIG. 1, two front forks 103 supported by a steering head pipe 102 to be rotatable left and right are provided on a front portion of a body frame 101 made of steel or an aluminum alloy material.
Is provided. A handlebar 104 is fixed to the upper end of the front fork 103, and grips 105 are provided at both ends of the handlebar 104. A front wheel 106 is rotatably supported on the lower portion of the front fork 103, and
The front fender 107 covers the upper portion of the front wheel 106.
Is fixed. The front wheel 106 has a brake disc 108 that rotates integrally with the front wheel 106.

A swing arm 109 is swingably provided at the rear portion of the body frame 101, and a rear shock absorber 110 is mounted between the body frame 101 and the swing arm 109. Swing arm 10
A rear wheel 111 is rotatably supported at the rear end of the rear wheel 9.
11 is rotationally driven via a driven sprocket 113 around which a chain 112 is wound.

The engine 1 (solid line portion) mounted on the vehicle body frame 101 is supplied with an air-fuel mixture from an intake pipe 115 connected to an air cleaner 114, and the exhaust gas after combustion is exhausted through an exhaust pipe 116. It The air cleaner 114 is installed behind the engine 1 and in a large space below the fuel tank 117 and the seat 118 in order to secure the capacity. Therefore, the intake pipe 115 is connected to the rear side of the engine 1, and the exhaust pipe 116 is connected to the front side of the engine 1. Further, a fuel tank 117 is mounted above the engine 1, and a seat 118 and a seat cowl 119 are continuously provided behind the fuel tank 117.
Here, an accelerator motor 54, which will be described later, is attached to a predetermined portion of the cylinder head 2 to the cylinder head cover 2a of the engine 1. The accelerator motor 54 is provided so as to project from the rear portion of the cylinder head 2 as in the illustrated example. In that case, the accelerator motor 54 is arranged in the recess provided in the lower portion of the fuel tank 117, and the fuel tank 117 and the cylinder head cover 2a are arranged so as not to interfere with each other.

If the accelerator motor 54 uses a link,
It can be installed on either the intake side or the exhaust side, but when it is installed on the exhaust side, the recess formed in the fuel tank 117 is exposed,
Since the external appearance deteriorates as it is, it is preferable to provide the accelerator motor 54 on the intake side in consideration of it.

Further, in FIG. 1, 120 is a head lamp, 121 is a meter unit including a speedometer, tachometer or various indicator lamps, and 122 is a rearview mirror supported by the handlebar 104 via a stay 123. Further, a main stand 124 is swingably attached to a lower portion of the vehicle body frame 101 so that the rear wheel 111 can be grounded or floated from the ground. The body frame 101 includes a head pipe 102 provided at a front portion.
The tank rail 101 is provided with a pivot 109a, which is a pivotal support of the swing arm 109, after being formed so as to extend obliquely downward and rearward from the engine 1 and curved so as to wrap around the lower side of the engine 1.
a and the seat rail 101b.

The body frame 101 is provided with a radiator 125 in parallel with the body frame in order to avoid interference with the front fender 107, and a cooling water hose 126 is arranged from the radiator 125 along the body frame 101. It communicates with the engine 1 without interfering with the exhaust pipe 116.

2 to 4 show the main constitution of the present invention, FIG. 2 is a sectional view of the essential part of the device of the present invention, and FIG. 3 is a sectional view taken along the line A--A of FIG. 4 is a sectional view taken along the line BB of FIG. As shown in these figures, in this embodiment, the parallel two-cylinder engine has two valves (that is, four valves) on each of the intake side (IN) and the exhaust side (EX) for each cylinder. ing. In this embodiment, the example is applied to the intake side, but it may be applied to both the intake side and the exhaust side. A cylinder head 2 is arranged above a piston 3 (see FIG. 3) that reciprocates up and down in a cylinder, and a valve operating device is housed in the cylinder head 2.

The valve operating system includes a cam / camshaft unit 10, a tappet unit 30 arranged below the cam / camshaft unit 10, a valve unit 40 for intake control in this example, and an accelerator opening degree. Accelerator shaft unit 50 for displacing the cam. The valve unit 40 may have the same configuration on the exhaust side.

In the cam / camshaft unit 10, four in this example, that is, the camshaft 11 for each valve is arranged in the cylinder arrangement direction (crankshaft axial direction).
Are arranged orthogonally to. The arrangement pitch of the camshafts 11 is set to 1/2 of the cylinder pitch P between the two cylinders. Further, the central axis of each camshaft 11 is set on the mating surface of the cylinder head 2 and the cylinder head cover 2a.

Each camshaft 11 has a bearing 12
It is rotatably supported by the cylinder head 2 via (angular bearing), 12 '. A cam 13, which will be described later, is slidably attached to each cam shaft 11 in its axial direction.
It has a linear ball spline 11a, and its guide is adapted to make a linear motion through the ball 14. The camshaft 11 may have a hollow structure, and a lubricating oil passage may be formed inside the hollow to lubricate the cam 13 and the like.

A gear 16 is connected to one end of the camshaft 11 and is connected to the sprocket 15 via a bevel gear described later.
(Spur gear; driven side) is stuck. In this example, the camshaft 11 arranged on the rightmost side in the cylinder arrangement direction
The gear 16 of the sprocket 15 via a bevel gear or the like.
Connect with. A sprocket 15 _Ex is fixed to one end of the exhaust-side camshaft 11 _Ex , and a cam chain 5 is interposed between these sprockets 15 and 15 _Ex and a drive sprocket 4 fixed to one end of a crankshaft (not shown). Is wound and mounted (see FIG. 6). As shown in FIG. 6, a chain guide 6, a chain tensioner 7, a chain adjuster 8 and the like are included so that the cam chain 5 can travel properly.

The bevel gear 17 (drive side) has bearings 18 (double-row angular ball bearings), 18 ', so that its shaft portion 17a is coaxial with the sprocket 15.
It is rotatably supported by the cylinder head 2 via. Bevel gear 19 that meshes with bevel gear 17 (driven side)
Is rotatably supported by the cylinder head 2 via a bearing 20 (angular bearing) so that its shaft portion 19a is parallel to the camshaft 11. A gear 21 (spur gear; drive side) that meshes with the gear 16 described above is fixed to one end of the shaft portion 19a of the bevel gear 19.

The gears 16 of each camshaft 11 mesh with each other so that adjacent gears mesh with each other, and thus the sprocket 1
The drive force from 5 causes the four camshafts 11 to rotate synchronously. In this case, the camshafts 11 adjacent to each other rotate in opposite directions. Regarding the direction of rotation of the cam shaft 11, all the cams 13 can be properly operated by adjusting the phase relationship of the cams 13 described later.

Here, the cam 13 is constructed as a so-called "three-dimensional cam", and one cam 13 is provided for each cylinder. As shown in FIG. 7, a cam portion 13a that gently inclines in the longitudinal direction (axial direction of the cam shaft 11) is extended and shaped to continuously change the valve lift amount. In this case, the cam working angle and the lift timing change simultaneously with the cam height, that is, the cam working angle increases as the valve lift amount increases,
Furthermore, the valve lift timing is set so that it can be changed.

FIG. 8 shows an example of specific three-dimensional cam structure specifications of the cam 13. By moving such a cam 13 along the cam shaft 11, the lift amount, working angle and lift timing of the intake valve can be variably controlled steplessly. As described above, the cam shaft 11 and hence the cam 13 rotate in the reverse direction. When one of the adjacent cams 13 has a cam phase curve indicated by a solid line, the cam phase curve of the other cam 13 may be line-symmetrical at a phase angle of 360 ° as indicated by a dotted line.

Further, in the present invention, each cylinder has two or more intake (IN) and exhaust (EX) valves, but the camshaft 11 for each valve is orthogonal to the cylinder arrangement direction. Are arranged. Thus the camshaft 1
By disposing No. 1, it is possible to secure a large slide stroke of the cam 13 along the cam shaft 11 regardless of the valve disposition pitch (camshaft 11 disposition pitch P / 2). As a result, the inclination angle α (FIG. 2) of the cam portion 13a along the cam shaft 11 can be reduced.

In the tappet unit 30, a substantially disk-shaped tappet 31 (roller tappet) is arranged for each valve. In this example, in particular, the tappet 31 is arranged so that its diameter direction matches the cylinder arrangement direction (see FIG. 3, etc.). A tappet holder 32 is arranged and fixed at an appropriate position on the cylinder head 2. The tappet holder 32 has a guide hole 32a, and the tappet 31 has this guide hole 32a.
At a, it is held in a floating manner while being housed inside the tappet holder 32. The tappet unit 30 (tappet 31) functions as a valve lifter that is pushed by the cam surface of the cam 13 to move the valve back and forth.

The outer peripheral surface of the tappet 31 is typically formed in an arc shape (R shape) and is in point contact with the cam 13. Further, the tappet 31 is slidably guided by guide holes 32a provided on the tappet holder 32 on both side surfaces thereof, and is movable only in the axial direction of the valve stem.
In this example, one cylinder has one tappet holder 32, and a single tappet holder 32 holds a pair of tappets 31 in each cylinder.

In this example, in particular, as shown in FIG. 2, the angle β formed by the inclined surface of the cam portion 13a of the cam 13 and the tappet stroke axis of the tappet 31 is set to be substantially a right angle.

In this embodiment, the exhaust side is
As shown in FIG. 2 or 4, the flat cam 13 _Ex
It has a disk-shaped tappet 31 _Ex having a (planar cam) and a contact plane that abuts on it.

In the valve unit 40, each valve stem 41a includes two intake valves 41 guided by a valve guide 42. Further, a tappet shim 43 that abuts the tappet 31 is provided at the end of each valve stem 41 a, and a valve spring 46 is mounted between the valve retainer 44 and the spring seat 45. Further, in particular, as shown in FIG. 3, the valve stem 41a of the valve 41 in each cylinder is inclined by an angle θ in the central axis direction of the cylinder when viewed in the crankshaft axial direction.

In the accelerator shaft unit 50,
It includes a pair of accelerator shafts 51 _R and 51 _L arranged parallel to the cam shaft 11 and on the left and right outer sides, and a slider 52 fixed to the accelerator shafts 51 _R and 51 _L and connected to the cam 13. Accelerator shaft 51 _R
Is rotatably supported by the cylinder head 2 and is engaged with the slider 52 via a screw lip spline 51a. A driven gear 53 is fixed to one end of the accelerator shaft 51 _R , and the driven gear 53 is used for the accelerator motor 5
4 meshes with the drive gear 55 fixed to the output shaft of No. 4. The configuration on the side of the accelerator shaft 51 _L is similar to that of the accelerator shaft 51 _R , and the slider 52 is slid on both sides of the cam / camshaft unit 10 by a pair of left and right accelerator motors 54 via a screw respline 51a.

The output shaft of the accelerator motor 54 rotates in response to a change in the accelerator (accelerator opening, acceleration / deceleration direction, etc.), and the rotation of the accelerator motor 54 via a drive gear 55 and a driven gear 53 causes the accelerator shaft 51 _R , It is transmitted to 51 _L and is further converted into a sliding movement of the slider 52 via the screw lip spline 51 a. In this example, the accelerator motor 54 is arranged along the axial direction of the camshaft 11. In the case of a motorcycle, for example, the rotational operation amount of the accelerator grip may correspond to the rotational amount of the output shaft of the accelerator motor 54. Further, when the accelerator motor 54 is driven, drive control is performed by a controller (not shown) so as to match the traveling condition (output) at that time.

The slider 52 is connected via a bearing 56 to
It is rotatable with respect to each cam 13, and is fixedly engaged in the axial direction of the cam shaft 11. As a result, each cam 13 slides along the cam shaft 11 in conjunction with or in synchronization with the slider 52 sliding in the axial direction of the accelerator shafts 51 _R and 51 _L.

In the above structure, when the accelerator grip (or accelerator pedal) is operated, the accelerator motor 5
4 operates and the output gear rotates to drive gear 55
Further, the slider 52 slides via the driven gear 53 and further via the screw respline 51a of the accelerator shafts 51 _R and 51 _L.

For example, when the engine speed is low, the tappet 31 is in contact with the cam 13 at a portion where the cam height is low, as shown in FIG. When acceleration is performed in this state, that is, when the accelerator is opened, the driven gear 53 is rotated by the operation of the accelerator motor 54, and the slider 52 slides to the left in the figure. The cam 13 has a bearing 56,
In association with the movement of the slider 52, the slider 52 also slides to the left in the figure along the camshaft 11. At this time, the sliding amount and speed of the cam 13 correspond to the opening degree and opening speed of the accelerator. As the cam 13 slides, the tappet 31 gradually abuts on a portion where the cam height is high, whereby the valve lift amount increases according to the lift characteristic shown in FIG. On the other hand, by returning the accelerator during deceleration, the valve lift amount is reduced by the operation opposite to the above.

Here, in the above-described valve operating system or internal combustion engine of the present invention, one camshaft 11 is arranged for each valve in each cylinder. The valves can be controlled in units of one, and swirl flow can be generated. Further, in that case, the camshafts 11 are arranged orthogonally to the cylinder arrangement direction (crankshaft axial direction). By arranging the camshaft 11 in this way,
A large slide stroke of the cam 13 along the camshaft 11 can be secured without being restricted by the arrangement pitch of the valves.

As a result, the inclination angle α of the cam portion 13a of the cam 13 can be reduced, so that the frictional resistance of the sliding contact portion of the cam 13 is reduced, and the mechanical loss can be effectively reduced. . Further, abrasion of the sliding contact portion of the cam 13 is suppressed, and abrasion resistance is improved. Further, since the sliding stroke of the cam 13 is increased, the cam portion 13a has a fine three-dimensional map cam curve, and the valve lift amount can be finely and delicately controlled.

Also, in this example, two cylinders have four cams 13 on the intake side, but these cams 13 are a single slider 5
It is driven to slide by 2. The plurality of cams 13 can be driven in perfect synchronization, and even though the plurality of cams 13 are used, drive control can be uniformly and evenly balanced between cylinders or within each cylinder.

Further, as is apparent from FIG. 2, the cam portion 13a of the cam 13 is formed and arranged so that it becomes higher toward the outside of the so-called "valve V bank" (V-shaped valve arrangement). Moreover, when increasing the valve lift amount, the cam 13 is driven so as to move inward of the valve V bank. As a result, as described above, the angle β formed by the inclined surface of the cam portion 13a of the cam 13 and the tappet stroke axis of the tappet 31 is set to a substantially right angle, and wear of the cam 13 and the tappet 31 is suppressed.

Further, since each cam shaft 11 is set on the mating surface of the cylinder head 2 and the cylinder head cover 2a, especially in the cylinder head 2 having a plurality of cam shafts 11, workability, assembling property, etc. Is extremely advantageous in. Since the arrangement pitch of the camshafts 11 is set to 1/2 of the cylinder pitch P between the cylinders,
The four gears 16 can have the same specifications. Since it is not necessary to use an idle gear or the like, the structure can be simplified.

Further, as described above, the valve stem 41a of the valve 41 is inclined by the angle θ in the central axis direction of the cylinder (FIG. 3). This makes it possible to reduce the S / V ratio and make the combustion chamber spherical. Then, this spheroidization can reduce heat loss and increase combustion efficiency. Since the outer peripheral surface of the tappet 31 is formed in an arc shape, it is possible to provide the inclination angle θ in this way.

Although the present invention has been described above in connection with various embodiments, the present invention is not limited to these embodiments, and modifications and the like can be made within the scope of the present invention.
For example, the specific numerical values and the like described in the above embodiment (for example, the three-dimensional cam configuration specifications shown in FIG. 8) are not necessarily limited to these, and can be changed as necessary.
Further, in each embodiment, the example of the case of the two-cylinder engine has been described, but the present invention can be effectively applied to the engine of one cylinder or three or more cylinders.

[0050]

As described above, according to the present invention, in this type of engine, the valve lift amount, the operating angle, and the lift timing are continuously and variably controlled according to the accelerator opening. In this case, by disposing the camshaft in the direction orthogonal to the crankshaft axial direction for each valve, it is possible to secure a large cam slide stroke, reduce the friction resistance of the cam, and effectively reduce mechanical loss. can do. Further, since the sliding stroke of the cam is increased, the valve lift amount can be finely and delicately controlled, smooth operation and high output can be achieved, and an engine having excellent durability and the like can be realized.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration example of a motorcycle including an engine periphery according to an application example of the present invention.

FIG. 2 is a side sectional view of the main part of the valve gear of the present invention.

3 is a sectional view taken along the line AA of FIG.

FIG. 4 is a plan view of a main part of a valve train of the present invention.

FIG. 5 is a main part plan view showing an example of the arrangement configuration of the bevel gear according to the valve gear of the present invention.

FIG. 6 is a diagram showing a rotary drive system of a camshaft according to the valve gear of the present invention.

FIG. 7 is a perspective view showing a three-dimensional cam according to the valve gear of the present invention.

FIG. 8 is a diagram showing an example of specific three-dimensional cam configuration specifications of the cam according to the valve gear of the present invention.

[Explanation of symbols]

1 Engine 2 Cylinder Head 3 Piston 4 Drive Sprocket 5 Cam Chain 6 Chain Guide 7 Chain Tensioner 8 Chain Adjuster 10 Cam / Camshaft Unit 11 Camshaft 12 Bearing 13 Cam 15, 15 _Ex Sprocket 16 Gear 17, 19 Bevel Gear 20 Bearing 21 Gear 30 tappet unit 31 tappet 32 tappet holder 40 valve unit 41 intake valve 42 valve guide 43 tappet shim 44 tappet retainer 45 spring seat 46 valve spring 50 accelerator shaft unit 51 _R , 51 _L accelerator shaft 51a screw respline 52 slider 53 driven gear 54 accelerator motor 55 Drive gear

Continued front page    F term (reference) 3G016 AA06 AA12 AA19 BA24 BA30                       BA34 BA35 BA36 BA39 BA40                       BA43 BB03 BB04 BB06 CA09                       CA11 CA14 CA16 CA42 CA44                       CA45 DA01 DA23 FA13 FA36                       FA38 FA40 GA01                 3G018 AA05 AA06 AB02 AB07 AB16                       BA03 BA05 BA21 BA38 CA13                       DA03 DA17 DA28 DA29 DA83                       DA85 FA01 FA06 FA07 GA01                 3H063 AA01 CC03 DB14 GG03 GG19

Claims (8)

[Claims] 1. A cam which is formed so that a cam height and a cam working angle are continuously changed, and which rotates integrally with a cam shaft and is relatively movable in an axial direction thereof, and is pressed against a cam surface of the cam. And a valve lifter for advancing and retracting the valve, wherein a cam is provided for each of a plurality of valves, and a camshaft that rotates integrally with each cam is arranged in a direction orthogonal to the axial direction of the crankshaft. Valve operating device. 2. The valve lifter includes a roller tappet whose contact portion with the cam is formed in an arc shape, and is arranged such that a central axis direction of the roller tappet is orthogonal to an axial direction of the crankshaft. The valve operating system according to claim 1, wherein: 3. The valve operating system according to claim 1, wherein an angle formed by the inclined surface of the cam portion of the cam and the tappet stroke axis of the tappet is set to be substantially right angle. 4. The valve operating system according to claim 1, wherein the camshaft is set on a mating surface of a cylinder head and a cylinder head cover. 5. The valve operating system according to claim 1, wherein the valve stem of the valve is arranged so as to be inclined by a predetermined angle in the central axis direction of the cylinder. 6. The valve operating system according to claim 1, wherein the camshaft is arranged at a pitch of ½ of a cylinder pitch between the cylinders. 7. An internal combustion engine in which intake and exhaust are controlled by an intake valve and an exhaust valve, the valve operating device according to claim 1 being provided on at least an intake side. Characterized internal combustion engine. 8. A steering head pipe rotatably supporting a front fork, a fuel tank mounted on a vehicle body frame connected to the steering head pipe, and a seat continuously provided behind the fuel tank. In a motorcycle having an air cleaner arranged below the seat and the fuel tank, an intake pipe mounted in front of the air cleaner and connecting the rear part and the air cleaner to the opposite side of the intake pipe from each other An internal combustion engine having an exhaust pipe connected to a camshaft, formed so that the cam height and the cam working angle change continuously, and configured to rotate integrally with the camshaft and relatively move in the axial direction thereof. A cam and a valve lifter that is pushed by the cam surface of the cam to move the valve back and forth,
An internal combustion engine having a valve mechanism for each of a plurality of valves, wherein a camshaft that rotates integrally with each cam is arranged in a direction orthogonal to the axial direction of the crankshaft.