JP2001107708A - Valve system for overhead valve type internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce size and weight of a bearing of a camshat and miniaturize an internal combustion engine in a valve system of an overhead valve type internal combustion engine. SOLUTION: This valve system of an overhead valve type internal combustion engine 30 has a camshaft 57 supported by a bearing and provided with an intake cam 75 and a supercharge cam 77, an intake cam follower 78, a supercharge cam follower 80, an intake rocker arm 85, a supercharge rocker arm 87, an intake pull-rod 82 and a push rod 84. The intake cam follower 78 abuts against the intake cam 75 on the side of a cylinder 46 of an attaching surface B of the cylinder 45 and the cylinder head 43. The supercharge cam follower 80 abuts against the supercharge cam 77 on the side of the cylinder head 43 of the attaching surface B.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overhead valve type internal combustion engine in which the movement of a cam follower oscillated by a cam provided on a cam shaft is transmitted to a rocker arm via a rod to open an engine valve. The present invention relates to a valve train.

[0002]

2. Description of the Related Art Conventionally, as a valve train of an overhead valve type internal combustion engine, an intake cam and an exhaust cam are provided on a single camshaft arranged near a crankshaft, and the valve opening driving force of both cams is reduced. It is known that an intake valve and an exhaust valve are transmitted to an intake and exhaust rocker arms provided on a cylinder head via a pair of tappets and a pair of push rods, respectively, so that the intake valve and the exhaust valve are driven to open. 2503
No. 24).

[0003]

In the prior art, when the intake valve and the exhaust valve are opened, one of the bearings that rotatably supports the camshaft is opened based on the valve spring and the pressure in the combustion chamber. The valve load acts in a concentrated manner via the camshaft. Therefore, the bearing is required to have strength and durability that can withstand the valve opening load, resulting in an increase in the size and weight of the bearing.

Further, since the push rod for transmitting the driving force for opening the cam to the rocker arm extends from the vicinity of the crankshaft to the inside of the cylinder head, the diameter of the rod is increased to prevent buckling. And yet
Its weight was also large. Therefore, in order to dispose the push rod, it is necessary to secure a relatively large space beside the cylinder and the cylinder head, so that the internal combustion engine becomes large and the push rod moves the cam from the intake valve to the exhaust valve. The inertial mass of the resulting valve train increases, causing a decrease in the followability of the intake valve and the exhaust valve with respect to the cam in a high rotation range of the internal combustion engine.

[0005] The present invention has been made in view of such circumstances, and the invention according to claims 1 to 3 is directed to a valve gear for an overhead valve type internal combustion engine in which a camshaft bearing is provided. It is a common object to reduce the size and weight of the engine and the size of the internal combustion engine. Another object of the present invention is to improve the followability of the engine valve in a high rotation range.

[0006]

Means for Solving the Problems and Effects of the Invention The invention according to claim 1 of the present application is directed to a single camshaft rotatably supported by a bearing and having a cam, and a camshaft provided on the camshaft. A first cam follower and a second cam follower that swing in contact with each other, and the first and second engine valves that are swingably provided on a cylinder head to open and drive the first engine valve and the second engine valve, respectively. Overhead comprising: a first rocker arm and a second rocker arm capable of contacting the first and second rocker arms, respectively; and a first rod and a second rod for transmitting the movement of the first and second cam followers to the first and second rocker arms, respectively. In the valve train for a valve type internal combustion engine, the first
And a second rocker arm is disposed on one side in the axial direction of the cylinder with respect to a plane including the axis of the camshaft,
The first cam follower abuts the cam on a side opposite to the one side, the second cam follower abuts the cam on the one side, and the first rod is a pull rod, and the second rod is a pull rod. The rod is a valve operating device of an overhead valve type internal combustion engine which is a push rod.

According to the first aspect of the present invention, the first and second cam followers abut against the cam on one side of the plane and on the opposite side thereof, so that the first and second cam followers contact the cam.
The valve-opening load acting on the camshaft when the engine valve is opened is distributed to two locations on the bearing. As a result, it is not necessary to increase the strength of the bearing as compared with the case where the valve opening load is concentrated at one location of the bearing, and the bearing can be reduced in size and weight.

In addition, the first and second rocker arms disposed on one side of the plane are located farther from the first rocker arm than the second cam follower and swing in a direction away from the first rocker arm. The rod that transmits the movement of the first cam follower to the first rocker arm is a pull rod, which is located closer to the second rocker arm than the first cam follower, and swings in the direction approaching the second rocker arm. Is transmitted to the second rocker arm by a push rod, the shape of the cam follower and the arrangement of the rod can be simplified, and the space for disposing the cam follower and the rod can be reduced, so that the internal combustion engine can be downsized. Becomes

According to a second aspect of the present invention, in the valve train for an overhead valve type internal combustion engine according to the first aspect, the length of the push rod is shorter than the length of the pull rod.

According to the second aspect of the present invention, the length of the push rod whose diameter is increased for preventing the buckling of the rod is reduced because it is not necessary to consider the buckling of the rod. By making the pull rod shorter than the length of the pull rod, the weight of the rod can be reduced, and the inertial mass of the valve train can be reduced. Can be improved.

According to a third aspect of the present invention, in the valve gear for an overhead valve type internal combustion engine according to the first or second aspect, the camshaft is arranged on a side of the cylinder so as to be offset from the cylinder. The pull rod extends between the first cam follower and the first rocker arm while passing between the cam shaft and the cylinder.

According to the third aspect of the present invention, since the pull rod is disposed by utilizing the space formed between the cylinder and the camshaft, the amount of the cylinder or the cylinder head projecting laterally is suppressed. In addition, since the rod is a pull rod whose diameter is smaller than that of the push rod, the offset amount of the camshaft can be reduced, and therefore the amount of protrusion of the camshaft to the side of the cylinder or cylinder head can be reduced. Thus, the size of the internal combustion engine can be reduced.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a left side view of a scooter type motorcycle equipped with an overhead valve type internal combustion engine having the valve gear of the present invention. In this specification, “front, rear, left and right” means front, rear, left and right in a vehicle body. The “center of the vehicle body” means a vertical plane passing through a center position in the left-right direction of a wheel mounted on the motorcycle.

The motorcycle 1 has a main frame including a front frame 3 and a rear frame 4 connected by bolts 2. A front suspension mechanism for suspending the front wheels 5 and a steering mechanism for steering the front wheels 5 are provided at a front portion of the front frame 3, and a power unit 7 for driving rear wheels 6 is provided behind and in front of the rear frame 4. The rear wheel 6 is located at the rear of the rear frame 4.
Is provided, and a seat 8 is provided above the rear frame 4.

A front fender 9, a front cover 10, a step floor 11, a frame body cover 12, and a rear fender 13 are attached to the motorcycle 1 in order from the front to the rear. A cover 14 is provided. A storage box 15 for storing a helmet or the like is provided in the frame body cover 12 below the seat 8.

The front suspension mechanism is a swing arm 16 located on the right side of the front wheel 5 and supported on a support shaft at the front lower end of the front frame 3 so as to be vertically swingable.
And a shock absorber 17 having one end pivotally attached to the swing arm 16 and the other end pivotally attached to the front frame 3. An axle holder 19 is attached to the front end of the swing arm 16 via a king pin 18 so as to be swingable in the left-right direction, and the front wheel 5 is rotatably supported by an axle 20 attached to the axle holder 19. .

The steering mechanism includes a front frame 3
A handle post 22 rotatably supported by a head pipe 21 attached to the front upper end of the handle post;
A steering arm 23 is attached to the lower end of the axle, and a link 24 is pivotally attached at one end to the steering arm 23 and at the other end to an arm 19a of the axle holder 19. In this way, the steering mechanism and the front suspension mechanism are mutually independent mechanisms to improve the maneuverability.

A front portion of the power unit 7 has a hanger hole 26 of a bracket 25 attached to the pair of right and left rear frames 4 and a lower crankcase of an internal combustion engine 30 described later.
The pair of hanger bolts respectively inserted into pipe bushes 46 (see FIG. 2) provided at the front end of 42L and the front end of cylinder head 43 are swingably supported by rear frame 4. . On the other hand, the rear part of the power unit 7 is
Mounted via 27. This allows the power unit 7 to swing up and down in accordance with the ups and downs of the road surface during traveling.

The power unit 7 includes an internal combustion engine 30 and a power transmission device 100 having a planetary gear type transmission 101 and a final reduction gear 120. The internal combustion engine 30 is a four-cycle single cylinder overhead valve type internal combustion engine. A flexible air introduction pipe 33 extending from an air cleaner 32 disposed inside the frame body cover 12 has a throttle body disposed on the right side of the vehicle body. 34 is connected to the upstream end. At the downstream end of the throttle body 34, an intake port 51 of the cylinder head 43 is provided.
A fuel injection valve 36 is attached to the intake pipe 35. This fuel injection valve
Fuel is supplied to 36 from a fuel tank 37 arranged below the step floor 11. On the right side of the vehicle body, an exhaust muffler 39 connected to an exhaust pipe 38 connected to an exhaust port 52 of the cylinder head 43 is arranged. Further, a fan cover 40 attached to a front end of the crankcase 42 is provided.
A radiator 41 to which cooling air from a cooling fan 64 (see FIG. 3) disposed therein is applied is disposed above the crankcase.

The output of the transmission 101 of the power transmission device 100 is transmitted to the axle of the rear wheel 6 by a shaft drive mechanism having a drive shaft 121 of the final reduction device 120, so that the rear wheel 6 is driven.

Next, FIG. 2 is a schematic sectional view of a main part when the crankcase 42, the cylinder 45 and the cylinder head 43 are cut along the line II-II in FIG. 1, and FIG.
The power unit 7 will be further described with reference to FIG. 3 which is a sectional view taken along the line I, FIG. 4 which is a sectional view taken along the line IV-IV of FIG. 2, and FIG. 5 which is a sectional view taken along the line VV of FIG.

The internal combustion engine 30 has a structure in which a crankcase 42, a cylinder head 43, and a cylinder head cover 44 are sequentially stacked and assembled. Crankcase 42
Includes an axis C1 of the crankshaft 31 of the internal combustion engine 30 and is divided into upper and lower crankcases 42U and 42L by a split plane A inclined with respect to a horizontal plane. The split plane A in the lower crankcase 42L is It is directed to the upper right of the vehicle body. A cylinder 45 having an axis C2 inclined upward and to the right of the vehicle body with respect to the axis C1 of the crankshaft 31 is integrally formed on an upper portion of the upper crankcase 42U, and a mounting surface facing the upper right of the cylinder 45 is formed. A cylinder head 43 is attached to B.

The two crankcases 42U and 42L are provided with a power transmission device 100 for transmitting the power of the crankshaft 31 to the rear wheel 6.
Of the transmission case that covers the front portion of the transmission 101. Further, the power unit 7 is attached to the bracket 25 of the rear frame 4 on the outer surface of the front end of the lower crankcase 42L.
There is provided a tube bush 46 through which a hanger bolt for supporting the pipe is inserted. This pipe bush 46
A cylindrical portion 46a integrally formed with 42L, an elastic member 46b made of a cylindrical rubber or the like whose outer peripheral surface is fixed to the inner peripheral surface of the cylindrical portion 46a, and an outer peripheral surface formed on the inner peripheral surface of the elastic member 46b. And a metal insertion tube 46c which is fixed and through which a hanger bolt passes. Further, a tube bush 46 having the same structure is also provided on the cylinder head 43.

The crankshaft 31 is so-called vertically disposed with its axis C1 pointing in the front-rear direction of the vehicle body, and is supported by the crankcase 42 via a pair of main bearings 49 and 50. Each of the main bearings 49 and 50 is held in a semi-cylindrical concave groove formed on the split surface A of each of the crankcases 42U and 42L so that the axis C1 of the crankshaft 31 is located on the split surface A. Has been.

A connecting rod 48 having a small end pivotally connected to a piston pin of a piston 47 slidably fitted in a cylinder bore of the cylinder 45 and a large end pivotally connected to a crankpin of the crankshaft 31 is provided. The crankshaft 31 is driven to rotate by the reciprocating piston 47.

Here, the relationship between the split surface A, the mounting surface B, and the axis C2 of the cylinder 45 will be described in more detail. In a reference plane orthogonal to the axis C1 of the crankshaft 31 and including the axis C2 of the cylinder 45, an intersection line between the split plane A and the reference plane and a point above the intersection of the axis C1 of the crankshaft 31 and the reference plane. The angle α formed by a reference vertical line, which is a vertical half line extending to the vertical axis, is an acute angle. Also, the axis of the cylinder 45
The angle β between C2 and the reference vertical line is also acute, and the angles α and β are substantially equal. An angle γ that is an angle formed by an extension of an intersection of the mounting surface B and the reference plane and the reference vertical line, and is an isotope of the angle α.
Is smaller than the angle α. Therefore, an intersection line between the split plane A and the reference plane, an intersection line between the mounting surface B and the reference plane, and an axis C2 of the cylinder 45 are formed between the intersection line between the vehicle center C0 and the reference plane. The angles are also an angle α, an angle β, and an angle γ, respectively. The values of the angles α, β, and γ are appropriately set in consideration of the size of the bank angle to be set and the like.

As a result, with respect to the split surface A and the mounting surface B which are inclined from the lower right to the upper left, the mounting surface B is inclined at a larger angle with respect to the horizontal plane than the split surface A. The plane including the split surface A and the plane including the mounting surface B intersect below the cylinder 45.

In addition to the intake port 51 and the exhaust port 52, the cylinder head 43 has a double-acting piston type supercharger 56.
A supercharging port 53 to which the discharge air conduit is connected is formed, and each of the ports 51, 52, 53 communicates with a combustion chamber 54 formed on the lower surface of the cylinder head 43. The mixture of fuel and air injected from the fuel injection valve 36 toward the intake port 51 is supplied to the combustion chamber 54. An ignition plug 55 for igniting the air-fuel mixture is attached to the cylinder head 43 so as to face the combustion chamber 54.

At the rear end of each of the cylinder head 43 and the upper crankcase 42U, a hole formed by a semi-cylindrical concave groove formed on the mounting surface B is provided. A supercharging cylinder 56a forming the housing of the machine 56 is fitted.

Further, a single camshaft 57 having its axis C3 oriented in the front-rear direction of the vehicle body is mounted on the cylinder head 43.
Are rotatably supported via a pair of bearings 60, 61 fixed respectively by a pair of cam holders 58, 59 attached to the cam (see FIG. 3). The axis C3 of the cam shaft 57 is the same as the axis C3.
And is located on the mounting surface B which is also a plane orthogonal to the axis C2 of the cylinder 45, and the cam shaft 57 itself is
It is arranged on the side of the cylinder 45 so as to be offset from the cylinder 45, that is, so that the axis C3 of the cam shaft 57 does not cross the cylinder 45.

As shown in FIG. 3, an AC generator 62 is provided at a front end portion of the crankshaft 31 which is located forward of the main bearing 49 on the front side, and a rotor 62a of the AC generator 62 is provided.
Is the crankshaft by the nut 63 at the front end of the crankshaft 31
Fixed to 31. Also, the rotor 62a of the AC generator 62
Has a cooling fan 64 that sends cooling air to the radiator 41
Are attached by bolts.

On the other hand, behind the main bearing 50 on the rear side of the crankshaft 31, a first drive gear 65 and a second drive gear 66 are sequentially mounted rearward so as to rotate integrally with the crankshaft 31. ing. A fitting hole coaxial with the crankshaft 31 is formed on the rear end face of the crankshaft 31, and a drive shaft 67 a of a hollow oil pump 67 is fitted into the fitting hole, and is integrally formed with the crankshaft 31. It is designed to rotate.

The oil stored at the bottom of the lower crankcase 42L is sucked into an oil pump 67 through a suction passage 68 formed in the transmission case 102, and the oil discharged from the oil pump 67 is The cam shaft 57 passes through an oil passage and an oil pipe provided in the transmission case 102,
It is supplied to the center shaft 103 of the transmission 101 and each bearing. Further, the discharged oil is supplied to the two main bearings 49 and 50 of the crankshaft 31 and the sliding portion between the crankpin and the large end of the connecting rod 48 through the inside of the drive shaft 67a of the oil pump 67. .

The first drive gear 65 meshes with a large gear 70 mounted so as to rotate integrally with the idler shaft 69. Since the idler shaft 69 also serves as a balancer shaft as described later, the number of teeth of the large gear 70 is made equal to the number of teeth of the first drive gear 65 so that the idler shaft 69 rotates at the same rotation speed as the crankshaft 31. Further, a small gear 71 meshing with a cam gear 72 provided to rotate integrally with the cam shaft 57 is provided integrally with the large gear 70 in order to drive the cam shaft 57 to rotate.
The camshaft 57 rotates once every two rotations of the crankshaft 31 by the series of gear trains 65, 70, 71, 72.

The cam gear 72 is a double-acting piston type supercharger.
Supercharging crankshaft 56c for reciprocating 56 supercharging piston 56b
Is splined. The camshaft 57 is formed with a hollow portion serving as an oil passage for supplying oil to a sliding portion between a cam and each rocker arm described later.
An extension of the supercharged crankshaft 56c is press-fitted into the end on the 56 side. As a result, the cam shaft 57 is
And rotate together.

The valve gear includes a cam, a cam follower, a pull rod, a push rod, and a rocker arm described below. As shown in FIGS. 2 and 4, the camshaft 57 has an intake cam 73 for opening and driving an intake valve 73, an exhaust valve (not shown), and a supercharging valve 74, which are three engine valves. 75, an exhaust cam 76 and a supercharging cam 77 located between the two cams 75, 76 are provided at intervals in the direction of the axis C3 of the cam shaft 57.

The intake rocker arm 85 and the exhaust rocker arm 86
The supercharged rocker arm 87 is swingably provided on the cylinder head 43 on the side of the cylinder head 43 which is one side of the mounting surface B in the direction of the axis C2 of the cylinder 45.
73, the exhaust valve and the supercharging valve 74 can be brought into contact with each other.

The intake cam 75, the exhaust cam 76 and the supercharging cam 77
At the base ends of the intake cam follower 78, the exhaust cam follower 79 and the supercharged cam follower 80 located between the two cam followers 78, 79, cylindrical support portions 78a, 79a,
A mounting surface B is formed on each of the bearings 78a, 79a, and 80a.
Above, both cam holders 58, 59 and cylinder head 43
Each of the cam followers 78, 79, 80 is inserted by inserting a support shaft 81 fitted and fixed in a semi-cylindrical concave groove formed in the cam follower.
Are swingably supported by a support shaft 81. In addition,
FIG. 5 illustrates a groove 58a formed in the cam folder 58 and a groove 43a formed in the cylinder head 43 corresponding to the groove 58a. The support shaft 81 has an axis parallel to the axis C3 of the camshaft 57, and is located on the mounting surface B at a position separated from the camshaft 57 with respect to the axis C1 of the cylinder 31 and below the camshaft 57. It is located in.

Further, an engagement portion 78b with which one end of the intake pull rod 82 engages is formed at the tip of the intake cam follower 78. A contact portion 78c that contacts the intake cam 75 is formed between the support portion 78a and the engagement portion 78b of the intake cam follower 78. Similarly to the intake cam follower 78, the exhaust cam follower 79 has an engagement portion 79b at one end of the exhaust cam follower 78, which is engaged with one end of the exhaust pull rod 83.The exhaust cam follower 79 is provided between the engagement portion 79a and the support portion 79b. A contact portion that contacts with 76 is formed. And the intake cam follower
Each of the engaging portion 78b and the contact portion 78c of 78 and the engaging portion 79b and the contact portion of the exhaust cam follower 79 are opposite to the one side in the direction of the axis C2 of the cylinder 45 with respect to the mounting surface B. Is located on the cylinder 45 side, which is the other side.

On the other hand, the supercharged cam follower 80 is formed at its tip with a receiving portion 80b with which the push rod 84 is in contact and a contact portion 80c with which the supercharged cam 77 is in contact. And
The receiving part 80b and the contact part 80c are
45 is located on the cylinder head 43 side, which is one side in the direction of the axis C2.

The intake pull rod 82 extends between the intake cam follower 78 and the intake rocker arm 85 through a space formed between the cam shaft 57 and the cylinder 45. Similarly, the exhaust pull rod 83 Cam shaft 57 and cylinder 45
And extends between the exhaust cam follower 79 and the exhaust rocker arm 86 through a space formed between them.

The push rod 84 is provided with a supercharged rocker arm 87.
The cylinder head 43 is secured by bolts 88 that swingably support
The push rod 84 penetrates a guide hole formed in a guide plate 89 fixed to the push rod 84 so that the push rod 84 can stably move in the axial direction.

Further, the diameter of the push rod 84 is required to prevent the buckling of the rod.
Is larger than the diameter. Also, push rod 84
Is shorter than the length of both pull rods 82, 83.

With such a valve train, the intake valve 73 is
An intake rocker arm 85 oscillated by an intake pull rod 82 pulled down by an intake cam follower 78 oscillated in contact with the intake cam 75 is driven to open the valve against the spring force of the valve spring 90.

Like the intake valve 73, the exhaust valve is also an exhaust rocker arm that is oscillated by an exhaust pull rod 83 that is pulled down by an exhaust cam follower 79 that is oscillated by contacting the exhaust cam 76.
By 86, the valve is driven to open against the spring force of a valve spring (not shown).

Further, the supercharging valve 74 is provided with a spring force of a valve spring 91 by a supercharging rocker arm 87 which is oscillated by a push rod 84 which is pushed up by a supercharging cam follower 80 which is oscillated in contact with a supercharging cam 77. The valve is driven to open. Then, the supercharging valve 74 is opened when the internal combustion engine 30 is in the compression stroke.

The cylinder head 43 is provided with a rotation position sensor 92 for detecting the rotation position of the cam shaft 57 by a rotating plate fixed to the front end of the cam shaft 57. An engine stroke state necessary for timing control is detected.

The idler shaft 69 whose axis C4 is oriented in the front-rear direction of the vehicle body is formed in a cylindrical shape, and has a large cylindrical portion 69a and a small cylindrical portion 69b.
The large cylindrical portion 69a and the small cylindrical portion 69b are
U and 42L are rotatably supported by a pair of bearings 93 and 94, respectively. Each of the bearings 93 and 94 is, like the main bearings 49 and 50 of the crankshaft 31, provided with the two crankcases 42 and 94.
U and 42L are held in semi-cylindrical concave grooves formed on the split surface A, respectively, and the axis C4 of the idler shaft 69 is positioned on the split surface A.

The housing 95a of the cooling water pump 95 is housed inside the large cylindrical portion 69a with a radial gap from the inner peripheral surface of the large cylindrical portion 69a. Housing 95a
The cover 95b of the cooling water pump 95 is attached in a liquid-tight manner, and the cover 95b is connected to a water pipe 96 from the outlet tank of the radiator 41. Further, the cylinder 45 has a discharge hole 97 communicating with a discharge portion of the cooling water pump 95 and communicating with a cooling water jacket formed around the cylinder bore.
(See FIG. 2).

The pump chamber formed by the housing 95a and the cover 95b extends in the pump chamber in the axial direction.
A rotation shaft 95c is provided, one end of which is rotatably supported on the top of the cover 95b and the other end of which is rotatably supported on the bottom of the housing 95a. The cooling water pump 95 has an impeller 95d integrally attached to the rotating shaft 95c, and a permanent magnet 95e is attached to the shaft of the impeller 95d in the circumferential direction. In the gap between the inner peripheral surface of the large cylindrical portion 69a of the idler shaft 69 and the housing 95a, the housing 9 is provided on the inner peripheral surface of the large cylindrical portion 69a.
Permanent magnets 95f are attached in the circumferential direction with a small gap between the permanent magnets 5a and 5a, and form a magnetic coupling with the permanent magnets 95e on the shaft of the impeller 95d.

The radiator 41 has an upper crankcase.
It is disposed between a V-shaped portion formed by 42U and a cylinder head 43, and both left and right ends thereof are fixed to the upper crankcase 42U and the cylinder head 43, respectively.

Therefore, when the idler shaft 69 rotates,
The impeller 95d rotates through this magnetic coupling,
The cooling water flowing into the pump chamber via the water pipe 96 is
The pressure is increased by 95d, and the pressure is sent to the cooling water jacket through the discharge hole 97.

As shown in FIG. 2, the cooling water that has finished cooling the high-temperature portions of the cylinder 45 and the cylinder head 43 is
The coolant flows from the cooling water outlet of the cylinder head 43 into the inlet side tank of the radiator 41 via the thermostat 98. As described above, the radiator 41 can be compactly disposed by utilizing the V-shaped space formed by the upper crankcase 42U and the cylinder head 43, and the power unit 7 can be downsized.

Further, on the outer peripheral surface of the large cylindrical portion 69a of the idler shaft 69, a cylindrical weight 99 partially provided with an opening is provided.
Is mounted to form a balancer that suppresses the vibration generated by the rotation of the crankshaft 31 having the balance weight and the vibration generated by the reciprocating motion of the piston 47 and the connecting rod 48.

Therefore, the idler shaft 69 is a drive shaft for driving the cooling water pump 95, and is also a balancer shaft as described above. As described above, by forming the idler shaft 69 provided in the drive mechanism for driving the cam shaft 57 as a coaxial two-axis rotary shaft, the idler shaft 69 can also function as a drive shaft of the cooling water pump 95 and a balancer shaft. it can. As a result, costs can be reduced as compared with the case where a rotating shaft having these functions is provided separately from the idler shaft.

The cam shaft 57 and the idler shaft 69
Is disposed on the side where the plane including the split surface A and the plane including the mounting surface B intersect with each other with respect to the axis C2 of the cylinder 45, that is, the side where the split surface A and the mounting surface B approach each other.
Therefore, the idler shaft 69 supported on the split surface A and the cam shaft 57 supported on the mounting surface B can be arranged close to each other, and another intermediate between the idler shaft 69 and the cam shaft 57 can be provided. Both rotating shafts 57 and 69 can be directly connected by the small gear 71 and the cam gear 72 without any intervening shafts and without increasing the size of the small gear 71 and the cam gear 72.
As a result, the length of the cylinder 45 of the internal combustion engine in the direction of the axis C2 can be suppressed, the size of the internal combustion engine 30 projecting leftward becomes smaller, and the power unit 7 becomes smaller.

Further, a cam shaft 57 is provided in a narrow space between the split surface A and the mounting surface B on the intersecting side of the cylinder 45.
And the idler shaft 69, which is a coaxial two-axis type rotary shaft having a plurality of functions, is concentrated, so that a large space without the rotary shaft can be formed on the side surface of the cylinder 45 on the opposite side. , Peripheral components can be arranged in the space.

On the other hand, a planetary gear type transmission 101 which is a component of the power transmission device 100 includes a center shaft 103, an input gear 104,
The vehicle includes a start clutch 105, second-speed, third-speed, and fourth-speed transmission clutches 106, 107, and 108, and an output shaft 109. The center shaft 103 cannot be rotated by the detent member 110 covering the shaft end attached to the case of the final reduction gear 120.

Hereinafter, the operation of the transmission 101 will be mainly described. A second drive gear 66 of the crankshaft 31 is provided with an input gear 104 attached to a flange provided at the axial center of a flanged boss 111 rotatable about the center shaft 103.
Is engaged. The rear part of the flanged boss 111 is coupled so as to rotate integrally with the clutch inner 105a of the starting clutch 105, and the front part meshes with a small gear 114 of an idler shaft constituting a speed reduction mechanism of a starting motor. A starting driven gear 115 is mounted via a one-way clutch 116. And at the time of starting, the rotation of the starting motor
Pinion 112, large idler shaft gear 113, small idler shaft gear 114, starting driven gear 115, one-way clutch 116,
Through the input gear 104 and the second drive gear 66, the crankshaft 31
Is transmitted to

The starting clutch 105 is provided coaxially with the center shaft 103, and includes a clutch inner 105a and an outer clutch 105b.
And the centrifugal weight 105c
When the centrifugal weight 105c is actuated when the rotation speed of the clutch 105a reaches a predetermined value, the clutch inner 105a and the outer clutch 105b are connected to rotate together, so that the starting clutch 105 is completely connected.

Each of the speed change clutches 106, 107, 108
It has a planetary gear mechanism and a clutch mechanism. The clutch outer of the clutch mechanism is integrally connected to the internal gear of the planetary gear mechanism, and the clutch inner of the clutch mechanism is integrally connected to the carrier that supports the planetary gear of the planetary gear mechanism. Further, the carrier has a centrifugal weight that integrates the clutch outer and the clutch inner via a plurality of clutch plates when the rotation speed reaches a predetermined rotation speed. The sun gear is mounted on the center shaft 103 via a one-way clutch.

The clutch outer 105b of the starting clutch 105
Are integrally connected to the clutch outer 106a of the second speed transmission clutch 106, and the carrier 106b of the second speed transmission clutch 106
Are integrally connected to the clutch outer 107a of the third-speed transmission clutch 107. Similarly, the third-speed transmission clutch 107
Is the clutch outer of the fourth speed transmission clutch 108, and the carrier of the fourth speed transmission clutch 108 is the output shaft 109.
Are integrally connected.

In the second-speed transmission clutch 106, the one-way clutch 106d is operated until the clutch mechanism operates to reach a predetermined rotational speed at which the internal gear, which is also the clutch outer 106a, and the carrier 106b, which is also the clutch inner, are integrated.
Due to the sun gear 106c not rotating due to the carrier 106
b rotates at a predetermined reduction ratio, and the clutch outer 107a of the third-speed transmission clutch 107 rotates at the reduced rotation speed. Similarly, the clutch outer of the fourth-speed transmission clutch 108 is rotated at a predetermined reduction ratio by the deceleration operation of the third-speed transmission clutch 107, and the output shaft is output at a predetermined reduction ratio by the deceleration operation of the fourth-speed transmission clutch 108. By rotating 109,
The maximum reduction ratio is obtained.

Next, in the second-speed transmission clutch 106, when the rotation speed of the carrier 106b reaches a predetermined rotation speed and the clutch mechanism operates to unite the internal gear and the carrier 106b, the second-speed transmission clutch 106 The entire body rotates together without deceleration, and the carrier rotates at a predetermined reduction ratio until the carrier of the third-speed transmission clutch 107 reaches a predetermined number of rotations. The clutch outer of the clutch 108 rotates. Further, the output shaft 109 is rotated at a predetermined reduction ratio by the deceleration operation of the fourth speed transmission clutch 108, so that a smaller reduction ratio can be obtained.

Similarly, when the third-speed transmission clutch 107 rotates integrally without deceleration by the operation of the clutch mechanism, the output shaft is driven at a predetermined reduction ratio by the deceleration operation of the fourth-speed transmission clutch 108. 109 is rotated to obtain a smaller reduction ratio. And the fourth-speed transmission clutch 10
When the clutch mechanism 9 operates as a whole and rotates integrally without deceleration, the clutch inner 105a of the starting clutch 105 and the output shaft 109 are directly connected, and the output shaft 109 rotates in the same rotation as the clutch inner 105a. Rotated by number.

The predetermined rotational speeds have different values, and are appropriately set in consideration of the speed change characteristics.

The output of the transmission 101 operating as described above is
The power is transmitted to the rear wheel 6 by the shaft drive mechanism. That is, the output gear attached to the output shaft 109 of the transmission 101
117 meshes with a gear 122 fixed to the drive shaft 121 of the final reduction gear 120. Body center compared to center shaft 103
A bevel gear is formed at the rear end of the drive shaft 121 which is located at a position close to C0 and whose axis C6 is oriented in the front-rear direction of the vehicle body. Meshes with a driven bevel gear attached to the motor. Thereby, the rotation of the output shaft 109 is reduced, and the rear wheel 6 is driven.

For controlling the internal combustion engine 30, a rotation speed sensor 123 for detecting a rotation signal of the drive shaft 121 is attached to the case of the final reduction gear 120. The rotation speed of the output shaft 109 is detected.

This embodiment has the following effects because it is configured as described above. The intake cam follower 78 and the exhaust cam follower 79 contact the intake cam 75 and the exhaust cam 76 on the cylinder 45 side of the mounting surface B, respectively.
On the other hand, the supercharged cam follower 80 is
The valve opening load acting on the camshaft 57 when the intake valve 73, the exhaust valve, and the supercharge valve 74 are opened is distributed to two portions of the bearings 60 and 61 because the supercharging cam 77 contacts the charging cam 77 on the side. As a result, the bearing 60,
There is no need to increase the strength of the bearing 61, and the bearings 60 and 61 can be reduced in size and weight.

The intake, exhaust and supercharger rocker arms 85, 86 and 87 arranged on the cylinder head 43 side of the mounting surface B are located farther from the intake and exhaust rocker arms 85 and 86 than the supercharged cam follower 80. The rods that transmit the movements of the intake and exhaust cam followers 78 and 79 oscillating in the direction away from the intake and exhaust rocker arms 85 and 86 to the intake and exhaust rocker arms 85 and 86 are intake and exhaust pull rods 82 and 83, respectively. A push rod 84 is provided at a position closer to the supercharged rocker arm 87 than the exhaust cam followers 78 and 79, and transmits the movement of the supercharged cam follower 80 swinging in a direction approaching the supercharged rocker arm 87 to the supercharged rocker arm 87. , Each cam follower 7 for swinging each rocker arm 85, 86, 87
The shape of 8, 79, 80 and the arrangement of rods 82, 83, 84 can be simplified, and the cam followers 85, 86, 87 and rods 82, 8
The space for arranging 3,84 can be reduced,
The size of the internal combustion engine 30 can be reduced.

The length of the push rod 84 whose diameter is increased to prevent buckling of the rod is changed by the length of the intake and exhaust pull rods 82 and 83 whose diameter is reduced because it is not necessary to consider the buckling of the rod. By making it shorter than this, it is possible to reduce the weight of the rod that transmits the cam valve opening driving force,
Since the inertial mass of the valve train can be reduced, the intake valve for each of the cams 75, 76, 77 can be controlled in the high rotation range of the internal combustion engine 30.
73, the followability of the exhaust valve and the supercharging valve 74 can be improved.

Further, since the axis C3 of the cam shaft 57 is located on the mounting surface B, the push rod 84
And the length of the pull rods 82, 83 can be reduced, the space for arranging the rods 82, 83, 84 can be reduced, and the inertial mass of the valve train can be reduced. In the high rotation range of the engine 30, each cam 75,
The follow-up of the intake valve 73, the exhaust valve, and the supercharging valve 74 with respect to 76, 77 is further improved.

Since the intake and exhaust pull rods 82 and 83 are arranged by utilizing the space formed between the cylinder 45 and the cam shaft 57, the amount of the cylinder 45 or the cylinder head 43 projecting laterally can be suppressed. And both pull rods 82,
Since the diameter of the rod 83 is smaller than that of the push rod 84, the offset amount of the cam shaft 57 from the cylinder 45 can be reduced, and therefore, the amount of protrusion of the cam shaft 57 to the side of the cylinder 45 or the cylinder head 43 can be reduced. The size can be reduced, and the internal combustion engine 30 can be reduced in size.

The cam shaft 57 comprises a cylinder 45 and a cylinder head.
Since it is assembled on the mounting surface B with the mounting surface 43, its assemblability is improved.

In the above-described embodiment, the plane including the axis C3 of the cam shaft 57 and perpendicular to the axis C2 of the cylinder 45 is the mounting surface B, but the plane perpendicular to the axis is the surface located on the cylinder 45 or the crankcase 42. For example, a surface other than the mounting surface B may be used.

In the above embodiment, the push rod
Although the supercharged rocker arm 87 is swung by 84, a rocker arm other than the supercharged rocker arm 87, for example, any one of an intake rocker arm and an exhaust rocker arm may be used. Furthermore, the engine may be an internal combustion engine without a supercharging valve, in which case a push rod is used to swing either the intake rocker arm or the exhaust rocker arm. And in these cases,
One of the contact portion 78c of the intake cam follower 78 and the contact portion of the exhaust cam follower 79 is located on one side of the orthogonal plane, and the other is located on the other side of the plane.

Further, in addition to the camshaft provided with the intake cam and the exhaust cam, a camshaft provided with a common cam for swinging the intake cam follower and the exhaust cam follower may be used. And also in this case,
One of the contact portion 78c of the intake cam follower 78 and the contact portion of the exhaust cam follower 79 is located on one side of the orthogonal plane, and the other is located on the other side of the plane.

In the above-described embodiment, the plane separating the contact portion 78c of the intake cam follower 78 and the contact portion of the exhaust cam follower 79 from the contact portion 80c of the supercharging cam follower 80 corresponds to the axis C2 of the cylinder 45. However, any plane other than the plane orthogonal to the plane may be used as long as the plane includes the axis C3 of the cam shaft 57 and intersects with the axis C2 of the cylinder 45.

[Brief description of the drawings]

FIG. 1 is a left side view of a scooter type motorcycle equipped with an overhead valve type internal combustion engine having a valve gear of the present invention.

FIG. 2 is a schematic cross-sectional view of main parts when a crankcase, a cylinder, and a cylinder head are cut along line II-II in FIG.

FIG. 3 is a sectional view taken along line III-III in FIG. 2;

FIG. 4 is a sectional view taken along line IV-IV of FIG. 2;

FIG. 5 is a sectional view taken along line VV of FIG. 4;

[Explanation of symbols]

1 ... motorcycle, 2 ... bolt, 3 ... front frame,
4: Rear frame, 5: Front wheel, 6: Rear wheel, 7: Power unit, 8: Seat, 9: Front fender, 10: Front cover, 11: Step floor, 12: Frame body cover, 13: Rear fender, 14: Side cover , 15… storage box, 16… swing arm, 17… shock absorber, 18…
King pin, 19 ... axle holder, 20 ... axle, 21 ... head pipe, 22 ... handle post, 23 ... steering arm,
24 link, 25 bracket, 26 hanger hole, 27 shock absorber, 30 internal combustion engine, 31 crankshaft, 32 air cleaner, 33 air inlet pipe, 34 throttle body, 35 intake pipe, 36 ... Fuel injection valve, 37 ... fuel tank, 38 ... exhaust pipe, 39
... exhaust muffler, 40 ... fan cover, 41 ... radiator, 42
... Crankcase, 43 ... Cylinder head, 44 ... Cylinder head cover, 45 ... Cylinder, 46 ... Pipe bush, 47 ... Piston, 48 ... Connecting rod, 49,50 ... Main bearing, 51 ... Intake port, 52 ... Exhaust port, 53 ... Supercharging port, 54 ... combustion chamber,
55 ... Ignition plug, 56 ... Supercharger, 57 ... Cam shaft, 58,59 ... Cam holder, 60,61 ... Bearing, 62 ... AC generator, 63 ... Nut, 64
… Cooling fan, 65, 66… Gear, 67… Oil pump, 68…
Inlet passage, 69 ... idler shaft, 70, 71, 72 ... gear, 73 ... intake valve, 74 ... supercharging valve, 75 ... intake cam, 76 ... exhaust cam, 77 ...
Supercharged cam, 78… Intake cam follower, 79… Exhaust cam follower, 80… Supercharged cam follower, 81… Support shaft, 82… Intake pull rod, 83… Exhaust pull rod, 84… Push rod, 85
... intake rocker arm, 86 ... exhaust rocker arm, 87 ... supercharged rocker arm, 88 ... bolt, 89 ... guide plate, 90, 91 ... valve spring, 92 ... rotational position sensor, 93, 94 ... bearing, 95 ... cooling water pump, 96 ... water pipe, 97 ... discharge hole, 98 ... thermostat,
99: weight, 100: power transmission device, 101: planetary gear type transmission, 102: transmission case, 103: center shaft, 104: input gear, 105: starting clutch, 106, 107, 108: transmission clutch, 109: Output shaft, 110: detent member, 111: boss with flange, 112: pinion, 113, 114, 115: gear, 116
... one-way clutch, 117 ... output gear, 120 ... final reduction gear, 121 ... drive shaft, 122 ... gear, 123 ... rotation speed sensor, A ... split surface, B ... mounting surface, C0 ... body center, C1-C6 ...
Axis.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3G016 AA02 AA05 AA19 BA02 BA05 BA10 BA27 BB08 BB13 CA13 CA17 CA22 CA27 CA41 CA45 CA47 CA48 CA57 GA01

Claims (3)

[Claims] 1. A single cam shaft rotatably supported by a bearing and provided with a cam, a first cam follower and a second cam follower swinging in contact with the cam, and a first engine valve. And the second engine valve to drive the respective valves to open.
A first rocker arm and a second rocker arm that are swingably provided on the cylinder head and can contact the first and second engine valves, respectively; and the first and second cam followers move the first and second cam followers. In a valve operating apparatus for an overhead valve type internal combustion engine having a first rod and a second rod respectively transmitting to a second rocker arm, the first and second rocker arms are arranged such that the first and second rocker arms move relative to a plane including an axis of the camshaft. The first cam follower is disposed on one side in the axial direction, the first cam follower abuts the cam on a side opposite to the one side, the second cam follower abuts the cam on the one side, The first rod is a pull rod, and the second rod is a push rod. 2. The valve train for an overhead valve type internal combustion engine according to claim 1, wherein a length of said push rod is shorter than a length of said pull rod. 3. The camshaft is disposed on a side of the cylinder so as to be offset from the cylinder, and the pull rod passes between the camshaft and the cylinder and the first cam follower and the first cam follower. 3. The valve gear of an overhead valve type internal combustion engine according to claim 1, wherein the valve gear extends between the rocker arm and the rocker arm.