JP2694898B2 - Valve system for 4-cycle engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a valve train used in, for example, a water-cooled 4-cycle single-cylinder engine for motorcycles, and more particularly, an intake valve and two valves with one camshaft. In the OHC engine in which the exhaust valve is driven to open and close, the rigidity of the central bearing portion formed in the cylinder head can be improved when the central portion of the camshaft is also pivotally supported.

[Conventional technology]

Generally, a valve train of an OHC engine is configured such that one camshaft is arranged so as to cross over the center of a combustion chamber, and the camshaft drives both an intake valve and an exhaust valve through a rocker arm to open and close. Have been. In this case, as the displacement increases and the combustion chamber diameter increases, the cam shaft lengthens correspondingly, the shaft diameter increases in order to secure the required rigidity, and the problem of weight increase easily occurs. Therefore, conventionally, there is an example in which not only the left and right ends of the cam shaft but also the center thereof are supported to reduce the diameter of the cam shaft (for example, Japanese Patent Laid-Open No.
-102506).

[Problems to be solved by the invention]

By the way, when the central portion of the camshaft is pivotally supported, it is naturally necessary to form the lower half portion of the central bearing portion in the cylinder head, but simply bulging a part of the cylinder head to form this lower half portion. Then, the rigidity of the portion is insufficient, or the weight of the cylinder head itself increases due to the reinforcing wall for improving the rigidity of the portion, and as a result, the effect of reducing the diameter of the cam shaft is likely to be offset.

In view of such a conventional situation, an object of the present invention is to provide a valve train for a four-stroke engine that can significantly improve the rigidity of a center bearing of a camshaft while suppressing an increase in the weight of a cylinder head. I have.

[Means for solving the problem]

The present invention is configured such that at least the vicinity of the combustion chamber 15 of the cylinder head 11 is cooled by the liquid, and the three intake valves 23 to 25 and the two exhaust valves 26, 27 are connected to the intake rocker arm,
In a valve operating system for a liquid-cooled 4-cycle engine in which a single camshaft 36 is driven to open and close via an exhaust rocker arm, the intake valves 23 to 25 and the exhaust valves 26 and 27 are respectively arranged in a direction perpendicular to the camshaft 36. Each valve shaft 23a to 25 on one side and the other side in plan view
Arrange so that the upper ends of a, 26a to 27a are located, and
36 is arranged so as to cross substantially the center above the combustion chamber 15,
A substantially central portion of the cam shaft 36 is rotatably supported by a central bearing portion 39, a cam 36b for driving the central intake valve 24 is arranged on one side of the combustion chamber center C in the cam axis direction, and the central bearing portion 39 is provided. Is disposed on the other side in the cam axis direction with respect to the center C of the combustion chamber by a dimension D1 and is inserted between the exhaust valves 26 and 27 and at a position facing the central bearing portion 39. Hole
29 is formed, and the lower half portion 39a of the central bearing portion 39 is connected to the peripheral wall of the head side insertion hole 29a integrally formed with the cylinder head 11 of the ignition plug insertion hole 29.

Here, the application range of the present invention is a liquid-cooled engine that cools with water or oil, in the case of a liquid-cooled engine,
A cylindrical plug insertion hole 29 for inserting the ignition plug from the outside of the cylinder head is formed in the plug hole formed in the ceiling wall of the combustion chamber. This is to improve the rigidity of the bearing portion 39.

[Action]

According to the valve gear of the present invention, since the central portion of the cam shaft 36 is pivotally supported by the central bearing portion 39, it is not necessary to increase the diameter of the cam shaft 36 and the weight of the cam shaft 36 can be reduced. Since the lower half portion 39a of the central bearing portion 39 is connected to the peripheral wall of the head side insertion hole 29a of the plug insertion hole 29 located between the exhaust valves 26, 27, the rigidity of the central bearing portion 39 can be greatly improved. Moreover, this improvement in rigidity can be realized only by connecting the lower half portion 39a of the central bearing portion 39 to the peripheral wall of the head side insertion hole 29a which is close to and adjacent to the central bearing portion 39, and an extra wall surface is formed in the cylinder head 11. Since it is not necessary, there is no problem of weight increase due to the bearing reinforcing wall portion of the cylinder head 11.

Further, in the present invention, since the central bearing portion 39 is located in the central portion surrounded by the valves 23 to 27 and does not interfere with these valves, the height position of the cam shaft 36 can be lowered, and the cylinder head is accordingly reduced. 11 can be made compact.

Furthermore, in the present invention, when the substantially central portion of the cam shaft 36 is pivotally supported by the central bearing portion 39, the cam 36b for the central intake valve 24 is provided.
Is arranged on one side of the combustion chamber center C, and the central bearing portion 39 is arranged on the other side of the combustion chamber center C, that is, the cam.
Since the cam 36b for the central intake valve is offset toward the side of the center C of the combustion chamber, that is, the gap between the cam 36b and the central intake valve 24 in the cam axis direction is made as small as possible because the cam 36b for the central intake valve is offset to the side opposite to 36b. Can be located in the central intake valve 24
The rocker arm for the vehicle can be made close to the shape extending in the direction perpendicular to the cam shaft 36, and the opening / closing operation of the central intake valve 24 can be smoothly performed.

〔Example〕

 Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

1 to 4 are views for explaining a valve train of a four-stroke engine according to one embodiment of the present invention.

In the figure, reference numeral 1 denotes a motorcycle equipped with a four-stroke engine to which the apparatus of this embodiment is applied, and a front fork 4 for supporting a front wheel 3 at a lower end thereof is supported at a front end of a body frame 2 of the motorcycle. A rear arm 6 that pivotally supports the rear wheel 5 at the rear end is pivotally supported up and down at the center lower end, and a large fuel tank 7 is further provided at the rear and a seat 8 is provided above the fuel tank 7. It is installed. Reference numerals 62 to 64, 58 denote an oil tank, a radiator, an air cleaner, and a vaporizer, respectively.

A water-cooled four-cycle single-cylinder engine unit 9 is mounted at the front of the body frame 2. The engine unit 9 includes a cylinder 10, a cylinder head 11,
And a head cover 12 laminated on a crankcase 14.

The cylinder 10 is configured by press-fitting a cylindrical cylinder liner 10c in a cylinder body 10b having a water cooling jacket 10a, and a piston 14 is provided in the cylinder liner 10c.
Are slidably inserted.

A combustion chamber recess 16 which forms a combustion chamber 15 with the upper surface of the piston 14 is provided substantially at the center of the lower surface of the cylinder head 11.
Is recessed. The three intake valve openings 17 to 19 and the two exhaust valve openings are formed on a substantially circumference along the periphery of the combustion chamber recess 16.
20,21 are formed. A plug hole 22 is formed in the center of the combustion chamber recess 16, and the plug hole 22 is led out by a plug insertion hole 29 for inserting an ignition plug from the outside. The plug insertion hole 29 has a cylindrical shape surrounded by a peripheral wall, and has a head side insertion hole 29a formed linearly in the cylinder head 11 and the head cover 12,
The cover side insertion hole 29b is formed. An ignition plug 30 is mounted in the plug hole 22.

The three intake valve openings 17 to 19 correspond to the cylinder head 11.
After being joined to one common intake passage 31 formed in the vehicle, it is led to the rear side in the vehicle longitudinal direction, and the two exhaust valve openings 20 and 21 are led to the front side by separate exhaust passages 32 and 33, respectively. ing. And these exhaust passages 32, 33, intake passage
A head-side water-cooling jacket 19 is formed around 31, 31 and the combustion chamber recess 16, and the jacket 19 communicates with the cylinder-side water-cooling jacket 10a.

The intake valve openings 17 to 19 and the exhaust valve openings 20 and 21 are provided with valve plates of intake valves 23 to 25 and exhaust valves 26 and 27 for opening and closing the openings. The valve stems (valve shafts) 23a to 27a of the intake and exhaust valves 23 to 27 penetrate the ceiling wall portions of the intake and exhaust passages 31 to 33 and project above the cylinder head 11. In this case, the valve stem 24a is more upright than 23a, 25a, the plug insertion hole 29 is located between the exhaust valves 26, 27,
Moreover, it is parallel to both the exhaust valves 26, 27. Further, the projecting ends of the intake valve stems 23a to 25a and the projecting ends of the exhaust valve stems 26a, 27a are located on parallel straight lines A and B, respectively, as shown in FIG. Further, a biasing spring 35 is arranged between a spring stopper 34 attached to the upper ends of the valve stems 23a to 27a and a spring seat 11a attached to the cylinder head 11.
As a result, the valves 23 to 27 are urged to close the valve openings 17 to 21.

Between the straight lines A and B, a single cam shaft 36 is arranged in parallel with the straight lines A and B, and across a position displaced from the center C of the combustion chamber 15 in plan view by D2 toward the rear of the vehicle. .
The left and right ends and the center of the camshaft 36 when viewed from the front of the vehicle (rightward in FIG. 1) are supported by left and right bearing portions 37, 38 and a central bearing portion 39, respectively. 39 is offset to the right from the center C, that is, to the opposite side of the first intake cam 36b that drives the center intake valve 24 to open and close with respect to the center C by D1. The central bearing portion 39 is located between the central intake valve 24 and the plug insertion hole 29 and faces both of them. A drive sprocket 40 is attached to a protruding portion of the camshaft 36 from the left bearing portion 37, and is connected to a crankshaft by a cam chain 41.

The first exhaust and intake cams 36a and 36b are provided between the bearing portions 37 and 39 of the cam shaft 36, and the second intake air is provided between the bearing portions 39 and 38.
Exhaust cams 36c and 36d are integrally formed, and the first intake cam 36b is for driving both of the intake valves 24 and 25, and is located approximately in the middle of the both valves 24 and 25. . The cams 36a to 36d are in sliding contact with the sliding portions 42a to 45a of the first exhaust and intake rocker arms 42 and 43, the second intake and exhaust rocker arms 44 and 45, respectively. Both the intake rocker arms 43 and 44 and the exhaust rocker arms 42 and 45 are respectively arranged in parallel with the cam shaft 36, and the intake and exhaust rocker arm shafts 4 and
It is swingably supported by 6,47. The other end of the first intake rocker arm 43 is branched into two actuating parts 43b, 43c, and adjustment bolts are provided on the actuating parts 43b, 43c and actuating parts 42b, 44b, 45b of the other rocker arms. Each of the adjusting bolts 48 is screwed into the valve stems 23a to 27a.
Is in contact with the upper end of the

The left and right bearings 37 and 38 and the central bearing 39 have a two-part structure consisting of a lower half formed on the cylinder head 11 side and an upper half formed on the head cover 12 side.
The front and rear portions of the lower half portion 39a of the central bearing portion 39 are integrally connected to the peripheral wall of the head side insertion hole 29a and the ceiling wall 31a of the common intake passage 31, respectively.

Further, a fastening bolt 12b for fastening and fixing the cylinder head 11 and the head cover 12 is inserted into the connecting portion. The bolt 12b is located in a suspension flange 12a formed integrally with the head cover 12, and the flange 12a is formed by a pair of suspension brackets 61, 61 and bolts 61a,
It is suspended on the tension pipe 2a of the body frame 2 via 61b.

 Next, the operation and effect of this embodiment will be described.

In the valve gear of this embodiment, when the camshaft 36 is rotationally driven by the crankshaft via the cam chain 41, each cam 36a
Each of the rocker arms 42 to 45 swings by .about.36d, and the respective intake and exhaust valves 23 to 27 are driven to open and close.

In the valve operating device that performs such an operation, when the number of valves per cylinder is large, for example, five, the total length of the cam shaft becomes long, and the cam shaft diameter becomes large in order to secure the rigidity of the cam shaft. Therefore, the problem of weight increase easily occurs. On the other hand, in the present embodiment, the camshaft 36 is supported not only by the left and right bearings 37 and 38 but also by the center bearing 39, so that the diameter of the camshaft can be reduced and an increase in weight can be prevented.

On the other hand, if the cam shaft is also supported in the central portion, a reinforcing wall is required to secure the rigidity of the central bearing portion depending on the design, and therefore the weight of the cylinder head itself tends to increase. On the other hand, in the present embodiment, the central bearing 39
Is disposed between the central intake valve 24 and the plug insertion hole 29, and the front and rear portions of the lower half portion 39a of the central bearing portion 39 are the peripheral wall of the plug insertion hole 29 and the ceiling wall 31 of the common intake passage 31, respectively.
Since it is connected to a, the rigidity of the central bearing portion 39 can be greatly improved as compared with, for example, the case where the lower half portion is formed in an overhang shape. Moreover, in improving the rigidity, since the engine is water-cooled, the plug insertion hole 29 is formed in a tubular shape having a peripheral wall, and as described above, the central bearing portion 39 is shared with the plug insertion hole 29. From the point of being close to and facing the intake passage 31, the lower half portion 39a of the central bearing portion 39 can be easily connected to the peripheral wall of the head-side insertion hole 29a and the ceiling wall 31a of the intake passage 31, and the cylinder head Since it is not necessary to form an additional bearing wall portion on 11, the problem of increased weight of the cylinder head 11 does not occur.

In addition, in this embodiment, five valves are arranged separately on the left side of the central bearing portion 39 and the right side of the central bearing portion 39, and the central bearing portion 39 is viewed from the plane of the combustion chamber 15. With respect to the center C, the number of valves is small and the space is relatively displaced, so that the first intake cam 36b is moved to the center C side by the distance D1 by effectively utilizing the extra space. The first intake cam 36b and the central intake valve 24 in the cam axis direction can be reduced, and the rocker arm can be disposed.
The central intake valve 24 actuating portion 43c of 43 can be made close to a shape perpendicular to the cam shaft 36, and the opening / closing operation can be made smooth, and the valve operating device and hence the cylinder head 11 can be made compact. Further, in the present embodiment, the cam shaft 36 passes between the five valves, and the central bearing 39 does not interfere with these, so that the cam shaft 36 can be arranged low, and from this point as well, the area around the cylinder head 11 is compact. Can be converted.

Further, in this embodiment, the camshaft 36 is eccentric to the rear side with respect to the center C of the combustion chamber by D2, and the eccentricity makes the plug insertion hole 29 in the center C of the combustion chamber on the front side which is advantageous in terms of space. Since the exhaust rocker arm shaft 47 is formed with a notch 47a for preventing interference when the spark plug is inserted, the spark plug can be formed without complicating the structure.
The verticality of 30 can be greatly improved. Incidentally, conventionally, in order to improve the perpendicularity, the rocker arm shaft is divided into two or a through hole is formed in the shaft, which causes problems such as an increase in the number of parts and a complicated structure. Was.

In this embodiment, the notch 47 of the rocker arm shaft 47 is used.
The a surface constitutes a part of the inner peripheral wall of the cover-side insertion hole 29b, whereby the space can be effectively used and the weight can be reduced.

Furthermore, in this embodiment, the vicinity of the insertion portion of the fastening bolt 12b between the cylinder head 11 and the head cover 12 is suspended around the vehicle body frame 2, so that the strength can be improved accordingly.

In the above embodiment, the motorcycle engine has been described. However, the present invention can of course be applied to other engines.

〔The invention's effect〕

As described above, according to the valve operating system for a liquid-cooled four-cycle engine according to the present invention, a plug insertion hole is formed between two exhaust valves and at a position facing the central bearing of the cam shaft, and the central bearing is formed. Since the lower half of the part is connected to the peripheral wall of the plug insertion hole,
There is an effect that the rigidity of the central bearing portion can be improved while preventing an increase in the weight of the cylinder head.

Further, in the present invention, since the central bearing portion is offset to the opposite side of the center of the combustion chamber from the cam that drives the central intake valve, the gap between the central intake valve cam and the central intake valve in the cam axis direction is increased. Can be made as small as possible, and the central intake valve rocker arm can be brought close to a shape extending in the direction perpendicular to the cam shaft, so that the central intake valve can be smoothly opened and closed.

[Brief description of the drawings]

1 to 4 are views for explaining a valve train according to one embodiment of the present invention. FIG. 1 is a plan view of the valve drive with its head cover removed, and FIG. Figure II _a -I
_Ia line cross-sectional side view, FIG. 2 (b) is a cross-sectional view showing a suspended state, FIG. 3 is a bottom view of a cylinder head, and FIG. 4 is a left side view of a motorcycle to which the present embodiment device is applied. is there. In the figure, 9 is an engine unit, 15 is a combustion chamber, 23-
Reference numeral 25 is an intake valve, 26 and 27 are exhaust valves, 29 is a plug insertion hole, 36 is a cam shaft, 39 is a central bearing portion, and 39a is a lower half portion.

Claims (1)

(57) [Claims] 1. At least the vicinity of a combustion chamber of a cylinder head is configured to be cooled by a liquid, and three intake valves and two exhaust valves are opened and closed by a single cam shaft via an intake rocker arm and an exhaust rocker arm. In the valve operating system of the liquid-cooled 4-cycle engine, the intake valve,
The exhaust valves are arranged so that the upper ends of the respective valve shafts are respectively located on one side and the other side in the direction perpendicular to the cam shaft in a plan view, and the cam shaft is arranged so as to cross substantially above the center of the combustion chamber. The substantially central portion of the cam shaft is supported by a central bearing portion, the cam for driving the central intake valve is arranged on one side in the cam axis direction of the center of the combustion chamber, and the central bearing portion is located with respect to the center of the combustion chamber. It is arranged on the other side in the cam axis direction with an offset of dimension D1, and a cylindrical spark plug insertion hole is formed between the exhaust valves and at a position facing the central bearing portion, and the lower half of the central bearing portion is formed. A valve operating device for a four-cycle engine, wherein the portion is connected to a peripheral wall of a head side insertion hole integrally formed with the cylinder head of the ignition plug insertion hole.