JP2000329002A - Engine for motorcycle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To hold durability of a bearing for a camshaft positioned on a cam chain chamber side at a high level by improving rigidity of a wall of the cam chain chamber side of a cylinder head. SOLUTION: In this engine for a motorcycle, rocker shaft holes 7a of supporting parts 7 for a rocker shaft in a cylinder head are drilled so as to open rocker shaft inserting ports 24 on end parts opposed to a cam chain chamber 23. The supporting parts 7 for the rocker shaft positioned on the cam chain chamber 23 side are formed so as to prevent the rocker shaft holes 7a from penetrating, and thereby, rigidity of wall formed between head bolts of the cam chain chamber 23 side, that is a wall for holding a bearing for a camshaft of the cam chain chamber 23 side is increased more than a prior art. Since the bearing for supporting the end parts of the cam chain 23 side in the camshaft can be forcibly held, durability of the bearing for the camshaft can be held at a high level even if two intake valves are disposed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motorcycle engine in which an intake valve and an exhaust valve are driven by a single camshaft.

[0002]

2. Description of the Related Art As a conventional motorcycle engine of this type, for example, there is one configured as shown in FIGS. FIG. 12 is a longitudinal sectional view of a cylinder head of a conventional motorcycle engine, and FIG. 13 is a transverse sectional view of a rocker shaft portion of the cylinder head. The broken position in FIG. 13 is shown by the line XIII-XIII in FIG.

[0003] In these figures, reference numeral 1 denotes a cylinder head of a SOHC single cylinder engine for a motorcycle. The cylinder head 1 is formed by casting, has a combustion chamber forming portion 6 having a concave portion 5 for forming an intake port 2, an exhaust port 3 and a combustion chamber 4, a support portion 7 for a rocker shaft and two maintenance members. The upper part 9 forming the opening 8 is integrally formed with the upper part 9 to support all the members of the valve gear 10, and is fixed to a cylinder body (not shown) by four head bolts 11.

[0004] The valve gear 10 has a single intake valve 1.
2, the exhaust valve 13, and the rocker arms 14, 15 for each valve.
And one camshaft 16 and the like. As shown in FIG. 13, the rocker arms 14 and 15 integrally include a boss 18 through which a rocker shaft 17 passes, an arm 19 connected to the intake valve 12 or the exhaust valve 13, and a slipper 20 slidingly contacting the cam shaft 16. The boss 18 is rotatably supported by the rocker shaft support 7 by the rocker shaft 17. Rocker shaft 1
Reference numeral 7 is press-fitted into the rocker shaft holes 7a of the two rocker shaft support portions 7, 7 provided so as to face each other.

[0005] The boss 18 is formed in a substantially cylindrical shape in which both end faces in the axial direction are opposed to the support portion 7 with a small gap therebetween, and the slipper is so protruded from one end face toward the support portion 7 side. 20 are protruding.

The cam shaft 16 has bearings 21 and 2 at both ends.
A cam chain sprocket (not shown) is attached to the lower end in FIG. The cam chain is housed in a cam chain chamber 23 formed on one side of the cylinder head 1 and the cylinder body, and is wound around the sprocket and a crankshaft side sprocket (not shown).

A locker shaft insertion port 24 is opened in the cam chain chamber 23, and the rocker shaft 17 is inserted into the rocker shaft hole 7a from the cam chain chamber 23 side.

In the conventional engine thus constructed, the rocker arms 14 and 15 are assembled by using the intake / exhaust valve 1.
After assembling the camshafts 16, 13 and the camshaft 16 to the cylinder head 1, as shown in FIG.
5 is inserted into the cylinder head 1 from the maintenance opening 8 by inclining it 90 degrees in the direction in which it is twisted. The rocker arm 15 shown in the figure is for an exhaust valve.

That is, first, the rocker arm 15 is inserted between two opposing rocker shaft support portions 7 on the exhaust side in a state where the rocker arm 15 is inclined at 90 ° as described above, and the boss 18 is attached to the support portion. 7 and the camshaft 16. From this state, the rocker arm 15 is inclined in the opposite direction so as to return to the upright position, and the boss 18 is inserted from above between the two rocker arm support portions 7,7. The rocker shaft 17 is inserted into the rocker shaft hole 7a from the cam chain chamber 23 in a state where the shaft hole of the boss 18 and the rocker shaft hole 7a of the support portion 7 are positioned on the same axis. The rocker arm 14 for the intake valve is also assembled in the same manner as the rocker arm 15 for the exhaust valve.

[0010] This type of motorcycle engine is
There is a demand for increasing the engine output by increasing the intake flow rate by using two intake valves.

[0011]

However, in the conventional motorcycle engine constructed as described above,
There is a problem that the wall supporting the camshaft support bearing 21 in the cylinder head 1 is easily deformed. This is because the rocker shaft support 7 located on the cam chain chamber 23 side of the rocker shaft support 7 on the intake valve 12 side has a rocker shaft hole 7a as shown in FIG.
This is because the head bolt 11 penetrates the portion where the hole is drilled, and the rigidity becomes relatively low. Moreover, in order to provide two intake valves, the load for rotating the camshaft 16 also increases, so it is important to improve the rigidity of the wall.

When the rocker shaft support 7 on the cam chain chamber 23 side is deformed, the outer ring of the cam shaft bearing 21 located near the cam chain chamber 23 is deformed, and the durability of the bearing 21 tends to be reduced. In particular, the bearing 21 on the cam chain chamber 23 side
Since the chain tension acts on the bearing 21, the load on the bearing 21 increases.

The rocker shaft support 7 is easily deformed due to the difference in the coefficient of thermal expansion between the aluminum alloy forming the cylinder head 1 and the steel forming the head bolt 11. One of the causes is that both an increase in the tightening force of the bolt 11 and a decrease in the strength of the cylinder head 1 due to an increase in the temperature of the cylinder head 1 due to an increase in the engine output overlap. It is one.

Such problems are caused by increasing the distance between the head bolts 11 to improve the rigidity of the rocker shaft support 7 or by supporting the rocker shaft support 7 on the intake valve side and the rocker shaft support on the exhaust valve side. The problem can be solved to some extent by reducing the distance from the part 7.

However, if the distance between the head bolts 11 is increased, the sealing property between the cylinder head 1 and the cylinder body (particularly, the combustion chamber) tends to be reduced, and the rocker arm support portions 7 are connected to each other. Becomes smaller, it becomes impossible to assemble the rocker arms 14 and 15.

The reason why the rocker arms 14 and 15 cannot be assembled is that the distance D (see FIG. 12) between the rocker shaft support 7 on the intake valve side and the rocker shaft support 7 on the exhaust valve side is narrow. As a result, the rocker arms 14 and 15 cannot be rotated in the cylinder head 1 due to being interrupted by the support portion 7 and the cam shaft 16,
Even if it can rotate, the length of the slipper 20 (FIG. 12)
This is because the distance D becomes narrower than that shown by the reference numeral L in the drawing), and the slipper 20 cannot be moved in parallel to the camshaft 16 side.

In order to be able to assemble the rocker arms 14 and 15 even if the distance between the two rocker arm support portions 7 is small, the cylinder head 1 is mounted on the upper portion 9 having the rocker shaft support portions 7. And the combustion chamber forming portion 6 on the cylinder body side. That is, the rocker arms 14 and 1 are provided on the upper portion 9 divided from the combustion chamber forming portion 6.
5 is assembled from the combustion chamber forming portion 6 side, so that the rocker arms 14 and 1 can be mounted without any obstacles.
5 can be assembled.

However, in such a structure in which the cylinder head 1 is formed of two members, the number of parts is increased and the cost is increased, and the member (to which heat is transmitted from the combustion chamber 4 in the cylinder head 1) The volume of the lower portion of the cylinder head), that is, the heat capacity is reduced, and the cooling performance is reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and has improved the rigidity of the wall of the cylinder head on the cam chain chamber side, thereby improving the durability of the camshaft bearing located on the cam chain chamber side. The purpose is to be able to maintain high.

[0020]

In order to achieve this object, a motorcycle engine according to the present invention has a rocker shaft hole formed in a rocker shaft support portion of a cylinder head at an end opposite to a cam chain chamber. Only the rocker shaft insertion hole is formed so as to open.

According to the present invention, since the rocker shaft hole does not penetrate the rocker shaft supporting portion located on the cam chain chamber side, the wall formed between the head bolts on the cam chain chamber side, that is, the cam chain chamber. The rigidity of the wall holding the camshaft bearing on the side can be increased as compared with the related art.

On the other hand, comparing the load on the bearings at both ends of the camshaft, the load on the bearing on the opposite side is smaller than the bearing on the cam chain chamber side where the tension of the cam chain acts, and the bearing size is smaller. Therefore, even if the rocker shaft hole penetrates, the rigidity of the wall holding the bearing can be ensured.

A motorcycle engine according to a second aspect of the present invention has a structure in which two intake valves are provided for each cylinder and these intake valves are driven by one rocker arm. Is provided on a boss through which the camshaft slides so that the position in the axial direction of the rocker shaft is located inside a range sandwiched between both end surfaces of the boss in the axial direction of the rocker shaft.

According to the present invention, it is possible to insert the rocker arm between the two opposing rocker shaft support portions while moving in parallel while maintaining the posture in which the sliding surface of the slipper faces the cam shaft. it can. Therefore, interference between the rocker shaft hole and the head bolt hole can be avoided while improving the assemblability of the rocker arm, and the rigidity of the wall holding the camshaft bearing can be improved.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment A first embodiment of a motorcycle engine according to the present invention will be described in detail with reference to FIGS. FIG. 1 is a side view of a motorcycle equipped with an engine according to the present invention,
FIG. 2 is a longitudinal sectional view of the engine according to the present invention, FIG. 3 is a transverse sectional view of the cylinder head, FIGS. 4 and 5 are longitudinal sectional views of the cylinder head, and FIG. 5 shows a state in the middle of the rocker arm mounting step.

FIG. 6 is a sectional view showing a rocker arm supporting portion, FIG. 7 is a side view of the cylinder head, FIG. 8 is a view showing an end surface of the cylinder head on the cylinder body side, and FIG. 9 is a sectional view taken along line IX-IX in FIG. FIG. 10 is a bottom view showing a state where the cylinder head is viewed from the road surface side. In these drawings, the same or equivalent members as those described in FIGS. 12 and 13 are denoted by the same reference numerals, and detailed description is omitted.

In FIG. 1, reference numeral 31 denotes a motorcycle according to this embodiment. In the motorcycle 31, a front frame 34 is rotatably and steerably supported by a body frame 32 via a front fork 33, and a rear arm 36 rotatably supporting a rear wheel 35 is vertically swung by a pivot shaft 37. They are freely supported. In the figure, reference numeral 38 denotes a steering handle,
Reference numeral 39 denotes a sheet.

The motorcycle 1 has an air-cooled SOHC single-cylinder engine 41 mounted between a front wheel 34 and a rear wheel 35 so that the cylinder axis is parallel to the front-rear direction of the vehicle body. The engine 41 has a crankcase 42 supported by the body frame 32,
A cylinder 43 is mounted on the front end of the vehicle body. The cylinder body of the cylinder 43 is indicated by reference numeral 44 in the figure, and the cylinder head is indicated by reference numeral 45.

An intake pipe 4 is provided on the upper surface of the cylinder head 45.
A carburetor 47 is connected to the exhaust pipe 48 via an exhaust pipe 48. The carburetor 47 is disposed above the cylinder head 45, and connects an air cleaner 50 via an intake duct 49 to an intake opening that opens toward the front of the vehicle body. The side and upper sides of the cylinder 43, the carburetor 47, and the air cleaner 50 are covered with a leg shield 51 and a vehicle body cover 52.

The cylinder head 45 is formed by casting in the same manner as the conventional one, and as shown in FIGS.
A combustion chamber forming portion 6 having an intake port 2, an exhaust port 3, a concave portion 5 for forming a combustion chamber 4, and the like, and an upper portion 9 having a rocker shaft support portion 7 and a maintenance opening 8 are integrally formed. ing.

The intake port 2 is, as shown in FIG.
It is formed so as to branch into a forked shape in the cylinder head 45. The exhaust port 3 is an intake outlet 2a on the cam chain chamber 23 side of the two intake outlets 2a of the intake port 2.
Is formed in the vicinity of the exhaust port 3a. This exhaust inlet 3
A screw hole 54 for screwing a spark plug 53 (see FIG. 3) is formed on the side of a and near the other intake outlet 2a.

The cylinder head 45 includes two intake valves 12 and 12 and one exhaust valve 13 and one camshaft 1.
6 and a valve gear 57 driven by rocker arms 55 and 56 for each valve. The camshaft 1 of the valve train 57
6, the intake cam 16a located on the right side of the vehicle body (the right side in FIG. 3) is arranged to be closer to the cam chain chamber 23 side so as to intersect the cylinder axis C as shown in FIG. Sprocket 58 for cam chain at the end
Is installed.

By disposing the camshaft 16 in this manner, the space between the camshaft 16 and the ignition plug 53 is widely opened, so that the cylinder head 45 utilizes this wide space to improve the cooling performance. Is being planned. More specifically, as shown in FIG. 3, a recess 59 is formed between the ignition plug 53 and the camshaft 16 and opens toward the right side of the vehicle body, and the recess 59 extends downward from the bottom of the recess 59 as shown in FIG. A cooling air passage 60 extending in the direction (in the direction of the road surface) is formed. The opening at the lower end of the cooling air passage 60 is indicated by reference numeral 60a in FIG.

That is, during traveling, the traveling wind flows into the cooling air passage 60 from the opening 60a at the lower end, and flows out to the right side of the vehicle body through the concave portion 59 formed near the combustion chamber 4 and the ignition plug 53. Therefore, the combustion chamber 4 and the spark plug 53 can be efficiently cooled. Even when the vehicle is stopped, the air in the cooling air passage 60 rises by convection due to the heat of the cylinder head 45 and is discharged from the recessed portion 59, so that the cooling efficiency is lower than that of the conventional cylinder head 45. Get higher.

As shown in this embodiment, the camshaft 1
6 is disposed near the cam chain chamber 23 and the ignition plug 53
By widely opening the vicinity of the recess, the recess 5
9 also has the advantage that it is possible to reduce what blocks hot air radiated into the atmosphere. Moreover, the spark plug 5
The cooling performance of No. 3 can also be improved.

As shown in FIG. 3, the bottom of the recess 59 is opposed to the bottom of a recess 62 extending from the cam chain chamber 23 along the combustion chamber forming wall 61 into the cylinder head 45. As shown in this embodiment, the cylinder 4
In the engine 1 in which the lubricating oil 3 is provided substantially horizontally, the lubricating oil easily adheres to the cam chain and flows into the cylinder head 45 side, so that the lubricating oil easily flows into the concave portion 62 opened in the cam chain chamber 23. Can be. The opening of the recess 62 is indicated by reference numeral 63 in FIG. As the lubricating oil flows into the concave portion 62 on the cam chain chamber 23 side, the bottom of the air cooling concave portion 59 where hot air easily flows can be cooled by the lubricating oil.

The intake valve 12 and the exhaust valve 13 are arranged so that the included angle is narrower than in the prior art. Along with this, the rocker shaft support 7 for the intake valve and the rocker shaft support 7 for the exhaust valve are formed so that the distance between them is smaller than in the prior art. For this reason, the rocker arms 55 and 56
The interference between the rocker shaft hole 7a and the head bolt hole can be avoided while improving the assemblability of the camshaft bearing 21.
Can be improved in rigidity of the wall for holding the wall.

As described above, the rocker arms 55 and 56 have a structure that can be easily assembled even if the distance between the two support portions 7 is small. To elaborate,
As shown in FIG. 6, the rocker arms 55 and 56 include a boss 64 that penetrates the rocker shaft 17 and an intake valve 12.
Alternatively, an arm 65 for connecting the exhaust valve 13 and the camshaft 16
Is formed integrally with a slipper 66 that slides on the boss 6.
4, the slipper 66 is provided such that its position in the axial direction of the rocker shaft is located inside a range sandwiched between both end surfaces of the boss 64 in the axial direction of the rocker shaft.
The intake valve rocker arm 55 includes two intake valves 12, 1
Two arms 65 are provided so that the arm 2 can be driven.

In this embodiment, the slipper 66 of the intake valve rocker arm 55 is positioned near the center of the cylinder bore (indicated by the symbol A in FIG. 6).
As shown in FIG. 6, the two arms 65, 65 are arranged in a substantially Y-shape when viewed from the axial direction of the cylinder 43. By adopting this structure, two intake valves 1
In spite of the structure in which the rockers 2 and 12 are driven by one rocker arm 55, it is possible to prevent the load from being applied to one of the arms 65 unevenly, and to prevent uneven wear.

Next, a procedure for assembling the rocker arms 55 and 56 to the cylinder head 45 will be described with reference to FIGS. As shown in FIG. 4, the cylinder head 45 sucks and sucks before the rocker arms 55 and 56 are assembled.
The exhaust valves 12, 13 and the camshaft 16 are assembled in advance.
When assembling the rocker arms 55 and 56, first,
The rocker arms 55 and 56 are inserted into the cylinder head 45 from the maintenance opening 8 of the cylinder head 45,
The boss 64 is inserted between the pair of rocker shaft support portions 7 formed so as to face each other.

This insertion operation is performed by moving the rocker arms 55, 56 in parallel while maintaining the posture in which the sliding surface 66a of the slipper 66 faces the cam shaft 16, as shown in FIG. Thereafter, the positions of the rocker arms 55 and 56 are adjusted so that the shaft hole of the boss 64 and the rocker shaft hole 7a are positioned on the same axis, and the rocker shaft 1 is adjusted.
7 into the rocker shaft hole 7a from the cam chain chamber 23 side.
Press-fit. Then, a stopper 67 (see FIGS. 6 and 7) for locking the rocker shaft is attached to the cylinder head 45. The stopper 67 is provided with the rocker shaft hole 7.
The two protruding pieces 67a facing the inside a and the protruding piece 67b contacting the outer end surface of the camshaft bearing 21 are integrally formed, so that the camshaft bearing 21 also serves as a stopper.

Therefore, in the engine 41, the rocker arms 55, 56 are provided between the two rocker shaft support portions 7, 7 facing each other, and the sliding contact surfaces 66 of the slippers 66 are provided.
a can be inserted while being moved in parallel while maintaining the posture facing the camshaft 16.
13 can easily be rocker arms 55 and 5
6 can be assembled to the cylinder head 45. For this reason, while improving the assemblability of the rocker arms 55 and 56, the angle between the intake and exhaust valves 12 and 13 can be set to be smaller than in the past, and the engine output can be improved.

When the sandwiching angle is reduced, the cylinder head 4
Although the height of 5 is increased, a space for rotating the rocker arm at the time of assembling as in the related art is not required, so that it can be reduced. Therefore, it can be mounted without extending the wheel base.

Second Embodiment A cylinder head 45 can be configured as shown in FIG. FIG. 11 is a sectional view showing one embodiment of the invention described in claim 1. In this figure, the same or equivalent members as those described with reference to FIGS. 1 to 10 and FIGS. 12 and 13 are denoted by the same reference numerals, and detailed description is omitted.

In the cylinder head 45 shown in FIG. 11, the rocker shaft hole 7a is formed so that the rocker shaft insertion opening 24 is opened only on the side opposite to the cam chain chamber 23 (the right side of the vehicle body (the left side in FIG. 11)). are doing. Therefore, the rocker shaft supporting portion 7 on the cam chain chamber 23 side does not have through holes formed on both the intake valve 12 side and the exhaust valve 12 side, and the two head bolts 11, Wall 71 formed between 11
Rigidity can be improved. Since the cam shaft bearing 21 on the cam chain chamber 23 side is fitted and held on the wall 71, the cylinder head 45 can firmly hold the bearing 21.

[0046]

As described above, according to the present invention, since the rocker shaft hole does not penetrate the rocker shaft support located on the cam chain chamber side, it is formed between the head bolts on the cam chain chamber side. The rigidity of the wall, that is, the wall holding the camshaft bearing on the cam chain chamber side can be increased as compared with the conventional case.

Therefore, the bearing for supporting the cam chain chamber side end of the camshaft can be firmly held, so that the durability of the camshaft bearing can be maintained high even with two intake valves.

According to the second aspect of the present invention, the rocker arm is translated between the two rocker shaft support portions facing each other while maintaining the posture in which the sliding surface of the slipper faces the cam shaft. Can be inserted.

Therefore, while improving the assemblability of the rocker arm, interference between the rocker shaft hole and the head bolt hole can be avoided, and the rigidity of the wall holding the camshaft bearing can be improved. By adopting this structure, there is also an effect that the sandwiching angle of the exhaust valve becomes narrower than before and the engine output can be improved. Moreover, since the cylinder head 45 is not divided, the heat capacity can be increased and the cooling performance is not impaired.

[Brief description of the drawings]

FIG. 1 is a side view of a motorcycle equipped with an engine according to the present invention.

FIG. 2 is a longitudinal sectional view of the engine according to the present invention.

FIG. 3 is a cross-sectional view of a cylinder head.

FIG. 4 is a longitudinal sectional view of a cylinder head.

FIG. 5 is a longitudinal sectional view of a cylinder head.

FIG. 6 is a cross-sectional view showing a rocker arm supporting portion.

FIG. 7 is a side view of the cylinder head.

FIG. 8 is a view showing an end surface of a cylinder head on a cylinder body side.

9 is a sectional view taken along line IX-IX in FIG.

FIG. 10 is a bottom view showing a state where the cylinder head is viewed from a road surface side.

FIG. 11 is a sectional view showing one embodiment of the invention described in claim 1;

FIG. 12 is a longitudinal sectional view of a cylinder head of a conventional motorcycle engine.

FIG. 13 is a cross-sectional view of a rocker shaft portion of the cylinder head.

[Explanation of symbols]

6: Combustion chamber forming part, 7: Rocker shaft support,
7a: rocker shaft hole, 9: upper part, 12: intake valve,
13: Exhaust valve, 16: Cam shaft, 17: Rocker shaft, 23: Cam chain chamber, 24: Rocker shaft insertion port 41: Engine, 45: Cylinder head, 55, 5
6 ... rocker arm, 64 ... boss, 66 ... slippers.

Claims (2)

[Claims] In a motorcycle engine in which an intake valve and an exhaust valve are driven by one camshaft and a rocker arm for each valve, a rocker shaft hole of a rocker shaft support portion in a cylinder head is formed in a cam chain chamber. A motorcycle engine characterized in that a rocker shaft insertion opening is opened only at an end opposite to the end of the motorcycle. 2. A part forming a combustion chamber in a cylinder head, and a pair of rocker shaft support parts supporting both ends of a rocker shaft are integrally formed, and an intake valve and an exhaust valve are combined with one cam shaft. A motorcycle engine driven by a rocker arm for each valve, having a structure in which two intake valves are provided for each cylinder, and these intake valves are driven by one rocker arm, and a rocker shaft in the rocker arm penetrates. A motorcycle engine, wherein a slipper with a camshaft slidingly contacting the boss is provided so that its position in the rocker shaft axial direction is located inside a range sandwiched between both end surfaces of the boss in the rocker shaft axial direction. .