JPS6220644Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The invention is a horizontally opposed internal combustion engine.
This relates to a bearing for a camshaft that operates a type valve mechanism.

[Conventional technology]

In a horizontally opposed internal combustion engine, the crankcase is divided into left and right halves, the crankshaft is installed at the joint of the left and right crankcases, and the cylinder head and cylinder head are installed on the sides of the left and right crankcases, respectively.
A rocker cover with a valve mechanism is attached.
In the case of an OHV type valve mechanism, one camshaft that operates the left and right valve mechanisms is mounted at the center of the engine body, that is, at the same joint of the left and right crankcases as the above-mentioned crankshaft. The camshaft has two cams that open and close the intake and exhaust valves, respectively.
It has a total of four cams, and has a three-bearing structure with journals at both ends and in the center, and each journal is supported by a receiving part of the crankcase itself.

By the way, the valve lifter at one end of the push rod is in relatively strong sliding contact with each cam of the camshaft due to the elasticity of a valve spring, etc., and after long-term operation, the camshaft may be forced to be replaced due to wear of the cams.

[Problem that the invention attempts to solve]

However, in the past, the mating part of the left and right crankcases had a large opening to support the journal when the crankshaft was installed, and the joint strength between the crankcases was likely to be lacking. The opening diameter of the journal receiving portion of the camshaft installed in the camshaft is made as small as possible. For this reason, the diameter of the journal of the camshaft and its receiving portion is not so large as to include the cam crest of the cam, but is only slightly larger than the base circular portion of the cam. For this reason, when replacing the camshaft mentioned above, even if you try to move the camshaft in the axial direction, the cam crest of the cam will hit the journal receiver, making it impossible to pull it out, and the cylinder head and crankcase will have to be disassembled. They are forced to do very complicated tasks such as:

Furthermore, Japanese Utility Model Publication No. 55-28767 discloses that a camshaft with a large diameter journal at both ends that is higher than the cam crest of the cam can be inserted and removed from the receiving parts provided on both side walls of the integrated engine body. In addition, in Japanese Utility Model Publication No. 45-22402, the camshaft, which is supported by a receiving part provided on both outer walls of the cylinder head, has a central part. A protrusion is provided for attaching a drive wheel for driving the shaft, and the drive wheel is provided with a recess on the periphery of a hole through which the camshaft passes through which the cam crest passes. Each is listed.

[Means for solving problems]

In view of these circumstances, the present invention has been developed by providing a recess corresponding to the part of the cam crest that touches the cam crest in the camshaft journal receiving part on the crankcase side where the force of the valve train does not act. Provided is a camshaft bearing for a horizontally opposed internal combustion engine, which allows the camshaft to be removed in the axial direction by passing it through a journal receiving part while rotating the camshaft appropriately, thereby greatly simplifying the work of replacing the camshaft. It is something to do.

〔Example〕

Hereinafter, one embodiment of the present invention will be specifically described with reference to the drawings. First, to explain the outline of a horizontally opposed internal combustion engine to which the present invention is applied in Fig. 1, the left crankcase 1a is divided into left and right halves.
and right crankcase 1b are integrally joined and installed horizontally, and a crankshaft 2 and a camshaft 3 of an OHV type valve mechanism are rotatably supported at the joint of these crankcases 1a and 1b. .

Next, the operation of the crankshaft and camshaft in the case of a four-cylinder engine will be explained with reference to FIGS. 2a and 2b. Four cylinders 6a to 6d arranged
The pistons 7a to 7d are connected to each other. In addition, the camshaft 3 has journals 8a at three locations at both ends and at the center.
A pair of intake and exhaust cams 9a, 8c are supported by three bearings, and between the journals 8a and 8b, a pair of intake and exhaust cams 9a,
9b, and also has a pair of intake and exhaust cams 9c and 9d between the journals 8b and 8c.
The cams a and 9b are commonly used for the two cylinders 6a and 6b that are arranged close to each other, and the cams 9c and 9d are similarly used for the other two cylinders 6c and 6d. Here, the crank pins 4a to 4d of the crankshaft 2 are arranged in the same direction or in a phase of 180 degrees as shown in a, and the pistons 7a and 7b of the two cylinders 6a and 6b move up and down at the same time. The other two cylinders 6c, 6
The pistons 7c and 7d of d also move up and down at the same time in a reverse relationship.

The intake and exhaust strokes of the cylinder 6a are shown, for example, as shown in FIG. 3a, which allows the opening and closing of the intake and exhaust valves and the positions of the cam crests of the cams 9a and 9b to be specified. In the cylinder 6b, which commonly uses the cams 9a and 9b from opposite directions, the camshaft 3 is set at 1/2 rotation relative to the crankshaft 2, and the crankshaft 2 causes the cylinder 6b to rotate as described above.
Since the pistons 7a and 7b of cylinders a and 6b move up and down at the same time, if cylinder 6a is in the explosion stroke, it will be in the intake stroke on the opposite side. Moreover, other cam shafts 9c, 9 are connected to such cams 9a, 9b.
d are exactly 180 degrees out of phase, and when cylinder 6a is in the explosion stroke, cylinder 6c is in the compression stroke, cylinder 6d is in the exhaust stroke, and cylinders 6a, 6c, 6
Explosions will occur in the order of b and 6d. From this, the intake cam 9a on the camshaft 3,
The positional relationship between the cam 9d and the cam crests of the exhaust cams 9b and 9c is as shown in FIG. 3b.

On the other hand, as shown in FIG.
Three receiving parts 10a to 10c are formed corresponding to a to 8c, and these receiving parts 10a to 1
Each of the journals 8a to 8c is fitted into the shaft 0c and rotatably supported. Here, it is assumed that the camshaft 3 is pulled out in the direction of the arrow, and that the journal 8c has a large diameter that includes the cam ridges of the cams 9a to 9d and will not cause problems when being pulled out.
It is assumed that only the receiving portion 10b of the center journal 8b is in the way of the cams 9a, 9b.

Therefore, as shown in FIG. 5, a recess 11 is provided in the upper part of the receiving part 10b where the force of the valve train in the horizontal direction is difficult to be applied, corresponding to the part where the cam ridges 9b' of the cams 9a and 9b come into contact. It is.

[Effect of idea]

Thus, according to the present invention, by aligning the cam peak 9b' of the cam 9b with the recess 11 while rotating the camshaft 3, the cam 9b can pass through the receiving part 10b, and then by rotating the camshaft 3, the cam 9b can pass through the receiving part 10b. Similarly, the cam crest of the cam 9a can be aligned with the recess 11 to allow it to pass through the receiving part 10b.In this way, the camshaft 3 can be easily pulled out or inserted without disassembling the crankcases 1a, 1b, etc. In addition to being replaceable, the recess 11 is provided at a location on the receiving section where the force of the valve train is not applied, so the receiving section has a sufficient pressure receiving area for the above force. Therefore, the camshaft can be smoothly supported and rotated for a long period of time without being damaged.

In the embodiment, the center journal 8 of the camshaft 3
Although the explanation has been made only for the receiving portion 10b of the journal 8c, it is of course applicable to the receiving portion 10c of the journal 8c, and in this case, it is necessary to provide the recesses 11 at a plurality of locations.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an embodiment of a horizontally opposed internal combustion engine to which the present invention is applied;
Figures a and b are diagrams showing the operation of the crankshaft, the camshaft, and the arrangement of the cams, Figure 4 is an exploded perspective view of the camshaft bearing, and Figure 5 is a perspective view showing an embodiment of the structure according to the present invention. It is. 1a, 1b...Crankcase, 3...Camshaft, 8a to 8c...Journal, 9a to 9d...Cam, 9d'...Cam crest, 10a to 10c...Receiving part, 11...Indentation.

Claims (1)

[Scope of utility model registration request] In a system in which the camshaft is rotatably supported by fitting the camshaft into the mating part of the left and right crankcases and fitting the journal of the camshaft into the receiving part of the crankcase itself, the part where the force of the valve train is not applied to the receiving part. A camshaft bearing for a horizontally-opposed internal combustion engine, characterized in that the camshaft is provided with a recess corresponding to a portion where the cam ridge of the cam contacts, thereby making it possible to remove the camshaft in the axial direction.