JPH11218007A - Shaft assembling structure for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable an erroneously assembled state to be understood at first glance to improve the workability in the assembling process. SOLUTION: The distance from one side vertical wall part up to the first screw hole center in most close proximity to the one side vertical wall part is expressed by Al, the distance from the one side vertical wall part up to the second screw hole center in the second most close proximity to the one side vertical wall part is expressed by A2, the distance from the other end of a rocker shaft located on the other side vertical wall part side up to the first mounting hole part center in most close proximity to the other end is expressed by B1, and the distance from the other end of the rocker shaft up to the second mounting hole part center in the second most close proximity to the other end, is expressed by B2. All relations of inequalities A1<B1, A2<B2, (B2-B1)<(A2-A1) are adapted to be satisfied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shaft mounting structure for an internal combustion engine, and more particularly to an inequality A1 <B1 A2 <B2 (B2-B1) <at a position where a screw hole of a cylinder head and a mounting hole of a rocker shaft are formed. (A2-A1) The present invention relates to a shaft mounting structure for an internal combustion engine that has a configuration that satisfies all the relationships of (A2-A1), can understand at a glance that it is in an erroneous assembly state, and can improve workability in an assembly process.

[0002]

2. Description of the Related Art Generally, a vehicle uses a multi-cylinder internal combustion engine. In this internal combustion engine, a camshaft and a rocker shaft are provided above the cylinder head.

A shaft mounting structure for the internal combustion engine is disclosed in Japanese Utility Model Publication No. 5-7442. The camshaft shafting device for a four-stroke engine disclosed in this publication includes a lower bearing provided on the upper surface of a cylinder head, a camshaft adapted to the lower bearing, and a camshaft that is hung on the camshaft and fastened to the cylinder head. And a temporary holding piece for temporarily holding the camshaft.
A head cover attached to the cylinder head and integrally provided with an upper bearing portion, a camshaft is mounted around the upper bearing portion so as to align with the lower bearing portion, and it is possible to confirm a proper assembly state.

[0004]

By the way, in the conventional shaft mounting structure for an internal combustion engine, in order to prevent the rocker shaft from being erroneously mounted in the front-rear direction, one of a plurality of mounting holes is required.
At different locations, the pitch, which is the distance between the mounting holes, was varied, and the rocker shaft was machined for front and rear recognition.

More specifically, as shown in FIGS. 6A and 6B, a plurality of, for example, five first
To fifth mounting hole portions 114-1, 114-2, 114-3,
When forming 114-4, 114-5, the first to fifth mounting holes 114-1, 114-2, 114-3, 114-
4, 114-5, the pitch P1 of the first and second mounting holes 114-1 and 114-2 is changed to the second to fifth mounting holes 114-2, 114-3, 114-4, and 114. −
5, the pitch P2 is formed differently to satisfy the inequality P2 <P1.

In the cylinder head of the internal combustion engine, as shown in FIG. 7C, a plurality of, for example, two, first to fifth screw holes 112-1, 112-2, 112-3,
112-4 and 112-5 are formed.

At this time, when the rocker shaft is mounted on the cylinder head with its front and back reversed, as shown in FIG. 7B, the second to fourth mounting holes 114-2 and 114-3 of the rocker shaft 110 are provided. , 114-4 with the second to fourth screw holes 112-2, 112-3, 112- of the cylinder head.
4, the first and fifth mounting holes 114-1 and 114-5 located at both ends of the rocker shaft 110 become the first and fifth screw holes 112-1 and 112 of the cylinder head.
As shown in FIG. 7 (c), the first and fifth mounting holes 114-1, 114-5 of the rocker shaft 110 are displaced from the first and fifth cylinder heads as shown in FIG. Screw holes 112-1, 112-5
, The second to fourth mounting holes 114-2, 114-3, 1-1 located at the intermediate portion of the rocker shaft 110.
14-4 are the second to fourth screw holes 112- of the cylinder head.
2, 112-3, and 112-4.

As a result, in order to prevent the rocker shaft from being erroneously assembled to the cylinder head, two or more of the first and fifth mounting holes and the second to fourth mounting holes in the rocker shaft must be aligned. It is necessary to check the state, and there is an inconvenience that the workability of mounting the rocker shaft is poor.

[0009]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a cylinder block, a cylinder head mounted on an upper surface of the cylinder block, and an oil pan provided below the cylinder block. A plurality of screw holes are provided in the upper part of the cylinder head of the internal combustion engine having a plurality of mounting holes at the rocker shaft portion corresponding to the screw holes, and the screw holes and the mounting holes are used to fix the fixing holes. In a shaft mounting structure for an internal combustion engine in which a rocker shaft is disposed on a cylinder head, one side and another side vertical wall portion protruding upward on both sides of the cylinder head in a longitudinal direction are provided on the cylinder head. A1 is the distance from the center to the center of the first screw hole of the cylinder head closest to this one side vertical wall.
A distance from the one vertical wall portion to the center of a second screw hole of the cylinder head second closest to the one vertical wall portion is A2, and the rocker shaft located on the other vertical wall portion side. The distance from the other end of the rocker shaft to the center of the first mounting hole of the rocker shaft closest to the other end is B1, and the second mounting of the rocker shaft second closest to the other end from the other end of the rocker shaft. When the distance to the center of the hole is B2, the configuration is such that all the relationships of the inequalities A1 <B1 A2 <B2 (B2-B1) <(A2-A1) are satisfied.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION
When arranging the rocker shaft on the cylinder head of the internal combustion engine, the rocker shaft is turned back and forth by a setting that satisfies all the relations of inequalities A1 <B1 A2 <B2 (B2-B1) <(A2-A1). Even if you try to attach to the cylinder head, all the mounting holes of the rocker shaft do not match with all the screw holes of the cylinder head, and furthermore, shift the rocker shaft and force the mounting holes to match the screw holes of the cylinder head. Also, it can be understood that the other end of the rocker shaft interferes with one side vertical wall portion of the cylinder head, the rocker shaft cannot be attached to the cylinder head, and that the assembly is erroneously assembled at a glance. The workability in the attaching process has been improved.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings.

1 to 5 show an embodiment of the present invention. 2 to 4, reference numeral 2 denotes an internal combustion engine, 4 and a cylinder head.

The internal combustion engine 2 includes a cylinder block (not shown), a cylinder head 4 mounted on an upper surface of the cylinder block, a cylinder head cover 6 mounted on an upper portion of the cylinder head 4, and an oil provided on a lower portion of the cylinder block. And a pan (not shown).

A camshaft 8 is provided above the cylinder head 4 in parallel with the longitudinal direction of the cylinder head 4, and a rocker shaft 10 is provided in parallel with the camshaft 8. You.

That is, a plurality of screw holes 12 are provided in the upper portion of the cylinder head 4, and a plurality of mounting holes 14 are provided in a portion of the rocker shaft 10 corresponding to the screw holes 12. The rocker shaft 10 is disposed on the cylinder head 4 by the fixing bolt 16 using the portion 14.

In FIG. 1, reference numeral 18 denotes a rocker arm mounted on the rocker shaft 10, and reference numeral 20 denotes a distributor.

Then, above the cylinder head 4,
On one side and the other side vertical wall portions 22 and 24 projecting upward on both sides in the longitudinal direction of the cylinder head, for example, from the one side vertical wall portion 22 on the left side in FIG. The distance between the center of the first screw hole 12-1 of the cylinder head 4 and the center of the first screw hole 12-1 is A1, and the cylinder head 4 that is second closest to the one-side vertical wall 22 from the one-side vertical wall 22
The distance from the center of the second screw hole 12-2 of FIG.
The first mounting hole 14-of the rocker shaft 10 closest to the other end 10 b from the other end 10 b of the rocker shaft 10 located on the side of the other vertical wall portion 24 on the right side in FIG.
The distance to the center is B1, and the rocker shaft 10
Inequality A1 <B1 A2 <B2 (B2-B1) where B2 is the distance from the other end 10b of the rocker shaft 10 to the center of the second mounting hole 14-2 of the rocker shaft 10 which is second closest to the other end 10b. ) <(A2-A1) The configuration satisfies all of the following relationships.

More specifically, as shown in FIGS. 1 and 5, a plurality of semi-circular rocker shaft bearing portions 26 are formed on the upper portion of the cylinder head 4, and each of the rocker shaft bearing portions 26 is provided for each of the rocker shaft bearing portions 26. From the one side vertical wall portion 22 side, for example, five first to fifth screw holes 12-1, 12-2, 12-
3, 12-4 and 12-5 are respectively formed.

Further, the rocker shaft 10 has a structure shown in FIG.
As shown in (a), for example, five first to fifth mounting holes 14-1, 14-2, 14- are formed from the other end 10b of the rocker shaft 10 located on the other vertical wall portion 24 side. 3, 1
4-4 and 14-5 are formed respectively.

At this time, the distance A1 from the one side vertical wall portion 22 to the center of the first screw hole 12-1 of the cylinder head 4 closest to the one side vertical wall portion 22 is set to be equal to that of the rocker shaft 10. The distance is set smaller than the distance B1 from the end 10b to the center of the first mounting hole 14-1 of the rocker shaft 10 closest to the other end 10b.

Further, the second side of the cylinder head 4 which is second closest to the one side vertical wall portion 22 from the one side vertical wall portion 22 is formed.
The distance A2 from the other end 10b of the rocker shaft 10 to the center of the second mounting hole portion 14-2 of the rocker shaft 10 which is second closest to the other end 10b is determined by the distance B2 from the other end 10b of the rocker shaft 10 to the center of the screw hole 12-2. Is also set to small.

Furthermore, the relation of inequality (B2-B1) <(A2-A1), that is, the distance (B2-B1) from the center of the first mounting hole 14-1 to the center of the second mounting hole 14-2. Is the first
The distance (A2-A1) from the center of the screw hole 12-1 to the center of the second screw hole 12-2 is set to be smaller.

The distance from the other vertical wall portion 24 to the center of the fifth screw hole 12-5 of the cylinder head 4 closest to the other vertical wall portion 24 is A3 (see FIG. 5). The distance from one end 10a of the rocker shaft 10 located on the side vertical wall portion 22 side to the center of the fifth mounting hole portion 14-5 of the rocker shaft 10 closest to the one end 10a is B.
3 is assumed. Then, the setting is made so as to satisfy the inequality A1 <A3, and the setting is also made so as to satisfy the inequality B3 <B1.

Reference numeral 28 denotes a spark plug.

Next, the operation will be described.

When arranging the rocker shaft 10 on the cylinder head 4 of the internal combustion engine 2, first, as shown in FIG. 1D, one side wall portion 22 of the cylinder head 4 is positioned on the left side in FIG. Also, the other side vertical wall portion 24 is shown in FIG.
At the right side.

Then, the rocker shaft 10 is
As shown in (a), one end 10a of the rocker shaft 10 is on the left side in FIG.
1 is set to the right side in FIG. 1, as shown in FIGS. 1A and 1D, the first screw hole 12-1 of the cylinder head 4 and the fifth attachment of the rocker shaft 10 are formed. Hole 14-5, second screw hole 12-2 and fourth mounting hole 14-4, third screw hole 12-3 and third mounting hole 14-.
3, the fourth screw hole 12-4 and the second mounting hole 14-2, the fifth
Each of the screw hole 12-5 and the first mounting hole portion 14-5 match.

That is, the rocker arm 10 is fitted to the fifth mounting hole 1 at the first tightening point T1 in FIGS.
4-5 coincides with the first screw hole 12-1 of the cylinder head 4, and the fourth mounting hole 14-
4 matches the second screw hole 12-2 of the cylinder head 4,
At the third tightening point T3, the third mounting hole portion 14-3 matches the third screw hole 12-3 of the cylinder head 4, and the fourth tightening point T4
The second mounting hole portion 14-2 matches the fourth screw hole 12-4 of the cylinder head 4 at, and the first attachment hole portion 14-2 at the fifth fastening point T5.
The mounting hole 14-1 is the fifth screw hole 12 of the cylinder head 4.
-5.

Here, the rocker shaft 10 is shown in FIG.
(B) and FIG. 1 (c), the rocker shaft 10
Of the rocker shaft 1 on the right side in FIG.
1, when the other end 10b of the rocker shaft 10 is set to the left side in FIG. 1, the other end 10b of the rocker shaft 10 coincides with the vertical wall 22 on one side of the cylinder head 4 as shown in FIG. Then, all the mounting holes 14 do not match with all the screw holes 12.

Further, the rocker shaft 10 is shifted to match the screw hole 12 of the cylinder head 4, and FIG.
As shown in FIG.
When the mounting holes 14 of the rocker shaft 10 are to be matched with the two second to fourth screw holes 12-2, 12-3, and 12-4, the other end of the rocker shaft 10 is set by the inequality A1 <B1. 10b interferes with one side vertical wall portion 22 of the cylinder head 4, and the rocker shaft 10 cannot be attached to the cylinder head 4.

Thus, the rocker shaft 1 can be set by satisfying all the relations of inequality A1 <B1 A2 <B2 (B2-B1) <(A2-A1).
0, the mounting holes 14 of the rocker shaft 10 do not correspond to all the screw holes 12 of the cylinder head 4 and the mounting state is incorrect at first glance. Can be understood, and the workability in the assembling process can be improved, which is practically advantageous.

Further, with the rocker shaft 10 turned upside down, the rocker shaft 10 is shifted so that the mounting hole 1
When the rocker shaft 10 is forcibly aligned with the screw hole 12 of the cylinder head 10, the other end 10 b of the rocker shaft 10 interferes with the vertical wall portion 22 on one side of the cylinder head 4, and the rocker shaft 10 is attached to the cylinder head 4. Cannot be performed, and can be immediately understood to be in an erroneously assembled state.

Further, the screw holes 12 of the cylinder head 4 are formed.
In addition, since it can be dealt with only by changing the drilling position of the mounting hole portion 14 of the rocker shaft 10, there is no fear that the configuration becomes complicated, the manufacture is easy, the cost can be maintained at low cost, and the economy can be maintained. This is also advantageous.

[0034]

As described above in detail, according to the present invention, a cylinder head for an internal combustion engine having a cylinder block, a cylinder head mounted on the upper surface of the cylinder block, and an oil pan provided below the cylinder block. A plurality of screw holes are provided in the upper part, and a plurality of mounting holes are provided in the rocker shaft portion corresponding to the screw holes, and the rocker shaft is disposed on the cylinder head with fixing bolts using the screw holes and the mounting holes. In the shaft mounting structure of the internal combustion engine, one side and the other vertical wall portion projecting upward on both sides in the longitudinal direction of the cylinder head are provided on the upper portion of the cylinder head, and from the one vertical wall portion to the one vertical wall portion. The distance to the center of the first screw hole of the closest cylinder head is A1, and the second closest to the one side vertical wall portion from one side vertical wall portion. The distance from the center of the second screw hole of the cylinder head to the center of the second screw hole is A2, and the distance from the other end of the rocker shaft located on the other vertical wall portion side to the center of the first mounting hole portion of the rocker shaft closest to the other end. When the distance from the other end of the rocker shaft to the center of the second mounting hole of the rocker shaft that is second closest to the other end is B2, the inequality A1 <B1 A2 <B2 (B2-B1) <(A2-A1) Since the configuration that satisfies all the relations of (1) and (2), even if the rocker shaft is mounted on the cylinder head in the reverse direction,
All mounting holes of the rocker shaft do not match with all the screw holes of the cylinder head, and it can be understood at a glance that the mounting state is incorrect, and the workability in the mounting process can be improved. It is practically advantageous. In addition, even if the rocker shaft is turned upside down and the mounting hole is forcibly aligned with the screw hole of the cylinder head by displacing the rocker shaft, the other end of the rocker shaft is formed on one side of the vertical wall of the cylinder head. , The rocker shaft could not be attached to the cylinder head, and it can be understood immediately that the assembly state was incorrect. Further, since it can be dealt with only by changing the positions of the screw holes of the cylinder head and the mounting holes of the rocker shaft, there is no fear that the configuration is complicated, the production is easy, and the cost is reduced. It can be maintained and is economically advantageous.

[Brief description of the drawings]

FIGS. 1A and 1B are assembled states of a cylinder head according to an embodiment of the present invention, wherein FIG. 1A is a cross-sectional view of a rocker shaft in a regular assembled state, and FIG. FIG. 6C is a cross-sectional view of the rocker shaft, FIG. 7C is a cross-sectional view of the rocker shaft showing a second example of the erroneously assembled state, and FIG.

FIG. 2 is a plan view of the internal combustion engine with a cylinder head cover partially cut away.

FIG. 3 is a sectional front view of the internal combustion engine.

FIG. 4 is a sectional left side view of the internal combustion engine.

FIG. 5 is a plan view of a cylinder head.

6A and 6B are rocker shafts showing the prior art of the present invention, wherein FIG. 6A is a front view, and FIG. 6B is V〓b-V〓b of FIG.
FIG.

FIG. 7 is a schematic view of the rocker shaft, showing an assembled state of the rocker shaft, in which (a) shows a first example of an incorrectly assembled state;
(B) is a schematic diagram of a rocker shaft showing a second example of an erroneously assembled state, and (c) is a schematic diagram showing screw hole positions of a cylinder head.

[Explanation of symbols]

 Reference Signs List 2 internal combustion engine 4 cylinder head 6 cylinder head cover 8 camshaft 10 rocker shaft 10a one end 10b other end 12 screw hole 12-1 first screw hole 12-2 second screw hole 14 mounting hole 14-1 first mounting hole 14 -2 second mounting hole 16 fixing bolt 18 rocker arm 20 distributor 22 one vertical wall 24 other vertical wall 26 rocker shaft bearing 28 spark plug

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[Procedure amendment]

[Submission date] March 30, 1998

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Name of invention

[Correction method] Change

[Correction contents]

[Title of the Invention] Shaft assembly structure of internal combustion engine

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0001

[Correction method] Change

[Correction contents]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure for assembling a shaft of an internal combustion engine, and more particularly to an inequality A1 <B1 A2 <B2 (B2-B1) at a position where a screw hole of a cylinder head and a mounting hole of a rocker shaft are formed. <A2-A1> The present invention relates to a shaft assembly structure for an internal combustion engine that has a configuration that satisfies all the relationships of (A2-A1), can understand at a glance that the assembly is in an erroneous assembly state, and can improve workability in the assembly process. .

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0003

[Correction method] Change

[Correction contents]

[0003] An example of a structure for assembling the shaft of the internal combustion engine is disclosed in Japanese Utility Model Publication No. 5-7442. The camshaft shafting device for a four-stroke engine disclosed in this publication includes a lower bearing provided on the upper surface of a cylinder head, a camshaft adapted to the lower bearing, and a camshaft that is hung on the camshaft and fastened to the cylinder head. And a temporary holding piece for temporarily holding the camshaft.
A head cover attached to the cylinder head and integrally provided with an upper bearing portion, a camshaft is mounted around the upper bearing portion so as to align with the lower bearing portion, and it is possible to confirm a proper assembly state.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0004

[Correction method] Change

[Correction contents]

[0004]

By the way, in the conventional shaft assembly structure of the internal combustion engine, in order to prevent erroneous assembly of the rocker shaft in the front-rear direction, one of the plurality of mounting holes is required.
At different locations, the pitch, which is the distance between the mounting holes, was varied, and the rocker shaft was machined for front and rear recognition.

[Procedure amendment 6]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction contents]

[0009]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a cylinder block, a cylinder head mounted on an upper surface of the cylinder block, and an oil pan provided below the cylinder block. A plurality of screw holes are provided in the upper part of the cylinder head of the internal combustion engine having a plurality of mounting holes at the rocker shaft portion corresponding to the screw holes, and the screw holes and the mounting holes are used to fix the fixing holes. In a shaft assembling structure of an internal combustion engine in which a rocker shaft is disposed on a cylinder head, one side and another side vertical wall portion protruding upward on both sides in the longitudinal direction of the cylinder head are provided on the upper part of the cylinder head. The distance from the wall to the center of the first screw hole of the cylinder head closest to the one side vertical wall is A1.
A distance from the one vertical wall portion to the center of a second screw hole of the cylinder head second closest to the one vertical wall portion is A2, and the rocker shaft located on the other vertical wall portion side. The distance from the other end of the rocker shaft to the center of the first mounting hole portion of the rocker shaft closest to the other end is B1, and the second mounting hole of the rocker shaft second closest to the other end from the other end of the rocker shaft. When the distance to the center of the part is B2, the inequality A1 <B1 A2 <B2 (B2-B1) <(A2-A1) is satisfied.

[Procedure amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0034

[Correction method] Change

[Correction contents]

[0034]

As described above in detail, according to the present invention, a cylinder head for an internal combustion engine having a cylinder block, a cylinder head mounted on the upper surface of the cylinder block, and an oil pan provided below the cylinder block. A plurality of screw holes are provided in the upper part, and a plurality of mounting holes are provided in the rocker shaft portion corresponding to the screw holes, and the rocker shaft is disposed on the cylinder head with fixing bolts using the screw holes and the mounting holes. In the shaft assembly structure of the internal combustion engine, one side and the other side vertical wall portion which protrude upward on both sides in the longitudinal direction of the cylinder head are provided on the upper portion of the cylinder head, and the one side vertical wall portion is provided from the one side vertical wall portion. A1 is the distance from the center of the first screw hole of the cylinder head closest to to the center of the first screw hole. The distance from the center of the second screw hole of the cylinder head to the center of the second screw hole is A2, and the distance from the other end of the rocker shaft located on the other vertical wall portion side to the center of the first mounting hole portion of the rocker shaft closest to the other end. When B2 is the distance from the other end of the rocker shaft to the center of the second mounting hole of the rocker shaft that is second closest to the other end, the inequality A1 <B1 A2 <B2 (B2-B1) <(A2-A1) Since the configuration that satisfies all the relations of (1) and (2), even if the rocker shaft is mounted on the cylinder head in the reverse direction,
All mounting holes of the rocker shaft do not match with all the screw holes of the cylinder head, and it can be understood at a glance that the mounting state is incorrect, and the workability in the mounting process can be improved. It is practically advantageous. Also, even if the rocker shaft is turned upside down, the rocker shaft is displaced and the mounting hole is forcibly aligned with the screw hole of the cylinder head. , The rocker shaft could not be attached to the cylinder head, and it can be understood immediately that the assembly state was incorrect. Further, since the arrangement can be dealt with only by changing the positions of the screw holes of the cylinder head and the mounting holes of the rocker shaft, there is no fear that the configuration is complicated, and the production is easy and the cost is reduced. It can be maintained and is economically advantageous.

Claims (1)

[Claims] A plurality of screw holes are provided in an upper portion of a cylinder head of an internal combustion engine having a cylinder block, a cylinder head mounted on an upper surface of the cylinder block, and an oil pan provided in a lower portion of the cylinder block. In a shaft mounting structure for an internal combustion engine, a plurality of mounting holes are provided at a rocker shaft portion corresponding to the screw holes, and the rocker shaft is disposed on a cylinder head by a fixing bolt using the screw holes and the mounting holes. On the upper part of the cylinder head, one side and the other side vertical wall portion protruding upward on both sides in the longitudinal direction of the cylinder head are provided, and the first screw of the cylinder head closest to the one side vertical wall portion from the one side vertical wall portion The distance to the center of the hole is A1, and the second screw of the cylinder head that is second closest to the one-side vertical wall from the one-side vertical wall. The distance from the center of the hole to the center of the first mounting hole of the rocker shaft closest to the other end from the other end of the rocker shaft located on the other side of the vertical wall portion is referred to as B1, When the distance from the other end of the rocker shaft to the center of the second mounting hole of the rocker shaft that is second closest to the other end is B2, the inequality A1 <B1 A2 <B2 (B2-B1) <(A2 -A1) A shaft mounting structure for an internal combustion engine, wherein the structure satisfies all of the following relationships.