EP1895111A1

EP1895111A1 - Installation method for camshaft of internal combustion engine and internal combustion engine

Info

Publication number: EP1895111A1
Application number: EP06757085A
Authority: EP
Inventors: Yasuo Yamaha Hatsudoki Kabushiki Kaisha Okamoto
Original assignee: Yamaha Motor Co Ltd
Current assignee: Yamaha Motor Co Ltd
Priority date: 2005-06-06
Filing date: 2006-06-06
Publication date: 2008-03-05
Anticipated expiration: 2026-06-06
Also published as: WO2006132255A1; EP1895111A4; JPWO2006132255A1; EP1895111B1; EP1731720A2; JP4279337B2

Abstract

A method of assembling a camshaft for an internal combustion engine in which the camshaft is assembled to a cylinder head via a plurality of sets of cam carriers and cam caps separately provided in each journal section, the method including the steps of: preparing a shaft-shaped jig the length of which is as long as the whole of a plurality of the cam carriers and, further, the shaft diameter of which in a fitting section in a part corresponding to the journal section is larger than the shaft diameter of the journal section; and positioning a plurality of the cam carriers in a predetermined position by attaching the shaft-shaped jig on the cylinder head via a plurality of the cam carriers.

Description

[Technical Field]

The present invention relates to a method of assembling a camshaft for an internal combustion engine and also relates to an internal combustion engine having the camshaft that is assembled with such method.

[Background Art]

One of conventional techniques in this field is disclosed, for example, in Patent Document 1. According to Patent Document 1, a lower cam holder (a cam carrier) disposed commonly on both of intake and exhaust camshafts and an upper cam holder (a cam cap) provided on each of the both intake and exhaust camshafts are included, in which both ends of the lower cam holder are fastened to a cylinder head by a first fastening member, two upper cam holders are respectively fastened to a part of the lower cam holder more inward than the first fastening member by a pair of second fastening members having a diameter smaller than that of the first fastening member. Further, according to the disclosure of Patent Document 1, the cylinder head can be downsized, and the first fastening member also functions as a stopper for preventing the turn of a rocker shaft.

[Patent Document 1]
JP-A-2000-170506

[Disclosure of the Invention]

[Problem to be Solved by the Invention]

According to the conventional technique, there is a clearance provided between a journal section of the camshaft and a bearing section formed by the cam carrier and the cam cap in which the journal section is fitted. Consequently, when the camshaft is assembled to the cylinder head, if the camshaft is mounted on the cylinder head via a plurality of sets of cam carriers and cam caps each having the bearing section formed beforehand, the accuracy of the assembly positions of for example the carriers becomes worsened because of the clearance. As a result, there is possibility of deterioration of the contact condition in the journal section and of increase of friction in the journal section.
As a countermeasure to this problem, a plurality of cam carriers and cam caps may be mounted in series on the cylinder head, followed by a machining process for improving the assembly condition in order to ensure the accuracy of the assembly positions of the carriers and other components before the camshaft is mounted. In this case, however, large-scale machining equipment is required for the machining process for improvement of the assembly condition.
Moreover, when the machining process for improvement of the assembly condition is performed for a plurality of the cam carriers and the cam caps as described above, it is necessary to replace all of the cam carriers and the cam caps corresponding to those for one camshaft even if one carrier (or one cam cap) is deficient. Consequently, a large number of those components are replaced, causing the increase of cost.
An object of the present invention made in view of the drawbacks described above is to provide a method of assembling a camshaft for an internal combustion engine and an internal combustion engine in which the accuracy of the assembly positions of parts for supporting the journal section can be ensured without using large-scale machining equipment necessary for avoiding deterioration of the contact condition in the journal section and increase of friction in the journal section and further in which only a minimum number of components need to be replaced even if a problem is caused in the cam carrier or in other components.

[Means for Solving the Problem]

In order to solve the foregoing problem, a first aspect of the present invention is directed to a method of assembling a camshaft for an internal combustion engine in which the camshaft is assembled to a cylinder head via a plurality of sets of cam carriers and cam caps separately provided in each journal section, the method including the steps of: preparing a shaft-shaped jig the length of which is as long as the whole of a plurality of the cam carriers, and the shaft diameter of which in a fitting section in a part corresponding to the journal section is larger than the shaft diameter of the journal section; and positioning a plurality of the cam carriers in a predetermined position by mounting the shaft-shaped jig on the cylinder head via a plurality of the cam carriers.
A second aspect of the present invention is directed to a method of assembling a camshaft for an internal combustion engine in which the camshaft is assembled to a cylinder head via a plurality of sets of cam carriers and cam caps separately provided in each journal section, the method including the steps of: preparing a shaft-shaped jig the shaft diameter of which in a fitting section in a part corresponding to the journal section of the camshaft to be actually assembled is larger than the shaft diameter of the journal section; positioning a plurality of the cam carriers in a predetermined position by mounting the shaft-shaped jig on the cylinder head via a plurality of sets of the cam carriers and the cam caps; removing a plurality of the cam caps with a plurality of the cam carriers being fastened to the cylinder head; replacing the shaft-shaped jig with the camshaft to be actually used; and fastening a plurality of the cam caps.
A third aspect of the present invention is directed to a method of assembling a camshaft for an internal combustion engine in which the camshaft is assembled to a cylinder head via a plurality of sets of cam carriers and cam caps separately provided in each journal section, the method including the steps of: preparing a shaft-shaped jig the shaft diameter of which in a fitting section in a part corresponding to the journal section of the camshaft to be actually assembled is larger than the shaft diameter of the journal section; positioning a plurality of the cam carriers in a predetermined position by mounting the shaft-shaped jig on the cylinder head via a plurality of the cam carriers; replacing the shaft-shaped jig with the camshaft to be actually used with a plurality of the cam carriers being fastened to the cylinder head; and fastening the cam caps.
In addition to a constitution of any one of the first to third aspects of the present invention, according to a fourth aspect of the present invention, a positioning section is formed on the shaft-shaped jig in order to determine the position of the cam carrier in the axial direction of the shaft-shaped jig by the positioning section.
In addition to a constitution of any one of the first to fourth aspects of the present invention, according to a fifth aspect of the present invention, a circular section having a diameter as large as the diameter of the base circle of the cam section is formed in a position on the shaft-shaped jig corresponding to the cam section of the camshaft.
A sixth aspect of the present invention provides a method of assembling a camshaft for an internal combustion engine in which the camshaft is assembled to a cylinder head via a plurality of cam carriers and cam caps separately provided in each journal section and in which the camshaft also functions as a shaft-shaped jig for positioning the cam carrier, a journal section supported by a bearing section of the cam carrier and the cam cap is provided on the camshaft, a fitting section thicker than the journal section is provided in a part adjoining the journal section, a fitted section to be fitted by the fitting section is provided on the cam carrier and the cam cap in a part adjoining the bearing section, a clearance between the outer surface of the fitting section and the inner surface of the fitted section is smaller than a clearance between the outer surface of the journal section and the inner surface of the bearing section, the camshaft is mounted on the cylinder head via the cam carrier and the cam cap by fitting the camshaft fitting section to the cam carrier and the cam cap fitted section, and the slide of the camshaft is restricted by attaching a slide restricting member while the camshaft slides in the axial direction by a predetermined amount in order to release the fitting section from the fitted section.
In addition to the constitution of the sixth aspect of the present invention, according to a seventh aspect of the present invention, a portion of the bearing section also functions as the fitted section, and the outer diameter of the fitting section is larger than the outer diameter of the journal section.
In addition to the constitution of the sixth aspect of the present invention, according to an eighth aspect of the present invention, the outer diameter of the fitting section is larger than the outer diameter of the journal section, while the inner diameter of the fitted section is larger than the inner diameter of the bearing section.
In addition to the constitution of the sixth aspect of the present invention, according to a ninth aspect of the present invention, the slide restricting member is a housing cap provided on an end of the camshaft.
In addition to the constitution of any one of the first to ninth aspects of the present invention, according to a tenth aspect of the present invention, a plurality of the cam carriers are disposed along the camshaft, a rocker shaft independent of each other is disposed on each of the cam carriers, and a rocker arm is disposed for pivotal motion on the rocker shaft.
An eleventh aspect of the present invention is an internal combustion engine, in which the camshaft is assembled to the cylinder head via the cam carrier and the cam cap by the method of assembling a camshaft for an internal combustion engine according to any one of the first to tenth aspects of the present invention.

[Effect of the Invention]

According to the first aspect of the present invention, the method of assembling a camshaft for an internal combustion engine includes the steps of: preparing the shaft-shaped jig the length of which is as long as the whole of a plurality of the cam carriers and, further, the shaft diameter of which in a fitting section in a part corresponding to the journal section is larger than the shaft diameter of the journal section; and positioning a plurality of the cam carriers in a predetermined position by mounting the shaft-shaped jig on the cylinder head via a plurality of the cam carriers. As a result, the accuracy of the assembly positions of the parts for supporting the journal section can be ensured without using large-scale machining equipment necessary for avoiding deterioration of the contact condition in the journal section and increase of friction in the journal section, and further only a minimum number of components need to be replaced even if a problem is caused in the cam carrier or in other components.
According to the second aspect of the present invention, the method of assembling a camshaft for an internal combustion engine includes the steps of: preparing the shaft-shaped jig the shaft diameter of which in a part corresponding to the journal section of the camshaft to be actually assembled is larger than the shaft diameter of the journal section, mounting the shaft-shaped jig on the cylinder head via the cam carrier and the cam cap; removing the cam cap with the cam carrier being fastened to the cylinder head; replacing the shaft-shaped jig with the camshaft to be actually used; and fastening the cam cap. As a result, the accuracy of the assembly positions of the parts for supporting the journal section can be ensured without using large-scale machining equipment necessary for avoiding deterioration of the contact condition in the journal section and increase of friction in the journal section, and further only a minimum number of components need to be replaced even if a problem is caused in the carrier or in other components.
According to the third aspect of the present invention, it is not necessary to attach or detach the cam cap when the shaft-shaped jig is disposed (when the base position is determined). As a result, work efficiency is excellent.
According to the fourth aspect of the present invention, the positioning section is formed on the shaft-shaped jig in order to determine the position of the cam carrier in the axial direction of the shaft-shaped jig by the positioning section. Consequently, the position accuracy of the base position of the cam carrier and the position of the cam carrier in the axial direction are improved by the shaft-shaped jig. As a result, the widths of the cam section and the journal section can be reduced and the weight thereof can be reduced.
According to the fifth aspect of the present invention, the circular section having a diameter as large as the diameter of the base circle of the cam section is formed in a position on the shaft-shaped jig corresponding to the cam section of the camshaft. As a result, the clearance between the rocker arm disposed on the cam carrier and the base circle section of the cam section can be adjusted by the circular section without turning the camshaft.
According to the sixth to the ninth aspects of the present invention, the camshaft also functions as the shaft-shaped jig for positioning the cam carrier. Consequently, it is not necessary to use a separate shaft-shaped jig, and an effect the same as that of the first aspect of the present invention can be obtained only by sliding the camshaft. As a result, the work efficiency can be improved.
According to the tenth aspect of the present invention, the rocker shaft independent of each other is disposed on each of the cam carriers. As a result, when the rocker shaft is disposed, it is not necessary to perform the machining process for improving the assembly condition, and further it is not necessary to use large-scale machining equipment.
According to the eleventh aspect of the present invention, the camshaft in the internal combustion engine is assembled to the cylinder head via the cam carrier and the cam cap by the method of assembling a camshaft for an internal combustion engine according to any one of the first to tenth aspects of the present invention. As a result, the accuracy of the assembly positions of the parts for supporting the journal section can be ensured, and a minimum number of components need to be replaced even if a problem is caused in the carrier or in other components.

[Brief Description of Drawings]

FIG. 1 is a cross-sectional view, illustrating a shaft-shaped jig, cam carriers, cam caps, and so forth according to a first embodiment of the present invention.
FIG. 2 is an oblique exploded view, illustrating a cylinder head, camshafts, cam carriers, cam caps, and so forth according to the first embodiment of the present invention.
FIG. 3 is a cross-sectional view, illustrating a shaft-shaped jig, cam carriers, cam caps, and so forth according to a second embodiment of the present invention.
FIG. 4 is an enlarged view, illustrating a part of FIG. 3 according to the second embodiment.
FIG. 5 is a cross-sectional view, illustrating a circular section of the shaft-shaped jig according to the second embodiment.
FIG. 6 is a cross-sectional view, illustrating camshafts, cam carriers, cam caps, and so forth according to a third embodiment of the present invention. FIG. 6(a) shows a state in which the camshaft is on the point of being mounted, and FIG. 6(b) shows a state in which the camshaft has been mounted.
FIG. 7 is an enlarged view, illustrating a part of FIG. 6 according to the third embodiment. FIG. 7 (a) shows a state in which the camshaft is on the point of being mounted, and FIG. 7 (b) shows a state in which the camshaft has been mounted.
FIG. 8 is an explanatory drawing, showing an effect according to the third embodiment. FIG. 8(a) shows a state in which the camshaft is on the point of being mounted, and FIG. 8(b) shows a state in which the camshaft has been mounted.
FIG. 9 is a cross-sectional view, illustrating camshafts, cam carriers, cam caps, and so forth according to a fourth embodiment of the present invention. FIG. 9(a) shows a state in which the camshaft is on the point of being mounted, and FIG. 9(b) shows a state in which the camshaft has been mounted.
FIG. 10 is an enlarged view, illustrating a part of FIG. 9 according to the fourth embodiment. FIG. 10(a) shows a state in which the camshaft is on the point of being mounted, and FIG. 10 (b) shows a state in which the camshaft has been mounted.

[Best Mode for Carrying out the Invention]

Some embodiments according to the present invention will be described hereinafter.

[First embodiment]

FIG. 1 and FIG. 2 show a first embodiment according to the present invention.
First, the constitution of the first embodiment will be described. An engine 11 in FIG. 2 is an "internal combustion engine" of the present invention. An intake camshaft 13 and an exhaust camshaft 14 are supported for rotation on a cylinder head 12 of the engine 11 via a plurality of sets of cam carriers 17 and cam caps 18 and one set of a cam carrier 21 and a cam cap 22.
A plurality of intake cam sections 13a and a plurality of exhaust cam sections 14a are formed on the intake camshaft 13 and the exhaust camshaft 14 respectively. Journal sections 13b and 14b are formed between the adjoining intake cam sections 13a and between the adjoining exhaust cam sections 14a respectively. In addition, one ends 13c and 14c of the camshafts 13 and 14 are power transmitting sections. The diameters of these ends are larger than those of any other part and supported for rotation by the cam carrier 21 and the cam cap 22. Flange sections 13d and 13e and flange sections 14d and 14e for receiving thrust are formed on the both sides of these ends 13c and 14c respectively. Further, cam sensor rotors 13g and 14g for a VVT are provided on the other ends.
Further, a bearing recess 17a forming lower halves of bearing sections 15 and 16 of the journal sections 13b and 14b of the both camshafts 13 and 14 is formed on each of the cam carriers 17.
Still further, a rocker shaft 24 independent of each other is disposed on each of the cam carriers 17, and a rocker arm 25 is disposed for pivotal motion on the rocker shaft 24. In addition, a bolt hole 17c into which a bolt 26 for installing the cam carrier to the cylinder head 12 is inserted is formed in each of the cam carriers 17 and, further in addition, a bolt hole 17d into which a bolt 27 for installing the cam cap 18 and the cam carrier 17 to the cylinder head 12 is inserted is formed.
Still further in addition, a bearing recess 18a forming upper halves of the bearing sections 15 and 16 is formed on the cam cap 18, and a bolt hole 18b into which the bolt 27 is inserted is formed.
Moreover, bearing recesses 21a and 22a for supporting the both camshafts 13 and 14 are formed on the cam carrier 21 and the cam cap 22.
On the other hand, a plurality of knock-pins 12a fitted in the cam carrier 21 on one end thereof and the cam carrier 17 on the other end thereof is formed on the upper surface of the cylinder head 12.
A shaft-shaped jig 30 shown in FIG. 1 is used to assemble these camshafts 13 and 14 and so forth.
A shaft diameter d1 of the shaft-shaped jig 30 in a fitting section 30a in a part corresponding to the journal sections 13b and 14b of the camshafts 13 and 14 to be actually assembled is larger than the shaft diameter of the journal sections 13b and 14b by a predetermined amount. The predetermined amount is set to an amount by which a necessary amount of clearance is secured between the outer surfaces of the journal sections 13b and 14b of the camshafts 13 and 14 and the inner surfaces of the bearing sections 15 and 16 with differences in relevant components considered.
In addition, a pair of flange sections 30b is formed on the right end of the shaft-shaped jig 30 in FIG. 1. The cam cap 22 is fitted between a pair of the flange sections 30b in order that the movement in the direction of thrust may be restricted.
A case in which the camshafts 13 and 14 are assembled by using the shaft-shaped jig 30 will be described hereinafter.
The cam carrier 21 on one end and the cam carrier 17 on the other end are positioned by the knock-pin 12a. The bolt 26 is inserted into the bolt hole 17c, which is sufficiently large, on the cam carriers 21 and 17, and the cam carriers are loosely fixed onto the cylinder head 12 by the bolt 26.
Next, the bolt 26 is inserted into the bolt hole 17c in the cam carrier 17, which is sufficiently large, between the cam carrier 21 on one end and the cam carrier 17 on the other end, and the bolt 26 is loosely screwed into the cylinder head 12 in a state in which a plurality of the cam carriers 17 can slightly move.
Two shaft-shaped jigs 30 are then placed on the bearing recesses 17a and 21a on the intake side and on the exhaust side of the cam carriers 17 and 21, respectively. On these components, the cam cap 22 and the cam cap 18 are covered and fixed completely by the bolts 26 and 27. When the bearing recesses on the intake side and on the exhaust side are formed on a separate carrier, it is only necessary to place one shaft-shaped jig.
In this state, it should be confirmed that the shaft-shaped jig 30 is smoothly rotated by hand or by a jig.
Following this, the bolt 27 is loosened, and the cam caps 18 and 22 are removed. Then, the shaft-shaped jig 30 is removed and replaced with the camshafts 13 and 14. Finally, the cam caps 18 and 22 are attached once again.
The clearance at a time when the shaft-shaped jig 30 is used as described above is smaller than the clearance at a time when the actual camshafts 13 and 14 are used for the assembly between the outer surface of the fitting section 30a of the shaft-shaped jig 30 and the inner surface of the bearing sections 13 and 14. As a result, unlike the conventional technique, the cam carrier 17 and the cam cap 18 can be attached with a little clearance or play with respect to the shaft-shaped jig 30.
Accordingly, a plurality of the cam carriers 17 can be accurately attached to the cylinder head 12 by completely fixing the cam carrier 17 and so forth in this state.
As a result, it is possible to prevent deterioration of the contact condition in the journal sections 13b and 14b of the camshafts 13 and 14. Further, it is possible to avoid increase of friction in the journal sections 13b and 14b.
Therefore, even if large-scale machining equipment is not used, the accuracy of the assembly positions of the support sections for the journal sections 13b and 14b can be ensured.
In addition, even if the cam carrier 17 or any other component causes a problem, it is not necessary to perform the machining process for improving the assembly condition in the conventional manner. Consequently, it is only necessary to replace the cam carrier 17 or any other component having caused a problem before the components are assembled with the shaft-shaped jig 30 used as described above. Therefore, only a minimum number of components need to be replaced.
Moreover, the rocker shaft 24 independent of each other is disposed on a multiplicity of the cam carriers 17. Therefore, after a multiplicity of the cam carriers 17 are attached to the cylinder head 12, it is not necessary to perform the machining process for improving the assembly state in order to improve the accuracy of the assembly position of the rocker shaft 24.
In the embodiment, the cam cap 18 is fastened to the cylinder head 12. Unlike this embodiment, however, the cam cap 18 may be fastened to the cam carrier 17.
Further, in the first embodiment, when the shaft-shaped jig 30 is disposed, the cam cap 18 is also attached. Unlike this embodiment, however, it is possible to attach solely the cam carrier 17 to the cylinder head 12 by the bolt 26 before centering by use of the shaft-shaped jig 30.
In this case, the cam cap 18 is not attached, and the cam carrier 17 is centered by the shaft-shaped jig 30. After this, the shaft-shaped jig 30 is removed and replaced with the camshafts 13 and 14. Then, the cam cap 18 is attached.
In this case, it is not necessary to attach or detach the cam cap 18 when the shaft-shaped jig 30 is disposed (when centered). As a result, work efficiency is excellent.
In this embodiment, the knock-pin 12a is fitted into the both of the cam carriers 21 and 17 on the both ends. Unlike this embodiment, however, the knock-pin 12a may be fitted solely into the cam carrier 21 or 17 on one side in order that it is not necessary for the knock-pin to be fitted on the other side.

[Second embodiment]

FIG. 3 to FIG. 5 show a second embodiment according to the present invention.
The second embodiment is different from the first embodiment in that a positioning section 40a and a circular section 40b are provided on a shaft-shaped jig 40.
Specifically, a shaft diameter "d" of the shaft-shaped jig 40 in a fitting section 40c in a part corresponding to the journal sections 13b and 14b of the camshafts 13 and 14 to be actually assembled is larger than the shaft diameter of the journal sections 13b and 14b by a predetermined amount. The predetermined amount is set to an amount by which a necessary amount of the clearance is secured between the outer surfaces of the journal sections 13b and 14 b of the camshafts 13 and 14 and the inner surfaces of the bearing sections 15 and 16 with differences in relevant components considered.
The positioning section 40a in the shape of a step adjoins the fitting section 40c. The positioning section 40a is engaged with engaging sections 17e and 18c of the cam carrier 17 and the cam cap 18.
The circular section 40b of the shaft-shaped jig 40 is formed in a position corresponding to the cam sections 13a and 14a of the camshafts 13 and 14 and has a diameter the same as that of the base circle of the cam sections 13a and 14a.
Moreover, a pair of flange sections 40d for receiving a thrust is formed on an end of the shaft-shaped jig 40.
In this case, the positioning section 40a is formed on the shaft-shaped jig 40 in order to determine the position of the cam carrier 17 in the axial direction of the shaft-shaped jig 40 by the positioning section 40a. Consequently, the position accuracy of the base position of the cam carrier 17 and the position of the cam carrier 17 in the axial direction are improved by the shaft-shaped jig 40. As a result, the widths of the cam section and the journal section can be reduced and the weight thereof can be reduced.
In addition, the circular section 40b having a diameter as large as the diameter of the base circle of the cam sections 13a and 14a is formed in a position on the shaft-shaped jig 40 corresponding to the cam sections 13a and 14a of the camshafts 13 and 14. As a result, the clearance between the rocker arm 25 disposed on the cam carrier 17 and the base circle section of the cam sections 13a and 14a can be adjusted by the circular section 40b without turning the camshafts 13 and 14.
The other compositions and operations are the same as those in the first embodiment. Therefore, the description thereof is not repeated.
Also in the second embodiment, when the shaft-shaped jig 40 is disposed, the cam cap 18 is also attached. Unlike this embodiment, however, it is possible to attach solely the cam carrier 17 to the cylinder head 12 before centering by use of the shaft-shaped jig 40.

[Third embodiment]

FIG. 6 to FIG. 8 show a third embodiment according to the present invention.
The third embodiment is different from the first embodiment in that the intake camshaft 13 and the exhaust camshaft 14 also function as the shaft-shaped jig for positioning the cam carrier 17. With this embodiment, the method of assembling the intake camshaft 13 will be described with reference to the accompanying drawings. The description of the method of assembling the exhaust camshaft 14 is omitted because the method of assembling the exhaust camshaft 14 is the same as that of the intake camshaft 13. When the bearing recesses 17a and 21a on the sides of the intake camshaft and the exhaust camshaft are integrally formed, the intake camshaft 13 and the exhaust camshaft 14 are simultaneously assembled to the cam carriers 17 and 21. On the other hand, when the bearing recesses 17a and 21a on the sides of the intake camshaft and the exhaust camshaft are separately formed, the intake camshaft and the exhaust camshaft are assembled not simultaneously but separately.
Specifically, a fitting section 13f adjoining a journal section 13b is provided on the intake camshaft 13, while a fitted section 15a adjoining a bearing section 15 to be fitted with the fitting section 13f is provided on the cam carrier 17 and on the cam cap 18. In this embodiment, a part of the bearing section 15 also functions as the fitted section 15a. As shown in FIG. 7 and FIG. 8, an outer diameter "d2" of the fitting section 13f is larger than an outer diameter "d3" of the journal section 13b.
As a result, a clearance c1 between the outer surface of the fitting section 13f and the inner surface of the fitted section 15a is smaller than a clearance c2 between the outer surface of the journal section 13b and the inner surface of the bearing section 15.
The method of assembling the camshaft 13 will be described hereinafter.
As illustrated in the first embodiment, the cam carriers 17, 21 are loosely fixed onto the cylinder head 12 by the bolt 26. Then the intake camshaft 13 is mounted, and the flange section 13e is made to be in contact with the side of the cam carrier 21. Each fitting section 13f of the intake camshaft 13 is fitted with the fitted section 15a of each cam carrier 17. On these components, the cam caps 18, 22 are covered and fixed completely by the bolts 26, 27 (refer to FIG. 7(a) and FIG. 8(a)).
The camshaft 13 slides in the axial direction (to the left side in FIGs. 6, 7, and 8) by a predetermined amount in order to release the fitting section 13f from the fitted section 15a.
In this state, the cam cap 22 as a "slide restricting member" of the present invention is attached to the cam carrier 21. Since the cam cap 22 is fitted between a pair of the flange sections 13d, 13e of the camshaft 13, the slide of the camshaft 13 is restricted, and the intake camshaft 13 is held in the final position.
Further, the side of the cam cap 22 and the flange sections 13d and 13e of the intake camshaft 13 receive a thrust when the intake camshaft 13 is turning.
According to the embodiment, it is only necessary to slide the camshaft 13 in order for the cam cap 22 to restrict the position. Accordingly, it is not necessary to use the shaft-shaped jig 30 as illustrated in the first embodiment. Nevertheless, an effect equivalent to that of the first embodiment is achieved. Thus, the work efficiency can be improved.
The other compositions and operations are the same as those in the first embodiment. Therefore, the description thereof is not repeated.

[Fourth embodiment]

FIG. 9 and FIG. 10 show a fourth embodiment according to the present invention.
The fourth embodiment is different from the third embodiment in that the structure of the fitting section 13f of the camshaft 13 and the structure of the fitted section 15a are different.
Specifically, the outer diameter d2 of the fitting section 13f is larger than the outer diameter d3 of the journal section 13b, while the inner diameter d4 of the fitted section 15a is larger than the inner diameter d5 of the bearing section 15.
According to the embodiment, the camshaft 13 is slid in order to engage or disengage the fitting section 13f with or from the fitted section 15a. Consequently, in a manner similar with the third embodiment, the accuracy of mounting positions of the cam carrier 17 and other components can be improved.
The other compositions and operations are the same as those in third embodiment. Therefore, the description thereof is not repeated.

[Description of Reference Numerals and Symbols]

11: engine (internal combustion engine)
12: cylinder head
13: intake camshaft
14: exhaust camshaft
13a: intake cam section
14a: exhaust cam section
13b, 14b: journal section
13f: fitting section
15, 16: bearing section
15a: fitted section
17: cam carrier
17a: bearing recess
18: cam cap
18a: bearing recess
21: cam carrier
22: cam cap
24: rocker shaft
25: rocker arm
30, 40: shaft-shaped jig
30a: fitting section
40a: positioning section
40b: circular section
d1: shaft diameter of the shaft-shaped jig
d2: outer diameter of the fitting section
d3: outer diameter of the journal section
d4: internal diameter of the fitted section
d5: internal diameter of the bearing section
c1: clearance
c2: clearance

Claims

A method of assembling a camshaft for an internal combustion engine in which the camshaft is assembled to a cylinder head via a plurality of sets of cam carriers and cam caps separately provided in each journal section, the method comprising the steps of:
preparing a shaft-shaped jig the length of which is as long as the whole of a plurality of the cam carriers and the shaft diameter of which in a fitting section in a part corresponding to the journal section is larger than the shaft diameter of the journal section; and

positioning a plurality of the cam carriers in a predetermined position by attaching the shaft-shaped jig on the cylinder head via a plurality of the cam carriers.
A method of assembling a camshaft for an internal combustion engine in which the camshaft is assembled to a cylinder head via a plurality of sets of cam carriers and cam caps separately provided in each journal section, the method comprising the steps of:
preparing a shaft-shaped jig the shaft diameter of which in a fitting section in a part corresponding to the journal section of the camshaft to be actually assembled is larger than the shaft diameter of the journal section; and

positioning a plurality of the cam carriers in a predetermined position by attaching the shaft-shaped jig on the cylinder head via a plurality of the cam carriers and cam caps;

removing a plurality of the cam caps with a plurality of the cam carriers being fastened to the cylinder head;

replacing the shaft-shaped jig with the camshaft to be actually used; and

fastening a plurality of the cam caps.
A method of assembling a camshaft for an internal combustion engine in which the camshaft is assembled to a cylinder head via a plurality of sets of cam carriers and cam caps separately provided in each journal section, the method comprising the steps of:
preparing a shaft-shaped jig the shaft diameter of which in a fitting section in a part corresponding to the journal section of the camshaft to be actually assembled is larger than the shaft diameter of the journal section; and

positioning a plurality of the cam carriers in a predetermined position by attaching the shaft-shaped jig on the cylinder head via a plurality of the cam carriers;

replacing the shaft-shaped jig with the camshaft to be actually used with a plurality of the cam carriers being fastened to the cylinder head; and

fastening a plurality of the cam caps.
The method of assembling a camshaft for an internal combustion engine according to any one of Claims 1 to 3,
wherein a positioning section is formed on the shaft-shaped jig in order to determine the position of the cam carrier in the axial direction of the shaft-shaped jig by the positioning section.
The method of assembling a camshaft for an internal combustion engine according to any one of Claims 1 to 4,
wherein a circular section having a diameter as large as the diameter of a base circle of a cam section is formed in a position on the shaft-shaped jig corresponding to the cam section of the camshaft.
A method of assembling a camshaft for an internal combustion engine in which the camshaft is assembled to a cylinder head via a plurality of cam carriers and cam caps separately provided in each journal section,
wherein the camshaft also functions as a shaft-shaped jig for positioning the cam carrier, a journal section supported by a bearing section of the cam carrier and the cam cap is provided on the camshaft, and a fitting section thicker than the journal section is provided in a part adjoining the journal section,
a fitted section to be fitted by the fitting section is provided on the cam carrier and the cam cap in a part adjoining the bearing section,
a clearance between the outer surface of the fitting section and the inner surface of the fitted section is smaller than a clearance between the outer surface of the journal section and the inner surface of the bearing section,
the camshaft is attached to the cylinder head via the cam carrier and the cam cap by fitting the camshaft fitting section to the cam carrier and the cam cap fitted section, and
the slide of the camshaft is restricted by attaching a slide restricting member while the camshaft slides in the axial direction by a predetermined amount in order to release the fitting section from the fitted section.
The method of assembling a camshaft for an internal combustion engine according to Claim 6,
wherein a part of the bearing section also functions as the fitted section, and
the outer diameter of the fitting section is larger than the outer diameter of the journal section.
The method of assembling a camshaft for an internal combustion engine according to Claim 6,
wherein the outer diameter of the fitting section is larger than the outer diameter of the journal section, and
the inner diameter of the fitted section is larger than the inner diameter of the bearing section.
The method of assembling a camshaft for an internal combustion engine according to Claim 6,
wherein the slide restricting member is a housing cap provided on an end of the camshaft.
The method of assembling a camshaft for an internal combustion engine according to any one of Claims 1 to 9,
wherein a plurality of the cam carriers are disposed along the camshaft, a rocker shaft independent of each other is disposed on each of the cam carriers, and a rocker arm is disposed for pivotal motion on the rocker shaft.
An internal combustion engine,
wherein the camshaft is assembled to the cylinder head via the cam carrier and the cam cap by the method of assembling a camshaft for an internal combustion engine according to any one of Claims 1 to 10.