JP2009121282A - Camshaft structure and assembling method of camshaft structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a camshaft structure capable of securely blocking burrs generated on the inner side of a joint portion of a camshaft and an end piece from a hollow hole of the camshaft since an outer peripheral face of a projecting part is securely engaged with an inner peripheral face of an engagement ring, and of securely preventing mixture of foreign matters such as metal powder generated from the burrs with lubricating oil. <P>SOLUTION: The camshaft structure is provided with the camshaft 21 fitted with a cam piece and having the hollow hole 28 formed thereon and with the end piece 26 jointed to the camshaft 21. The camshaft 21 has the engagement ring 27 projecting to the inner side of the camshaft 21 in an end part on the side jointed to the end piece 26, and the end piece 26 has the cylindrical projecting part 32 projecting axially. With a clearance between the outer peripheral face of the projecting part 32 and the inner peripheral face 27c of the engagement piece 27 blocked from the hollow hole 28 of the camshaft 21, the projecting part 32 is expanded in the radial direction and engaged with the engagement ring 27. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a camshaft structure for connecting a camshaft and an end piece, and a method for assembling the camshaft structure.

Conventionally, as this kind of camshaft structure, a structure in which an end piece and a camshaft composed of a hollow shaft are coupled by friction welding is known.
This friction welding process is a method in which members to be joined are brought into contact with each other and rotated, and joined by frictional heat generated on the contact surfaces. In this friction welding process, no welding material or the like is required, and it is not necessary to perform high-precision machining on the members to be joined in advance, so that the assembly process is simplified and the assembly cost is reduced. There is. On the other hand, in the case of this friction welding, burrs are generated around the joint during friction welding, and metal powder may be generated from these burrs. In particular, in the case of a camshaft consisting of an end piece and a hollow shaft with a lubricating oil passage formed inside, metal powder generated from the burr enters the lubricating oil and adversely affects lubrication. It is necessary to remove burrs.

  The burrs generated on the outside of the joined portion are removed relatively easily by a cutting tool or the like. However, since the burr generated inside the joint portion is located at the back of the camshaft formed of a hollow shaft, a relatively long cutting tool is required. It is not easy to cut a burr at the tip of such a long cutting tool because the material of the burr is hardened by friction welding. Therefore, there is known a camshaft structure in which the metal powder generated from the burr is prevented from being mixed into the lubricating oil without removing the burr generated inside the joined portion.

  As this type of conventional camshaft structure, a space is defined in a camshaft and an end piece made of a hollow shaft, and burrs generated during friction welding are confined in this space ( For example, see Patent Document 1). In this camshaft structure, the end piece has a confinement portion that protrudes from the end surface to the camshaft side and is enlarged in diameter at the tip portion. When the camshaft is friction-welded to the end piece, the confinement portion A space is defined by the outer peripheral surface, the end surface of the end piece, and the inner peripheral surface of the camshaft. In this space, burrs generated inside the joint portion between the camshaft and the end piece are confined.

JP 2000-213551 A

  However, in the conventional camshaft structure as described above, when the camshaft is friction-welded to the end piece, the confinement portion of the end piece is inserted into the camshaft formed of a hollow shaft, so that the above-described space is reduced. Since it is defined, a gap is formed between the outer peripheral surface of the confinement portion and the inner peripheral surface of the camshaft. As a result, the lubricating oil enters the space from the gap, and metal powder generated from the burr confined in the space is mixed into the lubricating oil and is discharged from the gap to the outside of the space, which may adversely affect the lubrication. There was a problem. That is, there is a problem that burr generated inside the joint portion between the camshaft and the end piece is insufficiently confined.

  The present invention has been made to solve the above-described conventional problems, and can seal burrs generated inside the joint portion between the camshaft and the end piece, such as metal powder generated from the burrs. It is an object of the present invention to provide a camshaft structure and an assembling method of the camshaft structure that can reliably prevent foreign matters from being mixed into the lubricating oil.

  In order to achieve the above object, a camshaft structure according to the present invention includes: (1) a camshaft structure in which a campiece is mounted and a hollow hole is formed; and an endpiece coupled to the camshaft. The camshaft has an annular protrusion protruding inwardly at an end portion on the side to be coupled with the end piece, and the end piece has a cylindrical protrusion portion protruding in the axial direction, and the protrusion portion The protrusion is enlarged in the radial direction and engaged with the annular protrusion in a state in which a gap between the outer peripheral surface of the annular protrusion and the inner peripheral surface of the annular protrusion is blocked from the hollow hole of the camshaft. To do.

  With this configuration, the end piece is coupled to the camshaft, and when the protrusion is enlarged in the radial direction and engaged with the annular protrusion, the outer peripheral surface of the protrusion and the side surface of the annular protrusion are engaged, The hollow hole of the camshaft is cut off from the joint part between the end piece and the camshaft, so even if foreign matter such as burrs or metal powder is generated in the joint part, the foreign substance is not discharged into the hollow hole of the camshaft. Absent. As a result, it is possible to reliably prevent foreign matters generated from burrs from being mixed into, for example, the lubricating oil flowing in the hollow holes. Here, the hollow hole includes not only a through-hole penetrating the camshaft but also one in which the end of the camshaft is closed.

  The camshaft structure described in the above (1) is preferably configured such that (2) the outer peripheral surface of the protruding portion and the inner peripheral surface of the annular protrusion abut.

  With this configuration, the gap between the outer peripheral surface of the projecting portion and the inner peripheral surface of the annular protrusion is sealed, so even if burrs or foreign matter are generated at the joint between the end piece and the camshaft, the foreign matter can enter the hollow space. Emission can be reliably prevented.

  In the camshaft structure described in the above (1) or (2), preferably, (3) the end piece has an annular coupling protrusion facing the end of the camshaft, and the tip of the coupling protrusion is It is configured to be coupled to the end of the camshaft.

  With this configuration, when the distal end portion of the coupling protrusion is joined to the axial end portion of the camshaft, the distal end portion of the coupling projection and the axial end portion of the camshaft can be formed in substantially the same shape. When both are substantially the same shape, for example, when both are friction welded, heat generated in the coupling protrusion and the camshaft is uniformly transmitted to the coupling protrusion and the camshaft, and a uniform coupling without unevenness is obtained. The rigidity of the joint portion is increased. In this case, a sealed space is defined by the end face of the end piece, the inner peripheral face of the coupling protrusion, the outer peripheral face of the protrusion, and the inner face of the annular protrusion on the end piece side. Since burrs generated on the inner peripheral side of the joint between the end piece and the camshaft are sealed in this space, even if foreign matter such as metal powder is generated from the burrs, the foreign matter is discharged outside the space. Absent. Here, the sealed space refers to a sealed space in which foreign matter is not discharged from the space to the outside, and no lubricating oil flows into the space from the outside.

  In the camshaft structure described in the above (1) to (3), preferably, (4) the end piece has a liquid passage through the inside of the protrusion.

  With this configuration, the protrusion is enlarged in the radial direction and engaged with the annular protrusion, and the gap between the outer peripheral surface of the protrusion and the inner peripheral surface of the annular protrusion is liquid-tightly blocked from the hollow hole of the camshaft. In addition to having a function, the protrusion has a function as a passage tube having a liquid passage communicating from the end piece to the hollow hole of the camshaft, and the camshaft structure is simplified.

  The camshaft structure according to any one of the above (1) to (4) is preferably (5) formed by an engagement ring in which the annular protrusion is screwed to the camshaft.

  With this configuration, since the engagement ring is manufactured separately from the camshaft, for example, the camshaft can be formed of a pipe material, and the camshaft can be easily manufactured. Further, since the engagement ring is screwed to the camshaft, the annular protrusion is formed in a surely sealed state.

  The camshaft structure according to any one of the above (1) to (4) is preferably (6) formed by an engagement ring in which the annular protrusion is press-fitted into the camshaft.

  With this configuration, since the engagement ring is manufactured separately from the camshaft, for example, the camshaft can be formed of a pipe material, and the camshaft can be easily manufactured. Moreover, since the engagement ring is press-fitted into the camshaft, the engagement ring is securely sealed.

  In order to achieve the above object, the camshaft structure assembling method according to the present invention includes (7) a mounting step in which a cam piece is mounted and a camshaft having a hollow hole is mounted with an engaging ring protruding inward. A disposing step of arranging an end piece having a cylindrical projecting portion projecting toward the cam shaft in the vicinity of an end portion of the cam shaft; a coupling step of coupling the end piece to the cam shaft; and the projecting portion. An engagement step of engaging the protrusion with the engagement ring in a state where a gap between the outer peripheral surface of the annular projection and the inner peripheral surface of the annular protrusion is blocked from the hollow hole of the camshaft. To do.

  With this configuration, the engagement ring is assembled into the camshaft in the mounting process or mounted in advance by integral molding, the endpiece is disposed in the vicinity of the end of the camshaft in the positioning process, and the endpiece and the camshaft are connected in the coupling process The protrusions of the end pieces are engaged with the engagement ring in the engagement step. Since the protrusion of the end piece is separated from the inner peripheral surface of the camshaft when inserted into the inner peripheral surface of the engagement ring, the protrusion can be reliably engaged with the engagement ring.

  In the method for assembling the camshaft structure according to (7), preferably, (8) the engaging step presses the tip portion of a tool having a conical tip portion against the projecting portion of the end piece. As a result, the protrusion is expanded and engaged with the engagement ring.

  With this configuration, in the engaging step, the engaging portion of the end piece is uniformly spread all around by the pressing force of the tool and is plastically deformed, and the clearance between the outer peripheral surface of the protruding portion and the inner peripheral surface of the engaging ring And the protrusion is engaged with the engagement ring.

  According to the present invention, since the outer peripheral surface of the protrusion and the inner peripheral surface of the engagement ring can be reliably engaged, the burr generated on the inner side of the coupling portion between the camshaft and the end piece can be prevented. Therefore, foreign matter such as metal powder generated from burrs can be reliably prevented from entering the lubricating oil that lubricates and cools the camshaft.

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

(First embodiment)
The camshaft structure 10 according to the first embodiment is a specific example of a camshaft structure in which the camshaft structure according to the present invention is applied to a variable valve timing device for an internal combustion engine.

  First, a variable valve timing device 1 for an internal combustion engine to which the camshaft structure 10 according to the first embodiment is applied will be described.

  FIG. 1 is a perspective view of a variable valve timing device showing an example in which the camshaft structure according to the first embodiment of the present invention is applied to the camshaft structure of a variable valve timing device for an internal combustion engine.

  As shown in FIG. 1, a variable valve timing device 1 for an internal combustion engine includes a valve timing changing mechanism 2, an intake side camshaft 3, an exhaust side camshaft 4, an intake valve 5, and an exhaust valve 6. It is configured.

  The valve timing changing mechanism 2 includes a timing sprocket 11 connected to the intake camshaft 3, a timing sprocket 12 connected to the exhaust camshaft 4, a sprocket 14 connected to the crankshaft 13, a timing chain 15, It is comprised including.

  The intake camshaft 3 has a cam piece 16 made of an intake cam or the like, and opens and closes the intake valve 5 by its rotation. Further, the exhaust side camshaft 4 also has a cam piece 18 made of an exhaust cam or the like, and the exhaust valve 6 is opened and closed by its rotation.

  In the valve timing changing mechanism 2, the rotation of the crankshaft 13 is transmitted from the timing sprocket 11 to the intake side camshaft 3 by the timing chain 15 through the sprocket 14, and the intake valve 5 is opened and closed through the cam piece 16. It has become so. In addition, the exhaust valve 6 is transmitted from the timing sprocket 12 to the exhaust camshaft 4 and the exhaust valve 6 is opened and closed via the cam piece 18. Each opening / closing timing of the intake valve 5 and the exhaust valve 6 is controlled by an engine electronic control unit (ECU) (not shown) according to the operating state of the internal combustion engine.

  FIG. 2 is a perspective view of the camshaft structure according to the first embodiment of the present invention.

  As shown in FIG. 2, the camshaft structure 10 according to the first embodiment is applied to, for example, the exhaust side camshaft 4 of the variable valve timing device 1, and includes a camshaft 21 and cam pieces 22, 23, 24, 25, an end piece 26, and an engagement ring 27.

  The camshaft 21 is made of, for example, a metal material such as carbon steel for machine structure, is formed in a cylindrical shape having a hollow hole 28, and includes a shaft portion 21a and a journal portion 21b that contacts the bearing. . A plurality of lubricating oil supply ports 21c are formed in the shaft portion 21a and the journal portion 21b. The hollow hole 28 of the camshaft 21 constitutes a lubricating oil flow path, and the lubricating oil flowing in the flow path is supplied to the lubricating member from the lubricating oil supply port 21c. Cam pieces 22, 23, 24, and 25 are incorporated into the camshaft 21 by a known fixing method such as press-fitting, and rotate with the rotation of the camshaft 21.

The cam piece 22 is made of a highly wear-resistant metal material such as a forged product or a sintered material, and has an annular base portion and a nose portion that is integrally formed with the base portion and protrudes from the base portion. The camshaft 21 is incorporated into the shaft portion 21a.
The cam piece 22 is provided with a through hole, and when the cam piece 22 is incorporated in the shaft portion 21a, the through hole formed in the shaft portion 21a and the through hole in the cam piece 22 communicate with each other. The lubricating oil in the flow path 21 may flow into the through-hole and supplied to the outer peripheral surface of the cam piece 22 to lubricate the cam piece 22.
The cam pieces 23, 24, and 25 are also configured in the same manner as the cam piece 22, and are incorporated at positions on the shaft portion 21a corresponding to the positions of the respective cylinders (not shown).

  FIG. 3 is a sectional view of the camshaft structure according to the first embodiment of the present invention, FIG. 3A is a sectional view of the end piece, and FIG. 3B is a partial sectional view of the camshaft. FIG.

  As shown in FIG. 3A, the end piece 26 is made of, for example, a metal material such as carbon steel for mechanical structure similar to the camshaft 21 and is formed in a columnar shape. It has a protruding portion 32 that protrudes from the end surface portion 31a in the axial direction with a predetermined length a and is formed into a cylindrical shape with a predetermined outer diameter b. A hole 33 having an axial line that matches the axis of the protruding part 32 is formed in the protruding part 32. The predetermined length a and the predetermined outer diameter b are appropriately selected according to design conditions such as the material, shape, and size of the end piece 26.

  A hole 34 is formed in the main body 31 so as to communicate with the hole 33 in the axial direction of the main body 31, and a communication hole 35 that is orthogonal to the hole 34 and that communicates the hole 34 with an external space is formed. Has been. The holes 33 and 34 and the communication hole 35 constitute a part of the flow path of the lubricating oil, and the lubricating oil flowing into the communication hole 35 passes through the hole 34 and the hole 33 and is a hollow hole in the camshaft 21. 28 is supplied. The distal end portion of the protrusion 32 constitutes an engagement portion 36 that is enlarged in the radial direction and engages with the engagement ring 27.

  As shown in FIG. 3B, the engagement ring 27 as an annular protrusion is made of a metal material, has a through hole 27a having an inner diameter c, is formed in an annular shape, and the end piece 26 is formed in the through hole 27a. The protruding portion 32 is inserted. For this reason, the inner diameter c of the engagement ring 27 is slightly larger than the outer diameter b of the protrusion 32. In the engagement ring 27, the inner peripheral surface 21d of the shaft portion 21a and the outer peripheral surface 27e of the engagement ring 27 are fitted so that the distance from the end portion 21e of the shaft portion 21a of the cam shaft 21 to the side surface portion 27b is d. And fixed to the inside of the shaft portion 21a.

  FIG. 4 is a cross-sectional view of the camshaft structure according to the first embodiment of the present invention. FIG. 4A shows a state where the end piece is separated from the camshaft, and FIG. Shows a state where the end piece is in contact with the camshaft, and FIG. 4C shows a state where the endpiece is joined to the camshaft.

  As shown in FIG. 4B, when the protruding portion 32 of the end piece 26 is inserted into the through hole 27a of the engagement ring 27 and the end portion 21e of the shaft portion 21a contacts the end surface portion 31a of the end piece 26. The engaging portion 36 in the protruding portion 32 protrudes from the side surface portion 27b of the engaging ring 27 by a length ab.

Next, an assembling method of the camshaft structure 10 according to the present embodiment will be described.
The assembling method of the camshaft structure 10 includes a preparation process, a mounting process, an arrangement process, a coupling process, and an engagement process.

  As shown in FIG. 4A, in the preparation step, the camshaft 21, the end piece 26, the engagement ring 27, and production equipment such as tools, a rotating device, and a fixing device for assembling them are prepared. The In this case, the camshaft 21 may incorporate components constituting the camshaft 21 such as the cam pieces 22, 23, 24, and 25, or only the shaft portion 21a.

  In the mounting process, the engagement ring 27 is inserted into the shaft portion 21a with a predetermined tool so that the distance from the end portion 21e of the shaft portion 21a to the side surface portion 27b is d, and is fitted inside the shaft portion 21a. And fixed.

  In the arrangement step, the end 31b side of the end piece 26 is attached to a rotating device (not shown), and the end of the shaft portion 21a is fixed to a fixing device (not shown). At this time, position adjustment such as centering of the end piece 26 and the shaft portion 21a is performed, and the end piece 26 and the shaft portion 21a are arranged so that the axis of the end piece 26 and the axis of the shaft portion 21a coincide.

As shown in FIG. 4 (b), in the joining step, a part of the end surface portion 31a of the end piece 26 and the end portion 21e of the shaft portion 21a are welded by a known friction welding method. 26 and the shaft portion 21a are coupled.
In the joining step, first, the end piece 26 is rotated at a predetermined speed (rpm) by a rotating device. In this state, the shaft portion 21a is pressed against the end piece 26 in the direction of the arrow by the fixing device, and a predetermined pressing force F (MPa) is applied. The predetermined speed (rpm) and the predetermined pressing force F (MPa) are appropriately selected according to design conditions such as the material, shape, and size of the end piece 26 and the shaft portion 21a. Since the shaft portion 21a fixed to the rotating end piece 26 is pressed and brought into contact, frictional heat is generated on the contact surface. The predetermined pressing force F is applied until the frictional heat reaches a temperature necessary for pressure welding, and at the same time as the pressure temperature is reached, a higher pressing force F is applied, and the end piece 26 and the shaft portion 21a are welded.

  As shown in FIG. 4C, when the end piece 26 and the shaft portion 21a are joined by the joining step, burrs 38 and 39 are generated outside and inside the joining portion of the end piece 26 and the shaft portion 21a. To do.

  FIG. 5 is a cross-sectional view of the camshaft structure according to the first embodiment of the present invention. FIG. 5A shows a state where the outer peripheral surface of the camshaft is polished, and FIG. FIG. 5 shows a state in which the engaging portion of the protruding portion of the end piece is pressed by a tool, and FIG. 5C shows a state in which the engaging portion of the protruding portion of the end piece is engaged.

  As shown in FIG. 5 (a), the burrs 38 generated outside the joint portion are removed by a tool 41 made of a cutting tool, a polishing tool or the like.

  As shown in FIG. 5B, in the engaging step, the engaging portion 36 of the end piece 26 is engaged with the engaging ring 27 by a known engaging method. Further, in the engaging step, the tip 42a of the tool 42 having the tip 42a formed in a conical shape is pressed against the engaging portion 36 with a predetermined pressure (MPa), as shown in FIG. In this manner, the engaging portion 36 is expanded and plastically deformed to engage with the engaging ring 27. At this time, the outer peripheral surface 32a of the protruding portion 32 and the inner peripheral surface 27c of the engaging ring 27 come into contact with each other, and the engaging portion 36 is uniformly plastically deformed. The engagement portion 36 and the engagement ring 27 are engaged with each other in a state where the gap with the inner peripheral surface 27c is liquid-tightly sealed.

  Thus, since the clearance gap between the outer peripheral surface 32a of the protrusion part 32 and the inner peripheral surface 27c of the engagement ring 27 is liquid-tightly sealed, the end surface part 31a of the end piece 26 and the outer peripheral surface of the protrusion part 32 are sealed. A space 43 sealed by 32a, the inner side surface 27d of the engagement ring 27, and the inner peripheral surface 21d of the shaft portion 21a is defined. The burr 39 is enclosed in the space 43.

Next, the operation of the camshaft structure 10 according to the present embodiment will be described.
FIG. 6 is a cross-sectional view showing a state where the end piece of the camshaft structure and the camshaft are combined according to the first embodiment of the present invention.

  As shown in FIG. 6, when lubricating oil flows in the direction of the arrow from the communication hole 35, it flows in the order of the hole 34 and the hole 33 and flows into the hollow hole 28 of the camshaft 21. The lubricating oil flowing in the hollow hole 28 is supplied to a lubricating member (not shown) located near the camshaft 21 from the lubricating oil supply port 21c shown in FIG. 2 provided in the shaft portion 21a and the journal portion 21b. The At this time, foreign matter such as metal powder generated from the burr 39 in the space 43 is not discharged to the outside from the space 43, and the lubricating oil does not enter the space 43 from the outside.

  As described above, in the camshaft structure 10 according to the present embodiment, the camshaft 21 to which the cam pieces 22, 23, 24, 25 for opening and closing the exhaust valve of the internal combustion engine are mounted and the hollow hole 28 is formed, An end piece 26 coupled to the camshaft 21, and the camshaft 21 has an engagement ring 27 projecting inward thereof at an end portion coupled to the endpiece 26, and the endpiece 26 is axially In a state where the gap between the outer peripheral surface 32 a of the protrusion 32 and the inner peripheral surface 27 c of the engagement ring 27 is liquid-tightly blocked from the hollow hole 28 of the camshaft 21. The protrusion 32 is enlarged in the radial direction and engaged with the engagement ring 27.

  In this case, when the protrusion 32 is engaged with the engagement ring 27, the burr 39 generated inside the joint portion of the end piece 26 and the camshaft 21 is sealed in the space 43 described above. Even if foreign matter such as powder is generated, the foreign matter is not discharged outside the space 43, and the lubricating oil does not enter the space 43 from the outside. As a result, it is possible to reliably prevent foreign matters generated from the burr 39 from being mixed into the lubricating oil. The protrusion 32 is enlarged in the radial direction and engages with the engagement ring 27, and the gap between the outer peripheral surface of the protrusion 32 and the inner peripheral surface of the engagement ring 27 is liquid-tight from the hollow hole 28 of the camshaft 21. Since the projecting portion 32 also has a function as a passage tube having a hole 33 as a liquid passage that communicates from the end piece 26 to the hollow hole 28 of the camshaft 21. Has the effect of simplifying.

  In the camshaft structure 10 according to the first embodiment of the present invention, the case where the end surface portion 31a of the end piece 26 is formed flat has been described. However, the coupling protrusion protruding toward the camshaft side is provided on the end surface portion 31a. It may be formed. Hereinafter, a second embodiment in which the coupling protrusion is formed on the end surface portion 31a will be described.

(Second Embodiment)
The camshaft structure 20 according to the second embodiment is a specific example of a camshaft structure in which the camshaft structure according to the present invention is applied to a variable valve timing device for an internal combustion engine.

  The camshaft structure 20 according to the second embodiment is different from the camshaft structure 10 according to the first embodiment in that a coupling protrusion is formed on the end piece, but the other configurations are the same. It is configured. Therefore, the same configuration will be described using the same reference numerals as those of the first embodiment shown in FIGS. 1 to 6, and only differences will be described in detail.

  FIG. 7 is a perspective view of a camshaft structure according to the second embodiment of the present invention.

  As shown in FIG. 7, the camshaft structure 20 according to the second embodiment is applied to the exhaust-side camshaft 4 of the variable valve timing device 1 as in the first embodiment. , Cam pieces 52, 53, 54, 55, an engagement ring 57, and an end piece 56.

  Similar to the first embodiment, the camshaft 51 is made of a metal material such as carbon steel for machine structure, is formed in a cylindrical shape having a hollow hole 58, and is a journal that contacts the shaft portion 51a and the bearing. Part 51b. A plurality of lubricating oil supply ports 51c are formed in the shaft portion 51a and the journal portion 51b. The hollow hole 58 of the camshaft 51 forms a lubricating oil flow path, and the lubricating oil flowing in the flow path is supplied to the lubricating member from the lubricating oil supply port 51c. Cam pieces 52, 53, 54, and 55 are incorporated into the camshaft 51 by a known fixing method such as press fitting, and are rotated with the rotation of the camshaft 51.

  Similar to the first embodiment, the cam piece 52 is made of a highly wear-resistant metal material such as a forged product or a sintered material, and is formed integrally with the annular base portion and the base portion. A protruding nose portion, and is incorporated into the shaft portion 51 a of the camshaft 51. The cam pieces 53, 54, 55 are also configured in the same manner as the cam piece 52, and are incorporated at positions on the shaft portion 51a corresponding to the positions of the respective cylinders (not shown).

  FIG. 8 is a cross-sectional view of the camshaft structure according to the second embodiment of the present invention, FIG. 8A shows a cross-sectional view of the end piece, and FIG. 8B shows a portion of the camshaft. It is sectional drawing.

  As shown in FIG. 8A, the end piece 56 is made of, for example, a metal material such as carbon steel for mechanical structure similar to the camshaft 21 of the camshaft structure of the first embodiment, and is formed in a columnar shape. The main body 61 and the end surface 61a in the axial direction of the main body 61 project with a predetermined length f and have a predetermined length from the projecting portion 62 and the end surface 61a formed in a cylindrical shape with a predetermined outer diameter b. It has a coupling protrusion 67 that protrudes at i and is formed in a cylindrical shape. A hole 63 formed in the protrusion 62 so as to have an axis that matches the axis of the protrusion 62 constitutes a part of the flow path of the lubricating oil. The predetermined length f, the predetermined outer diameter b, the predetermined length i, the predetermined outer diameter h, and the predetermined inner diameter g are appropriately selected according to design conditions such as the material, shape, and size of the end piece 56.

  A hole 64 is formed in the main body 61 so as to communicate with the hole 63 in the axial direction of the main body 61, and a communication hole 65 that is orthogonal to the hole 64 and communicates the hole 64 with an external space is formed. Has been. The hole 64 and the communication hole 65 also constitute a part of the flow path of the lubricating oil, and the lubricating oil flowing into the communication hole 65 passes through the hole 64 and the hole 63 in the hollow hole 28 of the camshaft 21. To be supplied. The distal end portion of the protruding portion 62 constitutes an engaging portion 66 that is enlarged in the radial direction and engages with the engaging ring 27.

  As shown in FIG. 8B, the engagement ring 57 is configured in the same manner as in the first embodiment, is made of a metal material, has a through hole 57a with an inner diameter c, and is formed in an annular shape. The protruding portion 62 of the end piece 56 is inserted into the through hole 57a. For this reason, the inner diameter c of the engagement ring 57 is formed to be slightly larger than the outer diameter b of the protrusion 62. In the engagement ring 57, the inner peripheral surface 51d of the shaft portion 51a and the outer peripheral surface 57e of the engagement ring 57 are fitted so that the distance from the end portion 51e of the shaft portion 51a of the cam shaft 51 to the side surface portion 57b becomes j. And fixed to the inside of the shaft portion 51a.

  FIG. 9 is a cross-sectional view of the camshaft structure according to the second embodiment of the present invention. FIG. 9A shows a state in which the end piece is separated from the camshaft, and FIG. Shows a state in which the end piece is in contact with the camshaft, and FIG. 9C shows a state in which the endpiece is joined to the camshaft.

  As shown in FIG. 9B, when the projecting portion 62 of the end piece 56 is inserted into the through hole 57 a of the engagement ring 57 and the end portion 51 e of the shaft portion 51 a contacts the end surface portion 61 a of the end piece 56. The engaging portion 66 in the protruding portion 62 protrudes from the side surface portion 57b of the engaging ring 57 by the length fj. The outer shape h and the inner diameter g of the coupling protrusion 67 are formed to be substantially the same as the outer shape h and the inner diameter g of the shaft portion 51a.

Next, a method for assembling the camshaft structure 20 according to the present embodiment will be described.
Similar to the first embodiment, the assembly method of the camshaft structure 20 includes a preparation process, an installation process, an arrangement process, a coupling process, and an engagement process.

  As shown in FIG. 9A, in the preparation step, the camshaft 51, the end piece 56, the engagement ring 57, and production equipment such as tools, a rotating device, and a fixing device for assembling them are prepared. The In this case, the camshaft 51 may incorporate components constituting the camshaft 51 such as the cam pieces 52, 53, 54, and 55, or only the shaft portion 51a.

  In the mounting process, the engagement ring 57 is inserted into the shaft portion 51a with a predetermined tool so that the distance from the end portion 51e of the shaft portion 51a to the side surface portion 57b is j, and is fitted inside the shaft portion 51a. And fixed.

  In the arrangement step, the end 61b side of the end piece 56 is attached to a rotating device (not shown), and the end of the shaft portion 51a is fixed to a fixing device (not shown). At this time, position adjustment such as centering of the end piece 56 and the shaft portion 51a is performed, and the end piece 56 and the shaft portion 51a are arranged so that the axis of the end piece 56 and the axis of the shaft portion 51a coincide.

  As shown in FIG. 9B, in the coupling step, the end piece 56 and the end 51e of the shaft portion 51a are welded to each other by a known friction welding method, so that the end piece is welded. 56 and the shaft portion 51a are coupled together.

  In the joining step, first, the end piece 56 is rotated at a predetermined speed (rpm) by a rotating device. In this state, the shaft 51a is pressed against the end of the coupling protrusion 67 in the direction of the arrow by the fixing device, and a predetermined pressing force F (MPa) is applied. The predetermined speed (rpm) and the predetermined pressing force F (MPa) are appropriately selected according to design conditions such as the material, shape, and size of the end piece 56 and the shaft portion 51a. Since the shaft portion 51a fixed to the rotating end piece 56 is pressed and brought into contact, frictional heat is generated on the contact surface. The predetermined pressing force F is applied until the frictional heat reaches a temperature required for pressure welding, and at the same time as the pressure temperature is reached, a higher pressing force F is applied, and the end portion of the coupling protrusion 67 and the shaft portion 51a are welded. Is done.

  As shown in FIG. 9C, when the end portion of the coupling protrusion 67 and the shaft portion 51a are coupled by the coupling step, the end portion of the coupling projection 67 and the outer portion and the inner side of the coupling portion of the shaft portion 51a. Burrs 78 and 79 are generated.

  FIG. 10 is a cross-sectional view of the camshaft structure according to the second embodiment of the present invention. FIG. 10A shows a state where the outer peripheral surface of the camshaft is polished, and FIG. FIG. 10 shows a state where the engaging portion of the protruding portion of the end piece is pressed by a tool, and FIG. 10C shows a state where the engaging portion of the protruding portion of the end piece is engaged.

  As shown in FIG. 10A, the burrs 38 generated outside the coupling portion are removed by a tool 71 made of a cutting tool, a polishing tool, or the like.

  As shown in FIG. 10B, in the engagement step, the engagement portion 66 of the end piece 56 is engaged with the engagement ring 57 by a known engagement method. Further, in the engaging step, the tip 72a of the tool 72 having the tip 72a formed in a conical shape is pressed against the engaging portion 66 with a predetermined pressure (MPa), as shown in FIG. As described above, the engaging portion 66 is expanded by being plastically deformed, and is engaged with the engaging ring 57. At this time, the outer peripheral surface 62a of the protruding portion 62 and the inner peripheral surface 57c of the engaging ring 57 come into contact with each other, and the engaging portion 66 is uniformly plastically deformed. Therefore, the outer peripheral surface 62a of the protruding portion 62 and the engaging ring 57 The engagement portion 66 and the engagement ring 57 are engaged with each other in a state where the gap with the inner peripheral surface 57c is liquid-tightly sealed.

  Thus, since the clearance gap between the outer peripheral surface 62a of the protrusion part 62 and the inner peripheral surface 57c of the engagement ring 57 is liquid-tightly sealed, the end surface part 61a of the end piece 56 and the outer peripheral surface of the protrusion part 62 are sealed. A sealed space 73 is defined by 62a, the inner side surface 57d of the engagement ring 57 on the end piece 56 side, and the inner peripheral surface 51d of the shaft portion 51a. The burr 79 is enclosed in the space 73.

Next, the operation of the camshaft structure 20 according to the present embodiment will be described.
FIG. 11 is a cross-sectional view showing a state where the end piece of the camshaft structure and the camshaft are combined according to the second embodiment of the present invention.

  As shown in FIG. 11, when the lubricating oil flows in the direction of the arrow from the communication hole 65, it flows in the order of the hole 64 and the hole 63 and flows into the hollow hole 58 of the camshaft 51. Lubricating oil flowing in the hollow hole 58 is supplied to a lubricating member (not shown) located in the vicinity of the camshaft 51 from a lubricating oil supply port 51c provided in each of the shaft portion 51a and the journal portion 51b shown in FIG. The At this time, foreign matters such as metal powder generated from the burr 79 in the space 73 are not discharged from the space 73 to the outside, and the lubricating oil does not enter the space 73 from the outside.

  Thus, in the camshaft structure 20 according to the present embodiment, the camshaft 51 in which the hollow hole 58 having the cam pieces 52, 53, 54, 55 for opening and closing the exhaust valve of the internal combustion engine is formed, and the camshaft 51 An end piece 56 that is coupled to the end piece 56, and the camshaft 51 has an engagement ring 57 that projects inwardly at the end of the camshaft 51. And the gap between the outer peripheral surface 62a of the protrusion 62 and the inner peripheral surface 57c of the engagement ring 57 is liquid-tightly blocked from the hollow hole 58 of the camshaft 51. In this state, the protrusion 62 is enlarged in the radial direction and engaged with the engagement ring 57.

  In this case, when the protrusion 62 is engaged with the engagement ring 57, the burr 79 generated inside the coupling portion between the end piece 56 and the camshaft 51 is sealed in the space 73. Even if foreign matter such as powder is generated, the foreign matter is not discharged outside the space 73, and the lubricating oil does not enter the space 73 from the outside. As a result, foreign matters generated from the burr 79 can be reliably prevented from entering the lubricating oil.

  Hereinafter, modified examples of the camshaft structure 20 according to the second embodiment of the present invention will be described.

  12 is a partial cross-sectional view of the camshaft structure according to the second embodiment of the present invention. FIG. 12A shows a modification in which the engaging portion engages with the engaging ring. (B) shows the other modification in which an engaging part engages with an engagement ring.

  As shown in FIG. 12A, in the camshaft structure 20 of the present embodiment, the thread groove 51m is formed on the inner peripheral surface 51d of the camshaft 51, and the thread 87y corresponding to the thread groove 51m is formed. An engagement ring 87 formed on the outer peripheral surface portion and having a through hole 87 h may be manufactured, and the engagement ring 87 may be screwed to the camshaft 51.

  In this case, the engaging portion 66 of the protruding portion 62 is inserted into the through hole 87h and engaged with the end surface portion 87t of the engaging ring 87, and the end surface portion 61a of the end piece 56, the outer peripheral surface 62a of the protruding portion 62, A space 88 sealed in a liquid-tight manner is defined by the inner peripheral surface 67a of the coupling protrusion 67 and the inner surface 87n of the engagement ring 87 on the end piece 56 side.

  As a result, since the burrs 99 generated inside the joint portion of the end piece 56 and the camshaft 51 are sealed in the space 88, foreign matters such as metal powder generated from the burrs 99 in the space 88 are moved from the space 88 to the outside. Since the lubricating oil is not discharged and the lubricating oil does not enter the space 88 from the outside, foreign matter generated from the burr 99 is reliably prevented from entering the lubricating oil.

  As shown in FIG. 12B, in the camshaft structure 20 of the present embodiment, the end surface portion 106 a of the end piece 106 is replaced with the protruding portion 62 formed integrally with the end surface portion 61 a of the end piece 56. And a screw thread 101y corresponding to the screw hole 106b is formed on the outer peripheral surface portion, and the through hole 101h, the engagement portion 101k having an enlarged diameter at the end portion, and the tightening tool 103 are engaged. After the end piece 106 and the camshaft 51 are coupled together, the projecting ring 101 is screwed into the screw hole 106b and fixed by the tightening tool 103, and the engaging portion 101k is fixed. You may make it engage with the engagement ring 57.

  In this case, the end face portion 106a of the end piece 106, the outer peripheral surface portion of the protruding ring 101, the inner peripheral surface 107a of the coupling protrusion 107, and the inner side surface 57d of the engagement ring 57 on the end piece 106 side are sealed in a liquid-tight manner. A stopped space 102 is defined.

  As a result, the burr 109 generated inside the joint portion of the end piece 106 and the camshaft 51 is sealed in the space 102, so that foreign matters such as metal powder generated from the burr 109 in the space 102 are external to the space 102. Since the lubricant oil does not enter the space 102 from the outside, foreign matter generated from the burr 109 is reliably prevented from entering the lubricant oil.

  FIG. 13 is a partial cross-sectional view of the camshaft structure according to the second embodiment of the present invention. FIG. 13A shows a modification in which the engaging portion engages with the engaging ring. (B) shows the other modification in which an engaging part engages with an engagement ring.

  As shown in FIG. 13A, in the camshaft structure 20 of the present embodiment, an engagement ring 117 having a through hole 117h formed in place of the engagement ring 27 and having a seal member 118 at the end 117t. The engagement ring 117 may be press-fitted into the camshaft 51 and fixed. In this case, the engaging portion 66 of the projecting portion 62 may be inserted into the through hole 117h and engaged with the seal member 118 provided on the engaging ring 117k.

  In this case, the end face part 61a of the end piece 56, the outer peripheral face 62a of the projecting part 62, the inner peripheral face 67a of the coupling protrusion 67, and the inner side face 117n of the engagement ring 117 on the end piece 56 side are liquid-tight. A sealed space 119 is defined.

  As a result, the burr 79 generated inside the coupling portion between the end piece 56 and the camshaft 51 is sealed in the space 119, so that foreign matters such as metal powder generated from the burr 79 in the space 119 are moved from the space 119 to the outside. Since the lubricating oil is not discharged and the lubricating oil does not enter the space 119 from the outside, foreign matter generated from the burr 79 is reliably prevented from entering the lubricating oil.

  As shown in FIG. 13B, in the camshaft structure 20 of the present embodiment, an end piece having a protruding portion 122 in which a sealing member 128 is integrally formed with the engaging portion 126, instead of the protruding portion 62. 121 may be manufactured, the protrusion 122 may be inserted into the engagement ring 57, and the seal member 128 and the side surface 57b of the engagement ring 57 may be engaged.

  In this case, the end surface 121 a of the end piece 121, the outer peripheral surface 122 a of the protrusion 122, the inner peripheral surface 127 a of the coupling protrusion 127, and the inner surface 57 d of the engagement ring 57 on the end piece 121 side are liquid-tight. A sealed space 129 is defined.

  As a result, since the burr 125 generated inside the joint portion of the end piece 121 and the camshaft 51 is sealed in the space 129, foreign matters such as metal powder generated from the burr 125 in the space 129 are moved from the space 129 to the outside. Since the lubricant oil is not discharged and the lubricating oil does not enter the space 129 from the outside, foreign matter generated from the burr 125 is reliably prevented from entering the lubricating oil.

  FIG. 14 is a partial cross-sectional view of a camshaft structure according to a second embodiment of the present invention. FIG. 14A is a modification of the camshaft structure in which an annular protrusion is integrally formed inside the camshaft. An example is shown and FIG.14 (b) shows the other modification of the camshaft structure which formed the annular protrusion integrally in the inner side of the camshaft.

  As shown in FIG. 14A, in the camshaft structure 20 of the present embodiment, instead of the camshaft 21, a camshaft 131 in which an annular protrusion 132 is formed on the inner peripheral portion 131a is produced, and the end piece 56 The protruding portion 62 may be inserted into a through hole defined by the inner peripheral portion 132 a of the annular protrusion 132, and the engaging portion 66 may be engaged with the end surface portion 132 b of the annular protrusion 132.

  In this case, the end face 56 of the end piece 56, the outer peripheral face 62a of the protrusion 62, the inner peripheral face 67a of the coupling protrusion 67, and the inner face 132c of the annular protrusion 132 on the end piece 56 side are sealed in a liquid-tight manner. A stopped space 138 is defined.

  As a result, the burr 139 generated inside the coupling portion between the end piece 56 and the camshaft 131 is sealed in the space 138, so that foreign matters such as metal powder generated from the burr 139 in the space 138 are moved from the space 138 to the outside. Since the lubricant oil is not discharged and the lubricating oil does not enter the space 138 from the outside, foreign matter generated from the burr 139 is reliably prevented from entering the lubricating oil.

  As shown in FIG. 14B, in the camshaft structure 20 of the present embodiment, instead of the camshaft 21, a camshaft 141 having an annular protrusion 142 formed on the inner peripheral portion 141a is produced, and the end piece 56 The protruding portion 62 is inserted into a through hole defined by the inner peripheral portion 142a of the annular protrusion 132, and the engaging portion 66 is pressed and expanded to engage with the inner peripheral portion 142a of the annular protrusion 142. May be.

  In this case, the end surface portion 61a of the end piece 56, the outer peripheral surface 62a of the projecting portion 62, the inner peripheral surface 67a of the coupling projection 67, and the inner side surface 142c of the annular projection 142 on the end piece 56 side are sealed in a liquid-tight manner. A stopped space 148 is defined.

  As a result, the burr 149 generated inside the coupling portion between the end piece 56 and the camshaft 141 is sealed in the space 148, so that foreign matters such as metal powder generated from the burr 149 in the space 148 are moved from the space 148 to the outside. Since the lubricant oil is not discharged and the lubricating oil does not enter the space 148 from the outside, foreign matter generated from the burr 149 is reliably prevented from entering the lubricating oil.

  The camshaft structure 10 in the first embodiment and the camshaft structure 20 in the second embodiment have been described as applied to the exhaust camshaft 4 of the variable valve timing device 1 of the internal combustion engine. The camshaft structure according to the present invention may be applied to other camshafts. For example, the exhaust side camshaft of a variable valve timing device, the intake camshaft and exhaust camshaft of a valve operating mechanism such as OHV (Over Head Valve), DOHC (Double Over Head Camshaft), SOHC (Single Over Head Camshaft), machine tool You may apply to the camshaft in other apparatuses, such as a camshaft.

  Further, in the camshaft structure 10 in the first embodiment and the camshaft structure 20 in the second embodiment, the coupling between the end piece 26 and the camshaft 21 and the coupling between the endpiece 56 and the camshaft 51 are frictioned. Although the case of carrying out by pressure welding has been described, the camshaft structure according to the present invention may be carried out by other coupling means. For example, it may be a welding means such as arc welding or laser welding for melting the joint portion, or may be a joining means such as brazing using a welding material.

  Further, in the camshaft structure 10 in the first embodiment and the camshaft structure 20 in the second embodiment, the end piece 26 and the camshaft 21 are joined by friction welding, and the endpiece 56 and the camshaft 51 are connected. The case where the end pieces 26 and 56 are mounted on the rotating device and the camshafts 21 and 51 are fixed to the fixing device has been described. However, in the camshaft structure according to the present invention, the friction welding is performed. When the end piece and the camshaft are joined by processing, the endpiece may be attached to a fixing device and the camshaft may be fixed to the rotating device.

  As described above, according to the present invention, the outer peripheral surface of the projecting portion and the inner peripheral surface of the engagement ring can be reliably engaged with each other. The burr can be surely liquid-tightly blocked from the hollow hole of the camshaft, and foreign matter such as metal powder generated from the burr can be reliably prevented from entering the lubricating oil that lubricates and cools the camshaft. It is useful for general camshaft structures.

1 is a perspective view of a variable valve timing device showing an example in which a camshaft structure according to a first embodiment of the present invention is applied to a camshaft structure of a variable valve timing device for an internal combustion engine. 1 is a perspective view of a camshaft structure according to a first embodiment of the present invention. It is sectional drawing of the camshaft structure concerning the 1st Embodiment of this invention, Fig.3 (a) shows sectional drawing of an end piece, FIG.3 (b) is partial sectional drawing of a camshaft. It is sectional drawing of the camshaft structure which concerns on the 1st Embodiment of this invention, Fig.4 (a) shows the state which the end piece has separated from the camshaft, FIG.4 (b) shows the endpiece. FIG. 4C shows a state in which the end piece is joined to the camshaft. It is sectional drawing of the camshaft structure concerning the 1st Embodiment of this invention, Fig.5 (a) shows the state by which the outer peripheral surface of the camshaft was grind | polished, FIG.5 (b) shows an end piece. FIG. 5C shows a state in which the engaging portion of the protruding portion of the end piece is engaged, and FIG. 5C shows a state in which the engaging portion of the protruding portion of the end piece is engaged. It is sectional drawing which shows the state which the end piece and camshaft of the camshaft structure concerning the 1st Embodiment of this invention couple | bonded. It is a perspective view of the camshaft structure concerning the 2nd Embodiment of this invention. It is sectional drawing of the camshaft structure concerning the 2nd Embodiment of this invention, Fig.8 (a) shows sectional drawing of an end piece, FIG.8 (b) is a fragmentary sectional view of a camshaft. It is sectional drawing of the camshaft structure which concerns on the 2nd Embodiment of this invention, Fig.9 (a) shows the state which has separated the end piece from the camshaft, FIG.9 (b) shows the endpiece. FIG. 9C shows a state in which the end piece is joined to the camshaft. It is sectional drawing of the camshaft structure concerning the 2nd Embodiment of this invention, Fig.10 (a) shows the state by which the outer peripheral surface of the camshaft was grind | polished, FIG.10 (b) shows an end piece. FIG. 10C shows a state where the engaging portion of the protruding portion of the end piece is engaged, and FIG. 10C shows a state where the engaging portion of the protruding portion of the end piece is engaged. It is sectional drawing which shows the state which the end piece and camshaft of the camshaft structure concerning the 2nd Embodiment of this invention couple | bonded. It is a fragmentary sectional view of the camshaft structure concerning a 2nd embodiment of the present invention, and Drawing 12 (a) shows the modification which an engaging part engages with an engagement ring, and Drawing 12 (b) The other modification which an engaging part engages with an engagement ring is shown. It is a fragmentary sectional view of the camshaft structure concerning a 2nd embodiment of the present invention, and Drawing 13 (a) shows a modification in which an engaging part engages with an engagement ring, and Drawing 13 (b) The other modification which an engaging part engages with an engagement ring is shown. FIG. 14 (a) is a partial sectional view of a camshaft structure according to a second embodiment of the present invention, and FIG. 14 (a) shows a modification of the camshaft structure in which an annular protrusion is integrally formed inside the camshaft; FIG. 14B shows another modification of the camshaft structure in which the annular protrusion is integrally formed inside the camshaft.

Explanation of symbols

10, 20 Camshaft structure 21, 51, 131, 141 Camshaft 21d, 51d Inner surface portion 21e, 51e End portion 22, 23, 24, 25, 52, 53, 54, 55 Cam piece 26, 56 End piece 27, 57, 87, 117, 132, 142 Engagement ring (annular protrusion)
28, 58 Hollow hole 31, 61 Main body part 32, 62 Protruding part 32a, 62a Outer peripheral surface 33, 34, 63, 64 Hole 35, 65 Communication hole 36, 66 Engaging part 38, 39, 78, 79, 99, 125 139, 149 Burr 41, 42, 71, 72 Tool 42a, 72a Tip 43, 73, 77, 88, 102, 119.129, 138, 148 Space 67, 107, 127 Coupling projection 101 Protruding ring (coupling projection)
103 Tightening tool 118 Seal member

Claims (8)

In a camshaft structure comprising a camshaft on which a campiece is mounted and a hollow hole is formed, and an endpiece coupled to the camshaft,
The camshaft has an annular protrusion protruding inward thereof at an end portion on the side to be coupled with the end piece,
The end piece has a cylindrical protrusion protruding in the axial direction,
The protrusion is enlarged in the radial direction and engaged with the annular protrusion in a state where a gap between the outer peripheral surface of the protrusion and the inner peripheral surface of the annular protrusion is blocked from the hollow hole of the camshaft. Camshaft structure characterized by   The camshaft structure according to claim 1, wherein an outer peripheral surface of the projecting portion and an inner peripheral surface of the annular protrusion are in contact with each other.   The end piece has an annular coupling protrusion facing the end of the camshaft, and the tip of the coupling protrusion is coupled to the end of the camshaft. 2. The camshaft structure according to 2.   The camshaft structure according to any one of claims 1 to 3, wherein the end piece has a liquid passage that passes through the inside of the protrusion.   The camshaft structure according to any one of claims 1 to 4, wherein the annular protrusion is formed by an engagement ring screwed to the camshaft.   The camshaft structure according to any one of claims 1 to 4, wherein the annular protrusion is formed by an engagement ring press-fitted into the camshaft. A mounting step of mounting an engagement ring projecting inwardly on a camshaft on which a cam piece is mounted and having a hollow hole;
An arrangement step of arranging an end piece having a cylindrical projecting portion projecting toward the cam shaft in the vicinity of the end portion of the cam shaft;
A coupling step of coupling the end piece to the camshaft;
An engagement step of engaging the protrusion with the engagement ring in a state where a gap between the outer peripheral surface of the protrusion and the inner peripheral surface of the annular protrusion is blocked from the hollow hole of the camshaft;
A method of assembling a camshaft structure comprising:   In the engaging step, by pressing the tip of the tool having a conical tip against the protrusion of the end piece, the protrusion is expanded and engaged with the engagement ring. A method for assembling the camshaft structure according to claim 7.

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