JPH06272519A - Camshaft for engine - Google Patents

Abstract

PURPOSE:To facilitate assembly by way of reducing the number of parts by forming an engagement groove on an inner peripheral surface of a hollow shaft furnished with a cam element, forming an engagement projection on a boss part projectively provided on a driving force transmission member and integrally fixing the hollow shaft and the driving force transmission member while engaging the engagement groove and the engagement projection with each other. CONSTITUTION:A camshaft 1 is furnished with a hollow shaft 2 with a cam element 6 fastened on it and a toothed pulley 4 which is a driving force transmission member. On the inner surface of the hollow shaft 2, an engagement groove 2a positioned in the circumferential direction against a cam profile is formed. On the toothed pulley 4, a roughly cylindrical boss part 5 is projectively provided, and on its outer peripheral surface, a projective part 5a positioned to have a phase in the specified circumferential direction against a pitch of a tooth 4a is provided. As the pitch of the tooth 4a and the phase in the circumferential direction are decided only by fitting the boss part 5 in one opening end part of the hollow shaft 2 by way of engaging the engagement groove 2a and the projective part 5a, assembly is easy and the number of parts is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine camshaft used in a reciprocating internal combustion engine or the like, and more particularly to an improvement of a fixing means for mounting a driving force transmission member on a camshaft formed of a hollow shaft.

[0002]

2. Description of the Related Art In recent years, the performance of internal combustion engines has been improved with respect to engine camshafts used in reciprocating internal combustion engines and the like.
There is an increasing demand for better fuel economy, and it is desired to make it lighter and more durable. Therefore, there is one in which the cam shaft is hollow and the weight is reduced.

On the other hand, as a camshaft drive mechanism for driving a valve mechanism in a reciprocating internal combustion engine or the like, a system in which timing is achieved by meshing of teeth of a sprocket mounted on a crankshaft and a camshaft and a chain, and a toothed pulley There is a method of timing both shafts by a belt, or a method of timing by meshing the gears mounted on both shafts.The cam shaft has driven parts such as these sprockets, toothed pulleys and gears at one end. It is necessary to mount a driving force transmission member having

Therefore, in order to mount the driving force transmission member on the end of the cam shaft made of a hollow shaft, a solid mounting member which is conventionally formed as a separate body is previously joined to the end of the hollow cam shaft by welding or the like. After that, the driving force transmission member is bolted and fixed to the mounting member. FIG. 7 is a partial cross-sectional view of a conventional engine camshaft. The cam shaft 31 includes a hollow shaft 32 formed of a hollow tube, a cam element 37 and a journal element (not shown) fixed to a predetermined position of the hollow shaft 32, and the hollow shaft 3
2 and the mounting member 34 welded to the end of the second bolt 35.
And a toothed pulley 33 which is a driving force transmission member fastened to the mounting member 34.

The toothed pulley 33 has teeth 33a, which are driven portions, on its outer peripheral portion, and is timed by a timing belt suspended between the toothed pulley 33 and a toothed pulley mounted on a crankshaft (not shown). Since it is driven by the crankshaft, it is necessary to accurately determine the phase between the pitch of the teeth 33a and the profile of the cam element 37. Therefore,
The attachment member 34 has a screw pin 34a and a knock pin hole 34b formed at the other end opposite to the one end welded to the hollow shaft 32. The knock pin 36 attaches the knock pin 36 to the attachment member 34 in the circumferential direction. A toothed pulley 33 having a predetermined length is fastened to a mounting member 34 by a bolt 35.

When the cam shaft 31 as described above is assembled to the engine body, the alignment mark provided on the toothed pulley 33 is aligned with the reference mark provided on the engine body side, and the phase of the crank shaft and the cam shaft 31 is adjusted. By aligning with a predetermined position, the cam profile of the cam element 37 fixed to the hollow shaft 32 and the crankshaft can be aligned in phase.
You are getting the desired valve timing.

[0007]

However, the toothed pulley 33 and the hollow shaft 32 in the cam shaft 31 as described above are provided.
According to the fixing means, since the mounting member 34 is joined to the end of the hollow shaft 32 by welding or the like, it is difficult to accurately determine the phase between the cam profile of the cam element 37 and the pitch of the teeth 33a. Further, since positioning means such as the knock pin 36 and the key is required to accurately determine the mounting position of the mounting member 34 and the toothed pulley 33 in the circumferential direction, the mounting member 34 has a knock pin hole 34b or Since a key groove or the like must be provided, the shape becomes complicated and the number of processing steps increases.

Therefore, the cam shaft 31 as described above has a problem that the manufacturing cost is high because the number of parts increases, the processing is complicated, and the assembly is complicated. Therefore,
It is an object of the present invention to solve the above problems, and to provide a lightweight and high-strength camshaft for an engine at a low cost, which reduces the number of parts and facilitates assembly.

[0009]

The above object of the present invention is to provide an engine camshaft comprising a hollow shaft having a cam element on its outer peripheral surface and a driving force transmission member fixed to one end of the hollow shaft. Forming an engagement groove extending in the axial direction of the hollow shaft and positioned circumferentially with respect to the cam profile of the cam element on the inner peripheral surface of the hollow shaft,
A boss portion fitted to one open end of the hollow shaft is provided on the driving force transmission member so as to be positioned in the circumferential direction with respect to the driven portion of the driving force transmission member and corresponds to the engaging groove. By forming an engaging protrusion that can be engaged with the boss portion, the hollow shaft and the driving force transmitting member are integrally formed while engaging the engaging groove and the engaging protrusion corresponding to each other. It is achieved by a camshaft for an engine characterized by being fixed to the.

In order to integrally fix the hollow shaft and the driving force transmitting member, the boss portion may be press-fitted and fixed to one open end of the hollow shaft. Further, a screwing member is press-fitted in advance inside one opening end of the hollow shaft, and a driving force transmitting member is bolted to the screwing member to integrally fix the hollow shaft and the driving force transmitting member. You can also

[0011]

According to the above structure of the present invention, the boss portion of the driving force transmitting member is connected to the one opening end of the hollow shaft while engaging the engaging projections corresponding to the engaging grooves formed on the inner peripheral surface of the hollow shaft. By fixing to the portion, the phase of the cam profile of the cam element and the pitch of the driven portion in the circumferential direction can be easily determined, so that positioning means such as a knock pin or a key is not required, and the assembling becomes easy. Along with this, the number of parts is reduced.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the accompanying drawings. 1 and 2 show a first embodiment of the present invention.
It is a principal part sectional view of the camshaft for engines based on an Example.
The cam shaft 1 includes a hollow shaft 2 formed of a hollow tube, a cam element 6 and a journal element (not shown) fixed to the outer peripheral surface of the hollow shaft at a predetermined interval in the axial direction, and at the end of the hollow shaft 2. A toothed pulley 4 which is a fixed driving force transmission member, and a cam element 6 and a journal element which are separately made of a material having good wear resistance; and a hollow shaft 2 which can reduce the weight. By separately making and assembling, the cam shaft is lightweight and has high strength.

On the inner peripheral surface of the hollow shaft 2, four engagement grooves 2a extending in the axial direction and positioned in the circumferential direction with respect to the cam profile of the cam element 6 are formed in the circumferential direction. It is formed at equal intervals. That is, for example, the width center of any one of the engagement grooves 2a and the cam top portion 6 of the predetermined cam element 6 are provided.
By forming these engagement grooves 2a such that a has a predetermined circumferential phase (the same phase in FIG. 2), the phase between the engagement groove 2a and the cam element 6 is preset. To be done.

The toothed pulley 4 has teeth 4a, which are driven parts, on its outer peripheral portion, and a substantially cylindrical boss portion 5 protruding in the axial direction is provided at the center of rotation thereof. , The outer peripheral surface of the boss portion 5 is positioned so as to have a predetermined circumferential phase with respect to the pitch of the teeth 4a, and can be engaged in correspondence with the engaging groove 2a. Four projecting portions 5a, which are projections, are formed along the axial direction of the boss portion 5.

Therefore, the boss portion 5 of the toothed pulley 4 is attached to the one opening end of the hollow shaft 2 while engaging the protruding portion 5a corresponding to the engaging groove 2a formed on the inner peripheral surface of the hollow shaft 2. By simply fitting the cam profile of the cam element 6 and the pitch of the teeth 4a in the circumferential direction, the toothed pulley 4 can determine the mounting position in the circumferential direction with respect to the hollow shaft 2. Since no positioning means such as the above is required, the assembling becomes easy and the number of parts is reduced.

Further, in the camshaft 1 according to this embodiment, the outer diameter of the boss portion 5 excluding the protruding portion 5a is the hollow shaft 2 described above.
Is formed slightly larger than the inner diameter of the hollow opening other than the engaging groove 2a, and the protrusion 5 is formed in the corresponding engaging groove 2a.
The toothed pulley 4 can be permanently fixed to the hollow shaft 2 by press-fitting the boss portion 5 into one opening end of the hollow shaft 2 while engaging a. Of course, the outer diameter of the protruding portion 5a is made slightly larger than the inner diameter of the engaging groove 2a so that the boss portion 5a
May be press-fitted into one open end of the hollow shaft 2 or a combination thereof. Therefore, in order to mount the toothed pulley 4 on the end of the hollow shaft 2, it is not necessary to previously weld to the hollow shaft 2 a conventional mounting member having a complicated shape and a large number of processing steps.

In the camshaft 1 of this embodiment, the cam element 6 penetrated by the hollow shaft 2 has grooves 6b extending in the axial direction on the inner peripheral surface at circumferentially spaced intervals, and the cam element 6 extends radially outward. A camshaft configured such that the cam element 6 and the hollow shaft 2 are permanently fixed to each other by expanding the wall of the hollow shaft 2 deformed toward the inside into the groove 6b. The step of inserting a diameter-expanding tool having a projection configured to expand the wall of the second shaft into the groove 6b of the cam element 6 into the hollow shaft 2 causes the inner peripheral surface of the hollow shaft 2 to extend in the axial direction. A groove extending in the vertical direction is formed.

Therefore, the groove 6b of the cam element 6 is circumferentially positioned with respect to the cam profile, and the projection of the diameter-expanding tool is made to correspond to the groove 6b, so that the groove is circled with respect to the cam profile. Since the engagement groove 2a positioned in the direction can be formed on the inner peripheral surface of the hollow shaft 2, it is not necessary to form the engagement groove 2a on the inner peripheral surface of the hollow shaft 2 by a separate process.

Therefore, it is obvious that the present invention is more suitable for a cam shaft in which a separately formed cam element 6 is fixed to the hollow shaft 2 by such means, but other means are possible. Therefore, even in the case of a hollow shaft having a cam element on the outer peripheral surface, the effect of the present invention can be sufficiently enjoyed only by forming a desired engaging groove on the inner peripheral surface of the hollow shaft, and therefore the present invention is not limited to this. It is not limited to this, and may be, for example, a hollow shaft integrally cast with a cam element.

Further, the toothed pulley 11 of the engine camshaft according to the second embodiment of the present invention shown in FIG. 3 has teeth 12a which are driven portions on its outer peripheral portion, and has its rotation center portion at its rotation center portion. Is a substantially cylindrical boss portion 13 protruding in the axial direction.
On the outer peripheral surface of the tip of the boss portion 13 so as to have a predetermined circumferential phase with respect to the pitch of the teeth 4a and correspond to the engaging groove 2a. Four protrusions 13a that are engaging protrusions that can be engaged with each other are formed.

That is, the protrusion 13a does not extend greatly along the axial direction, which is the press-fitting direction of the boss portion 13, and the boss portion 13 of the toothed pulley 11 of this embodiment has the toothed portion of the first embodiment. Compared with the boss portion 5 of the pulley 4, it is easier to press fit into the open end of the hollow shaft 2. Furthermore, FIGS.
The cam shaft 21 according to the third embodiment of the present invention shown in FIG. 2 includes a hollow shaft 2 formed of a hollow tube, a cam element 6 and a journal element fixed to the outer peripheral surface of the hollow shaft at predetermined intervals in the axial direction (see FIG. (Not shown), a toothed pulley 24 that is a driving force transmission member that is fitted to the end of the hollow shaft 2, a screwing member 22 and a bolt 26 that are press-fitted inside one open end of the hollow shaft 2. ing.

The toothed pulley 24 has teeth 24a, which are driven portions, on its outer peripheral portion, and a substantially cylindrical boss portion 25 projecting in the axial direction may be provided at the center of rotation of the toothed pulley 24. On the outer peripheral surface of the boss portion 5, an engagement protrusion is positioned so as to have a predetermined circumferential phase with respect to the pitch of the teeth 4a and is engageable in correspondence with the engagement groove 2a. Are formed so as to extend along the axial direction of the boss portion 25. Further, a through hole 25b into which the bolt 26 is inserted is formed in the shaft center of the boss portion 25.

On the outer peripheral surface of the screw member 22, four protrusions 22a, which are engaging protrusions capable of engaging with the engaging groove 2a, are formed along the axial direction. Cage,
A screw hole 22b for screwing a bolt 26 to the shaft core
Are formed. The protrusion 22a is not always necessary, and may be formed in a simple cylindrical shape as long as it can be securely fixed inside the opening of the hollow shaft 2.

Therefore, after the projection 22a corresponding to the engagement groove 2a is engaged in advance, the screwing member 22 is press-fitted and fixed inside the one open end of the hollow shaft 2, and then the projection of the boss 25 is formed. The toothed pulley 2 while engaging the portion 25a with the engaging groove 2a
The boss portion 25 of No. 4 is fitted into one open end of the hollow shaft 2. Then, the toothed pulley 24 is fixed to one open end of the hollow shaft 2 by screwing the bolt 26, which is inserted through the washer 27 and the through hole 25b, into the screw hole 22b of the screwing member 22.

At this time, the toothed pulley 24 fits the boss portion 25 into one opening end of the hollow shaft 2 while engaging the protrusion 25a with the engaging groove 2a formed on the inner peripheral surface of the hollow shaft 2. Only by determining the phase of the cam profile of the cam element 6 and the pitch of the teeth 24a in the circumferential direction, the toothed pulley 24 can accurately determine the mounting position in the circumferential direction with respect to the hollow shaft 2. Since a positioning means such as a key is not required, the assembly becomes easy. Also, the toothed pulley 24
Since the boss portion 25 is slidable in the axial direction only in the mounting position in the circumferential direction with respect to the hollow shaft 2 and is fixed by the fastening force of the bolt 26, the bolt 26 is detachable. By doing so, disassembly and assembly becomes easy.

The members constituting the engine camshaft of the present invention are not limited to the shapes in the above-mentioned embodiments, and it goes without saying that various forms can be adopted based on the gist of the present invention. is there. For example, although the toothed pulley is used as the driving force transmitting member in each of the above embodiments, other driving force transmitting members such as sprockets and gears may be used.

Further, it goes without saying that the cross-sectional shapes, the number of engaging grooves and the forming positions of the engaging grooves and the like of the engaging grooves and the engaging projections in the present invention can be appropriately changed. For example, when assembling the camshaft to the engine body, the phase of the crankshaft and the camshaft is aligned to a predetermined position by aligning the alignment mark provided on the driving force transmission member with the reference mark provided on the engine body side. In order to fix the force transmission member to the cam shaft, it is necessary to match not only the pitch of the driven part and the cam profile of the cam element, but also the phase of the alignment mark and the cam profile of the cam element. Therefore, the engaging grooves are formed at unequal intervals in the circumferential direction, or the depths of the engaging grooves and the heights of the engaging protrusions are appropriately changed to fit the engaging protrusions to the engaging grooves. If the possible combinations are limited, it will not be possible to fit when the alignment mark and the cam profile of the cam element are out of phase, and there will be no chance of accidentally assembling a cam shaft out of phase. Furthermore, it is not necessary that the number of the engaging projections is always the same as the number of the engaging grooves, and if one or more engaging projections are provided, alignment in the circumferential direction is possible.

[0028]

According to the camshaft for an engine of the present invention, the boss portion of the driving force transmission member is attached to the hollow shaft while engaging the engaging projections corresponding to the engaging grooves formed on the inner peripheral surface of the hollow shaft. By fixing the cam profile of the cam element and the pitch of the driven part in the circumferential direction by fixing it to one opening end of the cam element, positioning means such as a knock pin or a key is not required, and the assembling is eliminated. And the number of parts can be reduced.

Therefore, the number of parts can be reduced and the assembling can be facilitated, and the lightweight and high-strength camshaft can be provided at a low cost.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part of an engine camshaft according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along the line AA of the engine camshaft shown in FIG.

FIG. 3 is a side view of a toothed pulley that constitutes an engine camshaft according to a second embodiment of the present invention.

FIG. 4 is a partially exploded perspective view of an engine camshaft according to a third embodiment of the present invention.

5 is a partial cross-sectional view of the engine camshaft shown in FIG.

6 is a cross-sectional view of the camshaft for engine shown in FIG. 5 taken along the line BB.

FIG. 7 is a partial cross-sectional view of a conventional engine camshaft.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cam shaft 2 Hollow shaft 2a Engagement groove 4 Toothed pulley 4a Tooth 5 Boss portion 5a Projected portion 6 Cam element

Claims (1)

[Claims] 1. A camshaft for an engine comprising a hollow shaft having a cam element on its outer peripheral surface and a driving force transmission member fixed to one end of the hollow shaft, the camshaft extending along the axial direction of the hollow shaft. An engaging groove positioned circumferentially with respect to the cam profile of the cam element is formed on the inner peripheral surface of the hollow shaft, and a boss portion fitted to one open end of the hollow shaft is provided. Forming an engaging projection on the boss portion projecting from the driving force transmitting member, positioned circumferentially with respect to the driven portion of the driving force transmitting member, and engageable in correspondence with the engaging groove; The camshaft for an engine, wherein the hollow shaft and the driving force transmission member are integrally fixed while engaging the engaging groove and the engaging protrusion corresponding to each other.