JP2001198645A - Manufacturing method for cam lobe used for assembly type cam shaft - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method for a cam lobe which is high in accuracy in the dimensional relationship between a hole in the axial direction and a cam surface and low in manufacturing costs, and a manufacturing method for manufacturing the cam lobe which requires no mechanical grinding for the finish, or requires only a small finish cost even when the mechanical grinding is required. SOLUTION: A hole which is larger than the hole 3 in the axial direction of the completed cam lobe 1 in internal and external contours in the section orthogonal to the axis and a cam lobe stock 10 smaller than the cam surface 2 are placed in an intermediate die 53 and an outer die 51 with a space therebetween. The cam lobe stock 10 placed in the die is pressed by a press die 54. The intermediate die 53 is supported at both ends, and thus, a cam lobe with high accuracy can be formed in order to sufficiently withstand the unbalance of the force.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hollow assembled camshaft used for a reciprocating internal combustion engine or the like, and more particularly to a method for manufacturing a cam lobe for use in such an assembled camshaft.

[0002]

2. Description of the Related Art Heretofore, camshafts for opening and closing supply / exhaust valves of a reciprocating internal combustion engine and the like have been manufactured by casting and then machining. In recent years, there has been an increasing demand for improving the performance of an internal combustion engine and improving fuel economy, and a camshaft having a hollow camshaft and a lighter weight has been developed.

[0003] Such a lightweight camshaft can be seen in JP-A-1-125506. In the camshaft disclosed herein, the camshaft components such as the cam element and the journal element are formed as individual parts using a material having excellent wear resistance, and a hollow shaft is inserted through their axial holes to a predetermined shape. After positioning in phase and axial spacing, the hollow shaft is radially expanded to secure these cam components to the hollow shaft, and is an integrally assembled camshaft.

The above cam element, that is, a cam lobe (finished product)
Usually has a shape as shown in FIG. The cam lobe 1 has a non-circular cam surface 2 on its outer surface, and has an axial hole 3 inserted into the hollow shaft in the middle of the cam lobe 1. The inner surface 19 of the axial hole 3 is formed with a wavy or other concave groove 6 along the axial direction to ensure engagement with the hollow shaft. Up and down when viewed on FIG. 1 (axial direction)
The end faces 4 and 5 are planes parallel to each other, and a chamfer 7 descending from these end faces 4 and 5 toward the axial hole 3 so that stress concentration does not occur due to corners when engaged with the hollow shaft.
(A straight or arc-shaped cross section).

[0005] An example of a conventional method for manufacturing a cam lobe will be briefly described below.

First, a material corresponding to the volume of a finished product is prepared. As shown in FIG. 7, this material is subjected to upsetting with an upper die and a lower die, thereby obtaining an intermediate material in which the nose portion 8 of the cam lobe when completed is thicker than the other.

Next, as shown in FIG. 8, the intermediate material is put into a space formed by a die having an inner curved surface corresponding to a cam shape and a lower die, and a cylindrical intermediate press punch is formed together with an outer punch. Press down and press the middle punch into the material while compressing the material with the outer punch. As a result, a concave portion is formed in the material. This recess serves as a nominal hole for facilitating punching of an axial hole in a later step.

Next, as shown in FIG. 9, the outer punch is pushed in while the space between the inner press punch and the recess is formed, and a part of the material is caused to flow toward the central portion (recess) by this force. Then, the concave portion of the material is reduced and molded as shown in FIG.

Next, as shown in FIG. 11, a central portion is punched by a punch. At this time, the inner surface of the hole in the axial direction of the material is shaved on the side surface of the punch,
A cam lob is obtained.

When a cam lobe manufactured by the above-described conventional manufacturing method is measured, it is often found that the position and the diameter of the axial hole with respect to the outer shape (cam surface) include values including a considerably large error with respect to a design value. is there. Therefore, there is a problem in using it as a cam in practice as it is,
The cam lobe obtained by the above manufacturing method is finished by further machining.

Further, even if the cam lobe is fixed to the hollow shaft without machining, and the cam shaft is assembled, the respective cam surfaces must be ground in the assembled state.

To obtain cam precision by grinding,
It means that it is necessary to provide a grinding allowance in advance corresponding to the error in the cam lobe to be machined, and it is necessary to prepare various settings such as setup for grinding the cam shaft with a cam grinder, management of grinding wheel wear to ensure accuracy, etc. There is a problem that it is a bottleneck for reducing the manufacturing cost of the camshaft due to factors.

[0013]

The reason why the above-mentioned finishing machining is required is considered as follows.

The cam lobe is asymmetric in its attribute with respect to the central axis (the axis of the axial hole). For this reason, in the process shown in FIG. 8, when the concave portion is formed by the middle press punch, the flow of the material of the material becomes asymmetric, and the force acting on the middle press punch in the left-right direction in this figure is not balanced.

Since the middle press punch is in a cantilever-supported state as is apparent from the figure, displacement in the left-right direction is inevitably caused when the unbalanced force is received. The displacement in the left-right direction of the middle press punch makes the positional accuracy of the concave portion to be formed unstable, and also forms a concave portion whose side surface is slightly inclined.

Such recesses are formed in the steps after FIG.
It acts as a kind of guide hole (nominal hole) for guiding the middle punch and punch used. For this reason, it is considered that the recess formed in the initial process affects the accuracy of the product to the end, and as a result, this error remains in the final product.

An object of the present invention is to provide a method of manufacturing a cam lobe which is highly accurate and can be manufactured at a low cost. Further, the present invention does not require a mechanical grinding process for finishing. An object of the present invention is to provide a manufacturing method for manufacturing a cam lobe that requires only a very small finishing margin, even when required.

[0018]

The above objects of the present invention can be attained by the following means. That is,
In the method for manufacturing a cam lobe of the first invention, the thickness is larger than the thickness of the cam lobe to be manufactured, the nose corresponding portion to be the nose portion of the cam lobe is thicker than other portions, and slightly smaller than the contour shape of the cam lobe. A small external shape, slightly larger than the shape of the axial hole (thickness direction hole) of the cam lobe, having a hole almost coaxial with this axial hole, a cam lobe material manufactured by hot or warm plastic working, By pressing cold in the thickness direction to obtain a predetermined contour shape and hole shape, an assembly cam lobe having a non-circular contour shape on the outer periphery and an axial hole in the center portion is manufactured.

Further, in the method for manufacturing a cam lobe according to the second aspect of the present invention, the thickness of the cam lobe to be manufactured is larger than the thickness of the nose corresponding portion to be a nose portion of the cam lobe, The cam lobe material, which is slightly smaller than the outer shape and slightly larger than the shape of the axial hole of the cam lobe and has a hole substantially coaxial with the axial hole, is manufactured by hot or warm plastic working. Placed in a mold having a wall surface and a bottom surface having side faces complementary to the contour shape of the cam lobe and the shape of the axial hole of the cam lobe, the cam lobe material placed in the mold is pressed with a die having the same cross-sectional shape as the cam lobe. By forming the cam lobe by pressing in the cold direction in the axial direction of the cam lobe, an assembly cam lobe having a non-circular contour on the outer periphery and an axial hole in the center is manufactured. That.

Further, in the third invention, the mold according to the second invention has an outer mold having a wall having side faces complementary to the contour shape of the cam lobe, and a shape complementary to the shape of the axial hole of the cam lobe. And a lower mold having a bottom surface and a receiving hole with which the middle mold engages.

In these inventions, a cam lobe material in which holes corresponding to the axial holes are provided in advance is used, so that it is not necessary to form a recess as in the prior art. Therefore, an error caused by a lateral force applied to the mold when forming the concave portion does not affect the accuracy of the axial hole.

In addition, since sufficient accuracy can be obtained by these manufacturing methods, after the cam lobe is assembled, the cam surface does not need to be particularly finished as in the prior art, and can be used as it is. Costs can be significantly reduced.

Further, when a camshaft is assembled using the cam lobe obtained by the method for manufacturing a cam lobe of the present invention as it is, even if accuracy may not be allowed, if a slight grinding allowance is taken for post-processing, I'm done,
From this point, the manufacturing cost of the camshaft can be reduced.

In the second and third aspects of the present invention, the middle mold is in a double-supported state at the time of molding. Therefore, even if the middle mold receives a large force in the lateral direction due to the uneven flow of the material, the conventional technique can be used. A mechanically much stronger support can be obtained as compared with the case of such a cantilever, and the accuracy can be improved from this point as well.

From the above effects, the dimensional accuracy and the inclination accuracy of the relative positional relationship between the axial hole of the formed cam lobe and the cam surface can be further improved as compared with the conventional manufacturing method.

Further, in the fourth invention, in each of the above-mentioned inventions, a cam lobe material from which a decarburized layer on the surface is removed in advance is used. Thus, there is no problem that the hardness and wear resistance of the cam surface are reduced.

Further, in the fifth aspect of the present invention, the cam lobe material is pressed by the hydraulic press, and the wall thickness at that time is released in the thickness direction, so that even if there is some error in the volume of the cam lobe material, it is excessive. No load occurs. Also, even if the relief portion causes the flesh to rise on the side of the cam lobe, the cam lobe used on the one-side basis does not cause any obstacle.

Further, the sixth and seventh aspects of the present invention relate to a cam lobe manufactured by the above manufacturing method and an assembled camshaft using the same, and these cam lobes and camshafts are low in cost and sufficiently practical. .

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a perspective view showing a cam lobe manufactured by the method of manufacturing a cam lobe according to the present invention, as described above.

FIG. 2 is a top sectional view and a side sectional view showing the cam lobe blank 10 used in the method for manufacturing a cam lobe of the present invention. In FIG. 2, the dotted line indicates the position of each surface after finishing, and the solid line indicates the cam lobe material 1.
0 is shown schematically. That is, the cam lobe material 10
When viewed in a cross section perpendicular to the camshaft, the shape is thinner than the completed cam lobe 1.

The cam lobe blank 10 has a contour smaller than the contour of the finished cam surface 2 and a hole larger than and substantially coaxial with the finished axial hole 3 with respect to the finished cam lobe. That is, the cam lobe material 10 has a shape thinner than the completed cam lobe 1 when viewed in a cross section perpendicular to the cam shaft.

On the other hand, the interval (height, thickness) between the end faces of the cam lobe blank 10 is set to be larger than the finish, so that the volume corresponding to the meat in this portion just makes up the difference between the contour and the hole. It has become. Further, in the cam lobe material 10, the nose corresponding portion 18, which becomes the nose portion 8 at the time of finishing, is formed higher (thicker) than the other portion, that is, the base circular portion corresponding portion.

Such a cam lobe material 10 is an intermediate molded material and can be produced by hot or warm plastic working. For the production of cam lobe material, it is also possible to use the above-mentioned prior art, wherein the cam lobe material 10 obtained by this technology is, of course, as described above for the cam lobe to be produced. It is necessary to have a proper dimensional relationship.

Further, if a decarburized layer is present on the cam surface, the wear resistance of the cam will be weakened. Therefore, the cam lob material 10 used is one from which the decarburized layer on the surface has been removed in advance. That is, since the cam lobe material 10 itself is manufactured from a raw material bar having a decarburized layer on the surface in an initial state (when the raw material is received), the decarburized layer is removed at the raw material stage before the cam lobe material 10 is formed. . In the process of manufacturing the cam lobe material, a slight decarburized layer is formed on the surface of the cam lobe material when hot working is performed. However, the decarburized layer remaining on the surface of the cam lobe is extremely thin. Is also good.

FIG. 3 is a cross-sectional view of a mold for molding the cam lobe blank 10 to obtain a completed cam lobe. In addition, the following shaping | molding is performed cold.

The outer mold 51 has an inner surface having a cross section complementary to the outer shape (cam surface 2) of the finished cam lobe. The lower mold 52 has an outer surface having a cross section that closely engages with the inner surface of the outer mold 51, and is provided with a receiving hole 55 into which an end of a later-described middle mold 53 fits exactly. When using the mold, the lower mold 52 is fitted to the outer mold 51.

Since the space formed by the outer mold 51 and the lower mold 52 is formed so that the cam lobe material 10 can be inserted with a gap, the cam lobe material 10 is removed with the middle mold 53 removed. Insert into the space as shown in and place it horizontally. Thereafter, the middle mold 53 is lowered from above, passes through the hole of the cam lobe material 10, and
Into the receiving hole 55.

Subsequently, when the pressing mold 54 is inserted and pressurized to cause the material of the cam lobe material 10 to flow,
The material flows so as to follow the inner surface of the outer die 51, the outer surface of the middle die 53, the upper surface of the lower die 52, and the lower surface of the pressing die 54, and is formed into the cam lobe 1. In addition, of course, the pressing mold 5
4 is the cam surface 2 of the finished cam lobe 1 and the axial hole 3
It has an inner surface and an outer surface having the same shape as that of FIG.

When the molding is completed, the lower die 52 is lowered, and the pressing die 54 is further depressed to remove the formed cam lobe from the outer die 51.

In order to press the pressing mold 54, it is preferable to use a hydraulic press. This is a cam lob material 10
This is to prevent an excessive load from being generated even if there is a slight error in the volume of the battery.

FIG. 6 is a sectional view of a mold showing another embodiment. Although the receiving hole 55 shown in FIG. 3 does not particularly have a tapered portion, as shown in FIG. 6, the tip of the middle mold 53 and the receiving hole 55 can be provided with a complementary taper. A more secure engagement of the lower mold 52 is obtained.

FIG. 5 is a sectional view of a mold showing another embodiment. This embodiment is different from the above-described embodiment in that, when imbalance occurs in the driving (flowing) of the meat of the cam lobe material, the pressing mold 54 is provided with a relief portion 56 for absorbing the imbalance. Even if the relief portion 56 causes the meat bulge 57 to be formed on the cam lobe, the one end surface (the end surface 5 in the figure) of the formed cam lobe 1 is flat, so that the cam lobe 1 can be assembled on the basis of one side. In a camshaft of a simple design, it can be used to the fullest extent possible. If this is unacceptable by design, the swelling 57 is cut off, so that it can be used as before.

The boundary between the axial hole 3 and the end surfaces 4 and 5 is usually subjected to chamfering 7. In the above-described embodiment, near the boundary between such surfaces, the flow of the material (meat) is compared. The rounding of the corners, which is inevitable in the plastic working of metal, occurs relatively uniformly, so this phenomenon is used.If possible, the stress concentration can be maintained without reworking the corners. It can also be used as a chamfered surface to avoid the problem.

The thus obtained cam lobe 1 is fixed to a hollow shaft by the method disclosed in the above-mentioned JP-A-1-125506, and a camshaft as shown in FIG. 12 is obtained.

As described above, in any of the embodiments, the cam lobe blank 10 is provided with a hole (having an outer shape larger than the outer shape of the middle mold 53) corresponding to the axial hole 3 in advance. Since there is no need to form a recess and it does not play a role of a guide for punching or the like, the deformation caused by the force which the mold receives from the lateral direction at the time of forming the recess as in the prior art is accurate in the position of the axial hole 3. There is nothing to impair.

Further, in these embodiments, since the middle mold 53 is in a double-supported state at the time of molding, even if the middle mold 53 receives a large force in the lateral direction due to the uneven flow of the material, the same as in the prior art. You can get much stronger mechanical support than you have.

Therefore, the dimensional accuracy and the inclination accuracy of the relative positional relationship between the axial hole 3 and the cam surface 2 of the formed cam lobe 1 can be much improved as compared with the above-described conventional manufacturing method. .

Further, since sufficient accuracy can be obtained, the cam surface can be used as it is after the assembling of the cam lobe without particularly finishing the cam surface, and the cost of manufacturing the camshaft can be greatly reduced. Even when the degree of demand is high and the cam surface is further ground, the degree of surface roughness can be reduced.

[0049]

According to the present invention, a cam lobe material in which holes corresponding to the axial holes are provided in advance is used, so that it is not necessary to form a concave portion as in the prior art. Since it does not play the role of the guide, there is an effect that an error caused by a force which the mold receives from the lateral direction when forming the concave portion does not affect the accuracy of the axial hole.

Since the middle mold is doubly supported at the time of molding, even if the middle mold receives a large force in the lateral direction due to the uneven flow of the material, it is much more mechanically dynamic than the cantilever of the prior art. It is possible to obtain a strong support, and from this point, it is possible to improve the accuracy.

From the above effects, the dimensional accuracy and the inclination accuracy of the relative positional relationship between the axial hole of the formed cam lobe and the cam surface can be further improved as compared with the conventional manufacturing method. To play.

In addition, since sufficient accuracy can be obtained by this, after the cam lobe is assembled, the cam surface does not need to be particularly finished as in the prior art, and can be used as it is, and the cost of manufacturing the camshaft is greatly increased. This has the effect of being able to be lowered.

Further, when a camshaft is assembled using the cam lobe obtained by the cam lobe manufacturing method of the present invention as it is, even if accuracy and surface roughness may not be acceptable, slight grinding for post-processing may be required. Since the cost can be reduced, the camshaft manufacturing cost can be reduced from this point.

Further, in the present invention, since the decarburized layer on the surface of the cam lobe material has been removed in advance, there is an effect that the hardness and wear resistance of the cam surface are not reduced.

Since a hydraulic press is used to press the cam lobe material, the meat is driven into the pressing die (flow).
In combination with the provision of the relief portion for absorbing the imbalance of the above, even if there is some error in the volume of the cam lobe material, there is an effect that an excessive load is not generated.

Further, even if flesh is formed on the side surface of the cam lobe by the above-described relief portion, there is an effect that the cam lobe used on the one-side basis does not cause any obstacle.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a cam lobe manufactured by a cam lobe manufacturing method of the present invention.

FIG. 2 is a top view and a side sectional view showing a cam lobe material 10 used in the cam lobe manufacturing method of the present invention.

FIG. 3 is a sectional view of a mold for forming a cam lobe material 10 to obtain a completed cam lobe.

FIG. 4 is a cross-sectional view showing a state in which a cam lobe is formed by the inner surface of the outer die 51, the outer surface of the middle die 53, the upper surface of the lower die 52, and the lower surface of the pressing die 54.

FIG. 5 is a mold sectional view showing another embodiment.

FIG. 6 is a mold sectional view showing still another embodiment.

FIG. 7 is an example of a conventional method for manufacturing a cam lobe, and is a view showing a state in which an intermediate material is obtained.

FIG. 8 is an example of a conventional method for manufacturing a cam lobe, and shows a state in which a concave portion is formed in a material.

FIG. 9 is an example of a conventional method for manufacturing a cam lobe, showing a state in which an outer punch is pushed in, a part of the material flows toward a central portion (recess), and the recess is reduced.

FIG. 10 is an example of a conventional method for manufacturing a cam lobe,
It is a figure showing signs that a concave part of a material was reduced.

FIG. 11 is an example of a conventional method for manufacturing a cam lobe,
It is a figure which shows a mode that a center part is punched by a punch.

FIG. 12 is a perspective view of a completed camshaft.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 cam lobe 2 cam surface 3 axial hole 4, 5 end surface 6 concave groove 7 chamfer 8 nose portion 10 cam lobe material 19 inner side surface 51 outer die 52 lower die 53 middle die 54 press die 55 receiving hole 56 relief part 57 bulge

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3G016 BA25 BA34 CA04 CA13 CA32 FA06 4E087 AA10 BA20 CA13 CB03 DA04 EA12 EB03 EC02 ED01 HA33

Claims (7)

[Claims] 1. A method of manufacturing an assembling cam lobe having a non-circular contour on an outer periphery and an axial hole in a central portion, comprising: a thickness larger than a thickness of a cam lobe to be manufactured; The nose-corresponding portion to be a part has a thickness larger than other portions, an outer shape slightly smaller than the contour shape of the cam lobe, and a hole slightly larger than the shape of the axial hole of the cam lobe and substantially coaxial with the axial hole. A cam lobe material manufactured by hot or warm plastic working is pressed cold in its thickness direction to obtain a predetermined contour shape and a hole shape, to an assembling type camshaft. A method of manufacturing a cam lobe for use. 2. A method for producing an assembling cam lobe having a non-circular contour on the outer periphery and having an axial hole in a central portion, comprising: a thickness larger than a thickness of the cam lobe to be produced; and a nose of the cam lobe. The nose corresponding portion to be a part has a thickness larger than other portions, an outer shape slightly smaller than the outer shape of the cam lobe, and a shape slightly larger than the shape of the axial hole of the cam lobe, and a hole substantially coaxial with the axial hole. In a mold having a cam lob material produced by hot or warm plastic working, a mold having a wall surface and a bottom surface having side surfaces complementary to the contour shape of the cam lobe and the shape of the axial hole of the cam lobe. Wherein the cam lobe material placed in the mold is cold-pressed in the axial direction of the cam lobe with a pressing die having the same cross-sectional shape as the cam lobe to form. A method for manufacturing a cam lobe for use in a vertical camshaft. 3. A method of manufacturing a cam lobe for use in an assembling camshaft according to claim 2, wherein said mold has an outer mold having a side wall having a side surface complementary to said contour shape of said cam lobe. And a middle mold having a wall surface having a side surface complementary to the shape of the axial hole of the cam lobe, and a lower mold having a bottom surface and having a receiving hole with which the middle mold engages. A method for producing a cam lobe for use in an assembling camshaft, which is a mold. 4. A method of manufacturing a cam lobe for use in an assembling camshaft according to any one of claims 1 to 3, wherein the decarburized layer on the surface of the cam lobe material is removed in advance. A method of manufacturing a cam lobe for use in an assembled camshaft. 5. A method of manufacturing a cam lobe for use in an assembling camshaft according to claim 1, wherein the pressing of the cam lobe material is performed by a hydraulic press. A method of manufacturing a cam lobe for use in an assembling camshaft, characterized in that the pre-fill is released in the thickness direction. 6. A cam lobe for use in an assembling camshaft, which is manufactured by the manufacturing method according to claim 1. Description: 7. A camshaft provided with the cam lobe according to claim 6.