JP3405372B2 - Manufacturing method of cam lobe for assembly - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an assembling cam lobe for use in an assembling hollow cam shaft of a reciprocating internal combustion engine or the like. 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 improved fuel economy, and there is a demand for improved lightness and durability. Therefore, the camshaft components such as the cam lobe and the journal are made as individual parts using a material having good wear resistance, and the hollow shaft is inserted into the axial hole thereof to be positioned at a predetermined phase and axial interval. Some camshafts have their weight reduced by expanding the shaft radially outward to secure these camshaft components to the hollow shaft and assembling them together. Since such a camshaft component is required to have high shape and dimensional accuracy together with excellent mechanical properties, it is integrally formed into a desired shape in advance by a plastic working method such as forging separately from the hollow shaft. . A forging method for integrally forming such a camshaft component is disclosed in, for example, Japanese Patent Laid-Open No. 4-350.
As in the method of manufacturing a camshaft disclosed in Japanese Patent No. 307, for example, there is a method in which a cam lobe is integrally formed in a desired shape in advance by cold forging. However, in the forging method by cold forging, it is difficult to give a large deformation because the deformation resistance of the molding material is high, and a plurality of intermediate moldings are required, and a pretreatment such as a heat treatment or a lubrication treatment is required. . In addition, since the molding load is high, a tough and highly rigid mold tool and a highly rigid and accurate press are required. In particular, in order to obtain a high-precision cam surface on the outer peripheral surface of a cam lobe having a non-circular / non-axisymmetric contour shape, finishing work by machining such as shaving and cutting / grinding is also required, so manufacturing costs are reduced. There is a problem of becoming high. [0004] As a forging method for integrally forming such a camshaft component, continuous working of hot forging, which can reduce the number of steps as compared with cold forging, can be considered. That is, hot forging has higher fluidity of the molding material and lower deformation resistance than cold forging, so that a large deformation can be given by one molding, and the number of steps can be reduced, which is advantageous in cost. is there. FIG. 10 to FIG. 12 are schematic process charts when a cam lobe 51 used for an assembling hollow cam shaft is continuously worked by hot forging. The cam lobe 51 is a cam lobe for assembly having a non-circular and non-axisymmetric contour shape as shown in FIG. 13 and having an axial hole 52 at the center. First, as shown in FIG. 10, a billet 41 which is a columnar cam lobe material formed by cutting a steel rod or wire into a predetermined size or weight according to the volume of a forged product is heated, and then heated. It is formed into a barrel shape by open-type upsetting in which the mold 42 and the lower mold 43 open and compress. Next, the billet 41 is placed in a forming die having a final product contour shape by the die 50 having the curved surface 49 corresponding to the cam shape, the outer punch 45, and the lower die 46, as shown in FIG. As shown in the figure, the column-shaped intermediate press punch 44 is pressurized and lowered together with the outer punch 45, and the inner press punch 44 is pressed into the billet while compressing the billet 41 with the outer punch 45, thereby forming the mold in a completely sealed mold. The material is allowed to flow to the outer periphery and the profile of the cam lobe is extruded. Then, as shown in FIG. 11 (b), an intermediate molded material 47 having a concave portion 48 formed by the middle press punch 44 is obtained. Then, as shown in FIG. 12, an axial hole 52 for inserting a hollow shaft through the intermediate molding material 47 is punched by a punch 54 along the recess 48, and FIG.
The assembly cam lobe 51 having a desired shape as shown in FIG. However, when the assembling cam lobe 51 having a non-circular and non-axisymmetric contour is formed by hot forging as described above, the outer peripheral surface is formed as shown in FIG.
Since the surface sagging 57 as shown in (1) tends to occur and the position and size of the occurrence are uneven, it is difficult to form a cam lobe with high precision. Further, in extruding the intermediate molding material 47 forming the contour shape of the cam lobe, the outer punch 45 and the intermediate pressing punch 44 are further strongly lowered to fill the local surface sagging portion with the molding material. When the material 47 is pressurized, the compression surface pressure becomes too high, causing deformation of the molding die and early breakage of the die. That is, it is difficult to flow the molding material of the intermediate molding material 47 that is entirely confined in the completely closed molding die toward a part of the surface sagging portion, and furthermore, the portion that is thinned under the intermediate pressing punch 44 Since it is more difficult for the molding material to move, it is difficult to fill the local surface sagging portion with the molding material. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned problems, and to provide a method for manufacturing a cam lobe for assembling, which can efficiently form a high-precision cam lobe while preventing deformation and early damage of a mold. To provide. SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for manufacturing an assembling cam lobe having a non-circular contour on the outer periphery and an axial hole in the center. After the material is confined in a molding die, a preforming step of forming a rough contour shape while pressing a middle press punch so as to form a recess near the center of the cam lobe material, and an intermediate forming formed by the preforming step At the same time as the intermediate press punch is pushed into the concave portion of the material, the upper and lower surfaces of the intermediate molded material are pressed while forming a gap between the surface of the intermediate molded material and the mold surface in the vicinity of the concave portion to form a predetermined contour shape. This is achieved by a method for manufacturing a cam lobe for assembly including a finish forming step and a punching step of forming an axial hole along a concave portion of the finished formed material formed in the finish forming step. The gap is preferably formed by making the pushing length of the middle punch in the finish forming step smaller than the pushing length of the middle punch in the preliminary forming step. Further, the gap is preferably formed by a concave portion formed on the pressing end face of the intermediate pressing punch in the finish forming step. Further, the gap is preferably formed by a concave portion formed on the inner wall of the mold opposite to the pressing end face of the intermediate press punch in the finish forming step. In the preforming step of forming the intermediate molding material, since only the rough contour of the cam lobe is molded, the molding material is filled and the punch pressure is reduced so that a local surface sagging portion does not occur. Also, there is no need to increase the molding load. Further, in the finish molding step, the upper and lower surfaces are pressed so as to leave a gap near the center of the intermediate molding material and the predetermined contour shape of the cam lobe is molded, so that the molding material in the molding die has a restricted degree. It becomes lower and easier to flow. At this time, an intermediate press punch is pushed into the concave portion of the intermediate molding material formed in the preliminary molding step, and the internal pressure of the molding material when a predetermined contour shape is formed is maintained. Therefore, a predetermined contour shape can be obtained by filling the outer peripheral surface with the molding material even with a low punch pressure and a low molding load. The trace of the void formed near the center of the finish formed material formed in the finish forming step is punched out together with the recess in the punching step of forming an axial hole, and does not remain in the finished cam lobe. . An embodiment of the present invention will be described below in detail with reference to the accompanying drawings. FIGS. 1 to 5 show a cam lobe 1 used in an assembled hollow camshaft according to an embodiment of the present invention.
FIG. 7 is a schematic process diagram when continuously processing No. 7 by hot forging. This cam lobe 17 is an assembly cam lobe having a non-circular and non-axisymmetric contour shape as shown in FIG. 8 and having an axial hole 18 in the center. First, as shown in FIG. 1, a billet 3 which is a columnar cam lobe material formed by cutting a steel rod or wire into a certain size or weight according to the volume of a forged product,
As a pretreatment, for example, after being heated at about 1150 to 1200 ° C., it is formed into a substantially barrel shape by upsetting in which the upper mold 1 and the lower mold 2 open and compress the cam lobes 17. In this embodiment, step-upsetting is performed to adjust the volume distribution of the molding material. Next, the billet which has been subjected to the pretreatment in a molding die having a rough product contour shape by the die 10 having the curved surface 16 corresponding to the cam shape, the outer punch 4, the middle punch 6 and the lower die 5. Place 3 and lock it. still,
When the billet 3 is placed in a molding die, the side on which the cam top is molded (FIG. 2) to adjust the volume distribution of the molding material.
To the left). However, Cam Rob 1
In the case where the degree of irregularity of 7 is low, it is sufficient to adopt either of the above-mentioned stepped upsetting and the offset mounting of the billet 3 in the forming die. Thereafter, as shown in FIG.
At the same time, the column-shaped middle press punch 6 is pressurized and lowered, and the middle press punch 6 is pushed into the billet while compressing the billet 3 with the outer punch 4, so that the molding material flows to the outer peripheral portion in the closed mold. The intermediate molded material 7 having the approximate contour of the cam lobe 17 is preformed by extrusion. Therefore, a recess 11 is formed near the center of the intermediate molding material 7 as shown in FIG. 2 (b). That is, by forming the concave portion 11 near the center by the middle press punch 6 having substantially the same diameter as the punch for punching the axial hole 18,
A nominal hole for punching out the axial hole 18 in a later step is provided in the intermediate molding material 7, so that the thickness of the punched portion can be reduced to facilitate punching. At this time, the contour shape in the forming die in the preforming step is close to the final shape of the cam lobe 17, but the restraint of the intermediate forming material 7 in the forming die is not strengthened.
The surface sag 8 is left on the outer peripheral surface or the like. That is, in the present embodiment, the thickness H ₁ of the intermediate molding material 7 is
It is formed to be thicker than the final thickness of H _2. Therefore, the intermediate molding material 7 can be molded with a low punch thickness and a low molding load. Next, the intermediate press 7 is pressed into the recess 11 of the intermediate formed material 7 formed in the preforming step, and at the same time, the upper and lower surfaces of the intermediate formed material 7 are pressed to obtain a predetermined thickness H ₂ of the final thickness H ₂ . A finish forming material 12 having a contour shape is finish formed. Here, as shown in FIG. 3, the middle press punch 9 has a pressing length h ₂ protruding from the pressing surface of the outer punch 14.
There has been less than the indentation length h ₁ of the inner press punch 6 in the preforming step. Therefore, when the press punch 9 is lowered together with the outer punch 14 and the pressurized surface of the outer punch 14 is brought into contact with the outer portion of the intermediate molding material 7, the bottom surface of the concave portion 11 which is the surface of the intermediate molding material near the concave portion 11 is A gap 13 is formed between the pressing end face of the middle press punch 9 as a mold surface. Then, the intermediate punch 9 together with the outer punch 14 is further pressurized and lowered, and the pressing force of the outer punch 14 is applied to the outer portion of the intermediate molding material 7 so that the molding material is moved to the central portion in the molding die. While flowing, the portion of the surface sag 8 remaining on the outer peripheral surface or the like of the intermediate molding material 7 is filled with the molding material. It should be noted that a gap 13 is left between the bottom surface of the concave portion 11 and the pressing end surface of the intermediate pressing punch 9 even at the end of the molding in which the surface sag 8 is almost completely filled with the molding material. That is, the intermediate molding material 7
Even if the surface sagging 8 greatly varies, in the finish forming step, the size of the space 13 is reduced and the center thereof is merely shifted from the center of the intermediate pressing punch 9. The material is evenly filled. Therefore, the molding material in the completely closed mold is not a completely closed closed forging, but a forged having a free portion in the center of the mold and having a reduced degree of restraint. , With low punch pressure and low forming load. At this time, the molding material flows in the molding die so as to fill a part of the space 13, but the intermediate molding material 7 in the preliminary molding step is so filled that the surface sag 8 is filled first. shape (i.e., the thickness of the recess 11, the amount and thickness H ₁ and the like of dullness portion) must be determined. That is, in the preforming step, the portion having a small surface sag is filled with the molding material at the surface sagging portion 8 at the early stage of the molding in the final forming step, and thereafter, the molding material flows only into the gap 13. Further, in the portion where the surface droop is large in the preforming step, the molding material flows into both the surface droop 8 and the gap 13, so that the surface droop 8 is finally filled with the molding material. In any case, there is a relief area for the molding material in the center of the mold to prevent the punch surface pressure from becoming excessive, and at the same time, to prevent unbalance due to the non-circular and non-axisymmetric contour shape. Surface sagging during molding can also be absorbed. Therefore, even if the processing accuracy in the preforming step is low, the finishing material 12 having a high-precision contour shape is obtained in the finishing forming step.
Is possible. In the above-mentioned finish forming step, the nominal press hole 9 for punching out the axial hole 18 is formed only by pressing the intermediate press punch 9 into the concave portion 11 of the intermediate forming material 7 formed in the preliminary forming step. Instead, the flow of the molding material into the cavity 13 is appropriately restricted,
Maintains an appropriate internal pressure of the molding material when molded. That is, if the gap 13 is too large, the molding material rapidly flows into the gap 13 in the finish molding step, the inner diameter of the concave portion 11 collapses, and the surface sag 8 is not filled with the molding material. It is necessary to increase the internal pressure of the molding material in the molding die to such an extent that the molding material fills the portion 8. Therefore, in order to control the degree of constraint of the flowing molding material and increase the internal pressure of the molding material in the molding die to a necessary degree, the middle press punch 9 pushed into the concave portion 11 in the finish molding step is effective. Finally, as shown in FIG. 5, the concave portion 11 of the finished molding material 12 formed by the above-mentioned finishing molding step.
The hole 18 in the axial direction is punched in a round shape by the punch 15 to form the cam lobe 17. At this time, the axial holes 18
In order to prevent the occurrence of a step on the peripheral wall surface of the hole and improve the inner diameter shape and accuracy, the punch 11
Punching while shaving (edge finishing) the peripheral wall surface. Further, when the axial hole 18 is punched by the punch 15, the cam lobe 17 to be punched can be prevented from being deformed by punching while restraining the outer part of the concave portion 11 of the finished molded material 12. That is, the void mark 13a left in the finish forming material 12 formed in the finish forming step is formed by the axial hole 1
8 is punched out together with the concave portion 11 in the punching step of molding, and does not remain in the finished cam lobe 17. Therefore,
In the preforming step and the finish forming step as described above,
Since the cam lobe 17 can be efficiently formed with high precision even with a low forming load by lowering the surface pressure of the punches 6, 9 and the outer punches 4, 14, deformation and early damage of the forming die can be prevented. . In the finish forming step of this embodiment,
Gap formed between the intermediate profiled surface and the mold surface of the recess near in accordance with the present invention, indentation length of the inner press punch 6 indentation length h ₂ of the inner press punch 9 in finish forming process in the pre-forming step It was formed as a void 13 formed by smaller than h _1, but the invention is not limited thereto. For example, according to another embodiment of the present invention shown in FIG. 6, the gap according to the present invention is formed by a recess 22 formed in the lower die 21 facing the pressing end face of the intermediate pressing punch 9 in the finish forming step. Formed by That is, the indentation length h ₂ of the inner press punch 9 is substantially equal to the pushing length h ₁ of the inner press punch 6 in the preforming step, the recess 11 of the intermediate molded material 7 formed by preforming step the inner press punch 9 press writing at the same time, to press the upper and lower surfaces of the intermediate formed member 7 is molded finish the finish forming material 23 having a predetermined outline shape of the final thickness H _2. Therefore, when the outer punch 14 is lowered together with the intermediate press punch 9 and the pressurized surfaces of the intermediate press punch 9 and the outer punch 14 are brought into contact with the upper surface of the intermediate molding material 7, the intermediate molding material surface near the recess 11 is formed. Lumber 7
Is formed between the bottom surface of the recess 22 and the bottom surface of the recess 22 serving as a mold surface. Then, the middle punch 9 together with the outer punch 14 is further subjected to a pressure drop, so that the outer punch 14
By applying the pressing force of the intermediate pressing punch 9, the molding material in the molding die is caused to flow into the recess 22, which is the central portion, while remaining on the outer peripheral surface of the intermediate molding material 7 as shown in FIG. The portion of the surface sag 8 can be filled with the molding material. Further, according to another embodiment of the present invention shown in FIG. 7, the gap according to the present invention is formed by the depression 32 formed on the pressing end face of the intermediate pressing punch 31 in the finish forming step. That is, substantially equal to the pushing length h ₁ of the inner press punch 6 indentation length h ₂ of the inner press punch 31 in the pre-forming step, the inner press punch 31 into the recess 11 of the intermediate molded material 7 formed by preforming step press At the same time, the upper and lower surfaces of the intermediate molded material 7 are pressed, and the final thickness H ₂
The finish forming material 33 having the predetermined contour shape is finish-formed. Therefore, in a state where the outer punch 34 is lowered together with the middle press punch 31 and the pressing surfaces of the middle press punch 9 and the outer punch 34 are brought into contact with the upper surface of the intermediate forming material 7, the concave portion 11 which is the surface of the intermediate forming material near the concave portion 11 is formed. Is formed between the bottom surface of the recess 22 and the bottom surface of the recess 22 serving as a mold surface. Then, the middle punch 31 together with the outer punch 34 is further subjected to a pressure drop, and the outer punch 3
4 and the pressing force of the intermediate pressing punch 31, the molding material in the molding die is caused to flow into the concave portion 32 at the center as shown in FIG.
The portion of the surface sag 8 remaining on the outer peripheral surface or the like can be filled with the molding material. Further, in the punching step of the above embodiment, the round hole 1
8 was punched out by a punching punch 15 to form a cam lobe 17, but when a groove 37 is necessary in the peripheral wall of the axial hole 36 as in a cam lobe 35 shown in FIG. May have a circular cross section, and the groove 37 may be formed by a punching punch in a punching step. According to the method for manufacturing a cam lobe for assembly of the present invention, in the preforming step of forming an intermediate molded material,
Since only the approximate contour shape of the cam lobe is formed, it is not necessary to increase the punch pressure and the forming load so that the forming material is filled and a local surface sagging portion does not occur. In the finish forming step, the upper and lower surfaces are pressed so as to leave a gap near the center of the intermediate formed material, and the predetermined shape of the cam lobe is formed. Degree becomes low and it becomes easy to flow.
At this time, an intermediate press punch is pushed into the concave portion of the intermediate molding material formed in the preliminary molding step, and the internal pressure of the molding material when a predetermined contour shape is formed is maintained. Therefore, a predetermined contour shape can be obtained by filling the outer peripheral surface with the molding material even with a low punch pressure and a low molding load. That is, in the preforming step and the finish forming step as described above, a high-precision cam lobe can be formed efficiently even with a low forming load with a reduced punch surface pressure. Can be prevented. Therefore, it is possible to provide a method of manufacturing a cam lobe for assembly, which can efficiently form a high-precision cam lobe while preventing deformation and early damage of a molding die.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of a main part and a top view of a billet for explaining an upsetting process in a method of manufacturing a cam lobe for assembly according to the present invention. FIG. 2 is a cross-sectional view of a main part and a top view of an intermediate molding material for describing a preforming step in the method of manufacturing a cam lobe for assembly according to the present invention. FIG. 3 is a cross-sectional view of a main part for describing a finish forming step in the method of manufacturing a cam lobe for assembly according to the present invention. FIG. 4 is a cross-sectional view of a main part and a top view of a finished formed material for describing a finish forming step in the method for manufacturing a cam lobe for assembly according to the present invention. FIG. 5 is a cross-sectional view of a main part for describing a punching step in the method for manufacturing a cam lobe for assembly according to the present invention. FIG. 6 is a cross-sectional view of a main part for describing a finish forming step based on another embodiment in the method of manufacturing an assembling cam lobe of the present invention. FIG. 7 is a cross-sectional view of a main part for describing a finish forming step based on another embodiment of the method for manufacturing a cam lobe for assembly according to the present invention. FIG. 8 is an overall perspective view of a cam lobe formed by the method for manufacturing a cam lobe for assembly according to the present invention. FIG. 9 is an overall perspective view showing a modified example of the cam lobe formed by the method of manufacturing an assembling cam lobe of the present invention. FIG. 10 is a cross-sectional view of a main part for describing an upsetting process in a conventional method for manufacturing a cam lobe for assembly. FIG. 11 is a cross-sectional view of a main part and a top view of an intermediate molding material for explaining a molding step in a conventional method of manufacturing a cam lobe for assembly. FIG. 12 is a cross-sectional view of a main part for describing a punching step in a conventional method of manufacturing a cam lobe for assembly. FIG. 13 is an overall perspective view of a cam lobe formed by a conventional method of manufacturing a cam lobe for assembly. [Description of Signs] 1 Upper die 2 Lower die 3 Billet 4 Outer punch 5 Lower die 6 Middle press punch 7 Intermediate molding material 8 Surface sag 9 Medium press punch 10 Dies 11 Recess 12 Finished molding material 13 Void

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-60-126464 (JP, A) JP-A-6-246389 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F01L 1/04 B21J 5/06

Claims (1)

(57) [Claim 1] In a method of manufacturing an assembling cam lobe having a non-circular contour on the outer periphery and having an axial hole in a central portion, a pretreated cam lobe material is placed in a molding die. After confined to
A preforming step of forming a rough outline shape while pressing a middle press punch so as to form a concave portion near the center of the cam lobe material; and pressing a middle press punch into a concave portion of the intermediate formed material formed by the preform step. At the same time, a finish molding step of pressing the upper and lower surfaces of the intermediate molded material to form a predetermined contour shape while leaving a gap between the surface of the intermediate molded material near the concave portion and the mold surface, A punching step of forming an axial hole along a concave portion of the formed finish formed material.