JPH11192596A - Molding equipment for powder molding used in the manufacture of Oldham rings - Google Patents

Abstract

(57) [Summary] [PROBLEMS] In manufacturing Oldham rings by powder metallurgy, it is possible to increase the accuracy such as the perpendicularity of a key portion without performing cutting. SOLUTION: In a powder molding die apparatus for molding a green compact to be an Oldham ring, a lower second punch 29 and a lower third punch 29 which form a portion corresponding to an end face of a key portion of the Oldham ring or a back side of the key portion. Punch 32 and upper second punch 38
Are the punch fitting grooves of the lower first punch 26 and the upper first punch.
Fits 26a. The punch fitting groove 26a is formed as a concave groove, and the outer peripheral portions of the lower first punch 26 and the upper first punch are formed as a cylindrical portion 26b which is continuous over the entire circumference. Thus, it is possible to suppress the width of the punch fitting groove 26a forming the side surface of the key portion from changing due to the pressing of the raw material powder. After sintering and straightening, the outer peripheral surface of the green compact is cut, and
The grooves created by the process are eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a powder molding die apparatus used for manufacturing Oldham rings by powder metallurgy.

[0002]

FIGS. 8 to 10 show an example of an Oldham ring 1 which is a component used for an Oldham shaft coupling for transmitting torque between shafts whose axes are slightly shifted. 8 to 10, reference numeral 2 denotes a ring main body, and the outer peripheral surface and the inner peripheral surface of the ring main body 2 are coaxial cylindrical surfaces, and both end surfaces are planes orthogonal to the cylindrical surface. . A pair of key portions 3 and 4 as protrusions are formed on both end surfaces of the ring main body 2, respectively. The key portions 3 and 4 on each end face are located at axially symmetric positions with respect to the central axis of the ring main body 2, and the key portions 3 and 4 on both end faces are located at 90 ° apart from each other with respect to the central axis of the ring main body 2. It is in. These key parts 3 and 4 are
Although not shown, in the Oldham shaft coupling, it engages with the key grooves of the input-side component and the output-side component, and slides in the radial direction of the ring main body 2 with respect to these key grooves. Therefore, for the reliable operation of the Oldham's shaft coupling, the accuracy of each of the side surfaces 3a and 4a of the key portions 3 and 4 is particularly important. The squareness of the key portion 4 with the side surface 4a also requires high accuracy.

As a method for manufacturing the Oldham ring 1 as described above, there is a method using powder metallurgy. In powder metallurgy, after a raw material powder containing a metal as a main component is compressed to form a green compact, the green compact is heated and sintered. Further, in the manufacture of the Oldham ring 1, after sintering, the sintered body is subjected to straightening, which is recompression to obtain a predetermined shape and a predetermined size, and further deburring and cutting are performed. Gas nitrocarburizing treatment is applied to improve the properties and fatigue strength. In the cutting, the outer peripheral surface of the work to be the Oldham ring 1 is cut, and the diameter of the outer peripheral surface is set to a predetermined size. Fig. 13 shows the workpiece before cutting the outer peripheral surface.
1A, and a portion on the outer peripheral side from the chain line a is cut. In the completed Oldham ring 1, the key portions 3, 4 protrude radially outward from the outer peripheral surface of the ring main body 2, whereas in the work 1A, the entire outer peripheral surface including the key portions 3, 4 is provided. Has one cylindrical surface. The entire inner peripheral surface of the work 1A also forms one cylindrical surface. In addition, both sides 3a and 4a of the key portions 3 and 4 are conventionally subjected to cutting so as to obtain necessary accuracy at a right angle or the like.

FIGS. 11 and 12 show an example of a mold apparatus of a conventional powder molding press used for molding a green compact. In these figures, 51 is a die, 52 is a core rod, 53 is a lower first punch, 54 is a lower second punch, and 55 is a lower third punch.
A punch, 56 is an upper first punch, and 57 is an upper second punch.
The core rod 52 has a cylindrical shape and is coaxially located in a cylindrical die 51. Also, the lower first punch
53 has a substantially cylindrical shape, but has four cut grooves 53a opened to the inner and outer peripheral surfaces thereof. And
Lower first punch 53, lower second punch 54, and lower third punch 55
Is fitted between the die 51 and the core rod 52 so as to be slidable up and down from below. The lower second punch 54 and the lower third punch 54
Numerals 55 are respectively fitted to the cut grooves 53a of the lower first punch 53 so as to be slidable up and down. The upper first punch 56 also has a substantially cylindrical shape, but has two cut grooves opened to the inner peripheral surface and the outer peripheral surface thereof, similarly to the lower first punch 53. The upper first punch 56 and the upper second punch 57 are fitted between the die 51 and the core rod 52 so as to be able to be inserted and removed from above and to be slidable up and down. Each of the first punches 56 is fitted slidably up and down in a groove.

[0005] At the time of molding, the upper first punch 56 and the upper second punch 57 are removed from between the die 51 and the core rod 52 as shown in FIG. The raw material powder P is filled. Thereafter, the upper first punch 56 and the upper second punch 57 descend to fit between the die 51 and the core rod 52, and the die 51
Is lowered, the raw material powder P is compressed between the die 51 and the core rod 52, and a green compact (work 1A) is formed. At this time, the position of the lower third punch 55 is fixed, but the lower first punch 53 descends by a smaller amount than the die 51, and the lower second punch 54 descends by a smaller amount. As a result, the compressed amount of the raw material powder P is appropriately adjusted between the portion having the key portions 3 and 4 and the portion not having the key portions 4. The upper end surface of the lower second punch 54 is located lower than the upper end surface of the lower first punch 53, while the upper end surface of the lower punch 55 is located at the same height. After the pressurization, the upper first punch 56 and the upper second punch 57 are lifted and come out from between the die 51 and the core rod 52, and the die 51
Is further lowered, so that the formed work 1A is extracted as shown in FIG. 12 (b). At this time, the lower first punch 53 also slightly descends, whereby the key portion 3 is pulled out from the lower first punch 53. Further, when the upper first punch 56 moves upward, the key portion 4 is pulled out from the upper first punch 56 by keeping the upper second punch 57 stopped for a predetermined period.

As described above, after sintering, cutting is performed on both side surfaces 3a and 4a of the key portions 3 and 4 because sufficient precision cannot be obtained at the stage of powder compaction. The reason is
Inner peripheral surface of die 51, outer peripheral surface of core rod 52, lower first punch
Since the outer peripheral surface and the inner peripheral surface of 53 and the upper first punch 56 are cylindrical surfaces, the raw material powder P
When pressurized and compressed by 54, 55, 56, 57, the lower first punch 53 and the upper first punch 56 are subjected to a twisting force due to the density difference of the raw material powder P and the like. This is because the first punch 53 and the upper first punch 56 slightly rotate from a predetermined position. For example, if the upper first punch 56 does not rotate and only the lower first punch 53 rotates, an error occurs in the positional relationship between the key 3 on one end of the Oldham ring 1 and the key 4 on the other end. The perpendicularity between the side surface 3a of the portion 3 and the side surface 4a of the key portion 4 on the other end surface is deteriorated.

Further, the lower first punch 53 and the upper first punch 56 are composed of the lower second punch 54, the lower third punch 55 and the upper second punch 55.
Since each of the punches 57 has a cut groove 53a to be fitted and is formed in a shape divided in the circumferential direction, the width of the cut groove 53a forming the side surface of the key portions 3 and 4 is set to the width of the raw material powder P. It is easy to change due to pressure and the like, and particularly easy to spread, which also causes the accuracy of the key portions 3 and 4 to decrease.

For this purpose, the side surfaces 3a and 4a need to be cut. However, if the number of cuts increases, the number of steps increases and the cost increases.

SUMMARY OF THE INVENTION The present invention is intended to solve such a problem. In manufacturing a compact to be an Oldham ring having projections to be positioned at a predetermined angle on both end surfaces, a cutting process is performed. It is an object of the present invention to provide a powder molding die apparatus capable of improving the positional accuracy of a projection without performing the above.

[0010]

According to a first aspect of the present invention, there is provided a powder molding die apparatus for use in manufacturing an Oldham ring, wherein the peripheral surface has a substantially circular shape to achieve the above object.
A powder molding die apparatus for molding a green compact that has projections on both end surfaces and forms an Oldham ring in which the projections on both end surfaces are positioned at a predetermined angle with respect to the circular central axis, A die that forms the outer peripheral surface of the green compact, a core rod that forms the inner peripheral surface of the green compact, and portions other than the protrusions on the end surface of the green compact that are slidably fitted between the die and the core rod; A main punch forming a side surface of the protrusion, and a portion corresponding to the end face of the protrusion of the green compact or the end face of the green compact, which is provided slidably in the same direction as the main punch. The main punch has a concave groove-shaped punch fitting groove which is opened to the inner peripheral surface thereof and into which the sub punch is slidably fitted, and the outer peripheral portion extends over the entire circumference. Forming a continuous cylindrical part, and the inner peripheral surface of the die And one of the outer peripheral surfaces of the main punch is formed with a concave groove extending in the moving direction of the die and the main punch, and the other is formed with a ridge slidably fitted in the concave groove. .

[0011] The fitting of the concave groove and the ridge prevents the main punch from being twisted by the pressing force when the raw material powder is compressed by the main punch and the sub-punch in the die. As a result, the positions of the projections formed by the separate punches on both end surfaces of the green compact are accurately regulated, and the accuracy of the predetermined angle formed by the projections on both end surfaces is improved. The sub-punch forming the end face of the projection of the green compact or the portion corresponding to the back side of the projection on the end face of the green compact is fitted in the punch fitting groove in the main punch. The fitting groove has a concave shape and is open on the inner peripheral surface of the main punch, and since the outer peripheral portion of the main punch has a continuous cylindrical portion over the entire circumference, the side surface of the protrusion is formed. The width of the formed punch fitting groove is suppressed from changing due to the pressing of the raw material powder. This further improves the accuracy of the protrusion.

According to a second aspect of the present invention, in the powder molding die apparatus used for manufacturing the Oldham ring according to the first aspect of the present invention, the cross-sectional shape of the concave groove and the convex ridge is substantially rectangular.

Thus, when the raw material powder is compressed by the punch in the die, the punch is more reliably prevented from being twisted by the pressing force.

According to a third aspect of the present invention, in the powder molding die apparatus used for manufacturing the Oldham ring according to the first or second aspect of the present invention, after the green compact is sintered, the outer peripheral surface is cut. And the ridge or the groove is formed at a position corresponding to a portion to be cut in the green compact.

The grooves or protrusions formed on the outer peripheral surface of the green compact by the protrusions or grooves of the die disappear by cutting after sintering and do not remain in the final product.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of a powder molding die apparatus used for manufacturing an Oldham ring according to the present invention.
This will be described with reference to FIG. Note that the powder molding die apparatus of the present embodiment uses the above-described green compact, which is the work 1B (shown in FIGS. 4 to 6) that becomes the Oldham ring 1 as shown in FIGS. It is to be molded. FIG.
In the figure, 11 is a die plate, 12 is a lower first punch plate, 13 is a lower first punch holder erected on the lower first punch plate 12, and 14 is an erected lower second punch plate (not shown). The lower second punch holder 15 is a lower third punch holder erected on a base plate not shown, and the reference numeral 16 is a core holder erected on a core plate not shown. The position of the base plate on which the lower third punch holder 15 is erected is fixed. The core plate is connected to a lower ram (not shown) of the powder molding press, and moves up and down by driving the lower ram.
The die plate 11 moves up and down integrally with the core plate and the core holder 16. The lower first punch plate 12 on which the lower first punch holder 13 is erected, and the lower second punch plate on which the lower second punch holder 14 is erected,
It moves up and down in conjunction with the die plate 11 by an interlock mechanism (not shown) of the powder molding press, but moves differently. Reference numeral 17 denotes an upper first punch plate, and reference numeral 18 denotes an upper second punch plate. Upper first punch plate 17
Is connected to an upper ram (not shown) of the powder molding press, and moves up and down by driving the upper ram. Upper second
The punch plate 18 is incorporated in the upper first punch plate 17 so as to be vertically movable, and is vertically moved by driving a cylinder device (not shown).

A die 21 is attached to the die plate 11 by a die holder 22 and die holder holders 23 and 24. A lower first punch adapter 25 is mounted on the lower first punch holder 13, and a lower first punch 26 as a main punch is mounted on the lower first punch adapter 25 by a lower first punch holder 27. Have been. A lower second punch adapter 28 is mounted on the lower second punch holder 14, and a pair of lower second punches 29 as sub-punches is mounted on the lower second punch adapter 28. Attached by 30. A lower third punch adapter 31 is mounted on the lower third punch holder 15, and a pair of lower third punches 32 as auxiliary punches is mounted on the lower third punch adapter 31. Attached by 33. Further, a core rod 34 is mounted on the core holder 16 by a core rod holder 35. Also,
An upper first punch 36 as a main punch is attached to the lower side of the upper first punch plate 17 by an upper first punch holder 19 and an upper first punch holder 37. further,
A pair of upper second punches 38 as sub-punches are attached to the lower side of the upper second punch plate 18 by upper second punch holders 39. Then, the die 21 and each punch 2
6, 29, 32, 36, 38 and the core rod 34 are slidably fitted to each other in the vertical direction to form a green compact 1B having a predetermined shape.

The die 21 has a key portion 3 as a protrusion,
It forms the outer peripheral surface of the work 1B except for the reference numeral 4, and has a substantially cylindrical shape whose axial direction is the vertical direction. The lower first punch 26 forms a portion other than the key portions 3 and 4 on one end surface of the work 1B and an outer peripheral surface and a side surface 3a of the key portion 3, and has a substantially cylindrical shape whose axial direction is the vertical direction. And is slidably fitted between the die 21 and the core rod 34 from below. The lower first punch 26 is provided with four punch fitting grooves 26a extending vertically.
They are formed 90 ° apart. These punch fitting grooves 26
a has a concave groove shape opened on the inner peripheral surface and the upper end surface of the lower first punch 26, and the outer peripheral portion of the lower first punch 26 has a cylindrical shape continuous over the entire circumference up to the upper end surface. It is a part 26b. The lower second punch 29 forms an end face of the key portion 3 and has a square rod shape with the vertical direction as the axial direction, and slides into the punch fitting groove 26a of the lower first punch 26. It is movably fitted. The lower third punch 32
Is formed in a portion corresponding to the back side of the key portion 4 on one end surface of the work 1B, and has a square rod shape whose axial direction is the vertical direction.
Fits inside a. Further, the core rod 34 forms the inner peripheral surface of the work 1B including the key portions 3 and 4, and has a substantially cylindrical shape.

The upper first punch 36 forms the outer peripheral surface and side surface 4a of the key portion 4 and the other end surface of the work 1B. The upper first punch 36 has a substantially cylindrical shape whose axial direction is the vertical direction. It fits between the core rod 21 and the core rod 34 slidably and removably from above. And the first
The punch 36 has two punch fitting grooves 36 extending vertically.
a are formed 180 ° apart from each other. These punch fitting grooves 36a are formed as concave grooves opened on the inner peripheral surface and the lower end surface of the upper first punch 36, and the outer peripheral portion of the upper first punch 36 extends over the entire circumference up to the lower end surface. Continuous cylindrical part
36b. Further, the upper second punch 38 forms an end face of the key portion 4 and has a square rod shape whose axial direction is the vertical direction, and fits in the punch fitting groove 36a of the upper first punch 36. I agree.

Further, as shown in FIGS. 1 and 2, on the inner peripheral surface of the die 21, four convex strips 41, 42 extending in the vertical direction are provided.
Are formed. These ridges 41, 42 are located at positions about 45 ° apart from the key portions 3, 4 of the green compact 1B. on the other hand,
Recessed grooves 43, 44, 45, and 46 are formed on the outer peripheral surfaces of the lower first punch 26 and the upper first punch 36 so as to extend in the vertical direction and slidably fit into the ridges 41, 42 of the die 21, respectively. ing. A pair of the ridges 41 and 42 and the grooves 43, 44, 45 and 46 has a substantially arc-shaped cross section, while the other pair has a substantially rectangular cross section. And has two substantially right-angled corners.

Next, the operation of the above configuration will be described. When the Oldham ring 1 is manufactured, first, a green compact is formed by a powder forming press in which the powder molding die apparatus is assembled (powder forming step). In this powder molding step, as shown in FIG. 3A, first, the upper first punch 36 and the upper second punch 38 are pulled out of the die 21 and the raw material is fed into the die 21 by a feeder (not shown). The powder P is filled. At this time, in the die 21,
The upper ends of the lower second punch 29 and the lower third punch 32 are located lower than the upper end of the lower first punch 26, and the key portions 3 and 4 are filled with the corresponding amount of the raw material powder P. .

Thereafter, the upper first punch 36 and the upper second punch 38 are lowered and fitted into the die 21, and the die 21 is lowered, and the punches 26, 29,
The raw material powder P is compressed by 32, 36, and 38. At the same time, the lower first punch 26 is lowered, and when pressurization is completed, the upper end of the lower first punch 26 and the upper end of the lower third punch 32 are located at the same height. The lower second punch 29 is lowered, and at the time of completion of pressurization, the upper end of the lower second punch 29 is located lower than the upper end of the lower first punch 26, but the lowering amount of the lower second punch 29 is lower than the lower first punch 29. It is smaller than the descending amount of the punch 26. Thus, the key portions 3 and 4 of the work 1B and the ring main body 2 are compressed at the same compression ratio.

After the pressurization is completed and the lower second punch 29 and the lower third punch 32 are stopped, the lower first punch 26 is slightly lowered, whereby the key portion 3 is removed from the lower first punch 26. Will be issued. After that, the die 21 continues to descend further, whereby the work 1B formed as shown in FIG.
Extracted from 21. Next, the upper first punch 36 and the upper second punch 38 are raised, but when the upper first punch 36 is raised, the cylinder device is driven to hold the upper second punch 38 in a stopped state for a predetermined period of time. The part 4 is extracted from the upper first punch 36.

After the work 1B extracted as described above is paid out, the die 21 and the punches 26, 29, 32, 36, 38 are formed.
Then, the core rod 34 returns to the state shown in FIG. 3A, the raw material powder P is filled again, and the molding is repeated. 4 to 6 show the formed work 1B.

The work 1B thus formed is heated and sintered in a sintering furnace (sintering step). Next, the sintered work (sintered body) 1B is recompressed and straightened by a straightening press (straightening step). This straightening step is for adjusting the shape and dimensions. Next, the work 1B is subjected to deburring and cutting (cutting step). In this cutting step, the outer peripheral portion of the work 1B (the portion on the outer peripheral side from the chain line a in FIG. 5) is cut.
As shown in FIGS. 8 to 10, the key portions 3, 4 protrude radially outward from the ring main body 2. By this cutting, the concave grooves 5 and 6 formed on the outer peripheral surface of the work 1B by the ridges 41 and 42 of the die 21 disappear, and do not remain in the Oldham ring 1 as a final product. That is, the die
This is because the 21 ridges 41 and 42 are formed at positions corresponding to the cut portions of the work 1B. Further, a gas nitrocarburizing process, which is a heat treatment for forming a nitride film for improving wear resistance and fatigue strength, is performed (gas nitrocarburizing process).

According to the configuration of the above embodiment, when the raw material powder P is compressed by the punches 26, 29, 32, 36, and 38 in the die 21 in the powder molding process, the protrusions 41 and 42 of the die 21 The grooves 43 and 44 of the first punch 26 and the grooves of the upper first punch 36
The fitting of the first and second punches 45 and 46 prevents the lower first punch 26 and the upper first punch 36 from being twisted by the pressurizing force, that is, preventing a positional shift in the circumferential direction. Moreover, since the pair of the ridges 41 and the concave grooves 43 and 45 have a substantially rectangular cross section, the lower first punch 26 and the upper first
The rotation of the punch 36 is more reliably prevented. Thus, the position of the side surface 3a of the key portion 3 on one end surface of the work 1B formed by the lower first punch 26 and the side surface 4a of the key portion 4 on the other end surface of the work 1B formed by the upper first punch 36 The positions are accurately regulated, and the accuracy of the predetermined angle θ formed by the side surfaces 3a and 4a of the key portions 3 and 4 on both end surfaces of the work 1B can be improved.

The lower second punch 29 and the lower third punch 29
32 is fitted in the punch fitting groove 26a of the lower first punch 26, and the upper second punch 38 is fitted in the punch fitting groove 36 of the upper first punch 36.
a, but these punch fitting grooves 26a and 36a are concave grooves opened on the inner peripheral surfaces of the punches 26 and 36, and the outer peripheral portions of the punches 26 and 36 are continuous over the entire circumference. Cylindrical part 26
b, 36b, the punches 26, 36 have high rigidity and the punch fitting grooves forming the side surfaces 3a, 4a of the key portions 3, 4
It is suppressed that the widths of 26a and 36a change and become wider due to the pressing of the raw material powder P. Thereby, the accuracy of the key portions 3 and 4 is further improved.

In this way, the position accuracy of the side surfaces 3a and 4a of the key portions 3 and 4 can be increased in the powder molding stage, and the side surfaces 3a and 4a of the key portions 3 and 4 are cut to improve the accuracy. It is no longer necessary to perform That is, the perpendicularity of the side surfaces 3a and 4a of the key portions 3 and 4 can be increased without performing this cutting process. Therefore, the reliability of the operation of the Oldham ring 1 can be ensured, and the number of cutting steps can be reduced, so that the manufacturing cost can be reduced.

As described above, the ridge 41 and the groove 43,
To make the cross-sectional shape of 45 almost rectangular, punch 26,
36 has the advantage of being able to prevent twisting more reliably,
Processing is easier if it is constituted by a smooth curved surface such as 42 and concave grooves 44 and 46. In the above embodiment, the torsion of the punches 26 and 36 is achieved by combining the ridges 41 and the grooves 43 and 45 having a substantially rectangular cross section with the ridges 42 and the grooves 44 and 46 having a substantially arc-shaped cross section. The aim is to achieve both the prevention effect and the suppression of increase in processing cost.

Further, a work 1B manufactured by powder metallurgy
Has pores, but when it is cut, the pores on the surface are sealed. In the Oldham ring 1, a nitride film is formed on the surface by a gas nitrocarburizing treatment as a surface treatment at the last stage of the production, but if the pores on the surface of the work 1B are crushed, the gas does not penetrate into the inside. , The effect of the processing is weakened. On the other hand, in the present embodiment, the side surfaces 3a and 4a of the key portions 3 and 4 of the work 1B are not subjected to the cutting process, and the pores are not sealed on the side surfaces 3a and 4a. Effective gas nitrocarburizing can be performed. Therefore, the wear resistance and fatigue strength of both side surfaces 3a and 4a of the key portions 3 and 4 are surely improved, and the reliability of the operation of the Oldham ring 1 is further improved.

Further, the concave grooves 5 and 6 formed on the outer peripheral surface of the work 1B by the convex strips 41 and 42 of the die 21 are formed at positions where the outer peripheral portion of the work 1B is finally cut. Irrespective of the final product shape, twisting of the punches 26, 36 by the ridges 41, 42 and the concave grooves 43, 44, 45, 46 can be realized.

It should be noted that the present invention is not limited to the above embodiment, and various modifications can be made. For example,
FIG. 7 shows the ridges 41 of the die 21 and the grooves 43, 43 of the punches 26, 36.
A work 1B formed when all of the cross-sectional shapes of 45 are substantially rectangular is shown. According to this configuration, the prevention of the rotation of the punches 26 and 36 with respect to the die 21 can be further ensured. In the above embodiment, the ridges 41 and 42 are formed on the die 21.
And the grooves 43, 44, 45 and 46 are formed in the punches 26 and 36. However, the grooves may be formed in the die and the ridges may be formed in the punch. This configuration is advantageous particularly when a large cutting allowance cannot be secured on the outer peripheral surface of the work. On the other hand, when the cutting allowance of the outer peripheral surface of the work is large, as in the above-described embodiment,
The ridges 41 and 42 are formed on the die 21, and the grooves 43 and 42 are formed on the punches 26 and 36.
The configuration in which 44, 45, and 46 are formed also has the effect of reducing waste of raw materials. Further, the shapes, numbers and positions of the ridges and grooves formed on the die and the punch are not limited to those in the above-described embodiment, but can be set as appropriate.

[0033]

According to the first aspect of the present invention, the peripheral surface has a substantially circular shape and has projections on both end surfaces, and the projections on both end surfaces form a predetermined angle with respect to the center axis of the circle. Molding apparatus for molding a green compact to be an Oldham's ring, comprising a concave portion extending on one of an inner peripheral surface of a die and an outer peripheral surface of a main punch, the concave extending in the moving direction of the die and the main punch. Since the groove is formed and a ridge slidably fitted in the groove is formed on the other side, it is possible to prevent the main punch from being twisted when the raw material powder is pressed. The sub-punch forming the end face of the protrusion of the green compact or the portion corresponding to the back side of the protrusion on the end face of the green compact is fitted in the punch fitting groove of the main punch. The groove was formed as a concave groove opening on the inner peripheral surface of the main punch, and the outer peripheral portion of the main punch was formed as a continuous cylindrical portion over the entire circumference. Changes due to the pressing of the raw material powder can be suppressed, and the accuracy of the projection can be further improved. Therefore, the positional accuracy of the projections can be increased at the stage of powder molding, and cutting of the projections for improving the accuracy can be eliminated.

According to the second aspect of the present invention, in addition to the effect of the first aspect, the sectional shape of the concave groove and the convex ridge is substantially rectangular. Therefore, the punch can be more reliably prevented from being twisted when the raw material powder is pressed.

According to the third aspect of the present invention, there is provided a powder molding die apparatus used for manufacturing an Oldham ring.
In addition to the effect of the invention of the present invention, the green compact is the one whose outer peripheral surface is cut after sintering, while the ridges or grooves correspond to the cut portion in the green compact. Therefore, it is possible to prevent the punch from being twisted by the ridges and grooves regardless of the shape of the final product.

[Brief description of the drawings]

FIG. 1 is a horizontal sectional view showing an embodiment of a powder molding die apparatus used for manufacturing an Oldham ring of the present invention, including a position including a lower punch.

FIG. 2 is a horizontal sectional view of a position including the upper punch.

FIG. 3 is a longitudinal sectional view of the powder molding die apparatus, in which (a) on the left side of the center line shows a filling step, and (b) on the right side of the center line shows a drawing step.

FIG. 4 is a perspective view of a work which is a green compact to be molded;

FIG. 5 is a plan view of the work.

FIG. 6 is a sectional view of the work.

FIG. 7 is a plan view of a work showing another embodiment of a powder molding die apparatus used for manufacturing the Oldham ring of the present invention.

FIG. 8 is a perspective view of an Oldham ring to be manufactured.

FIG. 9 is a plan view of the same Oldham ring.

FIG. 10 is a side view of the same Oldham ring.

FIG. 11 is a horizontal sectional view showing an example of a conventional powder molding die apparatus.

FIG. 12 is a longitudinal sectional view of the powder molding die apparatus, in which (a) on the left side of the center line shows a filling step, and (b) on the right side of the center line shows a removing step.

FIG. 13 is a perspective view of a work which is a green compact formed by a conventional powder molding die apparatus.

[Explanation of symbols]

 1B Work (compact) 3, 4 Key part (projection) 21 Die 26 Lower first punch (main punch) 26a Punch fitting groove 26b Tubular part 29 Lower second punch (sub punch) 32 Lower third punch (Auxiliary punch) 36 Upper first punch (Main punch) 36a Punch fitting groove 36b Tubular portion 38 Upper second punch (Auxiliary punch) 41,42 Convex ridges 43,44,45,46 Concave groove

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Junkichi Soma 3-1, Koganecho, Niigata City, Niigata Prefecture Mitsubishi Materia Co., Ltd. Niigata Works (72) Inventor Kazushi Koda 3-1, Koganecho, Niigata City, Niigata Mitsubishi Material Co., Ltd. Niigata Works

Claims (3)

[Claims] 1. A powder compact which is an Oldham ring whose peripheral surface is substantially circular and has projections on both end surfaces, and the projections on both end surfaces are positioned at a predetermined angle with respect to the center axis of the circle. A powder molding die apparatus for molding a body, a die forming an outer peripheral surface of a green compact, a core rod forming an inner peripheral surface of the green compact, and slidably fitted between the die and the core rod. A main punch that forms a portion other than the protrusion and a side surface of the protrusion on the end face of the green compact; and an end face or the powder of the protrusion of the green compact that is slidably provided in the same direction as the main punch. A sub-punch forming a portion corresponding to the back side of the protrusion on the end surface of the body, wherein the main punch is opened to an inner peripheral surface thereof and has a groove-shaped punch into which the sub-punch is slidably fitted. With a fitting groove, the outer circumference extends all around. A continuous groove is formed on one of the inner peripheral surface of the die and the outer peripheral surface of the main punch, and a groove extending in the moving direction of the die and the main punch is formed on the other. A mold apparatus for powder molding used for manufacturing an Oldham ring, wherein a ridge that is slidably fitted is formed. 2. The powder molding die apparatus for use in manufacturing an Oldham ring according to claim 1, wherein the cross-sectional shape of the concave groove and the convex ridge is substantially rectangular. 3. An outer peripheral surface of the green compact is cut after being sintered, and the ridges or grooves are formed at positions corresponding to cut portions in the green compact. A mold apparatus for powder molding used for manufacturing the Oldham ring according to claim 1 or 2.