JPH0819444B2 - Manufacturing method of sintered parts - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION OBJECT OF THE INVENTION (a) Field of Industrial Application This invention relates to a method of combining two or more green compacts to sinter in order to form a part having a complicated shape by the powder metallurgy method, and high positioning accuracy and high transmission torque. The present invention relates to a method of manufacturing a component having a.

(B) Prior art Conventionally, in order to manufacture a component having a complicated shape by powder metallurgy, two or more green compacts (molded products before press-molding and sintering metal powder) are produced, and the uneven portions are fitted. It is performed by heat-sintering together and using the difference in shrinkage dimension change in the sintering process depending on the material.

This method is inexpensive because it does not require brazing and machining, but since shrinkage occurs at high temperature during sintering of the sintered part, strength like shrinkage fitting of metal cannot be obtained, and therefore weak torque ( It is rarely used because the displacement between parts occurs due to the rotational moment) and the displacement between the positions in the axial direction becomes large.

On the other hand, the applicant has proposed a utility model registration application as a Japanese Utility Model Application No. 61-46833 by devising a sintered component which makes positioning in the rotational direction and transmission torque large when a gap is not provided between the two components.

The manufacturing method of the present invention (hereinafter referred to as the first method) is obtained by combining and sintering the green compact of the cam part (10) shown in FIG. 7 (a) and the circular part (13) shown in FIG. 7 (b). Section 7th
When manufacturing parts such as those shown in Fig. 7 (d) and perspective view (c), we decided to combine concave parts (12) and convex parts (15) on the mating surfaces of both parts and sinter them together. Therefore, it is a method that improves positioning and torque transmission.

As another method (hereinafter referred to as the second method), as shown in FIG. 8 (a), in the case of a component having a gap between the components, for example, a spur gear and a chain sprocket are coaxially combined. A spur gear (16) with a D cut (17) (thickness circle) in part of the shaft hole and a sprocket part shown in Fig. 8 (b) with a D cut (18) (thickness circle) in the shaft Fig. 7 (c) is a cross section of the green compact of (19) combined and sintered.
There is also a method of manufacturing a combination part as shown in FIG.

(C) Problems to be Solved by the Invention However, in the first method, (1) it can be used only for a component in which end faces of a bonded component are in close contact with each other.

(2) Since it is necessary to assemble while looking for the uneven positions of the two green compacts, the work efficiency of the assembly is poor.

(3) Due to the technical reason of press molding of green compact, the size of the uneven portion is limited, and thus it is not suitable for products requiring high transmission torque.

There are problems such as.

On the other hand, in the second method (1) Considering the spring back during press molding and the dimensional change during sintering, the D-cut portion must have a shape having a slight gap r as shown in FIG. 8 (d). Therefore, as shown in the figure, an error of the angle θ occurs in the positioning in the rotation direction, and the accuracy thereof is deteriorated.

(2) Due to the same reason as in (1), it is difficult to make the dimensions such that the entire circumference including the D-cut portion is joined uniformly, and the joining area is reduced, and the joining strength in the drawing direction (vertical direction) is reduced. Is reduced.

(3) Since the hole and the shaft are simply combined, the positioning accuracy in the height direction is poor.

There are problems such as.

The present invention is an inexpensive method which eliminates the drawbacks of the above-mentioned conventional method for producing a joined component having a gap, particularly a component required to have a high transmission torque and a high dimensional accuracy of the gap by combining a plurality of green compacts and sintering. The purpose is to provide a joining method.

B. Configuration of the Invention (a) Means for Solving the Problem To manufacture a coupling component having a gap by fitting and sintering two or more green compacts each having a hole and a shaft, The convex and concave portions are provided at two or more portions on the inner surface of the body hole and the outer surface of the shaft. In that case, the dimensions are different between each of the two or more irregularities. Furthermore, on the shaft side of the mating surface, 0 according to the size of the gap of the connected parts.
There is a step of 1 mm or more.

Due to the mutual dimensional difference between the concave and convex portions, there is an effect of preventing directional mistakes in the combination work. Further, in such a jointed part in which a green compact is combined, the uneven portion functions as a key after sintering. Therefore, in addition to the torque resistance in the rotation direction of the joining (fitting) surface due to the difference in shrinkage ratio, the key (unevenness A high torque resistance is obtained by adding torque resistance enough to break the part). Further, since the step of the shaft portion of the green compact can be formed easily, that is, inexpensively and precisely by using the press die, it is possible to obtain high accuracy of positioning and gap dimension.

 Specific examples of the present invention will be described below with reference to the drawings.

As shown in the cross section in FIG. 1 (c), a sprocket wheel (3) on the upper part and a spur gear (1) on the lower part are coaxially connected with a shaft part (6) with a space between them. Figure 1 (a)
1 and the powder compact of the sprocket component (2) having the sprocket wheel (3) shown in FIG. 1 (b) are combined and sintered.

According to the present invention, as shown in FIGS. 3 and 4, the green compact of the gear part (1) is provided with holes (9) having a diameter D ₂ , and two radii are formed inside the holes (9). A semi-circular convex portion (4) of R _{1 and} a semi-circular convex portion (5) of radius R ₂ (R ₁ and R ₂ are different dimensions) are provided. The sprocket part (2) is provided with a shaft (6) having a diameter D ₁ = D ₂ -α which fits into the hole (9) of the gear part (1), and the shaft (6) has a hole (9) Recesses (7) with radius R ₁ and radius R _{2 at} the positions corresponding to the protrusions, respectively.
The recess (8) is provided. The shaft (6) has a large diameter with a step of β in the figure compared with the part fitted into the hole at a part at a distance h from the sprocket wheel (3). The two green compacts are assembled by fitting the hole (9) and the shaft (6) to the step portion while aligning the convex portion and the concave portion.
The assembled combined green compact is sintered to produce a joined part.

A sectional view of another embodiment of the method of the present invention is shown in FIG. In this example, a part in which a sprocket wheel (20), a stepped gear (21), and a flanged heart cam (22) are combined is manufactured. In this case, the hole of the stepped gear (21) in the state of green compact,
Each of the holes of the flanged heart cam (22) has a plurality of protrusions, and the shaft portion of the sprocket wheel component has a recess at a position corresponding to the protrusion of the hole. Further, as shown in the drawing, the stepped gear (21) of the sprocket wheel (20),
A step of 0.1 mm or more is sequentially formed on the shaft according to the distance between the stepped gear (21) and the flanged heart cam (22). When such powder compacts are combined and sintered to form a joint part, a composite sintered part having three functions of a sprocket, a gear and a cam can be manufactured with high accuracy and high torque resistance. .

(B) Action The features of the method of the present invention will be described with reference to the first specific example. When two green compacts are assembled, the shapes of the positioning protrusions and recesses at two locations (a plurality of locations) in the rotational direction, Since the dimensions are made so that the difference can be easily recognized with the naked eye, the efficiency of the assembling work can be improved and the assembling defect can be prevented. For example, if the concavo-convex part is placed at a position shifted by 180 °, the assembly may be shifted by 180 °. Because they are crazy and assembled.

The protrusions and recesses are molded with a powder compacting mold, and this mold can be manufactured with high accuracy, but it requires clearance between the molds and the difference in the amount of powder filling filling, that is, the density difference. Due to the difference in the amount of spring back, if there is only one uneven portion, a slight deviation occurs in the rotational direction of the connected component, and the positioning accuracy in the rotational direction becomes poor. If this deviation is provided at two or more convex portions and concave portions, the angular error becomes small and the positioning accuracy is improved.

The diameter D ₂ of the hole in the fitting portion of the green compact is larger than the diameter D ₁ of the shaft by α, and this α amount is the assembly clearance. The smaller this clearance is, the higher the bonding strength at the time of sintering will be, which is preferable, but if it is too small, the efficiency of the combining operation will be deteriorated. Normally set to 0.01 to 0.04 mm. Therefore, the step difference β for positioning in the height direction may be equal to or more than the above clearance, and accordingly may be 0.1 mm or more, which is a very small dimension. With such an extremely small size of 0.1 mm or more, it is possible to integrally mold the green compact. The precision of the die that determines the position of the step (gap, h dimension) is about ± 0.02 mm, and it is possible to transfer to the green compact with that precision. For example, in the case of the parts shown in FIG.
With respect to the positioning accuracy of (1), it is possible to obtain a highly accurate joint component by the positioning h dimension of the step of the green compact.

The case where two green compacts are combined has been described above.
It is clear that the same applies to the case where a plurality of green compacts are combined to produce a composite sintered component which requires three or more functions such as a sprocket, a gear and a cam as shown in FIG. is there.

(C) Example Gear powder compact as shown in FIG. 3 (a) and FIG. 3 (b)
The sprocket green compact shown in FIG. The gear green compact had 2 teeth and 24 teeth, and the sprocket wheel had 17 teeth. In that case, one set was provided with uneven portions at two places as in the present invention, and the step difference of the shaft was 0.1 mm. As another set, a D-cut hole and a shaft were provided to obtain a green compact having no step. Fifth that this green compact was fitted and sintered
We made a joint part whose cross section is shown in the figure, and conducted various tests while comparing the two. That is, the following steps are performed.

Sintering was performed at 1160 ° C. for 60 minutes in N ₂ gas atmosphere.

 The raw materials used are as follows.

The test results are shown in the table below.

From the above results, the parts manufactured by the method of the present invention have very good accuracy in the rotation direction and the clearance (height direction) and high torque resistance strength as compared with the parts manufactured by the conventional D-cut method. It can be seen that the pull-out strength indicating the mutual bonding strength is also strong.

C. Effects of the Invention As described in detail above, according to the method of the present invention, it is possible to easily and easily process a sintered part having a complicated shape, which is difficult to manufacture by integral molding using the powder metallurgy method, in the rotation direction and the height direction. Since it can be manufactured with a high degree of accuracy in positioning, it is possible to expand the applicable range in which a sintered part manufactured by the powder metallurgy method can be used as a substitute for a part manufactured by another method such as a precision casting part manufactured by a different manufacturing method (lost wax method). Further, since the transmission torque strength is higher than that of the conventional sintered parts, not only the parts used in a comparatively low load range such as office equipment but also the positioning accuracy is increased and the high strength sintered material is used by the method of the present invention. As a result, the application of parts by the powder metallurgy method can be applied to parts with a high precision and a high load range such as a power transmission mechanism of an automobile, which is very effective as a method for manufacturing a sintered part.

[Brief description of drawings]

1 (a) and 1 (b) are perspective views showing a green compact in the case of the method of the present invention, and FIG. 1 (c) is a cross-sectional view of manufactured parts. 2 (a), (b) and (c) are front sectional views of the same component. FIG. 3 is a plan sectional view of a green compact of the same part,
FIG. 4 is a sectional view taken along the line AA, and FIG. 5 is a front sectional view of the component. FIG. 6 shows 3 manufactured by the method of the present invention.
It is a sectional view of a part having a function, that is, a part in which a sprocket wheel, a stepped gear, and a cam part are combined. 7 (a) and 7 (b) are perspective views of a powder compact when a cam component is manufactured by the conventional first method, and FIGS. 7 (c) and 7 (d) are perspective views and cross sections of the same finished product. It is a figure. 8 (a) and 8 (b) are perspective views of a green compact when manufacturing a gear part having a gap by the conventional second method, and FIG. 8 (c) is a sectional view of the same finished product,
FIG. 8D is a sectional view taken along line BB. (1), (16) …… Gear parts, (2), (19), (20) …… Sprocket parts, (3) …… Sprocket wheels, (4), (5), (15) …… Convex part, (6), (14),
(18) …… Axis, (7), (8), (12) …… Concave, (9), (11),
(17) …… Hole, (10), (22) …… Cam parts, (13) …… Circular parts, (21) …… Stepped gears.

Claims (1)

[Claims] 1. A manufacturing method for manufacturing a joined component having a gap by fitting two or more green compacts by means of a hole and a shaft and sintering the same, at two or more positions on the inner surface of the hole. A green compact that has a convex or concave part with a size, a concave or convex part with a size corresponding to the corresponding position on the outer surface of the shaft, and a step of 0.1 mm or more according to the size of the gap on the shaft Sintered part manufacturing method characterized by mating