JPH0372007A - Manufacture of sintered cam - Google Patents

Abstract

PURPOSE:To easily manufacture a light hollow sintered cam piece by injecting raw material for sintering into cavity, which is formed by assembling a die for forming and plural movable pins, and sintering the obtd. hollow formed body. CONSTITUTION:In the cavity 2 for forming the cam piece, a first movable pin 3 is inserted and into the formed cavity 2a for forming a cam nose part, the material for injection molding is injected to form the cam nose part formed body W1'. The first movable pin 3 is retreated and a second movable pin 4 is inserted to close an opening part with a third movable pin 5. Into the formed cavity 2b for forming a cam base part, the raw material for forming is injected to form the cam base part formed body W2'. The hollow cam piece formed body W' with the above both formed bodies W1', W2' joined, is sintered under nitrogen atmosphere, etc., to manufacture the hollow sintered cam piece W.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a method for manufacturing a sintered cam.

(Prior art and invention or problem to be solved) In recent years,
As the demand for higher output and lighter weight automobile engines increases, lightweight camshafts using hollow vibrators are being developed to meet these demands, and are being put into practical use in some cases. . It is obvious that in such a lightweight camshaft, if not only the shaft part but also the cam piece part can be made lighter, the weight reduction effect can be further increased. However, it has not yet been put into practical use due to the accompanying problems.

Now, various processing and forming techniques have traditionally been selected for forming metal parts in terms of the required shape, cost, and material properties, but in recent years, various processing and forming techniques have been selected that can produce composite parts, save resources, etc. Powder metallurgy technology is attracting attention because of its characteristics.

As the above-mentioned powder metallurgy technology, for example, sintering, which sinters metal powder, is well known. The sintering process involves forming metal powder into a predetermined shape using methods such as press molding, slurry casting, extrusion, and injection molding, followed by sintering and, if necessary, post-processing. A method is adopted in which the product is manufactured by applying

Among the above-mentioned moldability methods, in the injection molding method, an injection molded product is obtained by injecting a raw material for injection molding, which is made by adding a binder to metal powder and kneading it, into a predetermined mold. This method has good dimensional accuracy, homogeneity, and relatively ms
In recent years, this method has been attracting particular attention as a method for obtaining molded products for sintering, as it has the advantage of being able to produce molded products of various shapes in large quantities.

Therefore, the present inventors made various attempts to obtain a hollow cam molded product for sintering by mold injection molding. ! We have come to know that hollow injection molded products for sintering can be manufactured extremely easily by combining several movable pins.

Note that Japanese Patent Publication No. 58-25723 discloses a method for manufacturing a cam 7 shaft by press-fitting a sintering molded body into a cam shape into a hollow/yaft member and then subjecting it to sintering treatment. However, in this known example, the point that the cam piece has a hollow structure is not considered at all.

The present invention has been made in view of the above points, and by combining an indexing mold and a plurality of movable pins,
It is an object of the present invention to make it possible to injection mold a hollow injection molded product for sintering, thereby making it possible to manufacture a sintered hollow cam extremely easily.

(Means for Solving the Problems) In the present invention, as a means for solving the above problems, a first movable pin is inserted into a cam piece molding cavity formed by an injection mold. After forming a cam nose molding cavity around the movable pin and injecting the sintering raw material into the cam nose molding cavity, the first movable pin is moved out of the cam piece molding cavity 11'l, and the cam piece is molded. A second movable pin that has a diameter corresponding to the shaft hole of the cam piece and moves orthogonally to the first movable pin is inserted into the space formed at the exit mark of the first movable pin in the molding cavity, and further, An opening formed in the exit direction of the first movable pin in the cam piece molding cavity is closed by a third movable pin to form a cam base molding cavity surrounded by the second and third movable pins, and the cam base molding is performed. By injecting the raw material for sintering into the cavity,
An internally hollow sintered cam molded body is molded and then sintered.

(Function) In the present invention, the following effects can be obtained by the above means.

That is, injection molding into the cam nose molding cavity after the first movable pin is inserted into the cam piece molding cavity, pushing the second movable pin into the cam piece molding cavity after the first movable pin is withdrawn, and the second movable pin is inserted into the cam piece molding cavity. A hollow part in the molded body for sintering the cam piece is formed by injection molding into the cavity for molding the cam base part formed by closing the opening in the direction of exit of the first movable pin by the third movable pin.

(Effects of the Invention) According to the present invention, the first movable pin is inserted into the cam piece molding cavity formed by the injection mold, and the cam nose molding cavity is formed around the first movable pin. After injecting the sintering raw material into the cam nose immediate molding cavity, the first movable pin is moved out of the cam piece molding cavity, and a sintering material is formed at the exit trace of the first movable pin in the cam piece molding cavity. A second movable pin having a diameter corresponding to the shaft hole of the cam piece and moving orthogonally to the first movable pin is inserted into the space, and further, a second movable pin is formed in the cam piece molding cavity in the exit direction of the first movable pin. By closing the opening with a third movable pin to form a cam base molding cavity surrounded by the second and third movable pins, and injecting raw material for sintering into the cam base ready molding cavity, the internal hollow is closed. Since the sintered cam molded body is molded and then sintered, injection molding into the cam nose molding cavity after the first movable pin is inserted into the cam piece molding cavity, and the first movable pin are performed. The cam piece is sintered by injection molding into the cam base molding cavity formed by inserting the second movable pin into the cam piece molding cavity and closing the opening in the exit direction of the first movable pin with the third movable pin after the withdrawal of the cam piece. The hollow portion in the molded body for sintering the cam piece can be formed very easily, and by sintering this molded body for sintering the cam piece, there is an excellent effect that a lightweight cam piece can be manufactured extremely easily.

(Example) Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

The sintered cam manufactured according to this embodiment is used as a hollow cam piece W that is fitted onto a hollow camshaft S, as shown in FIG.

The cam piece W is obtained by sintering a cam piece-shaped injection molded product that has been injection molded using the cam piece molding die 1 shown in FIGS. 1 to 4.

The mold 1 consists of a fixed mold 1a and a movable mold 1b which can be joined to and separated from the fixed mold 1a, and a cam piece molding cavity 2 is formed between the two. ing.

A first movable pin 3 inserted into the cam piece molding cavity 2 is attached to the fixed mold 1a so as to be movable forward and backward. The first movable pin 3 has a similar shape to the cam nose portion W of the cam piece W (see FIGS. 6 and 7), and is configured to be moved forward and backward from the cam nose portion molding side of the cam piece molding cavity 2. It has become. Reference numeral 3a is a boss portion for preventing the injection molding raw material from entering the portion of the cam piece W where the shaft hole W 3 (see FIGS. 6 and 7) is formed. When the first movable pin 3 is inserted into the cam piece molding cavity 2, a cam nose molding cavity 2a is formed around the first movable pin 3 (see Fig. 1). and Figure 2). Further, in the fixed mold 1a, after the first movable pin 3 leaves the cam piece molding cavity 2, a second movable pin 4 is inserted into a portion corresponding to the shaft hole W3 in the cam piece molding cavity 2. is attached so that it can move forward and backward. The second movable pin 4 has the same diameter as the shaft hole W3.

Furthermore, a pair of third movable pins 5°5 are attached to the fixed mold 1a, and are movable in a direction opposite to the first movable pin 3 and perpendicular to the second movable pin 4. There is. The third movable pins 5, 5 have a molded surface 5a having the same shape as the surface shape of half of the cam base portion W in the cam piece W;
5a, and a guide member 5b5b having the same shape as the half-top surface of the first movable pin 3, and both are movable toward or away from each other. and,
After the first movable pin 3 leaves the cam piece molding cavity 2, the second movable pin 4 is inserted into the cam piece molding cavity 2, and the third movable pins 5, 5 are inserted into the cam piece molding cavity 2.
By bringing them close together, the cam base molding cavity 2 surrounded by the second movable pin 4 and the third movable pin 5.5 is formed.
(See Figures 3 and 4). Reference numeral 6 denotes a first injection gate for injecting raw material for injection molding into the cavity 2a for molding the cam nose part, 7 a second injection gate for injecting raw material for injection molding into the cavity 2b for molding the cam base part, and 8 a cam base. This is an air vent gate for venting air from the molding cavity 2b.

Next, the method for manufacturing a sintered cam of the present invention will be explained in detail based on a specific example.

First, raw materials for injection molding are prepared as follows.

Examples of metal powder used as a raw material for sintering include iron powder with a particle size of 20 μm or less (Si: 0.8% by weight, Cr
: I3.5fiffi%, Mo: 0.2% by weight, V: 0
, 2% by weight, C: 2.0% by weight, balance Fe).

In addition, as a binder added to the above raw material for sintering,
For example, ethylene acetate M vinyl alcohol and acrylic resin are used as thermoplastic resins, wax and dibutyl phthalate as plasticizers, and sublimable hydrocarbons as sublimation agents.

Then, the metal powder and binder are kneaded in the following proportions to prepare a raw material for injection molding.

The α-ray temperature and time at this time are 1200CX 30m
This was done by adding metal powder to the molten binder.

Metal powder 90% by weight ethylene vinyl acetate alcohol 3.7% by weight ft% acrylic resin
2.0% by weight Wanox
2.0% by weight dibutyl phthalate
1.2% by weight sublimable hydrocarbon 1.1
% by weight Thereafter, the raw material for injection molding prepared as described above is injected into the injection mold (2) to form an injection molded product W' in the shape of a cam piece.The procedure is as follows. explain.

First, the movable mold 1b is fitted to the fixed mold 1a in the mold l, and the first movable pin 3 is inserted into the cam piece molding cavity 2 formed between the two. A cavity 2a for the cam nose portion I is formed around it (see FIGS. 1 and 2). At this time, the second movable pin 4 and the third movable pins 5, 5 are positioned at the standby position.

Under this condition, when the injection molding raw material prepared as described above is injected from the first injection gate 6 into the cam nose molding cavity 2a, the cam nose ready molded body W,' shown in FIG. 5 is molded. . The injection molding conditions at this time were a molding temperature of 90°C, an injection pressure of 243Q kg/cm', and a molding time of 1 minute. Thereafter, the first movable pin 3 is withdrawn from the cam piece molding cavity 2, and the second movable pin 4 is inserted into the space formed in the exit trace of the first movable pin 3 in the cam piece molding cavity 2. , the first in the cam piece molding cavity 2
The opening formed in the exit direction of the movable pin 3 is closed by the third movable pins 5, 5 to form a cam base molding cavity 2b surrounded by the second movable pin 4 and the third movable pin 5, 5 ( (See Figures 3 and 4). Under this condition, when the raw material for injection molding prepared as described above is injected from the second injection gate 7 into the cam base molding cavity 2b, the cam base molded body W is joined to the cam nose molded body W+'. , ' are formed, and a hollow cam piece molded body W' is formed by both. The injection molding conditions at this time were as described above: molding crystallinity: 90'CJ injection pressure: 2430 kg/cm', molding time: 1 minute.

The cam piece molded body W' obtained as described above was heated at 600°C for 5 hours in a nitrogen atmosphere (5 atm).
r.

After performing degreasing treatment by increasing the temperature at 10°C/hr to remove the binder in the cam piece molded body W, the temperature was increased to 1110°C.
When sintering was performed at x 30 m1n (in vacuum), a hollow sintered cam piece W was obtained (FIGS. 6 and 7).

For the sintered cam piece W obtained as above,
Quenching (900°CX 30ml → oil quenching) and tempering (550X 100ml → oil cooling) are performed.

The sintered cam piece W thus obtained is fixedly joined to a predetermined position of a hollow shaft S made of a high-strength material (for example, STKM16A) (see FIG. 8).

In this embodiment, a pin having a head shape similar to that of the cam nose is used as the first movable pin, but it may be of any other shape as long as a hollow portion can be formed in the cam nose. . Also.

A pair of two movable pins are used as the third movable pin, but 1
You can also use the one from the book.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of the main part of the injection mold used in the method of manufacturing a sintered cam of the present invention at the time of the first injection, and Fig. 2 is a cross-sectional view taken along Figure 3 shows the second injection mold used for manufacturing the sintered cam of the present invention.
Figure 4 is a sectional view of the main parts showing the state at the time of re-injection.
5 is a front view of the molded body molded by the first injection in the injection mold used in the method of manufacturing a sintered cam of the present invention, and FIG. 6 is a sectional view of the present invention. FIG. 7 is a front view of the sintered cam piece manufactured by the method of the invention, FIG. 7 is a sectional view taken along the line ■-■ of FIG. 6, and FIG. FIG. 1... Injection mold 2... Cam piece molding cavity 2a... Cam nose part molding cavity 2b... Cam base part molding cavity 3... First movable pin 4... Second movable pin 5 ...Third movable pin W...Cam piece W,...Cam nose part W,...Cam base part W3...Shaft hole Ws...-l Ya 7 To 8

Claims (1)

[Claims] 1. Insert a first movable pin into a cam piece molding cavity formed by an injection mold to form a cam nose molding cavity around the first movable pin, and into the cam nose molding cavity. After injecting the sintering raw material, the first movable pin is moved out of the cam piece molding cavity, and a space formed at the exit trace of the first movable pin in the cam piece molding cavity corresponds to the shaft hole of the cam piece. A second movable pin having a diameter and moving orthogonally to the first movable pin is inserted, and further, an opening formed in the exit direction of the first movable pin in the cam piece molding cavity is closed by a third movable pin. A cam base molding cavity surrounded by the second and third movable pins is formed, and a sintering raw material is injected into the cam base molding cavity to mold a hollow sintered cam molded body. A method for manufacturing a sintered cam, which comprises: and then sintering.