JPH09267198A - Powder compacting equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form parts with excellent accuracy by providing core rod supporting parts at two parts, i.e., at an upper part and a lower part of a lower punch with its center as a relief part, and supporting the core rod at two points to prevent eccentricity of a shaft hole. SOLUTION: The raw material powder is filled in a die cavity comprising a die 10, a lower punch 20, and a core rod 30, and compressed between an upper punch 40 and the lower punch 20 to obtain a green compact of the desired shape. In a powder compacting equipment, an inner diameter center part of the lower punch 20 is made to be relief part 22 of larger diameter than the core rod 30. An upper end supporting part 21 and a lower end supporting part 23 to the slidably fitted to the core rod 30 are provided on an upper end and a lower end of the inner diameter of the lower punch 20, and the core rod 30 is supported at two points. Eccentricity of the core rod 30 is hardly generated and parts of less deflection of a shaft hole can be manufactured without machining.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a powder molding apparatus mainly used in the field of powder metallurgy, and particularly in the case of molding a sintered machine part having a shaft hole such as a gear, the central axis of the product and its The present invention relates to a device capable of molding high-precision parts that are not displaced from the shaft hole.

[0002]

2. Description of the Related Art A powder molding in powder metallurgy is briefly described by taking a sintered gear as an example. A die cavity formed by a die for forming a gear tooth profile, a lower punch, and a core rod for forming a shaft hole of the gear is filled. By compressing the raw material powder between the upper punch and the lower punch, a product (compact) having a desired shape is obtained.

When powder is molded, the die and the lower punch move up and down relatively. Depending on which one is fixed to the press, the die set is assembled into the die fixed type and the lower punch movable type. It is roughly classified into a lower punch fixed type and a movable die type called the withdrawal die set. The former is often used for small mechanical presses, and the latter is suitable for mass-producing complex shaped parts with a relatively large press, and is the mainstream method for forming sintered mechanical parts.

FIG. 2 shows a general structure of a lower punch fixed die set, in which the lower punch 20 is a ground plate 5.
2 to the base of the press. Die 1
0 is fixed to the die plate 51, the core rod 30 is fixed to the column plate 53 fixed to the lower ram 60 of the press,
The die plate and the column plate are connected by a column 54 passing through the ground plate. So die 10
And the core rod 30 moves up and down at the same time according to the operation of the lower ram 60. By the way, the state shown in the drawing shows the compression molding state during the molding process in which the die cavity formation-raw material powder filling-compression molding-compacted powder discharge is one cycle.

[0005]

In the conventional powder molding die, in order to reduce the frictional resistance between the pressing die forming the die, for example, in the case of the lower punch 20, as shown in FIG. Only the upper end support portion 21 that slides with is finished to have a size that slides with the core rod, and a relief portion 22 having a large diameter is provided below it to prevent friction with the core rod. This is the same on the core rod side. There is a required clearance between the die and the upper and lower punches, and between the lower punch and the core rod that fit together, but the value is generally 10 to 3
It is about 0 mμ.

As can be seen from the structure of the die set, the total length of the core rod 30 is significantly longer than its diameter. Due to the clearance with the lower punch mentioned above, the core rod 30 originally standing in line with the center axis of the mold as shown by the dotted line in FIG. 2 is deformed and bent as shown by the solid line during compression molding. , Misalignment (generally called eccentricity) occurs.

Since the shaft hole of the sintered gear is formed by the core rod, if the core rod is eccentric, a powder compact with an eccentric shaft hole will be formed. Normally, the sizing after sintering is performed to correct the sintered part. However, even if the eccentricity of the shaft hole is sized, sufficient correction is almost impossible due to the springback of the member.

Further, although it is possible to turn and correct the shaft hole by using the outer diameter of the sintered body and the tooth surface as a proof, additional setup and shaving of chips and other extra man-hours and costs are required, and the powder metallurgy method is essential. The benefits of are lost. Under such circumstances, there has been a demand for the development of a powder molding device that does not cause eccentricity of the shaft hole.

[0009]

In the conventional apparatus, the core rod 30 has its upper portion supported only by the upper end supporting portion 21 of the lower punch 20, and the long lower portion is free, which causes a problem. it is conceivable that.

Therefore, core rod support portions are provided at two positions above and below the lower punch, and a clearance portion is provided in the middle thereof, and the core rod is supported at two points in the vicinity of the main portion thereof, thereby preventing the eccentricity of the core rod and causing a problem. Resolved.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION As shown in FIG. 1, the inner structure of the lower punch 20 is slightly improved while the overall structure of the die set remains unchanged. That is, in addition to the conventional upper end support portion 21 on the upper portion of the lower punch, the lower end support portion 2 is also formed on the lower portion of the lower punch.
3 and a large diameter relief portion 22 is provided in the middle, and the core rod 3
0 support has been improved to two-point support at the upper and lower ends of the lower punch.

Next, the molding apparatus according to the present invention and FIG.
Spur gears having a tooth tip diameter of 50 mm, a shaft hole diameter of 20 mm, and a thickness of 40 mm were molded by each of the conventional molding devices shown in FIG. In this case, the lower punch and the core rod were individually manufactured according to the new and old methods, but the same die and upper punch were used to eliminate the cause of the error.

As a result, the outer diameter (the tip diameter) and the deflection of the shaft hole, which were 0.04 in the conventional method, were reduced to 0.006 in the method of the present invention, and the accuracy of the gear was remarkably improved. It was confirmed.

Incidentally, although the core rod 30 may be fixed to the column plate 53 as in the conventional case, the lower end support portion 23 depends on the diameter and the total length of the core rod set from the specifications of the molded product.
Bending may occur further downward, and the effect may reach the shaft hole. In such a case, it is effective to rotatably support the core rod by the steel ball 70 illustrated in FIG. 1 or other appropriate means.

[0015]

In the molding apparatus of the present invention, since the eccentricity of the core rod hardly occurs, it is possible to manufacture a sintered gear having a shaft hole whose runout is significantly smaller than in the conventional case without machining.

[Brief description of drawings]

FIG. 1 is a diagram illustrating an embodiment of a powder molding apparatus according to the present invention.

FIG. 2 is a diagram illustrating a problem in a conventional powder molding apparatus.

[Explanation of symbols]

10 ... Die, 30 ... Core rod, 40 ... Upper punch 20 ... Lower punch, 21 ... Upper end support part, 22 ... Relief part, 2
3 ... Lower end support 51 ... Die plate, 52 ... Ground plate 53 ... Column plate, 54 ... Column 60 ... Lower ram, 70 ... Steel ball

Claims (2)

[Claims] 1. A raw material powder filled in a die cavity formed by a die 10, a lower punch 20, and a core rod 30 penetrating the die 10 is compressed between an upper punch 40 and a lower punch to press a raw material powder into a desired shape. In a powder molding apparatus for obtaining powder, the central portion of the inner diameter of the lower punch is a relief portion 22 having a diameter larger than that of the core rod, and an upper end support portion 21 and a lower end support portion 23 that slide with the core rod are respectively provided on the upper end and the lower end of the inner diameter of the lower punch. The powder molding apparatus characterized in that the core rod is supported at two points at the upper and lower ends of the lower punch by being provided. 2. The powder molding apparatus according to claim 1, wherein the attachment of the core rod to the apparatus is rotatably attached.