JPS61279329A - Gear forming metallic die - Google Patents

Abstract

PURPOSE:To prevent an insert from being damaged, etc., by dividing the insert into plural segments, and also providing a slit of a diameter direction and a hole linked with its slit, on each segment. CONSTITUTION:An insert 1 is divided into plural segments 1a-1d. As for each segment 1a-1d a slit 3 extending in a diameter direction is formed in a bottom corner part, respectively, and also a stress absorbing hole 4 is provided on the tip of the slit 3. The slit 3 is worked by a wire-cut discharge, and a polishing finish is executed to a mating face of each segment 1a-1d. By dividing the insert 1, a stress of its inside peripheral direction is decreased, and also by the slit 3 and the hole 4, a stress concentration and a bend of the bottom corner part are absorbed. Accordingly, a damage of the insert 1 is prevented, and also the gear accuracy is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a gear molding die used for forging gears having external teeth.

(Prior Art) This type of mold is formed from an insert having a tooth profile and a shrink ring into which the insert is fitted, and the insert is generally formed from an integral ring.

(Problem to be solved by the invention) However, the insert is prone to breakage due to stress concentration in most of the root cores on the inner periphery, and in particular, sealing forging is performed within the insert in an attempt to obtain a tooth profile with no underfill. For products, the stress that can withstand the use of a punch, that is, 200 to 25 ONf
An internal pressure P close to f/- acts on the insert, and a compressive stress δ in the radial direction is created within the insert due to the internal pressure P.
r, and a tensile stress δt in the circumferential direction is generated, and the tensile stress is defined as r, 2+ ro2 δ@ - (/ r, 2-r02 ), where the inner diameter of the tooth profile of the insert is .・P, which is larger than the internal pressure P, and therefore is weak against tensile stress. No matter how much the shrink ring is made double or triple, and the tightness is set large, there is a limit to how much it can be reinforced. Shrink rings are generally fitted in order from the inside to the outside in consideration of the reinforcing effect, so if the insert is damaged, even if you try to remove it and replace it, the tightness will be different from the original. Therefore, instead of just replacing the insert, the shrink ring must also be modified, resulting in problems such as short mold life and increased manufacturing costs.

(Means for Solving the Problems) The present invention aims to solve the problems, and provides a gear molding die comprising an insert having a gear and a shrink ring into which the insert is inserted. In,
The insert is divided into a plurality of segments, a radial slit and a hole connected to the slit are provided in the bottom corner of the segment, and the segment is press-fitted into a shrink ring having a tapered hole. shall be.

(Example) An example of the present invention will be described below based on the drawings (1)
indicates an insert, the insert (1) having a plurality of segments, four segments (1a) (
1bH1cH1d), and each segment (1a
) (1b)... A slit (3) extending in the radial direction is formed in the bottom corner of the tooth profile (2), and the slit (
A hole (4) was provided at the tip of (3). The shape of the hole (4) is a round hole that is elliptical in the radial direction and is formed smoothly to reduce stress concentration near the hole. Slit (3
) is the segment (1) as the wire-cut discharge surface.
a) (lb)... The mating surface between them was polished.

The shrink ring (5) into which each segment (1aH1b) is inserted is made into a - piece, and its insertion hole (6) is a tapered hole that expands downward, and the ring (5) Segment (la) (1b)...
By pressing down from the top of the segment (Ia)
(1b)...... bend inward, each slit (3
) so that the gaps in the tooth grooves are in close contact with each other at the tooth groove corners, and then finish the tooth grooves (assembled).

<Effects of the Invention> As described above, according to the present invention, since the insert (1) is divided into a plurality of segments, the stress in the inner peripheral direction of the insert (1) is reduced by the segmentation, and the stress of each segment is reduced. Radial slit in bottom corner (3)
and a hole (4) connected to the insert (1), the stress concentration and bending at the root corner due to stress in the circumferential direction are absorbed by the slit (3) and hole (4). Even when a large molding pressure is applied, the mold does not break, making it easy to forge the gear in a sealed manner and making it possible to form precise gears with no missing material.Furthermore, the shrink ring (5) can be used as a tapered hole (6) for each shape. Since the segments are press-fitted, even if the insert (1) is damaged, the shrink ring (5) can be used again to release the tabular fit, and the manufacturing cost does not increase.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention, and FIG. 1 is a plan view;
FIG. 2 is a sectional view taken along the line A--A in FIG. 1, and FIG. 3 is a perspective view of the segment. (1)...Insert (1aH1b)...Segment (3)...Slit (4)...Hole (5)...Shrink ring (6>...Taber hole

Claims (1)

[Claims] In a gear forming mold consisting of an insert having a gear and a shrink ring into which the insert is inserted, the insert is divided into a plurality of segments, and a radial slit is formed in the bottom corner of the segment, and a shrink ring is inserted into the insert. 1. A gear molding die, characterized in that a hole connected to a slit is provided, and the segment is press-fitted into a shrink ring having a tapered hole.