JPH0234242A - Sizing method - Google Patents

Abstract

PURPOSE:To prevent a punch from being broken and to improve the accuracy of a finished shape by drawing the outer periphery of the blank slightly to be adhered to the punch, in the state that the blank is fitted outside the punch then, ironing the blank by the outer peripheral surface as the blank is put round the punch. CONSTITUTION:The blank 2 is put round the punch 36 fixed to the upper surface part of a 1st die 32 and a die 48 is displaced to the side of the punch 36 to draw the outer peripheral part of the blank 2. The inner peripheral surface of the blank 2 is adhered to the outer peripheral surface of the punch 36 and when the lower edge of a bulged part formed in the hole 48 comes in contact with the bottom part of the blank 2, the drawing to bring the blank 2 into contact with the outer peripheral surface of the punch 36 is finished. Then, when the die 48 is displaced further to the side of punch 36, the outer peripheral part of the blank 2 is extended to the 1st die 32 to be formed into the final shape. Especially, the thick material parts of projecting parts 8a-8c are ironed strongly by the outer peripheral part to receive such plastic deformation that material flows into the jaw parts on both sides of the projecting parts 8a-8c. In this case, since the blank 2 adheres to the punch 36, concentration of stress to the punch 36 is avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a sizing method. When finishing an item that requires precision into its final shape, the material is fitted around the punch and the outer circumference of the material is first squeezed slightly to make it adhere to the punch, then ironing is performed from the outer circumferential surface of the material. The present invention relates to a sizing method that processes a product in a two-step process, thereby preventing breakage of the punch and improving the precision of the finished shape.

[Background of the Invention] Conventionally, a cold working method for bringing an article processed by forging or casting to its final finished size is called sizing. For example, in the wheel drive unit of an automobile, the above-mentioned sizing method is employed in the manufacturing process of the outer wheel of a constant velocity joint that connects a differential device and a rear wheel shaft.

The outer ring of the constant velocity joint has a cup shape, and a plurality of track grooves are formed in the axial direction on its inner surface. Since a bearing comes into contact with the track groove, the track groove needs to be formed with considerable precision. Therefore, the track groove must be finished with high dimensional accuracy and surface accuracy by sizing.

Therefore, the structure of the outer ring of the constant velocity joint and its sizing process will be briefly explained.

First, a blank 2, which is a preformed body having the shape shown in FIGS. 1a and 1b, is formed by forging a billet. In this case, the blank 2 has a cup shape in which the driven shaft 4 is integrally formed at one end and is open at the other end, and a trunnion (not shown) is provided inside the blank 2, extending in the axial direction. Three concave portions 6a to 6C that receive the circular portions 6a to 60, and three convex portions 8a to 8C that protrude into the hollow portion of the blank 2 between the respective circular portions 6a to 60 are formed. Each circular portion 6a to 6C is connected to the ceiling surface 10a to 1
0C and track grooves 12a to 12 on both sides of which the slide rollers constituting the trunnion are transferred.
f. Further, the track grooves 12a to 12f
and the convex portions 18a to 8c are bulged into hollow portions to become jaw portions 14a to 14f, respectively, and track grooves 12a to 12f are formed between the jaw portions 14a to 14f and the track grooves 12a to 12f. Undercut portions 16a to 16f are formed, respectively, to restrict the lateral movement range of the shifting slide rollers and improve the performance of the constant velocity joint.

Next, a punch 18 corresponding to the finished shape of the outer ring is inserted into the hollow part of the blank 2 constructed as described above, and in this state, the outer peripheral part is squeezed by the die 20 (Fig. 2 a and b). Reference.

As a result, the inner circumferential surface of the blank 2 is patterned along the outer circumferential shape of the punch 18, and sizing is performed.

As can be understood from FIG. 1, the blank 2 has a complicated inner circumferential surface with grooves and protrusions. This means that when considering blank 2 as the main body, it is extremely difficult to process it with high precision.
Conversely, when looking at the punch 18 that fits into the blank 2 as the main body, a considerable load is applied to the punch 18, and in particular, local stress concentration due to the shape of the blank 2 is applied to each part. Therefore, it means that it is easy to break and it is difficult to ensure a long service life.

In fact, as shown in FIG. 3, when the outer periphery of the blank 2 is ironed to imitate the outer shape of the punch 18, in the case of the bontier 8, especially the notch-shaped portion, that is, the jaw portion of the blank 2. Stress is concentrated at the portions 14a to 14f that receive the punches 14a to 14f, and racks often occur in the punch 18 as shown in the figure.

For this reason, the punch 18 must be discarded after long-term use, and improving the durability of the punch 18 is a major technical issue.

[Object of the Invention] The present invention has been made to overcome the above-mentioned disadvantages.
First, the outer periphery of the blank is squeezed by a predetermined amount to bring the blank into close contact with the punch, and then, while maintaining the tight contact state, the outer periphery is squeezed by the amount of squeezing that corresponds to the thickness of the blank. The purpose of the present invention is to provide a sizing method that reduces the load on the punch and improves the useful life of the punch by forming the punch into a product shape.

[Means for Achieving the Object] In order to achieve the above-mentioned object, the present invention provides a preform having a cup shape, a protrusion that bulges into a hollow part, and several grooves in the axial direction. A sizing method in which a die and a punch work together to perform ironing and shape the preform to a predetermined dimensional accuracy, and the preform has a constant clearance between the inner circumferential surface and the outer circumferential surface of the punch. The first step is to fit the body into the punch and apply a squeeze from the outer peripheral surface of the preform to bring it into close contact with the punch.Following the first step, the preform is restrained against the punch. It is characterized by comprising a second step of applying ironing from the outer circumferential surface depending on the wall thickness.

[Embodiments] Next, preferred embodiments of the sizing method according to the present invention will be described in detail with reference to the accompanying drawings.

First, by carrying out the sizing method according to the present invention, the blank that is finally processed into the outer ring of the constant velocity joint is the same blank as blank 2 shown in FIG. Elements will be given the same reference numerals and detailed descriptions will be omitted.

Next, a sizing device for carrying out the sizing method according to the present invention will be described.

As shown in FIG. 4, the sizing device 30 includes a first mold 32 and a second mold 34, and the first mold 32 and the second mold 34 are arranged as indicated by arrows in the figure. In addition, they can be relatively displaced in directions toward and away from each other under the driving action of an actuator (not shown). Said first mold 32
A punch 36 is attached to the upper surface of. The punch 36
The external shape is formed to correspond to the internal shape of the outer ring of the constant velocity joint, and the three prismatic portions 40 correspond to the three concave portions 6a to 6C of the blank 2, respectively.
a to 40c are formed to bulge, and these prismatic portions 4
Long grooves 42a to 42c substantially corresponding to the convex portions 8a to 8C of the blank 2 are formed between 0a to 40c.

Here, the prismatic parts 40a to 40C are the flat parts 44a to 44C for finishing the ceiling surfaces 10a to 10C of the recessed parts 6a to 6C formed in the blank 2, and the flat parts 4
Track grooves 12a to 1 are located on both sides of 4a to 44C.
It includes side parts 46a to 46f for finishing 2C.

In contrast to the first mold 32 configured as described above, the second mold 34 has a substantially cylindrical shape, and a die 48 is attached to the lower end thereof. The die 48 also has a cylindrical shape, and as shown in FIG. 5, a bulge 50 for squeezing the outer periphery of the blank 2 is formed on its inner peripheral surface.

A cylindrical surface 52 having a smooth, perfectly circular curved surface shape is formed on the inner circumferential surface of the die 48 at a lower portion that is continuous with the bulging portion 50 . The diameter of this cylindrical surface 52 is selected to be slightly smaller than the outer diameter of the blank 2.

Further, the width of the cylindrical surface 52 in the axial direction is set to be approximately equal to or slightly longer than the height H of the blank 2.

The apparatus for carrying out the sizing method according to the present invention is basically constructed as described above. Next, the sizing process is performed on the actual blank 2 using this sizing apparatus 30, and the final Formed into the shape of the outer ring of a constant velocity joint.

First, as shown in FIG. 5, the blank 2, which is a preformed body formed by forging, is fitted onto the punch 36 fixed to the upper surface of the first mold 32. At this time, on the inner circumferential surface of the blank 2, ceiling surfaces 10a to 10c, rack grooves 12a to 1 defining each part of the inner circumferential surface, respectively.
2f$ and the surfaces of the convex portions 8a to 8C and the flat portions 44a to 44a facing these on the outer peripheral surface of the punch 36.
1 side surface portions 46a to 46f and long grooves 42a to 42c
A predetermined clearance is defined between the
(see figure a). Therefore, the punch 36 is smoothly inserted into the hollow part of the blank 2.

Therefore, as shown in FIG. 5, the die 48 mounted on the second mold 34 is displaced toward the punch 36 to apply a squeeze to the outer circumference of the blank 2. At this time, die 48
The cylindrical surface 52 formed on the inner circumferential portion of the blank 2 presses the entire outer circumferential surface of the blank 2 to extend it toward the first mold 32, and also brings the inner circumferential surface of the blank 2 into close contact with the outer circumferential surface of the punch 36. (See Figure 6).

In the process of displacing the die 48 toward the punch 36, the clearance between the blank 2 and the punch 360 is increased between the jaws 14a to 14f of the blank 2 and the long groove 42a of the punch 36.
The inner circumferential surface of the blank 2 is brought into close contact with the outer circumferential surface of the punch 36, except for a slight clearance remaining between both side edges of the blanks 2 to 42c. At the stage where the lower edge of the bulge 50 formed on the die 48 comes into contact with the bottom of the blank 2, the blank 2 is inserted into the punch 3.
6. The aperture to bring it into close contact with the outer circumferential surface is completed. In this case, the diameter of the cylindrical surface 52 of the die 48 is made slightly smaller than the outer diameter of the blank 2 in order to provide a certain amount of drawing margin, and the punch 36 is not subjected to much load.
The drawing process of the blank 2 is suitably performed.

Next, when the die 48 is further displaced toward the punch 36 side, the die 48 is moved as shown in FIGS. 5C and 6C.
8, the outer peripheral part of the blank 2 is extended to the first mold 32 and molded into the final shape, and in particular, the thick parts of the convex parts 8a to 8C are largely squeezed from the outer peripheral part. Therefore, the jaws 14a to 14' on both sides of the convex portions 8a to 8C undergo plastic deformation such that the flesh flows.In this case, since the above-mentioned reduction by the cylindrical surface 52 of the die 48 has already been performed, Since the blank 2 is in substantially close contact with the punch 36, it is possible to avoid a phenomenon in which the stress applied to the punch 36 is locally concentrated.
Since there is a clearance between the blank 2 and the punch 360, if the blank 2 is squeezed all at once, the degree of adhesion to the punch 36 will vary depending on the wall thickness of the blank 2, and this will cause local stress concentration. It was causing this.

In particular, the jaws 14a to 14 of the blank 2 where it is difficult to obtain adhesion.
Stress is concentrated on the side edges of the long grooves 42a to 42C of the punch 36 facing the direction f, and the flat part 44
Cracks were generated from a to 44C. However, as in this embodiment, by first applying a reasonable drawing, the adhesiveness between the blank 2 and the punch 36 is secured to a certain extent, so that the effect of reinforcing the punch 36 is produced. Then, even if a predetermined ironing process is performed in accordance with the wall thickness of the blank 2 in the next step, the jaw portion 1
4a to 14f are restrained to some extent by the punch 36, so that localized stress concentration can be avoided from acting on the punch 36. Therefore, it is possible to considerably extend the useful life of the punch 36.

[Effects of the Invention] As described above, according to the present invention, after first ensuring the degree of adhesion between the punch and the blank by a predetermined reduction amount, ironing is performed from the outer periphery of the blank in order to perform finish forming.

For this reason, the blank itself restrains and reinforces the punch, and the punch is squeezed once a certain degree of adhesion is achieved, thereby preventing local stress concentration. Therefore, it is possible to improve the durability of the blank without damaging it.

Although the present invention has been described above with reference to preferred embodiments, the present invention is not limited to these embodiments.
Of course, various improvements and changes in design are possible without departing from the gist of the present invention.

[Brief explanation of the drawing]

Figures 1a and b are partially omitted longitudinal and cross-sectional views showing the configuration of a blank processed into the outer ring of a constant velocity joint according to the prior art, and Figures 2a and b are sizing methods according to the prior art. 3 is a diagram illustrating how cracks occur in the punch in the sizing method according to the prior art. FIG. 4 is a perspective view illustrating the configuration of an apparatus for carrying out the sizing method according to the present invention. 6 is an explanatory diagram of the sizing method according to the present invention, and FIG. 6 is a sectional view showing the progress of deformation of the punch and blank corresponding to FIG. 5.

Claims (2)

[Claims] (1) A die and a punch work together to iron a preform that has a cup shape and has a protrusion that bulges into the hollow part and has several grooves in the axial direction, and the preform is A sizing method for forming a body to a predetermined dimensional accuracy, in which a preform whose inner peripheral surface has a certain clearance with respect to the outer peripheral surface of the punch is fitted onto the punch, and drawing is performed from the outer peripheral surface of the preform. A first step of bringing it into close contact with the
A sizing method characterized in that, following the first step, a second step is performed in which ironing is applied from the outer peripheral surface of the preform according to the wall thickness of the preform while the preform is restrained by a punch. . (2) The sizing method according to claim 1, wherein the preform is a preform for constructing an outer ring of a constant velocity joint.