JPH0722798B2 - Extrusion molding method for cup-shaped molded products - Google Patents

Description

The present invention relates to a method for extruding a cup-shaped component such as a constant velocity joint outer ring at a temperature below a transformation point.

(Prior Art) Japanese Patent Application Laid-Open No. 59-22 is a method for molding cup-shaped parts and the like.
As disclosed in No. 0243, a method of cold forging a material between a die (die) and a punch at a temperature below a transformation point is widely used. Further, if the material is forged, the seizure will occur unless the lubricant film is formed. Therefore, conventionally, a chemical conversion film is formed on the surface of the material by a bond treatment, or a lubricating oil is sprayed on the material or the mold before forging.

(Problems to be Solved by the Invention) Among various lubrication means described above, the bonder treatment cannot be applied to continuous molding because the coating thickness is drastically reduced in one molding, and the molding rate is large. There is a disadvantage that the lubrication effect is lost. Further, it is difficult for the means for spraying the lubricating oil to uniformly spray the material or the mold, and when the molding rate is increased, the oil film is cut off, which is not preferable in terms of work environment hygiene.

Therefore, the present applicant previously proposed, as Japanese Patent Application No. 62-324515, an oil bath molding method in which a cavity is preliminarily filled with lubricating oil, and a raw material is put into this cavity for forging.

However, in the case of extrusion molding by the oil bath method, there is a case in which the lubricating oil is trapped between the material and the bottom surface of the cavity during molding depending on the shape of the material. In such a case, as shown in FIG. 5, a lubricating oil discharge passage 102 is opened on the bottom surface of the cavity 101 of the mold 100,
It is necessary to smoothly discharge the contained lubricating oil to the tank outside the mold, but simply forming the discharge path 102 causes the molded part W to cling to the punch 103 when raising the punch 103 after molding. Rise with the punch,
The adverse effect such as double hitting occurs.

(Means for Solving the Problem) In order to solve the above problems, the present invention has a cavity bottom of a mold having a lubricating oil discharge passage open to a tank outside the mold, and a cavity bottom face formed in the middle of the discharge passage. A check valve is provided to open the discharge passage when the pressure of the lubricating oil enclosed between the material and the material reaches a predetermined value and to close the discharge passage when the pressure is equal to or less than the predetermined value.

(Operation) Lubricant oil existing between the bottom surface of the cavity and the material during molding is returned to the tank through the discharge passage because the check valve opens, and the discharge passage is closed after molding and the parts after molding Is closely contacted with the bottom surface of the cavity, and therefore does not adhere to the punch side and remains in the cavity when the punch is raised.

(Example) Below, the Example of this invention is described based on an accompanying drawing.

FIG. 1 is a sectional view of an extrusion molding apparatus according to the present invention,
A cavity 2 that opens upward is formed in a plurality of molds 1, a punch 3 is provided above the cavity 2 so as to be movable up and down, and a payout pin 4 is arranged in the mold below the cavity 2. Further, a lubricating oil O supply passage 5 is opened above the cavity 2 so that the lubricating oil O is pumped up from a tank 6 arranged outside the mold 1 by a pump and poured into the cavity 2 through the supply passage 5. ing. As the lubricating oil, for example, a heat-reactive lubricating oil that reacts with the heat of the material W to form a lubricating film on the material surface is used.

Further, a discharge passage 7 for overflow is formed in the upper portion of the cavity 2 at a height position substantially equal to the supply passage 5 and further, a discharge passage for returning the lubricating oil O enclosed between the material W and the bottom surface of the cavity 2 to the tank 6. 8 is formed in the mold. The discharge passage 8 is formed by a plurality of small-diameter passages 8a in the vertical direction, which are open at the bottom of the cavity 2.
And a large-diameter passage 8b in the lateral direction where these small-diameter passages 8a are gathered, and a check valve 9 is provided at the end of the large-diameter portion 8b on the side of the die 1 side surface.
Is provided.

This check valve 9 closes the flow path with a steel ball 11 urged by a spring 10, so that the pressure in the discharge path 8, that is, the space S formed between the bottom surface of the cavity 2 and the material W during molding has a constant value. When it exceeds, the flow path is opened against the spring and the lubricating oil in the space S is returned to the tank 6.

A procedure for forming a cup-shaped component such as an outer ring of a constant velocity joint by subjecting a material to backward extrusion molding by using the apparatus configured as described above will be described below. In the description, the time when the punch 3 is at the top dead center (see FIG. 4) is taken as the starting point.

First, the material W is set in the cavity 2 with the punch 3 being lifted up to near the top dead center. At this point, the lubricating oil O is not supplied to the cavity 2 at all, or the lubricating oil O is supplied to the portion of the space S. This is because it is difficult to set the material W in the cavity 2 because the gap between the material W and the inner surface of the cavity 2 is extremely small if the cavity 2 is filled with the lubricating oil first.

Next, when the lubricating oil O is supplied to a position higher than the upper end surface of the material W, the punch 3 is lowered and the lower end of the punch 3 is brought into contact with the upper end surface of the material W as shown in FIG. 1, and then the punch 3 is lowered. By doing so, the material W is extruded backward as shown in FIG. 2 to obtain a cup-shaped component. During this molding, the space S between the bottom surface of the cavity 2 and the material W is compressed and the space S
Lubricating oil O inside is pressurized, and when this pressure becomes a constant value, that is, larger than the elastic force of the spring 10 of the check valve 9, the steel ball 11 retracts and the discharge passage 8 opens, and the space S
The lubricating oil inside is returned to the tank 6. In this way, by constantly applying a constant pressure to the lubricating oil during molding, the hydrostatic pressure effect ensures that the lubricating oil reaches the entire surface of the material W.

Further, when the molding is completed, the pressure in the discharge passage 8 is lowered, so that the check valve 9 causes the steel ball 11 to close the passage by the elastic force of the spring 10.

After this, the punch 3 is retracted upward to prepare for the next forming. When the punch 3 is raised, the check valve 9
Since the cup-shaped component is closed, even if the cup-shaped component clings to the lower end of the punch 3 and tries to ascend together with the punch 3, the cup-shaped component is in a vacuum state between the cup-shaped component and the bottom surface of the cavity 2 and the cup-shaped component is shown in FIG. So that it remains in the cavity 2. After that, the payout pin 4 is raised to take out the cup-shaped component from the cavity 2.

(Effect of the invention) As described above, according to the present invention, when the lubricant is contained between the cavity and the material when the material is extrusion-molded, the enclosed lubricant is discharged to the outside. Since a check valve that opens at a constant pressure is provided in the middle of the passage, the hydrostatic pressure effect spreads the lubricating oil to the details during molding, and after molding, even if the punch rises due to the vacuum effect, the product remains in the cavity. Can be left, and the adverse effects such as double strikes can be prevented.

Furthermore, the mechanism can be simplified by using a check valve that automatically opens and closes without using an electromagnetic valve.

[Brief description of drawings]

1 to 3 are longitudinal sectional views of an extrusion molding apparatus according to the present invention, FIG. 4 is a view showing a relationship between a molding cycle and a check valve, and FIG. 5 is a view for explaining a conventional defect. In the drawings, 1 is a mold, 2 is a cavity, 3 is a punch, and 5 is a die.
Is a lubricating oil supply path, 8 is a lubricating oil discharge path, 9 is a check valve, O is a lubricating oil, and W is a material.

Claims (1)

[Claims] 1. A material is set in a cavity of a die, and a lubricant is injected into the cavity from a lubricating oil supply passage at an upper portion of the material. In a method of extruding and molding a cup-shaped molded article while discharging the lubricating oil from a lower lubricating oil discharge path, a check valve is provided in the lubricating oil supply path, and during molding, the punch is lowered to lower the material The check valve is opened by increasing the pressure of the lubricating oil in the space formed between the bottom surface of the cavity and the lubricating oil is discharged to perform molding, and the punch is lifted after the molding is completed. By closing the check valve by lowering the pressure of the lubricating oil, the material after molding is put into the cavity when raising the punch. Extrusion method of the cup-like molded article is characterized in that so as to pressure holding.