JP3504828B2 - Mold for warm powder molding - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold device for warm powder molding.

[0002]

2. Description of the Related Art Iron-based metal powder containing a special lubricant is used
It is known that when heated to a temperature of about 0 ° C. and compressed, a compact having a higher density than that obtained by compacting by a normal method can be obtained, and it is used for manufacturing a sintered machine part.
As one of the devices used for this powder molding, there is a withdrawal system. FIG. 3 is a vertical sectional view showing the basic structure.

In the figure, rod-shaped heaters 16 and 25 are attached to the upper punch 13 and the die 21, respectively, and the current to the heaters 16 and 25 is adjusted while measuring the temperature with a thermometer (not shown). Adjust the temperature around the molding cavity to a suitable temperature. Further, using a shuttle feeder equipped with a heating means, metal powder is filled by a usual method, compressed by upper and lower punches, and then extracted from the die 21.

In the conventional molding apparatus shown in FIG. 3, the upper punch plate 10, the die plate 23, and the base plate 40 are used.
Because of different temperatures, squeaking, galling, or abnormal wear occur between the guide post 14 and the bearing 24 and between the guide rod 60 and the bearing 41 of the base plate 40, leading to a decrease in precision of the molding apparatus, and There is a problem that the life is shortened, and it has been desired to solve them.

In order to solve this problem, the applicant of the present invention has proposed, in Japanese Patent Application No. 8-93507, a molding apparatus having a structure as shown in FIGS. In the structure shown in FIG. 4, a cooling pipe 29 is provided between the die 21 and the die plate 23, and the die plate receiving plate 26 is provided on the lower surface of the die plate 23 via a gap A and heat insulating means by a heat insulating material 27.
The guide rod 60 is fixed to the die plate receiving plate 26, and the guide post 14 is fixed to the die plate receiving plate 26 without being connected to the die plate 23. What is shown in FIG. 5 is the cooling pipe 29.
Instead of the above, the outer periphery and the upper end surface of the die 21 are coated with a heat insulating material 20 such as fluororesin or zirconia.

In the molding apparatus thus constructed, the die plate 23 and the guide post 14 are free from each other, and the temperature rise of the die plate receiving plate 26 to which the guide post 14 and the guide rod 60 are fixed or fitted is controlled. As a result, the thermal expansion of the bearings 24 and 41 is reduced because the thermal expansion of the bearings 24 and 41 becomes substantially the same as the axial expansion of the upper punch plate 10, the die plate receiving plate 26, the guide post 14 of the base plate 40 or the guide rod 60. It is possible to reduce wear without increasing an unbalanced load or a radial load with respect to.

[0007]

However, in the structure shown in FIG. 4, if a large amount of cooling water is flown through the cooling pipe 29 in order to lower the temperature of the die plate 23, the temperature of the die 21 is also lowered. Therefore, the amount of electric power supplied to the heater 25 increases. On the other hand, in the structure shown in FIG. 5, since the heat conduction suppressing means is only the heat insulating material, the die plate receiving plate 26
Since the temperature does not decrease so much, it is unavoidable that the bearing part is squeaked and the improvement of the molding speed is hindered.

[0008]

In order to solve these problems, in the mold for warm powder molding of the withdrawal type having a heater for heating the die of the present invention, the die plate 23 is fitted. The die 21 is fixed to the inner hole of the die case 28 via the heat insulating material 20, and the cooling pipe 29a is provided between the die case 28 and the heat insulating material 20, and the cooling pipe 29b is provided between the die plate 23 and the die case 28. Set up. Further, in this powder molding die, the outer cooling pipe 2
The temperature of the cooling medium supplied to 9b is normal temperature, and the temperature of the cooling medium supplied to the inner cooling pipe 29a is the outer cooling pipe 29a.
The temperature is higher than the temperature of the cooling medium of b and lower than the temperature of the die.

[0009]

DETAILED DESCRIPTION OF THE INVENTION FIG. 1 shows a cross-sectional structure around a die. The die plate 23 is supported by the guide rod 60, and the bearing 24 axially supports the guide post 14, which is similar to the structure of the conventional mold. A ring-shaped electric heater 25 is provided at the lower end of the die 21. Die 21
If it is made of cemented carbide, the thermal conductivity is relatively good, so the temperature difference in the entire die case 28 can be reduced. Further, controlling the heater current with a thermometer (not shown) is the same as in the conventional case.

The outer periphery of the die 21 is covered with a ring of heat insulating material 20. The heat insulating material 20 may have a low thermal conductivity and a certain degree of mechanical strength and heat resistance, but zirconia is most suitable. The die 21 and the heat insulating material 20 are joined to each other and fixed in the inner hole of the die case 28 to form a unit. A spiral groove communicating with the cooling pipe 29a is formed on the inner hole surface of the die case 28, and the heat insulating material 20 is press-fitted or fitted to form a flow path for a coolant such as water. Refrigerant flows in the direction of the arrow inside. The refrigerant is water or oil. The temperature of the coolant is lower than the temperature of the die 21 and higher than normal temperature, and is about 50 to 90 ° C., although it depends on the size of the mold device. This refrigerant is preheated in a reserve tank (not shown) and pumped by a pump. In the figure, an example in which the die 21 and the heat insulating material 20 are press-fitted is shown, but it is easier to assemble by fitting and using a refrigerant leakage prevention seal.

A cooling pipe 29 is also provided on the inner surface of the die plate 23.
b to form a spiral groove communicating with the die 21 and the heat insulating material 2
When the unit of 0 and die case 28 is attached,
A coolant passage is formed and the coolant is supplied in the direction of the arrow in the figure. Although the temperature and flow rate of the coolant vary depending on the size of the mold device, the temperature of the die plate 23 is close to room temperature of about 10 to 25 ° C. so that the temperature of the die plate 23 is almost the same as the temperatures of the base plate 40 and the upper punch plate 10. Use a relatively low temperature and change the flow rate according to the situation.

The die 21 of the mold apparatus having the above structure is
It is uniformly heated by the heater 25 provided below. Since the heat insulating material 20 is provided outside the die 21, heat conduction in the lateral direction is suppressed. The outside of the heat insulating material 20 is cooled with a refrigerant having a temperature lower than the temperature of the die 21 but relatively high,
Although the heat insulating material 20 is cooled relatively strongly, it does not deprive the temperature of the die 21 and increase the power consumption of the heater 25. Further, the temperature of the die case 28 around it is also lowered to some extent. The temperature of the die case 28 is between the temperature of the die 21 and room temperature, and the temperature conducted from the die case 28 can be discharged to the outside of the system by the cooling means (cooling pipe 29b) outside the die case 28. This prevents the temperature of the die plate 23 on the outside thereof from rising.

FIG. 2 is a graph showing the temperature distribution in the lateral direction of the die set. A solid line A shows the case of the mold apparatus of the present invention shown in FIG. 1, a chain line B shows the case of the conventional apparatus shown in FIG. 4, and a broken line C shows the case of the conventional apparatus shown in FIG. Both are test examples in which the die 21 is heated to 150 ° C. Further, water having a temperature of 25 ° C. was passed through the cooling pipe 29 of the device indicated by the chain line B and cooling pipe outside the device indicated by the solid line A, and hot water having a temperature of 90 ° C. was caused to flow through the cooling pipe inside the device indicated by the solid line A. In the device indicated by the broken line C, the temperature in the vicinity of the guide post 14 is 90 ° C. In the device of the chain line B, the ambient temperature is about 90 ° C. due to the cooling pipe 29, and the temperature in the vicinity of the guide post 14 is about 7 ° C.
It is 0 ° C. In order to further reduce the temperature, the temperature of the cooling medium may be lowered and the flow rate may be increased.
The required power amount of 5 will be increased. In the apparatus indicated by the solid line A, heat conduction is suppressed by the heat insulating material 20, and the average temperature of the die case 28 is about 100 ° C. by cooling with hot water inside, and the die case 28 of about 100 ° C. is cooled outside. After water cooling with a tube, the entire die plate reached about 30 ° C. From this, it can be seen that the thermal expansion of the lateral member is suppressed.

[0014]

As described above, the mold for warm forming of the present invention suppresses heat conduction by the heat insulating material around the die,
By adopting a cooling structure in which the temperature is gradually decreased in two steps from the higher temperature side, the increase in power consumption required for the heater for the die is reduced, and the temperature of the die plate rises to cause thermal expansion. According to this mold, there is no squeak or damage to the mold, and therefore the efficiency of powder molding can be improved.

[Brief description of drawings]

FIG. 1 is a partial vertical cross-sectional view of a warm powder molding die of the present invention.

FIG. 2 is a graph showing temperature distributions of a mold of the present invention and a conventional mold.

FIG. 3 is a vertical sectional view of a conventional mold.

FIG. 4 is a partial vertical sectional view of an improved conventional die.

FIG. 5 is a partial vertical cross-sectional view of another improved conventional mold.

[Explanation of symbols]

14 Guide post 20 insulation 21 die 23 die plate 24 bearing 25 heater 28 die case 29a, 29b Cooling pipe 60 Guide rod

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) B30B 11/02 B22F 3/035

Claims (2)

(57) [Claims] 1. A die plate 2 in a withdrawal type die apparatus having a heater for heating a die of a die.
3, the die 21 is fixed to the inner hole of the die case 28 fitted with the heat insulating material 20, and the cooling pipe 29a is provided between the die case 28 and the heat insulating material 20, and the die plate 23 and the die case 28. A mold for warm powder molding, characterized in that a cooling pipe 29b is provided between the molds. 2. The temperature of the cooling medium supplied to the outer cooling pipe 29b is room temperature, the temperature of the cooling medium supplied to the inner cooling pipe 29a is higher than the temperature of the cooling medium of the cooling pipe 29b, and the die 21. The temperature is lower than the temperature of 21.
The mold for warm powder molding according to 1.