KR102035633B1 - Die cooling apparatus - Google Patents

Abstract

The mold cooling apparatus is configured to supply a refrigerant in a two-phase state in which a liquid and a gas state exist together to a cooling channel formed in the mold to cool the mold by using latent heat of the refrigerant. By cooling the mold by using the latent heat of the refrigerant, the temperature of the refrigerant in the cooling channel of the mold can be kept the same, thereby achieving the effect of uniformly cooling the mold.

Description

Mold Cooling Device {DIE COOLING APPARATUS}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a die cooling device, and more particularly, to a cooling device capable of more uniformly and effectively cooling a die for hot stamping.

In general, the proportion of parts to which high-strength steel is applied to materials used in automobiles is increased in order to cope with environmental regulations by lightening the vehicle.

The high-strength steel sheet material has low room temperature formability and dimensional deformation after molding, which is a factor that limits the expansion of the application of high-strength steel in the manufacture of automotive body parts.

Recently, the ratio of applying hot stamping to the manufacture of body parts for increasing weight and strength of vehicles is increasing.

For hot stamping the steel blank is heated to Ac3, eg in the range of 850-950 ° C. The heated blank is transferred to the press mold in a few seconds and quenched at the same time as the molding. The mold is provided with a cooling channel for cooling the mold.

Hot stamping is excellent in formability and dimensional accuracy for forming hot steel sheets. And by hot stamping it is possible to obtain a vehicle component having a tensile strength of more than 1,500MPa.

Cooling water is supplied to the cooling channel of the hot stamping die. As the coolant flows along the cooling channel, it takes away the heat from the mold and gradually increases the temperature. Coolant temperature is lowest at the coolant inlet of the mold and highest at the coolant outlet. In other words, the cooling efficiency is good near the inlet, while the cooling efficiency decreases toward the outlet. This leads to non-uniform cooling of the mold, which in turn leads to deterioration of the hot stamped part.

Meanwhile, the Tailor Welded Blanks (TWB) method is a technology applied to the manufacture of vehicle parts for light weight and improved crash safety. TWB is a technology for making products of the desired shape by cutting steel plates of different thicknesses or materials into appropriate sizes and shapes and then welding them with a laser.

When hot stamping with TWB blanks, there is a difference in cooling rate between thick and relatively thin sections. In this case, the cooling performance of the mold has to be designed based on a thick portion, excessive cooling water flow rate is required, and there is a problem that the cooling performance in the thick portion is not improved to a satisfactory level.

The present invention has been proposed to solve the above problems, and an object thereof is to provide a mold cooling apparatus capable of cooling the mold more uniformly and effectively.

As one of the methods for achieving the above object, the present applicant has developed a mold cooling apparatus using a refrigerant and has filed it with Korean Patent Application No. 2017-0046830. The cooling device is configured to cool the mold by using the latent heat of the coolant while a coolant in a liquid and gaseous state flows along the cooling channel formed inside the mold.

The refrigerant flowing into the cooling channel of the mold may not be in very precise two-phase coexistence conditions or saturated conditions. The temperature of the refrigerant supplied to the cooling channel may be a temperature slightly lower than the evaporation temperature of the refrigerant, preferably 97 to 99.5% of the refrigerant evaporation temperature. This temperature condition allows the evaporation enthalpy of the refrigerant, i.e., latent heat, to be sufficiently used for cooling the mold while the temperature difference between the refrigerant temperature supplied to the mold and the refrigerant discharged from the mold is small.

The mold cooling apparatus proposed by Korean Patent Application No. 2017-0046830 is based on the fact that the cooling performance using latent heat enthalpy of refrigerant is superior to the cooling performance using sensible heat enthalpy of cooling water. When the temperature of the cooling water and the refrigerant is the same at the inlet of the mold cooling channel and the same flow rate is supplied to the cooling channel, the cooling performance of the refrigerant using latent heat is 3 to 5 times better than that of the cooling water.

For reference, when the temperature of the cooling water at the inlet of the cooling channel is 40 ° C and the temperature of the cooling water at the outlet of the cooling water flow path is 50 ° C, the heat taken by the cooling water from the mold while passing through the cooling channel is about 42 kJ / kg. In comparison, the evaporation enthalpy difference of R-134a is 163kJ / kg, the evaporation enthalpy difference of R-245fa is 181kJ / kg, and the evaporation enthalpy difference of R-1234yf is about 132kJ / kg at 40 ° C. Compared with water, the difference in evaporation enthalpy is more than three times in the refrigerant. The use of refrigerants can reduce flow rates and reduce the energy consumption of the overall system compared with the use of cooling water.

Matters related to the mold cooling apparatus introduced in Korean Patent Application No. 2017-0046830 as described above are also referred to in the present invention, and may constitute one aspect of the present invention.

On the other hand, Korean Patent Application No. 2017-0046830 did not limit the size of the cooling device, but did not specifically mention the advantages that can be obtained when the device is compactly configured.

In addition, the mold cooling apparatus shown as an example in the Korean Patent Application No. 2017-0046830, it may be considered that if the mold must be removed from the press apparatus for repair, it is necessary to disconnect the connection between the mold and the cooling apparatus. Once the connection between the mold and the chiller is disconnected and reconnected, almost all of the coolant line except for the storage tank and at least some of the chillers in the mold is actually vacuumed. This not only delays the process time but also causes problems such as refrigerant loss and environmental pollution.

The problem to be solved in the present invention is not necessarily limited to the above-mentioned matters, and other problems not mentioned above may be understood by the matters described below.

Mold cooling apparatus according to the present invention comprises a condensation unit for cooling the refrigerant discharged from the cooling channel outlet of the mold; A receiver into which the coolant cooled in the condenser is introduced; And a heating unit for heating the refrigerant supplied from the receiver to the inlet of the cooling channel of the mold. The cooling device may be configured to cool the mold by latent heat of the refrigerant while the refrigerant in which the two phases of the liquid phase and the gas phase coexist along the cooling channel of the mold.

Typical air conditioners consist of a compressor, a condenser, an expansion valve, and an evaporator. Mold cooling apparatus according to the present invention is configured to cool the mold using the latent heat of the refrigerant while minimizing the temperature change. A heater is used, not an expansion valve, and no compressor is used. Pumps for the circulating flow of refrigerant can be used.

The hot stamping mold has an upper mold and a lower mold. The cooling apparatus according to the present invention may be installed in the upper mold or the lower mold, and may be configured to be removed together when the mold is removed. This eliminates the need to remove the chiller from the mold when removing the mold.

According to the present invention, at least the condensation unit and the receiver may be mounted together in the casing, and may be configured to be removed together with the mold in which the casing is mounted.

The mold cooling apparatus according to the present invention may be configured such that when the casing is mounted on the mold, the refrigerant line connecting the condenser, the receiver, and the heating unit and the cooling channel of the mold may form a closed circuit for circulation of the refrigerant. The heating portion may be mounted together in the casing or disposed between the casing and the cooling channel inlet of the mold.

According to the present invention, the mold cooling device may be a unit compactly packed by a casing, and a part of the configuration may be provided in the casing, and another part may be provided outside the casing, and in a broad sense including a mold having a cooling channel. May be

The refrigerant is a cooling medium other than water, and examples thereof include halogenated carbon, hydrocarbons, organic compounds, inorganic compounds, and the like. The refrigerant should be able to be in a two-phase coexistence zone of liquid and gas at the temperature and pressure conditions of the cooling channel of the mold. Without environmental problems, the greater the evaporation enthalpy of the refrigerant, the better.

According to the mold cooling apparatus according to the present invention, by cooling the mold by using the latent heat of the refrigerant, it is possible to maintain the same refrigerant temperature in the cooling channel of the mold, thereby obtaining the effect of uniformly cooling the mold.

In addition, according to the present invention, an effect of effectively cooling the mold at a small flow rate can be obtained by using a refrigerant having a large evaporation enthalpy.

In addition, according to the present invention, since the temperature of the refrigerant circulating in the mold and the cooling device does not vary significantly between sections, it is possible to prevent the energy consumption of the cooling device from being large.

In addition, according to the present invention, the cooling device is compactly configured to effectively cool the mold portion requiring cooling.

In addition, according to the present invention, it is additionally installed in the existing water cooling system can prevent the deterioration of the molding quality due to the cooling of the non-uniform mold.

In addition, according to the present invention, a closed circuit in which the refrigerant circulates in a state where the cooling device is mounted on the mold may be formed, and thus, a conventional problem, that is, when the cooling device needs to be removed from the mold or when the cooling device and the mold are connected again, Conventional problems, such as making the refrigerant circulation line vacuum, can be avoided.

1 is a view schematically showing a mold to which a mold cooling apparatus according to an embodiment of the present invention is applied;
2 is a view showing an application example of a mold cooling apparatus according to an embodiment of the present invention,
3 is a view showing the internal structure of a mold cooling apparatus according to an embodiment of the present invention.

Hereinafter, a mold cooling apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

The same components or parts in the drawings are denoted by the same reference numerals as much as possible for convenience of description, and the drawings may be exaggerated and schematically illustrated for a clear understanding and explanation of the features of the present invention.

1 shows a mold 10 to which a cooling apparatus according to an embodiment is applied.

Referring to FIG. 1, the mold 10 typically includes an upper mold 11 and a lower mold 12. Each mold 11, 12 is provided with a cooling water channel 13 flowing therein. As one example, heat may accumulate and cooling may be insufficient at a specific portion indicated by A in FIG. 1. The cooling apparatus according to the embodiment can be used for cooling such a portion (A).

Insufficient cooling as indicated by A in FIG. 1 may occur when TWB or patchwork blanks are used having regions of different thicknesses. In addition, such a region may be generated for a variety of reasons, such as a complicated shape of the molded article or the inability to form the coolant channel 13 in close proximity to the molding surface of the mold 10.

According to the exemplary embodiment, in addition to the coolant channel 13, the coolant channels 14a and 14b: 14 may be formed in the A portion of the lower mold 12. 14a may be an inlet of the refrigerant channel, and 14b may be an outlet of the refrigerant channel. In the mold 10, a refrigerant channel 14 connecting the inlet 14a and the outlet 14b may be formed.

In FIG. 1, the A mark is shown on the surface of the mold 10, but the portion of the mold 10 that is not sufficiently cooled may be generated inside the mold 10 corresponding to A.

Referring to FIG. 2, the lower mold 12 may be provided with a cooling device having a compactly packed structure in the casing 20. In FIG. 2, reference numeral 23 denotes a port for supplying and discharging cooling water into the casing 20. As shown in FIG. 2, the cooling device is attached to the lower mold 12.

Referring to FIG. 3, a condenser 30 and a receiver 40 may be mounted in the casing 20. In addition, the pump 50 and / or the heating part 60 may be mounted together in the casing 20.

The refrigerant inlet 21a of the casing 20 is connected to the outlet 14b of the refrigerant channel of the lower mold 12, and the refrigerant outlet 21b of the casing 20 is connected to the inlet 14a of the refrigerant channel. The refrigerant line from the refrigerant inlet 21a to the refrigerant outlet 21b is a refrigerant recovery line 101, 102 from the inlet 21a to the receiver 40, and a refrigerant supply line from the receiver 40 to the outlet 21b. 102, 103).

The condenser 30 is an element for cooling and further liquefying the refrigerant discharged through the outlet 14b of the refrigerant channel.

The dryness of the refrigerant discharged from the refrigerant channel outlet 14b of the mold is controlled to be in the range of 0.5 to 1.0. As is known, dryness represents the dryness of the refrigerant with a saturated liquid line as 0 and a saturated steam line as 1. According to the embodiment, when the coolant dryness at the outlet 14b exceeds 1.0, it becomes a superheated gas, and the temperature and the pressure increase rapidly, which may adversely affect the stability of the cooling apparatus, and uniform cooling of the mold is not guaranteed. In addition, when the outlet 14b dryness is 0.5 or less, the efficiency of the cooling device decreases.

The condenser 30 cools the refrigerant having a dryness of 0.5 to 1.0 discharged from the refrigerant channel outlet 14b of the mold and further condenses it into the liquid phase. The refrigerant absorbing heat while passing through the mold 10 increases in pressure as it becomes saturated steam or gaseous phase, which may cause rapid pressure fluctuations and impair stable operation of the mold cooling apparatus. By liquefying the gaseous refrigerant in the condenser 30 can absorb the pressure fluctuations, it is also possible to reduce the volume of the device.

The condenser 30 may be cooled by cooling water for cooling the mold 10. By way of example, the condenser 30 may be connected to a line branching from a coolant line for supplying coolant to the coolant channel 13. Cooling water may flow from the cooling water inlet 23a of the casing 20, and may be discharged to the cooling water outlet 23b after the soft exchange in the condenser 30.

The refrigerant cooled or liquefied in the condenser 30 flows into the receiver 40. The receiver 40 accommodates the liquid refrigerant and also serves to damp the pressure change due to the refrigerant in the gas phase flowing from the refrigerant channel outlet 14b of the mold.

The pump 50 and the heating unit 60 are provided in the refrigerant supply lines 102 and 103 extending from the receiver 40 to the refrigerant outlet 21b. The pump and / or the heating unit 60 may be provided outside the casing 20.

The pump 50 is for circulating the refrigerant in one direction, and the liquid refrigerant contained in the receiver 40 flows to the refrigerant outlet 21b by the operation of the pump 50.

The heating unit 60 heats the refrigerant supplied to the refrigerant channel inlet 14a of the mold 10 to become almost saturated liquid. According to the embodiment, the temperature of the refrigerant supplied to the refrigerant channel inlet 14a of the mold 10 needs to be controlled to be 97 to 99.5% of the evaporation temperature. This temperature condition allows the evaporation enthalpy, that is, latent heat, of the refrigerant to be sufficiently used for cooling the mold 10 while the temperature difference between the refrigerant temperature supplied to the mold 10 and the refrigerant discharged from the mold 10 is small.

According to the embodiment, a refrigerant is used, which can be easily evaporated even at low temperatures. For example, known refrigerants such as R-134a, R-245fa, R-1234yf, and R-1233zd may be used as the refrigerant.

In the embodiments described above, detailed components such as a temperature sensor for measuring the refrigerant temperature and a valve for adjusting the flow rate are not mentioned. These components may be appropriately added as needed. In addition, a control unit for controlling the valve, the heating unit, etc. using the input data from the sensor may be provided.

While specific embodiments of the present invention have been shown and described, it should be understood that the present invention may be variously modified or modified without departing from the spirit of the invention as set forth in the claims below.

10, 11, 12: mold 13: coolant channel
14, 14a, 14b: refrigerant channel 20: casing
30: condensation unit 40: receiver
50: pump 60: heating

Claims (8)

A condenser for cooling the refrigerant discharged from the cooling channel outlet of the mold to the liquid phase;
A receiver into which the coolant cooled in the condenser is introduced; And
A heating unit for heating the refrigerant supplied from the receiver to the cooling channel inlet of the mold,
It is configured to cool the mold by the latent heat of the refrigerant flows along the cooling channel of the refrigerant flows along the liquid channel and the two phases of the gas phase,
The coolant in the heating unit is heated to a temperature lower than the evaporation temperature, the mold cooling apparatus, characterized in that controlled so that the dryness of the refrigerant discharged from the outlet of the cooling channel of the mold is in the range of 0.5 ~ 1.0. According to claim 1, At least the condensation unit, the receiver further comprises a casing mounted therein,
The casing is mounted to be attached to the mold and configured to be removed together when the mold is removed.
When the casing is mounted on the mold, the mold cooling device, characterized in that the refrigerant line connecting the condensation unit, the receiver and the heating unit and the cooling channel of the mold to form a closed circuit for circulation of the refrigerant. The mold cooling apparatus according to claim 1, further comprising a pump for forming a refrigerant flow in one direction between the receiver and the mold. A mold having a first cooling channel for water cooling and a second cooling channel for cooling by a refrigerant;
A condenser for cooling the refrigerant discharged from the outlet of the second cooling channel of the mold to the liquid phase;
A receiver into which the coolant cooled in the condenser is introduced; And
A heating unit for heating the refrigerant supplied from the receiver to the inlet of the second cooling channel of the mold,
It is configured to cool the mold by the latent heat of the refrigerant flows along the cooling channel of the refrigerant flows along the liquid channel and the two phases of the gas phase,
The coolant in the heating unit is heated to a temperature lower than the evaporation temperature, the mold cooling apparatus, characterized in that controlled so that the dryness of the refrigerant discharged from the outlet of the cooling channel of the mold is in the range of 0.5 ~ 1.0. The method according to claim 4, At least the condensation unit, the receiver further comprises a casing mounted therein,
The casing is mounted on the upper mold or the lower mold of the mold, and when the mold is removed, the casing is detached together with the mounted mold.
The casing is attached to the mold and can be removed together when removing the mold.
When the casing is mounted on the mold, the mold cooling device, characterized in that the refrigerant line connecting the condensation unit, the receiver and the heating unit and the second cooling channel of the mold to form a closed circuit for the circulation of the refrigerant. The method of claim 5, wherein the condensation unit,
And a coolant line for supplying coolant to the first cooling channel of the mold and configured to be cooled by the coolant supplied from the coolant line. The method according to any one of claims 1 to 6,
Mold cooling apparatus characterized in that the temperature of the refrigerant supplied to the inlet of the cooling channel of the mold is controlled to be in the range of 97 ~ 99.5% of the evaporation temperature. delete

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