JP2724869B2 - Electrodeposition equipment using heat pump - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrodeposition coating apparatus using a heat pump, and more particularly, to a pretreatment tank and an electrodeposition coating apparatus that effectively utilizes heat of evaporation and condensation in a heat pump cycle. The present invention relates to an electrodeposition coating apparatus for controlling the temperature of a tank.

"Prior art" Conventionally, in an electrodeposition coating apparatus, in order to enable smooth and prompt pretreatment in pretreatment steps such as hot water washing, degreasing, and chemical conversion treatment, the treatment liquid for pretreatment is 50 to 70%. It is necessary to control the heating to ℃, while in the electrodeposition bath, while applying the coating liquid, the coating is applied to the object to be coated after the completion of the pre-treatment, the temperature is likely to rise, and the temperature rise is also left. It is necessary to control the cooling of the coating liquid in the electrodeposition tank to a temperature of about 25 to 30 ° C., since proper coating processing cannot be performed if the coating is performed.

Conventionally, the heating control and the cooling control have been performed using independent (cold) heat sources, but using such independent heat sources is not rational in terms of thermal efficiency.
2. Description of the Related Art An electrodeposition coating apparatus has been proposed in which the heat of evaporation (cooling) and the heat of condensation (heating) in a heat pump cycle are effectively used to control the temperature of an electrodeposition tank and a pretreatment tank. (Tokukosho 60
In order to operate such a system smoothly, it is necessary to maintain a heat balance between the evaporation side and the condensation side of the heat pump cycle.

In this case, ideally, the object to be charged into the pretreatment tank and the electrodeposition tank is the same, in other words, the heat capacity to be heated / cooled is constant. If it is possible to maintain the temperature of the body, in other words, the temperature of the electrodeposition tank, at about the same as the ambient temperature, the heat loss and heat absorption capacity between the evaporation side and the condensation side will be the same, and the evaporation side will easily condense with the evaporation side. It is possible to maintain the heat balance between the sides, but in practice, the environmental temperature is not only maintained at around 20 to 25 ° C. (indoor air conditioning temperature) lower than the temperature of the electrodeposition tank, The temperature difference between the pretreatment tank and the environmental temperature is several steps larger than the temperature difference between the electrodeposition tank and the environmental temperature, and furthermore, because each of the tanks is an open tank, it is caused by the temperature difference from the environmental temperature. Heat losses are further increased.

For this reason, the amount of heat deprived on the pretreatment tank side becomes several steps larger than that on the electrodeposition tank side, so that the thermal imbalance generated between both tanks inevitably becomes extremely large. In, it was necessary to provide a boiler as an auxiliary heat source on the pretreatment tank side. (Japanese Patent Publication No. 61-60918) "Problems to be Solved by the Invention" However, as described above, it is not rational in terms of thermal efficiency to use an independent heat source such as a boiler, even as an auxiliary heat source. For this reason, even if the heat pump cycle is applied to the electrodeposition coating system, dissatisfaction occurs in terms of the overall thermal efficiency.

Also in terms of load fluctuation, in the above-mentioned known electrodeposition coating apparatus, cooling of the electrodeposition liquid and pretreatment liquid (chemical conversion liquid and degreasing liquid)
Is performed by a single heat pump unit, so that it may not be possible to cope with the load.

In view of the drawbacks of the prior art, the present invention provides an electrodeposition coating apparatus in which two heat pump cycles are effectively combined without using an independent auxiliary heat source such as a boiler, thereby greatly improving thermal efficiency. Aim.

[Means for Solving the Problems] As shown in FIG. 1, the present invention heats the pretreatment tank B side where the amount of heat deprived is several steps larger than that of the electrodeposition tank A side. It is the same as the above-described known technology in that the auxiliary heating is performed without using only the condensation heat of the first heat pump C that uses the refrigeration load for cooling as a heat source, but a boiler is used as the auxiliary heat source as in the known technology. Without using, the first heat pump C is provided with a second heat pump D for heating the pretreatment tank by utilizing the heat of condensation thereof, and the heat source of the second heat pump includes the temperature in the electrodeposition tank and the temperature of the pretreatment tank. By using a latent heat loss of low-temperature steam or the like radiated from the pretreatment tank B corresponding to a substantially intermediate temperature of the internal temperature, substantially two-stage compression between the first and second heat pumps C and D is performed. It is characterized in that it is set to have a configuration.

That is, the present invention focuses on the temperature difference between the pretreatment tank B and the environmental temperature, in other words, by making the environmental temperature substantially function as an intercooler, the low-temperature steam radiated from the pretreatment tank B The latent heat loss corresponding to the intermediate temperature of the two-stage compressor is set so that a substantially two-stage compression configuration is formed between the first and second heat pumps C and D. .

E is a hot water tank for storing the heat of condensation of the heat pumps C and D.

"Action" The present invention effectively utilizes the heat loss caused by the temperature difference between the pretreatment tank and the environmental temperature, in other words, the environmental temperature functions as an intercooler so as to take a two-stage compression structure. With this configuration, the driving load of the second heat pump D is reduced, and the second heat pump D reduces the heat loss on the condenser side of the first heat pump C without using a special heat source. D efficiently recovers the heat, and substantially closes the thermal energy cycle, thereby achieving significant energy savings.

Also, the electrodeposition liquid is cooled only by the first heat pump C, and the pretreatment liquid is heated by summing the heat of condensation of both heat pumps C and D. Therefore, imbalance is caused in terms of heat loss. The heat balance between the generated electrodeposition tank and the pretreatment tank B can be easily achieved.

More specifically, since the low-temperature steam is at about 40 ° C., which is higher than the control temperature of the electrodeposition liquid, it can function as an intermediate temperature.
The compression load is small, and therefore the power consumption is small. In addition, large latent heat energy can be obtained when the vapor is liquefied, and sufficient heat of condensation can be obtained as auxiliary energy for the pretreatment tank B. is there.

The present invention stabilizes the energy load capacity to be supplied to the pretreatment tank B by setting the heat of condensation of the heat pumps C and D to the same value. Even when the fluctuation occurs, the heating temperature control can be performed with high accuracy.

Hereinafter, preferred embodiments of the present invention will be illustratively described in detail with reference to the drawings. However, unless otherwise specified, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention thereto, but are merely illustrative examples. It's just

FIG. 2 is a schematic view of an electrodeposition coating apparatus according to an embodiment of the present invention.
Is a chemical tank, and 3 is a degreasing tank. As is well known, the coating liquid or processing liquid stored in these tanks is stored in a cold water tank 18 or a hot water tank 9 via heat exchangers 4, 6, and 7, respectively. It can be cooled or heated by cold water (hot water).

Reference numeral 5 denotes a first heat pump unit which cools cold water which has exchanged heat with the coating liquid via the heat exchanger 4 on the side of the electrodeposition tank 1 on the side of the evaporator 30 and then returns the cold water to the cold water tank 18. After heating the hot water guided from the low-temperature tank 10 of the hot water tank 9 on the low-temperature side on the condenser 31 side, another part of the hot water is guided to the high-temperature tank 11 of the hot water tank 9 while another heat water is passed through the heat exchanger 6. After the heat exchange with the chemical conversion solution, the liquid is guided to the low-temperature tank 10 of the hot water tank 9.

Reference numeral 8 denotes a second heat pump unit that guides low-temperature steam radiated from the chemical conversion tank 2 and the degreasing tank 3 to the evaporator 32 and generates heat of condensation using the latent heat loss as a heat source. After the hot water guided from the low temperature tank 10 is heated, the hot water can be returned to the high temperature tank 11 of the hot water tank 9.

On the other hand, the degreasing solution in the degreasing tank 3 is configured to be able to exchange heat with the hot water guided from the high temperature tank 11 of the hot water tank 9 via the heat exchanger 7, and the hot water after the heat exchange returns to the low temperature side hot water tank 9. Is done.

Reference numeral 12 denotes an outside air heat exchanger for absorbing load fluctuations in the tanks 8, 9, which function as a heating tower and a cooling tower, respectively.

 Next, the operation based on the actual cooling will be described.

The coating liquid in the electrodeposition tank 1 is circulated through the pipe line 34 by the pump 13 and exchanges heat with the cold water cooled by the evaporator 30 of the first heat pump unit 5 by the heat exchanger 4 to 27 ° C. ± 1 ° C.
Is cooled. Further, the liquid in the evaporator 30 and the electrodeposition tank 1 may be directly heat-exchanged without using cold water. On the other hand, the hot water heated by the condenser 31 of the heat pump unit 5 is heat-exchanged in the heat exchanger 6 with the chemical liquid in the chemical conversion tank 2 circulating through the pipes 41-44 by the pump 14, thereby heating the chemical liquid. 50 ℃ ± 1
C., and is led to the high temperature tank 11 of the hot water tank 9 via the pipe 42 and stored as 58 ° C. hot water.

The degreasing liquid in the degreasing tank 3 is circulated through a pipe 36 by a pump 19, and is heated by the heat exchanger 7 by exchanging heat with hot water pumped by the pump 16 from the high temperature tank 11 of the hot water tank 9. ° C
Maintained at ± 1 ° C.

On the other hand, since the processing liquid in the chemical conversion tank 2 and the degreasing tank 3 is maintained at 50 ° C. ± 1 ° C., which is higher than the ambient temperature, the processing liquid evaporates as low-temperature steam, and the low-temperature steam is supplied to the intake fans 20, 21 respectively.
Is sucked into the pipe 52 by the second heat pump unit 8
The heat pump unit 8 is operated to heat the 53 ° C. hot water pumped by the pump 22 from the low temperature tank 10 of the hot water tank 9 to 58 ° C. and is led to the high temperature tank 11 of the hot water tank 9. The hot water tank 9 is divided into a high-temperature water tank 11 and a low-temperature water tank 10 on the return side.

If the temperature of the hot water in the high-temperature tank 11 of the hot water tank 9 rises to 60 ° C. or higher, or if the temperature of the cold water tank 18 rises above a specified temperature (about 20 ° C.), the outside air heat exchanger 12 is connected to the cooling tower. When the temperature of the chilled water in the chilled water tank 18 drops considerably, the heat exchanger 12 is operated as a heating tower.

[Effects of the Invention] As described above, according to the present invention, thermal efficiency can be significantly improved by effectively combining two heat pump cycles without using an independent auxiliary heat source such as a boiler.

Further, the present invention is configured such that the electrodeposition liquid is cooled only by the first heat pump, and the pretreatment liquid is heated by adding the heat of condensation of both heat pumps, so that imbalance occurs in terms of heat loss. The heat balance between the electrodeposition tank 1 and the pretreatment tank can be easily attained, and the second heat pump does not use a special heat source. Since the latent heat loss is used as a heat source, significant energy savings can be achieved as compared with the prior art.

And so on.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a basic configuration of the present invention, and FIG. 2 is a schematic diagram of an electrodeposition coating apparatus according to an embodiment of the present invention. A, 1: Electrodeposition tank, B, 2,3: Pretreatment tank C, 5: First heat pump D, 8: Second heat pump

Claims (2)

(57) [Claims] 1. A refrigerating load for cooling an electrodeposition tank in an electrodeposition coating apparatus in which a temperature between a pretreatment step tank and an electrodeposition tank is controlled by effectively utilizing heat of evaporation and condensation in a heat pump cycle. The latent heat loss of the low-temperature steam radiated from the pretreatment step tank heated by the heat of condensation of the first heat pump as a heat source is used as the heat source of the second heat pump, and the pretreatment step tank is heated by the heat of condensation of the second heat pump. The first and second heat pumps are substantially in a two-stage compression configuration. 2. The electrodeposition coating apparatus according to claim 1, wherein the heats of condensation of both heat pumps are set to the same temperature.