2. Description of the Related Art A constant temperature-humidity oven provides space, in which an experimental object is arranged, with a specific temperature and humidity environment.

FIG. 1 illustrates the structure of a conventional constant temperature- humidity oven, and FIG. 2 illustrates the structure of an air conditioning unit employed in FIG. 1. As shown in Fig. 1, the constant temperature-humidity oven includes a chamber 10, in which an experimental object is arranged, a first heater 11 for controlling temperature in the chamber 10, a humidifier 12 for controlling humidity in the chamber 10, a blower 13 for circulating the air in the chamber 10, and an air conditioning unit for controlling temperature and humidity in the chamber 10. The humidifier 12 includes a container 12b, in which water is contained, and a second heater 12a arranged in the container 12b, for heating water. The heated water is vaporized by the air flowing on the water surface, and flowed in the chamber 10, and the humidity of the chamber 10 is thereby increased.

The air conditioning unit, as shown in FIG. 2, in which many radiating fins are installed, includes a heat-absorbing and dehumidifying evaporator 14 for heat- absorbing and dehumidifying, a compressor 15 for compressing a high temperature and low pressure refrigerant gas passed through the heat-absorbing and dehumidifying evaporator 14 into a high pressure vapor, and a condenser 16 for emitting the heat of the refrigerant as a condensing heat to an outdoor air by changing a high temperature and pressure refrigerant gas into a high pressure liquid.

The air conditioning unit also further includes an expansion valve 17 for lowering pressure so that the high pressure refrigerant liquid flowed in the heat- absorbing and dehumidifying evaporator 14 may be easily evaporated, and a by- pass valve 18 for guiding the refrigerant flowed from the condenser 16 directly to the compressor 15.

The high pressure liquid refrigerant flowed from the condenser 16 passes through the expansion valve 17 and is changed into low pressure and is evaporated in the heat-absorbing and dehumidifying evaporator 14, and thereby the air conditioning unit absorbs an ambient latent heat, and the heat-absorbing and dehumidifying evaporator 14 lowers temperature and humidity in the chamber 10.

After that, the heat-absorbed high temperature and low pressure vapor refrigerant passes through the compressor 15 and is changed into a high temperature and pressure vapor and passes through the condenser 16, and the high temperature heat is cooled by the outdoor air and forms a cooling cycle to be the state of a high pressure liquid. Through this process, heat is absorbed from the air in the chamber 10, and vapor is removed, and thereby temperature and humidity are lowered.

In the structure of the constant temperature-humidity oven, it is substantially impossible for cooling capacity to be exactly controlled on the characteristics of the air conditioning unit. Accordingly, in order to form the state of a constant temperature, power must be applied, and the first heater 11 must be heated, and simultaneously the air conditioning unit must be operated so that the heat-absorbing and dehumidifying evaporator 14 may absorb heat.

In addition, in order to form the state of a constant humidity, the heat- absorbing and dehumidifying evaporator 14 must absorb heat, and simultaneously, the first heater 11 must be heated, and the humidifying amount of the humidifier 12 must be changed.

That is, the control of temperature and humidity can be performed by controlling the calorific value of the first heater 11 and the humidifying amount of the humidifier 12 in the state that the heat-absorbing and dehumidifying evaporator 14 absorbs heat constantly.

In order to form the state of a low temperature and high humidity, an ambient temperature must be lowered by heightening the endothermic value of the heat- absorbing and dehumidifying evaporator 14. However, when the endothermic value of the heat-absorbing and dehumidifying evaporator 14 is heightened, the ambient humidity is also lowered. Therefore, in order to offset the drop of humidity and to keep the state of high humidity, the humidifying amount of the humidifier 12 must be very much heightened. Since the water of the humidifier 12 in the state of a low temperature is not well evaporated, the calorific value of the second heater 12a must be heightened so as to induce evaporation for high humidity. In other words, since much energy is consumed, and temperature rises when the humidifying amount of the humidifier 12 is heightened, it is not easy to keep the state of a low temperature and high humidity.

In order to form the state of a high temperature and low humidity, an ambient humidity must be lowered by heightening the endothermic value of the heat- absorbing and dehumidifying evaporator 14 and thereby heightening the dehumidifying amount. However, when the endothermic value of the heat-absorbing and dehumidifying evaporator 14 is heightened, the ambient temperature is also lowered. Therefore, in order to offer the drop of temperature and to keep the state of a high temperature, the calorific value of the first heater 11 must be very much heightened. Here, since the water of the humidifier 12 is easily and naturally evaporated as a high temperature is formed, the endothermic value of the heat- absorbing and dehumidifying evaporator 14 must be better heightened, and the dehumidifying amount of the heat-absorbing and dehumidifying evaporator 14 must be heightened so as to remove the vapor occurred as a result of this natural evaporation. That is, the calorific value of the first heater 11 must be heightened, and the dehumidifying amount of the heat-absorbing and dehumidifying evaporator 14 must be heightened, since in this process, much energy is consumed and temperature is lowered, it is not easy to keep the state of a high temperature and low humidity.

Meanwhile, in order to form the state of a low temperature and humidity, for example, in a case where the control of humidity is made at the low temperature of about 10°C, as shown in FIG. 8, since saturation vapor pressure in 10°C is

9.2mmHg, when humidity is about 50% controlled, saturation vapor pressure at the surface temperature of the heat-absorbing and dehumidifying evaporator 14 must be less than 4.6mmHg. However, in a case where saturation vapor pressure is less than 4.6mmHg, the surface temperature of the heat-absorbing and dehumidifying evaporator 14 drops to below 0°C, and thereby frost grows on the surface. Then, an air circulation is hindered by a grown frost, and in order to remove the frost, a defroster (not shown) should have installed. Also, when defrosting by the defroster, a frozen frost is melt, and thereby humidity is increased, and it is impossible to keep the state of a low temperature and humidity for a long time.

SUMMARY OF THE INVENTION To solve the above problems, it is an object of the present invention to provide a constant temperature-humidity oven, which enables a low temperature and humidity, a low temperature and high humidity, a high temperature and low humidity, and a high temperature and humidity to be easily formed and is capable of minimizing the consumption of energy.

Accordingly, to achieve the above object, there is provided a constant temperature-humidity oven. The constant temperature-humidity oven includes a chamber 100, in which an experimental object is arranged, a first heater 110 for rising in the temperature of the chamber 100, a humidifier 120 for controlling humidity in the chamber 100, a blower 130 for circulating the air in the chamber 100, and an air conditioning unit. The air conditioning unit includes an evaporator 150 for cooling arranged in the chamber 100, in which radiating fins 150a are installed, a compressor 220 for compressing a in-flowed refrigerant, a condenser 230 for emitting the heat of the refrigerant, an inlet pipe R1 for connecting the evaporator 150 for cooling and the condenser 230, an outlet pipe R2 for connecting the evaporator 150 for cooling and the compressor 220, and a by-pass valve 240 connected between the inlet pipe R1 and the outlet pipe R2, for guiding the refrigerant flowed from the condenser 230 directly to the compressor 220. The air conditioning unit includes a heat medium container 140, in which a heat medium 144 is contained, a heat medium evaporator 210 contained in the heat medium 144 for cooling the heat medium 144, a means arranged between the heat medium

evaporator 210 and the inlet pipe R1 for controlling the flow quantity of the refrigerant, and a heat medium circulating pipe 160 arranged in the chamber 100 for circulating the heat medium 144.

Here, the air conditioning unit further includes at least more than one means for controlling the flow quantity of the refrigerant connected between the evaporator 150 for cooling and the condenser 230.

In addition, the air conditioning unit further includes a means for controlling the flow quantity of the refrigerant for controlling the flow quantity of an in-flowed refrigerant, a first evaporator 170 for dehumidifying, in which the refrigerant passed through the means for controlling the flow quantity of the refrigerant is flowed, and a means for controlling the evaporating pressure of the refrigerant for controlling the evaporating pressure of the refrigerant passed through the first evaporator 170 for dehumidifying, connected between the inlet pipe R1 and the outlet pipe R2, respectively.

Also, the air conditioning unit further includes a means for controlling the flow quantity of the refrigerant for controlling the flow quantity of an in-flowed refrigerant, and a second evaporator 180 for dehumidifying arranged between the first evaporator 170 for dehumidifying and the humidifier 120, in which the refrigerant passed through the means for controlling the flow quantity of the refrigerant is flowed, connected between the inlet pipe R1 and the outlet pipe R2, respectively.

Meanwhile, the air conditioning unit further includes a means for controlling the flow quantity of the refrigerant for controlling the flow quantity of an in-flowed refrigerant, a first humidifier evaporatcr 190 arranged on the surface of the fluid of the humidifier 120, in which the refrigerant passed through the means for controlling the flow quantity of the refrigerant is flowed, connected between the inlet pipe R1 and the outlet pipe R2, respectively, and a means for controlling the flow quantity of the refrigerant for controlling the flow quantity of an in-flowed refrigerant, and a second humidifier evaporator 200 arranged in the fluid of the humidifier 120, in which the refrigerant passed through the means for controlling the flow quantity of the refrigerant is flowed, serially connected between the inlet pipe R1 and the outlet pipe R2, respectively.

BRIEF DESCRIPTION OF THE DRAWINGS The above object and advantages of the present invention will become more apparent by describing in detail preferred embodiments thereof with reference to the attached drawings in which : FIG. 1 illustrates the structure of a conventional constant temperature- humidity oven ; FIG. 2 illustrates the structure of an air conditioning unit employed in FIG. 1 ; FIG. 3 illustrates the structure of a constant temperature-humidity oven according to the present invention; FIG. 4 illustrates the structure of a first embodiment of the air conditioning unit employed in FIG. 3 ; FIG. 5 is a sectional view of a tubular nozzle employed in FIG. 4 : FIG. 6 illustrates the structure of a second embodiment of the air conditioning unit employed in FIG. 3 ; FIG. 7 illustrates the structure of a third embodiment of the air conditioning unit employed in FIG. 3; and FIG. 8 is a graph illustrating the humidity pressure of water by temperature.

DETAILED DESCRIPTION OF THE INVENTION FIG. 3 illustrates the structure of a constant temperature-humidity oven according to the present invention, and FIG. 4 illustrates the structure of a first embodiment of the air conditioning unit employed in FIG. 3, and FIG. 5 is a sectional view of a tubular nozzle employed in FIG. 4.

As shown in FIG. 3, the constant temperature-humidity oven includes a chamber 100, in which an experimental object is arranged ; a first heater 110 for rising in the temperature of the chamber 100 ; a humidifier 120 for controlling humidity in the chamber 100 ; a blower 130 for circulating the air in the chamber 100 ; a heat medium container 140, in which a heat medium 144 supplied to the inside of the chamber 100 is contained, and an air conditioning unit for controlling the temperature of the heat medium 144 with the control of the temperature and humidity in the chamber 100.

The humidifier 120 consists of a humidifier container 121, in which water is contained, and a second heater 122 installed in the humidifier container 121, for heating water. The heated water is vaporized by the second heater 122, and the humidity of the chamber 100 is thereby increased.

A heat medium heater 141 in the heat medium 144 for rising in the temperature, and a pump for compulsorily sending the heat medium 144 into a heat medium circulating pipe 160 to be later mentioned, are installed in the heat medium container 140. The pump consists of a fan 142, which is sunk in the heat medium 144 and rotated, and a motor 143 for rotating the fan 142.

The air conditioning unit, as shown in FIG. 4, includes a compressor 220, a condenser 230, an inlet pipe R1 connected to the condenser 230, and an outlet pipe R2 connected to the compressor 220. An evaporator 150 for cooling. a first evaporator 170 for dehumidifying, a second evaporator 180 for dehumidifying, first and second humidifier evaporators 190 and 200 arranged in the humidifier container 121, and a heat medium evaporator 210 sunk in the heat medium 144 are connected in parallel between the inlet pip R1 and the outlet pipe R2, respectively.

Also, a by-pass valve 240 for guiding the refrigerant flowed from the condenser 230 directly to the compressor 220 is connected between the inlet pipe R1 and the outlet pipe R2.

The evaporator 150 for cooling, which is exclusively for cooling the temperature of the chamber 100, controls an ambient temperature below zero.

Radiating fins 150a having many faces are installed in the evaporator 150 for cooling so as to extend a contacting area with the air. The evaporator 150 for cooling is connected to the inlet pipe R1 and the outlet pipe R2 in a state of being connected in series to a means for controlling the flow quantity of an in-flowed refrigerant. Here, preferably, at least more than one means for controlling the flow quantity of the refrigerant is in parallel connected. Therefore, in this embodiment, two means for controlling the flow quantity of the refrigerant are employed. Each means for controlling the flow quantity of the refrigerant consists of a tubular nozzle 151 and a solenoid valve 152, and a second tubular nozzle 153 and a second solenoid valve 154 serially connected.

Radiating fins are not installed in the first evaporator 170 for dehumidifying otherwise than the evaporator 150 for cooling, and the first evaporator 170 for dehumidifying is located between the heat medium circulating pipe 160 and the second evaporator 180 for dehumidifying. The means for controlling the flow quantity of the refrigerant having the same structure as the above-mentioned structure is connected to the one side of the first evaporator 170 for dehumidifying, and a means for controlling the evaporating pressure of the refrigerant, which controls the evaporating temperature of the refrigerant by controlling the evaporating pressure of a liquid refrigerant, is connected to the other side of the first evaporator 170 for dehumidifying. The means for controlling the evaporating pressure of the refrigerant, the first evaporator 170 for dehumidifying, and the means for controlling the flow quantity of the refrigerant are connected to the inlet pipe R1 and the outlet pipe R2 in a state of being connected in series.

The means for controlling the flow quantity of the refrigerant consist of a tubular nozzle 171 and a solenoid valve 172 having the same structure as the above-mentioned structure.

The means for controlling the evaporating pressure of the refrigerant consist of a tubular nozzle 173, and a tubular nozzle 175 and a solenoid valve 176 serially connected in the state connected in parallel to the tubular nozzle 173. The tubular nozzle 173 of the means for controlling the evaporating pressure of the refrigerant prevents frost from growing in the first evaporator 170 for dehumidifying by the sudden drop of temperature by getting the refrigerant slightly flowed through itself.

The solenoid valve 176 improves the distribution of temperature and endothermic value over the first evaporator 170 for dehumidifying by inducing the stepwise evaporation of the liquid refrigerant. Here, preferably, the inside diameters of the tubular nozzles 173 and 175 are larger than those of other tubular nozzles to be later mentioned, and preferably, the inside diameter of the solenoid valve 176 is also large than those of other solenoid valves to be later mentioned. This is to extend the controlling range of temperature by relatively enlarging the evaporating range of the first evaporator 170 for dehumidifying.

The second evaporator 180 for dehumidifying is arranged between the first evaporator 170 for dehumidifying and the humidifier 120. The second evaporator

180 for dehumidifying is connected to the inlet pipe R1 and the outlet pipe R2 in a state of being connected in series to the means for controlling the flow quantity of the refrigerant having the same structure as the above-mentioned structure. Here, the means for controlling the flow quantity of the refrigerant consist of a tubular nozzle 181 and a solenoid valve 182 serially connected.

The second evaporator 180 for dehumidifying forms the evaporating temperature of the lowest temperature of the refrigerant so as to have strong dehumidifying capacity. Here, according to a graph illustrated in FIG. 8, since the quantity of saturation vapor in a low temperature region is very small, frost can occur in the second evaporator 180 for dehumidifying. In this case, the second evaporator 180 for dehumidifying is arranged in the space where air flows in the upper part of the humidifier 120 so as to remove obstacles to the flow of the air.

Accordingly, when the thickness of the frost grown in the second evaporator 180 for dehumidifying becomes somewhat thick, the temperature of the second evaporator 180 for dehumidifying conducted on the surface of the frost balances with the temperature of air flowing on the surface of the frost. Therefore, the thickness of the frost doesn't become thick any more. The second evaporator 180 for dehumidifying is used for controlling a low humidity region.

The first humidifier evaporator 190 is arranged so that it may contact with the surface of the water contained in the humidifier 120. The first humidifier evaporator 190 is connected to the inlet pipe R1 and the outlet pipe R2 in a state of being connected in series to the means for controlling the flow quantity of the refrigerant having the same structure as the above-mentioned structure. The means for controlling the flow quantity of the refrigerant consist of a tubular nozzle 191 and a solenoid valve 192 serially connected. The first humidifier evaporator 190 is capable of controlling minor humidity by selectively cooling or freezing a part of the water surface of the humidifier 120 and especially, it enables low humidity to be easily controlled.

The second humidifier evaporator 200 is located under the second heater 122 of the humidifier 120. The second humidifier evaporator 200 is connected to the inlet pipe R1 and the outlet pipe R2 in a state of being connected in series to the means for controlling the flow quantity of the refrigerant having the same structure

as the above-mentioned structure, and the means for controlling the flow quantity of the refrigerant consist of a tubular nozzle 201 and a solenoid valve 202 serially connected. The second humidifier evaporator 200 can control minor humidity by cooling all water in the humidifier 120.

According to a graph illustrated in FIG. 8, since the quantity of saturation vapor in a low temperature region is very small, frost can occur in the second evaporator 180 for dehumidifying. In this case, when the temperature of the first humidifier evaporator 190 is more lowered than the temperature of the second evaporator 180 for dehumidifying, frost is formed in the first humidifier evaporator 190 contacted with water, and frost doesn't occur in the second evaporator 180 for dehumidifying. That is, it is possible for minor humidifying amount to be controlled by forming ice on the water surface by the first humidifier evaporator 190. Here, in order to control low humidity more easily, the second humidifier evaporator 200 can cool the overall temperature of water.

Like this, the first and second humidifier evaporators 190 and 200 suppresses the natural evaporation of water by energy of the air circulating the chamber 100 and suppresses the occurrence of frost in the second evaporator 180 for dehumidifying by lowering the temperature of water than the surface temperature of the second evaporator 180 for dehumidifying. Through the above-mentioned structure, even if frost occurs in the second evaporator 180 foe dehumidifying, some frost occurs and is not increased any more, and use of a defroster conventionally employed to remove frost can be excluded.

The heat medium evaporator 210 for dropping in the temperature of the heat medium 144 is arranged in the heat medium container 140. The heat medium evaporator 210 is connected to the inlet pipe R1 and the outlet pipe R2 in a state of being connected in series to the means for controlling the flow quantity of an in- flowed refrigerant. Here, the means for controlling the flow quantity of the refrigerant consist of a tubular nozzle 211 and a solenoid valve 212 serially connected to the tubular nozzle 211. Since the flow quantity of the refrigerant flowed from the inlet pipe R1 can be controlled when the solenoid valve 212 is controlled, the temperature of the heat medium 144 can be dropped. The cooling

temperature range of the heat medium 144 is controlled in the temperature above zero closely to 0°C.

The heat medium circulating pipe 160 for circulating the heat medium 144 cooled in the range of temperature above zero by the heat medium evaporator 210, is arranged in the chamber 100. The heat medium 144 is compulsorily transferred by a fan 142 and flows in the heat medium circulating pipe 160. Here, since the temperature of the heat medium 144 is cooled at the lower temperature (beyond 0°C) than the setting temperature of the chamber 100, frost doesn't occur on the surface of the heat medium circulating pipe 160. Therefore, the heat medium circulating pipe 160 lowers the temperature of the ambient air, however the dehumidifying capacity for removing moisture in the air is very small. Accordingly, it is effective on keeping the state of high humidity.

A sensor 145 is installed in the heat medium container 140. The sensor 145 for constantly keeping the temperature of the heat medium 144, generates a signal operating the heat medium heater 141 when the temperature of the heat medium 144 drops and the sensor 145 generates a signal operating the heat medium evaporator 210 when the temperature of the heat medium 144 rises. The signals are used for signals, which are transmitted to a controller (not shown) and operate the heat medium heater 141 or the heat medium evaporator 210.

The compressor 220 compresses an in-flowed high temperature and low pressure refrigerant gas into a high pressure gas, and the condenser 230 emits the heat of the refrigerant as a condensing heat to an outdoor air by changing a high pressure and temperature refrigerant gas into a high pressure liquid.

The by-pass valve 240 consists of a tubular nozzle 241 and a solenoid valve 242 having the same structure as that of the means for controlling the flow quantity of the refrigerant, serially connected. The by-pass valve 240 control the state of a high temperature. Also, the by-pass valve 240 mixes a refrigerant gas cooled from the condenser 230 with a high temperature refrigerant gas passed through the evaporators 150,170,180,190 and 200 in the outlet pipe R2 and lowers temperature and flows in the compressor 220 in order to prevent the damage of the compressor 220 by overload, which may be occurred in a case where a high temperature refrigerant gas passed through the evaporator 150 for cooling or the

first and second evaporators 170 and 180 for dehumidifying, and the first and second humidifier evaporators 190 and 200 are flowed directly in the compressor 220, Accordingly, overload by high temperature can be prevented, and the damage of the compressor 230 can be thereby prevented.

The structures of the tubular nozzles 151,153,171,173,175,181,191,201, 211, and 241 are same, as shown in FIG. 5, which illustrates the extracted tubular nozzle 151, a through ball 151 b is formed in the tube 151 a. The resistance of the refrigerant passed through the tubular nozzle 151 depends on an inside diameter d and a length L. Therefore, the standard of the tubular nozzle 151 is properly set according to the capacity or use of an air conditioning unit. In this embodiment, the tubular nozzle, of which inside diameter d is between about 0.3mm and 2mm and length L is between about o. 5mm and 30mm, is used. Since the functions of the tubular nozzles are same, the functions of the constant temperature-humidity oven employing the tubular nozzles are same.

Since the solenoid valves 152,154,172,176,182,192,202,212 and 242 for controlling the flow quantity of the refrigerant are generally used in the air conditioning unit, a detailed description thereof will be omitted.

FIG. 6 illustrates the structure of a second embodiment of the air conditioning unit employed in FIG. 3, and FIG. 7 illustrates the structure of a third embodiment of the air conditioning unit employed in FIG. 3. Here, the same reference numerals as those of FIG. 4 denote the same items having the same function.

The difference between the second embodiment of the air conditioning unit and the first embodiment of the air conditioning unit is that the tubular nozzles 151, 153, 171, 173, 176, 181, 191, 201 and 221 in the first embodiment are replaced with the known capillary tubes 251,253,271,273,275,281,291 and 301, in which holes are formed.

The difference between the third embodiment of the air conditioning unit and the first embodiment of the air conditioning unit is that the means for controlling the flow quantity of the refrigerant, the means for controlling the evaporating pressure of the refrigerant, and the by-pass valve are replaced with the diaphragm-shaped needle valves 452,454,472,476,482,492,502,522 and 540, in which stepping motors are installed. Since the diaphragm-shaped needle valves are very general

valves for controlling the flow of the refrigerant by applied power, a detailed description thereof will be omitted. The operations of the second and third embodiments of the constant temperature-humidity oven employed the air conditioning unit are very similar to that of the first embodiment.

Hereinafter, the operation of the constant temperature-humidity oven will be described.

1) In case of high temperature and humidity Only when there is no cooling or small cooling in the state of high temperature having a great difference from room temperature, the power consumption of the first heater 110 requiring to heat is minimized. Only when there is no dehumidifying or small dehumidifying in the state of high humidity, the power consumption of the second heater 122 requiring to humidify is minimized.

In order to make the state of the evaporator 150 for cooling satisfying this, for example (although it depends on the setting of temperature and humidity), a. The supply of the refrigerant to the evaporators 150,170,180,190, and 200 must be stopped, and the first and second heaters 110 and 122 must be operated. b. The first evaporator 170 for dehumidifying must be in the state of high pressure evaporation (The solenoid valve 176 is turned off.) so as to rise the evaporating temperature, and the endothermic value must be lowered, and then, the first and second heaters 110 and 122 must be operated.

2) In case of high temperature and low humidity Only when there is no cooling or small cooling in the state of high temperature having a great difference from room temperature, the power consumption of the heater requiring to heat is minimized. Dehumidifying capacity in the state of low humidity must be heightened, or the evaporating energy of the water contained in the humidifier container 121 must be lowered. In order to make the state of the evaporator for dehumidifying satisfying this, for example (although it depends on the setting of temperature and humidity), a. The second evaporator 180 for dehumidifying for an exclusive use in low temperature must be operated and perform strong dehumidifying, and then, the first and second heaters 110 an 122 must be operated.

b. One of the first and second humidifier evaporators 190 and 200 in the humidifier container 121 must be operated, and natural evaporation must be suppressed by removing the evaporating energy of the water contained in the humidifier container 121, and then, the first and second heaters 110 and 122 must be operated.

3) In case of low temperature and high humidity Only when cooling and heating are together performed in the state of lower temperature than room temperature, it is possible for temperature to be exactly controlled. In the state of high humidity, an evaporator having a small dehumidifying effect must be operated. In order to make the state of the evaporator for dehumidifying satisfying this, for example (although it depends on the setting of temperature and humidity), a. The temperature of the heat medium 144 flowing in the heat medium circulating pipe 160 must be slightly lower than the setting temperature (between about 0.5°C and about 5°C, beyond 0°C), and then, the first and second heaters 110 and 122 must be operated. b. The first evaporator 170 for dehumidifying must be in the state of high pressure evaporation (The solenoid valve 176 is turned off, but the evaporating temperature must be higher than the setting temperature.) so as to rise the evaporating temperature, and the endothermic value must be lowered, and then, the first and second heaters 110 and 122 must be operated.

4) In case of low temperature and humidity Only when cooling and heating are together performed in the state of lower temperature than room temperature, it is possible for temperature to be exactly controlled. In the state of low temperature and humidity, an evaporator having a pretty large dehumidifying effect must be used. In order to make the state of the evaporator for dehumidifying satisfying this, for example (although it depends on the setting of temperature and humidity), a. The first evaporator 170 for dehumidifying must be in the state of low pressure evaporation (The solenoid valve 176 is turned on.) so as to drop the evaporating temperature, and then, the first heater 110 must be operated. After that, the second evaporator 180 for dehumidifying for an exclusive use in low

temperature must be operated and perform strong dehumidifying, and then, the second heater 122 must be operated. b. The first evaporator 170 for dehumidifying must be in the state of low pressure evaporation (The solenoid valve 176 is turned on.) so as to drop the evaporating temperature, and then, the first heater 110 must be operated. After that, one of the first and second humidifier evaporators 190 and 200 in the humidifier container 121 must be operated, and natural evaporation must be suppressed by removing the evaporating energy of the water contained in the humidifier container 121, and then, the second heater 122 must be operated. Next, the second evaporator 180 for dehumidifying for an exclusive use in low temperature must be operated and perform strong dehumidifying, and then, the second heater 122 must be operated.

5) In the case of controlling temperature below zero After emptying the water contained in the humidifier container 121, the evaporator 150 for exclusively cooling must be operated, and then, temperature is controlled by the first heater 110.

As described above, the present invention enables temperature and humidity in the constant temperature-humidity oven to be controlled in a wider range by employing the evaporator for cooling, the first and second evaporators for dehumidifying, the first and second humidifier evaporators 190 and 200, the heat medium circulating pipe, the means for controlling the flow quantity of the refrigerant, and the means for controlling the evaporating pressure of the refrigerant, and the present invention can reduce the consumption of energy.

Also, by employing the first humidifier evaporator arranged to be contacted with the water surface and the second humidifier evaporator arranged in the water, the present invention can control humidity in the case of below 0°C or beyond 100°C.

In addition, since frost is hardly formed in the present invention, use of a defroster for removing frost can be excluded.

While this invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.