Background Technique An electric clothing dryer used in ordinary households uses an electric heater as a heat source which is necessary for drying. Due to the current carrying capacity of a domestic convenience receptacle, its amount of heat is limited, and this causes a bottleneck in reduction of time required for drying clothing. Further, heat used for drying clothing is not reused and is only discharged out, and this is waste of energy.

There is proposed a clothing dryer in which a heat pump apparatus is used as a heat source for drying clothing, a portion of drying air is discharged out from a body of the apparatus, thereby reducing the required electricity and achieving high dehumidification efficiency (see patent document 1 for example). Fig. 17 is a block diagram showing the conventional drying apparatus described in the patent document 1.

In this drying apparatus, a rotation drum 22 is a dry chamber which is rotatably provided in a body 21 of the drying apparatus and which dries clothing 39 in the rotation drum 22.

A rotation drum 22 is driven by a motor 27 through a drum belt 35. A blower 23 sends drying air from the rotation drum 22 toward a circulation duct 26 through a filter 24 and a rotation drum-side air intake 25 in the flowing direction showing by an arrow M. The blower 23 is driven by the motor 27 through a fan belt 28.

An evaporator 29 is disposed in the circulation duct 26.

The evaporator 29 evaporates a refrigerant, thereby cooling and dehumidifying the drying air. A condenser 30 condenses a refrigerant, thereby heating the drying air flowing in the circulation duct 26. The heated drying air is introduced into the circulation duct 26 and is again returned to the dry chamber.

The compressor 31 generates a pressure difference in a refrigerant. A throttle apparatus 32 comprising a capillary tube and the like maintains the pressure difference of the refrigerant. The evaporator 29, the condenser 30, the compressor 31 and the throttle apparatus 32 are connected to one another through pipes 33 to constitute a heat pump apparatus.

(Patent Document 1) Japanese Patent Application Laid-open No. H7-178289 (pages 4 to 5, Fig. 1) However, when the clothing is to be dried using such a drying apparatus, since the temperature of the drying air, a heat exchange loss between the body and outside, and a moisture amount included in the clothing to be dried are gradually varied with drying time, it is necessary to always control the optimal amount of heat to be discharged outside. If heat greater than the optimal amount of heat to be discharged is discharged outside, the drying time is increased, and the electricity consumption amount is increased.

If the amount of heat of the drying air is excessively increased, pressure in a refrigeration cycle of the heat pump apparatus adversely rises, and the stable operation can not be carried out in the refrigeration cycle. Thereupon, there is proposed a drying apparatus which can be operated in a stable refrigeration cycle by cooling the drying air to avoid an influence on the refrigeration cycle caused by increase in the amount of heat of the drying air. However, this technique has a problem that heat required for drying an object to be dried is discarded or discharged outside.

Therefore, it is an object of the present invention to provide a drying apparatus and an operating method thereof which can operate a heat pump apparatus in a stable refrigeration cycle without excessively discarding heat.

It is another object of the invention to provide a drying apparatus having high reliability and an operating method of the drying apparatus.

Disclosure of the Invention A first aspect of the present invention provides a drying apparatus comprising a heat pump apparatus, in which the heat pump apparatus includes a main circuit and a bypass circuit, in the main circuit, a refrigerant is circulated through a compressor, a radiator, a first throttle apparatus, a gas-liquid separator, a second throttle apparatus and an evaporator in this order, a portion of the refrigerant flows through the bypass circuit from an upper portion of the gas-liquid separator to the compressor via a flow rate control valve, air heated by the radiator is introduced into a dry chamber, the heated air dries a subject to be dried in the dry chamber, the air attracted moisture due to this drying operation is dehumidified by the evaporator, and the dehumidified air is again heated by the radiator, wherein the drying apparatus further comprises flow rate control means for controlling an opening degree of the flow rate control valve.

According to this aspect, the drying apparatus can be controlled such that the radiator ability, the evaporator ability and the like are equal to each other. Therefore, unlike the conventional technique, the heat pump apparatus can be operated in a stable refrigeration cycle without discharging excessive heat quantity outside. That is, the radiator ability is enhanced, the drying time can be shortened, electricity amount to be consumed can be reduced, and energy can be saved.

A second aspect of the invention provides a drying apparatus comprising a heat pump apparatus, in which the heat pump apparatus includes a main circuit and a bypass circuit, in the main circuit, a refrigerant is circulated through a compressor, a radiator, an ejector, a gas-liquid separator and a flow rate control valve in this order, a liquid refrigerant of the refrigerant flows through the bypass circuit from a lower portion of the gas-liquid separator to a suction portion of the ejector via the evaporator, air heated by the radiator is introduced into a dry chamber, the heated air dries a subject to be dried in the dry chamber, the air attracted moisture due to this drying operation is dehumidified by the evaporator, and the dehumidified air is again heated by the radiator, wherein the drying apparatus further comprises flow rate control means for controlling an opening degree of the flow rate control valve.

According to this aspect, the drying apparatus can be controlled such that the radiator ability, the evaporator ability and the like are equal to each other. Therefore, unlike the conventional technique, the heat pump apparatus can be operated in a stable refrigeration cycle without discharging excessive heat quantity outside. That is, the radiator ability is enhanced, the drying time can be shortened, electricity amount to be consumed can be reduced, and energy can be saved.

According to a third aspect of the invention, in the drying apparatus of the first or second aspect, the drying apparatus further comprises discharge pressure detecting means for detecting a discharge pressure of the compressor, and flow rate control means for controlling the opening degree of the flow rate adjusting valve using a detection value detected by the discharge pressure detecting means.

With this aspect, the throttle opening degree of the flow rate control valve is controlled in accordance with the discharge pressure of the compressor. Therefore, reliability of the compressor and the drying apparatus can reliably be secured, and the heat pump apparatus can be operated in a stable and efficient refrigeration cycle, the drying time can be shortened, and input to the compressor can be reduced to save energy.

According to a fourth aspect of the invention, in the drying apparatus of the first or second aspect, the drying apparatus further comprises discharge temperature detecting means for detecting discharge temperature of the compressor, and flow rate control means for controlling the opening degree of the flow rate adjusting valve using a detection value from the discharge temperature detecting means.

With this aspect, the throttle opening degree of the flow rate control valve is controlled in accordance with the discharge temperature of the compressor. Therefore, reliability of the compressor and the drying apparatus can reliably be secured, and the heat pump apparatus can be operated in a stable and efficient refrigeration cycle, the drying time can be shortened, and input to the compressor can be reduced to save energy.

According to a fifth aspect of the invention, in the drying apparatus of the first aspect, the drying apparatus further comprises operation time detecting means for detecting operation time of the compressor, and a first throttle apparatus opening degree control means for controlling an opening degree of the first throttle apparatus using a detection value detected by the operation time detecting means.

With this aspect, the operation time of the compressor is detected, and when the discharge pressure of the compressor exceeds a set value for more than constant time, the throttle opening degree of the first throttle apparatus is controlled.

Thus, reliability of the compressor and the drying apparatus can reliably be secured, and the heat pump apparatus can be operated in a stable and efficient refrigeration cycle.

According to a sixth aspect of the invention, in the drying apparatus of the second aspect, the drying apparatus further comprises operation time detecting means for detecting operation time of the compressor, and operation frequency control means for controlling operation frequency of the compressor using a detection value detected by the operation time detecting means.

With this aspect, the operation time of the compressor is detected, and when the discharge pressure of the compressor exceeds the set value for more than constant time, the operation frequency of the compressor is controlled. Thus, reliability of the compressor and the drying apparatus can reliably be secured, and the heat pump apparatus can be operated in a stable and efficient refrigeration cycle.

A seventh aspect of the invention provides an operating method of a drying apparatus comprising a heat pump apparatus, in which the heat pump apparatus includes a main circuit and a bypass circuit, in the main circuit, a refrigerant is circulated through a compressor, a radiator, a first throttle apparatus, a gas-liquid separator, a second throttle apparatus and an evaporator in this order, a portion of the refrigerant flows through the bypass circuit from an upper portion of the gas-liquid separator to the compressor via a flow rate control valve, air heated by the radiator is introduced into a dry chamber, the heated air dries a subject to be dried in the dry chamber, the air attracted moisture due to this drying operation is dehumidified by the evaporator, and the dehumidified air is again heated by the radiator, wherein an opening degree of the flow rate control valve is controlled such that a heat quantity released to air in the radiator becomes equal to a sum of a heat quantity obtained from air in the evaporator and a heat quantity leaking outside.

With this aspect, the opening degree of the flow rate control valve is controlled. Therefore, the radiator heat quantity, the evaporator heat quantity and the like can be set equal to each other. Therefore, unlike the conventional technique, the heat pump apparatus can be operated in a stable refrigeration cycle without discharging excessive heat quantity outside. Thus, the heat pump apparatus can be operated in a stable refrigeration cycle.

According to an eighth aspect of the invention, in the operating method of the drying apparatus of the seventh aspect, when a discharge pressure of the compressor is greater than a set pressure, the opening degree of the flow rate control valve is increased, and when the discharge pressure of the compressor is smaller than the set pressure, the opening degree of the flow rate control valve is reduced.

With this aspect, the throttle opening degree of the flow rate control valve is controlled in accordance with the discharge pressure of the compressor. Therefore, the heat pump apparatus can be operated in a stable and efficient refrigeration cycle.

According to a ninth aspect of the invention, in the operating method of the drying apparatus of the seventh aspect, when a discharge temperature of the compressor is greater than set temperature, the opening degree of the flow rate control valve is increased, and when the discharge temperature of the compressor is smaller than the set temperature, the opening degree of the flow rate control valve is reduced.

With this aspect, the throttle opening degree of the flow rate control valve is controlled. Therefore, in accordance with the discharge temperature of the compressor, the heat pump apparatus can be operated in a stable and efficient refrigeration cycle.

According to a tenth aspect of the invention, in the operating method of the drying apparatus of any one of the seventh to ninth aspects, when the discharge pressure of the compressor is smaller than the set pressure, the opening degree of the flow rate control valve is reduced, and when the discharge pressure of the compressor is greater than the set pressure, the opening degree of the flow rate control valve is increased. The operation time of the compressor is measured, and when the operation time is greater than the set time, the opening degree of the first throttle apparatus is increased.

With this aspect, the operation time of the compressor is detected, and when the discharge pressure of the compressor exceeds the set value for more than constant time, the opening degree of the first throttle apparatus is controlled. Thus, the heat pump apparatus can be operated in a stable and efficient refrigeration cycle.

An eleventh aspect of the invention provides an operating method of the drying apparatus comprising a heat pump apparatus, in which the heat pump apparatus includes a main circuit and a bypass circuit, in the main circuit, a refrigerant is circulated through a compressor, a radiator, an ejector, a gas-liquid separator and a flow rate control valve in this order, a portion of the refrigerant flows back through the bypass circuit from a lower portion of the gas-liquid separator to a suction portion of the ejector via the evaporator, air heated by the radiator is introduced into a dry chamber, the heated air dries a subject to be dried in the dry chamber, the air attracted moisture due to this drying operation is dehumidified by the evaporator, and the dehumidified air is again heated by the radiator, wherein an opening degree of the flow rate control valve is controlled such that a heat quantity released to air in the radiator becomes equal to a sum of a heat quantity obtained from air in the evaporator and a heat quantity leaking outside.

With this aspect, the opening degree of the flow rate control valve is controlled. Therefore, the radiator heat quantity, the evaporator heat quantity and the like can be set equal to each other. Therefore, unlike the conventional technique, the heat pump apparatus can be operated in a stable refrigeration cycle without discharging excessive heat quantity outside. Thus, the heat pump apparatus can be operated in a stable refrigeration cycle.

According to a twelfth aspect of the invention, in the operating method of the drying apparatus of the eleventh aspect, when a discharge pressure of the compressor is greater than a set pressure, the opening degree of the flow rate control valve is reduced, and when the discharge pressure of the compressor is smaller than the set pressure, the opening degree of the flow rate control valve is increased.

With this aspect, the throttle opening degree of the flow rate control valve is controlled in accordance with the discharge pressure of the compressor. Therefore, the heat pump apparatus can be operated in a stable and efficient refrigeration cycle.

According to a thirteenth aspect of the invention, in the operating method of the drying apparatus of the eleventh aspect, when a discharge temperature of the compressor is greater than set temperature, the opening degree of the flow rate control valve is reduced, and when the discharge temperature of the compressor is smaller than the set temperature, the opening degree of the flow rate control valve is increased.

With this aspect, the throttle opening degree of the flow rate control valve is controlled in accordance with the discharge temperature of the compressor. Therefore, the heat pump apparatus can be operated in a stable and efficient refrigeration cycle.

According to a fourteenth aspect of the invention, in the operating method of the drying apparatus of the twelfth or thirteenth aspect, the operation time of the compressor is measured, and when the operation time is greater than the set time, operation frequency of the compressor is reduced.

With this aspect, the operation time of the compressor is detected, and when the discharge pressure of the compressor exceeds the set value for more than constant time, the operation frequency of the compressor is controlled. Thus, the heat pump apparatus can be operated in a stable and efficient refrigeration cycle.

According to a fifteenth aspect of the invention, in the operating method of the drying apparatus of the seventh or eleventh aspect, carbon dioxide is used as the refrigerant, the drying apparatus is operated under pressure in which high pressure-side pressure exceeds critical pressure.

With this aspect, if the inlet side temperature of the radiator is the same, higher outlet air temperature can be obtained as compared with flon refrigerant, and the drying time can be shortened.

Brief Description of the Drawings Fig. 1 is a block diagram showing a drying apparatus of a first embodiment of the present invention ; Fig. 2 shows a relation between an injection flow rate and ability in the first embodiment; Fig. 3 shows a relation between ability difference and a flow rate control valve throttle opening degree set value in the first embodiment; Fig. 4 is a Mollier diagram showing a refrigeration cycle in the first embodiment; Fig. 5 is a control flowchart of a drying apparatus of a second embodiment of the invention; Fig. 6 is a control flowchart of a drying apparatus of a third embodiment of the invention; Fig. 7 is a control flowchart of a drying apparatus of a fourth embodiment of the invention; Fig. 8 is a is a block diagram showing a drying apparatus of a fifth embodiment of the invention; Fig. 9 shows a relation between flow rate of refrigerant flowing through a flow rate control valve and ability in the fifth embodiment; Fig. 10 shows a relation between ability difference and a flow rate control valve opening degree set value in the fifth embodiment; Fig. 11 is a Mollier diagram showing a refrigeration cycle in the fifth embodiment; Fig. 12 is a control flowchart of a drying apparatus of a sixth embodiment of the invention; Fig. 13 is a control flowchart of a drying apparatus of a seventh embodiment of the invention; Fig. 14 is a control flowchart of a drying apparatus of an eighth embodiment of the invention; Fig. 15 is a schematic diagram showing temperature variation of refrigerant and air in a radiator of a drying apparatus of a ninth embodiment of the invention; Fig. 16 is a schematic diagram showing temperature variation of refrigerant and air in a radiator of a drying apparatus when a flon refrigerant is used; and Fig. 17 is a block diagram of a conventional drying apparatus.

Best Mode for Carrying Out the Invention (First Embodiment) Embodiments of a drying apparatus of the present invention will be explained below with reference to the drawings. Fig. 1 is a block diagram of a drying apparatus of a first embodiment of the invention.

In the drying apparatus of this embodiment, a refrigerant such as flon and carbon dioxide is used as a working fluid.

The drying apparatus includes a heat pump apparatus having a main circuit and a bypass circuit 8A. In the main circuit, a compressor 1, a radiator 2, a first throttle apparatus 3A, a gas-liquid separator 4, a second throttle apparatus 5 and an evaporator 6 are connected to one another in this order using pipes. The bypass circuit 8A connects an upper portion of the gas-liquid separator 4 and the compressor 1 through a flow rate control valve 7. The drying apparatus includes flow rate control means 14 for controlling an opening degree of the flow rate control valve 7.

The drying apparatus includes a dry chamber 11 for drying a subject to be dried 10 such as clothing by means of drying air 9 heated by the radiator 2, and a blower 12 for sending drying air 9. The drying air 9 is circulated through the radiator 2, the dry chamber 11 and the evaporator 6 through a duct 13 by means of the blower 12.

The operation of the drying apparatus will be explained below.

First, a subject to be dried 10 is put into the dry chamber 11. If the blower 12 is rotated, a flow of the drying air 9 is generated. The drying air 9 is heated by the radiator 2 and enters the dry chamber 11, absorbs moisture from the subject to be dried 10 in the dry chamber 11 and thus, the drying air 9 becomes humid and then, the drying air 9 is sent to the evaporator 6 by the blower 12. The drying air sent to the evaporator 6 is dehumidified and sent to the radiator 2, and is again heated by the radiator 2 and sent to the dry chamber 11. Through this drying cycle, the subject to be dried 10 is dried.

Next, the operation of the heat pump apparatus will be explained using Figs. 2 and 3. Fig. 2 shows a relation between an injection flow rate and ability in the first embodiment.

Fig. 3 shows a relation between ability difference and a flow rate control valve throttle opening degree set value in the first embodiment.

A refrigerant discharged from the compressor 1 is absorbed in heat by the drying air 9 in the radiator 2, and the refrigerant is reduced in pressure by the first throttle apparatus 3A, and the refrigerant flows into the gas-liquid separator 4. In the gas-liquid separator 4, the refrigerant is separated into liquid and gas. The liquid refrigerant flows into the second throttle apparatus 5 from a lower portion of the gas-liquid separator 4, and is again reduced in pressure and then, the liquid refrigerant absorbs heat from the drying air 9 in the evaporator 6 and returns into the compressor 1.

The gas refrigerant (injection refrigerant, hereinafter) flows into the bypass circuit 8A connected to an upper portion of the gas-liquid separator 4, is adjusted in flow rate by the flow rate control valve 7, and returns into the compressor 1.

At that time, if a flow rate of the injection refrigerant becomes greater than a certain value (A point), a total sum of evaporator ability Qe and heat quantity QL which leaks outside of the duct 13 becomes greater than radiator ability Qh as shown in Fig. 2. That is, if the ability difference AW is expressed as AW=Qh- (Qe+QL), the ability difference AW is varied by controlling the opening degree of the flow rate control valve 7 as shown in Fig. 3, and when a flow rate control valve opening degree set value is at B point, the ability difference AW becomes zero.

Here, in the refrigeration cycle, if the circulation of the drying air 9 is continued in a state in which a quantity of heat radiated to the drying air 9 in the radiator 2 is greater than a quantity of heat absorbed from the drying air 9 in the evaporator 6, the heat quantity of the entire drying air is increased, and the heat quantity of the refrigerant in the heat pump apparatus is increased, the refrigerant pressure is increased and finally, this exceeds a motor toque of the compressor 1.

On the other hand, if the circulation of the drying air 9 is continued in a state in which the quantity of heat radiated to the drying air 9 in the radiator 2 is smaller than the quantity of heat absorbed from the drying air 9 in the evaporator 6, the heat quantity of the entire drying air is reduced, the heat quantity of the refrigerant in the heat pump apparatus is reduced, the refrigerant pressure 6 is reduced, the refrigerant temperature in the evaporator is reduced to 0°C or lower, frost is generated on the evaporator 6, and heat-exchanging ability is largely deteriorated.

Therefore, in order to stably operate the heat pump apparatus, it is necessary to control the opening degree of the flow rate control valve 7 such that the heat quantity Qh that the drying air 9 receives from the radiator 2 and a total sum of the heat quantity Qe absorbed by the evaporator 6 and the heat quantity QL leaking outside of the duct 13 are equal to each other.

The operation of the flow rate control means 14 of the flow rate control valve 7 will be explained using Fig. 4. Fig.

4 is a Mollier diagram showing a refrigeration cycle in the first embodiment.

If a refrigerant weight circulating amount flowing through the evaporator 6 is defined as Ge and a refrigerant weight circulating amount flowing through the bypass circuit 8A is defined as Gi, a refrigerant weight circulating amount flowing through the radiator 2 can be expressed as Ge+Gi. That is, since ability Qh of the radiator 2 is a product of weight circulating amount and enthalpy difference, the ability Qh is expressedasQh= (Ge+Gi) x (h2-h3). Similarly, abilityQeofthe evaporator 6 is expressed as Qe=Gex (hl-h4). Here, if the opening degree of the flow rate control valve 7 is increased <BR> <BR> by the flow rate control means 14, a value of a specific enthalpy value h4 is reduced and thus, an enthalpy difference of the evaporator 6 is increased and the evaporator ability Qe is increased. If the opening degree of the flow rate control valve 7 is reduced, the enthalpy difference of the radiator 2 is increased and the radiator ability Qh is increased.

Thus, in the drying apparatus of this embodiment, the opening degree of the flow rate control valve 7 is controlled <BR> <BR> such that the ability difference AW becomes zero, i. e. , such that the radiator ability and a total sum of the evaporator ability and the heat quantity leaking outside are equal to each other. According to this control, unlike the conventional technique, the radiator ability is enhanced without discharging excessive heat quantity outside, the drying time is shortened, electricity to be consumed is reduced and thus, energy can be saved.

(Second Embodiment) Fig. 5 is a control flowchart of a drying apparatus of a second embodiment of the invention. Only different structure and operation of the drying apparatus of the second embodiment from those of the first embodiment will be explained.

The same can be applied to third and subsequent embodiments also.

Based on the structure of the first embodiment shown in Fig. 1, the drying apparatus of the second embodiment includes discharge pressure detecting means (not shown) for detecting a discharge pressure of the compressor 1.

The operation of the flow rate control means 14 of the drying apparatus will be explained.

In Fig. 5, in step 41, a discharge pressure Pd detected by the discharge pressure detecting means and a target set pressure Pm (e. g., lOMPa) are compared with each other. If Pd is greater than Pm, it is judged that the ability of the radiator 2 is greater than ability of the evaporator 6 and heat quantity leaking outside, procedure is proceeded to step 42, control for increasing the opening degree of the flow rate control valve 7 is carried out and then, the procedure is returned to step 41. If Pd is smaller than Pm in step 41, it is judged that the ability of the radiator 2 is smaller than ability of the evaporator 6 and heat quantity leaking outside, procedure is proceeded to step 43, control for reducing the opening degree of the flow rate control valve 7 is carried out and then, the procedure is returned to step 41. With this control, a refrigeration cycle can be operated stably.

In the drying apparatus of the second embodiment, the discharge pressure of the compressor 1 is detected, and the opening degree of the flow rate control valve 7 is controlled based on the detected discharge pressure. Therefore, the reliability of the compressor and the drying apparatus can reliably be ensured, and the refrigeration cycle can be operated stably and efficiently. Further, the drying time is shortened, input to the compressor is reduced and thus, energy can be saved.

(Third Embodiment) Fig. 6 is a control flowchart of a drying apparatus of a third embodiment of the invention. Different portions of the structure of the drying apparatus of the third embodiment from those of the first embodiment will be explained.

Based on the structure of the first embodiment shown in Fig. 1, the drying apparatus of the third embodiment includes discharge temperature detecting means (not shown) for detecting discharge temperature of the compressor 1.

The operation of the flow rate control means 14 of the drying apparatus will be explained below.

In Fig. 6, in step 51, a discharge temperature Td detected by the discharge temperature detecting means and a target set temperature Tm (e. g., 100°C) are compared with each other. If Td is greater than Tm, it is judged that the ability of the radiator 2 is greater than ability of the evaporator 6 and heat quantity leaking outside, procedure is proceeded to step 52, control for increasing the opening degree of the flow rate control valve 7 is carried out and then, the procedure is returned to step 51. If Td is smaller than Tm in step 51, it is judged that the ability of the radiator 2 is smaller than ability of the evaporator 6 and heat quantity leaking outside, procedure is proceeded to step 53, control for reducing the opening degree of the flow rate control valve 7 is carried out and then, the procedure is returned to step 51. With this control, a refrigeration cycle can be operated stably.

In the drying apparatus of the third embodiment, the discharge temperature of the compressor 1 is detected, and the opening degree of the flow rate control valve 7 is controlled based on the detected discharge temperature. Therefore, the reliability of the compressor and the drying apparatus can reliably be ensured, and the refrigeration cycle can be operated stably and efficiently. The drying time is shortened, input to the compressor is reduced and thus, energy can be saved.

(Fourth Embodiment) Fig. 7 is a control flowchart of a drying apparatus of a fourth embodiment of the invention. Different portions of the drying apparatus of the fourth embodiment from those of the first embodiment will be explained.

Based on the structure of the first embodiment shown in Fig. 1, the drying apparatus of the fourth embodiment includes discharge pressure detecting means (not shown) for detecting discharge pressure of the compressor 1, operation time detecting means (not shown) for detecting operation time of the compressor 1, and first throttle apparatus opening degree control means (not shown) for controlling the opening degree of the first throttle apparatus 3A.

The operation of the flow rate control means 14 of the drying apparatus will be explained.

In Fig. 7, in step 61, a discharge pressure Pd detected by the discharge pressure detecting means and a target set pressure Pm (e. g., lOMPa) are compared with each other. If Pd is greater than Pm, it is judged that the ability of the radiator 2 is greater than ability of the evaporator 6 and heat quantity leaking outside, procedure is proceeded to step 62, control for increasing the opening degree of the flow rate control valve 7 is carried out and then, the procedure is proceeded to step 64. If Pd is smaller than Pm in step 61, it is judged that the ability of the radiator 2 is smaller than ability of the evaporator 6 and heat quantity leaking outside, procedure is proceeded to step 63, control for reducing the opening degree of the flow rate control valve 7 is carried out and then, the procedure is returned to step 61.

In step 64, set time Tm (e. g., three minutes) and operation time Ti detected by the operation time detecting means of the compressor 1 are compared with each other. If Ti is greater than Tm, it is judged that the ability of the radiator 2 is extremely great or since the load is high, there is an adverse possibility that the discharge pressure exceeds a safety operation region. Thus, control for increasing the opening degree of the first throttle apparatus 3A is carried out by the first throttle apparatus opening degree means and then, the procedure is returned to step 61. If Ti is smaller than Tm, procedure is returned to step 61.

In the drying apparatus of the fourth embodiment, the operation time of the compressor is detected, and the opening degree of the first throttle apparatus is controlled when the discharge pressure of the compressor exceeds the set value for more than constant time. Therefore, the reliability of the compressor and the drying apparatus can reliably be ensured, and the refrigeration cycle can be operated stably and efficiently.

The drying apparatus may includes the discharge temperature detecting means explained in the drying apparatus of the third embodiment, instead of the discharge pressure detecting means of the fourth embodiment.

(Fifth Embodiment) A drying apparatus of a fifth embodiment of the invention will be explained with reference to the drawing. Fig. 8 is a block diagram showing the drying apparatus of the fifth embodiment.

The drying apparatus of this embodiment uses refrigerant such as flon and carbon dioxide as the working fluid. The drying apparatus includes a heat pump apparatus which has a main circuit and a bypass circuit 8B. In the main circuit, the compressor 1, the radiator 2, an ejector 3B, the gas-liquid separator 4 and the flow rate control valve 7 are connected to one another in this order. The bypass circuit 8B connects a lower portion of the gas-liquid separator 4 and a suction portion of the ejector 3B to each other through the evaporator 6. The drying apparatus also includes the flow rate control means 14 which controls the opening degree of the flow rate control valve 7.

The drying apparatus includes a dry chamber 11 for drying the subject to be dried 10 such as clothing by means of drying air 9 heated by the radiator 2, the blower 12 for sending drying air 9, and the duct 13 through which the drying air 9 is circulated from the radiator 2 to the dry chamber 11 and the evaporator 6.

The operation of the drying apparatus will be explained below.

First, a subject to be dried 10 is put into the dry chamber 11. If the blower 12 is rotated, a flow of the drying air 9 is generated. The drying air 9 is heated by the radiator 2 and enters the dry chamber 11, absorbs moisture from the subject to be dried 10 in the dry chamber 11 and thus, the drying air 9 becomes humid and then, the drying air 9 is sent to the evaporator 6 by the blower 12. The drying air sent to the evaporator 6 is dehumidified and sent to the radiator 2, and is again heated by the radiator 2 and sent to the dry chamber 11. Through this drying cycle, the subject to be dried 10 is dried.

Next, the operation of the heat pump apparatus will be explained using Figs. 9 and 10. Fig. 9 shows a relation between flow rate of refrigerant flowing through a flow rate control valve and ability in the fifth embodiment. Fig. 10 shows a relation between ability difference and a flow rate control valve opening degree set value in the fifth embodiment.

A refrigerant discharged from the compressor 1 is absorbed in heat by the drying air 9 in the radiator 2 and then, the refrigerant flows into the ejector 3B. Here, the ejector 3B converts pressure energy of high pressure refrigerant flowing out from the radiator 2 into velocity energy, thereby decompressing the refrigerant and allowing the refrigerant to expand, and a refrigerant evaporated in the evaporator 6 by high speed refrigerant stream (jet stream) generated at that time is sucked and mixed and in this state, velocity energy is converted into pressure energy, thereby increasing the pressure of the refrigerant.

The refrigerant flowing out from the ejector 3B flows into the gas-liquid separator 4 where the refrigerant is separated into a liquid refrigerant and a gas refrigerant. The liquid refrigerant flows into the evaporator 6, absorbs heat from the drying air 9 and then, flows into the bypass circuit 8B and is again sucked by the suction portion of the ejector 3B. The gas refrigerant separated by the gas-liquid separator 4 is adjusted in flow rate by the flow rate control valve 7 and returns into the compressor 1.

At that time, if the flow rate of the refrigerant flowing through the flow rate control valve 7 becomes greater than a certain value (A point) as shown in Fig. 9, the radiator ability Qh becomes greater than a total sum of the evaporator ability Qe and the heat quantity QL leaking outside from the duct 13.

That is, if the ability difference AW is expressed as AW=Qh-(Qe+QL), the ability difference AW is varied by controlling the opening degree of the flow rate control valve 7 as shown in Fig. 10, and when the flow rate control valve opening degree set value is at B point, the ability difference AW becomes zero.

Here, in the refrigeration cycle, if the circulation of the drying air 9 is continued in a state in which a quantity of heat radiated to the drying air 9 in the radiator 2 is greater than a quantity of heat absorbed from the drying air 9 in the evaporator 6, the heat quantity of the entire drying air is increased, and the heat quantity of the refrigerant in the heat pump apparatus is increased, the refrigerant pressure is increased and finally, this exceeds a motor toque of the compressor 1.

Here, in the refrigeration cycle, if the circulation of the drying air 9 is continued in a state in which a quantity of heat radiated to the drying air 9 in the radiator 2 is greater than a quantity of heat absorbed from the drying air 9 in the evaporator 6, the heat quantity of the entire drying air is increased, and the heat quantity of the refrigerant in the heat pump apparatus is increased, the refrigerant pressure is increased and finally, this exceeds a motor toque of the compressor 1.

On the other hand, if the circulation of the drying air 9 is continued in a state in which the quantity of heat radiated to the drying air 9 in the radiator 2 is smaller than the quantity of heat absorbed from the drying air 9 in the evaporator 6, the heat quantity of the entire drying air is reduced, the heat quantity of the refrigerant in the heat pump apparatus is reduced, the refrigerant pressure is reduced, the refrigerant temperature in the evaporator 6 is reduced to 0°C or lower, frost is generated on the evaporator 6, and heat-exchanging ability is largely deteriorated.

Therefore, in order to stably operate the heat pump apparatus, it is necessary to control the opening degree of the flow rate control valve 7 such that the heat quantity Qh that the drying air 9 receives from the radiator 2 and a total sum of the heat quantity Qe absorbed by the evaporator 6, and the heat quantity QL leaking outside of the duct 13 are equal to each other.

The operation of the flow rate control means 14 of the flow rate control valve 7 will be explained using Fig. 11. Fig.

11 is a Mollier diagram showing a refrigeration cycle in this embodiment.

If a refrigerant weight circulating amount flowing through the evaporator 6 is defined as Ge and a refrigerant weight circulating amount flowing through the flow rate control valve 7 is defined as Gi, and a refrigerant weight circulating amount flowing through the radiator 2 is defined as Gh, the refrigerant weight circulating amount Gh flowing through the radiator 2 becomes equal to Gi. That is, by controlling the flow rate of the flow rate control valve 7, the refrigerant weight circulating amounts flowing through the evaporator 6 and the radiator 2 can be controlled. Since the ability Qh of the radiator 2 is a product of the weight circulating amount and enthalpy difference, the ability Qh is expressed as Qh=Ghx (h2-h3). Similarly, ability Qe of the evaporator 6 is expressed as Qe=Gex (hl-h4).

Here, if the opening degree of the flow rate control valve 7 is increased by the flow rate control means 14, the refrigerant flow rate Gi is increased, the refrigerant weight circulating amount Gh flowing through the radiator 2 is also increased, and the radiator ability Qh is increased. If the opening degree of the flow rate control valve 7 is increased, since the value of the specific enthalpy value h4 is reduced, the enthalpy difference of the evaporator 6 is increased.

However, since the refrigerant weight circulating amount Ge flowing through the evaporator 6 is reduced, the increasing amount of the evaporator ability Qe is smaller than the radiator ability Qh. Therefore, an increasing ratio of the (evaporator ability Qe + leaking heat quantity QL) to the refrigerant flow rate flowing through the flow rate control valve 7 is different from an increasing ratio of the radiator ability Qh as shown in Fig. 9.

Thus, in the drying apparatus of this embodiment, the opening degree of the flow rate control valve 7 is controlled <BR> <BR> such that the ability difference AW becomes zero, i. e. , such that the radiator ability and a total sum of the evaporator ability and the heat quantity leaking outside are equal to each other. According to this control, unlike the conventional technique, the radiator ability is enhanced without discharging excessive heat quantity outside, the drying time is shortened, electricity to be consumed is reduced and thus, energy can be saved.

(Sixth Embodiment) Fig. 12 is a control flowchart of a drying apparatus of a sixth embodiment of the invention. Only different structure and operation of the drying apparatus of the sixth embodiment from those of the fifth embodiment will be explained. The same can be applied to seventh and subsequent embodiments also.

Based on the structure of the fifth embodiment shown in Fig. 8, the drying apparatus of the sixth embodiment includes discharge pressure detecting means (not shown) for detecting a discharge pressure of the compressor 1.

The operation of the flow rate control means 14 of the drying apparatus will be explained.

In Fig. 12, in step 41, a discharge pressure Pd detected by the discharge pressure detecting means and a target set pressure Pm (e. g., lOMPa) are compared with each other. If Pd is greater than Pm, it is judged that the ability of the radiator 2 is greater than ability of the evaporator 6 and heat quantity leaking outside, procedure is proceeded to step 42, control for reducing the opening degree of the flow rate control valve 7 is carried out and then, the procedure is returned to step 41. If Pd is smaller than Pm in step 41, it is judged that the ability of the radiator 2 is smaller than ability of the evaporator 6 and heat quantity leaking outside, procedure is proceeded to step 43, control for increasing the opening degree of the flow rate control valve 7 is carried out and then, the procedure is returned to step 41. With this control, a refrigeration cycle can be operated stably.

In the drying apparatus of the sixth embodiment, the discharge pressure of the compressor 1 is detected, and the opening degree of the flow rate control valve 7 is controlled based on the detected discharge pressure. Therefore, the reliability of the compressor and the drying apparatus can reliably be ensured, and the refrigeration cycle can be operated stably and efficiently. Further, the drying time is shortened, input to the compressor is reduced and thus, energy can be saved.

(Seventh Embodiment) Fig. 13 is a control flowchart of a drying apparatus of a seventh embodiment of the invention. Different portions of the structure and the operation of the drying apparatus of the seventh embodiment from those of the fifth embodiment will be explained.

Based on the structure of the fifth embodiment, the drying apparatus of the seventh embodiment includes discharge temperature detecting means (not shown) for detecting discharge temperature of the compressor 1.

The operation of the flow rate control means 14 of the drying apparatus will be explained below.

In Fig. 13, in step 51, a discharge temperature Td detected by the discharge temperature detecting means and a target set temperature Tm (e. g. , 100°C) are compared with each other. If Td is greater than Tm, it is judged that the ability of the radiator 2 is greater than ability of the evaporator 6 and heat quantity leaking outside, procedure is proceeded to step 52, control for reducing the opening degree of the flow rate control valve 7 is carried out and then, the procedure is returned to step 51. If Td is smaller than Tm in step 51, it is judged that the ability of the radiator 2 is smaller than ability of the evaporator 6 and heat quantity leaking outside, procedure is proceeded to step 53, control for increasing the opening degree of the flow rate control valve 7 is carried out and then, the procedure is returned to step 51. With this control, a refrigeration cycle can be operated stably.

In the drying apparatus of the seventh embodiment, the discharge temperature of the compressor 1 is detected, and the opening degree of the flow rate control valve 7 is controlled based on the detected discharge temperature. Therefore, the reliability of the compressor 1 and the drying apparatus can reliably be ensured, and the refrigeration cycle can be operated stably and efficiently. The drying time is shortened, input to the compressor is reduced and thus, energy can be saved.

(Eighth Embodiment) Fig. 14 is a control flowchart of a drying apparatus of an eighth embodiment of the invention. Different portions of the structure and the operation of the drying apparatus of the eighth embodiment from those of the fifth embodiment will be explained.

Based on the structure of the fifth embodiment, the drying apparatus of the eighth embodiment includes operation time detecting means (not shown) for detecting the operation time of the compressor 1, and operation frequency control means (not shown) for controlling the operation frequency of the compressor 1.

The operation of the flow rate control means 14 of the drying apparatus will be explained.

In Fig. 14, in step 61, a discharge pressure Pd detected by the discharge pressure detecting means and a target set pressure Pm (e. g., lOMPa) are compared with each other. If Pd is greater than Pm, it is judged that the ability of the radiator 2 is greater than ability of the evaporator 6 and heat quantity leaking outside, procedure is proceeded to step 62, control for reducing the opening degree of the flow rate control valve 7 is carried out and then, the procedure is proceeded to step 64. If Pd is smaller than Pm in step 61, it is judged that the ability of the radiator 2 is smaller than ability of the evaporator 6 and heat quantity leaking outside, procedure is proceeded to step 63, control for increasing the opening degree of the flow rate control valve 7 is carried out and then, the procedure is returned to step 61.

In step 64, set time Xm (e. g. , three minutes) and operation time Ti detected by the operation time detecting means of the compressor 1 are compared with each other. If Ti is greater than Xm, it is judged that the ability of the radiator 2 is extremely great or since the load is high, there is an adverse possibility that the discharge pressure exceeds a safety operation region. Thus, control for reducing the operation frequency of the compressor 1 is carried out by the operation frequency control means and then, the procedure is returned to step 61. If Ti is smaller than Xm, the procedure is returned to step 61.

In the drying apparatus of the eighth embodiment, the operation time of the compressor 1 is detected, and when the discharge pressure of the compressor 1 exceeds the set value for more than constant time, the operation frequency of the compressor 1 is controlled. Therefore, the reliability of the compressor and the drying apparatus can reliably be ensured, and the refrigeration cycle can be operated stably and efficiently.

The drying apparatus may includes the discharge temperature detecting means explained in the drying apparatus of the seventh embodiment, instead of the discharge pressure detecting means of the eighth embodiment.

(Ninth Embodiment) A drying apparatus of a ninth embodiment of the invention will be explained with reference to Figs. 15 and 16.

In the drying apparatus of the ninth embodiment, carbon dioxide is used as a refrigerant in the heat pump apparatus of any of the fifth to eighth embodiments. The drying apparatus is operated under pressure in which high pressure-side pressure exceeds critical pressure. Fig. 15 is a schematic diagram showing temperature variation of refrigerant and air in the radiator of the drying apparatus of the ninth embodiment. Fig. 16 is a schematic diagram showing temperature variation of a refrigerant and air in the radiator 2 when a flon refrigerant is used.

That is, as shown in Fig. 16, in the case of the flon refrigerant, the refrigerant is brought from a superheat state into a gas-liquid two phase state and then into a supercool state, in the radiator 2. The refrigerant heat-exchanges with air, and the air side outlet temperature in the radiator 2 rises to C.

On the other hand, as shown in Fig. 15, when carbon dioxide is used as a refrigerant and the apparatus is operated in a state in which the high pressure side pressure exceeds the critical pressure, the heat exchange in the radiator 2 does not cause the gas-liquid phase change.

Therefore, a temperature difference At between the air side outlet temperature and the refrigerant side inlet temperature when the carbon dioxide refrigerant is used can be made smaller than a temperature difference AT in the case of the flon refrigerant, and the outlet air temperature of the radiator 2 becomes D. That is, if the refrigerant side inlet temperature To is the same temperature, the outlet air temperature D in the case of carbon dioxide refrigerant can be made higher than the outlet air temperature C in the case of the flon refrigerant.

In the drying apparatus of the ninth embodiment, if carbon dioxide is used in the heat pump apparatus as a refrigerant in which the heat exchange of the radiator 2 can be carried out in the supercritical state, the temperature of the drying air 9 can further be increased. Therefore, it is possible to further shorten the drying time, and to provide a drying apparatus having high drying efficiency.

According to the drying apparatus of the present invention, the throttle opening degree of the flow rate control valve is controlled in accordance with the discharge pressure and discharge temperature of the compressor. With this, the heat pump apparatus can be operated in the stable and efficient refrigeration cycle. Therefore, the reliability of the compressor and the drying apparatus can reliably be ensured, and the drying time is shortened, input to the compressor is reduced and thus, energy can be saved.

Industrial Applicability According to the present invention, the drying apparatus can be used for other application such as for drying plateware, garbage and the like.