US20070271942A1

US20070271942A1 - Ejector cycle

Info

Publication number: US20070271942A1
Application number: US11/805,142
Authority: US
Inventors: Naoki Yokoyama; Hirotsugu Takeuchi; Makoto Ikegami; Yasuhiro Yamamoto
Original assignee: Denso Corp
Current assignee: Denso Corp
Priority date: 2006-05-23
Filing date: 2007-05-22
Publication date: 2007-11-29
Also published as: DE102007023691A1; JP2007315632A

Abstract

An object of the invention is to effectively defrost multiple a vaporizing devices provided in an ejector cycle. In one of the embodiments, electric heating devices are provided for the respective first and second vaporizing devices, to carry out defrosting operations for each vaporizing device. In addition, a defrosting operation is carried out for the second vaporizing device by hot-gas from a compressor.

Description

CROSS REFERENCE TO RELATED APPLICATION

This application is based on Japanese Patent Application No. 2006-143205, which is filed on May 23, 2006, the disclosure of which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to an ejector cycle having a first vaporizing device for vaporizing working fluid at a higher vaporizing temperature and a second (and a third) vaporizing device for vaporizing the working fluid at a lower vaporizing temperature, wherein the ejector cycle is operated by use of an ejector for pressurizing the working fluid. In particular, the present invention relates to the ejector cycle, in which a defrosting operation is performed for the vaporizing devices.

BACKGROUND OF THE INVENTION

An ejector cycle is known in the art, for example, as disclosed in Japanese Patent Publication Nos. H5-312421 and 2005-308380. The conventional ejector cycle has a refrigerant circuit being composed of a compressor, a heat radiating device, an ejector, and a first vaporizing device, and another refrigerant circuit bifurcated from the first refrigerant circuit. The other refrigerant circuit has a restricting device and a second vaporizing device, wherein the working fluid is sucked into the ejector through the restricting device and the second vaporizing device.
In the above conventional ejector cycle having the first vaporizing device (the vaporizing temperature is higher) and the second (and third, as the case may be) vaporizing device (the vaporizing temperature is lower), however, it is a problem that frost may not be completely defrosted due to a shortage of defrosting capacity, or an electric energy consumption may be increased for the defrosting operation, in the case that an appropriate defrosting means is not provided for the respective first and second vaporizing devices, wherein different defrosting capacities are necessary depending on the respective operating circumstances.

SUMMARY OF THE INVENTION

The present invention is made in view of the above problems. It is an object of the present invention to provide an ejector cycle, in which the frost can be surely and effectively defrosted in each of the vaporizing devices, while an increase of the electric energy consumption for the defrosting operation is suppressed.
According to a feature of the present invention, an ejector cycle has: a compressor for sucking refrigerant and for compressing the same; a heat radiating device for radiating heat of high pressure refrigerant discharged from the compressor; an ejector for depressurizing and expanding refrigerant of a downstream side of the heat radiating device, and for sucking refrigerant; and a first vaporizing device for vaporizing refrigerant discharged from the ejector. A refrigerant flow circuit is composed of the above compressor, the heat radiating device, the ejector, and the first vaporizing device.
The ejector cycle further has; a bifurcating circuit bifurcated from the refrigerant flow circuit and for supplying the refrigerant to the ejector; and a second vaporizing device provided in the bifurcating circuit and for vaporizing the refrigerant.
In such ejector cycle, the first vaporizing device is arranged in a first cooling space, and the second vaporizing device is arranged in a second cooling space, and a first defrosting device is provided at the first vaporizing device, and a second defrosting device is provided at the second vaporizing device, for removing frost attached to the first and second vaporizing devices.
According to another feature of the present invention, an ejector cycle has; a compressor for sucking refrigerant and for compressing the same; a heat radiating device for radiating heat of high pressure refrigerant discharged from the compressor; a depressurizing device for depressurizing refrigerant of a downstream side of the heat radiating device; a first vaporizing device provided between an outlet side of the depressurizing device and an inlet side of the compressor for vaporizing low pressure refrigerant discharged from the depressurizing device; and an ejector for depressurizing and expanding refrigerant of the downstream side of the heat radiating device, and for sucking refrigerant. A refrigerant flow circuit is composed of the above compressor, the heat radiating device, and the ejector.
The ejector cycle further has; a bifurcating circuit bifurcated from the refrigerant flow circuit and for supplying the refrigerant to the ejector; and a second vaporizing device provided in the bifurcating circuit and for vaporizing the refrigerant.
In such ejector cycle, the first vaporizing device is arranged in a first cooling space, and the second vaporizing device is arranged in a second cooling space, and a first defrosting device is provided at the first vaporizing device, and a second defrosting device is provided at the second vaporizing device, for removing frost attached to the first and second vaporizing devices.
According to a further feature of the present invention, an ejector cycle has; a compressor for sucking refrigerant and for compressing the same; a heat radiating device for radiating heat of high pressure refrigerant discharged from the compressor; a depressurizing device for depressurizing refrigerant of a downstream side of the heat radiating device; a first vaporizing device provided between an outlet side of the depressurizing device and an inlet side of the compressor for vaporizing low pressure refrigerant discharged from the depressurizing device; an ejector for depressurizing and expanding refrigerant of the downstream side of the heat radiating device, and for sucking refrigerant; and a second vaporizing device for vaporizing the refrigerant discharged from the ejector. A refrigerant flow circuit is composed of the above compressor, the heat radiating device, the ejector, and the second vaporizing device.
The ejector cycle further has; a bifurcating circuit bifurcated from the refrigerant flow circuit and for supplying the refrigerant to the ejector; and a third vaporizing device provided in the bifurcating circuit and for vaporizing the refrigerant.
In such ejector cycle, the first vaporizing device is arranged in a first cooling space, and the second and third vaporizing devices are arranged in a second cooling space, and a first defrosting device is provided at the first vaporizing device, and a second defrosting device is provided at the second vaporizing device, for removing frost attached to the first and second vaporizing devices.
According to a still further feature of the present invention, an ejector cycle has; a compressor for sucking refrigerant and for compressing the same; a heat radiating device for radiating heat of high pressure refrigerant discharged from the compressor; an ejector for depressurizing and expanding refrigerant of a downstream side of the heat radiating device, and for sucking refrigerant; and a first vaporizing device for vaporizing refrigerant discharged from the ejector. A refrigerant flow circuit is composed of the above compressor, the heat radiating device, the ejector, and the first vaporizing device.
The above ejector cycle further has; a bifurcating circuit bifurcated from the refrigerant flow circuit and for supplying the refrigerant to the ejector; and a second vaporizing device provided in the bifurcating circuit and for vaporizing the refrigerant.
In such ejector cycle, the first and second vaporizing devices are arranged in the same cooling space in such a manner that the second vaporizing device is arranged at a downstream side of the first vaporizing device, and a first defrosting device is provided for the first vaporizing device, and a second defrosting device is provided for the second vaporizing device, in order to remove frost attached to the first and second vaporizing devices.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description made with reference to the accompanying drawings. In the drawings:

FIG. 1A is a schematic structure showing an ejector cycle according to a first embodiment of the present invention;

FIG. 1B is a time chart showing a defrosting operation of the first embodiment;

FIG. 2 is a schematic cross sectional view showing an ejector of the present invention;

FIGS. 3A and 3B are schematic views showing modifications of a vaporizing device, in which an electric heater device is provided;

FIGS. 4A and 4B are a schematic structure showing a modified ejector cycle (first modification) and a time chart showing a defrosting operation thereof according to the present invention;

FIGS. 5A and 5B are also a schematic structure showing a modified ejector cycle (second modification) and a time chart showing a defrosting operation thereof according to the present invention;

FIGS. 6A and 6B are also a schematic structure showing a modified ejector cycle (third modification) and a time chart showing a defrosting operation thereof according to the present invention;

FIGS. 7A and 7B are also a schematic structure showing an ejector cycle and a time chart showing a defrosting operation thereof according to a second embodiment of the present invention;

FIGS. 8A and 8B are also a schematic structure showing an ejector cycle and a time chart showing a defrosting operation thereof according to a third embodiment of the present invention;

FIGS. 9A and 9B are also a schematic structure showing an ejector cycle and a time chart showing a defrosting operation thereof according to a fourth embodiment of the present invention;

FIGS. 10A and 10B are also a schematic structure showing an ejector cycle and a time chart showing a defrosting operation thereof according to a fifth embodiment of the present invention;

FIGS. 11A and 11B are also a schematic structure showing an ejector cycle and a time chart showing a defrosting operation thereof according to a sixth embodiment of the present invention;

FIGS. 12A and 12B are also a schematic structure showing an ejector cycle and a time chart showing a defrosting operation thereof according to a seventh embodiment of the present invention;

FIGS. 13A and 13B are also a schematic structure showing an ejector cycle and a time chart showing a defrosting operation thereof according to an eighth embodiment of the present invention;

FIGS. 14A and 14B are also a schematic structure showing an ejector cycle and a time chart showing a defrosting operation thereof according to a ninth embodiment of the present invention; and

FIGS. 15A and 15B are also a schematic structure showing an ejector cycle and a time chart showing a defrosting operation thereof according to a tenth embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following embodiments, a refrigerating cycle having an ejector according to the present invention is applied to an air conditioning apparatus or a cooling apparatus for a vehicle. In a table 1 below, temperature ranges are shown for each of vaporizing devices (evaporators) and for each of spaces to be air-conditioned or cooled.

	TABLE 1

	EXAMPLE 1	EXAMPLE 2

First Evaporator 14,	For Air Conditioning	For Cold Storage
Cooling Space R1	10-30° C.	0-5° C.
Second Evaporator
17,	For Cold Storage	For Freezing
Cooling Space R2	0-5° C.	−10-−30° C.

More exactly, in an air-conditioning and cold storage apparatus of an EXAMPLE 1, a first vaporizing device 14 (described below) is used as a vaporizing device (evaporator) for an air-conditioning apparatus, so that an air-conditioned space R1 (the cooling space R1) is controlled at a temperature range of 10 to 30° C. And a second vaporizing device 17 (also described below) is used as a vaporizing device (evaporator) for a cold storage apparatus, so that a cold storage space R2 (the cooling space R2) is controlled at a temperature range of 0 to 5° C.
Furthermore, in a cold storage and a freezing apparatus of an EXAMPLE 2, the first vaporizing device 14 (described below) is used as a vaporizing device for the cold storage apparatus, so that a cooled space R1 (the cooling space R1) is controlled at the temperature range of 0 to 5° C. And the second vaporizing device 17 (also described below) is used as the vaporizing device for the freezing apparatus, so that a freezing space R2 (the cooling space R2) is controlled at a temperature range of −10 to −30° C.
Each of the first and second vaporizing devices 14 and 17 has a first and second defrosting device, as explained below. According to the present invention, the defrosting device comprises a heating device and/or a hot-gas defrosting device, in which hot-gas discharged from a compressor 11 (described below) is supplied to one of (or each of) the vaporizing devices to melt the frost attached to the vaporizing devices.
In the following table 2, combinations of the heating device (heater) and the hot-gas defrosting device (hot-gas) for the first and second defrosting devices are shown for the respective embodiments of the present invention.

TABLE 2

First		Third		Fifth
Embod-	Second	Embod-	Fourth	Embod-
iment	Embodiment	iment	Embodiment	iment

First	Heater	Hot-gas	Hot-gas	Hot-gas	Heater
Defrosting				(Smaller	(smaller
Means				Amount)	Capacity)
Second	Hot-gas +	Hot-gas +	Heater	Hot-gas	Heater
Defrosting	Heater	Heater		(larger	(larger
Means				Amount)	Capacity)

In the following table 3, combinations of the heating device (heater) and the hot-gas defrosting device (hot-gas) for the first and second defrosting devices are likewise shown for the respective embodiments of the present invention. In the embodiments, shown in the table 3, the same space R is cooled by the first and second vaporizing devices 14 and 17, a defrosting capacity of the first defrosting device for the first vaporizing device 14, which is arranged at an upstream side of air flow, is made larger than that of the second defrosting device for the second vaporizing device 17, which is arranged at a downstream side of the air flow. Generally, the frost is likely to be more generated at the upstream side than at the downstream side of the air flow.

TABLE 3

Sixth		Eighth		Tenth
Embod-	Seventh	Embod-	Ninth	Embod-
iment	Embodiment	iment	Embodiment	iment

First	Hot-gas +	Hot-gas +	Heater	Hot-gas	Heater
Defrosting	Heater	Heater		(larger	(larger
Means				Amount)	Capacity)
Second	Heater	Hot-gas	Hot-gas	Hot-gas	Heater
Defrosting				(smaller	(smaller
Means				Amount)	Capacity)

The above first to tenth embodiments will be explained hereinafter.

(First Embodiment)

The first embodiment will be explained in detail with reference to FIGS. 1 to 3. FIG. 1A is a schematic structure showing an ejector cycle according to a first embodiment of the present invention. FIG. 1B is a time chart showing a defrosting operation of the first embodiment. An ejector cycle has a refrigerant circuit for circulating a refrigerant, and a compressor 11 is provided in the refrigerant circuit for sucking and compressing the refrigerant.
According to the embodiment, the compressor 11 is driven to rotate via a belt by an engine (not shown) for driving a vehicle. A heat radiating device 12 is provided at a downstream side of the compressor 11 in a refrigerant flow. The heat radiating device 12 cools down the high pressure refrigerant discharged from the compressor 11 by heat-exchanging with outside air of the vehicle blown by a cooling fan (not shown).
An ejector 13 of a variable type is provided at a downstream side of the heat radiating device 12 in the refrigerant flow. FIG. 2 is a cross sectional view schematically showing a structure of the ejector 13. The ejector 13 operates not only as a depressurizing device but as a kinetic pump for transporting kinetic momentum by a suck-in function of working fluid ejecting at a high speed.
As shown in FIG. 2, the ejector 13 has a nozzle portion 13a having a small cross-sectional area for restricting high pressure liquid-phase refrigerant from the heat radiating device 12, and a suck-in portion 13 b opening to a space, into which the refrigerant is ejected from the nozzle portion 13 a. The suck-in portion 13 b sucks a gas-phase refrigerant from a second vaporizing device 17 (described below). The ejector 13 is of the variable type, in which an opening degree of the nozzle portion 13 a can be varied. A needle valve 130 a is arranged in the nozzle portion 13 a, more specifically coaxially with an ejecting opening of the nozzle portion 13 a, for controlling the opening degree of the ejecting opening of the nozzle portion 13 a. The needle valve 130 a is movable in its axial direction, an axial position of which is controlled by an actuator 130 b.
The needle valve 130 a and the actuator 130 b form a variable nozzle mechanism 130, which is operated by an output signal from an electronic control unit (ECU) 30. The variable nozzle mechanism 130 functions as a means for restricting a driving flow of the ejector 13 and as a means for controlling a flow rate of the refrigerant. The variable nozzle mechanism 130 may be formed by an electrically controlled expansion device.
A mixing portion 13 c and a defusing portion (a pressure increasing portion) 13 d are formed at a downstream side of the nozzle portion 13 a. The refrigerant sucked from the suck-in portion 13 b and the refrigerant ejected from the nozzle portion 13 a are mixed together in the mixing portion 13 c. The pressure of the mixed refrigerant is increased in the defusing portion 13 d. In the defusing portion 13 d, a cross-sectional area for the refrigerant flow is gradually increased in the direction of the refrigerant flow, so that refrigerant flow is decelerated and the refrigerant pressure is increased. Namely, the defusing portion 13 d functions as a means for converting speed energy into pressure energy.
The ejector 13 has a first connecting portion communicated with a space formed on a large-diameter side of the nozzle portion 13 a, a second connecting portion formed at a downstream side of the ejector 13 and communicated with the defusing portion 13 d, and a third connecting communicated with a space (a suck-in space) formed on a small-diameter side of the nozzle portion 13 a. The refrigerant flowing out from the defusing portion 13 d flows into a first vaporizing device 14.
The first vaporizing device 14 is arranged, for example, in an air flow path of a cooling unit (not shown) of a cold storage R1 for cooling the inside of the cold storage R1. More specifically, the air in the cold storage R1 is circulated by an electric blowing device (not shown) of the cooling unit, so that the air is supplied to the first vaporizing device 14. The low pressure refrigerant depressurized by the ejector 13 is vaporized in the first vaporizing device 14 by absorbing heat from the air in the cold storage R1, so that the air in the cold storage R1 is cooled down. Thus, the cooling operation is performed by the first vaporizing device 14.
The gas-phase refrigerant vaporized in the first vaporizing device 14 is sucked into the compressor 11 and compressed by the compressor so that the refrigerant is again circulated in the refrigerant flow circuit. A bifurcating circuit 15 is formed in the ejector cycle such that one end thereof is bifurcated from a bifurcating point between the heat radiating device 12 and the ejector 13. The other end of the bifurcating circuit 15 is connected to the ejector 13 such that the refrigerant flows into the ejector 13 at the suck-in portion 13 b.
A variable type expansion valve 16 (also referred to as a depressurizing means/device or an expansion valve) is provided in the bifurcating circuit 15. The variable type expansion valve 16 not only depressurizes the refrigerant but changes an opening degree (a restricting area). The depressurizing means may be formed by a fixed restricting device, such as a capillary tube, an orifice and so on. A second vaporizing device 17 is provided at a downstream side of the expansion valve 16. The second vaporizing device 17 is arranged, for example, in an air flow path of a cooling unit (not shown) of a freezing space R2 for cooling the inside of the freezing space R2.
More specifically, the air in the freezing space R2 is circulated by an electric blowing device (not shown) of the cooling unit, so that the air is supplied to the second vaporizing device 17. The low pressure refrigerant depressurized by the expansion valve 16 is vaporized in the second vaporizing device 17 by absorbing heat from the air in the freezing space R2, so that the air in the freezing space R2 is cooled down. Thus, the cooling operation is performed by the second vaporizing device 17. The operation of the compressor 11 and the electric blowing devices is controlled by output signals from the ECU 30.
A first and a second electric heater (first and second defrosting device) 21 and 22 are respectively provided in the air flow paths of the cooling units, at an upstream side of the first and second vaporizing devices 14 and 17, for heating the first and second vaporizing devices 14 and 17 in order to remove the frost produced and attached to the respective vaporizing devices 14 and 17. FIGS. 3A and 3B show examples of the electric heaters 21. The electric heater 21 may be formed as a pipe heater 21A of a contact type in contact with the vaporizing device (14), as shown in FIG. 3A. Furthermore, the electric heater 21 may be formed as a glass tube heater 21B of a contact-less type, as shown in FIG. 3B.
A temperature sensor 23, such as a thermister, is provided at the second vaporizing device 17, the vaporizing temperature at which is lower so that the frost is likely to be generated and attached. The temperature sensor 23 is preferably provided at such a portion, which is the hardest portion of the second vaporizing device 17 for increasing the temperature thereof.
A detected signal of the temperature sensor 23 is inputted to the ECU 30. Electric current supply to the heaters 21 and 22 is controlled by the output signals from the ECU 30 in a defrosting operation for melting and removing the frost generated and attached to the first and second vaporizing devices 14 and 17. The temperature of the second vaporizing device 17 is generally low during the defrosting operation. According to the present embodiment, therefore, a hot-gas defrosting means is provided for the second vaporizing device 17 in addition to the electric heater 22, so that hot-gas discharged from the compressor 11 is forced to flow through the second vaporizing device 17 to melt the frost generated and attached at the second vaporizing device 17.
More specifically, when starting the defrosting operation by the hot-gas for the second vaporizing device 17, the opening degree of the nozzle portion of the ejector 13 is fully closed on one hand and the expansion valve 16 is almost fully opened on the other hand, as indicated in FIG. 1B. And the compressor 11 is operated, so that the hot-gas flows through the expansion valve 16 and the second vaporizing device 17 to the ejector 13. The refrigerant (hot-gas) is sucked into the ejector 13 and flows back to the compressor 11. As a result, a defrosting capacity of the second defrosting means for the second vaporizing device 17, which is provided in the freezing space R2 and the temperature of which is lower than the first vaporizing device 14, is made larger than a defrosting capacity of the first defrosting means for the first vaporizing device 14, which is provided in the cooling space R1.
An operation of the above first embodiment will be explained. When the compressor 11 is driven by the engine for the vehicle, the high temperature and high pressure refrigerant is discharged to flow in a direction indicated by arrows, and flows into the heat radiating device 12. The high temperature refrigerant is cooled down by the outside air at the heat radiating device 12, so that the refrigerant is condensed. The liquid-phase refrigerant from the heat radiating device 12 is separated into a flow in the refrigerant flow circuit and a flow in the bifurcating circuit 15.
The refrigerant flowing through the refrigerant flow circuit flows into the ejector 13, and depressurized and expanded at the nozzle portion 13 a. The pressure energy of the refrigerant is converted into the speed energy at the nozzle portion 13 a, so that the refrigerant is ejected from the ejecting portion of the nozzle portion 13 a at a high speed. Then, the refrigerant pressure is decreased to suck in the gas-phase refrigerant from the second vaporizing device 17 through the suck-in portion 13 b.
The refrigerant ejected from the nozzle portion 13 a and the refrigerant sucked from the suck-in portion 13 b are mixed at the downstream side of the nozzle portion 13 a, and flows into the defusing portion 13 d. The speed (expansion) energy of the refrigerant is converted into the pressure energy at the defusing portion 13 d due to the gradual increase of the cross sectional flow path area, so that the pressure of the mixed refrigerant is increased in the defusing portion 13 d. The refrigerant from the defusing portion 13 d flows into the first vaporizing device 14.
The refrigerant is vaporized in the first vaporizing device 14, by absorbing the heat from the air blown to the first vaporizing device 14 by the electric blowing device (not shown) in the cooling space R1. The gas-phase refrigerant after the vaporization is sucked into the compressor 11 and compressed again to be circulated in the refrigerant flow circuit. On the other hand, the refrigerant flowing through the bifurcating circuit 15 is depressurized by the expansion valve 16 to become the low pressure refrigerant. The low pressure refrigerant is vaporized in the second vaporizing device 17, by absorbing the heat from the air blown to the second vaporizing device 17 by the electric blowing device (not shown) in the freezing space R2. The cooling operation for the freezing space R2 is carried out by the second vaporizing device 17 and the gas-phase refrigerant from the second vaporizing device 17 is sucked into the ejector 13 through the suck-in portion 13 b.
The defrosting operation will be explained. FIG. 1B is a time chart showing the defrosting operation in the ejector cycle of the present invention. The defrosting operation is started when the temperature of the second vaporizing device 17 detected by the temperature sensor 23 becomes lower than a predetermined temperature T1. The defrosting operation may be alternatively started when an accumulated operating time period of the compressor 11 exceeds a predetermined value, or such accumulated operating time period may be further varied depending on the ambient temperature.
When the defrosting operation is started, the current supply to the first and second electric heaters 21 and 22 starts to heat the first and second vaporizing devices 14 and 17, in order to remove the frost generated and attached to the vaporizing devices 14 and 17. In addition to the above defrosting operation, the compressor 11 is continuously operated, so that the hot-gas discharged from the compressor 11 flows through the expansion valve 16 to the second vaporizing device 17. The above hot-gas flow to the second vaporizing device 17 is carried out, when the opening degree of the nozzle portion of the ejector 13 is fully closed and the expansion valve 16 is almost fully opened. Then, the refrigerant (hot-gas) is sucked into the ejector 13 and flows back to the compressor 11.
When the temperature of the second vaporizing device 17 exceeds another predetermined temperature T2, the current supply to the first and second electric heaters 21 and 22 is cut off. At the same time, the nozzle opening degree of the ejector 13 as well as the restricting degree of the expansion valve 16 is returned to its normal positions, so that the refrigerating (cooling) operation is re-started. The predetermined temperature (T1 and T2) may be varied depending on the ambient temperature, as in the same manner to the accumulated operating time period for the compressor 11.
Characteristic features and advantages of the present embodiment will be explained. The ejector cycle is composed of: the compressor 11 for sucking and compressing the refrigerant; the heat radiating device 12 for radiating the heat of the high temperature refrigerant discharged from the compressor 11; the ejector 13 for depressurizing and expanding the refrigerant at the downstream side of the heat radiating device 12 and also for sucking the refrigerant; the first vaporizing device 14 for vaporizing the refrigerant from the ejector 13; the bifurcating circuit 15 bifurcated from the refrigerant flow circuit (comprising the compressor 11, the heat radiating device 12, the ejector 13 and the first vaporizing device 14) for supplying the refrigerant to the ejector 13 so that the refrigerant is sucked into the ejector 13; and the second vaporizing device 17 provided in the bifurcated circuit 15 for vaporizing the refrigerant. In the above ejector cycle, the first vaporizing device 14 is provided in the first cooling space (the cold storage) R1, whereas the second vaporizing device 17 is provided in the second cooling space (the freezing space) R2. The first and second defrosting devices 21 and 22 are respectively provided at the respective vaporizing devices 14 and 17, for removing the frost generated and attached to the vaporizing devices 14 and 17.
According to the ejector cycle of the present embodiment, the different cooling spaces R1 and R2 are cooled down by the multiple (the first and second) vaporizing devices 14 and 17, and the multiple defrosting devices 21 and 22 are provided to the respective vaporizing devices 14 and 17. According to the ejector cycle, therefore, useless consumption of the electric power can be suppressed in the defrosting operation, and the multiple vaporizing devices 14 and 17 can be effectively operated.
The defrosting capacity of the second defrosting device is made larger than that of the first defrosting device. This is because the vaporizing temperature at the second vaporizing device 17 is lower than that at the first vaporizing device 14. In other words, the temperature of the second vaporizing device 17 (that is, the temperature of the cooling space R2) is lower than that of the first vaporizing device 14 (that is, the temperature of the cooling space R1). The frost at the second vaporizing device 17 is harder to melt.
According to the present embodiment, therefore, the defrosting capacity of the second defrosting device, which is provided in the cooling space R2 having the lower temperature, is made larger than that of the first defrosting device, which is provided in the cooling space R1 having the higher temperature, so that the respective defrosting capacities correspond to the respective operating circumstances of the vaporizing devices. As the defrosting devices having the different defrosting capacities are provided at the respective vaporizing devices, the useless consumption of the electric power can be suppressed in the defrosting operation and the multiple vaporizing devices 14 and 17 can be effectively operated.
According to the present embodiment, the electric heater 21 is used as the first defrosting device, whereas the electric heater 22 and the hot-gas defrosting means are used as the second defrosting device. In the hot-gas defrosting means, the hot-gas discharged from the compressor 11 flows through the second vaporizing device 17 to melt and remove the frost generated and attached to the second vaporizing device 17. As above, the defrosting device using the external thermal source (such as, the electric heater) and the defrosting device using the internal thermal source (such as, the hot-gas defrosting means) can be combined, so that the defrosting capacities can be made at the different values for the first and second vaporizing devices, and/or the defrosting capacities can be selected at such values which match the operating circumstances of the vaporizing devices.
According to the present embodiment, the temperature sensor 23 is further provided to detect the temperature of the second vaporizing device 17, so that the defrosting operation is stopped when the temperature detected by the temperature sensor 23 becomes higher than the predetermined value T2. The temperature sensor 23 is provided at the portion, which is the hardest portion of the second vaporizing device 17 for increasing the temperature thereof. As the defrosting operation is continuously carried out until the temperature detected by the temperature sensor 23 exceeds the predetermined value T2, the frost can be completely molten and removed. As a result, the decrease of the cooling performance, which is otherwise caused by the frost remaining at the vaporizing device, can be avoided.
Furthermore, according to the present embodiment, the variable type ejector 13 is used, wherein the nozzle opening degree can be adjusted. The variable type expansion valve 16 is also provided in the bifurcating circuit 15, so that the refrigerant to be supplied to the second vaporizing device 17 is depressurized and the restricting degree thereof can be adjusted. The opening degree of the nozzle portion of the ejector 13 is fully closed and the expansion valve 16 is fully opened, when starting the defrosting operation by the hot-gas for the second vaporizing device 17. When the compressor 11 is operated under such nozzle and valve situation, the hot-gas flows through the expansion valve 16 and the second vaporizing device 17 to the ejector 13, and flows back to the compressor 11.
According to such arrangement, the hot-gas can be supplied to the second vaporizing device 17 by controlling the opening or closing condition of the nozzle and valve, without any other devices or means, such as a three-way valve 24, a hot-gas supply passage 25, and so on which will be explained below.

(First Modification)

FIG. 4A is a schematic structure showing a modified ejector cycle (first modification) and FIG. 4B is a time chart showing a defrosting operation thereof according to the first modification. The ejector cycle of this modification differs from the first embodiment in that an expansion valve 19 and the first vaporizing device 14 are provided in parallel to the ejector 13 at the downstream side of the heat radiating device 12. The refrigerant is depressurized by the expansion valve 19 and the depressurized refrigerant is vaporized in the first vaporizing device 14. And the vaporized refrigerant is sucked into the compressor 11.
The ejector 13, the expansion valve 16, and the second vaporizing device 17 are the same to the first embodiment, except that the downstream side of the ejector 13 is directly connected to the compressor 11. A variable three-way valve 18 is provided at the bifurcating point at the downstream side of the heat radiating device 12, so that the refrigerant circuit is bifurcated to the first vaporizing device 14 and to the ejector 13. The variable three-way valve 18 changes a ratio of the refrigerant flow to be separated to the first vaporizing device 14 and to the ejector 13 (that is, the second vaporizing device 17).
In the above ejector cycle, the first vaporizing device 14 is provided in the cooling space R1 (the cold storage), and the second vaporizing device 17 is provided in the cooling space R2 (the freezing space). The electric heaters 21 and 22 are likewise provided at the respective vaporizing devices 14 and 17 as the defrosting device. The hot-gas defrosting means is also provided at the second vaporizing device 17, as in the same manner to the first embodiment, so that the defrosting capacity for the second vaporizing device 17 is larger than that for the first vaporizing device 14. An operation of the first modification (FIG. 4B) is the same to the first embodiment (FIG. 1B), except for an operation of the three-way valve 18. Both outlets A and B of the three-way valve 18 are generally opened. However, in the defrosting operation, only the outlet B to the ejector 13 is opened so that the hot-gas from the compressor 11 may flow into the second vaporizing device 17.
According to the above modified ejector cycle, the same effect to the first embodiment is obtained. The variable three-way valve 18 is provided at the bifurcating point at the downstream side of the heat radiating device 12, so that the refrigerant circuit is bifurcated to the first vaporizing device 14 and to the ejector 13. Accordingly, the cooling capacity of the first and second vaporizing devices 14 and 17 can be controlled by changing the ratio of distributing the refrigerant. In addition, the defrosting capacity of the first and second vaporizing devices 14 and 17, which is performed by the hot-gas defrosting operation, can be likewise controlled by changing the ratio of distributing the hot-gas.

(Second Modification)

FIG. 5A is a schematic structure showing a modified ejector cycle (second modification) and FIG. 5B is a time chart showing a defrosting operation thereof according to the second modification. The ejector cycle of the second modification differs from the first modification (FIG. 4A) in the following points. The second vaporizing device 17 is arranged at the downstream side of the ejector 13, and a third vaporizing device 20 is provided in the bifurcating circuit 15 through which the refrigerant is sucked into the ejector 13.
In the ejector cycle of the second modification, the first vaporizing device 14 is provided in the cooling space R1 (the cold storage), and the second and third vaporizing devices 17 and 20 are provided in the cooling space R2 (the freezing space). The temperature sensor 23 is provided at the third vaporizing device 20. The first electric heater 21 is provided at the first vaporizing device 14, and the second electric heater 22 is provided at the second and the third vaporizing devices 17 and 20 (between the both vaporizing devices), as the defrosting device. The hot-gas defrosting operation can be carried out for the second and third vaporizing devices 17 and 20, so that the defrosting capacity for the second and third vaporizing devices 17 and 20 is larger than that for the first vaporizing device 14. An operation of the second modification (FIG. 5B) in the defrosting operation is the same to the first modification (FIG. 4B).

(Third Modification)

FIG. 6A is a schematic structure showing a modified ejector cycle (third modification) and FIG. 6B is a time chart showing a defrosting operation thereof according to the third modification.
The ejector cycle of the third modification (FIG. 6A) differs from the first embodiment (FIG. 1A) in the following points. A three-way valve 24 is provided between the compressor 11 and the heat radiating device 12 for switching over the refrigerant flow path. And a hot-gas supply passage 25 is provided between the three-way valve 24 and the bifurcating circuit 15 so that the hot-gas is supplied through the three-way valve 24 to the second vaporizing device 17 in the hot-gas defrosting operation.
In the first embodiment, the opening and/or closing conditions for the ejector 13 and the expansion valve 16 are controlled in the defrosting operation, as shown in FIG. 1B. According to the third modification, as shown in FIG. 6B, the three-way valve 24 is switched over so that the outlet A is closed and the outlet B is opened in the hot-gas defrosting operation.
According to the third modification, it is not necessary to use the variable-type ejector 13 and expansion valve 16. The hot-gas from the compressor can be supplied to the second vaporizing device 17 through the three-way valve 24 and the hot-gas supply passage 25. The combination of the three-way valve and the hot-gas supply passage is also possible in the following embodiments, although such modified drawings are not shown.

(Second Embodiment)

FIG. 7A is a schematic structure showing an ejector cycle according to a second embodiment and FIG. 7B is a time chart showing a defrosting operation thereof. The ejector cycle of the second embodiment (FIG. 7A) differs from the first embodiment (FIG. 1A) in the following points. The electric heater 21 is not provided at the first vaporizing device 14 in the second embodiment, so that the defrosting operation for the first vaporizing device 14 is carried out by the hot-gas from the compressor 11. The defrosting operation for the second vaporizing device 17 is carried out by the electric heater 22 and the hot-gas from the compressor 11.
As shown in FIG. 7B, the second electric heater 22 is turned on (electric power is supplied), both of the ejector 13 and the expansion valve 16 are fully opened, and the compressor 11 is operated, so that the hot-gas from the compressor 11 is supplied to the first and second vaporizing devices 14 and 17 for the defrosting operation. As a result, the same effect to the first embodiment can be obtained.

(Third Embodiment)

FIG. 8A is a schematic structure showing an ejector cycle according to a third embodiment and FIG. 8B is a time chart showing a defrosting operation thereof. The ejector cycle of the third embodiment (FIG. 8A) differs from the first embodiment (FIG. 1A) in the following points. The structure of the third embodiment is the same to the second embodiment. The electric heater 21 is not provided at the first vaporizing device 14 in the third embodiment, so that the defrosting operation for the first vaporizing device 14 is carried out by the hot-gas from the compressor 11. The defrosting operation for the second vaporizing device 17 is carried out by the electric heater 22.
As shown in FIG. 8B, the second electric heater 22 is turned on (electric power is supplied), the ejector 13 is fully opened, the expansion valve 16 is fully closed, and the compressor 11 is operated, so that the hot-gas from the compressor 11 is supplied to the first vaporizing device 14 for the defrosting operation. As a result, the same effect to the first embodiment can be also obtained.

(Fourth Embodiment)

FIG. 9A is a schematic structure showing an ejector cycle according to a fourth embodiment and FIG. 9B is a time chart showing a defrosting operation thereof. The ejector cycle of the fourth embodiment (FIG. 9A) differs from the first embodiment (FIG. 1A) in the following points. The electric heaters 21 and 22 are not provided at the first and second vaporizing devices 14 and 17 in the fourth embodiment, so that the defrosting operation for both of the first and second vaporizing devices 14 and 17 is carried out by the hot-gas from the compressor 11. The flow amount of the hot-gas to the second vaporizing device 17 is made larger than the flow amount of the hot-gas to the first vaporizing device 14. As shown in FIG. 9B, the expansion valve 16 for the second vaporizing device 17 is fully opened, whereas the ejector 13 for the first vaporizing device 14 is partially opened. Even with such an arrangement, the same effect to the first embodiment can be also obtained.

(Fifth Embodiment)

FIG. 10A is a schematic structure showing an ejector cycle according to a fifth embodiment and FIG. 10B is a time chart showing a defrosting operation thereof. A structure of the ejector cycle of the fifth embodiment (FIG. 10A) is the same to that of the first embodiment (FIG. 1A), however, the defrosting operation differs from the first embodiment (FIG. 1B) in the following points. Namely, the defrosting operation for both of the vaporizing devices 14 and 17 is carried out by the electric heaters 21 and 22, wherein the heating capacity of the second electric heater 22 for the second vaporizing device 17 is made larger than that for the first electric heater 21 for the first vaporizing device 14. The operation of the compressor 11 is stopped during the defrosting operation, so that no defrosting operation by the hot-gas is carried out. According to such an arrangement, the same effect to the first embodiment can be also obtained.

(Sixth Embodiment)

FIG. 11A is a schematic structure showing an ejector cycle according to a sixth embodiment and FIG. 11B is a time chart showing a defrosting operation thereof. In the above first to fifth embodiments, the multiple vaporizing devices 14, 17 and 20 are arranged to cool down the different cooling spaces R1 and R2. In the following sixth to tenth embodiments, the multiple vaporizing devices 14 and 17 are arranged to cool down the same single cooling space R. The ejector cycle, similar to the second modification (FIG. 5A) having the third vaporizing device 20, may be also applied to the following embodiments.
The defrosting operation is carried out in such a way that the first and second electric heaters 21 and 22 are turned on (the electric power is supplied), the ejector 13 is fully opened, the expansion valve 16 is fully closed, and the compressor 11 is operated, so that the hot-gas from the compressor 11 is supplied to the first vaporizing device 14.
The ejector cycle of the sixth embodiment (FIG. 11A) differs from the first embodiment (FIG. 1A) in the following points. The first and second vaporizing devices 14 and 17 are arranged in the same cooling space R, in such a way that the second vaporizing device 17 is arranged at the downstream side of the first vaporizing device 14. The temperature sensor 23 is provided at the first vaporizing device 14. The first and second electric heaters 21 and 22 are respectively provided to the first and second vaporizing devices 14 and 17. A fan 14 a is provided at the upstream side of the first vaporizing device 14.
Even in the case that the single cooling space R is cooled down by the multiple (first and second) vaporizing devise 14 and 17 of the ejector cycle, the useless consumption of the electrical energy for the defrosting operation can be suppressed and the first and second vaporizing devices 14 and 17 can be effectively defrosted, when the defrosting devices are provided respectively at the first and second vaporizing devices.
The defrosting capacity of the first defrosting device for the first vaporizing device 14 is made larger than that of the second defrosting device for the second vaporizing device 17. This is because the frost is generated at the upstream vaporizing device 14 more than at the downstream vaporizing device 17. The defrosting devices and the defrosting operation are properly applied to the operating circumstances of the vaporizing devices, namely the defrosting devices having the different defrosting capacity are provided to the multiple vaporizing devices. As a result, the useless consumption of the electrical energy for the defrosting operation can be suppressed and the first and second vaporizing devices 14 and 17 can be surely and effectively defrosted.
As explained above, the defrosting operation for the first vaporizing device 14 is carried out by the first electric heater 21 and the hot-gas from the compressor 11, whereas the defrosting operation for the second vaporizing device 17 is carried out by the second electric heater 22.
As above, the defrosting device using the external thermal source (such as, the electric heater) and the defrosting device using the internal thermal source (such as, the hot-gas defrosting means) can be combined, so that the defrosting capacities can be made at the different values between the first and second vaporizing devices. Accordingly, the defrosting capacities can be selected at such values which match the operating circumstances of the vaporizing devices.
Furthermore, according to the sixth embodiment, the temperature sensor 23 is provided, so that the defrosting operation for the first and second vaporizing devices 14 and 17 is terminated when the detected temperature exceeds the predetermined value (T2).
The temperature sensor 23 is provided at such a portion of the first vaporizing device 14, at which the frost is easily generated and attached but hardly molten, for example at a last heat exchanging portion for the refrigerant. As the defrosting operation is continuously carried out until the temperature detected by the temperature sensor 23 exceeds the predetermined value T2, the frost can be completely molten and removed from the first and second vaporizing device 14 and 17. As a result, the decrease of the cooling performance, which is otherwise caused by the frost remaining at the vaporizing device, can be avoided.

(Seventh Embodiment)

FIG. 12A is a schematic structure showing an ejector cycle according to a seventh embodiment and FIG. 12B is a time chart showing a defrosting operation thereof. The seventh embodiment (FIG. 12A) is different from the sixth embodiment (FIG. 11A), in that the electric heater 22 is not provided for the second vaporizing device 17. The defrosting operation for the first vaporizing device 14 is carried out by the electric heater 21 and the hot-gas from the compressor 11, whereas the defrosting operation for the second vaporizing device 17 is carried out by the hot-gas from the compressor 11.
Accordingly, as shown in FIG. 12B, the first electric heater 21 is turned on, both of the ejector 13 and the expansion valve 16 are fully opened, and the compressor 11 is operated, so that the hot-gas from the compressor 11 is supplied to both of the first and second vaporizing devices 14 and 17 in the defrosting operation. The same effect to the first embodiment can be also obtained in the seventh embodiment.

(Eighth Embodiment)

FIG. 13A is a schematic structure showing an ejector cycle according to an eighth embodiment and FIG. 13B is a time chart showing a defrosting operation thereof. A structure of the eighth embodiment (FIG. 13A) is different from that (FIG. 12A) of the seventh embodiment, in that a three-way valve 26 is provided at the downstream side of the second vaporizing device 17, and a second bifurcating passage 27 is provided between the three-way valve 26 and the compressor 11. The eighth embodiment (FIG. 13B) is further different from the seventh embodiment (FIG. 12B) in its defrosting operation. The defrosting operation for the first vaporizing device 14 is carried out by the electric heater 21, whereas the defrosting operation for the second vaporizing device 17 is carried out by the hot-gas from the compressor 11.
The three-way valve 26 and the second bifurcating passage 27 are provided in this embodiment, so that the hot-gas from the compressor 11 may not flow into the first vaporizing device 14 but to the second vaporizing device 17. As shown in FIG. 13B, the first electric heater 21 is turned on, the ejector 13 is fully closed, the expansion valve 16 is fully opened, the compressor 11 is operated, and the three-way valve 26 is switched over to a position so that the outlet B is opened. As a result, the hot-gas from the compressor 11 is supplied only to the second vaporizing device 17 in the defrosting operation. The same effect to the first embodiment can be also obtained in the embodiment.

(Ninth Embodiment)

FIG. 14A is a schematic structure showing an ejector cycle according to a ninth embodiment and FIG. 14B is a time chart showing a defrosting operation thereof. The ninth embodiment (FIG. 14A) is different from the sixth embodiment (FIG. 11A) in that the first and second electric heaters 21 and 22 are not provided in the ninth embodiment, and the defrosting operation for both of the first and second vaporizing devices 14 and 17 is carried out by the hot-gas from the compressor 11. The flow amount of the hot-gas to the first vaporizing device 14 is made larger than the flow amount of the hot-gas to the second vaporizing device 17. As shown in FIG. 14B, the ejector 13 for the first vaporizing device 14 is fully opened, whereas the expansion valve 16 for the second vaporizing device 17 is partially opened. Even with such an arrangement, the same effect to the first embodiment can be also obtained.

(Tenth Embodiment)

FIG. 15A is a schematic structure showing an ejector cycle according to a tenth embodiment and FIG. 15B is a time chart showing a defrosting operation thereof. A structure (FIG. 15A) of the tenth embodiment is identical to that (FIG. 11A) of the sixth embodiment. However, the defrosting operation for the first and second vaporizing devices 14 and 17 is respectively carried out by the first and second electric heaters 21 and 22, wherein the heating capacity of the first electric heater 21 for the first vaporizing device 14 is made larger than that of the second electric heater 22 for the second vaporizing device 17. The operation of the compressor 11 is stopped during the defrosting operation, as shown in FIG. 15B. Even with such an arrangement, the same effect to the first embodiment can be also obtained.

(Other Embodiments)

In the above embodiments, the ejector cycle of the present invention is applied to the cold storage for the vehicle. However, the ejector cycle of the present invention may be applied to a vapor compression cycle, such as a heat pump cycle for hot water storage apparatus. In the above embodiments, the refrigerant is not specified. However, Freon gas, carbon hydride, carbon dioxide, or the like may be used as the refrigerant. And the present invention may be applied to a supercritical cycle or a subcritical cycle operating with one of the above refrigerants. Freon gas here is a general word for a organic compound including carbon, fluorosis, chlorine, and hydrogen. And the Freon gas is widely used as the refrigerant.
As the fluorocarbon refrigerant, a refrigerant of a hydro-, chloro- and fluorocarbon (HCFC), or a refrigerant of hydro-, and fluorocarbon (HFC) is included. Those are the refrigerant, which do not destroy the ozone shield, and which is called as alternatives for chlorofluorocarbon. The hydrocarbon refrigerant means a refrigerant including the hydrogen and carbon and existing in the natural world. R600a having isobutene, R290 having propane or the like are included in the hydrocarbon refrigerant.
The compressor 11 may be formed as a capacitor variable type compressor. Furthermore, the compressor 11 may be formed as a capacitor fixed type compressor, which is controlled by an electromagnetic clutch in an ON-OFF manner, so that discharge amount of the compressor 11 is controlled by changing the ON-OFF ratio. In the case that an electrically driven compressor is used as the compressor 11, the discharge amount of the refrigerant may be controlled by adjusting the rotational speed of the compressor 11.

Claims

1. An ejector cycle comprising:

a compressor for sucking refrigerant and for compressing the same;

a heat radiating device for radiating heat of high pressure refrigerant discharged from the compressor;

an ejector for depressurizing and expanding refrigerant of a downstream side of the heat radiating device, and for sucking refrigerant;

a first vaporizing device for vaporizing refrigerant discharged from the ejector;

a refrigerant flow circuit being composed of the compressor, the heat radiating device, the ejector, and the first vaporizing device;

a bifurcating circuit bifurcated from the refrigerant flow circuit and for supplying the refrigerant to the ejector; and

a second vaporizing device provided in the bifurcating circuit and for vaporizing the refrigerant,

wherein the first vaporizing device is arranged in a first cooling space, and the second vaporizing device is arranged in a second cooling space, and

wherein a first defrosting device is provided at the first vaporizing device, and a second defrosting device is provided at the second vaporizing device, for removing frost attached to the first and second vaporizing devices.

2. An ejector cycle comprising:

a compressor for sucking refrigerant and for compressing the same;

a depressurizing device for depressurizing refrigerant of a downstream side of the heat radiating device;

a first vaporizing device provided between an outlet side of the depressurizing device and an inlet side of the compressor for vaporizing low pressure refrigerant discharged from the depressurizing device;

an ejector for depressurizing and expanding refrigerant of the downstream side of the heat radiating device, and for sucking refrigerant;

a refrigerant flow circuit being composed of the compressor, the heat radiating device, and the ejector;

3. An ejector cycle comprising:

a compressor for sucking refrigerant and for compressing the same;

a second vaporizing device for vaporizing the refrigerant discharged from the ejector;

a refrigerant flow circuit being composed of the compressor, the heat radiating device, the ejector, and the second vaporizing device;

a third vaporizing device provided in the bifurcating circuit and for vaporizing the refrigerant,

wherein the first vaporizing device is arranged in a first cooling space, and the second and third vaporizing devices are arranged in a second cooling space, and

4. An ejector cycle according to the claim 1, wherein

a defrosting capacity of the second defrosting device is larger than that of the first defrosting device.

5. An ejector cycle according to the claim 1, wherein

the first defrosting device comprises a first heating device, and

the second defrosting device comprises a second heating device and a hot-gas defrosting device,

wherein the hot-gas defrosting device supplies hot-gas from the compressor to the second or third vaporizing device so that frost attached to the second or third vaporizing device is molten.

6. An ejector cycle according to the claim 1, wherein

the first defrosting device comprises a hot-gas defrosting device for supplying hot-gas from the compressor to the first vaporizing device so that frost attached to the first vaporizing device is molten, and

the second defrosting device comprises a heating device and a hot-gas defrosting device for supplying the hot-gas from the compressor to the second or third vaporizing device so that frost attached to the second or third vaporizing device is molten.

7. An ejector cycle according to the claim 1, wherein

the second defrosting device comprises a heating device.

8. An ejector cycle according to the claim 1, wherein

the second defrosting device comprises a hot-gas defrosting device for supplying hot-gas from the compressor to the second vaporizing device so that frost attached to the second vaporizing device is molten,

wherein a flow amount of the hot-gas to the second vaporizing device is made larger than that to the first vaporizing device.

9. An ejector cycle according to the claim 1, wherein

the first defrosting device comprises a first heating device, and

the second defrosting device comprises a second heating device,

wherein a heating capacity of the second heating device for the second or the third vaporizing device is made larger than that of the first heating device for the first vaporizing device.

10. An ejector cycle according to the claim 2, wherein

a distribution ratio variable valve is provided at a bifurcating point of the refrigerant flow circuit, which is at a downstream side of the heat radiating device, and at which the refrigerant flow circuit is bifurcated to the first vaporizing device and to the ejector, wherein a distribution ratio of the refrigerant to the first vaporizing device and to the ejector is changed by the distribution ratio variable valve.

11. An ejector cycle according to the claim 1, further comprising:

a temperature sensor provided at the second or third vaporizing device for detecting temperature of the vaporizing device,

wherein the defrosting operation carried out by the first and second defrosting devices is stopped, when the temperature detected by the temperature sensor exceeds a predetermined value.

12. An ejector cycle comprising:

a compressor for sucking refrigerant and for compressing the same;

wherein the first and second vaporizing devices are arranged in the same cooling space in such a manner that the second vaporizing device is arranged at a downstream side of the first vaporizing device, and

wherein a first defrosting device is provided for the first vaporizing device, and a second defrosting device is provided for the second vaporizing device, in order to remove frost attached to the first and second vaporizing devices.

13. An ejector cycle according to the claim 12, wherein

a defrosting capacity of the first defrosting device is larger than that of the second defrosting device.

14. An ejector cycle according to the claim 12, wherein

the first defrosting device comprises a first heating device and a hot-gas defrosting device, wherein the hot-gas defrosting device supplies hot-gas from the compressor to the first vaporizing device so that frost attached to the first vaporizing device is molten, and

the second defrosting device comprises a second heating device.

15. An ejector cycle according to the claim 12, wherein

the second defrosting device comprises a hot-gas defrosting device, wherein the hot-gas defrosting device supplies hot-gas from the compressor to the second vaporizing device so that frost attached to the second vaporizing device is molten.

16. An ejector cycle according to the claim 12, wherein

the first defrosting device comprises a first heating device, and

17. An ejector cycle according to the claim 12, wherein

wherein a flow amount of the hot-gas to the first vaporizing device is made larger than that to the second vaporizing device.

18. An ejector cycle according to the claim 12, wherein

the first defrosting device comprises a first heating device, and

the second defrosting device comprises a second heating device,

wherein a heating capacity of the first heating device for first vaporizing device is made larger than that of the second heating device for the second vaporizing device.

19. An ejector cycle according to the claim 12, wherein

the ejector is of a variable type, a nozzle opening of which can be changed,

a depressurizing device is provided in the bifurcating circuit for depressurizing the refrigerant to be supplied to the second or third vaporizing device,

a nozzle portion of the ejector is fully closed and the compressor is operated during the defrosting operation for the second or third vaporizing device, in order that hot-gas from the compressor is supplied to the second or third vaporizing device through the depressurizing device, and further that the hot-gas is supplied to the ejector through a suction port thereof and back to the compressor.

20. An ejector cycle according to the claim 12, further comprising:

a three-way valve is provided between the compressor and the heat radiating device for switching over the refrigerant flow path,

wherein the three-way valve switches over the refrigerant flow path to such a position, at which hot-gas from the compressor is directly supplied to an upstream side of one of the vaporizing devices, for which the defrosting operation is carried out by the hot-gas from the compressor.

21. An ejector cycle according to the claim 12, further comprising:

a temperature sensor provided at the first vaporizing device for detecting temperature of the vaporizing device,