Ejector refrigerant cycle device and control method thereof

Abstract

An ejector refrigerant cycle device includes an ejector that has a nozzle portion for reducing pressure of refrigerant on a downstream side of a radiator to expand the refrigerant, and a refrigerant suction port from which refrigerant is drawn by a high-velocity refrigerant flow jetted from the nozzle portion, an evaporator that evaporates refrigerant and flows out the evaporated refrigerant to the refrigerant suction port, a flow amount changing unit that changes a refrigerant flow amount flowing into the evaporator, and a pressure abnormality detecting portion for detecting a pressure abnormality of a high-pressure refrigerant on an upstream side of the nozzle portion. In the ejector refrigerant cycle device, when the pressure abnormality detecting portion detects the pressure abnormality, the flow amount changing unit makes the refrigerant flow amount flowing into the evaporator larger than that in a normal pressure state of the high-pressure refrigerant.

Description

CROSS REFERENCE TO RELATED APPLICATION

This application is based on Japanese Patent Application No. 2005-359093 filed on Dec. 13, 2005, the contents of which are incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to an ejector refrigerant cycle device having an ejector, and a control method of an ejector refrigerant cycle device.

BACKGROUND OF THE INVENTION

U.S. Pat. No. 6,837,069 (corresponding to JP-A-2004-53028) describes an ejector refrigerant cycle device that is so constructed as to avoid an abnormal increase in a high-pressure side refrigerant pressure in order to secure the reliability of refrigerant piping and functional parts which receive the high-pressure side refrigerant pressure of the cycle.

In the ejector refrigerant cycle device of U.S. Pat. No. 6,837,069 (corresponding to JP-A-2004-53028), a branch point for branching a high-pressure refrigerant flow is provided on an upstream side of a nozzle portion of an ejector, a bypass passage for relieving high-pressure refrigerant to a portion between a downstream side of an evaporator and a refrigerant suction port of the ejector from this branch point is provided, and a mechanical control valve that is opened when the high-pressure side refrigerant pressure on the upstream side of the nozzle portion satisfies a specified pressure condition (for example, not less than about 10 MPa at a refrigerant temperature of 40° C.) is arranged in this bypass passage.

According to the above-mentioned construction, when the high-pressure side refrigerant pressure satisfies the specified condition, the control valve is opened to relieve the high-pressure refrigerant on the upstream side of the nozzle portion to the position between the downstream side of an evaporator and the refrigerant suction port via the bypass passage, thereby an abnormal increase in the high-pressure side refrigerant pressure of the cycle can be avoided.

However, in the ejector refrigerant cycle device described in U.S. Pat. No. 6,837,069 (corresponding to JP-A-2004-53028), because the high-pressure refrigerant is relieved to the downstream side of the evaporator when the high-pressure side refrigerant pressure satisfies the specified pressure condition, the pressure of the high-pressure side refrigerant is applied to the evaporator. For this reason, the evaporator is required to have resistance to the pressure of the high-pressure refrigerant, which results in enlarging the size of the evaporator and increasing cost. Accordingly, the size and cost of the whole ejector refrigerant cycle device are increased.

SUMMARY OF THE INVENTION

In view of the above-mentioned problems, an object of the present invention is to provide an ejector refrigerant cycle device which can prevent the pressure of high-pressure side refrigerant from being applied to an evaporator, and avoid an abnormal increase in the pressure of the high-pressure side refrigerant.

It is another object of the present invention to provide a control method of an ejector refrigerant cycle device.

According to an aspect of the present invention, an ejector refrigerant cycle device includes a compressor that draws, compresses and discharges refrigerant, a radiator that radiates heat of refrigerant discharged from the compressor, and an ejector that has a nozzle portion for reducing pressure of refrigerant on a downstream side of the radiator to expand the refrigerant, and a refrigerant suction port from which refrigerant is drawn by a high-velocity refrigerant flow jetted from the nozzle portion. Here, the ejector mixes refrigerant drawn from the refrigerant suction port and refrigerant jetted from the nozzle portion, and reduces the velocity of the mixed refrigerant so as to increase its pressure. The ejector refrigerant cycle device further includes an evaporator that evaporates refrigerant and flows out the evaporated refrigerant to the refrigerant suction port, a flow amount changing unit that changes a refrigerant flow amount flowing into the evaporator, and a pressure abnormality detecting means that detects a pressure abnormality of a high-pressure side refrigerant on an upstream side of the nozzle portion. In the ejector refrigerant cycle device, the compressor draws refrigerant on a downstream side of the ejector, and the flow amount changing unit makes the refrigerant flow amount flowing into the evaporator larger than that in a normal pressure state of the high-pressure side refrigerant when the pressure abnormality detecting means detects the pressure abnormality.

Because the flow amount changing unit makes the refrigerant flow amount flowing into the evaporator larger than that in the normal pressure state of the high-pressure side refrigerant when the pressure abnormality detecting means detects the pressure abnormality, the flow amount of suction refrigerant drawn into the refrigerant port is increased. Here, the normal pressure state of the high-pressure refrigerant is a state where the pressure abnormality detecting means does not detect a pressure abnormality.

When the flow rate of suction refrigerant drawn into the refrigerant suction port of the ejector increases, in the velocity energy of the high-velocity refrigerant flow jetted from the nozzle portion, the amount of energy consumed to suck refrigerant increases, thereby the velocity of the high-velocity refrigerant flow decreases.

Further, because the flow rate of suction refrigerant which is slow in the velocity of flow with respect to the high-velocity refrigerant flow increases, the velocity of the flow of the mixed refrigerant flowing into the diffuser portion decreases.

The diffuser portion converts the kinetic energy of the mixed refrigerant flow to pressure energy to increase the pressure of refrigerant. Thus, when the velocity of the mixed refrigerant flowing into the diffuser portion decreases, the amount of pressure increase of refrigerant in the diffuser portion also decreases. With this, the pressure of refrigerant flowing out of the ejector decreases.

For this reason, the pressure of refrigerant flowing out of the ejector and drawn by the compressor decreases, and the pressure of the high-pressure side refrigerant can be decreased in the ejector refrigerant cycle device. As a result, the pressure of high-pressure side refrigerant is not applied to the evaporator, and an abnormal increase in the high-pressure side refrigerant pressure can be avoided.

Further, even when the evaporator refrigerant flow amount increases, a predetermined amount of refrigerant evaporates in the evaporator to exert a heat absorbing action. Thus, the ejector refrigerant cycle device can perform a cooling operation even at the time of avoiding an abnormal increase in the high-pressure side refrigerant pressure. Here, the refrigerant flow amount in the present invention may be a mass flow rate.

For example, an accumulator for separating refrigerant flowing out of the ejector into vapor refrigerant and liquid refrigerant may be arranged in a liquid refrigerant passage such that the liquid refrigerant flows from the accumulator into the evaporator. In this case, the flow amount changing unit is arranged in the liquid refrigerant passage.

Alternatively, a branch passage may be provided to be branched from a point between a downstream side of the radiator and an upstream side of the nozzle portion, and to be joined to the refrigerant suction port of the ejector. In this case, the flow amount changing unit is arranged in the branch passage.

The pressure abnormality detecting means may be provided such that, when a high-pressure refrigerant pressure on the upstream side of the nozzle portion becomes not less than a predetermined value, the pressure abnormality detecting means detects the pressure abnormality. Alternatively, the pressure abnormality detecting means may be provided such that, when the pressure-increase amount per unit time of the high-pressure refrigerant on the upstream side of the nozzle portion becomes not less than a predetermined amount, the pressure abnormality detecting means detects the pressure abnormality.

Furthermore, the flow amount changing unit may be a variable throttle mechanism that is constructed to change an area of a refrigerant passage. In this case, the flow amount changing unit can decompress refrigerant flowing into the evaporator.

According to another aspect of the present invention, a control method of an ejector refrigerant cycle device having an ejector includes a step of detecting a pressure abnormality of a high-pressure side refrigerant on an upstream side of a nozzle portion of the ejector, and a step of reducing a pressure increasing amount in a diffuser portion of the ejector than that in a normal pressure state of the high-pressure refrigerant. Therefore, when the pressure abnormality is detected, the pressure of high-pressure side refrigerant can be reduced, thereby preventing the pressure of high-pressure side refrigerant from being applied to the evaporator, and avoiding an abnormal increase in the pressure of the high-pressure side refrigerant.

For example, the reducing can be performed by increasing a refrigerant amount flowing into the evaporator, which has a refrigerant outlet coupled to the refrigerant suction port of the ejector, to be larger than that in the normal pressure state of the high-pressure refrigerant.

BRIEF DESCRIPTION OF THE DRAWINGS

Additional objects and advantages of the present invention will be more readily apparent from the following detailed description of preferred embodiments when taken together with the accompanying drawings.

FIG. 1 is a general construction diagram of an ejector refrigerant cycle device of a first embodiment of the present invention.

FIG. 2 is a flow chart to show the control of a variable throttle mechanism of an air-conditioning control unit of the first embodiment.

FIG. 3 is a general construction diagram of an ejector refrigerant cycle device of a second embodiment of the second embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

In this embodiment, refrigerant (e.g., carbon dioxide) in which a high-pressure side refrigerant pressure is higher than a supercritical pressure is used as the refrigerant of an ejector refrigerant cycle device. Thus, the ejector refrigerant cycle device of this embodiment constructs a supercritical refrigerant cycle.

First, in an ejector refrigerant cycle device 10, a compressor 11 draws, compresses and discharges refrigerant, and increases the pressure of refrigerant to a supercritical pressure in this embodiment. This compressor 11 has a driving force transmitted thereto from a vehicle running engine (not shown) via a pulley and a belt, thereby being rotated and driven. Moreover, in this embodiment, a well-known swash-plate type variable displacement compressor capable of controlling a discharge volume variably and continuously by a control signal from the outside is used as the compressor 11.

Here, the discharge volume means the geometric volume of an operating space in which refrigerant is drawn and compressed and, specifically, means the cylinder volume between the top dead center and the bottom dead center of the stroke of a piston in the compressor 11. By changing the discharge volume, the discharge capacity of the compressor 11 can be adjusted. The changing of the discharge volume of the compressor 11 is performed by controlling the pressure Pc of a swash plate chamber (not shown) constructed in the compressor 11 so as to change the slant angle of a swash plate and change the stroke of the piston.

The pressure Pc of the swash plate chamber is controlled by-changing a ratio of a discharge refrigerant pressure Pd to a suction refrigerant pressure Ps by using an electromagnetic volume control valve 11a, in the compressor 11. The electromagnetic volume control valve 11a is driven by the output signal of an air-conditioning control unit 20 to be described later. With this, the compressor 11 can change the discharge volume (displacement) continuously within a range of from nearly 0% to 100%.

Moreover, because the compressor 11 can change the discharge volume continuously within a range of nearly from 0% to 100%, the compressor 11 can be brought to an operating stop state by decreasing the discharge volume to nearly 0%. Thus, this embodiment adopts a clutch-less construction in which the rotary shaft of the compressor 11 is always coupled to the vehicle running engine via the pulley and the belt.

The variable displacement compressor 11 may be provided such that power is transmitted from the vehicle running engine to the compressor 11 via an electromagnetic clutch. Moreover, when a fixed displacement compressor is used as the compressor 11, it is also recommend that an on-off control of operating the compressor intermittently by an electromagnetic clutch is performed to control the ratio of the on operation to the off operation of the compressor. Even in this case, the discharge volume of refrigerant of the compressor can be effectively controlled.

A radiator 12 is connected to a downstream side of the refrigerant flow of the compressor 11. The radiator 12 is a heat exchanger that exchanges heat between high-pressure refrigerant discharged from the compressor 11 and outside air (i.e., air outside a vehicle compartment) blown by a blower fan 12a, so as to cool the high-pressure refrigerant. The blower fan 12a is an electrically operated fan driven by a motor 12b. Moreover, the motor 12b is rotated and driven by control voltage outputted from the air-conditioning control unit 20 (A/C control unit) to be described later.

This embodiment constructs a supercritical refrigerant cycle, so refrigerant is not condensed in the radiator 12 and radiates heat as it is held in a supercritical pressure state.

An ejector 13 is connected to the downstream side of the refrigerant flow of the radiator 12. The ejector 13 includes: a nozzle portion 13a that throttles refrigerant flowing from the radiator 12 so as to reduce the pressure of refrigerant and to expand refrigerant in an isentropic manner; and a refrigerant suction port 13b that is arranged so as to communicate with the jet port of the nozzle portion 13a and draws refrigerant on the downstream side of an evaporator 17 to be described later.

Further, the ejector 13 further includes: a mixing portion 13c that is arranged on the downstream side of the nozzle portion 13a and the refrigerant suction port 13b and mixes a high-velocity refrigerant flow from the nozzle portion 13a with suction refrigerant drawn from the refrigerant suction port 13b; and a diffuser portion 13d that is arranged on the downstream side of the mixing portion 13c and reduces the velocity of the refrigerant flow so as to increase the pressure of refrigerant.

This diffuser portion 13d is formed in a shape to gradually increase the area of passage of refrigerant and has a function of reducing the velocity of the refrigerant flow so as to increase the pressure of refrigerant, that is, a function of converting the velocity energy of refrigerant to pressure energy thereof.

An accumulator 14 is connected to the downstream side of the refrigerant flow of the diffuser portion 13d of the ejector 13. The accumulator 14 is formed in the shape of a tank and is a vapor/liquid separating unit. The accumulator 14 separates refrigerant in a vapor/liquid mixed state, flowed from the diffuser portion 13d of the ejector 13, into vapor-phase refrigerant and liquid-phase refrigerant by a difference in density. Thus, the vapor-phase refrigerant is collected on the upper side in the vertical direction of the inner space of a tank part of the accumulator 14 and the liquid-phase refrigerant is collected in the lower side on the vertical direction.

Further, a vapor-phase refrigerant outlet 14a is provided in the top of tank-shaped accumulator 14. The vapor-phase refrigerant outlet 14a is connected to the refrigerant suction side of the compressor 11. On the other hand, a liquid-phase refrigerant outlet 14b is provided in the bottom of the tank part of the accumulator 14. The liquid-phase refrigerant outlet 14b is connected to a liquid-phase refrigerant passage 15.

This liquid-phase refrigerant passage 15 is refrigerant piping for connecting the liquid-phase refrigerant outlet 14b of the accumulator 14 to the refrigerant suction port 13b of the ejector 13. In the liquid-phase refrigerant passage 15 are arranged a variable throttle mechanism 16 and an evaporator 17. The variable throttle mechanism 16 reduces the pressure of liquid-phase refrigerant flowing out of the accumulator 14 to adjust the evaporation pressure of refrigerant in the evaporator 17. In this embodiment, the variable throttle mechanism 16 is an electric variable throttle mechanism controlled by the control signal of the air-conditioning control unit 20.

For example, the variable throttle mechanism 16 is a flow rate adjusting valve that includes a valve mechanism 16a constructed so as to change the area of passage of refrigerant and a stepping motor 16b rotated and driven by a control signal (pulse signal) outputted from the air-conditioning control unit 20. When the stepping motor 16 is rotated, the valve body of the valve mechanism 16a is displaced to adjust the area of passage of refrigerant continuously.

Thus, the valve mechanism 16a of the variable throttle mechanism 16 constructs flow amount changing unit for changing an evaporator refrigerant flow amount Ge flowing into the evaporator 17, and the stepping motor 16b constructs drive means for changing the area of passage of refrigerant of the valve mechanism 16a.

The evaporator 17 is a heat exchanger that is arranged on the downstream side of the refrigerant flow of the variable throttle mechanism 16 in the liquid-phase refrigerant passage 15 and exchanges heat between low-pressure refrigerant having pressure reduced by the variable throttle mechanism 16 and air blown by the blower fan 17a. The low-pressure refrigerant in the evaporator 17 absorbs heat from air so as to cool air in a compartment to be cooled.

Moreover, the blower fan 17a is an electrically operated fan driven by a motor 17b. The motor 17b is rotated and driven by control voltage outputted from the air-conditioning control unit 20 to be described later. Further, as described above, the downstream side of the evaporator 17 is connected to the refrigerant suction port 13b of the ejector 13, such that the refrigerant from the evaporator 17 is drawn into the refrigerant suction port 13b of the ejector 13.

Next, an electric control operation of this embodiment will be described. The air-conditioning control unit 20 is constructed of a well-known microcomputer including a CPU, a ROM, a RAM and the like and its peripheral circuit, and performs various kinds of computations and processing on the basis of control programs stored in the ROM to control the operations of the above-mentioned various kinds of devices 11a, 12b, 16b, 17b, for example.

Moreover, to the air-conditioning control unit 20, detection signals from a group of various kinds of sensors and various operating signals from operating panel (not shown) are inputted. Specifically, the group of sensors include a temperature sensor 21 for detecting a refrigerant temperature Tev on the downstream side of the evaporator 17, a pressure sensor 22 for detecting a refrigerant pressure Pev on the downstream side of the evaporator 17, and a pressure sensor 23 for detecting a refrigerant pressure Pnoz on the upstream side of the nozzle portion 13a. Moreover, the operating panel is provided with an operating switch for operating a refrigerating unit and a temperature setting switch for setting temperature in the compartment to be cooled (e.g., refrigeration compartment).

Next, operation of the ejector refrigerant cycle device in the above-mentioned construction will be described. First, when the vehicle running engine is operated, a rotational drive force is transmitted from the vehicle running engine to the compressor 11. Further, when the operating signal of the operating switch is inputted to the air-conditioning control unit 20 from the operating panel, an output signal is outputted from the air-conditioning control unit 20 to the electromagnetic volume control valve 11a on the basis of the previously stored control program.

The discharge volume (displacement) of the compressor 11 is determined by this output signal, and the compressor 11 draws vapor-phase refrigerant from the vapor-phase refrigerant outlet 14a of the accumulator 14 and compresses the vapor-phase refrigerant to a supercritical state and then discharges the vapor-phase refrigerant. The refrigerant in the supercritical state, discharged from the compressor 11, flows into the radiator 12 and is cooled by outside air. Further, refrigerant flowing out of the radiator 12 flows into the nozzle portion 13a of the ejector 13.

The refrigerant flowing into the nozzle portion 13a of the ejector 13 has its pressure reduced in the nozzle portion 13a, thereby being brought to a two-phase state of vapor and liquid. The pressure energy of high-pressure refrigerant is converted to velocity energy by the nozzle portion 13a, thereby refrigerant is brought to a high-velocity refrigerant flow and is jetted from the jet port of the nozzle portion 13a. Refrigerant on the downstream side of the evaporator 17 is drawn from the refrigerant suction port 13b by a pressure drop produced near the jet port of the nozzle portion 13a at this time.

The refrigerant jetted from the nozzle portion 13a and the refrigerant drawn from the refrigerant suction port 13b are mixed with each other in the mixing portion 13c on the downstream side of the nozzle portion 13a, and flows into the diffuser portion 13d. In this diffuser portion 13d, the velocity energy of the refrigerant is converted to pressure energy by the area of passage being enlarged, so the pressure of the refrigerant on the downstream side of the ejector 13 is increased according to the velocity of the flow of the refrigerant flowing into the diffuser portion 13d.

The refrigerant flowing out of the diffuser portion 13d of the ejector 13 flows into the accumulator 14, and is separated into vapor-phase refrigerant and liquid-phase refrigerant. The vapor-phase refrigerant in the accumulator 14 is again drawn into and compressed by the compressor 11.

On the other hand, the liquid-phase refrigerant in the accumulator 14 flows into the liquid-phase refrigerant passage 15 by the suction function of the ejector 13. This liquid-phase refrigerant has flow-rate adjusted and pressure-reduced by the variable throttle mechanism 16, and flows into the evaporator 17. When the liquid-phase refrigerant is evaporated in the evaporator 17, the liquid-phase refrigerant absorbs heat from air in the refrigeration compartment (i.e., the compartment to be cooled) blown by the blower fan 17a, thereby air in the refrigeration compartment is cooled.

The refrigerant flowing out of the evaporator 17 is drawn into the refrigerant suction port 13b and is mixed with a high-velocity refrigerant flow jetted from the nozzle portion 13a.

The air-conditioning control unit 20 in this embodiment controls the stepping motor 16b of the variable throttle mechanism 16 so as to change the area of passage of refrigerant of the valve mechanism 16a. The operation of the air-conditioning control unit 20 will be described on the basis of a flow chart shown in FIG. 2. First, at step S1, the control signals of a refrigerant temperature Tev on the downstream side of the evaporator 17, a refrigerant pressure Pev on the downstream side of the evaporator 17, and a refrigerant pressure Pnoz on the upstream side of the nozzle portion 13a are read.

Next, at step 82, it is determined on the basis of Pnoz read at step S1 whether or not the high-pressure side refrigerant pressure of the cycle is abnormal. Specifically, it is determined whether or not the detected refrigerant pressure Pnoz is not higher than a reference high-pressure refrigerant pressure KPnoz.

Here, the reference high-pressure refrigerant pressure KPnoz is a value previously set to determine that a high-pressure side refrigerant pressure on the upstream side of the nozzle portion 13a becomes abnormally high within a range not exceeding the pressure resistance value of the refrigerant piping and the functional parts (for example, radiator 12), which receive the high-pressure side refrigerant pressure on the upstream side of the nozzle portion 13a.

Thus, when it is determined that Pnoz≦Kpnoz at step S2, it is determined that the high-pressure side refrigerant pressure of the cycle is not in the state of abnormal pressure and the control routine proceeds to step S3. When it is not determined that Pnoz≦KPnoz, it is determined that the high-pressure side refrigerant pressure of the cycle is in the state of abnormal pressure and the control routine proceeds to step S5. For this reason, in this embodiment, step S2 is a determination means for determining whether or not the high-pressure side refrigerant pressure of the cycle is in the state of abnormal pressure on the basis of the detection value of the pressure sensor 23.

At step S3, a normal operation control is performed because the high-pressure side refrigerant pressure is not in the state of abnormal pressure. In this normal operation control, the refrigerant passage area of the valve mechanism 16a is controlled in such a way that refrigerant on the downstream side of the evaporator 17 has a set degree of superheat.

For example, the degree of superheat of refrigerant on the downstream side of the evaporator 17 is computed on the basis of the refrigerant temperature Tev and the refrigerant pressure Pev which are read at step S1 by the air-conditioning control unit 20, and a control signal (pulse signal) is outputted to the stepping motor 16b so that this degree of superheat approaches to a previously set value.

By controlling the degree of superheat of refrigerant on the downstream side of the evaporator 17 to a predetermined degree of superheat, when liquid-phase refrigerant flowing into the evaporator 17 is evaporated, the liquid-phase refrigerant absorbs heat from air blown by the blower fan 17 to cool the air blown. Therefore, it can prevent the evaporator refrigerant flow amount Ge flowing into the evaporator 17 from being increased unnecessarily.

For this reason, the flow rate of suction refrigerant drawn into the refrigerant suction port 13b of the ejector 13 is not increased unnecessarily either, thereby the velocity of flow of a mixed flow produced by mixing the suction refrigerant with the high-velocity refrigerant flow jetted from the nozzle portion 13a is not reduced. The velocity energy of the mixed flow is converted to pressure energy in the diffuser portion 13d to increase the pressure of refrigerant on the downstream side of the ejector 13.

Thus, the refrigerant evaporation pressure of the evaporator 17 connected to the refrigerant suction port 13b becomes lower than the refrigerant pressure on the downstream side of the ejector 13. Even when the refrigerant evaporation temperature in the evaporator 17 is set to a cooling temperature (for example, from −5° C. to 5° C.) suitable for refrigeration, the pressure of refrigerant drawn by the compressor 11 can be made higher than the refrigerant evaporation pressure in the evaporator 17. As a result, the drive power of the compressor 11 can be reduced and the operation efficiency of the cycle can be improved.

When the normal operation control at step S3 is performed, the control routine proceeds to step S4 and then after a set time T (e.g., a unit time) elapses, the control routine returns again to step S1.

Next, when it is not determined at step S2 that Pnoz≦KPnoz, it is determined that the high-pressure side refrigerant pressure of the cycle is in the state of abnormal pressure and the control routine proceeds to step S5. At step S5, the air-conditioning control unit 20 outputs a control signal (pulse signal) to the stepping motor 16b so as to expand the refrigerant passage area of the valve mechanism 16a by a specified value and then routine proceeds to step S6.

Next, Pnoz is read again at step S6 and the control routine proceeds to step S7. At step S7, it is determined whether or not Pnoz is not less than the previously set reference high-pressure refrigerant pressure KPnoz—α. Here, α is a predetermined value for setting a hysteresis width so as to prevent the refrigerant passage area control of the valve mechanism 16a from hunting.

Specifically, it is determined at step S7 whether or not Pnoz≦KPnoz—α. When it is determined that Pnoz≦KPnoz—α, it is determined that the high-pressure side refrigerant pressure becomes out of the state of abnormal pressure and the control routine proceeds to step S4. That is, when Pnoz≦KPnoz—α at step S7, it is determined that the high-pressure side refrigerant pressure becomes the normal state. On the other hand, when it is not determined that Pnoz≦KPnoz—α, it is determined that the high-pressure side 10 refrigerant pressure continues to be in the state of abnormal pressure, that is, is abnormally high pressure, and the control routine returns to step S5. Thus, the air-conditioning control unit 20 outputs a control signal (pulse signal) to the stepping motor 16b so as to expand the refrigerant passage area of the valve mechanism 16a.

In this manner, when it is determined that the high-pressure side refrigerant pressure is in the state of abnormal pressure, the air-conditioning control unit 20 controls the stepping motor 16b so as to expand the refrigerant passage area of the valve mechanism 16a. In this case, the evaporator refrigerant flow amount Ge flowing into the evaporator 17 is increased. For this reason, the flow rate of suction refrigerant drawn into the refrigerant suction port 13b of the ejector 13 is also increased.

Thus, the velocity of flow of the mixed refrigerant produced by the mix of the suction refrigerant flow with the high-velocity refrigerant flow is also decreased so as to reduce also the velocity energy of the mixed refrigerant flow to be converted to the pressure energy in the diffuser portion 13d of the ejector 13. In this case, the amount of increase in the refrigerant pressure in the diffuser portion of the ejector 13 is reduced. As a result, the pressure of refrigerant drawn by the compressor 11 is reduced as compared with pressure at the time of a normal operation and the pressure of refrigerant discharged from the compressor 11 is also reduced, thereby an abnormal increase in the high-pressure side refrigerant pressure of the cycle can be avoided.

Further, even when the evaporator refrigerant flow amount Ge (refrigerant flow rate) is increased, because a part of liquid-phase refrigerant flowing into the evaporator 17 from the accumulator 14 is evaporated, this part absorbs heat from air blown from the blower fan 17a and hence can cool the air blown from the air blower fan 17a. That is, the cycle can perform a cooling operation even in this abnormal operation control.

In this embodiment, in the normal operation control in which a pressure abnormality in the high-pressure side refrigerant pressure of the cycle is not detected, it is possible to reduce the drive force of the compressor 11 and to improve the operation efficiency of the cycle by increasing the pressure of refrigerant to be drawn by the compressor 11 using the pressure increasing function of the diffuser portion 13d.

Further, when a pressure abnormality on the high-pressure side refrigerant pressure of the cycle is detected, the evaporator refrigerant flow amount Ge (refrigerant flow rate) is increased and the abnormal operation control is performed. Accordingly, in the abnormal operation control, it is possible to suppress the refrigerant pressure increase in the diffuser portion 13d while performing the cooling operation of the cycle, and to avoid the abnormally high pressure of the cycle. Therefore, in the ejector refrigerant cycle device of this embodiment, the cooling operation can be performed without applying the pressure of high-pressure side refrigerant to the evaporator 12.

Second Embodiment

In the above-described first embodiment, refrigerant cycle is provided with the liquid-phase refrigerant passage 15 for connecting the liquid-phase refrigerant outlet 14b of the accumulator 14 to the refrigerant suction port 13b of the ejector 13, and the variable throttle mechanism 16 and the evaporator 17 are arranged in this liquid-phase refrigerant passage 15. In the second embodiment, however, as shown in FIG. 3, the liquid-phase refrigerant passage 15 is not provided but there is provided a branch passage 25 for branching the refrigerant flow at a branch point Z that is positioned between the downstream side of the radiator 12 and the upstream side of the nozzle portion 13a of the ejector 13.

This branch passage 25 is a refrigerant passage for connecting the branch point Z to the refrigerant suction port 13b of the ejector 13. In this embodiment, the variable throttle mechanism 16 is arranged in the branch passage 25, and the evaporator 17 is arranged on the downstream side of the refrigerant flow of the variable throttle mechanism 16 in the branch passage 25. The variable throttle mechanism 16 and the evaporator 17 have structures, respectively, similar to those described in the first embodiment. Here, in this embodiment, in order to avoid confusion with a second evaporator 26 to be described later, the evaporator 17 is referred to as a first evaporator in the following description.

Moreover, in this embodiment, the second evaporator 26 is arranged between the downstream side of the ejector 13 and the accumulator 14. The second evaporator 26 is a heat exchanger that exchanges heat between low-pressure refrigerant on the downstream side of the ejector 13 and air in the refrigeration compartment (compartment to be cooled), blown from the blower fan 17a, to make the low-pressure refrigerant absorb heat to cool air in the refrigeration compartment.

Further, in this embodiment, the pressure sensor 23 for detecting the refrigerant pressure Pnoz on the upstream side of the nozzle portion 13a is arranged on the upstream side of the branch point Z. Of course, the position of the pressure sensor 23 is not limited to this position, but for example, may be arranged between the branch point Z and the nozzle portion 13a. In the second embodiment, the other structures of the ejector refrigerant cycle device can be made similar to those of the above-described first embodiment.

Next, the operation of the ejector refrigerant cycle device according to this embodiment will be described. First, when the vehicle running engine is operated, just as in the first embodiment, refrigerant in a supercritical state flows from the compressor 11 into the condenser 12, thereby being cooled by the outside air.

Further, refrigerant flowing out from the radiator 12 is branched at the branch point Z into a refrigerant flow flowing into the nozzle portion 13a of the ejector 13 and a refrigerant flow flowing into the branch passage 25. Thus, in this embodiment, the flow rate of the refrigerant flowing into the branch passage 25 becomes the evaporator refrigerant flow amount Ge.

The refrigerant flowing into the nozzle portion 13, just as in the first embodiment, is pressure-reduced in the nozzle portion 13a and draws refrigerant on the downstream side of the first evaporator 17 from the refrigerant suction port 13b. Further, refrigerant jetted from the nozzle portion 13a and refrigerant drawn from the refrigerant suction port 13b are mixed with each other in the mixing portion 13c and is pressure-increased in the diffuser portion 13d according to the velocity energy of the mixed refrigerant flow.

Refrigerant flowing out from the diffuser portion 13d flows into the second evaporator 26. In the second evaporator 26, the low-pressure refrigerant having pressure-reduced in the nozzle portion 13a absorbs heat from air blown from the blower fan 17a and evaporates. The refrigerant after having passed through the second evaporator 26 flows into the accumulator 14 and is separated into vapor-phase refrigerant and liquid-phase refrigerant. The vapor-phase refrigerant in the accumulator 14 is drawn and compressed again by the compressor 11.

On the other hand, the refrigerant flowing into the branch passage 25 is flow-rate adjusted and pressure-reduced by the variable throttle mechanism 16 and flows into the first evaporator 17. In the first evaporator 17, the low-pressure refrigerant flowing therein absorbs heat from air flowing from the second evaporator 26 and evaporates. With this, air blown by the blower fan 17a and cooled by the second evaporator 26 is further cooled in the first evaporator 17. The refrigerant on the downstream side of the first evaporator 17 is drawn into the refrigerant suction port 13b and is mixed with high-velocity refrigerant flow from the nozzle portion 13a.

Also in the above-mentioned construction, the degree of throttle opening of the variable throttle mechanism 16 can be controlled as shown by the flow chart in FIG. 2, just as in the first embodiment. That is, in the normal operation control in which a pressure abnormality in the high-pressure side refrigerant pressure of the cycle is not detected, it is possible to reduce the drive force of the compressor 11 and to improve the operation efficiency of the cycle by increasing the pressure of refrigerant to be drawn by the compressor 11, by using the pressure increase of refrigerant in the diffuser portion 13d.

Further, when a pressure abnormality in the high-pressure side refrigerant pressure of the cycle is detected, the evaporator refrigerant flow amount Ge is increased. Accordingly, it is possible to suppress the pressure increase of refrigerant in the diffuser portion 13d, thereby preventing an abnormal high pressure of the cycle while performing the cooling operation of the cycle. Therefore, a high pressure is not applied to the first evaporator 17.

Still further, in this embodiment, because the refrigerant flow is branched at the branch point Z on the upstream side of the nozzle portion 13a, the variable throttle mechanism 16 increases the evaporation refrigerant flow amount Ge and at the same time reduces the flow rate of the refrigerant flowing into the nozzle portion 13a. As a result, the velocity of the mixed refrigerant flowing into the diffuser portion 13d is reduced, thereby reducing the amount of pressure increase in the refrigerant in the diffuser portion 13d.

Other Embodiment

The present invention is not limited to the above-mentioned embodiments but can be modified variously as described below.

(1) In the above-mentioned embodiments, the electric variable throttle mechanism is used as the variable throttle mechanism 16 that has the flow rate adjustment function, but a mechanical variable throttle mechanism also can be employed as the variable throttle mechanism 16 having the flow rate adjustment function.

For example, a pressure responding means displaced in response to the high-pressure side refrigerant on the upstream side of the nozzle portion 13a may be provided. In this case, the pressure responding means is constructed of a diaphragm or a bellows. Furthermore, a load is applied to the pressure responding means by elastic means such as a coil spring from a direction opposite to the force that the pressure responding means receives from the high-pressure refrigerant pressure. With this, pressure abnormality detecting means can be constructed such that, when the high-pressure refrigerant pressure becomes not less than a predetermined value determined by the elastic means, the pressure responding means is displaced.

Further, a valve mechanism of the flow amount changing unit for changing the evaporator refrigerant flow amount Ge can be combined with the variable throttle mechanism so as to expand the refrigerant passage area according to the amount of displacement of this pressure responding means. This construction can mechanically construct the variable throttle mechanism (flow amount changing unit) that increases the evaporator refrigerant flow amount Ge when the high-pressure side refrigerant pressure increases.

(2) In the above-mentioned embodiment, at step S2 of the control program executed by the air-conditioning control unit 20, a pressure abnormality is detected when the refrigerant pressure Pnoz on the upstream side of the nozzle 13a is larger than the reference high-pressure refrigerant pressure KNnoz. However, a pressure abnormality may be detected on the basis of the amount of increase per unit time in the refrigerant pressure Pnoz on the upstream side of the nozzle portion 13a.

For example, the discharge side refrigerant pressure of the compressor 12 may be abruptly increased by an abrupt increase in the number of revolutions of the compressor 11, even if the actual refrigerant pressure on the upstream side of the nozzle portion 13a is not increased to the reference high-pressure refrigerant pressure Kpnoz. Even in this case, a pressure abnormality can be actually detected on the basis of the amount of increase per unit time in Pnoz. With this, it is possible to more surely ensure the reliability of the refrigerant piping and the functional parts.

(3) In the above-mentioned second embodiment, the first and second evaporators 17, 26 cool the same compartment to be cooled (e.g., air in the refrigeration compartment). However, the first and second evaporators 17, 26 may cool different objects or spaces to be cooled.

For example, it is possible to use the first evaporator 17 for cooling air in the compartment of a refrigerator for a vehicle and to use the second evaporator 26 for cooling air in a passenger compartment of the vehicle. In this case, since the outlet side of the first evaporator 17 is connected to the refrigerant suction port 13b of the ejector 13, it is possible to apply the lowest pressure immediately after reducing pressure in the nozzle portion 13a to the outlet side of the first evaporator 17 and to apply pressure after being increased in the diffuser portion 14b as the refrigerant pressure of the second evaporator 26.

With this, the refrigerant evaporation pressure (refrigerant evaporation temperature) of the first evaporator 17 can be made lower than the refrigerant evaporation pressure (refrigerant evaporation temperature) of the second evaporator 26. Thus, it is possible to perform a cooling operation in a relatively high temperature range suitable for cooling the passenger compartment by the second evaporator 26, and at the same time to perform a cooling operation in a further lower temperature range suitable for cooling the refrigerator by the first evaporator 17.

Even when the second evaporator 26 is arranged on the downstream side of the diffuser portion 13d of the ejector 13 in the first embodiment, it is possible to produce the effect described in the first embodiment.

(4) In the above-mentioned embodiments, the first evaporator 17 and the second evaporator 26 are used as use-side heat exchangers for cooling air in the refrigeration compartment, which is the compartment to be cooled, while the radiator 12 is as a heat exchanger for radiating heat to the atmosphere. On the contrary to this, the present invention may be applied to a construction (heat pump cycle) having the first evaporator 17 and the second evaporator 26 as heat exchangers for absorbing heat from a heat source such as the atmosphere, and having the radiator 12 as a use-side heat exchanger for heating air or water which is an object to be heated.

In other words, the refrigeration cycle according to the embodiments may be used as a heat pump cycle that constructs the radiator 12 as a use-side heat exchanger (e.g., heater).

(5) In the above-mentioned embodiments, there may be provided an inner heat exchanger for exchanging heat between high-pressure refrigerant on the downstream side of the radiator 12 and low-pressure refrigerant on the suction side of the compressor 11. According to this construction, refrigerant on the downstream side of the radiator 12 is cooled, so it is possible to increase a difference in enthalpy (cooling capacity) of refrigerant between the refrigerant inlet and outlet in each of the first evaporator 17 and the second evaporator 26.

(6) In the above-mentioned embodiments has been described an example of using carbon dioxide as refrigerant and constructing a supercritical refrigerant cycle in which high-pressure side refrigerant pressure exceeds a supercritical pressure. However, fron-based or HC-based refrigerant may be used as the refrigerant. Further, the present invention may be applied also to a case of constructing a vapor compression type subcritical refrigerant cycle in which high pressure does not exceed a supercritical pressure.

(7) In the above-mentioned embodiments, a fixed nozzle having a constant refrigerant passage area has been shown as an example of the nozzle portion 13a. However, a variable ejector having a variable nozzle portion capable of adjusting the refrigerant passage area may be used as the ejector 13. As an example, the variable nozzle portion can be employed, for example, a mechanism in which the position of a needle inserted into the passage of the variable nozzle portion is controlled by an electric actuator to adjust the refrigerant passage area.

Such changes and modifications are to be understood as being within the scope of the present invention as defined by the appended claims.

Claims

1. An ejector refrigerant cycle device comprising:

a compressor that draws, compresses and discharges refrigerant;

a radiator that radiates heat of refrigerant discharged from the compressor;

an ejector that has a nozzle portion for reducing pressure of refrigerant on a downstream side of the radiator to expand the refrigerant, and a refrigerant suction port from which refrigerant is drawn by a high-velocity refrigerant flow jetted from the nozzle portion, wherein the ejector mixes refrigerant drawn from the refrigerant suction port and refrigerant jetted from the nozzle portion, and reduces the velocity of the mixed refrigerant so as to increase its pressure;

an evaporator that evaporates refrigerant and flows out the evaporated refrigerant to the refrigerant suction port;

a flow amount changing unit that changes a refrigerant flow amount flowing into the evaporator; and

a pressure abnormality detecting means that detects a pressure abnormality of a high-pressure refrigerant on an upstream side of the nozzle portion,

wherein the compressor draws refrigerant on a downstream side of the ejector, and

wherein when the pressure abnormality detecting means detects the pressure abnormality, the flow amount changing unit makes the refrigerant flow amount flowing into the evaporator larger than that in a normal pressure state of the high-pressure refrigerant.

2. The ejector refrigerant cycle device as in claim 1, further comprising:

an accumulator that separates refrigerant flowing out of the ejector into vapor refrigerant and liquid refrigerant; and

a liquid refrigerant passage through which the liquid refrigerant flows from the accumulator into the evaporator,

wherein the flow amount changing unit is arranged in the liquid refrigerant passage.

3. The ejector refrigerant cycle device as in claim 1, further comprising:

a branch passage branched from a point between a downstream side of the radiator and an upstream side of the nozzle portion, and is joined to the refrigerant suction port of the ejector,

wherein the flow amount changing unit is arranged in the branch passage.

4. The ejector refrigerant cycle device as in claim 1,

wherein when a high-pressure refrigerant pressure on the upstream side of the nozzle portion becomes not less than a predetermined value, the pressure abnormality detecting means detects the pressure abnormality.

5. The ejector refrigerant cycle device as in claim 1,

wherein when a pressure-increase amount per unit time of the high-pressure refrigerant on the upstream side of the nozzle portion becomes not less than a predetermined amount, the pressure abnormality detecting means detects the pressure abnormality.

6. The ejector refrigerant cycle device as in claim 1,

wherein the flow amount changing unit is a variable throttle mechanism that is constructed to change an area of a refrigerant passage.

7. The ejector refrigerant cycle device as in claim 1, further comprising:

a drive member that drives the flow amount changing unit to change a refrigerant passage area in the flow amount changing unit; and

a control unit that controls operation of the drive member,

wherein the pressure abnormality detecting means includes a pressure sensor for detecting a pressure of high-pressure refrigerant on the upstream side of the nozzle portion, and determination means that determines whether or not a detection value of the pressure sensor corresponds to the pressure abnormality, and

wherein when the determination means determines that the detection value of the pressure sensor corresponds to the pressure abnormality, the control unit controls the drive member so as to expand the refrigerant passage area.

8. The ejector refrigerant cycle device as in claim 1, wherein the ejector further includes a mixing portion in which the refrigerant jetted from the nozzle portion and the refrigerant drawn from the refrigerant suction port are mixed, and a diffuser portion which increases pressure of the mixed refrigerant from the mixing portion, the device further comprising

reducing means for reducing a pressure increasing amount of the mixed refrigerant in the diffuser portion,

wherein when the pressure abnormality detecting means detects the pressure abnormality, the reducing means reduces the pressure increasing amount of the mixed refrigerant in the diffuser portion than that in the normal pressure state of the high-pressure refrigerant.

9. The ejector refrigerant cycle device as in claim 8, wherein the flow amount changing unit is used as the reducing means.

10. The ejector refrigerant cycle device according to claim 3, further comprising

an another evaporator for evaporating refrigerant flowing out of an outlet port of the ejector.

11. An ejector refrigerant cycle device comprising:

a compressor that draws, compresses and discharges refrigerant;

a radiator that radiates heat of refrigerant discharged from the compressor;

an ejector that has a nozzle portion for reducing pressure of refrigerant on a downstream side of the radiator to expand the refrigerant, a refrigerant suction port from which refrigerant is drawn by a high-velocity refrigerant flow jetted from the nozzle portion, a mixing portion in which the refrigerant jetted from the nozzle portion and the refrigerant drawn from the refrigerant suction port are mixed, and a diffuser portion which increases pressure of the mixed refrigerant from the mixing portion;

an evaporator that evaporates refrigerant and flows out the evaporated refrigerant to the refrigerant suction port;

a pressure abnormality detecting means that detects a pressure abnormality of a high-pressure refrigerant on an upstream side of the nozzle portion; and

reducing means for reducing a pressure increasing amount of the mixed refrigerant in the diffuser portion of the ejector,

wherein the compressor draws refrigerant on a downstream side of the ejector, and

wherein when the pressure abnormality detecting means detects the pressure abnormality, the reducing means reduces a pressure increasing amount of the mixed refrigerant in the diffuser portion than that in a normal pressure state of the high-pressure refrigerant.

12. The ejector refrigerant cycle device according to claim 11, wherein the pressure abnormality detecting means detects the pressure abnormality when the pressure of refrigerant at the upstream side of the nozzle portion is higher than a predetermined amount.

13. A control method of an ejector refrigerant cycle device having an ejector that includes a nozzle portion for reducing pressure of a high-pressure refrigerant, a refrigerant suction port from which refrigerant from an evaporator is drawn by a high-velocity refrigerant flow jetted from the nozzle portion, a mixing portion in which the refrigerant jetted from the nozzle portion and the refrigerant drawn from the refrigerant suction port are mixed, and a diffuser portion which increases pressure of the mixed refrigerant from the mixing portion, the control method comprising:

detecting a pressure abnormality of the high-pressure refrigerant on an upstream side of the nozzle portion; and

reducing a pressure increasing amount of the mixed refrigerant in the diffuser portion than that in a normal pressure state of the high-pressure refrigerant.

14. The control method according to claim 13, wherein

the reducing is performed by increasing a refrigerant amount flowing into the evaporator, which has a refrigerant outlet coupled to the refrigerant suction port of the ejector, to be larger than that in the normal pressure state of the high-pressure refrigerant.