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Ejector refrigerant cycle device and control method thereofRelated Patent Categories: Refrigeration, Refrigeration Producer, Compressor-condenser-evaporator Circuit, Jet Powered By Circuit FluidEjector refrigerant cycle device and control method thereof description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070180852, Ejector refrigerant cycle device and control method thereof. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS REFERENCE TO RELATED APPLICATION [0001] 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 [0002] 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 [0003] 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. [0004] 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.degree. C.) is arranged in this bypass passage. [0005] 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. [0006] 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 [0007] 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. [0008] It is another object of the present invention to provide a control method of an ejector refrigerant cycle device. [0009] 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. [0010] 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. [0011] 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. [0012] 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. [0013] 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. [0014] 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. [0015] 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. [0016] 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. [0017] 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. [0018] 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. [0019] 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. [0020] 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. 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