JP2004003717A - Air conditioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that in an air conditioner using an electronic linear expansion valve (LEV) as a decompression device, flow of cooling medium is reversed at cooling / heating operation by switching a four-way valve, but on structure of LEV, a counter pressure valve-opening pressure gap before and after the LEV to the flow from the opposite direction is high, and stability can not be obtained at low opening-valve pulse of the LEV and control of cooling medium flow might be disabled. <P>SOLUTION: In an air conditioner having a decompression device provided on cooling medium piping connected to the upstream and the downstream of a receiver for storing surplus cooling medium, the decompressing device made of the LEV is used and the LEV on the receiver downstream side is connected in the forward direction flow so that inflow / outflow opposing the receiver can be obtained. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a refrigeration cycle for an air conditioner or the like.
[0002]
[Prior art]
FIG. 6 is a block diagram showing a refrigerant circuit diagram of a conventional air conditioner described in JP-A-2001-174091. In the figure, a high-temperature and high-pressure gas refrigerant is discharged from a compressor 1 and enters an outdoor heat exchanger 3 (cooling condenser) through a four-way valve 2. This gas refrigerant is heat-exchanged with the outside air by the outdoor heat exchanger 3 to become a liquid refrigerant, which is decompressed through the first throttle 4a and enters the receiver 7. The low-dryness high-temperature two-phase refrigerant that has entered the receiver 7 is cooled to a saturated liquid state by the low-temperature low-pressure refrigerant flowing inside the suction pipe 9 installed in the receiver 7 and flows out of the receiver 7. After the pressure is reduced through the second throttle 4b, it flows to the indoor heat exchanger 5 (evaporator during cooling). Switching between cooling and heating is performed by a four-way valve, and the flow of the refrigerant is reversed.
[0003]
When an electronic linear expansion valve (LEV) is used as a pressure reducing device, the refrigerant inflow path to the LEV is, as shown in FIG. 4, from the side (A) and from below (B) to the LEV main body. There are two places. In FIG. 4, reference numeral 21 denotes a valve main body having a built-in refrigerant throttle mechanism including a valve rod and a valve seat, 22 denotes an electromagnetic coil for driving the valve rod, 23 denotes a lead wire for supplying current to the electromagnetic coil, and 24 denotes a valve main body. Reference numeral 21 denotes a horizontal copper pipe connected from the lateral side, and reference numeral 25 denotes a lower copper pipe connected from the lower side of the valve body 21 in the valve rod driving direction. When performing the cooling / heating switching operation, the flow of the refrigerant includes a flow from the side to the bottom (defined as the forward direction) and a flow from the bottom to the side (defined as the reverse direction) with respect to the valve body. It will be. Here, FIG. 5 shows an internal structure diagram of the LEV. In the figure, 21 is a valve body, 26 is a valve seat fixed to the valve body, 27 is a valve stem that has a conical tip and moves toward or away from the valve seat 26, and 28 is inside the valve body. It is a space provided and through which the refrigerant flows. In the method of adjusting the flow rate of the refrigerant in the LEV, the gap area between the valve stem 27 and the valve seat 26 fixed to the valve body 21 is changed by operating the valve stem 27 in the vertical direction (in FIG. 5). The flow rate of the refrigerant passing therethrough is adjusted. At this time, if the pressure difference between the front and rear of the LEV exceeds a certain value, the drive control of the valve stem body becomes impossible, and the valve stem position is not fixed, so that the flow rate adjustment may be impossible. Generally, a working pressure difference range is defined. In addition, the refrigerant flow is more affected by the refrigerant pressure in the case of the reverse flow (downward → lateral flow with respect to the valve body) than in the forward direction flow (lateral → downward flow with respect to the valve body). Due to its easy structure, the use of a reverse flow is specified at a lower pressure difference. This pressure condition value is defined as the back pressure opening pressure difference, and the pressure value limit may be changed by the opening pulse of the LEV. This will be described with reference to the relationship diagram between the LEV opening and the back pressure opening pressure difference shown in FIG. In the figure, the horizontal axis indicates the LEV valve opening pulse, and the vertical axis indicates the reverse pressure opening pressure difference. On the low valve opening pulse side, the reverse pressure opening pressure difference of P2 is obtained from the lower limit value of the valve opening pulse. On the other hand, on the valve opening pulse side higher than the lower limit set value, the reverse pressure valve opening pressure difference has a characteristic of increasing to P1 (P2 <P1).
[0004]
[Problems to be solved by the invention]
In the refrigerant circuit of the conventional air conditioner as described above, the flow of the refrigerant is reversed because the cooling / heating operation is switched by the four-way valve, and the electronic linear expansion valve (LEV) is used as the pressure reducing device. , The flow of the refrigerant in the LEV must be in both forward flow (flow from side to bottom with respect to the valve body) and reverse flow (flow down from side to side with respect to the LEV valve body). become. When an LEV is used as a pressure reducing device, in the above-described reverse flow state, particularly in the case of a slight throttle (low valve opening pulse), the differential pressure in the refrigerant flow before and after the LEV decreases because the reverse pressure valve opening pressure difference becomes small. When the back pressure opening pressure difference of the LEV used exceeds the valve opening pulse of the LEV, there is a problem that the valve opening pulse of the LEV is not stabilized, and it becomes difficult to secure the compressor reliability due to a state in which the refrigerant flow cannot be controlled. .
[0005]
The present invention has been made in order to solve the above-described problems, and in an air conditioner including a refrigerant circuit having a pressure reducing device before and after a receiver for storing excess refrigerant, it is impossible to control the refrigerant flow instability and the like. It is an object of the present invention to obtain an air conditioner that can always operate stably without falling into a state.
[0006]
[Means for Solving the Problems]
The air conditioner according to claim 1 of the present invention includes a compressor, a four-way switching valve connected to the compressor via a pipe, and an outdoor heat exchanger connected to the four-way switching valve via a pipe. An indoor heat exchanger connected to the four-way switching valve via a pipe, a receiver connected to the outdoor heat exchanger on one side and the indoor heat exchanger on the other side via a pipe, and storing excess refrigerant. A first throttle device provided between the receiver and the outdoor heat exchanger, and a second throttle device provided between the receiver and the indoor heat exchanger, An electronic linear expansion valve (LEV) is used for the second throttle device, and the electronic linear expansion valve (LEV) provided downstream of the receiver is arranged in the forward flow direction.
[0007]
The air conditioner according to claim 2 of the present invention is a control device that controls the electronic linear expansion valve provided on the upstream side of the receiver so that the pressure difference is equal to or less than an opening pulse in which a back pressure opening pressure difference is limited. It is provided.
[0008]
In the air conditioner according to claim 3 of the present invention, after starting the compressor, the opening pulse of the electronic linear expansion valve provided on the upstream side of the receiver for a predetermined time is fixed to be slightly open and provided on the downstream side of the receiver. Starting the throttle operation from the electronic linear expansion valve, and when the differential pressure between the outlet and the inlet of the electronic linear expansion valve provided on the upstream side of the receiver becomes equal to or lower than a predetermined pressure, the throttle operation of the electronic linear expansion valve provided on the upstream side. A control device for performing control is provided.
[0009]
In the air conditioner according to a fourth aspect of the present invention, a part of a suction pipe penetrating through the inside of the receiver is disposed so as to exchange heat with surplus refrigerant stored in the receiver.
[0010]
The air conditioner according to claim 5 of the present invention uses an HFC refrigerant as a refrigerant.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiment 1 FIG.
Hereinafter, Embodiment 1 of the present invention will be described. FIG. 1 shows a refrigerant circuit diagram of the air conditioner according to the first embodiment. 1 is a compressor, 2 is a four-way switching valve (four-way valve) for switching between cooling and heating operations, 3 is an outdoor heat exchanger, 4a and 4b are electronic linear expansion valves (LEVs) as expansion devices, 5 is an indoor heat exchanger, 6 is a discharge pipe, 7 is a receiver for storing excess refrigerant, 8 is a discharge temperature thermistor provided in the discharge pipe 6, 9 is a suction pipe, 10 is an outdoor heat exchanger temperature thermistor, and 11 is an indoor heat exchanger temperature thermistor. is there.
[0012]
First and second expansion devices are provided on the connection pipe between the outdoor heat exchanger and the receiver and on the connection pipe between the indoor heat exchanger and the receiver, respectively, on the upstream side and the downstream side of the receiver 7 of the refrigerant circuit. I have. The electronic linear expansion valve (LEV) used as the expansion device is, as described with reference to FIGS. 4 and 5 described above, a cross copper pipe connected from the side of the valve body and a lower copper pipe below the valve body. The structure is such that the refrigerant is connected so as to circulate from the two locations. As shown in FIG. 1, both the first and second expansion devices (LEVs) are connected to the receiver side with the pipes connected in the direction of inflow / outflow from the horizontal copper pipes, and the lower copper pipes on the opposite side of the LEV entrance / exit. The side is connected and fixed to the indoor or outdoor heat exchanger side. With the above configuration, the LEV disposed downstream of the receiver is provided so as to be in the forward flow direction with respect to the flow of the refrigerant.
[0013]
Next, the operation of the air conditioner using this refrigerant circuit will be described. The high-temperature and high-pressure gas refrigerant discharged from the compressor 1 enters the four-way switching valve 2 through the discharge pipe 6. During the cooling operation, as shown by a solid line, the air flows from the four-way switching valve 2 into the outdoor unit heat exchanger 3 (working as a condenser), exchanges heat with outdoor air to be cooled and condensed and liquefied, and then reaches the electronic expansion valve 4a. After the pressure is reduced by the electronic expansion valve 4a to become a wet refrigerant, the refrigerant enters the receiver 7. Inside the receiver 7, a part of a suction pipe 9 penetrating through the upper part of the receiver 7 and connected to the suction part of the compressor 11 from the four-way switching valve 2 is disposed. The excess refrigerant stored in the receiver is cooled to a saturated liquid state by the refrigerant, and flows out of the receiver 7. After passing through the electronic expansion valve 4b and being decompressed again, it flows into an indoor unit heat exchanger (working as an evaporator), exchanges heat with indoor air, is heated and evaporated, and then passes through the four-way switching valve 2. After passing through the suction pipe 9 and performing heat exchange with the excess refrigerant in the receiver, the flow returns to the compressor 1. Since a part of the suction pipe 9 is arranged inside the receiver 7 so as to exchange heat with the stored excess refrigerant, an air conditioner with good operation efficiency can be obtained.
[0014]
The discharge temperature thermistor 8 in FIG. 1 is for detecting the temperature of the discharge gas refrigerant discharged from the compressor 1, and a control device provided in the outdoor unit so that the discharge temperature detected here becomes a predetermined value. (Not shown) controls the valve opening pulse of the LEV located downstream of the receiver. Controlling the compressor discharge temperature detected by the discharge temperature thermistor 8 to a value equal to or higher than a predetermined value according to the operation state suppresses the return of the liquid refrigerant to the compressor, and improves the reliability and performance of the compressor. It is very important to secure Accordingly, by detecting the temperature of the refrigerant discharged from the compressor 1 by the discharge temperature thermistor 8 and controlling the valve opening degree pulse of the LEV on the downstream side of the receiver (cooling: 4b, heating: 4a), the refrigerant is always controlled by the controlled LEV. Flow becomes a forward flow (flow from the side to the bottom with respect to the LEV valve main body), so that stable control characteristics can be obtained without being affected by the differential pressure for opening the reverse pressure valve.
[0015]
Further, when the LEV to be controlled is a throttle device on the upstream side of the receiver, the opening pulse having a small back pressure opening pressure difference is obtained from the relationship between the opening pulse and the back pressure opening pressure difference as shown in FIG. By providing the lower limit set value as the limit of the opening pulse change so as not to be below, stable control characteristics can be obtained.
[0016]
Further, when performing the opening pulse change control of the receiver upstream LEV, the outdoor heat exchanger temperature thermistor 10 that detects the temperature of the two-phase refrigerant installed at the center of the outdoor unit heat exchanger 3 and the indoor unit heat exchanger The indoor heat exchanger temperature thermistor 11, which detects the temperature of the two-phase refrigerant, is installed at the center of 5 to detect the condensing temperature and the evaporating temperature of the refrigerant, convert the condensing pressure and the evaporating pressure from the respective temperatures, and convert Calculate the high / low pressure difference between the discharge side and the suction side. Further, from the characteristics of the LEV opening pulse and the pressure difference before and after the LEV due to the refrigerant flow, the differential pressure between the inlet and the outlet of the upstream LEV is estimated from the receiver upstream LEV opening pulse and the receiver downstream LEV opening pulse. By performing the upstream LEV opening pulse control so as to be equal to or less than the limit value of the back pressure opening pressure difference, stable control characteristics can be obtained.
[0017]
FIG. 3 is a time chart illustrating the control operation of the above-described LEV opening pulse. In the figure, the horizontal axis represents time, and the vertical axis represents the LEV opening pulse (corresponding to the refrigerant flow rate), and shows the changing state of the opening pulse of LEV1 (receiver upstream) and LEV2 (receiver downstream) during cooling operation. . First, at the start of operation, the control device provided in the outdoor unit is set and controlled to a predetermined valve opening pulse Lo (opening degree slightly open), the compressor is started, the refrigerant flows, and a pressure difference between high and low pressures is generated. When it comes, the valve opening pulse amount of LEV2 is lowered from the point C in the figure to perform the throttle operation. During this time, the opening pulse of the LEV1 is slightly widened and fixed, but then the LEV1 is moved from the point D in the figure. A control operation for lowering the valve opening pulse to advance the throttle operation is performed. Thus, the LEV on the downstream side of the receiver makes the throttle amount slightly open (small opening), while the LEV on the upstream side of the receiver makes the throttle amount slightly open (large opening), so that the LEV opening control is performed. Operation.
[0018]
In the above-described embodiment, the description has been given of the refrigerant circuit in which the compressor suction pipe is penetrated into the receiver and heat is exchanged between the surplus refrigerant in the receiver and the refrigerant in the suction pipe. However, the present invention is not limited to this, and can be applied regardless of the presence or absence of the high / low pressure heat exchange unit using the suction pipe provided in the receiver.
[0019]
The air conditioner according to the first embodiment uses an HFC-based refrigerant (for example, R407C, R410A or the like) as the refrigerant, and uses a refrigerant oil incompatible with the refrigerant as the refrigerant oil. When the excess refrigerant is stored in the accumulator as in the conventional refrigeration cycle, the temperature of the excess refrigerant is low, so the solubility is low, and the refrigerating machine oil separates and floats on the upper layer of the refrigerant, so that it cannot be returned to the compressor. However, when the excess refrigerant is stored in the receiver as shown in the present embodiment, the temperature of the excess refrigerant is as high as about 50 ° C., so that the normal oil can be returned to the compressor without being separated, and the reliability is improved. I do.
[0020]
Furthermore, in the above-described embodiment, an example in which the present invention is applied to an air conditioner using an HFC refrigerant as a refrigerant has been described. However, the present invention is not limited to such an example, and can be applied regardless of the type of refrigerant. .
[0021]
【The invention's effect】
As described above, the air conditioner according to claim 1 of the present invention includes a compressor, a four-way switching valve connected to the compressor via a pipe, and an outdoor connected to the four-way switching valve via a pipe. A heat exchanger, an indoor heat exchanger connected to the four-way switching valve via a pipe, one of which is connected to the outdoor heat exchanger, and the other of which is connected to the indoor heat exchanger via a pipe, respectively. A first throttle device provided between the receiver and the outdoor heat exchanger, and a second throttle device provided between the receiver and the indoor heat exchanger, An electronic linear expansion valve (LEV) is used for the first and second expansion devices, and an electronic linear expansion valve (LEV) provided downstream of the receiver is disposed in the forward flow direction. In the circuit shown in FIG. The opening angle can be set to the positive direction, and even if the opening pulse is reduced, there is no need to consider the influence of opening degree instability when the opening pressure difference exceeds the reverse pressure valve opening pressure, and a stable control system is obtained. Can do things.
[0022]
In the air conditioner according to claim 2 of the present invention, the electronic linear expansion valve provided on the upstream side of the receiver is controlled so as to control the pressure difference to be equal to or less than the opening pulse in which the reverse pressure opening pressure difference is limited. Since the device is provided, the reverse pressure valve opening pressure difference of the receiver upstream LEV is also reduced, and by preventing it from becoming smaller than the opening pulse, it is possible to prevent the refrigerant flow from becoming unstable and to obtain a stable control system. Can do things.
[0023]
Further, in the air conditioner according to claim 3 of the present invention, after the compressor is started, the opening pulse of the electronic linear expansion valve provided upstream of the receiver for a predetermined time is fixed so as to be wide open and the downstream side of the receiver. The throttle operation is started from the electronic linear expansion valve provided on the electronic linear expansion valve provided on the upstream side, and when the differential pressure between the outlet and the inlet of the electronic linear expansion valve provided on the upstream side of the receiver becomes equal to or lower than a predetermined pressure, the electronic linear expansion valve provided on the upstream side Since the control device for controlling the narrowing-down operation is provided, it is possible to prevent the refrigerant flow from becoming unstable and to obtain a stable control system.
[0024]
Also, in the air conditioner according to claim 4 of the present invention, a part of the suction pipe penetrating the inside of the receiver is disposed so as to exchange heat with the surplus refrigerant stored in the receiver. A harmony machine is obtained.
[0025]
Further, according to the invention of claim 5, since the HFC refrigerant is used as the refrigerant, reliability can be improved.
[Brief description of the drawings]
FIG. 1 is a refrigerant piping system diagram of an air conditioner according to Embodiment 1 of the present invention.
FIG. 2 is a relationship diagram between an LEV opening and a back pressure opening pressure difference according to the first embodiment of the present invention.
FIG. 3 is a time chart of changes in the upper LEV and lower LEV opening pulse according to Embodiment 1 of the present invention;
FIG. 4 is an external view of the electronic linear expansion valve according to the first embodiment of the present invention.
FIG. 5 is an internal structure diagram of the electronic linear expansion valve according to the first embodiment of the present invention.
FIG. 6 is a refrigerant circuit diagram of a conventional air conditioner.
[Explanation of symbols]
Reference Signs List 1 compressor, 2 four-way switching valve, 3 outdoor heat exchanger, 4a, 4b electronic linear expansion valve, 5 indoor heat exchanger, 6 discharge pipe, 7 receiver, 8 discharge temperature thermistor, 9 suction pipe, 10 outdoor heat exchanger Temperature thermistor, 11 indoor heat exchanger temperature thermistor, 21 valve body, 22 electromagnetic coil, 23 lead wire, 24 cross copper pipe, 25 lower copper pipe, 26 valve seat, 27 valve stem, 28 space.

Claims (5)

A compressor, a four-way switching valve connected to the compressor via a pipe, an outdoor heat exchanger connected to the four-way switching valve via a pipe, and a pipe connected to the four-way switching valve. An indoor heat exchanger, one of which is connected to the outdoor heat exchanger, and the other of which is connected to the indoor heat exchanger via pipes, respectively, and a receiver for storing excess refrigerant, between the receiver and the outdoor heat exchanger. And a second throttle device provided between the receiver and the indoor heat exchanger. An electronic linear expansion valve (LEV) is provided for the first and second throttle devices. An air conditioner, wherein an electronic linear expansion valve (LEV) provided downstream of the receiver is disposed in a forward direction. 2. The control device according to claim 1, further comprising a control device that controls the electronic linear expansion valve provided on the upstream side of the receiver so that the reverse pressure valve opening pressure difference is equal to or less than an opening pulse that is limited. Air conditioner. After starting the compressor, the opening degree pulse of the electronic linear expansion valve provided on the receiver upstream side for a predetermined time is fixed to be slightly open, and a throttle operation is started from the electronic linear expansion valve provided on the receiver downstream side, When the differential pressure between the outlet and the inlet of the electronic linear expansion valve provided on the upstream side of the receiver becomes equal to or less than a predetermined pressure, a control device for controlling the throttle operation of the electronic linear expansion valve provided on the upstream side is provided. The air conditioner according to claim 1 or 2, wherein The air conditioner according to any one of claims 1 to 3, wherein a part of a suction pipe passing through the inside of the receiver is arranged to exchange heat with surplus refrigerant stored in the receiver. Machine. The air conditioner according to any one of claims 1 to 4, wherein an HFC refrigerant is used as the refrigerant.

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