JP5473213B2 - Air conditioner - Google Patents

Description

  The present invention relates to an air conditioner having a high-pressure shell type compressor, and more particularly to an air conditioner that can prevent a decrease in the oil level of the compressor at the initial stage of startup.

  The air conditioner forms an air conditioning function by forming a refrigerant circuit in which a compressor, a condenser, a throttle mechanism, and an evaporator are connected in this order, and circulating the refrigerant in the refrigerant circuit. In such an air conditioner, an oil separator is interposed between the discharge port of the compressor and the condenser, and the oil separated by the oil separator is returned to the compressor through an oil return channel. ing.

In addition to this configuration, a bypass flow path having a control valve is formed in parallel with the oil return flow path between the discharge port and the suction port of the compressor, and the discharge port pressure due to some unforeseen factor. An apparatus in which an increase in (high pressure) and a decrease in suction port pressure (low pressure) are prevented by opening this bypass channel is also known (Patent Document 1).
JP-A-9-318116

  However, the configuration described in Patent Document 1 is intended only for adjusting the high and low pressures of the gas pipe. When the compressor is started, the liquid refrigerant contains a large amount of oil and the indoor unit side There is no consideration given to spillage.

  This type of air conditioner is in a state where a large amount of liquid refrigerant is stored in the compressor when the outside air temperature is low and it has been stopped for a long time. When the compressor is started in this state, in addition to the stored liquid refrigerant, liquid refrigerant formed by condensing the gas refrigerant in the compressor is also discharged, and the oil separator can be returned to the compressor by the oil return channel. Since it exceeds the amount of liquid component that can be produced, a large amount of liquid refrigerant and oil contained therein will flow out to the indoor unit side. As a result, in multi-models with long piping lengths, it may take several tens of minutes for the oil that has flowed out to the indoor unit to return to the compressor, resulting in a problem that the oil level of the compressor continues for a long time. obtain. Even if the pipe length is short, while the temperature in the compressor shell is low, liquid refrigerant continues to be generated due to the condensation of the refrigerant. Therefore, it takes several tens of minutes for all the liquid refrigerant to evaporate. The oil level may be lowered for a long time.

  Therefore, the present invention prevents the liquid refrigerant containing oil from flowing out to the indoor unit side at the time of starting the compressor while increasing the temperature in the compressor in a short time while using the conventional gas piping. It is an intended task to eliminate the oil level drop of the compressor.

  That is, the present invention is configured such that an oil separator is interposed between the discharge port of the high-pressure shell compressor and the condenser, and the oil separated by the oil separator is returned to the compressor through an oil return channel. The air conditioner includes: a bypass flow path provided in parallel with the oil return flow path; a control valve that opens and closes the bypass flow path; and a valve control unit that controls the opening of the control valve. The part opens the control valve from the start of the start of the compressor until after a predetermined time has elapsed, and circulates the liquid refrigerant and the contained oil discharged from the compressor through the bypass flow path. It is said.

  In such a case, since the bypass flow path is opened for a predetermined period from the start of the compressor, the liquid refrigerant discharged from the compressor and the oil contained therein are not only supplied from the oil separator to the oil return flow path. It can also flow in parallel to the bypass flow path and return to the compressor. That is, since the amount of oil returned from the oil separator to the compressor can be increased, it is possible to prevent the oil from flowing out from the oil separator to the indoor unit side together with the liquid refrigerant.

  Further, by opening the bypass flow path at the time of startup, a part of the high-temperature and high-pressure refrigerant discharged from the compressor can be returned to the low-temperature compressor, so that it is shorter than when the bypass flow path is not opened. The temperature in the compressor can be increased over time. As a result, the liquid refrigerant does not flow out to the indoor unit side, and the temperature in the compressor rises in a short time. Therefore, the time until all the liquid refrigerant evaporates and the oil level drop of the compressor is eliminated. Shorter.

  Further, by opening the bypass channel for a predetermined period and closing the bypass channel after the liquid refrigerant has evaporated, it is possible to prevent the refrigerant from returning to the compressor via the bypass channel during normal operation. Therefore, it is possible to prevent a decrease in operating efficiency due to the provision of the bypass flow path.

  In addition, when the high-pressure gas pipe becomes too high for some reason or the low-pressure gas pipe becomes too low, the high-low pressure can be adjusted by opening the bypass passage.

  If it is possible to detect when the liquid refrigerant is no longer discharged from the compressor while preventing the oil from flowing out from the oil separator to the indoor unit at the time of start-up, at that point, the bypass flow path is closed and switching to normal operation is performed. The predetermined period during which the bypass flow path is opened can be minimized, and the operating efficiency of the air conditioner can be improved. For this purpose, the apparatus further includes a refrigerant state determination unit that determines the state of the refrigerant based on the discharge pressure and discharge temperature of the refrigerant discharged from the compressor, and the valve control unit is configured to start the start of the compressor. It is preferable that the control valve is opened until the refrigerant state determination unit determines that the refrigerant is saturated or overheated.

  In order to increase the return amount of the liquid refrigerant from the oil separator to the compressor at the start-up without impairing the high / low pressure adjustment function of the gas pipe, which is the original function of the bypass flow path, The upper limit of the discharge amount may be set based on the flow rate that can flow per unit time of the bypass flow path.

  If the liquid refrigerant can be evaporated by reducing the pressure in the compressor shell that is stopped at the time of startup, the liquid refrigerant can be prevented from being stored in the stopped compressor. For this purpose, a second bypass which is arranged in parallel with the compressor and is started at the start of the compressor or after the start of the compressor and a discharge port and a suction port of the second compressor are connected. And a second control valve that opens and closes the second bypass flow path, wherein the valve control unit is between the start of activation of the compressor and after a lapse of a predetermined time, and the second control valve. It is preferable to control the opening of the second control valve before the start of the compressor.

  Thus, according to the present invention, the existing high / low pressure adjusting bypass flow path can be used, and the return amount of the liquid refrigerant and the contained oil at the start-up can be increased without impairing the original function. It is possible to prevent a large amount of oil from flowing out together with the liquid refrigerant from the indoor unit to the indoor unit side. Furthermore, by returning the high-temperature and high-pressure refrigerant to the compressor, the temperature inside the compressor can be raised and the liquid refrigerant can be evaporated in a short time. Therefore, the oil level drop of the compressor can be eliminated in a short time. This effect is particularly noticeable in multi-models with long piping.

  Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.

  The air conditioning apparatus 100 according to the present embodiment includes an indoor unit B and an outdoor unit A as shown in the circuit configuration diagram of FIG.

  As shown in FIG. 1, the indoor unit B is a multi-model in which a plurality of second throttle mechanisms B1 and evaporators B2 are arranged in parallel.

  The outdoor unit A includes two first and second compressors 1a and 1b arranged in parallel, an oil separator 3, a four-way valve A1 that switches between heating and cooling, a condenser A2 that performs heat exchange, A first throttle mechanism A3 and a check valve A4 connected in parallel thereto, a port A5 connected to the indoor unit B, and an accumulator A6 that performs gas-liquid separation of the refrigerant returned from the indoor unit are provided by piping. It is connected.

  The piping around the compressors 1a and 1b will be described in detail.

  A high pressure pipe 15 for discharging refrigerant is connected to the oil separator 3 from the discharge ports 11a and 11b of the compressors 1a and 1b, and a low pressure pipe 14 for sucking the refrigerant is connected to the suction ports 12a and 12b. It is connected. An oil return channel 4 for returning oil is provided from the oil separator 3 to the low-pressure pipe 14, and a bypass channel 5 is provided in parallel with the oil return channel 4. A first oil equalizing passage 7a is provided between the first compressor 1a and the low pressure pipe 14 on the suction port 1b side of the second compressor 1b, and the suction of the second compressor 1b and the first compressor 1a is provided. A second oil leveling circuit 7b is provided between the low pressure pipe 14 on the port 1a side.

  Each part will be described.

  The first compressor 1a and the second compressor 1b are high-pressure shell type compressors, and the first compressor 1a is a variable speed compressor. In the present embodiment, the first compressor 1a is configured to operate first when activated.

  The oil separator 3 separates the liquid refrigerant or oil and gas refrigerant discharged from the compressors 1a and 1b, returns the liquid component to the oil return channel 4, and flows the gas refrigerant to the indoor unit side. It has been done. A pressure sensor 9 for measuring the pressure of the refrigerant is provided in a pipe for supplying the gaseous refrigerant from the oil separator 3 to the indoor unit B side.

  The high-pressure gas pipe 15 extends from the discharge ports 11a and 11b and joins the oil separator 3 after joining. Between the junction point G and the compressors 1a and 1b, check valves 13a and 13b are provided so that the refrigerant does not flow back from the high-pressure pipe 15 to the compressors 1a and 1b. , 13b and the compressors 1a, 1b are provided with temperature sensors 8a, 8b. The temperature sensors 8a and 8b are attached to both pipes and measure the temperature of the refrigerant discharged from the compressors 1a and 1b.

  The low-pressure gas pipe 14 extends from the accumulator A6, branches at a branch point D, and is connected to the suction ports 1a and 1b.

  The oil return channel 4 is connected to the low pressure pipe 14 between the branch point D and the accumulator A6, and an oil return channel decompression unit 42 for decompressing the fluid passing therethrough is provided in the middle thereof. .

  The bypass channel 5 is connected between the connection point 43 of the oil return channel 4 of the low pressure pipe 14 and the accumulator A6 from the upstream side of the oil return channel decompression section 42 of the oil return channel 4. It is. The bypass flow path 5 adjusts the pressure between the high-pressure pipe 15 and the low-pressure pipe 14 and is designed so that a flow rate suitable for adjusting the high and low pressures can flow. Furthermore, in this embodiment, a control valve 51 for opening and closing the bypass flow path 5 is provided.

  The control valve 51 can be remotely controlled to open and close by receiving an open / close signal, and the open / close control is performed by a valve control mechanism 6 (not shown in FIG. 1). The valve control mechanism 6 is configured by, for example, a dedicated electric circuit or a computer.

As shown in FIG. 2, the valve control mechanism 6 includes at least a refrigerant state determination unit 61 and a valve control unit 62.
As shown in FIG. 2, the refrigerant state determination unit 61 determines the refrigerant state from the refrigerant temperatures of the compressors 1 a and 1 b measured by the temperature sensors 8 a and 8 b and the refrigerant pressure measured by the pressure sensor 9. It is configured.

  The valve control unit 62 commands the control valve 51 to open and close in accordance with the refrigerant state indicated by the refrigerant state determination unit 61.

  Next, the control method at the time of starting will be described together with the behavior of the liquid refrigerant.

  First, in the present embodiment, only the first compressor 1a is activated, and at the same time, the valve control unit 62 commands the opening of the control valve 51. The liquid refrigerant discharged from the compressor 1a and the oil contained therein return from the oil separator 3 to the compressors 1a and 1b from the low-pressure pipe 14 via the oil return passage 4 or the bypass passage 5.

  The open state of the control valve 51 is determined based on the temperature measured by the temperature sensors 8a and 8b and the pressure measured by the pressure sensor 9, and the refrigerant state determination unit 61 determines that the refrigerant is saturated or overheated. The liquid refrigerant is maintained until it is determined that all the compressors 1a and 1b do not exist. As an example of the determination of the refrigerant state, with respect to the saturation temperature calculated from the refrigerant pressure measured by the pressure sensor 9, the temperature sensor 8a, 8b calculates that the degree of superheat is greater than 5K from the refrigerant temperature. For example, what determines that a liquid refrigerant does not exist in compressor 1a, 1b is mentioned.

  Further, during the period in which the bypass flow path 5 is open, the discharge amount per unit time of the first compressor 1a is matched with the flow rate per unit time of the liquid refrigerant that can be passed through the bypass flow path 5. There are restrictions. The flow rate per unit time that the bypass channel 5 can flow is determined by, for example, the pipe diameter of the bypass channel 5 or the pressure that can be applied to the bypass channel 5. The discharge amount is limited by controlling the rotation speed of the first compressor 1a.

  While the control valve 51 is open, the liquid refrigerant continues to circulate in the order of the compressors 1a and 1b, the oil separator 3, the oil return channel 4 or the bypass channel 5, and the compressors 1a and 1b. Further, some of the high-temperature and high-pressure gas discharged from the first compressor 1a returns to the compressors 1a and 1b via the bypass flow path 5 and raises the temperature inside them. As a result, the liquid refrigerant evaporates.

  When the refrigerant state determination unit 61 determines that the temperatures of all the compressors 1a and 1b have risen and the liquid refrigerant has evaporated and does not exist, the control valve 51 is closed and the stopped compressor 1b is started, Transition to normal operation.

  Thus, according to the first embodiment, the bypass flow path 5 is opened by the control valve 51 at the time of start-up, so that the liquid refrigerant discharged from the first compressor 1a and the oil contained therein are separated from the oil separator. By returning from 3 to the compressors 1a and 1b via the oil return passage 4 or the bypass passage 5, the amount of oil returned can be increased. As a result, even if liquid refrigerant is stored in the compressors 1a and 1b because the outside air temperature is low and the engine has been stopped for a long time, oil can be prevented from flowing out to the indoor unit B side.

  Moreover, by opening the bypass flow path 5, it is possible to return a part of the high-temperature and high-pressure gas from the first compressor 1a to the compressors 1a and 1b, thereby promoting the temperature rise inside the compressors 1a and 1b. The discharged liquid refrigerant flows through the oil separator 3 to the oil return passage 4 or the bypass passage 5 and returns to the compressor 1a, so that it can be evaporated in a short time. it can.

  And from these effects, even if it does not use a crankcase heater etc. for compressor 1a, 1b, the oil level fall of a compressor can be eliminated in a short time.

  Further, the refrigerant is obtained from the pressure measured by the temperature sensors 8a and 8b provided between the compressors 1a and 1b and the check valves 13a and 13b and the temperature measured by the pressure sensor 9 provided downstream of the oil separator 3. The state determination unit 61 can determine whether the refrigerant is saturated or overheated. Since the opening period of the bypass flow path 5 is determined by the state determination, the bypass flow path 5 can be closed at the time when the liquid refrigerant is not discharged from all the compressors 1a, 1b, and the normal operation can be performed. . As a result, the operating efficiency of the air conditioner 100 can be improved.

  Moreover, since the upper limit of the discharge amount per unit time of the 1st compressor 1a at the time of starting is determined based on the flow volume which the bypass flow path 5 can flow, from the oil separator 3 to the indoor unit B side The outflow of the liquid refrigerant can be prevented. Furthermore, since the control at the time of activation is determined based on the bypass flow path 5, the bypass flow path 5 does not need to be newly redesigned to flow the liquid refrigerant. Therefore, the high / low pressure adjustment function is not impaired, the conventional one can be used, and a new cost is not increased.

  Next, a second embodiment of the present invention will be described. In the following description, the same reference numerals are assigned to members corresponding to the first embodiment.

  As shown in the circuit configuration diagram of FIG. 3, the air conditioner 100 according to the second embodiment is similar to the air conditioner 100 according to the first embodiment. And a second bypass passage 10 for connecting the suction port 12b.

  The second bypass flow path 10 connects the discharge port 11b of the high-pressure pipe 15 and the junction G to the branch point D of the low-pressure pipe and the suction port 12b. Two control valves 11 are provided.

  In this embodiment, as shown in FIG. 4, the valve control mechanism 6 performs not only the opening / closing control of the control valve 51 but also the opening / closing control of the second control valve. The opening / closing control of the control valve 51 at the time of start-up is the same as that of the previous embodiment. Therefore, it is opened until it is determined that no liquid refrigerant is present in all the compressors 1a, 1b.

  As described above, in this embodiment, the inside of the shell of the compressor 1b is connected to the low-pressure side pipe, and the pressure in the shell of the compressor 1b that is stopped is released by opening the second control valve 51. The liquid refrigerant in the shell of the compressor 1b can be evaporated.

  The present invention is not limited to the above embodiment.

  The control valve for the bypass flow path may be a variable capacity expansion valve instead of the on-off valve.

  For example, the time for opening the bypass flow path may be determined by the control valve by experimentally obtaining the time until all of the liquid refrigerant evaporates without using the refrigerant state determination unit.

  In the above embodiment, the flow rate per unit time is controlled by the rotation speed of the compressor. However, a variable capacity compressor may be used.

  The upper limit discharge amount per unit time of the compressor at the time of start-up was determined from the flow rate that the bypass flow path can flow, but conversely, for example, from the amount of liquid refrigerant that is desired to flow at the start-up, the bypass flow path You may determine the flow volume which can be flowed.

  The temperature sensor used for judging the refrigerant state may be provided only on one side instead of being provided on both the compressors. In this case, for example, if the determination based on the degree of superheat is set to a safer side, the liquid refrigerant can be prevented from flowing out to the indoor unit side.

  A temperature sensor may be provided in the low-pressure pipe between the suction port and the branch point of the compressor.

  In addition, the present invention is not limited to the illustrated examples and embodiments, and various modifications can be made without departing from the gist thereof.

The block diagram of the refrigerant circuit in one Embodiment of this invention. The functional block diagram of the valve control mechanism in the embodiment. The block diagram of the refrigerant circuit in another embodiment of this invention. The functional block diagram of the valve control mechanism in another embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Air conditioning apparatus 1a, 1b ... Compressor 11a, 11b ... Discharge port A2 ... Condenser 3 ... Oil separator 4 ... Oil return flow path 5 ... Bypass flow path 51 ... Control valve 62 ... Valve control unit 61 ... Refrigerant state determination unit 1b ... Second compressor 12b ... Suction port 10 ... Second bypass channel 11 ... Second Control valve

Claims (3)

An oil separator is interposed between the discharge port of the high-pressure shell-type first compressor and the condenser, and the oil separated by the oil separator is returned to the first compressor through an oil return channel. In the air conditioner
A first bypass channel provided in parallel with the oil return channel;
A first control valve for opening and closing the first bypass flow path;
A second compressor arranged in parallel with the first compressor and started at the start of the first compressor or after the start of the start;
A second bypass flow path connecting the discharge port and the suction port of the second compressor;
A second control valve for opening and closing the second bypass flow path;
A valve control unit for controlling the opening of the first control valve and the second control valve;
The valve control unit opens the first control valve from a start time of starting the first compressor until a predetermined time elapses when all of the liquid refrigerant in the first compressor and the second compressor evaporates. And circulating the liquid refrigerant and the contained oil discharged from the compressor through the first bypass flow path,
The valve control unit is configured to start from the start of the first compressor until a predetermined time elapses when all of the liquid refrigerant in the first compressor and the second compressor evaporates , and the second compressor An air conditioner that performs opening control of the second control valve before the start of activation. A refrigerant state determination unit that determines a state of the refrigerant based on a discharge pressure and a discharge temperature of the refrigerant discharged from the first compressor;
The valve control unit opens the first control valve from the start of activation of the first compressor until the refrigerant state is determined to be saturated or overheated by the refrigerant state determination unit. Item 1. An air conditioner according to Item 1. 3. The air according to claim 1, wherein the upper limit of the discharge amount per unit time of the first compressor is set based on a flow rate that can flow per unit time of the first bypass flow path. Harmony device.