JP2010210144A - Refrigerating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To select a temperature-sensing type expansion valve by capacity of low refrigerant circulation amount to prevent hunting, and exhibit intended cooling capacity. <P>SOLUTION: This refrigerating device includes a refrigerant circuit (10) in which a refrigerant is circulated to perform a vapor compression type refrigerating cycle. The refrigerant circuit (10) includes an inverter type compressor (31) of which operation frequency is controlled by an inverter circuit and the temperature-sensing type expansion valve (22), and the refrigerating device is used for cooling a use side. The refrigerating device further includes a solenoid valve (23) and a throttle mechanism (24) connected to the temperature-sensing type expansion valve (22) in parallel via the solenoid valve (23) and switched by the solenoid valve (23) to either of a first state where a refrigerant is made to flow or a second state where no refrigerant is made to flow. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a refrigeration apparatus that performs a vapor compression refrigeration cycle by circulating a refrigerant.

  There is a refrigeration apparatus that performs a refrigeration cycle, for example, a refrigerator (or a freezer) that is installed in a store or the like and stores food or the like (see, for example, Patent Document 1).

The refrigeration apparatus of Patent Document 1 includes an outdoor unit having a compressor and an outdoor heat exchanger (heat source side heat exchanger), a refrigeration heat exchanger (a use side heat exchanger of the first system), and an expansion mechanism. A refrigeration unit (first usage side unit), a refrigeration unit (second usage side unit), a refrigeration heat exchanger (second usage side heat exchanger), and an expansion mechanism. Yes. Further, this refrigeration apparatus includes a compressor in which the electric motor is inverter-controlled and its capacity can be changed stepwise or continuously, that is, a so-called inverter-type compressor whose operation frequency is controlled by an inverter circuit, in the outdoor unit.
JP 2003-004318 A

  By the way, in a refrigerator installed in a store or the like, a temperature-sensitive expansion valve is often used as an expansion mechanism in the refrigerant circuit that performs the refrigeration cycle.

  However, in general, the variable range of the capacity of the temperature-sensitive expansion valve is smaller than the variable range of the capacity of the inverter compressor. Therefore, when this temperature-sensitive expansion valve is combined with the inverter compressor, the following Such a problem may occur.

  For example, if the rated capacity of the temperature-sensitive expansion valve is determined according to the maximum operating frequency of the inverter compressor in order to maximize the cooling capacity, when operating the inverter compressor at a low frequency, The capacity of the temperature-sensitive expansion valve becomes excessive with respect to the flow rate of the refrigerant (that is, the state where the throttle action cannot be sufficiently exerted). When the capacity is excessive, a phenomenon (hunting) in which the degree of superheat fluctuates easily occurs, and as a result, the low-pressure pressure in the refrigerant circuit decreases. In a general refrigeration system, the compressor is stopped when the low pressure decreases to a value below a certain level (referred to as a low pressure cut value). Therefore, when hunting occurs, the compressor starts and stops frequently. In particular, in a refrigeration system in which the use side is cooled (for example, the refrigerator having an internal temperature of −5 ° C. or lower), the compressor is frequently stopped because the difference between the target low pressure value and the low pressure cut value is small. It is thought that it is easy to be made.

  Thus, even if the compressor starts and stops frequently, the internal temperature becomes higher than the set temperature in this state, so the operating frequency is increased and eventually the internal temperature becomes the set temperature. In other words, this hunting is generally not noticeable as long as it can be cooled to the set temperature, and does not lead to poor quality of stored items (eg food), so there is no inconvenience in use. Conceivable.

  However, when the compressor starts and stops frequently, the deterioration of the compressor proceeds. Moreover, the quality of the compressor is deteriorated due to the shortage of the refrigeration oil caused by taking out the refrigeration oil in the compressor, and the power consumption is increased due to the frequent increase in the operating frequency. In addition, when the temperature-sensitive expansion valve cannot sufficiently exhibit the throttling action, a phenomenon that the liquid refrigerant returns to the compressor (liquid return) occurs, which leads to dilution of the lubricating oil or so-called liquid compression. The dilution and liquid compression of the lubricating oil cause a compressor failure while the refrigeration apparatus is used for a long time. If the compressor breaks down, the internal temperature does not drop to the set value, which may lead to poor quality of the stored items.

  Of course, it is conceivable to select a temperature-sensitive expansion valve in accordance with the minimum value of the refrigerant flow rate. However, with a general temperature-sensitive expansion valve, the maximum flow rate of the refrigerant can be controlled by the temperature-sensitive expansion valve. The range may be exceeded. In this case, the capacity of the compressor is reduced and the desired cooling capacity cannot be exhibited. That is, it is difficult to select a temperature-sensitive expansion valve so that hunting does not occur and a desired cooling capacity can be exhibited with respect to the inverter compressor.

  The present invention has been made by paying attention to the above-mentioned problems, so that a temperature-sensitive expansion valve can be selected with a low refrigerant circulation capacity so that hunting does not occur, and a desired cooling capacity can be exhibited. The purpose is to do.

In order to solve the above-mentioned problem, the first invention
A refrigerant circuit (10) that performs a vapor compression refrigeration cycle through circulation of the refrigerant, and includes an inverter compressor (31) that is controlled in operating frequency by an inverter circuit and a temperature-sensitive expansion valve (22) A refrigeration system for cooling the user side, including in the refrigerant circuit (10),
An on-off valve (23),
A first state in which the refrigerant flows through the on-off valve (23) and a second state in which the refrigerant does not flow are connected in parallel to the temperature-sensitive expansion valve (22) via the on-off valve (23). An aperture mechanism (24) that switches to either
It is characterized by having.

  Thereby, when the on-off valve (23) is closed, the refrigerant flowing into the temperature-sensitive expansion valve (22) is expanded only by the temperature-sensitive expansion valve (22). When the on-off valve (23) is opened, the refrigerant is expanded by both the temperature-sensitive expansion valve (22) and the throttle mechanism (24).

  In the present invention, the temperature-sensitive expansion valve (22) is selected according to the minimum value of the refrigerant flow rate so that the minimum value of the refrigerant flow rate is included in the controllable range of the temperature-sensitive expansion valve (22). If the throttle mechanism (24) is switched to the second state when the flow rate is minimum, the opening degree of the temperature-sensitive expansion valve (22) can be used in a state where the opening degree is not less than the minimum opening degree. In this state, the temperature-sensitive expansion valve (22) can sufficiently exhibit a throttling action, and so-called hunting does not occur. Further, if the squeezing action can be sufficiently exerted in this way, the liquid return can be prevented.

  In the present invention, when the capacity is insufficient even if the temperature-sensitive expansion valve (22) is selected as described above and the maximum value of the refrigerant flow rate exceeds the upper limit value of the controllable range. If the throttle mechanism (24) is switched to the first state and the refrigerant is expanded by both the temperature-sensitive expansion valve (22) and the throttle mechanism (24), the throttle mechanism (24) can provide the shortage. Can be supplemented. That is, both the temperature-sensitive expansion valve (22) and the throttling mechanism (24) can sufficiently exert a throttling action, and a desired cooling capacity can be obtained. As described above, in the present invention, the temperature-sensitive expansion valve (22) can be selected with the capability of the low refrigerant circulation amount so that hunting does not occur, and the desired cooling capability can be exhibited.

In addition, the second invention,
In the refrigeration apparatus of the first invention,
The apparatus further includes a control device (33) that switches the throttle mechanism (24) to the second state when the operating frequency is controlled to be equal to or lower than a predetermined value.

  Thereby, for example, when the operation frequency is controlled to be low when the heat load is small, the refrigerant flowing into the temperature-sensitive expansion valve (22) is expanded only by the temperature-sensitive expansion valve (22). Further, when the operation frequency is controlled to be high when the heat load is large, the refrigerant is expanded by both the temperature-sensitive expansion valve (22) and the throttle mechanism (24).

  According to the first invention, since hunting can be prevented, the start and stop of the inverter compressor (31) due to the hunting can be prevented. If the number of start and stop of the inverter compressor (31) can be reduced, the refrigeration oil will not be brought out and the refrigeration oil will be insufficient, resulting in poor quality of the inverter compressor (31), and the operating frequency will frequently There is no increase in power consumption due to the increase. Further, since the liquid return can be prevented, the lubricating oil is not diluted by the liquid refrigerant and liquid compression does not occur, and the compressor failure due to these is prevented.

  Further, according to the second invention, the occurrence of hunting is prevented when the operating frequency is low. That is, both energy saving operation by controlling the inverter circuit and prevention of hunting can be achieved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following embodiments are essentially preferable examples, and are not intended to limit the scope of the present invention, its application, or its use.

  FIG. 1 is a piping diagram of a refrigerant circuit (10) in a refrigeration apparatus (1) according to an embodiment of the present invention. This refrigeration apparatus (1) performs a vapor compression refrigeration cycle so that the user side is cooled. Specifically, this refrigeration apparatus (1) is realized, for example, as a refrigerator (or a freezer) that is installed in a store or the like and stores food products or the like, and its internal temperature is cooled to, for example, -5 ° C or lower.

<Overall configuration of refrigeration system (1)>
As shown in FIG. 1, the refrigeration apparatus (1) includes an indoor unit (20) installed indoors and an outdoor unit (30) installed outdoor. The indoor unit (20) and the outdoor unit (30) are connected to each other via a first connection pipe (11) and a second connection pipe (12), and a refrigerant circulates to form a vapor compression refrigeration cycle. The refrigerant circuit (10) for performing the above is configured.

<Outdoor unit>
The outdoor unit (30) includes an inverter compressor (31), a heat source side heat exchanger (32), and a control device (33).

  The inverter type compressor (31) is configured by a positive displacement compressor such as a scroll compressor, for example. This inverter type compressor (31) is a compressor in which electric power is supplied through an inverter circuit, the operation frequency is controlled by the inverter circuit, and the operation capacity is variable. The inverter circuit of this embodiment changes this operating frequency in the range of 19 Hz to 109 Hz. The discharge port of the inverter compressor (31) is connected to the gas side end of the heat source side heat exchanger (32) via a refrigerant pipe. The suction port of the inverter compressor (31) is connected to the indoor unit (20) via the first connection pipe (11).

  The heat source side heat exchanger (32) is a cross fin type fin-and-tube heat exchanger, and in this heat source side heat exchanger (32), the refrigerant and the heat source side air (outdoor air) Heat exchange is performed between them. An outdoor fan (not shown) is provided in the vicinity of the heat source side heat exchanger (32). Outdoor air is sent to the heat source side heat exchanger (32) by the outdoor fan. The liquid source end of the heat source side heat exchanger (32) is connected to the indoor unit (20) via the second connection pipe (12).

  The control device (33) corresponds to the control device of the present invention, and controls opening and closing of a solenoid valve (23) described later. The control device (33) closes the electromagnetic valve (23) when the operating frequency is controlled to be equal to or lower than a predetermined value (threshold frequency) by the inverter circuit, and the electromagnetic valve (23) when the operating frequency is higher than that. open. The threshold frequency will be described later.

<Indoor unit>
The indoor unit (20) includes a use-side heat exchanger (21), a temperature-sensitive expansion valve (22), a solenoid valve (23), and a throttle mechanism (24), and cools the air in the refrigerator (use side) To do.

  The use side heat exchanger (21) is a cross-fin type fin-and-tube heat exchanger, and in this use side heat exchanger (21), the refrigerant and the use side air (air in the refrigerator) Heat exchange between the two. An indoor fan (not shown) is provided in the vicinity of the use side heat exchanger (21). The use side air is sent to the use side heat exchanger (21) by the indoor fan.

  The temperature-sensitive expansion valve (22) is a so-called automatic temperature expansion valve whose opening degree is adjusted according to the detected temperature of the temperature-sensitive cylinder (22a). Specifically, when the detected temperature of the temperature sensing cylinder (22a) rises, the temperature sensitive expansion valve (22) is adjusted to open, and when the detected temperature falls, the temperature sensitive expansion valve (22) closes. Adjusted to

  A typical temperature-sensitive expansion valve has a controllable range of 60% to 120% of the rated capacity. In conventional refrigeration equipment, it is usually near the upper limit of this controllable range when the heat load is maximum. A temperature sensitive expansion valve is selected for use in In the present embodiment, the temperature-sensitive expansion valve having such a general controllable range is adopted as the temperature-sensitive expansion valve (22), but the selection criterion is different from the conventional one.

  In the present embodiment, the temperature-sensitive expansion valve (22) is selected according to the case where the heat load is minimum, and the capacity of the temperature-sensitive expansion valve (22) is prevented from becoming excessive when the heat load is small. More specifically, the temperature-sensitive expansion valve (22) of the present embodiment has a refrigerant flow rate (minimum refrigerant flow rate) that flows when the inverter compressor (31) is operated at the minimum operation frequency (19 Hz). Is selected based on the minimum refrigerant flow rate so as to be included in the controllable range of the temperature-sensitive expansion valve (22). When the temperature-sensitive expansion valve (22) is selected in this way, in principle, if the lower limit value of the controllable range is the minimum refrigerant flow rate, the throttling action can be exhibited during operation at the minimum refrigerant flow rate. However, it is preferable to select a temperature-sensitive expansion valve having a certain margin in consideration of various variations.

  Thus, when the selection is made based on the minimum refrigerant flow rate, in a general temperature-sensitive expansion valve, the refrigerant flow rate (maximum) that flows when the inverter compressor (31) is operated at the maximum operation frequency (109 Hz). It is considered that the refrigerant flow rate may exceed the upper limit (120% of the rated capacity) of the controllable range. However, in this refrigeration apparatus (1), as will be described in detail later, even if the maximum refrigerant flow rate exceeds the upper limit value, the inverter compressor (31) can be operated at the maximum flow rate. In the following description, it is assumed that the maximum refrigerant flow rate is higher than the upper limit value of the controllable range.

  The temperature-sensitive expansion valve (22) thus selected has its refrigerant inflow side connected to the liquid side end of the heat source side heat exchanger (32) via the second connection pipe (12). The outflow side is connected to the liquid side end of the use side heat exchanger (21). The temperature sensing cylinder (22a) is disposed at the gas side end on the refrigerant outflow side of the use side heat exchanger (21), and is connected to the temperature sensing type expansion valve (22) by a capillary tube.

  The electromagnetic valve (23) corresponds to the opening / closing valve of the present invention, and the opening / closing is controlled according to the control of the control device (33). The refrigerant inflow side of the electromagnetic valve (23) is connected to the second connection pipe (12), and the refrigerant outflow side is connected to the refrigerant inflow side of the throttle mechanism (24).

  The aperture mechanism (24) is constituted by a capillary tube made of, for example, a copper tube. The throttle mechanism (24) has the refrigerant inflow side connected to the electromagnetic valve (23) as described above, and the refrigerant outflow side connected to the refrigerant outflow side of the temperature-sensitive expansion valve (22). That is, the throttle mechanism (24) is connected in parallel to the temperature-sensitive expansion valve (22) via the electromagnetic valve (23). The electromagnetic valve (23) causes the first state in which the refrigerant flows, and the refrigerant Is switched to one of the second states in which no flow occurs. The inner diameter and length of the capillary tube constituting the throttle mechanism (24) are set so that the opening degree of the temperature-sensitive expansion valve (22) is maximized during operation at the maximum operating frequency (109 Hz), and the solenoid valve (23) is It is set so that the desired throttle action can be obtained by both the temperature-sensitive expansion valve (22) and the throttle mechanism (24) in the open state (the throttle mechanism (24) in the first state).

  Switching between the first and second states is controlled by the control device (33) as described above. Specifically, when the flow rate of the refrigerant flowing from the outdoor unit (30) is within the controllable range of the temperature-sensitive expansion valve (22), the throttle mechanism (24) is switched to the second state to make the temperature-sensitive type. Let the refrigerant flow only through the expansion valve (22). Further, when the flow rate of the refrigerant flowing from the outdoor unit (30) increases and approaches the upper limit value of the controllable range, the throttle mechanism (24) is switched to the first state before the upper limit value is exceeded, and the temperature-sensitive type. Refrigerant flows through both the expansion valve (22) and the throttle mechanism (24).

  For example, if the refrigerant flow rate exceeds the upper limit of the controllable range of the temperature-sensitive expansion valve (22) when the operation frequency exceeds 60 Hz (about 65% of the maximum operation frequency (109 Hz)), the threshold frequency Is set to a frequency slightly lower than 60 Hz. When the operation frequency is controlled to be equal to or lower than the threshold frequency, the solenoid valve (23) is closed and switched to the second state, and when the operation frequency is controlled to be higher than the threshold frequency, the solenoid valve (23 ) To switch to the first state.

<< Operation of refrigeration system (1) >>
When the inverter compressor (31) is put into an operating state, the refrigerant circulates in the refrigerant circuit (10) in the direction indicated by the solid line arrow in FIG. Specifically, the refrigerant discharged from the inverter compressor (31) flows into the heat source side heat exchanger (32), and the heat source side heat exchanger (32) converts the outdoor air taken in by the outdoor fan. It dissipates heat and condenses. The condensed refrigerant flows into the indoor unit (20) through the second connection pipe (12).

  For example, when the temperature in the refrigerator is higher than the set temperature, that is, when the heat load is large, the operation frequency is increased by the inverter circuit, and is set to the maximum operation frequency (109 Hz), for example. In this setting, since the operating frequency is higher than the threshold frequency, the electromagnetic valve (23) is controlled to be in the open state by the control device (33). Thereby, the throttle mechanism (24) is connected in parallel to the temperature-sensitive expansion valve (22) via the electromagnetic valve (23), and switches to the first state in which the refrigerant flows through the throttle mechanism (24). On the other hand, when the heat load increases, the temperature of the temperature sensing cylinder (22a) rises. As a result, the temperature sensing expansion valve (22) is adjusted in the opening direction, for example, the capacity of the temperature sensing expansion valve (22) The upper limit of the controllable range (120% of the rated capacity) is reached.

  In the first state, the refrigerant flowing into the indoor unit (20) from the heat source side heat exchanger (32) is expanded by both the temperature-sensitive expansion valve (22) and the throttle mechanism (24). That is, even if the upper limit of the controllable range (120% of the rated capacity) is selected as the temperature-sensitive expansion valve (22) with a rated capacity smaller than the maximum refrigerant flow rate, this throttling mechanism (24) The shortage of the capacity of the temperature sensitive expansion valve (22) can be compensated. As a result, the refrigeration apparatus (1) can exhibit a desired cooling capacity.

  The refrigerant thus expanded by both the temperature-sensitive expansion valve (22) and the throttle mechanism (24) is introduced into the usage-side heat exchanger (21), and the usage-side heat exchanger (21) It absorbs heat from the (use side) air and evaporates. Thereby, the air in a refrigerator is cooled. Thereafter, the evaporated refrigerant is sucked into the inverter compressor (31) through the first connection pipe (11) and compressed. Then, the compressed refrigerant flows into the heat source side heat exchanger (32).

  When the air in the refrigerator is thus cooled and the temperature of the air gradually approaches the set temperature, the heat load is gradually reduced and the operation frequency is gradually lowered. When the operating frequency decreases and reaches the threshold frequency, the control device (33) controls the electromagnetic valve (23) to be closed. Thereby, a throttle mechanism (24) switches to the 2nd state in which a refrigerant does not flow. On the other hand, as the heat load decreases, the temperature of the temperature sensing cylinder (22a) decreases, and as a result, the temperature sensing expansion valve (22) is adjusted in the closing direction, and the gas side of the use side heat exchanger (21) The opening degree depends on the degree of superheat at the end. That is, the refrigerant flowing into the indoor unit (20) from the heat source side heat exchanger (32) is expanded only by the temperature-sensitive expansion valve (22).

  Further, when the operating frequency is lowered to the minimum operating frequency (19 Hz), the refrigerant flow rate is minimized. In this embodiment, since the temperature-sensitive expansion valve (22) is selected so that the minimum refrigerant flow rate is included in the controllable range of the temperature-sensitive expansion valve (22), the inverter compressor (31 ) Is operated at the minimum operating frequency, the opening of the temperature-sensitive expansion valve (22) is opened at the lower limit value (20% of the rated capacity) of the controllable range of the temperature-sensitive expansion valve (22). A little more open than the degree. In this state, the temperature-sensitive expansion valve (22) can sufficiently exhibit a throttling action, and so-called hunting does not occur. That is, in the present embodiment, the temperature-sensitive expansion valve (22) can be selected with the capability of a low refrigerant circulation amount so that hunting does not occur.

  And if hunting is prevented in this way, the frequency | count of start / stop of the inverter type compressor (31) based on a low voltage | pressure cut value can be reduced. If the number of start and stop of the inverter compressor (31) can be reduced, the refrigeration oil in the inverter compressor (31) is taken out and the refrigeration oil becomes insufficient, resulting in poor quality of the inverter compressor (31). It does not occur or increase in power consumption due to frequent increase in operating frequency.

  Further, as described above, since the temperature-sensitive expansion valve (22) can sufficiently exhibit the throttle action, the liquid return does not occur. In other words, there is no dilution of the lubricating oil or so-called liquid compression caused by this liquid return, and the failure of the inverter compressor (31) caused by the dilution or liquid compression of the lubricating oil is prevented.

  In the above example, the opening / closing of the solenoid valve (23) is controlled according to the operating frequency. However, if the thermal load can be detected by other methods, the opening / closing control may be performed based on the detection result.

  Further, the capillary tube used as the throttle mechanism (24) in the above embodiment is an example, and an expansion mechanism having another structure may be adopted.

  Moreover, in the said embodiment, although the control apparatus (33) was provided in the outdoor unit (30) side, you may provide in the indoor unit (20) side.

  The present invention is useful as a refrigeration apparatus that performs a vapor compression refrigeration cycle by circulating a refrigerant.

It is a piping system diagram of the refrigerant circuit (10) in the refrigeration apparatus (1) according to the embodiment of the present invention.

DESCRIPTION OF SYMBOLS 1 Refrigerating device 10 Refrigerant circuit 22 Temperature-sensitive expansion valve 23 Solenoid valve (open / close valve)
24 Aperture mechanism 31 Inverter compressor 33 Controller

Claims (2)

A refrigerant circuit (10) that performs a vapor compression refrigeration cycle by circulating refrigerant and having an inverter compressor (31) and a temperature-sensitive expansion valve (22) controlled in operating frequency by the inverter circuit A refrigeration system for cooling the user side, including in the refrigerant circuit (10),
An on-off valve (23),
A first state in which the refrigerant flows through the on-off valve (23) and a second state in which the refrigerant does not flow are connected in parallel to the temperature-sensitive expansion valve (22) via the on-off valve (23). An aperture mechanism (24) that switches to either
A refrigeration apparatus comprising: The refrigeration apparatus of claim 1,
The refrigeration apparatus further comprising a control device (33) that switches the throttle mechanism (24) to the second state when the operating frequency is controlled to be equal to or lower than a predetermined value.

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