Patent Description:
A typical refrigerating apparatus includes a compressor, a condenser, an expansion valve, and an evaporator. The high-temperature and high-pressure gaseous refrigerant produced by the compressor is first sent to the condenser. In the condenser, heat exchange between the refrigerant and air is performed, and the refrigerant becomes a high-temperature and high-pressure liquid refrigerant. Document <CIT> presents an example of known refrigerator apparatus.

Thereafter, by passing through the expansion valve, the temperature and pressure of the refrigerant are lowered, and the refrigerant becomes a low-temperature and low-pressure liquid refrigerant. Further, by exchanging heat with air in the evaporator, the refrigerant becomes a low-temperature and low-pressure gaseous refrigerant. In this process, the temperature of the space where the condenser or evaporator is installed is adjusted.

Here, in order to improve the output of the refrigerating apparatus, in recent years, a two-stage compression configuration in which a plurality of compressors is arranged in series may be adopted (see <CIT>). In this case, an intermediate heat exchanger is generally disposed between the compressor on the low-pressure side and the compressor on the high-pressure side. The intermediate heat exchanger is provided to improve the efficiency of the refrigerating apparatus.

When the intermediate heat exchanger as described above is provided, if the outside air temperature is excessively low, the liquid refrigerant may remain in the intermediate heat exchanger. If this liquid refrigerant is sent to the high-pressure side compressor as it is when the refrigerating apparatus is started, liquid compression occurs, which affects the stable operation of the compressor.

The present disclosure has been made to solve the above problems, and an object of the present disclosure is to provide a refrigerating apparatus that can be operated more stably.

In order to solve the above problems, a refrigerating apparatus as defined in claim <NUM> is provided, which includes a main circuit that is a circulation passage through which a refrigerant flows, a first compressor and a second compressor that are arranged in series on the main circuit, an intermediate heat exchanger that is disposed between the first compressor and the second compressor, a condenser that is disposed on a downstream side of the second compressor, a first expansion valve that is disposed on a downstream side of the condenser, a receiver that is disposed on a downstream side of the first expansion valve, a second expansion valve that is disposed on a downstream side of the receiver, an evaporator that is disposed on a downstream side of the second expansion valve, a three-way valve provided between the intermediate heat exchanger and the second compressor on the main circuit, a first bypass passage that couples the three-way valve and the receiver, a second bypass passage that couples the receiver, the three-way valve, and the second compressor, a check valve that is provided in the first bypass passage and allows the refrigerant to flow only in a direction from the three-way valve toward the receiver, a first solenoid valve that is provided in the second bypass passage and switches over to an open state of the second bypass passage, and a second solenoid valve that is provided between the receiver and the second expansion valve in the main circuit and switches over to an open state of the main circuit.

According to the present disclosure, it is possible to provide a refrigerating apparatus that can be operated more stably.

Hereinafter, a refrigerating apparatus <NUM> according to an embodiment of the present disclosure will be described with reference to <FIG>. The refrigerating apparatus <NUM> is a heat pump type apparatus that exchanges heat between a refrigerant and air by operating in a refrigeration cycle.

As shown in <FIG>, the refrigerating apparatus <NUM> includes a main circuit <NUM> formed as a circulation passage, a first compressor <NUM>, a second compressor <NUM>, an intermediate heat exchanger <NUM>, a condenser <NUM>, a first expansion valve <NUM>, a receiver <NUM>, a second expansion valve <NUM>, an evaporator <NUM>, a first three-way valve <NUM>, a first bypass passage <NUM>, a second bypass passage <NUM>, a first check valve <NUM>, a first solenoid valve <NUM>, a second solenoid valve <NUM>, an accumulator <NUM>, a third bypass passage <NUM>, a second three-way valve <NUM>, a second check valve <NUM>, a control unit <NUM>, and the like.

The main circuit <NUM> is filled in a state of a refrigerant in a liquid or a gas. The first compressor <NUM> and the second compressor <NUM> are arranged in series on the main circuit <NUM>. That is, the discharge side of the first compressor <NUM> faces the suction side of the second compressor <NUM>. As the first compressor <NUM> and the second compressor <NUM>, for example, a scroll compressor, a rotary compressor, or a rotary compressor can be used. In the following description, on the main circuit <NUM>, the side on which the second compressor <NUM> is located when viewed from the first compressor <NUM> may be referred to as a downstream side, and the opposite side thereof may be referred to as an upstream side.

The first three-way valve <NUM> and the second check valve <NUM> are arranged in this order on the downstream side of the first compressor <NUM>. The details of the first three-way valve <NUM> will be described later. The second check valve <NUM> is configured to allow the refrigerant to flow only in the direction from the upstream side toward the downstream side.

The intermediate heat exchanger <NUM> is disposed between the first compressor <NUM> and the second compressor <NUM>. In the intermediate heat exchanger <NUM>, the high-temperature refrigerant discharged from the first compressor <NUM> is cooled by exchanging heat with the external air in the intermediate heat exchanger <NUM> and then sent to the second compressor <NUM>. The intermediate heat exchanger <NUM> is provided for improving the efficiency of the refrigerating apparatus <NUM>.

The condenser <NUM> is disposed on the downstream side of the second compressor <NUM>. The condenser <NUM> is a heat exchanger for exchanging heat between the external air and the refrigerant. A fan (not shown) is provided in the vicinity of the condenser <NUM>, and it is possible to forcibly exchange heat between the air and the refrigerant. The high-temperature and high-pressure gaseous refrigerant produced by the second compressor <NUM> is condensed by passing through the condenser <NUM> and becomes a high-temperature and high-pressure liquid refrigerant.

The first expansion valve <NUM> is provided on the downstream side of the condenser <NUM>. The high-temperature and high-pressure liquid refrigerant supplied from the condenser <NUM> passes through the first expansion valve <NUM>, the pressure and temperature decrease, and the refrigerant becomes a low-temperature and low-pressure liquid refrigerant.

The receiver <NUM> is coupled to the downstream side of the first expansion valve <NUM>. The receiver <NUM> is a container for storing at least a part of the liquid refrigerant that has passed through the first expansion valve <NUM>. The amount of liquid refrigerant that can exist in the main circuit <NUM> varies depending on the operating conditions. The receiver <NUM> is provided to cope with this variation.

The second solenoid valve <NUM> and the second expansion valve <NUM> are arranged in this order on the downstream side of the receiver <NUM>. As will be described in detail later, the second solenoid valve <NUM> is provided to switch over to the open state of the main circuit <NUM>. The second expansion valve <NUM> is provided to further reduce the temperature and pressure of the low-temperature and low-pressure liquid refrigerant that has passed through the receiver <NUM>. The first expansion valve <NUM> and the second expansion valve <NUM> are electromagnetic expansion valves that can be switched between the open and closed states by an electric signal from the outside.

The evaporator <NUM> is provided on the downstream side of the second expansion valve <NUM>. The evaporator <NUM> is a heat exchanger for exchanging heat between the external air and the refrigerant. A fan (not shown) is provided in the vicinity of the evaporator <NUM> so that heat exchange between air and the refrigerant can be forcibly performed. The low-temperature and low-pressure liquid refrigerant that has passed through the second expansion valve <NUM> evaporates by exchanging heat with the outside air when passing through the evaporator <NUM> and becomes a low-temperature and low-pressure gaseous refrigerant.

The accumulator <NUM> is provided on the downstream side of the evaporator <NUM>. The accumulator <NUM> is a container for storing the liquid refrigerant that could not be completely evaporated by the evaporator <NUM>. After the liquid component is removed by the accumulator <NUM>, the gaseous refrigerant is sent to the first compressor <NUM> again and compressed. By continuously repeating such a cycle (refrigeration cycle), the refrigerating apparatus <NUM> is operated.

The first bypass passage <NUM> is a passage coupling the first three-way valve <NUM> and the receiver <NUM>. That is, the first bypass passage <NUM> branches from the main circuit <NUM> via the first three-way valve <NUM> and extends to the receiver <NUM>. The first check valve <NUM> is provided on the first bypass passage <NUM>. The first check valve <NUM> is configured to allow the refrigerant to flow only in the direction from the first three-way valve <NUM> toward the receiver <NUM>.

The second bypass passage <NUM> couples the above-mentioned second check valve <NUM> and the second compressor <NUM>, and the receiver <NUM>. The first solenoid valve <NUM> is provided on the second bypass passage <NUM>. The open and closed states of the first solenoid valve <NUM> can be switched by an electric signal from the outside.

The third bypass passage <NUM> is a passage that bypasses the downstream side of the accumulator <NUM> and between the first compressor <NUM> and the intermediate heat exchanger <NUM>. The second three-way valve <NUM> is provided on the upstream side of the third bypass passage <NUM>. That is, the third bypass passage <NUM> branches from the main circuit <NUM> via the second three-way valve <NUM>.

The control unit <NUM> is provided to switch between the open and closed states of each valve device described above and the operating state of the first compressor <NUM> and the second compressor <NUM> by an electric signal. Specifically, the control unit <NUM> can switch between the open and closed states of the first expansion valve <NUM>, the first three-way valve <NUM>, the second three-way valve <NUM>, the first solenoid valve <NUM>, and the second solenoid valve <NUM>. Further, the control unit <NUM> can place at least one of the first compressor <NUM> and the second compressor <NUM> in an operating state and the other in a stopped state.

Subsequently, an example of the operation of the refrigerating apparatus <NUM> will be described. As shown in <FIG>, in normal operation of the refrigerating apparatus <NUM>, the control unit <NUM> closes the first solenoid valve <NUM>. Further, the control unit <NUM> switches over to the open state of the first three-way valve <NUM> so that the first three-way valve <NUM> is opened only in the direction from the intermediate heat exchanger <NUM> toward the second compressor <NUM>. Further, the control unit <NUM> switches over to the open state of the second three-way valve <NUM> so that the second three-way valve <NUM> is opened only in the direction from the accumulator <NUM> toward the first compressor <NUM>. As a result, the first bypass passage <NUM>, the second bypass passage <NUM>, and the third bypass passage <NUM> are closed, and the refrigerant circulates only in the main circuit <NUM>. In the middle of circulating in the main circuit <NUM>, the above-mentioned refrigeration cycle occurs continuously.

Here, a part of the gaseous refrigerant may be condensed inside the intermediate heat exchanger <NUM> to generate a liquid refrigerant. In particular, if the outside air temperature is excessively low, the liquid refrigerant may remain in the intermediate heat exchanger <NUM>. If this liquid refrigerant is sent to the compressor as it is when the refrigerating apparatus <NUM> is started, liquid compression occurs, which affects the stable operation of the compressor.

Therefore, in the present embodiment, as described above, the first bypass passage <NUM>, the second bypass passage <NUM>, and the third bypass passage <NUM> are provided, respectively. For example, a case where only the second compressor <NUM> is started will be described. As shown in <FIG>, in this case, the control unit <NUM> switches over to the open state of the first three-way valve <NUM> so that the first three-way valve <NUM> is opened only in the direction from the intermediate heat exchanger <NUM> toward the receiver <NUM>. That is, the first bypass passage <NUM> is in an open state. Further, the control unit <NUM> opens the first solenoid valve <NUM> so that the second bypass passage <NUM> is opened. Further, the control unit <NUM> switches over to the open state of the second three-way valve <NUM> so that the refrigerant flows into the third bypass passage <NUM>.

In this state, the flow of the refrigerant as shown by the arrow in <FIG> occurs. When only the second compressor <NUM> is started, the pumping force of the second compressor <NUM> is transmitted to the receiver <NUM> through the second bypass passage <NUM>. As a result, the pressure in the receiver <NUM> is lowered. When the pressure in the receiver <NUM> is lowered, the liquid refrigerant remaining in the intermediate heat exchanger <NUM> flows toward the receiver <NUM> through the first bypass passage <NUM>. This makes it possible to recover the liquid refrigerant in the intermediate heat exchanger to the receiver <NUM>. In the receiver <NUM>, only the liquid component is separated from the refrigerant and stored in the receiver <NUM>. By performing such an operation for several minutes as an example, the liquid refrigerant is removed from the intermediate heat exchanger <NUM>. Thereafter, the above-mentioned normal operation is started.

The third bypass passage <NUM> is placed in an open state in order to prevent the stopped first compressor <NUM> from being in a reverse pressure state when only the second compressor <NUM> is started.

Further, as another example, when only the first compressor <NUM> is started, the state is as shown in <FIG>. In this case, the control unit <NUM> closes the first solenoid valve <NUM> and switches over to the open state of the first three-way valve <NUM> so that the first bypass passage <NUM> is opened. Further, the control unit <NUM> places the second solenoid valve <NUM> in an open state. Further, the third bypass passage <NUM> is in a closed state.

In this state, the flow of the refrigerant as shown by the arrow in <FIG> occurs. When only the first compressor <NUM> is started, the liquid refrigerant in the intermediate heat exchanger <NUM> located on the downstream side of the first compressor <NUM> is pumped through the first bypass passage <NUM> by the pumping force of the first compressor <NUM>. The liquid refrigerant pumped through the first bypass passage <NUM> is stored in the receiver <NUM>. In this way, the liquid refrigerant in the intermediate heat exchanger <NUM> can be recovered to the receiver <NUM>. In the receiver <NUM>, only the liquid component is separated from the refrigerant and stored in the receiver <NUM>. By performing such an operation for several minutes as an example, the liquid refrigerant is removed from the intermediate heat exchanger <NUM>. Thereafter, the above-mentioned normal operation is started.

As described above, in the refrigerating apparatus <NUM> according to the present embodiment, it is possible to remove the liquid refrigerant remaining in the intermediate heat exchanger <NUM> in advance prior to the normal operation. This reduces the possibility of liquid compression occurring in the second compressor <NUM>. As a result, damage to the second compressor <NUM> is avoided, and the refrigerating apparatus <NUM> can be operated stably for a longer period of time.

Although the embodiment of the present disclosure has been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment and includes design changes and the like within a range not deviating from the gist of the present disclosure.

Claim 1:
A refrigerating apparatus (<NUM>) comprising:
a main circuit (<NUM>) that is a circulation passage through which a refrigerant flows;
a first compressor (<NUM>) and a second compressor (<NUM>) that are arranged in series on the main circuit (<NUM>);
an intermediate heat exchanger (<NUM>) that is disposed between the first compressor (<NUM>) and the second compressor (<NUM>);
a condenser (<NUM>) that is disposed on a downstream side of the second compressor (<NUM>);
a first expansion valve (<NUM>) that is disposed on a downstream side of the condenser (<NUM>);
a receiver (<NUM>) that is disposed on a downstream side of the first expansion valve (<NUM>);
a second expansion valve (<NUM>) that is disposed on a downstream side of the receiver (<NUM>);
an evaporator (<NUM>) that is disposed on a downstream side of the second expansion valve (<NUM>);
a three-way valve (<NUM>) provided between the intermediate heat exchanger (<NUM>) and the second compressor (<NUM>) on the main circuit;
a first bypass passage (<NUM>) that couples the three-way valve (<NUM>) and the receiver (<NUM>),
a second bypass passage (<NUM>) that couples the receiver (<NUM>), the three-way valve (<NUM>), and the second compressor (<NUM>);
a check valve (<NUM>) that is provided in the first bypass passage (<NUM>) and allows the refrigerant to flow only in a direction from the three-way valve (<NUM>) toward the receiver (<NUM>), characterized by
a first solenoid valve (<NUM>) that is provided in the second bypass passage (<NUM>) and is configured to switch over to an open state of the second bypass passage (<NUM>);
a second solenoid valve (<NUM>) that is provided between the receiver (<NUM>) and the second expansion valve (<NUM>) in the main circuit (<NUM>) and is configured to switch over to an open state of the main circuit (<NUM>); and
a control unit (<NUM>) that is configured to switch between open and closed states of the first expansion valve (<NUM>), the three-way valve (<NUM>), the first solenoid valve (<NUM>), and the second solenoid valve (<NUM>), and to switch over to an operating state of the first compressor (<NUM>) and the second compressor (<NUM>),
wherein the control unit (<NUM>) is configured to, when only the second compressor (<NUM>) is started, close the first expansion valve (<NUM>), open the first solenoid valve (<NUM>), and open the three-way valve (<NUM>) only in a direction from the main circuit (<NUM>) toward the first bypass passage (<NUM>).