JP7633097B2 - Heat pump water heater - Google Patents

Description

The present invention relates to a heat pump water heater, and more specifically to a heat pump water heater equipped with a twin rotary compressor.

Conventionally, twin rotary compressors using carbon dioxide as a refrigerant have been used in refrigeration equipment for showcases and the like. In this case, it has been technically established to use the twin rotary compressor in a general two-stage compression refrigeration cycle. When such twin rotary compressors using carbon dioxide as a refrigerant are used in heat pump water heaters for public baths, spas, and other facilities that require large amounts of hot water, the refrigerant needs to be made into a high-pressure, high-temperature gas to generate high-temperature water. For this reason, a special way of using the twin rotary compressor as a single-stage compression refrigeration cycle rather than the general two-stage compression refrigeration cycle was required.

In such special usage, the twin rotary compressor itself vibrates a lot, and the vibrations can cause excessive stress to be applied to the refrigerant piping that is connected to the twin rotary compressor and circulates the refrigerant between the condenser and evaporator, which can damage the refrigerant piping and lead to refrigerant leakage. For this reason, vibration-damping material is installed in the refrigerant piping to prevent the vibrations of the twin rotary compressor from being transmitted to the refrigerant piping. It is also preferable to connect a sound-absorbing device (hereinafter referred to as a muffler) for the drive and vibration noise generated by the twin rotary compressor to the twin rotary compressor.

In addition, when the twin rotary compressor is started, the vanes used in the rolling pistons malfunction (i.e., the vanes fly off). This malfunction causes the twin rotary compressor to vibrate, which then transmits to the refrigerant piping connecting the twin rotary compressor to the muffler, damaging the refrigerant piping and causing refrigerant leakage.

In order to absorb such compressor vibrations, a heat pump water heater has been disclosed in which the legs of the compressor body of the heat pump water heater are fixed with anti-vibration rubber, and a two-layer insulation material consisting of a flexible insulation material and a highly rigid soundproofing material is tightly wrapped around the compressor body and the periphery of the suction muffler, eliminating gaps in the insulation material and forming an airtight structure, which prevents the vibrations of the compressor from being transmitted to the outside, provides excellent soundproofing, has a large insulation effect, reduces heat loss from the compressor body, and improves efficiency (see, for example, Patent Document 1).

JP 2009-008363 A

However, the heat pump water heater in Patent Document 1 is a small water heater that houses the compressor and refrigerant circuit in the hot water heat source unit (so-called outdoor unit), so there is no space to retrofit a muffler to reduce the drive and vibration noise of the compressor.

In addition, the twin rotary compressor cannot be used in a special way, such as as a single-stage compression refrigeration cycle rather than the general two-stage compression refrigeration cycle, to generate high-temperature water as a heat pump water heater used in public baths, spas, and other places that require a large amount of hot water.

The present invention has been made to solve the above problems, and aims to provide a heat pump water heater equipped with a twin rotary compressor that can be retrofitted to the twin rotary compressor as an integrated unit with a muffler, and that can prevent vane malfunctions (i.e., vane jumping) when the twin rotary compressor is started, or can shorten the time during which vane malfunctions occur.

The present invention provides a heat pump water heater that uses a twin rotary compressor that uses carbon dioxide as a refrigerant in a single-stage compression refrigeration cycle, and that is characterized in that a muffler is connected to the refrigerant discharge port of the twin rotary compressor in order to suppress vibrations that occur when the refrigerant is compressed by the twin rotary compressor, and the twin rotary compressor and the muffler are connected together to form a unit.

In addition, in order to reduce the pressure of the refrigerant drawn into the compression space in the rotary cylinder when the twin rotary compressor is started, an intermediate flow path for the refrigerant that discharges the refrigerant is provided outside the twin rotary compressor, and the intermediate pressure of the refrigerant inside the twin rotary compressor is reduced by controlling the opening and closing of a second expansion valve installed in the intermediate flow path, thereby preventing malfunction of the vanes in the rotary cylinder used during the second stage compression of the refrigerant, or shortening the time during which the vanes malfunction.

The heat pump water heater of the present invention can suppress as low as possible the vibration of the twin rotary compressor itself, which occurs when the twin rotary compressor is used in a single-stage compression refrigeration cycle, by connecting the muffler. This prevents the refrigerant piping, which is connected to the twin rotary compressor and circulates the refrigerant between the condenser and the evaporator, from being damaged by excessive stress due to vibration, which can lead to refrigerant leakage. Furthermore, by connecting the twin rotary compressor and the muffler as a unit, the compressor and the muffler can be synchronized, and the problem of the refrigerant piping connecting the twin rotary compressor and the muffler being damaged by the vibration of the twin rotary compressor, which can lead to refrigerant leakage, can be prevented.

In addition, in order to reduce the pressure of the refrigerant drawn into the compression space in the rotary cylinder when the twin rotary compressor is started, an intermediate flow path for the refrigerant that discharges the refrigerant is provided outside the twin rotary compressor, and the intermediate pressure of the refrigerant inside the twin rotary compressor is reduced by controlling the opening and closing of a second expansion valve installed in the intermediate flow path. This makes it possible to prevent malfunction of the vanes pressed against the outer circumferential surface of the rolling piston in the rotary cylinder used during the second stage compression of the refrigerant (vane jumping) or to shorten the time during which the vane malfunction occurs, thereby making it possible to keep vibrations generated in the twin rotary compressor due to vane malfunction as low as possible.

1 is a refrigerant circuit diagram of a heat pump water heater according to an embodiment of the present invention. FIG. 2 is a diagram illustrating a connection between a twin rotary compressor and a muffler according to an embodiment of the present invention. FIG. 2 is a diagram illustrating a connection between a twin rotary compressor and a muffler according to an embodiment of the present invention. FIG. 2 is a diagram illustrating the operation of a rotary cylinder of the twin rotary compressor according to one embodiment of the present invention. FIG. 2 is a diagram illustrating the operation of a rotary cylinder of the twin rotary compressor according to one embodiment of the present invention.

The present invention relates to a heat pump water heater that uses a twin rotary compressor with carbon dioxide as a refrigerant in a single-stage compression refrigeration cycle, and is characterized in that a muffler is connected to the refrigerant discharge port of the twin rotary compressor in order to suppress vibrations that occur when the refrigerant is compressed by the twin rotary compressor, and the twin rotary compressor and the muffler are connected together as a unit.

Hereinafter, a heat pump water heater according to an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a refrigerant circuit diagram of a heat pump water heater according to an embodiment of the present invention. FIG. 2 is a diagram explaining the connection between a twin rotary compressor and a muffler according to an embodiment of the present invention. FIG. 3 is a diagram explaining the connection between a twin rotary compressor and a muffler according to an embodiment of the present invention. FIG. 4 is a diagram explaining the operation of a rotary cylinder of a twin rotary compressor according to an embodiment of the present invention. FIG. 5 is a diagram explaining the operation of a rotary cylinder of a twin rotary compressor according to an embodiment of the present invention.

As shown in FIG. 1, the refrigerant circuit of the heat pump water heater in this embodiment is composed of a refrigerant pipe 7 through which the refrigerant (carbon dioxide) circulates, and various devices connected to this refrigerant pipe 7 (twin rotary compressor 2, muffler 3, water-side heat exchanger 4 (condenser), air-side heat exchanger 5 (evaporator), internal heat exchanger 6, intermediate flow path 7a, accumulator 8, strainer 9, first expansion valve 10, and second expansion valve 11).

The water-side heat exchanger 4 is also arranged so that the hot water supply pipe 12 passes through it. Water passing through the water-side heat exchanger 4 via the flow rate sensor 14 by the pump 13 on the water supply side of the hot water supply pipe 12 is heat exchanged and heated within the water-side heat exchanger 4. The hot water heated here is supplied from the hot water outlet side of the hot water supply pipe 12 as hot water at a predetermined temperature. The flow rate sensor 14 measures the flow rate of water passing through the water-side heat exchanger 4, and by adjusting the output of the pump 13 according to the water flow rate measured here, it is possible to adjust the temperature of the hot water supplied from the hot water outlet side of the hot water supply pipe 12.

In this embodiment, water is supplied from the water supply side of the hot water supply pipe 12, and the hot water heated by the water-side heat exchanger 4 is supplied from the hot water outlet side, but a hot water storage tank may be installed on the hot water outlet side, and the heated hot water may be temporarily stored in the hot water storage tank and then supplied from the hot water outlet side.

The refrigerant (carbon dioxide) compressed to high temperature and high pressure by the twin rotary compressor 2 is discharged into the muffler 3 which is integrated with the twin rotary compressor 2 as a unit. In this embodiment, the twin rotary compressor 2 and the muffler 3 are connected together by two upper and lower plate-shaped connecting plates 30, 30 to form a unit, as will be described in detail later. The refrigerant that passes through the muffler 3 circulates through the refrigerant piping 7 and flows into the water-side heat exchanger 4. Then, the water that passes through the water-side heat exchanger 4 by the pump 13 on the water supply side of the hot water supply piping 12 is heat exchanged and heated in the water-side heat exchanger 4.

The refrigerant discharged from the water-side heat exchanger 4 after heat exchange circulates through the refrigerant pipe 7, undergoes further heat exchange in the internal heat exchanger 6, is depressurized by the first expansion valve 10, and flows into the air-side heat exchanger 5 (evaporator). The strainer 9 installed on the refrigerant pipe 7 before the first expansion valve 10 is a filter that filters out debris and the like from the refrigerant circulating through the refrigerant pipe 7. The refrigerant in the refrigerant pipe 7 that flows into the air-side heat exchanger 5 by opening the first expansion valve 10 absorbs heat from the outside air blown by the fan F, is evaporated into gas, circulates through the refrigerant pipe 7, and flows into the internal heat exchanger 6.

The refrigerant in the refrigerant pipe 7 is reheated in the internal heat exchanger 6, and after the liquefied refrigerant is separated in the accumulator 8, it is supplied again to the twin rotary compressor 2. In the internal heat exchanger 6, heat is exchanged between the refrigerant flowing through the refrigerant pipe 7 from the outlet of the air-side heat exchanger 5 (evaporator) to the twin rotary compressor 2 and the refrigerant flowing through the refrigerant pipe 7 from the outlet of the water-side heat exchanger 4 to the air-side heat exchanger 5. The flow rate of the refrigerant flowing from the outlet of the water-side heat exchanger 4 to the internal heat exchanger 6 is adjusted to the required flow rate by the capillary tube 15. This capillary tube 15 is a copper capillary tube with an inner diameter of about 0.7 to 2.5, and is a type of expansion valve that does not fluctuate in condensation pressure or evaporation pressure and passes the required flow rate of refrigerant depending on the pressure difference before and after.

In this way, in the refrigerant circuit of the heat pump hot water heater in this embodiment, the refrigerant circulating through the refrigerant piping 7 is compressed to high temperature and pressure by the twin rotary compressor 2 and supplied to the water-side heat exchanger 4, where it exchanges heat with water passing through the hot water supply piping 12, thereby supplying hot water at a predetermined temperature.

The twin rotary compressor 2 is also connected to an intermediate flow path 7a for the refrigerant. This intermediate flow path 7a can reduce the pressure of the refrigerant inside the twin rotary compressor 2 by opening a second expansion valve 11 provided in the intermediate flow path 7a and allowing the refrigerant to flow from the refrigerant pipe 7 to the air-side heat exchanger 5 via the intermediate flow path 7a. This is a configuration for reducing the pressure of the refrigerant supplied to the rotary cylinder used during the second stage compression of the twin rotary compressor 2, to eliminate vane malfunctions, as will be described in detail later. In addition, the strainer 9 installed before the second expansion valve 11 of the intermediate flow path 7a functions as a filter to filter out debris and the like from the refrigerant passing through the intermediate flow path 7a.

Below, with reference to Figures 2 and 3, we will explain the two upper and lower plate-shaped connecting plates 30, 30 that connect the twin rotary compressor 2 and the muffler 3 together to form a unit in this embodiment.

As shown in Figures 2 and 3, the twin rotary compressor 2 is placed on the top of a base K equipped with a vibration prevention function at the bottom. The twin rotary compressor 2 and the muffler 3 are connected horizontally and parallel at two points, top and bottom, by two connecting plates 30, 30 to form a unit. The connecting plate 30 is formed as a flat plate having an internal space shaped like glasses in a plan view, and is divided into three parts: a left outer peripheral clamping plate 30a that abuts against the left half of the outer periphery of the twin rotary compressor 2, a middle outer peripheral clamping plate 30b that abuts against the right half of the outer periphery of the twin rotary compressor 2 and the left half of the outer periphery of the muffler 3, and a right outer peripheral clamping plate 30c that abuts against the right half of the outer periphery of the muffler 3.

A connecting portion 30A having bolt insertion holes formed horizontally opposite each other is provided at the left end of the middle outer peripheral clamping plate 30b corresponding to the right end of the left outer peripheral clamping plate 30a. By inserting a bolt B into this bolt insertion hole and fastening it with a nut N, the outer peripheral surface of the twin rotary compressor 2 is clamped by the left outer peripheral clamping plate 30a and the middle outer peripheral clamping plate 30b.

A connecting portion 30B having a bolt insertion hole formed horizontally opposite to the right end of the middle and middle outer peripheral clamping plate 30b is provided at the left end of the right outer peripheral clamping plate 30c corresponding to the right end of the middle and middle outer peripheral clamping plate 30b. By inserting a bolt B into this bolt insertion hole and tightening it with a nut N, the outer peripheral surface of the muffler 3 is clamped by the middle and middle outer peripheral clamping plate 30b and the right outer peripheral clamping plate 30c.

The connecting plates 30, 30 are preferably made of steel plate of a specified thickness, but it is desirable to attach a cushioning material such as hard rubber to the contact surface of the connecting plate 30 with the outer circumferential surface of the twin rotary compressor 2 and the contact surface with the outer circumferential surface of the muffler 3. This allows the connecting plate 30 to be attached by clamping it without damaging the outer circumferential surfaces of the twin rotary compressor 2 and the muffler 3, even if the joints 30A, 30B are tightened tightly with bolts B and nuts N.

In this way, the twin rotary compressor 2 is placed on top of the base K, which has a vibration prevention function at the bottom, and the high-pressure refrigerant discharged from the twin rotary compressor 2 is circulated through the refrigerant piping 7 (see Figure 1) via the muffler 3. This makes it possible to suppress as low as possible the high vibration of the compressor itself, which occurs when the twin rotary compressor 2 is used in a single-stage compression refrigeration cycle, by connecting the muffler 3.

In addition, because the vibrations of the twin rotary compressor 2 can be prevented from reaching the refrigerant piping 7 (see FIG. 1), there is no need to install vibration-damping materials, etc., that are required in conventional devices to suppress vibrations in the refrigerant piping 7 to which multiple devices are connected. In addition, because the muffler 3 can be retrofitted to the twin rotary compressor 2, the muffler 3 can also be retrofitted to equipment that uses an existing twin rotary compressor 2 in a single-stage compression refrigeration cycle.

Furthermore, by connecting the twin rotary compressor 2 and the muffler 3 together as a unit using two connecting plates 30, 30 at the top and bottom, the vibrations of the twin rotary compressor 2 and the muffler 3 can be synchronized, preventing the problem of the connection of the refrigerant piping 7 connecting the twin rotary compressor 2 and the muffler 3 being damaged by the vibration of the twin rotary compressor 2, causing refrigerant leakage.

The configuration and operation of the rotary cylinder 20, which is a compression section that compresses the refrigerant (carbon dioxide) to a high pressure and is provided inside the twin rotary compressor 2 of this embodiment, will be described below with reference to Figures 4 and 5. Figures 4 and 5 are horizontal cross-sectional views of the rolling piston type rotary cylinder 20.

The twin rotary compressor 2 is equipped with two rotary cylinders 20, one above the other. The refrigerant compressed in the first rotary cylinder 20 is compressed to a higher pressure in the second rotary cylinder 20. The basic configuration of both the first rotary cylinder 20 and the second rotary cylinder 20 is the same.

As shown in Figures 4 and 5, a refrigerant compression space 25, closed at the top and bottom, is formed in the center of the rolling piston type rotary cylinder 20. In the compression space 25, a rolling piston 22 is eccentrically supported by the drive shaft 21 so that it can rotate horizontally. A vane 27 is inserted into the vane sliding portion 26 so that its tip abuts against the outer periphery of the rolling piston 22 and its rear end is slidably pressed against the rolling piston 22 by the discharge pressure of the refrigerant.

One end of the drive shaft 21 is connected to an electric motor (not shown), and the rotation of the drive shaft 21 (clockwise in the figure) causes the rolling piston 22 to rotate eccentrically clockwise horizontally within the compression space 25. The rotary cylinder 20 is provided with a refrigerant intake port 23 and a discharge port 24. The refrigerant sucked into the compression space 25 from the intake port 23 changes the volume of the compression space 25 due to the eccentric rotation of the rolling piston 22, and is compressed to a predetermined pressure, and then discharged from the discharge port 24 to the outside of the rotary cylinder 20.

The discharge port 24 is closed by a discharge valve 28. This discharge valve 28 keeps the discharge port 24 closed until the refrigerant in the compression space 25 reaches a predetermined pressure, and when the refrigerant in the compression space 25 reaches or exceeds the predetermined pressure, it automatically opens the discharge port 24 as shown in FIG. 5 and discharges the refrigerant compressed to high pressure to the outside of the rotary cylinder 20.

The pressure inside the second-stage rotary cylinder 20 varies between intermediate pressure and high pressure, and the average is between the intermediate pressure and high pressure. In other words, during normal operation, the discharge pressure pressing the vane 27 from the back is higher than the pressure inside the second-stage rotary cylinder 20. Therefore, during normal operation, the pressure on the back of the vane 27 presses the vane 27 against the outer circumferential surface of the rolling piston 22, and the vane 27 can remain pressed against the outer circumferential surface of the rolling piston 22.

However, when the twin rotary compressor 2 starts up, the pressure of the refrigerant drawn into the compression space 25 from the suction port 23 may be higher than the discharge pressure pressing against the back surface of the vane 27. In such a situation, it becomes difficult to keep the vane 27 pressed against the outer circumferential surface of the rolling piston 22, causing a malfunction of the vane 27 known as vane jumping.

When vane jumping occurs, the suction and compression of the refrigerant in the compression space 25 becomes incomplete, and the refrigerant is not compressed to the specified pressure in the second-stage rotary cylinder 20. In this case, the vane 27 may break away from the outer circumferential surface of the rolling piston 22 and repeatedly collide with the rolling piston 22, resulting in a chattering phenomenon. This can lead to damage to the vane 27 or the rolling piston 22, and increased vibration and noise in the twin rotary compressor 2.

To prevent this, in this embodiment, as shown in FIG. 1, an intermediate flow path 7a for the refrigerant is connected to the twin rotary compressor 2. This intermediate flow path 7a opens the second expansion valve 11 provided in the intermediate flow path 7a to allow the refrigerant to flow into the air-side heat exchanger 5, reducing the pressure of the refrigerant inside the twin rotary compressor 2. As a result, the pressure of the refrigerant supplied to the rotary cylinder 20 used during the second stage compression is reduced, and the tip of the vane 27 can be abutted against the outer circumferential surface of the rolling piston 22 with the discharge pressure of the rotary cylinder 20 used during the second stage compression, preventing malfunction of the vane 27 (vane jumping) or shortening the time of malfunction.

In this case, the opening angle and opening time for opening and closing the second expansion valve 11 are controlled by a control unit (not shown). As an example, the second expansion valve 11 of the intermediate flow path 7a connected to the twin rotary compressor 2 is controlled to open to a maximum angle (e.g., 300 degrees) during a predetermined opening time (e.g., 35 seconds) and then closed stepwise by a predetermined angle (50 degrees). The second expansion valve 11 is opened and closed by this control unit twice when the twin rotary compressor 2 is started. This is based on the verification results that, according to experiments conducted by the applicant of the present application, opening and closing the second expansion valve 11 once is insufficient to eliminate the malfunction (vane jump) of the vane 27 or to shorten the time of the malfunction.

As described above, in the heat pump water heater of this embodiment, the vibration of the twin rotary compressor 2 itself, which occurs when the twin rotary compressor 2 is used in a single-stage compression refrigeration cycle, can be suppressed as low as possible by connecting the muffler 3. This prevents the refrigerant piping 7, which circulates the refrigerant between the condenser (water-side heat exchanger 4) and the evaporator (air-side heat exchanger 5) that are connected to the twin rotary compressor 2 to form a refrigerant circuit, from being damaged by excessive stress due to vibration, causing refrigerant leakage. Furthermore, by connecting the twin rotary compressor 2 and the muffler 3 as a unit, the twin rotary compressor 2 and the muffler 3 can be synchronized, and the problem of the refrigerant piping 7 connecting the twin rotary compressor 2 and the muffler 3 being damaged by the vibration of the twin rotary compressor 2 and causing refrigerant leakage can be prevented.

In addition, in order to reduce the pressure of the refrigerant sucked into the compression space 25 in the rotary cylinder 20 when the twin rotary compressor 2 is started, an intermediate flow path 7a for the refrigerant that discharges the refrigerant outside the twin rotary compressor 2 is provided, and the second expansion valve 11 installed in the intermediate flow path 7a is controlled to open and close to reduce the intermediate pressure of the refrigerant inside the twin rotary compressor 2. This prevents malfunction (vane jump) of the vane 27 pressed against the outer circumferential surface of the rolling piston 22 in the rotary cylinder 20 used during the second stage compression of the refrigerant, or shortens the time during which the vane 27 malfunctions. This makes it possible to keep vibrations generated in the twin rotary compressor 2 due to malfunction of the vane 27 as low as possible.

Although an example of an embodiment of the present invention has been described above, the specific configuration of the present invention is not limited to the above embodiment, and design changes that do not deviate from the gist of the invention are also included in the present invention.

1 Heat pump water heater 2 Twin rotary compressor 3 Muffler 4 Water side heat exchanger (condenser)
5. Air side heat exchanger (evaporator)
6 Internal heat exchanger 7 Refrigerant piping 8 Accumulator 9 Strainer 10 First expansion valve 11 Second expansion valve 12 Hot water supply piping 13 Pump 14 Flow sensor 15 Capillary tube 20 Rotary cylinder 21 Drive shaft 22 Rolling piston 23 Suction port 24 Discharge port 25 Compression space 26 Vane sliding portion 27 Vane 28 Discharge valve 30 Connecting plate B Bolt N Nut F Fan K Base

Claims (2)

In a heat pump water heater that uses a twin rotary compressor to compress the refrigerant in a single-stage compression refrigeration cycle,
In order to suppress vibrations that occur when the refrigerant is compressed by the twin rotary compressor, a muffler is connected to the refrigerant discharge port of the twin rotary compressor, and the twin rotary compressor and the muffler are connected to each other by a connector to form a unit ;
The connector is
a first clamping body that contacts one half of a right or left side of an outer circumferential surface of the twin rotary compressor;
a second clamping body that contacts the other left and right half circumference of an outer circumferential surface of the twin rotary compressor and the other left and right half circumference of an outer circumferential surface of the muffler and clamps the twin rotary compressor together with the first clamping body;
a third clamping body that contacts the other half of the left and right sides of the outer circumferential surface of the muffler and clamps the muffler together with the second clamping body.
A heat pump water heater characterized by the above. The heat pump water heater according to claim 1, characterized in that, in order to reduce the pressure of the refrigerant drawn into the compression space in the rotary cylinder when the twin rotary compressor is started, an intermediate flow path for the refrigerant that discharges the refrigerant is provided outside the twin rotary compressor, and the intermediate pressure of the refrigerant inside the twin rotary compressor is reduced by controlling the opening and closing of a second expansion valve installed in the intermediate flow path, thereby preventing malfunction of the vanes in the rotary cylinder used during second-stage compression of the refrigerant, or shortening the time during which the vanes malfunction.

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