Patent ID: 12228315

DESCRIPTION OF EMBODIMENTS

Now, a heat pump according to an embodiment of the present invention will be described below with reference to the drawings.

FIG.1is a simplified circuit diagram illustrating a refrigerant circuit of a heat pump according to an embodiment of the present invention.

The heat pump1has an outdoor unit to perform heat exchange with outdoor air and an indoor unit to perform heat exchange with indoor air. The outdoor unit includes compressors2(a first compressor2a, a second compressor2b, and a third compressor2c), an oil separator3, a four-way valve4, an outdoor heat exchanger5, an accumulator7, and an outdoor expansion valve11. The indoor unit has an indoor heat exchanger6and an indoor expansion valve12.

The first compressor2a, the second compressor2b, and the third compressor2cis driven with a driving source such as a gas engine, for example. The three compressors2are configured to be driven with a single gas engine via a belt or a flywheel, or each of them may be selectively driven by providing a clutch. The compressors2are not limited thereto, and they may be electric compressors which can be driven electrically. A discharge path of the first compressor2a(first discharge path41), a discharge path of the second compressor2b(second discharge path42), and a discharge path of the third compressor2c(third discharge path43) are integrated with a fluid merging part44into a single gas path40.

High temperature and high pressure gaseous refrigerant discharged from the compressors2are directed to the outdoor heat exchanger5or the indoor heat exchanger6with the four-way valve4. During a heating operation (solid line) the four-way valve4delivers the gaseous refrigerant to the indoor heat exchanger6, and during cooling operation (one-dot chain line) the four-way valve4delivers the gaseous refrigerant to the outdoor heat exchanger5.

During the heating operation, the indoor heat exchanger6transfers heat from the refrigerant to the indoor air and causes the gaseous refrigerant to change into a liquid state with low temperature and high pressure. Then, the refrigerant is delivered to the outdoor heat exchanger5via the indoor expansion valve12and the outdoor expansion valve11. A degree of opening of each of the indoor expansion valve12and the outdoor expansion valve11is controlled by a controller or the like where appropriate.

During the heating operation, the outdoor expansion valve11expands the liquid refrigerant and causes the liquid refrigerant to change into a liquid state (fog state) with low temperature and low pressure. Then, the outdoor heat exchanger5transfers heat from the outdoor air to the refrigerant and causes the refrigerant to change into a gaseous state with low temperature and low pressure. After passing through the outdoor heat exchanger5, the refrigerant passes through the four-way valve4and is delivered to a suction path50of the compressors2.

The accumulator7is provided in a path between the four-way valve4and the compressors2. The accumulator7temporarily stores the gaseous refrigerant. The gaseous refrigerant contains a small amount of a liquid refrigerant. These are separated in the accumulator7, and the liquid refrigerant is accumulated in the accumulator7.

The suction path50connecting the accumulator7and the compressors2has the branch part51connected to a plurality of paths and is branched into three paths (a first suction path71, a second suction path72, and a third suction path73) via the branch part51. The first suction path71, the second suction path72, and the third suction path73are connected to the first compressor2a, the second compressor2b, and the third compressor2c, respectively. The structure in the vicinity of the suction path50will be described in detail with reference toFIG.2later.

A filter52is housed in the branch part51to adsorb a foreign matter contained in the refrigerant. By providing the filter52, dirt from the refrigerant and oil can be removed as well as the refrigerant and the oil can be kept clean. In addition, a branch part51from which the path branches can handle multiple paths at a single location, this makes it possible to prevent extra filters52from being provided.

On the other hand, during a cooling operation, the high temperature and high pressure gaseous refrigerant discharged from the compressors2are delivered via the four-way valve4to the outdoor heat exchanger5which performs heat exchange with the outdoor air to bring the refrigerant into a low temperature and high pressure liquid state. The refrigerant having passed through the outdoor heat exchanger5is brought into a low temperature and low pressure liquid state (fog state) by passing through the indoor expansion valve12. Then, the refrigerant is delivered to the indoor heat exchanger6which performs heat exchange with the indoor air to bring the refrigerant into a low temperature and low pressure gaseous state. The refrigerant delivered from the indoor heat exchanger6is then delivered to the suction path50of the compressors2after passing through the four-way valve4and the accumulator7.

The oil separator3is provided between a discharge path of the compressors2and the four-way valve4. The oil separator3separates oil contained in the refrigerant. The oil separator3is connected to an oil return piping20(as an example of a first piping) for supplying the separated oil to the compressors2. The oil return piping20is branched into three pipings, a first oil return piping21, a second oil return piping22, and a third oil return piping23, which correspond to the first suction path71, the second suction path72, and the third suction path73, respectively. Specifically, the first oil return piping21, the second oil return piping22, and the third oil return piping23are connected to the first suction path71, the second suction path72, and the third suction path73, respectively. The first oil return piping21, the second oil return piping22, and the third oil return piping23may be each provided with a solenoid valve or the like to control a supply of oil separately.

The oil separator3is also connected to a bypass circuit30thorough which the separated gas refrigerant (hot gas) is delivered. The bypass circuit30is connected in the suction path50between the accumulator7and the branch part51. A bypass valve13(as an example of a valve), which controls the degree of valve opening and adjusts the flow rate of the gaseous refrigerant to be delivered, is provided in the bypass circuit30.

In addition, an oil path60independent of the oil return piping20, through which oil passes, is connected to the oil separator3. The oil path60is connected to the bypass circuit30, and by causing oil to pass through the oil path60, oil can be delivered to the filter52housed in the branch part51. By delivering an adequate amount of oil, performance of adsorbing debris of the filter52can be improved. An oil sensor15to detect the amount of oil passing through the oil path60and an oil valve14to control the delivery of oil are provided in the oil path60. By providing the oil path60, while the amount of oil can be detected by the oil sensor15, oil can be delivered to the filter through the bypass circuit30.

A second piping53, which returns oil to the accumulator7, is connected to the branch part51. Oil stored in the branch part51is delivered through the second piping53and accumulated in the accumulator7.

In the heat pump1, there is a case where oil is stored in the accumulator7while a system is turned off. According to this embodiment, the suction path50reaching the compressors2is connected to the bypass circuit30. Even if oil is stored in a piping of the accumulator7when getting started, since the gaseous refrigerant flowing in from the bypass circuit30is mixed with oil, this makes it possible to prevent oil from rushing into the compressors2and damaging the same.

FIG.2is a schematically perspective view illustrating a structure in the vicinity of the accumulator and the suction path, andFIG.3is a schematically side view illustrating a structure in the vicinity of the accumulator and the suction path.FIG.3shows the accumulator7in a transparent manner for the convenience of viewing.

The accumulator7encloses a U-shaped tube, and the refrigerant flowing into the accumulator7passes through the inside of the U-shaped tube. Oil delivered through the second piping53is once stored outside the U-shaped tube. An orifice (small hole) is provided on the lower side of the U-shaped tube, so that the refrigerant and oil stored outside the U-shaped tube are gradually drawn into the inside of the U-shaped tube through the orifice. A discharge port of the U-shaped tube is connected to the suction path50upside the accumulator7.

As mentioned above, the suction path50to deliver the refrigerant to the compressors2leads from the accumulator7. The suction path50has the branch part51located above the accumulator7in the vertical direction. The first suction path71leading from the branch part51has a first upward extending part71aextending upward, a first downward extending part71cextending downward, and a first connection part71bconnecting between the first upward extending part71aand the first downward extending part71c. The first oil return piping21is connected to the first upward extending part71a. A shape of the first connection part71bis not limited and may be variable to some extent in the vertical direction.

The first suction path71has the first upward extending part71a, the first connection part71b, and the first downward extending part71cin the stated order along the refrigerant delivery direction between the upstream side where the branch part51is located and the downstream side where the first compressor2ais located. Upon the system gets started, although the refrigerant (oil) flows along the delivery direction, but while the system is turned off, the refrigerant moves down by gravity. Namely, the refrigerant returns upstream at the first upward extending part71a, it does not move significantly at the first connection part71b, as well as it moves downstream at the first downward extending part71c. Therefore, while the compressors2are stopped, oil flowing into the first upward extending part71areturns to the accumulator7, and thus it is possible to prevent oil from flowing into the compressors2. Furthermore, since oil flowing in through the first oil return piping21naturally flows downward, it is possible to prevent from producing an oil lump.

Furthermore, the second piping53is connected to the branch part51located below the oil return piping20(the first oil return piping21) in the vertical direction. Accordingly, in a state where the compressors2are stopped, oil flowing in through the oil return piping20returns to the accumulator7through the branch part51and the second piping53. Namely, this makes it possible to be such a structure through which oil naturally returns without providing an additional power source.

Each of the second suction path72and the third suction path73has a shape substantially similar to the first suction path71, and the second suction path and the third suction path respectively have the second upward extending part72aand the third upward extending part73a, which correspond to the first upward extending part71a, and the second connection part72band the third connection part73b, which correspond to the first connection part71b, as well as the second downward extending part72cand the third downward extending part73c, which correspond to the first downward extending part71c. Since the flow of the refrigerant in the second suction path72and the third suction path73is the same as in the first suction path71, a detail explanation thereof is omitted except that they are configured so that oil can return to the accumulator7while the compressors2are stopped.

Next, the control of the degree of opening of the bypass valve13when the system gets started will be explained below with reference toFIG.4.

FIG.4is an explanatory diagram illustrating variations of the degree of opening of the bypass valve and a rotation speed of a compressor over time.

FIG.4shows a degree of valve opening change characteristic line K1, which indicates a time-change in the degree of valve opening of the bypass valve13, and a rotation speed change characteristic line R1, which indicates a time-change in the rotation speed of the compressors2, and the horizontal axis represents a lapse of time. With respect to the degree of valve opening change characteristic line K1, the higher the vertical axis goes, the greater the degree of opening becomes, as well as with respect to the rotation speed change characteristic line R1, the higher the vertical axis goes, the greater the rotation speed becomes. Taking into account of variation to some extent, the rotation speed of the compressors2may be a rough value, and thus a slight error is allowed.

InFIG.4, a time when the system gets started is shown as “0”. At time “0”, the bypass valve13is set to an upper limit degree of valve opening (upper limit degree of valve opening Km), and the rotation speed of the compressors is set to zero. The rotation speed of the compressors2increases over time, and it reaches a stable rotation speed (stable rotation speed Rr) at time “T1.” The stable rotation speed Rr is maintained thereafter. The bypass valve13is set to the upper limit degree of valve opening Km until the time “T1”, and after the time “T1”, the valve is gradually closed (the degree of valve opening is reduced).

Namely, the bypass valve13is controlled so that the degree of valve opening thereof is reduced over time after the heat pump1is started. While the bypass valve13is opened, as the gaseous refrigerant is delivered to the suction path50through the bypass circuit30, it is possible to prevent excessive oil from flowing into. After the lump of oil is diminished by flowing oil gradually, by decreasing the delivery amount of the gaseous refrigerant to control so that the proper amount of oil is delivered, a normal operating environment of the system can be returned.

FIG.4shows a part of an operation transition when the system gets started, and the rotation speed of the compressors2may be controlled to exceed the stable rotation speed Rr as appropriate thereafter. Furthermore, although the bypass valve13, in which the degree of valve opening is linearly decreased, is illustrated as an example, it is not limited thereto, and the degree of valve opening may be decreased in a step by step manner or the like if only the bypass valve13is closed finally.

It should be noted that embodiments disclosed above are exemplary in all respects, and the invention is not limitedly construed on a basis thereof. Therefore, the technical scope of the present invention should not be construed based on only above described embodiments but be defined based on the statement of the claims. Furthermore, any changes and modifications within the meaning and range equivalent to the claims fall within the scope of the invention.

This application claims the benefit of priority to Japanese Patent Application No. 2020-053960 filed as of Mar. 25, 2020. The entirety thereof is incorporated herein by reference. In addition, the entirety of the references cited is incorporated herein by reference.

DESCRIPTION OF REFERENCE NUMERALS

1Heat pump2Compressor3Oil separator4Four-way valve5Outdoor heat exchanger6Indoor heat exchanger7Accumulator11Outdoor expansion valve12Indoor expansion valve13Bypass valve (an example of a valve)14Oil valve15Oil sensor20Oil return piping (an example of a first piping)30Bypass circuit40Gas path44Fluid merging part50Suction path51Branch part52Filter53Second piping60Oil path71First suction path71aFirst upward extending part (an example of an upward extending part)71bFirst connection part (an example of a connection part)71cFirst downward extending part (an example of a downward extending part)72Second suction path72aSecond upward extending part (an example of an upward extending part)72bSecond connection part (an example of a connection part)72cSecond downward extending part (an example of a downward extending part)73Third suction path73aThird upward extending part (an example of an upward extending part)73bThird connection part (an example of a connection part)73cThird downward extending part (an example of a downward extending part)