JP2020094759A - Multi-stage compression system - Google Patents

Abstract

To solve such the problem that each of the compressors in a refrigeration device using a plurality of multi-stage compressors needs to keep a proper amount of refrigeration oil and, when oil discharged from a high-stage side compressor is returned on a refrigerant suction side of a low-stage side compressor, a heat loss and a pressure loss occur, causing degradation of system efficiency.SOLUTION: A multi-stage compression system 20 includes a low-stage compressor 21, a high-stage compressor 23 and an oil return pipe 31. The low-stage compressor 21 includes a compression part 50, a motor 40, a container 30 and oil guides 47, 47a, 31p. The oil guides 47, 47a, 31p are arranged while facing on outlet of the oil return pipe 31 inside the container 30.SELECTED DRAWING: Figure 2

Description

A multi-stage compression system that uses refrigerant and oil.

In a refrigeration system, a multistage compression mechanism using a plurality of compressors is recommended and used depending on the working refrigerant. In a multi-stage compression mechanism using a plurality of compressors, it is important to control the refrigerating machine oil in an appropriate amount in the plurality of compressors. In other words, it is necessary to control so that oil is not excessively unevenly distributed in one compressor.

In Patent Document 1 (Japanese Patent Laid-Open No. 2008-261227), in order to keep the height of the oil level of the low-stage and high-stage compressors at a constant level, the low-stage compressor has a low stage. The side oil drain passage is provided with an oil return passage for returning the oil discharged on the high stage side to the suction pipe of the low stage compressor.

However, if the oil discharged from the high-stage compressor is returned to the refrigerant suction side of the low-stage compressor, the following two losses may occur.

The first loss is the loss of heat. The oil discharged from the high-stage compressor has a high temperature. When high temperature oil is mixed with the suction refrigerant, heat loss occurs in which the temperature of the suction refrigerant is increased. The second loss is the loss of pressure. A pressure loss occurs in which high-pressure oil is mixed with low-pressure suction refrigerant (gas).

The multistage compression system of the first aspect uses a refrigerant and oil. The multi-stage compression system has a low stage compressor, a high stage compressor, and an oil return pipe. The low-stage compressor compresses the refrigerant. The high-stage compressor further compresses the refrigerant compressed by the low-stage compressor. The oil return pipe returns the oil discharged from the high-stage compressor to the low-stage compressor. Here, the oil discharged by the high-stage compressor means not only the oil directly discharged from the high-stage compressor but also the oil once discharged from the high-stage compressor to another device, for example, an oil separator. Including. In addition, the low-stage compressor has a compression unit, a motor, a container, and an oil guide. The compression unit compresses the refrigerant. The motor drives the compression unit. The motor is located above the compression section. The container houses the compression unit and the motor. The oil guide is arranged inside the container so as to face the outlet of the oil return pipe.

In the multistage compression system according to the first aspect, the oil guide is arranged so as to face the outlet of the oil return pipe, so that the oil can collide with the oil guide and drop into the oil sump. Is the system according to the first aspect, and is arranged such that the angle of the oil introduction portion of the oil return pipe into the container is within 15° from the horizontal.

In the multi-stage compression system of the second aspect, the angle of the oil introduction portion into the container of the oil return pipe is close to horizontal, so that the oil is collided with the oil guide to change the direction of the oil and supply the oil to the oil sump. It's easy to do.

The multistage compression system of the third aspect is the system of the first aspect or the second aspect, wherein the oil guide is arranged within 25% of the inner diameter D of the horizontal cross section of the container from the inner circumference of the container.

In the multistage compression system of the third aspect, the oil guide is arranged near the inner surface of the container, so that the oil introduced from the oil return pipe can be made to collide with the oil guide in a short distance, and the direction of the oil can be controlled. It's easy to do.

A multistage compression system according to a fourth aspect is the system according to any one of the first to third aspects, in which the oil guide is a plate-shaped member that extends vertically.

In the multistage compression system according to the fourth aspect, since the oil guide is a plate-shaped member extending vertically, it is possible to increase the area of the portion where the oil collides from the oil return pipe into the container.

A multistage compression system according to a fifth aspect is the system according to the fourth aspect, in which the motor includes an insulator. The oil guide is a portion that is continuous with the insulator and extends downward from the insulator.

A multistage compression system according to a sixth aspect is the system according to any one of the first aspect to the third aspect, and the motor includes a stator. The oil guide is the outer surface of the stator.

A multistage compression system according to a seventh aspect is the system according to any one of the first to third aspects, in which the oil guide is a part of a pipe through which oil passes, and is a bent part of the pipe.

It is a refrigerant circuit diagram of refrigeration equipment 1 of a 1st embodiment. It is a longitudinal cross-sectional view of the low-stage compressor 21 of the first embodiment. It is an AA sectional view of low-stage compressor 21 of a 1st embodiment. It is a BB sectional view of low-stage compressor 21 of a 1st embodiment. It is CC sectional drawing of the low stage compressor 21 of 1st Embodiment. It is a longitudinal cross-sectional view of the low-stage compressor 21 of 2nd Embodiment. It is a longitudinal cross-sectional view of the low-stage compressor 21 of 3rd Embodiment.

<First Embodiment>
(1) Refrigerant circuit of refrigeration apparatus 1 (1-1) Entire refrigerant circuit of refrigeration apparatus 1 The refrigerant circuit configuration of the refrigeration apparatus 1 of the first embodiment is shown in FIG. The refrigeration system 1 of the present embodiment is a device that performs a two-stage compression refrigeration cycle using carbon dioxide, which is a refrigerant that operates in the supercritical range. The refrigerating apparatus 1 of this embodiment can be used for an air conditioning apparatus that performs cooling and heating, an air conditioning apparatus dedicated to cooling, a hot and cold water dispenser, a refrigerating apparatus, a freezing storage apparatus, and the like.

The refrigeration system 1 of the present embodiment includes a multi-stage compression system 20, a four-way switching valve 5, a heat source side heat exchanger 2, a bridge circuit 3, expansion mechanisms 8 and 9, a use side heat exchanger 4, and an economizer. And a heat exchanger 7.

The multi-stage compression system 20 compresses the refrigerant. The gas refrigerant is introduced into the first accumulator 22 at the inlet of the low-stage compressor 21 via the four-way switching valve 5 and the refrigerant pipe 13. The refrigerant is compressed by the low-stage compressor 21 and the high-stage compressor 23, and reaches the four-way switching valve 5 via the pipe 18.

The four-way switching valve 5 switches between the heat source side heat exchanger 2 and the use side heat exchanger 4 in which direction the refrigerant from the multi-stage compression system 20 flows. For example, when the refrigeration system 1 is an air conditioner and the cooling operation is performed, the refrigerant flows from the four-way switching valve 5 to the heat source side heat exchanger 2 (condenser). The refrigerant flowing through the heat source side heat exchanger 2 (condenser) reaches the receiver 6 via the check valve 3a of the bridge circuit 3, the pipe 11, and the check valve 11e. The liquid refrigerant from the receiver 6 continues to flow through the pipe 11, is decompressed by the expansion mechanism 9, and goes to the use side heat exchanger 4 (evaporator) via the check valve 3c of the bridge circuit 3. The refrigerant heated by the utilization side heat exchanger 4 (evaporator) is compressed again by the multi-stage compression system 20 via the four-way switching valve 5. On the other hand, during the heating operation, the refrigerant flows from the four-way switching valve 5 to the use side heat exchanger 4 (condenser), the check valve 3b of the bridge circuit 3, the pipe 11, the receiver 6, the expansion mechanism 9, and the reverse of the bridge circuit 3. The stop valve 3d, the use side heat exchanger 4 (evaporator), and the four-way switching valve 5 flow in this order.

The economizer heat exchanger 7 is arranged in the middle of the refrigerant pipe 11 between the receiver 6 and the expansion mechanism 9. A part of the refrigerant is branched at a branch 11a of the pipe 11 and is reduced to an intermediate pressure by the expansion mechanism 8. The intermediate-pressure refrigerant is heated by the high-pressure refrigerant flowing through the pipe 11 in the economizer heat exchanger 7, and is injected into the intermediate-pressure merging portion 15b of the multistage compression system 20 via the intermediate injection pipe 12. Further, the gas component of the refrigerant from the receiver 6 merges with the intermediate injection pipe 12 via the pipe 19.

(1-2) Flow of Refrigerant and Oil in Multi-Stage Compression System 20 As shown in FIG. 1, the multi-stage compression system 20 of the present embodiment includes a first accumulator 22, a low-stage compressor 21, an intercooler 26, The second accumulator 24, the high-stage compressor 23, the oil separator 25, the oil cooler 27, and the pressure reducer 31a are provided.

In the present embodiment, the refrigerant compressed by the low-stage compressor 21 is further compressed by the high-stage compressor 23. The compressors 21 and 23 include accumulators 22 and 24, respectively. The accumulators 22 and 24 play a role of temporarily storing the refrigerant before entering the compressor and preventing the liquid refrigerant from being sucked into the compressor.

Next, the flow of refrigerant and oil in the multi-stage compression system 20 of the present embodiment will be described with reference to FIG.

In the present embodiment, the low-pressure gas refrigerant heated by the evaporator (use-side heat exchanger 4 or heat-source-side heat exchanger 2) flows into the first accumulator 22 via the refrigerant pipe 13. The gas refrigerant in the first accumulator 22 flows to the low-stage compressor 21 via the suction pipe 14. The refrigerant compressed by the low-stage compressor 21 is discharged from the discharge pipe 15a, flows through the intermediate pressure refrigerant pipe 15, and reaches the second accumulator 24.

The intercooler 26 is arranged in the middle of the intermediate pressure refrigerant pipe 15. The intercooler 26 is a heat exchanger that cools the intermediate-pressure refrigerant with, for example, outdoor air. The intercooler 26 may be disposed adjacent to the heat source side heat exchanger 2 and may exchange heat with air by a common fan. The intercooler 26 enhances the efficiency of the refrigeration system 1 by cooling the intermediate pressure refrigerant.

Further, the intermediate pressure refrigerant is injected into the merging portion 15b of the intermediate pressure refrigerant pipe 15 from the intermediate injection pipe 12. In the present embodiment, the joining portion 15b of the intermediate injection pipe 12 to the pipe 15 is arranged on the downstream side of the intercooler 26. The temperature of the refrigerant injected by the intermediate injection is lower than that of the refrigerant flowing through the pipe 15. Therefore, the intermediate injection reduces the temperature of the refrigerant flowing through the pipe 15 and improves the efficiency of the refrigeration system 1.

The multi-stage compression system 20 of the present embodiment further includes an oil discharge pipe 32 that discharges excess oil of the low-stage compressor. The oil discharge pipe 32 connects the low-stage compressor 21 and the intermediate pressure pipe 15. The oil discharge pipe 32 discharges not only the excess oil accumulated in the oil sump 30a of the low-stage compressor but also the excess refrigerant accumulated in the oil sump 30a. The connecting portion of the oil discharge pipe 32 with the intermediate pressure refrigerant pipe 15 is a portion downstream of the intercooler 26 and the joining portion 15b of the intermediate injection.

The refrigerant sent to the second accumulator 24 through the pipe 15 is introduced into the high-stage compressor 23 through the suction pipe 16. The refrigerant is compressed in the high-stage compressor 23, becomes a high pressure, and is discharged to the discharge pipe 17.

The refrigerant discharged to the discharge pipe 17 flows to the oil separator 25. The oil separator 25 separates the refrigerant and the oil. The separated oil is returned to the low-stage compressor 21 via the oil return pipe 31.

The multi-stage compression system 20 of the present embodiment further includes an oil discharge pipe 33 that discharges excess oil of the high-stage compressor. The oil discharge pipe 33 connects the high-stage compressor 23 and the discharge pipe 17 of the high-stage compressor 23.

A pressure reducer 31 a is arranged in the middle of the oil return pipe 31. The decompressor 31a is for decompressing the high-pressure oil discharged from the oil separator 25. As the decompressor 31a, specifically, for example, a capillary tube is used.

An oil cooler 27 is arranged in the middle of the oil return pipe 31. The oil cooler 27 is a heat exchanger that cools the oil flowing through the oil return pipe 31 with, for example, outdoor air. The oil cooler 27 is for cooling the high temperature oil discharged from the oil separator 25. The oil cooler 27 may be arranged, for example, in the vicinity of the heat source side heat exchanger 2 and exchange heat with air by a common fan. The oil cooler 27 may be arranged, for example, below the heat source side heat exchanger 2.

The oil (refrigerating machine oil) of the present embodiment is not particularly limited as long as it is a refrigerating machine oil used as a CO ₂ refrigerant, but an oil incompatible with the CO 2 refrigerant is particularly suitable. Examples of refrigerating machine oil include PAG (polyalkylene glycols) and POE (polyol esters).

The refrigeration system 1 of this embodiment performs two-stage compression with two compressors. Two or more stages of compression may be performed using three or more compressors. Moreover, you may perform compression of three steps or more.

(2) Configuration of compressor, piping connected to the compressor, and device The low-stage compressor 21 and the high-stage compressor 23 of the present embodiment are both 2-cylinder type and swing type rotary compressors. is there. Since the compressors 21 and 23 have almost the same configuration, the low-stage compressor 21 will be used for the detailed description.

2 is a vertical sectional view of the low-stage compressor 21, and FIGS. 3 to 5 are horizontal sectional views at positions AA to CC in FIG. 2, respectively. However, in the BB sectional view of FIG. 4, the portion of the motor 40 is not shown.

The low-stage compressor 21 includes a container 30, a compression unit 50, a motor 40, a crankshaft 60, and a terminal 35.

(2-1) Container 30
The container 30 has a substantially cylindrical shape with the rotation axis RA of the motor 40 as a central axis. The inside of the container is kept airtight, and the intermediate pressure is maintained in the low-stage compressor 21 and the high pressure is maintained in the high-stage compressor 23 during operation. The lower part inside the container 30 is an oil reservoir 30a for storing oil (lubricating oil). Although the liquid surface of the oil sump 30a is tentatively shown in FIG. 2, the height of the liquid surface of the oil sump 30a is not constant and increases or decreases during the operation of the compressor.

The container 30 accommodates the motor 40, the crankshaft 60, and the compression unit 50 inside. A terminal 35 is arranged on the top of the container 30. Further, the container 30 is connected with refrigerant suction pipes 14 a and 14 b and a discharge pipe 15 a, an oil return pipe 31, and an oil discharge pipe 32.

(2-2) Motor 40
The motor 40 is a brushless DC motor. The motor 40 generates power for rotating the crankshaft 60 around the rotation axis RA. The motor 40 is arranged in the space inside the container 30, below the upper space, and above the compression section 50. The motor 40 has a stator 41 and a rotor 42. The stator 41 is fixed to the inner wall of the container 30. The rotor 42 rotates by magnetically interacting with the stator 41.

The stator 41 has a stator core 46 and an insulator 47. The stator core 46 is made of steel. The insulator 47 is made of resin. The insulator 47 is arranged above and below the stator core 46, and has a winding wound around it.

(2-3) Crankshaft 60
The crankshaft 60 transmits the power of the motor 40 to the compression unit 50. The crankshaft 60 has a main shaft portion 61, a first eccentric portion 62a, and a second eccentric portion 62b.

The main shaft portion 61 is a portion that is concentric with the rotation axis RA. The main shaft portion 61 is fixed to the rotor 42.

The first eccentric portion 62a and the second eccentric portion 62b are eccentric with respect to the rotation axis RA. The shape of the first eccentric portion 62a and the shape of the second eccentric portion 62b are symmetric with respect to the rotation axis RA.

An oil tube 69 is provided at the lower end of the crankshaft 60. The oil tube 69 draws up oil (lubricating oil) from the oil sump 30a. The pumped lubricating oil rises in the oil passage inside the crankshaft 60 and is supplied to the sliding portion of the compression unit 50.

(2-4) Compressor 50
The compression unit 50 is a two-cylinder type compression mechanism. The compression unit 50 has a first cylinder 51, a first piston 56, a second cylinder 52, a second piston 66, a front head 53, a middle plate 54, a rear head 55, and front mufflers 58a and 58b.

A first compression chamber 71 and a second compression chamber 72 are formed in the compression section 50. The first and second compression chambers are spaces in which the refrigerant is supplied and compressed.

(2-4-1) First Compression Chamber 71 and Flow of Refrigerant Compressed in First Compression Chamber 71 The first compression chamber 71 includes a first cylinder 51 and a first cylinder 51, as shown in FIG. It is a space surrounded by the piston 56, the front head 53, and the middle plate 54.

As shown in FIG. 5, the first cylinder 51 is provided with a suction hole 14e, a discharge recess 59, a bush accommodating hole 57a, and a blade moving hole 57b. The first cylinder 51 accommodates the main shaft 61 of the crankshaft 60, the first eccentric portion 62 a, and the first piston 56. The suction hole 14e connects the first compression chamber 71 and the inside of the suction pipe 14a. A pair of bushes 56c are housed in the bush housing holes 57a.

The first piston 56 has an annular portion 56a and a blade 56b. The first piston 56 is a swing piston. The first eccentric portion 62a of the crankshaft 60 is fitted into the annular portion 56a. The blade 56b is sandwiched by a pair of bushes 56c. The first piston 56 divides the first compression chamber 71 into two. One is a low pressure chamber 71a communicating with the suction hole 14e. The other is a high-pressure chamber 71b communicating with the discharge recess 59. In FIG. 5, the annular portion 56a revolves clockwise, the volume of the high pressure chamber 71b becomes small, and the refrigerant in the high pressure chamber 71b is compressed. When the annular portion 56a revolves, the tip of the blade 56b reciprocates between the blade moving hole 57b side and the bush accommodating hole 57a side.

As shown in FIG. 2, the front head 53 is fixed inside the container 30 by an annular member 53a.

Front mufflers 58a and 58b are fixed to the front head 53. The front muffler reduces noise when the refrigerant is discharged.

The refrigerant compressed in the first compression chamber 71 is discharged to the first front muffler space 58e between the front muffler 58a and the front head 53 via the discharge recess 59. After the refrigerant further moves to the second front muffler space 58f between the two front mufflers 58a and 58b, the refrigerant is discharged below the motor 40 from the discharge holes 58c and 58d (see FIG. 4) provided in the front muffler 58b. Is blown out into the space.

The refrigerant that has been compressed and blown from the discharge holes 58c and 58d of the front muffler 58a moves to the upper space of the container 30 through the gap of the motor 40, is blown from the discharge pipe 15a, and goes to the high-stage compressor 23.

In the multi-stage compression system 20 of the first embodiment, the compressors 21 and 23 are both 2-cylinder type compressors. Both or one compressor may be a one cylinder type compressor.

(2-4-2) Second Compression Chamber 72 and Flow of Refrigerant Compressed in Second Compression Chamber 72 The second compression chamber 72 includes the second cylinder 52, the second piston 66, the rear head 55, and the middle. It is a space surrounded by the plate 54.

Since the flow of the refrigerant compressed in the second compression chamber 72 is almost the same as the flow of the refrigerant compressed in the first compression chamber 71, detailed description will be omitted. However, in the case of the refrigerant compressed in the second compression chamber 72, it is first sent to the rear muffler space 55a provided in the rear head 55 and then sent to the front muffler spaces 58e and 58f by the front mufflers 58a and 58b. However, it is different.

(2-5) Compressor and Connection Position of Oil Return Pipe 31 and Oil Discharge Pipe 32 The oil return pipe 31 is located below the motor 40 in the space above the compression unit 50, as shown in FIG. It is connected to the container 30 so that the internal flow paths communicate with each other. Below the motor 40 includes a space (core cut or the like) beside the motor 40. However, the space below the motor 40 and above the compression unit 50 is more preferable. The oil return pipe 31 is connected to the container 30 so that the oil flows substantially vertically to the side surface of the container 30 and the oil flows substantially horizontally. The angle of the oil introduction portion of the oil return pipe 31 to the inside of the container 30 is arranged to be within 15° from the horizontal.

The oil blown from the oil return pipe 31 into the container 30 collides with the insulator 47 of the motor 40, and then falls onto the front muffler 58b and the annular member 53a for fixing the front head 53, and further, the container It joins the oil sump 30a in the lower part of the inside of 30. In other words, the insulator 47 plays a role of an oil guide that causes the oil that flows through the oil return pipe 31 and is introduced into the container 30 to collide with the oil and direct the oil toward the oil sump 30a side of the lower portion of the container 30. The oil guide portion of the insulator 47 is a plate-shaped member that extends vertically. All of the oil blown from the oil return pipe 31 into the container 30 does not have to collide with the oil guide. It may be a part. It may be all.

The oil guide is arranged in the container 30 so as to face the outlet of the oil return pipe 31. The outlet of the oil return pipe 31 means a connecting portion between the container 30 and the oil return pipe 31 inside the container 30. The oil guide is arranged within 25% of the inner diameter D of the horizontal cross section of the container 30 from the inner circumference of the container 30. By arranging the oil guide relatively near the side wall of the container 30, the controllability of the oil direction becomes good.

The oil return pipe 31 is preferably connected to the space above the second compression chamber 72. If the oil return pipe 31 is connected to the space below the second compression chamber 72, there is a high possibility that the oil return pipe 31 will be below the oil level of the oil sump 30a, and this will cause forming, which is not preferable.

The oil return pipe 31 may be connected to the upper portion of the container 30. For example, it may be connected to the core cut portion of the stator 41 of the motor 40. However, it is preferable to connect to a low portion as close as possible to the oil sump 30a, because oil is supplied to the sliding portions (near the compression chambers 71 and 72) sooner.

The inner diameter of the oil return pipe 31 is, for example, 10 mm or more and 12 mm or less.

As shown in FIG. 2, the oil discharge pipe 32 is connected to the container 30 under the motor 40 so that the internal flow path communicates with the space above the compression unit 50.

If the connection position of the oil discharge pipe 32 to the container 30 is lower than the compression chamber 72, the oil may be excessively lost from the oil reservoir 30a. Further, when the position is higher than the motor 40, the difference from the discharge pipe 15a becomes small, and the significance of providing the oil discharge pipe 32 is lost.

Further, in the present embodiment, as shown in FIG. 2, the mounting height position of the oil discharge pipe 32 to the container 30 is the same as the mounting height position of the oil return pipe 31 to the container 30. This facilitates the height adjustment of the oil surface of the oil sump 30a.

Further, as shown in FIG. 4, the oil discharge pipe 32 is attached to the flat container 30 at a position opposite to the rotation axis RA of the motor 40 from the discharge holes 58c and 58d of the front muffler 58b. .. Here, the opposite position means a range of 180° other than a total of 180°, which is 90° to the left and right with respect to the rotation axis RA from the connection position of the oil discharge pipe 32. In addition, in FIG. 4, the discharge holes 58c are not partly opposite to each other, but here it is meant that more than half of the area of the discharge holes 58c and 58d is on the opposite side.

In this embodiment, since the connection position of the oil discharge pipe 32 to the container 30 is separated from the positions of the discharge holes 58c and 58d of the front muffler 58b, the refrigerant discharged from the discharge holes 58c and 58d of the front muffler 58b is The direct oil discharge pipe 32 can reduce discharge from the low-stage compressor 21.

The inner diameter of the oil discharge pipe 32 is equal to the inner diameter of the oil return pipe 31. A pipe having a diameter smaller than the inner diameter of the discharge pipe 15a is used. More specifically, the inner diameter of the oil discharge pipe 32 is, for example, 10 mm or more and 12 mm or less.

Further, as shown in FIG. 5, when the planar positional relationship between the oil discharge pipe 32 and the oil return pipe 31 is seen, the connection position of the oil discharge pipe 32 to the container 30 is the position of the oil return pipe 31 to the container 30. It is a position away from the connection position by 90° or more in the rotation direction of the motor 40 (direction of arrow in FIG. 5). Preferably, the position is 180° or more. In the present embodiment, this angle is represented by θ. Theta is 270° or more. Further, θ should be 330° or less.

In the present embodiment, since the positions of the oil discharge pipe 32 and the oil return pipe 31 are sufficiently separated, the oil introduced into the container 30 of the low-stage compressor 21 by the oil return pipe 31 is directly transferred to the oil discharge pipe 32. It is possible to reduce discharge to the outside of the container 30 and easily realize oil equalization of the low-stage compressor 21.

In the multi-stage compression system 20 of the first embodiment, the height of the connection position of the oil return pipe 31 to the container 30 was equal to the height of the connection position of the oil discharge pipe 32 to the container 30. The height of the connection position of the oil return pipe 31 to the container 30 may be higher than the height of the connection position of the oil discharge pipe 32 to the container 30.

(2-6) Accumulator 22
In the multistage compression system 20 of the present embodiment, the first accumulator 22 is arranged upstream of the low stage compressor 21, and the second accumulator 24 is arranged upstream of the high stage compressor 23. The accumulators 22 and 24 temporarily store the flowing refrigerant, prevent the liquid refrigerant from flowing into the compressor, and prevent the liquid compression of the compressor. Since the first accumulator 22 and the second accumulator 24 have almost the same configuration, the first accumulator 22 will be described with reference to FIG.

The low-pressure gas refrigerant heated by the evaporator flows through the refrigerant pipe 13 via the four-way switching valve 5 and is introduced into the accumulator 22. The gas refrigerant is introduced into the first and second compression chambers 71 and 72 from the suction pipes 14a and 14b of the compressor 21. Liquid refrigerant and oil are accumulated below the inside of the accumulator. Small holes 14c and 14d are formed in the suction pipes 14a and 14b below the inside of the accumulator. The diameter of the holes 14c and 14d is, for example, 1 mm to 2 mm. The oil, together with the liquid refrigerant, joins the gas refrigerant through the holes 14c and 14d little by little, and is sent to the compression chamber.

(3) Features (3-1)
The multi-stage compression system 20 of this embodiment includes a low-stage compressor 21, a high-stage compressor 23, and an oil return pipe 31. The oil return pipe 31 returns the oil discharged from the high-stage compressor to the low-stage compressor 21. The low-stage compressor 21 has a compression unit 50, a motor 40, a container 30, and an oil guide. The container houses the compression unit 50, the motor 40, and the oil guide. The oil guide is arranged in the container 30 so as to face the outlet of the oil return pipe 31. The oil guide collides with the oil introduced into the container 30 by flowing through the oil return pipe 31, and directs the oil toward the oil sump 30a side below the container 30.

In the present embodiment, the oil guide is achieved by the insulator 47 that is a part of the motor 40.

Since the multi-stage compression system 20 of this embodiment has the oil guide, oil can be supplied more directly to the oil sump 30a. Therefore, the amount of oil in the low-stage compressor 21 can be quickly increased.

On the other hand, if the connection position of the oil return pipe 31 to the container 30 is set to a position lower than the liquid surface of the oil sump 30a, such as under the compression part 50, a forming phenomenon may occur, which is not preferable.

Further, since the oil is directly supplied to the oil sump, the amount of oil can be increased more rapidly than in the case where the oil is conventionally supplied to the suction pipe. Further, as compared with the case where high-temperature and high-pressure oil is mixed with the refrigerant sucked into the compressor, the oil is directly supplied to the oil sump, so that loss of pressure and temperature can be reduced. it can.

(3-2)
The multi-stage compression system 20 of the present embodiment is arranged so that the angle of the oil introduction portion into the container of the oil return pipe is within 15° vertically from the horizontal.

In the multi-stage compression system 20 of the present embodiment, since the angle of the oil introduction portion into the container of the oil return pipe is close to horizontal, the oil is collided with the oil guide, the direction of the oil is changed, and the oil is collected in the oil sump. Easy to supply.

(3-3)
In the multi-stage compression system 20 of the present embodiment, the oil guide is arranged within 25% of the inner diameter D of the horizontal cross section of the container 30 from the inner circumference of the container 30.

In the multi-stage compression system 20 of the present embodiment, since the oil guide is arranged near the inner surface of the container, the oil introduced from the oil return pipe 31 can be made to collide with the oil guide in a short distance, and the direction of the oil can be changed. Easy to control.

(4) Modified Example (4-1) Modified Example 1A
In the first embodiment, the oil guide that changes the direction of the oil introduced from the oil return pipe 31 into the low-stage compressor 21 is the insulator 47 of the motor 40. In Modification 1A, the oil guide is the outer surface of the stator core 46 of the stator 41 of the motor 40. In the modification 1A, the oil return pipe 31 is connected to the height of the stator core 46 on the side wall of the container 30. As shown in FIG. 3, a core cut portion 46 a, which is a gap, is formed between the container 30 and the stator core 46. In the modification 1A, the oil return pipe 31 is connected to a portion of the side wall of the container 30 that faces the core cut portion 46a. Other configurations are the same as those in the first embodiment.

In the multi-stage compression system of Modification 1A, the outer surface of the stator 41 serves as an oil guide, and the oil from the oil return pipe 31 can be quickly supplied to the oil sump 30a. However, as compared with the first embodiment, the vertical distance from the oil sump becomes longer, and the oil supply time becomes slightly longer.

(4-2) Modification 1B
In the first embodiment, the oil return pipe 31 returns the oil from the oil separator 25 to the low-stage compressor 21. In the modified example 1B, the oil return pipe 31 returns the oil discharged from the high-stage compressor 23 directly to the low-stage compressor 21. Other configurations are similar to those of the first embodiment.

The multistage compression system 20 of Modification 1B also has the same features as the multistage compression system 20 of the first embodiment. However, in the case of the modified example 1B, since the excess refrigerant discharged from the high-stage compressor 23 and the oil are mixed, the oil flowing through the oil return pipe 31 is different from the case where the oil is passed through the oil separator 25 of the first embodiment. The amount of the refrigerant mixed with is increased.

Further, the oil separated from the oil separator 25 may be added to the oil discharged from the high-stage compressor 23 and returned to the container 30 of the low-stage compressor 21.

(4-3) Modification 1C
In addition to the configuration of the multi-stage compression system 20 of the first embodiment, the multi-stage compression system of Modification 1C includes a liquid level gauge that measures the amount of oil in the oil sump 30a of the low-stage compressor 21 and the middle of the oil return pipe 31. And a control valve for controlling the flow rate of oil flowing through the oil return pipe 31. Then, based on the liquid level data measured by the liquid level gauge, when the liquid level is higher than the predetermined value, the flow rate of the control valve is reduced, and when the liquid level is lower than the predetermined value, the flow rate of the control valve is reduced. Control to increase.

The multistage compression system of Modification 1C includes a liquid level gauge and a control valve, and the oil return pipe 31 can be used to feedback control the amount of oil in the low stage compressor 21. The multistage compression system 20 of Modification 1C has the same characteristics as the multistage compression system 20 of the first embodiment.

<Second Embodiment>
(5) Oil guide of the low-stage compressor 21 of the second embodiment In the first embodiment, the oil that flows through the oil return pipe 31 and is introduced into the container 30 collides, and the oil sump 30a side below the container 30 is provided. The oil guide directed to was part of the insulator 47 of the motor 40. In the second embodiment, as shown in FIG. 6, a part of the insulator extends downward. The insulator 47 and the extended portion 47a of this insulator serve as an oil guide. The extension portion is a plate-shaped member that extends vertically. Other configurations are the same as those in the first embodiment.

In the second embodiment, as described above, since the extended portion 47a in which a part of the insulator is extended functions as an oil guide, more oil from the oil return pipe is made to collide, and the direction of the oil sump is increased. Can be turned to.

As a modified example of the second embodiment, instead of using the extension portion 47a of the insulator, a completely different component may be arranged inside the container 30 as an oil guide. However, in this case, the number of parts increases and it is necessary to fix a new oil guide to the oil passage.

<Third Embodiment>
(6) Oil Guide of Low-Stage Compressor 21 of Third Embodiment In the first and second embodiments, the oil guide is one component of the motor 40 or an extension of one component. In the third embodiment, as shown in FIG. 7, the extended portion 31p of the oil return pipe 31 into the container 30 serves as an oil guide. The extension portion 31p may be integral with the oil return pipe 31 or may be a separate member. Other configurations of the third embodiment are similar to those of the first embodiment. The oil guide of the third embodiment also exhibits the same effect as the oil guide of the first embodiment.

While the embodiments of the present disclosure have been described above, it will be understood that various changes in form and details can be made without departing from the spirit and scope of the present disclosure described in the claims. ..

1 Refrigerator 2 Heat Source Side Heat Exchanger 3 Bridge Circuit 4 Utilization Side Heat Exchanger 5 Four-way Switching Valve 6 Receiver 7 Economizer Heat Exchanger 8, 9 Expansion Mechanism 12 Intermediate Injection Pipe 15 Intermediate Pressure Refrigerant Pipe 15b Confluence of Intermediate Injection Passage 20 multi-stage compression system 21 low-stage compressor 22 first accumulator 23 high-stage compressor 24 second accumulator 25 oil separator 26 intercooler 30 container 31 oil return pipe 31a pressure reducer 31p extended part of oil return pipe 32 oil discharge pipe 40 Motor 47 Insulator 47a Insulator extension 50 Compressor 71 First compression chamber 72 Second compression chamber 58a, 58b Muffler 58c, 58d Discharge hole

Japanese Patent Laid-Open No. 2008-261227

Claims (7)

A multi-stage compression system (20) utilizing refrigerant and oil,
A low-stage compressor (21) for compressing the refrigerant,
A high-stage compressor (23) for further compressing the refrigerant compressed by the low-stage compressor,
An oil return pipe (31) for returning the oil discharged from the high-stage compressor to the low-stage compressor,
And the low-stage compressor is
A compression unit (50) for compressing the refrigerant,
A motor (40) for driving the compression unit, the motor (40) arranged above the compression unit;
A container (30) for containing the compression unit and the motor,
An oil guide (47, 47a, 31p) arranged in the container so as to face the outlet of the oil return pipe;
Has,
Multi-stage compression system. The angle of the oil introduction portion of the oil return pipe into the container is arranged so that the angle is within 15° from the horizontal.
The multi-stage compression system according to claim 1. The oil guide is arranged within 25% of the inner diameter D of the horizontal cross section of the container from the inner circumference of the container,
The multi-stage compression system according to claim 1. The oil guide is a plate-shaped member that extends vertically.
The multi-stage compression system according to claim 1. The motor (40) includes an insulator (47),
The oil guide (47a) is a portion that is continuous with the insulator and extends downward from the insulator.
The multi-stage compression system according to claim 4. The motor includes a stator (41),
The oil guide is an outer surface of the stator,
The multi-stage compression system according to claim 1. The oil guide (31p) is a part of a pipe through which the oil passes, and is a bent part of the pipe.
The multi-stage compression system according to claim 1.

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