JP6791234B2 - Multi-stage compression system - Google Patents

Description

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

In the refrigeration system, a multi-stage 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 the oil is not extremely unevenly distributed in one compressor.

In Patent Document 1 (Japanese Unexamined Patent Publication No. 2008-261227), in order to keep the height of the oil level of the compressors on the lower stage side and the upper stage side at a constant height, the oil was discharged by the compressor on the higher stage side. It has been considered to return the oil to the refrigerant suction side of the compressor on the lower stage side.

During operation, the compressor of the refrigerating device is repeatedly heated and cooled in accordance with changes in the surrounding environment and the operating load. Comparing the piston and cylinder of a compressor, the heat capacity of the piston is smaller, so the piston is easily heated and cooled, and expands and contracts. On the other hand, since the cylinder has a relatively large heat capacity, the temperature change is small and the deformation is small. If the expansion and contraction amounts of the two are different, a problem may occur in the fitting of the two, which may hinder the movement of the piston.

The multi-stage compression system of the first aspect uses a refrigerant and oil. The multi-stage compression system includes 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 is not only the oil directly discharged from the high-stage compressor, but also the oil once discharged from the high-stage compressor to other equipment, for example, an oil separator. including. Further, the low-stage compressor has a compression unit, a motor, and a container. The compression unit compresses the refrigerant. The motor drives the compression unit. The container houses the compression unit and the motor. The compression unit has a piston and a cylinder. The piston is driven by a motor. The cylinder houses the piston. The oil return pipe is connected to the container. The connection position of the oil return pipe to the container is a position where the oil flowing through the oil return pipe is applied to the cylinder or a member in contact with the upper and lower parts of the cylinder. Here, the members that are in contact with the top and bottom of the cylinder include a member that is in direct contact with the cylinder and a member that is in contact with the member that is in direct contact with the cylinder.

In the multi-stage compression system of the first aspect, the oil having a high temperature from the oil return pipe can be applied to the cylinder or the members in contact with the upper and lower sides of the cylinder, so that the cylinder having a relatively large heat capacity can be heated. Therefore, the temperature difference between the cylinder and the piston can be suppressed.

The multi-stage compression system of the second aspect is the system of the first aspect, and the motor is arranged above the compression part.

The multi-stage compression system of the third aspect is the system of the first aspect or the second aspect, and the compression part further has a vane. The vane partitions the space between the piston and the cylinder. The connection position of the oil return pipe to the container is 120 in the rotation direction of the motor, with the direction from the center of rotation of the motor to the center of the notch for accommodating the vanes on the inner circumference of the cylinder as 0 ° in the top view. It is in the range up to °.

The multi-stage compression system of the third aspect can heat the cylinder near the suction hole of the compression chamber. Therefore, it is possible to heat the cylinder near the piston, which is heated by the suction refrigerant, and it is easy to eliminate the temperature difference between the two.

The multi-stage compression system of the fourth aspect is any of the systems of the first aspect to the third aspect, and the oil flowing through the oil return pipe is applied to the cylinder or the members in contact with the upper and lower parts of the cylinder from above. The oil return pipe is connected to the container.

The multi-stage compression system of the fourth aspect can heat the cylinder over a large area.

The multi-stage compression system of the fifth aspect is any of the systems of the first aspect to the third aspect, and the connection position of the oil return pipe to the container is the same height as the cylinder.

In the multi-stage compression system of the fifth aspect, the side surface of the cylinder can be heated with oil. The cylinder can be heated directly, facilitating control of the cylinder temperature.

The multi-stage compression system of the sixth aspect is the system of the fifth aspect, and the tip of the oil return pipe extends closer to the cylinder than the connection position to the container.

In the multi-stage compression system of the sixth aspect, since the tip of the oil return pipe extends closer to the cylinder than the connection position to the container, the cylinder can be heated more reliably.

The multi-stage compression system of the seventh aspect is the system of the fifth or sixth aspect, and the oil outlet in the container of the oil return pipe is provided to face the cylinder or a member in contact with the upper and lower parts of the cylinder. There is.

In the multi-stage compression system of the seventh aspect, since the oil outlet in the container of the oil return pipe is arranged so as to face the vicinity of the cylinder, it is possible to more reliably collide the hot oil with the vicinity of the cylinder. It is possible.

It is a refrigerant circuit diagram of the refrigerating apparatus 1 of 1st Embodiment. It is a vertical sectional view of the low-stage compressor 21 of 1st Embodiment. It is an AA sectional view of the low-stage compressor 21 of 1st Embodiment. It is BB sectional view of the low-stage compressor 21 of 1st Embodiment. It is a CC sectional view of the low-stage compressor 21 of 1st Embodiment. It is a vertical sectional view of the low-stage compressor 21 of the modification 1A. It is a vertical cross-sectional view of the low-stage compressor 21 of the modification 1B. It is a vertical sectional view of the low-stage compressor 21 of the modification 1C.

<First Embodiment>
(1) Refrigerant circuit of refrigerating device 1 (1-1) Overall refrigerant circuit of refrigerating device 1 The refrigerant circuit configuration of refrigerating device 1 of the first embodiment is shown in FIG. The refrigerating device 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 a supercritical region. The freezing device 1 of the present embodiment can be used for an air conditioner for heating and cooling, an air conditioner dedicated to cooling, a water cooler / heater, a refrigerator, a freezing storage device, and the like.

The refrigerating device 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 user side heat exchanger 4, and an economizer. It has 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 in which direction the refrigerant from the multi-stage compression system 20 flows, the heat source side heat exchanger 2 or the user side heat exchanger 4. For example, when the refrigerating device 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, the pipe 11, and the check valve 11e of the bridge circuit 3. The liquid refrigerant continues to flow from the receiver 6 through the pipe 11, is depressurized by the expansion mechanism 9, and goes to the user side heat exchanger 4 (evaporator) via the check valve 3c of the bridge circuit 3. The refrigerant heated by the user-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 is from the four-way switching valve 5 to the user 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 check valve 3d, the heat exchanger 4 (evaporator) on the user side, and the four-way switching valve 5 flow in this order.

The economizer heat exchanger 7 is arranged between the receiver 6 and the expansion mechanism 9 in the middle of the refrigerant pipe 11. At the branch 11a of the pipe 11, a part of the refrigerant branches, and the expansion mechanism 8 reduces the pressure to an intermediate pressure. 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 confluence portion 15b of the multi-stage compression system 20 via the intermediate injection pipe 12. Further, the gas component of the refrigerant from the receiver 6 joins the intermediate injection pipe 12 via the pipe 19.

(1-2) Flow of Refrigerant and Oil in Multistage Compression System 20 As shown in FIG. 1, the multistage compression system 20 of the present embodiment includes a first accumulator 22, a low stage compressor 21, an intercooler 26, and the like. It includes a second accumulator 24, a high-stage compressor 23, an oil separator 25, and a decompressor 31a.

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 are provided with 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 the refrigerant and the 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 (utility side heat exchanger 4 or heat source side heat exchanger 2) flows to the first accumulator 22 via the refrigerant pipe 13. The gas refrigerant of 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 an intermediate pressure refrigerant with, for example, outdoor air. The intercooler 26 may be arranged adjacent to the heat source side heat exchanger 2 and exchange heat with air by a common fan. The intercooler 26 enhances the efficiency of the refrigerating apparatus 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 merging portion 15b of the intermediate injection pipe 12 with 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 lowers the temperature of the refrigerant flowing through the pipe 15 and improves the efficiency of the refrigerating device 1.

The multi-stage compression system 20 of the present embodiment further includes an oil discharge pipe 32 for discharging excess oil from 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 connection portion of the oil discharge pipe 32 with the intermediate pressure refrigerant pipe 15 is a portion downstream of the intercooler 26 and the confluence portion 15b of the intermediate injection.

The refrigerant sent to the second accumulator 24 by the pipe 15 is introduced into the high-stage compressor 23 from the suction pipe 16. The refrigerant is compressed in the high-stage compressor 23 to 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 for discharging excess oil from 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 decompressor 31a 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. Specifically, for the decompressor 31a, for example, a capillary tube is used.

An oil cooler (not shown) may be arranged in the middle of the oil return pipe 31. The oil cooler is a heat exchanger that cools the oil flowing through the oil return pipe 31 with, for example, outdoor air. The oil cooler is for cooling the high temperature oil discharged from the oil separator 25. Also in this embodiment, it can be used when the temperature of the oil is too high, the cylinder is sufficiently heated during operation, and it is better to return the low temperature oil. The oil cooler may be arranged in the vicinity of the heat source side heat exchanger 2, for example, and may exchange heat with air by a common fan. The oil cooler may be arranged, for example, under 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 oils include PAG (polyalkylene glycols) and POE (polyester esters).

The refrigerating apparatus 1 of the present embodiment performs two-stage compression with two compressors. Two or more stages of compression may be performed using three or more compressors. Further, three or more stages of compression may be performed.

(2) Configuration of compressor and piping and device connected to the compressor The low-stage compressor 21 and high-stage compressor 23 of this 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 described in detail here.

FIG. 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 of FIG. 2, respectively. However, in the BB sectional view of FIG. 4, the portion of the motor 40 is not described.

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 the 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 pressure is maintained in the high-stage compressor 23 during operation. The lower part inside the container 30 is an oil sump 30a for storing oil (lubricating oil). Although the liquid level of the oil sump 30a is tentatively shown in FIG. 2, the height of the liquid level of the oil sump 30a is not constant and increases or decreases during the operation of the compressor.

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

(2-2) Motor 40
The motor 40 is a brushless DC motor. The motor 40 generates power to rotate the crankshaft 60 about the rotation shaft RA. The motor 40 is arranged in the space inside the container 30, below the space above, 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 windings are wound around the insulator 47.

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

The spindle portion 61 is a portion concentric with the rotation shaft RA. The spindle 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 symmetrical 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 pumps 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 portion 50.

(2-4) Compression unit 50
The compression unit 50 is a two-cylinder type compression mechanism. The compression unit 50 includes 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, front mufflers 58a and 58b, and an annular member 53a.

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

(2-4-1) Flow of refrigerant compressed in the first compression chamber 71 and the first compression chamber 71 The first compression chamber 71 has a first cylinder 51 and a first cylinder 51 as shown in FIG. 2 or 5. 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 62a, and the first piston 56. The suction hole 14e communicates the first compression chamber 71 with the inside of the suction pipe 14a. A pair of bushes 56c are accommodated in the bush accommodating 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 blades 56b are sandwiched between 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 side of the blade moving hole 57b and the side of the bush accommodating hole 57a.

As shown in FIG. 2, the front head 53 is fixed to the inside of the container 30 by the 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. The refrigerant further moves to the second front muffler space 58f between the two front mufflers 58a and 58b, and then is below the motor 40 from the discharge holes 58c and 58d (see FIG. 4) provided in the front muffler 58b. It is blown out into the space of.

The refrigerant compressed and blown out 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 out from the discharge pipe 15a, and heads for 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 of the compressors may be a one-cylinder type compressor.

(2-4-2) Flow of refrigerant compressed in the second compression chamber 72 and the second compression chamber 72 The second compression chamber 72 includes a second cylinder 52, a second piston 66, a rear head 55, and a 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 thereof will be omitted. However, in the case of the refrigerant compressed in the second compression chamber 72, it is once sent to the rear muffler space 55a provided in the rear head 55, and then further sent to the front muffler spaces 58e and 58f by the front mufflers 58a and 58b. However, it is different.

(2-5) Connection Position of Low Stage Compressor 21, Oil Return Pipe 31 and Oil Discharge Pipe 32 In the multistage compression system 20 of the present embodiment, as shown in FIG. 2, the oil return pipe 31 is a container. It is connected to the space of 30 below the motor 40 and above the compression section 50.

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 upper member of the compression unit 50, and further, the oil sump 30a in the lower part inside the container 30. Join in. Here, the member on the upper part of the compression portion is a member that is on the cylinder 51 and is in direct or indirect contact with the cylinder 51. Specifically, the front head 53, the front mufflers 58a and 58b, and the annular member 53a.

In other words, the cylinders 51 and 52 can be indirectly heated by the hot oil separated by the oil separator 25.

Next, the connection position of the oil return pipe 31 to the container in the top view will be described with reference to FIG.

First, the axis RA is the center. Then, the straight line passing through the center of the shaft RA and the bush accommodating hole 57a is set to 0 ° as a reference. In other words, the direction of the center of the notch for accommodating the vane (blade 56b) on the inner circumference of the cylinder 51 is 0 °. Let α be the angle from this reference direction to the center of the portion to which the oil return pipe 31 is connected in the top view. In this embodiment, α is 0 ° or more and 120 ° or less. More preferably, it is 30 ° or more and 90 ° or less.

Since the oil return pipe 31 of the present embodiment is connected to the container 30 so that α is 0 ° or more and 120 ° or less, the oil from the oil return pipe 31 is applied to this angle range above the compressor 50. Introduced in. Therefore, the vicinity of the suction hole 14e of the cylinder 51 can be heated.

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

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

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 level of the oil sump 30a.

The inner diameter of the oil discharge pipe 32 is equivalent to the inner diameter of the oil return pipe 31. Use a discharge pipe smaller than the inner diameter of the discharge pipe 15a. 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 looking at the planar positional relationship between the oil discharge pipe 32 and the oil return pipe 31, the connection position of the oil discharge pipe 32 to the container 30 is the connection position of the oil return pipe 31 to the container 30. It is a position 90 ° or more away from the connection position in the rotation direction of the motor 40 (the direction of the arrow in FIG. 5). It is preferably a position separated by 180 ° or more.

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 by the oil discharge pipe 32. It is possible to reduce the amount of oil discharged to the outside of the container 30 and easily realize the leveling of oil in 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 equivalent 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 multi-stage 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 once store the flowing refrigerant, prevent the liquid refrigerant from flowing to the compressor, and prevent the liquid compression of the compressor. Since the configurations of the first accumulator 22 and the second accumulator 24 are almost the same, 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 collect in the lower part of the accumulator. In the suction tubes 14a and 14b, small holes 14c and 14d are formed below the inside of the accumulator. The diameters of the holes 14c and 14d are, for example, 1 mm to 2 mm. The oil, together with the liquid refrigerant, gradually joins the gas refrigerant through the holes 14c and 14d and is sent to the compression chamber.

(3) Features (3-1)
The multi-stage compression system 20 of the present 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 by the high-stage compressor to the low-stage compressor 21. The low-stage compressor 21 includes a compression unit 50, a motor 40, and a container 30. The container houses the compression unit 50 and the motor 40. The compression unit 50 has a piston and a cylinder. The cylinder houses the piston.

In the present embodiment, the oil return pipe 31 is connected to the container 30 so that the oil flowing through the oil return pipe 31 is applied to the cylinders 51, 52 or the members in contact with the upper and lower sides of the cylinder. Here, the members that are in contact with the cylinders 51 and 52 above and below include members that are in direct contact with the cylinders 51 and 52 and members that are in direct contact with the cylinders 51 and 52. Specifically, the front head 53, the middle plate 54, the rear head 55, the front mufflers 58a and 58b, and the annular member 53a. Further, here, when the oil is applied, not only when the oil ejected from the oil return pipe 31 directly collides with these members, but also when it collides with another object once and then collides with these members. Including cases. Another is the insulator 47 in this embodiment.

In the multi-stage compression system 20 of the present embodiment, the high temperature oil from the oil return pipe 31 can be applied to the cylinders 51 and 52 or the members in contact with the upper and lower sides of the cylinders, so that the cylinders 51 and 52 having a relatively large heat capacity are heated. can do. As a result, the temperature difference between the pistons 56 and 66 and the cylinders 51 and 52 can be suppressed.

(3-2)
In the multi-stage compression system 20 of the present embodiment, the characteristics of the attachment position of the oil return pipe 31 to the container 30 in the top view are as follows. The connection position of the oil return pipe 31 to the container 30 is from the center of rotation of the motor to 120 ° in the rotation direction of the motor, with the direction of the center of the notch for accommodating the vanes on the inner circumference of the cylinder as 0 °. Is within the range of.

The multi-stage compression system 20 of the present embodiment can heat the cylinder near the suction hole 14e of the compression chamber. Therefore, it is possible to heat the cylinder near the piston, which is heated by the suction refrigerant, and it is easy to eliminate the temperature difference between the two.

(3-3)
In the multi-stage compression system 20 of the present embodiment, the oil return pipe 31 is connected to the container 30 so that the oil flowing through the oil return pipe 31 is applied to the cylinders 51, 52 or a member in contact with the cylinder from above. There is. Here, the members in contact with the cylinder are the front head 53, the front mufflers 58a and 58b, and the annular member 53a.

The multi-stage compression system 20 of the present embodiment can heat the cylinder in a wide area.

(4) Modification example (4-1) Modification example 1A
In the first embodiment, as shown in FIG. 2, the oil return pipe 31 is connected to the container 30 of the low-stage compressor 21, and the oil introduced into the container 30 is above the cylinder 51 in the space inside the container. It fell on the front head 53, the front mufflers 58a and 58b, and the annular member 53a, which are the members of the above. In the modified example 1A, as shown in FIG. 6, the low-stage compressor 21 has a pipe 31p that controls the direction of oil inside the container 30. The pipe 31p may be formed integrally with the oil return pipe 31, or a separate pipe 31p may be connected to the oil return pipe 31 so that the oil flow path is connected. Other configurations of the modified example 1A are the same as those of the first embodiment.

In the multi-stage compression system of the first modification 1A, the oil flow is controlled by the pipe 31p, so that the oil having a higher temperature than the oil return pipe 31 can be more reliably applied to the member in contact with the cylinder. It can be heated efficiently.

(4-2) Modification 1B
The multi-stage compression system of the modified example 1B will be described with reference to the drawings. In FIG. 7, the oil return pipe 31 and the oil discharge pipe 32 are two separate pipes, but they are overlapped and drawn as one pipe. The oil return pipe 31 should be drawn on the right side surface of the container 30 in FIG. 7, but is drawn on the left side surface due to space limitations.

In the multi-stage compression system of the first embodiment and the modified example 1A, the oil return pipe 31 is connected to the container 30 so that the oil having a high temperature from the oil return pipe 31 is applied to the member in contact with the cylinder from above. Was there. In other words, the connection position of the oil return pipe 31 was above the member in contact with the cylinder. On the other hand, in the modified example 1B, as shown in FIG. 7, the connection position of the oil return pipe 31 to the container 30 is the same height as the cylinder 51. Other configurations are the same as those in the first embodiment.

In the multi-stage compression system 20 of the modification 1B, the side surface of the cylinder 51 can be heated with oil. The cylinder 51 can be directly heated, and the temperature of the cylinder 51 can be easily controlled.

Further, in the multi-stage compression system 20 of the modified example 1B, the oil outlet in the container 30 of the oil return pipe 31 is provided so as to face the cylinder 51.

In the multi-stage compression system 20 of the modification 1B, since the oil outlet in the container 30 of the oil return pipe 31 is arranged to face the vicinity of the cylinder, the high temperature oil collides with the vicinity of the cylinder more reliably. It is possible to make it.

(4-3) Modification 1C
The multi-stage compression system of the modified example 1C will be described with reference to the drawings. In FIG. 8, the oil return pipe 31 and the oil discharge pipe 32 are two separate pipes, but they are overlapped and drawn like one pipe. Further, the oil return pipe 31 and its extended pipe 31q should be drawn on the right side surface of the container 30 in FIG. 8, but are drawn on the left side surface due to space limitations.

In the modified example 1B, as shown in FIG. 7, the connection position of the oil return pipe 31 to the container 30 was the same height as the cylinder 51. Then, the oil introduced from the oil return pipe 31 was released into the space inside the container 30. As shown in FIG. 8, the low-stage compressor 21 of the modified example 1C has a pipe 31q that is connected to the oil return pipe 31 and guides the flow of oil inside the container 30. The pipe 31q may be formed integrally with the oil return pipe 31, or a separate pipe 31q may be connected to the oil return pipe 31 so that the oil flow path is connected.

In the multi-stage compression system 20 of the modified example 1C, since the oil outlet in the container of the oil return pipe is arranged so as to face the vicinity of the cylinder, the high temperature oil collides with the cylinder 51 more reliably. Is possible.

(4-4) Modification 1D
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 1D, the oil return pipe 31 directly returns the oil discharged from the high-stage compressor 23 to the low-stage compressor 21. Other configurations are the same as those in the first embodiment.

The multi-stage compression system 20 of the modified example 1D also has the same features (3-1) to (3-3) as the multi-stage compression system 20 of the first embodiment. However, in the case of the modified example 1D, 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 compared with the case of passing through the oil separator 25 of the first embodiment. The amount of refrigerant mixed in will increase.

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.

Although the embodiments of the present disclosure have been described above, it will be understood that various modifications of the forms and details are possible without departing from the purpose and scope of the present disclosure described in the claims. ..

1 Refrigerator 2 Heat source side heat exchanger 3 Bridge circuit 4 User side heat exchanger 5 Four-way switching valve 6 Receiver 7 Economizer heat exchanger 8, 9 Expansion mechanism 20 Multi-stage compressor 21 Low-stage compressor 22 First accumulator 23 High-stage Compressor 24 2nd accumulator 25 Oil separator 26 Intercooler 30 Container 31 Oil return pipe 31a Decompressor 31p, 31q Pipe for extension of oil return pipe 32 Oil discharge pipe 40 Motor 47 Insulator 50 Compressor 51 1st cylinder 52 No. 2 cylinder 53 front head 54 middle plate 55 rear head 56 first piston 56b blade (vane)
58a, 58b Front muffler 66 2nd piston

Japanese Unexamined Patent Publication No. 2008-261227

Claims (7)

A multi-stage compression system (20) that uses a refrigerant and oil.
A low-stage compressor (21) that compresses the refrigerant, and
A high-stage compressor (23) that further compresses the refrigerant compressed by the low-stage compressor, and
An oil return pipe (31) for returning the oil discharged by the high-stage compressor to the low-stage compressor, and
The low-stage compressor is equipped with
A compression unit (50) that compresses the refrigerant, and
The motor (40) that drives the compression unit and
A container (30) that accommodates the compression unit and forms a high-pressure space that accommodates the motor and is filled with the compressed refrigerant .
Have,
The compression unit is
The pistons (56, 66) driven by the motor and
Cylinders (51, 52) accommodating the piston and
Have,
The oil return pipe is such that the oil flowing through the oil return pipe is applied to the cylinder or members (53, 54, 55, 53a, 58a, 58b) in contact with the upper and lower sides of the cylinder in the high pressure space. Connected to the container,
Multi-stage compression system. The motor is arranged above the compression unit.
The multi-stage compression system according to claim 1. The compression unit further
A vane (56b) that partitions the space between the piston and the cylinder,
Have,
The connection position of the oil return pipe to the container is 0 ° from the center of rotation of the motor to the center of the notch for accommodating the vane on the inner circumference of the cylinder in the top view. Within the range of up to 120 ° in the direction of rotation of the motor,
The multi-stage compression system according to claim 1 or 2. The oil return pipe is connected to the container so that the oil flowing through the oil return pipe is applied to the cylinder or members in contact with the upper and lower parts of the cylinder from above.
The multi-stage compression system according to any one of claims 1 to 3. The connection position of the oil return pipe to the container is the same height as the cylinder.
The multi-stage compression system according to any one of claims 1 to 3. The tip of the oil return pipe extends closer to the cylinder than the connection position to the container.
The multi-stage compression system according to claim 5. The oil outlet of the oil return pipe in the container is provided so as to face the cylinder or a member in contact with the upper and lower sides of the cylinder.
The multi-stage compression system according to any one of claims 1 to 3 .

Images