WO2023058106A1

WO2023058106A1 - Compressor

Info

Publication number: WO2023058106A1
Application number: PCT/JP2021/036773
Authority: WO
Inventors: 直人上中居
Original assignee: 三菱電機株式会社
Priority date: 2021-10-05
Filing date: 2021-10-05
Publication date: 2023-04-13

Abstract

This compressor is provided with: a casing having a low-pressure space and a high-pressure space having pressure higher than that of the low-pressure space; a motor accommodated in the casing; a screw shaft that is fixed to the motor and rotationally driven by the motor; a screw rotor that is fixed to the screw shaft, rotates with rotation of the screw shaft, and has a compression room that compresses a refrigerant flowing in from the low-pressure space and flows out the compressed refrigerant to the high-pressure space; and a slide valve that is arranged along an outer peripheral surface of the screw rotor and changes an inner volume ratio showing the ratio of a suction volume to an ejection volume of the compression room by sliding along an axial direction of the screw shaft. The slide valve has a valve body part having a bypass hole that connects the low-pressure space to the high-pressure space, and a valve body that is provided in the valve body part and brings the bypass hole into an open state when the pressure of the high-pressure space exceeds a threshold.

Description

compressor

The present disclosure relates to a compressor that compresses refrigerant.

Conventionally, a screw compressor is known as a compressor that compresses and discharges a fluid such as a refrigerant. A screw compressor is provided with a motor, a screw shaft, and a screw rotor inside a casing. When the screw shaft is rotated by the motor, the screw rotor provided on the screw shaft also rotates. A screw groove is formed in the screw rotor, and a gate rotor that meshes with the screw groove is provided. A compression chamber for compressing the refrigerant is formed between the screw groove of the screw rotor and the gate rotor. When the refrigerant that has flowed from the low-pressure space flows into the compression chamber, the volume of the compression chamber formed between the screw groove of the screw rotor and the gate rotor is reduced, thereby compressing the refrigerant. The compressed refrigerant is discharged into the high pressure space. If the timing for starting the discharge of the compressed refrigerant is fixed, there is a risk that the compression loss will increase due to overcompression or insufficient compression depending on the operating conditions.

For the purpose of solving this problem, Patent Document 1 discloses a screw-type compressor equipped with a slide valve that adjusts the discharge start timing to vary the internal volume ratio Vi, which is the ratio of the suction volume to the discharge volume. disclosed. A slide valve is also called a variable Vi valve. In a screw compressor, a compression chamber is formed by a screw groove of a screw rotor, a gate rotor, a casing, and a slide valve. The internal volume is adjusted by moving the slide valve in the axial direction of the screw rotor to change the discharge start position of the high-pressure refrigerant in the compression chamber. In Patent Document 1, a system in which the slide valve is connected to the piston is adopted. A high pressure always acts on the front chamber of the piston, and a high pressure and a low pressure act on the back chamber of the piston, respectively, so that the pressure difference moves the slide valve and changes the internal volume.

JP 2011-43084 A

However, the compressor disclosed in Patent Document 1 requires a separate safety valve. A safety valve (pressure relief valve) is sometimes installed in a compressor to prevent damage to the compressor when the internal high pressure becomes abnormally high. In Patent Document 1, in order to install the safety valve, an installation space must be secured separately.

The present disclosure has been made to solve the above problems, and provides a compressor that does not require a mounting space for installing a safety valve.

A compressor according to the present disclosure includes a casing in which a low-pressure space and a high-pressure space having a higher pressure than the low-pressure space are formed, a motor housed inside the casing, and a screw fixed to the motor and driven to rotate by the motor. a shaft, a screw rotor formed with a compression chamber that is fixed to the screw shaft, rotates with the rotation of the screw shaft, compresses the refrigerant flowing from the low-pressure space and flows out to the high-pressure space, and the outer peripheral surface of the screw rotor. and a slide valve arranged along the low-pressure space for changing the internal volume ratio, which is the ratio of the suction volume to the discharge volume of the compression chamber, by sliding along the axial direction of the screw shaft. and a valve body formed with a bypass hole connecting the high-pressure space and a valve body provided in the valve body part to open the bypass hole when the pressure in the high-pressure space exceeds a threshold value.

According to the present disclosure, the slide valve has a valve body portion and a valve body. A bypass hole connecting the low-pressure space and the high-pressure space is formed in the valve body portion, and the valve body opens and closes the bypass hole. That is, the valve body portion and the valve body have the function of a safety valve that prevents damage to the compressor when the internal high pressure becomes abnormally high. Since the slide valve thus functions as a safety valve, there is no need to install a separate safety valve. Therefore, no mounting space is required for installing the safety valve.

1 is a circuit diagram showing an air conditioner according to Embodiment 1. FIG. 1 is a cross-sectional view showing a compressor according to Embodiment 1; FIG. FIG. 2 is a cross-sectional view showing the slide valve according to Embodiment 1; FIG. 4 is a schematic diagram showing the position of the valve body in Embodiment 1; FIG. 2 is a cross-sectional view showing the slide valve according to Embodiment 1;

Hereinafter, embodiments of the compressor of the present disclosure will be described with reference to the drawings. It should be noted that the present disclosure is not limited by the embodiments described below. In addition, in the following drawings, including FIG. 1, the size relationship of each constituent member may differ from the actual one. In addition, in the following description, directional terms are used as appropriate to facilitate understanding of the present disclosure, but this is for the purpose of describing the present disclosure, and these terms are intended to limit the present disclosure. isn't it. Directional terms include, for example, "up", "down", "right", "left", "front" or "back". In some drawings, hatching in cross-sectional views is partially omitted.

Embodiment 1.
FIG. 1 is a circuit diagram showing an air conditioner 100 according to Embodiment 1. FIG. As shown in FIG. 1 , an air conditioner 100 is a device that adjusts air in an indoor space, and includes an outdoor unit 30 and an indoor unit 40 connected to the outdoor unit 30 . The outdoor unit 30 is provided with a compressor 1 , a channel switching device 52 , an outdoor heat exchanger 53 , an outdoor fan 54 and an expansion section 55 . The indoor unit 40 is provided with an indoor heat exchanger 56 and an indoor fan 57 .

The compressor 1, the flow switching device 52, the outdoor heat exchanger 53, the expansion section 55, and the indoor heat exchanger 56 are connected by refrigerant pipes 51 to form a refrigerant circuit 50 through which the refrigerant flows. The compressor 1 sucks a low-temperature, low-pressure refrigerant, compresses the sucked refrigerant, converts it into a high-temperature, high-pressure refrigerant, and discharges it. The flow switching device 52 switches the direction in which the refrigerant flows in the refrigerant circuit 50, and is, for example, a four-way valve. The outdoor heat exchanger 53 exchanges heat, for example, between outdoor air and refrigerant. The outdoor heat exchanger 53 acts as a condenser during cooling operation and acts as an evaporator during heating operation.

The outdoor blower 54 is a device that sends outdoor air to the outdoor heat exchanger 53. The expansion part 55 is a pressure reducing valve or an expansion valve that reduces the pressure of the refrigerant to expand it. The expansion part 55 is, for example, an electronic expansion valve whose opening is adjusted. The indoor heat exchanger 56 exchanges heat, for example, between indoor air and refrigerant. The indoor heat exchanger 56 acts as an evaporator during cooling operation, and acts as a condenser during heating operation. The indoor air blower 57 is a device that sends indoor air to the indoor heat exchanger 56 .

(Operating mode, cooling operation)
Next, operation modes of the air conditioner 100 will be described. First, the cooling operation will be explained. In the cooling operation, the refrigerant sucked into the compressor 1 is compressed by the compressor 1 and discharged in a high-temperature and high-pressure gas state. The high-temperature and high-pressure gaseous refrigerant discharged from the compressor 1 passes through the flow switching device 52 and flows into the outdoor heat exchanger 53 acting as a condenser. It is heat-exchanged with outdoor air sent by 54 and condenses and liquefies. The condensed liquid refrigerant flows into the expansion section 55, where it is expanded and decompressed to become a low-temperature, low-pressure gas-liquid two-phase refrigerant. Then, the gas-liquid two-phase refrigerant flows into the indoor heat exchanger 56 acting as an evaporator, where it exchanges heat with the indoor air sent by the indoor blower 57 to evaporate and become gas. do. At this time, the indoor air is cooled, and cooling is performed in the room. The vaporized low-temperature, low-pressure gaseous refrigerant passes through the flow switching device 52 and is sucked into the compressor 1 .

(Operating mode, heating operation)
Next, the heating operation will be explained. In the heating operation, the refrigerant sucked into the compressor 1 is compressed by the compressor 1 and discharged in a high-temperature and high-pressure gas state. The high-temperature and high-pressure gaseous refrigerant discharged from the compressor 1 passes through the flow switching device 52 and flows into the indoor heat exchanger 56 acting as a condenser. It is heat exchanged with the room air sent by 57 and condenses and liquefies. At this time, the indoor air is warmed, and heating is performed in the room. The condensed liquid refrigerant flows into the expansion section 55, where it is expanded and decompressed to become a low-temperature, low-pressure gas-liquid two-phase refrigerant. Then, the gas-liquid two-phase refrigerant flows into the outdoor heat exchanger 53 acting as an evaporator, where it is heat-exchanged with the outdoor air sent by the outdoor fan 54 to evaporate and gasify. do. The vaporized low-temperature, low-pressure gaseous refrigerant passes through the flow switching device 52 and is sucked into the compressor 1 .

FIG. 2 is a cross-sectional view showing the compressor 1 according to Embodiment 1. FIG. Next, the compressor 1 will be explained in detail. The compressor 1 compresses a refrigerant, and as shown in FIG. , a gate rotor 6 and a slide valve 10 .

(Casing 2)
The casing 2 forms an outer shell of the compressor 1 and has a cylindrical shape. Inside the cylindrical wall 2a of the casing 2, a low pressure space 13 located on the motor 4 side and a high pressure space 14 located on the opposite side to the motor 4 side are formed. A low-temperature, low-pressure gaseous refrigerant flows into the low-pressure space 13 . The high-pressure space 14 is a space having a higher pressure than the low-pressure space 13, and a high-temperature and high-pressure gaseous refrigerant flows therein. The high-pressure space 14 is formed with a discharge port 8 through which the refrigerant is discharged from the compression chamber 12 formed by the screw rotor 3 and the gate rotor 6, and a discharge passage 7 through which the refrigerant discharged from the discharge port 8 flows. there is The casing 2 has a high-low pressure partition wall 70 that protrudes inward. The high-low pressure partition wall 70 partitions the low-pressure space 13 and the high-pressure space 14 . A semi-cylindrical slide valve housing groove 9 for housing the slide valve 10 is formed along the bearing housing 20 and the screw rotor 3 inside the casing 2 .

(Bearing housing 20)
The bearing housing 20 is provided inside the casing 2 on the side of the high-pressure space 14 and accommodates the bearing 21 .

(Bearing 21)
The bearing 21 is a cylindrical member, and the screw shaft 5 is rotatably supported by inserting the screw shaft 5 into the inner peripheral portion thereof.

(motor 4)
The motor 4 is provided inside the casing 2, the number of revolutions of which is changed by inverter control or the like, and has a motor stator 4a and a motor rotor 4b. The motor stator 4 a has a cylindrical shape, and the outer peripheral surface thereof is fixed to the cylindrical wall 2 a of the casing 2 . A coil (not shown) to which power is supplied from an external power supply (not shown) is wound around the motor stator 4a. The motor rotor 4b has a cylindrical shape, and is arranged with a space in the inner peripheral portion of the motor stator 4a. The motor rotor 4b rotates when power is supplied to the motor stator 4a.

(Screw shaft 5)
The screw shaft 5 is a cylindrical member provided in the center of the casing 2 inside the casing 2 and connects the motor 4 and the screw rotor 3 . The screw shaft 5 is fixed to the motor 4 and driven to rotate by the motor 4 .

(Screw rotor 3)
The screw rotor 3 is fixed to the screw shaft 5 and rotates as the screw shaft 5 rotates. be. The screw rotor 3 is formed with a plurality of screw grooves 3a that are spiral grooves. The screw rotor 3 and the motor rotor 4 b are arranged coaxially with each other, and both are fixed to the screw shaft 5 .

(Gate rotor 6)
A pair of gate rotors 6 are arranged in the radial direction of the screw rotor 3 . The gate rotor 6 has a plurality of radially extending gates 6a, and the gates 6a mesh and engage with the screw grooves 3a of the screw rotor 3. As shown in FIG. A compression chamber 12 in which the refrigerant is compressed is provided between the gate 6a and the screw groove 3a.

(Slide valve 10)
The slide valve 10 is arranged along the outer peripheral surface of the screw rotor 3 and housed in the slide valve housing groove 9 . The slide valve 10 changes the internal volume ratio, which is the ratio of the suction volume to the discharge volume of the compression chamber 12 . The slide valve 10 slides along the axial direction of the screw shaft 5 to change the discharge start position of the refrigerant compressed in the compression chamber 12, thereby freely changing the internal volume in two stages. In addition, the change stage of the internal volume of the slide valve 10 is not limited to two stages, and may be changed in three or more stages or steplessly. The slide valve 10 has a drive mechanism 11, a guide portion 10a, a connecting portion 10b, and a valve body 10c.

The drive mechanism 11 drives the valve body 10c to slide. The guide portion 10a has a guide surface 19 that faces and contacts the bearing housing 20, and guides the valve body 10c to slide in the axial direction. The connecting portion 10b is a rod-shaped member that connects the guide portion 10a and the valve body 10c. The valve body 10c faces the screw rotor 3, forms the compression chamber 12 and the discharge port 8, and is a member that slides in the axial direction.

(Operation of compressor 1)
Next, operation of the compressor 1 will be described. When electric power is supplied to the motor stator 4a, the motor rotor 4b rotates. As a result, the screw shaft 5 fixed to the motor rotor 4b rotates, and the screw rotor 3 fixed to the screw shaft 5 rotates. When the compression chamber 12 and the low-pressure space 13 are connected as the screw rotor 3 rotates, refrigerant flows into the compression chamber 12 from the low-pressure space 13 . When the screw rotor 3 rotates further, the compression chamber 12 and the low pressure space 13 are cut off, and compression starts. As the screw rotor 3 rotates, the volume of the compression chamber 12 formed by the screw rotor 3, the gate rotor 6 and the slide valve 10 decreases, compressing the refrigerant. As the screw rotor 3 rotates further, the compression chamber 12 and the discharge port 8 are connected. As a result, the compressed refrigerant is discharged from the compression chamber 12 to the discharge port 8 .

(Function of safety valve)
3 is a sectional view showing the slide valve 10 according to Embodiment 1. FIG. Next, the function of the safety valve provided in the slide valve 10 will be described. A safety valve is a valve that prevents damage to the compressor 1 when the internal high pressure becomes abnormally high. As shown in FIG. 3 , the valve body 10 c of the slide valve 10 has a valve body portion 18 , a valve body 16 and a spring 17 . The valve body portion 18 is a cylindrical member forming the outer shell of the valve body 10c. A bypass hole 15 connecting the low-pressure space 13 and the high-pressure space 14 is formed in the valve body portion 18 .

The bypass hole 15 has a first hole 15a and a second hole 15b. The first hole 15 a is a hole that is connected to the discharge port 8 in the high pressure space 14 and extends along the axial direction of the screw shaft 5 . The first hole 15 a has a high pressure space side horizontal hole 61 and a low pressure space side horizontal hole 62 . The high-pressure space side horizontal hole 61 is a long hole connected to the high-pressure space 14 . The low-pressure space-side horizontal hole 62 is connected to the high-pressure space-side horizontal hole 61 and the low-pressure space 13 and has a larger diameter than the high-pressure space-side horizontal hole 61 . Since the low-pressure space side hole 62 has a larger diameter than the high-pressure space side hole 61 , the connection portion between the high-pressure space side hole 61 and the low-pressure space side hole 62 forms a step 63 .

The second hole 15b is a hole that extends from the first hole 15a in a direction away from the screw rotor 3 and is connected to the low pressure space 13. That is, the first hole 15a and the second hole 15b intersect perpendicularly. The valve body 16 is provided in the valve body portion 18 and opens the bypass hole 15 when the pressure in the high-pressure space 14 exceeds a threshold value. The valve body 16 is arranged at a portion where the first hole 15a and the second hole 15b are connected. Here, as shown in FIG. 3, the valve body 16 is inserted into the first hole 15a from the low-pressure space 13 side, and the bypass hole 15 is closed when the tip portion 16a exceeds the second hole 15b. Closed. When the distal end portion 16 a of the valve body 16 comes into contact with the step 63 , the bypass hole 15 is closed.

FIG. 4 is a schematic diagram showing the position of the valve body 16 in the first embodiment. As shown in FIG. 4 , the valve body 16 is positioned off the center of the rod of the drive mechanism 11 . This is because the other bypass hole 15 and the valve body 16 are provided at symmetrical positions with respect to the central axis when it is desired to speed up the bypass between the low-pressure space 13 and the high-pressure space 14 . This avoids difficulty in providing another bypass hole 15 or valve element 16 in a space other than the central axis when the bypass hole 15 is provided in the central axis.

FIG. 5 is a cross-sectional view showing the slide valve 10 according to Embodiment 1. FIG. A spring 17 is provided in the valve body portion 18 and biases the valve body 16 in a direction to close the bypass hole 15 . The spring 17 expands and contracts in the axial direction, and as shown in FIG. 3, the valve body 16 closes the bypass hole 15 when the spring 17 is expanded. Thereby, the connection between the high-pressure space 14 and the low-pressure space 13 is cut off. On the other hand, as shown in FIG. 5, the valve body 16 opens the bypass hole 15 when the spring 17 is compressed. Thereby, the high pressure space 14 and the low pressure space 13 are connected. Note that the spring 17 may be an elastic body having a similar function. Further, the spring constant of the spring 17 is determined so as to open and close according to a predetermined differential pressure between the high pressure space 14 and the low pressure space 13 .

The valve body 16 receives the differential pressure between the high-pressure space 14 and the low-pressure space 13 , but normally the valve body 16 closes the bypass hole 15 due to the biasing force of the spring 17 attached to the valve body 16 . Therefore, by adjusting the biasing force of the spring 17, the valve body 16 can be set to open the bypass hole 15 with an arbitrary differential pressure. That is, the slide valve 10 can reduce the high pressure by releasing the high pressure to the low pressure space 13 with an arbitrary differential pressure. Thus, the slide valve 10 has the function of a safety valve.

According to Embodiment 1, the slide valve 10 has the valve body portion 18 and the valve body 16 . A bypass hole 15 connecting the low-pressure space 13 and the high-pressure space 14 is formed in the valve body portion 18 , and the valve body 16 opens and closes the bypass hole 15 . That is, the valve body portion 18 and the valve body 16 have the function of a safety valve that prevents damage to the compressor 1 when the internal high pressure becomes abnormally high. Thus, since the slide valve 10 has the function of a safety valve, it is not necessary to separately install a safety valve. Therefore, a separate mounting space for installing the safety valve is not required.

Although the single-screw compressor 1 is exemplified in the first embodiment, the twin-screw compressor 1 or the open-type compressor 1 may be used. Further, the compressor 1 may be driven by constant-speed driving in which the motor 4 is driven at a constant number of revolutions, or by inverter driving in which the number of revolutions of the motor 4 is controlled.

1 compressor, 2 casing, 2a cylindrical wall, 3 screw rotor, 3a screw groove, 4 motor, 4a motor stator, 4b motor rotor, 5 screw shaft, 6 gate rotor, 6a gate, 7 discharge flow path, 8 discharge port, 9 Slide valve storage groove 10 Slide valve

10a Guide part

10b Connection part

10c Valve body 11 Drive mechanism 12 Compression chamber 13 Low pressure space 14 High pressure space 15 Bypass hole 15a First hole 15b Second hole, 16 valve body, 16a tip, 17 spring, 18 valve body part, 19 guide surface, 20 bearing housing, 21 bearing, 30 outdoor unit, 40 indoor unit, 50 refrigerant circuit, 51 refrigerant piping, 52 flow switching Device, 53 outdoor heat exchanger, 54 outdoor fan, 55 expansion part, 56 indoor heat exchanger, 57 indoor fan, 61 high pressure space side hole, 62 low pressure space side hole, 63 step, 70 high and low pressure partition wall, 100 air harmony machine.

Claims

a casing in which a low-pressure space and a high-pressure space having a higher pressure than the low-pressure space are formed;
a motor housed inside the casing;
a screw shaft fixed to the motor and driven to rotate by the motor;
a screw rotor that is fixed to the screw shaft, rotates with the rotation of the screw shaft, and has a compression chamber that compresses the refrigerant flowing in from the low-pressure space and causes it to flow out to the high-pressure space;
a slide valve arranged along the outer peripheral surface of the screw rotor for changing the internal volume ratio, which is the ratio of the suction volume to the discharge volume of the compression chamber, by sliding along the axial direction of the screw shaft; prepared,
The slide valve is
a valve body portion formed with a bypass hole connecting the low-pressure space and the high-pressure space;
a valve body provided in the valve body portion, the valve body opening the bypass hole when the pressure in the high-pressure space exceeds a threshold value.
The slide valve is
The compressor according to claim 1, further comprising a spring that biases the valve body in a direction to close the bypass hole.
The compressor according to claim 2, wherein a spring constant of said spring is set so as to open and close according to a predetermined differential pressure between said high-pressure space and said low-pressure space.
The bypass hole is
a first hole connected to the high-pressure space and extending along the axial direction of the screw shaft;
a second hole connected to the first hole, extending from the first hole in a direction away from the screw rotor, and connected to the low-pressure space;
The compressor according to any one of claims 1 to 3, wherein the valve body is arranged at a portion where the first hole and the second hole are connected.
5. The compressor according to claim 4, wherein the valve body is inserted into the first hole from the low-pressure space side, and closes the bypass hole when a tip portion thereof exceeds the second hole. .
The first hole is
a high-pressure space side horizontal hole connected to the high-pressure space;
a low-pressure space-side lateral hole connected to the high-pressure space-side lateral hole and the low-pressure space and having a larger diameter than the high-pressure space-side lateral hole;
6. The compressor according to claim 4, wherein the tip portion of the valve body closes the bypass hole when coming into contact with a step that is a connecting portion between the high-pressure space-side horizontal hole and the low-pressure space-side horizontal hole. .
The slide valve is
further comprising a drive mechanism for driving the valve body portion and the valve body to slide;
The valve body
The compressor according to any one of claims 1 to 6, wherein the compressor is provided at a position offset from the center of the rod of the drive mechanism.