Screw compressors and refrigeration equipment

Abstract

To inhibit circulation of a refrigerant at a suction side end of a compression chamber of a screw compressor.SOLUTION: In a screw compressor, a compression chamber (25) is formed by a screw rotor (40) and a gate (53) within a cylinder part (16). A suction side end (42) of the screw rotor (40) is formed in a cylindrical shape so that an outer peripheral surface (42a) is arranged along an inner peripheral surface of the cylinder part (16). A seal part (80) which inhibits circulation of a fluid is provided on a first surface (F) facing the outer peripheral surface (42a) of the suction side end (42) or a first end surface (42b) as seen in an axial direction at the suction side end (42).SELECTED DRAWING: Figure 10

Description

[Technical field]

[0001] The present disclosure relates to screw compressors and refrigeration systems. [Background technology]

[0002] Patent Document 1 discloses a screw compressor including a screw rotor and a gate rotor. The screw rotor is inserted into a cylinder, and a gate of the gate rotor is engaged with a screw groove of the screw rotor to form a compression chamber. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2009-197794 A Summary of the Invention [Problem to be solved by the invention]

[0004] In some screw compressors, the suction end of the screw rotor is formed without a suction cutter, closing off the compression chamber. The suction end is formed in a cylindrical shape with its outer circumferential surface aligned with the inner circumferential surface of the cylinder.

[0005] Due to this suction cutless shape, the refrigerant may flow through the gap between the suction end and the cylinder inner surface due to the pressure difference between the space near the suction end in the compression chamber and the space outside the compression chamber adjacent to the suction end. For example, if the refrigerant at an intermediate pressure in the space outside the compression chamber adjacent to the suction end leaks into the suction side of the compression chamber, the suction pressure increases and the compression efficiency decreases.

[0006] An object of the present disclosure is to suppress the flow of refrigerant at the suction end of a compression chamber of a screw compressor. [Means for solving the problem]

[0007] The first aspect of the present disclosure is A casing (11) having a cylinder portion (16) therein; an electric motor (13) disposed within the casing (11); a drive shaft (19) connected to the electric motor (13) and driven to rotate axially; a screw rotor (40) disposed in the cylinder portion (16) and connected to the drive shaft (19); a gate rotor (50) having a gate (53) that meshes with the screw groove (41) of the screw rotor (40), a compression chamber is formed inside the cylinder portion (16) by the screw rotor (40) and a gate (53), The suction side end (42) of the screw rotor (40) is formed into a cylindrical shape such that an outer circumferential surface (42a) thereof fits along an inner circumferential surface of the cylinder portion (16), The screw compressor is provided with a seal portion (80) that suppresses the flow of fluid on a first surface (F) that faces the outer circumferential surface (42a) at the suction side end (42) or a first axial end surface (42b) at the suction side end (42).

[0008] The space of the compression chamber (25) near the suction end (42) is at a low pressure due to the suctioned refrigerant. Therefore, when the space adjacent to the compression chamber (25) through the suction end (42) is at an intermediate pressure, the refrigerant tries to flow into the compression chamber (25) through the gap between the first surface (F) and the suction end (42) due to a pressure difference (differential pressure) of the refrigerant. However, in the first aspect, the seal portion (80) provided on the first surface (F) can prevent the refrigerant from flowing through the gap between the first surface (F) and the suction end (42). As a result, the high-low pressure difference in the compression chamber (25) can be sufficiently ensured, and a decrease in the performance of the screw compressor can be suppressed.

[0009] A second aspect of the present disclosure relates to the first aspect, a bearing portion (21) fixed in the cylinder portion (16) and supporting the drive shaft (19); The bearing portion (21) is disposed adjacent to the suction side end portion (42), The seal portion (80) is provided on the bearing portion (21).

[0010] In the second aspect, the first surface (F) facing the suction end portion (42) is located on the bearing portion (21). A seal portion (80) formed on the first surface (F) of the bearing portion (21) can prevent refrigerant from flowing between the suction end portion (42) and the bearing portion (21). In this manner, the bearing portion (21) has both a bearing function and a sealing function.

[0011] A third aspect of the present disclosure relates to the second aspect, The seal portion (80) is provided on the first surface (F) of the bearing portion (21) facing the axial end surface of the suction end portion (42).

[0012] In the third embodiment, the seal portion (80) can be provided on the end face of the bearing portion (21).

[0013] A fourth aspect of the present disclosure relates to the second or third aspect, the bearing portion (21) has a flange portion (21c) disposed between an inner surface of the cylinder portion (16) and the outer circumferential surface (42a) of the suction side end portion (42), The seal portion (80) is provided on the flange portion (21c).

[0014] In the fourth aspect, the inner circumferential surface of the flange portion (21c) is defined as the first surface (F), and the seal portion (80) is provided on the inner circumferential surface of the flange portion (21c). In this manner, the seal portion (80) can be provided even on the bearing portion (21) having the flange portion (21c).

[0015] A fifth aspect of the present disclosure is any one of the first to fourth aspects, The gate rotor (50) has a first gate rotor (50a) and a second gate rotor (50b), The compression chamber (25) is a first compression chamber (23) formed by the first gate rotor (50a) and the screw rotor (40) and configured to compress a fluid at a suction pressure introduced into the casing (11) to an intermediate pressure; The compressor includes a second compression chamber (24) that is formed by the second gate rotor (50b) and the screw rotor (40) and compresses the fluid at the intermediate pressure to a discharge pressure.

[0016] In the fifth aspect, the screw compressor is configured as a two-stage compression type, and it is possible to prevent the intermediate-pressure refrigerant discharged from the first compression chamber (23) from passing through the gap between the first surface (F) and the suction end portion (42) and being sucked back into the first compression chamber (23) while moving toward the suction port of the second compression chamber (24).

[0017] A sixth aspect of the present disclosure is any one of the first to fifth aspects, The seal portion (80) is formed of a labyrinth seal.

[0018] A seventh aspect of the present disclosure is any one of the first to fifth aspects, The sealing portion (80) comprises a surface texture.

[0019] An eighth aspect of the present disclosure is the screw compressor according to any one of the first to seventh aspects. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 is a schematic piping diagram of a refrigeration device according to an embodiment. [Diagram 2] FIG. 2 is a vertical cross-sectional view showing a schematic configuration of a main part of the screw compressor according to the embodiment. [Diagram 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. [Figure 4] FIG. 4 is a perspective view showing a state in which the screw rotor and the gate rotor are engaged with each other. [Diagram 5] FIG. 5 is a schematic plan view showing the suction stroke, compression stroke, and discharge stroke of the screw compressor. [Figure 6] FIG. 6 is a perspective view showing the flow of a refrigerant compressed in a low stage. [Figure 7] FIG. 7 is a perspective view showing the flow of refrigerant compressed in a high stage. [Figure 8] FIG. 8 is a side cross-sectional view illustrating the flow of the refrigerant in the compression mechanism. [Figure 9] FIG. 9 is an enlarged side cross-sectional view illustrating the flow of refrigerant around a first end portion in the compression mechanism. [Figure 10] FIG. 10 is a side cross-sectional view and an enlarged view of a portion of the compression mechanism for illustrating the seal portion of the present embodiment. [Figure 11] FIG. 11 is an enlarged view of the screw compressor according to the second modification, equivalent to FIG. [Figure 12] FIG. 12 is a view of a screw compressor according to the third modification, which corresponds to an enlarged view of FIG. [Figure 13] FIG. 13 is a view corresponding to FIG. 10 of a screw compressor according to the fourth modification. [Figure 14] FIG. 14 is a piping diagram of a refrigerant circuit to which the screw compressor according to the fifth modification is connected. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the following embodiments are essentially preferred examples, and are not intended to limit the scope of the present invention, its applications, or its uses. Furthermore, each configuration of the embodiments, each modification, and other embodiments described below can be combined or partially substituted within the scope in which the present invention can be implemented.

[0022] (1) Air conditioners As shown in Fig. 1, a screw compressor (10) of the present embodiment is provided in an air conditioner (1) that conditions an indoor space. The air conditioner (1) is an example of a refrigeration device (1) of the present disclosure. The air conditioner (1) has a refrigerant circuit (2) filled with a refrigerant.

[0023] The refrigerant circuit (2) has a screw compressor (10), a condenser (3), an expansion valve (4), and an evaporator (5). The refrigerant circuit (2) performs a vapor compression refrigeration cycle. The arrows in FIG. 1 indicate the direction in which the refrigerant flows. In the refrigeration cycle, the refrigerant compressed by the screw compressor (10) dissipates heat in the condenser (3). The refrigerant from which heat has been dissipated is reduced in pressure by the expansion valve (4), evaporated in the evaporator (5), and then sucked into the screw compressor (10).

[0024] (2) Screw compressor The screw compressor (10) compresses a refrigerant. The screw compressor (10) draws in low-pressure gas refrigerant and compresses the drawn gas refrigerant. The screw compressor (10) discharges the compressed high-pressure gas refrigerant. The screw compressor (10) of the present embodiment is configured to compress the refrigerant in two stages.

[0025] 2 to 4, the screw compressor (10) includes a casing (11), an electric motor (13), a drive shaft (19), and a compression mechanism (30). In the following, "upper," "lower," "right," and "left" refer to directions when the side of the screw compressor (10) shown in FIG. 2 is viewed from the front.

[0026] (2-1) Casing The casing (11) is formed in a horizontally long cylindrical shape. The casing (11) is formed with a suction port and a discharge port (not shown). A low pressure space (S1) and a high pressure space (S2) are formed inside the casing (11). The low pressure space (S1) is a space into which low pressure gas refrigerant sucked into the compression mechanism (30) through the suction port flows. The high pressure space (S2) is a space into which high pressure gas refrigerant discharged from the compression mechanism (30) flows. The refrigerant in the high pressure space (S2) flows out of the screw compressor (10) through the discharge port. A cylinder portion (16) is formed inside the casing (11). The cylinder portion (16) is formed in a horizontally long, generally cylindrical shape. A screw rotor (40) (described later) is disposed inside the cylinder portion (16).

[0027] (2-2) Electric motor The electric motor (13) is accommodated in the casing (11). The electric motor (13) is disposed at one end side within the casing (11). The electric motor (13) has a stator (14) and a rotor (15). The stator (14) is fixed to an inner wall of the casing (11). The rotor (15) is disposed inside the stator (14). A drive shaft (19) is fixed inside the rotor (15). The rotation speed of the electric motor (13) is variable. In this example, the electric motor (13) is an inverter-driven electric motor.

[0028] (2-3) Drive shaft The drive shaft (19) is disposed within the casing (11). The drive shaft (19) extends along the longitudinal direction of the casing (11). The drive shaft (19) extends in a substantially horizontal direction. The drive shaft (19) is inserted through the cylinder portion (16) along the cylindrical axis direction. The drive shaft (19) is disposed such that its axial center coincides with the cylindrical axis center of the cylinder portion (16).

[0029] The drive shaft (19) is driven by the electric motor (13). The rotation speed of the drive shaft (19) changes with the change in the rotation speed of the electric motor (13). In other words, the rotation speed of the drive shaft (19) is variable. The drive shaft (19) connects the electric motor (13) and the compression mechanism (30).

[0030] The drive shaft (19) is rotatably supported by a first bearing portion (21) and a second bearing portion (22) fixed in the cylinder portion (16). The first bearing portion (21) is disposed in an intermediate portion of the drive shaft (19). The second bearing portion (22) is disposed at the discharge side end portion of the drive shaft (19) (the end portion opposite the electric motor (13)).

[0031] The first bearing portion (21) is composed of a first bearing (21a) and a first bearing holder (21b). The second bearing portion (22) is composed of a second bearing (22a) and a second bearing holder (22b). The drive shaft (19) is supported by the bearing holders (21b, 22b) via the bearings (21a, 22a). In the following description, the first bearing (21a) and the second bearing (22a) may be collectively referred to simply as bearings (21a, 22a). Also, the first bearing holder (21b) and the second bearing holder (22b) may be collectively referred to simply as bearing holders (21b, 22b).

[0032] The bearing holders (21b, 22b) are formed in a generally cylindrical shape surrounding the entire circumference of the bearings (21a, 22a). The outer peripheral surface of the bearing holder is fixed to the inner peripheral surface of the cylinder portion (16). The first bearing holder (21b) and the second bearing holder (22b) are disposed to sandwich the screw rotor (40).

[0033] Each of the bearing portions (21) has a cylindrical peripheral wall (21c, 22c). The peripheral wall (21c, 22c) is provided on the outer circumferential edge of the axial end face of the bearing holder (21b, 22b). The peripheral wall (21c, 22c) is formed to fit the inner circumferential surface of the cylinder portion (16). Specifically, the peripheral wall (21c, 22c) is disposed between the inner circumferential surface of the cylinder portion (16) and the outer circumferential surface of the end portion (42, 43) of the screw rotor (40). The outer circumferential surface of the peripheral wall (21c, 22c) is fixed to the inner circumferential surface of the cylinder portion (16). The inner circumferential surface of the peripheral wall (21c, 22c) is close to the outer circumferential surface of the end portion (42, 43) of the screw rotor (40). The peripheral walls (21c, 22c) of the first bearing portion (21) are referred to as a first peripheral wall (21c), and the peripheral walls (21c, 22c) of the second bearing portion (22) are referred to as a second peripheral wall (22c). The first peripheral wall (21c) is an example of the flange portion (21c) of the present disclosure.

[0034] (2-4) Compression mechanism The compression mechanism (30) has one cylinder portion (16), one screw rotor (40), two gate rotors (50), and two slide valves (65).

[0035] (2-4-1) Cylinder section The cylinder portion (16) accommodates the screw rotor (40). A first slit (16a) and a second slit (16b) are formed in the cylinder portion (16). The first slit (16a) and the second slit (16b) are elongated openings extending in the axial direction of the cylinder. The first slit (16a) and the second slit (16b) are disposed adjacent to each other in the circumferential direction. The gate rotor (50) passes through each of the first slit (16a) and the second slit (16b). The first slit (16a) and the second slit (16b) will be described in detail later.

[0036] The cylinder portion (16) is provided with a valve accommodation portion (66) in which a slide valve (65) is accommodated. Two valve accommodation portions (66) are provided in the circumferential direction of the cylinder portion (16). Each valve accommodation portion (66) is formed so as to bulge radially outward from the cylinder portion (16). The outer peripheral wall of the valve accommodation portion (66) has a partition wall (66a) that separates the low pressure space (S1) and the high pressure space (S2), and a guide wall (66b) that extends in the axial direction from a widthwise central position of the partition wall (66a) toward the high pressure space (S2).

[0037] (2-4-2) Screw rotor The screw rotor (40) is disposed inside the cylinder portion (16). The screw rotor (40) is a metal member formed into a generally cylindrical shape. The screw rotor (40) is fixed to the drive shaft (19). The screw rotor (40) rotates in conjunction with the rotation of the drive shaft (19). The outer circumferential surface of the screw rotor (40) is adjacent to the inner circumferential surface of the cylinder portion (16).

[0038] One of the ends of the screw rotor (40) in the cylindrical axis direction is called the first end (42), and the other end is called the second end (43). The first end (42) and the second end (43) are both formed in a cylindrical shape. The first end (42) is an end on the suction side of a compression chamber (25) described below. The first end (42) is the suction side end (42) of the present disclosure. The second end (43) is an end on the discharge side of the compression chamber (25).

[0039] The first end (42) is disposed adjacent to the first bearing portion (21). The second end (43) is disposed adjacent to the second bearing portion (22). Hereinafter, the outer circumferential surface of the first end (42) is referred to as the first outer circumferential surface (42a), and the end face of the first end (42) is referred to as the first end face (42b). In addition, the outer circumferential surface of the second end (43) is referred to as the second outer circumferential surface (43a), and the end face of the second end (43) is referred to as the second end face (43b).

[0040] The first outer peripheral surface (42a) and the second outer peripheral surface (43a) are aligned along the inner peripheral surface of the cylinder portion (16). Specifically, the first outer peripheral surface (42a) is adjacent to the inner surface of the first peripheral wall (21c) of the first bearing portion (21), and the second outer peripheral surface (43a) is adjacent to the inner surface of the second peripheral wall (22c) of the second bearing portion (22).

[0041] The first end face (42b) and the second end face (43b) are formed on flat surfaces perpendicular to the cylindrical axis direction. The first end face (42b) faces the end face of the first bearing holder (21b). The second end face (43b) faces the end face of the second bearing holder (22b). Specifically, the first end face (42b) is close to the end face of the first bearing holder (21b), and the second end face (43b) is close to the end face of the second bearing holder (22b).

[0042] A plurality of spirally extending screw grooves (41) are formed on the outer circumferential surface of the screw rotor (40). The screw grooves (41) extend from a first end (42) to a second end (43) in the axial direction of the screw rotor (40).

[0043] (2-4-3) Gate rotor The gate rotor (50) includes a first gate rotor (50a) and a second gate rotor (50b). Each gate rotor (50) has a plurality of gates (53) arranged radially. The gates (53) pass through the slits (16a, 16b) of the cylinder portion (16) and mesh with the screw groove (41).

[0044] Each gate rotor (50) is supported by a gate rotor shaft (58). The gate rotor shaft (58) extends in a direction perpendicular to the axial direction of the drive shaft (19). The gate rotor shaft (58) is accommodated in a bearing housing (55) defined within the casing (11). The gate rotor shaft (58) is rotatably supported via a ball bearing (56) provided within the bearing housing (55). The gate rotor (50) and the gate rotor shaft (58) are disposed in the gate rotor chamber (18).

[0045] The gate rotor chamber (18) is defined within the casing (11) and is adjacent to the cylinder portion (16). The gate rotor chamber (18) includes a first gate rotor chamber (18a) and a second gate rotor chamber (18b). A first gate rotor (50a) is disposed in the first gate rotor chamber (18a). A second gate rotor (50b) is disposed in the second gate rotor chamber (18b). The first gate rotor chamber (18a) is configured to supply refrigerant to a first compression chamber (23) described below. The second gate rotor chamber (18b) is configured to supply the refrigerant flowing out of the first compression chamber (23) to a second compression chamber (24) described below.

[0046] (2-4-4) Slide valve The slide valve (65) is accommodated in the valve accommodation portion (66). The slide valve (65) is configured to be slidable in the axial direction of the cylinder portion (16) by a drive mechanism (71) described below. When inserted into the valve accommodation portion (66), the slide valve (65) faces the outer circumferential surface of the screw rotor (40).

[0047] The drive mechanism (71) includes a cylinder portion (16), a piston (73), a piston rod (74), an arm (75), a connecting rod (76), and a spring (77). The cylinder portion (16) is formed on the right side wall surface of the fixed plate (29). The piston (73) is mounted in the cylinder portion (16). One end of the piston rod (74) is fixed to the center of the piston (73) and extends to the left. The arm (75) is connected to the other end of the piston rod (74). The connecting rod (76) connects the arm (75) to the slide valve (65). The spring (77) is provided on the connecting rod (76) so as to bias the arm (75) to the right. The drive mechanism (71) controls the movement of the piston (73) by adjusting the gas pressure acting on the left and right end surfaces of the piston (73), thereby adjusting the position of the slide valve (65).

[0048] The slide valve (65) is a valve capable of adjusting the axial position of the screw rotor (40). The slide valve (65) can be used as an unloading mechanism that returns the refrigerant being compressed in the compression chamber (25) to the suction side to change the operating capacity. The slide valve (65) can also be used as a compression ratio adjustment mechanism that adjusts the compression ratio (internal volume ratio) by adjusting the timing of discharging the refrigerant from the compression chamber (25).

[0049] (2-4-5) Compression chamber In the compression mechanism (30) of the present embodiment, a compression chamber (25) is defined which is surrounded by the inner circumferential surface of the cylinder portion (16), the screw groove (41) of the screw rotor (40), and the two gate rotors (50).

[0050] A fixed discharge port (not shown) that always communicates with the compression chamber (25) regardless of the position of the slide valve (65) is formed in the cylinder portion (16). This fixed port is provided so that the compression chamber (25) is not sealed in order to avoid liquid compression during start-up or low load of the screw compressor (10).

[0051] The compression chamber (25) includes a first compression chamber (23) which is a low-stage side of the two-stage compression, and a second compression chamber (24) which is a high-stage side. The first compression chamber (23) and the second compression chamber (24) are formed by a screw rotor (40) and a gate rotor (50) inside the cylinder portion (16). The first compression chamber (23) compresses the refrigerant at a suction pressure introduced into the casing (11) to an intermediate pressure which is higher than the suction pressure. The second compression chamber (24) compresses the refrigerant at the intermediate pressure to a discharge pressure (high pressure) which is higher than the intermediate pressure.

[0052] In this embodiment, the low-pressure space (S1) communicates with the first compression chamber (23) through the first gate rotor chamber (18a). The low-pressure space (S1), the first gate rotor chamber (18a), the first compression chamber (23), the second gate rotor chamber (18b) which is an intermediate-pressure space, the second compression chamber (24), and the high-pressure space (S2) are connected in order from the side with the lowest refrigerant pressure to the side with the highest refrigerant pressure.

[0053] The first slit (16a) communicates the low-pressure space (S1) and the first gate rotor chamber (18a) with the first compression chamber (23). The second slit (16b) communicates the second gate rotor chamber (18b), which is an intermediate-pressure space, with the second compression chamber (24). The first slit (16a) constitutes a first suction port through which low-pressure refrigerant in the low-pressure space (S1) is introduced into the first compression chamber (23). The second slit (16b) constitutes a second suction port through which refrigerant in the intermediate-pressure space is introduced into the second compression chamber (24).

[0054] (3) Operation of the compression mechanism During the suction stroke shown in Fig. 5, the shaded compression chamber (25) (strictly speaking, the suction chamber) communicates with the space on the suction side. The screw groove (41) corresponding to this compression chamber (25) meshes with the gate (53) of the gate rotor (50). When the screw rotor (40) rotates, the gate (53) moves relatively toward the end of the screw groove (41), thereby increasing the volume of the compression chamber (25). As a result, the refrigerant is sucked into the compression chamber (25).

[0055] When the screw rotor (40) rotates further, the compression stroke shown in FIG. 5 is performed. During the compression stroke, the shaded compression chambers (25) are fully closed. That is, the screw grooves (41) corresponding to the compression chambers (25) are separated from the suction side space by the gates (53). As the screw rotor (40) rotates, the gates (53) approach the end of the screw grooves (41), and the volume of the compression chambers (25) gradually decreases. As a result, the refrigerant in the compression chambers (25) is compressed.

[0056] When the screw rotor (40) rotates further, the discharge stroke shown in Fig. 5 is performed. During the discharge stroke, the shaded compression chambers (25) (strictly speaking, discharge chambers) communicate with the fixed discharge port through the discharge end. As the screw rotor (40) rotates, the gate (53) approaches the end of the screw groove (41), and the compressed refrigerant is pushed out of the compression chambers (25) through the fixed discharge port into the space on the discharge side.

[0057] (3-1) Two-stage compression Next, the operation of the two-stage compression will be described with reference to Figures 6 and 7. The refrigerant sucked into the casing (11) flows into the low-pressure space (S1) and is introduced from the low-pressure space (S1) into the first gate rotor chamber (18a).

[0058] The low-pressure refrigerant in the first gate rotor chamber (18a) passes through the first slit (16a) and is sucked into the first compression chamber (23). The intermediate-pressure refrigerant compressed in the first compression chamber (23) flows out of the first compression chamber (23) and into the second gate rotor chamber (18b), which is an intermediate-pressure space.

[0059] The intermediate-pressure refrigerant in the second gate rotor chamber (18b) is sucked into the second compression chamber (24) through the second slit (16b). The high-pressure refrigerant compressed in the second compression chamber (24) flows out of the second compression chamber (24) and into the second space, the high-pressure space (S2). The refrigerant that has flowed into the high-pressure space (S2) has oil separated therefrom in an oil separator (not shown), and the refrigerant flows out of the casing (11) through the discharge port (10b).

[0060] (4) Issues caused by pressure differences between inside and outside the compression chamber In a screw compressor having a structure in which two-stage compression is performed in the first compression chamber (23) and the second compression chamber (24) as in this embodiment, the suction end of the screw rotor is required to have an suction cutless structure that seals between the inner circumferential surface of the cylinder portion and the outer circumferential surface of the screw rotor (corresponding to the first end (42) in this example).

[0061] As shown in FIG. 8, the refrigerant sucked into such a screw compressor flows through the low-pressure space (S1), the first gate rotor chamber (18a), the first compression chamber (23), the second gate rotor chamber (18b) which is an intermediate-pressure space, the second compression chamber (24), and the high-pressure space (S2), in that order.

[0062] As shown in Fig. 9, the intermediate-pressure discharged refrigerant compressed in the first compression chamber (23) passes through the outside of the first end (42), which is the suction-side end of the screw rotor (40), before flowing into the second gate rotor chamber (18b). The inside of the first end (42) is at a low pressure due to the refrigerant sucked into the first compression chamber (23), and a pressure difference occurs between the outside and the inside of the first end (42). Therefore, the intermediate-pressure refrigerant on the outside of the first end (42) may flow through the gap between the first end (42) and the cylinder portion (16) and flow into the first compression chamber (23) (dashed line in Fig. 9). When the intermediate-pressure refrigerant flows into the suction side of the first compression chamber (23), the pressure difference between the suction pressure and the discharge pressure of the refrigerant in the first compression chamber (23) becomes small, and the compression efficiency decreases.

[0063] In response to this, the screw compressor (10) of this embodiment is configured so that a seal portion (80) for suppressing refrigerant flow is provided on a first surface (F) that faces the outer circumferential surface (42a) of the first end portion (42) that is the suction side end portion or the first axial end surface (42b) of the suction side end portion (42). The seal portion (80) will be described in detail below.

[0064] (5) Sealing section 10, the seal portion (80) of the present embodiment is provided on the first bearing portion (21). Specifically, the seal portion (80) is provided on the inner circumferential surface (F) of the first circumferential wall (21c). The inner circumferential surface (F) of the first circumferential wall (21c) is an example of the first surface (F) that faces the first end portion (42) of the present disclosure.

[0065] The seal portion (80) of the present embodiment is a labyrinth seal. Specifically, the first peripheral wall (21c) has a plurality of grooves (81) formed around the entire circumference of the inner peripheral surface (F) of the first peripheral wall (21c), which are arranged side by side at regular intervals in the axial direction. The plurality of grooves (81) form an expansion chamber. For example, the intermediate-pressure refrigerant that flows into the gap (flow passage) between the first end portion (42) and the first bearing holder (21b) and flows toward the first compression chamber (23) flows into the groove (81) and expands (reduced in pressure) before flowing into the flow passage. The refrigerant flows into the next groove (81) and expands (reduced in pressure) before flowing into the flow passage. In this way, the intermediate-pressure refrigerant flows from the expansion chamber into the flow passage multiple times. When the refrigerant flows from the expansion chamber into the flow passage, the ease of flow is suddenly hindered, causing flow resistance and generating a pressure loss. The generation of the pressure loss can suppress the flow of the intermediate refrigerant into the first compression chamber (23).

[0066] (6) Features (6-1) Feature 1 In the screw compressor (10) of the present embodiment, the first end (42) (suction side end) of the screw rotor (40) is formed in a cylindrical shape such that the first outer peripheral surface (42a) is aligned along the inner peripheral surface of the cylinder portion (16). A seal portion (80) that suppresses the flow of refrigerant is provided on the first surface (F) that faces the first end (42).

[0067] The intermediate-pressure refrigerant discharged from the first compression chamber (23) flows through the space outside the first end (42) when moving to the inlet of the second compression chamber (24). The space inside the first end (42) is the first compression chamber (23) and forms a space into which low-pressure refrigerant is drawn, so that a pressure difference occurs through the first end (42). In this embodiment, the seal portion (80) is provided on the first surface (F) that faces the first end (42), thereby making it possible to prevent the intermediate-pressure refrigerant from flowing between the first end (42) and the first surface (F). As a result, a sufficient pressure difference can be ensured in the compression chamber, and a decrease in the performance of the screw compressor can be suppressed.

[0068] (6-2) Feature 2 The screw compressor (10) of the present embodiment includes a first bearing portion (21) that is fixed inside the cylinder portion (16) and supports the drive shaft (19). The first bearing portion (21) is disposed adjacent to the first end portion (42), and the seal portion (80) is provided in the first bearing portion (21).

[0069] According to this embodiment, the first surface (F) of the first end (42) is located in the first bearing holder (21b), and the seal portion (80) is provided in the first bearing holder (21b). This makes it possible to suppress the flow of refrigerant between the first bearing holder (21b) and the first end (42). In this manner, the first bearing portion (21) has a bearing function for the drive shaft (19) and a sealing function for suppressing the flow of refrigerant. In addition, since the seal portion (80) can be provided before the first bearing holder (21b) is attached to the cylinder portion (16), the seal portion (80) can be formed more easily than when the seal portion (80) is provided in the cylinder portion (16).

[0070] (6-3) Feature 3 In the screw compressor (10) of the present embodiment, the first bearing portion (21) has a first peripheral wall (21c) (rib portion) arranged between the inner surface of the cylinder portion (16) and the outer circumferential surface of the first end portion (42), and the seal portion (80) is provided on the first peripheral wall (21c).

[0071] According to this embodiment, a seal portion (80) can be provided on the inner circumferential surface of the first peripheral wall (21c). Also, the inner circumferential surface of the first peripheral wall (21c) and the first end face (42b) can increase the area of ​​contact between the first bearing holder (21b) and the first end portion (42). Increasing this area can lengthen the flow path through which the refrigerant flows, which is the gap between the first bearing holder (21b) and the first end portion (42). In addition to the seal portion (80), this can increase the effect of suppressing the flow of the refrigerant.

[0072] (6-4) Feature 4 In the screw compressor (10) of this embodiment, the compression chamber (25) includes a first compression chamber (23) that compresses the fluid at suction pressure introduced into the casing (11) to an intermediate pressure, and a second compression chamber (24) that compresses the fluid at the intermediate pressure to a discharge pressure.

[0073] According to this embodiment, it is possible to prevent a portion of the intermediate-pressure fluid discharged from the first compression chamber (23) from being sucked back into the first compression chamber (23) through the suction side end (42) during the process of moving to the second compression chamber (24).

[0074] (6-5) Feature 5 In the screw compressor (10) of the present embodiment, the seal portion (80) is a labyrinth seal, which makes it possible to relatively easily configure the seal portion (80).

[0075] (7) Variations The above embodiment may have the following configuration: Configurations different from the above embodiment will be described below.

[0076] (7-1) Variation 1 The seal portion (80) in this example is a surface texture (surface texturing). The surface texture is formed on the inner circumferential surface of the first circumferential wall (21c). In the surface texture, Rayleigh steps that generate positive pressure and inverse Rayleigh steps that generate negative pressure are appropriately formed. The Rayleigh steps can reduce friction between the inner circumferential surface of the first circumferential wall (21c) and the outer circumferential surface of the first end (42). The inverse Rayleigh steps can suck back the refrigerant that flows into the gap between the inner circumferential surface of the first circumferential wall (21c) and the outer circumferential surface of the first end (42). In this example, the inverse Rayleigh steps may be adopted to prevent the intermediate pressure refrigerant from flowing into the first compression chamber (23).

[0077] (7-2) Variation 2 11, the seal portion (80) of this example is formed on a surface facing the first end surface (42b) of the first bearing holder (21b). The surface facing the first end surface (42b) is an example of the first surface (F) of the present disclosure. For example, when the seal portion (80) is a labyrinth seal, a plurality of grooves (81) are formed at regular intervals on the first end surface (42b) in a concentric pattern centered on the cylindrical axis of the first bearing holder (21b).

[0078] (7-3) Variation 3 12, the seal portion (80) of this example is formed on the inner circumferential surface of the first peripheral wall (21c) and the first end face (42b) of the first bearing holder (21b). By providing the seal portion (80) on both sides facing the first end portion (42) in this manner, it is possible to reliably prevent the refrigerant from flowing through the gap between the first end portion (42) and the bearing holder (21b, 22b).

[0079] (7-4) Variation 4 As shown in FIG. 13, the first bearing portion (21) of this example does not have a first bearing holder (21b). In this case, the first bearing (21a) is embedded inside the cylinder portion (16), and a cylinder end surface (26) facing the first end surface (42b) is formed on the inside of the cylinder portion (16). In this example, the first surface (F) of the present disclosure is the inner peripheral surface of the cylinder portion (16) facing the first outer peripheral surface (42a) and the cylinder end surface (26) facing the first end surface (42b). In this example, the seal portion (80) is provided on the inner peripheral surface of the cylinder portion (16) facing the first outer peripheral surface (42a). The seal portion (80) may be provided on the cylinder end surface (26) facing the end surface of the first end portion (42). In addition, the seal portion (80) may be provided on both the inner peripheral surface of the cylinder portion (16) facing the first outer peripheral surface (42a) and the cylinder end surface (26) facing the end face of the first end portion (42).

[0080] (7-5) Variation 5 As shown in Fig. 14, the refrigerant circuit (2) of this example has an economizer circuit (90). The economizer circuit (90) of this example supplies intermediate-pressure refrigerant to the compression chamber (25). The arrows in Fig. 14 indicate the direction of refrigerant flow.

[0081] In this embodiment, a gas-liquid separation space (S3) is formed in the casing (11) where the refrigerant is separated into gas and liquid. The gas-liquid separation space (S3) is adjacent to the suction side of the compression chamber (25). The high pressure space (S2) in the casing (11) is adjacent to the discharge side of the compression chamber (25). A refrigerant suction port is provided on the suction side of the compression chamber (25). The screw compressor (10) in this embodiment is configured as a single stage.

[0082] In the refrigerant circuit (2) of this example, an inlet side of the condenser (3) communicates with a high-pressure space of the screw compressor (10). An outlet side of the condenser (3) communicates with a gas-liquid separation space (S3) of the screw compressor (10). A first expansion valve (4a) is provided between the condenser (3) and the gas-liquid separation space (S3).

[0083] An inlet side of the evaporator (5) communicates with the gas-liquid separation space (S3) of the screw compressor (10). An outlet side of the evaporator (5) communicates with the suction side of the compression chamber (25) of the screw compressor (10). A second expansion valve (4b) is provided between the gas-liquid separation space (S3) and the evaporator (5).

[0084] The economizer circuit (90) connects the gas-liquid separation space (S3) and the compression chamber (25). In the economizer circuit (90), the gas-phase intermediate-pressure refrigerant in the gas-liquid separation space (S3) flows into the intermediate-pressure space of the compression chamber (25). A flow rate control valve (91) is connected to the economizer circuit (90). The flow rate control valve (91) controls the flow rate of the refrigerant flowing through the economizer circuit (90).

[0085] In the configuration of the screw compressor (10) of the present example, the compression chamber (25) is adjacent to the gas-liquid separation space (S3) on the suction side thereof. Therefore, the seal portion (80) can prevent the intermediate-pressure refrigerant in the gas-liquid separation space (S3) from flowing through the gap between the first end portion (42) of the screw rotor (40) and the cylinder portion (16) and entering the compression chamber (25).

[0086] (8) Other embodiments In the above embodiment and each modified example, the seal portion 80 may also be provided on the second bearing holder 22b. For example, the seal portion 80 may also be provided on the inner circumferential surface of the second circumferential wall 22c.

[0087] In the above embodiment, the first bearing holder (21b) may not have the first peripheral wall (21c). In this case, the first surface (F) of the present disclosure is the inner peripheral surface of the cylinder portion (16) facing the first outer peripheral surface (42a) and the end surface of the bearing holder (21b, 22b) facing the first end surface (42b). In this case, the seal portion (80) is provided on the inner peripheral surface of the cylinder portion (16) facing the first outer peripheral surface (42a), the end surface of the bearing holder (21b, 22b) facing the first end surface (42b), or both.

[0088] In the above embodiment and each of the above modified examples, the seal portion (80) is required to suppress flow between the inside (compression chamber) of the first end (42) and the space outside the first end (42), and may be configured to suppress flow in only one direction.

[0089] There is no particular limitation on the structure of the labyrinth of the seal portion 80. The labyrinth may be an axial labyrinth, a radial labyrinth, an aligning labyrinth, or the like.

[0090] The refrigeration device (1) may be applied to a water heater, a chiller unit, or a cooling device that cools the air inside a storage unit.

[0091] Although the embodiments and modifications have been described above, it will be understood that various modifications of form and details are possible without departing from the spirit and scope of the claims. Furthermore, the above embodiments and modifications may be appropriately combined or substituted as long as the functions of the subject of this disclosure are not impaired. The descriptions "first", "second", ... described above are used to distinguish the words to which these descriptions are attached, and do not limit the number or order of the words. [Industrial Applicability]

[0092] INDUSTRIAL APPLICABILITY As described above, the present disclosure is useful for screw compressors and refrigeration systems. [Explanation of symbols]

[0093] 1. Air conditioner (refrigeration unit) 10. Screw Compressor 11 Casing 13 Electric motor 16 Cylinder section 19 Drive shaft 21 1st bearing part (bearing part) 21c First perimeter wall (rib) 23 Compression chamber 24 First Compression Chamber 25 Second Compression Chamber 40 Screw rotor 41 Screw groove 42 1st end (suction side end) 50 Gate Rotor Gate 53 80 Seal part F 1st surface (inner surface)

Claims

1. a casing (11) having a cylinder portion (16) therein; an electric motor (13) disposed within the casing (11); a drive shaft (19) connected to the electric motor (13) and driven to rotate axially; a screw rotor (40) disposed in the cylinder portion (16) and connected to the drive shaft (19); a gate rotor (50) having a gate (53) meshing with the screw groove (41) of the screw rotor (40), a compression chamber is formed inside the cylinder portion (16) by the screw rotor (40) and a gate (53), The suction side end (42) of the screw rotor (40) is formed into a cylindrical shape such that an outer circumferential surface (42a) thereof fits along an inner circumferential surface of the cylinder portion (16), a bearing portion (21) fixed in the cylinder portion (16) and supporting the drive shaft (19), the bearing portion (21) has a flange portion (21c) that is disposed adjacent to the suction side end portion (42) and that is disposed between an inner surface of the cylinder portion (16) and the outer circumferential surface (42a) of the suction side end portion (42); a seal portion (80) for restricting the flow of a fluid is formed on a first surface (F) of the flange portion (21c) facing the outer circumferential surface (42a) of the suction side end portion (42), The gate rotor (50) has a first gate rotor (50a) and a second gate rotor (50b), The compression chamber (25) a first compression chamber (23) formed by the first gate rotor (50a) and the screw rotor (40) and configured to compress a fluid at a suction pressure introduced into the casing (11) to an intermediate pressure; a second compression chamber (24) formed by the second gate rotor (50b) and the screw rotor (40) and configured to compress the fluid at the intermediate pressure to a discharge pressure, The intermediate-pressure refrigerant discharged from the first compression chamber (23) flows through the space outside the suction end portion (42) when moving to the inlet of the second compression chamber (24). A screw compressor characterized by:

2. 2. The screw compressor according to claim 1, wherein the seal portion (80) is provided on the first surface (F) of the bearing portion (21) facing an axial end surface of the suction side end portion (42).

3. 3. The screw compressor according to claim 1, wherein the seal portion (80) is a labyrinth seal.

4. The screw compressor according to claim 1 or 2, characterized in that the sealing portion (80) is configured with a surface texture.

5. A refrigeration system comprising the screw compressor according to claim 1 or 2.

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