GB2528214A

GB2528214A - Screw compressor and refrigeration cycle device

Info

Publication number: GB2528214A
Application number: GB1519248.7A
Authority: GB
Inventors: Mihoko Shimoji; Toshihide Koda; Soichi Shiraishi; Kazuyuki Tsukamoto; Masaaki Kamikawa; Naoto Uenakai
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2013-05-30
Filing date: 2013-05-30
Publication date: 2016-01-13
Anticipated expiration: 2033-05-30
Also published as: GB2528214B; WO2014192114A1; GB201519248D0; GB2528214C; JP5951125B2; JPWO2014192114A1; CN105247216A; CN105247216B

Abstract

The present invention is provided with a variable port (16), the aperture area of which and the initial discharge timing of which can be changed by the movement of a slide valve (12), and a fixed port (17), the aperture area of which does not change when the slide valve (12) moves. When the slide valve (12) is positioned the farthest to the intake side, the shape of the intake-side end surface of a discharge port aperture part substantially forms the shape of a letter 'Z', the angles of which are formed by connecting a slanted surface (12d) on the variable port (16) side, a slide surface (16l), which is the boundary between the fixed port (17) and the variable port (16), and a slanted surface (17a) on the fixed port (17) side.

Description

DESCRIPTION

Title of Invention

SCREW COMPRESSOR AND REFRIGERATION CYCLE APPARATUS

Technical Field

[0001] The present invention relates to a screw compressor used in a refrigeration cycle for the purposes of refrigeration, air conditioning, and so forth, and also relates to a refrigeration cycle apparatus.

Background Art

[0002] As this type of screw compressor, there is provided a screw compressor including a columnar slide valve that is provided at the outer periphery of a screw rotor having one end serving as a suction side of fluid and an other end serving as a discharge side of the fluid and that moves in a sliding manner in a rotation-axis direction of the screw rotor (for example, see Patent Literature 1 Patent Literature 2, Patent Literature 3, and Patent Literature 4). The slide valve changes a discharge start (compression completion) position of high-pressure gas compressed in a compression chamber, and changes a ratio of a discharge volume to a suction volume by changing a discharge area.

[0003] In Patent Literature 1, a slide stop position of the slide valve is controlled to obtain a volume ratio that provides high compressor efficiency, with respect to a compression ratio (discharge pressure/suction pressure) corresponding to an operation load. That is, the position of the slide valve is changed depending on whether an operating state is full load operation or partial load operation. To be specific, the position of the slide valve is changed to be positioned at the suction side in partial load operation to increase the opening degree of a discharge port, and the slide valve is positioned at the discharge side in full load operation to decrease the opening degree of the discharge port.

[0004] The discharge port of the screw compressor in Patent Literature 1 is formed of an inner wall surface of an opening pod provided at a casing that houses the screw rotor and a discharge-side end surface of the slide valve. The discharge port includes a variable port and a fixed pod. The variable port is a pod having an area that is changed if a closed portion by the slide value is opened by movement of the slide valve or if an open portion is closed by movement in an opposite direction of the slide valve. The fixed port is a port that is provided between the variable port and an opening port (hereinafter, referred to as gate-rotor opening port) at the casing to which gate rotor teeth are inserted, and that is constantly in an open state irrespective of the position of the slide valve.

[0005] The screw compressor of related ad described in Patent Literature 1 further includes a plurality of sub-ports for the purpose of an increase in discharge area in partial load operation, in addition to the fixed pod and the variable port. The plurality of sub-ports each are formed in a parallelogram shape, and are arranged at the suction side of the fixed port, at a position between the variable port and the gate-rotor opening port.

[0006] In this case, the fixed port is formed to ensure the discharge area in accordance with the position of the slide valve in full load operation. Also, the sub-ports are formed in a separated manner from the fixed port so that the sub-ports communicate with the compression chamber and the variable port in partial load operation in which the slide valve slides to the suction side, and the sub-ports are closed by the slide valve in full load operation in which the slide valve slides to the discharge side.

[0007] In Patent Literature 1, by providing the fixed port and the sub-ports as described above, compression chambers with different pressures are prevented from communicating with each other and the discharge area with a sufficient size can be ensured in the operating state with the partial load.

[0008] Also, for a screw compressor of related art described in Patent Literature 2, provision of a sub-port in addition to the variable port and the fixed port is disclosed for the purpose of ensuring the discharge area with the partial load.

The sub-port in Patent Literature 2 is provided at a non-rotation side of the screw rotor with respect to the slide valve. The sub-port causes the compression chamber to communicate with a space at the discharge side of the screw rotor in partial load operation with a partial load being 50% to 75% of the full load.

[0009] Also, Patent Literature 3 discloses a screw compressor in which the inclination of the discharge-side end surface of the slide valve is aligned with the inclination of a screw groove at a discharge start time point of partial load operation. Accordingly, a higher priority is given to efficiency of partial load operation than efficiency of full load operation.

[0010] Also, in any one of Patent Literatures 1 to 3, since the slide valve is coupled to a guide portion through a rod-shaped coupling portion and the guide portion is driven by a driving mechanism, the slide valve can move in a sliding manner. This coupling portion is arranged across an area above the discharge port, and hence closes a flow path of discharge fluid. Hence this arrangement of the coupling portion is a factor of a decrease in flow path area and an increase in discharge pressure loss.

[0011] Therefore, Patent Literature 4 discloses a technique of arranging the coupling portion at a position deviated toward a non-rotation direction side of the variable port, so that the discharge flow path is not blocked as much as possible.

Citation List Patent Literature [0012] Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2011-1 32834 (Page 11, Fig. 6) Patent Literature 2: Japanese Unexamined Patent Application Publication No. 2011-32957 (Paragraph [0033], Fig. 2) Patent Literature 3: Japanese Patent No. 4735757 (Page 12, Fig. 6) Patent Literature 4: Japanese Patent No. 3214100 (Paragraph [0020], Fig. 3)

Summary of Invention

Technical Problem [0013] As an index of energy conservation of a refrigerator with the screw compressor mounted, in related art, a coefficient of performance (capacity/electric energy consumption) under a rating condition (full load condition: 100%) was mainly used. However, an index close to an actual operating condition, for example, IPLV (Integrated Part Load Value) determined in the United States is recently drawing attention.

[0014] In case of a typical refrigerator, a period in which the refrigerator is operated under the rating condition throughout the year is very short, and the refrigerator is operated with a partial load in a period being 90% or more of the operating time through the year. The partial load in the operation is mainly a load being 75% to 50% of the full load. In full load operation and partial load operation, the refrigerant circuit flow rate is different and the operation compression ratio is different, and hence the coefficient of performance is changed. With regard to the situation of the actual operation, IPLV is receiving attention. That is, IPLV is an index emphasized on the coefficient of performance under the partial load condition.

[0015] Regarding the above-described background, the screw compressor described in any one of Patent Literature 1 and Patent Literature 2 employs the above-described configuration to increase the discharge area under the partial load condition for the purpose of increasing the efficiency of the partial load condition. That is, the sub-port that communicates with the space at the discharge side only in partial load operation is provided in addition to the variable port of related art.

[0016] However, since the sub-port is provided to communicate with the compression chamber in the middle of compression in full load operation, the sub-port may be a capacity portion (dead volume) that is wastefully compressed from a suction pressure to a discharge pressure, and the capacity portion may be a factor of causing a loss to be generated.

[0017] Also, in the screw compressor described in Patent Literature 3, since the discharge-side end surface of the slide valve is formed along the inclination of the screw groove at the discharge start time point with the partial load, the discharge area at the discharge start time point can be sufficiently ensured under the partial load condition, the operation efficiency is increased, and hence the screw compressor is effective. However, under the full load condition, the discharge-side end surface of the slide valve is no longer aligned with the inclination of the screw groove at the discharge start time point under the full load condition. Owing to this, due to the difference in inclination, the discharge area at the discharge start time point when the inclination of the screw groove is aligned in partial load operation becomes smaller than that when the inclination of the screw groove is aligned in full load operation. There may be a problem in which the discharge pressure loss is increased and the efficiency is decreased.

[0018] Also, in the screw compressor in Patent Literature 4, although the position of the coupling portion is well thought out so that the coupling portion less likely blocks the discharge flow path, the coupling portion is still constantly arranged above the variable port in both full load operation and partial load operation.

Owing to this, the problem in which the coupling portion blocks the discharge flow path and the discharge pressure loss is increased still remains. An improvement for the decrease in operation efficiency by the coupling portion is required.

[0019] Also, in the screw compressor in any one of Patent Literature 1 to Patent Literature 4, for example, the center of the slide valve is at about 30 degrees from the gate-rotor opening surface so as to ensure the variable port area if mechanical volume control is executed by a pair of the slide valves. The mechanical volume control executes volume control with a delayed compression start timing by moving the slide valve to the discharge side and opening a bypass port (an opening that causes the screw groove arranged at the suction side to communicate with a low-pressure space). A partition wall is arranged outside the outer peripheral surface of the slide valve provided at this angular position.

The partition wall provides a partition for the suction pressure and the discharge pressure. When the slide valve is moved to the suction side in accordance with the discharge start time point in low compression-ratio operation, the positional relationship between the slide valve and the partition wall is set so that the discharge-side end surface of the slide valve is positioned at the suction side with respect to the partition wall. Owing to this, there may be a problem in which leakage of fluid from the compression chamber to the suction pressure side is generated.

[0020] To solve the problems in Patent Literatures 1, 2, and 4, for example, a method with a configuration that satisfies the following points is conceivable.

That is, first, the length of the slide valve in the screw-rotor circumferential direction may be as long as a length that covers the screw groove at the discharge start time point with the partial load and hence the discharge area may be sufficiently largely ensured. Then, to prevent the coupling portion from blocking the discharge flow path, the coupling portion may be arranged at the slide valve with a larger length in the screw-rotor circumferential direction, in a further deviated manner toward the non-rotation direction side as compared with the position in Patent Literature 4, and hence the coupling portion may be completely separated from the discharge port. However, even though these two points are satisfied, the same problem as that in Patent Literature 3 still remains.

[0021] Also, to solve the problems in Patent Literatures 1, 2, and 4, if the length of the slide valve in the screw-rotor circumferential direction is increased as described above, there may be newly generated a problem in which the length of a seal line of a seal portion between the outer peripheral surface of the slide valve and the partition wall provided outside the outer peripheral surface is increased, and a leakage loss is increased. Further, there may be a problem in which a gate-rotor support part provided outside the outer peripheral surface of the slide valve interferes with the slide valve.

[0022] As described above, with the technique of any one of Patent Literature 1 to Patent Literature 4, various techniques each for restricting an increase in discharge loss within a wide operation range from a high compression ratio to a low compression ratio; however, a further improvement is required.

[0023] The present invention is made to solve at least one of the above-described problems, and an object of the invention is to obtain a screw compressor and a refrigeration cycle apparatus that can restrict an increase in discharge loss within a wide operation range.

Solution to Problem [0024] A screw compressor according to the present invention includes a screw rotor having a plurality of threads of screw grooves formed at an outer peripheral surface of the screw rotor, the screw rotor having one end serving as a suction side of fluid and an other end serving as a discharge side of the fluid; a gate rotor having a plurality of teeth formed at an outer peripheral portion of the gate rotor, the teeth being configured to mesh with the screw grooves; a casing having a housing portion for housing the screw rotor, and a discharge port; a slide groove formed at an inner wall surface of the casing and extending in a rotation-axis direction of the screw rotor; a slide valve housed in the slide groove movably in a sliding manner in the rotation-axis direction, the slide valve being configured to slide in the rotation-axis direction and change a discharge start timing; and a gate-rotor opening port provided at the casing and being open at the housing portion. The plurality of teeth of the gate rotor are inserted into the housing portion through the gate-rotor opening port, the teeth mesh with the screw grooves, the screw rotor rotates, hence the fluid is sucked into a compression chamber being a space surrounded by an inner wall surface of the housing portion, the screw grooves, and the gate rotor, the sucked fluid is compressed in the compression chamber, and the compressed fluid is discharged from the discharge port. The discharge port includes a variable port having an opening area and a discharge start timing that can be changed by the movement of the slide valve, and a fixed port provided between the variable port and the gate rotor, the fixed port having an opening area that is not changed even when the slide valve moves. A suction-side end surface shape of the discharge port when the slide valve is arranged at a most suction side is formed to have a Z-like shape in which an inclined surface at the variable port side, a slide surface arranged at a boundary between the fixed port and the variable port and extending in the rotation-axis direction, and an inclined surface at the fixed port side are mutually connected to each other at angles, and the inclined surface at the fixed port side is formed at the discharge side with respect to the inclined surface at the variable port side.

Advantageous Effects of Invention [0025] With the present invention, the screw compressor that can restrict an increase in discharge loss within the wide operation range can be obtained.

Brief Description of Drawings

[0026] [Fig. 1] Fig. 1 is a schematic cross-sectional view (a plan cross-sectional view) of a screw compressor 100 according to Embodiment 1 of the present invention.

[Fig. 2] Fig. 2 is a cross-sectional view taken along line A-A in Fig. 1.

[Fig. 3] Fig. 3 provides perspective views showing a configuration around a discharge port 15 (a housing portion) of the screw compressor 100 according to Embodiment 1 of the present invention.

[Fig. 4] Fig. 4 provides explanatory views of the configuration around the discharge port 15 of the screw compressor 100 according to Embodiment 1 of the present invention.

[Fig. 5] Fig. 5 provides explanatory views showing a compression theory of the screw compressor 100 according to Embodiment 1 of the present invention.

[Fig. 6] Fig. 6 provides explanatory views for explaining the relationship between the screw rotation angle and the discharge area in a state in which a slide valve 12 of the screw compressor 100 according to Embodiment 1 of the present invention is arranged at a discharge side.

[Fig. 7] Fig. 7 is a graph showing the relationship between the screw rotation angle and the change in discharge area in the state in Fig. 6.

[Fig. 8] Fig. 8 provides explanatory views for explaining the relationship between the screw rotation angle and the discharge area in a state in which the slide valve 12 of the screw compressor 100 according to Embodiment 1 of the present invention is arranged at a suction side.

[Fig. 9] Fig. 9 is a graph showing the relationship between the screw rotation angle and the change in discharge area in the state in Fig. 8.

[Fig. 10] Fig. 10 provides explanatory views of a configuration around a discharge port 150 of related art being a comparative subject.

[Fig. 11] Fig. 11 provides explanatory views for explaining the relationship between the screw rotation angle and the discharge area in a state in which a slide valve 120 of related art in Fig. 10 is arranged at the discharge side in high compression-ratio operation.

[Fig. 12] Fig. 12 is an illustration showing the comparison result of the discharge area between related art and Embodiment 1 in the state in which the slide valve is arranged at the discharge side.

[Fig. 13] Fig. 13 provides explanatory views for explaining the relationship between the screw rotation angle and the discharge area in a state in which the slide valve 120 of related art in Fig. 10 is arranged at the suction side in low compression-ratio operation.

[Fig. 1 3A] Fig. 1 3A provides explanatory views for explaining the difference in area of the variable port in low compression-ratio operation due to the difference in arrangement of the slide valve between related art and Embodiment 1.

[Fig. 14] Fig. 14 is an illustration showing the comparison result of the discharge area between related art and Embodiment 1 in the state in which the slide valve is arranged at the suction side.

[Fig. 1 4A] Fig. 1 4A is an illustration showing the relationship of the change in discharge area when the center of the slide valve 12 is arranged at 90 degrees from a gate-rotor opening surface.

[Fig. 1 4B] Fig. 1 4B is an illustration showing the comparison result of the discharge area between a case in which the center of the slide valve 12 is provided at 90 degrees from the gate-rotor opening surface 1 aa and related art.

[Fig. 15] Fig. 15 provides lateral cross-sectional views in low compression-ratio operation in the state in which the slide valves 12 and 120 are arranged at the suction side.

[Fig. 16] Fig. 16 is an illustration showing another example of a suction-side wall surface ofafixed port 17.

[Fig. 17] Fig. 17 is a refrigerant circuit diagram of a refrigeration cycle apparatus 300 according to Embodiment 2 of the present invention.

[Fig. 18] Fig. 18 is a primary-portion end-surface diagram of a screw compressor 200 provided in the refrigeration cycle apparatus 300 according to Embodiment 2 of the present invention.

[Fig. 19] Fig. 19 provides perspective views showing a configuration around a discharge port 15 (a housing portion) of the screw compressor 200 provided in the refrigeration cycle apparatus 300 according to Embodiment 2 of the present invention.

[Fig. 20] Fig. 20 provides explanatory views of the configuration around the discharge port 15 of the screw compressor 200 provided in the refrigeration cycle apparatus 300 according to Embodiment 2 of the present invention.

[Fig. 21] Fig. 21 provides explanatory views of a configuration around an economizer port according to Embodiment 2 of the present invention.

[Fig. 22] Fig. 22 is a refrigeration cycle explanatory diagram in economizer operation of the refrigeration cycle apparatus 300 according to Embodiment 2 of the present invention.

[Fig. 23] Fig. 23 is a pressure-specific enthalpy diagram in full load operation of the refrigeration cycle apparatus 300 according to Embodiment 2 of the present invention.

[Fig. 24] Fig. 24 is a pressure-specific enthalpy diagram in partial load operation of the refrigeration cycle apparatus 300 according to Embodiment 2 of the present invention when a high-low differential pressure is small.

[Fig. 25] Fig. 25 provides explanatory views for explaining the relationship between the screw rotation angle and an economizer port i2p in the screw compressor 200 according to Embodiment 2 of the present invention.

[Fig. 26] Fig. 26 provides explanatory views for explaining the relationship between the screw rotation angle and the economizer port 12p in the screw compressor 200 according to Embodiment 2 of the present invention.

[Fig. 26A] Fig. 26A provides explanatory views of a modification of the positional relationship between the economizer port 12p and an economizer flow path 50 in the screw compressor 200 according to Embodiment 2 of the present invention.

[Fig. 27] Fig. 27 provides explanatory views of a modification of the diameter of the economizer port i2p, (a) being a developed view of an inner wall surface of a housing portion lAand an outer peripheral surface of a screw rotor 4, (b) being a cross-sectional view taken along line d-d in (a).

Description of Embodiments

[0027] Embodiment 1 A screw compressor 100 according to Embodiment 1 of the present invention is described below.

Fig. 1 is a schematic cross-sectional view (a plan cross-sectional view) of the screw compressor 100 according to Embodiment 1 of the present invention.

Also, Fig. 2 is a cross-sectional view taken along line A-A in Fig. 1. In Figs. 1 and 2, and the drawings described below, configurations with the same reference sign are the same or corresponding to each other, and this is common to the whole text in the specification. Further, a form of a component expressed in the whole text in the specification is merely an example, and is not limited thereto.

[0028] The screw compressor 100 includes a casing 1, a screw rotor 4, a gate rotor 7, a motor 8 that rotationally drives the screw rotor 4, a slide valve 12, and so forth. The casing 1 houses the screw rotor 4, the gate rotor 7, the motor 8, the slide valve 12, and so forth. The casing 1 has a discharge port 15 (see Fig. 3 described later) open at a housing portion 1A. It is to be noted that the discharge port 15 is described later in detail.

[0029] The housing portion lAbeing a substantially columnar space is formed in the casing 1. The screw rotor 4 having a substantially columnar shape is housed in the housing portion 1A. The screw rotor 4 has one end serving as a suction side of fluid, and an other end serving as a discharge side of the fluid.

Screw grooves 10 having a plurality of threads are formed in a spiral shape at an outer peripheral surface of this screw rotor 4. Also, a rotating shaft 9 serving as a driving shaft is provided at the center of the screw rotor 4 so that the rotating shaft 9 rotates together with the screw rotor 4. The rotating shaft 9 is rotatably supported by a high-pressure-side bearing 2 and a low-pressure-side bearing 3 provided at the casing 1. Also, the motor 8 is connected to an end portion of the rotating shaft 9 at the low-pressure-side bearing 3 side. The motor 8 is controlled by frequency control by, for example, an inverter (not illustrated).

[0030] In the casing 1, a pair of gate-rotor support chambers 6 are formed in an opposed manner about the housing portion 1A (that is, the screw rotor 4). The gate rotor 7 having a substantially disk shape is housed in each of the gate-rotor support chambers 6. The gate rotor 7 is provided at a gate rotor support 5 housed in each gate-rotor support chamber 6.

[0031] The gate rotor support 5 is arranged so that a center shaft (a rotating shaft) Sb thereof is substantially perpendicular to the rotating shaft 9 of the screw rotor 4. The gate rotor support 5 is rotatably supported by bearings 5a separated from each other in a direction along the center shaft 5b and hence arranged in an opposed manner.

[0032] In Fig. 2, the gate rotor 7 and the gate rotor support 5 arranged in each of the gate-rotor support chamber 6 formed at the left side of the housing portion 1A and the gate-rotor support chamber 6 formed at the right side of the housing portion 1 A are in 180-degree-rotated arrangement about the rotating shaft 9 of the screw rotor 4.

[0033] The gate rotor 7 forms a compression chamber 11 together with the housing portion 1A and the screw rotor 4. A plurality of gate rotor teeth 7a are formed at an outer peripheral portion of the gate rotor 7. The gate rotor teeth 7a mesh with the screw grooves 10. To be more specific, a gate-rotor opening port 1 a is formed at the casing 1 so that the gate-rotor opening port 1 a extends in a direction along the rotating shaft 9 (see Fig. 1). Also, the gate-rotor opening port 1 a is formed to extend along the inclination of the screw groove 10 at the rear surface to connect to a suction wall 1 c of the housing portion 1 A and forms the compression chamber at the rear surface.

[0034] Also, the outer peripheral portion of the gate rotor 7 is inserted into the gate-rotor opening port 1 a provided at the casing 1. That is, the gate rotor teeth 7a of the gate rotor 7 are inserted into the housing portion 1A through the gate-rotor opening port la, and mesh with the screw grooves 10. Accordingly, a space surrounded by the gate rotor 7, the inner wall surface of the housing portion 1 A, and the screw rotor 4 (in other words, the screw groove 10 partitioned by the gate rotor teeth 7a of the gate rotor 7 and the housing portion 1A) is formed, and this space serves as the compression chamber 11.

[0035] Also, two slide grooves 14 extending in the direction along the rotating shaft 9 of the screw rotor 4 are formed at the inner wall surface of the casing 1.

The slide valve 12 is housed in each of the slide grooves 14 movably in a sliding manner. To be specific, the two slide grooves 14 each are formed in a substantially columnar shape. A portion of an inner peripheral surface of each slide groove 14 communicates with the housing portion 1A. The two slide grooves 14 are in 180-degree-rotated arrangement about the rotating shaft 9 of the screw rotor 4.

[0036] The slide valve 12 provided at the slide groove 14 is formed in a substantially columnar shape similarly to the slide groove 14. Also, the slide valve 12 has a shape in which a portion of the column is cut to be a shape in which a counter surface le of the slide valve 12 facing the housing portion 1A extends along an outer peripheral wall of the housing portion 1A. The slide valve 12 is connected to a direct-acting actuator (not illustrated) through a coupling portion 12c. By driving the direct-acting actuator, the slide valve 12 moves in the slide groove 14 in the direction along the rotating shaft 9 of the screw rotor 4.

[0037] (Specific Configuration around Discharge Port 15) Next, a detailed configuration around a discharge port 15 of the screw compressor 100 according to Embodiment 1 of the present invention is described.

Fig. 3 provides perspective views showing the configuration around the discharge port 15 (the housing portion) of the screw compressor 100 according to Embodiment 1 of the present invention. It is to be noted that Fig. 3 provides perspective views viewed from a blank arrow B side in Fig. 2. Also! Fig. 3(a) shows a state in which the slide valve 12 moves to the discharge side, and Fig. 3(b) shows a state in which the slide valve 12 moves to the suction side. Also, in Fig. 3, illustration of a guide portion and so forth coupled to the coupling portion 12c is omitted for easier understanding of the configuration around the discharge port 15.

[0038] Fig. 4 provides explanatory views of the configuration around the discharge port 15 of the screw compressor 100 in Fig. 3, and shows a state in which the slide valve 12 is positioned at the most suction side. It is to be noted that "the most suction side" mentioned here represents "the most suction side" within a moving range of the slide valve 12 for adjusting a discharge timing, and therefore may not correspond to "the most suction side" within the entire sliding range of the slide valve 12. That is, both "the most suction sides" correspond to each other if the moving range of the slide valve 12 for adjusting the discharge timing corresponds to the sliding range of the slide valve 12; however, if not, "the most suction side" in this case may be positioned at the discharge side as compared with "the most suction side" within the sliding range of the slide valve 12. This is similarly applied to "the most discharge side" in the following

description.

[0039] As shown in Fig. 3, the slide valve 12 is movably housed in the slide groove 14 (see Fig. 4) in parallel to the rotating shaft 9 (see Fig. 1). The slide valve 12 adjusts a discharge start timing by changing the position of a discharge-side end surface 12d of the slide valve 12. That is, the slide valve 12 slides to the suction side and advances the discharge start timing in the case of partial load operation with a relatively small compression ratio, and slides to the discharge side and delays the discharge start timing in the case of full load operation or in the case of partial load operation with a relatively large compression ratio.

[0040] That is, the discharge port 15 is formed by an inner wall surface of an opening port 1 B formed at the casing 1 (more specifically, an opening port open at the housing portion lAin the casing 1), and the discharge-side end surface 12d of the slide valve 12.

[0041] Here, in the following description, the discharge port 15 is defined as shown in Fig. 4. That is, the discharge port 15 includes a variable port 16 (a thick oblique-line portion in the drawing) and a fixed port 17 (a thin oblique-line portion in the drawing).

[0042] The variable port 16 in the discharge port 15 is configured of a region open within a screw-rotor center angle range 41 being the same as that of the slide valve 12. In other words, the variable port 16 in the discharge port 15 is configured of a region portion overlapping with a region where the counter surface le of the slide valve 12 extends in the sliding direction. Also, the variable port 16 changes the discharge start timing in accordance with the position of a discharge-side end portion of the slide valve 12. Also, the variable port 16 can change the opening area thereof in accordance with the position of the discharge-side end portion of the slide valve 12.

[0043] The fixed port 17 in the discharge port 15 is a region other than the variable port 16, and is a portion formed between the variable port 16 and the gate rotor 7 (see Fig. 3).

Here, reference sign 161 denotes a rotation-side slide surface of the variable port 16, and reference sign 16r denotes a non-rotation-side slide surface of the variable pod 16. Also, a suction-side end surface of the fixed port 17 has a step. In the following description, an inclined surface 17a and a vertical surface 17b are defined from the variable port 16 side while the step portion serves as the border. Also, in the following description, the fixed port 17 is divided into two portions in the circumferential direction at the step portion, and the two portions may be occasionally distinguished from each other, as a divided fixed port l7ax being a portion including the inclined surface 17a and a divided fixed port l7bx being a portion including the vertical surface 17b.

[0044] As shown in the left drawing in Fig. 4, when the slide valve 12 is positioned at the most suction side, the shape of the suction-side end surface of the discharge port 15 is a substantially 7-like shape. That is, the suction-side end surface of the discharge port 15 is formed to have a Z-like shape in which the discharge-side end surface 12d (hereinafter, occasionally referred to as inclined surface 12d) of the slide valve 12, the slide surface 161, and the inclined surface 1 7a are mutually connected to each other at angles, and thus the suction-side end surface of the discharge port 15 entirely has a substantially Z-like shape, although the suction-side end surface of the discharge port 15 is not a complete Z-like shape because the suction-side end surface includes the vertical surface 1 7b. The 7-like shape is a 7-like shape in which the inclined surface 1 7a at the fixed port 17 side is formed at a high-pressure side with respect to the inclined surface 12d at the variable port 16 side in the suction-side end surface of the discharge port 15.

[0045] It is to be noted that the divided fixed port 1 7bx in the fixed port 17 is provided at the casing 1 so that the divided fixed port 1 7bx can discharge fluid until the last in a final phase of a discharge process. Specifically, the suction-side end surface of the divided fixed port 1 7bx is the vertical surface 1 7b.

However, the shape and position are not limited thereto.

[0046] Next, the mount position of the slide valve 12 is described. In this case, as shown in Fig. 4, an angle from an end surface (hereinafter, referred to as gate-rotor opening surface) 1 aa of the gate-rotor opening port 1 a at the slide valve 12 side to the center of the slide valve 12 is defined as 43, and the mount position of the slide valve 12 is indicated at the angle 43. It is assumed that the lower limit of 3 is a larger value than 30 degrees of related art at which the discharge area can be. The upper limit of 43 is an angle at which the slide valve 12 does not interfere with a gate-rotor support part at the opposite surface. This angle varies depending on the size of the slide valve 12. If the size of the slide valve 12 is as large as related art (a width of about 40 degrees at the center angle 41 of the screw rotor 4), the upper limit of 43 is 100 degrees. The formation range of the divided fixed port 1 7bx portion is a screw-rotor center-angle range being 2, and is, for example, about 10 degrees.

[0047] (Explanation for Operation) Described next is an operation of the screw compressor 100 configured as described above.

Fig. 5 provides explanatory views showing a compression theory of the screw compressor 100 according to Embodiment 1 of the present invention.

[0048] As shown in Fig. 5, since the screw rotor 4 is rotated by the motor 8 (see Fig. 1) through the rotating shaft 9 (see Fig. 1), the gate rotor teeth 7a of the gate rotor 7 moves relatively in the screw grooves 10. Accordingly, a suction process, a compression process, and a discharge process are executed in the compression chamber 11 as a single cycle, and this cycle is repeated. Here, respective processes are described while focusing on the compression chamber 11 indicated with gray in Fig. 5.

[0049] Fig. 5(a) shows a state of the compression chamber 11 in the suction process. When the screw rotor 4 is driven by the motor 8 and rotates in a direction indicated by a solid line arrow, the gate rotor 7 at the lower side shown in Fig. 5 rotates in a direction indicated by a blank arrow by the rotation of the screw rotor 4. Also, the gate rotor 7 at the upper side shown in Fig. 5 is rotated as indicated by a blank arrow in a direction opposite to the direction of the gate rotor 7 at the lower side. In the suction process, the compression chamber 11 has the largest capacity, communicates with a low-pressure space of the casing 1 (see Fig. 1), and is filled with low-pressure refrigerant gas.

[0050] When the screw rotor 4 further rotates, the gate rotor teeth 7a of the two gate rotors 7 are successively rotated and moved toward the discharge port 15.

Accordingly, the capacity (the volume) of the compression chamber 11 is decreased as shown in Fig. 5(b). Although illustration of the slide valve 12 is omitted in Fig. 5(b), the variable port 16 is almost closed by the slide valve 12 in Fig. 5(b), the capacity of the compression chamber 11 is decreased more than Fig. 5(a), and the refrigerant gas in the compression chamber 11 is compressed.

[0051] When the screw rotor 4 continuously rotates, as shown in Fig. 5(c), the compression chamber 11 communicates with the discharge port 15.

Accordingly, the high-pressure refrigerant gas compressed in the compression chamber 11 is discharged from the discharge port 15 to the outside. Then, similar compression is executed again at the rear surface of the screw rotor 4.

The inside of the screw grooves 10 not covered with the casing 1 (that is, the inner wall surface of the housing portion 1A) is open communicates with the gate rotor 7 and the gate-rotor support chamber 6 at the opposite side, and has a suction pressure atmosphere.

[0052] Next, a change in discharge area is described in detail with reference to Figs. 6 to 9. Fig. 6 to Fig. 9 provide explanatory views for explaining the relationship between the screw rotation angle and the discharge area in the screw compressor 100 according to Embodiment 1 of the present invention.

Figs. 6 and 8 each show a developed view of the inner wall surface of the housing portion lAand the outer peripheral surface of the screw rotor 4. Fig. 6 shows a state when the slide valve 12 is arranged at the discharge side (in an operating state with a relatively large compression ratio). Fig. 8 shows a state when the slide valve 12 is arranged at the suction side (in an operating state with a relatively small compression ratio even in partial load operation).

[0053] The substantial discharge area of the screw compressor 100 is a facing region area between the discharge port 15 and the screw groove 10. In Figs. 6 and 8, grid-line portions Cl to C3, oblique-line portions Dl to D3 indicated by oblique lines directed to the lower right side, and lateral-line portions El to E2 represent respective substantial discharge areas (the facing regions between the discharge port 15 and the screw groove 10).

[0054] Figs. 7 and 9 are characteristic diagrams showing discharge areas respectively corresponding to Figs. 6 and 8. In each of Figs. 7 and 9, the horizontal axis plots the screw rotation angle and the vertical axis plots the discharge area. In each of Figs. 7 and 9, (a) indicates a change in variable port area and (b) indicates a change in fixed port area, each change is expressed with a parabola protruding to the upper side, and the total sum of (a) and (b) indicates the discharge port area.

[0055] (Case of High Compression-ratio Operation) Hereinafter, with reference to Figs. 6 and 7, a case of high compression ratio operation, that is, changes in discharge area in a case of full load operation and in a case of partial load operation with a relatively large compression ratio are described. In high compression-ratio operation, an operation is executed in a state in which the slide valve 12 is moved to the discharge side.

[0056] Fig. 6(a) shows a discharge area Cl at a screw rotation angle BA(1) and a discharge area Dl at a screw rotation angle OA(4). Fig. 6(b) shows a discharge area C2 at a screw rotation angle BA(2) and a discharge area D2 at a screw rotation angle BA(S). Also, Fig. 6(c) shows a discharge area C3 at a screw rotation angle BA(3) and a discharge area D3 at a screw rotation angle BA(6).

That is, Fig. 6 shows a state in which the screw grooves 10 advance in the order of the rotation angle BA(1) => BA(2) => BA(3) => BA(4) => BA(S) => BA(6), and the discharge area (facing region) is changed in the order of Cl => C2 => C3 => Dl => D2 => D3.

[0057] That is, the inside of the compression chamber 11 reaches the discharge pressure and the fixed port 17 of the discharge pod 15 starts to be open (Cl) almost when the screw rotation angle reaches OA(1) (Fig. 6(a)). The suction-side end surface (the inclined surface 1 7a) of the fixed port 17 at this time is formed along the inclination of the facing screw groove 10 so as to ensure the maximum discharge area. That is, if the suction-side end surface of the fixed port 17 is formed along the inclination of the facing screw groove 1°: when the screw groove 10 is moved downward in Fig. 6 by the rotation of the screw rotor 4, the discharge area is expanded from the entire inclined surface 17a.

Accordingly, the maximum discharge area can be ensured.

[0058] Alternatively, the inclined surface 1 7a of the fixed port 17 does not have to be formed along the inclination of the facing screw groove 10, and is only required to be formed in consideration with that the opening area of the discharge pod 15 at discharge start is ensured as large as possible.

[0059] At OA(2) (Fig. 6(b)), the discharge area of the fixed pod 17 is increased and the variable port 16 starts to be open (C2). Then, the discharge area of the variable pod 16 is decreased, and disappears at 0A as shown in Fig. 7; however, the discharge area of the fixed port 17 reaches the maximum at an angle near OA*. In this way, since the discharge area of the variable port 16 is added in the first half of the discharge process in which the discharge area is decreased and the discharge flow rate is increased, an increase in discharge loss can be restricted.

[0060] Then, at the angle near BAt and later the discharge area of the fixed port 17 starts to be decreased as shown in Fig. 7, and the discharge area is decreased as the rotation of the screw rotor 4 advances in the order of BA(3) => BA(4) => BA(S) => BA(6).

[0061] As described above, in the case of full load operation or in the case of partial load operation with the relatively high compression-ratio, the slide valve 12 is moved to the discharge side, so that the compressed fluid is discharged mainly from the fixed port 17 side.

[0062] (Case of Low Compression-ratio Operation) Hereinafter, with reference to Figs. 8 and 9, a change in discharge area in a case of low compression-ratio operation, that is, in a case of partial load operation with a relatively small compression ratio is described.

[0063] Fig. 8(a) shows a discharge area Cl at a screw rotation angle 83(1), a discharge area Dl at a screw rotation angle BB(4), and a discharge area El at a screw rotation angle OB(7). Fig. 8(b) shows a discharge area C2 at a screw rotation angle OB(2), a discharge area D2 at a screw rotation angle OB(5), and a discharge area [2 at a screw rotation angle 03(8). Also, Fig. 8(c) shows a discharge area C3 at a screw rotation angle 8B(3) and a discharge area D3 at a screw rotation angle BB(6). That is, Fig. 8 shows a state in which the screw grooves 10 advance in the order of the rotation angle of 83(1) => 83(2) => BB(3) => BB(4) => BB(5) => BB(6) => BB(7) => (8), and the discharge area (facing region) is changed in the order of Cl => C2=> C3=> Dl => D2=> D3=> El => E2.

[0064] That is, the inside of the compression chamber 11 reaches the discharge pressure and the variable port 16 of the discharge port 15 starts to be open (Cl) almost when the screw rotation angle reaches OB(1) (Fig. 8(a)). The discharge-side end surface 12d of the slide valve 12 at this time is formed along the inclination of the facing screw groove 10 so as to ensure the maximum discharge area. That is, if the discharge-side end surface 12d of the slide valve 12 is formed along the inclination of the facing screw groove 10, when the screw groove 10 is moved downward in Fig. 8 by the rotation of the screw rotor 4, the discharge area is expanded from the entire discharge-side end surface 12d of the slide valve 12. Accordingly, the maximum discharge area can be ensured.

[0065] Alternatively, the discharge-side end surface 12d of the slide valve 12 does not have to be formed along the inclination of the facing screw groove 10, and is only required to be formed in consideration with that the opening area of the discharge port 15 at discharge start is ensured as large as possible.

[0066] At 03(2) (Fig. 8(b)), the discharge area of the variable port 16 is increased (C2). Further, at 03(3) (Fig. 8(c), Fig. 9), a discharge area C3' of the fixed port 17 is added (C3).

[0067] Then, as the rotation of the screw rotor 4 advances from OB(4) to GB(S), the variable port 16 is decreased, and at BB* (Fig. 9), the variable port 16 is no longer provided. While the variable port 16 is decreased, the discharge area of the fixed port 17 is increased. Hence, a state (see Fig. 8) is continuously provided in which the discharge area of the discharge port 15 is relatively largely ensured with a gradual change from BB(3) to GB*. Then, at BB(3) and later, the discharge area of the discharge port 15 is changed as indicated by D3 => El => E2 in Fig. 8, similarly to Dl => D2 => D3 in Fig. 7.

[0068] As described above, even in the case of partial load operation, if the compression ratio is relatively small, the slide valve 12 is moved to the suction side, and the compressed fluid is discharged from both the variable pod 16 and the fixed port 17.

[0069] A difference in discharge port shape between related art and Embodiment 1 is described here. Fig. 10 provides explanatory views of a configuration around a discharge pod 150 of related art being a comparative subject.

The discharge pod 150 includes a variable port 160, and a substantially rectangular-shaped fixed port 170. Also, the position of a slide valve 120 is different from the position of the slide valve 12 in Embodiment 1. In this example, the slide valve 120 has an angle width of 1 = 40 degrees, and the center of the slide valve 120 is provided at a position of 43 = 30 degrees from the gate-rotor opening surface 1 aa. Also, a formation range of the fixed port 170 is a screw-rotor center angle range being 42, and is, for example, about 10 degrees being equivalent to 2 shown in Fig. 4.

[0070] In the following description, the specific description of the operation is omitted, and only an operation of related ad different from the present invention is described.

[0071] (Case of High Compression-ratio Operation) Fig. 11 provides explanatory views for explaining the relationship between the screw rotation angle and the discharge area in a state in which the compression ratio is large and the slide valve 120 of related art in Fig. 10 is arranged at the discharge side. Fig. 12 is an illustration showing the comparison result of the discharge area between related art and Embodiment 1 in the state in which the slide valve is arranged at the discharge side.

[0072] The way of viewing Fig. 11 is similar to the way of viewing Fig. 6. That is, Fig. 11 shows that the screw rotation angle is changed in the order of OA(1) => OA(2), OA(3), OA(4), OA(5), and then OA(6), and the discharge area is changed in the order of Cl => C2 => C3 => Dl => D2 => D3.

[0073] In the configuration of related art, in the case of high compression-ratio operation, as shown in Fig. 11, the compressed fluid is discharged from the variable pod 160 from the first half to the latter half of the discharge process.

Accordingly, a coupling portion 120c of the slide valve 120 is constantly positioned above the discharge port 150, and the discharge flow path is closed.

[0074] In contrast, Embodiment 1 has the following configuration so that the coupling portion 12c does not block the discharged fluid discharged from the discharge port 15 and the maximum discharge area at discharge start can be ensured. That is, in a state in which the slide valve 12 is arranged at the non-rotation direction side (the upper side in Fig. 15 (described later)) as compared with the slide valve 120 of related art and the slide valve 12 is arranged at the discharge side, the compressed fluid is discharged mainly from the fixed port 17 side. The variable port 16 side of the suction-side end surface of the fixed port 17 is the inclined surface 1 7a instead of a vertical surface. The point that the inclined surface 1 7a is effective for ensuring the maximum discharge area at discharge start is as described above.

[0075] With this configuration, as it is found from Fig. 6, the discharge flow path in the discharge port 15 is hardly closed by the coupling portion 12c. Accordingly, an advantageous effect of decreasing a discharge loss is attained.

[0076] Further, as it is found from Fig. 12, regarding the discharge area of Embodiment 1, the discharge area from the variable port 16 can be increased in addition to the discharge area of the fixed port 17 of related art without changing the discharge start timing. Accordingly, the discharge area in the first half of the discharge process, in which the discharge area is small and the discharge flow rate is increased, can be increased, and hence an advantageous effect of further decreasing the discharge loss is attained.

[0077] (Case of Low Compression-ratio Operation) Fig. 13 provides explanatory views for explaining the relationship between the screw rotation angle and the discharge area in a state in which the slide valve of related art in Fig. 10 is arranged at the suction side in low compression-ratio operation. Fig. 13A provides explanatory views for explaining the difference in area of the variable port in low compression-ratio operation due to the difference in arrangement of the slide valve between related art and Embodiment 1. Fig. 14 is an illustration showing the comparison result of the discharge area between related art and Embodiment 1 in the state in which the slide valve is arranged at the suction side. Fig. 14A is an illustration showing a change in discharge area in a case in which the center of the slide valve 12 is provided at 90 degrees from the gate-rotor opening surface 1 aa. Fig. 1 4B is an illustration showing the comparison result of the discharge area between the case in which the center of the slide valve 12 is provided at 90 degrees from the gate-rotor opening surface 1 aa and related art.

[0078] The way of viewing Fig. 13 is similar to the way of viewing Fig. 6. That is, Fig. 13 shows that the screw rotation angle is changed in the order of the rotation angle of OB(1) => OB(2) => OB(3) => OB(4) => GB(S) => OB(6) > OB(7) > OB(8), and the discharge area is changed in the order of Cl => C2 => C3 => Dl => D2 D3 => El => E2.

[0079] In the configuration of related art in low compression-ratio operation, as shown in Fig. 13, the slide valve 120 of related art is arranged at the suction side as compared with Embodiment 1. A change in discharge area due to the aforementioned difference is described with reference to Fig. 13A.

[0080] Fig. 1 3A is an illustration that shows the slide valve 120 of related art and the slide valve 12 of Embodiment 1 arranged next to each other and comparison is made for the difference in discharge area due to the difference in position of the slide valve. Fig. 13 shows a state from the first half of the discharge process to the middle of the discharge process (OB(1) => OB(2) => OB(4)), in the order of (a) => (b) => (c). Also, in Fig. 1 3A, an oblique-line portion represents the discharge area in the case of the position of the slide valve 12, and a grid-line portion represents the discharge area in the case of the position of the slide valve 120.

[0081] In the screw compressor, the facing surface between the opening port provided at the casing 1 and the screw groove 10 serves as the discharge area.

Owing to this, if the screw groove 10 is formed at the discharge side and the suction side at the same inclination with no limit from the suction side toward the discharge side as indicated by dotted-chain lines in Fig. 13A(b), the discharge area of the variable port 16 is the same irrespective of the position of the slide valve 12. However, the shape of the screw groove 10 at the suction side is different from the discharge side. As shown in Fig. 13A(a), an inclination angle iD with respect to the screw-axis direction has a relationship of suction-side inclination angle ms > discharge-side inclination angle cDd. Further, the screw groove 10 is no longer provided at the discharge-side end surface 12d.

[0082] That is, the change in discharge area is different depending on the mount position of the slide valve 12. In Embodiment 1 in which the discharge-side end surface 12d of the slide valve 12 is positioned at the discharge side as compared with a discharge-side end surface 120d of the slide valve 120 of related art, as shown in Fig. I 3A(a) and (b), the inclination angle c1 of the screw groove 10 is small and the variable port area can be largely ensured in the first half of the discharge process as compared with related art. That is, comparing the oblique-line portion with the grid-line portion in Fig. 1 3A(a) and (b), the area of the oblique-line portion becomes larger than the area of the grid-line portion.

However, in the middle of the discharge process in Fig. 13A(c) and later, since the screw groove 10 at the slide valve 12 is no longer provided, the variable port area at the slide valve 12 side becomes smaller than the variable port area at the slide valve 120 side of related art. However, in Embodiment 1, since the divided fixed port l7ax is provided, the discharge area can be ensured with the divided fixed port 1 Yax in the middle of the discharge process and later.

[0083] Consequently, the discharge area in Embodiment 1 is as shown in Fig. 14.

The total discharge area in the discharge process is equivalent to that of related art, and the discharge area in the discharge process can become uniform.

[0084] If the slide valve 12 is excessively separated from the gate-rotor opening surface laa (see Fig. 4), the discharge area may be decreased. This point is described below in comparison with a case in which the slide valve 12 is further separated from the gate-rotor opening surface 1 aa as compared with the position shown in Fig. 13A and the center of the slide valve 12 is provided at 90 degrees from the gate-rotor opening surface laa.

[0085] Fig. 14B is an illustration showing the comparison result of the discharge area between the case in which the center of the slide valve 12 is provided at9O degrees from the gate-rotor opening surface 1 aa and related art.

Since the screw groove 10 is no longer provided at the discharge-side end surface 12d, as shown in Fig. 14A(a), the variable pod area of the slide valve 12 is small, and the variable port area disappears in an early phase. Consequently, if the center of the slide valve 12 is provided at 90 degrees from the gate-rotor opening surface laa, as compared with related art as shown in Fig. 14B, the discharge area in the first half of the discharge process is decreased, and further the total discharge area is also decreased.

As described above, in Embodiment 1, an optimal point for the center position of the slide valve 12 is within a range of 30 degrees <3 < 90 degrees.

[0086] Here, the shape of the suction-side end surface of the discharge port 15 is reviewed. In order to improve closing of the flow path by the coupling portion 1 2c and to increase the discharge area in the first half of the discharge process, in the case of operation with the high compression ratio as described above, it is effective to form the divided fixed port 1 7ax in the suction-side end surface of the slide valve 12 as the inclined surface 17a instead of a vertical surface. Also, in the case of operation with the low compression ratio, that is, in the state in which the slide valve 12 is positioned at the most suction side, it is effective to form the discharge-side end surface 12d of the slide valve 12 as the inclined surface extending along the inclination of the screw groove 10. Therefore, if the suction-side end surface shape of the discharge port 15 is considered with regard to the above-described configuration, in the state in which the slide valve 12 is positioned at the most suction side, it is effective to form the shape of the suction-side end surface of the discharge port 15 as a substantially Z-like shape.

[0087] Next, improvement in leakage of fluid at the partition wall portion provided at the outer peripheral surface of the slide valve 12 is described.

[0088] Fig. 15 provides lateral cross-sectional views in low compression-ratio operation in the state in which the slide valves 12 and 120 are arranged at the suction side. (a) shows related art, and (b) shows Embodiment 1. Also, Fig. 15(a) and (b) shows the case of the same screw rotation angle OB1 (see Fig. 8 and Fig. 13).

In Fig. 15, reference sign 18 denotes a partition wall that provides a partition for a suction pressure and a discharge pressure, and a thick dotted-chain line indicates the center of the seal surface.

[0089] As shown in Fig. 15(a), in related art, if the axial-direction position of the slide valve 120 is adjusted to the suction side in accordance with the discharge start timing when the compression ratio is small, the discharge-side end surface 120d of the slide valve 120 may extend across the partition wall 18 and be positioned at the suction-pressure side. Accordingly, the seal surface is not formed, and fluid leaks from the compression chamber to the suction-pressure side as indicated by a blank arrow.

[0090] In contrast, in Embodiment 1, the slide valve 12 is arranged at the non-rotation direction side (the upper side in Fig. 15) from the mount position of the gate rotor 7 as compared with the slide valve 120 of related art. Owing to this, in an end edge 1 Oa at the rotation direction side (the lower side in Fig. 15) of the compression chamber, a portion overlapping with the slide valve position in the screw-rotor circumferential direction (the up-down direction in Fig. 15) is positioned at the discharge side (the left side in Fig. 15) in Embodiment 1 as compared with related art. Accordingly, the position of the discharge-side end surface 12d of the slide valve 12 determined in accordance with the position of the end edge 1 Oa at the screw rotation angle eBi at the discharge start time point is at the discharge side (the left side in Fig. 15) as compared with related art.

Therefore, since the discharge-side end surface 12d of the slide valve 12 is positioned at the discharge side with respect to the partition wall 18, the seal surface is formed and leakage does not occur [0091] As described above, in Embodiment 1, since the suction-side end surface shape of the discharge port 15 when the slide valve 12 is arranged at the most suction side is the 7-like shape, advantageous effects are obtained as follows.

[0092] That is, in the case of operation with the high compression ratio, an advantageous effect is obtained such that the discharge flow path that is not blocked by the coupling portion 12c can be formed and the discharge pressure loss can be decreased.

[0093] Also, in the case of operation with the low compression ratio, the variable port area can be largely ensured in the first half of the discharge process with the small discharge area, and also the fixed port area is added in the middle of the discharge process. Thus, a change in discharge area can become uniform.

Accordingly, an advantageous effect is obtained such that the discharge area can be (effectively) increased, the discharge flow path that is not blocked by the coupling portion 1 2c in the latter half of the discharge process is formed, and hence the discharge loss can be decreased.

[0094] Also, with the structure of related art, as shown in Fig. 15, since the discharge-side end surface 1 20d of the slide valve 120 in the case of operation with the low compression ratio is positioned at the suction side with respect to the partition wall 18, leakage may occur, and the leakage may result in a decrease in efficiency. However, in Embodiment 1, the slide valve 12 is arranged at the non-rotation direction side (the upper side in Fig. 15) as compared with the slide valve of related art. Hence, the position of the slide valve 12 when the slide drive 12 is adjusted in accordance with the screw groove 10 at the discharge start time point is positioned at the discharge side as compared with related art.

Accordingly, an advantageous effect is obtained such that the operation range at the low compression-ratio side, in which an operation can be made while the discharge-side end surface 12d of the slide valve 12 does not extend across the partition wall 18 that divides the suction pressure and the discharge pressure (without leakage), can be expanded.

[0095] Consequently, the screw compressor 100 that can decrease the discharge pressure loss within the wide operation range from the high compression ratio to the low compression ratio, and therefore, can make an operation with high efficiency throughout the year can be obtained.

[0096] Also, since the above-described advantageous effects can be obtained without an increase in length of the slide valve 12 in the circumferential direction of the screw rotor 4, the disadvantageous problems, such as an increase in leakage loss and interference between the gate-rotor support part and the slide valve 12, which may possibly occur when the slide valve 12 is elongated in the circumferential direction, do not occur [0097] It is to be noted that Embodiment 1 is merely an example, and the angular range in which the slide valve 12 is provided is not limited to the range shown in Fig. 4 and so forth.

[0098] Also, in Embodiment 1, a portion of the suction-side end surface of the fixed port 17 has the vertical surface 17b; however, it is not limited thereto.

Alternatively, for example, the vertical surface 17b may not be provided as shown in Fig. 16, and an entirely inclined surface 17c formed by extending the inclined surface 1 7a with the same inclination may be provided.

[0099] Also, in Embodiment 1 described above, the screw compressor of a type provided with the two gate rotors 7 is described. However, it is not limited thereto. Even with a screw compressor of a type provided with a single gate rotor 7, by forming the discharge port 15 in the shape shown in Embodiment 1, the screw compressor generally having a small loss and high efficiency can be obtained.

[0100] Consequently, the screw compressor 100 that can restrict an increase in discharge loss within the wide operation range from the high compression ratio to the low compression ratio can be obtained.

[0101] Embodiment 2 Embodiment 2 relates to a refrigeration cycle apparatus.

[0102] Fig. 17 is a refrigerant circuit diagram of a refrigeration cycle apparatus 300 according to Embodiment 2 of the present invention.

The refrigeration cycle apparatus 300 includes a refrigerant circuit in which a screw compressor 200 driven by an inverter 101, a condenser 102, a high pressure portion of an intermediate cooler 103, an expansion valve 104 being a pressure reducing device, and an evaporator 105 are connected in that order through a refrigerant pipe. The refrigeration cycle apparatus 300 further includes an economizer pipe 107 that is branched from a position between the intermediate cooler 103 and the expansion valve 104 and that is connected to the screw compressor 100 through an intermediate-cooler expansion valve 106 and a low pressure portion of the intermediate cooler 103.

[0103] The condenser 102 cools and condenses discharge gas from the screw compressor 200. The expansion valve 104 expands the branched liquid of the condenser 102 by throttle expansion. The evaporator 105 evaporates the refrigerant flowing out from the expansion valve 104. The intermediate cooler 103 exchanges heat between a high-pressure side refrigerant between the condenser 102 and the expansion valve 104 and a low-pressure side refrigerant obtained by reducing the pressure of a portion of the high-pressure side refrigerant by the intermediate-cooler expansion valve 106, and hence cools the high-pressure side refrigerant.

[0104] The refrigeration cycle apparatus 300 further includes a controller 301 that controls the inverter 101, the expansion valve 104, and the intermediate-cooler expansion valve 106; controls the position of the slide valve 12 of the screw compressor 200; and controls the entire refrigeration cycle apparatus such as driving and stop of an economizer operation (described later).

[0105] Fig. 18 is a primary-portion end-surface diagram of the screw compressor provided in the refrigeration cycle apparatus 300 according to Embodiment 2 of the present invention. Fig. 19 provides perspective views showing a configuration around a discharge port 15 (a housing portion) of the screw compressor 200 provided in the refrigeration cycle apparatus 300 according to Embodiment 2 of the present invention. Fig. 20 provides explanatory views of the configuration around the discharge port 15 of the screw compressor 200 provided in the refrigeration cycle apparatus 300 according to Embodiment 2 of the present invention.

[0106] The screw compressor 200 is substantially similar to the screw compressor in Embodiment 1. Points of the screw compressor 200 different from the screw compressor 100 are mainly described below. The screw compressor 200 includes an economizer flow path 50 in the casing 1. The economizer flow path guides refrigerant gas from the intermediate cooler 103 to the compression chamber 11 (the screw groove lOin the compression process). The economizer flow path 50 is provided at the casing 1 to allow the outside of the casing 1 to communicate with the slide groove 14.

[0107] An economizer pipe 107 is connected to the economizer flow path 50, and couples the intermediate cooler 103 with the economizer flow path 50. Also, the screw compressor 200 further has an economizer port 12p at a columnar portion of the slide valve 12. As shown in the right drawing of Fig. 20, the economizer port 12p is formed to penetrate from an outer peripheral surface of the slide valve 12 being a slide contact surface with respect to the slide groove 14, to an inner peripheral surface of the slide valve 12 being a slide contact surface with respect to the screw rotor 4.

[0108] As described in Embodiment 1, the inside of the screw grooves 10 (see Fig. 19) not covered with the casing 1 (that is, the inner wall surface of the housing portion 1A) communicates with the gate rotor 7 and the gate-rotor support chamber 6 at the opposite side (the gate rotor 7 and the gate-rotor support chamber 6 not illustrated in Fig. 19), and has a suction pressure atmosphere. Hereinafter, a space in the casing 1 not covered with the inner wall surface of the housing portion lAand has the suction pressure atmosphere (including the gate-rotor support chamber 6) is defined as a suction pressure chamber 1G.

[0109] (Specific Configuration around Economizer Port l2p) Next, a specific configuration around the economizer port 12p according to Embodiment 2 is described.

Fig. 21 provides explanatory views of the configuration around the economizer port according to Embodiment 2 of the present invention.

The economizer flow path 50 that allows the economizer pipe 107 to communicate with the slide groove 14 is provided at the casing 1 as shown in Fig. 21. The economizer flow path 50 includes a pipe path 50a connected to the economizer pipe 107 and a long groove 50b connected to the slide groove 14 side. The long groove 50b extends along the slide surface of the slide valve 12.

The long groove 5Db has a length I corresponding to a slide-valve control position within an operation range for an economizer operation.

[0110] The economizer operation is an operation that opens the intermediate-cooler expansion valve 106, allows the economizer pipe 107 to communicate with the screw compressor 100, and injects economizer gas after passing through the low pressure portion of the intermediate cooler 103 to the compression chamber 11 of the screw compressor 100. Also, the long groove 5Db has a groove width (a length in the screw-rotor circumferential direction) being larger than the diameter d of the economizer port i2p as shown in the right drawing in Fig. 21. The economizer port diameter d is a maximum diameter (equal to or smaller than a minimum tooth thickness) that does not allow neighbor compression chambers of the screw rotor 4 to communicate with each other.

[0111] (Explanation for Operation) Next, an operation in Embodiment 2 is described.

First, an operation of the refrigerant circuit in full load operation is described.

[0112] Fig. 22 is an explanatory view of a refrigeration cycle in an economizer operation of the refrigeration cycle apparatus 300 according to Embodiment 2 of the present invention. Fig. 23 is a pressure-specific enthalpy diagram in full load operation of the refrigeration cycle apparatus 300 according to Embodiment 2 of the present invention. In Fig. 22, an arrow indicates the flow of a refrigerant. A solid line indicates refrigerant liquid, and a broken line indicates refrigerant gas. Refrigerant states at positions with parenthesized numbers in Fig. 23 respectively correspond to refrigerant states at pipe positions with corresponding numbers in Fig. 22.

[0113] In Figs. 22 and 23, the refrigerant gas (1) with a pressure Ps output from the evaporator 105 is sucked into the screw compressor 100, is compressed to a pressure Pd, and then is discharged. The discharged refrigerant gas (5) is subcooled in the condenser 102 to a state of (6). The high-pressure subcooled liquid (6) enters the high pressure portion of the intermediate cooler 103, is further cooled, and becomes a state of (8). The high-pressure liquid (8) output from the intermediate cooler 103 is partly branched, the branched portion is expanded by throttle expansion to an intermediate pressure Pm by the intermediate-cooler expansion valve 106, and the portion in a state of (7) flows into the low pressure portion of the intermediate cooler 103 again.

[0114] The high pressure liquid (high-pressure-side refrigerant) (6) flowing into the high pressure portion of the intermediate cooler 103 directly after output from the condenser 102 exchanges heat with the refrigerant liquid (the low-pressure-side refrigerant) flowing into the low pressure portion of the intermediate cooler 103 again through the intermediate-cooler expansion valve 106, the subcooled state is enhanced to the state of (8). That is, the increase by subcooling enhances the refrigeration effect of the evaporator 105.

[0115] In contrast, the refrigerant liquid (the low-pressure side refrigerant) (7) flowing again into the low pressure portion of the intermediate cooler 103 is evaporated by heat exchange with the high-pressure side refrigerant and becomes refrigerant gas (7a). The refrigerant gas (7a) passes through the economizer pipe 107 and the economizer flow path 50, is injected from the economizer port 12p provided at the slide valve 12 to the screw groove 10 in compression, and is mixed with the compressed gas ((2)-(3)).

[0116] At this time, the compression power is changed in accordance with the in-flow rate and in-flow timing of the gas to the screw compressor 200.

Therefore, increasing a refrigeration capacity without increasing a compression power as far as possible is a point to increase a coefficient of performance, and an optimal intermediate pressure Pm is present.

[0117] Next, an operation of the refrigerant circuit in the case of partial load operation with a small high-low differential pressure is described.

Fig. 24 is a pressure-specific enthalpy diagram in partial load operation of the refrigeration cycle apparatus 300 according to Embodiment 2 of the present invention when a high-low differential pressure is small.

When the high-low differential pressure is small in partial load operation, as shown in Fig. 24, the differential pressure between the intermediate pressure (intermediate cooler outlet) and the compression chamber is small, a relationship of intermediate pressure < compression chamber is transiently established in the economizer operation, and hence the operation becomes unstable. In addition, since the increasing effect of the refrigeration capacity is decreased and the increase in power due to the inflow of the economizer gas in the middle of compression is enhanced, the coefficient of performance is decreased.

Accordingly, under a condition with a small high-low differential pressure, the intermediate-cooler expansion valve 106 in Fig. 22 is closed so that the economizer operation is not executed.

[0118] Next, the positional relationship between the economizer port 12p and the screw groove 10 is described with reference to Figs. 25 and 26.

Fig. 25 and Fig. 26 provide explanatory views for explaining the relationship between the screw rotation angle and the economizer port in the screw compressor 200 according to Embodiment 2 of the present invention.

Fig. 25 shows a state when the slide valve 12 is arranged at the discharge side (in an operating state with a large compression ratio such as in full load operation). Fig. 26 shows a state when the slide valve 12 is arranged at the suction side (in an operating state with a small compression ratio even in partial load operation). Also, Fig. 25(a) to (c) and Fig. 26(a) to (c) each are a developed view of the outer peripheral surface of the screw rotor 4. Fig. 25(d) and Fig. 26(d) are cross-sectional views respectively taken along lines C-C in Fig. 25(a) and Fig. 26(a).

[0119] Al toA9 in Fig. 25 and B1 to Bll in Fig. 26 represent the screw grooves 10 at the screw rotation angles OA(1) to OA(9), and OB(1) to BB(1 1). That is, Fig. shows that the screw grooves 10 advance in the order of the rotation angle BA(1) => BA(2) => BA(3) => BA(4) => BA(S) => BA(6) => BA(7) => BA(8) => BA(9) and that the capacities of the screw grooves 10 are decreased. Fig. 26 shows that the screw grooves 10 advance in the order of the rotation angle BB(l) => BB(2) => BB(3) => BB(4) => BB(5) => BB(6) =>BB(7) => BB(8) => BB(9) => BB(10) => BB(l 1), and that the capacities of the screw grooves 10 are decreased.

[0120] In Fig. 26, the screw grooves Bi and B2 hatched with oblique lines are the screw grooves 10 in the suction process. That is, the screw grooves Bi and B2 are at positions not in a completely closed state by the gate rotor 7 and the inner wall surface of the housing portion 1A. Also, the screw grooves Al, A2, A3, and B3 illustrated in a filled manner in Figs. 25 and 26 represent the screw grooves in the compression process. Also, the screw grooves A4 to AG, and B4 to Bil not filled are the screw grooves 10 in the discharge process. The substantial discharge area in the discharge process is the facing region area between the discharge port 15 and the screw grooves 10, and is indicated by grid-line portions in Figs. 25 and 26.

[0121] (Case of Full Load Operation) A positional relationship between the economizer port 12p and the screw grooves 10 in full load operation is described with reference to Fig. 25.

The economizer operation is executed in full load operation. In the economizer operation, the slide valve 12 moves to the discharge side as shown in Fig. 25(d), and is arranged at a position at which the slide valve 12 completely closes the variable port 16 as shown in Fig. 25(a) to (c). Also, the economizer flow path 50 provided at the casing 1 communicates with the economizer port 12p.

[0122] The economizer pod 12p shown in Fig. 25(a) starts communicating with the screw groove Al at a low pressure immediately after suction is completed.

Then, the economizer port 12p advances on the screw groove of A2 and thenA3 in the compression process. While the economizer port i2p advances on the screw groove of A2 and thenA3, due to the differential pressure between the intermediate pressure Pm and the screw groove 10, the economizer gas is injected from the economizer port 12p to the screw groove 10. If the economizer port 12p is open to the screw groove 10 that becomes a high pressure, the intermediate pressure is increased, and the capacity increasing effect by the economizer operation (degree of subcooling of (8) in Fig. 23) is decreased. Hence, in this case, the economizer gas is injected to the screw groove 10 having as low pressure as possible.

[0123] Also, when a large amount of refrigerant gas is injected to the screw groove 10 in the suction process, the refrigerant circuit amount is decreased, and the decrease in refrigerant circuit amount becomes a factor of decreasing the refrigeration capacity. Owing to this, the economizer port i2p communicates with the screw groove 10 at a timing at which suction is almost completed. That is, the economizer port 12p starts communicating with the screw groove Al at compression start as shown in Fig. 25(a), passes through the screw grooves A2 and A3 in the compression process, and is no longer open to the screw groove completely at the screw groove A4. This process is repeated.

[0124] It is to be noted that under the condition in which the high-low differential pressure is relatively large even in partial load operation and the economizer effect can be obtained, the economizer flow path 50 provided at the casing 1 and the economizer port i2p are allowed to communicate with each other and the economizer operation is executed. In the economizer operation in partial load operation, the slide valve 12 is moved to the suction side as compared with the full load operation, or is positioned at the same slide position as the full load operation.

[0125] (Case with Small High-low Differential Pressure in Partial Load Operation) Next, the positional relationship between the economizer port 12p and the screw groove 10 when the high-low differential pressure is small in partial load operation is described with reference to Fig. 26.

When the high-low differential pressure is small in partial load operation, the economizer operation is stopped. If the economizer operation is stopped, the slide valve 12 is moved to the suction side as shown in Fig. 26(d), and the economizer port 12p is arranged at a portion (the suction pressure chamber 1G) of the housing portion lAwithout the inner wall surface of the housing portion 1A as shown in Fig. 19(b). In this state, the economizer flow path 50 provided at the casing 1 does not communicate with the economizer port i2p. Also, while the economizer operation is stopped, the economizer port i2p constantly communicates with the suction pressure chamber 1 C. Accordingly, when the high-low differential pressure is small in partial load operation, the operation is executed in a state in which the economizer port 12p does not relate to the screw groove 10 from the suction process to the discharge process.

[0126] Meanwhile, as a screw compressor of related art available for the economizer operation, there is a screw compressor having a configuration that allows an economizer pipe and a compression chamber to communicate with each other through a path provided at an outer peripheral surface side of a casing, a flow path provided in a slide valve, and an economizer port provided at an inner peripheral surface side of the casing (for example, Japanese Unexamined Patent Application Publication No. 4-1 3663). With this technique, even if the economizer operation is stopped, the slide valve is moved, and hence the flow path in the slide valve is separated from the compression chamber, the economizer port provided at the casing continuously communicates with the compression chamber Owing to this, the economizer port serves as a capacity portion (dead volume) that is wastefully compressed from a suction pressure to a discharge pressure. Accordingly, a re-expansion loss may be generated when the economizer port passes above a screw groove while the economizer operation is stopped.

[0127] However, with the configuration of Embodiment 2, the economizer port 12p no longer relates to an operation that stops the economizer operation, and a decrease in performance due to the re-expansion loss can be prevented. Also, the partial load operation has a small volume and influence of leakage between neighbor compression chambers is noticeable; however, with the configuration of Embodiment 2, the economizer port i2p has no relation when the economizer operation is stopped. Therefore, leakage between the screw grooves 10, which may occur because of passing through the economizer port 12p, can be prevented from occurring.

[0128] In Embodiment 2, if the economizer operation is not executed, the economizer flow path 50 does not communicate with the economizer port 12p.

However, as shown in Fig. 26A (the case in which the slide valve is located at the suction side), if the economizer pipe 107 is closed with the intermediate-cooler expansion valve 106 or the like, a phenomenon in which the economizer gas leaks to the suction side and the suction gas flows into the compression chamber 11, does not occur. Owing to this, in a viewpoint of commonality of parts, the economizer flow path 50 may communicate with the economizer port i2p. Even in this case, similar advantageous effects are attained.

[0129] Fig. 27 provides explanatory views of a modification of the diameter of the economizer port i2p, (a) being a developed view of the inner wall surface of the housing portion 1 A and the outer peripheral surface of the screw rotor 4, (b) being a cross-sectional view taken along line d-d in (a).

In Embodiment 2, the economizer port i2p has a diameter that does not allow neighbor compression chambers to communicate with each other.

However, if the economizer port 1 2p is used only in the economizer operation, as long as the flow of the injected refrigerant is a flow indicated by a blank arrow in Fig. 27(b), leakage does not occur between the neighbor compression chambers.

Therefore, the economizer port 12p may be larger than a land width (a width of a groove mountain between the neighbor screw grooves) shown in Fig. 27(a).

Even in this case, advantageous effects similar to those of Embodiment 2 are attained.

[0130] The land width of the screw rotor 4 is increased as the position of the slide valve 12 is more separated from the gate rotor 7. Owing to this, in a design in which the economizer-port diameter is smaller than the land width, the mount position of the slide valve 12 is desirably set within a range from a value larger than 43 = 30 degrees of related art to about 100 degrees at which the slide valve 12 does not interfere with the support part of the gate rotor 7 at the opposite side.

With this range, an advantageous effect can be attained in which the economizer-port diameter is largely ensured and stable flow control is executed.

[0131] As described above, in Embodiment 2, advantageous effects similar to those of Embodiment 1, and the following advantageous effects can be obtained.

That is, in Embodiment 2, the position of the economizer port 12p provided at the slide valve 12 is at a position at which the economizer port i2p communicates with the economizer flow path 50 when the slide valve 12 is positioned at the most discharge side, and at a position at which the economizer port i2p communicates with the suction pressure chamber 1C when the slide valve 12 is positioned at the most suction side. With this configuration, in full load operation with a large high-low differential pressure with a large economizer effect, the coefficient of performance by the economizer operation can be improved. In contrast, in partial load operation with a low differential pressure that does not expect an improvement in coefficient of performance by the economizer operation, the economizer operation is stopped, and further a high coefficient of performance without generation of the re-expansion loss or the leakage loss by the economizer port i2p can be obtained.

[0132] Consequently, the screw compressor 200 and the refrigeration cycle apparatus 300 that can provide the high coefficient of performance within the wide operation range from the high compression ratio to the low compression ratio, and therefore, can make an operation with high efficiency throughout the year can be obtained.

Reference Signs List [0133] 1 casing 1A housing portion lB opening port 1C suction pressure chamber 1 a gate-rotor opening port 1 aa gate-rotor opening surface ic suction wall le counter surface 2 high-pressure-side bearing 3 low-pressure-side bearing 4 screw rotor 5 gate-rotor support 5a bearing 5b center shaft 6 gate-rotor support chamber 7 gate rotor 7a gate rotor teeth 8 motor 9 rotating shaft 10 screw groove 1 Oa end edge 11 compression chamber 12 slide valve 12c coupling portion 12d inclined surface at variable port side (discharge-side end surface) 12p economizer pod 14 slide groove 15 discharge port 16 variable port 161 slide surface (rotation-side slide surface) 16r non-rotation-side slide surface 17 fixed port 17a inclined surface at fixed port side 1 7ax divided fixed port 1 7b vertical surface l7bx divided fixed port 17c inclined surface 18 partition wall 50 economizer flow path 50a pipe path 50b long groove 100 screw compressor 101 inverter 102 condenser 103 intermediate cooler 104 expansion valve 105 evaporator 106 intermediate-cooler expansion valve 107 economizer pipe 120 slide valve 120c coupling portion 120d discharge-side end surface 150 discharge port 160 variable port 170 fixed port 200 screw compressor 300 refrigeration cycle apparatus 301 controller