WO2011114636A1 - Single screw compressor - Google Patents

Abstract

Disclosed is a single screw compressor equipped with a regulating mechanism (3) that regulates the compression ratio of a compression chamber (23) within a prescribed range. The regulating mechanism (3) is configured in a manner so as to set the compression ratio of the compression chamber (23) to the minimum compression ratio during at least the activation of a driving mechanism (15).

Description

Single screw compressor

The present invention relates to a single screw compressor, and relates to a measure for reducing the load of the starting mechanism at the time of starting the single screw compressor.

Conventionally, a single screw compressor provided with a compression mechanism that compresses a refrigerant by the rotational movement of a screw rotor is known.

For example, in a single screw compressor described in Patent Document 1 (hereinafter simply referred to as a screw compressor), a screw rotor is accommodated in a cylinder, and a gate rotor is engaged with the screw rotor. Thereby, inside the spiral groove formed on the outer periphery of the screw rotor, a compression chamber is defined between the gate of the gate rotor, the screw rotor, and the cylinder inner wall. In the screw compressor, a suction port is formed on one end side (suction side) in the axial direction of the screw rotor, and a discharge port is formed on the other end side (discharge side) in the axial direction of the screw rotor.

流体 During operation of the single screw compressor, fluid flows into the spiral groove through the suction port. In this spiral groove, a compression chamber is defined as the screw rotor rotates. When the screw rotor further rotates from this state, the volume of the compression chamber in a state where the fluid is sealed is gradually reduced. Thereby, the fluid in the compression chamber is gradually compressed. When the screw rotor further rotates from this state, the compression chamber and the discharge port communicate with each other. As a result, the high-pressure fluid in the compression chamber is discharged into a predetermined space through the discharge port.

JP 2004-137934 A

By the way, in the screw compressor as described above, the compression ratio of the compressor (that is, the ratio of the suction volume Vs to the discharge volume Vd (volume ratio: VI (= Vs / Vd)) is a predetermined value depending on the application. When such a compression ratio is set to be relatively high, a load (for example, a motor starting torque or a starting current) for rotationally driving the screw rotor becomes large when the screw compressor is started. End up.

The present invention was devised in view of such problems, and its purpose is to reduce the load required to rotate the screw rotor when the screw compressor is started.

In the first invention, a spiral groove (41) is formed on the outer peripheral surface, and one end in the axial direction meshes with the screw groove (40) having the fluid suction side and the other end being the discharge side, and the spiral groove (41). A plurality of gates (51) formed radially, a gate rotor (50), a drive mechanism (15) for rotating the screw rotor (40), and a fluid compression chamber (41) in the spiral groove (41) 23) a cylinder (31) for accommodating the screw rotor (40) so as to define a discharge port, and a discharge port (25) for allowing the fluid in the compression chamber (23) to flow out to the discharge side of the screw rotor (40) And a single screw compressor provided with. The single screw compressor further includes an adjustment mechanism (3) that adjusts the compression ratio of the compression chamber (23) within a predetermined range, and the adjustment mechanism (3) is provided with the drive mechanism (15). It is characterized in that the compression ratio of the compression chamber (23) is set to the lowest compression ratio at least at the time of activation.

In the single screw compressor of the first invention, when the screw rotor (40) is rotationally driven by the drive mechanism (15), the fluid is sucked into the spiral groove (41). When the volume of the compression chamber (23) in the spiral groove (41) decreases with the rotation of the screw rotor (40), the fluid in the compression chamber (23) is compressed. When the screw rotor (40) further rotates and the compression chamber (23) and the discharge port (25) communicate with each other, the fluid in the compression chamber (23) passes through the discharge port (25) to the outside of the compression chamber (23). Discharged.

In the single screw compressor of the present invention, an adjustment mechanism for adjusting the compression ratio of the compression chamber (23) (that is, the ratio of the suction volume Vs to the discharge volume Vd (volume ratio: VI (= Vs / Vd)). For this reason, in the single screw compressor of the present invention, the compression ratio of the compression chamber (23) can be changed within a predetermined range according to the operating conditions and applications.

In the present invention, the adjustment mechanism (3) sets the compression ratio to the lowest compression ratio when the drive mechanism (15) is started. That is, the compression ratio of the compression chamber (23) of the present invention can be changed by the adjustment mechanism (3) within a range from a predetermined minimum compression ratio to a predetermined maximum compression ratio, but the drive mechanism (15) The compression ratio at the time of start-up is the lowest compression ratio in the compression ratio adjustment range. Therefore, when starting the drive mechanism (15) and starting the rotation of the screw rotor (40), the load on the drive mechanism (15) required to rotate the screw rotor (40) is reduced.

In a second aspect based on the first aspect, the adjusting mechanism (3) includes a slide groove (33) formed in the inner wall of the cylinder (31) along the axial direction of the cylinder (31), and the slide. A slide valve (4) that is slidably fitted in the groove (33) to change the communication position between the compression chamber (23) and the discharge port (25), and the slide valve (4) is the screw rotor. The displacement part (10b, 31a) for displacing the slide valve (4) so as to be the first position closest to the suction side of (40) and the drive in a state where the slide valve (4) is in the first position. And a control unit (80) for starting the mechanism (15).

The adjusting mechanism (3) of the second invention has a slide groove (33), a slide valve (4), a displacement part (10b, 31a), and a control part (80). When the slide valve (4) is displaced axially within the slide groove (33), the communication position between the compression chamber (23) and the discharge port (25) is changed. Specifically, when the slide valve (4) approaches the suction side of the screw rotor (40), the timing at which the compression chamber (23) and the discharge port (25) communicate with each other is advanced. As a result, the compression ratio of the compression chamber (23) becomes relatively small. On the other hand, when the slide valve (4) is separated from the suction side of the screw rotor (40), the timing at which the compression chamber (23) and the discharge port (25) communicate with each other is delayed. As a result, the compression ratio of the compression chamber (23) becomes relatively large. As described above, in the adjusting mechanism (3) of the present invention, the timing at which the compression chamber (23) and the discharge port (25) communicate with each other is adjusted by adjusting the position of the slide valve (4). The compression ratio of the chamber (23) is adjusted within a predetermined range.

In the present invention, before the drive mechanism (15) is started, the slide valve (4) is adjusted to the first position (position closest to the suction side of the screw rotor) by the displacement portion (10b, 31a). As a result, the timing at which the compression chamber (23) and the discharge port (25) communicate with each other is the earliest, and the compression ratio is the lowest. Since the controller (80) starts the drive mechanism (15) from this state, the compression ratio of the compression chamber (23) is surely the lowest compression ratio when the drive mechanism (15) is started. Therefore, when starting the drive mechanism (15) and starting the rotation of the screw rotor (40), the load on the drive mechanism (15) required to rotate the screw rotor (40) is reduced.

In a third aspect based on the second aspect, the displacement portion (10b, 31a) includes a biasing mechanism (10b) for biasing the slide valve (4) toward the suction side of the screw rotor (40). And a contact portion (31a) for holding the slide valve (4) in the first position by contacting the slide valve (4) biased by the biasing mechanism (10b).

The displacement part (10b, 31a) of the third invention has an urging mechanism (10b) and a contact part (31a). That is, the slide valve (4) of the present invention is urged toward the suction side of the screw rotor (40) by the urging mechanism (10b). The slide valve (4) urged by the urging mechanism (10b) abuts against the abutment portion (31a) and is held at the first position. By such a mechanism of the displacement portions (10b, 31a), the compression ratio can be surely set to the lowest compression ratio when the drive mechanism (15) is started.

In a fourth aspect based on the second aspect, the adjustment mechanism (3) is configured such that the differential pressure between the fluid on the suction side and the fluid on the discharge side of the compression chamber (23) during the operation of the screw rotor (40). Has a pressure adjusting mechanism (70) that displaces the slide valve (4), and the pressure adjusting mechanism (70) moves the slide valve (4) immediately before stopping the operating screw rotor (40). The displacement part (10b, 31a) to be displaced to the first position is configured.

The adjusting mechanism (3) according to the fourth aspect of the present invention uses a difference between the pressure of the fluid on the suction side of the compression chamber (23) and the pressure of the fluid on the discharge side of the compression chamber (23), It has a pressure adjustment mechanism (70) that displaces 4). That is, during the operation of the screw rotor (40), fluid is compressed in the compression chamber (23), so that a predetermined pressure difference is generated between the suction side and the discharge side of the compression chamber (23). In the present invention, during the operation of the screw rotor (40), this pressure difference is used to displace the slide valve (4) in the slide groove (33), thereby adjusting the compression ratio.

On the other hand, when the single screw compressor (that is, the screw rotor (40)) is stopped, the pressure difference between the suction side and the discharge side of the compression chamber (23) becomes smaller. Accordingly, it is difficult to displace the slide valve (4) to the first position using such a pressure difference when the screw rotor (40) is stopped or when the drive mechanism (15) is subsequently started. Therefore, in the present invention, the slide valve (4) is displaced to the first position in advance immediately before the screw rotor (40) is stopped.

That is, immediately before the screw rotor (40) is stopped, there is still a pressure difference between the suction side and the discharge side of the compression chamber (23). It can be displaced to the first position. Therefore, after that, when the screw rotor (40) is stopped and the drive mechanism (15) is started again and rotation of the screw rotor (40) is started, the slide valve (4) remains in the first position. In this state, the compression ratio becomes the minimum compression ratio.

According to a fifth invention, in any one of the first to fourth inventions, the adjustment mechanism (3) controls the compression ratio of the compression chamber (23) to a predetermined value during steady operation of the screw rotor (40). The minimum compression ratio is configured to be adjusted within a range, and is characterized by being smaller than the control range of the compression ratio during steady operation of the screw rotor (40).

In the fifth invention, the compression ratio is adjusted within a predetermined control range by the adjusting mechanism (3) during the steady operation in which the rotational speed of the screw rotor (40) reaches the steady state. Thereby, during the steady operation of the screw rotor (40), for example, the compression ratio of the compression chamber (23) can be changed so as to correspond to a change in operating conditions.

On the other hand, when the drive mechanism (15) is started, the compression ratio of the compression chamber (23) is adjusted to a minimum compression ratio smaller than the control range of the compression ratio during such steady operation. Therefore, when the single screw compressor is started, the load on the drive mechanism (15) is reduced as compared with the steady operation.

The sixth invention is characterized in that, in any one of the first to fifth inventions, the lowest compression ratio is 1.0.

In the sixth invention, when the single screw compressor is started, the compression ratio of the compression chamber (23) is 1.0. Thereby, when rotation of the screw rotor (40) is started, the fluid is not substantially compressed in the spiral groove (41). As a result, when the single screw compressor is started, the load required for the rotation of the screw rotor (40) can be suppressed to the minimum load.

According to the present invention, when the drive mechanism (15) is started, the compression ratio is adjusted to the lowest compression ratio. Therefore, when starting the rotation of the screw rotor (40), the screw rotor (40) is rotated. The required load can be reduced. Therefore, it is possible to avoid the drive mechanism (15) from being overloaded when the single screw compressor is started.

Also, the so-called liquid compression phenomenon in the compression chamber (23) can be avoided by setting the compression ratio to the lowest compression ratio when the drive mechanism (15) is started. This point will be specifically described. For example, when a single screw compressor is applied to the refrigerant circuit of a refrigeration system (air conditioner, cooler, etc.), when the single screw compressor is stopped, the fluid (refrigerant) on the suction side of the compression chamber (23) is condensed. May be liquid. When the drive mechanism (15) is started from such a state, the liquid refrigerant sucked into the compression chamber (23) may be compressed. Such a liquid compression phenomenon may further increase the load on the drive mechanism (15) or may destroy the components of the single screw compressor. In contrast, in the present invention, since the compression ratio is set to the lowest compression ratio when the single screw compressor is started, such a liquid compression phenomenon can be avoided in advance.

In the second invention, the drive mechanism (15) is started after the slide valve (4) is displaced to the first position (position closest to the suction side of the screw rotor (40)). For this reason, at the time of starting of a single screw compressor, a compression ratio can be reliably made into the minimum compression ratio, and there can exist the effect of this invention mentioned above.

In the third invention, the slide valve (4) is biased to the first position side by the biasing mechanism (10b), and the slide valve (4) is held at the first position by the contact portion. For this reason, the compression ratio at the time of starting of a single screw compressor can be made into the minimum compression ratio, using a comparatively simple structure.

In the fourth aspect of the invention, the compression ratio of the compression chamber (23) can be adjusted as appropriate using the differential pressure between the suction side fluid and the discharge side fluid of the compression chamber (23). For this reason, a compression ratio can be adjusted so that optimal efficiency may be obtained according to the operating conditions (the load of cooling object, the outside air temperature, etc.) of the refrigerating device to which this single screw compressor is applied.

In the present invention, the slide valve (4) is displaced to the first position using the above-described differential pressure immediately before the single screw compressor is stopped. For this reason, when the single screw compressor is operated again thereafter, the compression ratio can be reliably set to the lowest compression ratio without displacing the slide valve (4) using the differential pressure.

In the fifth invention, since the compression ratio (minimum compression ratio) at the start of the single screw compressor is made smaller than the compression ratio at the time of steady operation, the load at the start of the drive mechanism (15) is suppressed. Can do. In particular, in the sixth invention, since the compression ratio (minimum compression ratio) at the start of the single screw compressor is 1.0, the load at the start of the drive mechanism (15) can be minimized. .

FIG. 1 is a longitudinal sectional view showing a configuration of a main part of a screw compressor according to an embodiment of the present invention in a maximum VI operation state corresponding to a rated load. FIG. 2 is a longitudinal sectional view showing a configuration of a main part of the screw compressor of FIG. 1 in a low VI operation state corresponding to a partial load. 3 is a cross-sectional view taken along line III-III in FIG. FIG. 4 is a perspective view showing an essential part of the screw compressor. FIG. 5 is a perspective view showing a screw rotor of the screw compressor. 6 is a plan view showing the operation of the compression mechanism of the screw compressor, FIG. 6 (A) shows the suction stroke, FIG. 6 (B) shows the compression stroke, and FIG. 6 (C) shows the discharge stroke. Show. FIG. 7 is a development view showing the operation of the compression mechanism in the maximum VI operation state, and the screw rotor is arranged in the order of FIGS. 7 (A), 7 (B), 7 (C), and 7 (D). It shows that it is rotating. FIG. 8 is a development view showing the operation of the compression mechanism in the intermediate VI operation state, and the screw rotor is arranged in the order of FIGS. 8 (A), 8 (B), 8 (C), and 8 (D). It shows that it is rotating. FIG. 9 is a longitudinal sectional view showing the configuration of the main part of the screw compressor in the lowest VI operation state at the time of startup. FIG. 10 is a development view showing the operation of the compression mechanism in the lowest VI operation state. The screw rotors are arranged in the order of FIGS. 10 (A), 10 (B), 10 (C), and 10 (D). It shows that it is rotating. FIG. 11 is a longitudinal sectional view showing the configuration of the main part of the screw compressor according to Modification 1 in the maximum VI operation state corresponding to the rated load. FIG. 12 is a longitudinal sectional view showing the configuration of the main part of the screw compressor according to Modification 1 in the lowest VI operation state at the time of startup. FIG. 13 is a development view of the compression mechanism of the screw compressor according to the second modification.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

A single screw compressor (1) according to the present invention (hereinafter simply referred to as a screw compressor) is applied to a chilling unit for air conditioning a room in a relatively large building or the like. This chilling unit constitutes a refrigeration apparatus that performs a vapor compression refrigeration cycle by circulating the refrigerant in the refrigerant circuit, and a screw compressor (1) is connected to the refrigerant circuit.

The screw compressor (1) includes a compression mechanism (20), a drive mechanism (15) for driving the compression mechanism (20), and a variable VI mechanism (for adjusting the volume ratio VI of the compression mechanism (20)). And 3). The screw compressor (1) includes a casing (30) that houses the compression mechanism (20) and the drive mechanism (15).

As shown in FIGS. 1 to 3, the compression mechanism (20) includes a cylinder wall (31) formed in the casing (30) and one of the cylinder walls (31) rotatably disposed in the cylinder wall (31). A screw rotor (40) and two gate rotors (50) meshing with the screw rotor (40) are provided.

The casing (30) is divided into a suction chamber (S1) facing the suction port (24) of the compression mechanism (20) and a discharge chamber (S2) facing the discharge port (25) of the compression mechanism (20). Has been. A communication portion (32) is formed at two locations in the circumferential direction of the cylinder wall (31) so as to bulge radially outward and to connect the suction chamber (S1) and the discharge chamber (S2). Yes. The communication part (32) includes a slide groove (33) extending along the axial direction of the cylinder wall (31), and a slide valve (4) described later can be moved in the axial direction in the slide groove (33). It is attached to. The discharge port (25) includes a valve side discharge port (27) formed in the slide valve (4) and a cylinder side discharge port (28) formed in the cylinder wall (31). Yes.

The drive mechanism (15) has a drive shaft (21) inserted through the screw rotor (40) and an electric motor (16) that rotates the drive shaft (21). The screw rotor (40) and the drive shaft (21) are connected by a key (22). Thereby, the screw rotor (40) is rotationally driven by the drive mechanism (15).

The drive shaft (21) is arranged coaxially with the screw rotor (40). The tip of the drive shaft (21) is freely rotatable by a bearing holder (60) located on the discharge side of the compression mechanism (20) (the right side when the axial direction of the drive shaft (21) in FIG. 1 is the left-right direction). It is supported by. The bearing holder (60) supports the drive shaft (21) via a ball bearing (61). The screw rotor (40) is rotatably fitted to the cylinder wall (31), and its outer peripheral surface is in sliding contact with the inner peripheral surface of the cylinder wall (31) via an oil film.

The electric motor (16) is configured to be able to adjust the rotation speed by inverter control. Thus, the screw compressor (1) can change the operating capacity by adjusting the rotational speed of the electric motor (16). The operating capacity of the screw compressor (1) (the amount of refrigerant discharged from the compression mechanism (20) per unit time) is controlled according to the load on the usage side of the refrigerant circuit. At that time, the slide valve (4) of the variable VI mechanism (3) has a volume ratio (compression ratio) at which optimum compression efficiency is obtained with respect to the operating capacity controlled according to the load on the use side. Be controlled. Specifically, the slide valve (4) moves in the axial direction of the screw rotor (40) according to the operating capacity that changes depending on whether the operating state is a rated load (100% load) state or a partial load state. The position changes. In the screw compressor (1), when the slide valve (4) is compared with the rated load operating state (the state shown in FIG. 1) and the partial load operating state (the state shown in FIG. 2), In FIG. 1, the position changes to the left side (suction side) so that the area of the cylinder side discharge port (28) becomes larger.

The screw rotor (40) shown in FIGS. 4 and 5 is a metal member formed in a substantially cylindrical shape. On the outer peripheral surface of the screw rotor (40), a spiral groove extending spirally from one end of the screw rotor (40) (end on the fluid (refrigerant) suction side) to the other end (end on the discharge side) 41) are formed (six in this embodiment).

Each spiral groove (41) of the screw rotor (40) has a left end (end portion on the suction side) in FIG. 5 as a start end and a right end in the drawing ends (end on the fluid discharge side). Further, the screw rotor (40) has a tapered left end in the figure. In the screw rotor (40) shown in FIG. 5, the start end of the spiral groove (41) is opened at the left end face formed in a tapered surface, while the end of the spiral groove (41) is not opened at the right end face. . The spiral groove (41) of the screw rotor (40) is opened to the suction chamber (S1) at the suction side end, and this open part is the suction port (24) of the compression mechanism (20).

Each gate rotor (50) is a resin member. Each gate rotor (50) is provided with a plurality of (11 in this embodiment) gates (51) formed in a rectangular plate shape in a radial pattern. Each gate rotor (50) is arranged outside the cylinder wall (31) so as to be axially symmetric with respect to the rotational axis of the screw rotor (40). That is, in the screw compressor (1) of the present embodiment, the two gate rotors (50) are arranged at equiangular intervals (180 ° intervals in the present embodiment) around the rotation center axis of the screw rotor (40). Yes. The axis of each gate rotor (50) is orthogonal to the axis of the screw rotor (40). Each gate rotor (50) is arranged so that the gate (51) penetrates a part (not shown) of the cylinder wall (31) and meshes with the spiral groove (41) of the screw rotor (40).

The gate rotor (50) is attached to a metal rotor support member (55) (see FIG. 4). The rotor support member (55) includes a base portion (56), an arm portion (57), and a shaft portion (58). The base (56) is formed in a slightly thick disk shape. The same number of arms (57) as the gates (51) of the gate rotor (50) are provided and extend radially outward from the outer peripheral surface of the base (56). The shaft portion (58) is formed in a rod shape and is erected on the base portion (56). The central axis of the shaft portion (58) coincides with the central axis of the base portion (56). The gate rotor (50) is attached to a surface of the base portion (56) and the arm portion (57) opposite to the shaft portion (58). Each arm part (57) is in contact with the back surface of the gate (51).

The rotor support member (55) to which the gate rotor (50) is attached is accommodated in a gate rotor chamber (90) defined in the casing (30) adjacent to the cylinder wall (31) (FIG. 3). See). The rotor support member (55) disposed on the right side of the screw rotor (40) in FIG. 3 is installed in such a posture that the gate rotor (50) is on the lower end side. On the other hand, the rotor support member (55) disposed on the left side of the screw rotor (40) in the figure is installed in such a posture that the gate rotor (50) is on the upper end side. The shaft portion (58) of each rotor support member (55) is rotatably supported by a bearing housing (91) in the gate rotor chamber (90) via ball bearings (92, 93). Each gate rotor chamber (90) communicates with the suction chamber (S1).

In the compression mechanism (20), a space surrounded by the inner peripheral surface of the cylinder wall (31), the spiral groove (41) of the screw rotor (40), and the gate (51) of the gate rotor (50) is compressed. (23) The compression chamber (23) includes a first compression chamber (23a) located above the horizontal center line in FIG. 3 and a second compression chamber (23b) located below the center line. (See FIG. 5).

As described above, the screw compressor (1) includes the variable VI mechanism (adjustment mechanism) (3) for adjusting the volume ratio VI of the compression mechanism (20). The volume ratio VI means the ratio (Vs / Vd) of the suction volume Vs to the discharge volume Vd in the compression mechanism (20), in other words, the compression ratio of the compression mechanism (20).

The variable VI mechanism (3) includes the above-described slide groove (33) and slide valve (4), and a valve displacement mechanism (18) for changing the position of the slide valve (4) in the slide groove (33). Have. Furthermore, the valve displacement mechanism (18) has a hydraulic cylinder (5) and a pressure adjustment mechanism (70) (see FIGS. 1 and 2).

One slide valve (4) is provided in each of the compression chambers (23a, 23b) so as to correspond to the first compression chamber (23a) and the second compression chamber (23b), respectively. The slide valve (4) is slidably fitted in the slide groove (33). In the slide groove (33), the slide valve (4) is located closest to the suction side (suction port (24)) of the screw rotor (40) (first position) and farthest from the suction port (24). It is configured to be able to advance and retreat between (second position). When the slide valve (4) is in the first position, the inner wall on one end side (suction side) in the axial direction of the slide groove (33) comes into contact with the end portion on one end side in the axial direction of the slide valve (4). . That is, the cylinder wall (31) is formed with a contact portion (31a) that contacts the slide valve (4) so as to hold the slide valve (4) in the first position.

Further, an inclined surface (4a) that is inclined with respect to the axial direction is formed at the other axial end of the slide valve (4) (see FIG. 7A). The inclined surface (4a) is formed so as to increase the opening width of the discharge port (25) as it proceeds in the rotation direction of the screw rotor (40) (the arrow direction shown in FIG. 7A).

In the compression mechanism (20), the opening area of the discharge port (25) changes according to the position of the slide valve (4) (see FIGS. 7, 8, and 10). As a result, the communication position between the compression chamber (23a, 23b) and the discharge port (25) is changed. As a result, the timing of the discharge stroke in which the refrigerant is discharged from the compression chambers (23a, 23b) is adjusted, and the volume ratio VI is adjusted. The cylinder-side discharge port (28) described above has an opening shape with reference to the time when the slide valve (4) is in the second position. Specifically, the cylinder-side discharge port (28) is not blocked by the slide valve (4) regardless of the position of the slide valve (4) between the first position and the second position. And the refrigerant can be discharged.

When the slide valve (4) is in the second position shown in FIG. 7, the compression chamber (23a, 23b) and the discharge port are located at the position farthest from the suction port (24) (the position closest to the discharge chamber (S2)). (25) communicates. As a result, the discharge stroke start timing (compression stroke end timing) of the compression chambers (23a, 23b) becomes the latest, and the volume ratio VI becomes the maximum volume ratio VImax (that is, the maximum compression ratio). On the other hand, when the slide valve (4) is in the first position shown in FIG. 10, the compression chambers (23a, 23b) and the discharge port (25) communicate with each other at a position closest to the suction port (24). As a result, the discharge stroke start timing (compression stroke end timing) of the compression chambers (23a, 23b) becomes the earliest, and the volume ratio VI becomes the lowest volume ratio VImin (that is, the lowest compression ratio).

The hydraulic cylinder (5) has a cylinder tube (6), a piston (7) loaded in the cylinder tube (6), and an arm (9) connected to the piston rod (8) of the piston (7). And a connecting rod (10a) for connecting the arm (9) and the slide valve (4), and the arm (9) in the left direction of FIG. 1 (direction in which the arm (9) is pulled toward the casing (30)). And a spring (10b). The spring (10b) constitutes a biasing mechanism that biases the slide valve (4) toward the suction side of the screw rotor (40).

Two cylinder chambers (11, 12) defined by the piston (7) are formed inside the cylinder tube (6). Specifically, a first cylinder chamber (11) is formed on one end side in the axial direction of the piston (7) (left side of the piston (7) in FIG. 1), and the other end side in the axial direction of the piston (7). A second cylinder chamber (12) is formed on the right side of the piston (7) in FIG. The pressure inside the cylinder chambers (11, 12) is basically substantially equal to that of the high-pressure refrigerant (discharge refrigerant).

The pressure adjustment mechanism (70) displaces the slide valve (4) by utilizing the difference between the refrigerant pressure on the suction side of the compression chamber (23) and the pressure on the discharge side of the compression chamber (23). is there. The pressure adjustment mechanism (70) includes first to third communication pipes (71, 72, 73) and first to third on-off valves (74, 74) corresponding to the communication pipes (71, 72, 73). , 75, 76). Each communication pipe (71, 72, 73) has one end connected to the second cylinder chamber (12) and the other end connected to the suction chamber (S1). In the second cylinder chamber (12), the connection port of the first communication pipe (71) is provided closer to the piston (7) than the connection port of the second communication pipe (72). In the second cylinder chamber (12), the connection port of the second communication pipe (72) is provided closer to the piston (7) than the connection port of the third communication pipe (73). Each on-off valve (74, 75, 76) is composed of an electromagnetic valve for opening and closing the corresponding communication pipe (71, 72, 73). The screw compressor (1) controls the open / close state of each open / close valve (74, 75, 76) and the operating state of the electric motor (16) (ON / OFF of the electric motor (16) and operating frequency). A controller (control unit) (80)) (see FIGS. 1 and 2).

The screw compressor (1) of the present embodiment is configured to appropriately change the volume ratio VI during steady operation when the rotational speed of the screw rotor (40) reaches a predetermined rotational speed. Specifically, during the steady operation of the screw compressor (1), the operating capacity of the compression mechanism (20) is changed in accordance with the load on the usage side of the refrigerant circuit. The ratio VI is changed.

More specifically, for example, when the load on the use side is a rated load (100% load), the rotational speed of the drive shaft (21) is relatively large and the operation capacity is also relatively large. In this case, the position of the slide valve (4) is adjusted so that the volume ratio VI becomes the maximum volume ratio VImax (for example, VImax = 3.0). For example, when the load on the use side is a partial load, the rotational speed of the drive shaft (21) is relatively small and the operation capacity is also relatively small. In this case, the position of the slide valve (4) is adjusted so that the volume ratio VI becomes a predetermined volume ratio smaller than the maximum volume ratio VImax (for example, the intermediate volume ratio VImid = 1.5). As described above, during the steady operation of the screw compressor (1), the volume ratio VI of the compression mechanism (20) is adjusted within a predetermined control range (for example, a range of VI = 1.5 to 3.0).

In this embodiment, the volume ratio VI is adjusted to the lowest volume ratio when the screw compressor (1) is started. Specifically, in this embodiment, the screw compressor (1) is stopped, and the difference between the pressure on the suction side and the pressure on the discharge side of the compression chamber (23) is eliminated, so that the spring (10b) is urged. The slide valve (4) in the state of contact is brought into contact with the contact portion (31a) and held at the first position. As a result, after that, when the electric motor (16) is turned on by the controller (80), the volume ratio VI becomes the minimum volume ratio VImin. As described above, in this embodiment, the spring (10b) and the contact portion (31a) are the displacement portions for displacing the slide valve (4) to the first position when the screw compressor (1) is started. Is configured.

Note that the optimum volume ratio VImin of the present embodiment is smaller than the control range (VI = 1.5 to 3.0) of the volume ratio VI in steady operation. In the present embodiment, the optimum volume ratio VImin is set to 1.0. Therefore, even if the electric motor (16) is turned on with the slide valve (4) held in the first position, the refrigerant is not substantially compressed by the compression mechanism (20) (details will be described later).

-Driving operation-
The operation of the screw compressor (1) will be described.

<Basic operation>
First, the basic operation of the screw compressor (1) will be described with reference to FIG.

In the compression mechanism (20) of the screw compressor (1) in operation, the suction stroke shown in FIG. 6 (A), the compression stroke shown in FIG. 6 (B), and the discharge stroke shown in FIG. Repeatedly. In the following description, attention is focused on the compression chamber (23) with dots in FIG.

In FIG. 6A, the compression chamber (23) with dots is in communication with the suction chamber (S1). Further, the spiral groove (41) in which the compression chamber (23) is formed meshes with the gate (51) of the gate rotor (50) located on the lower side of the figure. When the screw rotor (40) rotates, the gate (51) relatively moves toward the terminal end of the spiral groove (41), and the volume of the compression chamber (23) increases accordingly. As a result, the low-pressure gas refrigerant in the suction chamber (S1) is sucked into the compression chamber (23) through the suction port (24).

When the screw rotor (40) further rotates, the state shown in FIG. 6 (B) is obtained. In the figure, the compression chamber (23) to which dots are attached is completely closed. That is, the spiral groove (41) in which the compression chamber (23) is formed meshes with the gate (51) of the gate rotor (50) located on the upper side of the drawing, and the suction chamber (51) is formed by the gate (51). It is partitioned from S1). Then, when the gate (51) moves toward the end of the spiral groove (41) as the screw rotor (40) rotates, the volume of the compression chamber (23) gradually decreases. As a result, the gas refrigerant in the compression chamber (23) is compressed.

When the screw rotor (40) further rotates, the state shown in FIG. 6 (C) is obtained. In the figure, the compression chamber (23) with dots is in communication with the discharge chamber (S2) via the discharge port (25). When the gate (51) moves toward the end of the spiral groove (41) as the screw rotor (40) rotates, the compressed high-pressure gas refrigerant is pushed out from the compression chamber (23) to the discharge chamber (S2). It will be.

<Adjustment of volume ratio VI during steady operation>
Next, the operation for adjusting the volume ratio VI during steady operation of the screw compressor (1) will be described. At the time of steady operation of the screw compressor (1), at least the maximum VI operation and the intermediate VI operation can be performed.

[Maximum VI operation]
When the load of the refrigeration apparatus is the rated load, the volume ratio VI of the compression chamber (23) of the compression mechanism (20) is adjusted to the maximum volume ratio VImax (for example, VImax = 3.0). Specifically, when the load of the refrigeration apparatus is the rated load, the controller (80) controls the operating frequency of the electric motor (16) to the maximum frequency, and the rotational speed of the drive shaft (21) becomes high. As a result, the operating capacity of the compression mechanism (20) is also the maximum capacity. Further, the controller (80) controls the first on-off valve (74) and the second on-off valve (75) to the closed state, and the third on-off valve (76) to the open state.

When the third on-off valve (76) is opened, the internal pressure of the second cylinder chamber (12) communicating with the suction chamber (S1) is relatively lower than the internal pressure of the first cylinder chamber (11). . For this reason, the piston (7) is displaced toward the second cylinder chamber (12) (the right side in FIG. 1). As shown in FIG. 1, when the piston (7) is displaced to a position where the third communication pipe (73) is closed, the pressure in the second cylinder chamber (12) rises and the piston (7) is moved into the first cylinder chamber. (11) Displace to the side (left side in FIG. 1). Then, the open end of the third communication pipe (73) is opened again, and the internal pressure of the second cylinder chamber (12) is reduced again. As a result, the piston (7) is displaced again to a position where it closes the open end of the third communication pipe (73). As described above, the piston (7) is substantially held near the opening end of the third communication pipe (73) (see FIG. 1). As a result, the slide valve (4) connected to the piston (7) is held at the second position farthest from the suction port (24).

As shown in FIG. 7, in the state where the slide valve (4) is in the second position, the opening area of the discharge port (25) becomes the smallest, and the start timing of the discharge stroke (that is, the end timing of the compression stroke). Is the slowest. This point will be specifically described while paying attention to the spiral groove (41) (spiral groove (41a)) in the thick line shown in FIG. In FIGS. 7B, 7C, and 7D, the slide valve (4) is not shown, while the discharge port (25) is indicated by a broken line. In FIGS. 7B, 7C, and 7D, dots are attached to the compression chamber (23) formed in the spiral groove (41a) of interest.

In the state of FIG. 7 (A), the inlet (24) and the spiral groove (41a) are not yet partitioned by the gate (51). Further, the spiral groove (41a) and the discharge port (25) are partitioned by the slide valve (4). Therefore, the above-described suction stroke is performed in the spiral groove (41a) in the state shown in FIG.

When the screw rotor (40) in the state of FIG. 7 (A) is rotated to the state shown in FIG. 7 (B), the inlet (24) and the spiral groove (41a) are partitioned by the gate (51). Further, the spiral groove (41a) and the discharge port (25) are partitioned by the slide valve (4). For this reason, in the spiral groove (41a) in the state shown in FIG. 7B, the suction stroke ends and the compression stroke described above is started.

When the screw rotor (40) in the state of FIG. 7 (B) rotates, the volume of the compression chamber (23) in the spiral groove (41a) gradually decreases. As a result, the compression process is continued, and the pressure of the refrigerant in the compression chamber (23) increases. When the screw rotor (40) is in the state shown in FIG. 7 (C), the compression chamber (23) and the discharge port (25) communicate with each other. As a result, the compression stroke ends, and the discharge stroke described above is started. As described above, in the operation at the rated load, the timing at which the compression chamber (23) and the discharge port (25) communicate with each other is the latest. For this reason, since the discharge capacity Vd becomes small, the volume ratio VI becomes the maximum volume ratio Vmax.

As shown in FIG. 7D, when the screw rotor (40) further rotates, the high-pressure gas refrigerant flows out from the discharge port (25). This discharge process is performed until the compression chamber (23) and the discharge port (25) in the spiral groove (41a) are shut off.

[Intermediate VI operation]
When the load of the refrigeration apparatus is a partial load, the volume ratio VI of the compression chamber (23) of the compression mechanism (20) is adjusted to an intermediate volume ratio VImid (for example, VImid = 1.5). Specifically, when the load of the refrigeration apparatus is a partial load, the controller (80) controls the operating frequency of the electric motor (16) to a predetermined frequency (a frequency smaller than the maximum frequency), and the drive shaft (21) The rotational speed is lower than that during the maximum VI operation. As a result, the operating capacity of the compression mechanism (20) is also smaller than the maximum VI operation. Further, the controller (80) controls the second on-off valve (75) to the open state, and controls the first and third on-off valves (74, 76) to the closed state.

When the second on-off valve (75) is opened, the internal pressure of the second cylinder chamber (12) communicating with the suction chamber (S1) is relatively lower than the internal pressure of the first cylinder chamber (11). . For this reason, the piston (7) is displaced toward the second cylinder chamber (12) (the right side in FIG. 2). As shown in FIG. 2, when the piston (7) is displaced to a position where it closes the second communication pipe (72), the pressure in the second cylinder chamber (12) rises and the piston (7) is moved into the first cylinder chamber. (11) Displace to the side (left side in FIG. 2). Then, the opening end of the second communication pipe (72) is opened, so that the pressure in the second cylinder chamber (12) decreases again. As a result, the piston (7) is displaced again to a position where it closes the open end of the second communication pipe (72). As described above, the piston (7) is substantially held near the open end of the second communication pipe (72) (see FIG. 2). As a result, the slide valve (4) connected to the piston (7) is held at a predetermined position (intermediate position) between the first position and the second position.

As shown in FIG. 8, when the slide valve (4) is in the middle position, the opening area of the discharge port (25) is also an intermediate area (a predetermined area between the maximum area and the minimum area), and the discharge stroke The start timing is later than during rated load operation.

In the state of FIG. 8 (A), the inlet (24) and the spiral groove (41a) are not yet partitioned by the gate (51). Further, the spiral groove (41a) and the discharge port (25) are partitioned by the slide valve (4). Therefore, the above-described suction stroke is performed in the spiral groove (41a) in the state shown in FIG.

When the screw rotor (40) in the state shown in FIG. 8 (A) rotates to reach the state shown in FIG. 8 (B), the suction port (24) and the spiral groove (41a) are partitioned by the gate (51). Further, the spiral groove (41a) and the discharge port (25) are partitioned by the slide valve (4). For this reason, in the spiral groove (41a) in the state shown in FIG. 8B, the suction stroke is completed and the compression stroke described above is started.

When the screw rotor (40) in the state of FIG. 8 (B) rotates, the volume of the compression chamber (23) in the spiral groove (41a) gradually decreases. As a result, the compression process is continued, and the pressure of the refrigerant in the compression chamber (23) increases. When the screw rotor (40) is in the state shown in FIG. 8 (C), the compression chamber (23) and the discharge port (25) communicate with each other. As a result, the compression stroke ends, and the discharge stroke described above is started. As described above, in the operation at the rated load, the timing at which the compression chamber (23) and the discharge port (25) communicate with each other is earlier than the operation at the rated load (see FIG. 7). For this reason, since the discharge capacity Vd increases, the volume ratio VI becomes the intermediate volume ratio Vmid.

As shown in FIG. 8D, when the screw rotor (40) further rotates, the high-pressure gas refrigerant flows out from the discharge port (25). This discharge process is performed until the compression chamber (23) and the discharge port (25) in the spiral groove (41a) are shut off.

<Start-up operation with minimum VI>
During the period from the start of the operation of the screw compressor (1) to the steady operation as described above, the load on the electric motor (16) increases. Therefore, since the motor (16) requires a relatively large starting torque and starting current, the motor (16) may be increased in size, energy saving may be impaired, and reliability during startup may be impaired. There is.

Also, when the refrigeration system is stopped, the refrigerant in the low-pressure line of the refrigerant circuit (the suction side of the screw compressor (1)) may condense and become a liquid state. If the operation of the screw compressor (1) is started from this state, a so-called liquid compression phenomenon may occur in which the liquid refrigerant is compressed in the compression chamber (23). As a result, the compression mechanism (20) may be destroyed.

Therefore, in the present embodiment, the screw compressor (1) is configured such that the volume ratio of the compression mechanism (20) becomes the minimum volume ratio VImin at the time of startup. This point will be specifically described.

When the above-described steady operation is completed and the screw compressor (1) is stopped, the high pressure and the low pressure of the refrigerant circuit of the refrigeration apparatus are equalized. Thereby, in the screw compressor (1), the differential pressure between the suction chamber (S1) and the high pressure chamber (S2) is also reduced. Therefore, the pressure acting on one end side (suction chamber (S1) side) of the slide valve (4) in the axial direction and the pressure acting on the other end side (discharge chamber (S2) side) of the slide valve (4) in the axial direction The difference from the pressure to be reduced is also reduced. Moreover, the difference between the internal pressure of the first cylinder chamber (11) and the internal pressure of the second cylinder chamber (12) is also reduced. As a result, when the screw compressor (1) is stopped, the slide valve (4) biased by the spring (10b) comes into contact with the contact portion (31a), and the slide valve (4) is held in the first position. (See FIG. 9).

At the start of operation of the screw compressor (1), the drive mechanism (15) is started with the slide valve (4) held in the first position. Specifically, when the electric motor (16) is turned on with the slide valve (4) in the position shown in FIG. 10 (A), the refrigerant is sucked into the spiral groove (41a) and the suction stroke starts. . When the screw rotor (40) in the state of FIG. 10 (A) rotates to reach the state shown in FIG. 10 (B), the suction port (24) and the spiral groove (41a) are partitioned by the gate (51).

Here, when the slide valve (4) is in the first position, the inlet (24) and the spiral groove (41a) are separated from the spiral groove (41a) almost simultaneously with the gate (51). The exit (25) communicates. That is, in the starting operation at the lowest VI, the discharge stroke is started almost simultaneously with the end of the suction stroke, and therefore the compression stroke is not substantially performed. Therefore, in this starting operation at the lowest VI, the rotational speed of the drive shaft (21) becomes faster with the volume ratio (compression ratio) VI being 1.0.

When the screw rotor (40) further rotates in the order of FIG. 10 (C) and FIG. 10 (D), the refrigerant in the spiral groove (41a) flows out from the discharge port (25) to the discharge chamber (S2). Go. When the drive shaft (21) (screw rotor (40)) driven by the drive mechanism (15) reaches a predetermined rotational speed, the refrigerant is compressed in the above-described steady operation. As described above, in the present embodiment, the volume ratio is controlled to the lowest volume ratio VI until the rotational speed of the screw rotor (40) reaches a predetermined speed after the drive mechanism (15) is activated.

-Effects of the embodiment-
In the above embodiment, when the screw compressor (1) is started, the volume ratio VI of the compression mechanism (20) is controlled to the minimum volume ratio VImin. For this reason, the starting torque and starting current of the electric motor (16) can be suppressed, and the electric motor (16) can be reduced in size, improved in energy saving, and improved in starting reliability.

Also, when the screw compressor (1) is started, by setting the volume ratio VI to the minimum volume ratio VI, the liquid compression phenomenon that compresses the liquid refrigerant in the compression chamber (23) can be avoided.

In particular, in the above embodiment, since the minimum volume ratio VImin is 1.0, the starting torque and starting current of the electric motor (16) can be minimized. Moreover, the liquid compression phenomenon can be avoided reliably.

In the above embodiment, since the slide valve (4) is urged to the first position by the spring (10b), even if the differential pressure between the suction side and the discharge side of the screw rotor (40) disappears, the slide The valve (4) can be reliably moved to the first position side. Further, since the slide valve (4) can be moved to the first position in advance while the screw compressor (1) is stopped, the operation of the minimum volume ratio VImin is surely performed when the screw compressor (1) is started. be able to. Further, since the slide valve (4) biased to the first position is brought into contact with the contact portion (31a), the slide valve (4) can be reliably held at the first position.

<< Modification of Embodiment >>
About the said embodiment, it is good also as a structure of the following modifications.

<Configuration without spring (Modification 1)>
As shown in FIGS. 11 and 12, the above embodiment may have a configuration in which the spring (10b) is omitted. In this first modification, the slide valve (4) is moved to the first position by the differential pressure between the suction chamber (S1) and the discharge chamber (S2) immediately before the screw compressor (1) in operation is stopped. ing.

More specifically, first, during the steady operation of the screw compressor (1), the internal pressure of the second cylinder chamber (S2) is adjusted by the pressure adjusting mechanism (70) as in the above-described embodiment. The position of 4) and thus the volume ratio VI are adjusted. When the stop signal of the screw compressor (1) is input to the controller (80) from such a steady operation, the controller (80) is connected to all the open / close valves (74) before the drive mechanism (15) is stopped. , 75, 76) are controlled to be fully closed.

When all the open / close valves (74, 75, 76) are closed, the internal pressure of the first cylinder chamber (11) and the internal pressure of the second cylinder chamber (12) become substantially uniform. On the other hand, the suction pressure (low pressure) on the suction chamber (S1) side and the discharge pressure (high pressure) on the discharge chamber (S2) side act on the slide valve (4), and the drive mechanism (15) is stopped. Before the discharge, the pressure in the discharge chamber (S2) is higher than the pressure in the suction chamber (S1). For this reason, the slide valve (4) moves to the suction chamber (S1) side by such a differential pressure, and is held in the first position in contact with the contact portion (31a) (see FIG. 12).

After that, when a stop signal is output to the drive mechanism (15) and the screw compressor (1) stops, the differential pressure between the suction chamber (S1) and the discharge chamber (S2) is almost eliminated, but the slide valve (4 ) Remains in the first position. When the operation of the screw compressor (1) is started from such a state, the slide valve (4) can be reliably set to the first position when the drive mechanism (15) is started. As a result, when starting the operation of the screw compressor (1), the volume ratio VI can be made the minimum volume ratio Vmin, and the starting torque and starting current of the electric motor (16) can be reduced, and the liquid compression phenomenon can be avoided. I can do it.

<Configuration with different slide valve shapes (Modification 2)>
As shown in FIG. 13, the shape of the slide valve (4) may be different from that of the above embodiment. When the slide valve (4) of the second modification is in the first position (that is, the volume ratio VI is the minimum volume ratio VImin), the opening area of the discharge port (25) is maximized. In addition, the width (diameter) around the axis of the slide valve (4) is determined. Specifically, the diameter of the slide valve (4) is such that one end portion (in FIG. 13) of the inclined surface (4a) at the timing when the spiral stroke (41a) and the discharge port (25) communicate with each other after the suction stroke is completed. It is determined that the left end) straddles the spiral groove (41a), and the other end (right end in FIG. 13) of the inclined surface (4a) straddles the discharge side end of the screw rotor (40).

In this way, by maximizing the opening area of the discharge port (25) formed by the slide valve (4) in the first position, the pressure loss of the discharge port (25) can be effectively reduced. That is, when the slide valve (4) is in the first position, the volume ratio VI becomes the minimum volume ratio VImin, so that the flow rate of the refrigerant passing through the discharge port (25) increases, and the pressure loss easily increases accordingly. Become. However, by increasing the opening area of the discharge port (25) at the maximum volume ratio VImin in this way, the flow rate of the refrigerant is reduced, and thus the pressure loss can be reduced.

<< Other Embodiments >>
About the said embodiment, it is good also as the following structures.

The position of the spring (10b) in the above embodiment is merely an example. For example, the spring (10b) may be directly connected to the slide valve (4) to bias the slide valve (4) toward the first position. Further, a spring (10b) may be connected to the second cylinder chamber (12) so as to urge the piston (7) toward the suction chamber (S1).

Also, the valve displacement mechanism (18) may have other configurations. Specifically, for example, the slide valve (4) may be slid with a small motor or the like. Further, instead of the plurality of communication pipes (71, 72, 73) and the plurality of on-off valves (74, 75, 76), for example, one communication pipe connecting the second cylinder chamber (12) and the suction chamber (S1). And it is good also as a structure which can adjust the internal pressure of a 2nd cylinder chamber (12) using the motorized valve etc. which can finely adjust the opening degree of this communicating pipe.

In the above embodiment, the minimum volume ratio VImin at the time of starting the screw compressor (1) is 1.0. However, the minimum volume ratio is not limited to this, and the volume ratio is larger than 1.0. Also good.

In the above embodiment, for example, as shown in FIG. 7B, the suction port (24) and the spiral groove (41a) are partitioned by the gate (51), and at the same time, the spiral groove (41a) and the discharge port. By communicating with (25), the volume ratio is set to 1.0. However, before the suction port (24) and the spiral groove (41a) are partitioned by the gate (51), the first position of the slide valve (4) is set so that the spiral groove (41a) and the discharge port (25) communicate with each other. One position may be set. Even if it does in this way, in a spiral groove (41a), since a refrigerant | coolant is not compressed, a volume ratio can be set to 1.0. That is, “volume ratio = 1.0” means that the refrigerant is completely compressed in the spiral groove (41a) by connecting the suction port (24) and the discharge port (25) through the spiral groove (41a). It is meant to include not being done.

In addition, the above embodiment is an essentially preferable example, and is not intended to limit the scope of the present invention, its application, or its use.

As described above, the present invention is useful as a measure for reducing the load on the drive mechanism when starting the screw compressor.

1 Screw compressor (single screw compressor)
3 Variable VI mechanism (adjustment mechanism)
4 Slide valve 10b Spring (biasing mechanism, displacement part)
15 Drive mechanism 23 Compression chamber 25 Discharge port 31 Cylinder wall (cylinder)
31a Contact part (displacement part)
33 Slide groove 40 Screw rotor 41 Spiral groove 50 Gate rotor 51 Gate 80 Controller (control unit)

Claims (6)

A screw rotor (40) in which a spiral groove (41) is formed on the outer peripheral surface and one end in the axial direction is on the fluid suction side and the other end is on the discharge side, and a plurality of gates meshed with the spiral groove (41) ( 51) a radially formed gate rotor (50), a drive mechanism (15) for rotating the screw rotor (40), and a fluid compression chamber (23) in the spiral groove (41). A cylinder (31) that houses the screw rotor (40) and a discharge port (25) for allowing the fluid in the compression chamber (23) to flow out to the discharge side of the screw rotor (40). A screw compressor,
An adjustment mechanism (3) for adjusting the compression ratio of the compression chamber (23) within a predetermined range;
The single screw compressor characterized in that the adjustment mechanism (3) is configured so that the compression ratio of the compression chamber (23) is the lowest compression ratio at least when the drive mechanism (15) is started. . In claim 1,
The adjusting mechanism (3) is slidably fitted into the slide groove (33) formed along the axial direction of the cylinder (31) on the inner wall of the cylinder (31). The slide valve (4) for changing the communication position between the compression chamber (23) and the discharge port (25), and the slide valve (4) is the first closest to the suction side of the screw rotor (40). A displacement portion (10b, 31a) for displacing the slide valve (4) so as to be in a position, and a control portion (80) for starting the drive mechanism (15) in a state where the slide valve (4) is in the first position. And a single screw compressor. In claim 2,
The displacement portion (10b, 31a) is biased by the biasing mechanism (10b) for biasing the slide valve (4) toward the suction side of the screw rotor (40), and the biasing mechanism (10b). And a contact portion (31a) that contacts the slide valve (4) and holds the slide valve (4) in the first position. In claim 2,
The adjustment mechanism (3) is a pressure adjustment that displaces the slide valve (4) by the pressure difference between the suction side fluid and the discharge side fluid of the compression chamber (23) during the operation of the screw rotor (40). Having a mechanism (70),
The pressure adjusting mechanism (70) constitutes the displacement part (10b, 31a) for displacing the slide valve (4) to the first position immediately before stopping the operating screw rotor (40). Features a single screw compressor. In any one of Claims 1 thru | or 4,
The adjustment mechanism (3) is configured to adjust the compression ratio of the compression chamber (23) within a predetermined control range during steady operation of the screw rotor (40).
The single screw compressor, wherein the minimum compression ratio is smaller than a control range of the compression ratio during steady operation of the screw rotor (40). In any one of Claims 1 thru | or 5,
The single screw compressor, wherein the minimum compression ratio is 1.0.

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