JP2011196272A - Screw compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure the reliability of a hydraulic cylinder even when refrigerator oil in which a refrigerant is dissolved is used as the hydraulic oil of the hydraulic cylinder in a screw compressor equipped with a hydraulic cylinder for driving a slide valve for unloading.SOLUTION: The screw compressor (1) includes an oil heater (2a) for separating the refrigerant from the refrigerator oil supplied as a hydraulic oil from an oil reservoir chamber (26) to the hydraulic cylinder (5).

Description

  The present invention relates to a screw compressor provided with a hydraulic capacity adjustment mechanism.

  2. Description of the Related Art Conventionally, screw compressors that include a compression mechanism that compresses refrigerant by the rotational movement of a screw rotor are known. In this type of screw compressor, as shown in Patent Document 1, the unloading amount is changed to adjust the operating capacity of the compression mechanism by moving the unloading slide valve back and forth with a hydraulic cylinder. There is something that is possible.

  Here, the oil passage extending from the cylinder chamber of the hydraulic cylinder is connected to an oil reservoir chamber formed in the casing of the screw compressor. The oil reservoir chamber stores refrigerating machine oil discharged together with the discharged refrigerant from the discharge port of the compression mechanism. Note that the refrigerant discharged is dissolved in the refrigerating machine oil.

  The refrigerating machine oil in the oil reservoir chamber is supplied to the hydraulic cylinder as working oil through the oil passage, and the slide valve is advanced and retracted using the pressure of the refrigerating machine oil.

Japanese Patent Laid-Open No. 2001-254691

  By the way, depending on the operation state of the screw compressor, a large amount of refrigerant may be dissolved in the refrigerating machine oil in the oil reservoir chamber. For example, there is a case where the compression mechanism is forcedly stopped due to a wet operation, or a case where the compression mechanism is stopped for a long time. When the compressor mechanism is restarted in such a state that the refrigerating machine oil containing a large amount of refrigerant is supplied to the hydraulic cylinder, it is considered that excessive pressure more than necessary is applied to the hydraulic cylinder.

  That is, when the compression mechanism is activated, the discharge chamber communicating with the discharge port of the compression mechanism is in a high temperature and high pressure state. When the hydraulic cylinder is arranged in the discharge chamber, the heat in the discharge chamber is transmitted to the hydraulic cylinder, and the temperature of the refrigerating machine oil supplied to the hydraulic cylinder rises.

  As described above, a large amount of refrigerant is dissolved in the refrigerating machine oil. For this reason, when the temperature of the refrigerating machine oil increases, the solubility of the refrigerant in the refrigerating machine oil decreases as the temperature increases. Then, a part of the refrigerant dissolved in a large amount in the refrigerating machine oil can no longer be dissolved and is separated and vaporized from the refrigerating machine oil. It is considered that this vaporized refrigerant causes an increase in the pressure in the hydraulic cylinder, and an excessive pressure is applied to the hydraulic cylinder, thereby impairing the reliability of the hydraulic cylinder.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a screw compressor including a hydraulic cylinder that drives a slide valve for unloading. It is intended to ensure the reliability of the hydraulic cylinder even when used as oil.

  The first invention relates to a compression mechanism (20) for compressing refrigerant, an oil reservoir (26) for storing refrigerating machine oil containing the refrigerant, and a hydraulic cylinder (a hydraulic cylinder for advancing and retracting an unload slide valve (4)). 5) and a screw compressor provided with a capacity adjustment mechanism (3) for adjusting the operating capacity of the compression mechanism (20) by changing the unloading amount by the forward and backward movement of the slide valve (4) Yes.

  The screw compressor includes a refrigerant separation mechanism (2a) that separates refrigerant from refrigerating machine oil supplied as hydraulic oil from the oil reservoir (26) to the hydraulic cylinder (5). .

  In the first invention, the refrigerant is separated from the refrigerating machine oil by the refrigerant separation mechanism (2a). Then, the refrigeration oil after the refrigerant is separated can be sent to the hydraulic cylinder (5).

  In a second aspect based on the first aspect, the refrigerant separation mechanism (2a) is a heater member (2a) for heating the refrigerating machine oil.

  In the second invention, the temperature of the refrigerating machine oil in the oil reservoir (26) is higher than that in the case where the heater member (2a) is not used. As the temperature of the refrigerating machine oil increases, the solubility of the refrigerant in the refrigerating machine oil decreases. For this reason, the refrigerant that has become insoluble in the refrigerating machine oil is separated from the refrigerating machine oil and vaporized, and then sent to the hydraulic cylinder (5).

  According to a third aspect, in the second aspect, the heater member (2a) is configured to constantly heat the refrigerating machine oil.

  In the third invention, the refrigerating machine oil is always heated. Thereby, while making the solubility of the refrigerant | coolant with respect to the said refrigerating machine oil smaller than before the heating, the solubility of the refrigerant | coolant with respect to the said refrigerating machine oil is maintained with the state small by this regular heating.

  In a fourth aspect based on the second aspect, the heater member (2a) heats the refrigerating machine oil when the degree of superheat of the refrigerant discharged from the compression mechanism (20) is a predetermined value or less. It is characterized by being configured.

  In the fourth aspect of the invention, unlike the third aspect of the invention, when the degree of superheat of the discharged refrigerant becomes a predetermined value or less, the refrigerating machine oil is heated to reduce the solubility of the refrigerant in the refrigerating machine oil. This saves energy for heating the refrigerating machine oil as compared with the case of constantly heating the refrigerating machine oil as in the third aspect of the invention.

  Here, as described above, when the degree of superheat of the discharged refrigerant is not more than a predetermined value, the refrigerating machine oil is heated by the heater member (2a). This is because, for example, when the oil reservoir (26) is disposed on the discharge side of the compression mechanism (20), the degree of superheat of the discharged refrigerant decreases, and the compression mechanism (20) eventually becomes wet. Suppose you are driving. Then, the droplet-shaped refrigerant contained in the discharged refrigerant is dissolved in the refrigerating machine oil in the oil reservoir chamber (26). When the refrigerant in the form of droplets is mixed with the refrigerating machine oil, the ratio of the refrigerant in the refrigerating machine oil rises more rapidly than when the gaseous refrigerant is dissolved in the refrigerating machine oil.

  As described above, in order to prevent the droplet-like refrigerant from being dissolved in the refrigerating machine oil, before the compression mechanism (20) enters a wet operation, that is, when the degree of superheat of the discharged refrigerant becomes a predetermined value or less. The refrigerating machine oil is heated.

  According to the present invention, by providing the refrigerant separation mechanism (2a), the refrigerating machine oil after the refrigerant is separated can be sent to the hydraulic cylinder (5). If it carries out like this, even if the temperature rise of the said hydraulic cylinder (5) mentioned above occurs, the vaporization amount of the refrigerant | coolant from the said refrigeration oil will decrease by the part which the refrigerant | coolant isolate | separated from the said refrigeration oil. Thereby, the excessive pressure concerning the said hydraulic cylinder (5) reduces, and the reliability of the said hydraulic cylinder (5) can be ensured.

  According to the second aspect of the invention, the refrigerant can be separated from the refrigerant oil mixed with the refrigerant by heating the refrigerant oil mixed with the refrigerant by the heater member (2a). Thereby, the refrigerating machine oil after the refrigerant is separated can be sent to the hydraulic cylinder (5), and the reliability of the hydraulic cylinder (5) can be ensured.

  According to the third aspect of the present invention, not only the refrigerant is separated from the refrigerating machine oil by constant heating by the heater member (2a), but also the solubility of the refrigerant in the refrigerating machine oil is maintained in a small state. it can. Thereby, for example, even when the compression mechanism (20) is forcedly stopped due to a wet operation, or when the compression mechanism (20) has been stopped for a long period of time, the oil reservoir (26) It can suppress that a refrigerant | coolant melt | dissolves in this refrigerator oil.

  Further, according to the fourth aspect of the invention, the heating operation of the heater member (2a) with respect to the refrigerating machine oil is not always performed, but only when the degree of superheat of the discharged refrigerant becomes a predetermined value or less. it can. If it carries out like this, the solubility of the refrigerant | coolant with respect to the refrigerating machine oil of the said oil reservoir (26) can be maintained with a small state, saving the energy for heating the said refrigerating machine oil. Thereby, even if the situation where a large amount of refrigerant is likely to be dissolved in the refrigerating machine oil in the oil reservoir (26) occurs, it is possible to suppress the refrigerant from being dissolved in the refrigerating machine oil in the oil reservoir (26).

It is a longitudinal cross-sectional view which shows the structure of the principal part of a screw compressor. It is a cross-sectional view in the II-II line of FIG. It is a perspective view which extracts and shows the principal part of a screw compressor. It is a perspective view which shows the screw rotor of a screw compressor. It is a top view which shows operation | movement of the compression mechanism of a single screw compressor, (A) shows a suction stroke, (B) shows a compression stroke, (C) shows a discharge stroke. It is a figure which shows the structure of the capacity | capacitance adjustment mechanism in this embodiment. It is a figure which shows the structure of the capacity | capacitance adjustment mechanism in the modification 1 of this embodiment. It is a figure which shows the structure of the capacity | capacitance adjustment mechanism in the modification 2 of this embodiment.

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

  The single screw compressor (1) of the present embodiment (hereinafter simply referred to as a screw compressor) is provided in a refrigerant circuit that performs a refrigeration cycle and compresses the refrigerant.

  The screw compressor (1) includes a compression mechanism (20), a capacity adjustment mechanism (3), and an oil heater (2a) as a refrigerant separation mechanism (2a), which is a feature of the present invention. First, the oil heater (2a) will be described after the compression mechanism (20) and the capacity adjustment mechanism (3) are described.

<Compression mechanism>
As shown in FIGS. 1 and 2, the compression mechanism (20) includes a cylindrical wall (31) formed in the casing (30) of the screw compressor (1), and a cylindrical wall (31). 1 screw rotor (40), and two gate rotors (50) meshing with the screw rotor (40).

  In the casing (30), there are 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). A communication portion (2) is formed at the two circumferential locations on the cylindrical wall (31) so as to bulge radially outward and to communicate the suction chamber (S1) and the discharge chamber (S2). 32) is formed. The communication portion (32) accommodates a slide valve (4) of the capacity adjusting mechanism (3) described later.

  A drive shaft (21) extending from an electric motor (not shown) is inserted through the screw rotor (40). The screw rotor (40) and the drive shaft (21) are connected by a key (22). The drive shaft (21) is arranged coaxially with the screw rotor (40). The tip of the drive shaft (21) is freely rotatable on a bearing holder (60) located on the discharge side of the compression mechanism (20) (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 cylindrical wall (31), and the outer peripheral surface thereof is in sliding contact with the inner peripheral surface of the cylindrical wall (31).

  As shown in FIGS. 3 and 4, the screw rotor (40) is a metal member formed in a substantially cylindrical shape. A plurality (six in this embodiment) of spiral grooves (41) extending spirally from one end to the other end of the screw rotor (40) are formed on the outer periphery of the screw rotor (40).

  Each spiral groove (41) of the screw rotor (40) has a left end in FIG. 4 as a start end, and a right end in the drawing ends. Further, the screw rotor (40) has a left end portion (end portion on the suction side) in FIG. In the screw rotor (40) shown in FIG. 4, 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. .

  Each said gate rotor (50) is a resin-made 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 disposed outside the cylindrical 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 of the cylindrical 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. 3). 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 cylindrical wall (31) (see FIG. 2). The rotor support member (55) disposed on the right side of the screw rotor (40) in FIG. 2 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), the space surrounded by the inner peripheral surface of the cylindrical wall (31), the spiral groove (41) of the screw rotor (40), and the gate (51) of the gate rotor (50) is compressed. (23) The spiral groove (41) of the screw rotor (40) is open to the suction chamber (S1) at the suction side end, and this open part is the suction port (24) of the compression mechanism (20).

<Capacity adjustment mechanism>
The capacity adjusting mechanism (3) is fixed to the discharge side of the slide valve (4) and the bearing holder (60) accommodated in the communicating part (32) of the cylindrical wall (31), and the discharge chamber (S2 ) (See FIG. 1).

  The slide valve (4) is formed with a discharge port (25) of the compression mechanism (20). The discharge port (25) connects the compression chamber (23) and the discharge chamber (S2). Communicate. Further, the inner surface of the slide valve (4) constitutes a part of the inner peripheral surface of the cylindrical wall (31) and is slidable in the axial direction of the cylindrical wall (31). With this configuration, one end of the slide valve (4) faces the discharge chamber (S2), and the other end faces the suction chamber (S1). Therefore, during the activation of the compression mechanism (20), the slide valve (4) has a pressing force that presses the slide valve (4) from the discharge chamber (S2) side to the suction chamber (S1) side. .

  When the slide valve (4) slides toward the discharge chamber (S2) (to the right when the axial direction of the drive shaft (21) in FIG. 1 is the left-right direction), the end face of the communication part (32) An axial clearance is formed between (P1) and the end face (P2) of the slide valve (4). The axial gap serves as a bypass passage (33) for returning the refrigerant from the compression chamber (23) to the suction chamber (S1). When the slide valve (4) is moved to change the opening of the bypass passage (33), the capacity of the compression mechanism (20) changes. In this embodiment, when the slide valve (4) moves toward the discharge chamber (S2), the opening of the bypass passage (33) increases, and the slide valve (4) moves toward the suction chamber (S1). Is set so that the opening degree of the bypass passage (33) becomes small.

  The hydraulic cylinder (5) includes 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). ), A connecting rod (10a) for connecting the arm (9) and the slide valve (4), and the arm (9) in the right direction in FIG. 1 (direction in which the arm (9) is separated from the casing (30)). And a spring (10b) for biasing. Further, on both sides of the piston (7) in the cylinder tube (6), a first cylinder chamber (11) (left side of the piston (7) in FIG. 1) and a second cylinder chamber (12) (piston (in FIG. The right side of 7) is formed.

  Further, as shown in FIG. 6, the capacity adjusting mechanism (3) includes first to third passages (13, 14, 15). The first passage (13) communicates the first cylinder chamber (11) and an oil reservoir chamber (26) provided in the discharge chamber (S2) in the casing (30). A first solenoid valve (SV1) is attached to the first passage (13), and a capillary tube (CP1) is attached in parallel with the first solenoid valve (SV1). A check valve (13) is provided between the oil reservoir (26) and the first electromagnetic valve (SV1) in the first passage (13). The check valve (13) allows the flow of refrigeration oil from the oil reservoir (26) side to the first electromagnetic valve (SV1) side and prohibits the flow of refrigeration oil in the reverse direction. It is attached.

  The second passage (14) communicates the second cylinder chamber (12) and the suction chamber (S1) in the casing (30). A second solenoid valve (SV2) is attached to the second passage (14).

  The third passage (15) includes a first passage (13) on the first cylinder chamber (11) side in the first solenoid valve (SV1) and a suction chamber (S1) side on the second solenoid valve (SV2). The second passage (14) is connected. A capillary tube (CP1) and a third electromagnetic valve (SV3) are attached to the third passage (15) in order from the first passage (13) side to the second passage (14) side.

  The wall of the cylinder tube (6) that defines the second cylinder chamber (12) is formed with a communication hole (6a) that communicates the first cylinder chamber (11) and the discharge chamber (S2). ing.

  The capacity adjusting mechanism (3) includes a capacity adjusting section (16a) for operating the first to third solenoid valves (SV1, SV2, SV3) to adjust the operating capacity of the compression mechanism (20). Is provided. A controller (17) for controlling the operation of the screw compressor (1) is connected to the input part of the capacity adjusting part (16a) via a signal line, and the output part of the capacity adjusting part (16a) is connected to the output part. 1 to 3 solenoid valves (SV1, SV2, SV3) are connected via signal lines (not shown).

  An operation signal is input from the controller (17) toward the capacity adjustment unit (16a). In the operation signal, a load up signal for increasing the operation capacity of the compression mechanism (20), a load down signal for decreasing the operation capacity of the compression mechanism (20), and an activation of the compression mechanism (20) are notified. A start signal and a stop signal for notifying the stop of the compression mechanism (20) are included.

  When these signals are input to the capacity adjustment unit (16a), based on the input signal, the capacity adjustment unit (16a) opens or opens the solenoid valves (SV1, SV2, SV3). A closing signal for closing the solenoid valves (SV1, SV2, SV3) is output for each solenoid valve (SV1, SV2, SV3). Each solenoid valve (SV1, SV2, SV3) opens and closes based on the above open signal or close signal.

<Oil heater>
The oil reservoir chamber (26) is disposed in the discharge chamber (S2) as described above, and is for storing the refrigerating machine oil discharged together with the refrigerant discharged from the compression mechanism (20). This refrigerating machine oil is supplied as hydraulic oil to the hydraulic cylinder (5).

  The oil reservoir (26) is provided with an oil heater (2a) as a refrigerant separation mechanism that is a feature of the present invention. The oil heater (2a) is an electric heater for heating the refrigerating machine oil in the oil reservoir (26). The oil heater (2a) is electrically connected to a heater adjustment section (16b). The heater adjustment section (16b) is electrically connected to the controller (17), and operates the oil heater (2a) based on a command from the controller (17).

-Driving action-
First, after describing the operation of the compression mechanism (20) and the capacity adjustment mechanism (3) in the screw compressor (1), the oil heater (2a) will be described.

<Compression mechanism>
When the electric motor is started, the screw rotor (40) rotates as the drive shaft (21) rotates. As the screw rotor (40) rotates, the gate rotor (50) also rotates, and the compression mechanism (20) repeats the suction stroke, the compression stroke, and the discharge stroke. Here, the description will be given focusing on the compression chamber (23) with dots in FIG.

  In FIG. 5A, 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. 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). 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. 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 refrigerant gas is pushed out from the compression chamber (23) to the discharge chamber (S2). Go.

<Capacity adjustment mechanism>
Next, the operation of the capacity adjustment mechanism (3) will be described.

-Operation when stopped-
The stop operation is an operation performed when the screw compressor (1) is stopped. When the stop signal from the controller (17) is input, the capacity adjusting unit (16a) outputs an open signal to the first and second solenoid valves (SV1, SV2), and the third solenoid valve (SV3 ) To output a close signal. As a result, the first and second solenoid valves (SV1, SV2) are opened, and the third solenoid valve (SV3) is closed.

  When the first solenoid valve (SV1) is opened and the third solenoid valve (SV3) is closed, the first cylinder chamber (11) and the oil reservoir chamber (26) are equalized. On the other hand, when the second solenoid valve (SV2) is opened, the pressure in the second cylinder chamber (12) and the suction chamber (S1) is equalized.

  Here, since the operation of the screw compressor (1) is stopped, the suction chamber (S1) and the oil reservoir chamber (26) of the discharge chamber (S2) are equalized, so that the first and second cylinder chambers (11 , 12) equalize each other in the same way. Further, the pressing force of the slide valve (4) becomes zero by the operation stop of the screw compressor (1).

  Then, the piston (7) is moved by the restoring force of the spring (10b) in the capacity adjustment mechanism (3). By the movement of the piston (7), the slide valve (4) returns to a position where the opening of the bypass passage (33) is fully opened, that is, the operating capacity of the compression mechanism (20) is minimum.

-Operation at startup-
The start-up operation is an operation performed when the screw compressor (1) is started. When the start signal from the controller (17) is input, the capacity adjusting unit (16a) outputs an open signal to the second solenoid valve (SV2), and the first and third solenoid valves (SV1, SV3) A close signal is output. As a result, the second solenoid valve (SV2) is opened and the first and third solenoid valves (SV1, SV3) are closed.

  When the second electromagnetic valve (SV2) is opened, the pressure in the discharge chamber (S2) acting on the second cylinder chamber (12) through the communication hole (6a) is changed to the second electromagnetic valve ( SV2) escapes to the suction chamber (S1), and the pressure in the second cylinder chamber (12) decreases. On the other hand, when the third solenoid valve (SV3) is closed, the pressure of the discharge chamber (S2) acts on the first cylinder chamber (11) through the capillary tube (CP1) of the first passage (13). .

  As a result, the pressure in the first cylinder chamber (11) becomes larger than that in the second cylinder chamber (12), the piston (7) is pressed toward the second cylinder chamber (12), and finally the slide valve ( 4) is fixed at a position where the opening of the bypass passage (33) is fully open. That is, when starting the screw compressor (1), the compression mechanism (20) is operated with the minimum capacity.

−Load-up operation−
The load-up operation is an operation performed when it is desired to increase the operation capacity of the compression mechanism (20). When the load-up signal from the controller (17) is input, the capacity adjusting unit (16a) outputs an open signal to the third solenoid valve (SV3), and the first and second solenoid valves (SV1, SV2) A close signal is output. As a result, the third solenoid valve (SV3) is opened and the first and second solenoid valves (SV1, SV2) are closed.

  By opening the third solenoid valve (SV3), the pressure of the refrigerating machine oil in the oil reservoir chamber (26) acting on the first cylinder chamber (11) passes through the third solenoid valve (SV3). Escape to the suction chamber (S1) side, and the pressure in the first cylinder chamber (11) decreases. On the other hand, when the second solenoid valve (SV2) is closed, the pressure of the discharge chamber (S2) acts on the second cylinder chamber (12) through the communication hole (6a).

  As a result, the force acting on the first cylinder chamber (11) side is reduced, so that the force acting on the second cylinder chamber (12) side of the piston (7) is relatively reduced to the first cylinder chamber (11). ) Side, and the piston (7) starts to move toward the first cylinder chamber (11). Thereafter, when the opened third solenoid valve (SV3) is closed, the pressure of the refrigerating machine oil in the first cylinder chamber (11) does not escape to the suction chamber (S1) side. Then, the pressure of the refrigerating machine oil in the oil reservoir chamber (26) acts on the first cylinder chamber (11) again, and the pressure in the first cylinder chamber (11) is restored. As a result, the forces acting on both sides of the piston (7) come to balance each other, and the piston (7) stops.

  As the piston (7) moves, the slide valve (4) moves toward the suction chamber (S1). Then, the opening degree of the bypass passage (33) decreases, the amount of refrigerant returning to the suction chamber (S1) decreases, and the discharge amount of the compression mechanism (20) increases. This increases the operating capacity of the compression mechanism (20).

−Load-down operation−
The load down operation is an operation performed when it is desired to reduce the operation capacity of the compression mechanism (20). When the load down signal from the controller (17) is input, the capacity adjusting unit (16a) outputs an open signal to the second solenoid valve (SV2), and the first and third solenoid valves (SV1, SV3) A close signal is output. As a result, the second solenoid valve (SV2) is opened and the first and third solenoid valves (SV1, SV3) are closed.

  When the second solenoid valve (SV2) is opened, the pressure in the discharge chamber (S2) acting on the second cylinder chamber (12) through the communication hole (6a) is changed to the second solenoid valve (SV2). Through the suction chamber (S1), the pressure in the second cylinder chamber (12) decreases. On the other hand, when the first and third solenoid valves (SV1, SV3) are closed, the oil reservoir chamber (26) enters the first cylinder chamber (11) through the capillary tube (CP1) of the first passage (13). The pressure of refrigeration oil at

  As a result, the force acting on the second cylinder chamber (12) side is reduced, so that the force acting on the first cylinder chamber (11) side of the piston (7) is relatively reduced to the second cylinder chamber (12). ) Side, and the piston (7) starts to move toward the second cylinder chamber (12). Thereafter, when the opened second solenoid valve (SV2) is closed, the pressure in the second cylinder chamber (12) does not escape to the suction chamber (S1) side. Then, the pressure in the discharge chamber (S2) acts on the second cylinder chamber (12) again through the communication hole (6a), and the pressure in the second cylinder chamber (12) is restored. As a result, the forces acting on both sides of the piston (7) come to balance each other, and the piston (7) stops.

  As the piston (7) moves, the slide valve (4) moves toward the discharge chamber (S2). Then, the opening degree of the bypass passage (33) increases, the amount of refrigerant returning to the discharge chamber (S2) increases, and the discharge amount of the compression mechanism (20) decreases. Thereby, the operating capacity of the compression mechanism (20) is reduced.

<Oil heater>
When the controller (17) is powered on, energization from the external power source to the controller (17) is started. Then, a permission signal for permitting energization of the oil heater (2a) is output from the controller (17) toward the heater adjustment section (16b). Thereby, the oil heater (2a) heats the refrigerating machine oil in the oil reservoir (26). The heating operation of the oil heater (2a) is continued until the controller (17) is turned off. Accordingly, regardless of whether the compression mechanism (20) is started or stopped, the refrigerating machine oil in the oil reservoir (26) is constantly heated by the oil heater (2a).

-Effect of the embodiment-
According to this embodiment, the temperature of the refrigerating machine oil in the oil reservoir (26) is higher than that in the case where the refrigerating machine oil is not heated by the oil heater (2a). As the temperature of the refrigerating machine oil increases, the solubility of the refrigerant in the refrigerating machine oil decreases. For this reason, the refrigerant that cannot be completely dissolved in the refrigerating machine oil is separated from the refrigerating machine oil and is vaporized.

  In this way, even if the temperature of the hydraulic cylinder (5) rises when the compression mechanism (20) is restarted, the amount of refrigerant vaporized from the refrigerating machine oil is reduced by the amount separated from the refrigerating machine oil. Become. As a result, excessive pressure generated in the hydraulic cylinder (5) due to the temperature rise of the hydraulic cylinder (5) is reduced, and the reliability of the hydraulic cylinder (5) can be ensured.

  According to this embodiment, the refrigerating machine oil is always heated by the oil heater (2a). When constantly heated in this way, not only can the refrigerant be separated from the refrigerating machine oil, but also the solubility of the refrigerant in the refrigerating machine oil can be kept low. Thereby, for example, even when the compression mechanism (20) is forcedly stopped due to a wet operation, or when the compression mechanism (20) has been stopped for a long period of time, the oil reservoir (26) It can suppress that a refrigerant | coolant melt | dissolves in this refrigerator oil.

-Modification 1 of embodiment-
The capacity adjustment mechanism (3) of Modification 1 shown in FIG. 7 is different from the capacity adjustment mechanism (3) of the above-described embodiment in the configuration of the heater adjustment section (16b). A pressure sensor (18) and a temperature sensor (19) are electrically connected to the heater adjustment section (16b). The pressure sensor (18) detects the pressure of the refrigerant in the discharge chamber (S2), and the temperature sensor (19) detects the temperature of the refrigerant in the discharge chamber (S2). And the said heater adjustment part (16b) calculates the superheat degree of the refrigerant | coolant of the said discharge chamber (S2) based on the detected value of these two sensors (18,19). After that, the heater adjustment unit (16b) turns on the oil heater (2a) when the calculated value (superheat degree) is equal to or less than a set value, and when the calculated value (superheat degree) is larger than the set value, Turn off the oil heater (2a).

  According to the first modification of the embodiment, the heating operation of the oil heater (2a) with respect to the refrigerating machine oil is not always performed, but when the degree of superheat of the refrigerant in the discharge chamber (S2) becomes a predetermined value or less. Limited to If it carries out like this, the solubility of the refrigerant | coolant with respect to the refrigerating machine oil of the said oil reservoir (26) can be maintained with a small state, saving the energy for heating the said refrigerating machine oil. Thereby, even if the situation where a large amount of refrigerant is likely to be dissolved in the refrigerating machine oil in the oil reservoir (26) occurs, it is possible to suppress the refrigerant from being dissolved in the refrigerating machine oil in the oil reservoir (26).

  Here, as described above, the refrigerating machine oil is heated by the oil heater (2a) when the degree of superheat of the refrigerant in the discharge chamber (S2) is equal to or less than a predetermined value. This is because it is assumed that the degree of superheat of the refrigerant in the discharge chamber (S2) has decreased, and that the compression mechanism (20) has finally become wet. Then, the liquid refrigerant in the discharge chamber (S2) is dissolved in the refrigerating machine oil in the oil reservoir chamber (26). When the refrigerant in the form of droplets is mixed with the refrigerating machine oil, the ratio of the refrigerant in the refrigerating machine oil rises more rapidly than when the gaseous refrigerant is dissolved in the refrigerating machine oil.

  As described above, in order to prevent the refrigerant in the droplet form from being dissolved in the refrigeration oil, the degree of superheat of the refrigerant in the discharge chamber (S2) is equal to or less than a predetermined value before the compression mechanism (20) enters a damp operation. When this happens, the refrigerating machine oil is heated.

-Modification 2 of embodiment-
Unlike the embodiment, the capacity adjustment mechanism (3) of Modification 2 shown in FIG. 8 includes a stirrer (2b) instead of the oil heater (2a). The stirrer (2b) stirs the refrigerating machine oil in the oil reservoir (26). As a result of the stirring operation of the stirrer (2b), the solubility of the refrigerant in the refrigerating machine oil is reduced. If it becomes like this, the refrigerant | coolant which became impossible to melt | dissolve in the said refrigerator oil will isolate | separate from this refrigerator oil.

  Further, when the temperature of the refrigerating machine oil in the oil reservoir (26) becomes lower than the critical dissolution temperature, the refrigerant and the refrigerating machine oil are separated into two phases. By agitating the refrigerant and the refrigerating machine oil during the two-phase separation with the agitator (2b), the refrigerant and the refrigerating machine oil can be efficiently separated by the centrifugal separation action by the agitation.

  By this stirring operation of the stirrer (2b), the refrigerating machine oil after the refrigerant is separated can be sent to the hydraulic cylinder (5). If it carries out like this, even if the temperature rise of the said hydraulic cylinder (5) mentioned above occurs, the vaporization amount of the refrigerant | coolant from the said refrigeration oil will decrease by the part which the refrigerant | coolant isolate | separated from the said refrigeration oil. Thereby, the excessive pressure concerning the said hydraulic cylinder (5) reduces, and the reliability of the said hydraulic cylinder (5) can be ensured.

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

  In the present embodiment, an electric oil heater (2a) is used as the refrigerant separation mechanism (2a), but the invention is not limited to this. For example, when the compression mechanism (20) is restarted, A refrigerant-type oil heater that heats the refrigerating machine oil with the refrigerant discharged from the compression mechanism (20) may be used.

  In addition, the above embodiment is an essentially preferable illustration, Comprising: It does not intend restrict | limiting the range of this invention, its application thing, or its use.

  As described above, the present invention is useful for a screw compressor provided with a hydraulic capacity adjustment mechanism.

1 Screw compressor
2a Oil heater (refrigerant separation mechanism)
3 Capacity adjustment mechanism
4 Slide valve
5 Hydraulic cylinder
7 Piston
11 First cylinder chamber
12 Second cylinder chamber
13 First passage
14 Second passage
15 Third passage
16a Capacity adjustment section
16b Heater adjustment part
17 Controller
20 Compression mechanism
26 Oil reservoir
S1 suction chamber
S2 Discharge chamber
SV1 1st solenoid valve
SV2 2nd solenoid valve
SV3 3rd solenoid valve

Claims (4)

The compressor has a compression mechanism (20) for compressing refrigerant, an oil reservoir (26) for storing refrigerating machine oil mixed with the refrigerant, and a hydraulic cylinder (5) for advancing and retracting an unload slide valve (4). A screw compressor including a capacity adjustment mechanism (3) that adjusts an operating capacity of the compression mechanism (20) by changing an unload amount by advancing and retracting the slide valve (4);
A screw compressor comprising: a refrigerant separation mechanism (2a) for separating refrigerant from refrigerating machine oil supplied as hydraulic oil from the oil reservoir (26) to the hydraulic cylinder (5). In claim 1,
The screw compressor, wherein the refrigerant separation mechanism (2a) is a heater member (2a) for heating the refrigerating machine oil. In claim 2,
The screw compressor, wherein the heater member (2a) is configured to constantly heat the refrigerating machine oil. In claim 2,
The heater member (2a) is configured to heat the refrigerating machine oil when the degree of superheat of the refrigerant discharged from the compression mechanism (20) is a predetermined value or less. Machine.

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