JP5389755B2 - Screw compressor - Google Patents

Description

  The present invention relates to a screw compressor suitable for use in an apparatus constituting a refrigeration cycle such as an air conditioner, a chiller unit, or a refrigerator.

  When a screw compressor is used for an air conditioner, chiller unit, etc., it is used in a wide range of suction pressures and discharge pressures, so the pressure in the screw rotor tooth gap becomes higher than the discharge pressure depending on the operating conditions (hereinafter referred to as excess Compression). Then, the screw compressor for reducing overcompression is proposed (for example, refer patent document 1).

  A screw compressor described in Patent Document 1 includes a male rotor (main rotor) and a female rotor (subrotor) that rotate while being substantially in parallel with each other, and bores that house the teeth of the male rotor and the female rotor. And a main casing (housing) having an end face opened on the rotor axial discharge side of the bore, and a discharge casing (housing wall) connected to the rotor axial discharge side of the main casing. The discharge casing is formed in the discharge side end face that contacts the end face of the main casing and covers the opening of the bore, the discharge port (discharge window) formed in the discharge side end face, and the tooth groove of the male rotor and the female rotor. A position opposite to the rotor rotation direction on at least one of the male rotor side and the female rotor side in the vicinity of the discharge port on the discharge side end face in the vicinity of the discharge port from the compression working chamber through the discharge port And a bypass passage that communicates the valve hole and the discharge chamber, and a valve device (overflow valve) that opens and closes the valve hole is provided.

  The valve device includes a valve body disposed in the valve hole and a spring (pressing spring) that biases the valve body toward the main casing. For example, when the valve body is moved to the main casing side and the valve hole is closed, the compressed gas is discharged from the compression working chamber to the discharge chamber through the discharge port. On the other hand, when the valve body is moved to the side opposite to the main casing side to open the valve hole, the compressed gas is discharged into the discharge chamber not only through the discharge port but also through the valve hole and the bypass channel. As a result, over-compression is reduced.

  In addition, a step portion is formed in the valve body and the valve hole as a stopper of the valve body. Thus, for example, when the valve body moves to the main casing side, the front end surface of the valve body is flush with the end surface of the discharge casing, and the valve body is prevented from coming into contact with the tooth end surface of the rotor. It has become.

JP 61-79886 A

However, it has been found that the above prior art has the following problems to be improved.
That is, in the above prior art, since the pressure from the compression working chamber acts on the valve body, the compression working chamber is in an overcompressed state (compression working chamber pressure> discharge chamber pressure (discharge pressure)). The valve body opens when the pressing force of the spring is overcome. However, when the valve body opens, the pressure on the compression working chamber side of the valve body immediately becomes the same as the pressure on the discharge chamber side. On the other hand, since the back pressure of the valve body is always the pressure of the discharge chamber, the pressure acting on the valve body is balanced immediately. For this reason, the valve body is immediately closed by the action of the spring that biases the valve body toward the main casing. Therefore, when the compression working chamber is over-compressed, the valve body repeatedly opens and closes every time the compression working chamber passes the valve body as the rotor rotates, and the valve body hits the stopper. There is a problem that vibration occurs.

  The objective of this invention is obtaining the screw compressor which can reduce the impact sound and vibration of the valve body which reduce overcompression.

In order to achieve the above object, the present invention provides a male rotor and a female rotor that rotate while being substantially parallel with each other in rotation, a main casing having a bore for housing the male rotor and the female rotor, and a rotor of the main casing. A discharge casing having a discharge side end face that is connected to the axial discharge side and abuts the end face of the main casing and covers the opening of the bore; from the compression working chamber formed by the male rotor and the female rotor; A discharge chamber or a discharge passage through which compressed gas is discharged through a discharge port formed in at least one of the main casing and the discharge casing, and the male rotor or the female rotor in the vicinity of the discharge port. A valve hole formed at a position on the discharge side end face of the discharge casing and opening to the compression working chamber, and the valve And a valve body drive device for opening and closing the valve body in a screw compressor comprising: a bypass flow path communicating with the discharge chamber or the discharge flow path; and a valve body disposed in the valve hole; A control device that detects whether or not overcompression has occurred in the compression working chamber, and controls the valve body drive device to open the valve body when the occurrence of overcompression is detected , The control device obtains a pressure ratio during operation based on the suction pressure to the compressor and the discharge pressure of the compressor, compares the pressure ratio with a preset pressure ratio stored in advance, and determines the pressure during operation. When the ratio becomes smaller than the set pressure ratio, it is determined that overcompression has occurred, and the valve body driving device is controlled to open the valve body, and the valve body driving device Reciprocatingly moves in and out of the cylinder provided on the back side of the cylinder And a rod that connects the piston and the valve body, and is configured to open the valve body by applying pressure to the piston when overcompression occurs in a cylinder on the valve body side of the piston. Is provided with a spring that presses the piston against the valve body, and guides the compressed gas on the discharge side of the compressor into the cylinder on the valve body side of the piston so that the valve is not over-compressed. A structure that closes the body and opens the valve body by moving the piston to the counter valve body side by applying a pressure on the discharge side of the compressor in the cylinder on the valve body side of the piston when overcompression occurs. and said that the content was.

  ADVANTAGE OF THE INVENTION According to this invention, the screw compressor which can reduce the striking sound and vibration of the valve body which reduce overcompression can be obtained.

The longitudinal cross-sectional view which shows Example 1 of the screw compressor of this invention. The right view of FIG. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 1. FIG. 4 is a sectional view taken along line IV-IV in FIG. 1. The figure explaining the positional relationship of the compression working chamber in Example 1 of this invention, a discharge port, a valve hole, and a bypass flow path. FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. 2 and shows a closed state of the valve body. FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. 2 and shows an open state of the valve device. FIG. 8 is a cross-sectional view taken along line VIII-VIII in FIG. 6. It is a figure explaining the modification 1 of Example 1, and is a figure which shows the discharge side end surface of a discharge casing. FIG. 10 is a diagram for explaining a second modification of the first embodiment and corresponding to FIG. 9. FIG. 10 is a diagram for explaining a third modification of the first embodiment and corresponding to FIG. 9. The refrigeration cycle block diagram explaining the example of the chiller unit incorporating the screw compressor shown in Example 1. FIG.

  Embodiments of the present invention will be described below with reference to the drawings.

A screw compressor according to a first embodiment of the present invention will be described with reference to FIGS.
1 is a longitudinal sectional view showing a first embodiment of a screw compressor according to the present invention, FIG. 2 is a right side view of FIG. 1, and FIG. 3 is a sectional view taken along arrow III-III in FIG. 4 shows the position of the bore on the end face of the main casing by a two-dot chain line), and FIG. 4 is a sectional view taken along the line IV-IV in FIG. 1 (showing the end face of the main casing on the discharge side of the discharge casing). FIG. 5 is a diagram for explaining the positional relationship among the compression working chamber, the discharge port, the valve hole, and the bypass channel in the first embodiment of the present invention.

  In FIG. 1, the screw compressor includes a compressor main body 1, a motor (electric motor) 2 that drives the compressor main body 1, and a motor casing 13 that houses the motor 2. The motor casing 13 forms a suction chamber (low pressure chamber) 5 on the anti-compressor main body side of the motor 2, and gas flows into the suction chamber 5 from the suction port 6 through the strainer 7. Yes. The motor 2 includes a rotor 11 attached to a rotary shaft 10 and a stator 12 disposed on the outer peripheral side of the rotor 11, and the stator is fixed to an inner surface of the motor casing 13. ing.

  The compressor body 1 includes a main casing 15 that is connected to the motor casing 13 and incorporates a screw rotor 14, and a discharge casing 16 that is connected to the discharge side of the main casing 15.

  The main casing 15 is formed with a cylindrical bore 20 that accommodates the tooth portion of the screw rotor 14, and the rotor 20 in the rotor axial direction discharge side is opened. A radial discharge port 23 is formed on the end face 21 side of the main casing 15 forming the opening, and a discharge flow path 90 connected to the discharge port 23 is also formed.

  As shown in FIG. 4, the screw rotor 14 is composed of a male rotor 14 </ b> A and a female rotor 14 </ b> B that rotate while being parallel to each other and meshing with each other. The bore 20 is composed of a bore 20A for housing a male rotor and a bore 20B for housing a female rotor, and the discharge port 23 is also composed of a discharge port 23A on the male rotor side and a discharge port 23B on the female rotor side. Yes.

  A rotor axial suction side (the left side in FIG. 1) of the main casing 15 is connected to the motor casing 13, and a gap between the rotor 11 and the stator 12 inside the motor casing 13 is defined by the suction chamber. 5 and a suction passage for communicating the compressor main body 1 with each other.

  As shown in FIG. 4, compression working chambers 36 </ b> A and 36 </ b> B are formed in the tooth grooves of the male rotor 14 </ b> A and the female rotor 14 </ b> B, and these compression working chambers are formed on the suction side (motor casing 13 side) of the main casing 15. A compression working chamber for the intake stroke communicating with the suction port 22, a compression working chamber for the compression stroke compressing the sucked gas, and a compression working chamber for the discharge stroke discharging the compressed gas communicating with the discharge ports 23 and 25 In addition, it changes sequentially with the rotation of the screw rotor. The discharge ports 23A and 23B are formed on the outer side in the radial direction of the male rotor or the female rotor (upper side in FIG. 1) with respect to the compression working chamber of the discharge stroke.

  As shown in FIGS. 1 and 3, the discharge side end face 24 of the discharge casing 16 is formed with an axial discharge port 25 and a discharge chamber 26. That is, the discharge casing 16 is in contact with the end surface 21 of the main casing 15 so as to cover the openings of the bores 20A and 20B, the male rotor-side discharge port 25A and the female ports formed on the discharge-side end surface 24. A rotor-side discharge port 25B and a discharge chamber 26 into which compressed gas discharged from the compression working chamber through the discharge ports 23A, 23B, 25A, and 25B flows.

  As shown in FIG. 1, the suction-side shaft portion of the male rotor 14A is supported by a roller bearing 17 disposed in the main casing 15 and a ball bearing 91 disposed in the motor casing 13, and the male rotor 14A. The discharge side shaft portion is supported by a roller bearing 18 and a ball bearing 19 disposed in the discharge casing 16. The suction-side shaft portion of the female rotor 14B is supported by a roller bearing (not shown) disposed in the main casing 15, and the discharge-side shaft portion of the female rotor 14B is disposed in the discharge casing 16. Are supported by a roller bearing and a ball bearing (not shown). The suction-side shaft portion of the male rotor 14A is directly connected to the rotating shaft 10 of the motor 2, and the male rotor 14A is rotated by driving the motor 2, and the female rotor 14B rotates while meshing with the male rotor 14A.

  The gas compressed by the screw rotor 14 flows out from the discharge ports 23 and 25 into the discharge chamber 26 or the discharge flow path 90 and flows from the discharge passage 90 to the discharge port 9 provided in the main casing 15. The oil is sent to an oil separator 92 through a discharge pipe 94 connected to the discharge port 9. The oil separator 92 separates the gas compressed in the compressor body 1 and the oil mixed in the gas. The oil separated by the oil separator 92 is returned to the oil tank 95 provided at the lower portion of the compressor body 1 through the oil return pipe 93 and is stored therein, and then the shaft portion of the screw rotor 14 and the motor. In order to lubricate the bearings 17, 18, 19, 91 supporting the two rotary shafts 10, these bearings are supplied again. On the other hand, the high-pressure gas from which the oil has been separated by the oil separator 92 is supplied to the outside (for example, a condenser constituting the refrigeration cycle) via the pipe 96.

  The gas sucked into the suction chamber 5 from the suction port 6 cools the rotor 11 and the stator 12 when passing through the inside of the motor casing 13, and then the screw rotor via the suction port 22 of the compressor body 1. 14, the volume is reduced while the compression working chambers 36A and 36B move in the rotor axial direction with the rotation of the male rotor 14A and the female rotor 14B, and the gas is compressed. The gas compressed in the compressor working chamber flows into the discharge passage 90 through the discharge ports 23A, 23B, 25A, 25B and the discharge chamber 26, and is sent out from the discharge port 9 to the discharge pipe 94. Yes.

  As shown in FIG. 3, the discharge casing 16 has a discharge side end face 24 in the vicinity of the discharge port 25B on the female rotor 14B side, on the side opposite to the rotation direction of the female rotor 14B (right side in FIG. 3). A valve hole (cylinder) 28 that opens at a position is formed, and the approximate center of the valve hole 28 is located at the opening edge of the bore 20 </ b> B on the female rotor 14 </ b> B side in the end surface 21 of the main casing 15. Further, the discharge casing 16 has a bypass groove 29 that is located on the outer side in the rotor radial direction from the opening edge of the bore 20B on the female rotor 14B side on the end surface 21 of the main casing 15, and communicates the valve hole 28 and the discharge chamber 26. The bypass channel 29 is formed by the bypass groove 29 and the end surface 21 of the main casing 15 covering the bypass groove 29. The valve hole 28 is provided with a valve body 31 for opening and closing the valve hole 28.

Next, a valve body driving device for driving the valve body 31 will be described with reference to FIGS.
6 and 7 are cross-sectional views taken along the line VI-VI in FIG. 2 and are views for explaining the structure of the valve body drive device for driving the valve body 31. FIG. FIG. 7 is a view showing an open state of the valve body 31. 8 is a cross-sectional view taken along line VIII-VIII in FIG.

  6 and 7, the valve body driving device 30 includes a rod 53 having one end connected to the back side (right side in FIG. 6) of a valve body 31 slidably provided in the valve hole 28, the rod A piston 51 connected to the other end of 53 via a bolt 52 and a cylinder 35 for slidably storing the piston 51 are provided. The cylinder 35 is formed in the discharge casing 16, and the discharge casing 16 is also provided with a rod hole 101 for supporting the rod 53 slidably. A seal ring 50 is provided in the rod hole 101 so as to seal between the cylinder chamber of the cylinder 35 and the back pressure chamber 28a of the valve body 31. Further, the pressure on the discharge side of the compressor is introduced into the back pressure chamber 28 a through a communication hole 102 formed in the discharge casing 16. That is, as shown in FIGS. 6 and 8, one end side of the communication hole 102 opens into the back pressure chamber 28a, and the other end side of the communication hole 102 communicates with the discharge chamber 26 (see FIG. 3). ing.

  A seal ring 54 for preventing leakage between the cylinder chambers 35 </ b> A and 35 </ b> B formed on both sides of the piston 51 is mounted on the outer periphery of the piston 51. In addition, in the cylinder chamber 35A (inside the cylinder 35 on the counter-valve body side), one end side of the communication hole 32 opens at a portion outside the moving range of the piston 51 (right end side of the cylinder chamber 35A). As shown in FIG. 8, the other end side of the nozzle is opened to the discharge chamber 26. That is, the cylinder chamber 35A communicates with the discharge chamber 26 (see FIG. 3) through the communication hole 32, and is configured such that the pressure on the compressor discharge side is always introduced into the cylinder chamber 35A. .

  In the cylinder chamber 35B (in the cylinder on the valve body side), as shown in FIGS. 6 and 7, one end of the communication hole 34 opens to a portion outside the moving range of the piston 51 (on the left end side of the cylinder chamber 35B). The other end side of the communication hole 34 communicates with the oil tank 95 via the capillary tube 120 as shown in FIG. 2 to form a hydraulic pressure supply path. Further, the communication hole 34 is configured to communicate with a low pressure space (suction port 22 in FIG. 6) via a communication path (hydraulic discharge path) 80, and the communication path 80 is provided in the middle of the communication path 80. An electromagnetic valve 42 for opening and closing is provided. With this configuration, by opening and closing the electromagnetic valve 42, high pressure oil in the oil tank 95 is introduced into the cylinder chamber 35B, and oil in the cylinder chamber 35B is introduced into the suction port 22 via the communication passage 80 and the electromagnetic valve 42. It can be discharged to the side. The cylinder chamber 35B is provided with a spring 33 that urges the piston 51 toward the end cover 60 (on the counter valve body 31 side, the right side in FIG. 6).

  The valve body 31 is controlled to be closed when the compression working chambers 36A and 36B are not over-compressed, but when the valve body 31 is closed, the electromagnetic valve 42 is opened. As a result, the cylinder chamber 35 </ b> B is communicated to the suction port 22 side via the communication hole 34 and the communication passage 80, and becomes a low pressure. On the other hand, the gas pressure on the discharge side of the compressor is constantly acting on the cylinder chamber 35A. Therefore, as shown in FIG. 6, the piston 51 overcomes the pressing force of the spring 33 and moves to the main casing 15 side, the valve body 31 is pressed against the end surface 21 of the main casing 15, and the valve hole 28 is closed. It is done.

  The side of the capillary tube 120 on the side of the communication hole 34 is also connected to the suction port 22, but the amount of oil discharged from the oil tank 95 to the suction port 22 is reduced because the oil flow is throttled by the capillary tube 120. Can be reduced to a sufficiently small amount, and the intake gas (for example, refrigerant gas) to the compressor is suppressed from being overheated with the oil to suppress a decrease in volume efficiency. Further, in the present embodiment, the oil is discharged to the suction port 22, so that the time during which the refrigerant gas sucked into the compressor is superheated with the oil can be minimized, and also from this point, the refrigerant gas is Since it can reduce heating with oil, the fall of volumetric efficiency can be suppressed.

  When overcompression occurs in the compression working chambers 36A and 36B, the valve body 31 is controlled to open. In this case, the high pressure oil in the oil tank 95 is introduced into the cylinder chamber 35B by closing the electromagnetic valve 42. That is, by closing the electromagnetic valve 42, the high-pressure oil in the oil tank 95 is introduced into the cylinder chamber 35B via the capillary tube 120, and the pressure in the cylinder chamber 35B becomes substantially the discharge pressure. Accordingly, the pressure acting on the piston 51 is substantially the same on both the cylinder chamber 35A side and the cylinder chamber 35B side, so that the piston 51 is placed on the counter valve body side (end cover 60) by the pressing force of the spring 33 provided in the cylinder chamber 35B. Side) is increased. Accordingly, as shown in FIG. 7, the piston 51 moves to the end cover 60 side, the valve body 31 is separated from the main casing 15, and the valve hole 28 is opened.

Although the valve body drive device 30 for opening and closing the valve body 31 has the above-described configuration, in this embodiment, it is further detected whether or not overcompression occurs in the compression working chambers 36A and 36B. A control device that controls the valve body driving device 30 to open the valve body 31 when the occurrence of compression is detected is provided, which will be described below with reference to FIG.
In FIG. 1, 110 is a suction pressure sensor for detecting the pressure of gas sucked from the suction port 6, and 111 is a discharge pressure sensor for detecting the pressure of compressed gas discharged from the compressor main body 1. These pressure sensors Signals from 110 and 111 are sent to the control device 112. Based on the signals from the pressure sensors 110 and 111, the control device 112 calculates the pressure ratio (discharge pressure / suction pressure) during operation at that time. The control device 112 stores a preset pressure ratio and compares it with the calculated pressure ratio during operation.

  As a result of this comparison, if the calculated pressure ratio during operation is the same or higher than the preset pressure ratio, it is determined that overcompression has not occurred in the compression working chambers 36A and 36B, and electromagnetic By opening the valve 42, the valve body 31 is controlled to move to the main casing 15 side and be pressed to close the valve hole 28.

  On the other hand, when the pressure ratio during operation calculated with respect to the preset pressure ratio is low, it is determined that overcompression occurs in the compression working chambers 36A and 36B, and the electromagnetic valve 42 is closed. By doing so, the valve body 31 is moved to the side opposite to the main casing 15 (the right side in FIG. 6), and the valve hole 28 is controlled to be opened. As a result, the compressed gas is discharged from the compression working chambers 36A and 36B to the discharge chamber 26 through the valve hole 28 and the bypass flow path (bypass groove 29), so that the pressure in the compression working chamber is almost equal to the pressure in the discharge chamber 26. Reduce until Accordingly, over-compression can be reduced and wasteful power consumption can be suppressed.

  In this embodiment, the set volume ratio Vs / Vd, which is the ratio of the volume Vs of the compression working chamber when the suction is closed and the volume Vd of the compression working chamber when the discharge is started by the valve hole 28, is 1.5 to The range is 3.0.

  Further, in the present embodiment, the valve hole 28 in the discharge side end surface 24 of the discharge casing 16 is configured such that the approximate center thereof is located at the opening edge of the bore 20 </ b> B in the end surface 21 of the main casing 15. That is, as shown in FIG. 3, the valve hole 28 has an inner area located on the inner side in the rotor radial direction from the opening edge of the bore 20B and opens in the compression working chamber 36B. An outer region located outside the opening edge in the rotor radial direction is covered with an end surface 21 of the main casing 15. Thereby, the end surface 21 of the main casing 15 covering the outer region of the valve hole 28 can function as a stopper of the valve body 31. (That is, it is possible to prevent the valve body 31 from tilting against the end face 21.) Therefore, as in the prior art, the stopper for positioning the valve body is formed by forming step portions in the valve body and the valve hole. Compared to the case, in the present embodiment, the stopper for positioning the valve body can be simplified, and since high-precision processing is not required as in the prior art, the productivity can be increased.

  Further, for example, compared to the case where the approximate center of the valve hole 28 is located on the inner side in the rotor radial direction from the opening edge of the bore 20B, the valve body driving device 30 can be disposed on the outer side in the rotor radial direction. Interference with the roller bearing 18 and the ball bearing 19 provided in the discharge casing 16 for supporting the discharge side shaft portion can also be avoided. Therefore, since it is not necessary to lengthen the discharge side shaft portion of the screw rotor 14, an increase in the size of the compressor can be suppressed.

  Furthermore, in the present embodiment, the bypass flow path is constituted by the bypass groove 29 formed on the discharge side end face 24 of the discharge casing 16 and the end face 21 of the main casing 15 covering the bypass groove 29. Can be formed at the casting stage. For example, the number of processing steps can be reduced as compared with the case of forming a bypass hole as a bypass flow path.

  Next, a modification of the above-described first embodiment will be described. In the first embodiment, as shown in FIG. 3, the example in which one valve hole 28 is provided on the female rotor 14B side on the discharge side end face 24 of the discharge casing 16 has been described. However, the present invention is not limited to this, and may be configured as, for example, Modifications 1 to 3 shown in FIGS. 9 to 11 described below.

FIG. 9 shows a first modification, in which one valve hole 37 is provided only on the male rotor 14 </ b> A side of the discharge side end face 24 of the discharge casing 16. That is, the valve hole 37 is provided in the vicinity of the discharge port 25A on the male rotor 14A side on the discharge side end face 24 of the discharge casing 16 on the opposite side of the rotation direction of the male rotor 14A. A bypass groove 38 communicates the valve hole 37 and the discharge chamber 26. The valve hole 37 is also provided with a valve body 31 and a valve body driving device 30 for opening and closing the valve body 31 as shown in FIGS. The set volume ratio Vs / Vd, which is the ratio of the volume Vs of the compression working chamber when the suction is closed and the volume Vd of the compression working chamber when the discharge is started by the valve hole 37, is also the same as in the first embodiment. , 1.5 to 3.0. Further, the center of the valve hole 37 in the discharge-side end surface 24 of the discharge casing 16 is also configured to be positioned substantially at the opening edge of the bore 20A in the end surface 21 of the main casing 15 as in the first embodiment.
Therefore, the modification 1 shown in FIG. 9 can obtain substantially the same effect as the first embodiment.

  FIG. 10 is a diagram showing Modification Example 2. In this example, one valve hole 28 or 37 is provided on each of the male rotor 14A side and the female rotor 14B side on the discharge-side end face 24 of the discharge casing 16 respectively. is there. That is, on the female rotor 14B side of the discharge casing 16, a valve hole 28, a bypass groove 29, a valve body drive device 30 and the like are provided in the same manner as shown in FIG. 3, and the male rotor 14A of the discharge casing 16 is provided. On the side, similar to that shown in FIG. 9, a valve hole 37, a bypass groove 38, a valve body driving device, and the like are provided. In this example, on the valve hole 28 side and the valve hole 37 side, the ratio is a ratio between the volume Vs of the compression working chamber when the suction is closed and the volume Vd of the compression working chamber when starting discharge by each valve hole. The volume ratios Vs / Vd may be the same or different from each other.

  Also in the second modification, the same effect as in the above embodiment can be obtained, and the valve hole 28 or 37 is provided on both the male rotor 14A side and the female rotor 14B side, respectively. The overcompressed gas from the chamber can be discharged to the discharge side more quickly, and it is possible to prevent overcompression and further suppress wasteful power consumption.

  FIG. 11 is a diagram showing a third modification. In each example described above, one valve hole 28 or 38 is provided on the female rotor 14B side or the male rotor 14A side, or one valve hole 28 or 38 is provided on both the female rotor 14B side and the male rotor 14A side. What provided 38 was demonstrated. In contrast, in the third modification, a plurality of valve holes are provided on either the female rotor 14B side or the male rotor 14A side, or a plurality of valve holes are provided on each of both. . For example, as shown in FIG. 11, the discharge casing 16 is provided with two valve holes 28A, 28B on the female rotor 14B side, and further, a bypass groove 29A that connects these valve holes 28A, 28B and the discharge chamber 26 is formed. Is. Similar to the above embodiment, each of the valve holes 28A and 28B is provided with a valve body, and a valve body driving device for opening and closing these valve bodies is also provided.

  In this example, the set volume ratio Vs / Vd, which is the ratio of the volume Vs of the compression working chamber when the suction is closed and the volume Vd of the compression working chamber when starting discharge by the valve holes 28A and 28B, is the valve hole 28A. Both the side and the 28B side are in the range of 1.5 to 3.0. However, since the valve hole 28A side and the 28B side are arranged so as to be shifted from each other in the rotation direction of the female rotor, the set volume ratios Vs / Vd are different from each other. Also in this example, the centers of the valve holes 28 </ b> A and 28 </ b> B on the discharge-side end surface 24 of the discharge casing 16 are substantially located at the opening edge of the bore 20 </ b> B on the end surface 21 of the main casing 15.

  Also in this modified example 3, the same effect as in the above embodiment can be obtained, and a plurality of valve holes are arranged so as to be shifted from each other in the rotation direction of the rotor. It is possible to efficiently form a large size without causing interference.

FIG. 12 is a refrigeration cycle configuration diagram illustrating an example in which the screw compressor shown in Embodiment 1 of the present invention is incorporated in a chiller unit.
In FIG. 12, reference numeral 130 denotes the screw compressor shown in the first embodiment. The refrigerant gas discharged from the compressor 130 enters the oil separator 92 through the discharge pipe 94, where oil is separated, and the refrigerant gas Is sent to the condenser 140 via a pipe (refrigerant pipe) 96. In the condenser, the refrigerant gas is cooled and condensed by the outside air, becomes a liquid refrigerant, is sent to the electronic expansion valve 142, and expands. An evaporator 141 is provided downstream of the electronic expansion valve 142, and the expanded refrigerant evaporates by taking heat from outside cooling water or the like by the evaporator 141 and is sucked into the compressor 130 again. The cooling water cooled by the evaporator 141 is used for cooling applications.

  A suction pressure sensor 110 is provided on the suction side of the compressor 130, and a discharge pressure sensor 111 is provided on the discharge side of the compressor 130 to detect the suction pressure and the discharge pressure of the refrigerant gas. 42 is the same solenoid valve as the solenoid valve 42 shown in FIGS. 6 and 7, and this solenoid valve 42 is opened and closed by a command from the control device 112. The control device 112 obtains a pressure ratio during operation based on the suction pressure to the compressor 130 and the discharge pressure of the compressor 130, and compares this pressure ratio with a preset pressure ratio stored in advance. When the pressure ratio during operation becomes smaller than the set pressure ratio, it is determined that over-compression has occurred, and the electromagnetic drive device 30 opens the valve body 31 as shown in FIG. The valve 42 is controlled.

  In the chiller unit, the temperature of the cooling water is normally controlled so as to reach the target value, so there is not much fluctuation in the suction pressure that is affected by the cooling water temperature, but the condensation pressure in the condenser is low. Therefore, the pressure on the discharge side of the compressor detected by the discharge pressure sensor 111 varies. For this reason, overcompression is likely to occur in the compressor 130, but by using the screw compressor shown in the present embodiment, the occurrence of overcompression can be reduced and a chiller unit with less power loss can be obtained. .

  According to the present embodiment described above, when the pressure ratio calculated from the suction pressure and the discharge pressure measured with respect to the preset pressure ratio (discharge pressure / suction pressure) is high, the cylinder on the valve body side of the piston When the pressure ratio calculated from the suction pressure and the discharge pressure measured with respect to a preset pressure ratio is low, the valve body is closed by discharging the hydraulic pressure inside the compressor to the suction side. Since the valve body is opened by confining the hydraulic pressure, over-compression can be reduced by reliably opening and closing the valve body. As a result, it is possible to improve performance while suppressing wasteful power consumption. Compared to the conventional case where the valve is opened and closed by the balance between the pressure of the compression working chamber acting on the valve body, the pressure on the discharge side, and the spring force, not only can the valve body be opened and closed reliably, but also the pressure in the compression working chamber Since it is possible to prevent the valve body from flapping due to fluctuations, it is possible to obtain a screw compressor that can reduce the impact sound and vibration of the valve body.

  In particular, the spring on the valve body side of the piston is provided with a spring that presses the piston against the valve body side, so even if pressure fluctuations occur in the compression chamber, the spring does not strike the stopper against the stopper. The striking sound of the valve body hitting the stopper and the vibration of the valve body can be eliminated, and the spring provided in the cylinder does not repetitively expand and contract, so that the reliability can be improved.

  Furthermore, in the conventional one described in Patent Document 1, when the gas passes through the valve portion when the valve body is opened and closed, the flow is throttled, so that the fluid friction increases and the overcompression cannot be sufficiently reduced. . On the other hand, according to the present embodiment, the valve body is controlled to be fully opened and fully closed by the control device, so that the gas flowing out from the valve body portion is throttled by changing the opening of the valve body as in the conventional case. Further, since it is possible to prevent the fluid friction from increasing, it is possible to sufficiently reduce over-compression.

1: Compressor body 2: Motor 5: Suction chamber 6: Suction port 9: Discharge port 10: Rotating shaft 13: Motor casing 14: Screw rotor (14A: male rotor, 14B: female rotor)
15: Main casing (21: End face)
16: Discharge casing (24: Discharge end face)
17, 18: Roller bearing, 19, 91: Ball bearing 20: Bore (20A: male rotor side bore, 20B: female rotor side bore)
22: Suction port (low pressure space)
23, 23A, 23B: radial discharge ports 25, 25A, 25B: axial discharge ports 26: discharge chambers 28, 28A, 28B, 37: valve holes (28a: back pressure chamber)
29, 29A, 38: Bypass groove (bypass flow path)
30: Valve body drive device 31: Valve body 32: Communication hole (gas pressure supply path)
34, 120: Hydraulic supply path (34: communication hole, 120: capillary tube)
35: Cylinder (35A, 35B: Cylinder chamber)
36A, 36B: Compression working chamber 42: Solenoid valve 50, 54: Seal ring 51: Piston, 52: Bolt, 53: Rod,
60: End cover 80: Communication path (hydraulic discharge path)
90: Discharge flow path 92: Oil separator 93: Oil return pipe, 94: Discharge pipe, 96: Pipe (refrigerant pipe)
95: Oil tank 102: Communication hole 110: Suction pressure sensor 111: Discharge pressure sensor 112: Control device 130: Screw compressor 140: Condenser, 141: Evaporator, 142: Electronic expansion valve

Claims (11)

A male rotor and a female rotor that rotate while the rotating shafts are substantially parallel and mesh with each other, a main casing having a bore that houses the male rotor and the female rotor, and a rotor axial discharge side of the main casing that is connected to the rotor axial discharge side. A discharge casing having a discharge-side end face that contacts the end face and covers the opening of the bore, and from the compression working chamber formed by the male rotor and the female rotor to at least one of the main casing and the discharge casing A discharge chamber or a discharge passage through which the compressed gas is discharged through the formed discharge port; and a discharge side end surface of the discharge casing on at least one side of the male rotor or the female rotor in the vicinity of the discharge port. A valve hole formed at a position opening in the working chamber, and the valve hole and the discharge chamber or the discharge flow path are connected. In the bypass passage and, screw compressor and an arranged valve body within the valve bore which,
A valve body driving device for opening and closing the valve body;
A controller that detects whether or not overcompression occurs in the compression working chamber, and controls the valve body drive device to open the valve body when the occurrence of overcompression is detected ;
The control device obtains a pressure ratio during operation based on the suction pressure to the compressor and the discharge pressure of the compressor, compares this pressure ratio with a preset pressure ratio stored in advance, When the pressure ratio is smaller than the set pressure ratio, it is determined that overcompression has occurred, and the valve body driving device is controlled to open the valve body,
The valve body driving device includes a cylinder provided on the back side of the valve body, a piston that reciprocates in the cylinder, and a rod that connects the piston and the valve body, and over-compression occurs. It is configured to open the valve body by applying pressure to the piston,
A spring is provided in the cylinder on the valve body side of the piston to press the piston to the counter valve body side, and overcompression occurs by introducing compressed gas on the compressor discharge side into the cylinder on the counter valve body side of the piston. When the valve body is not in the closed state, the valve body is closed.When over-compression occurs, the piston on the valve body side of the piston is applied with pressure on the discharge side of the compressor to move the piston to the counter-valve body side. A screw compressor characterized in that the valve body is opened by being moved . The screw compressor according to claim 1, wherein the pressure in the cylinder on the valve body side of the piston and the pressure are set.
The discharge side of the compressor is connected with a passage having a capillary tube, and further, the cylinder side of this passage
A communication passage that connects the low pressure space of the compressor and the compressor is provided, and the communication passage is opened and closed in the middle of the communication passage.
If over-compression has not occurred, the communication path is opened and over-compression occurs.
If it occurs, the compressor is placed in the cylinder on the valve body side of the piston by closing the communication passage.
A screw compressor characterized in that a pressure on the discharge side is applied to open the valve body . 2. The screw compressor according to claim 1, wherein the valve hole in the discharge-side end face of the discharge casing is positioned substantially at the opening edge of the bore in the end face of the main casing. . 3. The screw compressor according to claim 2 , wherein the passage having a capillary tube is opened in a cylinder chamber outside the moving range of the piston, and the communication passage communicated with the low pressure space is opened at a suction port of the compressor. A screw compressor characterized by that. 5. The screw compressor according to claim 4, wherein the passage having the capillary tube is a hydraulic pressure supply passage that opens to an oil tank whose upstream side communicates with the discharge side of the compressor. 2. The screw compressor according to claim 1, wherein a gas pressure supply path that connects a cylinder inner end side of the piston on the counter valve body side and a discharge side of the compressor is formed in the discharge casing. Machine. 2. The screw compressor according to claim 1 , wherein the bypass flow path includes a bypass groove formed on a discharge side end face of the discharge casing and an end face of the main casing covering the bypass groove. A featured screw compressor. 2. The screw compressor according to claim 1 , wherein the valve hole is a set volume ratio which is a ratio of a volume Vs of the compression working chamber when the suction is closed and a volume Vd of the compression working chamber when starting discharge by the valve hole. Vs / Vd is formed in the range of 1.5-3.0, The screw compressor characterized by the above-mentioned. 2. The screw compressor according to claim 1 , wherein a plurality of the valve holes are formed, and a ratio between a volume Vs of the compression working chamber when the suction is closed and a volume Vd of the compression working chamber when the discharge is started by each valve hole. A screw compressor characterized in that the set volume ratio Vs / Vd is different from each other . 2. The screw compressor according to claim 1, comprising a suction pressure sensor for detecting suction pressure and a discharge pressure detection sensor for detecting discharge pressure . The screw compressor according to claim 1, wherein the discharge port includes a radial discharge port formed at a discharge side end portion of the main casing and an axial discharge port formed at a discharge side end surface of the discharge casing. The screw compressor characterized by comprising by these .

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