JPWO2015193974A1 - Two stage screw compressor - Google Patents

Abstract

The two-stage screw compressor includes a low-stage compression mechanism that compresses a fluid, a high-stage compression mechanism that further compresses the fluid compressed by the low-stage compression mechanism, and a screw shaft that drives the low-stage compression mechanism and the high-stage compression mechanism. The low-stage compression mechanism includes a low-stage screw rotor, a pair of low-stage gate rotors, and a low-stage casing, and the high-stage compression mechanism includes the high-stage screw rotor, one The low-stage screw rotor and the high-stage screw rotor have the same diameter, and the compression groove of the low-stage screw rotor has a stroke from the start of compression to the completion of discharge. The rotation angle is formed to be smaller than 180 °, and the compression groove of the high-stage screw rotor has a rotation angle from the start of compression to the completion of discharge of greater than 180 ° and smaller than 360 °. It is formed.

Description

  The present invention relates to a two-stage screw compressor.

  Patent Document 1 describes a two-stage screw compressor including a low-stage compression mechanism and a high-stage compression mechanism. In this two-stage screw compressor, the low-stage side rotary shaft and the high-stage side rotary shaft are formed with an integral substantially coaxial diameter. Moreover, the low stage screw rotor and the high stage screw rotor are made common. Furthermore, a pair of low stage gate rotors are fitted to the low stage screw rotor, and only one high stage gate rotor is fitted to the high stage screw rotor.

Japanese Patent No. 4120733

  In the high-stage compression mechanism of the two-stage screw compressor of Patent Document 1, the refrigerant discharged from the low-stage compression mechanism is compressed in a stroke with a screw rotation angle of 180 ° or less. For this reason, the compression speed at which the refrigerant is compressed in one stroke increases, and the flow velocity and acceleration of the refrigerant discharged from the discharge port increase. For this reason, especially when the motor speed is increased by driving the inverter, or when a high-pressure or high-density refrigerant is used, overshoot and discharge resistance at the discharge port increase, and pressure loss and There was a problem that pulsation would increase.

  The present invention has been made to solve the above-described problems, and can suppress overshoot and discharge resistance in a high-stage compression mechanism, and can reduce pressure loss and pulsation during fluid discharge. An object of the present invention is to provide a two-stage screw compressor.

  The two-stage screw compressor according to the present invention includes a low-stage compression mechanism that compresses a fluid, a high-stage compression mechanism that further compresses the fluid compressed by the low-stage compression mechanism, the low-stage compression mechanism, and the high-stage compression mechanism. A screw shaft that drives a compression mechanism, and the low-stage compression mechanism includes a low-stage screw rotor that has a helical compression groove formed on an outer peripheral surface and is driven to rotate by the screw shaft, and the low-stage screw rotor. A pair of low-stage gate rotors that rotate following the rotation of the low-stage screw rotor, and a cylindrical inner cylinder surface that rotatably accommodates the low-stage screw rotor. A high-stage compression mechanism, wherein the high-stage compression mechanism includes a high-stage screw rotor having a helical compression groove formed on an outer peripheral surface and driven to rotate by the screw shaft; One high-stage gate rotor that has a plurality of teeth that mesh with the compression grooves of the Liu rotor, and that rotates following the rotation of the high-stage screw rotor, and a cylindrical inner cylinder surface that rotatably accommodates the high-stage screw rotor The low-stage screw rotor and the high-stage screw rotor have the same diameter, and the compression groove of the low-stage screw rotor rotates in the stroke from the start of compression to the completion of discharge. The compression groove of the high stage screw rotor is formed so that the angle is smaller than 180 °, and the rotation angle of the stroke from the start of compression to the completion of discharge is larger than 180 ° and smaller than 360 °. Is formed.

  According to the present invention, since the compression speed of the high-stage compression mechanism can be reduced, overshoot and discharge resistance at the discharge port of the high-stage compression mechanism can be suppressed, and pressure loss and pulsation during fluid discharge can be reduced. Can be reduced.

It is sectional drawing which shows schematic structure of the two-stage screw compressor which concerns on Embodiment 1 of this invention. It is a perspective view which shows schematic structure of the low stage compression mechanism 12 of the two-stage screw compressor which concerns on Embodiment 1 of this invention. It is a perspective view which shows schematic structure of the high stage compression mechanism 13 of the two-stage screw compressor which concerns on Embodiment 1 of this invention. It is an expanded view which shows the structure of the outer peripheral surface of the low stage screw rotor 3 in the two stage screw compressor which concerns on Embodiment 1 of this invention. It is an expanded view which shows the structure of the outer peripheral surface of the low stage screw rotor 3 in the two stage screw compressor which concerns on Embodiment 1 of this invention. It is an expanded view which shows the structure of the outer peripheral surface of the high stage screw rotor 4 in the two-stage screw compressor which concerns on Embodiment 1 of this invention. It is an expanded view which shows the structure of the outer peripheral surface of the high stage screw rotor 4 in the two-stage screw compressor which concerns on Embodiment 1 of this invention.

Embodiment 1 FIG.
A two-stage screw compressor according to Embodiment 1 of the present invention will be described. FIG. 1 is a cross-sectional view showing a schematic configuration of a two-stage screw compressor according to the present embodiment. FIG. 2 is a perspective view showing a schematic configuration of the low-stage compression mechanism 12 of the two-stage screw compressor according to the present embodiment. FIG. 3 is a perspective view showing a schematic configuration of the high-stage compression mechanism 13 of the two-stage screw compressor according to the present embodiment. A two-stage screw compressor is one of the components of a refrigeration cycle apparatus used in a refrigerator or the like. In the following drawings including FIG. 1 to FIG. 3, the dimensional relationship and shape of each component may be different from the actual ones. Moreover, the form of the component shown by the whole specification is an illustration to the last, and is not limited to these description.

  As shown in FIGS. 1 to 3, the two-stage screw compressor in the present embodiment includes a low-stage compression mechanism 12 that compresses a fluid (for example, a refrigerant that circulates in the refrigeration cycle apparatus), and a low-stage compression mechanism 12. A high-stage compression mechanism 13 that further compresses the compressed fluid, a low-stage compression mechanism 12, a screw shaft 5 that drives the high-stage compression mechanism 13, and an electric motor 2 that rotates the screw shaft 5 are provided. The two-stage screw compressor of this example is a single screw type in which the low-stage compression mechanism 12 and the high-stage compression mechanism 13 are driven by a common screw shaft 5. The low-stage compression mechanism 12, the high-stage compression mechanism 13, the screw shaft 5, and the electric motor 2 are accommodated in a cylindrical casing body 1 that is an outer shell of the entire two-stage screw compressor. In the cylinder axis direction of the casing body 1, the electric motor 2 is disposed on one end side, the high-stage compression mechanism 13 is disposed on the other end side, and the low-stage compression mechanism 12 includes the electric motor 2 and the high-stage compression mechanism 13. It is arranged between.

  The low-stage compression mechanism 12 includes a low-stage casing 1a (not shown in FIG. 2), a low-stage screw rotor 3, and a pair of low-stage gate rotors 7. The low-stage casing 1a constitutes a part of the casing body 1 and has a cylindrical inner cylindrical surface 1c. The inner cylinder surface 1c is provided with a low-stage discharge port 10 (described later) for discharging the compressed fluid. The low-stage screw rotor 3 is rotatably accommodated in the low-stage casing 1 a (inner cylinder surface 1 c) and is rotationally driven by the screw shaft 5. A plurality of helical compression grooves 3 a (screw grooves) are formed on the outer peripheral surface of the low-stage screw rotor 3. Each of the pair of low-stage gate rotors 7 is provided with a plurality of teeth 7a that mesh with the compression grooves 3a in a radial manner, and is rotated by the rotation of the low-stage screw rotor 3. The pair of low stage gate rotors 7 are arranged at positions whose phases are different by 180 ° in the circumferential direction of the low stage screw rotor 3. In the space surrounded by the compression groove 3 a of the low stage screw rotor 3, the low stage gate rotor 7, and the inner cylindrical surface 1 c of the low stage casing 1 a, the low stage whose volume changes as the low stage screw rotor 3 rotates. A compression chamber 6 is formed. In this example, the number of grooves of the low stage screw rotor 3 (the number of the compressed grooves 3a) is 6, and the number of teeth of the low stage gate rotor 7 (the number of teeth 7a) is 11. That is, the gear ratio of the low-stage compression mechanism 12 is 6:11.

  The high-stage compression mechanism 13 includes a high-stage casing 1b (not shown in FIG. 3), a high-stage screw rotor 4, and one high-stage gate rotor 9. The high-stage casing 1b constitutes a part of the casing body 1 and has a cylindrical inner cylindrical surface 1d. The inner cylinder surface 1d is provided with a high-stage discharge port 11 (described later) for discharging the compressed fluid. The high stage screw rotor 4 is rotatably accommodated in the high stage casing 1 b (inner cylinder surface 1 d) and is driven to rotate by the screw shaft 5. A plurality of helical compression grooves 4 a (screw grooves) are formed on the outer peripheral surface of the high-stage screw rotor 4. The high stage gate rotor 9 is radially provided with a plurality of teeth 9 a that mesh with the compressed grooves 4 a, and is rotated by the rotation of the high stage screw rotor 4. In the space surrounded by the compression groove 4a of the high stage screw rotor 4, the high stage gate rotor 9, and the inner cylindrical surface 1d of the high stage casing 1b, the high stage whose volume changes as the high stage screw rotor 4 rotates. A compression chamber 8 is formed. In this example, the number of grooves of the high stage screw rotor 4 (the number of the compressed grooves 4a) is 3, and the number of teeth of the high stage gate rotor 9 (the number of teeth 9a) is 11. That is, the gear ratio of the high-stage compression mechanism 13 is 3:11.

  The electric motor 2 includes an electric motor stator 2a that is inscribed and fixed to the casing main body 1, and an electric motor rotor 2b that is disposed inside the electric motor stator 2a. In this example, an inverter power source 14 that can change the drive rotation speed (frequency) of the screw shaft 5 is used as a power source for supplying electric power to the motor stator 2a. In addition, as a power supply which supplies electric power to the motor stator 2a, a general commercial power supply with a frequency of 50 Hz or 60 Hz can also be used. The electric motor rotor 2b, the low-stage screw rotor 3 and the high-stage screw rotor 4 are arranged on the same axis, and are all fixed to the screw shaft 5. In this example, the low-stage screw rotor 3 and the high-stage screw rotor 4 have the same diameter. The pair of low-stage gate rotor 7 and high-stage gate rotor 9 both have the same diameter and the same configuration.

  4 and 5 are development views showing the configuration of the outer peripheral surface of the low-stage screw rotor 3. 4 and 5 also show the position and shape of the low-stage discharge port 10 formed on the inner cylindrical surface 1c of the low-stage casing 1a. 4 and 5, the vertical direction represents the circumferential direction of the outer peripheral surface of the low-stage screw rotor 3 (360 ° from the upper end to the lower end), and the white thick arrow indicates the rotational direction (deployment) of the low-stage screw rotor 3. In the drawing, the direction in which the compressed groove 3a advances is shown. The upper and lower ends in the figure represent the position of one low-stage gate rotor 7, and the central portion in the vertical direction represents the position of the other low-stage gate rotor 7. 4 and 5, the right side represents the suction side where the fluid is sucked into the low stage compression chamber 6, and the left side represents the discharge side where the compressed fluid is discharged from the low stage compression chamber 6. ing. FIG. 4 shows a state at the time when fluid compression is started in the low-stage compression chamber 6 within the broken line in the drawing (when the fluid suction is completed), and FIG. 5 shows the state within the broken line in the drawing. The state at the time when the discharge of the fluid from the low stage compression chamber 6 is started (when the compression of the fluid is completed) is shown.

  As shown in FIGS. 4 and 5, the compression groove 3a of the low stage screw rotor 3 is formed so that the rotation angle φ1 of the stroke from the start of compression to the completion of discharge is smaller than 180 ° (φ1 <180). °). In the configuration of this example, the rotation angle φ1 is about 160 °. Further, the two low-stage discharge ports 10 formed on the inner cylindrical surface 1c are arranged at positions where the phases are different from each other by 180 °. Each of the low-stage discharge ports 10 is provided at an end portion on the discharge side, and is formed to have a substantially right triangle shape in the developed view. That is, each of the low-stage discharge ports 10 includes two sides that are parallel or perpendicular to the axial direction of the screw shaft 5 (the left-right direction in the drawing) and the compressed groove 3a (or the adjacent compressed groove). And a slant side 10a on the suction side that is formed in a straight line shape or a curved shape along the crest portion 3a. The angle formed by the hypotenuse 10a of the low-stage discharge port 10 with respect to the axial direction of the screw shaft 5 is θ1 (see FIG. 5).

  6 and 7 are development views showing the configuration of the outer peripheral surface of the high-stage screw rotor 4. 6 and 7 also show the position and shape of the high-stage discharge port 11 formed on the inner cylindrical surface 1d of the high-stage casing 1b. 6 and 7, the vertical direction represents the circumferential direction of the outer peripheral surface of the high-stage screw rotor 4 (360 ° from the upper end to the lower end), and the white thick arrow represents the rotational direction (deployment) of the high-stage screw rotor 4. In the drawing, the direction in which the compressed groove 4a advances is shown. The upper end and the lower end of the figure represent the position of the high stage gate rotor 9. 6 and 7, the right side represents the suction side where the fluid is sucked into the high-stage compression chamber 8, and the left side represents the discharge side where the compressed fluid is discharged from the high-stage compression chamber 8. ing. FIG. 6 shows a state at the time when the compression of the fluid is started in the high-stage compression chamber 8 within the broken line in the drawing (when the suction of the fluid is completed), and FIG. 7 shows the state within the broken line in the drawing. The state at the time when the discharge of fluid from the high-stage compression chamber 8 is started (when the compression of the fluid is completed) is shown.

  As shown in FIGS. 6 and 7, the compression groove 4a of the high stage screw rotor 4 is formed so that the rotation angle φ2 of the stroke from the start of compression to the completion of discharge is larger than 180 ° and smaller than 360 °. (180 ° <φ2 <360 °). In the configuration of this example, the rotation angle φ2 is about 320 °, which is twice the rotation angle φ1 of the low-stage screw rotor 3. That is, the compression groove 4 a of the high-stage screw rotor 4 is formed so as to have a larger inclination with respect to the axial direction (left-right direction in the drawing) of the screw shaft 5 than the compression groove 3 a of the low-stage screw rotor 3. Yes. Further, the high-stage discharge port 11 is provided at an end portion on the discharge side, and is formed to have a substantially right triangle shape in the developed view. That is, the high-stage discharge port 11 is along the two sides that are parallel or perpendicular to the axial direction of the screw shaft 5 and the compressed groove 4a (or the peak between adjacent compressed grooves 4a) in the development view. And a hypotenuse 11a on the suction side that is formed in a straight or curved shape. The angle formed by the hypotenuse 11a of the high stage discharge port 11 with respect to the axial direction of the screw shaft 5 is θ2 (see FIG. 7). Since the inclination of the compression groove 4a with respect to the axial direction of the screw shaft 5 is larger than the inclination of the compression groove 3a, the angle θ2 is larger than the angle θ1 (θ2> θ1).

  Here, the low stage screw rotor 3 and the high stage screw rotor 4 are formed with the same dimension (same diameter). The pair of low stage gate rotors 7 and one high stage gate rotor 9 are formed in the same shape and the same dimensions. In the low-stage compression mechanism 12, the gear ratio is 6:11 and the number of the low-stage gate rotor 7 is two, whereas in the high-stage compression mechanism 13, the gear ratio is 3:11 and the high stage gate. The number of rotors 9 is one. For this reason, the ratio of the volume of the compression groove 4a of the high-stage compression mechanism 13 and the volume of the compression groove 3a of the low-stage compression mechanism 12 is approximately 1: 2.

  In the high-stage screw rotor 4 of the present embodiment, the rotation angle φ2 of the compression groove 4a is increased, so that the angle of the compression groove 4a with respect to the screw shaft 5 is also increased. Thereby, the angle of the hypotenuse 11a of the high stage discharge port 11 formed in the shape along the peak part of the compression groove 4a can be enlarged, and the area of the high stage discharge port 11 can be expanded. 6 and 7 show the high-stage discharge port 11 when the area is maximized.

(Description of operation)
Next, the operation of the two-stage screw compressor according to this embodiment will be described.
When the motor stator 2a of the motor 2 is energized, the motor rotor 2b rotates. As the motor rotor 2 b rotates, the low-stage screw rotor 3 and the high-stage screw rotor 4 are rotated via the screw shaft 5. As the low-stage screw rotor 3 rotates, the pair of low-stage gate rotors 7 follow and rotate. Moreover, when the high stage screw rotor 4 rotates, the high stage gate rotor 9 is driven and rotated.

  In the low stage compression mechanism 12, the teeth 7 a of the low stage gate rotor 7 relatively move in the compression groove 3 a of the low stage screw rotor 3. Thus, in the low-stage compression mechanism 12, a suction stroke for sucking fluid (for example, refrigerant) into the low-stage compression chamber 6, a compression stroke for compressing fluid in the low-stage compression chamber 6, and the low-stage compression chamber 6. The discharge process of discharging the fluid compressed inside from the low-stage discharge port 10 is sequentially repeated. For example, when attention is paid to the low-stage compression chamber 6 in the broken line in FIGS. 4 and 5, the suction stroke is finished at the time shown in FIG. 4 and the compression stroke is started, and the compression stroke is finished at the time shown in FIG. The discharge stroke is started. The fluid compressed and discharged by the low stage compression mechanism 12 is sucked by the high stage compression mechanism 13 and further compressed.

  In the high stage compression mechanism 13, the teeth 9 a of the high stage gate rotor 9 relatively move in the compression groove 4 a of the high stage screw rotor 4. Thereby, in the high-stage compression mechanism 13, the suction stroke for sucking fluid into the high-stage compression chamber 8, the compression stroke for compressing the fluid in the high-stage compression chamber 8, and the fluid compressed in the high-stage compression chamber 8 And the discharge stroke of discharging from the high-stage discharge port 11 are sequentially repeated. For example, when attention is paid to the high-stage compression chamber 8 within the broken line in FIGS. 6 and 7, the suction stroke is completed at the time shown in FIG. 6 and the compression stroke is started, and the compression stroke is completed at the time shown in FIG. The discharge stroke is started. The fluid compressed by the high stage compression mechanism 13 is discharged to the outside of the two-stage screw compressor.

  Thus, in the two-stage screw compressor according to the present embodiment, the low-stage compression mechanism 12 and the high-stage compression mechanism 13 are connected by the same screw shaft 5. The fluid sucked into the two-stage screw compressor is discharged twice after the process from the start of compression to the completion of discharge is performed twice by the low-stage compression mechanism 12 and the high-stage compression mechanism 13. The rotation angle φ2 of the stroke from the compression start to the discharge completion in the compression groove 4a of the high-stage compression mechanism 13 is about twice that of the conventional compression groove. For this reason, the time required for compression by the high-stage compression mechanism 13 is also about twice that of the prior art, and the compression speed of the high-stage compression mechanism 13 can be reduced. Thereby, the flow velocity and acceleration of the fluid discharged from the high stage discharge port 11 can be reduced. Therefore, overshoot and discharge resistance at the high-stage discharge port 11 of the high-stage compression mechanism 13 can be suppressed, and pressure loss and pulsation during fluid discharge can be reduced. Therefore, the performance of the two-stage screw compressor can be improved, and vibration and noise of the two-stage screw compressor can be reduced. Moreover, according to this Embodiment, since the performance of a two-stage screw compressor can be improved, the size and weight reduction and energy saving of a two-stage screw compressor can also be achieved.

  In the present embodiment, the angle θ2 formed by the hypotenuse 11a of the high stage discharge port 11 with respect to the axial direction of the screw shaft 5 can be increased, so that the high stage discharge port 11 can be formed large. Therefore, the flow rate of the fluid discharged from the high stage discharge port 11 can be suppressed, and the discharge loss and the overshoot loss can be reduced. Therefore, the performance of the two-stage screw compressor can be further improved.

  Pressure loss and pulsation during fluid discharge are particularly problematic when the rotational speed of the electric motor 2 is high. For this reason, a bigger effect is acquired by applying this Embodiment to the two-stage inverter screw compressor provided with the electric motor 2 driven to variable rotation speed with an inverter.

  In the present embodiment, since the pair of low stage gate rotors 7 and one high stage gate rotor 9 have the same configuration, they can be made into a common part. In the present embodiment, since the number of high stage gate rotors 9 is one, the number of parts can be reduced. Therefore, in the present embodiment, it is possible to obtain a two-stage screw compressor with improved performance while securing the advantages of common parts and a reduced number of parts.

  In this embodiment, since the volume ratio between the high stage compression mechanism 13 and the low stage compression mechanism 12 is approximately 1: 2, the high stage screw rotor 4 and the low stage screw rotor 3 have the same diameter, and the high stage gate is provided. When the rotor 9 and the low stage gate rotor 7 have the same diameter, the number of the low stage gate rotor 7 is two and the number of the high stage gate rotor 9 is one. When the rotation angle of the stroke from the start of compression to the completion of discharge is greater than 180 °, the number of gate rotors cannot be reduced to two. Therefore, in the high-stage compression mechanism 13 that originally has one gate rotor, the rotation angle φ2 is set to 180 °. Can be larger. Therefore, in the present embodiment, it is possible to reduce the loss while ensuring the advantages of the two-stage screw compressor described in Patent Document 1 (peripheral parts are common and the number of parts is reduced).

  As described above, the two-stage screw compressor according to the present embodiment includes the low-stage compression mechanism 12 that compresses the fluid, and the high-stage compression mechanism 13 that further compresses the fluid compressed by the low-stage compression mechanism 12. A low-stage compression mechanism 12 and a screw shaft 5 that drives the high-stage compression mechanism 13. The low-stage compression mechanism 12 is formed with a helical compression groove 3 a on the outer peripheral surface and is driven to rotate by the screw shaft 5. A low-stage screw rotor 3, a plurality of teeth 7 a meshing with the compression grooves 3 a of the low-stage screw rotor 3, a pair of low-stage gate rotors 7 that rotate following the rotation of the low-stage screw rotor 3, A high-stage compression mechanism 13 having a helical compression groove 4a formed on the outer peripheral surface, and a low-stage casing 1a having a cylindrical inner cylinder surface 1c that rotatably accommodates the screw rotor 3. Screw shaft 5 A high-stage screw rotor 4 that is driven to rotate further, and a plurality of teeth 9 a that mesh with the compression grooves 4 a of the high-stage screw rotor 4, and one high-stage gate rotor 9 that rotates following the rotation of the high-stage screw rotor 4. And a high stage casing 1b having a cylindrical inner cylinder surface 1d for rotatably accommodating the high stage screw rotor 4, and the low stage screw rotor 3 and the high stage screw rotor 4 have the same diameter. The compression groove 3a of the low-stage screw rotor 3 is formed such that the rotation angle φ1 of the stroke from the start of compression to the completion of discharge is smaller than 180 °, and the compression groove 4a of the high-stage screw rotor 4 is compressed The rotation angle φ2 of the stroke from the start to the completion of discharge is formed to be larger than 180 ° and smaller than 360 °.

  Further, in the two-stage screw compressor according to the present embodiment, the pair of the low-stage gate rotor 7 and the high-stage gate rotor 9 have the same diameter. Here, even when the component materials of the low-stage gate rotor 7 and the high-stage gate rotor 9 are made common, the diameter of the low-stage gate rotor 7 and the high-stage gate rotor 9 are obtained in the processing stage and the product incorporation stage. The diameter may be changed by about several mm to several tens of mm. In other words, when the difference between the diameter of the low-stage gate rotor 7 and the diameter of the high-stage gate rotor 9 is several mm to several tens of mm (maximum 20 mm), the diameter of the low-stage gate rotor 7 and the high-stage gate As in the case where the diameter of the rotor 9 is completely the same, the effect of sharing parts can be obtained. Therefore, in the present embodiment, the “same diameter” between the low-stage gate rotor 7 and the high-stage gate rotor 9 has the same diameter as the low-stage gate rotor 7 and the high-stage gate rotor 9. And the case where the difference between the diameter of the low-stage gate rotor 7 and the diameter of the high-stage gate rotor 9 is 20 mm or less.

  In the two-stage screw compressor according to the present embodiment, the low-stage discharge port 10 for discharging the fluid compressed in the compression groove 3a of the low-stage screw rotor 3 is provided on the inner cylindrical surface 1c of the low-stage casing 1a. A high-stage discharge port 11 for discharging the fluid compressed in the compression groove 4a of the high-stage screw rotor 4 is provided on the inner cylindrical surface 1d of the high-stage casing 1b. Has an inclined side 10a inclined with respect to the screw shaft 5 on the suction side of the low-stage casing 1a, and the high-stage discharge port 11 has an inclined side 11a inclined with respect to the screw shaft 5 at the intake of the high-stage casing 1b. The angle θ2 formed by the hypotenuse 11a of the high stage discharge port 11 with respect to the screw shaft 5 is larger than the angle θ1 formed by the hypotenuse 10a of the low stage discharge port 10 with respect to the screw shaft 5. is there.

  The two-stage screw compressor according to the present embodiment further includes an electric motor 2 that rotates the screw shaft 5, and the electric motor 2 is driven by an inverter.

  The above embodiments and modifications can be implemented in combination with each other.

  DESCRIPTION OF SYMBOLS 1 Casing main body, 1a Low stage casing, 1b High stage casing, 1c, 1d Inner cylinder surface, 2 Electric motor, 2a Electric motor stator, 2b Electric motor rotor, 3 Low stage screw rotor, 3a, 4a Compression groove, 4 High stage screw rotor, 5 Screw shaft, 6 Low stage compression chamber, 7 Low stage gate rotor, 7a, 9a Teeth, 8 High stage compression chamber, 9 High stage gate rotor, 10 Low stage discharge port, 10a, 11a Oblique side, 11 High stage discharge port, 12 Low stage compression mechanism, 13 High stage compression mechanism, 14 Inverter power supply.

The two-stage screw compressor according to the present invention includes a low-stage compression mechanism that compresses a fluid, a high-stage compression mechanism that further compresses the fluid compressed by the low-stage compression mechanism, the low-stage compression mechanism, and the high-stage compression mechanism. A screw shaft that drives a compression mechanism, and the low-stage compression mechanism includes a low-stage screw rotor that has a helical compression groove formed on an outer peripheral surface and is driven to rotate by the screw shaft, and the low-stage screw rotor. of comprising a plurality of teeth which mesh with the compressed grooves, the comprises a low-stage gate rotor you rotated by the rotation of the low-stage screw rotors, the cylindrical inner circumferential surface for rotatably accommodating the low-stage screw rotor A high-stage compression mechanism, wherein the high-stage compression mechanism has a helical compression groove formed on an outer peripheral surface and is driven to rotate by the screw shaft; and the high-stage screw. Comprising a plurality of teeth which mesh with the compressed grooves of the rotor, and a high-stage gate rotor you rotated by the rotation of the high-stage screw rotors, a cylindrical inner circumferential surface for rotatably accommodating the high-stage screw rotors a high-stage casing having has a compression groove of the low-stage screw rotors is formed to be smaller than the rotation angle is 180 ° stroke from the compression start to discharge completion, the high stage The compression groove of the screw rotor is formed so that the rotation angle of the stroke from the start of compression to the completion of discharge is larger than 180 ° and smaller than 360 °.

Claims (4)

A low-stage compression mechanism for compressing fluid;
A high-stage compression mechanism for further compressing the fluid compressed by the low-stage compression mechanism;
A screw shaft for driving the low-stage compression mechanism and the high-stage compression mechanism;
With
The low-stage compression mechanism is
A low-stage screw rotor having a helical compression groove formed on the outer peripheral surface and driven to rotate by the screw shaft;
A plurality of teeth that mesh with the compression grooves of the low-stage screw rotor, and a pair of low-stage gate rotors that rotate following the rotation of the low-stage screw rotor;
A low-stage casing having a cylindrical inner cylindrical surface that rotatably accommodates the low-stage screw rotor,
The high-stage compression mechanism is
A helical compression groove formed on the outer peripheral surface, and a high stage screw rotor that is driven to rotate by the screw shaft;
A plurality of teeth that mesh with the compression grooves of the high-stage screw rotor, and one high-stage gate rotor that rotates following the rotation of the high-stage screw rotor;
A high-stage casing having a cylindrical inner cylindrical surface that rotatably accommodates the high-stage screw rotor,
The low-stage screw rotor and the high-stage screw rotor have the same diameter,
The compression groove of the low-stage screw rotor is formed so that the rotation angle of the stroke from the start of compression to the completion of discharge is smaller than 180 °,
The compression groove of the high-stage screw rotor is a two-stage screw compressor formed so that the rotation angle of the stroke from the start of compression to the completion of discharge is larger than 180 ° and smaller than 360 °.   The two-stage screw compressor according to claim 1, wherein the pair of low-stage gate rotors and the high-stage gate rotor have the same diameter. On the inner cylinder surface of the low-stage casing, a low-stage discharge port for discharging the fluid compressed in the compression groove of the low-stage screw rotor is provided,
The inner cylinder surface of the high-stage casing is provided with a high-stage discharge port for discharging the fluid compressed in the compression groove of the high-stage screw rotor,
The low stage discharge port has a hypotenuse inclined with respect to the screw shaft on the suction side of the low stage casing,
The high stage discharge port has an oblique side inclined with respect to the screw shaft on the suction side of the high stage casing,
The angle formed by the oblique side of the high-stage discharge port with respect to the screw shaft is greater than the angle formed by the oblique side of the low-stage discharge port with respect to the screw shaft. Two-stage screw compressor. An electric motor for rotating the screw shaft;
The two-stage screw compressor according to any one of claims 1 to 3, wherein the electric motor is driven by an inverter.

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