Patent Application
20250035115
The present invention relates to a screw compressor, and more specifically, relates to a screw compressor that cools a screw rotor by using a coolant.
Screw compressors include screw rotors that rotate and a casing that houses the screw rotors. Screw compressors suck in and compress a gas by causing the volumes of a plurality of working chambers defined by screw rotors and the inner wall surface of a casing surrounding the screw rotors to increase and decrease along with rotation of the screw rotors.
A representative one of causes of deterioration of the performance of screw compressors is an internal leak of a compressed gas. An internal leak of a compressed gas is a phenomenon in which the compressed gas flows backward undesirably from a high-pressure space (working chamber) with an increased pressure where the compression has progressed, to a space with a relatively low pressure where the compression has not yet started or has not progressed. The internal leak causes energy loss since the gas for which energy has been consumed for compression returns to a low-pressure state undesirably. Inner gaps that serve as the paths for internal leaks of a compressed gas include a gap between meshing portions of screw rotors, a gap between lobe tips of a screw rotor and the inner wall surface (inner circumferential surface) of a casing, a gap between the discharge-side end face of a screw rotor and the discharge-side inner wall surface of the casing facing the discharge-side end face (hereinafter, referred to as a discharge-side end face gap in some cases), and the like.
Since a compressed gas has a high temperature in a screw compressor, the casing and the screw rotors increase in temperature, resulting in thermal deformation. Due to the thermal deformation of the casing and the screw rotors, the inner gaps mentioned above tend to enlarge.
As a measure to reduce thermal deformation of a screw rotor, there are known methods in which the screw rotor is cooled by supplying a coolant to a cooling flow path (hole) provided inside the screw rotor. As an example of such screw-rotor cooling methods, there is a technology described in Patent Document 1, for example. In a rotor of a compressor element described in Patent Document 1, an inner cooling channel extending in the axial direction at the center of the rotor is provided with inwardly directed fins.
In order to attempt to improve the compressor efficiency, it is necessary to suppress enlargement of the inner gaps mentioned above by further improving the capability to cool a screw rotor. It has become clear that the discharge-side end face gap mentioned above enlarges due to thermal deformation of a screw rotor in the axial direction. Therefore, it is required to reduce the thermal deformation of the screw rotor that enlarges the discharge-side end face gap. In particular, it is expected that thermal deformation of a discharge-side shaft section of the screw rotor has a significant influence on the enlargement of the discharge-side end face gap.
One possible example of methods of improving the capability to cool a screw rotor is to lower the temperature of a coolant to be supplied to a cooling flow path of the screw rotor. However, this method requires a size increase of a cooler for cooling the coolant, and undesirably increases the cost. Further, in a case where the cooler is an air-cooling type cooler that cools the coolant by using outside air, the temperature of the coolant is undesirably restricted to a temperature equal to or higher than the temperature of the outside air.
Another possible example of the methods of improving the cooling capability is to increase the flow rate of a coolant to be supplied to a cooling flow path. However, this method requires a size increase of a pump for supplying the coolant, and, as a result, undesirably increases the overall motive power of a compressor system.
Accordingly, it is required to enhance the capability to cool a screw rotor without varying the temperature or flow rate of a coolant to be supplied to a cooling flow path.
In addition, it is considered that, according to the technology described in Patent Document 1, the presence of the multiple fins in the cooling channel increases the surface area of heat exchange with a coolant flowing through the cooling channel, and accordingly, the capability to cool the screw rotor is improved. However, the configuration in which the inwardly directed fins are provided in the cooling channel of the screw rotor complicates the structure.
The present invention has been made to solve the problems described above, and one of objects thereof is to provide a screw compressor that can enhance the capability to cool a discharge-side shaft section of a screw rotor, by using a simple structure.
A preferable example of the present invention is a screw compressor including a screw rotor and a discharge-side bearing, the screw rotor including a rotor lobe section that has a twisted lobe and also has a discharge-side end face on one side in an axial direction, and a discharge-side shaft section provided on the one side in the axial direction at the rotor lobe section, and the discharge-side bearing being mounted on the discharge-side shaft section. The screw rotor has a cooling flow path extending in the axial direction at least inside the discharge-side shaft section. A groove structure is provided at at least a part of a region on a wall surface of the cooling flow path between a position of the discharge-side end face in the axial direction and a mounting position of the discharge-side bearing. The groove structure includes grooves or a groove that has a lengthwise component in a circumferential direction of the screw rotor and that are spaced apart in the axial direction. A nozzle that is a stationary member for supplying a coolant is arranged inside the cooling flow path with a gap between the nozzle and the wall surface. The nozzle is arranged in such a manner as to overlap at least a part of the groove structure in the axial direction.
According to the preferable example of the present invention, a relative speed of the coolant, which flows through a region near a wall surface positioned between the groove(s) of the groove structure in the cooling flow path, relative to the wall surface increases due to an influence of the coolant flowing through regions at groove positions adjacent in the axial direction. In addition, a relative speed of the coolant, which flows on the side of the wall surface of the cooling flow path, relative to the wall surface increases due to an influence of the coolant flowing near the nozzle. These enhance the heat transfer coefficient on the wall surface of the cooling flow path having the groove structure, thereby improving the capability to cool the discharge-side shaft section of the screw rotor. That is, the capability to cool the discharge-side shaft section of the screw rotor can be enhanced with a simple structure.
Problems, configurations, and advantages other than those described above are made clear by the following explanation of embodiments.
Hereinbelow, embodiments of a screw compressor according to the present invention are illustratively explained by using the figures. The embodiments explained here depict examples in which the present invention is applied to an oil-free screw compressor.
The configuration of a screw compressor according to a first embodiment is explained by using
In
The male rotor 2 includes a rotor lobe section 21 having a plurality of helical, twisted male lobes 21a (four male lobes 21a in
The female rotor 3 includes a rotor lobe section 31 having a plurality of helical, twisted female lobes 31a (six female lobes 31a in
The casing 4 includes a main casing 41, a suction-side cover 42 mounted on the suction side (the left side in
The casing 4A has a housing chamber 45 that houses the rotor lobe section 21 of the male rotor 2 and the rotor lobe section 31 of the female rotor 3 in a mutually meshing state. The housing chamber 45 has two partially-overlapping cylindrical spaces formed inside the casing 4. The wall surface defining the housing chamber 45 (the inner wall surface of the casing 4) includes a substantially cylindrical male-side inner circumferential surface 46 covering the radially outer side of the rotor lobe section 21 of the male rotor 2, a substantially cylindrical female-side inner circumferential surface 47 covering the radially outer side of the rotor lobe section 31 of the female rotor 3, a discharge-side inner wall surface 48 on one side (the right side in
As depicted in
The suction-side bearing 8 on the side of the male rotor 2 and the suction-side bearing on the side of the female rotor 3 are arranged at an end of the main casing 41 on the side of the suction flow path 51. In addition, a shaft seal member 12 is arranged, on a portion closer to the motor 90 with respect to the suction-side bearing 8, on the suction-side shaft section 23 of the male rotor 2. The suction-side cover 42 is mounted on the main casing 41 in such a manner as to cover the suction-side bearing 8 and the shaft seal member 12. The suction-side cover 42 is provided with an oil supply path 53 for supplying a lubricant to the suction-side bearing 8 and the shaft seal member 12.
The discharge-side bearings 6 and 7 and the timing gear 10 on the side of the male rotor 2 and the discharge-side bearings and the timing gear on the side of the female rotor 3 are arranged at an end of the main casing 41 on the side of the discharge flow path 52. The main casing 41 is provided with the oil supply path 53 for supplying a lubricant to the discharge-side bearings 6 and 7 and the timing gear 10. The discharge-side cover 43 is mounted on the main casing 41 in such a manner as to cover the discharge-side bearings 6 and 7 and the timing gear 10.
As depicted in
As depicted in
Note that, in an example depicted in the present embodiment, by using the lubricant as the coolant for the male and female rotors 2 and 3, the external cooling system that supplies the coolant to the cooling flow paths 25 and 35 of the male and female rotors 2 and 3 and a lubrication system that supplies the lubricant to the discharge-side bearings 6 and 7 and the suction-side bearing 8 are configured integrally. However, it is possible to use, as the coolant, a liquid such as cooling water or a gas, other than the lubricant. In this case, the external cooling system is configured as a system separate from the lubrication system. For example, it is possible to configure the external cooling system to introduce the coolant such as cooling water to both of the male and female rotors 2 and 3 and the motor 90.
Next, the configuration and structure of the cooling flow path of the screw rotor (male rotor) in the screw compressor according to the first embodiment are explained by using
In the screw compressor 1 having the configuration mentioned above, when the motor 90 depicted in
Temperatures of regions around the discharge flow path 52 in the male and female rotors 2 and 3 and a region on the discharge-side in the axial direction in the housing chamber 45 of the casing 4 increase since heat generated in the compression process of the gas is transferred to those regions. The heat transfer causes thermal deformation of the male and female rotors 2 and 3. In particular, thermal deformation of the discharge-side shaft sections 22 and 32 of the male and female rotors 2 and 3 positioned near the discharge flow path 52 where the high-temperature compressed gas flows becomes significant. The thermal deformation causes a relative distance from the mounting position of the discharge-side bearing 6 to the position of the discharge-side end face 21b at the male rotor 2 and a relative distance from the mounting position of the discharge-side bearing to the position of the discharge-side end face at the female rotor 3 to enlarge in some cases. If the enlargement of the relative distances causes a discharge-side end face gap which is a gap between the discharge-side end faces 21b of the male and female rotors 2 and 3 and the discharge-side inner wall surface 48 of the casing 4 facing the discharge-side end faces 21b to enlarge, an internal leak of the compressed gas via the discharge-side end face gap increases undesirably.
The screw compressor 1 according to the present embodiment includes a cooling system to cool both of the male and female rotors 2 and 3. For example, as depicted in
In the present embodiment, a wall surface 25a (the inner circumferential surface of the through-hole) defining the cooling flow path 25 of the male rotor 2 is provided with a groove structure 26. For example, the groove structure 26 is provided over a region between the position of the discharge-side end face 21b and the mounting position of the discharge-side bearing 6 of the male rotor 2. The groove structure 26 includes grooves that have a length component in a circumferential direction (rotation direction) of the male rotor 2 and that is spaced apart in the axial direction. For example, the groove structure 26 includes a plurality of circular grooves 27 arranged at intervals in the axial direction.
A nozzle 15 for supplying the coolant is arranged inside the cooling flow path 25. The nozzle 15 is configured as a stationary member and is arranged with a gap between the nozzle 15 and the wall surface 25a of the cooling flow path 25. That is, the nozzle 15 has such a relation that the wall surface 25a of the cooling flow path 25 is relatively displaceable in the circumferential direction relative to an outer circumferential surface 15a of the nozzle 15. The nozzle 15 is arranged in such a manner as to overlap at least a part of the groove structure 26 of the wall surface 25a of the cooling flow path 25 at a position in the axial direction. For example, the nozzle 15 is inserted from an opening on the side of the discharge-side shaft section 22 of the cooling flow path 25, and extends from a position near the discharge-side end face 21b of the male rotor 2 to the distal end of the discharge-side shaft section 22, in the cooling flow path 25. A portion of the region of the nozzle 15 where the nozzle 15 overlaps the groove structure 26 is provided with a plurality of side holes 15b at intervals in the axial direction. The side holes 15b are configured as outlets of the coolant to the cooling flow path 25. The nozzle 15 is connected to the coolant supply line 74a of the external cooling system 70 directly or via a connection pipe.
In this manner, in the present embodiment, a predetermined region on the wall surface 25a of the cooling flow path 25 of the male rotor 2 (a region between the position of the discharge-side end face 21b of the male rotor 2 and the mounting position of the discharge-side bearing 6) is provided with the groove structure 26, and the nozzle 15, which is a stationary member, is arranged inside the cooling flow path 25 in such a manner as to overlap at least a part of the groove structure 26 in the axial direction. The inventors have found out that the groove structure 26 of the wall surface 25a of the cooling flow path 25 and the nozzle 15 as a stationary member in the cooling flow path 25 enhances the heat transfer coefficient between the coolant and the wall surface 25a of the cooling flow path 25, thereby allowing the capability to cool the discharge-side shaft section 22 of the male rotor 2 to be improved.
Next, effects and advantages of the cooling system of the screw rotors in the screw compressor according to the first embodiment are explained by using
In the screw compressor 1 depicted in
In the present embodiment, the coolant is supplied to the cooling flow path 25 of the male rotor 2 from the nozzle 15 via the coolant supply line 74a of the external cooling system 70. As depicted in
Meanwhile, one possible example of measures to improve the capability to cool the male rotor 2 is to lower the temperature of the coolant to be supplied to the cooling flow path 25. However, since the size of the cooler 72 of the external cooling system 70 needs to be increased in this case, the cost increases by a corresponding amount. Moreover, since the temperature of the coolant is restricted to a temperature equal to or higher than the temperature of the outside air in a case where the cooler 72 is an air-cooling type cooler, it is difficult to improve the cooling capability by lowering the temperature of the coolant.
Another possible measure to improve the cooling capability is to increase the flow rate of the coolant to be supplied to the cooling flow path 25. In this case, the flow rate of the coolant in the axial direction increases to improve the heat transfer coefficient near the wall surface 25a of the cooling flow path 25. However, since the size of the pump 71 of the external cooling system 70 needs to be increased in this case, the motive power of the pump 71 increases by a corresponding amount. Thus, the overall motive power of the compressor system increases in some cases.
In contrast, the present embodiment aims to improve the capability to cool the male rotor 2 by providing the groove structure 26 mentioned above to the predetermined region mentioned above on the wall surface 25a of the cooling flow path 25 of the male rotor 2, and arranging the nozzle 15 as a stationary member inside the cooling flow path 25 in such a manner as to overlap at least a part of the groove structure 26 in the axial direction, even in a case where the temperature or flow rate of the coolant of the male rotor 2 is set equivalent to those in conventional techniques.
As can be seen by referring to
On the other hand, as can be seen by referring to
That is, since the heat transfer coefficient between the coolant and the wall surface 25a with the groove structure 26 in the cooling flow path 25 of the male rotor 2 increases in the present embodiment, the amount of heat that moves from the male rotor 2 to the coolant increases even in a case where the temperature or flow rate of the coolant is set equivalent to those in conventional techniques. As a result, a temperature increase of the male rotor 2 is suppressed, and accordingly, the thermal deformation amount of the male rotor 2 in the axial direction can be reduced. This results in suppressing enlargement of the gap between the discharge-side end face 21b of the male rotor 2 and the discharge-side inner wall surface 48 of the casing 4 (discharge-side end face gap) to reduce the internal leak amount of the compressed gas, and thus the efficiency of the compressor can be improved.
Here, a reason why the heat transfer coefficient on the wall surface of the cooling flow path is increased by providing the groove structure on the wall surface is explained by using
It is generally known that the heat transfer coefficient increases as the relative speed of a fluid relative to a solid wall surface increases.
The relative speed (circumferential speed) of the coolant relative to the wall surface 25a of the cooling flow path 25 lowers in the region D positioned near the curved surface region Wc (e.g., a region of a cylindrical surface) that is positioned between one circular groove 27 and another circular groove 27 (between one groove and another groove that are positioned at an interval in the axial direction) of the groove structure 26 on the wall surface 25a of the cooling flow path 25 and that is free from irregularities. This is because a shear force generated between the coolant and the wall surface 25a of the cooling flow path 25 that moves in the rotation direction of the male rotor 2 causes the coolant to move in the same direction (circumferential direction) as the wall surface 25a of the cooling flow path 25.
On the other hand, in regions E that are regions adjacent to the region D in the axial direction of the male rotor 2, the distances to the bottom surfaces or side surfaces of the circular grooves 27 of the groove structure 26 as the wall surface of the cooling flow path 25 positioned in the radial direction are relatively long, as compared with the distances between the region D and the curved surface regions Wc without irregularities. Because of this, a shear force that acts on the coolant flowing in the regions E is relatively small as compared with a case of the coolant flowing in the region D, and accordingly, relative speeds (circumferential speeds) of the coolant in the regions E relative to the wall surface 25a of the cooling flow path 25 are great as compared with the case of the coolant in the region D.
This causes speed differences to be generated between the coolant in the region D and the coolant in the regions E. Accordingly, the viscous force acting between the coolant in the region D and the coolant in the regions E functions as a brake on the coolant in the region D, and the flow rate (circumferential speed) in the region D lowers. Hence, the relative speed of the coolant flowing in the region D relative to the wall surface 25a of the cooling flow path 25 increases, and the heat transfer coefficient in the region D thus increases by a corresponding amount as compared with the case of the wall surface 25a of the cooling flow path 25P without the groove structure 26 (see
In addition, in the present embodiment, as depicted in
In this manner, providing the groove structure 26 on the wall surface 25a of the cooling flow path 25 causes the relative speed (circumferential speed) of the coolant relative to the wall surface 25a of the cooling flow path 25 to increase. In addition, arranging the nozzle 15, which is a stationary member, inside the cooling flow path 25 in such a manner as to overlap at least a part of the groove structure 26 in the axial direction causes the relative speed (circumferential speed) of the coolant relative to the wall surface 25a of the cooling flow path 25 to increase. Therefore, the heat transfer coefficient between the coolant and the wall surface 25a having the groove structure 26 of the cooling flow path 25 can be enhanced.
As mentioned above, the screw compressor 1 according to the present embodiment includes the male rotor 2 (screw rotor) and the discharge-side bearing 6. The male rotor 2 (screw rotor) includes the rotor lobe section 21 that has the twisted lobes 21a and has the discharge-side end face 21b on one side in the axial direction, and the discharge-side shaft section 22 provided on the one side in the axial direction at the rotor lobe section 21. The discharge-side bearing 6 is mounted on the discharge-side shaft section 22. The male rotor 2 (screw rotor) has the cooling flow path 25 extending in the axial direction at least inside the discharge-side shaft section 22. The groove structure 26 is provided at least at a part of the region on the wall surface 25a of the cooling flow path 25 between the position of the discharge-side end face 21b in the axial direction and the mounting position of the discharge-side bearing 6, and the groove structure 26 includes the grooves 27 that have a lengthwise component in the circumferential direction of the male rotor 2 (screw rotor) and that is spaced apart in the axial direction. The nozzle 15 which is a stationary member for supplying the coolant is arranged inside the cooling flow path 25 with a gap between the nozzle 15 and the wall surface 25a, and is arranged in such a manner as to overlap at least a part of the groove structure 26 in the axial direction.
According to this configuration, the relative speed of the coolant, which flows in the region D near a wall surface Wc positioned between the grooves 27 of the groove structure 26 in the cooling flow path 25, relative to the wall surface Wc increases due to an influence of the coolant flowing in the regions E at groove positions adjacent in the axial direction. In addition, the relative speed of the coolant flowing on the side of the wall surface 25a of the cooling flow path 25 relative to the wall surface 25a increases due to an influence of the coolant flowing near the nozzle 15 as a stationary member. Those enhance the heat transfer coefficient on the wall surface 25a of the cooling flow path 25 having the groove structure 26, thereby improving the capability to cool the discharge-side shaft section 22 of the male rotor 2 (screw rotor). That is, the capability to cool the discharge-side shaft section 22 of the male rotor 2 (screw rotor) can be enhanced with a simple structure.
In addition, in the present embodiment, the groove structure 26 includes the plurality of circular grooves 27 arranged at intervals in the axial direction. According to this configuration, the groove structure 26 has a simple structure, and accordingly, the groove structure 26 can be machined easily.
In addition, in the present embodiment, the groove structure 26 is provided over the entire region between the position of the discharge-side end face 21b and the mounting position of the discharge-side bearing 6. This configuration can enhance the capability to cool the entire region that significantly influences enlargement of the discharge-side end face gap at the discharge-side shaft section 22, and can therefore reduce more effectively enlargement of the discharge-side end face gap due to thermal deformation of the discharge-side shaft section 22.
A screw compressor according to a modification example of the first embodiment is illustratively explained by using
A difference of the screw compressor according to the modification example of the first embodiment depicted in
Also in the case where the groove structure 26A of the cooling flow path 25 includes the helical groove 27A, as in the first embodiment, a speed difference is generated between the coolant flowing in the region D (see
In this manner, increase of the heat transfer coefficient between the coolant and the wall surface 25a having the groove structure 26A in the cooling flow path 25 of the male rotor 2A causes the amount of heat that transfers from the male rotor 2A to the coolant to increase even in a case where the temperature or flow rate of the coolant is set equivalent to those in conventional techniques. As a result, a temperature increase of the male rotor 2A is suppressed, and accordingly, the thermal deformation amount of the male rotor 2A in the axial direction can be reduced. This suppresses enlargement of the gap between the discharge-side end face 21b of the male rotor 2A and the inner wall surface 48 of the casing 4 (discharge-side end face gap) to reduce the internal leak amount of the compressed gas, and thus the efficiency of the compressor can be improved.
Note that the groove structure 26A of the cooling flow path 25 includes the one helical groove 27A in the example depicted in the present modification example. However, the groove structure 26A of the cooling flow path 25 can include a plurality of helical grooves 27A, in another possible manner of configuration.
In the modification example of the first embodiment mentioned above, as in the first embodiment, the groove structure 26A is provided on the wall surface 25a of the cooling flow path 25, and the nozzle 15 which is a stationary member is arranged inside the cooling flow path 25 in such a manner as to overlap at least a part of the groove structure 26A. This enhances the heat transfer coefficient on the wall surface 25a of the cooling flow path 25 having the groove structure 26A, thereby improving the capability to cool the discharge-side shaft section 22 of the male rotor 2A (screw rotor). That is, the capability to cool the discharge-side shaft section 22 of the male rotor 2A (screw rotor) can be enhanced with a simple structure.
Also in the present modification example, the groove structure 26A includes the helical groove 27A. According to this configuration, the helical groove 27A as the groove structure 26A can be provided over a wide range in the axial direction on the wall surface of the cooling flow path 25 by machining performed once, and man-hours and manufacturing costs can be therefore reduced as compared with the case of the first embodiment.
A screw compressor according to a second embodiment is illustratively explained by using
A difference of the screw compressor according to the second embodiment depicted in
In the present embodiment, as depicted in
Meanwhile, in the modification example (see
In contrast, in the present embodiment, entry of a gas to the inside of the cooling flow path 25 is inhibited by providing the sealing members 28 to the openings of the cooling flow path 25. This causes the coolant supplied to the cooling flow path 25 from the nozzle 15 to fill the inside of the cooling flow path 25, and thus a decrease of the area size of contact between the outer circumferential surface 15a of the nozzle 15 and the coolant is avoided. Accordingly, the advantage of increase of the relative speed of the coolant relative to the wall surface 25a of the cooling flow path 25 attained by arranging the nozzle 15, which is a stationary member, in the cooling flow path 25 can be attained surely.
In the second embodiment mentioned above, as in the modification example of the first embodiment, the groove structure 26A is provided on the wall surface 25a of the cooling flow path 25, and the nozzle 15 which is a stationary member is arranged inside the cooling flow path 25 in such a manner as to overlap at least a part of the groove structure 26A. This enhances the heat transfer coefficient on the wall surface 25a of the cooling flow path 25 having the groove structure 26A, thereby improving the capability to cool the discharge-side shaft section 22 of the male rotor 2B (screw rotor). That is, the capability to cool the discharge-side shaft section 22 of the male rotor 2B (screw rotor) can be enhanced with a simple structure.
In addition, in the present embodiment, the cooling flow path 25 is formed by the through-hole penetrating the male rotor 2B (screw rotor) in the axial direction, and the sealing members 28 that prevent entry of a fluid other than the coolant into the cooling flow path 25 are provided to the openings of the cooling flow path 25 in the axial direction.
According to this configuration, the sealing members 28 can inhibit entry of a fluid other than the coolant to the inside of the cooling flow path 25, thereby avoiding a decrease of the area size of contact between the outer circumferential surface 15a of the nozzle 15 and the coolant, which decrease might be caused by the fluid having entered. This allows the advantage of increase of the relative speed of the coolant relative to the wall surface 25a of the cooling flow path 25 to be attained surely. Accordingly, the heat transfer coefficient on the wall surface 25a having the groove structure 26A of the cooling flow path 25 is enhanced, and the capability to cool the discharge-side shaft section 22 of the male rotor 2B (screw rotor) is improved.
A screw compressor according to a third embodiment is illustratively explained by using
A difference of the screw compressor according to the third embodiment depicted in
In the present embodiment, as depicted in
In this manner, the cooling flow path 25C of the male rotor 2C is formed by a bottomed hole having an opening on one side. This can inhibit entry of outside air to the cooling flow path 25C. Accordingly, as in the second embodiment, it is possible to prevent a decrease of the area size of contact between the outer circumferential surface 15a of the nozzle 15 and the coolant, which decrease might be caused by the formation of a layer on the outer circumferential surface 15a of the nozzle 15 by a gas having entered the cooling flow path 25C. That is, without using the sealing members 28 in the second embodiment, entry of outside air to the cooling flow path 25C can be inhibited as in the case of the second embodiment.
In the third embodiment mentioned above, as in the modification example of the first embodiment, the groove structure 26A is provided on the wall surface 25a of the cooling flow path 25C, and the nozzle 15 which is a stationary member is arranged inside the cooling flow path 25C in such a manner as to overlap at least a part of the groove structure 26A. This enhances the heat transfer coefficient on the wall surface 25a of the cooling flow path 25C having the groove structure 26A, thereby improving the capability to cool the discharge-side shaft section 22 of the male rotor 2C (screw rotor). That is, the capability to cool the discharge-side shaft section 22 of the male rotor 2C (screw rotor) can be enhanced with a simple structure.
In addition, in the present embodiment, the cooling flow path 25C is formed by a bottomed hole having an opening on the side of the distal end of the discharge-side shaft section 22. According to this configuration, the coolant supplied to the cooling flow path 25C makes a turn at the bottom 25b of the cooling flow path 25C and flows out from the opening of the cooling flow path 25C. This allows entry of a fluid other than the coolant to the cooling flow path 25C to be inhibited without using sealing members 28 like those in the second embodiment. Accordingly, as compared with the second embodiment, it is possible to reduce the number of parts, and also to attempt to reduce man-hours and manufacturing costs.
A screw compressor according to a fourth embodiment is illustratively explained by using
A difference of the screw compressor according to the fourth embodiment depicted in
In the male rotor 2D according to the present embodiment, the groove structure 26A can be machined on the wall surface 25a of the cooling flow path 25 of the discharge-side shaft section 22D at a step before the discharge-side shaft section 22D is joined to the rotor lobe section 21. This allows a machining device for machining the groove structure 26A to be inserted from the opening on the joined side of the discharge-side shaft section 22D in the cooling flow path 25. This machining method makes it easy to insert the machining device as compared with a case where the machining device is inserted from the opening on the side of the distal end of the discharge-side shaft section, and thus leads to reduction in machining time for the groove structure 26A.
In the fourth embodiment mentioned above, as in the modification example of the first embodiment, the groove structure 26A is provided on the wall surface 25a of the cooling flow path 25, and the nozzle 15 which is a stationary member is arranged inside the cooling flow path 25 in such a manner as to overlap at least a part of the groove structure 26A. This enhances the heat transfer coefficient on the wall surface 25a of the cooling flow path 25 having the groove structure 26A, thereby improving the capability to cool the discharge-side shaft section 22D of the male rotor 2D (screw rotor). That is, the capability to cool the discharge-side shaft section 22 of the male rotor 2D (screw rotor) can be enhanced with a simple structure.
In addition, in the present embodiment, the discharge-side shaft section 22D is formed as a member separate from the rotor lobe section 21, and the cooling flow path 25 penetrates the discharge-side shaft section 22D. According to this configuration, the groove structure 26A can be machined on the wall surface 25a of the cooling flow path 25 of the discharge-side shaft section 22D before the discharge-side shaft section 22D is joined to the rotor lobe section 21. This makes it easy to align the discharge-side shaft section 22D relative to a machining device for machining the groove structure 26A or to insert the machining device into the cooling flow path 25 as compared with the case where the rotor lobe section 21 and the discharge-side shaft section 22 are formed as one integrated member, and it thus becomes easier to machine the groove structure 26A.
A screw compressor according to a modification example of the fourth embodiment is illustratively explained. First, the structure of a screw rotor in the screw compressor according to the modification example of the fourth embodiment is explained by using
A difference of the screw compressor according to the modification example of the fourth embodiment depicted in
Specifically, the male rotor 2E includes the rotor lobe section 21E and the suction-side shaft section 23 as one member formed integrally, and the discharge-side shaft section 22D as one member. A through-hole penetrating the discharge-side shaft section 22D in the axial direction is formed as the cooling flow path 25E. The one member including the rotor lobe section 21E and the suction-side shaft section 23 is configured without a cooling flow path. That is, the cooling flow path 25E is positioned only in the discharge-side shaft section 22D. The recess 21f is provided on an end face (at the position of the discharge-side end face 21b) of the rotor lobe section 21E on the side of the portion at which the discharge-side shaft section 22D is joined. As depicted in
Next, effects and advantages of the screw rotor in the screw compressor according to the modification example of the fourth embodiment are explained by using
Friction welding is to soften the base materials by frictional heat that is generated by rubbing the base materials against each other at high speed and further apply a pressure so as to join base materials in their solid phase states by plastically deforming both. In friction welding, a material that is a factor inhibiting joining, such as an oxidized film, is pushed as a burr to the outside from joined surfaces of both base materials.
A screw rotor 102 according to the comparative example is configured by joining a discharge-side shaft section 122 having a cooling flow path 125 with a planar discharge-side end face 121b without a recess on a rotor lobe section 121 by friction welding. That is, while the joined surface of the rotor lobe section 121 according to the comparative example is a flat surface, the joined surface of the discharge-side shaft section 122 having the cooling flow path 125 is a circular flat surface. Because of this, when the rotor lobe section 121 and the discharge-side shaft section 122 are joined by friction welding, a burr B is generated near an outer circumferential surface of the discharge-side shaft section 122 and a wall surface 125a of the cooling flow path 125. There is a concern that, if the burr B generated near the wall surface 125a of the cooling flow path 125 covers the wall surface 125a of the cooling flow path 125, the area size of heat transfer between the wall surface 125a of the cooling flow path 125 and the coolant decreases.
In contrast, in the present embodiment, as depicted in
In the modification example of the fourth embodiment mentioned above, as in the fourth embodiment, the groove structure 26A is provided on the wall surface 25a of the cooling flow path 25E, and the nozzle 15 (not depicted) which is a stationary member is arranged inside the cooling flow path 25E in such a manner as to overlap at least a part of the groove structure 26A. This enhances the heat transfer coefficient on the wall surface 25a of the cooling flow path 25E having the groove structure 26A, thereby improving the capability to cool the discharge-side shaft section 22D of the male rotor 2E (screw rotor). That is, the capability to cool the discharge-side shaft section 22D of the male rotor 2E (screw rotor) can be enhanced with a simple structure.
In addition, in the present modification example, the rotor lobe section 21E has the recess 21f at a portion to be joined with the discharge-side shaft section 22D. The diameter of the recess 21f is set smaller than the outer diameter of the discharge-side shaft section 22D but greater than the diameter of the cooling flow path 25E.
According to this configuration, the burr B that is pushed out of the joined surfaces 21j and 22j when the rotor lobe section 21E and the discharge-side shaft section 22D are joined by friction welding is generated not inside the cooling flow path 25E but in the recess 21f of the rotor lobe section 21E, and thus the wall surface 25a of the cooling flow path 25E can be prevented from being covered with the burr B generated by friction welding. Accordingly, the capability to cool the discharge-side shaft section 22D of the male rotor 2E (screw rotor) can be prevented from being impaired by friction welding.
Note that the present invention is not limited to the embodiments mentioned above and includes various modification examples. The embodiments described above are explained in detail for explaining the present invention in an easy-to-understand manner, and the present invention is not necessarily limited to those including all the constituent elements explained. That is, it is possible to replace some of constituent elements of an embodiment with constituent elements of another embodiment, and it is also possible to add constituent elements of an embodiment to the constituent elements of another embodiment. In addition, some of the constituent elements of each embodiment can also have other constituent elements additionally, be deleted, or be replaced.
Whereas the oil-free screw compressor 1 is taken and explained as an example in the first to fourth embodiments and modification examples thereof mentioned above, the present invention can be applied also to a liquid-flooded-type screw compressor that supplies a liquid such as oil or water to the working chambers C.
In addition, the screw compressor 1 of a twin-screw type including the pair of screw rotors (the male rotor and the female rotor 3) is taken and explained as an example in the embodiments mentioned above. However, the present invention can be applied also to a screw compressor of a multi-screw type including three or more screw rotors. In addition, the present invention can be applied also to a screw compressor of a single-screw type including one screw rotor and a pair of gate rotors.
In addition, the configuration examples in which the groove structure 26 or 26A is provided only on the wall surface 25a of the cooling flow path 25, 25C, or 25E of the male rotor 2 are depicted in the embodiments mentioned above. However, a configuration in which a groove structure is provided only on a wall surface 35a of the cooling flow path 35 of the female rotor 3 or a configuration in which groove structures are provided on both the wall surface 25a of the cooling flow path 25, 25C, or 25E of the male rotor 2 and the wall surface 35a of the cooling flow path 35 of the female rotor 3 is also possible.
In addition, the configuration examples in which the groove structure 26 or 26A is provided over the entire region, between the position of the discharge-side end face 21b and the mounting position of the discharge-side bearing 6, on the wall surface 25a of the cooling flow path 25 of the male rotor 2 are depicted in the embodiments mentioned above. However, a configuration in which a groove structure is provided at a portion of the region, between the position of the discharge-side end face 21b and the mounting position of the discharge-side bearing 6, on the wall surface 25a of the cooling flow path 25 is also possible. In addition, a configuration in which a groove structure is provided extending beyond the region on the wall surface 25a of the cooling flow path 25 between the position of the discharge-side end face 21b and the mounting position of the discharge-side bearing 6 is also possible.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-182696 | Nov 2021 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2022/036621 | 9/30/2022 | WO |
