JPWO2018109939A1 - Screw compressor - Google Patents

Abstract

At least a part of the area where the tip of the tooth portion of the gate rotor and the discharge side wall which is the wall on the discharge side forming the screw groove with which the tip of the tooth portion engages when the screw rotor reversely rotates , Non-contact structure.

Description

  BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a screw compressor, and more particularly to a measure for preventing damage to a gate rotor.

  Conventionally, a single screw compressor used as a compressor for refrigeration air conditioning etc. is known. For example, the single screw compressor of Patent Document 1 includes a screw rotor having a plurality of screw grooves in an outer peripheral portion, and two disk-shaped gate rotors in which a plurality of tooth portions are radially arranged. The screw rotor is rotatably disposed in a cylindrical wall provided in a casing of the compressor. Further, the gate rotor is configured such that the teeth penetrate the cylindrical wall and engage with the screw groove. The axis of the two gate rotors is orthogonal to the axis of the screw rotor, and provided symmetrically about the screw rotor. Then, two compression chambers are formed in the cylindrical wall by the inner peripheral surface of the cylindrical wall, the screw groove, and the teeth of the gate rotor.

  In this single screw compressor, with the rotation of the screw rotor, the teeth of the gate rotor move in the screw groove, and the volume of the compression chamber is repeatedly expanded and then reduced. While the volume of the compression chamber is expanded, the refrigerant is drawn into the compression chamber, and the drawn refrigerant is compressed when the volume of the compression chamber starts to decrease. Then, when the screw groove forming the compression chamber communicates with the discharge port, the compressed high-pressure refrigerant is discharged from the compression chamber via the discharge port.

  In the single screw compressor in operation, of the pair of side surfaces facing in the circumferential direction in the tooth portion of the gate rotor, the suction side surface positioned on the suction side in a state in which the tooth portion engages with the screw groove, and the screw groove The screw rotor rotates while being in contact with the wall. On the other hand, at the time of stop, the screw rotor reversely rotates due to the difference between high and low pressure of the refrigerant. When the screw rotor reversely rotates, the screw rotor rotates while the discharge side surface of the pair of side surfaces of the tooth portion comes in contact with the wall portion forming the screw groove. This reverse rotation may cause damage or wear to the gate rotor.

  Therefore, in the single screw compressor of Patent Document 1, the reverse rotation time is suppressed by injecting the refrigerant gas from the economizer port into the screw groove at the time of stoppage to reduce the difference in high and low pressure, and damage or wear of the gate rotor. To suppress.

JP, 2013-136957, A

  However, since the structure of Patent Document 1 is premised to have the economizer port for introducing the refrigerant gas into the compression chamber, it can not be applied to a compressor without the economizer port.

  The present invention has been made in view of such problems, and an object thereof is to suppress damage or wear of the gate rotor during reverse rotation of the screw rotor.

  In the screw compressor according to the present invention, the screw rotor has a plurality of screw grooves formed on the outer peripheral surface, one end on the suction side of the fluid and the other end on the discharge side, and the plurality of tooth portions meshed with the screw grooves A screw rotor having a gate rotor formed in the housing and rotating the gate rotor to compress the fluid as the screw rotor rotates, wherein the tips of the teeth and the teeth are rotated during reverse rotation of the screw rotor At least a part of a region facing the discharge side wall portion, which is a wall on the discharge side forming a screw groove in which the front end portion of the portion engages, has a noncontact structure.

  According to the screw compressor according to the present invention, in the reverse rotation, the tip end portion of the tooth portion of the gate rotor and the discharge side wall portion forming the screw groove in which the tip end portion of the tooth portion engages Since at least a part has a noncontact structure, damage or wear of the gate rotor can be suppressed.

1 is a schematic cross-sectional view of a screw compressor according to Embodiment 1 of the present invention. It is a perspective view which shows the meshing part of the screw groove of the screw rotor and the teeth part of a gate rotor in the screw compressor which concerns on Embodiment 1 of this invention. It is operation | movement explanatory drawing of the screw compressor which concerns on Embodiment 1 of this invention. It is explanatory drawing of the position of the tooth | gear part of the gate rotor with respect to a screw groove at the time of positive rotation of a screw rotor. It is explanatory drawing of the position of the tooth | gear part of the gate rotor with respect to a screw groove at the time of reverse rotation of a screw rotor. It is the schematic enlarged view which expands and shows a part of screw compressor which concerns on Embodiment 1 of this invention. It is a schematic sectional drawing of the principal part of the screw compressor which concerns on Embodiment 2 of this invention. It is the figure which expand | deployed the groove bottom of the screw groove of the screw compressor which concerns on Embodiment 2 of this invention. It is a schematic sectional drawing of the principal part of the screw compressor which concerns on Embodiment 3 of this invention. It is the figure which expand | deployed the groove bottom of the screw groove of the screw compressor which concerns on Embodiment 3 of this invention.

Hereinafter, embodiments of the present invention will be described based on the drawings.
In each of the drawings, the same reference numerals denote the same or corresponding parts, which are common to the entire specification. Furthermore, the form of the component shown in the specification full text is an illustration to the last, and is not limited to these descriptions.

Embodiment 1
The screw compressor according to the first embodiment will be described with reference to FIGS. 1 to 6. The screw compressor is connected to a refrigeration circuit that circulates a refrigerant and performs a vapor compression refrigeration cycle.

  FIG. 1 is a schematic cross-sectional view of a screw compressor according to Embodiment 1 of the present invention. In FIG. 1, the right side is the suction side, and the left side is the discharge side. FIG. 2 is a perspective view showing a meshing portion between a screw groove of a screw rotor and a tooth portion of a gate rotor in a screw compressor according to Embodiment 1 of the present invention. In FIG. 2, the right back side is the suction side, and the lower left side is the discharge side. Further, in FIG. 2, solid arrows indicate the rotation direction of the screw shaft, and white arrows indicate that the suction gas is sucked.

  The screw compressor 1 according to the first embodiment is a single screw compressor, and in this embodiment, the screw compressor 1 is an example of a single screw compressor of a type in which two gate rotors 7 are engaged with one screw rotor 5. 1 will be described.

  As shown in FIG. 1, the screw compressor 1 is fixed to a cylindrical casing 2, a motor 3 accommodated in the casing 2, and the motor 3, and a screw shaft 4 rotationally driven by the motor 3, and a screw A screw rotor 5 and the like fixed to the shaft 4 are provided. The end of the screw shaft 4 not fixed to the motor 3 is rotatably supported by a bearing 6.

  The motor 3 is composed of a stator 3a fixed inward in the casing 2 and a motor rotor 3b disposed inside the stator 3a. The motor rotor 3 b is fixed to the screw shaft 4 in the same manner as the screw rotor 5, and is disposed coaxially with the screw rotor 5.

  The screw rotor 5 has a cylindrical shape, and a plurality of screw grooves 5 a spirally extending from one end of the screw rotor 5 toward the other end are formed on the outer peripheral portion. One end side (right side in FIG. 1) of the screw rotor 5 is a suction side of the refrigerant gas, and the other end side (left side in FIG. 1) is a discharge side of the refrigerant gas. The inside of the casing 2 is separated by a partition (not shown) between a suction pressure space filled with a low pressure refrigerant gas and a discharge pressure space filled with a high pressure refrigerant gas, and one end of the screw rotor 5 communicates with the suction pressure space The other end communicates with the discharge pressure space.

  Further, on the side surface of the screw rotor 5, two gate rotors 7 are disposed so as to be axially symmetrical with respect to the screw shaft 4.

  The gate rotor 7 has a disk shape, and a plurality of tooth portions 7 a are radially provided on the outer circumferential surface along the circumferential direction and supported by the gate rotor support 8. The gate rotor 7 is disposed such that the teeth 7a mesh with the screw grooves 5a of the screw rotor 5, and is surrounded by the screw grooves 5a, the teeth 7a of the gate rotor 7, the inner peripheral surface of the casing 2 and the slide valve 9. The compression chamber 10 is formed in the space. The compression chamber 10 is filled with the refrigerant gas sucked from the suction pressure space, and oil for lubricating the bearing 6 and sealing the compression chamber 10 is injected.

  A slide valve 9 is disposed between the inner peripheral surface of the casing 2 and the screw rotor 5. The slide valve 9 is provided slidably along the outer peripheral surface of the screw rotor 5 in the screw shaft 4 direction of the screw rotor 5 and has an opening 9 a.

  In the casing 2, a discharge port 2 a (see FIG. 3 to be described later) connected to a discharge chamber 11 formed in the casing 2 is formed. Then, after passing through the opening 9 a of the slide valve 9, the high-pressure refrigerant gas and oil filled in the compression chamber 10 are discharged into the discharge chamber 11 through the discharge port 2 a.

Next, the operation of the screw compressor 1 according to the first embodiment will be described.
FIG. 3 is an operation explanatory view of the screw compressor according to Embodiment 1 of the present invention.
When the motor 3 is activated in the screw compressor 1, the screw rotor 5 rotates as the screw shaft 4 rotates. The rotation here is positive. As the screw rotor 5 rotates, the gate rotor 7 also rotates, and in the compression chamber 10, the suction stroke, the compression stroke, and the discharge stroke are repeated. Here, the compression operation will be described focusing on the shaded compression chamber 10 in FIG.

  FIG. 3A shows the state of the compression chamber 10 in the suction stroke. The screw groove 5 a in which the compression chamber 10 is formed is engaged with the tooth portion 7 a of the gate rotor 7. Then, when the screw rotor 5 is driven by the motor 3 to rotate in the direction of the solid line arrow, the tooth rotor 7 moves relative to the end of the screw groove 5a, so that the gate rotor 7 has a thin white arrow. Rotate in the direction. The compression chamber 10 in the suction stroke has the largest volume, is in communication with the space on the suction side of the casing 2, and is filled with a low pressure refrigerant gas.

  When the screw rotor 5 further rotates, the teeth 7a of the gate rotor 7 sequentially rotate toward the discharge port 2a in conjunction with the rotation, whereby the volume of the compression chamber 10 is reduced as shown in FIG. 3 (b). The refrigerant gas in the compression chamber 10 is compressed.

  Then, when the screw rotor 5 continues to rotate, as shown in FIG. 3C, the compression chamber 10 is in communication with the discharge port 2a. Thereby, the high-pressure refrigerant gas compressed in the compression chamber is discharged from the discharge port 2 a to the discharge chamber 11 through the opening 9 a of the slide valve 9 not shown in FIG. 3. The refrigerant discharged to the discharge chamber 11 is discharged to the outside of the screw compressor 1.

  During the operation of the screw compressor 1 as described above, the pressure in the compression chamber 10 gradually increases in the order of (a) => (b) => (c), and is high in (c). Then, when the operation of the screw compressor 1 is stopped, the screw rotor 5 reversely rotates as described above due to the pressure difference between the low pressure side and the high pressure side of the screw rotor 5. When the screw rotor 5 reversely rotates, the pressure in the compression chamber 10 becomes lower than the pressure on the suction side, and the gate rotor 7 is damaged in the conventional configuration without the improvement of the present invention. This phenomenon will be described again with reference to FIG. 4 and FIG.

  FIG. 4 is an explanatory view of the position of the tooth portion of the gate rotor with respect to the screw groove at the time of forward rotation of the screw rotor. FIG. 5 is an explanatory view of the positions of the teeth of the gate rotor with respect to the screw grooves at the time of reverse rotation of the screw rotor. 4 and 5 both show one screw groove unfolded with the teeth of the gate rotor meshing with the screw groove. The arrow in FIG. 4 indicates the moving direction at the time of forward rotation of the screw rotor 5 and the arrow in FIG. 5 indicates the moving direction at the time of reverse rotation of the screw rotor 5. In FIGS. 4 and 5, the right side is the suction side, and the left side is the discharge side.

  During operation of the screw compressor 1, that is, while the screw rotor 5 is positively rotating, the tooth portion 7a of the gate rotor 7 constitutes a screw groove 5a in which the tooth portion 7a is engaged as shown in FIG. 2 and FIG. It contacts the suction side wall 5bb which is a wall on the suction side among the two wall parts 5b. More specifically, the suction side surface 7c of the tooth 7a contacts the suction side wall 5bb. The suction side surface 7c is a suction side surface in a state in which the tooth portion 7a is engaged with the screw groove 5a among a pair of side surfaces opposed in the circumferential direction of the tooth portion 7a. Hereinafter, the discharge side of the pair of side surfaces opposed in the circumferential direction of the tooth portion 7a will be referred to as a discharge side surface 7b. Of the two wall portions 5b, the wall portion on the discharge side is referred to as a discharge side wall portion 5ba.

  On the other hand, when the screw rotor 5 is reversely rotated and the pressure in the compression chamber 10 becomes lower than the pressure in the suction chamber, a pressing force in the reverse direction to that during operation acts on the gate rotor 7, as shown in FIG. The discharge side surface 7b of the tooth portion 7a contacts the discharge side wall 5ba. The portion shown by the dotted line in FIG. 5 shows the shape of the tooth portion of the conventional configuration in which the tooth width of the tooth portion 7a is the same from the root portion to the tip portion, and the solid line shows the tooth portion of the first embodiment. 7a is shown.

  When the teeth 7a of the gate rotor 7 are engaged with the screw rotor 5 at the time of reverse rotation, the discharge side surface 7b of the teeth 7a contacts the discharge side wall 5ba. Here, the tip end portion 70 of the discharge side surface 7b of the tooth portion 7a always contacts the discharge side wall portion 5ba during reverse rotation.

  Here, it is considered focusing attention on the tooth portion 7a meshing with the screw groove 5a communicating with the discharge port 2a when switching from normal rotation to reverse rotation. In the state of FIG. 2, the tooth portion 7a communicating with the discharge port 2a does not contact the discharge sidewall portion 5ba from the central portion to the root portion of the discharge side surface 7b of the tooth portion 7a, and only the tip portion 70 It is in contact. Then, the distal end portion 70 of the discharge side 7b of the tooth 7a is always in contact with the discharge side wall 5ba until the tooth 7a is disengaged from the screw groove 5a by reverse rotation from this state. .

  Thus, the tip 70 of the discharge side 7b of the tooth 7a is damaged or worn because it has a longer time of contact with the discharge side wall 5ba during reverse rotation than the center and root of the discharge side 7b. Is easy to occur.

  Further, as shown in FIGS. 4 and 5, the tooth 7a of the gate rotor 7 has an obtuse angle between the surface 7d of the tooth 7a and the suction side 7c, whereas the tooth 7a of the gate rotor 7 has the obtuse angle. The angle formed is an acute angle, that is, the thickness on the discharge side of the tooth portion 7a is thin. In the tooth portion 7a of the gate rotor 7, the acute angle between the surface 7d and the discharge side surface 7b is not the entire discharge side of the tooth portion 7a but the tip end portion on the discharge side, and the other portion Is obtuse. The fact that the thickness of the tip portion on the discharge side of the tooth portion 7a is thin as described above is also a factor that the tooth portion 7a is easily damaged. The above-mentioned angle of the tooth portion 7a is formed to be different from the acute angle and the obtuse angle depending on the place, because the tangent angle of the screw groove 5a with respect to the discharge side wall 5b becomes closer to the discharge side.

  So, in this Embodiment 1, in order to avoid damage to the gate rotor 7, the following structures are employ | adopted.

FIG. 6 is a schematic enlarged view showing a part of the screw compressor according to Embodiment 1 of the present invention.
In the first embodiment, as shown in FIG. 6, a gap 12 is provided between the discharge side wall 5ba and the tip end of the tooth 7a. That is, the tip portion 7ba of the discharge side 7b of the tooth portion 7a is positioned closer to the suction side than the other portions, and the tooth width of the tip portion of the tooth portion 7a is shorter than the tooth width of the other portion It has become. More specifically, the tooth portion 7a has a shape obtained by cutting out a corner portion formed by the discharge side surface 7b and the tip end surface 7e of the conventional tooth portion 7a shown by a dotted line in FIG. As described above, in the state in which the tooth portion 7a is in mesh with the screw groove 5a, the tip 7ba of the discharge side 7b of the tooth 7a does not contact the discharge side wall 5ba.

  In each of the tooth portions 7 a of the gate rotor 7, the gap 12 is uniform, and is set to, for example, 20 μm to 70 μm as a suitable gap size. The clearance 12 is always formed while the tooth portion 7a is engaged with the screw groove 5a.

  With such a configuration, during reverse rotation, as shown in FIG. 5, although the teeth 7a are close to the discharge side wall 5ba side of the screw rotor 5 and are in contact with the discharge side wall 5ba, the teeth are in contact It is an operation from the central part to the root part of 7a and the tip end does not contact. Thus, damage to the tip end of the tooth 7a can be suppressed.

-Effect of Embodiment 1-
According to the first embodiment, since the gap 12 is provided between the discharge side wall 5ba at the tip of the tooth 7a of the gate rotor 7, damage to the tip of the tooth 7a of the gate rotor 7 during reverse rotation And wear can be suppressed. By providing the gap 12 in this way, the portion of the tooth 7a in contact with the discharge side wall 5ba during the reverse rotation becomes the root from the center of the tooth 7a. The central portion of the tooth portion 7a to the root portion is a portion where the angle between the suction side surface 7c of the tooth portion 7a and the surface 7d is not an acute angle but an obtuse angle like a tip portion and the strength is high. Therefore, also from this point, damage to the gate rotor 7 can be suppressed, and deterioration in performance with age can be suppressed.

  Further, since it is not necessary to provide a complicated control mechanism or parts in order to suppress the damage of the gate rotor 7 in this way, it is only necessary to simply provide the gap 12, so the gate rotor 7 is easily damaged without increasing the number of components. The suppression can be realized. Further, in order to provide the gap 12, it is only necessary to change the tip shape of the tooth portion of the conventional configuration in which the tooth width of the tooth portion 7a is the same from the root portion to the tip portion. It can be easily applied to the following products.

Second Embodiment
In the first embodiment, as a configuration for forming a gap between the tip of the tooth 7a and the discharge side wall 5ba, the position of the tip 7ba of the discharge side 7b of the tooth 7a is closer to the suction side The tooth width of the tip end of the tooth portion 7a is shorter than the tooth width of the root side of the tooth portion 7a. On the other hand, in the second embodiment, a form different from the first embodiment is described as a configuration for forming a gap between the tip end of the tooth 7a and the discharge side wall 5ba. Hereinafter, differences from the first embodiment will be mainly described, and configurations not described in the second embodiment are the same as the first embodiment.

FIG. 7 is a schematic cross-sectional view of the main part of the screw compressor according to Embodiment 2 of the present invention. FIG. 8 is a developed view of a groove bottom of a screw groove of a screw compressor according to a second embodiment of the present invention.
In the second embodiment, the region 5c facing the tip of the tooth 7a in the discharge side wall 5ba during reverse rotation is positioned closer to the discharge than the other regions, and the tip of the tooth 7a and the discharge sidewall 5ba A gap 13 is formed between the In FIG. 8, the two-dotted line indicates the position of the discharge side wall 5 ba in the other region where the gap 13 is not formed in the discharge side wall 5 ba.

  Region 5c is a region corresponding to the thickness of tooth portion 7a from the groove bottom in discharge side wall portion 5ba and extending in the groove direction of screw groove 5a (the direction of the arrow in FIG. 8). The length of the gap 13 in the groove direction is at least a length by which the tooth portion 7a moves in the screw groove 5a during the time when the tooth portion 7a is engaged with the screw groove 5a during reverse rotation until the engagement is released. The clearance 13 is always formed while the tooth portion 7a is engaged with the screw groove 5a.

-Effect of Embodiment 2-
According to the second embodiment, the same effect as that of the first embodiment can be obtained.

Third Embodiment
In the second embodiment, the gap 13 is formed extending in the screw groove 5a. In the third embodiment, the length of the gap 13 in the groove direction is shorter than that of the second embodiment, and the position thereof is limited. Hereinafter, differences from the second embodiment will be mainly described, and the configuration not described in the third embodiment is the same as the second embodiment.

FIG. 9 is a schematic cross-sectional view of the main parts of a screw compressor according to Embodiment 3 of the present invention. FIG. 10 is a developed view of a groove bottom of a screw groove of a screw compressor according to a third embodiment of the present invention.
In the third embodiment, a region of the discharge side wall 5ba facing the tip of the tooth 7a in the reverse rotation, that is, a part of the region extending in the groove direction (arrow direction in FIG. 10) is more than the other regions. The groove width on the discharge side is wider and wider on the discharge side. Specifically, the term "a part" refers to an end area which is the tip side of the rotational direction of the screw rotor 5 at the time of reverse rotation in the area extending in the groove direction (arrow direction in FIG. 10). It is a region communicating with (see FIG. 2).

  By providing the gap 13 in this region, the contact between the screw rotor 5 and the gate rotor 7 in the region communicating with the discharge port 2a at the time of reverse rotation, that is, the discharge side wall portion 5ba of the screw rotor 5 and the discharge side surface of the gate rotor 7 There is no contact with 7b. As a result, the time for which the front end of the gate rotor 7 contacts the discharge side wall 5 ba of the screw rotor 5 is shortened, so that the damage suppressing effect of the gate rotor 7 can be sufficiently obtained.

  Further, by narrowing the region in which the gap 13 is provided to the region of the screw groove 5a that communicates with the discharge port 2a, the length in the groove direction of the gap 13 becomes shorter than that in the second embodiment. Thus, by shortening the length of the gap 13 in the groove direction, it is possible to suppress refrigerant leakage from the gap 13 during normal rotation, that is, during normal operation. Therefore, in the third embodiment, the performance at the time of normal operation is improved as compared with the first embodiment and the second embodiment.

-Effect of Embodiment 3-
According to the third embodiment, the same effect as that of the second embodiment can be obtained, and the position of the gap 13 is more effective than the second embodiment in suppressing the breakage of the tooth portion 7a, that is, the discharge port 2a. The following effects can be obtained, because the area in communication with the That is, refrigerant leakage from gap 13 during normal operation can be suppressed as compared to the first and second embodiments. Therefore, in the third embodiment, the performance at the time of normal operation is improved as compared with the first embodiment and the second embodiment.

  Reference Signs List 1 screw compressor, 2 casing, 2a discharge port, 3 motor, 3a stator, 3b motor rotor, 4 screw shaft, 5 screw rotor, 5a screw groove, 5b wall portion, 5ba discharge side wall portion, 5bb suction side wall portion, 5c region, 6 bearings, 7 gate rotors, 7a teeth, 7b discharge side, 7ba end, 7c suction side, 7d surface, 7e end, 8 gate rotor support, 9 slide valve, 9a opening, 10 compression chamber, 11 Discharge chamber, 12 gaps, 13 gaps, 70 tips.

Claims (5)

A screw rotor having a plurality of screw grooves formed on the outer peripheral surface, one end on the suction side of the fluid and the other end on the discharge side, and a gate rotor having a plurality of tooth portions meshed with the screw grooves formed on the outer peripheral portion A screw compressor that rotates the gate rotor to compress the fluid as the screw rotor rotates.
At least a part of a region where the tip end of the tooth and the discharge side wall which is the wall on the discharge side forming the screw groove with which the tip of the tooth engages, when the screw rotor reversely rotates There is a non-contact screw compressor.   The screw compressor according to claim 1, wherein a gap is provided between the tip of the tooth portion and the discharge side wall portion, and the non-contact structure is configured.   Among the pair of side surfaces facing in the circumferential direction in the tooth portion, the tip end portion of the discharge side surface which becomes the discharge side when the tooth portion engages with the screw groove is closer to the suction side than the portions other than the tip portion The screw compressor according to claim 1 or 2, wherein the tooth portion is located, and the tooth width of the tip portion of the tooth portion is shorter than the other portions.   The region facing the tip of the tooth in the discharge side wall at the time of reverse rotation is positioned closer to the discharge than the other regions, and the groove width of the screw groove is spread on the discharge side, and the tip of the tooth is The screw compressor according to claim 1 or 2, wherein the gap is formed between the discharge side wall portion. A casing having a discharge port for discharging the compressed fluid;
Of the regions facing the tip of the tooth in the discharge side wall during reverse rotation, the region on the tip side in the direction of rotation of the screw rotor during reverse rotation and communicating with the discharge port is the other region 3. The apparatus according to claim 1, wherein the groove width of the screw groove is located on the discharge side, the groove width of the screw groove is extended to the discharge side, and the gap is formed between the tip of the tooth and the discharge side wall. Screw compressor.

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