JP2010203422A - Roots type vacuum pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a roots type vacuum pump that prevents the generation of an abnormal sound by a confining phenomenon of liquid between root rotors and prevents the shortening of a bearing service life caused by the infiltration of moisture into a shaft seal part. <P>SOLUTION: A clearance groove 17 of a cross-sectional shape such as a shape for expanding a clearance with an inner peripheral surface 1a of a casing 1 toward the rotational direction is formed over the total length of respective lobes on a peripheral surface of a position separated by a predetermined dimension to a side in the rotational direction from the center line of the respective lobes 16 of the root rotor 15. The shaft seal part 8 fixes a moisture shake-off ring 30 arranged between a collar 26 and a bearing 9 to a rotary shaft 18 of the root rotor 15 by installing one or a plurality of housing oil seals 25 and the collar 26 in order from a place near to an installation surface 7b to the casing 1 in an inner diameter part of the housing 7. A clearance formed on an opposed surface between the collar 26 and the ring 30 is formed so as to form a labyrinth seal, and a passage 7c for returning the liquid stored in the shaft seal part 8 to a vacuum chamber is arranged at the discharge port side of the housing 7. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a single-stage or multi-stage roots type vacuum pump that enables inflow of liquid into sealed water or a vacuum chamber.

  The roots rotor in the conventional three-leaf roots vacuum pump has three lobes arranged at equiangular intervals from the center of the rotation axis, and the circumferential surface connecting the lobes is a concave arc curve. The root rotor is formed into a shape, and the two roots rotors are inserted into the casing while maintaining a clearance between the inner surface of the casing and the outer surface of the lobe and a mutual clearance of about 0.1 to 0.3 mm.

  When the wet chamber is filled with 1-5 &#8467; of water per minute in the vacuum chamber or when liquid is generated from the gas flowing into the vacuum chamber, the clearance is set as large as about 0.5 to 1 mm. Variations in the pump performance due to changes in the quantity of water to be enclosed cause abnormal noise and vibration due to a confinement phenomenon (so-called liquid smear) in which the liquid is confined between the root rotors. In addition, when water has vigorously entered the shaft sealing portion in the housing that supports the rotation shaft of the roots rotor, there has been a problem that the oil in the bearing is washed away, resulting in poor lubrication and shortening the life of the bearing.

  Patent Document 1 discloses a roots rotor in which a substantially V-shaped cut groove is formed in the axial direction on a circumferential surface slightly beyond the center line of the lobe in the rotational direction. The object of the application is to cause wear when solid particles are mixed in a pumping liquid or gas, and the particles are caught between the outer surface of the lobe and the inner peripheral surface of the casing. This document does not describe anything related to the bearing life reduction due to the ingress of moisture into the shaft seal described above.

Japanese Utility Model Publication No. 54-58605

  An object of the present invention is to provide a roots-type vacuum pump that prevents occurrence of abnormal noise and vibration due to a liquid confinement phenomenon between roots rotors and a decrease in bearing life due to moisture intrusion into a shaft seal. .

In order to achieve the object, the invention described in claim 1 is provided with a pair of three-leaf root rotors in a casing in which a suction port and a discharge port are formed, and is attached so as to close a side opening of the casing. A shaft seal is provided to support the rotating shaft of the roots rotor by a bearing mounted on the housing and prevent air from entering and exiting between the rotor side and the bearing so that the suction port and the discharge port do not communicate with each other. In the roots-type vacuum pump that discharges air sucked from the suction port by rotating both roots rotors from the discharge port,
Each lobe is provided with a relief groove having a cross-sectional shape on the circumferential surface at a position away from the center line of each lobe of the roots rotor by a predetermined dimension in the rotational direction so that a gap with the inner circumferential surface of the casing widens in the rotational direction. Formed over the entire length of
The shaft seal portion is provided with one or more housing oil seals and a collar on the inner diameter portion of the housing in order from a position close to the mounting surface to the casing, and a water shaker disposed between the collar and the bearing. The housing is provided with a passage for returning the liquid accumulated in the shaft seal portion to the vacuum chamber, in which a labyrinth seal is formed so that a clearance formed between the collar and the ring is fixed to the rotating shaft. It is characterized in that it is provided on the discharge port side.

In order to achieve the same object, the invention described in claim 2 is provided so that a pair of three-leaf root rotors are provided in a casing in which a suction port and a discharge port are formed, and a side opening of the casing is closed. A shaft seal is provided to support the rotating shaft of the roots rotor by a bearing mounted on the housing and prevent air from entering and exiting between the rotor side and the bearing, and the suction port and the discharge port communicate with each other. In a roots-type vacuum pump that discharges air sucked from the suction port by rotating both roots rotors so that there is no discharge from the discharge port,
Each lobe is provided with a relief groove having a cross-sectional shape on the circumferential surface at a position away from the center line of each lobe of the roots rotor by a predetermined dimension in the rotational direction so that a gap with the inner circumferential surface of the casing widens in the rotational direction. Formed over the entire length of
The shaft seal portion is provided with one or more housing oil seals and a collar on the inner diameter portion of the housing in order from a position close to the mounting surface to the casing, and a water shaker disposed between the collar and the bearing. A ring for fixing the ring to the rotary shaft and a gap formed on the facing surface of the collar and the ring so that a labyrinth seal is formed,
A drain passage for discharging the liquid accumulated in the shaft seal portion as a drain to the outside is provided in the housing, and a drain discharge valve is provided on the outlet side of the drain passage.

  In order to achieve the same object, the invention described in claim 3 is the Roots-type vacuum pump according to claim 1 or 2, wherein the relief groove is formed in a triangular cross section. Is.

(Invention of Claim 1)
According to this Roots type vacuum pump, it is possible to prevent the occurrence of abnormal noise and vibration due to the confinement phenomenon of the liquid between the Roots rotors. Furthermore, since the moisture / liquid that has entered the shaft seal portion of the housing is blown off by the moisture swing-off ring and collected in the shaft seal portion and returned to the vacuum chamber through the passage, it is possible to prevent the bearing life from being reduced.

(Invention of Claim 2)
According to this Roots type vacuum pump, it is possible to prevent the occurrence of abnormal noise and vibration due to the confinement phenomenon of the liquid between the Roots rotors. Furthermore, the moisture / liquid that has entered the shaft seal portion of the housing is blown off by the water swing ring and collected in the shaft seal portion, and can be discharged outside as a drain by a drain discharge valve at an appropriate time.

(Invention of Claim 3)
In this Roots-type vacuum pump, the escape groove is formed in a triangular cross section, and it is possible to prevent the liquid confined between the Roots rotor from entering the escape groove and abnormally increasing the pressure of the liquid. Smooth rotation operation can be obtained without generating sound and abnormal vibration.

Longitudinal side view of a three-leaf roots vacuum pump according to the present invention Same vertical section front view Sectional drawing which shows the principal part of a shaft seal part Illustration of the housing as seen from the mounting surface Vertical side view of a three-leaf roots vacuum pump according to another embodiment of the present invention

  The best mode of the present invention will be described below with reference to the drawings.

  A three-stage three-leaf roots vacuum pump P according to the present invention is shown in FIG. The present invention is not limited to a multi-stage three-leaf roots vacuum pump, but can also be applied to a single-stage three-leaf roots vacuum pump.

  This roots type vacuum pump P is provided with a pair of upper and lower three-leaf root rotors (hereinafter referred to as “roots rotor”) 15 in a casing 1 in which a suction port 4 and a discharge port 5 are formed. As shown in FIG. 1, a first vacuum chamber 2 a, a second vacuum chamber 2 b, and a third vacuum chamber 2 c are formed in the casing 1, and are directed from the first vacuum chamber 2 to the subsequent vacuum chambers 2 b and 2 c. Accordingly, the volume is reduced. The roots rotor 15 is provided so that the axial lengths of the rotor portions 15a to 15c are different according to the sizes of the vacuum chambers 2a to 2c. Reference numerals 7 and 7 denote housings attached so as to close the side openings of the casing 1. The bearings 9 and 9 attached to the housings 7 and 7 support the rotating shaft 18 of the roots rotor 15 at both ends. Reference numeral 8 denotes a shaft seal provided in the housing 7 in order to prevent air from entering and leaving between the root rotor 15 side and the bearing 9. Reference numeral 10 denotes a snap ring for preventing the bearing 9 from coming off.

  Timing gears 19 and 19 are attached to one end of the rotation shafts 18 and 18 of the roots rotors 15 and 15 and are fixed by nuts 20 and 20, respectively. A gear cover 11 is attached to the housing 7. Lubricating oil is contained in the gear cover 11 to such an extent that the lower portion of the lower timing gear 19 is immersed. A cover 12 to which a seal 13 for inserting a rotary shaft 18 as a drive shaft of the upper roots rotor 15 is attached is attached to the other housing 7. The coupling 21 attached to the rotating shaft 18 is provided so as to be driven by an electric motor (not shown).

  In FIG. 2, in each lobe 16 of the rotor portions 15a to 15c, a gap with the inner peripheral surface 1a of the casing 1 is rotated on a peripheral surface 16a at a position away from the center line o by a predetermined dimension in the rotational direction. A relief groove 17 having a triangular cross section extending in the direction is formed over the entire length of the lobe. The escape groove 17 is provided in order to prevent the above-described confinement phenomenon due to water sealed in the casing 1 during wet specifications.

  The reason why the escape groove 17 is provided at a position away from the tip of the lobe 16 is to prevent air leakage from the tip of the lobe 16. As for the volume of the escape groove 17, about 1 to 3 percent of the volume surrounded by the outer peripheral surface of the rotor portions 15a to 15c and the inner peripheral surface 1a of the casing 1 is appropriate. Moreover, about 0.2 to 0.5 percent of the theoretical volume of the roots type vacuum pump P is appropriate for the amount of water sealed in the casing 1.

  In FIG. 3, with respect to the shaft seal portion 8, one or a plurality of inner diameter portions 7 a of the housing 7, in this embodiment, two housing oil seals 25 and collars 26 are located close to the mounting surface 7 b to the casing 1 ( It is worn in order from the back. Specifically, one housing oil seal 25 is mounted in the seal fixing hole 26 a of the collar 26. The seal portion 25 a of the housing oil seal 25 is elastically contacted with the outer peripheral surface of the sleeve 23 fitted to the rotating shaft 18 of the roots rotor 15. Reference numeral 24 denotes an o-ring mounted inside the sleeve 23. Reference numeral 27 denotes an o-ring attached to the outside of the collar 26. Reference numeral 28 denotes a gland packing attached to the housing 7, and an inner peripheral portion of the gland packing 28 is provided so as to contact the rotating shaft 18 of the roots rotor 15.

  Reference numeral 30 denotes a moisture swinging ring which is disposed between the collar 26 and the bearing 9 and is fixed to the rotating shaft 18. The moisture swing-off ring 30 and the collar 26 are provided so that a known labyrinth seal is formed in a gap formed on the opposed surfaces of both.

  As shown in FIGS. 3 and 4, a first vacuum is formed between the location of the inner diameter portion 7 a of the housing 7 where the moisture swing-off ring 30 is located and the mounting surface 7 b of the housing 7 on the discharge port 5 side. A passage 7c is provided for returning the moisture / liquid entering the shaft seal 8 from the chamber 2a and the third vacuum chamber 2c to the vacuum chambers 2a and 2c.

  The housing 7 is provided with a passage 7 d for returning to the gear chamber 19 a so that a part of the lubricating oil that has fallen on the bearing 9 due to the rotation operation of the timing gear 19 does not enter the shaft seal portion 8.

  Thus, by rotating both roots rotors 15 and 15 so that the suction port 4 and the discharge port 5 do not communicate with each other, the air sucked from the suction port 4 is sucked into the first vacuum chamber 2a and compressed. A three-stage three-leaf roots vacuum pump P according to the present invention is constructed which discharges from the discharge port 5 while sucking and compressing in the order of the second vacuum chamber 2b and the third vacuum chamber 2c.

Next, a specific action of the three-stage three-leaf roots vacuum pump P according to the present invention will be described.
(1) When the roots type vacuum pump P is wet-type and water is enclosed in the casing 1 or when the water is mixed by being used for drying the washing machine, the compressed air sucked into the casing 1 Since the moisture inside flows into the escape groove 17, a closing phenomenon does not occur between the rotor portions 15 a to 15 c of the roots rotor 15, and abnormal noise and abnormal vibration due to the closing phenomenon do not occur.
(2) In the case of (1) above, even if moisture or liquid enters the shaft seal portion 8 from the first vacuum chamber 2a or the third vacuum chamber 2c, it is blown off by the moisture swing-off ring and collected in the shaft seal portion. . Since they are returned to the vacuum chambers 2a and 2c via the passages 7c, the lubricating oil of the bearings 9 is maintained well without being washed away.

  By the way, in the above-described three-stage three-leaf root type vacuum pump P, the liquid collected in the shaft seal part is returned to the vacuum chamber (corresponding to the invention of claim 1), and the liquid collected in the shaft seal part is used as a drain. It can also be configured to discharge to the outside (corresponding to the invention of claim 2).

  That is, a three-stage three-leaf roots type vacuum pump P ′ according to another embodiment of the present invention shown in FIG. 5 is provided with a drain passage 7e in the housing 7 for discharging the liquid accumulated in the shaft seal portion 8 as a drain. ing. A drain discharge valve 33 is provided in the drain pipe 32 connected to the outlet side of the drain passage 7e.

  The three-stage three-leaf roots vacuum pump P ′ has the same configuration as that of the three-stage three-leaf roots vacuum pump P except that the liquid accumulated in the shaft seal is discharged to the outside as a drain. Therefore, the same components as those are denoted by reference numerals and are described in the drawings, and the description thereof is omitted. Further, the drain passage 7e is represented by a two-dot chain line in FIG.

  In the above-described three-leaf root type vacuum pump P and three-leaf root type vacuum pump P ′, each has a vertical structure in which a pair of three-leaf root rotors 15 are arranged in the vertical direction. It is also possible to adopt a horizontal structure arranged in parallel. The other components in the case of the horizontal structure are configured according to the vertical structure.

P: Three-stage three-leaf root vacuum pump 1 according to the present invention ... Casing 4 ... Suction port 5 ... Discharge port 7 ... Housing 7c ... Passage 7e ... Drain passage 8 ... Shaft seal 9 ... Bearing 15 ... 3-leaf root rotor 16 ... Robe 17 ... Relief groove 18 ... Rotating shaft 25 ... Housing oil seal 26 ... Collar 30 ..Moisture swing ring 33 ... Drain discharge valve

Claims (3)

A pair of three-leaf root rotors are provided in a casing in which a suction port and a discharge port are formed, and the rotation shaft of the roots rotor is supported by a bearing mounted on a housing that is mounted so as to close an opening on the side of the casing. A shaft seal is provided to prevent air from entering and exiting between the side and the bearing, and the air sucked from the suction port is rotated by rotating both roots rotors so that the suction port and the discharge port do not communicate with each other. In the roots type vacuum pump that discharges from the discharge port,
Each lobe is provided with a relief groove having a cross-sectional shape on the circumferential surface at a position away from the center line of each lobe of the roots rotor by a predetermined dimension in the rotational direction so that a gap with the inner circumferential surface of the casing widens in the rotational direction. Formed over the entire length of
The shaft seal portion is provided with one or more housing oil seals and a collar on the inner diameter portion of the housing in order from a position close to the mounting surface to the casing, and a water shaker disposed between the collar and the bearing. The housing is provided with a passage for returning the liquid accumulated in the shaft seal portion to the vacuum chamber, in which a labyrinth seal is formed so that a clearance formed between the collar and the ring is fixed to the rotating shaft. A roots type vacuum pump characterized by being provided on the discharge port side. A pair of three-leaf root rotors are provided in a casing in which a suction port and a discharge port are formed, and the rotation shaft of the roots rotor is supported by a bearing mounted on a housing that is mounted so as to close an opening on the side of the casing. A shaft seal is provided to prevent air from entering and exiting between the side and the bearing, and the air sucked from the suction port is rotated by rotating both roots rotors so that the suction port and the discharge port do not communicate with each other. In the roots type vacuum pump that discharges from the discharge port,
Each lobe is provided with a relief groove having a cross-sectional shape on the circumferential surface at a position away from the center line of each lobe of the roots rotor by a predetermined dimension in the rotational direction so that a gap with the inner circumferential surface of the casing widens in the rotational direction. Formed over the entire length of
The shaft seal portion is provided with one or more housing oil seals and a collar on the inner diameter portion of the housing in order from a position close to the mounting surface to the casing, and a water shaker disposed between the collar and the bearing. A ring for fixing the ring to the rotary shaft and a gap formed on the facing surface of the collar and the ring so that a labyrinth seal is formed,
A roots-type vacuum pump characterized in that a drain passage for discharging the liquid accumulated in the shaft seal portion to the outside as a drain is provided in the housing and a drain discharge valve is provided on the outlet side of the drain passage.   The roots type vacuum pump according to claim 1 or 2, wherein the escape groove is formed in a triangular cross section.

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