Roots blower

Abstract

The invention provides a Roots blower capable of preventing water leaked from a pump chamber from reaching a bearing without using a sealing member. The Roots blower is provided with: a rotating shaft (drive shaft 13) fixed to an axial center portion of a rotor (drive-side rotor 11) for the Roots blower; a first bearing (17) that rotatably supports the rotating shaft; a housing (3) defining a pump chamber (10) and a first bearing chamber (19); and a first slinger (27) attached to the rotating shaft and positioned between the first bearing (17) and the pump chamber (10). The Roots blower is provided with a first circulation hole (24) which extends from the lower end of the first bearing chamber (19) to the pump chamber (10) at a descending slope and which connects the first bearing chamber (19) and the pump chamber (10). A first slinger (27) is formed so as to rotate between a first bearing (17) and an opening on the upper side of a first circulation hole (24) that opens in a first bearing chamber (19).

Description

Technical Field

[0001] The present invention relates to a Roots blower. Background Art

[0002] As a conventional Roots blower, for example, there is a Roots blower described in Patent Document 1. The Roots blower disclosed in Patent Document 1 includes a sealing member between a bearing that supports a rotating shaft of a rotor and a pump chamber. The sealing member is housed in a sealing chamber formed in a wall of the pump chamber. The sealing chamber communicates with the pump chamber through a communication hole.

[0003] When the Roots blower described in Patent Document 1 is used to process a gas containing moisture, the moisture seeps from the pump chamber along the rotating shaft into the sealing chamber. The seepage path of the moisture that has seeped into the sealing chamber is blocked by the sealing member and is discharged from the sealing chamber to the pump chamber through the communication hole.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Patent No. 4779669 Gazette Summary of the Invention

[0007] Problems to be Solved by the Invention

[0008] In a conventional Roots blower as shown in Patent Document 1, wear powder generated by the sealing member enters the pump chamber together with water and may adhere to a sliding contact surface of the rotor or the pump chamber, impairing the function.

[0009] An object of the present invention is to provide a Roots blower that can prevent moisture leaking from the pump chamber from reaching the bearing without using a sealing member.

[0010] Means for Solving the Problems

[0011] To achieve this object, the Roots blower of the present invention is characterized by including: a rotor for a Roots blower; a rotating shaft fixed to an axial center portion of the rotor for a Roots blower; a bearing that rotatably supports the rotating shaft; a housing that defines a pump chamber for housing the rotor for a Roots blower and a bearing chamber for housing the bearing; an oil slinger installed on the rotating shaft, disposed in the bearing chamber and located between the bearing and the pump chamber; and a circulation hole that extends from a lower end portion of the bearing chamber to the pump chamber with a downward slope to communicate the bearing chamber with the pump chamber, and the oil slinger is formed to rotate between an opening portion on an upper side of the circulation hole that opens in the bearing chamber and the bearing.

[0012] Advantages of the Invention

[0013] According to the present invention, there is provided a Roots blower that can prevent moisture leaking from the pump chamber from reaching the bearing without using a sealing member. Description of the Drawings

[0014] Figure 1 FIG. 6 is a side view of a Roots blower according to an embodiment of the present invention.

[0015] Figure 2 FIG. 7 is a front view of a Roots blower according to an embodiment of the present invention.

[0016] Figure 3 is Figure 1 a cross-sectional view taken along line III-III in FIG. 8.

[0017] Figure 4 is Figure 2 a cross-sectional view taken along line IV-IV in FIG. 9.

[0018] Figure 5 FIG. 10 is an enlarged cross-sectional view showing the bearing portion on the front side of a Roots blower according to an embodiment of the present invention.

[0019] Figure 6 FIG. 11 is an enlarged cross-sectional view showing a part of the front housing of a Roots blower according to an embodiment of the present invention.

[0020] Figure 7 FIG. 12 is an enlarged cross-sectional view showing the bearing portion on the rear side of a Roots blower according to an embodiment of the present invention.

[0021] Figure 8 FIG. 13 is an enlarged cross-sectional view showing a part of the rear housing of a Roots blower according to an embodiment of the present invention.

[0022] Figure 9 is Figure 2 a cross-sectional view taken along line IX-IX in FIG. 14.

[0023] Description of Reference Numerals:

[0024] 1... Roots blower; 7... rear housing; 10... pump chamber; 11... drive-side rotor (rotor for Roots blower); 12... driven-side rotor (rotor for Roots blower); 13... drive shaft (rotating shaft); 14... driven shaft (rotating shaft); 16... front wall; 17... first bearing; 17b, 18b... inner ring; 17d, 18d... bearing seal; 18... second bearing; 19... first bearing chamber; 22, 33... bottom wall (wall of bearing chamber); 24... first circulation hole; 27... first oil slinger; 27a, 37a... protrusion; 27b, 37b... circular plate portion; 31... second bearing chamber; 35... second circulation hole; 37... second oil slinger. Detailed Description of the Invention

[0025] Hereinafter, with reference toFigures 1 - 9 A specific embodiment of the roots blower of the present invention will be described in detail. In this embodiment, a roots blower using hydrogen as a fluid will be taken as an example for description.

[0026] In Figure 1 , the roots blower 1 is driven by the motor 2 to operate, sucking in the fluid from the suction port 4 (refer to Figure 3 ) of the housing 3 and discharging it from the discharge port 5.

[0027] This roots blower 1 is conceived to be constituted with moisture contained in hydrogen. Hereinafter, on the basis of describing each component of the roots blower 1, the direction in which the motor 2 is located relative to the housing 3 is set as the front, the direction in which the suction port 4 is located is set as the upper side, and the side where the discharge port 5 is located is set as the lower side.

[0028] (Housing)

[0029] The housing 3 is formed by a plurality of components combined with each other. The plurality of components refer to the front housing 6 that forms the front wall of the housing 3, the rear housing 7 connected to the rear end of the front housing 6, and the rear cover 8 connected to the rear end of the rear housing 7, etc. As Figure 4 shown, the rear housing 7 and the rear cover 8 are fixed to the front housing 6 by a plurality of fixing bolts 9 penetrating these components from the rear.

[0030] As Figure 1 and Figure 2 shown, the front housing 6 is respectively provided with mounting flanges 6a at the front end portion and the rear end portion. This roots blower 1 is used in a posture where the front-rear direction of the housing 3 is the horizontal direction and the suction port 4 is located above. The suction port 4 is formed at the central portion in the front-rear direction of the upper end portion of the front housing 6. The discharge port 5 is formed at the central portion in the front-rear direction of the lower end portion of the front housing 6.

[0031] As Figure 4 shown, the front housing 6 is formed in a bottomed cylindrical shape and opens toward the rear. The opening portion of the front housing 6 is closed by the rear housing 7. In this way, by connecting the rear housing 7 to the front housing 6, a pump chamber 10 is formed inside the front housing 6. As Figure 3 shown, the pump chamber 10 is defined by the inner walls of the front housing 6 and the rear housing 7 as an oval shape that is longer in the left-right direction. The suction port 4 is opened at the upper end portion of the pump chamber 10, and the discharge port 5 is opened at the lower end portion of the pump chamber 10.

[0032] A pair of roots blower rotors that rotate while meshing with each other, namely the drive side rotor 11 and the driven side rotor 12, are accommodated in the pump chamber 10.

[0033] The driving-side rotor 11 and the driven-side rotor 12 are each formed of a plastic material and have a cross-sectional shape perpendicular to the rotating shaft that is approximately cocoon-shaped. As the driving-side rotor 11 and the driven-side rotor 12 rotate while meshing with each other in the pump chamber 10, the roots blower 1 sucks hydrogen into the pump chamber 10 from the suction port 4 and discharges it through the discharge port 5 between the inner wall of the pump chamber 10. In Figure 3 the direction of rotation of the driving-side rotor 11 and the driven-side rotor 12 is indicated by an arrow R.

[0034] (Driving shaft and driven shaft)

[0035] The driving shaft 13 is fixed to the axial center portion of the driving-side rotor 11 by insert molding. The driven shaft 14 is fixed to the axial center portion of the driven-side rotor 12 by insert molding.

[0036] The driving-side rotor 11 rotates integrally with the driving shaft 13 as the driving shaft 13 rotates. The driven-side rotor 12 rotates integrally with the driven shaft 14 as the driven shaft 14 rotates. The driving shaft 13 and the driven shaft 14 are connected to each other at their rear ends via a gear coupling structure 15 and rotate at the same rotational speed in opposite rotational directions. The description of the gear coupling structure 15 will be given later.

[0037] As Figure 4 shown, the driving shaft 13 penetrates through the front wall 16 of the front housing 6 that forms the front side wall of the pump chamber 10 and the rear housing 7 that forms the rear side wall of the pump chamber 10 in the front-rear direction, and is rotatably supported by a first bearing 17 provided on the front wall 16 and a second bearing 18 provided on the rear housing 7. Although not shown, the driven shaft 14 is rotatably supported by the front housing 6 and the rear housing 7 in a state parallel to the driving shaft 13 by a support structure similar to the support structure that supports the driving shaft 13.

[0038] As Figure 5 shown, the first bearing 17 is housed in a first bearing chamber 19 formed in the front wall 16 of the front housing 6. As Figure 6 shown, the first bearing chamber 19 is formed by a first circular recess 21 that opens on the front surface of the front wall 16 and a first through hole 23 that penetrates the bottom wall 22 of the first circular recess 21. The first circular recess 21 has a bottom wall 22 and two peripheral walls with different inner diameters. These two peripheral walls refer to a first peripheral wall 21a that extends forward from the bottom wall 22 and a second peripheral wall 21b that is formed with a larger inner diameter than the first peripheral wall 21a and extends from the first peripheral wall 21a to the front surface of the front wall 16.

[0039] (First circulation hole)

[0040] At the lower end and the lowest part of the first bearing chamber 19, a first circulating hole 24 is provided. The first circulating hole 24 extends from the lower end of the first bearing chamber 19 with a descending slope to the pump chamber 10, connecting the first bearing chamber 19 and the pump chamber 10. The upper opening of the first circulating hole 24, that is, the opening on the first bearing chamber 19 side, is formed such that a part (the lowermost part) of the first peripheral wall 21a and a part (the lowermost part) of the second peripheral wall 21b are cut by the first circulating hole 24.

[0041] As Figure 3 shown, the lower opening of the first circulating hole 24, that is, the opening on the pump chamber 10 side, is formed at a position on the discharge side of the pump chamber 10 and avoiding the area where the pair of rotors 11, 12 mesh with each other (the central part in the left - right direction). The first circulating holes 24 are provided on both the drive shaft 13 side and the driven shaft 14 side. The first circulating hole 24 on the driven shaft 14 side connects the first bearing chamber (not shown) on the driven shaft 14 side and the pump chamber 10.

[0042] (First bearing)

[0043] The first bearing 17 is a single - row ball bearing. As Figure 5 shown, the first bearing 17 is fixed to the front wall 16 in a state where the outer ring 17a is fitted to the second peripheral wall 21b of the first circular recess 21. A first O - ring 25 is provided between the outer ring 17a and the front wall 16 (second peripheral wall 21b).

[0044] The first bearing 17 of the Roots blower 1 in this embodiment has an outer ring 17a, an inner ring 17b, and balls 17c, and is a hydrogen - resistant bearing formed of a high - chromium material. Annular bearing seals 17d for sealing the inside of the first bearing 17 are respectively provided between the outer ring 17a and the inner ring 17b at both axial ends of the first bearing 17.

[0045] The wall through - hole 13a on the front side of the drive shaft 13 penetrates the inner ring 17b of the first bearing 17 in a fitted state. The inner ring 17b is fixed to the wall through - hole 13a. A second O - ring 26 is provided between the inner ring 17b and the wall through - hole 13a.

[0046] A first oil - throwing ring 27 is disposed between the rear of the inner ring 17b of the first bearing 17 and the rotor mounting portion 13b which is thicker than the wall through - hole 13a of the drive shaft 13. The drive - side rotor 11 is fixed to the rotor mounting portion 13b of the drive shaft 13. The driven shaft 14 also has a front - side wall through - hole 14a (refer to Figure 2 ) and a rotor mounting portion 14b (refer to Figure 3). The wall through-hole 14b on the front side of the driven shaft 14 is rotatably supported by the front wall 16 via the first bearing 17 on the driven shaft side. The driven-side rotor 12 is fixed to the rotor mounting portion 14b of the driven shaft 14. A first slinger ring 27 (see Figure 3 ).

[0047] (Slinger ring)

[0048] As Figure 5 shown, the first slinger ring 27 has a cylindrical protrusion 27a for fitting the drive shaft 13 and a circular plate portion 27b extending radially outward from the protrusion 27a along the first bearing 17. The front end portion of the protrusion 27a contacts the inner ring 17b of the first bearing 17. The rear end portion of the protrusion 27a is inserted into the first through-hole 23 and contacts the rotor mounting portion 13b of the drive shaft 13. The protrusion 27a is fixed to the wall through-hole 13a of the drive shaft 13.

[0049] The circular plate portion 27b is housed in the space surrounded by the first peripheral wall 21a. The axial length of the first peripheral wall 21a of the Roots blower 1 in this embodiment is shorter than the thickness of the circular plate portion 27b. Therefore, the front half portion of the circular plate portion 27b enters the inside of the second peripheral wall 21b. Between the circular plate portion 27b and the pump chamber 10, the bottom wall 22 of the first bearing chamber 19 is provided so as to face the circular plate portion 27b with a predetermined gap.

[0050] The outer diameter of the first slinger ring 27 is larger than the outer diameter of the bearing seal 17d of the first bearing 17 and smaller than the inner diameter of the first peripheral wall 21a. The outer peripheral edge of the circular plate portion 27b of the first slinger ring 27 is formed to be separated from the first peripheral wall 21a with a predetermined gap. Therefore, when the drive shaft 12 rotates, the first slinger ring 27 rotates while passing between the opening of the first circulation hole 24 opening in the first bearing chamber 19 and the first bearing 17.

[0051] (Second bearing)

[0052] As Figure 7 shown, the second bearing 18 is housed in the second bearing chamber 31 formed in the rear housing 7. As Figure 8 shown, the second bearing chamber 31 is formed by a second circular recess 32 opening on the rear surface of the rear housing 7 and a second through-hole 34 penetrating the bottom wall 33 of the second circular recess 32. The second circular recess 32 has a bottom wall 33 and three peripheral walls with different inner diameters. These three peripheral walls are the third peripheral wall 32a extending rearward from the bottom wall 33, the fourth peripheral wall 32b formed to have a larger inner diameter than the third peripheral wall 32a and extending rearward from the third peripheral wall 32a, and the fifth peripheral wall 32c formed to have a larger inner diameter than the fourth peripheral wall 32b and extending from the fourth peripheral wall 32b to the rear surface of the rear housing 7.

[0053] A second circulation hole 35 is formed at the lower end of the second bearing chamber 31. The second circulation hole 35 extends from the lower end of the second bearing chamber 31 to the pump chamber 10 at a descending slope, connecting the second bearing chamber 31 and the pump chamber 10. As Figure 8 shown, the upper opening of the second circulation hole 35, that is, the opening on the second bearing chamber 31 side, is formed such that the lowermost part of the third peripheral wall 32a and the lowermost part of the end face 36 that forms the boundary between the third peripheral wall 32a and the fourth peripheral wall 32b are cut by the second circulation hole 35.

[0054] The lower opening of the second circulation hole 35, that is, the opening on the pump chamber 10 side, is formed on the discharge side of the pump chamber 10 and at a position avoiding the meshing area (the central part in the left - right direction) of the pair of rotors 11, 12. The second circulation holes 35 are provided on both the driving shaft 13 side and the driven shaft 14 side. That is, the second circulation hole 35 on the driven shaft 14 side connects the second bearing chamber (not shown) on the driven shaft 14 side and the pump chamber 10.

[0055] The second bearing 18 is a double - row ball bearing. As Figure 7 shown, it is fixed to the rear housing 7 in a state where the outer ring 18a is fitted into the fourth peripheral wall 32b of the second circular recess 32. The second bearing 18 of the roots blower 1 in this embodiment is a hydrogen - resistant bearing in which its outer ring 18a, inner ring 18b, and balls 18c are respectively formed of high - chromium materials. Annular bearing seals 18d for sealing the inside of the second bearing 18 are respectively provided between the outer ring 18a and the inner ring 18b at both axial ends of the second bearing 18.

[0056] The rear wall through - hole 13c, which is thinner than the rotor mounting portion 13b of the driving shaft 13, penetrates the inner ring 18b of the second bearing 18 in a fitted state. The inner ring 18b is fixed to the wall through - hole 13c.

[0057] (Second oil - throwing ring)

[0058] A second oil - throwing ring 37 is disposed between the front of the inner ring 18b of the second bearing 18 and the rotor mounting portion 13b of the driving shaft 13. The second oil - throwing ring 37 is formed with the same structure as the first oil - throwing ring 27 and has a raised portion 37a and a circular plate portion 37b. The front end portion of the raised portion 37a is inserted into the second through - hole 34 and contacts the rotor mounting portion 13b of the driving shaft 13. The rear end portion of the raised portion 37a contacts the inner ring 18b of the second bearing 18. The raised portion 37a is fixed to the rear wall through - hole 13c of the driving shaft 13.

[0059] The disk portion 37b of the second slinger ring 37 is received in the space surrounded by the third peripheral wall 32a. The axial length of the third peripheral wall 32a is set such that the entire disk portion 37b of the second slinger ring 37 is received in the space surrounded by the third peripheral wall 32a. The second bearing 18 abuts against an end face 36 that forms the boundary between the third peripheral wall 32a and the fourth peripheral wall 32b. Accordingly, the rear end face of the disk portion 37b of the second slinger ring 37 is formed to be separated from the front end of the second bearing 18 with a predetermined gap. Between the disk portion 37b and the pump chamber 10, the bottom wall 33 of the second bearing chamber 31 is provided so as to face the disk portion 37b with a predetermined gap.

[0060] The outer diameter of the second slinger ring 37 is larger than the outer diameter of the bearing seal 18d of the second bearing 18 and smaller than the inner diameter of the third peripheral wall 32a. The disk portion 37b of the second slinger ring 37 is formed such that its outer peripheral edge is separated from the third peripheral wall 32a with a predetermined gap. Accordingly, when the drive shaft 13 rotates, the second slinger ring 37 rotates while passing between the opening of the second circulation hole 35 opening into the second bearing chamber 31 and the second bearing 18.

[0061] (Rear side of the rear housing)

[0062] A seal member 41 is provided inside the fifth peripheral wall 32c of the rear housing 7. The seal member 41 has the functions of an oil seal and a hydrogen seal, and is provided between a cylindrical sliding collar 42 fixed to the rear side wall through-hole 13c of the drive shaft 13 in a fitted state and the fifth peripheral wall 32c. A third O-ring 43 is provided between the sliding collar 42 and the wall through-hole 13c.

[0063] The seal member 41 is arranged to be separated from the second bearing 18 by a predetermined distance toward the rear.

[0064] At the rear end portion of the wall through-hole 13c on the rear side of the drive shaft 13, a drive-side gear 44 forming part of the gear engagement structure 15 is mounted so as to rotate integrally with the drive shaft 13. The second slinger ring 37, the inner ring 18b of the second bearing 18, the sliding collar 42, and the drive-side gear 44 pass through the wall through-hole 13c in this order and are fastened by a fixing nut 45 screwed to the rear end of the wall through-hole 13c.

[0065] The wall through-hole at the rear side of the driven shaft 14 is not shown, but has the same structure as the drive shaft 13. That is, a second slinger ring (not shown), the inner ring of the second bearing, a sliding collar, and a driven-side gear that together with the drive-side gear 44 form a gear coupling structure 15 are assembled in the wall through-hole at the rear side of the driven shaft 14, and are fastened by a fixing nut screwed to the rear end of the wall through-hole. The driven-side gear is formed to have the same number of teeth as the drive-side gear 44 and meshes with the drive-side gear 44. The drive shaft 13 and the driven shaft 14 are connected via the gear coupling structure 15 formed by the drive-side gear 44 and the driven-side gear. The rotation of the drive shaft 13 is transmitted to the driven shaft 14 via the gear coupling structure 15, and the drive shaft 13 and the driven shaft 14 rotate in opposite directions at the same rotational speed.

[0066] The drive-side gear 44 and the driven-side gear are arranged behind the rear housing 7 and are housed in the rear cover 8. The rear cover 8 is formed in a bottomed cylindrical shape and opens forward. The opening of the rear cover 8 is closed by mounting the rear cover 8 on the rear housing 7. Oil 46 is accumulated in the rear cover 8 (see Figure 4 ). The amount of oil 46 accumulated is such that the lower ends of the drive-side gear 44 and the driven-side gear enter the oil 46. By accumulating the oil 46 in the rear cover 8 in this way, the lower end of the second circular recess 32 is immersed in the oil 46. At the upper end of the rear cover 8, an oil gauge 47 is detachably mounted for checking the amount of oil 46 accumulated.

[0067] The oil 46 that enters the rear end portion of the second circular recess 32 and the oil 46 that penetrates between the drive shaft 13, the drive-side gear 44, and the sliding collar 42 are restricted from further penetration by the sealing member 41 and the third O-ring 43.

[0068] The sealing member 41 may deteriorate due to long-term use. If the sealing member 41 deteriorates, the oil 46 may leak through the sealing member 41 to the second bearing 18 side. In the Roots blower 1 of this embodiment, in order to prevent the leaked oil 46 from penetrating into the pump chamber 10 through the second bearing 18, a structure for discharging the oil 46 from between the second bearing 18 and the sealing member 41 is adopted.

[0069] As Figure 7 shown, an oil receiving chamber 48 formed of an annular space surrounded by a fifth peripheral wall 32c is formed between the second bearing 18 and the sealing member 41. An oil discharge hole 49 is provided in the lower part of the oil receiving chamber 48.

[0070] As Figure 9 shown, the oil discharge hole 49 extends from the lower end portion of the fifth peripheral wall 32c to the lower end of the rear housing 7. When the oil 46 flows into the oil receiving chamber 48, the oil 46 flows down in the oil discharge hole 49 and is discharged downward of the rear housing 7.

[0071] (Operation of the Roots Blower)

[0072] In the Roots blower 1 thus constructed, the drive shaft 13 is driven by the motor 2, so that the drive shaft 13 and the drive side rotor 11 rotate in opposite directions and at the same rotation speed as the driven shaft 14 and the driven side rotor 12. In this way, the hydrogen gas is sucked into the suction port 4 and discharged from the discharge port 5 by the rotation of the drive side rotor 11 and the driven side rotor 12. A part of the hydrogen gas sucked into the pump chamber 10 flows from the pump chamber 10 along the drive shaft 13 and the driven shaft 14 and leaks into the first bearing chamber 19 and the second bearing chamber 31. In the case where the hydrogen gas contains moisture, the moisture also penetrates into the first bearing chamber 19 and the second bearing chamber 31.

[0073] The first slinger 27 is arranged at the portion of the first bearing chamber 19 closest to the pump chamber 10. In addition, the second slinger 37 is arranged at the portion of the second bearing chamber 31 closest to the pump chamber 10. Therefore, the water that penetrates into the first bearing chamber 19 and the second bearing chamber 31 together with the hydrogen gas is blown away by the first slinger 27 and the second slinger 37 rotating at high speed. The water blown away by the first slinger 27 is concentrated to the lower end of the first bearing chamber 19 along the portion of the first peripheral wall 21a and the second peripheral wall 21b that is on the rear side of the first bearing 17 due to gravity. The water thus concentrated at the lower end of the first bearing chamber 19 flows down in the first circulation hole 24 and is discharged to the pump chamber 10. In particular, the outer peripheral portion of the first slinger 27 overlaps with the first circulation hole 24, so that the thrown water is easily guided to the first circulation hole 24.

[0074] On the other hand, the water that has penetrated into the second bearing chamber 31 and is blown away by the second oil slinger 37 is gathered at the lower end of the second bearing chamber 31 along the third peripheral wall 32a due to gravity. Thus, the water gathered at the lower end of the second bearing chamber 31 flows down in the second circulation hole 35 and is discharged to the pump chamber 10. In particular, the outer peripheral portion of the second oil slinger 37 overlaps with the second circulation hole 35, so that the thrown water is easily guided to the second circulation hole 35.

[0075] The first oil slinger 27 rotates by passing between the upper opening of the first circulation hole 24 and the first bearing 17. The second oil slinger 37 rotates by passing between the upper opening of the second circulation hole 35 and the second bearing 18.

[0076] Therefore, although the lower ends of the first circulation holes 24 and the second circulation holes 35 are open on the discharge side where the pressure in the pump chamber 10 is relatively high, even if the discharge pressure acts on the first circulation holes 24 and the second circulation holes 35, moisture does not enter the first bearing chamber 19 and the second bearing chamber 31 from the discharge side through the first circulation holes 24 and the second circulation holes 35. The reason is that a part of the upper opening of the first circulation holes 24 and the second circulation holes 35 is blocked by the outer peripheral part of the rotating first oil slinger 27 and the second oil slinger 37, and the hydrogen gas and moisture blown off by the centrifugal force become substantial blocking objects and exert a sealing function.

[0077] Therefore, a Roots blower capable of preventing moisture leaking from the pump chamber from reaching the bearing without using a sealing member can be provided.

[0078] In the Roots blower 1 of this embodiment, the openings on the pump chamber 10 side of the first circulation hole 24 and the second circulation hole 35 are formed on the discharge side of the pump chamber 10 and at positions avoiding the region where the pair of rotors (the drive-side rotor 11 and the driven-side rotor 12) mesh with each other.

[0079] Therefore, it is possible to prevent water discharged from the first circulation hole 24 and the second circulation hole 35 from being contained in the meshing portion of the drive-side rotor 11 and the driven-side rotor 12 and being conveyed upward and returning to the suction side of the pump chamber 10, and the water can be quickly discharged from the Roots blower 1.

[0080] The first oil slinger 27 and the second oil slinger 37 of the Roots blower 1 of this embodiment include: cylindrical convex portions 27a and 37a that are in contact with the inner rings 17b and 18b of the first bearing 17 and the second bearing 18 in a state where the drive shaft 13 and the driven shaft 14 are fitted; and circular plate portions 27b and 37b that extend radially outward from the convex portions 27a and 37a along the first bearing 17 and the second bearing 18. The outer diameters of the first oil slinger 27 and the second oil slinger 37 are larger than the outer diameters of the bearing seals 17d and 18d located between the inner rings 17b and 18b and the outer rings 17a and 18a of the first bearing 17 and the second bearing 18.

[0081] Therefore, it is possible to reliably prevent the moisture blown by the first oil slinger 27 and the second oil slinger 37 from penetrating into the first bearing 17 and the second bearing 18. That is, it is possible to simultaneously achieve the discharge of water and the waterproofing of the first bearing 17 and the second bearing 18.

[0082] In this embodiment, the walls (bottom walls 22 and 33) of the first bearing chamber 19 and the second bearing chamber 31 are arranged to face the circular plate portions 27b and 37b with a prescribed gap therebetween.

[0083] Therefore, the minute-width gap between the circular plate portions 27b and 37b and the walls (bottom walls 22 and 33) of the first bearing chamber 19 and the second bearing chamber 31 has a sealing function, and thus it is difficult for moisture to penetrate into the first bearing chamber 19 and the second bearing chamber 31.

[0084] In the above embodiment, the second bearing 18 is arranged between the pump chamber 10 and the sealing member 41. Therefore, it is possible to prevent the wear powder generated by the sealing member 41 from entering the pump chamber 10 through the second bearing 18.

[0085] The second bearing 18 of the wall through-hole 13c on the rear side of the drive shaft 13 of the Roots blower 1 that supports this embodiment is arranged at a position closer to the pump chamber 10 side than the sealing member 41. The sealing member 41 seals between the sliding collar 42 fitted into the wall through-hole 13c on the rear side and the rear housing 7. Between the sliding collar 42 and the wall through-hole 13c on the rear side, it is sealed by a third O-ring 43.

[0086] The bearing seal 18d of the second bearing 18 is used to prevent the infiltration of water. Therefore, it is impossible to seal hydrogen with the bearing seal 18d, and hydrogen permeates through the second bearing 18. In addition, there is no sealing material in the minute gap generated between the inner ring 18b of the second bearing 18 and the drive shaft 13, so hydrogen permeates through this gap.

[0087] When the Roots blower 1 is operating, hydrogen infiltrates from the pump chamber 10 through the inside of the second bearing 18 and the minute gap between the second bearing 18 and the drive shaft 13 into the oil receiving chamber 48. This hydrogen is blocked from infiltrating into the rear cover 8 by the sealing member 41 and the third O-ring 43, so it is impossible to flow out from the oil receiving chamber 48 into the rear cover 8 on the rear side. Therefore, when the Roots blower 1 is operating, the pressure in the oil receiving chamber 48 rises and becomes in a balanced state with the pressure in the pump chamber 10. As a result, the pressures in the two spaces (the pump chamber 10 and the oil receiving chamber 48) of the second bearing 18 become uniform. Therefore, the pressure difference acting on the bearing seal 18d from both sides in the axial direction disappears, the load acting on the bearing seal 18d is reduced, and thus the durability of the bearing seal 18d is improved. The phenomenon in which the pressure difference on both sides in the axial direction of such a second bearing 18 disappears also occurs in the second bearing of the wall through-hole on the rear side that supports the driven shaft 14.

[0088] (Supplementary Note)

[0089] Regarding the above embodiment, the following supplementary note items are also disclosed.

[0090] (Supplementary Note 1)

[0091] A Roots blower, characterized in that

[0092] the Roots blower includes:

[0093] a rotor for a Roots blower;

[0094] a rotating shaft fixed to the axial center part of the rotor for the Roots blower;

[0095] a bearing that rotatably supports the rotating shaft;

[0096] a housing that defines a pump chamber for housing the rotor for the Roots blower and a bearing chamber for housing the bearing;

[0097] An oil slinger, which is installed on the rotating shaft, arranged in the bearing chamber and located between the bearing and the pump chamber; and

[0098] A circulation hole, which extends from the lower end of the bearing chamber to the pump chamber at a descending slope to connect the bearing chamber and the pump chamber,

[0099] The oil slinger is formed to rotate between the opening part above the circulation hole opening in the bearing chamber and the bearing.

[0100] (Supplementary Note 2)

[0101] In the Roots blower described in Supplementary Note 1, it is characterized in that

[0102] The Roots blower rotor includes a pair of rotors,

[0103] The opening on the pump chamber side of the circulation hole is formed at the discharge side of the pump chamber and at a position avoiding the meshing area of the pair of rotors.

[0104] (Supplementary Note 3)

[0105] In the Roots blower described in Supplementary Note 1 or 2, it is characterized in that

[0106] The bearing includes an inner ring, an outer ring, and a bearing seal located between the inner ring and the outer ring,

[0107] The oil slinger includes: a cylindrical protrusion that contacts the inner ring of the bearing when the rotating shaft is fitted; and a circular plate portion that extends radially outward from the protrusion along the bearing,

[0108] The outer diameter of the oil slinger is larger than the outer diameter of the bearing seal of the bearing.

[0109] (Supplementary Note 4)

[0110] In the Roots blower described in Supplementary Note 3, it is characterized in that

[0111] The wall of the bearing chamber and the circular plate portion are opposed to each other with a specified gap.

Claims

1. A Roots blower, characterized in that: The Roots blower includes: A rotor for Roots blower; A rotating shaft fixed to the axial center part of the rotor for Roots blower; Bearings that support the rotating shaft so that it can rotate freely; A housing that defines a pump chamber for housing the rotor for Roots blower and a bearing chamber for housing the bearings; An oil slinger installed on the rotating shaft, disposed in the bearing chamber and located between the bearing and the pump chamber; and A circulation hole that extends from the lower end of the bearing chamber to the pump chamber at a descending gradient, connecting the bearing chamber and the pump chamber, The oil slinger is formed to rotate between the opening part on the upper side of the circulation hole opening in the bearing chamber and the bearing.

2. The Roots blower according to claim 1, characterized in that: The rotor for Roots blower includes a pair of rotors, The opening on the pump chamber side of the circulation hole is formed at the discharge side of the pump chamber and at a position avoiding the area where the pair of rotors mesh with each other.

3. The Roots blower according to claim 1 or 2, characterized in that: The bearing includes an inner ring, an outer ring, and a bearing seal located between the inner ring and the outer ring, The oil slinger includes: a cylindrical convex portion that contacts the inner ring of the bearing in a state where the rotating shaft is fitted; and a circular plate portion that extends radially outward from the convex portion along the bearing, The outer diameter of the oil slinger is larger than the outer diameter of the bearing seal of the bearing.

4. The Roots blower according to claim 3, characterized in that: The wall of the bearing chamber and the circular plate portion face each other with a specified gap.

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