Roots blower

Abstract

To provide a roots blower capable of preventing moisture leaked from a pump chamber from reaching a bearing, without using a sealing member.SOLUTION: A roots blower comprises: a rotary shaft (drive shaft 13) fixed to an axial center of a rotor for the roots blower (drive-side rotor 11); a pump chamber 10; a first bearing 17 housed in a first bearing chamber 19 formed in a wall (front wall 16) surrounding the pump chamber 10; a first flinger 27 located between the first bearing 17 and the pump chamber 10 and mounted on the rotary shaft; and a first recirculation hole 24 that extends from a lower end of the first bearing chamber 19 to the pump chamber 10 with a downward slope and communicates the first bearing chamber 19 with the pump chamber 10. The first flinger 27 is formed to rotate while passing between an opening on the upper side of the first recirculation hole 24, which opens into the first bearing chamber 19, and the first bearing 17.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a Roots blower having a flinger between a pump chamber and a bearing. [Background technology]

[0002] A conventional Roots blower is described, for example, in Patent Document 1. The Roots blower disclosed in Patent Document 1 has a seal member between a bearing supporting the rotor shaft and a pump chamber. The seal member is housed in a seal chamber formed in the wall of the pump chamber. The seal chamber is connected to the pump chamber via a communication hole.

[0003] When the Roots blower described in Patent Document 1 handles gas containing moisture, moisture infiltrates from the pump chamber along the rotating shaft into the seal chamber. The moisture that has infiltrated into the seal chamber is blocked by the seal member, and is discharged from the seal chamber through the communication hole into the pump chamber. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4779669 Summary of the Invention [Problem to be solved by the invention]

[0005] In conventional Roots blowers such as that shown in Patent Document 1, there was a risk that wear powder generated by the seal member would enter the pump chamber from the seal chamber along with water and adhere to the sliding surfaces of the rotor and the pump chamber, causing a loss of function.

[0006] An object of the present invention is to provide a Roots blower that can prevent moisture leaking from a pump chamber from reaching a bearing without using a sealing member. [Means for solving the problem]

[0007] In order to achieve this object, the Roots blower of the present invention comprises a rotating shaft fixed to the axial center of a Roots blower rotor, a pump chamber that houses the Roots blower rotor, a bearing housed in a bearing chamber formed in a wall surrounding the pump chamber and rotatably supporting the rotating shaft, a flinger that is disposed in the bearing chamber between the bearing and the pump chamber and attached to the rotating shaft, and a reflux hole that extends downward from the lower end of the bearing chamber to the pump chamber and connects the bearing chamber to the pump chamber, and the flinger is formed to rotate between the upper opening of the reflux hole that opens into the bearing chamber and the bearing.

[0008] In the Roots blower of the present invention, the opening of the reflux hole on the pump chamber side may be formed on the discharge side of the pump chamber, at a position that avoids the area where the pair of Roots blower rotors mesh with each other.

[0009] In the Roots blower of the present invention, the flinger comprises a cylindrical boss portion 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 boss portion along the bearing, and the outer diameter of the flinger may be larger than the outer diameter of a bearing seal located between the inner ring and outer ring of the bearing.

[0010] In the Roots blower of the present invention, the wall of the bearing chamber may be arranged between the disc portion and the pump chamber so as to face the disc portion with a predetermined clearance. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a Roots blower that can prevent moisture leaking from the pump chamber from reaching the bearings without using a sealing member. [Brief description of the drawings]

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Embodiments for Carrying Out the Invention

[0013] Hereinafter, an embodiment of the roots blower according to the present invention will be described in detail with reference to FIGS. 1 to 9. The roots blower 1 shown in Figure 1 is driven by a motor 2 depicted on the far left in Figure 1 and operates to suck fluid from a suction port 4 (see Figure 3) of a housing 3 and discharge it from a discharge port 5. In this embodiment, an example of a roots blower that uses hydrogen gas as the fluid will be described.

[0014] This roots blower 1 is configured assuming that moisture is contained in the hydrogen gas. In the following description of each component of the roots blower 1, when indicating the direction, the direction in which the motor 2 is located with respect to the housing 3 is taken as the front, the direction in which the suction port 4 is located is taken as the upper side, and the direction in which the discharge port 5 is located is taken as the lower side, and it is indicated by the direction when the roots blower 1 is viewed from the front (as shown in Figure 2).

[0015] (Description of the housing) The housing 3 is formed by combining multiple parts. These multiple parts include a front housing 6 that forms the front wall of the housing 3, a rear housing 7 that is connected to the rear end of the front housing 6, and a rear cover 8 that is connected to the rear end of the rear housing 7. As shown in FIG. 4, the rear housing 7 and the rear cover 8 are fixed to the front housing 6 by multiple fixing bolts 9 that penetrate these components from the rear.

[0016] As shown in Figures 1 and 2, the front housing 6 has mounting flanges 6a at both the front and rear ends. This Roots blower 1 is used with the front-to-rear direction of the housing 3 horizontal and the suction port 4 positioned at the top. The suction port 4 is formed at the upper end in the center of the front-to-rear direction of the front housing 6, and the discharge port 5 is formed at the lower end in the center of the front-to-rear direction of the front housing 6.

[0017] As shown in Fig. 4, the front housing 6 is formed in a cylindrical shape with a bottom that opens rearward. The opening of the front housing 6 is closed by the rear housing 7. By connecting the front housing 6 to the rear housing 7 in this manner, a pump chamber 10 is formed inside the front housing 6. The pump chamber 10 is formed with the front housing 6 and the rear housing 7 as walls, and has an elliptical cross section that is long in the left-right direction, as shown in Fig. 3. An inlet port 4 opens at the upper end of the pump chamber 10, and a discharge port 5 opens at the lower end of the pump chamber 10.

[0018] The pump chamber 10 houses a drive rotor 11 and a driven rotor 12 that rotate while meshing with each other. In this embodiment, the drive rotor 11 and the driven rotor 12 correspond to the "Roots blower rotor" of the present invention. The driving-side rotor 11 and the driven-side rotor 12 are each formed of a plastic material so as to have a substantially cocoon-shaped cross-sectional shape. The driving-side rotor 11 and the driven-side rotor 12 rotate while meshing with each other in the pump chamber 10, thereby sucking hydrogen gas from the suction port 4 into the pump chamber 10 and discharging it from the discharge port 5 through the space between them and the inner wall of the pump chamber 10. The rotation directions of the driving-side rotor 11 and the driven-side rotor 12 are indicated by arrows R in FIG. 3.

[0019] (Explanation of the driving shaft and the driven shaft) A driving shaft 13 is fixed to the axial center portion of the driving-side rotor 11 by insert molding. A driven shaft 14 is fixed to the axial center portion of the driven-side rotor 12 by insert molding. In this embodiment, the driving shaft 13 and the driven shaft 14 correspond to the "rotating shaft" in the present invention. The driving-side rotor 11 rotates integrally with the driving shaft 13 when the driving shaft 13 rotates. The driven-side rotor 12 rotates integrally with the driven shaft 14 when the driven shaft 14 rotates. The driving shaft 13 and the driven shaft 14 are connected to each other via a gear coupling structure 15 at the rear end and rotate at the same rotational speed in opposite rotational directions. The explanation of the gear coupling structure 15 will be described later.

[0020] As shown in FIG. 4, the driving shaft 13 penetrates through the front wall 16 of the front housing 6, which is the front wall of the pump chamber 10, and the rear housing 7, which is the rear 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 the same support structure as the support structure that supports the driving shaft 13.

[0021] As shown in Fig. 5, the first bearing 17 is accommodated in a first bearing chamber 19 formed in the front wall 16 of the front housing 6. As shown in Fig. 6, the first bearing chamber 19 is formed by a first circular recess 21 that opens to the front surface of the front wall 16 and a first through-hole 23 that penetrates a 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 are a first peripheral wall 21a that extends forward from the bottom wall 22 and a second peripheral wall 21b that is formed to have 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.

[0022] (Explanation of the first reflux hole) A first return flow hole 24 opens at the lower end, which is the lowest part, of the first bearing chamber 19. The first return flow hole 24 extends from the lower end of the first bearing chamber 19 at a downward slope to the pump chamber 10, and connects the first bearing chamber 19 to the pump chamber 10. The upper opening of the first return flow hole 24, i.e., the opening on the first bearing chamber 19 side, is formed so that a part (the lowest part) of the first peripheral wall 21a and a part (the lowest part) of the second peripheral wall 21b are cut out by the first return flow hole 24.

[0023] 3, the lower opening of the first return flow hole 24, i.e., the opening on the pump chamber 10 side, is formed on the discharge side of the pump chamber 10, avoiding the area (the center in the left-right direction) where the pair of rotors 11, 12 mesh with each other. The first return flow hole 24 is provided on both the drive shaft 13 side and the driven shaft 14 side. The first return flow hole 24 on the driven shaft 14 side connects the pump chamber 10 to a first bearing chamber (not shown) on the driven shaft 14 side.

[0024] (Explanation of the first bearing) 5, the first bearing 17 is a single-row ball bearing, and is fixed to the front wall 16 with the outer ring 17a fitted into 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). The first bearing 17 according to this embodiment is a hydrogen-compatible bearing in which the outer ring 17a, inner ring 17b, and balls 17c are each made of a high-chromium material. Annular bearing seals 17d that seal the inside of the first bearing 17 are provided between the outer ring 17a and the inner ring 17b at both axial ends of the first bearing 17. The front wall-penetrating portion 13a of the drive shaft 13 is fitted and penetrates the inner ring 17b of the first bearing 17. The inner ring 17b is fixed to the wall-penetrating portion 13a. A second O-ring 26 is provided between the inner ring 17b and the wall-penetrating portion 13a.

[0025] A first flinger 27 is disposed behind the inner ring 17b of the first bearing 17 and between the inner ring 17b and the rotor mounting portion 13b, which is thicker than the wall-penetrating portion 13a of the drive shaft 13. The drive-side rotor 11 is fixed to the rotor mounting portion 13b of the drive shaft 13. Like the drive shaft 13, the driven shaft 14 also has a front wall-penetrating portion 14a (see FIG. 2) and a rotor mounting portion 14b (see FIG. 3). The front wall-penetrating portion 14b of the driven shaft 14 is rotatably supported on 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. Like the drive shaft 13, the driven shaft 14 is also provided with a first flinger 27 (see FIG. 3).

[0026] (Flinga's explanation) 5, the first flinger 27 has a cylindrical boss portion 27a into which the drive shaft 13 fits, and a disk portion 27b that extends radially outward from the boss portion 27a along the first bearing 17. The front end of the boss portion 27a contacts the inner ring 17b of the first bearing 17. The rear end of the boss portion 27a is inserted into the first through-hole 23 and contacts the rotor mounting portion 13b of the drive shaft 13. The boss portion 27a is fixed to the wall-penetrating portion 13a of the drive shaft 13. The disk portion 27b is accommodated inside the first peripheral wall 21a. The axial length of the first peripheral wall 21a according to this embodiment is shorter than the thickness of the disk portion 27b. For this reason, the front half portion of the disk portion 27b extends inward of the second peripheral wall 21b. Between the disk portion 27b and the pump chamber 10, the bottom wall 22 of the first bearing chamber 19 is provided so as to face the disk portion 27b with a predetermined clearance.

[0027] The outer diameter of the first flange 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 disk portion 27b of the first flange 27 is formed such that the outer peripheral edge is spaced apart from the first peripheral wall 21a with a predetermined clearance. For this reason, the first flange 27 rotates passing between the opening of the first circulation hole 24 that opens into the first bearing chamber 19 and the first bearing 17.

[0028] (Description of the second bearing) As shown in FIG. 7, the second bearing 18 is accommodated in a second bearing chamber 31 formed in the rear housing 7. As shown in FIG. 8, the second bearing chamber 31 is formed by a second circular recess 32 that opens to the rear surface of the rear housing 7 and a second through hole 34 that penetrates 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 a third peripheral wall 32a that extends rearward from the bottom wall 33, a fourth peripheral wall 32b that is formed so as to have a larger inner diameter than the third peripheral wall 32a and extends rearward from the third peripheral wall 32a, and a fifth peripheral wall 32c that is formed so as to have a larger inner diameter than the fourth peripheral wall 32b and extends from the fourth peripheral wall 32b to the rear surface of the rear housing 7.

[0029] A second circulation hole 35 opens 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 with a downward gradient, and communicates the second bearing chamber 31 and the pump chamber 10. As shown in FIG. 8, 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 is the boundary between the third peripheral wall 32a and the fourth peripheral wall 32b are cut out by the second circulation hole 35.

[0030] The lower opening of the second circulation hole 35, that is, the opening on the pump chamber 10 side, is located on the discharge side of the pump chamber 10 and is formed at a position avoiding the region (the central part in the left - right direction) where the pair of rotors 11, 12 mesh with each other. The second circulation hole 35 is provided on both the drive shaft 13 side and the driven shaft 14 side. That is, the second circulation hole 35 on the driven shaft 14 side communicates the second bearing chamber (not shown) on the driven shaft 14 side and the pump chamber 10.

[0031] The second bearing 18 is a double - row ball bearing. As shown in FIG. 7, the outer ring 18a is fixed to the rear housing 7 in a state of fitting into the fourth peripheral wall 32b of the second circular recess 32. The second bearing 18 according to this embodiment is a hydrogen - resistant bearing in which the outer ring 18a, the inner ring 18b, and the balls 18c are each formed of a high - chromium material. Annular bearing seals 18d for sealing the inside of the second bearing 18 are provided between the outer ring 18a and the inner ring 18b at both axial ends of the second bearing 18. A rear - side wall through - hole 13c that is thinner than the rotor mounting portion 13b of the drive shaft 13 penetrates the inner ring 18b of the second bearing 18 in a fitting state. The inner ring 18b is fixed to the wall through - hole 13c.

[0032] (Description of the second flange) A second flange 37 is disposed in front of the inner ring 18b of the second bearing 18 and between the rotor mounting portion 13b of the drive shaft 13. The second flange 37 is formed to have the same structure as the first flange 27 and has a boss portion 37a and a disk portion 37b. The front end portion of the boss portion 37a is inserted into the second through hole 34 and contacts the rotor mounting portion 13b of the drive shaft 13. The rear end portion of the boss portion 37a contacts the inner ring 18b of the second bearing 18. This boss portion 37a is fixed to the wall through portion 13c on the rear side of the drive shaft 13.

[0033] The disk portion 37b is accommodated inside 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 flange 37 is accommodated inside the third peripheral wall 32a. The second bearing 18 abuts against an end face 36 that is the boundary between the third peripheral wall 32a and the fourth peripheral wall 32b. Therefore, the rear end face of the disk portion 37b of the second flange 37 is formed to be spaced apart from the front end of the second bearing 18 with a predetermined clearance. The bottom wall 33 of the second bearing chamber 31 is provided to face the disk portion 37b with a predetermined clearance between the disk portion 37b and the pump chamber 10.

[0034] The outer diameter of the second flange 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 outer peripheral edge of the disk portion 37b of the second flange 37 is formed to be spaced apart from the third peripheral wall 32a with a predetermined clearance. Therefore, the second flange 37 rotates passing between the opening of the second circulation hole 35 that opens into the second bearing chamber 31 and the second bearing 18.

[0035] (Description of the rear side of the rear housing) A seal member 41 is provided on the inside of the fifth peripheral wall 32c of the rear housing 7. This seal member 41 functions as an oil seal and a hydrogen seal, and is provided between the fifth peripheral wall 32c and a cylindrical sliding collar 42 that is fitted and fixed to the wall-penetrating portion 13c on the rear side of the drive shaft 13. A third O-ring 43 is provided between the sliding collar 42 and the wall-penetrating portion 13c. The seal member 41 is disposed rearwardly from the second bearing 18 by a predetermined distance.

[0036] A drive-side gear 44, which constitutes part of the gear coupling structure 15, is attached to the rear end of the wall-through portion 13c on the rear side of the drive shaft 13 so as to rotate integrally with the drive shaft 13. The second flinger 37, the inner ring 18b of the second bearing 18, the sliding collar 42, and the drive-side gear 44 are passed through the wall-through portion 13c in this order and are fastened together by a fixing nut 45 that is threaded onto the rear end of the wall-through portion 13c. Although not shown, the rear wall-through portion of the driven shaft 14 has the same configuration as the drive shaft 13. That is, a second flinger (not shown), an inner ring of a second bearing, a sliding collar, and a driven gear that, together with the drive gear 44, constitutes the gear coupling structure 15 are assembled in the rear wall-through portion of the driven shaft 14, and are fastened together by a fixing nut threaded onto the rear end of the wall-through portion. The driven gear is formed so that the number of teeth matches that of the drive gear 44, and is in mesh with the drive gear 44. By connecting the drive shaft 13 and the driven shaft 14 via the gear coupling structure 15, which is made up of the drive gear 44 and the driven 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 rotation speed.

[0037] The drive-side gear 44 and the driven-side gear are disposed behind the rear housing 7 and housed in a rear cover 8. The rear cover 8 is formed in a cylindrical shape with a bottom that opens forward. The opening of the rear cover 8 is closed when the rear cover 8 is attached to the rear housing 7. Oil 46 (see FIG. 4) is stored inside the rear cover 8. The amount of oil 46 stored is such that the lower ends of the drive-side gear 44 and the driven-side gear are submerged in the oil 46. By storing the oil 46 inside the rear cover 8 in this way, the lower end of the second circular recess 32 is immersed in the oil 46. An oil gauge 47 is detachably attached to the upper end of the rear cover 8 to allow for checking the amount of stored oil 46.

[0038] Oil 46 that has entered the rear end of the second circular recess 32 and oil 46 that has seeped between the drive shaft 13 and the drive side gear 44 and sliding collar 42 is prevented from further seeping in by the sealing member 41 and the third O-ring 43. The seal member 41 may deteriorate over a long period of use. If the seal member 41 deteriorates, oil 46 may pass through the seal member 41 and leak toward the second bearing 18. In the Roots blower 1 according to this embodiment, a structure is adopted in which the oil 46 is discharged from between the second bearing 18 and the seal member 41 to prevent the leaked oil 46 from passing through the second bearing 18 and entering the pump chamber 10.

[0039] 7, an oil receiving chamber 48, which is an annular space surrounded by the fifth peripheral wall 32c, is formed between the second bearing 18 and the seal member 41. An oil discharge hole 49 opens at the bottom of this oil receiving chamber 48. 9, the oil discharge hole 49 extends from the lower end of the fifth peripheral wall 32c to the lower end of the rear housing 7. When oil 46 flows into the oil receiving chamber 48, the oil 46 flows down through the oil discharge hole 49 and is discharged below the rear housing 7.

[0040] (Explanation of Roots Blower Operation) In the Roots blower 1 configured as described above, when the drive shaft 13 is driven by the motor 2, the drive shaft 13 and drive-side rotor 11, and the driven shaft 14 and driven-side rotor 12 rotate in opposite directions at the same rotational speed. As the drive-side rotor 11 and driven-side rotor 12 rotate in this manner, hydrogen gas is drawn into the suction port 4 and discharged from the discharge port 5. Some of the hydrogen gas drawn into the pump chamber 10 flows from the pump chamber 10 along the drive shaft 13 and driven shaft 14 and leaks into the first bearing chamber 19 and the second bearing chamber 31. If moisture is contained in the hydrogen gas, the moisture will also penetrate into the first and second bearing chambers 19, 31.

[0041] A first flinger 27 is disposed in the first bearing chamber 19 at a portion closest to the pump chamber 10. A second flinger 37 is disposed in the second bearing chamber 31 at a portion closest to the pump chamber 10. Therefore, moisture that has entered the first and second bearing chambers 19 and 31 together with hydrogen gas is blown away by the first and second flingers 27 and 37, which rotate at high speed. The moisture blown away by the first flinger 27 rotates along the first circumferential wall 21a and the portion of the second circumferential wall 21b rearward of the first bearing 17, and is collected by gravity at the lower end of the first bearing chamber 19. The water collected at the lower end of the first bearing chamber 19 in this way flows down the first return hole 24 and is discharged into the pump chamber 10. In particular, since the outer periphery of the first flinger 27 overlaps with the first return hole 24, the shaken-off water is more easily guided to the first return hole 24.

[0042] On the other hand, the water that has entered the second bearing chamber 31 and been blown away by the second flinger 37 rotates along the third peripheral wall 32a and is collected by gravity at the lower end of the second bearing chamber 31. The water collected at the lower end of the second bearing chamber 31 in this manner flows down through the second return hole 35 and is discharged into the pump chamber 10. In particular, because the outer periphery of the second flinger 37 overlaps with the second return hole 35, the spun-off water is more easily guided to the second return hole 35. The first fringer 27 rotates through the space between the upper opening of the first circulation hole 24 and the first bearing 17. The second fringer 37 rotates through the space between the upper opening of the second circulation hole 35 and the second bearing 18.

[0043] Therefore, even though the lower ends of the first and second circulation holes 24 and 35 open at the discharge side in the pump chamber 10 where the pressure is relatively high, and even if the discharge pressure acts on the first and second circulation holes 24 and 35, water will not enter the first and second bearing chambers 19 and 31 from the discharge side through the first and second circulation holes 24 and 35. The reason is that a part of the upper openings of the first and second circulation holes 24 and 35 is blocked by the outer peripheral parts of the rotating first and second fringes 27 and 37, and moreover, the hydrogen gas and water that are blown away by centrifugal force act as substantial shields to perform a sealing function. Therefore, it is possible to provide a roots blower that can prevent water leaked from the pump chamber from reaching the bearing without using a sealing member.

[0044] The openings of the first and second circulation holes 24 and 35 on the pump chamber 10 side according to this embodiment are formed at the discharge side of the pump chamber 10 and at a position avoiding the region where the pair of rotors (the driving side rotor 11 and the driven side rotor 12) mesh with each other. For this reason, it is possible to prevent the water discharged from the first and second circulation holes 24 and 35 into the pump chamber 10 from being sent upward so as to be included in the meshing portion between the driving side rotor 11 and the driven side rotor 12 and returned to the suction side of the pump chamber 10, and the water can be quickly discharged from the roots blower 1.

[0045] The first and second flingers 27, 37 according to this embodiment include cylindrical boss portions 27a, 37a that contact the inner rings 17b, 18b of the first and second bearings 17, 18 when the drive shaft 13 and the driven shaft 14 are fitted thereto, and disk portions 27b, 37b that extend radially outward from the boss portions 27a, 37a along the first and second bearings 17, 18. The outer diameters of the first and second flingers 27, 37 are larger than the outer diameters of the bearing seals 17d, 18d that are located between the inner rings 17b, 18b and outer rings 17a, 18a of the first and second bearings 17, 18. This reliably prevents the moisture blown away by the first and second flingers 27 and 37 from entering the first and second bearings 17 and 18. In other words, it is possible to achieve both water discharge and waterproofing of the first and second bearings 17 and 18.

[0046] In this embodiment, the walls (bottom walls 22, 33) of the first and second bearing chambers 19, 31 are provided between the disk portions 27b, 37b and the pump chamber 10 so as to face the disk portions 27b, 37b with a predetermined clearance therebetween. As a result, the minute gaps between the disk portions 27b, 37b and the walls (bottom walls 22, 33) of the first and second bearing chambers 19, 31 have a sealing function, making it difficult for moisture to penetrate into the first and second bearing chambers 19, 31. In the embodiment described above, the second bearing 18 is disposed between the pump chamber 10 and the seal member 41. Therefore, the second bearing 18 can prevent wear powder generated at the seal member 41 from entering the pump chamber 10.

[0047] In this embodiment, the second bearing 18 that supports the rear wall-penetrating portion 13c of the drive shaft 13 is disposed closer to the pump chamber 10 than the seal member 41. The seal member 41 provides a seal between a sliding collar 42 that fits into the rear wall-penetrating portion 13c and the rear housing 7. A third O-ring 43 provides a seal between the sliding collar 42 and the rear wall-penetrating portion 13c. The bearing seal 18d of the second bearing 18 is intended to prevent water from entering. Therefore, the bearing seal 18d cannot seal out hydrogen gas, and hydrogen gas permeates through the second bearing 18. Furthermore, since there is no sealing material in the minute gap that occurs between the inner ring 18b of the second bearing 18 and the drive shaft 13, hydrogen gas also permeates through this gap.

[0048] When the Roots blower 1 is in operation, hydrogen gas enters the oil receiving chamber 48 from the pump chamber 10 through the second bearing 18 and the minute gap between the second bearing 18 and the drive shaft 13. This hydrogen gas is prevented from entering the rear cover 8 by the seal member 41 and the third O-ring 43, preventing it from escaping into the rear cover 8 behind the oil receiving chamber 48. Therefore, during operation of the Roots blower 1, the pressure in the oil receiving chamber 48 rises and reaches equilibrium with the pressure in the pump chamber 10. This equalizes the pressures in the two spaces (pump chamber 10 and oil receiving chamber 48) where the second bearing 18 is located. This eliminates the pressure difference acting on the bearing seal 18d from both axial sides, reducing the load on the bearing seal 18d and improving its durability. This phenomenon of eliminating the pressure difference on both axial sides of the second bearing 18 also occurs in the second bearing supporting the rear wall-penetrating portion of the driven shaft 14. [Explanation of symbols]

[0049] 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 reflux hole, 27...first flinger, 27a, 37a...boss portion, 27b, 37b...disc portion, 31...second bearing chamber, 35...second reflux hole, 37...second flinger.

Claims

1. a rotating shaft fixed to the axial center of a rotor for a roots blower, a pump chamber that houses the roots blower rotor, a bearing housed in a bearing chamber formed in a wall surrounding the pump chamber, the bearing rotatably supporting the rotating shaft, a flange disposed in the bearing chamber, positioned between the bearing and the pump chamber, and attached to the rotating shaft, a circulation hole that extends from the lower end of the bearing chamber to the pump chamber in a downward gradient and communicates the bearing chamber and the pump chamber, The roots blower is characterized in that the flange is formed to rotate through a space between an upper opening of the circulation hole opening into the bearing chamber and the bearing.

2. The roots blower according to claim 1, wherein an opening of the circulation hole on the pump chamber side is located on the discharge side of the pump chamber and is formed at a position avoiding a region where the pair of roots blower rotors mesh with each other.

3. The roots blower according to claim 1 or claim 2, wherein the flange includes a cylindrical boss portion that contacts the inner ring of the bearing with the rotating shaft fitted therein, and a disk portion that extends radially outward from the boss portion along the bearing, The roots blower is characterized in that an outer diameter of the flange is larger than an outer diameter of a bearing seal positioned between the inner ring and the outer ring of the bearing.

4. The roots blower according to claim 3, wherein a wall of the bearing chamber is provided to face the disk portion with a predetermined clearance between the disk portion and the pump chamber.

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