Fluid Machinery

Abstract

To provide a fluid machine which can inhibit a foamy oil from being discharged from a breather passage to the outside of a housing.SOLUTION: A root pump includes a breather passage 40 which has a bending part 43 and releases a pressure in a power transmission chamber 24 to the outside of a housing 11. A gas containing an oil and discharged from the power transmission chamber 24 is separated into an oil and a gas at the bending part 43. An oil recirculation passage 50 connected to an opening surface S2 of a second through hole 27 is connected to the bending part 43. The oil separated in the bending part 43 is drawn into a bearing through the oil recirculation passage 50 by rotation of a drive shaft 16. The gas separated in the bending part 43 is discharged to the outside of the housing 11 through the breather passage 40.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a fluid machine. [Background technology]

[0002] Patent Document 1 describes a fluid compressor as a fluid machine. The above-mentioned fluid compressor includes a rotating shaft, a motor, an actuating unit, a power transmission unit, and a housing. The rotating shaft is composed of a drive shaft and a driven shaft. The motor rotates the rotating shaft. The actuating unit is composed of a drive rotor and a driven rotor. The actuating unit rotates synchronously with the rotating shaft, and sucks in and discharges fluid. The power transmission unit is composed of a drive gear and a driven gear. The power transmission unit transmits power from the rotating shaft to the actuating unit. The housing is formed with a motor chamber, an actuating chamber, and a power transmission chamber. The motor chamber accommodates the motor. The actuating unit is accommodated in the actuating chamber. The power transmission chamber accommodates the power transmission unit and oil. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2005-188326 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, the oil is agitated by the power transmission unit, causing it to splash around in the power transmission chamber. This causes oil bubbles to form in the power transmission chamber, a mixture of air and oil. In other words, gas containing oil is generated in the power transmission chamber. Furthermore, as the power transmission unit continues to operate, the temperature of the power transmission chamber increases, causing some of the oil to turn into steam. This causes the pressure in the power transmission chamber to increase.

[0005] In view of this, it is conceivable to add a breather passage to the fluid machine, which releases the pressure in the power transmission chamber to the outside of the housing. If the fluid machine is equipped with a breather passage, there is a risk that foamy oil will be released from the breather passage to the outside of the housing. [Means for solving the problem]

[0006] The fluid machine that solves the above problem includes a cylindrical housing, a rotating shaft supported by bearings on the housing, a motor that rotates the rotating shaft, an operating section that rotates synchronously with the rotating shaft and sucks in and discharges fluid, and a power transmission section that transmits the power of the rotating shaft to the operating section, and the housing has a motor chamber that accommodates the motor, an operating chamber that accommodates the operating section, a power transmission chamber that accommodates the power transmission section and oil that lubricates the power transmission section, and the bearings are provided. a breather passage for releasing pressure in the transmission chamber to the outside of the housing, and the oil-containing gas discharged from the power transmission chamber is separated into the oil and gas at the bent portion, and an oil return passage connecting to the vicinity of the bearing in the through hole is connected to the bent portion, and the oil separated at the bent portion is drawn into the bearing through the rotation of the rotating shaft via the oil return passage, and the gas separated at the bent portion is released to the outside of the housing via the breather passage.

[0007] According to the above configuration, when the oil-containing gas discharged from the power transmission chamber reaches the bent portion, the oil-containing gas collides with a partition surface that partitions the bent portion. As a result, the oil-containing gas is separated into oil and gas at the bent portion. That is, even if the oil-containing gas contains foamy oil, the foamy oil is broken down at the bent portion. The gas separated from the oil-containing gas is discharged to the outside of the housing via the breather passage. The oil separated from the oil-containing gas flows from the oil return passage to the through hole. The oil that has flowed to the through hole is returned to the power transmission chamber while lubricating the bearing. Therefore, it is possible to prevent foamy oil from being discharged from the breather passage to the outside of the housing.

[0008] In the above-mentioned fluid machine, the motor chamber, the power transmission chamber, and the working chamber are arranged in this order, a sealing member is provided in the through hole to seal the working chamber and the power transmission chamber, the oil return passage opens into an inner surface that defines the through hole between the bearing and the sealing member, and when the direction in which the oil flows on the inner surface in the rotational direction of the rotating shaft is defined as the flow direction, the space between the inner surface and the rotating shaft is narrower on the downstream side of the flow direction relative to the opening of the oil return passage than on the upstream side of the flow direction.

[0009] According to the above configuration, the oil drawn from the oil return passage into the bearing is more likely to flow upstream of the oil flow direction with respect to the opening of the oil return passage in the space between the inner surface defining the through hole and the rotating shaft. That is, the flow of oil can be rectified so that the flow direction of the oil inside the through hole is the rotation direction of the rotating shaft. Therefore, the oil drawn from the oil return passage into the bearing flows smoothly without stagnation inside the through hole. Then, the oil flowing without stagnation inside the through hole is smoothly returned to the power transmission chamber. Therefore, it is easier to create a flow of oil between the bent portion, the oil return passage, the through hole, and the power transmission chamber, and it is possible to suppress the accumulation of oil in the bent portion.

[0010] In the above-mentioned fluid machine, a partition surface defining the bent portion may be provided with a recess against which the oil-containing gas discharged from the power transmission chamber directly impinges. According to the above configuration, the gas containing oil discharged from the power transmission chamber stagnates inside the recess. Then, the gas containing oil is accommodated in the recess, making it difficult for the bubbly oil to flow downstream of the breather passage. Then, the bubbly oil accommodated in the recess is easily separated into oil and gas inside the recess. Therefore, not only is the oil and gas separated by colliding the gas containing oil with the partition surface, but the separation of the oil and gas due to the stagnation of the gas containing oil in the recess can be promoted. Therefore, since the gas containing oil is easily separated into oil and gas, it is possible to further suppress the release of the bubbly oil from the breather passage to the outside of the housing.

[0011] In the above-mentioned fluid machinery, a vent that allows gas to pass but does not allow liquid to pass is provided on the outside of the housing, a case that forms part of the breather passage is fixed, and a mesh that defoams the oil foam is provided in the breather passage between the bent portion and the case.

[0012] According to the above configuration, the mesh breaks down foamy oil in the breather passage. This makes it possible to further prevent the foamy oil from being released from the breather passage to the outside of the housing. The foamy oil broken down by the mesh is separated into oil and gas. The oil separated by the mesh flows along the surface that defines the breather passage to the oil return passage. The oil separated by the mesh is then returned from the oil return passage to the power transmission chamber via the through hole.

[0013] The gas separated by the mesh may be oil vapor. Because the case is provided outside the housing, the case is cooled by the outside air. That is, the oil vapor is cooled and liquefied inside the case. Then, like the oil separated by the mesh, it is returned to the power transmission chamber via the oil return passage and the through hole. Even if the oil vapor liquefies near the vent, the liquefied oil does not pass through the vent. Therefore, the configuration of the vent, case, and mesh improves the oil sealing performance of the fluid machinery.

[0014] In the above-mentioned fluid machinery, the mesh is provided in the breather passage between the bent portion and the case, the space between the case and the housing is sealed with a gasket, and a portion of the gasket overlaps the breather passage, thereby restricting movement of the mesh toward the case, and the breather passage is provided with a restricting portion that sandwiches a portion of the gasket and the mesh and restricts movement of the mesh toward the bent portion.

[0015] According to the above-mentioned configuration, the mesh is fixed in the breather passage by being sandwiched between the gasket and the restricting portion. Since no bolts are used to fix the mesh, it is not necessary to give the mesh excessive strength. Therefore, the weight of the mesh does not need to be increased.

[0016] In addition, part of the gasket is used to secure the mesh in place. The gasket serves both to ensure a seal between the case and the housing and to secure the mesh in place. This simplifies the mesh-fixing structure compared to using a separate member that provides the mesh-fixing function.

[0017] In the above fluid machine, the oil return passage may be open toward the mesh on an inner surface defining the through hole. According to the above-described configuration, the oil separated by the mesh can easily flow into the oil return passage, and therefore the oil is less likely to accumulate in the bent portion.

[0018] In the above fluid machine, the bearing has an outer ring, an inner ring, and rolling elements arranged between the outer ring and the inner ring, and an internal space is formed between the outer ring and the inner ring, and further includes a blade that rotates integrally with the rotating shaft, where the direction in which the axis of the rotating shaft extends is the axial direction and the direction perpendicular to the axis of the rotating shaft is the radial direction, and the blade has an insertion portion having an insertion hole through which the rotating shaft is inserted, and a protrusion portion that protrudes radially outward from the insertion portion, and in the axial direction, the protrusion portion faces the internal space.

[0019] According to the above-mentioned configuration, the oil drawn into the bearing enters the internal space of the bearing, thereby lubricating the bearing. After lubricating the bearing, the oil reaches the protrusion. The blade rotates integrally with the rotating shaft. Oil that reaches the protrusion is thrown radially outward from the tip of the protrusion by centrifugal force. When the oil is thrown radially outward by the protrusion, the oil in the internal space of the bearing is drawn into the blade. That is, the blade draws the oil in the internal space of the bearing toward the power transmission chamber. This prevents the oil from stagnating in the internal space of the bearing. This promotes the flow of oil drawn into the bearing, allowing the oil to be returned smoothly to the power transmission chamber.

[0020] In the above fluid machine, the power transmission unit is configured by a gear that rotates integrally with the rotating shaft, the power transmission chamber includes an oil catch tank in which the oil stirred by the rotation of the gear is stored and which is connected to the breather passage, gas containing the oil that enters the oil catch tank flows to the breather passage, the housing is further formed with a communication hole that communicates the oil catch tank with the through hole, the oil stored in the oil catch tank is drawn into the bearing through the communication hole, when the direction in which the axis of the rotating shaft extends is defined as the axial direction, the gear has a first end face that faces the bearing in the axial direction and a second end face located on the opposite side to the first end face in the axial direction, the gear is provided with a flow hole that passes through the gear, and the flow hole extends in a direction opposite to the rotational direction of the gear in which the flow hole is provided, while intersecting the axial direction as it moves from the first end face to the second end face.

[0021] According to the above configuration, the gas containing oil that enters the oil catch tank flows into the breather passage. The oil stored in the oil catch tank is drawn into the bearing through the communication hole. The oil drawn into the bearing lubricates the bearing and is then returned toward the gear. The oil that reaches the first end face of the gear flows toward the second end face along the surface that defines the flow hole and is located in the opposite direction to the rotation direction of the rotating shaft as the gear rotates. In other words, a part of the surface that defines the flow hole guides the oil that reaches the first end face toward the second end face as the gear rotates. Therefore, the oil returned toward the gear flows through the flow hole.

[0022] The oil stirred by the gears flows through the oil catch tank, the communication hole, and the through hole in that order, and then flows through the flow hole in the gear in the axial direction of the rotating shaft away from the bearing. This allows the oil to flow in the order of the oil catch tank, the communication hole, the through hole, and the flow hole. This prevents the oil from stagnating in the oil catch tank, and therefore prevents the oil level in the oil catch tank from rising. This prevents the oil level in the oil catch tank from reaching the breather passage. Effect of the Invention

[0023] According to this invention, it is possible to prevent foamy oil from being discharged from the breather passage to the outside of the housing. [Brief description of the drawings]

[0024] [Figure 1] FIG. 1 is a cross-sectional view showing an embodiment of a Roots pump. [Diagram 2] 2 is a cross-sectional view taken along line 2-2 in FIG. 1. [Diagram 3] 3 is a cross-sectional view taken along line 3-3 in FIG. 1. [Figure 4] FIG. 4 is an enlarged cross-sectional view of a portion of the cross-sectional view of FIG. [Diagram 5] 5A to 5C are schematic diagrams showing through holes and extensions in a gasket. [Figure 6] 6 is a cross-sectional view taken along line 6-6 in FIG. [Figure 7] 7 is a cross-sectional view taken along line 7-7 in FIG. [Figure 8] 8 is a cross-sectional view taken along line 8-8 in FIG. 7. [Figure 9] 2 is a cross-sectional view taken along line 9-9 in FIG. 1. [Figure 10] 10 is a cross-sectional view taken along line 10-10 in FIG. 9. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] An embodiment in which the fluid machine is a Roots pump will be described below with reference to Figs. 1 to 10. The Roots pump of this embodiment is an auxiliary component mounted on a fuel cell vehicle. The fuel cell vehicle is equipped with a fuel cell system that supplies oxygen and hydrogen to generate electricity. The Roots pump is used as a hydrogen pump for the fuel cell vehicle, which supplies hydrogen off-gas, which is a fluid discharged from the fuel cell, back to the fuel cell.

[0026] <Overall configuration of fluid machinery> 1, the Roots pump 10 includes a cylindrical housing 11. The housing 11 includes a motor housing 12, a gear housing 13, a rotor housing 14, and a cover member 15.

[0027] The motor housing 12 has a plate-shaped end wall 12a and a cylindrical peripheral wall 12b. The peripheral wall 12b extends from the outer periphery of the end wall 12a. The gear housing 13 has a plate-shaped end wall 13a and a cylindrical peripheral wall 13b. The peripheral wall 13b extends from the outer periphery of the end wall 13a.

[0028] The gear housing 13 is connected to the motor housing 12. An end wall 13a of the gear housing 13 abuts against an open end surface of the peripheral wall 12b of the motor housing 12. The end wall 13a of the gear housing 13 closes the opening of the peripheral wall 12b of the motor housing 12. The direction in which the axis of the peripheral wall 12b extends coincides with the direction in which the axis of the peripheral wall 13b extends.

[0029] The rotor housing 14 has a plate-shaped end wall 14a and a cylindrical peripheral wall 14b. The peripheral wall 14b extends from the outer periphery of the end wall 14a. The peripheral wall 14b of the rotor housing 14 in this embodiment has an elliptical cylindrical shape.

[0030] The rotor housing 14 is connected to the gear housing 13. An end wall 14a of the rotor housing 14 abuts against an open end face of the peripheral wall 13b of the gear housing 13. The end wall 14a of the rotor housing 14 closes the opening of the peripheral wall 13b of the gear housing 13. The direction in which the axis of the peripheral wall 13b extends coincides with the direction in which the axis of the peripheral wall 14b extends.

[0031] The cover member 15 is plate-shaped. When viewed from above in the thickness direction, the cover member 15 has an elliptical shape. The cover member 15 is connected to the rotor housing 14. The cover member 15 abuts against an opening end surface of the peripheral wall 14b of the rotor housing 14. The cover member 15 closes the opening of the peripheral wall 14b of the rotor housing 14.

[0032] The Roots pump 10 includes a drive shaft 16 and a driven shaft 17. The drive shaft 16 and the driven shaft 17 are rotating shafts. The drive shaft 16 and the driven shaft 17 are arranged in parallel to each other in the housing 11. The drive shaft 16 and the driven shaft 17 are rotatably supported by the housing 11. The direction in which the axis r1 of the drive shaft 16 and the axis r2 of the driven shaft 17 extend is defined as the axial direction A of the rotating shaft. The direction perpendicular to each of the axis r1 of the drive shaft 16 and the axis r2 of the driven shaft 17 is defined as the radial direction B of the rotating shaft. The axial direction A coincides with the direction in which the axes of the peripheral walls 12b, 13b, and 14b extend.

[0033] The Roots pump 10 includes a power transmission unit 110. The power transmission unit 110 includes a disk-shaped drive gear 18 and a disk-shaped driven gear 19. The drive gear 18 is fixed to the drive shaft 16. The drive gear 18 rotates integrally with the drive shaft 16. The driven gear 19 is fixed to the driven shaft 17. The driven gear 19 rotates integrally with the driven shaft 17. The drive gear 18 and the driven gear 19 mesh with each other. The drive gear 18 and the driven gear 19 are gears that rotate integrally with the drive shaft 16 and the driven shaft 17.

[0034] The Roots pump 10 includes an actuating unit 120. The actuating unit 120 is composed of a drive rotor 20 and a driven rotor 21. The drive rotor 20 is fixed to the drive shaft 16. The drive rotor 20 rotates integrally with the drive shaft 16. The driven rotor 21 is fixed to the driven shaft 17. The driven rotor 21 rotates integrally with the driven shaft 17. The drive rotor 20 and the driven rotor 21 mesh with each other.

[0035] The Roots pump 10 includes a motor 22. A motor chamber 23 that houses the motor 22 is formed in the housing 11. The motor chamber 23 is defined by an end wall 12a of the motor housing 12, a peripheral wall 12b of the motor housing 12, and an end wall 13a of the gear housing 13.

[0036] The motor 22 has a cylindrical motor rotor 22a and a cylindrical stator 22b. The motor rotor 22a is fixed to the drive shaft 16. The motor rotor 22a rotates integrally with the drive shaft 16. The stator 22b is fixed to the inner circumferential surface of the peripheral wall 12b. The stator 22b surrounds the motor rotor 22a. When the stator 22b is supplied with electric power, a rotating magnetic field is generated in the stator 22b, causing the motor rotor 22a to rotate. That is, the motor 22 rotates the drive shaft 16 by the rotation of the motor rotor 22a. The rotation of the drive shaft 16 causes the drive gear 18 to rotate. The rotation of the drive gear 18 causes the driven gear 19 and the driven shaft 17 to rotate. Thus, the motor 22 rotates the drive shaft 16 and the driven shaft 17.

[0037] The direction in which the drive shaft 16 rotates is referred to as a first rotation direction C, and the direction in which the driven shaft 17 rotates is referred to as a second rotation direction D. The first rotation direction C and the second rotation direction D are opposite to each other. The first rotation direction C and the second rotation direction D are the rotation directions of the rotating shaft. The drive gear 18 rotates in the first rotation direction C. The driven gear 19 rotates in the second rotation direction D.

[0038] A power transmission chamber 24 is formed in the housing 11 to accommodate the drive gear 18 and the driven gear 19. The power transmission chamber 24 is defined by an end wall 13a of the gear housing 13, a peripheral wall 13b of the gear housing 13, and an end wall 14a of the rotor housing 14. The power transmission chamber 24 also accommodates oil for lubricating the drive gear 18 and the driven gear 19. The oil also contributes to suppressing an increase in temperature of the drive gear 18 and the driven gear 19. The drive gear 18 and the driven gear 19 rotate while immersed in oil, enabling them to rotate at high speeds without seizing or wearing out.

[0039] The housing 11 defines an operating chamber 25 that houses the drive rotor 20 and the driven rotor 21. The operating chamber 25 is defined by an end wall 14a of the rotor housing 14, a peripheral wall 14b of the rotor housing 14, and a cover member 15. In this embodiment, the motor chamber 23, the power transmission chamber 24, and the operating chamber 25 are arranged in this order in the axial direction A. The end wall 13a of the gear housing 13 separates the power transmission chamber 24 from the motor chamber 23 in the axial direction A. The end wall 14a of the rotor housing 14 separates the power transmission chamber 24 from the operating chamber 25 in the axial direction A. The cover member 15 separates the operating chamber 25 from the outside in the axial direction A.

[0040] The drive shaft 16 passes through the end wall 13a of the gear housing 13 and the end wall 14a of the rotor housing 14. The drive shaft 16 is rotatably supported by a bearing Br relative to the motor housing 12. The bearing Br is received in a cylindrical boss portion 12c provided on the end wall 12a of the motor housing 12. The driven shaft 17 passes through the end wall 14a of the rotor housing 14.

[0041] A first through hole 26 is formed in the end wall 13a of the gear housing 13 as a through hole. The first through hole 26 penetrates the end wall 13a in the thickness direction. The first through hole 26 has a first bearing accommodating recess 26a and a first seal member accommodating recess 26b. The first bearing accommodating recess 26a is a circular hole. The first bearing accommodating recess 26a opens to the inner side surface 13c of the end wall 13a. The first seal member accommodating recess 26b is a circular hole. The first seal member accommodating recess 26b opens to the bottom of the first bearing accommodating recess 26a. The diameter of the first bearing accommodating recess 26a is larger than the diameter of the first seal member accommodating recess 26b. The first through hole 26 is a stepped cylindrical hole.

[0042] The drive shaft 16 is inserted through the first through hole 26. A first bearing Br1 serving as a bearing is accommodated in the first bearing accommodating recess 26a. The first bearing Br1 supports the drive shaft 16 rotatably relative to the gear housing 13. A first seal member Se1 is accommodated in the first seal member accommodating recess 26b. The first seal member Se1 is an oil seal. The drive shaft 16 passes through the first seal member Se1. The first seal member Se1 seals between the power transmission chamber 24 and the motor chamber 23.

[0043] The first bearing Br1 is separated from the bottom of the first bearing accommodating recess 26a. The first bearing Br1 is fixed to an inner surface 26c that defines the first bearing accommodating recess 26a, excluding the bottom. A portion of the inner surface 26c that is located between the first bearing Br1 and the first seal member Se1 is defined as an opening surface S1.

[0044] A second through hole 27 is formed in the end wall 14a of the rotor housing 14 as a through hole. The second through hole 27 penetrates the end wall 14a in the thickness direction. The second through hole 27 has a second bearing accommodating recess 27a and a second seal member accommodating recess 27b. The second bearing accommodating recess 27a is a circular hole. The second bearing accommodating recess 27a opens to the outer side surface 14c of the end wall 14a. The second seal member accommodating recess 27b is a circular hole. The second seal member accommodating recess 27b opens to the bottom of the second bearing accommodating recess 27a. The diameter of the second bearing accommodating recess 27a is larger than the diameter of the second seal member accommodating recess 27b. The second through hole 27 is a stepped cylindrical hole.

[0045] The drive shaft 16 is inserted through the second through hole 27. The second bearing accommodating recess 27a accommodates a second bearing Br2 as a bearing. The second bearing Br2 supports the drive shaft 16 rotatably relative to the rotor housing 14. The drive shaft 16 is supported by the bearings Br1 and Br2 relative to the housing 11. The second seal member accommodating recess 27b accommodates a second seal member Se2 as a seal member. The second seal member Se2 is an oil seal. The drive shaft 16 passes through the second seal member Se2. The second seal member Se2 seals between the power transmission chamber 24 and the operating chamber 25.

[0046] The second bearing Br2 is separated from the bottom of the second bearing accommodating recess 27a. The second bearing Br2 is fixed to an inner surface 27c that defines the second bearing accommodating recess 27a, excluding the bottom. A portion of the inner surface 27c that is located between the second bearing Br2 and the second seal member Se2 is defined as an opening surface S2.

[0047] A third through hole 28 is formed in the end wall 14a of the rotor housing 14 as a through hole. The third through hole 28 penetrates the end wall 14a in the thickness direction. The third through hole 28 has a third bearing accommodating recess 28a and a third seal member accommodating recess 28b. The third bearing accommodating recess 28a is a circular hole. The third bearing accommodating recess 28a opens to the outer side surface 14c of the end wall 14a. The third seal member accommodating recess 28b is a circular hole. The third seal member accommodating recess 28b opens to the bottom of the third bearing accommodating recess 28a. The diameter of the third bearing accommodating recess 28a is larger than the diameter of the third seal member accommodating recess 28b. The third through hole 28 is a stepped cylindrical hole.

[0048] The driven shaft 17 is inserted through the third through hole 28. A third bearing Br3 serving as a bearing is accommodated in the third bearing accommodating recess 28a. The third bearing Br3 supports the driven shaft 17 rotatably relative to the rotor housing 14. A third seal member Se3 serving as a seal member is accommodated in the third seal member accommodating recess 28b. The third seal member Se3 is an oil seal. The driven shaft 17 passes through the third seal member Se3. The third seal member Se3 seals between the power transmission chamber 24 and the operating chamber 25.

[0049] The third bearing Br3 is separated from the bottom of the third bearing accommodating recess 28a. The third bearing Br3 is fixed to an inner surface 28c that defines the third bearing accommodating recess 28a, excluding the bottom. A portion of the inner surface 28c that is located between the third bearing Br3 and the third seal member Se3 is defined as an opening surface S3.

[0050] A fourth bearing accommodating recess 29 is formed in the end wall 13a of the gear housing 13. The fourth bearing accommodating recess 29 opens to an inner surface 13c of the end wall 13a. A fourth bearing Br4 is accommodated in the fourth bearing accommodating recess 29. The fourth bearing Br4 supports the driven shaft 17 rotatably relative to the gear housing 13. The driven shaft 17 is supported by the bearings Br3 and Br4 relative to the housing 11. The bearings Br, Br1, Br2, Br3, and Br4 are, for example, ball bearings.

[0051] Each of the through holes 26, 27, 28 is a through hole through which a rotating shaft is inserted. Therefore, the first bearing Br1, the second bearing Br2, and the third bearing Br3 are provided in the through holes. The inner surfaces 26c, 27c, 28c are inner surfaces that define the through holes. The opening surfaces S1, S2, S3 are portions of the through holes near the bearings. The opening surfaces S2, S3 are inner surfaces that define the through holes between the bearings and the seal members.

[0052] As shown in Fig. 2, the drive rotor 20 and the driven rotor 21 are arranged adjacent to each other in the longitudinal direction of the peripheral wall 14b. The axis r1 of the drive shaft 16 and the axis r2 of the driven shaft 17 are positioned on a straight line extending in the horizontal direction. The direction perpendicular to the axes r1 and r2 and perpendicular to the horizontal direction is defined as the vertical direction Z1.

[0053] The drive rotor 20 and the driven rotor 21 are formed in a bilobal shape in cross section when cut in the radial direction B. The drive rotor 20 has two lobe teeth 20a and valley teeth 20b. The valley teeth 20b are formed between the lobe teeth 20a. The driven rotor 21 has two lobe teeth 21a and valley teeth 21b. The valley teeth 21b are formed between the lobe teeth 21a.

[0054] The drive rotor 20 and the driven rotor 21 rotate in the working chamber 25 while repeatedly meshing the lobe teeth 20a of the drive rotor 20 with the valley teeth 21b of the driven rotor 21 and the valley teeth 20b of the drive rotor 20 with the lobe teeth 21a of the driven rotor 21. The drive rotor 20 rotates in a first rotation direction C of the drive shaft 16. The driven rotor 21 rotates in a second rotation direction D of the driven shaft 17. The drive rotor 20 and the driven rotor 21 rotate synchronously with the drive shaft 16 and the driven shaft 17.

[0055] The rotor housing 14 has an intake port 45 and a discharge port 46. The intake port 45 and the discharge port 46 communicate between the working chamber 25 and the outside. The intake port 45 and the discharge port 46 are formed in opposing positions on the peripheral wall 14b of the rotor housing 14 with the working chamber 25 in between. The intake port 45 is an inlet for drawing hydrogen off-gas as a fluid into the working chamber 25. The discharge port 46 is an outlet for discharging hydrogen drawn into the working chamber 25 to the outside.

[0056] As shown in Figs. 1 and 2, when the drive shaft 16 is rotated by the drive of the motor 22, the driven shaft 17 rotates in the opposite direction to the drive shaft 16 through the gear connection of the drive gear 18 and the driven gear 19 which are meshed with each other. As a result, the drive rotor 20 and the driven rotor 21 rotate in the opposite directions while meshing with each other. In the Roots pump 10, hydrogen is sucked into the working chamber 25 through the intake port 45 and discharged from the working chamber 25 through the discharge port 46 by the rotation of the drive rotor 20 and the driven rotor 21. That is, the operating unit 120 sucks in and discharges hydrogen off-gas. The power transmission unit 110 transmits the power of the rotating shaft to the operating unit 120.

[0057] <Flow section configuration> As shown in Figs. 1 and 3, the Roots pump 10 includes a flow section 30 that causes oil stirred by the rotation of the drive gear 18 and the driven gear 19 to flow to the second bearing Br2 and the third bearing Br3. The flow section 30 has an oil catch tank 31. The oil catch tank 31 is formed in the housing 11. The oil catch tank 31 is formed in the rotor housing 14. The oil catch tank 31 is disposed above the second bearing accommodating recess 27a and the third bearing accommodating recess 28a in the vertical direction Z1. The oil catch tank 31 is disposed so as to overlap a portion of the second through hole 27 in the vertical direction Z1. The oil catch tank 31 is disposed so as to overlap the entire third through hole 28 in the vertical direction Z1.

[0058] The oil catch tank 31 is formed by partially recessing an outer surface 14c of the end wall 14a toward the working chamber 25. The oil catch tank 31 is a part of the power transmission chamber 24. The power transmission chamber 24 includes the oil catch tank 31.

[0059] 3, the flow portion 30 has two communication holes 32. The two communication holes 32 are formed in the housing 11. The two communication holes 32 are formed in the rotor housing 14.

[0060] One communication hole 32 communicates between the oil catch tank 31 and the second through hole 27. One communication hole 32 extends in a straight line from the oil catch tank 31 to the second through hole 27. One communication hole 32 opens to the opening surface S2 of the second bearing accommodating recess 27a.

[0061] The remaining communication hole 32 communicates between the oil catch tank 31 and the third through hole 28. The remaining communication hole 32 extends linearly from the oil catch tank 31 to the third through hole 28. The remaining communication hole 32 opens to the opening surface S3 of the third bearing accommodating recess 28a.

[0062] <Breather passage configuration> As shown in Fig. 3, the Roots pump 10 includes a breather passage 40 that releases pressure in the power transmission chamber 24 to the outside of the housing 11. The breather passage 40 is formed in the housing 11. The breather passage 40 is disposed above the second through-hole 27 in the vertical direction Z1. The breather passage 40 is disposed adjacent to the oil catch tank 31. The breather passage 40 has a first passage 41 and a second passage 42. The first passage 41 and the second passage 42 are formed in the rotor housing 14.

[0063] The first passage 41 is a circular hole. The first passage 41 communicates with the oil catch tank 31. The first passage 41 opens to the side of the oil catch tank 31. An opening 41a of the first passage 41 to the oil catch tank 31 is located above the openings 32a of each communication hole 32 to the oil catch tank 31 in the vertical direction Z1. The first passage 41 is located above the second through hole 27 in the vertical direction Z1. The first passage 41 extends linearly upward in the vertical direction Z1 as it moves away from the opening 41a. The first passage 41 is inclined with respect to the vertical direction Z1. The direction in which the first passage 41 extends from the power transmission chamber 24 is defined as an extension direction E.

[0064] The second passage 42 is a circular hole. The second passage 42 is continuous with the first passage 41. The second passage 42 extends in the vertical direction Z1. The second passage 42 opens to the upper side of the rotor housing 14 in the vertical direction Z1. A fitting groove 14d is formed on the upper side of the rotor housing 14 in the vertical direction Z1. The second passage 42 opens to the bottom of the fitting groove 14d.

[0065] The Roots pump 10 includes a case 90. The case 90 is provided outside the housing 11. The case 90 is provided above the rotor housing 14 in the vertical direction Z1. The case 90 is fitted into the fitting groove 14d. The case 90 has a pressure release passage 91 that communicates with the second passage 42. The pressure release passage 91 opens to a side of the case 90. A vent 92 is provided at an opening 91a at the side of the case 90 in the pressure release passage 91. The vent 92 is a ventilation membrane that allows gas to pass but does not allow liquid to pass through. The pressure release passage 91 is a part of the breather passage 40. The breather passage 40 is composed of the first passage 41, the second passage 42, and the pressure release passage 91. The case 90 constitutes a part of the breather passage 40. The breather passage 40 communicates between the power transmission chamber 24 and the outside of the housing 11.

[0066] A gasket 80 is provided at the bottom of the fitting groove 14d. The gap between the case 90 and the housing 11 is sealed by the gasket 80. A through hole 80a is formed in the gasket 80. The second passage 42 and the pressure release passage 91 communicate with each other through the through hole 80a.

[0067] As shown in Fig. 4, the second passage 42 has a small diameter passage 42a and a large diameter passage 42b. The first passage 41 opens into a partition surface 42d that divides the small diameter passage 42a. The small diameter passage 42a and the first passage 41 intersect with each other. The first passage 41 and the small diameter passage 42a form a bent portion of the breather passage 40. The first passage 41 and the small diameter passage 42a form a bent portion 43 of the breather passage 40. Therefore, the breather passage 40 has the bent portion 43.

[0068] The lower side of the partition surface 42d in the vertical direction Z1 is a tapered surface 42e that gradually reduces in diameter as it goes downward in the vertical direction Z1. The partition surface 42d is provided with a recess 42f. The recess 42f is formed by recessing a part of the partition surface 42d. The recess 42f is provided at a position facing the first passage 41 in the extension direction E. The partition surface 42d is a partition surface that defines the bent portion 43.

[0069] The diameter of the large diameter passage 42b is larger than the diameter of the small diameter passage 42a. The small diameter passage 42a opens to a bottom surface 42c of the large diameter passage 42b. The bottom surface 42c of the large diameter passage 42b is an annular surface. The large diameter passage 42b opens to the bottom of the fitting groove 14d.

[0070] As shown in Figures 4 and 5, the diameter of the large diameter passage 42b is larger than the diameter of the through hole 80a of the gasket 80. The axis of the large diameter passage 42b and the axis of the through hole 80a are aligned. The gasket 80 has a portion that extends to the inside of the large diameter passage 42b. The portion of the gasket 80 that extends to the inside of the large diameter passage 42b is called the extension portion 80b. The extension portion 80b is annular. The extension portion 80b is a part of the gasket 80 that overlaps with the breather passage 40.

[0071] 4, a mesh 60 is provided in the breather passage 40. The mesh 60 is a member formed by weaving metal fibers into a mesh shape. The mesh 60 has a size that can break up foamy oil Ob and allows gas to pass through.

[0072] The mesh 60 is provided in the large diameter passage 42b. That is, the mesh 60 is provided in the breather passage 40 between the bent portion 43 and the case 90. The mesh 60 is placed on the bottom surface 42c of the large diameter passage 42b. The mesh 60 is in contact with the extension portion 80b of the gasket 80. The mesh 60 is sandwiched between the extension portion 80b and the bottom surface 42c of the large diameter passage 42b. The movement of the mesh 60 toward the case 90 side is restricted by the extension portion 80b. The movement of the mesh 60 toward the bent portion 43 side is restricted by the bottom surface 42c of the large diameter passage 42b. That is, the breather passage 40 is provided with the bottom surface 42c as a restricting portion that sandwiches the mesh 60 with the extension portion 80b and restricts the movement of the mesh 60 toward the bent portion 43 side. The mesh 60 may be provided in the small diameter passage 42a. In other words, it is sufficient that the mesh 60 is provided in the breather passage 40 between the bent portion 43 and the case 90 .

[0073] <Configuration of Oil Return Passage and Second Through Hole> The Roots pump 10 includes an oil return passage 50 for returning the oil in the bent portion 43 to the second through hole 27. The oil return passage 50 is formed in the housing 11. The oil return passage 50 is formed in the rotor housing 14. The oil return passage 50 is a circular hole. The oil return passage 50 extends in the vertical direction Z1. The oil return passage 50 connects the small diameter passage 42a and the second through hole 27. The oil return passage 50 opens below the small diameter passage 42a in the vertical direction Z1. The surface defining the oil return passage 50 is continuous with the tapered surface 42e of the small diameter passage 42a. The oil return passage 50 opens to the opening surface S2 of the second bearing accommodating recess 27a. That is, the oil return passage 50 that is connected to the bent portion 43 and is connected to the vicinity of the second bearing Br2 in the second through hole 27 is connected.

[0074] The oil return passage 50 has an opening 50a that opens to the inner surface 27c. The oil return passage 50 extends from the opening 50a toward the upper side in the vertical direction Z1. The oil return passage 50 extends from the opening 50a toward the mesh 60. That is, the oil return passage 50 opens toward the mesh 60 with respect to the inner surface 27c.

[0075] The inner surface 27c of the second through hole 27 has an arc surface 271 and an expanding arc surface 272. The arc surface 271 is a surface passing through an imaginary circle Vc drawn with a radius L1 centered on the axis r1 of the drive shaft 16. The expanding arc surface 272 has a distance L2 from the axis r1 of the drive shaft 16 gradually decreasing as it moves from the opening 50a toward the first rotation direction C. The arc surface 271 is a surface connecting a portion of the opening 50a opposite to the first rotation direction C and the expanding arc surface 272. The distance L2 is largest at a position adjacent to the opening 50a. The distance L2 is smallest at a position advanced by a predetermined angle from the opening 50a toward the first rotation direction C. The smallest value of the distance L2 is the same value as the radius L1. That is, the magnitude of the distance L2 is equal to or larger than the radius L1. The expanding arc surface 272 is a surface away from the imaginary circle Vc toward the outside in the radial direction B. In other words, the diameter expansion arc surface 272 is a surface that is located farther away from the drive shaft 16 than the circular arc surface 271 is.

[0076] The oil returned from the oil return passage 50 to the second through hole 27 flows in the first rotation direction C due to the rotation of the drive shaft 16. On the inner surface 27c, the direction in which the oil flows in the first rotation direction C of the drive shaft 16 is defined as a flow direction F. In the flow direction F, the side of the expanding diameter arc surface 272 with respect to the opening 50a is defined as the upstream side of the flow direction F, and the side opposite the expanding diameter arc surface 272 with respect to the opening 50a is defined as the downstream side of the flow direction F. The space between the inner surface 27c and the drive shaft 16 is narrower on the downstream side of the flow direction F with respect to the opening 50a than on the upstream side of the flow direction F.

[0077] <Blade 70 Configuration> As shown in Fig. 1, the Roots pump 10 includes a blade 70 that draws oil that has lubricated the second bearing Br2 and the third bearing Br3 toward the power transmission chamber 24. The Roots pump 10 includes two blades 70. The two blades 70 are plate-shaped and have a thickness in the axial direction A. One blade 70 is disposed between the drive gear 18 and the second bearing Br2 in the axial direction A. The remaining blade 70 is disposed between the driven gear 19 and the third bearing Br3 in the axial direction A.

[0078] 6, each of the bearings Br2 and Br3 has an outer ring 81, an inner ring 82, and a plurality of rolling elements 83. The plurality of rolling elements 83 are disposed between the outer ring 81 and the inner ring 82. In a state in which the plurality of rolling elements 83 are disposed between the outer ring 81 and the inner ring 82, an internal space Sp is formed between the outer ring 81 and the inner ring 82.

[0079] The blade 70 has an insertion portion 71 and a protruding portion 72. The insertion portion 71 is annular. The insertion portion 71 has an insertion hole 71a. The drive shaft 16 is inserted through the insertion hole 71a of one of the blades 70. The driven shaft 17 is inserted through the insertion hole 71a of the remaining blades 70. The diameter of the insertion hole 71a of one of the blades 70 is the same as the diameter of the drive shaft 16. The diameter of the insertion hole 71a of the remaining blades 70 is the same as the diameter of the driven shaft 17. The outer diameter R1 of the inner ring 82 is larger than the outer diameter R2 of the insertion portion 71.

[0080] The protruding portion 72 protrudes outward from the insertion portion 71 in the radial direction B. The tip of the protruding portion 72 faces the internal space Sp in the axial direction A. A distance R3 from the axes r1, r2 to the tip of the protruding portion 72 is smaller than a radius R4 of the outer ring 81. In other words, the protruding portion 72 does not contact the outer ring 81.

[0081] As shown in Fig. 1, one blade 70 is sandwiched between the drive gear 18 and the inner ring 82 of the second bearing Br2, and thus rotates integrally with the drive shaft 16. The remaining blade 70 is sandwiched between the driven gear 19 and the inner ring 82 of the third bearing Br3, and thus rotates integrally with the driven shaft 17. Thus, the blade 70 rotates integrally with the rotating shaft. The blade 70 may be press-fitted and fixed to the rotating shaft by making the diameter of the insertion hole 71a smaller than the diameter of each of the drive shaft 16 and the driven shaft 17. In this manner, the blade 70 still rotates integrally with the rotating shaft.

[0082] <Configuration of the driving gear 18 and the driven gear 19> As shown in Fig. 1, the Roots pump 10 has a structure for creating an oil flow within the housing 11. The structure is provided on a drive gear 18 and a driven gear 19. The drive gear 18 has a first end face 18a and a second end face 18b. The first end face 18a faces the second bearing Br2 in the axial direction A. The second end face 18b is located on the opposite side to the first end face 18a in the axial direction A.

[0083] 7, the drive gear 18 has three flow holes 18c. The flow holes 18c are arranged at predetermined intervals in the first rotation direction C of the drive gear 18. The distance between each flow hole 18c and the axis r1 is greater than the distance R3. That is, each flow hole 18c does not overlap with the protruding portion 72 of the blade 70 in the axial direction A.

[0084] 7 and 8, each flow hole 18c penetrates the drive gear 18. Each flow hole 18c extends in a direction opposite to the first rotation direction C while intersecting the axial direction A from the first end face 18a toward the second end face 18b.

[0085] 1, the driven gear 19 has a first end face 19a and a second end face 19b. The first end face 19a faces the third bearing Br3 in the axial direction A. The second end face 19b is located on the opposite side to the first end face 19a in the axial direction A.

[0086] 9, the driven gear 19 has three flow holes 19c. The flow holes 19c are arranged at predetermined intervals in the second rotation direction D of the driven gear 19. The distance between each flow hole 19c and the axis r2 is greater than the distance R3. That is, each flow hole 19c does not overlap with the protruding portion 72 of the blade 70 in the axial direction A.

[0087] 9 and 10, each flow hole 19c penetrates the driven gear 19. Each flow hole 19c extends in a direction opposite to the second rotation direction D while intersecting the axial direction A from the first end face 19a toward the second end face 19b.

[0088] <Action of this embodiment> The operation of this embodiment will now be described. The oil contained in the power transmission chamber 24 is stirred by the rotation of the drive gear 18 and the driven gear 19. The stirred oil flows into the oil catch tank 31 from the outer surface 14c of the end wall 14a. The oil is then stored in the oil catch tank 31. A portion of the oil stored in the oil catch tank 31 is drawn into the opening surface S2 through one of the communication holes 32. The oil drawn into the opening surface S2 lubricates the second bearing Br2. A portion of the oil stored in the oil catch tank 31 is drawn into the opening surface S3 through the remaining communication hole 32. The oil drawn into the opening surface S3 lubricates the third bearing Br3.

[0089] The rotation of the drive gear 18 and the driven gear 19 causes oil to splash in the power transmission chamber 24. This generates oil bubbles Ob in the power transmission chamber 24, a mixture of air and oil. Furthermore, as the drive gear 18 and the driven gear 19 continue to rotate, the temperature of the power transmission chamber 24 increases, causing part of the oil to turn into steam. This generates gas containing oil bubbles Ob and steam in the power transmission chamber 24. That is, gas containing oil is generated in the power transmission chamber 24. The pressure in the power transmission chamber 24 increases as a result of the generation of gas containing oil. The pressure in the power transmission chamber 24 becomes higher than the atmospheric pressure outside the housing 11. Due to the pressure difference between the power transmission chamber 24 and the outside of the housing 11, the gas containing oil tries to escape to the outside of the housing 11 through the breather passage 40.

[0090] As shown in FIG. 4, the gas containing oil enters the oil catch tank 31. The gas containing oil that has entered the oil catch tank 31 flows into the breather passage 40. The gas containing oil discharged from the power transmission chamber 24 passes through the first passage 41 and reaches the small diameter passage 42a. When the gas containing oil reaches the bent portion 43, the gas containing oil collides with the partition surface 42d. More specifically, the gas containing oil discharged from the power transmission chamber 24 directly collides with the recessed portion 42f. The oil in the form of bubbles Ob is separated into oil and gas by colliding with the partition surface 42d. The gas containing oil also stagnates inside the recessed portion 42f. Then, the gas containing oil is separated into oil and gas to the extent that the gas stagnates inside the recessed portion 42f. As a result, the gas containing oil is separated into oil and gas at the bent portion 43. Even if the gas containing oil contains bubbles of oil Ob, the bubbles of oil Ob are broken down at the bent portion 43.

[0091] Even if a small amount of oil bubbles Ob remain in the gas containing oil at the bent portion 43, the oil bubbles Ob are broken down by the mesh 60 within the breather passage 40. 3, the gas separated by the bent portion 43 and the mesh 60 contains oil vapor. The oil vapor flows into the pressure release passage 91. Since the case 90 is cooled outside the housing 11, the oil vapor is cooled inside the case 90 and liquefied.

[0092] The gas separated from the oil-containing gas by the bent portion 43, the mesh 60, and the case 90 is released to the outside of the housing 11 through the vent 92. That is, the gas separated from the oil-containing gas is released to the outside of the housing 11 through the breather passage 40. Therefore, the pressure in the power transmission chamber 24 is released to the outside of the housing 11 through the breather passage 40.

[0093] The oil separated by the bent portion 43 and the mesh 60 and the oil liquefied inside the case 90 flow by gravity along the surface that defines the breather passage 40 and reach the oil return passage 50. The oil that reaches the oil return passage 50 is drawn into the second through hole 27 by the rotation of the drive shaft 16. That is, the oil that reaches the oil return passage 50 is drawn into the second bearing Br2. The oil drawn into the second through hole 27 is returned to the power transmission chamber 24 while lubricating the second bearing Br2.

[0094] The oil drawn into each of the bearings Br2 and Br3 enters the internal space Sp of each of the bearings Br2 and Br3. This lubricates each of the bearings Br2 and Br3. After lubricating each of the bearings Br2 and Br3, the oil reaches the protruding portion 72 of the blade 70.

[0095] The blade 70 rotates integrally with the drive shaft 16 and the driven shaft 17. The oil that reaches the protrusion 72 is thrown outward in the radial direction B from the tip of the protrusion 72 by centrifugal force. When the oil is thrown outward in the radial direction B by the protrusion 72, the oil in the internal space Sp of each of the bearings Br2, Br3 is drawn into the blade 70. That is, the blade 70 draws out the oil in the internal space Sp of each of the bearings Br2, Br3 toward the power transmission chamber 24. Therefore, the oil does not stagnate in the internal space Sp of each of the bearings Br2, Br3.

[0096] The oil drawn into the bearings Br2, Br3 lubricates the bearings Br2, Br3, and then is returned toward the drive gear 18 and the driven gear 19. 7, the oil that has reached the first end face 18a flows along a surface that defines the flow hole 18c and is located in the opposite direction to the first rotation direction C toward the second end face 18b as the drive gear 18 rotates. Therefore, the stirred oil flows through the oil catch tank 31, one communication hole 32, and the second through hole 27 in this order, and then flows through the flow hole 18c in the axial direction A in a direction away from the second bearing Br2.

[0097] 9, the oil that has reached the first end face 19a flows along a surface that defines the flow hole 19c and is located in the opposite direction to the second rotation direction D toward the second end face 19b as the driven gear 19 rotates. Therefore, the stirred oil flows through the oil catch tank 31, the remaining communication holes 32, and the third through hole 28 in this order, and then flows through the flow hole 19c in the axial direction A in a direction away from the third bearing Br3.

[0098] In other words, a part of the surface defining the flow holes 18c, 19c guides the oil that has reached the first end surface 18a, 19a toward the second end surface 18b, 19b as the drive gear 18 or the driven gear 19 rotates. Thus, the oil returned toward the drive gear 18 and the driven gear 19 flows through the flow holes 18c, 19c. Thus, the flow holes 18c, 19c create oil flows among the oil catch tank 31, the communication holes 32, and the through holes 27, 28.

[0099] <Effects of this embodiment> The effects of this embodiment will be described. (1) Even if oil foam Ob is contained in the gas containing oil discharged from the power transmission chamber 24, the oil foam Ob is broken down at the bent portion 43. The gas separated from the gas containing oil is discharged to the outside of the housing 11 via the breather passage 40. Therefore, it is possible to prevent the oil foam Ob from being discharged from the breather passage 40 to the outside of the housing 11.

[0100] (2) The inner surface 27c of the second through hole 27 has a circular arc surface 271 and an expanding arc surface 272. Therefore, the oil drawn from the oil return passage 50 to the second bearing Br2 is likely to flow to the upstream side of the oil flow direction F with respect to the opening 50a of the oil return passage 50 in the space between the inner surface 27c and the drive shaft 16. That is, the flow of oil can be rectified so that the oil flow direction F is the first rotation direction C of the drive shaft 16 inside the second through hole 27. Therefore, the oil drawn from the oil return passage 50 to the second bearing Br2 flows smoothly without stagnation inside the second through hole 27. Then, the oil flowing without stagnation inside the second through hole 27 is smoothly returned to the power transmission chamber 24. Therefore, it is easy to create a flow of oil between the bent portion 43, the oil return passage 50, the second through hole 27, and the power transmission chamber 24, so that the accumulation of oil in the bent portion 43 can be suppressed.

[0101] (3) The gas containing oil discharged from the power transmission chamber 24 stagnates inside the recess 42f. Then, the gas containing oil is accommodated in the recess 42f, so that the foamy oil Ob is less likely to flow downstream of the breather passage 40. Then, the foamy oil Ob accommodated in the recess 42f is more likely to separate into oil and gas inside the recess 42f. Therefore, not only is the oil and gas separated by colliding the gas containing oil against the partition surface 42d, but the separation of the oil and gas due to the stagnation of the gas containing oil inside the recess 42f can be promoted. Therefore, the gas containing oil is more likely to separate into oil and gas, so that the release of the foamy oil Ob from the breather passage 40 to the outside of the housing 11 can be more effectively suppressed.

[0102] (4) The mesh 60 breaks down the foamed oil Ob in the breather passage 40. This makes it possible to further prevent the foamed oil Ob from being discharged from the breather passage 40 to the outside of the housing 11.

[0103] If the gas separated by the mesh 60 is oil vapor, it is cooled and liquefied inside the case 90. Then, like the oil separated by the mesh 60, it is returned to the power transmission chamber 24 via the oil return passage 50 and the second through hole 27. Even if the oil vapor liquefies near the vent 92, the liquefied oil does not pass through the vent 92. Therefore, the configuration of the vent 92, the case 90, and the mesh 60 improves the oil sealing performance of the Roots pump 10.

[0104] (5) For example, a configuration is conceivable in which the mesh 60 is disposed between the case 90 and the housing 11, and the case 90 and the housing 11 are fastened together with bolts. When this configuration is adopted, stress is locally concentrated on the mesh 60. It is conceivable to increase the strength of the mesh 60 by increasing its weight so that the mesh 60 can withstand the stress. However, the mesh 60 only needs to have the function of defoaming the foamy oil Ob, and excessive strength is not required.

[0105] In this regard, in the present embodiment, the mesh 60 is fixed in the breather passage 40 by being sandwiched between the gasket 80 and the bottom surface 42c of the large diameter passage 42b. Since no bolts are used to fix the mesh 60, there is no need to provide the mesh 60 with excessive strength. Therefore, there is no need to increase the weight of the mesh 60 in order to increase its strength.

[0106] Moreover, the extension 80b, which is a part of the gasket 80, is used to fix the mesh 60. The gasket 80 serves both to ensure the seal between the case 90 and the housing 11 and to fix the mesh 60. Therefore, compared to the case where a separate member having the function of fixing the mesh 60 is used, the fixing structure of the mesh 60 can be simplified.

[0107] (6) The oil return passage 50 opens toward the mesh 60 with respect to the inner surface 27c of the second through hole 27. Therefore, the oil separated by the mesh 60 easily flows into the oil return passage 50. As a result, oil is less likely to accumulate in the bent portion 43.

[0108] (7) When the oil is splashed outward in the radial direction B by the protrusion 72, the oil in the internal space Sp of each of the bearings Br2, Br3 is drawn into the blade 70. That is, the oil in the internal space Sp of each of the bearings Br2, Br3 is drawn toward the power transmission chamber 24 by the blade 70. Therefore, the flow of the oil drawn into each of the bearings Br2, Br3 is promoted, and the oil can be returned to the power transmission chamber 24 smoothly.

[0109] (8) The driving gear 18 has a flow hole 18c, and the driven gear 19 has a flow hole 19c. The stirred oil flows through the oil catch tank 31, one communication hole 32, and second through hole 27 in this order, and then flows through the flow hole 18c in a direction away from the second bearing Br2 in the axial direction A. For this reason, an oil flow can be created such that the oil flows through the oil catch tank 31, one communication hole 32, second through hole 27, and flow hole 18c in this order.

[0110] The stirred oil flows through the oil catch tank 31, the remaining communication holes 32, and the third through hole 28 in that order, and then flows through the flow hole 19c in a direction away from the third bearing Br3 in the axial direction A. For this reason, an oil flow can be created in which the oil flows through the oil catch tank 31, the remaining communication holes 32, the third through hole 28, and the flow hole 19c in that order.

[0111] This prevents the oil from stagnating in the oil catch tank 31, thereby preventing the oil level from rising in the oil catch tank 31. This prevents the oil level in the oil catch tank 31 from reaching the breather passage 40.

[0112] (9) In recent years, the demand for fuel cell vehicles has been increasing, and for example, consideration is being given to installing fuel cell systems in commercial vehicles such as buses and trucks. In consideration of the usage environment of commercial vehicles such as buses and trucks, there is a demand for extending the life of auxiliary parts installed in fuel cell vehicles.

[0113] The breather passage 40 allows the pressure in the power transmission chamber 24 to be released to the outside of the housing 11. This suppresses an increase in pressure acting on each of the seal members Se1, Se2, Se3. In other words, the seal members Se1, Se2 are prevented from being pressed excessively against the drive shaft 16, and the third seal member Se3 is prevented from being pressed excessively against the driven shaft 17. This suppresses excessive wear of the seal members Se1, Se2, Se3, thereby achieving a longer life for each of the seal members Se1, Se2, Se3. As a result, a longer life for the Roots pump 10 can be achieved.

[0114] (10) Lubrication of the bearings Br2, Br3 is promoted by the flow portion 30 and the oil return passage 50. This extends the life of the bearings Br2, Br3, thereby extending the life of the Roots pump 10.

[0115] <Example of change> The present embodiment can be modified as follows: The present embodiment and the following modified examples can be combined with each other to the extent that there is no technical contradiction.

[0116] The number of the flow holes 18c, 19c may be one or two, or may be four or more. The drive gear 18 does not necessarily have to have the flow hole 18c. The driven gear 19 does not necessarily have to have the flow hole 19c.

[0117] The oil catch tank 31 and the two communication holes 32 may be omitted from the rotor housing 14. In this case, the opening 41a of the first passage 41 of the breather passage 40 may be provided on the outer surface 14c of the end wall 14a of the rotor housing 14.

[0118] When the blade 70 is press-fitted to the drive shaft 16, the blade 70 does not need to be in contact with the drive gear 18 and the second bearing Br2. When the blade 70 is press-fitted to the driven shaft 17, the blade 70 does not need to be in contact with the driven gear 19 and the third bearing Br3.

[0119] When adopting a configuration in which the blade 70 does not contact the driving gear 18 or the driven gear 19, the distance R3 may be larger than the radius R4 of the outer ring 81. The number of protrusions 72 on the blade 70 may be two or more.

[0120] The blade 70 of the Roots pump 10 may be omitted. The oil return passage 50 may extend in a direction intersecting the vertical direction Z1. That is, the oil return passage 50 does not have to extend from the opening 50a toward the mesh 60. In other words, the oil return passage 50 does not have to open toward the mesh 60 from the inner surface 27c.

[0121] The diameter of the through hole 80a may be larger than the diameter of the large diameter passage 42b. In this case, the gasket 80 may have a long plate-shaped extension portion 80b that extends from the inner circumferential surface of the through hole 80a to the inside of the large diameter passage 42b.

[0122] The extension 80b of the gasket 80 may be omitted. In other words, it is sufficient that the gasket 80 has the function of sealing between the case 90 and the housing 11. In this case, it is preferable to newly form a structure that restricts movement of the mesh 60 towards the case 90 on the cylindrical surface that defines the large diameter passage 42b, excluding the bottom surface 42c.

[0123] The extension portion 80b may be omitted. In this case, the mesh 60 may be press-fitted into the cylindrical surface that defines the large diameter passage 42b, excluding the bottom surface 42c. The bottom surface 42c of the large diameter passage 42b does not have to be an annular surface. As long as the bottom surface 42c of the large diameter passage 42b can restrict the movement of the mesh 60 toward the bent portion 43, the shape of the bottom surface 42c of the large diameter passage 42b may be changed as appropriate.

[0124] The diameter of the large diameter passage 42b and the diameter of the small diameter passage 42a may be the same. In this case, a plate-shaped protruding plate protruding from the inner surface that defines the second passage 42 may be newly added, and the mesh 60 may be placed on the protruding plate. In this modification, the protruding plate is a restricting portion that restricts the movement of the mesh 60 toward the bent portion 43.

[0125] In the case of such a modification, the mesh 60 may be press-fitted and fixed to the inner surface that defines the second passage . Mesh 60 may be omitted.

[0126] The case 90 may be omitted. The fitting groove 14d of the rotor housing 14 may also be omitted. In such a modification, the breather passage 40 is composed of the first passage 41 and the second passage 42. Also, a vent 92 may be provided at the opening of the large diameter passage 42b to the rotor housing 14. It is sufficient that the breather passage 40 is formed at least in the housing 11.

[0127] Instead of the recess 42f, a plate-shaped partition wall protruding from the partition surface 42d may be provided on the partition surface 42d. The partition wall may be disposed slightly above the position on the partition surface 42d that faces the first passage 41 in the extension direction E. Even with this modification, the oil-containing gas can be stagnated below the partition wall. This can promote separation of the oil and the gas due to the length of residence time of the oil-containing gas.

[0128] The recess 42f provided in the partition surface 42d may be omitted. The space between the inner surface 27c and the drive shaft 16 does not have to be narrower on the downstream side in the flow direction F than on the upstream side in the flow direction F with respect to the opening 50a of the oil return passage 50. Specifically, the inner surface 27c of the second through hole 27 may be formed only by the arc surface 271, without the expanding arc surface 272.

[0129] The second bearing Br2 may be in contact with the bottom of the second bearing accommodating recess 27a. In this case, the oil return passage 50 or one communication hole 32 may be connected to a portion of the inner surface 27c of the second bearing accommodating recess 27a that is not in contact with the second bearing Br2. In this modification, the portion of the inner surface 27c that is not in contact with the second bearing Br2 is a portion of the through hole near the bearing.

[0130] The breather passage 40 may be disposed above the third through hole 28 in the vertical direction Z1. The oil catch tank 31 may be modified in shape so as to overlap a part of the third through hole 28 in the vertical direction Z1 and to overlap the entire second through hole 27 in the vertical direction Z1. The breather passage 40 may be disposed above the third through hole 28 in the vertical direction Z1. Even in this modification, the first passage 41 opens to the side of the oil catch tank 31. The oil return passage 50 may connect the small diameter passage 42a and the third through hole 28. The opening 50a of the oil return passage 50 in this modification may open to the opening surface S3 of the third through hole 28.

[0131] Also, the third bearing Br3 may be in contact with the bottom of the third bearing accommodating recess 28a. In this case, it is preferable to connect the oil return passage 50 or the remaining communication hole 32 to a portion of the inner surface 28c of the third bearing accommodating recess 28a that is not in contact with the third bearing Br3. In such a modification, the portion of the inner surface 28c that is not in contact with the third bearing Br3 is a portion of the through hole near the bearing.

[0132] In the above modified example, when the oil return passage 50 is connected to the third through hole 28, the inner surface 28c of the third through hole 28 may have the same structure as the inner surface 27c of the present embodiment. Specific examples will be described below.

[0133] The opening 50a of the oil return passage 50 is formed on the inner surface 28c. The inner surface 28c may have an arcuate surface 271 and an expanding arcuate surface 272. The expanding arcuate surface 272 of the inner surface 28c is a surface that extends from the opening 50a that opens on the inner surface 28c toward the second rotation direction D. The arcuate surface 271 of the inner surface 28c is a surface that connects a portion of the opening 50a of the inner surface 28c on the opposite side to the second rotation direction D and the expanding arcuate surface 272 of the inner surface 28c.

[0134] The oil catch tank 31 may be formed on the inner surface 13c of the end wall 13a of the gear housing 13. In this case, one of the communication holes 32 may communicate between the oil catch tank 31 and the first through hole 26. One of the communication holes 32 may communicate with the opening surface S1 of the first through hole 26. The remaining communication holes 32 may communicate between the oil catch tank 31 and the inner circumferential surface of the fourth bearing accommodating recess 29. When the remaining communication holes 32 are communicated with the inner circumferential surface of the fourth bearing accommodating recess 29, a portion of the inner circumferential surface that does not come into contact with the fourth bearing Br4 may be formed. Then, the remaining communication holes 32 may communicate with the portion of the inner circumferential surface that does not come into contact with the fourth bearing Br4.

[0135] In this modified example, the first passage 41 and the second passage 42 are formed in the gear housing 13. The second passage 42 opens to the upper side of the gear housing 13 in the vertical direction Z1. A fitting groove 14d is formed on the upper side of the gear housing 13 in the vertical direction Z1. The second passage 42 opens to the bottom of the fitting groove 14d. The case 90 is modified to be provided in the gear housing 13. That is, the breather passage 40 may be disposed above the first through hole 26 in the vertical direction Z1. The oil return passage 50 may connect the small diameter passage 42a and the first through hole 26. The opening 50a of the oil return passage 50 in this modified example may open to the opening surface S1 of the first through hole 26.

[0136] Also, the first bearing Br1 may be in contact with the bottom of the first bearing accommodating recess 26a. In this case, the oil return passage 50 may be connected to a portion of the inner surface 26c of the first bearing accommodating recess 26a that is not in contact with the first bearing Br1. In such a modification, the portion of the inner surface 26c that is not in contact with the first bearing Br1 is a portion of the through hole near the bearing. Note that in this modification, the inner surface 26c may have a circular arc surface 271 and an expanding diameter arc surface 272, similar to the inner surface 27c.

[0137] In this embodiment, for example, the first passage 41 may be formed to straddle both the rotor housing 14 and the gear housing 13, and the second passage 42 may be formed in the gear housing 13. Alternatively, the first passage 41 may be formed in the rotor housing 14, and the second passage 42 may be formed to straddle both the rotor housing 14 and the gear housing 13. Even in this modification, it is sufficient that the breather passage 40 has a bent portion 43 formed by the first passage 41 and the small diameter passage 42a. When making this modification, it is preferable to provide the fitting groove 14d and the case 90 on the upper side of the gear housing 13 in the vertical direction Z1.

[0138] In the above modification, it is assumed that the oil catch tank 31 is formed in the gear housing 13. For example, the first passage 41 may be formed to straddle both the rotor housing 14 and the gear housing 13, and the second passage 42 may be formed in the rotor housing 14. Alternatively, the first passage 41 may be formed in the gear housing 13, and the second passage 42 may be formed to straddle both the rotor housing 14 and the gear housing 13. Even in this modification, it is sufficient that the breather passage 40 has a bent portion 43 formed by the first passage 41 and the small diameter passage 42a. In addition, when this modification is made, it is preferable to provide the fitting groove 14d and the case 90 on the upper side of the rotor housing 14 in the vertical direction Z1.

[0139] In the above modified example, if the first passage 41 is formed in the gear housing 13 and the oil catch tank 31 is not formed in the gear housing 13, the first passage 41 may be opened to the inner surface 13c of the end wall 13a of the gear housing 13.

[0140] In this embodiment, the cross section of the drive rotor 20 and the driven rotor 21 taken in the radial direction B may be trilobal or quadrilobal. In this embodiment, the drive rotor 20 and the driven rotor 21 may have, for example, a helical shape.

[0141] The bearings Br, Br1, Br2, Br3, and Br4 are not limited to ball bearings and may be, for example, sliding bearings. In this embodiment, the Roots pump 10 does not have to be a hydrogen pump for a fuel cell vehicle that supplies hydrogen to a fuel cell, and may be used for other purposes. [Explanation of symbols]

[0142] 10...Roots pump, 11...housing, 16...drive shaft, 17...driven shaft, 18...drive gear, 18a...first end face, 18b...second end face, 18c...flow hole, 19...driven gear, 19a...first end face, 19b...second end face, 19c...flow hole, 20...drive rotor, 21...driven rotor, 22...motor, 23...motor chamber, 24...power transmission chamber, 25...operating chamber, 26...first through hole, 26c...inner surface, 27...second through hole, 27c...inner surface, 28...third through hole, 28c...inner surface, 31...oil catch tank, 32...communication hole, 40...breather passage, 42c...bottom surface, 42d...partition surface, 42f...recess, 43...bent portion , 50...oil return passage, 60...mesh, 70...blade, 71...insertion portion, 71a...insertion hole, 72...protrusion, 80...gasket, 80b...extension, 81...outer ring, 82...inner ring, 83...rolling element, 90...case, 92...vent, 110...power transmission portion, 120...actuating portion, Br1...first bearing, Br2...second bearing, Br3...third bearing, Sp...internal space, Se2...second seal member, Se3...third seal member, S1, S2, S3...opening surface, r1...axis of drive shaft, r2...axis of driven shaft, A...axial direction, B...radial direction, C...first rotation direction, D...second rotation direction, F...flow direction, Ob...foamy oil.

Claims

1. A cylindrical housing; a rotating shaft supported by a bearing relative to the housing; A motor that rotates the rotary shaft; an actuating portion that rotates synchronously with the rotating shaft and sucks in and discharges a fluid; a power transmission unit that transmits power of the rotating shaft to the operating unit, The housing includes: a motor chamber that houses the motor; An actuation chamber that accommodates the actuation unit; a power transmission chamber that accommodates the power transmission unit and oil that lubricates the power transmission unit; a through hole in which the bearing is provided and through which the rotating shaft is inserted; a breather passage having a bent portion and configured to release pressure in the power transmission chamber to the outside of the housing; The oil-containing gas discharged from the power transmission chamber is separated into the oil and the gas at the bent portion, an oil return passage that is connected to the bent portion and that is connected to a portion of the through hole adjacent to the bearing; The oil separated at the bent portion is drawn into the bearing by the rotation of the rotating shaft through the oil return passage, The gas separated at the bent portion is discharged to the outside of the housing through the breather passage, the motor chamber, the power transmission chamber, and the operating chamber are arranged in this order, a seal member that seals between the working chamber and the power transmission chamber is provided in the through hole, the oil return passage opens to an inner surface that defines the through hole between the bearing and the seal member, a flow direction of the oil on the inner surface in the rotational direction of the rotating shaft, the space between the inner surface and the rotating shaft being narrower on the downstream side of the flow direction with respect to an opening of the oil return passage than on the upstream side of the flow direction.

2. A cylindrical housing; a rotating shaft supported by a bearing relative to the housing; A motor that rotates the rotary shaft; an actuating portion that rotates synchronously with the rotating shaft and sucks in and discharges a fluid; a power transmission unit that transmits power of the rotating shaft to the operating unit, The housing includes: a motor chamber that houses the motor; An actuation chamber that accommodates the actuation unit; a power transmission chamber that accommodates the power transmission unit and oil that lubricates the power transmission unit; a through hole in which the bearing is provided and through which the rotating shaft is inserted; a breather passage having a bent portion and configured to release pressure in the power transmission chamber to the outside of the housing; The oil-containing gas discharged from the power transmission chamber is separated into the oil and the gas at the bent portion, an oil return passage that is connected to the bent portion and that is connected to a portion of the through hole adjacent to the bearing; The oil separated at the bent portion is drawn into the bearing by the rotation of the rotating shaft through the oil return passage, The gas separated at the bent portion is discharged to the outside of the housing through the breather passage, A fluid machine characterized in that a partition surface defining the bent portion is provided with a recess against which the oil-containing gas discharged from the power transmission chamber directly collides.

3. A cylindrical housing; a rotating shaft supported by a bearing relative to the housing; A motor that rotates the rotary shaft; an actuating portion that rotates synchronously with the rotating shaft and sucks in and discharges a fluid; a power transmission unit that transmits power of the rotating shaft to the operating unit, The housing includes: a motor chamber that houses the motor; An actuation chamber that accommodates the actuation unit; a power transmission chamber that accommodates the power transmission unit and oil that lubricates the power transmission unit; a through hole in which the bearing is provided and through which the rotating shaft is inserted; a breather passage having a bent portion and configured to release pressure in the power transmission chamber to the outside of the housing; The oil-containing gas discharged from the power transmission chamber is separated into the oil and the gas at the bent portion, an oil return passage that is connected to the bent portion and that is connected to a portion of the through hole adjacent to the bearing; The oil separated at the bent portion is drawn into the bearing by the rotation of the rotating shaft through the oil return passage, The gas separated at the bent portion is discharged to the outside of the housing through the breather passage, a vent that allows gas to pass but does not allow liquid to pass through is provided on the outside of the housing, and a case that constitutes a part of the breather passage is fixed to the housing; a mesh for defoaming foamed oil provided in the breather passage between the bent portion and the case;

4. the mesh is provided in the breather passage between the bent portion and the case, A gasket is provided between the case and the housing to seal the gap therebetween. A portion of the gasket overlaps with the breather passage, thereby restricting the mesh from moving toward the case, 4. The fluid machine according to claim 3, wherein the breather passage is provided with a restricting portion that sandwiches a part of the gasket and the mesh and restricts movement of the mesh toward the bent portion.

5. 5. The fluid machine according to claim 3, wherein the oil return passage is open toward the mesh on an inner surface that defines the through hole.

6. A cylindrical housing; a rotating shaft supported by a bearing relative to the housing; A motor that rotates the rotary shaft; an actuating portion that rotates synchronously with the rotating shaft and sucks in and discharges a fluid; a power transmission unit that transmits power of the rotating shaft to the operating unit, The housing includes: a motor chamber that houses the motor; An actuation chamber that accommodates the actuation unit; a power transmission chamber that accommodates the power transmission unit and oil that lubricates the power transmission unit; a through hole in which the bearing is provided and through which the rotating shaft is inserted; a breather passage having a bent portion and configured to release pressure in the power transmission chamber to the outside of the housing; The oil-containing gas discharged from the power transmission chamber is separated into the oil and the gas at the bent portion, an oil return passage that is connected to the bent portion and that is connected to a portion of the through hole adjacent to the bearing; The oil separated at the bent portion is drawn into the bearing by the rotation of the rotating shaft through the oil return passage, The gas separated at the bent portion is discharged to the outside of the housing through the breather passage, The bearing is The outer ring and With the inner circle, a rolling element disposed between the outer ring and the inner ring, An internal space is formed between the outer ring and the inner ring, If the direction in which the axis of the rotating shaft extends is defined as an axial direction, and the direction perpendicular to the axis of the rotating shaft is defined as a radial direction, The rotary shaft further includes a blade that rotates integrally with the rotary shaft. The blade is an insertion portion having an insertion hole through which the rotating shaft is inserted; a protruding portion protruding radially outward from the insertion portion, The fluid machine, characterized in that the protrusion faces the internal space in the axial direction.

7. A cylindrical housing; a rotating shaft supported by a bearing relative to the housing; A motor that rotates the rotary shaft; an actuating portion that rotates synchronously with the rotating shaft and sucks in and discharges a fluid; a power transmission unit that transmits power of the rotating shaft to the operating unit, The housing includes: a motor chamber that houses the motor; An actuation chamber that accommodates the actuation unit; a power transmission chamber that accommodates the power transmission unit and oil that lubricates the power transmission unit; a through hole in which the bearing is provided and through which the rotating shaft is inserted; a breather passage having a bent portion and configured to release pressure in the power transmission chamber to the outside of the housing; The oil-containing gas discharged from the power transmission chamber is separated into the oil and the gas at the bent portion, an oil return passage that is connected to the bent portion and that is connected to a portion of the through hole adjacent to the bearing; The oil separated at the bent portion is drawn into the bearing by the rotation of the rotating shaft through the oil return passage, The gas separated at the bent portion is discharged to the outside of the housing through the breather passage, the power transmission unit is configured with a gear that rotates integrally with the rotating shaft, the power transmission chamber includes an oil catch tank in which the oil stirred by the rotation of the gears is stored and which communicates with the breather passage, and the gas containing the oil that enters the oil catch tank flows into the breather passage, The housing is further formed with a communication hole that communicates between the oil catch tank and the through hole, and the oil stored in the oil catch tank is drawn into the bearing through the communication hole, If the direction in which the axis of the rotation shaft extends is defined as the axial direction, The gear is a first end surface facing the bearing in the axial direction; a second end surface located on the opposite side to the first end surface in the axial direction, The gear has a flow hole passing therethrough, A fluid machine characterized in that the flow hole extends in a direction opposite to the rotational direction of the gear in which the flow hole is provided, while intersecting the axial direction as it moves from the first end face toward the second end face.

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