Centrifugal compressor with a pressure relief passage

Abstract

First and second pressure relief passages extend from an oil pan in a branching manner and merge into each other to form a transition section. A pressure relief hole is arranged above the transition section, and a first pressure relief passage is arranged below the transition section. The minimum cross-sectional area of ​​the second pressure relief passage is smaller than the minimum cross-sectional area of ​​the first pressure relief passage. The second pressure relief passage includes a bent section formed by bending the second pressure relief passage. The bent section is configured to perform gas / liquid separation by crushing bubbles. When the oil from the bent section reaches the transition section, it is returned to the oil pan via the first pressure relief passage.When the gas from the bent section reaches the transition section, it is discharged to the outside of the housing via the pressure relief hole.

Description

[0001] The present disclosure relates to a centrifugal compressor.

[0002] Published Japanese patent application JP 2016-186238 A discloses a centrifugal compressor. The centrifugal compressor includes a low-speed shaft, an impeller attached to a high-speed shaft, and a speed increaser that transfers power from the low-speed shaft to the high-speed shaft. The centrifugal compressor further includes a housing and a partition wall. The housing includes an impeller chamber containing the impeller and a speed increaser chamber containing the speed increaser. The partition wall separates the impeller chamber and the speed increaser chamber. The partition wall has an insertion hole through which the high-speed shaft passes. The centrifugal compressor further includes a sealing element, an oil pan, and an oil passage. The sealing element is provided between the outer peripheral surface of the high-speed shaft and the inner peripheral surface of the insertion hole.The oil pan stores oil to be supplied to the speed increaser. The oil passage carries oil stored in the oil pan to the speed increaser and returns the oil to the oil pan. The oil supplied to the speed increaser reduces friction and prevents friction welding in the sliding sections of the high-speed shaft and the speed increaser. The sealing element prevents the oil stored in the speed increaser chamber from leaking through the inlet hole into the impeller chamber.

[0003] When gas is compressed by impeller rotation, the internal pressure of the impeller chamber increases. The compressed gas flows from the edge of the impeller back surface to the clearance at the impeller back surface. This increases the pressure in the clearance at the impeller back surface. The gas can escape from the clearance at the impeller back surface into the speed-increasing chamber through the gap between the outer peripheral surface of the high-speed shaft and the inner peripheral surface of the insertion hole, which can increase the pressure in the speed-increasing chamber. In addition, the pressure in the impeller chamber may become lower than the pressure in the speed-increasing chamber, for example, when the impeller rotates at a low speed or when the centrifugal compressor is stopped.In this case, the oil in the speed increasing chamber can escape into the impeller chamber through the gap between the outer peripheral surface of the fast rotating shaft and the inner peripheral surface of the insertion hole.

[0004] For example, published Japanese patent application JP 2019-157707 A discloses a centrifugal compressor including a pressure relief passage. The pressure relief passage connects an oil pan and the outside of the centrifugal compressor (the atmosphere side) to limit a pressure increase in the speed-increasing chamber. This configuration releases pressure through the pressure relief passage when the pressure in the speed-increasing chamber increases. This limits a pressure increase in the speed-increasing chamber.

[0005] As oil is supplied to the speed increaser, the oil accumulates in the speed increaser chamber. The oil accumulated in the speed increaser chamber is stirred by the speed increaser, generating bubbles in the oil. The bubbles generated in the oil accumulate in the oil passage connected to, for example, the pressure relief passage of the oil pan. In the centrifugal compressor disclosed in Japanese Patent Application Publication No. JP 2019-157707 A, the oil pan and the outside of the casing are always connected via the pressure relief passage. Accordingly, the oil stored in the oil pan with trapped bubbles can flow to the pressure relief passage, allowing the bubbles to flow out of the pressure relief passage. This reduces the amount of oil supplied to the speed increaser.

[0006] JP 2020-56321 A discloses a centrifugal compressor comprising: a low-speed shaft rotated by a drive source; an impeller fixed to a high-speed shaft rotating at a higher speed than the low-speed shaft; a speed increaser transmitting the power of the low-speed shaft to the high-speed shaft; a casing including a drive source chamber accommodating the drive source, an impeller chamber accommodating the impeller, a speed increaser chamber accommodating the speed increaser, and a partition wall having an insertion hole through which the high-speed shaft is passed, the partition wall separating the impeller chamber and the speed increaser chamber from each other; a sealing member provided between an outer peripheral surface of the high-speed shaft and an inner peripheral surface of the insertion hole;an oil pan that stores the oil supplied to the speed increaser; an oil passage that supplies oil stored in the oil pan to the speed increaser and returns the oil to the oil pan; and a pressure relief passage that connects the oil pan to a pressure relief hole that opens onto an outer surface of the housing.

[0007] The object of the present disclosure is to provide a centrifugal compressor capable of limiting a reduction in the amount of oil supplied to a speed increaser.

[0008] This summary is intended to introduce, in a simplified form, a selection of concepts that are further described below in the detailed description. This summary is not intended to identify important features or essential characteristics of the claimed subject matter, nor is it intended to be an aid in determining the scope of the claimed subject matter.

[0009] In a general aspect, a centrifugal compressor includes a low-speed shaft (low-speed shaft) rotated by a power source, an impeller / vane attached to a high-speed shaft (high-speed shaft) rotating at a higher speed than the low-speed shaft, a speed increaser that transfers the energy of the low-speed shaft to the high-speed shaft, a casing, an oil pan, an oil passage, and a pressure relief passage. The casing includes a power source chamber housing the power source, an impeller chamber housing the impeller, a speed increaser chamber housing the speed increaser, and a partition wall having an insertion hole through which the high-speed shaft passes. The partition wall separates the impeller chamber and the speed increaser chamber.The sealing element is provided between an outer peripheral surface of the high-speed shaft and an inner peripheral surface of the insertion hole. The oil pan stores the oil supplied to the speed increaser. The oil passage supplies the oil stored in the oil pan to the speed increaser and returns the oil to the oil pan. The pressure relief passage connects the oil pan to a pressure relief hole opened in an outer surface of the housing. The pressure relief passage includes a first pressure relief passage and a second pressure relief passage extending from the oil pan in a branching manner. The second pressure relief passage merges with the first pressure relief passage to form a transition portion / merging portion. The pressure relief hole is arranged above the transition portion in a direction of gravity.The first pressure relief passage is arranged below the transition section in the direction of gravity. A minimum cross-sectional area of ​​the second pressure relief passage is smaller than a minimum cross-sectional area of ​​the first pressure relief passage. The second pressure relief passage includes a bent section formed by bending / angling / curving the second pressure relief passage. The bent section is configured to perform gas / liquid separation by crushing bubbles. When the oil from the bent section reaches the transition section, it is returned to the oil pan via the first pressure relief passage. Upon reaching the transition section from the bent section, gas is discharged / discharged to an outside of the housing via the pressure relief hole.

[0010] Further features and aspects will become apparent from the following detailed description, drawings and claims. Fig. 1 is a side cross-sectional view showing a centrifugal compressor according to an embodiment. Fig. 2 is a cross-sectional view taken along a line 2-2 in Fig. 1. Fig. 3 is a cross-sectional view taken along a line 3-3 in Fig. 1. Fig. 4 is a cross-sectional view taken along a line 4-4 in Fig. 1. Fig. 5 is a cross-sectional view taken along a line 5-5 in Fig. 1.

[0011] In the drawings and detailed description, the same reference numerals refer to the same elements. The drawings may not be to scale, and the relative size, proportions, and representation of elements in the drawings may be exaggerated for clarity, illustration, and simplicity.

[0012] This description provides a comprehensive understanding of the described methods, devices, and / or systems. Modifications and equivalents of the described methods, devices, and / or systems will be apparent to one skilled in the art. The sequences of operations are exemplary and can obviously be changed by one skilled in the art, except for operations that necessarily occur in a particular order. Descriptions of functions and structures known to those skilled in the art may be omitted.

[0013] Example embodiments may take various forms and are not limited to the described examples. However, the described examples are thorough and complete, and will fully convey the scope of the disclosure to one skilled in the art.

[0014] A centrifugal compressor 10 according to an embodiment will now be described with reference to the Fig. 1 to 5. The centrifugal compressor 10 of the present embodiment is mounted on a fuel cell vehicle that runs on a fuel cell as a power source. The centrifugal compressor 10 supplies air to the fuel cell. In the following description, the terms "upper," "upward," "above," "lower," "downward," "below," and other terms indicating vertical positional relationships are defined with respect to the direction of gravity.

[0015] How Fig. As shown in Figure 1, a housing 11 of the centrifugal compressor 10 includes a motor housing member 12, a speed increaser housing member 13 coupled to the motor housing member 12, a plate 14 coupled to the speed increaser housing member 13, a compressor housing member 15 coupled to the plate 14, and a rear housing member 16 coupled to the motor housing member 12 on a side opposite the speed increaser housing member 13. The motor housing member 12, the speed increaser housing member 13, the plate 14, the compressor housing member 15, and the rear housing member 16 are made of metal, such as aluminum. The housing 11 is substantially tubular. The rear housing member 16, the motor housing member 12, the speed increaser housing member 13, the plate 14 and the compressor housing member 15 are arranged in this order in the axial direction of the housing 11.

[0016] The motor housing member 12 includes a disc-shaped bottom wall 12a and a cylindrical outer wall 12b extending from the outer (peripheral) edge of the bottom wall 12a. The motor housing member 12 has a cylindrical shape with a closed end. The speed increaser housing member 13 includes a disc-shaped bottom wall 13a and a cylindrical outer wall 13b extending from the outer edge of the bottom wall 13a. The speed increaser housing member 13 has a cylindrical shape with a closed end.

[0017] An opening of the outer wall 12b on a side opposite the bottom wall 12a is closed by the bottom wall 13a of the speed increaser housing element 13. The bottom wall 13a has a through hole 13h in a central portion.

[0018] An opening in the outer wall 13b on a side opposite the bottom wall 13a is closed by the plate 14. The plate 14 has an insertion hole 14h in a central section.

[0019] The compressor housing element 15 is connected to a surface of the plate 14 on a side opposite the speed increaser housing element 13. The compressor housing element 15 includes a suction port 15a through which air, which is a fluid, is sucked in. The suction port 15a is located in a central portion of the end surface of the compressor housing element 15 on the side opposite the plate 14. The suction port 15a extends in the axial direction of the housing 11 from the central portion of the end surface of the compressor housing element 15.

[0020] The centrifugal compressor 10 includes an electric motor 18 as a drive source and a slow-rotating shaft 17 rotated by the electric motor 18. The electric motor 18 is housed in the motor housing member 12. The housing 11 includes a motor chamber 12c as a drive source chamber in which the electric motor 18 is housed. The motor chamber 12c is defined by the inner surface of the bottom wall 12a and the inner peripheral surface of the outer wall 12b of the motor housing member 12, as well as by the outer surface of the bottom wall 13a of the speed increaser housing member 13. The axial direction of the slow-rotating shaft 17 coincides with the axial direction of the motor housing member 12. In this state, the slow-rotating shaft 17 is housed in the motor housing member 12. The slow-rotating shaft 17 is made of metal such as iron or an alloy.

[0021] The bottom wall 12a has a tubular protrusion 12f protruding from the inner surface. The slow-rotating shaft 17 has a first end inserted into the protrusion 12f. A first bearing 19 is provided between the first end of the slow-rotating shaft 17 and the protrusion 12f. The first end of the slow-rotating shaft 17 is rotatably supported by the bottom wall 12a of the motor housing member 12 with the first bearing 19. The first end of the slow-rotating shaft 17 extends through the bottom wall 12a of the motor housing member 12.

[0022] The slow-rotating shaft 17 has a second end inserted into the through-hole 13h. A second bearing 20 is provided between the second end of the slow-rotating shaft 17 and the through-hole 13h. The second end of the slow-rotating shaft 17 is rotatably supported by the bottom wall 13a of the speed increaser housing member 13 with the second bearing 20. The slow-rotating shaft 17 is thus rotatably supported in the housing 11. The second end of the slow-rotating shaft 17 extends from the motor chamber 12c through the through-hole 13h and projects into the speed increaser housing member 13.

[0023] A sealing member 21 is provided between the second end of the slow-rotating shaft 17 and the inner peripheral surface of the through hole 13h. The sealing member 21 is arranged between the second bearing 20 and the motor chamber 12c. The sealing member 21 serves as a seal between the outer peripheral surface of the slow-rotating shaft 17 and the inner peripheral surface of the through hole 13h.

[0024] The rear housing member 16 is arranged so that it is adjacent to the motor housing member 12 in the axial direction of the slow-rotating shaft 17. The rear housing member 16 is a block-shaped housing. The rear housing member 16 is coupled to the bottom wall 12a of the motor housing member 12. The rear housing member 16 has an insertion hole 16a into which the slow-rotating shaft 17, which is guided through the bottom wall 12a, is inserted. The first end of the slow-rotating shaft 17 extends through the rear housing member 16 and protrudes to the outside of the rear housing member 16.

[0025] The centrifugal compressor 10 includes screws 80 that secure the motor housing member 12 and the rear housing member 16 together. The screws 80 extend through the rear housing member 16 in the axial direction of the low-speed shaft 17 and are screwed into the bottom wall 12a of the motor housing member 12, thereby securing the motor housing member 12 and the rear housing member 16 together.

[0026] The electric motor 18 includes a tubular stator 22 and a rotor 23 disposed inside the stator 22. The rotor 23 is fixed to the low-speed shaft 17 and rotates integrally with the low-speed shaft 17. The stator 22 surrounds the rotor 23. The rotor 23 includes a cylindrical rotor core 23a fixed to the low-speed shaft 17 and permanent magnets (not shown) provided in the rotor core 23a. The stator 22 includes a tubular stator core 22a and a coil 22b. The stator core 22a is fixed to the inner peripheral surface of the outer wall 12b of the motor housing member 12. The coil 22b is wound around the stator core 22a. Current through the coil 22b causes the rotor 23 and the low-speed shaft 17 to rotate integrally.

[0027] The centrifugal compressor 10 includes a high-speed shaft 31 rotating at a higher speed than the low-speed shaft 17, and a speed increaser 30 transmitting the power of the low-speed shaft 17 to the high-speed shaft 31. The housing 11 has a speed increaser chamber 13c that houses the speed increaser 30. The speed increaser chamber 13c is defined by the inner surface of the bottom wall 13a and the inner peripheral surface of the outer wall 13b of the speed increaser housing member 13, as well as the plate 14. The speed increaser chamber 13c stores oil. The sealing member 21 prevents the oil stored in the speed increaser chamber 13c from leaking into the motor chamber 12c through the gap between the outer peripheral surface of the low-speed shaft 17 and the inner peripheral surface of the through hole 13h.

[0028] The rotating shaft 31 is made of metal such as iron or an alloy. The axial direction of the rotating shaft 31 coincides with the axial direction of the speed increaser housing member 13. In this state, a portion of the rotating shaft 31 is housed in the speed increase chamber 13c. One end of the rotating shaft 31, located on a side opposite the motor housing member 12, extends through the insertion hole 14h of the plate 14 and protrudes into the compressor housing member 15.

[0029] The axis of the fast rotating shaft 31 coincides with the axis of the slow rotating shaft 17.

[0030] The centrifugal compressor 10 includes an impeller 24 fixed to the rotating shaft 31. The housing 11 has an impeller chamber 15b containing the impeller 24. The impeller chamber 15b is defined by the compressor housing member 15 and the plate 14. The plate 14 is a partition wall separating the impeller chamber 15b and the speed-increasing chamber 13c. The plate 14, which is a partition wall, has an insertion hole 14h formed therein, through which the rotating shaft 31 is passed. The housing 11 includes the motor chamber 12c, which houses the electric motor 18, the impeller chamber 15b, which houses the impeller 24, and the speed-increasing chamber 13c, which houses the speed increaser 30. The casing 11 also has the insertion hole 14h through which the high-speed shaft 31 is passed, and the plate 14 which separates the impeller chamber 15b and the speed-increasing chamber 13c.

[0031] The centrifugal compressor 10 includes a sealing element 71 provided in the insertion hole 14h. The sealing element 71 serves as a seal between the outer peripheral surface of the high-speed shaft 31 and the inner peripheral surface of the insertion hole 14h. The sealing element 71 is a mechanical seal. The sealing element 71 prevents oil stored in the speed-increasing chamber 13c from leaking into the impeller chamber 15b through the insertion hole 14h.

[0032] The impeller chamber 15b and the suction port 15a are connected to each other. The impeller chamber 15b is substantially frustoconical, with its diameter gradually increasing with increasing distance from the suction port 15a. The rapidly rotating shaft 31 has one end that protrudes into the impeller chamber 15b in the compressor housing element 15.

[0033] The impeller 24 is tubular and has a diameter that gradually decreases from a proximal end surface 24a to a distal end surface 24b. The impeller 24 has an insertion hole 24c extending in the axial direction of the impeller 24. The rotating shaft 31 can be passed through the insertion hole 24c. The end of the rotating shaft 31 that protrudes into the compressor housing member 15 is passed through the insertion hole 24c. The impeller 24 is fixed to the rotating shaft 31 in this state. When the rotating shaft 31 rotates, the impeller 24 rotates, so that the air sucked through the suction port 15a is compressed. The impeller 24 rotates integrally with the rotating shaft 31 to compress the air. The proximal end surface 24a is an impeller back surface.

[0034] The centrifugal compressor 10 also includes a diffuser passage 25 into which the air compressed by the impeller 24 flows, and an outlet chamber 26 into which the air that has passed through the diffuser passage 25 flows.

[0035] The diffuser passage 25 is defined by the surface of the compressor housing member 15 opposite the plate 14 and the surface of the plate 14 opposite the compressor housing member 15. The diffuser passage 25 is located outside the impeller chamber 15b in the radial direction of the high-speed shaft 31 and surrounds the impeller chamber 15b. The diffuser passage 25 is annular.

[0036] The outlet chamber 26 is located outside the diffuser passage 25 in the radial direction of the high-speed shaft 31 and is connected to the diffuser passage 25. The outlet chamber 26 is annular. The impeller chamber 15b and the outlet chamber 26 are connected to each other by the diffuser passage 25. Air compressed by the impeller 24 flows through the diffuser passage 25 to be further compressed and flows to the outlet chamber 26 to be discharged from the outlet chamber 26.

[0037] The speed increaser 30 accelerates the rotation of the low-speed shaft 17 and transmits the rotation to the high-speed shaft 31. The speed increaser 30 is a traction drive type (a friction roller type). The speed increaser 30 includes a ring member 32 connected to the second end of the low-speed shaft 17. The ring member 32 is made of metal. The ring member 32 includes a disc-shaped base 33 coupled to the second end of the low-speed shaft 17 and a tubular portion 34 cylindrically extending from the outer edge of the base 33. The ring member 32 has a cylindrical shape with a closed end. The base 33 extends in the radial direction of the low-speed shaft 17 with respect to the low-speed shaft 17. The axis of the tubular portion 34 coincides with the axis of the low-speed shaft 17.

[0038] As in Fig. As shown in Figure 2, a part of the rotating shaft 31 is disposed inside the tubular portion 34. The speed increaser 30 includes three rollers 35 provided between the tubular portion 34 and the rotating shaft 31. The three rollers 35 are made of metal, such as iron or an iron alloy, which is the same metal as the rotating shaft 31. The three rollers 35 are arranged at predetermined intervals (e.g., 120 degrees) in the circumferential direction of the rotating shaft 31. The three rollers 35 have the same shape. The three rollers 35 contact both the inner peripheral surface of the tubular portion 34 and the outer peripheral surface of the rotating shaft 31.

[0039] As in Fig. As shown in Figure 1, each roller 35 includes a columnar roller portion 35a, a columnar first projection 35c, and a columnar second projection 35e. The first projection 35c protrudes from a first end surface 35b in the axial direction of the roller portion 35a. The second projection 35e protrudes from a second end surface 35d in the axial direction of the roller portion 35a. The axis of the roller portion 35a, the axis of the first projection 35c, and the axis of the second projection 35e coincide with each other. The axial direction of the roller portion 35a of each roller 35 and the axial direction of the high-speed shaft 31 coincide with each other.

[0040] As in the Fig. 1 and Fig. 2, the speed increaser 30 includes a support member 39 that cooperates with the plate 14 to rotatably support the rollers 35. The support member 39 is arranged inside the tubular portion 34. The support member 39 includes a disc-shaped support base 40 and three columnar upright walls 41 projecting from the support base 40. The support base 40 is arranged to oppose the plate 14 in the axial direction of the rollers 35. The three upright walls 41 extend from a surface 40a of the support base 40 closest to the plate 14 toward the plate 14. The three upright walls 41 are arranged to fill the three spaces, each of which is defined by the outer peripheral surfaces of two adjacent ones of the roller portions 35a and the inner peripheral surface of the tubular portion 34.

[0041] The support member 39 has three screw insertion holes 45 through which screws 44 are passed. Each screw insertion hole 45 extends in the axial direction of the rollers 35 through a corresponding one of the three upright walls 41. As Fig. As shown in Figure 1, the plate 14 has internally threaded holes 46 in a surface 14a closest to the support member 39. The internally threaded holes 46 are connected to the screw insertion holes 45. The support member 39 is attached to the plate 14 by screwing the screws 44, which pass through the screw insertion holes 45, into the internally threaded holes 46.

[0042] The plate 14 has three recesses 51 (in Fig. 1 (only one of the recesses 51 is shown) in the surface 14a closest to the support element 39. The three recesses 51 are arranged at predetermined intervals (e.g., 120 degrees) in the circumferential direction of the rapidly rotating shaft 31. The positions of the three recesses 51 correspond to the positions of the three rollers 35, respectively. The three recesses 51 each accommodate an annular roller bearing 52.

[0043] The support base 40 has three recesses 53 (in Fig. 1 (only one of the recesses 53 is shown) in the surface 40a closest to the plate 14. The three recesses 53 are arranged at predetermined intervals (e.g., 120 degrees) in the circumferential direction of the rapidly rotating shaft 31. The positions of the three recesses 53 correspond to the positions of the three rollers 35, respectively. The three recesses 53 each accommodate an annular roller bearing 54.

[0044] The first projection 35c of each roller 35 is inserted into the roller bearing 52 in the corresponding recess 51 and is rotatably supported by the plate 14 with the roller bearing 52. The second projection 35e of each roller 35 is inserted into the roller bearing 54 in the corresponding recess 53 and is rotatably supported by the support member 39 with the roller bearing 54.

[0045] The rotating shaft 31 includes two flanges 31f that are spaced apart from each other in the axial direction of the rotating shaft 31. The roller portions 35a of the three rollers 35 are held by the two flanges 31f. This prevents a positional shift of the rotating shaft 31 and the roller portions 35a of the three rollers 35 in the axial direction of the rotating shaft 31.

[0046] As in Fig. As shown in Figure 2, the three rollers 35 are pressed against the rotating shaft 31 and the tubular portion 34. In this state, the three rollers 35, the ring member 32, and the rotating shaft 31 are connected to form a single unit. The rotating shaft 31 is rotatably supported by the three rollers 35.

[0047] The contact portion between the outer peripheral surface of the roller portion 35a of each of the three rollers 35 and the inner peripheral surface of the tubular portion 34 is referred to as the ring-side contact portion Pa, to which a pressing load is applied. The contact portion between the outer peripheral surface of each of the three rollers 35 and the outer peripheral surface of the rotating shaft 31 is referred to as the shaft-side contact portion Pb, to which a pressing load is applied. The ring-side contact portions Pa and the shaft-side contact portions Pb extend in the axial direction of the rotating shaft 31.

[0048] When the electric motor 18 is driven to rotate the low-speed shaft 17 and the ring member 32, the rotational force of the ring member 32 is transmitted to the three rollers 35 via the ring-side contact portions Pa. When the three rollers 35 rotate, the rotational force of the three rollers 35 is transmitted to the high-speed shaft 31 via the shaft-side contact portions Pb.

[0049] Accordingly, the high-speed shaft 31 rotates. At this time, the ring member 32 rotates at the same speed as that of the low-speed shaft 17, and the three rollers 35 rotate at a higher speed than that of the low-speed shaft 17. The high-speed shaft 31, whose outer diameter is smaller than the outer diameter of the three rollers 35, rotates at a higher speed than that of the three rollers 35. That is, the speed increaser 30 causes the high-speed shaft 31 to rotate at a higher speed than that of the low-speed shaft 17.

[0050] As in Fig. As shown in Figure 1, the centrifugal compressor 10 includes an oil pan 56, an oil passage 60, an oil cooler 55, and an oil pump 57. The oil pan 56 stores oil supplied to the speed increaser 30. The oil passage 60 supplies oil stored in the oil pan 56 to the speed increaser 30 and returns the oil to the oil pan 56. The oil cooler 55 cools the oil flowing to the oil passage 60. The oil pump 57 pumps the oil stored in the oil pan 56 and discharges the oil.

[0051] The oil cooler 55 includes a cover member 55a having a tubular shape with a closed end and is attached to the outer peripheral surface of the outer wall 12b of the engine housing member 12. The inner surface of the cover member 55a and the outer peripheral surface of the outer wall 12b of the engine housing member 12 define a space 55b. The oil cooler 55 includes a cooling tube 55c disposed in the space 55b. The opposite ends of the cooling tube 55c are supported by the engine housing member 12. The cooling tube 55c forms part of the oil passage 60.

[0052] The cover element 55a includes an inlet pipe 55d and an outlet pipe 55e. Low-temperature fluid is introduced into the space 55b through the inlet pipe 55d. The low-temperature fluid introduced into the space 55b is discharged from the outlet pipe 55e and then cooled by a cooling device (not shown). The low-temperature fluid is then reintroduced into the space 55b through the inlet pipe 55d. The low-temperature fluid is, for example, water.

[0053] The oil pan 56 is provided in the rear housing member 16. The oil pan 56 is located in an outer part of the rear housing member 16. The oil pump 57 is located in the rear housing member 16. The oil pump 57 is, for example, a trochoid pump. The oil pump 57 is coupled to the first end of the slowly rotating shaft 17. The oil pump 57 is driven by the rotation of the slowly rotating shaft 17. The oil pump 57 is mounted in the rear housing member 16 by three of the (in Fig. 3) screws 80.

[0054] The oil passage 60 includes a first connecting passage 61 that connects the speed increase chamber 13c and the oil cooler 55. The first connecting passage 61 extends through the speed increase housing member 13 and into the outer wall 12b of the motor housing member 12. The first connecting passage 61 has a first end that opens into the speed increase chamber 13c. The first connecting passage 61 has a second end that is connected to the first end of the cooling tube 55c.

[0055] The centrifugal compressor 10 is mounted on the fuel cell vehicle such that the opening of the first connecting passage 61, which opens into the speed-increasing chamber 13c, is located in the lower portion. This allows the oil in the speed-increasing chamber 13c to flow into the first connecting passage 61.

[0056] The oil passage 60 includes a second connecting passage 62 that connects the oil cooler 55 and the oil pan 56. The second connecting passage 62 has a first end that extends from the inside of the engine housing member 12 into the rear housing member 16. The first end of the second connecting passage 62 is connected to the second end of the cooling pipe 55c. The second connecting passage 62 has a second end that opens into the oil pan 56.

[0057] The oil stored in the speed-increasing chamber 13c flows into the first connecting passage 61 and passes through the first connecting passage 61, the cooling pipe 55c, and the second connecting passage 62. The oil flowing through the cooling pipe 55c is cooled by heat exchange with low-temperature fluid drawn into the space 55b of the oil cooler 55. The oil cooled by the oil cooler 55 is stored in the oil pan 56.

[0058] The oil passage 60 includes a third communication passage 63 that connects the oil pan 56 and the oil pump 57. The third communication passage 63 is formed in the rear housing member 16. The third communication passage 63 has a first end that protrudes into the oil pan 56. The third communication passage 63 has a second end that is connected to a suction port 57a of the oil pump 57.

[0059] The oil passage 60 includes a fourth connecting passage 64 connected to an outlet port 57b of the oil pump 57. The fourth connecting passage 64 extends through the rear housing member 16 and the outer wall 12b of the motor housing member 12 and into the outer wall 13b of the speed increaser housing member 13. The fourth connecting passage 64 has a first end connected to the outlet port 57b of the oil pump 57. The fourth connecting passage 64 has a second end located within the outer wall 13b of the speed increaser housing member 13.

[0060] The oil passage 60 includes a first branch passage 65 and a second branch passage 66 branching from the second end of the fourth connecting passage 64. The first branch passage 65 extends from the second end of the fourth connecting passage 64 toward the motor housing member 12 and extends through the outer wall 13b of the speed increaser housing member 13 and the bottom wall 13a of the speed increaser housing member 13. The first branch passage 65 has a first end connected to the second end of the fourth connecting passage 64. The first branch passage 65 has a second end opening into the through hole 13h.

[0061] The second branch passage 66 extends from the second end of the fourth connecting passage 64 toward the plate 14 and extends through the outer wall 13b of the speed increaser housing member 13 and into the plate 14. The second branch passage 66 has a first end connected to the second end of the fourth connecting passage 64. The second branch passage 66 has a second end located within the plate 14.

[0062] The oil passage 60 includes a common passage 67 connected to the second end of the second branch passage 66. The common passage 67 extends perpendicular to the second branch passage 66 and extends linearly downward from the second end of the second branch passage 66. The oil passage 60 includes a seal-element-side supply passage 69 and a speed-increaser-side supply passage 70 branching from the common passage 67. The seal-element-side supply passage 69 has a first end connected to the common passage 67. The seal-element-side supply passage 69 has a second end opening into the insertion bore 14h. Each speed-increaser-side supply passage 70 extends linearly from the common passage 67 to a side opposite the compressor housing member 15 and through the plate 14.Each speed-increasing-side supply passage 70 extends through the corresponding vertical wall 41 and opens into a portion of the vertical wall 41 opposite the outer peripheral surfaces of the roller portions 35a. The speed-increasing-side supply passages 70 are thus connected to the speed-increasing chamber 13c.

[0063] When the electric motor 18 is activated, rotation of the slowly rotating shaft 17 drives the oil pump 57. Then, the oil stored in the oil pan 56 is sucked into the oil pump 57 through the third communication passage 63 and the suction port 57a and discharged into the fourth communication passage 64 through the discharge port 57b. The oil pump 57 is driven such that as the rotational speed of the slowly rotating shaft 17 increases, the amount of oil discharged from the discharge port 57b increases proportionally. The oil delivered to the fourth communication passage 64 flows through the fourth communication passage 64 and is distributed to the first branch passage 65 and the second branch passage 66.

[0064] The oil distributed from the fourth connecting passage 64 to the first branch passage 65 flows through the first branch passage 65 and into the through hole 13h to be supplied to the sealing element 21 and the second bearing 20. This ensures favorable lubrication of the sliding portions of the sealing element 21 and the low-speed shaft 17, as well as the sliding portions of the second bearing 20 and the low-speed shaft 17.

[0065] The oil distributed from the fourth connecting passage 64 to the second branch passage 66 flows into the common passage 67 via the second branch passage 66. Part of the oil flowing in the common passage 67 is distributed to the seal-element-side supply passage 69, and the remaining oil flows into the speed-increaser-side supply passages 70. The oil distributed from the common passage 67 to the seal-element-side supply passage 69 flows in the seal-element-side supply passage 69 to flow into the insertion hole 14h to be supplied to the seal element 71. The oil flowing in the speed-increaser-side supply passages 70 is supplied to the outer peripheral surfaces of the roller portions 35a. This ensures favorable lubrication of the sliding sections of the roller sections 35a and the fast-rotating shaft 31.The oil supplied to the sealing member 71 and the outer peripheral surfaces of the roller portions 35a is returned to the speed increasing chamber 13c.

[0066] The centrifugal compressor 10 includes a pressure relief hole 90b opening in the outer surface of the housing 11 and a pressure relief passage 90 connecting the pressure relief hole 90b and the upper part of the oil pan 56.

[0067] As in the Fig. 1, Fig. 3 and Fig. 4, the pressure relief passage 90 includes a communication passage 90a, a first buffer chamber 91, a second buffer chamber 92, and a communication passage 93. The communication passage 90a, the first buffer chamber 91, the second buffer chamber 92, and the communication passage 93 are formed in the rear housing member 16.

[0068] The first buffer chamber 91 is arranged above the oil pan 56. The first buffer chamber 91 has a rectangular shape that extends in the direction of gravity, viewed in the axial direction of the slow-rotating shaft 17 and in the radial direction of the slow-rotating shaft 17. The connecting passage 90a connects the oil pan 56 and the first buffer chamber 91 to each other. The connecting passage 90a has a first end that opens into the oil pan 56 at the upper portion. The connecting passage 90a has a second end that opens into the first buffer chamber 91 at the lower portion. The connecting passage 90a has a rectangular shape that extends in the direction of gravity, viewed in the axial direction of the slow-rotating shaft 17 and in the radial direction of the slow-rotating shaft 17. As shown in Fig. 1, in the axial direction of the slowly rotating shaft 17, the width of the connecting passage 90a and the width of the first buffer chamber 91 are equal (a width H1). In the axial direction of the slowly rotating shaft 17, the position of the connecting passage 90a and the position of the first buffer chamber 91 are consistent. As shown in Fig. 3, in the radial direction of the slowly rotating shaft 17, a width H3 of the communication passage 90a is smaller than a width H4 of the first buffer chamber 91.

[0069] As in Fig. 1, Fig. 3 and Fig. As shown in Figure 4, the second buffer chamber 92 is connected to the oil pan 56. The second buffer chamber 92 extends upward from the oil pan 56 and is parallel to the first buffer chamber 91. The second buffer chamber 92 extends to a height comparable to the height of the first buffer chamber 91 in the direction of gravity.

[0070] Of the horizontal directions perpendicular to the direction of gravity, a direction perpendicular to the slowly rotating shaft 17 is referred to as a first horizontal direction A. As Fig. 1, the second buffer chamber 92 has a rectangular shape extending in the direction of gravity as viewed in the first horizontal direction A. In the axial direction of the slowly rotating shaft 17, a width H2 of the second buffer chamber 92 is the same as the width H1 of the connecting passage 90a and the first buffer chamber 91.

[0071] The connecting passage 90a and the first buffer chamber 91 are offset from the second buffer chamber 92 in the axial direction of the slow-rotating shaft 17. The second buffer chamber 92 is arranged between the first buffer chamber 91 and the motor housing member 12 in the axial direction of the slow-rotating shaft 17.

[0072] As in the Fig. 3 and Fig. 4, the first buffer chamber 91 and the second buffer chamber 92 are offset from each other in the first horizontal direction A when viewed in the axial direction of the slowly rotating shaft 17.

[0073] The housing 11 has a first side surface 91a and a second side surface 91b, which oppose each other in the first horizontal direction A and define the first buffer chamber 91. The first side surface 91a is located closest to the second buffer chamber 92, and the second side surface 91b is located on a side opposite the second buffer chamber 92. The housing 11 has a first side surface 92a and a second side surface 92b, which oppose each other in the first horizontal direction A and define the second buffer chamber 92. When the second buffer chamber 92 is viewed in the axial direction of the slowly rotating shaft 17, the second buffer chamber 92 is adjacent to the first side surface 91a in the first horizontal direction A. When the second buffer chamber 92 is viewed in the axial direction of the slowly rotating shaft 17, the first side surface 92a is adjacent to the first side surface 91a in the first horizontal direction A.The second side surface 92b is located on the side opposite the first buffer chamber 91 in the first horizontal direction A.

[0074] As in Fig. 1, Fig. 3 and Fig. As shown in Figure 4, the connecting passage 93 connects the first buffer chamber 91 and the second buffer chamber 92. The connecting passage 93 connects the upper part of the first buffer chamber 91 and the upper part of the second buffer chamber 92. The connecting passage 93 extends in the axial direction of the low-speed shaft 17.

[0075] How Fig. 1 and Fig. 3, a rectangular columnar projection 16b is disposed in the first buffer chamber 91. The projection 16b has an insertion hole 16a through which the slow-rotating shaft 17 is inserted. In the first buffer chamber 91, the projection 16b is disposed to connect two inner walls opposite each other in the axial direction of the slow-rotating shaft 17. The projection 16b is formed integrally with the two inner walls.

[0076] As in Fig. 3, the projection 16b is located halfway between the first side surface 91a and the second side surface 91b in the first horizontal direction A. The projection 16b is located between the upper part of the first buffer chamber 91 and the lower part of the first buffer chamber 91. The projection 16b is arranged at a position below the center of the first buffer chamber 91 in the direction of gravity.

[0077] The cross section of the protrusion 16b, cut in the radial direction of the low-speed shaft 17, is square. The width of the space between the first side surface 91a and a side surface of the protrusion 16b opposite to the first side surface 91a is defined as a width W1. The width of the space between the second side surface 91b and a side surface of the protrusion 16b opposite to the second side surface 91b is defined as a width W2. The width W1 and the width W2 are equal to each other. The width of the space between the lower part of the first buffer chamber 91 and a side surface of the protrusion 16b opposite to the lower part of the first buffer chamber 91 is defined as a width W3. The width W3 is the same as the widths W1, W2. The widths W1, W2, W3 are larger than the width H3 of the communication passage 90a.

[0078] The first buffer chamber 91 includes a first passage 911 formed between the protrusion 16b and the second side surface 91b. The first buffer chamber 91 includes a second passage 912. The second passage 912 includes a passage formed between the protrusion 16b and the lower part of the first buffer chamber 91, and a passage formed between the protrusion 16b and the first side surface 91a. The lower part of the first passage 911 is connected to the communication passage 90a. The second passage 912 extends from the first passage 911 toward the first side surface 91a and extends upward, bypassing the protrusion 16b.

[0079] The first passage 911 and the second passage 912 are connected to each other in an area in the first buffer chamber 91 located above the projection 16b. The first passage 911 and the second passage 912 share the area in the first buffer chamber 91 located above the projection 16b. Three of the screws 80 that connect the motor housing member 12 and the rear housing member 16 are passed through the projection 16b.

[0080] As in Fig. 1, the pressure relief hole 90b is formed in the wall of the rear housing member 16, which is located on the side opposite the motor housing member 12. The pressure relief hole 90b has a first end that opens into the first buffer chamber 91 at the upper part. The pressure relief hole 90b has a second end that opens into the outer surface of the rear housing member 16. That is, the first buffer chamber 91 is connected to the outer surface of the housing 11 via the pressure relief hole 90b.

[0081] The pressure relief hole 90b is formed to extend in the axial direction of the slow-rotating shaft 17. A pressure relief tube 94 is provided on the outer surface of the rear housing member 16, into which the pressure relief hole 90b opens. The pressure relief tube 94 is a tubular member bent in an L-shape. The pressure relief tube 94 has a first end connected to the pressure relief hole 90b. The pressure relief tube 94 has a second end located above the first end of the pressure relief tube 94 and open at the top. A ventilation film / sheet 90c is arranged in the second end of the pressure relief tube 94. The ventilation film 90c allows the passage of gas but blocks liquid.

[0082] As in Fig. 3 and Fig. 4, the connecting passage 90a, the first passage 911, and the area in the first buffer chamber 91 located above the projection 16b form a first pressure relief passage 95. The pressure relief passage 90 thus includes the first pressure relief passage 95. The pressure relief hole 90b is provided in the upper part of the first pressure relief passage 95.

[0083] The second passage 912 and the area in the first buffer chamber 91 located above the projection 16b form a bypass pressure relief passage 97. Thus, the pressure relief passage 90 includes the bypass pressure relief passage 97. The first passage 911 and the second passage 912 share an area in the upper part in the first buffer chamber 91. Therefore, the bypass pressure relief passage 97 extends from the lower part of the first pressure relief passage 95 to the area above the projection 16b, bypassing the projection 16b.

[0084] The second buffer chamber 92 and the connecting passage 93 form a second pressure relief passage 96. The pressure relief passage 90 thus contains the second pressure relief passage 96. The second pressure relief passage 96 is connected via the connecting passage 93 to the upper region in the first buffer chamber 91, which is located near the first side surface 91a. The first pressure relief passage 95 and the second pressure relief passage 96 extend from the oil pan 56 in a branching manner. The second pressure relief passage 96 merges into the first pressure relief passage 95 to form a transition portion 98. The transition portion 98 refers to a connecting portion where the first buffer chamber 91 and the connecting passage 93 are connected to each other.

[0085] The first pressure relief passage 95 and the bypass pressure relief passage 97 share the area in the upper part in the first buffer chamber 91. The bypass pressure relief passage 97 and the second pressure relief passage 96 are thus connected to the transition section 98.

[0086] The transition portion 98 is located in a region above the second passage 912, which is formed near the first side surface 91a. The transition portion 98 is formed in an upper region near the first side surface 92a of the second buffer chamber 92 in the first horizontal direction A. Accordingly, the first pressure relief passage 95 and the bypass pressure relief passage 97 are provided below the transition portion 98.

[0087] The pressure relief hole 90b is located in a region above the first passage 911, which is formed near the second side surface 91b. The pressure relief hole 90b is formed in an upper region in the direction of gravity, which is located near the second side surface 91b of the first buffer chamber 91 in the first horizontal direction A.

[0088] The pressure relief hole 90b and the transition portion 98 are spaced apart from each other in the first horizontal direction A. When the position in the direction of gravity is referred to as height, the height of the transition portion 98 from the oil pan 56 is smaller than the height of the pressure relief hole 90b from the oil pan 56. That is, the pressure relief hole 90b is arranged at a position obliquely above the transition portion 98. That is, the pressure relief hole 90b is arranged above the transition portion 98.

[0089] As in Fig. As shown in Figure 4, the second buffer chamber 92 includes a proximal side passage 92c, an upper side passage 92d, and a stagnation / accumulation section 92e. The proximal side passage 92c is the lower end of the second pressure relief passage 96 and is connected to the upper part of the oil pan 56. The stagnation section 92e is the upper end of the second pressure relief passage 96 and is connected to the communication passage 93.

[0090] The proximal side passage 92c extends upward from the oil pan 56. The proximal side passage 92c has a first end connected to the oil pan 56. The proximal side passage 92c has a second end located above the oil pump 57. A width H5 of the proximal side passage 92c in the first horizontal direction A is smaller than the width H3 of the connecting passage 90a.

[0091] The upper side passage 92d is connected to the proximal side passage 92c. The upper side passage 92d extends upward from the second end of the proximal side passage 92c. The upper side passage 92d has a first end connected to the second end of the proximal side passage 92c. The upper side passage 92d is formed to extend between the bolts 80 other than the three bolts 80 used to fix the oil pump 57. A width H6 of the upper side passage 92d in the first horizontal direction A is smaller than the width H5 of the proximal side passage 92c. The distance in the first horizontal direction A between the screws 80 on the opposite sides of the upper side passage 92d is set such that the cross-sectional area of ​​the upper side passage 92d is smaller than the cross-sectional area of ​​the proximal side passage 92c.

[0092] The stagnation section 92e is connected to the upper side passage 92d. The stagnation section 92e is connected to the second end of the upper side passage 92d. The stagnation section 92e is formed in the end of the second buffer chamber 92 located on a side opposite the oil pan 56. A width H7 of the stagnation section 92e is greater than the width H5 of the proximal side passage 92c and the width H6 of the upper side passage 92d.

[0093] The stagnation section 92e includes a wall surface 92f located on a side opposite the upper side passage 92d and intersecting the direction of gravity. The wall surface 92f extends in the first horizontal direction A. The stagnation section 92e is formed in the upper part of the second buffer chamber 92.

[0094] As in the Fig. 3 and Fig. 4, an upper portion of the first buffer chamber 91 near the first side surface 91a and a part of the stagnation portion 92e, which is an upper portion of the second buffer chamber 92 near the first side surface 92a, overlap in the axial direction of the low-speed shaft 17.

[0095] The communication passage 93 is formed in a part where the upper portions of the first buffer chamber 91 and the second buffer chamber 92 overlap in the axial direction of the slow-rotating shaft 17. The communication passage 93 extends in the axial direction of the slow-rotating shaft 17. The communication passage 93 connects the second buffer chamber 92 and the first buffer chamber 91 downstream in the flow direction of the oil with respect to the wall surface 92f of the stagnation portion 92e.

[0096] How Fig. As shown in Figure 5, the direction in which the second buffer chamber 92 extends and the direction in which the communication passage 93 extends intersect with each other. Thus, the second pressure relief passage 96 includes a bent portion 99 in which the direction extending from the oil pan 56 is bent. The bent portion 99 includes the stagnation portion 92e. In the bent portion 99, the direction in which the oil flows is changed from the direction of gravity to the axial direction of the slowly rotating shaft 17.

[0097] The following describes the cross-sectional areas of the first pressure relief passage 95, the second pressure relief passage 96, and the bypass pressure relief passage 97 in the pressure relief passage 90. The cross-sectional areas refer to cross-sectional areas when the passage is cut in a direction perpendicular to the flow direction of the oil.

[0098] As in Fig. 3 and Fig. 4, in the first pressure relief passage 95, the cross-sectional area of ​​the connecting passage 90a is smaller than the cross-sectional area of ​​the first passage 911. The cross-sectional areas of the connecting passage 90a and the first passage 911 are smaller than the cross-sectional area of ​​the portion in the first buffer chamber 91 above the protrusion 16b. That is, the minimum cross-sectional area of ​​the first pressure relief passage 95 is the cross-sectional area of ​​the connecting passage 90a.

[0099] In the bypass pressure relief passage 97, the cross-sectional area of ​​a passage formed between the protrusion 16b and the lower part of the first buffer chamber 91 and the cross-sectional area of ​​a passage formed between the protrusion 16b and the first side surface 91a are the minimum cross-sectional areas. In the present embodiment, the minimum cross-sectional area of ​​the bypass pressure relief passage 97 is the same as the cross-sectional area of ​​the first passage 911.

[0100] In the second pressure relief passage 96, the cross-sectional area of ​​the proximal side passage 92c is larger than the cross-sectional area of ​​the upper side passage 92d. The cross-sectional areas of the proximal side passage 92c and the upper side passage 92d are smaller than the cross-sectional area of ​​the stagnation section 92e. The cross-sectional areas of the proximal side passage 92c and the upper side passage 92d are larger than the cross-sectional area of ​​the connecting passage 93. That is, the largest cross-sectional area of ​​the second pressure relief passage 96 is the cross-sectional area of ​​the stagnation section 92e. The minimum cross-sectional area of ​​the second pressure relief passage 96 is the cross-sectional area of ​​the connecting passage 93. The cross-sectional area of ​​the connecting passage 93 is smaller than the cross-sectional area of ​​the connecting passage 90a, which is the minimum cross-sectional area of ​​the first pressure relief passage 95.The cross-sectional area of ​​the upper side passage 92d is smaller than the cross-sectional areas of the stagnation section 92e and the proximal side passage 92c. In the second pressure relief passage 96, the upper side passage 92d serves as a constriction.

[0101] The cross-sectional area of ​​the stagnation portion 92e, which is the largest cross-sectional area of ​​the second pressure relief passage 96, is smaller than the cross-sectional area of ​​the connecting passage 90a, which is the minimum cross-sectional area of ​​the first pressure relief passage 95. That is, the cross-sectional area of ​​the second pressure relief passage 96 is smaller than the cross-sectional area of ​​the first pressure relief passage 95 over the entire length in the direction of gravity. The cross-sectional area of ​​the stagnation portion 92e, which is the largest cross-sectional area of ​​the second pressure relief passage 96, is smaller than the cross-sectional area of ​​the second passage 912, which is the minimum cross-sectional area of ​​the bypass pressure relief passage 97.

[0102] An operation of the present embodiment will now be described.

[0103] As in Fig. As shown in Figure 1, the oil in the speed-increasing chamber 13c is stirred by the speed increaser 30. This creates bubbles B in the oil. The bubbles B in the oil created in the speed-increasing chamber 13c enter the oil pan 56 through the oil passage 60.

[0104] As in Fig. 3 and Fig. As shown in Figure 4, the bubbles B that have reached the oil pan 56 are retained in the oil pan 56. This raises the level of the oil stored in the oil pan 56. The oil level then reaches the first pressure relief passage 95 and the second pressure relief passage 96.

[0105] In the present embodiment, the bubbles B of the oil sucked into the second pressure relief passage 96 are crushed by the bent portion 99 upon reaching the bent portion 99. Upon reaching the transition portion 98 from the bent portion 99, the oil is returned to the oil pan 56 via the first pressure relief passage 95. Upon reaching the transition portion 98 from the bent portion 99, gas is discharged to the outside of the housing 11 via the pressure relief hole 90b. That is, the oil stored in the oil pan 56 with the bubbles B is unlikely to flow out of the pressure relief hole 90b.

[0106] The stagnation section 92e formed in the bent portion 99 has the wall surface 92f that intersects with the flow direction of the oil flowing in the second buffer chamber 92. The oil flowing into the second buffer chamber 92 thus stagnates / accumulates at the stagnation section 92e. Therefore, the pressure at the stagnation section 92e is higher than the pressure in a portion of the second buffer chamber 92 on the upstream side of the stagnation section 92e. Thus, the bubbles B in the oil are broken by the pressure at the stagnation section 92e.

[0107] The cross-sectional area of ​​the first buffer chamber 91 is larger than the cross-sectional area of ​​the connecting passage 93. Therefore, when the bubbles B that have not been removed at the stagnation section 92e enter the first buffer chamber 91, which is larger than the connecting passage 93, via the connecting passage 93, the pressure acting on the bubbles B changes. The bubbles B entering the first buffer chamber 91 are removed by the pressure change.

[0108] The present embodiment has the following advantages. (1) The bubbles B in the oil drawn into the second pressure relief passage 96 are crushed by the bent portion 99 upon reaching the bent portion 99. Upon reaching the transition portion 98 from the bent portion 99, the oil is returned to the oil pan 56 via the first pressure relief passage 95. Upon reaching the transition portion 98 from the bent portion 99, gas is discharged to the outside of the housing 11 via the pressure relief hole 90b. That is, the oil stored in the oil pan 56 with the bubbles B is unlikely to flow out of the pressure relief hole 90b. This limits a reduction in the amount of oil supplied to the speed increaser 30. (2) The bubbles B in the oil flowing into the second pressure relief passage 96 enter the first buffer chamber 91 via the bent portion 99 and the transition portion 98. In the present embodiment, the pressure relief hole 90b is spaced apart from the bent portion 99 and the transition portion 98. This prevents oil from the transition portion 98 from entering the pressure relief hole 90b. (3) Oil stagnates at the stagnation section 92e. Therefore, the pressure at the stagnation section 92e is higher than the pressure in a portion of the second buffer chamber 92 on the upstream side of the stagnation section 92e. Thus, the bubbles B in the oil are broken by the pressure at the stagnation section 92e.

[0109] When the bubbles B that were not removed at the stagnation portion 92e enter the first buffer chamber 91, which is larger than the communication passage 93, via the communication passage 93, the bubbles B in the oil that has reached the first buffer chamber 91 are removed by pressure changes. Accordingly, the oil stored in the oil pan 56 is prevented from flowing out of the pressure relief hole 90b of the pressure relief passage 90 with bubbles B. This limits a reduction in the amount of oil supplied to the speed increaser 30.

[0110] (4) The bubbles B in the oil that have reached the stagnation section 92e collide with the wall surface 92f of the stagnation section 92e and disappear upon impact with the wall surface 92f.

[0111] (5) The flow cross-sectional area of ​​the second pressure relief passage 96 is smaller than the flow cross-sectional area of ​​the first pressure relief passage 95 over the entire length. The bubbles B in the oil stored in the oil pan 56 are therefore drawn into the second pressure relief passage 96 rather than the first pressure relief passage 95 by capillary action. The bubbles B in the oil are therefore unlikely to reach the pressure relief hole 90b in the first pressure relief passage 95. This prevents the oil level from reaching the atmosphere-side opening of the pressure relief passage 90.

[0112] (6) The pressure relief passage 90 includes the bypass pressure relief passage 97. Thus, even if the oil reaches the first pressure relief passage 95 in the oil pan 56 and the oil level reaches the long-dash-short-dash line L1 in the Fig. 3 and Fig.4 rises, is sucked into the bypass pressure relief passage 97. This prevents the oil level from reaching the pressure relief hole 90b of the pressure relief passage 90.

[0113] (7) The bubbles B in the oil flowing into the second pressure relief passage 96 enter the bypass pressure relief passage 97 via the transition portion 98. In the present embodiment, the pressure relief hole 90b is spaced apart from the transition portion 98. This prevents oil that has reached the transition portion 98 from reaching the pressure relief hole 90b, which is the atmosphere-side opening of the pressure relief passage 90.

[0114] (8) The second pressure relief passage 96 includes the upper side passage 92d, which serves as a constriction. This locally reduces the flow cross-sectional area of ​​the second pressure relief passage 96. The bubbles B in the oil stored in the oil pan 56 thereby easily flow to the second pressure relief passage 96. This further reduces the amount of bubbles B in the oil flowing into the first pressure relief passage 95. This prevents the oil level from reaching the atmosphere-side opening of the pressure relief passage 90.

[0115] (9) The pressure relief hole 90b is located above the transition portion 98. Therefore, the oil that has reached the transition portion 98 is returned to the first pressure relief passage 95 located below the transition portion 98 and is unlikely to enter the pressure relief hole 90b. This prevents the oil level from reaching the atmosphere-side opening of the pressure relief passage 90.

[0116] (10) The bubbles B in the oil flow into the second buffer chamber 92 rather than the first buffer chamber 91, and the bubbles B are removed by the stagnation portion 92e and the bent portion 99. This prevents oil from leaking from the pressure relief hole 90b. Accordingly, the reliability of the centrifugal compressor 10 is improved.

[0117] (11) Considering oil leakage from the pressure relief hole 90b, the centrifugal compressor 10 preferably stores a large amount of oil. In this regard, the present embodiment prevents oil leakage and thus enables a reduction in the total amount of trapped oil of the centrifugal compressor 10. This reduces the manufacturing cost of the centrifugal compressor 10.

[0118] (12) The pressure relief passage 90 is provided with the vent film 90c, which allows the passage of gas but blocks liquid. The vent film 90c prevents foreign matter and water from entering the centrifugal compressor 10 through the pressure relief passage 90.

[0119] (13) Since the bubbles B in the oil are prevented from reaching the pressure relief hole 90b, the ventilation film 90c is prevented from being clogged.

[0120] The above-described embodiment may be modified as described below. The above-described embodiment and the following modifications may be combined as long as the combined modifications remain technically consistent with each other.

[0121] The oil pan 56, the oil pump 57, the oil passage 60, the first buffer chamber 91 and the second buffer chamber 92 can be formed in the motor housing member 12 without fixing the rear housing member 16 to the motor housing member 12 with the bolts 80.

[0122] The pressure relief bore 90b may be located above the second passage 912. In this case, the pressure relief bore 90b is located above the transition section 98.

[0123] In the above-described embodiment, the communication passage 90a and the first buffer chamber 91 are offset from the second buffer chamber 92 in the axial direction of the slow-rotating shaft 17, and the second buffer chamber 92 is disposed between the first buffer chamber 91 and the motor housing member 12 in the axial direction of the slow-rotating shaft 17. However, the present disclosure is not limited to this. For example, the communication passage 90a may be disposed at the same position in the axial direction of the slow-rotating shaft 17 as the first buffer chamber 91 and the second buffer chamber 92. In this case, the communication passage 93 may be changed to extend in the first horizontal direction A, and the first buffer chamber 91 and the second buffer chamber 92 may be connected to each other.

[0124] The connecting passage 90a may be inclined with respect to the direction of gravity as long as the connecting passage 90a connects the oil pan 56 and the first buffer chamber 91.

[0125] The wall surface 92f of the stagnation portion 92e extends in the first horizontal direction A in the embodiment described above. However, the wall surface 92f may be inclined so as to intersect with the direction of the gravitational force.

[0126] In the above-described embodiment, the second buffer chamber 92 extends upward from the oil pan 56. However, the second buffer chamber 92 may extend in a direction that intersects the direction of gravity. In this case, the wall surface 92f of the stagnation portion 92e simply needs to be arranged to intersect the direction in which the oil flows in the second buffer chamber 92.

[0127] The width H1 of the first buffer chamber 91 and the width H2 of the second buffer chamber 92 are the same in the above-described embodiment. However, the widths H1 and H2 may be different. The widths H1 and H2 may be changed as long as the flow cross-sectional area of ​​the second pressure relief passage 96 is smaller than the flow cross-sectional area of ​​the first pressure relief passage 95 over its entire length. The same change may also be made in the above-described modifications.

[0128] In the embodiment described above, the proximal side passage 92c has the second end located above the oil pump 57. However, the second end may also be located below the oil pump 57. In this case, the first end of the upper side passage 92d may extend to the second end of the proximal side passage 92c.

[0129] The second buffer chamber 92 may be modified to connect the proximal side passage 92c directly to the stagnation section 92e.

[0130] The centrifugal compressor 10 can be used in any suitable application to compress any type of gas. For example, the centrifugal compressor 10 can be used in an air conditioning system to compress refrigerant gas. Furthermore, the centrifugal compressor 10 can be mounted on any structure other than a vehicle.

Claims

[1] Centrifugal compressor (10), comprising: a slowly rotating shaft (17) rotated by a drive source (18); an impeller (24) attached to a fast-rotating shaft (31) rotating at a higher speed than a speed of the slow-rotating shaft (17); a speed increaser (30) which transfers the energy of the slowly rotating shaft (17) to the rapidly rotating shaft (31); a housing (11) which a drive source chamber (12c) accommodating the drive source (18), an impeller chamber (15b) which accommodates the impeller (24), a speed increase chamber (13c) which accommodates the speed increaser (30), and a partition wall (14) having an insertion bore (14h) through which the high-speed shaft (31) is guided, the partition wall (14) separating the impeller chamber (15b) and the speed-increasing chamber (13c) from one another; a sealing member (71) provided between an outer peripheral surface of the high-speed shaft (31) and an inner peripheral surface of the insertion hole (14h); an oil pan (56) which stores the oil supplied to the speed increaser (30); an oil passage (60) which supplies oil stored in the oil pan (56) to the speed increaser (30) and returns the oil to the oil pan (56); and a pressure relief passage (90) connecting the oil pan (56) to a pressure relief bore (90b) opening onto an outer surface of the housing (11), wherein the pressure relief passage (90) comprises a first pressure relief passage (95) and a second pressure relief passage (96) branching from the oil pan (56), the second pressure relief passage (96) merges into the first pressure relief passage (95) to form a transition section (98), the pressure relief bore (90b) is arranged above the transition section (98) in a direction of gravity, the first pressure relief passage (95) is arranged below the transition section (98) in the direction of gravity, a minimum cross-sectional area of ​​the second pressure relief passage (96) is smaller than a minimum cross-sectional area of ​​the first pressure relief passage (95), the second pressure relief passage (96) has a bent portion (99) formed by bending the second pressure relief passage (96), the bent portion (99) being adapted to perform gas / liquid separation by crushing bubbles, wherein upon reaching the transition section (98) from the bent section (99), oil is returned to the oil pan (56) via the first pressure relief passage (95), and upon reaching the transition section (98) from the bent section (99), gas is discharged via the pressure relief bore (90b) to an outside of the housing (11). [2] Centrifugal compressor (10) according to claim 1, wherein of the horizontal directions, a direction perpendicular to an axis of the slowly rotating shaft (17) is defined as a first horizontal direction (A), the first pressure relief passage (95) contains a first buffer chamber (91) in the housing (11), the housing (11) has a first side surface (91a) and a second side surface (91b) opposite each other in the first horizontal direction (A), the first buffer chamber (91) is defined by the first side surface (91a) and the second side surface (91b), the bent portion (99) is formed in a vicinity of the first side surface (91a) of the first buffer chamber (91) in the first horizontal direction (A) and in an upper region in the direction of gravity, and the pressure relief hole (90b) is formed near the second side surface (91b) of the first buffer chamber (91) in the first horizontal direction (A) and in an upper region in the direction of gravity. [3] Centrifugal compressor (10) according to claim 2, wherein the second pressure relief passage (96) comprises a second buffer chamber (92) and a connecting passage (93) in the housing (11), the housing (11) has a first side surface (92a) and a second side surface (92b) opposite each other in the first horizontal direction (A), the second buffer chamber (92) is defined by the first side surface (92a) and the second side surface (92b), and the second pressure relief passage (96) is connected to the first buffer chamber (91) through the connecting passage (93). [4] The centrifugal compressor (10) according to claim 3, wherein the transition portion (98) is a connecting portion at which the first buffer chamber (91) and the connecting passage (93) are connected to each other. [5] Centrifugal compressor (10) according to claim 3 or 4, wherein the second buffer chamber (92) a proximal side passage (92c) connected to the oil pan (56), and an upper side passage (92d) connected to the proximal side passage (92c), and a width (H6) of the upper side passage (92d) in the first horizontal direction (A) is smaller than a width (H5) of the proximal side passage (92c). [6] Centrifugal compressor (10) according to one of claims 2 to 5, wherein in the first buffer chamber (91) a projection (16b) is provided through which the slowly rotating shaft (17) is guided, a first passage (911) and a second passage (912) are formed in the first buffer chamber (91), the first passage (911) is formed between the projection (16b) and the second side surface (91b), the second passage (912) has a passage formed between the projection (16b) and a lower part of the first buffer chamber (91) and a passage formed between the projection (16b) and the first side surface (91a), and a bypass pressure relief passage (97) is formed by the second passage (912) and a region in the first buffer chamber (91) located above the projection (16b).

Images