JP2023131372A - Root pump - Google Patents

Abstract

To provide a root pump which can inhibit contact of a rotor end surface with a rotor chamber end surface.SOLUTION: In a root pump 10, a rotor chamber 25 has: rotor chamber end surfaces 26 which face each other across a rotor 22 in an axial direction of a rotary shaft 16; and a rotor chamber peripheral surface 27 which surrounds a radial outer peripheral area of the rotor 22. The rotor 22 has rotor end surfaces 22c facing the rotor chamber end surfaces 26. The rotor end surface 22c is provided with pressing force generation grooves 28 which generate a pressure distribution of a hydrogen gas between the rotor chamber end surface 26 and the rotor end surface 22c by rotation of the rotor 22. The pressing force generation grooves 28 are provided so as to apply pressing force which separates the rotor 22 from each rotor chamber end surface 26 to the rotor 22.SELECTED DRAWING: Figure 2

Description

The present invention relates to roots pumps.

The Roots pump disclosed in Patent Document 1 has a drive shaft and a driven shaft parallel to the drive shaft. The drive shaft is rotatably supported by the rotor housing and the gear housing via bearings. The driven shaft is rotatably supported by the rotor housing via a bearing. Roots pumps have a drive rotor and a driven rotor housed in a rotor chamber. The drive rotor is fixed to the drive shaft. The driven rotor is fixed to the driven shaft.

The Roots pump sucks fluid into a rotor chamber from a suction port as a driving rotor and a driven rotor rotate synchronously. Fluid is trapped between the drive rotor, the driven rotor, and the inner peripheral surface of the rotor chamber. The trapped fluid is transferred toward the discharge port with the synchronous rotation of the drive rotor and the driven rotor. After the fluid is internally compressed within the rotor chamber, it is discharged from the discharge port to the outside of the rotor chamber.

JP2006-283665A

The drive rotor and the driven rotor may undergo thermal expansion in the axial direction due to internal compression of the fluid. Furthermore, the drive shaft and the driven shaft may move in the axial direction due to play caused by internal clearances of the bearings. For these reasons, there is a possibility that the axial end faces of each of the drive rotor and the driven rotor come into contact with the end faces defining the rotor chamber.

A Roots pump for solving the above problems includes a housing, a rotor chamber defined in the housing and having a suction hole for sucking fluid and a discharge hole for discharging fluid, and a rotor chamber rotatable through a bearing in the housing. A roots pump having a pair of supported rotating shafts, and a rotor that is attached to each of the pair of rotating shafts and rotates in opposite directions in the rotor chamber, the rotor chamber is configured to rotate in opposite directions to each other in the rotor chamber. In the axial direction, the rotor has rotor chamber end surfaces facing each other with the rotor in between, and a rotor chamber circumferential surface surrounding a radial outer peripheral area of the rotor, and the rotor has a rotor chamber end surface facing the rotor chamber end surface. At least one of the rotor chamber end surface and the rotor end surface is provided with a pressing force generating groove that generates pressure distribution in the fluid between the rotor chamber end surface and the rotor end surface by rotation of the rotor, The gist is that the pressing force generating groove is provided so as to apply a pressing force to the rotor to separate the rotor from the end surface of the rotor chamber.

According to this, the pressing force generating groove applies pressing force to the rotor as the rotor rotates. The pressing force separates the rotor from the end face of the rotor chamber. Therefore, it is possible to suppress the rotor end surface from coming into contact with the rotor chamber end surface during rotation of the rotor.

Regarding the Roots pump, the pressing force generating groove may be a long groove extending along the rotational direction of the rotor, and may be provided so that the groove depth changes along the rotational direction.
According to this, a pressing force along the rotational direction of the rotor can be applied to the rotor. Therefore, it is possible to suppress the generation of a pressing force that is not along the rotational direction of the rotor. As a result, even if a pressing force is applied to the rotor by the pressing force generating groove, the rotation of the rotor along the rotation direction can be prevented from being hindered by the pressing force.

In the Roots pump, the pressing force generating grooves are a pair of long grooves provided at point-symmetrical positions with respect to the rotational axis, and the pair of long grooves are such that a change in the groove depth of each groove causes the rotational axis to move toward the rotational axis. It may be set to be symmetrical with respect to a reference point.

According to this, since the pressing force applied to the rotor by the pair of pressing force generating grooves is also point symmetrical with respect to the rotation axis, it is possible to suppress the rotor from tilting due to the applied pressing force.
Regarding the Roots pump, the pressing force generating groove is a linear long groove extending in the tangential direction of the rotation circle of the rotor, and is provided so that the groove depth changes along the tangential direction, and The straight long groove is provided so as to extend in a direction perpendicular to a line passing through the end face of the rotor chamber and the axes of the pair of rotating shafts, and is provided on at least a line segment connecting the axes of the rotating shafts. Good too.

According to this, the linear long groove extends linearly along the tangential direction, and the groove depth changes in the tangential direction. Therefore, due to the pressing force generating grooves, a linear pressure distribution is generated in the fluid between the end face of the rotor chamber and the rotor. Therefore, a pressing force is applied to the rotor regardless of the rotational direction of the rotor. The straight long groove is provided on a line segment connecting the axes of the rotating shafts. This line segment is in the area where both rotor end faces face each other. Therefore, it is possible to prevent the pressing force applied to one rotor from being different from the pressing force applied to the other rotor.

Regarding the Roots pump, the pressing force generating groove is provided on both the rotor chamber end face and the rotor end face, and the pressing force generating groove on the rotor chamber end face is formed from the rotation locus of the pressing force generating groove on the rotor end face. It may be provided at a different position.

According to this, the pressing force generating grooves on the end face of the rotor and the pressing force generating grooves on the end face of the rotor chamber do not interfere with each other. Pressure fluctuations can be suppressed. Therefore, tilting of the rotor due to uneven pressing force can be suppressed.

According to the present invention, contact of the rotor end surface with the rotor chamber end surface can be suppressed.

It is a sectional view showing the roots pump of a 1st embodiment. It is a sectional view showing the roots pump of a 1st embodiment. FIG. 3 is a sectional view taken along the line 3-3 in FIG. 2 showing a pressing force generation groove, and a diagram illustrating pressure distribution. It is a sectional view of the Roots pump of a 2nd embodiment. It is a figure explaining a pressing force generation groove and pressure distribution. It is a sectional view showing another example of a Roots pump.

[First embodiment]
A first embodiment of a Roots pump will be described below with reference to FIGS. 1 to 3.
<Overall Roots Pump>
Roots pumps are installed in fuel cell vehicles as hydrogen pumps. A fuel cell vehicle is equipped with a fuel cell system that supplies oxygen and hydrogen to generate electricity. The Roots pump supplies hydrogen gas discharged from the fuel cell to the fuel cell again.

<Housing>
As shown in FIG. 1, the Roots pump 10 has 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.

Motor housing 12 is connected to gear housing 13. Further, the rotor housing 14 is connected to the gear housing 13. Cover member 15 is connected to rotor housing 14 .

The motor housing 12 has a plate-shaped bottom wall 12a and a peripheral wall 12b extending in a cylindrical shape from the outer circumference of the bottom wall 12a. The gear housing 13 has a plate-shaped bottom wall 13a and a peripheral wall 13b extending in a cylindrical shape from the outer circumference of the bottom wall 13a. The rotor housing 14 has a plate-shaped bottom wall 14a and a peripheral wall 14b extending in a cylindrical shape from the outer periphery of the bottom wall 14a.

The bottom wall 13a of the gear housing 13 and the peripheral wall 12b of the motor housing 12 are butted against each other. The bottom wall 14a of the rotor housing 14 and the peripheral wall 13b of the gear housing 13 are butted against each other. The cover member 15 has a plate shape. The cover member 15 is abutted against the peripheral wall 14b of the rotor housing 14.

A gear chamber 24 is defined in the housing 11 . The gear chamber 24 is defined by the bottom wall 13a of the gear housing 13, the peripheral wall 13b of the gear housing 13, and the bottom wall 14a of the rotor housing 14.

<Rotor room>
Roots pump 10 has a rotor chamber 25 defined in housing 11 . The rotor chamber 25 is defined by the bottom wall 14 a of the rotor housing 14 , the peripheral wall 14 b of the rotor housing 14 , and the cover member 15 .

The rotor chamber 25 has a pair of rotor chamber end surfaces 26 and a rotor chamber peripheral surface 27. One of the pair of rotor chamber end surfaces 26 is formed by the inner wall surface 14c of the bottom wall 14a of the rotor housing 14, and the other of the pair of rotor chamber end surfaces 26 is formed by the inner wall surface 15a of the cover member 15. has been done. The pair of rotor chamber end surfaces 26 are located on opposite sides of the rotor chamber 25. The rotor chamber peripheral surface 27 is formed by the inner peripheral surface 14d of the peripheral wall 14b.

<Rotation axis>
The Roots pump 10 has a driving shaft 16a and a driven shaft 16b as the rotating shaft 16. The drive shaft 16a and the driven shaft 16b are arranged in parallel. The direction in which the axis L of the rotating shaft 16 extends is defined as the axial direction. The drive shaft 16a passes through the bottom wall 13a of the gear housing 13 and the bottom wall 14a of the rotor housing 14. The driven shaft 16b passes through the bottom wall 14a of the rotor housing 14.

The first drive bearing 31a is arranged on the bottom wall 13a of the gear housing 13. The second drive bearing 31b is arranged on the bottom wall 14a of the rotor housing 14. The third drive bearing 31c is arranged on the bottom wall 12a of the motor housing 12. The drive shaft 16a is rotatably supported by the housing 11 via a first drive bearing 31a, a second drive bearing 31b, and a third drive bearing 31c.

The first driven bearing 41a is arranged on the bottom wall 13a of the gear housing 13. The second driven bearing 41b is arranged on the bottom wall 14a of the rotor housing 14. The driven shaft 16b is rotatably supported by the housing 11 via a first driven bearing 41a and a second driven bearing 41b.

The first seal member 32a is provided on the bottom wall 13a of the gear housing 13. The first seal member 32a seals between the drive shaft 16a and the bottom wall 13a of the gear housing 13. The second seal member 32b is provided on the bottom wall 14a of the rotor housing 14. The second seal member 32b seals between the drive shaft 16a and the bottom wall 14a. The third seal member 32c is provided on the bottom wall 14a of the rotor housing 14. The third seal member 32c seals between the driven shaft 16b and the bottom wall 14a.

<Electric motor>
Roots pump 10 includes an electric motor 50 that rotates a drive shaft 16a. The electric motor 50 is housed in a motor chamber 23 defined in the housing 11. The motor chamber 23 is defined by the bottom wall 12a of the motor housing 12, the peripheral wall 12b of the motor housing 12, and the bottom wall 13a of the gear housing 13. The electric motor 50 rotates the drive shaft 16a.

The Roots pump 10 includes a disk-shaped drive gear 18 fixed to a drive shaft 16a, and a disk-shaped driven gear 19 fixed to a driven shaft 16b. The driving gear 18 and the driven gear 19 are housed in the gear chamber 24. The driven gear 19 meshes with the drive gear 18 and rotates. The driven gear 19 is rotated by the drive gear 18 and the driven gear 19 in the opposite direction to the drive shaft 16a.

<Suction hole and discharge hole>
The rotor chamber 25 has a suction hole 45 for sucking hydrogen gas into the rotor chamber 25, and a discharge hole 46 for discharging the hydrogen gas inside the rotor chamber 25. The suction hole 45 and the discharge hole 46 are formed in the peripheral wall 14b of the rotor housing 14. The suction hole 45 and the discharge hole 46 face each other with the rotor chamber 25 in between. The suction hole 45 and the discharge hole 46 communicate the rotor chamber 25 with the outside.

<Drive rotor and driven rotor>
The Roots pump 10 includes a drive rotor 20 as a bilobed cocoon-shaped rotor 22 and a driven rotor 21 .

Drive rotor 20 is a rotor rotated by drive gear 18. The driven rotor 21 is a rotor rotated by the driven gear 19. The pair of rotors 22 is housed in a rotor chamber 25. The drive rotor 20 is attached to the drive shaft 16a. The driven rotor 21 is attached to the driven shaft 16b. The driven rotor 21 rotates together with the drive rotor 20. Therefore, it can be said that the drive rotor 20 and the driven rotor 21 are a pair of rotors 22 that are rotated in opposite directions within the rotor chamber 25.

The pair of rotor chamber end surfaces 26 face each other with the pair of rotors 22 in between in the axial direction of the pair of rotating shafts 16 . The rotor chamber peripheral surface 27 surrounds the outer periphery of the pair of rotors 22 in the radial direction. Note that the radial direction of the drive rotor 20 matches the radial direction of the drive shaft 16a, and the radial direction of the driven rotor 21 matches the radial direction of the driven shaft 16b.

As shown in FIG. 2, each of the pair of rotors 22 has a pair of leaf portions 22a. The rotor 22 has a tip portion P1 on each leaf portion 22a. The tip portion P1 is a portion that faces the rotor chamber circumferential surface 27 as the rotor 22 rotates.

The tip portion P1 of the rotor 22 is spaced apart from the rotor chamber circumferential surface 27. Although not shown, there is a clearance within a predetermined range between the tip portion P1 and the rotor chamber circumferential surface 27. Therefore, it can be said that the rotor chamber circumferential surface 27 faces the tip end P1 of the rotor 22 with a predetermined clearance therebetween. The clearance is set within a predetermined range so as to prevent hydrogen gas from leaking from the high pressure side to the low pressure side through the clearance.

As shown in FIG. 1, the rotor 22 has a pair of rotor end surfaces 22c and a rotor peripheral surface 22d. The pair of rotor end surfaces 22c are both end surfaces of the rotor 22 in the axial direction. One rotor end surface 22c faces the bottom wall 14a, which is one rotor chamber end surface 26, and the other rotor end surface 22c faces the inner wall surface 15a, which is the other rotor chamber end surface 26.

As shown in FIGS. 2 and 3, the rotor end surface 22c is spaced apart from the rotor chamber end surface 26. That is, an axial clearance CL within a predetermined range exists between the rotor end surface 22c and the rotor chamber end surface 26. The axial clearance CL is set within a predetermined range so as to prevent hydrogen gas from leaking from the high pressure side to the low pressure side through the axial clearance CL.

<Press force generation groove>
A pressing force generating groove 28 is provided in each rotor end surface 22c. The pressing force generating groove 28 is provided to apply a pressing force to the rotor 22 to separate the rotor 22 from the rotor chamber end surface 26. The pressing force generating groove 28 is an arcuate long groove extending in the rotational direction R of the rotor 22.

The center line N is an imaginary line extending along the rotor end surface 22c and passing through the tip portions P1 of the pair of leaf portions 22a. The direction in which this center line N extends is defined as the longitudinal direction of the rotor end surface 22c. It can be said that the tip portion P1 is located at both ends of the rotor 22 in the longitudinal direction.

Eight pressing force generating grooves 28 are provided on each rotor end surface 22c. Four pressing force generating grooves 28 are provided on both sides of the rotor end surface 22c in the longitudinal direction. That is, each of the pair of leaf portions 22a is provided with four pressing force generating grooves 28.

The four pressing force generating grooves 28 provided in each leaf portion 22a are provided two each on both sides of the center line N. The four pressing force generating grooves 28 provided in each leaf portion 22a are divided into two stages along the longitudinal direction of the rotor end surface 22c. Among the pressing force generating grooves 28 divided into two stages, the two pressing force generating grooves 28 near the tip P1 of the leaf portion 22a are the first pressing force generating grooves 281, and the two pressing force generating grooves 28 near the axis L The generating groove 28 is defined as a second pressing force generating groove 282. One rotor end surface 22c is provided with four first pressing force generating grooves 281 and four second pressing force generating grooves 282.

The four first pressing force generation grooves 281 are arranged on one virtual circle G1, and the four second pressing force generation grooves 282 are arranged on another virtual circle G2 different from the virtual circle G1. . That is, the first pressing force generating groove 281 is an arcuate long groove extending along the virtual circle G1. The second pressing force generating groove 282 is an arcuate long groove extending along the virtual circle G2. The center point of the virtual circle G1 and the virtual circle G2 is the axis L. The radius of virtual circle G1 is larger than the radius of virtual circle G2.

Each pressing force generating groove 28 has a groove starting end 28a and a groove ending end 28b. The pressing force generating groove 28 extends from the groove end 28b toward the groove start end 28a along the rotation direction R of the rotor 22. The groove starting end 28a is located on the leading side of each rotor 22 in the rotation direction R. The groove end 28b is located on the trailing side of each rotor 22 in the rotation direction R. The groove starting end 28a and the groove ending end 28b are separated from the edge of the rotor end surface 22c. Therefore, the groove starting end 28a and the groove ending end 28b are located within the plane of the rotor end surface 22c.

Each pressing force generating groove 28 has a groove bottom surface 28d. The groove bottom surface 28d gradually slopes from the groove start end 28a to the groove end 28b. The groove bottom surface 28d slopes away from the rotor end surface 22c as it goes from the groove start end 28a to the groove end 28b.

The pressing force generating groove 28 has a groove depth F that becomes shallower as the arc extends in the rotation direction R from the groove end 28b toward the groove start end 28a. Therefore, the pressing force generating groove 28 is provided so that the groove depth F changes along the rotation direction R. Specifically, the groove depth F of the pressing force generating groove 28 gradually becomes deeper from the leading side to the trailing side in the rotation direction R.

The pressing force generating grooves 28 are provided at point-symmetrical positions with respect to the rotating shaft 16. More specifically, in the axial direction of the rotating shaft 16, the pressing force generating grooves 28 are point symmetrical with respect to the axis L, which is the center point of the rotating shaft 16.

In one rotor end surface 22c, the four first pressing force generating grooves 281 have two sets of first pressing force generating grooves 281 provided at point-symmetrical positions. In the pair of first pressing force generating grooves 281, the groove starting end 28a and the groove ending end 28b are located in point-symmetrical positions with respect to the axis L of the rotating shaft 16. Therefore, the pair of first pressing force generating grooves 281 are set so that the change in the groove depth F of each groove is symmetrical with respect to the axis L of the rotating shaft 16. Specifically, in the pair of first pressing force generating grooves 281 provided at point-symmetrical positions, the groove depth F becomes deeper from the groove start end 28a toward the groove end 28b.

In one rotor end surface 22c, the four second pressing force generating grooves 282 have two sets of second pressing force generating grooves 282 provided at point-symmetrical positions. In the pair of second pressing force generating grooves 282, the groove starting end 28a and the groove ending end 28b are located in point-symmetrical positions with respect to the axis L of the rotating shaft 16. Therefore, the pair of second pressing force generating grooves 282 are set so that the change in the groove depth F of each groove is symmetrical with respect to the axis L of the rotating shaft 16. Specifically, the pair of second pressing force generating grooves 282 provided at point-symmetrical positions are configured such that the groove depth F increases from the groove starting end 28a to the groove ending end 28b.

When the pair of rotors 22 rotate, a flow rate of hydrogen gas is generated relative to the rotor end surface 22c. Note that the rotational speeds of the pair of rotors 22 are constant. The flow rate of hydrogen gas becomes slower as the groove depth F of the pressing force generation groove 28 becomes deeper. Therefore, the flow rate of hydrogen gas gradually decreases from the groove start end 28a toward the groove end 28b. Due to the generation of this difference in flow velocity of the hydrogen gas, the pressing force generation groove 28 generates a pressure distribution in the hydrogen gas. That is, the pressing force generating groove 28 generates a pressure distribution in the hydrogen gas between the rotor chamber end surface 26 and the rotor 22 due to the rotation of the rotor 22.

The graph of FIG. 3 shows the relationship between the groove depth F of the pressing force generating groove 28 and the pressure distribution. The horizontal axis of the graph in FIG. 3 corresponds to the groove depth F, and the vertical axis of the graph in FIG. 3 indicates the magnitude of the pressure generated in the hydrogen gas. The pressure distribution becomes larger as the groove depth F of the pressing force generation groove 28 becomes deeper.

In each rotor end surface 22c, two pressing force generating grooves 28 are lined up in the rotation direction R. Therefore, pressure distribution occurs in the hydrogen gas between the rotor end surface 22c and the rotor chamber end surface 26 at two locations along the rotation direction R. In each rotor end surface 22c, the pressing force generating grooves 28 are arranged in two stages in the longitudinal direction of the rotor 22 in each leaf portion 22a. Therefore, pressure distribution occurs at two locations along the longitudinal direction of the rotor 22 in the hydrogen gas between the rotor end surface 22c and the rotor chamber end surface 26 at the leaf portion 22a. Therefore, pressure distribution occurs at eight locations in the hydrogen gas between the entire rotor end surface 22c and the rotor chamber end surface 26.

A pair of first pressing force generation grooves 281 are provided symmetrically with respect to the rotation axis 16, and a pair of second pressing force generation grooves 282 are provided symmetrically with respect to the rotation axis 16. It is set symmetrically. The change in the groove depth F of the pressing force generating groove 28 is also point symmetrical with respect to the rotating shaft 16. Therefore, the hydrogen gas between the entirety of one rotor end face 22c and the rotor chamber end face 26 has almost no bias even if pressure distribution occurs at eight locations.

When a pressure distribution is generated in the hydrogen gas by the pressing force generation groove 28, a pressing force is applied to the rotor 22 to separate it from the rotor chamber end surface 26. Since the pressing force generation grooves 28 are provided on both rotor end faces 22c, a pressing force is applied to the rotor 22 to separate it from both rotor chamber end faces 26.

The groove depth F and the dimension in the longitudinal direction of the pressing force generation groove 28 are appropriately adjusted by the pressing force from both ends of the rotor 22 in the axial direction so that the axial clearance CL can be maintained within a predetermined range. For example, it is assumed that among the axial clearances CL on both sides of the rotor 22 in the axial direction, one axial clearance CL is smaller than the other axial clearance CL. In this case, the groove depth F of one pressing force generating groove 28 is made deeper than the groove depth F of the other pressing force generating groove 28. By doing so, the pressing force applied to the rotor 22 by one pressing force generating groove 28 becomes larger than the pressing force applied to the rotor 22 by the other pressing force generating groove 28. Thereby, while the rotor 22 is rotating, the axial clearance CL is maintained within a predetermined range by the pressing force from both ends of the rotor 22 in the axial direction.

[Operation of the first embodiment]
Next, the operation of this embodiment will be explained.
The drive shaft 16a is rotated by the drive of the electric motor 50. Then, the driven shaft 16b rotates in the opposite direction to the drive shaft 16a through the gear connection of the drive gear 18 and the driven gear 19. As a result, the pair of rotors 22 rotate in opposite directions. The Roots pump 10 sucks hydrogen gas into the rotor chamber 25 through the suction hole 45 and discharges hydrogen gas from the rotor chamber 25 through the discharge hole 46 by rotating the pair of rotors 22 .

As the hydrogen gas is internally compressed, the rotor 22 may thermally expand in the axial direction. Furthermore, due to the play of the drive shaft 16a with respect to the first to third drive bearings 31a to 31c and the play of the driven shaft 16b with respect to the first driven bearing 41a and the second driven bearing 41b, the rotating shaft 16 is moved in the axial direction. It may move.

At these times, in the rotor 22, the axial clearance CL between one rotor end surface 22c of the pair of rotor end surfaces 22c and one opposing rotor chamber end surface 26 tends to decrease. As the axial clearance CL becomes narrower, the pressing force applied to the rotor 22 by the pressing force generating groove 28 increases, so the rotor 22 moves in a direction that increases the axial clearance CL. Since the pressing force generating grooves 28 are provided on both rotor end faces 22c, the pressing force generating grooves 28 suppress a decrease in both axial clearances CL. As a result, since both axial clearances CL are maintained within a predetermined range, contact between the rotor end surface 22c and the rotor chamber end surface 26 can be suppressed.

[Effects of the first embodiment]
According to the above embodiment, the following effects can be obtained.
(1-1) The roots pump 10 has a pressing force generating groove 28. As the pair of rotors 22 rotate, a pressing force is applied to the rotor 22 by the pressing force generating groove 28 in a direction to separate the rotor end surface 22c from the rotor chamber end surface 26.

The rotor 22 thermally expands in the axial direction due to internal compression of hydrogen gas in the rotor chamber 25, and the rotating shaft 16 moves in the axial direction due to play caused by internal gaps between the bearings 31a to 31c and 41a to 41b. Sometimes. Even if such thermal expansion or axial movement occurs, the rotor 22 can be separated from the rotor chamber end surface 26 by the pressing force. Therefore, even if thermal expansion or movement in the axial direction occurs, it is possible to suppress the rotor end surface 22c from coming into contact with the rotor chamber end surface 26 during rotation of the rotor 22. Therefore, it is possible to prevent the rotor 22, the cover member 15, and the rotor housing 14 from being scraped due to contact between the rotor end surface 22c and the rotor chamber end surface 26 during rotation. As a result, it is possible to suppress excessive increase in the axial clearance CL and generation of foreign matter due to contact.

(1-2) The pressing force generating groove 28 is a long groove extending in an arc shape along the rotation direction R. The pressing force generating groove 28 has a groove depth F that changes along the rotation direction R. Therefore, a pressure distribution can be generated in the hydrogen gas due to a change in the groove depth F as the rotor 22 rotates. Further, a pressing force along the rotational direction R can be applied to the rotor 22 by the pressing force generating groove 28. As a result, even if a pressing force is applied to the rotor 22 by the pressing force generating groove 28, the rotation of the rotor 22 along the rotational direction R can be prevented from being hindered by the pressing force.

(1-3) Each of the first pressing force generating groove 281 and the second pressing force generating groove 282 is provided at a point symmetrical position with respect to the rotation axis 16. The pair of first pressing force generating grooves 281 and the pair of second pressing force generating grooves 282 are arranged so that the change in groove depth F is point symmetrical with respect to the rotation axis 16. It is set to be. Therefore, the pressing force applied to the rotor 22 by the pair of first pressing force generating grooves 281 and the pair of second pressing force generating grooves 282 is also point symmetrical with respect to the rotation axis 16, so that the applied pressing force Therefore, tilting of the rotor 22 can be suppressed.

(1-4) The pressing force generating groove 28 is arranged inside the edge of the rotor end surface 22c. That is, the pressing force generating groove 28 is arranged within the plane of the rotor end surface 22c. Therefore, the rooms defined within the rotor chamber 25 are not connected to each other by the pressing force generating grooves 28. As a result, even if the pressing force generating groove 28 is provided in the rotor end face 22c, the hydrogen gas transfer efficiency by the Roots pump 10 does not decrease.

(1-5) The groove bottom surface 28d of the pressing force generating groove 28 is inclined so that the groove depth F gradually increases from the groove start end 28a to the groove end 28b. For example, compared to the case where the groove bottom surface 28d is stepped, it is easier to generate a difference in the flow velocity of hydrogen gas, and therefore it is easier to generate a pressure distribution in the hydrogen gas.

(1-6) The pressing force generating groove 28 has a first pressing force generating groove 281 and a second pressing force generating groove 282 having different lengths, and further includes a first pressing force generating groove 281 and a second pressing force generating groove 282. Two of the generation grooves 282 are provided side by side in the rotation direction R. Therefore, pressing force is applied to the rotor 22 at eight locations. Therefore, for example, contact between the rotor end surface 22c and the rotor chamber end surface 26 can be suppressed more favorably than when the pressing force is applied only to one location.

[Second embodiment]
Next, a second embodiment of the Roots pump 10 will be described with reference to FIGS. 4 and 5. In addition, since the second embodiment has a configuration in which the position and shape of the pressing force generating grooves of the first embodiment are changed, a detailed description of the similar parts will be omitted.

As shown in FIGS. 4 and 5, an arc-shaped long arc groove 39 and a linear long groove 40 serving as pressing force generating grooves are provided in each rotor chamber end surface 26. The arc long groove 39 and the straight long groove 40 are provided in the bottom wall 14a of the rotor housing 14 and the cover member 15, respectively. Each of the arcuate long grooves 39 and the linear long grooves 40 is provided to apply a pressing force to the rotor 22 to separate the rotor 22 from the rotor chamber end surface 26 .

When looking at the drive rotor 20 in the axial direction, the rotation circle drawn by the tip end P1 of the drive rotor 20 is defined as a rotation locus C1. When this rotation trajectory C1 is projected onto the rotor chamber end surface 26, a circular first region T1 is formed on the rotor chamber end surface 26. The first area T1 is an area inside the rotation locus C1.

When the driven rotor 21 is viewed in the axial direction, the rotation circle drawn by the tip end P1 of the driven rotor 21 is defined as a rotation locus C2. When this rotation trajectory C2 is projected onto the rotor chamber end surface 26, a circular second region T2 is formed on the rotor chamber end surface 26. The second area T2 is an area inside the rotation locus C2.

A common region T3 is formed in the rotor chamber end surface 26, where the first region T1 and the second region T2 overlap. The shared area T3 is an area through which both the drive rotor 20 and the driven rotor 21 pass.
A straight line extending along the rotor chamber end surface 26 is defined as a first imaginary line M1. The first imaginary line M1 is a straight line connecting the axial center L of the drive shaft 16a and the axial center L of the driven shaft 16b. In other words, the first imaginary line M1 can be said to be a straight line connecting the axes L of the pair of rotating shafts 16.

A pair of parallel straight lines extending along the rotor chamber end surface 26 are defined as a second imaginary line M2 and a third imaginary line M3. The second imaginary line M2 passes through the axis L of the drive shaft 16a and is orthogonal to the first imaginary line M1. The third imaginary line M3 passes through the axis L of the driven shaft 16b and is orthogonal to the first imaginary line M1. The second virtual line M2 extends in the tangential direction of the rotation trajectory C1. The third virtual line M3 extends in the tangential direction of the rotation trajectory C2. The direction in which the second imaginary line M2 and the third imaginary line M3 extend is defined as a tangential direction.

Eight arcuate long grooves 39 and eight straight long grooves 40 are provided in each of the first region T1 and the second region T2. Four arcuate long grooves 39 are provided at both ends of the imaginary lines M2 and M3. The four long arc grooves 39 provided at each end of the imaginary lines M2, M3 are provided two each on both sides of the imaginary lines M2, M3. The four long arc grooves 39 provided at each end of the virtual lines M2 and M3 are divided into two stages in the tangential direction. The arcuate long grooves 39 divided into two stages are arranged on two concentric circles with the axis L as the center point.

Of the two-stage arcuate long grooves 39, the arcuate long grooves 39 closer to the rotation trajectories C1 and C2 are defined as the first arcuate long grooves 391, and among the two-stage arcuate long grooves 39, the arcuate long grooves 39 closer to the axis L is the second circular arc long groove 392. The first circular arc long groove 391 is arranged on one virtual circle, and the second circular arc long groove 392 is arranged on another virtual circle different from the virtual circle.

Each arc long groove 39 has a groove start end 39a and a groove end 39b. The groove starting end 39a is located on the trailing side of each rotor 22 in the rotation direction R. The groove end 39b is located on the leading side of each rotor 22 in the rotation direction R. The length along the arc from the groove start end 39a to the groove end 39b is shorter than the length along the rotation direction R of the rotor end surface 22c. Therefore, all of the four arc long grooves 39 can be opposed to one leaf portion 22a of the rotor end surface 22c.

The arc long groove 39 has a groove bottom surface 39d. The groove bottom surface 39d gradually slopes from the groove start end 39a to the groove end 39b. The groove bottom surface 39d slopes away from the rotor chamber end surface 26 as it goes from the groove start end 39a to the groove end 39b. The arcuate long groove 39 has a groove depth F that gradually increases from the groove start end 39a to the groove end 39b along the rotational direction R of the rotor 22. Therefore, the arc long groove 392 is provided so that the groove depth F changes along the rotation direction R. Specifically, the groove depth F of the arcuate long groove 39 becomes gradually shallower from the leading side to the trailing side in the rotation direction R.

The arc long grooves 39 are provided at point-symmetrical positions with respect to the rotating shaft 16. More specifically, in the axial direction of the rotating shaft 16, the arc long grooves 39 are point symmetrical with respect to the axis L, which is the center point of the rotating shaft 16.

In each region T1, T2, the first circular arc long groove 391 has two sets of first circular arc long grooves 391 provided at point-symmetrical positions. In the pair of first circular arc long grooves 391, the groove starting end 39a and the groove ending end 39b are located in point-symmetrical positions with respect to the axis L of the rotating shaft 16. For this reason, the change in the groove depth F of the pair of first circular arc long grooves 391 is set to be point symmetrical with respect to the axis L of the rotating shaft 16. Specifically, the pair of first circular arc long grooves 391 provided at point-symmetrical positions are configured such that the groove depth F becomes deeper from the groove start end 39a toward the groove end 39b.

In each region T1, T2, the second circular arc long groove 392 has two sets of second circular arc long grooves 392 provided at point-symmetrical positions. In the pair of second circular arc long grooves 392, the groove starting end 39a and the groove ending end 39b are located in point-symmetrical positions with respect to the axis L of the rotating shaft 16. For this reason, the change in the groove depth F of the pair of second circular arc long grooves 392 is set to be point symmetrical with respect to the axis L of the rotating shaft 16. Specifically, the pair of second circular arc elongated grooves 392 provided at point-symmetrical positions are configured such that the groove depth F becomes deeper from the groove start end 39a toward the groove end 39b.

Four straight long grooves 40 are provided on both sides of the imaginary lines M2 and M3. The four straight long grooves 40 provided in the common area T3 are the four straight long grooves 40 in the first area T1, and also the four straight long grooves 40 in the second area T2. The straight long groove 40 provided in the common area T3 is provided so as to be orthogonal to the rotor chamber end surface 26 and the first imaginary line M1. Moreover, the straight long grooves 40 provided in the common area T3 are provided in a direction that is orthogonal to the first imaginary line M1. Therefore, the straight long groove 40 provided in the common area T3 is provided on a line segment connecting the pair of axes L in the first imaginary line M1.

The four straight long grooves 40 provided on both sides of the imaginary lines M2 and M3 are divided into two stages in the direction in which the first imaginary line M1 extends.
Among the straight long grooves 40 divided into two stages, the straight long grooves 40 closest to the rotation loci C1 and C2 are the first straight long grooves 401, and among the straight long grooves 40 divided into two stages, the straight long grooves 40 close to the axis L is the second straight long groove 402.

The length of the straight long groove 40 extends in the tangential direction. The straight long groove 40 is parallel to the imaginary lines M2 and M3. The straight long groove 40 has a groove start end 40a and a groove end 40b. The groove starting end 40a is located on the trailing side of the rotor 22 in the rotation direction R. The groove end 40b is located on the leading side of the rotor 22 in the rotation direction R. The length from the groove start end 40a to the groove end 40b is shorter than the length of the rotor end surface 22c of the leaf portion 22a along the rotation direction R. Therefore, all four straight long grooves 40 can be opposed to one leaf portion 22a of the rotor end surface 22c.

Each straight long groove 40 has a groove bottom surface 40d. The groove bottom surface 40d is inclined from the groove starting end 40a to the groove ending end 40b. The groove bottom surface 40d slopes away from the rotor chamber end surface 26 as it goes from the groove start end 40a to the groove end 40b. Therefore, the groove depth F of the straight long groove 40 increases as it goes from the groove start end 40a to the groove end 40b along the rotational direction R of the rotor 22. Therefore, the linear long groove 40 is provided so that the groove depth F changes along the rotation direction R. Specifically, the groove depth F of the straight long groove 40 becomes gradually shallower from the leading side to the trailing side in the rotation direction R.

The straight long grooves 40 are provided at point-symmetrical positions with respect to the rotating shaft 16. More specifically, in the axial direction of the rotating shaft 16, the straight long grooves 40 are point symmetrical with respect to the axis L, which is the center point of the rotating shaft 16.

In each region T1, T2, the first linear long groove 401 has two sets of first linear long grooves 401 provided at point-symmetrical positions. In the pair of first linear long grooves 401, the groove starting end 40a and the groove ending end 40b are located in point-symmetrical positions with respect to the axis L of the rotating shaft 16. For this reason, the change in the groove depth F of the pair of first straight long grooves 401 is set to be point symmetrical with respect to the axis L of the rotating shaft 16. Specifically, the pair of first linear long grooves 401 provided at point-symmetrical positions are configured such that the groove depth F increases from the groove start end 40a to the groove end 40b.

In each region T1, T2, the second straight long groove 402 has two sets of second straight long grooves 402 provided at point-symmetrical positions. In the pair of second linear long grooves 402, the groove starting end 40a and the groove ending end 40b are located in point-symmetrical positions with respect to the axis L of the rotating shaft 16. For this reason, the change in the groove depth F of the pair of second linear long grooves 402 is set to be point symmetrical with respect to the axis L of the rotating shaft 16. Specifically, the pair of second straight long grooves 402 provided at point-symmetrical positions are configured such that the groove depth F becomes deeper from the groove start end 40a toward the groove end 40b.

Regarding the straight long grooves 40 provided in the common area T3, the straight long grooves 40 which become the first straight long grooves 401 when facing the rotor end surface 22c of the drive rotor 20 are the second straight long grooves 40 when facing the rotor end surface 22c of the driven rotor 21. This becomes a straight long groove 402. The groove depth F of the straight long groove 40 in the shared region T3 becomes gradually shallower from the leading side to the trailing side in the rotation direction R.

Focusing on the rotor end surface 22c at one leaf portion 22a of the rotor end surface 22c, there are two points in time: when only the circular long grooves 39 are opposed to the rotor end surface 22c of the leaf portion 22a, and when only the straight long grooves 40 are opposed. , and a point in time when it faces both the arcuate long groove 39 and the straight long groove 40.

As the rotor 22 rotates, the rotor end surface 22c of the leaf portion 22a transitions from a state in which it faces the four arcuate long grooves 39 to a state in which it faces the second straight long groove 402 of the straight long grooves 40. At this time, the rotor end surface 22c faces both the arcuate long groove 39 and the linear long groove 40. Thereafter, as the rotor 22 rotates, the rotor end surface 22c of the leaf portion 22a transitions to a state where it faces the first linear long groove 401 and the second linear long groove 402. Also at this time, the rotor end surface 22c faces both the arcuate long groove 39 and the straight long groove 40. Thereafter, as the rotor 22 rotates, the rotor end surface 22c transitions to a state where it faces the four straight long grooves 40. In this way, it can be said that at least one of the arcuate long grooves 39 and the linear long grooves 40 always opposes the rotor end surface 22c of the leaf portion 22a. Since both the arc long grooves 39 and the straight long grooves 40 face the rotor end surface 22c, the shortest distance between the second arc long grooves 392 and the second straight long grooves 402 is larger than the maximum dimension of the leaf portion 22a in the rotation direction R. There is.

The graph of FIG. 5 shows the relationship between the groove depth F of the straight long groove 40 and the pressure distribution. The horizontal axis of the graph in FIG. 5 corresponds to the groove depth F, and the vertical axis of the graph in FIG. 5 indicates the magnitude of the pressure generated in the hydrogen gas. The pressure distribution becomes larger as the groove depth F of the straight long groove 40 becomes deeper.

[Operation of the second embodiment]
As described above, when the pair of rotors 22 rotate, a flow velocity of hydrogen gas is generated relative to the rotor end surface 22c. The flow rate of hydrogen gas gradually decreases from the groove starting ends 39a, 40a toward the groove endings 39b, 40b. Due to the generation of such a flow velocity difference, a pressure distribution is generated in the hydrogen gas by the arc long grooves 39 and the straight long grooves 40. Since at least one of the arcuate long grooves 39 and the straight long grooves 40 always faces the rotor end face 22c, a pressure distribution always occurs in the hydrogen gas between the rotor end face 22c and the rotor chamber end face 26.

[Effects of the second embodiment]
Therefore, according to the second embodiment, in addition to the effect (1-1) described in the first embodiment, the following effect can be obtained.

(2-1) The arc long groove 39 is a long groove that extends in an arc shape along the rotation direction R. The arcuate long groove 39 has a groove depth F that changes along the rotation direction R. Therefore, a pressure distribution can be generated in the hydrogen gas due to a change in the groove depth F as the rotor 22 rotates in the rotational direction R. As a result, a pressing force along the rotational direction R can be applied to the rotor 22. Therefore, generation of a pressing force not along the rotational direction R of the rotor 22 can be suppressed. As a result, even if a pressing force is generated by the arcuate long groove 39, the rotation of the rotor 22 along the rotation direction R is not hindered by the pressing force.

(2-2) The straight long groove 40 is a long groove extending in the tangential direction. The straight long grooves 40 are arranged on both sides of the imaginary lines M2 and M3. Therefore, when the rotor end face 22c faces the linear long grooves 40 on both sides of the imaginary lines M2 and M3, it is possible to suppress the pressing force applied to the rotor 22 from being biased across the imaginary lines M2 and M3. Therefore, even if a pressing force is applied to the rotor 22, tilting of the rotor 22 due to the pressing force can be suppressed.

(2-3) The straight long groove 40 provided in the common area T3 is a long groove extending in the tangential direction. The straight long grooves 40 provided in the area opposite to the common area T3 across the virtual lines M2 and M3 are also long grooves extending in the tangential direction. Therefore, when the rotor end face 22c faces the straight long groove 40 of the common area T3, the pressing force applied to the rotor 22 can be prevented from being biased across the imaginary lines M2 and M3. Therefore, tilting of the rotor 22 to which the pressing force is applied can be suppressed.

(2-4) Around the axis L, arc long grooves 39 and straight long grooves 40 are arranged alternately at intervals. During rotation of the rotor 22, the rotor end surface 22c always faces at least one of the arcuate long grooves 39 and the linear long grooves 40. Therefore, the arc long grooves 39 and the straight long grooves 40 can always generate a pressure distribution for the hydrogen gas between the rotor end surface 22c and the rotor chamber end surface 26. In other words, the arcuate long grooves 39 and the linear long grooves 40 can always apply a pressing force that separates the rotor 22 from the rotor chamber end surface 26.

This embodiment can be modified and implemented as follows. This embodiment and the following modified examples can be implemented in combination with each other within a technically consistent range.
As shown in FIG. 6, the pressing force generating grooves may be provided on both the rotor chamber end surface 26 and the rotor end surface 22c. In this case, the pressing force generating groove 38 of the rotor chamber end surface 26 is provided at a position deviated from the rotation locus K of the pressing force generating groove 28 of the rotor end surface 22c.

Specifically, the rotor chamber end face 26 is provided with arc long grooves 39 and linear long grooves 40 as the pressing force generating grooves 38 . The rotor end surface 22c is provided with a first pressing force generating groove 281 and a second pressing force generating groove 282 as the pressing force generating groove 28. The inner peripheral edge of the first pressing force generation groove 281 and the outer peripheral edge of the second pressing force generation groove 282 each pass through a circular rotation trajectory K. Note that the first pressing force generating groove 281 and the second pressing force generating groove 282 are spaced apart in the longitudinal direction of the rotor 22 compared to the first embodiment. The arcuate long grooves 39 and straight long grooves 40, which are the pressing force generating grooves 38 on the rotor chamber end surface 26, correspond to the rotation locus K of the first pressing force generating groove 281 and the second pressing force generating groove 282 on the rotor end surface 22c. It is provided at a position away from the rotation locus K. Each of the arcuate long grooves 39 and the linear long grooves 40 is arranged between the rotation locus K of the first pressing force generation groove 281 and the rotation locus K of the second pressing force generation groove 282.

The position of the pressing force generating groove 38 on the rotor chamber end face 26 may be changed as appropriate as long as it is provided at a position deviating from the rotation locus K of the pressing force generating groove 28.
According to this, a pressing force is applied to each of the pair of rotors 22 by the pressing force generating groove 28 of the rotor end surface 22c and the pressing force generating groove 38 of the rotor chamber end surface 26. The pressing force separates the rotor 22 from the rotor chamber end surface 26. Therefore, contact of the rotor end surface 22c with the rotor chamber end surface 26 is suppressed. It is possible to suppress variations in the pressing force due to interference between the pressing force generating groove 28 on the rotor end surface 22c and the pressing force generating groove 38 on the rotor chamber end surface 26. Therefore, the inclination of the rotor 22 due to uneven pressing force can be suppressed.

The pressing force generating groove 28 of the rotor end face 22c may be provided only on one of the pair of rotor end faces 22c. In this case, the axial clearance CL between the rotor end surface 22c where the pressing force generation groove 28 is not provided and the opposing rotor chamber end surface 26 is the same as the axial clearance CL between the rotor end surface 22c where the pressing force generation groove 28 is provided and the rotor end surface 22c where the pressing force generation groove 28 is provided. It is slightly larger than the axial clearance CL with the chamber end surface 26.

The pressing force generating groove 28 of the rotor end face 22c may be only one of the first pressing force generating groove 281 and the second pressing force generating groove 282.
The pressing force generating grooves 28 on the rotor end surface 22c may be provided one step at a time in the longitudinal direction of the rotor end surface 22c, or may be provided in three or more steps.

The number of pressing force generating grooves 28 on the rotor end surface 22c does not need to be two in the rotational direction R, may be one in the rotational direction R, or may be three or more.
The pressing force generating groove 28 on the rotor end face 22c does not have to be arcuate. The pressing force generating groove 28 may be, for example, a straight long groove.

The groove depth F of the pressing force generating groove 28 on the rotor end face 22c may vary in stages. As long as a pressing force can be applied to the rotor 22 by the pressing force generating groove 28, the groove depth F and shape of the pressing force generating groove 28 may be changed as appropriate.

The arc long groove 39 of the rotor chamber end face 26 may be a straight long groove 40.
The arcuate long grooves 39 on the rotor chamber end surface 26 may be provided one step at a time in the direction in which the virtual lines M2 and M3 extend, or may be provided in three or more steps. Similarly, the linear long grooves 40 may be provided one step at a time in the direction in which the first imaginary line M1 extends, or may be provided in three or more steps.

The number of arcuate long grooves 39 or straight long grooves 40 on the rotor chamber end surface 26 may not be two in the rotational direction R, may be one in the rotational direction R, or may be three or more.
The groove depth F of the arc long grooves 39 and the straight long grooves 40 of the rotor chamber end surface 26 may change in stages. As long as a pressing force can be applied to the rotor 22 by the arc long grooves 39 and the straight long grooves 40, the groove depth F and shape may be changed as appropriate.

The rotor 22 may have, for example, a trilobal shape or a quadrilobal shape in a cross-sectional view orthogonal to the axial direction of the rotating shaft 16.
The roots pump 10 may be driven by, for example, an engine. In this case, the drive shaft 16a passes through the bottom wall 13a of the gear housing 13 in order to be connected to an engine that is a drive source provided outside the gear chamber 24.

The Roots pump 10 does not have to be a fuel cell hydrogen pump that supplies hydrogen gas to a fuel cell, and may be used for other purposes. In short, the fluid sucked into the rotor chamber 25 is not limited to hydrogen gas.

F...groove depth, K...rotation locus, 10...roots pump, 11...housing, 16...rotating shaft, 22...rotor, 22c...rotor end face, 25...rotor chamber, 26...rotor chamber end face, 27...rotor chamber circumference Surface, 28... Pressing force generation groove, 31a... First driving bearing, 31b... Second driving bearing, 31c... Third driving bearing, 38... Pressing force generating groove, 39... Arc long groove as pressing force generating groove. , 40... Straight long groove as a pressing force generating groove, 41a... First driven bearing, 41b... Second driven bearing, 45... Suction hole, 46... Discharge hole.

Claims (5)

housing and
a rotor chamber defined in the housing and having a suction hole for sucking in fluid and a discharge hole for discharging fluid;
a pair of rotating shafts rotatably supported by the housing via bearings;
A Roots pump, comprising rotors that are respectively attached to the pair of rotating shafts and rotated in mutually opposite directions within the rotor chamber,
The rotor chamber has rotor chamber end surfaces facing each other with the rotor in between in the axial direction of the rotating shaft, and a rotor chamber peripheral surface surrounding a radial outer peripheral area of the rotor,
The rotor has a rotor end face opposite to the rotor chamber end face,
At least one of the rotor chamber end surface and the rotor end surface is provided with a pressing force generating groove that generates pressure distribution in the fluid between the rotor chamber end surface and the rotor end surface due to rotation of the rotor,
The Roots pump is characterized in that the pressing force generating groove is provided so as to apply a pressing force to the rotor to separate the rotor from an end surface of the rotor chamber. The roots according to claim 1, wherein the pressing force generating groove is a long groove extending along the rotational direction of the rotor, and is provided so that the groove depth changes along the rotational direction. pump. The pressing force generating grooves are a pair of long grooves provided at points symmetrical positions with respect to the rotation axis, and each of the pair of long grooves has a change in groove depth at a point with respect to the rotation axis. Roots pump according to claim 2, characterized in that it is set to be symmetrical. The pressing force generating groove is a linear long groove extending in the tangential direction of the rotation circle of the rotor, and is provided so that the groove depth changes along the tangential direction,
The straight long groove is provided so as to extend in a direction perpendicular to a line passing through the end surface of the rotor chamber and the axes of the pair of rotating shafts, and is provided on at least a line segment connecting the axes of the rotating shafts. The roots pump according to claim 1, characterized in that: The pressing force generating groove is provided on both the rotor chamber end surface and the rotor end surface, and the pressing force generating groove on the rotor chamber end surface is located at a position deviating from the rotation locus of the pressing force generating groove on the rotor end surface. Roots pump according to claim 1, characterized in that it is provided.

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