US20080193315A1 - Roots-type fluid machine - Google Patents
Roots-type fluid machine Download PDFInfo
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- US20080193315A1 US20080193315A1 US12/027,513 US2751308A US2008193315A1 US 20080193315 A1 US20080193315 A1 US 20080193315A1 US 2751308 A US2751308 A US 2751308A US 2008193315 A1 US2008193315 A1 US 2008193315A1
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- twisted portion
- rotation axis
- twist angle
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- 238000010030 laminating Methods 0.000 claims description 8
- 230000010349 pulsation Effects 0.000 description 100
- 238000005192 partition Methods 0.000 description 9
- 239000000446 fuel Substances 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
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Images
Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01C—ROTARY-PISTON OR OSCILLATING-PISTON MACHINES OR ENGINES
- F01C1/00—Rotary-piston machines or engines
- F01C1/08—Rotary-piston machines or engines of intermeshing engagement type, i.e. with engagement of co- operating members similar to that of toothed gearing
- F01C1/12—Rotary-piston machines or engines of intermeshing engagement type, i.e. with engagement of co- operating members similar to that of toothed gearing of other than internal-axis type
- F01C1/126—Rotary-piston machines or engines of intermeshing engagement type, i.e. with engagement of co- operating members similar to that of toothed gearing of other than internal-axis type with elements extending radially from the rotor body not necessarily cooperating with corresponding recesses in the other rotor, e.g. lobes, Roots type
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01C—ROTARY-PISTON OR OSCILLATING-PISTON MACHINES OR ENGINES
- F01C1/00—Rotary-piston machines or engines
- F01C1/08—Rotary-piston machines or engines of intermeshing engagement type, i.e. with engagement of co- operating members similar to that of toothed gearing
- F01C1/082—Details specially related to intermeshing engagement type machines or engines
- F01C1/084—Toothed wheels
Abstract
A roots-type fluid machine including a set of rotors and a rotor housing is disclosed. The rotor housing accommodates the rotors and has a suction space. The set of rotors mesh with each other and rotate in the rotor housing so that fluid is drawn into the suction space and discharged from the rotor housing. Each of the set of rotors includes a tooth having a twisted portion and a different shape variation portion. The twisted portion has a twist angle that changes linearly or non-linearly about a rotation axis of the corresponding rotor with respect to the variation of the position in the direction of the axis. The different shape variation portion has a twisted angle that changes by a smaller degree than the variation of the twist angle of the twisted portion.
Description
- The present invention relates to a roots-type fluid machine in which a set of rotors mesh with each other and rotate in a rotor housing so that fluid is drawn into a suction space in the rotor housing and discharged from the rotor housing.
- A roots-type fluid machine with rotors having helical teeth is disclosed in, for example, Japanese Laid-Open Patent Publication No. 2-227588. The teeth of the rotors are monotonically twisted into helical form around the rotation axes of the rotors. In the roots-type fluid machine that uses helical rotors, the rotors are helically twisted from one end to the other end. When the following equation (1), in which the twist angle of the rotors is expressed by Φ, is satisfied, the volumetric change (the suction amount of fluid to a suction space per unit time) does not fluctuate in the suction space, which is located between the pair of meshed rotors and communicates with an inlet formed in the rotor housing.
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Φ=(360°/2n)×X (1) - in which n is the number of the teeth of the rotors (number of lobes), and X is a positive integer. In a structure where the volumetric change in the suction space does not fluctuate, the suction pulsation basically does not occur.
- However, in the roots-type fluid machine, which is operated without providing oil between the rotor housing and the rotors and between the rotors for lubrication, since a clearance is provided for avoiding sliding contact between the rotor housing and the rotors and between the rotors, fluid leaks between the rotor housing and the rotors and between the rotors. Thus, although the volumetric change of the suction space does not fluctuate, the suction pulsation does not become zero, and the suction pulsation of fundamental order caused by fluid leakage remains. For example, if the rotors each have a three-lobe transverse cross section as disclosed in Japanese Laid-Open Patent Publication No. 2-227588, the suction pulsation of the fundamental order of sixth order remains.
-
FIGS. 17A and 17B show a roots-type fluid machine with three-lobe rotors FIG. 17A shows a state where the distal end portion of atooth 371 of therotor 37 is fitted in atooth bottom portion 382 of therotor 38.FIG. 17B shows a state where therotors FIG. 17A , and where the side portion of thetooth 371 of therotor 37 has come close to the side portion of thetooth 381 of therotor 38. - The size of a minimum clearance CL1 at a closest portion K1 shown in
FIG. 17A is equal to the size of a minimum clearance CL2 at a closest portion K2 shown inFIG. 17B . The clearance increases as the distance from the minimum clearance CL1 increases along circumferential direction of the distal end portion of thetooth 371 of therotor 37. The clearance increases as the distance from the minimum clearance CL2 increases along the circumferential direction of the side portion of thetooth 371 of therotor 37. - However, the change in the size of the clearance of the closest portion K1 shown in
FIG. 17A (the change along the circumferential direction of the distal end portion of thetooth 371 of the rotor 37) is smaller than the change in the size of the clearance at the closest portion K2 shown inFIG. 17B (the change along the circumferential direction of the side portion of thetooth 371 of the rotor 37). Thus, the fluid leakage between therotors FIG. 17A (fluid leakage to the suction space S from the discharge space P via the space between therotors 37, 38) is small, and the fluid leakage between therotors FIG. 17B is great. - The state similar to that shown in
FIG. 17A occurs six times while therotors FIG. 17B occurs six times while therotors helical rotors - If the transverse cross-sectional view of the rotors is two-lobe in shape, the suction pulsation of the fundamental order of fourth order caused by fluid leakage remains.
- Accordingly, it is an objective of the present invention to reduce suction pulsation caused by fluid leakage in a roots-type fluid machine that uses rotors including twisted portions. The twist angle of each twisted portion about the rotation axis of the associated rotor changes linearly or nonlinearly with respect to changes in the position in the axial direction of the rotation axis of the rotor.
- To achieve the above objective, and in accordance with one aspect of the present invention, a roots-type fluid machine including a set of rotors and a rotor housing is provided. The rotor housing accommodates the rotors and has a suction space. The set of rotors mesh with each other and rotate in the rotor housing so that fluid is drawn into the suction space and discharged from the rotor housing. Each of the set of rotors includes a tooth having a twisted portion and a different shape variation portion. The twisted portion has a twist angle that changes linearly or non-linearly about a rotation axis of the corresponding rotor with respect to the variation of the position in the direction of the axis. The different shape variation portion has a twisted angle that changes by a smaller degree than the variation of the twist angle of the twisted portion.
- Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.
- The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which:
-
FIG. 1A is a plane cross-sectional view illustrating a fluid machine according to a first embodiment of the present invention; -
FIG. 1B is a side view illustrating one of the rotors; -
FIG. 1C is a side view illustrating one of the rotors; -
FIG. 2A is a cross-sectional view taken alongline 2A-2A inFIG. 1A ; -
FIG. 2B is a cross-sectional view taken alongline 2B-2B inFIG. 2A ; -
FIG. 3A is a graph showing a variation in a twist angle; -
FIG. 3B is a graph showing suction pulsation; -
FIG. 3C is a graph showing antiphase pulsation; -
FIG. 4A is a side view illustrating a rotor according to a second embodiment; -
FIG. 4B is a side view illustrating a rotor according to the second embodiment; -
FIG. 5 is a graph showing a variation in a twist angle; -
FIG. 6A is a side cross-sectional view illustrating a rotor according to a third embodiment; -
FIG. 6B is a side cross-sectional view illustrating a rotor according to the third embodiment; -
FIG. 7 is a cross-sectional view illustrating the rotors according to the third embodiment; -
FIG. 8A is a side view illustrating a rotor according to a fourth embodiment; -
FIG. 8B is a side view illustrating a rotor according to the fourth embodiment; -
FIG. 9 is a graph showing a variation in a twist angle; -
FIG. 10A is a side view illustrating a rotor according to a fifth embodiment; -
FIG. 10B is a side view illustrating a rotor according to the fifth embodiment; -
FIG. 11A is a graph showing a variation in twist angle; -
FIG. 11B is a graph showing suction pulsation; -
FIG. 11C is a graph showing antiphase pulsation; -
FIG. 12A is a cross-sectional view illustrating rotors according to a sixth embodiment; -
FIG. 12B is a side view illustrating one of the rotors; -
FIG. 12C is a side view illustrating one of the rotors; -
FIG. 13A is a graph showing a variation in a twist angle; -
FIG. 13B is a graph showing the suction pulsation; -
FIG. 13C is a graph showing antiphase pulsation; -
FIG. 14 is a graph showing a modified embodiment; -
FIG. 15 is a graph showing a modified embodiment; -
FIG. 16 is a graph showing a modified embodiment; -
FIG. 17A is a schematic diagram for explaining suction pulsation caused by fluid leakage; and -
FIG. 17B is a schematic diagram for explaining suction pulsation caused by fluid leakage. - A first embodiment of the present invention will now be described with reference to
FIGS. 1A to 3C . - As shown in
FIG. 1A , apartition wall 12 is coupled to the rear end of afront housing member 11, and an electric motor M is coupled to thepartition wall 12 with agear housing member 13. Thefront housing member 11, thepartition wall 12, thegear housing member 13, and a housing member M1 of the electric motor M configure a housing assembly of a roots-type fluid machine 10. - The
front housing member 11 and thepartition wall 12 configure arotor housing 23, which forms apump chamber 231. Ashaft hole 121 extends through thepartition wall 12, and ashaft hole 141 is formed in anend wall 14 of thefront housing member 11. Theend wall 14 of thefront housing member 11 and thepartition wall 12 rotatably support arotary shaft 15 of the electric motor M withradial bearings shaft hole 122 extends through thepartition wall 12, and ashaft hole 142 is formed in theend wall 14 of thefront housing member 11. Arotary shaft 18 is inserted in the shaft holes 122, 142. Theend wall 14 of thefront housing member 11 and thepartition wall 12 rotatably support therotary shaft 18 withradial bearings rotary shafts - As shown in
FIG. 2B , arotor 21 is secured to therotary shaft 15, and arotor 22 is secured to therotary shaft 18. Therotors pump chamber 231 in a state where therotors - The
rotor 21 has threeteeth 24, which protrude in the radial direction of therotary shaft 15. Therotor 22 has threeteeth 25, which protrude in the radial direction of therotary shaft 15. The threeteeth 24 of therotor 21 are arranged at equal angular intervals of 120° about arotation axis 151 of therotary shaft 15, and therotor 21 has rotational symmetry of 120° about therotation axis 151. Similarly, the threeteeth 25 of therotor 22 are arranged at equal angular intervals of 120° about arotation axis 181 of therotary shaft 18, and therotor 22 has rotational symmetry of 120° about therotation axis 181. - As shown in
FIG. 1B , eachtooth 24 includes a firsttwisted portion 241, which is helically twisted clockwise about the rotation axis of the rotor 21 (that is, therotation axis 151 of the rotary shaft 15), and a secondtwisted portion 242, which is helically twisted clockwise about therotation axis 151. Furthermore, eachtooth 24 includes anon-twisted portion 240, which is located between the firsttwisted portion 241 and the secondtwisted portion 242. The twist angle of the firsttwisted portion 241 and the secondtwisted portion 242 changes linearly along the axial direction of therotation axis 151. Thenon-twisted portion 240 is a straight line, which is parallel to therotation axis 151. That is, thenon-twisted portion 240 does not twist along the axial direction of therotation axis 151. - As shown in
FIGS. 1C and 2A , eachtooth 25 includes a firsttwisted portion 251, which is helically twisted counterclockwise about the rotation axis of the rotor 22 (that is, therotation axis 181 of the rotary shaft 18), and a secondtwisted portion 252, which is helically twisted counterclockwise about therotation axis 181. Furthermore, eachtooth 25 includes anon-twisted portion 250, which is located between the firsttwisted portion 251 and the secondtwisted portion 252. The twist angle of the firsttwisted portion 251 and the secondtwisted portion 252 changes linearly along the axial direction of therotation axis 181. Thenon-twisted portion 250 is a straight line, which is parallel to therotation axis 181. That is, thenon-twisted portion 250 does not twist along the axial direction of therotation axis 181. - The length of the first
twisted portion 241 in the direction of therotation axis 151 is equal to the length of the firsttwisted portion 251 in the direction of therotation axis 181. The length of the secondtwisted portion 242 in the direction of therotation axis 151 is equal to the length of the secondtwisted portion 252 in the direction of therotation axis 181. The length of thenon-twisted portion 240 in the direction of therotation axis 151 and the length of thenon-twisted portion 250 in the direction of therotation axis 181 are the same length L (shown inFIGS. 1B , 1C, and 3A). The length L of thenon-twisted portions twisted portions twisted portions twisted portion 241 of therotor 21 meshes with the firsttwisted portion 251 of therotor 22, and the secondtwisted portion 242 of therotor 21 meshes with the secondtwisted portion 252 of therotor 22. Thenon-twisted portion 240 of therotor 21 meshes with thenon-twisted portion 250 of therotor 22. - As shown in
FIG. 1A , therotary shaft 18 extends through thepartition wall 12 and protrudes inside thegear housing member 13.Gears rotary shafts gear housing member 13 in a state where thegears rotary shaft 15 is rotated in the direction of arrow R1, and therotor 21 is rotated integrally with therotary shaft 15 in the direction of arrow R1. Therotary shaft 18 receives driving power from the electric motor M via thegears rotary shaft 18 is rotated in the opposite direction from therotary shaft 15 as shown by arrow R2, and therotor 22 is rotated integrally with therotary shaft 18 in the direction of arrow R2. - As shown in
FIG. 2B , aninlet 281 and anoutlet 282 are formed in acircumferential wall 28 of thefront housing member 11 to be connected to thepump chamber 231. Therotors inlet 281, in thepump chamber 231. When the electric motor M is operated, therotary shaft 15 is rotated in the direction of arrow R1, and therotary shaft 18 is rotated in the direction of arrow R2, and therotors rotary shafts rotors inlet 281. The air that is drawn into the suction space S is transferred to theoutlet 282, and the air that is transferred to theoutlet 282 is discharged from theoutlet 282. - In the first embodiment, the air that is discharged from the
outlet 282 is supplied to a fuel cell (not shown). A restrictor is located in a passage (not shown) downstream of the fuel cell, and the air discharged from theoutlet 282 is supplied to the fuel cell as compressed air. - A variation line E1 in the graph of
FIG. 3A shows the relationship between the position H in the axial direction of therotation axis 151 and the twist angle Φ regarding parts of therotor 21 where the lengths of the radial lines, which extend from therotation axis 151 of therotor 21 to the circumferential surfaces of theteeth 24, are equal (for example, the vertexes of theteeth 24 of the rotor 21). The position of anend surface 211 of therotor 21 is represented by the position H=0, the position of anend surface 212 of therotor 21 is represented by the position H=He. The twist angle corresponding to the position of theend surface 211 is represented by the twist angle Φ=0°, and the twist angle corresponding to the position of theend surface 212 is represented by the twist angle Φ=Φe. A straight segment E11 of the variation line E1 represents a variation in the twist angle of the firsttwisted portion 241, and a straight segment E12 of the variation line E1 represents a variation in the twist angle of the secondtwisted portion 242. A straight segment E10 of the variation line E1 represents a variation in the twist angle of thenon-twisted portion 240. - The first
twisted portion 241 and the secondtwisted portion 242 are twisted portions where the twist angle Φ about therotation axis 151 monotonically (in this case, linearly) changes with respect to the change in the position H in the axial direction of therotation axis 151. The twist angle variation of the firsttwisted portion 241 is equal to the twist angle variation of the secondtwisted portion 242. Thenon-twisted portion 240 is a different shape variation portion having a twist angle, which varies by a smaller degree compared to the twist angle variations of the firsttwisted portion 241 and the secondtwisted portion 242. - A variation line E2 in the graph of
FIG. 3A represents the relationship between the twist angle Φ and the position H in the axial direction of therotation axis 181 regarding parts of therotor 22 where the lengths of the radial lines, which extend from therotation axis 181 of therotor 22 to the circumferential surfaces of theteeth 25, are equal (for example, the vertexes of theteeth 25 of the rotor 22). The position of anend surface 221 of therotor 22 is represented by the position H=0, the position of anend surface 222 of therotor 22 is represented by the position H=He. The twist angle corresponding to the position of theend surface 221 is represented by the twist angle Φ=0°, and the twist angle corresponding to the position of theend surface 222 is represented by the twist angle Φ=−Φe. A straight segment E21 of the variation line E2 represents a variation in the twist angle of the firsttwisted portion 251, and a straight segment E22 of the variation line E2 represents a variation in the twist angle of the secondtwisted portion 252. A straight segment E20 of the variation line E2 represents a variation in the twist angle of thenon-twisted portion 250. - The first
twisted portion 251 and the secondtwisted portion 252 are twisted portions where the twist angle Φ about therotation axis 181 monotonically (in this case, linearly) changes with respect to the change in the position H in the axial direction of therotation axis 181. The twist angle variation of the firsttwisted portion 251 is equal to the twist angle variation of the secondtwisted portion 252. Thenon-twisted portion 250 is a different shape variation portion having a variation in a twist angle that is smaller than the twist angle variations of the firsttwisted portion 251 and the secondtwisted portion 252. - In the first embodiment, Φe=60°, and −Φe=−60°. Also, the straight segment E10 is at a position of Φ=30°, and the straight segment E20 is at a position of Φ=−30°. That is, the length of the first
twisted portion 241 of therotor 21 in the direction of therotation axis 151 is equal to that of the secondtwisted portion 242. Furthermore, thenon-twisted portion 240 is located between the position corresponding to the twist angle Φ=30° of firsttwisted portion 241 and the position corresponding to the twist angle Φ=30° of the secondtwisted portion 242. Thenon-twisted portion 240 is located at a position overlapping the center of therotor 21 in the direction of therotation axis 151. Similarly, the length of the firsttwisted portion 251 of therotor 22 in the direction of therotation axis 181 is equal to that of the secondtwisted portion 252. Furthermore, thenon-twisted portion 250 is located between the position corresponding to the twist angle Φ=−30° of the firsttwisted portion 251 and the position corresponding to the twist angle Φ=−30° of the secondtwisted portion 252. Thenon-twisted portion 250 is located at a position overlapping the center of therotor 22 in the direction of therotation axis 181. - A waveform G1 in
FIG. 3C represents the pulsation generated by fluctuation of the volumetric change in the suction space S. The volumetric change in the suction space S refers to the amount of change in the volume of the suction space S per unit time (suction amount of fluid to the suction space S per unit time). The rotational angle θ=0° represents the rotation position of therotors FIG. 2B . In the case of conventional helical rotors, which do not have thenon-twisted portions twisted portions twisted portions rotors non-twisted portions non-twisted portion 240 is located between the position corresponding to the twist angle Φ=30° of the firsttwisted portion 241 and the position corresponding to the twist angle Φ=30° of the secondtwisted portion 242, and thenon-twisted portion 250 is located between the position corresponding to the twist angle Φ=−30° of the firsttwisted portion 251 and the position corresponding to the twist angle Φ=−30° of the secondtwisted portion 252. Here, n is an integer greater than or equal to one. Hereinafter, the pulsation shown by the waveform G1 is referred to as an antiphase pulsation G1. - A waveform Fo6 shown in
FIG. 3B shows one example of the suction pulsation caused by fluid leakage in a case where rotors without thenon-twisted portions - A waveform F1 in
FIG. 3B shows one example of suction pulsation when therotors non-twisted portions non-twisted portions - The first embodiment has the following advantages.
- (1) The combination of the
non-twisted portions twisted portions FIG. 3B ) is reduced compared to the degree of the suction pulsation Fo6 caused by fluid leakage (the difference Ao between the maximum amplitude and the minimum amplitude of the suction pulsation Fo6 caused by fluid leakage shown inFIG. 3B ). That is, the suction pulsation caused by fluid leakage is reduced by selecting an optimum phase of the fluctuation of the volumetric change in the suction space S by combining thenon-twisted portions twisted portions - (2) Increasing the length L of the
non-twisted portions FIGS. 1B , 1C, and 3A) increases the fluctuation of the volumetric change in the suction space S, and reducing the length L of thenon-twisted portions non-twisted portions - (3) Changing the arrangement position of the
non-twisted portions non-twisted portions - As described above, by changing the setting position of the different shape variation portions (non-twisted portion 240) in the axial direction of the rotation axes 151, 181 of the rotors and changing the range of the different shape variation portions in the axial direction of the rotation axes 151, 181, the phase of the pulsation generated by the fluctuation of the volumetric change in the suction space S is changed. By matching the valleys of the phase of the pulsation generated by the fluctuation of the volumetric change with the peaks of the suction pulsation caused by the fluid leakage, the suction pulsation caused by the fluid leakage is reduced. That is, the suction pulsation caused by fluid leakage is reduced by setting the phase of the suction pulsation caused by the fluctuation of the volumetric change such that the waveform of the suction pulsation generated by the fluctuation of the volumetric change caused by providing the different shape variation portions and the waveform of the suction pulsation caused by fluid leakage cancel each other to be reduced. That is, if an optimum phase of the pulsation, which is caused by the fluctuation of the volumetric change in the suction space S, is selected by combining the different shape variation portions and the twisted portions, the suction pulsation caused by fluid leakage is reduced.
- (4) The periodical fluctuation of the volumetric change in the suction space S is preferably great in a range where the rotational angle θ is narrow. The
non-twisted portions - (5) The configuration in which the
non-twisted portions rotors - A second embodiment will now be described with reference to
FIGS. 4A to 5 . Like or the same reference numerals are given to those components that are like or the same as the corresponding components of the first embodiment. - As shown in
FIG. 4A ,teeth 24A of a rotor 21A have a loosely twistedportion 244 between the firsttwisted portion 241 and the secondtwisted portion 242. As shown inFIG. 4B ,teeth 25A of arotor 22A have a loosely twistedportion 254 between the firsttwisted portion 251 and the secondtwisted portion 252. A straight segment E10 a in the graph ofFIG. 5 represents the twist angle variation of the loosely twistedportion 244, and a straight segment E20 a represents the twist angle variation of the loosely twistedportion 254. The loosely twistedportion 244 has the twist angle Φ about therotation axis 151 which monotonically (in this case, linearly) changes with respect to the change in the position H in the axial direction of therotation axis 151. The loosely twistedportion 254 has the twist angle Φ about therotation axis 181 which changes monotonically (in this case, linearly) with respect to the change in the position H in the axial direction of therotation axis 181. The looselytwisted portions twisted portions twisted portions - When the length of the
non-twisted portions portions - A third embodiment will now be described with reference to
FIGS. 6A to 7 . Like or the same reference numerals are given to those components that are like or the same as the corresponding components of the first embodiment. - As shown in
FIG. 6A , arotor 21B is configured by laminatingflat plates 31 in the axial direction of therotation axis 151, and anon-twisted portion 240B of therotor 21B is configured by laminating the flat plates 31 (four in the third embodiment). Similarly, as shown inFIG. 6B , arotor 22B is configured by laminatingflat plates 32 in the axial direction of therotation axis 181, and anon-twisted portion 250B of therotor 22B is configured by laminating the flat plates 32 (four in the third embodiment). Theflat plates non-twisted portions flat plates - The third embodiment also has the same advantages as the first embodiment. Furthermore, in the third embodiment, first
twisted portions twisted portions flat plates non-twisted portions flat plates - A fourth embodiment will now be described with reference to
FIGS. 8 to 9 . Like or the same reference numerals are given to those components that are like or the same as the corresponding components of the first embodiment. - As shown in
FIG. 8A ,teeth 24C of a rotor 21C each have a nonlineartwisted portion 245 between a firsttwisted portion 241 and a secondtwisted portion 242. The twist angle Φ of the nonlineartwisted portion 245 changes with respect to the variation of the position in the axial direction of therotation axis 151 in a manner represented by a nonlinear function (for example, quadratic function). As shown inFIG. 8B ,teeth 25C of a rotor 22C each have a nonlineartwisted portion 255 between a firsttwisted portion 251 and a secondtwisted portion 252. The twist angle Φ of the nonlineartwisted portion 255 changes with respect to the variation of the position in the axial direction of therotation axis 181 in a manner represented by a nonlinear function (for example, quadratic function). A curved segment E10 c in the graph ofFIG. 9 represents the twist angle variation of the nonlineartwisted portion 245, and a curved segment E20 c represents the twist angle variation of the nonlineartwisted portion 255. The nonlineartwisted portions twisted portions twisted portions - The fourth embodiment provides an antiphase pulsation represented by a waveform, in which the peaks and the valleys of the antiphase pulsation G1 in
FIG. 3C in a bent form is turned into a curved line. With such an antiphase pulsation also, the suction pulsation caused by fluid leakage is reduced. That is, the different shape variation portions (255) the twist angle Φ of which changes in a manner represented by a nonlinear function reduce the suction pulsation caused by fluid leakage. - A fifth embodiment will now be described with reference to
FIGS. 10A to 11C . Like or the same reference numerals are given to those components that are like or the same as the corresponding components of the first embodiment. - As shown in
FIG. 10A ,teeth 24D of arotor 21D each include a helically twisted first twistedportion 241D, a helically twisted second twisted portion 242D, and a helically twisted thirdtwisted portion 243. Furthermore, eachtooth 24D includes anon-twisted portion 246, which is located between the firsttwisted portion 241D and the second twisted portion 242D, and anon-twisted portion 247, which is located between the second twisted portion 242D and the thirdtwisted portion 243. - As shown in
FIG. 10B ,teeth 25D of arotor 22D each include a helically twisted first twistedportion 251D, a helically twisted second twistedportion 252D, and a helically twisted thirdtwisted portion 253. Furthermore, eachtooth 25D includes anon-twisted portion 256, which is located between the firsttwisted portion 251D and the secondtwisted portion 252D, and anon-twisted portion 257, which is located between the secondtwisted portion 252D and the thirdtwisted portion 253. - A straight segment E31 of a variation line E3 in the graph of
FIG. 11A represents the twist angle variation of the firsttwisted portion 241D, a straight segment E32 of the variation line E3 represents the twist angle variation of the second twisted portion 242D, and a straight segment E33 of the variation line E3 represents the twist angle variation of the thirdtwisted portion 243. A straight segment E34 of the variation line E3 represents the twist angle variation of thenon-twisted portion 246, and a straight segment E35 of the variation line E3 represents the twist angle variation of thenon-twisted portion 247. - A straight segment E41 of a variation line E4 in the graph of
FIG. 11A represents the twist angle variation of the firsttwisted portion 251D, a straight segment E42 of the variation line E4 represents the twist angle variation of the secondtwisted portion 252D, a straight segment E43 of the variation line E4 represents the twist angle variation of the thirdtwisted portion 253. A straight segment E44 of the variation line E4 represents the twist angle variation of thenon-twisted portion 256, and a straight segment E45 of the variation line E4 represents the twist angle variation of thenon-twisted portion 257. - The
non-twisted portion 246 is located between the position corresponding to the twist angle Φ=15° of the firsttwisted portion 241D and the position corresponding to the twist angle Φ=15° of the second twisted portion 242D, and thenon-twisted portion 247 is located between the position corresponding to the twist angle Φ=45° of the second twisted portion 242D and the position corresponding to the twist angle Φ=45° of the thirdtwisted portion 243. That is, thenon-twisted portion 246 is located at a position midway between the center of therotor 21D in the axial direction of therotation axis 151 and one end of therotor 21D (the end surface 211), and thenon-twisted portion 247 is located at a position midway between the center of therotor 21D in the axial direction of therotation axis 151 and the other end of therotor 21D (the end surface 212). - The
non-twisted portion 256 is located between the position corresponding to the twist angle Φ=−15° of the firsttwisted portion 251D and the position corresponding to the twist angle Φ=−15° of the secondtwisted portion 252D, and thenon-twisted portion 257 is located between the position corresponding to the twist angle Φ=−45° of the secondtwisted portion 252D and the position corresponding to the twist angle Φ=−45° of the thirdtwisted portion 253. That is, thenon-twisted portion 256 is located at a position midway between the center of therotor 22D in the axial direction of therotation axis 181 and one end of therotor 22D (the end surface 221), and thenon-twisted portion 257 is located at a position midway between the center of therotor 22D in the axial direction of therotation axis 181 and the other end of therotor 22D (the end surface 222). - A waveform G2 in
FIG. 11C represents the pulsation generated by the fluctuation of the volumetric change in the suction space S. In the case with therotors non-twisted portions - A waveform Fo12 in
FIG. 11B shows one example of the order component that is double the fundamental order of the suction pulsation caused by fluid leakage when rotors without thenon-twisted portions - The waveform F2 in
FIG. 11B shows one example of the suction pulsation when therotor 21D having thenon-twisted portions rotor 22D having thenon-twisted portions non-twisted portions - The fifth embodiment is advantageous in reducing the suction pulsation component of the order that is double the fundamental order.
- A sixth embodiment will now be described with reference to
FIGS. 12A to 13C . Like or the same reference numerals are given to those components that are like or the same as the corresponding components of the first embodiment. - As shown in
FIG. 12A , arotor 33 includes twoteeth 35, which protrude in the radial direction of therotary shaft 15, and arotor 34 includes twoteeth 36, which protrude in the radial direction of therotary shaft 18. The twoteeth 35 of therotor 33 are located at equal angular intervals of 180° about therotation axis 151 of therotary shaft 15, and therotor 33 has a rotational symmetry of 180° about therotation axis 151. Similarly, the twoteeth 36 of therotor 34 are located at equal angular intervals of 180° about therotation axis 181 of therotary shaft 18, and therotor 34 has a rotational symmetry of 180° about therotation axis 181. - As shown in
FIG. 12B , eachtooth 35 includes a firsttwisted portion 351, which is helically twisted clockwise about the rotation axis of the rotor 33 (that is, therotation axis 151 of the rotary shaft 15), a secondtwisted portion 352, which is helically twisted clockwise about therotation axis 151, and anon-twisted portion 350, which is located between the firsttwisted portion 351 and the secondtwisted portion 352. The twist angle of the firsttwisted portion 351 and the secondtwisted portion 352 change linearly along the axial direction of therotation axis 151. Thenon-twisted portion 350 has a straight line form parallel to the rotation axis 151 (that is, a form that does not twist along the axial direction of the rotation axis 151). - As shown in
FIG. 12C , eachtooth 36 includes a first twisted portion 361, which is helically twisted counterclockwise about the rotation axis of the rotor 34 (that is, therotation axis 181 of the rotary shaft 18), a second twisted portion 362, which is helically twisted counterclockwise about therotation axis 181, and a non-twisted portion 360, which is located between the first twisted portion 361 and the second twisted portion 362. The twist angle of the first twisted portion 361 and the second twisted portion 362 change linearly along the axial direction of therotation axis 181. The non-twisted portion 360 has a straight line form parallel to the rotation axis 181 (that is, a form that does not twist along the axial direction of the rotation axis 181). - The first
twisted portion 351 of therotor 33 meshes with the first twisted portion 361 of therotor 34, and the secondtwisted portion 352 of therotor 33 meshes with the second twisted portion 362 of therotor 34. Thenon-twisted portion 350 of therotor 33 meshes with the non-twisted portion 360 of therotor 34. - A variation line E7 in the graph of
FIG. 13A represents the relationship between the twist angle Φ and the position H in the axial direction of therotation axis 151 regarding parts of therotor 33 where the lengths of the radial lines, which extend from therotation axis 151 of therotor 33 to the circumferential surfaces of theteeth 35, are equal (for example, the vertexes of theteeth 35 of the rotor 33). The position of anend surface 331 of therotor 33 is represented by the position H=0, the position of anend surface 332 of therotor 33 is represented by the position H=He. The twist angle corresponding to the position of theend surface 331 is represented by the twist angle Φ=0°, and the twist angle corresponding to the position of theend surface 332 is represented by the twist angle Φ=Φe. A straight segment E71 of the variation line E7 represents the twist angle variation of the firsttwisted portion 351, and a straight segment E72 of the variation line E7 represents the twist angle variation of the secondtwisted portion 352. A straight segment E70 of the variation line E7 represents the twist angle variation of thenon-twisted portion 350. - A variation line E8 in the graph of
FIG. 13A represents the relationship between the twist angle Φ and the position H in the axial direction of therotation axis 181 regarding parts of therotor 34 where the lengths of the radial lines, which extend from therotation axis 181 of therotor 34 to the circumferential surfaces of theteeth 36, are equal (for example, vertexes of theteeth 36 of the rotor 34). The position of anend surface 341 of therotor 34 is represented by the position H=0, the position of anend surface 342 of therotor 34 is represented by the position H=He. The twist angle corresponding to the position of theend surface 341 is represented by the twist angle Φ=0°, and the twist angle corresponding to the position of theend surface 342 is represented by the twist angle Φ=−Φe. A straight segment E81 of the variation line E8 represents the twist angle variation of the first twisted portion 361, and a straight segment E82 of the variation line E8 represents the twist angle variation of the second twisted portion 362. A straight segment E80 of the variation line E8 represents the twist angle variation of the non-twisted portion 360. - In the sixth embodiment, Φe=90°, and −Φe=−90°. Also, the straight segment E70 is at the position of Φ=45°, and the straight segment E80 is at the position of Φ=−45°. That is, the length of the first
twisted portion 351 of therotor 33 in the direction of therotation axis 151 is equal to that of the secondtwisted portion 352. Furthermore, thenon-twisted portion 350 is located between the position corresponding to the twist angle Φ=45° of the firsttwisted portion 351 and the position corresponding to the twist angle Φ=45° of the secondtwisted portion 352, and thenon-twisted portion 350 is located at a position overlapping the center of therotor 33 in the direction of therotation axis 151. Similarly, the length of the first twisted portion 361 of therotor 34 in the direction of therotation axis 181 is equal to that of the second twisted portion 362. Furthermore, the non-twisted portion 360 is located between the position corresponding to the twist angle Φ=−45° of the first twisted portion 361 and the position corresponding to the twist angle Φ=−45° of the second twisted portion 362, and the non-twisted portion 360 is located at a position overlapping the center of therotor 34 in the direction of therotation axis 181. - A waveform G3 in
FIG. 13C represents the pulsation generated by the fluctuation of the volumetric change in the suction space S. In the case where therotors non-twisted portions 350, 360. The valleys of the pulsation shown by the waveform G3 are in the vicinity of the rotational angle θ=45°×(2n−1). Here, n is an integer greater than or equal to one. Hereinafter, the pulsation shown by the waveform G3 is referred to as an antiphase pulsation G3. - A waveform Fo4 in
FIG. 13B shows one example of the suction pulsation caused by fluid leakage in a case where rotors without thenon-twisted portions 350, 360 are used. In the case of the roots pump which uses the rotors with two teeth, the fundamental order of the suction pulsation caused by fluid leakage is fourth order. Hereinafter, the suction pulsation shown by the waveform Fo4 is referred to as a suction pulsation Fo4 caused by fluid leakage. The valleys of the suction pulsation Fo4 caused by fluid leakage are in the vicinity of the rotational angle θ=45°×(2n−1), and the peaks of the suction pulsation Fo4 caused by fluid leakage are in the vicinity of the rotational angle θ=45°×2n. Here, n is an integer greater than or equal to one. - A waveform F3 in
FIG. 13B shows one example of the suction pulsation when therotors non-twisted portions 350, 360 are used. The suction pulsation shown by the waveform F3 is obtained by overlapping the suction pulsation Fo4 caused by fluid leakage on the antiphase pulsation G3. Hereinafter, the suction pulsation shown by the waveform F3 is referred to as a suction pulsation F3. Since the valleys of the antiphase pulsation G3 generated due to the existence of thenon-twisted portions 350, 360 are in the vicinity of the rotational angle θ=415°×(2n−1), the upper limit of the peaks of the suction pulsation F3 is suppressed. Here, n is an integer greater than or equal to one. - The present invention may also be embodied in the following forms.
- A pair of rotors (rotors having three teeth) represented by variation lines E13, E14 shown in
FIG. 14 may be used. Straight segments E130, E140 of the variation lines E13, E14 correspond to the straight segments E10, E20 ofFIG. 3A , and curved segments E131, E132, E141, E142 represent the twist angle variation of the twisted portions the twist angle of which monotonically (in this case, nonlinearly) changes. Changing monotonically means that the twist angle varies in a manner represented by a monotonically increasing function or a monotonically decreasing function. - A pair of rotors (rotors having three teeth) represented by variation lines E15, E16 shown in
FIG. 15 may be used. Straight segments E150, E160 of the variation lines E15, E16 correspond to the straight segments E10, E20 ofFIG. 3A , and curved segments E151, E152, E161, E162 represent the twist angle variation of the twisted portions the twist angle of which monotonically (in this case, nonlinearly) changes. - A pair of rotors (rotor having three teeth) represented by variation lines E17, E18 shown in
FIG. 16 may be used. Curved segments E170, E180 of the variation lines E17, E18 correspond to the curved segments E10 c, E20 c ofFIG. 9 , and straight segments E171, E172, E181, E182 represent the twist angle variation of the twisted portions the twist angle of which monotonically (in this case, linearly) change. - According to the first to fifth embodiments, and embodiments illustrated in
FIGS. 14 , 15, and 16, the rotors including three teeth are used, and the twist angle Φ is set to 60°. In such a case where the rotors including three teeth are used, the twist angle Φ may be greater than 60°, and may be an integral multiple of 60°. - In the case where the rotors including three teeth are used, it is optimal that the twist angle Φ satisfies the equation (1) when 3 is substituted for n. However, the present invention may be applied even when the twist angle Φ does not satisfy the equation (1).
- In the sixth embodiment, the rotors including two teeth are used, and the twist angle Φ is set to 90°. In such a case where the rotors including two teeth are used, the twist angle Φ may be greater than 90°, and may be an integral multiple of 90°.
- In the case when the rotors including two teeth are used, it is optimal that the twist angle Φ satisfies the equation (1) when 2 is substituted for n. However, the present invention may be applied even when the twist angle Φ does not satisfy the equation (1).
- The present invention may be applied to rotors including four or more teeth.
- The
rotors - The present invention may be applied to a serial or parallel roots-type fluid machine, in which a set of rotors (the set of
rotors pump chamber 231, which communicates with theinlet 281, and at least one pump chamber different from thepump chamber 231 are arranged next to one another in the axial direction of the rotation axis. - The present invention may be applied to a roots-type fluid machine in which a set of three or more rotors are accommodated in the rotor housing.
Claims (8)
1. A roots-type fluid machine comprising a set of rotors and a rotor housing, which accommodates the rotors and has a suction space, the set of rotors meshing with each other and rotate in the rotor housing so that fluid is drawn into the suction space and discharged from the rotor housing,
wherein each of the set of rotors includes a tooth having a twisted portion and a different shape variation portion, the twisted portion having a twist angle that changes linearly or non-linearly about a rotation axis of the corresponding rotor with respect to a variation of the position in the direction of the axis, and the different shape variation portion having a twisted angle that changes by a smaller degree than the variation of the twist angle of the twisted portion.
2. The fluid machine according to claim 1 , wherein the twisted potion is helical and the different shape variation portion has a straight line form parallel to the rotation axis.
3. The fluid machine according to claim 1 , wherein the twisted potion is helical and the different shape variation portion has a form the twist angle of which changes with respect to the variation of the position in the axial direction of the rotation axis in a manner represented by a nonlinear function.
4. The fluid machine according to claim 1 , wherein the different shape variation portion is provided at a position including the center of the rotor in the direction of the rotation axis.
5. The fluid machine according to claim 4 , wherein the twisted portion is provided on each side of the different shape variation portion in the direction of the rotation axis, and the lengths of the twisted portions are equal.
6. The fluid machine according to claim 1 , wherein the different shape variation portion is provided at a position including midway between the center of the rotor in the direction of the rotation axis and each of the ends of the associated rotor.
7. The fluid machine according to claim 1 , wherein each rotor is configured by laminating a plurality of flat plates having the same shape and the same size in the direction of the rotation axis, and the length of the different shape variation portion in the direction of the rotation axis is greater than the thickness of each flat plate.
8. The fluid machine according to claim 1 , wherein, in each rotor, the length of the different shape variation portion in the direction of the rotation axis is shorter than the length of the twisted portion in the direction of the rotation axis.
Applications Claiming Priority (8)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2007029183 | 2007-02-08 | ||
JP2007-029183 | 2007-02-08 | ||
JP2007033473 | 2007-02-14 | ||
JP2007-033473 | 2007-02-14 | ||
JP2008-025310 | 2008-02-05 | ||
JP2008025310A JP2008215346A (en) | 2007-02-08 | 2008-02-05 | Roots pump |
JP2008025311A JP2008223759A (en) | 2007-02-14 | 2008-02-05 | Roots-type fluid machine |
JP2008-025311 | 2008-02-05 |
Publications (1)
Publication Number | Publication Date |
---|---|
US20080193315A1 true US20080193315A1 (en) | 2008-08-14 |
Family
ID=39685985
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US12/027,513 Abandoned US20080193315A1 (en) | 2007-02-08 | 2008-02-07 | Roots-type fluid machine |
Country Status (2)
Country | Link |
---|---|
US (1) | US20080193315A1 (en) |
DE (1) | DE102008008156A1 (en) |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2015063252A1 (en) * | 2013-10-31 | 2015-05-07 | ENVA Systems GmbH | Positive displacement blower with a sealing system |
WO2017156236A1 (en) * | 2016-03-09 | 2017-09-14 | Eaton Corporation | Optimized energy recovery device rotor |
CN108916047A (en) * | 2018-09-14 | 2018-11-30 | 安徽达来电机有限公司 | A kind of two impeller shafts and associated gear of Anti-dislocation |
WO2019027844A1 (en) * | 2017-07-31 | 2019-02-07 | Magnuson Products, Llc | Improved inlet port configuration for roots-type supercharger |
CN114607598A (en) * | 2020-12-09 | 2022-06-10 | 东北大学 | Roots rotor with gradually-changed shape coefficient and design method thereof |
Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3807911A (en) * | 1971-08-02 | 1974-04-30 | Davey Compressor Co | Multiple lead screw compressor |
US4666385A (en) * | 1984-03-13 | 1987-05-19 | Aisin Seiki Kabushiki Kaisha | Roots type blower |
US4792294A (en) * | 1986-04-11 | 1988-12-20 | Mowli John C | Two-stage screw auger pumping apparatus |
US5056995A (en) * | 1989-02-28 | 1991-10-15 | Aisin Seiki Kabushiki Kaisha | Displacement compressor with reduced compressor noise |
US6508639B2 (en) * | 2000-05-26 | 2003-01-21 | Industrial Technology Research Institute | Combination double screw rotor assembly |
-
2008
- 2008-02-07 US US12/027,513 patent/US20080193315A1/en not_active Abandoned
- 2008-02-08 DE DE102008008156A patent/DE102008008156A1/en not_active Withdrawn
Patent Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3807911A (en) * | 1971-08-02 | 1974-04-30 | Davey Compressor Co | Multiple lead screw compressor |
US4666385A (en) * | 1984-03-13 | 1987-05-19 | Aisin Seiki Kabushiki Kaisha | Roots type blower |
US4792294A (en) * | 1986-04-11 | 1988-12-20 | Mowli John C | Two-stage screw auger pumping apparatus |
US5056995A (en) * | 1989-02-28 | 1991-10-15 | Aisin Seiki Kabushiki Kaisha | Displacement compressor with reduced compressor noise |
US6508639B2 (en) * | 2000-05-26 | 2003-01-21 | Industrial Technology Research Institute | Combination double screw rotor assembly |
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2015063252A1 (en) * | 2013-10-31 | 2015-05-07 | ENVA Systems GmbH | Positive displacement blower with a sealing system |
WO2017156236A1 (en) * | 2016-03-09 | 2017-09-14 | Eaton Corporation | Optimized energy recovery device rotor |
WO2019027844A1 (en) * | 2017-07-31 | 2019-02-07 | Magnuson Products, Llc | Improved inlet port configuration for roots-type supercharger |
US10968910B2 (en) | 2017-07-31 | 2021-04-06 | Magnuson Products, Llc | Inlet port configuration for roots-type supercharger |
CN108916047A (en) * | 2018-09-14 | 2018-11-30 | 安徽达来电机有限公司 | A kind of two impeller shafts and associated gear of Anti-dislocation |
CN114607598A (en) * | 2020-12-09 | 2022-06-10 | 东北大学 | Roots rotor with gradually-changed shape coefficient and design method thereof |
Also Published As
Publication number | Publication date |
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DE102008008156A1 (en) | 2008-10-09 |
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