U.S. patent application number 12/519964 was filed with the patent office on 2010-04-15 for uniaxial eccentric screw pump.
This patent application is currently assigned to HEISHIN SOBI KABUSHIKI KAISHA. Invention is credited to Teruaki Akamatsu, Tetsuo Nomachi, Nobuhisa Suhara.
Application Number | 20100092317 12/519964 |
Document ID | / |
Family ID | 39536140 |
Filed Date | 2010-04-15 |
United States Patent
Application |
20100092317 |
Kind Code |
A1 |
Suhara; Nobuhisa ; et
al. |
April 15, 2010 |
Uniaxial Eccentric Screw Pump
Abstract
An object of the present invention is to provide a uniaxial
eccentric screw pump capable of transferring and filling a fluid
while realizing high flow rate accuracy, low pulsation, and long
life. A uniaxial eccentric screw pump (11) in which an external
screw type rotor (12) is fittingly inserted in an inner hole (13a)
of an internal screw type stator (13), the rotor (12) and the
stator (13) are separately, rotatably supported, and a rotation
central axis of the rotor (12) and a rotation central axis of the
stator (13) are spaced apart from each other is configured such
that the rotor (12) and the stator (13) are separately rotated by a
rotor driving portion (27) and a stator driving portion (19),
respectively, and the rotor (12) and the stator (13) are rotated
with the rotor (12) and the stator (13) not contacting each
other.
Inventors: |
Suhara; Nobuhisa; (Shiga,
JP) ; Nomachi; Tetsuo; (Kyoto-shi, JP) ;
Akamatsu; Teruaki; (Kyoto-shi, JP) |
Correspondence
Address: |
ALLEMAN HALL MCCOY RUSSELL & TUTTLE LLP
806 SW BROADWAY, SUITE 600
PORTLAND
OR
97205-3335
US
|
Assignee: |
HEISHIN SOBI KABUSHIKI
KAISHA
Kobe-shi, Hyogo
JP
|
Family ID: |
39536140 |
Appl. No.: |
12/519964 |
Filed: |
November 7, 2007 |
PCT Filed: |
November 7, 2007 |
PCT NO: |
PCT/JP2007/071621 |
371 Date: |
September 11, 2009 |
Current U.S.
Class: |
417/410.4 ;
418/48 |
Current CPC
Class: |
F04C 15/008 20130101;
F16C 32/0429 20130101; F16C 2360/42 20130101; F04C 2/1071 20130101;
F04C 2240/402 20130101; F04C 2240/40 20130101 |
Class at
Publication: |
417/410.4 ;
418/48 |
International
Class: |
F04C 2/107 20060101
F04C002/107; F04C 18/107 20060101 F04C018/107; F04C 15/00 20060101
F04C015/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 20, 2006 |
JP |
2006-343187 |
Sep 11, 2007 |
JP |
2007-235008 |
Claims
1. A uniaxial eccentric screw pump in which: an external screw type
rotor is inserted in an inner hole of an internal screw type
stator; the rotor and the stator are separately, rotatably
supported; and a rotation central axis of the rotor and a rotation
central axis of the stator are arranged to be spaced apart from
each other, wherein the rotor and the stator are separately
rotated.
2. The uniaxial eccentric screw pump according to claim 1, wherein:
a geometric center axis of the rotor and the rotational center axis
of the rotor coincide with each other; and a geometric center axis
of the inner hole of the stator and the rotational center axis of
the stator coincide with each other.
3. The uniaxial eccentric screw pump according to claim 1, wherein:
the rotor is rotatably supported by a driving shaft provided at one
end of the rotor, and the driving shaft is rotated by a rotor
driving portion; a stator driving portion is provided with respect
to an outer peripheral surface of the stator, and the stator is
rotated by the stator driving portion; and the stator is
hermetically stored in a pump casing, and the pump casing includes
a first opening communicated with one opening of the inner hole of
the stator and a second opening communicated with another opening
of the inner hole of the stator.
4. The uniaxial eccentric screw pump according to claim 1, further
comprising a magnetic pole type power transmission structure
configured to transfer to the rotor a rotational force for causing
the rotor to rotate, wherein the magnetic pole type power
transmission structure includes: a driving magnetic pole portion
configured to generate a plurality of driving magnetic poles; a
driven magnetic pole portion configured to generate a plurality of
driven magnetic poles; and a dividing wall portion configured to
seal the driving magnetic pole portion and the driven magnetic pole
portion, the plurality of driving magnetic poles are arranged in a
circumferential direction of the driving magnetic pole portion, the
plurality of driven magnetic poles are arranged in a
circumferential direction of the driven magnetic pole portion, and
the driven magnetic pole portion rotates by rotation of the
plurality of driving magnetic poles.
5. The uniaxial eccentric screw pump according to claim 4, wherein:
the plurality of driving magnetic poles and the plurality of driven
magnetic poles are generated by magnets arranged such that the
north poles and south poles are arranged in alternation; and the
driving magnetic pole portion is rotated by the rotor driving
portion.
6. The uniaxial eccentric screw pump according to claim 4, wherein
the plurality of driving magnetic poles are rotating magnetic
fields generated by fixed winding wires, and the plurality of
driven magnetic poles are generated by magnets arranged such that
that the north poles and south poles are arranged in
alternation.
7. The uniaxial eccentric screw pump according to claim 1, wherein
the rotor driving portion causes the rotor to rotate and the stator
driving portion causes the stator to rotate with the rotor and the
stator not contacting each other.
8. The uniaxial eccentric screw pump according to claim 1, wherein:
the stator has a double thread internal screw type inner hole or a
triple thread internal screw type inner hole, and a cross-sectional
shape of the inner hole is an elliptical shape or a substantially
triangle shape each of whose three corners is a circular-arc shape;
the rotor is a single thread external screw type or a double thread
external screw type, and a cross-sectional shape of the rotor is a
circular shape or a substantially oval shape; a ratio of a pitch of
the rotor to a pitch of the inner hole is 1 to 2 or 2 to 3; and a
ratio of a rotating speed of the rotor to a rotating speed of the
stator is 2 to 1 or 3 to 2.
9. The uniaxial eccentric screw pump according to claim 1, wherein
the stator is made of engineering plastic, and the rotor is made of
a metal.
10. The uniaxial eccentric screw pump according to claim 1, wherein
one or both of the rotor and the stator is rotatably supported by a
magnetically-levitated bearing, and one or both of the rotor and
the stator is rotatably supported by a magnetic noncontact thrust
bearing.
11. The uniaxial eccentric screw pump according to claim 1, wherein
one or both of the rotor and the stator is rotatably supported by a
magnetic noncontact bearing capable of receiving both a radial load
and a thrust load.
12. A uniaxial eccentric screw pump in which: an external screw
type rotor is inserted in an inner hole of an internal screw type
stator; the rotor and the stator are separately, rotatably
supported; and a rotation central axis of the rotor and a rotation
central axis of the stator are arranged to be spaced apart from
each other, the uniaxial eccentric screw pump comprising a rotor
driving portion and a stator driving portion configured to
respectively cause the rotor and the stator to rotate with the
rotor and the stator not contacting each other.
Description
TECHNICAL FIELD
[0001] The present invention relates to a uniaxial eccentric screw
pump which is capable of transferring various fluids, such as
gases, liquids, and powder, and in which a rotor and a stator
separately rotate.
BACKGROUND ART
[0002] One example of a conventional uniaxial eccentric screw pump
will be explained in reference to FIG. 12 (see Patent Document 1
for example). As shown in FIG. 12, in a uniaxial eccentric screw
pump 1, an external screw type rotor 2 is fittingly inserted in an
inner hole 3a of an internal screw type stator 3, the rotor 2 is
rotatably provided on a pump casing 6 via bearings 4, and the
stator 3 is rotatably provided on the pump casing 6 via bearings 5.
A driven magnet 7 is provided in an annular shape at an outer
peripheral portion of the stator 3. A driving magnet 8 is provided
in a substantially short cylindrical shape outside the driven
magnet 7 so as to be spaced apart from the driven magnet 7 and
surround the driven magnet 7. The driving magnet 8 is rotatably
provided on the pump casing 6 via two bearings 9.
[0003] In accordance with the uniaxial eccentric screw pump 1 shown
in FIG. 12, when the driving magnet 8 is rotated in a predetermined
direction by an electric motor, not shown, the driven magnet 7 and
the stator 3 rotate in the same direction as the driving magnet 8
according to the rotation of the driving magnet 8. When the stator
3 rotates in the predetermined direction, an inner surface forming
the inner hole 3a of the stator 3 presses an outer surface of the
rotor 2 in the direction of rotation of the stator 3, and this
causes the rotor 2 to rotate in the same direction as the stator 3.
At this time, spaces 10 formed in the stator 3 move from a suction
port 6a side to a discharge port 6b side. Therefore, for example, a
liquid can be suctioned from the suction port 6a, and the suctioned
liquid can be discharged from the discharge port 6b.
[0004] Patent Document 1: Japanese Laid-Open Patent Application
Publication SHO 63-302189
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0005] However, since the conventional uniaxial eccentric screw
pump 1 shown in FIG. 12 is configured such that the stator 3 is
rotated in the predetermined direction by the electric motor, the
inner surface forming the inner hole 3a of the stator 3 presses the
outer surface of the rotor 2 in the direction of rotation of the
stator 3, and this causes the rotor 2 to rotate in the same
direction as the stator 3, such that the inner surface forming the
inner hole 3a of the stator 3 and the outer surface of the rotor 2
inevitably contact each other. As a result, these contact portions
wear away.
[0006] Moreover, when the uniaxial eccentric screw pump 1 transfers
a fluid, such as a liquid, pressure in the discharge port 6b
becomes comparatively high, and the high-pressure fluid in the
discharge port 6b generates a torque which becomes a resistance to
the rotation of the rotor 2 in the predetermined direction. With
this, contact pressure between the outer surface of the rotor 2 and
the inner surface forming the inner hole 3a of the stator becomes
comparatively high. As a result, an outer peripheral surface of the
rotor 2 and an inner peripheral surface of the inner hole 3a of the
stator further significantly wear away.
[0007] Thus, if the outer peripheral surface of the rotor 2 and the
inner peripheral surface of the inner hole 3a of the stator wear
away, a flow rate accuracy deteriorates, and pulsation becomes
high. This shortens the life of the uniaxial eccentric screw pump
1. Further, wear powder of the rotor 2 and the stator 3 gets mixed
in the fluid being transferred, and causes the rotor 2 and the
stator 3 to further wear away.
[0008] The reason why the flow rate accuracy deteriorates is
because the volume of the space 10 formed by a contact portion
(seal line) between the outer peripheral surface of the rotor 2 and
the inner peripheral surface of the inner hole 3a of the stator
changes, and the reason why the pulsation becomes high is because
the shape of the seal line changes.
[0009] The present invention was made to solve the above problems,
and an object of the present invention is to provide a uniaxial
eccentric screw pump capable of transferring and filling fluids
while realizing high flow rate accuracy, low pulsation, and long
life.
Means for Solving the Problems
[0010] A uniaxial eccentric screw pump according to the invention
recited in claim 1 is a uniaxial eccentric screw pump in which: an
external screw type rotor is inserted in an inner hole of an
internal screw type stator; the rotor and the stator are separately
rotatably supported; and a rotation central axis of the rotor and a
rotation central axis of the stator are arranged to be spaced apart
from each other, wherein the rotor and the stator are separately
rotated.
[0011] In accordance with the uniaxial eccentric screw pump of the
invention recited in claim 1, for example, the stator has a double
thread internal screw type inner hole, a cross-sectional shape of
the inner hole is elliptical, a cross-sectional shape of the rotor
is circular, a ratio of a pitch of the rotor to a pitch of the
inner hole is 1 to 2, and a ratio of a rotating speed of the rotor
to a rotating speed of the stator is 2 to 1. With this, the rotor
and the stator can be rotated in the same direction about their
respective central axes. At this time, since spaces formed by an
inner surface of the inner hole of the stator and an outer surface
of the rotor move from one opening side to another opening side of
the inner hole of the stator, a fluid can be transferred in this
direction. Moreover, since the rotor and the stator are separately
rotated, the rotor and the stator can be rotated such that either
the inner surface forming the inner hole of the stator and the
outer surface of the rotor do not contact each other, or the inner
surface forming the inner hole of the stator and the outer surface
of the rotor contact each other with appropriate contact pressure.
With this, it is possible to prevent or suppress the rotor and the
stator from wearing away.
[0012] In the invention recited in claim 1, the uniaxial eccentric
screw pump according to the invention recited in claim 2 is
configured such that: a central axis of the rotor and the rotation
central axis of the rotor coincide with each other; and a central
axis of the inner hole of the stator and the rotation central axis
of the stator coincide with each other.
[0013] In accordance with the uniaxial eccentric screw pump of the
invention recited in claim 2, since the center of gravity of the
rotor can be located on the rotation central axis thereof, and the
center of gravity of the stator can be located on the rotation
central axis thereof, it is possible to reduce the vibration
generated when the rotor and the stator rotate. Then, since the
rotor and the stator rotate such that the rotor is in the inner
hole of the stator and their rotation central axes coincide with
their centers of gravity, respectively, it is possible to reduce
the volume of the rotor and the volume of the stator.
[0014] In the invention recited in claim 1 or 2, the uniaxial
eccentric screw pump according to the invention recited in claim 3
is configured such that: the rotor is rotatably supported by a
driving shaft provided at one end of the rotor, and the driving
shaft is rotated by a rotor driving portion; a stator driving
portion is provided with respect to an outer peripheral surface of
the stator, and the stator is rotated by the stator driving
portion; and the stator is hermetically stored in a pump casing,
and the pump casing includes a first opening communicated with one
opening of the inner hole of the stator and a second opening
communicated with another opening of the inner hole of the
stator.
[0015] In accordance with the uniaxial eccentric screw pump of the
invention recited in claim 3, the rotor driving portion can cause
the rotor to rotate, and the stator driving portion can cause the
stator to rotate. Then, when the rotor and the stator are rotated
in a normal direction or a reverse direction at a predetermined
rotating speed according to need, a fluid can be suctioned through
the first opening or the second opening, and the suctioned liquid
can be transferred in the stator to be discharged through the
second opening or the first opening.
[0016] In the invention recited in claim 1, the uniaxial eccentric
screw pump according to the invention recited in claim 4 further
includes a magnetic pole type power transmission structure
configured to transfer to the rotor a rotational force for causing
the rotor to rotate, wherein the magnetic pole type power
transmission structure includes: a driving magnetic pole portion
configured to generate a plurality of driving magnetic poles; a
driven magnetic pole portion configured to generate a plurality of
driven magnetic poles; and a dividing wall portion configured to
seal the driving magnetic pole portion from the driven magnetic
pole portion, the plurality of driving magnetic poles are arranged
in a circumferential direction of the driving magnetic pole
portion, the plurality of driven magnetic poles are arranged in a
circumferential direction of the driven magnetic pole portion, and
the driven magnetic pole portion rotates according to rotation of
the plurality of driving magnetic poles.
[0017] In accordance with the uniaxial eccentric screw pump of the
invention recited in claim 4, when the plurality of driving
magnetic poles of the driving magnetic pole portion rotate in a
predetermined direction, the driven magnetic pole portion rotates
in the same direction as the plurality of driving magnetic poles by
the attractive force and repulsive force generated between the
plurality of driving magnetic poles and the plurality of driven
magnetic poles. Then, the rotation of the driven magnetic pole
portion is transferred to the rotor, and the rotor can be rotated
in a predetermined direction. Moreover, since the dividing wall
portion seals the driving magnetic pole portion from the driven
magnetic pole portion, it is possible to prevent, for example, the
fluid having flowed into the driven magnetic pole portion side from
flowing into the driving magnetic pole portion side.
[0018] Further, since the dividing wall portion seals the driving
magnetic pole portion from the driven magnetic pole portion, for
example, a shaft sealing structure (such as a sealing member) for
sealing the rotor driving shaft from the rotor becomes unnecessary.
With this, it is possible to realize cost reduction, easy
maintenance, and improvement of the durability performance of the
uniaxial eccentric screw pump. In addition, it is possible to
simplify disassembling, assembling, and cleaning operations.
[0019] In the invention recited in claim 4, the uniaxial eccentric
screw pump according to the invention recited in claim 5 is
configured such that: the plurality of driving magnetic poles and
the plurality of driven magnetic poles are generated by magnets
arranged such that the north poles and south poles are arranged in
alternation; and the driving magnetic pole portion is rotated by
the rotor driving portion.
[0020] In accordance with the uniaxial eccentric screw pump of the
invention recited in claim 5, when the rotor driving portion causes
the driving magnetic pole portion to rotate in a predetermined
direction, the driven magnetic pole portion rotates in the same
direction as the driving magnetic pole portion according to the
rotation of the driving magnetic pole portion. The rotation of the
driven magnetic pole portion according to the rotation of the
driving magnetic pole portion is caused by the attractive force and
repulsive force of the magnets provided at the magnetic pole
portions.
[0021] In the invention recited in claim 4, the uniaxial eccentric
screw pump according to the invention recited in claim 6 is
configured such that the plurality of driving magnetic poles are
rotating magnetic fields generated by fixed winding wires, and the
plurality of driven magnetic poles are generated by magnets
arranged such that a north pole and a south pole are alternately
arranged.
[0022] In accordance with the uniaxial eccentric screw pump of the
invention recited in claim 6, when current is supplied to the fixed
winding wire to generate the rotating magnetic field, the driven
magnetic pole portion can be rotated in the same direction as the
rotating magnetic field by the rotating magnetic field. The
rotation of the driven magnetic pole portion by the rotating
magnetic field of the driving magnetic pole is caused by the
attractive force and repulsive force generated between respective
magnetic poles.
[0023] In the invention recited in claim 1, the uniaxial eccentric
screw pump according to the invention recited in claim 7 is
configured such that the rotor driving portion causes the rotor to
rotate and the stator driving portion causes the stator to rotate
with the rotor and the stator not contacting each other.
[0024] In accordance with the uniaxial eccentric screw pump of the
invention recited in claim 7, since the rotor and the stator can be
rotated with the rotor and the stator not contacting each other,
the wear powder generated in a case where the rotor and the stator
contact each other does not get mixed in the transfer fluid, and
noise is not generated by friction between the rotor and the
stator. Moreover, the dimension of the gap between the outer
peripheral surface of the rotor and the inner peripheral surface of
the stator can be appropriately set in accordance with the property
of the transfer fluid (such as a fluid containing slurry). With
this, it is possible to transfer and fill the fluid while realizing
high flow rate accuracy, low pulsation, and long life in accordance
with various properties of the fluid. Further, since the rotor and
the stator can be rotated with the rotor and the stator not
contacting each other, they can be rotated at a comparatively high
speed, and a comparatively high transfer ability can be
obtained.
[0025] In the invention recited in claim 1, the uniaxial eccentric
screw pump according to the invention recited in claim 8 is
configured such that: the stator has a double thread internal screw
type inner hole or a triple thread internal screw type inner hole,
and a cross-sectional shape of the inner hole is an elliptical
shape or a substantially triangle shape each of whose three corners
is a circular-arc shape; the rotor is a single thread external
screw type or a double thread external screw type, and a
cross-sectional shape of the rotor is a circular shape or a
substantially oval shape; a ratio of a pitch of the rotor to a
pitch of the inner hole is 1 to 2 or 2 to 3; and a ratio of a
rotating speed of the rotor to a rotating speed of the stator is 2
to 1 or 3 to 2.
[0026] In accordance with the uniaxial eccentric screw pump of the
invention recited in claim 8, the number of threads of the stator
is two or three, and the number of threads of the rotor is one or
two. Therefore, as compared to a case where the number of threads
of each of the stator and the rotor is larger than the above, it is
possible to simplify the shape of the rotor and the shape of the
stator, and form the rotor and the stator with comparatively high
size accuracy. Therefore, it is possible to provide the uniaxial
eccentric screw pump which realizes low-cost and quick
delivery.
[0027] In the invention recited in claim 1, the uniaxial eccentric
screw pump according to the invention recited in claim 9 is
configured such that the stator is made of engineering plastic, and
the rotor is made of a metal.
[0028] In accordance with the uniaxial eccentric screw pump of the
invention recited in claim 9, since the stator is made of
engineering plastic, and the rotor is made of a metal, the change
in size due to the temperature change can be comparatively
suppressed as compared to the rotator and stator which are made of
rubber. With this, it is possible to suppress the deterioration of
the flow rate accuracy due to the temperature change.
[0029] In the invention recited in claim 1, the uniaxial eccentric
screw pump according to the invention recited in claim 10 is
configured such that one or both of the rotor and the stator is
rotatably supported by a magnetically-levitated bearing, and one or
both of the rotor and the stator is rotatably supported by a
magnetic noncontact thrust bearing.
[0030] In accordance with the uniaxial eccentric screw pump of the
invention recited in claim 10, the rotor and the stator rotate in a
state where one or both of the rotor and the stator levitates in
the radial direction or in a state where the rotor and the stator
do not contact each other in the thrust direction. Therefore, it is
possible to realize low noise and low vibration, and cause the
rotor and the stator to smoothly rotate. Then, for example, shaft
sealing members and contact type bearings may be omitted or
reduced, and maintenances thereof may also be omitted or reduced.
Moreover, it is possible to improve the durability performance of
the uniaxial eccentric screw pump, and simplify disassembling,
assembling, and cleaning operations.
[0031] In the invention recited in claim 1, the uniaxial eccentric
screw pump according to the invention recited in claim 11 is
configured such that one or both of the rotor and the stator is
rotatably supported by a magnetic noncontact bearing capable of
receiving both a radial load and a thrust load.
[0032] In accordance with the uniaxial eccentric screw pump of the
invention recited in claim 11, one or both of the rotor and the
stator are rotatably supported by the magnetic noncontact bearings
capable of receiving both the radial load and the thrust load.
Therefore, as compared to the case of using the bearings capable of
receiving the radial load and the bearings capable of receiving the
thrust load, it is possible to simplify the configuration and
comparatively reduce the volume of the uniaxial eccentric screw
pump.
EFFECTS OF THE INVENTION
[0033] Since the uniaxial eccentric screw pump according to the
present invention is configured such that the rotor and the stator
separately rotate, it is possible to prevent or suppress the
rotating rotor and stator from wearing away by contacting each
other. With this, the volume of the space formed by a closure
portion (closure line) or a contact portion (seal line) between the
outer peripheral surface of the rotor and the inner peripheral
surface of the inner hole of the stator can be prevented from
changing when the rotor and the stator rotate. Therefore, it is
possible to realize high flow rate accuracy. Then, since the shape
of the closure line or the seal line does not change when the rotor
and the stator rotate, the pulsation can be reduced. Therefore, it
is possible to transfer and fill the fluid while realizing high
flow rate accuracy, low pulsation, and long life.
BRIEF DESCRIPTION OF THE DRAWINGS
[0034] FIG. 1 is a longitudinal sectional view showing a uniaxial
eccentric screw pump according to Embodiment 1 of the present
invention.
[0035] FIG. 2 are schematic diagrams showing the configuration of
the uniaxial eccentric screw pump according to Embodiment 1 of the
present invention. FIG. 2(a) is a diagram showing cross-sectional
shapes at respective positions, and FIG. 2(b) is a side view.
[0036] FIGS. 3(a) to 3(d) are schematic diagrams showing the states
of the rotor and the states of the stator at respective rotation
angles in the uniaxial eccentric screw pump according to Embodiment
1 of the present invention.
[0037] FIGS. 4(a) to 4(d) are schematic diagrams showing the states
of the rotor and the states of the stator at respective rotation
angles in the uniaxial eccentric screw pump according to Embodiment
1 of the present invention.
[0038] FIGS. 5(a) and 5(b) are schematic diagrams showing the
states of the rotor and the states of the stator at respective
rotation angle in the uniaxial eccentric screw pump according to
Embodiment 1 of the present invention.
[0039] FIG. 6 is a longitudinal sectional view showing the uniaxial
eccentric screw pump according to Embodiment 2 of the present
invention.
[0040] FIG. 7 show a magnetic pole type power transmission
structure included in the uniaxial eccentric screw pump according
to Embodiment 2 of the present invention. FIG. 7(a) is a diagram
showing a driving magnetic pole portion, and FIG. 7(b) is a diagram
showing a driven magnetic pole portion.
[0041] FIG. 8 is a longitudinal sectional view showing the uniaxial
eccentric screw pump according to Embodiment 3 of the present
invention.
[0042] FIG. 9 is a longitudinal sectional view showing the uniaxial
eccentric screw pump according to Embodiment 4 of the present
invention.
[0043] FIG. 10 is a longitudinal sectional view showing the
uniaxial eccentric screw pump according to Embodiment 5 of the
present invention.
[0044] FIG. 11 is a longitudinal sectional view showing the
uniaxial eccentric screw pump according to Embodiment 6 of the
present invention.
[0045] FIG. 12 is a longitudinal sectional view showing a
conventional uniaxial eccentric screw pump.
EXPLANATION OF REFERENCE NUMBERS
[0046] 11 uniaxial eccentric screw pump [0047] 12 rotor [0048] 13
stator [0049] 13a inner hole [0050] 14 pump casing [0051] 15 end
stud [0052] 16 first casing [0053] 17 second casing [0054] 18, 25,
29 bearing [0055] 19 stator driving portion [0056] 19a, 27a rotor
portion [0057] 19b, 27b stator portion [0058] 20, 28 seal portion
[0059] 21 first opening [0060] 22 second opening [0061] 23 central
axis of inner hole [0062] 24 driving shaft [0063] 26 driving
portion casing [0064] 27 rotor driving portion [0065] 30 central
axis of rotor [0066] 31, 32, 33 reference line [0067] 34 space
[0068] 35 parallel surface of inner hole [0069] 37, 67, 72, 74, 88
uniaxial eccentric screw pump [0070] 38 magnetic pole type power
transmission structure [0071] 39 dividing wall portion [0072] 40
first magnetically-levitated bearing [0073] 41 second
magnetically-levitated bearing [0074] 42 third
magnetically-levitated bearing [0075] 43 fourth
magnetically-levitated bearing [0076] 44 first magnetic noncontact
thrust bearing [0077] 45 second magnetic noncontact thrust bearing
[0078] 46 third magnetic noncontact thrust bearing [0079] 47 fourth
magnetic noncontact thrust bearing [0080] 48 second rotor driving
portion [0081] 49, 58, 69 driving magnetic pole portion [0082] 50,
57 driven magnetic pole portion [0083] 51, 52 space [0084] 53
driven magnet [0085] 54 driving magnet [0086] 55, 59 outer ring
magnet portion [0087] 56, 60 inner ring magnet portion [0088] 61,
63 first magnet portion [0089] 62, 64, 70 second magnet portion
[0090] 65, 68 fixed winding wire [0091] 71 rotor driving portion
[0092] 75, 76, 77, 78 magnetic noncontact bearing [0093] 79, 80,
81, 82 outer ring magnet portion [0094] 83, 84, 85, 86 inner ring
magnet portion
BEST MODE FOR CARRYING OUT THE INVENTION
[0095] Hereinafter, Embodiment 1 of a uniaxial eccentric screw pump
according to the present invention will be explained in reference
to FIGS. 1 to 5. As shown in FIG. 1, a uniaxial eccentric screw
pump 11 can cause a rotor 12 and a stator 13 to separately rotate.
Therefore, the uniaxial eccentric screw pump 11 can transfer and
fill any fluid, such as low-viscosity fluids and high-viscosity
fluid, while realizing high flow rate accuracy, low pulsation, and
long life.
[0096] As shown in FIG. 1, the uniaxial eccentric screw pump 11 is
a rotary volume type pump, and includes an internal screw type
stator 13 and an external screw type rotor 12.
[0097] As shown in FIGS. 1 and 2, the stator 13 is formed to have a
substantially short cylindrical shape having a double thread
internal screw type inner hole 13a for example. A longitudinal
cross-sectional shape of the inner hole 13a is elliptical. The
stator 13 is made of engineering plastic, such as Teflon
(trademark), polyacetal, or cast nylon. The stator 13 is
hermetically attached to an inside of a pump casing 14. As shown in
FIG. 1, the pump casing 14 includes an end stud 15, a first casing
16, and a second casing 17 which are arranged in this order from a
right tip end side. The stator 13 is rotatably provided on inner
peripheral surfaces of the first and second casings 16 and 17 via
two bearings 18, and a stator driving portion 19 is provided
between these two bearings 18. To prevent a transfer liquid from
contacting the stator driving portion 19, two seal portions 20 are
attached on left and right outer sides, respectively, of the
bearings 18.
[0098] As shown in FIG. 1, in the pump casing 14, a first opening
21 is formed on the end stud 15, and a second opening 22 is formed
on the second casing 17. The first opening 21 can be used as a
discharge port and a suction port, and the second opening 22 can be
used as a suction port and a discharge port. The first opening 21
is communicated with a tip end side opening of the inner hole 13a
of the stator 13, and the second opening 22 is communicated with a
rear end side opening of the inner hole 13a of the stator 13.
[0099] The stator driving portion 19 is an electric motor, such as
a stepping motor or a servo motor, and includes a rotor portion 19a
and a stator portion 19b. As shown in FIG. 1, the rotor portion 19a
is provided at an outer peripheral portion of the stator 13, and
the stator portion 19b is provided at inner peripheral surfaces of
the first and second casings 16 and 17. The stator driving portion
19 causes the stator 13 to rotate in a normal direction and a
reverse direction for example. The stator 13 is provided such that
a central axis 23 of the inner hole 13a and a rotation central axis
of the stator 13 coincide with each other.
[0100] As shown in FIGS. 1 and 2, the rotor 12 is formed to have a
single thread external screw shape for example. A longitudinal
cross-sectional shape of the rotor 12 is a substantially perfect
circle. A pitch of a spiral shape of the rotor 12 is set to half a
pitch of the stator 13. The rotor 12 is made of a metal, such as
stainless steel, and is fittingly inserted in the inner hole 13a of
the stator 13. A rear end portion of the rotor 12 is coupled to a
driving shaft 24, and the driving shaft 24 is rotatably provided on
an inner peripheral surface of a driving portion casing 26 via two
bearings 25. A rotor driving portion 27 is provided between these
two bearings 25. A seal portion 28 is attached to prevent the
transfer liquid from contacting the rotor driving portion 27.
Moreover, a tip end portion of the rotor 12 is rotatably supported
by an inner surface of the end stud 15 via a bearing 29.
[0101] The rotor driving portion 27 is an electric motor, such as a
stepping motor or a servo motor, and includes a rotor portion 27a
and a stator portion 27b. As shown in FIG. 1, the rotor portion 27a
is provided on an outer peripheral surface of the driving shaft 24,
and the stator portion 27b is provided on an inner peripheral
surface of the driving portion casing 26. The rotor driving portion
27 causes the rotor 12 coupled to the driving shaft 24 to
rotate.
[0102] The rotor 12 is provided such that a central axis 30 of the
rotor 12 and a rotation central axis of the rotor 12 coincide with
each other. The central axis 30 of the rotor 12 and the central
axis 30 of the driving shaft 24 coincide with each other. Moreover,
both of the stator driving portion 19 and the rotor driving portion
27 may be the servo motors, or one of them may be the servo motor
and the other one may be the stepping motor. The bearings 18 and 25
shown in FIG. 1 can support load in a radial direction and a thrust
direction.
[0103] FIG. 2 are schematic diagrams showing the uniaxial eccentric
screw pump 11 shown in FIG. 1, and show the states of the rotor 12
and the states of the stator 13 in cross section when the rotor 12
and the stator 13 are not moving.
[0104] FIGS. 3 to 5 are schematic diagrams showing that the rotor
12 and the stator 13 rotate in a predetermined direction
(counterclockwise direction) when viewed from an A-A direction of
FIG. 1. The rotor 12 is rotated in the counterclockwise direction
by the rotor driving portion 27, and the stator 13 is rotated in
the counterclockwise direction by the stator driving portion 19. A
ratio of the rotating speed of the rotor 12 to the rotating speed
of the stator 13 is 2 to 1.
[0105] In FIG. 3(a), the inner hole 13a, shown as an ellipse, of
the stator 13 extends in a vertical direction. Then, the rotor 12
whose cross section is shown as a circle is located at an upper end
portion of the inner hole 13a. In FIG. 3(a), reference numbers 31,
32, and 33 denote reference lines of the pump casing 14, the stator
13, and the rotor 12, respectively. In, for example, an initial
state shown in FIG. 3(a), these three reference lines 31, 32, and
33 coincide with one another. A reference number 23 denotes a
rotation central axis of the stator 13, and a reference number 30
denotes a rotation central axis of the rotor 12.
[0106] FIGS. 3(b), 3(c), and 3(d) show that the rotor 12 and the
stator 13 rotate in the counterclockwise direction about the
central axes 30 and 23, respectively. The rotation angle of the
rotor 12 and the rotation angle of the stator 13 are respectively
45.degree. and 22.5.degree. in FIG. 3(b), 90.degree. and 45.degree.
in FIG. 3(c), and 135.degree. and 67.5.degree. in FIG. 3(d).
[0107] FIGS. 4(a) to 4(d), 5(a), and 5(b) show that the rotor 12
and the stator 13 rotate in the counterclockwise direction about
the central axes, respectively. The rotation angle of the rotor 12
and the rotation angle of the stator 13 are respectively
180.degree. to 450.degree. and 90.degree. to 225.degree. in FIGS.
4(a) to 4(d); 540.degree. and 270.degree. in FIG. 5(a); and
630.degree. and 315.degree. in FIG. 5(b). Then, as shown in FIG.
3(a), the rotation angle of the rotor 12 and the rotation angle of
the stator 13 become 720.degree. and 360.degree., respectively.
Thus, the rotor 12 rotates twice, and the stator 13 rotates once,
thereby terminating the operation of one stroke of the uniaxial
eccentric screw pump 11.
[0108] As shown in FIGS. 3 to 5, when the rotor 12 and the stator
13 rotate, each axial portion of the rotor 12 reciprocates along a
radial direction perpendicular to the central axis 30 of the rotor
12, i.e., along a length direction of an elliptical cross section
of the inner hole 13a of the stator 13. Then, as shown in FIG. 3(d)
for example, spaces 34 are formed by the outer surface of the rotor
12 and the inner surface of the inner hole 13a of the stator. The
spaces 34 can move from the tip end portion side (the first opening
21 side) of the rotor 12 shown in FIG. 1 to the rear end portion
side (the second opening 22 side) of the rotor 12. By the movement
of the spaces 34 in this direction, the fluid can be suctioned
through the first opening 21 and discharged through the second
opening 22 with a predetermined pressure.
[0109] A diameter D1 of the rotor 12 shown in FIGS. 2(a) and 2(b)
is slightly smaller than a horizontal width D2 of the inner hole
13a of the stator 13. The rotor driving portion 27 cause the rotor
12 to rotate and the stator driving portion 19 cause the stator 13
to rotate with the rotor 12 and the stator 13 not contacting each
other. The rotor driving portion 27 and the stator driving portion
19 are controlled by a controller, not shown.
[0110] In accordance with the uniaxial eccentric screw pump 11
configured as shown in FIGS. 1 to 5, the stator 13 has the double
thread internal screw type inner hole 13a, the cross-sectional
shape of the inner hole 13a is elliptical, the cross-sectional
shape of the rotor 12 is circular, the ratio of the pitch of the
rotor 12 to the pitch of the inner hole 13a is 1 to 2, and the
ratio of the rotating speed of the rotor 12 to the rotating speed
of the stator 13 is 2 to 1. With this, the rotor 12 and the stator
13 can be rotated in the same direction as each other about the
predetermined central axes 30 and 23, respectively. At this time,
since the spaces 34 formed by the inner surface of the inner hole
13a of the stator and the outer surface of the rotor 12 move from
the first opening 21 side to the second opening 22 side, the fluid
can be transferred in this direction. Moreover, since the rotor 12
and the stator 13 are separately rotated, the rotor 12 and the
stator 13 can be rotated such that the inner surface forming the
inner hole 13a of the stator and the outer surface of the rotor 12
do not contact each other. Therefore, it is possible to prevent the
rotor 12 and the stator 13 from wearing away.
[0111] Therefore, the volume of the space 34 formed by the closure
portion (closure line) between the outer peripheral surface of the
rotor 12 and the inner peripheral surface of the inner hole 13a of
the stator is prevented from changing when the rotor 12 and the
stator 13 rotate. Therefore, it is possible to realize high flow
rate accuracy. Then, since the shape of the closure line does not
change when the rotor 12 and the stator 13 rotate, the pulsation
can be reduced. Therefore, the fluid can be transferred and filled
while realizing high flow rate accuracy, low pulsation, and long
life.
[0112] In accordance with the uniaxial eccentric screw pump 11
according to the present embodiment shown in FIG. 1, when filling
the fluid of 0.01 to 0.10 ml for example, a filling accuracy of
.+-.0.0002 ml can be realized. The filling accuracy of the
conventional uniaxial eccentric screw pump is about .+-.0.005 ml
for example.
[0113] In the uniaxial eccentric screw pump 11 shown in FIG. 1, the
rotor 12 is configured such that the central axis 30 of the rotor
12 and the rotation central axis of the rotor 12 coincide with each
other, and the stator 13 is configured such that the central axis
23 of the inner hole 13a of the stator 13 and the rotation central
axis of the stator 13 coincide with each other.
[0114] With this, since the center of gravity of the rotor 12 can
be located on the rotation central axis of the rotor 12, and the
center of gravity of the stator 13 can be located on the rotation
central axis of the stator 13, vibrations can be reduced when the
rotor 12 and the stator 13 rotate. Then, since the rotor and the
stator rotate such that the rotor is in the inner hole of the
stator and their rotation central axes coincide with their centers
of gravity, respectively, the volume of the rotor 12 and the volume
of the stator 13 can be reduced.
[0115] Moreover, in accordance with the uniaxial eccentric screw
pump 11, since the rotor 12 and the stator 13 can be rotated with
the rotor 12 and the stator 13 not contacting each other, the wear
powder generated in a case where the rotor 12 and the stator 13
contact each other does not get mixed in the transfer fluid, and
noise is not generated by friction between the rotor 12 and the
stator 13. Moreover, the dimension of the gap between the outer
peripheral surface of the rotor 12 and the inner peripheral surface
of the stator 13 can be appropriately set in accordance with the
property of the transfer fluid (such as a fluid containing slurry).
With this, it is possible to transfer and fill the fluid while
realizing high flow rate accuracy, low pulsation, and long life in
accordance with various properties of the fluid. Further, since the
rotor 12 and the stator 13 can be rotated with the rotor 12 and the
stator 13 not contacting each other, they can be rotated at a
comparatively high speed, and a comparatively high transfer ability
can be obtained.
[0116] Further, in accordance with the uniaxial eccentric screw
pump 11, the stator 13 has the double thread internal screw type
inner hole 13a, the cross-sectional shape of the inner hole 13a is
elliptical, the rotor 12 is a single thread external screw type,
the cross-sectional shape of the rotor 12 is circular, and the
ratio of the pitch of the rotor 12 to the pitch of the inner hole
13a is 1 to 2. With this, the rotor 12 and the stator 13 are
comparatively simple in shape, so that they can be formed with
comparatively high size accuracy. Therefore, it is possible to
provide the uniaxial eccentric screw pump 11 which realizes low
cost and quick delivery.
[0117] Then, in accordance with the uniaxial eccentric screw pump
11, since the stator 13 is made of engineering plastic, such as
Teflon (trademark), and the rotor 12 is made of a metal, the change
in size due to the temperature change can be comparatively
suppressed as compared to the rotator 12 and stator 13 which are
made of rubber. With this, it is possible to suppress the
deterioration of the flow rate accuracy due to the temperature
change.
[0118] Moreover, in accordance with the uniaxial eccentric screw
pump 11, the rotor 12 and the stator 13 can be rotated at a
predetermined rotating speed according to need in the normal
direction and the reverse direction. With this, the fluid can be
suctioned through the first opening 21 or the second opening 22,
and the suctioned liquid can be transferred in the stator 13 to be
discharged through the second opening 22 or the first opening
21.
[0119] Next, a uniaxial eccentric screw pump 37 according to
Embodiment 2 of the present invention will be explained in
reference to the longitudinal sectional view of FIG. 6. Differences
between Embodiment 2 shown in FIG. 6 and Embodiment 1 shown in FIG.
1 are as follows. As shown in FIG. 1, Embodiment 1 is configured
such that: the driving shaft 24 and the rotor 12 are directly
coupled to each other; and the gap between the driving shaft 24 and
an inner peripheral surface of an insertion hole formed on a wall
portion of the second casing 17 through which the driving shaft 24
penetrates is sealed by the seal portion 28. In contrast, as shown
in FIG. 6, Embodiment 2 is configured such that: the seal portion
28 is omitted; the driving shaft 24 and a base end portion 12a of
the rotor 12 are provided to be spaced apart from each other; a
rotational force of the driving shaft 24 is transferred to the
rotor 12 by a magnetic pole type power transmission structure 38;
and the driving shaft 24 is sealed from the base end portion 12a of
the rotor 12 by a dividing wall portion 39.
[0120] Moreover, the difference between Embodiment 1 and Embodiment
2 is as follows. As shown in FIG. 1, Embodiment 1 is configured
such that the rotor 12 and the stator 13 are rotatably supported by
the ball bearings 25, 29, and 18 of a contact type in the radial
direction and the thrust direction. In contrast, as shown in FIG.
6, Embodiment 2 is configured such that the rotor 12 and the stator
13 are rotatably supported by first to fourth
magnetically-levitated bearings 40, 41, 42, and 43 and first to
fourth magnetic noncontact thrust bearings 44, 45, 46, and 47.
[0121] Further, the difference between Embodiment 1 and Embodiment
2 is as follows. As shown in FIG. 1, Embodiment 1 is configured
such that a second rotor driving portion 48 is not provided at the
tip end portion of the rotor 12. In contrast, as shown in FIG. 6,
Embodiment 2 is configured such that the tip end portion of the
rotor 12 is rotated by the second rotor driving portion 48 which
uses the magnetic pole type power transmission structure.
[0122] Other than the above, the uniaxial eccentric screw pump 37
of Embodiment 2 is the same in configuration as the uniaxial
eccentric screw pump 11 of Embodiment 1 and operates in the same
manner as the uniaxial eccentric screw pump 11 of Embodiment 1, so
that same reference numbers are used for the same components, and
explanations thereof are omitted.
[0123] The magnetic pole type power transmission structure 38 of
the uniaxial eccentric screw pump 37 of Embodiment 2 shown in FIG.
6 can transfer the rotational force of the rotor driving portion 27
to the rotor 12, and includes a driving magnetic pole portion 49, a
driven magnetic pole portion 50, and the dividing wall portion 39.
The driving magnetic pole portion 49 is stored in a driving side
space 51 formed by the driving portion casing 26, the driven
magnetic pole portion 50 is stored in a driven side space 52 formed
by the second casing 17, and the dividing wall portion 39 having a
plate shape is fixedly sandwiched between the driving portion
casing 26 and the second casing 17. The driving side space 51 in
which the driving magnetic pole portion 49 is provided and the
driven side space 52 in which the driven magnetic pole portion 50
is provided are liquid-tightly sealed by the dividing wall portion
39.
[0124] As shown in FIG. 7(b), the driven magnetic pole portion 50
has a circular plate shape, and, for example, eight driven magnets
(permanent magnets for example) 53 are hermetically attached to an
inside of the driven magnetic pole portion 50 along a
circumferential direction of the driven magnetic pole portion 50 so
as to be equally spaced apart from one another. These eight driven
magnets 53 are arranged such that magnetic poles thereof, i.e., the
north pole and the south pole are alternately arranged when viewed
from the driving magnetic pole portion 49 shown in FIG. 6. The
magnetic poles (the north poles and the south poles) of these eight
driven magnets 53 are driven magnetic poles. Moreover, the base end
portion 12a of the rotor 12 is coupled to a center portion of the
driven magnetic pole portion 50.
[0125] As shown in FIG. 7(a), the driving magnetic pole portion 49
has the same circular plate shape as the driven magnetic pole
portion 50, and, for example, eight driving magnets (permanent
magnets for example) 54 are hermetically attached to the inside of
the driving magnetic pole portion 49 along a circumferential
direction of the driving magnetic pole portion 49 so as to be
equally spaced apart from one another. These eight driving magnets
54 are arranged such that magnetic poles thereof, i.e., the north
pole and the south pole are alternately arranged when viewed from
the driven magnetic pole portion 50 shown in FIG. 6. The magnetic
poles (the north poles and the south poles) of these eight driving
magnets 54 are driving magnetic poles. Moreover, the driving shaft
24 is coupled to a center portion of the driving magnetic pole
portion 49.
[0126] Moreover, the driving shaft 24 coupled to the driving
magnetic pole portion 49 shown in FIG. 6 is rotated by the rotor
driving portion 27, and the driven magnetic pole portion 50 is
rotated by the driving magnetic pole portion 49. The driving shaft
24, the driving magnetic pole portion 49, the driven magnetic pole
portion 50, and the rotor 12 are configured to be rotatable about
the central axis 30. Moreover, the dividing wall portion 39 has a
circular plate shape for example, and is formed by a non-magnetic
material.
[0127] In accordance with the magnetic pole type power transmission
structure 38 configured as above, when the driving magnetic pole
portion 49 (driving shaft 24) shown in FIG. 6 is rotated by the
rotor driving portion 27 in a predetermined direction, and eight
driving magnetic poles (driving magnets 54) N and S arranged
alternatively are rotated in a predetermined direction, the driven
magnetic pole portion 50 rotates in the same direction as the
driving magnetic poles by a attractive force and a repulsive force
generated between eight driving magnetic poles N and S arranged
alternatively and eight driven magnetic poles (driven magnets 53) S
and N arranged alternatively.
[0128] As above, when the driven magnetic pole portion 50 is
rotated in a predetermined direction by the driving magnetic pole
portion 49, the rotor 12 rotates in the same direction as the
driven magnetic pole portion 50, so that, for example, the fluid
can be suctioned through the first opening 21 and discharged
through the second opening 22 by a constant volume.
[0129] Moreover, since the driving magnetic pole portion 49 and the
driven magnetic pole portion 50 are sealed by the dividing wall
portion 39, it is possible to prevent, for example, the fluid
having flowed into the driven magnetic pole portion 50 side from
flowing into the driving magnetic pole portion 49 side. Further, a
shaft sealing structure (such as the seal portion 28 shown in FIG.
1) for sealing the driving shaft 24 and the rotor 12 becomes
unnecessary. With this, it is possible to realize cost reduction,
easy maintenance, and improvement of the durability performance of
the uniaxial eccentric screw pump. Then, it is possible to simplify
disassembling, assembling, and cleaning operations.
[0130] Next, the first to fourth magnetically-levitated bearings
40, 41, 42, and 43 and the first to fourth magnetic noncontact
thrust bearings 44, 45, 46, and 47 of the rotor 12 and the stator
13 will be explained in reference to FIG. 6.
[0131] As shown in FIG. 6, the first and second
magnetically-levitated bearings 40 and 41 provided for the rotor 12
support the rotor 12 by utilizing the repulsive force of magnets so
as to be able to receive load in the radial direction of the rotor
12 and allow the rotor 12 to rotate at a predetermined position
with the rotor 12 and the pump casing 14 not contacting each other.
Each of the first and second magnetically-levitated bearings 40 and
41 includes an outer ring magnet portion (permanent magnet) 55 and
an inner ring magnet portion (permanent magnet) 56.
[0132] As shown in FIGS. 6 and 7(b), the inner ring magnet portion
56 of the first magnetically-levitated bearing 40 is an annular
magnet, and is hermetically attached to an outer peripheral portion
of the driven magnetic pole portion 50. Then, as shown in FIG. 6,
the outer ring magnet portion 55 is an annular magnet, and is
hermetically attached to an inner peripheral portion of the second
casing 17 so as to be located outside the inner ring magnet portion
56 in the radial direction, spaced apart from the inner ring magnet
portion 56, and opposed to the inner ring magnet portion 56. Then,
the outer ring magnet portion 55 and the inner ring magnet portion
56 are arranged such that the magnetic poles opposed to each other
in the radial direction are the same poles (N and N, or S and
S).
[0133] Similarly, as shown in FIG. 6, the inner ring magnet portion
56 of the second magnetically-levitated bearing 41 is an annular
magnet, and is hermetically attached to an outer peripheral portion
of a driven magnetic pole portion 57 provided at the tip end
portion of the rotor 12. The outer ring magnet portion 55 is an
annular magnet, and is hermetically attached to an inner peripheral
portion of the first casing 16 so as to be located outside the
inner ring magnet portion 56 in the radial direction, spaced apart
from the inner ring magnet portion 56, and opposed to the inner
ring magnet portion 56. Then, the outer ring magnet portion 55 and
the inner ring magnet portion 56 are arranged such that the
magnetic poles opposed to each other in the radial direction are
the same poles (N and N, or S and S).
[0134] As shown in FIG. 6, the third and fourth
magnetically-levitated bearings 42 and 43 provided for the stator
13 support the stator 13 by utilizing the repulsive force of
magnets so as to be able to receive load in the radial direction of
the stator 13 and allow the stator 13 to rotate at a predetermined
position with the stator 13 and the pump casing 14 not contacting
each other. Each of the third and fourth magnetically-levitated
bearings 42 and 43 includes an outer ring magnet portion (permanent
magnet) 59 and an inner ring magnet portion (permanent magnet)
60.
[0135] As shown in FIG. 6, the inner ring magnet portion 60 of the
third magnetically-levitated bearing 42 (or the fourth
magnetically-levitated bearing 43) is an annular magnet, and is
hermetically attached to an outer peripheral portion of a second
opening 22 side (or a first opening 21 side) end portion of the
stator 13. The outer ring magnet portion 59 is an annular magnet,
and is hermetically attached to the inner peripheral portion of the
second casing 17 (or the first casing 16) so as to be located
outside the inner ring magnet portion 60 in the radial direction,
spaced apart from the inner ring magnet portion 60, and opposed to
the inner ring magnet portion 60. Then, the outer ring magnet
portion 59 and the inner ring magnet portion 60 are arranged such
that the magnetic poles opposed to each other in the radial
direction are the same poles (N and N, or S and S).
[0136] As shown in FIG. 6, the first and second magnetic noncontact
thrust bearings 44 and 45 provided for the rotor 12 support the
rotor 12 by utilizing the repulsive force of magnets so as to be
able to receive load in the thrust direction of the rotor 12 and
allow the rotor 12 to rotate at a predetermined position with the
rotor 12 and the pump casing 14 not contacting each other.
Therefore, the repulsive forces of the first and second magnetic
noncontact thrust bearings 44 and 45 are set to be balanced in the
thrust direction. Each of the first and second magnetic noncontact
thrust bearings 44 and 45 includes a first magnet portion
(permanent magnet) 61 and a second magnet portion (permanent
magnet) 62.
[0137] As shown in FIGS. 6 and 7(a), the first magnet portion 61 of
the first magnetic noncontact thrust bearing 44 is a short columnar
magnet, and is hermetically attached to a center position (on the
central axis 30) of the driving magnetic pole portion 49. The
second magnet portion 62 is a short columnar magnet, and is
hermetically attached to a center position (on the central axis 30)
of the driven magnetic pole portion 50. Then, the first magnet
portion 61 and the second magnet portion 62 are arranged to be
spaced apart from each other in the thrust direction (direction
along the central axis 30) such that the magnetic poles opposed to
each other are the same poles (S and S, or N and N).
[0138] Similarly, as shown in FIG. 6, the first magnet portion 61
of the second magnetic noncontact thrust bearing 45 is a short
columnar magnet, and is hermetically attached to a center position
(on the central axis 30) of the driven magnetic pole portion 57
provided at the tip end portion of the rotor 12. The second magnet
portion 62 is a short columnar magnet, and is hermetically attached
to a center position (on the central axis 30) of the end stud 15.
Then, the first magnet portion 61 and the second magnet portion 62
are arranged to be spaced apart from each other in the thrust
direction (direction along the central axis 30) such that the
magnetic poles opposed to each other are the same poles (N and N,
or S and S).
[0139] As shown in FIG. 6, the third and fourth magnetic noncontact
thrust bearings 46 and 47 provided for the stator 13 support the
stator 13 by utilizing the repulsive force of magnets so as to be
able to receive load in the thrust direction of the stator 13 and
allow the stator 13 to rotate at a predetermined position with the
stator 13 and the pump casing 14 not contacting each other.
Therefore, the repulsive forces of the third and fourth magnetic
noncontact thrust bearings 46 and 47 are set to be balanced in the
thrust direction. Each of the third and fourth magnetic noncontact
thrust bearings 46 and 47 includes a first magnet portion
(permanent magnet) 63 and a second magnet portion (permanent
magnet) 64.
[0140] As shown in FIG. 6, the first magnet portion 63 of the third
magnetic noncontact thrust bearing 46 (or the fourth magnetic
noncontact thrust bearing 47) is an annular magnet, and is
hermetically attached to the outer peripheral portion of the second
opening 22 side (or the first opening 21 side) end portion on of
the stator 13. The second magnet portion 64 is an annular magnet,
and is hermetically attached to the inner peripheral portion of the
second casing 17 (or the first casing 16) so as to be spaced apart
from the first magnet portion 63 and opposed to the first magnet
portion 63 in the thrust direction (direction along the central
axis 23) of the first magnet portion 63. Then, the first magnet
portion 63 and the second magnet portion 64 are arranged such that
the magnetic poles opposed to each other in the thrust direction
are the same poles (N and N, or S and S).
[0141] In accordance with the first to fourth
magnetically-levitated bearings 40, 41, 42, and 43 and the first to
fourth magnetic noncontact thrust bearings 44, 45, 46, and 47 of
the rotor 12 and the stator 13 configured as above as shown in FIG.
6, both the rotor 12 and the stator 13 that are rotating portions
levitate with respect to the pump casing 14 and the driving portion
casing 26 that are fixing portions, and rotate with the rotor 12
and the stator 13 not contacting each other. Therefore, it is
possible to realize low noise and low vibration, and cause the
rotor 12 and the stator 13 to smoothly rotate. Then, for example,
contact type bearings and bearing sealing members become
unnecessary, and maintenances thereof are also unnecessary. Then,
it is possible to improve the durability performance of the
uniaxial eccentric screw pump 37 and simplify disassembling,
assembling, and cleaning operations.
[0142] Next, the second rotor driving portion 48 using the magnetic
pole type power transmission structure for causing the tip end
portion of the rotor 12 to rotate will be explained in reference to
FIG. 6. The second rotor driving portion 48 rotates in
synchronization with the rotor driving portion 27 to cause the
rotor 12 to rotate, and includes the driven magnetic pole portion
57 and a driving magnetic pole portion 58.
[0143] The driven magnetic pole portion 57 is the same as the
driven magnetic pole portion 50 shown in FIG. 7(b), has a circular
plate shape, and, for example, eight driven magnets (permanent
magnets for example) 53 are hermetically attached to an inside of
the magnetic pole portion 57 along a circumferential direction of
the magnetic pole portion 57 so as to be equally spaced apart from
one another. These eight driven magnets 53 are arranged such that
magnetic poles thereof, i.e., the north pole and the south pole are
alternately arranged when viewed from the driving magnetic pole
portion 58 of the second rotor driving portion 48 shown in FIG. 6.
The magnetic poles (the north poles and the south poles) of these
eight driven magnets 53 are driven magnetic poles. Moreover, the
tip end portion of the rotor 12 is coupled to a center portion of
the driven magnetic pole portion 57.
[0144] Moreover, the driving magnetic pole portion 58 shown in FIG.
6 is configured such that: a plurality of fixed winding wires 65,
such as eight fixed winding wires 65, are fixedly provided on the
end stud 15; these eight fixed winding wires 65 generate rotating
magnetic fields N and S arranged alternatively; and the driven
magnetic pole portion 57 and the rotor 12 are rotated in the same
direction as the rotating magnetic fields by the rotating magnetic
fields. These eight fixed winding wires 65 are arranged to
correspond to the eight driven magnets 53, respectively, of the
driven magnetic pole portion 57. Moreover, an iron core is attached
to each of the eight fixed winding wires 65.
[0145] In accordance with the second rotor driving portion 48, when
current is supplied from a known power supply (not shown) to the
eight fixed winding wires 65 shown in FIG. 6 to generate the
rotating magnetic fields of the south pole and the north pole, the
driven magnetic pole portion 57 is rotated in the same direction as
the rotating magnetic fields by the rotating magnetic fields. The
rotation of the driven magnetic pole portion 57 by the rotating
magnetic fields generated by the fixed winding wires 65 is caused
by the attractive force and repulsive force between respective
magnetic poles. Thus, the second rotor driving portion 48 can
rotate in synchronization with the rotor driving portion 27 to
cause the rotor 12 to rotate with a predetermined torque.
[0146] As a method for starting the driven magnetic pole portion
57, there are various known methods. For example, first, the driven
magnetic poles (N, S) of the driven magnetic pole portion 57 are
detected with the driven magnetic pole portion 57 not rotating.
Then, in order to cause the driven magnetic pole portion 57 to
rotate in a desired rotational direction, the rotating magnetic
fields may be generated such that appropriate magnetic poles are
generated at the fixed winding wires 65 of the driving magnetic
pole portion 58. As another method for starting the driven magnetic
pole portion 57, a start winding wire may be provided.
[0147] Next, a uniaxial eccentric screw pump 67 according to
Embodiment 3 of the present invention will be explained in
reference to FIG. 8. Differences between Embodiment 3 shown in FIG.
8 and Embodiment 2 shown in FIG. 6 are as follows. Embodiment 2
shown in FIG. 6 is configured such that the rotor driving portion
27 causes the driving magnetic pole portion 49 to rotate to cause
the driven magnetic pole portion 50 and the rotor 12 to rotate in
the same direction as the driving magnetic pole portion 49. In
contrast, Embodiment 3 shown in FIG. 8 is configured such that: the
rotor driving portion 27 and the driving magnetic pole portion 49
are omitted; a driving magnetic pole portion 69 including a
plurality of fixed winding wires 68, such as eight fixed winding
wires 68, is fixedly provided on the driving portion casing 26; the
rotating magnetic fields N and S arranged alternatively are
generated by these eight fixed winding wires 68; and the driven
magnetic pole portion 50 and the rotor 12 are rotated by the
rotating magnetic fields in the same direction as the rotating
magnetic fields. These eight fixed winding wires 68 are arranged to
correspond to the eight driving magnets 54, respectively, of the
driving magnetic pole portion 49 of Embodiment 2. The iron core is
attached to each of the eight fixed winding wires 68. The driving
magnetic pole portion 69 and the driven magnetic pole portion 50
constitute a rotor driving portion 71.
[0148] With the above configuration, the driven magnetic pole
portion 50 and the rotor 12 can be directly rotated by the rotating
magnetic field generated by the driving magnetic pole portion 69.
Therefore, it is possible to reduce transfer loss of the rotational
force and comparatively reduce the volume of the uniaxial eccentric
screw pump 67.
[0149] Moreover, Embodiment 2 shown in FIG. 6 is configured such
that the second rotor driving portion 48 is provided at the tip end
portion of the rotor 12, but Embodiment 3 shown in FIG. 8 is
different from Embodiment 2 shown in FIG. 6 in that the second
rotor driving portion 48 is omitted.
[0150] Further, Embodiment 2 shown in FIG. 6 is configured such
that the repulsive force in the thrust direction is generated
between the second magnet portion 62 having the short columnar
shape provided at the center position of the end stud 15 and the
first magnet portion 61 having the short columnar shape provided at
the center position of the driven magnetic pole portion 57, but
Embodiment 3 shown in FIG. 8 is different from Embodiment 2 shown
in FIG. 6 in that the first magnet portion 61 is omitted such that
the repulsive force in the thrust direction is generated between an
annular second magnet portion 70 provided at the end stud 15 and
the inner ring magnet portion 56 of the second
magnetically-levitated bearing 41 provided at the tip end portion
of the rotor 12.
[0151] The second magnet portion 70 and the inner ring magnet
portion 56 are arranged to be spaced apart from each other in the
thrust direction (direction along the central axis 30) such that
magnetic poles thereof opposed to each other are the same poles (S
and S, or N and N). Since the first magnet portion 61 can be
omitted as above, it is possible to comparatively reduce the volume
of the uniaxial eccentric screw pump 67. Other than the above, the
uniaxial eccentric screw pump 67 of Embodiment 3 is the same as the
uniaxial eccentric screw pump 37 of Embodiment 2 shown in FIG. 6,
so that same reference numbers are used for the same components,
and explanations thereof are omitted.
[0152] Next, a uniaxial eccentric screw pump 72 according to
Embodiment 4 of the present invention will be explained in
reference to FIG. 9. A difference between Embodiment 4 shown in
FIG. 9 and Embodiment 1 shown in FIG. 1 is as follows. Embodiment 1
shown in FIG. 1 is configured such that the stator 13 is rotatably
supported by the rolling bearings 18 applicable to the load in the
radial direction and the thrust direction. In contrast, Embodiment
4 shown in FIG. 9 is configured such that the stator 13 is
rotatably supported by the third and fourth magnetically-levitated
bearings 42 and 43 applicable to the load in the radial direction
and the third and fourth magnetic noncontact thrust bearings 46 and
47 applicable to the load in the thrust direction. Other than the
above, the uniaxial eccentric screw pump 72 of Embodiment 4 is the
same as the uniaxial eccentric screw pump 11 of Embodiment 1 shown
in FIG. 1, so that same reference numbers are used for the same
components, and explanations thereof are omitted. With this, it is
possible to omit the contact type bearings 18 and the seal portions
20 for sealing the bearings 18. Further, it is possible to realize
low noise and low vibration, and cause the stator 13 to smoothly
rotate.
[0153] Next, a uniaxial eccentric screw pump 74 according to
Embodiment 5 of the present invention will be explained in
reference to FIG. 10. A difference between Embodiment 5 shown in
FIG. 10 and Embodiment 2 shown in FIG. 6 is as follows. Embodiment
2 shown in FIG. 6 is configured such that the rotor 12 and the
stator 13 are rotatably supported by the first to fourth
magnetically-levitated bearings 40, 41, 42, and 43 and the first to
fourth magnetic noncontact thrust bearings 44, 45, 46, and 47. In
contrast, Embodiment 5 shown in FIG. 10 is configured such that the
rotor 12 and the stator 13 are rotatably supported by magnetic
noncontact bearings 75, 76, 77, and 78 capable of receiving both
radial load and thrust load.
[0154] The magnetic noncontact bearings 75, 76, 77, and 78 are the
same as one another, and include outer ring magnet portions 79, 80,
81, and 82, respectively, and inner ring magnet portions 83, 84,
85, and 86, respectively. Then, the outer ring magnet portion 79
and the like are provided at the pump casing 14 that is the fixing
portion, and the inner ring magnet portion 83 and the like are
provided at the rotor 12 and the stator 13 that are the rotating
portions. Then, a surface of, for example, the outer ring magnet
portion 79 and a surface of, for example, the inner ring magnet
portion 83 which surfaces are repulsive to each other are formed as
inclined surfaces inclined with respect to the central axis.
[0155] As above, the rotor 12 and the stator 13 are rotatably
supported by the magnetic noncontact bearings 75 to 78 capable of
receiving both the radial load and the thrust load. Therefore, as
compared to the case of using the bearings capable of receiving the
radial load and the bearings capable of receiving the thrust load,
it is possible to simplify the configuration and comparatively
reduce the volume of the uniaxial eccentric screw pump 74.
[0156] Then, Embodiment 5 shown in FIG. 10 is configured such that
the driving magnetic pole portion 49 having the annular shape is
provided outside the outer peripheral surface of the driven
magnetic pole portion 50 to be spaced apart from the driven
magnetic pole portion 50. With this, an axial length of the
uniaxial eccentric screw pump 74 can be shortened. Other than the
above, the uniaxial eccentric screw pump 74 of Embodiment 5 shown
in FIG. 10 is the same as the uniaxial eccentric screw pump 37 of
Embodiment 2 shown in FIG. 6, so that same reference numbers are
used for the same components, and explanations thereof are
omitted.
[0157] Next, a uniaxial eccentric screw pump 88 according to
Embodiment 6 of the present invention will be explained in
reference to FIG. 11. A difference between Embodiment 6 shown in
FIG. 11 and Embodiment 3 shown in FIG. 8 is as follows. Embodiment
3 shown in FIG. 8 is configured such that the rotor 12 and the
stator 13 are rotatably supported by the first to fourth
magnetically-levitated bearings 40, 41, 42, and 43 and the first to
fourth magnetic noncontact thrust bearings 44, 45, 46, and 47. In
contrast, Embodiment 6 shown in FIG. 11 is configured such that the
rotor 12 and the stator 13 are rotatably supported by the magnetic
noncontact bearings 75 to 78 capable of receiving both the radial
load and the thrust load. These magnetic noncontact bearing 75 to
78 are the same as those in Embodiment 5 shown in FIG. 10.
[0158] With the above configuration, same functions and effects as
Embodiment 5 shown in FIG. 10 are obtained, so that explanations
thereof are omitted.
[0159] Then, Embodiment 6 shown in FIG. 11 is configured such that
the driving magnetic pole portion 69 having the annular shape is
provided outside the outer peripheral surface of the driven
magnetic pole portion 50 to be spaced apart from the driven
magnetic pole portion 50. With this, an axial length of the
uniaxial eccentric screw pump 88 can be shortened. Other than the
above, the uniaxial eccentric screw pump 88 of Embodiment 6 shown
in FIG. 11 is the same as the uniaxial eccentric screw pump 67 of
Embodiment 3 shown in FIG. 8, so that same reference numbers are
used for the same components, and explanations thereof are
omitted.
[0160] Each of Embodiment 2 shown in FIG. 6 and Embodiment 3 shown
in FIG. 8 is configured such that the stator 13 is rotatably
supported by the third and fourth magnetically-levitated bearings
42 and 43 applicable to the load in the radial direction and the
third and fourth magnetic noncontact thrust bearings 46 and 47
applicable to the load in the thrust direction. Alternatively,
although not shown, the stator 13 may be rotatably supported by the
rolling bearings 18 applicable to both the load in the radial
direction and the load in the thrust direction, as shown in FIG.
1.
[0161] Moreover, as shown in FIG. 1, Embodiment 1 is configured
such that the tip end portion of the rotor 12 and the driving shaft
24 are rotatably supported by the bearings 29 and 25.
Alternatively, the tip end portion of the rotor 12 may be a free
end, and the driving shaft 24 of the rotor may be rotatably
supported by the bearings 25.
[0162] Then, in Embodiments 1 to 6, the rotor 12 and the stator 13
are separately rotated with the outer peripheral surface of the
rotor 12 and the inner peripheral surface of the inner hole 13a of
the stator not contacting each other as shown in FIGS. 3 to 5.
Alternatively, the rotor 12 and the stator 13 may be separately
rotated at a predetermined speed such that: one of parallel
surfaces 35 of the inner hole 13a of the stator and the rotor 12
contact each other at an appropriate pressure; and the other one of
the parallel surfaces 35 of the inner hole 13a of the stator and
the rotor 12 do not contact each other. Even with this, the fluid
can be transferred and filled while realizing high flow rate
accuracy, low pulsation, and long life.
[0163] Moreover, as shown in FIG. 1 for example, Embodiments 1 to 6
are configured such that: the uniaxial eccentric screw pump 11
includes the rotor driving portion 27 and the stator driving
portion 19, and these driving portions directly rotate the rotor 12
and the stator 13. Alternatively, although not shown, the rotor
driving portion and the stator driving portion may be provided
separately from the uniaxial eccentric screw pump 11, each of the
driving portions may be coupled to the rotor 12 or the stator 13 by
a joint for example to cause the rotor 12 or the stator 13 to
rotate.
[0164] Further, in Embodiments 1 to 6, the stator 13 is made of
engineering plastic, such as Teflon (trademark). However, the
stator 13 may be made of synthetic rubber, a metal, or the like.
Then, the rotor 12 is made of a metal, such as stainless steel, but
may be made of engineering plastic, such as Teflon (trademark).
[0165] Further, in Embodiments 1 to 6, the rotor 12 and the stator
13 are formed to rotate such that the inner surface forming the
inner hole 13a of the stator and the outer surface of the rotor 12
do not contact each other. Alternatively, the inner hole 13a of the
stator and the rotor 12 may be formed to rotate such that the rotor
12 and both parallel surfaces 35 of the inner hole 13a of the
stator contact each other by an appropriate pressure. Even with
this, it is possible to prevent the rotor 12 and the stator 13 from
significantly wearing away and prevent different sizes of wearing
from being generated on respective surfaces. Therefore, the fluid
can be transferred and filled while realizing high flow rate
accuracy, low pulsation, and long life.
[0166] Then, as shown in FIG. 3 and the like, in Embodiments 1 to
6, the stator 13 has the double thread internal screw type inner
hole 13a, the cross-sectional shape of the inner hole 13a is
elliptical, the rotor 12 is the single thread external screw type,
the cross-sectional shape of the rotor 12 is circular, the ratio of
the pitch of the rotor 12 to the pitch of the inner hole 13a is 1
to 2, and the ratio of the rotating speed of the rotor 12 to the
rotating speed of the stator 13 is 2 to 1. Alternatively, the
stator 13 may have a triple thread internal screw type inner hole
13a, the cross-sectional shape of the inner hole 13a may be a
substantially triangle shape each of whose three corner portions
has a circular-arc shape, the rotor 12 may be a double thread
external screw type, the cross-sectional shape of the rotor 12 may
be substantially oval, the ratio of the pitch of the rotor 12 to
the pitch of the inner hole 13a may be 2 to 3, and the ratio of the
rotating speed of the rotor 12 to the rotating speed of the stator
13 may be 3 to 2. Even with this, the rotor 12 and the stator 13
are comparatively simple in shape, so that they can be formed with
comparatively high size accuracy. Therefore, it is possible to
provide the uniaxial eccentric screw pump 11 which has same
functions and effects as the above embodiments, and realizes
low-cost and quick delivery.
INDUSTRIAL APPLICABILITY
[0167] As above, a uniaxial eccentric screw pump according to the
present invention has an excellent effect of being able to transfer
and fill a fluid while realizing high flow rate accuracy, low
pulsation, and long life. Thus, the present invention is suitable
for the application to the uniaxial eccentric screw pump and the
like.
* * * * *