U.S. patent application number 12/216483 was filed with the patent office on 2009-01-08 for internal gear pump.
This patent application is currently assigned to YAMADA MANUFACTURING CO., LTD.. Invention is credited to Kenichi Fujiki, Masashi Sadatomi, Takatoshi Watanabe.
Application Number | 20090010791 12/216483 |
Document ID | / |
Family ID | 39820942 |
Filed Date | 2009-01-08 |
United States Patent
Application |
20090010791 |
Kind Code |
A1 |
Fujiki; Kenichi ; et
al. |
January 8, 2009 |
Internal gear pump
Abstract
An internal gear pump which has a crescent disposed between an
outer rotor and an inner rotor having a trochoidal tooth profile,
and which reduces vibrations caused by pulsations generated when
the fluid is discharged. The internal gear pump has an outer rotor
having internal teeth formed therein, an inner rotor disposed on
the inner peripheral side of the outer rotor and having formed
therein external teeth that mesh with the internal teeth, and a
crescent disposed in a clearance between the outer rotor and the
inner rotor. Pitch spacings of the external teeth of the inner
rotor are formed as non-equal spacings, and pitch spacings of the
internal teeth of the outer rotor correspond to the pitch spacings
of the external teeth of the inner rotor.
Inventors: |
Fujiki; Kenichi; (Gunma-ken,
JP) ; Watanabe; Takatoshi; (Gunma-ken, JP) ;
Sadatomi; Masashi; (Gunma-ken, JP) |
Correspondence
Address: |
MCGINN INTELLECTUAL PROPERTY LAW GROUP, PLLC
8321 OLD COURTHOUSE ROAD, SUITE 200
VIENNA
VA
22182-3817
US
|
Assignee: |
YAMADA MANUFACTURING CO.,
LTD.
Kiryu-shi
JP
|
Family ID: |
39820942 |
Appl. No.: |
12/216483 |
Filed: |
July 7, 2008 |
Current U.S.
Class: |
418/166 |
Current CPC
Class: |
F04C 2/101 20130101;
F04C 15/0049 20130101; F04C 2/084 20130101 |
Class at
Publication: |
418/166 |
International
Class: |
F01C 1/10 20060101
F01C001/10 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 6, 2007 |
JP |
2007-178177 |
Jun 6, 2008 |
JP |
2008-148955 |
Claims
1. An internal gear pump, comprising: an outer rotor having
internal teeth formed therein; an inner rotor disposed on the inner
peripheral side of the outer rotor and having formed therein
external teeth that mesh with the internal teeth; and a crescent
disposed in a clearance between the outer rotor and the inner
rotor, wherein pitch spacings of the external teeth of the inner
rotor are formed as non-equal spacings, and pitch spacings of the
internal teeth of the outer rotor correspond to the pitch spacings
of the external teeth of the inner rotor.
2. The internal gear pump according to claim 1, wherein a row of
teeth with the number of teeth equal to the common divisor of the
number of external teeth of the inner rotor and the number of
internal teeth of the outer rotor is taken as a non-equal spacing
pitch row, and identical non-equal spacing pitch rows are formed
repeatedly.
3. The internal gear pump according to claim 2, wherein the number
of the non-equal spacing pitch rows is 3 or more.
4. The internal gear pump according to claim 1, wherein the number
of teeth of the inner rotor is 6 or more, and the number of teeth
of the outer rotor is 9 or more.
5. The internal gear pump according to claim 1 wherein the tooth
thicknesses of the external teeth and internal teeth in the
non-equal spacing pitch rows are set to differ.
6. The internal gear pump according to claim 1, wherein the tooth
profile of the inner rotor is a trochoidal tooth profile.
7. An internal gear pump, comprising: an outer rotor having
internal teeth formed therein; an inner rotor disposed on the inner
peripheral side of the outer rotor and having formed therein
external teeth that mesh with the internal teeth; and a crescent
disposed in a clearance between the outer rotor and the inner
rotor, wherein tooth thickness dimensions of the external teeth of
the inner rotor are formed to be non-uniform, and the tooth
thicknesses of the internal teeth of the outer rotor correspond to
the tooth thickness dimensions of the inner rotor.
8. The internal gear pump according to claim 7, wherein the number
of external teeth of the inner rotor and the number of internal
teeth of the outer rotor are multiples of a common divisor of the
number of external teeth and the number of internal teeth, a
plurality of unit external tooth rows having the number of teeth at
least equal to the greatest common divisor and also having
different tooth thicknesses are provided in the external teeth of
the inner rotor, and a plurality of unit internal tooth rows in
which the internal teeth corresponding to the unit external tooth
row of the inner rotor are arranged consecutively are provided in
the outer rotor.
9. The internal gear pump according to claim 8, wherein the number
of unit external tooth rows of the inner rotor is 3 or more.
10. The internal gear pump according to claim 7, wherein the number
of teeth of the inner rotor is 6 or more, and the number of teeth
of the outer rotor is 9 or more.
11. The internal gear pump according to claim 7, wherein the tooth
profile of the inner rotor is a trochoidal tooth profile.
12. The internal gear pump according to claim 7, wherein a pitch
angle of the external teeth of the inner rotor is formed to be
non-uniform, and a pitch angle of the internal teeth of the outer
rotor corresponds to the pitch angle of the external teeth.
13. The internal gear pump according to claim 8, wherein a pitch
angle of the external teeth of the unit external tooth row of the
inner rotor is formed to be non-uniform, and a pitch angle of the
internal teeth of the unit internal tooth row of the outer row
corresponds to the pitch angle of the external teeth of the unit
external tooth row.
14. The internal gear pump according to claim 2, wherein the number
of teeth of the inner rotor is 6 or more, and the number of teeth
of the outer rotor is 9 or more.
15. The internal gear pump according to claim 2, wherein the tooth
thicknesses of the external teeth and internal teeth in the
non-equal spacing pitch rows are set to differ.
16. The internal gear pump according to claim 2, wherein the tooth
profile of the inner rotor is a trochoidal tooth profile.
17. The internal gear pump according to claim 8, wherein the number
of teeth of the inner rotor is 6 or more, and the number of teeth
of the outer rotor is 9 or more.
18. The internal gear pump according to claim 8, wherein the tooth
profile of the inner rotor is a trochoidal tooth profile.
19. The internal gear pump according to claim 8, wherein a pitch
angle of the external teeth of the inner rotor is formed to be
non-uniform, and a pitch angle of the internal teeth of the outer
rotor corresponds to the pitch angle of the external teeth.
20. The internal gear pump according to claim 9, wherein a pitch
angle of the external teeth of the unit external tooth row of the
inner rotor is formed to be non-uniform, and a pitch angle of the
internal teeth of the unit internal tooth row of the outer row
corresponds to the pitch angle of the external teeth of the unit
external tooth row.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an internal gear pump which
comprises a crescent disposed between an outer rotor and an inner
rotor and which is provided with the inner rotor with a trochoidal
tooth profile, the internal gear pump making it possible to reduce
vibrations caused by pulsations generated during fluid
discharge.
[0003] 2. Description of the Related Art
[0004] Internal gear pumps comprising a crescent have been used for
a long time because they can increase the discharge pressure above
that in the internal gear pumps having no crescent. In recent
years, the use or rotors with a trochoidal tooth profile in the
internal gear pumps having a crescent has been studied as means for
further increasing the efficiency and raising the discharge
pressure. These developments can improve efficiency and discharge
performance, but the problem associated therewith is that the peak
value of discharge pulsations increases accordingly, the vibrations
of the pump body increase, and an adverse effect is produced on the
peripheral equipment.
[0005] Accordingly, in order to raise further the discharge
pressure in the crescent-type internal gear pumps using rotors with
a trochoidal tooth profile, such pumps have to be studied more
thoroughly. Japanese Patent Application Laid-open No. 7-253083
discloses a technique for reducing the peak value of discharge
pulsations.
SUMMARY OF THE INVENTION
[0006] With the invention disclosed in Japanese Patent Application
Laid-open No. 7-253083, it is possible that the peak value of
discharge pulsations will not be sufficiently or effectively
reduced by merely creating a difference in pitches between the
teeth, without specifying the tooth profile and the like. Further,
the invention disclosed in Japanese Patent Application Laid-open
No. 7-253083 is concerned only with the reduction of audible noise
level, and technical issues relating to other effects or
improvement of discharge performance remain unresolved. Moreover,
no description concerning a specific method for reducing discharge
pulsations is provided, and a specific method for reducing
discharge pulsations remains unclear. It is an object of the
present invention to prevent the discharge amount of liquid from
assuming a constant value, reduce the peak of pulsations generated
when the fluid is discharged, and decrease the vibrations and noise
of the pump.
[0007] The inventors have conductive a comprehensive study to
attain the above-described object. The results obtained demonstrate
that the aforementioned problems are resolved by the invention of
claim 1 that provides an internal gear pump, comprising an outer
rotor having internal teeth formed therein, an inner rotor disposed
on the inner peripheral side of the outer rotor and having formed
therein external teeth that mesh with the internal teeth, and a
crescent disposed in a clearance between the outer rotor and the
inner rotor, wherein pitch spacings of the external teeth of the
inner rotor are formed as non-equal spacings, and pitch spacings of
the internal teeth of the outer rotor correspond to the pitch
spacings of the external teeth of the inner rotor.
[0008] The aforementioned problems are resolved by the invention of
claim 2 that provides the internal gear pump of the above-described
configuration, wherein a row of teeth with the number of teeth
equal to the common divisor of the number of external teeth of the
inner rotor and the number of internal teeth of the outer rotor is
taken as a non-equal spacing pitch row, and identical non-equal
spacing pitch rows are formed repeatedly. The aforementioned
problems are resolved by the invention of claim 3 that provides the
internal gear pump of the above-described configuration, wherein
the number of the non-equal spacing pitch rows is 3 or more. The
aforementioned problems are resolved by the invention of claim 4 or
claim 14 that provides the internal gear pump of the
above-described configuration, wherein the number of teeth of the
inner rotor is 6 or more, and the number of teeth of the outer
rotor is 9 or more. The aforementioned problems are resolved by the
invention of claim 5 or claim 15 that provides the internal gear
pump of the above-described configuration, wherein the tooth
thicknesses of the external teeth and internal teeth in the
non-equal spacing pitch rows are set to differ. The aforementioned
problems are resolved by the invention of claim 6 or 16 that
provides the internal gear pump of the above-described
configuration, wherein the tooth profile of the inner rotor is a
trochoidal tooth profile.
[0009] The aforementioned problems are resolved by the invention of
claim 7 that provides an internal gear pump comprising an outer
rotor having internal teeth formed therein, an inner rotor disposed
on the inner peripheral side of the outer rotor and having formed
therein external teeth that mesh with the internal teeth, and a
crescent disposed in a clearance between the outer rotor and the
inner rotor, wherein tooth thickness dimensions of the external
teeth of the inner rotor are formed to be non-uniform, and the
tooth thicknesses of the internal teeth of the outer rotor
correspond to the tooth thickness dimensions of the inner
rotor.
[0010] The aforementioned problems are resolved by the invention of
claim 8 that provides the internal gear pump of the above-described
configuration, wherein the number of external teeth of the inner
rotor and the number of internal teeth of the outer rotor are
multiples of a common divisor of the number of external teeth and
the number of internal teeth, a plurality of unit external tooth
rows having the number of teeth at least equal to the greatest
common divisor and also having different tooth thicknesses are
provided in the external teeth of the inner rotor, and a plurality
of unit internal tooth rows in which the internal teeth
corresponding to the unit external tooth row of the inner rotor are
arranged consecutively are provided in the outer rotor.
[0011] The aforementioned problems are resolved by the invention of
claim 9 that provides the internal gear pump of the above-described
configuration, wherein the number of unit external tooth rows of
the inner rotor is 3 or more. The aforementioned problems are
resolved by the invention of claim 10 or 17 that provides the
internal gear pump of the above-described configuration, wherein
the number of teeth of the inner rotor is 6 or more, and the number
of teeth of the outer rotor is 9 or more. The aforementioned
problems are resolved by the invention of claim 11 or 18 that
provides the internal gear pump of the above-described
configuration, wherein the tooth profile of the inner rotor is a
trochoidal tooth profile.
[0012] The aforementioned problems are resolved by the invention of
claim 12 or 19 that provides the internal gear pump of the
above-described configuration, wherein a pitch angle of the
external teeth of the inner rotor is formed to be non-uniform, and
a pitch angle of the internal teeth of the outer rotor corresponds
to the pitch angle of the external teeth. The aforementioned
problems are resolved by the invention of claim 13 or 20 that
provides the internal gear pump of the above-described
configuration, wherein a pitch angle of the external teeth of the
unit external tooth row of the inner rotor is formed to be
non-uniform, and a pitch angle of the internal teeth of the unit
internal tooth row of the outer row corresponds to the pitch angle
of the external teeth of the unit external tooth row.
[0013] With the invention of claim 1, in an internal gear pump
comprising a crescent in a void between an outer rotor and an inner
rotor, the pitch spacings of the external teeth of the inner rotor
are made different from each other. As a result, the size of cells
that are formed by the inner rotor and outer rotor at the time of
discharge differ from each other, the amount of discharge from the
cells is irregular, and the peak value of discharge pulsations is
reduced, whereby the audible noise level and vibrations can be
decreased.
[0014] With the invention of claim 2, a row of teeth with the
number of teeth equal to the common divisor of the number of
external teeth of the inner rotor and the number of internal teeth
of the outer rotor is taken as a non-equal spacing pitch row, and
identical non-equal spacing pitch rows are formed repeatedly. As a
result, the irregular discharge state produced by non-equal
(uneven) discharge amount is generated periodically and
consecutively, and the peak value of discharge pulsations can be
reduced even more significantly. With the invention of claim 3, the
period of pitch spacings is 3 or more. As a result, three or more
different pitch spacings can be created consecutively, the period
of pitch spacings can be made even more complex, and the
irregularity of discharge pulsations can be further increased.
[0015] With the invention of claim 4 or claim 14, the number of
teeth of the inner rotor is 6 or more, and the number of teeth of
the outer rotor is 9 or more. As a result, the common divisor of
the numbers of teeth of the inner rotor and outer rotor can be made
equal to or more than 3, and three or more different irregular
discharge states can be realized. With the invention of claim 5 or
claim 15, the tooth thicknesses of the external teeth and internal
teeth in the non-equal spacing pitch rows are set to differ. As a
result, irregular pulsations are produced due to non-equally spaced
pitches and also irregular pulsations are produced from cells of
different size due to a sequential difference in tooth thickness.
With the invention of claim 6 or 16, the tooth profile of the inner
rotor is a trochoidal tooth profile. As a result, the discharge
performance can be improved, while reducing the peak of
pulsations.
[0016] With the invention of claim 7, tooth thickness dimensions of
the external teeth of the inner rotor are formed to be non-uniform,
and the tooth thicknesses of the internal teeth of the outer rotor
correspond to the tooth thickness dimensions of the inner rotor. As
a result, the tooth thickness dimensions of the external teeth of
the inner rotor differ from each other, and the volume (capacity)
of spaces bounded by the adjacent external teeth and the crescent
differ from each other. In the outer rotor, the tooth thickness
dimensions of the internal teeth also differ from each other, and
the volume (capacity) of spaces bounded by the adjacent internal
teeth and the crescent differ from each other. Therefore, the size
of cells that are formed by the inner rotor and outer rotor at the
time of discharge differ from each other, the amount of discharge
from the cells is irregular, and the peak value of discharge
pulsations is reduced, whereby the audible noise level and
vibrations can be decreased.
[0017] With the invention of claim 8, the number of external teeth
of the inner rotor and the number of internal teeth of the outer
rotor are multiples of a common divisor of the number of external
teeth and the number of internal teeth, a plurality of unit
external tooth rows having the number of teeth at least equal to
the greatest common divisor and also having different tooth
thicknesses are provided in the external teeth of the inner rotor,
and a plurality of unit internal tooth rows in which the internal
teeth corresponding to the unit external tooth row of the inner
rotor are arranged consecutively are provided in the outer rotor.
As a result, by using a configuration comprising unit external
tooth rows and unit internal tooth rows, it is possible to generate
consecutively and periodically the irregular discharge states with
different discharge amounts, thereby further reducing the peak
value of discharge pulsations.
[0018] With the invention of claim 9, the number of unit external
tooth rows of the inner rotor is 3 or more. As a result, three or
more external teeth with different tooth thickness dimensions can
be arranged sequentially, the configuration of the unit external
tooth row can be further complicated, and the irregularity of the
discharge pulsations can be further increased. With the invention
of claim 10 or 17, the number of teeth of the inner rotor is 6 or
more, and the number of teeth of the outer rotor is 9 or more. As a
result, the common divisor of the numbers of teeth of the inner
rotor and outer rotor can be made equal to or more than 3, and
three or more irregular different discharge states can be realized.
With the invention of claim 11 or 18, the tooth profile of the
inner rotor is a trochoidal tooth profile. As a result, the
discharge performance can be improved, while reducing the peak of
pulsations.
[0019] With the invention of claim 12 or 19, a pitch angle of the
external teeth of the inner rotor is formed to be non-uniform, and
a pitch angle of the internal teeth of the outer rotor corresponds
to the pitch angle of the external teeth. As a result, a more
complex configuration of the unit external tooth row and unit
internal tooth row can be obtained and the peak value of discharge
pulsations can be further reduced. With the invention of claim 13
or 20, a pitch angle of the external teeth of the unit external
tooth row of the inner rotor is formed to be non-uniform, and a
pitch angle of the internal teeth of the unit internal tooth row of
the outer row corresponds to the pitch angle of the external teeth
of the unit external tooth row. As a result, a more complex
configuration of the unit external tooth row and unit internal
tooth row can be obtained and the peak value of discharge
pulsations can be further reduced.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1A is a plan view illustrating the configuration in
accordance with the present invention, and FIG. 1B is a plan view
illustrating the assembly of the inner rotor and crescent with the
outer rotor;
[0021] FIG. 2A is a plan view of the inner rotor, FIG. 2B is a plan
view of the outer rotor, and FIG. 2C is a plan view of the
crescent;
[0022] FIG. 3A is a process diagram showing the position of a
random external tooth in which the inner rotor starts rotating,
and
[0023] FIG. 3B is a process diagram illustrating the state in which
the random external tooth has moved by one tooth;
[0024] FIG. 4A is a process diagram illustrating the state in which
the random external tooth has reached the crescent, and FIG. 4B is
a process diagram illustrating the state in which the random
external tooth has reached the crescent center;
[0025] FIG. 5A is a process diagram illustrating the state in which
the random external tooth has reached the end side of the crescent,
and FIG. 5B is a process diagram illustrating the state in which
the random external tooth has separated from the crescent;
[0026] FIG. 6A is a rotor assembly configuration of the second
embodiment of the present invention, and FIG. 6B is a plan view of
the outer rotor of the second embodiment;
[0027] FIG. 7A is a graph illustrating the discharge pulsations in
accordance with the present invention, and FIG. 7B is a graph
illustrating the discharge pulsations of the conventional type;
[0028] FIG. 8A is a plan view illustrating the configuration of the
second embodiment of the present invention, and FIG. 8B is a plan
view illustrating the assembly of the inner rotor and crescent with
the outer rotor;
[0029] FIG. 9A is a plan view of the inner rotor, FIG. 9B is a plan
view of the outer rotor, and FIG. 9C is a plan view of the
crescent;
[0030] FIG. 10A is a process diagram showing the position of a
random external tooth in which the inner rotor of the second
embodiment of the present invention starts rotating, and FIG. 10B
is a process diagram illustrating the state in which the random
external tooth has moved by one tooth;
[0031] FIG. 11A is a process diagram illustrating the state in
which the random external tooth of the second embodiment of the
present invention has reached the crescent, and FIG. 11B is a
process diagram illustrating the state in which the random external
tooth has reached the crescent center;
[0032] FIG. 12A is a process diagram illustrating the state in
which the random external tooth of the second embodiment of the
present invention has reached the end side of the crescent, and
FIG. 12B is a process diagram illustrating the state in which the
random external tooth has separated from the crescent;
[0033] FIG. 13A is a plan view of the inner rotor of the third
embodiment of the present invention, FIG. 13B is a plan view of the
outer rotor, and FIG. 13C is a plan view of the crescent;
[0034] FIG. 14A is a process diagram showing the position of a
random external tooth in which the inner rotor of the third
embodiment of the present invention starts rotating, and FIG. 14B
is a process diagram illustrating the state in which the random
external tooth has moved by one tooth;
[0035] FIG. 15A is a process diagram illustrating the state in
which the random external tooth of the third embodiment of the
present invention has reached the crescent, and FIG. 15B is a
process diagram illustrating the state in which the random external
tooth has reached the crescent center; and
[0036] FIG. 16A is a process diagram illustrating the state in
which the random external tooth of the third embodiment of the
present invention has reached the end side of the crescent, and
FIG. 16B is a process diagram illustrating the state in which the
random external tooth has separated from the crescent.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0037] The embodiments of the present invention will be described
below with reference to the appended drawings. The configuration of
the first embodiment of the present invention, as shown in FIG. 1A,
mainly comprises an inner rotor 1, an outer rotor 2, a crescent 3,
and a pump casing 4. The pump casing 4 has formed therein a rotor
chamber 41, a suction port 42, and a discharge port 43. The suction
port 42 and discharge port 43 are formed as flow channels
communicating with the outside of the pump casing 4. Further, the
pump casing 4 can be used together with a casing cover (this
configuration is not shown in the figure).
[0038] As shown in FIG. 2A, the inner rotor 1 has a plurality of
external teeth 11, 11, . . . formed on the outer periphery thereof.
The external teeth 11 can be also formed with trochoidal tooth
profiles (including tooth profiles of an almost trochoidal shape).
A tooth bottom portion 12 is formed between the external teeth 11,
11. Different spacings, that is, pitch spacings Pa, are set between
the adjacent external teeth 11, 11, and these different pitch
spacings Pa will be described below.
[0039] As shown in FIG. 2B, the outer rotor 2 has a plurality of
internal teeth 21, 21, . . . formed on the inner periphery thereof,
and tooth bottom portions 22 are formed between the internal teeth
21, 21, . . . . The inner rotor 1 is disposed on he inner
peripheral side of the outer rotor 2, and the external teeth 11,
11, . . . of the inner rotor 1 mesh with the internal teeth 21, 21,
. . . of the outer rotor 2. Likewise, pitch spacings Pb of the
internal teeth 21, 21, . . . of the outer rotor 2 are formed
correspondingly to the pitch spacings Pa of the external teeth 11,
11, . . . of the inner rotor 1 so as to enable effective meshing
with the external teeth 11, 11, . . . of the inner rotor 1.
Further, when the external teeth 11 of the inner rotor 1 have a
trochoidal tooth profile (including a tooth profile of an almost
trochoidal shape), the internal teeth 21 of the outer rotor 2 have
a tooth profile enabling effective meshing with the external teeth
11 of the inner rotor 1. Thus, by forming the external teeth 11 of
the inner rotor 1 to have a trochoidal tooth profile (including a
tooth profile of an almost trochoidal shape), it is possible to
increase a discharge performance, while reducing the peak of
pulsations.
[0040] As shown in FIG. 1, the crescent 3 is inserted and disposed
in a gap formed between the outer rotor 2 and inner rotor 1. This
gap is called an almost crescent-like space formed between the
inner peripheral side of the outer rotor 2 and the outer periphery
of the inner rotor 1. As shown in FIG. 2C, the crescent 3 has an
almost crescent-like or arcuate shape and is composed of an arcuate
concave surface side 31 and an arcuate convex surface side 32.
[0041] Interior cells Sa are formed between the arcuate concave
surface side 31 of the crescent 3 and the external teeth 11, 11, .
. . of the inner rotor 1 (see FIG. 1B). Likewise, exterior cells Sb
are formed between the arcuate convex surface side 32 of the
crescent 3 and the internal teeth 21, 21, . . . of the outer rotor
2 (see FIG. 1B). The interior cells Sa are voids formed in a
portion bounded by the external teeth 11, 11 of the inner rotor 1
and the arcuate concave surface side 31 of the crescent 3, and the
exterior cells Sb are voids formed in a portion bounded by the
internal teeth 21, 21, . . . and the arcuate convex surface side 32
of the crescent 3.
[0042] The configuration of the external teeth 11, 11, . . . of the
inner rotor 1 and the internal teeth 21, 21, . . . of the outer
rotor 2 is determined by the following relationship. First, in a
plurality of the external teeth 11, 11, . . . of the inner rotor 1,
the pitch spacings Pa, Pa, . . . between he adjacent external teeth
11, 11 are formed to differ from each other. The pitch spacings Pb
between the internal teeth 21, 21, . . . of the outer rotor 2 are
formed correspondingly to the pitch spacings Pa between the
external teeth 11, 11, . . . of the inner rotor 1, so as to ensure
the meshing of the external teeth 11, 11, . . . and internal teeth
21, 21, . . . , and these pitch spacings Pb, Pb, . . . are also
different from each other.
[0043] The size of the pitch spacing Pa is determined by the pitch
angle of the adjacent external teeth 11, 11, and the size of the
range of the tooth bottom portion 12 between the adjacent external
teeth 11, 11 is determined thereby. Regions 13 between the teeth
that configure the interior cells Sa are set between the adjacent
external teeth 11, 11 to center on the tooth bottom portions 12
positioned between the adjacent external teeth 11, 11 (see FIG. 1B
and FIG. 2A). The regions 13 between the teeth are equal to the
corresponding pitch spacings Pa. More specifically, as shown in
FIG. 2A, where the pitch angles of three appropriate external teeth
11, 11, . . . in the inner rotor 1 are denoted by .alpha.1,
.alpha.1, .beta.1, the relationship between the pitch spacings Pa
will be .alpha.1<.gamma.1<.beta.1. The regions 13 between the
teeth match the size of the pitch angles .alpha.1, .gamma.1,
.beta.1, and are denoted by 13.alpha., 13.gamma., and 13.beta. (see
FIG. 2A).
[0044] Accordingly, the size of these regions satisfies the
conditions 13.alpha.<13.gamma.<13.alpha.. Thus, the size of
regions changes in the following order in the rotation direction of
the inner rotor 1: small (13.alpha.), large (13.gamma.), and
intermediate (13.beta.). The volumes of interior cells Sa, Sa, . .
. formed between the inner rotor 1 and the crescent 3 also differ
from each other, and there are small and large volumes. Therefore,
the amount of liquid transferred by the plurality of interior cells
Sa varies among the interior cells Sa.
[0045] The pitch spacings Pb of the internal teeth 21, 21, . . . of
the outer rotor 2 are made to correspond to the pitch spacings Pa
of the external teeth 11, 11, . . . of the inner rotor 1 so as to
ensure the meshing of the teeth. With such a configuration, the
volumes of the interior cell Sa and exterior cell Sb formed by he
crescent 3 in the inner rotor 1 and outer rotor 2 differ from each
other, the discharged amount varies among the cells (interior cell
Sa, exterior cell Sb), the peak value of discharge pulsations is
reduced, and vibrations and noise level that can be heard are
reduced.
[0046] The pitch spacings of the external teeth 11, 11, . . . of
the inner rotor 1 and the internal teeth 21, 21, . . . of the outer
rotor 2 are defined as follows. First, a tooth row with a number of
teeth equal to a numerical value N that is a common divisor of the
number Za of the external teeth 11, 11, . . . of the inner rotor 1
and the number Zb of the internal teeth 21, 21, . . . of the outer
rotor 2 is taken as a non-equal spacing pitch row Pi in the inner
rotor 1, and the identical non-equal spacing pitch rows Pi are
formed repeatedly (see FIG. 2A). Thus, a plurality of non-equal
spacing pitch rows Pi are included in one inner rotor 1.
[0047] However, when the greatest common divisor N of the number of
teeth Za of the inner rotor 1 and the number of teeth Zb of the
outer rotor 2 is equal to the number of teeth Za of the inner rotor
1, only one non-equal spacing pitch row Pi is present in the inner
rotor 1. An actual embodiment of this case is shown in FIG. 6
wherein the number of teeth Za of the inner rotor 1 is 6 and the
number of teeth Zb of the outer rotor 2 is 12. In this case, 6 that
is the number of teeth Za of the inner rotor 1 is the greatest
common divisor, and one non-equal spacing pitch row Pi is present
in the inner rotor 1. In such a case, all the pitch spacings Pa of
the external teeth 11, 11, . . . of the inner rotor 1 differ from
each other.
[0048] In the non-equal spacing pitch row Pi, the teeth with
different pitch spacing Pa are formed as a unit (group) by the N
(common divisor) external teeth 11, 11, . . . . Thus, in the
non-equal spacing pitch row Pi, the pitch spacings Pa vary
depending on whether the pitch angle (.alpha., .beta., .gamma.) is
large, medium, or small, and the regions 13 between the teeth in
the non-equal spacing pitch row Pi also vary. Further, it is
preferred that the arrangement order of the size of a plurality
regions 13, 13, . . . between the teeth in the non-equal spacing
pitch row Pi be non-regular (random). However, the order of sizes
of regions 13 between the teeth in a plurality of non-equal spacing
pitch rows Pi in one inner rotor 1 is such that they all are formed
with the same pattern. In the outer rotor 2, there is present a
non-equal spacing pitch row Po in which N (common divisor) internal
teeth 21, 21, . . . are configured with different pitch spacings
Pb, in the same manner as in the non-equal spacing pitch row
Pi.
[0049] The number of teeth Za, number of teeth Zb, and numerical
value N, which is a common divisor, will be explained below as
specific integer values. The number of teeth Za of the inner rotor
1 is taken as 6, and the number of teeth Zb of the outer rotor 2 is
taken as 9. The common divisor (numerical value N) of the number of
teeth Za and number of teeth Zb is "3". This value is not
necessarily the greatest common divisor of the number of teeth Za
and number of teeth Zb. The non-equal spacing pitch row Pi is
composed of three external teeth 11, 11, . . . with a different
pitch spacing Pa. The three regions 13, 13, . . . between the teeth
that are set by the three external teeth 11, 11, . . . are composed
of three different pitch angles and, as described above, denoted by
.alpha.1, .beta.1, .gamma.1. Where the size relationship thereof is
assumed to be .alpha.1<.gamma.1<.beta.1, as described
hereinabove, the size relationship of the regions 13 between the
teeth will be 13.alpha.<13.gamma.<13.beta. (see FIG. 2A).
[0050] Further, the non-equal spacing pitch row Po of the outer
rotor 2 is composed of three internal teeth 21, 21, . . . with a
different pitch spacing Pb. The regions 23, 23, . . . between the
teeth that are formed by the three internal teeth 21, 21, . . . are
composed of three pitch angles and, as described above, denoted by
.alpha.2, .beta.2, .gamma.2. The order of sizes of a plurality of
regions 23, 23, between the teeth in the non-equal spacing pitch
row Po has a pattern identical to the order of sizes of the regions
13, 13, between the teeth in the non-equal spacing pitch row Pi of
the inner rotor 1. Two non-equal spacing pitch rows Pi are present
in the inner rotor 1, and three non-equal spacing pitch rows Po are
present in the outer rotor 2 (see FIG. 2B).
[0051] The non-equal spacing pitch row Pi and non-equal spacing
pitch row Po have three (common divisor) external teeth 11, 11, . .
. and internal teeth 21, 21, . . . , respectively. The arrangement
of the order of sizes of the regions 13 between the teeth and
regions 23 between the teeth can be an appropriate irregular
arrangement. For example, the order of sizes of the pitch angles
(.alpha., .beta., .gamma.) of the regions 13, 13, . . . between the
teeth in the rotation direction of the rotor can be small, medium,
large, or large, medium, small. However, the order of sizes of the
regions 23, 23, . . . in the non-equal spacing pitch row Po of the
outer rotor 2 is identical to that of the non-equal spacing pitch
row Pi.
[0052] With such a configuration, the period of the size of volume
of the interior cells Sa (exterior cells Sb) formed by regions 13
(23) between the teeth of different size varies non-monotonically
rather than monotonically when the external teeth 11 (internal
teeth 21) move with different pitch spacings Pa (Pb). As a result,
the discharge pulsations with a larger irregularity (randomness)
can be realized. The non-monotonous changes as referred to herein
mean that the regions 13 (23) between the teeth of different size
move through a predetermined position with irregular periods
because of the irregular pitch spacing Pa (Pb).
[0053] FIG. 3 to FIG. 5 show the operation states in which the
interior cells Sa and exterior cells Sb that differ in volume due
to the difference in pitch angle between the regions 13.alpha.,
13.beta., 13.gamma. between the teeth or regions 23.alpha.,
23.beta., 23.gamma. between the teeth are discharged successively
into the discharge port 43 as the inner rotor 1 makes one
revolution. One of the external teeth 11 of the inner rotor 1 is
marked with a black dot, and the external tooth 11 with a dot makes
one revolution as shown in FIG. 3 to FIG. 5.
[0054] The size of the shape, that is, a tooth thickness dimension
Wa, differs between the external teeth 11, 11, . . . arranged with
the irregular pitch spacing Pa in the non-equal spacing pitch row
Pi. Because there is a difference in size between the external
teeth 11, 11, . . . , as described above, the volume of interior
cells Sa also varies (see FIG. 2A). Likewise, the size of the
shape, that is, a tooth thickness dimension Wb, differs between the
internal teeth 21, 21, . . . of the outer rotor 2 that are arranged
in the irregular pitch spacing Pb in the non-equal spacing pitch
row Po, and because there is a difference in size between the
internal teeth 21, 21, . . . , as described above, the volume of
exterior cells Sb also varies.
[0055] FIG. 6 illustrates a configuration in which the number of
teeth Za of the inner rotor 1 is 6 and the number of teeth Zb of
the outer rotor 2 is 12. The value of the common divisor of the
number of teeth Za and number of teeth Zb is 6, and the number of
non-equal spacing pitch rows Po of the outer rotor 2 formed thereby
is 2. Thus, the value of the common divisor is equal to the number
of teeth Za of the inner rotor 1. FIG. 7A is a graph illustrating
the discharge pulsations in accordance with the present invention.
FIG. 7B is a graph illustrating the discharge pulsations of the
conventional configuration. The comparison of the two graphs shows
that in accordance with the present invention the pulsations are
dispersed, whereby the peak of discharge pulsations is reduced (see
FIG. 7A).
[0056] The second embodiment of the present invention will be
described below with reference to FIG. 8 to FIG. 12. In the second
embodiment, in the internal gear pump having the configuration
similar to that of the first embodiment of the present invention,
as shown in FIG. 9A, the tooth thickness dimension Wa of the tooth
thickness of the external teeth 11, 11, . . . of the inner rotor 1
is not uniform. The pitch angles .theta.a, .theta.a, . . . of the
adjacent external teeth 11, 11 in a plurality of external teeth 11,
11, . . . of the inner rotor 1 are all formed as equal angles (see
FIG. 8B, FIG. 9A). Thus, the pitch spacing Pa of the external teeth
11, 11, . . . is uniform. The tooth thickness dimension Wb of the
internal teeth 21, 21, . . . of the outer rotor 2 corresponds to
the tooth thickness Wa of the inner rotor 1 and is not uniform. The
term "corresponds" as used herein means that the internal teeth 21,
21, . . . of the outer rotor 2 can mesh with the external teeth 11,
11, . . . of the inner rotor 1 in the internal gear pump and the
inner rotor 1 and outer rotor 2 can rotate effectively (see FIG. 10
to FIG. 12).
[0057] The tooth thickness dimension Wa of the external tooth 11 of
the inner rotor 1 is a dimension of the portion that crosses a
reference pitch circle Ca (see FIG. 9A). The reference pitch circle
Ca is a virtual circle that passes through the intermediate
position between the tooth tip and tooth bottom of the external
tooth 11, this circle having the center of the diameter of the
inner rotor 1 as a center. The shape of the tooth bottom portion 12
between the adjacent external teeth 11, 11 differs depending on the
tooth thickness dimension Wa of the external teeth 11. The volumes
of the interior cells Sa, Sa, . . . formed between the adjacent
external teeth 11, 11 of the inner rotor 1 and the crescent 3
differ accordingly, and there are large volumes and small volumes.
Therefore, the amount of liquid transferred by a plurality of the
interior cells Sa varies from one interior cell Sa to another. The
outer rotor 2 also has a reference pitch circle Cb (see FIG.
9B).
[0058] In the external teeth 11, 11, . . . of the inner rotor 1,
which have different tooth thickness dimensions Wa, the number Za
of external teeth 11, 11, of the inner rotor 1 and the number Zb of
internal teeth 21, 21, . . . of the outer rotor 2 are multiples of
the common divisor of Za and Zb. In the external teeth 11 of the
inner rotor 1, a tooth row is composed of the number of teeth at
least equal to the greatest common divisor, and the external teeth
11 in this tooth row have different tooth thickness dimensions Wa.
This tooth row is called a unit external tooth row Li (see FIG.
9A). As described above, the unit external tooth row Li is composed
of N external teeth 11, where the numerical value N is the
(greatest) common divisor, and the unit external tooth rows Li are
formed repeatedly. Thus, one inner rotor 1 comprises a plurality of
unit external tooth rows Li.
[0059] Where the numerical value N, which is the greatest common
divisor of the number of teeth Za of the inner rotor 1 and the
number of teeth Zb of the outer rotor 2, is equal to the number of
teeth Za of the inner rotor 1, only one unit external tooth row Li
is contained in the inner rotor 1. For example, such is the case
with the number of teeth Za of the inner rotor 1 equal to 6 and the
number of teeth Zb of the outer rotor 2 equal to 12. In this case,
the number 6, which is the number of teeth Za of the inner rotor 1,
is the greatest common divisor, and the inner rotor 1 is composed
only of one unit external tooth row Li. In this case, the tooth
thickness dimensions Wa of the external teeth 11, 11, . . . are all
different from each other.
[0060] The arrangement order of sizes of tooth thickness dimensions
Wa, Wa, . . . of a plurality of external teeth 11, 11, contained in
the unit external tooth row Li is preferably irregular (random).
However, the arrangement orders of sizes of the tooth thickness
dimensions Wa in a plurality of unit external tooth rows Li in one
inner rotor 1 are all formed according to the same pattern. In the
outer rotor 2, a unit internal tooth row Lo composed of a total of
N (common divisor) internal teeth 21, 21, with different tooth
thickness dimensions Wb is provided similarly to the
above-described unit external tooth row Li (see FIG. 9B). Thus,
where the inner rotor 1 and outer rotor 2 mesh and rotate normally,
the unit external tooth rows Li of the inner rotor 1 and the unit
internal tooth rows Lo of the outer rotor 2 mesh periodically (see
FIG. 8A, FIG. 9 to FIG. 12).
[0061] Specific integer values of the numerical value N, which is
the common divisor, will be explained below for the number of teeth
Za of the inner rotor 1 and the number of teeth Zb of the outer
rotor 2. The number of teeth Za of the inner rotor 1 is taken as 6,
and the number of teeth Zb of the outer rotor 2 is taken as 9 (see
FIGS. 9A, 9B). The common divisor (numerical value N) of the number
of teeth Za and the number of teeth Zb is "3". Depending on the
numerical values of the number of teeth Za and the number of teeth
Zb, this numerical value "3" is not necessarily the greatest common
divisor. The unit external tooth row Li is composed of three
external teeth 11, 11, . . . having mutually different tooth
thickness dimensions Wa. Here, the tooth thickness dimension Wa1,
tooth thickness dimension Wa2, and tooth thickness dimension Wa3
are used to indicate that the three external teeth 11, 11, . . . of
the unit external tooth row Li have different tooth thickness
dimensions Wa. The size relationship of the tooth thickness
dimensions is such that the tooth thickness dimension Wa1 is the
maximum dimension and the tooth thickness dimension Wa3 is the
minimum dimension. Thus, the size relationship of the tooth
thickness dimensions is Wa1>Wa2>Wa3 (see FIG. 9A).
[0062] Further, the unit internal tooth row Lo of the outer rotor 2
is composed of three internal teeth 21, 21, . . . having mutually
different tooth thickness dimensions Wb. The tooth thickness
dimension Wb1, tooth thickness dimension Wb2, and tooth thickness
dimension Wb3 are used to indicate that the internal teeth 21, 21,
. . . contained in the unit internal tooth row Lo also have
different tooth thickness dimensions Wb. Thus, the inner rotor 1
has two unit external tooth rows Li, Li, and the outer rotor 2 has
three unit internal tooth rows Lo, Lo, . . . (see FIGS. 9A,
9B).
[0063] The external tooth 11 with the tooth thickness dimension Wa1
meshes with the tooth bottom portion 22 located between the
internal tooth 21 with the tooth thickness dimension Wb3 and the
internal tooth 21 with the tooth thickness dimension Wb1, the
external tooth 11 with the tooth thickness dimension Wa2 engages
with tooth bottom portion 22 located between the internal tooth 21
with the tooth thickness dimension Wb1 and the internal tooth 21
with the tooth thickness dimension Wb2, the external tooth 11 with
the tooth thickness dimension Wa3 meshes with the tooth bottom
portion 22 located between the internal tooth 21 with the tooth
thickness dimension Wb2 and the internal tooth 21 with the tooth
thickness dimension Wb3, and such engagement state of the inner
rotor 1 and outer rotor 2 is repeated (see FIG. 10 to FIG. 12).
[0064] With such a configuration, the period of the size of volume
of the interior cells Sa formed by the external teeth 11, 11, . . .
having mutually different tooth thickness dimensions Wa (Wa1, Wa2,
Wa3) that are contained in the unit external tooth row Li of the
inner rotor 1 and the crescent 3 varies non-monotonically rather
than monotonically. As a result, the discharge pulsations with a
larger irregularity (randomness) can be realized. Likewise, the
period of the size of volume of the interior cells Sb formed by the
internal teeth 21, 21, . . . having mutually different tooth
thickness dimensions Wb (Wb1, Wb2, Wb3) that are contained in the
unit internal tooth row Lo of the outer rotor 2 and the crescent 3
also varies non-monotonically rather than monotonically. As a
result, the discharge pulsations with a larger irregularity
(randomness) can be realized, and the peak of discharge pulsations
can be reduced.
[0065] FIG. 10 to FIG. 12 show how the volume of interior cells Sa,
Sa, . . . successively configured by the external teeth 11, 11, . .
. having mutually different tooth thickness dimensions (Wa1, Wa2,
Wa3) of the unit external tooth row Li and the crescent 3 varies as
the inner rotor 1 makes one revolution. The figures also show the
variation of the volume of exterior cells Sb, Sb, . . .
successively configured by the crescent 3 and the internal teeth
21, 21, . . . having mutually different tooth thickness dimensions
(Wb1, Wb2, Wb3) of the unit internal tooth row Lo of the outer
rotor 2 that rotates together with the inner rotor 1.
[0066] The third embodiment of the present invention will be
described below with reference to FIG. 13 to FIG. 16. In the third
embodiment, in the internal gear pump having the configuration
similar to that of the second embodiment of the present invention,
the pitch angles .theta.a of the external teeth 11, 11, . . . of
the inner rotor 1 differ from each other. Thus, in the inner rotor
1, the tooth thickness dimensions Wa and pitch angles .theta.a of
the external teeth 11, 11, . . . are not uniform and differ from
each other. The tooth thickness dimensions Wb of the external teeth
21, 21, . . . of the outer rotor 2 correspond to the tooth
thickness dimensions Wa of the external teeth 11 of the inner rotor
1.
[0067] The term "corresponds" as used herein means that the
external teeth 11, 11, . . . of the inner rotor 1 and the internal
teeth 21, 21, . . . of the outer rotor 2 mesh effectively in the
internal gear pump in the same manner as in the first and second
embodiments. The definition of the tooth thickness dimension Wa of
the external tooth 11 of the inner rotor 1 is identical to that
given in the second embodiment. As a result, the volumes of
interior cells Sa, Sa, . . . formed between the adjacent external
teeth 11, 11 of the inner rotor 1 and the crescent 3 differ from
each other and there are small and large volumes. Likewise, the
volumes of exterior cells Sb, Sb, . . . formed between the adjacent
internal teeth 21, 21 of the outer rotor 2 and the crescent 3 also
differ from each other. Therefore, the amount of liquid transferred
by the plurality of interior cells Sa and exterior cells Sb varies
among the interior cells Sa and exterior cells Sb.
[0068] Also in the third embodiment, the inner rotor 1 has unit
external teeth rows Li and the outer rotor 2 has unit internal
tooth rows Lo, and the unit external tooth rows Li and unit
internal tooth rows Lo are configured similarly to the unit
external tooth rows Li and unit internal tooth rows Lo in the
second embodiment described above. The arrangement order of sizes
of tooth thickness dimensions Wa, Wa, . . . of a plurality of
external teeth 11, 11, . . . contained in the unit external tooth
row Li is preferably irregular (random).
[0069] Further, similarly to the second embodiment, the arrangement
orders of sizes of the tooth thickness dimensions Wa in a plurality
of unit external tooth rows Li in one inner rotor 1 are all formed
according to the same pattern. In the outer rotor 2, a unit
internal tooth row Lo composed a total of N (common divisor) of
internal teeth 21, 21, . . . with different tooth thickness
dimensions Wb is provided similarly to the above-described unit
external tooth row Li. Where the inner rotor 1 and outer rotor 2
mesh and rotate normally, the unit external tooth rows Li of the
inner rotor 1 and the unit internal tooth rows Lo of the outer
rotor 2 mesh periodically.
[0070] Further, similarly to the second embodiment, the following
specific integer values are taken for the number of teeth Za of the
inner rotor 1 and the number of teeth Zb of the outer rotor 2.
Thus, the number of teeth Za of the inner rotor 1 is taken as 6 and
the number of teeth Zb of the outer rotor 2 is taken as 9 (see
FIGS. 13A, 13B). The tooth thickness dimension Wa1, tooth thickness
dimension Wa2, and tooth thickness dimension Wa3 are used to
indicate that the three external teeth 11, 11, . . . contained in
the unit external tooth row Li have different tooth thickness
dimensions Wa. The size relationship of the tooth thickness
dimensions is Wa1>Wa2>Wa3 (see FIG. 13A).
[0071] Furthermore, the pitch angles .theta.a of the external teeth
11, 11, . . . contained in the unit external tooth row Li are
assumed to differ from each other. More specifically, the pitch
angle of the external teeth 11, 11 with the tooth thickness
dimension Wa1 and tooth thickness dimension Wa2 is taken as
.theta.a1, the pitch angle of the external teeth 11, 11 with the
tooth thickness dimension Wa2 and tooth thickness dimension Wa3 is
taken as .theta.a2, and the pitch angle of the external teeth 11,
11 with the tooth thickness dimension Wa3 and tooth thickness
dimension Wa1 is taken as .theta.a3. Here, the pitch angle of the
external teeth 11, 11 with the tooth thickness dimension Wa3 and
tooth thickness dimension Wa1 is a pitch angle of the pitch angle
of the external tooth 11 with the tooth thickness dimension Wa3 and
the pitch angle of the external tooth 11 with the tooth thickness
dimension Wa1 of the adjacent unit external rows Li, Li.
[0072] Further, similarly to the configuration of the second
embodiment, the unit internal tooth row Lo of the outer rotor 2 is
also composed of three internal teeth 21, 21, . . . having mutually
different tooth thickness dimensions Wb, and the internal teeth 21,
21, . . . contained in the unit internal tooth row Lo also have
respectively different tooth thickness dimensions Wb1, Wb2, Wb3.
The inner rotor 1 has two unit external tooth rows Li, Li, and the
outer rotor 2 has three unit internal tooth rows Lo, Lo, . . . (see
FIGS. 13A, 13B). The pitch angles .theta.b of the internal teeth
21, 21, . . . in the unit internal tooth row Lo of the outer rotor
2 also differ from each other correspondingly to the external teeth
11, 11, . . . of the inner rotor 1. More specifically, as shown in
FIG. 13B, the pitch angle .theta.b1, pitch angle .theta.b2, and
pitch angle .theta.b3 differ from each other.
[0073] With such a configuration, the teeth contained in the unit
external tooth row Li of the inner rotor 1 have mutually different
tooth thickness dimensions Wa (Wa1, Wa2, Wa3) and the pitch angles
.theta.a (.theta.a1, .theta.a2, .theta.a3) of the external teeth
11, 11, . . . also differ from each other. As a result, the period
of the size of volume of the interior cells Sa configured by the
external teeth 11, 11, . . . and crescent 3 varies
non-monotonically rather than monotonically. Therefore, discharge
pulsations with a larger irregularity (randomness) can be realized.
Likewise, the period of the size of volume of the exterior cells Sb
configured by the crescent 3 and the internal teeth 21, 21, . . .
having mutually different tooth thickness dimensions Wb (Wb1, Wb2,
Wb3) and contained in the unit internal tooth row Lo of the outer
rotor 2 also varies non-monotonically rather than monotonically.
Therefore, discharge pulsations with a larger irregularity
(randomness) can be realized.
[0074] FIG. 14 to FIG. 16 show how the volume of interior cells Sa,
Sa, . . . successively configured by the external teeth 11, 11, . .
. having mutually different tooth thickness dimensions (Wa1, Wa2,
Wa3) of the unit external tooth row Li and the crescent 3 varies as
the inner rotor 1 makes one revolution in the third embodiment. The
figures also show the variation of the volume of exterior cells Sb,
Sb, . . . successively configured by the crescent 3 and the
internal teeth 21, 21, . . . having mutually different tooth
thickness dimensions (Wb1, Wb2, Wb3) of the unit internal tooth row
Lo of the outer rotor 2 that rotates together with the inner rotor
1.
* * * * *