U.S. patent application number 15/764666 was filed with the patent office on 2018-09-27 for internal gear pump.
The applicant listed for this patent is NTN CORPORATION. Invention is credited to Hiroshi AKAI, Hajime ASADA, Kei HATTORI, Takayuki ITO.
Application Number | 20180274539 15/764666 |
Document ID | / |
Family ID | 58423734 |
Filed Date | 2018-09-27 |
United States Patent
Application |
20180274539 |
Kind Code |
A1 |
ASADA; Hajime ; et
al. |
September 27, 2018 |
INTERNAL GEAR PUMP
Abstract
To provide an internal gear pump which is able to stably ensure
the sealing property between a resin casing constituting a trochoid
accommodating portion and a cover, to omit the seal ring at the
portion, and to stabilize the discharging ability. An internal gear
pump 1 has a trochoid 4 in which an inner rotor 3 having a
plurality of outer teeth is accommodated in an outer rotor 2 having
a plurality of inner teeth in a state in which outer teeth mesh
with inner teeth and are eccentric, and a casing 5 having a
trochoid accommodating recess 5a formed therein, and a cover 6
which closes the recess 5a. The casing 5 is an injection-molded
body of a resin composition. The casing 5 and the cover 6 are fixed
with bolts. A metallic bush 7 is provided in the bolt fixing hole
portion of the casing 5. In the cross-section of the joining
portion between the casing 5 and the cover 6, the position of the
end surface 7a of the bush 7 is higher than the bush formation
surface 5e around the bush of the casing 5 and lower than the
sealing surface 5d around the recess of the casing 5, as viewed
from the bottom surface 5c of the recess 5a.
Inventors: |
ASADA; Hajime; (Aichi,
JP) ; HATTORI; Kei; (Mie, JP) ; ITO;
Takayuki; (Mie, JP) ; AKAI; Hiroshi; (Mie,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NTN CORPORATION |
Osaka |
|
JP |
|
|
Family ID: |
58423734 |
Appl. No.: |
15/764666 |
Filed: |
September 29, 2016 |
PCT Filed: |
September 29, 2016 |
PCT NO: |
PCT/JP2016/078755 |
371 Date: |
March 29, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F04C 2/102 20130101;
F04C 2230/60 20130101; F04C 2240/805 20130101; F05C 2253/20
20130101; F01C 21/108 20130101; F04C 2240/56 20130101; F04C 15/0003
20130101; F04C 2230/22 20130101; F04C 2240/30 20130101 |
International
Class: |
F04C 15/00 20060101
F04C015/00; F04C 2/10 20060101 F04C002/10 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 30, 2015 |
JP |
2015-193242 |
Sep 30, 2015 |
JP |
2015-193292 |
Claims
1. An internal gear pump having a trochoid in which an inner rotor
having a plurality of outer teeth is rotatably accommodated inside
an outer rotor having a plurality of inner teeth in a state in
which the outer teeth mesh with the inner teeth and are eccentric,
and an suction side volume chamber configured to suck a liquid, and
a discharge side volume chamber configured to discharge the liquid
sucked into the suction side volume chamber are formed between the
inner teeth and the outer teeth, the internal gear pump comprising:
a casing having a recess which accommodates the trochoid; and a
cover which closes the recess of the casing, wherein the casing is
an injection-molded body of a resin composition, the casing and the
cover are fixed with bolts, a metallic bush is provided in a bolt
fixing hole portion of the casing, and a position of an end surface
of the bush on the cover side in a cross-section of a joining
portion between the casing and the cover is higher than a bush
formation surface of the casing around the bush, and is the same as
or lower than a sealing surface around the recess of the casing, as
seen from a bottom surface of the recess.
2. The internal gear pump according to claim 1, wherein the sealing
surface is a surface which is continuous from an inner surface of
the recess of the casing, and the sealing surface comes into close
contact with the surface of the cover to seal the recess.
3. The internal gear pump according to claim 1, wherein a seal ring
is not interposed at a joining portion between the casing and the
cover.
4. The internal gear pump according to claim 1, wherein an inner
surface of the recess of the casing is made of an injection-molded
body of the resin composition, and a bottom surface of the recess
is made of a metal body.
5. The internal gear pump according to claim 1, wherein the resin
composition is a resin composition in which a polyphenylene sulfide
resin is used as a base resin, and the base resin is blended with
at least one selected from a glass fiber, a carbon fiber, and an
inorganic filler.
6. An internal gear pump having a trochoid in which an inner rotor
having a plurality of outer teeth is rotatably accommodated inside
an outer rotor having a plurality of inner teeth in a state in
which the outer teeth mesh with the inner teeth and are eccentric,
and an suction side volume chamber configured to suck a liquid, and
a discharge side volume chamber configured to discharge the liquid
sucked into the suction side volume chamber are formed between the
inner teeth and the outer teeth, the internal gear pump comprising:
a trochoid accommodating portion made of sintered metal configured
to accommodate the trochoid; and a casing joined to the outside of
the trochoid accommodating portion, wherein the casing is an
injection-molded body of a resin composition, and the trochoid
accommodating portion and the casing are joined such that a part of
the casing enters a sintered pore on the outer surface of the
trochoid accommodating portion.
7. The internal gear pump according to claim 6, wherein the
trochoid accommodating portion includes a main body portion having
a cylindrical inner surface and a flat plate-like inner bottom
surface, and a lid portion which closes an opening portion of the
main body portion.
8. The internal gear pump according to claim 7, wherein the lid
portion is caulked and fixed to the opening portion of the main
body portion.
9. The internal gear pump according to claim 7, wherein the
trochoid accommodating portion and the casing are joined such that
a part of the casing enters the sintered pore of the main body
portion and the outer surface of the lid portion.
Description
TECHNICAL FIELD
[0001] The present invention relates to an internal gear pump (a
trochoid pump) which feeds a liquid such as oil, water, and
chemical liquid.
BACKGROUND ART
[0002] The internal gear pump (a trochoid pump) is a pump in which
an outer rotor and an inner rotor having a trochoid tooth profile
are accommodated in a casing in a sealed state, and with rotation
of a drive shaft, the inner rotor and the outer rotor fixed to the
drive shaft rotate and act to suck and discharge liquid. In recent
years, as a pump of this type, a pump having a casing made of resin
has been known as a pump capable of reducing the machining process
and capable of being manufactured at low cost (see Patent
Literature 1).
[0003] The structure of this type of internal gear pump will be
described on the basis of FIGS. 4 and 8.
[0004] FIG. 4 is a cross-sectional view of a conventional internal
gear pump. As illustrated in FIG. 4, a pump 21 mainly includes a
trochoid 24 in which an inner rotor 23 having a plurality of outer
teeth is accommodated in an annular outer rotor 22 having a
plurality of inner teeth. The trochoid 24 is rotatably accommodated
in a circular trochoid accommodating recess 25a formed in a flanged
columnar casing 25. A cover 26 which closes the trochoid
accommodating recess 25a is fixed to the casing 25.
[0005] The trochoid 24 is configured such that the inner rotor 23
is rotatably accommodated in the outer rotor 22 in a state in which
the outer teeth of the inner rotor 23 mesh with the inner teeth of
the outer rotor 22 and are eccentric. Volume chambers on a suction
side and a discharge side are formed between the partition points
on which the respective rotors are in contact with each other, in
accordance with the rotation direction of the trochoid 24. A drive
shaft 29 rotated by a drive source (not illustrated) passes through
and is fixed to the axial center of the inner rotor 23. When the
drive shaft 29 rotates and the inner rotor 23 rotates, as the outer
teeth mesh with the inner teeth of the outer rotor 22, the outer
rotor 22 rotates in the same direction, and liquid is sucked from
the suction port into the suction side volume chamber in which the
volume increases by the rotation to obtain a negative pressure. The
suction side volume chamber changes to a discharge side volume
chamber in which the volume decreases and the internal pressure
rises by the rotation of the trochoid 24. From this, the sucked
liquid is discharged to the discharge port.
[0006] The cover 26 is made of a sintered metal, and the casing 25
is an injection-molded body manufactured by injection molding,
using a resin composition. A metallic bush 27 is integrated with a
bolt fixing hole portion of the casing 25 by composite molding at
the time of injection molding, and the casing 25 and the cover 26
are fastened and fixed to the fixing plate 30 of the device main
body by a bolt 28 made to pass via the bush 27. The bush 27 is
interposed between the casing 25 and the cover 26 to secure the
fastening strength at the fastening portion.
[0007] A seal ring (O-ring) 31 is assembled in a groove 32 formed
on the outer circumference of the recess of the casing 25 on the
joining surface (a mating surface) between the casing 25 and the
cover 26. Therefore, the trochoid accommodating recess 25a is
sealed, and it is possible to prevent leakage of liquid from the
mating surface between the casing 25 and the cover 26. In the
internal gear pump, in order to effectively exhibit the pump
function, it is important to stably secure the sealing property
(sealing property of the trochoid accommodating recess 25a) on the
mating surface between the casing 25 and the cover 26. Hydrogenated
nitrile rubber (H-NBR type) or the like is used as the material of
the seal ring 31, because the material has heat resistance of about
-30.degree. C. to 120.degree. C. and oil resistance, and can be
applied to a scroll-type compressor of an air conditioner.
[0008] FIG. 8 is a cross-sectional view of another conventional
internal gear pump. As illustrated in FIG. 8, a pump 61 mainly
includes a trochoid 64 in which an inner rotor 63 having a
plurality of outer teeth is accommodated in an annular outer rotor
62 having a plurality of inner teeth. The trochoid 64 is rotatably
accommodated in a circular trochoid accommodating recess 65a formed
in a flanged columnar casing 65. A cover 66 that closes the
trochoid accommodating recess 65a is fixed to the casing 65.
[0009] The trochoid 64 is configured such that the inner rotor 63
is rotatably accommodated in the outer rotor 62 in a state in which
the outer teeth of the inner rotor 63 mesh with the inner teeth of
the outer rotor 62 and are eccentric. Volume chambers on a suction
side and a discharge side are formed between the partition points
on which the respective rotors are in contact with each other, in
accordance with the rotation direction of the trochoid 64. A drive
shaft 69 rotated by a drive source (not illustrated) passes through
and is fixed to the axial center of the inner rotor 63. When the
drive shaft 69 rotates and the inner rotor 63 rotates, as the outer
teeth mesh with the inner teeth of the outer rotor 62, the outer
rotor 62 rotates in the same direction, and liquid is sucked from
the suction port into the suction side volume chamber in which the
volume increases by the rotation to obtain a negative pressure. The
suction side volume chamber changes to a discharge side volume
chamber in which the volume decreases and the internal pressure
rises by the rotation of the trochoid 64. From this, the sucked
liquid is discharged to the discharge port.
[0010] The cover 66 is made of a sintered metal, and the casing 65
is an injection-molded body manufactured by injection molding using
a resin composition. The casing 65 and the cover 66 are fastened
and fixed to the fixing plate 70 of the device main body by a bolt
68. A seal ring 71 is assembled to a groove formed on the outer
circumference of the recess of the casing 65 on the joining surface
(mating surface) between the casing 65 and the cover 66. Therefore,
the trochoid accommodating recess 65a is sealed, and leakage of
liquid from the mating surface between the casing 65 and the cover
66, which is a combination of resin and sintered metal, is
prevented.
[0011] By using the casing 65 as an injection-molded body (resin
molded body), machining is unnecessary and the process is
economical. Further, the casing 65 makes sliding contact with the
outer rotor 62 and the inner rotor 63 at the bottom surface 65c and
the inner surface 65b constituting the trochoid accommodating
recess 65a. Since the inner surface 65b of the trochoid
accommodating recess 65a is an injection-molded body portion of the
resin composition, the inner surface 65b has excellent frictional
wear characteristics with respect to the outer rotor 62. The bottom
surface 65c of the trochoid accommodating recess 65a is constituted
by a disc-shaped metal plate 67 integrated with the casing 65 by
composite molding. Therefore, there is no problem such as sink
marks when the bottom surface 65c is formed of resin, flatness is
excellent, and variation in discharging performance is
suppressed.
CITATIONS LIST
Patent Literature
[0012] Patent Literature 1: JP 2014-51964 A
SUMMARY OF INVENTION
Technical Problems
[0013] As described above, in the internal gear pump in which the
casing of FIG. 4 is made of resin, in order to secure the fastening
strength at the fastening portion of the pump, the metallic bush
which is composite-molded (insert-molded) with the casing is used.
Here, in order to stably hold the fastening force, it is necessary
to prevent the resin from being covered on the cover side end
surface, which is the joining surface with the bush cover, at the
time of molding. For this purpose, for example, it is conceivable
that a bush formation surface of the casing around the bush is
recessed from the sealing surface (mating surface with the cover)
or the bush end surface, and the bush slightly protrudes from the
bush formation surface.
[0014] However, in the related art, a positional relation between
the sealing surface, the bush formation surface, and the bush end
surface after molding is not determined, and depending on the
protrusion amount of the bush and the molding conditions of the
casing, the sealing surface may be lower than the end surface of
the bush. In that case, the bush is in contact with the cover
because it is a bolt fastening portion, but the sealing surface is
not in contact with the cover, and the sealing property at the
sealing portion is not secured. In this case, the sealing property
is ensured by the seal ring.
[0015] When the sealing property is ensured by a seal ring of H-NBR
type or the like, the seal ring cannot be used in an atmosphere
having a higher temperature than the heat resistant temperature of
120.degree. C. Further, in the pump manufacturing process, a
process of assembling the seal ring is required.
[0016] The present invention (first aspect described below) has
been made to cope with such a problem, and an object thereof is to
provide an internal gear pump which is able to stably ensure the
sealing property between the resin casing constituting the trochoid
accommodating portion and the cover, to omit the seal ring at the
portion, and to stabilize the discharging ability.
[0017] Further, in the internal gear pumps as described above with
reference to FIGS. 4 and 8, the casing is manufactured by injection
molding of resin in order to manufacture the pump at low cost.
However, the depth dimension and the diameter dimension of the
trochoid accommodating portion remain as injection-molded finish,
and there are slight variations for each product. In particular,
since the depth of the accommodating portion affects the discharge
amount, the variation in depth can be a variation in the discharge
amount.
[0018] The present invention (a second aspect described below) has
been made to cope with such a problem, and an object thereof is to
provide an internal gear pump capable of reducing variations in the
depth of a trochoid accommodating portion among the individual
parts, and having stable discharging ability.
Solutions To Problems
[0019] According to a first aspect of the present application,
there is provided an internal gear pump having a trochoid in which
an inner rotor having a plurality of outer teeth is rotatably
accommodated inside an outer rotor having a plurality of inner
teeth in a state in which the outer teeth mesh with the inner teeth
and are eccentric, and an suction side volume chamber configured to
suck a liquid, and a discharge side volume chamber configured to
discharge the liquid sucked into the suction side volume chamber
are formed between the inner teeth and the outer teeth, the
internal gear pump including: a casing having a recess which
accommodates the trochoid, and a cover which closes the recess of
the casing. The casing is an injection-molded body of a resin
composition. The casing and the cover are fixed with bolts, a
metallic bush is provided in a bolt fixing hole portion of the
casing, and a position of an end surface of the bush on the cover
side in a cross-section of a joining portion between the casing and
the cover is higher than a bush formation surface of the casing
around the bush, and is the same as or lower than the sealing
surface around the recess of the casing, as seen from a bottom
surface of the recess.
[0020] The sealing surface may be a surface which is continuous
from an inner surface of the recess of the casing, and the sealing
surface may come into close contact with the surface of the cover
to seal the recess.
[0021] A seal ring may not be interposed at a joining portion
between the casing and the cover, in the internal gear pump.
[0022] An inner surface of the recess of the casing may be made of
an injection-molded body of the resin composition, and a bottom
surface of the recess may be made of a metal body.
[0023] The resin composition may be a resin composition in which a
polyphenylene sulfide resin is used as a base resin, and the base
resin is blended with at least one selected from a glass fiber, a
carbon fiber, and an inorganic filler.
[0024] According to a second aspect of the present application,
there is provided an internal gear pump having a trochoid in which
an inner rotor having a plurality of outer teeth is rotatably
accommodated inside an outer rotor having a plurality of inner
teeth in a state in which the outer teeth mesh with the inner teeth
and are eccentric, and an suction side volume chamber configured to
suck a liquid, and a discharge side volume chamber configured to
discharge the liquid sucked into the suction side volume chamber
are formed between the inner teeth and the outer teeth, the
internal gear pump including: a trochoid accommodating portion made
of sintered metal configured to accommodate the trochoid, and a
casing joined to the outside of the trochoid accommodating portion,
in which the casing is an injection-molded body of a resin
composition, and the trochoid accommodating portion and the casing
are joined such that a part of the casing enters a sintered pore on
the outer surface of the trochoid accommodating portion.
[0025] The trochoid accommodating portion may include a main body
portion having a cylindrical inner surface and a flat plate-like
inner bottom surface, and a lid portion which closes an opening
portion of the main body portion. Further, the lid portion may be
caulked and fixed to the opening portion of the main body
portion.
[0026] Further, in the configuration in which the trochoid
accommodating portion includes the main body portion and the lid
portion, the trochoid accommodating portion and the casing maybe
joined such that a part of the casing enters the sintered pore of
the main body portion and the outer surface of the lid portion in
the trochoid accommodation portion.
Advantageous Effects of Invention
[0027] The internal gear pump according to the first aspect of the
present application has a casing having a trochoid accommodating
recess and a cover which closes the recess, and the casing is an
injection-molded body of a resin composition. The casing and the
cover are fixed with bolts, a metallic bush is provided in a bolt
fixing hole portion of the casing, and a position of an end surface
of the bush in a cross-section of a joining portion between the
casing and the cover is higher than a bush formation surface of the
casing around the bush, and is the same as or lower than the
sealing surface around the recess of the casing, as seen from a
bottom surface of the trochoid accommodating recess. Thus, it is
possible to prevent the end surface of the bush from being covered
with resin at the time of molding of the casing. Further,
regardless of the molding conditions of the casing, the sealing
surface preferentially comes in close contact with the cover at the
time of fastening the bolt and is always in constant with the
cover, the sealing ability of the trochoid accommodating recess can
be stably ensured at that portion, and the discharging ability is
stabilized.
[0028] Further, since the sealing property is ensured as described
above, the seal ring conventionally arranged on the outer
circumference of the sealing surface can be omitted. Therefore, in
the pump manufacturing process, a process of assembling the seal
ring is unnecessary, and the assembling is easy. Further, the
internal gear pump can be used even in an atmosphere having a
higher temperature than 120.degree. C. which is the heat resistant
temperature of the H-NBR type 0 ring.
[0029] The sealing surface is a surface which is continuous from
the inner surface of the trochoid accommodating recess of the
casing and comes into close contact with the surface of the cover
to seal the recess. Thus, it is possible to prevent the liquid from
entering between the cover and the casing from the trochoid
accommodating recess.
[0030] Since the inner surface of the trochoid accommodating recess
of the casing is made of an injection-molded body of a resin
composition and the bottom surface of the recess is made of a metal
body, it is possible to suppress variations in the discharge
performance on the bottom surface, while improving the frictional
wear characteristics on the inner surface.
[0031] Since the resin composition forming the casing is a resin
composition in which a polyphenylene sulfide resin is used as a
base resin, and the base resin is blended with at least one
selected from a glass fiber, a carbon fiber, and an inorganic
filler, oil resistance and chemical resistance are excellent, and a
dimensional accuracy is also greatly improved.
[0032] An internal gear pump according to a second aspect of the
present application includes a trochoid accommodating portion made
of a sintered metal configured to accommodate the trochoid, and a
casing joined to the outside of the trochoid accommodating portion,
in which the casing is an injection-molded body of the resin
composition, and the trochoid receiving portion and the casing are
joined such that a part of the casing enters the sintered pore on
the outer surface of the trochoid accommodating portion. That is,
the trochoid accommodating portion is a separate component from the
casing, and by performing the composite molding (insert molding) of
the casing around the trochoid accommodating portion manufactured
in advance, a configuration in which both members are joined is
obtained. By manufacturing the entire trochoid accommodating
portion as a separate component, it is possible to reduce
variations in the depth of the accommodating portion among the
individual parts. In addition, the depth itself can be processed
with high accuracy. As a result, there is no variation in the
discharge amount among the individual parts, and an internal gear
pump having a stable discharging ability is obtained.
[0033] In a case where the trochoid accommodating portion is formed
in the casing as in the related art, it is necessary to process the
entire casing in order to suppress the variation in the depth of
the accommodating portion. However, by forming only the trochoid
accommodating portion as a separate component, there is no need to
process the entire casing. The trochoid accommodating portion with
the adjusted depth may be composite-molded with the casing, and it
is possible to suppress additional processing cost. Furthermore,
since the trochoid accommodating portion is made of a sintered
metal, it can be easily manufactured, and it is strongly joined to
the resin casing due to the anchor effect to the sintered pores at
the time of composite molding.
[0034] Further, by setting the trochoid accommodating portion as an
independent part, it is possible to design the discharge amount
only with this part. Therefore, the trochoid accommodating portion
can be made into a common component. At the time of molding the
casing, only composite molding is performed using this trochoid
accommodating portion, and the degree of freedom of design can be
expanded.
[0035] Since the trochoid accommodating portion includes the main
body portion having the cylindrical inner surface and the flat
plate-like inner bottom surface and the lid portion for closing the
opening portion of the main body portion, the accommodating portion
depth can be adjusted only by planar processing of the axial
cross-section of the cylinder, and the machining is easy.
[0036] Since the lid portion is caulked and fixed to the opening
portion of the main body portion, the bolt tightening process as in
the related art becomes unnecessary. Further, in the case of
fastening the resin body and the metal body with bolts, there is a
risk of looseness of the fastening portion, but there is no such
risk by fixing the main body portion and the lid portion by
caulking.
[0037] In addition, the trochoid accommodating portion and the
casing are joined such that a part of the casing enters the
sintered pores on the outer surface of the main body portion and
the lid portion in the trochoid accommodating portion, that is, the
casing is formed to cover the lid portion side. Accordingly, it is
possible to prevent the lid portion from being detached from the
main body portion and the like.
BRIEF DESCRIPTION OF DRAWINGS
[0038] FIG. 1 is an assembled perspective view illustrating an
example of an internal gear pump according to a first aspect of the
present application.
[0039] FIG. 2 is an axial cross-sectional view and an enlarged view
of the internal gear pump of FIG. 1.
[0040] FIG. 3 is an axial cross-sectional view and an enlarged view
illustrating another example of the internal gear pump of the first
aspect of the present application.
[0041] FIG. 4 is an axial cross-sectional view of a conventional
internal gear pump.
[0042] FIG. 5 is an axial cross-sectional view illustrating an
example of an internal gear pump according to a second aspect of
the present application.
[0043] FIG. 6 is an axial cross-sectional view illustrating another
example of the internal gear pump according to the second aspect of
the present application.
[0044] FIG. 7 is an axial cross-sectional view illustrating another
example of the internal gear pump according to the second aspect of
the present application.
[0045] FIG. 8 is an axial cross-sectional view of a conventional
internal gear pump.
DESCRIPTION OF EMBODIMENTS
[0046] An embodiment of an internal gear pump according to the
first aspect of the present invention will be described with
reference to FIGS. 1 and 2. FIG. 1 is an assembled perspective view
of an internal gear pump, FIG. 2(a) is an axial cross-sectional
view of the internal gear pump, and FIG. 2(b) is an enlarged view
of the circumference of the sealing surface of the casing in the
internal gear pump. As illustrated in FIG. 1, an internal gear pump
1 includes a trochoid 4 in which an inner rotor 3 is accommodated
in an annular outer rotor 2, a casing 5 formed with a recess
(trochoid accommodating recess) 5a which rotatably accommodates the
trochoid 4, and a cover 6 that closes the trochoid accommodating
recess 5a of the casing 5. The cover 6 has a shape that
substantially conforms to the outer shape of the upper surface of
the casing 5 in which the trochoid accommodating recess 5a opens.
As illustrated in FIG. 2(a), the casing 5 and the cover 6 are
fastened and fixed to a fixing plate 11 of a device main body with
bolts 9. Further, a drive shaft 10 coaxially fixed to the rotation
center of the inner rotor 3 is provided. The drive shaft 10 is
supported by a bearing (not illustrated) which is press-fitted to
the cover 6 or the like.
[0047] The number of outer teeth of the inner rotor 3 is smaller by
one than the number of inner teeth of the outer rotor 2, and the
inner rotor 3 is accommodated in the outer rotor 2 in an eccentric
state in which the outer teeth are inscribed in and mesh with the
inner teeth. Volume chambers on the suction side and the discharge
side are formed between the partition points on which the
respective rotors are in contact with each other, in accordance
with the rotation direction of the trochoid 4. A suction port
communicating with the suction side volume chamber, and a discharge
port communicating with the discharge side volume chamber are
formed on a bottom surface 5c of the trochoid accommodating recess
5a of the casing 5. The suction port communicating with the suction
side volume chamber and the discharge port communicating with the
discharge side volume chamber may be formed in at least one of the
casing 5, the cover 6, and the drive shaft 10.
[0048] In the internal gear pump 1, as the trochoid 4 is rotated by
the drive shaft 10, liquid is sucked from the suction port into the
suction side volume chamber in which the volume increases and a
negative pressure is obtained. The suction side volume chamber is
changed to a discharge side volume chamber in which the volume
decreases and the internal pressure rises by rotation of the
trochoid 4, and the sucked liquid is discharged from the discharge
side volume chamber to the discharge port. The above-described pump
action is continuously performed by the rotation of the trochoid 4,
and the liquid is continuously fed. Further, by the liquid sealing
effect of enhancing the sealing property of each volume chamber by
the sucked liquid, the differential pressure generated between the
respective volume chambers increase, and a large pump action is
obtained.
[0049] The cover 6 is made of metal, and the casing 5 is an
injection-molded body of a resin composition. When the casing 5
made of resin is fastened to the device main body with the bolts,
there is a risk of looseness of the fastening portion due to creep
deformation of the resin. Creep measures can also be taken, by
utilizing a predetermined resin composition blended with a
reinforcing agent or the like to be described below as a resin
material. However, in some cases, it may be brittle and inferior in
impact resistance. Therefore, a metallic bush 7 is provided in the
bolt fixing hole portion of the casing 5 in order to maintain the
fastening strength at the fastening portion. The casing 5 and the
cover 6 are fastened and fixed to the fixing plate 11 of the device
main body, with bolts 9 which have passed via the bush 7.
[0050] The metallic bush 7 has a cylindrical shape having a flange
7b, and is provided to pass through the flange portion 5g of the
casing 5. The bush 7 can be fixed to the casing 5 by press-fitting,
or can be fixed by disposing the bush in the metal mold to be
integrated (insert molding) by composite molding at the time of
injection molding of the casing 5. In particular, by adopting the
insert molding and by utilizing the bush 7 made of sintered metal,
the resin enters the surface recess of the sintered body, and the
bush 7 and the casing 5 are firmly joined by the anchor effect.
[0051] As illustrated in FIG. 2(b), the sealing surface 5d is a
surface which is continuous from the inner surface 5b of the
trochoid accommodating recess 5a, and is in close contact with the
surface of the cover to seal the mating surface between the casing
5 and the cover, thereby sealing the trochoid accommodating recess
5a. In the casing 5, by providing the surface of the cover side
adjacent to and continuous with the inner surface 5b as the sealing
surface 5d, it is possible to prevent the liquid from entering
between the cover and the casing from the trochoid accommodating
recess.
[0052] The internal gear pump according to the first aspect of the
present application is characterized by the positional relation
between the sealing surface of the casing and the end surface of
the bush after molding. That is, the height position of the end
surface 7a on the cover side of the bush 7 is set to a position
which is (1) higher than a bush formation surface 5e of the casing
5 around the bush, and is (2) lower than the sealing surface 5d
around the recess of the casing 5, as viewed from the bottom
surface 5c, on the basis of the bottom surface 5c of the trochoid
accommodating recess 5a. This relation is a positional relation
after molding of the casing 5.
[0053] By the relation of (1), it is possible to prevent the end
surface 7a of the bush 7 from being covered with the resin at the
time of the composite molding of the casing 5 and the bush 7. A
protrusion amount h.sub.1 of the end surface 7a of the bush 7 from
the bush formation surface 5e is, for example, 0.01 mm to 0.3 mm.
If the end surface 7a of the bush 7 protrudes even slightly, it is
possible to prevent the aforementioned covering of resin.
[0054] By the relation of (2), since the sealing surface 5d is
located at a position higher than the end surface 7a of the bush 7,
the sealing surface 5d preferentially comes into close contact with
the cover at the time of bolt fastening. Since the relation is
defined as the positional relation after molding, regardless of the
molding conditions, the sealing surface 5d is always in contact
with the cover, the sealing property of the trochoid accommodating
recess 5a can be stably ensured, and the discharging ability is
also stabilized. Further, since sufficient sealing property can
also be ensured on the sealing surface 5d, a seal ring
conventionally disposed on the outer circumference of the sealing
surface 5d can be omitted as illustrated in FIGS. 1 and 2.
[0055] Further, the height of the end surface 7a of the bush 7 and
the height of the sealing surface 5d of the casing 5 may be the
same. Also in this case, similarly, it is possible to ensure the
sealing property on the sealing surface 5d. Since the sealing
surface 5d and the cover can be more stably brought into contact
with each other, it is preferable to locate the sealing surface 5d
at a position slightly higher than the end surface 7a. A difference
h.sub.2 between the height of the end surface 7a of the bush 7 and
the height of the sealing surface 5d of the casing 5 is, for
example, 0.01 mm to 0.3 mm.
[0056] In FIG. 2(a), the casing 5 comes into sliding-contact with
the outer rotor 2 and the inner rotor 3 on the bottom surface 5c
and the inner surface 5b constituting the trochoid accommodating
recess 5a. Since the inner surface 5b of the trochoid accommodating
recess 5a is an injection-molded body portion of the resin
composition, the inner surface 5b has excellent frictional wear
characteristics with respect to the outer rotor 2. Further, the
bottom surface 5c of the trochoid accommodating recess 5a is
constituted by a disk-shaped metal plate 8 integrated with the
casing 5 by composite molding. As a result, as compared with the
case of forming the bottom surface 5c with a resin, the flatness is
excellent, and variations in the discharging performance can be
suppressed. As the metal plate 8, a sintered metal body or a melted
metal body (sheet metal pressed article) can be adopted.
[0057] Further, by forming the casing 5 as an injection-molded body
of the resin composition, a liquid suction nozzle 5h can be
integrally formed with the casing 5 with the resin composition. If
necessary, the filter 13 can be fixed to the end portion of the
liquid suction nozzle 5h, which serves as a communication path
inlet (liquid suction port) to the suction side volume chamber, by
welding or the like. Foreign matter can be prevented from entering
the pump by the filter 13. In the internal gear pump according to
the first aspect of the present application, the configuration of
the trochoid accommodating recess is not limited to the
configuration illustrated in FIG. 2, and it may be an
injection-molded body of a resin composition including the bottom
surface. This makes it possible to form the trochoid accommodating
recess, without machining by injection molding, and the process is
economical.
[0058] Another embodiment of the internal gear pump according to
the first aspect of the present invention will be described with
reference to FIG. 3. FIG. 3(a) is an axial cross-sectional view of
the internal gear pump, and FIG. 3(b) is an enlarged view of the
circumference of the sealing surface of the casing in the internal
gear pump. As illustrated in FIGS. 3(a) and 3(b), in the internal
gear pump 1, an annular groove 5f is provided in a portion which
seals the outer circumference of the trochoid accommodating recess
5a, and a seal ring 12 is assembled to the groove 5f. Other
configurations are the same as those of the internal gear pump
illustrated in FIG. 2. As illustrated in FIG. 3(b), the sealing
surface 5d is a surface continuous from the inner surface 5b of the
trochoid accommodating recess 5a, and comes into close contact with
the surface of the cover to primarily seal the trochoid
accommodating recess 5a. The height position of the end surface 7a
of the bush 7 on the cover side is set as a position which is (1)
higher than the bush formation surface 5e of the casing 5 around
the bush, and is (2) lower than the sealing surface 5d around the
recess of the casing 5, as viewed from the bottom surface 5c, on
the basis of the bottom surface 5c of the trochoid accommodating
recess 5a.
[0059] In the internal gear pump of FIG. 3, in addition to the
sealing structure, the seal ring 12 is assembled to secondarily
seal the trochoid accommodating recess 5a from the seal ring 12.
Therefore, the sealing property of the trochoid accommodating
recess 5a can be more stably secured, and the safety factor rises.
Also in a case where the seal ring 12 is provided, the protrusion
amount of the bush in the above-described sealing structure and the
like are the same. That is, also in the embodiment of FIG. 3, the
protrusion amount h.sub.1 of the end surface 7a of the bush 7 from
the bush formation surface 5e, and a difference h.sub.2 between the
height of the end surface 7a of the bush 7 and the height of the
sealing surface 5d of the casing 5 each are, for example, set to
0.01 mm to 0.3 mm.
[0060] The material of the seal ring is not particularly limited,
and rubber materials, such as hydrogenated nitrile rubber,
fluororubber, and acrylic rubber, which conform to the usage and
the use environment, may be selected. For example, in a scroll-type
compressor of an air conditioner, it is preferable to use a
hydrogenated nitrile rubber (H-NBR type) because heat resistance of
about -30.degree. C. to 120.degree. C. and oil resistance are
required.
[0061] The resin composition forming the casing uses
injection-moldable synthetic resin as a base resin. As the base
resin, for example, thermoplastic polyimide resin, polyether ketone
resin, polyether ether ketone (PEEK) resin, polyphenylene sulfide
(PPS) resin, polyamideimide resin, polyamide (PA) resin,
polybutylene terephthalate (PBT) resin, polyethylene terephthalate
(PET) resin, polyethylene (PE) resin, polyacetal resin, phenol
resin and the like are adopted. Each of these resins may be used
alone, or a polymer alloy obtained by mixing two or more of them
may be used. Among these heat-resistant resins, it is particularly
preferable to use a PPS resin, because the PPS resin is excellent
in creep resistance, load resistance, abrasion resistance, chemical
resistance and the like of molded body.
[0062] Glass fiber, carbon fiber, or inorganic filler, which is
effective for high strength, high elasticity, high dimensional
accuracy, impartation of wear resistance, and anisotropy removal of
injection molding contraction, is preferably used alone or in
appropriate combination. In particular, the combined use of glass
fiber and inorganic filler is excellent in economy and excellent in
frictional wear characteristics in oil.
[0063] In the first aspect of the present application, it is
particularly preferable to use a resin composition in which a
linear-type PPS resin is used as a base resin and glass fiber and
glass beads are blended as fillers with the base resin. With this
constitution, the oil resistance and chemical resistance are
excellent, the toughness is excellent, the warpage of the flange
portion is small due to the removal of the anisotropy of the
injection molding contraction, and the dimensional accuracy is also
greatly improved. In addition to this constitution, by omitting the
rubber seal ring as illustrated in FIG. 2, it is possible to
suitably use the internal gear pump even in a high-temperature
atmosphere exceeding 120.degree. C.
[0064] Means for mixing and kneading these various raw materials is
not particularly limited, the powder raw materials may be dry-mixed
by a Henschel mixer, a ball mixer, a ribbon blender, a Lodige
mixer, an Ultra Henschel mixer or the like, and the powder raw
materials are melt-kneaded with a melt extruder such as a
twin-screw extruder to obtain molding pellets. Further, side
feeding may be adopted for injecting the filler, when performing
the melt-kneading with a twin-screw extruder or the like. The
casing is formed, using this molding pellet, by the injection
molding. At the time of molding, a metallic bush is placed in the
metal mold and integrated by the composite molding. Further, at the
time of molding, the shape of the metal mold and the molding
conditions are set such that the bush and the casing satisfy the
above-mentioned relations (1) and (2) after molding.
[0065] In the internal gear pump of the first aspect of the present
application, in addition to the above-mentioned metals (iron,
stainless steel, sintered metal, aluminum alloy, or the like),
resin (similar to casing) can be used for the cover, and the cover
may be a composite-molded body of metal and resin. Sintered metal
(iron type, copper iron type, copper type, stainless steel type or
the like) is preferably used for the outer rotor and the inner
rotor, and iron type is particularly preferable in terms of price.
However, in a trochoid pump for pumping water, chemical liquid or
the like, a stainless steel type or the like having high rust
prevention ability may be adopted.
[0066] An embodiment of the internal gear pump according to a
second aspect of the present invention will be described with
reference to FIG. 5. FIG. 5 is an axial cross-sectional view of the
internal gear pump. As illustrated in FIG. 5, the internal gear
pump 41 includes a trochoid 44 in which an inner rotor 43 is
accommodated in an annular outer rotor 42, a trochoid accommodating
portion 46 which rotatably accommodates the trochoid 44, and a
casing 45 joined to the outside of the trochoid accommodating
portion 46 to support the trochoid accommodating portion 46. The
trochoid accommodating portion 46 includes a main body portion 47
having a cylindrical inner surface 47b and a flat plate-like inner
bottom surface 47c, and a lid portion 48 which closes an opening
portion 47a of the main body portion 47. Further, a drive shaft 49
coaxially fixed to the rotation center of the inner rotor 43 is
provided. The drive shaft 49 is supported by bearings (not
illustrated) provided in the casing 45 or the like. The lid portion
48 and the casing 45 have opening portions at portions through
which the drive shaft 49 passes. The internal gear pump 41 is
fastened and fixed to a member (not illustrated) of a device main
body with bolts via bolt fixing holes 50 formed in the flange 45b
of the casing 45.
[0067] The number of outer teeth of the inner rotor 43 is smaller
by one than the number of inner teeth of the outer rotor 42, and
the inner rotor 43 is accommodated in the outer rotor 42 in an
eccentric state in which the outer teeth are inscribed in and mesh
with the inner teeth. Volume chambers on the suction side and the
discharge side are formed between the partition points on which the
respective rotors are in contact with each other, in accordance
with the rotation direction of the trochoid 44. On the inner bottom
surface 47c of the main body portion 47 of the trochoid
accommodating portion 46 of the casing 45, a suction port
communicating with the volume chamber of the suction side and a
discharge port communicating with the volume chamber of the
discharge side are formed.
[0068] In the internal gear pump 41, as the trochoid 44 is rotated
by the drive shaft 49, liquid is sucked from the suction port into
the suction side volume chamber in which the volume increases and a
negative pressure is obtained. The suction side volume chamber is
changed to a discharge side volume chamber in which the volume
decreases and the internal pressure rises by the rotation of the
trochoid 44. The sucked liquid is discharged from the discharge
side volume chamber to the discharge port. The above-described pump
action is continuously performed by the rotation of the trochoid
44, and the liquid is continuously fed. Further, due to the liquid
sealing effect of enhancing the sealing property of each volume
chamber by the sucked liquid, the differential pressure generated
between the respective volume chambers increases, and a large pump
action is obtained.
[0069] The trochoid accommodating portion 46 (the main body portion
47 and the lid portion 48) is made of a sintered metal, and the
casing 45 is an injection-molded body of a resin composition. The
trochoid accommodating portion 46 and the casing 45 are integrally
formed (insert-molded) by composite molding, by disposing the
trochoid accommodating portion 46 in the mold at the time of the
injection molding of the casing 45. In terms of the structure,
there is a state in which a part of the resin constituting the
casing 45 enters a part of the sintered pores on the outer surface
of the trochoid accommodating portion which is a sintered body, and
is firmly joined by the anchor effect.
[0070] In the configuration illustrated in FIG. 5, a casing 45 is
formed to cover not only the main body portion 47 of the trochoid
accommodating portion 46 but also the lid portion 48. In order to
make this form, at the time of manufacturing, first, after
inserting the inner rotor 43 and the outer rotor 42 in combination
from the side of the opening portion 47a into the main body portion
47 of the trochoid accommodating portion 46, the lid portion 48 is
closed to form the trochoid accommodating portion 46 including the
rotor. By placing the trochoid accommodating portion 46 in the
injection molding metal mold to perform the above-described
composite molding, the lid portion 48 is covered and the casing 45
can be formed. With this structure, it is possible to prevent the
lid portion 48 from detaching from the main body portion 47.
[0071] Examples of the sintered metal material that can be used for
forming the trochoid accommodating portion 46 include an iron type,
a copper iron type, a copper type, a stainless steel type, and the
like. Since the price is low and adhesion to the resin casing is
excellent, it is preferable to adopt a sintered metal containing
iron as the main component (which may contain copper). Further, by
adopting a sintered metal containing iron as amain component,
higher mechanical strength can be obtained. Further, in the case of
containing copper, since copper is inferior in adhesion
(adhesiveness) to resin to iron, the content of copper is
preferably 10% by weight or less. More preferably, the copper
content is 5% by weight or less. In the trochoid pump for feeding
water, chemical liquid or the like, it is preferable to adopt a
stainless steel type or the like having high rust prevention
ability.
[0072] It is preferable to use a sintered metal that is not
impregnated with oil, as the sintered metal which forms the
trochoid accommodating portion 46. Further, when oil is used in the
molding or recompression shaping (sizing) process of the sintered
metal, it is preferable to use a non-oil-containing sintered metal
from which oil is removed by solvent washing or the like. Further,
the theoretical density ratio of the sintered metal is preferably
0.7 to 0.9. By setting the theoretical density ratio to 0.7 to 0.9,
it is possible to obtain the required denseness for securing the
strength of the trochoid accommodating portion, and to secure the
surface unevenness (sintered pores) for firmly sticking the resin
casing to the trochoid accommodating portion.
[0073] Adjustment of the accommodating portion depth in the
trochoid accommodating portion 46 can be executed by flattening the
axial cross-section of the cylindrical side wall of the main body
portion 47 and can be easily adjusted by machining.
[0074] Since the casing 45 is an injection-molded body of the resin
composition and the discharge amount design can be adjusted only
with the trochoid accommodating portion 46, the degree of design
freedom of the pump shape and the like is widened. Further, the
liquid suction nozzle 45a can be integrally formed with the casing
45 with the resin composition. If necessary, a filter for
preventing mixing of foreign matter may be fixed to the end portion
of the liquid suction nozzle 45a, which serves as a communication
path inlet (liquid suction port) to the suction side volume
chamber, by welding or the like.
[0075] The resin composition forming the casing 45 uses a synthetic
resin that can be injection-molded as a base resin. Examples of the
base resin include thermoplastic polyimide resin, polyether ketone
resin, polyether ether ketone (PEEK) resin, polyphenylene sulfide
(PPS) resin, polyamide imide resin, polyamide (PA) resin,
polybutylene terephthalate (PBT) resin, polyethylene terephthalate
(PET) resin, polyethylene (PE) resin, polyacetal resin, phenol
resin and the like. Each of these resins may be used alone, or a
polymer alloy obtained by mixing two or more kinds may be used.
Among these heat-resistant resins, it is particularly preferable to
use a PPS resin because the PPS resin is excellent in creep
resistance, load resistance, abrasion resistance, chemical
resistance and the like of molded body.
[0076] It is preferable to use glass fiber, carbon fiber, or
inorganic filler which is effective for high strength, high
elasticity, high dimensional accuracy, impartation of wear
resistance and removal of anisotropy of injection molding
contraction, alone or in combination. In particular, the combined
use of glass fiber and inorganic filler is excellent in economy and
excellent in frictional wear characteristics in oil.
[0077] In the second aspect of the present application, it is
particularly preferable to use a resin composition in which a
linear-type PPS resin is used as a base resin, and glass fiber and
glass beads are blended as fillers with the base resin. With this
constitution, the oil resistance and chemical resistance are
excellent, the toughness is excellent, the warpage of the flange
portion is small due to the removal of the anisotropy of the
injection molding contraction, and the dimensional accuracy is
greatly improved. In addition to this constitution, since the
internal gear pump has an independent trochoid accommodating
portion and does not require a rubber seal ring as in the related
art, the internal gear pump can be suitably used even in a
high-temperature atmosphere exceeding 120.degree. C.
[0078] Means for mixing and kneading these various raw materials is
not particularly limited, and the powder raw materials may be
dry-mixed by a Henschel mixer, a ball mixer, a ribbon blender, a
Lodige mixer, an Ultra Henschel mixer or the like, and the powder
raw materials may be further melted and mixed by a melt extruder
such as a twin-screw extruder or the like to obtain molding
pellets. In addition, side feeding may be adopted for charging the
fillers when performing the melt-kneading of the filler with the
twin-screw extruder or the like. The casing is formed using this
molding pellet, by injection molding. At the time of molding, the
whole of the trochoid accommodating portion or only the main body
portion is arranged in the metal mold and integrated by the
composite molding.
[0079] In the internal gear pump according to the second aspect of
the present application, it is preferable to use a sintered metal
(iron type, copper iron type, copper type, stainless steel type, or
the like) for the outer rotor and the inner rotor in the same
manner as the trochoid accommodating portion.
[0080] Another embodiment of the internal gear pump according to
the second aspect of the present invention will be described with
reference to FIG. 6. FIG. 6 is an axial cross-sectional view of the
internal gear pump. As illustrated in FIG. 6, an internal gear pump
41 has a structure in which a lid portion 48 is exposed from a
casing 45. The remaining configurations are the same as those of
the internal gear pump illustrated in FIG. 5. In the embodiment
illustrated in FIG. 6, it is possible to manufacture the internal
gear pump by a procedure of inserting each rotor into a main body
portion 47, and closing the lid portion 48, after performing the
composite molding of the main body portion 47 of a trochoid
accommodating portion 46 and the casing 45. Further, as in the case
of FIG. 5, after the trochoid accommodating portion 46 including
the rotor is assembled, it may be composite-molded with the casing.
By caulking and fixing the main body portion 47 and the lid portion
48, a bolt tightening process and the like are unnecessary, and the
main body portion 47 and the lid portion 48 can be simply and
firmly fixed.
[0081] Another embodiment of the internal gear pump according to
the second aspect of the present invention will be described with
reference to FIG. 7. FIG. 7 is an axial cross-sectional view of the
internal gear pump. As illustrated in FIG. 7, the internal gear
pump 41 has a structure in which a lid portion 48 and a casing 45
are fastened with bolts 51. Therefore, in a trochoid accommodating
portion 46, a main body portion 47 and the lid portion 48 are
brought into close contact with each other. The remaining
configurations are the same as those of the internal gear pump
illustrated in FIG. 5. If necessary, a metallic bush may be
interposed in a bolt fixing hole 50 in a flange portion 45b of the
casing 45, and the bolt fastening may be performed through the
bush. In the embodiment illustrated in FIG. 7, after performing the
composite molding of the main body portion 47 of the trochoid
accommodating portion 46 and the casing 45, each rotor is inserted
into the main body portion 47. Thereafter, the lid portion 48 is
fixed to the casing 45 by a bolt.
[0082] As described above with reference to FIGS. 5 to 7, the
configuration of the internal gear pump according to the second
aspect of the present application is not limited thereto. In any of
the embodiments, the trochoid accommodating portion is a separate
component from the casing, and by performing the composite-molding
of the casing around the trochoid accommodating portion
manufactured by precisely machining the accommodating portion depth
in advance, a configuration in which both members are joined is
obtained. As a result, there is no variation in the discharge
amount among the individual parts, and an internal gear pump having
a stable discharging ability is obtained.
INDUSTRIAL APPLICABILITY
[0083] The internal gear pump according to the first aspect and the
second aspect of the present application can be suitably used as an
internal gear pump (trochoid pump) for feeding liquid such as oil,
water, chemical liquid or the like, and in particular, the internal
gear pump can be preferably used as an electric water heater using
alternative fluorocarbon, carbon dioxide or the like as a
refrigerant, a room air conditioner, and a pump for supplying
liquid to sliding parts of a scroll-type compressor for a car air
conditioner.
REFERENCE SIGNS LIST
[0084] 1 Internal gear pump
[0085] 2 Outer rotor
[0086] 3 Inner rotor
[0087] 4 Trochoid
[0088] 5 Casing
[0089] 6 Cover
[0090] 7 Bush
[0091] 8 Metal plate
[0092] 9 Bolt
[0093] 10 Drive shaft
[0094] 11 Fixing plate of device main body
[0095] 12 Seal ring
[0096] 13 Filter
[0097] 41 Internal gear pump
[0098] 42 Outer rotor
[0099] 43 Inner rotor
[0100] 44 Trochoid
[0101] 45 Casing
[0102] 46 Trochoid accommodating portion
[0103] 47 Main body portion
[0104] 48 Lid portion
[0105] 49 Drive shaft
[0106] 50 Bolt fixing hole
[0107] 51 Bolt
* * * * *