U.S. patent application number 16/472453 was filed with the patent office on 2021-05-06 for internal gear pump.
The applicant listed for this patent is NTN CORPORATION. Invention is credited to Hiroshi AKAI, Kei HATTORI, Takayuki ITO, Tomokazu SONOZAKI.
Application Number | 20210131428 16/472453 |
Document ID | / |
Family ID | 1000005383427 |
Filed Date | 2021-05-06 |
![](/patent/app/20210131428/US20210131428A1-20210506\US20210131428A1-2021050)
United States Patent
Application |
20210131428 |
Kind Code |
A1 |
HATTORI; Kei ; et
al. |
May 6, 2021 |
INTERNAL GEAR PUMP
Abstract
To provide an internal gear pump capable of suppressing a liquid
discharge amount during a high-speed rotation by controlling
discharge pressure while achieving reduction in size, weight, cost,
and the like. An internal gear pump 1 includes: a trochoid 4 in
which an inner rotor 3 having a plurality of external teeth is
accommodated inside an outer rotor 2 having a plurality of internal
teeth in an eccentrically rotatable manner with the external teeth
and the internal teeth interdigitated with each other, and a
suction-side volume chamber for sucking liquid and a discharge-side
volume chamber for discharging the liquid sucked into the
suction-side volume chamber are formed between the internal teeth
and the external teeth; a casing formed with a recessed part 8 for
accommodating the trochoid 4; and a cover 6 that closes the
recessed part 8. An ejector 9 is provided to communicate with a
flow passage of the liquid formed on a bottom surface of the
recessed part 8 and to partially discharge the liquid in an
accommodation space of the trochoid formed by the casing and the
cover 6.
Inventors: |
HATTORI; Kei; (Mie, JP)
; AKAI; Hiroshi; (Mie, JP) ; SONOZAKI;
Tomokazu; (Mie, JP) ; ITO; Takayuki; (Mie,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NTN CORPORATION |
Osaka |
|
JP |
|
|
Family ID: |
1000005383427 |
Appl. No.: |
16/472453 |
Filed: |
December 21, 2017 |
PCT Filed: |
December 21, 2017 |
PCT NO: |
PCT/JP2017/045940 |
371 Date: |
June 21, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F04C 2240/30 20130101;
F04C 2/10 20130101 |
International
Class: |
F04C 2/10 20060101
F04C002/10 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 22, 2016 |
JP |
2016-249898 |
Mar 16, 2017 |
JP |
2017-051812 |
Nov 30, 2017 |
JP |
2017-230482 |
Claims
1. An internal gear pump including a trochoid in which an inner
rotor having a plurality of external teeth is accommodated inside
an outer rotor having a plurality of internal teeth in an
eccentrically rotatable manner with the external teeth and the
internal teeth interdigitated with each other, and a suction-side
volume chamber for sucking liquid and a discharge-side volume
chamber for discharging the liquid sucked into the suction-side
volume chamber are formed between the internal teeth and the
external teeth, the internal gear pump comprising: a casing formed
with a recessed part for accommodating the trochoid; and a cover
that closes the recessed part of the casing, wherein an ejector is
provided to communicate with a flow passage of the liquid formed on
a bottom surface of the recessed part and to partially discharge
the liquid in an accommodation space of the trochoid formed by the
casing and the cover.
2. The internal gear pump according to claim 1, wherein the ejector
comprises: a housing; a cylindrical body provided in the housing;
and an elastic body that presses the cylindrical body in a
direction opposite to pressure of the liquid in the flow passage of
the liquid, wherein the liquid is partially discharged from a
discharge flow passage between the cylindrical body and the housing
formed when the elastic body is contracted in a direction opposite
to the pressing direction by the pressure of the liquid via the
cylindrical body, and the housing and the cylindrical body include
a resin body.
3. The internal gear pump according to claim 2, wherein a through
hole communicating with the ejector is provided in a part of the
flow passage of the liquid formed on the bottom surface of the
recessed part, and a chamfered portion of an end portion of the
cylindrical body is pressed to a chamfered portion of the through
hole facing a side of the ejector.
4. The internal gear pump according to claim 1, wherein an inner
side surface of the recessed part of the casing includes a resin
body, the bottom surface of the recessed part includes a metal
body, and the ejector is fixed to the metal body.
5. The internal gear pump according to claim 1, wherein the casing
includes a liquid suction part forming a part of a flow passage to
the suction-side volume chamber of the liquid, and in the casing, a
part including the recessed part and a part including the liquid
suction part are configured separately from each other.
6. The internal gear pump according to claim 1, wherein the
internal gear pump includes a suction port for introducing the
liquid inside the accommodation space of the trochoid and the
ejector on the bottom surface of the recessed part, and the ejector
is configured to partially discharge the liquid from the suction
port through a discharge flow passage by forming the discharge flow
passage communicating the flow passage and the suction port in
accordance with pressure of the liquid.
7. The internal gear pump according to claim 6, wherein the inner
side surface of the recessed part of the casing includes a resin
body, the bottom surface of the recessed part includes a metal
plate embedded in the resin body of the casing, and the ejector is
installed within a thickness of the metal plate.
8. The internal gear pump according to claim 6, wherein the ejector
comprises: a cylindrical body; and an elastic body that presses the
cylindrical body in a direction opposite to the pressure of the
liquid in the flow passage of the liquid and is a horizontal
direction of the metal plate, wherein the elastic body is deformed
by the pressure of the liquid via the cylindrical body, so that the
pressing is released and the discharge flow passage is formed.
9. The internal gear pump according to claim 8, wherein the elastic
body includes a coil spring, a torsion spring, a leaf spring, or a
tension spring.
10. The internal gear pump according to claim 8, wherein the
cylindrical body is made of a resin and the elastic body does not
come into contact with the outer rotor and the inner rotor.
11. The internal gear pump according to claim 8, wherein a through
hole communicating with the ejector is provided in a part of the
flow passage of the liquid formed on the bottom surface of the
recessed part, and in a state in which the pressing is not
released, a tapered portion of the cylindrical body is pressed to
an inclined portion of the through hole facing a side of the
ejector, so that the flow passage is sealed by surface contact.
12. The internal gear pump according to claim 1, wherein at least
one member of the casing and the cover includes a molded body of a
resin composition, and the casing and the cover are fixed by
fitting a plurality of protrusion parts protruding from one member
to another member.
13. The internal gear pump according to claim 12, wherein the
casing and the cover are integrated with each other by a fixing
member passing through a metal bush across the casing and the
cover, and at least one of the protrusion parts is a protrusion
part of the metal bush protruding from one member of the casing and
the cover and fixed to the one member.
14. The internal gear pump according to claim 12, wherein at least
one of the protrusion parts is a claw part protruding as a part of
the molded body in one member of the casing and the cover.
15. The internal gear pump according to claim 12, wherein the resin
composition is a resin composition in which a polyphenylene sulfide
resin is used as a base resin, and at least one selected from a
glass fiber, a carbon fiber, and an inorganic filler is blended in
the polyphenylene sulfide resin.
Description
TECHNICAL FIELD
[0001] The present invention relates to an internal gear pump (a
trochoid pump) that pumps liquid such as oil, water, and chemical
solution, and more particularly, to an internal gear pump used in
an industrial machinery field, for example, an air conditioning
compressor.
BACKGROUND ART
[0002] An 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 the inner rotor
and the outer rotor fixed to a driving shaft rotate together with
the rotation of the driving shaft, so that liquid is sucked and
discharged. As such a type of pump, for example, Patent Literature
1 has been proposed. In recent years, as a pump which can reduce a
machining process and can be manufactured at a low cost, a pump
having a resin casing has been known (see Patent Literature 2).
[0003] On the basis of FIG. 19, the structure of such a type of
internal gear pump will be described. FIG. 19 is a sectional view
of an internal gear pump of the related art. As illustrated in FIG.
19, this pump 21 is mainly composed of a trochoid 24 in which an
inner rotor 23 having a plurality of external teeth is accommodated
in an annular outer rotor 22 having a plurality of internal teeth.
The trochoid 24 is rotatably accommodated in a circular trochoid
accommodation recessed part 25a formed in a columnar casing 25 with
a flange. A cover 26 is fixed to the casing 25 to close the
trochoid accommodation recessed part 25a.
[0004] The trochoid 24 is configured in such a manner that the
external teeth of the inner rotor 23 are engaged with the internal
teeth of the outer rotor 22 and the inner rotor 23 is rotatably
accommodated in the outer rotor 22 in an eccentric state. A volume
chamber on a suction-side and a discharge-side is formed between
partition points, where the rotors come into contact with each
other, in accordance with the rotation direction of the trochoid
24. A driving shaft 27 rotated by a driving source (not
illustrated) penetrates and is fixed to an axial center of the
inner rotor 23. When the inner rotor 23 rotates by the rotation of
the driving shaft 27, since the external teeth are engaged with the
internal teeth of the outer rotor 22 and the outer rotor 22 rotates
in the same direction, liquid is sucked from a suction port into
the suction-side volume chamber where its volume is increased due
to the rotation and a negative pressure state is reached. Then, the
suction-side volume chamber is changed to the discharge-side volume
chamber where the volume is decreased by the rotation of the
trochoid 24 and internal pressure is increased, so that the sucked
liquid is discharged from the discharge-side volume chamber to a
discharge port.
[0005] In an internal gear pump that is intended to send lubricant
oil to a sliding part such as a compression part and a sliding
bearing supporting a driving shaft like a scroll type compressor,
since it is difficult to form an oil film in a lower speed rotation
than a higher speed rotation, the lubrication state of the sliding
part is designed to ensure a discharge flow rate required in the
low-speed rotation. In the internal gear pump, since the flow rate
of liquid to be discharged according to the rotation of the driving
shaft is approximately proportional to the number of rotations, the
flow rate is increased and oil is oversupplied in the high-speed
rotation in view of the aforementioned design, which is not
preferable in terms of the efficiency and the like of the
compressor. In order to solve such a problem, for example, Patent
Literature 3 proposes an internal gear pump in which a liquid
discharge groove (a bypass passage) for partially discharging
liquid in a trochoid accommodation space to the exterior is
provided to a slide part between a driving shaft and a slide
bearing for supporting the driving shaft.
PRIOR ART DOCUMENTS
Patent Documents
[0006] Patent Literature 1: JP 4215160
[0007] Patent Literature 2: JP 2014-51964
[0008] Patent Literature 3: JP 2015-183631
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0009] However, in the case of employing the mechanism that
provides the bypass passage and allows the bypass passage to be
communicated, the type of the mechanism may lead to an increase in
size and weight. Furthermore, since the amount of discharge depends
on a groove shape, a groove position, and the like, it is not easy
to finely adjust an oil discharge amount and discharge pressure of
excess supply during the high-speed rotation.
[0010] In addition, there is a case where all parts constituting a
relief mechanism (a mechanism that liberates discharge pressure by
using a plunger and the like when the discharge pressure reaches
predetermined pressure) used in a general pump and the like are
manufactured by cutting or a case where they are formed integrally
with other pump members by cutting. In such a case, the
manufacturing cost is increased, and partial replacement of the
relief mechanism is not easy at the time of the occurrence of
malfunction.
[0011] An object of the present invention is, in order to solve
such a problem, to provide an internal gear pump capable of
suppressing a liquid discharge amount during a high-speed rotation
by controlling discharge pressure while achieving reduction in
size, weight, cost, and the like.
Means for Solving the Problem
[0012] An internal gear pump according to the present invention
including a trochoid in which an inner rotor having a plurality of
external teeth is accommodated inside an outer rotor having a
plurality of internal teeth in an eccentrically rotatable manner
with the external teeth and the internal teeth interdigitated with
each other, and a suction-side volume chamber for sucking liquid
and a discharge-side volume chamber for discharging the liquid
sucked into the suction-side volume chamber are formed between the
internal teeth and the external teeth, includes: a casing formed
with a recessed part for accommodating the trochoid; and a cover
that closes the recessed part of the casing, wherein an ejector is
provided to communicate with a flow passage of the liquid formed on
a bottom surface of the recessed part and to partially discharge
the liquid in an accommodation space (simply referred to as a "pump
inside") of the trochoid formed by the casing and the cover.
[0013] The ejector includes: a housing; a cylindrical body provided
in the housing; and an elastic body that presses the cylindrical
body in a direction opposite to pressure of the liquid in the flow
passage of the liquid, wherein the liquid is partially discharged
from a discharge flow passage between the cylindrical body and the
housing formed when the elastic body is contracted in a direction
opposite to the pressing direction by the pressure of the liquid
via the cylindrical body, and the housing and the cylindrical body
include a resin body.
[0014] A through hole communicating with the ejector is provided in
a part of the flow passage of the liquid formed on the bottom
surface of the recessed part, and a chamfered portion of an end
portion of the cylindrical body is pressed to a chamfered portion
of the through hole facing a side of the ejector.
[0015] An inner side surface of the recessed part of the casing
includes a resin body, the bottom surface of the recessed part
includes a metal body, and the ejector is fixed to the metal
body.
[0016] The casing includes a liquid suction part forming a part of
a flow passage to the suction-side volume chamber of the liquid,
and in the casing, a part including the recessed part and a part
including the liquid suction part are configured separately from
each other.
[0017] The internal gear pump includes a suction port for
introducing the liquid inside the accommodation space of the
trochoid and the ejector on the bottom surface of the recessed
part, and the ejector is configured to partially discharge the
liquid from the suction port through a discharge flow passage by
forming the discharge flow passage communicating the flow passage
and the suction port in accordance with pressure of the liquid.
[0018] The inner side surface of the recessed part of the casing
includes a resin body, the bottom surface of the recessed part
includes a metal plate embedded in the resin body of the casing,
and the ejector is installed within a thickness of the metal
plate.
[0019] The ejector includes: a cylindrical body; and an elastic
body that presses the cylindrical body in a direction opposite to
the pressure of the liquid in the flow passage of the liquid and is
a horizontal direction of the metal plate, wherein the elastic body
is deformed by the pressure of the liquid via the cylindrical body,
so that the pressing is released and the discharge flow passage is
formed. In particular, the elastic body includes a coil spring, a
torsion spring, a leaf spring, or a tension spring.
[0020] The cylindrical body is made of a resin and the elastic body
does not come into contact with the outer rotor and the inner
rotor.
[0021] A through hole communicating with the ejector is provided in
a part of the flow passage of the liquid formed on the bottom
surface of the recessed part, and in a state in which the pressing
is not released, a tapered portion of the cylindrical body is
pressed to an inclined portion of the through hole facing a side of
the ejector, so that the flow passage is sealed by surface
contact.
[0022] At least one member of the casing and the cover includes a
molded body of a resin composition, and the casing and the cover
are fixed by fitting a plurality of protrusion parts protruding
from one member to the other member.
[0023] The casing and the cover are integrated with each other by a
fixing member passing through a metal bush across the casing and
the cover, and at least one of the protrusion parts is a protrusion
part of the metal bush protruding from one member of the casing and
the cover and fixed to the one member.
[0024] At least one of the protrusion parts is a claw part
protruding as a part of the molded body in one member of the casing
and the cover.
[0025] The resin composition is a resin composition in which a
polyphenylene sulfide (PPS) resin is used as a base resin, and at
least one selected from a glass fiber, a carbon fiber, and an
inorganic filler is blended in the polyphenylene sulfide resin.
Effects of the Invention
[0026] The internal gear pump according to the present invention is
provided with the ejector that communicates with the flow passage
of the liquid formed on the bottom surface of the recessed part
accommodating the trochoid and partially discharges the liquid in
the pump formed by the casing and the cover, so that it is possible
to partially discharge the liquid in the pump and to suppress
excess liquid supply during a high-speed rotation. Furthermore, it
is possible to achieve reduction in size and weight compared to a
case where a bypass passage is formed.
[0027] Furthermore, the ejector includes a housing, a cylindrical
body provided in the housing, and an elastic body that presses the
cylindrical body in a direction opposite to pressure of the liquid
in the liquid flow passage, and the liquid is partially discharged
from a discharge flow passage between the cylindrical body and the
housing formed when the elastic body is contracted in a direction
opposite to the pressing direction by the pressure of the liquid
via the cylindrical body, so that a discharge amount can be
constantly held by liberating discharge pressure in the pump when
the discharge pressure reaches a certain level. In this way, it is
possible to stabilize the discharge amount by controlling the
discharge pressure during a high-speed rotation, and to prevent
oversupply of oil to the compressor. Furthermore, in the ejector,
since the housing and the cylindrical body include a resin body,
the pump can be made smaller and lighter. In particular, the
housing and the cylindrical body include an injection molded body,
so that cutting and the like are not required and the ejector can
be easily manufactured at a low cost.
[0028] Since the through hole communicating with the ejector is
provided in a part of the liquid flow passage formed on the bottom
surface of the recessed part, and the chamfered portion of the end
portion of the cylindrical body is pressed to the chamfered portion
of the through hole facing a side of the ejector, when the ejector
is closed (when the cylindrical body is not lowered), it is
possible to prevent the liquid from being leaked from the liquid
flow passage to the discharge flow passage. In this way, it is
possible to accurately control the discharge pressure.
[0029] The inner side surface of the recessed part of the casing
includes a resin body and the bottom surface of the recessed part
includes a metal body, so that it is possible to improve friction
and abrasion properties on inner side surface and to suppress the
variation of the discharge performance on the bottom surface.
[0030] Since the casing includes the liquid suction part forming a
part of the flow passage to the suction-side volume chamber of the
liquid, and in the casing, a part including the trochoid
accommodation recessed part and a part including the liquid suction
part are configured separately from each other, the fitting
performance of the ejector is improved, so that it is possible to
easily manufacture the pump having the aforementioned
configuration.
[0031] When the aforementioned excess oil supply state is continued
in the internal gear pump, since oil in an oil tank is decreased
and finally the oil in the oil tank is exhausted, there are many
cases of burning. The internal gear pump according to the present
invention forms the liquid flow passage on the bottom surface of
the recessed part accommodating the trochoid and includes the
suction port for introducing liquid inside the trochoid
accommodation space and the ejector on the bottom surface, and the
ejector is configured to partially discharge the liquid from the
suction port through the discharge flow passage by forming the
discharge flow passage communicating the flow passage and the
suction port in accordance with pressure of the liquid, so that it
is possible to partially discharge the liquid in the pump, to
suppress excess liquid supply during a high-speed rotation, and to
prevent burning.
[0032] Furthermore, when a relief mechanism used in a general pump
and the like is arranged as a separate member, the number of parts
is increased, the external appearance is greatly changed depending
on the size or arrangement thereof, and it is difficult to meet the
requirement of space saving in some cases. In the internal gear
pump according to the present invention, the ejector is provided by
the improvement of the internal structure using a part of the
existing suction port as a discharge port, so that the number of
parts is decreased and it is possible to meet the requirement of
the space saving. In particular, the bottom surface of the recessed
part of the casing includes the metal plate embedded in the resin
body of the casing and the ejector is installed within a thickness
of the metal plate, so that it is not necessary to change an
external appearance or a size compared to the existing product.
[0033] Furthermore, the ejector includes a cylindrical body, and an
elastic body that presses the cylindrical body in a direction
opposite to the pressure of the liquid in the flow passage of the
liquid and is a horizontal direction of the metal plate, and the
elastic body is deformed by the pressure of the liquid via the
cylindrical body, so that the pressing is released and the
discharge flow passage is formed. Consequently, the discharge
amount can be constantly held by liberating the discharge pressure
in the pump when the discharge pressure reaches a certain level. In
this way, it is possible to stabilize the discharge amount by
controlling the discharge pressure during a high-speed rotation,
and to prevent oversupply of oil to the compressor.
[0034] Furthermore, in the ejector, since the cylindrical body is
made of a resin and the elastic body does not come into contact
with the outer rotor and the inner rotor, even when a metal spring
and the like are used as the elastic body, it is possible to
prevent abrasion of each rotor, deterioration of the relief
mechanism, and the like.
[0035] Furthermore, the through hole communicating with the ejector
is provided in a part of the flow passage of the liquid formed on
the bottom surface of the recessed part, and in a state in which
the pressing of the cylindrical body is not released, the tapered
portion of the cylindrical body is pressed to the inclined portion
of the through hole facing a side of the ejector, so that the flow
passage is sealed by surface contact. Consequently, in the state
(that is, in a state in which the ejector is closed), it is
possible to prevent the liquid from being leaked from the liquid
flow passage to the discharge flow passage. In this way, it is
possible to accurately control the discharge pressure.
[0036] Furthermore, at least one member of the casing and the cover
includes a molded body of a resin composition, and the casing and
the cover are fixed by fitting a plurality of protrusion parts
protruding from one member to the other member, so that positioning
during assembling is facilitated, it is possible to prevent
separation or falling off of these two members, and workability is
improved.
[0037] Since the casing and the cover are integrated with each
other by the fixing member passing through the metal bush across
the casing and the cover and at least one of the protrusion parts
is a protrusion part of the metal bush protruding from one member
of the casing and the cover and fixed to the one member, when the
casing and the cover are assembled, it is possible to facilitate
the positioning of the casing and the cover by fitting the
protrusion part of the metal bush in one member to the fitting part
for the protrusion part of the other member. Furthermore, the
strength of the fastening part of the casing and the cover is
improved by the metal bush and it is possible to prevent the
loosening of the fastening part due to the creep deformation of a
resin.
[0038] Since at least one of the protrusion parts is the claw part
protruding as a part of the molded body in one member of the casing
and the cover, the claw part is also a part of the resin molded
body, is easily elastically deformed, and is superior in toughness,
and it is possible to prevent breakage and the like during
assembling.
[0039] Since the resin composition is a resin composition in which
a PPS resin is used as a base resin and at least one selected from
a glass fiber, a carbon fiber, and an inorganic filler is blended
in the PPS resin, it is superior in dimensional accuracy or
toughness and the aforementioned effect is easily obtained.
Furthermore, it is superior in oil resistance and chemical
resistance, and can also be used in a high temperature atmosphere
exceeding 120.degree. C. of a compressor and the like.
BRIEF DESCRIPTION OF THE DRAWINGS
[0040] FIG. 1 is an exploded perspective view illustrating an
example of an internal gear pump according to a first
embodiment.
[0041] FIG. 2 is an axial sectional view illustrating the internal
gear pump (a finished product) of FIG. 1.
[0042] FIG. 3 is a perspective view of a part including a pump
casing and an ejector.
[0043] FIG. 4 is a view illustrating an operation of the
ejector.
[0044] FIG. 5 is a plan view illustrating a cylindrical body and a
housing of the ejector.
[0045] FIG. 6 is a view illustrating a relation between the number
of rotations and a discharge amount.
[0046] FIG. 7 is an exploded perspective view illustrating an
example of an internal gear pump according to a second
embodiment.
[0047] FIG. 8 is an axial sectional view illustrating the internal
gear pump of FIG. 7.
[0048] FIG. 9 is a perspective view of a casing constituting the
internal gear pump.
[0049] FIG. 10 is an enlarged view of the periphery of an
ejector.
[0050] FIG. 11 is a horizontal sectional view of the periphery of
the ejector.
[0051] FIG. 12 is a schematic view illustrating a configuration
example of the ejector.
[0052] FIG. 13 is a schematic view illustrating a configuration
example of the ejector.
[0053] FIG. 14 is a schematic view illustrating a configuration
example of the ejector.
[0054] FIG. 15 is an exploded perspective view illustrating an
example of an internal gear pump according to a third
embodiment.
[0055] FIG. 16 is an axial sectional view of the internal gear pump
of FIG. 15.
[0056] FIG. 17 is an exploded perspective view illustrating another
example of the internal gear pump according to the third
embodiment.
[0057] FIG. 18 is a complete perspective view of the internal gear
pump of FIG. 17.
[0058] FIG. 19 is an axial sectional view of an internal gear pump
of the related art.
MODE FOR CARRYING OUT THE INVENTION
First Embodiment
[0059] An example of an internal gear pump according to a first
embodiment will be described on the basis of FIG. 1 and FIG. 2.
FIG. 1 illustrates an assembled perspective view of the internal
gear pump, and FIG. 2 illustrates an axial sectional view of the
internal gear pump. As illustrated in FIG. 1 and FIG. 2, the
internal gear pump 1 includes a trochoid 4 in which an inner rotor
3 is accommodated in an annular outer rotor 2, a pump casing 5a
formed with a circular recessed part (a trochoid accommodation
recessed part) 8 for rotatably accommodating the trochoid 4, a
suction casing 5b formed with a liquid suction part 5c, and a cover
6 that closes the trochoid accommodation recessed part 8 of the
pump casing 5a. The cover 6 has a shape coinciding with an outer
shape of an upper surface of a casing 5 in which the trochoid
accommodation recessed part 8 is opened. The casing 5 is composed
of the pump casing 5a and the suction casing 5b. As illustrated in
FIG. 2, the pump casing 5a, the suction casing 5b, and the cover 6
are integrated with one another by a fixing screw 13 passing
through a bush 11, and are fastened and fixed to a plate (not
illustrated) of the device body. Furthermore, the internal gear
pump 1 has a driving shaft 10 fixed coaxially to the rotation
center of the inner rotor 3.
[0060] The number of external teeth of the inner rotor 3 is smaller
than that of internal teeth of the outer rotor 2 by 1, and the
inner rotor 3 is accommodated in the outer rotor 2 in an eccentric
state in which the external teeth are inscribed in and
interdigitated with the internal teeth. A volume chamber on a
suction-side and a discharge-side is formed between partition
points, where the rotors come into contact with each other, in
accordance with the rotation direction of the trochoid 4. A bottom
surface 8a of the trochoid accommodation recessed part 8 of the
casing 5 is provided with a liquid flow passage 15 including a
suction port communicating with the volume chamber on the suction
side and a discharge port communicating with the volume chamber on
the discharge side. Liquid is pumped from the discharge port to a
compression part (not illustrated) at an upper side in the drawing
through a discharge flow passage at the center of the driving shaft
10.
[0061] In the internal gear pump 1, liquid is sucked from the
suction port into the suction-side volume chamber of the pump,
where its volume is increased and a negative pressure state is
reached due to the rotation of the trochoid 4 by the driving shaft
10. The suction-side volume chamber is changed to the
discharge-side volume chamber where its volume is decreased and
internal pressure is increased due to the rotation of the trochoid
4, so that the sucked liquid is discharged from the discharge-side
volume chamber to the discharge port. The aforementioned pump
operation is continuously performed by the rotation of the trochoid
4, so that liquid is continuously pumped. Moreover, due to the
liquid seal effect that the sealability of each volume chamber is
enhanced by the sucked liquid, differential pressure between the
volume chambers is increased, so that a large pump operation is
obtained.
[0062] In the internal gear pump 1, although the material of each
member is not particularly limited, it is preferable that the inner
side surface of the recessed part of the casing is made of a resin
body and the bottom surface of the recessed part is made of a metal
body. As illustrated in FIG. 2, the pump casing 5a is in sliding
contact with the outer rotor 2 and the inner rotor 3 at the bottom
surface 8a and the inner side surface 8b constituting the trochoid
accommodation recessed part 8. The inner side surface 8b of the
trochoid accommodation recessed part 8 is made of a resin body, so
that the friction and abrasion properties with the outer rotor 2
are improved. Furthermore, the bottom surface 8a of the trochoid
accommodation recessed part 8 is composed of a disk-like metal
plate 7 integrated with the pump casing 5a by composite molding. In
this way, flatness is improved compared to a case where the bottom
surface 8a is made of a resin, and it is possible to suppress the
variation of discharge performance. As the metal plate 7, it is
possible to employ a sintered metal body or a molten metal body (a
sheet-pressed component).
[0063] The casing 5 is composed of two members of the pump casing
5a and the suction casing 5b, so that an ejector 9 to be described
below is fixed to the pump casing 5a and then can be integrated
with the suction casing 5b and the cover 6. In this way, the
fitting performance of the ejector 9 is improved, so that it is
possible to easily manufacture the pump having the ejector.
Furthermore, the liquid suction part 5c is provided in the suction
casing 5b. As needed, a filter 14 can be fixed to an end portion of
the liquid suction part 5c serving as a communication passage inlet
(a liquid suction port) up to the suction-side volume chamber by
welding and the like. It is possible to prevent a foreign matter
from entering the pump by the filter 14.
[0064] In the internal gear pump 1, as a material of the cover 6,
the pump casing 5a, and the suction casing 5b, it is possible to
use a metal (an iron, a stainless steel, a sintered metal, an
aluminum alloy and the like) or a resin (a PPS resin, a
polybutylene terephthalate (PBT) resin, a resin composition
containing a filler blended in the PPS resin and the PBT resin, and
a composite product of the metal and the resin may be used. As
described above, preferably, at least the pump casing 5a is made of
a resin material and is a composite product with the metal plate 7.
Furthermore, it is preferable to use a sintered metal (an
iron-based, a copper iron-based, a copper-based, a stainless-based
metal, and the like) as a material of the outer rotor and the inner
rotor, and the iron-based metal is more preferable in terms of
cost. In addition, in the trochoid pump that pumps water, chemical
solution, and the like, it is sufficient if the stainless-based
metal with high rust preventing capacity and the like are
employed.
[0065] Furthermore, in the pump casing 5a, the trochoid
accommodation recessed part 8 is provided on the outer peripheral
part thereof with a groove, and a seal ring 12 is assembled to the
groove. By assembling the seal ring 12, it is possible to prevent
leakage of liquid from the matching surface of the pump casing 5a
and the cover 6 and to suppress the variation of a discharge
amount, and the safety rate becomes higher.
[0066] In the internal gear pump 1, the liquid flow passage 15 is
provided with the ejector 9 for partially discharging liquid in the
accommodation space of the trochoid 4 to the exterior. As
illustrated in FIG. 1 and FIG. 2, the ejector 9 includes a housing
9a, a cylindrical body 9c provided in the housing 9a, and a spring
9b serving as an elastic body pressing the cylindrical body 9c in a
direction toward the inside of the pump. The direction toward the
inside of the pump is a direction opposite to the pressure of
liquid in the liquid flow passage. A diameter of the cylindrical
body 9c, which faces the spring side, is smaller than that of the
inside of the pump, and the small diameter part is inserted and
fitted to the spring 9b. An accommodation part of the housing 9a
for accommodating the cylindrical body 9c is provided with a space
where the cylindrical body 9c is displaceable by elastic
deformation of the spring 9b. Furthermore, the metal plate 7 is
formed with a through hole 7a for communicating the accommodation
part of the cylindrical body of the ejector 9 and the liquid flow
passage 15. The elastic force of the spring 9b can be adjusted by
an adjustment screw 9g.
[0067] On the basis of FIG. 3, the fixing mode of the ejector will
be described. FIG. 3 is a perspective view of a part including the
pump casing (including the metal plate) and the ejector. The
housing 9a of the ejector 9 is fixed to the metal plate 7
constituting the trochoid accommodation recessed part by fixing
screws 9d. The cylindrical body 9c is pressed by the spring 9b so
as to close the aforementioned through hole 7a. The through hole 7a
is provided in the liquid flow passage 15 (see FIG. 2) including
the discharge port communicating with the discharge-side volume
chamber. The ejector 9 is fixed to an approximate center of the
metal plate 7. The ejector 9 is configured not to interfere with a
suction port 7b communicating with the suction-side volume chamber
and the pump casing 5a. Furthermore, as illustrated in FIG. 2, the
ejector 9 is arranged inside the liquid suction part 5c of the
suction casing 5b.
[0068] On the basis of FIG. 4, the operation of the ejector will be
described. (a) of FIG. 4 is an enlarged sectional view of the
periphery of the ejector when no liquid is discharged, and (b) of
FIG. 4 is an enlarged sectional view of the periphery of the
ejector when liquid is discharged. The pressure (discharge
pressure) of the liquid in the liquid flow passage 15 is applied to
the end portion of the cylindrical body 9c, which faces the liquid
flow passage 15 side. As illustrated in (a) of FIG. 4, in the range
in which the discharge pressure generated inside the pump does not
exceed prescribed pressure (a setting value at which discharge is
started), the spring 9b is not pushed and the cylindrical body 9c
is pressed by the spring 9b so as to close the through hole 7a of
the metal plate 7. Specifically, a chamfered portion 9e of the end
portion of the cylindrical body 9c is pressed to a chamfered
portion 7c of the through hole 7a, which faces the ejector side. In
this way, when the discharge pressure does not exceed the
prescribed pressure, the end portion of the cylindrical body 9c
slightly enters the through hole 7a and the flow passage is sealed
by surface contact between the chamfered portions of both the
members, so that it is possible to prevent liquid from being leaked
from the liquid flow passage 15 to a discharge flow passage.
[0069] As illustrated in (b) of FIG. 4, in the range in which the
discharge pressure exceeds the prescribed pressure due to an
increase in the number of rotations, the spring 9b is pushed by the
pressure of the liquid via the cylindrical body 9c and contracted,
so that the cylindrical body 9c is separated from the through hole
7a. In such a state, a discharge flow passage 9f is formed between
the cylindrical body 9c and the housing 9a and the liquid in the
pump is partially discharged to the exterior through the discharge
flow passage 9f. In this way, it is possible to suppress excess
liquid supply during a high-speed rotation. When the aforementioned
spring is employed as an elastic body, the prescribed pressure can
be set by specifying elastic force by a spring constant and a free
length thereof. In this way, it is also possible to appropriately
set a liquid discharge amount. In addition, as the elastic body, a
rubber material and the like may also be employed.
[0070] A process in which liquid is discharged by the discharge
flow passage will be described on the basis of FIG. 4 and FIG. 5.
(a) of FIG. 5 is a plan view illustrating the housing of the
ejector and (b) of FIG. 5 is a plan view illustrating a state in
which the cylindrical body is accommodated in the housing. As
illustrated in FIG. 5, in the ejector 9, a gap is formed between
the cylindrical body 9c and the housing 9a as the discharge flow
passage 9f. As illustrated in (a) of FIG. 4, in the state in which
the cylindrical body 9c is pressed to the through hole 7a, since
there is no gap between the cylindrical body 9c and the through
hole 7a and the discharge flow passage 9f and the liquid flow
passage 15 do not communicate with each other, the liquid in the
pump is not discharged. As illustrated in (b) of FIG. 4, when the
cylindrical body 9c is pushed to the side of the housing 9a, since
the discharge flow passage 9f and the through hole 7a are connected
to each other and the discharge flow passage 9f and the liquid flow
passage 15 communicate with each other. In this way, the liquid in
the pump can be partially discharged to the exterior from the
discharge flow passage 9f.
[0071] In the ejector 9, it is preferable that the cylindrical body
9c and the housing 9a are made of a resin body. The resin body is a
molded body of a resin composition, and is preferably an injection
molded body of a resin composition. When the resin is employed as a
material, it is possible to achieve reduction in size and weight
compared to metal cutting products. Furthermore, when the injection
molded body of the resin is employed, it is possible to easily
manufacture the ejector 9 at a low cost. As examples of an
injection-moldable synthetic resin (base resin) constituting such a
resin composition, there are a thermoplastic polyimide resin, a
polyether ketone (PEK) resin, a polyether ether ketone (PEEK)
resin, a PPS resin, a polyamide-imide resin, a polyamide (PA)
resin, a PBT resin, a polyethylene terephthalate (PET) resin, a
polyethylene (PE) resin, a polyacetal resin, a phenol resin, and
the like. These resins may be used alone or may be a polymer alloy
in which two or more types of resins are mixed. Among these resins,
it is more preferable to use the PPS resin because it is superior
in creep resistance, load resistance, abrasion resistance, chemical
resistance, and the like of molded body.
[0072] It is preferable to use a glass fiber, a carbon fiber, or an
inorganic filler, which is effective for high strength, high
elasticity, high dimension accuracy, and imparting abrasion
resistance and removing anisotropy of injection molding shrinkage,
alone or in combination as appropriate. Among them, the combination
of the glass fiber and the inorganic filler is superior in economic
efficiency and is superior in friction and abrasion properties in
oil. In particular, since the cylindrical body is pressed to the
metal plate and the like, it is preferable to employ the
aforementioned resin material superior in abrasion resistance as
the material of the cylindrical body.
[0073] So far, the ejector has been described on the basis of FIG.
1 to FIG. 5; however, the ejector according to the first embodiment
is not limited thereto and any mechanism can be employed that is
fixable to the bottom surface side of the trochoid accommodation
recessed part and is configured to partially discharge liquid in
the trochoid accommodation space by communicating with the liquid
flow passage formed on the bottom surface.
[0074] FIG. 6 illustrates a relation between the number of
rotations and the discharge flow rate in the internal gear pump. A
change in the relation between the number of rotations and the
discharge flow rate was evaluated in the pump (the present
invention in the drawing) including the ejection structure (FIG. 1
to FIG. 5) according to the first embodiment and the pump (the
related art in the drawing) in which only the ejection structure is
not provided and the other configurations are the same. As
illustrated in FIG. 6, the number of rotations and the discharge
amount are roughly directly proportional to each other. In the pump
of the related art, the discharge amount increases in the
high-speed rotation region (after 8000 rotations), but in the pump
according to the first embodiment, the discharge amount is
approximately constant in the equivalent high-speed rotation
region. This is considered to be because the ejector operates (the
cylindrical body is pushed) in the high-speed rotation region and
excess oil is discharged in the pump according to the first
embodiment. In an internal gear pump such as a scroll type
compressor, since it is designed to ensure a discharge flow rate
required in the low-speed rotation, the flow rate is likely to
increase during the high-speed rotation, and when there is no
ejector as in the related art, oil may be oversupplied. In
contrast, in the present invention, the liquid in the pump can be
partially discharged to the exterior by the ejector, so that it is
possible to suppress excess liquid supply during the high-speed
rotation.
Second Embodiment
[0075] An example of an internal gear pump according to a second
embodiment will be described on the basis of FIG. 7 and FIG. 8.
FIG. 7 illustrates an assembled perspective view of the internal
gear pump, and FIG. 8 illustrates an axial sectional view of the
internal gear pump. As illustrated in FIG. 7 and FIG. 8, the
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 circular recessed part (a trochoid accommodation recessed
part) 8 for rotatably accommodating the trochoid 4, and a cover 6
that closes the trochoid accommodation recessed part 8 of the
casing 5. In the second embodiment, differently from the first
embodiment, the casing 5 is composed of one member. The cover 6 has
a shape coinciding with an outer shape of an upper surface of the
casing 5 in which the trochoid accommodation recessed part 8 is
opened. As illustrated in FIG. 8, the casing 5 and the cover 6 are
integrated with each other by a fixing screw 13 passing through a
bush 11, and are fastened and fixed to the plate (not illustrated)
of the device body.
[0076] The bottom surface 8a of the trochoid accommodation recessed
part 8 of the casing 5 is provided with a suction port 7b (see FIG.
10) communicating with a volume chamber on a suction side, a
discharge port communicating with a volume chamber on a discharge
side, and a liquid flow passage 15. Liquid is pumped from the
discharge port to a compression part (not illustrated) at an upper
side in the drawing through a discharge flow passage at the center
of a driving shaft 10. The other basic configurations of the pump
are the same as those in the first embodiment.
[0077] In the internal gear pump 1', as a material of the cover 6
and the casing 5, similarly to the first embodiment, it is possible
to use a metal or a resin, and a composite product of the metal and
the resin may be used. Furthermore, it is preferable to use a
sintered metal (an iron-based, a copper iron-based, a copper-based,
a stainless-based metal, and the like) as a material of the outer
rotor and the inner rotor, and the iron-based metal is more
preferable in terms of cost. In addition, in the trochoid pump that
pumps water, chemical solution, and the like, it is sufficient if
the stainless-based metal with high rust preventing capacity and
the like are employed.
[0078] In the internal gear pump 1', although the material of the
aforementioned casing and the like is not particularly limited, it
is preferable that the inner side surface of the recessed part of
the casing is made of a resin body and the bottom surface of the
recessed part is made of a metal body such as a metal plate. As
illustrated in FIG. 8, the casing 5 is in sliding contact with the
outer rotor 2 and the inner rotor 3 at the bottom surface 8a and
the inner side surface 8b constituting the trochoid accommodation
recessed part 8. The inner side surface 8b of the trochoid
accommodation recessed part 8 is made of a resin body, so that the
friction and abrasion properties with the outer rotor 2 are
improved. Furthermore, the liquid suction part 5c is provided in
the casing 5. The casing 5 is made of a resin body, so that the
liquid suction part 5c can also be integrally formed at the time of
molding.
[0079] Furthermore, in the embodiment illustrated in FIG. 8, the
bottom surface 8a of the trochoid accommodation recessed part 8 is
composed of the disk-like metal plate 7 integrally embedded in the
resin body by composite molding with the casing 5. In this way,
flatness is improved compared to a case where the bottom surface 8a
is made of a resin, and it is possible to suppress the variation of
discharge performance. As the metal plate 7, it is possible to
employ a sintered metal body or a molten metal body (a
sheet-pressed component).
[0080] The internal gear pump 1' according to the second embodiment
has an ejector 9' for partially discharging liquid in the
accommodation space of the trochoid. The ejector will be described
on the basis of FIG. 9 to FIG. 11. FIG. 9 is a perspective view of
the casing, FIG. 10 is an enlarged view of the periphery of the
ejector, and FIG. 11 is a horizontal sectional view of the
periphery of the ejector. As illustrated in FIG. 9 and FIG. 10, in
the composite molded article of the casing 5 and the metal plate 7,
the bottom surface 8a of the recessed part 8 of the casing 5 is
provided with the suction port 7b for introducing liquid into the
inside of the pump, the liquid flow passage 15, and the ejector 9'
for partially discharging the liquid in the pump. The ejector 9' is
configured to partially discharge the liquid from the suction port
7b through the discharge flow passage 9j by forming a discharge
flow passage 9j communicating the liquid flow passage 15 and the
suction port 7b in accordance with the pressure of the liquid. In
the internal gear pump, when liquid is introduced into the inside
of the pump from the suction port 7b, the liquid is discharged from
the discharge port (a part connected to the discharge flow passage
at the center of the driving shaft) via the liquid flow passage 15
and the volume chamber in the trochoid. In the second embodiment,
the discharge flow passage 9j is formed in the middle of the liquid
flow passage 15 to partially recirculate the liquid to the suction
port 7b. The discharge flow passage 9j is a flow passage that is
temporarily formed by a relief mechanism, which is different from a
normal liquid flow passage directed to the discharge port from the
suction port 7b.
[0081] As illustrated in FIG. 10, the ejector 9' of this embodiment
includes a cylindrical body 9h and a spring 9i for pressing the
cylindrical body in a predetermined direction. The pressing
direction is a direction opposite to the pressure of the liquid in
the liquid flow passage 15 and is a horizontal direction of the
metal plate 7. A diameter of the cylindrical body 9h, which faces
the spring side, is smaller than that of the liquid flow passage 15
side, and the small diameter part is inserted and fitted to the
spring 9i. An accommodation part of the metal plate 7 for
accommodating the cylindrical body 9h is provided with a space
where the cylindrical body 9h is displaceable by elastic
deformation of the spring 9i. The metal plate 7 is formed with a
through hole 7a for communicating a space where the cylindrical
body 9h of the ejector 9' is accommodated and the liquid flow
passage 15.
[0082] As illustrated in FIG. 11, the spring 9i is fitted and fixed
to a spring fixing part 7d provided on the metal plate 7. The
spring fixing part 7d is integrated with the metal plate 7 by
post-processing and the like of the metal plate 7 and may be fixed
by bonding, fitting, and the like of a separate member. Preferably,
the spring fixing part 7d is integrated with the metal plate 7
because the number of parts can be reduced and a failure rate is
also lowered. The cylindrical body 9h is pressed by the spring 9i
so as to close the through hole 7a. The pressure (discharge
pressure) of the liquid in the liquid flow passage 15 is applied to
the end portion of the cylindrical body 9h, which faces the liquid
flow passage 15 side. In this configuration, when the discharge
pressure exceeds prescribed pressure due to an increase in the
number of rotations, the spring 9i is pushed by the pressure of the
liquid via the cylindrical body 9h and contracted, so that the
cylindrical body 9h is separated from the through hole 7a and the
pressing is released. In such a state, the discharge flow passage
9j (see FIG. 12 and the like) passing through between the
cylindrical body 9h and the wall surface of the metal plate 7 is
formed, so that the liquid in the pump is partially discharged to
the exterior through the discharge flow passage 9j. In this way, it
is possible to suppress excess liquid supply during a high-speed
rotation.
[0083] As illustrated in FIG. 11, the ejector 9' is installed
within the thickness of the metal plate 7. Due to the structure of
the space-saving ejector, the thickness of the metal plate 7 can be
allowed to be constant regardless of the presence or absence of the
ejector. Therefore, it is possible to appropriately employ the
ejector without changing an external appearance or a size of the
internal gear pump with the conventional structure and dimension.
Furthermore, the ejector 9' has a structure in which only the
cylindrical body 9h comes into contact with the outer rotor 2 or
the inner rotor 3 and the spring 9i or the spring fixing part 7d do
not come into contact with the outer rotor 2 or the inner rotor 3.
In such a structure, the cylindrical body 9h is made of a resin
body, so that it is possible to prevent abrasion of each rotor,
deterioration of the relief mechanism, and the like.
[0084] In the ejector 9', preferably, the cylindrical body 9h is
made of a resin body as described above. The resin body is a molded
body of a resin composition, and is preferably an injection molded
body of a resin composition. When the resin is employed as a
material, it is easy to achieve reduction in size and weight and it
is also superior in a sliding property. Furthermore, when the
injection molded body of the resin is employed, it is possible to
easily manufacture the ejector 9' at a low cost. An
injection-moldable synthetic resin (base resin) constituting such a
resin composition is the same as that used for the cylindrical body
9c or the housing 9a of the ejector 9 according to the first
embodiment, and it is more preferable to use the PPS resin because
it is superior in creep resistance, abrasion resistance, chemical
resistance, and the like of molded body.
[0085] It is preferable to use a glass fiber, a carbon fiber, or an
inorganic filler, which is effective for high strength, high
elasticity, high dimension accuracy, and imparting abrasion
resistance and removing anisotropy of injection molding shrinkage,
alone or in combination as appropriate. Among them, the combination
of the glass fiber and the inorganic filler is superior in economic
efficiency and is superior in friction and abrasion properties in
oil. In particular, since each surface of the cylindrical body is
in sliding contact with the metal plate or each rotor, it is
preferable to employ the aforementioned resin material superior in
abrasion resistance as the material of the cylindrical body.
[0086] Furthermore, in order to prevent abrasion of the cylindrical
body, a lid may be provided on the ejector to separate the rotors
from each other. In addition, the ejector may be disposed on the
outer side (a part may protrude from the recessed part) of the
bottom surface, or may be disposed in a position where the ejector
is not in sliding contact with the inner rotor.
[0087] When the spring is employed as an elastic body, the
prescribed pressure can be set by specifying elastic force by a
spring constant and a free length thereof. In this way, it is also
possible to appropriately set a liquid discharge amount. As the
spring, it is possible to employ a torsion spring, a leaf spring,
or a tension spring, in addition to the coil spring illustrated in
FIG. 9 to FIG. 11. Furthermore, as the elastic body, a rubber
material and the like may be employed.
[0088] Hereinafter, configuration examples of the ejector will be
described on the basis of FIG. 12 to FIG. 14. FIG. 12 to FIG. 14
are schematic views of the periphery of the ejector. The ejector
illustrated in (a) of FIG. 12 is an example in which the coil
spring 9i is used as the elastic body similarly to FIG. 9 to FIG.
11. In the range in which the discharge pressure generated inside
the pump does not exceed the prescribed pressure, the coil spring
9i is not pushed and the cylindrical body 9h is pressed by the coil
spring 9i so as to close the through hole 7a of the metal plate. In
the state in which the cylindrical body 9h is pressed to the
through hole 7a, since there is no gap between the cylindrical body
9h and the through hole 7a and the discharge flow passage 9j is not
formed between the suction port 7b and the liquid flow passage 15,
the liquid in the pump is not discharged. When the cylindrical body
9h is pushed, the coil spring 9i is contracted and the discharge
flow passage 9j is formed, so that the liquid in the pump can be
partially discharged to the exterior from the discharge flow
passage 9j and the suction port 7b.
[0089] The ejector illustrated in (b) of FIG. 12 is an example in
which a leaf spring 9k is used as the elastic body. The leaf spring
9k is provided by fixing its one end to the metal plate so as to
close the through hole 7a of the metal plate. In the range in which
the discharge pressure generated inside the pump does not exceed
the prescribed pressure, the leaf spring 9k is not deformed and the
through hole 7a is blocked. In this way, since the discharge flow
passage 9j is not formed between the suction port 7b and the liquid
flow passage 15, the liquid in the pump is not discharged. When the
leaf spring receives the pressure of the liquid and is deformed
such that a non-fixed side end portion is pushed, the discharge
flow passage 9j is formed.
[0090] The ejector illustrated in (a) of FIG. 13 is an example in
which a separate leaf spring 9k is used as the elastic body. The
leaf spring 9k is provided by fixing its both ends to the metal
plate and supports the cylindrical body 9h. In the range in which
the discharge pressure generated inside the pump does not exceed
the prescribed pressure, the cylindrical body 9h is pressed by the
leaf spring 9k so as to close the through hole 7a of the metal
plate. When the cylindrical body 9h is pushed, the leaf spring 9k
is deformed, so that the discharge flow passage 9j is formed.
[0091] The ejector illustrated in (b) of FIG. 13 is an example in
which torsion springs 9l are used as the elastic body. Each torsion
spring 9l is provided by fixing its one end to the metal plate, so
that the two torsion springs 9l support the cylindrical body 9h
from both end walls of the flow passage. In the range in which the
discharge pressure generated inside the pump does not exceed the
prescribed pressure, the cylindrical body 9h is pressed by the
torsion springs 9l so as to close the through hole 7a of the metal
plate. When the cylindrical body 9h is pushed, the torsion springs
9l are deformed, so that the discharge flow passage 9j is
formed.
[0092] The ejector illustrated in FIG. 14 is an example in which a
tension spring 9m is used as the elastic body. The tension spring
9m is provided by fixing its one end to a part of the flow passage
of the metal plate and pulls a lid 9n against the pressure of the
liquid. In the range in which the discharge pressure generated
inside the pump does not exceed the prescribed pressure, the lid 9n
is pulled by the tension spring 9m so as to close the through hole
7a of the metal plate. When the lid 9n is moved by the pressure of
the liquid, the tension spring 9m is deformed, so that the
discharge flow passage 9j is formed.
[0093] As illustrated in FIG. 12, FIG. 13, and the like,
preferably, the cylindrical body 9h forms a tapered portion and the
like at its end portion facing the through hole 7a side and seals
the flow passage by surface contact with an inclined portion formed
at the edge of the through hole 7a. In this way, it is possible to
prevent liquid from being leaked from the liquid flow passage 15 to
the suction port 7b.
[0094] So far, the ejector has been described on the basis of FIG.
9 to FIG. 14; however, the ejector according to the second
embodiment is not limited thereto and any means can be employed
that is configured to partially discharge the liquid from the
suction port through the discharge flow passage by forming the
discharge flow passage communicating the liquid flow passage and
the suction port in accordance with the pressure of liquid.
[0095] Normally, the number of rotations and the discharge amount
are roughly directly proportional to each other, and in the pump of
the related art, the discharge amount tends to increase in the
high-speed rotation region (after 8000 rotations) (see FIG. 6). In
an internal gear pump such as a scroll type compressor, since it is
designed to ensure a discharge flow rate required in the low-speed
rotation, the flow rate is likely to increase during the high-speed
rotation, and when there is no ejector as in the related art, oil
may be oversupplied. In contrast, in the second embodiment,
similarly to the first embodiment, the liquid in the pump can be
partially discharged to the exterior by the ejector, so that it is
possible to suppress excess liquid supply during the high-speed
rotation.
Third Embodiment
[0096] In the aforementioned first embodiment and second
embodiment, in the internal gear pump, as the material of the
casing and the cover, it is possible to use a metal or a resin and
the material is not particularly limited. For example, in recent
years, as a pump which can reduce a machining process and can be
manufactured at a low cost, a pump having a resin casing has been
known.
[0097] A mounting structure of the casing and the cover in such a
pump will be described using FIG. 19. In FIG. 19, 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.
The casing 25 and the cover 26 are fastened and fixed to a fixed
plate 30 of an actual device by a bolt 29 passing through a metal
bush 28 provided in the casing 25. The casing 25 and the cover 26
have a mutually flat planar shape and seal the trochoid
accommodation recessed part 25a.
[0098] As described above, such an internal gear pump is bolted in
a state in which the resin casing and the metal cover overlap each
other when being mounted on an actual device. In general, since a
resin molded article has a low mechanical strength, the strength of
the fastening part is improved by insert-molding the aforementioned
metal bush. However, since a boundary surface between the casing
and the cover is a plane, it is necessary to visually confirm a
deviation and the like of a bolt hole in the metal bush on the
casing side and the cover, and to perform the positioning of the
casing and the cover. Furthermore, when being mounted on the actual
device or during transport, the housing and the cover may separate
or may fall off. In particular, when being mounted on the actual
device, the housing and the cover may fall off and workability may
deteriorate due to the mounting posture of the pump.
[0099] In this regard, in the internal gear pump according to the
third embodiment, in order to facilitate the positioning of the
casing and the cover during assembling and to prevent separation or
falling off of these two members, the casing and the cover are
fixed by allowing a plurality of protruding parts protruding from
one member to be fitted to the other member. As the protruding
part, for example, a metal bush fixed to a resin casing may be
used, or a claw part provided on a resin casing or cover may be
used.
[0100] The internal gear pump according to the third embodiment
using the metal bush will be described on the basis of FIG. 15 and
FIG. 16. FIG. 15 is an assembled perspective view of an example of
the internal gear pump, and FIG. 16 is an axial sectional view of
the internal gear pump. The internal gear pump 1'' illustrated in
FIG. 15 and FIG. 16 is a pump which does not have the
aforementioned ejector (for example, the ejector 9 or the ejector
9').
[0101] As illustrated in FIG. 15 and FIG. 16, the internal gear
pump 1'' includes a trochoid 4 in which an inner rotor 3 is
accommodated in an annular outer rotor 2, a pump casing 5a formed
with a circular recessed part (a trochoid accommodation recessed
part) 8 for rotatably accommodating the trochoid 4, a suction
casing 5b formed with a liquid suction part 5c, and a cover 6 that
closes the trochoid accommodation recessed part 8 of the pump
casing 5a. A casing 5 is composed of two members of the pump casing
5a and a suction casing 5b. Three metal bushes 16 are fixed to the
suction casing 5b. As illustrated in FIG. 16, the pump casing 5a,
the suction casing 5b, and the cover 6 are fixed to a fixed plate
of an actual device with bolts 13, which are fixing members passing
through the metal bushes 16 across the casings and cover, and
integrated with one another. The fixing member is not limited to
the bolt 13, and any members may be used if they can fix each
member and for example, a screw, a pin, and the like may be
used.
[0102] The bottom surface 8a of the trochoid accommodation recessed
part 8 of the casing 5 is provided with a liquid flow passage
including a suction port communicating with a volume chamber on a
suction side and a discharge port communicating with a volume
chamber on a discharge side. Liquid is pumped from the discharge
port to a compression part (not illustrated) at an upper side in
the drawing through a discharge flow passage at the center of a
driving shaft 10. The other basic configurations of the pump are
the same as those in the first embodiment.
[0103] In the internal gear pump according to the third embodiment,
at least one member of the casing and the cover is a molded body (a
resin body) of a resin composition. In this way, the pump can
reduce a machining process and can be manufactured at a low cost.
The internal gear pump according to the third embodiment has a
configuration employing such a resin casing and the like,
facilitates the positioning of the casing and the cover during
assembling, and prevents separation or falling off of these two
members. In the embodiment of FIG. 15 and FIG. 16, the almost whole
of the casing 5 and the cover 6, that is, the cover 6, the pump
casing 5a, and the suction casing 5b are made of a resin body and
are integrated with one another by the metal bush 16 and the bolt
13. In addition, it is sufficient if a member for fixing at least
the metal bush 16 is a resin body, and for example, the cover 6 may
be made of a metal (iron, a stainless steel, a sintered metal, an
aluminum alloy, and the like).
[0104] As illustrated in FIG. 15 and FIG. 16, the metal bush 16 is
fixed to a flange part 5d of the suction casing 5b. A protruding
part of the metal bush 16 from the suction casing 5b is allowed to
be fitted to a fitting part 5e of the pump casing 5a and a fitting
part 6a of the cover 6, so that it is possible to facilitate the
positions of these members. Furthermore, by interposing the metal
bush 16, even when one or both of the casing 5 and the cover 6 is
made of a resin body, it is possible to improve the strength of the
fastening parts of both members and to prevent the loosening of the
fastening part due to the creep deformation of a resin. Moreover,
during mounting or transport, it is possible to prevent separation
or falling off of a temporary assembly (the casing and the cover).
In addition, it is possible to prevent a foreign matter from
entering the rotor part.
[0105] Furthermore, preferably, the length of the metal bush 16 is
adjusted such that the distal end of the metal bush 16 during
assembling does not protrude from the upper end surface 6b of the
fitting part 6a of the cover 6. More preferably, the distal end of
the metal bush 16 is shaped to be recessed from the upper end
surface 6b of the fitting part 6a of the cover 6. In this way, it
is possible to prevent interference between the fixed plate of an
actual device and the metal bush 16.
[0106] The metal bush 16 can be made of an arbitrary metal such as
an iron, a stainless steel, and a sintered metal; preferably, the
metal bush 16 is made of the sintered metal. When the metal bush is
made of the sintered metal and is subjected to composite molding
(insert molding) with the suction casing, since the resin enters
the recess of the surface of the sintered metal of the bush, it is
firmly bonded by an anchor effect. In this way, even when the metal
bush is designed to protrude longer from the injection molded body
such as the casing, it is possible to prevent detachment of the
metal bush during transport or mounting.
[0107] In the pump casing, preferably, the inner side surface of
the trochoid accommodation recessed part is made of a resin body
and the bottom surface of the recessed part is made of a metal
body. As illustrated in FIG. 16, the pump casing 5a is in sliding
contact with the outer rotor 2 and the inner rotor 3 at the bottom
surface 8a and the inner side surface 8b constituting the trochoid
accommodation recessed part 8. The inner side surface 8b of the
trochoid accommodation recessed part 8 is made of a resin body, so
that the friction and abrasion properties with the outer rotor 2
are improved. Furthermore, the bottom surface 8a of the trochoid
accommodation recessed part 8 is composed of a disk-like metal
plate 7 integrated with the pump casing 5a by composite molding. In
this way, flatness is improved compared to a case where the bottom
surface 8a is made of a resin, and it is possible to suppress the
variation of discharge performance. As the metal plate 7, it is
possible to employ a sintered metal body or a molten metal body (a
sheet-pressed component).
[0108] The casing 5 is composed of two members of the pump casing
5a and the suction casing 5b, so that the aforementioned composite
molding (insert molding) of the metal plate 7 is facilitated. In
the third embodiment, even when the number of parts is increased by
separating the casing into a plurality of members, positioning is
facilitated and assembling performance is improved due to a fitting
structure using a plurality of protruding parts.
[0109] An internal gear pump using claw parts will be described on
the basis of FIG. 17 and FIG. 18. FIG. 17 is an assembled
perspective view illustrating another example of the internal gear
pump, and FIG. 18 is a complete perspective view of the internal
gear pump. As illustrated in FIG. 17 and FIG. 18, the 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
trochoid accommodation recessed part 8, and a cover 6 that closes
the trochoid accommodation recessed part 8. The cover 6 has a shape
coinciding with an outer shape of an upper surface of a casing 5 in
which the trochoid accommodation recessed part 8 is opened. The
casing 5 is made of a resin. The casing 5 and the cover 6 are fixed
to a fixed plate of an actual device with bolts (not illustrated)
passing through the metal bushes 16 fixed to the casing 5, and
integrated with one another. The other basic configurations of the
pump are the same as those illustrated in FIG. 15 and FIG. 16.
[0110] In this embodiment, the metal bush 16 is not fitted to the
cover 6. On the other hand, the casing 5 is provided with four claw
parts 17 protruding therefrom. These claw parts 17 are integrated
with the casing 5 and are formed simultaneously with the molding of
the resin casing 5. As illustrated in FIG. 18, at the time of
assembling, the claw parts 17 are fitted (engaged) so as to hold an
outer peripheral portion of the cover 6, so that positioning can be
easily performed. Furthermore, since the claw part is made of a
resin, it is easy to be elastically deformed and is superior in
toughness, and it is possible to prevent breakage and the like
during assembling. In addition, the shape or the number of the claw
parts 17 is not particularly limited if the positioning of both
members is possible.
[0111] In the aforementioned each embodiment, a resin composition
forming the casing or the cover mainly employs an
injection-moldable synthetic resin as a base resin. As the base
resin, for example, there are a PPS resin, a thermoplastic
polyimide resin, a PEK resin, a PEEK resin, a polyamide-imide
resin, a PA resin, a PBT resin, a PET resin, a PE resin, a
polyacetal resin, a phenol resin, and the like. These resins may be
used alone or may be a polymer alloy in which two or more types of
resins are mixed. Among these heat-resistant resins, it is more
preferable to use the PPS resin because it is superior in creep
resistance, load resistance, abrasion resistance, chemical
resistance, and the like of molded body.
[0112] It is preferable to use a glass fiber, a carbon fiber, or an
inorganic filler, which is effective for high strength, high
elasticity, high dimension accuracy, and imparting abrasion
resistance and removing anisotropy of injection molding shrinkage,
alone or in combination as appropriate. In particular, the
combination of the glass fiber and the inorganic filler is superior
in economic efficiency and is superior in friction and abrasion
properties in oil.
[0113] In the third embodiment, it is more preferable to use a
resin composition in which the straight-chain type PPS resin is
used as a base resin and glass fibers and glass beads are blended
in the base resin as a filler. Since this structure is superior in
oil resistance, chemical resistance, and toughness, has a small
warpage due to removal of the anisotropy of injection molding
shrinkage, and significantly improves dimensional accuracy, it is
particularly effective when both of the cover and the casing are
made of a resin.
[0114] The casing or the cover is molded by injection molding using
molding pellets obtained from these raw materials. In the case of
the members illustrated in FIG. 15 or FIG. 16, the aforementioned
metal bush is arranged in a mold and is integrated by composite
molding when the suction casing is molded. Furthermore, when the
pump casing is molded, the aforementioned metal bush is arranged in
a mold and is integrated by composite molding.
[0115] Furthermore, in the internal gear pump according to the
third embodiment, as a material of the outer rotor and the inner
rotor, it is preferable to use a sintered metal (an iron-based, a
copper iron-based, a copper-based, a stainless-based metal, and the
like), and the iron-based metal is more preferable in terms of
cost. In addition, in the trochoid pump that pumps water, chemical
solution, and the like, it is sufficient if the stainless-based
metal with high rust preventing capacity and the like are
employed.
[0116] So far, the case where the metal bush and the claw part are
used as the protruding part has been described on the basis of FIG.
15 to FIG. 18; however, the internal gear pump according to the
third embodiment is not limited thereto. For example, both of the
metal bush and the claw part may be used. In addition, it is
possible to employ an arbitrary structure in which a plurality of
protruding parts protruding from one member are allowed to be
fixedly fitted to the other member. Furthermore, the ejector 9
according to the first embodiment or the ejector 9' according to
the second embodiment may also be provided in the internal gear
pump illustrated in FIG. 15 to FIG. 18. In this way, it is possible
to partially discharge liquid in the pump to the exterior by the
ejector and to suppress excess liquid supply during the high-speed
rotation while facilitating positioning at the time of
assembling.
INDUSTRIAL APPLICABILITY
[0117] The internal gear pump according to the present invention
can suppress a liquid discharge amount during a high-speed rotation
by controlling discharge pressure while achieving reduction in
size, weight, cost, and the like, so that it can be used as an
internal gear pump (a trochoid pump) that pumps liquid such as oil,
water, and chemical solution. In particular, the internal gear pump
can be suitably used as a pump for supplying liquid to sliding
parts of a scroll type compressor for an electric hot-water supply
machine, a room air conditioner, or a car air conditioner, which
uses alternatives for chlorofluorocarbon, carbon dioxide, and the
like as a refrigerant.
REFERENCE SIGNS LIST
[0118] 1, 1', 1'', 1''': internal gear pump [0119] 2: outer rotor
[0120] 3: inner rotor [0121] 4: trochoid [0122] 5: casing [0123]
5a: pump casing [0124] 5b: suction casing [0125] 5c: liquid suction
part [0126] 5d: flange part [0127] 5e: fitting part (suction
casing) [0128] 6: cover [0129] 6a: fitting part (cover) [0130] 6b:
upper end surface [0131] 7: metal plate [0132] 7a: through hole
[0133] 7b: suction port [0134] 7c: chamfered portion [0135] 7d:
spring fixing part [0136] 8: trochoid accommodation recessed part
[0137] 8a: bottom surface [0138] 8b: inner side surface [0139] 9,
9': ejector [0140] 9a: housing [0141] 9b: spring [0142] 9c:
cylindrical body [0143] 9d: fixing screw (for ejector) [0144] 9e:
chamfered portion [0145] 9f: discharge flow passage [0146] 9g:
adjustment screw [0147] 9h: cylindrical body [0148] 9i: spring
(coil spring) [0149] 9j: discharge flow passage [0150] 9k: leaf
spring [0151] 9l: torsion spring [0152] 9m: tension spring [0153]
9n: lid [0154] 10: driving shaft [0155] 11: bush [0156] 12: seal
ring [0157] 13: fixing screw (for casing) [0158] 14: filter [0159]
15: liquid flow passage [0160] 16: metal bush [0161] 17: claw
part
* * * * *