U.S. patent application number 14/600327 was filed with the patent office on 2015-07-30 for double-headed piston type swash plate compressor.
This patent application is currently assigned to KABUSHIKI KAISHA TOYOTA JIDOSHOKKI. The applicant listed for this patent is KABUSHIKI KAISHA TOYOTA JIDOSHOKKI. Invention is credited to Nobutoshi BANNO, Norikazu DETO, Toshiyuki KOBAYASHI, Masashi NAKAMORI.
Application Number | 20150211505 14/600327 |
Document ID | / |
Family ID | 53678608 |
Filed Date | 2015-07-30 |
United States Patent
Application |
20150211505 |
Kind Code |
A1 |
NAKAMORI; Masashi ; et
al. |
July 30, 2015 |
DOUBLE-HEADED PISTON TYPE SWASH PLATE COMPRESSOR
Abstract
A double-headed piston type swash plate compressor includes a
housing and a rotary shaft. The housing defines a swash plate
chamber and includes a cylinder block, a front housing member
coupled to a front end of the cylinder block, and a rear housing
member coupled to a rear end of the cylinder block. The rotary
shaft is supported by the housing. A protrusion is provided in a
suction chamber of the rear housing member and protrudes toward an
opening of an axial passage formed in the rotary shaft. A
restrictor through which refrigerant passes when flowing from the
suction chamber to the axial passage is formed between the
protrusion and the rear end of the rotary shaft. The protrusion has
a distal end sized such that the distal end can be inserted in the
opening of the axial passage.
Inventors: |
NAKAMORI; Masashi;
(Kariya-shi, JP) ; DETO; Norikazu; (Kariya-shi,
JP) ; BANNO; Nobutoshi; (Kariya-shi, JP) ;
KOBAYASHI; Toshiyuki; (Kariya-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KABUSHIKI KAISHA TOYOTA JIDOSHOKKI |
Aichi-ken |
|
JP |
|
|
Assignee: |
KABUSHIKI KAISHA TOYOTA
JIDOSHOKKI
Aichi-ken
JP
|
Family ID: |
53678608 |
Appl. No.: |
14/600327 |
Filed: |
January 20, 2015 |
Current U.S.
Class: |
417/307 |
Current CPC
Class: |
F04B 39/0055 20130101;
F04B 39/123 20130101; F04B 27/1081 20130101; F04B 27/12
20130101 |
International
Class: |
F04B 25/04 20060101
F04B025/04; F04B 39/12 20060101 F04B039/12; F04B 39/00 20060101
F04B039/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 24, 2014 |
JP |
2014-011548 |
Claims
1. A double-headed piston type swash plate compressor, comprising:
a housing defining a swash plate chamber, wherein the housing
includes a cylinder block, a front housing member coupled to a
front end of the cylinder block, and a rear housing member coupled
to a rear end of the cylinder block; a rotary shaft supported by
the housing; a swash plate that is accommodated in the swash plate
chamber and configured to rotate with the rotary shaft; a
double-headed piston engaged with the swash plate; a cylinder bore
that is formed in the cylinder block and accommodates the
double-headed piston; a first compression chamber defined in the
front end of the cylinder bore by the double-headed piston; a
second compression chamber defined in the rear end of the cylinder
bore by the double-headed piston; a suction chamber formed in the
rear housing member; an axial passage that is formed in the rotary
shaft to be connected to the suction chamber and includes an
opening that opens to the suction chamber; a first rotary valve
that selectively connects and disconnects the axial passage to and
from the first compression chamber in accordance with rotation of
the rotary shaft; a second rotary valve that selectively connects
and disconnects the axial passage to and from the second
compression chamber in accordance with rotation of the rotary
shaft; and a protrusion provided in the suction chamber and
protruding toward the opening of the axial passage, wherein a
restrictor through which refrigerant passes when flowing from the
suction chamber to the axial passage is formed between the
protrusion and the rear end of the rotary shaft, and the protrusion
has a distal end sized such that the distal end is insertable in
the opening of the axial passage.
2. The compressor according to claim 1, wherein the distal end of
the protrusion is inserted in the axial passage.
3. The compressor according to claim 1, wherein the protrusion is
tapered.
4. The compressor according to claim 1, wherein the protrusion
extends in the axial direction of the rotary shaft and has a
constant cross-sectional shape and cross-sectional area in the
axial direction of the rotary shaft.
5. The compressor according to claim 1, wherein the distal end of
the protrusion is semi-spherical.
6. The compressor according to claim 1, wherein the protrusion is
formed integrally with the rear housing member.
7. The compressor according to claim 1, wherein the rear housing
member includes an introduction port for introducing refrigerant
into the suction chamber, and the introduction port extends in a
direction intersecting the axial direction of the rotary shaft.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a double-headed piston type
swash plate compressor.
[0002] A double-headed piston type swash plate compressor includes
a cylinder block, a front housing member coupled to the front end
of the cylinder block, and a rear housing member coupled to the
rear end of the cylinder block. The cylinder block defines a swash
plate chamber, and the swash plate chamber accommodates a swash
plate that rotates together with a rotary shaft. To the swash plate
are engaged double-headed pistons. The cylinder block defines
cylinder bores, which accommodate the double-headed pistons. Each
double-headed piston reciprocates in the corresponding cylinder
bore in accordance with rotation of the swash plate. The
double-headed piston divides the inside of the cylinder bore into a
first compression chamber on the front end and a second compression
chamber on the rear end. In accordance with the reciprocation of
the double-headed pistons, refrigerant is drawn into the first
compression chambers and the second compression chambers to be
compressed, and the compressed refrigerant is discharged into a
first discharge chamber formed in the front housing member and a
second discharge chamber formed in the rear housing member.
[0003] Structures for drawing refrigerant into the first
compression chambers and the second compression chambers include
the structure employed by the compressor disclosed in, for example,
Japanese Laid-Open Patent Publication No. 5-133325. The compressor
of the publication includes a first suction chamber in the front
housing member and a second suction chamber in the rear housing
member. The cylinder block includes a suction passage that connects
the swash plate chamber to the first suction chamber and a suction
passage that connects the swash plate chamber to the second suction
chamber. Refrigerant is introduced into the swash plate chamber,
and the refrigerant that has been introduced to the swash plate
chamber is supplied to the first suction chamber and the second
suction chamber through the corresponding suction passage.
Furthermore, when the pressure in each cylinder bore is reduced and
a suction reed valve opens, the refrigerant is drawn from the first
suction chamber into the associated first compression chamber or
from the second suction chamber into the associated second
compression chamber.
[0004] In Japanese Laid-Open Patent Publication No. 5-133325, the
refrigerant presses open the suction reed valves to be drawn from
the first suction chamber and the second suction chamber into the
first compression chambers and the second compression chambers.
Thus, suction loss of refrigerant occurs when the refrigerant
presses open the suction reed valves. This consequently reduces the
compression efficiency. Furthermore, the refrigerant introduced
into the swash plate chamber is heated by the heat generated in
sliding parts such as the swash plate and the rotary shaft.
[0005] The compressor disclosed in, for example, Japanese Laid-Open
Patent Publication No. 2004-278460 includes a suction chamber only
in the rear housing member and has an axial passage formed in the
rotary shaft to be connected to the suction chamber. The rotary
shaft includes a first rotary valve corresponding to the first
compression chambers and a second rotary valve corresponding to the
second compression chambers. Each rotary valve is selectively
opened and closed in accordance with rotation of the rotary shaft.
This draws the refrigerant, which is introduced from the suction
chamber into the axial passage, into the compression chambers
through the rotary valves. The compressor of Japanese Laid-Open
Patent Publication No. 2004-278460 eliminates the suction loss of
the refrigerant that occurs by pressing open the suction reed
valves and has favorable compression efficiency. In addition, since
the refrigerant is not introduced into the swash plate chamber, the
refrigerant is prevented from being heated by the heat generated in
the sliding parts such as the swash plate and the rotary shaft.
[0006] However, unlike the compressor of Japanese Laid-Open Patent
Publication No. 5-133325, the compressor of Japanese Laid-Open
Patent Publication No. 2004-278460 does not introduce the
refrigerant into a relatively large space like the swash plate
chamber. Thus, suction pulsation of refrigerant tends to occur
during suction strokes. The dimensional restriction of the
double-headed piston type swash plate compressor restricts increase
in the size of the suction chamber formed in the rear housing
member like the structure in Japanese Laid-Open Patent Publication
No. 2004-278460. Thus, the suction pulsation of the refrigerant is
relatively great in the compressor of Japanese Laid-Open Patent
Publication No. 2004-278460.
SUMMARY OF THE INVENTION
[0007] Accordingly, it is an objective of the present invention to
provide a double-headed piston type swash plate compressor that has
reduced suction pulsation of refrigerant.
[0008] To achieve the foregoing objective and in accordance with
one aspect of the present invention, a double-headed piston type
swash plate compressor is provided that includes a housing defining
a swash plate chamber. The housing includes a cylinder block, a
front housing member coupled to a front end of the cylinder block,
and a rear housing member coupled to a rear end of the cylinder
block. The compressor further includes a rotary shaft supported by
the housing, a swash plate that is accommodated in the swash plate
chamber and configured to rotate with the rotary shaft, a
double-headed piston engaged with the swash plate, a cylinder bore
that is formed in the cylinder block and accommodates the
double-headed piston, a first compression chamber defined in the
front end of the cylinder bore by the double-headed piston, a
second compression chamber defined in the rear end of the cylinder
bore by the double-headed piston, a suction chamber formed in the
rear housing member, an axial passage that is formed in the rotary
shaft to be connected to the suction chamber and includes an
opening that opens to the suction chamber, a first rotary valve
that selectively connects and disconnects the axial passage to and
from the first compression chamber in accordance with rotation of
the rotary shaft, and a second rotary valve that selectively
connects and disconnects the axial passage to and from the second
compression chamber in accordance with rotation of the rotary
shaft. The rear housing member includes a protrusion provided in
the suction chamber and protruding toward the opening of the axial
passage. A restrictor through which refrigerant passes when flowing
from the suction chamber to the axial passage is formed between the
protrusion and the rear end of the rotary shaft. The protrusion has
a distal end sized such that the distal end can be inserted in the
opening of the axial passage.
[0009] Other aspects and advantages of the present invention will
become apparent from the following description, taken in
conjunction with the accompanying drawings, illustrating by way of
example the principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The invention, together with objects and advantages thereof,
may best be understood by reference to the following description of
the presently preferred embodiments together with the accompanying
drawings in which:
[0011] FIG. 1 is a cross-sectional side view illustrating a
double-headed piston type swash plate compressor according to a
first embodiment;
[0012] FIG. 2 is an enlarged cross-sectional view illustrating a
protrusion and its surroundings in the compressor of FIG. 1;
[0013] FIG. 3 is an enlarged cross-sectional view illustrating a
protrusion and its surroundings of a double-headed piston type
swash plate compressor according to a second embodiment; and
[0014] FIG. 4 is an enlarged cross-sectional view illustrating a
protrusion and its surroundings of a double-headed piston type
swash plate compressor according to a third embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0015] A double-headed piston type swash plate compressor 10
according to a first embodiment will now be described with
reference to FIGS. 1 and 2.
[0016] As shown in FIG. 1, the double-headed piston type swash
plate compressor 10 has a housing H. The housing H includes front
and rear cylinder blocks 11, 12 coupled to each other, a front
housing member 13 coupled to the front end of the front cylinder
block 11, and a rear housing member 14 coupled to the rear end of
the rear cylinder block 12. The cylinder blocks 11, 12 and the
housing members 13, 14 are secured together with multiple bolts
B.
[0017] The compressor 10 includes a first valve plate 15, a first
valve sub-plate 16, and a first retainer plate 17 between the front
housing member 13 and the front cylinder block 11. The compressor
10 further includes a second valve plate 18, a second valve
sub-plate 19, and a second retainer plate 20 between the rear
housing member 14 and the rear cylinder block 12. The first valve
plate 15 includes multiple first discharge ports 15a, and the
second valve plate 18 includes multiple second discharge ports 18a.
The first valve sub-plate 16 includes multiple first discharge
valves 16a, and the second valve sub-plate 19 includes multiple
second discharge valves 19a. The discharge valves 16a, 19a
selectively open and close the corresponding discharge ports 15a,
18a. The first retainer plate 17 includes multiple first retainers
17a, and the second retainer plate 20 includes multiple second
retainers 20a. The retainers 17a, 20a regulate the opening degree
of the corresponding discharge valves 16a, 19a.
[0018] The front housing member 13 and the first valve plate 15
define a first discharge chamber 13a. The rear housing member 14
and the second valve plate 18 define a second discharge chamber 14a
and a suction chamber 14b. The first discharge chamber 13a and the
second discharge chamber 14a are connected to a non-illustrated
discharge passage, and the discharge passage is connected to a
non-illustrated external refrigerant circuit.
[0019] The cylinder blocks 11, 12 rotationally support a rotary
shaft 21, and the rotary shaft 21 has a central axis L. The front
end of the rotary shaft 21 is inserted in a shaft hole 11a formed
in the front cylinder block 11. The rear end of the rotary shaft 21
is inserted in a shaft hole 12a formed in the rear cylinder block
12. The front end of the rotary shaft 21 is rotationally supported
by the front cylinder block 11. The rear end of the rotary shaft 21
is rotationally supported by the rear cylinder block 12. The rear
end of the rotary shaft 21 extends through the second valve plate
18, the second valve sub-plate 19, and the second retainer plate 20
and protrudes in the suction chamber 14b.
[0020] Between the front housing member 13 and the rotary shaft 21
is provided a lip seal, which is a shaft seal 22. The shaft seal 22
is accommodated in an accommodation chamber 13b formed in the front
housing member 13. The first discharge chamber 13a is provided
around the accommodation chamber 13b.
[0021] On the rotary shaft 21 is mounted a swash plate 23, which
rotates with the rotary shaft 21. The swash plate 23 is
accommodated in the internal space of the cylinder blocks 11, 12,
that is, a swash plate chamber 24 defined in the housing H. The
swash plate 23 includes an annular base 23a around the rotary shaft
21. Between the front cylinder block 11 and the base 23a of the
swash plate 23 is provided a first thrust bearing 25. Between the
rear cylinder block 12 and the base 23a of the swash plate 23 is
provided a second thrust bearing 26. The thrust bearings 25, 26
sandwich the swash plate 23 to limit the movement of the swash
plate 23 along the central axis L of the rotary shaft 21.
[0022] The front cylinder block 11 includes multiple through holes
11h (only one is shown in FIG. 1) arranged around the rotary shaft
21. The rear cylinder block 12 includes multiple through holes 12h
(only one is shown in FIG. 1) arranged around the rotary shaft 21.
Pairs of one of the front through holes 11h and an associated one
of the rear through holes 12h form cylinder bores 27. Each cylinder
bore 27 accommodates a double-headed piston 28 to reciprocate in
the front and rear direction. Each double-headed piston 28 is
engaged with the swash plate 23 via a pair of shoes 29. The swash
plate 23 rotates integrally with the rotary shaft 21. The rotation
of the swash plate 23 is transmitted to each double-headed piston
28 via the associated pair of shoes 29 and reciprocates the
double-headed piston 28 back and forth in the associated cylinder
bore 27.
[0023] In the front section of each cylinder bore 27, the first
valve plate 15 and the associated double-headed piston 28 define a
first compression chamber 27a. In the rear section of each cylinder
bore 27, the second valve plate 18 and the associated double-headed
piston 28 define a second compression chamber 27b.
[0024] The inner circumferential surfaces of the shaft holes 11a,
12a have sealing circumferential surfaces 11b, 12b. The rotary
shaft 21 is directly supported by the cylinder blocks 11, 12 on the
sealing circumferential surfaces 11b, 12b. The rotary shaft 21
includes an axial passage 21a inside the rotary shaft 21. The axial
passage 21a has an opening 211a that opens in a rear direction of
the rotary shaft 21, that is, toward the rear housing member 14.
The opening 211a opens in the suction chamber 14b. That is, the
axial passage 21a is connected to the suction chamber 14b via the
opening 211a.
[0025] The rotary shaft 21 includes a first introduction passage 31
at a position corresponding to the front cylinder block 11 in the
axial direction. The first introduction passage 31 connects the
axial passage 21a to the outer circumference of the rotary shaft
21. The rotary shaft 21 also includes a second introduction passage
32 at a position corresponding to the rear cylinder block 12 in the
axial direction. The second introduction passage 32 connects the
axial passage 21a to the outer circumference of the rotary shaft
21.
[0026] The front cylinder block 11 includes multiple first suction
passages 33 (only one is shown in FIG. 1), and each first suction
passage 33 connects the front section of the corresponding cylinder
bore 27 to the shaft hole 11a. Each first suction passage 33 has an
opening that opens to the sealing circumferential surface 11b to
connect the first suction passage 33 to the shaft hole 11a. The
rear cylinder block 12 includes multiple second suction passages 34
(only one is shown in FIG. 1), and each second suction passage 34
connects the rear section of the corresponding cylinder bore 27 to
the shaft hole 12a. Each second suction passage 34 has an opening
that opens to the sealing circumferential surface 12b to connect
the second suction passage 34 to the shaft hole 12a.
[0027] The first introduction passage 31 is formed at a position
where the first introduction passage 31 is intermittently connected
to the first suction passages 33 in accordance with the rotation of
the rotary shaft 21. The second introduction passage 32 is formed
at a position where the second introduction passage 32 is
intermittently connected to the second suction passages 34 in
accordance with the rotation of the rotary shaft 21. That is, the
first introduction passage 31 is arranged at the same position as
the openings of the suction passages 33 in the axial direction of
the rotary shaft 21, and the second introduction passage 32 is
arranged at the same position as the openings of the suction
passages 34 in the axial direction of the rotary shaft 21. The
rotary shaft 21 includes a first rotary valve 35 at a portion
surrounded by the sealing circumferential surface 11b, and the
first rotary valve 35 is formed integrally with the front portion
of the rotary shaft 21. The rotary shaft 21 also includes a second
rotary valve 36 at a portion surrounded by the sealing
circumferential surface 12b, and the second rotary valve 36 is
formed integrally with the rear portion of the rotary shaft 21.
[0028] When the first introduction passage 31 is connected to one
of the first suction passages 33 in accordance with the rotation of
the rotary shaft 21, the first rotary valve 35 is in an open state
that permits connection between the axial passage 21a and the
associated first compression chamber 27a via the passages 31, 33.
When the first introduction passage 31 and the first suction
passage 33 are disconnected in accordance with the rotation of the
rotary shaft 21, the first rotary valve 35 is in a closed state
that blocks the connection between the axial passage 21a and the
first compression chamber 27a via the passages 31, 33. Thus, the
first rotary valve 35 selectively connects and disconnects the
axial passage 21a with and from the first compression chambers 27a
in accordance with the rotation of the rotary shaft 21.
[0029] When the second introduction passage 32 is connected to one
of the second suction passages 34 in accordance with the rotation
of the rotary shaft 21, the second rotary valve 36 is in an open
state that permits connection between the axial passage 21a and the
associated second compression chamber 27b via the passages 32, 34.
When the second introduction passage 32 and the second suction
passage 34 are disconnected in accordance with the rotation of the
rotary shaft 21, the second rotary valve 36 is in a closed state
that blocks the connection between the axial passage 21a and the
second compression chamber 27b via the passages 32, 34. Thus, the
second rotary valve 36 selectively connects and disconnects the
axial passage 21a with and from the second compression chambers 27b
in accordance with the rotation of the rotary shaft 21.
[0030] The rear housing member 14 includes an introduction port 37
connected to the suction chamber 14b. The introduction port 37 is
connected to the external refrigerant circuit and introduces the
refrigerant from the external refrigerant circuit into the suction
chamber 14b. The introduction port 37 extends in a direction
perpendicular to the axial direction of the rotary shaft 21, that
is, in the radial direction of the rotary shaft 21.
[0031] As shown in FIG. 2, the rear housing member 14 includes, in
the suction chamber 14b, a conical protrusion 40, which protrudes
toward the opening 211a of the axial passage 21a. The protrusion 40
is formed, through die casting, integrally with the inner wall of
the rear housing member 14, which defines the suction chamber 14b
and faces the rear end of the rotary shaft 21. The protrusion 40 is
tapered toward a distal end 40e and has a diameter decreasing
toward the distal end 40e. The distal end 40e of the protrusion 40
has a flat end face. The distal end 40e of the protrusion 40
extends into the axial passage 21a. Between the protrusion 40 and
the rear end of the rotary shaft 21, or more specifically, between
the protrusion 40 and the periphery of the opening 211a located
around the protrusion 40 is formed an annular restricting portion
41. The restricting portion 41 restricts the flow of the
refrigerant flowing through the restricting portion 41. The
cross-sectional area of the distal end 40e of the protrusion 40
perpendicular to the central axis L of the rotary shaft 21 is
smaller than the cross-sectional area of the opening 211a of the
axial passage 21a, which is perpendicular to the central axis L of
the rotary shaft 21. That is, the distal end 40e of the protrusion
40 is sized such that the distal end 40e can be inserted in the
axial passage 21a.
[0032] Operation of the first embodiment will now be described.
[0033] When refrigerant is introduced from the external refrigerant
circuit to the suction chamber 14b through the introduction port
37, the refrigerant introduced to the suction chamber 14b collides
against the protrusion 40. The refrigerant is guided along the
protrusion 40 toward the axial passage 21a and flows into the axial
passage 21a through the restrictor 41. When the first rotary valve
35 and the second rotary valve 36 are opened in accordance with the
rotation of the rotary shaft 21, the refrigerant that has flowed
into the axial passage 21a is drawn into the associated first
compression chamber 27a and the associated second compression
chamber 27b. During suction of the refrigerant from the suction
chamber 14b to the first compression chamber 27a and the second
compression chamber 27b, the refrigerant passes through the
restrictor 41 so that the suction pulsation of the refrigerant is
reduced.
[0034] The first embodiment achieves the following advantages.
[0035] (1) The rear housing member 14 has the protrusion 40, which
protrudes toward the opening 211a of the axial passage 21a in the
suction chamber 14b. The restrictor 41 is formed between the
protrusion 40 and the rear end of the rotary shaft 21. The
structure allows the refrigerant introduced in the suction chamber
14b to flow into the axial passage 21a through the restrictor 41.
When the first rotary valve 35 and the second rotary valve 36 are
opened in accordance with the rotation of the rotary shaft 21, the
refrigerant that has flowed into the axial passage 21a is drawn
into the associated first compression chamber 27a and the
associated second compression chamber 27b. During suction of the
refrigerant from the suction chamber 14b to the first compression
chamber 27a and the second compression chamber 27b, the refrigerant
passes through the restrictor 41 so that the suction pulsation of
the refrigerant is reduced.
[0036] (2) The distal end 40e of the protrusion 40 extends into the
axial passage 21a. The structure allows the restrictor 41 to be
easily formed as compared to a case where the distal end 40e of the
protrusion 40 extends to the same position as the rear end of the
rotary shaft 21 in the axial direction and does not extend into the
axial passage 21a. As a result, the suction pulsation of the
refrigerant is further reduced in a suitable manner.
[0037] (3) The protrusion 40 is tapered. The structure allows the
refrigerant introduced into the suction chamber 14b to be guided by
the protrusion 40 toward the axial passage 21a. Thus, the
refrigerant smoothly flows from the suction chamber 14b into the
axial passage 21a. This reduces the suction loss of the refrigerant
and also reduces the suction pulsation of the refrigerant.
[0038] (4) The introduction port 37 extends in the direction
perpendicular to the axial direction of the rotary shaft 21. The
structure allows the refrigerant introduced from the introduction
port 37 into the suction chamber 14b to be more smoothly guided
along the protrusion 40 toward the axial passage 21a as compared to
a case where the introduction port 37 extends parallel to the axial
direction of the rotary shaft 21. This reduces the suction loss of
the refrigerant and further reduces the suction pulsation of the
refrigerant.
[0039] (5) The protrusion 40 is formed integrally with the inner
wall of the rear housing member 14. The structure improves the
productivity of the protrusion 40 as compared to a case where, for
example, a protrusion formed as a separate member from the rear
housing member 14 is attached to the rear housing member 14.
[0040] The first embodiment may be modified as follows.
[0041] Like a second embodiment shown in FIG. 3, the distal end 40e
of the protrusion 40 may be semi-spherical. The structure allows
the refrigerant to smoothly flow around the distal end 40e of the
protrusion 40 and further reduces the suction loss of the
refrigerant.
[0042] Like a third embodiment shown in FIG. 4, the protrusion 40
may be columnar. That is, the protrusion 40 does not need to be
tapered. The protrusion 40 may be a column extending in the axial
direction of the rotary shaft 21, or more specifically, the
protrusion 40 may have a constant cross-sectional shape and
cross-sectional area in the axial direction of the rotary shaft 21.
Furthermore, the distal end 40e of the columnar protrusion 40 may
be semi-spherical as shown in FIG. 3.
[0043] The introduction port 37 may extend in a direction
intersecting the axial direction of the rotary shaft 21.
[0044] The introduction port 37 may extend parallel to the axial
direction of the rotary shaft 21.
[0045] The distal end 40e of the protrusion 40 does not necessarily
have to extend into the axial passage 21a, but may extend to the
same position as the rear end of the rotary shaft 21 in the axial
direction. In other words, the distal end 40e of the protrusion 40
may be located at any position where the restrictor 41 can be
formed between the protrusion 40 and the rear end of the rotary
shaft 21.
[0046] The protrusion 40 may be formed as a separate member from
the rear housing member 14.
[0047] Therefore, the present examples and embodiments are to be
considered as illustrative and not restrictive and the invention is
not to be limited to the details given herein, but may be modified
within the scope and equivalence of the appended claims.
* * * * *