U.S. patent application number 14/429666 was filed with the patent office on 2015-09-10 for clutch.
This patent application is currently assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA. The applicant listed for this patent is Daisuke Kobayashi, Shintaro Nakano, Masao Nakayama, Hirotaka Sunada, Hideki Tsutsui. Invention is credited to Daisuke Kobayashi, Shintaro Nakano, Masao Nakayama, Hirotaka Sunada, Hideki Tsutsui.
Application Number | 20150252857 14/429666 |
Document ID | / |
Family ID | 50388265 |
Filed Date | 2015-09-10 |
United States Patent
Application |
20150252857 |
Kind Code |
A1 |
Sunada; Hirotaka ; et
al. |
September 10, 2015 |
CLUTCH
Abstract
The clutch is provided with a drive-side rotational body, a
driven-side rotational body, driven-side rotational body, and an
urging member. The driven-side rotational body is movable in the
axial direction of the drive-side rotational body between a first
position, at which the driven-side rotational body is coupled to
the drive-side rotational body, and a second position, at which the
driven-side rotational body is decoupled from the drive-side
rotational body. The urging member urges the driven-side rotational
body from the second position toward the first position. The
driven-side rotational body includes a helical groove that extends
in the urging direction of the urging member. The clutch is further
provided with a pin that can be inserted into the helical
groove.
Inventors: |
Sunada; Hirotaka;
(Nagoya-shi, JP) ; Nakayama; Masao; (Nagoya-shi,
JP) ; Tsutsui; Hideki; (Yokkaichi-shi, JP) ;
Nakano; Shintaro; (Toyota-shi, JP) ; Kobayashi;
Daisuke; (Okazaki-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Sunada; Hirotaka
Nakayama; Masao
Tsutsui; Hideki
Nakano; Shintaro
Kobayashi; Daisuke |
Nagoya-shi
Nagoya-shi
Yokkaichi-shi
Toyota-shi
Okazaki-shi |
|
JP
JP
JP
JP
JP |
|
|
Assignee: |
TOYOTA JIDOSHA KABUSHIKI
KAISHA
Toyota-shi, Aichi-ken
JP
|
Family ID: |
50388265 |
Appl. No.: |
14/429666 |
Filed: |
September 25, 2013 |
PCT Filed: |
September 25, 2013 |
PCT NO: |
PCT/JP2013/075873 |
371 Date: |
March 19, 2015 |
Current U.S.
Class: |
192/66.1 |
Current CPC
Class: |
F16D 23/12 20130101;
F16D 27/108 20130101; F16D 15/00 20130101; F16D 2023/123 20130101;
F16D 13/76 20130101; F16D 41/088 20130101 |
International
Class: |
F16D 23/12 20060101
F16D023/12; F16D 27/108 20060101 F16D027/108; F16D 15/00 20060101
F16D015/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 25, 2012 |
JP |
2012-211046 |
Jul 25, 2013 |
JP |
2013-154986 |
Sep 19, 2013 |
JP |
2013-194686 |
Claims
1. A clutch comprising: a drive-side rotational body; a driven-side
rotational body movable in an axial direction of the drive-side
rotational body between a first position at which the driven-side
rotational body is coupled to the drive-side rotational body and a
second position at which the driven-side rotational body is
decoupled from the drive-side rotational body; an urging member for
urging the driven-side rotational body from the second position
toward the first position; a helical groove formed in the
driven-side rotational body and extended in an urging direction of
the urging member; and a pin that can be inserted into the helical
groove.
2. The clutch according to claim 1, wherein the pin is immovable in
the axial direction of the drive-side rotational body.
3. The clutch according to claim 1, wherein the helical groove is
formed in an outer circumferential surface of the drive-side
rotational body and has a stepped shape having a diameter becoming
smaller forward in the urging direction.
4. The clutch according to claim 1, wherein the driven-side
rotational body has an annular groove arranged forward of the
helical groove in the urging direction and extended in a
circumferential direction of the driven-side rotational body, the
annular groove being connected to the helical groove, and the
annular groove allows the pin to slide on the annular groove when
the driven-side rotational body is arranged at the second
position.
5. The clutch according to claim 1, further comprising a ball
through which the driven-side rotational body is coupled to the
drive-side rotational body, wherein the ball is non-rotationally
caught between the driven-side rotational body and the drive-side
rotational body to couple the two rotational bodies to each other
when the driven-side rotational body is located at the first
position, and the ball is released from the driven-side rotational
body and the drive-side rotational body to decouple the rotational
bodies from each other when the driven-side rotational body is
arranged at the second position.
6. The clutch according to claim 1, further comprising a solenoid
that switches the pin selectively between an inserted state in
which the pin is inserted into the helical groove and a retracted
state in which the pin is retracted from the helical groove,
wherein the solenoid has a coil, and the solenoid switches the pin
from one of the inserted state and the retracted state to the other
when the coil is energized and maintains the pin in a state to
which the pin has been switched when the coil is de-energized.
Description
TECHNICAL FIELD
[0001] The present disclosure relates to a clutch that switches
power transmission states between a drive-side rotational body and
a driven-side rotational body by selectively coupling and
decoupling the rotational bodies to and from each other.
BACKGROUND ART
[0002] As proposed by Patent Document 1, a clutch may be arranged
between a crankshaft and an auxiliary device to decrease friction
related to an internal combustion engine. A clutch described in
Patent Document 1 includes a drive-side rotational body and a
driven-side rotational body. The drive-side rotational body is
coupled to a crankshaft and thus rotated. The driven-side
rotational body is coupled to an auxiliary device and rotational
relative to the drive-side rotational body. The rotational bodies
are pressed against each other by magnetic force produced by
magnets. This maintains the clutch in an engaged state. The clutch
is disengaged by energizing the coil arranged in the clutch to
produce a magnetic field that cancels the aforementioned magnetic
force.
PRIOR ART DOCUMENTS
Patent Documents
[0003] Patent Document 1: Japanese Laid-Open Patent Publication No.
2010-203406
SUMMARY OF THE INVENTION
Problems that the Invention is to Solve
[0004] As described in Patent Document 1, in the configuration in
which the clutch is engaged by pressing the drive-side rotational
body and the driven-side rotational body against each other, the
force needed for such pressing becomes greater as the torque that
needs to be transmitted through the clutch, or, in other words, the
torque needed by the auxiliary device driven by the driven-side
rotational body, becomes greater. To increase the pressing force,
magnets with a greater magnetic force must be employed. This
necessitates a larger-sized coil to cancel the magnetic force, and
the clutch may become larger in size.
[0005] Accordingly, it is an objective of the present disclosure to
provide a clutch capable of switching power transmission states
without being enlarged in size to transmit greater torque.
Means for Solving the Problems
[0006] To achieve the foregoing objective and in accordance with
one aspect of the present invention, a clutch is provided that
includes a drive-side rotational body, a driven-side rotational
body, an urging member, a helical groove, and a pin. The
driven-side rotational body is movable in an axial direction of the
drive-side rotational body between a first position at which the
driven-side rotational body is coupled to the drive-side rotational
body and a second position at which the driven-side rotational body
is decoupled from the drive-side rotational body. The urging member
urges the driven-side rotational body from the second position
toward the first position. The helical groove is formed in the
driven-side rotational body and extended in an urging direction of
the urging member. The pin can be inserted into the helical
groove.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 is a cross-sectional view showing a clutch according
to one embodiment;
[0008] FIG. 2 is a side view showing a sliding piece of the clutch
illustrated in FIG. 1;
[0009] FIG. 3 is a perspective view showing the sliding piece shown
in FIG. 2;
[0010] FIG. 4 is a perspective cross-sectional view showing a
groove portion of the sliding piece of FIG. 3;
[0011] FIG. 5 is a perspective view showing the sliding piece with
a holding device fixed to the sliding piece;
[0012] FIG. 6A is a diagram illustrating the clutch in an engaged
state;
[0013] FIG. 6B is a diagram illustrating the clutch in a disengaged
state;
[0014] FIG. 7 is a front view showing the sliding piece of FIG. 2,
a solenoid, and a pin;
[0015] FIGS. 8A and 8B are cross-sectional views each showing the
solenoid illustrated in FIG. 7; and
[0016] FIGS. 9A, 9B, 9C, 9D, 9E, and 9F are diagrams each
illustrating operation of the clutch.
MODES FOR CARRYING OUT THE INVENTION
[0017] A clutch according to one embodiment will now be described
with reference to FIGS. 1 to 9. The present embodiment is a clutch
adapted for a vehicle, or, more specifically, a clutch arranged
between the crankshaft of an engine and the compressor of an air
conditioner to switch power transmission states between the
crankshaft and the compressor.
[0018] As illustrated in FIG. 1, the clutch includes a pulley 10
and a sliding piece 20. The pulley 10 corresponds to a drive-side
rotational body and the sliding piece 20 corresponds to a
driven-side rotational body.
[0019] The pulley 10 is formed substantially in a conical shape
having an outer diameter that increases toward the basal end of the
pulley 10 (toward the right end as viewed in FIG. 1). A plurality
of grooves 11, over which a belt is looped, are formed in the outer
circumferential surface of the basal end portion of the pulley 10.
The belt is also looped over the crankshaft and thus allows
synchronous rotation of the crankshaft and the pulley 10. A
projection 12, which axially projects from the inner
circumferential surface of the pulley 10, is formed on the inner
circumferential surface of the pulley 10. The projection 12 has an
annular shape extending about the axis of the pulley 10. The pulley
10 is supported by a compressor shaft 70 of a compressor through a
bearing 13, which is arranged at the distal end of the pulley 10
(the left end as viewed in FIG. 1), in a manner rotational relative
to the compressor shaft 70.
[0020] The compressor shaft 70 is supported by an engine body 72
through a bearing 71 in a manner rotational relative to the engine
body 72. When the compressor shaft 70 rotates, the compressor is
driven to compress refrigerant. An annular plate assembly 73 is
fixed to the surface of the engine body 72 that faces the pulley
10.
[0021] A straight spline 74 is formed in the outer circumferential
surface of the portion of the compressor shaft 70 between the
bearings 13 and 17. The sliding piece 20 is meshed with the
straight spline 74. This allows the sliding piece 20 to rotate
integrally with the compressor shaft 70 and move axially relative
to the compressor shaft 70. The sliding piece 20 is urged by a coil
spring 21, which is arranged between the sliding piece 20 and the
engine body 72, toward the pulley 10 (toward the left end as viewed
in FIG. 1). The spring 21 corresponds to an urging member. A
plurality of balls 22 are provided in the outer circumferential
surface of the sliding piece 20. The diameter Db of each of the
balls 22 is substantially equal to the distance from the outer
circumferential surface of the sliding piece 20 to the projection
12 of the pulley 10. The balls 22 thus contact the outer
circumferential surface of the sliding piece 20 and the inner
circumferential surface of the projection 12. A holding device 23,
which restricts movement of the balls 22, is fixed to the outer
circumferential surface of the sliding piece 20. The pulley 10, the
compressor shaft 70, and the sliding piece 20 are arranged
coaxially. Hereinafter, the extending direction of the axis of
these components will be referred to as the axial direction.
[0022] The configuration of the sliding piece 20 will hereafter be
described with reference to FIGS. 2 to 5.
[0023] With reference to FIGS. 2 and 3, the sliding piece 20
includes a holding portion 24, which holds the balls 22 at the
outer circumferential surface and a groove portion 25, which is
arranged close to the engine body 72 (on the right side as viewed
in FIG. 2) with respect to the holding portion 24.
[0024] The holding portion 24 has a pillar portion 26 having a
substantially circular cross section and a hexagonal column portion
27 having a regular hexagonal cross section. The hexagonal column
portion 27 has six sides 28 and six corners 29. The diameter of the
imaginary circle including midpoints 30 of the sides 28 is equal to
the outer diameter of an end surface 31 of the pillar portion 26.
In contrast, the diameter of the imaginary circle including the
corners 29 is greater than the outer diameter of the end surface 31
of the pillar portion 26. The cross section of the pillar portion
26 is thus varied gradually from the circular shape to the
hexagonal shape toward the hexagonal column portion 27.
[0025] A hole 32, which extends in the axial direction and is
meshed with the straight spline 74 of the compressor shaft 70, is
formed in a central portion of the holding portion 24.
[0026] The configuration of the groove portion 25 of the sliding
piece 20 will now be described.
[0027] As illustrated in FIGS. 2 and 4, the groove portion 25 has a
helical groove 33 and an annular groove 34. The helical groove 33
extends in a manner revolving by 540.degree. clockwise about the
axis of the sliding piece 20 from a starting point 35 (0.degree.),
which is the uppermost point of the helical groove 33 as viewed in
FIGS. 2 to 4. The diameter of the helical groove 33 becomes smaller
in a direction circumferentially separating from the starting point
35. That is, an extended surface of the helical groove 33 facing
the hexagonal column portion 27 of the holding portion 24, which is
a side surface (or a side wall) 36, becomes closer to the pulley 10
in the direction circumferentially separating from the starting
point 35. In the helical groove 33, the radially inner edge of a
first-cycle side surface 361 is connected to the radially outer
edge of a second-cycle side surface 362 via a circumferential
surface 37. As a result, as shown in FIG. 2, the helical groove 33
has a stepped cross section.
[0028] In the present embodiment, the direction in which the
helical groove 33 converges toward the axis of the sliding piece 20
is the extending direction of the helical groove 33. That is, a
direction axially extending toward the pulley 10, which is, in
other words, the direction in which the spring 21 urges the sliding
piece 20, is the extending direction of the helical groove 33.
[0029] The annular groove 34, which extends circumferentially about
the axis of the sliding piece 20, is arranged at a position forward
(to the left as viewed in FIG. 2) of the helical groove 33 in the
urging direction of the spring 21 and extended along the entire
circumference of the sliding piece 20. The helical groove 33 has an
ending point 38, which is located at the position revolved by
540.degree. from the starting point 35. The annular groove 34
extends continuously from the helical groove 33 and starts from a
starting point 40, which is the ending point 38 of the helical
groove 33. The annular groove 34 is formed such that an extended
surface, or a side surface (or a side wall) 39, of the annular
groove 34 extends substantially at a constant axial position. The
radial length of the side surface 39 becomes gradually smaller in a
direction circumferentially separating from the starting point 40
of the side surface 39. Accordingly, the cycle of revolution (from
540.degree. to 900.degree.) along which the annular groove 34
extends ends at the ending point 38 of the helical groove 33.
[0030] The configuration of the holding device 23, which is fixed
to the outer circumferential surface of the sliding piece 20, will
hereafter be described with reference to FIG. 5.
[0031] Referring to FIG. 5, the holding device 23 is shaped like a
tube and includes an inner hole 41 having a shape substantially
identical with the cross section of the hexagonal column portion 27
of the holding portion 24, which is the regular hexagonal shape.
The holding portion 24 of the sliding piece 20 is inserted into the
inner hole 41 to fix the holding device 23 to the hexagonal column
portion 27 of the sliding piece 20. The holding device 23 thus
rotates integrally with the sliding piece 20. Holding holes 42,
each of which extends about the associated one of the midpoints 30
of the holding portion 24, are formed in the respective portions of
the holding device 23 corresponding to the midpoints 30. Each
holding hole 42 is shaped such that the circumferential length of
the holding hole 42 becomes smaller in a direction approaching the
pillar portion 26 of the holding portion 24. The balls 22 are
arranged in the associated holding holes 42 and thus maintained at
predetermined positions on the outer circumferential surface of the
sliding piece 20. The balls 22 are permitted to move to the outer
circumferential surface of the pillar portion 26 and the outer
circumferential surface of the hexagonal column portion 27. Also,
when located on the outer circumferential surface of the hexagonal
column portion 27, the balls 22 are permitted to move
circumferentially in a predetermined range.
[0032] A manner in which the clutch having the above-described
configuration switches power transmission states will hereafter be
described.
[0033] FIG. 6A illustrates the balls 22 each in a state located on
the outer circumference of the hexagonal column portion 27 of the
holding portion 24 of the sliding piece 20. From the midpoint 30 of
each side 28 toward the associated corner 29, the clearance between
the outer surface of each of the sides 28 of the hexagonal column
portion 27 and the projection 12 of the pulley 10 becomes smaller
with respect to the diameter Db of each ball 22. Accordingly, as
the pulley 10 rotates clockwise as viewed in FIG. 6A, for example,
the balls 22 contacting the inner circumferential surface of the
projection 12 are moved clockwise and caught in the portions
corresponding to the smaller clearance to be in a non-rotational
state. This couples the pulley 10 and the sliding piece 20 to each
other, or, in other words, engages the clutch. The rotational force
of the pulley 10 is thus transmitted to the sliding piece 20. This
rotates the compressor shaft 70, switching the compressor to an
operating state.
[0034] In contrast, when the balls 22 are located on the outer
circumference of the pillar portion 26 of the sliding piece 20 as
illustrated in FIG. 6B, the clearance between the outer
circumferential surface of the pillar portion 26 and the projection
12 is maintained substantially equal to the diameter Db of each
ball 22 throughout the entire circumference. Accordingly, when the
pulley 10 rotates clockwise as viewed in FIG. 6B in this state, for
example, the balls 22 are permitted to rotate between the sliding
piece 20 and the projection 12. The pulley 10 and the sliding piece
20 are thus in a decoupled state, or, in other words, the clutch is
disengaged. This prevents transmission of the rotational force of
the pulley 10 to the sliding piece 20. Rotation of the compressor
shaft 70 is thus suspended, and the compressor is in a
non-operating state.
[0035] As shown in FIG. 7, the plate assembly 73 has a solenoid 50,
which is arranged radially outside of the sliding piece 20, and a
pin 60 coupled to the solenoid 50. The pin 60 has an elongated hole
61 formed in an end and an inserting portion 62, which is formed in
the opposite end of the pin 60 and can be inserted into the groove
portion 25 of the sliding piece 20. The plate assembly 73 also has
a shaft 63, which is arranged between the end portions of the pin
60 to support the pin 60 in a manner rotational and immovable in
the axial direction of the pulley 10. In FIG. 1, illustration of
the solenoid 50 and the pin 60 is omitted.
[0036] A movable iron core 51 of the solenoid 50 is connected to
the elongated hole 61 of the pin 60 through a coupling member 64.
When the movable iron core 51 is projected from the solenoid 50 as
represented by the corresponding solid lines in FIG. 7, the pin 60
is pivoted about the shaft 63 to insert the inserting portion 62 of
the pin 60 into the groove portion 25. In contrast, when the
movable iron core 51 is retracted into the solenoid 50 as
represented by the long dashed double-short dashed line in FIG. 7,
the pin 60 is pivoted about the shaft portion 63 to retract the
inserting portion 62 from the groove portion 25.
[0037] The configuration of the solenoid 50 will hereafter be
described.
[0038] With reference to FIG. 8A, the solenoid 50 has the movable
iron core 51, a yoke 52 holding the movable iron core 51, a coil 53
arranged in the yoke 52, a receiving portion (a fixed iron core)
58, and a magnet 54. A hole 55 is formed in a distal end portion of
the movable iron core 51. The aforementioned coupling member 64 is
attached to the hole 55 and inserted into the elongated hole 61 of
the pin 60 (see FIG. 7). A ring member 56 is attached to the outer
circumference of the movable iron core 51. A spring 57 is provided
between the ring member 56 and the yoke 52. The spring 57 produces
urging force acting in a direction in which the movable iron core
51 is projected from the yoke 52 (in the rightward direction as
viewed in FIG. 8A).
[0039] When the movable iron core 51 is in a projected state as
illustrated in FIG. 8A and the coil 53 is energized, the magnetic
force produced by the coil 53 retracts the movable iron core 51
into the yoke 52. Then, when the movable iron core 51 comes into
contact with the receiving portion 58, the attracting force (the
magnetic force) by which the magnet 54 attracts the movable iron
core 51 exceeds the elastic force of the spring 57. If the coil 53
is de-energized in this state, the attracting force of the magnet
54 exceeding the elastic force of the spring 57 maintains the
movable iron core 51 in a retracted state, as illustrated in FIG.
8B.
[0040] In contrast, if the coil 53 is energized with the movable
iron core 51 held in the retracted state such that a reverse field
is produced to cancel the magnetic force of the magnet 54, the
attracting force of the magnet 54 decreases and the elastic force
of the spring 57 exceeds the attracting force. This projects the
movable iron core 51 to such a position where the ring member 56
contacts the yoke 52. When the movable iron core 51 is in a state
projected and separated from the receiving portion 58 in this
manner, the elastic force of the spring 57 exceeds the attracting
force of the magnet 54. Accordingly, once the coil 53 is energized
to separate the movable iron core 51 from the receiving portion 58,
the elastic force of the spring 57 maintains the movable iron core
51 in the projected state as illustrated in FIG. 8A, even after the
coil 53 is de-energized.
[0041] Accordingly, by energizing the coil 53 of the solenoid 50,
the movable iron core 51 is moved to switch the pin 60 selectively
between an inserted state, in which the pin 60 is inserted into the
helical groove 33, and a retracted state, in which the pin 60 is
retracted from the helical groove 33. Further, even after the coil
53 is de-energized, the pin 60 is maintained in a state to which
the pin 60 has been switched.
[0042] Operation of the clutch according to the present embodiment
will now be described with reference to FIG. 9.
[0043] FIG. 9A illustrates a state in which the sliding piece 20 is
urged by the urging force of the spring 21 and closest to the
pulley 10 in the axial direction. Referring to the drawing, when
the sliding piece 20 is closest to the pulley 10, the balls 22 are
located on the outer circumference of the hexagonal column portion
27 of the sliding piece 20. If the pulley 10 rotates in this state,
the balls 22 are caught between the projection 12 of the pulley 10
and the sliding piece 20 in a non-rotational state, thus coupling
the pulley 10 and the sliding piece 20 to each other in a manner
permitting power transmission. This switches the clutch to an
engaged state such that the sliding piece 20 and the compressor
shaft 70 rotate integrally with the pulley 10 to operate the
compressor. The position at which the sliding piece 20 is located
when the clutch engaged corresponds to a first position.
[0044] If the coil 53 is energized in this state, the inserting
portion 62 of the pin 60 is inserted into the helical groove 33 of
the sliding piece 20, which is in a rotating state, as illustrated
in FIG. 9B. This causes the pin 60 to slide on the side surface 36
of the helical groove 33 to convert some of the rotational force of
the sliding piece 20 into axial force. As a result, as illustrated
in FIG. 9C, the sliding piece 20 is moved rightward in the axial
direction, or, in other words, in the direction separating from the
pulley 10. At this stage, as the sliding piece 20 moves in the
axial direction, the balls 22, which are arranged in the outer
circumference of the sliding piece 20, move from the positions on
the outer circumferential surface of the hexagonal column portion
27 to the positions on the outer circumferential surface of the
pillar portion 26.
[0045] Then, referring to FIG. 9D, as the pin 60 slides on the side
surface 36 of the helical groove 33 and the axial movement amount
of the sliding piece 20 increases, the balls 22 are guided by the
corresponding holding holes 42 of the holding device 23 and moved
to the outer circumference of the pillar portion 26. When the balls
22 are located on the outer circumference of the pillar portion 26,
the balls 22 are in a state permitted to rotate between the sliding
piece 20 and the projection 12. The sliding piece 20 and the
projection 12 are thus decoupled from each other. This switches the
clutch to a disengaged state, thus stopping operation of the
compressor. The position at which the sliding piece 20 is located
when the clutch is disengaged corresponds to a second position.
[0046] Even after the pulley 10 and the sliding piece 20 are
decoupled from each other, the sliding piece 20 may be maintained
in a rotating state by inertial force in some cases. However, if
the pin 60 slides on the side surface 39 of the annular groove 34
as illustrated in FIG. 9D, the rotational force of the sliding
piece 20 is prevented from being converted into the axial force.
This restricts axial movement of the sliding piece 20 after the
sliding piece 20 and the pulley 10 are decupled from each
other.
[0047] To switch the clutch from the disengaged state back to the
engaged state, the coil 53 is energized to retract the inserting
portion 62 of the pin 60 from the annular groove 34, as illustrated
in FIG. 9E. After the pin 60 is retracted from the annular groove
34, the sliding piece 20 is pressed by the urging force of the
spring 21. This moves the sliding piece 20 leftward in the axial
direction, which is the direction approaching the pulley 10. Such
movement of the sliding piece 20 moves the balls 22 from the
positions on the outer circumferential surface of the pillar
portion 26 to the positions on the outer circumferential surface of
the hexagonal column portion 27. Then, when the sliding piece 20 is
pressed to such a position where the sliding piece 20 becomes
closest to the pulley 10 referring to FIG. 9F, the balls 22 are
arranged on the outer circumference of the hexagonal column portion
27. As a result, the balls 22 are caught between the pulley 10 and
the sliding piece 20, thus engaging the clutch.
[0048] The above described embodiment has the following
advantages.
[0049] (1) In the present embodiment, to disengage the clutch, the
pin 60 is inserted into the helical groove 33 of the sliding piece
20, which is in a rotating state. This converts some of the
rotational force of the sliding piece 20 into the axial force,
which moves the sliding piece 20 to the second position. The force
necessary for disengaging the clutch is thus generated from the
rotational force of the sliding piece 20. As a result, even to
transmit relatively great torque, the clutch does not have to be
enlarged in size to be capable of switching power transmission
states.
[0050] (2) In the present embodiment, the helical groove 33 is
formed in a stepped shape as viewed along an axial cross section.
The axial length of the portion corresponding to the helical groove
33 is thus decreased, and size enlargement of the clutch is
restrained in a more desirable manner.
[0051] (3) In the present embodiment, the pin 60 is caused to slide
on the annular groove 34 to restrict axial movement of the sliding
piece 20 after the pulley 10 and the sliding piece 20 are decoupled
from each other. The axial length of the clutch thus can be
decreased to reduce the size of the space needed to install the
clutch.
[0052] (4) In the present embodiment, the clutch includes the balls
22. When the sliding piece 20 is located at the first position, the
balls 22 are caught between the sliding piece 20 and the pulley 10
in a non-rotational manner to couple the sliding piece 20 to the
pulley 10. When the sliding piece 20 is arranged at the second
position, the balls 22 are released from the sliding piece 20 and
the pulley 10 to decouple the sliding piece 20 and the pulley 10
from each other. As a result, unlike a pressing type clutch, for
example, the clutch is capable of transmitting greater torque
without being enlarged in size.
[0053] (5) In the present embodiment, a self-holding type solenoid
50 is employed as the solenoid 50. Thus, the coil 53 needs to be
energized only when the power transmission states of the clutch
must be switched. This decreases the power consumed by the
solenoid.
[0054] Although the self-holding type solenoid 50 is used as the
solenoid 50 in the above illustrated embodiments, a solenoid that
inserts the pin 60 into the helical groove 33 only while being
energized may be employed. In this configuration, the clutch is
disengaged only when the coil 53 is energized. Therefore, if the
solenoid 50 fails to energize the coil, the clutch is maintained in
the engaged state. As a result, the compressor is operated
regardless of such failure of the solenoid 50.
[0055] In the above illustrated embodiment, the solenoid switches
the pin 60 selectively between the inserted state and the retracted
state. However, the states of the pin 60 may be switched using any
suitable actuator other than the solenoid, such as a hydraulic type
actuator.
[0056] In the above illustrated embodiment, the sliding piece 20
and the pulley 10 are selectively coupled to and decoupled from
each other by means of the balls 22. However, a pressing type
clutch having a pressing surface formed in a portion of the outer
circumferential surface of the sliding piece 20 may be employed.
The clutch switches to the engaged state by pressing the pressing
surface against the pulley 10.
[0057] In the above illustrated embodiment, the groove portion 25
is formed in the outer circumferential surface of the sliding piece
20. However, the groove portion 25 may be formed in the inner
circumferential surface of the sliding piece 20.
[0058] Although the above illustrated embodiment employs the
helical groove 33 having the stepped cross section the diameter of
which decreases in the axial direction toward the pulley 10, such
configuration may be modified.
[0059] Although the above illustrated embodiment includes the
annular groove 34, the annular groove 34 may be omitted.
[0060] In the above illustrated embodiment, the helical groove is
shaped to extend in a manner revolving clockwise by 540.degree.
from the starting point 35 (0.degree.). However, the range in which
the helical groove 33 extends in a revolving manner may be set to
any other suitable range, such as the range corresponding to
180.degree. or 720.degree.. That is, any suitable range may be
employed as long as the sliding piece 20 can be moved to the second
position by the pin 60 sliding on the helical groove 33.
[0061] Although the coil spring 21 is used as the urging member in
the above illustrated embodiment, any other suitable member such as
a spring or a rubber member having any other shape than the
coil-like shape may be employed as the urging member.
[0062] In the above illustrated embodiment, the clutch is arranged
between the crankshaft and the compressor to switch the power
transmission states between the crankshaft and the compressor.
However, the clutch according to the present disclosure may be used
as a clutch provided between any other suitable auxiliary device,
such as a water pump or an oil pump, and the crankshaft. Further,
the clutch according to the present disclosure is not restricted to
a clutch for switching states of power transmission from a
crankshaft but may be employed as a clutch for switching states of
power transmission from any other suitable drive source.
[0063] In the above illustrated embodiment, the axial position of
the pin 60 is restricted. However, as long as the sliding piece 20
can be moved to the second position by engaging the pin 60 with the
groove portion 25, the pin 60 may be allowed to move in the axial
direction.
* * * * *