Abstract:
A power transmission for a compressor includes a driven member rotable by an engine. The power transmission includes a drive member rotable coaxially with the driven member to rotate a shaft of a compressor for regulating displacement of the compressor. The power transmission includes a link interconnecting the driven member and the drive member with each other in a crossing direction relative to the drive shaft. The link is disengageable from one member of the driven member and the drive member.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to a power transmission and a compressor employing the power transmission. The compressor includes a displacement compressor and a turbocompressor. The displacement compressor includes a reciprocating compressor and a rotating compressor. The reciprocating compressor includes a swash-plate, a wobble-plate, a crank, and a Scotch yoke compressor. 
   A conventional power transmission is adapted to a clutchless compressor, as referred in Japanese Patent Application Publication Laid-open No. 2000-87850. The compressor includes a boss in a housing. The boss rotatably supports a pulley, using a bearing. The housing houses a shaft. The shaft is disposed coaxially with the boss, projecting outwardly from the boss. The shaft has an end fixed to a hub. 
   The hub has a cover member fixed thereto, using a rivet. The cover member has recesses at the peripheral edge. The recesses are arranged on the identical circle about the shaft at an angular interval. Each of the recesses has a cushioning rubber therein which are adhered thereto. Each end of the recesses has a hole which rotatably houses a ball, a part of which is projected from the hole. 
   The pulley has a face opposed to the cover member. The face has a first hole on the identical circle, in which the ball is rotatably housed. The identical circle has a second hole thereon, in which the ball, disengaged from the first hole, drops. 
   The outer periphery of the pulley has a belt applied thereto. The belt is connected to a crank shaft. When driving an engine, the pulley is rotated, and power is transmitted to the shaft through the cushioning rubber, the cover member and the hub. 
   It is supposed that the clutchless compressor produces an abnormality such as seizing therein, and load torque goes over a predetermined value. Respective cushioning rubbers are deformed to disengage from balls. Respective balls are pressed by the cover member and are disengaged from first holes, going into second holes. This cuts off transmission of power from the pulley to the shaft, thus idling the pulley. 
   The conventional art has a complicated structure, the large number of components and productive steps, and high productive cost. In the conventional art, wear or age deterioration on the cushioning rubber reduces the threshold value of load torque when transmission of torque toward the compressor is cut off. 
   SUMMARY OF THE INVENTION 
   The invention is directed to a power transmission and a compressor, which has a simplified structure for shortening production time and reducing production cost. 
   The invention is directed to a power transmission and a compressor, which reduces a shaft of a compressor in axial dimension. 
   The invention is directed to a power transmission and a compressor, which prevents reduction of the threshold of load torque when transmission of power toward the compressor is cut off, thus enhancing reliability. 
   A first aspect of the invention provides a power transmission for a compressor. The power transmission includes a driven member rotatable by an engine. The power transmission includes a drive member rotatable coaxially with the driven member to rotate a shaft of a compressor for regulating displacement of the compressor. The power transmission includes a link interconnecting the driven member and the drive member with each other in a crossing direction relative to the drive shaft. The link is disengageable from one member of the driven member and the drive member. 
   Preferably, the link is rotatably mounted to the other member of the driven member and the drive member. 
   Preferably, the other member includes a locking member configured to lock with the link disengaged from the one member. 
   Preferably, the locking member includes a resilient member slidably pressing the link against the other member. 
   Preferably, the one member includes a first engagement member. The other member of the driven member and the drive member includes a second engagement member. The link includes a first hole fitted with the first engagement member. The link includes a guide extending from the first hole to an end edge of the link. The link includes a second hole fitted with the second engagement member. 
   Preferably, the first engagement member is deformable. 
   Preferably the first engagement member is integrated with the one member. The second engagement member is integrated with the other member. 
   Preferably, the link is interposed between the driven member and the drive member. 
   Preferably, the link includes plates of an identical shape and dimension stacked on each other. 
   Preferably, the link is deformable to disengage from the one member. 
   Preferably, the first engagement member passes through the guide to disengage from the link. 
   Preferably, links are arranged about the shaft at an equal angular interval. 
   A second aspect of the invention provides a compressor for a vehicle. The compressor includes a shaft for regulating displacement. The compressor includes a driven member rotatable by an engine. The compressor includes a drive member rotatable coaxially with the driven member to rotate the shaft. The compressor includes a link interconnecting the driven member and the drive member. The link is deformable to disengage from one member of the driven member and the drive member. 

   
     BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS 
       FIG. 1  is a schematic view of an air conditioning system according to the first embodiment of the invention; 
       FIG. 2  is a cross-sectional view of a compressor in  FIG. 1 ; 
       FIG. 3  is an elevation view of a power transmission in  FIG. 2 ; 
       FIG. 4  is a cross-sectional of the power transmission taken along IV-IV in  FIG. 3 ; 
       FIG. 5  is an elevation view of the power transmission after power-off; 
       FIG. 6  is a plane view of a leaf spring in  FIG. 3 ; 
       FIG. 7  is a partial sectional view of a power transmission according to the second embodiment; 
       FIG. 8  is a partially broken elevation view of a power transmission according to the third embodiment; 
       FIG. 9  is a sectional view of the power transmission taken along IX-IX in  FIG. 8 ; 
       FIG. 10  is a partial sectional view of the power transmission taken along X-X in  FIG. 8 ; 
       FIGS. 11A to 11E  are elevation views illustrating operation of the power transmission in  FIG. 8 ; 
       FIG. 12  is a partially broken elevation view of the power transmission of  FIG. 8  after cutting off power; 
       FIG. 13  is a graph showing results where release torque is repeatedly measured relative to the power transmission in  FIG. 8 ; and 
       FIGS. 14A and 14B  are enlarged elevation views of a leaf spring that is adapted for the power transmission according to the fourth embodiment. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Embodiments of the invention will hereby be described with reference to the drawings. 
   In  FIG. 1 , an air conditioning system includes a refrigeration-cycle and a controller thereof. The refrigeration-cycle includes a swash plate compressor  100  to compress a vaporized coolant. The refrigeration-cycle includes a condenser  111  to liquefy a coolant. The refrigeration-cycle includes an evaporator  121  to vaporize a liquefied coolant. 
   The compressor  100  includes a pulley  4  for drive which is coupled to a pulley  101   a  of engine  101 , using a belt B. The compressor includes an electronic control valve  102  downstream. 
   The condenser  111  has a cooling fan  113 . The condenser includes a liquid tank  112 . 
   The controller includes an AC computer  131  driven by a battery  133 . The AC computer  131  obtains information from sensors S 1 , S 6 , S 7  and S 8 . The sensor S 1  detects a temperature at the outlet of evaporator  121 . The sensor S 6  detects a temperature of vehicle&#39;s interior. The sensor S 7  has a solar radiation sensor. The sensor S 8  detects a temperature outside the vehicle. The AC computer  131  controls the electronic control valve  102 . 
   The controller includes ECCS (electronic concentrated engine control system)  132 . The ECCS  132  obtains information from sensors S 2 , S 3 , S 4  and S 5  to control engine  101 . The sensor S 2  detects vehicle&#39;s speed. The sensor S 3  detects the opening rate of an accelerator. The sensor S 4  detects the rotational speed of a wheel or an axle. The sensor S 5  detects a suction air pressure of engine  101 . 
   In.  FIG. 2 , the swash plate compressor  100  includes a cylinder block  32  defining six cylinder bores  33  around a shaft  7  in a housing  1 . Each of the cylinder bores  33  houses a cylinder  48  axially slidable therein. The compressor  100  includes a front housing  1  defining a crank chamber  35  adjacent to the cylinder block  32 . 
   The compressor  100  includes a rear housing  36  which defines coolant suction chamber  37  and coolant discharge chamber  38  in communication with the cylinder bores  33 . The cylinder bores  33  and coolant suction and discharge chambers  37 ,  38  are separated from each other by a valve plate  39 . The valve plate  39  has inlets  53  and outlets  56  interconnecting cylinder bores and suction and discharge chambers  37 ,  38 . The valve plate  39  has suction plates  54  which cover inlets  53  on the cylinder bores  33 . The valve plate has discharge plates  55  which cover outlets  56  on the discharge chamber  38 . 
   The crank chamber  35  includes a drive plate  41  fixed to a shaft  7 . The crank chamber  35  includes a sleeve  42  slidably fitted with the shaft  7 . The crank chamber  35  includes a journal  44  swingably connected to shaft  7 , using pin  43 . The crank chamber  35  includes a swash plate  45  fixed to the outer end of journal  44 . 
   The journal  44  connects to an elongated arced hole  46  of drive plate  41  which restricts a swing motion. 
   The pistons  48  are connected to the swash plate  45 , using a pair of shoes  49 , with the swash plate  45  interposed between shoes  49 . 
   The shaft  7  is connected to the pulley  4  for rotation. The pulley  4  is rotatably supported by bearing  3  on the front housing  1 . 
   The compressor  100  includes an electronic control valve  102  and a check valve  103  in a rear housing  36 . The control valve  102  feeds a part of a compressed coolant in discharge chamber  38  to the crank chamber  35  through a passage  52  for regulating pressure in crank chamber  35 . 
   The swash plate  45  is controlled at an inclined angle by differential pressure between suction chamber  37  and crank chamber  35 . The angular change of swash plate  45  changes the stroke of each piston  48 , which changes the discharge volume of a coolant. 
   In  FIG. 4 , clutchless compressor  100  has housing  1  with a boss  2 . The boss  2  has the pulley  4  rotatably supported thereon, using the bearing  3 . The pulley  4  has drive plate  5  fixed on the end face thereof, using a bolt. The drive plate  5  includes cylinder-shaped protrusions  6  on the side thereof. The protrusions  6  are arranged on the identical circle about shaft  7  at an angular interval. The pulley  4  and drive plate  5  constitutes a first transmission member or a driven member. 
   The housing  1  is coaxial with the boss  2 , and houses shaft  7  which projects outward from the boss  2 . The shaft  7  has an end which is fixed to hub  10  (second transmission member or drive member), using a bolt  8  and a washer  9 . As shown in  FIG. 3 , hub  10  is shaped as a triangle. The hub  10  has pin insertion holes  11  (refer to  FIG. 4 ), which are positioned on the identical circle about shaft  7  at an angular interval of 120 degree. 
   The hub  10  connects with drive plate  5 , using belt-plate shaped leaf springs or links  12 A of the identical shape and dimension. The leaf spring  12 A is made of a spring of a high-carbon steel. The leaf springs  12 A are arranged between drive plate  5  and hub  10  and parallel with a direction normal to the shaft  7 . For example, the leaf springs  12 A extend tangentially from hub  10  to pulley. In  FIG. 6 , each of leaf springs  12 A has a through-hole  14  at one longitudinal end, which is rotatably fitted with the outer periphery of pin (protrusion)  13  that passes through insertion-hole  11 . Each of the leaf springs  12 A has a second through-hole  15  at the other longitudinal end, which is rotatably fitted with the outer periphery of a protrusion  6 . 
   Each of the leaf springs  12 A has a slit  16  extending longitudinally from one end edge toward the other end and over the first through-hole  14 . One end of leaf spring  12 A includes a pair of side pieces  12 A a ,  12 A b  opposed to each other. Each of side pieces  12 A a ,  12 A b  defines slit  16  and first through-hole  14  therebetween. The first through-hole  14  is slightly smaller in size than the pin  13 . The fitting of pin  13  into the first through-hole  14  allows the inner periphery of first through-hole  14  to be pressed against the outer periphery of pin  13  under a resilient force of leaf spring  12 A. This allows both peripheries to be in tight contact with each other without a gap. It is supposed that compressor  100  produces seizing inside thereof, and load torque goes over a predetermined value. The width of slit  16  is set for the pin  13  fitted in first through-hole  14  to press and widen the slit  16  so as to come out of the slit  16 . 
   Each of leaf springs  12 A has a slit  18  extending longitudinally from the second through-hole  15  toward the other end. The second through-hole  14  is slightly smaller in size than protrusion  6 . The protrusion  6  is pressed into the second through-hole  15  before the head of protrusion  6  is riveted. The pressing allows the inner periphery of second through-hole  15  to be pressed against the outer periphery of protrusion  6  under resilient force by leaf spring  12 , thus eliminating the gap between both peripheries. The riveting of the head of protrusion  6  as a flange prevents the leaf spring  12 A from coming out of protrusion  6 , as shown in  FIG. 4 . 
   Next, operation of the power transmission is described. Power of the engine  101  is applied to pulley  4  through the belt B. It is supposed that load torque on the compressor is lower than a predetermined value. Power from engine  101  is transmitted to hub  10  through the protrusion  6 , leaf spring  12 A, and pin  13 , rotating shaft  7 . The rotating shaft  7  rotates swash plate  45  to control the stroke of pistons  48 . 
   It is supposed that seizing inside the compressor  100  causes the load torque to go over a predetermined value. Each of pins  13  is firmly pressed against the portion of slit  16  in proximity to the tip end of leaf spring  12 A. The portion of slit  16  or side pieces  12 A a ,  12 A b  are pressed and widened transversely. This allows the pin  13  fitted in the first through-hole  14  to be disengaged from the leaf spring  12 A through the slit  16 . The disengagement cuts off transmission of power from pulley  4  to shaft  7 , thus idling pulley  4 . The pin  13  may be replaced by a resilient cylinder, which is resiliently deformed to pass through the slit  16 . 
   The leaf spring  12 A of a spring or resilient material resists time-varying or wearing, and the leaf spring  12 A is deformed to cut off transmission of power. This stabilizes the threshold value of load torque, achieving accurate cutting-off of transmission of power. 
   Especially, the embodiment is structured as the leaf springs  12 A of the identical shape and dimension are arranged symmetrically about shaft  7  at an equal angular interval. The arrangement reduces influence on leaf springs  12 A due to variation of strength and dimension, and advantageously facilitates to cut off power due to the threshold value of a desired load torque. 
   Each of the leaf springs  12 A disengaged from the pin  13  is rotatable about protrusion  6 . A leaf spring  12 A hits upon a neighboring pin  13  to rotate toward the outer periphery of pulley  4 . The leaf spring  12 A runs on and locks with protrusion-shaped locking member  19  formed to drive plate  5 , under centrifugal force (refer to  FIG. 5 ). In this state, the hub  10  and pin  13  do not contact with the leaf spring  12 A, and noise does not occur. 
   The power transmission has a simple structure, and a smaller number of components and production steps in comparison with the conventional art&#39;s structure. This shortens production time and reduces production cost. 
   Each of the leaf springs  12 A in a plate-shape is arranged between the drive plate  5  and hub  10  and parallel to a direction normal to the shaft  7 . Thus, the shaft  7  has a small dimension in an axial direction, which advantageously facilitates installation of the clutchless compressor at a position. 
   Next, the second embodiment of the invention is described. In respective embodiments, portions identical to ones of the first embodiment are applied to the identical reference numerals, and overlapped description is omitted. 
   In  FIG. 7 , the embodiment has protrusions  20  formed integrally to the face hub  10 , in place of the pins  13  of the first embodiment. The protrusions  20  are fitted in one ends of leaf springs  12 A. The other ends of leaf springs  12 A has protrusions  6  rotatably fitted therein. The protrusions  6  are integrally formed to the pulley  4 . This further reduces the number of components, which shortens production time and reduces production cost. 
   According to the embodiment, the leaf springs  12 A are interposed between the hub  10  and pulley  4 , and are restricted to move in a thickness direction thereof This requires no riveting of protrusions  6  for preventing of leaf springs  12 A from coming out of protrusions  6 . This further reduces production cost. 
   Next, the third embodiment of the invention is described. 
   Referring to  FIG. 8 , in the embodiment, respective leaf springs  12 B include a pair of bifurcate side pieces  12 Ba,  12 Bb connected to each other. Each of leaf springs  12 B has the side pieces  12 Ba,  12 Bb on one end side, which radially crimp the outer periphery of protrusion  6 . Each of leaf springs  12 B has the other end side rotatably supported by pin  13 . Leaf spring  12 B has two plates  12 B 1 ,  12 B 2  of the identical shape and dimension. The plates  12 B 1 ,  12 B 2  are stamped out in a shape, and are stacked on each other in the thickness direction. This facilitates stamping for enhancing workability, and resists burr and deformation for enhancing dimensional accuracy. 
   The embodiment has a locking member  19  of a resilient member as a washer. The locking member  19  is a fitted concentrically with the outer periphery of shaft part  10   a  of hub  10 . The locking member has a peripheral edge bent toward the flange  10   b  of hub  10 . The locking member  19  slidably presses respective leaf springs  12 B against the rear side of flange  10   b  of hub  10  for locking. 
   According to the power transmission, it is supposed that the compressor has a load torque over a certain value. In  FIGS. 11B ,  11 C, each of protrusions  6  presses and widens the ends of the side pieces  12 B a ,  12 B b  on one end side of leaf spring  12 B, disengaging from the leaf spring  12 B. The disengagement cuts off transmission of power from the pulley  4  to hub  10 . In  FIG. 11D , each of leaf springs  12 B comes against a protrusion  6  that rotates along an orbit T indicated by the dotted line. In  FIGS. 11E and 12 , leaf springs  12 B rotate inside of the orbit, sliding on the locking member  19 . The leaf springs  12 B is locked in a region without contacting protrusions  6 . 
   According to the embodiment, the leaf springs  12 B disengages from pulley  4  rotating after cutting off transmission of power. In the case, leaf springs  12 B does not rotate during maintenance. Thus, the embodiment prevents hitting of the leaf springs  12 B upon an operator and injury to the operator. 
   The clearance between the leaf spring  12 B and pulley  4  requires width X more than a predetermined size, as referred in  FIG. 9 . Without means for positioning the leaf springs  12 B in an axial direction of the shaft  7 , dimensional variation of components causes a width X less than a predetermined size. Thus, a shim is required to be inserted between the tip face of shaft  7  and hub  10  for adjustment. As the embodiment, the locking member  19  presses the leaf springs  12 B against hub  10 . This ensures a width X more than a predetermined size, advantageously saving time for adjustment. 
   Referring to  FIG. 13 , release torque of leaf spring  12 B and protrusion  6  is repeatedly measured five times. The test&#39;s object is the identical leaf spring  12 B and protrusion  6 . That is, after disengagement of the leaf spring  12 B and protrusion  6  from each other, the leaf spring  12 B and protrusion  6  is engaged again for test. As a result, release torques are stabilized at about 80 Nm. 
   Next, the fourth embodiment of the invention is described. 
   In  FIG. 14A , a leaf spring  12 C has an end with both sides projecting transversely outward. The leaf spring  12 C has side-pieces  12 C a ,  12 C b  at the end. The side pieces  12 C a ,  12 C b  are opposed to each other, with a slit  22  intervening between the side-pieces  12 C a ,  12 C b  at the end. The side pieces  12 C a ,  12 C b  are resiliently deformable. The slit  22  extends longitudinally from the end edge to the other end of the leaf spring  12 C. The hub  10  has locking parts  21  with fitting recess  23  in which the end of leaf spring  12 C is fitted. 
   It is supposed that the clutchless compressor has a load torque less than a predetermined value. The side-pieces  12 C a ,  12 G b  at the end of leaf spring  12 C is maintained to fit in the fitting recess  23  of locking part  21 , as shown in  FIG. 14A . With load torque over a predetermined value, the end or side pieces  12 C a ,  12 G b  of leaf spring  12 C is resiliently deformed, with the width being reduced. The leaf spring  12 C is disengaged from the fitting recess  23 , thus cutting off power, as shown in  FIG. 14B . 
   Although the invention has been described above by reference to certain embodiments of the invention, the invention is not limited to the embodiments described above. Modifications and variations of the embodiments described above will occur to those skilled in the art, in light of the above teachings. The scope of the invention is defined with reference to the following claims. 
   The entire contents of Japanese Patent Applications P2003-8315 (filed Jan. 16, 2003), P2003-8309 (filed Jan. 16, 2003), P2002-306139 (filed Oct. 21, 2002), and P2002-306124 (filed Oct. 21, 2002) are incorporated herein by reference. 
   According to the invention, a power transmission is manufactured with a small number of components and production steps. This shortens production time and reduces production cost. The arrangement of a link reduces a shaft in the axial dimension. 
   The link does not contact with the other member of the driven member and the drive member after cutting off power, and noise does not occurs. 
   The invention requires no riveting for preventing the link from coming out of a first or second engagement member. This further shortens production time and reduces production cost. 
   The link includes plates of an identical shape and dimension, which enhances workability during stamping and dimensional accuracy. In addition, in comparison with a link of a single plate, torque is further stabilized, when excessive torque cuts off transmission of power. 
   The link resists time-varying or wearing, which stabilizes the threshold value of load torque, enhancing reliability. 
   The influence on the link, depending on variation of strength and dimension, is reduced, which facilitating cutting off of power due to the threshold value of a desired load torque, thus enhancing reliability.