JP5106502B2 - Power transmission structure - Google Patents

Description

  The present invention relates to a power transmission structure that transmits torque from a drive shaft to a driven shaft, and more particularly, to a power transmission structure that transmits torque via an Oldham coupling that allows deviation of the axial center between the drive shaft and the driven shaft.

  As this type of power transmission structure, for example, a structure described in Patent Document 1 has been proposed. In the technique described in Patent Document 1, groove-shaped fitting recesses extending in the radial direction of the drive joint are formed as receiving portions at both ends of a drive joint that is an Oldham joint, respectively, and a rotary shaft that is a drive shaft and a driven shaft The fitting convex part formed in the front-end | tip of the spindle which is a shaft is each fitted to the corresponding receiving part. The receiving portions are formed so as to be substantially orthogonal to each other on a projection plane orthogonal to the axial direction of the drive joint, and the fitting convex portions and the receiving portions slide relative to each other. Thus, a deviation of the axial center from the rotation shaft and the support shaft is allowed.

JP 2002-31152 A

  Here, when trying to mold the Oldham joint with a metal material, while forming a molding surface corresponding to one receiving portion on the mold element that controls the molding of one end in the axial direction of the Oldham joint, A molding surface corresponding to the other receiving portion is formed on the mold element that controls the molding of the other end in the axial direction.

  However, since molding surfaces corresponding to both receiving portions are formed in different mold elements, there is a risk that the accuracy of the relative angular position of both receiving portions may be reduced.

  The present invention has been made in view of such a problem, and an object of the present invention is to provide a power transmission structure in which the accuracy of the relative angular position of both the receiving portions is improved.

  According to the first aspect of the present invention, the width of each of the fitting protrusions protruding from the tip surfaces of the drive shaft and the driven shaft is made different, while the Oldham joint is a flat shape extending in the radial direction of the Oldham joint. The cross section of the Oldham coupling is penetrated in the axial direction, and one of the fitting protrusions with a small width is inserted from one end side in the axial direction of the Oldham joint, and its width A first receiving portion whose dimension is set smaller than the other fitting convex portion having a larger width dimension among the both fitting convex portions, and a depth from the other end surface in the axial direction of the Oldham joint to the intermediate portion in the axial direction The Oldham joint is recessed with a flat cross-sectional shape extending in the radial direction, and intersects with the first receiving portion in such a manner that the central portion in the longitudinal direction in the cross section is shared with the first receiving portion. And To is characterized in that it comprises a second receiving unit for the other fitting convex portion is inserted, the.

  In the invention according to claim 2, the longitudinal dimensions of the fitting convex portions respectively protruding from the tip surfaces of the drive shaft and the driven shaft are made different from each other, while the Oldham joint is a radial direction of the Oldham joint. The Oldham joint is penetrated in the axial direction with a flat cross-sectional shape extending in the direction, and one of the fitting protrusions having a small longitudinal dimension is inserted from one end side in the axial direction of the Oldham joint. A first receiving portion whose longitudinal dimension is set smaller than the other fitting convex portion having a larger width dimension among the both fitting convex portions, and an axial direction from the other axial end surface of the Oldham joint. The first receiving part is recessed with a flat cross-sectional shape extending in the radial direction of the Oldham joint at a depth to the middle part, and a central part in the longitudinal direction in the cross section is shared with the first receiving part. Together are formed so as to cross, is characterized in that it comprises a second receiving unit for the other fitting convex portion is inserted, the.

  That is, in the first and second aspects of the invention, the first receiving portion is formed as a through hole, and the both receiving portions are communicated with each other. The receiving part can be formed with a common mold element. Moreover, although both said receiving parts will each open in the axial direction other end surface of the said Oldham coupling, the cross-sectional shape of the said 1st receiving part is set so that the said other fitting convex part cannot be inserted. Therefore, it is possible to prevent erroneous assembly that the other fitting convex portion to be inserted into the second receiving portion is inserted into the first receiving portion.

  According to the present invention, the accuracy of the relative angular position of both receiving parts can be improved by forming both receiving parts with a common mold element.

1 is a system configuration diagram of a power steering apparatus to which a power transmission structure according to the present invention is applied. The longitudinal cross-sectional view of the pump unit shown in FIG. The exploded perspective view which shows the power transmission structure from the motor drive shaft shown in FIG. 2 to a pump drive shaft as a power transmission structure which concerns on the 1st Embodiment of this invention. The perspective view which shows the detail of the Oldham coupling shown in FIG. Sectional drawing which shows the metal mold | die for shape | molding the Oldham coupling shown in FIG. Explanatory drawing which shows the relationship between the width dimension of a fitting convex part, and a moment span. The figure which shows the axial direction one end surface of an Oldham coupling as the 2nd Embodiment of this invention.

  FIG. 1 is a system configuration diagram of a power steering apparatus to which a power transmission structure according to the present invention is applied.

  As shown in FIG. 1, when the driver steers the steering wheel SW, the pinion 4 is driven through the shaft 2, and the rack shaft 5 is moved in the axial direction by a so-called rack and pinion mechanism, and the left and right front wheels 6a and 6b are moved. Steer. The shaft 2 is provided with a torque sensor TS that detects the steering torque of the driver, and outputs a torque signal to the control unit 7.

  The rack shaft 5 is provided with a power steering mechanism that assists the movement of the rack shaft 5 according to the steering torque of the driver. This power steering mechanism includes a motor M as a drive source, a pump unit P including a reversible pump 3 and a control unit 7 as driven elements driven by the motor M, and a power cylinder that moves the rack shaft 5 to the left and right. 8.

  In addition to the torque signal from the torque sensor TS and the transmission signal, the control unit 7 receives a switch signal from the ignition switch, an engine speed signal from the engine speed sensor, a vehicle speed signal from the vehicle speed sensor, and the like. The steering assist force is determined based on these various signals, and a command signal is output to the motor M and an electromagnetic switching valve 18 described later. As a result, hydraulic pressure is supplied to the power cylinder 8 and steering assist is performed.

  Further, a piston 8c that can move in the axial direction is provided inside the power cylinder 8, and the first cylinder chamber 8a and the second cylinder chamber 8b are separated inside the power cylinder 8 by the piston 8c.

  The first cylinder chamber 8 a is connected to the pump 3 via the first oil passage 10, while the second cylinder chamber 8 b is connected to the pump 3 via the second oil passage 11. Further, both the oil passages 10 and 11 are connected to the reservoir tank 9 via the first and second replenishment oil passages 12 and 13 and the first and second suction check valves 14 and 15, respectively. The suction check valves 14 and 15 prevent the backflow of hydraulic oil to the reservoir tank 9 and replenish the hydraulic oil from the reservoir tank 9 when the hydraulic oil in both the oil passages 10 and 11 is insufficient. become.

  Both the oil passages 10 and 11 are connected to each other via the communication passage 16 without passing through the pump 3, and the communication passage 16 is connected to a drain oil passage 19 provided with an electromagnetic switching valve 18 at a connection portion 17. The communication path 16 is connected to the reservoir tank 9 via a drain oil path 19, and the communication path 16 and the reservoir tank 9 are communicated and blocked by the electromagnetic switching valve 18. In addition, check valves 20 and 21 are provided on the communication path 16 and between the connecting portion 17 and both the oil passages 10 and 11 to allow only the flow to the connecting portion 17 side. That is, the electromagnetic switching valve 18 is shut off during normal operation, and is opened during failure to enable manual steering operation.

  Both oil passages 10 and 11 are connected to the reservoir tank 9 via the bypass valve 1 and the back pressure valve 22. The bypass valve 1 includes a first valve 1a that opens and closes between the first oil passage 10 and the back pressure valve 22, a second valve 1b that opens and closes between the second oil passage 11 and the back pressure valve 22, and both oil passages. And a piston member 1c that opens and closes the first and second valves 1a and 1b in accordance with the differential pressure of 10 and 11.

  When the first oil passage 10 is at a high pressure, the piston member 1c opens the second valve 1b, and the second oil passage 11 and the reservoir tank 9 communicate with each other via the back pressure valve 22, while the second oil passage 11 When the pressure is high, the piston member 1c opens the first valve 1a, and the first oil passage 10 and the reservoir tank 9 communicate with each other via the back pressure valve 22.

  The back pressure valve 22 allows only the flow from the first and second valves 1 a and 1 b toward the reservoir tank 9 and prevents backflow from the reservoir tank 9. That is, the balance of the amount of hydraulic oil is adjusted by providing this back pressure valve 22.

  FIG. 2 is a longitudinal sectional view of a pump unit P to which the power transmission structure according to the present invention is applied. As shown in FIG. 2, the pump 3 includes a so-called trochoid pump element 23 that controls the pump action, and a pump housing 24 that houses the pump element 23.

  The pump element 23 is slidably and rotatably held in the pump housing 24, and is disposed inside the outer rotor 25 with an annular outer rotor 25 having a plurality of inner teeth formed on the inner peripheral side. Mainly from an inner rotor 26 having external teeth meshing with the respective inner teeth, and a pump drive shaft 28 which is a driven shaft fixed so as to be integrally rotatable with the inner rotor 26 while inserting the shaft center of the inner rotor 26. It is configured.

  The pump drive shaft 28 is formed in an internal solid shape, and is fixed to the inner rotor 26 via a pin 27. The shaft drive shaft 28 extends in the axial direction from the tip of the shaft main body 29 on the electric motor M side. And a pump-side fitting convex portion 30 which is a driven shaft-side fitting convex portion.

  The pump housing 24 is configured by sandwiching an annular cam ring 33 between a first housing 31 on the motor M side and a second housing 32 on the non-motor M side. The rotors 25 and 26 are accommodated.

  A hollow reservoir tank 9 that stores hydraulic oil therein is fixed to the outer peripheral side of the first housing 31 so as to cover the second housing 32 and the cam ring 33. The upper end opening of the reservoir tank 9 is closed by a cap 34.

  The motor M includes a motor element 35 that drives the pump 3 to rotate forward and backward, a motor casing 36 that has an opening on the side opposite to the pump 3 so as to cover the motor element 35 from the pump 3 side, and the motor casing 36 that is opposite to the motor casing 36. A substantially bottomed cylindrical motor cover 37 that closes the opening on the pump 3 side.

  The motor casing 36 has a substantially block-shaped first casing 36 a that houses the pump 3 side of the motor element 35 and the control unit 7 therein, and a second casing that closes the opening on the pump 3 side of the first casing 36 a. 36b.

  The motor element 35 includes a motor drive shaft 39 as a drive shaft rotatably supported by a motor casing 36 and a motor cover 37 via bearings 38a and 38b, and a substantially cylindrical shape fixed to the outer peripheral side of the motor drive shaft 39. Of the rotor 35a and a cylindrical stator 35b around which the coil is wound and arranged in a non-contact state on the outer periphery of the rotor 35a.

  The motor drive shaft 39 has an inner solid outer peripheral surface formed in a stepped shape, a large diameter portion 40 having a rotor 35a fixed to the outer periphery, and an axial direction extending from the large diameter portion 40 to the pump 3 side. The small-diameter portion 41 and a motor-side fitting convex portion 42 that is a driving-shaft-side fitting convex portion that extends in the axial direction from the distal end side of the small-diameter portion 41 are configured. Then, the pump-side fitting convex portion 30 of the pump driving shaft 28 and the motor-side fitting convex portion 42 of the motor driving shaft 39 are connected via the Oldham coupling 43, so that the motor driving shaft 39 to the pump driving shaft 28 is connected. Torque is transmitted. The motor drive shaft 39 is set to have a hardness lower than that of the pump drive shaft 28 because both bearings 38a and 38b and the rotor 35a are press-fitted and fixed to the outer peripheral surface thereof.

  3 and 4 are views showing a power transmission structure for transmitting torque from the motor drive shaft 39 to the pump drive shaft 28 as a first embodiment of the present invention. FIG. 3 is an exploded perspective view of the power transmission structure. 4 and 4 are perspective views showing details of the Oldham coupling 43. FIG.

  As shown in FIG. 3, the motor-side fitting convex portion 42 has a substantially rectangular cross section formed in a horizontally long shape from the axial center position of the motor drive shaft 39 in the radial direction. In other words, the motor-side fitting convex portion 42 has a flat shape in which a cross-sectional shape perpendicular to the axis of the motor drive shaft 39 extends in the radial direction of the motor drive shaft 39. And on the outer peripheral surface of the motor side fitting convex part 42, a pair of flat power transmission surfaces 42a are formed in the width direction of the motor side fitting convex part 42, respectively. The width dimension W1 is set to be smaller than the width dimension W2 of the pump-side fitting convex portion 30 described later. Note that both end surfaces 42b in the longitudinal direction of the motor-side fitting convex portion 39 are formed as curved surfaces that are curved along the outer peripheral edge portion of the distal end surface 41a in the small diameter portion 41.

  Similarly, the pump-side fitting convex portion 30 has a substantially rectangular cross section formed in a horizontally long shape from the axial center position of the pump-side drive shaft 28 in the radial direction. In other words, the pump-side fitting convex portion 28 has a flat shape in which a cross-sectional shape orthogonal to the axis of the pump drive shaft 28 extends in the radial direction of the pump drive shaft 28. And on the outer peripheral surface of the pump side fitting convex part 30, a pair of flat power transmission surfaces 30a are formed in the width direction of the pump side fitting convex part 30, respectively. Note that both end surfaces 30b in the longitudinal direction of the pump-side fitting convex portion 30 are formed as curved surfaces curved along the outer peripheral edge portion of the tip end surface 29a of the shaft body 29. Further, the tip surface 29 a of the shaft body 29 is formed to have the same diameter as the tip surface 41 a of the small diameter portion 41.

  On the other hand, the Oldham joint 43 is formed in a substantially cylindrical shape, and has a long hole-like fitting hole 44 formed as a first receiving portion in the Oldham joint 43, and a shaft on the pump drive shaft 28 side of the Oldham joint 43. And a long hole-shaped fitting recess 45 provided as a second receiving portion at a depth from the direction end surface 43b to the axially intermediate portion. And the fitting recessed part 45 is formed so that it may communicate with the fitting hole 44 in the shape which shares the longitudinal direction center part with the fitting hole 44, and the fitting hole 44 and the fitting recessed part 45 are abbreviate | omitted. It intersects in a cross shape to form an angle of 90 °.

  More specifically, as shown in FIG. 4, the fitting hole 44 is formed between a pair of power transmission surfaces 44 a formed as a flat surface, and has a diameter from the axial center position of the Oldham joint 43. It has a substantially rectangular cross section formed in a horizontally long shape in the direction. In other words, the cross-sectional shape of the fitting hole 44 has a flat shape extending in the radial direction of the Oldham joint 43. The width dimension W3 between the power transmission surfaces 44a in the fitting hole 44 is larger than the width dimension W1 of the motor side fitting convex part 42 and smaller than the width dimension W2 of the pump side fitting convex part 30. Is set. That is, the fitting hole 44 is formed in a shape that can receive the motor-side fitting convex portion 42 and cannot receive the pump-side fitting convex portion 30. Further, the longitudinal dimension L3 of the fitting hole 44 is set to be larger than the longitudinal dimension L1 of the motor-side fitting convex portion 42.

  The fitting recess 45 is formed between a pair of power transmission surfaces 45 a formed as a flat surface, and is horizontally long in a direction substantially orthogonal to the fitting hole 44 from the axial center position of the Oldham joint 43. The formed cross section is substantially rectangular. In other words, the cross-sectional shape of the fitting recess 45 has a flat shape extending in the radial direction of the Oldham joint 43. Further, in the fitting recess 45, the width dimension W4 and the longitudinal dimension L4 between the two power transmission surfaces 45a are set larger than the width dimension W2 and the longitudinal dimension L2 of the pump side fitting projection 30, respectively. Thereby, the pump side fitting convex part 30 can be received in the fitting concave part 45.

  Further, in the Oldham joint 43, the corners formed by the axial end surfaces 43a and 44a and the power transmission surfaces 44a and 45a are inclined downward toward the inside of the fitting hole 44 or the fitting recess 45. Each inclined surface 46 is formed. That is, in the assembled state of the drive shafts 28 and 39, a gap is formed between the inclined surfaces 46 and the power transmission surfaces 30a and 42a of the fitting projections 30 and 42, so that the power is transmitted. The bending deformation of the Oldham coupling 43 is absorbed.

  Here, the Oldham joint 43 is made of a sintered alloy formed by a so-called powder metallurgy method. And the cross section of the metal mold | die 48 for compression-molding the compact 47 which should become the Oldham coupling 43 is shown in FIG. Note that FIG. 5 illustrates the mold clamping state of the mold 48.

  As shown in FIG. 5, the mold 48 is provided so as to close a die 49 having a cylindrical inner peripheral surface and a lower end opening of the die 49, and only the fitting hole 44 of the Oldham joint 43 is opened. The lower die 50 for forming the axial end surface 43a (see FIG. 4) and the axial end surface 43b (see FIG. 4) in which the fitting hole 44 and the fitting recess 45 of the Oldham joint 43 are respectively opened. An upper die 51, and a punch 52 that is slidably inserted through the upper die 51 and the lower die 50 and controls the formation of the power transmission surfaces 44a and 45a (see FIG. 4), which are the inner surfaces of the Oldham joint. ing. The lower die 50 and the punch 52 are formed with molding surfaces for molding the inclined surfaces 46 (see FIG. 4) of the Oldham joint 43.

  In the mold 48 configured in this manner, the metal powder is filled on the inner peripheral side of the die 49 in the mold open state, and then the upper mold 51 and the punch 52 are lowered to uniformly pressurize and compress the entire metal powder. Thus, the green compact 47 is formed. Then, the Oldham joint 43 is formed by baking the green compact 47 formed with the mold 58 in a sintering furnace (not shown).

  Then, in order to assemble the drive shafts 28 and 39 to the Oldham joint 43 formed as described above, as shown in FIG. 3, the motor is started from the axial end face 43a where only the fitting hole 44 of the Oldham joint 43 is opened. While the side fitting convex portion 42 is inserted into the fitting hole 44, the pump side fitting convex portion 30 is fitted from the axial end surface 43b in which both the fitting hole 44 and the fitting concave portion 45 of the Oldham joint 43 are opened. It will be inserted into the recess 45. As a result, the fitting protrusions 30 and 42 are connected to each other via the Oldham joint 43 at a circumferential position that forms an angle of approximately 90 °. In addition, since the fitting hole 44 is formed in such a shape that the pump side fitting convex portion 30 cannot be inserted as described above, the pump side fitting convex portion 30 is erroneously inserted into the fitting hole 44. There is no such thing.

  In a state where both the drive shafts 28 and 39 are coupled, the fitting convex portions 30 and 42 are displaced relative to the Oldham joint 43 in the respective longitudinal directions, so that the shaft centers of the drive shafts 28 and 39 are displaced. On the other hand, torque is transmitted from the motor drive shaft 39 to the pump drive shaft 28 via each power transmission surface 30a, 42a, 44a, 45a.

  Here, when torque is transmitted from the motor drive shaft 39 to the pump drive shaft 28, the power transmission surfaces 30a, 42a of the fitting projections 30, 42 are in the longitudinal direction with the power transmission surfaces 30a, 42a. Since the power transmission surfaces 44a and 45a on the Oldham coupling 43 side are pressed against the corner portion formed by the both end surfaces 30b and 42b or in the vicinity thereof, the motor-side fitting convex portion 42 having a relatively small width dimension W1 has a width. This is more advantageous in strength than the pump-side fitting convex portion 30 having a relatively large dimension W2. This is because, as shown in FIG. 6, the moment span D when the width dimension of the fitting projection is small is larger than the moment span C when the width dimension of the fitting projection is large. As a result, the strength of the motor-side fitting convex portion 42 having a lower hardness than the pump-side fitting convex portion 30 is compensated.

  Therefore, according to the present embodiment, the fitting hole 44 and the fitting recess 45 are respectively formed with the punch 52 which is a common mold element, so that the relative angle between the fitting hole 44 and the fitting recess 45 is increased. Position accuracy can be improved.

  In addition, since the fitting hole 44 is formed in such a shape that the pump-side fitting convex portion 30 cannot be inserted, an error that erroneously inserts the pump-side fitting convex portion 30 into the fitting hole 44. Assembly can be prevented.

  In the present embodiment, by setting the width dimension W3 of the fitting hole 44 smaller than the width dimension W2 of the pump side fitting convex part 30, the pump side fitting convex part 30 is provided in the fitting hole 44. Although it cannot be inserted, by setting the longitudinal dimension L3 of the fitting hole 44 to be smaller than the longitudinal dimension L2 of the pump-side fitting convex part 30, the fitting hole 44 has a pump-side fitting convex part. It is also possible to prevent 30 from being inserted.

  Specifically, the longitudinal dimension L2 of the pump-side fitting convex part 30 is set larger than the longitudinal dimension L1 of the motor-side fitting convex part 42, and the longitudinal dimension L3 of the fitting hole 44 is set to the pump-side fitting. It is good to set smaller than the longitudinal direction dimension L2 of the joint convex part 30, and larger than the longitudinal direction dimension L1 of the motor side fitting convex part 42. FIG. In this case, the width dimensions W1 and W2 of the fitting protrusions 30 and 42 need not be different from each other, and the width dimensions W3 and W4 of the fitting hole 44 and the fitting recess 45 are different. There is no need to make each different. In this case, it goes without saying that the same effects as those of the first embodiment described above can be obtained.

  Further, in the present embodiment, the width dimension W1 of the motor-side fitting convex part 42 is set smaller than the width dimension W2 of the pump-side fitting convex part 30, and the motor-side fitting convex part 42 is set to the fitting hole 44. The pump side fitting convex part 30 is inserted into the fitting concave part 45, respectively, but the width dimension W1 of the motor side fitting convex part 42 is set larger than the width dimension W2 of the pump side fitting convex part 30, The pump-side fitting convex portion 30 may be inserted into the fitting hole 44, and the motor-side fitting convex portion 42 may be inserted into the fitting concave portion 45, respectively. In this case, since the width dimension W1 of the motor-side fitting convex portion 42 is larger than that in the first embodiment described above, the rigidity of the motor-side fitting convex portion 42 having a relatively low hardness as described above. There is a merit that can be improved.

  FIG. 7 is a diagram showing an axial end face 53a in which only the fitting hole 54 serving as the first receiving portion of the Oldham joint 53 is opened as the second embodiment of the present invention. In FIG. 7, only the two power transmission surfaces 54a of the fitting hole 54 are shown as representative examples of the power transmission surfaces of the Oldham coupling, but both power transmission surfaces in the fitting recess are also formed in the same manner. Yes.

  In the second embodiment shown in FIG. 7, both power transmission surfaces 54 a of the fitting hole 54 are formed as convex surfaces curved in an arc shape on a cross section orthogonal to the axis of the Oldham coupling 53. Other parts are the same as those in the first embodiment.

  Therefore, in the second embodiment, the two power transmission surfaces 42a of the motor-side fitting convex portion 42 have fitting holes at or near the corner portion formed by the two power transmission surfaces 42a and both longitudinal end surfaces 42b. Thus, it is possible to prevent the two power transmission surfaces 54a from being in pressure contact with each other, so that there is a merit that wear generated on each of the power transmission surfaces 42a and 54a can be suppressed.

  Here, technical ideas other than those described in the scope of claims that can be grasped from the above embodiments will be described below together with the effects thereof.

  (1) The power transmission structure according to claim 1 or 2, wherein an inclined surface is formed at each corner portion formed by the inner peripheral surface and both end surfaces of the Oldham joint.

  According to the technical idea described in (1), a gap is formed between the inclined surface and the fitting convex portions, so that the deformation deformation of the Oldham joint can be absorbed.

  (2) The front end surface of the motor drive shaft as the drive shaft that is rotationally driven by the motor is formed to have the same diameter as the front end surface of the pump drive shaft as the driven shaft that rotationally drives the oil pump; A width dimension of the driving shaft side fitting convex portion formed on the motor driving shaft is set smaller than a width dimension of the driven shaft side fitting convex portion formed on the pump driving shaft. The power transmission structure according to claim 1 or 2.

  According to the technical idea described in (2), the motor drive shaft must be set to a relatively low hardness due to the structure of the motor, but the drive shaft side fitting formed on the motor drive shaft By forming the convex portion narrower than the driven shaft side fitting convex portion, the moment span of the driving shaft side fitting convex portion during power transmission is larger than that of the driven shaft side fitting convex portion. Thus, the strength of the drive shaft side fitting convex portion can be supplemented.

  (3) The tip surface of the motor drive shaft as the drive shaft that is rotationally driven by the motor is formed to have the same diameter as the tip surface of the pump drive shaft as the driven shaft that rotationally drives the oil pump, and The width dimension of the driving shaft side fitting convex portion formed on the motor driving shaft is set larger than the width dimension of the driven shaft side fitting convex portion formed on the pump driving shaft. The power transmission structure according to claim 1 or 2.

According to the technical idea described in (3), the motor drive shaft must be set to a relatively low hardness due to the structure of the motor, but the drive shaft side fitting formed on the motor drive shaft By forming the convex portion wider than the driven shaft side fitting convex portion, the rigidity of the driving shaft side fitting convex portion can be improved.
(4) Both the receiving portions are formed between a pair of power transmission surfaces, and the respective power transmission surfaces in both receiving portions are curved in an arc shape on a cross section perpendicular to the axis of the Oldham joint. The power transmission structure according to claim 1, wherein the power transmission structure is formed as a convex surface.
According to the technical idea described in (4), the both fitting protrusions can be prevented from being in pressure contact with the respective power transmission surfaces of the Oldham joint at or near the corners of the outer peripheral surface. Wear of each power transmission surface of the Oldham coupling and both fitting convex portions can be suppressed.

3 ... Pump (driven element)
28 ... Pump drive shaft (driven shaft)
30 ... Pump-side fitting convex part (driven shaft-side fitting convex part)
39 ... Motor drive shaft (drive shaft)
42 ... Motor side fitting convex part (drive shaft side fitting convex part)
43 ... Oldham coupling 44 ... Fitting hole (first receiving part)
45 .. fitting recess (second receiving part)
53 ... Oldham's joint 54 ... Fitting hole (first receiving part)
M ... Motor (drive source)

Claims (2)

The tip of the drive shaft in the drive source and the tip of the driven shaft in the driven element are connected by an Oldham joint molded with a metal material, while allowing deviation of the axis between the drive shaft and the driven shaft. In the power transmission structure for transmitting torque from the drive shaft to the driven shaft,
A drive shaft side fitting convex portion protruding from the tip surface of the drive shaft and having a flat shape in which a cross-sectional shape perpendicular to the axis of the drive shaft extends in the radial direction of the drive shaft;
The cross-sectional shape projecting from the tip surface of the driven shaft and perpendicular to the axis of the driven shaft exhibits a flat shape extending in the radial direction of the driven shaft, and the width dimension of the cross-sectional shape is A driven shaft side fitting convex portion that is different from the driving shaft side fitting convex portion; and
The Oldham joint has a flat cross-sectional shape extending in the radial direction, penetrates the Oldham joint in the axial direction, and one of the fitting protrusions has one fitting convex portion having a small width dimension, and is one end in the axial direction of the Oldham joint. A first receiving part that is inserted from the side and whose width dimension is set smaller than the other fitting convex part having a larger width dimension among the both fitting convex parts,
The Oldham joint is recessed with a flat cross-sectional shape extending in the radial direction of the Oldham joint at a depth from the other axial end surface of the Oldham joint to the axially intermediate portion, and the longitudinal center in the cross section is the first receiving portion. And a second receiving part formed so as to intersect with the first receiving part and having the other fitting convex part inserted therein,
A power transmission structure characterized by comprising: The tip of the drive shaft in the drive source and the tip of the driven shaft in the driven element are connected by an Oldham joint molded with a metal material, while allowing deviation of the axis between the drive shaft and the driven shaft. In the power transmission structure for transmitting torque from the drive shaft to the driven shaft,
A drive shaft side fitting convex portion protruding from the tip surface of the drive shaft and having a flat shape in which a cross-sectional shape perpendicular to the axis of the drive shaft extends in the radial direction of the drive shaft;
The cross-sectional shape projecting from the tip surface of the driven shaft and perpendicular to the axis of the driven shaft exhibits a flat shape extending in the radial direction of the driven shaft, and the longitudinal dimension of the cross-sectional shape is A driven shaft side fitting convex portion that is different from the driving shaft side fitting convex portion;
The Oldham joint has a flat cross-sectional shape extending in the radial direction, passes through the Oldham joint in the axial direction, and one of the fitting protrusions has a smaller longitudinal dimension in the axial direction of the Oldham joint. A first receiving part that is inserted from one end side and whose longitudinal dimension is set smaller than the other fitting convex part having a larger width dimension among the two fitting convex parts;
The Oldham joint is recessed with a flat cross-sectional shape extending in the radial direction of the Oldham joint at a depth from the other axial end surface of the Oldham joint to the axially intermediate portion, and the longitudinal center in the cross section is the first receiving portion. And a second receiving part formed so as to intersect with the first receiving part and having the other fitting convex part inserted therein,
A power transmission structure characterized by comprising:

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