JP2011149472A - Driving force transmitting device and lubricating oil - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a driving force transmitting device which can suppress dragging torque when towed without adding a part for reducing the dragging torque, and lubricating oil therefor. <P>SOLUTION: A driving force transmitting device 1 includes: an inner clutch plate 4a rotating in company with a rotation of front wheel 104 of four wheels driving vehicle 101; an outer clutch plate 4b rotating in company with a rotation of rear wheel 105 of the four wheels driving vehicle 101; a pressing mechanism 10 engaging in friction the inner clutch plate 4a and outer clutch plate 4b; and lubricating oil 20 which is interposed between the inner clutch plate 4a and outer clutch plate 4b when the pressing mechanism 10 is not operated, and generates bubbles by cavitation between these clutch plates in differential rotation of the inner clutch plate 4a and outer clutch plate 4b when towed in two wheels where either of the front wheels 104 and rear wheels 105 rotate. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a driving force transmission device and a lubricating oil.

  As a conventional driving force transmission device, for example, mounted on a four-wheel drive vehicle, a pair of rotating members are coupled so as to be able to transmit torque by a clutch, and the two-wheel cover is pulled while one of the front wheels or the rear wheels is in contact with the road surface. There is one configured to reduce drag torque due to the viscosity of lubricating oil interposed between clutch plates during towing (see, for example, Patent Document 1).

  This driving force transmission device connects a bottomed cylindrical front housing that rotates together with an input shaft, a shaft-shaped inner shaft that can rotate on the axis of the front housing, and the front housing and the inner shaft so that torque can be transmitted. Main clutch, a pilot clutch arranged in parallel along the axis of the main clutch, and a cam mechanism that converts the rotational force from the front housing into the pressing force toward the main clutch by the operation of the pilot clutch. The housing space of the front housing that houses the main clutch, pilot clutch, and cam mechanism is filled with lubricating oil.

  The cam mechanism includes a first cam member connected to the pilot clutch, and a second cam member connected to the inner shaft so as not to be relatively rotatable and axially movable. The first cam member and the second cam member The axial rotation force is generated by the relative rotation. Seal members are provided on the outer peripheral surface and the inner peripheral surface of the second cam member, and the housing space of the front housing is separated from the first clutch chamber on the main clutch side and the second clutch chamber on the pilot clutch side by the second cam member. It is partitioned liquid-tightly.

  The main clutch is a wet multi-plate clutch composed of an inner clutch plate and an outer clutch plate, and is disposed between the front housing and the inner shaft. The main clutch is configured to frictionally engage the inner clutch plate and the outer clutch plate by a pressing force received from the second cam member of the cam mechanism, and to connect the front housing and the inner shaft so as to transmit torque. Yes.

  A pump device that is operated by differential rotation between the front housing and the inner shaft is disposed at the bottom of the front housing in the axial direction. This pump device pumps lubricating oil from the first clutch chamber to the second clutch chamber when towed. Thereby, the second cam member receives a force in a direction away from the main clutch due to the pressure difference of the lubricating oil, and the drag torque of the main clutch is reduced.

JP 2008-14387 A

  However, in the driving force transmission device of Patent Document 1, it is necessary to add new parts such as a pump device, and there is still room for improvement in terms of downsizing and cost reduction.

  Accordingly, an object of the present invention is to provide a driving force transmission device and a lubricating oil that can suppress drag torque during towing without adding a component for reducing drag torque.

  In order to achieve the above object, the present invention provides a first clutch plate that rotates as the front wheels of the four-wheel drive vehicle rotate, and a second clutch plate that rotates as the rear wheels of the four-wheel drive vehicle rotate. A clutch plate, a pressing mechanism for frictionally engaging the first clutch plate and the second clutch plate, and a lubricating oil interposed between the first and second clutch plates when the pressing mechanism is inoperative. And the lubricating oil is cavitation between the first and second clutch plates by differential rotation of the first and second clutch plates when the two wheels are towed when one of the front wheels or the rear wheels rotates. Provided is a driving force transmission device that generates air bubbles.

  According to this configuration, the lubricating oil between the first and second clutch plates is discharged by the bubbles generated by the differential rotation of the first and second clutch plates.

  In addition, the lubricating oil increases with the increase in the differential rotation speed by increasing the bubbles in response to the increase in the differential rotation speed of the first and second clutch plates when the two-wheel is towed. The drag torque between the first and second clutch plates may be reduced.

  According to this configuration, the drag torque can be reduced as the differential rotational speed of the first and second clutch plates increases.

  In order to achieve the above object, the present invention provides a first clutch plate that rotates as the front wheels of the four-wheel drive vehicle rotate, and a second clutch that rotates as the rear wheels of the four-wheel drive vehicle rotate. Between the first and second clutch plates due to differential rotation of the first and second clutch plates when the two wheels are towed. A lubricant that generates bubbles by cavitation is provided.

  According to this configuration, the lubricating oil between the first and second clutch plates is discharged by the bubbles generated by the differential rotation of the first and second clutch plates.

  According to the present invention, the drag torque during towing can be suppressed without adding a component for reducing the drag torque.

FIG. 1 is a plan view for explaining an outline of a vehicle on which a driving force transmission device according to an embodiment of the present invention is mounted. FIG. 2 is a cross-sectional view for explaining the driving force transmission device according to the embodiment of the present invention. FIG. 3 is a cross-sectional view schematically showing the pilot clutch of the driving force transmission apparatus according to the embodiment of the present invention. FIG. 3 is a cross-sectional view schematically illustrating the main clutch of the driving force transmission apparatus according to the embodiment of the present invention. FIG. 5 is a characteristic diagram showing the relationship between the differential rotation speed and the drag torque of the driving force transmission device according to the embodiment of the present invention.

[Embodiment]
FIG. 1 schematically shows a four-wheel drive vehicle. As shown in FIG. 1, the four-wheel drive vehicle 101 includes a driving force transmission device 1, an engine 102, a transaxle 103, a pair of front wheels 104, and a pair of rear wheels 105.

  The driving force transmission device 1 is disposed on a driving force transmission path from the front wheel side to the rear wheel side in the four-wheel drive vehicle 101 and is supported on a vehicle body (not shown) of the four-wheel drive vehicle 101 via a differential carrier 106. Has been.

  The driving force transmission device 1 is configured to connect the propeller shaft 107 and the drive pinion shaft 108 so that torque can be transmitted, and to transmit the driving force of the engine 102 to the rear wheel 105 in this connected state. Details of the driving force transmission device 1 will be described later.

  The engine 102 drives the pair of front wheels 104 by outputting the driving force to the front axle shaft 109 via the transaxle 103.

  The engine 102 outputs the driving force to the propeller shaft 107, the driving force transmission device 1, the drive pinion shaft 108, the rear differential 110 and the rear axle shaft 111 via the transaxle 103, so that the pair of rear wheels 105 is output. To drive.

[Overall configuration of the driving force transmission device 1]
FIG. 2 shows the entire driving force transmission device. As shown in FIG. 2, the driving force transmission device 1 includes a housing 2 as a first rotating member that can rotate relative to a differential carrier 106 (shown in FIG. 1), and a second member that can rotate relative to the housing 2. 2, an inner shaft 3 as a rotating member, a main clutch 4 interposed between the inner shaft 3 and the housing 2, a pilot clutch 5 parallel to the main clutch 4 along the rotation axis O, and the pilot clutch 5 and a cam mechanism 7 for converting the rotational force of the housing 2 into the pressing force of the main clutch 4 by the generation of the pressing force of the pilot clutch 5 by the driving mechanism 6. Yes. The drive mechanism 6 and the cam mechanism 7 constitute a pressing mechanism 10 that presses and frictionally engages the main clutch 4.

(Configuration of housing 2)
As shown in FIG. 2, the housing 2 includes a front housing 8 and a rear housing 9 coupled to the front housing 8 so as to be integrally rotated by screwing or the like, and is provided in a differential carrier 106 (shown in FIG. 1). The rotary axis O is accommodated so as to be rotatable about the central axis. The housing 2 is provided with a storage space 2 a for storing the lubricating oil 20. The lubricating oil 20 is filled in the accommodating space 2a at a filling rate of about 80% and is sealed by seal members 15 and 16 described later.

  The front housing 8 is formed as a bottomed cylindrical member that opens to the rear housing 9 side, has a straight spline fitting portion 8a on the inner peripheral surface thereof, and is connected to the engine 102 (shown in FIG. 1) with a transaxle 103 (FIG. 1). And a propeller shaft 107 (shown in FIG. 1). The front housing 8 is configured to receive the driving force of the engine 102 from the propeller shaft 107 and rotate around the rotation axis O together with the rear housing 9.

  The rear housing 9 is formed by integrally joining the first to third housing elements 91 to 93 by welding or the like, is screwed to the inner peripheral surface of the opening of the front housing 8, and can be rotated to the yoke 94 via a bearing 95. It is supported by. The rear housing 9 is provided with an annular housing space 9 a that opens in the same direction as the opening direction of the front housing 8. The yoke 94 is fixed to the coupling case in the accommodating space 9a and is formed by a stepped cylindrical member.

  The first housing element 91 is disposed on the inner peripheral side of the rear housing 9 and is formed of a cylindrical member made of a magnetic material. A seal member 15 is interposed between the inner peripheral surface of the first housing element 91 and the outer peripheral surface of the small-diameter cylindrical portion 3 b of the inner shaft 3.

  The second housing element 92 is disposed on the outer peripheral side of the rear housing 9 and is formed of a cylindrical member made of a magnetic material, like the first housing element 91. The seal member 16 is interposed between the outer peripheral surface of the second housing element 92 and the inner peripheral surface of the front housing 8.

  The third housing element 93 is interposed between the first housing element 91 and the second housing element 92, and is formed by an annular member for connecting the housing element made of a nonmagnetic material such as stainless steel.

(Configuration of inner shaft 3)
As shown in FIG. 2, the inner shaft 3 includes two cylindrical portions 3a and 3b having different outer diameters, and a step portion 3c interposed between the cylindrical portions 3a and 3b. It is formed by a cylindrical member that is disposed on the axis O and supported by the housing 2 via bearings 17 and 18 so as to be relatively rotatable.

  A straight spline fitting portion 30a exposed to the accommodation space 2a is provided on the outer peripheral surface of the large-diameter cylindrical portion 3a.

  A housing space 3d for housing the tip of the drive pinion shaft 108 (shown in FIG. 1) is formed on the inner circumferential surface of the small-diameter cylindrical portion 3b, and the outer circumferential surface of the drive pinion shaft 108 is formed on the inner circumferential surface of the housing space 3d. A straight spline fitting portion 30b is provided on the surface for spline fitting.

  An accommodation space 3e that opens toward the bottom side of the front housing 8 is formed on the inner periphery of the large-diameter cylindrical portion 3a. The housing space 3e is partitioned from the housing space 3d by the wall 3f, and the inside thereof is filled with the lubricating oil 20.

  The step portion 3 c is disposed outside the inner shaft 3 so as to be interposed between the cylindrical portions 3 a and 3 b, and is formed by a plane facing a main cam 7 a (described later) in the cam mechanism 7.

(Configuration of main clutch 4)
As shown in FIG. 2, the main clutch 4 has a plurality of outer clutch plates 4b (first clutch plates) and a plurality of inner clutch plates 4a (second clutch plates). It consists of a wet multi-plate clutch with lubricating oil 20 interposed therebetween. The main clutch 4 is disposed between the front housing 8 and the inner shaft 3 and is accommodated in the accommodating space 2a. The main clutch 4 frictionally engages the adjacent clutch plates of the inner clutch plate 4a and the outer clutch plate 4b, and releases the frictional engagement between the housing 2 and the inner shaft 3 (torque). Transmission) is configured to be connected.

  The inner clutch plate 4a and the outer clutch plate 4b are formed in an annular shape, and are alternately arranged on the rotation axis O with their side surfaces 40a and side surfaces 40b facing each other.

  The inner clutch plate 4a has a straight spline fitting portion 41a on the inner periphery thereof, and the straight spline fitting portion 41a is fitted to the straight spline fitting portion 30a so as to be integrally rotatable with the cylindrical portion 3a of the inner shaft 3. It is connected so as to be movable along the direction of the rotation axis O. As a result, the inner clutch plate 4a rotates as the rear wheel 105 rotates.

  Of the plurality of inner clutch plates 4a, the inner clutch plate 4a at the end of the pilot clutch side functions as an input portion of the main clutch 4, and receives a pressing force from the main cam 7a (described later) of the cam mechanism 7 toward the main clutch 4 side. The inner clutch plate 4a and the outer clutch plate 4b are frictionally engaged by the movement in the pressing direction. The inner clutch plate 4a is provided with oil holes 42a that are arranged in parallel along the circumferential direction and open in the direction of the rotation axis O.

  The outer clutch plate 4b has a straight spline fitting portion 41b on the outer periphery thereof, and the straight spline fitting portion 41b is fitted to the straight spline fitting portion 8a so as to be integrally rotatable with the front housing 8 (housing 2). It is connected so as to be movable along the direction of the rotation axis O. As a result, the outer clutch plate 4 b rotates with the rotation of the front wheel 104.

(Configuration of pilot clutch 5)
The pilot clutch 5 includes a plurality of inner clutch plates 5a and a plurality of outer clutch plates that are formed of annular friction plates that can be frictionally engaged with each other by movement of an armature 6b toward the electromagnetic coil 6a by driving of a drive mechanism 6 (described later). 5b, and a wet multi-plate clutch in which lubricating oil 20 is interposed between the clutch plates when not engaged. The pilot clutch 5 is disposed between the armature 6b and the rear housing 9, and is accommodated in the accommodating space 2a.

  The inner clutch plate 5a and the outer clutch plate 5b are formed in an annular shape, and are alternately arranged on the rotation axis O with the friction surfaces 50a and 50b formed on the side surfaces thereof facing each other.

  The inner clutch plate 5a has a straight spline fitting portion 51a on the inner periphery thereof, and the straight spline fitting portion 51a is fitted to a straight spline fitting portion 70b of a pilot cam 7b described later to rotate relative to the pilot cam 7b. Impossible and connected in an axially movable manner.

  The outer clutch plate 5b has a straight spline fitting portion 51b on the outer peripheral portion thereof, and the straight spline fitting portion 51b is fitted to the straight spline fitting portion 8a so that it cannot be rotated relative to the front housing 8 but can move in the axial direction. It is connected to.

(Configuration of drive mechanism 6)
As shown in FIG. 2, the drive mechanism 6 includes an electromagnetic coil 6 a and an armature 6 b and is disposed on the rotation axis O of the housing 2. The drive mechanism 6 is configured to frictionally engage the inner clutch plate 5a and the outer clutch plate 5b of the pilot clutch 5 by the movement of the armature 6b toward the electromagnetic coil 6a due to the generation of electromagnetic force of the electromagnetic coil 6a. Yes.

  The electromagnetic coil 6 a is housed in the housing space 9 a of the rear housing 9 and is attached to the yoke 94. 2, the electromagnetic coil 6a forms a magnetic circuit G across the yoke 94, the pilot clutch 5, the armature 6b, the rear housing 9 and the like by energization, as shown by a broken line in FIG. 2, and the armature 6b is moved to the rear housing 9 side. The electromagnetic force for applying the moving force is generated.

  The armature 6b has a straight spline fitting portion 60b along the rotation axis O on the outer peripheral portion thereof, and the straight spline fitting portion 60b is fitted to the straight spline fitting portion 8a so as not to rotate relative to the front housing 8. It is connected so as to be movable in the axial direction.

(Configuration of cam mechanism 7)
As shown in FIG. 2, the cam mechanism 7 includes an annular main cam 7 a that rotates by receiving the rotational force from the inner shaft 3, an annular pilot cam 7 b that is parallel to the main cam 7 a along the rotation axis O of the housing 2, The cam follower 7c is interposed between the pilot cam 7b and the main cam 7a, is disposed between the main clutch 4 and the rear housing 9, and is accommodated in the accommodating space 2a. The cam mechanism 7 is configured to receive a rotational force from the housing 2 by the clutch operation of the pilot clutch 5 and convert it into a pressing force that becomes a clutch force of the main clutch 4.

  The main cam 7a has a clutch plate pressing portion 70a that receives cam thrust generated by the rotation of the pilot cam 7b from the cam follower 7c and presses the inner clutch plate 4a on the input side among the plurality of inner clutch plates 4a of the main clutch 4. The cam mechanism 7 is disposed on the main clutch 4 side so as to be movable along the rotation axis O.

  The clutch plate pressing portion 70 a is provided with a straight spline fitting portion 700 a that is fitted to the straight spline fitting portion 30 a of the inner shaft 3. Further, the clutch plate pressing portion 70a is provided with a plurality of oil holes 701a that are arranged in parallel along the circumferential direction and open to both end faces in the axial direction.

  The pilot cam 7 b is disposed so as to be rotatable relative to the inner shaft 3 with a bearing 19 interposed between the pilot cam 7 b and the first housing element 91 of the rear housing 9.

  On the outer peripheral edge of the pilot cam 7b, there is provided a straight spline fitting portion 70b which is fitted to the straight spline fitting portion 51a of the inner clutch plate 5a so as not to be relatively rotatable and movable.

  A plurality of cam grooves 702a and 702b extending in the circumferential direction are formed on opposing surfaces of the main cam 7a and the pilot cam 7b, respectively. The cam grooves 702a and 702b are formed so that the axial depth is deepest at the center portion in the circumferential direction and becomes shallow toward the end portion. The cam follower 7c is disposed between the cam grooves 702a and 702b, and rolls in the circumferential direction from the center (neutral position) of the cam grooves 702a and 702, thereby separating the main cam 7a and the pilot cam 7b from each other. A pressing force is generated as a clutch force.

(Composition and action of lubricating oil 20)
The lubricating oil 20 is, for example, at least one selected from a lubricating base oil mainly composed of a hydrocarbon-based synthetic oil, a phosphorus compound, an alkaline earth metal sulfonate, an alkaline earth metal phenate, and an alkaline earth metal salicylate. Contains organic acid salt. The kinematic viscosity at 100 ° C. of the lubricating oil 20 is, for example, ^{2 to} 20 mm ² / s.

  Lubricating oil used in conventional driving force transmission devices includes antifoaming materials such as silicon oil, fatty acid, and phosphoric acid so that cavitation does not occur when the vehicle is running and towed. The lubricating oil 20 according to the embodiment is adjusted so that the content of the defoaming material is reduced as compared with the conventional case and cavitation can occur when towed. Here, “cavitation” refers to a phenomenon in which, when the lubricating oil is agitated, a low pressure portion is vaporized and bubbles are generated in the lubricating oil.

  FIG. 3 shows a circumferential section of the inner clutch plate 5a and the outer clutch plate 5b of the pilot clutch 5 when the four-wheel drive vehicle 101 is towed. At the time of towing, the electromagnetic coil 6a is not energized and the pilot clutch 5 is in a non-engaged state.

  On the friction surface 50a of the inner clutch plate 5a, fine irregularities are formed in order to improve the sliding characteristics with the outer clutch plate 5b. The friction surface 50b of the outer clutch plate 5b is formed with an oil groove 51b for discharging the lubricating oil 20 from between the clutch plates when the pilot clutch 5 is frictionally engaged at a predetermined interval in the circumferential direction. Has been.

  For example, when the front wheel 104 is lifted by a towing vehicle and the rear wheel 105 is towed while only the rear wheel 105 is grounded, the inner shaft 3 rotates with the rotation of the rear wheel 105, and the rotational force is applied to the main cam 7 a and the cam follower. 7c is transmitted to the inner clutch plate 5a via the pilot cam 7b, and the inner clutch plate 5a rotates in the direction of arrow A. On the other hand, since the front wheel 104 does not rotate, the housing 2 and the outer clutch plate 5b do not rotate. Therefore, a large differential rotation that cannot occur during normal traveling occurs between the inner clutch plate 5a and the outer clutch plate 5b.

  Due to this differential rotation, the lubricating oil 20 interposed between the inner clutch plate 5a and the outer clutch plate 5b is agitated, a low pressure portion is generated in a part thereof, and a large number of bubbles 21 due to cavitation are generated. The bubbles 21 act to push out the lubricating oil 20 from between the inner clutch plate 5a and the outer clutch plate 5b. As a result, the area where the lubricating oil 20 is interposed between the friction surface 50a and the friction surface 50b is reduced. . For this reason, the drag torque of the pilot clutch 5 due to the viscosity of the lubricating oil 20 is reduced.

  FIG. 4 shows a circumferential section of the inner clutch plate 4a and the outer clutch plate 4b of the main clutch 4 when the four-wheel drive vehicle 101 is towed.

  A plurality of friction materials 43a made of, for example, wood pulp or aramid fibers are attached to the side surface 40a of the inner clutch plate 4a. The surface of the friction material 43a is a friction surface 430a that frictionally engages the friction surface 400b formed on the side surface 40b of the outer clutch plate 4b. The friction surface 400b of the outer clutch plate 4b is formed into a flat surface.

  When the front wheel 104 of the four-wheel drive vehicle 101 is lifted and the two wheels are towed, the inner shaft 3 rotates as the rear wheel 105 rotates, and the inner clutch plate 4a rotates in the direction of arrow A integrally with the inner shaft 3. . On the other hand, since the front wheel 104 does not rotate, the housing 2 and the outer clutch plate 4b do not rotate. Therefore, a large differential rotation occurs between these two clutch plates.

  Due to this differential rotation, cavitation occurs in the lubricating oil 20 interposed between the inner clutch plate 4a and the outer clutch plate 4b, and a large number of bubbles 21 are generated. The bubbles 21 act to push out the lubricating oil 20 from both of these clutch plates. As a result, the area where the lubricating oil 20 is interposed between the friction surface 430a and the friction surface 400b is reduced. For this reason, the drag torque of the main clutch 4 due to the viscosity of the lubricating oil 20 is reduced.

[Operation of Driving Force Transmission Device 1]
Next, the operation of the driving force transmission apparatus shown in this embodiment will be described with reference to FIGS. When the engine 102 of the four-wheel drive vehicle 101 generates torque, the rotational driving force is transmitted to the housing 2 via the transaxle 103 and the propeller shaft 107, and the housing 2 is rotationally driven.

  When the electromagnetic coil 6a is in a non-energized state, the magnetic circuit G based on the electromagnetic coil 6a is not formed, and the inner and outer clutch plates in the pilot clutch 5 are not frictionally engaged.

  Therefore, the cam mechanism 7 does not generate a pressing force as the clutch force of the main clutch 4, the inner clutch plate 4a and the outer clutch plate 4b of the main clutch 4 are not frictionally engaged with each other, and the rotational driving force of the engine 102 is It is not transmitted from the housing 2 to the inner shaft 3.

  On the other hand, when the electromagnetic coil 6a is energized, a magnetic circuit G is formed, and the armature 6b moves in a direction in which the inner and outer clutch plates in the pilot clutch 5 are frictionally engaged.

  For this reason, the clutch plates of the pilot clutch 5 are frictionally slid by the pressure due to the movement of the armature 6b, and the differential rotational force between the housing 2 and the inner shaft 3 is transmitted to the pilot cam 7b of the cam mechanism 7 via the pilot clutch 5. Is done.

  Along with this, the pilot cam 7b rotates relative to the main cam 7a, and this rotational force is converted into a pressing force that becomes the clutch force of the main clutch 4 by the cam action generated in the cam mechanism 7, and this pressing force causes the main clutch to The main cam 7a moves in a direction in which the inner and outer clutch plates 4 are frictionally engaged.

  Thereby, the inner and outer clutch plates of the main clutch 4 are frictionally engaged with each other, the rotational driving force of the engine 102 is transmitted from the housing 2 to the inner shaft 3, and the rear differential 110 is further transmitted from the inner shaft 3 through the drive pinion shaft 108. Is transmitted to. Then, it is transmitted from the rear differential 110 to the rear wheel 105 via the rear axle shaft 111, and the rear wheel 105 is rotationally driven.

  By the way, for example, when the four-wheel drive vehicle 101 cannot travel by itself due to an engine failure or the like, the front wheel 104 of the four-wheel drive vehicle 101 is lifted by a towing vehicle and the rear wheel 105 is grounded. There are cases where two wheels are towed. When the two-wheel is towed, a large differential rotation occurs between the inner clutch plate 4a and the outer clutch plate 4b of the main clutch 4 and between the inner clutch plate 5a and the outer clutch plate 5b of the pilot clutch 5, as described above. A drag torque due to the viscosity of the lubricating oil 20 is generated.

  In the pilot clutch 5, heat is generated because the inner clutch plate 5a and the outer clutch plate 5b rotate differentially against drag torque. Further, the drag torque generated in the pilot clutch 5 operates the cam mechanism 7, and the drag torque is amplified to become a cam thrust force that presses the main clutch 4. Since the inner clutch plate 4a and the outer clutch plate 4b rotate differentially while the main clutch 4 is pressed by the main cam 7a, the main clutch 4 generates more heat than the pilot clutch 5.

  If this heat generation amount is excessive, the performance of the lubricating oil 20 and the friction material 43a may be deteriorated. However, in the driving force transmission device 1 according to the present embodiment, cavitation is generated in the lubricating oil 20 as described above. Thus, drag torque in the main clutch 4 and the pilot clutch 5 is reduced.

  FIG. 5 shows the driving force transmission device according to the present embodiment, in which the horizontal axis represents the differential rotational speed and the vertical axis represents drag torque (the drag torque obtained by combining the drag torques of the main clutch 4 and the pilot clutch 5). The characteristics when using 1 and the characteristics when ATF (Automatic Transmission Fluid), which is generally used as a lubricating oil of a conventional driving force transmission device, is used instead of the lubricating oil 20 as a comparative example, Show.

  The differential rotation between the housing 2 and the inner shaft 3 occurs, for example, when the front wheel 104 slips or turns, but the differential rotation at that time is at most several hundred rpm. However, when the two-wheel is towed as described above, differential rotation may occur exceeding 1000 rpm.

  As shown in FIG. 5, when the ATF is applied as in the conventional driving force transmission device, the drag torque increases as the differential rotational speed increases. On the other hand, when the lubricating oil 20 according to the present invention is used, cavitation occurs at about 1000 rpm or more, and bubbles 21 are generated between the clutch plates. Therefore, the lubricating oil 20 between the clutch plates is pushed out by the bubbles 21 and dragged. Torque is reduced.

  This phenomenon becomes conspicuous with an increase in the differential rotational speed, and by increasing the number of generated bubbles, the drag torque decreases with an increase in the differential rotational speed in the region of about 1250 rpm or more. " That is, in this region, the graph of FIG. In the present embodiment, the antifoaming material so that the differential rotational speed between the housing 2 and the inner shaft 3 when the two wheels are towed at a speed of at least 40 km / h (legal speed during towing) is included in the drag torque reduction region. Has been adjusted.

  Thereby, heat_generation | fever of the driving force transmission apparatus 1 is suppressed compared with the conventional driving force transmission apparatus.

  As mentioned above, although the driving force transmission device of the present invention has been described based on the above embodiment, the present invention is not limited to the above embodiment, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are possible.

(1) In the above embodiment, the content of the antifoaming material is adjusted so that cavitation occurs when towed, but the antifoaming material may not be contained at all. Moreover, you may contain additives, such as a low molecular weight silicone which functions as a foaming agent, for example, whose molecular weight is thousands or less.

(2) In the above embodiment, the defoaming material is adjusted so that cavitation does not occur in the differential rotation speed range in the normal traveling that is not towed by two wheels. However, the cavitation may be generated even in the normal traveling. Good.

(3) In the above embodiment, the driving force transmission device 1 including the pilot clutch 5, the cam mechanism 7, and the main clutch 4 has been described. However, the pilot clutch 5 and the cam mechanism 7 are not provided. The lubricating oil 20 according to the above-described embodiment may be applied to a driving force transmission device configured to press 4.

  DESCRIPTION OF SYMBOLS 1 ... Differential carrier, 2 ... Housing, 3 ... Inner shaft, 3a ... Cylindrical part, 30a ... Straight spline fitting part, 3b ... Cylindrical part, 30b ... Straight spline fitting part, 3c ... Step surface, 4 ... Main clutch, 4a ... Inner clutch plate, 40a ... Side, 41a ... Straight spline fitting part, 42a ... Oil hole, 43a ... Friction material, 430a ... Friction surface, 4b ... Outer clutch plate, 40b ... Side, 41b ... Straight spline fitting part , 400b ... friction surface, 5 ... pilot clutch, 5a ... inner clutch plate, 50a ... friction surface, 51a ... straight spline fitting portion, 5b ... outer clutch plate, 50b ... friction surface, 51b ... straight spline fitting portion, 6 ... drive mechanism, 6a ... electromagnetic coil, 6b ... armature, 0b ... Straight spline fitting part, 7 ... Cam mechanism, 7a ... Main cam, 70a ... Clutch plate pressing part, 700a ... Straight spline fitting part, 701a ... Oil hole, 702a ... Cam groove, 7b ... Pilot cam, 70b ... Straight Spline fitting portion, 702b ... cam groove, 7c ... cam follower, 8 ... front housing, 8a ... straight spline fitting portion, 9 ... rear housing, 9a ... receiving space, 91 ... first housing element, 92 ... second housing element 93 ... Third housing element, 94 ... Yoke, 95 ... Bearing, 10 ... Pressing mechanism, 15 ... Sealing member, 16 ... Sealing member, 17-19 ... Bearing, 20 ... Lubricating oil, 21 ... Bubble, 101 ... Four-wheel Driving car, 102 ... Engine, 103 ... Transaxle, 104 ... Front wheel, 105 ... Wheels, 106 ... differential carrier, 107 ... plug peller shaft, 108 ... drive pinion shaft, 109 ... front axle shafts, 110 ... rear differential, 111 ... rear axle shafts, G ... magnetic circuit, O ... Rotation axis

Claims (3)

A first clutch plate that rotates as the front wheels of the four-wheel drive vehicle rotate;
A second clutch plate that rotates as the rear wheels of the four-wheel drive vehicle rotate;
A pressing mechanism for frictionally engaging the first clutch plate and the second clutch plate;
A lubricating oil interposed between the first and second clutch plates when the pressing mechanism is not operated,
The lubricating oil causes bubbles due to cavitation between the first and second clutch plates due to differential rotation of the first and second clutch plates when the two wheels are towed when one of the front wheels or the rear wheels rotates. Driving force transmission device to be generated.   The lubricating oil increases in response to an increase in the differential rotational speed of the first and second clutch plates when the two-wheel is towed. The driving force transmission device according to claim 1, wherein drag torque between the first clutch plate and the second clutch plate is reduced.   It is interposed between a first clutch plate that rotates as the front wheel of the four-wheel drive vehicle rotates and a second clutch plate that rotates as the rear wheel of the four-wheel drive vehicle rotates. Lubricating oil that generates bubbles due to cavitation between the first and second clutch plates due to differential rotation of the first and second clutch plates during two-wheel towing where one of the wheels rotates.

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