JP2007032822A - Torque distributor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable a maximum value of a differential limit torque to be amplified without increasing capacity of a differential controller for controlling a main clutch. <P>SOLUTION: A differential limiter 31 is provided for a planetary gear mechanism 10 for distributing driving torque from a transmission output shaft 4 to a front drive shaft 5 and a rear drive shaft 6. When one of front and rear wheels slips, differential of the planetary gear mechanism 10 is limited by providing differential limiting torque to the main clutch 25 mounted at the differential limiter 31. Then, when one of the front and rear wheels nearly slips exceeding the differential limiting torque provided to the main clutch 25, a torque cam mechanism 20 provided between a clutch hub 21 for supporting the main clutch 25 and a front output shaft 19 for engaging with the front drive shaft 5 conducts a cam-action and assisting force is generated and the main clutch 25 is engaged more strongly. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a torque distribution device that limits a differential of a differential unit that distributes a drive torque from a first output shaft to two output shafts according to an operating state.

  Conventionally, in a full-time four-wheel drive vehicle, a center differential (differential means) using a planetary gear mechanism is known as a torque distribution device. Many of these types of center differentials are also provided with a differential limiting mechanism for appropriately distributing torque by limiting the differential between the front and rear wheels in accordance with the torque acting on the center differential.

  For example, Japanese Patent Application Laid-Open No. 2004-225716 discloses a differential device including an electronically controlled differential limiting device (differential limiting means) and a torque-sensitive differential limiting mechanism. That is, in this document, the ring gear member constituting the planetary gear mechanism is divided into an input side ring gear member and an output side ring gear member, the input side ring gear member is engaged with the planetary pinion, and the output side ring gear member is connected via the main clutch. A torque cam mechanism is disposed between the input side ring gear member and the output side ring gear member while being connected to the sun gear shaft.

When an input torque generated by resistance during travel is applied to the input side ring gear member and a cam thrust force acting in the axial direction is generated on the torque cam mechanism, the output side ring gear member is differentially limited to the main clutch via the pressure plate. Torque (clutch pressing force) is applied. As a result, regardless of the operation of the electronically controlled differential limiting device, it is possible to obtain a differential limitation corresponding to the input torque.
JP 2004-225716 A

  By the way, in the technique disclosed in the above-mentioned document, the clutch pressing force (differential limit torque) applied to the main clutch is the maximum value generated at the time of the maximum input torque. It cannot be granted to the clutch.

  As a technique for amplifying the clutch pressing force applied to the main clutch, it is conceivable to increase the capacity of the electromagnetic coil constituting the differential limiting device or increase the number of pilot clutches, but the overall size of the device increases. Not only is the structure complicated, it is not feasible.

  In view of the above circumstances, the present invention provides a maximum differential limiting torque without increasing the capacity of the differential limiting means for electronically controlling the differential limiting torque, and irrespective of the input torque generated by the resistance during travel. An object is to provide a torque distribution device capable of amplifying a value.

  In order to achieve the above object, a torque distribution device according to the present invention is provided with differential means for distributing torque from the first output shaft to the second output shaft and the third output shaft, and the differential means. A rotating member connected to one of the second output shaft and the third output shaft; friction fastening means interposed on the other of the rotating member, the second output shaft, and the third output shaft; Differential limiting means for electronically controlling the differential limiting torque applied to the frictional engagement means in accordance with the driving state of the vehicle, and the rotating member on the other side of the second output shaft and the third output shaft Is divided into a first rotating member provided continuously to the friction fastening means side and a second rotating member provided continuously to the friction fastening means side, and the second rotating member is slidable in a direction to release / fasten the friction fastening means. Providing the difference between the first rotating member and the second rotating member. Characterized in that a torque cam mechanism for generating the assist force with respect to the friction engagement means in accordance with the differential rotation when at limiting means to impart the differential limiting torque to the frictional engagement means.

  According to the present invention, the torque cam mechanism is operated only when the differential limiting means is operated to assist the differential limiting torque for the main clutch, so regardless of the input torque generated by the resistance during travel, In addition, the maximum value of the differential limiting torque can be amplified without increasing the capacity of the differential limiting means.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1 to 5 show a first embodiment of the present invention. FIG. 1 is a cross-sectional side view along the axial direction of the center differential device, and FIG. 2 is an enlarged view of a main part of the torque cam mechanism.

  A center differential device 1, which is an example of a torque distribution device, is housed in a transfer case 2 and an extension case 3 joined to a rear portion of a transmission case, and serves as a first output shaft extending from a transmission (not shown). An input shaft 8 of the center differential device 1 is coupled to the rear end of the transmission output shaft 4.

  Further, a front drive shaft 5 as a second output shaft is inserted and supported in the transmission output shaft 4 so as to be relatively rotatable. A rear drive shaft 6 as a third output shaft is rotatably supported at the rear portion of the front drive shaft 5 via a bearing. A boss portion 6a projects from the rear portion of the rear drive shaft 6, and a bearing 7 is fitted to the boss portion 6a. The boss portion 6 a is rotatably supported by the extension case 3 via the bearing 7. The rear drive gear 6b formed on the rear drive shaft 6 is connected to a transfer shaft extending to the rear wheel side via a reduction gear (not shown). Is connected to the rear wheel shaft via a propeller shaft and a rear differential device.

  Further, a planetary gear mechanism 10 as a differential means for absorbing the differential between the front and rear wheels on the shaft circumference between the front drive shaft 5, the transmission output shaft 4 and the rear drive shaft 6, and the difference between the planetary gear mechanism 10 Each member constituting an electronically controlled differential limiting device (hereinafter referred to as “differential limiting device”) 31 as a differential limiting means for limiting movement is disposed.

  The planetary gear mechanism 10 includes a sun gear 11, a ring gear 13 disposed on the outer periphery of the sun gear 11, and a differential case 12 that engages with the outer periphery of the ring gear 13 and rotates integrally with the ring gear 13. . Further, a planetary pinion 14 is interposed between the sun gear 11 and the ring gear 13. A drum 39 is integrally formed at the rear end of the differential case 12 via a clutch housing 38 constituting the differential limiting device 31.

  In this embodiment, a plurality (for example, six) of planetary pinions 14 are arranged at equal intervals, and both ends of each planetary pinion 14 are supported by the front and rear planetary carriers 15 and 16 via bearings so as to be rotatable. . Further, the planetary carriers 15 and 16 are integrally coupled via bolts 17 at a portion that does not interfere with the planetary pinion 14.

  An input shaft 8 formed integrally with the front planetary carrier 15 is engaged with the rear portion of the transmission output shaft 4. A support plate 18 is rotatably inserted into the outer periphery of the input shaft 8, and the outer periphery of the support plate 18 is engaged with the differential case 12.

  Further, a front output shaft 19 as a first rotating member is interposed between the sun gear 11 and the front drive shaft 5. The inner periphery and outer periphery of the front output shaft 19 are spline-engaged with the front drive shaft 5 and the front output shaft 19.

  Further, the inner periphery of the clutch hub 21 as the second rotating member is inserted into the outer periphery of the rear portion of the front output shaft 19, and the inner peripheral rear side edge of the clutch hub 21 and the rear portion of the front output shaft 19 are engaged. The torque cam mechanism 20 is provided at the engagement portion.

  The detailed configuration of the torque cam mechanism 20 will be described later, but its operation will be briefly described. The tooth surfaces of the torque cam mechanism 20 that engage with each other are trapezoidal cam teeth, and when a later-described main clutch 25 is engaged and a differential rotation occurs between the front output shaft 19 and the clutch hub 21, the torque cam mechanism 20. Slip in the axial direction occurs between the trapezoidal cam teeth, and the front output shaft 19 and the clutch hub 21 try to slide away from each other. However, since the tip of the front output shaft 19 is hooked on the side wall of the sun gear 11 via the snap ring 9, the clutch hub 21 slides to the left in FIG.

  A rear clutch plate 22 is integrally formed with the clutch hub 21. On the other hand, a front clutch plate 23 is fixed to the side surface of the rear planetary carrier 16. Between the front clutch plate 23 and the rear clutch plate 22, a main clutch (wet multi-plate clutch in this embodiment) 25 as a friction engagement means is disposed. When the main clutch 25 is engaged, the differential rotation of the planetary gear mechanism 10 is limited, and the outer periphery is splined to the differential case 12 and the inner periphery is splined to the clutch hub 21. The plates that are fitted are alternately arranged.

  A pressure plate 24 is spline-fitted on the back surface of the rear clutch plate 22 so as to be integrally rotatable. Further, the differential limiting device 31 described above is disposed behind the pressure plate 24. The configuration of the differential limiting device 31 is described in detail in Japanese Patent Laid-Open No. 6-320973 filed earlier by the present applicant.

  Here, the configuration of the differential limiting device 31 will be briefly described. The differential limiting device 31 includes an electromagnet 33 that houses an electromagnetic coil 32, and the electromagnet 33 is rotatably supported by a drum 39. The drum 39 is spline-fitted to the rear drive shaft 6 and integrally rotated. Further, the differential case 12 is integrally formed with the drum 39.

  In addition, a clutch housing 38 is provided in front of the electromagnet 33, and a device-side pressure plate 34 that is spline-engaged with the clutch housing 38 and supported so as to advance and retract is provided in front of the clutch housing 38. A pilot clutch 35 is disposed between the device-side pressure plate 34 and the clutch housing 38.

  The pilot clutch 35 has a configuration in which a drive plate and a driven plate are alternately arranged at a predetermined interval, and the outer periphery of the drive plate is spline-fitted to the inner periphery of the differential case 12, while the driven plate The inner periphery is splined to the clutch hub 36. The clutch hub 36 is externally mounted on the rear drive shaft 6 so as to be rotatable and restricted in movement in the axial direction. Further, cam grooves are formed on the opposed surfaces of the clutch hub 36 and the pressure plate 24, and cam balls 37 are accommodated between the cam grooves.

  Then, a control current I is applied to the electromagnetic coil 32 housed in the electromagnet 33 from a control unit (not shown) to magnetize the electromagnet 33 and is interposed between the device-side pressure plate 34 and the electromagnet 33. When the pilot clutch 35 is engaged and the clutch hub 36 is rotated, if a differential rotation occurs between the clutch hub 36 and the pressure plate 24, a phase shift occurs between the cam grooves facing each other. The cam ball 37 presses the pressure plate 24 forward. The control unit responds to the thrust force generated on the pressure plate 24 based on the values detected by the sensors that detect the behavior of the vehicle, such as the wheel speed sensor that detects the rotational speed of each wheel and the longitudinal acceleration sensor. The control current I is set.

  Further, a boss portion 16 a is projected from the side surface of the rear planetary carrier 16. The boss portion 16a is faced between the sun gear 11 and the ring gear 13 at a portion that does not interfere with the planetary pinion 14, and the side wall of the front planetary carrier 15 is brought into contact with the tip thereof. By bringing the side surface of the front planetary carrier 15 into contact with the tip of the boss portion 16a, the distance between the planetary carriers 15 and 16 can be kept constant. Further, the bolt 17 is screwed into the boss portion 16a from the front planetary carrier 15 side, and both the planetary carriers 15 and 16 are fastened and fixed. Further, a pin 17a projects from the tip of the bolt 17, and the front clutch plate 23 is engaged with the pin 17a. Accordingly, the front clutch plate 23 and the rear planetary carrier 16 are integrally rotated via the pin 17a.

  The torque cam mechanism 20 provided at the engagement portion between the front output shaft 19 and the clutch hub 21 has trapezoidal cam teeth 41 and 42 that mesh with each other, and each of these trapezoidal cam teeth 41 and 42 is a front output. The outer periphery of the rear portion of the shaft 19 and the inner peripheral rear side edge portion of the clutch hub 21 are formed with a certain interval. In FIG. 2, the trapezoidal cam teeth 41 and 42 are shown in a developed state, and the direction indicated by the arrow in FIG. 2 is the rotational direction during forward travel.

  The trapezoidal cam teeth 41 and 42 are formed with cam surfaces 41a and 42a and 41b and 42b, respectively, which are engaged with each other by differential rotation during driving and coasting. The cam angle of one cam surface 41a, 42a (the angle formed between the axis in the thrust direction of the trapezoidal cam teeth 41, 42 when the trapezoidal cam teeth 41, 42 are deployed) and the cam surfaces 41a, 42a, θ1, The cam angle of the other cam surface 41b, 42b (the angle formed between the axis in the thrust direction of the trapezoidal cam teeth 41, 42 when the trapezoidal cam teeth 41, 42 are deployed) and the cam surfaces 41b, 42b) θ2 The value is set so that the optimum differential limiting torque can be obtained according to the state.

Next, the effect | action of this form by such a structure is demonstrated.
During forward travel, the drive torque that is shifted by the transmission and output from the transmission output shaft 4 is input to the input shaft 8 of the center differential device 1 that is coupled to the transmission output shaft 4. The planetary pinion 14 supported by the front planetary carrier 15 and the rear planetary carrier 16 is revolved through the front planetary carrier 15 of the planetary gear mechanism 10 formed integrally with the input shaft 8.

  This planetary pinion 14 is meshed with the sun gear 11 and the ring gear 13. The sun gear 11 is connected to the front drive shaft 5 via the front output shaft 19, while the differential case 12 is splined to the outer periphery of the ring gear 13. Further, a drum 39 provided in the differential limiting device 31 is integrally formed at the rear end of the differential case 12, and the drum 39 is splined to the rear drive shaft 6.

  Accordingly, the driving torque output from the transmission output shaft 4 is transmitted to the sun gear 11 side and the ring gear 13 side by the planetary pinion 14 based on the basic torque distribution ratio determined by the gear ratio of the sun gear 11 and the ring gear 13 (for example, , Front wheel 4: rear wheel 6) and transmitted to front drive shaft 5 and rear drive shaft 6, and drive torque is transmitted to front and rear wheels via both drive shafts 5 and 6 to drive four wheels. Driving is performed.

  On the other hand, the differential limiting device 31 energizes the electromagnetic coil 32 with a control current I set according to the driving conditions during traveling from a control unit (not shown), and controls the clutch pressing force on the main clutch 25. In this case, for example, when the control current I supplied from a control unit (not shown) is set to zero on a relatively high μ road surface such as a dry road surface, the pilot clutch 35 is in a released state. 25 is also released.

  In the state where the main clutch 25 is released, the relative rotation between the sun gear 11 and the ring gear 13 is allowed, so that the drive torque output from the transmission output shaft 4 is as shown by the solid line in the center of FIG. According to the basic torque distribution ratio (for example, front wheel 4: rear wheel 6) set by the planetary gear mechanism 10, the front wheel side transmission torque TF and the rear wheel side transmission torque TR are distributed.

  On the other hand, a control unit (not shown) that detects when one of the front and rear wheels slips when the vehicle is started on a road surface in a low μ road state such as a rainy road, a snowy road, or while traveling on a curve or the like Then, the control current I corresponding to the slip state is output to the electromagnetic coil 32. Then, the electromagnet 33 disposed in the electromagnetic coil 32 is magnetized, and the device-side pressure plate 34 provided through the pilot clutch 35 is attracted.

  When the device-side pressure plate 34 is attracted by the electromagnet 33, the pilot clutch 35 interposed between the device-side pressure plate 34 and the clutch housing 38 is engaged, and the rotation of the differential case 12 causes the pilot clutch 35 to rotate. To the clutch hub 36, and the clutch hub 36 rotates.

  On the other hand, the pressure plate 24 facing the clutch hub 36 is spline-engaged with the rear clutch plate 22, and the rear clutch plate 22 is connected to the front output shaft 19 via the torque cam mechanism 20. The front output shaft 19 is spline-engaged between the sun gear 11 and the front drive shaft 5. Accordingly, the pressure plate 24 rotates integrally with the front drive shaft 5.

  As described above, since the control unit detects one slip of the front and rear wheels to engage the pilot clutch 35, a differential rotation occurs between the clutch hub 36 and the pressure plate 24. When a differential rotation occurs between the clutch hub 36 and the pressure plate 24, the cam grooves formed on the opposing surfaces of the two members are out of phase, so that the cam balls 37 interposed between the cam grooves are pressurized. The plate 24 is pressed forward, a predetermined thrust force is generated on the pressure plate 24, the main clutch 25 is pressed on the front clutch plate 23, and a predetermined clutch pressing force (differential limiting torque) is generated.

  Since the front clutch plate 23 rotates integrally with the rear planetary carrier 16, if a clutch pressing force is generated in the main clutch 25, the differential rotation between the front clutch plate 23 and the differential case 12, and the front clutch plate 23 The differential rotation with the clutch hub 36 is gradually reduced, and the differential between the drive shafts 5 and 6 is limited.

  At that time, if the front wheel or the rear wheel tries to slip beyond the clutch pressing force of the main clutch 25, the trapezoidal cam teeth 41 and 42 constituting the torque cam mechanism 20 provided between the clutch hub 36 and the front output shaft 19. A torque cam transmission torque TA acting in the rotational direction and a cam thrust force TS as an assisting force acting in the axial direction are generated on the cam surfaces 41a, 42a (or 41b, 42b) meshing with each other (see FIG. 2).

  In this case, since the front end portion of the front output shaft 19 is hooked on the front side surface of the sun gear 11 by the snap ring 9, the front output shaft 19 is restricted from moving backward (right side in FIG. 1). Therefore, the cam surface 42a formed on the trapezoidal cam teeth 42 on the clutch hub 21 side is moved forward (left in FIG. 1) by the cam thrust force TS generated between the cam surfaces 41a and 42a (or 41b and 42b) meshing with each other. Direction) to assist the clutch pressing force on the main clutch 25 and generate a stronger clutch pressing force.

  As a result, when the front wheel or the rear wheel tries to slip beyond the clutch pressing force controlled by the differential limiting device 31, the torque pressing force to the main clutch 25 is assisted by the torque cam mechanism 20. The occurrence of slip can be suppressed even in an instantaneous fluctuation region that cannot be controlled by the limiting device 31.

  As described above, in the present embodiment, the torque cam mechanism 20 assists the clutch pressing force controlled by the differential limiting device 31, so that the maximum value of the clutch pressing force generated in the main clutch 25 is determined as the input torque. Can be set independently. Accordingly, since the maximum value of the clutch pressing force can be amplified without increasing the capacity of the differential limiting device 31, it is possible to suppress an increase in the size of the entire device.

  In this case, when the capacity of the main clutch 25 is sufficient with the conventional specification, it is possible to relatively reduce the capacity of the electromagnetic coil 32 of the differential limiting device 31 and the number of pilot clutches 35, thereby simplifying the structure. And downsizing of the entire apparatus can be realized.

  Next, referring to FIG. 4 and FIG. 5, from the relationship between the front wheel side rotational speed NF and the rear wheel side rotational speed NR, drive torque transmitted to the front wheel side (hereinafter referred to as “front wheel side transmission torque TF”). Next, a change in driving torque transmitted to the rear wheel side (hereinafter referred to as “rear wheel side transmission torque TR”) will be described.

  FIG. 4 shows a state in which a slip has occurred on the front wheel and a clutch pressing force is applied to the main clutch 25. When a clutch pressing force is generated in the main clutch 25, a differential case 12 connected to the rear drive shaft 6 via a clutch housing 38 and the like, and a clutch hub 21 connected to the front drive shaft 5 via a front output shaft 19 are provided. The torque path is bypassed via the main clutch 25. Further, a torque path is bypassed between the rear planetary carrier 16, the differential case 12 and the clutch hub 21 via the main clutch 25.

  In the state where slip occurs in the front wheel, the front wheel side rotational speed NF is higher than the rear wheel side rotational speed NR (NF> NR), and therefore, as shown by the middle arrow in FIG. A part of the side transmission torque TF is moved at a certain rate from the front output shaft 19 and the clutch hub 21 to the rear drive shaft 6 through a torque path formed by the main clutch 25. As a result, rear wheel side transmission torque TR (indicated by a thick line arrow), which is the sum of drive torques (indicated by a medium line arrow) input via the torque path, is input to the rear drive shaft 6, It is transmitted to the rear wheel.

  On the other hand, in coasting, the engine brake torque from the transmission output shaft 4 is input to the front planetary carrier 15 and a clutch pressing force is generated in the main clutch 25 as described above, and the rear drive shaft 6 and the front drive shaft are A torque path is bypassed between As a result, as in normal driving, a constant rate of torque movement is performed between the rear drive shaft 6 and the front drive shaft 5 via a torque path from the larger rotational speeds NR and NF to the smaller one. Is called.

  FIG. 5 shows a state in which a slip occurs on the rear wheel and a clutch pressing force is applied to the main clutch 25. Similarly to the above, the torque path is bypassed by the main clutch 25, and the torque path is bypassed between the rear planetary carrier 16, the differential case 12 and the clutch hub 21 via the main clutch 25.

  In the state where the slip occurs in the rear wheel, the rear wheel side rotational speed NR is higher than the front wheel side rotational speed NF (NR> NF), so that the differential case from the planetary pinion 14 as shown by the middle arrow in the figure. A portion of the rear-wheel-side transmission torque TR transmitted to 12 is moved at a constant rate to the front drive shaft 5 via the main clutch 25, the clutch hub 21, and the front output shaft 19.

  Then, a front wheel side transmission torque TF (indicated by a thick line arrow), which is a sum of driving torques (indicated by a medium line arrow) input via the torque path, is input to the front drive shaft 5 and is input to the front wheel. Communicated.

  Next, the relationship between the front wheel side rotational speed NF and the rear wheel side rotational speed NR, the front wheel side transmission torque TF, and the rear wheel side transmission torque TR will be described using the characteristic diagram shown in FIG.

  When the front wheel speed NF and the rear wheel speed NR are equal and the main clutch 25 is in the disengaged state, as shown by the solid line in the center of the figure, the basic torque distribution set by the planetary gear mechanism 10 Transmission torque TF and rear wheel side transmission torque TR are set.

  On the other hand, as indicated by hatching in the figure, the region in which the front wheel speed NF tends to be larger than the rear wheel speed NR, and the rear wheel speed NR tends to be larger than the front wheel speed NF. In the region, the differential limiting device 31 operates, and the main clutch 25 is engaged with the differential limiting amount by the pilot clutch 35, so that the differential is limited. At that time, in a region where the front wheel side rotational speed NF is going to be larger than the rear wheel side rotational speed NR, a part of the driving torque transmitted to the front wheel side is transmitted to the rear wheel side, and the rear wheel side transmitted torque TR. Becomes larger. On the other hand, in the region where the rear wheel side rotational speed NR tends to be larger than the front wheel side rotational speed NF, a part of the driving torque transmitted to the rear wheel side is transmitted to the front wheel side, and the front wheel side transmission torque TF is increased. Become.

  As a result, for example, it is possible to suppress the occurrence of slip when starting and running on a low μ road surface. In this case, as indicated by a one-dot chain line in the figure, in a region where the front wheel or the rear wheel slips beyond the limit of the fastening force of the main clutch 25, the torque cam mechanism 20 operates and the differential limiting device 31 Assists and amplifies the set clutch pressing force. By amplifying the clutch pressing force by the operation of the torque cam mechanism 20, the occurrence of slip can be suppressed even in an instantaneous fluctuation region that cannot be controlled by the differential limiting device 31. Therefore, the responsiveness is good compared with the control operation of the differential limiting device 31 and good overall driving performance can be obtained.

  6 and 7 show a second embodiment of the present invention. In the first embodiment described above, the torque cam mechanism 20 is constituted by the trapezoidal cam teeth 41 and 42 meshing with each other, and the cam thrust force generated between the cam surfaces 41a and 42a (or 41b and 42b) of the trapezoidal cam teeth 41 and 42. Although the main clutch 25 is pressed by TS, in this embodiment, a so-called ball cam is adopted as the torque cam mechanism 20. Since the configuration other than the torque cam mechanism 20 is the same as that of the first embodiment, the same components are denoted by the same reference numerals as those of the first embodiment, and description thereof will be omitted.

  In the torque cam mechanism 20 according to the present embodiment, a plurality of cam grooves 46 and 47 are formed at predetermined intervals on the circumference of the opposing surface of the front output shaft 19 and the clutch hub 21, and between these cam grooves 46 and 47. A cam ball 48 is interposed in such a manner that it can roll freely. Cam surfaces 46b, 46c, and 47b, 47c are formed in the respective cam grooves 46, 47, the depths of which become shallower from the deepest neutral grooves 46a, 47a toward both sides in the circumferential direction. In addition, the inclination angle of each cam surface 46b, 46c, 47b, 47c can be set arbitrarily. Furthermore, the inclination angles of the cam surfaces 46b, 46c, 47b, 47c do not have to be the same, and may have different inclination angles.

  In such a configuration, as shown in FIG. 6, when no differential rotation occurs between the front output shaft 19 and the clutch hub 21, that is, when the main clutch 25 is in the released state, the cam ball 48 is It faces between the neutral grooves 46a and 47a.

  When a differential rotation occurs between the front output shaft 19 and the clutch hub 21 with the main clutch 25 engaged by the operation of the differential limiting device 31, both cam grooves 46, The phase difference between the 47 and the cam ball 48 rolls on the cam surfaces 46c and 47b (or 46b and 47c) facing each other, so that the clutch hub 21 is pressed and set by the differential limiting device 31. An assist force for assisting the clutch pressing force is generated, and the main clutch 25 is tightened more firmly.

  Since the cam ball 48 presses the clutch hub 21 while rolling, the hysteresis is smaller than when the trapezoidal cam surfaces 41a and 42a (or 41b and 42b) are slid to perform the cam operation as in the first embodiment. The occurrence of the tight corner braking phenomenon can be suppressed. The formation of the cam grooves 46 and 47 is easier than when the trapezoidal cam teeth 41 and 42 as in the first embodiment are formed, and the manufacturing cost can be reduced. Furthermore, since the design angle of the cam grooves 46 and 47 can be easily changed, the clutch pressing force can be easily adjusted as compared with the first embodiment.

Sectional side view along the axial direction of the center differential device according to the first embodiment Same part enlarged view of torque cam mechanism Explanatory drawing showing the characteristics of differential limiting torque FIG. 5 is an explanatory diagram showing the flow of drive torque due to the operation of the torque cam mechanism when the front wheel side rotational speed is higher than the rear wheel side rotational speed. FIG. 5 is an explanatory diagram showing the flow of drive torque due to the operation of the torque cam mechanism when the rear wheel side rotational speed is higher than the front wheel side rotational speed. The principal part enlarged view of the torque cam mechanism by a 2nd form Fig. 6 is an enlarged view of the main part according to the state of Fig. 6.

Explanation of symbols

1 Center differential device,
4 Transmission output shaft,
5 Front drive shaft,
6 Rear drive shaft,
8 input shaft,
10 Planetary gear mechanism,
11 Sungear,
12 Differential case,
13 Ring gear,
15 Front planetary carrier,
16 Rear planetary carrier,
19 Front output shaft,
20 torque cam mechanism,
21 clutch hub,
25 Main clutch,
31 differential limiting device,
35 Pilot clutch,
38 clutch housing,
41, 42 trapezoidal cam teeth,
41a, 41b, 42a, 42b cam surface,
46, 47 Cam groove,
46a, 47a Neutral groove,
46b, 46c, 47b, 47c cam surface,
48 Camball,
NF Front wheel side rotation speed,
NR Rear wheel side rotation speed,
TA transmission torque,
TF Front wheel side transmission torque,
TR rear wheel side transmission torque,
TS Cam thrust force

Claims (3)

Differential means for distributing torque from the first output shaft to the second output shaft and the third output shaft;
A rotating member provided alongside the differential means and connected to one of the second output shaft and the third output shaft;
Friction fastening means interposed on the other of the rotating member, the second output shaft and the third output shaft;
Differential limiting means for electronically controlling the differential limiting torque applied to the frictional engagement means according to the driving state of the vehicle,
The rotating member is divided into a first rotating member connected to the other side of the second output shaft and the third output shaft and a second rotating member connected to the friction fastening means side,
The second rotating member is slidably provided in a direction for releasing / fastening the friction fastening means,
Between the first rotating member and the second rotating member, with respect to the friction fastening means according to the differential rotation when the differential limiting torque is applied to the friction fastening means by the differential limiting means. A torque distribution device comprising a torque cam mechanism for generating an assist force. The torque distribution according to claim 1, wherein the torque cam mechanism has trapezoidal cams that are formed between opposing surfaces of the first rotating member and the second rotating member and engage with each other. apparatus. The torque cam mechanism is a ball cam in which cam grooves are respectively provided between opposing surfaces of the first rotating member and the second rotating member, and cam balls are interposed between the cam grooves. Item 2. The torque distribution device according to Item 1.

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