JP4376745B2 - Driving force distribution device for four-wheel drive vehicle - Google Patents

Description

  The present invention relates to a driving force distribution device for a four-wheel drive vehicle capable of switching between a two-wheel drive state and a four-wheel drive state by a torque transmission means having variable transmission characteristics such as a multi-plate clutch and a viscous coupling.

  As a first conventional example of a driving force distribution device for a four-wheel drive vehicle, a multi-plate clutch is arranged on a propeller shaft, and engagement of the multi-plate clutch is performed by an actuator based on a sensor signal for detecting a vehicle driving state. It is known to control and transmit torque from a main drive shaft to a slave drive shaft via a differential device.

  Various actuators such as a hydraulic clutch, an electromagnetic solenoid, a ball ramp mechanism (torque-thrust conversion mechanism) are employed as actuators for controlling the engagement of the multi-plate clutch. In the ball ramp mechanism, the rotational force of the motor is boosted by a reduction gear, the rotational force is converted into thrust by the ball ramp mechanism, and the multi-plate clutch is engaged.

  In addition, a so-called differential device with LSD, which incorporates an LSD (Limited Slip Differential) into the differential device, is aimed at improving stable driving performance on rough roads such as “slimy” and “snowy road” and turning performance. Are known.

  Various types of LSD, such as those that press the multi-plate clutch using the gear reaction force in the differential device, those that use friction between the gears of the helical gear, or those that press the multi-plate clutch with an actuator such as a hydraulic piston Has been proposed.

As a second conventional example of a driving force distribution device for a four-wheel drive vehicle, there is known a driving force distribution device in which two multi-plate clutches are arranged on a driven shaft and each clutch is controlled independently. According to this driving force distribution device, it is possible to control the torque transmission amount from the main drive shaft to the driven shaft and at the same time control the torque transmission amount to the left and right driven wheels. The driving performance can be improved.
JP 2002-316546 A Japanese Patent Laid-Open No. 11-141649 JP-A-10-194003 Japanese Examined Patent Publication No. 62-19617

  In the first conventional example described above, since the multi-plate clutch is arranged on the propeller shaft, the total length of the driving force distribution device becomes long, and when mounted on the vehicle, other vehicle structures such as a fuel tank, a suspension beam, etc. There is a problem that buffering occurs.

  In the second conventional example, the total length of the driving force distribution device can be shortened, so that interference with other vehicle structures does not occur. However, since two multi-plate clutches are mounted, the structure is complicated and expensive.

  Further, since the multi-plate clutch is disposed on the driven shaft, the torque transmission of the clutch is transmitted by the reduction ratio of the hypoid gear as compared with the case where the multi-plate clutch is disposed on the propeller shaft as in the first conventional example. In order to ensure the same amount of torque transmission due to the shortage of the amount, the clutch must be enlarged, which is undesirable because it increases costs and weight.

  Accordingly, an object of the present invention is to provide a driving force distribution device for a four-wheel drive vehicle that solves the problems of the prior art described above and is compact and inexpensive.

  According to the first aspect of the present invention, there is provided a driving force distribution device for a four-wheel drive vehicle having a main drive wheel pair and a slave drive wheel pair that are directly driven by a drive source, and is connected to one of the slave drive wheel pair. A first axle, a second axle connected to the other of the driven wheel pair, an input shaft connected to the drive source, and an operatively connected to the input shaft and driven to rotate by the input shaft. A differential device having a differential case, first and second side gears, an output shaft having one end connected to the first side gear, a first clutch hub connected to the other end of the output shaft, and the first The clutch guide connected to the axle, the plurality of first clutch disks attached to the first clutch hub, and the clutch so as to be alternately arranged with the first clutch disks. A first clutch having a plurality of first clutch plates attached to a guide, one end connected to the differential case, an LSD shaft arranged in parallel to the output shaft, and the other end of the LSD shaft A second clutch hub, a second clutch disk attached to the second clutch hub, and a second clutch plate attached to the clutch guide, and being arranged in series with the first clutch. A driving force distribution device for a four-wheel drive vehicle is provided, comprising: a clutch; and an actuator that simultaneously operates the first clutch and the second clutch.

  According to a second aspect of the present invention, there is provided a driving force distribution device for a four-wheel drive vehicle further comprising a friction plate disposed between the differential case and the second side gear.

  According to a third aspect of the present invention, there is provided a driving force distribution device for a four-wheel drive vehicle, further comprising a friction reducing means arranged between the differential case and the first side gear. . For example, a thrust bearing can be employed as the friction reducing means.

  According to a fourth aspect of the present invention, in the first aspect of the present invention, the friction plate disposed between the differential case and the second side gear, and the friction reducing means disposed between the differential case and the first side gear. And a driving force distribution device for a four-wheel drive vehicle.

  According to the fifth aspect of the present invention, in the first to fourth aspects of the present invention, the LSD shaft is constituted by a hollow shaft, and the output shaft is a driving force of a four-wheel drive vehicle that is rotatably disposed in the hollow shaft. A dispensing device is provided.

  According to the first aspect of the present invention, the overall length of the driving force distribution device can be suppressed, and interference with other vehicle structures can be avoided when the vehicle is mounted. Further, since the second clutch is arranged in series with the first clutch and both clutches are simultaneously operated by the actuator, the unevenness of the left and right driving force during straight traveling can be eliminated.

  Furthermore, the LSD function by the second clutch can improve the stability and turning performance when driving on rough roads, and only one actuator is required, so the weight and cost can be reduced.

  According to the second aspect of the present invention, since the friction plate is disposed between the differential case and the second side gear, a greater LSD effect can be obtained, and stability and turning performance when traveling on a rough road can be improved. it can.

  According to the third aspect of the present invention, since the friction reducing means is disposed between the differential case and the first side gear, it is possible to eliminate the difference in effectiveness of the LSD when turning left and right. In other words, approximately the same TBR (torque bias ratio) can be obtained for the left turn and the right turn.

  According to the fourth aspect of the present invention, a large LSD effect can be obtained, and the difference in the effectiveness of the LSD when turning left and right can be solved.

  According to the invention described in claim 5, since the LSD shaft is constituted by a hollow shaft and the output shaft is rotatably arranged in the hollow shaft, a compact shaft arrangement can be realized.

  Referring to FIG. 1, there is shown a schematic diagram of a power transmission system of a four-wheel drive vehicle based on a front engine / front drive (FF) vehicle suitable for application of the driving force distribution device of the present invention.

  The power of the engine 2 disposed in front of the vehicle is transmitted to the front axles 8 and 10 via the transmission 4 and the front differential device 6 to drive the front wheels 12 and 14.

  The power of the engine 2 is also transmitted to the propeller shaft 18 via the transmission 4, the front differential device 6 and the transfer gear mechanism 16. The power of the propeller shaft 18 is transmitted to the rear differential device 24 via the hypoid pinion gear 20 and the hypoid ring gear 22.

  As will be described in detail later, one side gear of the rear differential device 24 is connected to the output shaft 26, and the other side gear is connected to the rear axle 30. A differential case (hereinafter abbreviated as a differential case) of the rear differential device 24 is connected to the hollow shaft 28.

  A clutch unit 34 is interposed between the right rear axle 32 and the output shaft 26 and the hollow shaft 28. The degree of engagement of the clutch unit 34 is controlled by the actuator 36 in accordance with the driving state of the vehicle. The rear axles 30 and 32 are connected to rear wheels 38 and 40, respectively.

  When the clutch unit 34 is sufficiently engaged by the actuator 36, half of the driving force of the engine 2 is transmitted to the rear wheels 38 and 40, and the vehicle enters the four-wheel drive mode. On the other hand, when the clutch unit 34 is completely released, all the power of the engine 2 is transmitted to the front wheels 12 and 14, and the vehicle enters the FF drive mode.

  Next, the driving force distribution device according to the first embodiment of the present invention will be described with reference to FIG. In the description of each embodiment, the same components will be described with the same reference numerals.

  The differential case 42 of the rear differential device 24 is coupled to the hypoid ring gear 22 and rotates integrally with the hypoid ring gear 22. The differential case 42 is connected to a hollow shaft 28 as an LSD shaft.

  The rear differential device 24 includes a pair of side gears 50 and 52 that are disposed in the differential case 42 so as to face left and right, a pair of pinion gears 46 and 48 that connect the side gears 50 and 52, and the pinion gears 46 and 48. Is constituted by a pinion shaft 44 that rotatably supports the shaft.

  The side gear 50 is connected to the rear axle 30, and the side gear 52 is connected to the output shaft 26 that is rotatably disposed in the hollow shaft 28. The clutch unit 34 includes a main clutch 54 and an LSD clutch (limited slip differential clutch) 56 arranged in series with each other.

  A clutch hub 58 of the main clutch 54 is connected to the output shaft 26. A clutch guide 62 of the main clutch 54 is connected to the rear axle 32. A plurality of clutch disks 60 are attached to the clutch hub 58 so as not to rotate but to move in the axial direction. On the other hand, a plurality of clutch plates 64 are attached to the clutch guide 62 so as to be non-rotatable and axially movable so as to be alternately arranged with the clutch disks 60.

  A clutch hub 66 of the LSD clutch 56 is connected to the hollow shaft 26. The LSD clutch 56 shares the main clutch 54 and the clutch guide 62. A clutch disc 68 is attached to the clutch hub 66 of the LSD clutch 56 so as not to be rotatable and axially movable, and a clutch plate 70 is attached to the clutch guide 62 so as not to be rotatable and axially movable.

  Reference numeral 36 denotes an actuator, which includes an electric motor 72, a speed reduction mechanism 74 composed of a plurality of gears, and a ball ramp mechanism (torque-thrust conversion mechanism) 76. A conventionally known structure can be adopted for the ball ramp mechanism 76, and the structure and operation thereof are described in detail in, for example, Japanese Patent Publication No. 8-19971.

  A piston 78 is moved in the axial direction by the actuator 36 and engages the main clutch 54 and the LSD clutch 56. Thrust bearings 80 and 84 are interposed between the piston 78 and the ball ramp mechanism 76 and between the body frame or housing 82 and the ball ramp mechanism 76, respectively.

  For example, as shown in FIG. 3, the actuator 36 is controlled by providing a load sensor 86 between the housing 82 and the thrust bearing 84 and controlling the rotation of the motor 72 based on a signal from the load sensor 86.

  As an alternative, as shown in FIG. 4, a rotation angle sensor 88 such as a resolver is attached to the output shaft of the motor 72, and the rotation of the motor 72 is controlled based on the signal of the rotation angle sensor 88 to Control the amount of movement in the direction.

  Thus, when both the main clutch 54 and the LSD clutch 56 are released, the driving force of the engine 2 is all directed to driving the front wheels 12 and 14, and the four-wheel drive vehicle is in the two-wheel drive mode (FF mode). Works with.

  When the actuator 36 is operated to move the piston 78 in the axial direction, both the main clutch 54 and the LSD clutch 56 are engaged (fastened). When the main clutch 54 and the LSD clutch 56 are completely engaged, the driving force of the engine 2 is distributed by 50% to the front wheels 12 and 14 and the rear wheels 38 and 40, respectively. Works with.

  The degree of engagement of the main clutch 54 and the LSD clutch 56 can be controlled by controlling the actuator 36 based on a signal from a sensor that detects the running state of the vehicle. , 40 can be distributed within a range of 0 to 50%.

  In the present embodiment, since the LSD clutch 56 that transmits the rotation of the differential case 42 to the rear axle 32 at the time of engagement is provided in series with the main clutch 54, the unevenness of the left and right driving force when traveling straight can be eliminated. Further, the LSD function of the LSD clutch 56 can improve the stability and turning performance when traveling on a rough road.

  Referring to FIG. 5, there is shown a schematic configuration diagram of a driving force distribution device according to a second embodiment of the present invention. In the present embodiment, a friction plate 90 is interposed between the side gear 50 and the differential case 42 opposite to the side where the clutch unit 34 is provided. Other configurations of the present embodiment are the same as those of the first embodiment described above.

  The friction plate 90 is publicly known, and any commercially available friction plate 90 can be adopted. The friction plate 90 may be either fixed to the differential case 42 or fixed to the side gear 50.

  Since the friction plate 90 is interposed between the differential case 42 and the side gear 50, a greater LSD effect can be obtained compared to the first embodiment shown in FIG. In other words, the TBR (torque bias ratio) can be increased. Here, TBR is the ratio of the torque of the inner ring to the torque of the outer ring during turning, and represents the amount of LSD effect during turning.

  Referring to FIG. 6, there is shown a schematic configuration diagram of a driving force distribution device according to a third embodiment of the present invention. In the present embodiment, a thrust bearing 92 is interposed between the side gear 52 and the differential case 42 on the same side as the side where the clutch unit 34 is provided. Instead of the thrust bearing 92, other friction reducing means may be provided. Other configurations of the present embodiment are the same as those of the first embodiment shown in FIG.

  In the present embodiment, since the thrust bearing 92 is interposed between the side gear 52 on the same side as the clutch unit 34 and the differential case 42, the difference in effectiveness of the LSD when turning left and right can be solved. In other words, the difference in TBR when turning left and right can be reduced.

  Referring to FIG. 7, there is shown a schematic configuration diagram of a driving force distribution device according to a fourth embodiment of the present invention. In the present embodiment, a friction plate 90 is interposed between the side gear 50 opposite to the side where the clutch unit 34 is provided and the differential case 42, and a thrust bearing 92 is interposed between the side gear 52 and the differential case 42 on the same side. It is a disguise.

  According to the present embodiment, a large LSD effect can be obtained by providing the friction plate 90, and a difference in effectiveness of the LSD when turning left and right can be eliminated by providing the thrust bearing 92.

Next, the operation of this embodiment will be described with reference to the diagram of FIG. In FIG. 8, Δω _FR represents the differential rotation of the front and rear wheels, and Δω _RL represents the differential rotation of the left and right rear wheels.

  In the area (A), torque is equally distributed to the left and right rear wheels. In other words, this area is an LSD insensitive area, and the uneven driving force when driving straight can be eliminated. However, since the radius of curvature during turning is large, the LSD effect by the LSD clutch 56 and the friction plate 90 can be almost ignored. It is.

In predetermined radius of curvature less the leftward turning upon area (B), the LSD effect by LSD clutch 56 and friction plate 90, the torque of the [Delta] T _L is distributed from the right rear wheel 40 to the left rear wheel 38.

In predetermined radius of curvature less right turn at the region (C), the torque of the [Delta] T _R is distributed from the left rear wheel 38 to the right rear wheel 40. In the present embodiment, T _R ≈T _L since the difference in effectiveness of LSD during left and right turning can be resolved.

  In each of the embodiments described above, the configuration in which the output shaft 26 is accommodated in the hollow shaft 28 has been described. However, the present invention is not limited to this configuration, and the second output shaft is replaced with the output shaft instead of the hollow shaft 28. 26 and the LSD clutch 56 may be coupled to the second output shaft.

  Next, the detailed structure of the driving force distribution device of the fourth embodiment described above will be described with reference to FIG. Reference numeral 94 denotes a fixed housing, which includes a central housing 94a and left and right side housings 94b and 94c.

  Reference numeral 96 denotes a companion flange, which is fastened to the propeller shaft 18 shown in FIG. The input shaft 102 is rotatably supported in the housing 94 by a pair of needle bearings 98 and 100.

  Input shaft 102 is coupled to companion flange 96 by splines 104. A hypoid pinion gear 20 is formed at the tip of the input shaft 102.

  The hypoid pinion gear 20 meshes with the hypoid ring gear 22. The hypoid ring gear 22, the differential case 42 of the rear differential device 24, and the hollow shaft 28 are fastened together by screws 106 and coupled to each other. Therefore, when the hypoid ring gear 22 is rotated by the input shaft 102, both the differential case 42 and the hollow shaft 28 are rotated.

  The rear differential device 24 is disposed on the left and right sides of a pair of pinion gears 46 and 48 that are rotatably mounted around pinion shafts 44 and 45 fixed to the differential case 42, and the differential case 42 that connects and meshes with the pinion gears 46 and 48. It comprises a pair of side gears 50 and 52.

  A plurality of friction plates 90 are interposed between the side gear 50 and the differential case 42, and a thrust bearing 92 is interposed between the side gear 52 and the differential case 42.

  The side gear 50 and the left side shaft 130 are coupled by a spline 112, and the side gear 52 and the output shaft 26 are coupled by a spline 114. The left side shaft 130 is coupled to the left rear axle 30.

  The hypoid ring gear 28, the differential case 42, and the hollow shaft 28 coupled to each other are supported by a housing 94 so as to be rotatable by a pair of bearings 108 and 110. The right side shaft 132 is rotatably supported by the housing 94 via a bearing 116. The right side shaft 132 is coupled to the right rear axle 32.

  The clutch unit 34 includes a main clutch 54 and an LSD clutch 56 arranged in series. A clutch hub 58 of the main clutch 54 is splined to the output shaft 26, and a plurality of clutch discs 60 are attached so as not to rotate and to move in the axial direction.

  The clutch guide 62 of the main clutch 54 is formed integrally with the right side shaft 132, and a plurality of clutch plates 64 are attached so as to be non-rotatable and axially movable so as to alternate with the clutch disk 60.

  The clutch hub 66 of the LSD clutch 56 is spline-coupled to the hollow shaft 28, and a plurality of clutch disks 68 are attached so as not to rotate but to move in the axial direction.

  The LSD clutch 56 shares the clutch guide 62 with the main clutch 54, and a plurality of clutch plates 70 are attached to the clutch guide 62 so as to be alternated with the clutch disk 68 so as not to rotate but to move in the axial direction.

  The actuator 36 includes an electric motor 72, a speed reduction mechanism 74 including a plurality of gears, and a ball ramp mechanism (torque-thrust conversion mechanism) 76. The rotation angle of the motor 72 is detected by a rotation angle sensor 88 such as a resolver.

  The reduction mechanism 74 includes a base gear 118 and a sub gear 120 having a larger diameter than the base gear 118. The ball ramp mechanism 76 includes a base cam gear 122 rotatably attached to the hollow shaft 28 so as to mesh with the base gear 118, and a sub cam gear 124 rotatably attached to the hollow shaft 28 so as to mesh with the sub gear 120. Yes.

  A plurality of indentations spaced apart at equal intervals in the circumferential direction are formed on the opposing surfaces of the base cam gear 122 and the sub cam gear 124, and balls 126 are respectively accommodated in these indentations.

  A piston 78 is moved in the axial direction to engage the main clutch 54 and the LSD clutch 56. When the piston is returned by the return spring 128, the engagement of the main clutch 54 and the LSD clutch 56 is released.

  A thrust bearing 80 is interposed between the sub cam gear 124 and the piston 78, and a thrust bearing 84 is interposed between the pressure plate 127 attached to the housing 94 and the base cam gear 122. The movement of the base cam gear 122 in the left direction is restricted by the pressure plate 127.

  Thus, when the motor 72 is rotated, the base cam gear 122 and the sub cam gear 124 of the ball ramp mechanism 76 are rotated via the base gear 118 and the sub gear 120 of the speed reduction mechanism 74, respectively.

  Since the base gear 118 has a smaller diameter than the sub gear 120 and the base cam gear 122 has a larger diameter than the sub cam gear, the sub cam gear 124 rotates faster than the base cam gear 122.

  In response to this differential rotation, since the ball 126 changes from being completely accommodated in the recess to being partially accommodated, a thrust force is generated, and the base cam gear 122 is regulated by the plate 127. 124 is moved to the right in FIG.

  Thereby, the piston 78 is driven, the clutch disks 60 and 68 of the main clutch 54 and the LSD clutch 56 and the clutch plates 64 and 70 are pressed against each other, and the main clutch 54 and the LSD clutch 56 are engaged (fastened). The degree of engagement of the main clutch 54 and the LSD clutch 56 is controlled by the amount of movement of the sub cam gear 124, that is, the rotation angle of the motor 72.

It is a figure which shows roughly the power transmission system of the four-wheel drive vehicle suitable for applying the driving force distribution apparatus of this invention. It is a schematic block diagram of 1st Embodiment of this invention. It is a schematic block diagram of the actuator which controls a motor based on the signal of a load sensor. It is a schematic block diagram of the actuator which controls a motor based on the signal of a rotation angle sensor. It is a schematic block diagram of 2nd Embodiment of this invention. It is a schematic block diagram of 3rd Embodiment of this invention. It is a schematic block diagram of 4th Embodiment of this invention. It is a figure explaining the effect | action of 4th Embodiment. It is a longitudinal cross-sectional view which shows the detailed structure of 4th Embodiment of this invention.

Explanation of symbols

24 Rear differential device 26 Output shaft 28 Hollow shaft 30, 32 Rear axle 34 Clutch unit 36 Actuator 42 Differential case 50, 52 Side gear 54 Main clutch 56 LSD clutch 58, 66 Clutch hub 62 Clutch guide 74 Deceleration mechanism 76 Ball ramp mechanism 78 Piston

Claims (5)

A driving force distribution device for a four-wheel drive vehicle having a main drive wheel pair and a sub drive wheel pair driven directly by a drive source,
A first axle connected to one of the driven wheel pair;
A second axle connected to the other of the pair of driven wheels,
An input shaft coupled to the drive source;
A differential case operatively connected to the input shaft and driven to rotate by the input shaft; and a differential device having first and second side gears;
An output shaft having one end connected to the first side gear;
A first clutch hub coupled to the other end of the output shaft; a clutch guide coupled to the first axle; a plurality of first clutch disks attached to the first clutch hub; and the first clutch disk. A first clutch having a plurality of first clutch plates attached to the clutch guide so as to be alternately arranged;
An LSD shaft having one end connected to the differential case and disposed parallel to the output shaft;
A second clutch hub connected to the other end of the LSD shaft; a second clutch disk attached to the second clutch hub; and a second clutch plate attached to the clutch guide. A second clutch arranged in series with the clutch;
An actuator for simultaneously operating the first clutch and the second clutch;
A driving force distribution device for a four-wheel drive vehicle.   The driving force distribution device for a four-wheel drive vehicle according to claim 1, further comprising a friction plate disposed between the differential case and the second side gear.   2. The driving force distribution device for a four-wheel drive vehicle according to claim 1, further comprising friction reducing means disposed between the differential case and the first side gear. A friction plate disposed between the differential case and the second side gear;
Friction reducing means disposed between the differential case and the first side gear;
The driving force distribution device for a four-wheel drive vehicle according to claim 1, further comprising:   5. The driving force distribution of a four-wheel drive vehicle according to claim 1, wherein the LSD shaft is constituted by a hollow shaft, and the output shaft is rotatably disposed in the hollow shaft. apparatus.

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