JP2010116966A - Driving force distributing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a driving force distributing device capable of largely reducing drag torque, capable of maintaining a stable excellent friction characteristic and durability over a long period without applying expensive surface treatment, and capable of also preventing a variation in a clutch transmission torque characteristic. <P>SOLUTION: This driving force distributing device 1 has an electromagnet 70 moving toward a pilot clutch 50 by magnetic attraction force acting between a wall part 23a of a coupling case 20 and itself, and a pressing member 53 for adjusting operation force of the pilot clutch 50 in response to the movement of the electromagnet 70. The pressing member 53 is pushed back to a predetermined initial position to the wall part 23a of the coupling case 20 in response to abrasion of the pilot clutch 50 when an electric current is not carried to the electromagnet 70, and is adjusted so that a pressing surface of the pressing member 53 and an inner end surface of a step height wall part 23 of the coupling case 20 coincide with each other. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a driving force distribution device using an electromagnetic friction clutch.

  Conventionally, for example, various driving force distribution devices in a four-wheel drive vehicle including an electromagnetic friction clutch have been proposed (see, for example, Patent Document 1). In the conventional driving force distribution device described in Patent Document 1, the fastening of the main clutch that transmits torque between the input member and the output member is adjusted by a pilot clutch that is fastened by energization of an electromagnet. The pilot clutch is provided in the front housing, and an armature is disposed on one side of the pilot clutch. A rear housing is disposed on the other side of the pilot clutch, and an electromagnet fitted in the yoke is disposed in the rear housing.

  According to this conventional driving force distribution device, a magnetic circuit that circulates between the yoke, the rear housing, the armature, the pilot clutch, the rear housing, and the yoke is formed by energizing the electromagnet. The pilot clutch is fastened by attracting the armature with the electromagnet and pressing the pilot clutch. The cam mechanism that generates a thrust force by the engagement converts the pressing force to the main clutch, and transmits the pressing force to the main clutch, whereby the driving force is transmitted from the input member to the output member.

  The pressing force against the pilot clutch is generated when the magnetic flux excited by the electromagnetic coil of the electromagnet penetrates the pilot clutch and attracts the armature. For this reason, the pilot clutch requires a configuration that has both the characteristics of being easily magnetized and the friction characteristics of the clutch plate. As a result, the pilot clutch is made of iron, and the sliding surface of the iron clutch plate is subjected to a surface treatment that suppresses wear due to frictional engagement. A nonmagnetic material is embedded in a portion corresponding to the intermediate portion of the pilot clutch of the rear housing constituting a part of the magnetic circuit.

  As a surface treatment of the pilot clutch, a number of fine width grooves or a number of grid-like grooves are formed concentrically on the sliding surface of the clutch plate, and the composition of the sliding surface is nitrided. Alternatively, it is changed by quenching and tempering, or a diamond-like carbon thin film is applied to the sliding surface of the clutch plate. By this surface treatment, the sliding surface of the clutch plate is strengthened to reduce wear.

  Another example of this type of driving force distribution device is a driving force distribution device in which friction clutch paper that functions optimally when lubricated with oil is provided on the sliding surface of the clutch plate of the pilot clutch (for example, patents) Reference 2).

In the conventional driving force distribution device described in Patent Document 2, an electromagnet is fixed in a housing that rotatably supports an input member. The pilot clutch is provided on the inner surface of the input member, and the electromagnets are arranged to face each other through the input member. On the side opposite to the input member of the pilot clutch, an armature (action plate) connected to the plunger of the electromagnet is arranged to face.
JP 2003-28218 A JP 2005-61629 A

  By the way, when lubricated with oil, drag torque is generated by the viscous resistance of the oil interposed between the two surfaces where the clutch plates face each other. One cause of the large drag torque is that the clutch plate sliding surface (friction surface) is wide. That is, the drag torque due to oil viscosity is proportional to the area of the two surfaces where the clutch plates face each other.

  In the conventional driving force distribution device described in Patent Document 1, since the pilot clutch constitutes a part of the magnetic circuit, the cross-sectional area of the magnetic path of the pilot clutch is set to a predetermined size that facilitates magnetism. Must be set. Therefore, in addition to the sliding surface of the clutch plate, a magnetic path cross section that is not required as the sliding surface of the clutch plate has to be formed, and the pilot clutch has to be formed large. As a result, there is a limit in reducing the drag torque, and there is a problem that it is difficult to reduce the drag torque. In particular, the strength of the differential and the drive shaft must be designed on the premise of a large drag torque at low temperatures, which increases the size, weight, and manufacturing cost. In addition, there is a problem that maneuverability is deteriorated, for example, the occurrence of a tight corner braking phenomenon cannot be avoided at low temperatures.

  In addition, this conventional driving force distribution device is prone to vibration and noise due to stick-slip due to the friction between iron and the pilot clutch. As a countermeasure, various oil grooves are provided on the sliding surface and wear resistance is reduced. For example, a nitriding treatment or a quenching / tempering treatment or a diamond-like carbon thin film is applied, but there is a problem that the processing cost is increased. In addition, even with these processing treatments, the wear characteristics (μ-V characteristics) of the pilot clutch deteriorate during use due to wear of oil grooves, etc., and there is a problem that vibration and noise of the vehicle are generated. It was. In addition, this conventional driving force distribution device arranges an armature on the front housing side and an electromagnet on the rear housing side with a non-magnetic material embedded in a rear housing constituting a part of the magnetic circuit. There is a problem that the pilot clutch is arranged between the non-magnetic members, and the manufacturing cost of the joint structure with the non-magnetic member is increased.

  On the other hand, in the conventional driving force distribution device described in Patent Document 2, the gap between the electromagnet yoke and the armature (plunger) is maintained through a ball bearing that is largely deformed with respect to an axial load. Has been. Therefore, this conventional driving force distribution device is affected by the positional relationship between the electromagnetic coupling and the housing, the gap length between the electromagnet yoke and the armature (plunger) becomes unstable, and the clutch transmission torque characteristics vary from product to product. Has a problem of occurrence.

  Therefore, the present invention has been made to solve the above-described conventional problems, and a specific object thereof is to greatly reduce the drag torque, and it is possible to achieve long processing without expensive surface treatment. It is an object of the present invention to provide a driving force distribution device that makes it possible to maintain stable and good friction characteristics and durability over a period of time, and further to prevent variations in clutch transmission torque characteristics.

[1] In order to achieve the above object, the present invention is provided between the input member and the output member, and between the input member and the output member, the first friction clutch for transmitting torque between these members. A second friction clutch for adjusting the transmission torque of the first friction clutch, a cam mechanism for converting the transmission torque of the second friction clutch into a pressing force against the first friction clutch, and the input member A housing including the first friction clutch, the cam mechanism, and the second friction clutch, and provided on the same axis as the housing outside the wall portion of the housing. An electromagnet that moves toward the second friction clutch by a magnetic attraction acting between the housing and the inside of the wall portion of the housing A pressing member that adjusts an operating force of the second friction clutch according to the movement of the electromagnet, and a pressing member that is attached to the predetermined wall portion of the housing according to wear of the second friction clutch. A driving force distribution device is provided with push-back means for pushing back to the initial position.
[2] In the invention according to the above [1], the second friction clutch is provided with a paper facing on a sliding surface of one of the plurality of clutch plates frictionally engaged with each other. It is characterized by that.
[3] In the invention described in [1] above, the push-back means is the inner peripheral surface of the housing on the clutch plate side located at the outermost end in the clutch pressing direction of the second friction clutch, or the first And an adjustment nut screwed into the inner peripheral surface of the housing on the clutch plate side located at the outermost end opposite to the clutch pressing direction of the friction clutch, and a spring member that pressurizes the adjustment nut in the tightening direction. The spring member is provided on an inner peripheral surface of the adjustment nut.
[4] In the invention described in [3] above, an engagement hook is formed on the inner peripheral surface of the adjustment nut, and ratchet teeth are formed on the inner peripheral surface excluding the engagement hook. The spring member is formed with a winding spring that urges the adjusting nut in the tightening direction and a ratchet claw that prevents the adjusting nut from rotating in the loosening direction. The ratchet pawl is engaged with the hook, and the ratchet pawl is engaged with the ratchet teeth.
[5] In the invention described in [4] above, the winding spring is bent from an outer peripheral edge of the spring member and is formed in a plate shape that circulates along the peripheral surface of the spring member; The ratchet pawl is composed of a leaf spring bent from the outer peripheral edge of the spring member and is more outward than the coil spring. It is characterized by being arranged in.
[6] In the invention according to any one of [3] to [5], a clutch notch portion is formed in the clutch plate of the second friction clutch, and an outer peripheral edge of the spring member is formed on the outer peripheral edge of the spring member. The rotation stopper piece that engages with the locking notch is formed.
[7] In the invention according to any one of [4] to [6], the spring member includes first and second ratchet claws, and the first and second ratchet claws are connected to each other. The ratchet teeth are arranged with a phase shifted by approximately half the pitch of the ratchet teeth.
[8] In the invention described in [1] above, a clutch plate positioned at an outermost end opposite to a clutch pressing direction of the second friction clutch is disposed inside the wall portion of the housing. A preload spring that biases the pressing member toward the pressing member is provided.
[9] In the invention described in [1], an outer case that rotatably supports the housing is provided, and the electromagnet is supported on an inner peripheral surface of the outer case.
[10] The invention according to [1], further including an outer case that rotatably supports the housing, wherein the electromagnet is supported so as to be relatively rotatable and axially movable with respect to a shaft portion of the housing. In addition, the outer case is supported so as not to rotate.
[11] In the invention described in [1], a thrust needle bearing and a plate member are interposed between the electromagnet and the pressing member.

  In the present invention, since the magnetic attraction acting on the electromagnet is directly applied to the second friction clutch without passing the magnetism through the second friction clutch, the clutch of the second friction clutch. The area of the plate sliding surface can be reduced. As a result, the drag torque due to the oil viscosity can be reduced, and the strength of the differential and the drive shaft can be reduced. Thus, it is small and light and can be manufactured at low cost.

  Further, the present invention can automatically adjust the gap length between the electromagnet and the housing, and can prevent a change in torque due to wear of the second friction clutch. In addition, the gap length between the electromagnet and the housing can be stabilized, and variations in clutch transmission torque characteristics can be suppressed.

  Preferred embodiments of the present invention will be specifically described below with reference to the accompanying drawings.

[First Embodiment]
(Configuration of driving force distribution device)
FIG. 1 is a cross-sectional view showing an internal structure of a driving force distribution device according to a typical embodiment of the present invention. In the same figure, the code | symbol 1 has shown roughly the whole structure of the driving force distribution apparatus arrange | positioned between the propeller shaft and rear differential of a four-wheel drive vehicle. The typical driving force distribution device 1 according to the first embodiment includes a coupling case 20 having a rotary shaft portion 21 as an input member. The coupling case 20 is covered with rear differential cases 2 and 2 which are external cases formed by combining a pair of cases extending in the rotation axis direction (vehicle body longitudinal direction). The inner peripheral surface of the rear differential case 2 and the coupling case 20 are covered. A required first internal space 3 is formed between the outer peripheral surfaces of the two. Inside the rear differential case 2, a drive pinion shaft 4, which is an output member that rotationally drives the rear differential, is disposed on the same axis as the rotary shaft portion 21 of the coupling case 20.

  As shown in FIG. 1, the rotating shaft portion 21 of the coupling case 20 is fastened and fixed by a nut 6 in the cylindrical portion of the flange 5 on the propeller shaft side to which the driving force from the engine is transmitted. A flange attached integrally with the propeller shaft is connected and fixed to the flange 5.

(Rear differential case configuration)
As shown in FIG. 1, a cylindrical wall portion 9 serving as a bearing portion of the coupling case 20 extends toward the coupling side at the rear end portion of the rear differential case 2. In the coupling case 20, the drive pinion shaft 4 is accommodated through the opening cylinder portion 25 of the second housing 24. The front end portion of the drive pinion shaft 4 is spline-connected to the inner peripheral surface of the cylindrical hub 26 and supported by the coupling case 20 via the bearing 8 so as to be relatively rotatable. A rear end portion of the drive pinion shaft 4 is rotatably supported on the inner peripheral surface of the rear differential case 2 via a pair of tapered roller bearings 12 and 12, and is integrated by a spacer and a nut. A gear 17 that meshes with a rear differential gear mechanism is integrally formed at the front end of the rear end of the drive pinion shaft 4.

  An oil seal 13 is disposed between the inner peripheral surface of the cylindrical wall portion 9 of the rear differential case 2 and the drive pinion shaft 4 as shown in FIG. An oil seal 14 is disposed between an opening formed at the front end of the rear differential case 2 and the outer peripheral surface of the flange 5 on the propeller shaft side. The oil seals 13 and 14 partition the first internal space 3 of the rear differential case 2 and the second internal space 15 on the rear differential side, and the internal space 3 is sealed. A dust cover 16 is fixed to the flange 5 on the propeller shaft side to prevent dust and the like from entering the internal space 3 of the rear differential case 2.

(Composition of coupling case)
As shown in FIG. 1, the coupling case 20 includes a cylindrical portion 22 having a larger diameter than the rotating shaft portion 21, a first housing 23 having a larger diameter than the cylindrical portion 22, and the rear of the first housing 23. It has a multi-stage shape including an annular second housing 24 in which the end opening is fixed in a liquid-tight manner. A cylindrical opening tube portion 25 is formed on the rear end surface of the second housing 24. The rotating shaft portion 21 of the coupling case 20 is rotatably supported in the rear differential case 2 via the bearing 7, and the opening cylinder portion 25 of the second housing 24 is connected to the rear differential case 2 via the bearing 11 with seal. The cylindrical wall portion 9 is rotatably supported on the inner peripheral surface. The opening edge of the opening cylinder part 25 has the annular collar part 25a which protruded to the inner peripheral side. A lubricating oil supply hole is formed by an annular gap between the flange portion 25 a and the drive pinion shaft 4. In the illustrated example, the coupling case 20 and the rotating shaft portion 21 are integrated by casting or the like, but may be connected and fixed by welding, for example.

  As shown in FIG. 1, an annular arrangement space 10 for the electromagnet 70 is formed between the outer peripheral surface of the first housing 23 and the inner peripheral surface of the rear differential case 2. An annular stepped wall portion 23a that forms a stepped surface facing the electromagnet 70 is provided at a portion corresponding to the arrangement space 10 of the first housing 23, and an annular recessed portion 23b is formed in the stepped wall portion 23a. Has been. A plurality of through-holes 23c for accommodating a pressing member 53 for adjusting the pressing force of the pilot clutch 50 are formed in the bottom surface of the annular recess 23b so as to penetrate in the axial direction with a predetermined phase difference in the circumferential direction. A spline portion that splines connect the main clutch 40 and the pilot clutch 50 extends along the axial direction on the inner peripheral surface of the first housing 23.

(Configuration of clutch mechanism)
As shown in FIG. 1, the driving force distribution device 1 has a clutch mechanism that controls torque transmission between the coupling case 20 and the drive pinion shaft 4 arranged in the coupling case 20 on the same axis as the rotary shaft portion 21. is doing. In this clutch mechanism, by applying current to the electromagnet 70, the magnetic attractive force acting on the electromagnet 70 between the stepping wall portion 23 a of the coupling case 20 and the operating force that moves the electromagnet 70 toward the pilot clutch 50 It is comprised so that it may become.

  As shown in FIG. 1, the basic structure of this clutch mechanism includes a main clutch 40 that is a first friction clutch, an electromagnetic pilot clutch 50 that adjusts the transmission torque of the main clutch 40, and the transmission torque of the pilot clutch 50. Is converted to a pressing force for the main clutch 40, an electromagnet 70 for intermittently operating the clutch mechanism, and a pressing member 53 for pressing the pilot clutch 50 with a magnetic attractive force acting on the electromagnet 70. The main clutch 40, the pilot clutch 50 and the cam mechanism 60 are provided between the rotary shaft portion 21 and the drive pinion shaft 4. When the main clutch 40 and the pilot clutch 50 are fastened, the rotary shaft portion 21 moves to the drive pinion shaft 4. Driving force is transmitted.

(Configuration of main clutch)
As shown in FIG. 1, the main clutch 40 is splined to a plurality of annular outer clutch plates 41 splined to the inner circumferential surface of the first housing 23 of the coupling case 20 and the outer circumferential surface of the hub 26. And a plurality of annular inner clutch plates 42. A plurality of circular oil holes 43,..., 43 having a predetermined phase difference are formed on the same circumference around the rotation axis of the coupling case 20 at portions other than the friction engagement surface of the inner clutch plate 42. Has been. It is preferable to attach a paper facing to one of the sliding surfaces of the outer clutch plate 41 and the inner clutch plate 42. Between the main clutch 40 and the second housing 24, an annular spacer 44 for regulating the clutch clearance is disposed. The main clutch 40 is fastened via a pressure ring 61 of a cam mechanism 60 that moves to the main clutch 40 side when the pilot clutch 50 is fastened. When the main clutch 40 is engaged, the first housing 23 and the hub 26 are connected, so that driving force is transmitted from the coupling case 20 to the drive pinion shaft 4.

(Configuration of pilot clutch)
As shown in FIG. 1, the pilot clutch 50 includes two annular outer clutch plates 51, 51 and one annular inner clutch plate 52. The outer clutch plate 51 is splined to the inner peripheral surface of the first housing 23. One inner clutch plate 52 is splined to a cam ring 62 of the cam mechanism 60. In the illustrated example, the number of inner clutch plates 52 of the pilot clutch 50 is set to one, but is not limited to this. In the first embodiment, for example, the number of inner clutch plates 52 may be set to two or three or more.

  In the clutch mechanism according to the first embodiment, the magnetic attractive force acting on the electromagnet 70 is directly applied to the pilot clutch 50 without causing the pilot clutch 50 to pass magnetism. A paper facing can be used for the sliding surface of the inner clutch plate 52. A paper facing may be attached to the sliding surface of the outer clutch plate 51. Since paper facing can be used for the pilot clutch 50, the area of the clutch plate sliding surface can be reduced as compared with the conventional clutch plate. As a result, it is possible to reduce the generation of drag torque due to the viscous resistance of the oil interposed between the opposed sliding surfaces of the clutch plate when lubricated with oil. A clutch having good wear characteristics and excellent shudder performance and durability can be obtained.

(Composition of cam mechanism)
As shown in FIG. 1, the cam mechanism 60 includes a pressure ring 61, a cam ring 62, and a cam ball 63 disposed between the pressure ring 61 and the cam ring 62. The cam mechanism 60 is disposed on the outer peripheral surface of the hub 26 via a thrust bearing 64 on the inner peripheral surface of the step wall portion 23 a of the first housing 23 of the coupling case 20. In the pressure ring 61, oil holes 65 are formed through the same circumference around the rotation axis of the coupling case 20 with a predetermined phase difference.

  As shown in FIG. 1, the cam mechanism 60 controls the fastening force of the main clutch 40 steplessly. When the pilot clutch 50 is engaged by energization of the electromagnet 70, rotational torque is generated between the cam ring 62 and the pressure ring 61 connected to the pilot clutch 50. Due to the thrust force that the cam ball 63 presses the cam ring 62 and the pressure ring 61 away from each other, the pressure ring 61 moves to the main clutch 40 side, and the main clutch 40 is fastened.

(Configuration of electromagnet)
As shown in FIG. 1, the electromagnet 70 is provided outside the step wall portion 23 a of the first housing 23 and on the same axis as the rotary shaft portion 21. The electromagnet 70 is formed in an annular shape by a yoke 71 and a coil 72. The yoke 71 has an annular recess 73 having a U-shaped cross section that is open to the main clutch 40 side. In the recess 73, an annular coil 72 held concentrically is liquid-tightly sealed and fixedly fitted. An annular nonmagnetic member 74 made of stainless steel or the like is embedded in a portion facing the coil 72. The electromagnet 70 is supported on the inner peripheral surface of the rear differential case 2 so as to be non-rotatable and axially movable with a predetermined gap G length between the electromagnet 70 and the stepped wall portion 23a of the coupling case 20. Since the electromagnet 70 and the stepped wall portion 23a of the coupling case 20 are arranged close to each other, magnetic flux leakage can be reduced and magnetic force can be used efficiently.

  As shown in FIG. 1, the electromagnet 70 is electrically connected to the rear differential case 2 through a grommet 75 to lead wires 76 drawn to the outside. When the electromagnet 70 is energized through the lead wire 76, a magnetic path L that circulates between the yoke 71 and the step wall portion 23a of the coupling case 20 without passing magnetism through the pilot clutch 50 is formed. A load (a magnetic attractive force acting on the electromagnet 70) attracted to the stepped wall portion 23a of the coupling case 20 is directly applied to the pilot clutch 50. By adjusting the energization power to the electromagnet 70, the pressing force to the pilot clutch 50 can be adjusted.

  In the first embodiment, the configuration in which the electromagnet 70 is supported on the inner peripheral surface of the rear differential case 2 is exemplified, but the present invention is not limited to this. Instead of this configuration, for example, the electromagnet 70 can be supported on the cylindrical portion 22 of the coupling case 20. The electromagnet 70 is supported on the outer peripheral surface of the cylindrical portion 22 so as to be relatively rotatable via a bearing, and is supported so as to be non-rotatable with respect to the inner peripheral surface of the rear differential case 2 by supporting the electromagnet 70 so as to be axially movable. It can be.

(Configuration of pressing member)
In the through hole 23c of the annular recess 23b formed in the stepped wall portion 23a of the coupling case 20, a predetermined position is placed on the same circumference around the rotation axis of the coupling case 20, as shown in FIG. A plurality of pressing members 53 are arranged to be movable in the axial direction with a phase difference. According to the illustrated example, the pressing member 53 is formed of a circular block body, and the pressing surface on the output side of the pressing member 53 and the inner end surface of the stepped wall portion 23a of the coupling case 20 are provided on the same plane. . The arrangement position of the pressing member 53 is the initial position of the pressing member 53 when the electromagnet 70 is turned off. A thrust needle bearing 54 facing the nonmagnetic member 74 of the electromagnet 70 and a ring plate 55 facing the pressing member 53 are juxtaposed in the annular recess 23 b of the coupling case 20. The magnetic attractive force acting on the electromagnet 70 is transmitted to the nonmagnetic member 74, the thrust needle bearing 54, the ring plate 55, and the pressing member 53, and becomes a pressing force to the pilot clutch 50.

(Effects of the first embodiment)
According to the driving force distribution device 1 configured as described above, when the electromagnet 70 is energized, the electromagnet 70 pilots the magnetic attraction force that acts on the electromagnet 70 between the first housing 23 of the rotating shaft portion 21. Since it has the structure which made the operating force which moves toward the clutch 50, the following various effects are acquired.
(1) By directly applying the load attracted by the electromagnet 70 to the coupling case 20 to the pilot clutch 50, paper facing can be used for the pilot clutch 50, and the clutch plates 51, 52 are used. It is possible to reduce the area of the sliding surface. As a result, the drag torque due to the viscosity of the oil can be greatly reduced, and the fuel consumption can be improved.
(2) Since the area of the sliding surface of the clutch plates 51 and 52 can be reduced, the drag torque at low temperatures due to the viscosity of the oil can be greatly reduced, increasing the strength of the differential and drive shaft. By avoiding this, it is possible to achieve a reduction in size and weight and to manufacture at a low cost.
(3) Since the pilot clutch 50 does not require oil groove processing and does not require expensive surface treatment, it is possible to reduce the processing cost and maintain stable and good friction characteristics and durability over a long period of time. be able to.
(4) It is not necessary to provide the coupling case 20 with a special non-magnetic bonding structure for blocking magnetism, and the manufacturing cost can be reduced.
(5) The armature disposed in the coupling case 20 is eliminated, the installation structure of the clutch mechanism is simplified, and the installation space in the coupling case 20 can be used effectively.
(6) By eliminating the armature arranged in the coupling case 20 by the configuration of the electromagnet 70 moving in the axial direction, the number of components can be reduced, and the components constituting the actuator of the pilot clutch 50 can be moved in the axial direction. A shortened design becomes possible. As a result, the design can be made compact, and various components can be accommodated in the rear differential case 2 in a compact manner.
(7) By applying a magnetic attractive force to the electromagnet 70 between the rotating shaft portion 21 and the coupling case 20, the gap G length between the electromagnet 70 and the coupling case 20 is stabilized, and the clutch transmission torque characteristics The variation of the can be reduced.
(8) Since a large torque can be controlled with a small current, the cost of the controller is also low.

  By the way, when the clutch plates 51 and 52 of the pilot clutch 50 are worn due to long-term use, the gap G length between the step wall portion 23a of the coupling case 20 and the electromagnet 70 changes, and the magnetic force acting on the electromagnet 70 is changed. The suction force changes. When the magnetic attraction force changes, even if the current is the same, the pressing force of the pressing member 53 against the pilot clutch 50 also changes, and the transmission torque transmitted to the main clutch 40 via the pressing member 53, the pilot clutch 50, and the cam mechanism 60. Variation occurs. Therefore, even if the driving force distribution device 1 according to the first embodiment further changes in the gap G length between the step wall portion 23a of the coupling case 20 and the electromagnet 70 due to long-term use, Pushing means for pushing back the pressing member 53 to a predetermined initial position in the step wall portion 23a of the coupling case 20 according to wear of the pilot clutch 50 when the electromagnet 70 is not energized is provided.

(Configuration of push-back means)
2 is an enlarged cross-sectional view of the main part showing the internal structure of the driving force distribution device, FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2, and FIG. 4 shows an adjustment nut in the driving force distribution device. FIG. 5A is a developed enlarged view showing a spring member in the driving force distribution device, and FIG. 5B is an enlarged plan view of a spring member formed by bending the spring member of FIG. 5A. FIG. 6 is an enlarged plan view showing an outer clutch plate of the pilot clutch.

  2 and 3, the basic structure of the push-back means includes an adjustment nut 80 that is screwed into the inner peripheral surface of the coupling case 20, and a ring plate-like spring member 83 that pressurizes the adjustment nut 80 in the tightening direction. ing. In the illustrated example, the adjustment nut 80 is screwed into the inner peripheral surface of the coupling case 20 on the clutch plate side located at the outermost end of the pilot clutch 50 in the clutch pressing direction. A ring plate-like spring member 83 is disposed on the inner peripheral surface of the adjustment nut 80.

  As shown in FIGS. 3 and 4, an engagement hook 81 is formed on the inner peripheral surface of the adjustment nut 80. A plurality of ratchet teeth 82,..., 82 are formed on the entire inner peripheral surface other than the portion where the engagement hook 81 is installed. The engagement hook 81 and the ratchet teeth 82 are formed in a forward direction different from the rotation direction of the adjustment nut 80 so as to allow rotation only in the tightening direction of the adjustment nut 80, and the adjustment nut 80 is allowed to rotate. It has a locking surface on the opposite side to the direction.

  As shown in FIGS. 3 and 5, a pair of first and second cutouts 83 a and 83 b that are opposed in the circumferential direction are formed on the outer peripheral edge of the spring member 83. In this first notch 83a, an elongated belt-like spring 84 engaged with the engaging hook 81 is bent so as to form an annular shape, and on the side opposite to the tightening direction of the adjusting nut 80. It curves and extends in the circumferential direction. The winding spring 84 is engaged with a plate-like circumferential portion 84a that is bent radially inward from the outer peripheral edge of the spring member 83 and circulates along the circumferential surface, and the distal end of the circumferential portion 84a is bent radially outward. The engaging piece 84b is engaged with the hook 81.

  As shown in FIGS. 3 and 5, a strip-shaped elastic piece 85 is extended toward the tightening direction of the adjusting nut 80 on the outer peripheral edge adjacent to the second notch 83 b of the spring member 83, It is arranged outward from the winding spring 84. With this configuration, an arrangement space for the winding spring 84 and the elastic piece 85 is secured. The distal end of the elastic piece 85 of the spring member 83 has an elastic end 85a bent outward in the radial direction of the spring member 83, and the elastic end 85a is hooked on the ratchet teeth 82 of the adjustment nut 80. The adjustment nut 80 is prevented from rotating in the loosening direction. Even when a load is applied in the loosening direction of the adjusting nut 80 when the current to the electromagnet 70 is cut off, the leading end of the elastic piece 85 is engaged with the ratchet teeth 82 of the adjusting nut 80, so that the adjusting nut 80 is loosened. The rotation in the direction is restricted, and the adjustment nut 80 can be prevented from returning.

  As shown in FIGS. 3 and 5, a pair of first and second detent pieces 86 a and 86 b are formed on the outer peripheral edge of the spring member 83 at equal intervals in the circumferential direction. The rotation stoppers 86a and 86b are bent in an L shape at the intermediate portion of the spring member 83. On the other hand, as shown in FIG. 6, a plurality of concave locking notches 51a are formed on the entire inner circumference of the outer clutch plate 51 located at the outermost end in the pilot clutch pressing direction. The locking notches 51a are arranged at every other portion corresponding to the spline portion 51b of the outer clutch plate 51, and engage and hold the rotation stoppers 86a and 86b of the spring member 83.

  In assembling the push-back means configured as described above into the coupling case 20, first, the pilot clutch 50 is assembled into the coupling case 20. Next, the adjusting nut 80 is screwed into the inner screw provided on the inner peripheral surface of the coupling case 20 with a predetermined torque. The spring members 83 are assembled on the inner peripheral surface of the adjustment nut 80 by aligning the rotation stop pieces 86 a and 86 b of the spring member 83 with the locking notches 51 a of the outer plate 51 of the pilot clutch 50. At this time, the elastic piece 85 of the spring member 83 is hooked on the ratchet teeth 82 of the adjustment nut 80. Next, the winding spring 84 of the spring member 83 is bent from the free state along the circumferential surface in the direction opposite to the rotation direction of the adjustment nut 80 and hooked on the engagement hook 81 of the adjustment nut 80. With the above assembling work, the work of assembling the component part as the push-back means into the coupling case 20 is completed.

  The push-back means configured as described above constantly pressurizes the adjusting nut 80 in the tightening direction by the winding spring 83, and automatically sets the gap G length between the step wall portion 23a of the coupling case 20 and the electromagnet 70. It has a gap adjustment function to adjust to. The initial tightening torque of the adjusting nut 80 and the pressurizing torque by the winding spring 83 are set to be slightly larger than the attractive force due to the residual magnetism of the electromagnet 70. When the pilot clutch 50 is worn, the adjustment nut 80 reduces the amount of clutch wear, so that the pressing member 53 pushes back the electromagnet 70. Therefore, the pressing surface on the output side of the pressing member 53 and the step wall portion 23a of the coupling case 20 The position can be adjusted to the initial position when the electromagnet 70 whose inner end face coincides with the non-energized state. By adopting this configuration, the gap G length between the step wall portion 23 a of the coupling case 20 and the electromagnet 70 becomes smaller than the initial gap G length, and the electromagnet 70 is coupled to the coupling case 20. It is possible to prevent an increase in the magnetic attractive force acting on the. Further, it is possible to prevent the dragging torque of the clutch from becoming too large due to excessive application of the pressurizing torque.

  In the first embodiment, the push-back means is arranged on the inner peripheral surface of the coupling case 20 adjacent to the outer clutch plate 51 located at the outermost end in the pilot clutch pressing direction. However, the present invention is not limited to this. For example, the push-back means can be provided on the inner peripheral surface of the coupling case 20 between the outer clutch plate 51 and the pressing member 53 located at the outermost end opposite to the pilot clutch pressing direction.

(Other effects of the first embodiment)
In addition to the effect of the first embodiment, the following effect can be obtained by providing the clutch mechanism with the push-back means.
(1) Torque change due to wear of the pilot clutch 50 can be prevented. The pressing member 53 can be accurately positioned with respect to the step wall portion 23a of the coupling case 20, and the gap G length for adjusting the torque characteristics can be easily adjusted.
(2) The number of parts for shim selection can be reduced.

(Modification of push-back means)
FIG. 7 is an enlarged cross-sectional view of an essential part schematically showing another configuration example of the push-back means in the driving force distribution device of the present invention, showing a meshing portion between the ratchet teeth of the adjustment nut and the ratchet claws of the spring member. Yes. In the figure, the substantially same members as those in the first embodiment are given the same member names and symbols. Therefore, the detailed description regarding these members is omitted.

  Even in this modification, there is no difference in the basic configuration from the push-back means according to the first embodiment. In FIG. 7, the main difference from the first embodiment is that in the first embodiment, the single ratchet pawl 85 is engaged with the ratchet teeth 82 by one pitch, thereby adjusting the adjustment pitch. In this modified example, the configuration in which the pitch is the same as the pitch of the teeth 82 is one of the two ratchet claws 85, 85, and one of the ratchet claws 85 is substantially half the pitch of the ratchet teeth 82. It is in the point provided with the phase shifted pitch.

  As shown in FIG. 7, the ratchet teeth 82 according to this modification are formed at the same pitch and the same phase as the ratchet teeth 82 of the first embodiment. 85 and 85 are shifted from each other in the circumferential direction by a distance d corresponding to approximately half the pitch of the ratchet teeth 82. Accordingly, the adjustment pitch is set to approximately half the pitch of the ratchet pawl 85. Since the two ratchet claws 85 and 85 are provided with a phase shifted by approximately half a pitch, the two ratchet claws 85 and 85 are alternately meshed each time the ratchet teeth 82 rotate by approximately half a pitch.

  According to this modification, the pitch of the ratchet teeth 82 can be substantially finely set to about half. The ratchet teeth 82 can be enlarged, and a sufficient spring allowance can be obtained, and the ratchet teeth 82 can be easily formed. It goes without saying that this modification has the same effect as the effect of the first embodiment.

[Second Embodiment]
FIG. 8 is an enlarged cross-sectional view of the main part showing another configuration example of the push-back means in the driving force distribution device of the present invention. In the figure, the substantially same members as those in the first embodiment are given the same member names and symbols. Therefore, the detailed description regarding these members is omitted.

  In the second embodiment, the push-back means according to the first embodiment is provided, and the outer clutch plate 51 located at the outermost end opposite to the clutch pressing direction is connected to the coupling case 20. A plurality of annular plate-shaped spring members 87, which are preload springs urging toward the inner end face of the stepped wall portion 23a, are provided. The spring material 87 is arranged with a predetermined phase difference on the same circumference around the rotation axis of the coupling case 20. The radially inner side of the spring material 87 is fixedly supported by screwing on the inner end surface of the step wall portion 23a of the coupling case 20. The radially outer side of the spring material 87 is elastically contacted with an annular stepped portion 51 c cut out at the inner peripheral edge of the outer clutch plate 51.

  Due to the elasticity of the spring material 87, the pressing surface on the output side of the pressing member 53 is a stepped wall of the coupling case 20 against the residual magnetism that tries to pull back the electromagnet 70 in the clutch fastening direction after the energization to the electromagnet 70 is stopped. It can be adjusted to match the inner end face of the portion 23a. Since the spring material 87 can be adjusted so as to push the electromagnet 70 back to its original position with a weak elasticity, it is possible to effectively suppress the generation of friction. Of course, the second embodiment has the same effect as that of the first embodiment.

  As is clear from the above description, the driving force distribution device according to the present invention is applied to the driving force distribution between the front and rear wheels, so that only the front wheels or only the rear wheels are driven in the 2WD mode, depending on the vehicle state. An auto mode that automatically controls the driving force between the front and rear wheels and a lock mode that maintains the maximum driving force can be provided. Therefore, the present invention is not limited to the above-described embodiments and modifications, and various design changes can be made within the scope described in each claim.

  INDUSTRIAL APPLICABILITY The present invention can be effectively used for a driving force distribution device in various vehicles such as work vehicles such as agricultural machines, construction engineering machines, and transport machines, buggy cars, and automobiles.

It is sectional drawing which shows the internal structure of the driving force distribution apparatus which is typical embodiment of this invention. It is a principal part expanded view which shows the internal structure of a driving force distribution apparatus. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. It is a plane enlarged view which shows the adjustment nut in a driving force distribution apparatus. (A) is an expansion | deployment enlarged view which shows the spring member in a driving force distribution apparatus, (b) is a plane enlarged view of the spring member which bent the spring member of (a). It is a top view which shows the outer clutch plate of a pilot clutch. It is a principal part cross-sectional enlarged view which shows schematically the other structural example of the push-back means in the driving force distribution apparatus of this invention. It is a principal part expanded sectional view which shows the further another structural example of the pushing-back means in the driving force distribution apparatus of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Drive force distribution apparatus 2 Rear differential case 3,15 Internal space 4 Drive pinion shaft 5 Flange 6 Nut 7, 8 Bearing 9 Cylindrical wall part 10 Space 11 Sealed bearing 12 Tapered roller bearing 13, 14 Oil seal 16 Dust cover 17 Gear 20 Coupling case 21 Rotating shaft part 22 Cylindrical part 23, 24 Housing 23a Stepped wall part 23b Annular recess 23c Through hole 25 Open cylinder part 25a Collar part 26 Hub 40 Main clutch 41, 51 Outer clutch plate 42, 52 Inner clutch plate 43 , 65 Oil hole 44 Spacer 50 Pilot clutch 51a Locking notch 51b Spline 51c Step 53 Pressing member 54 Thrust needle bearing 55 Ring plate 60 Cam mechanism 61 Pressure ring 62 Camry 63 Cam ball 64 Thrust bearing 70 Electromagnet 71 Yoke 72 Coil 73 Recess 74 Nonmagnetic member 75 Grommet 76 Lead wire 80 Adjustment nut 81 Engagement hook 82 Ratchet teeth 83 Spring members 83a and 83b Notch 84 Winding spring 84a Circumferential portion 84b Engagement Piece 85 Elastic piece 85a Elastic end 86a, 86b Non-rotating piece 87 Spring material G Air gap L Magnetic path

Claims (11)

A first friction clutch between the input member and the output member for transmitting torque between these members;
A second friction clutch between the input member and the output member for adjusting a transmission torque of the first friction clutch;
A cam mechanism for converting a transmission torque of the second friction clutch into a pressing force against the first friction clutch;
A housing that is provided on the same axis as the input member, and that houses the first friction clutch, the cam mechanism, and the second friction clutch;
An electromagnet provided on the same axis as the housing on the outside of the wall portion of the housing and moving toward the second friction clutch by a magnetic attraction acting between the housing by energization;
A pressing member that is movably disposed inside the wall portion of the housing and adjusts the operating force of the second friction clutch according to the movement of the electromagnet;
Push-back means for pushing back the pressing member to a predetermined initial position of the wall portion of the housing in accordance with wear of the second friction clutch;
A driving force distribution device comprising:   2. The driving force distribution device according to claim 1, wherein the second friction clutch is provided with a paper facing on a sliding surface of one of the plurality of clutch plates that are frictionally engaged with each other. . The push-back means is the inner peripheral surface of the housing on the clutch plate side located at the outermost end in the clutch pressing direction of the second friction clutch, or the outermost side opposite to the clutch pressing direction of the second friction clutch. An adjustment nut screwed into the inner peripheral surface of the housing on the clutch plate side located at the outer end, and a spring member that pressurizes the adjustment nut in the tightening direction;
The driving force distribution device according to claim 1, wherein the spring member is provided on an inner peripheral surface of the adjustment nut. An engagement hook is formed on the inner peripheral surface of the adjustment nut, and a ratchet tooth is formed on the inner peripheral surface excluding the engagement hook,
The spring member is formed with a winding spring that urges the adjustment nut in the tightening direction and a ratchet claw that prevents the adjustment nut from rotating in the loosening direction,
The driving force distribution device according to claim 3, wherein a tip end of the winding spring is engaged with the engagement hook, and the ratchet pawl is engaged with the ratchet teeth. The winding spring is bent from the outer peripheral edge of the spring member and formed in a plate-like shape that circulates along the peripheral surface of the spring member, and the tip of the peripheral portion is bent to engage with the engagement hook. And an engaging part
5. The driving force distribution device according to claim 4, wherein the ratchet pawl is made of a leaf spring bent from an outer peripheral edge of the spring member, and is arranged outward from the winding spring. The clutch plate of the second friction clutch is formed with a locking notch,
The driving force distribution device according to claim 3, wherein an anti-rotation piece that engages with the locking notch is formed on an outer peripheral edge of the spring member.   The spring member includes first and second ratchet claws, and the first and second ratchet claws are arranged with a phase shifted from each other by a substantially half pitch of the pitch of the ratchet teeth. The driving force distribution device according to any one of 4 to 6.   A preload spring is provided on the inner side of the wall portion of the housing to urge a clutch plate located at the outermost end opposite to the clutch pressing direction of the second friction clutch toward the pressing member. The driving force distribution device according to claim 1. An outer case for rotatably supporting the housing;
The driving force distribution device according to claim 1, wherein the electromagnet is supported on an inner peripheral surface of the outer case. An outer case for rotatably supporting the housing;
2. The drive according to claim 1, wherein the electromagnet is supported so as to be relatively rotatable and axially movable with respect to a shaft portion of the housing, and is supported so as not to be rotatable with respect to the outer case. Power distribution device.   The driving force distribution device according to claim 1, wherein a thrust needle bearing and a plate member are interposed between the electromagnet and the pressing member.

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