Planetary gear transmission systems or components – Differential planetary gearing – Differential or nondifferential planetary combined with...
Reexamination Certificate
2003-02-05
2004-07-13
Marmor, Charles A. (Department: 3681)
Planetary gear transmission systems or components
Differential planetary gearing
Differential or nondifferential planetary combined with...
C192S084910, C192S084960, C188S161000
Reexamination Certificate
active
06761662
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electromagnetic coupling apparatus such as brake or clutch and a drive force distributing apparatus for a vehicle using the electromagnetic coupling apparatus.
2. Description of the Related Art
A differential is located in a power train of a vehicle to maintain torque distribution between right and left wheels of the vehicle such that torque is equally divided between the right and left wheels and to rotate the outside wheel faster than the inside wheel in cornering, thereby reliably obtaining smooth cornering. While the primary role of the differential is to obtain smooth cornering as mentioned above, there is a case that one of the right and left wheels may be caught to slip in a muddy place during rough-road running. In this case, the resistance from the road to the wheel caught to slip in the muddy place is small, so that torque is almost transmitted to this slipping wheel and hardly transmitted to the other wheel. As a result, the drive force for driving the wheels becomes lacking to cause a problem that the slipping wheel cannot escape from the muddy place. This problem is a defect inherent to a general differential.
Known is a special type of differential having a differential motion limiting mechanism capable of compensating for the above inherent defect of a general differential. This type of differential is referred to as a limited slip differential (LSD). A planetary gear type differential is generally known in the art. For example, such a planetary gear type differential gear assembly having a limited slip differential mechanism composed of an electromagnetic clutch and a multiplate clutch is disclosed in Japanese Patent Laid-open No. Hei 6-33997. In this differential gear assembly, an attraction force between a solenoid and an armature forming the electromagnetic clutch is applied to the multiplate clutch to press it and selectively control an engaging force generated in the multiplate clutch.
A connecting member consisting of a plurality of bars is located between a pressure plate of the multiplate clutch and the armature. That is, one end of each bar of the connecting member is fixed to the pressure plate of the multiplate clutch, and the other end comes into abutment against an inner circumferential portion of the armature when the solenoid is operated. In the conventional differential gear assembly mentioned above, the plural bars fixed to the pressure plate extend in a direction substantially perpendicular to the pressure plate. Accordingly, in the case that any of these bars are inclined to the pressure plate, there is a problem that a pressing force of the armature attracted by the solenoid to press the pressure plate of the multiplate clutch may not be uniformly transmitted to the pressure plate.
Further, in the conventional differential gear assembly described in the above publication, the electromagnetic clutch controls the engaging force of the multiplate clutch, so that the plural bars as pressure members are located so as to correspond to the inner circumferential portion of the armature. However, in a multiplate brake structure having a plurality of brake plates and a plurality of brake discs, these brake plates and brake discs are generally located so as to correspond to an outer circumferential portion of the armature from the viewpoint of the structure. Accordingly, it is difficult that the conventional structure described in the above publication such that the multiplate clutch is operatively connected to the armature at its inner circumferential portion is applied to the multiplate brake structure without any changes.
In the differential gear assembly described in the above publication, the opposed portion between the armature and a core having a solenoid coil is formed by flat opposed surfaces. This structure has a problem that high accuracy is required for control of an air gap between the core and the armature, because the relation between current and attraction force is sensitive to a change in this air gap.
Japanese Patent Laid-open No. Hei 11-260632 discloses a technique such that the opposed surfaces of a linear solenoid core and an armature are inclined with respect to their radial directions to increase the opposed area between the core and the armature, thereby improving the responsivity. Japanese Utility Model Laid-open No. Hei 6-26213 discloses an electromagnet configured so that one of the opposed surfaces of a core and an armature is formed with a V-groove and the other is formed with a wedge to be fitted with the V-groove. In each of these techniques described in the above publications, the opposed surfaces of the core and the armature are inclined with respect to their radial directions, so as to increase the opposed area between the core and the armature, thereby improving the responsivity. However, no attention has been paid to such an object of the present invention that the relation between current and attraction force is to be insensitive to a change in the air gap.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an electromagnetic coupling apparatus which can make the relation between current and attraction force insensitive to a change in the air gap between the core and the armature.
In accordance with an aspect of the present invention there is provided an electromagnetic coupling apparatus interposed between a fixed housing and a rotating member at least partially accommodated in the fixed housing. This electromagnetic brake includes a multiplate brake mechanism having a plurality of brake plates mounted on the fixed housing and a plurality of brake discs mounted on the rotating member so as to be arranged in alternate relationship with the brake plates; a ringlike core member fixed in the fixed housing, said core member having an annular groove and a first outer diameter; an annular exciting coil accommodated in the annular groove of the core member; and a ring-like armature member arranged in opposed relationship with the annular groove of the core member, said armature member having a second outer diameter larger than the first outer diameter.
The electromagnetic coupling apparatus further includes a cylindrical pressure member provided so as to surround the outer circumferential surface of the core member and be movable in a direction of pressing the multiplate brake mechanism as being guided by the core member, said pressure member having a first end fixed to an outer circumferential portion of the armature member and a second end engaged with the multiplate brake mechanism. The term “electromagnetic coupling apparatus” may include an electromagnetic brake and an electromagnetic clutch.
The ringlike core member has a first radially outside tapered end surface formed radially outside of the annular groove and inclined at a first angle with respect to the axis of the core member, and a first radially inside tapered end surface formed radially inside of the annular groove and inclined at a second angle with respect to the axis of the core member. The ringlike armature member has a second radially outside tapered end surface complementary to the first radially outside tapered end surface, a second radially inside tapered end surface complementary to the first radially inside tapered end surface, and an intermediate end surface opposed to the annular exciting coil.
If the air gap between the ringlike core member and the ringlike armature member changes in the electromagnetic brake having the multiplate brake mechanism, the attraction force of the ringlike core member changes to result in a change in the pressing force of the cylindrical pressure member to the multiplate brake mechanism. Therefore, high accuracy is required for control of the air gap. This air gap changes according to manufacturing variations or aged deterioration (wearing) of the plural brake plates and the plural brake discs of the multiplate brake mechanism.
For example, in the case that the opposed portion between the ring
Aoki Shin
Iwazaki Akihiro
Kunii Rikiya
Abdelnour Dennis
Honda Giken Kogyo Kabushiki Kaisha
Marmor Charles A.
Westerman Hattori Daniels & Adrian LLP
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