JPH036375B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to electromagnetic powder clutches, and more particularly to improving the filling of ferromagnetic material powder into the gap between a driving member and a driven member.

An electromagnetic powder clutch generally includes a drive member having an inner circumferential friction surface and rotated about a centerline;
A driven member is provided with an outer circumferential friction surface facing the inner circumferential friction surface across a gap on the inside of the drive member, and is provided to be rotatable relative to the drive member, and an excitation coil provided on the drive member; The ferromagnetic material powder is filled in the gap between the driving member and the driven member by excitation of the excitation coil and transmits the rotation of the former to the latter.

Conventionally, in this type of electromagnetic powder clutch,
A so-called powder barrier is formed between the driving member and the driven member, that is, at both ends of the powder gap, which obstructs the movement of powder toward the center of the gap, and reduces the packing density of powder at the center of the gap. As a result, the overall torque transmission capacity decreases, and the magnetomotive force consumed within the powder gap increases, inevitably resulting in a decrease in power efficiency.

The present invention was made against such a background, and was made with the purpose of providing an electromagnetic powder clutch that can fill powder into a powder gap as uniformly and densely as possible. It is.

The gist of this is that a tapered surface whose diameter increases from both ends in the width direction toward the center is formed on the outer peripheral friction surface of the driven member, and When a plurality of extending protrusions are formed at intervals in the circumferential direction, and the protrusions are traced from both ends in the width direction of the outer circumferential friction surface to the center, the inner periphery in the process of connecting the clutch in the circumferential direction. It is at a point tilted so that the relative movement vector of the friction surface with respect to the outer peripheral friction surface moves in the same direction.

If a tapered surface as described above is formed on the outer peripheral friction surface of the driven member, the powder gap becomes wider at both ends and narrower at the center, which increases the magnetic flux density at the center of the powder gap and causes the powder to flow. There is a tendency for the center to be filled first, and powder barriers are less likely to be formed at both ends of the powder gap, making it easier for powder to be filled into the center of the gap. Moreover, as the powder moves from both ends of the gap to the center, the gap becomes narrower and the powder is compressed by that amount, which also improves the packing density of the powder in the center of the gap. .

Furthermore, the protrusions provided on the outer circumferential friction surface of the drive member allow the powder, which moves along with the inner circumferential friction surface, to move relative to the outer circumferential friction surface during the engagement process of the clutch, from both ends of the gap. This acts to provide a motion component that moves toward the center, and this also improves the packing density of the powder at the center of the powder gap.

If the packing density of the powder at the center of the powder gap is improved in this manner, the average packing density of the entire powder gap is improved, and the torque transmission ability of the clutch is improved. Furthermore, an improvement in the packing density of the powder leads to a reduction in the consumed magnetomotive force within the powder gap, resulting in an improvement in the power efficiency of the clutch.

Embodiments of the present invention will be described in detail below based on the drawings.

The clutch shown in FIG. 1 is for an automobile, and is built into a clutch housing 2 fixed to an engine (not shown), and transmits the rotation of the engine's crankshaft 4, which serves as an input shaft, to an output shaft 6. It is something that can be blocked or blocked.

A disk 8 is fixed to the end of the crankshaft 4, and a yoke 14 as a driving member consisting of a first yoke member 10 and a second yoke member 12 is fixed to this disk 8. The yoke 14 has a cylindrical shape and includes an excitation coil 19 therein and an inner friction surface 18 on its inner circumferential surface. Further, a front labyrinth member 20 and a rear labyrinth member 22 are fixed to the yoke 14, and the rear labyrinth member 22 is integrally provided with a cylindrical bearing case 24.

A ball bearing 26 is disposed within the bearing case 24, and a boss portion 29 of a rotor 28, which is a driven member, is rotatably supported by the ball bearing 26. Rotor 28
is inside the yoke 14 and concentrically with the yoke 14,
and is provided so as to be relatively rotatable, and the rotor 28
The outer peripheral friction surface 30 faces the inner peripheral friction surface 18 with a small gap 32 in between. And an annular space 34 that is substantially closed by the yoke 14, both labyrinth members 20 and 22, and the rotor 28.
is formed, and a predetermined amount of ferromagnetic material powder 36 is enclosed in this annular space 34. Front labyrinth member 20 and rear labyrinth member 2
2 prevent this powder 36 from leaking out of the annular space 34 by being very close to the rotor 28 at their respective tips. The rotor 28 is an annular member with two
Two plates 38 and 40 are secured by bolts 42 and carry a plurality of equiangularly spaced rubber torsion springs 44.

On the other hand, a clutch hub 48 is attached to the spline shaft portion 46 of the output shaft 6 so as to be slidable in the axial direction and relatively rotatable. This clutch hub 48 consists of two plates 3 fixed to the rotor 28.
8 and 40, and is provided with an opening 50 having a size capable of accommodating the torsion spring 44. Rotation of rotor 28 is transmitted to clutch hub 48 via plates 38 and 40 and torsion spring 44.

Further, a slip ring 52 is fixed to the outer peripheral surface of the bearing case 24, and this slip ring 52 comes into sliding contact with a brush 56 held by a phenolic resin bracket 54 fixed to the clutch housing 2. Conductive member 58
Electric power is supplied to the excitation coil 16 via the conductive wire 60.

Take out the yoke 14 and rotor 28,
It is schematically shown in FIG. The inner peripheral friction surface 18 of the yoke 14 is a cylindrical surface having the same diameter over its entire width as in the past, but the outer peripheral friction surface 30 of the rotor 28 has a shape shown in an exaggerated manner in FIG. That is, an annular groove 62 is formed in the center of the outer peripheral friction surface 30 to prevent the generation of short-circuit magnetic flux in cooperation with a paramagnetic annular member 64 provided on the yoke 14 shown in FIG. However, the outer peripheral friction surface 30 has the largest diameter at the edge of the annular groove 62, and the diameter decreases linearly toward the width direction side, forming a tapered surface 66. This tapered surface 66 is provided with protrusions 68 extending from both ends of the outer peripheral friction surface 30 toward the center. In this embodiment, as is clear from FIG. 5, the protrusions 68 are formed in pairs on each of the left and right tapered surfaces 66 so as to be symmetrical with respect to the annular groove 62. Further, this protrusion 68 is formed on the outer peripheral friction surface 3.
It is formed to be inclined with respect to the width direction of 0. The direction of this inclination is determined by tracing each protrusion 68 from both ends of the outer circumferential friction surface 30 in the width direction toward the center.
It is determined that the clutch will move in the direction of the vector shown by the arrow Y in the figure, and this arrow Y will move toward the inner circumferential friction surface of the yoke 14 during the clutch engagement process.
8 shows the direction of relative movement with respect to the outer peripheral friction surface 30. For convenience, the side surface of the protrusion 68 facing the arrow Y will be referred to as a front surface 70, and the opposite side surface will be referred to as a rear surface 72. As is clear from FIG. 2, a plurality of pairs of protrusions 68 are formed at equal angular intervals on the outer circumferential friction surface 30 of the rotor 28, and the top surface of all the protrusions 68 is concentric with the inner circumferential friction surface 18 of the yoke 14. It is positioned on one cylindrical surface of the cylindrical surface.

In the clutch configured as described above, the state in which the yoke 14 is rotated by the engine without power being supplied to the excitation coil 16 is described as a state in which the yoke 14 is rotated by the engine.
It is schematically shown in the figure. The powder 36 is pressed against the inner circumferential friction surface 18 of the yoke 14 by centrifugal force, forming a powder layer with a substantially uniform thickness. In this embodiment, the amount of powder 36 is determined so that the thickness a of this powder layer is 0.52 mm, and the size of the gap 32 between the tapered surface 66 and the inner peripheral friction surface 18 is determined. The maximum value c is 0.85mm, and the minimum value b is 0.57mm.
It is said that The size of this gap 32 is about 0.6 to 1.0 mm in conventional clutches, but in the clutch according to the present invention, the size is set to the minimum value because it is easy to fill the center of the gap with powder 36. b is (or (a+c)/2 is)
It is possible to make it smaller than conventional methods, at around 0.3 to 0.8 mm. Since the gap 32 has a low magnetic permeability, 30 to 50% of the magnetomotive force of the excitation coil 16 was conventionally consumed in the gap 32, but by narrowing the gap 32 as described above. If this can be done, the power consumption required to transmit the same torque can be reduced by 10 to 30%.

When excitation power is supplied to the excitation coil 16 in the state shown in FIG. is the 8th
As shown in the figure, the gap 32 is filled with powder, but at both ends of the gap where the tapered surface 66 is away from the inner peripheral surface of the powder layer, the powder 36 first fills the protrusion 68 as shown in FIG. The particles gather as a core, and the powder distribution becomes dense around the protrusion 68 and sparse at distant positions. The powder 36 gathered around the protrusion 68 works together with the front surface 70 of the protrusion 68 to scrape up the powder in front, but at this time the protrusion 68 is formed to be inclined as described above. As a result, the powder 36 is given a motion component from both ends of the gap 32 toward the center, and the powder 36 is not only drawn toward the center of the gap by the magnetic force but also mechanically It is also pushed toward the center of the gap by the action of Therefore, the powder distribution density at the center of the gap is increased.

As described above, the surrounding powder 36 gathers around the part where the distribution density has become high as a core, but in this case, the distribution density of the powder 36 is low at both ends of the gap 32, creating a powder barrier. Therefore, the movement of the powder 36 toward the center of the gap is not hindered. As is clear from FIG. 7, a powder barrier is formed in front of the protrusion 68, but since this powder barrier is formed at an angle along the protrusion 68, it does not move toward the center of the powder 36. Rather than hindering the movement of the object, it actually pushes it toward the center. In this way, the powder 36 is first filled from the center of the gap 32, but eventually the entire gap 32 is filled as shown in FIGS. 9 and 10. Therefore, the packing density of the powder 36 in the gap 32 becomes uniform throughout the width direction, and the average density is increased. and,
This improves the clutch's torque transmission ability.

On the other hand, if it becomes necessary to disconnect the clutch in the connected state, the power supply to the excitation coil 16 is cut off. As a result, the magnetic attraction force on the powder 36 disappears, and the powder 36 is forced out of the gap 32 by the action of centrifugal force, but the gap 32 increases from the center to both ends. Because the clutch is made of Moreover, during the clutch disengaging process, a relative rotation occurs between the yoke 14 and the rotor 28 in the opposite direction to the clutch connecting process, so that the back surface 72 of the protrusion 68 moves the powder 36 from the center side of the gap 32 to both ends. It has the effect of actively pushing it out. Therefore, the powder 36 is discharged from the gap 32 more quickly than in conventional clutches, and the time required from when the power supply to the excitation coil is cut off to when the clutch actually enters the disconnected state is shorter than in conventional clutches. This means that the clutch is shortened compared to the clutch. This improves the so-called clutch grip.

Although one embodiment of the present invention has been described in detail above,
This is literally an example, and the present invention is not limited to the above embodiment.

For example, as in the rotor 80 shown in FIGS. 11 to 13, the outer peripheral friction surface 82 may be provided with a tapered surface 84 on both ends in the width direction and a cylindrical surface 86 on the center side, In this way, it is possible to increase the portion facing the inner circumferential friction surface of the yoke across a small gap. Further, the protrusions do not need to be formed over the entire width direction of the outer circumferential friction surface 82, and for example, protrusions 88 that extend from both ends and disappear halfway are also possible. In this way, the powder packing density near the annular groove 90 at the center of the gap can be locally lowered to effectively prevent the generation of short-circuit magnetic flux.

Furthermore, if a circumferential groove 94 is formed in the longitudinally intermediate portion of the protrusion 92 as shown in FIGS. 14 to 16, the powder collected by the protrusion 92 during the clutch connection process can be It becomes possible to cause the powder to flow into a portion behind the powder 92 where the distribution density is relatively low.

Further, as shown in FIGS. 17 to 19, it is also possible to form a shallower groove 98 outside the central circumferential groove 96. In this way, the powder can easily flow in the center of the gap, and the powder collected in front of the protrusion 100 during the clutch connection process can be effectively supplied to the rear of the protrusion 100.

Further, the cross-sectional shape of the protrusion is not necessarily limited to the rectangular shape as in each of the above embodiments.
For example, as shown in FIG. 20, the protrusion 102 can have a triangular cross section. In this way, a wedge-shaped gap is formed between the protrusion 102 and the inner circumferential friction surface of the yoke opposing the protrusion 102, and the compressing effect of the powder due to the wedge action can be obtained during the clutch connection process. Further, the protrusions do not necessarily have to be formed in pairs symmetrically with respect to the center line in the width direction, and may be formed offset from each other in the circumferential direction on both sides of the center line.

Furthermore, the inner circumferential friction surface of the yoke, which is the driving member, is not limited to a simple cylindrical surface. For example, as shown in FIG. It is also possible to form the surface 104, and by doing so, it is possible to further improve the packing density of powder at the center of the gap. Furthermore, even if the volume of the powder holding portions at both ends of the inner friction surface increases and a sufficient amount of powder is supplied to fill the entire gap, the outer friction surface 108 of the rotor 106 and the powder layer It becomes possible to sufficiently reduce the drag torque due to contact with the Further, the tapered surface 104 is formed by powder 110 due to centrifugal force during the clutch disengaging process.
This makes it easier for the clutch to flow out of the gap, resulting in better clutch disengagement.

Further, as shown in FIG. 22, the inner peripheral friction surface of the yoke 112 is provided with an annular stepped portion 114 extending in the circumferential direction.
It is also possible to provide a stepped surface 116 having a .
As is clear from the figure, the stepped portion 114 is connected to the rotor 118.
It is formed at a position closer to the center than both ends of the outer peripheral friction surface 120 of the gap, thereby making it possible to move the position where the powder barrier is generated closer to the center side of the gap. Further, as in the previous embodiment, the capacity of the powder holding portion is increased and the drag torque in the clutch disengaged state is reduced.

In addition, it goes without saying that the present invention can be implemented with various modifications and improvements based on the knowledge of those skilled in the art without departing from the scope of the claims.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of an electromagnetic powder clutch for an automobile, which is an embodiment of the present invention. FIG. 2 is a schematic diagram showing only the yoke and rotor of the clutch. 3 to 5 are diagrams schematically showing the rotor, with FIG. 3 being a longitudinal cross-sectional view, FIG. 4 being a perspective view of a main part, and FIG. 5 being a plan view of a main part. FIG. 6 is a longitudinal cross-sectional view of a main part showing the clutch in a disengaged state. 7 and 8 are diagrams schematically showing the process of connecting the clutch, and FIG.
The figure is a side view, and FIG. 8 is a longitudinal sectional view. FIGS. 9 and 10 are views corresponding to FIGS. 7 and 8, respectively, in the clutch-connected state.
11 to 13 are views showing essential parts of a rotor in another embodiment of the present invention, in which FIG. 11 is a perspective view, FIG. 12 is a longitudinal sectional view, and FIG. 13 is a plan view. 14 to 16 are views showing essential parts of a rotor in still another embodiment of the present invention, in which FIG. 14 is a perspective view, FIG. 15 is a longitudinal sectional view, and FIG. 16 is a plan view. . 17 to 19 are views showing essential parts of a rotor in still another embodiment of the present invention, in which FIG. 17 is a perspective view, FIG. 18 is a longitudinal sectional view, and FIG. 19 is a plan view. . FIG. 20 is a perspective view of a main part of a rotor in still another embodiment of the present invention. FIGS. 21 and 22 are vertical cross-sectional views schematically showing a clutch disengaged state in still another embodiment of the present invention. 14, 103, 112: Yoke (driving member),
16: Excitation coil, 18: Inner peripheral friction surface, 28, 8
0,106,118: Rotor (driven member), 3
0, 82, 108, 120: outer peripheral friction surface, 32:
Gap, 36,110: Powder, 62,90,9
6: Annular groove, 66, 84, 104: Tapered surface, 6
8, 88, 92, 100, 102: protrusion, 86:
Cylindrical surface, 94, 98: groove, 114: step, 11
6: Stepped surface.

Claims (1)

[Scope of Claims] 1. A drive member having an inner circumferential friction surface and rotated around a center line, and an outer circumferential friction surface facing the inner circumferential friction surface with a gap spaced inside the drive member. a driven member provided to be rotatable relative to the driving member; an excitation coil provided on the driving member; and excitation of the excitation coil fills the gap and directs the rotation of the driving member to the driven member. In an electromagnetic powder clutch including a powder made of ferromagnetic material that transmits transmission to When a plurality of protrusions extending from both ends to the center are formed at intervals in the circumferential direction, and the protrusions are traced from both ends to the center in the width direction, the connection of the clutch in the circumferential direction is An electromagnetic powder clutch characterized in that the clutch is tilted so that the relative movement vector of the inner peripheral friction surface with respect to the outer peripheral friction surface moves in the same direction during the process.