192 clutches and power-stop control – Clutches – Plural clutch-assemblage
Reexamination Certificate
2001-06-15
2002-12-10
Rodriguez, Saul (Department: 3681)
192 clutches and power-stop control
Clutches
Plural clutch-assemblage
C192S038000, C192S039000, C192S044000
Reexamination Certificate
active
06491150
ABSTRACT:
BACKGROUND
This invention pertains to a switchable clamp-type locking mechanism. In this type of clamp-type locking mechanism, an output shaft is locked against rotating in either rotational direction with respect to a rotatably fixed part, in particular a housing, when a rotational moment is introduced to the output shaft. These types of clamp-type locking mechanisms often provide a drive means that transmits a rotational moment to the output means so that elements that are connected to the output shaft can be activated. In the transfer of rotational moment from the drive to the output means, the clamped connection between the output shaft and the rotatably fixed part is released in the selected direction of rotation. Switchable clamp-type locking mechanisms can, for example, be used in gear units that have an output shaft fixed in both rotational directions when a rotational moment is introduced to this output shaft. Such gear units are, for example, used in automobile seat adjustment systems or in devices to raise or lower windows in automobiles. In these cases, a rotational moment introduced from the outside to the output shaft, i.e. the load imposed on the seat by a person, for example, is taken up by a housing, for example, so that no rotational motion of the output means occurs.
From WO 96/20352 A, for example, a clamp-type locking mechanism is known that is provided in a seat height adjustment system. The clamp-type locking mechanism has two self-enclosed elements, the outer element of which is designed as a housing having a cylindrical track on its interior wall surface and the other element of which is designed as an output shaft whose external surface facing the cylindrical track is provided with a number of locking ramps with opposite slopes distributed along the perimeter. Each locking ramp forms a wedge-shaped clamping gap with the cylindrical track. A spring force pushes clamping rollers into this clamping gap. Since the virtual peaks of these wedge-shaped clamping gaps either face toward or away from one another, the clamping rollers that are pushed by a spring force into-the clamping gap prevent a rotational motion of the inner element with respect to the outer element in both rotational directions. The clamping rollers are pushed by a spring force into the clamping gap in their clamped position and engage with the locking ramps and the cylindrical track. When the clamping rollers are freed, i.e. when they are located in the released position, only those clamping rollers that are functionally relevant to this rotational direction are freed. The clamping rollers are located in the pocket of a cage with play in the perimeter direction, wherein the cage can be tilted with respect to the inner element just a bit. This tilting path is used to free the clamping rollers from their associated clamping gaps. A rotational moment acts on the inner element, which is caused by a force acting on the seat. In the clamped position, these types of clamp-type locking mechanisms hold the seat in its adjusted height.
Now, it is conceivable that not only static rotational moments can act on these types of clamp-type locking mechanisms in their clamped position, but also oscillating, dynamic loads with alternating rotational moments. If these types of clamping mechanisms are provided in automobiles, for example in seat adjustment systems, vibrations in the internal combustion engine can generate these types of loads. In an alternating load of this type, for example, the clamping force of the above clamp-type locking mechanism that is transmitted from the inner element to the outer element through the clamping rolls in their clamped position is first reduced until the alternating load reaches a value at least approaching zero. The rotational moment imposed between the working shaft and the housing can be reduced under this oscillating load to approximately 18 Nm or less. In this situation, of course, the clamping rollers are still being pushed by the spring force into their clamping gaps by means of the springs provided, but relative shifts are possible here between the inner element and the outer element due to the reduced clamping effect under the alternating load. As a result, an undesired slip can occur. In case of the seat height adjustment system, these types of relative shifts can result in the seat height undergoing an unwanted change.
SUMMARY
The object of this invention is thus to securely prevent a slip between the clamped elements in switchable clamp-type locking mechanisms.
According to the invention, this object is met in that a slide that is fixed to the output shaft is form-locked to the rotatably fixed part in the clamped position of the clamping elements and disengages with the rotatably fixed part in the released position of the clamping elements. In the clamped position of the clamping elements, a rotational moment can be introduced to the output shaft and can be transferred through the clamping elements to the rotatably fixed part. In addition to this, a form-locked connection between the output means and the housing exists to prevent an undesired slip, as a result of oscillations, between the output means and the rotatably fixed part, for example the housing. The form-locked connection can be designed for small loads since most of the load is transmitted through the clamp-type locking mechanism and not through the form-locked connection between the output means and the housing. In case of oscillating or alternating loads that approach zero or pass through this value, the form-locked connection will be subjected to these minimum dynamic loads, preferably where zero is crossed. Of course, the form-locked connection can be designed to withstand maximum occurring rotational moments.
In a clamp-type locking mechanism according to the invention, the housing can be provided with a cylindrical track on its inner perimeter and the output shaft can be provided with the locking ramps on its outer perimeter. It is also possible to design the output shaft as a hollow shaft and to design the locking ramps into the inner perimeter of the hollow shaft and to design the cylindrical track at the outer perimeter of a part of the axis of the housing. Furthermore, it is possible for the locking ramps to be designed at the back of the output shaft and for the flat, circular closed track to be designed at the back of the housing. In any case, the track associated with the housing is flat in the sense that it is either flat or has a smooth bend.
A further development according to the invention provides that a mechanism is located between the drive shaft and the slide to convert a rotational motion of the drive shaft into a longitudinal shift of the slide. The rotational motion of the drive shaft is thus first used to release the form-locked connection between the slide and the housing by shifting the slide. The continued rotational motion of the drive shaft is transmitted to the output shaft.
Another further development according to the invention provides that a ramp is provided at the slide and an attachment for the ramp is provided at the drive shaft and at a distance from the rotating axis of the drive shaft. As the drive shaft rotates, the attachment B for example a pin located coaxial to the drive shaft B is turned in the circumferential direction. Since the slide is initially locked to the housing, it cannot follow the turning of the pin in the circumferential direction, resulting in the pin pressing up against the ramp. Under the force of the pin pushing against the ramp, the slide, which can shift lengthwise, now is forced to shift because the ramp—and thus the slide—slides along the pin until the slide finally is disengaged from the housing. Then, the continued rotation of the drive shaft can be transmitted to the output shaft. The slope of the ramp determines the length of the path of the slide relative to the amount of the rotational angle of the drive shaft.
The slide can be made to move parallel to the output shaft. In this case, the ramp is provided at the back of the s
Hochmuth Harald
Quitzrau Dirk
Ina Walzlager Schaeffler OHG
Rodriguez Saul
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