192 clutches and power-stop control – Field responsive frictional media type
Reexamination Certificate
1999-06-29
2001-08-07
Lorence, Richard M. (Department: 3681)
192 clutches and power-stop control
Field responsive frictional media type
C192S058610, C192S058800
Reexamination Certificate
active
06269925
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a viscous coupling in a torque transmitting device
2. Description of the Related Art
DE 196 45 478 A1 discloses a viscous coupling having a coupling housing and a drivable rotor, which is arranged therein and is provided for the transmission of torque via shearing areas in a working chamber filled with viscous fluid. This working chamber is partitioned off from a supply chamber for viscous fluid by a dividing wall. The viscous fluid can be directed from the working chamber via a pumping opening into the supply chamber or from the supply chamber via a feed line back into the working chamber. The feed line interacts with a control opening, which can be varied in its width by a lever of a valve operable by an electromagnet. As soon as the lever comes to bear on the control opening, the volumetric flow of the viscous fluid between the supply chamber and the working chamber ceases so that the working chamber is emptied due to the effect of the pumping opening and thus the torque-transmitting capacity decreases. At the other extreme, the lever is completely lifted from the control opening so that the working chamber can rapidly fill with viscous fluid from the supply chamber and the torque-transmitting capacity approaches a maximum. The position of this lever can be set by the electromagnet. Therefore, the electromagnet together with the valve having the lever is effective as a volumetric-flow setting means for the viscous fluid between supply chamber and working chamber.
Such a valve is relatively complicated and, on account of the lever affected by mass, sluggish, so that setting operations proceed relatively slowly. At the same time, the electromagnet, has to be very powerful on account of its distance from the lever of the valve, which distance is normally large, this configuration has unfavorable consequences for its dimensioning.
EP 0 317 186 B1 discloses a viscous coupling which does without such a valve and also (does without a supply chamber for viscous fluid. Instead, the viscous fluid, in the embodiment according to
FIG. 3
, is magnetorheological, with its viscosity being variable by means of an electromagnet provided on side of the viscous coupling facing a drive, such as, for example, an internal combustion engine. The torque-transmitting capacity of the viscous coupling can thus be influenced.
It is known that such a magnetorheological viscous fluid is formed by magnetizable particles, such as, for example, iron particles, being introduced into a carrier medium. When current is applied to the electromagnet, these magnetizable particles become interlinked under the effect of the magnetic field. The result of which is a high viscosity of the viscous fluid can be achieved. Conversely, however, if no torque transmission is desired at the viscous coupling, the magnetic field must be switched off in order to neutralize the effect of the magnetizable particles. However, since the working chamber has still not been emptied by this measure, the torque-transmitting capacity, although reduced, is not neutralized. The consequence of this is undesirable running of the coupling housing with the rotor during rotation of the rotor. This problem may be remedied by a very thin-bodied carrier fluid being used. Although the maximum torque-transmitting capacity of the viscous coupling is in turn considerably reduced.
A further problem turns out to be that the electromagnet must also act on the viscous fluid which is located in the part of the working chamber axially on the other side of the rotor. The electromagnet must be moved correspondingly close to the coupling housing, so that there is no possibility of forming cooling blades on the corresponding side of the coupling housing. During operation with high slip, the viscous coupling is thus constantly exposed to the risk of overheating. Furthermore, recourse must be had to a very powerful and therefore correspondingly expensive and heavy electromagnet.
SUMMARY OF THE INVENTION
The object of the invention is to design a viscous coupling such that a virtually inertia-free setting of the torque-transmitting capacity can be realized with the least possible design and production outlay and high maximum torque-transmitting capacity is achieved.
This and other objects are achieved according to the invention by enrichment of the viscous fluid with magnetizable particles, a magnetorheological behavior is achieved for this viscous fluid. However, the variation in the viscosity of this fluid is not used directly for varying the torque-transmitting capacity but for setting the flow velocity in a feed line which leads from a supply chamber of the viscous coupling into a working chamber. In accordance with the intensity of a magnetic field in the extension region of the feed line, the viscous fluid can be braked and, in the extreme case, even stopped by corresponding activation of an electromagnet, so that a “magnetized fluid plug” forms virtually inside the feed line, which at best, permits an insignificantly small leakage flow from the supply chamber into the working chamber. Conversely, if the electromagnet is switched off and thus the effect of the magnetizable particles in the viscous fluid is neutralized, the viscous fluid, with its actual viscosity, flows through the feed line without hindrance and thus the working chamber is supplied with adequate viscous fluid originating from the supply chamber. Of course, during appropriate activation of the electromagnet, any intermediate values with regard to the flow velocity of the viscous fluid and therefore its volumetric flow can also be set between these two extremes described. The magnetizable particles in the viscous fluid therefore come into effect in such a way as corresponds to the valve in DE 196 45 478 A1 described previously. On account of the low mass of the magnetizable particles and the potential high operating frequency of the electromagnet (which consequently serves as a volumetric-flow setting means) such setting operations can be carried out virtually free of inertia. The torque-transmitting behavior of the viscous coupling can be varied in a correspondingly rapid manner.
The feed line is preferably a two-piece design. More specifically, a first line section leads to the supply chamber from a pumping opening assigned to the working chamber, and a second line section which leads from the supply chamber back to the working chamber. The arrangement of these two line sections with an axial offset relative to one another makes it possible to move one line section, preferably the second, spatially close to the electromagnet of the volumetric-flow setting means, while the other line section (i.e., preferably the first), is further away from the electromagnet. This configuration provides a space for cooling blades on the coupling housing remaining axially between the electromagnet and the corresponding line section. However, the greater distance between the first line section and the electromagnet is also of considerable importance with regard to the fact that this line section must run outside the magnetic field. The reason for this lies in the fact that the pumping of viscous fluid out of the working chamber into the supply chamber must, by all means, be maintained when the electromagnet is switched on for producing the magnetic field in the extension region of the second line section in order to ensure emptying of the working chamber. Since both line sections lead out into the supply chamber, and the line section connecting the supply chamber to the working chamber preferably leads out in the peripheral region of the working chamber in order to help it fill quickly, both line sections run in comparable radial regions of the coupling housing, but are offset relative to one another in the peripheral direction. This likewise ensures: (i) that a magnetic field which is highly effective for the fed line is built up at the second line section by a very light and low-power electromagnet; (ii) that there is an adequat
Cohen & Pontani, Lieberman & Pavane
Lorence Richard M.
Mannesmann Sachs AG
LandOfFree
Viscous coupling with a volumetric-flow setting means does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Viscous coupling with a volumetric-flow setting means, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Viscous coupling with a volumetric-flow setting means will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2442311