The invention relates to liquid friction clutches.
A liquid friction clutch of said type is known from EP 1 731 787 B1.
Also, DE 197 49 342 A1 discloses a viscous clutch for driving motor vehicle air-conditioning compressors, in which, to control the filling level of fluid in a working chamber, the throughput of fluid through the pipe section adjoining an inlet section of a scoop pipe is controlled by means of a valve. Tests however yielded that such a valve causes problems in that it is extremely difficult to achieve acceptable performance results.
It is therefore an object of the present invention to provide a liquid friction clutch by means of which it is possible in a simple manner, without using a valve, to obtain a variable clutch fluid flow.
By means of the provision of a rotatably mounted pump element which, with the housing, defines a shear gap, it is made possible in a simple manner, by utilizing a rotational speed difference between the pump element and the housing or the primary side of the liquid friction clutch, to generate a variable volume flow from the storage chamber into the working chamber, without it being necessary for this purpose to additionally integrate a controllable valve into the flow path.
The particular advantages of the liquid friction clutch according to the invention include firstly that only a small quantity of clutch fluid is required, because on account of the above-explained arrangement, an active feed pump is formed in the oil reservoir, which with regard to the clutch fluid quantity is advantageous over the known utilization of centrifugal forces for filling the working chamber.
Furthermore, the response behavior of the liquid friction clutch according to the invention is faster on account of the smaller clutch fluid component.
An extremely compact design is also generated because the outer diameter of the storage chamber or of the reservoir can be made larger than the inner diameter of the working chamber.
The compact design is improved further in that, as already explained above, a variability of the clutch fluid flow is made possible without the use of a valve arrangement.
The pump element which builds up a pressure, with a volume flow being generated as a result of friction of the clutch fluid in the shear gap which is preferably kept small, can be mounted either on the stationary clutch part or clutch housing of the active element (for example pump wheel, impeller, direct-current compressor etc.) or it is also possible for said pump element to be mounted on the shaft of the liquid friction clutch.
The pressure which is built up, or the volume flow which is generated, is a function of the relative rotational speed of the rotatable pump element in relation to the housing, with it being possible for the relative rotational speed to be controlled for example by means of a compensation of the drag torque of the fluid friction pump in relation to the torque that is generated by an actuating mechanism or by a brake device which may for example be designed as an eddy-current brake. Said brake device may in principle be designed as any type of magnetic brake device or friction brake. In addition to the abovementioned eddy-current brake, further examples are electric motors, generators or else viscous brakes.
If an eddy-current brake is provided as a brake device, said eddy-current brake is actuated by means of a magnetic field which is generated in a solenoid or electromagnet which compensates the magnetic field of permanent magnets provided as a further part of the brake device. A brake device of said type may be used as a fail-safe facility such that the variable feed pump or the pump element rotates at maximum throughflow rate (minimum rotational speed), specifically in a situation in which no electrical energy is applied to the solenoid.
Further details, advantages and features of the present invention will emerge from the following description of exemplary embodiments on the basis of the drawings, in which:
Arranged in the housing 2, 3 is a clutch disk 4 which is rotatable relative to the housing 2, 3. Here, the clutch disk 4 is rotationally fixedly arranged on an end 5 of a shaft 6 which is mounted centrally within the housing 2, 3. Fixed to the other end 8 of the shaft is a drivable active element 7 which is illustrated in schematically simplified form and which may be designed for example as a pump wheel or as an impeller.
A working chamber 9 is arranged between the housing 2, 3 and the clutch disk 4, which working chamber 9, as can be seen from
Furthermore, a storage chamber 10 for said clutch fluid is provided, with a supply duct 11 (see
As can be seen in particular from
A drive element 21, such as for example a belt pulley, is also connected to the housing 2, 3. The liquid friction clutch 1 also has a stationary clutch part 13 on which the housing 2, 3 is mounted via a main bearing 22. The stationary clutch part 13 is mounted on the shaft 6 via secondary bearings 18 and 19.
As is also shown by a juxtaposition of
In the illustrated example, the pump element 14 has at its radial outer edge a shear gap recess 12 which, according to the detailed illustration in
With regard to the volume flow explained above, reference should be made in particular to the detailed illustration of
To generate said rotational speed difference, it is possible to design the pump element 14 such that it can be braked. For this purpose, in
The illustrated eddy-current brake has firstly an electromagnet or solenoid 23 which is mounted at the position shown in
For further explanation, in particular of these latter components, reference may also be made to
In addition to the written disclosure of the invention, reference is hereby explicitly made to the diagrammatic illustration thereof in
Although the invention has been described with respect to preferred embodiments, it is to be also understood that it is not to be so limited since changes and modifications can be made therein which are within the full scope of this invention as detailed by the following claims.
Number | Date | Country | Kind |
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09010417 | Aug 2009 | EP | regional |
This application is a continuation of U.S. patent application Ser. No. 13/386,940 filed on Jan. 25, 2012 (now U.S. Pat. No. 8,875,861 issued on Nov. 4, 2014), which is a National Stage Entry of International Patent Application No. PCT/US2010/044061 filed on Aug. 2, 2010, which claims the benefit of European Patent Application No. 09010417.5 filed on Aug. 12, 2009.
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Number | Date | Country | |
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20150053524 A1 | Feb 2015 | US |
Number | Date | Country | |
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Parent | 13386940 | US | |
Child | 14530780 | US |