The invention relates to a component assembly with a holding function, having at least one first element and at least one second element which are arranged movably with respect to one another and which can be brought into operational connection with one another via a magnetorheological fluid or a magnetic powder. The invention furthermore relates to a method for the operation of such a component assembly, to a holding-open system having such a component assembly and to a method for the operation of such a holding-open system.
Magnetic clutches or brakes are realized using magnetorheological fluids or magnetic powders. Two elements are connected via the magnetorheological fluid or the magnetic powder. The viscosity of the magnetorheological fluid or the magnetic powder solidifies due to an outer magnetic field so that the two elements come into solid operational connection. If the element is, for example, a rotor and if the other element is a stator, a brake can be realized in this manner. If e.g. both elements are rotatably supported, it is a case of a clutch.
DE 100 29 227 A1 shows a controllable braking system in which a magnetic field is constantly maintained with the help of a permanent magnet at the location of the magnetorheological fluid. There is accordingly always an operational connection between two elements. To cancel this operational connection, a coil is provided which generates a counter-field to the permanent magnetic field with a flow of current. To neutralize the magnetic field of the permanent magnet, sufficiently large magnetic fields and in this respect voluminous or weighty coils are required.
The known system serves, for example, as a controllable braking system, in particular for a hinge system for the rotatable and brakable fastening of a vehicle door. Applying the magnetic counter-field to the magnetorheological fluid for the neutralization of the magnetic field of the permanent magnet allows a mutual movement of the elements. In the open state of the vehicle door, the with a flow of current to the coil can be interrupted so that the magnetic field of the permanent magnet is applied to the magnetorheological fluid at fall strength. This hardens and holds the vehicle door in the open state. To close the vehicle door, the counter-field is again generated using the coil so that the magnetic effect of the permanent magnet is neutralized. The magnetorheological fluid liquefies so that the two elements are freely rotatable with respect to one another. The vehicle door can be closed.
On a failure of the onboard power system, the field of the permanent magnet is generally fully effective at the location of the magnetorheological fluid in the known solution and holds said fluid in the solid state. In such a case, the two elements cannot be moved with respect to one another. The vehicle door can in particular not be opened. There is therefore, for example, a safety risk in the event of an accident.
Other solutions dispense with the use of a permanent magnet. A coil is provided with which a magnetic field can be generated which acts at the location of the magnetorheological fluid. A hardening of the magnetorheological fluid so that the first element and the second element are in operational connection with one another is therefore only present when the coil has a with a flow of current. To realize a holding function, for example to hold a vehicle door open, the coil must have a permanent with a flow of current.
It is the object of the present invention to provide a component assembly with a holding function, a holding-open system and a method for the operation of such a component assembly which have a simple and cost-effective design and which allow a secure operation.
This object is satisfied using a component assembly with a holding function having the features of claim 1, a holding-open system having the features of claim 12 and a method having the features of claim 15. Advantageous aspects form the subject of the dependent claims.
A component assembly in accordance with the invention with a holding function has at least one first element and at least one second element which are arranged movably with respect to one another. At least one magnetizable component having magnetic remanence, i.e. with degradable residual magnetism, is provided. The component assembly includes a magnetorheological medium (magnetorheological fluid or magnetic powder) which is located in the magnetic field of the at least one magnetizable component when it is magnetized. Magnetorheological fluids are characterized in that their viscosity increases in a magnetic field, which can in particular result in a hardening of the magnetorheological fluid. If the magnetizable component is magnetized, the magnetorheological fluid accordingly has an increased viscosity or is hardened so that the two elements are in operational connection with one another, i.e. the two elements are mechanically coupled.
For example, with a rotatable support of the one element with respect to the other element, a torque can be transmitted via this operational connection.
Instead of a magnetorheological fluid, a magnetic powder can also be used which is located in the magnetic field of the at least one magnetizable component when it is magnetized. If a magnetic field is present at the location of the magnetic powder due to the magnetization of the magnetizable component, said magnetic powder has become solid and provides an operational connection between the first element and the second element.
The component assembly in accordance with the invention furthermore has a coil which can generate a magnetic field for the sufficient magnetization of the at least one magnetizable component on a current flow to it. The coil and a control device associated with the coil are therefore made to actively change the magnetization state of the magnetizable component, i.e. to actively magnetize or demagnetize the magnetizable component. Unlike in the use of a permanent magnetic element as described in DE 100 29 227 A1, for example, not only a temporary superimposition of an external magnetic field thus takes place via the magnetic field generated by a permanent magnet. Instead, the coil and a control device associated with the coil are made to selectively set such a flow of current to the coil that a magnetization or an at least partial demagnetization of the magnetizable component takes place. A magnetization of the magnetizable component set in this manner can also be maintained in a currentless state of the coil or with a flow of current to the coil with a reduced current strength (relative to the current strength for the magnetization of the magnetizable component) takes place in addition to the thus set magnetization of the magnetizable component until the magnetization is again actively changed by a corresponding change of the with a flow of current to the coil.
The magnetizable component and the coil are therefore arranged and designed such that a first currentless state or current flow state of the coil can be generated in which the magnetizable component provides a magnetic field after its magnetization in which the magnetorheological fluid or the magnetic powder has such a sufficiently solid structure that it maintains an operational connection between the first element and the second element. A magnetic field which magnetizes the magnetizable component is first generated using the coil. The magnetic field thereby arising at the location of the magnetorheological fluid or of the magnetic powder increases the viscosity or hardens the magnetorheological fluid or the magnetic powder. After the switching off or reducing of the current in the coil and of the external magnetic field thus generated, the magnetic field brought about by the magnetizable component remains due to the remanent magnetization. It is in particular possible only to greatly reduce the strength of the electrical current conducted through the coil instead of a complete switching off of the coil current. A stronger operational connection between the first element and the second element is hereby set with a small energy consumption than with a current strength of zero.
Materials having high saturation remanence are particularly suitable for the magnetizable component so that a large magnetic field remains even without application of an external magnetic field.
It is therefore also possible realize the holding function with the component assembly in accordance with the invention without current because the magnetic field is maintained by the magnetizable component at the location of the magnetorheological fluid or of the magnetic powder.
The component assembly in accordance with the invention is moreover designed such that a second currentless state of the coil can be generated in which the magnetizable component is substantially demagnetized, whereby the operational connection between the first element and the second element can be cancelled. Unlike the use, for example, of a permanent magnet, a currentless state is therefore also possible here in which the magnetorheological fluid or the magnetic powder are not hardened and a substantially free movement of the two elements with respect to one another is possible. Since the magnetizable component is made magnetically remanent and since the hysteresis loop of the magnetizable component thus has a certain width which cannot be neglected, the magnetizable component is actively demagnetized by a corresponding with a flow of current to the coil on the basis of an associated control device before the coil is switched to currentless. To achieve a demagnetization which is as complete as possible on the use of a small coil and a small current strength, materials are of advantage with a small coercive force, that is with a small hysteresis curve, compared with a permanent magnet.
If, for example, a vehicle door is realized with the component assembly in accordance with the invention, a particularly reliable solution is present. With a closed vehicle door, the second currentless state is generated in which the magnetizable component is substantially demagnetized. The door is held in a manner known per se by the lock catch. On the failure of the onboard network, for example on an accident, nothing changes in the magnetically generated operational connection. The door can be opened without hindrance.
It is therefore possible using the component assembly in accordance with the invention to maintain both a state currentless or with only a small with a flow of current to the coil in which the magnetorheological fluid or the magnetic powder are exposed to a magnetic field and a state currentless in which no magnetic field is present. A particularly economic and secure operation is possible.
The component assembly in accordance with the invention is connected or connectable to a power supply which can provide a current which can serve for the generation of a magnetic field with the coil sufficient for the magnetization of the magnetizable component. In a preferred embodiment, this power supply is connected to a control device which allows a with a flow of current to the coil for the generation of a magnetic alternating field with a strength reducing over time. An automatic demagnetization of the magnetizable component is almost completely possible using such a control device by application of an alternating field of reducing strength.
The component assembly in accordance with the invention can include a second element, for example, which is supported rotatably or pivotably relative to the first element. A brake can, for example, be realized using such a component assembly. Such a component assembly can, for example, be used in a door or flap, in particular of a motor vehicle. After the opening of the door (with a currentless coil), the magnetizable component is magnetized with the help of the coil and the magnetorheological fluid or the magnetic powder harden, with a with a flow of current to the coil only being necessary for the generation of the magnetic field required for the magnetization of the magnetizable component for a short time and being switched off or at least considerably reduced thereafter. A magnetic field is also maintained after the termination or reduction of the with a flow of current to the coil due to the magnetization of the magnetic component, the magnetorheological fluid or the magnetic powder remain solid and the door is kept open. Before the closing of the door, the magnetic field active in the magnetorheological medium is initially cancelled by continuous with a flow of current to the coil with a DC current in that the coercive field strength corresponding to the magnetizable component is generated by means of the coil such that the magnetorheological fluid or the magnetic powder is no longer solid and does not stand in the way of the closing movement of the door. In the course of the closing movement of the door, a comparatively small magnetic field can optionally be generated at the location of the magnetorheological medium by a corresponding with a flow of current to the coil such that the fluid or magnetic powder effects a damped closing or moving procedure.
In the closed state of the vehicle door, a very largely complete demagnetization of the magnetizable component is carried out by a corresponding with a flow of current to the coil (generation of a magnetic alternating field with a strength reducing over time) in order also no longer to impede a subsequent opening of the door with a coil now not having any flow of current. Alternatively, the complete demagnetization of the magnetizable component can already be carried out before the start o the closing movement, that is without any intermediate flow of DC current to the coil.
With a suitable design, the component assembly in accordance with the invention can also be used directly as a hinge of a door or flap.
Both elements are rotatably supported with a clutch. After the magnetization of the magnetizable component, the magnetized component maintains a sufficient magnetic field at the location of the magnetorheological fluid or of the magnetic powder so that a torque transmission is possible between the two elements. After the magnetization, a further power supply is no longer necessary since the magnetic field is maintained by the magnetized component.
In other designs of the component assembly in accordance with the invention, the first element and the second element are arranged displaceably, in particular linearly displaceably, with respect to one another. The one element, for example, moves in the magnetorheological fluid which is received in the other element. Generating a sufficient magnetic field magnetizes the magnetizable component. A magnetic field which acts at the location of the magnetorheological fluid and hardens it also remains after the switching off of the external magnetic field on the basis of the magnetized component. The two elements can no longer be displaced relative to one another. With a suitable arrangement, a door stopper function can likewise be realized using such a component assembly.
In an embodiment, the magnetorheological fluid or the magnetic powder is located between the first element and the second element which in this respect form the vessel for the fluid or for the powder.
In another embodiment the vessel for the magnetorheological fluid or the magnetic field is formed by one of the elements and the other element dips into the magnetorheological fluid or into the magnetic powder, at least partly. Hardening the magnetorheological fluid or the magnetic powder with the help of the magnetic field of the magnetized component holds the second element in the first element so that the two elements are in operational connection with one another.
In such an embodiment, it is in particular advantageous if the first element, which also serves as a vessel for the magnetorheological fluid or for the magnetic powder, includes the at least one magnetizable component, that is, it is in particular manufactured from the magnetizable material.
In other embodiments, the second element or both elements can comprise the magnetizable material and can in this respect include the magnetizable component.
With respect to the remanence properties of the magnetizable component, it is preferred if the magnetizable component has a coercive field strength in the range from approx. 103 to 104 A/m. That magnetic field strength is called the coercive field strength (customary abbreviation: HK or HC) for which—starting from a saturation magnetization of the magnetizable component after a complete magnetization—a magnetic induction (customary abbreviation: B; unit T=tesla) or a magnetization (M) of zero results.
It is furthermore preferred if the magnetizable component has a saturation remanence in the range from approx. 0.5 to 2 T (tesla). That magnetic induction is called the saturation remanence (customary abbreviation: BR) which—starting from a saturation magnetization of the magnetizable component which is still present after a complete demagnetization—is still present when the magnetic field applied from the outside is reduced to a field strength of zero (H=0).
It is particularly advantageous if the magnetizable component has a coercive field strength in the range from approximately 103 to 104 A/m and at the same time a saturation remanence in the range of approximately 0.5 to 2 T. In this case, the magnetizable component, on the one hand—unlike a permanent magnet—is magnetically soft (comparatively small coercive field strength) so that the coil required for the desired magnetization and demagnetization can be dimensioned correspondingly small and small current strengths can be used. The hysteresis loop of the magnetizable component is therefore smaller than with a permanent magnet. On the other hand, a saturation remanence of approximately 0.5 to 2 T means a comparatively strong magnetic field and thus an advantageously strong operational connection between the first element and the second element even in the currentless state or with only a small with a flow of current to the coil. Even with a great steepness of the hysteresis loop, this ultimately means that the material has to have a certain width of the hysteresis loop or a certain coercive field strength, as specified above.
A holding-open system in accordance with the invention has a component assembly in accordance with the invention and serves for a door or a flap, in particular in automobiles. The door or flap is pivotally connected to a holder fixed relative to the door or flap. Either the first element or the second element of the component assembly in accordance with the invention move at least indirectly—for example via an interposed transmission—with the door or with the flap, while the other elements is fastened to the fixed holder.
In particular with a holding-open system with a component assembly in which the first element serves for the holding of the magnetorheological fluid or of the magnetic powder and the second element dips at least partly into the magnetorheological fluid or into the magnetic powder, it is particularly simple if the first element is arranged at the fixed holder.
A particularly compact arrangement is possible when the component assembly in accordance with the invention does not represent an additional element, but is rather used as a hinge, which is in particular possible when the component assembly in accordance with the invention is a component assembly in which the first element and the second element are pivotable with respect to one another.
In a method in accordance with the invention for the operation of a component assembly in accordance with the invention or of a holding-open system in accordance with the invention, a first relative position of the first element and of the second element relative to one another is selected. This can, for example, be an open door or flap. The coil has a flow of current so that a magnetic field is generated which is sufficient for the magnetization of the magnetizable component. Due to the magnetization of the magnetizable component, there is a magnetic field at the location of the magnetorheological fluid or of the magnetic powder which is sufficient for the increase of the viscosity or the hardening of the magnetorheological fluid or of the magnetic powder. The magnetization of the magnetic component is also maintained on the basis of the remanent properties after switching off or reducing the external magnetic field, that is after the switching off or reducing of the current. The viscosity of the magnetorheological fluid remains increased and the magnetorheological fluid or the magnetic powder remains solid. The holding function is therefore also maintained after the switching of or reduction of the current. The two element remain in operational connection with one another. A door is kept open, for example.
In a particularly preferred aspect of the method in accordance with the invention this state can be cancelled again by a with a flow of current to the coil with an alternating current of a strength reducing over time. A magnetic field of reducing strength which successively results in demagnetization is applied to the magnetizable component by such a flow of current. After the demagnetization of the magnetizable component, it no longer generates any magnetic field at the location of the magnetorheological fluid or of the magnetic powder. The magnetorheological fluid or the magnetic powder are no longer solid and a free movement is possible between the first element and the second element. A second relative position can now be set, for example, a vehicle door can be closed.
In another aspect which can in particular be used with doors or flaps, the door is closed against the force of the solid fluid or powder by physical force without previously demagnetizing the magnetizable component. The solid fluid or magnetic powder in this manner allows a damped closing or movement procedure. In the closed state, the demagnetization is then carried out as described in order no longer to impede an opening of the door.
The component assembly in accordance with the invention, the holding-open system in accordance with the invention and the method in accordance with the invention are in particular characterized in that the two extreme states can be maintained currentless. After the magnetization of the magnetizable component, it also maintains the magnetic field when the magnetizing external magnetic field is switched off. A vehicle door is, for example, kept open. After the demagnetization, the movement of the two elements with respect to one another is free since no magnetic field is effective at the magnetorheological fluid or at the magnetic powder. This state can also be maintained currentless with the component assembly in accordance with the invention, with the holding-open system in accordance with the invention and with the method in accordance with the invention. The system in accordance with the invention or the method in accordance with the invention has the advantage with respect to a known solution using a permanent magnet that no large coils are required to generate a counter-field opposite to the magnetic field of the permanent magnet. The system in accordance with the invention or the method in accordance with the invention has the advantage with respect to a known solution in which the magnetic field for the hardening of the magnetorheological fluid or of the magnetic powder is generated only with the help of a coil that no permanent with a flow of current is required to maintain a state.
The invention will be explained in detail with reference to the enclosed Figures which show different embodiments of component assemblies in accordance with the invention in a schematic representation. There are shown:
a and 9b a hysteresis loop or the dependence of a transmitted torque on the coil current for a material without magnetic remanence; and
a and 10b a hysteresis loop or the dependence of a transmitted torque on the coil current for a material with high magnetic remanence.
A pot disk 26 which is connected to a fastening element 14 which is provided at a pivotable part, for example at a door, projects into the cylindrical gap between the housing 16 and the field-generating component 18. The pivotable part 14 and the fixed parts 16 and 18 are supported rotatably with respect to one another at the bearings 29 in a manner known per se. The arrangement in particular has a termination 34 with which the pivotable part 14 contacts the housing 16 sealingly, but rotatably. Reference numeral 30 designates the axis around which the pivotable element 14 is pivotable together with the pot disk 26. The pot disk 26 is supported on a slide bearing 32 in the housing 16. A rotary angle sensor 28 can be provided in the bearing 29 and serves for the measurement of the pivoting of the fastening element 14 with respect to the fixed elements 12, 16, 18.
Magnetorheological fluid 38 is located in the space between the field-generating element 18 and the housing 16.
Reference numeral 40 designates a magnetic field line indicated by way of example such as is generated by a group of coil wires 21. The other drawn groups of coil wires which produce the coil 20 overall also generate corresponding magnetic field lines. For reasons of clarity, however, not all the magnetic field lines are drawn around the groups 21.
Both the field-generating element 18 and the housing 16 are made from magnetizable material with high saturation remanence and a small hysteresis curve. Such a material is, for example, a heat-treated steel V155 of the company Böhler Edelstahl GmbH & Co. KG, Kapfenberg (Austria).
An embodiment in accordance with
Alternatively or additionally to a complete switching of the magnetic field generated by the coil 20 (current strength zero), an only reduced current strength can also selectively be set which is, however, larger than zero. An operational connection between the pot disk 26, on the one hand, and the housing 16 and the field-generating component 18, on the other hand, is hereby maintained with a low holding current and thus with a low current consumption, said operational connection being stronger than with a current strength of zero and being considerably stronger than on the setting of the same current strength when using a non-remanent material.
In both cases, the holding force which results from the remanent magnetization of the housing 16 and of the field-generating component 18 and from the operational connection to the pot disk 26 caused hereby must be reduced for the closing of the vehicle door. For this purpose, the coil 20 first has a current flow such that the magnetic field active at the location of the magnetorheological fluid 38 is reduced by generation of the required coercive field strength in the magnetizable component and remains reduced until the door is latched in accordance with its purpose, i.e. the coil initially still remains under current. The door is then held in the closed state by the lock catch. By a subsequent generation of an alternating field of reducing strength, which can be generated, for example, by applying an AC current of reducing strength to the coil 20, as is shown schematically in
The curve a, b, c, d, e is e.g. moved through for the demagnetization in an aspect of the method in accordance with the invention. A substantially demagnetized state can be achieved in this manner. A possibly remaining small residual magnetization which cannot be cancelled in this manner is harmless when it is selected to be so small that the viscosity of the magnetorheological fluid in the magnetic field of the magnetizable component is only insignificantly increased with respect to the magnetic field free case.
A demagnetization of the magnetizable components, in this embodiment that is the field-generating element 18 and the housing 16, which is as complete as possible has the result that a magnetic field is no longer effective at the location of the magnetorheological fluid 38 and in this respect the pot disk 26 is no longer held in the magnetorheological field 38. A free movement of the pivotable fastening element 14 is then possible.
a and 10b likewise show a hysteresis loop and the generated torque M in dependence on the coil current I; here, however, for a magnetizable component with high saturation remanence (vertical axial section in
The operation of the second embodiment is similar to the operation of the first embodiment. However, due to the multiply mutually engaging pot disks 25, 26, 27, the holding effect is increased which is exerted onto the pot disks by the magnetorheological fluid. The number of the mutually engaging pot disks is not restricted to the three pot disks shown.
The coil can e.g. also be provided in or around the housing 16 in both the first embodiment and in the second embodiment.
A third embodiment is shown in
It is alternatively possible that the coil is not provided in the piston 54, but rather in or around the cylinder 52.
The cylinder/piston arrangement 50 can be used as follows. First, the cylinder 52 and the piston 54 are demagnetized. The piston 54 can be moved freely in the magnetorheological fluid 66. The piston can be moved to the right in
The cylinder 52 and the piston 54 are largely demagnetized by demagnetization of the magnetic material of the piston 54 and of the cylinder 52, for example by a flow of current to the coil 56 in accordance with the diagram of
A possible application of the third embodiment is given, for example, in a holding-open system for a vehicle door. The piston rod of the piston 54 can be connected to a vehicle door for example, while the cylinder 52 is connected to the body.
The fourth embodiment can be used as follows: The yoke 72 is initially not magnetized. The magnetorheological fluid 84 can flow freely through the passage 82. The pistons 76, 78 are movable freely, but together.
Applying a current to the coil 90 generates a magnetization in the yoke 72. The magnetization results in a magnetic field 86 in the region of the passage 82. The magnetorheological fluid 84 is hardened in the region of the passage 82 by this magnetic field and the free movement of the pistons 76, 78 is suppressed.
Applying current to the coil 90 with an AC current of reducing strength, such as is shown in
Similar to the embodiment of
After switching of the coil current, a magnetic field remains on the basis of the magnetization of the rotor 104 and of the vessel 102, whereby the magnetorheological fluid 118 remains hardened, such as has already been described with reference to the example of
The described embodiments are characterized in that a proportion of the parts conducting the magnetic field which is as large as possible is made in each case from material of high remanence that, on the other hand, has a small hysteresis curve, that is it is in particular soft magnetic.
The described embodiments use a magnetorheological fluid. Corresponding aspects are, however, also possible when a magnetic powder is used which hardens on application of a magnetic field and thus enables a power transmission between two elements.
Number | Date | Country | Kind |
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10 2006 037 992.6 | Aug 2006 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP07/06767 | 7/31/2007 | WO | 00 | 2/12/2009 |