Coil spring cassette

Abstract

The invention relates to a coil spring cassette comprising a stationary stator housing part and a rotatable rotor housing part, between which a coil gap is formed in which a flexible flat cable that has electric conductors and a flexible ribbon cable are arranged in such a manner that the flat cable and the ribbon cable are wound in opposite directions such that a respective first section of the flat cable and the ribbon cable rests against the inner lateral surface of the stator housing part and a respective second section rests against the outer lateral surface of the rotor housing part such that a U-shaped turning section which reverses the winding direction is formed between the two respective sections of the flat cable and the ribbon cable. The invention is characterized in that the ribbon cable is designed as a thin steel strip, and a permanent magnet is installed in the region of the outer lateral surface of the rotor housing part such that the permanent magnet exerts an attractive effect on the ribbon cable section resting thereon.

Description

[0001] Winder cat forward

[0002] The invention relates to a coil spring cassette with a fixed, at least partially cylindrical stator housing part and a cylindrical rotor housing part arranged coaxially thereto and rotatable about its longitudinal axis, wherein a winding gap is formed which is delimited by the inner circumferential surface of the cylindrical portion of the outer stator housing part and the outer circumferential surface of the inner rotor housing part, in which winding gap at least one flexible flat cable having an electrical conductor and at least one flexible flat strip serving to mechanically stabilize the flat cable are arranged in such a way that their respective first ends are fastened to the stator housing part and their respective second ends are fastened to the rotor housing part,and that they are wound in opposite directions with a first section of their length against the inner surface of the stator housing part and with a second section of their length against the outer surface of the rotor housing part, so that a U-shaped turning section reversing the winding direction is formed between the two sections of the flat cable and the flat strip.

[0003] Such coil spring cassettes are designed, for example, to reliably transmit power and / or data in motor vehicles between connection points that are rotatably mounted in the steering wheel and those that are fixed in the area of ​​the steering column. The connection points of such a device can be used to supply an airbag system, a steering wheel heater, a switching device, etc., with the voltage and signals necessary for their operation.

[0004] EP 0 556 779 B1 discloses such a coil spring cassette in which several flexible flat cables are accommodated within an annular cavity of a housing. One end of each flexible flat cable is secured to the stator part, and the other end is secured to a rotor part of the housing that is rotatable relative to the stator part. The flexible flat cables can each be wound with their two broad sides via a U-shaped turning section with at least one turn onto the axially aligned inner wall and, at a distance therefrom, conversely with at least one further turn onto the axially aligned outer wall of the housing.

[0005] If a plurality of flat cables is required to provide the necessary electrical connections, this plurality of flat cables is

[0006] Flat cables are arranged in such a way that their respective end sections overlap on the outer surface of the inner housing part and on the inner surface of the outer housing part, and the U-shaped turning sections of each of the flat cables generate an elastic compressive force which ensures that the inside or outside wound areas of the other flat cables are securely attached to the housing surfaces.

[0007] If fewer flat cables are needed to provide the necessary electrical connections than are required to ensure the perfect mechanical function of the clock spring cassette, so-called dummy cables are used instead of additional flat cables. These are elastic flat strips that have the same mechanical properties as flat cables, but unlike flat cables, do not contain electrical conductors. Plastic strips, e.g. made of PET, are usually used as dummy cables. In practice, the use of at least four or five cables or dummy cables has proven advantageous in order to ensure the perfect mechanical function of the clock spring cassette. These four or five cables orDummy cables must be arranged in such a way that their U-shaped turning sections, which reverse the winding direction, are distributed as evenly as possible over the circumference of the winding gap.

[0008] For steering systems based on the so-called steer-by-wire principle, which no longer feature a mechanical steering spindle, the steering wheel no longer needs to be able to rotate several revolutions. Typically, rotation of less than 360 degrees is even required, which means that the clock spring cassette no longer needs to encompass the entire steering spindle. The housing of the clock spring cassette no longer needs to be completely ring-shaped in cross-section. Rather, it is sufficient for the housing to form only a segment of a ring, which creates additional installation space in this area compared to the state of the art.

[0009] However, if multiple flat cables are required, they must be arranged much closer together, so that the previously described mechanical stabilization provided by the U-shaped turning sections of the flat cables evenly distributed around the circumference is no longer possible. It turns out that, particularly near the connection of the flat cables to the inner rotor housing section, the flat cables no longer adhere securely to the outer surface of this rotor housing section.

[0010] Therefore, a different form of mechanical stabilization is required, which the clock spring cassette according to the present invention provides in a simple and robust manner.

[0011] This is achieved according to the invention in that the at least one flat strip is designed as a thin steel strip, and in that at least one permanent magnet is mounted in the region of the outer surface of the rotor housing part in such a way that it exerts an attractive effect on the second section of the length of the flat strip lying there. An advantageous embodiment of the subject matter according to the invention is explained in more detail with reference to an exemplary embodiment illustrated in the drawings.

[0012] Show

[0013] Fig. 1 : a schematic representation of an embodiment of a coil spring cassette according to the invention in cross section

[0014] Fig. 2: a schematic representation of a clock spring cassette according to the state of the art in cross section

[0015] To clarify the general functioning of the clock spring cassette in question here, Fig. 2 shows a schematic cross-section of a clock spring cassette according to the prior art with the aforementioned minimum number of four cables or dummy cables. This clock spring cassette essentially consists of a housing having a stator housing part 1 and a rotor housing part 2 and flexible flat cables 6 or flat strips 7 as dummy cables accommodated within an annular cavity in the housing forming a winding gap 5. In the known embodiment shown here, there are three flexible flat strips 7 without electrical conductors and one electrical flat cable 6. The flat cable 6 is shown in dashed lines in the drawing.

[0016] The rotor housing part 2, which is located on the inside in the embodiment shown, is rotatable about its own longitudinal axis and thus also about that of the stator housing part 1, which is arranged coaxially to the outside. The inner surface 3 of the stator housing part 1 and the outer surface 4 of the rotor housing part 2 form a winding gap 5 in which the flexible flat cable 6 is received. The flexible flat cable 6 is fastened with its first end to the stator housing part 1 and with its second end to the rotor housing part 2 and is arranged in the winding gap 5 such that it is wound in the opposite direction with a section of its length adjacent to its first end against the inner surface 3 of the stator housing part 1 and with a section of its length adjacent to its second end against the outer surface 4 of the rotor housing part 2.Between these two sections of the flat cable 6 there is a U-shaped turning section 6' that reverses its winding direction. When the rotor housing part 2 rotates in one direction or the other, this U-shaped turning section 6' moves along the circumference of the winding gap 5, and the flat cable 6 is unwound on one side and wound on the other. To mechanically stabilize the flat cable 6, in particular to ensure that its end sections are firmly attached to the lateral surfaces 3, 4, three additional elastic flat bands 7 are accommodated in the winding gap 5 in the same way as the flat cable 6, namely in such a way that the four U-shaped turning sections 6', 7' of the one flat cable 6 and the three flat bands 7 are arranged at the same angular distance of approximately 90° from one another.The respective first and second ends of the flat strips 6 and the flat strips 7, which are fastened on the one hand to the stator housing part 1 and on the other hand to the rotor housing part 2, also each have an equal angular distance of approximately 90° from one another.

[0017] In the clock spring cassette according to the present invention shown in Fig. 1, whose housing is no longer completely annular in cross-section, but only forms a segment of a ring, a different arrangement of the flat cables 6 and flat strips 7 must be made. The respective first and second ends of the flat cables 6 and of the only one flat strip 7 in this case are fastened to the same point on the stator housing part 1 on the one hand and on the rotor housing part 2 on the other. In contrast to the previously described embodiment according to the prior art, in which all flat cables 6 and flat strips 7 can, at least theoretically, be essentially the same length, their lengths must necessarily be different here. The flat strip 7 located on the inside with regard to the winding gap 5 has the shortest length.The flat cable 6 located on the outside with respect to the winding gap 5 is the longest and, in this embodiment, also the only one that lies directly against both the inner surface 3 of the stator housing part 1 and the outer surface 4 of the rotor housing part 2.

[0018] The flat strip 7, which is located on the inside with respect to the winding gap 5, is designed according to the invention as a thin steel strip and serves solely to mechanically stabilize the flat cables 6. For this purpose, permanent magnets 8 are attached in the area of ​​the outer surface 4 of the rotor housing part 2 in such a way that they exert an attractive effect on the section of the length of the flat strip 7 that lies there. The areas of the flat cables 6 lying between the flat strip 7 and the outer surface 4 of the rotor housing part 2 are thus fixed to the outer surface 4 of the rotor housing part 2 by the flat strip 7. The number and strength of the permanent magnets 8 used can be used to change the strength and extent of the area of ​​the attractive effect on the flat strip 7. This allows adaptation to different maximum angle of rotation ranges or a different number of flat cables 6 present, for example.In the embodiment shown here, there are three permanent magnets 8.

Claims

Patent claims 1. A coil spring cassette comprising a stationary, at least partially cylindrical stator housing part (1) and a cylindrical rotor housing part (2) arranged coaxially thereto and rotatable about its longitudinal axis, wherein a winding gap (5) is formed which is delimited by the inner circumferential surface (3) of the cylindrical portion of the outer stator housing part (1) and the outer circumferential surface (4) of the inner rotor housing part (2), in which at least one flexible flat cable (6) having an electrical conductor and at least one flexible flat strip (7) serving to mechanically stabilize the flat cable (6) are arranged in such a way that their respective first ends are fastened to the stator housing part (1) and their respective second ends are fastened to the rotor housing part (2).and that they are wound in opposite directions with a respective first section of their length against the inner circumferential surface (3) of the stator housing part (1) and with a respective second section of their length against the outer circumferential surface (4) of the rotor housing part (2), so that a U-shaped turning section (6', 7') reversing the winding direction is formed between the respective two sections of the flat cable (6) and the flat strip (7), characterized in that the at least one flat strip (7) is designed as a thin steel strip, and in that at least one permanent magnet (8) is mounted in the region of the outer circumferential surface (4) of the rotor housing part (2) in such a way that it exerts an attractive effect on the second section of the length of the flat strip (7) lying there.

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