Steering wheel arrangement for a motor vehicle

Abstract

The invention relates to a steering wheel arrangement for a motor vehicle, comprising a steering wheel, a steering angle measuring arrangement for detecting the steering wheel position at a given moment, an electrical steering wheel heater, and a coil spring cassette that contains at least one ribbon cable through which flows the operating current of said electrical steering wheel heater, wherein a current control device is provided for the steering wheel heater which limits the operating current of the electrical steering wheel heater depending on the steering wheel position that was detected.

Description

[0001] Steering wheel arrangement for a motor vehicle

[0002] The invention relates to a steering wheel arrangement for a motor vehicle, comprising a steering wheel, a steering angle measuring arrangement for detecting the current steering wheel position, an electric steering wheel heater, and a clock spring cassette which contains at least one ribbon cable through which the operating current of the electric steering wheel heater flows.

[0003] Modern motor vehicles almost always feature a steering angle measurement system that electronically detects the current steering wheel position. The detected steering angle is needed, for example, to control an electric power steering system. The steering angle measurement system comprises analog or digital steering angle sensors located on the steering wheel and / or steering column.

[0004] The signals from these steering angle sensors are usually transmitted via ribbon cables that are arranged in a coil spring cassette. A coil spring cassette generally serves to electrically connect components of a steering wheel assembly that are arranged so that they can rotate relative to one another. It comprises at least one stationary housing part (stator) connected to the steering column and a housing part (rotor) that can rotate relative to the stator and is connected or coupled to the steering wheel.

[0005] An increasingly popular feature in motor vehicles is a device for electrically heating the steering wheel rim, referred to here for short as a steering wheel heater. The operating current for the steering wheel heater is generally also supplied via at least one ribbon cable within the clock spring cassette. To achieve comfortable, rapid heating of the steering wheel rim, relatively high currents must be transmitted.

[0006] The electrical power that can be transmitted through a coil spring cassette depends on the position of the ribbon cables within the cable chamber. The most unfavorable cases in this regard occur in steering wheel positions where the ribbon cables are completely wound around the rotor or stator of the coil spring cassette, as this results in the highest electrical power density in the ribbon cables. The unavoidable ohmic heat generation in the ribbon cables is thus concentrated in a small space. Furthermore, the compact arrangement of the ribbon cables makes it difficult to dissipate the resulting heat.

[0007] The situation is significantly better in the steering wheel positions, where the ribbon cables are evenly distributed between the rotor and stator, as well as the space between them within the clock spring cassette. The electrical heat is distributed over a relatively large area, and a larger portion of the ribbon cable surface is surrounded by air, allowing the generated heat to dissipate.

[0008] The exact steering wheel positions in which the at least one ribbon cable carrying the steering wheel heating power is most tightly wound within the clock spring cassette depend on the precise arrangement of the ribbon cable within the clock spring cassette. Without loss of generality, it is assumed below that these most unfavorable cases occur in the two steering wheel positions in which the steering wheel is deflected as far as possible to the right or left.

[0009] The least critical positions are the middle steering wheel positions near the straight-ahead driving of the vehicle, since here the ribbon cable is loosely positioned in the clock spring cassette.

[0010] To prevent overheating of ribbon cables, the maximum transmittable current was previously limited to the most critical condition, "ribbon cable completely wound up." However, this limitation, assuming the worst case scenario, also means that the steering wheel rim takes a relatively long time to heat up.

[0011] The task was to create a steering wheel arrangement that enables quick and safe heating of the steering wheel by means of a steering wheel heater.

[0012] This object is achieved according to the invention in that a current control device is provided for the steering wheel heating, which limits the operating current of the electric steering wheel heating as a function of the detected steering wheel position.

[0013] According to the invention, a steering angle-dependent steering wheel heating current control is provided. Based on the steering angle information from the steering angle measuring system, the steering wheel heating electronics specify a maximum possible current for each steering wheel position.

[0014] These maximum current intensities to be observed for the various steering angle positions can be determined empirically in advance, for example under the condition that a predetermined limit temperature within the clock spring cassette and in particular on the ribbon cable carrying the operating current of the steering wheel heating is not exceeded.

[0015] It is particularly advantageous if the at least one ribbon cable which carries the operating current for the steering wheel heating is arranged in the clock spring cassette in such a way that it is wound up least in the center position of the steering wheel and most in the maximum deflected steering wheel positions within the clock spring cassette and if the limitation of the operating current of the steering wheel heating is minimal in the straight-ahead position of the steering wheel and maximal in the maximum deflected steering wheel position.

[0016] During normal ferry operation, the steering wheel is located near the center position most of the time. In these steering positions, at least one ribbon cable is wound the least tightly, allowing the steering wheel heater to operate at maximum current. Extreme steering wheel angles, for which the transmitted electrical current must be severely limited, occur relatively rarely. For steering wheel positions in between, the transmitted electrical current can be adjusted accordingly to a medium value.

[0017] The current intensity can be adjusted either in steps or continuously, depending on the steering wheel's angle of rotation. Electronics are used that use either the output signals from the steering angle sensors or appropriately processed signals or data to regulate the current to the steering wheel heater. The control electronics can be implemented as either an analog or digital circuit.

Claims

Patent claims Steering wheel arrangement for a motor vehicle, with a steering wheel, with a steering angle measuring arrangement for detecting the current steering wheel position, with an electric steering wheel heater, and with a clock spring cassette which contains at least one ribbon cable through which the operating current of the electric steering wheel heater flows, characterized in that a current control device for the steering wheel heater is provided which limits the operating current of the electric steering wheel heater as a function of the detected steering wheel position. Steering wheel arrangement according to claim 1, characterized in that the ribbon cable is wound up least in the center position of the steering wheel and most tightly in the maximum deflected steering wheel positions within the clock spring cassette, and that the limitation of the operating current of the steering wheel heater is minimal in the straight-ahead position of the steering wheel and maximum in the maximum deflected steering wheel position.