CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of International Application PCT/EP03/02933, published in German, with an international filing date of Mar. 20, 2003, and which claims priority to DE 102 12 824.3 filed on Mar. 22, 2002.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a device for the optoelectronic detection of switching positions of a mechanically actuated, positively driven switching element that engages in a detent curve in which the device has an optical transmitter positioned to illuminate an optical receiver, and the device further has a shutter which is displaceable relative to the transmitter and the receiver and displaces in response to movement of the switching element between switching positions.

2. Background Art

Devices for the detection of switching positions are used in switches with which a plurality of functions can be switched, and in which the mechanical haptics and electrical switching position detection device are separated. Switches like these are used as lighting or steering column switches in motor vehicles, for example. Such switches are designed to be displaceable in a plurality of directions, so that the numerous functions can be performed independently from each other and parallel to each other. A switching position detection device makes the respective switching position directly accessible to the switched devices, or even as a data input of a data processing system, e.g., an onboard computer in a motor vehicle, for monitoring and control purposes.

In addition, back-lighted symbols can be allocated to the switch for displaying the respective switching position. In this case, the symbols standing for the actually switched functions are back-lighted as a function of the respective switching position.

Such switches are conventionally designed as contact switches, so that a switching position is reached once the switching component has established the corresponding electrical connection. Even though numerous different functions can be switched with such a multifunction switch, the effort increases disproportionately for complicated switch structures if the object is to detect the respective switching positions in the manner described above. In addition, the elements provided for mechanical contacting are subjected to wear and ageing.

As known from DE 43 32 748 A1, multifunction switches can be designed as contact-less, optoelectronically operating switches. The switch described in this document is characterized in an electrical contact is not established to detect a switching position. Rather, a photosensitive element is exposed to light as the receiver with the switching element in a specific switching position. In addition to the photosensitive element, such an optical switch encompasses a light source, e.g., which can be arranged on the same printed circuit board as the photosensitive element.

An optical fiber whose area on the light decoupling side faces the photosensitive surface of the photoelectric element conveys the required light to the photoelectric element. A movement gap is between the decoupling side of the optical fiber and the photoelectric element. A shutter is in the movement gap. The shutter is coupled to the coupled to the displacement of the switching element and moves in the movement gap as the switching element moves between switching positions. The shutter has an opening at a predetermined position, so that, after the switching element has been displaced to a specific switching position, the opening is aligned with the area of the optical fiber on the decoupling side and the photosensitive surface of the photoelectric element, so that the photoelectric element can be exposed to light.

If the switching element is displaced from this position again, the photoelectric element is shaded, and the device moves out of the switching position. Therefore, each switching position is realized by the object of this document by means of an optoelectronic switch. Suitably arranging a plurality of such optical switches also makes it possible to detect complicated switching displacements. However, it is difficult to realize complicated switching displacements in the manner described given tight mounting spaces.

In conceiving this known device, it is necessary that the transmitter and the receiver be precisely aligned relative to each other, in particular when a distinction is to be made as intended between even small make-and-break cycles. Due to the resultant tolerance chains during the manufacture and positioning of photoelectric barrier and the shutter, it can happen that an optical receiver in a specific switching position is not sufficiently irradiated by an optical transmitter after the elements have been installed, e.g., in the housing of a steering column switch, to determine its switching positions, so that there might not be enough illumination intensity for detecting this switching position under certain conditions.

SUMMARY OF THE INVENTION

Proceeding from this discussed prior art, an object of the present invention is to further develop a device for the optoelectronic detection of switching positions of a switching element in such a way as to reduce, if not entirely avoid, the tolerance disadvantages encountered in the prior art.

This object is achieved by two features of the present invention. First, a part of the switching position detection device (i.e., either the optical transmitter(s) or the optical receiver(s)) is positioned behind a section as part of an opaque element forming a detent curve when viewed from the direction of the respective complementary part of the switching position detection device (i.e., the other of the optical transmitter(s) or the optical receiver(s)).

Second, light-beam apertures are incorporated in the section of the opaque element forming the detent curve at individual positions defining the switching points on the detent curve. The light-beam apertures are open or sufficiently transparent relative to the respective complementary part of switching position detection device (i.e., the other of the optical transmitter(s) or the optical receiver(s)). As such, the light-beam apertures define the switching points on the detent curve.

As part of the element forming the detent curve, the light-beam aperture(s) is advantageously fabricated as a single piece with the detent curve, if possible, for example in an injection molding process. Light-beam apertures are respectively incorporated at the positions on the detent curve corresponding to the mechanical switching points, e.g., in a flange that projects from the actual detent curve. Either of the optical transmitters, e.g., LED's, or the optical receivers are positioned behind the light-beam apertures viewed from the direction of the other of the optical transmitters or optical receivers. The light-beam apertures are dimensioned in such a way with respect to their inside diameter that tolerances resulting from the configuration of the elements positioned behind the light-beam aperture (i.e., the elements being either the optical transmitter(s) or the optical receiver(s)) are compensated without any problem.

For example, when an optical transmitter is positioned behind a respective light-beam aperture, the shutter aperture provided by the light-beam aperture is designed to be smaller than the light-emitting surface of such an optical transmitter projected into the plane of the optical receiver. This ensures that the optical receiver can still be illuminated as intended, even when the optical transmitter is positioned behind the light-beam aperture within a certain tolerance. The light-beam apertures and the areas of the detent curve section forming the light-beam aperture also reduce scattered radiation.

The elements of the optical switch assemblies (i.e., the set of optical transmitter(s) and optical receiver(s) forming each optical switch assembly) are preferably positioned on a shared, flexible printed circuit board. The elements (i.e., the optical transmitter(s) and the optical receiver(s)) face each other to form the desired optical switch assemblies in the sections accommodating the optical transmitters and the optical receivers, and are each fixed in a corresponding abutment.

A particularly advantageous embodiment provides for either only one optical receiver and a plurality of optical transmitters, or only one optical transmitter and a plurality of optical receivers to form a light-beam assembly (i.e., an optical switch assembly). At least two optical receivers or two optical transmitters are correspondingly spaced apart by at least one make-and-break cycle in the actuating direction of the switching element. The shutter has a shading area that causes a change only in the respective state of a single optical receiver or only in the state of a single optical transmitter relative to an illumination of the optical receiver given a change in switching positions to an adjacent switching position of the switching element.

In such an embodiment, using a light-beam assembly having an optical transmitter and two optical receivers as an example, essentially four make-and-break cycles can be detected, because a state in which both optical receivers are shadowed can also be defined as a switching position. For this reason, the shutter has a shading area, with which both optical receivers can be shaded at the same time, if required. Therefore, only two optical receivers are necessary in the absence of partial shading for individual optical receivers, so that the number of optical receivers used is reduced by 50% in comparison to the number of required optical receivers in the prior art.

Partial shading can reduce the number of required optical receivers even further in comparison to the prior art. To avoid misinterpretations, the object of the claimed switching position detection device further provides that only a single optical receiver changes its state given a change in the switching position to an adjacent switching position of the switching element. This change in state can be triggered by illuminating a previously unlighted optical receiver or vice versa, or also by changing the illumination intensity, e.g., by shading sections of an optical receiver with the shutter.

Such a switching position detection device can easily also be used to detect a switching position if the switching element can be displaced in two or more directions. An optical receiver assembly consisting of at least two optical receivers and a shutter having its shading area is conceived in each displacement direction of the switching element, as already described above. The lower hardware cost in comparison with the prior art makes it possible to use this type of switching position detection device to optoelectronically detect even complicated switching displacements without a larger installation space being required for this purpose.

A microprocessor is unnecessary for evaluating the switching position detection device in accordance with the present invention. Evaluation can take place via a digital circuit that relays the output signal directly to an apparatus that further processes the output signal of the switching position detection device. For example, such a digital circuit can be a binary decoder.

As shown by this configuration of the switching position detection device in accordance with the present invention, even a plurality of different switching positions is possible at a reduced hardware cost as compared to the prior art.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be described in greater detail below based on a preferred embodiment with reference to the attached figures:

FIG. 1 illustrates a three-dimensional schematic view inside the housing of a steering column switch with a switching ram guided into a detent curve and a device for optoelectronically detecting the switching positions of the switching ram;

FIG. 2 illustrates a longitudinal view through the housing as shown in FIG. 1; and

FIG. 3 illustrates a horizontal view through the housing as shown in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

A steering column switch for a motor vehicle is incorporated in a housing 1. Housing 1 is part of a steering column module. A detent curve 2 is situated inside housing 1. A spring-loaded switching ram 3 (i.e., a switching element) engages and is guided in detent curve 2. Detent curve 2 engaged by switching ram 3 is used to generate the desired haptics. The individual switching positions of switching ram 3 along detent curve 2 have a haptic, tactile design.

A switching position detection device 4 in accordance with the present invention is used to electrically detect the individual switching positions of switching ram 3 inside detent curve 2. Switching ram 3 moves relative to detent curve 2 in order to move to different switching positions. Switching position detection device 4 operates optoelectronically and includes an optical receiver 5 and a plurality of optical transmitters S₁-S₄. Optical transmitters S₁-S₄are positioned on one side of device 4 to illuminate optical receiver 5 which is positioned on the opposite side of device 4. Optical transmitters S₁-S₄and optical receiver 5 together form a light-beam assembly (i.e., an optical switching assembly). Only optical transmitters S₁and S₂are illustrated in FIG. 1.

Optical transmitters S₁-S₄are LED's that sequentially emit light beams. Optical receiver 5 is designed as a photodiode. Optical receiver 5 and optical transmitters S₁-S₄are positioned together on a flexible printed circuit board 6 and form part of a light-beam assembly (i.e., an optical switch assembly). The desired photoelectric barrier assembly between optical transmitters S₁-S₄and optical receiver 5 is formed by abutments 7, 8 molded to housing 1, which have secured to them the printed conductor sections bearing optical receiver 5 and optical transmitters S₁-S₄Optical transmitters S₁-S₄and optical receiver 5 are fixed in position.

A shutter 9 is connected to switching ram 3 and is positioned between optical receiver 5 on the one side of device 4 and optical transmitters S₁-S₄on the other side of device 4. Shutter 9 may be formed as part of switching ram 3. Shutter 9 moves in accordance with the movement of switching ram 3 along detent curve 2 as the switching ram moves between switching positions. As switching ram 3 moves in detent curve 2 between switching points, shutter 9 moves relative to optical transmitters S₁-S₄and optical receiver 5 which are fixed in position. In the embodiment shown, shutter 9 includes two shutter apertures 10, 11. Depending on the position of switching ram 3, and hence of shutter 9, all or some individual optical transmitters S₁-S₄are shaded, while the light of the remaining optical transmitters S₁-S₄pass through shutter apertures 10, 11 or even by the edge of shutter 9 to optical receiver 5 in a given switching position of switching ram 3. Given a change in the switching position of switching ram 3, either a wider light path from one of optical transmitters S₁-S₄to optical receiver 5 can be opened, or an already opened light path can be shaded.

In the switching position shown in FIG. 1, optical transmitter S₃illuminates optical receiver 5 as shutter aperture 10 of shutter 9 does not impede the related beam path. By contrast, shutter 9 shades optical receiver 5 against illumination by optical transmitters S₁, S₂and S₄.

A part of detent curve 2 designed as a plastic injection molded part is a flange 12 that incorporates four light-beam apertures L₁-L₄on a part of an opaque element forming the detent curve. Light-beam apertures L₁-L₄are conical and taper away from optical receiver 5. Situated immediately behind flange 12 is abutment 7. The section of printed circuit board 6 which carries optical transmitters S₁-S₄is secured to abutment 7. Optical transmitters S₁-S₄are hence located right in back of light-beam apertures L₁-L₄viewed from the direction of optical receiver 5.

A separate light-beam aperture L₁-L₄is allocated to each respective optical transmitter S₁-S₄. The inside diameter in the narrowed section of each light-beam aperture L₁-L₄is less than the light-emitting surface of the respective LED S₁-S₄projected into the plane of optical receiver 5. Light-beam apertures L₁-L₄hence act as a quasi-shutter. The quasi-shutter prevents stray radiation, but in particular makes it possible to orient the light beam of each optical transmitter S₁-S₄as intended, directed at optical receiver 5, even if the individual optical transmitters S₁-S₄are situated behind light-beam apertures L₁-L₄with specific tolerances. Arranging the emitted light beams as intended hence depends on the tolerance of the assembly of light-beam apertures L₁-L₄. However, the latter can be disregarded, as light-beam apertures L₁-L₄or flange 12 with light-beam apertures L₁-L₄are part of detent curve 2.

FIG. 2 illustrates housing 1 of the steering column switch in a longitudinal section. As evident from this assembly, optical transmitters S₁-S₄can also be positioned at a varying height relative to optical receiver 5.

FIG. 3 illustrates the assembly of optical transmitters S₁-S₄that are adjacent to the curved abutment. As is also evident, flange 12 of detent curve 2 has recesses for accommodating a respective optical transmitter S₁-S₄, so that each optical transmitter S₁-S₄is quasi-encapsulated, and light can only exit through light-beam apertures L₁-L₄. This especially helps to avoid stray radiation.

The detection of different switching positions will be described below based on an embodiment in which one optical transmitter and a plurality of optical receivers are provided. The optical receivers are positioned behind the light-beam apertures as part of the detent curve viewed from the direction of the optical transmitter.

The switching element of the switching position detection device is pivoted around two rotational axes. The switching element displacement is coupled with a shutter, which in the embodiment shown consists of a retainer that carries horizontal and perpendicular shading strips. Each shading area is used for detecting the switching position of a respective receiver assembly. A receiver assembly having optical receivers E₁and E₂with the horizontal shading strip lying in front viewed from the position of the optical transmitter is used for switching position determination to ascertain switching element displacement in a y-direction. The other receiver assembly having optical receivers E₃-E₅with the perpendicular shading strips lying in front viewed from the position of the optical transmitter is used to determine a switching position of the switching element in an x-direction.

The optical receivers E₁, E₂or E₃-E₅are each spaced one make-and-break cycle apart respectively. The height of the horizontal shading strip corresponds to two perpendicular make-and-break cycles, while the width of the perpendicular shading strip measures three horizontal make-and-break cycles. Two optical receivers E₁, E₂can be used in the y-direction to detect four switching positions. Three optical receivers E₃-E₅can be used in the x-direction to detect six switching positions in this embodiment. The states of the individual optical receivers E₁-E₅in the different switching positions are specified in the following table:

y-positionE₁E₂x-positionE₃E₄E₅1brightdark1brightbrightdark2darkdark2brightdarkdark3darkbright3darkdarkdark4brightbright4darkdarkbright5darkbrightbright6brightbrightbright

Reference List

1 Housing
2 Detent curve
3 Switching ram
4 Switching position detection device
5 Optical receiver
6 Flexible printed circuit board
7 Abutment
8 Abutment
9 Shutter
10 Shutter aperture
11 Shutter aperture
12 Flange
L₁-L₄Light-beam apertures
S₁-S₄Transmitters

While embodiments of the present invention have been illustrated and described, it is not intended that these embodiments illustrate and describe all possible forms of the present invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the present invention.