EP1620929A1

EP1620929A1 - Slipring comprising a slideway that is subject to loss

Info

Publication number: EP1620929A1
Application number: EP04727871A
Authority: EP
Inventors: Nils Krumme
Original assignee: Schleifring und Apparatebau GmbH
Current assignee: Schleifring und Apparatebau GmbH
Priority date: 2003-04-28
Filing date: 2004-04-16
Publication date: 2006-02-01
Also published as: DE10319248A1; US20060089009A1; DE10319248B4; WO2004098018A1; US7547212B2

Abstract

The invention relates to a device for transferring electrical energy between at least two units that can move relative to one another, for example, to a device provided in the form of a slideway or slipring. A moving pick-off is displaced over a slideway, which is situated along the path of motion, and is in contact with said slideway. According to the invention, the slideways are subject to loss and attenuate the transmitted signal whereby eliminating the need for additional terminating resistors on the slideways.

Description

Slip ring with lossy slideway

Technical field

The invention relates to systems for electrical transmission between two mutually movable units. These are used, for example, as linear grinding tracks in linearly movable units, such as crane systems, or as slip rings for the transmission of rotation, for example in machine tools or in computer computers.

PRIOR ART Contacting and contactless transmission techniques are known for slip rings or grinding tracks. Since the technical principle of operation of slip rings for rotary transmission and of linear slide tracks for linear or curved slide tracks is the same, no further distinction is made between them in the following explanations. The terms are used synonymously.

The functioning of an electrical signal transmission is briefly explained below using the example of a slip ring. Circular or ring-shaped slideways are attached to a first unit. Opposite this, a second unit moves, with a sliding contact, which rests on the sliding track and is in sliding contact with it during the movement. Electrical current can now be transmitted via this galvanic contact. As an alternative to a loop contact is also possible without contact. In this case, the coupling is preferably capacitive or inductive, for example via a field probe. Such contactless transmissions are preferably used at medium to high frequencies. Reference is made here to the term of the grinding track, although in principle this is also suitable for contactless and contacting transmission. Furthermore, no distinction is made between the transmission of electrical signals and energy, since the mechanisms of transmission are basically identical here.

Especially with medium and high frequency signals, a problem with these arrangements is to transmit these signals along the slideway with as little interference as possible. With the normally used slideways, only electrical signals can be transmitted whose wavelength is long compared to the electrical path length of the slideways. In the case of small devices, for example slip rings with a diameter of only a few millimeters, the length of the slide track is generally negligible, so high bandwidths can be achieved here. In the case of large arrangements, for example with slip rings as used in computer tomographs, and which have a circumference of more than five meters, only relatively low bandwidths can be realized.

A solution shown in US Pat. No. 5,018,174 improves the transmission properties of the slideways. There will be a terminating resistor here arranged diametrically opposite the feed position. The disadvantage of this arrangement is that no reflection-free termination can actually be achieved with this so-called terminating resistor. At the point of the so-called terminating resistor, reflections still occur, which lead to interference in the signal. Furthermore, in particular when a signal is fed in from the second unit, a further movable tap (brush or brush block) must be provided on the second unit. This further tap is arranged diametrically opposite (offset by 180 degrees with respect to the coupling point). With such an arrangement, two movable taps are therefore always necessary. This leads to increased manufacturing costs and increased wear in the case of a sliding contact arrangement. In fact, the benefits of this increased effort are very limited.

Furthermore, contactless transmission systems are known from the prior art, such as, for example, from DE 44 12 958, which have no self-contained conductor track. Thus, the conductor track is interrupted at at least one point. This is acceptable for contactless transmission. As a result, these conductor tracks can be terminated without reflection at each end by connecting them to a resistor which corresponds to the characteristic impedance of the conductor track. This means that a signal that is fed in at any point on the conductor track can be transmitted in both directions from the point of the feed to each of the spread closed ends. There it is finally absorbed and can therefore no longer be reflected back into the conductor track. If the signal were reflected, it would be received by the receiver again. Such multiple reception can lead to impairment or even a massive interference in the transmission. However, slip rings, in which a brush preferably runs on a slide track, cannot be produced economically with one interruption. For example, increased brush wear occurs at the interruption. Furthermore, a closed path is also preferred for manufacturing reasons, since the mechanical stresses are distributed evenly over the circumference. Finally, when passing with a brush of such an interruption, a short circuit of this interruption occurs, which at least for a short time leads to the interference of the signal to be avoided. At high data rates of several 100 Mbit / s, this can lead to high data losses.

Presentation of the invention

The object of the invention is to improve slip rings or slip tracks in such a way that they have an improved signal transmission, in particular with reduced reflections, compared to the prior art, with simpler and therefore less expensive manufacture.

A solution to this problem according to the invention is specified in the independent claim. Further developments of the invention are the subject of the dependent claims. A device according to the invention for the transmission of electrical signals or energy between at least two mutually movable units u includes at least one preferably circular and self-contained slideway made of electrically conductive material arranged along the path of movement and at least one tap movable along this slideway for or decoupling of electrical signals. Slideways according to the invention have damping along their path, which dampens the signal transmitted via the slideway.

The previous state of the art is based on the fact that the signal is to be transmitted over the slideway with as little loss as possible and that the slideway is terminated at a discrete point with as little reflection as possible. Studies have shown, however, that a reflection-free finish cannot be achieved, especially with closed grinding tracks. Closed grinding tracks are, however, particularly inexpensive to manufacture and, particularly in the case of contacting tapping, have significantly less wear on the contact brushes. In the case of interrupted grinding tracks, greater wear results from the fact that the contact brushes must run over at least one threshold or groove. However, if one has to do without such a groove precisely for reasons of wear, the rotating taps known from the prior art cited above also offer an inadequate effect. In contrast, the invention takes a fundamentally different approach. The slideways themselves are lossy so that the signal is weakened as soon as it traverses the slideways. The terminating resistors on the slideways can thus be omitted. Any reflections at the ends of open slideways or other interferences are attenuated and thus have only an insignificant influence on the signal to be transmitted. It goes without saying that a grinding track according to the invention can be used not only with grinding brushes, but also with contactless taps. It is essential to the invention that this is a closed track or grinding track. The damping of the slideway must now be so great that an electrical signal is significantly weakened during a complete revolution and does not significantly falsify the original signal. Tests have shown that the attenuation over the complete cycle must be greater than 6 dB. An attenuation greater than 10 dB is advantageous. If a signal is attenuated by 6 dB, that is to half the amplitude of the signal voltage, in particular in slip rings, a clear evaluation of the signal is still possible despite a superposition of the currently received signal. Higher attenuation values result in better signal quality. However, the received signal amplitude also decreases due to the damping of the slideways, so that the optimal damping of the slideway must be determined from case to case.

A slideway according to the invention for the transmission of electrical signals is therefore lossy, so that it attenuates a transmitted signal in such a way that the signal amplitude is reduced by at least β dB, preferably at least 10 dB, when the entire length of the slideway is traversed.

In a particularly advantageous embodiment of the invention, the slideways comprise a resistance material. Resistance materials of this type are, for example, coal, ceramic-metal compounds or also high-resistance metal alloys. Such a configuration creates the losses for damping the transmitted signal into the slideways themselves.

A further advantageous embodiment of the invention is that the sliding tracks are provided with additional damping resistors. This means that conventional slideways can be used in which the damping is produced by connecting them with additional damping resistors. These additional damping resistances must have at least one lossy component. In addition, they can have inductive or capacitive components. This enables frequency-dependent damping. According to the invention, the damping resistors are connected in parallel between two slideways or from one slideway to a ground path or ground surface.

In a further advantageous embodiment of the invention, the number of damping resistors is greater than two. According to the invention, the grinding tracks should not be terminated exclusively, rather, damping should be realized in the course of the grinding tracks. This requires at least three damping resistors. With a higher number of damping resistors, the course of the damping becomes more continuous and the reflections generated at the locations of the damping resistors decrease. However, the production costs increase with the number of damping resistors. Tests to optimize the transmission properties have shown that with 3, 4 or even 5 damping resistors, a significant improvement over the prior art can be achieved.

In a further advantageous embodiment of the invention, the damping resistances are distributed uniformly over the length of the sliding tracks. This results in an even damping curve. However, the damping curve could also be adapted for special requirements. For example, a higher number of damping resistors could be installed in certain locations. The damping resistances preferably all have the same value.

In a further advantageous embodiment of the invention, the damping resistors are optionally arranged in series or parallel to the slideways. A parallel connection to known slideways, be it with solid brass slideways or in printed circuit technology, is particularly simple. In particular, the conductor tracks need not be interrupted for this. Dampers can also be used in series with the grinding tracks (preferably at interrupted points). tion resistors are attached, in which case the gap is closed again by the damping resistor. A significantly higher damping with better impedance matching can be achieved via a combined series and parallel connection. The dimensioning can take place here, for example, in accordance with the known attenuators (T-link or Pi-link).

Description of the drawings

The invention is described below by way of example without limitation of the general inventive concept on the basis of exemplary embodiments with reference to the drawings.

Fig. 1 shows schematically an arrangement according to the invention in general form.

Fig. 2 shows a symmetrical conductor arrangement.

Fig. 3 shows an asymmetrical conductor arrangement.

Fig. 4 shows an arrangement according to the prior art.

5 shows the conclusion of a closed grinding track.

6 shows the end of an interrupted grinding track.

Fig. 7 shows the equivalent circuit diagram of a prior art arrangement with a closed sliding track.

8 shows an equivalent circuit diagram of an arrangement corresponding to the prior art with an interrupted grinding track. FIG. 9 shows the equivalent circuit diagram of an arrangement according to the invention with damping resistors connected in parallel.

10 shows the equivalent circuit diagram of an arrangement according to the invention with damping resistors connected in series.

11 shows the equivalent circuit diagram of an arrangement according to the invention with damping resistors connected in series and additionally in parallel.

1 shows a device according to the invention in schematic form. A sliding track (10) is used to transmit electrical signals. In practice, of course, arrangements consisting of several slideways, such as those shown in FIG. 2 or 3, are used. For the sake of simplicity, the following explanations only refer to one slideway

(10) Referenced. An arrangement with a transmitter which is fixedly coupled to the sliding track and a receiver which is movably arranged relative to it is explained here by way of example. The direction arrow shows the possible directions of the movement. Of course, the subject matter of the invention can also be transferred to arrangements in which, for example, the transmitter is arranged movably with respect to the sliding track and the receiver is firmly connected to it. Likewise, the transmitter and receiver can also be arranged so as to be movable relative to the sliding track. At the coupling point (5) a signal from the transmitter (4) the sliding track (10) is coupled. A movably arranged receiver (6) decouples a received signal from the slideway at its current position, the decoupling point (7). Furthermore, 4 damping resistors (15) are arranged at different positions of the slideway as an example. The effect is as follows: a signal fed in at the coupling point (5) propagates in both directions along the ring-shaped slideway. The signal component, which propagates clockwise, reaches the decoupling point (7) after a short time with relatively little damping. The other signal component, which propagates in the opposite direction, reaches the decoupling point (7) with a delay and with significant damping due to the lossy slideway (10). This second signal can therefore hardly influence the first signal.

2 shows a typical structure of a conductor system, which consists of two sliding tracks (1) and (2) and is used to carry electrical signals. Both slideways are fastened in a carrier made of a dielectric (3). Such a conductor arrangement preferably transmits symmetrical signals.

A further arrangement in the form of an asymmetrical conductor system is shown by way of example in FIG. 3. An outer conductor (2) and an inner conductor (1) are provided, spaced apart by a dielectric (3). 4 shows a slip ring arrangement according to the prior art. A closed sliding track (10) has a transmitter (4) at the coupling point (5). A termination (8) is arranged at a diametrically opposite termination position (9). A signal is picked up at the decoupling point (7) by a movably arranged receiver (6).

5 shows the arrangement of the termination on a closed sliding track (10). The termination (8) is attached to the connection position (9). The arrows (11) indicate a cut to by the grinding track (10) on the ^'later reference still is made.

In FIG. 6, the arrangement of the termination on an interrupted grinding track (10) is shown in accordance with FIG. 5. The two ends of the sliding track are connected to the terminations (8) and (12) at the termination positions (9) and (13). The section through the sliding track (10) is marked with the arrows (14).

FIG. 7 schematically shows an equivalent circuit diagram of a closed conductor arrangement corresponding to the prior art with a termination corresponding to FIG. 5. The electrical impedances are viewed in the direction of the sectional arrow (11). If we now consider the impedances of the slideway from the base of the arrows (11), the following arrangement can be seen:

• a piece of the track (10) followed by

• the degree (8) followed by • the entire grinding path (10), here shown as (10 ') for the sake of clarity, followed by

• The termination (8), which is now run through a second time by the electric shaft and is accordingly represented here as (8 ').

In the case of further runs, the grinding track (10) and the end (8) are run through again, shown here as (10 ″) and (8 ″) for the second complete run.

With this arrangement, a reflection-free termination cannot be achieved, since the trajectory (10) is followed again by the termination (8). This results in a parallel connection of the impedance of the termination (8) and the transformed impedance of the line (10). Furthermore, the shaft can theoretically run through the line as often as required. However, it is somewhat weakened from run to run. Nevertheless, clear superposition with signals staggered in time, corresponding to the running time of the entire length of the slideway (10), can also be determined here in practice.

FIG. 8 shows the equivalent circuit diagram of a corresponding arrangement with an interrupted sliding path (10) from FIG. 6. It can be seen here that, starting from the base of the cutting arrow (14), there is a piece of grinding track (10) completed with the closure (8). In this case, a largely reflection-free conclusion can actually be achieved. However, for this purpose the grinding path has to be interrupted and furthermore an arrangement with a transmitter movable to the grinding path cannot be realized, since the interruption must be located exactly opposite the transmitter. To explain the effect, reference is made to US 5,018,174, the content of which is to be part of this document.

In Fig. 9, the equivalent circuit diagram of an arrangement according to the invention is shown with damping resistors connected in parallel. According to the sections from FIGS. 5 and 6, there is a series connection of short pieces of a slideway (10) followed by damping resistors (15). The damping resistors are arranged parallel to the pieces of the sliding track (10). In Fig. 2 this would mean, for example, a connection of the two sliding tracks (1) and (2) by means of a damping resistor (15). Analogously, in Fig. 3 the inner track (1) would be connected to the surrounding track (2). The pieces of the slideway are much shorter than the entire length of the slideway (10). Thus, a signal which is fed into the slideway (10) is significantly attenuated even after a short piece of slideway, without this having to run through the entire length of the slideway (10) several times, as explained above. This eliminates interference due to the superimposition of time-delayed signals, which occur when the entire ring is run several times.

FIG. 10 shows an equivalent circuit diagram of a device according to the invention analogous to FIG. 9. However, instead of the parallel resistors, the damping resistors (16) are connected in series with the line sections of the slide track (10). 11 finally shows an equivalent circuit diagram analogous to FIGS. 9 and 10, damping resistors being connected in series and in parallel with the line sections.

Besugsseichenliste

1 First grinding track

2 Second slideway 3 Dielectric

4 transmitters

5 coupling point

6 receivers

7 decoupling point 8 termination

9 Closing position

10 slideways

11 Cut through grinding tracks

12 Completion 13 Completion position

14 Cut through grinding tracks

15 damping resistance (parallel!

16 damping resistor (serial)

Claims

1. Device for the transmission of electrical signals or energy between at least two mutually rotatable units comprising at least one closed and arranged along the path of rotation and closed track (10) made of electrically conductive material and at least one tap movable along this track for on or off Coupling of electrical signals into or out of the slideway, characterized in that at least one slideway is lossy and attenuates a transmitted signal in such a way that the signal amplitude is reduced by at least 6 dB, preferably at least 10 dB when the entire length of the slideway is passed.

2. Device according to claim 1, characterized in that the slideways comprise a resistance material, such as coal or ceramic-metal compounds.

3. Device according to claim 1 or 2, characterized in that the sliding tracks are provided with additional damping resistors (15, 16).

4. The device according to claim 3, characterized in that the number of damping resistances is greater than two.

5. Apparatus according to claim 3 or 4, characterized in that the damping resistances are evenly distributed over the length of the slideway and have approximately the same values.

6. Device according to one of claims 3 to 5, characterized in that the damping resistors are optionally arranged in series or parallel to the slideways.

7. Slideway for the transmission of electrical signals or energy between at least two mutually rotatable units, characterized in that the slideway is lossy and attenuates a transmitted signal such that the signal amplitude when passing through the entire length of the slideway by at least 6 dB, preferably two - se at least lOdB reduced.