SE468143B - DEVICE FOR SATISFACTION OF PHYSICAL SIZES AND THEIR CONVERSION TO ELECTRICAL SIZES, SPECIFICALLY FOR SOCIETY OR DISTANCE Saturation - Google Patents

Description

The object of the invention is thus to provide a wear-free position or distance sensor. which is able to convert even larger linear movements or positions (of the order of 10-20 cm) to a corresponding analog electrical quantity with high accuracy. without the requirement for good magnetic coupling, as in the known systems, being of decisive importance.

Advantages of the invention The device according to the invention solves this problem in accordance with the features of the main claim and has the advantage that in simple construction a very accurate position determination is possible, whereby the degree of coupling between the transmitter coil and then an intermediate coil, as well as between this and two receiver coils . Even one that is unavoidable for construction reasons, for example. only weak coupling can be compensated for by correspondingly higher transmitter level and, for example, several winding turns on the intermediate coil within wide limits.

Under certain circumstances, an even weaker magnetic coupling between the intermediate coil, which transmits the transmitter signal. to the frequency modified, to the receiver coils, and the receiver coils. does not, however, affect the basic function. since a trouble-free smoothing can be achieved by a correspondingly higher sensitivity of the receiver coupling. which can be achieved by suitable amplifiers and other couplings without major problems.

It is therefore a further essential advantage of the present invention that there is great design freedom with regard to the arrangement of the various coils in the position measuring device, these being preferably also suitable for additional installation or superstructure on existing functional units, such as shock absorbers and the like. The invention thus has a preferred area of use as a position sensor in the level control of motor vehicles and corresponding mounting on, for example, shock absorbers, which will be explained more below. 10 15 20 25 30 35 468 143 The features specified in the subclaims make it possible to further develop and improve the device specified in the main claim for measuring physical quantities and their conversion to electrical quantities. Particularly advantageous is the unambiguous reference of the receiver coils, exclusively in relation to the moving intermediate coil by selective frequency coupling, which certainly prevents a signal energy emanating from the transmitter coil which is not affected by a position shift, will be immediately evaluated by the receiver coil. the take-up coils.

Drawings The drawings show exemplary embodiments of the invention, which will be described in more detail. Figs. 1 and 2 schematically show possible devices of transmitter coil, movable intermediate coil and receiver coils in relation to each other, and Fig. 3 shows the distance dependence of the obtained output quantity in the form of a diagram, while Fig. 4 shows a possible embodiment of a electrical wiring diagram, where transmitter-. the intermediate and receiver coils form part of the overall connection. Fig. 5 shows the course of the coil current in the intermediate coil in a time diagram, and Fig. 6 shows in a possible application example the installation of the transmitter, intermediate and receiver coils in the shock absorber of a motor vehicle. which by extension with a rubber bellows can also function as an additional spring.

Description of exemplary embodiments The basic idea in the present invention is that one does not have a pure magnetic damping element between transmitter and receiver coils, but connects an additional, movable intermediate coil. wherein the whole thing is electrically so done. that the intermediate coil from the transmitter energy emits a harmonic wave to the receiver coils, so that the receiver coils are selectively affected only by the intermediate coil and so far also affected by its position and can reproduce this.

Fig. 1 schematically shows a first possible arrangement of the coils in relation to each other. The stationary transmitter coil 10 15 20 25 30 35 468 143 1 has a displaceability within one in relation to the position or the linear distance to be determined. thus movable intermediate coil 2, wherein next to this construction and in the exemplary embodiment shown in Fig. 1 next to the transmitter coil on each side there is a receiver coil 3a. 3b. In end view you thus have the rotationally symmetrical shape shown on the right in Fig. 1. The symmetrical arrangement of the two receiver coils 3a. 3b on the sides of the transmitter coil is not mandatory. To the extent that constructive coercive conditions allow. For example, the receiver coils can also be arranged in other places, for example orthogonally to the transmitter coil 1, as shown in Fig. 2 by the receiver coils 3a ', 3b'.

From this coil configuration the block diagram in Fig. 4 is then derived, so that an oscillator 10 generates a suitable oscillation frequency, for example a square wave signal with a fixed frequency in the order of magnitude between 10-50 kHz. After halving the frequency at 11, it reaches via a level adjuster 12 and a bandpass filter 13 for filtering out the fundamental frequency of the signal to the transmitter coil 1. The resonant frequency of the bandpass device or filter 13, where the transmitter coil 1 can also constitute a component, is thus at 1/2 fosc. The transmitter coil therefore radiates an electromagnetic alternating field with half the oscillator frequency, and the filter 13 is also arranged to ensure that this signal is sufficiently low on harmonics.

In accordance with a feature of the present invention, the intermediate coil 2, which can be arranged without the need to take into account the coupling conditions to the transmitter coil 1, and in which a voltage with this half oscillator frequency from the transmitter coil will be induced, is connected in series with a diode or any other rectifying unit. so that in the intermediate coil 2 flows a current, as shown in the timing diagram in Fig. 5, namely a rectified alternating current, which basically forms a frequency mixture, which is characterized by the following formula also with respect to its harmonic content: 468 145 Tr 2 3 f (mt) = A “[d + ïcoswt + åcos2wt - ïšcos4mt + ...] This current Ii the intermediate coil 2 in turn generates a magnetic alternating field. so that in the receiver coils 3a, 3b; 3a ', 3b', voltages are induced which arise from the sinusoidal current in the transmitter coil 1 and from the harmonic-containing current in the intermediate coil 2.

To this extent, the movable intermediate coil 2 constitutes its own transmitter, which obtains the energy necessary for the transmission by magnetic connection to the fixed transmitter coil 1, whereby by the intermediate coil 2 being connected in series with the diode 2a, a current flows in the intermediate coil. containing a particularly large signal share with double frequency. corresponding to the above formula 6šcos2ut).

However, the frequency mixture intercepted by the receiver coils (3a, 3a ', 3b, 3b') is also position dependent. and since the intermediate coil 2 preferably changes its position in relation to the receiver coils in the reverse relationship. also in different ways.

A weak magnetic coupling between the coils 1 and 2 on one side and 2 and 3a, 3a '. 3b, 3b ', on the other hand, can be equalized within wide limits by a correspondingly higher output level of the transmitter signal and by increasing the sensitivity of the receiving electronics, whereby it can be controlled. Due to the ratiometric measurement from the amplitude ratio between the signals from the two receiver coils, the position provides a position indication.

The further processing of the signals from the receiver coils is thus such that the signal part coming from the transmitter coil 1 is suppressed in post-coupled band-blocking circuits 14a, 14b for the two receiver coils, whereby naturally in a similar manner In this way, bandpass filters with steep throughput curves can be used, which are set exclusively on the second harmonic of the intermediate coil signal. However, by suppressing the transmitter frequency in the band latches 14a, 14b, the total harmonic signal content in the receiver coils can be used for position determination. After the belt locks l4a, l4b are thus more uniformly connected. which rectify the harmonic signals, preferably using rectifiers 15 which are controlled by the rate of the oscillator 10 for both signals. In order to obtain the amplitude ratio between the harmonic signals emitted from the receiver coils, a difference can then either be formed immediately, or it is preferably possible via a control amplifier 16 for the receiver coil 3a connected, for example, after the rectifier. 3a 'and feedback via line 16 set the level adjuster 12 to a fixed value, independent of the position of the intermediate coil 2. Since the gain or attenuation factor of the level adjuster 12 also affects the DC voltage obtained after rectification from the second receiver coil 3b, 3b ', its magnitude immediately gives the ratio between the amplitudes of the harmonic voltages in the two receiver coils. This DC voltage signal can then be used via a low-pass filter 17 connected and further processed as corresponding to the position of the intermediate coil.

The following formulas apply to the control loop: U1 = Uo || ... n 'v' ko - k1 - a and 1 V- Uo-EQ-k1a where: the amplitude of the fundamental before the level adjuster the gain of the level adjuster O for the harmonic. induced in the receiver coil 1 hJF-'IUI-'C the amplitude of the harmonic, induced in the receiver coil 2 NCZCIWFWCG the gain factor for the rectification 10 15 20 25 30 35 468 143 '7 For the level control the following applies: U = UC ° v' ko - k2 - a Ü = U 'k ° k1 - = kl U - k - kz kz In the exemplary embodiment with the coil device corresponding to Fig. 2 is. Due to possible or desired constructive boundary conditions, the receiver coils 3a 'and 3b' are arranged orthogonal to the transmitter coil, so that in the receiver coils only that voltage can be induced. since the harmonic current in the intermediate coil 2. Since in the case according to Fig. 2 the two receiver players 3a ', 3b' are arranged symmetrically symmetrically with respect to the displacement movement performed by the intermediate coil 2, in the case of phase-correct rectification with the the rectifiers 15 control an output voltage profile U. which has the principal approximate flat S-shape shown in Fig. 3 depending on the distance and position s, respectively. In this case, s = 0 means that the intermediate coil 2 is in the middle position.

It is possible without problems by the position-dependent design of the coupling factor ko between transmitter coil 1 and intermediate coil 2, for example by special design of the transmitter coil, to achieve a linearisation of the function U = s (s) shown in Fig. 3 within the working range.

Due to the available constructive freedom in the coil placement, the invention can preferably be used for additional installation or extension to existing functional units.

In the production according to Fig. 6, a shock absorber 18 is shown, for example for a passenger car. which by adding a rubber bellows 19 can also function as an additional spring. In this shock absorber, the transmitter coil is built-in annularly and on each side thereof, i.e. at the top and bottom adjacent to it the two receiver coils 3a, 3b, while the intermediate coil is arranged in the outer part of the relative shock absorber telescopically in the same movable inner part It is further recognized that the block diagram shown in Fig. 5, which shows the invention with discrete coupling steps, does not restrict it. but in particular serves to illustrate the functional basic principles and special functions of the invention in a possible embodiment.

It is understood that the individual components and blocks can be constructed analogously, digitally or even in hybrid technology, or even in whole or in part, corresponding areas of program-controlled digital systems, for example also microprocessors, microcomputers, digital or analog logic connections and the like.

All in the description. the features shown in the appended claims and the drawings may, both individually and in any combination, be essential to the invention.

Claims (10)

468 145 Patent claims Device for measuring physical quantities and their conversion into electrical quantities, in particular for position or distance measurements and in particular for determining the suspension condition of vehicles or the like, by sensing the current length of a shock absorber, with a stationary transmitter coil and two stationary receiver coils, characterized in that an intermediate coil (2) movable in relation to the said coils (1, 3a, 3b; 3a ', 3b') is arranged to move from the transmitter coil (1) to the receiver coils (3a, 3b; 3a ', 3b') transmit a respective position-dependent, different signal with a frequency which is different in relation to the transmitter frequency. Device according to claim 1, characterized in that the short coil intermediate coil (2) is arranged inside the transmitter coil (1) extending over the length of the longitudinal displacement, each with a receiver coil (3a, 3b) at the opposite ends of the transmitter coil (1). Device according to claim 1, characterized in that the intermediate coil (2) of shorter length is arranged inside the transmitter coil (1) extending along the position offset, the receiver coils (3a ', 3b') being arranged orthogonally in relation to the transmitter coil ( 1) along a common axis and orthogonally to the intermediate coil movable inside the transmitter coil. Device according to one of Claims 1 to 3, characterized in that the signal induced by the transmitter coil (1) in the movable intermediate coil (2) by electromagnetic coupling by arranging a non-linear electrical coupling element to the intermediate coil in its form and thus changes in its frequency, at least in part, to the extent that after the receiver coils (3a, 3a ', 3b, 3b') coupled evaluation units under suppression of the transmitter coil signal receive exclusively position-dependent harmonic signals from the intermediate coil. Device according to one of Claims 1 to 4, characterized in that a diode (2a) is connected in series with the intermediate coil (2) in such a way that the uniform alignment of the one in the intermediate coil (2) of the transmitter coil (1) induced alternating current, a harmonic-containing and at the same time position-dependent signal is obtained in the receiver coils (3a, 3a ', 3b, 3b'), which in case of asymmetrical arrangement of the receiver coils (3a, 3b) in relation to the intermediate coil offset both receiver coils are positioned depending on the position, different amplitudes of the received signal and when symmetrically positioning the receiver coils (3a ', 3b') in relation to the displacement path of the intermediate coil, a polarity of a linearized DC output signal is changed over the center passage. Device according to one of Claims 1 to 5, characterized in that an oscillator (10) for generating a square signal with a given frequency (10-50 kHz) and a frequency divider (11) connected thereto, a level switches (12) and a harmonic suppressing bandpass filter (13) are provided, to which the latter transmitter coil (1), possibly as a component therein, is connected, and that after the two receiver coils (3a, 3a ', 3b, 3b') are coupled filters (14a, 14b), which suppress at least the fundamental tone of the oscillator signal which feeds the transmitter coil (1) so that exclusively the harmonic-containing and thus position-dependent receiver coil signal is rectified for evaluation. Device according to one of Claims 1 to 6, characterized in that after the two receiver coils (3a, 3a ', 3b, 3b'), after filtering out the transmitter coil fundamental, for rectifying the frequency-shifted, position-dependent transmissions, -68 143 The tone signals, possibly rectifiers controlled by the oscillator, are connected. Device according to one of Claims 1 to 7, characterized in that the rectifier output of one of the receiver coils (3a, 3a ', 3b, 3b') is fed back to the input of the level switch (12) before the transmitter coil (1) in such a way , that the final output value of the second receiver coil represents the ratio between the amplitudes of the harmonic voltages induced in the two receiver coils of the intermediate coil (2). Device according to one of Claims 1 to 8, characterized in that the coil device is built in for position determination in a shock absorber (18) of a vehicle, the stationary transmitter coil (1) having a receiver adjacent to each side. coils (3a, 3b) are so mounted at the inner circumference of a first shock absorber part that over the displacement path of an inner, relative to the outer movable shock absorber portion, the intermediate coil (2) attached thereto can change its position in relation to the receiver coils. Device according to one of Claims 1 to 9, characterized in that the controlled rectification of the harmonic signal can be performed by means of the oscillator frequency through the frequency division before the transmitter coil (1).