JPH0754258B2 - A device that measures physical quantities and converts them into electricity - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device having a transmitter coil and at least one receiver coil for measuring a physical quantity and converting it into an electric quantity, such as measuring a position or a displacement amount. The invention relates to a device for measuring the spring damping of a vehicle or the like by detecting the actual length of the shock absorber.

PRIOR ART Known device of this type (US Pat. No. 4162083)
Is used, for example, for measuring and adjusting the height of an automobile by controlling the supply of pressure medium to the shock absorber of the automobile. This height measurement is performed using a mechanical-electrical converter, which translates the shaft twist into an electrical output signal. Therefore, the height sensor has a coil with an electric core, by which the tubular member can be mechanically rotated, including all or part of the coil. The coil current of this inductive converter is then a measure of the height of the vehicle and can be evaluated accordingly.

In addition, a similar or comparable transmitter mechanism for vehicle height adjustment (level control) is described in West German Utility Model Specification No. 2084.
No. 762 and European Patent Application Publication No. 0091017.

Generally, inductive displacement sensors are known in which the fixed coil is braked in a position-dependent manner by means of a movable short-circuit ring, so that the degree of braking has position data. 2 more
It is known to apply a so-called ratiometric measurement braking to one coil (a so-called differential transmitter), but in that case the entire braking action works and can be fully evaluated between the coil and the short-circuit ring. Only if there is sufficient magnetic coupling between. However, it is not always possible to achieve such a degree of magnetic coupling for design reasons, and furthermore, linearity problems arise with such a mechanism.

OBJECTS OF THE INVENTION The problem underlying the invention is therefore the ability to convert even a relatively large linear movement or position (on the order of 10 to 20 cm) into a corresponding analog quantity of electricity with a high degree of accuracy and yet with sufficient magnetic coupling. The need is to provide a wear-free position or displacement transmitter that is not critically a central problem as in known mechanisms.

Structure of the Invention The above-mentioned object or problem is solved by the constituent features of the first aspect of the invention.

By means defined in the second and subsequent claims, suitable modifications and improvements of the device according to the first claim for measuring a physical quantity and converting an electric quantity are possible.
Particularly preferred is that the receiving state of the receiving coil is uniquely related only to the moving intermediate coil, which is provided by selective frequency coupling, so that, for example, the output from the transmitting coil that is not affected by position displacement is output. It is ensured that the signal energy which is applied is not evaluated directly by the receiving coil.

In this case, a simple frequency change can be realized by connecting the movable intermediate coil and the diode in series.
In that case, the aim is to evaluate the harmonics of the transmission frequency.

Claim 7, that is, "both receiving coils 3a, 3'a;
A rectifier, which is clocked by an oscillator in each case, is connected to 3b, 3'b after filtering of the transmitter coil fundamental wave for rectification of the position-dependent harmonic signal subjected to frequency displacement. The output characteristics shown in Fig. 3 may not always be obtained by means of the rectifier 15 (Fig. 4) described in "Devices described in Section 6".
Claim 8, that is, the receiving coils 3a, 3'a; 3b,
One rectifier output side of 3'b is fed back to the input side of the level adjuster 12 in front of the transmitting coil 1, and the changing output value of the other receiving coil is the intermediate coil 2 of both receiving coils.
The output characteristic as shown in FIG. 3 can be obtained for the first time by the device according to any one of claims 1 to 7 which represents the ratio of the amplitude of the harmonic voltage induced by.

Drawings Embodiments of the invention are shown in the drawings and will be explained in more detail in the description below.

Description of Embodiments The essence of the basic idea of the present invention is as follows. That is, instead of disposing a pure magnetic damping member between the transmission coil and the reception coil, another movable intermediate coil is inserted, and the intermediate coil transfers only harmonics from the transmission energy to the reception coil, That is, the receiving coil responds selectively to the intermediate coil, and to that extent also to its position,
The point is to design it electrically so that it can be regenerated.

FIG. 1 schematically shows a first possible array of coils between the coils. The fixed transmission coil 1 has an intermediate coil, i.e., a movable intermediate coil 2, which moves within it corresponding to the position to be measured or the linear displacement length, adjacent to this component and shown in FIG. In the embodiment, receiving coils 3a and 3b are arranged adjacent to the transmitting coil 1 on both sides. In that case, in plan view, the rotationally symmetrical shape on the right side of the drawing of FIG. 1 is obtained. It is not essential to dispose both receiving coils 3a, 3b next to the transmitting coil. The receiver coil may be located elsewhere, e.g. perpendicular to the transmitter coil 1, if design limit conditions permit. Second
As in the case of the receiver coils 3'a, 3'b in the figure.

From this coil arrangement, in that case, the structure diagram structure of FIG.
Oscillator 10 is provided to generate a square signal having a suitable oscillation frequency, for example a fixed frequency in the range 10 to 50 kHz. This frequency is sent to the transmitter coil 1 via a level adjuster 12 and a bandpass filter 13 for filtering only the fundamental wave of the signal, in the halving of the frequency at 11. Therefore, the resonance frequency of the band filter, that is, the filter 13, which the transmission coil 1 may be a constituent element of, is 1 / 2f _OSZ .
The transmitter coil thus radiates an alternating electromagnetic field with half the oscillator frequency and the filter 13 is also provided to ensure that the harmonics of this signal are sufficiently low.

According to the configuration of the invention, it is possible to arrange the transmitter coil 1 without having to comply with the coupling conditions, in which case a voltage whose frequency is half the oscillator frequency is induced by the transmitter coil 1. The intermediate coil 2 is connected in series with a diode or other rectifying element, so that a current flows through the intermediate coil 2 as shown by the current-time curve in FIG. That is, it is rectified alternating current, and as a result it forms a frequency mixed wave, and this mixed wave is also displayed by its formula in the Fourier series expansion of the half-wave rectified alternating current.

This current I flowing through the intermediate coil 2 in turn produces an alternating magnetic field, so that a voltage is induced in the receiving coils 3a, 3b; 3'a, 3'b which is the sinusoidal current of the transmitting coil 1 and the intermediate coil 2. This is due to the current including the harmonics of.

In this respect, the movable intermediate coil 2 is a special transmitter, the energy required for transmission is supplied by magnetic coupling with the fixed transmitting coil 1, in which case the intermediate coil 2 and the diode 2a are connected in series and are thus intermediate. A current flows in the coil 2, which contains a particularly large signal component with a doubled frequency, which corresponds to the above equation (2 / 3cos, 2wt).

However, the frequency-mixed waves received by the receiver coils (3a, 3'a, 3b, 3'b) are furthermore position-dependent, and at different times they differ because the intermediate coil 2 changes its position with respect to the receiver coil. This is because it is advantageous to change in an inversely proportional relationship.

Between coils 1 and 2 on the one hand, coils 2 and 3a, 3'on the other hand
The low degree of magnetic coupling between a, 3b and 3'b can be compensated over a wide range by a correspondingly large output level of the transmitted signal and by an increase in the sensitivity of the receiving electronics. Therefore, it is controllable. In this case, the present invention obtains the position data from the amplitude ratio of the signals of both receiving coils by ratiometric measurement.

The subsequent processing of the signal received by the receive coil is therefore
The signal coming from the transmitting coil 1 is suppressed by the band elimination filters 14a and 14b provided after both receiving coils. In that case, of course, it is likewise possible to use a bandpass filter with a steeply sloping characteristic curve in this case, which is aimed at the second harmonic of the intermediate coil signal. However, due to the suppression of the transmitter frequency in the band stop filters 14a, 14b, the entire harmonic signal of the receiving coil is used for position measurement. Therefore, band stop filters 14a, 14
A rectifier is connected downstream of b to rectify the harmonic signal, in which case a rectifier 15, which is controlled by the pulses of the oscillator 10, is used for both signals. In order to obtain the amplitude ratio of the harmonic signal output from the receiving coil, an immediate difference formation can then be performed, or in particular a control amplifier 16 and a control amplifier 16 placed after the rectifier of the receiving coil 3a, 3'a, for example. The level adjuster 12 is controlled based on a fixed value that does not depend on the position of the intermediate coil 2 via the feedback of the line 16a. Since the amplification factor or attenuation factor of the level adjuster 12 also affects the DC voltage obtained by the other receiving coils 3b and 3'b after rectification, its magnitude is directly related to the harmonic voltage of both receiving coils. Represents the amplitude ratio. This DC voltage signal can then be evaluated and subsequently processed as a position of the intermediate coil by a low-pass filter 17 that follows.

In that case, the following formula is applied to the control circuit.

U ₁ = U ₀ · V · K ₀ · K ₁ · a = 1 and However, U ₀ : Amplitude of fundamental wave before level adjuster V: Amplification factor of level adjuster K ₀ : Coupling coefficient between transmitting coil and intermediate coil K ₁ : Coupling coefficient between intermediate coil and receiving coil 1 K ₂ : Coupling coefficient between the intermediate coil and the receiving coil 2 U ₁ : Amplitude of the harmonic induced in the receiving coil 1 U ₂ : Amplitude of the harmonic induced in the receiving coil 2 a: Amplification factor level control during rectification The following formula applies:

= U ₀ · V · K ₀ · K ₂ · a In the embodiment of the coil arrangement corresponding to FIG. 2, the receiving coils 3'a and 3'b are arranged perpendicular to the transmitting coil in correspondence with possible or desired design limit conditions, so that Only the voltage resulting from the harmonically rich current in the intermediate coil can be induced. In the case of FIG. 2, both receiving coils 3'a, 3'b are arranged symmetrically with respect to the displacement movement carried out by the intermediate coil 2, so that a controlled rectifier 15 is provided. Therefore, if proper rectification of the phase is performed, the output voltage having a shape corresponding to S which is basically flat as shown in FIG. 3 for the displacement amount or the relationship with the position S is obtained. The change U is obtained. At that time, S = 0 means that the intermediate coil 2 is at the center position.

By designing the coupling ratio K ₀ between the transmission coil 1 and the intermediate coil 2 in a position-dependent manner, for example, by the special shaping of the transmission coil, the function u = S (S) shown in FIG.
Can be linearized in the operating range without problems.

Because of the design freedom available during coil positioning, the present invention is particularly useful for retrofitting or expansion of a given functional unit. FIG. 6 shows, for example, a shock absorber 18 for passenger cars, which can also be used as an additional spring by supplementing a rubber strap or belly 19. In this shock absorber, a transmitter coil is annularly incorporated in 1, and the two sides, that is, the upper and lower sides are adjacent to the transmitter coil, are connected to each other.
One receiving coil 3a, 3b and the other intermediate coil are arranged relative to the shock absorber outer member and on an inner member 20 which can be telescopically inserted in and out of this member.

Incidentally, although the configuration diagram shown in FIG. 4 shows the present invention based on individual circuit stages, it does not limit the present invention, and in particular, the functional basic operation of the present invention is specifically explained,
Obviously, it is used to illustrate the special functional processes in possible implementations. The individual components and blocks can be assembled in analog, digital or combined fashion, or they can also be wholly or partly centrally programmed in corresponding areas of a digital mechanism, for example a microprocessor. It is obvious that a microcomputer, a digital or analog logic circuit or the like can be provided.

All of the features shown in the detailed description, the claims and the drawings can be important to the invention individually or in any combination with one another.

The advantage of the device according to the present invention is that the above-mentioned problems are solved by the features of the first claim, and they are as follows. That is, it is possible to perform very precise position evaluation under a simple structure, and in that case, between the transmitter coil and the first intermediate coil, and secondly the intermediate coil.
The degree of coupling between the two receiving coils is of secondary importance only. The fact that, for example, only a few structurally unavoidable couplings can also be compensated for to a large extent by correspondingly higher transmission levels and, for example, more windings of the intermediate coil.

The magnetic coupling between the receiving coil and the intermediate coil, which frequency-modulates the transmitted signal and transmits it to the receiving coil, is in some cases less, but the basic function is likewise not impaired thereby. This is because problem-free compensation is provided by the correspondingly higher sensitivity of the receiver circuit, which can be realized without problems by suitable amplification means and other circuits.

Therefore, another important advantage of the present invention is that it provides great design freedom in the placement of the coils of the position measuring device at any given time. In that case, it is particularly suitable for additional integration or expansion into a given functional unit, for example a shock absorber. The invention therefore has an advantageous field of application as a position sensor in the level control of motor vehicles and is suitable as a position sensor, for example by a corresponding arrangement on a shock absorber.

[Brief description of drawings]

FIG. 1 and FIG. 2 are layout diagrams showing possible layout examples of the transmission coil, the movable intermediate coil, and the reception coil, and FIG. 3 is a diagram showing the relationship between the obtained electrical output amount and the displacement length,
FIG. 4 is a block diagram of an embodiment in which the transmitting coil, the intermediate coil and the receiving coil are members of the entire circuit, FIG. 5 is a waveform diagram showing the temporal change of the coil current of the intermediate coil, and FIG. 6 is a possible application. FIG. 5 is a structural diagram showing an example of incorporating a transmitter coil, an intermediate coil and a receiver coil into a shock absorber of an automobile which can be used as an additional spring at any time by supplementing a rubber band or belly. 1 ... Transmission coil, 2 ... Intermediate coil, 3a, 3b, 3'a, 3 '
b …… Reception coil

Claims (10)

[Claims] 1. A device having a transmitter coil and at least one receiver coil for measuring a physical quantity and converting it into an electric quantity, wherein a fixed transmitter coil (1) and two similarly fixed receiver coils (3a, 3b). 3'a, 3'b) are provided, and the configuration of each coil is such that each coil (1, 3a, 3b;
A movable intermediate coil (2) is arranged with respect to 3'a, 3'b), and the intermediate coil (2) is provided in association with the intermediate coil. ), A signal having a frequency different from the transmission frequency, which is different depending on the position, is transmitted from the fixed transmission coil (1) to each of the reception coils. 2. An intermediate coil (2) having a relatively short length is arranged inside a transmitting coil (1) extending over the length of positional displacement, and one receiving coil (3a, 3b) is provided for each. 2. The device according to claim 1, wherein the transmitter coils are provided at opposite ends of the transmitter coil. 3. An intermediate coil (2) of relatively short length is arranged inside the transmitter coil (1) extending over the length of the displacement, in which case the receiver coil (3'a, 3'b) is arranged along one common axis perpendicular to the transmitter coil (1) and perpendicular to the intermediate coil (2) moving inside the transmitter coil. Range second
The device according to the item. 4. A signal induced by electromagnetic coupling in a movable intermediate coil (2) by a transmitter coil (1), by assigning a non-linear electric circuit element to the intermediate coil, the shape of the signal and the signal In terms of frequency, it is at least partially modified, said modification comprising receiving coils (3a, 3'a; 3b,
The evaluation device connected after 3'b) is adapted to detect only the position-dependent harmonic signal of the movable intermediate coil when suppressing the transmission coil signal. The device described in any one of up to. 5. A diode (2a) as a non-linear electric circuit element is connected in series to the intermediate coil (2), and the intermediate coil (2) formed thereby is induced by the transmission coil (1). AC rectification contains harmonics and at the same time position-dependent signals are received by the receiving coils (3a, 3'a; 3b,
3'b), and this signal causes the receiving coil (3a, 3b)
In the case of asymmetrical positioning with respect to the intermediate coil displacement, the amplitudes of the signals received by both receiving coils differ depending on the position, and the symmetrical positioning of the receiving coils (3'a, 3'b) with respect to the displacement path of the intermediate coil. 5. A device according to claim 4, in which case a linearized DC output signal whose polarity changes when passing the center is induced over the displacement path. 6. An oscillator (10) for generating a square signal of a supported frequency (10 to 50 kHz), a frequency divider (11) connected behind the oscillator, a level adjuster (12) and harmonic suppression. A bandpass filter (13) is provided, to which the transmitting coil (1) is connected, possibly as part of the filter, both receiving coils (3a, 3 ').
a; 3b, 3'b) is connected with a filter (14a, 14b) in the back, and the filter suppresses the fundamental wave of the oscillator signal to be supplied to at least the transmission coil (1) and suppresses harmonics. A device according to any of claims 1 to 5, comprising, and therefore also only position-dependent receiving coils are commutated for evaluation. 7. Both receiving coils (3a, 3'a; 3b, 3'b),
7. Device according to claim 6, characterized in that after the transmission coil fundamental has been filtered for the rectification of the frequency-shifted position-dependent harmonic signal, a rectifier, which is in each case clocked by an oscillator, is connected behind it. . 8. The rectifier output side of one of the receiving coils (3a, 3'a; 3b, 3'b) is fed back to the input side of the level adjuster (12) before the transmitting coil (1), The varying output value of the other receiving coil represents the ratio of the amplitudes of the harmonic voltages induced in the two receiving coils by the intermediate coil (2) according to any one of claims 1 to 7. apparatus. 9. A coil device for position measurement is incorporated in a shock absorber (18) of a vehicle, and a fixed transmitting coil (1) having receiving coils (3a, 3b) adjacent to each other on a first side is provided. An intermediate coil (2) fixed to this inner part changes its position with respect to the receiving coil, on the displacement path of the inner buffer part, which is arranged on the inner circumference of the shock absorber part and is relatively movable to this outer part. Claims capable of being claimed 1 to 8
The device according to any one of items 1 to 7. 10. A controlled rectification of a harmonic signal having an oscillator frequency by frequency division in front of the transmitter coil (1). Equipment.