DE102006031139A1 - Connecting device for contactless measurement of linear position of rotor, has pair of triangular coils of same surface with form depicts square in former level and another pair of coils of same surface with form arranged in later level - Google Patents

Abstract

The device includes a pair of triangular coils (3.1,3.2) of same surface with a form depicts a square in a former level. Another pair of triangular coils (3.3,3.4) of same surface is provided with a form arranged in later level. The coil of the former level rests congruently above one another. The measuring direction (X) is parallel to the side of the square. A rotor (2) is provided, which has an electrically conductive layer or an electrically conductive material. The rotor is equipped as a flat, square surface parallel to the levels and has an expansion in (Y) direction.

Description

The The present invention relates to a non-contact device and wear-free measurements with flat coils of the absolute linear position of device, machine or actuators, this element itself being able to represent the function of the runner. she is particularly suitable for the use at high temperature and heavy pollution.

she is applicable as a replacement of potentiometers, but also as a position sensor in gearboxes, logistics systems, car seats, as a level sensor in containers, in short everywhere the linear position is of interest.

In known devices for contactless measuring In the absolute linear position, differential coils with proportional transmission ratio of the coil of the runner stimulated, the magnetic flux with magnets in the rotor proportionally steamed or over transformed the effect of magnetostriction into a sound wave whose position-dependent Runtime can be measured.

Of the obvious disadvantage of most solutions is that considerable parts of the measuring device both on the side of the stator, as also on the runner's must be provided and that the costs associated with these systems of metrology the installation in mass production obviously only conditionally allow.

easy Solutions, like the magnet on the runner, are inexpensive. The obvious disadvantage of this approach is that that magnets are only stable up to the so-called Curie temperature, against hard blows are very sensitive and the attachment of ferromagnetic abrasion the function in question.

One further approach to the solution This problem now aims to use a planar coil in the runner magnetic alternating field and its proportional distribution on two receiver coils to measure on the stator. The obvious disadvantage of this solution is in that at the runner additionally this coil is required and also flexible electrically conductive must be connected to the evaluation electronics. This is the uses limited and the costs are higher.

task It is therefore advantageous for the present invention to have a sensor arrangement form, with which the absolute linear position between runner and stator inductively and contactlessly determined and the accuracy of the measurement reaches about 0.2%.

Two elongated, Symmetrical, triangular coils are side by side on the stator opposite arranged in a plane and with a current of known size each generates a common electromagnetic field. The longitudinal axis of the The quadrilateral described by the 2 triangles is the measuring direction.

in the Moment of turning off the power becomes the energy of the electromagnetic Field for each coil is converted into a negative voltage pulse and causes via one each Diode the charge flow from one capacitor each, until the field degrades is. In the consequence can at the capacitors these are proportional to the energy content, negative Voltages are measured. At the same time, the degradation of the electromagnetic Field in the electrically conductive runner induces an eddy current, thus reducing its energy to what is the capacitors as a lower voltage swing is measurable.

Because the energy loss due to eddy current is proportional to the covered one area the triangular coils and their distance from the runner can be with a second Pair of such coils in a second, coplanar plane out directly differentially determines the absolute linear position and a change of the distance in the work area can be compensated.

moreover It is beneficial that the runner orthogonal to the measuring direction can be moved freely, without to change the reading, if he is longer as this route is.

These Task is with the characterizing parts by the patent claim (1) solved. Advantageous embodiments of the device according to the invention will become apparent from the measures in the dependent Claims.

The inventive arrangement two triangular planar coil pairs with the same area and Shape has respectively on the top and bottom of a carrier Compared to previously known solutions the advantage that the runner only from a flat surface an electrically conductive Material exists, or a thin one electrically conductive layer and thus can be part of the mechanical application.

Farther it is an advantage that the runner is orthogonal can be moved to the measuring direction without affecting the measurement, as far as its length this is permitted or required.

Further Advantages and details of the device according to the invention arise from the following description of several embodiments with reference to enclosed figures.

there shows

1 the planar support with two mutually juxtaposed, triangular coils, the measuring direction X, the zero point 0, the rotor, the electrically conductive connections of the coil system and congruent with the top, another pair of coils on the bottom;

2 the two levels of coils, the carrier, rotor and coil system in cross section, and a mechanical protective layer on the coils, a ferromagnetic shield on the bottom and the attachment of the rotor to the mechanical application;

3 shows a section of the tips of two coils on the top and bottom and the use of contact bridges to guide the respective innermost conductor for connection to the outside;

4 shows an exemplary circuit diagram for detecting the shutdown pulse with current switch, electrically conductive connection, planar coil, rotor, diode, capacitor, inverting operational amplifier for level adjustment of the negative signal voltage at the capacitor, three circuit diagrams same arrangements and logic circuit or microcontroller with analog / digital converter for evaluation;

5 shows a further exemplary circuit diagram for detecting the switch-on with current switch, electrically conductive connection, planar coil, rotor, diode, capacitor, three circuit diagrams same arrangements and logic circuit or microcontroller with analog / digital converter for evaluation in the shading with positive signal voltage at the capacitor;

6 shows a further exemplary circuit diagram for detecting the shutdown pulse with power switch, electrically conductive connection, planar coil, rotor, diode, capacitor, three circuit diagrams same arrangements and logic circuit or microcontroller with analog / digital converter for evaluation in the shading with positive signal voltage at the capacitor;

7 shows a longitudinal section through the carrier and coil system and rotor, with measuring direction X and bent by 90 ° ends of the coil, with housing and partial, ferromagnetic shield inward and outward.

8th shows a cylinder as the carrier of the coil system, the rotor bent around it circularly and the measuring direction X.

9 shows a further cylinder as a carrier of the coil system and the rotor as a piston in the interior and the measuring direction X.

In 1 a first embodiment of the coil arrangement according to the invention is shown. Two coils ( 3.1 . 3.1 ) are in a plane E1 on the surface of the substrate ( 1 ) arranged in opposite directions as triangles. They consist of a few turns of electrically conductive material, such as a copper conductor on FR4, have as much as possible the same area and take together the shape of a rectangle. With the coordinates X and Y of the sensor arrangement according to the invention X is the measuring direction and Y orthogonal thereto. Here l denotes the length, m the measuring range and b the largest width of the coils. Opposite under the two coils of the surface are on the bottom E2 two more triangular coils ( 3.3 . 3.4 ), which together form the coil system and up to eight electrical connections 4.xx be connected. The runner ( 2 ) has a flat surface and has in the direction Y two mutually parallel edges and can be moved in the measuring direction X due to. A movement in direction Y can be added. The vertical projection of the surface of the runner ( 1 ) to the plane of the coils ( 3.1 . 3.2 ) creates the surfaces 12.1 and 12.2 characterized by the fact that their total area when moving the runner ( 2 ) remains constant and justifies the differential measuring principle. The same projection and condition applies to the coils of the underside ( 3.3 . 3.4 ).

Of the Measuring range is located in the conductor-free, inner area of the Coils in which largely the homogeneous conditions of a Helmholtz coil be valid. The runner covers Tracks only in Y, with this overlap by moving not changed.

The zero point 0 of the measurement is the line parallel to Y at which the coils 3.1 and 3.2 such as 3.3 and 3.4 have the same width.

2 shows the cross section through the carrier ( 1 ) with the coils and the distance d1 of the rotor ( 2 ) to the upper coil pair ( 3.1 . 3.2 ) and d2 to the lower ( 3.3 . 3.4 ). Additionally shown is a layer ( 13 ) as a mechanical protection or housing of the coil system, a ferromagnetic layer or foil ( 14 ) for closing the magnetic circuit of the coils at the rear and the connection of the rotor ( 2 ) to the mechanical application to be measured ( 37 ). The runner can thus form an identical unit solely by the shaping with the mechanical application and, for example, be an electrically conductive layer on a support.

Furthermore, the carrier can 1 made of ceramic, plastic or other electrically non-conductive material of thickness d, on which the conductors be applied with a reasonable process. In particular, it can be firm or flexible. It is also possible that each of the planes E1 and E2 represents its own fixed or flexible carrier with the distance d to each other, so that the carrier 1 can be omitted.

3 describes in addition by way of example the arrangement of the tracks of the upper ( 3.2 ) and lower ( 3.4 ) Spool at the top in the cutout. Via a contact bridge ( 3.23 ) on the underside, the innermost turn of the upper coil ( 3.2 ) and then next to the outer winding ( 3.2.1 ) over part of the triangle as the outermost conductor ( 3.2.2 ) to the connection ( 4.22 ) on one side of the carrier 1 guided.

The turns of the lower coil ( 3.4 ) run congruently under the turns of the upper ( 3.2 ) except for the area in the top. Here they are in front of the contact bridge ( 3.23 ) guided on the bottom E2 and the innermost turn over another contact bridge ( 3:43 ) outward ( 3:42 ) and to connection ( 4:42 ) returned.

The conductor guide in the other two coils ( 3.1 . 3.3 ) is carried out in the same way and thus makes it possible to attach and connect four coils on the top and bottom of a substrate in the required manner and to attach without having to attach conductors in another level. Thus, this arrangement is also suitable for carriers made of materials that do not allow inner layers, such as ceramic or plastic.

The Tip of the triangle was chosen as possible small area differences between upper and lower coil, and rectangular, dull cut off to the length as short as possible to keep.

4 shows an exemplary circuit diagram of the sensor arrangement according to the invention, supplemented by a current-limiting resistor ( 5.1 ), a switching element ( 6.1 ), the electrical connections ( 4.11 . 4.12 ) to the planar coil ( 3.1 ), the runner ( 2 ), a diode ( 7.1 ), a capacitor ( 8.1 ) and the inverting-connected operational amplifier ( 9.1 ). As long as the switching element ( 6.1 ) is conductive, flows through resistance ( 5.1 ) and coil ( 3.1 ) a current and generates around this an electromagnetic field. At the moment of turning off the power, the energy of the electromagnetic field causes a negative voltage pulse (mutual induction) and electric charge from the capacitor is pumped through the now conducting diode. With the decay of this voltage pulse, the diode is again blocking and on the capacitor a negative voltage is maintained, which can be measured in the sequence. Proportional to that of the runner ( 2 ) covered area of the coil ( 3 ) is switched off when the current in the rotor ( 2 ) induces an eddy current. The energy converted in the eddy current is removed from the energy of the negative voltage pulse and as a lower voltage swing across the capacitor ( 8th ) measurable.

The inverting operational amplifier ( 9 ) is used to convert this negative voltage to a positive value that can be easily fed to an ASIC or microcontroller ( 11 ) can be connected with analog-to-digital converter for further processing. Overall, this circuit is ( 10.1 ) four times ( 10.2 . 10.3 . 10.4 ) available. It should be stressed that the electronic components ( 5 . 6 . 7 . 8th . 9 . 11 ) and planar coils ( 3 ) on the same support ( 1 ) or via flexible conductors ( 4 ).

Between the circuit ( 10 ) and the control unit ( 11 ), further components can be inserted, in particular by analogy, the differences of the signals ( 10.x ) with limited resolution of the analog / digital conversion with higher accuracy.

5 shows a further exemplary circuit diagram of the sensor arrangement according to the invention, largely analogous to 4 , Differently, the omission of the operational amplifier and the forward direction of the diode ( 21.1 ). So the capacitor ( 18.1 ) when switching on the current with the switching element ( 16.1 ) via the diode ( 17.1 ) are positively charged until the induction voltage at the coil ( 3.1 ) has dropped and the rated current flows. Even when switching an eddy current is induced in the rotor and thus changes the signal voltage across the capacitor ( 18.1 ).

6 2 shows a further exemplary circuit diagram of the sensor arrangement according to the invention in a connection of the planar coil (FIG. 3 ) with the other electronic components ( 4 . 25 . 26 . 27 . 28 ) arranged so that at the moment of switching off the coil current via the diode ( 27.1 ) electrical charges in the capacitor ( 28.1 ) and a measurable increase in the voltage beyond the supply voltage on the capacitor ( 28.1 ), which depend on the position of the runner ( 2 ) is dependent.

7 shows a longitudinal section to the measuring direction X by the coil system according to the invention ( 3 ), with left and right each part of the carrier ( 1 ) at right angles to the runner ( 2 ) is arranged away. This ensures that the regions of the tip and the regions of the coils of the coil triangles do not contribute to the length L of the sensor and the measurement path m reaches almost the length L. The ferromagnetic Protective layer ( 14 ) partially also laterally outwards, allows the mounting of the sensor directly into electrically conductive materials such as aluminum.

8th shows the carrier ( 30 ) as a cylinder with the coil system 3 on its inside and outside and runners ( 32 ) as a semicircular, pluggable element that can be moved perpendicular to the image plane in X, and a protective layer ( 33 ) inside this cylinder for mechanical protection of the coils. Likewise, the runner ( 1 ) are formed as a ring.

By turning the coil system ( 3 ) on the surfaces of the cylinder ( 30 90 ° can also be the rotation of the runner ( 32 ) are measured around X.

9 shows the carrier ( 30 ) again as a cylinder in longitudinal section with the coil system 3 and a piston ( 31 ) inside as a runner with movement in X.

A coil with the inductance L is traversed by a current I. Describing the relationship between these quantities and the energy of the electromagnetic field generated around the coil e L = 1/2 · L · I 2 (1)

Will this energy e _L through a diode 7 completely transloaded into a capacitance C, the energy e _C remains constant and a voltage can be measured at the capacitor: e L = e C (2) e C = ½ · C · U 2 (3)

This reloading takes place, for example, with the circuit in 4 in the moment of turning off the current, so that the negative mutual induction voltage of the coil L via the now conducting diode pumps charges from the condenser and so generates a proportional, negative voltage U _C. U C = Root (L / C · I 2 ) (4)

This negative voltage is converted and amplified via an inverting rail-to-rail operational amplifier into a positive signal voltage U ₀ . As a result, the capacitor is discharged through the resistors again, so that periodic measurements are possible.

Then two planar coils 3.1 . 3.2 arranged as right-angled triangles with an acute angle and the same area and geometry in a plane E1 so that the hypotenuses are opposite and the triangles are complementary to a quadrangle. The measuring direction X is then the direction of the Ankatheten, parallel to the longitudinal side of the quadrangle.

About the two coils d1 is also the plane runner at a short distance 2 made of an electrically conductive material, movable in X and possibly also in Y. Thus, the rotor is in the electromagnetic field of the coils and it arises at the moment of switching off the coil current by induction, an eddy current that deprives the electromagnetic field of the coil energy.

How much energy is converted into eddy current depends on the distance d1 e ln = e L · (1 - e -1 / (w · d1) ) (5) and the area covered by the runner a ( 12.1 ), b ( 12.2 ) of the coils 3.1 . 3.2 , The factor w depends on the area of the planar coils and can be determined empirically for the working range between approx. 1 mm and 5 mm. It is this covered area with the displacement of the rotor 2 in the direction X linearly variable e L1 = e L · (1 - e -1 / (w · d1) ) · A (x) (6) and gets on the capacitor 8.1 with equation (4) as voltage U ₁ , or capacitor 8.2 (the coil 3.2 ) as voltage U ₂ with U 1 = U 0 · (1 - e -1 / (w · d1) ) · A (x) (7) U 2 = U 0 · (1 - e -1 / (w · d1) ) · B (x) (8) measurable. Because of the differential arrangement of the coils remains the sum of the runner 2 covered areas a (x) ( 12.1 ) and b (x) ( 12.2 ) even when moving in X constant a (x) + b (x) = const (9)

On the underside of the carrier 1 are in a second plane E2 with the distance d to the plane E1 congruent two other planar triangular coils 3.3 . 3.4 appropriate. For them applies mutatis mutandis U 3 = U 0 · (1 - e -1 / (w · (d1 + d)) ) · A (x) (10) U 4 = U 0 · (1 - e (-1 / (w · (d1 + d)) ) · B (x) (11) and the equations 7, 8, 9, 10, 11 form a complete system of equations with which the position of the rotor in the measuring direction X can be determined independently of U ₀ , w, d and the distance d1.

By inserting and extensive reshaping one determines the solution of this system of equations a (x) / b (x) = (U 2 - U 1 ) / (U 4 - U 3 ) (12)

With the normalization of const in Equation (9) to 1 and set the zero point for the point where the covered surfaces 12.1 and 12.2 are the same a (x) = b (x) = 0.5 (13) is the solution of the measuring task according to the invention X = (U 2 - U 1 ) / (U 4 - U 3 ) (14) as long as the measurement takes place within the virtually homogeneous measuring section m. Practically this means the runner 2 must not be above the tracks of the coil tip or the coils of the coil or move out.

It also becomes obvious that the width of the runner 2 has no essential meaning, as long as it remains within the measuring distance m and that the rotor can be moved orthogonal to the measuring direction in Y, without affecting the measurement in X.

Further embodiments of the sensor according to the invention will become apparent from the arrangement of contact bridges for conductor track guidance of the coils according to 3 that allows it with a two-ply carrier 2 get along. This is important for carriers made of ceramic or plastic.

In addition, each level E1, E2 can be arranged on its own flexible circuit board to the terminals 4 lead out of a range of very high temperature without solder joints until a suitable temperature level for electronic parts is reached.

As well can Angled the "ends" of the carrier to adjust the length visible in the application to the usable measuring path and to reduce the size.

The order of a robust material on the carrier 1 serves for the mechanical protection of the coils and can be produced by overmolding or encapsulation.

Besides causes the attachment of a ferromagnetic layer or foil at the bottom E2 or the sides a shield against electrical conductive Materials nearby of the sensor, about housing parts made of aluminium.

In safety-critical applications requiring a redundant design require the sensor array to be placed opposite each other, leaving a runner Intervene on both coil systems acts. The evaluation in the Electronics are also separated and can act in opposite directions Generate output signals.

It is also interesting to bend the coil plane by X and to arrange it on a cylinder. Then the runner 2 as a piston 31 placed inside the cylinder and its position measured.

Or the runner works from the outside as a semicircle or ring on the coil system and its linear displacement can be contactless be measured.

at curvature of the coil system by Y and mounting on a cylinder, the Runner rectangular remain and its rotational position about the X-axis is now measured. This rotational positions can be measured up to +/- 135 °, z. B. the position the throttle grip on the motorcycle.

Another area of application opens up when the flat coil system is curved in the plane on a circular path. The basic relationships of evaluation and interpretation of the signals are retained and the runner 2 now has to move on this circular path. Then the rotational position of the runner 2 measurable in the range of about +/- 135 °.

These Arrangement can for Safety-critical applications also carried out twice and with a runner to be controlled. The sensor system then face each other and the runner is in between.

It is also possible by analogy to equip the coil system with rectangular coils and the triangular shape on the rotor 2 transferred to. Wiring and evaluation remain the same.

All in all It can be said that the measurements are relatively low-impedance and the stability against Disturbing influences very much good is. So good that even the application in electromagnetic Field of an electric motor possible is.

Claims (10)

Device for non-contact measurement of the linear position X of a runner ( 2 ) above the sensor array ( 3 ) of planar coils and electrically conductively connected to an evaluation unit 10 , characterized in that A is a first pair of triangular coils ( 3.1 . 3.2 ) same a plane and shape in the plane E1 side by side and in opposite directions a quadrilateral describes and that B a second pair of triangular coils ( 3.3 . 3.4 ) is also arranged in a second plane E2 and C the planes E1 and E2 are parallel to each other and the distance d from each other and D is the planar coil ( 3.1 ) of the plane E1 congruent over the coil ( 3.3 ) the plane E2 and the other two coils ( 3.2 . 3.4 ) are equally congruent and E the measuring direction X is set parallel to one side of the quadrilateral and F is the rotor ( 2 ) comprises at least one electrically conductive layer or consists entirely of an electrically conductive material and G the rotor ( 2 ) is advantageously designed as a flat, quadrangular surface parallel to the planes E1 and E2 and its extension in Y larger than the width b of the coil assembly and in the measuring direction X is substantially smaller than the length 1 is and the plane E1 has the distance d1 and H the runner ( 2 ) of the mechanical application ( 37 ) is moved at least in the direction X and I the coil system ( 3 ) with the evaluation electronics ( 10 ) via electrical conductors ( 4 ) is rigidly or flexibly connected. Device according to claim 1, characterized in that A the coils ( 3.1 . 3.2 ) of the plane E1 on top of a solid support ( 1 ) and the coils ( 3.3 . 3.4 ) of the plane E2 on the underside of this carrier ( 1 ) are arranged and B with contact bridges ( 3.13 . 3.23 . 3:33 . 3:43 ) in the tips ( 35 ) of the coil triangles the innermost turn is guided over the other turns and then as outermost turn ( 3.12 . 3.22 . 3:32 . 3:42 ) next to the other turns on the same level to the electrical connections ( 4 ) or C is a multilayer carrier ( 1 ) is used with multiple connection levels. Device according to claim 1 or 2, characterized in that A is the carrier ( 1 ) can also be made of a flexible material and B for the coil system ( 3 ) Each level E1 and E2 a separate carrier is used. Device according to at least one of the preceding claims, characterized in that areas of the carrier ( 1 ) with the tips ( 35 ) and counter cathedrals ( 36 ) of the coil triangles ( 3 ) are angled at right angles to the planes E1 and E2 and so the length l of the carrier ( 1 ) to reduce. Device according to at least one of the preceding claims, characterized in that on the coils ( 3.3 . 3.4 ) of the bottom E2 facing away from the runner ( 2 ) or the outside E1 in the angled area above the tips ( 35 ) and counter catheters ( 36 ) a ferromagnetic layer ( 14 ) or film is attached. Device according to at least one of the preceding claims, characterized in that A is the planar coil system ( 3 ) is rolled about the axis X or Y and subsequently the plane E1 the outer surface of a cylinder ( 30 ) and the plane E2 forms the inner or vice versa and B the runner ( 2 ) as a piston ( 31 ) or ring or part of a ring ( 32 ) is configured. Device according to at least one of the preceding claims, characterized in that A each coil ( 3.1 . 3.2 . 3.3 . 3.4 ) via electrical conductors ( 4.x1 . 4.x2 ) each with an electronic circuit ( 19.1 . 19.2 . 19.3 . 19.4 ) and B any circuit ( 19 ) at least one resistor ( 15 ) and a switching element ( 16 ) connected in series between a supply voltage and ground and C is the anode of the diode ( 17 ) with the connection of the coil ( 3 ), at which the current flows into the coil and D the cathode of the diode ( 17 ) with a capacitor ( 18 ) and other electronic components and E further evaluation of all circuits ( 19 ) in an integrated circuit ( 11 ), such as an ASIC, FPGA or microcontroller with ADC. Device according to at least one of the preceding claims, characterized in that A each coil ( 3.1 . 3.2 . 3.3 . 3.4 ) via electrical conductors ( 4.x1 . 4.x2 ) each with an electronic circuit ( 10.1 . 10.2 . 10.3 . 10.4 ) and B any circuit ( 10 ) at least one resistor ( 5 ) and a switching element ( 6 ), which are connected in series between a supply voltage and ground and C is the cathode of the diode ( 7 ) with the connection of the coil ( 3 ) at which the current flows into the coil and D the anode of the diode ( 7 ) with a capacitor ( 8th ) and other electronic components and E further evaluation of all circuits ( 10 ) in an integrated circuit ( 11 ), such as an ASIC, FPGA or microcontroller with ADC. Device according to at least one of the preceding claims, characterized in that A each coil ( 3.1 . 3.2 . 3.3 . 3.4 ) via electrical conductors ( 4.x1 . 4.x2 ) each with an electronic circuit ( 20.1 . 20.2 . 20.3 . 20.4 ) is connected and B every circuit ( 20 ) at least one resistor ( 25 ) and a switching element ( 26 ) and a coil ( 3 ) connected in series between a supply voltage and ground and C is the anode of the diode ( 27 ) with the connection of the coil ( 3 ) is connected, at which the current exits from the coil and D the cathode of the diode ( 27 ) with a capacitor ( 28 ) and other electronic components and E further evaluation of all circuits ( 20 ) in an integrated circuit ( 11 ), such as an ASIC, FPGA or microcontroller with ADC. Device according to one of claims 1 to 9, characterized in that in each of the aforementioned electronic circuit variants 10 . 19 . 20 between coil ( 3 ) and diode ( 7 . 17 , or 27 ) Another capacitor can be attached.