CN1739031A - Position detector - Google Patents

Abstract

The present invention relates to a position detector which in its simplest embodiment has two induction coils but only one independent impulse line. All the information required, for example for counting, can be obtained instantaneously from the triggering direction of the magnetic field reversal and the direction of the magnetic field reversal of the pulse line, as well as the information of the newly established and stored position and polarity. Such a position detector operates using a memory element, such as FRAM, that consumes low power and does not require an external power source. In order to enable the use of such a position detector at high temperatures, an EEPROM may also be mounted therein.

Description

position detector

The invention relates to a position detector for detecting translational and/or rotational movements by using ferromagnetic elements.

Ferromagnetic elements of this type can be in the form of impulse line motion detectors as described in US 4363013 or in the form of Wiegand sensors as described in DE 4107847C1 and DE 2817169 C2. In these cases, for example, an impulse line of ferromagnetic material is surrounded by a sensor coil. The magnetic regions in the ferromagnetic material—also known as magnetic domains or "Weiss" regions—are initially oriented in a random fashion, but under the action of an external force, these magnetic regions can become oriented into a single domain ( single domain). When an external magnetic field is applied in a specific direction and strength, the area will immediately flip or "flips." As a result, a voltage pulse is generated in the sensor coil as an output signal.

In a known design of a rotation angle sensor (see e.g. EP 0724712B1), switching and resetting magnets will be conducted through these pulse lines, some of which will be distributed around the circumference, so that magnetic fields of opposite polarity pass successively. through each impulse line. As a result of the repeated magnetization of all magnetic domains of each pulse line, a voltage pulse of defined period, amplitude and polarity is generated in the sensor coil. An electronic counting circuit evaluates these voltage pulses. Said reset magnet will generate a magnetic field of opposite polarity which restores the magnetic domains of the pulse line to their original state, so that the pulse line under consideration is ready to trigger a new pulse. This mode of operation is said to be "asymmetric". In symmetric mode, pulses that can be evaluated are also generated during the reset.

As described in the aforementioned EP 0724712 B1, it is necessary to distribute at least two of the above-mentioned sensors around the circumference along the direction of motion, so that not only can each complete rotation of the rotating shaft be determined, but also when considering the setting In the case of a discriminative position difference between the process and the reset process, the direction of rotation is determined, wherein the generated voltage pulse can be uniquely assigned to the corresponding angular position of the axis of rotation.

Creating such a system is very cumbersome since at least two sensors need to be distributed around the circumference and the impulse line sensors need to have a defined size. This means that it is not possible to implement a small-diameter spin counter. Also, these sensors are quite expensive.

It is known to also use a position detector of the above-mentioned type comprising only one sensor to determine the rotation of the rotary shaft and its direction of rotation. In this case, the sensor is designed as a Wiegand line, which forms a certain angle with the direction of movement of the rotating shaft part, and has a definite magnetic pole facing the Wiegand line; thus, the Wiegand lines can generate direction-dependent pulses (compare the aforementioned DE2817169 C2).

A disadvantage of this arrangement is that, although the direction of rotation can be identified, the predetermined polarization means that only the direction of rotation predetermined by said polarization can be detected. That is, only one direction of rotation can be determined.

In order to be able to determine both directions of rotation of the rotary shaft, therefore, at least two such sensors and their corresponding evaluation circuits are required. In addition, this structure has the disadvantage of a very low energy yield under certain conditions, since the angle between the direction of motion and the orientation of the sensor plays a decisive role. Thus, this type of structure will hardly work without an external energy source.

The object of the invention is to provide a modification to the above-mentioned solution.

Due to the very strong interaction of the magnetic moments between adjacent atoms with different magnetization directions in ferromagnetic materials, the magnetic moments are aligned with each other in a small spatial region, the so-called Weiss region. These regions are separated from each other by transition layers called "Bloch walls". It has been found that permanent single domains with consistent magnetization directions can be obtained, for example, by mechanically extending ferromagnetic wires. When this type of domain is introduced into an external magnetic field of defined field strength and direction, the domain does not invert as a whole; instead, its unit magnets begin to reverse from a defined starting position—preferably is reversed from one end of the ferromagnetic wire - and the reversal proceeds in a domino fashion towards the external magnetic field. Although the reverse wave introduced into the ferromagnetic element in this way has a finite speed, it is fast enough to compare with the speed of the excited magnet, so that the magnetic domain can be said to be "instantaneously flipped".

By exploiting the above physical relationship, for a position detector of the type discussed here comprising at least one excitation magnet, the aforementioned tasks are solved according to the invention by using a position detector having a single ferromagnetic element, at least one induction coil, and at least one additional sensor element for determining information about the polarity and position of the excitation magnet, wherein the set of information available upon activation of the single ferromagnetic element is for determining All the information needed to drive the direction of motion of the magnet.

In a very simple variant of the invention, using the Bloch wall effect through the ferromagnetic element, it is possible to detect the position of the excitation magnet by determining the triggering direction of the remagnetization of the ferromagnetic element. This repeated magnetization can start from either of the two end surfaces of the element.

But the triggering direction of the repeated magnetization should not be confused with the direction of the repeated magnetization itself, which can be described by the pole to which the Weiss region will "flip" or from which pole . In this case, said reversing magnetization direction has the effect of making the region in question of the same polarity as the trigger pole of the excitation magnet.

When the unit magnet is turned in the direction of the external magnetic field in the form of a continuous rotation axis, the kinetic energy generated by the unit magnet will be large enough to obtain the electrical energy required for the signal pulse from the coil corresponding to the ferromagnetic element, and count The energy required by the circuit and the Hall sensor.

Once the current position and polarity of the excitation magnet EM are known, their relation to the most recently stored position and polarity values can be considered. This relationship provides all the information needed to determine the direction of motion of the excitation magnet EM and its permanently connected rotational axis.

In order to understand the present invention more clearly, the following description is based on a rotation counter.

In the usual case characterized by an excitation magnet and a resolution of half a revolution, the described rotation counter system can be fully described by the four basic states of the excitation magnet, which can be combined with the latest stored magnet data through each Combination of forms, namely:

Z1.) North pole to the right of the reference line,

Z2.) North pole to the left of the reference line,

Z3.) the south pole to the right of the reference line, and

Z4.) South pole to the left of the reference line.

According to the present invention, when only one pulse line and one induction coil are used, the four states can be combined with each other in various ways to form three groups of two states in each group. The combination that occurs in practice will depend on the direction in which the repeated magnetization is triggered.

Group 1: Two trigger directions for repeated magnetization are defined; see Figures 1, 2 and 3.

a.) North pole to the right of reference line L or south pole to the left of reference line L (Z1 or Z4);

b.) North pole to the left of reference line L or south pole to the right of reference line L (Z2 or Z3).

Here, the position of the excitation magnet EM can be determined by measuring the direction in which the remagnetization is triggered using a further sensor element, eg a second induction coil or a Hall sensor. The measurement is done directly when the second coil SP2 is provided on the ferromagnetic element FE. By contrast, when Hall sensors HS are used, the measurement takes place indirectly. When using the Hall sensor HS, the detected polarity of the excitation magnet EM is irrelevant. The only thing that matters is whether or not the energizing magnet is energized. By measuring the remagnetization direction using the induction coil SP1 or SP of the ferromagnetic element FE, the polarity of the excitation magnet EM can always be derived from the polarity of the voltage pulse.

Group 2: Only one trigger direction for repeated magnetization is defined; see Figure 4.

a.) North pole to the right of reference line L or north pole to the left of reference line L (Z1 or Z2);

b.) South pole to the right of reference line L or south pole to the left of reference line L (Z3 or Z4).

In this case, the position of the excitation magnet EM can always be determined directly via the Hall sensor, ie by determining whether the excitation magnet is activated or not. The polarity of the excitation magnet EM can be determined independently by measuring the direction of repeated magnetization using the induction coil SP.

The third group: Undefined repeated magnetization trigger direction; refer to Figure 5.

a.) North pole at the upper right of reference line L or south pole at the lower right of reference line L (Z1 or Z2);

b.) North pole at the bottom right of reference line L or south pole at the top right of reference line L (Z4 or Z3).

The relevant polarity is analyzed as a function of the position of the Hall sensor HS, ie on the right (as shown in FIG. 5 ) or on the left. The polarity of the excitation magnet EM can here be given directly by the Hall sensor HS. Now the position of the excitation magnet EM (north or south pole above or below) can be determined indirectly by measuring the remagnetization direction.

All the above solutions are mathematically equivalent and have the same industrial value.

With the inventive solution described above it is possible to realize a position detector with the simplest mechanical design imaginable, comprising only a ferromagnetic element which can fail at approximately zero speed, even with normal power supply Afterwards, work satisfactorily in both directions of motion of the excitation magnet. A significant advantage of this position detector is that all the information required to determine the polarity and direction of movement of the excitation magnet EM is available at the moment Ts, ie the moment when the ferromagnetic element FE is triggered. Thus, in addition to the stored data, all necessary signals are present at the output terminals of the induction coil and/or Hall sensor under consideration. In order to achieve this goal, the ferromagnetic element FE, the Hall sensor HS, and one or more excitation magnets EM must be arranged with each other in a very specific spatial pattern, eg in one position.

A position detector with such an optimized simplified design can also derive energy from the induction coil SP or the induction coils SP1, SP2 for the output signal as well as for the evaluation circuit comprising at least one counting device, non-volatile volatile memory, and capacitors.

Additional features of the invention can be obtained from the dependent claims.

The invention will be described below on the basis of five exemplary embodiments, which will be more or less shown in the drawings.

- Figure 1 shows a schematic diagram of the design of a position detector according to the invention, said position detector having a ferromagnetic element, two corresponding induction coils, and two ferromagnetic flux-conducting parts;

- Fig. 2 shows a schematic diagram of the design of the position detector according to the second exemplary embodiment of the present invention, the position detector has a ferromagnetic element, an induction coil, a Hall sensor, and two ferromagnetic magnets through conductive parts;

- Figure 3 shows a schematic diagram of a position detector according to a third exemplary embodiment of the present invention, said position detector having a ferromagnetic element, an induction coil, a Hall sensor, excitation magnets, and two a ferromagnetic flux conducting part;

- FIG. 4 shows a schematic diagram of a position detector according to a fourth exemplary embodiment of the present invention, said position detector having a ferromagnetic element, an induction coil, and a Hall sensor;

- Fig. 5 shows a schematic diagram of a position detector according to a fifth exemplary embodiment of the present invention, said position detector having a ferromagnetic element, an induction coil, a Hall sensor, and two Cross-placed ferromagnetic flux-conducting parts;

- Figure 6 shows a block diagram of an evaluation circuit suitable for the embodiments shown in Figures 1-5;

- FIG. 7 shows a structure corresponding to the position detector shown in FIG. 5, wherein the rotation axis of the excitation magnet is rotated by 90 degrees, that is to say, the angle set as in FIG. 4; and

- Figure 8 shows a structure corresponding to the position detector shown in Figure 7, where the axis of rotation of the excitation magnets is rotated by 90 degrees relative to the position shown in Figure 5, two excitation magnets are shown in Figure 8 for the sake of clarity .

In the embodiment of the position detector shown in FIG. 1 , the moving body is a rotating shaft 10 , which can rotate in the directions indicated by arrows R1 and R2 , ie clockwise or counterclockwise. In order to be able to count the rotations of the shaft 10 , an exciter magnet EM with a north pole N and a south pole S is provided. Via the ferromagnetic flux conducting parts FL1 and FL2, the ferromagnetic element FE can be influenced by the magnetic field generated by the excitation magnet EM. The ends 14 and 15 of the flux-conducting part are located on the circular arc described by the path (path) of the exciting magnet EM, while the end 16 (located on the left side of the reference line L on the FE) and the end 17 (on the The right side of the reference line L (set on FE) faces the end face of the ferromagnetic element FE.

The ferromagnetic element FE parallel to the direction of motion of the excitation magnet is surrounded by two sensor coils SP1 and SP2. When the excitation magnet EM moves past the ferromagnetic element FE, it remagnetizes said ferromagnetic element and thus generates a voltage pulse of corresponding polarity. These pulses can be extracted from the outputs 22 and 23 of the two coils. Here the second induction coil SP2 will serve as an additional sensor element for determining the direction in which the remagnetization is triggered. The direction in which the remagnetization is triggered and thus the position of the excitation magnet can be derived from the time offset between the voltage maxima delivered by the two coils. Strictly speaking, only the coil that is in logic state "1" needs to be evaluated, i.e. the first coil to reach its voltage maximum. At this point the other coil has not yet reached its maximum value and is therefore considered to be in logic state "0". Here a pulse line is used as the ferromagnetic element.

In the exemplary embodiment described with reference to FIG. 2 , elements corresponding to those in FIG. 1 have the same reference numerals.

In contrast to FIG. 1 , only one sensor coil SP is assigned to the ferromagnetic element FE. In order to be able to determine the position of the excitation magnet when the excitation magnet passes the ferromagnetic element, a Hall sensor HS is provided here as an additional sensor element, at whose output 24 a signal is present or absent. As in the case shown in FIG. 1, the polarity of the ferromagnetic element FE is determined by the coil SP of the ferromagnetic element FE. The polarity determined by the Hall sensors is not relevant for the evaluation to be carried out, but serves as redundant information for monitoring the operation of the device.

Thus, the complete set of information obtained at time Ts for determining the polarity and direction of motion of the excitation magnet comprises: data stored in non-volatile memory, signals obtained at the output of said induction coil, or at The signal obtained at the output of the induction coil and the output of the Hall sensor.

In the embodiment of the position detector shown in FIG. 3 , said position detector has elements corresponding to those of the exemplary embodiment described above. In addition, in order to improve the resolution, a Four excitation magnets EM1-EM4 are placed 90 degrees apart and have alternating polarity. Thus, when the rotating shaft 10 rotates, first the north pole and then the south pole pass in turn through each end face of the ferromagnetic element FE via the magnetic flux conducting parts FL1 and FL2. Here, the Hall sensors required to determine the position of the excitation magnets are assigned to the ends of the excitation magnets EM1-EM4, facing away from the direction of the ferromagnetic elements.

In the embodiment of the position detector shown in Figure 4, said position detector has the same elements as the previously described embodiments, but in this embodiment no ferromagnetic flux conducting parts are present. In this variant, the fact that the ferromagnetic element FE is activated before the excitation magnet EM is aligned with the ferromagnetic element FE is mainly used. By extending the sensing range of the Hall sensor HS close to the reference line L, the sensing range of the Hall sensor HS required for determining the position of the excitation magnet EM can be calculated.

In the embodiment of the position detector shown in Figure 5, said position detector also has the same elements as the previously described embodiments, but in this embodiment, the flux conducting parts FL1 and FL2 facing the excitation magnet The ends are set 180 degrees apart from each other. Here, the Hall sensor as an auxiliary sensor element required to determine the polarity of the excitation magnet passes through the center of rotation of the axis of rotation 10 at right angles to the reference line L and is arranged in such a way that when the ferromagnetic element is triggered, it The corresponding polarity of the excitation magnet EM can still be sensed. This tends to happen at a certain angle α before the polarity is aligned with the flux conducting part. The position of the excitation magnet EM is determined by the coil of the ferromagnetic element FE which measures the direction of repeated magnetization. The current variant according to FIG. 5 can be operated with very small excitation magnets EM, especially if the required flux conducting means in the form of magnetic lenses are used to confine the flux.

In the exemplary embodiment shown in Figures 1-5, the excitation magnet EM and the ferromagnetic element FE are located in the same plane with respect to the axis of rotation. Of course, the ferromagnetic element FE and the excitation magnet EM can also be located in different planes - as shown in Fig. 7 - or in the same plane but parallel to the axis of rotation - as shown in Fig. 8, which may even be benefit.

The inputs 32 , 33 of the evaluation circuit, denoted as a whole by the reference numeral 30 , are connected to the sensor coils SP1 and SP2 , or to the coil SP and the Hall sensor. This type of circuit can be used in various position detectors as shown in Figures 1-5 and 7-8. Figure 6 shows a block diagram of such an evaluator. Recognition circuits 34 , 35 are provided downstream of the input. Via a rectifier D, a capacitor C for supplying energy is also connected to the input 32 . The signals from the identification circuits 34 , 35 are evaluated in a counter 38 with its own non-volatile memory 36 . From the historical information contained in the stored data and from the information provided by the identification circuits 34, 35 about the current position and polarity of the excitation magnets, the new counter state can be obtained. This new state will then be stored in a non-volatile memory cell, typically a FRAM cell.

The energy used to evaluate the circuit usually comes from the signals sent by the induction coils SP, SP1 and SP2. If only one induction coil SP is used, the Hall sensor is also powered by this coil.

The connection line 41 is part of the power supply for the previously described evaluation circuit. Data can be read out via tap 39 and interface 40 . Line 42 (if present) is used to harvest power from the outside world, especially when EEPROM is used in addition to FRAM. EEPROM usually allows evaluation circuits to operate at very high temperatures, where configuration data stored in FRAM is lost in a short period of time.

All the exemplary embodiments described above have in common that the rotation and/or direction of rotation of the rotating shaft 10 can be precisely determined by only a single electromagnetic element, such as an impulse line, which can also Sufficient energy is available for the evaluation circuit and the Hall sensors as additional sensor elements. In the simplest inventive variant of the impulse line circuit, the two ends of the impulse line are equivalent in terms of measurement technology, and the voltage pulses generated contain information about the position and polarity of the triggering excitation magnet.

Another important point is that all information about the triggering direction of the repeated magnetization of the ferromagnetic element, the triggering polarity of the excitation magnet EM, and the latest stored polarity and position of the excitation magnet relative to the axis of rotation can be obtained at the triggering time Ts of the ferromagnetic element obtained, that is, simultaneously within the response time of the selected elements.

Capacitor C in the evaluation circuit is used to store the supply energy obtained from the signal pulses at least until the signal has been evaluated and the counter value has been stored into the non-volatile memory element.

Other types of ferromagnetic elements can also be used instead of the impulse lines or Wiegand lines, as long as the condition of immediate reversal of the Weiss region can be satisfied.

To avoid misunderstandings, it should be noted that the ferromagnetic element FE is characterized by having only one magnetic input and one magnetic output, neglecting stray fields. While it is conceivable that there could be any number of parallel and/or serial interrupts between the input and output, such interrupts do not depart from the inventive concept of using a single component in the present invention.

Instead of the Hall sensors, other sensors, such as field plates, can also be used to determine the polarity or position of the excitation magnet. It is also possible to prepare the excitation magnet in such a way that its position and/or polarity can be determined by capacitive measurements instead of Hall sensors. The previously described position detectors can be used in combination with precise rotational angle sensors of the so-called "multi-turn" form, such as described and shown in EP 0658745. In this case, the reference line L corresponds to the zero point position of the precise rotational angle sensor used.

For example, when using a Wiegand line, in order to synchronize with an accurate rotation angle sensor, it is necessary to acquire accurate data of the magnetization state of the ferromagnetic element FE. For this purpose, a structure with two coils as shown in Fig. 1 is applicable. By supplying an external current to one of the coils, eg coil SP1, a voltage pulse can be triggered in a second coil, eg coil SP2, as a function of the magnetization of the ferromagnetic element. The same process as above can also be achieved when the two coils are placed one on top of the other. It is also possible to trigger a voltage pulse with a short current pulse or a slowly linearly rising current, but in this case only one coil SP is required.

List of reference signs

10 axis of rotation

14 end

15 end

16 end

17 end

22 output terminal

23 output terminal

24 output terminal

30 evaluation circuit

32 input

33 input terminal

34 identification circuit

35 Identification circuit

36 non-volatile memory

38 counter

39 taps

40 interface

41 connecting line

42 lines

α firing angle

C capacitance

D rectifier

EM excitation magnet

EM1 excitation magnet

EM2 excitation magnet

EM3 excitation magnet

EM4 excitation magnet

FE ferromagnetic element

FL1 Flux conducting parts

FL2 Flux Conduction Parts

HS Hall sensor

L reference line

N North Pole

R1 Arrow

R2 arrow

S South Pole

SP sensor coil

SP1 sensor coil

SP2 sensor coil

SE additional sensor element

Ts The moment when the ferromagnetic element FE is triggered

Z1 Basic state of excitation magnet

Z2 Basic state of excitation magnet

Z3 Excitation magnet basic state

Z4 Excitation magnet basic state

Claims (13)

1. A position detector for detecting translational and/or rotational movements, with at least one excitation magnet (EM), only one ferromagnetic element (FE), at least one induction coil (SP or SP1), and at least one Additional sensor element (SE) for determining information about the polarity and position of the excitation magnet (EM), where all the information required to determine the direction of motion of the excitation magnet (EM) is available in the only ferromagnetic element (FE) The triggered moment (Ts) is obtained. 2. A position detector as claimed in claim 1, wherein said ferromagnetic element is an impulse line. 3. Position detector according to claims 1 and 2, characterized in that said induction coil (SP or SP1) is used to measure the direction of repeated magnetization and in combination with said additional sensor element (SE) is used to determine The direction in which the repeated magnetization of the ferromagnetic element (FE) is triggered. 4. Position detector according to any one of claims 1 to 3, characterized in that said additional sensor element (SE) is a further induction coil (SP2) located above the ferromagnetic element (FE) , the coil is used to determine the direction in which the repeated magnetization of the ferromagnetic element (FE) is triggered. 5. Position detector according to any one of claims 1 to 3, characterized in that said additional sensor element (SE) is used to measure the polarity of said excitation magnet (EM) or to determine its position Hall sensor (HS). 6. A position detector as claimed in any one of claims 1 to 5, characterized in that the set of information obtained at time Ts for determining the polarity and direction of motion of the excitation magnet (EM) comprises: non-volatile The data in the permanent memory, and the signal obtained at the output (22, 23) of the induction coil (SP1, SP2) or at the output (22) of the induction coil (SP) and at the Hall sensor (HS) The signal obtained at the output terminal (24). 7. A position detector according to any one of claims 1 to 6, characterized in that the axis of the ferromagnetic element (FE) is parallel to the direction of motion of the excitation magnet (EM). 8. A position detector according to any one of claims 1 to 6, characterized in that the axis of the ferromagnetic element (FE) is perpendicular to the direction of motion of the excitation magnet (EM). 9. Position detector according to any one of claims 1 to 8, characterized in that at least one ferromagnetic flux conducting part (FL1 and/or FL2) for guiding and/or confining the magnetic flux is assigned For ferromagnetic elements (FE). 10. The position detector according to any one of claims 1 to 9, characterized in that the energy supply for the evaluation circuit (30) can be obtained from an induction coil (SP, obtained from the signal sent by SP1, SP2). 11. The position detector according to any one of claims 1 to 10, characterized in that the evaluation circuit (30) comprises at least one counter (38), a non-volatile memory unit (36) and a capacitor ( C). 12. A position detector according to any one of claims 1 to 11, characterized in that the non-volatile memory unit (36) is a FRAM and or EEPROM unit. 13. Position detector according to one or more of the preceding claims, characterized in that one of said coils (SP/SP1) can be powered by an external current pulse whose effect is to initialize the ferromagnetic element (FE) bias or maintain this bias.

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