DE102008063226A1 - Magnetic revolution counter for unambiguous determining revolutions of rotating element, has resistance unit providing measurement for magnetic domain corresponding to loop segments and definite condition of revolution of rotating element - Google Patents

Abstract

The counter (1) has elongated loop segments (3a, 3b, 3c, 3d) provided in a sensor at a predetermined angle in a reference direction. The loop segment is provided with an electrical potential acted on contacts (6a, 6b), which serially or parallelly expand to utilize an electrical resistance unit. The contacts are provided in a curve region of other contacts (7a, 7b) with sliding arrangement, and the electrical resistance unit provides a direct measurement for a magnetic domain corresponding to the loop segments and a definite condition of a revolution of a rotating element.

Description

The The invention relates to a magnetic revolution counter for counting N revolutions, where N should in particular be> 10. Such revolution counter find advantageous application with different linear or rotary actuators to the position of a drive spindle over several To detect revolutions.

An already advantageous sensor for counting revolutions is off EP 1 740 909 B1 known. This sensor has the shape of an elongated spiral with N turns and consists of a layer stack which preferably has the giant magnetoresistance effect (GMR). The GMR layer system of the sensor consists essentially of a hard magnetic layer and a soft magnetic layer separated by a non-magnetic intermediate layer. The outer magnetic field to be detected is strong enough to rotate the magnetization direction of the soft magnetic layer but too weak for a change in the magnetization direction of the hard magnetic layer that is parallel to the straight lines of the elongated spiral. The 2N elongated, parallel strips, between the two electrode covered curve segments, are the sensor elements of the sensor. A rotating magnetic field changes within the countable range of 0 to N turns the magnetization order within the 2N stripes. In total, there are 2N + 1 different magnetization orders, which are assigned one-half and one-half rotations, are stored in the sensor and can be read out as resistance values via the GMR effect. If you apply the resistance to the angle of rotation of the magnetic field, the sensor signal is 2N + 1 resistor plateaus. Particularly advantageous arrangements of this sensor provide for its use in a Wheatstone bridge circuit, in which two sensors with a sense of rotation of the spiral are connected in a clockwise direction with two sensors with opposite directions of rotation of the spiral to form a common sensor. This circuit gives 2N + 1 one-to-one voltage values for the 2N + 1 countable half revolutions. These voltage values are temperature-independent in contrast to the resistance values of the individual sensor. An ideal sensor, or a Wheatstone bridge circuit of four sensors, would switch to a different resistance or voltage value after each 180 ° magnetic field rotation, so that over the entire counting range of 0 to N revolutions the sensor always delivers a clear signal. The real sensor element, however, switches hysterically, so that the resistance or voltage plateaus are not 180 ° wide, but for example only 120 °. The sensor must not be read out within the hysteretic switchover ranges because the information is not unique there. One turn counter after EP 1 740 909 B1 , which is positioned in an axial rotating magnetic field, thus contains at least two closely adjacent sensors, or two closely spaced Wheatstone bridge circuits of four sensors each, which are arranged (approximately) at 90 ° to each other, whereby two signals offset by 90 ° be generated. Since the magnetization direction of the hard magnetic layer according to a possible embodiment according to EP 1 740 909 B1 is set homogeneously over a wafer and then preferably oriented parallel to the long strips, requires an angular difference between the two closely adjacent sensors, so that these sensors are positioned on two separate chips. At a revolution counter to EP 1 740 909 B1 , Which is positioned in a radial, rotating magnetic field, the two sensors or two Wheatstone bridge circuits from four sensors can also be arranged spatially widely separated on two chips and also take other angles than 90 ° to each other, z. B. 180 °. In the radial magnetic field z. B. an angular position of 180 °, that the two chips are stationary, with the rotating shaft in the middle. The magnet system is fixed to the shaft, to which the sensors react. An angle counter tells a reading electronics at what angle the magnetic field is applied, and which sensor or which Wheatstone bridge circuit of the magnetic rotation counter is in the one-to-one state and may be read out.

For a better understanding of the present invention will be described below, as the known from the prior art sensor of the magnetic revolution counter after EP 1 740 909 B1 Turns counts and stores in magnetization patterns. It will be off EP 1 740 909 B1 the particular design chosen, in which the sensor has the shape of an elongated spiral with N turns, which has an enlarged area at the beginning of the spiral. The spiral has 2N elongated strips and 2N curvature segments connecting two strip segments each. 1 schematically shows such a sensor 1 to EP 1 740 909 B1 for N = 2. The enlarged area at the beginning of the spiral acts as a domain wall generator 2 , The spiral has 2N stretched strip segments 3a . 3b . 3c and 3d , as well as four curvature segments 4a . 4b . 4c and 4d ,

If the sensor 1 is exposed to a rotating magnetic field of corresponding intensity arises in the domain wall generator 2 for each 180 ° magnetic field rotation, a 180 ° magnetic domain wall. A magnetic domain wall is an area where the magnetization is within a short distance of a few 100 nm to a few microns length changes from one direction to another direction. 2 schematically shows a 180 ° magnetic domain wall in which the magnetization direction rotates through 180 °. In 2a 1 to 7 magnetization directions are shown forming a 180 ° domain wall. This occurs when the magnetic field is rotated clockwise by 180 ° from right to left. Further rotation of the magnetic field by a further 180 ° from left to right produces another 180 ° domain wall with magnetization directions 7-13, as in FIG 2 B shown.

3 shows in a section schematically how magnetic domain walls are generated and in the sensor 1 be transported. The magnetic domain walls become in the domain wall generator 2 generated because in the domain wall generator 2 the magnetization rotates almost parallel to the rotating magnetic field and at the same time the magnetization in the adjacent narrow strip 3a due to the shape anisotropy, remains virtually unchanged over large angular ranges of the rotating magnetic field. Starting from a homogeneous magnetization ( 3a ) forms, due to the rotating magnetic field, at the beginning of the strip a domain wall 5 out ( 3b ). When a sufficiently large magnetic field component is shown in the stripe direction ( 3c ), this domain wall becomes 5 transported in the strip. 3d shows the position of the domain wall 5 after a 180 ° magnetic field rotation. She is through the strip 3a transported in the further strip section, not shown here, whereby the strip shown 3a magnetization reversal.

In the sensor 1 is at the end of the strip 3a the curvature 4a , so that the domain wall 5 after 180 ° magnetic field rotation in the curvature 4a located.

4 schematically shows the 2N + 1 = 5 magnetization states of a sensor 1 with N = 2 turns, and like these five magnetization states with the number of magnetic domain walls 5 in the sensor 1 correlate. Starting from the empty initial state at 0 ° magnetic field rotation ( 4a ), the magnetic field is rotated clockwise by 180 ° ( 4b ), 360 ° ( 4c ), 540 ° ( 4d ) and 720 ° ( 4e ), which produces a 180 ° domain wall after each 180 ° magnetic field rotation. In 4a (0 °) there is no magnetic domain wall in the sensor 1 , After 180 ° magnetic field rotation ( 4b ) became a newly created domain wall 5a through the strip 3a in the curve 4a transported. After 360 ° magnetic field rotation ( 4c ) became the domain wall 5a in the curve 4b transported, causing the strip 3b was remagnetized. At the same time became a second domain wall 5b generated and in the curvature 4a transported, causing the strip 3a was re-magnetized again. In ( 4d ) after 540 ° magnetic field rotation are three magnetic domain walls 5a . 5b and 5c in the bends 4a . 4b and 4c and after 720 ° magnetic field rotation ( 4e ) four magnetic domain walls 5a . 5b . 5c and 5d in the bends 4a . 4b . 4c and 4d ,

The in the 4 The five magnetization orders shown are uniquely linked to five different resistance values. 5 schematically shows these resistance values over the rotation angle of the magnetic field. The resistance values are shown for a sensor 1 in which the reference direction 8th (please refer 4a ) from left to right, ie strips magnetized to the right are lower impedance than bands magnetized to the left. For each resistance value, the associated magnetization order of 4 (Partial image) specified.

In 4 and 5 the magnetization state with 0 magnetic domain walls is defined as the number of revolutions 0. It could also be defined as a rotation number N (generalized for an N-wind spiral) when counting from 0 to N. However, it could also be defined as a number of revolutions -N / 2 or + N / 2 when counting from -N / 2 to + N / 2. The count from -N / 2 to + N / 2 is useful if you have to distinguish between right and left rotation, eg. B. at a steering wheel. For this count, N should be a number divisible by 2. The count from 0 to N or from N to 0 is useful for cases in which an object is only rotated forward or backward.

5 shows the measurable voltage swings on the sensor as a function of the magnetization states of the individual strip conductors during the magnetic field rotation and thus the switching behavior of an ideal sensor. However, a real sensor switches hysterically, so that there are angular ranges in which it may not be read out. For the magnetic revolution counter this means that a second sensor must be arranged so that at each angle at least one of the two sensors is not in the hysteretic state and may be read.

• – die Anzahl der zählbaren Umdrehungen N ist begrenzt auf ca. zehn Umdrehungen, weil sonst die messbaren Spannungshübe nicht mehr sicher differenzierbar sind;
• – es werden wegen des hysteretischen Schaltverhaltens mindestens zwei Sensoren oder mindestens zwei Wheatstone-Brücken aus jeweils vier Sensoren benötigt;
• – der Umdrehungszähler nach EP 1 740 909 B1 erfordert zudem zwei räumlich getrennte Chips.

The disadvantages of the present invention on the next coming magnetic revolution counter after EP 1 740 909 B1 are:

• - The number of countable revolutions N is limited to about ten revolutions, because otherwise the measurable voltage swings are no longer differentiable;
• - Due to the hysteretic switching behavior, at least two sensors or at least two Wheatstone bridges each consisting of four sensors are required;
• - the revolution counter after EP 1 740 909 B1 also requires two spatially separated chips.

typically, have above magnetic revolution counter depending on the layer system a GMR effect of 5% to 8%. The size the GMR effect and the technically required minimum distance between the measurable resistance values (or voltage values at a voltage measurement) limits the number of countable revolutions N to about ten, since the corresponding 2N + 1 resistance values (Equidistant) on the resistance range of the GMR effect split. At N> 10 The individual resistance levels are so small that a safe Separation can no longer be guaranteed.

The sensor of the magnetic revolution counter intrinsically exhibits a hysteresis. That is, with left-hand rotation of the external magnetic field influencing the revolution counter, the sensor switches back and forth at an angle other than a right turn between two states of magnetization. The distance between these switching angles is the hysteresis, which depends on many parameters, eg. Of the strength of the external magnetic field, the GMR layer stack, the thickness of the sensor layer, the smoothness of the edges of the sensor element. The hysteresis thus enforces the use of at least two sensors or Wheatstone bridges, which are arranged to each other so that at each angle at least one sensor or a Wheatstone bridge is in a one-way magnetization state outside the hysteresis and can be read. Would you after EP 1 740 909 B1 If you want to suppress the hysteresis of the revolution counter safely, you would need eight sensors. This multitude of sensors, together with the required bond areas, increases the chip size and thus increases the cost per chip.

Of the present invention is based on the object, a magnetic Turn counter to create a secured and differentiable count basically allows substantially more than ten turns and the known in known comparable revolution sensors Hysteresis problem solved by the use of only one sensor.

The The object is achieved by the characterizing features of the first patent claim solved. Advantageous embodiments are the subject of the subordinate Claims.

The Invention will be described below with reference to several embodiments be explained in more detail. They show schematically:

1 a part of a prior art magnetic revolution counter;

2 a magnetic 180 ° domain wall in which the direction of magnetization rotates 180 °;

3 in a section, how magnetic domain walls generated and in the sensor 1 be transported;

4 the transport of magnetic domain walls upon rotation of an external magnetic field around 720 °;

5 to 4 associated resistance values via the angle of rotation of the magnetic field;

6 a first principal embodiment of the invention;

7 a partial section after 6 with different magnetization states in the presence or absence of a domain wall;

8th Potential curves and hysteretic regions according to the first embodiment with rotation of the external magnetic field;

9 a second embodiment of the invention;

10 four different possible magnetization arrangements in a partial section after 9 ;

11 Potential curves and hysteretic regions according to the second embodiment with rotation of the external magnetic field;

12 an advantageous Beschaltungsvariante the second embodiment;

13 Exemplary sensor signals for reading both sides of a variant according to 12 ;

14 a first special contact training for a sensor after 12 ;

15 a further embodiment of a variant according to the 12 and 14 in diamond form with further differentiated contact formations and

16 separate strip sections for the formation of reference signals.

For the sake of clarity and without limitation of the generality to be achieved with the present invention, will be in the following only examples of two revolutions are described in the figures instead of sensors for the revolution counting of ten or more revolutions. These differ from actually realizable according to the invention revolution counters only in the number of turns and the associated electrical contacts from each other.

A clear, although not preferred first embodiment of the invention provides a special, in principle EP 1 740 909 B1 to use known sensor, in which, however, novel an elongated spiral, is connected as a voltage divider. As with the classic Wheatstone bridge circuit, this makes the sensor signal temperature independent. In this embodiment of the invention, the sensor - the elongated spiral with N turns and 2N strips - applied via two common contacts on each N strips with a potential and measured the potential drop for each turn between one of these common contacts and further provided in the bends individual contacts , The potential drop depends on the magnetization of the respective turn and on the position of the reference direction. For a better understanding of this solution, the sensor will be considered below so that the elongated strips, as in FIG 6 shown, are horizontal and that the strip connecting curvatures are right or left of the strips.

• 1. es existiert keine magnetische Domänenwand in der Krümmung 4a, die beiden lang gestreckten Streifenabschnitte 3a, 3b sind im Uhrzeigersinn magnetisiert (Streifen-Abschnitt 3a nach rechts und Streifenabschnitt 3b nach links, 7a);
• 2. es existiert eine magnetische Domänenwand in der Krümmung 4a, so dass die lang gestreckten Streifenabschnitte 3a und 3b nach links magnetisiert sind (7b)
• 3. es existiert keine magnetische Domänenwand in der Krümmung 4a, die beiden lang gestreckten Streifenabschnitte 3a und 3b sind im Gegenuhrzeigersinn magnetisiert (7c);
• 4. es existiert eine magnetische Domänenwand in der Krümmung 4a, so dass die lang gestreckten Streifen 3a und 3b nach rechts magnetisiert sind (7d).

The sensor 1 , according to 6 , is according to the invention with two electrical contacts 6a and 6b provided, in this example, each of the strips 3b and 3d and 3a and 3c contact the top or bottom together. In preferred embodiments, these contacts are located 6a . 6b each in the middle of the illustrated elongated strip. About these two contacts 6a . 6b the sensor is subjected to an electrical potential. In the bends 4b . 4d The spiral in the example on the left are further individual electrical contacts 7a . 7b provided, each contact a turn. The preferred readout principle of this so wired magnetic sensor provides that all windings on the common contacts 6a . 6b be subjected to a potential and that the potential drop is read sequentially for each turn. This is preferably done by a conventional per se and therefore not further described here multiplexer circuit, the common contact 6a or 6b successively the connection to the individual contacts 7a . 7b produced in the bends. The voltage drop is thus measured in the substantially elongated strip sections ( 3b or 3d , respectively. 3a or 3c ) (Winding segments). In the context of the invention, the contacts 7a and 7b in terms of area, preferably be designed so large that the concrete position of a domain wall within the curved strip area is meaningless. In principle exist in each turn between the contacts 6a and 6b in the intermediate strip sections 3a and 3b , respectively. 3c and 3d exactly four magnetic states, as in 7 shown schematically for the first turn:

• 1. There is no magnetic domain wall in the curve 4a , the two elongated strip sections 3a . 3b are magnetized clockwise (strip section 3a to the right and strip section 3b to the left, 7a );
• 2. There is a magnetic domain wall in the bend 4a so that the elongated strip sections 3a and 3b magnetized to the left ( 7b )
• 3. There is no magnetic domain wall in the curve 4a , the two elongated strip sections 3a and 3b are magnetized counterclockwise ( 7c );
• 4. There is a magnetic domain wall in the bend 4a so the long stripe 3a and 3b magnetized to the right ( 7d ).

• 1. < 50% (im Folgenden L (= low)), da Streifenabschnitt 3a einen geringeren Widerstand aufweist als Streifenabschnitt 3b;
• 2. 50% (im Folgenden auch als M (= median), da die Widerstände der Streifenabschnitte 3a und 3b gleich groß sind;
• 3. > 50%, (im Folgenden H (= high)), da Streifenabschnitt 3a einen größeren Widerstand aufweist als Streifenabschnitt 3b;
• 4. 50%, da die Widerstände der Streifenabschnitte 3a und 3b gleich groß sind.

If the reference direction 8th in the sensor 1 , as in 7 pointing to the right and the potential drop across the strip section 3a is measured, thus resulting in the following potential drops for the magnetization states 1-4:

• 1. <50% (hereinafter L (= low)), because strip section 3a has a lower resistance than strip portion 3b ;
• 2. 50% (hereinafter also referred to as M (= median), since the resistances of the strip sections 3a and 3b are the same size;
• 3.> 50%, (hereinafter H (= high)), because strip section 3a has a greater resistance than strip portion 3b ;
• 4. 50%, as the resistances of the strip sections 3a and 3b are the same size.

The deviation from the potential value 50% for the magnetization states 1 and 3 depends on the magnitude of the GMR effect and on the cosine of the angle between the reference direction 8th and strip section 3a ,

The initial state of the sensor 1 is, such as in 4a shown free of magnetic domain walls. That is, each turn is in the first magnetic state so that the potential drop is <50%. (If the reference direction points in the other direction, the potential drop is> 50%.)

The preferred readout process of the sensor according to the invention 1 provides that controlled by a multiplexer, one after the other an electrical connection from the contact 6a to the contacts 7a and 7b is closed and each of the potential drop is measured. If the potential drop of the first turn <50% of the voltage between the contacts 6a and 6b is (voltage drop between contact 6a after contact 7a ), is the sensor 1 free of magnetic domain walls and thus in the initial state = zero revolutions. If the potential drop of the first turn = 50%, only the magnetization state 360 ° or 720 ° can be present. Which of the two states is present is determined by measuring the potential drop from the contact 6a to contact 7b the second turn determined. If the potential drop is <50%, then one revolution was counted, if the potential drop = 50%, two revolutions were counted.

8th shows the above schematically. In 8a ) is the signal of the outermost first turn (in 8th designated W1; Voltage at the contact 7a ) and in 8b ) the signal of the second turn (W2, voltage at the contact 7b ) is plotted over the angle of rotation of the magnetic field. For an ideal sensor, the signal would be in 8a ) at exactly 360 ° from the low low level to the middle 50% level. At the second turn, the voltage swing would be in 8b ) exactly at a further rotation by 360 °, ie at 720 ° magnetic field rotation, done. Since the real sensor is hysteretic, depending on the direction of rotation, the jumps occur at an angle of> 360 ° or> 720 ° (magnetic field rotation in the spiral sense of rotation) or at an angle <360 ° or <720 ° (magnetic field rotation counter to spiral rotation direction). As a consequence, the sensor must not be in one of the hysteretic angular ranges ( 10 respectively. 10a ) are read out by rectangles in 8th are symbolized. These angular ranges have a periodicity of 180 °. In the first hysteretic angle range 10a For example, the voltage signal may take any value between the L level and the M level in the hysteretic angular ranges 10 every value between the L level and the H level.

In order to be able to read the revolution counter at any time, a second sensor is activated 1 required, which is positioned rotated by 90 ° to the first sensor in the magnetic revolution counter. This provides a signal phase-shifted by 90 °, which must then be read when the first sensor in a hysteretic angular range ( 10 respectively. 10a ) is located. If the first sensor is readable, the second sensor must not be read out, since it will then be in one of the hysteretic angular ranges ( 10 respectively. 10a ) is located. Since the hysteresis is <90 °, there are also angular ranges in which both sensors may be read out. The information about the angle provides an unillustrated, conventional angle sensor to the readout electronics, which then decides which sensor may be read out.

• 1. Winkelsensor-kontrolliert nur dann ausgelesen wird, wenn der Sensor nicht in einem hysteretischen Winkelbereich ist,
• 2. das zuerst das Spannungssignal der ersten Windung, die an den Domänenwandgenerator sich anschließt ausgelesen wird
• 3. und danach nacheinander die zweite Windung bis zur N. Windung ausgelesen wird.

Once in a sensor 1 one turn is domain-wall-free, then the further inward turns are domain-wall-free, since the magnetic domain walls successively from the outer beginning of the spiral, the domain wall generator 2 to be transported to the end of the spiral. The preferred readout method of the sensor provides that

• 1. Angle sensor-controlled is only read out when the sensor is not in a hysteretic angular range,
• 2. First read out the voltage signal of the first turn connected to the domain wall generator
• 3. and then successively the second turn is read to the N. Winding.

That is, the windings of the sensor 1 are read from outside to inside. The reading of the turns can be stopped as soon as a turn delivers a low-level voltage signal. The low-level signal means that no domain wall has passed under the read individual contact and thus no domain wall can be present in further turns inside. In 8th is it enough for. Example, read out at 270 ° magnetic field rotation, only the first turn, as this is in the low-level state. At 450 ° magnetic field rotation, the first turn is in the median state, so that also the second turn must be read, which is at this angle in the low-level state. Only at a magnetic field rotation of 720 ° both windings are in the M state.

• 1. Durch die Messung des Potentialabfalls in jeder Windung ist der dort messbare Potentialhub unabhängig von der Anzahl der Umdrehungen. Dadurch ist die Anzahl an zählbaren Umdrehungen nicht mehr durch die Größe des GMR-Effektes auf ca. zehn Umdrehungen begrenzt. Die einzige Begrenzung ist herstellungsbedingt, denn jede Windung verlängert den Sensor und erhöht damit die Wahrscheinlichkeit, dass die Spirale, aufgrund eines Defektes, unterbrochen ist. Mit guter Ausbeute realisierbare Spirallängen ermöglichen Sensoren, die 40–50 Umdrehungen zählen könnten, welche aber nach EP 1 740 909 B1 , wie oben erläutert, nicht mehr ausgewertet werden könnten.
• 2. Ein weiterer Vorteil ist, dass nicht mehr vier Spiralen in einer Wheatstone-Brücke zusammen geschaltet werden müssen, sondern durch die Art der Beschaltung schon eine Spirale als Sensor allein, wie eine Wheatstone-Brücke, ein temperaturunabhängiges Signal liefert.
• 3. Ein besonderer Vorteil der erfindungsgemäßen Lösung ist, dass der Sensor 1 überdreht werden darf. Bei der Verwendung von vier Spiralen, die in einer Wheatstonebrücke geschaltet sind, hat man nämlich das große Problem, dass bei einer Überdrehung die sich in dem innersten Spiralenarm befindlichen Domänen an die Enden der Spiralen wandern und dort verschwinden. Wenn dies bei allen Spiralen einer Wheatstonebrücke erfolgt, erhält man wieder definierte Verhältnisse. Wenn aber, was prinzipiell nicht auszuschließen ist, dies nicht an allen vier Spiralen erfolgt, ist die Kennlinie undefiniert geändert und der Sensor liefert keine gültigen Signale mehr. Deshalb muss bei der Wheatstonebrückenlösung nach dem Stand der Technik immer ein mechanischer Anschlag vorhanden sein, der ein Überdrehen sicher verhindert. Die hier vorgeschlagene Lösung funktioniert jedoch selbst bei nur einer Spirale, so dass deshalb auf einen mechanischen Anschlag verzichtet werden kann.

Already this first solution according to the invention has several advantages over the known prior art:

• 1. By measuring the potential drop in each turn, the potential swing measurable there is independent of the number of turns. As a result, the number of countable revolutions is no longer limited by the size of the GMR effect to approximately ten revolutions. The only limitation is manufacturing, as each turn lengthens the sensor, increasing the likelihood that the spiral will be broken due to a defect. Spiral lengths that can be realized with good yield enable sensors that could count 40-50 revolutions, but which can after EP 1 740 909 B1 as explained above, could no longer be evaluated.
• 2. Another advantage is that no longer four spirals in a Wheatstone bridge must be connected together, but by the type of wiring already provides a spiral as a sensor alone, such as a Wheatstone bridge, a temperature-independent signal.
• 3. A particular advantage of the solution according to the invention is that the sensor 1 be overrun may. In fact, when using four spirals connected in a Wheatstone bridge, the major problem is that, when over-rotated, the domains located in the innermost spiral arm migrate to and disappear from the ends of the spirals. If this happens with all spirals of a Wheatstone bridge, one gets again defined conditions. If, however, which can not be ruled out in principle, this is not done on all four spirals, the characteristic curve is undefined and the sensor no longer supplies valid signals. Therefore, in the Wheatstone bridge solution of the prior art, there must always be a mechanical stop which reliably prevents over-rotation. However, the solution proposed here works even with only one spiral, so that therefore can be dispensed with a mechanical stop.

A second embodiment of the invention provides that the elongated spiral is distorted to a symmetrical rhombus, in which each turn consists of four strip segments, each arranged at a 90 ° angle one behind the other, and in each case two strip segments as a voltage divider or Wheatstone Half bridge are wired. 9 shows such a sensor 11 , The sensor 11 has a domain wall generator 12 on, in the example at N = 2 turns 4N + 1 = 9 strip segments ( 13a to 13i ) with 4N = 8 bends ( 14a to 14h ) connect. In practice, these curvatures have radii of curvature in the order of 1 .mu.m, which is therefore not shown separately. Two big contacts 16a and 16b serve for potential feed. In the example are left in the curvatures, between the big first contacts 16a and 16b , individual contacts 17a and 17b provided, each contact only one turn.

The sensor is read out by the potential difference between one of the two large contacts 16a or 16b and the contacts 17a and 17b sequentially or in parallel (if, for example, N voltage potential measuring AD converters are provided) is determined to the potential drops in the strip segments ( 13e respectively. 13i ) to eat. Preferred, described below embodiments of this second embodiment of the invention provide that the strip segments 13a to 13i between all electrical contacts are the same length.

• 1. es existiert keine magnetische Domänenwand in der Krümmung 14d, die beiden langgestreckten Streifenabschnitte 13d, 13e sind im Uhrzeigersinn magnetisiert (Streifen-Abschnitt 13d nach rechts und Streifenabschnitt 13e nach links, 10a);
• 2. es existiert eine magnetische Domänenwand in der Krümmung 14d, so dass die langgestreckten Streifenabschnitte 13d und 13e nach links magnetisiert sind (10b);
• 3. es existiert keine magnetische Domänenwand in der Krümmung 14d, die beiden langgestreckten Streifenabschnitte 13d und 13e sind im Gegenuhrzeigersinn magnetisiert (10c);
• 4. es existiert eine magnetische Domänenwand in der Krümmung 14d, sodass die langgestreckten Streifen 13d und 13e nach rechts magnetisiert sind (10d).

In each turn there are the following, in 10 exemplified, four magnetization orders in the strip segments left between the contacts 16a and 16b (shown for 13d and 13e ):

• 1. There is no magnetic domain wall in the curve 14d , the two elongated strip sections 13d . 13e are magnetized clockwise (strip section 13d to the right and strip section 13e to the left, 10a );
• 2. There is a magnetic domain wall in the bend 14d so that the elongated strip sections 13d and 13e magnetized to the left ( 10b );
• 3. There is no magnetic domain wall in the curve 14d , the two elongated strip sections 13d and 13e are magnetized counterclockwise ( 10c );
• 4. There is a magnetic domain wall in the bend 14d so the elongated strips 13d and 13e magnetized to the right ( 10d ).

• 1. < 50%, (L = low), da Streifenabschnitt 13e einen geringeren Widerstand aufweist als Streifenabschnitt (13d;
• 2. 50% (M = median), da die Widerstände der Streifenabschnitte 13d und 13e gleich groß sind;
• 3. > 50%, (H = high), da Streifenabschnitt 13e einen größeren Widerstand aufweist als Streifenabschnitt 13d;
• 4. 50%, da die Widerstände der Streifenabschnitte 13d und 13e gleich groß sind.

When the magnetization direction of the hard magnetic layer 18 in the sensor 11 , as in 9 indicated to the right (at the preferred 45 ° angle to the strips) and the potential drop across the strip portion 13e is measured, thus resulting in the following potential drops for the magnetization states 1-4:

• 1. <50%, (L = low), because strip section 13e has a lower resistance than strip section ( 13d ;
• 2. 50% (M = median), because the resistances of the strip sections 13d and 13e are the same size;
• 3.> 50%, (H = high), because strip section 13e has a greater resistance than strip portion 13d ;
• 4. 50%, as the resistances of the strip sections 13d and 13e are the same size.

During a full revolution of the external magnetic field, a 180 ° magnetic domain wall passes through a full turn of the sensor 11 and thus switches over the four magnetization states in this winding one after the other every 90 °. The preferred read-out principle of this second embodiment according to the invention is similar to the first solution according to the invention. One measures, preferably multiplexer controlled, all turns successively, starting at the first turn after the domain wall generator (contact 17a in the bend 14d ). The measurement can be terminated in the winding in which the potential drop is <50% for the first time. Generalized for N-wind spirals to count N revolutions in this read-out principle is the counted revolution number, which is a one-to-one magnetization pattern in the sensor 11 is stored:
Number of revolutions = first number of turns (with low-level signal) - one
or
Number of revolutions = N, if no low-level signal is detected.

11 again shows this schematically. In 11a ) is the potential of the first turn (ge measure at the contact 17a ) and in 11b ) the potential of the second turn (measured at the contact 17b ) is plotted against the magnetic field rotation. For an ideal sensor, the signal would be in 11a ) jump for the first time at exactly 360 ° from the low low level to the middle 50% level. At the second turn, the jump would be in 11b ) after another 360 ° for the first time at exactly 720 ° magnetic field rotation. After the first signal jump, there is again a signal jump every 90 °, since the magnetic domain wall is transported to the next bend, whereby the strip in between is re-magnetized. In an ideal sensor, in the first turn, signal jumps at 450 ° magnetic field turn from 50% level to high level, 540 ° magnetic field turn from high level to 50% level, and 630 ° magnetic field turn from 50% level into the low level. The signal is thus periodically from the first revolution (360 °) with a periodicity of 360 °. In the second turn, the signal is periodic from the second turn (720 °).

There the real sensor switches hysteretically, the first-time ones take place Jumps depending on the direction of rotation at an angle> 360 ° or> 720 ° (magnetic field rotation in spiral rotation) or at an angle <360 ° or <720 ° (magnetic field rotation against spiral rotation).

When As a consequence, the sensor must not be in the hysteretic angular ranges be read, in which he switches from the low level in the 50% level.

In 11 are the hysteretic angular ranges due to rectangles ( 20 . 21 ) symbolizes. In order to be able to read the revolution counter at any time, either a second sensor is activated 11 required, which is positioned rotated 90 ° to the first sensor in the magnetic revolution counter, or the sensor 11 is how in 12 shown, preferably with further individual contacts ( 17c and 17d ) in the curves ( 14b and 14f ) Mistake. These two solutions provide two 180 ° out of phase signals.

• – 13a) zeigt das Spannungssignal des Kontaktes 17c, bei dem der erstmalige Signalsprung bei 180° erfolgt,
• – 13b) zeigt das dazu um 180° phasenverschobene Spannungssignal des Kontaktes 17a, bei dem der erstmalige Signalsprung bei 360° erfolgt,
• – 13c) zeigt das Spannungssignal des Kontaktes 17d, bei dem der erstmalige Signalsprung bei 540° erfolgt,
• – 13d) zeigt das dazu um 180° phasenverschobene Spannungssignal des Kontaktes 17b, bei dem der erstmalige Signalsprung bei 720° erfolgt.

13 schematically shows the sensor signals when the sensor after 12 read on both sides. In 13a ) and 13b ) are signals of the first turn and in 13c ) and 13d ) Signals of the second turn are plotted:

• - 13a ) shows the voltage signal of the contact 17c in which the first signal jump occurs at 180 °,
• - 13b ) shows the 180 ° phase-shifted voltage signal of the contact 17a in which the first signal jump occurs at 360 °,
• - 13c ) shows the voltage signal of the contact 17d in which the first signal jump occurs at 540 °,
• - 13d ) shows the 180 ° phase-shifted voltage signal of the contact 17b , in which the first signal jump takes place at 720 °.

The signal from the contact 17d is opposite the signal of the contact 17c from 540 ° magnetic field rotation in phase and the signal from the contact 17b is opposite to the signal from the contact 17a from 720 ° magnetic field rotation in phase. Due to the phase shift of 180 ° between the voltage signals from the left contacts ( 17a and 17b ) to the voltage signals from the right contacts ( 17c and 17d ) This sensor can be advantageously always read without the need for a separate second sensor.

The readout principle of the sensor according to the invention 11 examines whether a threshold 19 between low-level state and 50% level (median-level) is exceeded. The low-level signal means that no domain wall has passed under the read-out single contact and thus no domain wall is present in further turns inside. The voltage signal of this contact may only be read out if the magnetic field rotation is in a hysteretic angular range 20 is at which the voltage signal switches from the low-level state to the M-level state. Otherwise, this voltage signal must always be read out, even in the hysteretic angular ranges 21 in which the voltage signal switches from the M level to the high level. Since all voltage values between M-level and H-level are above the threshold to be detected 19 The relevant information that a domain wall has passed the relevant individual contact is always given. Thus, the phase shift of the voltage signals between left and right contacts in the sensor allows 11 that at any time the voltage signals can be read out either via the left or via the right individual contacts. This means that the magnetic revolution counter only needs one sensor 11 with single contacts left and right, instead of two sensors 11 with individual contacts either left or right in the sensor 11 or with two sensors 1 according to the first embodiment of the invention.

Another advantage of this second embodiment of the invention is that the 180 ° domain wall runs every 90 ° magnetic field rotation in the next strip. As a result, the intrinsically present in the real sensor hysteresis is narrower than in the sensor according to the first embodiment of the invention. In this solution, the magnetic domain wall runs only for every 180 ° magnetic field rotation in the adjacent stripes, so that the hysteresis is greater for the same magnetic field. As a result, from the theoretically usable working window H _min to H _max , in which the sensor counts error-free, in the second embodiment according to the invention the upper half and in the first embodiment only the upper third are used. H _min refers to the magnetic field in which the domain walls are transported without error through the spiral, ie not pinned to defects unintentionally. H _max is the magnetic field at which a magnetic domain wall is not yet formed in an uncontrolled manner in the strip.

In 14 an embodiment of the sensor is shown, in which the individual contacts 37a and 37b are formed so that the long straight webs between them have the same length for all parts of the spiral.

This has the advantage that the current load is identical for all branches. 14 is self-explanatory and therefore needs no further explanation.

Another invention, in 15 illustrated embodiment provides that the diamond described above within a turn has at least one angle deviating from 90 °. Preferred embodiments provide symmetrical diamonds with alternating blunt and acute angles, e.g. 25 ° / 155 ° / 25 ° / 155 °. The preferred embodiment of this solution according to the invention provides that the reference direction 38 along the long side of the rhombus and the individual contacts are positioned at the obtuse angles. This makes better use of the GMR effect than the second solution (90% of the GMR stroke is available at an acute angle of 25 ° instead of 71% at an angle of 90 °). Due to the angular difference between the acute and obtuse angles in the rhombus, a "geometric hysteresis" is built into the sensor signal, which corresponds to the difference between the two angles. The sensor in 15 has the peculiarity that the contacts 36a and 36b of the 14 are now executed individually for each loop. This gives the user the option of using either the electrodes as common electrodes 36a and 36b or 37a or 37b embody. This does not lead to a fundamentally different characteristic and can also be found in the 14 shown solution used.

Another embodiment of the invention, as in 16 is shown, provides that in addition to the sensor one or more separated from the rest of the spiral individual strips 39a and 39b are provided, which in the example in each case parallel to the strip 33a and 33b and or 33c and 33d are positioned. These stripes may be due to lack of connection to the domain wall generator 32 not be remagnetized, ie the magnetization of the sensor layer in this strip always points in the same direction. As a result, the center contact has the potential drop of 50% when applied to the potential at its ends, as the sensor 1 or 11 in the previous examples. This signal can serve as a reference signal in the measurement of the potential drops in the individual windings of the sensor.

Further inventive solutions provide that instead of in 6 sensor shown a variant is used, in which on both sides of the spiral individual contacts are provided in all curvatures. This sensor provides similar to the second solution according to the invention with two-sided individual contacts two signals phase-shifted by 180 °. These signals are useful if you want to use a 180 ° angle sensor instead of a 360 ° angle sensor.

 All in the description, the specific embodiments, the claims and / or drawings recognizable features can be used individually or in any combination be essential to the invention with each other.

1, 11, 31

magnetic revolution counter

2, 32

Domain wall generator

3a, 3b, 3c, 3d

elongated Strip segments of a first embodiment

4a, 4b, 4c, 4d

Curvature segments of a first embodiment

5a, 5b, 5c, 5d

domain walls

6a, 6b, 16a, 16b, 36a, 36

bmehrere elongated strip sections detecting contacts

7a, 7b, 17a, 17b, 37a, 37b

Single contacts

8th, 18, 38

impressed Reference direction in the GMR sensor

10 10a, 20, 21

hysteresis

13a until 13i

just Strip segments in a second embodiment

14a until 14h

curvatures

33a to 33d

of equal length executed strip segments

39a until 39

'non reversible strip sections

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - EP 1740909 B1 [0002, 0002, 0002, 0002, 0003, 0003, 0003, 0011, 0011, 0013, 0034, 0044]

Claims (9)

Magnetic revolution counter for unambiguously determining a predefinable number of revolutions N of a rotating element to be determined, in which a sensor ( 1 ; 11 ; 31 ) substantially constituted by an N-looped arrangement consisting of a GMR stack of layers into which magnetic 180 ° domains are introduced, stored and readable by measurement of electrical resistance, characterized in that stretched executed loop sections at a predeterminable angle to the embossed in the sensor reference direction ( 8th ; 18 ) are provided, which preferably in the center with, can be acted upon by an electrical potential contacts ( 6a . 6b ; 16a . 16b ; 36a . 36b ), which are provided serially or in parallel with the reading of electrical resistance ratios of individual loop sections to further individual contacts provided in regions of curvature of the loop-like arrangement (US Pat. 7a . 7b ; 17a . 17b ; 37a . 37b ), wherein the determined resistance conditions provides a direct measure of the presence or absence of a magnetic domain in the corresponding loop portion and thus a clear statement about the number of completed revolutions. Magnetic revolution counter according to claim 1, characterized in that the longitudinal extent alignment of stretched executed loop sections ( 3a - 3d ) parallel to the reference direction ( 8th ) in the sensor ( 1 ), the stretched first loop sections ( 3a . 3c ) of a first common, with on the loop sections ( 3a . 3c ) centrally arranged first contact ( 6b ) and the opposite elongated second loop portions (FIG. 3b . 3d ) from a likewise centrally arranged second contact ( 6b ), wherein between these contacts an electrical potential is applied and the serial or parallel readout of the electrical resistance ratios of loop sections to further individual contacts provided at least on one side in a curved region of the loops ( 7a . 7b ) he follows. Magnetic revolution counter according to claim 1, characterized in that the longitudinal extent alignment of stretched adjacent loop sections [ 13a and 13b . 13e and 13f ] - [ 13c and 13d . 13g and 13h ]; [ 33a and 33d etc.]-[ 33b and 33c etc.]) at an angle, in the order of magnitude of 45 ° to the reference direction ( 18 ; 38 ) in the sensor ( 11 ; 31 ), and preferably in the middle in said elongated adjacent loop sections with an electrical potential acted upon contacts ( 16a . 16b ; 36a . 36b ) are provided, which serially or in parallel the readout of the electrical resistance ratios of individual loop sections to further individual contacts provided in regions of curvature of the loop sections (US Pat. 17a . 17b ; 37a . 37b ) enable. Magnetic revolution counter according to claim 3, characterized in that the entire loop-like arrangement is diamond-shaped in plan view, wherein in opposite Rautenecken the acted upon by an electrical potential contacts ( 16a . 16b ; 36a . 36b ) are provided and in each of the remaining Rautenecken provided for separate resistance ratio measurement individual contacts ( 17a . 17b ; 37a . 37b ) are arranged. Magnetic revolution counter according to claim 4, characterized in that the diamond-shaped training the loop-like arrangement is such that adjacent Diamond legs include an angle of 90 °. Magnetic revolution counter according to claim 4, characterized in that the diamond-shaped training the loop-like arrangement is such that the diamonds distorted are designed so that each opposite Rough corners include a dull, respectively acute angle. Magnetic revolution counter according to one of claims 1 to 4, characterized in that the acted upon by an electrical potential contacts ( 6a . 6b ; 16a . 16b ; 36a . 36b ) and electrically contact each loop portion to which they are associated. Magnetic revolution counter after one of the preceding claims, characterized in that all provided electrical contacts area by area are so large that between adjacent Contacts remaining uncontacted loop sections all loops have the same length. Magnetic revolution counter according to one of the preceding claims, characterized in that in addition to the loop-like arrangement separated individual, non-magnetizable strip sections ( 39a to 39d ) are provided, which are each arranged parallel to adjacent, closed loop sections.