JP5245114B2 - Position detection device - Google Patents

Description

  The present invention relates to a rotation or linear motion position detection device for a machine product such as an industrial machine or automobile, or a jog dial of a portable information terminal.

  A ring or linear scale magnetized so that the magnetic poles are alternately reversed at a predetermined equal pitch are made to face each other, and the relative rotation of the ring and magnetic sensor or relative movement of the linear scale and magnetic sensor is accompanied. A rotary or linear pulse encoder is well known that converts the magnetic flux density in the direction of penetrating the sensor, which changes at the sensor section, into a Hall output voltage, and further outputs the converted analog signal via a Schmitt circuit. (See, for example, Non-Patent Document 1). Here, the above-described linear scale is considered to be a part of an alternating magnetized ring having an infinite radius, and therefore will be described below by taking a rotary pulse encoder as an example.

  FIG. 3 is a diagram showing an example of a conventional rotary pulse encoder. Reference numeral 11 is a ring magnetized so that the magnetic poles are alternately reversed at a predetermined equal pitch, and reference numerals 12 and 13 are Hall ICs as magnetic sensors arranged in the vicinity thereof. Here, in order to detect the rotation angle or the rotation speed, it is only necessary to count the number of pulses. In this case, only one sensor is used. FIG. 4 is a block diagram of the Hall IC used in such a case, in which the Hall element 21, the amplifier 22, the Schmitt circuit 23, and the driver are integrated. Such a Hall IC is widely used.

  In FIG. 3, Hall elements 12 and 13 are shown. At some point, the Hall IC 12 is depicted as being located at the center of the S pole, and the Hall IC 13 is located at the boundary of the pole. Such an arrangement of the Hall ICs with respect to the magnetized ring 11 indicates a configuration in the case of detecting the rotation direction. This case will be further described with reference to FIG. FIG. 6 is a diagram for easily explaining the relationship between the positional relationship between the magnetized ring and the sensor and the magnetic flux density received by the sensor, and the magnetized ring is drawn linearly. As shown in FIG. 6, at least two sensors (sensor A and sensor B indicated by reference numerals 12 and 13) are arranged, for example, at intervals of half the pitch of the magnetized ring, and the rise of the output of either sensor or It is also possible to detect the direction of rotation by triggering at the fall and looking at the output of the other sensor.

  FIG. 7 shows the relative movement of the sensors A and B when the sensors A and B in FIG. 6 move or rotate with respect to the magnetized ring 11 at a relatively constant speed or a constant angular speed. FIG. 6 is a diagram showing changes in magnetic flux density detected by Hall elements in sensors A and B. Here, the point of t = 0 indicates, for example, the positional relationship between the pitch of the magnetized ring shown in FIG. 6 and the sensor. For example, regardless of which direction the sensor A rotates, the detected magnetic flux decreases because the sensor A is at the center of the N pole at the time t = 0. On the other hand, since the sensor B is at the boundary portion of the magnetic pole at the time of t = 0, the sensor B moves to the N pole side or the S pole side depending on the moving direction. When going to the N pole, the sensor A changes so as to receive the magnetic flux received at the time of t = 0, and when going to the S pole, the opposite is made.

  In FIG. 7, when moving in the forward direction, the output of sensor B when the output of sensor A falls is low, indicating that it is high when moving in the reverse direction.

  Here, the interval between the two sensors is preferably π / 2 in terms of an electrical angle of the phase difference between the output signals. In this case, the arrangement of the sensors A and B depends on the pitch of the magnetized ring. When the phase difference is π / 2, the number of pulses can be doubled as compared with the case of one sensor by taking the exclusive OR of the output states of the two sensors. Even when the magnetized ring is used, the detection resolution can be doubled as compared with the case where only the output of one sensor is used. In this case, ideally, the magnitude of magnetization and the dimension in the rotation direction of the magnetized rings are equal, and the change in magnetic flux received by the two sensors is required to be equal only by different phases. In this case, the duty ratio of the above-mentioned exclusive OR output is 1: 1, which is a constant cycle.

Asahi Kasei Microdevices Hall IC catalog 1999.7.1-96303HE version P3, P6 reference

  However, disposing the two sensors separately on the magnetized ring with a predetermined interval depending on the pitch of the magnetized ring is not suitable for mounting position deviation especially when the pitch of the magnetized ring is narrow. Is relatively large, and it is difficult to improve detection accuracy. That is, since the pitch becomes narrower, the mechanical angle corresponding to the electrical angle π / 2 becomes smaller. As a result, variations in the mechanical positions of the two sensors have a greater influence on the electrical angle phase difference. This means that the optimum distance between the two sensors varies depending on the distance from the ring.

  In order to solve these problems, two sensors are formed on the same substrate with a predetermined interval, or two sensors with uniform characteristics are formed on the same lead frame with a predetermined interval. It can be sealed in one package. However, the size and magnetization pitch of the magnetized ring to be detected vary, so depending on the magnetized ring or depending on the distance from it, it is necessary to accurately detect magnetized rings with different pitches. It was necessary to change the interval between the two sensors.

  The present invention has been made in view of such problems, and the object of the present invention is that each time the phase difference shifts due to sensitivity variations of two elements or mounting position shifts, and the magnetization pitch of the rotor changes. An object of the present invention is to provide a position detection device that solves the need to change the sensor mounting interval, that is, to provide a position detection device that does not depend on the magnetizing pitch of the rotating rotor and the interval therebetween.

In order to achieve such an object, the present invention provides a position detection device combined with an annular or linear magnetic flux generation source in which magnetic poles are alternately inverted at a predetermined equal pitch. Two Hall elements arranged at intervals of each other, a protective film arranged on the magnetic sensitive parts of the two Hall elements so as to cover the magnetic sensitive part, and arranged on the protective film A thin-film magnetic plate disposed so as to cover the magnetically sensitive portions of the two Hall elements, a first circuit for generating a sum signal of the outputs of the two Hall elements, and the two And a second circuit for generating a difference signal between the outputs of the Hall elements .
According to a second aspect of the present invention, there is provided the position detecting device according to the first aspect, wherein the output signal of the first circuit is compared with a predetermined Schmitt level and a comparison result is output. It comprises a Schmitt circuit and a second Schmitt circuit that compares the output signal of the second circuit with a predetermined Schmitt level and outputs the comparison result.
According to a third aspect of the present invention, there is provided the position detection device according to the second aspect, wherein the direction output generates a direction-related output from the output of the first Schmitt circuit and the output of the second Schmitt circuit. A circuit is provided.
According to a fourth aspect of the present invention, there is provided the position detecting device according to the third aspect, wherein outputs of the first Schmitt circuit and the second Schmitt circuit are inputted, and an exclusive OR of these inputs is inputted. A pulse output circuit for generating an output is provided.
Further, the invention according to claim 5 is the position detection device according to claim 1, wherein the direction output generates a direction-related output from the output signal of the first circuit and the output signal of the second circuit. A circuit is provided.

The invention according to claim 6 is the position detecting device according to any one of claims 1 to 5 , wherein each of the portions covering the magnetically sensitive portion of the thin-film magnetic plate has the band shape. It is an edge part which opposes a thin film-shaped magnetic board, It is characterized by the above-mentioned.

The invention according to claim 7 is the position detecting device according to any one of claims 1 to 5 , wherein each of the portions of the thin film magnetic plate that covers the magnetically sensitive portion has two Hall elements. It is divided in the direction perpendicular to the straight line connecting the two Hall elements at the intermediate point.

The invention according to claim 8 is the position detection device according to claim 4, wherein the two Hall elements, the first and second circuits, and the first and second Schmitts. The circuit, the direction output circuit, and the pulse output circuit are formed on one substrate.

The invention according to claim 9 is the position detecting device according to claim 4, wherein the two Hall elements, the first and second circuits, and the first and second Schmitts. The circuit, the direction output circuit, and the pulse output circuit are housed in one envelope.

  According to the position detection device of the present invention, when combined with a magnetizing ring, two signals dependent on the rotation direction can be obtained at a position of π / 2 without depending on the magnetizing pitch or the interval therebetween. It becomes possible to accurately detect the phase difference. In addition, since a magnetic plate is provided in the vicinity of the two Hall elements and the sum / difference of the outputs of the two Hall elements is used, an effect equivalent to the doubled sensitivity of the Hall elements can be obtained. Thereby, it can be set as the position detection apparatus which is smaller than before, does not restrict | limit the mounting interval (position) of a sensor, and can detect a rotational position with high precision.

(First embodiment)
FIG. 1A is a diagram illustrating the relationship between the Hall IC and the magnetized ring according to the first embodiment of the present invention, and FIG. 1B is a diagram illustrating the plane of the Hall IC in FIG. 1A. 1A and 1B are not enlarged views, and are not intended to represent the relative relationship between the dimensions of the magnetized ring and the Hall IC. In this Hall IC, two Hall elements are formed separately on a Si substrate, a protective film is attached on the upper part, and then the two Hall elements are plated in a rectangular shape so that they overlap at the ends. A thin film magnetic plate 14 made of a Ni—Fe alloy is formed. The surface shown in FIG. 1B is a surface arranged parallel to the circumferential surface of the magnetic pole, and the Hall elements 12 and 13 detect the magnetic flux density in the direction perpendicular to the surface shown in FIG. 1B. In FIG. 1A, the Hall ICs are oriented so that the two Hall elements are located on a straight line along the rotation direction.

  Note that, as shown in FIG. 11, the surface shown in FIG. 1B may be a surface that is disposed perpendicular to the circumferential surface of the magnetic pole. Even in this case, the Hall elements 12 and 13 detect the magnetic flux density in the direction perpendicular to the plane shown in FIG. 1B. Also in this case, the Hall IC is oriented so that the two Hall elements are located on a straight line along the rotation direction in FIG. 1A.

  In FIG. 1B, the magnetic plate 14 has a band shape having a width that can cover the magnetic sensing part of the Hall element, and the magnetic sensing part of the Hall element is located at the opposite end of one band shape. Placed in.

  FIG. 5 is a block diagram showing a circuit other than the Hall element formed on the same Si substrate. In the block diagram of FIG. 5, reference numeral 21 is a Hall element, reference numeral 22 is an amplifier, reference numeral 25 is an addition circuit, reference numeral 26 is a subtraction circuit, reference numerals 23 and 24 are Schmitt circuits having a predetermined Schmitt level, reference numeral 27 Is a direction output circuit, and 28 is an XOR circuit.

  Here, unlike the comparator having a single reference level, the Schmitt circuits 23 and 24 have different input levels (Schmitt levels) for changing the output depending on the output state, and the input / output characteristics have hysteresis characteristics. Have. A Schmitt circuit is used to prevent noise from being included in the output of the adder circuit and the subtractor circuit, thereby preventing an erroneous output from being output as the direction output or the pulse output. It is also conceivable that the output of the addition circuit or subtraction circuit is input to the Schmitt circuit through a filter.

  The outputs of the Schmitt circuits 23 and 24 are connected to the directional output circuit 27. The directional output circuit 27 observes the output of the Schmitt circuit 24 at the rising edge or falling edge of the output signal of the Schmitt circuit 23, and the output of the Schmitt circuit 24 is L level at the rising edge, or the Schmitt circuit 24 at the falling edge. Is output at H level, for example, an H signal is output. Further, if the output of the Schmitt circuit 24 is H level at the rising edge, or the output of the Schmitt circuit 24 is L level at the falling edge, for example, an L signal is output. As a result, the direction output circuit 27 outputs the rotation direction. The pulse output of the exclusive OR of the signals of the Schmitt circuit 23 and the Schmitt circuit 24 is used as a rotation pulse output.

  Here, the position detection apparatus of the present invention shown in FIGS. 1A, 1B, and 5 will be considered below.

  First, focus on the magnetic field distribution around the magnetic pole of the magnetized ring. Here, the rotation direction parallel to the circumferential surface of the magnetized ring is defined as the X direction, and the direction perpendicular to the circumferential surface is defined as the Z direction. As shown in FIG. 6, the magnetic flux density Bz perpendicular to the plane shown in FIG. 1B (perpendicular to the circumferential surface of the magnetized ring) that can be detected by the Hall element 13 with the relative movement of the magnetized ring and the Hall element. Changes sinusoidally. It is this change in magnetic flux density Bz that is converted into a signal used for rotation detection by a normal ferromagnetic thin film magnetoresistive element. On the other hand, when attention is paid to the magnetic flux density component Bx in the X direction orthogonal to the magnetic flux density Bz, this also changes in a substantially sinusoidal shape.

  FIG. 8 shows changes in Bz and Bx with respect to the relative movement with the ring at the time of calculation, calculated by magnetic field simulation. It can be seen that Bx changes with a phase difference of Bz and π / 2 (although its peak value is generally different from Bz). Here, the period corresponds to the rotation of the pitch of the magnetized ring. Since the zero-cross points of both Bz and Bx have a phase difference of exactly π / 2, if the zero-cross positions of Bz and Bx generated by the magnetizing ring can be detected simultaneously, the phase difference of the electrical angle will be π / 2 can be output. Actually, in the zero-crossing comparator, the output may fluctuate due to electrical and magnetic noises in the circuit and surroundings. Therefore, a Schmitt circuit having a predetermined hysteresis characteristic is used.

  Further, since the phase relationship between Bz and Bx depends on the rotation direction, the rotation direction can be detected by detecting which phase of the two signals is advanced. Phase detection can be performed by looking at the waveform level of the other phase at the rising or falling edge of one phase in the waveform shaped by the Schmitt circuit. The principle of detecting Bz and Bx will be described below.

  First, as a method of taking out Bx, two Hall elements arranged opposite to the magnetic pole to detect magnetic flux and a magnetic element arranged so as to bridge between the magnetic sensing portions of the two Hall elements. Consider combining boards.

  FIG. 10 is a diagram showing a state of magnetic lines of force induced near the magnetic plate when a magnetic field is applied in the X direction to the magnetic plate 14 shown in FIG. 1A. Here, the horizontal axis is the X direction, and the vertical axis is the Z direction. Magnetic field lines are sucked into the magnetic plate 14 at both ends of the magnetic plate 14, and this is because the magnetic flux density in the Z direction is generated in this portion, in other words, the magnetic flux density Bx applied in the X direction is It means that it has been converted to the magnetic flux density Bzx in the Z direction. The converted magnetic flux density Bzx in the Z direction is proportional to Bx with the function of the shape of the magnetic body and the relative position from the magnetic body as a coefficient. Further, at the right end and left end of the magnetic plate, the distribution of Bzx is also symmetric due to the symmetry of the magnetic field, the vertical distance from the magnetic plate is equal, and at the positions symmetrical in the horizontal direction, the signs are different and have the same absolute value. Therefore, a signal proportional to the X-direction magnetic flux density Bx can be extracted by arranging Hall elements in the vicinity of both ends of the magnetic body 14 and taking the difference between the output signals of both Hall elements. At this time, even if a signal in which Z-direction magnetic flux densities Bz and Bzx are superimposed is obtained, Bz applied to the two Hall elements should be the same in size and polarity due to the presence of the magnetic plate 14. Therefore, or by configuring the same so as to be the same, the influence of this Bz is canceled by taking the difference between the output signals of both Hall elements.

  On the other hand, by taking the sum of the output voltages of the two Hall elements, a signal proportional to Bz can be obtained while canceling the influence of Bzx.

  In other words, a signal proportional to Bx shown in FIG. 8 can be obtained by taking the difference between the output signals of both Hall elements, and Bz can be obtained by taking the sum of the output voltages of the two Hall elements. It is possible to obtain a signal proportional to Therefore, the Hall IC in the present invention is independent of the pitch of the magnetized ring, in other words, independently of the relationship between the distance between the two Hall elements of the Hall IC of the present invention and the pitch of the magnetized ring. A signal corresponding to the output signals of the Hall elements A and B shown in FIG.

  Here, in order to extract Bzx at a large level, it is preferable that the aspect ratio of the magnetic body 14 is large and that the distance in the Z direction between the magnetic sensing portion and the magnetic body 14 is short. Therefore, the planar shape of the magnetic body 14 is preferably rectangular or oblong, and the positional relationship between the magnetic body 14 and the magnetic sensitive portions (Hall elements 12 and 13) is applied to each Hall element itself. In order to make the magnetic flux density uniform, it is preferable that the magnetic body has a shape that envelops the entire magnetosensitive portion.

  Needless to say, in order to see Bz and Bx at the same point, it is preferable that the distance between the two Hall elements is small.

  As discussed above, the two signals obtained by the position detection device shown in FIGS. 1A, 1B and 5, for example, the signal of the difference between the outputs of the two Hall elements, and the two Hall elements The sum signal of each output has an exact phase difference of π / 2 regardless of the magnetizing pitch of the magnetizing ring and the interval between the magnetizing ring and the Hall element, and therefore the exclusive OR of the two signals. The number of pulses per rotation can be accurately doubled with a duty ratio of 1: 1. That is, the resolution can be doubled.

  FIG. 9 is a diagram showing this relationship, and is a diagram showing the same conditions as in FIG. Basically, the same results as in FIG. 7 can be obtained.

  The Hall element and the integrated circuit are preferably formed on one substrate. However, a magnetic plate is formed on two Hall elements formed on a compound semiconductor substrate to form one piece. A structure that is electrically connected to an integrated circuit formed on Si or the like may be used. Moreover, these can also be set as the structure accommodated in one envelope.

(Second Embodiment)
FIG. 2 is a diagram showing a main part of the Hall IC according to the second embodiment of the present invention. This figure is from the same viewpoint as FIG. 1B. In this Hall IC, two Hall elements are formed close to each other on a Si substrate, a protective film is attached, and then divided into two so as to have a gap between the two Hall elements. A thin film magnetic plate made of a Ni—Fe alloy is formed in a rectangular shape by plating so as to overlap the Hall elements. In this figure, for the purpose of concentrating the peripheral magnetic flux on the Hall element, the planar shape of the magnetic body 14 is increased on the side opposite to the opposing Hall element and the width in the direction perpendicular to the straight line passing through the two Hall elements is increased. The width in the vicinity of the hall element is narrowed down. Even with this configuration, the same effect as in FIG. 1B can be obtained.

  In the position detection device (Hall IC) of the present invention, it can be understood from the above-described consideration that the distance W between the two Hall elements is preferably smaller than the pitch P of the magnetic poles of the combined magnetizing ring. . Ideally, W << P is desirable. The same is true for the lengths of the two thin film magnetic plates in FIG. 2 in the direction of the straight line passing through the two Hall elements. In other words, it is desired that the distance between the bottom sides of the two thin film magnetic plates in FIG. 2 is smaller than, preferably smaller than, the pitch P of the magnetic poles of the magnetized ring.

  According to the characteristic configuration of the present invention, the difference signal between the two Hall elements can be extracted with high sensitivity even though the distance between the two Hall elements is smaller than the magnetic pole pitch P of the magnetizing ring.

  The present invention can be applied not only to machine products such as industrial machines and automobiles, but also to rotation or linear motion position detection devices such as a jog dial of a portable information terminal in which small size, thinness, and low power consumption are indispensable.

It is a figure explaining the relationship between Hall IC and the magnetized ring of the 1st Embodiment of this invention. It is a figure explaining the plane of Hall IC in Drawing 1A. It is a figure which shows the principal part of Hall IC in 2nd Embodiment of this invention. It is explanatory drawing which showed an example of the prior art. It is a figure which shows the example of the block diagram of Hall IC used for the example shown in FIG. It is the block diagram which showed an example of the integrated circuit in embodiment of this invention. It is explanatory drawing which showed a magnetized ring, distribution of the magnetic flux density of the surface vicinity, and an example of the prior art. In FIG. 6, it is explanatory drawing which showed the rotation direction of the magnetizing ring, and the change of the output of two Hall IC. It is a calculated value by simulation of the magnetic flux density in the Z direction and the X direction near the surface of the magnetized ring. It is explanatory drawing which showed the rotation direction of the magnetizing ring in this invention, and the change of Bx detection output and Bz detection output. It is the figure which showed the result of having calculated the magnetic force line near a magnetic board in the uniform magnetic flux density field of a direction parallel to a X direction by the simulation including the X-axis and the Z-axis. It is another figure which shows the principal part of Hall IC in 1st Embodiment of this invention.

Explanation of symbols

11 Magnetized Rings 12 and 13 Hall Element 14 Magnetic Plate 15 Substrate 16 Electrode 21 Hall Element 22 Amplifier 23 and 24 Schmitt Circuit 25 Adder Circuit 26 Subtractor Circuit 27 Logic Circuit 28 Logic Circuit

Claims (9)

A position detection device combined with an annular or linear magnetic flux generation source in which magnetic poles are alternately inverted at a predetermined equal pitch,
Two Hall elements arranged at a predetermined interval;
A protective film disposed on the magnetic sensitive portions of the two Hall elements so as to cover the magnetic sensitive portions;
A thin-film magnetic plate disposed on the protective film and disposed so as to cover the magnetically sensitive portions of the two Hall elements ;
A first circuit for generating a sum signal of the outputs of the two Hall elements;
A second circuit for generating a difference signal between the outputs of the two Hall elements;
A position detection device comprising: A first Schmitt circuit that compares an output signal of the first circuit with a predetermined Schmitt level and outputs a comparison result;
A second Schmitt circuit that compares an output signal of the second circuit with a predetermined Schmitt level and outputs a comparison result;
The position detection device according to claim 1, further comprising: The position detection device according to claim 2, further comprising a direction output circuit that generates an output related to a direction from the output of the first Schmitt circuit and the output of the second Schmitt circuit. The position detection device according to claim 3, further comprising a pulse output circuit that inputs outputs of the first Schmitt circuit and the second Schmitt circuit and generates an exclusive OR output of these inputs. The position detection device according to claim 1, further comprising a direction output circuit that generates an output related to a direction from the output signal of the first circuit and the output signal of the second circuit. Each of the portion covering the sensing section of the thin-film magnetic plate, the position detection according to any one of claims 1 to 5, characterized in that the end portion to oppose the thin-film magnetic plate of band-shaped apparatus. 2. Each of the portions of the thin film magnetic plate covering the magnetically sensitive portion is divided at a midpoint between two Hall elements in a direction perpendicular to a straight line connecting the two Hall elements. The position detection device according to any one of 1 to 5 .   The two Hall elements, the first and second circuits, the first and second Schmitt circuits, the direction output circuit, and the pulse output circuit are formed on one substrate. The position detection device according to claim 4.   The two Hall elements, the first and second circuits, the first and second Schmitt circuits, the direction output circuit, and the pulse output circuit are housed in one envelope. The position detection device according to claim 4, wherein

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