JP2006250580A - Magnetic detection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic detection device for detecting magnetism without increasing the number of components and without being affected by disturbance magnetic fields. <P>SOLUTION: The magnetic detection device 10 comprises Hall elements 1, 2; packaging substrates 3, 4; amplifiers 5, 6; a differential output circuit 7; and a detection magnet 8, and the like. The detection magnet 8 has the magnetization region of positive and negative magnetic poles arranged symmetrically while being rotated by 180 degrees to a rotary axis (r). The Hall elements 1, 2 are arranged at positions, where the direction of magnetic field vector from the detection magnet 8 while being packaged onto the packaging substrates 3, 4 is the same and the strength differs. Then, the differential output circuit 7 outputs a signal, which is the difference of Hall voltages from the Hall elements 1, 2 amplified by the amplifiers 5, 6. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a magnetic detection device. In particular, the present invention is applied to a rotation detection sensor and a position sensor of a rotating body.

  Conventionally, there has been one disclosed in Patent Document 1 as a magnetic detection device that accurately performs magnetic detection without being affected by a disturbance magnetic field.

FIG. 6 is a cross-sectional view illustrating a schematic configuration of the magnetic detection device disclosed in Patent Document 1. As illustrated in FIG. As shown in FIG. 6, the magnetic detection device disclosed in Patent Document 1 is disposed apart from a gear 30 having a magnetic material. The magnetic sensor element 40 of the magnetic detection device is disposed to face the gear 30. A magnetic shield case 50 made of a magnetic material covers the periphery of the magnetic sensor element 40.
Japanese Patent Laid-Open No. 7-27571

  However, the magnetic detection device disclosed in Patent Document 1 has a problem that the number of components increases because the magnetic shield case 50 is used.

  The present invention has been made in view of the above problems, and an object thereof is to provide a magnetic detection device capable of performing magnetic detection without increasing the number of parts and without being affected by a disturbance magnetic field.

  In order to achieve the above object, the magnetic detection device according to claim 1 is coupled to the rotation shaft of the detection object and rotates with the rotation of the detection object, and is rotationally symmetric with respect to the rotation axis by 180 degrees. A magnet having a magnetized region of positive and negative magnetic poles arranged and a detection signal corresponding to the rotation of the magnet are output, and the magnetic field vectors from the magnets are arranged in the same direction but at different strengths. A plurality of Hall elements, and a differential output circuit that differentially outputs detection signals from the plurality of Hall elements are provided.

  The magnetism detection device may cause an error in output when a magnet or the like is disposed nearby. However, a disturbance magnetic field may be applied to the magnetic detection device by another magnetic detection device or a load heater. These magnetic detection devices and load heaters that generate a disturbance magnetic field are located at a relatively long distance from the magnetic detection device, so that the magnetic field vectors from the magnets have the same direction and different strengths. By arranging in this manner, the direction and intensity of the disturbance magnetic field vector applied to each Hall element are approximately the same. Therefore, by providing a differential output circuit that differentially outputs detection signals from a plurality of Hall elements, the influence of a disturbance magnetic field can be canceled.

  According to a second aspect of the present invention, the plurality of Hall elements are arranged side by side on the rotation axis of the magnet.

  In this way, by arranging a plurality of Hall elements side by side on the rotation axis of the magnet, the magnetic field vectors from the magnet can have the same direction and different strengths.

  Moreover, as shown in claim 3, the magnet can be formed in a cylindrical shape having a plane perpendicular to the rotation axis.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the magnetic detection apparatus 10 of this invention is applied to the rotation detection sensor and position sensor of a rotary body.

  1A and 1B are diagrams showing a schematic configuration of a magnetic detection device according to an embodiment of the present invention. FIG. 1A is a perspective view, and FIG.

  A magnetic detection device 10 shown in FIG. 1 includes Hall elements 1 and 2, mounting boards 3 and 4, a detection magnet 8, and the like. As shown in FIGS. 1A and 1B, the Hall elements 1 and 2 are arranged at positions where the directions of the magnetic field vectors from the detection magnet 8 are the same and the strengths are different when mounted on the mounting boards 3 and 4. The The Hall elements 1 and 2 are arranged side by side on the rotation axis r of the detection magnet 8 while being separated from the detection magnet 8. The Hall elements 1 and 2 output a detection signal (Hall voltage) corresponding to the rotating magnetic field generated by the detection magnet 8.

  The detection magnet 8 is made of ferrite or the like, and includes a magnetized region of a positive magnetic pole (hereinafter also referred to as N pole) and a negative magnetic pole (hereinafter also referred to as S pole) arranged in a rotational symmetry of 180 degrees with respect to the rotation axis r. It is a cylindrical magnet provided. In the detection magnet 8, a magnetic field indicated by an arrow from the north pole to the south pole in FIG. 1B is generated. Since the detection magnet 8 is connected to the detection object and rotates as the detection object rotates, the detection magnet 8 rotates about the rotation axis r on an arbitrary XY plane perpendicular to the rotation axis r. Generate a magnetic field.

  Next, the circuit configuration and operation of the magnetic detection device 10 will be described. FIG. 2 is a circuit diagram showing a circuit configuration of the magnetic detection device according to the embodiment of the present invention. FIG. 3 is an output waveform diagram showing an output waveform of the magnetic detection device according to the embodiment of the present invention.

  As shown in FIG. 2, the magnetic detection device 10 includes Hall elements 1 and 2, amplifiers 5 and 6, a differential output circuit 7, and the like. The Hall elements 1 and 2 are connected to a current source and are connected to a differential output circuit 7 through amplifiers 5 and 6. The Hall elements 1 and 2 are each supplied with a bias current and generate a Hall voltage proportional to the magnetic field component. The amplifiers 5 and 6 amplify the Hall voltage output from the Hall elements 1 and 2 and output the amplified voltage to the differential output circuit 7. The differential output circuit 7 outputs a signal obtained by taking a Hall voltage differential by the Hall elements 1 and 2 amplified by the amplifiers 5 and 6.

  Since the Hall elements 1 and 2 are arranged at positions where the directions of the magnetic field vectors from the detection magnet 8 are the same and have different intensities, as shown in FIG. 3, the Hall elements 1 and 2 output Hall voltages having the same phase but different amplitudes. Therefore, the magnetic detection device 10 outputs a voltage having an output waveform as shown in FIG. 3 because the Hall voltage output by the Hall element 1 and the Hall voltage output by the Hall element 2 are differentiated.

  Here, the operation of the magnetic detection device 10 when a disturbance magnetic field is generated in the magnetic detection device 10 will be described. FIG. 4 is a vector diagram illustrating a magnetic field applied to the Hall element of the magnetic detection device according to the embodiment of the present invention. FIG. 5 is an output waveform diagram showing an output waveform when a disturbance is applied to the magnetic detection device according to the embodiment of the present invention.

  In the magnetic detection device 10, when a disturbance magnetic field is applied, the Hall elements 1 and 2 are arranged at positions where the directions of the magnetic field vectors from the detection magnet 8 are the same and the strengths are different. The magnetic field vectors generated by the disturbance magnetic field applied to are approximately the same in direction and intensity.

  As shown in FIG. 5, the output waveform of the Hall elements 1 and 2 when the disturbance magnetic field is applied to the magnetic detection device 10 as described above is the Hall element 1 when the disturbance magnetic field is not applied to the magnetic detection device 10. , 2 to which the offset voltages ΔA and ΔB having substantially the same value are added.

  Therefore, since the magnetic detection device 10 takes the differential between the Hall voltage output by the Hall element 1 and the Hall voltage output by the Hall element 2, it can cancel the offset voltages ΔA and ΔB, as shown in FIG. As described above, a voltage having an output waveform substantially equal to that when no disturbance magnetic field is applied to the magnetic detection device 10 is output. Therefore, the magnetic detection device 10 can perform magnetic detection without being affected by a disturbance magnetic field without using a magnetic shield case or the like.

  Although the detection magnet 8 in the present embodiment has been described using a cylindrical shape, the present invention is not limited to this. Any magnet that is connected to the rotation axis of the detected object and rotates with the rotation of the detected object, and has a magnetized region of positive and negative magnetic poles arranged 180 degrees rotationally symmetrically with respect to the rotation axis. Good.

It is drawing which shows schematic structure of the magnetic detection apparatus in embodiment of this invention, (a) is a perspective view, (b) is sectional drawing. It is a circuit diagram which shows the circuit structure of the magnetic detection apparatus in embodiment of this invention. It is an output waveform diagram which shows the output waveform of the magnetic detection apparatus in embodiment of this invention. It is a vector diagram explaining the magnetic field applied to the Hall element of the magnetic detection apparatus in the embodiment of the present invention. It is an output waveform diagram which shows the output waveform at the time of the disturbance application of the magnetic detection apparatus in embodiment of this invention. It is sectional drawing which shows schematic structure of the magnetic detection apparatus shown in patent document 1.

Explanation of symbols

1, 2 Hall elements, 3, 4 Mounting board, 5, 6 Amplifier, 7 Differential output circuit, 8 Detector magnet, 10 Magnetic detector

Claims (3)

A magnet connected to the rotation axis of the detection object and rotating with the rotation of the detection object, and having a magnetized region of positive and negative magnetic poles arranged in a rotational symmetry of 180 degrees with respect to the rotation axis;
A detection signal corresponding to the rotation of the magnet, a plurality of Hall elements arranged at positions where the direction of the magnetic field vector from the magnet is the same and the intensity is different;
A differential output circuit that differentially outputs detection signals from the plurality of Hall elements;
A magnetic detection device comprising:   The magnetic detection apparatus according to claim 1, wherein the plurality of Hall elements are arranged side by side on a rotation axis of the magnet.   The magnetic detection apparatus according to claim 1, wherein the magnet has a cylindrical shape having a plane perpendicular to the rotation axis.

Images