JP5566871B2 - Rotation detector - Google Patents

Description

  The present invention relates to a rotation detection device.

  Conventionally, a vertical Hall element is formed on a semiconductor substrate and detects a magnetic field parallel to the surface thereof, and a resistance value is determined by the strength of the magnetic field formed on the semiconductor substrate formed with the vertical Hall element and parallel to the surface. There is a rotation detection device that includes a changing magnetoresistive element and detects the rotation of a detection object using an output signal of a vertical Hall element and a signal obtained by the magnetoresistive element (for example, see Patent Document 1). ). In this apparatus, an Arctan calculator is used to calculate Arctan from a signal obtained from the magnetoresistive element and a signal obtained from the magnetoresistive element. According to this apparatus, the output signal of the magnetoresistive element is pulsed by the signal processing circuit, and the signal from the Arctan calculator and the signal from the pulse circuit are synthesized by the synthesizer to obtain a linear output at an angle of 0 to 360 °. It is supposed to be done.

JP 2006-185406 A

  However, when the digital technique as described above is used, for example, it is necessary to store numerical data corresponding to sin and cos in a memory as a table and calculate Arctan while referring to them. Therefore, there is a problem that the signal processing circuit becomes large-scale, the IC used for the signal processing becomes large, and the cost increases.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a rotation detection device having a simple configuration with only an analog circuit.

[1] In order to achieve the above object, the present invention provides a detection unit including a first detection unit and a second detection unit that output sine wave signals having different phases according to the rotation angle of the rotation detection unit, A division unit that divides the output of the first detection unit and the output of the second detection unit of the detection unit; an analog calculation unit that outputs a linear sum of the output of the division unit and the output of the detection unit; has, in some range of the rotation angle, the have a linear output corresponding to the rotation angle row, the phase is 90 °, sin [theta output of the first detector for rotation angle theta, the If the output of the second detection unit is cos θ, the output of the analog calculation unit is (cot θ + 4 cos θ) / 5, and the linear output at 50 ≦ θ ≦ 150 ° is the output corresponding to the rotation angle of the rotation detection unit. A rotation detecting device is provided.

[2] before Symbol first detector and the second detector is constituted by an MR element, respectively, above, characterized in that it is arranged to detect two directions of the magnetic field by shifting the 45 ° directions [ 1] may be used.

  ADVANTAGE OF THE INVENTION According to this invention, the rotation detection apparatus by the simple structure only of an analog circuit can be provided.

FIG. 1 is an overall schematic configuration diagram of a rotation detection device according to an embodiment of the present invention. FIG. 2 is a pattern configuration example of the detection unit. FIG. 3 is an electric circuit diagram of the analog operation unit of the rotation detection device according to the embodiment of the present invention. FIG. 4 is a graph showing the relationship between the rotation angle of the rotation detectors of the first detector and the second detector and the output signal. FIG. 5 is a graph showing the relationship between the rotation angle of the rotation detector of the analog calculator and the output signal of the calculation result. FIG. 6 is an electric circuit diagram illustrating a circuit configuration example of a division unit used in the analog operation unit.

[Configuration of rotation detector]
FIG. 1 is an overall schematic configuration diagram of a rotation detection device according to an embodiment of the present invention. FIG. 2 is a pattern configuration example of the detection unit. FIG. 3 is an electric circuit diagram of the rotation detection device according to the embodiment of the present invention.

  The rotation detection device 10 includes a rotation detection unit 100 that generates a rotation angle of a measurement target, and a first detection unit and a second detection unit that output sine wave signals having different phases according to the rotation angle of the rotation detection unit 100. It comprises a magnetic sensor device 200 as a detection unit, and an analog operation circuit 300 as an analog operation unit that outputs a linear sum of the output of the division unit and the output of the detection unit.

  The rotation detection unit 100 is configured such that a magnet 102 magnetized in S and N poles is mounted on a rotating member 101, and a magnetic sensor device 200 is placed in close proximity to the magnet 102. The rotating operation causes the magnet 102 to rotate together with the rotating member 101, and a magnetic field change is applied to the magnetic sensor device 200.

  This magnetic sensor device 200 is an MR sensor, and eight magnetoresistive elements arranged in a ring on the same semiconductor substrate in such a manner that the magnetic sensing surfaces for sensing the change of the magnetic field formed by the magnet 102 are inclined by 45 ° each. Ra to Rd and Re to Rh are provided. Here, these magnetoresistive elements Ra to Rd, Re to Rh are made of a magnetoresistive film mainly composed of a ferromagnetic metal, and the resistance value thereof changes according to the applied magnetic field and has a predetermined size. It has a physical property that its resistance value is saturated when a magnetic flux density exceeding the value is applied. The magnetoresistive elements Ra to Rd, Re to Rh are arranged radially, and each magnetoresistive element is formed longer as it goes outward, and the ends of a plurality of linear films are alternately connected to form a zigzag shape. It is formed in a pattern. In the magnetic sensor device 200, the thicknesses of the magnetoresistive films forming the magnetoresistive elements Ra to Rd and Re to Rh are set to constant thicknesses. That is, in this magnetic sensor device 200, a magnetic detection unit that detects changes in the magnetic vector and magnetic flux density of a magnetic field is configured as an MR sensor by a magnetic detection unit including eight magnetoresistive elements Ra to Rd and Re to Rh. Yes.

  The above configuration is an example, and as shown in FIG. 3, the magnetoresistive elements Ra to Rd and Re to Rh each constitute a bridge circuit, and the two bridge circuits are arranged at an angle of 45 ° to each other. Just do it.

  FIG. 3 is an electric circuit diagram of the rotation detecting device according to the embodiment of the present invention, and is composed of a magnetic sensor device 200 and an analog arithmetic circuit 300.

  A power supply voltage Vcc is supplied to the magnetoresistive element Ra and the magnetoresistive element Rc, and the magnetoresistive element Rb and the magnetoresistive element Rd are connected to the ground. The connection point between the magnetoresistive element Rc and the magnetoresistive element Rd is input to the inverting input terminal of the operational amplifier 301 via the resistor R1 as the first midpoint voltage V1, and the connection point between the magnetoresistive element Ra and the magnetoresistive element Rb is the first connection point. 2 is input to the non-inverting input terminal of the operational amplifier 301 through the resistor R2.

  Similarly, the bridge circuit composed of the magnetoresistive elements Ra to Rd and the bridge circuit composed of the magnetoresistive elements Re to Rh arranged at an angle of 45 ° are supplied with the power supply voltage Vcc to the magnetoresistive element Re and the magnetoresistive element Rg. The resistance element Rf and the magnetoresistance element Rh are connected to the ground. The connection point between the magnetoresistive element Rg and the magnetoresistive element Rh is input to the inverting input terminal of the operational amplifier 302 via the resistor R4 as the third midpoint voltage V3, and the connection point between the magnetoresistive element Re and the magnetoresistive element Rf is 4 is input to the non-inverting input terminal of the operational amplifier 302 through the resistor R5.

  The operational amplifier 301 operates as a differential amplifier between the midpoint voltage V1 and the midpoint voltage V2. When the differential output is Vs, Vs = − (V1−V2) · Rf1 / R1. The operational amplifier 302 operates as a differential amplifier of the above-described midpoint voltage V3 and midpoint voltage V4. When the differential output is Vc, Vc = − (V3−V4) · Rf2 / R4.

  The operational amplifier 301 is a subtraction circuit and functions as a first detection unit that obtains the differential output Vs. The operational amplifier 302 is a subtraction circuit and functions as a second detection unit that obtains the differential output Vc. Here, FIG. 4 is a graph showing the relationship between the rotation angle θ of the rotation detectors of the first detector and the second detector and the output signal. By setting the angle θ between the rotation detection unit 100 and the magnetic sensor device 200 shown in FIG. 1 and setting R1, Rf1, R4, and Rf2, as shown in FIG. The differential output Vc can be cos θ (cos wave) having a phase difference of 90 °.

The division circuit 303 is an analog circuit in which the output V _T is V _T = X / Y, where X and Y are inputs. When the differential output Vc is the input X and the differential output Vs is the input Y, the output V _T is V _T = Vc / Vs , which is cot θ . The division circuit 303 can be realized by an analog circuit including a combination of operational amplifiers A1 to A4, transistors Q1 to Q4, resistors R101 to R108, capacitors C1 to C7, and diodes D1 and D2, as shown in FIG.

  The operational amplifier 304 is an inverting amplifier. The differential output Vc of the operational amplifier 302 is input to the inverting input terminal and amplified by a gain of 4. As shown in FIG. 3, by setting Rf3 / R7 to 4, the output becomes -4Vc.

The operational amplifier 305 is a subtraction circuit. The output _{V T} of the division circuit 303 is input to the inverting input terminal, an output of the operational amplifier 304 (-4Vc) is input to the non-inverting input terminal. Here, by setting Rf4 / R9 to 1/5, the output _Vout can be set to _Vout = − (V _T + 4Vc) / 5. In other words, if the polarity is reversed, the output of the analog arithmetic circuit 300 can be expressed as V _out = ( cot θ +4 cos θ) / 5.

FIG. 5 is a graph showing the relationship between the rotation angle θ of the rotation detector of the analog arithmetic circuit 300 and the output signal of the calculation result. From the output sin θ of the first detection unit and the output cos θ of the second detection unit, ( cot θ +4 cos θ) / 5 can be output by analog calculation. The linearity with respect to the angle θ is good in a part of this output ( cot θ + 4 cos θ) / 5. As shown in FIG. 5, for example, rotation detection with good linearity that approximates an ideal straight line (target) by setting the output at 50 ≦ θ ≦ 150 ° according to the rotation angle θ of the rotation detection unit. The device 10 can be realized.

[Effects of the embodiment of the present invention]
(1) According to the embodiment of the present invention, since it is not necessary to calculate Arctan from the sine wave and cosine wave that are the outputs of the rotation detection unit, conversion to a linear output signal by analog technology without using digital technology can do. Therefore, since the linear output signal calculated from the sine wave and cos wave can be configured only by an analog circuit such as an operational amplifier, a sensor that converts the rotation angle into a linear output signal can be realized with a simple circuit configuration.
(2) The rotation angle is converted into a linear output signal from the four arithmetic operations of the output sine wave of the first detector and the output cosine wave of the second detector and their linear sum. In the embodiment described above, the output of the calculation result is ( cot θ + 4 cos θ) / 5, but the combination of linear sums and each coefficient can be appropriately changed according to the linearity of the linear output with respect to the rotation angle.
(3) In the embodiment of the present invention, the rotation angle is in the range of 50 ≦ θ ≦ 150 °, but the range of this linear output can be changed. In order to improve the accuracy of the straight line output with respect to the rotation angle, the rotation angle range can be narrowed to provide a rotation detection device with excellent linearity. In addition, it is possible to provide a rotation detection device that expands the range of the rotation angle by reducing the accuracy of the linear output with respect to the rotation angle, and it is possible to realize a rotation detection device with high applicability constituted only by an analog circuit.
(4) As described above, since the embodiment of the present invention can be configured only by an analog circuit, a large-scale signal processing circuit is not required and the area can be reduced. Therefore, the cost can be reduced even when an IC is used.

  The preferred embodiment of the present invention has been described above, but the present invention is not limited to this embodiment, and various modifications can be made without departing from the scope of the present invention.

DESCRIPTION OF SYMBOLS 10 ... Rotation detection apparatus 100 ... Rotation detection part 101 ... Rotating member 102 ... Magnet 200 ... Magnetic sensor device 300 ... Analog arithmetic circuit 301, 302 ... Operational amplifier 303 ... Dividing circuit 304, 305 ... Operational amplifier R1, R2, R3, R4 ... Resistors Rf1, Rf2, Rf3, Rf4 ... Resistors Ra, Rb, Rc, Rd ... Magnetoresistive elements Re, Rf, Rg, Rh ... Magnetoresistive elements V1, V2, V3, V4 ... Midpoint voltages Vs, Vc ... Differential output Vcc ... Power supply voltage _Vout ... Output _VT Output X, Y ... Input θ ... Rotation angle

Claims (2)

A detection unit including a first detection unit and a second detection unit that output sine wave signals having different phases according to the rotation angle of the rotation detection unit;
A division unit that divides the output of the first detection unit and the output of the second detection unit of the detection unit; an analog calculation unit that outputs a linear sum of the output of the division unit and the output of the detection unit; Have
Wherein the portion of the range of rotation angles, the linear output line stomach corresponding to the rotation angle,
The phase is 90 °, and the output of the first detector with respect to the rotation angle θ is sin θ, and the output of the second detector is cos θ.
The output of the analog calculation unit is (cot θ + 4 cos θ) / 5, and the linear output at 50 ≦ θ ≦ 150 ° is used as an output corresponding to the rotation angle of the rotation detection unit. The first detector and the second detector is constituted by an MR element, respectively, according to claim 1, characterized in that it is arranged to detect two directions of the magnetic field by shifting the 45 ° directions Rotation detection device.

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