JP4735362B2 - Rotation angle detector - Google Patents

Description

  The present invention relates to a rotation angle detection device mainly used for detecting a rotation angle of a steering wheel of an automobile.

  2. Description of the Related Art In recent years, as automobiles have become more sophisticated, in order to perform various controls such as braking and skidding prevention, the number of devices that detect the rotation angle of a steering using various rotation angle detection devices is increasing.

  Such a conventional rotation angle detection device will be described with reference to FIGS.

  FIG. 5 is a block diagram of a main part of a conventional rotation angle detecting device, and FIG. 6 is a perspective view thereof. In FIG. 5, 1 is a rotating body having a spur gear portion 1A formed on the outer periphery, and is inserted in the central portion. An engaging portion 1B that engages with a shaft of a steering (not shown) is provided.

  Reference numeral 2 denotes a first detector having a spur gear portion 2A formed on the outer periphery, and reference numeral 3 denotes a second detector having a spur gear portion 3A having a different number of teeth from the first detector 2 on the outer periphery. The first detection body 2 meshes with the rotating body 1 and the second detection body 3 meshes with the first detection body 2, respectively. At the center of the first detection body 2 and the second detection body 3, Magnets 4 and 5 are mounted by insert molding or the like.

  Reference numeral 6 denotes a wiring board disposed substantially parallel to the upper surfaces of the first detection body 2 and the second detection body 3, and a plurality of wiring patterns (not shown) are formed on the upper and lower surfaces. An anisotropic magnetoresistive element (hereinafter referred to as an AMR element) 7 is provided on the surface of the detector 2 facing the magnet 4, and an AMR element 8 is provided on the surface of the second detector 3 facing the magnet 5. Each is installed.

  As shown in FIG. 5, the AMR elements 7 and 8 are composed of a first Wheatstone bridge 11 and a second Wheatstone bridge 12 in which four magnetoresistive elements 9 are connected in a substantially rectangular shape, and are inclined at 45 degrees. The power terminals 11A and 12A derived from the coupling point of these two Wheatstone bridges are used as a 5V power source, and the ground terminals 11B and 12B derived from the diagonal coupling point of the power terminals 11A and 12A are grounded. Are connected to each other.

  Further, the −output terminals 11C and 12C and the + output terminals 11D and 12D derived from the coupling points at different diagonal positions are connected to the amplification means 13 formed on the wiring board 6 by electronic components such as transistors, respectively. In addition to being connected, the output terminals 13A and 13B of the amplifying means 13 are connected to a control means 14 such as a microcomputer to constitute a rotation angle detecting device.

  The AMR elements 7 and 8, the amplifying means 13, the control means 14 and the like as described above are formed by, for example, a first Wheatstone bridge 11 and a second Wheatstone bridge which are formed by being inclined at 45 degrees on a silicon wafer. 12 and the like are covered with a mold made of an insulating resin, and the terminals extending from the mold so as to be arranged at a predetermined interval are connected to the wiring pattern of the wiring board 6 by soldering.

  In such a rotation angle detection device, the control means 14 is connected to an electronic circuit (not shown) of the automobile body through a connector (not shown) or the like, and is connected to the engaging portion 1B at the center of the rotating body 1. The steering shaft (not shown) is inserted through and is mounted on the automobile.

  In the above configuration, during operation, when the steering is rotated with an ignition switch (not shown) turned on, the rotating body 1 rotates accordingly, and the spur gear portion 2A is connected to the spur gear portion 1A on the outer periphery. The meshed first detector 2 and the second detector 3 in which the spur gear portion 3A meshes with the first detector 2 rotate in conjunction with each other.

  As the first detection body 2 and the second detection body 3 rotate, the magnetic directions of the magnets 4 and 5 mounted in the center thereof change, and this is detected by the AMR elements 7 and 8, respectively. Then, for example, from the negative output terminal 12C of the second Wheatstone bridge 12 of the AMR element 7 facing the magnet 4, the voltage is about 2.4V to 2 as shown in the voltage waveform diagram of FIG. A sine wave output signal at .6 V, and a sine wave output signal as shown in FIG.

  Further, from the negative output terminal 11C of the first Wheatstone bridge 11 of the AMR element 7, a cosine wave output signal having a voltage of about 2.4 V to 2.6 V as shown in the voltage waveform diagram of FIG. However, output signals of cosine waves as shown in FIG. 3D are input to the amplifying means 13 from the + output terminal 11D.

  In other words, a sine wave output signal is output from the second Wheatstone bridge 12 of the AMR element 7 in accordance with the magnetic direction of the magnet 4 that changes with rotation, and the first Wheatstone tilted 45 degrees relative thereto. The bridge 11 outputs a cosine wave output signal.

  Further, similarly, the output signals of the sine wave and the cosine wave are respectively output from the AMR element 8 facing the magnet 5 to the amplifying means 13, but the first detector 2 to which the magnet 4 is attached and the magnet 5. Since the number of teeth of the second detector 3 to which is attached is different, these are output to the amplifying means 13 as a waveform having a phase difference.

  Further, the amplifying means 13 differentially amplifies the output signals of these sine wave and cosine wave. For example, the voltage from the output terminal 13A is about 1.5 V as shown in the voltage waveform diagram of FIG. A sine wave output signal at .about.3.5 V is output from the output terminal 13B to the control means 14 as shown in FIG.

  Then, the control means 14 calculates these input sine wave and cosine wave output signals, and from the rotation angles of the first detector 2 and the second detector 3, the rotation angle of the rotor 1, that is, the steering. Thus, the rotation angle detecting device is configured to detect the rotation angle.

As prior art document information related to the invention of this application, for example, Patent Document 1 is known.
JP 2006-29792 A

  However, in the conventional rotation angle detection device, conductive foreign matters such as metal powder enter the vicinity of the AMR elements 7 and 8 in the device, for example, the −output terminals 11C and 12C, or the + output terminal 11D. When a short circuit occurs between 12D and the like, the control unit 14 cannot determine that the output signals output from the output terminals 13A and 13B of the amplification unit 13 are abnormal output signals.

  That is, for example, when the output terminals 11C and 12C are short-circuited, the output terminal 13A outputs a sine waveform that is out of phase but distorted, and the output terminal 13B outputs a sine waveform that is also out of phase and distorted. Therefore, there is a problem that the control means 14 cannot distinguish between the shorted output signal and the normal output signal, and detects an incorrect rotation angle.

  The present invention solves such a conventional problem, and an object of the present invention is to provide a rotation angle detection device capable of detecting a short circuit between output terminals of an AMR element and performing a reliable detection without erroneous determination. To do.

In order to achieve the above object, the present invention provides a rotating body that rotates in conjunction with a steering, a detecting body that rotates in conjunction with the rotating body, a magnet mounted in the center of the detecting body, Two Wheatstone bridges that are arranged opposite to each other and have four rectangular magnetoresistive elements connected in a substantially rectangular shape are connected to the anisotropic magnetoresistive element formed by tilting 45 degrees and the anisotropic magnetoresistive element. The ground terminal of any one of the Wheatstone bridges is connected to the ground via a resistor, and the switching means provided in parallel with the resistor is connected to the control means. by switching the switching means, when said ground terminal is connected to ground without passing through the resistor, the rotating body by an output signal from the anisotropic magnetoresistive element Detecting a rotation angle, the control means switches said switching means at a predetermined timing, which the ground terminal to constitute a rotation angle detection device so as to be connected to the ground via the resistor, the control means Switches the switching means, detects the rotation angle of the rotating body based on the output signal from the anisotropic magnetoresistive element, and the control means switches the switching means at a predetermined timing and connects the ground terminal to the ground via the resistor When this is done, a short circuit between these output terminals can be detected by the difference in the output signal from the anisotropic magnetoresistive element, so that it is possible to obtain a rotation angle detection device capable of reliable detection without erroneous determination. It has the effect | action.

  As described above, according to the present invention, it is possible to obtain an advantageous effect that it is possible to realize a rotation angle detection device that can detect a short circuit between terminals and can perform reliable detection without erroneous determination.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

  In addition, the same code | symbol is attached | subjected to the part of the structure same as the structure demonstrated in the term of background art, and detailed description is simplified.

(Embodiment)
FIG. 1 is a block circuit diagram of a main part of a rotation angle detecting device according to an embodiment of the present invention, FIG. 2 is a perspective view thereof, and in FIG. 1, 1 is a rotating body having a spur gear portion 1A formed on the outer periphery. The central portion is provided with an engaging portion 1B that engages with a shaft of a steering (not shown) to be inserted.

  Reference numeral 2 denotes a first detector having a spur gear portion 2A formed on the outer periphery, and reference numeral 3 denotes a second detector having a spur gear portion 3A having a different number of teeth from the first detector 2 on the outer periphery. The first detection body 2 meshes with the rotating body 1 and the second detection body 3 meshes with the first detection body 2, respectively. At the center of the first detection body 2 and the second detection body 3, Magnets 4 and 5 are mounted by insert molding or the like.

  Reference numeral 6 denotes a wiring board disposed substantially parallel to the upper surfaces of the first detection body 2 and the second detection body 3, and a plurality of wiring patterns (not shown) are formed on the upper and lower surfaces. An anisotropic magnetoresistive element (hereinafter referred to as an AMR element) 7 is provided on the surface of the detector 2 facing the magnet 4, and an AMR element 8 is provided on the surface of the second detector 3 facing the magnet 5. Each is installed.

  As shown in FIG. 1, the AMR elements 7 and 8 are composed of a first Wheatstone bridge 11 and a second Wheatstone bridge 12 in which four magnetoresistive elements 9 are connected in a substantially rectangular shape, with an inclination of 45 degrees. The power terminals 11A and 12A derived from the coupling point of the two Wheatstone bridges are connected to the 5V power source, and the ground terminal 11B derived from the diagonal coupling point of the power terminal 11A is connected to the ground. Has been.

  Further, -output terminals 11C and 12C and + output terminals 11D and 12D derived from the coupling points at different diagonal positions are connected to the amplification means 13 formed on the wiring board 6 by electronic components such as transistors, respectively. In addition to being connected, output terminals 13A and 13B of the amplifying means 13 are connected to a control means 17 such as a microcomputer.

  Further, the ground terminal 12B and the like derived from the coupling point of the diagonal position of the power supply terminal 12A of the AMR elements 7 and 8 are connected to the ground through the resistor 18, and the FET 19A and the like are connected in parallel to the resistor 18. The FET 19A is connected to the IO port 19B of the control means 17 to form a switching means 19 to constitute a rotation angle detecting device.

  The AMR elements 7 and 8, the amplifying means 13, the control means 17 and the like as described above are formed by, for example, a first Wheatstone bridge 11 and a second Wheatstone bridge which are formed by being inclined at 45 degrees on a silicon wafer. 12 and the like are covered with a mold made of an insulating resin, and the terminals extending from the mold so as to be arranged at a predetermined interval are connected to the wiring pattern of the wiring board 6 by soldering.

  Further, in FIG. 1, the first Wheatstone bridge 11 and the second Wheatstone bridge 12 are shown side by side so as to be easily understood, but actually, the first Wheatstone bridge 11 and the second Wheatstone bridge 12 are illustrated. Are formed so as to overlap with each other in a state where they are inclined coaxially by 45 degrees.

  In such a rotation angle detecting device, the control means 17 is connected to an electronic circuit (not shown) of the automobile body through a connector (not shown) or the like, and is connected to the engaging portion 1B at the center of the rotating body 1. The steering shaft (not shown) is inserted through and is mounted on the automobile.

  In the above configuration, during operation, when the steering is rotated with an ignition switch (not shown) turned on, the rotating body 1 rotates accordingly, and the spur gear portion 2A is connected to the spur gear portion 1A on the outer periphery. The meshed first detector 2 and the second detector 3 in which the spur gear portion 3A meshes with the first detector 2 rotate in conjunction with each other.

  As the first detection body 2 and the second detection body 3 rotate, the magnetic directions of the magnets 4 and 5 mounted in the center thereof change, and this is detected by the AMR elements 7 and 8, respectively. Then, for example, from the negative output terminal 12C of the second Wheatstone bridge 12 of the AMR element 7 facing the magnet 4, the voltage is about 2.4V to 2 as shown in the voltage waveform diagram of FIG. A sine wave output signal at .6 V, and a sine wave output signal as shown in FIG.

  Further, from the negative output terminal 11C of the first Wheatstone bridge 11 of the AMR element 7, a cosine wave output signal having a voltage of about 2.4 V to 2.6 V as shown in the voltage waveform diagram of FIG. However, output signals of cosine waves as shown in FIG. 3D are input to the amplifying means 13 from the + output terminal 11D.

  In other words, a sine wave output signal is output from the second Wheatstone bridge 12 of the AMR element 7 in accordance with the magnetic direction of the magnet 4 that changes with rotation, and the first Wheatstone tilted 45 degrees relative thereto. The bridge 11 outputs a cosine wave output signal.

  At this time, the IO port 19B of the switching means 19 is switched to the power supply side, and the FET 19A is ON, so that the ground terminal 12B of the second Wheatstone bridge 12 is connected to the ground without going through the resistor 18. .

  Further, similarly, the output signals of the sine wave and the cosine wave are respectively output from the AMR element 8 facing the magnet 5 to the amplifying means 13, but the first detector 2 to which the magnet 4 is attached and the magnet 5. Since the gears of the second detector 3 to which is attached are different, these are output to the amplifying means 13 as a waveform having a phase difference.

  Further, the amplifying means 13 differentially amplifies the output signals of these sine wave and cosine wave. For example, the voltage from the output terminal 13A is about 1.5 V as shown in the voltage waveform diagram of FIG. A sine wave output signal at .about.3.5 V is output from the output terminal 13B to the control means 17 as shown in FIG.

  Then, the control means 17 calculates these input sine wave and cosine wave output signals, and from the rotation angles of the first detection body 2 and the second detection body 3, the rotation angle of the rotation body 1, that is, the steering. The rotation angle detector is configured to detect the rotation angle of the rotation angle.

  Further, at a predetermined timing, for example, immediately after turning on the ignition switch, the control means 17 switches the IO port 19B of the switching means 19 to the ground side, turns off the FET 19A, and causes a current to flow through the resistor 18, thereby When conductive foreign substances such as metal powder enter the vicinity of the elements 7 and 8 and a short circuit occurs between the output terminals, this is detected.

  That is, when the output terminals of the AMR elements 7 and 8, for example, the −output terminals 11C and 12C and the + output terminals 11D and 12D are not short-circuited, the −output terminal 11C of the first Wheatstone bridge 11 is used. From the + output terminal 11D, output signals of cosine waves as shown in FIGS. 3C and 3D are output to the amplifying means 13, respectively.

  Further, from the − output terminal 12C and the + output terminal 12D of the second Wheatstone bridge 12, compared with FIGS. 3A and 3B, for example, the center voltage is 2.5V to 3.5V by the amount of the resistor 18. Thus, although the amplitude is small, sine wave output signals are respectively output to the amplifying means 13.

  These output signals are differentially amplified by the amplifying means 13 to become voltages within the normal output range, and are output to the control means 17 as output signals of a sine wave from the output terminal 13A and a cosine wave from the output terminal 13B. Is output.

  On the other hand, for example, when the -output terminals 11C and 12C are short-circuited, since the -output terminals 11C and 12C are connected, a negative sine is generated from both of the -output terminals near the voltage of 3V. An output signal obtained by combining the wave and the cosine wave is output to the amplifying unit 13.

  Therefore, when the amplification means 13 differentially amplifies this, a voltage 0V obtained by amplifying a negative voltage value obtained by subtracting the −output terminal 12C from the voltage at the + output terminal 12D is output from the output terminal 13B. The voltage 5V obtained by amplifying the positive voltage value obtained by subtracting the −output terminal 11C from the voltage at the + output terminal 11D is output to the control means 17.

  When the control means 17 detects this voltage and an output signal having a sine waveform or cosine waveform is input from the output terminals 13A and 13B, there is no short circuit between the output terminals 11C and 12C, and the voltage 0V or If 5V is input as an output signal, it is determined that there is a short circuit. If there is no short circuit, the IO port 19B of the switching means 19 is switched to the power supply side, the FET 19A is turned on, and the subsequent steering rotation. If the angle is detected and there is a short circuit, for example, the output of the rotation angle detection signal to the electronic circuit of the vehicle is stopped.

  In other words, immediately after the ignition switch is turned on, the control means 17 switches the switching means 19 to pass a current through the resistor 18, and a short circuit between these output terminals is detected by the difference in the output signals from the AMR elements 7 and 8. Therefore, the rotation angle can be reliably detected without erroneous determination.

  In the same manner as described above, between the negative output terminal 11C and the positive output terminal 12D, the positive output terminal 11D and the negative output terminal 12C, the positive output terminal 11D and 12D, or between the respective output terminals of the AMR element 8. Short circuit detection can also be performed.

  As described above, according to the present embodiment, the ground terminal 12B of the AMR elements 7 and 8 is connected to the ground via the resistor 18, and the switching means 19 provided in parallel to the resistor 18 is connected to the control means 17. By connecting, the control means 17 switches the switching means 19 to detect the rotation angle of the rotating body 1 based on the output signals from the AMR elements 7 and 8, and the difference in these output signals causes the AMR elements 7 and 8 to Since a short circuit between the output terminals can be detected, a rotation angle detection device capable of reliable detection without erroneous determination can be obtained.

  In the above description, the structure in which the first detection body 2 is engaged with the rotating body 1 and the second detection body 3 is engaged with the first detection body 2 has been described. The present invention can also be implemented with a configuration in which both of the second detection bodies 3 are engaged with the rotating body 1.

  In the above description, spur gear portions are formed on the outer periphery of the rotating body 1 and the first and second detection bodies 2 and 3, and these are engaged and rotated in conjunction with each other. In addition to the spur gear portion, a configuration using other shapes such as a bevel gear, or an uneven portion or a high friction portion that can transmit rotation is formed on the outer periphery of the rotating body or the detecting body instead of the gear. It is good also as a structure which rotates in response to each other.

  The rotation angle detection device according to the present invention can detect a short circuit between terminals of an AMR element and can be reliably detected without erroneous determination, and is useful for detecting the rotation angle of a steering wheel of an automobile.

1 is a block diagram of a main part of a rotation angle detection device according to an embodiment of the present invention. Same perspective view Voltage waveform diagram Voltage waveform diagram Main part block circuit diagram of conventional rotation angle detection device Same perspective view

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rotating body 1A, 2A, 3A Spur gear part 1B Engagement part 2 First detection body 3 Second detection body 4, 5 Magnet 6 Wiring board 7, 8 AMR element 9 Magnetoresistive element 11 First Wheatstone bridge 12 Second Wheatstone bridge 11A, 12A Power supply terminal 11B, 12B Ground terminal 11C, 12C -Output terminal 11D, 12D + Output terminal 13 Amplifying means 13A, 13B Output terminal 17 Control means 18 Resistor 19 Switching means 19A FET
19B IO port

Claims (1)

A rotating body that rotates in conjunction with the steering, a detecting body that rotates in conjunction with the rotating body, a magnet mounted in the center of the detecting body, and four magnetoresistors arranged opposite to the magnet two Wheatstone bridge connecting the device to a substantially rectangular shape, and 45-degree tilted anisotropic magnetoresistance device formed consists control means connected to the anisotropic magnetoresistive element, one of the The ground terminal of the Wheatstone bridge is connected to the ground via a resistor, and switching means provided in parallel with the resistor is connected to the control means, the control means switches the switching means, and the ground terminal when connected to the ground without passing through the resistor, to detect the rotation angle of the rotating body by an output signal from the anisotropic magnetoresistive element, said control means By switching the switching means at a constant timing, the rotation angle detecting device and the ground terminal is connected to ground via the resistor.

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