JP2007256138A - Rotation angle detection apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rotation angle detection apparatus used for the detection of the angle of rotation of a steering of an automobile etc. and capable of detecting short circuits between terminals of AMR (anisotropic magneto resistance) elements, preventing incorrect determination, and performing reliable detection. <P>SOLUTION: Since it is possible to change over a switching means 19 to make a control means 17 detect the angle of rotation of a rotator 1 on the basis of output signals of the AMR elements 7 and 8 and detect short circuits between adjacent output terminals of the AMR elements 7 and 8 on the basis of the difference in output voltages from an amplification means 13 by connecting negative output terminals 11C and positive output terminals 12D of the AMR elements 7 and 8 to the control means 17 via a rectifying device 18 and the switching means 19, it is possible to achieve the rotation angle detection apparatus capable of preventing an incorrect determination and performing a reliable detection. <P>COPYRIGHT: (C)2008,JPO&INPIT

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 adjacent -output terminal 11C and + output terminal 11D, Alternatively, when the output terminal 12C or the + output terminal 12D is short-circuited, the output signal from the output terminals 13A and 13B of the amplifying means 13 is different from the sine wave and cosine wave as shown in FIG. Is output to the control means 14, but the control means 14 cannot determine that this is an abnormal output signal.

  That is, the output signal when the adjacent output terminals are short-circuited is linear and always has a voltage waveform of 2.5 V, but the sine waveform in FIG. 4A is also a voltage at 0 ° and 90 °. Is 2.5V, and the cosine waveform in FIG. 4B is also 2.5V at 45 ° and 135 °. Therefore, it is impossible to distinguish these output signals from the short-circuited output signal, and an incorrect rotation angle. There has been a problem of detecting this.

  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 has the following configuration.

  According to a first aspect of the present invention, an output terminal derived from a coupling point of a Wheatstone bridge of an anisotropic magnetoresistive element is connected to a control means via a rectifying element and a switching means to By switching the switching means, the control means detects the rotation angle of the rotating body from the output signal of the anisotropic magnetoresistive element, and depending on the difference in the output voltage from the anisotropic magnetoresistive element, these Since a short circuit between adjacent output terminals can be detected, there is an effect that it is possible to obtain a rotation angle detection device capable of reliable detection without erroneous determination.

  The invention according to claim 2 is the invention according to claim 1, wherein the output terminals having different polarities of the two Wheatstone bridges are connected to the control means via the rectifying element and the switching means, and are differentially amplified. In addition, it is possible to detect a short circuit between the output terminals from the amplifying means or the like.

  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 terminals 11B and 12B derived from the diagonal coupling point of the power terminals 11A and 12A are Each is connected to ground.

  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 output terminals of the AMR elements 7 and 8, for example, the −output terminal 11C and the + output terminal 12D which are adjacent to each other and have different polarities are connected to the control means 17 via the rectifying element 18 such as a diode, and the control means. 17, a switching means 19 such as an IO port is formed 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.

  In addition, in FIG. 1, the Wheatstone bridge 11 and the Wheatstone bridge 12 are shown side by side so as to be easy to understand. Overlaid.

  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, since the switching means 19 is switched to the power supply side, the rectifying element 18 is in a reverse bias state, and almost no current flows through the rectifying element 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, immediately after the ignition switch is turned on at a predetermined timing, for example, the control means 17 switches the switching means 19 to the ground side, and a current flows through the rectifying element 18, so that a metal powder is placed near the AMR elements 7 and 8 in the apparatus. In the case where a conductive foreign material such as the like enters and there is a short circuit between adjacent output terminals, this is detected.

  That is, when the adjacent output terminals of the AMR elements 7 and 8, for example, the -output terminal 12C and the + output terminal 12D of the second Wheatstone bridge 12 are not short-circuited, the voltage 2 from the -output terminal 12C is, for example, .6V output signal is output to the amplifying means 13, but the voltage at the + output terminal 12D is switched to the ground side by the switching means 19 and a current flows through the connected rectifying element 18, so that the order of the rectifying element 18 is increased. An output signal having a voltage of about 0.7 V is output to the amplifying means 13.

  Then, the amplification means 13 differentially amplifies these output signals. When the voltage 2.6V of the −output terminal 12C is subtracted from the voltage 0.7V of the + output terminal 12D and amplified by a factor of ten, the value is obtained. Becomes a voltage of minus several tens of volts, and the output voltage after differential amplification is saturated, so that the voltage 0 V is output to the control means 17 from the output terminal 13A.

  On the other hand, when the −output terminal 12C and the + output terminal 12D are short-circuited, the −output terminal 12C and the + output terminal 12D are connected. An output signal is output to the amplifying means 13.

  Therefore, when the amplifying means 13 differentially amplifies this, since the output signals from the −output terminal 12C and the + output terminal 12D are the same voltage 0.7V, the subtracted difference becomes 0, and the output terminal 13A 2.5 V is output to the control means 17.

  When this voltage is detected by the control means 17 and the voltage 0V is input from the output terminal 13A, there is no short circuit between the negative output terminal 12C and the positive output terminal 12D, and the voltage 2.5V is input. Is determined that there is a short circuit, and if there is no short circuit, the switching means 19 is switched to the power supply side, and then the steering rotation angle is detected. The output of the rotation angle detection signal to is stopped.

  The negative output terminal 11 C of the first Wheatstone bridge 11 of the AMR element 7 and the two output terminals of the two Wheatstone bridges of the AMR element 8 are also connected to the control means 17 via the rectifying element 18 and the switching means 19. Therefore, it is possible to detect a short circuit between these adjacent output terminals in the same manner.

  That is, immediately after the ignition switch is turned on, the control means 17 switches the switching means 19 to pass a current through the rectifying element 18, and the difference between the output voltages from the AMR elements 7 and 8 causes a difference between these adjacent output terminals. Therefore, a reliable rotation angle can be detected without erroneous determination.

  Further, the output terminals of the two Wheatstone bridges connected to the control means 17 via the rectifying element 18 and the switching means 19 are the first Wheatstone bridge 11 -the output terminal 11C, and the second Wheatstone bridge 12 is the + output terminal. Since the polarity is different from 12D, a short circuit between the output terminals 13A and 13B from the amplification means 13 to the control means 17 can be detected.

  That is, unlike FIG. 1, when the rectifying element 18 and the switching means 19 are connected to, for example, the -output terminals 11C and 12C, when the switching means 19 is switched and a current is passed through the rectifying element 18, a short circuit occurs. If not, a voltage of 5 V is output to the control means 17 from both the output terminals 13A and 13B.

  Even when the output terminals 13A and 13B are short-circuited, they are connected, and the voltage 5V is also output to the control means 17, so that the control means 17 is short-circuited between the output terminals 13A and 13B. Cannot be detected.

  On the other hand, when the rectifying element 18 and the switching means 19 are connected to output terminals having different polarities, such as −output terminal 11C and + output terminal 12D, when the output terminals 13A and 13B are not short-circuited, A voltage 0V is output from the output terminal 13A and a voltage 5V is output from the output terminal 13B to the control means 17, respectively, but when they are short-circuited, they are connected and both the output terminals 13A and 13B are connected. Thus, a voltage of 2.5 V is output to the control means 17.

  That is, the difference in output voltage between the output terminals 13A and 13B is obtained by connecting the rectifier 18 and the switching means 19 to the output terminals having different polarities, such as the −output terminal 11C and the + output terminal 12D of the two Wheatstone bridges. Therefore, the control means 17 can also detect the presence or absence of a short circuit between the output terminals 13A and 13B.

  The two output terminals of the two Wheatstone bridges of the AMR element 8 are also connected to the control means 17 via the rectifying element 18 and the switching means 19 because the output terminals having different polarities are used. The short circuit between the output terminals can be similarly detected.

  As described above, according to the present embodiment, the negative output terminal 11C and the positive output terminal 12D of the AMR elements 7 and 8 are connected to the control means 17 via the rectifying element 18 and the switching means 19, whereby the switching means 19 The control means 17 detects the rotation angle of the rotating body 1 from the output signals of the AMR elements 7 and 8, and the adjacent output terminals of the AMR elements 7 and 8 due to the difference in the output voltage from the amplifying means 13. Since a short circuit can be detected, a rotation angle detection device capable of reliable detection without erroneous determination can be obtained.

  Then, by connecting the -output terminal 11C and the + output terminal 12D of two Wheatstone bridges having different polarities to the control means 17 via the rectifying element 18 and the switching means 19, the differentially amplified amplification means 13 is connected. It is also possible to detect a short circuit between the output terminals 13A and 13B.

  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 Rectifying element 19 Switching means

Claims (2)

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 bridges in which the elements are connected in a substantially rectangular shape are composed of an anisotropic magnetoresistive element formed by tilting 45 degrees and a control means connected to the anisotropic magnetoresistive element. The output terminal derived from the connection point of the Wheatstone bridge of the resistance element is connected to the control means via the rectifier element and the switching means, and the control means switches the switching means, and the output from the anisotropic magnetoresistive element. A rotation angle detection device for detecting a rotation angle of the rotating body based on an output signal. The rotation angle detection device according to claim 1, wherein output terminals having different polarities of the two Wheatstone bridges are connected to the control means via a rectifying element and switching means.

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