CN101042294A - Rotation angle detector - Google Patents

Rotation angle detector Download PDF

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Publication number
CN101042294A
CN101042294A CN 200710005360 CN200710005360A CN101042294A CN 101042294 A CN101042294 A CN 101042294A CN 200710005360 CN200710005360 CN 200710005360 CN 200710005360 A CN200710005360 A CN 200710005360A CN 101042294 A CN101042294 A CN 101042294A
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China
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terminal
output terminal
lead
rotary body
wheatstone bridge
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CN100465577C (en
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冨野泰范
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Panasonic Holdings Corp
Panasonic Automotive Systems Co Ltd
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Matsushita Electric Industrial Co Ltd
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Abstract

A rotation angle detector includes a rotator, a detecting rotator, a magnet, an anisotropic magnetoresistive element, an amplifier, and a controller. The controller connects an output terminal of the anisotropic magnetoresistive element to the ground so as to detect a short circuit between adjacent output terminals based on the difference in output voltage from the amplifier. When there is no short circuit, the controller releases the connection from the output terminal to the ground, and detects the rotation angle of the rotator from the output signal that is differentially amplified by the amplifier based on the output signal of the anisotropic magnetoresistive element.

Description

Rotation angle detection apparatus
Technical field
The present invention relates to mainly the rotation angle detection apparatus of use in the anglec of rotation detection of automobile steering device etc.
Background technology
In recent years, the high performance of automobile is making progress rapidly.As a ring wherein, to brake and to prevent the various purposes that are controlled to be such as sideslips, in order to detect the anglec of rotation use rotation angle detection apparatus of steering gear.About this existing rotation angle detection apparatus, use Fig. 6, Fig. 7 to describe.Fig. 6 is the stereographic map of existing rotation angle detection apparatus, and Fig. 7 is its circuit block diagram.
Rotary body 31 inboards that are formed with the 31A of straight spur gear portion in periphery are provided with holding section 31B.Holding section 31B engages with steering column shaft (not shown) in being inserted in rotary body 31.First periphery that detects rotary body 32 is formed with the 32A of straight spur gear portion, and second periphery that detects rotary body 33 is formed with first and detects the different 33A of straight spur gear portion of rotary body 32 numbers of teeth.Be respectively that the first detection rotary body 32 detects rotary body 33 with rotary body 31 engagements, second and the first detection rotary body 32 meshes.Be equipped with magnet 34 in first central authorities of detecting rotary body 32 respectively by plug-in unit moulding (イ Application サ one ト shaping) etc., be equipped with magnet 35 in second central authorities of detecting rotary body 33.Wiring substrate 36 is configured to detect with the top of the first detection rotary body 32 and second the top almost parallel of rotary body 33.Form a plurality of wiring graphs (not shown) on the top and bottom of wiring substrate 36, and on the face relative, be equipped with anisotropic magnetic resistance element (to call the AMR element in the following text) 37 respectively, on the face relative, be equipped with AMR element 38 with magnet 35 with magnet 34.
As shown in Figure 7, AMR element 37 has first Wheatstone bridge 41 and second Wheatstone bridge 42 that four magnetoresistive elements 39 is connected into essentially rectangular respectively.It is overlapping that first Wheatstone bridge 41 and second Wheatstone bridge 42 form 45 ° of ground.The power supply terminal 41A, the 42A that derive from the binding site of these two Wheatstone bridges are connected with the power supply of 5V.On the other hand, ground wire terminal 41B, the 42B that derives from the diagonal position binding site of power supply terminal 41A, 42A is connected with ground wire.
And then the negative output terminal 41C, the 42C that derive from the binding site of different therewith diagonal positions are connected with the enlarging section 43 that wiring substrate 36 forms respectively with positive output terminal 41D, 42D.Lead-out terminal 43A, the 43B of enlarging section 43 is connected with control part 44 by computer formations such as (マ イ コ Application).And AMR element 38 also is same structure.So just constituted rotation angle detection apparatus.
The control part 44 of this rotation angle detection apparatus is connected with the electronic circuit (not shown) of car body by connector (not shown) etc.
In above structure, in motion, be under the state of ON in ignition switch (not shown), when rotation steering gear (not shown), then rotary body 31 rotates thereupon.Along with this rotation, first detects rotary body 32 and second detects the rotation of rotary body 33 interlocks.
Along with first rotation and second that detects rotary body 32 detects the rotation of rotary body 33, the magnetic direction that is assemblied in the magnet 34,35 of their central authorities changes. AMR element 37,38 detects this variation.For example from the negative output terminal 42C of AMR element 37 sinusoidal wave output signal to enlarging section 43 inputs, from positive output terminal 42D handle with from the sine wave signal output of 90 ° of the phase shiftings of the sine wave of negative output terminal 42C to enlarging section 43 inputs.In addition, from negative output terminal 41C the output signal of cosine wave (CW) to enlarging section 43 input, from positive output terminal 41D handle with from the cosine wave (CW) output signal of 90 ° of the phase shiftings of the cosine wave (CW) of negative output terminal 41C to enlarging section 43 inputs.That is, according to the magnetic direction of the magnet 34 that changes along with rotation, from the output signal of second Wheatstone bridge, 42 sine wave outputs of AMR element 37, from the output signal of first Wheatstone bridge, the 41 output cosine wave (CW)s of 45 ° of relative tilts with it.
And from AMR element 38 similarly respectively to the output signal of enlarging section 43 sine wave outputs and cosine wave (CW).But because the number of teeth of the number of teeth of the first detection rotary body 32 and the second detection rotary body 33 is different, so they become with the dephased waveform of the output device of AMR element 37 to enlarging section 43 outputs.Enlarging section 43 is these sine waves and cosine wave (CW) that output signal is carried out differential amplification, and to control part 44 outputs.
Control part 44 performs calculations to these signals, detects the anglec of rotation of rotary body 32 and the anglec of rotation that second anglec of rotation that detects rotary body 33 detects rotary body 31 according to first.Control part 44 detects the anglec of rotation of steering gear like this.It is disclosed that this rotation angle detection apparatus is for example opened the 2006-29792 communique by (Japan) spy.
But in above-mentioned existing rotation angle detection apparatus, in the time of near conductive impurities such as metal powder invade AMR element 37,38, output of 43 lead-out terminal and the sinusoidal wave signal different from the enlarging section sometimes with cosine wave (CW).For example between adjacent negative output terminal 41C and positive output terminal 41D, or just produce this situation between negative output terminal 42C and the positive output terminal 42D etc. during short circuit.It is unusual output signal that yet control part 44 can not be differentiated this.
Output signal between this adjacent lead-out terminal during short circuit is the waveform of certain voltage.But no matter be that sinusoidal waveform or cosine waveform voltage on the angle of regulation are identical with this certain voltage.Therefore, control part 44 can not be discerned the output signal of these output signals and short circuit, can be rotated the detection of angle mistakenly.
Summary of the invention
The present invention solves this existing problem, is a kind of short circuit that can detect between the AMR element lead-out terminal, not erroneous judgement, the rotation angle detection apparatus that can detect reliably.Rotation angle detection apparatus of the present invention has: rotary body, first detects rotary body, first magnet, the first anisotropic magnetic resistance element, enlarging section and control part.First detects rotary body and the rotation of rotary body interlock.First magnet cartridge fits over the central authorities of the first detection rotary body.The first anisotropic magnetic resistance element has first Wheatstone bridge and second Wheatstone bridge.First Wheatstone bridge constitutes by relative configuration with first magnet and by four magnetoresistive elements that connect into rectangle.Second Wheatstone bridge constitutes by relative configuration with magnet and by four magnetoresistive elements that connect into rectangle, forms with first Wheatstone bridge to tilt 45 °.First Wheatstone bridge has first ground wire terminal, first power supply terminal, the first positive output terminal and the first negative output terminal.Second Wheatstone bridge has second ground wire terminal, second source terminal, the second positive output terminal and the second negative output terminal.The enlarging section is connected with the first anisotropic magnetic resistance element, and carrying out differential amplification from the output signal of the first anisotropic magnetic resistance element.When in the first positive output terminal and the first negative output terminal any during as first lead-out terminal, then the control part that is connected with the enlarging section detects the short circuit of the first positive output terminal and the first negative output terminal by first lead-out terminal is connected with ground wire according to the output voltage from the enlarging section.And disconnect from of the connection of first lead-out terminal, according to from the output signal of the first anisotropic magnetic resistance element and based on the anglec of rotation from the input rotary body of enlarging section output to ground wire.Because control part can detect short circuit between the lead-out terminal like this, so detection angles and can detect the anglec of rotation reliably mistakenly not.
Description of drawings
Fig. 1 is the stereographic map of the rotation angle detection apparatus of the embodiment of the invention;
Fig. 2 is the circuit block diagram of the rotation angle detection apparatus of the embodiment of the invention 1;
Fig. 3 A~Fig. 3 D is the voltage oscillogram from anisotropic magnetic resistance element output shown in Figure 2;
Fig. 4 A, Fig. 4 B are the voltage oscillograms from enlarging section output shown in Figure 2;
Fig. 5 is the circuit block diagram of the rotation angle detection apparatus of the embodiment of the invention 2;
Fig. 6 is the stereographic map of existing rotation angle detection apparatus;
Fig. 7 is the circuit block diagram of rotation angle detection apparatus shown in Figure 6.
Embodiment
(embodiment 1)
Fig. 1 is the stereographic map of the rotation angle detection apparatus of the embodiment of the invention 1, and Fig. 2 is the circuit block diagram of this rotation angle detection apparatus.This rotation angle detection apparatus has rotary body 1, first and detects the rotary body 2 and the second detection rotary body 3.The inboard that is formed with the rotary body 1 of the 1A of straight spur gear portion in periphery is provided with holding section 1B.Holding section 1B engages with the steering column shaft that is inserted in rotary body 1 central portion (not shown).First periphery that detects rotary body 2 is formed with the 2A of straight spur gear portion, and second periphery that detects rotary body 3 is formed with first and detects the different 3A of straight spur gear portion of rotary body 2 numbers of teeth.Be respectively that the first detection rotary body 2 detects rotary body 3 with rotary body 1 engagement, second and the first detection rotary body 2 meshes.Be equipped with first magnet 4 in first central authorities of detecting rotary body 2 respectively by plug-in unit moulding etc., be equipped with second magnet 5 in second central authorities of detecting rotary body 3.Wiring substrate 6 is configured to detect with the top of the first detection rotary body 2 and second the top almost parallel of rotary body 3.Form a plurality of wiring graphs (not shown) on the top and bottom of wiring substrate 6, and on the face relative, be equipped with the first anisotropic magnetic resistance element (to call the AMR element in the following text) 7 respectively, on the face relative, be equipped with the second anisotropic magnetic resistance element (to call the AMR element in the following text) 8 with magnet 5 with magnet 4.
As shown in Figure 2, AMR element 7 has first Wheatstone bridge 11 and second Wheatstone bridge 12 that four magnetoresistive elements 9 is connected into essentially rectangular respectively.It is overlapping that first Wheatstone bridge 11 and second Wheatstone bridge 12 form 45 ° of ground.Find out easily that from Fig. 2 though Wheatstone bridge 11,12 is arranged above and below, in fact Wheatstone bridge 11 and Wheatstone bridge 12 are to overlap to form with tilt 45 ° state of mutual concentric.First Wheatstone bridge 11 has the first power supply terminal 11A, the first ground wire terminal 11B, the first positive output terminal 11D and the first negative output terminal 11C, and second Wheatstone bridge 12 has second source terminal 12A, the second ground wire terminal 12B, the second positive output terminal 12D and the second negative output terminal 12C.
The first power supply terminal 11A, the second source terminal 12A that derive from the binding site of these two Wheatstone bridges are connected with the power supply of 5V.On the other hand, the first ground wire terminal 11B, the second ground wire terminal 12B that derives from the binding site of the diagonal position of power supply terminal 11A, 12A is connected with ground wire.
And the first negative output terminal 11C, the second negative output terminal 12C, the first positive output terminal 11D and the second positive output terminal 12D that derive from the binding site of the diagonal position different with them are connected with the enlarging section 13 that forms on the wiring substrate 6 respectively by electronic units such as transistors.Lead-out terminal 13A, the 13B of enlarging section 13 is connected with the control part 14 that is made of computer etc.
And the lead-out terminal of AMR element 7, positive output terminal 12D for example adjacent and that polarity is different is connected with the switch portion 19 that is made of IO interface etc. by the first rectifier cell 18A, the second rectifier cell 18B respectively with negative output terminal 11C.Rectifier cell 18A, 18B are made of diode etc., to interconnect along direction.Switch portion 19 is connected with control part 14.Also can form as one switch portion 19 and rectifier cell 18A, 18B and control part 14.
AMR element 8 also has the 3rd Wheatstone bridge 21 and the 4th Wheatstone bridge 22, is same structure.Promptly, the 3rd Wheatstone bridge 21 has the 3rd power supply terminal 21A, the 3rd ground wire terminal 21B, the 3rd negative output terminal 21C and the 3rd positive output terminal 21D, and the 4th Wheatstone bridge 22 has the 4th power supply terminal 22A, the 4th ground wire terminal 22B, the 4th negative output terminal 22C and the 4th positive output terminal 22D. Power supply terminal 21A, 22A are connected with power supply, and ground wire terminal 21B, 22B are connected with ground wire. Negative output terminal 21C, 22C, positive output terminal 21D, 22D are connected with enlarging section 13 respectively.Constitute rotation angle detection apparatus like this.
For example cover at the tilt 45 ° molded resin (not shown) of first Wheatstone bridge 11 that overlaps to form and second Wheatstone bridge, 12 usefulness insulating resin systems of silicon wafer.Be connected with control part 14 grades with enlarging section 13 with the wiring graph that extended each terminal of predetermined distance arrangement utilizes scolding tin to pass through wiring substrate 6 from this mould.
Control part 14 is connected with the electronic circuit (not shown) of car body by connector (not shown) etc.Steering column shaft (not shown) is inserted in the holding section 1B of rotary body 1 and is assemblied on the automobile.
In above structure, in motion, be under the state of ON in ignition switch (not shown), when rotation steering gear (not shown), rotary body 1 rotates thereupon.Along with this rotation, detect the rotation of rotary body 2 interlocks by first of 2A of straight spur gear portion and the 1A of straight spur gear portion engagement, detect second of rotary body 2 engagements by the 3A of straight spur gear portion and first and detect the rotation of rotary body 3 interlocks.Along with the rotation of the first detection rotary body 2, the magnetic direction of magnet 4 changes.Along with the rotation of the second detection rotary body 3, the magnetic direction of magnet 5 changes.AMR element 7,8 detects these variations respectively.
For example, the output signal shown in the negative output terminal 12C output map 3A of second Wheatstone bridge 12 of the AMR element 7 relative with magnet 4.This output signal is the sine wave of about 2.4V~2.6V voltage.On the other hand, the sine wave signal output shown in the positive output terminal 12D output map 3B.The cosine wave (CW) of the about 2.4V~2.6V voltage shown in the negative output terminal 11C output map 3C.Cosine wave (CW) shown in the positive output terminal 11D output map 3D.These output signals are imported into enlarging section 13.
Basis is along with the magnetic direction of the rotation of magnet 4 changes, from the output signal of Wheatstone bridge 12 sine wave outputs like this.On the other hand, from having tilted 45 ° the output signal of Wheatstone bridge 11 output cosine wave (CW)s.And,, almost there is not electric current to flow among rectifier cell 18A, the 18B so rectifier cell 18A, 18B become reverse biased (contrary バ イ ア ス) state because at this moment switch portion 19 is switched to mains side.
And, from AMR element 8 similarly respectively to the output signal of enlarging section 13 sine wave outputs and cosine wave (CW).But since be equipped with first of magnet 4 detect rotary body 2 be equipped with magnet 5 second to detect rotary body 3 is that gear is different, so phase differential is arranged from the output signal of AMR element 8 and from the output signal of AMR element 7.
Enlarging section 13 output signal sinusoidal wave these and cosine wave (CW) is carried out differential amplification respectively.The sine wave of the about 1.5V~3.5V voltage shown in the lead-out terminal 13A output map 4A for example.Cosine wave (CW) shown in the lead-out terminal 13B output map 4B.Lead- out terminal 13C, 13D export the dephased signal with lead-out terminal 13A, 13B respectively.These output signals are exported to control part 14.
Control part 14 performs calculations to the sine wave of these inputs and the output signal of cosine wave (CW), calculates first anglec of rotation and second that detects rotary body 2 and detects the anglec of rotation of rotary body 3, and detect the anglec of rotation of rotary body 1 according to its result.Control part 14 detects the anglec of rotation of steering gear like this.The calculation method of control part 14 is for example disclosed by No. 6870470 communique of United States Patent (USP).
In the moment of regulation, for example after ignition switch was changed to ON, control part 14 switched to the ground wire side to switch portion 19 at once.Like this, control part 14 makes current direction rectifier cell 18A, 18B, detects to have or not short circuit between two adjacent lead-out terminals.
Do not have under the situation of short circuit at negative output terminal 12C and positive output terminal 12D, export for example output signal of voltage 2.6V to enlarging section 13 from negative output terminal 12C.On the other hand, because being switched to ground wire side electric current, switch portion 19 flows, so the voltage of positive output terminal 12D becomes the promptly about 0.7V of forward voltage of the rectifier cell 18A that is connected to rectifier cell 18A.This output signal is exported to enlarging section 13.
Enlarging section 13 is carried out differential amplification to these output signals.That is, from the voltage 0.7V of positive output terminal 12D, deduct the voltage 2.6V of negative output terminal 12C, and it is amplified tens times.This value just becomes the voltage of negative ten V like this, and the output voltage after the differential amplification is saturated.Therefore, from the voltage of lead-out terminal 13A to control part 14 output 0V.
Under the situation of negative output terminal 12C and positive output terminal 12D short circuit, because negative output terminal 12C is connected with positive output terminal 12D, so from both sides' lead-out terminal output signal to enlarging section 13 output voltage 0.7V.Therefore, when enlarging section 13 is carried out differential amplification to it, then owing to the output signal from negative output terminal 12C and positive output terminal 12D is identical voltage 0.7V, so the difference of subtracting each other is 0.Therefore from the voltage of lead-out terminal 13A to control part 14 output 2.5V.
Control part 14 detects this voltage, and when the input of 0V voltage was arranged from lead-out terminal 13A, then being judged to be between negative output terminal 12C and the positive output terminal 12D did not have short circuit, when the input of 2.5V voltage is arranged, then has been judged to be short circuit.Do not having under the situation of short circuit, control part 14 switches to mains side to switch portion 19, and the anglec of rotation of carrying out steering gear then detects.Having under the situation of short circuit, stopping for example to export to the rotational angle detection signal of vehicle electric circuit.
Also be connected with rectifier cell 18B on the negative output terminal 11C, be connected with switch portion 19.Therefore, control part 14 similarly also can detect the short circuit of negative output terminal 11C and positive output terminal 11D.And as shown in Figure 2,, then also can similarly carry out the short-circuit detecting between these adjacent lead-out terminals as long as negative output terminal 21C, positive output terminal 22D also are connected with switch portion 19 by the 4th rectifier cell 18D, the 3rd rectifier cell 18C.
Promptly, will be behind the ignition switch ON, control part 14 flows current direction rectifier cell 18A, 18B, 18C, 18D at once with regard to change-over switch portion 19, difference according to from the output voltage of AMR element 7,8 can detect the short circuit between these adjacent lead-out terminals.Therefore, control part 14 can not have anglec of rotation misinterpretation, reliable to detect.
Rectifier cell 18A, 18B the positive output terminal 12D that connects separately different with the polarity of negative output terminal 11C, therefore, can also detect from the short circuit of enlarging section 13 between lead-out terminal 13A, the 13B of control part 14.
Different with Fig. 2, under rectifier cell 18A and the situation that negative output terminal 12C is connected, during when change-over switch portion 19 and to rectifier cell 18A, 18B streaming current, do not having 5V voltage is arranged to control part 14 outputs from these both sides of lead-out terminal 13A, 13B under the situation of short circuit.Even and have under the situation of short circuit at lead-out terminal 13A and lead-out terminal 13B, 5V voltage is still arranged to control part 14 outputs.Therefore, control part 14 can not detect the short circuit between lead-out terminal 13A and the lead-out terminal 13B.
Relative therewith, Fig. 2 is connected by rectifier cell 18A, 18B the negative output terminal 11C lead-out terminal different with the such polarity of positive output terminal 12D with switch portion 19.This structure does not have under the situation of short circuit between lead-out terminal 13A and lead-out terminal 13B, is respectively to export the 0V voltages, export the 5V voltages from lead-out terminal 13B to control part 14 to control part 14 from lead-out terminal 13A.On the other hand, between lead-out terminal 13A and lead-out terminal 13B, have under the situation of short circuit, from the voltage of this twocouese control part of lead-out terminal 13A, 13B 14 output 2.5V.
Promptly, by the different lead-out terminal of the polarity of two Wheatstone bridges is connected with switch portion 19 by rectifier cell 18A, 18B, control part 14 just can carry out having or not between lead-out terminal 13A, the 13B of enlarging section 13 detection of short circuit according to the difference of output voltage between the lead-out terminal.
Two lead-out terminals of two Wheatstone bridges of AMR element 8 also are that the different lead-out terminal of polarity is connected with switch portion 19 with rectifier cell 18C, 18D.Therefore, according to the output of AMR element 8, can detect from the short circuit between the lead-out terminal of enlarging section 13 similarly.
As above, the rotation angle detection apparatus of present embodiment has: rotary body 1, first detects rotary body 2, first magnet 4, AMR element 7, enlarging section 13 and control part 14.First detects rotary body 2 and the rotation of rotary body 1 interlock.First magnet 4 is assemblied in the central authorities of the first detection rotary body 2.AMR element 7 has first Wheatstone bridge 11 and second Wheatstone bridge 12.Wheatstone bridge 11 is by constituting with magnet 4 relative four magnetoresistive elements 9 that dispose and connect into rectangle.Wheatstone bridge 12 forms with Wheatstone bridge 11 to tilt 45 ° by constituting with magnet 4 relative four magnetoresistive elements 9 that dispose and connect into rectangle.Wheatstone bridge 11 has the first power supply terminal 11A, the first ground wire terminal 11B, the first negative output terminal 11C and the first positive output terminal 11D.Wheatstone bridge 12 has second source terminal 12A, the second ground wire terminal 12B, the second negative output terminal 12C and the second positive output terminal 12D.Enlarging section 13 is connected with AMR element 7, and carrying out differential amplification from the output signal of AMR element 7.When among the first positive output terminal 11D and the first negative output terminal 11C any during as first lead-out terminal, the control part 14 that then is connected with enlarging section 13 passes through first lead-out terminal is connected with ground wire, can detect between positive output terminal 11D and the negative output terminal 11C to have or not short circuit.Do not having under the situation of short circuit, control part 14 disconnects from the connection of first lead-out terminal to ground wire, according to from the output signal of AMR element 7 and based on the anglec of rotation of the input rotary bodies 1 of 13 outputs from the enlarging section.Therefore, this rotation angle detection apparatus can not have misinterpretation ground, detects the anglec of rotation reliably.
Preferably two different lead-out terminals of the polarity of two Wheatstone bridges are connected with switch portion 19 by rectifier cell.According to this structure, can also detect the short circuit between two lead-out terminal 13A, the 13B of enlarging section 13.
Present embodiment is that rectifier cell 18A is connected with positive output terminal 12D, rectifier cell 18B is connected with negative output terminal 11C, but also can be connected with positive output terminal 11D rectifier cell with negative output terminal 12C.That is,, and be connected with switch portion 19 with suitable direction and just can as long as rectifier cell 18B is arranged among different with the first lead-out terminal polarity, positive output terminal 12D and the negative output terminal 12C any promptly between second lead-out terminal and the switch portion 19.Control part 14 is by being connected with second lead-out terminal first lead-out terminal with ground wire, detect between the lead-out terminal of enlarging section 13 to have or not short circuit.
And any among the 3rd positive output terminal 21D and the 3rd negative output terminal 21C is the 3rd lead-out terminal, and control part 14 detects the short circuit of positive output terminal 21D and negative output terminal 21C by the 3rd lead-out terminal is connected with ground wire.
(embodiment 2)
Fig. 5 is the circuit block diagram of the rotation angle detection apparatus of the embodiment of the invention 2.The rotation angle detection apparatus of present embodiment is identical with the embodiment that uses Fig. 1 explanation in constructional structure.That is, the rotation angle detection apparatus of present embodiment is different on circuit structure with the rotation angle detection apparatus of embodiment 1.On identical structure, use identical Reference numeral to describe, omit detailed description one by one sometimes.
As shown in Figure 5, the power supply terminal 11A, the 12A that derive from the binding site of first Wheatstone bridge 11 that constitutes AMR element 7 and second Wheatstone bridge 12 are connected with the power supply of 5V, are connected with ground wire from the ground wire terminal 11B of the diagonal position binding site derivation of the power supply terminal 11A of first Wheatstone bridge 11.
And the ground wire terminal 12B that derives from the diagonal position binding site of the power supply terminal 12A of second Wheatstone bridge 12 is connected with ground wire by resistance 20C, and, be connected with FET20A etc. side by side with resistance 20C.FET20A is connected with IO interface 20B.FET20A and IO interface 20B form switch portion 20.The negative output terminal 11C, the 12C that derive from the binding site of the different diagonal positions of binding site that connect with power supply terminal 11A, 12A and positive output terminal 11D, 12D be connected with enlarging section 13 respectively aspect identical with embodiment 1.And similarly to Example 1, AMR element 8 is same structures with AMR element 7 also.
The rotation angle detection apparatus of this structure is assemblied in the steering gear of vehicle, because the detection method of the steering gear anglec of rotation is identical with embodiment 1, so omit explanation.The detection method that between the lead-out terminal of this explanation AMR element, has or not short circuit.
In the normal state, IO interface 20B is connected with FET20A with mains side, because FET20A is ON, so ground wire terminal 12B is connected with ground wire.In the moment of regulation, for example after ignition switch was changed to ON, control part 17 switched to the ground wire side to IO interface 20B at once.Like this, just FET20A is become OFF.So ground wire terminal 12B is connected with ground wire by resistance 20C.Promptly in resistance 20C, there is electric current to flow.
The lead-out terminal that AMR element 7 and AMR element 8 at first be described does not have the situation of short circuit.For example do not having under the situation of short circuit between negative output terminal 11C, the 12C and between positive output terminal 11D, the 12D etc., from negative output terminal 11C and positive output terminal 11D separately the output signal of cosine wave (CW) to enlarging section 13 outputs.The waveform of these output signals identical with shown in Fig. 3 C and Fig. 3 D, center voltage is 2.5V.
Reduce corresponding part comparing the voltage that center voltage only risen with resistance 20C with Fig. 3 B separately from negative output terminal 12C and positive output terminal 12D, and the little sine wave signal output of amplitude is to enlarging section 13 outputs with Fig. 3 A.Promptly the center voltage from the output signal of negative output terminal 12C and positive output terminal 12D for example becomes 3.5V from 2.5V.
Enlarging section 13 is carried out differential amplification to these output signals, exports to control part 17 respectively with the voltage in the normal output area from the sine wave signal output of lead-out terminal 13A with from the cosine wave (CW) output signal of lead-out terminal 13B.
Relative therewith, for example under the situation of short circuit between negative output terminal 11C, the 12C, near voltage 3V, the output signal of having synthesized sinusoidal wave and cosine wave (CW) is exported to enlarging section 13 from both sides' negative output terminal.
Therefore, when enlarging section 13 is carried out differential amplification to this composite signal, then export the 5V voltage that is exaggerated of the positive voltage value of the 3V voltage gained that from the 3.5V voltage of positive output terminal 12D, deducts negative output terminal 12C from lead-out terminal 13A.From the 2.5V voltage of positive output terminal 11D, deduct the 0V voltage that is exaggerated of negative value of the 3V voltage gained of negative output terminal 11C from lead-out terminal 13B output.These voltage outputs are imported into control part 17.
Control part 17 detects these voltages, and when input had output signal from the sinusoidal waveform of lead-out terminal 13A, 13B or cosine waveform, then judging between negative output terminal 11C, 12C did not have short circuit.When having 0V and 5V voltage to import as output signal, then judging has short circuit.Do not having under the situation of short circuit, control part 17 switches to IO interface 20B mains side and makes FET20A become ON, and the anglec of rotation of carrying out steering gear then detects.Having under the situation of short circuit, for example the rotational angle detection signal output to the vehicle electric circuit is being stopped.
After with ignition switch ON, control part 17 is change-over switch portion 20 at once, makes current direction resistance 20C like this.Detect short circuit between these lead-out terminals according to difference from the output signal of AMR element 7.Therefore, can not have misinterpretation ground, detect the anglec of rotation reliably.
Similarly, also can detect the negative output terminal 11C of AMR element 7 and the short circuit between positive output terminal 12D, positive output terminal 11D and negative output terminal 12C, positive output terminal 11D and the positive output terminal 12D.Present embodiment is that ground wire terminal 12B, 22B are connected with ground wire by resistance 20C, but also can be that ground wire terminal 11B, 21B are connected with ground wire by resistance 20C.That is, control part 17 becomes the state that is connected with ground wire by resistance 20C to ground wire terminal 11B or ground wire terminal 12B from the state that directly is connected with ground wire by change-over switch portion 20.Switch by this, detect that positive output terminal 11D organizes with negative output terminal 12C group, negative output terminal 11C and positive output terminal 12D with positive output terminal 12D group, positive output terminal 11D, negative output terminal 11C and negative output terminal 12C in organizing at least arbitrary group have or not short circuit.Do not having under the situation of short circuit, control part 17 change-over switch portions 20 so that ground wire terminal directly be connected with ground wire, according to output signal, and based on the anglec of rotation of input rotary bodies 1 of 13 outputs from the enlarging section from AMR element 7.
As shown in Figure 5, AMR element 8 is connected with resistance 20C the ground wire terminal of deriving from the binding site of the diagonal position of the power supply terminal of the 4th Wheatstone bridge 22 similarly with FET20A, also can detect the short circuit between AMR element 8 each lead-out terminal thus.
Like this, present embodiment is connected by resistance 20C the ground wire terminal of AMR element 7,8 with ground wire, and is provided with switch portion 20 side by side with resistance 20C.Control part 17 is by detecting the anglec of rotation of rotary body 1 from the output signal of AMR element 7,8, and change-over switch portion 20, and detects short circuit between AMR element 7,8 lead-out terminals according to the difference of these output signals.Therefore, control part 17 can not have misinterpretation ground, detects the anglec of rotation reliably.
Illustrated that in the above description rotary body 1 and first detects rotary body 2 engagements, first and detects the structure that rotary body 2 and second detects rotary body 3 engagements.In addition also can make first to detect rotary body 2 and second and detect rotary body 3 the two meshes with rotary body 1.
In addition, illustrated in rotary body 1, the first detection rotary body 2 and second periphery that detects rotary body 3 to be formed with straight spur gear portion, made their engagements and the structure of mutual interlock rotation.In addition, it also can be the structure of beyond straight spur gear portion, using other shape gears such as conical gear, also can substitute gear and form the jog that can transmit rotation or friction force portion etc. greatly, come mutual interlock to rotate thus in rotary body and the periphery that detects rotary body.
In addition, illustrated on the first detection rotary body 2 and the second detection rotary body 3 to be respectively fitted with magnet 4,5, and had the rotation angle detection apparatus of the AMR element 7,8 that is oppositely arranged with them.In addition, for example, (Japan) spy opens the disclosed rotation angle detection apparatus that does not use the second detection rotary body 3 and magnet 5 and AMR element 8 of 2003-148949 communique, also can be suitable for structure of the present invention.Even also can detect the short circuit between the lead-out terminal of AMR element 7 in this case.
As above, rotation angle detection apparatus of the present invention can detect the short circuit between the AMR element terminal, can not have misinterpretation ground, detects reliably.This rotation angle detection apparatus is useful in the anglec of rotation of automobile steering device detects.

Claims (5)

1, a kind of rotation angle detection apparatus is characterized in that, it comprises:
Rotary body;
First detects rotary body, and itself and described rotary body interlock rotate;
First magnet, it is assemblied in the central authorities of the described first detection rotary body;
The first anisotropic magnetic resistance element, it has first Wheatstone bridge and second Wheatstone bridge, first Wheatstone bridge is made of relative four magnetoresistive elements that dispose and connect into rectangle with described first magnet, second Wheatstone bridge is made of relative four magnetoresistive elements that dispose and connect into rectangle with described first magnet and forms with described first Wheatstone bridge to tilt 45 °, described first Wheatstone bridge has first ground wire terminal, first power supply terminal, the first positive output terminal and the first negative output terminal, described second Wheatstone bridge has second ground wire terminal, the second source terminal, the second positive output terminal and the second negative output terminal;
The enlarging section, it is connected with the described first anisotropic magnetic resistance element, and carrying out differential amplification from the output signal of the described first anisotropic magnetic resistance element;
Control part, it is connected with described enlarging section,
Any of the described first positive output terminal and the first negative output terminal is first lead-out terminal,
Described control part is by being connected described first lead-out terminal with ground wire, detect between described first positive output terminal and the described first negative output terminal and have or not short circuit, and, do not having under the situation of short circuit, disconnection is from the connection of described first lead-out terminal to ground wire, according to from the output signal of the described first anisotropic magnetic resistance element and based on the anglec of rotation from the described rotary body of input of described enlarging section output.
2, rotation angle detection apparatus as claimed in claim 1 is characterized in that, it possesses:
First rectifier cell, it is electrically connected with described first lead-out terminal;
Switch portion, it forward is connected with described first rectifier cell,
Described control part is connected described first lead-out terminal by switching described switch portion with ground wire, detect between described first positive output terminal and the described first negative output terminal to have or not short circuit.
3, rotation angle detection apparatus as claimed in claim 2, it is characterized in that, also possesses second rectifier cell, this second rectifier cell is arranged between second lead-out terminal and the described switch portion, forward be connected with described switch portion, this second lead-out terminal is the second positive output terminal different with the described first lead-out terminal polarity and any in the second negative output terminal
Described control part is by being connected with described second lead-out terminal described first lead-out terminal with ground wire, detect between the lead-out terminal of described enlarging section to have or not short circuit.
4, rotation angle detection apparatus as claimed in claim 1 is characterized in that, also possesses:
Second detects rotary body, and itself and described rotary body and described first detect any the interlock rotation in the rotary body, and is rotated with the rotational speed different with the described first detection rotary body;
Second magnet, it is assemblied in the central authorities of the described second detection rotary body;
The second anisotropic magnetic resistance element, it has the 3rd Wheatstone bridge and the 4th Wheatstone bridge, the 3rd Wheatstone bridge is made of relative four magnetoresistive elements that dispose and connect into rectangle with described second magnet, the 4th Wheatstone bridge is made of relative four magnetoresistive elements that dispose and connect into rectangle with described second magnet, and form with described the 3rd Wheatstone bridge to tilt 45 °
Described enlarging section also is connected with the described second anisotropic magnetic resistance element, and carrying out differential amplification from the output signal of the described second anisotropic magnetic resistance element,
Described control part is according to from the output signal of the output signal of the described first anisotropic magnetic resistance element and the described second anisotropic magnetic resistance element and based on the anglec of rotation from the described rotary body of input of described enlarging section output.
5, rotation angle detection apparatus as claimed in claim 4 is characterized in that,
Described the 3rd Wheatstone bridge has the 3rd ground wire terminal, the 3rd power supply terminal, the 3rd positive output terminal and the 3rd negative output terminal, described the 4th Wheatstone bridge has the 4th ground wire terminal, the 4th power supply terminal, the 4th positive output terminal and the 4th negative output terminal, in described the 3rd positive output terminal and the 3rd negative output terminal any is the 3rd lead-out terminal
Described control part is by being connected described the 3rd lead-out terminal with ground wire, detect between described the 3rd positive output terminal and described the 3rd negative output terminal and have or not short circuit, and, do not having under the situation of short circuit, disconnection from described first lead-out terminal to the connection of ground wire with from described the 3rd lead-out terminal being connected to ground wire, according to from the output signal of the described first anisotropic magnetic resistance element with from the output signal of the described second anisotropic magnetic resistance element, and based on the anglec of rotation from the described rotary body of input of described enlarging section output.
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