JP2007057500A - Angle detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an angle detector for accurately detecting a wide range of angles independently of temperature change in a use environment. <P>SOLUTION: This angle detector is a detector for detecting an operation angle of a component such as a shift lever by utilizing a plurality of (e.g. four) magnetoresistive elements. The magnetoresistive elements are mounted on a vehicle body, etc. at disposition intervals of 45°. A difference R<SB>13</SB>between resistance values R<SB>1</SB>and R<SB>3</SB>, and a difference R<SB>24</SB>between resistance values R<SB>2</SB>and R<SB>4</SB>are calculated, these values being of magnetoresistive elements leaving disposition intervals of 90° from each other. Rectilinear portions of characteristic waveforms S<SB>13</SB>and S<SB>24</SB>of these differences R<SB>13</SB>and R<SB>24</SB>are cut out to write straight-line expressions EQ<SB>1</SB>to EQ<SB>5</SB>of the rectilinear portions as approximate expressions in angle detection in a ROM in the angle detector. In detecting an operation angle of the shift lever, angle calculation is performed by using the straight-line expressions in the ROM based on the resistance values of the magnetoresistive elements. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an angle detection device that detects an angle when an operation component is operated.

  Conventionally, an angle detection device that detects an operation angle (that is, a rotation angle) of an operation component such as a shift lever using a magnetoresistive element has been widely used. In this angle detection device, for example, a magnet is attached to an operation component such as a shift lever, and a magnetoresistive element is disposed on a frame or the like that supports the operation component. When the operation component is operated, the direction of the magnetic field applied from the magnet to the magnetoresistive element as shown in FIG. 7 (hereinafter referred to as the magnetic field direction) is changed as the relative position between the magnet and the magnetoresistive element changes. Therefore, the magnetoresistive element detects the direction of the magnetic field and detects the rotation angle of the operation component.

By the way, the resistance characteristic (output characteristic) of the magnetoresistive element is such that the resistance value of the magnetoresistive element is R (θ), the output reference of the magnetoresistive element (the amplitude center of the output waveform) is R ₀ , and the magnetoresistive element receives from the magnet. When the magnetic field direction is θ and the maximum resistance of the magnetoresistive element is ΔR, the following equation (1) is given.
R (θ) = R ₀ + ΔR · cos ² θ (1)

Therefore, as shown in FIG. 8, the resistance characteristic of the magnetoresistive element is as follows. When the horizontal axis is the magnetic field direction θ and the vertical axis is the variable value (R (θ) −R ₀ ) / ΔR, the magnetic field direction θ is −90 degrees. When the angle is +90 degrees, the variable value takes the minimum value “0”, and when the magnetic field direction θ is 0 degrees, the sinusoidal characteristic waveform S ₀ where the variable value takes the maximum value “1” is satisfied. As can be seen from the figure, when the rotation angle is detected by using one magnetoresistive element, the characteristic waveform S ₀ has a symmetrical waveform centering on the magnetic field direction θ of 0 degree. The detectable angle detection range is limited to a range of 0 degrees to 90 degrees.

Further, in the curvilinear portion of the characteristic waveform S ₀ (that is, the magnetic field direction θ is around −90 degrees, 0 degrees, and +90 degrees), the same value is always obtained every time the angle is detected due to the performance of the magnetoresistive element. There is no guarantee of output. Therefore, if the rotation angle is detected using the curvilinear portion of the characteristic waveform S ₀ , there arises a problem that the detection accuracy deteriorates in the curvilinear portion. Therefore, it is conceivable to perform the rotation angle detected by using only linear portion of the characteristic waveform S _0, the use of this angle detection range is further reduced, it is not suitable for practical use.

Thus, for example, Patent Document 1 discloses a technique for accurately detecting a rotation angle over a wide range. In this technique, two (or three) Hall elements are used, a calibration level is set for the output voltage of these Hall elements, and the linear portion of the output voltage waveform of the Hall elements is cut out. Then, by detecting the rotation angle using the voltage output waveform of this linear portion, a rotation angle of 90 degrees or more is accurately detected.
JP 2002-303507 A

  By the way, since the output voltage of the Hall element varies depending on the temperature in the usage environment, it is necessary to correct the temperature of the output voltage of the Hall element in order to accurately detect the rotation angle. As an example of this temperature correction, for example, there is a method of responding to this temperature change by providing a temperature compensation circuit in the Hall element. However, this method requires a new temperature compensation circuit as a detection device for the rotation angle detection device, which increases the number of parts related to the angle detection device, thereby increasing the complexity, size, and cost of the device. It will cause problems such as.

  In addition, as another method for ensuring the detection accuracy of the rotation angle with respect to the temperature change in the use environment, for example, a calibration level table is prepared on the software, and each use temperature is referred to by referring to the calibration level table. There is also a method of correcting by appropriately setting a calibration level suitable for the above. However, since this method requires complicated calculation processing, it takes time for the correction processing, so it is not suitable for implementation, and if the correction processing is completed in a short time, the detection accuracy is reduced by that amount. However, it is difficult to obtain high detection accuracy by the method using the calibration level table. In addition, since the Hall element has a large variation between elements, this also becomes a factor that high detection accuracy cannot be obtained.

  An object of the present invention is to provide an angle detection device that can accurately detect a wide range of angles without depending on a temperature change in a use environment.

  According to the present invention, in the angle detection device that detects the angle formed by the operation component with respect to the support component that supports the operation component so as to be relatively movable when the operation component is operated, the operation to generate a magnetic field is performed. A plurality of magnetic field generating means provided on one of the component and the support component, and a plurality of mounting states provided on the other of the operation component and the support component and arranged at a predetermined angular interval to detect the magnetic field. A storage means for storing a linear expression of a linearity portion cut out from a characteristic waveform in a difference between characteristic values of the magnetoresistive element and a characteristic value of the magnetoresistive element having a constant interval of the constant angle; and the magnetoresistive element And a calculating means for calculating the angle using the linear equation based on the characteristic value.

  According to this configuration, a plurality of magnetoresistive elements are prepared, and these magnetoresistive elements are arranged and fixed to, for example, a support component with an interval of, for example, 45 degrees. Based on this mounting condition, the difference between the characteristic values (for example, resistance values) of these magnetoresistive elements having an arrangement interval of, for example, 90 degrees is taken, and the linear portion of each characteristic waveform derived from a plurality of sets is cut out. The linear expression of the cut-out part is written in advance in the storage means.

  When the operating component is operated, the operating component moves relative to the support component, so that the direction of the magnetic field applied from the magnetic field generating means to the magnetoresistive element changes according to the relative movement position. At this time, the magnetoresistive element outputs an output signal corresponding to the direction of the magnetic field to the calculating means. The calculation means calculates the operation angle of the operation component by performing an operation using the linear expression stored in the storage means based on the value of the output signal obtained from the magnetoresistive element.

  By the way, the characteristic waveform derived by taking the difference between the characteristic values of the magnetoresistive elements having an interval of 90 degrees in this way is a waveform having a larger amplitude than the characteristic waveform of the characteristic value obtained from one magnetoresistive element. Therefore, if the amplitude of the characteristic waveform increases, more linear portions can be obtained from the characteristic waveform. Therefore, when angle detection is performed using the linear expression of the linear portion as in this example, the angle detection range can be widened. Become. Therefore, for example, when two or more sets of characteristic waveforms derived by taking the difference between the characteristic values of the magnetoresistive elements are used and the angle is calculated using the linear expression of the linearity portion of these characteristic waveforms, one magnetoresistive element Angle detection can be performed in a wider range than in the case.

  In addition, the linear expression of the linearity portion cut out from the difference characteristic waveform cancels out the parameter affected by the temperature change in the calculation process of the angle calculation because of the calculation. Therefore, if angle detection is performed using a magnetoresistive element, even if the operating environment temperature of the angle detection device changes, the operation angle is calculated as a value that is not affected by the temperature change, thereby improving the angle detection accuracy. Is also effective.

The gist of the present invention is that a constant voltage circuit for supplying a constant voltage to the plurality of magnetoresistive elements connected in series is provided.
According to this configuration, since a constant voltage is constantly supplied to the magnetoresistive element group, the output signal (output voltage) of the magnetoresistive element is unlikely to change due to factors other than the change in the magnetic field direction. This is effective in improving the accuracy of angle detection.

The gist of the present invention is that the linearity portion is a continuous section between the top and bottom of the differential characteristic waveform forming the AC waveform.
By the way, it is possible to cut out in a state where the linearity portion is finely divided from the characteristic waveform of the difference, and it is possible to prepare a linear equation for the cut out portion, but then, as many linear equations as that amount are used, the angle Computation processing becomes complicated at the time of detection. However, even if angle detection is performed by cutting out a continuous section between the top and bottom of the difference characteristic waveform as a linear part, the error that occurs varies depending on the resolution of the angle detection. Since the apparatus falls within an allowable range, angle detection can be performed while ensuring sufficient detection accuracy. Therefore, according to this configuration, it is possible to secure the accuracy of angle detection while suppressing the number of prepared linear expressions as small as possible.

  According to this invention, when calculating the angle, the calculation unit uses the characteristic value obtained from each magnetoresistive element as a parameter, and uses the equation used from the plurality of linear equations stored in the storage unit. The gist is to specify.

  According to this configuration, since the characteristic value of the magnetoresistive element used for angle detection is used as a parameter for designating the linear equation from the storage means, it is necessary to prepare another parameter when designating the linear equation Therefore, the calculation process is not complicated.

  According to the present invention, it is possible to accurately detect a wide range of angles without depending on the temperature change in the use environment.

Hereinafter, an embodiment of an angle detection device embodying the present invention will be described with reference to FIGS.
As shown in FIG. 1, a shift lever 2 that is operated when a gear of an automatic transmission is switched is disposed in a vehicle (commonly referred to as an automatic vehicle) 1 in which gear shifting is performed by an automatic transmission. The shift lever 2 is supported by the vehicle body 3 so as to be rotatable about its base end as a fulcrum. The shift lever 2, the angle detection device 4 for detecting an operation angle of the shift lever 2 R _theta is disposed. The angle detection device 4 detects the operation position when the shift lever 2 is shifted to each position such as the P position, the R position, the N position, the D position, the second position, and the L position. The shift lever 2 corresponds to an operation part, and the vehicle body 3 corresponds to a support part.

  As shown in FIG. 2, a substrate 5 of the angle detection device 4 is attached to the vehicle body 3 in the vicinity of the shift lever 2, and a plurality of magnetoresistive elements 6 are mounted on the substrate 5. The magnetoresistive element 6 of this example is made of, for example, a NiCo (nickel cobalt) ferromagnetic material, and four are used in this example. These magnetoresistive elements 6a to 6d are attached to the vehicle body 3 in a state where the arrangement interval between adjacent elements is 45 degrees, and each is applied in the direction of the applied magnetic field H (hereinafter referred to as the magnetic field direction θ). The corresponding output voltages (output signals) Va to Vd (see FIG. 3) are output.

On the other hand, as shown in FIG. 2, a magnet 7 is attached to the shift lever 2 at a position facing the magnetoresistive elements 6 a to 6 d. The magnet 7 is made of a commonly used material such as a ferrite magnet, and is arranged at a position where the magnetic field directions applied to the magnetoresistive elements 6a to 6d change sequentially when the shift lever 2 is operated. Yes. When the shift lever 2 is operated, the direction of the magnetic field H around the magnetoresistive elements 6a to 6d changes as the magnet 7 moves, so that the magnetoresistive elements 6a to 6d detect the magnetic field direction θ. by the operation angle of the shift lever 2 R _theta it is detected. The magnet 7 corresponds to a magnetic field generating unit.

  As shown in FIG. 3, the magnetoresistive elements 6a to 6d are connected in series from the upstream side (power supply side) in the order of 6d, 6c, 6b, and 6a. A constant voltage circuit 8 for supplying a constant voltage to the magnetoresistive elements 6a to 6d is connected to the upstream side of the magnetoresistive element group. Examples of the constant voltage circuit 8 include a circuit composed of a Zener diode and a capacitor, and a circuit that outputs the voltage of the Zener diode by buffering it with a transistor.

The vehicle 1, the computer 9 to calculate the operating angle of the shift lever 2 R _theta on the basis of the output voltage (output signal) Va-Vd magnetoresistive elements 6a~6d are disposed. The computer 9 includes a central processing unit (CPU) 10 that centrally controls the angle detection device 4, a read only memory (ROM) 11 that stores various data, and a random access memory (RAM) that is used as a work area during program execution. ) 12, and an interface 13 serving as a data input / output port. These devices in the computer 9 are interconnected via a bus 14 in the computer 9. The magnetoresistive elements 6a to 6d are connected to the interface 13 via electric wiring. The CPU 10 corresponds to a calculation unit, and the ROM 11 corresponds to a storage unit.

The ROM 11 stores a plurality of linear equations EQ (EQ _{1 to} EQ ₅ ) used when the CPU 10 calculates the operation angle R _θ . This linear EQ is a characteristic waveform S ₁₃ , S derived by taking the difference in output in each of the magnetoresistive elements 6 a, 6 c and the magnetoresistive elements 6 b, 6 d, which are 90 ° apart from each other. ₂₄ (see FIG. 4) corresponds to the equation of the linear portion (the thick line portion in FIG. 4). When the engine is started, power is supplied to the angle detector 4, and the CPU 10 starts detecting the operating angle θ on condition that the power is supplied, and an angle signal D _θ corresponding to the operating angle θ is _output from the computer 9. Output to the outside.

Next, how to obtain the linear equations EQ _{1 to} EQ ₅ will be described.
First, the four magnetoresistive elements 6a to 6d in this example are arranged so that the interval between adjacent elements is 45 degrees. Therefore, the resistance values (characteristic values) R _{1 to} R ₄ of the magnetoresistive elements 6 a to 6 d are R ₀ and the magnetoresistive elements 6 a to 6 are the output reference (the amplitude center of the output waveform) of the magnetoresistive elements 6 a to 6 d. When the maximum resistance of 6d (maximum change value of resistance) is ΔR and the direction of the magnetic field applied to the magnetoresistive elements 6a to 6d is θ, values satisfying the following expressions (2) to (5) are obtained.
R ₁ = R ₀ + ΔR · cos ² (θ−45) (2)
R ₂ = R ₀ + ΔR · cos ² (θ) (3)
R ₃ = R ₀ + ΔR · cos ² (θ + 45) (4)
R ₄ = R ₀ + ΔR · cos ² (θ + 90) (5)

As shown in FIG. 4, the characteristic waveforms S _{1 to} S ₄ of the resistance values R _{1 to} R ₄ have an alternating waveform with an amplitude of “1”, and the arrangement interval of the magnetoresistive elements 6a to 6d forms 45 degrees. Therefore, in the waveform between adjacent magnetoresistive elements, the phase is displaced by 45 degrees. That is, phase shifted -45 degrees relative to the characteristic waveform _{S 1} characteristic waveform _{S 2} of the magnetoresistive element 6b magnetoresistive element 6a, characteristic waveform _{S 3} of the magnetoresistive element 6c magnetoresistive element 6b characteristic waveform _{S 2} phase shifted -45 degrees relative to the characteristic waveform _{S 4} of the magnetoresistive element 6d phase is shifted -45 degrees relative characteristic waveform _{S 3} of the magnetoresistive element 6c.

  However, in this example, the resistance characteristics of the magnetoresistive elements 6a to 6d are all the same. Here, as an example of manufacturing the magnetoresistive elements 6a to 6d having uniform resistance characteristics, for example, a manufacturing method in which four materials of the magnetoresistive elements 6a to 6d are simultaneously attached to the substrate 5 by sputtering or the like is employed. Further, when this manufacturing method is used, not only the resistance characteristics of the magnetoresistive elements 6a to 6d are uniform, but also the patterns of the magnetoresistive elements 6a to 6d become extremely small, and the size of the angle detection device 4 is reduced. Is also effective.

Subsequently, a difference R ₁₃ (= R ₁ −R ₃ ) between the resistance values R ₁ and R ₃ is obtained in the magnetoresistive elements 6a and 6c which are a set having a 90 ° interval, and the 90 ° interval is also obtained. set a is magnetoresistive element 6b, in 6d, obtains a difference R ₂₄ of the resistance value _R 2, _{R 4} a ₍₌ R 2 -R ₄₎ in a similar manner. These differences R ₁₃ and R ₂₄ take values that satisfy the following expressions (6) and (7).
R ₁₃ = R ₁ −R ₃ = ΔR · sin 2θ (6)
R ₂₄ = R ₂ −R ₄ = ΔR · cos 2θ (7)

As shown in FIG. 4, the characteristic waveforms S ₁₃ and S ₂₄ of the differences R ₁₃ and R ₂₄ are AC waveforms having amplitude ranges of “−1” to “+1”, and their phases are shifted by 45 degrees from each other. It becomes a waveform. That is, characteristics waveform S ₁₃ of the differential R ₁₃ takes the sine wave characteristic waveform S ₂₄ of the differential R ₂₄ is taking the cosine wave.

Subsequently, a linear portion is cut out in the characteristic waveforms S ₁₃ and S ₂₄ of the differences R ₁₃ and R ₂₄ . First, the point (−90, 0) on the characteristic waveform S ₁₃ when the characteristic waveform S ₁ and the characteristic waveform S ₃ intersect under the condition that the resistance value satisfies R ₄ > R ₂ and the resistance value is R ₃ > R. The point (−67.5, −2 ^1/2 / 2) on the characteristic waveform S ₁₃ when the characteristic waveform S ₁ and the characteristic waveform S ₂ (characteristic waveform S ₃ and characteristic waveform S ₄ ) intersect under the condition satisfying ₁ ) And the linear equation EQ ₁ connecting the two points is calculated. The linear equation EQ ₁ is an equation that satisfies the following equation (8).

この直線式ＥＱ_１は、特性波形Ｓ₁₃を１周期で見た場合、振幅が「０」以下の領域において波形の傾きが負となる区間の直線性部分に相当する式であり、抵抗値がＲ_４＞Ｒ_３＞Ｒ_１＞Ｒ_２の関係を満たす際には、この直線式ＥＱ_１を使用して操作角度Ｒ_θを算出する。

The linear equation EQ ₁ is an equation corresponding to a linear portion of a section where the slope of the waveform is negative in a region where the amplitude is “0” or less when the characteristic waveform S ₁₃ is viewed in one cycle. When satisfying the relationship of R ₄ > R ₃ > R ₁ > R ₂ , the operation angle R _θ is calculated using this linear equation EQ ₁ .

A point (−67.) On the characteristic waveform S ₂₄ when the characteristic waveform S ₁ and the characteristic waveform S ₂ (characteristic waveform S ₃ and characteristic waveform S ₄ ) intersect under the condition that the resistance value satisfies R ₃ > R ₁ . 5−2 ^1/2 / 2) and the characteristic when the characteristic waveform S ₁ and the characteristic waveform S ₄ (characteristic waveform S ₂ and characteristic waveform S ₃ ) intersect under the condition that the resistance value satisfies R ₂ > R _1. calculating the linear equation EQ ₂ that connects the two points of a point on the waveform ^{_{S 24 (-22.5,2 1/2 / 2)}} . The linear equation EQ ₁ is an equation that satisfies the following equation (9).

この直線式ＥＱ_２は、特性波形Ｓ₂₄を１周期で見た場合、波形の傾きが正となる区間の直線性部分に相当する式であり、抵抗値がＲ_３＞Ｒ_４及びＲ_２＞Ｒ_１の関係を満たす際には、この直線式ＥＱ_２を使用して操作角度Ｒ_θを算出する。

The linear equation EQ _2, when viewed characteristic waveform S ₂₄ in one cycle, an expression corresponding to the linear portion of the section gradient of the waveform is positive, the resistance value R _3> R ₄ and R _2> When satisfying the relationship of R ₁ , the operation angle R _θ is calculated using the linear equation EQ ₂ .

Similarly, a point (−22) on the characteristic waveform S ₁₃ when the characteristic waveform S ₁ and the characteristic waveform S ₄ (characteristic waveform S ₂ and characteristic waveform S ₃ ) intersect under the condition that the resistance value satisfies R ₂ > R _1. ., -2 ^1/2 / 2) and the characteristic waveform S ₁ and the characteristic waveform S ₂ (characteristic waveform S ₃ and characteristic waveform S ₄ ) meet under the condition that the resistance value satisfies R ₁ > R ₃ . A linear equation EQ ₃ connecting two points with the point (22.5, ^{2 1/2} / 2) on the characteristic waveform S ₁₃ is calculated. The linear equation EQ ₁ is an equation that satisfies the following equation (10).

この直線式ＥＱ_３は、特性波形Ｓ₁₃を１周期で見た場合、波形の傾きが正となる区間の直線性部分に相当する式であり、抵抗値がＲ_２＞Ｒ_３及びＲ_１＞Ｒ_４の関係を満たす際には、この直線式ＥＱ_３を使用して操作角度Ｒ_θを算出する。

This linear equation EQ ₃ is an equation corresponding to a linear portion of a section in which the waveform slope is positive when the characteristic waveform S ₁₃ is viewed in one cycle, and the resistance values are R ₂ > R ₃ and R ₁ > When satisfying the relationship of R ₄ , the operation angle R _θ is calculated using this linear equation EQ ₃ .

A point (22.5) on the characteristic waveform S ₂₄ when the characteristic waveform S ₁ and the characteristic waveform S ₂ (characteristic waveform S ₃ and characteristic waveform S ₄ ) intersect under the condition that the resistance value satisfies R ₁ > R _3. , 2 ^1/2 / 2), and the characteristic waveform S when the characteristic waveform S ₁ and the characteristic waveform S ₄ (characteristic waveform S ₂ and characteristic waveform S ₃ ) intersect under the condition that the resistance value satisfies R ₁ > R _2. A linear equation EQ ₄ connecting the two points with the point (67.5, -2 ^1/2 / 2) on ₂₄ is calculated. The linear equation EQ ₄ is an equation that satisfies the following equation (11).

この直線式ＥＱ_４は、特性波形Ｓ₂₄を１周期で見た場合、波形の傾きが負となる区間の直線性部分に相当する式であり、抵抗値がＲ_１＞Ｒ_２及びＲ_４＞Ｒ_３の関係を満たす際には、この直線式ＥＱ_４を使用して操作角度Ｒ_θを算出する。

This linear equation EQ ₄ is an equation corresponding to a linear portion of a section in which the slope of the waveform is negative when the characteristic waveform S ₂₄ is viewed in one cycle, and the resistance values are R ₁ > R ₂ and R ₄ > When satisfying the relationship of R ₃ , the operation angle R _θ is calculated using this linear equation EQ ₄ .

Further, a point (67.5) on the characteristic waveform S ₂₄ when the characteristic waveform S ₁ and the characteristic waveform S ₄ (characteristic waveform S ₂ and characteristic waveform S ₃ ) intersect under the condition that the resistance value satisfies R ₁ > R _2. , 2 ^1/2 / 2) and a point (90, 0) on the characteristic waveform S ₁₃ when the characteristic waveform S ₁ and the characteristic waveform S ₃ intersect under the condition that the resistance value satisfies R ₄ > R ₂ A linear equation EQ ₅ connecting the two points is calculated. The linear equation EQ ₅ is an equation that satisfies the following equation (12).

この直線式ＥＱ_５は、特性波形Ｓ₁₃を１周期で見た場合、振幅が「０」以上の領域において波形の傾きが負となる区間の直線性部分に相当する式であり、抵抗値がＲ_４＞Ｒ_１＞Ｒ_３＞Ｒ_２の関係を満たす際には、この直線式ＥＱ_５を使用して操作角度Ｒ_θを算出する。

The linear equation EQ ₅ is an equation corresponding to a linear portion of a section where the slope of the waveform is negative in a region where the amplitude is “0” or more when the characteristic waveform S ₁₃ is viewed in one cycle. When satisfying the relationship of R ₄ > R ₁ > R ₃ > R ₂ , the operation angle R _θ is calculated using the linear equation EQ ₅ .

Therefore, arranged in 45 ° arrangement interval four magnetoresistive elements 6a~6d as in this example, calculated magnetoresistive element 6a, the difference R ₁₃ and the magnetoresistive element 6b of 6c, 6d and the difference R ₂₄ of, The characteristic waveforms S ₁₃ and S ₂₄ of these differences R ₁₃ and R ₂₄ are cut out at a portion having good linearity, and the angle calculation is performed using the linear equations EQ _{1 to} EQ _{5 of the portion} as approximate equations. Therefore, since it is possible to obtain a characteristic with good linearity in the range of 180 degrees, it is possible to detect the angle in the range of 180 degrees with high accuracy.

Next, to verify the error of the operation angle R _theta calculated using the linear equation EQ ₁ ~EQ _5, here it will be described an example using a linear equation EQ ₃ to perform easily described.
As shown in FIG. 5, when the characteristic waveform S ₁₃ and the linear equation EQ ₃ output the same resistance value, the magnetic field direction calculated as an accurate value by the characteristic waveform S _{13 at} this time is θ and the linear equation EQ. _{When the} magnetic field direction calculated as an approximate value by ₃ is θa, the following equation (13) is established.

ここで、磁界向きθ，θａの間の誤差をΔθとすると、誤差Δθは次式(14)によって算出される。

Here, if the error between the magnetic field directions θ and θa is Δθ, the error Δθ is calculated by the following equation (14).

続いて、Δθの最大誤差は、Δθを微分してその微分式が「０」を満たすところに存在するので、誤差Δθが最大誤差Δθmaxをとる際には、次式(15)を満たすことになり、同式(15)を展開して磁界向きθを求めると、磁界向きθは次式(16)を満たす値をとる。

Subsequently, since the maximum error of Δθ exists where Δθ is differentiated and the differential equation satisfies “0”, when the error Δθ takes the maximum error Δθmax, the following equation (15) is satisfied. Thus, when the magnetic field direction θ is obtained by developing the same expression (15), the magnetic field direction θ takes a value satisfying the following expression (16).

そして、(16)式で得られた磁界向きθを(14)式に代入すると、最大誤差Δθmax は次式(17)を満たす値となる。

Then, when the magnetic field direction θ obtained by the equation (16) is substituted into the equation (14), the maximum error Δθmax becomes a value satisfying the following equation (17).

この(17)式を展開すると、最大誤差Δθmax は次式(18)に示す値で算出される。

When this equation (17) is developed, the maximum error Δθmax is calculated by the value shown in the following equation (18).

式(18)に示す最大誤差Δθmax を見ても分かるように、最大誤差Δθmax は「１度」以下の「０．９５度」度なる。ところで、シフトレバー２の多くは分解能が１度以下のものを要求しているものはほとんどないため、最大誤差が「０．９５度」であれば、近似式である本例の直線式ＥＱ_１〜ＥＱ_５用いて角度検出を行なっても、検出精度にはさほど影響を及ぼさずに済む。

As can be seen from the maximum error Δθmax shown in Expression (18), the maximum error Δθmax is “0.95 degrees” which is “1 degree” or less. By the way, since most of the shift levers 2 do not require a resolution of 1 degree or less, if the maximum error is “0.95 degrees”, the linear expression EQ _{1 of} this example which is an approximate expression. Even if angle detection is performed using .about.EQ ₅ , the detection accuracy is not significantly affected.

Moreover, the ambient temperature of the angle detection device 4 when (ambient temperature) changes under the influence magnetoresistive element 6a~6b within its temperature change, the resistance value _R 1 to R ₄ (resistance characteristics _S 1 _{to S} 4) Changes. That is, each resistivity r of each magnetoresistive element 6a~6d is the temperature of the use environment of T, resistivity when the r ₀ 0 degree, when a temperature coefficient of the α resistivity, the following equation (19) It changes with the relational expression.
r = r ₀ · (1 + αT) (19)

By the way, as can be seen from the linear equations EQ _{1 to} EQ ₅ shown in the equations (8) to (12), both the right side and the left side of these linear equations EQ _{1 to} EQ ₅ have resistance value parameters. Even if the ambient operating environment temperature changes, the temperature change parameter is canceled in the calculation process, and the final calculated value at the time of the angle calculation is calculated as a value that is not affected by the temperature change. Therefore, if the angle detection is performed using the magnetoresistive elements 6a to 6d, the temperature of the output of the computer 9 is compensated, and the operation angle R _θ that is a calculated value of the computer 9 even if the temperature changes in the use environment. Temperature error is less likely to occur.

According to the angle detection device 4 of the present embodiment, the following effects can be obtained.
(1) four mounting at arrangement intervals of 45 degrees magnetoresistive element 6 a to 6 d, the magnetoresistive element 6a, 6c and the magnetoresistive element 6b, respectively between 6d difference R ₁₃ constituting the arrangement interval of 90 degrees from each other, Taking R ₂₄ , angle calculation is performed using linear equations EQ _{1 to} EQ ₅ obtained from the linear portions of the characteristic waveforms S ₁₃ and S ₂₄ of the differences R ₁₃ and R ₂₄ . Therefore, when the magnetic field direction θ is in the range of −90 degrees to +90 degrees, the relational expression between the magnetic field direction θ and the resistance values R _{1 to} R ₄ is represented by the characteristic waveforms S _{1 to} S ₄ of these magnetoresistive elements 6a to 6d. Replaced by the linear expression of the linear part. Therefore, the linearity portion of the characteristic waveforms S _{1 to} S ₄ can be calculated in the magnetic field direction θ (that is, the operation angle R _θ ) in the range of −90 degrees to +90 degrees, and the magnetic field direction θ is highly accurate in the range of 180 degrees. Can be detected. In addition, since the magnetoresistive elements 6a to 6d are used as the elements for detecting the magnetic field, the magnetoresistive elements 6a to 6d have characteristics that the output does not easily change even when the use environment temperature changes. If angle detection is performed using the magnetoresistive elements 6a to 6d as described above, temperature compensation can be ensured.

(2) The magnetoresistive elements 6a to 6d are connected in series, and a voltage is applied to the magnetoresistive elements 6a to 6d via the constant voltage circuit 8 so that current flows through the magnetoresistive elements 6a to 6d. Accordingly, a constant voltage is supplied to the magnetoresistive element group, and the resistance values R _{1 to} R ₄ (output signals) of the magnetoresistive elements 6 a to 6 d change due to factors other than the magnetic field direction θ. It is difficult to become a situation, and high angle detection accuracy can be ensured.

(3) When the linearity portions of the characteristic waveforms S ₁₃ and S ₂₄ of the differences R ₁₃ and R ₂₄ are cut out, the continuous sections between the top and bottom of the characteristic waveforms S ₁₃ and S ₂₄ are linearized respectively. Cut out as a part. By the way, if the linearity portions of the characteristic waveforms S ₁₃ and S ₂₄ are cut out finely and angle detection is performed using this, it is possible to detect the angle with high accuracy, but it is necessary to prepare a large number of linear EQs accordingly. Therefore, the calculation process becomes complicated. However, as in this example, even if the continuous section between the top and bottom of the characteristic waveforms S ₁₃ and S ₂₄ is cut out as a linear part and angle detection is performed using the linear equations EQ _{1 to} EQ ₅ of this part. The maximum error Δθmax generated at that time falls within 0.95 degrees as shown in the equation (18). Therefore, when this angle detection device 4 is used for angle detection of the shift lever 2, if the maximum error Δθmax is such an error, the angle detection accuracy is large due to the resolution necessary for angle detection of the shift lever 2. There is no effect. Therefore, sufficient angle detection accuracy can be ensured while keeping the linear EQ prepared in the ROM 11 as small as possible.

(4) When selecting an expression to be used from among the plurality of linear expressions EQ _{1 to} EQ ₅ stored in the ROM 11, the angle values are calculated using the resistance values R _{1 to} R ₄ of the magnetoresistive elements 6a to 6d as parameters. Specify the appropriate one. Therefore, when the linear equations EQ _{1 to} EQ ₅ are designated, processing such as newly inputting another parameter is not required, so that the calculation process is not complicated.

In addition, this embodiment is not limited to the said structure, You may change into the following aspects.
The number of the magnetoresistive elements 6 is not limited to four as in the present example, and a configuration using, for example, six or eight may be used. Further, the arrangement interval of the magnetoresistive elements 6 is not limited to 45 degrees, and may be, for example, 30 degrees or 40 degrees as long as the angle can be detected in a range of 90 degrees or more.

The portion cut out as the linear portion is not limited to a continuous section between the top and bottom of the characteristic waveform S ₁₃ (characteristic waveform S ₂₄ ). For example, as shown in FIG. 6, a section that has been cut out as one linear portion until now may be cut out by a plurality of (four in FIG. 6) straight lines.

The attachment location of the magnetoresistive element 6 and the magnet 7 is not limited to the magnetoresistive element 6 being on the vehicle body 3 side and the magnet 7 being on the shift lever 2 side, and this combination may be reversed.
The writing destination of the linear EQ is not limited to the ROM 11, and for example, if an EEPROM (Electronically Erasable and Programmable ROM) is built in the angle detection device 4, this may be used as the writing destination of the linear EQ. .

The magnetic field generation means is not limited to the magnet 7 as long as it can generate a magnetic field.
The angle detection device 4 of this example is not limited to the shift lever 2 but may be a seat inclination detection device that detects the amount of inclination of the seat back, for example, and the installation target of the angle detection device 4 is particularly limited. Not.

Next, technical ideas that can be grasped from the above-described embodiment and other examples will be described below together with their effects.
(1) In any one of Claims 1-4, the said magnetoresistive element is attached to the said support component side. In this case, since the magnetoresistive element is attached to the support component on the fixed side with respect to the operation component, even if the operation component is operated, it is not necessary for the magnetoresistive element to move along with the operation component. It is difficult for the magnetoresistive element to be detached from the mounting location due to centrifugal force or vibration at the time.

  (2) In an angle detection device that detects an angle formed by the operation component with respect to a support component that supports the operation component so as to be relatively movable when the operation component is operated, the operation component and the A magnetism generating means provided on one of the support parts, and a plurality of magnetic field resistance elements provided on the other of the operation part and the support part and attached at an arrangement interval of 45 degrees to detect the magnetic field, and 90 Based on the characteristic value of the magnetoresistive element, the storage means storing the linear expression of the linearity portion cut out from each characteristic waveform obtained by taking the difference in the characteristic value of the magnetoresistive element forming the arrangement interval of the degree, An angle detection apparatus comprising: a calculation unit that calculates the angle using a linear equation.

The perspective view which shows the vehicle interior in one Embodiment. The top view which shows the attachment state of the magnetoresistive element and magnet which comprise an angle detection apparatus. The block diagram which shows the electric constitution of an angle detection apparatus. The wave form diagram which shows the characteristic waveform of a magnetoresistive element. Explanatory drawing at the time of calculating the maximum error of the detection angle calculated using the linear formula which is an approximation formula. The wave form diagram which shows the characteristic waveform derived | led-out from the difference of the magnetoresistive element in another example. The top view which shows the state in which the magnetic field of the predetermined direction was applied to the conventional magnetoresistive element. The wave form diagram which shows the characteristic waveform of a magnetoresistive element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 ... Shift lever as operation component, 3 ... Vehicle body as support component, 4 ... Angle detection device, 6 (6a-6d) ... Magnetoresistive element, 7 ... Magnet as magnetic field generation means, 8 ... Constant voltage circuit, 10 ... ROM as CPU, 11 ... storage means as calculation means, H ... field, R _theta ... operating angle, R _13, R ₂₄ ... difference, S _13, S ₂₄ ... characteristic _waveform, EQ (EQ 1 _~EQ 5) ... Linear type.

Claims (4)

In an angle detection device that detects an angle formed by the operation component with respect to a support component that supports the operation component so as to be relatively movable when the operation component is operated,
Magnetic field generating means provided on one of the operating component and the support component to generate a magnetic field;
A plurality of magnetoresistive elements that are provided on the other of the operation component and the support component and have a mounting state at a certain angle from each other to detect the magnetic field;
Storage means for storing a linear expression of the linearity portion cut out from the characteristic waveform in the difference in characteristic value of the magnetoresistive element forming an arrangement interval of a constant multiple of the constant angle;
An angle detection apparatus comprising: a calculation unit that calculates the angle using the linear equation based on a characteristic value of the magnetoresistive element.   The angle detection device according to claim 1, further comprising a constant voltage circuit that supplies a constant voltage to the plurality of magnetoresistive elements connected in series.   The angle detection device according to claim 1, wherein the linear portion is a continuous section between a top and a bottom of the differential characteristic waveform forming an AC waveform.   The calculating means designates an expression to be used from among the plurality of linear expressions stored in the storage means, using the characteristic value obtained from each magnetoresistive element as a parameter when calculating the angle. The angle detection device according to any one of claims 1 to 3.

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