Rotation angle detector

A rotation angle detector for detecting a rotation angle of a magnet rotator includes: the rotator with a magnet mounted on a rotation shaft; a sensor chip; and an operation element. The chip includes: first and second normal component detection elements for detecting a magnetic field along with a normal direction and first and second rotation component detection elements for detecting a magnetic field along with a rotation direction. A phase difference Δθ, output signals S1, S2, C1, C2 of the detection elements, a value ΔθbR obtained by differentiating a component of the magnetic field along with the normal direction with respect to the rotation direction, and a value Δθbθ obtained by differentiating a component of the magnetic field along with the rotation direction with respect to the rotation direction satisfies:The operation element calculates:

CROSS REFERENCE TO RELATED APPLICATION

This application is based on Japanese Patent Application No. 2010-170898 filed on Jul. 29, 2010, the disclosure of which is incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a rotation angle detector including a magnet rotator having a pair of magnetic poles and a sensor chip with a magnetic field detection element on a semiconductor substrate.

BACKGROUND

Conventionally, as described in Japanese Patent No. 4273363 corresponding to US-2009/0206827, a rotation angle detector includes a magnet rotator having four or more magnetic poles (i.e., two ore more pairs of magnetic poles), and first and second sensing devices for detecting a direction of magnetic flux generated by the magnet rotator.

Each of the first and second sensing devices is a spin-valve type giant magneto-resistance effect element having a fixed layer and a variable layer. A magnetization direction of the fixed layer is fixed to a certain direction. A magnetization direction of the variable layer is varied with a direction of a magnetic field. The giant magneto-resistance effect element has a property such that a resistance of the element is changed according to an angle between the magnetization direction of the fixed layer and the magnetization direction (i.e., the magnetic field direction) of the variable layer. When the magnet rotator rotates by an electric angle (which is an angle calculated by dividing the rotation angle with the number of pairs of the magnetic poles), the sensing device having the resistor element outputs a signal corresponding to one period of a waveform. For example, when the magnet rotator includes two pairs of magnetic poles, and the magnet rotator rotates one revolution, the sensing device outputs the signal corresponding to two periods of the waveform.

A rotation angle detector described in Japanese Patent No. 4273363 will be explained. The first sensing device includes two sensing bridges X01, Y01, each of which provides a full bridge composed of four resistor elements. The second sensing device includes two sensing bridges X02, Y02, each of which provides a full bridge composed of four resistor elements. The full bridge includes a pair of resistor elements coupled in series with each other and another pair of resistor elements coupled in series with each other. The pair of resistor elements and the other pair of resistor elements are coupled in parallel to each other between a power source and a ground. Thus, each full bridge (i.e., each sensing bridge X01, X02, Y01, Y02) is prepared. The magnetization direction of the fixed layer in the resistor element on a power source side of one pair of the resistor elements is opposite to the magnetization direction of the fixed layer in the resistor element on a power source side of the other pair of the resistor elements. The magnetization direction of the fixed layer in the resistor element on a ground side of the one pair of the resistor elements is opposite to the magnetization direction of the fixed layer in the resistor element on a ground side of the other pair of the resistor elements.

The magnetization direction of the fixed layer in the resistor elements of the sensing bridge Y01is in parallel to a rotation direction of the magnet rotator. Further, the magnetization direction of the fixed layer in the resistor elements of the sensing bridge Y01is perpendicular to the magnetization direction of the fixed layer in the resistor elements of the sensing bridge X01. The magnetization direction of the fixed layer in the resistor elements of the sensing bridge Y02is in parallel to a rotation direction of the magnet rotator. Further, the magnetization direction of the fixed layer in the resistor elements of the sensing bridge Y02is perpendicular to the magnetization direction of the fixed layer in the resistor elements of the sensing bridge X02. The magnetization direction of the fixed layer in the resistor elements of the sensing bridge X01and the magnetization direction of the fixed layer in the resistor elements of the sensing bridge X02are arranged to differentiate a phase by the electric angle of 90 degrees.

The first sensing device has a magnetic field sensitive direction as a reference of the magnet rotator. The rotation angle of the first sensing device with respect to the magnet rotator is defined as θ. When the sensing bridge X01outputs the detection signal depending on a term of cos θ, the sensing bridge Y01outputs the detection signal depending on a term of −sin θ since the magnetization direction of the fixed layer in the resistor elements of the sensing bridge Y01is perpendicular to the magnetization direction of the fixed layer in the resistor elements of the sensing bridge X01.

Since the magnetization direction of the fixed layer in the resistor elements of the sensing bridge X01and the magnetization direction of the fixed layer in the resistor elements of the sensing bridge X02are arranged to differentiate the phase by the electric angle of 90 degrees, the sensing bridge X02outputs the detection signal depending on a term of sin θ. Since the magnetization direction of the fixed layer in the resistor elements of the sensing bridge Y02is perpendicular to the magnetization direction of the fixed layer in the resistor elements of the sensing bridge X02, the sensing bridge Y02outputs the detection signal depending on a term of cos θ.

The factors depending on the term of θ in the detection signals of the sensing bridges X01, Y01are defined as (X01θ, Y01θ). (X01θ, Y01θ) is equal to (cos θ, −sin θ). The factors depending on the term of θ in the detection signals of the sensing bridges X02, Y02are defined as (X02θ, Y02θ). (X02θ, Y02θ) is equal to (sin θ, cos θ). Thus, the detection signals of the sensing bridges X01, Y02depend on the term of cos θ. The detection signals of the sensing bridges Y01, X02depend on the term of sin θ. Accordingly, the detection signal of the sensing bridge Y02is reversed so that the reversed detection signal is obtained, and the factor depending on the term of θ in the reversed detection signal of the sensing bridge Y02is defined as Y02θ′. When an operation amplifier calculates a difference of (X01θ−Y02θ′) and a difference of (X02θ−Y01θ), the value of cos θ and the value of sin θ in each detection signal are obtained. Here, a high frequency noise having the same phase is canceled in value of cos θ and the value of sin θ. Based on the value of cos θ and the value of sin θ, the value of tan θ is calculated. Then, an angle calculator executes a calculation with using an arctangent function so that the angle θ is calculated.

Here, the first sensing device is formed in a chip, which is different from the second sensing device. In this case, the rotation angle detector includes multiple chips, so that a manufacturing cost of the detector is high.

To improve the manufacturing cost, the first and second sensing devices may be formed in one chip. However, in this case, when the high frequency noise is removed from the detection signal, as described above, since the magnetization direction of the fixed layer in the resistor elements of the sensing bridge X01and the magnetization direction of the fixed layer in the resistor elements of the sensing bridge X02are arranged to differentiate a phase by the electric angle of 90 degrees, the electric angle increases in a case where the number of magnetic poles of the magnet rotator is small, and the dimensions of the chip increases. Here, when the number of magnetic poles of the magnet rotator is large, the electric angle is reduced, and therefore, the dimensions of the chip are limited. However, when the number of magnetic poles of the magnet rotator is large, the rotation frequency of the rotation magnetic field increases. Thus, a processing speed of the angle calculator with respect to the input signal may not be sufficient.

The magnet rotator together with the magnet is attached to and fixed to a rotation shaft. The rotation shaft is rotated by a magnetic flux, which is generated by windings. The windings surround the magnet rotator. In this case, the chip is arranged between the windings and the magnet rotator. The magnetic flux of the windings and the magnetic flux of the magnet rotator are applied to the chip. In order to detect the rotation angle of the magnet rotator based on the magnetic flux of the magnet rotator, it is necessary to remove the magnetic flux of the windings. Thus, the magnetic flux generated by the windings provides a noise, which is defined as an inductive noise.

The rotation shaft is rotated by a repulsion force between the inductive noise and the magnetic flux generated by the magnet fixed to the rotation shaft. Accordingly, the rotation direction of the inductive noise is opposite to the rotation direction of the rotation magnetic field of the magnet rotator. When the inductive noise is removed by a noise reduction method described in Japanese Patent No. 4273363, it is necessary to arrange the magnetization direction of the fixed layer in the resistor elements of the sensing bridge X01and the magnetization direction of the fixed layer in the resistor elements of the sensing bridge X02so as to differentiate a phase by the electric angle of 180 degrees. Thus, since the electric angle is doubled for removing the inductive noise, the dimensions of the chip much increase.

SUMMARY

In view of the above-described problem, it is an object of the present disclosure to provide a rotation angle detector including a magnet rotator having a pair of magnetic poles and a sensor chip with multiple magnetic field detection elements on a semiconductor substrate. The dimensions of the chip are improved without increasing the number of magnetic poles of the magnet rotator.

According to an aspect of the present disclosure, a rotation angle detector includes: a magnet rotator including at least one pair of magnetic poles, wherein the magnet rotator together with a magnet is mounted on a rotation shaft; a sensor chip including a semiconductor substrate and a magnetic field detection element in the semiconductor substrate, wherein the magnetic field detection element detects a magnetic field; and an operation element. The rotation shaft and the sensor chip are arranged in a magnetic field, which provides to rotate the rotation shaft. The rotation angle detector detects a rotation angle of the magnet rotator based on an electric signal output from the magnetic field detection element. The magnetic field detection element includes a first magnetic field detection element and a second magnetic field detection element, which are spaced apart from each other by a distance corresponding to a predetermined phase difference. The first magnetic field detection element includes a first normal component detection element for detecting a magnetic field along with a normal direction and a first rotation component detection element for detecting a magnetic field along with a rotation direction. The normal direction passes a center of the rotator and is perpendicular to the rotation direction. The second magnetic field detection element includes a second normal component detection element for detecting the magnetic field along with the normal direction and a second rotation component detection element for detecting the magnetic field along with the rotation direction. The phase difference satisfies a condition that a value obtained by dividing a difference between an output signal of the first normal component detection element and an output signal of the second normal component detection element with the phase difference is approximated to a value obtained by differentiating a component of the magnetic field along with the normal direction around the sensor chip with respect to the rotation direction, and a value obtained by dividing a difference between an output signal of the first rotation component detection element and an output signal of the second rotation component detection element with the phase difference is approximated to a value obtained by differentiating a component of the magnetic field along with the rotation direction with respect to the rotation direction. The phase difference is defined as Δθ, the output signal of the first normal component detection element is defined as S1, the output signal of the second normal component detection element is defined as S2, the output signal of the first rotation component detection element is defined as C1, the output signal of the second rotation component detection element is defined as C2, a first term depending on the magnetic field for rotating the rotation shaft is defined as α, and a second term depending on the magnetic field for rotating the rotation shaft is defined as β. The operation element calculates a value of:

and a value of:

The phase difference Δθ does not depend on the electric angle. The electric angle depends on the number of magnetic poles in the rotator. The phase difference Δθ can be a value such that a differential calculation can be approximated. Accordingly, even when the first magnetic field detection element and the second magnetic field detection element are formed in the semiconductor substrate, the dimensions of the sensor chip is restricted from increasing. Since the number of the magnetic poles of the rotator is not increased in order to reduce the electric angle, the frequency of the rotation magnetic field is restricted from increasing.

DETAILED DESCRIPTION

First Embodiment

FIG. 1shows a plan view of a rotation angle detector according to a first embodiment.FIG. 2shows a cross sectional view of the detector taken along line II-II inFIG. 1.FIG. 3shows electric connection between a magnetic field detection element, an operation element and a calculator.FIG. 4shows a plan view of a relationship between a sensor chip and a magnet rotator. A rotating direction of a magnet rotator10is defined as a rotation direction. A direction along with a thickness of a semiconductor substrate31is defined as a thickness direction. A direction perpendicular to the thickness direction and the rotation direction and passing a center O of the magnet rotator is defined as a normal direction.

The detector100mainly includes the magnet rotator10, a sensor chip30, the operation element50and a calculator70. As shown inFIGS. 1 and 2, a winding20for generating a magnetic field surrounds the rotator10. The sensor chip30is arranged between the rotator10and the winding20. Thus, the magnetic field generated by the rotator10and the magnetic field generated by the winding20are applied to the chip30. Further, as shown inFIG. 3, the magnetic field detection element32of the sensor chip30is electrically coupled with the operation element50. The operation element50is electrically coupled with the calculator70. Thus, the electric signal detected by the magnetic field detection element32is input into the calculator70via the operation element50.

As described later, the sensor chip30detects a change of the magnetic field of the rotator10so that the chip30executes a measuring function for measuring the rotation angle of the rotator10. However, not only the magnetic flux of the magnet rotator10but also the magnetic flux of the winding20are applied to the chip30. The magnetic flux of the winding20provides a noise when the rotation angle of the rotator10is detected. The detector100according to the present embodiment removes the noise as an inductive noise in an output signal from the chip30without increasing the dimensions of the chip30. Here, the magnetic field corresponding to the magnetic flux generated by the winding20corresponds to the magnetic field for rotating the rotation shaft of the rotator10.

As shown inFIGS. 1 and 2, the rotator10has a ring shape. The rotation shaft11having a column shape is inserted into a hole, which is formed by an inner wall of the rotator10. Thus, the rotator10together with a rotor12made of permanent magnet is fixed to the shaft11, which is mounted in a vehicle. The center O of the rotator10is positioned at the shaft11. The rotator10includes a pair of magnetic poles composed of a S pole and a N pole. The rotor12includes two pairs of magnetic poles. The shaft11together with the rotator10is rotated by the repulsive force between the magnetic flux generated by the winding20and the magnetic flux generated by the rotor12. Here, the shaft11provides a rotation axis. The rotor12provides a permanent magnet.

When the rotator10rotates, the rotation magnetic field along with a rotation direction is generated by the rotation and the magnetic flux of the rotator10around the chip30. As described above, the shaft11(i.e., the rotator10) is rotated by the repulsive force between the magnetic flux generated by the winding20and the magnetic flux generated by the rotor12. Accordingly, the rotation direction of the magnetic field corresponding to the magnetic flux of the winding20is opposite to the rotation direction of the rotation magnetic field corresponding to the magnetic flux generated by the rotator10. Here, inFIGS. 1 and 2, although the rotator10is spaced apart from the shaft11, the rotator10is fixed to the shaft11with adhesive and the like. Further, inFIGS. 1 and 2, although the chip30is spaced apart from the shaft11, the chip30is fixed to a frame, which accommodates the shaft11and the winding20.

The winding20generates the magnetic field for rotating the shaft11. The winding20includes multiple coils as a winding element, which are fixed to the stator21. Current flows in each coil so that a magnetic field is generated. one magnetic pole of the rotor12corresponds to six coils20. Twenty-four coils20of the wining20are fixed to the stator21.

The sensor chip30includes a semiconductor substrate31and the magnetic field detection element32, which is formed in the substrate31. The magnetic field detection element32includes a first magnetic field detection element33and a second magnetic field detection element34, which are separated from each other by a phase difference of Δθ in the rotation direction of the rotator10. The first magnetic field detection element33includes a first normal component detection element35for detecting the magnetic field along with the normal line and a first rotation component detection element36for detecting the magnetic field along with the rotation direction. The second magnetic field detection element34includes a second normal component detection element37for detecting the magnetic field along with the normal line and a second rotation component detection element38for detecting the magnetic field along with the rotation direction.

As shown inFIG. 4, the first normal component detection element35and the first rotation component detection element36are spaced apart from each other by a predetermined distance in the normal direction. The second normal component detection element37and the second rotation component detection element38are spaced apart from each other by a predetermined distance in the normal direction. The first normal component detection element35and the second normal component detection element37are arranged to be spaced a part from the center O by an equal distance. The first rotation component detection element36and the second rotation component detection element38are arranged to be spaced a part from the center O by another equal distance.

The first and second normal component detection elements35,37and the first and second rotation component detection elements36,38as a component detection element are magneto-electric transducers for converting a magnetic signal to an electric signal. Each of the detection elements35-38is a magneto-resistance sensor having a fixed layer and a variable layer. The magnetization direction of the fixed layer is fixed. The magnetization direction of the variable layer is changed according to the magnetic field direction. An arrow inFIG. 4shows the magnetization direction of the fixed layer. The magnetization direction of the fixed layer in the first and second normal component detection elements35,37is arranged along with the normal direction. The magnetization direction of the fixed layer in the first and second rotation component detection elements36,38is arranged along with the rotation direction. More specifically, the magnetization direction of the fixed layer in the first and second rotation component detection elements36,38is arranged along with a tangential direction of the rotation direction. The magnetization direction of the fixed layer in the first and second normal component detection elements35,37directs to a direction moving away from the center O. The magnetization direction of the fixed layer in the first and second rotation component detection elements36,38directs to a counter-clockwise direction around the center O.

The above magneto-resistance sensor has a property such that a resistance of the sensor is changed according to an angle between the magnetization direction of the fixed layer and the magnetization direction of the variable layer. Accordingly, when the rotator10rotates by the electric angle, which is defined by dividing the rotation angle with the number of pairs of the magnetic poles, the sensor chip30outputs a signal corresponding to one period waveform. The rotator10has one pair of magnetic poles, and therefore, the sensor chip30outputs the signal corresponding to one period waveform when the rotator10rotates one revolution.

The operation element50is electrically coupled with the sensor chip30. The operation element50removes the magnetic flux (i.e., the inductive noise) of the winding20from each output signal S1, S2, C1, C2based on the output signals S1, S2of the first and second normal component detection elements35,37and the output signals C1, C2of the first and second rotation component detection elements36,38. On the other hand, the calculator70is electrically coupled with the operation element50. Based on the output signal from the operation element50, the calculator70performs a calculation function of the rotation angle θ of the rotator10. As shown inFIG. 3, the operation element50and the calculator70together with the magnetic field detection element32are formed in the semiconductor substrate31.

The characteristics of the rotation angle detector100will be explained as follows. The first magnetic field detection element33and the second magnetic field detection element34are spaced apart from each other by a distance corresponding to the phase difference of Δθ in the rotation direction of the rotator10. Specifically, as shown inFIG. 4, first and second normal component detection elements35,37are spaced apart from each other by a distance corresponding to the phase difference of Δθ. The first and second rotation component detection elements36,38are spaced apart from each other by a distance corresponding to the phase difference of Δθ. A value obtained by dividing the difference between the output signal S1and the output signal S2with the phase difference of Δθ is approximated to a value ΔθbR, which is obtained by differentiating a component bRof the magnetic field B along with the normal direction around the sensor chip30with respect to the rotation direction. A value obtained by dividing the difference between the output signal C1and the output signal C2with the phase difference of Δθ is approximated to a value Δθbθ, which is obtained by differentiating a component bθof the magnetic field B along with the rotation direction with respect to the rotation direction. Thus, the following equations are satisfied.

Further, based on the following calculations, the inductive noise is removed. When the operation element calculates the angle θ, the following calculations are performed.

The terms α, β in the above equations depend on a ratio γ between an amplitude of the normal line component of the magnetic flux (i.e., the inductive noise) generated by the winding20and the amplitude of the rotation component of the magnetic flux. The operation element50is electrically coupled with a circuit (not shown) for flowing current to the winding20. The operation element50includes a detector for detecting current flowing through the winding20. The operation element50further includes a memory for storing the information of a relation ship between the current flowing through the winding20and the ratio γ corresponding to the current. After the operation element50detects the current flowing through the winding20, the operation element50reads out the ratio γ corresponding to the current from the memory. Then, the operation element50calculates the equations F3 and F4.

Next, in order to explain the functions and the effects of the detector100according to the present embodiment, the calculation method of the magnetic field generated around the sensor chip30and the calculation method of removing the magnetic flux (i.e., the inductive noise) of the winding20in the magnetic field will be explained.

As described above, the rotation direction of the magnetic field corresponding to the magnetic flux of the winding20is opposite to the rotation direction of the rotation magnetic field corresponding to the magnetic flux of the rotator10. Thus, the magnetic field generated by the winding20is defined as BN, and the amplitude of the component of the magnetic field BNalong with the rotation direction is defined as BNθ. The amplitude of the component of the magnetic field BNalong with the normal direction is defined as BNR. The number of the pairs of the magnetic poles in the rotor12is defined as NN. The rotation magnetic field generated by the rotator10is defined as BS. The amplitude of the component of the magnetic field BSalong with the rotation direction is defined as BSθ. The amplitude of the component of the magnetic field BSalong with the normal direction is defined as BSR. The number of the pairs of the magnetic poles in the rotator10is defined as NS. An angle in the rotation direction is defined as θ. The following equations are satisfied.
BN=(BNθcos(−NNθ),BNRsin(−NNθ)  (F5)
BS=(BSθcos(NSθ),BSRsin(NSθ))  (F6)

Here, as described above, since the rotor12includes two pairs of the magnetic poles, the number of the pairs of the magnetic poles in the rotor12NNis two (i.e., NN=2). Since the rotator10includes one pair of the magnetic poles, the number of the pairs of the magnetic poles in the rotator10NSis one (i.e., NS=1). Based on the equations F5 and F6, the magnetic field B generated around the sensor chip30is calculated by the following equation F7.
B=BN+BS=(bθ,bR)=(BNθcos(−NNθ)+BSθcos(NSθ),BNRsin(−NNθ)+BSRsin(NSθ)  (F7)

Thus, the fine change amount of the magnetic field B in the rotation direction, i.e., the differential value of the magnetic field B in the rotation direction, is obtained by the following equation F8.

Thus, the component bθof the magnetic field B along with the rotation direction and the value ΔθbRdepend on the value of cos θ. The component bRof the magnetic field B along with the normal direction and the value Δθbθdepend on the value of sin θ. Accordingly, in order to remove the inductive noise, the following equations are calculated with using the terms α, β.
bθ+αΔθbR=BNθcos(−NNθ)+BSθcos(NSθ)−αBNRNNcos(−NNθ)+αBSRNScos(NSθ)  (F9)
bR−βΔθbθ=BNRsin(−NNθ)+BSRsin(NSθ)−βBNθNNsin(−NNθ)+βBSθNSsin(NSθ)  (F10)

A term including the amplitude BNθof the component of the magnetic field BNalong with the rotation direction and another term including the amplitude BNRof the component of the magnetic field BNalong with the normal direction in the equations F9 and F10 provide the inductive noise. In order to remove the inductive noise, the terms α, β should be satisfied with the following equations.

When the terms α, β obtained from the equations F11 and F12 are substituted into the equations F9 and F10, the following equations are obtained.

Thus, when the component bθ, the component bR, the value Δθbθ, the value ΔθbRand the terms α, β are given, the terms of cos(NSθ) and sin (N5θ), in each detection signal, from which the inductive noise is cancelled, are obtained.

Based on the above, the functions and the effects of the detector100will be explained. In the detector100, the equations F1 and F2 are satisfied.

The output signals S1, S2of the first and second normal component detection elements35,37are in proportion to the component bRof the magnetic field B along with the normal direction. The output signals C1, C2of the first and second rotation component detection elements36,38are in proportion to the component bθof the magnetic field B along with the rotation direction. Thus, the following equations are satisfied.
S1∝bR(F15)
C1∝bθ(F16)

Thus, the following equations are satisfied.

Accordingly, the right side of each of the equations F17 and F18, i.e., the equations F3 and F4, are calculated by the operation element50, so that the terms of cos(NSθ) and sin (NSθ) shown in the equations F13 and F14, from which the inductive noise is cancelled, are obtained. After the signals corresponding to the terms of cos(NSθ) and sin (NSθ) are obtained, the calculator70performs calculation with using an arctangent function or a tracking calculation, so that the angle θ is obtained. Here, the tracking calculation is as follows. An angle is defined as φ, and a difference between a value obtained by multiplying the obtained term of sin (NSθ) with the term of cos φ and a value obtained by multiplying the obtained term of cos(NSθ) with the term of sin φ is calculated so that the term of sin(NSθ−φ) is calculated. Then, the angle φ is varied until the term of sin(NSθ−φ) is equal to or smaller than a predetermined fine amount, i.e., an error range. Thus, this loop calculation is executed so that the angle φ approaches the angle θ. Finally, the angle θ is obtained.

The terms α, β are expressed by the ratio γ between the amplitude BNθof the component of the magnetic field BNand the amplitude BNRof the component of the magnetic field BNand the number NNof the pairs of the magnetic poles in the rotor12, as described in the equations F11 and F12. In the present embodiment, the number NNof the pairs of the magnetic poles is two, and the ratio γ is detected by the operation element50. Thus, each parameter in the equations F11 and F12 is detected or obtained, so that the equations F11 and F12 can be calculated.

As described above, the phase difference Δθ does not depend on the electric angle. The electric angle depends on the number of magnetic poles in the rotator10. The phase difference Δθ can be a value such that a differential calculation can be approximated. Accordingly, even when the first magnetic field detection element33and the second magnetic field detection element34are formed in the semiconductor substrate31, the dimensions of the sensor chip30is restricted from increasing. Since the number of the magnetic poles of the rotator10is not increased in order to reduce the electric angle, the frequency of the rotation magnetic field is restricted from increasing.

The operation element50and the calculator70together with the magnetic field detection element32are formed in the semiconductor substrate31. In this case, the dimensions of the detector100are restricted from increasing, compared with a case where at least one of the operation element50and the calculator70is formed in another semiconductor substrate, which is different from the semiconductor substrate31, in which the magnetic field detection element32is formed.

In the present embodiment, the rotator10includes one pair of the magnetic poles. In this case, the rotation frequency of the rotation magnetic field is restricted from increasing, so that a difficulty that the processing speed of the operation element50is not sufficient to process the input signal is improved.

In the present embodiment, the shaft11and the winding20are accommodated in the frame (not shown), and the sensor chip30is fixed to the frame. In this case, the structure of the detector is simplified, compared with a case where the sensor chip30is fixed to a member different from the frame.

In the present embodiment, each component detection element35-38is the magneto-resistance effect element having the fixed layer and the variable layer. The magnetization direction of the fixed layer is fixed to a certain direction. The magnetization direction of the variable layer is varied with the direction of the magnetic field. Alternatively, each component detection element35-38may be a magneto-electric transducer for converting a magnetic signal to an electric signal, and the component detection element35-38is not limited to the magneto-resistance effect element. The magneto-electric transducer may be a magneto-resistance sensor, of which the change of the resistance caused by the magnetic flux depends on the shape of the sensor. Alternatively, the magneto-electric transducer may be a vertical Hall element, in which the current flows in the thickness direction of the semiconductor substrate. The magneto-resistance sensor is a tunnel type magneto-resistance sensor or a giant magneto-resistance effect element.

In the present embodiment, the rotator10includes only one pair of the magnetic poles composed of the S pole and the N pole. Alternatively, the rotator10may include two or more pairs of the magnetic poles. For example, the rotator10may include three pairs of the magnetic poles.

In the present embodiment, the rotor12includes two pairs of the magnetic poles composed of the S pole and the N pole. Alternatively, the rotor12may include three or more pairs of the magnetic poles. For example, the rotor12may include four pairs of the magnetic poles. In this case, forty-eight winding elements20are fixed to the stator21.

In the present embodiment, as shown inFIG. 3, the operation element50and the calculator70together with the magnetic field detection element32are formed in the semiconductor substrate31. Alternatively, for example, as shown inFIG. 5, both of the operation element50and the calculator70may not be formed in the semiconductor substrate31. Alternatively, only the operation element50together with the magnetic field detection element32may be formed in the semiconductor substrate31. Alternatively, the calculator70together with the magnetic field detection element32may be formed in the semiconductor substrate31. In these cases, the dimensions of the detector100increases, compared with a case where the operation element50and the calculator70together with the magnetic field detection element32are formed in the semiconductor substrate31.FIGS. 5 and 6are block diagrams showing electric connection between the operation element50, the calculator70and the magnetic field detection element32.

In the present embodiment, the first normal component detection element35and the first rotation component detection element36are spaced apart from each other by a predetermined distance in the normal direction. The second normal component detection element37and the second rotation component detection element38are spaced apart from each other by a predetermined distance in the normal direction. Alternatively, the first normal component detection element35and the second normal component detection element37may be arranged to be spaced a part from the center O by an equal distance. The first rotation component detection element36and the second rotation component detection element38may be arranged to be spaced a part from the center O by another equal distance. For example, the first and second normal component detection elements35,37and the first and second rotation component detection elements36,38may be arranged to be spaced a part from the center O by an equal distance.

In the present embodiment, the magnetization direction of the fixed layer in each of the first and second normal component detection elements35,37directs to a direction moving away from the center O. The magnetization direction of the fixed layer in the first and second rotation component detection elements36,38directs to a counter-clockwise direction around the center O. Alternatively, the magnetization direction of the fixed layer in each of the first and second normal component detection elements35,37may direct to a direct approaching the center O. The magnetization direction of the fixed layer in the first and second rotation component detection elements36,38may direct to a clockwise direction around the center O.

Alternatively, the magnetization direction of the fixed layer in the first normal component detection element35may direct to a direction moving away from the center O, and the magnetization direction of the fixed layer in the second normal component detection element37may direct to a direction approaching the center O. The magnetization direction of the fixed layer in the first rotation component detection element36may direct to a counter-clockwise direction around the center O, and the magnetization direction of the fixed layer in the second rotation component detection element38may direct to a clockwise direction around the center O. In this case, a sum of the output signal S1of the first normal component detection element35and the output signal S2of the second normal component detection element37corresponds to the difference between the output signal S1of the first normal component detection element35and the output signal S2of the second normal component detection element37in the above equations. Thus, the term of S1+S2corresponds to the term S1−S2in the above equations. A sum of the output signal C1of the first rotation component detection element36and the output signal C2of the second rotation component detection element38corresponds to the difference between the output signal C1of the first rotation component detection element36and the output signal C2of the second rotation component detection element38in the above equations. Thus, the term of C1+C2corresponds to the term C1−C2in the above equations.

The above disclosure has the following aspects.

According to an aspect of the present disclosure, a rotation angle detector includes: a magnet rotator including at least one pair of magnetic poles, wherein the magnet rotator together with a magnet is mounted on a rotation shaft; a sensor chip including a semiconductor substrate and a magnetic field detection element in the semiconductor substrate, wherein the magnetic field detection element detects a magnetic field; and an operation element. The rotation shaft and the sensor chip are arranged in a magnetic field, which provides to rotate the rotation shaft. The rotation angle detector detects a rotation angle of the magnet rotator based on an electric signal output from the magnetic field detection element. The magnetic field detection element includes a first magnetic field detection element and a second magnetic field detection element, which are spaced apart from each other by a distance corresponding to a predetermined phase difference. The first magnetic field detection element includes a first normal component detection element for detecting a magnetic field along with a normal direction and a first rotation component detection element for detecting a magnetic field along with a rotation direction. The normal direction passes a center of the rotator and is perpendicular to the rotation direction. The second magnetic field detection element includes a second normal component detection element for detecting the magnetic field along with the normal direction and a second rotation component detection element for detecting the magnetic field along with the rotation direction. The phase difference satisfies a condition that a value obtained by dividing a difference between an output signal of the first normal component detection element and an output signal of the second normal component detection element with the phase difference is approximated to a value obtained by differentiating a component of the magnetic field along with the normal direction around the sensor chip with respect to the rotation direction, and a value obtained by dividing a difference between an output signal of the first rotation component detection element and an output signal of the second rotation component detection element with the phase difference is approximated to a value obtained by differentiating a component of the magnetic field along with the rotation direction with respect to the rotation direction. The phase difference is defined as Δθ, the output signal of the first normal component detection element is defined as S1, the output signal of the second normal component detection element is defined as S2, the output signal of the first rotation component detection element is defined as C1, the output signal of the second rotation component detection element is defined as C2, a first term depending on the magnetic field for rotating the rotation shaft is defined as α, and a second term depending on the magnetic field for rotating the rotation shaft is defined as β. The operation element calculates a value of:

and a value of:

The phase difference Δθ does not depend on the electric angle. The electric angle depends on the number of magnetic poles in the rotator. The phase difference Δθ can be a value such that a differential calculation can be approximated. Accordingly, even when the first magnetic field detection element and the second magnetic field detection element are formed in the semiconductor substrate, the dimensions of the sensor chip is restricted from increasing. Since the number of the magnetic poles of the rotator is not increased in order to reduce the electric angle, the frequency of the rotation magnetic field is restricted from increasing.

Alternatively, the operation element may be disposed in the semiconductor substrate. In this case, the dimensions of the detector are reduced.

Alternatively, the rotation angle detector may further include: a calculator for calculating the rotation angle of the magnet rotator based on the values output from the operation element. After the operation element calculates the value of cos(NSθ) and the value of sin(NSθ), the signals corresponding to the values are input into the calculator so that the calculator calculates the rotation angle of the magnet rotator.

Alternatively, the calculator may be disposed in the semiconductor substrate. In this case, the dimensions of the detector are reduced.

Alternatively, the magnet rotator may include only one pair of magnetic poles. In this case, the rotation frequency of the rotation magnetic field is restricted from increasing. Thus, a difficulty that the processing speed of the operation element50is not sufficient to process the input signal is improved.

Alternatively, each of the first normal component detection element, the second normal component detection element, the first rotation component detection element and the second rotation component detection element may be a magneto-resistance sensor. The magneto-resistance sensor includes a fixed layer and a variable layer. The fixed layer has a fixed magnetization direction fixed to a predetermined direction. The variable layer has a variable magnetization direction varied with a direction of the magnetic field. Further, the magneto-resistance sensor may be a tunnel magneto-resistance sensor. Furthermore, the fixed magnetization direction of the fixed layer in each of the first and second normal component detection elements may direct to a direction moving away from the center of the magnet rotator, and the fixed magnetization direction of the fixed layer in each of the first and second rotation component detection elements may direct to one direction around the center of the magnet rotator.

Alternatively, the fixed magnetization direction of the fixed layer in each of the first and second normal component detection elements may direct to a direction approaching the center of the magnet rotator, and the fixed magnetization direction of the fixed layer in each of the first and second rotation component detection elements may direct to one direction around the center of the magnet rotator.

Alternatively, the first normal component detection element and the first rotation component detection element may be arranged to be spaced apart from each other by a predetermined distance in the normal direction, and the second normal component detection element and the second rotation component detection element may be arranged to be spaced apart from each other by the predetermined distance in the normal direction.

Alternatively, the first and second normal component detection elements and the first and second rotation component detection elements may be arranged to be spaced a part from the center of the magnet rotator by an equal distance.

Alternatively, the rotation shaft may be a shaft of a vehicle.

Alternatively, the rotation shaft may be accommodated in a frame, and the sensor chip may be fixed to the frame.

Alternatively, the rotation angle detector may further include: a winding for generating a magnetic field, which provides to rotate the rotation shaft. The winding surrounds the rotator. The sensor chip is disposed between the winding and the rotator. The magnet rotator includes only one pair of magnetic poles. The magnet includes two pairs of magnetic poles.

Alternatively, the number of pairs of the magnet is defined as NN. An amplitude of a component of the magnetic field generated by the winding along with the rotation direction is defined as BNθ, and an amplitude of a component of the magnetic field generated by the winding along with the normal direction is defined as BNR. The first term of a satisfies an equation of:

The second term of β satisfies an equation of:

Alternatively, the rotation angle detector may further include: a calculator for calculating the rotation angle of the magnet rotator based on the values output from the operation element. The operation element and the calculator are disposed in the semiconductor substrate. Each of the first normal component detection element, the second normal component detection element, the first rotation component detection element and the second rotation component detection element is a tunnel magneto-resistance sensor. The tunnel magneto-resistance sensor includes a fixed layer and a variable layer. The fixed layer has a fixed magnetization direction fixed to a predetermined direction. The variable layer has a variable magnetization direction varied with a direction of the magnetic field. The fixed magnetization direction of the fixed layer in each of the first and second normal component detection elements directs to a direction moving away from the center of the magnet rotator. The fixed magnetization direction of the fixed layer in each of the first and second rotation component detection elements directs to one direction around the center of the magnet rotator.

Alternatively, the first and second normal component detection elements may be arranged to be spaced a part from the center of the magnet rotator by an equal distance. The first and second rotation component detection elements may be arranged to be spaced a part from the center of the magnet rotator by another equal distance.

Alternatively, the first normal component detection element and the first rotation component detection element may be disposed on a normal line of the magnet rotator, and the second normal component detection element and the second rotation component detection element may be disposed on another normal line of the magnet rotator.