JP4532417B2 - Rotation sensor - Google Patents

Description

  The present invention relates to a rotation sensor that is attached to a rotating body and used to detect the rotation angle of the rotating body.

  For example, a so-called rotation sensor is used when detecting a rotation angle of a handle that is attached to a rotating shaft such as a steering shaft of an automobile and integrated with the shaft (see, for example, Patent Document 1 and Patent Document 2).

  The rotation sensor described in Patent Document 1 is a rotation sensor that measures the rotation angle of a main rotating body that rotates in conjunction with two sub-rotating bodies. Each rotating body also has a gear. The number of teeth of the gear of the main rotating body and the number of teeth of each gear of the sub rotating body are different from each other, and the gear of the main rotating body and the gear of one sub rotating body are meshed with each other, The gear of the other auxiliary rotating body is engaged. Each of the sub-rotators is provided with a magnet, and two AMR sensors for detecting the magnetic flux of each magnet are provided in a fixed portion of the rotation sensor.

  Then, the absolute rotation angle of the main rotor is calculated using the phase difference between detection output values having different phases obtained from the two AMR sensors.

On the other hand, the rotation sensor described in Patent Document 2 includes a rotor having a sensing unit that is attached to a rotating shaft and has a width that varies along the circumferential direction, and an axis of the shaft that is attached to a fixed member and that is attached to the sensing unit. And a fixed core disposed to face each other with an interval in the direction. The fixed core includes a first excitation coil that forms a magnetic circuit between the rotor and an AC excitation current, and a first core that is formed of an insulating magnetic material and holds the first excitation coil. have. The rotation sensor further includes a conductor layer whose width changes along the rotation direction and a Geneva gear that is sent at a predetermined rotation angle for each rotation of the rotor, on one fixing member that sandwiches the rotation surface of the rotor. Yes. In addition, it has a second excitation coil and a second core that holds this excitation coil, and detects the number of rotations of the rotor by changing the output stepwise according to the amount of Geneva gear feed (rotation number of the rotor) A detection coil is provided.
JP-T-2001-505667 (page 6-10, FIG. 1) JP 2001-337049 A (page 2-4, FIG. 1)

  As described above, in the rotation sensor described in Patent Document 1, the gears of the sub rotator are engaged with the gears of the main rotator, and the rotation of the main rotator, that is, the rotator to be measured, is detected from the respective rotation detection values of the sub rotators. The absolute rotation angle is calculated. Therefore, the detected angle error due to the backlash between the gears of one of the sub-rotators and the main rotor and the detected angle error due to the backlash between the gears of the other sub-rotor and the main rotor are the rotation of the main rotor. It will be superimposed as an angle error of the angle. Therefore, the rotation sensor described in Patent Document 1 is not suitable for accurately detecting the rotation angle of the rotating body to be measured.

  On the other hand, the rotation sensor described in Patent Document 2 measures the rotation angle of the main rotating body from a combination of a ring-shaped sensing unit made of a conductive member and a coil core that generates a magnetic flux so as to intersect the sensing unit. It has become. Therefore, compared with the rotation sensor described in Patent Document 1 described above, the absolute rotation angle of the rotating body to be measured can be detected with high accuracy. However, since the rotation speed of the main rotor is output step by step by the Geneva gear, the conductive layer, and the detection coil, if the level difference of the output stage corresponding to each rotation speed of the main rotor is small In some cases, it was difficult to detect the rotational speed of the main rotor.

  An object of the present invention is to provide a rotation sensor with high detection accuracy that improves the resolution of the absolute rotation angle detection of a rotating body to be measured and has improved noise resistance.

In order to solve the above-mentioned problem, the rotation sensor according to the present invention is:
A main rotating body that moves integrally with the rotating body to be measured, a sub-rotating body that rotates at a rotational speed different from the rotational speed of the main rotating body corresponding to the rotation of the main rotating body, and the rotation of the main rotating body. A first detecting means for detecting and a second detecting means for detecting the rotation of the auxiliary rotating body, and measuring from the detection signal of the first detecting means and the detection signal of the second detecting means; In the rotation sensor that detects the absolute rotation angle of the power rotor,
The main rotating body and the sub-rotating body are transmitted with rotation via gears,
Each detection signal obtained from the first detection means and the second detection means is periodically output corresponding to the rotation of each rotating body, and the period of the detection signal of the first detection means is Tc, When the period of the detection signal of the second detection means is Tm,
(Tm-Tc × i) × n = Tm (i and n are positive integers) meet the relationship,
The first detection means includes a conductive sensing portion that rotates integrally with the main rotating body and changes in width along a circumferential direction; and the electromagnetic wave induction cooperates with the sensing portion to detect the main rotating body. An excitation coil for detecting a rotation angle, and the second detection means includes a magnet provided in the sub-rotator, and a magnetic flux detection element that detects a change in magnetic flux of the magnet according to the rotation of the sub-rotator. Prepared ,
The excitation coil is wound in a track shape so that a direction intersecting the sensing unit is a longitudinal direction .

  By detecting the rotation angle of the main rotating body and the rotating angle of the sub-rotating body rotating at a different rotational speed under the condition that the detection cycle of each detecting means satisfies the above-described relationship, The resolution of detecting the rotation angle of the power rotating body is improved and the noise resistance is improved.

Further, by using such a detection method, the detection accuracy is significantly improved as compared with a rotation sensor that uses two gears for the auxiliary rotating body. In addition, the detection accuracy and vibration resistance can be improved and the assembly of the rotation sensor itself can be improved as compared with a rotation sensor that detects the number of rotations of the main rotating body with a Geneva gear.

  More specifically, the disadvantage of the conventional rotation sensor equipped with the Geneva gear, that is, the main rotating body is output step by step by the Geneva gear, the conductive layer, and the detection coil. This solves the drawback that it is difficult to detect the rotational speed of the main rotor if the output stage corresponding to each rotational speed is small.

  In addition, the problem of reduced vibration resistance of the rotation sensor itself due to the possibility that the Geneva gear may rotate due to vibration or the like, which is a further disadvantage of the rotation sensor according to the prior art, is solved.

  Furthermore, another problem with the rotation sensor according to the prior art is assembling and cost problems, that is, a Geneva gear is provided with a rotor whose width varies depending on the direction of rotation, and a coil / core pair is provided at a position sandwiching the rotor. In this case, it is possible to solve the disadvantage that the assembly of the rotation sensor itself is not good because the positioning of the parts is not easy and the cost of the parts and assembly man-hours is increased.

The rotation sensor according to claim 2 is the rotation sensor according to claim 1 ,
The exciting coil is held by a core body made of a mixed soft magnetic material obtained by mixing Mn—Zn soft magnetic material ferrite with polyphenylene sulfide.

  By using such a so-called soft ferrite as the material of the core body, molding is easy, so that the degree of freedom in setting the shape of the core can be improved.

The rotation sensor according to claim 3 is the rotation sensor according to claim 1 ,
The exciting coil is held by a core body made of a mixed soft magnetic material in which Fe-Si-Al based sendust is mixed with epoxy resin.

  By using such sendust for the core body, the magnetic permeability can be increased and the detection characteristics can be improved. Further, the temperature characteristic of the magnetic permeability can be improved, and the rotation sensor can be used in a wide temperature range of usage environment without being affected by the ambient temperature.

  According to the present invention, it is possible to provide a high-resolution rotation sensor with high detection accuracy that improves the resolution of absolute rotation angle detection of a rotating body to be measured and improves noise resistance, vibration resistance, and assembly. .

  Hereinafter, a rotation sensor according to an embodiment of the present invention will be described with reference to the drawings. In the present embodiment, a case will be described in which the rotation sensor is attached to the steering shaft and the rotation sensor is used to detect the rotation angle of the steering wheel with respect to the automobile steering apparatus.

  As shown in FIGS. 1 and 2, a rotation sensor 1 according to an embodiment of the present invention is fitted into a steering shaft S (hereinafter simply referred to as “shaft S”) that is a rotating body to be measured and has an outer peripheral portion. The first gear 11, the second gear 12 that meshes with the first gear 11 of the rotor 10, the lower case 21 that rotatably supports the rotor 10 and the second gear 12, and the lower case 21. And an upper case 22 that forms a box-like case 20.

  The rotor 10 is made of a synthetic resin excellent in strength and moldability. A stay 15a extends from a predetermined position around the rotor 10, and a plate-shaped sensing portion 15 having a plate thickness of, for example, about 0.5 mm is formed by the stay 15a. Is provided around the rotor 10 in a ring shape. The sensing unit 15 is made of a conductive member such as brass, silver, aluminum, or copper. In the present embodiment, the width of the sensing unit 15 regularly changes from 90 mm in the circumferential direction, for example, from 2 mm to 5 mm. ing. In this manner, by changing the width of the sensing unit 15 by 90 degrees in the circumferential direction, the change in the detection signal from the coil core 50 with respect to the actual rotation angle of the rotor 10 is greatly increased.

  Further, the upper case 22 and the lower case 21 are made of a shielding material made of a metal or an insulating magnetic material that has excellent strength and has an AC magnetic field shielding property, and the upper case 22 and the lower case 21 cooperate to form a box. The body is configured to house the rotor 10, the sensing unit 15, and the second gear 12. Further, the lower case 21 is provided with a connector 25 for supplying electric power to the rotation sensor 1 and transmitting a detection signal of the rotation sensor 1 to the outside.

  Further, as shown in FIGS. 1 and 3, two sets of coil cores 50 are attached to the upper case 22 and the lower case 21 so as to face each other with a predetermined distance from the sensing surface of the sensing unit 15 of the rotor 10. It has been. The sensing unit 15 and the coil core 50 cooperate to constitute a first detection unit.

  As shown in FIG. 1, the two sets of coil cores 50 are attached at a predetermined angle with respect to the circumferential direction of the sensing unit 15 so that output values of respective phase shift amounts described later are shifted by 22.5 degrees. As shown in FIG. 1, each outer peripheral edge has a track shape of a so-called athletics in a plan view shown in FIG. In the present embodiment, since one cycle of the sensing unit 15 is 90 degrees as will be described later, the two sets of coil cores 50 are arranged so as to deviate from this 1/4 cycle, that is, 22.5 degrees.

  The coil core 50 includes a core main body 51 made of an insulating soft magnetic material such as a plastic magnet (for example, a mixed soft magnetic material in which Mn-Zn soft magnetic ferrite is mixed in PPS (polyphenylene sulfide)), and the core main body 51. An exciting coil 52 wound around a track-like inner circumferential groove formed along the outer peripheral portion and accommodated in the core body 51 is provided. In this case, the core body 51 is formed by injection molding, and the magnetic powder filling rate is about 50% by weight. By forming the core body 51 by injection molding a soft magnetic material containing soft ferrite at such a filling rate, molding becomes easy and the degree of freedom in setting the shape of the core can be improved.

  Instead of holding the exciting coil with the core body 51 using so-called soft ferrite, the core body is held by the core body made of a mixed soft magnetic material in which Fe-Si-Al based sendust is mixed with epoxy resin. May be. In this case, the core body is formed by compacting, and the magnetic powder filling rate is 90% by weight or more. By forming the core body by compacting a soft magnetic material containing sendust at such a filling rate, the magnetic permeability can be increased and the detection characteristics can be improved. Further, the temperature characteristics of the magnetic permeability can be improved, and the rotation sensor can be used in a wide temperature range environment.

  Further, the exciting coils 52 facing each other are connected in series, and are electrically connected within the case 20 to a printed circuit board of a rotation angle detection unit (not shown). Then, an alternating excitation magnetic field is passed through the opposing exciting coil 52 to form an alternating magnetic field around the core body 51. The alternating magnetic field intersects the sensing surface of the sensing unit 15 between the paired core bodies 51. Yes.

  An eddy current is generated in the sensing unit 15 of the conductive member due to the alternating magnetic field generated from the coil core 50, and the generated eddy current corresponds to the change in the width of the sensing unit 15 according to the rotation of the rotor 10. The coil core 50 detects the rotation angle of the rotor 10 at a period of 90 degrees by detecting impedance fluctuation based on the change.

  The reason why the coil cores 50 are opposed to each other with the sensing unit 15 interposed therebetween is that when the position of the rotor 10 fluctuates in the axial direction of the shaft S due to vibration or the like, the output from each coil core 50 is also accompanying this. Although the output from one coil core 50 decreases, the output from the other coil core 50 decreases, so if the output from the two opposing coil cores 50 is detected, the output fluctuation of each coil core 50 is offset. Because it can.

  A signal processing method for detecting the rotation angle of the rotor 10 is as follows. In addition, illustration is abbreviate | omitted about each circuit structure. First, the oscillation circuit outputs an oscillation signal having a specific frequency to the phase shift unit including the resistor, the excitation coil 52, and the capacitor via the frequency divider circuit. At this time, the impedance of each exciting coil 52 changes according to the magnitude of eddy current generation in the sensing unit 15, and the phase of the voltage signal at each end of each capacitor also changes due to this impedance change. The voltage signals at both ends of the capacitor are output to the phase shift amount detection unit, and the detection unit detects the phase shift amount of the voltage signal at both ends of each capacitor. Then, the converter converts the detected phase shift amount into a corresponding voltage value.

  In the present embodiment, the coil core 50 is made to correspond to the circumferential direction of the sensing unit 15 so that the phase of the phase shift amount output signal obtained by the cooperation of each coil core 50 and the sensing unit 15 is shifted by 22.5 degrees. The phase shift amount output value SA of one coil core 50 and the phase shift amount output value of the other coil core 50 are obtained by the signal processing as described above, as shown in FIG. As in SB, an output value of a phase shift amount having a period of 90 degrees with a phase shift of 22.5 degrees is obtained.

  A method of detecting the rotation angle of the rotor 10 with a period of 90 degrees from the output value of the phase shift amount thus obtained is as follows.

  As shown in FIG. 5A, the output values (SA, SB) of the rotation angle of the rotor 10 obtained from each coil core 50 and the output values (RSA, RSB) obtained by inverting these are superimposed. And from the magnitude relation of each phase shift amount detection value, the rotation angle of the rotor 10 is 0 degrees to 22.5 degrees, 22.5 degrees to 45 degrees, 45 degrees to 67.5 degrees, 67.5 degrees to 90 degrees, It is judged in which range. And while using the linear part of these four phase shift amount detection values, this linear part is jointed (joined). Next, based on the determination result of which of the four angle ranges described above, the rotation angle of the rotor 10 is determined from the output signal of the sawtooth waveform that changes at a cycle of every 90 degrees shown in FIG. It is obtained in a cycle of 90 degrees.

  On the other hand, as shown in FIGS. 1 and 2, the lower case 21 includes a magnet 61 that rotates integrally with the second gear 12 at the center portion of the second gear 12, and the lower case 21 that faces the magnet 61. An MR element (magnetic flux detecting element) 62 for detecting the magnetic flux of the magnet 61 is provided in the portion. The magnet 61 and the MR element 62 cooperate to constitute a second detection means.

  The MR element 62 has a detection output obtained as a sin curve-shaped detection output and a cos curve-shaped detection output, and these detection outputs are converted into a tan function detection output as shown in FIG. It is output as an output signal of a sawtooth waveform that changes at a period of every degree. This signal processing method is known as described in, for example, Japanese Patent Application Laid-Open No. 2004-53444. In this embodiment, the period of the detection output of the MR element 62 is 191.25 degrees because the number of teeth of the first gear 11 provided in the rotor 10 is 80 and the number of teeth of the second gear 12 is Since the number is 85, the period of the detection signal of the MR element 62 detected according to the rotation of the second gear 12 is 180 degrees × 85/80 = 191.25 degrees because of the relationship between the number of teeth. Because it is.

  As described above, in the rotation sensor 1 according to the present embodiment, the first detection signal obtained from the first detection means configured by the coil core 50 and the sensing unit 15 cooperating with each other corresponds to the rotation of the rotor 10. Corresponding to the rotation of the second gear 12 and the second detection signal obtained from the second detection means which is output at a period of degrees and is obtained by the cooperation of the magnet 61 and the MR element 62 is 191.25 degrees. The rotation sensor 1 according to the present invention is required to satisfy the following relationships between the periods of these detection signals.

First, as a first relationship to be satisfied by the period of each detection signal, the period of the detection signal of the coil core (first detection means) 50 is Tc, and the period of the detection signal of the MR element (second detection means) 62 is Tm. If
The relationship (Tm−Tc × i) × n = Tm (i and n are positive integers) is satisfied. By satisfying such a relationship, the resolution of detecting the absolute rotation angle of the rotor 10, that is, the shaft S to be measured is improved and the noise resistance is improved. In the case of the rotation sensor 1 according to the present embodiment, when Tc = 90 degrees and Tm = 191.25 degrees, i = 2 and n = 17,
(191.25−90 × 2) × 17 = 191.25, which satisfies the above relational expression.

  Further, in the multiples obtained by multiplying the cycle Tm and the cycle Tc by different positive integers, assuming that the common minimum is Tx, the relationship of Tx ≧ 1440 degrees is satisfied. By satisfying such a relationship, a combination of two output values obtained by the coil core 50 constituting the first detection means and the MR element 62 constituting the second detection means is within a range of ± 720 degrees of the measurement range. A plurality of solutions of the absolute rotation angle of the corresponding rotor 10, that is, the shaft S is avoided, and the absolute value of the rotor 10, that is, the shaft S is surely and uniquely determined from the output value of the coil core 50 and the output value of the MR element 62. The rotation angle can be obtained.

  In the case of the rotation sensor 1 according to this embodiment, Tc = 90 degrees, Tm = 191.25 degrees, and Tx = 90 × 17 = 191.25 × 8 = 1530 degrees, which satisfies the above relational expression. Yes.

  Further, the relationship of Tx = Tc × n is satisfied. As a result, the interval between the calibration curves adjacent to the calibration curve defined by the combination of the two output values of the first detection means and the second detection means is widened. As a result, the range of combinations of Tm and Tc is made narrower, and the combination of the two output values of the first detection means and the second detection means corresponding to the absolute angle is reduced and effective in reducing the combination where the detection performance is not improved. It is possible to narrow down the range of combinations.

  In the case of the rotation sensor 1 according to the present embodiment, since Tc = 90 degrees and Tx = 1530 degrees, 1530 = 90 × 17, and thus n = 17, which satisfies the above relational expression.

  Since the rotor 10 that is the main rotor, that is, the shaft S, makes one round at 360 degrees, Tc is inevitably 360 degrees or less, and satisfies the relationship of Tc = 360 degrees / k (k is a positive integer). become.

  In the case of the present embodiment, among the periods satisfying the relational expression as described above, the period Tc of the detection signal of the rotor 10 that is the main rotating body is 90 degrees as described above, and the second gear that is the auxiliary rotating body. The period Tm of the detection signal is 191.25 degrees. According to this combination of periods, the combination of the two output values of the first detection means and the second detection means is optimally associated with the absolute rotation angle of the rotor 10 as the main rotor.

  However, the period of the rotation detection signal of the rotor 10 obtained from the coil core 50 as the first detection means and the period of the rotation detection signal of the second gear 12 obtained from the MR element 62 as the second detection means. The relationship is not limited to 90 degrees and 191.25 degrees as in this embodiment, and other periods may be used as long as each period satisfies the above-described relational expression.

  By satisfying these relationships, as described later, the rotor 10, that is, the shaft, is obtained from the combination of the first detection signal obtained from the coil core 50 and the sensing unit 15 and the second detection signal obtained from the magnet 61 and the MR element 62. A calibration curve for obtaining the absolute rotation angle of S is evenly distributed over a wide range of absolute rotation angles as shown in FIG. That is, the region where the calibration curve is distributed is made as wide as possible, and the calibration curve is distributed at equal intervals in this widened region. This makes it possible to clarify the correspondence relationship between the absolute rotation angle of the rotor 10, that is, the shaft S, corresponding to the combination of the rotation detection signal from the coil core 50 and the rotation detection signal from the MR element 62.

  For example, as another example, even if the period of the rotation detection signal from the coil core 50 is 120 degrees and the period of the rotation detection signal from the MR element 62 is 130 degrees, the first detection signal and the second detection signal The period with the signal can satisfy the relational expression described above, and the absolute rotation angle of the rotor 10, that is, the shaft S can be detected with high accuracy. That is, even in this case, the calibration curves shown in FIG. 6 are defined as being dispersed throughout the range of the absolute rotation angle of the rotor 10 to be measured, that is, the shaft S.

  Then, the measuring method of the absolute rotation angle of the shaft S using the rotation sensor 1 mentioned above is demonstrated. In the rotation sensor 1 according to the present embodiment, since the cycle of the detection signal of the coil core 50 and the cycle of the detection signal of the second gear 12 satisfy a special relationship as described above, the output of the coil core 50 corresponding to the rotation of the rotor 10. The correspondence relationship between the signal cycle and the cycle of the output signal of the MR element 62 provided in the second gear 12 is limited to the calibration curve in FIG. Accordingly, as shown in FIG. 7, the rotation signal detection value of the rotor 10 by the coil core 50 and the sensing unit 15 is continuously output in a sawtooth waveform every 90 degrees from −750 degrees to +750 degrees. At the same time, the rotation angle detection output cycle of the second gear 12 by the MR element 62 and the magnet 61 is alternately and continuously output in a sawtooth waveform every 191.25 degrees.

  Therefore, by comparing the period detected from the coil core 50 and the sensing unit 15 with the period detected from the MR element 62 and the magnet 61, the absolute rotation of the shaft S rotating integrally with the rotor 10 as shown below. The angle can be obtained with high accuracy.

  FIG. 8 shows a detection output value of a small steering angle in which the rotation angle of the rotor 10 is detected every 90 degrees, and a detection of a large steering angle in which the rotation angle of the second gear 12 is detected every 191.25 degrees. It is the list | wrist which showed an example of the correspondence of the output value and the absolute rotation angle of the rotor 10 which is a rotating body which should be measured calculated | required based on these detected output values, ie, the shaft S. Here, the rotation sensor 1 according to the present embodiment may store all the relationships of the absolute rotation angles corresponding thereto in a one-to-one correspondence in the memory, but in the present embodiment, the small steering angle is detected. The absolute rotation angle is uniquely obtained by calculation of the microcomputer from the output value and the detected output value of the large steering angle.

  Hereinafter, a method for determining the absolute rotation angle from the detected output value of the small steering angle and the detected output value of the large steering angle will be described in more detail. In the present embodiment, the angle detected by the MR element 62 that detects the large steering angle is −95.625 degrees to +95.625 degrees (a total of 191.25 degrees). The angle determined by the coil core 50 that detects the small steering angle is 0 degree to +90 degrees. Further, at the origin, both the MR element 62 and the coil core 50 are assumed to be 0 degrees.

Here, as the sensing range, since the detection cycle Tc of the coil core 50 is 90 degrees and the detection cycle Tm of the MR element 62 is 191.25 degrees, considering the least common multiple,
90 × 17 = 191.25 × 8 = 1530 degrees.

  That is, if the rotor 10 is rotated 1530 degrees in either direction, the small steering angle detection output obtained from the coil core 50 and the large steering angle detection output obtained from the MR element 62 have the same relationship. In the case of the embodiment, the absolute range of the rotor 10, that is, the shaft S is measured by setting the sensing range specification to a range of 1530 degrees (−765 degrees to +765 degrees).

For example, if the MR element 62 has a period of 192 degrees, the coil core period Tc = 90 degrees and the MR element period Tm = 192 degrees.
90 × 32 = 192 × 15 = 2880 degrees,
Thus, the sensing range is from −1440 degrees to +1440 degrees.

  Next, how the large steering angle corresponds to a specific small steering angle will be described. In the case of this embodiment, the angle of the large rudder angle changes with respect to the small rudder angle in increments of 191.25− (90 × 2) = 11.25 degrees. However, since the cycle of the MR element 62 is twice, the large steering angle is two series (44 and -46 degrees are base points) as seen from the small steering angle.

  The table in FIG. 8 shows the large steering angle and the absolute angle when the small steering angle is 44 degrees. In this case, the small rudder angle and the large rudder angle have the same relationship when the absolute rotation angle is −766 degrees and 764 degrees. Even in other cases, the same relationship is obtained where there is a difference of 1530 degrees in absolute angle.

  Further, the relationship of Tx = Tc × n is satisfied. Thereby, the interval between the calibration curves adjacent to the calibration curve defined by the combination of the two output values of the first detection means and the second detection means is widened. As a result, the range of combinations of Tm and Tc is made narrower, and the combination of the two output values of the first detection means and the second detection means corresponding to the absolute angle is reduced and effective in reducing the combination where the detection performance is not improved. The range of combinations is limited.

  Since the rotor 10 that is the main rotating body, that is, the shaft S, makes one revolution at 360 degrees, Tc is inevitably 360 degrees or less, and satisfies the relationship of c = 360 degrees / k (k is a positive integer). Yes.

Next, a method for determining the absolute rotation angle of the rotor 10, that is, the shaft S, to be measured from the detected large steering angle and small steering angle will be described. In this case, the range of the absolute rotation angle is −750 degrees to +750 degrees. It is assumed that the small steering angle is detected as 44.00 degrees from the detection value of the coil core 50. In this case, the large steering angle is determined from the detection value of the MR element 62. Assume that the detected value of the MR element 62 is about -12.25 degrees as shown in FIG. In this case, the sign of the large steering angle (minus) is reversed from the sign of the small steering angle (plus) and +/-
44-90 = -46 degrees, and add 11.25 degrees toward --12.2 degrees from the base point. in this case,
-46 / -34.75 / -23.5 / -12.25
3 times and 11.25 degrees, the MR element 62 becomes a value close to the detected large steering angle, so there is a memory table corresponding to the detected small steering angle output value and the detected large steering angle output value. Even if not, from the detection output value of the small rudder angle and large rudder angle by the calculation of the microcomputer,
Absolute rotation angles (−586 degrees) shown in the list of FIG. 8 can be obtained as −46−180 × 3 = −586 degrees.

  FIG. 9 is a diagram for explaining another example of a method for uniquely determining the absolute rotation angle from the detected output value of the small steering angle and the detected output value of the large steering angle. In this case, when the small steering angle is 44 degrees and the large steering angle is -46 degrees, the absolute rotation angle is defined as -46 degrees. As shown in FIG. 9, for example, a case where the absolute rotation angle is calculated when the small steering angle is detected to be 44 degrees from the output of the coil core 50 and the large steering angle is detected to be −68.5 degrees from the output of the MR element 62 will be described. . In this case, 11.25 degrees is subtracted from -46 degrees of the large steering angle to calculate the number of subtractions for -68.5 degrees. If 11.25 degrees is subtracted twice from the small steering angle of −46 degrees, the large steering angle reaches −68.5 degrees, so the absolute rotation angle is −46 degrees + (180 × (number of subtractions = 2)) = 314 It can be uniquely determined as a degree.

  As described above, the rotation sensor 1 according to the present invention detects the rotation angle of the rotor 10 every 90 degrees through the coil core 50 and the sensing unit 15 as the small steering angle, and also uses the magnet 61 as the large steering angle. The rotation of the second gear 12 is detected at intervals of 191.25 degrees via the MR element 62. That is, the period of the first detection signal obtained from the rotor 10 that is the main rotating body, that is, the shaft S, and the period of the second detection signal obtained from the second gear 12 that is the auxiliary rotating body are described above. The rotation sensor satisfies the relational expression of the period. Thus, for example, when the cycle is defined as described above, the absolute rotation angle can be calculated uniquely with high accuracy simply by obtaining the detection output of the small steering angle and the detection output of the large steering angle as shown in FIG. Thus, it is possible to perform absolute rotation angle detection with high accuracy and excellent noise resistance.

  In the present embodiment, the coil core and the sensing unit, the magnet and the MR element are provided in cooperation for the first and second detection, but the present invention is not limited to this, and these may be used interchangeably. Needless to say, other magnetic flux detection means such as an AMR element, a Hall element, and a GMR element may be used instead of the MR element. In addition, the coil core has a track shape in plan view, but is not limited thereto, and may have a circular shape in plan view.

  The following may be considered as a modification of the above-described embodiment. As shown in FIGS. 10 and 11, in this modification, one set of coil cores 150 (the coil 151 that is the coil A1 and the coil 152 that is the coil B1) are arranged at appropriate positions of the sensing unit 115, and the other set. The coil core 160 (the coil 161 that is the coil A2 and the coil 162 that is the coil B2) is disposed at a suitable position on the sensing unit 115 different from the coil core 150. Here, FIG. 10 shows only the rotor 110, the sensing unit 115, and the coil cores 150 and 160, and the sensing unit 115 has a sensing width constant in the circumferential direction in FIG. For example, the change period of the sensing width may be divided into three in the sensing unit circumferential direction with a period of 120 degrees, or may be divided into four in the sensing part circumferential direction with one period of 90 degrees, or one period 72 degrees may be divided into five in the circumferential direction of the sensing section, and any form may be employed as long as one period is equally divided in the circumferential direction of the sensing section at an arbitrary frequency.

  In addition, the core main body used for the coil core in this case is also made of a mixed soft magnetic material in which Mn—Zn soft magnetic material ferrite is mixed with polyphenylene sulfide as in the above-described embodiment. In this case, the core body is formed by injection molding, and the magnetic powder filling rate is about 50% by weight. By forming the core body by injection molding a soft magnetic material containing soft ferrite at such a filling rate, molding becomes easy and the degree of freedom in setting the shape of the core can be improved.

  Alternatively, the core body may be made of a mixed soft magnetic material in which an Fe-Si-Al system sendust is mixed with an epoxy resin. In this case, the core body is formed by compacting, and the magnetic powder filling rate is 90% by weight or more. By forming the core body by compacting a soft magnetic material containing sendust at such a filling rate, the magnetic permeability can be increased and the detection characteristics can be improved. Further, the temperature characteristics of the magnetic permeability can be improved, and the rotation sensor can be used in a wide temperature range environment.

And one set of coil core 150 (coil A1 and coil B1) is mutually shifted and arrange | positioned in the circumferential direction of the sensing part 115 as follows. Specifically, the number of times the change in the width of the sensing unit 115 is repeated per 360 degrees in the circumferential direction of the sensing unit 115 is defined as the division number, and S = 360 degrees / division number. The angle θ to the direction is
θ = n × S + S / 4 (where n is an integer). Similarly, the other set of coil cores 160 are also arranged so as to be offset from each other in the circumferential direction of the sensing unit 115 so as to form this angle θ.

  FIG. 11 shows a signal processing circuit according to this modification. The signal generation units 250 and 260 amplify the signals detected by the coil cores 150 and 160 and output them to the signal processing units 350 and 360, respectively. Plays. In addition, the signal processing units 350 and 360 serve to process input signals by the CPUs and output the data to the ECU 400. The ECU 400 plays a role of detecting the rotation angle of the rotating body from the input data.

  When detecting the rotation angle of the main rotating body by confirming the output data based on the signal from one set of coil cores and the output data based on the signal from the other set of coil cores by the configuration of such a modification. Redundancy can be ensured.

  As described above, the rotation sensor according to the prior art detects the rotation angle of the main rotor using the rotor and the coil core whose width changes in the rotation direction, and has a rotation angle of 360 degrees or more of the main rotor. In order to enable measurement, a Geneva gear that rotates in connection with the main rotating body is provided, and the rotation of the Geneva gear is detected using a rotor and a coil core whose width changes in the rotation direction.

  However, the rotation sensor according to the present invention does not use such a Geneva gear. That is, a sub-rotor connected to the main rotor via a gear is provided, and a magnet is provided in the sub-rotator instead of the Geneva gear, and a sensor element for detecting a magnetic flux change such as an MR element is provided in the fixed member. Thus, the rotation angle of the auxiliary rotating body is detected by a combination of the magnet and the sensor element. In this way, the rotation of the main rotating body is detected by the electromagnetic induction method and the rotation of the sub rotating body is detected by the method of detecting the magnetic flux change by the combination of the magnet and the sensor. A rotation angle in a range of 360 degrees or more is calculated.

  And since this invention has such a structure, the fault of the conventional rotation sensor provided with the Geneva gear, ie, the number of rotations of the main rotator, step by step by the Geneva gear, the conductive layer, and the detection coil. By outputting, it was possible to solve the problem that it was difficult to detect the rotational speed of the main rotor if the output stage corresponding to each rotational speed of the main rotor was small.

  In addition, when the detection angle is wide, the Geneva method requires many step-like signals, and the mechanism portion becomes large, which is disadvantageous for miniaturization. However, according to the method of the present invention, miniaturization is possible.

  In addition to this, the rotation sensor according to the present invention is a further disadvantage of the rotation sensor according to the prior art, and the vibration resistance of the rotation sensor itself is reduced due to the possibility that the Geneva gear rotates due to vibration or the like. The problem was solved.

  Further, the rotation sensor according to the present invention is a further disadvantage of the rotation sensor according to the prior art, that is, the problem of assembly and cost, that is, the Geneva gear is provided with a rotor whose width varies depending on the rotation direction, and the position where the rotor is sandwiched. In the case of providing a coil and core pair, it is possible to solve the disadvantage that the positioning of the parts is not easy and the assembling property of the rotation sensor itself is not good and the cost of parts and assembly man-hours is high.

  The rotation sensor according to the present invention is suitable for detecting the rotation angle of an automobile steering device. However, the rotation sensor according to the present invention is applicable to any sensor as long as it obtains the relative rotation angle and the rotation torque between the rotating shafts that rotate with each other, such as a robot arm.

It is the top view which showed the rotation sensor concerning one Embodiment of this invention in the state which permeate | transmitted the upper case. FIG. 2 is a side view showing a partially transparent internal configuration of a rotation sensor corresponding to FIG. 1. It is the perspective view which expanded and showed the relationship between the coil core of the rotation sensor shown in FIG. 1, and a sensing part. It is the perspective view which expanded and showed only one coil core of the coil core shown in FIG. It is explanatory drawing which showed the method of detecting the rotation angle of a rotor from the combination of the coil core and sensing part shown in FIG. 3 in order of FIG. 5 (a) to FIG.5 (b). It is a calibration curve showing a combination corresponding to the absolute rotation angle between the ratio of the coil core detection output to the period and the ratio of the MR element detection output to the period. It is the figure which showed the ratio with respect to the period of the absolute rotation angle of the rotary body which should be measured, a coil core detection output, and the period of MR element detection output. It is the list | wrist which showed the relationship of a small rudder angle, a large rudder angle, and an absolute rotation angle in order of absolute rotation angle in the range of the small rudder angle of 44 degree | times to 46 degree | times. It is explanatory drawing which shows the method of calculating an absolute rotation angle by calculation without using a memory table from the detection output of a small steering angle and a large steering angle. It is the top view which showed the rotation sensor concerning the modification of one Embodiment of this invention in the state which permeate | transmitted the upper case partially. It is a signal processing circuit of the modification shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rotation sensor 10 Rotor 11 1st gear 12 2nd gear 15 Sensing part 15a Stay 20 Case 21 Lower case 22 Upper case 25 Connector 50 Coil core 51 Core main body 52 Excitation coil 61 Magnet 62 MR element (magnetic flux detection element)
DESCRIPTION OF SYMBOLS 110 Rotor 115 Sensing part 150 Coil core 151,152 Coil 160 Coil core 161,162 Coil 250,260 Signal generation part 350,360 Signal processing part 400 ECU
S shaft

Claims (3)

A main rotating body that moves integrally with the rotating body to be measured, a sub-rotating body that rotates at a rotational speed different from the rotational speed of the main rotating body corresponding to the rotation of the main rotating body, and the rotation of the main rotating body. A first detecting means for detecting and a second detecting means for detecting the rotation of the auxiliary rotating body, and measuring from the detection signal of the first detecting means and the detection signal of the second detecting means; In the rotation sensor that detects the absolute rotation angle of the power rotor,
The main rotating body and the sub-rotating body are transmitted with rotation via gears,
Each detection signal obtained from the first detection means and the second detection means is periodically output corresponding to the rotation of each rotating body, and the period of the detection signal of the first detection means is Tc, When the period of the detection signal of the second detection means is Tm,
(Tm-Tc × i) × n = Tm (i and n are positive integers) meet the relationship,
The first detection means includes a conductive sensing portion that rotates integrally with the main rotating body and changes in width along a circumferential direction; and the electromagnetic wave induction cooperates with the sensing portion to detect the main rotating body. An excitation coil for detecting a rotation angle, and the second detection means includes a magnet provided in the sub-rotator, and a magnetic flux detection element that detects a change in magnetic flux of the magnet according to the rotation of the sub-rotator. Prepared ,
The rotation sensor, wherein the exciting coil is wound in a track shape so that a direction intersecting the sensing unit is a longitudinal direction . 2. The rotation sensor according to claim 1 , wherein the excitation coil is held by a core body made of a mixed soft magnetic material in which Mn—Zn soft magnetic material ferrite is mixed with polyphenylene sulfide. 3. 2. The rotation sensor according to claim 1 , wherein the exciting coil is held by a core body made of a mixed soft magnetic material in which an Fe—Si—Al based sendust is mixed with an epoxy resin.

Images