JP4028559B2 - 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 to detect a rotation angle of a handle attached to a rotating shaft such as a steering shaft of an automobile and integrated with the shaft.

  As an example of such a rotation sensor, there is one in which a fixed core is disposed opposite to a rotor at a predetermined interval. (For example, refer to Patent Document 1).

  As shown in Patent Document 1, the rotation sensor includes a rotor attached to a rotating shaft, a core body made of an insulating magnetic material, a fixed core having at least one exciting coil housed in the core body, and a rotation angle. A detection unit is provided. The excitation coil is composed of two excitation coils as shown in FIG. 2A, for example, and is arranged at a predetermined center angle such as 90 degrees in the circumferential direction of the rotor. The fixed core is attached to a fixed member located in the vicinity of the shaft, and is housed together with a rotor in a case made of a metal or insulating magnetic material having an AC magnetic field shielding property, or an insulating resin material.

  The rotor includes a rotor mounting portion made of an insulating magnetic material or an insulating resin material and a sensing portion that is connected to the rotor via a stay member and has a width that continuously changes in the circumferential direction. The sensing part is made of a conductive metal having a narrow part with the smallest width and a wide part with the largest width on the opposite side in the radial direction, and corresponds to the rotation angle of the rotor. The sensing part is formed so that its radial width changes, and an eddy current of a magnitude corresponding to the width accompanying rotation is induced by the alternating magnetic field on the sensing part surface. The impedance of each exciting coil varies with the variation.

  As shown in FIG. 13, the circuit block diagram of the rotation sensor includes an oscillation unit 500 that includes an oscillation circuit 501 and outputs an oscillation signal of a specific frequency, and an oscillation unit 500 that corresponds to the magnitude of eddy current generated in the sensing unit. A phase shift unit 510 (511, 512) for shifting the phase of the input oscillation signal, a phase shift amount detection unit 520 (521, 522) for detecting the phase shift amount, and a parameter corresponding to the detected phase shift amount Based on the output from the amplifying unit 540, the phase shift amount converting unit 530 (531, 532) for converting to, the amplifying unit 540 (541 542) for amplifying the phase shift amount output from the phase shift amount converting unit 530, and the like. A rotation angle detection unit 550 that calculates the rotation angle and detects the rotation angle input to the phase shift unit 510. .

  In addition, the phase shift unit 510 includes a resistance of an electronic circuit, a capacitor, and a coil as shown in FIG. As described above, since the rotor sensing portion has a shape whose width continuously changes in the circumferential direction, the impedance of the coil changes as the rotor sensing portion rotates in conjunction with the rotation of the rotating shaft. .

  When the rotation shaft rotates, the output of the phase shift amount detection unit 520 with respect to the input angle is determined by the shape of the sensing unit, and can be changed like a Sin waveform as shown in FIG. For example, as shown in FIG. 2B, when two fixed cores (coil A and coil B) are arranged at a central angle of 90 ° with respect to the center of the rotor rotation axis, the input angle is set as shown in FIG. On the other hand, the phase shift amount processed based on the impedance change of the coil A of one fixed core and the phase shift amount processed based on the impedance change of the coil B of the other fixed core have a phase difference of 90 °. Will change.

Then, the rotation angle of the rotor is detected by utilizing the fluctuation in impedance of the exciting coil accompanying the generation of the eddy current using the rotation sensor having such a configuration.
JP 2003-202240 A (page 4-5, FIG. 1)

  On the other hand, in the rotation sensor, the sensing part of the rotor is fixed to the rotation shaft, and the excitation coil is fixed to the case via a fixed core. That is, when attaching the rotation sensor, the rotor side of the rotation sensor is attached to the rotation shaft and the stator side is attached to a portion other than the rotation shaft by a bracket or the like. For this reason, in order to improve the attachment of the rotation sensor, a certain amount of deviation may occur between the sensing portion of the rotor and the exciting coil. If this deviation is within the allowable range, there is no problem. However, if the deviation exceeds the allowable range, due to backlash between the sensing part of the rotor and the exciting coil, temperature characteristics of the coil, etc., as shown in FIG. An unacceptable shift occurs in the phase shift amount. FIG. 4 shows a case where the phase shift amount is shifted (vertically shifted on the graph), but the input angle may be shifted (shifted horizontally on the graph), and both may be shifted. . Actually, the sensing part tends to be displaced in the radial direction between the sensing part of the rotor and the exciting coil. At this time, the rotation angle detection unit 550 detects an angle with a deviation from the actual input angle as it is, but it is difficult to detect such an unacceptable deviation with the current configuration alone. Further, if this is detected, additional parts are required, leading to an increase in cost. In this way, it is difficult to distinguish changes in detection output due to backlash or temperature between the sensing section of the rotor and the excitation coil from changes in the original detection angle. The diagnosis cannot be made and the rotation angle is erroneously detected. If an unacceptable misalignment between the sensing unit of the rotation sensor and the exciting coil can be determined, measures such as timely cancellation of the sensor output signal can be taken. If such misalignment cannot be determined, an appropriate measure is taken. It is difficult.

  An object of the present invention is to detect a rotation sensor abnormality without detecting a rotation angle while including a detection error when an unacceptable positional deviation occurs between a sensing portion of a rotor of a rotation sensor and an excitation coil. Is to provide.

In order to solve the above-mentioned problem, the rotation sensor according to the present invention is:
A rotor attached to a rotating shaft and having a conductive sensing portion whose width varies along the circumferential direction;
An excitation coil that forms a magnetic circuit with the sensing portion of the rotor by passing an AC excitation current, and a core body that is molded from a magnetic material and holds the excitation coil, and other than the rotating shaft In a rotation sensor comprising a fixed core attached to a fixed member to be attached and disposed opposite to the sensing portion of the rotor at an interval in the axial direction of the shaft,
A plurality of the fixed cores are arranged at predetermined intervals in the circumferential direction of the sensing unit of the rotor, and the excitation coil of each fixed core forms a phase shift unit, and the phase shift unit is connected to the oscillation unit and the phase shift amount detection unit. Connected,
The value of the phase shift amount obtained by the phase shift amount detection unit connected to any one of the excitation coils and the phase shift amount obtained by the phase shift amount detection unit connected to the other one excitation coil Means for detecting a sensor abnormality from the value of
The means for detecting the sensor abnormality includes a determination limit value including a flat portion formed by partially saturating the phase shift amount obtained by the phase shift amount detection unit connected to any one of the exciting coils. The phase shift amount at the boundary between the flat portion of the phase shift amount that constitutes the determination limit value and the normal change portion that is not the flat portion, and the phase shift amount detection unit connected to any one of the other excitation coils The difference between the phase shift amount at the same input angle is compared with a predetermined criterion value, and a sensor abnormality is detected when the difference exceeds the criterion value.

  The rotation sensor of the present invention has such a means, so that when the shift amount of the output due to the mounting displacement between the sensing portion of the rotation sensor and the exciting coil is in an unacceptable range, the device configuration is simple. Thus, the abnormality of the rotation sensor can be determined.

  That is, the means for detecting the sensor abnormality has a determination limit value including a flat portion formed by partially saturating the phase shift amount obtained by the phase shift amount detection unit connected to any one of the exciting coils. The phase shift amount at the boundary between the flat portion of the phase shift amount that constitutes the determination limit value and the normal change portion that is not flat and the same obtained by the phase shift amount detection unit connected to any one other exciting coil The difference between the phase shift amount at the input angle is compared with a predetermined criterion value, and when the difference exceeds the criterion value, a sensor abnormality is detected. When the output shift amount due to mounting displacement between the excitation coils is in an unacceptable range, it is possible to determine that the rotation sensor is abnormal with a simple configuration without adding a special abnormality diagnosis circuit. That.

A rotation sensor according to claim 2 of the present invention is
A rotor attached to a rotating shaft and having a conductive sensing portion whose width varies along the circumferential direction;
An excitation coil that forms a magnetic circuit with the sensing portion of the rotor by passing an AC excitation current, and a core body that is molded from a magnetic material and holds the excitation coil, and other than the rotating shaft In a rotation sensor comprising a fixed core attached to an attached fixed member and opposed to the sensing portion of the rotor at an interval in the axial direction of the shaft,
A plurality of the fixed cores are arranged at predetermined intervals in the circumferential direction of the sensing unit of the rotor, and the excitation coil of each fixed core forms a phase shift unit, and the phase shift unit is connected to the oscillation unit and the phase shift amount detection unit. Connected,
The value of the phase shift amount obtained by the phase shift amount detection unit connected to any one of the excitation coils and the phase obtained by the phase shift amount detection unit connected to any one of the other excitation coils A means for detecting a sensor abnormality from the value of the shift amount;
The means for detecting the sensor abnormality includes a phase shift amount obtained by a phase shift amount detector connected to any one of the excitation coils and a phase shift amount detection connected to any one of the other excitation coils. If the input angle corresponding to the intersection is between the minimum allowable limit value and the maximum allowable limit value, which are predetermined input angles, the sensor It is judged that the sensor is abnormal when it is determined to be normal and exceeds this range.

  According to the present invention, when an unacceptable phase shift amount deviation occurs in the rotation sensor, it is determined that the sensor is abnormal without detecting the rotation angle while including a detection error. Detection is possible.

  Hereinafter, a rotation sensor according to an embodiment of the present invention will be described with reference to the drawings. In this description, a case will be described in which the rotation angle of the steering wheel is detected by attaching the rotation sensor to the steering shaft in a steering apparatus for an automobile.

  As shown in FIGS. 1 and 12, a rotation sensor 1 according to an embodiment of the present invention includes a rotor 10 attached to a rotating shaft S, a core body made of an insulating magnetic material, and at least housed in the core body. A fixed core 31, 32 (41, 42) having one excitation coil, a holding member 90 for holding the fixed core 31, 32 (41, 42), a circuit board 95 provided in a part of the holding member 90, And a case 20 for housing them. In addition, the holding member 90 includes a coil core holder 92 in which the fixed cores 31 and 41 are opposed to each other with a gap G (see FIG. 12), and a coil core in which the fixed cores 32 and 42 are arranged to face each other with a gap G (see FIG. 12). A holder 93 is provided. The holding member 90 is assembled to the rotation sensor 1 so that the coil core holders 92 and 93 form a central angle of 90 degrees with respect to the shaft S, as shown in FIG. As a result, the fixed cores 31 and 41 of one set are arranged at a central angle of 90 ° with respect to the axis of the shaft S with respect to the fixed cores 32 and 42 of the other set. The fixed cores 31 and 32 are arranged on the lower case side of the holding member 90 so as to form a central angle of 90 ° with respect to the axis of the shaft S as described above. On the other hand, the fixed cores 41 and 42 are disposed on the upper case 21 side of the holding member 90 so as to form a central angle of 90 ° with respect to the axis of the shaft S.

  The fixed cores 31 and 32 on one side are made of an insulating magnetic material (for example, Ni—Zn, Mn—Zn, Mg—Zn ferrite, nylon, polypropylene (PP), polyphenylene sulfide (PPS), acrylonitrile. Made of a mixture of thermoplastic synthetic resins having electrical insulation properties such as butadiene styrene (ABS) or ceramics, etc., formed in a columnar shape, and having a ring-shaped void on the upper surface side in which an exciting coil is accommodated. It has the core main bodies 31a and 32a and the exciting coils 31b and 32b accommodated in the core main bodies 31a and 32a. Similarly, the other fixed cores 41 and 42 have core bodies 41a and 42a made of an insulating magnetic material and exciting coils 41b and 42b accommodated in the core bodies 41a and 42a. The exciting coils 31b and 32b and the exciting coils 41b and 42b are respectively connected in series and electrically connected to the signal processing circuit 99 of the holding member 90, and an alternating magnetic field is caused to flow so that an alternating magnetic field is generated around the coil. A magnetic circuit is formed between the fixed cores that are paired with each other. In the present embodiment, the fixed core exciting coils that are paired in the description of the signal processing circuit will be described as coil A and coil B, respectively.

  The holding member 90 is made of, for example, a synthetic resin (for example, polybutylene terephthalate (PBT), nylon, polyphenylene sulfide (PPS), acrylonitrile butadiene styrene (ABS), etc., and FRP (fiber reinforced plastic) in which a glass fiber is impregnated with an epoxy resin. ) And the like, and includes a base portion attached to the lower case 22. Coil core holders 92 and 93 are provided at one end of the base portion.

  Further, the holding member 90 provided with the fixed cores 31 and 32 (41, 42), the circuit board 95 provided with the signal processing circuit 99, and the rotor 10 are made of a metal or an insulating magnetic material having a shielding property against an alternating magnetic field. 20. The case 20 is attached to a fixing member (not shown) located in the vicinity of the shaft S via a bracket or the like (not shown).

  A signal processing circuit 99 shown in FIG. 3 is mounted on a circuit board 95 provided in a part of the holding member 90. The signal processing circuit 99 is connected to a power source and a signal transmission wire harness via a plurality of electric wires (not shown) extending from the case 20 to the outside, and is an external device provided outside the case 20. To be connected.

  As shown in FIGS. 1, 2, and 12, the rotor 10 is connected through a rotor mounting portion of an insulating magnetic material, and the rotor mounting portion and a stay member, and the width continuously changes in the circumferential direction. It comprises a sensing unit 12. The sensing unit 12 is made of a conductive metal such as aluminum, copper, silver, or brass. As shown in FIGS. 1 and 2, the sensing unit 12 includes a narrow portion having a minimum width and a wide portion having a maximum width on the opposite side to the narrow portion in the radial direction. A vortex having a size based on the area of the region corresponding to each coil of the sensing width is formed by an alternating magnetic field (to be described later) along with the rotation of the rotor. An electric current is induced.

  That is, when an alternating current is passed through each of the exciting coils 31b, 32b, 41b, and 42b, the exciting coils 31b, 32b, 41b, and 42b form an alternating magnetic field around them, and the opposing core body 31a and core body 41a are The magnetic circuit is formed by cooperation, and similarly, the core body 32a and the core body 42a facing each other also form the magnetic circuit. At this time, when the magnetic flux crosses the sensing unit 12, an eddy current is induced on the surface of the sensing unit 12, and the impedance of each exciting coil 31b, 32b, 41b, 42b is changed. The amount of variation in impedance varies in accordance with the amount of eddy current induced on the surface of the sensing unit 12. The amount of eddy current induced on the surface of the sensing unit 12 is the area of the sensing unit 12 corresponding to the fixed core (the projected area of the sensing unit with respect to the fixed core when viewed from the direction orthogonal to the sensing surface of the sensing unit 12, that is, “sensing The projected area of the part onto the fixed core "). Therefore, when the rotor 10 rotates, the width of the sensing unit 12 corresponding to each fixed core 31, 32, 41, 42 varies in proportion to the rotation angle of the rotor 10, and accordingly, each excitation coil 31b, 32b, 41b. , 42b also varies. At this time, output signals from the respective excitation coils 31b, 32b, 41b, and 42b are detected by a signal processing circuit (see FIG. 3) described later, converted into an angle signal of the rotor 10, and a rotation angle of the rotor 10 is detected. It is like that.

  As shown in the circuit block diagram of FIG. 3, the rotation sensor signal processing circuit includes an oscillation unit 100 including an oscillation circuit 101 that generates an oscillation signal of a specific frequency, and an eddy current generated in the sensing unit 12. A phase shift unit 110 (111, 112) for shifting the phase of the oscillation signal input from the oscillation unit 100 according to the magnitude, a phase shift amount detection unit 120 (121, 122) for detecting the phase shift amount, and a detection Phase shift amount conversion unit 130 (131, 132) for converting the phase shift amount into a corresponding parameter (for example, voltage value or digital value), and amplification for amplifying the phase shift amount output from phase shift amount conversion unit 130 Unit 140 (141, 142) and a signal for calculating a rotation angle from a parameter corresponding to the phase shift amount and determining sensor abnormality. And a processing unit 150, adapted to detect the rotation angle to be input to the phase shift unit 110. The signal processing unit 150 includes a rotation angle detection unit 151 and an abnormality detection unit 152. In addition to the detection of the rotation angle, the signal processing unit 150 also determines a sensor abnormality when the positional deviation between the rotor sensing unit and the excitation coil is not acceptable. It has become. Although not described in this embodiment, a frequency divider or a buffer amplifier (buffer) may be provided between the oscillation circuit 101 and the phase shift unit 110 as necessary.

  Subsequently, a specific signal processing method of the rotation sensor 1 according to the embodiment of the present invention will be described. First, the oscillation circuit 101 transmits an oscillation signal having a specific frequency to each excitation coil 31b and coil 41b (coil A), coil 32b and coil 42b (coil B). Thereby, each oscillation signal is output to each phase shift unit 110 including resistors R1 and R2, coils B1 and B2, and capacitors C1 and C2 shown in FIG. At this time, the phase of the voltage signal at both ends of the capacitors C1 and C2 changes due to fluctuations in impedance of the coils B1 and B2. The voltage signals across the capacitors C1 and C2 are output to each phase shift amount detection unit 120. Each phase shift amount detector 120 detects the phase shift amount of the voltage signal across the capacitors C1 and C2. Each phase shift amount conversion unit 130 converts each detected phase shift amount into a corresponding voltage.

  Then, this voltage value is transmitted to the amplifying unit 140 (141, 142) connected to the subsequent stage of the phase shift amount converting unit 130. The amplifier 140 is an electronic circuit composed of an operational amplifier, etc., and by adjusting the amplification factor of the operational amplifier, the upper limit is saturated with the positive power supply voltage of the operational amplifier, and the lower limit is saturated with the negative power supply voltage (or GND voltage) of the operational amplifier. A flat region is formed with a voltage value corresponding to the amount.

  The signal processing unit 150 uses, for example, a one-chip microprocessor as arithmetic processing means, and the rotation angle detection unit 151 measures the rotation angle of the rotor 2 and detects an abnormality based on the voltage value input from each amplification unit 140. The unit 152 detects an abnormality of the rotation sensor 1.

  Then, the specific structure of the abnormality diagnosis of the rotation sensor 1 in this embodiment is demonstrated. As shown in FIG. 3, the abnormality diagnosis configuration of the rotation sensor is amplified to the amplitude of the phase shift amount obtained by the phase shift amount detection unit 120 of at least one of the exciting coils (coil B in this embodiment). The unit 140 sets an upper limit and a lower limit, and saturates the phase shift amount at a constant value between the upper limit and the lower limit, thereby actively forming a flat region (see FIGS. 5 and 11). A sensor abnormality is detected by comparing the saturated phase shift amount with the phase shift amount obtained by the phase shift amount detection unit 120 of one of the other excitation coils (coil A in the present embodiment). It has become. The phase shift amount detection unit 120 of each coil A and coil B is connected to the amplification unit 140 via the phase shift amount conversion unit 130, and the signal for detecting the sensor abnormality is actually a voltage value of an analog signal. It has become.

  The abnormality diagnosis method for the rotation sensor 1 according to the present embodiment is as follows. As described above, the amplifying unit 140 gives the flat region defined by the upper and lower limits to the amplitude of the phase shift amount with respect to the input angle (see FIG. 11). Then, as shown in FIG. 5, the phase shift amount obtained from the impedance of the coil B at the point A which is the boundary between the flat region and the normal change portion in the voltage value indicating the phase shift amount of the coil B was obtained from the coil A. Compare with the amount of phase shift. The normal range of the difference X between the phase shift amounts obtained from the impedances of the coils A and B at the input angle including the point A is determined in advance by design. In FIG. 11, the upper limit value of the normal range is defined by the determination reference upper limit value, and the lower limit value is defined by the determination reference lower limit value.

  Thus, the phase shift amount with respect to the input angle has a flat portion. Then, as shown in FIG. 5, the phase shift amount at the point A which is the boundary between the saturation portion and the normal change portion in the phase shift amount of the coil B is the phase shift amount obtained from the impedance of the coil A at the same input angle. Compare. The phase shift amount difference X (judgment reference value) obtained from the impedances of the coil A and the coil B has a predetermined value that specifies a normal range in advance by design, and is rotated by comparing X with a predetermined value. It can be determined whether the sensor is normal.

  Specifically, when the difference X in the phase shift amount at the point A is the predetermined value x1 <= X <= x2, there is no deviation between the excitation coil of the rotation sensor and the sensing unit, or an allowable deviation range. It is determined that the rotation sensor is normal. Further, when the difference X in the phase shift amount at point A is X <predetermined value x1 or X> predetermined value x2, the rotation sensor is assumed to have an unacceptable deviation between the excitation coil of the rotation sensor and the sensing unit. Judge as abnormal. Similarly, the difference in the phase shift amount is obtained as described above at the boundary between the saturation region and the normal change portion at the lower limit of the voltage value indicating the phase shift amount, and the rotation sensor is determined by whether or not this is included in the predetermined range. Normality / abnormality may be judged.

  Instead of providing both the upper limit and the lower limit of the voltage value representing the phase shift amount as described above, only one of the upper limit or the lower limit of the phase shift amount is provided by using a limiter such as a diode, and this one phase shift amount is set. It is also possible to determine a sensor abnormality that accompanies the rotation sensor mounting position deviation only from the voltage value of the rotation sensor.

  Here, in the embodiment described above, as shown in FIGS. 6 to 8, the waveform of the phase shift amount obtained by the phase shift amount detection unit 120 of at least one of the exciting coils (coil B in the present embodiment). And detecting the sensor abnormality by determining the deviation of the intersection of the phase shift amount waveform obtained by the phase shift amount detection unit 120 of one of the other exciting coils (coil A in the present embodiment). Good. In this case, it is desirable to actively form a flat region by a method of setting an upper limit and a lower limit on at least one amplitude in the amplification unit 140 and saturating the phase shift amount at a constant value of the upper limit and the lower limit.

  Specifically, instead of the above-described sensor abnormality determination method, a signal processing method as shown in FIGS. 6 to 8 may be used. That is, in the linear region below the determination reference upper limit value of the phase shift amount shown in FIG. 6, for example, the intersection of the signal of the coil A and the signal of the coil B is obtained, and the allowable deviation of the phase shift amount of the coil A is also shown in the figure. It is determined as shown by a one-dot chain line, and an intersection of an allowable phase shift amount of the coil A and a phase shift amount of the coil B indicated by the one-dot chain line is set as an allowable limit value. Thereafter, as shown in FIG. 7, if this intersection is between the minimum allowable limit value W1 and the maximum allowable limit value W2 regarding the predetermined input angle, it is determined that the sensor is normal, and this range is reached. It may be determined that the sensor is abnormal when the value exceeds. Further, as shown in FIG. 8, when the intersection is between the minimum allowable limit value Z1 and the maximum allowable limit value Z2 of the phase shift amount, it is determined that the sensor is normal, and exceeds this range. Sometimes, it may be determined that the sensor is abnormal.

  Then, the modification of the rotation sensor concerning this invention is demonstrated. Specifically, in the case of this modification, as shown in the circuit block diagram of FIG. 9, the oscillation unit 200 that includes the oscillation circuit 201 and outputs an oscillation signal of a specific frequency, and the magnitude of the eddy current generated in the sensing unit 12 A phase shift unit 210 (211, 212) that shifts the phase of the oscillation signal input from the oscillation unit 200 in response to this, and a phase shift amount detection unit 220 (221, 222) that detects the phase shift amount are detected. The phase shift amount conversion unit 230 (231 and 232) that converts the phase shift amount into a corresponding parameter (for example, a voltage value or a digital value), and upper and lower limits are set for the phase shift amount output from the phase shift amount conversion unit 230 A signal that calculates the rotation angle from the setting calculation unit 240 (241, 242) and the parameter corresponding to the phase shift amount and determines the sensor abnormality. And a processing unit 250, adapted to detect the rotation angle to be input to the phase shift unit 210. The signal processing unit 250 includes a rotation angle detection unit 251 and an abnormality detection unit 252 so that, in addition to the detection of the rotation angle, a sensor abnormality is also determined when the positional deviation between the rotor sensing unit and the excitation coil is not acceptable. It has become. In this modification, the phase shift amount detection unit 220 of each coil A and coil B is connected to the setting calculation unit 240 via the phase shift amount conversion unit 230, and the signal for detecting the sensor abnormality is actually It is a digital signal obtained by converting the phase shift amount, not the phase shift amount of the analog signal. Although not described in this modification, a frequency divider or a buffer amplifier (buffer) may be provided between the oscillation circuit 201 and the phase shift unit 210 as necessary.

  Next, a specific signal processing method according to this modification will be described. First, the oscillation circuit 201 transmits an oscillation signal having a specific frequency to each excitation coil 31b and coil 41b (coil A), coil 32b and coil 42b (coil B). Thereby, each oscillation signal is output to each phase shift unit 210 including resistors R1 and R2, coils B1 and B2, and capacitors C1 and C2 shown in FIG. At this time, the phase of the voltage signal at both ends of the capacitors C1 and C2 changes due to fluctuations in impedance of the coils B1 and B2. The voltage signals across the capacitors C1 and C2 are output to each phase shift amount detection unit 220. Each phase shift amount detection unit 220 detects the phase shift amount of the voltage signal across the capacitors C1 and C2, respectively. Each phase shift amount conversion unit 230 converts each detected phase shift amount into a corresponding digital signal. Each setting calculation unit 240 determines an upper limit value and a lower limit value of the signal output from each phase shift amount conversion unit 230, and a digital value corresponding to the phase shift amount is determined by the upper limit value and the lower limit value. And for each phase shift amount of the coil B. The signal processing unit 250 uses, for example, a one-chip microprocessor as a calculation processing unit, and the rotation angle detection unit 251 measures the rotation angle of the rotor 10 based on the digital signal input from each setting calculation unit 240. The abnormality detection unit 252 detects an abnormality of the rotation sensor.

  Next, a specific configuration for abnormality diagnosis of the rotation sensor in the present modification will be described. As shown in FIG. 9, the abnormality diagnosis configuration of the rotation sensor has a phase shift amount obtained by the phase shift amount detection unit 220 of at least one of the exciting coils (coil B in FIG. 5 in this embodiment). The setting calculation unit 240 sets an upper limit and a lower limit on the amplitude to positively form a flat region of the phase shift amount (see FIGS. 5 and 11). Then, a sensor abnormality is detected by comparing this phase shift amount with the phase shift amount obtained by the phase shift amount detector 220 of one of the other exciting coils (coil A in FIG. 5 in this embodiment). It has become.

  The abnormality diagnosis method for the rotation sensor according to this modification is as follows. Specifically, as shown in FIG. 9, the phase shift amount obtained by the phase shift amount detection unit 220 is converted into a digital signal by the phase shift amount conversion unit 230, respectively. Then, this digital value is transmitted to the setting calculation unit 240 (241, 242) connected to the subsequent stage of the phase shift amount conversion unit 230. Then, an upper limit and a lower limit of the phase shift amount are provided in the setting calculation unit 240 connected to the subsequent stage of the phase shift amount conversion unit 230, and the phase shift amount is saturated at the upper limit and the lower limit. Specifically, the setting calculation unit 240 has a determination upper limit value (see FIG. 5) that is an upper limit value of the determination limit value that is set in advance and a determination lower limit value (see FIG. 11) that is a lower limit value. If the phase shift amount is a digital value greater than or equal to the determination reference upper limit value, a calculation process is performed to replace the determination reference upper limit value. If the phase shift amount is a digital value equal to or less than the determination reference lower limit value, an arithmetic process is performed. By this calculation processing, the digital value representing the phase shift amount is set such that the upper limit is the determination reference upper limit value and the lower limit is the determination reference lower limit value.

  As a result, as shown in FIG. 11, the upper and lower limits of the amplitude of the phase shift amount with respect to the input angle can be made flat. In FIG. 11, the phase shift amount is drawn as an analog value, but in this modification, this is quantized and the phase shift amount is output as a digital value for each rotation angle, and the upper limit value is the criterion reference upper limit value. The lower limit value is defined by the determination criterion lower limit value.

  Thus, the phase shift amount with respect to the input angle has a flat portion. Then, as shown in FIG. 5, the phase shift amount obtained from the impedance of the coil A at the same input angle as the phase shift amount at the point A which is the boundary between the flat portion and the normal change portion of the phase shift amount of the coil B is obtained. Compare with The phase shift amount difference X obtained from the impedances of the coil A and the coil B is determined in advance by design so that a normal value for specifying a normal range is determined. By comparing X with a predetermined value, whether the rotation sensor is normal or not is determined. Can be determined.

  Specifically, when the difference X in the phase shift amount at the point A is the predetermined value x1 <= X <= x2, there is no deviation between the excitation coil of the rotation sensor and the sensing unit, or an allowable deviation range. It is determined that the rotation sensor is normal. Further, when the difference X in the phase shift amount at point A is X <predetermined value x1 or X> predetermined value x2, the rotation sensor is assumed to have an unacceptable deviation between the excitation coil of the rotation sensor and the sensing unit. Judge as abnormal. Similarly, the difference of the phase shift amount is obtained as described above at the boundary between the flat region at the lower limit of the digital value of the phase shift amount and the normal change portion, and the rotation sensor is determined by whether or not this is included in the predetermined range. Normality / abnormality may be judged.

  Instead of providing both the upper limit and the lower limit of the digital value representing the phase shift amount as described above, only one of the upper limit or the lower limit is provided and only the digital value of the phase shift amount is shifted from the rotation sensor mounting position. It is also possible to determine the sensor abnormality that accompanies.

  Subsequently, a reference example of the above-described embodiment will be described. In this reference example, the excitation coil is disposed at a predetermined position in the circumferential direction of the rotor sensing unit, and the excitation coil is connected to the oscillation unit, the phase shift unit, and the phase shift amount detection unit.

  The signal processing circuit (not shown) of this reference example has the following configuration. That is, the phase shift amount detection unit is connected to the phase shift amount conversion unit, and the phase shift amount is converted into a voltage value. Further, the phase shift amount converting unit is connected to the amplifying unit and saturates the phase shift amount converted into the voltage value by changing the gain of the amplifying unit as in the above-described embodiment at the preset upper and lower limits. It has become. Then, the sensor abnormality is detected by comparing the saturation region of the saturated phase shift amount with a predetermined threshold value. Specifically, as shown in FIG. 10, the width Y of the flat portion in the saturation region of the voltage value of the phase shift amount is defined by a certain range of widths (allowable minimum width y1 and allowable maximum width y2) shown in FIG. If the threshold value is exceeded, the phase shift amount is shifted in the vertical direction to an unacceptable range. This indicates that the exciting coil has shifted to an unacceptable range in the radial direction of the sensing unit. In this case, it is determined that the rotation sensor is abnormal.

  In this way, even if the exciting coil is arranged only in one place in the circumferential direction of the sensing unit, the width of the saturation region of the voltage value of the saturated phase shift amount is compared with a predetermined threshold value. Thus, when the shift amount of the output accompanying the deviation in mounting of the rotation sensor falls within an unacceptable range, it is possible to determine that the rotation sensor is abnormal without adding a special abnormality diagnosis circuit.

  In addition, instead of saturating the phase shift amount at the preset upper limit and lower limit by changing the gain of the amplification unit as in this reference example, the upper limit or lower limit of the voltage value of the phase shift amount is set via a diode limiter circuit. Both or one of them may be saturated, and the abnormality of the rotation sensor may be determined based on the width of the saturated flat portion region.

  In this reference example, even if the phase shift amount conversion unit converts the phase shift amount into a digital value and performs abnormality diagnosis in the same manner as described above based on this digital value, as in the above-described modification. good.

  In this reference example, it is possible to determine the abnormality of the rotation sensor from only one excitation coil. However, even when the rotation sensor includes a plurality of excitation coils, only one of the excitation coils is used. It is also possible to determine the abnormality of the rotation sensor, and it is also possible to determine the abnormality of the rotation sensor for each excitation coil based on the phase shift amount of each excitation coil. As a result, the rotation sensor can be determined to be abnormal in all cases, particularly when the excitation coil is displaced to such an extent that it cannot be permitted in the radial direction of the sensing unit.

  In the above embodiment and its modifications, the coil core holder 92 may be configured to be placed on a holding member 90 as shown in FIG. In this case, the holding member 90 can also have a circuit board (not shown). Specifically, as shown in FIG. 12, the core main bodies 31a and 32a having ring-shaped gaps in which the excitation coils are accommodated on the upper surface side and the excitation coils 31b and 32b accommodated in the core main bodies 31a and 32a are provided. Have. Similarly, the other fixed cores 41 and 42 have core bodies 41a and 42a made of an insulating magnetic material and exciting coils 41b and 42b accommodated in the core bodies 41a and 42a. The exciting coils 31b and 32b and the exciting coils 41b and 42b are respectively connected in series, electrically connected to a signal processing circuit (not shown) of the holding member 90, and an AC exciting current is passed to surround the coils. An alternating magnetic field is formed on each other, and a magnetic circuit is formed between the pair of fixed cores.

  As described above, the rotation sensor according to the present invention is particularly suitable for detecting the rotation angle of a steering apparatus for a vehicle, in which a slight backlash must be allowed between the sensing portion of the rotor and the excitation coil in order to improve attachment. Yes. However, the rotation sensor according to the present invention may be a relative rotation angle or rotation torque between rotating shafts such as a robot arm as long as the sensing portion of the rotor and the exciting coil may be displaced in the attached state. It is also applicable to those that require

It is sectional drawing which showed the internal structure of the rotation sensor concerning one Embodiment of this invention. FIG. 2 is a plan view (FIG. 2A) showing an arrangement of a rotor sensing unit and a coil core of the rotation sensor shown in FIG. 1 and a circuit diagram related to the exciting coil (FIG. 2B). It is a circuit block diagram of the rotation sensor regarding this embodiment. FIG. 6 is a detection characteristic diagram showing a state where the phase shift amount of one exciting coil is shifted when a coil core is arranged at a central angle of 90 °. It is the elements on larger scale of the detection characteristic figure of phase shift amount which showed the principle of abnormality judgment of a rotation sensor about this embodiment and its modification. It is the detection characteristic figure which showed the similar example of the principle of abnormality determination of the rotation sensor concerning this embodiment. It is the elements on larger scale which showed the 1st method of abnormality determination in the detection characteristic figure shown in FIG. It is the elements on larger scale which showed the 2nd method of abnormality determination in the detection characteristic figure shown in FIG. It is a circuit block diagram of the rotation sensor regarding the modification of this embodiment. It is a detection characteristic figure of the amount of phase shift showing the principle of abnormality judgment of a rotation sensor about a reference example of this embodiment. It is a detection characteristic figure of the amount of phase shift showing the principle of abnormality judgment of a rotation sensor about this embodiment, a modification, and a reference example. It is XII-XII sectional drawing which showed the internal structure of the rotation sensor concerning one Embodiment of this invention in FIG. It is a circuit block diagram of the conventional rotation sensor. It is a detection characteristic figure of the phase shift amount of the specific coil core of the conventional rotation sensor. It is a detection characteristic figure of the amount of phase shifts when a coil core is arranged at a central angle of 90 °.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rotation sensor 10 Rotor 12 Sensing part 20 Case 21 Upper case 22 Lower case 31, 32, 41, 42 Fixed core 31a, 32a Core main body 31b, 32b Excitation coil 41a, 42a Core main body 41b, 42b Excitation coil 90 Holding member 92, 93 Coil core holder 100, 200 Oscillator 101, 201 Oscillator 110 (111, 112), 210 (211, 212) Phase shifter 120 (121, 122), 220 (221, 222) Phase shift amount detector 130 ( 131, 132), 230 (231, 232) Phase shift amount conversion unit 140 Amplification unit 150 Signal processing unit 151 Rotation angle detection unit 152 Abnormality detection unit 240 Setting calculation unit 500 Oscillation unit 501 Oscillation circuit 510 (511, 512) Phase shift Part 520 (52 1,522) Phase shift amount detection unit 530 (531, 532) Phase shift amount conversion unit 540 (541, 542) Amplification unit 550 Rotation angle detection unit S Shaft

Claims (1)

A rotor attached to a rotating shaft and having a conductive sensing portion whose width varies along the circumferential direction;
An excitation coil that forms a magnetic circuit with the sensing portion of the rotor by passing an AC excitation current, and a core body that is molded from a magnetic material and holds the excitation coil, and other than the rotating shaft In a rotation sensor comprising a fixed core attached to a fixed member to be attached and disposed opposite to the sensing portion of the rotor at an interval in the axial direction of the shaft,
A plurality of the fixed cores are arranged at predetermined intervals in the circumferential direction of the sensing unit of the rotor, and the excitation coil of each fixed core forms a phase shift unit, and the phase shift unit is connected to the oscillation unit and the phase shift amount detection unit. Connected,
The value of the phase shift amount obtained by the phase shift amount detection unit connected to any one of the excitation coils and the phase shift amount obtained by the phase shift amount detection unit connected to the other one excitation coil Means for detecting sensor abnormality from the value of
The means for detecting the sensor abnormality includes a determination limit value including a flat portion formed by partially saturating the phase shift amount obtained by the phase shift amount detection unit connected to any one of the exciting coils. The phase shift amount at the boundary between the flat portion of the phase shift amount that constitutes the determination limit value and the normal change portion that is not the flat portion, and the phase shift amount detection unit connected to any one of the other excitation coils A rotation characterized in that a difference in phase shift amount at the same input angle is compared with a predetermined criterion value, and a sensor abnormality is detected when the difference exceeds the criterion value. Sensor.

Images