JP4369839B2 - Rotation sensor - Google Patents

Description

  The present invention relates to a rotation sensor used for detecting a rotation angle of a rotating body attached to 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 FIGS. 1 to 3 of Patent Document 1, the rotation sensor includes a rotor attached to a rotating shaft, a core body made of an insulating magnetic material, and at least one exciting coil accommodated in the core body. A fixed core and a rotation angle detector are provided. The exciting coil is composed of, for example, four exciting coils, and is arranged at equal intervals 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 an insulating magnetic material each having an AC magnetic field shielding property.

  The rotor includes a rotor mounting portion made of an insulating magnetic material and a sensing portion that is connected to the rotor through a stay 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. Thus, the width of the sensing unit in the radial direction is changed, and an eddy current having a magnitude corresponding to the width accompanying rotation is induced by the AC magnetic field.

Using the rotation sensor having such a configuration, the rotation angle of the rotor from 0 ° to 360 ° is detected using the impedance fluctuation of the exciting coil accompanying the generation of the eddy current.
JP 2003-202240 A (page 4-5, FIG. 1)

  However, when such a rotation sensor is attached to, for example, a steering shaft of an automobile and the rotation angle of the steering shaft is detected, the gap between the sensing portion of the rotor and the coil core changes due to the vibration of the vehicle, which becomes a detection output error. In some cases, an accurate rotation angle cannot be detected.

  In order to solve this, as shown in FIGS. 13 to 16 of Patent Document 1, a rotation sensor having a structure in which four pairs of fixed cores are attached to a case with a sensing part of the rotor interposed therebetween is considered. Yes. Each pair of fixed cores has a core body made of an insulating magnetic material and an exciting coil accommodated in the core body. Predetermined excitation coils are connected in series, and a magnetic circuit is formed around the fixed core by an alternating excitation current from the measuring means.

  In this way, by arranging four sets of fixed cores with a 90 ° phase, with two pairs of upper and lower parts sandwiching the rotor's sensing part in one rotation sensor, the rotor radial direction generated by the vibration of the rotating part The output fluctuation due to the change of the interval with each fixed core is reduced.

  However, in the rotation sensor described above, the rotor sensing unit needs to be disposed between the upper and lower fixed cores of each set of fixed cores. The assembly process is divided.

  A specific assembling process is introduced as an example. As shown in FIG. 10, the lower fixed cores 51 to 54 are assembled to the coil core holder 71, and the assembled coil core holder 71 is assembled to the lower case 22. The sensing unit 12 integrated in advance with the rotor 10 is assembled to the lower case 22.

  On the other hand, as shown in FIG. 11, the upper fixed cores 61 to 64 are assembled to the coil core holder 72 so that the coil core holder 72 is united with the coil core holder 71, and the upper case (not shown) is connected to the lower case 22. The rotary connector is completed by being fitted in.

  That is, in assembling the rotary connector in this process, the coil core holder 71 (72) holding the fixed cores 51 to 54 (61 to 64) has a total of 4 due to the restrictions on the assembly described above. Like the lower fixed cores 51 to 54, the four upper fixed cores 61 to 64 are divided into coil core holders 71 and 72 for mounting each of them, and a two-part configuration is formed.

  Therefore, the concentricity of each pair of the upper and lower fixed cores 51 to 54 and 61 to 64 depends on the positional accuracy of the upper and lower coil core holders 71 and 72, and is ideal in terms of component tolerance and assembly tolerance. It is difficult to assemble the rotation sensor in a general dimensional relationship, and it is necessary to use appropriate equipment for assembling with high accuracy, resulting in a very high cost.

  Further, if the coil core holders 71 and 72 configured separately are to be integrated, it is necessary that the sensing unit 12 of the rotor 10 can be slid from the side between the integrated coil core holders. That is, a relationship of a> b is required between the dimension a and the dimension b shown in FIGS. 10 and 11, and the size of the rotation sensor itself is increased.

  As shown in FIGS. 12 and 13, a structure in which four sets of integrated coil core holders 81 to 84 for individually holding the upper and lower fixed cores 51 to 54 and 61 to 64 are provided is also conceivable. However, in this case, it is difficult to dispose each pair by being shifted by 90 ° with respect to the relative positions of the respective sets, that is, with respect to the axis of the shaft S. This is because the relative position of each set of the fixed cores 51 to 54 and 61 to 64 depends on the accuracy of the mounting position of the coil core holders 81 to 84 with respect to the lower case 22.

  As described above, it is difficult to assemble the rotation sensor in a state where the sensing portions 12 of the rotor 10 are interposed at appropriate positions between the fixed cores of each set while accurately facing each other.

  Further, when assembling such a rotation sensor, a total of eight fixed cores are required, resulting in high costs. In order to reduce the cost of the rotation sensor, it is effective to reduce the number of fixed cores. However, in order to reduce the number of fixed cores, it is necessary not to impair the output characteristics of the rotation sensor. The

  As described above, when the fixed cores 51 to 54 and 61 to 64 are arranged to face each other at the four positions of the rotation sensor, the sensing unit 12 of the rotor 10 must be provided between the fixed cores arranged to face each other. In addition to various restrictions on assembly and parts structure, a large number of fixed cores must be used for one rotation sensor, which is an obstacle to providing an inexpensive and accurate rotation sensor. Yes.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a rotation sensor that is excellent in assembling property, reduces costs, and has excellent detection accuracy over a wide range of rotation angles.

In order to solve the above-mentioned problem, the rotation sensor according to the present invention is:
An excitation coil that is attached to a rotating shaft and that forms a magnetic circuit between a rotor having a conductive sensing portion whose width varies along the circumferential direction and an AC excitation current flowing through the rotor. And a fixed core formed of an insulating magnetic material and including a core body that holds the exciting coil, and the fixed core is attached to a holding member and extends in the axial direction of the shaft with respect to the sensing portion of the rotor In the rotation sensor, which is arranged to face each other at intervals,
The fixed core is provided as two sets of fixed core pairs arranged opposite to each other with the sensing part of the rotor interposed therebetween, and the holding member is a single component provided with two coil core holders, The two coil core holders are arranged at two locations where the central angle of the two sets of fixed cores with respect to the shaft axis is substantially excluding 180 °. By holding the fixed cores, the concentricity of the opposed fixed cores is maintained, and the distance between the opposed fixed cores and the sensing portion of the rotor is kept substantially constant. It is characterized by.

The rotation angle of the rotor attached to the shaft can be detected by only two fixed cores because the fixed core is arranged at two positions with the central angle made with respect to the shaft axis excluding 180 °. This makes it possible to reduce the number of fixed cores while maintaining high detection accuracy of the rotation sensor, thereby reducing the cost of the rotation sensor.
In addition, by arranging the fixed core on the integral holding member, the concentricity of the fixed cores facing each other can be accurately maintained, improving the assembly of the rotation sensor while maintaining high detection accuracy of the rotation sensor. Can be made.
In addition, by making the fixed cores a fixed core pair that is placed opposite to each other with the sensing part of the rotor in between, each fixed core pair can cancel out fluctuations in output characteristics with respect to vibration, and rotation angles with excellent vibration resistance Can be detected.
Further, since the number of fixed cores can be reduced as compared with the structure of a conventional rotation sensor having vibration resistance, the cost can be reduced accordingly.
In addition, since the rotation sensor according to the present invention does not have a conventional structure for attaching a holding member composed of two or more parts, the fixed core and the rotor are maintained while maintaining the concentricity between the fixed cores. It can be easily assembled while keeping the distance from the sensing part constant.
That is, in the conventional rotation sensor, a total of four sets of fixed cores that are paired up and down across the rotor's sensing portion are arranged at a predetermined angle, whereas in the rotation sensor according to the present invention, the rotor A total of two sets of fixed cores that form a pair of upper and lower sides sandwiching the sensing portion of the sensor unit are arranged on the holding member at a central angle of a predetermined angle with respect to the shaft axis, and the holding member that holds each fixed core is a coil core Since it is configured to be integrated with the holder, the structure becomes extremely simple.
In addition, since the rotation sensor according to the present invention has a single holding member for holding each fixed core, the concentricity of the fixed cores for each set arranged opposite to each other and a predetermined angle other than 180 ° The relative position of the fixed cores for each set placed apart from each other is no longer affected by the assembly error between the parts, and the rotor sensing section and the fixed cores or fixed cores are connected in the assembly process of the rotation sensor. Positioning can be performed with higher accuracy.

Moreover, the rotation sensor according to claim 2 of the present invention is the rotation sensor according to claim 1 ,
A central angle formed by the two fixed cores with respect to the axis of the shaft is substantially 90 °.

By arranging the two fixed cores so as to form a substantially 90 ° central angle with respect to the shaft axis, the concentricity between the fixed cores facing each other can be more accurately maintained. As a result, it is possible to improve the assembly of the rotation sensor while maintaining high detection accuracy of the rotation sensor. Further, since the number of fixed cores can be reduced as compared with the structure of a conventional rotation sensor having vibration resistance, the cost can be reduced accordingly.
According to a second aspect of the present invention, the rotation sensor according to the present invention has a configuration in which the two fixed cores are arranged so as to form a central angle of substantially 90 ° with respect to the shaft axis. Therefore, the sensing portion of the rotor can be slid and assembled with respect to the holding member from the lateral direction, and the assembly workability of the rotation sensor is excellent.

Moreover, the rotation sensor according to claim 3 of the present invention is the rotation sensor according to claim 1 or 2 ,
Each excitation coil is connected to an oscillation unit, a phase shift unit, and a phase shift amount detection unit,
The rotation angle of the rotor is detected based on the phase shift amount obtained by the phase shift amount detection unit of each excitation coil and the phase shift amount obtained by inverting the phase shift amount.

  By using the phase shift amount obtained by inverting the phase shift amount in addition to the phase shift amount obtained by the phase shift amount detection unit of each excitation coil, even a simple configuration with a small number of fixed cores can be used. The rotation angle can be detected over a wide range.

  According to the present invention, it is possible to obtain a rotation sensor that is excellent in assembling property, reduces cost, and has excellent detection accuracy over a wide range of rotation angles.

  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 where 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 will be described.

  As shown in FIGS. 1 and 2, the 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 arranged to face each other and a coil core holder 93 in which the fixed cores 32 and 42 are arranged to face each other. The holding member 90 is assembled to the rotation sensor 1 such that the coil core holders 92 and 93 form a central angle of 90 degrees with respect to the axis of the shaft S.

  Hereinafter, the structure of the holding member 90 and the fixed cores 31, 32, 41, and 42 will be described in detail. The holding member 90 is, for example, a rectangular made of synthetic resin (for example, FRP (fiber reinforced plastic) obtained by impregnating a glass fiber such as polybutylene terephthalate (PBT), nylon, polyphenylene sulfide (PPS), or ABS resin with an epoxy resin). The base portion 91 is a plate member having a shape and is attached to the lower case 22, and coil core holders 92 and 93 provided at one end of the base portion 91.

  One coil core holder 92 of the holding member 90 is provided with the fixed cores 31 and 41 facing each other while maintaining concentricity, and the other coil core holder 93 of the holding member 90 has the fixed cores 32, 42 are opposed to each other while maintaining concentricity. Further, 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. As a result, the fixed core 31 (32) on one side is disposed opposite to the fixed core 41 (42) on the other side across the rotor 10 with a predetermined gap G (see FIG. 2).

  A part of the holding member 90 includes a circuit board 95, and the circuit board 95 includes the rotation angle detection circuit 100. The rotation angle detection circuit 100 is connected to a power harness and a signal transmission wire harness via a plurality of electric wires (not shown) extending from the case 20 to the outside, and is provided outside the case 20. Connected to the device.

  As described above, the fixed cores 31 and 32 are disposed 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. On the other hand, the fixed cores 41 and 42 are disposed on the upper 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.

  The fixed core 31 and the fixed core 41 are arranged to face each other while maintaining the concentricity with the sensing unit 12 of the rotor 10 interposed therebetween, and the fixed core 32 and the fixed core 42 are also concentric with the sensing unit 12 of the rotor 10 interposed therebetween. Are arranged opposite to each other.

  As shown in FIG. 2, the fixed cores 31 and 32 on one side are made of an insulating magnetic material (for example, Ni—Zn-based, Mn—Zn-based, Mg—Zn-based ferrite, nylon, polypropylene (PP), A ring-shaped air gap made of polyphenylene sulfide (PPS), a mixture of thermoplastic synthetic resins having electrical insulation properties such as ABS resin, or ceramics, etc., formed in a cylindrical shape and containing an exciting coil on the upper surface side Core body 31a, 32a having a portion and exciting coils 31b, 32b accommodated in the core body 31a, 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 excitation coil 31b and the excitation coil 41b, and the excitation coil 32b and the excitation coil 42b are connected in series, and are electrically connected to the rotation angle detection circuit 100 of the holding member 90, and an AC excitation current is supplied to the coil. An alternating magnetic field is formed in the periphery, and a magnetic circuit is formed between the fixed cores that are paired with each other.

  The holding member 90 provided with the fixed cores 31 and 32 (41, 42), the circuit board 95 provided with the rotation angle detection circuit 100, and the rotor 10 are made of a metal or an insulating magnetic material having an AC magnetic field shielding property. It is accommodated in the case 20. The case 20 includes an upper case 21 and a lower case 22, and is attached to a fixing member (not shown) located in the vicinity of the shaft S via a bracket or the like (not shown).

  As shown in FIG. 1, the rotor 10 includes a rotor mounting portion 11 made of an insulating magnetic material, and a sensing portion 12 that is connected to the rotor mounting portion 11 via the stays 12a and 12b and whose width continuously changes in the circumferential direction. It consists of. The sensing unit 12 is made of a conductive metal such as aluminum, copper, silver, or brass. Further, as shown in the figure, 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. Then, 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 which will be described later with the rotation of the rotor, according to the rotation angle of the rotor 10. 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. This variation in impedance corresponds to a variation in 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 as 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 can be detected by a rotation angle detection circuit 100 described later and converted into an angle signal of the rotor 10 to detect the rotation angle of the rotor 10. .

  As shown in the circuit block diagram of FIG. 3, the rotation angle detection circuit 100 of the rotation sensor 1 includes an oscillation circuit 110 that outputs an oscillation signal having a specific frequency and an eddy current generated in the sensing unit 12. The phase shift unit 120 (121, 122) that shifts the phase of the oscillation signal input from the oscillation unit 110 in response to this, and the phase shift amount detection unit 130 (131, 132) that detects the phase shift amount are detected. A phase shift amount conversion unit 140 (141, 142) that converts the phase shift amount into a corresponding parameter, an amplification unit 150 (151, 152) that amplifies the phase shift amount output from the phase shift amount conversion unit 140, A signal processing unit 160 that calculates a rotation angle from a parameter corresponding to the phase shift amount, and is input to the phase shift unit 120 And detects the rotation angle. Although not described in this embodiment, a frequency divider or a buffer may be provided between the oscillation circuit 111 and the phase shift unit 120 as necessary.

  The rotation sensor 1 having the above configuration uses the impedance variation of the excitation coils 31b, 32b, 41b, and 42b due to the rotation of the shaft S, and performs signal processing on the output by the rotation angle detection circuit 100. Is detected over the entire rotation angle of 0 ° to 360 °.

  Next, how to install the rotation sensor will be described. First, the fixed cores 31 and 41 are attached to the coil core holder 92 of the holding member 90, and the fixed cores 32 and 42 are attached to the coil core holder 93 of the holding member 90. Then, the sensing unit 12 of the rotor 10 is inserted between the fixed cores arranged to face the holding member 90. Thus, with one set of fixed cores 31, 41 maintaining concentricity and the other set of fixed cores 32, 42 maintaining concentricity, the rotor 10 is placed in a proper position between the fixed cores of each set. The sensing unit 12 is arranged. Then, the holding member 90 and the rotor 10 temporarily assembled in this way are attached to the lower case 22. Next, the upper case 21 is attached to the lower case 22 to finish the assembly of the rotation sensor 1.

  As described above, the rotation sensor 1 according to the present embodiment does not have a structure for attaching a conventional holding member composed of two or more parts, and thus maintains the concentricity between the fixed cores and The fixed cores 31 and 41 (32 and 42) and the sensing unit 12 of the rotor 10 can be easily assembled while keeping the distance between them constant.

  That is, in the conventional rotation sensor, a total of four sets of fixed cores that are paired up and down across the sensing part of the rotor are arranged at a phase of 90 °, whereas in the rotation sensor according to this embodiment, A total of two sets of fixed cores that form a pair of upper and lower sides sandwiching the sensing portion of the rotor are arranged on the holding member 90 with a central angle of 90 ° with respect to the shaft axis. The holding member 90 that holds the fixed cores 32 and 42 includes coil core holders 92 and 93 and is integrated. Further, since the holding member 90 is provided with the rotation angle detection circuit 100 via the circuit board 95, the fixed cores 31, 32, 41, 42 are arranged at positions close to the rotation angle detection circuit 100.

  Since the rotation sensor 1 according to the present embodiment has the above-described configuration, the sensing unit 12 of the rotor 10 can be slid and assembled with respect to the holding member 90 from the lateral direction. There is no need to divide 90 into two for the upper and lower fixed cores. Further, it is not necessary to divide the holding member 90 for each set of four fixed cores as in the prior art. As a result, the number of component parts can be reduced.

In addition to this, since the rotation sensor according to the present embodiment has a holding member 90 that holds each fixed core as one component, the same set of fixed cores 31 and 41 (32 and 42) for each set disposed facing each other. The relative position of the fixed cores 31, 4 1 (32, 42) for each group arranged at 90 ° apart from the core is not affected by the assembling error between components, and the rotation sensor 1 is assembled. In the process, the sensing unit 12 of the rotor 10 and the fixed cores 31, 32, 41, 42 and the fixed cores can be positioned with higher accuracy.

  In the case of the rotation sensor 1 according to the present embodiment, since the two sets of fixed cores 31, 32, 41, 42 are all disposed in the vicinity of the rotation angle detection circuit 100 provided in the holding member 90, the rotation angle The length of the coil wire for electrical connection between the detection circuit 100 and the fixed cores 31, 32, 41, and 42 can be shortened, thereby making it less susceptible to electrical noise.

  Next, a specific signal processing method for performing rotation angle detection using the rotation sensor 1 assembled as described above will be described. First, the oscillation circuit 111 transmits an oscillation signal having a specific frequency to each excitation coil 31b, the excitation coil 41b (coil B1), the excitation coil 32b, and the excitation coil 42b (coil B2). As a result, each oscillation signal is output to each phase shift unit 120 comprising resistors R1, R2, excitation coils B1, B2, and capacitors C1, C2. At this time, the phase of the voltage signal at both ends of the capacitors C1, C2 changes due to fluctuations in the impedance of the exciting coils B1, B2. The voltage signals at both ends of the capacitors C1 and C2 are output to each phase shift amount detection unit 130. Each phase shift amount detector 130 detects the phase shift amount of the voltage signal across the capacitors C1 and C2. Each phase shift amount conversion unit 140 converts each detected phase shift amount into a corresponding voltage.

  Then, this voltage value is transmitted to the amplification unit 150 (151 and 152) connected to the subsequent stage of the phase shift amount conversion unit 140. The amplifier 150 is an electronic circuit composed of an operational amplifier or the like.

  The signal processing unit 160 uses, for example, a one-chip microprocessor as an arithmetic processing unit, and the signal processing unit 160 measures the rotation angle of the rotor 10 based on the voltage value input from each amplification unit 150.

  Thereby, for example, the output voltage (V) of one exciting coil (coil B1) is obtained as shown in FIG. As is apparent from the relationship between the rotor rotation angle and the output voltage with respect to the excitation coil shown in the figure, peak-shaped protrusions corresponding to the two stays 12a and 12b of the sensing unit 12 appear at positions 180 ° apart. In addition, except for this portion, a detection band Q is obtained in which an output voltage improved in terms of a characteristic that linearly changes in direct proportion to the rotation angle as compared with the conventional rotation sensor can be obtained.

  Since the excitation coils 31b and 41b and the excitation coils 32b and 42b are arranged at a central angle of 90 ° as shown in FIG. 5, the linearity corresponding to the rotor rotation angle is excellent. As shown in FIG. 6, the detection band Q can be continuously generated while being shifted by a phase of 180 ° from the rotor rotation angle of 0 ° to 360 °. In FIG. 6, the peak-like protrusions are omitted.

  As apparent from FIG. 6, an area where the linearity of the output signal corresponding to the phase shift amount is excellent and an area where it is not so are generated according to the change of the rotor rotation angle. In order to facilitate understanding of FIG. 6, FIG. 7 shows a region having excellent linearity in the characteristic diagram corresponding to the phase shift amount by a bold line, and shows the other by a thin line. The area with excellent linearity is slightly larger than 90 °. In order to successfully joint the linearity portions of the two coil output signals, it is necessary that the arrangement positions of the respective excitation coils be shifted by 90 ° at the central angle as in the rotation sensor according to the present embodiment. Thus, it is most convenient to determine the angular position of the rotor that the coils are arranged with a central angle of 90 °.

  Next, a method for determining the rotational angle position of the rotor 10 will be described in detail. In the signal processing algorithm, in order to convert the two coil detection signals into a rotation angle of 360 °, it is necessary to appropriately select (discriminate) the two types of signals detected from the signal processing circuit upon detection.

  That is, among the signals S1 and S2 in which the signals corresponding to the phase shift amounts of the two exciting coils arranged with the rotor 10 at an arbitrary position and the detected center angles shifted from each other by 90 ° are respectively S1 and S2. It is necessary to select a coil signal with excellent linearity (the thick line portion in FIG. 7).

To do this, it is necessary to first determine the angle range. One coil signal as shown in FIGS. 6 and 7 has a period of 360 °. That is, if the two coils are arranged at a rotation angle of 90 °, the output signal level at angle θ = the output signal level at angle (θ + 90 °), and the same signal level is either angle θ or angle (θ + 90). It is necessary to determine whether or not This specific determination method is as follows.

First, the range of the linearity signal level is set. That is, as shown in FIG. 7, the angular position is calculated using a signal within the linearity interval range. Specifically:
In the case of the rotor rotation position area X1 (0 ° ≦ α <45 °, 315 ° ≦ α <360 °): the condition is S1> S2, and the linearity of the signal of S1 is excellent. Therefore, the angular position of 0 ° ≦ α <45 °, 315 ° ≦ α <360 ° is calculated using the S1 signal.
In the case of the rotor rotation position area X2 (45 ° ≦ α <135 °): the condition is S2> S1, and the signal linearity of S2 is excellent. Therefore, an angular position of 45 ° ≦ α <135 ° is calculated using the S2 signal.
In the case of the rotor rotational position area X3 (135 ° ≦ α <225 °): the condition is S2> S1, and the linearity of the signal of S1 is excellent. Therefore, an angular position of 135 ° ≦ α <225 ° is calculated using the S1 signal.
In the case of the rotor rotation position area X4 (225 ° ≦ α <315 °): the condition is S1> S2, and the signal linearity of S2 is excellent. Therefore, the angular position of 225 ° ≦ α <315 ° is calculated using the S2 signal.

  All the above determination processing is executed by the signal processing unit 160 shown in FIG. Specifically, as shown in FIG. 8, in addition to the signals S1 and S2 corresponding to the phase shift amount obtained by the phase shift amount detection unit 130 of each excitation coil, the phase shift in which the phase shift amount is inverted, respectively. Inverted signals S1R and S2R corresponding to the quantities are obtained, and an output signal having the best linearity is selected based on these signals and the inverted signals. FIG. 8 shows the signals S1R and S2R whose outputs are inverted with respect to the signals S1 and S2 that are 180 ° out of phase with each other and superimposed them.

  Next, the signal processing unit 160 determines which rotation section the rotor 10 is currently in from the magnitude relationship among the signal S1, the signal S2, the signal S1R, and the signal S2R according to the rotation angle of the rotor 10. Specifically, when the output of the phase shift amount is S2R <S1 <S1R <S2, it is determined that the rotor rotation position zone X1b is 0 ° <rotor rotation angle <45 °. When the output of the phase shift amount is S1 <S2R <S2 <S1R, it is determined that the rotor rotation position area X2a is 45 ° <rotor rotation angle <90 °. When the output of the phase shift amount is S1 <S2 <S2R <S1R, it is determined that the rotor rotation position area X2b is 90 ° <rotor rotation angle <135 °. When the output of the phase shift amount is S2 <S1 <S1R <S2R, it is determined that the rotor rotational position area X3a is 135 ° <rotor rotational angle <180 °. When the output of the phase shift amount is S2 <S1R <S1 <S2R, it is determined that the rotor rotation position area X3b is 180 ° <rotor rotation angle <225 °. When the output of the phase shift amount is S1R <S2 <S2R <S1, it is determined that the rotor rotational position area X4a is 225 ° <rotor rotational angle <270 °. When the output of the phase shift amount is S1R <S2R <S2 <S1, it is determined that the rotor rotational position area X4b is 270 ° <rotor rotational angle <315 °. When the output of the phase shift amount is S2R <S1R <S1 <S2, it is determined that the rotor rotational position zone X1a is 315 ° <rotor rotational angle <360 °.

  In this way, after determining which section the rotor rotation angle is in, when the rotor rotation angle is in the above-described rotor rotation position area X1, the linearity of the signal S1 is excellent. Detect the rotation angle. When the rotation angle of the rotor 10 is in the rotor rotation position area X2 described above, the rotation angle of the rotor 10 is detected from the inverted signal S2R of the signal S2 having excellent linearity. When the rotation angle of the rotor 10 is in the rotor rotation position area X3 described above, the rotation angle of the rotor is detected from the inverted signal S1R of the signal S1 having excellent linearity. Further, when the rotation angle of the rotor is in the rotor rotation position area X4 described above, the linearity of the signal S2 is excellent, so the rotation angle of the rotor is detected from the signal S2.

  As described above, when detecting the rotation angle of the rotor, the rotation angle of the rotor can be accurately measured over a wide range even with a simple configuration in which two sets of fixed cores having a central angle of 90 ° are provided with excitation coils. Can be detected.

  In the above-described embodiment, the rotor rotation angle detection method when 0 ° ≦ rotor rotation angle <360 ° has been described. However, the same principle applies to rotor rotation angle detection when −360 ° ≦ rotor rotation angle <0 °. It goes without saying that it can be done.

  Note that the central angle formed by the two fixed cores with respect to the shaft axis as in the rotation sensor according to the above-described embodiment is not necessarily 90 °. If the center angle formed is arranged at two positions substantially excluding 180 °, the effect of the present invention can be exhibited. However, since the center angle formed by the two fixed cores with respect to the shaft axis is substantially 90 °, the output characteristics shown in FIGS. 7 to 9 can be obtained. It can be said that the arrangement of the fixed core is most preferable in order to detect the rotation angle with high accuracy.

  In addition, the fixed cores do not necessarily need to be arranged as a pair of fixed cores arranged opposite to each other with the sensing part of the rotor interposed therebetween as in the rotation sensor according to the above-described embodiment. However, because the fixed cores are placed facing each other across the rotor sensing section, each fixed core pair can cancel out fluctuations in output characteristics with respect to vibration, and rotation angle detection with excellent vibration resistance can be achieved. Therefore, it can be said that the arrangement of the fixed cores facing each other with the sensing portion of the rotor interposed therebetween is a preferable arrangement mode.

  The rotation sensor according to the present invention is particularly suitable for detecting the rotation angle of a vehicle steering apparatus that is quite susceptible to vibration. However, the rotation sensor according to the present invention can be applied to any sensor as long as it obtains the relative rotation angle and rotation torque between rotating shafts that rotate while vibrating, such as a robot arm.

It is the top view which showed the internal structure of the rotation sensor concerning one Embodiment of this invention. It is the II-II sectional view shown in the state where the rotation sensor shown in Drawing 1 was attached to the steering shaft. It is a circuit block diagram explaining the signal processing circuit of the rotation sensor shown in FIG. FIG. 4 is a diagram illustrating a phase shift amount for each rotor rotation angle obtained by one amplification unit in the circuit block diagram of FIG. 3. It is the top view which showed clearly the arrangement | positioning relationship between the rotor sensing part of a rotation sensor shown in FIG. 1, and two exciting coils. It is a figure which shows the output characteristic corresponding to the phase shift amount of the two exciting coils shown in FIG. FIG. 4 is an output characteristic diagram showing a state in which outputs corresponding to phase shift amounts obtained by both amplifying units in the circuit block diagram of FIG. 3 are superimposed by a signal processing unit. FIG. 8 is an output characteristic diagram illustrating a state in which an output corresponding to the inverted phase shift amount is further superimposed on the output characteristic diagram of FIG. 7. FIG. 9 is an output characteristic diagram illustrating a state in which joint processing is performed on the output characteristic diagram of FIG. 8. It is the top view which showed the internal structure of the conventional rotation sensor. It is the top view which showed the upper side fixed core and upper side holding member of the rotation sensor shown in FIG. It is the top view which showed the internal structure of the conventional rotation sensor different from FIG. It is XIII-XIII sectional drawing of the rotation sensor shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rotation sensor 10 Rotor 11 Rotor attachment part 12 Sensing part 12a, 12b Stay 20 Case 21 Upper case 22 Lower case 31, 32 Fixed core 31a, 32a Core main body 31b, 32b Excitation coil 41, 42 Fixed core 41a, 42a Core main body 41b , 42b Excitation coil 51-54 Fixed core 61-64 Fixed core 71, 72 Coil core holder 81-84 Coil core holder 90 Holding member 91 Base part 92 Coil core holder 93 Coil core holder 95 Circuit board 100 Rotation angle detection circuit 110 Oscillation Unit 111 Oscillator 120 (121, 122) Phase shift unit 130 (131, 132) Phase shift amount detection unit 140 (141, 142) Phase shift amount conversion unit 150 (151, 152) Amplification unit 160 Signal processing unit S Yafuto

Claims (3)

An excitation coil that is attached to a rotating shaft and that forms a magnetic circuit between a rotor having a conductive sensing portion whose width varies along the circumferential direction and an AC excitation current flowing through the rotor. And a fixed core formed of an insulating magnetic material and including a core body that holds the exciting coil, and the fixed core is attached to a holding member and extends in the axial direction of the shaft with respect to the sensing portion of the rotor In the rotation sensor, which is arranged to face each other at intervals,
The fixed core is provided as two sets of fixed core pairs arranged opposite to each other with the sensing part of the rotor interposed therebetween, and the holding member is a single component provided with two coil core holders, The two coil core holders are arranged at two locations where the central angle of the two sets of fixed cores with respect to the shaft axis is substantially excluding 180 °. By holding the fixed cores, the concentricity of the opposed fixed cores is maintained, and the distance between the opposed fixed cores and the sensing portion of the rotor is kept substantially constant. A rotation sensor.   The rotation sensor according to claim 1, wherein a central angle formed by the two fixed cores with respect to the axis of the shaft is substantially 90 °. Each excitation coil is connected to an oscillation unit, a phase shift unit, and a phase shift amount detection unit,
Wherein based on the phase shift amount detected phase shift amount obtained by the unit and the phase shift amount obtained by inverting each said phase shift amount of the exciting coil, and detects the rotation angle of the rotor, claim The rotation sensor according to claim 1 or 2.

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