JP4003526B2 - Rotation angle sensor and torque sensor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a rotation angle sensor for measuring a rotation angle of a rotating body and a sensor for measuring a torque acting on a torsion bar from a difference between rotation angles generated at both ends of the torsion bar. The sensor of the present invention is suitable for measuring a steering angle and a steering torque for an electric power steering device of a vehicle.
[0002]
[Prior art]
Conventionally, an electric power steering apparatus includes a torque sensor having the following configuration. A conventional torque sensor includes a torsion bar that twists when a torque acts, a first rotation angle sensor fixed to the upper end of the torsion bar, and a second rotation angle sensor fixed to the lower end of the torsion bar. Each rotation angle sensor is a resolver type rotation angle sensor, and includes a rotor coil that rotates together with the torsion bar, and a stator coil that is fixed to a fixed cylinder.
The rotation angle of the upper end side of the torsion bar is measured from the output value of the stator coil on the upper end side of the torsion bar, and the rotation angle of the lower end side of the torsion bar is measured from the output value of the stator coil on the lower end side of the torsion bar. The magnitude of the torque causing twisting of the torsion bar is measured from the difference in rotation angle.
[0003]
[Problems to be solved by the invention]
The resolver-type rotation angle sensor requires a large number of rotor coils and stator coils, has a complicated structure, increases manufacturing costs, and is difficult to reduce in size. Furthermore, since this type of coil may be disconnected or short-circuited, there is a problem in terms of reliability.
Accordingly, an object of the present invention is to provide a rotation angle sensor and a torque sensor that have a simple structure, can be manufactured at low cost, are easily miniaturized, and have high reliability.
[0004]
[Means for solving the problem, operation and effect]
The rotation angle sensor according to the present invention generates an inner magnetic body, an outer magnetic body arranged on the outer side of the inner magnetic body with a gap, and a magnetic flux circulating through the inner magnetic body and the outer magnetic body through the gap. A magnet and an MI sensor arranged in the middle of the magnetic path are provided. The inner magnetic body and the outer magnetic body can be rotated relative to each other, and the magnitude of the magnetic flux circulating through the gap between the inner magnetic body and the outer magnetic body varies depending on the relative rotation angle between the inner magnetic body and the outer magnetic body. To do. The MI sensor detects the magnitude of the circulating magnetic flux that changes depending on the relative rotation angle between the inner magnetic body and the outer magnetic body. The relative rotation angle can be measured from the output of the MI sensor.
[0005]
Here, the “MI sensor” refers to an ultra-sensitive magnetic sensor using a so-called magnetic impedance effect (MI effect). The MI effect is as follows. That is, when a high-frequency current or a pulse current is passed through an elongated high magnetic permeability metal, a skin effect is produced in the metal. The square of the current path depth δ at this time is proportional to the electrical resistivity ρ, but inversely proportional to the angular frequency ω of the high-frequency current and the magnetic permeability μ in the magnetic field direction caused by the current. The magnetic permeability μ in the magnetic field direction varies with the external magnetic field Hex. Accordingly, the depth δ of the current path varies depending on the external magnetic field Hex. Therefore, the electric resistance and the inductance change at the same level, and the magnitude of the impedance changes with the external magnetic field Hex. For example, when an amorphous wire is used, the rate of change of the magnitude of the impedance Z can be easily set to about 100% per Oersted. Such an electromagnetic phenomenon is called the MI effect.
In the field of applied magnetism, an electromagnetic phenomenon called GMR (giant magnetoresistance) effect is known. Recently, a magnetic sensor using this effect has been proposed in part, but a magnetic sensor using the MI effect is proposed. The higher sensitivity can be realized. Note that a magnetic sensor using the MI effect has very low power consumption and also has a very fast response because a high-frequency current becomes a carrier for magnetic modulation.
[0006]
In the first aspect of the invention, when the inner magnetic body and the outer magnetic body rotate relative to each other, the magnetic resistance of the magnetic path formed by the gap between the inner magnetic body and the outer magnetic body changes, and the inner magnetic body and the outer magnetic body change. The magnitude of the magnetic flux that circulates between the body and the gap changes. The MI sensor detects the magnitude of the changing magnetic flux. The output of the MI sensor depends on the magnitude of the magnetic flux, the magnitude of the magnetic flux depends on the magnetic resistance, and the magnetic resistance depends on the relative rotation angle between the inner magnetic body and the outer magnetic body. The relative rotation angle between the magnetic body and the outer magnetic body can be measured.
In this sensor, an ultrasensitive MI sensor is used in place of the coil in order to detect the magnitude of the magnetic flux, so that a highly sensitive rotation angle sensor can be provided. This rotation angle sensor has a simple structure, can be manufactured at low cost, is easy to miniaturize, and has high reliability.
[0007]
  The rotation angle sensor of the present inventionSaThe shortest distance between the inner and outer magnetic bodies varies depending on the relative rotation angle between the inner and outer magnetic bodies.The
  The inner magnetic body and the outer magnetic body are separated by a gap (air gap) in which magnetic flux does not easily flow. However, as the shortest distance increases, the magnetic resistance of the magnetic path increases and the magnitude of the magnetic flux decreases. As the shortest distance becomes shorter, the magnetic resistance of the magnetic path decreases and the magnitude of the magnetic flux increases.
[0008]
  The rotation angle sensor of the present invention isThe outer shape of the inner magnetic body is formed in a substantially regular polygonal shape, and the inner shape of the outer magnetic body is formed in a circular shape having a protrusion protruding inward.TheThe shortest distance between the inner magnetic body and the outer magnetic body changes depending on the relative rotation angle between the inner magnetic body and the outer magnetic body, and the magnitude of the magnetic flux circulating through the gap between the inner magnetic body and the outer magnetic body is on the inner side. It varies depending on the relative rotation angle between the magnetic body and the outer magnetic body.
  In this case, when the inner magnetic body and the outer magnetic body rotate relative to each other, the MI sensor voltage becomes a clean signal having a sine wave or a waveform similar to the sine wave, and the mathematics for calculating and converting the signal waveform into a rotation angle is simplified. As a result, high accuracy can be achieved relatively easily.
[0009]
  The MI sensor is preferably fixed to the outer magnetic body.2).
  When the MI sensor is provided on the rotating body side, it is troublesome to take out the wiring. On the other hand, if the MI sensor is fixed to the outer magnetic body, the wiring drawing is simplified.
[0010]
  Preferably, the magnet is fixed to the outer magnetic body.3). In this case, the inner magnetic body is greatly simplified.
[0011]
  It is preferable that the MI sensor and the magnet are fixed to the outer magnetic body at symmetrical positions sandwiching the rotation center of the inner magnetic body.4). In this case, it is difficult for noise to be applied to the output voltage of the MI sensor, and an output voltage that varies greatly depending on the relative rotation is obtained.
[0012]
  In the rotation angle sensor of the present invention,The outer shape of the inner magnetic body is formed in a substantially regular n-square shape.AndPreferably, the first MI sensor and the second MI sensor are fixed at positions separated by an odd multiple of 360 ° / 2n on the inner circumference side of the outer magnetic body.5, 6).
  When two MI sensors are arranged in this positional relationship, one MI sensorIs approximately positive nWhen the inner magnetic body having a rectangular outer shape is opposed to the corner of the inner magnetic body, the other MI sensor is opposed to the midpoint of the side extending between the corners of the inner magnetic body. Therefore, the distance between the sensor installation part with the former MI sensor and the inner magnetic body is minimized, while the distance between the sensor installation part with the latter MI sensor and the inner magnetic body is maximized. The phase difference between the sensor outputs obtained by the two MI sensors is 180 °, and if a predetermined calculation is performed based on these two types of sensor outputs, the temperature variable can be eliminated. In other words, as a result of the temperature compensation being possible, it is possible to provide a highly accurate rotation angle sensor that is resistant to temperature changes.
[0015]
  By using a pair of the rotation angle sensors described above, a sensor that measures the torque acting on the torsion bar can be realized. That is, it is claimed at one end of a torsion bar extending along the rotation axis.Any one of 1 to 6A rotation angle sensor is connected to the other end of the torsion bar.Any one of 1 to 6A torque sensor can be realized by connecting a rotation angle sensor.7).
  In this case, the pair of rotation angle sensors can detect the rotation angle at one end of the torsion bar and the rotation angle at the other end of the torsion bar, and detect the difference between them, that is, the twist angle of the torsion bar. And the magnitude of the torque causing the twist can be measured.
[0017]
  OrA torsion bar extending along the rotation axis; a first magnetic body connected to one end of the torsion bar and having a first protrusion; and a second magnetic body connected to the other end of the torsion bar and facing the first protrusion. A second magnetic body having a protrusion, a first magnetic body, a third magnetic body disposed outside the second magnetic body, a “first magnetic flux circulating through the first magnetic body and the third magnetic body”, and a “first magnetic body” 1 magnetic body, 2nd magnetic body, and 2nd magnetic flux circulating through 3rd magnetic body "AndA magnet to be generated, a first MI sensor arranged in the middle of the first magnetic path through which the first magnetic flux flows, and a second MI sensor arranged in the middle of the second magnetic path through which the second magnetic flux flows.Can also be configured. This torque sensorIsWhen the torsion bar is twisted, the opposing area of the first protrusion and the second protrusion changes, and the output value of the first MI sensor and the output value of the second MI sensor change accordingly.8).
  The effect of temperature can be eliminated by processing both output values. Further, when the output of the first MI sensor increases, the output of the second MI sensor decreases. When the output of the first MI sensor decreases, the output of the second MI sensor increases. Therefore, a large output change is obtained by taking the difference between the two. be able to.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
The main features of the embodiments of the present invention to be described later will be described.
(Form 1) The rotation angle sensor according to claim 1, comprising a rotor that is an inner magnetic body and a stator that is an outer magnetic body, and the outer shape of the rotor is formed in a substantially square shape.
(Mode 2) The first sensor installation portion and the second sensor installation portion are protruded at different positions on the inner peripheral side of the stator, the first MI sensor is installed in the first sensor installation portion, and the second sensor installation portion is Install 2MI sensor. A rotation angle sensor, wherein the outer shape of the rotor is substantially square, and the angle formed by the first MI sensor and the second MI sensor with respect to the rotation center of the rotating body is set to an odd multiple of 45 °.
[0019]
【Example】
First Embodiment FIG. 1 shows a schematic diagram of the main part of a rotation angle sensor 2 of the first example, FIG. 2 shows a schematic diagram of the main part when the rotor 4 rotates 45 ° from the state of FIG. FIG. 3 shows a graph of the sensor output of the rotation angle sensor 2.
[0020]
As schematically shown in FIG. 1, the rotation angle sensor 2 of the present embodiment includes a rotor 4 that is an inner magnetic body made of a magnetic material such as steel and a stator 6 that is an outer magnetic body made of a similar magnetic material. And. A fixed hole 8 having a circular cross section is provided at the center of the rotor 4, and a motor shaft 10 that is a target for measuring a rotation angle is fixed to the fixed hole 8. When the motor shaft 10 rotates, the rotor 4 also rotates integrally.
[0021]
An annular stator 6 is disposed on the outer peripheral side of the rotor 4 so as to be coaxial with the motor shaft 10 and the rotor 4. The stator 6 and the rotor 4 are separated by a predetermined gap (air gap).
A projecting piece 12 extending toward the rotation center O of the motor shaft 10 is projected from a predetermined location on the inner peripheral side of the stator 6. A permanent magnet 14 is installed at the tip of the protruding piece 12. The permanent magnet 14 is arranged with the N pole facing the inner periphery and the S pole facing the outer periphery.
[0022]
On the inner peripheral side of the stator 6, another protruding piece 16 extending toward the rotation center O of the motor shaft 10 protrudes from a position (symmetrical position) facing the protruding piece 12 across the motor shaft 10. . An MI sensor 18 is installed at the tip of the projecting piece 16.
[0023]
The permanent magnet 14 generates a magnetic flux that circulates in the order of the magnet 14 → the gap (air gap) → the rotor 4 → the gap (air gap) → the MI sensor 18 → the projecting piece 16 → the stator 6 → the projecting piece 12. The MI sensor 18 is in the middle of the magnetic path through which the magnetic flux circulates, and detects the magnitude of the circulating magnetic flux.
[0024]
As described above, the “MI sensor” refers to an ultrasensitive magnetic sensor using the MI effect. The MI sensor 18 to be used is not particularly limited, but in this embodiment, an MI element in which pickup means is provided around an amorphous wire (composition: 4% Fe68% Co13% Si15% B) is used. In addition, canceling means for creating a magnetic field state that apparently cancels the external magnetic field may be provided. The amorphous wire is electrically connected to a pulse signal generation circuit provided separately from the MI element. The pulse signal generation circuit includes a DC power supply circuit and a chopper circuit, and outputs a predetermined pulse current to the amorphous wire. The pickup means is electrically connected to a signal processing circuit provided separately from the MI element. The current picked up by the pick-up means is processed by a signal processing circuit and then output as a sensor output signal. Since this type of MI sensor 18 is driven by a pulse signal, the power consumption is extremely small and is about several tens of mW at most.
[0025]
As shown in FIG. 1, in the rotation angle sensor 2 of the present embodiment, the outer shape of the rotor 4 is formed to be rotationally symmetric, more specifically, formed to have a substantially square shape. Yes. The four corners of the rotor 4 are somewhat rounded so that the sensor output waveform is a sine wave with respect to the rotation angle.
[0026]
The inner end surface part of the permanent magnet 14 installed at the tip of the projecting piece 12 and the inner end surface part of the MI sensor 18 installed at the tip of the projecting piece 16 are closer to the rotor 4 side than the other parts of the stator 6. is doing. Most of the magnetic flux emitted from the permanent magnet 14 is configured to flow preferentially through an air gap formed inside the permanent magnet 14 and an air gap formed inside the MI sensor 18. That is, the distance L1 between the inner end surface of the permanent magnet 14 and the outer periphery of the rotor 4 is the shortest distance between the rotor and the stator, and the distance L2 between the inner end surface of the MI sensor 18 and the outer periphery of the rotor 4 is between the rotor and the stator. The shortest distance. The inner shape of the remaining portion of the stator 6 is located outside, and the distance between the rotor and the remaining portion of the stator 6 is large. Clearly comparing FIG. 1 and FIG. 2, the shortest distances L1, L2 between the rotor and the stator vary depending on the relative rotation of the rotor and the stator. When the rotor 4 is at the rotational position shown in FIG. 1, the MI sensor 18 is in a state facing one corner of the rotor 4, and the permanent magnet 14 is in a state facing another corner of the rotor 4. At this time, the values of L1 and L2 are both minimum values. In other words, the two air gaps are both minimized. As a result, the magnitude of the magnetic flux flowing through the magnetic path R1 increases, and the largest voltage signal is output from the MI sensor 18 at this time. When the rotor 4 is at the rotational position shown in FIG. 2, the MI sensor 18 is in a state facing the midpoint of one side of the rotor 4, and the permanent magnet 14 is in a state facing the midpoint of another side of the rotor 4. At this time, the values of L1 and L2 are both maximum values. In other words, the two air gaps are both maximum values. As a result, the magnitude of the magnetic flux flowing through the magnetic path R1 decreases, and the smallest voltage signal is output from the MI sensor 18 at this time.
The shortest distances L1 and L2 and the magnitude of the magnetic flux flowing through the magnetic path R1 increase and decrease with a 90 ° period as the rotor 4 rotates. As a result, the output voltage of the MI sensor 18 has a sinusoidal waveform that changes at a cycle of 90 ° with respect to the relative rotation angle, as shown in the graph of FIG.
[0027]
The output voltage of the MI sensor 18 is input to a calculation means (not shown), and a predetermined calculation is performed. That is, the number of occurrences and the voltage value of the maximum value / minimum value of the signal voltage are specified, and the rotation angle θ (°) between the rotor 4 and the motor shaft 10 is obtained based on them.
[0028]
Now, according to the rotation angle sensor 2 of the present embodiment configured as described above, the following operational effects can be obtained.
In this embodiment, the magnitude of the magnetic flux flowing through the magnetic path R1 is detected by the MI sensor 18 provided in the middle of the magnetic path R1. Since the output of the MI sensor 18 changes according to the magnitude of the magnetic flux, the rotation angle is detected from this sensor output. In the present embodiment, since the MI sensor 18 is used as the magnetic flux detection means instead of the conventionally used coil, a highly sensitive rotation angle sensor 2 can be provided. Moreover, according to the present embodiment, the rotation angle sensor 2 that can be manufactured relatively easily can be provided because the winding of the coil is not necessary. Furthermore, in the rotation angle sensor 2 of the present embodiment, since the detection coil that causes an increase in size and the occurrence of a failure is not an essential component, the entire size can be easily reduced and the reliability can be improved.
Further, in the rotation angle sensor 2 of the present embodiment, the outer shape of the rotor 4 is formed in a substantially square shape so that the shortest distances L1 and L2 between the rotor 4 and the stator 6 are periodically changed as the rotor 4 rotates. ing. The approximate squares have the same distance from the center of gravity of the figure (here, the same as the rotation center O) to the four corners, the distances from the center of gravity to the four sides are also equal, and the corners are centered on the center of gravity. The angle also has properties such as being equal to 90 °. Therefore, when the rotor 4 whose outer shape is formed in a substantially square shape rotates, the shortest distances L1 and L2 between the rotor 4 and the stator 6 change with a 90 ° period. At this time, the MI sensor 18 outputs the maximum output value and the minimum output value alternately and regularly, and a clean sine wave signal waveform can be obtained. This is convenient when the rotation angle is detected by arithmetic processing based on the signal waveform, and as a result, high accuracy can be achieved relatively easily.
In the rotation angle sensor 2 described above, the MI sensor 18 is provided in the sensor installation portion 16 that protrudes from the inner peripheral side of the stator 6 that is a stationary member. Therefore, unlike the case where the MI sensor 18 is provided in the rotor 4 on the rotating side, it is not necessary to adopt a complicated wiring drawing structure. Therefore, simplification of the sensor structure, reduction in manufacturing cost, improvement in reliability, etc. can be achieved.
[0029]
(Second embodiment)
Next, the rotation angle sensor 22 of the second embodiment will be described. Here, the same components as those in the first embodiment are designated by the same member numbers, and detailed description thereof is omitted. FIG. 4 shows a schematic diagram of a main part of the rotation angle sensor 22 of the second embodiment. In this embodiment, the permanent magnet 14 on the stator 6 side is omitted, but a rotor 24 having a configuration different from that of the first embodiment is used. The rotor 24 made of a magnetic material has a circular outer shape and is magnetized so that the magnetic poles change every 45 ° along its circumferential direction. Further, the projecting piece 12 is provided at a position of 45 ° from the projecting piece 16. In this case, the remaining 315 ° range of the stator 6 can be omitted.
In the case of this configuration, even if the rotor 24 rotates, the values of the shortest distances L1 and L2 between the rotor and the stator do not change. However, the polarity of the magnet at the position facing the MI sensor 18 changes alternately such as N pole, S pole, N pole, S pole,. In synchronism with this, the polarities of the magnets facing the protruding pieces 12 are alternately changed to S pole, N pole, S pole, N pole, and so on. The polarity at the position facing the MI sensor 18 is opposite to the polarity at the position facing the protrusion 12.
[0030]
Even with this configuration, the magnitude of the magnetic flux circulating in the order of the projecting piece 12 → the gap (air gap L1) → the rotor 24 → the gap (air gap L2) → the MI sensor 18 → the projecting piece 16 → the stator 6 → the projecting piece 12 is Along with the rotation of the rotor 24, it can be greatly changed at a period of 90 °. A sensor output signal composed of a sine wave having a larger amplitude than in the first embodiment can be obtained, and the angular resolution can be made finer. As a result, higher sensitivity can be achieved.
Further, since the magnetized rotor 24 also serves as a means for generating a magnetic flux, there is an advantage that it is not necessary to provide the permanent magnet 14 as in the first embodiment.
[0031]
(Third embodiment)
Next, the rotation angle sensor 32 of the third embodiment will be described. Here, the same components as those in the first embodiment are designated by the same member numbers, and detailed description thereof is omitted. FIG. 5 shows a schematic diagram of the main part of the rotation angle sensor 32 of the third embodiment, and FIG. 6 shows a graph showing the change of the sensor output with respect to the rotation angle.
In the case of the rotation angle sensor 32, a projecting piece 16 that is a first sensor installing portion and a projecting piece 16 a that is a second sensor installing portion are projectingly provided at different positions on the inner peripheral side of the stator 6. The angle formed between the projecting pieces 16 and 16a with respect to the rotation center O of the motor shaft 10 is set to 45 °. A first MI sensor 18 is installed at the tip of the projecting piece 16, and a second MI sensor 18a is installed on the projecting piece 18a. Similarly, a projecting piece 12 and a second projecting piece 12a project from different positions on the inner peripheral side of the stator 6. The angle formed between the projecting pieces 12 and 12a with respect to the rotation center O of the motor shaft 10 is set to 45 °. A first magnet 14 is installed at the tip of the projecting piece 12, and a second magnet 14a is installed on the projecting piece 12a. In this case, two sets of magnet-MI sensor pairs of the first embodiment are arranged in a 45 ° relationship.
[0032]
The inner end surface part of the second MI sensor 18a installed on the stator 6 side is in a state closer to the rotor 4 side than the other part (annular part) of the stator 6. For this reason, in the rotation angle sensor 32 of the present embodiment, the magnetic flux emitted from the permanent magnets 14 and 14a branches and flows into an air gap formed inside the first MI sensor 18 and an air gap formed inside the second MI sensor 18a. It has become. That is, the magnetic flux circulating in the order of the rotor 4 → the clearance (air gap L2) → the first MI sensor 18 → the projecting piece 16 → the magnetic path R1 of the stator 6 and the rotor 4 → the clearance (air gap L3) → the second MI sensor 18a → the projection. A magnetic flux that circulates in the order of the piece 16a → the magnetic path R2 of the stator 6 is formed.
The distance between the inner end surface of the permanent magnet 14 and the outer peripheral portion of the rotor 4 is L1, and the distance between the inner end surface of the first MI sensor 18 and the outer peripheral portion of the rotor 4 is L2, and the inner end surface of the second MI sensor 18a and the rotor 4 are The distance from the outer peripheral portion is L3, and the distance between the inner end face of the permanent magnet 14a and the outer peripheral portion of the rotor 4 is L4.
[0033]
When the rotor 4 is in the rotational position shown in FIG. 5, the first MI sensor 18 is in a state facing one corner of the rotor 4, and the second MI sensor 18 a is in a state facing the midpoint of one side of the rotor 4. Become. At this time, L2 becomes the minimum value and L3 becomes the maximum value. As a result, the magnitude of the magnetic flux flowing through the magnetic path R1 increases, and the largest voltage signal is output from the first MI sensor 18 at this time. On the other hand, the magnetic flux flowing through the magnetic path R2 decreases, and at this time, the smallest voltage signal is output from the second MI sensor 18a.
When the rotor 4 is rotated 45 ° from the rotational position shown in FIG. 5, the first MI sensor 18 is in a state of facing the midpoint of one side of the rotor 4, and the second MI sensor 18 a is one corner of the rotor 4. It will be in the state of facing. At this time, L2 becomes the maximum value and L3 becomes the minimum value. As a result, the magnitude of the magnetic flux flowing through the magnetic path R1 decreases, and the smallest voltage signal is output from the first MI sensor 18 at this time. On the other hand, the magnitude of the magnetic flux flowing through the magnetic path R2 increases, and at this time, the largest voltage signal is output from the second MI sensor 18a.
Regardless of the rotation angle, the combination of the permanent magnet 14 and the permanent magnet 14a and the magnetic resistance formed between the rotors 4 are the same.
The phase difference between the sensor outputs obtained by the two MI sensors 18 and 18a is 180 ° as shown in FIG. In this figure, a solid sine wave curve indicates the output signal of the first MI sensor 18, and a broken sine wave curve indicates the signal output of the second MI sensor 18a. The two types of sensor output signals are input to a calculation means (not shown), and the following calculation is performed based on these sensor output signals.
[0034]
When the output of the first MI sensor 18 is VA (volts) and the output of the second MI sensor 18a is VB (volts), VA and VB can be expressed by the following equations 1 and 2, respectively. Note that a is a value determined by the magnetomotive force of the permanent magnets 14 and 14a, and is a so-called temperature variable in which the value of a also changes with temperature changes.
VA = a + sin θ Equation 1
VB = a + sin (θ + 180 °) Equation 2
Here, when the difference between VA and VB is taken, the following equation 3 is obtained.
VA−VB = sin θ−sin (θ + 180 °)
= 2sinθ Equation 3
Eventually, the term of the temperature variable disappears, so it can be seen that the value of VA-VB is not affected by the temperature change. Therefore, if the VA-VB value obtained from the two sensor outputs and the number of appearances of the maximum value of the VA-VB value are specified, the rotation angle θ (°) of the rotor 4 and the motor shaft 10 can be obtained. .
[0035]
In the present embodiment, the temperature variable can be eliminated by using two sensor outputs. That is, as a result of the temperature compensation being possible, it is possible to provide the rotation angle sensor 32 that is resistant to temperature changes and is extremely accurate. In addition, when such a calculation is performed, a sensor output signal having twice the amplitude as in the first embodiment can be obtained, so that the resolution becomes finer and higher sensitivity can be achieved.
[0036]
(Fourth embodiment)
Next, a description will be given of a fourth embodiment in which the present invention is embodied in a torque sensor 42 for electric power steering of a vehicle. 7 is a schematic cross-sectional view of the torque sensor 42, FIG. 8 is a schematic cross-sectional view of a main part taken along line AA in FIG. 7, and FIG. 9 is a partial cross-sectional view of the main part of the torque sensor 42. Yes.
[0037]
As shown in FIG. 7, a hollow input shaft 46 that is coaxial with the torsion bar 44 is connected to the upper end of the torsion bar 44 that constitutes the torque sensor 42. A vehicle steering (not shown) is connected to the upper portion of the input shaft 46. On the other hand, a hollow output shaft 48 that is coaxial with the torsion bar 44 is connected to the lower end of the torsion bar 44. The input shaft 46 and the output shaft 48 rotate relative to each other as the torsion bar 44 is twisted.
A first sensor ring 56 (first magnetic body 56) made of a magnetic material is fixed to the outer periphery of the input shaft 46. A second sensor ring 58 (second magnetic body 58) made of a magnetic material is fixed to the outer periphery of the output shaft 48.
As shown in FIGS. 7 and 9, the first sensor ring 56 has an annular shape extending in the circumferential direction surrounding the torsion bar 44, and a comb tooth shape is formed on the lower end side of the first sensor ring 56. A large number of rectangular teeth 56a are formed as the first protrusions to be formed. Further, the second sensor ring 58 also has an annular shape extending in the circumferential direction surrounding the torsion bar 44, and a plurality of rectangular shapes are formed as comb-shaped second protrusions on the upper end side of the second sensor ring 58. The tooth part 58a is formed.
Each tooth portion 56a is opposed to each tooth portion 58a with a gap in the phase while having a gap in the axial direction.
When the torsion bar 44 is not twisted, approximately half of the end area of each tooth portion 56a faces the end surface of each tooth portion 58a. When the torsion bar 44 is twisted to the right, the opposing area of each tooth 56a and each tooth 58a increases, and when the torsion bar 44 is twisted to the left, the opposing area of each tooth 56a and each tooth 58a decreases.
[0038]
On the outer periphery of the input shaft 46 and the output shaft 48, an upper housing 52 and an unillustrated under housing are provided via a bearing 50. In the upper housing 52, a third sensor ring 60 as a third magnetic body made of a magnetic material is fixed. The third sensor ring 60 is disposed so as to surround the first sensor ring 56 with a gap. Further, the third sensor ring 60 is disposed so as to surround the second sensor ring 58 with a gap.
[0039]
A permanent magnet 62, which is a means for generating magnetic flux, is disposed in a region on the first sensor ring 56 side of the third sensor ring 60, specifically, at the upper end portion of the inner peripheral surface of the third sensor ring 60. ing. A slight gap is provided between the inner end surface of the permanent magnet 62 and the outer peripheral surface of the first sensor ring 56.
A projecting piece 70 is provided on the inner peripheral surface of the third sensor ring 60 at an intermediate height, and a first MI sensor 66 is installed at the tip of the projecting piece 70. The first MI sensor 66 is disposed at a position close to the outer peripheral surface of the first sensor ring 56. A projecting piece 68 is provided at the lower end portion of the inner peripheral surface of the third sensor ring 60, and a second MI sensor 64 is installed at the tip of the projecting piece 68. The second MI sensor 64 is disposed at a position close to the outer peripheral surface of the second sensor ring 58.
[0040]
In the torque sensor 42 configured as described above, two magnetic paths R1 and R2 are formed as shown in FIG. The first magnetic path R1 can be formed inside the permanent magnet 62 → the third sensor ring 60 → the projecting piece 70 → the first MI sensor 66 → the inside of the first MI sensor 66 → the first sensor ring 56 → the inside of the permanent magnet 62. It becomes a path of air gap → permanent magnet 62. The second magnetic path R2 includes the permanent magnet 62 → the third sensor ring 60 → the protrusion 68 → the second MI sensor 64 → the air gap formed inside the second MI sensor 64 → the second sensor ring 58 → the teeth of the second sensor ring 58. Air gap between tooth part 58a of second sensor ring 58 and tooth part 56a of first sensor ring 56 → tooth part 56a of first sensor ring 56 → first sensor ring 56 → inside of permanent magnet 62 It becomes a path of air gap → permanent magnet 62.
[0041]
When torque is transmitted to the input shaft 46 by the steering operation, the torsion bar 44 is twisted to cause relative rotation between the input shaft 46 and the output shaft 48. Thereby, the opposing areas of the tooth portions 56a and 58a of the first sensor ring 56 and the second sensor ring 58 change. In this embodiment, the facing area between the tooth portions 56a and 58a, the amount of air gap, etc. are adjusted in advance so that the number of magnetic fluxes passing through the two MI sensors 64 and 66 is approximately the same in the initial state where no torque is applied. Has been.
[0042]
When torque is applied in the direction in which the opposing areas of the tooth portions 56a and 58a increase, the number of magnetic fluxes passing through the second MI sensor 64 increases and the number of magnetic fluxes passing through the first MI sensor 66 decreases. In this case, the output of the second MI sensor 64 is larger than the output of the first MI sensor 66. Conversely, when torque is applied in the direction in which the facing area decreases, the number of magnetic fluxes passing through the second MI sensor 64 decreases and the number of magnetic fluxes passing through the first MI sensor 66 increases. Therefore, in this case, the output of the second MI sensor 64 is smaller than the output of the first MI sensor 66.
[0043]
The two sensor outputs are input to the calculation means, where a predetermined calculation is performed. Here, the difference between the sensor output VA of the first MI sensor 64 and the sensor output VB of the second MI sensor 66 is calculated, and the rotation angle between the input shaft 46 and the output shaft 48 is obtained based on this value (VA−VB). Further, the torque at that time is calculated based on the result.
[0044]
Also in this embodiment, since the MI sensors 64 and 66 are used in place of the conventionally used coils as means for detecting the magnetic field strength, the highly sensitive torque sensor 42 can be provided. In addition, as a result of the fact that the winding of the coil becomes unnecessary, it can be manufactured relatively easily. Furthermore, since the detection coil that causes an increase in size and the occurrence of a failure is not an essential component, the torque sensor 42 can be easily reduced in size and excellent in reliability.
Further, in the present embodiment, since the torque is detected based on the output difference value (VA−VB) between the two MI sensors 64 and 66, the torque sensor 42 with higher sensitivity can be provided. Can do. In addition, the influence of temperature can be eliminated.
[0045]
(5th Example)
The projecting piece 70 and the first MI sensor 66 can be removed from the torque sensor of FIG. In this case, permanent magnet 62 → third sensor ring 60 → projection piece 68 → MI sensor 64 → air gap formed inside MI sensor 64 → second sensor ring 58 → tooth portion 58a of second sensor ring 58 → second sensor Air gap between the tooth portion 58a of the ring 58 and the tooth portion 56a of the first sensor ring 56 → the tooth portion 56a of the first sensor ring 56 → the first sensor ring 56 → the air gap formed inside the permanent magnet 62 → the permanent magnet 62 The magnitude of the magnetic flux circulating through the magnetic path is measured by the MI sensor 64. The magnitude of the measured magnetic flux depends on the magnetic resistance of the air gap between the tooth portion 58a of the second sensor ring 58 and the tooth portion 56a of the first sensor ring 56, and the magnetic resistance depends on the twist angle of the torsion bar 44. Therefore, the torque for twisting the torsion bar 44 by the MI sensor 64 can be measured.
[0046]
(Sixth embodiment)
The torque sensor can also be configured by providing the rotation angle sensors of FIG. 1 or FIG. 4 at the upper and lower ends of the torsion bar. The rotation angle can be measured from the output of each rotation angle sensor, the torsion angle of the torsion bar can be measured from the difference, and the torque can be measured from the torsion angle.
[0047]
Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.
For example, a configuration like the rotation angle sensor 72 of another embodiment shown in FIG. 10 may be used. In the rotation angle sensor 72, a protruding piece 16 that is a first sensor installation portion and a protruding piece 16a that is a second sensor installation portion protrude from different positions on the inner peripheral side of the stator 6. The angle formed between the projecting pieces 16 and 16a with respect to the rotation center O of the motor shaft 10 is set to 30 ° instead of 45 °. The first MI sensor 18 is installed at the tip of the projecting piece 16, and the second MI sensor 18a is installed on the projecting piece 16a. On the other hand, the outer shape of the rotor 74 is formed in a substantially regular hexagonal shape. Even with such a configuration, the same effects as those of the third embodiment can be achieved.
Note that the outer shape of the rotor is not limited to a substantially square shape or a substantially regular hexagonal shape, and other substantially regular n-corner shapes (for example, a substantially regular octagonal shape) may be employed, or a substantially regular n-number. It is also possible to adopt an irregular shape that is not square.
[0048]
In the first embodiment or the like, the installation position of the permanent magnet 14 is set at the tip of the projecting piece 12, but the present invention is not limited to this. For example, the permanent magnet 14 can be set at the annular portion of the stator 6. Similarly, the MI sensor 18 may be installed not on the projecting piece 18 but on the annular portion of the stator 6.
Instead of the configuration in which the MI sensor 18 and the permanent magnet 14 are provided on the stator 6 side, the MI sensor 18 and the permanent magnet 14 may be provided on the rotor 4 side.
[0049]
The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology illustrated in the present specification or the drawings can achieve a plurality of purposes at the same time, and has technical utility by achieving one of the purposes.
[Brief description of the drawings]
FIG. 1 is a schematic view of a main part of a rotation angle sensor according to a first embodiment embodying the present invention.
FIG. 2 is a schematic view of the main part when the rotor of the first embodiment is rotated 45 ° from the state of FIG. 1;
FIG. 3 shows a graph of sensor output in the rotation angle sensor of the first embodiment.
FIG. 4 is a schematic diagram of a main part of a rotation angle sensor according to a second embodiment.
FIG. 5 is a schematic view of a main part of a rotation angle sensor according to a third embodiment.
FIG. 6 is a graph of sensor output in the rotation angle sensor of the third embodiment.
FIG. 7 is a schematic sectional view of a torque sensor according to a fourth embodiment.
FIG. 8 is a schematic cross-sectional view of a main part of the torque sensor taken along line AA in FIG. 7;
FIG. 9 is a partial cross-sectional view of a main part of a torque sensor according to a fourth embodiment.
FIG. 10 is a schematic view of a main part of a rotation angle sensor according to another embodiment.
[Explanation of symbols]
2, 22, 32, 72, 82: rotation angle sensors.
4, 24, 74: Rotor which is an inner magnetic body
6: Stator as outer magnetic body
10: Motor shaft as a rotating body
14, 62: Permanent magnet
16: Projection piece as first sensor installation part
16a: Projection piece as second sensor installation part
18, 66: first MI sensor
18a, 64: second MI sensor
42: Torque sensor
44: Torsion bar
56: The first sensor ring which is the first magnetic body
56a: tooth part which is the first protrusion
58: Second sensor ring as second magnetic body
58a: tooth part which is the second protrusion
60: Third sensor ring as third magnetic body
R1, R2: Magnetic path
L1, L2, L3: Distance

Claims (8)

An inner magnetic body, an outer magnetic body arranged outside the inner magnetic body with a gap, a magnet that generates a magnetic flux circulating through the inner magnetic body and the outer magnetic body, and a magnetic path An MI sensor arranged,
The inner magnetic body and the outer magnetic body are rotatable relative to each other, and the shortest distance between the inner magnetic body and the outer magnetic body changes depending on the relative rotation angle between the inner magnetic body and the outer magnetic body. the magnitude of the circulating magnetic flux changes depending on the relative rotation angle detected by the MI sensor, a rotation angle sensor that measures the relative rotation angle from the output of the MI sensor,
A rotation angle sensor characterized in that the outer shape of the inner magnetic body is formed in a substantially regular polygonal shape, and the inner shape of the outer magnetic body is formed in a circular shape having a protrusion protruding inward. The rotation angle sensor according to claim 1, wherein the MI sensor is fixed to the outer magnetic body. The rotation angle sensor according to claim 1 or 2, wherein the magnet is fixed to the outer magnetic body. The rotation angle sensor according to any one of claims 1 to 3, wherein the MI sensor and the magnet are fixed to the outer magnetic body at symmetrical positions sandwiching the rotation center of the inner magnetic body. The outer shape of the inner magnetic body is formed in a substantially regular n-corner shape, and the first MI sensor and the second MI sensor are fixed at positions separated by an odd multiple of 360 ° / 2n on the inner peripheral side of the outer magnetic body. The rotation angle sensor according to any one of claims 1 to 4 . An inner magnetic body, an outer magnetic body arranged on the outside of the inner magnetic body with a gap, a magnet that generates a magnetic flux circulating through the gap between the inner magnetic body and the outer magnetic body, and in the middle of the magnetic path With the arranged MI sensor,
  The inner magnetic body and the outer magnetic body are relatively rotatable, and the MI sensor detects the magnitude of the circulating magnetic flux that changes depending on the relative rotation angle between the inner magnetic body and the outer magnetic body, and the output of the MI sensor. A rotation angle for measuring the relative rotation angle from
  The outer shape of the inner magnetic body is formed in a substantially regular n-corner shape, and the first MI sensor and the second MI sensor are fixed at positions separated by an odd multiple of 360 ° / 2n on the inner peripheral side of the outer magnetic body. A rotation angle sensor. A torsion bar extending along the rotation axis, a rotation angle sensor according to any one of claims 1, which is connected to one end of the torsion bar 6, claim 1, which is connected to the other end of the torsion bar 6 A torque sensor comprising the rotation angle sensor according to any one of the above . A torsion bar extending along the rotation axis; a first magnetic body connected to one end of the torsion bar and having a first protrusion; and a second magnetic body connected to the other end of the torsion bar and facing the first protrusion. A second magnetic body having a protrusion, a first magnetic body, a third magnetic body disposed outside the second magnetic body, a “first magnetic flux circulating through the first magnetic body and the third magnetic body”, and a “first magnetic body” A magnet that generates a first magnetic body, a second magnetic body, and a second magnetic flux that circulates through the third magnetic body, a first MI sensor disposed in the middle of a first magnetic path through which the first magnetic flux flows, and a second magnetic flux A second MI sensor disposed in the middle of the flowing second magnetic path,
When the torsion bar is twisted, the opposing area of the first protrusion and the second protrusion changes, and the output value of the first MI sensor and the output value of the second MI sensor both change accordingly, and the output value of the first MI sensor A torque sensor capable of measuring the magnitude of torque causing twisting of the torsion bar from the difference in output value of the second MI sensor.

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