JP2009069106A - Torque detection device and electric power steering system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a torque detection device and electric power steering system capable of constituting a double system. <P>SOLUTION: A magnetometric sensor 110a is connected with a first shaft 200a, a magnetometric sensor 110b is connected with a second shaft 200b, and the magnetometric sensors 110a and 110b output three-phase magnetic detection signals of different phases according to the rotation of a rotator to rotation information calculation devices 101a and 101b, respectively. The rotation information calculation devices 101a and 101b calculate an absolute rotation angle position θ1 of the first shaft 200a and an absolute rotation angle position θ2 of the second shaft 200b, respectively, based on a normal two-phase magnetic detection signal out of the three-phase magnetic detection signals. An arithmetic section 102 calculates a steering torque T based on the differential value between the absolute rotation angle positions θ1 and θ2. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a torque detection device that arranges two angle sensors at both ends of a torsion bar and detects torque from a twist angle of the torsion bar, and an electric power steering device using the torque detection device.

As a conventional torque detection device, a first target having a gear capable of multiple rotation is held by holding a first target that is connected to an input shaft and is magnetized with magnetic poles having different polarities alternately at equal intervals on the outer peripheral surface. A rotating body connected to the gear of the first rotating body and rotating at a lower speed than the first rotating body, and a magnet disposed at the center, and an output shaft connected to the outer peripheral surface. A third rotating body having a second target having magnetic poles of different polarities alternately magnetized at equal intervals and having a multi-rotatable gear, and first rotation angles for detecting the respective rotating angles. It is known that the absolute rotation angle and torque are detected with high accuracy and high resolution with a simple configuration comprising the second and third detection means (see, for example, Patent Document 1).
JP 2006-220529 A

However, in the conventional example described in Patent Document 1, angle sensors are provided at both ends (input shaft and output shaft) of the torsion bar, and only the rotation angle and torque are detected. Since it is not configured, improvement is desired.
Then, this invention makes it a subject to provide the torque detection apparatus and electric power steering device which can comprise a double system.

In order to solve the above problem, a torque detection device according to claim 1 is a torque detection device that detects a torque applied to a shaft in which an input shaft and an output shaft are coaxially connected via a torsion bar,
First angle detection means for detecting a rotational angle position of the input shaft;
Second angle detection means for detecting a rotational angle position of the output shaft;
Torque calculation means for calculating the torque based on the rotation angle position detected by the first angle detection means and the rotation angle position detected by the second angle detection means,
The first and second angle detecting means are supported by a magnet holder supported by a rotor, a magnet supported by the magnet holder, and a stator, and are arranged at predetermined intervals in the circumferential direction. Three magnetic detectors that output signals according to input magnetic flux, and magnetic flux from the magnets to the three magnetic detectors supported by the stator and disposed between the three magnetic detectors. A magnetic path member having three magnetic paths to be guided, and the three magnetic detectors whose phase changes according to the positional relationship between each magnetic path of the magnetic path member and the magnet when the rotor rotates. And rotation information calculation means for calculating the rotation angle position of the rotor based on the three-phase magnetic detection signals.

  According to a second aspect of the present invention, there is provided a torque detecting device according to the first aspect of the present invention, further comprising an abnormality detecting unit that detects an abnormality of the three-phase magnetic detection signal, and the rotation information calculating unit includes the abnormality detecting unit. When an abnormality is detected in any one of the three-phase magnetic detection signals, the rotation is performed based on the remaining two-phase magnetic detection signals except for the phase of the magnetic detection signal in which the abnormality is detected. It is characterized by calculating an angular position.

  Furthermore, the torque detector according to a third aspect is the invention according to the second aspect, wherein the abnormality detecting means is configured to detect three phases of the magnetic detector based on a sampling value of the three-phase magnetic detection signal. For each phase, the rotation angle position is calculated by at least two calculation methods, and the abnormality of the three-phase magnetic detection signal is detected based on the calculated rotation angle position.

  According to a fourth aspect of the present invention, there is provided the torque detector according to the third aspect, wherein the three phases of the magnetic detector are an A phase, a B phase, and a C phase, and each of the A phase, the B phase, and the C phase. Sampling values of the magnetic detection signal corresponding to A are respectively a, b, and c, and the abnormality detection means includes at least one of the sampling values a and b, the sampling values a and c, and the combination of the sampling values b and c. Based on the two combinations, using a different calculation method for each combination, calculate at least two rotation angle positions for each phase of the magnetic detector, and based on the calculated rotation angle positions of each phase, It is characterized by detecting abnormalities in the three-phase magnetic detection signals having different phases.

Furthermore, in the invention according to claim 3 or 4, the torque detection device according to claim 5 is characterized in that the abnormality detection means has three phases having different phases based on a difference value between the rotation angle positions with respect to the phases. It is characterized by detecting an abnormality in the magnetic detection signal.
According to a sixth aspect of the present invention, there is provided the torque detection device according to any one of the third to fifth aspects, wherein the rotation information calculating means detects abnormality among the three magnetic detection signals by the abnormality detection means. For each phase of the magnetic detection signal other than the detected magnetic detection signal, an average value of the rotation angle positions used for detecting the abnormality is calculated as the rotation angle position of the rotor.

Furthermore, the torque detection device according to claim 7 is the invention according to any one of claims 1 to 6, wherein the torque calculation means includes the absolute rotation angle position detected by the first angle detection means, The torque is calculated based on a difference value from the absolute rotation angle position detected by the second angle detection means.
An electric power steering device according to an eighth aspect is configured such that the torque detection device according to any one of the first to seventh aspects is disposed on a steering shaft, and the steering torque is detected by the torque detection device. It is characterized by being.

According to the torque detection device of the present invention, two angle sensors are arranged at both ends of the torsion bar, and the torque is detected from the torsion angle of the torsion bar. The angle sensor is a three-phase sensor from three magnetic detectors. Since the rotation angle position can be calculated based on the two-phase magnetic detection signal among the three-phase magnetic detection signals, an abnormality occurs in any one of the three-phase magnetic detection signals. Even if it exists, the absolute rotation angle can be detected based on the remaining normal two-phase magnetic detection signals. Therefore, a double system can be configured as the angle sensor, and a highly reliable torque detection device can be obtained.
Further, according to the electric power steering apparatus according to the present invention, a highly reliable steering torque can be obtained by arranging the torque detection device on the steering shaft. Furthermore, since the steering angle can be detected simultaneously by detecting the absolute rotation angle with the angle sensor, it is not necessary to provide a sensor for detecting the steering angle separately.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an overall configuration diagram showing an embodiment when a torque detection device according to the present invention is applied to an electric power steering device.
In the figure, reference numeral 1 denotes a steering wheel, and a steering force applied to the steering wheel 1 from a driver is transmitted to a steering shaft 2 having an input shaft 2a and an output shaft 2b. The steering shaft 2 has one end of an input shaft 2a connected to the steering wheel 1 and the other end connected to one end of an output shaft 2b via a torque sensor 3 as a torque detector.

  The steering force transmitted to the output shaft 2 b is transmitted to the lower shaft 5 via the universal joint 4 and further transmitted to the pinion shaft 7 via the universal joint 6. The steering force transmitted to the pinion shaft 7 is transmitted to the tie rod 9 via the steering gear 8 and steers steered wheels (not shown). Here, the steering gear 8 is configured in a rack and pinion type having a pinion 8a connected to the pinion shaft 7 and a rack 8b meshing with the pinion 8a, and the rotational motion transmitted to the pinion 8a is linearly moved by the rack 8b. It has been converted to movement.

A steering assist mechanism 10 for transmitting a steering assist force to the output shaft 2b is connected to the output shaft 2b of the steering shaft 2. The steering assist mechanism 10 includes a reduction gear 11 coupled to the output shaft 2b, and an electric motor 12 coupled to the reduction gear 11 and generating a steering assist force with respect to the steering system.
The torque sensor 3 is configured to detect a steering torque T applied to the steering wheel 1 and transmitted to the input shaft 2a. A specific configuration of the torque sensor 3 will be described later.

The steering torque T output from the torque sensor 3 is input to the controller 15. In addition to the steering torque T, a vehicle speed detection value V output from the vehicle speed sensor 16 is also input to the controller 15.
Then, the controller 15 calculates a current command value for generating the steering assist force according to the steering torque T and the vehicle speed V by the electric motor 12, and drives and controls the electric motor 12 based on the current command value.

Next, a specific configuration of the torque sensor 3 will be described in detail.
FIG. 2 is a block diagram showing the configuration of the torque sensor 3. As shown in FIG. 2, the torque sensor 3 includes a first rotation state detection device 100a that detects the rotation state of the first magnet 103a connected to the first shaft 200a (input shaft 2a), and a first rotation state detection device 100a. And a second rotation state detection device 100b connected to the second shaft 200b (output shaft 2b) for detecting the rotation state of the second magnet 103b.

An output signal from the first rotation state detection device 100a is input to the first rotation information calculation device 101a, and the first rotation information calculation device 101a calculates the absolute rotation angle position θ1 of the first shaft 200a. .
Similarly, an output signal from the second rotation state detection device 100b is input to the second rotation information calculation device 101b, where the absolute rotation angle position θ2 of the second shaft 200b is determined by the second rotation information calculation device 101b. Calculated.

The absolute rotation angle positions θ1 and θ2 calculated by the first and second rotation information calculation devices 101a and 101b are input to the calculation unit 102, and the calculation unit 102 determines the absolute rotation angle position θ1 and the absolute rotation angle. The difference value with respect to the position θ2 is calculated, the steering torque T is calculated based on the difference value, the absolute rotation angle position θ1 (or the absolute rotation angle position θ2) is set as the steering angle δ, and these are output. It has become.
2 is a torsion bar. The torsion bar 3a is coaxial with the first shaft 200a and the second shaft 200b between the first shaft 200a and the second shaft 200b. It is connected, and when a torsional torque is inputted, it is composed of an elastic member that causes a torsion in itself.

Next, the configuration of the first and second magnets 103a and 103b, the first and second rotation state detection devices 100a and 100b, and the first and second rotation information calculation devices 101a and 101b will be described.
The first magnet 103a and the second magnet 103b, the first rotation state detection device 100a and the second rotation state detection device 100b, and the first rotation information calculation device 101a and the second rotation information calculation device 101b. Since each has the same configuration, the following description will be simply referred to as a magnet 103, a rotation state detection device 100, and a rotation information calculation device 101.

  The rotation state detection device 100 and the magnet 103 are a magnet 103 attached to an end portion (first shaft 200a or second shaft 200b) of the torsion bar 3a, and a rotation state detection device 100 attached to a stationary member (not shown). As shown in FIG. 3, three magnetic detection signals are output to the rotation information calculation device 101. The magnetic sensor 110 shown in FIG. 3 is a sectional view in the radial direction.

Further, a detailed configuration of the magnetic sensor 110 will be described with reference to FIGS.
Here, FIG. 4 is an exploded perspective view of the magnetic sensor 110. FIG. 5 is a diagram showing magnetic detection signals output from the magnetic detectors 60 a to 60 c of the magnetic sensor 110. FIG. 6 is a diagram illustrating the output principle of the magnetic detection signal.
The magnetic sensor 110 of the present embodiment is fixed to a stationary member (not shown) and detects the rotation state of the rotating shaft.

Hereinafter, the configuration will be described.
An annular magnet holder 30 is supported on the rotating shaft. The magnet holder 30 is made of a magnetic material as a magnetic body. Further, the magnet holder 30 supports an annular magnet 40 (magnet 103). The magnet 40 has a semicircular circumferential surface magnetized to the S pole, and the other half circumferential surface is magnetized to the N pole. That is, the magnet 40 is magnetized in two poles.

On the other hand, the magnetic path member 50 and the circuit board 70 are supported by a stationary member (not shown). Three magnetic detectors 60a to 60c are mounted on the circuit board 70 so as to have a phase of an electrical angle of 120 °. In the present embodiment, analog Hall ICs are used for the magnetic detectors 60a to 60c.
The magnetic path member 50 made of a magnetic material forms three magnetic paths for guiding the magnetic flux from the magnet 40 to the magnetic detectors 60a to 60c. The three magnetic paths are formed by a gap 52 through which magnetic flux passes and a wall 50a protruding in the axial direction for guiding the magnetic flux through the gap 52. That is, the magnetic path is formed by making the projecting wall 50a and the wall 50a face each other with the gap 52 interposed therebetween.

  The magnetic path member 50 is disposed so that the magnetic detectors 60a to 60c are sandwiched between the wall 50a and the wall 50a forming the magnetic path, and the surface of the magnetic path member 50 where the protruding wall 50a is provided. The opposite surface is arranged at a position facing the magnet 40 in the axial direction. With this configuration, the magnetic flux of the magnet 40 is guided by two protruding walls 50a that form a magnetic path, and passes through the magnetic detectors 60a to 60c.

As shown in FIG. 4, the magnetic sensor 110 configured as described above has a structure in which the magnetic detectors 60a to 60c, the magnetic path member 50, the magnet 40, and the magnet holder 30 are laminated in the axial direction.
Further, there is a space gap between the magnet 40 and the magnetic path member 50. The narrower the gap, the larger the amount of magnetic flux guided to the magnetic detectors 60a to 60c. However, if the gap is too narrow, the magnet 40 and the magnetic path member 50 may come into contact with each other. It is desirable that the distance is from mm] to 2.0 [mm].

  And if a rotating shaft rotates, the magnet holder 30 and the magnet 40 will rotate in connection with it. By this rotation, the positional relationship (overlapping condition) between the magnet 40 and the magnetic path of the magnetic path member 50 changes periodically. Due to this change, the amount of magnetic flux passing through the magnetic detectors 60a to 60c and the magnetic pole change, respectively, and the magnetic detection signal is output as three sine waves that are 120 degrees out of phase as shown in FIG. The That is, since quadrant discrimination is possible, the rotational angle position θ and the like based on the magnetic detection signals cos θ, cos (θ-2π / 3), cos (θ-4π / 3) output from the magnetic detectors 60a to 60c. Can be calculated.

  6B is a diagram showing a positional relationship between the magnet 40 and the magnetic path member 50 when the radial cross section is viewed from the axial direction. FIG. The change of the output signal of the magnetic detector 60a located at the circled position in the middle) is shown. The positional relationship between the magnetic detector 60a and the magnet 40 is changed by rotating the magnet 40 to the right through the rotational positions 104 to 106 from the position 102 shown in FIG. However, the amount of magnetic flux passing through the magnetic detector 60a and the magnetic pole change. As a result, the output of the magnetic detector 60a also changes as shown in FIG. 6A, and this change in output forms a sine wave.

As described above, in this embodiment, the magnet holder 30 of the magnetic sensor 110a and the first shaft 200a are non-rotatably connected, and the magnet holder 30 of the magnetic sensor 110b and the second shaft 200b are non-rotatably connected. It becomes composition.
In addition, signal output units (not shown) of the magnetic detectors 60 a to 60 c are connected to a signal input unit (not shown) of the rotation information calculation device 101.

  Returning to FIG. 3, the rotation information calculation device 101 detects the abnormality of the three magnetic detection signals output from the magnetic sensor 110 and the absolute rotation angle position based on the output from the abnormality detection unit 101A. a rotation information calculation unit 101B that periodically calculates rotation information indicating the rotation state of the rotating wheel (rotating shaft) such as θ, rotation angular velocity ω, and rotation direction. Then, the calculated rotation information is output to the calculation unit 102 in FIG.

Further, the rotation information calculation device 101 calculates a rotation angular velocity ω, a pulse generator (not shown) that outputs a pulse signal corresponding to the rotation of the rotating wheel, a pulse counter (not shown) that counts the pulse signal, have.
Further, the rotation information calculation apparatus 101 holds the calculated absolute rotation angle position θ in the RAM in order to calculate the rotation direction.

Although not shown, the rotation information calculation device 101 includes an arithmetic processing unit (Processing Unit) responsible for various controls and arithmetic processing, a RAM (Random Access Memory) constituting a main storage (Main Storage), and a read-only device. It has a configuration that includes a ROM (Read Only Memory) that is a storage device and a bus that connects the devices so as to be able to exchange data.
Then, a dedicated computer program stored in advance in the ROM is loaded into the RAM, and the arithmetic processing unit controls various hardware and performs various arithmetic processes in accordance with instructions described in the program loaded in the RAM. Information calculation processing is realized.

Next, calculation formulas used in the abnormality detection unit 101A for calculating rotation angle positions for the A phase, B phase, and C phase of the magnetic detectors 60a to 60c will be described.
The sampling values a, b, and c of the magnetic detection signals from the A phase to the C phase of the magnetic detectors 60a to 60c can be expressed by the following expression (1).
Phase A: a = cos θ,
B phase: b = cos (θ-2π / 3),
Phase C: c = cos (θ-4π / 3) (1)
From the above equation (1), using the mathematical relationship between the sampling values a, b, and c, the abnormality detection for obtaining the calculation formula (the first to fourth formulas described later) of the rotation angle position for detecting the abnormality. The following equation (2) is obtained as a parameter.

  Furthermore, using the abnormality detection parameter shown in the above equation (2), a calculation formula for the rotational angle position using all sampling values a, b, and c for each of the A phase, the B phase, and the C phase. The first equation shown in the following equation (3) is obtained. Next, using the abnormality detection parameter shown in the above equation (2), the first equation is modified for each of the A phase, the B phase, and the C phase, and sampling is performed as shown in the following equation (3). The second equation with only the values a and b as variables is obtained. Similarly, using the abnormality detection parameter shown in the above equation (2), the first equation is modified for each of the A phase, the B phase, and the C phase, and sampling is performed as shown in the following equation (3). A third equation having only values a and c as variables and a fourth equation having only sampling values b and c as variables are obtained.

Then, abnormality detection processing is executed by the abnormality detection unit 101A using the second to fourth expressions shown in the above expression (3).
FIG. 7 is a flowchart showing an abnormality detection processing procedure executed by the abnormality detection unit 101A. This abnormality detection process is executed at predetermined time intervals. First, in step S200, the abnormality detection unit 101A outputs the three-phase magnetic detection signals A, B, and C output from the magnetic detectors 60a to 60c. Sampling values a, b, and c are simultaneously acquired, and the process proceeds to step S202.

In step S202, the abnormality detection unit 101A uses the sampling values a and b acquired in step S200 and the second equation corresponding to each of the A phase, the B phase, and the C phase to calculate the absolute rotation angle position θ _A2. , Θ _B2 , θ _C2 are calculated, and the process proceeds to step S204.
Note that θ _A2 , θ _B2 , and θ _C2 are absolute rotation angle positions calculated using the second equation for the A phase, the B phase, and the C phase. Similarly, θ _A3 , θ _B3 , and θ _C3 are absolute rotation angle positions calculated using the third equation for the A phase, the B phase, and the C phase, and θ _A4 , θ _B4 , and θ _C4 are the A phase, This is the absolute rotation angle position calculated using the fourth equation for the B phase and the C phase. That is, the alphabet of the subscript represents the phase type of the magnetic detectors 60a to 60c, and the number represents the type of the calculation formula.

In step S204, the abnormality detection unit 101A determines whether or not the three absolute rotation angle positions calculated by the second equation are equal.
First, for each of θ _A2 , θ _B2 , and θ _C2 calculated by the second equation, two difference values “θ _A2 −θ _B2 ”, “θ _A2 −θ _C2 ”, and “θ _B2 −θ _C2 ” are calculated. To do. Next, these difference values are compared with a preset threshold value E _t = ± 0.1 [°], and when all three difference values are within the range of the threshold value E _t , three absolute rotations It is determined that the angular positions are equal.

Here, the threshold value E _t was in the range of -0.1 [°] ~ + 0.1 [ °] , the error or due to noise, in order to consider the error due A / D conversion.
When the three absolute rotational angle position is determined to be equal all three, the process proceeds to step S206, when the difference value is outside the range of the threshold value E _t even one, three absolute rotational angular position It is determined that they are not equal, and the process proceeds to step S216 described later.

In step S206, the abnormality detection unit 101A uses the sampling values a and c acquired in step S200 and the third formula corresponding to each of the A phase, the B phase, and the C phase to calculate the absolute rotation angle position θ _A3. , Θ _B3 , θ _C3 are calculated, and the process proceeds to step S208.
In step S208, the abnormality detection unit 101A determines whether or not all three absolute rotation angle positions calculated by the third equation are equal.

Here, with respect to θ _A3 , θ _B3 , and θ _C3 calculated by the third equation, two difference values “θ _A3 −θ _B3 ”, “θ _A3 −θ _C3 ”, and “θ _B3 −θ _C3 ” are calculated. Calculate and compare these difference values with a preset threshold E _t = ± 0.1 [°], and when all three difference values are within the range of the threshold E _t , three absolute rotations It is determined that the angular positions are equal.
When the three absolute rotational angle position is determined to be equal all three, the process proceeds to step S210, when the difference value is outside the range of the threshold value E _t even one, three absolute rotational angular position It is determined that they are not equal, and the process proceeds to step S214 described later.

In step S210, the abnormality detection unit 101A uses the sampling values b and c acquired in step S200 and the fourth expression corresponding to each of the A phase, the B phase, and the C phase to calculate the absolute rotation angle position θ _A4. , Θ _B4 , θ _C4 are calculated, and the process proceeds to step S212.
In step S212, the abnormality detection unit 101A outputs the nine absolute rotation angle positions calculated by the second to fourth equations to the rotation information calculation unit 101B, and then ends the abnormality detection process.

Also, when it is determined in step S208 that the three absolute rotation angle positions are not equal, it is already known that the sampling values a and b are normal, so that only the sampling value c is abnormal. I can judge. Therefore, in step S214, the abnormality detection unit 101A outputs the three absolute rotation angle positions calculated by the second equation to the rotation information calculation unit 101B, and also indicates a C phase indicating that an abnormality has occurred in the sampling value c. After outputting the signal abnormality detection flag to an external device or the like, the abnormality detection process is terminated.
In step S216, the abnormality detection unit 101A uses the sampling values a and c and the third expression corresponding to each of the A phase, the B phase, and the C phase, as in step S206, to calculate the absolute rotation angle position θ. _A3 , _θB3 , and _θC3 are calculated, and the process proceeds to step S218.

  In step S218, the abnormality detection unit 101A determines whether or not the three absolute rotation angle positions calculated by the third formula are equal to each other, as in step S208, and determines that there are three three absolute rotation angle positions. If both are equal, it is determined that an abnormality has occurred only in the sampling value b, and the process proceeds to step S220. In step S220, the abnormality detection unit 101A outputs the three absolute rotation angle positions calculated by the third expression to the rotation information calculation unit 101B, and indicates that an abnormality has occurred in the sampling value b. After the phase signal abnormality detection flag is output to an external device or the like, the abnormality detection process is terminated.

On the other hand, when it is determined in step S218 that the three absolute rotation angle positions calculated by the third equation are not equal, the process proceeds to step S222, and the sampling value acquired in step S200 is acquired as in step S210. Absolute rotation angle positions θ _A4 , θ _B4 , and θ _C4 are calculated using b and c and the fourth formula corresponding to each of the A phase, the B phase, and the C phase, and the process proceeds to step S224.

In step S224, the abnormality detection unit 101A determines whether or not the three absolute rotation angle positions calculated by the fourth equation are all equal.
Here, with respect to θ _A4 , θ _B4 , and θ _C4 calculated by the fourth equation, two difference values “θ _A4 −θ _B4 ”, “θ _A4 −θ _C4 ”, and “θ _B4 −θ _C4 ” are calculated. Calculate and compare these difference values with a preset threshold E _t = ± 0.1 [°], and when all three difference values are within the range of the threshold E _t , three absolute rotations It is determined that the angular positions are equal.

  When it is determined that all three absolute rotation angle positions are equal, it is determined that an abnormality has occurred only in the sampling value a, and the process proceeds to step S226. In step S226, the abnormality detection unit 101A outputs the three absolute rotation angle positions calculated by the fourth expression to the rotation information calculation unit 101B, and indicates that an abnormality has occurred in the sampling value a. After the phase signal abnormality detection flag is output to an external device or the like, the abnormality detection process is terminated.

On the other hand, if it is determined in step S224 that the three absolute rotation angle positions calculated by the fourth equation are not equal, the process proceeds to step S228, and the abnormality detection flag for stopping operation is set to the internal operation control unit ( After outputting to an arithmetic processing device or an external device, the abnormality detection process is terminated.
As described above, the abnormality detection unit 101A performs abnormality determination for each sampling value, and outputs only the absolute rotation angle position calculated using the normal sampling value to the rotation information calculation unit 101B.

Next, the rotation information calculation process executed by the rotation information calculation unit 101B will be described.
FIG. 8 is a flowchart showing a rotation information calculation processing procedure executed by the rotation information calculation unit 101B. This rotation information calculation process is executed every predetermined time. First, in step S300, the rotation information calculation unit 101B determines whether or not the absolute rotation angle position has been acquired from the abnormality detection unit 101A, and determines that it has been acquired. If it is determined, the process proceeds to step S302, and if it is determined that it has not been acquired, the process waits until it is acquired.

In step S302, the rotation information calculation unit 101B calculates the average value of the plurality of absolute rotation angle positions acquired in step S300 as the final absolute rotation angle position θ of the rotation axis, and proceeds to step S304.
In step S304, the rotation information calculation unit 101B calculates the rotation angular velocity ω based on the absolute rotation angle position θ calculated in step S302 and the number of pulse signals corresponding to the rotation of the rotation axis counted by a pulse counter (not shown). calculate.
For example, one round is divided into 10 bits (1024), and a pulse signal is output from the pulse generator according to the rotation of the rotating shaft. The pulse signal is counted by a pulse counter, and a time t corresponding to the rotation is calculated from the count value. Then, the rotational angular velocity ω is calculated from the time t and the absolute rotational angular position θ.

Next, in step S306, the rotation information calculation unit 101B calculates the absolute rotation angle position θ calculated in step S302 and the absolute rotation angle position θ calculated in the past (for example, once before) held in the RAM. The rotation direction is calculated based on the above, and the process proceeds to step S308.
In step S308, the rotation information calculation unit 101B outputs the calculation result signal of steps S302 to S306 to the calculation unit 102, and ends the rotation information calculation process.
In FIG. 2, the first magnetic sensor 110a and the first rotation information calculation device 101a correspond to the first angle detection means, and the second magnetic sensor 110b and the second rotation information calculation device 101b are the second. The calculation unit 102 corresponds to the torque calculation means. 3 corresponds to the abnormality detection unit, and the rotation information calculation unit 101B of FIG. 3 and the process of FIG. 8 correspond to the rotation information calculation unit.

Next, operations and effects in the present embodiment will be described.
When the driver operates the steering wheel 1, the input shaft 2a connected to the steering wheel 1 rotates, and the magnet holder 30 of the first magnetic sensor 110a rotates in conjunction with this rotation. Since the magnet 40 is supported by the magnet holder 30, the magnet 40 also rotates together with the magnet holder 30. As the magnet 40 rotates, the positional relationship between each magnetic path of the magnetic path member 50 and the magnet 40 also changes periodically. Magnetic fluxes from the magnet 40 pass through the magnetic paths of the magnetic path member 50 through the magnetic detectors 60a to 60c, and magnetic detection signals cos θ, cos (θ-2π / 3), corresponding to the passing magnetic flux, respectively. cos (θ-4π / 3) is output.

Then, the first rotation information calculation device 101a calculates the absolute rotation angle position θ1 of the input shaft 2a based on the three-phase magnetic detection signal, and outputs this to the calculation unit 102.
When the input shaft 2a rotates, this rotational torque is transmitted to the output shaft 2b via the torsion bar 3a, so that the output shaft 2b rotates, and the magnet holder 30 of the second magnetic sensor 110b moves in conjunction with this rotation. Rotate. Then, the second rotation information calculation device 101b calculates the absolute rotation angle position θ2 of the output shaft 2b based on the three-phase magnetic detection signal output from the second magnetic sensor 110b, and calculates this as the calculation unit 102. Output to.

The computing unit 102 calculates a difference value between the absolute rotation angle position θ1 and the absolute rotation angle position θ2, calculates a steering torque T based on the difference value, and outputs this to the controller 15.
Thereby, the controller 15 calculates a current command value according to the steering torque T and the vehicle speed V, and the electric motor 12 is driven and controlled based on the current command value, so that the torque generated by the electric motor 12 is reduced. 11 is converted into rotational torque of the steering shaft 2 to assist the driver's steering force.

  The first and second magnetic sensors 110a and 110b can calculate the absolute rotation angle position based on the two-phase magnetic detection signal among the three-phase magnetic detection signals. Further, the abnormality detection of the magnetic detection signal of each phase is performed, and when an abnormality is detected in any one of the three-phase magnetic detection signals, based on the two-phase magnetic detection signals excluding the phase in which the abnormality is detected. Thus, the absolute rotation angle position can be calculated. Thus, in the present embodiment, a double system is configured as the angle sensor.

For example, assuming that an abnormality has occurred in the C-phase signal, the absolute rotation angle positions θ _A2 , θ _B2 , calculated using the sampling values a and b and the second equation shown in the above equation (3), Since all three θ _C2 are equal, in the abnormality detection process of FIG. 7 executed by the abnormality detection unit 101A, it is determined Yes in step S204, and the process proceeds to step S206. In step S206, the absolute rotation angle positions θ _A3 , θ _B3 , and θ _C3 are calculated using the sampling values a and c and the third equation shown in the above equation (3).

Next, in step S208, two difference values “θ _A3 −θ _B3 ”, “θ _A3 −θ _C3 ”, and “θ _B3 −θ _C3 ” are obtained for the absolute rotational angular positions θ _A3 , θ _B3 , and θ _C3 . calculated, it is determined whether these difference value is within the range of the threshold E _t. At this time, since there is an abnormality in the sampling values at least one of c, the difference value is beyond the scope of the threshold value E _t, 3 single absolute rotational angle position is determined to be not equal.

As a result, No is determined in step S208, and the process proceeds to step S214. The abnormality determination unit 101A calculates the absolute rotation angle positions θ _A2 , θ _B2 , θ _C2 calculated using the sampling values a and b and the second equation. Is output to the rotation information calculation unit 101B as the final three-phase magnetic detection signal, and a C-phase signal abnormality detection flag is output to an external device or the like.
Then, the rotation information calculation unit 101B calculates an average value (= (θ _A2 + θ _B2 + θ _C2 ) / 3) of the three absolute rotation angle positions θ _A2 , θ _B2 , and θ _C2 , and uses this as an absolute rotation for output. Calculated as the angular position θ.

As described above, when an abnormality occurs in the sampling value c, a message image indicating the abnormal part can be displayed on the display device by outputting the C-phase signal abnormality detection flag to an external computer or the like. In addition, it is understood that an abnormality has occurred in any of the magnetic detectors 60a to 60c, and the location where the abnormality has occurred is also understood, so that a quick response is possible.
Further, the abnormality detection unit 2a holds information that there is an abnormality in the C phase, and thereafter, using only the sampling values a and b from the A phase and the B phase, the three absolute rotation angle positions from the second equation are used. It is also possible to calculate θ _A2 , θ _B2 , and θ _C2 and output them to the rotation information calculation unit 2b. That is, even if there is an abnormality in the C phase (magnetic detector 60c) in the magnetic detectors 60a to 60c, if the remaining A phase and B phase (magnetic detectors 60a and 60b) are normal, the calculation of the rotational angle position is performed. The processing can be continued and the calculation result can be output to the rotation information calculation unit 2b.

Furthermore, in the abnormality detection unit 101A, for example, by performing an abnormality detection process periodically such as every time the power is turned on or every sampling timing, it is possible to cope with an abnormality occurring in the remaining two phases. Is possible.
Similarly, when an abnormality has occurred in the A-phase signal, the rotation information calculation unit 101B calculates the average value of the three absolute rotation angle positions calculated using the sampling values b and c and the fourth equation. (= (Θ _A4 + θ _B4 + θ _C4 ) / 3) is calculated as the absolute rotation angle position θ for output, and if an abnormality has occurred in the B-phase signal, the rotation information calculation unit 101B uses the sampling value. An average value (= (θ _A3 + θ _B3 + θ _C3 ) / 3) of the three absolute rotation angle positions calculated using a, c and the third equation is calculated as the absolute rotation angle position θ for output. It has become.

On the other hand, when the signals of all phases are normal, the rotation information calculation unit 101B uses the average value of the nine absolute rotation angle positions calculated using the second to fourth equations as the absolute rotation angle for output. The position θ is calculated.
As described above, the rotation information calculation apparatus 101 according to the present embodiment uses the abnormality detection unit 101A to detect the A phase and B phase values a, b, A phase, and C phase among the sampling values in the three-phase magnetic detection signal. Based on the values a and c, and the values b and c of the B phase and the C phase, and the second to fourth formulas of the above formula (3), the absolute rotational angular positions θ _{A2 to} θ _A4 , θ _{B2 to} θ _B4 , Θ _{C2 to} θ _C4 can be calculated. Further, it is possible to, based on the result of comparison between the difference value and the threshold E _t of each of the three absolute rotational angular position calculated in the calculation formula, for detecting an abnormality of the sampling values. Furthermore, when there is an abnormality, it is possible to output an abnormality detection flag for the phase of the corresponding sampling value or an abnormality detection flag for stopping the operation.

Thereby, it is possible to accurately determine which phase of the magnetic detectors 60a to 60c is abnormal, and to output the abnormality detection flag to an external device or the like to determine the presence / absence and abnormality location of the abnormality. Can be done quickly. Further, since the operation can be stopped when normal information cannot be calculated, it is possible to prevent a malfunction of the output target.
In addition, the rotation information calculation apparatus 101 according to the present embodiment has two remaining normal phases when an abnormality occurs in one of the A phase, the B phase, and the C phase corresponding to the magnetic detectors 60a to 60c. Using these sampling values, the absolute rotation angle position θ, the rotation angular velocity ω, and the rotation direction can be continuously calculated.

As a result, when an abnormality occurs in only one phase, the rotation information calculation process can be continued and the normal operation of the output target can be maintained, so that it is possible to prevent the output target from being damaged due to a malfunction. .
As described above, in the above embodiment, the torque is detected by the two angle sensors, and the angle sensor calculates the rotation state using the three-phase magnetic detection signals from the three magnetic detectors. Even if an abnormality occurs in any one of the magnetic detection signals, the rotation state can be detected based on the remaining two-phase magnetic detection signals. Therefore, a double system can be configured as the angle sensor, and a highly reliable torque sensor can be obtained.

Further, by providing a means for detecting an abnormality of the three-phase magnetic detection signal, the reliability of the rotational angle position detected by the angle sensor can be increased, and a more reliable torque sensor can be obtained.
Further, based on the sampling values of the three magnetic detection signals having different phases, the rotation angle position is calculated by at least two calculation methods for each phase constituting the magnetic detector, and based on the calculated rotation angle position. Since the abnormality of the three magnetic detection signals is detected, it is possible to easily detect which of the three phases has an abnormality in the magnetic detection signal.

  Further, based on at least two combinations of the sampling values a and b, a and c, and b and c, at least 2 for each phase of the magnetic detector using a different calculation method for each combination. Since one rotation angle position is calculated and the abnormality of the three magnetic detection signals is detected based on the calculated rotation angle position of each phase, the abnormality of the magnetic detection signal of each phase can be detected easily and appropriately. Can do.

Furthermore, since the abnormality of the three magnetic detection signals is detected based on the difference value between the rotation angle positions for each phase, for example, if the difference value between the rotation angle positions of the two phases is equal to or greater than a predetermined error, the abnormality is detected. More accurate abnormality detection can be performed in consideration of noise and errors due to A / D conversion, such as determining that the error has occurred.
In addition, among the three magnetic detection signals, for each phase of the magnetic detection signal other than the magnetic detection signal in which the abnormality is detected, the average value of the rotation angle position used for the detection of the abnormality is determined as the final rotation of the rotating wheel. Since it is calculated as an angular position, it is possible to calculate a more accurate rotational angle position.

Furthermore, since the steering torque is calculated from the difference value between the absolute rotation angle position of the input shaft and the absolute rotation angle position of the output shaft, the steering torque can be obtained with a simple calculation. Further, since the absolute rotation angle position is detected by the angle sensor, the steering angle can be obtained at the same time, and there is no need to provide a separate steering angle detection device.
Furthermore, since two absolute rotation angles, which are errors smaller than the torsion angle of the torsion bar, are detected, if the error is within an allowable range, a dual system can be configured as a steering angle sensor.

In the above embodiment, the abnormality determination function of the torque sensor 3 can be provided. In this case, the two absolute rotation angle positions calculated by the first and second rotation information calculation devices 101a and 101b are compared, and the torsion angle of the torsion bar 3a has a difference of a predetermined angle (for example, ± 5 °) or more. At some point, it can be determined that an abnormality has occurred.
Further, in the above embodiment, the case where the first magnetic sensor 110a is connected to the first shaft 200a (input shaft 2a) has been described. However, the rotational angle position of the input shaft 2a is detected by the first magnetic sensor 110a. The first magnetic sensor 110a may be connected to the end of the torsion bar 3a on the input shaft 2a side. Similarly, the 2nd magnetic sensor 110b can also be connected with the output-shaft 2b side edge part of the torsion bar 3a.

  In the above embodiment, the above formula (3) is obtained from the abnormality detection parameter in advance, and the abnormality detection unit 101A uses this calculation formula to execute the abnormality detection process. For example, the abnormality detection parameter calculation process and the rotation angle position calculation expression generation process shown in the above equation (3) may be performed every time the power is turned on or when the power is turned on for the first time after shipment. . In addition, the calculation formula once generated is held until the power is turned off, or is kept even after the power is turned off, thereby reducing the generation processing load of the formula (3). Is possible.

Furthermore, in the said embodiment, although the magnetic sensor 110 and the rotation information calculation apparatus 101 were set as the separate structure, it is good also as a structure which includes the magnetic sensor 110 in not only this but the rotation information calculation apparatus 101. In this case, the rotation information calculation device 101 may be integrated into the magnetic sensor 110.
Moreover, in the said embodiment, although it was set as the structure which calculates | requires rotation angle position (theta) by the average value of the rotation angle position with respect to A phase-C phase calculated by either of the said 2nd formula-4th formula, it is not restricted to this. Instead, the rotation angle position may be converted into two phases by three-phase to two-phase conversion, and a configuration obtained from the ratio (arc tangent) or other configurations may be used.

Moreover, in the said embodiment, although the structure where the magnet 40 was magnetized by 2 poles was demonstrated, it is good also as a structure of the multipolar magnetization which magnetized the magnet 40 to 4 poles or more without limiting to this. In this case, the absolute rotation angle position cannot be calculated, but the relative rotation angle position can be calculated accurately.
Furthermore, in the said embodiment, although the magnetic detectors 60a-60c demonstrated the structure which is analog Hall IC, not only this but another analog element may be sufficient.

However, in the case of a general analog element such as a Hall element, the sensitivity is low and an amplifier circuit is required outside. However, when an analog Hall IC is used, the amplifier circuit is built in the analog Hall IC. Since there is no need to provide an amplifier circuit outside, it is desirable to use an analog Hall IC.
Moreover, in the said embodiment, although the magnetic path member 50 was made into the thin plate-shaped structure, not only this but the arc-shaped member of the same thickness as the height of the wall 50a may be sufficient. However, a plate-like shape is preferable because it can realize weight reduction and material cost reduction.

1 is a schematic configuration diagram of an electric power steering apparatus according to an embodiment of the present invention. It is a block diagram which shows the structure of a torque sensor. It is a block diagram which shows the structure of a rotation information detection apparatus. It is a disassembled perspective view of a magnetic sensor. It is a figure which shows the magnetic detection signal output from the magnetic detector of a magnetic sensor. It is a figure which shows the output principle of a magnetic detection signal. It is a flowchart which shows the abnormality detection process performed in an abnormality detection part. It is a flowchart which shows the rotation information calculation process performed in a rotation information calculation part.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Steering wheel, 2 ... Steering shaft, 3 ... Torque sensor, 10 ... Steering assist mechanism, 11 ... Reduction gear, 12 ... Electric motor, 15 ... Controller, 16 ... Vehicle speed sensor, 100 ... Rotation information detection apparatus, 101 ... Rotation Information calculation device, 101A ... anomaly detection unit, 101B ... rotation information calculation unit, 102 ... calculation unit, 110 ... magnetic sensor, 30 ... magnet holder, 40 ... magnet, 50 ... magnetic path member, 60a-60c ... magnetic detector

Claims (8)

A torque detection device that detects torque applied to a shaft in which an input shaft and an output shaft are coaxially connected via a torsion bar,
First angle detection means for detecting a rotational angle position of the input shaft;
Second angle detection means for detecting a rotational angle position of the output shaft;
Torque calculation means for calculating the torque based on the rotation angle position detected by the first angle detection means and the rotation angle position detected by the second angle detection means,
The first and second angle detecting means are supported by a magnet holder supported by a rotor, a magnet supported by the magnet holder, and a stator, and are arranged at predetermined intervals in the circumferential direction. Three magnetic detectors that output signals according to input magnetic flux, and magnetic flux from the magnets to the three magnetic detectors supported by the stator and disposed between the three magnetic detectors. A magnetic path member having three magnetic paths to be guided, and the three magnetic detectors whose phase changes according to the positional relationship between each magnetic path of the magnetic path member and the magnet when the rotor rotates. And a rotation information calculating means for calculating a rotation angle position of the rotor based on the three-phase magnetic detection signals.   An abnormality detection unit that detects an abnormality of the three-phase magnetic detection signal, and the rotation information calculation unit detects an abnormality in any one of the three-phase magnetic detection signals by the abnormality detection unit. 2. The torque detection device according to claim 1, wherein the rotation angle position is calculated based on the magnetic detection signals of the remaining two phases excluding the phase of the magnetic detection signal in which the abnormality is detected.   The abnormality detection means calculates the rotational angle position by at least two calculation methods for each of the three phases constituting the magnetic detector based on the sampling value of the magnetic detection signal of the three phases. The torque detection device according to claim 2, wherein an abnormality of the three-phase magnetic detection signal is detected based on the calculated rotation angle position.   The three phases of the magnetic detector are A phase, B phase, and C phase, and the sampling values of magnetic detection signals corresponding to the A phase, B phase, and C phase are a, b, and c, respectively. Based on at least two combinations among the sampling values a and b, the sampling values a and c, and the combination of the sampling values b and c, the detection means uses the calculation method that differs for each combination, and At least two rotation angle positions are calculated for each phase of the detector, and abnormality of the three-phase magnetic detection signals having different phases is detected based on the calculated rotation angle positions of the respective phases. Item 4. The torque detection device according to Item 3.   5. The torque according to claim 3, wherein the abnormality detection unit detects an abnormality of the three-phase magnetic detection signals having different phases based on a difference value between the rotation angle positions with respect to the phases. Detection device.   The rotation information calculation means is the rotation angle position used for detecting the abnormality for each phase of the magnetic detection signal other than the magnetic detection signal in which an abnormality is detected by the abnormality detection means among the three magnetic detection signals. The torque detection device according to any one of claims 3 to 5, wherein an average value is calculated as a rotation angle position of the rotor.   The torque calculation means calculates the torque based on a difference value between the absolute rotation angle position detected by the first angle detection means and the absolute rotation angle position detected by the second angle detection means. The torque detection device according to any one of claims 1 to 6, characterized in that   An electric power steering device, wherein the torque detection device according to any one of claims 1 to 7 is arranged on a steering shaft, and the torque detection device detects the steering torque.

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