JP2012173258A - Torque measurement apparatus and steering apparatus mounting the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a torque measurement apparatus capable of accurately measuring torque applied between two shafts connected on the same axis through a torsion bar, allowed to be downsized and capable of quickly performing torque measurement even just after turning on a power supply or the like.SOLUTION: Annular sensor targets 1 and 2 on which a plurality of poles 1a and 2a to be detected are equally arranged in a circumferential direction are respectively arranged on two shafts 21 and 22. Magnetic sensors 3 and 4 for detecting the poles 1a and 2a to be detected of the sensor targets 1 and 2 are respectively arranged. Torque to be applied between the two shafts 21 and 22 is measured based on output signals from the respective magnetic sensors 3 and 4. The sensor targets 1 and 2 respectively include two magnetic tracks 401 and 402 on which the phases of the respective poles 1a and 2a to be detected are mutually shifted in the circumferential direction. The magnetic sensors 3 and 4 respectively detect and output positions of the two magnetic tracks 401 and 402 in one magnetic pole pair of the poles 1a and 2a to be detected and output one reference signal for each one magnetic pole pair of the poles 1a and 2a to be detected.

Description

  The present invention relates to a torque measuring device that measures torque applied between two shafts connected coaxially via a torsion bar, and a steering device equipped with the torque measuring device.

  As this type of torque measuring device, the one shown in Patent Document 1 has been proposed. The purpose is to suppress the fluctuation of the air gap between the sensor target and the magnetic sensor due to the bending deformation of the torsion bar, and to detect the rotational torque with high accuracy. As a configuration, a plurality of sensor targets each including a spiral protrusion are provided on each of an input shaft and an output shaft that are coaxially connected via a torsion bar. A magnetic sensor for detecting each sensor target is provided, and a torque applied between both shafts is detected based on a difference caused by displacement of the sensor target detected by each magnetic sensor due to torsion of the torsion bar.

  In addition, what is shown in Patent Document 2 has been proposed. The purpose is to increase the torque detection accuracy with a much simpler structure than before. As a configuration, a magnetic medium having at least two magnetic tracks is provided on each of an input shaft and an output shaft that are coaxially connected via a torsion bar. A magnetic detection element sensitive to each magnetic track is arranged facing each magnetic medium, and the torque applied between the two axes is detected based on the output signals of these magnetic detection elements.

In addition, there exists what provided the magnetic line sensor and the multiplication circuit as what aims at resolution | decomposability of rotation angle detection (for example, patent document 3, 4). This is because the signals from the magnetic line sensors arranged in a row are added to generate intermediate signals S1 and S2, and the intermediate signals S1 and S2 are further processed to calculate a two-phase signal that is 90 ° out of phase. In this configuration, the signals SIN and COS are obtained. According to this configuration, accurate signals SIN and COS can be obtained according to the magnetic encoder to be detected, and a highly accurate multiplied output can be generated based on the signals SIN and COS.
Further, an encoder with a reference signal pulse for generating a reference signal by a double-row magnetic encoder has been proposed (Patent Documents 5 and 6).

JP 2001-324394 A JP 2004-611149 A JP-T-2001-518608 Special Table 2002-541485 JP-T-2001-518609 Japanese translation of PCT publication No. 2002-512687

In the torque measuring device disclosed in Patent Document 1, it is necessary to repeatedly provide a partial spiral protrusion around the shaft as a sensor target, and there is a problem that the configuration becomes complicated.
The torque measuring device disclosed in Patent Document 2 requires a plurality of magnetic tracks and a plurality of magnetic sensors opposed to them. Therefore, there exists a problem that the whole apparatus becomes large in an axial direction, and the applicable range may be restricted.

  In order to solve the problem of the conventional torque measuring device, the present applicant made the following proposal (Japanese Patent Application No. 2009-230614). That is, in each of the torque measuring devices for measuring the torque applied between the two shafts by providing a sensor target and a magnetic sensor on each of the two shafts, each of the magnetic sensors is covered within the pitch of the detected pole in the corresponding sensor target. It has a plurality of sensor elements that are displaced from each other in the direction in which the detection poles are arranged, and obtains a two-phase signal output of SIN and COS. Alternatively, in the torque measuring device, each of the magnetic sensors includes a line sensor in which a plurality of sensor elements are arranged along the arrangement direction of the detected poles in the corresponding sensor target, and outputs a two-phase signal output of SIN and COS. Generate by calculation. According to the configuration of this proposed example, the torque applied between the two axes can be accurately measured, and further downsizing can be achieved. Furthermore, if the structure of the magnetic sensor is provided with a multiplication detection function, the detection resolution is increased, and the torque measurement accuracy is further improved.

  The torque measuring device of the proposed example is configured to detect a torsion amount between the magnetic sensors of both shafts by counting a rotation pulse signal output as the shaft rotates, and convert the torque. If the counters for both axes are not reset when the input torque is zero, accurate torque cannot be obtained. Therefore, if the torque is applied immediately after the power is turned on, if it is applied to some other state, for example, a steering device, the state where the input torque is zero is determined from the state of the vehicle, and the counter An operation to reset the value was necessary.

Further, the proposed example also presents a configuration in which the count is reset even if an erroneous count occurs in the count of the rotation pulse signal by outputting the reference signal once every rotation of the sensor target. . However, when there is no phase information from the reference signal, such as immediately after the power is turned on, a torque measurement error occurs. As described above, when the reference signal is output once per rotation, a state without phase information continues for a long time. A measurement error is not generated as much as possible, and even if it occurs, it is desirable to eliminate it in as short a time as possible.
If a sensor for outputting a reference signal is separately installed, the installation space and cost increase. Therefore, it is desirable to solve the above-described problem with the simplest possible configuration.

  In any of the encoders with reference signal pulses of Patent Documents 5 and 6, there is a singular pattern in a part of the circumferential direction for generating the reference signal, which may cause deterioration in pitch accuracy due to magnetic interference between tracks. .

The object of the present invention is to accurately measure the torque applied between two shafts connected coaxially via a torsion bar, to enable downsizing, and to measure the torque immediately after the power is turned on. It is to provide a measuring device.
Another object of the present invention is to provide a steering device capable of accurately measuring torque immediately after the power is turned on and the like and capable of downsizing the torque measuring device.

The torque measuring device according to the present invention has an annular shape in which a plurality of detected poles arranged concentrically with the first and second shafts coaxially connected via a torsion bar are arranged in the circumferential direction. Torque sensors for measuring the torque applied between the first and second shafts based on the output signals of the respective magnetic sensors. A measuring device,
Each sensor target has two magnetic tracks in which a plurality of detected poles are equally arranged, and both magnetic tracks are formed so that the phases of the detected poles are shifted from each other in one circumferential direction, Each magnetic sensor has two track-specific sensor units that respectively detect the detected poles of the two magnetic tracks in the opposing sensor target. From the detection signals of these two track-specific sensor units, one of the detected poles is detected. A rotation pulse signal representing each position obtained by dividing the pitch into a plurality of positions within the pitch of the magnetic pole pair and one reference signal for each magnetic pole pair of the detected pole are generated and output.

According to this configuration, a reference signal corresponding to the number of magnetic pole pairs formed on the sensor target and a rotation pulse signal representing each divided position within the pitch of one magnetic pole pair of the detected poles are obtained. Therefore, if the rotational motion for one magnetic pole pair is performed at the maximum, the absolute position in the magnetic pole pair can be acquired from the count value of the rotation pulse signal and the reference signal. For example, when 36 magnetic pole pairs are formed, the absolute position in the magnetic pole pair can be obtained if the magnetic pole pair rotates by 10 degrees at the maximum. Therefore, even if the relative angular deviation between the two magnetic sensors is unknown, such as immediately after the power is turned on, the magnitude of the angular deviation can be determined by applying a slight rotation, and thereby the first and second Accurate torque detection can be performed by detecting the twist angle between the shafts. There is no need to store the count value of each rotation pulse signal, and a simple detection circuit configuration is possible. That is, it is not necessary to determine the torque zero state from the operation state and perform a counter reset operation, and the configuration of the detection processing circuit and the processing software is simplified.
In the sensor target, two magnetic tracks are formed with a constant circumferential phase difference over the entire circumference, so that there is no singular pattern in the circumferential direction. Therefore, there is no deterioration in pitch accuracy due to magnetic interference between tracks, and high rotation detection accuracy can be obtained. Therefore, more accurate torque detection can be performed.

In the present invention, each track-specific sensor portion of the magnetic sensor has a line sensor in which sensor elements are arranged along the direction in which the detected poles of the opposing magnetic tracks are arranged, and outputs two-phase signal outputs of SIN and COS. It may be generated by calculation.
When the line sensor is used in this way, the position between the detected poles can be detected by the magnetic sensor while keeping the pitch of the detected poles of the sensor target equal to that of a normal ABS (anti-lock brake system) sensor or the like. Thus, it is possible to detect minute rotations of the first and second axes. Therefore, even a slight rotational deviation between the two axes can be detected, and even a minute torque applied between the two axes can be accurately measured from the difference in the detected rotation angles of the two magnetic sensors. As a result, it is possible to accurately measure the torque applied between the first and second shafts connected coaxially via the torsion bar.

In the present invention, the magnetic sensor includes a sensor element unit that detects the detected pole, and a detection processing circuit unit. The detection processing circuit unit multiplies the output signal of the sensor element unit and outputs the output signal. A multiplication circuit that generates a rotation pulse signal with higher resolution may be included.
By providing the multiplication circuit, a rotation pulse signal with higher resolution can be generated with a simple and compact configuration. As a result, even a slight rotational deviation between the two axes can be detected, and even a minute torque applied between the two axes can be accurately measured from the difference in the detected rotation angles of the two magnetic sensors.
As described above, by using a line sensor or providing a multiplication circuit, a minute rotation angle of the first and second axes is detected by counting rotation pulses, so one of two sensor targets. Even when is stopped, that is, even when one of the two axes is stationary, the torque applied between the two axes can be measured accurately.

In the present invention, the detection processing circuit unit may output two rotation pulse signals of A phase and B phase, which are 90 ° different from each other, as the multiplied rotation pulse signal.
When the two rotation pulse signals of the A and B phases are output, the rotation direction can be determined by these two phase signals. Therefore, it is possible to measure torque in either the positive or negative rotational direction.

  In the present invention, each magnetic sensor includes a sensor element unit for detecting the detected pole, and a detection processing circuit unit. The detection processing circuit unit is configured to detect one of the sensor targets from an output signal of the sensor element unit. One index signal may be generated by rotation. When one index signal is output in one rotation, detection of the absolute angle is further facilitated.

In the present invention, a counter for detecting a rotation angle of each corresponding sensor target from a count value of a rotation pulse signal generated by each magnetic sensor, and an angle difference calculating means for obtaining a difference between two rotation angles detected by the counter. And a torque calculating means for calculating a torque applied between the first and second shafts from the difference, and included in the calculated torque from the difference and the operating state of the first and second shafts. An offset canceling unit that estimates the steady offset amount and cancels the offset from the torque calculation may be provided.

When the rotation pulses generated by each magnetic sensor are counted with a counter and the rotation angle of the sensor target is held as a count value, a steady offset occurs due to mechanical rattling, or the counters of both counters count due to erroneous counters due to noise. An error may occur in the torque calculation due to the deviation of numerical values. When the offset canceling means performs the filtering process according to the operating state while monitoring the difference between the rotation pulses to extract the steady offset, and the offset is removed in the calculation process by the torque calculating means, the mechanical rattle Thus, it is possible to reduce the influence of offset caused by the above and to perform accurate torque measurement. The “operating state” refers to a distinction between a stopped state and an operating state of a device such as an automobile in which the torque measuring device is installed, a rotation direction of the shaft on the input side before starting torque measurement, and the like.

In the present invention, a counter for detecting the rotation angle of each corresponding sensor target from the number of rotation pulse signals generated by each magnetic sensor, and an angle difference calculation for obtaining a difference between the two rotation angles detected by these counters. And a torque calculating means for calculating a torque applied between the first and second shafts from the difference, and the count value in an operating state in which no torque is applied to the first and second shafts. Count value resetting means for resetting may be provided.
In the case of this configuration, it is possible to accurately measure the torque by removing the influence of noise accumulated on the count value.

In the present invention, a magnetic body for preventing magnetic interference may be provided between the two sensor targets.
Two magnetic sensors arranged close to each other may receive interference from a sensor target that is not a detection target. By interposing a magnetic body for preventing magnetic interference between the two sensor targets, it is possible to prevent the magnetic sensor from receiving interference from a sensor target that is not a detection target, thereby enabling accurate torque detection.

A steering device with a shaft torque measuring function according to the present invention is equipped with the torque measuring device according to any one of the above configurations of the present invention.
The torque measuring device according to the present invention can immediately and accurately measure the torque applied between the first and second shafts immediately after the power is turned on, and can be downsized. Therefore, for example, when mounted on a steering device such as an automobile, the torque applied between the input shaft connected to the steering wheel and the output shaft connected to the steering mechanism can always be accurately measured, such as power steering and steer-by-wire. This makes it possible to perform steering control at a higher level. Thereby, it is possible to contribute to easiness of driving, improvement of safety, and the like. Further, it is possible to avoid an increase in size while achieving high detection accuracy.

  The torque measuring device according to the present invention has an annular shape in which a plurality of detected poles arranged concentrically with the first and second shafts coaxially connected via a torsion bar are arranged in the circumferential direction. Torque sensors for measuring the torque applied between the first and second shafts based on the output signals of the respective magnetic sensors. In each of the sensor targets, each sensor target has two magnetic tracks in which a plurality of detected poles are equally arranged, and the phases of the detected poles are shifted from each other in one circumferential direction. Each of the magnetic sensors has two track-specific sensor portions that respectively detect the detected poles of the two magnetic tracks in the opposing sensor target. From the detection signals of the two track-specific sensor units, a rotation pulse signal representing each position obtained by dividing the pitch into a plurality of positions within the pitch of one magnetic pole pair of the detected pole, and one magnetic pole pair of the detected pole Since it generates and outputs one reference signal, it can accurately measure the torque applied between the two shafts that are coaxially connected via the torsion bar, and can be downsized. Torque can be measured.

  Since the steering device according to the present invention is equipped with the torque measuring device according to the present invention, the torque can be accurately measured immediately after the power is turned on, and the torque measuring device can be downsized.

It is a front view showing a schematic structure of a torque measuring device concerning one embodiment of this invention. (A) is sectional drawing which shows the specific structure of the torque measuring device, (B) is a figure which shows the magnetic pattern of the sensor target. It is a figure which shows the relationship between the magnetic pattern of the sensor target, and the output signal of a magnetic sensor. (B) Sectional drawing of the torque measuring device concerning other embodiment of this invention, (B) is a figure which shows the magnetic pattern of the sensor target. It is a block diagram which shows one structural example of the signal processing system in the torque measuring device of each embodiment. It is explanatory drawing which shows a specific example of the magnetic sensor in the torque measuring device of each embodiment. It is explanatory drawing which shows the other specific example of the magnetic sensor in the torque measuring device of each embodiment. It is a block diagram which shows the other structural example of the signal processing system in the torque measuring device. It is explanatory drawing which shows the further another structural example of the signal processing system in the torque measuring device. It is a block diagram which shows an example of the multiplication circuit in the same magnetic sensor. It is a front view which shows the further another schematic structural example in the torque measuring device concerning embodiment of this invention. It is explanatory drawing of schematic structure of the steering device using the torque measuring device concerning embodiment of this invention.

  A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a front view of a schematic configuration example of the torque measuring device. In the figure, the first and second shafts 21 and 22 are coaxially connected via a torsion bar 23. The first shaft 21 is an input-side rotating shaft, and the rotational torque thereof is transmitted to the second shaft 22 that is the output-side rotating shaft via the torsion bar 23. This torque measuring device measures the torque applied between the first and second shafts 21 and 22, and includes sensor targets 1 and 2 provided on the shafts 21 and 22, respectively, 2 and two magnetic sensors 3 and 4 provided to face each other. These magnetic sensors 3 and 4 include sensor element units 3C and 4C constituted by sensor elements such as Hall elements, and detection processing circuit units 3D and 4D for processing detection signals of the sensor element units 3C and 4C.

  The sensor targets 1 and 2 are annular members in which a plurality of detected poles 1a and 2a arranged in the circumferential direction concentrically with the shafts 21 and 22 are, for example, magnetic encoders. Here, an example of the radial type sensor targets 1 and 2 in which the detected poles are arranged on the peripheral surface is shown, and the peripheral surface is a detected surface detected by the magnetic sensors 3 and 4. The magnetic encoder alternately magnetizes N poles and S poles in the circumferential direction as the detected poles 1a and 2a, so that a plurality of magnetic pole pairs consisting of N poles and S poles are provided in the circumferential direction over the entire circumference. They are equally distributed. In the figure, only a part of the detected poles 1a and 2a in the circumferential direction is shown, and the others are not shown. As the sensor targets 1 and 2, a gear-shaped pulsar ring may be used in addition to the magnetic encoder. In the case of a gear-shaped pulsar ring, a combination part of a pair of tooth crests and troughs is one magnetic pole pair.

  Output signals of the detection processing circuit units 3D and 4D of the two magnetic sensors 3 and 4 are input to the signal processing circuit 6, and the torque applied between the first and second shafts 21 and 22 is measured by the arithmetic processing here. Is done. The two magnetic sensors 3 and 4 are configured as one sensor unit 5 and installed on the fixed side member 26. The sensor unit 5 may be integrated with only the sensor element portions 3C and 4C of the two magnetic sensors 3 and 4, or may be integrated with the detection processing circuit portions 3D and 4D. .

  As shown in FIG. 11, two magnetic sensors 3 and 4 are mounted on one semiconductor chip 7 together with the signal processing circuit 6 (not shown in FIG. 11) or the like, or on one substrate. A single sensor unit 5 may be configured by mounting. When the signal processing is performed in the sensor unit 5 as described above, the number of signal lines to be output to the outside can be minimized, and the number of wires can be reduced, the wire diameter can be reduced, and the installation space can be reduced. become.

  FIG. 2 shows a specific example of the torque measuring device of this embodiment. In FIG. 2A, the first and second shafts 21 and 22 are rotatably supported by a fixed member 26 serving as a measuring device housing via bearings 24 and 25, respectively. The torsion bar 23 has a smaller diameter than the first and second shafts 21 and 22. The sensor targets 1 and 2 attached to the first and second shafts 21 and 22 use radial type magnetic encoders in which annular multipolar magnets 1c and 2c are provided on the outer peripheral surfaces of the annular core bars 1b and 2b. ing. The core bars 1b and 2b are made of a magnetic material or a non-magnetic material. The multipolar magnets 1 c and 2 c are the outer peripheral surfaces of the sensor targets 1 and 2.

  Both sensor targets 1 and 2 protrude from the opposing end surfaces of the first and second shafts 21 and 22 so that the detection surfaces formed by the outer peripheral surfaces of the multipolar magnets 1c and 2c are close to each other in the axial direction. Installed. The core bars 1b and 2b have cylindrical collar-like fitting portions 1ba and 2ba fitted to the outer peripheral surfaces of the first and second shafts 21 and 22 so that the projecting attachment is possible. Projecting in the axial direction. By arranging the two sensor targets 1 and 2 close to each other in the axial direction, the magnetic sensors 3 and 4 that are opposed to the sensor targets 1 and 2 in the radial direction are close to each other in the axial direction (for example, 5 mm or less). (At intervals). In this way, the two sensor targets 1 and 2 are arranged close to each other in the axial direction, and the corresponding two magnetic sensors 3 and 4 are also arranged close to each other in the axial direction, so that the first and The torque applied between the second shafts 21 and 22 can be accurately detected.

  In this case, the two magnetic sensors 3 and 4 arranged close to each other may receive interference from the sensor target 2 or 1 that is not the detection target. Therefore, in this configuration example, a spacer 2d made of a magnetic material is provided in the axially intermediate portion where the detected poles 1a and 2a of the two sensor targets 1 and 2 are close to each other to prevent the interference. Specifically, the spacer 2d is configured by forming an end of the core metal 2a of one sensor target 2 facing the other sensor target 1 as a cylindrical flange portion extending to the outer diameter side. The spacer 2d may be provided on the other sensor target 1.

  As shown in FIG. 2B, the multipolar magnets 1c and 2c are magnets in which N poles and S poles are alternately magnetized in the circumferential direction C. The detected poles 1a and 2a are configured. The multipolar magnets 1c and 2c have two magnetic tracks 401 and 402 arranged in the axial direction. Each of the magnetic tracks 401 and 402 has a magnetic pattern of the same pitch with the same number of detected poles, and the phases of the detected poles 1a1 and 1a2 of the respective magnetic tracks 401 and 402 are shifted in the circumferential direction. FIG. 2B shows the magnetic tracks 401 and 402 of one sensor target 1, but the other target 2 as well as the sensor target 1 has the detected poles 2a1 and 2a1 of the magnetic tracks 401 and 402. The phases of 2a2 are shifted from each other in the circumferential direction. A combination of the detected poles 1a1 and 1a2 of the two magnetic tracks 401 and 402 and the detected poles 2a1 and 2a2 is referred to as the detected poles 1a and 2a of the sensor targets 1 and 2, respectively. Between the two magnetic tracks 401 and 402 of the sensor targets 1 and 2, it is preferable to interpose magnetic bodies 1e and 2e for preventing magnetic interference as shown in FIG.

In FIG. 2A, the two magnetic sensors 3 and 4 pass through a minute gap in the radial direction with respect to the detected surface so that the detected poles 1a and 2a of the corresponding sensor targets 1 and 2 can be detected. Are installed on the fixed-side member 26. In this example, the two magnetic sensors 3 and 4 are configured as one sensor unit 5 as described above, and are installed on the inner peripheral surface of the stationary member 26. Each of the magnetic sensors 3 and 4 includes a track-specific sensor unit 31 and 32 for detecting the detected poles 1a1 and 1a2 and the detected poles 2a1 and 2a2 of the magnetic tracks 401 and 402 of the sensor targets 1 and 2, respectively. It is composed of separate sensor units 41 and 42, respectively.
As described above with reference to FIG. 1, the magnetic sensors 3 and 4 include sensor element units 3C and 4C and detection processing circuit units 3D and 4D. The sensor element units 3C and 4C include the track-specific sensor units 31 and 32. , 4 1 and 4 2, but the detection processing circuit units 3D and 4D are provided separately for each of the track-specific sensor units 3 1, 3 2, 4 1 and 4 2. Alternatively, it may be composed of individual parts and common parts.

  Each of the magnetic sensors 3 and 4 is a rotation pulse signal representing the position of the detected poles 1a and 2a within the pitch λ of the detected poles 1a and 2a from the detection signals of the two track-specific sensor units 31, 32, 41 and 42. And one reference signal for each pair of magnetic poles to be detected. As the rotation pulse signal, it is preferable to output an A-phase signal and a B-phase signal as shown in FIG. The A-phase signal and the B-phase signal are signals whose phases are different from each other by a pulse period of 360 °. In this specification, the reference signal may be referred to as a Z-phase signal as shown in FIG. A method for generating these signals will be described later. Each of the magnetic sensors 3 and 4 outputs, in addition to the rotation pulse signal indicating the position in the magnetic pole pitch and the reference signal, an index signal for one rotation indicating the origin position of the sensor targets 1 and 2. It may be calculated from a pulse signal or a reference signal and output.

  FIG. 4 shows a torque measuring device according to an embodiment of the present invention. 4A, in this example, axial type magnetic encoders are used as the sensor targets 1 and 2 attached to the first and second shafts 21 and 22, respectively. Each of these sensor targets 1 and 2 includes core bars 1b and 2b and annular multipolar magnets 1c and 2c. Each of the core bars 1b and 2b extends from the cylindrical portions 1ba and 2ba and one end thereof toward the outer diameter side. It is L-shaped in cross section consisting of disc-shaped flange portions 1bb and 2bb. The multipolar magnets 1c and 2c are provided along the outer peripheral edges of the flange portions 1bb and 2bb of the core bars 1b and 2b. The detected surfaces of the multipolar magnets 1c and 2c are surfaces facing the axial direction. The two sensor targets 1 and 2 are arranged so that the multipolar magnets 1c and 2c constituting the detection surface are arranged concentrically on the outer side and the inner side in the radial direction. Further, these multipolar magnets 1c and 2c have their detection surfaces facing in the same direction and located on the same plane.

  Both sensor targets 1 and 2 have their detection surfaces arranged concentrically on the same plane as described above, but between the multipolar magnets 1c and 2c of both sensor targets 1 and 2 are for magnetic interference prevention. An annular spacer 2d is provided. The spacer 2d is made of a magnetic material, and is composed of a shallow cylindrical portion extending in the axial direction provided on the outer peripheral edge of the flange portion 2bb of the core metal 2b of one sensor target 2. A spacer 2d may be provided on the core metal 1b of the other sensor target 11.

  As shown in FIG. 4 (B), the multipolar magnets 1c and 2c are magnets in which N poles and S poles are alternately magnetized in the circumferential direction C. The detected poles 1a and 2a are configured. The multipolar magnets 1c and 2c have two magnetic tracks 401 and 402 arranged in the radial direction. Each of the magnetic tracks 401 and 402 has a magnetic pattern of the same pitch with the same number of detected poles, and the phases of the detected poles 1a1 and 1a2 of the respective magnetic tracks 401 and 402 are shifted in the circumferential direction. In the case of this axial type, “equal pitch” means that the pitches of the central angles of the annular magnetic tracks 401 and 402 are equal. FIG. 4B shows the magnetic tracks 401 and 402 of one sensor target 1, but the other target 2 as well as the sensor target 1 has detected poles 2 a 1 and 2 of the magnetic tracks 401 and 402. The phases of 2a2 are shifted from each other in the circumferential direction. A combination of the detected poles 1a1 and 1a2 of the two magnetic tracks 401 and 402 and the detected poles 2a1 and 2a2 is referred to as the detected poles 1a and 2a of the sensor targets 1 and 2, respectively. Between the two magnetic tracks 401 and 402 of the sensor targets 1 and 2, it is preferable to interpose magnetic bodies 1e and 2e for preventing magnetic interference as shown in FIG.

In FIG. 4A, the two magnetic sensors 3 and 4 pass through a minute gap in the axial direction with respect to the detected surface so that the detected poles 1a and 2a of the corresponding sensor targets 1 and 2 can be detected. Are installed on the fixed-side member 26. In this example, the two magnetic sensors 3 and 4 are configured as one sensor unit 5 as described above, and are installed on the inner peripheral surface of the stationary member 26. Each of the magnetic sensors 3 and 4 includes a track-specific sensor unit 31 and 32 for detecting the detected poles 1a1 and 1a2 and the detected poles 2a1 and 2a2 of the magnetic tracks 401 and 402 of the sensor targets 1 and 2, respectively. It is composed of separate sensor units 41 and 42, respectively.
As described above with reference to FIG. 1, the magnetic sensors 3 and 4 include sensor element units 3C and 4C and detection processing circuit units 3D and 4D (not shown in FIG. 4), and the sensor element units 3C and 4C. Is provided for each of the track-specific sensor units 31, 32, 41, and 42, but the detection processing circuit units 3D and 4D may be configured by one for each of the track-specific sensor units 31, 32, 41, and 42. Two of them may be provided individually, or may be constituted by an individual part and a common part.

  Each of the magnetic sensors 3 and 4 is a rotation pulse representing each position within the pitch λ of one magnetic pole pair of the detected poles 1a and 2a from the detection signals of the two track-specific sensor sections 31, 32, 41 and 42. A signal and one reference signal for each magnetic pole pair of the detected poles are generated and output. As the rotation pulse signal, it is preferable to output an A-phase signal and a B-phase signal as shown in FIG. The A-phase signal and the B-phase signal are signals whose phases are different from each other by a pulse period of 360 °. Other configurations in this embodiment are the same as those in the first embodiment described with reference to FIGS.

A configuration example of the detection processing circuit units 3D and 4D of the magnetic sensors 3 and 4 shown in FIG. In each of the magnetic sensors 3 and 4, a detection processing circuit unit 3D that generates a rotation pulse signal and a reference signal (Z-phase signal) as shown in FIG. , 4D (FIG. 1) and sensor element units 3C, 3D corresponding to the configuration can be roughly classified into the following three types.
(1) A configuration in which each of the track-specific sensor units 31, 32, 41, and 42 has one magnetic sensor element and generates a rotation pulse signal and a reference signal from the output.
(2) The sensor elements of the track-specific sensor units 3 1, 3 2, 4 1, 4 2 are set to two 90 ° phase differences as will be described later with reference to FIG. 6, and a rotation pulse signal and a reference signal are generated from the outputs. Constitution.
(3) A configuration in which the sensor elements of the track-specific sensor units 31, 32, 41, and 42 are line sensors as will be described later with reference to FIG.

A configuration example of the above (1) will be described. Since the configurations of both sensor targets 1 and 2 and magnetic sensors 3 and 4 are the same as each other, only one sensor target 1 and magnetic sensor 3 will be described, and description of the other sensor will be omitted.
The detected poles 1a1 and 1a2 of the two magnetic tracks 401 and 402 of the sensor target 1 have a phase difference of 90 ° in the circumferential direction with one magnetic pole pair λ as one period (note that The phase difference in the example of FIG. 3 is not 90 °). Each of the track-specific sensor units 31 and 32 is a magnetic sensor element such as a Hall element, and is installed at the same circumferential position. The two-phase detection signals obtained from these two magnetic sensor elements for each track are SIN signals and COS signals (sin φ, cos φ) having a phase difference of 90 ° due to the phase difference between the detected poles 1a1 and 1a2. It is. The detection processing circuit unit 3D calculates the magnetic pole phase φ from these two detection signals (sin φ, cos φ) by the following equation: φ = tan ⁻¹ (sin φ, cos φ). By outputting the phase in the magnetic pole as a pulse that is output every 90 °, for example, it is possible to detect the rotation of the detected pole 1a with a resolution of quadruple.

  For the reference signal, for example, a difference between two-phase detection signals (SIN signal, COS signal) obtained from two magnetic sensor elements for each track is detected, and a pulse whose range exceeds the threshold is generated. The pulse signal output at each end of the detected poles 1a1 and 1a2 is obtained. The threshold is set as appropriate. The detection processing circuit unit 3D outputs the pulse signal thus obtained as the reference signal.

An example in which the two sensor elements having the 90 ° phase difference (2) are used will be described with reference to FIG. In this example, for each of the two track-specific sensor units 3 1, 3 2, 4 1, 4 2 (FIGS. 2 and 3) in each magnetic sensor 3, 4, one magnetic pole pair is 360 °, and a 90 ° phase difference (λ / 4) ), Two magnetic sensor elements 3A and 3B (4A and 4B) such as Hall elements arranged so that the magnetic poles are arranged apart from each other are used. A magnetic pole phase (φ = tan ⁻¹ (sin φ / cos φ)) is calculated from the two-phase signals (sin φ, cos φ) obtained by these two magnetic sensor elements 3A, 3B (4A, 4B). By detecting the phase in the magnetic pole as a pulse output every 90 °, for example, it is possible to detect rotation with a resolution that is four times the number of poles to be detected. The waveform diagram of FIG. 6 shows the arrangement of magnetic poles in one magnetic track of the sensor targets 1 and 2 in terms of magnetic field strength.

  When the track-specific sensor units 31, 32, 41, and 42 of the magnetic sensors 3 and 4 are configured as described above, the positions within the detected poles 1 a and 2 a can be detected more finely, and the sensor targets 1 and 2 can be detected with higher accuracy. Can be detected. In this case, in order to reduce the influence of magnetic noise, the two magnetic sensor elements 3A and 3B (4A and 4B) may have a differential configuration so as to obtain a more stable signal.

  For the reference signal, for example, by detecting the difference between the two pulse signals for each track obtained as described above, and generating a pulse in a range where the difference exceeds the threshold value, one of the detected poles A pulse signal output at each end of 1a1, 1a2, (2a1, 2a2) is obtained. The detection processing circuit unit 3D in FIG. 1 outputs the pulse signal thus obtained as the reference signal.

  An example using the line sensor (3) will be described with reference to FIG. In this example, the direction in which the detected poles 1a and 2a of the corresponding sensor targets 1 and 2 are arranged for each of the two track-specific sensor sections 31, 32, 41 and 42 (FIGS. 2 and 3) in the magnetic sensors 3 and 4 respectively. Line sensors 3AA and 3AB (4AA and 4AB) in which the magnetic sensor elements 3a and 4a are arranged along the line are used. FIG. 7A is a waveform diagram in which the section of one detected pole 1a, 2a for one magnetic track in the sensor targets 1, 2 is converted into a magnetic field intensity. In this case, the first line sensors 3AA and 4AA of the magnetic sensors 3 and 4 are arranged in association with the 90 ° phase section of the 180 ° phase section in FIG. 7A, and the second line sensor 3AB. , 4AB are arranged in association with the remaining 90 ° phase interval. With such an arrangement, the signal S1 obtained by adding the detection signals of the first line sensors 3AA and 4AA by the adding circuit 31 and the signal S2 obtained by adding the detection signals of the second line sensors 3AB and 4AB by the adding circuit 32 are obtained. By adding by another adding circuit 33, a SIN signal corresponding to the magnetic field signal as shown in FIG. 7C is obtained. In addition, the signal S1 and the signal S2 via the inverter 35 are added by another adding circuit 34 to obtain a COS signal corresponding to the magnetic field signal as shown in FIG.

  FIG. 5 is a block diagram showing a schematic configuration of the signal processing circuit 6 for calculating the torque shown in FIG. The magnetic sensors 3 and 4 are configured in any one of the above (1) to (3), so that the number of detected poles 1a and 2a (FIG. 1) in the corresponding sensor targets 1 and 2 (FIG. 1) A multiplication function capable of detecting rotation with a resolution of several to several tens of times and a reference signal output function for each magnetic pole pair are provided.

  The phase detection circuits 8A and 8B provided in the next stage of each magnetic sensor 3 and 4 are based on the rotation pulse signals (SIN and COS signals) which are detection signals of the respective magnetic sensors 3 and 4, and corresponding sensor targets 1 and 2 magnetic phase is detected. The magnetic phase is a phase representing a position in one magnetic pole pair, and one magnetic pole pair is 360 °. The phase difference detection means 9 provided in the next stage outputs a phase difference between them based on the detection phase signals output from the phase detection circuits 8A and 8B. A twist angle between the first and second shafts 21 and 22 is obtained from this phase difference. The torque calculation means 10 provided in the next stage performs processing for calculating the torque applied between the shafts 21 and 22 from the phase difference obtained by the phase difference detection means 9 according to a preset calculation parameter. . The obtained torque value is output to the outside by the output circuit 11 in a data format through a communication interface such as a voltage value, a current value, a PWM signal, or a CAN bus (controller area network bus). The controller 12 has functions such as rewriting calculation parameters in the torque calculation means 10 and reading calculation results through communication with the outside. In addition to these functions, the sensor targets 1 and 2 may have a function of storing parameters that vary depending on the configuration of the magnetic sensors 3 and 4 such as the number of detected poles 1a and 2a.

  Thus, this torque measuring device generates a multiplied pulse based on the magnetic phase detected by the magnetic sensors 3 and 4, and outputs a rotation pulse signal of the A phase signal and the B phase signal. Thereby, the first and second shafts 21 and 22 are maintained while maintaining the pitch of the detected poles 1a and 2a of the sensor targets 1 and 2 made of a magnetic encoder or the like equivalent to that of a normal ABS (anti-lock brake system) sensor or the like. This makes it possible to detect minute rotations. Therefore, it is possible to detect rotation with high resolution even if the sensor is mounted on a harsh environment such as a steering apparatus for an automobile while keeping the mounting tolerances such as the sensor gap equal to the conventional case. As a result, it is possible to measure even a small torque applied between the two shafts 21 and 22 from the difference between the detected rotation angles of the magnetic sensors 3 and 4. For example, a magnetic encoder is used as the sensor targets 1 and 2, the magnetic pole widths of the N pole and the S pole in the detected poles 1 a and 2 a are about 2.5 mm, and the size is about 32 mm in which 20 pole pairs are formed. In this case, it becomes possible to detect with a high resolution of ± 2.1 degrees or less. Noise included in the detection result can be easily reduced by averaging processing.

  Furthermore, the torque measuring device having this configuration outputs a Z-phase signal that is a reference signal of one pulse for each pair of magnetic poles from the magnetic sensors 3 and 4. For this reason, the signal processing circuit 6 can detect the absolute position in one magnetic pole by using the A and B phase signals and the Z phase signal. For example, the phase information is in an unknown state immediately after the power is turned on, but the magnetic phase can be determined by rotating one magnetic pole pair at the maximum. Thereby, it is possible to calculate the torque between the two axes by detecting the twist angle between the first and second axes.

  The torque measuring device is configured to output a reference signal of one pulse for each pair of magnetic poles separately from a detection signal for detecting a magnetic phase, but each of the two magnetic tracks 401, Since the reference signal is generated in synchronization with the magnetic pattern of 402, it is not necessary to separately install a reference signal output sensor, and the installation space and cost can be reduced.

  FIG. 8 is a block diagram showing another configuration example of the signal processing circuit 6 shown in FIG. This example shows a circuit configuration when the torque measuring device having any one of the above configurations is applied to, for example, a power steering device for an automobile shown in FIG. FIG. 9 is a block diagram showing a schematic configuration of each of the magnetic sensors 3 and 4 in this case. Each of the magnetic sensors 3 and 4 in this case has a multiplication function capable of detecting rotation with a resolution several to several tens of times the number of the detected poles 1a and 2a in the corresponding sensor targets 1 and 2. . In order to satisfy this function, each of the magnetic sensors 3 and 4 includes a multiplication circuit 14 that multiplies the rotation detection signal output from the sensor element units 3C and 4C to generate a high-resolution rotation pulse, and the detection processing circuit unit 3D. , 4D. That is, the multiplication circuit 14 outputs a rotation pulse as multiplication position information in the detected poles 1a and 2a of the sensor targets 1 and 2.

  FIG. 10 shows a configuration example of the multiplication circuit 14 in this case. The multiplier circuit 14 includes a signal generating means 41, a fan-shaped detecting means 42, a multiplexer means 43, and a fine interpolation means 44.

  The signal generating means 41 has the same amplitude A0 and the same average value C0 from the two-phase signals that are the outputs of the sensor element portions 3C and 4C in the magnetic sensors 3 and 4, that is, the SIN signal and the COS signal, It is means for generating (2m−1) signals si whose phases are shifted by 2π / (2m−1) from each other. Note that m is a positive integer of n or less, and i is a positive integer of 1 to (2m−1).

  The sector generator 42 generates m digital signals bn−m + 1, bn−m + 2,..., Bn−1, bn encoded to define 2m equal sectors Pi, (2m−1). ) A means for detecting 2m fan-shaped Pi divided by the number of signals si.

  The multiplexer means 43 is controlled by the m digital signals bn−m + 1, bn−m + 2,..., Bn−1, bn generated from the sector generating means 42 and is generated from the signal generating means 41 (2m− 1) While processing the number of the signals si, the amplitude is constituted by a portion between the average value C0 of the series of (2m-1) number of the signals si and the first threshold value L1. Signal A and a portion of the series of (2m−1) signals si between the threshold L1 and a second threshold L2 higher than the threshold L1. Analog means for generating the other signal B.

  In order to obtain a desired resolution, the fine interpolation means 44 codes so as to subdivide each of the 2m sectors Pi having an angle 2π / 2m into (2n−m) same sub-segments having an angle 2π / 2n. To generate (n−m) digital signals b1, b2,..., Bn−m−1, bn−m, in each of 2m sectors Pi, generated from the multiplexer means 43. Means for finely interpolating the one signal A and the other signal B.

  By this multiplication circuit 14, the two-phase signals (SIN signal, COS signal) obtained by the sensor body 13 of the magnetic sensors 3, 4 are (nm) digital signals b1, b2, which are multiplication signals. ..., bn-m-1, bn-m (here, b1, b2, ..., b8, b9) are multiplied.

  In the configuration of FIG. 8, the rotation pulse difference calculation circuit 15 is means for counting the rotation pulses generated by the multiplication circuit 14 of each of the magnetic sensors 3 and 4, and obtaining the difference between these count values. The rotation pulse difference calculation means 15 includes a first counter 16 that counts rotation pulses generated by the multiplication circuit 14 on one magnetic sensor 3 side, and a rotation pulse generated by the multiplication circuit 14 on the other magnetic sensor 4 side. A second counter 17 for counting and an angle difference calculating means 18 for calculating the difference between the count values of both the counters 16 and 17 are provided.

  The torque calculation means 10A is a means for performing processing for calculating the torque applied between the shafts 21 and 22 from the difference obtained by the rotation pulse difference calculation means 15 according to a preset calculation parameter. The obtained torque value is output to the outside in a data format through a communication interface such as a voltage value, a current value, a PWM signal, or a CAN bus by the output circuit 11 as in the case of the previous embodiment.

  As described above, in this embodiment, the torque is calculated by calculating from the rotation pulses output from the magnetic sensors 3 and 4, which is impossible in the case of the previous embodiment in which the signal phase difference is detected. It is also possible to measure the torque when one of the two shafts 21 and 22 is stationary.

  In this embodiment, the two magnetic sensors 3 and 4 may have different resolutions. In this case, since the two counters 16 and 17 change at different speeds, before obtaining the difference between the respective count values, each count value is multiplied by a constant so as to be the common multiple of the two, and the speed change is the same. You should do so.

  By the way, in the case of this embodiment in which rotation pulses are counted and the rotation angles of the sensor targets 1 and 2 are held as count values, a steady offset occurs due to mechanical rattling or both counters 16 and 17 due to erroneous counting due to noise. May cause an error in torque calculation by the torque calculation means 10A. Therefore, the controller 12A in this embodiment includes an offset canceling means 19 and a total of the functions other than the functions such as rewriting of calculation parameters and reading of calculation results given in the case of the controller 12 in the signal processing circuit 6 of FIG. Numerical reset means 20 is provided. The offset cancel unit 19 performs file processing according to predetermined data indicating the driving state separately sent from the control unit of the automobile while monitoring the difference between the rotation pulses obtained by the rotation pulse difference calculation unit 15. Thus, the steady offset is extracted, and the steady offset included in the torque calculated by the torque calculation means 10A is removed. The count value resetting means 20 is a means for resetting the count values counted by the counters 16 and 17 in the rotation pulse difference calculating means 15 in an operating state where no torque is applied. The “driving state” sent from the control unit of the automobile is a steering direction and steering angle signal of the steering wheel, information on the distinction between stopping and running of the vehicle, and the like.

  As described above, the offset canceling means 19 in the controller 12A performs the filtering process according to the operating state while monitoring the difference between the rotation pulses obtained by the rotation pulse difference calculating means 15, and extracts the steady offset. Since the offset is removed in the calculation process in the calculation means 10A, the influence of the offset caused by mechanical backlash or the like can be reduced and accurate torque measurement can be performed.

  Further, since the count value canceling means 20 in the controller 12A periodically resets the counters 16 and 17 at the timing of the operating state where no torque is applied, an error due to the influence of noise accumulated in the counters 16 and 17 or the like. The accurate torque can be measured by removing the counter value. When the rotation pulse output from the magnetic sensors 3 and 4 includes the index signal Z0 once per rotation like the ABZ0 signal, an erroneous count value due to noise or the like is generated every time the index signal Z0 is input. Since resetting is performed, it is not necessary to issue a reset command from the count value canceling means 20.

  By these processes, a minute torsion angle between the first and second shafts 21 and 22 can be detected with high resolution, so that the torque applied between the both shafts 21 and 22 can be accurately measured. Further, in this embodiment, since the sensor main body 13 in each of the magnetic sensors 3 and 4 outputs two phase signals of A phase and B phase that are 90 ° different from each other, rotation is performed from these two phase signals. The direction can be determined. Depending on this phase difference, the multiplication circuit 14 of the magnetic sensors 3 and 4 may generate two pulse signals of A phase and B phase, which are 90 ° different from each other, as rotation pulses. Thereby, it is possible to detect torque in either positive or negative direction.

  As described above, when the torque measuring device described above is mounted on a steering device such as an automobile, the torque applied between the input shaft connected to the steering wheel and the output shaft connected to the steering mechanism is accurately measured. Therefore, the steering control by power steering, steer-by-wire, or the like can be performed with higher hardness, which can contribute to easiness of driving and improvement of safety.

  FIG. 12 is a conceptual diagram showing an example of a power steering apparatus according to an embodiment of the present invention. Between the first shaft 21 that is an input shaft that is rotated by the handle 51 and the second shaft 22 that is an output shaft to which a rotational force is applied by the drive motor 53 of the steering mechanism 52, a torque measuring device 50 is provided. Is provided. The steering mechanism 52 is a mechanism that changes the direction of the wheels 55. The torque measuring device 50 has any configuration in each of the above embodiments. The signal processing circuit 6 may have any of the above-described configurations, for example, the configuration shown in FIG. The control circuit 54 outputs a motor control signal for controlling the driving of the motor 53 based on the setting relationship between the torque value and the motor output in accordance with the torque value output from the signal processing circuit 6 of the torque measuring device 50. Device. The signal processing circuit 6 has a function of outputting a handle angle that is a rotation angle of the first shaft 21 or the second shaft 22, and the control circuit 54 has a torque value output from the signal processing circuit 6. The motor control signal may be output based on the setting relationship from both the steering wheel angle and the steering wheel angle.

1, 2 ... Sensor targets 1a, 2a ... Detected poles 1a1, 1a2, 2a1, 2a2 ... Detected poles 2d ... Magnetic interference preventing spacers 3, 4 ... Magnetic sensors 3A, 3B, 4A, 4B, 3a, 4a ... Magnetic Sensor elements 3AA, 3AB, 4AA, 4AB ... line sensors 3C, 3D ... sensor elements 3D, 4D ... detection processing circuit units 31, 32, 41, 42 ... track-specific sensor units 14 ... multiplication circuit 15 ... rotation pulse difference calculation means 16, 17 ... Counter 18 ... Angle difference calculating means 19 ... Offset canceling means 20 ... Count value resetting means 21 ... First axis 22 ... Second axis 23 ... Torsion bars 401, 402 ... Magnetic tracks

Claims (9)

Each of the first and second shafts connected coaxially via the torsion bar is provided with an annular sensor target in which a plurality of detection poles arranged concentrically with these shafts in the circumferential direction are equally arranged, A torque measuring device for providing a magnetic sensor for detecting the detected poles of these sensor targets, and measuring a torque applied between the first and second shafts based on an output signal of each magnetic sensor,
Each sensor target has two magnetic tracks in which a plurality of detected poles are equally arranged, and both magnetic tracks are formed so that the phases of the detected poles are shifted from each other in one circumferential direction, Each magnetic sensor has two track-specific sensor units that respectively detect the detected poles of the two magnetic tracks in the opposing sensor target. From the detection signals of these two track-specific sensor units, one of the detected poles is detected. A torque characterized by generating and outputting a rotation pulse signal representing each position obtained by dividing the pitch into a plurality of positions within the pitch of the magnetic pole pair, and one reference signal for each magnetic pole pair of the detected pole. measuring device.   2. The sensor unit for each track of the magnetic sensor according to claim 1, further comprising a line sensor in which sensor elements are arranged along an arrangement direction of detected poles of opposing magnetic tracks, and a two-phase signal output of SIN and COS. Is a torque measuring device that generates by calculation.   3. The magnetic sensor according to claim 1, wherein the magnetic sensor includes a sensor element unit that detects the detected pole and a detection processing circuit unit, and the detection processing circuit unit multiplies the output signal of the sensor element unit. And a torque measuring device having a multiplication circuit for generating a rotation pulse signal having a higher resolution than the output signal.   4. The torque measuring device according to claim 3, wherein the detection processing circuit unit outputs two rotation pulse signals of A phase and B phase, which are 90 ° different from each other, as the multiplied rotation pulse signal.   6. The magnetic sensor according to claim 1, wherein each magnetic sensor includes a sensor element unit that detects the detected pole and a detection processing circuit unit, and the detection processing circuit unit includes the sensor element unit. A torque measuring device that generates an index signal for one rotation of the sensor target from the output signal.   6. The counter according to claim 3, wherein the counter detects a rotation angle of each corresponding sensor target from the count value of the rotation pulse signal generated by each magnetic sensor, and the two detected by the counter. An angle difference calculating means for obtaining a difference in rotation angle and a torque calculating means for calculating a torque applied between the first and second axes from the difference are provided, and the difference between the first and second axes is provided. A torque measuring device provided with an offset canceling means for estimating a steady offset amount included in the calculated torque from an operating state and canceling the offset from the torque calculation.   6. The counter according to claim 3, wherein a counter for detecting a rotation angle of each corresponding sensor target from a count number of rotation pulse signals generated by each of the magnetic sensors, and 2 detected by these counters. Provided is an angle difference calculating means for obtaining a difference between two rotation angles, and a torque calculating means for calculating a torque applied between the first and second axes from the difference, and torque is applied to the first and second axes. A torque measuring device provided with count value resetting means for resetting the count value in an operating state where no voltage is applied.   8. The torque measuring device according to claim 1, wherein a magnetic body for preventing magnetic interference is provided between the two sensor targets. A steering device with a shaft torque measuring function, wherein the torque measuring device according to any one of claims 1 to 8 is mounted.

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