JP2010145099A - Magnetostrictive torque sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetostrictive torque sensor which makes detection coils multipolarized as many as possible. <P>SOLUTION: The magnetostrictive torque sensor 11 detects the torque of a rotating shaft S using the opposite effect of magnetostriction generated on the surface of the shaft. A plurality of first detection coils L1 and a plurality of second detection coils L2 are arranged so that they form two rows in the circumferential direction of the rotating shaft S. In the circumferential direction of the rotating shaft S, the first detection coils L1 and the second detection coils L2 are arranged alternately while in the axial direction of the rotating shaft S, the first detection coils L1 and the second detection coils L2 are arranged side by side. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a magnetostrictive torque sensor that detects the torque of a rotating shaft by utilizing the inverse effect of magnetostriction generated on a shaft surface.

  A magnetostrictive torque sensor is known that detects the torque of a rotating shaft by utilizing the inverse effect of magnetostriction generated on the shaft surface. The reverse effect of magnetostriction is a magnetic strain phenomenon in which when a metal (magnetostrictive film) is distorted, the permeability increases in the tensile direction while the permeability decreases in the compression direction. The sensor includes a detection coil that detects a change in magnetic permeability on the shaft surface as a change in inductance.

  Magnetostrictive torque sensors are classified into types that do not impart magnetic anisotropy to the shaft surface (for example, see Patent Document 1) and types that impart magnetic anisotropy to the shaft surface (for example, see Patent Documents 2 and 3). can do. For example, the latter gives magnetic anisotropy of + 45 ° and −45 ° to the two outer peripheral regions of the rotating shaft, respectively, and arranges a pair of solenoid type detection coils facing each outer peripheral region. A differential voltage generated between the detection coils is output. That is, when torque is applied to the rotating shaft, the magnetic permeability of each outer peripheral region changes inversely due to the inverse effect of magnetostriction, so that a differential voltage is generated between the detection coils, and an output proportional to the torque is obtained.

  However, in the conventional magnetostrictive torque sensor, a slight differential voltage generated between the detection coils is detected using a bridge circuit or the like, and this differential voltage is amplified in multiple stages by an amplifier. It was easily affected and it was difficult to detect with high accuracy.

  In addition, the magnetostrictive torque sensors of the methods shown in Patent Documents 2 and 3 need to process a ± 45 ° stripe pattern (magnetic anisotropic part) on the shaft surface with grooves, slits, thin films, etc. It was difficult to apply to a rotating shaft that is not allowed to be processed. In addition, this type of magnetostrictive torque sensor has a pair of solenoid-type detection coils in which the axial surface permeability detection region is displaced in the axial direction. There is a problem that the temperature error between the mold detection coils becomes remarkable, and the detection accuracy is significantly lowered. This means that it cannot be applied to applications in which a heat source such as an engine is connected to one end side of a rotating shaft that is a torque detection target (for example, torque detection of a power train in an automobile or a ship).

  On the other hand, in the magnetostrictive torque sensor of the method shown in Patent Document 1, the detection coil (core) forms a closed magnetic path between the shaft surface and limits the detection direction and detection region of the magnetic permeability on the shaft surface. It is not necessary to machine the magnetically anisotropic part on the shaft surface, but it exists in the circumferential direction of the shaft surface when applied to torque detection of the rotating shaft to detect the permeability change in a part of the circumferential direction on the shaft surface. The problem of being greatly affected by the error factor that occurs. The main error factors existing in the circumferential direction of the shaft surface include variations in the material present in the base material of the rotating shaft and the magnetostrictive film, and fluctuations in the gap between the shaft surface and the core accompanying rotation. Further, in this type of magnetostrictive torque sensor, the core shape is different between the pair of detection coils, and therefore, a detection error may occur between the pair of detection coils due to a difference in magnetic path length or the like.

  Therefore, the present applicant has previously proposed a new type magnetostrictive torque sensor that can solve the above-described problems (see Patent Document 4). The magnetostrictive torque sensor is arranged to detect a change in permeability in the first direction on the shaft surface, and detects a change in permeability as a change in inductance, and a permeability in the second direction on the shaft surface. A second detection coil that is arranged to detect a change and detects the change in permeability as an inductance change, and oscillates autonomously at a predetermined reference frequency, and an oscillation wave according to the inductance change of the first detection coil A first oscillation circuit that causes a phase shift in the first oscillation circuit, a second oscillation circuit that autonomously oscillates at a predetermined reference frequency, and causes a phase shift in an oscillation wave according to an inductance change of the second detection coil, A plurality of oscillation waves output from the first oscillation circuit are counted, and an oscillation wave count process is performed to determine whether or not the count number has reached a predetermined number N. Based on the time required for the oscillating wave counting process, a first direction permeability detecting means for detecting a change in permeability in the first direction, and counting a plurality of oscillating waves output from the second oscillating circuit, An oscillating wave counting process is performed to determine whether or not the count number has reached a predetermined number N, and based on the time required for the oscillating wave counting process, the second direction permeability is detected. It is characterized by comprising magnetic permeability detection means and torque detection means for detecting torque of the rotating shaft based on the difference between the magnetic permeability in the first direction and the magnetic permeability in the second direction.

  According to such a magnetostrictive torque sensor, it is possible to dramatically improve the torque detection accuracy. In other words, in the oscillation wave output from the first oscillation circuit and the second oscillation circuit configured as described above, the change in the magnetic permeability of the shaft surface clearly appears as a phase shift, and the phase shift in the oscillation wave occurs. Since the number of oscillation waves is accumulated, it is possible to detect the change in the magnetic permeability in the first direction and the second direction with high accuracy and to detect the torque of the rotating shaft with high accuracy from the difference. In addition, the number of oscillation waves output from the oscillation circuit is counted, and an oscillation wave count process is performed to determine whether or not the count number has reached a predetermined number N. Based on the time required for the oscillation wave count process Since the phase shift (permeability change) of the accumulated oscillating wave is measured, the phase shift component of the oscillated wave can be measured with high accuracy using an inexpensive digital circuit. In addition, since the resolution is determined by the counter speed for time measurement and does not depend on the reference frequency of the oscillation circuit, high-resolution stress detection can be performed while optimizing the reference frequency of the oscillation circuit according to the detection target. .

Furthermore, as shown in FIG. 9 of Patent Document 4, if a plurality of first detection coils and a plurality of second detection coils are arranged side by side on the same circumference of the rotating shaft, they exist in the circumferential direction of the shaft surface. Since variations in material and gap fluctuation between the detection coil and the shaft surface can be averaged, a decrease in detection accuracy due to these error factors can be avoided. Further, if the detection area of the first detection coil and the detection area of the second detection coil are arranged alternately, an error caused by a deviation between the detection area of the first detection coil and the detection area of the second detection coil. Can be suppressed. Further, in such an arrangement, it is not necessary to arrange the cores in an intersecting manner, so that the same shape core can be used in the first detection coil and the second detection coil.
JP 2001-133337 A JP 7-83769 A Japanese Patent Laid-Open No. 11-37863 WO / 2008/081573

  By the way, in the magnetostrictive torque sensor of the system shown in Patent Document 4, it is possible to easily improve the detection accuracy simply by increasing the count number N of oscillation waves. As the number of noise components increases, the S / N ratio is important to improve. In particular, since the influence of the error factor existing in the circumferential direction of the shaft surface is large, it is required to make it as small as possible.

  For the above problem, it is effective to increase the number of detection coils, that is, to increase the number of detection coils. However, since the number of detection coils arranged in the circumferential direction is limited, it is difficult to increase the number of detection coils. there were.

In view of the above circumstances, the magnetostrictive torque sensor of the present invention created for the purpose of solving these problems is a magnetostrictive type that detects the torque of the rotating shaft using the inverse effect of magnetostriction generated on the shaft surface. A torque sensor arranged to detect a change in permeability in a first direction on the shaft surface, and a plurality of first detection coils for detecting the change in permeability as a change in inductance; and a second direction on the shaft surface A plurality of second detection coils which are arranged to detect a change in permeability of the first detection coil and detect the change in permeability as an inductance change, and a first shift which causes a phase shift in the oscillation wave according to the inductance change of the first detection coil. One oscillation circuit, a second oscillation circuit that causes a phase shift in an oscillation wave in accordance with an inductance change of the second detection coil, and an output from the first oscillation circuit A plurality of oscillation waves are counted, and an oscillation wave count process is performed to determine whether or not the count number has reached a predetermined number N. Based on the time measurement required for the oscillation wave count process, the first direction First direction permeability detection means for detecting a change in permeability, and a plurality of oscillation waves output from the second oscillation circuit, and an oscillation wave for determining whether or not the count number has reached a predetermined number N A second direction permeability detecting means for performing a counting process and detecting a change in permeability in the second direction based on a time measurement required for the oscillation wave counting process; a permeability in the first direction; Torque detecting means for detecting the torque of the rotating shaft based on the difference between the magnetic permeability of the direction and the plurality of first detection coils for limiting the detection region and the detection direction on the shaft surface, respectively. Between the shaft surface, While comprising an inverted U-shaped core constituting a magnetic path and a coil wound around the core, the coils are connected in series or in parallel, and the plurality of second detection coils are respectively In order to limit the detection region and the detection direction on the shaft surface, it is configured to include an inverted U-shaped core that forms a closed magnetic path between the shaft surface and a coil wound around the core. The coils are connected in series or in parallel, and the plurality of first detection coils and the plurality of second detection coils are arranged in two rows along the circumferential direction of the rotating shaft, and the circumferential direction of the rotating shaft The first detection coil and the second detection coil are alternately arranged, and the first detection coil and the second detection coil are arranged in the axial direction of the rotation axis.
In this way, the plurality of first detection coils and the plurality of second detection coils are arranged so as to be arranged in two rows along the circumferential direction of the rotation axis. Thus, the detection coil can be multipolarized. Further, since the first detection coil and the second detection coil are alternately arranged in the circumferential direction of the rotation axis, it is caused by a deviation between the detection region of the first detection coil and the detection region of the second detection coil. Generation of errors can be suppressed. Further, since the first detection coil and the second detection coil are arranged in the axial direction of the rotation shaft, the plurality of first detection coils and the plurality of second detection coils are arranged along the circumferential direction of the rotation shaft. However, it is possible to suppress the influence of the temperature gradient existing in the axial direction of the shaft surface.
That is, when arranging the plurality of first detection coils and the plurality of second detection coils so as to be arranged in two rows along the circumferential direction of the rotation axis, the first detection coil is arranged in the circumferential direction of the rotation axis. When the first detection coil and the second detection coil are arranged in the axial direction of the rotation axis and the first detection coil and the second detection coil are arranged side by side, a center line passing between two rows is formed. The plurality of first detection coils and the plurality of second detection coils are respectively distributed in a zigzag manner, and the plurality of first detection coils and the plurality of second detection coils are centered on the center line passing between the two rows. Since the two detection coils are arranged symmetrically with each other, the plurality of first detection coils and the plurality of second detection coils cancel each other out of the influence of the temperature gradient existing in the axial direction of the shaft surface. Decrease detection accuracy as much as possible It can be divided.

  Next, embodiments of the present invention will be described with reference to the drawings.

[Basic Configuration of Magnetostrictive Torque Sensor According to the Present Invention]
FIG. 1 is a block diagram showing a basic configuration of a magnetostrictive torque sensor according to the present invention. The magnetostrictive torque sensor 1 shown in this figure shows the basic configuration of the present invention. In order to detect the torque of the rotating shaft S using the inverse effect of magnetostriction generated on the shaft surface, A detection coil L1, a second detection coil L2, a first oscillation circuit 2, a second oscillation circuit 3, and a detection circuit 4 are provided.

  The first detection coil L1 is arranged to detect a magnetic permeability change in the first direction (for example, + 45 ° direction) on the shaft surface, and detects the magnetic permeability change as a change in inductance. The second detection coil L2 is arranged to detect a change in permeability in the second direction (for example, −45 ° direction) on the shaft surface, and detects the change in permeability as a change in inductance.

  The detection coils L1 and L2 are formed using a high magnetic permeability material to limit the detection region and detection direction on the shaft surface, and the coils L1b and L2b wound around the cores L1a and L2a. And is configured. Specifically, coils L1b and L2b are wound around inverted U-shaped cores L1a and L2a made of ferrite, and both ends of the cores L1a and L2a are brought close to the shaft surface. A closed magnetic circuit is formed between the two. Thereby, it is possible to form magnetic paths in the first direction and the second direction in a limited region of the shaft surface, and to detect a change in permeability in the magnetic path. In addition, as long as the inverted U-shaped cores L1a and L2a include at least a pair of leg portions and a connecting portion that connects upper end portions of the leg portions, the specific shape is not limited to the inverted U-shape. For example, a U-shaped, inverted V-shaped, and E-shaped core can be applied to the present invention.

  The first oscillation circuit 2 is configured to autonomously oscillate at a predetermined reference frequency and to cause a phase shift in the oscillation wave in accordance with an inductance change of the first detection coil L1. Further, the second oscillation circuit 3 is configured to autonomously oscillate at a predetermined reference frequency and to cause a phase shift in the oscillation wave in accordance with an inductance change of the second detection coil L2. For example, if the detection coils L1 and L2 are arranged in the feedback circuit of the Schmitt oscillation circuit, it is possible to configure the oscillation circuits 2 and 3 in which a phase shift occurs in the oscillation wave according to the inductance change of the detection coils L1 and L2.

  The Schmitt oscillation circuit is an oscillation circuit that uses the hysteresis characteristics of the Schmitt inverter INV. The Schmitt inverter INV, the capacitor C connected to the input side of the Schmitt inverter INV, and the output of the Schmitt inverter INV are input to the Schmitt inverter INV. And a resistance element interposed in the feedback circuit.

In the Schmitt oscillation circuit in the initial state, since no charge is accumulated in the capacitor C, the voltage across the capacitor C is 0V. At this time, the Schmitt inverter INV has an output H level (5 V) because the input side voltage Vin is equal to or lower than _VL . When the output side voltage Vout of the Schmitt inverter INV is 5V, a current flows to the input side of the Schmitt inverter INV via the feedback circuit 2a, so that electric charges are gradually accumulated in the capacitor C, and the voltage at both ends thereof increases. When the input side voltage Vin of the Schmitt inverter INV reaches _VH , the output of the Schmitt inverter INV is switched to the L level (0 V). When the output side voltage Vout of the Schmitt inverter INV becomes 0V, the capacitor C is discharged, and the input side voltage Vin of the Schmitt inverter INV gradually decreases. When the input voltage Vin of the Schmitt inverter INV drops to _VL , the output of the Schmitt inverter INV is switched to the H level.

By repeating the above operation, a rectangular wave having a predetermined frequency is obtained from the output side of the Schmitt inverter INV. The Schmidt oscillation circuit of the oscillation frequency f (= 1 / T) is determined by the energy storage time period _{T H} discharge period _{T L,} the electric storage period _{T H} and the discharging period _{T L} is determined by the constants of the capacitor C and a resistor element. Therefore, if the detection coils L1 and L2 are arranged in the feedback circuit as resistance elements, it is possible to cause a phase shift in the oscillation wave of the Schmitt oscillation circuit according to the inductance change of the detection coils L1 and L2.

  Of course, the oscillation circuit of the present invention is not limited to the Schmitt oscillation circuit. If the oscillation circuit generates a phase shift in the oscillation wave according to the inductance change of the detection coils L1, L2, the CR oscillation circuit, LC An oscillation circuit, a crystal oscillation circuit, or the like may be used.

  The detection circuit 4 is configured using, for example, a microcomputer (one-chip microcomputer) including a CPU, a ROM, a RAM, an I / O, and the like, and performs a torque detection process to be described later according to a program written in the ROM. The detection circuit 4 may be composed of a plurality of microcomputers or one or a plurality of ICs.

  The detection circuit 4 counts a plurality of oscillation waves output from the first oscillation circuit 2, performs an oscillation wave count process for determining whether or not the count number has reached a predetermined number N, and performs the oscillation wave count process. The first direction permeability detection means for detecting the change in permeability in the first direction and the plurality of oscillation waves output from the second oscillation circuit 3 are counted based on the time required for the count, and the count number is a predetermined number. Oscillating wave counting processing for determining whether or not N has been reached, and based on the time required for the oscillating wave counting processing, second direction magnetic permeability detecting means for detecting a change in magnetic permeability in the second direction; Torque detecting means for detecting the torque of the rotating shaft S is provided based on the difference between the magnetic permeability in one direction and the magnetic permeability in the second direction.

  In this way, the torque detection accuracy of the magnetostrictive torque sensor 1 can be improved. That is, in the oscillating wave output from the first oscillating circuit 2 and the second oscillating circuit 3 configured as described above, the change in the magnetic permeability of the shaft surface clearly appears as a phase shift, Since the phase shift is accumulated by the number of oscillation waves, it is possible to detect the change in permeability in the first direction and the second direction with high accuracy, and to detect the torque of the rotating shaft S with high accuracy from the difference. Become. Also, the number of oscillation waves output from the oscillation circuits 2 and 3 is counted, and an oscillation wave count process is performed to determine whether or not the count number has reached a predetermined number N, which is necessary for the oscillation wave count process. Since the phase shift (permeability change) of the oscillation wave accumulated based on time is measured, the phase shift component of the oscillation wave can be measured with high accuracy using an inexpensive digital circuit. Moreover, since the resolution is determined by the counter speed for time measurement and does not depend on the reference frequency of the oscillation circuits 2 and 3, high-resolution stress can be achieved while optimizing the reference frequency of the oscillation circuits 2 and 3 according to the detection target. Detection can be performed.

  The first detection coil L1 and the second detection coil L2 form a closed magnetic circuit with the shaft surface in order to limit the detection region and the detection direction on the shaft surface. That is, in the magnetostrictive torque sensor 1 of the present invention, the phase shift of the oscillating wave corresponding to the torque is accumulated and detected by the number of oscillating waves, so that an error component included in the phase shift of the oscillating wave is also accumulated. However, by limiting the detection region and detection direction on the shaft surface, the SN ratio can be increased, so that accumulated error components can be suppressed and detection accuracy can be improved. Further, since the detection direction can be limited on the detection coils L1 and L2 side, it is not necessary to process a striped pattern with grooves, slits, thin films, or the like on the shaft surface. As a result, the torque detection according to the present invention can be applied even to the rotating shaft S in which these processes are not allowed.

  Further, the first oscillation circuit 2 and the second oscillation circuit 3 are preferably driven alternately in order to avoid mutual interference. For example, after the oscillation driving of the first oscillation circuit 2 is stopped after the oscillation drive of the first oscillation circuit 2 is stopped after the oscillation wave count processing related to the first oscillation circuit 2 is executed in a state where the oscillation drive of the second oscillation circuit 3 is stopped, 3 is executed, and then the difference in measurement time required for each oscillation wave count process is obtained. In this way, it is possible to avoid a decrease in detection accuracy due to mutual interference. In addition, since the detection area of the first detection coil L1 and the detection area of the second detection coil L2 can be arbitrarily set without considering mutual interference, it is easy to optimize the detection area according to use conditions. It becomes.

  The shaft surface of the rotating shaft S for detecting torque by the magnetostrictive torque sensor 1 is preferably a magnetostrictive film 5 formed by plating. For example, a magnetostrictive film 5 made of a nickel alloy is plated over the entire circumference of a part or the entire region of the rotating shaft S. In this way, not only can the torque be detected with high accuracy based on the inverse effect of magnetostriction in the magnetostrictive film 5 in accordance with the torque, but also hysteresis in torque detection can be suppressed. Moreover, in the magnetostrictive torque sensor 1 of the present invention, sufficient detection accuracy can be obtained even with the magnetostrictive film 5 formed by the plating method. Compared to the case of forming a magnetostrictive film, not only can the cost be reduced significantly, but also high-accuracy torque detection can be performed for existing members (including resin) that have been plated with nickel.

  Next, the phase shift accumulation action of the oscillation wave in the present invention will be described with reference to FIGS.

  FIG. 2 is an explanatory diagram showing the phase shift accumulation action of the oscillation wave (enlarged detection waveform start end), and FIG. 3 is an explanatory view showing the phase shift accumulation action of the oscillation wave (enlargement of the detection waveform end section). The waveforms shown in these figures are the output waveforms of the oscillation circuits 2 and 3 in one detection process. The number of oscillation waves output from the oscillation circuits 2 and 3 is counted, and the count number is set to a predetermined number N. Oscillation wave count processing is performed to determine whether or not the oscillation wave has been reached, and when measuring the phase deviation of the accumulated oscillation wave based on the time required for the oscillation wave count processing, the oscillation wave count in the oscillation wave count processing is counted. The waveform when the number N is 100 is shown. The upper waveform indicates a case where no torque is applied to the rotation axis S, and the lower waveform indicates a case where torque is applied to the rotation axis S. As is clear from these figures, since the phase shift is not accumulated so much at the beginning of the detected waveform, that is, at the stage where the number N of oscillation waves in the oscillation wave count processing is small, the difference is not clear ( It can be seen that when the count number N increases, the phase shift of the oscillation wave is accumulated and the difference becomes clear, so that the phase shift can be easily measured (see FIG. 3). Since the phase shift of the oscillation wave increases in proportion to the torque acting on the rotation axis S, the torque acting on the rotation axis S can be measured with high accuracy based on the phase shift of the oscillation wave. Become. Further, since the phase shift of the oscillation wave output from each oscillation circuit 2 and 3 appears in a contradictory direction based on the inverse effect of magnetostriction, it is only possible to detect the torque amount and torque polarity of the rotating shaft S based on the difference. Therefore, it is possible to obtain a detection value in which the temperature error and the displacement error are offset.

  Next, a specific detection processing procedure of the detection circuit 4 will be described with reference to FIGS.

  In the torque detection process (torque detection means) shown in FIG. 4, first, after initial setting (S11: including initial value setting of the oscillation wave count number N), the count number change process (S12), first direction transparent Magnetic permeability detection processing (S13: first direction magnetic permeability detection means) and second direction magnetic permeability detection processing (S14: second direction magnetic permeability detection means) are executed in order. Then, the difference between the first direction permeability detection value and the second direction permeability detection value obtained in the permeability detection process (S13, S14) is calculated (S15), and the calculated difference (torque detection value) is predetermined. Is converted into a detection signal format and output (S16), one torque detection process is completed.

  In the count number changing process shown in FIG. 5, first, the input of the count number change signal is determined (S21). If the determination result is YES, the oscillation wave count number N included in the count number change signal is read (S22). In accordance with this, the oscillation wave count number N is changed (S23).

  In the first direction magnetic permeability detection process shown in FIG. 6, after the drive of the first oscillation circuit 2 is started (S31), the counter clear process (S32), the oscillation wave count process (S33, S34), and the time measurement process (S35) is executed, and then the driving of the first oscillation circuit 2 is stopped (S36). The counter clear process is a process for clearing the oscillation wave counter and the time measurement counter (S32). The oscillation wave counting process is a process for counting the number of oscillation waves output from the first oscillation circuit 2 (S33) and determining whether the count number has reached a predetermined number N (S34). . The time measurement process is a process of reading a time measurement counter value (first-direction magnetic permeability detection value) when the count number of oscillation waves reaches N (S35).

  In the second direction magnetic permeability detection process shown in FIG. 7, after the driving of the second oscillation circuit 3 is started (S41), the counter clear process (S42), the oscillation wave count process (S43, S44), and the time measurement process (S45) is executed, and then the driving of the second oscillation circuit 3 is stopped (S46). The counter clear process is a process for clearing the oscillation wave counter and the time measurement counter (S42). The oscillation wave counting process is a process for counting the number of oscillation waves output from the second oscillation circuit 3 (S43) and determining whether or not the count number has reached a predetermined number N (S44). . The time measurement process is a process of reading a time measurement counter value (second-direction magnetic permeability detection value) when the count number of oscillation waves reaches N (S45).

[Characteristic Configuration of Magnetostrictive Torque Sensor According to the Present Invention]
Next, a characteristic configuration of the magnetostrictive torque sensor according to the present invention will be described with reference to FIGS. However, the above description is incorporated by attaching the same reference numerals to the portions common to the magnetostrictive torque sensor 1 shown in FIGS.

  A magnetostrictive torque sensor 11 shown in FIGS. 8 to 11 shows a characteristic configuration of the present invention, and each oscillation circuit 2 and 3 includes a plurality of detection coils L1 and L2, respectively. More specifically, the first oscillation circuit 2 includes a plurality (for example, 12) of first detection coils L1 connected in series (or parallel), and the second oscillation circuit 3 is in series (or parallel). A plurality of (for example, 12) second detection coils L2 connected to each other. In this way, by disposing a plurality of first detection coils L1 and second detection coils L2 on the shaft surface, variation in the material existing on the shaft surface, and further, the detection coils L1, L2 and the shaft surface It is possible to average the gap fluctuations between them, so that it is possible to avoid a decrease in detection accuracy due to these error factors.

  The cores 2a and 3a of the detection coils L1 and L2 shown in FIGS. 9 to 11 have a width W (for example, 4 mm) wider than that shown in FIG. For example, 2 mm) is narrowed. In this way, an alternating magnetic field is generated intensively between the legs of the cores 2a and 3a, and a slight change in permeability due to torque fluctuation can be detected with high accuracy. The plurality of first detection coils L1 and the plurality of second detection coils L2 are held at predetermined positions by the annular holder H. The holder H may be an integral type or a divided type.

  As shown in FIGS. 10 and 11, the plurality of first detection coils L <b> 1 and the plurality of second detection coils L <b> 2 are arranged in two rows along the circumferential direction of the rotation axis S. In this way, the detection coils L1 and L2 can be multipolarized as compared with the case where they are arranged in a line.

  Further, in the circumferential direction of the rotation axis S, the first detection coils L1 and the second detection coils L2 are arranged alternately. If it does in this way, generation | occurrence | production of the error resulting from the shift | offset | difference of the detection area of the 1st detection coil L1 and the detection area of the 2nd detection coil L2 can be suppressed.

  Furthermore, in the axial direction of the rotation axis S, the first detection coil L1 and the second detection coil L2 are arranged side by side. In this way, the plurality of first detection coils L1 and the plurality of second detection coils L2 are arranged in two rows along the circumferential direction of the rotation axis S, but in the axial direction of the shaft surface. The influence of the existing temperature gradient can be suppressed.

  That is, in arranging the plurality of first detection coils L1 and the plurality of second detection coils L2 so as to be arranged in two rows along the circumferential direction of the rotation axis S, the first detection is performed in the circumferential direction of the rotation axis S. When the coils L1 and the second detection coils L2 are alternately arranged and the first detection coil L1 and the second detection coil L2 are arranged in the axial direction of the rotation axis S, the coils L1 and the second detection coils L2 pass between the two rows. A plurality of first detection coils L1 and a plurality of second detection coils L2 are distributed in a zigzag manner across the center line CL, and a plurality of first detection coils L1 are arranged with the center line CL passing between the two rows as a symmetry axis. Since the one detection coil L1 and the plurality of second detection coils L2 are arranged in line symmetry, the temperature at which the plurality of first detection coils L1 and the plurality of second detection coils L2 exist in the axial direction of the shaft surface. Offset the effects of the gradients, It is possible to eliminate the reduction in the detection accuracy due to time gradient as possible.

1 is a block diagram showing a basic configuration of a magnetostrictive torque sensor according to the present invention. It is explanatory drawing which shows the phase shift accumulation effect | action (enlargement of a detection waveform start end part) of an oscillation wave. It is explanatory drawing which shows the phase shift accumulation effect | action (an enlarged detection waveform termination | terminus part) of an oscillation wave. It is a flowchart which shows the process sequence of the torque detection process in a detection circuit. It is a flowchart which shows the process sequence of the setting number change process in a detection circuit. It is a flowchart which shows the process sequence of the 1st direction magnetic permeability detection process in a detection circuit. It is a flowchart which shows the process sequence of the 2nd direction magnetic permeability detection process in a detection circuit. It is a block diagram which shows the characteristic structure of the magnetostrictive torque sensor which concerns on this invention. (A) is a top view of the detection coil, (B) is a front view of the detection coil, (C) is a bottom view of the detection coil, and (D) is a side view of the detection coil. It is an expansion | deployment top view which shows the example of arrangement | positioning of a detection coil. It is a side view which shows the example of arrangement | positioning of a detection coil.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Magnetostrictive torque sensor 2 First oscillation circuit 2a Core 3 Second oscillation circuit 3a Core 4 Detection circuit 11 Magnetostrictive torque sensor L1 First detection coil L2 Second detection coil S Rotating shaft

Claims (1)

A magnetostrictive torque sensor that detects the torque of a rotating shaft using the inverse effect of magnetostriction generated on the shaft surface,
A plurality of first detection coils arranged to detect a change in permeability in a first direction on the shaft surface, and detecting the change in permeability as a change in inductance;
A plurality of second detection coils arranged to detect a change in permeability in the second direction on the shaft surface, and detecting the change in permeability as a change in inductance;
A first oscillation circuit that causes a phase shift in an oscillation wave in accordance with an inductance change of the first detection coil;
A second oscillation circuit that causes a phase shift in an oscillation wave in accordance with an inductance change of the second detection coil;
Counting a plurality of oscillating waves output from the first oscillating circuit, performing an oscillating wave counting process to determine whether or not the count number has reached a predetermined number N, and measuring the time required for the oscillating wave counting process Based on the first direction permeability detection means for detecting a change in permeability in the first direction,
Counts a plurality of oscillating waves output from the second oscillating circuit, performs an oscillating wave counting process for determining whether or not the counted number has reached a predetermined number N, and measures the time required for the oscillating wave counting process A second direction permeability detecting means for detecting a change in permeability in the second direction,
Torque detection means for detecting the torque of the rotating shaft based on the difference between the magnetic permeability in the first direction and the magnetic permeability in the second direction;
Each of the plurality of first detection coils is wound around an inverted U-shaped core that forms a closed magnetic path with the shaft surface in order to limit the detection region and the detection direction on the shaft surface. And the coils are connected in series or in parallel,
Each of the plurality of second detection coils is wound around an inverted U-shaped core that forms a closed magnetic path with the shaft surface in order to limit the detection region and the detection direction on the shaft surface. And the coils are connected in series or in parallel,
The plurality of first detection coils and the plurality of second detection coils are arranged in two rows along the circumferential direction of the rotation axis,
The first detection coil and the second detection coil are alternately arranged in the circumferential direction of the rotation axis, and the first detection coil and the second detection coil are arranged in the axial direction of the rotation axis. A magnetostrictive torque sensor.

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