JP6039206B2 - Position detector and adjustment method thereof - Google Patents

Description

  The present invention relates to a position detector used in the fields of industrial machines, machine tools, and the like, and more particularly, to a position detector having a sensor unit that can handle a plurality of sizes of a detected object.

  A position detector of a rotating shaft such as a main shaft of a machine tool includes a detected object having a repeated pattern added to the outer periphery thereof, such as a gear, and a sensor unit that magnetically detects the detected object. Have often been used. As an advantage of such a configuration, there is a point that the sensor unit can be easily used for a plurality of sizes of the detection object. Even if the size of the detected object is changed by changing the number of teeth without changing the gear module, the basic pitch length in the relative movement direction between the detected object and the sensor unit may not be changed. It depends on what can be done.

  FIG. 2 is a perspective view showing a conventional position detector. A detection gear 201 made of a magnetic material is fixed concentrically with a marker disk 202 made of a magnetic material, is fixed to a rotating shaft (not shown), and is rotatable. The number of teeth of the detection gear 201 is 256. The marker disk 202 is provided with a cutout at only one location on the outer periphery. On the other hand, the magnetic sensor 203 facing the detection gear 201 with a gap is fixed to a fixed side (not shown).

  FIG. 3 is a front view showing the arrangement of detection elements included in the magnetic sensor 203 of FIG. The detection elements (magnetoresistive elements) 301a to 301p for detecting the detection gear 201 are arranged so as to be shifted by 3/4 pitch in the relative movement direction with respect to the basic pitch length of the unevenness of the detection gear 201. Yes. That is, the distance in the relative movement direction between the detection element 301a and the detection element 301b is 3/4 pitch, and the distance in the relative movement direction between the detection element 301a and the detection element 301c is 6/4 pitch. Therefore, the detection elements 301a, e, i, m are arranged at the same phase in the basic pitch of the repeated pattern of the detection gear 201. The detection element 301q is for detecting the marker disk 202. Although not shown, a bias magnet is disposed on the back side of the detection elements 301a to 301q (the side opposite to the detection gear 201).

4 is a schematic configuration diagram of signal processing of the magnetic sensor 203 in FIG. 2, and the same components as those in FIGS. 2 to 3 are denoted by the same reference numerals. The signal level (voltage level) generated by the detection elements 301a, 301c, 301e, 301g, 301i, 301k, 301m, and 301o for detecting the magnetic flux density that changes due to the unevenness of the gear portion of the detection gear 201 is strengthened by the difference in polarity. The positive sine phase is sent to the positive terminal of the differential amplifier 101d, and the negative phase is sent to the negative terminal of the differential amplifier 101d. Similarly, in the detection elements 301b, 301d, 301f, 301h, 301j, 301l, 301n, and 301p, the positive phase of the cosine is strengthened by the difference in polarity, the positive phase of the differential amplifier 101e is the same, and the negative phase is differential. The signal is sent to the negative terminal of the amplifier 101e. The two-phase signals Sa and Ca amplified by the differential amplifiers 101d and 101e show signal changes as shown in FIG. 5 according to the rotation of the detection gear 201. When the signal amplitude of the two-phase signals Sa and Ca is V and the respective DC components are Vsofs and Vcofs, the two-phase signals Sa and Ca are expressed by the following expressions 1 and 2.
Sa = V · sin (θp) + Vsofs Equation 1
Ca = V · cos (θp) + Vcofs Equation 2

Here, θp is a phase within the electrical angle of the two-phase signals Sa and Ca, and when the rotation angle of the detection gear 201 is θ, the relationship of the following Expression 3 is established between θp and θ. ing.
θp = 256 × θ Equation 3

The two-phase signals Sa and Ca are digitized by analog / digital converters 102a and 102b. From the digitized two-phase signals Sdo and Cdo, the offset correction values Sofs and Cofs stored in advance in the storage device 103 are removed by the subtracters 104a and 104b. The two-phase signals Sd and Cd from which the offset component has been removed are converted into tangent signals by the divider 105 by the calculation shown in Equation 4.
Sd / Cd = V · sin (θp) / V · cos (θp) = tan (θp) Equation 4

  Further, arc tangent is calculated by the calculator 106 to obtain an absolute position θp within the basic pitch of the detection gear 201.

  On the other hand, the signal level (voltage level) generated by the detection element 301q that detects the magnetic flux density that changes depending on the presence or absence of the notch in the marker disk 202 is sent to the counter circuit 107 after signal amplification. Further, the amplified signals Sa and Ca of the detection elements 301a to 301p are converted into pulse signals by the comparators 108a and 108b and sent to the counter circuit 107 as the pulse signals Sap and Cap. Further, the counter circuit 107 is sent and set with a numerical value of 256 teeth of the detection gear 201 from the control device 109 when the position detector is initialized. In the counter circuit 107, the pulse signal Sap, Cap is obtained by setting the position where the signal Za of the detection element 301i has a signal change corresponding to the fluctuation of the magnetic field at the notch of the marker disk 202 as a reference position within one rotation. By counting, information θu indicating which position of the 256 irregularities of the detection gear 201 is obtained. θp and θu are added by the adder 110, and the absolute position θ in one rotation is sent to the control device 109. A position detector having a similar configuration is well known in Japanese Patent Application Laid-Open No. 2001-4401. Moreover, although the above-mentioned position detector is a type using a magnetoresistive element as a detection element, Patent Document 2 (Japanese Patent Laid-Open No. 2006-17533) is a position detector that can handle different numbers of teeth of a detection gear. Some of them use an electromagnetic induction type detection principle, as in the example of FIG.

  In the example of FIG. 2, the number of teeth of the detection gear 201 is indicated as 256, but different sizes are often required depending on the design requirements of the rotating shaft to which the position detector is attached. However, if a gear with a different number of teeth is processed with the same module as the detection gear 201, the information on the different number of teeth needs to be obtained from the control device 109 at the time of initialization. Even a number of gears can be detected. This is because if the modules are the same, the arrangement in which the detection elements 301a to 301p are shifted by 3/4 pitch is effective as it is.

  Here, the adjustment of the gap amount between the detection gear 201 and the magnetic sensor 203 will be described. Conventionally, the detection gear 201 integrated with the marker disk 202 is attached to the rotating shaft or the like after adjusting the runout, and then the attachment of the magnetic sensor 203 is adjusted. In applications where rough mounting adjustment is allowed, the magnetic sensor 203 is fixed by sandwiching a plate material of a predetermined thickness such as a skimming gauge between the detection surface of the magnetic sensor 203 and the detecting gear 201, and then the skimming gauge is attached. Pull out. However, if you do not want to scratch the sensor surface part of the magnetic sensor 203 or the tooth tip part of the detection gear 201, or if you want to install with more precise control of the gap amount, use a measuring instrument such as an oscilloscope. Thus, while observing the waveforms of the two-phase signals Sa and Ca shown in FIG. 5, the gap of the magnetic sensor 203 is adjusted and attached so as to obtain a predetermined signal level.

  The mounting method of the magnetic sensor 203 as described above has been performed without change even if the detection gear 201 has a different number of teeth. In the example of FIG. 3, the detection elements 301g to 301j arranged relatively close to the center are not easily affected by the signal level even if the size of the detection gear 201 changes, but are arranged relatively outside. The detection elements 301a to 301f and 301k to 301p are greatly affected by the signal level because the gap amount changes due to the difference in curvature when the size of the detection gear 201 changes. That is, in the method of attaching the gap amount so as to obtain a desired signal level while observing the voltage levels Sa and Ca with an oscilloscope or the like, the larger the number of teeth of the detection gear 201, that is, the curvature of the gear outer circumference circle. Is smaller, the gap between the detection gear 201 and the magnetic sensor 203 is attached larger. Conversely, the smaller the number of teeth is, the smaller the gap is attached.

Japanese Patent Laid-Open No. 2001-4401 JP 2006-17533 A

  In the position detector shown in the conventional example, while observing the voltage level of the detection signal after amplification for different sizes of the detection gear, the gap between the magnetic sensor 203 and the detected object is set to a predetermined voltage level. The amount was adjusted. However, according to this method, the voltage level is adjusted to a predetermined voltage level. Therefore, when the size of the detection gear 201 is relatively large, the gap amount between the magnetic sensor 203 and the detected object becomes large. It was. When the amount of gap between the magnetic sensor 203 and the detection target increases, in the example of FIG. 2, the amount of magnetic flux (leakage magnetic flux) that goes to other than the detection gear 201 relative to the magnetic flux generated from the bias magnet is relatively large. It will increase. In the example of FIG. 1 of Patent Document 2, the leakage flux of the AC excitation magnetic flux from the coil 4 increases. In addition, when the size of the detection gear 201 is relatively small, the gap amount between the magnetic sensor 203 and the detected object becomes small, and the magnetic sensor 203 and the detection are detected in the case of an unexpected runout of the rotating shaft. There was a risk of contact with the gear 201 for use.

  In view of the circumstances as described above, the present invention can detect a position where the gap amount or voltage level between the detected object and the sensor unit is optimal or more preferable for different sizes of the detected object. The purpose is to provide a vessel.

The position detector of the present invention is a position detector comprising a disk-shaped detected object made of a magnetic material, and a sensor unit provided independently of the detected object, wherein the detected object is The sensor unit has a plurality of detection elements or detection patterns arranged in a relative movement direction of the detected object, and the plurality of detection elements or detection patterns. A variable gain amplifying circuit for amplifying a signal from a signal, and storing a correlation between a parameter value and a gain related to the curvature of the detected object, and a parameter value designated by a control device to which the position detector is connected And a memory for setting a corresponding gain value in the variable gain amplifier circuit.

In another method of adjusting the position detector is the invention, in the above-mentioned position detector, on the basis of a signal amplified by the variable gain amplifier circuit, intends row mounting adjustment of the sensor unit relative to the object to be detected.

In another preferred aspect, the size of the detected object is determined according to the number n of the repeated patterns, and the parameter relating to the curvature of the detected object is the number n of the repeated patterns. In another preferred embodiment, the parameters relating to the curvature of the body to be detected is the radius or curvature of the object to be detected.

  According to the position detector of the present invention, even when the sensor unit is combined with a detection object of a different size, the gap amount can be determined by the gain stored in advance. Can be a more preferable void amount. Specifically, for a large-sized object to be detected, the gain of the corresponding variable gain amplifier is reduced. In this case, the signal-to-noise ratio (S / N ratio) works more advantageously than in the past. Play. Even for a large-sized object to be detected, it was mounted and adjusted at the signal level after amplification of the variable gain amplifier of the present invention, because of an unnecessarily wide gap amount that was mounted and adjusted at the signal level after amplification of the conventional amplifier. Since an appropriate gap amount can be obtained, the leakage magnetic flux of the excitation magnetic flux constituted by the excitation magnetic field from the bias magnet or the AC excitation magnetic field from the coil can be reduced.

It is a schematic block diagram which shows an example of the processing circuit part of the position detector which is embodiment of this invention. It is a perspective view which shows the whole structure of a position detector. It is a front view which shows the arrangement | sequence of the detection element included in the magnetic sensor of FIG. It is a schematic block diagram of the processing circuit part of the conventional position detector. It is a graph which shows the waveform of the two-phase signal of a position detector.

[First embodiment]
FIG. 1 is a schematic configuration diagram showing an example of a processing circuit unit of the position detector of the present invention. The processing circuit unit in FIG. 1 processes the position detector having the configuration shown in FIGS. 2 and 3. The same components as those in FIGS. 2 to 4 are denoted by the same reference numerals. The signal level (voltage level) generated by the detection elements 301a, 301c, 301e, 301g, 301i, 301k, 301m, and 301o for detecting the magnetic flux density that changes due to the unevenness of the gear portion of the detection gear 201 is strengthened by the difference in polarity. The positive sine phase is sent to the positive terminal of the variable gain amplifier circuit 101a, and the negative phase is sent to the negative terminal of the variable gain amplifier circuit 101a. Similarly, in the detection elements 301b, 301d, 301f, 301h, 301j, 301l, 301n, and 301p, the positive phase of the cosine is transferred to the + side terminal of the variable gain amplifier circuit 101b and the negative phase is The signal is sent to the negative terminal of the variable gain amplifier circuit 101b. On the other hand, as in the example of FIG. 4, the counter circuit 107 is sent and set with a numerical value of 256 teeth of the detection gear 201 from the control device 109 when the position detector is initialized. The counter circuit 107 transmits information regarding the number of teeth to the storage device 103. In the storage device 103, when information related to the number of teeth of the detection gear 201 is input, a gain value corresponding to the information is selected and sent to the variable gain amplifier circuits 101a and 101b as gain information Gain (256). The variable gain amplifier circuits 101a and 101b set the gain based on the gain information Gain (256). Since the processing method of the two-phase signals Sa and Ca after signal amplification is the same as the conventional method, the description thereof is omitted.

  The gain value corresponding to the number of teeth of the detection gear 201 stored in advance in the memory 103 (repetitive pattern size, parameter relating to the shape of the detected portion) is used as the detection gear 201 used. This lineup is determined by measuring the signal amplitudes of the two-phase signals Sa and Ca after rigorously mounting and adjusting the optimum gap amount in combination with the magnetic sensor 203 in advance. These gain values are stored in a table in the memory 103 so that the number of teeth of the detection gear 201 and the gain value correspond to each other. Alternatively, a gain value with respect to the number of teeth (repetitive pattern size) of the detection gear 201 serving as an arbitrary reference is determined, and the FEM magnetic field analysis tool is used for the detection gear 201 having a different number of teeth. A signal amplitude at a predetermined air gap amount may be calculated by a simulator such as and the like, and a necessary gain value may be determined.

  In the above-described FEM magnetic field analysis, a correlation can be found between the number of teeth of the detection gear 201 (the size of the repeated pattern) and the gain value, and the relationship is expressed by a mathematical expression (including an approximate expression). Sometimes it can be sought. In that case, when the relational expression is stored in the storage device 103 and information on the number of teeth is input from the counter circuit 107, the optimum gain value may be derived from the stored relational expression. . That is, according to the number of teeth of the detection gear 201 (the size of the repetitive pattern), when amplifying signals from the detection elements 301a to 301p, information serving as a clue to amplify with an optimum or more preferable gain is obtained. If the gain is set based on the information stored in the memory 103 in advance, the position detector of the present invention is provided. Alternatively, in the above meaning, not the number of teeth of the detection gear 201 (the size of the repeated pattern) but the value of the gain according to the radius of the tooth circle of the detection gear 201 and the curvature is stored in the storage device 103. You may make it store. When information on the tip circle radius or curvature of the detection gear 201 is input from the counter circuit 107, a gain value corresponding to the information may be set from the storage 103. Even when information on the number of teeth is input from the counter circuit 107, the number of teeth and the inner diameter of the tip circle can be developed by a simple mathematical expression.

  The variable gain amplifier circuits 101a and 101b have a circuit configuration centered on a variable gain amplifier (VGA), but the designer can freely select and design the circuit configuration of electronic components such as preamplifiers and resistors. This is a requirement to be made, and the present invention does not limit the degree of freedom.

  With respect to the position detector of the present invention having the above processing circuit configuration, a method for adjusting the gap amount between the detection gear 201 and the magnetic sensor 203 will be described. First, the detection gear 201 integrated with the marker disk 202 is attached to the rotating shaft while adjusting the runout. Next, the number of teeth of the detection gear 201 is set in the counter circuit 107 by communication means having a function corresponding to communication at initialization in transmission / reception between the magnetic sensor 203 and the control device 109. This information on the number of teeth is also sent to the storage device 103, and the gain of the variable gain amplification circuits 101a and 101b is set from the storage device 103. Further, the gap of the magnetic sensor 203 is adjusted and attached so as to obtain a predetermined signal level while observing the waveforms of the two-phase signals Sa and Ca with a measuring instrument such as an oscilloscope.

  Alternatively, regarding the method of setting the number of teeth of the detection gear 201 in the counter circuit 107 at the time of mounting adjustment of the magnetic sensor 203, unless the information regarding the set number of teeth is subsequently initialized and reset, After making the configuration so that the information on the new number of teeth is not updated, the information about the number of teeth is set once by connecting to the control device 109, the connection with the control device 109 is disconnected, and the gap An amount of mounting adjustment may be made.

  The above-described configuration is an example and may be changed as appropriate. For example, the detection principle of the magnetic sensor unit has been described using a magnetoresistive element as the detection element. However, even with the electromagnetic induction type detection principle using a coil pattern for the detection unit, the position detector of the present invention can do. Moreover, in the above-mentioned example, although what used the gear for the to-be-detected body was described, it can be set as the position detector of this invention also in forms other than this. As an example, there may be mentioned a case where an object to be detected is a ring-shaped magnetic material that does not have a concavo-convex shape and is magnetized so that N and S poles are repeated in a regular pattern. This type of detection object can also effectively utilize the position detector technique of the present invention when it is desired to change the size while maintaining the basic pitch length of the repetitive magnetization pattern.

  In addition, as a technical field to which the present invention belongs, the position detector for controlling the rotary shaft in the field of industrial machines, machine tools, and the like has been described. However, as the applicability to other fields, the position of the present invention It is also conceivable that the detector is mounted on a gear inspection device, a gear testing machine, or the like, and is used as a measuring device that measures a work accuracy such as a gear pitch error or a tip roundness.

  101a, 101b Variable gain amplifier circuit, 101c to 101e Differential amplifier, 102a, 102b Analog / digital converter, 104a, 104b Subtractor, 105 Divider, 106 (Inverse tangent) calculator, 107 Counter circuit, 108a, 108b Comparator , 109 control device, 110 adder, 201 detection gear, 202 marker disk, 203 magnetic sensor, 301a to 301q detection element (magnetoresistance element)

Claims (4)

A position detector comprising a disk-like object to be detected made of a magnetic material, and a sensor unit provided independently of the object to be detected,
The detected object has a regular repeating pattern on its outer periphery,
The sensor unit is
A plurality of detection elements or detection patterns arranged in the relative movement direction of the detected object;
A variable gain amplifier circuit for amplifying signals from the plurality of detection elements or detection patterns;
The correlation between the value of the parameter relating to the curvature of the detected object and the gain is stored, and the gain value corresponding to the parameter value specified by the control device to which the position detector is connected is stored in the variable gain amplifier circuit. A storage device to be set;
A position detector comprising: The position detector according to claim 1 ,
The size of the detected object is determined according to the number n of the repeated patterns,
The parameter relating to the curvature of the detected object is the number n of the repeated patterns.
A position detector characterized by that. The position detector according to claim 1 ,
The parameter relating to the curvature of the detected object is a radius or a curvature of the detected object.   A position detector adjustment method for adjusting the position detector according to claim 1, comprising:
  An adjustment method for a position detector, characterized in that, based on the signal amplified by the variable gain amplifier circuit, the attachment of the sensor unit to the detected object is adjusted.

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