JP2009008638A - Linear absolute displacement sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a linear absolute displacement sensor which is high in resolution and has long stroke capable of detecting correct displacement of the testing body after power failure, and moreover, which will not make the configuration complex. <P>SOLUTION: The linear absolute displacement sensor 5 detecting the linear absolute displacement, based on the pitch information and minute displacement information in the pitch comprises a first sensor 6 for outputting the output of the first sensor; a second sensor 7 for outputting the output of the second sensor which is the same form as the output of the first sensor; a switching part 8 for outputting either of the first sensor output and the second sensor output as the selected output; and a processing part 9 for specifying the pitch of the inspection object, when the second sensor 7 is selected from the sensor output, and specifying the minute displacement, when the first sensor 6 is selected and furthermore holding the specified pitch and the minute displacement information. The second sensor 7 is selected accompanying the turning on of the power source, then the first sensor 6 is selected. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a linear absolute displacement sensor capable of detecting a linear absolute displacement of a subject.

  In recent years, displacement sensors that detect the displacement of a subject by developing detection signals corresponding to the relative positions of a plurality of coils and a magnetic material from each coil have been developed, and are being developed for various applications.

The displacement sensor is classified into an inductive type and an impedance type according to its operation principle. Furthermore, in any type, a plurality of coils are arranged in a straight line to detect the linear displacement x of the subject, and a plurality of coils are arranged in the circumferential direction to rotate the subject. There is a rotary type that detects the angular displacement θ (for example, see Patent Document 1).
First, in order to understand the present invention, basic detection principles of a conventionally known inductive / linear displacement sensor and impedance / linear displacement sensor will be described with reference to FIGS.

[Inductive / Linear displacement sensor]
7A is a perspective view and FIG. 7B is a schematic diagram showing the structure of a conventional inductive / linear displacement sensor.
In FIG. 7A, the displacement sensor 10 includes a solenoid-type primary coil 12 and a secondary coil 11 coaxially arranged inside thereof. The secondary coil 11 is composed of four identical coils L _a to _d arranged at equal intervals. The displacement sensor 10 further includes a connecting body formed by connecting a plurality of rod-like magnetic bodies 1 with array rods 2 made of a nonmagnetic material. This connection body is inserted in the secondary coil 11, and the secondary coil 11 can move in the arrow x direction along the central axis of the connection body.

As shown in FIG. 7 (b), when the center distance of the rod-shaped magnetic body 1 adjacent to the one pitch, center distance of adjacent coils (e.g., L _a and L _b) is 1/4 pitch.

が印加されている。このとき、コイルＬ_ｂとＬ_ｄの差動出力からは、誘起される正弦波Ｓｉｎωｔに、二次コイル１１と棒状磁性体１の相対的な位置に応じた係数ａＳｉｎｘを乗じた値、すなわち、

が得られる。ここで、ａは任意の定数である。
同様に、コイルＬ_ａとＬ_ｃの差動出力からは、誘起される正弦波Ｓｉｎωｔに、二次コイル１１と棒状磁性体１の相対的な位置に応じた係数ａＣｏｓｘを乗じた値、すなわち、

が得られる。ここで、ａは任意の定数である。 In the displacement sensor 10, when an AC signal is applied to the primary coil 12, an AC magnetic field is generated around the primary coil 12. At this time, an induction output signal corresponding to the relative positional relationship with the inserted rod-shaped magnetic body 1 can be obtained from the secondary coil 11 located in the alternating magnetic field.
In FIG. 7A, an AC signal is applied to the primary coil 12.

Is applied. At this time, from the differential output of the coils L _b and L _d , a value obtained by multiplying the induced sine wave Sinωt by a coefficient aSinx corresponding to the relative position of the secondary coil 11 and the rod-shaped magnetic body 1, that is,

Is obtained. Here, a is an arbitrary constant.
Similarly, from the differential output of the coil L _a and L _c, the induced sinusoidal sin .omega.t, a value obtained by multiplying the coefficient aCosx corresponding to the relative position of the secondary coil 11 and the rod-shaped magnetic body 1, i.e.,

Is obtained. Here, a is an arbitrary constant.

As shown in FIG. 7 (b), the conditions such as coil L _a is positioned at the center of the rod-like magnetic substance 1 as the initial position (x = 0), it is displaced along from there the secondary coil 11 in the arrow x Sinx and Cosx in the formulas (2) and (3) are periodically in the range of −1 to +1 every time the relative positions of the rod-shaped magnetic body 1 and the secondary coil 11 are displaced by 1 pitch. It changes with.
That is, the displacement sensor 10 can handle the fact that the bar-shaped magnetic body 1 is linearly displaced by 1 pitch with respect to the secondary coil 11 in correspondence with the change of the variable x of the sine function and cosine function by 2π. . Then, by calculating this variable x by a mathematical method, the linear displacement of the rod-shaped magnetic body 1 with respect to the secondary coil 11 can be detected.
Hereinafter, the variable x is referred to as a variable “displacement x” indicating the relative displacement of the bar-shaped magnetic body 1 with respect to the secondary coil 11.

FIG. 8 shows a circuit that realizes the detection of the displacement x described above. When the AC signal ASinωt is applied to the terminals S ₁ and S ₂ of the primary coil 12, the secondary coil 11 including the coils L _a to _d respectively outputs C ⁺ , S ⁺ , C ⁻ , S ⁻ output (hereinafter, Sensor output). These differential output signals can be expressed by the following equations, similarly to the displacement sensor 10 shown in FIGS.

が得られる。そして、この式（４）と式（３）を加法定理に基づいて合成すると、最終的に、

が得られる。 Among these, the signal represented by the expression (2) is shifted by 90 ° (= π / 2) in the calculation unit 13,

Is obtained. Then, combining this equation (4) and equation (3) based on the addition theorem, finally,

Is obtained.

FIG. 9 shows the signal waveforms represented by the equations (2), (3), and (5) and the procedure for deriving the displacement x from these signal waveforms.
FIG. 9A shows, from the top, the AC signal waveform (= ASinωt) applied to the primary coil 12, the signal waveform (= α) represented by Equation (2), and the signal waveform represented by Equation (3). (= Β). The horizontal axis of each signal waveform is displacement x, and the signal waveform represented by equations (2) and (3) changes periodically, with one pitch of displacement x (= 2π, 360 °) as one cycle. To do.

The displacement x is obtained using an N-bit counter 14 shown in FIG. The N-bit counter 14 receives the signal expressed by the equation (5) obtained by the arithmetic unit 13 and the same AC signal (= ASinωt) as that applied to the primary coil 12.
As shown in the upper graph of FIG. 9B, the waveform aSin (ωt ± x) expressed by the equation (5) is expressed as a waveform whose phase is shifted by x with respect to the original input signal ASinωt. . Therefore, the displacement x can be obtained by measuring the time from the zero cross point of the signal waveform ASinωt to the zero cross point of the signal waveform aSin (ωt ± x).

  In order to realize this, the N-bit counter 14 resets the output triggered by the zero cross point of the signal waveform ASinωt and starts counting. Then, with the zero cross point of the signal waveform aSin (ωt ± x) as a trigger, the count is stopped and the value is held (latched).

For example, when N = 4, the displacement sensor output in binary notation when the displacement x is 0 pitch (no displacement) is “0000”. As the displacement x increases from that state and approaches 1 pitch, this output is “ When the displacement x changes to 0001 ”→“ 0010 ”→“ 0011 ”→“ 0100 ”... And the displacement x reaches 1 pitch (maximum displacement),“ 1111 ”is obtained.
The displacement sensor output in decimal notation is calculated as a × 2 ³ + b × 2 ² + c × 2 ¹ + d × 2 ⁰ when the displacement sensor output in binary notation in the case of N = 4 is “abcd”. it can. For example, when the displacement sensor output in binary notation is the minimum “0000”, the displacement sensor output in decimal notation is 0 + 0 + 0 + 0 = 0, and when the displacement sensor output in binary notation is “1111” at the maximum, decimal notation The displacement sensor output is 8 + 4 + 2 + 1 = 15.
Thus, the N-bit counter 14 can detect the displacement x with a resolution of 1 pitch / ^2N by dividing 1 pitch into ^2N pieces.

More specifically, when 1 pitch is 16 mm and N = 4, the resolution is 16 mm / 2 ⁴ = 1 mm, and when the displacement sensor output indicates “1001”, the displacement x is 9 mm. When 1 pitch is 8.192 mm and N = 13, the resolution is 8.192 mm / 2 ¹³ = 0.001 mm, and when the displacement sensor output indicates “1 0100 0000 0000”, the displacement x is 5.120 mm. is there.

  The detection of the relative displacement between the coil and the magnetic material as described above is called a phase difference conversion (PD conversion) method, and a displacement sensor using this method is used in a mode as shown in FIG. The

A displacement sensor 10 shown in FIG. 10 (a) is composed of a secondary coil 11 composed of coils L _a to _d and a connected body in which 10 rod-like magnetic bodies 1 are connected by an array rod 2, and this is connected to a 13-bit counter, And a pitch counter 15 are combined. Reference numerals P _{1 to} P ₈ denote pitch (intervals between adjacent bar-shaped magnetic bodies 1) numbers, and each pitch is set to 8.192 mm (resolution: 0.001 mm) as an example.

When the secondary coil 11 advances in the direction of the arrow x, the displacement sensor output increases from 0 to the maximum value, and returns to 0 again when the pitch is switched. The switching of the pitch is detected and held by the pitch counter 15, and the displacement x can be specified by referring to both the displacement sensor output and the pitch counter output.
When it is desired to realize a long stroke (detectable displacement x range) without reducing the resolution, such displacement sensor output and pitch counter output are used in combination.
The pitch counter 15 detects the change of pitch by monitoring whether the displacement sensor output changes from the maximum value to the minimum value or vice versa.

As shown in FIG. 10 (b), if the displacement of X _1, indicates that the pitch counter output is P _1, the displacement sensor output is 0 in decimal notation. Therefore, the displacement x in this case is 8.192 mm × (1-1) +0.001 mm × 0 = 0 mm. Further, if the displacement of X _4, indicates that the pitch counter output is P _5, the displacement sensor output indicates a 5120 in decimal notation. Therefore, the displacement x in this case is 8.192 mm × (5-1) +0.001 mm × 5120 = 37.888 mm.

[Impedance / Linear displacement sensor]
Next, the impedance type / linear type displacement sensor will be described.
FIG. 11 is a diagram showing a basic detection principle of an impedance type sensor using a solenoid type coil. As shown in FIG. 11A, this type of sensor has a coil L and an impedance element R (for example, a resistor) connected in series as a basic unit. When an alternating signal ASinωt this sensor is inputted, the both ends of the coil L, the output signal V _o corresponding to the impedance ratio of the coil L and the impedance element R is generated.

The impedance of the coil L changes depending on the relative positional relationship with the rod-shaped magnetic body 1 ′ inserted into the coil, and becomes the highest when the rod-shaped magnetic body 1 ′ is located at the center of the coil L. On the other hand, the impedance of the impedance element R is constant. Accordingly, as shown in FIG. 11 (b), the amplitude of the output signal V _o is 'varies according to the displacement x of the rod-shaped magnetic body 1' rod-like magnetic substance 1 greatest when is located at the center of the coil L Become.

As shown in FIG. 12, four basic units of this sensor are arranged at a predetermined pitch at equal intervals to form a sensor coil 3 composed of coils L ₁ to L ₄ , and a rod-shaped magnetic body 1 ′ and an array rod 2 are connected in series thereto. When a connected body is combined, an impedance type / linear type displacement sensor 10 'is obtained.
In the displacement sensor 10 ′, the AC signal ASinωt is input to the terminals S ₁ and S ₂ of each basic unit, and output signals V _o1 to ₄ corresponding to the impedance ratio of the coil L and the impedance element R of each basic unit are output. It has come to be obtained. The output signal V _o1 ~ ₄ are conditions such as coil L ₁ is located on the first central rod-like magnetic body and the initial position (x = 0), the sensor coil 3 from this state will be displaced in the direction of arrow x And changes according to the amount of displacement.

When the sensor coil 3 will be described change of the output signal V _o1 ~ ₄ when displaced sequentially, first, in the initial position shown in FIG. 12, the output signal V _o1 of the coil L ₁ is larger than the other output signal, the When the sensor coil 3 is displaced in the x direction from the state, the output signal V _o1 decreases and the output signal V _o2 increases. When displaced to at the center of the rod-like magnetic substance 1 of the coil L ₂ ', the output signal V _o2 is maximized. Similarly, as the displacement x increases, the output signals V _o3 and V _o4 sequentially become maximum.

を得ることができる。そして、式（２）（３）で表される信号を、演算部１３及びＭビットカウンター１４’（図８のＮビットカウンター１４に相当）で処理することによって、変位ｘを検出することができる。演算部１３、Ｍビットカウンター１４’、及びピッチカウンター１５における信号処理は、上述した誘導型・直線型の変位センサ１０におけるものと同様なので、ここでは説明を省略する。
特開２００４−２３３３１１号 Even in the displacement sensor 10 'of the impedance type or linear type shown in FIG. 12, the output signals _V o1 _{~ 4} of the sensor coil 3, the sensor outputs ^{(C +, S +, C} -, S - Output) utilized be as By

Can be obtained. The displacement x can be detected by processing the signals represented by the equations (2) and (3) by the arithmetic unit 13 and the M-bit counter 14 ′ (corresponding to the N-bit counter 14 in FIG. 8). . The signal processing in the arithmetic unit 13, the M-bit counter 14 ′, and the pitch counter 15 is the same as that in the inductive / linear displacement sensor 10 described above, and thus the description thereof is omitted here.
JP 2004233331 A

  By the way, the conventional displacement sensors 10 and 10 ′ have a feature that, in principle, a minute displacement of the subject can be detected with high resolution, and the stroke can be lengthened without degrading resolution by using the pitch counter 15 together. On the other hand, however, there is a problem that an accurate displacement cannot be detected when an unexpected situation such as a power failure occurs.

For example, the displacement sensor 10 shown in FIG. 10 (a), occurs a power failure during the detection of the displacement X _3, during a power failure, consider the case where the secondary coil 11 is moved to the displacement X ₄ for some reason. After returning from the power failure, the displacement sensor output outputs the correct value corresponding to the current displacement X _4. However, the pitch counter output is reset by a power failure to indicate 0 (= P ₁ ) even though the current position is P ₅ , or the output value is held in a non-volatile memory. In this case, the value (= P ₃ ) before the power failure is shown. That is, after returning from a power failure, a correct detection result was obtained for a minute displacement within the pitch, but a correct detection result was not always obtained for what pitch the current position is.

Therefore, in the conventional displacement sensor 10, 10 ', back manually at the initial position of the secondary coil 11 or the sensor coil 3 after recovery from the power failure (displacement x = 0), (back to P ₁₎ of the pitch counter 15 reset It was necessary to do the troublesome work of doing. Further, if this work is neglected, there is a possibility that an erroneous displacement detection result is handled as a correct result, and reliability has been a problem.

  Further, in order to solve the above problem, by providing a sensor responsible for specifying the pitch at which the subject is located and a sensor responsible for detecting a minute displacement within the pitch, each sensor obtains a correct value after a power failure. A composite type sensor that can be obtained has also been studied. However, this composite sensor has a complicated structure as compared with the displacement sensors 10 and 10 'described above, and a significant increase in cost has been a problem.

  Therefore, the present invention can detect the accurate displacement even after a power failure while maintaining the conventional feature of high resolution and long stroke, and can suppress the complexity of the configuration as much as possible as compared with the conventional displacement sensor. It is an object of the present invention to provide a linear absolute displacement sensor that can be used.

In order to solve the above problems, a linear absolute displacement sensor according to the present invention is
A linear absolute displacement sensor that detects linear absolute displacement of a subject based on information about a pitch at which the subject is located and information about minute displacement of the subject within the pitch, i) a first sensor that outputs a first sensor output according to a relative positional relationship with the first magnetic body that is displaced with the subject based on the applied AC signal; and ii) is applied A second sensor that outputs a second sensor output in the same format as the first sensor output, in accordance with a relative positional relationship with a second magnetic body that is displaced with the subject based on the AC signal; Iii) a sensor selection unit for generating a selection signal based on a predetermined condition; vi) connected to the first sensor, the second sensor, and the sensor selection unit, and based on the selection signal, the first Sensor output and the second sensor A switching unit that outputs any one of the output signals as a selection sensor output; and v) connected to the switching unit and the sensor selection unit, and the second sensor is selected when the second sensor is selected from the selection sensor output. A processing unit that identifies the pitch of the specimen, identifies the minute displacement of the subject when the first sensor is selected, and further holds information regarding the identified pitch and the minute displacement; It is characterized by having.

  Preferably, the first sensor and the second sensor are each selected from an inductive linear displacement sensor or an impedance linear displacement sensor.

  More preferably, the sensor selecting unit a) selects the second sensor as the power is turned on, and b) the first sensor detects that the pitch is specified by the second sensor. A sensor is selected, and thereafter, the first sensor is continuously selected until it is determined that the power source is continuously turned off for a predetermined time or longer.

In addition, in order to solve the above problems, the method according to the present invention includes:
A method for detecting the absolute displacement of the subject using the linear absolute displacement sensor, wherein i) the selection signal for selecting the second sensor by the sensor selection unit when the power is turned on. Ii) a step of outputting the second sensor output from the second sensor as the selection sensor output by the switching unit that has received the selection signal; and iii) the second Receiving the selection sensor output based on two-sensor output, processing the selection sensor output, and storing the result in a memory as information on the pitch where the subject is located; and iv ) The selection is made so that the first sensor is selected by the sensor selection unit that detects that the information on the pitch is stored in the memory. V) a step of changing the signal; v) a step of outputting the first sensor output from the first sensor as the selection sensor output by the switching unit that has received the selection signal; The processing unit that receives the selection sensor output based on the first sensor output processes the selection sensor output, and the result is stored in the memory as information on the minute displacement of the subject; vii) The pitch stored in the memory when the subject is displaced and the pitch at which the subject is located is detected by monitoring the first sensor output by the processing unit. And viii) repeat steps v) to vii) until the power is turned off. Ix) determining whether or not the duration of the power OFF is a predetermined time or more, and if it is determined that the duration is less than the predetermined time, return to step v) And a step of ending the detection of the absolute displacement of the subject when it is determined that the time is equal to or longer than the predetermined time.

  According to the present invention, the combination of the second sensor responsible for specifying the pitch at which the subject is located and the first sensor responsible for specifying the minute displacement of the subject within the pitch enables high resolution and long length. Accurate displacement can be detected even after a power failure while maintaining the conventional feature of stroke. In addition, according to the present invention, since the same type of sensor output obtained from the first sensor and the second sensor is processed by one processing unit, the configuration is more complicated than the conventional displacement sensor. Therefore, it is possible to provide a linear absolute displacement sensor that can suppress this as much as possible.

  Note that the term “absolute displacement” in this specification means the displacement of the subject when the detection of the displacement of the subject is interrupted due to a power failure or the like and then returns from the suspended state. The term “linear absolute displacement sensor” means a sensor capable of detecting a linear displacement of the subject and capable of detecting an accurate displacement of the subject even after the return from interruption.

  In addition, the term “(power) ON” in the present specification means a state in which a predetermined power supply voltage is supplied so that each sensor can operate normally, and the term “(power) OFF”. Means a state in which the power supply voltage supplied to each sensor is lower than the predetermined power supply voltage.

  Hereinafter, the configuration of a linear absolute displacement sensor according to the present invention will be described with reference to the accompanying drawings.

  As shown in FIG. 1, the linear absolute displacement sensor 5 according to the present invention mainly has a high resolution, a first sensor 6 responsible for detecting a minute displacement within the pitch of the subject, and the subject is located. A second sensor 7 that is responsible for specifying a pitch, a sensor selection unit 18 that generates a selection signal, a switching unit 8 that switches an output signal of the first sensor 6 or the second sensor 7 based on the selection signal, It comprises a processing unit 9 that performs calculation of an output signal from the sensor.

As the first sensor 6 and second sensor 7, (in the present invention, the sensor output ^{(C +, S +, C} -, S - Output)) output of the same type is applicable various sensors that output. For example, an inductive / linear displacement sensor is applied to the first sensor 6 that requires high resolution, and the second sensor 7 that does not require a very high resolution has a simpler and less expensive impedance than the inductive type. A mold / linear displacement sensor can be applied.

Based on the selection signal generated by the sensor selection unit 18, the switching unit 8 processes only one of the first sensor output of the first sensor 6 and the second sensor output of the second sensor 7 as the selection sensor output. To the unit 9.
In the linear absolute displacement sensor 5 shown in FIG. 1, the AC signal ASinωt is always input to both the first sensor 6 and the second sensor 7. The AC signal ASinωt may be input to only one sensor.

The selection sensor output input to the processing unit 9 is processed by the calculation unit 13, the counter 14 ″ and the pitch counter 15, and the result is stored in the memory 16 as pitch data or in-pitch displacement data.
The counter 14 ″ has the functions of the N-bit counter 14 shown in FIG. 8 and the M-bit counter 14 ′ shown in FIG. 12. If the first sensor 6 is selected based on the selection signal, the counter 14 ″ It functions as a bit counter 14 and functions as an M bit counter 14 'when the second sensor 7 is selected, and the difference between the N bit counter 14 and the M bit counter 14' is that the number of bits to be processed is different. Since it is only “N” or “M”, most of the configuration can be shared.

  The output unit 17 outputs pitch data and in-pitch displacement data stored in the memory 16. This output may be performed only at a timing when an instruction is given from the outside, or may be performed constantly.

  To summarize the above, in the linear absolute displacement sensor 5 according to the present invention, the same type of sensor output obtained from each sensor is processed by one processing unit 9, so two sensors are simply installed. Compared with the composite sensor provided, it is possible to suppress the complexity and cost of the structure. Furthermore, in the linear absolute displacement sensor 5 according to the present invention, as shown in a specific sequence in the following embodiment, the first sensor 6 responsible for detecting a minute displacement within the pitch of the subject and the subject are located. By appropriately switching and using the second sensor 7 that is responsible for specifying the pitch that is present, even when an unexpected situation such as a power failure occurs, the accurate absolute displacement of the subject can be detected after the return.

  Next, a first embodiment of the linear absolute displacement sensor according to the present invention will be described with reference to FIGS.

The linear absolute displacement sensor 5 according to the first embodiment shown in FIG. 2 includes a first sensor 6 composed of an inductive / linear displacement sensor and a second sensor 7 composed of an impedance / linear displacement sensor arranged in parallel. and which, in response to linear displacement of the object, a secondary coil 11 consisting of coil L _a ~ _d, in conjunction the sensor coils 3 to a coil L ₁ ~ ₄ so as to move in the direction of arrow x Yes.

The pitch of the first sensor 6 is 8.192 mm, and the lengths of the first rod-shaped magnetic body 1 and the array rod 2 positioned between the first rod-shaped magnetic body 1 are 4.096 mm (= 1/2 pitch), respectively. . The eleven coils L _a to _d of the secondary coil are arranged adjacent to each other at ¼ pitch intervals. The pitch of the second sensor 7 is 65.536 mm, and the coils L ₁ to L ₄ are arranged adjacent to each other at an interval of 16.384 mm (= 1/4 pitch). And the length of 2nd rod-shaped magnetic body 1 'inserted in this coil is about 1/2 pitch (= 32.768 mm).
The stroke of the linear absolute displacement sensor 5 shown in FIG. 2 is equal to the pitch of the second sensor 7 and is 65.536 mm.

In linear absolute displacement sensor 5 according to the first embodiment, the coil L _a of the first sensor 6 is located in the center of the first rod-like magnetic substance 1, and the coil L ₁ of the second sensor 7 and the second rod-like magnetic substance 1 The state located at the center of 'is the initial position (x = 0 mm). Further, in this embodiment, so that the move in conjunction with the state right end are aligned right and the coil L ₁ of the coil L _a.
When the displacement x reaches the maximum displacement (= 65.536 mm) that can be detected by the linear absolute displacement sensor 5, the secondary coil 11 and the sensor coil 3, and the first and second rod-like magnetic bodies 1, 1 ′. The positional relationship is as shown in FIG.

As shown in FIG. 2, the output of the first sensor 6 changes from the minimum value to the maximum value within one pitch. If this output is processed by the 13-bit counter 14 ″, the displacement of the subject within the pitch can be detected with a resolution of 8.192 mm (1 pitch width) / 2 ¹³ = 0.001 mm.
On the other hand, the output of the second sensor 7 gradually increases as compared with the output of the first sensor 6, and reaches a maximum value when the displacement x becomes maximum. If this output is processed by the 5-bit counter 14 ″, the displacement of the subject within the stroke can be detected with a resolution of 65.536 mm (1 stroke width) / 2 ⁵ = 2.048 mm.

In the actual design of the linear absolute displacement sensor 5, the pitch width, the pitch number, and the bit number of the counter 14 ″ of the first sensor 6 are determined from the desired stroke and resolution. For the second sensor 7, The length and coil of the second rod-shaped magnetic body 1 ′ so that the displacement corresponding to the change from the minimum value to the maximum value of the second sensor output is larger than the maximum displacement (= stroke) of the subject to be detected. pitch L ₁ ~ ₄ is determined.

As described above, the linear absolute displacement sensor 5 according to the first embodiment does not require the first sensor 6 having a high resolution for detecting a minute displacement within the pitch of the subject and the resolution as high as the detection of the minute displacement. And a second sensor 7 for specifying the pitch. Information on the approximate displacement (= pitch, P ₁ to _{8 in the first} embodiment) of the subject obtained by the second sensor 7 and information on the minute displacement of the subject within the pitch obtained by the first sensor 6. The absolute displacement of the subject can be detected by referring to.

  Next, an absolute displacement detection sequence of the linear absolute displacement sensor 5 according to the present invention using two sensors together will be described with reference to FIG.

When the power source of the linear absolute displacement sensor 5 is turned on (step S1), the sensor selection unit 18 generates a selection signal for selecting the second sensor 7, and inputs this to the switching unit 8 and the counter 14 ″. Based on this selection signal, the switching unit 8 can output the second sensor output (C ⁺ , S ⁺ , C ⁻ , S ⁻ signal) as the selection sensor output, and the counter 14 ″ can output the second sensor. The number of processing bits corresponding to 7 (“5” in the first embodiment) is switched (step S2).
The second sensor 7, the calculation unit 13 and the counter 14 ″ specify the pitch of the subject by the above-described method (step S3), and the result is stored in the memory 16 as pitch data (step S4).

The data structure in the memory 16 is, for example, as shown in FIG. 5A, and the M-bit (5 bits in the first embodiment) pitch data obtained by the second sensor 7 is shown in FIG. In the conversion table shown in FIG. After being converted to, it is stored in the pitch data area. For example, when the obtained pitch data is “00110”, the pitch data is stored in the pitch No. It is converted to “2”, and “2” is stored in the pitch data area.
The relationship between the first sensor 6 and the pitch counter 15 and the memory 16 will be described later.

The sensor selection unit 18 that has detected that the pitch data is stored in the memory 16 generates a selection signal for selecting the first sensor 6 and inputs it to the switching unit 8 and the counter 14 ″. Is in a state in which the first sensor output (C ⁺ , S ⁺ , C ⁻ , S ⁻ output) of the first sensor 6 can be output based on this selection signal, and the counter 14 ″ corresponds to the first sensor 6 The number of processing bits is switched to “13” in the first embodiment (step S5).
The first sensor 6, the calculation unit 13, and the counter 14 ″ detect a minute displacement within the pitch of the subject by the above-described method (step S6). The result is shown in FIG. (In the first embodiment, 13 bits) is stored in the in-pitch displacement data area (step S7).

The pitch counter 15 monitors, for example, in-pitch displacement data stored in the memory 16, and this data is changed from a maximum value (for example, displacement X _{8 in} FIG. 2) to a minimum value (for example, displacement X _{9 in} FIG. 2). ) Is detected (“Yes” in step S8), “1” is added to the pitch data stored in the memory 16 (step S9).
Similarly, the pitch counter 15 also monitors the change from the minimum value (for example, displacement X _{9 in} FIG. 2) to the maximum value (for example, displacement X _{8 in} FIG. 2) of the displacement data in the pitch (step S10). When this change is detected, “1” is subtracted from the pitch data in the memory 16 (step S11).

  The detection of the minute displacement within the pitch by the first sensor 6 and the monitoring as to whether the pitch has been switched as shown in steps S6 to S11 are repeated until the power is turned off. The displacement data is updated almost in real time according to the displacement of the subject.

When the power is turned off (“Yes” in step S12), it is determined whether or not the duration of the power off is a predetermined time (for example, 15 ms) or more.
If it is determined that the duration of power OFF is less than the predetermined time (“No” in step S13), the absolute displacement detection sequence returns to step S6 and continues. That is, when the power-off time is very short, such as so-called momentary power failure, minute displacement detection within the pitch by the first sensor 6 is continuously performed (steps S6 to S12). In addition, when the above determination is made, it is desirable to notify the user that there was an instantaneous stop by an alarm sound or the like (step S14).
When it is determined that the duration of power OFF is equal to or longer than the predetermined time (“Yes” in step S13), a series of absolute displacement detection sequences by the linear absolute displacement sensor 5 according to the present invention ends. This is the case when the user intentionally turns off the power or a relatively long power outage occurs.

For example, in FIG. 2, the displacement X ₈ occurs outage during which detects, in a case where during power failure secondary coil 11 and the sensor coil 3 is moved to the displacement X ₇ is also linear absolute according to the present invention According to the displacement sensor 5, when the power failure recovery (power again oN) and, since so the pitch of the subject is identified always by the second sensor 7, the current position is P ₁ Certainly can be identified.
Further, according to the linear absolute displacement sensor 5 according to the present invention, following the specification of the pitch by the second sensor 7, the first sensor 6 is automatically selected by the sensor selection unit 18, and the subject within the pitch is detected. Therefore, there is no fear of handling an erroneous detection result as a correct result, and a highly reliable absolute displacement can be detected.

As described above, according to the linear absolute displacement sensor according to the present invention, the two subjects having different roles are appropriately switched and used without performing troublesome resetting work or the like after recovery from a power failure. The accurate absolute displacement can be detected.
Moreover, although the linear absolute displacement sensor according to the present invention is provided with two sensors, many of the components can be shared, so that it is simply provided with two sensors. Compared to the above, it is possible to prevent the configuration from becoming complicated.

  Next, a second embodiment of the linear displacement sensor according to the present invention will be described with reference to FIG.

A linear absolute displacement sensor 5 ′ according to the second embodiment shown in FIG. 6 includes a first sensor 6 composed of an inductive / linear displacement sensor and a second sensor 7 composed of an impedance / linear displacement sensor arranged in series. In response to the linear displacement of the subject, the secondary coil 11 composed of the coils L _a to _d and the sensor coil 3 composed of the coils L ₁ to ₄ move together in the direction of the arrow x. ing.
The stroke of each sensor, the coil interval, the arrangement of the rod-shaped magnetic body, and the like are the same as in the first embodiment.

In the linear absolute displacement sensor 5 ′, when the secondary coil 11 and the sensor coil 3 are displaced in the x direction, the first sensor output and the second sensor output similar to those in the first embodiment shown in FIG. can get.
Therefore, even with the linear absolute displacement sensor 5 ′ according to the second embodiment, the two sensors having different roles are appropriately switched and used without performing troublesome resetting after the recovery from the power failure. Accurate absolute displacement can be detected.

  Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above-described configuration, and it is obvious that those skilled in the art can conceive various modifications.

  For example, in each embodiment, an inductive / linear displacement sensor is used as the first sensor 6 and an impedance / linear displacement sensor is used as the second sensor 7, but various sensors that output signals of the same format are used. Can be used. As a replaceable sensor, for example, there is a sensor of a type that detects a relative displacement between a light emitting element and a light receiving element described in Japanese Patent Application No. 2005-371387.

In addition, the pitch of the first sensor 6 in each embodiment is set to 8.192 mm so as not to generate a fraction in resolution when combined with a ¹³ -bit counter (countable up to 2 ¹³ = 8192). Of course, the present invention is not limited to this, and other values can be used according to the number of bits of the counter or when a fraction may be generated in the resolution.

  Further, in each embodiment, the second sensor 7 is “not so high in resolution”, but the present invention is not limited to this. However, the role of the second sensor 7 is to identify the approximate displacement (= pitch) of the subject in the first place and not to detect the minute displacement of the subject, and therefore has a resolution higher than that of the first sensor 6, for example. Even so, the effects obtained by the present invention remain unchanged.

1 is a block diagram of a linear absolute displacement sensor according to the present invention. FIG. It is a figure which shows the structure and operation | movement of a linear absolute displacement sensor which concern on Example 1. FIG. It is a figure which shows the structure of the linear absolute displacement sensor which concerns on Example 1. FIG. It is a flowchart which shows the detection sequence of the linear absolute displacement sensor which concerns on this invention. It is a figure which shows the memory and conversion table which are used by this invention. 7 is a diagram illustrating a configuration of a linear absolute displacement sensor according to Embodiment 2. FIG. It is a figure which shows the structure of an induction | guidance | derivation type | mold and a linear displacement sensor, Comprising: (a) is a perspective view, (b) is a schematic diagram. It is a circuit diagram (block diagram) showing an inductive / linear displacement sensor and its peripheral circuit. It is a figure which shows the detection principle of an induction | guidance | derivation type | mold and a linear displacement sensor, Comprising: (a) is a graph which shows each signal waveform, (b) is a graph which shows the procedure which calculates | requires the displacement x of a subject. It is a figure which shows operation | movement of an induction | guidance | derivation type | mold and a linear displacement sensor, Comprising: (a) is a schematic diagram of a displacement sensor and the graph which shows the signal waveform which changes with the displacement of a test object, (b) is the displacement of a test object. It is the table | surface which put together the displacement sensor output which changes with it. It is a figure which shows the detection principle of the impedance type and linear displacement sensor using a coil, Comprising: (a) is a schematic diagram which shows the structure of a sensor, (b) is a graph which shows the output signal waveform of a sensor. It is a circuit diagram (block diagram) showing an impedance type / linear type displacement sensor and its peripheral circuit.

Explanation of symbols

1 first rod-shaped magnetic body 1 'the second rod-shaped magnetic body 2 sequence rod 3 sensor coils _L 1 _{~ 4} coil 5, 5' linear absolute displacement sensor 6 first sensor 7 switching unit 9 processor 10 displacement sensor the second sensor 8 11 Secondary coil L _a to _d Secondary coil 12 Primary coil 13 Operation unit 14 N-bit counter 14 ′ M-bit counter 14 ”Counter 15 Pitch counter 16 Memory 17 Output unit 18 Sensor selection unit

Claims (4)

A linear absolute displacement sensor that detects linear absolute displacement of a subject based on information about a pitch at which the subject is located and information about minute displacement of the subject within the pitch,
i) a first sensor that outputs a first sensor output corresponding to a relative positional relationship with a first magnetic body that is displaced with the subject based on an applied AC signal;
ii) Based on the applied AC signal, a second sensor output of the same type as the first sensor output is output according to the relative positional relationship with the second magnetic body that is displaced with the subject. A second sensor that,
iii) a sensor selection unit that generates a selection signal based on a predetermined condition;
vi) Switching connected to the first sensor, the second sensor, and the sensor selector, and outputting one of the first sensor output and the second sensor output as a selected sensor output based on the selection signal And
v) Connected to the switching unit and the sensor selection unit, and when the second sensor is selected from the output of the selection sensor, the pitch of the subject is specified and the first sensor is selected. A processing unit for identifying the minute displacement of the subject, and holding information regarding the identified pitch and the minute displacement;
A linear absolute displacement sensor comprising:   2. The linear absolute displacement according to claim 1, wherein each of the first sensor and the second sensor is selected from an inductive linear displacement sensor or an impedance linear displacement sensor. Sensor. The sensor selector is
a) Select the second sensor as the power is turned on,
b) The first sensor is selected when it is detected that the specification of the pitch by the second sensor is completed, and then the first sensor is determined until it is determined that the power source has been turned off continuously for a predetermined time or more. Keep selecting sensors,
The linear absolute displacement sensor according to claim 1 or 2, wherein the linear absolute displacement sensor is configured as described above. A method for detecting the absolute displacement of the subject using the linear absolute displacement sensor according to claim 1,
i) the step of generating the selection signal for selecting the second sensor by the sensor selection unit as the power is turned ON;
ii) the switching unit that receives the selection signal outputs the second sensor output output from the second sensor as the selection sensor output;
iii) The processing unit that has received the selection sensor output based on the second sensor output processes the selection sensor output, and the result is stored in the memory as information on the pitch at which the subject is located. Steps,
iv) The selection signal is changed so as to select the first sensor by the sensor selection unit that detects that the information on the pitch is stored in the memory;
v) The switching unit that receives the selection signal outputs the first sensor output output from the first sensor as the selection sensor output;
vi) The selection sensor output is processed by the processing unit that has received the selection sensor output based on the first sensor output, and the result is stored in the memory as information relating to the minute displacement of the subject; ,
vii) When it is detected by monitoring of the first sensor output by the processing unit that the subject is displaced and the pitch at which the subject is located is switched, stored in the memory Adding or subtracting information about the pitch;
viii) Steps v) to vii) are repeatedly executed until the power is turned off;
ix) It is determined whether or not the duration of the power OFF is a predetermined time or more. If it is determined that the duration is less than the predetermined time, the process returns to the step v) and is longer than the predetermined time. If it is determined that the detection of the absolute displacement of the subject ends,
A method characterized by comprising:

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