JP4740438B2 - Cylinder position detector - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cylinder position detecting device for detecting a piston stroke position of a fluid pressure cylinder or the like.
[0002]
[Prior art]
Conventionally, various types of position detecting devices for detecting a stroke position of a fluid pressure cylinder or the like are known. Among them, as an inductive cylinder position detection device using a coil, for example, one disclosed in Japanese Utility Model Publication No. 2-23003 is known. In this example, the surface of the piston rod is processed into a screw shape, and a linear displacement corresponding to one pitch of the screw is detected by an absolute. In addition, an example is shown in which the surface of the piston rod is processed to be uneven in a ring shape, and a linear displacement corresponding to one pitch of the uneven ring is detected by an absolute. The position detection method in this type of conventional apparatus is such that a plurality of primary coils are excited by a plurality of alternating current signals (for example, sin ωt and cos ωt) that are out of phase with each other, and a secondary induction signal is generated by each primary coil. Are combined to generate one secondary output signal, and an electric phase shift in the secondary output signal with respect to the excitation AC signal indicates a detection target piston position.
[0003]
[Problems to be solved by the invention]
The coil configuration of an inductive position sensor used in a conventionally known cylinder stroke position detection device requires a primary coil and a secondary coil, which increases the number of parts and limits the manufacturing cost. there were. In addition, there was a limit to downsizing. A position detector of the type that measures the self-inductance of the exciting coil is also known, which can reduce the number of coils, but since the amount of phase shift according to the displacement of the detection target can only be obtained in a narrow range, Actually, it was difficult to measure the amount of phase shift, and the detection resolution was poor, which was unsuitable for practical use.
The present invention has been made in view of the above-mentioned points, and has a small and simple structure, can widen a usable detectable stroke range, and can detect a displacement of a detection target at a high resolution even if the displacement is small. A cylinder position detecting device capable of detection is to be provided.
[0004]
[Means for Solving the Problems]
  The cylinder position detection device according to the present invention is fixed to the cylinder body side, a magnetic response portion arranged in a predetermined pattern having a section where the area gradually increases or decreases along the stroke displacement direction on the surface of the piston rod, A coil provided corresponding to the magnetic response unit;WhereThe coil is excited by a predetermined one-phase alternating current signal, and the corresponding area of the magnetic response portion with respect to the coil changes in accordance with the displacement of the linear stroke position of the piston rod. The inductance changes,TheThe voltage across the coil gradually increases or decreases corresponding to the interval in which the corresponding area of the magnetic response portion with respect to the coil gradually increases or decreases,The impedance means to which the AC signal is applied, and the voltages of the coil and the impedance means are respectively taken out, and based on the addition and subtractionAn analog arithmetic circuit for generating a plurality of AC output signals each having different amplitude characteristics with respect to the stroke position of the piston rodAnd equippedIt is characterized by this.
[0005]
  The magnetic response unit may include at least one of a magnetic body and a conductor. When the magnetic response portion is made of a magnetic material, the self-inductance of the coil increases as the corresponding area of the magnetic response portion with respect to the coil increases, and the voltage across the coil gradually increases. On the other hand, when a good conductor such as copper is used as the magnetic response part, the self-inductance of the coil decreases due to eddy current loss, and the self-inductance of the coil decreases as the corresponding area of the magnetic response part with respect to the coil increases. Then, the voltage across the coil gradually decreases. Also, a hybrid type that combines a magnetic body and a conductor may be used as the magnetic response section.Yes.
[0010]
  According to the present invention, substantially only one magnetic response portion arranged in a predetermined pattern having a section in which the area gradually increases or decreases along the stroke displacement direction is provided, and only one coil is correspondingly provided. You may make it provide. When there is only one coil, only one gradual increase (or gradual) change curve of the voltage generated from the coil according to the stroke position is generated. As such, a plurality of AC output signals each showing desired amplitude characteristics according to the detection target stroke position, typically two AC output signals each showing amplitude characteristics according to the sine and cosine function characteristics according to the detection target position. , Is difficult to generate. Therefore, impedance means to which the AC signal is applied is provided as a dummy voltage generating means, and a desired output is obtained according to the position to be detected by combining the output voltage of the coil and the output voltage of the dummy impedance means. A plurality of AC output signals each indicating an amplitude characteristic, typically two AC output signals each indicating an amplitude according to the sine and cosine function characteristics, can be generated according to the position to be detected. The dummy impedance means may be a resistance element or an inductance means such as a coil. In this case, in addition to being able to obtain the same effect as a type in which a plurality of magnetic response units arranged in different patterns or sections and coils corresponding to them are provided, only one coil is required. Suitable for detecting displacement.
[0011]
  A plurality of the magnetic response parts having a common pattern of gradually increasing or decreasing the area are arranged to be shifted by a predetermined angle in the circumferential direction of the piston rod, thereby providing each corresponding to each magnetic response part. The pattern of the gradual increase or decrease of the voltage across the coil with respect to the stroke displacement of the piston rod is common to each coil, and the piston rod is obtained by adding and synthesizing the output voltage of each coil. A circuit for generating one output voltage that gradually increases or decreases in accordance with the linear stroke displacement of the first and second impedances, and the one output voltage and the output voltage of the impedance means may be input to the analog arithmetic circuit. . In this case, even if the shaft misalignment occurs due to its own weight when the expansion / contraction stroke of the piston rod changes, the output voltage of each coil is averaged by addition, so that the stroke position detection accuracy is not adversely affected. Can do.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a perspective view schematically showing the appearance of a cylinder device 1 to which a cylinder position detecting device according to the present invention is applied. The cylinder device 1 may be any type of cylinder such as a hydraulic or pneumatic cylinder. As is generally known, the cylinder device 1 includes a cylinder body 2, a piston 3 housed in the cylinder body 2 and linearly displaced relative to the cylinder body 2, and one end connected to the piston 3. The other end protrudes to the outside from the end opening of the cylinder body 2 and includes a piston rod 4 that linearly displaces in the axial direction (arrow x in the drawing) in accordance with the linear displacement of the piston 3. Note that illustration of a hydraulic or pneumatic circuit or the like related to the cylinder body 2 is omitted.
[0013]
The cylinder position detecting device is fixed to the side of the cylinder body 2 and a magnetic response portion 5 arranged in a predetermined pattern having a section where the area gradually increases or decreases along the stroke displacement direction on the surface of the piston rod 4. And a coil sensor unit 6 made of a coil provided corresponding to the response unit 5. The magnetic response portion 5 is a portion formed so as to have different magnetic response characteristics from other portions of the surface of the piston rod 4. For example, in this portion, the permeance is increased or decreased (magnetic resistance) than the other portions. Decrease or increase), and typically includes at least one of a magnetic material and a conductor. When the magnetic response unit 5 is made of a magnetic material, the self-inductance of the coil increases as the area of the magnetic response unit 5 corresponding to the coil increases, and the voltage across the coil gradually increases. On the other hand, when a good conductor such as copper is used as the magnetic response unit 5, the self-inductance of the coil decreases due to eddy current loss, and the self-inductance of the coil decreases as the corresponding area of the magnetic response unit 5 with respect to the coil increases. The voltage across the coil gradually decreases. Alternatively, the magnetic response unit 5 may be a hybrid type in which a magnetic material and a conductor are combined (for example, a recess is formed in a predetermined pattern on the surface of the rod 4 made of iron, and a copper is formed in the recess. Embedded with a good conductor such as Below, the magnetic response part 5 shall consist of nonmagnetic good conductors, such as copper. For example, the magnetic response portion 5 having a desired arrangement pattern can be formed by performing copper plating on the surface of the piston rod 4 in a predetermined pattern. As will be described later, the coil sensor unit 6 can be considerably reduced in size, so that it can be accommodated in an existing cylinder head 7 (rod bearing).
[0014]
FIG. 2 is a development view showing an arrangement pattern of the magnetic response portions 5 on the surface of the piston rod 4. In the figure, the direction of linear displacement of the piston rod 4 is indicated by an arrow x. The magnetic response unit 5 includes two patterns 5a and 5b. The first pattern 5a has a triangular shape that gradually increases from left to right in the figure, and the pattern 5b is opposite from left to right. It has an inverted triangular shape that gradually decreases. That is, the section in which the area of the pattern 5a gradually increases and the section in which the area of the pattern 5b gradually decreases covers the entire length in the piston rod 4 axis direction.
[0015]
FIG. 3 is a conceptual schematic diagram showing a configuration example of the coil sensor unit 6, and is shown in the form of a front view as viewed from the end opening side of the cylinder body 2. The coil sensor unit 6 includes two coils La and Lb provided corresponding to the patterns 5a and 5b, respectively, so that each coil covers a half surface (a range of about 180 degrees) of the axis of the piston rod 4 respectively. Has been placed. That is, the coil La covers the arrangement area of the pattern 5a, and the coil Lb covers the arrangement area of the pattern 5b. The coils La and Lb have the same properties such as the number of turns and the coil length, and are arranged so that the internal magnetic flux of each coil is generated substantially perpendicularly (in the radial direction of the rod) on the surface of the rod 4.
[0016]
As shown in FIG. 2, the pattern 5a on the surface of the piston rod 4 has a triangular shape that gradually increases from left to right in the figure, and the pattern 5b has an inverted triangular shape that gradually decreases from left to right. Therefore, the corresponding area of the pattern 5a facing the coil La becomes small according to the linear stroke displacement of the piston rod 4 in the direction of the arrow x. Accordingly, the eddy current loss due to the conductive pattern 5a is reduced, and the self-inductance of the coil La is relatively increased. Therefore, the voltage across the coil La gradually increases corresponding to the gradual decrease of the area of the pattern 5a. To do. At this time, the corresponding area of the pattern 5b facing the coil Lb gradually increases, and the self-inductance of the coil Lb gradually decreases as the eddy current loss gradually increases, and the voltage across the coil Lb corresponds to the gradually increasing area of the pattern 5b. And then gradually decrease. Of course, when the piston rod 4 returns in the direction opposite to the arrow x, the corresponding areas of the patterns 5a and 5b with respect to the coils La and Lb gradually decrease or increase contrary to the above. In this way, the self-inductances of the coils La and Lb change in opposite directions according to the linear displacement of the piston rod 4.
[0017]
FIG. 4A is a circuit diagram showing an example of coil connection in the coil sensor unit 6. Each of the coils La and Lb is determined by a predetermined one-phase AC output signal (indicated by sin ωt) generated from the AC power source 8. Excited with voltage or constant current. When the voltages between both ends of the coils La and Lb are denoted by Va and Vb, respectively, terminals 9 to 11 are provided for taking out the respective voltages V and Vb. As described above, the self-inductance of each of the coils La and Lb changes according to the change of the corresponding area of the patterns 5a and 5b with respect to the coils La and Lb according to the displacement of the linear stroke position of the piston rod 4 in the arrow x direction. As shown in FIG. 4B, the voltage Va between both ends of the coil La changes gradually, and the voltage Vb between both ends of the coil Lb changes gradually. Typically, the gradual increase or decrease curve of the voltage across the coil in accordance with the change in the corresponding area of the pattern of the magnetic response unit 5 corresponding to the coil sensor unit 6 is an appropriate value less than 90 degrees in the sine function or cosine function. It can be compared to a function value change in the range. Therefore, two AC output signals sinθsinωt and cosθsinωt having amplitudes indicating sine and cosine function characteristics according to the stroke position of the piston rod 4 can be generated.
[0018]
That is, the gradually increasing change in the output voltage Va of the coil La as shown in FIG. 4B can be roughly compared to a change in the function value in an appropriate range that falls within the range of approximately 0 to 90 degrees in the sine function. . Therefore, an AC output signal having a sine function characteristic can be obtained by taking out the output voltage Va of the coil La through an appropriate analog buffer circuit 21, and this can be equivalently expressed as “sin θ sin ωt” ( However, θ is less than 0 to 90 degrees). Further, the gradual decrease in the voltage Vb across the coil Lb can be compared to a change in the function value within an appropriate range that falls within the range of approximately 0 to 90 degrees in the cosine function. Therefore, an AC output signal having a cosine function characteristic can be obtained by taking out the output voltage Vb of the coil Lb through an appropriate analog buffer circuit 21, and this can be equivalently expressed as “cos θ sin ωt” ( However, θ is less than 0 to 90 degrees).
[0019]
The phase angle θ in the sine and cosine functions, which are the amplitude components of each AC output signal, corresponds to the linear stroke position of the piston rod 4. In this case, as shown in FIG. 4C, the effective detection range corresponds to an appropriate range within a range from 0 degrees to 90 degrees where the sine function and the cosine function cross. That is, an appropriate range within the range of 0 to 90 degrees corresponds to the stroke position detectable range of the piston rod 4, and by detecting the value of the phase angle θ in this range, the piston rod 4 The absolute stroke position can be detected.
[0020]
Here, the two-phase AC output signals (sin θ sin ωt and cos θ sin ωt) obtained in the position detection apparatus of the present invention can be used in the same manner as the output of a conventionally known resolver. For example, as shown in FIG. 4A, each coil AC output signal of the sensor unit 6 is input to an appropriate phase detection circuit 12, and the phase value θ of the sine function sin θ and the cosine function cos θ is detected by a phase detection method. The digital data Dθ of the phase angle θ can be obtained. As a phase detection method adopted in the phase detection circuit 12, for example, a technique disclosed in Japanese Patent Laid-Open No. 9-126809 may be used. For example, the first AC output signal sin θ sin ωt is electrically shifted by 90 degrees to generate an AC output signal sin θ cos ωt, and this and the second AC output signal cos θ sin ωt are added and subtracted to form sin (ωt + θ) and sin Generates two AC output signals (a signal obtained by converting the amplitude phase component θ into an AC phase shift) that is (ωt−θ) and phase-shifted in the fast and slow phases according to θ, and measures the phase θ. Thus, stroke position detection data can be obtained. Alternatively, a known RD (resolver-digital) converter for processing the resolver output may be applied.
The detected digital data Dθ of the phase angle θ corresponds to the linear stroke position of the piston rod 4, so that the stroke position of the piston rod 4 can be detected by absolute. Needless to say, the present invention is not limited to the method of outputting digital data, and analog data indicating the detected stroke position may be output.
[0021]
As shown in FIG. 4B, the amplitude characteristics of the sine and cosine function characteristics of the AC output signals sin θ sin ωt and cos θ sin ωt are true if the correspondence relationship between the angle θ and the detection target position x is linear. The sine and cosine function characteristics are not shown. However, the phase detection circuit 12 may apparently perform phase detection processing assuming that the AC output signals sinθsinωt and cosθsinωt have amplitude characteristics of sine and cosine functions, respectively. As a result, the detected phase angle θ may not show linearity with respect to the detection target position x. However, in the position detection, the non-linearity between the detection output data (detected phase angle θ) and the actual detection target position does not have to be a serious problem. That is, it is only necessary that position detection can be performed with a predetermined reproducibility. Further, if necessary, the output data of the phase detection circuit 12 is converted using an appropriate data conversion table so that accurate linearity is provided between the detection output data and the actual detection target position. Can be done easily. Therefore, the AC output signals sin θ sin ωt and cos θ sin ωt having the sine and cosine function amplitude characteristics referred to in the present invention do not have to show the true sine and cosine function characteristics, and are as shown in FIG. In fact, it may be a triangular wave shape, and in short, it is only necessary to show such a tendency. That is, it may be a periodic function similar to a trigonometric function such as sine. In the example of FIG. 4B, if the viewpoint is changed and the scale on the horizontal axis is regarded as θ and the scale is made up of a required non-linear scale, the scale on the horizontal axis is regarded as the stroke position. In this case, even if it looks like a triangular wave, it can be said that θ is a sine function or a cosine function.
[0022]
Thus, according to the present invention, it is sufficient to provide only the primary coil, and no secondary coil is required. Therefore, it is possible to provide a cylinder position detecting device having a small and simple structure. Also, it is possible to easily generate a plurality of AC output signals each indicating an amplitude according to a predetermined periodic function characteristic (for example, two AC output signals each indicating an amplitude according to a sine and cosine function characteristic) according to the detection target stroke position. . Further, by detecting the phase value in a predetermined periodic function (for example, sine and cosine function) that defines the amplitude value from the correlation of the amplitude values in the plurality of AC output signals, even if the displacement of the detection target is very small, the resolution is high. Position detection is possible.
[0023]
Needless to say, the configuration of the coil used in the above embodiment is not limited to the above. FIG. 5 shows an example of a coil change example. FIG. 5A shows a perspective view, and FIG. 5B shows a developed view of the coil and magnetic response portion pattern. In this case, the piston rod 4 is configured to enter the central space of the coil, and the direction of the internal magnetic flux of the coil is directed to the axial direction of the rod 4. The coil LA corresponding to the pattern 5a and the coil LB corresponding to the pattern 5b are formed by adjacently arranging two coils having the same properties such as the number of turns and the coil length. Masking MA and MB are applied to the inner half of each coil (in the range of about 180 degrees) with a good conductor such as copper. As a result, output voltages corresponding to the corresponding areas of the magnetic response portions 5a and 5b corresponding only to the half surface not subjected to masking are generated from the coils LA and LB. The masking MA in the coil LA is applied to the half surface corresponding to the pattern 5b, and the coil LA does not respond to the pattern 5b but responds only to the pattern 5a. The masking MB in the coil LB is provided on the half surface corresponding to the pattern 5a, and the coil LB does not respond to the pattern 5a but responds only to the pattern 5b. Therefore, the output voltage from the coil LA gradually increases corresponding to the gradual decrease of the area corresponding to the coil of the pattern 5a, and the output voltage from the coil LB gradually decreases corresponding to the gradual increase of the area corresponding to the coil of the pattern 5b. The detection operation can be performed as shown in FIG.
[0024]
By the way, in the example of FIG. 2 or FIG. 5, when the piston rod 4 rotates, the corresponding positions of the magnetic response parts 5a and 5b with respect to the coils La and Lb of the sensor part 6 are shifted, and the output of the sensor part 6 is reduced. The linear stroke position of the piston rod 4 is not accurately reflected. This problem can be solved by configuring the piston rod 4 so as not to rotate, and may be used in an environment where the piston rod 4 does not rotate. On the other hand, when the cylinder device is large, the piston rod 4 is also heavy to some extent. Then, when the expansion / contraction stroke of the rod 4 is displaced, the rod 4 is easily bent due to its own weight. When the rod 4 bends, the axis with respect to the coil is displaced, thereby changing the gap between the sensor unit 6 and the magnetic response unit 5 and changing the self-inductance of the coil, and the output from the sensor unit 6 is The linear stroke position of the piston rod 4 is not accurately reflected. Accordingly, an embodiment in which detection errors due to rotation of the piston rod 4 and axial misalignment are removed will be described with reference to FIG.
[0025]
FIG. 6A is a development view of the surface of the piston rod 4 similar to FIG. The magnetic response unit 5 includes three common patterns 5a, 5b, and 5c, which are arranged in parallel corresponding to a range in which the side surface of the piston rod 4 is divided into three in the circumferential direction. In the figure (a), it forms a triangular shape that gradually decreases from left to right. The coil sensor unit 6 includes three coils La, Lb, and Lc corresponding to the patterns 5a, 5b, and 5c, respectively, and is arranged so as to correspond to each 120 degree range obtained by dividing the circumferential direction of the rod 4 into three. The coils La, Lb, and Lc are associated with the patterns 5a, 5b, and 5c of the magnetic response unit, respectively. As a result, the voltage between both ends of the coils La to Lc corresponding to the magnetic response unit patterns 5a to 5c is the same as the pattern of the gradual decrease or gradual change shown in accordance with the linear stroke position displacement of the piston rod 4. It becomes. FIG. 6B is a circuit diagram showing an example of coil connection. The output voltages from the coils La, Lb, and Lc are Va, Vb, and Vc. The output voltages Va, Vb, and Vc are averaged or added and synthesized by the averaging circuit 13, and the average value or synthesized value is set as one output VA.
[0026]
By adding and synthesizing the output voltages Va to Vc from the coils La to Lc to obtain one output VA, even if the piston rod 4 rotates, in the present invention, a plurality of coils La to Lc are used. Since the outputs having the same characteristics are added and synthesized, the output errors of the individual coils due to the rotation are canceled out. Further, when the axial center position of the piston rod 4 is displaced due to deflection or the like during expansion / contraction, the gap between a certain coil and the magnetic response unit 5 is narrowed, and the self-inductance of the coil is relatively decreased, and a corresponding output error is caused. Since the gap widens correspondingly on the opposite side and the self-inductance of the corresponding coil relatively increases and a reverse error equivalent to the output error also occurs on the opposite side, each output Va , Vb, and Vc are added and combined, the output error caused by the misalignment of the axis of the piston rod 4 is canceled out, and no adverse effect is caused by the misalignment of the axis of the piston rod 4.
[0027]
Corresponding areas of the patterns 5a, 5b, 5c facing the coils La, Lb, Lc gradually increase in accordance with the linear stroke position displacement of the piston rod 4 in the direction of the arrow x. The self-inductance of each coil gradually decreases due to the gradual increase of the eddy current loss accordingly, and the output voltages Va to Vc from the coils La to Lc change gradually. Then, as shown in FIG. 6C, the gradual change in the voltage VA, which is the result of adding and synthesizing the output voltages Va to Vc, is a cosine function in an appropriate range that falls within the range of about 0 to 90 degrees. It can be compared to characteristics. Here, assuming that the voltage obtained when the corresponding area of the pattern with respect to the coil is the smallest, that is, the maximum voltage is VN, a constant voltage VN is generated from an appropriate constant voltage generation circuit 14, and the voltage VA is subtracted from the constant voltage VN. Then, the obtained voltage “VN−VA” can be compared with a sine function characteristic in an appropriate range that falls within the range of approximately 0 to 90 degrees as shown in FIG.
[0028]
Therefore, in FIG. 6B, the voltages Va, Vb, and Vc across the coils La, Lb, and Lc are added and synthesized by the averaging circuit 13 and averaged, and the resultant output VA is an alternating current of cosine function characteristics. A signal corresponding to the output signal cos θ sin ωt can be generated. Further, by subtracting the composite output VA from the constant voltage VN generated from the constant voltage generation circuit 14 by the subtraction circuit 15, a signal corresponding to the AC output signal sin θsin ωt having a sine function characteristic is obtained as the subtraction result “VN−VA”. Can be generated. Therefore, the detection operation as shown in FIG. 4 can be performed as described above. The constant voltage generation circuit 14 is configured by using a dummy coil having characteristics equivalent to those of the coils La, Lb, and Lc, and if it is excited by the same excitation AC output signal, compensation for temperature drift is performed. Is good.
[0029]
In the above-described embodiment, the change range corresponding to one stroke of the phase component θ of the amplitude functions sin θ and cos θ in the AC output signals sin θ sin ωt and cos θ sin ωt having the sine and cosine function characteristics is less than an angle range from 0 degrees to 90 degrees. However, the present invention is not limited to this, and a wider angle range may correspond to one cylinder stroke. For example, it is possible to perform detection in a full phase angle range from 0 degrees to 360 degrees. Of course, the detection can be performed not only in the full phase angle range but also in a limited phase angle range such as 0 to 180 degrees. The usable phase range can be appropriately set according to the detection purpose and the like, and the magnetic response unit, the coil, the arithmetic circuit, and the like may be appropriately configured so as to obtain a desired phase change. Examples of such changes are shown below.
[0030]
FIG. 7 shows an embodiment that can produce a phase change from 0 degrees to 180 degrees. FIG. 7A is a development view showing a pattern arrangement example on the surface of the piston rod 4. The magnetic response unit is composed of six patterns 5a, 5b, 5c, 5d, 5e, and 5f, and these are arranged in parallel corresponding to the range in which the side surface of the piston rod 4 is divided into six in the circumferential direction. The patterns 5a, 5c and 5e are common patterns, and the patterns 5b, 5d and 5f are also common patterns. In patterns 5a, 5c and 5e, the area of the magnetic response portion gradually decreases from the left to the right in the left half section of the length direction of the rod 4 in FIG. This pattern has no part. In patterns 5b, 5d and 5f, the area of the magnetic response portion gradually decreases from left to right in the right half section of the length direction of the rod 4 in FIG. It is a pattern consisting of a magnetic response part. The coil sensor unit 6 includes coils L1, L2, L3, L4, L5, and L6 corresponding to the patterns 5a, 5b, 5c, 5d, 5e, and 5f, and 60 degrees each obtained by dividing the circumferential direction of the rod 4 into six. It is arranged so as to correspond to each of the ranges.
[0031]
When the piston rod 4 is displaced in the direction of the arrow x, the corresponding areas of the patterns 5b, 5d, 5f and the corresponding coils L2, L4, L6 gradually increase in the first half of the stroke, and the coils L2, L4, The output voltages V2, V4, and V6 of L6 change gradually. In this first half section, the output voltages V1, V3, and V5 of the coils L1, L3, and L5 corresponding to the other patterns 5a, 5c, and 5e maintain the maximum level because there is no magnetic response portion (conductor). When the piston rod 4 is displaced when the output voltages V1, V3, and V5 having the same gradual change pattern and the piston rod 4 are displaced, the patterns 5a, 5c, and 5e and the coils L1, L3, and L5 corresponding to the patterns 5a, 5c, and 5e The corresponding area gradually increases, and the output voltages V1, V3, V5 of the coils L1, L3, L5 change gradually. In this latter half section, the output voltages V2, V4, V6 of the coils L2, L4, L6 corresponding to the other patterns 5b, 5d, 5f always maintain the minimum level because the magnetic response part (conductor) is always present. . The output voltages V1, V3, and V5 having common change patterns are added and synthesized by the averaging circuit 16 in FIG. 7B to obtain an output VA. The output voltages V2, V4 and V6 are also added and synthesized by the averaging circuit 16 to obtain an output VB. An example of the combined outputs VA and VB is shown in FIG. The reason why the first common patterns 5a, 5c, and 5e and the second common patterns 5b, 5d, and 5f are alternately arranged and the respective outputs are added and synthesized is the same as in the example of FIG. This is so as not to be adversely affected by the rotation of the rod 4 and the axial misalignment.
[0032]
Assuming that the maximum voltage of the coil output voltage is VN, a constant voltage VN corresponding to this is generated from the constant voltage generation circuit 14 as shown in FIG. When the constant voltage VN is subtracted from the added value of the output voltages VA and VB, the obtained voltage “VA + VB−VN” is a cosine of a range that falls within the range of approximately 0 to 180 degrees as shown in FIG. It can be compared to function characteristics. On the other hand, when VB is subtracted from voltage VA, the obtained voltage “VA−VB” can be compared to a sine function characteristic in a range that falls within the range of approximately 0 to 180 degrees, as shown in FIG. .
Accordingly, in FIG. 7B, the subtraction circuit 17 subtracts the output voltages VA and VB, and the subtraction result is “VA−VB” to generate a signal corresponding to the AC output signal sin θsin ωt having the sine function characteristic. be able to. Further, the output voltages VA and VB are added by the adder circuit 18, and the constant voltage VN generated from the constant voltage generator circuit 14 is subtracted from the addition result by the subtractor circuit 19, so that the subtraction result is “VA + VB−VN”. 4 can generate a signal corresponding to the AC output signal cos θ sin ωt having the cosine function characteristic, so that the detection operation similar to the example of FIG. Detection can be performed by converting to an appropriate phase angle range within the range.
[0033]
FIG. 9 shows an example in which a phase change from 0 degrees to 360 degrees can be generated corresponding to one cylinder stroke as another embodiment. In this embodiment, the magnetic response unit 5 is a hybrid type in which a magnetic material and a conductor are combined. For example, a recess is formed in a predetermined pattern on the surface of the rod 4 made of iron, and a good conductor such as copper is embedded in the recess. In this embodiment, the iron convex portion is referred to as a magnetic response portion pattern. FIG. 9A is a development view showing a pattern arrangement example on the surface of the piston rod 4. The magnetic response unit 5 includes four patterns 5a, 5b, 5c, and 5d, and is arranged corresponding to a range in which the side surface of the rod 4 is divided into four in the circumferential direction. For convenience of explanation, in FIG. 5A, the rod 4 is divided into four in the length direction, and each quarter section is referred to as P1, P2, P3, and P4, respectively. The pattern 5a forms a triangular pattern in which the area of the magnetic body gradually decreases in the P1 section (the area of the conductor gradually increases) from the left to the right in the figure, and the area of the magnetic body gradually increases in the P4 section (conductivity). (The area of the body is gradually reduced.) A triangular pattern is formed. In the P2 and P3 sections, the entire region is made of a conductor. In the pattern 5b, the area of the magnetic body gradually increases in the P3 section, gradually decreases in the P4 section, and the entire area is made of a conductor in the other sections P1 and P2. In the pattern 5c, the area of the magnetic body gradually increases in the P2 section, gradually decreases in the P3 section, and the entire area is made of a conductor in the other sections P1 and P4. In the pattern 5d, the area of the magnetic body gradually increases in the P1 interval, gradually decreases in the P2 interval, and the entire area is a conductor in the other intervals P3 and P4. The coil sensor unit 6 includes coils L1, L2, L3, and L4 corresponding to the patterns 5a to 5d, respectively, and is arranged so as to correspond to each 90 degree range obtained by dividing the circumferential direction of the rod 4 into four. Yes.
[0034]
FIG. 9B shows a gradual increase and a gradual change in the output voltages V1 to V4 according to the change in the stroke position when the piston rod 4 is displaced in the direction of the arrow x. In order to clearly show the relationship between each pattern and the output voltage change, the corresponding positions of the divisions P1, P2, P3, and P4 are also shown in FIG. When V2 is subtracted from the output voltage V1, the obtained voltage “V1−V3” can be compared to a cosine function characteristic in a range that falls within the range of approximately 0 to 360 degrees as shown in FIG. 9C. On the other hand, when V4 is subtracted from voltage V2, the obtained voltage “V2−V4” can be compared to a sine function characteristic in a range that falls within the range of approximately 0 ° to 360 ° as shown in FIG. .
[0035]
FIG. 10 shows a circuit configuration example in the embodiment of FIG. As shown in the marrow 10, the output voltages V1 and V3 are subtracted by the analog arithmetic circuit 20, and the subtraction result is “V1−V3”. As shown in FIG. A signal corresponding to the AC output signal cos θ sin ωt can be generated. Further, the output voltages V2 and V4 are subtracted by the analog arithmetic circuit 20, and the subtraction result is “V2−V4”, and an AC output signal sinθsinωt having a sine function characteristic in a range of 360 degrees as shown in FIG. 9C. Can be generated. Therefore, the detection operation similar to the example of FIG. 4 described above can be performed, and detection can be performed in a phase angle range with a width of approximately 0 to 360 degrees.
[0036]
In each of the above-described embodiments, the example in which the magnetic response unit 5 includes a plurality of patterns has been described. FIG. 11 shows an example, and as shown in FIG. 11A, the pattern of the triangular magnetic response portion 5 whose area gradually decreases is arranged so as to draw a spiral on the surface of the piston rod 4. is there. The spiral pattern of the magnetic response unit 5 gradually increases or decreases along the stroke displacement direction of the rod 4. When this expands, the area increases from left to right as shown in FIG. Is equivalent to one triangular pattern that gradually decreases, and can be said to be substantially one pattern. In this case, since the magnetic response unit 5 has one pattern, the coil sensor unit 6 is composed of one corresponding coil, and the piston rod 4 enters the central space of the coil (the direction of the internal magnetic flux of the coil is the rod). 4) is adopted. Since there is only one coil, only one pattern of the change curve of the output voltage is generated. Therefore, dummy voltage generating means similar to the low voltage generating circuit 14 of FIG. 6B is provided, and the same as in FIG. 6C. The two voltage outputs VA and the dummy constant voltage output VN are appropriately combined with each other, and two AC output signals each indicating the amplitude in accordance with the sine and cosine function characteristics can be generated according to the position to be detected. The same effect as the example of providing the response part pattern can be obtained. Since the pattern of the magnetic response unit 5 is spiral and the coil covers the entire circumference of the rod 4, the detection error due to the rotation of the piston rod and the misalignment of the axis is similar to the example of FIG. It can be prevented from occurring. Therefore, even with only one pattern, position detection without detection errors due to rotation and axial misalignment is possible. Further, such a helical magnetic response part pattern is advantageous because it can be very easily formed on the piston rod. Furthermore, since only one coil of the sensor unit 6 is required, the configuration is simple. Of course, it is also suitable for ultra-compact, small displacement detection.
6, 7, and 9, the coil configuration is arranged so that the direction of the magnetic flux inside the coil is directed in the axial direction of the rod 4 as shown in FIG. Of course, it can change to the structure which provides a masking means corresponding to the range.
[0037]
【The invention's effect】
As described above, according to the present invention, it is sufficient to provide only the primary coil, and the secondary coil is not necessary. Therefore, it is possible to provide a cylinder position detecting device having a simple structure. It is also suitable for downsizing as required. In addition, the voltage to be detected is appropriately added and / or subtracted from the voltage between both ends of the coil that gradually increases (or gradually decreases) in accordance with the gradual increase (or gradual decrease) in the area corresponding to the magnetic response unit according to the change in the stroke position. A plurality of AC output signals each indicating an amplitude according to a predetermined periodic function characteristic (for example, two AC output signals each indicating an amplitude according to a sine and cosine function characteristic) can be easily generated and used according to the stroke position The phase angle range can be widened. By detecting the phase value of a predetermined periodic function (for example, sine and cosine function) that defines the amplitude value from the correlation between the amplitude values of the plurality of AC output signals, the position of the detection target can be positioned with high resolution even if the displacement of the detection target is minute. Detection is possible.
[Brief description of the drawings]
FIG. 1 is a perspective view schematically showing the appearance of a cylinder device to which a cylinder position detecting device according to the present invention is applied.
FIG. 2 is a developed surface of a piston rod surface showing an embodiment of the cylinder position detecting device.
FIG. 3 is a schematic front view of a configuration example of a coil sensor unit according to the embodiment viewed from an end opening of a cylinder body.
4A is an electric circuit diagram related to the coil section in the embodiment, FIG. 4B is a diagram showing an example of output of each coil, and FIG. 4C is a diagram for explaining a detection principle based on the coil output; .
FIG. 5 is a perspective view showing a modification of the coil arrangement in the embodiment of the present invention.
6A and 6B show another embodiment of the cylinder position detecting device according to the present invention, in which FIG. 6A is an exploded view of the surface of a piston rod, FIG. 6B is an electric circuit diagram related to a coil portion, and FIG. The figure which shows the example of an arithmetic synthesis of the output example of a coil, and a coil output.
7A and 7B show still another embodiment of the cylinder position detecting device according to the present invention, in which FIG. 7A is a developed view of the surface of a piston rod, and FIG. 7B is an electric circuit diagram related to a coil portion.
8A is a diagram illustrating an output example of each coil in the embodiment of FIG. 7, and FIG. 8B is a diagram illustrating an example of calculation / combination of coil outputs and a detection principle based on the coil output.
FIGS. 9A and 9B show another embodiment of the cylinder position detecting device according to the present invention, wherein FIG. 9A is a developed view of the piston rod surface, FIG. 9B is a diagram showing an example of each coil output, and FIG. The figure which shows the detection principle based on the example of an arithmetic synthesis of and coil output.
FIG. 10 is an electric circuit diagram related to the coil section in the embodiment of FIG. 9;
11A and 11B are diagrams showing a modification of the magnetic response part pattern in the embodiment of the present invention, where FIG. 11A is a schematic diagram of a piston rod and a coil, and FIG. 11B is a pattern that is substantially equivalent to the magnetic response part pattern. FIG.
[Explanation of symbols]
1 Cylinder device
2 Cylinder body
3 Piston
4 Piston rod
5 Magnetic response part
6 Coil sensor section
7 Cylinder head
8 AC power supply
9, 10, 11 terminals
12 Phase detection circuit
13,16 Average circuit
14 Constant voltage generator
15, 17, 19 Subtraction circuit
18 Adder circuit
20 Analog arithmetic circuit
21 Analog buffer circuit

Claims (4)

A magnetic response portion arranged in a predetermined pattern having a section where the area gradually increases or decreases along the stroke displacement direction on the surface of the piston rod;
Is fixed to the side of the cylinder body, and a coil provided so as to correspond to the magnetic responding unit, wherein said coil is excited with an AC signal of a predetermined single-phase, the displacement of the linear stroke position of the piston rod Accordingly, the corresponding area of the magnetic response portion with respect to the coil changes, the inductance of the coil changes with the change of the corresponding area, and the corresponding area of the magnetic response portion with respect to the coil gradually increases or decreases. The voltage across the coil gradually increases or decreases ,
Impedance means to which the AC signal is applied;
Taking out a voltage of the coil and the impedance means respectively, and analog operation circuit that generates a plurality of AC output signals respectively indicating different amplitude characteristics for the stroke position of the piston rod on the basis of these subtraction
A cylinder position detecting device comprising: The said analog arithmetic circuit produces | generates the alternating current output signal which shows the amplitude characteristic of a sine function with respect to the stroke position of the said piston rod, and the alternating current output signal which shows the amplitude characteristic of a cosine function. Cylinder position detector. A plurality of the magnetic response parts having a common pattern of gradually increasing or decreasing the area are arranged to be shifted by a predetermined angle in the circumferential direction of the piston rod, thereby providing each corresponding to each magnetic response part. The gradual increase or decrease pattern that the voltage across the coil is indicated with respect to the stroke displacement of the piston rod is common to each coil,
The circuit further includes a circuit for generating one output voltage that gradually increases or decreases in accordance with the linear stroke displacement of the piston rod by adding and synthesizing the output voltages of the respective coils. The cylinder position detecting device according to claim 1, wherein an output voltage is input to the analog arithmetic circuit. 2. The cylinder position detecting device according to claim 1, wherein the magnetic response unit has a shape in which an area gradually increases or decreases along a stroke displacement direction while drawing a spiral on a surface of the piston rod.

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