JP4628815B2 - Cylinder position measuring device - Google Patents

Description

  The present invention relates to a cylinder position measuring device that measures the position of a rod and piston that move linearly inside a cylinder tube.

  A permanent magnet is provided on the piston that moves directly with the rod inside the cylinder tube, such as a hydraulic cylinder, and a magnetic sensor is provided outside the cylinder tube to detect the magnetic force (line of magnetic force) that passes through the magnetic sensor. An apparatus for measuring the position of the (rod) is already known.

  In Patent Document 1 below, a rotary encoder that detects the amount of linear motion of the rod as a rotation amount is provided in the cylinder head, and a reset magnetic sensor is provided on the outer peripheral surface of the tube in the middle of the cylinder tube. The magnetic force generated by the magnet fixed to the piston that moves directly inside the tube is detected, and when the magnetic force reaches the peak value, the measurement position obtained from the detected value of the rotary encoder is reset to the origin position. The invention is described.

  Further, in Patent Document 2 below, a magnet is provided in a piston inside a cylinder tube of an air cylinder, and a magnetic sensor is provided outside the cylinder tube. The invention of measuring the movement position is described.

In Patent Document 3 below, a magnet is provided on the piston inside the cylinder tube of the cylinder, and two magnetic sensors are provided outside the cylinder tube and separated by a predetermined distance, so that the two magnetic sensors have a predetermined time difference. An invention is described in which it is determined that the piston is at a specific position when the signal level exceeds a predetermined detection signal level, and if it is not, it is determined that it is noise.
Japanese Utility Model Publication No. 5-75603 JP-A-7-103707 JP-A-6-249605

  As described above, in Patent Document 1, when the magnetic force detected by the reset magnetic sensor reaches a peak value, the measurement position obtained from the detection value of the rotary encoder is reset to the origin position. It is assumed that the peak value of magnetic force can be obtained accurately.

  However, when a magnetic sensor is provided outside the tube of the hydraulic cylinder, it is difficult to accurately determine the peak value of the magnetic force.

  That is, the tube of the hydraulic cylinder must be designed so that the internal high pressure oil is sealed so that it is not easily deformed or damaged by the high pressure oil. It is configured.

  For this reason, the wall of a cylinder tube functions as a magnetic shield which prevents the magnetic force line produced | generated by the internal permanent magnet from leaking outside. The signal level of the magnetic force detected by the magnetic sensor is extremely low compared to the base level, and the change in the signal level is extremely slow with respect to the amount of movement of the rod. For this reason, the signal level change near the peak value is gentle and wide. Further, the signal level is easily influenced by other magnetic field generation sources (noise), piston play, temperature, and the like, and for example, it may be difficult to distinguish between noise and peak value. Thus, since the signal level change near the peak value is small and easily affected by noise or the like, it is difficult to accurately obtain the peak value.

  The present invention has been made in view of such a situation, and is intended to accurately obtain the peak of a signal detected by a reset sensor so that the reset of the stroke position sensor to the origin position can be performed with high accuracy. This is a first problem to be solved.

  Further, when a magnetic sensor is provided outside the tube of the hydraulic cylinder, it is difficult to accurately determine the true stroke position (origin position) from the peak value of the magnetic force due to the influence of the moving speed of the internal piston.

  That is, since the tube of the hydraulic cylinder is made of a magnetic material, there is a certain time delay (transmission delay) until the magnetism generated inside the tube reaches the magnetic sensor outside the tube via the tube. On the other hand, the speed at which the piston inside the cylinder tube moves is not constant, and may move near the magnetic sensor at a slow speed or may move near the magnetic sensor at a high speed. For this reason, the stroke position obtained by the arithmetic processing when the magnetic force detected by the magnetic force sensor reaches the peak value is shifted from the true stroke position (origin position) depending on the piston moving speed.

  The present invention has been made in view of such a situation, and it is a second solution to make it possible to accurately measure the origin position regardless of the moving speed of the linear motion member such as the piston inside the cylinder tube. To do.

  In each of the above Patent Documents 1, 2, and 3, it is difficult to accurately determine the peak value of the magnetic force with the magnetic sensor, and when determining the stroke position from the detected value of the magnetic sensor, a piston or the like There is no indication of the problem that it is difficult to accurately determine the stroke position under the influence of the moving speed of the linear motion member, and there is no description that suggests technical problems corresponding to these problems.

The first invention is
In the cylinder position measuring device for measuring the position of the linear motion member (201, 202) that linearly moves inside the cylinder tube (250),
A stroke position sensor (100) for detecting a stroke position of the linear motion member;
A detection medium (350) provided on the linear motion member (201);
A reset sensor (external to the cylinder tube (250)) corresponding to the origin position of the linear motion members (201, 202) and detecting a physical quantity that changes according to the distance from the detection medium (350). 301, 302),
Determining the correspondence between the stroke position detected by the stroke position sensor (100) and the physical quantity detected by the reset sensor (301, 302);
Computational processing means (400) for obtaining a detected stroke position when the linear motion member reaches the origin position based on the correspondence relationship, and resetting the detected stroke position to the origin position. To do.

The second invention is the first invention,
The arithmetic processing means (400)
Both correspondences when the linear motion members (201, 202) make a stroke at least twice are obtained, and a detected stroke position when the linear motion member reaches the origin position is obtained on the basis of the deviation amount of both correspondences. The detection stroke position is reset to the origin position.

The third invention is
In the cylinder position measuring device for measuring the position of the linear motion member (201, 202) that linearly moves inside the cylinder tube (250),
A detection medium (350) provided on the linear motion member (201);
Sensors (301, 302) which are provided at known specific positions outside the cylinder tube (250) and detect physical quantities generated by the detection medium (350) and changing according to the position of the linear motion member (201). When,
Computation processing means (400) for correcting a physical quantity detected by the sensors (301, 302) based on a moving speed when the linear motion members (201, 202) pass through the specific position. It is characterized by.

4th invention is 1st invention or 2nd invention,
The arithmetic processing means (400)
The detection stroke position when the linear motion member reaches the origin position is corrected based on the moving speed when the linear motion member (201, 202) passes through the origin position.

The fifth invention is the first invention, the second invention or the fourth invention,
The reset sensor (301, 302)
Two reset sensors (301, 302) provided on the outside of the cylinder tube (250) and spaced apart from each other by a predetermined distance along the linear motion direction of the linear motion members (201, 202). The reset sensors (301, 302) output detection signals having different polarities,
The arithmetic processing means (400)
Calculation processing is performed based on a signal obtained by synthesizing detection signals of the two reset sensors (301, 302).

The sixth invention
In the cylinder position measuring device for measuring the position of the linear motion member (201, 202) that linearly moves inside the cylinder tube (250),
A detection medium (350) provided on the linear motion member (201);
Sensors (301, 302) which are provided at known specific positions outside the cylinder tube (250) and detect magnetic force generated by the detection medium (350) and changing according to the position of the linear motion member (201). When,
Computational processing means (400) for compensating for a delay when the magnetic force passes through the cylinder tube (250) and correcting a position detected by the sensors (301, 302). .

  FIG. 9A is a comparative example of the first invention, and shows the relationship between the time t and the detection signal Vn detected by the magnetic force sensor 301.

  The change in the signal detected by the magnetic sensor 301 is gradual and easily affected by noise or the like. For this reason, as shown in FIG. 9A, the point in time when noise is generated may be mistaken as the time when the piston 201 passes the origin position I0. Further, there is no guarantee that the piston 201 moves at a constant speed near the origin position I0. Therefore, as shown in FIG. 9B, the shape near the top of the curve varies under the influence of the moving speed of the piston 201. For this reason, it is difficult to accurately determine the true apex (peak) of the curve from noise or the like from the correspondence between time t and magnetic force (voltage value) Vn shown in FIG.

  Therefore, in the first invention, as shown in FIG. 8A, the measurement stroke position In of the rod 202 obtained from the rotation amount detected by the rotation sensor 100, the detection signal (magnetic force; voltage value) Vn of the magnetic sensor 301, and 8 is obtained, and as shown in FIG. 8B, the measurement stroke position Ip (peak position) when the origin position I0 is reached is obtained based on the correspondence relation 500, and this measurement stroke position (peak Position) Ip is reset to the origin position I0.

  The correspondence relationship 500 between the stroke position In and the magnetic sensor detection signal Vn is a stable shape without being affected by the moving speed of the piston 201. Therefore, the measurement stroke position (peak position) Ip can be accurately obtained from the correspondence relationship 500, and the origin position I0 can be reset with extremely high accuracy.

  According to the second invention, as shown in FIGS. 11A and 11B, the piston 201 (rod 202) is stroked at least twice, and the corresponding relationships 600 (model) and 500 ′ are obtained. Then, as shown in FIG. 11 (c), the measured stroke position (peak position) Ip when the piston 201 reaches the origin position I0 is obtained based on the deviations Sln and Srn of the correspondence relations 600 and 500 '. The measurement stroke position (peak position) Ip is reset to the origin position I0.

  In the fourth aspect of the invention, the correspondence between the origin position passing speed V and the positional deviation amount (peak position correction amount) ΔI from the origin position I0 is acquired, and the peak position obtained from the detection result of the rotation sensor 100 is obtained according to this correspondence. Ip is corrected.

  That is, the origin position passing speed V is obtained by measuring the distance between the peak positions Ipa and Ipb of the magnetic force sensors 301 and 302 and the time that the piston 201 has passed between the peak positions Ipa and Ipb.

  The peak position correction amount ΔI can be obtained by calculating the deviation between the true origin position I0 and the peak position Ip that is the average value of the peak positions Ipa and Ipb.

  Data of the origin position passing speed V and the peak position correction amount ΔI is acquired by changing the moving speed of the piston 201 and repeatedly performing the motion of passing the vicinity of the origin position. The acquired data is calculated in the form of a data table as data (Vj, ΔIj) of correspondence between the origin position passing speed V and the peak position correction amount ΔI for each magnitude j of the moving speed of the piston 201. It is stored in the storage device of the processing unit 400.

  Then, according to the data table (Vj, ΔIj), the detected stroke position (peak position Ip) of the stroke position sensor in the first invention or the second invention is corrected according to the moving speed V.

  In the fourth invention described above, the detected stroke position (peak position) of the stroke position sensor (rotation sensor 100) is corrected according to the moving speed, and the corrected stroke position (corrected peak position) is reset. However, the present invention can also be applied to a configuration in which the stroke position sensor (rotation sensor 100) is not provided and an implementation that does not assume reset processing of the stroke position sensor (rotation sensor 100) to the origin position.

  The third invention is applied, for example, to the case where the piston 201 passes a specific position from the detection signal of the magnetic force sensor 301 (302) without providing the stroke position sensor (rotation sensor 100). Similarly to the fourth invention, the measurement position of the magnetic sensor is corrected according to the moving speed V.

  According to the third and fourth inventions, the origin position or the specific position can be accurately measured regardless of the moving speed of the piston 201 inside the cylinder tube 250.

  In the fifth invention, as shown in FIG. 15A, detection signals 301a and 302a having different polarities are output from the two reset sensors 301 and 302, and the arithmetic processing unit 400 shows the signals shown in FIG. 15B. As described above, the detection signals 301a and 302a of the two reset sensors 301 and 302 are combined, and arithmetic processing (FIGS. 17A to 17F) is performed based on the combined signal 301c.

  According to the fifth invention, as shown in FIGS. 17A to 17F, the distance J between the amplitude values and the distance K between the peak positions are not affected by the fluctuation of the base level and have characteristics that do not vary. Since the reset is performed based on the synthesized signal 301c, the discrimination from the noise is accurately performed, and the comparison with the model 600 can be performed accurately. As a result, the process of resetting the calculated origin position Ip obtained from the detection result of the rotation sensor 100 to the true origin position I0 can be performed with extremely high accuracy.

  The sixth invention is a claim in which the third invention is described in a superordinate concept, the delay when the magnetic force passes through the cylinder tube 250 is compensated, and the positions detected by the reset sensors 301 and 302 are corrected. .

  Embodiments of a cylinder position measuring apparatus according to the present invention will be described below with reference to the drawings.

  FIG. 1A shows the positional relationship of the cylinder 200, the rotation sensor 100 as a stroke position sensor, and the magnetic force sensor 300 as a reset sensor in a longitudinal sectional view of the cylinder 200. FIG.

  As shown in FIG. 1A, a piston 201 is slidably provided on a cylinder tube 250 that is a wall of the cylinder 200. A rod 202 is attached to the piston 201. The rod 202 is slidably provided on the cylinder head 203. A chamber defined by the cylinder head 203, the piston 201, and the cylinder inner wall constitutes a cylinder head side oil chamber 204H. An oil chamber opposite to the cylinder head side oil chamber 204H via the piston 201 constitutes a cylinder bottom side oil chamber 204B.

  The cylinder head 203 is provided with a rod seal 205a and a dust seal 205b that seal a gap with the rod 202 and prevent contamination such as dust from entering the cylinder head side oil chamber 204H.

  The cylinder tube 250 is formed with hydraulic ports 206H and 206B. Pressure oil is supplied to the cylinder head side oil chamber 204H via the hydraulic port 206H, or pressure oil is discharged from the oil chamber 204H via the hydraulic port 206H. Pressure oil is supplied to the cylinder bottom side oil chamber 204B via the hydraulic port 206B, or pressure oil is discharged from the oil chamber 204B via the hydraulic port 206B.

  When pressure oil is supplied to the cylinder head side oil chamber 204H and pressure oil is discharged from the cylinder bottom side oil chamber 204B, the rod 202 is degenerated, or pressure oil is discharged from the cylinder head side oil chamber 204H, By supplying pressure oil to the cylinder bottom side oil chamber 204B, the rod 202 extends. That is, the rod 202 moves linearly in the left-right direction in the figure.

  A case 207 that covers the rotation sensor 100 and accommodates it inside is formed outside the cylinder head side oil chamber 204H and in close contact with the cylinder head 203. The case 207 is fixed to the cylinder head 203 by being fastened to the cylinder head 203 with a bolt or the like. That is, the case 207 (the rotation sensor 100) can be easily attached to or removed from the cylinder tube 250.

  A rotation roller 110 (to be described later) constituting the rotation sensor 100 has a surface in contact with the surface of the rod 202 and is rotatably provided in accordance with the linear movement of the rod 202. That is, the rotating roller 110 converts the linear motion of the rod 202 into rotational motion.

  The rotation roller 110 is arranged such that the rotation center shaft 110c is orthogonal to the linear movement direction of the rod 202 (the rear direction of the paper, the viewer direction). The case 207 is provided with a dust seal 208 that seals a gap with the rod 202 and prevents contamination such as dust from entering between the rotating roller 110 and the rod 202. As a result, it is possible to avoid a situation in which dust or the like enters between the rotating roller 110 and the rod 202 and the rotating roller 110 malfunctions. That is, the rotation sensor 100 has a dustproof structure by the dust seal 208 provided on the case 207 and the dust seal 205 b provided on the cylinder head 203.

  The rotation sensor 100 includes at least the above-described rotation roller 110 and a rotation sensor unit (not shown) that detects the rotation amount of the rotation roller 110. A signal indicating the rotation amount of the rotating roller 110 detected by the rotation sensor unit is sent to the arithmetic processing unit 400 and converted into the position (stroke) of the rod 202 of the cylinder 200.

  Slip (slip) is inevitably generated between the rotation roller 110 and the rod 202 of the rotation sensor 100, and the measurement position of the rod 202 obtained from the detection result of the rotation sensor 100 due to this slip and the actual state of the rod 202. An error (cumulative error due to slipping) occurs between the position and the position. Therefore, in order to reset the measurement position obtained from the detection result of the rotation sensor 100 to the origin position (reference position), a magnetic force sensor 300 as a reset sensor is provided outside the cylinder tube 250.

  That is, the piston 201 is provided with a magnet 350 that generates lines of magnetic force. The magnet 350 is provided on the piston 201 so that the N pole and the S pole are arranged in the vertical direction in the drawing perpendicular to the linear movement direction of the piston 201 and the rod 202. The magnet 350 may be provided on the piston 201 so that the N pole and the S pole are arranged along a direction parallel to the linear movement direction of the piston 201 and the rod 202.

  The magnetic force sensor 300 includes two magnetic force sensors 301 and 302 that are spaced apart from each other by a predetermined distance along the linear movement direction of the piston 201. The magnetic sensors 301 and 302 transmit the magnetic lines generated by the magnet 350, detect the magnetic force (magnetic flux density), and output an electric signal (voltage) corresponding to the magnetic force (magnetic flux density). The magnetic sensors 301 and 302 are provided at known origin positions. Based on the detection results of the magnetic sensors 301 and 302, the measurement position obtained from the detection result of the rotation sensor 100 is reset to the origin position (reference position).

  Further, the absolute movement distance of the piston 201 and the rod 202 can be measured based on the detection positions of the two magnetic sensors 301 and 302. For example, when the rotation roller 110 of the rotation sensor 100 is consumed due to aging, the movement distance of the rod 202 obtained from the detected rotation amount of the rotation sensor 100 is smaller than the actual movement distance of the rod 202, but the piston 201 is 2 The ratio L / L ′ of the moving distance L ′ obtained from the rotation amount detected by the rotation sensor 100 when moving between the magnetic sensors 301 and 302 and the actual distance L between the two magnetic sensors 301 and 302 Based on the above, the movement distance obtained from the rotation amount detected by the rotation sensor 100 can be corrected.

  As the magnetic sensors 301 and 302, for example, Hall ICs are used.

  The magnetic sensors 301 and 302 are attached to the eaves 310. The eaves 310 are attached to the band 320. The band 320 is fixed to the outer periphery of the cylinder tube 250. The band 320 is made of a magnetic material. As a material of the band 320, a magnetic material that is usually easily available, such as a general structural steel material, can be used.

  FIG. 1B shows a cross-sectional view taken along the line AA of FIG.

  The band 320 is fixed in pressure contact with the outer periphery of the cylinder tube 250. The band 320 includes a band member 320A having a semicircular cross section corresponding to the outer diameter of the cylinder tube 250, and a band member 320B having a semicircular cross section, and the band member 320A and the band member 320B are The cylinder tube 250 is pressed against the outer periphery by being fastened. The eaves 310 are attached to one band member 320A. For this reason, the magnetic force sensors 301 and 302 can be fixed to the outer periphery of the cylinder tube 250 without forming a screw hole in the cylinder tube 250 or performing processing such as welding the outer periphery of the cylinder tube 250. Moreover, since it is not necessary to process and process the cylinder tube 250, the thickness of the cylinder tube 250 can be maintained at a minimum thickness. That is, if the cylinder tube 250 is processed and processed, in order to maintain the strength, the tube itself must be thickened, but this is not necessary.

  In addition, the fixing position of the band 320 to the cylinder tube 250 can be easily and easily changed, and the magnetic force sensors 301 and 302 can be placed at arbitrary positions in the longitudinal direction of the cylinder tube 250 (the linear movement direction of the piston 201 and the rod 202). Can be easily and easily installed.

(First embodiment)
FIG. 2 shows details of the configuration of the magnetic sensors 301 and 302, the eaves 310, and the band 320.

  FIG. 2A is an enlarged longitudinal sectional view of the cylinder tube 250 corresponding to FIG. FIG. 2B shows an enlarged cross-sectional view of the cylinder tube 250 corresponding to FIG. 1B (view A in FIG. 2A). FIG.2 (c) is the figure which looked at Fig.2 (a) from Z view direction (direction which goes to the upper direction from the downward direction in the figure).

  FIG. 2D is a diagram for defining each surface of the magnetic sensors 301 and 302.

The magnetic sensor 300 (301, 302) is a rectangular parallelepiped member, and has a bottom surface 300B, an upper surface 300T, a front surface 300F, left and right side surfaces 300L, 300R, and a rear surface 300G.
As shown in FIG. 2, the magnet 350 is fixed to the surface of the piston 201 facing the cylinder head side oil chamber 204 </ b> H by a holder ring 351.

  The magnet 350 is fixed to the piston 201 by fastening the holder ring 351 and the magnet 350 together with the piston 201.

  The eaves 310 are made of a magnetic material, and are arranged so as to cover the upper surface 300T and the rear surface 300G of the magnetic force sensors 301 and 302. The eaves 310 can be made of a magnetic material that is usually readily available, such as carbon steel or general structural steel.

  The arrangement of the eaves 310 and the magnetic sensors 301 and 302 is symmetrical in the left-right direction in FIG. 2A and has the same positional relationship, and therefore, one magnetic sensor 301 will be described as a representative.

  The band fixing surface 310A of the eaves 310 is fixed to the band member 320A. The tube contact surface 310 </ b> B of the eaves 310 is in close contact with the outer peripheral surface of the cylinder tube 250.

  The magnetic sensor 301 is integrally formed with the molding material 303 so as to be surrounded by the molding material 303. In the molding material 303 including the magnetic sensor 301, the upper surface 300T side and the rear surface 300G side of the magnetic sensor 301 are fixed to the upper surface fixing surface 310T and the rear surface fixing surface 310R of the eaves 310, respectively. Further, the bottom surface 300 </ b> B side of the magnetic sensor 301 is in close contact with the outer peripheral surface of the cylinder tube 250.

  A brass plate 311 is provided on the front surface 300F and the left and right side surfaces 300L and 300R of the magnetic sensor 301.

  That is, since the bottom surface 300B of the magnetic force sensors 301 and 302 is disposed on the outer peripheral surface of the cylinder tube 250 and the magnetic force sensors 301 and 302 are covered with the eaves 310, the upper surface 300T side and the rear surface 300G side of the magnetic force sensor 301 are related. The magnetic material (the eaves 310) is arranged, but the magnetic material is not arranged (opened from the magnetic material) on the front surface 300F side and the left and right side surfaces 300L, 300R side of the magnetic force sensor 301. .

  Although one magnetic force sensor 301 has been described, the other magnetic force sensor 302 is similarly attached to the eaves 310.

  The eaves 310 incorporates a terminal block 313 having terminals 312. In addition, the eaves 310 are formed with a hole through which a harness (not shown) is inserted, and an insertion hole 314 communicating with the terminal 312. The magnetic sensors 301 and 302 and the terminal 312 are connected by an electric signal line (not shown). A harness is connected to the terminal 312 from the outside of the eaves 310 through an insertion hole 314. This harness is connected to the arithmetic processing unit 400. In the arithmetic processing unit 400, the detection signals of the magnetic sensors 301 and 302 and the detection signal of the rotation sensor 100 are subjected to arithmetic processing, and the linear motion position of the rod 202 (piston 201) is measured. That is, the position of the rod 202 is measured from the detection result of the rotation sensor 100, and the measurement position of the rod 202 obtained from the detection result of the rotation sensor 100 is based on the detection result of the magnetic field sensors 301 and 302. Position).

  FIG. 3A is a diagram corresponding to FIG. 2A and conceptually shows a path of magnetic lines of force starting from the magnetic pole N of the magnet 350 and ending with the magnetic pole S. FIG.

  FIG. 3B is a comparative example and conceptually shows a path of magnetic lines of force when the eaves 310 of the first embodiment are not provided.

  As can be seen by comparing FIG. 3 (a) and FIG. 3 (b), the presence of the eaves 310 causes the magnetic lines of force to start from the north pole of the magnet 350, the cylinder tube 250, the magnetic sensor 301, and the eaves 310. A path that passes through and returns to the south pole of the magnet 350 is generated, but when the eaves 310 are not provided, the magnetic force generated by the magnet 350 is blocked by the cylinder tube 250 and reaches the magnetic force sensor 301 outside the tube 250. Will not reach or only slightly. In FIG. 3, magnetic lines of force are shown for one magnetic sensor 301, but the same applies to the other magnetic line sensor 302.

  Further, since the band 320 is made of a magnetic material, it becomes a path of magnetic lines of force in the outer peripheral direction of the cylinder tube 250, and the magnetic lines of force pass through the band 320 and are provided at one point in the outer peripheral direction of the tube 250. The sensors 301 and 302 are collected in a concentrated manner. Thus, due to the synergistic effect of the eaves 310 and the band 320, the magnetic force generated by the magnet 350 is concentrated on the magnetic sensors 301 and 302.

  As described above, according to the first embodiment, the eaves 310 that covers the magnetic force sensors 301 and 302 are provided, and the lines of magnetic force starting from the magnet 350 pass through the cylinder tube 250, the magnetic force sensors 301 and 302, and the eaves 310, and Since the path back to 350 is formed, even if the cylinder tube 250 is made of a thick magnetic material to ensure strength, the magnetic force lines 301 and 302 provided outside the tube 250 are used to generate magnetic lines of force. It becomes possible to detect reliably. As a result, the position measurement accuracy of the rod 202 based on the detection results of the magnetic sensors 301 and 302 is greatly improved.

  Next, a modification of the first embodiment will be described.

(Second embodiment)
In the first embodiment described above, the magnetic force sensors 301 and 302 are fixed to the outer periphery of the cylinder tube 250 by the band 320, but the fixing method of the magnetic force sensors 301 and 302 is arbitrary. In the first embodiment, two magnetic force sensors 300 are provided. However, the magnetic force sensor 300 may include only one magnetic force sensor 301.

  FIG. 4 is a perspective view in which the eaves 310 having one magnetic sensor 301 mounted on the outer periphery of the cylinder tube 250 is fixed without a band.

  As shown in FIG. 4, similarly to the first embodiment, the magnetic sensor 301 has an upper surface 300T and a rear surface 300G fixed to the upper surface fixing surface 310T and the rear surface fixing surface 310R of the eaves 310, respectively. The bottom surface 300 </ b> B of the magnetic sensor 301 is disposed on the outer peripheral surface side of the cylinder tube 250.

  That is, since the bottom surface 300B of the magnetic sensor 301 is disposed on the outer peripheral surface of the cylinder tube 250 and the upper surface 300T and the rear surface 300G of the magnetic sensor 301 are covered with the eaves 310, the upper surface 300T side and the rear surface 300G side of the magnetic sensor 301 Has a structure in which the magnetic material (eave 310) is arranged, but the magnetic material is not arranged (opened from the magnetic material) on the front surface 300F side and the left and right side surfaces 300L and 300R side of the magnetic sensor 301. .

  FIG. 5 shows a mounting example in which the eaves 310 are fixed to the outer periphery of the cylinder tube 250 by a mounting member other than the band 320.

  That is, depending on the type of cylinder, there is a structure in which a plurality of tie rods 260 are bridged along the longitudinal direction of the outer periphery of the cylinder tube 250.

  Therefore, an insertion hole 260A through which a plurality (two) of tie rods 260, 260 are inserted is formed in the eaves 310, and the eaves 310 are inserted into the outer periphery of the cylinder tube 250 by inserting the tie rods 260 into the insertion holes 260A. It may be fixed.

(Third embodiment)
In the first and second embodiments described above, the eaves 310 are shaped and sized to cover the entire top surface 300T of the magnetic sensor 301, but it is not necessary to cover the entire top surface 300T.

  In the first and second embodiments described above, the eaves 310 are shaped and sized to cover the entire rear surface 300G of the magnetic force sensor 301. However, it is not always necessary to cover the entire rear surface 300G.

  FIG. 6 illustrates a first example of the eaves 310 formed in a shape and size that covers a part of the magnetic sensor 301.

  6A is a longitudinal sectional view of the cylinder tube 250 corresponding to FIG. 2A, and FIG. 6B is a view of FIG. 6A as viewed from above.

  As shown in FIGS. 6A and 6B, the eaves 310 are formed in a shape and size that covers the entire rear surface 300G of the magnetic sensor 301 but covers a part of the upper surface 300T.

  6C is a longitudinal sectional view of the cylinder tube 250 corresponding to FIG. 2A, and FIG. 6D is a view of FIG. 6C as viewed from above.

  As shown in FIGS. 6C and 6D, the eaves 310 are formed in a shape and size that partially covers the upper surface 300T and the rear surface 300G of the magnetic sensor 301.

  In any case, the length of the eaves 310 does not matter how much the magnetic sensor 301 (302) is covered. As conceptually shown in FIG. 3A, the magnetic field lines starting from the magnet 350 are magnetic field sensors. It may be formed in a shape and size so as to form a path through 301 and returning to the magnet 350.

(Fourth embodiment)
In the first to third embodiments described above, the magnetic force sensor 301 (302) is fixed to the outer periphery of the cylinder tube 250 via the eaves 310, but the magnetic force sensor is attached to the band 320 without using the eaves 310. You may fix to the outer periphery of the cylinder tube 250 by mounting | wearing 301 (302) directly.

  7A shows a longitudinal section of the cylinder tube 250 corresponding to FIG. 2A, FIG. 7B shows an AA section of FIG. 7A, and FIG. 7C shows FIG. It is the figure which looked at (a) from the upper surface.

  As shown in FIG. 7, the magnetic force sensor 301 is integrally formed with the molding material 303 so as to be surrounded by the molding material 303. The molding material 303 including the magnetic sensor 301 is covered with a cover 304, and the cover 304 is connected to the band 320. The cover 304 is made of a nonmagnetic material such as brass.

  The magnetic sensor 301 is attached to the band 320 such that the rear surface 300G is disposed on the side surface 320S of the band 320.

  For this reason, no magnetic material is disposed on the front surface 300F side, the upper surface 300T side, and the left and right side surfaces 300L and 300R of the magnetic sensor 301 (the magnetic material is released from the magnetic material). Has a structure in which a magnetic material (band 320) is arranged.

  Even in such a configuration, the band 320 becomes a path of magnetic lines of force in the outer peripheral direction of the cylinder tube 250, and the magnetic lines of force pass through the band 320 and are provided at one point in the outer peripheral direction of the tube 250. Since the light is concentrated on the sensor 301, the magnetic force generated by the magnet 350 inside the tube 250 can be reliably detected by the magnetic force sensor 301.

(5th Example)
Next, arithmetic processing performed in the arithmetic processing unit 400 will be described.

  FIGS. 8A and 8B are diagrams for explaining the fifth embodiment and for explaining the processing performed by the arithmetic processing unit 400. FIG. One of the magnetic sensors 301 and 302 will be described as a representative. First, a comparative example of this example will be described. FIG. 9 is a diagram for explaining a comparative example of the fifth embodiment.

  FIG. 9A shows the relationship between the time t and the detection signal Vn detected by the magnetic force sensor 301. The magnetic force sensor 301 detects a voltage value Vn corresponding to the magnetic force. Note that n is the data sampling order (n = 1, 2,...), And data sampling is performed at regular intervals.

  The magnetic sensor 301 detects a signal whose detection level (magnetic force; voltage value) Vn increases as the distance from the magnet 350 decreases. Since the magnetic force sensor 301 is provided at the origin position I0, when the magnet 350 reaches the origin position I0, the distance between the magnet 350 and the magnetic force sensor 301 is minimized, and the magnetic force sensor 301 causes the maximum level signal Vm. (Magnetic force; voltage value) should be detected.

However, actually, when the signal detected by the magnetic sensor 301 reaches the maximum level Vm, the piston 201 is not necessarily located at the origin position I0. As described above, the change in the signal detected by the magnetic force sensor 301 is gradual and easily affected by noise or the like. For this reason, as shown in FIG. 9A, the point in time when noise is generated may be mistaken as the time when the piston 201 passes the origin position I0. Further, there is no guarantee that the piston 201 moves at a constant speed near the origin position I0. Therefore, as shown in FIG. 9B, the shape near the top of the curve varies under the influence of the moving speed of the piston 201. For this reason, it is difficult to accurately determine the true apex (peak) of the curve from noise or the like from the correspondence between time t and magnetic force (voltage value) Vn shown in FIG.

  Therefore, in this embodiment, as shown in FIG. 8A, the measurement stroke position In of the piston 201 obtained from the rotation amount detected by the rotation sensor 100, the detection signal (magnetic force; voltage value) Vn of the magnetic sensor 301, and 8 is obtained, and as shown in FIG. 8B, based on this correspondence 500, a measurement stroke position Ip (hereinafter referred to as a peak position) when the piston 201 reaches the origin position I0 is obtained. The measurement stroke position (peak position) Ip is reset to the origin position I0.

  The correspondence relationship 500 between the stroke position In and the magnetic sensor detection signal Vn has a stable shape without being influenced by the moving speed of the piston 201 (see FIGS. 9B and 8B). Therefore, the measurement stroke position Ip can be accurately obtained from the correspondence relationship 500, and the origin position I0 can be reset with extremely high accuracy.

  Specifically, first, the rotation amount sequentially obtained from the detection value of the rotation sensor 100 is sequentially converted into the stroke position In (n = 1, 2,...) Of the piston 201 (rod 202).

  Each time the stroke position In of the piston 201 is measured, the detection signal Vn of the reset sensor 301 at that time is read, and the data In and Vn are associated with each other.

  Next, as shown in FIG. 8A, the correspondence relationship 500 between the measurement stroke position In obtained from the detection signal of the rotation sensor 100 and the detection signal (magnetic force; voltage value) Vn of the magnetic sensor 301 is represented by the horizontal axis. Is the stroke position In, and the vertical axis is the magnetic force (voltage value) Vn.

  Next, as shown in FIG. 8B, the model 600 is applied to the correspondence relationship 500, and the vertex 500P (stroke position Ip, magnetic force Vp) of the correspondence relationship 500 is obtained.

  Next, the measurement stroke position Ip when the piston 201 reaches the origin position, that is, the peak position Ip is read from the coordinate position (stroke position Ip, magnetic force Vp) of the vertex 500P.

  Next, the read measurement stroke position Ip is reset to the origin position I0 which is the true stroke position.

  The model 600 may be prepared in advance as a correspondence relationship between the ideal stroke position I and the magnetic force (voltage value) V, or may be created from data obtained after one stroke.

  FIG. 10 shows an algorithm of the present embodiment in which the model 600 is obtained from data obtained at the previous one stroke and reset is performed.

  For example, the piston 201 passes the origin position from the left position in FIG. 1A to reach the right position as the first stroke, and after the piston 201 reaches the right position, passes the origin position to the left Data is acquired with the second stroke as the second stroke.

  FIG. 11A shows a correspondence relationship (model) 600 obtained by the first stroke by a broken line and a correspondence relationship 500 obtained by the second stroke by a solid line.

  If a correspondence relationship 500 between the stroke position In and the voltage value Vn (n = 1, 2,...) Is obtained by the second stroke, it corresponds to the maximum voltage value (the maximum magnetic force value) from the data of the correspondence relationship 500. Determine the stroke position Im. This stroke position Im is set as a temporary peak position (step 1001).

  Next, as shown in FIG. 11 (b), the correspondence relationship 500 between the stroke position In and the voltage value Vn is shifted so that the stroke position Im coincides with the origin position I 0 of the model 600.

  The relationship between the shifted stroke position In ′ of the correspondence relationship 500 ′ and the stroke position In of the correspondence relationship 500 ′ before the shift is expressed by the following equation (1).

  In '= In-Im + I0 (1) (Step 1002).

  Next, as shown in FIG. 11C, stroke differences Sln and Srn between the correspondence relationship 500 ′ and the model 600 are obtained for each voltage value Vn ′ (step 1003).

  Of the obtained stroke differences Sln and Srn, the stroke difference having the smaller absolute distance is defined as a positional deviation Sn (= Σmin (Sln, Srn)) between the model 600 and the corresponding relationship 500 ′. As shown in the following equation (2), the positional deviation Sn is obtained for all voltage values Vn ′ (n = 1, 2,...), And the average positional deviation S is calculated.

S = Σmin (Sln, Srn) / n (2) (Step 1004)
Next, using the average position deviation S and the temporary peak position Im, the measured stroke position Ip when the piston 201 reaches the origin position Ip, that is, the peak position of the correspondence 500, as shown in the following equation (3). Ip is calculated.

Ip = Im-S (3) (Step 1005)
Next, the peak position Ip (calculated origin position obtained from the detection result of the rotation sensor 100) obtained in this way is reset to the true origin position I0 (step 1006).

  In the present embodiment, the model 600 is obtained from data obtained when the piston 201 is made to make one stroke near the origin position. However, the model 600 is obtained from data obtained by making two strokes around the origin position. Is also possible.

(Sixth embodiment)
In the fifth embodiment described above, the peak position Ip of the correspondence relationship 500 is obtained using the model 600 of the previous one-stroke data. However, a continuous curve 510 approximating the correspondence relationship 500 is obtained, and this continuous From the curve 510, the peak position Ip of the correspondence relationship 500 may be obtained.

  That is, as shown in FIG. 12A, a continuous curve 510 is obtained by the least square method using the data of each point (In, Vn) of the correspondence relationship 500, and the voltage value is maximum on the continuous curve 510. May be determined as the peak position Ip of the correspondence 500. Further, as shown in FIG. 12B, for example, a quartic function (V = f (I)) is obtained as a correlation function approximated to the correspondence relationship 500, and the voltage value is obtained on a continuous curve 520 of this quartic function. The maximum stroke position may be determined as the peak position Ip of the correspondence relationship 500.

(Seventh embodiment)
In Patent Document 3, it is determined that the piston is in a specific position when the two magnetic sensors become equal to or higher than a predetermined detection signal level (threshold value) with a predetermined time difference, otherwise noise is detected. Judging that there is. As shown in FIG. 13A, the present invention is based on the premise that the time width from the time when one magnetic sensor is turned on to the time when the other magnetic sensor is turned on is constant.

  However, the base level of the magnetic force detected by the magnetic sensor is not constant and can vary. For example, there is a gap play between the cylinder tube 250 and the piston 201, whereby the distance between the magnet 350 and the magnetic force sensor fluctuates, and the base levels are shown in FIGS. 13B, 13C, and 13D. As shown in the figure, it becomes higher or lower. In addition, the base level may change under the influence of the installation environment such as extraneous magnetism. For this reason, when it is determined whether or not the magnetic sensor is on with a certain threshold value, the time width from when one magnetic sensor is turned on until the other magnet is turned on changes. (FIGS. 13B and 13C) or may not turn ON at all (FIG. 13D).

  Further, even if the waveform detected by the magnetic sensor shown in FIG. 14A is determined to be the noise shown in FIG. 14B, it is difficult to determine it as noise.

  Further, in order to compare with the model 600, it is necessary to determine the base level of the detection waveform of the magnetic force sensor, and to increase, reduce, or shift the amplitude so as to coincide with the model 600. FIG. As indicated by the arrows in (c), the level of each point at the base of the detected waveform is different, so it is difficult to determine where the true base level is. This makes it difficult to compare with the model 600.

  Therefore, in this embodiment, two magnetic force sensors 301 and 302 are provided outside the cylinder tube 250 and separated by a predetermined distance along the linear motion direction of the piston 201 and the rod 202. FIG. As shown, detection signals 301a and 302a having different polarities are output from these two magnetic sensors 301 and 302, and the voltage levels of both detection signals 301a and 302a are averaged by an averaging circuit using a fixed resistor. Thus, arithmetic processing such as obtaining a stroke position is performed based on the averaged voltage level signal 301c.

  FIG. 15A shows signal waveforms 301a and 302a detected by the magnetic sensors 301 and 302, respectively. Both magnetic force sensors 301 and 302 are arranged so that the polarity of one magnetic sensor 302 is opposite to that of the other magnetic force sensor 301.

  FIG. 15B shows a composite signal 301c obtained by averaging the output signals of the magnetic force sensors 301 and 302 by the averaging circuit. The combined signal 301c is acquired by performing an arithmetic process of adding the output signals 301a and 302a of the magnetic force sensors 301 and 302 and averaging them.

  As shown in FIGS. 14D and 14E, the composite signal 301c obtained in this way is the minimum amplitude value (one) of the magnetic sensor 301 (even if the base level is reduced or increased). The change from the negative polarity) to the maximum amplitude value (positive polarity) of the other magnetic force sensor 302 (hereinafter, distance J between amplitude values) is very small (the total value of the amplitudes of both magnetic force sensors 301 and 302). Further, the distance from the peak position of one magnetic sensor 301 to the peak position of the other magnetic sensor 302 (hereinafter referred to as the peak position distance K) is between the known magnetic sensors 301 and 302 regardless of changes in the base level. It becomes a constant value according to the distance.

  As described above, the composite signal 301c has a characteristic that the distance J between the amplitude values and the distance K between the peak positions do not change without being affected by the change in the base level.

  FIG. 16 shows an algorithm of arithmetic processing performed based on the synthesized signal 301c.

  First, a correspondence relationship 500 between the stroke position In and the voltage value Vn (n = 1, 2,...) Is acquired based on the detection signal of the rotation sensor 100 and the composite signal 301c as shown in FIG. The data (In, Vn) of the correspondence relationship 500 between the stroke position In and the voltage value Vn is stored (step 1101).

  Next, based on the data (In, Vn) of the correspondence relationship 500, the distance J between the amplitude values and the distance K between the peak positions are obtained by calculation. The calculated distance J between amplitude values is within a predetermined width J1 (lower limit value) to J2 (upper limit value), and the calculated distance K between peak positions is a predetermined width K1 (lower limit value). ) To K2 (upper limit value) is judged (step 1102).

  If the determination in step 1102 is YES, the signal waveform indicated by the correspondence relationship 500 is not noise but is output from the sensor when the magnet 350 passes the origin position between the magnetic force sensors 301 and 302. Assuming that the signal waveform is a signal waveform, the process proceeds to the next step 1103. Otherwise (determination NO in step 1102), it is determined to be noise (step 1104).

  In step 1103, the correspondence relationship 500 is enlarged or reduced so as to coincide with the distance J0 between the amplitude values of the model 600. For example, as shown in FIGS. 17B, 17C, and 17D, when the distance J between amplitude values of the correspondence relationship 500 is smaller than the distance J0 between amplitude values of the model 600, the amplitude of the correspondence relationship 500 The distance J between the amplitude values in the correspondence relationship 500 is enlarged so that the distance J between the values coincides with the distance J0 between the amplitude values of the model 600 to obtain a correspondence relationship 500 ′. The enlargement / reduction processing of the correspondence relationship 500 is performed according to the arithmetic expression shown in the following equation (4). Note that the voltage value data of the correspondence relationship 500 ′ after conversion is Vn ′.

Vn ′ = (Vn−minimum amplitude value of correspondence 500) (maximum amplitude value of model 600−minimum amplitude value of model 600) / (maximum amplitude value of correspondence 500−minimum amplitude value of correspondence 500) + model 600 Minimum amplitude value (4)

(Step 1103)
Next, as shown in FIGS. 17E and 17F, the enlarged correspondence 500 ′ is divided into two parts 500a ′ and 500b ′ by threshold values Q1 and Q2. One part 500a ′ is a part corresponding to the detection waveform 301a of one magnetic sensor 301, and the other part 500b ′ is a part corresponding to the detection waveform 302a of the other magnetic sensor 302 (step 1105).

  Next, the divided portions 500a ′ and 500b ′ are respectively compared with the model 600 in the same manner as described in the fifth and sixth embodiments, and the respective peak positions Ipa and Ipb are obtained. Obtained (step 1106).

  Next, the peak positions Ip are obtained by averaging the calculated peak positions Ipa and Ipb. In this embodiment, it is assumed that the intermediate position between the magnetic sensors 301 and 302 is set to the origin position I0 (step 1107).

  Next, the peak position Ip (calculated origin position obtained from the detection result of the rotation sensor 100) obtained in this way is reset to the true origin position I0 (step 1108).

  As described above, according to the present embodiment, the distance J between the amplitude values and the distance K between the peak positions are reset based on the synthesized signal 301c having a characteristic that is not affected by the fluctuation of the base level. Therefore, the discrimination from noise can be performed accurately, and the comparison with the model 600 can be performed accurately. As a result, the process of resetting the calculated origin position Ip obtained from the detection result of the rotation sensor 100 to the true origin position I0 can be performed with extremely high accuracy.

(Eighth embodiment)
By the way, when the magnetism generated by the magnet 350 inside the cylinder tube 250 is transmitted through the cylinder tube 250, a magnetic transmission delay occurs. This magnetic transmission delay time is determined by the relative permeability and relative permittivity of the cylinder tube 250 and is constant. Therefore, the detection voltage levels of the magnetic force sensors 301 and 302 at the same stroke position are different between the case where the piston 201 and the rod 202 that move linearly together with the magnet 350 are moving at a high speed and the case where the piston 201 and the rod 202 are moving at a low speed.

  Therefore, the peak position Ip obtained from the detection result of the rotation sensor 100 varies depending on the moving speed V (hereinafter referred to as the origin position passing speed) when the piston 201 passes the origin position I0.

  Therefore, in this embodiment, the correspondence between the origin position passing speed V and the positional deviation amount (peak position correction amount) ΔI from the origin position I0 is acquired and stored in the data table format in the storage device, and according to this data table, The position In obtained from the detection result of the rotation sensor 100 is corrected.

  That is, the origin position passing speed V is obtained by measuring the distance between the peak positions Ipa and Ipb of the magnetic force sensors 301 and 302 and the time that the piston 201 has passed between these peak positions Ipa and Ipb.

  The peak position correction amount ΔI can be obtained by calculating the deviation between the true origin position I0 and the peak position Ip that is the average value of the peak positions Ipa and Ipb.

  Data of the origin position passing speed V and the peak position correction amount ΔI is acquired by changing the moving speed of the piston 201 and repeatedly performing the motion of passing the vicinity of the origin position. The acquired data is calculated in the form of a data table as data (Vj, ΔIj) of correspondence between the origin position passing speed V and the peak position correction amount ΔI for each magnitude j of the moving speed of the piston 201. It is stored in the storage device of the processing unit 400.

  Then, according to the data table (Vj, ΔIj), the measured peak position Ip is corrected according to the origin position passing speed V.

  For example, in the seventh embodiment, as described in step 1106 of FIG. 16, the peak positions Ipa and Ipb are calculated. The distance between these peak positions Ipa and Ipb and the distance between these peak positions Ipa and Ipb are calculated. Based on the time for which the piston 201 passes, the actual origin position passing speed V is obtained. Then, the peak position correction amount ΔI corresponding to the origin position passing speed V is read from the data table (Vj, ΔIj).

  In the seventh embodiment, the average value of the peak positions Ipa and Ipb is set as the peak position Ip (step 1107 in FIG. 16), but this peak position Ip includes an error corresponding to the peak position correction amount ΔI. According to the following equation (5), the peak position Ip is corrected and the corrected peak position Ip ′ is calculated.

Ip ′ = Ip + ΔI (5)
In this manner, the corrected peak position Ip ′ is accurately obtained regardless of the moving speed of the piston 201 inside the cylinder tube 250, and the reset to the origin position is accurately performed based on the corrected peak position Ip ′. Done.

  Although the eighth embodiment has been described in connection with the seventh embodiment, the eighth embodiment may be implemented in combination with the fifth and sixth embodiments. Further, the present invention can be applied not only when two magnetic sensors are provided, but also when one magnetic sensor is provided. When there is one magnetic sensor, the moving speed of the piston 201 cannot be obtained based on the distance between the peak positions Ipa and Ipb, but the moving speed of the piston 201 may be measured.

  In the above description, the measured peak position Ip is corrected according to the origin position passing speed V using the data table (Vj, ΔIj), but the correction amount is calculated using the following arithmetic expression. ΔI may be obtained.

ΔI = V × Td (6)
In the above equation (6), Td is a magnetic transmission delay time when the magnetism generated by the magnet 350 inside the cylinder tube 250 is transmitted through the cylinder tube 250 and is uniquely determined by the material of the cylinder tube 250 and the like. Is the value of

  In this embodiment, after obtaining the correspondence 500 between the measurement stroke position In of the piston 201 and the detection signal (magnetic force; voltage value) Vn of the magnetic sensor 301, the measurement peak position is obtained using a data table or an arithmetic expression. Although Ip is corrected, the correction may be performed in the process of obtaining the correspondence relationship 500.

  That is, for each successive measurement stroke position In of the piston 201, a correction stroke position In 'corrected by the moving speed is obtained, and the correction stroke position In' and a detection signal (magnetic force; voltage value) Vn of the magnetic sensor 301 are obtained. Based on the correspondence relationship 500, the peak position Ip may be obtained. In this case, the movement speed of the piston 201 may be measured for each measurement stroke position In of the piston 201, and the correction stroke position In ′ may be calculated according to this movement speed.

  In the above-described embodiment, the actual origin position passage speed V is calculated based on the distance between the peak positions Ipa and Ipb and the time during which the piston 201 passes between the peak positions Ipa and Ipb. However, the actual origin position passing speed V may be calculated based on the stroke position sequentially measured by the rotation sensor 100. For example, the actual origin position passing speed V can be calculated based on the previously measured stroke position, the currently measured stroke position, and the time difference from the previous time to the current time.

  In the eighth embodiment described above, the stroke position Ip (peak position) obtained from the detection result of the rotation sensor 100 is corrected according to the moving speed V of the piston 201, and this corrected stroke position Ip ′ ( The correction peak position) has been described on the assumption that it is reset to the origin position I0. However, the present invention is also applicable to a configuration in which the rotation sensor 100 is not provided, and an implementation that does not assume the reset processing of the rotation sensor 100 to the origin position. Can be applied. For example, when the rotation sensor 100 is not provided and the fact that the piston 201 has passed a specific position is measured based on the detection signal of the magnetic force sensor 301 (302), the present invention is used to correct the measurement position. Can be applied.

  In other words, the present invention only needs to compensate for the delay when the magnetic force passes through the cylinder tube 250 and correct the position detected by the reset sensors 301 and 302.

  In the fifth to eighth embodiments, the description has been made on the assumption that the detection medium is a magnet (magnetic force). However, the detection medium is not necessarily a magnet (magnetic force). For example, FIG. As shown in FIG. 4, any detection medium whose physical quantity changes so as to have a peak at the origin position may be used. For example, when the detection medium is a sound wave and the sound wave is detected by an ultrasonic sensor, the present invention according to the fifth to eighth embodiments can be applied.

1A and 1B are cross-sectional views of a cylinder tube used for explaining the relationship among a cylinder, a rotation sensor, and a reset sensor. FIGS. 2A, 2B, 2C and 2D are diagrams showing the configuration of the reset sensor of the first embodiment. FIGS. 3A and 3B are diagrams conceptually showing the path of the lines of magnetic force in contrast between the present example and the comparative example. FIG. 4 is a diagram illustrating the second embodiment, and is a diagram illustrating a mounting example in which the eaves are fixed to the outer periphery of the cylinder tube without a band. FIG. 5 is a diagram illustrating the second embodiment, and is a diagram illustrating a mounting example in which the eaves are fixed to the outer periphery of the cylinder tube with a mounting member other than the band. FIGS. 6A, 6 </ b> B, 6 </ b> C, and 6 </ b> D are diagrams illustrating the third embodiment, and are diagrams illustrating a configuration of an eaves that covers a part of the magnetic sensor. FIGS. 7A, 7B and 7C are configuration diagrams of the fourth embodiment. FIGS. 8A and 8B are views for explaining the fifth embodiment. FIGS. 9A and 9B are views showing a comparative example of the fifth embodiment. FIG. 10 is a diagram illustrating an algorithm of the fifth embodiment. FIGS. 11A, 11B, and 11C are diagrams for explaining the processing contents of FIG. FIGS. 12A and 12B are views for explaining the sixth embodiment. FIGS. 13A, 13B, 13C, and 13D are diagrams for explaining a comparative example of the seventh embodiment. 14A, 14B, and 14C are diagrams for explaining a comparative example of the seventh embodiment, and FIGS. 14D and 14E are diagrams for explaining characteristics of the synthesized signal of the seventh embodiment. It is. FIGS. 15A and 15B are diagrams for explaining signal processing in the seventh embodiment. FIG. 16 is a diagram illustrating an algorithm of the seventh embodiment. FIGS. 17A, 17B, 17C, 17D, 17E, and 17F are diagrams for explaining the processing contents of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 100 Rotation sensor 201 Piston 202 Rod 250 Cylinder tube 300 301, 302 Magnetic force sensor (reset sensor) 310 Eave 320 Band 350 Magnet 400 Arithmetic processing part

Claims (5)

In the cylinder position measuring device for measuring the position of the linear motion member (201, 202) that linearly moves inside the cylinder tube (250),
A stroke position sensor (100) for detecting a stroke position of the linear motion member;
A detection medium (350) provided on the linear motion member (201);
A detection signal is provided on the outside of the cylinder tube (250) corresponding to the origin position of the linear motion member (201, 202), and the detection level changes according to the distance from the detection medium (350). A reset sensor (301, 302) that outputs a detection signal whose detection level reaches a peak value when the linear motion member (201, 202) reaches the origin position;
One of the horizontal axis and the vertical axis is a stroke position detected by the stroke position sensor (100), and the other axis is a detection signal output from the reset sensor (301, 302). Find the curve showing
A cylinder position measuring device comprising: an arithmetic processing means (400) for resetting a detected stroke position corresponding to a vertex of the curve to the origin position. The arithmetic processing means (400)
The linear motion member (201, 202) is stroked twice to obtain two curves indicating the correspondence, and based on the deviation amount of the two curves, a detected stroke position corresponding to the vertex of the curve is obtained. 2. The cylinder position measuring apparatus according to claim 1, wherein the detected stroke position is reset to an origin position. The arithmetic processing means (400) has a correspondence relationship between the movement speed and the correction amount of the origin position for each magnitude of the movement speed when the linear motion members (201, 202) pass through the origin position. Is obtained in advance,
The actual movement speed when the linear motion member (201, 202) passes through the reset sensor (301, 302) is measured, and the correction amount of the origin position corresponding to the measured actual movement speed is the correspondence relationship. From
3. The cylinder position measuring apparatus according to claim 1, wherein the detected stroke position corresponding to the vertex of the curve is corrected based on the obtained correction amount of the origin position. The reset sensor (301, 302)
Two reset sensors (301, 302) provided on the outside of the cylinder tube (250) and spaced apart from each other by a predetermined distance along the linear motion direction of the linear motion members (201, 202). The reset sensors (301, 302) output detection signals having different polarities,
The arithmetic processing means (400)
Position measuring device of the cylinder according to any of claims 1 to 3, characterized in that the arithmetic processing based on the signal acquired by combining the detection signals of the two reset sensors (301, 302). In the cylinder position measuring device for measuring the position of the linear motion member (201, 202) that linearly moves inside the cylinder tube (250),
A detection medium (350) provided on the linear motion member (201);
A sensor (provided at a known specific position outside the cylinder tube (250)) that detects a magnetic force that changes according to a distance from the detection medium (350) as a position of the linear motion member (201, 202). 301, 302),
Computational processing means (400) for compensating for a delay when the magnetic force passes through the cylinder tube (250) and correcting a position detected by the sensors (301, 302). Cylinder position measuring device.

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