JP2014074662A - Cylinder position measurement device, and cylinder position measurement method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately measure a stroke amount of a cylinder even when a high pressure of oil in the cylinder is applied.SOLUTION: An arithmetic processing section 400 identifies a maximum pressure Pmax while a direct-acting member moves for a certain section and determines a pressure correction amount ΔSp at a peak position of a waveform detected by a magnetic force sensor 302 on the basis of a pressure correction table 413, determines a travel speed V of the direct-acting member on the basis of the variation in stroke amount Sd and determines a speed correction amount ΔSv at the peak position of the waveform detected by the magnetic force sensor 302 on the basis of a speed correction table 423, adds the pressure correction amount ΔSp and speed correction amount ΔSv to the stroke amount Sd indicating the peak position of the waveform detected by the magnetic force sensor 302 to determine a corrected correction stroke amount Sc, and resets the origin position of the stroke amount on the basis of the correction stroke amount Sc.

Description

  The present invention relates to a cylinder position measuring apparatus and a cylinder position measuring method for measuring the position of a linearly moving member that moves linearly inside a cylinder tube.

  A permanent magnet is provided on a piston that moves linearly with a rod inside a cylinder tube such as a hydraulic cylinder, and a magnetic sensor is provided outside the cylinder tube, and the position of the piston of the cylinder is detected by detecting the magnetic force passing through the magnetic sensor. There is something to measure.

  For example, a rotary encoder that detects the amount of linear movement of the rod as a rotation amount is provided on 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. There is a technique that detects a magnetic force generated by a magnet fixed to a linearly moving piston and resets a measurement position obtained from a detection value of a rotary encoder to an origin position when the magnetic force reaches a peak value.

  Here, 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 moving speed of the piston inside the cylinder tube is not constant. Therefore, when the magnetic force detected by the magnetic force sensor (reset sensor) reaches the peak, the stroke amount obtained by the arithmetic processing may be true depending on the moving speed of the piston. This is deviated from the stroke amount (origin position).

  For this reason, in Patent Document 1, the correspondence relationship between the passing speed of the piston immediately below the reset sensor and the amount of displacement from the origin position (peak position correction amount) is acquired in advance and stored in a table format. Sometimes the passage speed just below the reset sensor is detected to correct the origin position.

JP 2006-226909 A

By the way, in Patent Document 1, it is possible to measure the stroke amount by eliminating the influence of the piston moving speed. However, in a hydraulic cylinder, a high pressure of 200 to 400 kg / cm ² may be applied and magnetized by this. In some cases, a large strain occurs in the tube, the surface magnetic force decreases, the peak position of the magnetic force waveform detected by the reset sensor changes, and the detection accuracy decreases.

  The present invention has been made in view of the above, and a cylinder position measuring device and a cylinder position measuring device capable of accurately measuring the stroke amount of a cylinder even when high pressure of oil in the cylinder is applied. It aims to provide a method.

  In order to solve the above-described problems and achieve the object, a cylinder position measuring apparatus according to the present invention is a cylinder position measuring apparatus that measures the position of a linearly moving member that linearly moves inside a cylinder tube. A stroke amount sensor for detecting the stroke amount of the member, a magnet provided in the linear motion member, a magnetic force sensor provided outside the cylinder tube, a pressure sensor for detecting the pressure of oil in the cylinder, A pressure correction table showing a relationship between a pressure detected by a pressure sensor and a pressure correction amount which is a deviation from a peak position of a waveform detected by the magnetic force sensor; and the pressure is detected based on the pressure correction table. The pressure correction amount at the peak position of the waveform detected by the magnetic sensor is obtained, and the stroke amount indicating the peak position of the waveform detected by the magnetic sensor It said pressure correction amount calculated correction stroke amount that is corrected by adding, characterized in that and a processing unit for resetting the position of the origin of the stroke based on the correction stroke.

  Moreover, the cylinder position measuring apparatus according to the present invention shows the relationship between the moving speed of the linear motion member and a speed correction amount that is a deviation amount from a peak position of a waveform detected by the magnetic force sensor in the above invention. A speed correction table, and the arithmetic processing unit detects the pressure, obtains the pressure correction amount at a peak position of the waveform detected by the magnetic sensor based on the pressure correction table, and changes the stroke amount. Further, the moving speed of the linear motion member is obtained, the speed correction amount at the peak position of the waveform detected by the magnetic sensor is obtained based on the speed correction table, and the peak position of the waveform detected by the magnetic sensor is indicated. A corrected stroke amount obtained by adding the pressure correction amount and the speed correction amount to the stroke amount is obtained, and the stroke amount is calculated based on the corrected stroke amount. Characterized by resetting a point location.

  The cylinder position measuring apparatus according to the present invention is characterized in that, in the above invention, the pressure sensor is a pump discharge pressure sensor for detecting a discharge pressure of a hydraulic pump.

  In the cylinder position measuring method according to the present invention, the position of the linear motion member is determined by correcting the origin position of the linear motion member that linearly moves inside the cylinder tube using a magnetic sensor provided outside the cylinder tube. A cylinder position measuring method for measuring, wherein the pressure of oil in a cylinder is detected, and based on the relationship between the pressure and a pressure correction amount that is a deviation amount from a peak value of a waveform detected by the magnetic force sensor. A pressure correction amount calculating step for obtaining the pressure correction amount at the peak position of the waveform detected by the magnetic sensor, and a correction stroke corrected by adding the pressure correction amount to the stroke amount indicating the peak position of the waveform detected by the magnetic sensor And a reset process step of resetting the origin position of the stroke amount based on the corrected stroke amount.

  Further, the cylinder position measuring method according to the present invention is the above invention, wherein the moving speed of the linear motion member is obtained based on a change in stroke amount of the linear motion member that linearly moves inside the cylinder tube. Speed for obtaining the speed correction amount at the peak position of the waveform detected by the magnetic sensor based on the relationship between the moving speed of the member and the speed correction amount that is a deviation amount from the peak position of the waveform detected by the magnetic sensor. A correction amount calculating step, wherein the reset processing step calculates a correction stroke amount corrected by adding the pressure correction amount and the speed correction amount to the stroke amount indicating a peak position of a waveform detected by the magnetic force sensor, The origin position of the stroke amount is reset based on the corrected stroke amount.

  According to the present invention, the magnetic sensor detects the pressure of oil in the cylinder, and the magnetic sensor detects the pressure based on the relationship between the pressure and the pressure correction amount that is the deviation from the peak value of the waveform detected by the magnetic sensor. The pressure correction amount at the peak position of the waveform is obtained, the correction stroke amount corrected by adding the pressure correction amount to the stroke amount indicating the peak position of the waveform detected by the magnetic force sensor is obtained, and the correction stroke amount is determined based on the correction stroke amount. Further, since the origin position of the stroke amount is reset, the stroke amount of the cylinder can be accurately measured even when a high pressure of oil in the cylinder is applied.

FIG. 1 is a cross-sectional view showing a configuration of a cylinder according to an embodiment of the present invention. 2 is a cross-sectional view taken along line AA in FIG. FIG. 3A is an enlarged view of a cross-sectional view of the cylinder tube shown in FIG. 3-2 is a view on arrow A in FIG. 3-1. FIG. 3C is a diagram viewed from the arrow Z in FIG. 3-4 is a figure which defines each surface of a 1st magnetic force sensor and a 2nd magnetic force sensor. FIG. 4 is a diagram showing the stroke amount dependence of the detection output of the magnetic force sensor and the waveform fluctuation accompanying the speed change. FIG. 5 shows the contents of the speed correction table. FIG. 6 is a diagram showing the stroke amount dependency of the detection output of the magnetic sensor and the waveform fluctuation accompanying the pressure change. FIG. 7 is a diagram showing the contents of the pressure correction table. FIG. 8 is a block diagram illustrating a configuration of the arithmetic processing unit. FIG. 9 is a flowchart illustrating a reset processing procedure by the arithmetic processing unit.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to the accompanying drawings.

(Cylinder structure)
FIG. 1 is a cross-sectional view showing a configuration of a cylinder according to an embodiment of the present invention. As shown in FIG. 1, a piston 201 is slidably provided on a cylinder tube 250 of the cylinder 200. A rod 202 is attached to the piston 201. The linear motion member includes a piston 201 and a rod 202. The rod 202 is slidably provided on the cylinder head 203. A chamber defined by the cylinder head 203, the piston 201, and the inner wall of the cylinder 200 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 via the cylinder head side oil chamber 204H. Alternatively, the pressure oil is supplied to the cylinder bottom side oil chamber 204B via the hydraulic port 206B, or the pressure oil is discharged from the cylinder bottom side 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. As a result, the rod 202 moves linearly in the left-right direction in FIG.

  A case 207 that covers the stroke amount 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 can be easily attached to and detached from the cylinder tube 250.

  The surface of the rotating roller 110 that constitutes the stroke amount sensor 100 is in contact with the surface of the rod 202, and is provided so as to be rotatable 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 110 c is orthogonal to the linear movement direction of the rod 202. 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 causes the rotating roller 110 to malfunction. That is, the stroke amount sensor 100 has a dust-proof structure formed by a dust seal 208 provided on the case 207 and a dust seal 205 b provided on the cylinder head 203.

  The stroke amount sensor 100 includes a rotation roller 110, a rotation sensor unit (not shown) that detects the rotation amount of the rotation roller 110, and a stroke amount conversion unit that converts this rotation amount into a stroke amount of the rod 202 of the cylinder 200. A signal indicating the stroke amount converted by the stroke amount conversion unit is sent to the arithmetic processing unit 400.

  Slip (slip) is inevitably generated between the rotating roller 110 of the stroke amount sensor 100 and the rod 202, and the measurement position of the rod 202 obtained from the detection result of the stroke amount sensor 100 by this slip, and the rod An error (cumulative error due to slipping) occurs between the actual position 202 and the actual position. Therefore, in order to reset the measurement position obtained from the detection result of the stroke amount sensor 100 to the origin position (reference position), a magnetic force sensor 302 as a reset sensor is provided outside the cylinder tube 250.

  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 south pole and the north pole are disposed along 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 south pole and the north pole are disposed along a direction perpendicular to the linear movement direction of the piston 201 and the rod 202.

  The magnetic sensor 302 transmits the magnetic force lines generated by the magnet 350, detects the magnetic force (magnetic flux density), and outputs an electric signal (voltage) corresponding to the magnetic force. The magnetic sensor 302 is provided at a known origin position. Based on the detection result of the magnetic sensor 302, the measurement position obtained from the detection result of the stroke amount sensor 100 is reset to the origin position (reference position).

  As the magnetic sensor 302, for example, a Hall IC is used.

  The magnetic sensor 302 is 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. 2 is a cross-sectional view taken along line AA in FIG. 1 and shows a vertical cross-sectional view of the cylinder tube 250. The band 320 is fixed in pressure contact with the outer periphery of the cylinder tube 250. The band 320 includes band members 320 </ b> A and 320 </ b> B having semicircular cross sections corresponding to the outer diameter of the cylinder tube 250. The band member 320 </ b> A and the band member 320 </ b> B are fastened by bolts 321, and are pressed against the outer periphery of the cylinder tube 250 by this fastening. The eaves 310 are attached to one band member 320A. For this reason, the magnetic force sensor 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 or 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.

  Further, the fixing position of the band 320 to the cylinder tube 250 can be easily and easily changed, and the magnetic force sensor 302 can be easily placed at an arbitrary position in the longitudinal direction of the cylinder tube 250 (the linear movement direction of the piston 201 and the rod 202). And it can be easily installed.

  Note that the stroke amount Sd, the voltage value V2 indicating the magnetic force detected by the magnetic force sensor 302, and the pressure P detected by the pressure sensor 500 are input to the arithmetic processing unit 400. The pressure sensor 500 is a pump discharge pressure sensor that detects a discharge pressure of a hydraulic pump (not shown).

(Magnet collecting structure)
3A to 3D are diagrams illustrating the structure of the magnetic sensor 302 and the eaves 310. FIG. 3A is an enlarged cross-sectional view of the cylinder tube 250 shown in FIG. 3-2 is a view on arrow A in FIG. 3-1. FIG. 3C is a diagram viewed from the arrow Z in FIG. FIG. 3-4 is a diagram for defining each surface of the magnetic sensor 302.

  The magnetic sensor 302 is a rectangular parallelepiped member, and has a bottom surface 300B, an upper surface 300T, a front surface 300F, a left side surface 300L, a right side surface 300R, and a rear surface 300G. On the other hand, the magnet 350 is fixed to the surface of the piston 201 facing the cylinder head side oil chamber 204H 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 sensor 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 band fixing surface 310A of the eaves 310 is fixed to the band member 320A. The tube bonding 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 302 is integrally formed with the mold material 303 so as to be surrounded by the mold material 303. In the molding material 303 including the magnetic sensor 302, the upper surface 300T and the rear surface 300G side of the magnetic sensor 302 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 302 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 302.

  That is, the bottom surface 300B of the magnetic force sensor 302 is disposed on the outer peripheral surface of the cylinder tube 250 so that the magnetic force sensor 302 is covered with the eaves 310, so that the magnetic material is in the upper surface 300T side and the rear surface 300G side. Although the eaves 310 are arranged, the magnetic material is not arranged on the front surface 300F side and the left and right side surfaces 300L and 300R side of the magnetic sensor 302, and the structure is open from the magnetic material.

  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 sensor 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.

  Due to the presence of the eaves 310, the magnetic field lines start from the north pole of the magnet 350 and pass through the cylinder tube 250, the magnetic force sensor 302, and the eaves 310, and generate a path returning to the south pole of the magnet 350.

  On the other hand, 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 cylinder tube 250. Are concentrated on the magnetic sensor 302.

  In other words, the eaves 310 and the band 320 form a magnetic flux collecting structure in which the magnetic force generated by the magnet 350 is concentrated on the magnetic force sensor 302, so that the magnetic force can be reliably detected. As a result, the position measurement accuracy of the rod 202 based on the detection result of the magnetic sensor 302 can be increased.

(Magnetic sensor output waveform)
With reference to FIG. 4, the detection waveform of the magnetic force sensor 302 when the stroke amount is changed and the magnet 350 is moved will be specifically described.

  As shown in FIG. 4, the stroke amount dependency of the detection output by the magnetic force sensor 302 is as shown by a characteristic curve L2, which has a peak value at the stroke amount P2 where the magnet 350 is positioned immediately below, and has passed the stroke amount P2. Even at the position, the peak value is convex downward. That is, the magnetic sensor 302 takes two extreme values.

  Here, FIG. 4 shows a shift in the detection output waveform due to the moving speed of the piston 201, and each peak value of the magnetic force sensor 302 is delayed in the detection position of the peak value as the moving speed of the piston increases. Deviation has occurred.

  As shown in FIG. 5, the shift amount (speed correction amount ΔSv) of the peak position of the magnetic force sensor 302 due to the speed V of the piston 201 has a correspondence relationship in which the speed correction amount ΔSv increases as the speed V increases. This correspondence relationship is held in advance in the arithmetic processing unit 400 as a speed correction table 423.

  On the other hand, FIG. 6 shows a shift of the detection output waveform due to pressurization, and the peak values of the magnetic force sensor 302 are shifted as the pressure increases.

  As shown in FIG. 7, the shift amount (pressure correction amount ΔSp) of the peak position of the magnetic force sensor 302 due to the pressure of oil in the cylinder (maximum pressure Pmax during which the piston 201 moves in a certain section) is increased by the pressure Pmax. Accordingly, the pressure correction amount ΔSp increases, and this correspondence is stored in advance in the arithmetic processing unit 400 as the pressure correction table 413.

  In this embodiment, when the stroke amount reset process is performed using the peak value of the magnetic force sensor 302, the stroke amount is corrected using the speed correction table 423 and the pressure correction table 413, and reset based on the corrected stroke amount. Processing is performed.

(Configuration of processing unit and reset processing)
FIG. 8 is a block diagram illustrating a configuration of the arithmetic processing unit 400. FIG. 9 is a flowchart illustrating a reset processing procedure performed by the arithmetic processing unit 400. With reference to FIGS. 8 and 9, the stroke amount reset processing using the detection results of the pressure sensor 500, the magnetic force sensor 302, and the stroke amount sensor 100 will be described.

  First, the arithmetic processing unit 400 acquires a stroke amount Sd that is a linear motion amount of the rod 202 or the piston 201 output from the stroke amount sensor 100, and the stroke amount Sd is added to the maximum pressure specifying unit 411, the speed calculating unit 421, and the addition. It outputs to the part 430 (step S101).

  Thereafter, the maximum pressure specifying unit 411 specifies the maximum pressure Pmax of the pressure P detected by the pressure sensor 500 while the piston 201 moves a predetermined distance based on the stroke amount Sd (step S102). Further, the pressure correction amount calculation unit 412 calculates the pressure correction amount ΔSp using the pressure correction table 413 and the maximum pressure Pmax, and outputs the pressure correction amount ΔSp to the addition unit 430 (step S103).

  Thereafter, the speed calculation unit 421 calculates the speed V by differentiating the input stroke amount Sd with respect to time, and outputs the speed V to the speed correction amount calculation unit 422 (step S105). Thereafter, the speed correction amount calculation unit 422 calculates the speed correction amount ΔSv using the speed correction table 423 and the speed V, and outputs the speed correction amount ΔSv to the addition unit 430 (step S106).

  Thereafter, the addition unit 430 adds the pressure correction amount ΔSp and the speed correction amount ΔSv to the stroke amount Sd and outputs the corrected stroke amount Sc obtained by correcting the stroke amount Sd to the waveform storage unit 431. The waveform storage unit 431 The correction stroke amount Sc and the input voltage value V2 detected by the magnetic force sensor 302 are stored in association with each other (step S107). That is, the history of the voltage value V2 with respect to the correction stroke amount Sc is held.

  Thereafter, the reset sensor passage determination unit 432 determines whether or not a predetermined distance has been moved after the voltage value V2 reaches the maximum peak (step S108). That is, it is determined whether or not the magnet 350 has passed through the magnetic sensor 302.

  The reset position setting unit 433 determines the correction stroke amount Sc corresponding to the voltage value V2 having the maximum peak as the actual stroke amount when the voltage value V2 has moved a predetermined distance after the voltage value V2 has reached the maximum peak (step S108, Yes). Is reset (origin position correction) (step S109), the process proceeds to step S101 and the above-described processing is repeated. On the other hand, if the voltage value V2 has not moved a predetermined distance after the voltage value V2 has reached the maximum peak (No in step S108), the reset position setting unit 433 does not perform the step because the voltage value V2 has not yet reached the maximum peak. The process proceeds to S101 and the above-described processing is repeated.

  In the above-described process, the correction amount calculation process based on the pressures in steps S102 and 103 is performed, and then the correction amount calculation process based on the speeds in steps S105 and S106 is performed. After performing the correction amount calculation process based on the speeds in steps S105 and S106, the correction amount calculation process based on the pressures in steps S102 and S103 may be performed.

  In the reset, the origin position is corrected based on the position of the reset sensor (second magnetic force sensor 302), but actually, the origin position is further converted into the cylinder system coordinates.

  Furthermore, it is preferable to perform the reset process described above only when the piston 201 moves in one direction. This is because when the piston 201 is returned from the stroke movement in one direction, the magnetized state of the cylinder tube 250 is erased by the movement of the magnet 350, so that there is little need for pressure correction.

  Further, the origin position correction at the time of reset processing by the reset position setting unit 433 may be performed by, for example, storing the past 10 correction stroke amounts and performing the origin position correction based on the past 10 average correction stroke amounts. Good.

  Note that the peak value of the magnetic sensor 302 is calculated from the output value of the magnetic sensor 302 itself. However, the calculation method of the peak value is not limited to this, and for example, a known calculation method disclosed in Patent Document 1 is used. For example, the peak value may be obtained using a model for the output value of the magnetic force sensor 302. This model may be obtained in advance or may be obtained from a plurality of data. Moreover, an approximate curve may be drawn with respect to the discrete output value which the magnetic force sensor 302 outputs, and a peak value may be calculated | required from this approximate curve. Further, the peak value may be obtained from an average of the output values of the magnetic sensor 302 a plurality of times.

DESCRIPTION OF SYMBOLS 100 Stroke amount sensor 110 Rotating roller 110c Rotation center axis 200 Cylinder 201 Piston 202 Rod 203 Cylinder head 204H Cylinder head side oil chamber 204B Cylinder bottom side oil chamber 205a Rod seal 205b, 208 Dust seal 206H, 206B Hydraulic port 207 Case 250 Cylinder tube 302 Magnetic sensor 303 Mold material 310 Eaves 311 Brass plate 312 Terminal 313 Terminal block 314 Insertion hole 320 Band 320A, 320B Band member 350 Magnet 351 Holder ring 400 Arithmetic processing unit 411 Maximum pressure specifying unit 412 Pressure correction amount calculating unit 413, 513 Pressure correction Table 421 Speed calculation unit 422 Speed correction amount calculation unit 423, 523 Speed correction table 431 Waveform storage unit 43 Reset sensor passage determination unit 433 resets the position setting unit 500 pressure sensors ω rotation amount Sd stroke Sc correction stroke Pmax maximum pressure V speed V2 voltage value ΔSp pressure correction amount ΔSv speed correction amount

Claims (5)

A cylinder position measuring device that measures the position of a linear motion member that linearly moves inside a cylinder tube,
A stroke amount sensor for detecting a stroke amount of the linear motion member;
A magnet provided on the linear motion member;
A magnetic force sensor provided outside the cylinder tube;
A pressure sensor for detecting the pressure of oil in the cylinder;
A pressure correction table showing a relationship between a pressure detected by the pressure sensor and a pressure correction amount that is a deviation amount from a peak position of a waveform detected by the magnetic force sensor;
The pressure is detected, the pressure correction amount at the peak position of the waveform detected by the magnetic force sensor is obtained based on the pressure correction table, and the pressure correction is performed on the stroke amount indicating the peak position of the waveform detected by the magnetic force sensor. A correction stroke amount corrected by adding an amount, an arithmetic processing unit for resetting the origin position of the stroke amount based on the correction stroke amount;
A cylinder position measuring device comprising: A speed correction table showing a relationship between a moving speed of the linear motion member and a speed correction amount that is a deviation amount from a peak position of a waveform detected by the magnetic force sensor;
The arithmetic processing unit includes:
The pressure is detected and the pressure correction amount at the peak position of the waveform detected by the magnetic force sensor is determined based on the pressure correction table, and the moving speed of the linear motion member is determined based on the change in the stroke amount. The speed correction amount at the peak position of the waveform detected by the magnetic force sensor is obtained based on the speed correction table, and the pressure correction amount and the speed correction amount are added to the stroke amount indicating the peak position of the waveform detected by the magnetic force sensor. The cylinder position measuring device according to claim 1, wherein a corrected stroke amount corrected by adding is obtained, and an origin position of the stroke amount is reset based on the corrected stroke amount.   The cylinder position measuring device according to claim 1, wherein the pressure sensor is a pump discharge pressure sensor that detects a discharge pressure of a hydraulic pump. A cylinder position measuring method for measuring the position of the linear motion member by correcting the origin position of the linear motion member that linearly moves within the cylinder tube using a magnetic force sensor provided outside the cylinder tube,
At the peak position of the waveform detected by the magnetic sensor based on the relationship between the pressure and the pressure correction amount, which is the amount of deviation from the peak value of the waveform detected by the magnetic sensor. A pressure correction amount calculating step for obtaining the pressure correction amount;
A reset process for obtaining a corrected stroke amount corrected by adding the pressure correction amount to the stroke amount indicating the peak position of the waveform detected by the magnetic force sensor, and resetting the origin position of the stroke amount based on the corrected stroke amount Steps,
A cylinder position measuring method comprising: The movement speed of the linear motion member is obtained based on the change in the stroke amount of the linear motion member that linearly moves inside the cylinder tube, and from the movement speed of the linear motion member and the peak position of the waveform detected by the magnetic sensor. A speed correction amount calculating step for obtaining the speed correction amount at a peak position of a waveform detected by the magnetic sensor based on a relationship with a speed correction amount that is a shift amount of
The reset processing step obtains a corrected stroke amount obtained by adding the pressure correction amount and the speed correction amount to the stroke amount indicating the peak position of the waveform detected by the magnetic force sensor, and based on the corrected stroke amount. The cylinder position measuring method according to claim 4, wherein an origin position of the stroke amount is reset.

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