JPWO2018092252A1 - Hydraulic cylinder with stroke position detection function - Google Patents

Abstract

The object of the present invention is to measure the stroke position measured by the stroke position detection sensor when the stroke position is detected by the stroke position detection sensor in which the roller support portion supporting the rotating roller is inclined and the reset position detection sensor resets the stroke position. To provide a hydraulic cylinder with a stroke position detection function capable of reducing an error between a stroke and an actual stroke. The rotating roller (12) that rotates with the direct movement of the piston rod (3) is supported by the roller support (13), and the stroke position of the piston rod (3) is detected based on the rotation of the rotating roller (12). And a reset position detection sensor (15) for detecting a detected part (40) corresponding to a reset position provided at a predetermined position on the surface of the piston rod (3) attached to the roller support part (13). The stroke position detection sensor (10) is provided.

Description

  The present invention relates to the measurement stroke measured by the stroke position detection sensor when the stroke position detection sensor measures the stroke position and the reset position detection sensor resets the stroke position. The present invention relates to a hydraulic cylinder with a stroke position detection function capable of reducing an error from an actual stroke. This hydraulic cylinder with a stroke position detection function is used, for example, to accurately detect the stroke of a work machine arm cylinder or boom cylinder of a hydraulic excavator that is an information construction machine (ICT construction machine).

  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, and therefore the stroke position obtained by the arithmetic processing when the magnetic force detected by the magnetic sensor (reset sensor) reaches the peak may be true depending on the moving speed of the piston. It is shifted from the stroke position (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.

  In Patent Document 2, a plurality of detected recesses are provided at intervals in the circumferential direction on the outer peripheral surface of the cylinder block, and an electromagnetic pickup type rotation sensor detects the detected recess when the cylinder block rotates. What measures the rotation speed of a cylinder block is described.

JP 2006-226909 A JP 2002-310062 A

  By the way, the stroke position detection sensor provided in the cylinder tube measures the stroke position of the piston rod by converting the rotation amount of the rotating roller that is rotated by being pressed by the piston rod into the stroke amount. It is inevitable that slip occurs between the rotating roller and the piston rod, and the slip between the piston rod stroke position obtained from the detection result of the stroke position detection sensor and the actual stroke position of the piston rod is unavoidable. Causes a cumulative error due to slipping. For this reason, in order to reset the stroke position obtained from the detection result of the stroke position detection sensor to the origin position (reference position), the reset is separately detected by detecting the detected portion provided on the piston rod. A position detection sensor is provided.

  On the other hand, the rotating roller is supported by a roller support portion, and this roller support portion is pressed against the case from a direction perpendicular to the linear movement direction of the piston rod via a pressing spring or the like. For this reason, a gap exists on the sliding surface between the roller support portion and the case. Due to the presence of this gap, the roller support portion is inclined with respect to the linear movement direction of the piston rod, and an error occurs in the stroke position detected by the stroke position detection sensor. Since this error occurs in each direction of the linear movement of the piston rod, it occurs in both directions with respect to the measurement stroke assuming no error, and the error range is twice that of one tilt error. The range is the tolerance.

  However, if the error is caused by this tilt, i.e., after the stroke position is reset while the roller support is tilted, if the roller support is tilted in the opposite direction, one tilt error is detected from the measurement stroke position without error. A double error occurs, a large error deviating from the allowable error range described above, and the accuracy of the measurement stroke deteriorates.

  The present invention has been made in view of the above, and in the case where the stroke position is detected by the stroke position detection sensor in which the roller support portion supporting the rotating roller is inclined and the stroke position is reset by the reset position detection sensor. Another object of the present invention is to provide a hydraulic cylinder with a stroke position detection function capable of reducing an error between a measured stroke measured by a stroke position detection sensor and an actual stroke.

  In order to solve the above-described problems and achieve the object, a hydraulic cylinder with a stroke position detection function according to the present invention is a hydraulic cylinder with a stroke position detection function that measures the stroke position of a piston rod that moves linearly in a cylinder tube. A piston rod and a rotating roller that rotates as the piston rod linearly moves are supported by a roller support portion, and a stroke position of the piston rod is detected based on the rotation of the rotating roller; A stroke position detection sensor having a reset position detection sensor for detecting a detected portion corresponding to a reset position provided at a predetermined position on the surface of the piston rod attached to the support portion is provided.

  The hydraulic cylinder with a stroke position detection function according to the present invention is characterized in that, in the above invention, the reset position detection sensor is provided below a rotation center axis of the rotary roller.

  The hydraulic cylinder with a stroke position detection function according to the present invention is characterized in that, in the above invention, the reset position detection sensor is supported by the same fulcrum as the rotating roller.

  In the hydraulic cylinder with a stroke position detection function according to the present invention, the reset position detection sensor and the rotation roller are arranged on a straight line parallel to the linear movement direction of the piston rod. It is characterized by that.

  Further, in the hydraulic cylinder with a stroke position detection function according to the present invention, the reset position detection sensor is a magnetic sensor in the above invention, and the detected portion is in a groove provided in the ground of the piston rod. It is the site | part which performed the surface treatment by a nonmagnetic material, It is characterized by the above-mentioned.

  In the hydraulic cylinder with a stroke position detection function according to the present invention, the reset position detection sensor is an eddy current sensor, and the detected portion is in a groove provided on the ground of the piston rod. The resistance value is lower than the material of the piston rod.

  In the hydraulic cylinder with a stroke position detection function according to the present invention, in the above invention, the reset position detection sensor is an optical sensor, and the detected portion is a coloring provided on the sliding surface of the piston rod. The color of the colored portion is different from the color of the sliding surface of the piston rod.

In the hydraulic cylinder with a stroke position detection function according to the present invention, the reset position detection sensor is an optical sensor, and the detected portion is a light provided on the sliding surface of the piston rod. It is a reflecting member or a light absorbing member.

  According to the present invention, since the reset position detection sensor and the stroke position detection sensor are integrally arranged at the roller support portion, even if the roller support portion is inclined, the measurement stroke and the actual stroke measured by the stroke position detection sensor are not detected. The error can be reduced.

FIG. 1 is a diagram showing an external configuration of a hydraulic cylinder with a stroke position detection function according to the first embodiment of the present invention. FIG. 2 is a cross-sectional view showing a detailed configuration of the hydraulic cylinder shown in FIG. FIG. 3 is an enlarged view showing a detailed configuration of the stroke position detection sensor shown in FIG. FIG. 4 is a diagram illustrating a configuration of the reset position detection sensor illustrated in FIG. 3 and a reset position detection process. FIG. 5 is an explanatory diagram for explaining the weighted average process. FIG. 6 is a flowchart illustrating a reset processing procedure performed by the arithmetic processing unit. FIG. 7 is a diagram illustrating the relationship between the measurement stroke and the actual stroke of the stroke position detection sensor when the reset position detection sensor is disposed on the roller support portion of the stroke position detection sensor. FIG. 8 is a diagram illustrating the relationship between the measurement stroke and the actual stroke of the stroke position detection sensor in the case of a conventional configuration in which the reset position detection sensor is not disposed on the roller support. FIG. 9 is a diagram showing a configuration and an output waveform of the reset position detection sensor used in the second embodiment of the present invention. FIG. 10 is a diagram showing a configuration of a reset position detection sensor according to the third embodiment of the present invention. FIG. 11 is a diagram showing an output waveform of the reset position detection sensor shown in FIG. FIG. 12 is a diagram illustrating a configuration of a reset position detection sensor according to the fourth embodiment of the present invention. FIG. 13 is a diagram showing an output waveform of the reset position detection sensor shown in FIG. FIG. 14 is a diagram showing a configuration of a reset position detection sensor according to the fifth embodiment of the present invention. FIG. 15 is a diagram showing an output waveform of the reset position detection sensor shown in FIG. FIG. 16 is a diagram showing a configuration of a reset position detection sensor according to the sixth embodiment of the present invention. FIG. 17 is a diagram showing an output waveform of the reset position detection sensor shown in FIG.

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

[Embodiment 1]
(Cylinder structure)
FIG. 1 is a diagram showing an external configuration of a hydraulic cylinder with a stroke position detection function (hereinafter referred to as a hydraulic cylinder) 1 according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view showing a detailed configuration of the hydraulic cylinder 1 shown in FIG. 3 is an enlarged view showing a detailed configuration of the stroke position detection sensor 10 shown in FIG.

  As shown in FIGS. 1 and 2, the piston rod 3 that is a linear motion member is slidably provided on a cylinder tube 2 that is a wall of the hydraulic cylinder 1 via a piston 20. The piston 20 is attached to the vicinity of the cylinder bottom 9 side of the piston rod 3. The piston rod 3 is slidably provided on the cylinder head 8. A chamber defined by the cylinder head 8, the piston 20, the inner wall of the cylinder tube 2 and the piston rod 3 constitutes a cylinder head side oil chamber 13H. Further, the chamber defined by the cylinder bottom 9, the piston 20, the inner wall of the cylinder tube 2 and the piston rod 3 constitutes a cylinder bottom side oil chamber 13B. The cylinder head side oil chamber 13 </ b> H and the cylinder bottom side oil chamber 13 </ b> B are in positions facing each other in the cylinder tube 2 through the piston 20. The hydraulic oil LH flows into and out of the cylinder head side oil chamber 13H through the hydraulic port 4 provided in the vicinity of the cylinder head 8. Further, the hydraulic oil LB flows into and out of the cylinder bottom side oil chamber 13B through the hydraulic port 5 provided in the vicinity of the cylinder bottom 9.

  The hydraulic oil LH and LB are switched in flow rate and direction of hydraulic oil from a hydraulic pump (not shown) by adjusting a flow rate adjustment valve corresponding to the operation amount of an operating lever (not shown). When the hydraulic oil LH flows into the cylinder head side oil chamber 13H via the hydraulic port 4, the hydraulic oil LH pushes the piston 20 to the cylinder bottom 9 side, so that the piston rod 3 moves to the cylinder bottom 9 side. Then, the hydraulic oil LB in the cylinder bottom side oil chamber 13B flows out to a hydraulic oil tank (not shown) through the hydraulic port 5. On the other hand, when the hydraulic oil LB flows into the cylinder bottom side oil chamber 13B via the hydraulic port 5, the hydraulic oil LB pushes the piston 20 toward the cylinder head 8 to move the piston rod 3 toward the cylinder head 8. The hydraulic oil LH in the cylinder head side oil chamber 13H flows out to a hydraulic oil tank (not shown) via the hydraulic port 4. As a result, the piston rod 3 reciprocates in the linear movement direction AR in the cylinder tube 2 by the inflow of the hydraulic oils LH and LB.

  The cylinder head 8 is provided with a rod seal 30 and a dust seal 32 that seal a gap with the piston rod 3 and prevent contamination such as dust from entering the cylinder head side oil chamber 13H.

(Stroke position detection mechanism)
A stroke position detection sensor 10 is provided outside the cylinder head 8. The stroke position detection sensor 10 is covered with a case 11. The case 11 is fixed to the cylinder head 8 by being fastened to the cylinder head 8 with a bolt or the like. That is, the stroke position detection sensor 10 and the case 11 can be easily attached to and detached from the cylinder tube 2.

  The surface of the rotating roller 12 constituting the stroke position detection sensor 10 is in contact with the surface of the piston rod 3, is supported by the roller support portion 13, and is rotatably provided according to the reciprocating motion of the piston rod 3. That is, the linear movement amount of the piston rod 3 is converted into the rotation amount by the rotating roller 12.

  The rotation roller 12 is arranged such that the rotation center shaft 12 </ b> C is orthogonal to the reciprocating direction of the piston rod 3. The case 11 is provided with a dust seal 31 that seals a gap with the piston rod 3 and prevents contamination such as dust from entering between the rotating roller 12 and the piston rod 3. As a result, it is possible to avoid a situation in which dust or the like enters between the rotating roller 12 and the piston rod 3 and the rotating roller 12 malfunctions. That is, the stroke position detection sensor 10 is formed with a dustproof structure including a dust seal 31 provided on the case 11 and a dust seal 32 provided on the cylinder head 8.

  A pressing spring 14 is disposed between the roller support portion 13 and the case 11. The pressing spring 14 presses the rotating roller 12 toward the piston rod 3 via the roller support portion 13 so that the rotating roller 12 does not slide with respect to the piston rod 3.

  The stroke position detection sensor 10 includes a rotation sensor unit (not shown) that detects the rotation amount of the rotary roller 12. A signal indicating the rotation amount of the rotating roller 12 detected by the rotation sensor unit is sent to the arithmetic processing unit 7 and converted into a stroke position of the piston rod 3. The arithmetic processing unit 7 outputs the calculated stroke position to a controller (not shown). The arithmetic processing unit 7 may be provided in the stroke position detection sensor 10.

  Slip (slip) is inevitable between the rotary roller 12 of the stroke position detection sensor 10 and the piston rod 3, and the stroke of the piston rod 3 obtained from the detection result of the stroke position detection sensor 10 due to this slip. There is an error (cumulative error due to slip) between the position and the actual stroke position of the piston rod 3. Therefore, in order to reset the stroke position obtained from the detection result of the stroke position detection sensor 10 to the origin position (reference position), a reset position detection sensor 15 is provided in the roller support portion 13. The reset position detection sensor 15 is provided below the rotation center shaft 12 </ b> C of the rotating roller 12 (on the piston rod 3 side). This is because the lower portion of the roller support portion 13 is closer to the piston rod 3 and the detected portion 40 can be detected more accurately. The reset position detection sensor 15 is supported by the roller support portion 13 at the same fulcrum as the rotary roller 12. Further, the reset position detection sensor 15 and the rotating roller 12 are arranged on a straight line parallel to the linear movement direction AR of the piston rod 3.

  The reset position detection sensor 15 detects the position of one end of the detected portion 40 provided at a predetermined surface position of the piston rod 3. As shown in FIG. 4A, the reset position detection sensor 15 according to the first embodiment includes magnetic sensors S1 and S2 such as Hall elements arranged in the linear motion direction AR. A magnet 41 is disposed above the reset position detection sensor 15. The piston rod 3 is made of a magnetic material, and a film of a non-magnetic material 43 is formed thereon. Since the thickness of this film may be about 50 μm, for example, in the portion of the groove 42 having a depth of 50 μm, it becomes about 100 μm. The groove 42 is provided in a part of the background (surface) of the piston rod 3. The nonmagnetic material 43 is formed by surface treatment (plating treatment) for the entire ground including the groove 42.

(Reset processing)
As shown to Fig.4 (a), when the stroke direction is A1, the to-be-detected part 40 is detected in order of magnetic sensor S1, S2. When the magnetic sensors S1 and S2 reach the detected portion 40, the magnetic field decreases due to the decrease in the magnetic material, and the Hall voltage of the Hall element decreases. As a result, the magnetic sensors S1 and S2 output the output waveforms LS1 and LS2 shown in FIG. 4B, respectively. The output waveform LS1 is a detection result of the magnetic sensor S1, and the output waveform LS2 is a detection result of the magnetic sensor S2. As shown in FIG. 4C, the reset position detection sensor 15 outputs a differential waveform LΔV obtained by subtracting the output waveform LS2 from the output waveform LS1 to the arithmetic processing unit 7. The distance between the peaks of the differential waveform LΔV is characterized by being determined by the width W1 of the groove 42 of the detected portion 40.

  Here, the arithmetic processing unit 7 can set the position where the differential waveform LΔV is maximum as the reset position d. In the first embodiment, the first measurement value is evaluated by subtracting the second measurement value of the differential waveform behind the predetermined distance (the width W1 of the detected portion 40) from the first measurement value of the differential waveform. A value obtained by weighting and averaging each stroke position with each evaluation value is calculated as a reset position. FIG. 4D is a diagram illustrating a change in the evaluation value with respect to the stroke position. If the change in the evaluation value is weighted and averaged at the stroke position, the reset position d is obtained. Thus, by using the feature that the distance between the peaks of the differential waveform LΔV is the width W1 of the groove 42 of the detected portion 40, the reset position can be obtained without being affected by disturbance.

  FIG. 5 is an explanatory diagram for explaining the weighted average process. The differential waveform LΔV shown in FIGS. 5A to 5D corresponds to FIG. 4C and has sampling points SP1 to SP7. In FIG. 5A, the evaluation value “0” is obtained by subtracting the second measurement value at the sampling point SP1 from the first measurement value at the sampling point SP4. In FIG. 5B, the evaluation value “3” is obtained by subtracting the second measurement value at the sampling point SP2 from the first measurement value at the sampling point SP5. In FIG. 5C, the evaluation value “3” is obtained by subtracting the second measurement value at the sampling point SP3 from the first measurement value at the sampling point SP6. In FIG. 5D, the evaluation value “0” is obtained by subtracting the second measurement value at the sampling point SP4 from the first measurement value at the sampling point SP7. That is, the evaluation value shown in FIG. In the subtraction process for obtaining the evaluation value, the distance between the sampling points is set to the width W1, but when there is no sampling point corresponding to the width W1, the sampling point closest to the width W1 is substituted.

Here, when the evaluation value exceeds a predetermined value, for example, “2”, a weighted average process for obtaining the reset position d that is the end position P1 on the cylinder bottom side of the detected portion 40 is performed. When the stroke positions of the sampling points SP4 to SP7 at the respective sampling times are “1 mm”, “2 mm”, “3 mm”, and “4 mm”, the respective stroke positions are set to the respective evaluation values “0”, “3”, “3”. , “0” is used to calculate the reset position d by performing weighted average processing as in the following equation.
d = (1 mm × 0 + 2 mm × 3 + 3 mm × 3 + 4 mm × 0) / (0 + 3 + 3 + 0) = 2.5 mm

  Then, the arithmetic processing unit 7 resets the stroke position at the obtained reset position d. Specifically, when the reset position d is the origin (stroke position = 0 mm), a value obtained by subtracting the reset position d (= 2.5 mm) from the current stroke position is corrected as the true stroke position (origin).

  Here, the reset processing procedure by the arithmetic processing unit 7 will be described with reference to the flowchart shown in FIG. This process is performed at each sampling interval. First, the arithmetic processing unit 7 holds the stroke position detected by the stroke position detection sensor 10 and each output waveform (each output) detected by the magnetic sensors S1 and S2 which are two reset position detection sensors (steps). S101). Thereafter, the arithmetic processing unit 7 calculates a differential waveform obtained by taking the difference between the two output waveforms, and holds this differential waveform (step S102).

  Thereafter, as shown in FIGS. 5A to 5D, the evaluation value at the current sampling point is calculated (step S103). Further, it is determined whether or not the calculated evaluation value is a predetermined value or more, for example, “2” or more (step S104).

  If the evaluation value is greater than or equal to the predetermined value (step S104, Yes), the stroke position of a predetermined number of sampling points before and after the current sampling point (predetermined distance from the current sampling point) is weighted with the evaluation value at each sampling point. The average value is calculated as the reset position d (step S105). Thereafter, the stroke position is reset at the calculated reset position d (step S106), and the process at the current sampling point is terminated. On the other hand, if the evaluation value is not greater than or equal to the predetermined value (No at step S104), the process at the current sampling point is terminated as it is. And the process mentioned above is repeated for every sampling time.

  Note that the evaluation value need not be calculated every time. For example, the calculation of the evaluation value may be started when one of the two output waveforms decreases as a trigger.

(Location of reset position detection sensor)
In the first embodiment, as described above, the reset position detection sensor 15 is arranged on the roller support portion 13 of the stroke position detection sensor 10. As shown in the schematic diagram of state 1 in FIG. 7, since the roller support portion 13 moves up and down, a gap ΔG is provided on the sliding surface between the roller support portion 13 and the case 11. As a result, when the piston rod 3 slides, the rotating roller 12 and the roller support portion 13 may be inclined obliquely with respect to the linear movement direction of the piston rod 3. The inclination of the roller support portion 13 becomes a stroke error.

  FIG. 7 is a diagram illustrating the relationship between the measurement stroke and the actual stroke of the stroke position detection sensor 10 when the reset position detection sensor 15 is disposed on the roller support portion 13 of the stroke position detection sensor 10. In FIG. 7, the roller support 13 is in a neutral state with no inclination (state 1), the state 2 in which the roller support 13 is inclined in the positive direction (the stroke direction with respect to the piston rod 3) from state 1, and the reset position in state 2. Schematic diagram in the case where the detection sensor 15 detects the reset position, and the state 4 after the state 3 becomes the state 4 in which the roller support portion 13 is inclined in the negative direction (the direction opposite to the stroke direction with respect to the piston rod 3). In addition, detection characteristics of the measurement stroke and the actual stroke are shown. The straight line L1 shown in the detection characteristics indicates the characteristics of the measurement stroke and the actual stroke in the neutral state. A straight line L2 indicates the characteristics of the measurement stroke and the actual stroke when the inclination of the roller support portion 13 in the positive direction is maximum. A straight line L3 indicates the characteristics of the measurement stroke and the actual stroke when the inclination of the roller support portion 13 in the negative direction is maximum.

  First, in the state 1, the piston rod 3 is at the reference position, that is, the detected portion 40 is at the position of the actual stroke 0, the roller support portion 13 is not tilted, and the measurement stroke and the actual stroke are “0”. At this time, the position detected by the reset position detection sensor 15 is at a distance “B” in the positive direction (stroke direction) with respect to the reference position. The stroke position detection sensor 10 detects a relative stroke as a measurement stroke with the position of the detected portion 40 as a reference position “0”.

  Thereafter, when the piston rod 3 extends in the positive direction, the measurement stroke and the actual stroke change along the straight line L1. Here, when the roller support portion 13 is in a state 2 inclined in the forward direction, the stroke position detection sensor 10 causes the rotation roller 12 to rotate extraordinarily clockwise as indicated by the arrow due to the inclination. Therefore, the measurement stroke increases by “+ A”, and the measurement stroke and the actual stroke change along the straight line L2.

  In State 3, in which the reset position detection sensor 15 detects the detected portion 40 that is the reset position, the actual stroke is “BA”, but the measurement stroke is reset as “B”. Therefore, the measurement stroke has an error of “+ A” with respect to the actual stroke.

  Further, when the state 3 is shifted to the state 4, the roller support portion 13 is inclined in the negative direction (reverse stroke direction) from the state where the roller support portion 13 is inclined in the forward direction, and the rotating roller 12 is indicated by an arrow. In the figure, an extra counterclockwise rotation is performed, and the distance “−2A” for the amount of rotation is extra measured. For this reason, the measurement stroke is measured by “−A” less than the actual stroke. Therefore, the measurement stroke has an error of “−A” with respect to the actual stroke.

  On the other hand, as shown in FIG. 8, when the reset position detection sensor 115 is not disposed on the roller support 113, the measurement stroke has an error ΔE outside ± A with respect to the actual stroke, and the accuracy of the stroke measurement is lowered. .

  FIG. 8 is a diagram illustrating the relationship between the measurement stroke and the actual stroke of the stroke position detection sensor in the case of a conventional configuration in which the reset position detection sensor 115 is not disposed on the roller support portion 113. States 1 to 4 in FIG. 8 are the same as states 1 to 4 in FIG. The rotating roller 112 and the roller support portion 113 correspond to the rotating roller 12 and the roller support portion 13, respectively. The reset position detection sensor 115 corresponds to the reset position detection sensor 15, is disposed in the cylinder tube, and detects the detected portion 141 that is a magnet disposed in the piston 20.

  First, in the state 1 of FIG. 8, the piston rod 3 is at the reference position, that is, the detected portion 141 is at the actual stroke 0 position, the roller support portion 113 is not tilted, and the measurement stroke and actual stroke are “0”. . At this time, the position detected by the reset position detection sensor 115 is at a distance “B” in the positive direction (stroke direction) with respect to the reference position. The stroke position detection sensor detects a relative stroke as a measurement stroke with the position of the detected portion 141 as a reference position “0”.

  Thereafter, when the piston rod 3 extends in the positive direction, the measurement stroke and the actual stroke change along the straight line L1. Here, when the roller support portion 113 is in the state 2 inclined in the forward direction, the stroke position detection sensor causes the rotation roller 112 to rotate extraordinarily clockwise as indicated by the arrow due to the inclination. In order to measure the distance “A” excessively, the measurement stroke increases by “+ A”, and the measurement stroke and the actual stroke change along the straight line L2.

  In this state 2, in the state 3 in which the reset position detection sensor 115 detects the detected portion 141 that is the reset position, the measurement stroke by the stroke position sensor is “B + A”, but the measurement is performed by resetting the reset position detection sensor 115. The stroke is reset as “B”. Therefore, the measurement stroke is “B”, which is the same as the actual stroke.

  Further, when the state 3 is shifted to the state 4, the roller support 113 is inclined in the negative direction (reverse stroke direction) from the state in which the roller support 113 is inclined in the forward direction, and the rotating roller 112 is indicated by an arrow. In the figure, an extra counterclockwise rotation is performed, and the distance “−2A” for the amount of rotation is extra measured. For this reason, the measurement stroke is measured by “−2A” less than the reset actual stroke. Therefore, the measurement stroke has an error of “−2A” with respect to the actual stroke.

  That is, as shown in state 3 in FIG. 8, when the reset position detection sensor 115 detects the reset position while the roller support 113 is tilted in the forward direction, the measurement stroke “B” is reset to the actual stroke “B”. However, the reset is performed when the roller support 113 is tilted. In state 4, since the inclination of the roller support portion 113 changes from the positive direction to the negative direction, the measurement stroke decreases by “2A” from the straight line L1 (“−2A”), and is outside the range of the error ΔE. It will stick out.

  In the first embodiment, even when the roller support portion 13 is in the maximum inclination state in the positive direction or the negative direction, the reset position detection sensor 15 is disposed on the roller support portion 13, so that the measurement stroke is actual. The error ΔE is within ± A with respect to the stroke, and highly accurate stroke measurement is possible.

[Embodiment 2]
In the first embodiment described above, the two magnetic sensors S1 and S2 are used. However, in the second embodiment, the reset position d is detected using one magnetic sensor S3.

  FIG. 9 is a diagram showing the configuration and output waveform of the reset position detection sensor 15 used in Embodiment 2 of the present invention. As shown in FIG. 9, the reset position detection sensor 15 detects the detected portion 40 with one magnetic sensor S3. The magnetic sensor S3 outputs the output waveform LS3 shown in FIG. The arithmetic processing unit 7 detects the rising position of the output waveform LS3 as the reset position d.

[Embodiment 3]
In the first embodiment described above, the magnetic sensors S1 and S2 are used as the reset position detection sensor 15. However, in the third embodiment, eddy current sensors S51 and S52 are used as the reset position detection sensor 15. .

  As shown in FIG. 10, the eddy current sensors S <b> 51 and S <b> 52 are coils, and the detected portion 40 a of the piston rod 3 uses a metal having a lower resistance value than the material of the piston rod 3, such as copper.

  The arithmetic processing unit 57 corresponding to the arithmetic processing unit 7 corresponds to the eddy current sensors S51 and S52, and the oscillation circuit 50, the resonance circuits 51a and 51b, the detection circuits 52a and 52b, the amplification circuits 53a and 53b, and the differential amplification circuit. 54. The resonance circuits 51a and 51b are connected to the eddy current sensors S51 and S52, respectively, generate a high frequency resonance frequency corresponding to the oscillation frequency from the oscillation circuit 50, and generate a magnetic field of the resonance frequency from the eddy current sensors S51 and S52, respectively. ing. The detection circuits 52a and 52b detect the resonance waveforms of the resonance circuits 51a and 51b, respectively. The amplifier circuits 53a and 53b amplify the detected waveforms. The differential amplifier circuit 54 outputs a differential waveform obtained by subtracting the amplified waveform output from the amplifier circuit 53b from the amplified waveform output from the amplifier circuit 53a. Then, the arithmetic processing unit 57 detects the reset position based on the difference waveform and resets the stroke position in the same manner as in the first embodiment.

  When the eddy current sensors S51 and S52 approach, the detected portion 40a generates an eddy current in the detected portion 40a and increases its impedance. When the impedance of the detected part 40a increases, the resonance frequency of the resonance circuits 51a and 51b changes, and the amplitude of the detection waveform detected by the detection circuits 52a and 52b decreases. Therefore, as shown in FIG. 11A, the voltages of the amplified waveforms L53a and L53b output from the amplifier circuits 53a and 53b are lowered due to the proximity of the detected portion 40a.

  As described above, the differential amplifier circuit 54 generates a differential waveform L53ΔV obtained by subtracting the amplified waveform L53b from the amplified waveform L53a. The width W5 between the peak values of the differential waveform L53ΔV corresponds to the width W5 of the detected portion 40a. This differential waveform L53ΔV corresponds to the differential waveform LΔV shown in FIG.

[Embodiment 4]
In the third embodiment described above, the two eddy current sensors S51 and S52 are used. However, in the fourth embodiment, the reset position d is detected using one eddy current sensor S52.

  FIG. 12 is a diagram illustrating a configuration of a reset position detection sensor using the eddy current sensor S52 according to the fourth embodiment of the present invention. The reset position detection sensor shown in FIG. 12 deletes the eddy current sensor S51 shown in FIG. 10, and deletes the resonance circuit 51a, the detection circuit 52a, the amplification circuit 53a, and the differential amplification circuit 54 in the arithmetic processing unit 57. It is a thing. Therefore, as shown in FIG. 13, the arithmetic processing unit 57 ′ corresponding to the arithmetic processing unit 57 detects the rising position of the amplified waveform L53b output from the amplifier circuit 53b as a reset position and resets the stroke position.

[Embodiment 5]
In the first embodiment described above, the magnetic sensors S1 and S2 are used as the reset position detection sensor 15. However, in the fifth embodiment, an optical sensor is used as the reset position detection sensor 15. As shown in FIG. 14, the optical sensor has a light emitting element S60 and two light receiving elements S61a and S61b. That is, the reset position detection sensor according to the fifth embodiment includes two optical sensors, each having the light emitting element S60 and the light receiving element S61a as one optical sensor and the light emitting element S60 and the light receiving element S61b as one optical sensor.

  The arithmetic processing unit 67 corresponding to the arithmetic processing unit 7 receives light from the light projecting circuit 60 that emits light from the light emitting element S60, the light receiving circuits 61a and 61b that receive the light receiving signals from the light receiving elements S61a and S61b, and the output waveform of the light receiving circuit 61a. It has a differential amplifier circuit 62 that outputs a differential waveform obtained by subtracting the output waveform of the circuit 61b. The arithmetic processing unit 67 detects the reset position based on the difference waveform and resets the stroke position in the same manner as in the first embodiment.

  The detected part 40 b is a colored part, and the color of the colored part is different from the color of the sliding surface of the piston rod 3. Specifically, it is black and absorbs light. As the detected part 40b approaches the light reflection position, the reflection amounts of the light receiving circuits 61a and 61b decrease, and the voltages of the output waveforms L61a and L61b become smaller as shown in FIG. As shown in FIG. 15B, the differential amplifier circuit 62 generates a differential waveform L62ΔV obtained by subtracting the output waveform L61b from the output waveform L61a. The width W6 between the peak values of the differential waveform L62ΔV corresponds to the width W6 of the detected portion 40b. This differential waveform L62ΔV corresponds to the differential waveform LΔV shown in FIG.

  The detected part 40b may be a reflecting member that reflects light. Moreover, the member colored with the predetermined color may be sufficient. When colored with a predetermined color, it is preferable that the light receiving elements S61a and S61b can receive only the predetermined color.

[Embodiment 6]
In the fifth embodiment described above, two optical sensors are used. In the sixth embodiment, as shown in FIG. 16, the reset position is set by using one optical sensor including the light emitting element S60 and the light receiving element S61b. Detected.

  FIG. 16 is a diagram showing a configuration of a reset position detection sensor using one photosensor according to Embodiment 6 of the present invention. The reset position detection sensor illustrated in FIG. 16 is obtained by deleting the light receiving element S61a illustrated in FIG. 14 and deleting the light receiving circuit 61a and the differential amplifier circuit 62 in the arithmetic processing unit 67. Therefore, as shown in FIG. 17, the arithmetic processing unit 67 ′ corresponding to the arithmetic processing unit 67 detects the rising position of the output waveform L61b output from the light receiving circuit 61b as a reset position and resets the stroke position.

  Note that the reset process of the first embodiment shown in FIG. 6 can be applied to the third and fifth embodiments using two reset position detection sensors. In the second to sixth embodiments, by arranging the reset position detection sensor on the roller support portion 13, as shown in the first embodiment, the measurement stroke has an error ΔE within ± A with respect to the actual stroke. Thus, highly accurate stroke measurement is possible. Needless to say, the present invention is applied not only to hydraulic excavators but also to construction machines and industrial vehicles having work machines such as bulldozers, loaders, and graders.

DESCRIPTION OF SYMBOLS 1 Hydraulic cylinder, 2 Cylinder tube, 3 Piston rod, 4, 5 Hydraulic port, 7, 57, 57 ', 67, 67' Computation processing part, 8 Cylinder head, 9 Cylinder bottom, 10 Stroke position detection sensor, 11 Case, 12, 112 Rotating roller, 12C Rotation center shaft, 13H Cylinder head side oil chamber, 13B Cylinder bottom side oil chamber, 13
Roller support part, 14 pressure spring, 15, 115 reset position detection sensor, 20 piston, 30 rod seal, 31, 32 dust seal, 40, 40a, 40b detected part, 41 magnet, 42 groove, 43 non-magnetic material, 50 Oscillation circuit, 51a, 51b resonance circuit, 52a, 52b detection circuit, 53a, 53b amplification circuit, 54, 62 differential amplification circuit, 60 light projection circuit, 61a, 61b light reception circuit, 141 detected part, AR linear motion direction, d reset position, L1-L3 straight line, L53a, L53b amplified waveform, L53ΔV, L62ΔV, LΔV differential waveform, L61a, L61b, LS1, LS2, LS3 output waveform, LH, LB hydraulic oil, P1 end position, S1, S2, S3 Magnetic sensor, S51, S52 Eddy current sensor, S60 Light emitting element, S61a, S61b Light receiving element, SP ~SP7
Sampling points, W1, W5, W6 width, ΔE error, ΔG gap.

Claims (8)

A hydraulic cylinder with a stroke position detection function that measures the stroke position of a piston rod that moves directly in the cylinder tube,
A piston rod;
A rotating roller that rotates along with the linear movement of the piston rod is supported by a roller support portion, a stroke position of the piston rod is detected based on the rotation of the rotating roller, and the piston is further attached to the roller support portion. A hydraulic cylinder with a stroke position detection function, comprising a stroke position detection sensor having a reset position detection sensor for detecting a detected portion corresponding to a reset position provided at a predetermined position on a surface of a rod.   The hydraulic cylinder with a stroke position detection function according to claim 1, wherein the reset position detection sensor is provided below a rotation center axis of the rotation roller.   The hydraulic cylinder with a stroke position detection function according to claim 1 or 2, wherein the reset position detection sensor is supported by the same fulcrum as the rotation roller.   The stroke according to any one of claims 1 to 3, wherein the reset position detection sensor and the rotating roller are arranged on a straight line parallel to the linear movement direction of the piston rod. Hydraulic cylinder with position detection function. The reset position detection sensor is a magnetic sensor,
The stroke position according to any one of claims 1 to 4, wherein the detected portion is a portion subjected to a surface treatment with a nonmagnetic material in a groove provided on a ground of the piston rod. Hydraulic cylinder with detection function. The reset position detection sensor is an eddy current sensor,
The said to-be-detected part is a metal in the groove | channel provided in the ground of the said piston rod, and resistance value is lower than the material of the said piston rod, The any one of Claims 1-4 characterized by the above-mentioned. Hydraulic cylinder with stroke position detection function. The reset position detection sensor is an optical sensor,
The said to-be-detected part is a colored part provided in the sliding surface of the said piston rod, The color of the said colored part differs from the color of the sliding surface of the said piston rod. A hydraulic cylinder with a stroke position detection function according to any one of the above. The reset position detection sensor is an optical sensor,
5. The hydraulic pressure with a stroke position detecting function according to claim 1, wherein the detected portion is a light reflecting member or a light absorbing member provided on a sliding surface of the piston rod. Cylinder.

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