JP2012225656A - Stroke position detection apparatus for actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an actuator stroke position detection apparatus capable of grasping a stroke position even when an output signal from a position detecting sensor is changed due to a change of a pattern such as secular deterioration.SOLUTION: The actuator stroke position detection apparatus includes: a pattern X drawn on a rod 4 of a hydraulic cylinder 1 (actuator) and including a reference part having no change in a stroke direction range and an encoded part allowed to be changed so as to specify a stroke position; and a control part which determines a position signal outputted from a position detection sensor (position detection part) based on a reference signal outputted from a reference sensor (reference detection part) for detecting the reference part and grasps a stroke position.

Description

  The present invention relates to a stroke position detection device that detects a stroke position of an actuator.

  Conventionally, a construction machine or specially equipped vehicle equipped with a work device detects a stroke position (stroke position) of a hydraulic cylinder (actuator) that is a drive source of the work device, and grasps a posture of the work device from a detection result of the position. Thus, the speed of the working device is increased or decreased in a desired posture or the working device is stopped. Then, in order to grasp the stroke position of the hydraulic cylinder, for example, an encoded pattern is drawn on the rod of the hydraulic cylinder, a plurality of sensors (position detection units) are fixed to the cylinder tube, and the pattern and the plurality of sensors are relative to each other. The pattern is read by a plurality of sensors and the stroke position is grasped from the detection or non-detection state of the plurality of sensors.

  A process from the detection to the grasping of the stroke position will be described with reference to FIG. FIG. 7A shows a pattern drawn on a rod, which has three lines L01 to L03, and each line is divided into eight equal parts. The rough surface Xn is shown in black in the drawing, and is a portion where the surface of the rod is roughened by shot blasting so as to be rough. The other part is the bright surface Xp, which is the part that has been subjected to chrome plating. The lines L01 to L03 are encoded by selectively arranging the rough surface Xn and the bright surface Xp.

S01 to S03 shown in FIG. 7B are reflection type photoelectric proximity sensors that irradiate the detection object with the detection light, receive the reflection light, and output signals corresponding to the magnitude (light quantity) of the reflection light ( Voltage value). Sensors S01 to S03 detect lines L01 to L03, respectively. From the output signals from the sensors S01 to S03, for example, when S01 is “None”, S02 is “Yes”, and S03 is “None”, the control device C0 outputs S01 and S03 as output values. Therefore, it is determined that L01 and L03 have detected the rough surface Xn, and S02 has detected the bright surface Xp because of the output value. Then, “Position 7” is selected as a position that matches the combination of the bright surface Xp and the rough surface Xn from the table stored in advance in the memory of the control device C0, and the current stroke position is “Position 7”. recognize. Note that the combinations and positions of the detection results of the three sensors are set to be one-to-one (not overlapping).
Thus, according to the said detection apparatus, it can grasp | ascertain which position of the stroke position of a hydraulic cylinder exists in eight positions, and can operate a working device as desired.

JP 2002-48599 A

  However, when the encoded pattern becomes thinner due to aging, the pattern is detected even though the position detector originally had to detect the pattern and output the corresponding output signal. In some cases, only an output signal corresponding to the case of not being output is output. FIG. 8 is a diagram showing a state after aging degradation. FIG. 8A shows a degraded pattern, and FIG. 8B shows an output signal detected by each of the sensors S01 to S03. Here, a case where the cylinder has actually extended to a position corresponding to “position 7” will be described as an example. The rough surface Xn inherently diffuses light emitted from the sensor to reduce the amount of light returned to the sensor, but the rough surface Xn that has changed over time has less irregularities and reflects the light emitted from the sensor toward the sensor. It will be. Then, the output value of each sensor that detects the pattern (especially sensor S01) is “Yes” for S01, “Yes” for S02, and “Yes” for S03. The control device C0 considers that the bright surface Xp has been detected because all the output values are present, and determines that all of the positions match the combination of the bright surfaces Xp as “position 1”. In this way, the control device C0 misidentifies that the output signal from the sensors S01 to S03 “always detect the bright surface Xp”, and the actuator from the position corresponding to “all the sensors detect the bright surface Xp”. There is a risk of determining that is not working.

  The present invention has been made in view of the above circumstances, and even when a pattern deteriorates due to use over time, the encoding unit is appropriately recognized from the output from the position detection unit, and the stroke position is determined. It can be so.

  In order to achieve the above object, an actuator stroke position detection device according to the present invention is provided in an actuator, and changes a reference portion that does not change within the range in the stroke direction of the actuator and a coding portion that can change the stroke position. A reference detection unit that detects a reference part of the pattern and outputs a reference signal based on the detection result, and detects a coding unit of the pattern and outputs a position signal based on the detection result A detection unit having a position detection unit, and a control device that determines a position signal of the position detection unit based on a reference signal of the reference detection unit and determines an encoding unit by the position detection unit. . According to the present invention, even if the position signal from the position detection unit changes due to the pattern change, the reference signal of the reference detection unit that has changed to the same extent is used as a reference, so that the state of the encoding unit can be recognized. it can.

  Further, the reference portion of the pattern may be different from the portion where the pattern is not drawn, and thereby the reference detection portion indicates that the position of the pattern and the detection means has shifted due to the rotation of the rod. It can be known from the detection result.

  According to the present invention, even if the position signal from the position detection unit changes due to the pattern change, the reference signal of the reference detection unit that has changed to the same extent is used as a reference, so that the state of the encoding unit can be recognized. it can.

It is a partial cross section figure of the hydraulic cylinder provided with the stroke position detection apparatus of this invention. It is the figure which developed the pattern of the present invention on the plane. It is the figure which showed typically the process until the pattern X after aged deterioration is detected and a stroke position is grasped | ascertained. It is the figure which showed typically the correction process in a control apparatus. It is the figure which showed typically the correction process by the side of the bright surface in a control apparatus. It is the figure which showed the other process typically. It is the figure which showed the conventional process typically, and is a figure which shows the state before aged deterioration. It is the figure which showed the conventional process typically, and is a figure which shows the state after aged deterioration.

  FIG. 1 is a partially cutaway view of a hydraulic cylinder 1 to which the present invention is applied.

  The hydraulic cylinder 1 includes a cylinder tube 2, a piston 3 inserted into the cylinder tube 2, and a rod 4 fixed to the piston 3.

The cylinder tube 2 includes a cylindrical tube body 21, a head cap 23 welded and fixed to one end of the tube body 21, and a rod cover 24 fixed to the other end. A hole 23a is provided in the center of the head cap 23, and the rod cover 24 is fixed by fitting a male screw 24a provided on the outer periphery of the female screw 21a formed on the inner wall of the tube body 21 and screwing it. .
On the outer periphery of the tube body 21, an extension side port 21a and a contraction side port 21b are formed. The joints 22a and 22b are fixed to the port 21a and the port 21b, respectively.

  The piston 3 is fixed to one end of the rod 4 by a lock nut 41, and the other end of the rod 4 protrudes outside the cylinder tube 2 through a hole 24 b provided in the rod cover 24. And the ring 42 provided with the hole 42a is weld-fixed to the other end which the rod 4 protruded.

A pattern X is drawn on the outer periphery of the rod 4 by shot blasting.
A sensor group S for reading the pattern X of the rod 4 is fixed to the end surface of the rod cover 24. The output signal of the sensor group S is input to the control device C so that the stroke of the cylinder 1 can be grasped from the pattern X.

  FIG. 2 is a diagram in which a pattern X drawn on the outer periphery of the rod 4 is developed on a plane.

  The pattern X includes an encoding unit Xa and a reference unit Xb. The encoding part Xa of the pattern X has nine lines L1 to L9, generally draws a pattern called a gray code, and the lines L1 to L9 in the circumferential direction of the rod 4 (vertical direction in the figure). The combination of the rough surface Xn and the bright surface Xp does not overlap in all strokes of the hydraulic cylinder 1, and the stroke position of the hydraulic cylinder 1 is controlled by the combination of the rough surface Xn and the bright surface Xp of the lines L1 to L9. Device C can grasp.

  On the other hand, the reference portion Xb has a first reference row Ln and a second reference row Lp. The first reference row Ln is subjected to a surface treatment so that the entire surface becomes a rough surface Xn over the stroke direction of the hydraulic cylinder 1 in the range where the pattern X is drawn. In the second reference row Lp, the rough surface Xn is not applied in the stroke direction of the hydraulic cylinder 1 in the range where the pattern X is drawn, and the chrome plating is still applied.

The sensor group S detects position detection sensors S1 to S9 (position detection unit) that detect the lines L1 to L9 of the encoding unit Xa, respectively, and the first and second reference rows Ln and Lp of the reference unit Xb. It consists of reference sensors Bn and Bp (reference detection unit). Each sensor of the sensor group S is a reflective photoelectric proximity sensor. The position detection sensors S1 to S9 and the reference sensors Bn and Bp irradiate the detection object with the detection light, receive the reflected light, and output an output signal (voltage value) corresponding to the magnitude (light quantity) of the reflected light. . In the present embodiment, when the sensor group S detects the bright surface Xp, 10 mV is output as the output signal, and when the rough surface Xn is detected, 0 mV is output as the output signal. Yes.
The output signals output from the position detection sensors S1 to S9 are also referred to as position signals, and the output signals output from the reference sensors Bn and Bp are also referred to as reference signals.

  That is, the control device C receives the output signals of the position detection sensors S1 to S9 in the sensor group S, and the encoding units L1 to L9 corresponding to the position detection sensors S1 to S9 are brightened with the rough surface Xn from the output signals. It is determined which surface is the surface Xp. Then, the control device C calculates the stroke position of the hydraulic cylinder 1 from the combination of the rough surface Xn and the bright surface Xp of the encoding units L1 to L9.

  In addition, the direction shown by the arrow in the figure is the direction in which the rod 4 (pattern X drawn on the rod 4) and the sensor group S move relative to each other when the cylinder 1 expands and contracts.

Processing in the control device C of the present invention will be described with reference to FIGS.
FIG. 3 schematically shows a process until the pattern X after aging is detected and the position in the stroke is grasped. FIG. 4 schematically shows the correction process in the control device. FIG. In order to schematically show, the pattern X is a total of five lines of the first reference row Ln and the second reference row Lp of the reference portion Xb and the lines L1 to L3 of the encoding portion Xa, and the sensor group S is also composed of the reference sensors Bn and Bp. Only a total of five position detection sensors S1 to S3 aligned with the lines L1 to L3 of the encoding unit are shown.

  FIG. 3A schematically shows a part of the pattern X that has deteriorated over time. In the pattern X, the unevenness of the rough surface Xn is particularly smoothed by the seal 24d fixed to the inner surface of the rod cover 24, and the detection light of the sensor group S is easily reflected to the sensor group. When each sensor group S detects such a pattern X, the output signal shown in FIG. Specifically, when the reference sensors Bn and Bp and the position detection sensors S1 to S3 detect the bright surface Xp, the output signal is 10 mV, and when the rough surface Xn after aging is detected, the output signal Is 2 mV.

  A case where the cylinder extends to a position corresponding to “position 7” will be described as an example. When the pattern X shown in FIG. 3A is detected, the position detection sensors S1 to S3 output 2 mV for S1, 10 mV for S2, and 2 mV for S3, respectively. If this is the case, the control device C has all the output signals of the position detection sensors S1 to S3 (not 0 mV), so that the lines L1 to L3 are all in the “position 1” while misidentifying that they are the bright surface Xp. It will be recognized. Therefore, the control device C performs correction processing with reference to the output signal of the reference sensor Xn.

  As shown in FIG. 3B, since the output signal of the reference sensor Xn that always detects the rough surface Xn is 2 mV, when the control device C detects the rough surface Xn, the output signal changes to 2 mV. I can recognize that. Then, the control device C changes the threshold value for distinguishing the rough surface Xn and the bright surface Xp from 0 mV to 3 mV, for example. Then, before the correction process, as shown in FIG. 4A, the position detection sensors S1 and S3 exceed the threshold value of 0 mV, so that the control device C determines that all of them are the bright surface Xp. However, after the correction processing shown in FIG. 4B, since all areas A1 of 3 mV or less are determined to be rough surfaces Xn, it can be recognized that S1 and S3 are rough surfaces Xn. Thereby, the control apparatus C can recognize that L1-L3 exists in "position 7" from the combination of "rough surface Xn", "bright surface Xp", and "rough surface Xn".

  FIG. 5 is a diagram schematically showing correction processing on the bright surface Xp side in the control device. The brightness level of the bright surface Xp may be weakened due to aging of the plating. As a result, the amount of light reflected by the bright surface Xp also decreases, and the output signal of the position detection sensor naturally changes. In the illustrated example, it is assumed that the output signal of the position detection sensor S2 has decreased to 9 mV. When the output signal exceeds 10 mV, since it is determined as the bright surface Xp, the control device C cannot determine that L2 is “the bright surface Xp”. Therefore, since the output signal from the reference sensor Bp that always detects the bright surface Xp is also lowered to 9 mV, the threshold for determining the bright surface Xp is changed from 10 mV to, for example, 8 mV, so that L2 is bright. It can be recognized that the surface is Xp (see FIG. 5B). In this embodiment, by having an area A3 in which either the rough surface Xn or the bright surface Xp cannot be determined, erroneous recognition at the time of identification of the rough surface Xn and the bright surface Xp is suppressed. However, the threshold value for determining whether or not the surface is the rough surface Xn and the threshold value for determining whether or not the surface is the bright surface Xp are gradually approached by the correction process described above, and the area A3 disappears. In such a case, it can be determined that the rough surface Xn and the bright surface Xp drawn on the rod 4 have deteriorated to a state where they cannot be distinguished. Thus, the rod 4 can be exchanged or the pattern X can be redrawn.

  Next, another embodiment will be described with reference to FIG. In the present embodiment, the basic configuration and processing are the same as those of the above-described embodiment, and thus the description thereof will be omitted.

  FIG. 6 is a diagram schematically showing processing when either the rod 4 or the sensor group S is relatively moved in the circumferential direction by an external force. In the case shown in FIG. 6, when the sensor group S is rotated, the reference sensor Bn is the line L1 of the encoding unit Xa, the position detection sensor S1 is the line L2, the position detection sensor S2 is the line L3, and the position detection sensor. S3 detects the surface (corresponding to the second reference row Lp) of the rod 4 on which the encoding part X is not drawn.

The case where the cylinder has extended to the position corresponding to “position 7” will be described as an example. When the pattern X shown in FIG. 6A is detected, the output signals of the position detection sensors S1 to S3 are respectively Since S1 is 10 mV, S2 is 2 mV, and S3 is 10 mV, the control device C determines that the lines L1 to L3 are “bright surface Xp”, “rough surface Xn”, and “bright surface Xp”, respectively. It will be recognized as being in position 4 ”. However, if the hydraulic cylinder 1 is moved to the next “position 8” due to the expansion / contraction drive of the hydraulic cylinder 1, the output signals of the position detection sensors S1 to S3 do not change, but the reference sensor Bn detecting the line L1 does not change. The output signal changes to 10 mV. Then, since the reference sensor Bn that normally detects the rough surface Xn always detects the rough surface Xn, the control device C can determine that the rod 4 and the sensor group S are relatively moved. . By displaying an error on a display device (not shown) based on this determination, it is possible to notify that there is a risk of erroneous recognition or that it has already been erroneously recognized.
Note that the reference sensor Bp that always detects the bright surface Xp may determine that the rod 4 and the sensor group S are moving relative to each other when the rough surface Xn is detected.

In addition, this invention is not limited to the said Example, A various Example is possible within the scope of the present invention.
In the above-described embodiment, the pattern X is drawn on the rod 4, but it may be drawn on other than the rod 4, for example, on a member interlocked with the expansion and contraction of the cylinder. Further, although the reference portion Xb of the pattern X includes both the rough surface Xn and the bright surface Xp, only one of them may be provided. And the encoding part Xa of the pattern X can increase / decrease the lines L1-L9 according to the resolution and the stroke amount. The gray code is used to encode the encoding unit Xa, but it is a method of recognizing the stroke from the absolute type encoding or the count number at which the bright surface Xp and the rough surface Xn are switched. It may be an incremental type.

  Although the reflective photoelectric proximity sensor is used as the sensor of the sensor group S, other types of sensors may be used. For example, various sensors such as a transmission photoelectric sensor and an ultrasonic sensor can be used instead. The sensor group S is a combination of a plurality of sensors (11 sensors in the embodiment), but the single sensor has both the functions of the reference sensors Bn and Bp and the position detection sensors S1 to S9. A sensor that can detect the pattern encoding portion Xa and the reference portion Xb at a time, such as a CCD camera, may be used.

  In the above embodiment, the present invention is applied to a hydraulic cylinder. However, the present invention may be applied to a detection device that detects stroke positions of various other types of actuators such as a swing type and a rotary type.

DESCRIPTION OF SYMBOLS 1 Hydraulic cylinder 2 Cylinder tube 3 Piston 4 Rod S Sensor group (detection means)
Sa position detection unit Sb reference detection unit X pattern Xa encoding unit Xb reference unit C control device

Claims (2)

A pattern having a reference portion that is provided in the actuator and has a reference portion that does not change within the range in the stroke direction of the actuator and a coding portion that changes the stroke position so as to be specified;
A reference detection unit that detects a reference portion of the pattern and outputs a reference signal based on the detection result; and a position detection unit that detects the encoding unit of the pattern and outputs a position signal based on the detection result. Detection means;
An actuator stroke position detection device comprising: a control device that determines a position signal of a position detection unit based on a reference signal of the reference detection unit and determines an encoding unit by the position detection unit.   2. The stroke position detecting device for an actuator according to claim 1, wherein the reference portion of the pattern is different from a portion where the pattern is not drawn.

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