JP2010229663A - Determining method for cause of sensor failure in working vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a determining method for cause of sensor failure in a working vehicle. <P>SOLUTION: In this determining method for cause of sensor failure in the working machine, stroke values detected by the sensor when a hydraulic cylinder for the working machine reaches stroke limits on an extension side and a contraction side, respectively, are sampled to determine whether a state of the sensor belongs to a group of "positional deviation" or "normal" or "abnormality of sensor" or a group of "play" or "improper data" depending on whether both of standard deviation on the extension side and the contraction side are less than a fixed value or not. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a method for determining a cause of failure of a sensor in a work vehicle including a work machine operated by a work machine hydraulic cylinder and a sensor that indirectly or directly detects a stroke of the work machine hydraulic cylinder. Is.

  FIG. 1 shows the structure of a work machine 2 provided at the front part of the vehicle body 1a of the wheel loader 1.

  As shown in FIG. 1, the work implement 2 includes a boom 3 and a bucket 4, and the base of the boom 3 is rotatably attached to the vehicle body 1 a in the upward and downward directions. A bucket 4 is attached to the tip so as to be rotatable in the dumping direction and the tilting direction.

  A rod 5a of a boom hydraulic cylinder 5 is attached to the boom 3, and a body 5b of the boom hydraulic cylinder 5 is attached to the vehicle body 1a. When the rod 5a of the boom hydraulic cylinder 5 is extended, the boom 3 is operated upward, and when the rod 5a of the boom hydraulic cylinder 5 is retracted, the boom 3 is operated downward.

  A bell crank 7 is swingably attached to the boom 3. A rod 6 a of a bucket hydraulic cylinder 6 is attached to one side of the bell crank 7 in the longitudinal direction. A body 6b of a hydraulic cylinder 6 for bucket is attached to the vehicle body 1a. One end of a rod 8 is attached to the other longitudinal direction of the bell crank 7, and the other end of the rod 8 is attached to the bucket 4. When the rod 6a of the bucket hydraulic cylinder 6 extends, the bucket 4 operates in the tilt direction, and when the rod 6a of the bucket hydraulic cylinder 6 retracts, the bucket 4 operates in the dump direction.

  The boom 3 rotates about the rotation shaft 3a at the base, and a boom angle sensor 9 for detecting the rotation angle θ of the boom 3 (hereinafter referred to as boom angle θ) is provided on the rotation shaft 3a. ing.

The bucket 4 rotates in conjunction with the swing of the bell crank 7, and the swing shaft 7 a of the bell crank 7 detects the swing angle φ (hereinafter, bell crank angle φ) of the bell crank 7. A bell crank angle sensor 10 is provided. The boom angle sensor 9 and the bell crank angle sensor 10 are constituted by, for example, potentiometers.

Stroke Lk of bucket hydraulic cylinder 6 (hereinafter referred to as bucket cylinder stroke Lk) is uniquely calculated based on boom angle θ, bell crank angle φ, and known data relating to the link mechanism including bell crank 7 and rod 8. can do.

The stroke Lm of the boom hydraulic cylinder 5 (hereinafter referred to as the boom cylinder stroke Lm) can be uniquely calculated based on the boom angle θ and known data relating to the boom 3.

The boom 3 is operated by operating a boom operation lever 11 provided in the cab. The bucket 4 is operated by operating a bucket operation lever 12 provided in the cab.

The following Patent Document 1 describes an invention in which, for a hydraulic excavator, when a potentiometer that detects the angle of a work machine is deviated from a normal angle, the angle deviation is automatically corrected by a controller. Has been.

Further, the following Patent Document 2 discloses an invention in which a position sensor of a bucket provided in a hydraulic excavator is calibrated by an operator's operation to correct a slight error of each part during assembly or an individual difference of the position sensor itself. Is described.

Further, in Patent Document 3 below, when the change rate of the detected angle of the potentiometer that detects the angle of the work machine exceeds the normal change rate, it is determined that the potentiometer is abnormal. The invention has been described.

Japanese Patent Laid-Open No. 5-280074 Japanese Patent Laid-Open No. 7-3845 JP-A-8-74295

  Information on the stroke of the hydraulic cylinder for work implement, for example, information on the bucket cylinder stroke Lk is important information for controlling the work implement 2 of the wheel loader 1. If the boom angle sensor 9 and the bell crank angle sensor 10 composed of potentiometers are momentarily greatly deviated from the normal mounting position or gradually deviated from the normal mounting position due to aging, the bucket cylinder stroke Lk is calculated. The work machine 2 is not accurately controlled. For this reason, if the sensor is displaced from the mounting position, the amount of mounting position deviation is detected immediately, the sensor mounting position deviation is automatically corrected, and the sensor is quickly detected at the work site. Needs to be restored from the failure state to the normal state.

  However, the cause of a failure in which a detection error occurs in the sensor is not limited to a simple “positional deviation” in which a positional deviation occurs from a regular attachment position by a certain amount of deviation. In other words, the cause of the sensor failure is “position displacement” that can detect the mounting position deviation and automatically correct the sensor mounting position deviation, “roughness” that cannot simply correct the position deviation automatically, “sensor abnormality” There is. In the “backlash” of the sensor mounting portion, a positional shift occurs randomly, so that the positional shift cannot be automatically corrected, and the sensor mounting portion needs to be repaired. The “sensor abnormality” is a case where an abnormality has occurred inside the sensor. It is necessary to replace or repair the sensor itself, and automatic correction cannot be performed.

If the cause of the sensor failure is delayed and time is required for recovery, work efficiency will be greatly impaired.

  The present invention has been made in view of such circumstances, and by automatically determining and identifying the cause of failure of a sensor that directly or indirectly detects the stroke of a hydraulic cylinder for work implements in a work vehicle, The problem to be solved is to be able to take measures according to the cause of failure at an early stage.

Each of the inventions described in Patent Documents 1, 2, and 3 is based on the assumption that only a simple “positional deviation” that can automatically correct the positional deviation of the sensor occurs in the sensor. It is not assumed that other failures such as “rattle” and “sensor abnormality” will occur. Therefore, each patent document does not suggest any problem of the present invention.

The first invention is
A sensor failure cause determination method applied to a work vehicle having a work machine operated by a work machine hydraulic cylinder and a sensor for indirectly or directly detecting a stroke of the work machine hydraulic cylinder. There,
Sampling the stroke value detected by the sensor when the hydraulic cylinder for work implement reaches the stroke limit on each of the expansion side and the contraction side;
Calculating the standard deviation of the detected stroke value of the collected sensor separately for the expansion side and the contraction side;
Depending on whether both the standard deviation on the expansion side and the contraction side are less than a certain value, the sensor status is a group of “positional deviation”, “normal” or “sensor abnormality” or “backlash”. Or determining whether it is a “data inappropriate” group,
If it is determined that the sensor status is a group of “rattle” or “data inappropriate”, both the standard deviations on the expansion side and the contraction side are equal to or greater than a certain value, or the expansion side and the contraction side are Determining whether the state of the sensor is “backlash” or “data inappropriate” depending on whether only one of the standard deviations is greater than or equal to a certain value;
If it is determined that the sensor status is a group of “positional deviation”, “normal” or “sensor abnormality”, the positional deviation between the theoretical stroke limit value and the detected stroke value of the hydraulic cylinder for work implements is detected. Obtained for each of the stretch side and the contraction side, and depending on whether the deviation between the misalignment on the stretch side and the misalignment on the shrink side is less than a predetermined value or greater than a predetermined value, ”Or“ normal ”group or“ sensor abnormality ”, and
If it is determined that the sensor status is a group of “positional deviation” or “normal”, the positional deviation between the theoretical stroke limit value of the hydraulic cylinder for work implements and the detected stroke value is the expansion side and the contraction side. Determining whether the state of the sensor is “positional deviation” or “normal” according to whether or not at least one of them is equal to or greater than a predetermined value.
The second invention is the first invention,
When the sensor state is determined to be `` position deviation '', the sensor position deviation is corrected according to the position deviation between the theoretical stroke limit value of the hydraulic cylinder for work implements and the detected stroke value. To do.

The third invention is the first invention,
When the hydraulic pressure in the work machine hydraulic cylinder reaches the relief pressure on the expansion side and the contraction side, or when the discharge pressure of the hydraulic pump that supplies the hydraulic oil to the work machine hydraulic cylinder reaches the relief, the work machine It is characterized in that it is determined that the hydraulic cylinder has reached the stroke limit on each of the expansion side and the contraction side, and the detection stroke value of the sensor at that time is collected.

The fourth invention is the third invention,
When the hydraulic pressure in the hydraulic cylinder for work implements changes rapidly from the threshold value for detecting that it is operating at a light load to a pressure set slightly lower than the relief pressure, the stroke limit is reached. It is characterized by judging that it has reached.

The fifth invention is the third invention,
As the hydraulic pressure in the hydraulic cylinder for work implements has gradually changed from the threshold value for detecting operation with a light load to the pressure set slightly lower than the relief pressure over time. And determining that the stroke limit has been reached.

  According to the first aspect of the present invention, it is possible to accurately identify whether the sensor state is “normal”, “position shift”, “sensor abnormality”, or “backlash”, and the cause of the sensor failure is the position shift automatically. It is possible to discriminate whether it is “positional deviation” that can be corrected to “smooth”, “sensor abnormality” or “backlash” that cannot be automatically corrected. As a result, measures corresponding to the cause of the failure can be taken early. Furthermore, when the collected data is inappropriate, it can be determined that the data is “data inappropriate”, and it is not erroneously determined that the sensor is faulty. As a result, the cause of the failure is accurately identified, and the reliability of the determination result of the failure cause is improved.

In the second aspect of the invention, when the sensor state is determined to be “positional deviation”, the positional deviation of the sensor is corrected in accordance with the positional deviation between the theoretical stroke limit value and the detected stroke value of the hydraulic cylinder for the work implement. Therefore, the sensor can be automatically and quickly restored from the failure state to the normal state at the work site.

In the third invention, when the hydraulic pressure in the working machine hydraulic cylinder reaches the relief pressure on each of the expansion side and the contraction side, or the discharge pressure of the hydraulic pump that supplies the hydraulic oil to the working machine hydraulic cylinder reaches the relief. Sometimes, it was determined that the hydraulic cylinder for work equipment reached the stroke limit on each of the expansion side and the contraction side, and the detection stroke value of the sensor at that time was sampled to determine the cause of the sensor failure. Data can be collected sequentially during work in which the work vehicle normally operates the hydraulic cylinder for work implements to the stroke limit, and if a sensor failure occurs during the work, it is determined that there is a failure at an early stage. can do. As a result, if a failure that can correct the misalignment occurs during the work, the work can be automatically corrected during the work to quickly recover to a normal state, and the work can be continued. In addition, even if it is a failure that cannot be corrected for misalignment, the cause of the failure is identified early during the work, so it is possible to continue the work by quickly restoring the normal state without losing work efficiency. Become. Specifically, the hydraulic pressure in the hydraulic cylinder for work implements has rapidly changed from a threshold value for detecting that it is operating at a light load to a pressure set slightly lower than the relief pressure. From the threshold value for detecting that the stroke limit has been reached (fourth invention) or detecting that the hydraulic pressure in the hydraulic cylinder for work implements is operating with light load as time passes, It is determined that the stroke limit has been reached when the pressure has been changed to a pressure set slightly lower than the relief pressure (fifth invention).

FIG. 1 is a view showing a structure of a working machine provided at a front portion of a vehicle body of a wheel loader. FIG. 2 is a diagram showing a hydraulic circuit having a series circuit configuration mounted on the wheel loader. FIG. 3 is a diagram showing a hydraulic circuit having a parallel circuit configuration mounted on the wheel loader. FIG. 4 is a diagram showing the contents stored in the storage means of the controller. FIGS. 5A, 5B, 5C, 5D, and 5E are views showing respective postures of the work implement. FIGS. 6A, 6B, 6C, and 6D are diagrams for explaining a method of determining the time point when the stroke limit is reached. FIGS. 7A, 7B, 7C, and 7D are views for explaining conditions for determining the stroke limit time of the bucket hydraulic cylinder and measuring the detected stroke value. 8 (a) and 8 (b) are diagrams corresponding to FIG. 4, and a plurality of points of the work implement posture made up of the detected stroke value and the detected boom angle value are collected, and these collected points, It is the map figure which contrasted. FIGS. 9 (a) and 9 (b) are diagrams corresponding to FIG. 4, in which a plurality of work implement posture points made up of detected stroke values and detected boom angle values are collected. It is the map figure which contrasted. FIG. 10 is a flowchart showing a processing procedure performed by the controller. FIGS. 11A and 11B are histograms obtained from a specified number of data. 12A and 12B are histograms obtained from a specified number of data.

  Embodiments of a sensor failure cause determination method for a work vehicle according to the present invention will be described below with reference to the drawings.

FIG. 1 shows the structure of a work machine 2 provided at the front part of the vehicle body 1a of the wheel loader 1.

  As shown in FIG. 1, the work implement 2 includes a boom 3 and a bucket 4, and the boom 3 is attached to the vehicle body 1 a so as to be rotatable about a rotation shaft 3 a in an upward direction and a downward direction. The bucket 4 is attached to the tip of the boom 3 so as to be rotatable around the rotation shaft 3b in the dumping direction and the tilting direction.

  A rod 5a of a boom hydraulic cylinder 5 is attached to the boom 3, and a body 5b of the boom hydraulic cylinder 5 is attached to the vehicle body 1a. When the rod 5a of the boom hydraulic cylinder 5 is extended, the boom 3 is operated upward, and when the rod 5a of the boom hydraulic cylinder 5 is retracted, the boom 3 is operated downward.

  A bell crank 7 is swingably attached to the boom 3. A rod 6 a of a bucket hydraulic cylinder 6 is attached to one side of the bell crank 7 in the longitudinal direction. A body 6b of a hydraulic cylinder 6 for bucket is attached to the vehicle body 1a. One end of a rod 8 is attached to the other longitudinal direction of the bell crank 7, and the other end of the rod 8 is attached to the bucket 4. When the rod 6a of the bucket hydraulic cylinder 6 extends, the bucket 4 operates in the tilt direction, and when the rod 6a of the bucket hydraulic cylinder 6 retracts, the bucket 4 operates in the dump direction.

  A boom angle sensor 9 that detects a rotation angle θ of the boom 3 (hereinafter referred to as a boom angle θ) is provided on the pivot shaft 3 a at the base of the boom 3.

  Here, when the boom 3 is in a horizontal posture, that is, a posture in which a line segment connecting the boom rotation shafts 3a and 3b is parallel to the horizontal line, the boom angle θ is set to zero (θ = 0), and the boom horizontal The direction in which the boom 3 is raised with respect to the posture is a positive value, and the direction in which the boom 3 is lowered with respect to the horizontal posture of the boom is a negative value.

The bucket 4 rotates in conjunction with the swing of the bell crank 7, and the swing shaft 7 a of the bell crank 7 detects the swing angle φ (hereinafter, bell crank angle φ) of the bell crank 7. A bell crank angle sensor 10 is provided. The boom angle sensor 9 and the bell crank angle sensor 10 are constituted by, for example, potentiometers.

Stroke Lk of bucket hydraulic cylinder 6 (bucket cylinder stroke Lk) is uniquely calculated based on boom angle θ, bell crank angle φ, and known data relating to the link mechanism including bell crank 7 and rod 8. Can do. Note that the height of the boom 3 can be detected instead of the boom angle, and the bucket cylinder stroke Lk can be calculated based on the boom height. The bucket cylinder stroke Lk is defined as a value that increases as it extends toward the tilt side, with the stroke value at the time of the most contraction being 0.

The boom angle sensor 9 and the bell crank angle sensor 10 constitute a sensor that indirectly detects the bucket cylinder stroke Lk.

A sensor that directly detects the bucket cylinder stroke Lk may be provided.

The stroke Lm (boom cylinder stroke Lm) of the boom hydraulic cylinder 5 can be uniquely calculated based on the boom angle θ and the known data regarding the boom 3.

The boom angle sensor 9 constitutes a sensor that indirectly detects the boom cylinder stroke Lk.

A sensor that directly detects the boom cylinder stroke Lm may be provided.

The boom 3 is operated by operating a boom operation lever 11 provided in the cab.

The bucket 4 is operated by operating a bucket operation lever 12 provided in the cab.

  2 and 3 show a hydraulic circuit mounted on the wheel loader 1. 2 or 3 is mounted on the wheel loader 1.

  FIG. 2 shows a series circuit configuration in which the boom control valve 15 and the bucket control valve 16 are arranged in series with respect to the pump discharge oil passage 14. FIG. 3 shows a parallel circuit configuration in which the boom control valve 15 and the bucket control valve 16 are provided in the pump discharge oil passages 14a and 14b, respectively.

  As shown in FIG. 2, the hydraulic pump 13 is a variable displacement type, and its discharge port 13 a communicates with the pump discharge oil passage 14. The hydraulic pump 13 is driven by an engine (not shown) and sucks hydraulic oil from the tank 18 and discharges the pressure oil to the pump discharge oil passage 14. The swash plate 13 b of the hydraulic pump 13 is driven by a swash plate control valve 19. The controller 20 outputs a swash plate control command to the electric control valve 21 as an electric signal. The electric control valve 21 converts an electric signal into a hydraulic pressure signal and outputs it to the swash plate control valve 19.

  The pump discharge oil passage 14 is provided with a bucket control valve 16 on the upstream side and a boom control valve 15 on the downstream side, with the hydraulic pump 13 as the upstream side.

  A relief valve 17 is connected to the pump discharge oil passage 14 between the bucket control valve 16 and the hydraulic pump 13. The relief valve 17 relieves the pressure oil to the tank 18 when the pump discharge oil passage 14 between the bucket control valve 16 and the hydraulic pump 13 reaches a predetermined relief pressure.

  The boom control valve 15 and the bucket control valve 16 are flow direction control valves. The boom control valve 15 controls the direction and flow rate of the pressure oil supplied to the boom hydraulic cylinder 5. The bucket control valve 16 controls the direction and flow rate of the pressure oil supplied to the bucket hydraulic cylinder 6.

The boom control valve 15 and the bucket control valve 16 are electromagnetic proportional control valves.

The boom control valve 15 operates when a boom operation command signal as an electric signal output from the controller 20 is applied to the electromagnetic solenoid 15 a of the boom control valve 15.

  The boom operation lever 11 is provided with boom operation direction detection means 11a. The boom operation direction detection means 11a detects the operation direction of the boom operation lever 11, that is, the “up operation”, “neutral”, and “down operation” and the operation amount, and outputs them to the controller 20 as a boom operation signal. To do. The controller 20 outputs a boom operation command signal for setting the valve position according to the boom operation signal to the boom control valve 15. The boom control valve 15 operates according to a boom operation command signal.

  When the content of the boom operation signal is “lifting operation”, the valve position of the boom control valve 15 is switched to the bottom position 15B. As a result, the pressure oil passes through the opening having an opening area corresponding to the valve position, and the pressure oil having a flow rate corresponding to the opening area is supplied to the bottom chamber 5B of the boom hydraulic cylinder 5 through the oil passage 22B. The pressure oil in the head chamber 5H of the boom hydraulic cylinder 5 is discharged to the tank 18 through the oil passage 22H and the boom control valve 15. As a result, the rod 5a of the boom hydraulic cylinder 5 extends, and the boom 3 operates in the raising direction.

  Further, when the content of the boom operation signal is “lowering operation”, the valve position of the boom control valve 15 is switched to the head position 15H. Thus, the pressure oil passes through the opening having an opening area corresponding to the valve position, and the pressure oil having a flow rate corresponding to the opening area is supplied to the head chamber 5H of the boom hydraulic cylinder 5 through the oil passage 22H. The pressure oil in the bottom chamber 5B of the boom hydraulic cylinder 5 is discharged to the tank 18 through the oil passage 22B and the boom control valve 15. As a result, the rod 5a of the boom hydraulic cylinder 5 is retracted, and the boom 3 operates in the lowering direction.

  When the contents of the boom operation signal are “neutral”, the valve position of the boom control valve 15 is switched to the neutral position 15C. As a result, the opening is closed, and the pressure oil supply to the boom hydraulic cylinder 5 and the pressure oil discharge from the boom hydraulic cylinder 5 are blocked. As a result, the operation of the rod 5a of the boom hydraulic cylinder 5 is stopped, and the operation of the boom 3 is stopped.

On the other hand, the bucket control valve 16 is operated by applying a bucket operation command signal as an electric signal output from the controller 20 to the electromagnetic solenoid 16 a of the bucket control valve 16.

  The bucket operation lever 12 is provided with bucket operation direction detection means 12a. The bucket operation direction detection means 12a detects the operation direction of the bucket operation lever 12, that is, “tilt operation”, “neutral”, “dump operation”, and the operation amount, and outputs these to the controller 20 as a bucket operation signal. To do. The controller 20 outputs a bucket operation command signal for setting the valve position according to the bucket operation signal to the bucket control valve 16. The bucket control valve 16 operates according to a bucket operation command signal.

When the content of the bucket operation signal is “tilt operation”, the valve position of the bucket control valve 16 is switched to the bottom position 16B. Thus, the pressure oil passes through the opening having an opening area corresponding to the valve position, and the pressure oil having a flow rate corresponding to the opening area is supplied to the bottom chamber 6B of the bucket hydraulic cylinder 6 through the oil passage 23B. The pressure oil in the head chamber 6H of the bucket hydraulic cylinder 6 is discharged to the tank 18 through the oil passage 23H and the bucket control valve 16. As a result, the rod 6a of the bucket hydraulic cylinder 6 extends, and the bucket 4 operates in the tilt direction.

  When the content of the bucket operation signal is “dump operation”, the valve position of the bucket control valve 16 is switched to the head position 16H. As a result, the pressure oil passes through the opening having an opening area corresponding to the valve position, and the pressure oil having a flow rate corresponding to the opening area is supplied to the head chamber 6H of the bucket hydraulic cylinder 6 through the oil passage 23H. The pressure oil in the bottom chamber 6B of the bucket hydraulic cylinder 6 is discharged to the tank 18 through the oil passage 23B and the bucket control valve 16. As a result, the rod 6a of the bucket hydraulic cylinder 6 is retracted, and the bucket 4 operates in the dumping direction.

  When the content of the bucket operation signal is “neutral”, the valve position of the bucket control valve 16 is switched to the neutral position 16C. As a result, the opening is closed, and supply of pressure oil to the bucket hydraulic cylinder 6 and discharge of pressure oil from the bucket hydraulic cylinder 6 are blocked. As a result, the operation of the rod 6a of the bucket hydraulic cylinder 6 is stopped, and the operation of the bucket 4 is stopped.

  Suction valves 24B, 24H, 25B, and 25H configured by check valves are connected to the oil passages 22B, 22H, 23B, and 23H, respectively. Each of the suction valves 24B, 24H, 25B, 25H is only in the direction from the tank 18 to the bottom chamber 5B, from the tank 18 to the head 5H chamber, from the tank 18 to the bottom chamber 6B, and from the tank 18 to the head chamber 6H. By allowing the flow of pressure oil, when the bottom chamber 5B, the head 5H, the bottom chamber 6B, and the head chamber 6H have negative pressures, the bottom chamber 5B, the head 5H, and the bottom chamber are sucked in from the tank 18, respectively. 6B and the head chamber 6H act so as to be supplied to each.

  Relief valves 26B, 26H, 27B, and 27H are connected to the oil passages 22B, 22H, 23B, and 23H, respectively. The relief valves 26B, 26H, 27B, and 27H relieve the pressure oil to the tank 18 when the hydraulic pressure in the bottom chamber 5B, the head 5H, the bottom chamber 6B, and the head chamber 6H reaches the relief pressure.

A signal indicating the boom angle θ detected by the boom angle sensor 9 and a signal indicating the bell crank angle φ detected by the bell crank angle sensor 10 are input to the controller 20. The controller 20 calculates the bucket cylinder stroke Lk based on the boom angle θ and the bell crank angle φ. Further, the boom cylinder stroke Lm is calculated based on the boom angle θ.

As described above with reference to FIG. 2, in the parallel circuit configuration shown in FIG. 3, the pump discharge oil passage 14 is branched into the pump discharge oil passages 14 a and 14 b, and the boom control valve 15 is provided in each of the pump discharge oil passages 14 a and 14 b. Except that the bucket control valve 16 is provided, the series circuit configuration is the same as that shown in FIG.

In the series circuit configuration shown in FIG. 2, the bucket control valve 16 is disposed on the upstream side as viewed from the hydraulic pump 13, and is a bucket priority circuit. For this reason, when the full bucket operation is performed, it becomes difficult for the discharged oil to flow to the boom control valve 15 on the downstream side, and the operation of the boom 3 is suppressed.

On the other hand, in the parallel circuit configuration shown in FIG. 3, when both control valves 15 and 16 are operated in the same manner, the discharged oil easily flows to the control valve with the lighter load. Since the wheel loader 1 generally needs to give priority to buckets, when the boom operation is performed simultaneously with the bucket operation, the controller 20 outputs a boom operation command signal that suppresses the operation of the boom control valve 15. Thus, an operation equivalent to a series circuit can be performed.

The hardware configuration shown in FIGS. 2 and 3 is provided in the existing wheel loader 1. Hereinafter, the method of the present invention performed by the controller 20 will be described. The present invention can be easily implemented by adding or modifying a program to be installed in the controller 20 or data to be stored as appropriate without newly adding or modifying components to the existing hardware configuration. it can.

FIG. 4 shows the contents stored in the storage means 20M of the controller 20. In the storage means 20M, stroke limits on the expansion side and the contraction side of the bucket hydraulic cylinder 6 are stored in association with the work implement posture specified by the boom angle θ and the bucket cylinder stroke Lk. Hereinafter, FIG. 4 will be described in association with FIG.

The horizontal axis in FIG. 4 is the boom angle θ, the left direction in the figure is the direction in which the boom 3 is lowered, and the right direction in the figure is the direction in which the boom 3 is raised. The boom 3 has a lower work implement posture as it goes to the left in the figure, and the boom 3 has a higher work implement posture as it goes to the right in the drawing.

The vertical axis of FIG. 4 is the bucket cylinder stroke Lk, the upper direction in the figure is the direction in which the bucket 4 operates on the tilt side (extension side), and the lower direction in the figure is the bucket 4 on the dump side (contraction side). The direction of operation.

5A, 5B, 5C, 5D, and 5E respectively show the postures of the work implement 2.

5 (a), (b), (c), (d), and (e) are respectively the positions (a), (b), (c), and (d) in FIG. (E) Corresponds to the work machine posture at point. For example, assuming that the current posture of the work implement 2 is the posture of the point (a), by operating the boom 3 and the bucket 4 in the directions indicated by arrows, respectively, the points (b), (c), ( d) The working machine posture at the point (e).

  The lines LN1, LN2, LN3, and LN4 shown in FIG. 4 are “a line in which the bucket 4 is forcibly operated in the tilt direction by the boom raising operation”, “a line in which the bucket 4 is at the stroke end in the dump direction”, “Line in which the bucket 4 is forcibly operated in the dumping direction by the boom lowering operation” and “Line in which the bucket 4 is at the stroke end in the tilt direction”. These are “tilt side (extension of the bucket hydraulic cylinder 6). Side) and dumping side (shrinking side) ”.

  Here, “stroke limit” means “stroke end” or “mechanism limit”.

“Stroke end” means that the rod 6a of the bucket hydraulic cylinder 6 is in the most retracted position or the rod 6a is in the most extended position. The “mechanism limit” means that the movement of the rod 6a of the bucket hydraulic cylinder 6 is restricted when the work implement 2 is brought into contact with the stopper. When the mechanism limit is reached, the stroke end has not been reached.

  FIG. 5B (point (b) in FIG. 4) exemplifies the working machine posture that has reached the “mechanism limit” when the boom 3 is at a high position and the bucket 3 is in the dumping state. The work machine posture (b) is on the line LN1.

When the boom 3 is further raised from the state of the work implement posture (b), the bucket 4 is forcibly operated in the tilt direction along the line LN1. The movement at this time is indicated by an arrow A1 in FIG. Further, when the boom 3 is lowered from the state of the work implement posture (b), the bucket 4 is forcedly operated in the dump direction along the line LN1. The movement at this time is indicated by an arrow A2 in FIG.

The bucket cylinder stroke Lk when the working machine posture is on the line LN1 is referred to as “stopper end”. The value of the stopper end shifts to the tilt side and increases as the boom angle θ increases.

FIG. 5C (point (c) in FIG. 4) exemplifies a working machine posture in which the boom 3 is at a low position and the bucket 3 reaches the stroke end in the dumping direction. The work machine posture (c) is on the line LN2.

FIG. 5D (point (d) in FIG. 4) exemplifies the work implement posture that has reached the “mechanism limit” when the boom 3 is at a low position and the bucket 3 is in a tilted state. The work machine posture (d) is on the line LN3. If the bucket 3 is operated to the tilt side when the boom 3 is at a low position, the bucket 4 hits the stopper 3c before reaching the stroke end. At this time, it also becomes a “stopper end” (see FIG. 5D).

FIG. 5E (point (e) in FIG. 4) exemplifies a work implement posture in which the boom 3 is at a high position and the bucket 3 reaches the stroke end in the tilt direction. The work machine posture (e) is on the line LN4. When the boom angle θ is greater than a certain value and the boom 3 is at a high position, if the bucket 3 is operated to the tilt side, the stroke end is reached without hitting the stopper 3c (see FIG. 5E).

Each of the lines LN1, LN2, LN3, and LN4 is stored in advance as data of the theoretical stroke limit value Lk0 and the theoretical boom angle value θ0 of the bucket hydraulic cylinder 6.

However, if a failure such as displacement occurs in the bell crank angle sensor 10 due to the passage of time as described above, the detected bucket cylinder stroke value Lk when the stroke limit is reached shifts from the theoretical stroke limit value Lk0.

Here, during operation, when the hydraulic cylinder 6 for buckets is operated until it reaches the stroke limit, the oil on the bottom chamber 6B side or the head chamber 6H side of the bucket hydraulic cylinder 6 loses escape, and the bottom chamber 6B side or head chamber is lost. The hydraulic pressure on the 6H side reaches the set relief pressure of the relief valves 27B and 27H. Accordingly, if the boom angle θ and the bucket cylinder stroke Lk at the time when the working machine posture of the wheel loader 1 reaches the stroke limit and reaches the relief pressure set for the relief valves 27B and 27H during the work, the theoretical stroke limit is obtained. The positional deviation of the detected stroke value with respect to the value Lk0 can be obtained.

Further, if the bucket hydraulic cylinder 6 is operated during the operation until the stroke limit is reached, the discharge pressure of the hydraulic pump 13 (hereinafter referred to as pump pressure) reaches the set relief pressure of the relief valve 17. Accordingly, if the boom angle θ and the bucket cylinder stroke Lk at the time when the working machine posture of the wheel loader 1 reaches the stroke limit and the relief valve 17 reaches the set relief pressure during the work are measured, the theory is the same. The displacement of the detected stroke value with respect to the stroke limit value Lk0 can be obtained.

For example, as shown in FIGS. 2 and 3, a hydraulic pressure sensor 30 for detecting the hydraulic pressure in the pump discharge oil passage 14 is provided, and the relief valve 17 reaches the set relief pressure by taking the detection value of the hydraulic pressure sensor 30 into the controller 20. Can be judged.

FIG. 6 is a diagram for explaining a method of determining when the stroke limit is reached.

FIG. 6 (a) is a graph showing the relationship between time and pump pressure P, and FIG. 6 (b) shows the relationship between time and bucket cylinder stroke Lk in correspondence with FIG. 6 (a). It is a graph. 6A and 6B illustrate a case where the bucket cylinder stroke Lk extends to the tilt side (a case where the bucket cylinder stroke value Lk increases in the plus direction).

As indicated by LM1 and LM2 in FIGS. 6A and 6B, respectively, when the rod 6a of the bucket hydraulic cylinder 6 extends and reaches the stroke limit in a light load state, the pump pressure P Rises and reaches the relief pressure. Therefore, if the sudden fluctuation of the pump pressure P at this time is detected, it is possible to determine when the stroke limit is reached.

However, in the case of a work vehicle such as the wheel loader 1 whose load fluctuates during work, the following points are concerned.

(Concern 1)
That is, the load applied when the bucket hydraulic cylinder 6 expands and contracts varies depending on whether or not there is a load, the temperature condition of the hydraulic oil, and the like. When the load is heavy, the load changes as indicated by LM3 and LM4 in FIGS. 6A and 6B, respectively, and the pressure fluctuation (LM3) is smaller than the pressure fluctuation (LM1) in the case of a light load. .

  As described above, since the magnitude of the pressure fluctuation varies depending on the load, there is a concern that it is difficult to accurately measure the pressure fluctuation.

  Further, in the case of a work vehicle such as the wheel loader 1 in which a large force is applied to the work machine 2 from the outside due to the rock colliding with the work machine 2 during excavation work, the following points are concerned. FIGS. 6C and 6D are diagrams corresponding to FIGS. 6A and 6B, respectively, for explaining the influence of external force.

(Concern 2)
That is, for example, when a hard rock hits the bucket 4 during excavation work, it changes as indicated by LM5 and LM6 in FIGS. 6C and 6D, respectively, and the stroke limit, that is, a stroke value other than the stroke end and stopper end, The pump pressure P becomes the relief pressure. Therefore, in order to accurately obtain the detected stroke value at the stroke limit time, it is necessary to exclude the influence of such an external force.

  In order to solve the concern 1, in the embodiment, as shown in FIGS. 7A and 7B, the pump pressure P is rapidly increased by setting two-stage threshold values Pt1 and Pt2 to the pump pressure P. In addition, it is determined that the stroke limit has been reached by changing from P <Pt1 to P> Pt2, and the detected stroke value at the stroke limit time is measured. Further, it is possible to determine that the stroke limit has been reached by sequentially changing from P <Pt1 to P> Pt2 over time, and measure the detected stroke value at the stroke limit point.

7 (a) and 7 (b) correspond to FIGS. 6 (a) and 6 (b), respectively, and the tilt side stroke limit time point of the hydraulic cylinder 6 for bucket in the embodiment is judged and tilted. It is a figure explaining the conditions which measure a stroke value.

First, the thresholds Pt1 and Pt2 are set on the assumption that the bucket 4 is in an empty state and that a detectable factor such as hydraulic oil temperature is a general condition. The threshold value Pt1 is a threshold value for detecting that the bucket hydraulic cylinder 6 is operating on the tilt side when the load is light. The threshold value Pt2 is a pressure set slightly lower than the relief pressure, and is a threshold value for detecting that the pump pressure has reached the relief pressure. The values of Pt1 and Pt2 are set to 15 MPa and 30 MPa, for example.

  During the operation, when the bucket hydraulic cylinder 6 operates to the tilt side (extension side), the bucket cylinder stroke Lk stops growing, and the pump pressure P rapidly rises from P <Pt1 to P> Pt2. It is determined that the side stroke limit has been reached, the bucket cylinder stroke Lk at that time is measured as the tilt side stroke limit value, and the boom angle θ at that point is measured to collect data.

Similarly, FIGS. 7C and 7D are diagrams corresponding to FIGS. 7A and 7B, respectively, and determine the dump side stroke limit time of the bucket hydraulic cylinder 6 in the embodiment and perform dumping. It is a figure explaining the conditions which measure a side stroke value.

First, similarly, the thresholds Pd1 and Pd2 are set on the assumption that the bucket 4 is in an empty state and that a detectable factor such as hydraulic oil temperature is a general condition.

  During the operation, when the bucket hydraulic cylinder 6 is operated to the dump side (retraction side) and the contraction of the bucket cylinder stroke Lk stops and the pump pressure P becomes P> Pd2 through P <Pd1, the dump side It is determined that the stroke limit is reached, the bucket cylinder stroke Lk at that time is measured as the dump side stroke limit value, and the boom angle θ at that time is measured to collect data.

  Whether the bucket hydraulic cylinder 6 is operating on the expansion side (tilt side) or the contraction side (dump side) can be determined by the controller 20 from the detection signal of the bucket operation direction detection means 12a.

  Regarding issue 2, as will be described later, the collected data is statistically processed, and data that has a large standard deviation is discarded after the data far from the average value is excluded. Therefore, it is made to deal with by not judging that the sensor is faulty.

8 (a), 8 (b), 9 (a), and 9 (b) are diagrams corresponding to FIG. 4. From the detected stroke value Lk and the detected boom angle value θ detected as described in FIG. FIG. 6 is a map diagram in which a plurality of points PT (hereinafter, sampling points PT) of a working machine posture are sampled and each of these sampling points PT is compared with each line LN1, LN2, LN3, LN4.

The relationship between each state of the sensor and the map diagram will be described with reference to FIGS.

(1) “Position shift” (FIG. 8A)
When the sensor failure is “position shift”, the sampling point PT of the tilt side detection stroke value is shifted with respect to the lines LN3 and LN4 of the tilt side theoretical stroke limit value Lk0, and the dump side detection stroke value is The direction in which the sampling point PT is deviated from the lines LN1 and LN2 of the dump side theoretical stroke limit value Lk0 coincides ("distribution deviation in one direction"). In FIG. 8A, each sampling point PT on the tilt side is shifted from the tilt side lines LN3 and LN4 by an amount ΔLk that is substantially equal to the dump side, and each sampling point PT on the dump side is a line on the dump side. This shows a case where LN1 and LN2 are deviated by substantially the same amount ΔLk on the same dump side. In such a case, the cause of the sensor failure is a simple “positional deviation that can correct the positional deviation. Can be determined. Similarly, each sampling point PT on the tilt side is deviated from the tilt side lines LN3 and LN4 by substantially the same amount ΔLk on the tilt side, and each sampling point PT on the dump side is shifted to the line LN1 on the dump side. Also, even when the amount of deviation ΔLk is substantially equal to the same tilt side with respect to LN2, it can be determined that the cause of the sensor failure is a simple “positional deviation” that can correct the positional deviation.

“Position shift” is based on the assumption that the variation of each sampling point PT is within the normal distribution range on both the tilt side and the dump side, that is, the standard deviation σ of the position shift ΔLk is less than a predetermined level. It becomes. Further, when the amount of the positional deviation ΔLk is less than a predetermined threshold value, it can be determined that the sensor is “normal” rather than a sensor failure.

The value of the positional deviation ΔLk is a positive value when distributed on the tilt side from the normal values of the lines LN3 and LN4 of the tilt side theoretical stroke limit value Lk0 and the lines LN1 and LN2 of the dump side theoretical stroke limit value Lk0. Takes a negative value when distributed on the dump side.

(2) “Backlash” (FIG. 8B)
When the sensor failure is “backlash”, the sampling point PT of the tilt side detection stroke value varies greatly with respect to the lines LN3 and LN4 of the tilt side theoretical stroke limit value Lk0, and the sampling point PT of the dump side detection stroke value Greatly varies with respect to the lines LN1 and LN2 of the dump side theoretical stroke limit value Lk0 ("abnormal variation"). In FIG. 8B, each sampling point PT on the tilt side varies abnormally beyond the normal distribution range with respect to the tilt side lines LN3 and LN4, and each sampling point PT on the dump side is a line on the dump side. A case is shown in which the distributions of LN1 and LN2 vary more abnormally than normal distribution. In such a case, the cause of the sensor failure can be determined to be “backlash”. That is, when the standard deviation σ of the positional deviation ΔLk is equal to or higher than a predetermined level on both the tilt side and the dump side, it is determined that the cause of the sensor failure is “rattle”.

(3) “Data inappropriate”
Similarly to FIG. 8B, even when the variation of each sampling point PT is large, when the variation is large only on one of the tilt side and the dump side, for example, each sampling point PT on the tilt side is on the tilt side. The lines LN3 and LN4 vary more abnormally than the normal distribution range, but each sampling point PT on the dump side falls within the normal distribution range on the dump side lines LN1 and LN2 In this case, the collected data is determined to be “data inappropriate” because it includes a lot of data when a large force is applied to the work machine 2 from the outside. That is, when the standard deviation σ of the positional deviation ΔLk is equal to or higher than a predetermined level on only one of the tilt side and the dump side, it is determined that the collected data is “data inappropriate”. If it is determined that the data is inappropriate, data having a large standard deviation is discarded without being determined as a sensor failure.

(4) “Sensor Abnormality” (FIGS. 9A and 9B)
When the sensor failure is “sensor abnormality”, the direction in which the sampling point PT of the tilt side detection stroke value is deviated from the lines LN3 and LN4 of the tilt side theoretical stroke limit value Lk0 and the dump side detection stroke value The direction in which the sampling point PT is deviated from the lines LN1 and LN2 of the dump side theoretical stroke limit value Lk0 does not coincide with the direction ("distribution deviation in the reverse direction"). In FIG. 9A, each sampling point PT on the tilt side is shifted from the tilt side lines LN3 and LN4 by an approximately equal amount ΔLk on the dump side, and each sampling point PT on the dump side is on the dump side line. A case is shown in which the amount of deviation ΔLk is substantially equal to the opposite tilt side with respect to LN1 and LN2. Further, in FIG. 9B, each sampling point PT on the tilt side is shifted from the tilt side lines LN3 and LN4 by substantially the same amount ΔLk on the tilt side, and each sampling point PT on the dump side is on the dump side. This shows a case where the lines LN1 and LN2 are deviated by substantially the same amount ΔLk on the reverse dump side. In such a case, the cause of the sensor failure can be determined as “sensor abnormality”.

However, “sensor abnormality” means that the variation of each sampling point PT is within the normal distribution range on both the tilt side and the dump side, that is, the standard deviation σ of the positional deviation ΔLk is less than a predetermined level. It is a premise. Even if there is a position shift in the opposite direction, if the amount of the position shift ΔLk is less than a predetermined threshold, it can be determined that the sensor is “normal” rather than a sensor failure.

In the controller 20, the state of the sensor or the cause of failure is determined by the processing procedure shown in FIG.

(Data collection; steps 101-105)
First, according to FIG. 7, the detected stroke value Lk and the detected boom angle value θ when the bucket hydraulic cylinder 6 reaches the relief pressure on the tilt side (extension side) and the dump side (contraction side) are collected.

That is, first, it is determined whether or not the number of data at the sampling point PT exceeds a specified number (for example, 100) on each of the tilt side and the dump side (step 101).
If it is determined that the number of data at the sampling point PT does not exceed the specified number at least on one of the tilt side and the dump side (determination NO in step 101), it is determined that the data sampling has not been completed, and the next step 102 Thus, it is determined whether or not the dump-side measurement conditions shown in FIGS. 7C and 7D are satisfied. That is, it is determined whether or not the operation of the bucket hydraulic cylinder 6 toward the dump side has stopped and the pump pressure P has reached P> Pd2 via P <Pd1. In this case, the same determination can be made by detecting that the hydraulic pressure in the head chamber 6H of the bucket hydraulic cylinder 6 has reached the relief pressure (step 102; dump-side measurement condition; FIG. 7C). (D)). When the dump side measurement condition in step 102 is satisfied (YES in step 102), the bucket cylinder stroke Lk at that time is measured as the dump side detection stroke value, and the detected boom angle θ at that time is detected as the detected boom angle. It measures as a value and collects data of the point PT (step 104).

If the dump-side measurement condition in step 102 is not satisfied (determination NO in step 102), it is determined in the next step 103 whether the tilt-side measurement condition shown in FIGS. 7A and 7B is satisfied. Is done. That is, it is determined whether or not the operation of the bucket hydraulic cylinder 6 toward the tilt side has stopped and the pump pressure P has reached P> Pt2 via P <Pt1. In this case, the same determination can be made by detecting that the hydraulic pressure in the bottom chamber 6B of the bucket hydraulic cylinder 6 has reached the relief pressure (step 103; tilt side measurement condition; FIG. 7A). (B)). When the tilt-side measurement condition in step 103 is satisfied (determination YES in step 103), the bucket cylinder stroke Lk at that time is measured as the tilt-side detection stroke limit value, and the detected boom angle θ at that time is detected as the detection boom. Measurement is performed as an angle value, and data of the point PT is collected (step 105).

(Calculate mean value, variance, standard deviation separately for tilt side and dump side;
If it is determined that the number of data at the sampling point PT exceeds the specified number for each of the tilt side and the dump side (YES at Step 101), all the sampling points PT at the dump side (Step 104) For each sampling point PT (step 105), a positional deviation ΔLk between the theoretical stroke limit value Lk0 and the detected stroke value Lk is calculated (ΔLk = Lk−Lk0). Then, the average value Lkav, variance σ2, and standard deviation σ of the positional deviation ΔLk are calculated for every dump-side sampling point PT and tilt-side all sampling point PT. Here, after excluding data far from the average value Lkav, the average value Lkav may be recalculated, and the variance σ2 and the standard deviation σ may be recalculated. For example, the data in which the positional deviation ΔLk is within the average value Lkav ± σ is left, the data in which the positional deviation ΔLk is outside the average value Lkav ± σ is excluded, and the average value Lkav, variance σ2, and standard deviation σ are recalculated. can do. Furthermore, when the number of data whose positional deviation ΔLk is within the average value Lkav ± σ is not 90% or more of the total number of data, the collected data is discarded and the following sensor failure It is also possible not to use it for judgment. As a result, the concern 2 is resolved, and the failure of the sensor can be determined based on the reliable data (step 106).

Hereinafter, description will be made with reference to the histograms shown in FIGS. 11A, 11B, 12A, and 12B.

11 (a), 11 (b), 12 (a), and 12 (b) each show a histogram obtained from a prescribed number (100) of data. The horizontal axis indicates the positional deviation ΔLk, and the vertical axis indicates the frequency.

In FIG. 11A, the average value Lkav is 1.10 (cm), the variance σ2 is 0.00018379, and the standard deviation σ is 0.013555622, and the collected data converges very near the average value. I can see that

In FIG. 11B, the average value Lkav is 1.10 (cm), the variance σ 2 is 0.0003043, and the standard deviation σ is 0.0174421, which is slightly larger than the histogram of FIG. 11A. However, it can be seen that the collected data converged around the average value.

In FIG. 12A, the average value Lkav is 1.10 (cm), the variance σ 2 is 0.00062049, and the standard deviation σ is 0.02490964, and the variation is larger than the histogram of FIG. 11B. It is difficult to say that the collected data has already converged around the average value.

In FIG. 12 (b), the average value Lkav is 1.11 (cm), the variance σ2 is 0.00131353, and the standard deviation σ is 0.03624259. Not only the variation is large, but the peak is not near the average value. It can also be seen that a large amount of data other than the stroke limit was collected due to external force being applied.

(Determining whether the sensor state is a group of “positional deviation”, “normal” or “sensor abnormality”, or a group of “backlash” or “data improper”; step 107)
Next, depending on whether both the standard deviation σ on the tilt side and the dump side are less than a certain value, whether the sensor state is a group of “positional deviation” or “normal” or “sensor abnormality”, Alternatively, it is determined whether the group is “backlash” or “data inappropriate”. Here, the “constant value” that is the threshold value of the standard deviation σ is set to 0.02, for example (step 107).

(Determining whether the sensor state is “backlash” or “data inappropriate”; steps 108, 109, 110)
When at least one of the standard deviation σ on the tilt side and the standard deviation σ on the dump side is equal to or greater than a certain value (judgment in step 107 “at least one is equal to or greater than a certain value”), the sensor state is “rattle” Or the standard deviation σ on both the tilt side and the dump side is greater than a certain value, or the standard deviation σ on the tilt side and the dump side is Depending on whether only one of them is greater than or equal to a certain value, it is determined whether the sensor state is “backlash” or “data inappropriate” (step 108).

That is, as shown in FIG. 8B, each sampling point PT on the tilt side varies abnormally beyond the normal distribution range with respect to the lines LN3 and LN4 on the tilt side, and each sampling point PT on the dump side If the lines LN1 and LN2 on the dump side vary more abnormally than the normal distribution, the standard deviation σ of the positional deviation ΔLk becomes a certain value or more on both the tilt side and the dump side (determination in step 108) “Both are equal to or greater than a certain value”), it is determined that the cause of the sensor failure is “rattle”. For example, when both the tilt-side data and the dump-side data have the distribution shown in FIG. 12A, it is determined that the cause of the sensor failure is “rattle”. In this case, the operator or serviceman is notified by alarm, error code, or the like that the cause of the sensor failure is “rattle” (step 109). The collected data is stored in a predetermined storage area of the controller 20 for storing and analyzing evidence for a certain period, and then discarded (step 110).

On the other hand, even when the variation of each sampling point PT is large as in FIG. 8B, when the variation is large only on one of the tilt side and the dump side, for example, each sampling point PT on the tilt side. However, the sampling points PT on the dump side are in the normal distribution range with respect to the lines LN1 and LN2 on the dump side, although they vary more than the normal distribution range on the tilt side lines LN3 and LN4. If it is within the range, the standard deviation σ of the positional deviation ΔLk becomes a certain value or more on only one of the tilt side and the dump side (judgment in step 108 “one of them is a certain value or more”), and the collected data is It is determined that the data is inappropriate. For example, when the data on the tilt side exhibits the distribution of normal variations shown in FIG. 11B, but the data on the dump side exhibits the distribution of abnormal variations shown in FIG. 12B. The collected data is determined to be “data inappropriate”. In this case, the collected data is discarded without determining that there is a sensor failure, as including a lot of data when a large force is applied to the work machine 2 from the outside (step 110).

(Determining whether the sensor status is a group of “positional deviation” or “normal” or “sensor abnormal”; step 111)
When it is determined that both the standard deviation σ on the tilt side and the dump side are less than a certain value (judgment in step 107 “both are less than a certain value”), the sensor state is “positional deviation” or “normal”. Or, it is determined that the sensor is in the “sensor abnormality” group, and then a deviation between the tilt side average value Lkav and the dump side average value Lkav, that is, | tilt side average value Lkav−dump side average value Lkav | Depending on whether it is less than (for example, 10 mm) or more than a predetermined value (10 mm), whether the sensor state is a group of “positional deviation” or “normal” or “sensor abnormality” Judgment is made (step 111). As the predetermined value, a value that seems to be appropriate as compared with the stroke amount of the hydraulic cylinder 6 for bucket is used.

As shown in FIG. 9 (a), each sampling point PT on the tilt side is shifted from the tilt side lines LN3 and LN4 by substantially the same amount ΔLk on the dump side, and each sampling point PT on the dump side is dumped. When the side lines LN1 and LN2 are deviated by substantially the same amount ΔLk on the opposite tilt side, or as shown in FIG. 9B, each tilt-side sampling point PT is shifted to the tilt side line LN3, When the sampling point PT on the dump side is deviated by an amount ΔLk substantially equal to the opposite dump side with respect to the dump side lines LN1 and LN2 as well as being displaced by an amount ΔLk substantially equal to the tilt side with respect to LN4. The deviation | tilt side average value Lkav−dump side average value Lkav | is equal to or greater than a predetermined value (for example, 10 mm) (determination in step 111 is “predetermined value or more”). It is determined to be normal. " In this case, the operator or service person is notified that the cause of the sensor failure is “sensor abnormality” (step 112). The collected data is stored in a predetermined storage area of the controller 20 for storing and analyzing evidence for a certain period, and then discarded (step 110).

On the other hand, when it is determined that the deviation | tilt side average value Lkav−dump side average value Lkav | is less than a predetermined value (for example, 10 mm) (determination “less than predetermined value” in step 111), The state is determined to be in the “positional deviation” or “normal” group.

(Determining whether the sensor state is “positional deviation” or “normal”; step 113)
If it is determined in step 111 that the sensor state is the “positional deviation” or “normal” group, then at least one of the tilt-side average value Lkav and the dump-side average value Lkav is equal to or greater than a predetermined value. Whether or not the sensor state is “positional deviation” or “normal” is determined (step 113).

That is, when it is determined that at least one of the tilt-side average value Lkav and the dump-side average value Lkav is equal to or greater than a predetermined value (for example, 5 mm) (determination in step 113 “at least one is equal to or greater than the predetermined value”), FIG. As shown in (a), the positional deviation ΔLk occurs in the same direction on both the tilt side and the dump side, and the positional deviation ΔLk is out of the normal range. For example, the distribution of the positional deviation ΔLk exhibits the distribution shown in Fig. 11 (a) or Fig. 11 (b), and the positional deviation is detected in both the tilt side and the dump side data. If the directions match, the cause of the sensor failure is determined to be “positional deviation.” In this case, the sensor is determined according to the calculated tilt-side average value Lkav and dump-side average value Lkav. Is automatically corrected (step 114), and the data is then discarded (step 110).

On the other hand, when it is determined that both the tilt side average value Lkav and the dump side average value Lkav are less than a predetermined value (for example, 5 mm) (determination in step 113 “both are less than the predetermined value”), the sensor It is judged that there is no failure and is “normal”. The data is then discarded (step 110).

Assuming that the boom angle sensor 9 and the bell crank angle sensor 10 for indirectly detecting the bucket cylinder stroke Lk are provided, the state of failure of the boom angle sensor 9 and the bell crank angle sensor 10 is determined. However, in the case where one sensor that directly or indirectly detects the bucket cylinder stroke Lk is provided, it is possible to determine the state of failure or the like of this one sensor by a similar method. it can.

Similarly, the state of the boom angle sensor 9 that indirectly detects the boom cylinder stroke Lk and the state of the stroke sensor that directly detects the boom cylinder stroke Lk are also determined by the same method. be able to.

In the embodiment, the wheel loader has been described as a work vehicle. However, the work loader includes a work machine that is operated by a hydraulic cylinder for the work machine, and a sensor that directly or indirectly detects the stroke of the hydraulic cylinder for the work machine. The present invention can be similarly applied to other work vehicles such as a hydraulic excavator as long as it is a work vehicle.

As described above, according to the embodiment, it is possible to accurately identify whether the sensor state is “normal”, “position shift”, “sensor abnormality”, or “backlash”, and the cause of the sensor failure is the position shift. It is possible to determine whether it is “positional deviation” that can be automatically corrected, or “sensor abnormality” or “backlash” that cannot be automatically corrected. As a result, measures corresponding to the cause of the failure can be taken early. Furthermore, when the collected data is inappropriate, it can be determined that the data is “data inappropriate”, and it is not erroneously determined that the sensor is faulty. As a result, the cause of the failure is accurately identified, and the reliability of the determination result of the failure cause is improved.

Further, when it is determined that the sensor state is “positional deviation”, the positional deviation of the sensor is corrected in accordance with the positional deviation ΔLk between the theoretical stroke limit value and the detected stroke value of the working machine hydraulic cylinder. Therefore, the sensor can be automatically and quickly restored from the failure state to the normal state at the work site.

In addition, when the hydraulic pressure in the working machine hydraulic cylinder reaches the relief pressure on each of the expansion side and the contraction side, or when the discharge pressure of the hydraulic pump that supplies pressure oil to the working machine hydraulic cylinder reaches the relief, Since it was judged that the hydraulic cylinder for work equipment reached the stroke limit on each of the expansion side and the contraction side, the sensor detection stroke value at that time was collected and the cause of the sensor failure was judged. Data can be collected sequentially during work in which the machine hydraulic cylinder is normally operated to the stroke limit, and if a sensor failure occurs during the work, it can be determined early that the failure has occurred. . As a result, if a failure that can correct the misalignment occurs during the work, the work can be automatically corrected during the work to quickly recover to a normal state, and the work can be continued. In addition, even if it is a failure that cannot be corrected for misalignment, the cause of the failure is identified early during the work, so it is possible to continue the work by quickly restoring the normal state without losing work efficiency. Become.

  DESCRIPTION OF SYMBOLS 1 Wheel loader (work vehicle), 2 working machines, 3 boom, 4 bucket, 5 hydraulic cylinder for booms, 6 hydraulic cylinder for buckets, 9 boom angle sensor, 10 bell crank angle sensor, 20 controller, 20M storage means

Claims (5)

A sensor failure cause determination method applied to a work vehicle having a work machine operated by a work machine hydraulic cylinder and a sensor for indirectly or directly detecting a stroke of the work machine hydraulic cylinder. There,
Sampling the stroke value detected by the sensor when the hydraulic cylinder for work implement reaches the stroke limit on each of the expansion side and the contraction side;
Calculating the standard deviation of the detected stroke value of the collected sensor separately for the expansion side and the contraction side;
Depending on whether both the standard deviation on the expansion side and the contraction side are less than a certain value, the sensor status is a group of “positional deviation”, “normal” or “sensor abnormality” or “backlash”. Or determining whether it is a “data inappropriate” group,
If it is determined that the sensor status is a group of “rattle” or “data inappropriate”, both the standard deviations on the expansion side and the contraction side are equal to or greater than a certain value, or the expansion side and the contraction side are Determining whether the state of the sensor is “backlash” or “data inappropriate” depending on whether only one of the standard deviations is greater than or equal to a certain value;
If it is determined that the sensor status is a group of “positional deviation”, “normal” or “sensor abnormality”, the positional deviation between the theoretical stroke limit value and the detected stroke value of the hydraulic cylinder for work implements is detected. Obtained for each of the stretch side and the contraction side, and depending on whether the deviation between the misalignment on the stretch side and the misalignment on the shrink side is less than a predetermined value or greater than a predetermined value, ”Or“ normal ”group or“ sensor abnormality ”, and
If it is determined that the sensor status is a group of “positional deviation” or “normal”, the positional deviation between the theoretical stroke limit value of the hydraulic cylinder for work implements and the detected stroke value is the expansion side and the contraction side. Cause of failure of the sensor in the work vehicle including a step of determining whether the state of the sensor is “misalignment” or “normal” depending on whether or not at least one of them is a predetermined value or more Judgment method. When the sensor state is determined to be `` position deviation '', the sensor position deviation is corrected according to the position deviation between the theoretical stroke limit value of the hydraulic cylinder for work implements and the detected stroke value. The sensor failure cause determination method for a work vehicle according to claim 1. When the hydraulic pressure in the work machine hydraulic cylinder reaches the relief pressure on the expansion side and the contraction side, or when the discharge pressure of the hydraulic pump that supplies the hydraulic oil to the work machine hydraulic cylinder reaches the relief, the work machine 2. The sensor failure cause determination method for a work vehicle according to claim 1, wherein it is determined that the hydraulic cylinder has reached a stroke limit on each of the expansion side and the contraction side, and a detection stroke value of the sensor at that time is collected. . When the hydraulic pressure in the hydraulic cylinder for work implements changes rapidly from the threshold value for detecting that it is operating at a light load to a pressure set slightly lower than the relief pressure, the stroke limit is reached. 4. The sensor failure cause determination method for a work vehicle according to claim 3, wherein it is determined that the sensor has reached. As the hydraulic pressure in the hydraulic cylinder for work implements has gradually changed from the threshold value for detecting operation with a light load to the pressure set slightly lower than the relief pressure over time. 4. The method according to claim 3, wherein it is determined that the stroke limit has been reached.

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