JP7409267B2 - Method and device for measuring the weight held by working machines - Google Patents

Description

The present invention relates to a method and apparatus for measuring a held weight corresponding to the weight of an object held on a tip attachment of a working machine such as a hydraulic excavator.

2. Description of the Related Art Conventionally, methods and devices for measuring the weight of an object held by a tip attachment of a working machine or the corresponding weight held therein are known. Generally, a method is known in which the moment acting on the entire working device including the tip attachment and the working arm that displaces it is calculated, and the weight of the object held by the tip attachment is determined based on the moment. ing. However, this method requires a large number of sensors and complicated calculations in order to specify the posture of the entire working device and the load acting on it. Furthermore, there are many variables that affect the results of the calculation. For example, the static friction force in each hydraulic cylinder influences the measurement results, and the variation in the static friction force is large, making it difficult to specify accurately. Therefore, it is difficult to calculate the weight of the object to be held with high accuracy.

On the other hand, Patent Document 1 discloses a device for calculating the weight of an object to be held using a small number of sensors. This device is installed on a hydraulic excavator equipped with a bucket that is a tip attachment and a bucket cylinder that rotates the bucket. Calculate. Specifically, the device includes a pressure sensor, a tilt sensor, and a calculation means. The pressure sensor detects the bottom pressure of the bucket cylinder as a holding pressure. The inclination sensor detects the inclination angle of the arm to which the bucket is attached. The calculation means calculates the holding moment that the bucket cylinder gives to the bucket based on the bottom pressure and the inclination angle, and calculates the holding moment from the balance between this holding moment and the moment due to the weight of the bucket and the earth and sand therein. Calculate the weight of the earth and sand.

Japanese Patent Application Publication No. 10-245874

The bottom pressure of the bucket cylinder detected by the pressure sensor does not necessarily correspond to the weight of the load loaded on the bucket (work attachment). Therefore, the weight calculated based on the bottom pressure may include a large error. Specifically, the bottom pressure, which is the basis for calculating the weight, is detected when the bucket has completed its excavation and lifting operations and the bucket has stabilized its posture relative to the arm, and more specifically, when the bucket is being transported. This is often done during the swinging motion to reach a position above the vehicle's loading platform, but during such swinging motions, the operator must move the bucket in the digging direction, that is, in the direction of the arm, to prevent soil from spilling from the bucket. There is a tendency to make a full stroke of the bucket cylinder in the extension direction so as to move it toward the ventral surface. It is highly likely that the bottom pressure of the bucket cylinder that is making a full stroke has reached the maximum pressure (relief pressure), exceeding the pressure that is balanced against the actual weight of the earth and sand in the bucket, and the calculation is based on that bottom pressure. The estimated weight will be greater than the actual cargo load.

Further, even if the bucket cylinder is not fully stroked, the detection result of the bottom pressure is greatly influenced by static frictional force, so that a large error is likely to occur. The detection of the bottom pressure is often performed with the attitude of the bucket relative to the arm fixed, that is, with the bucket cylinder stationary. In this case, the measured value of the bottom pressure includes static friction force, That is, the frictional force in the direction of keeping the piston and rod stationary with respect to the cylinder body of the bucket cylinder has a large influence. This static frictional force has a larger variation than the dynamic frictional force, and the measurement error increases accordingly.

The problems described above occur not only when the tip attachment is a bucket. For example, even when the tip attachment is a so-called lifting magnet that holds an object by magnetic force, or a grapple that clamps an object, the tip attachment is based on the holding pressure of the attachment cylinder to rotate the tip attachment. When calculating the weight of the object to be held, problems similar to those described above may occur.

The present invention provides a method and device capable of accurately measuring, with a simple configuration, a held weight corresponding to the weight of an object held by the tip attachment in a working machine equipped with a working device including a tip attachment. The purpose is to provide

What is provided is a held weight measurement method for measuring a held weight corresponding to the weight of a held object of a work machine. The work machine includes a body and a work device connected to the body. The working device includes a working device main body, a tip attachment, and an attachment cylinder. The working device main body includes a proximal end portion connected to the machine body and a distal end portion on the opposite side thereof, and operates to change the distal end portion relative to the machine body. The tip attachment is attached to the tip of the working device main body so as to be rotatable about an attachment rotation axis, and is capable of holding an object. The attachment cylinder is provided between the working device main body and the tip attachment, and expands and contracts so as to rotate the tip attachment about the attachment rotation axis with respect to the working device main body. The attachment cylinder has a pair of hydraulic chambers located on opposite sides, and when hydraulic oil is supplied to one of the pair of hydraulic chambers, it expands or contracts to rotate the tip attachment. The holding weight measurement method involves squeezing a part of the hydraulic fluid supplied to the holding side hydraulic chamber when preset measurement start conditions are met with the tip attachment holding the object. a pressure relief step of releasing the pressure of the hydraulic oil by releasing it into a tank through the pressure relief step, and a specific physical quantity of the holding pressure and moment of the attachment cylinder at the time when preset measurement conditions are satisfied after the pressure relief step is started. and a holding weight calculation step of calculating the holding weight based on the detected holding pressure and the detected physical quantity. The holding pressure is the pressure of hydraulic oil in the holding side hydraulic chamber. The holding side hydraulic chamber is one of the pair of hydraulic chambers, and is operated to hold the tip attachment against the weight of the tip attachment and the object held thereon. This is a hydraulic chamber where oil is supplied. The moment specific physical quantity is a physical quantity necessary for specifying the radius of the holding moment. The holding moment is a moment around the attachment rotation axis that is applied to the tip attachment by the holding pressure. The moment specific physical quantity is, for example, a cylinder length that is the length of the attachment cylinder in the axial direction.

Also provided is a holding weight measuring device for measuring a holding weight corresponding to the weight of a held object held by the working machine, which includes a holding pressure detector, a physical quantity detector, and a pressure It includes a venting section, a pressure venting control section, and a retained weight calculation section. The holding pressure detector detects the holding pressure of the attachment cylinder. The holding pressure is the pressure of hydraulic oil in the holding side hydraulic chamber, and the holding side hydraulic chamber is one of the pair of hydraulic chambers, and the holding pressure is the pressure of the hydraulic oil in the holding side hydraulic chamber, and the holding pressure is the pressure of the hydraulic oil in the holding side hydraulic chamber, and the holding side hydraulic chamber is one of the hydraulic chambers of the pair of hydraulic chambers, and the holding pressure is the pressure of the hydraulic oil in the holding side hydraulic chamber. This is a hydraulic chamber to which hydraulic oil is supplied to hold the tip attachment against the pressure. The physical quantity detector detects a moment specific physical quantity. The moment specific physical quantity is a physical quantity necessary for specifying the radius of the holding moment, and is, for example, a cylinder length that is the length of the attachment cylinder in the axial direction. The pressure relief section is configured to perform a pressure relief operation. The pressure relief operation is an operation of releasing a portion of the hydraulic oil supplied to the holding side hydraulic chamber to a tank through a throttle to relieve the pressure of the hydraulic oil in the holding side hydraulic chamber. The pressure relief control section is configured to cause the pressure relief section to perform the pressure relief operation when a preset measurement start condition is satisfied with the tip attachment holding the object. Ru. The holding weight calculation unit obtains the holding pressure and the moment specific physical quantity as a detected holding pressure and a detected physical quantity, respectively, at a time point when a preset measurement condition is satisfied after the pressure release operation is started, and The holding weight is calculated based on the detected holding pressure and the detected physical quantity.

In the method and apparatus, the retained weight is calculated based on the retained pressure of the attachment cylinder after the pressure of the tip attachment is released after the measurement start condition is satisfied, so that the retained weight is more effective than the conventional method. It is possible to measure the retained weight with high accuracy. Specifically, before the pressure is released, the holding pressure of the tip attachment may have increased to a pressure (for example, relief pressure) higher than the pressure corresponding to the weight of the object to be held. In this state, calculation of the holding weight based on the holding pressure may involve a large error. Furthermore, if the expansion and contraction operation of the attachment cylinder continues to stop until the time of measurement, the static friction force in the tip attachment cylinder will affect the measurement results. On the other hand, when the pressure is released through the throttle of the attachment cylinder, the holding pressure is reduced until the moment due to the holding pressure of the attachment balances the moment due to the weight of the object to be held and the tip attachment, that is, This allows the holding pressure to approach a pressure that truly corresponds to the weight of the object to be held. Furthermore, since the pressure relief causes the attachment cylinder to perform a minute expansion and contraction operation, it is effectively possible to prevent static frictional force from influencing the measurement results. Although the stretching operation is accompanied by a dynamic frictional force, the variation in the dynamic frictional force is smaller than the variation in the static frictional force. Therefore, releasing the pressure from the holding side hydraulic chamber enables more accurate measurement of the held weight.

The held weight may be a weight that increases or decreases in accordance with the weight of the object to be held. For example, the held weight may be the weight of only the object to be held, or may be the total weight of the object to be held and the tip attachment that holds the object. The former measurement makes it possible, for example, to determine the total weight of the objects loaded on the carrier using the tip attachment. In this case, the method includes measuring and storing an initial holding moment that is a moment around the attachment rotation axis for holding the tip attachment in a state where the tip attachment is not holding the object to be held. It is preferable that the holding weight is calculated based on the initial holding moment, the detected holding pressure, and the detected physical quantity in the holding weight calculation step. Further, in the device, the held weight calculation unit is configured to store the initial held moment, and calculate the held weight based on the initial held moment, the detected holding pressure, and the detected physical quantity. But good.

The working machine includes, for example, a hydraulic pump that discharges hydraulic oil to be supplied to the attachment cylinder, and a hydraulic pump that is interposed between the hydraulic pump and the attachment cylinder and that is supplied from the hydraulic pump to the tip attachment. The control valve further includes a control valve that operates to change the flow rate of the oil. In such a working machine, it is preferable that the pressure relief section of the held weight measuring device includes a pressure relief line and a pressure relief switching valve. The pressure relief line is arranged to bypass the control valve and communicate the holding side hydraulic chamber with the tank. The pressure relief switching valve is provided in the pressure relief line and is configured to be switchable between a closed position and an open position. The pressure relief switching valve shuts off the pressure relief line in the closed position. In the open position, the pressure relief switching valve forms a throttle line that opens the pressure relief line and includes the throttle. In this case, the pressure relief control section holds the pressure relief switching valve in the closed position until it determines that the measurement condition is satisfied, and after determining that the measurement condition is satisfied, the pressure relief switching valve It is preferable to control the operation of the pressure relief switching valve so as to switch the pressure relief switching valve to the open position.

Since the pressure relief switching valve opens and closes a pressure relief line that bypasses the control valve, it is possible to perform a pressure relief operation independent of the operation of the control valve. For example, the pressure relief operation can be performed by slightly changing the stroke of the control valve, but controlling such a stroke is difficult, especially when setting the opening area of the throttle for pressure relief. is not easy. On the other hand, the combination of the pressure relief line and the pressure relief switching valve provided therein makes it possible to easily perform the pressure relief operation by opening and closing the pressure relief switching valve. Further, it is also easy to set the opening area of the throttle in the pressure release switching valve.

When the work machine further includes an attachment operation device, the attachment operation device receives an attachment operation for expanding and contracting the attachment cylinder and causes the control valve to perform an opening/closing operation corresponding to the attachment operation, Preferably, the held weight measuring device further includes an operation lock switching section and an operation lock control section. The operation lock switching section can be switched between an operation lock state and a lock release state. The operation lock state is a state in which, among the attachment operations given to the attachment operating device, an attachment operation that causes the control valve to perform a holding side valve opening operation is disabled and the control valve is forcibly closed; The holding side valve opening operation is an opening operation of the control valve in a direction of increasing the pressure in the holding side hydraulic chamber, that is, the holding pressure. The unlocked state is a state in which the attachment operating device allows the control valve to perform an opening/closing operation corresponding to the attachment operation. The operation lock control section keeps the operation lock switching section in the unlocked state until at least the measurement start condition is met, and the pressure release section starts the pressure release operation from the time the measurement start condition is met. The operation lock switching unit is configured to be switched to the operation lock state before the start of the operation.

The operation lock switching section and the operation lock control section make it possible to continue normal measurement of the held weight even when the attachment operation is applied to the attachment operation device during the pressure relief operation. Specifically, when the operator gives an attachment operation to the attachment operation device during the pressure relief operation, and in response to this attachment operation, the attachment operation device causes the control valve to perform a holding side valve opening operation. Regardless of the pressure relief operation, the pressure in the holding-side hydraulic chamber of the attachment cylinder may increase, which may impede accurate measurement of the holding weight. However, the operation lock control section sets the operation lock switching section to the operation lock state when the pressure relief operation is performed, so that when the operator performs the attachment operation for the holding side valve opening operation, This also allows the control valve to remain closed and normal measurements to continue.

The tip attachment is preferably a bucket capable of excavating and loading earth and sand, for example. In this case, the holding pressure detector is configured to operate, as the holding pressure, to rotate the bucket of the pair of hydraulic chambers of the attachment cylinder in the digging direction, that is, in the direction in which the cutting edge of the bucket approaches the working device main body. It is preferable to detect the pressure in the hydraulic chamber (holding side hydraulic chamber) to which oil is supplied.

Alternatively, the tip attachment may be one that holds the object to be held at a specific holding position away from the attachment rotation axis, for example, one that attracts or clamps the object by magnetic force. In these cases as well, the holding pressure detector detects, as the holding pressure, a moment due to the weight of the object held at the holding position among the pair of hydraulic chambers of the attachment cylinder and the weight of the tip attachment. It is preferable to detect the pressure in a hydraulic chamber (holding side hydraulic chamber) to which hydraulic oil is supplied for holding the tip attachment against the pressure.

As described above, according to the present invention, in a working machine equipped with a working device including a tip attachment, the held weight corresponding to the weight of the object held by the tip attachment can be accurately measured with a simple configuration. A method and apparatus are provided that allow this.

1 is a side view of a hydraulic excavator which is a working machine according to a first embodiment of the present invention. FIG. 2 is a side view showing a main part of the hydraulic excavator including a tip attachment mounted on the hydraulic excavator and an attachment cylinder that is a bucket cylinder for rotating the tip attachment. FIG. 3 is a diagram showing a hydraulic circuit for driving the attachment cylinder and a holding weight measuring device attached thereto. FIG. 2 is a block diagram showing a functional configuration of a controller that constitutes the held weight measuring device. It is a flowchart which shows the arithmetic control operation performed by the said controller. It is a side view which shows the main part of the working machine based on the 2nd Embodiment of this invention, and the part which includes a tip attachment and the attachment cylinder for rotating this. It is a side view which shows the main part of the working machine based on the 3rd Embodiment of this invention, and the part which includes a tip attachment and the attachment cylinder for rotating this.

Preferred embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a hydraulic excavator that is a working machine according to a first embodiment. The hydraulic excavator includes a lower traveling body 10, an upper rotating body 12, and a working device 14. The lower traveling body 10 has a left crawler 11L and a right crawler 11R. The entire lower traveling body 10 can travel on the ground G by driving the left and right crawlers 11L and 11R. The upper revolving body 12 is mounted on the lower traveling body 10 and together with the lower traveling body 10 constitutes a fuselage. The upper rotating body 12 can pivot about a pivot axis Z that is vertical with respect to the lower traveling body 10, and in conjunction with this pivoting, the working device 14 also pivots about the pivot axis Z. The upper revolving body 12 includes a revolving frame 15 and a plurality of elements mounted thereon. The plurality of elements include a cab 16 that is a driver's cabin, and an engine room 18 that stores an engine (not shown).

The working device 14 includes a boom 20, an arm 22, and a bucket 24. The boom 20 has a base end and an opposite tip. The base end portion is connected to the front end of the upper revolving body 12 so as to be able to rise and fall, that is, to be able to rotate up and down about a horizontal axis. The arm 22 has a base end and an opposite tip. The base end portion is rotatably connected to the distal end portion of the boom 20 about a horizontal axis, that is, in the vertical direction.

The boom 20 and the arm 22 constitute a working device main body. The base end of the boom 20 corresponds to the base end of the working device main body, and the distal end of the arm 22 corresponds to the distal end of the working device main body. The main body of the working device displaces the tip of the arm 22 and the bucket 24 attached thereto relative to the machine body by the raising and lowering motion of the boom 20 and the rotating motion of the arm 22.

The bucket 24 corresponds to the tip attachment according to the present invention, and is attached to the tip of the working device main body, that is, the tip of the arm 22, so as to be rotatable around the attachment rotation axis. The attachment rotation axis extends in a horizontal direction perpendicular to the longitudinal direction of the working device 14, that is, in the left-right direction. Therefore, the bucket 24 is vertically rotatable relative to the arm 22. Specifically, the bucket 24 is connected to the tip of the arm 22 via an attachment pin 23, and the central axis of the attachment pin 23 corresponds to the attachment rotation axis.

The bucket 24 is capable of excavating and loading earth and sand that constitutes the ground G. Specifically, the bucket 24 includes a container-shaped bucket body and a cutting edge 25 provided at the tip of the bucket body. The cutting edge 25 can penetrate the ground G and excavate it.

The hydraulic excavator further includes a plurality of hydraulic actuators. Each of the plurality of hydraulic actuators operates by receiving a supply of hydraulic oil to move a driven object. The plurality of hydraulic actuators include a swing motor, a pair of left and right travel motors, and a plurality of work actuators. The pair of left and right running motors are connected to the left crawler 11L and the right crawler 11R, respectively, and drive the left and right crawlers 11L and 11R to cause them to perform a running operation. The swing motor is connected to the upper rotating body 12 and rotates the upper rotating body 12 and the working device 14 mounted thereon with respect to the lower traveling body 11. The plurality of work actuators move the work device 14 and include a boom cylinder 26, an arm cylinder 27, and an attachment cylinder (bucket cylinder in this embodiment) 28.

The boom cylinder 26 is a hydraulic cylinder for raising and lowering the boom 20. Specifically, the boom cylinder 26 is disposed between the boom 20 and the upper revolving structure 12 so that the boom 20 rises and falls as the boom cylinder 26 expands and contracts.

The arm cylinder 27 is a hydraulic cylinder for rotating the arm 22 with respect to the boom 20. Specifically, the arm cylinder 27 is arranged between the arm 22 and the boom 20 so that the arm 22 rotates with respect to the boom 20 as the arm cylinder 27 expands and contracts.

The attachment cylinder 28 is a hydraulic cylinder for rotating the bucket 24, which is the tip attachment, with respect to the arm 22. Specifically, the attachment cylinder 28 is arranged so that the arm 22 and the bucket 24 rotate so that the bucket 24 rotates about the attachment rotation axis with respect to the boom 20 as the attachment cylinder 28 expands and contracts. connected to.

FIG. 2 shows details of the attachment cylinder 28 and the drive transmission mechanism 40. The drive transmission mechanism 40 is configured to transmit the thrust of the attachment cylinder 28 to the bucket 24, which is the tip attachment, and rotate the bucket 24.

The attachment cylinder 28 includes a cylinder body 30, a piston 32, and a rod 34. The cylinder body 30 surrounds a cylindrical cylinder chamber. The piston 32 is loaded into the cylinder body 30 and divides the cylinder chamber into a bottom chamber 36 and a rod chamber 38 on the opposite side. The rod 34 extends in the axial direction from the piston 32 to pass through the rod chamber 38 and protrudes to the outside of the cylinder body 30.

The bottom chamber 36 and the rod chamber 38 correspond to a pair of hydraulic chambers located on opposite sides in the axial direction. The attachment cylinder 28 expands or contracts by supplying hydraulic oil to either of the pair of hydraulic chambers. Specifically, the attachment cylinder 28 expands as hydraulic oil is supplied to the bottom chamber 36 while the hydraulic oil in the rod chamber 38 is discharged. In other words, the amount of protrusion of the rod 34 from the cylinder body 30 increases. On the contrary, the attachment cylinder 28 contracts as the hydraulic oil is supplied to the rod chamber 38 while the hydraulic oil in the rod chamber 38 is discharged. In other words, the amount of protrusion of the rod 34 from the cylinder body 30 is reduced.

The attachment cylinder 28 has both ends in the axial direction, and the both ends are connected to the arm 22 and the bucket 24, respectively. Specifically, one of both ends of the attachment cylinder 28 is a cylinder base end. The cylinder base end is one of both ends of the cylinder body 30 and is constituted by the end closer to the bottom chamber 36 (hereinafter referred to as the "bottom side end"). Ru. The bottom end portion is rotatably connected to the back surface of the arm 22 via a cylinder base end pin 29 shown in FIG. The other of both ends of the attachment cylinder 28 is a cylinder tip, which is formed by the tip of the rod 34. The tip of the cylinder is connected to the bucket 24 via the drive transmission mechanism 40.

The drive transmission mechanism 40 converts the movement of the attachment cylinder 28 in the expansion/contraction direction into rotation of the bucket 24 about the attachment rotation axis. In this embodiment, the drive transmission mechanism 40 is a link mechanism including a first link 41 and a second link 42 shown in FIG.

The first link 41 is an attachment link (bucket link in this first embodiment) that interconnects the tip of the rod 34 and the bucket 24. The first link 41 has both ends in the longitudinal direction of the first link 41 . One end of the two ends is rotatably connected to the tip of the rod 34 via a rod tip pin 44, and the other end is rotatably connected to the bucket 24 via a pin 46. connected.

The second link 42 is an idle link that interconnects the tip of the rod 34 and the tip of the arm 22. The second link 42 has both ends in the longitudinal direction of the second link 42 . One end of the two ends is rotatably connected to the tip of the rod 34 via the rod tip pin 44, and the other end is connected to the tip of the arm 22 with an arm tip pin 48. are rotatably connected through the

The drive transmission mechanism 40 rotates the bucket 24 in the excavation direction with the rotation of the first and second links 41 and 42 when the attachment cylinder 28 is extended, and conversely when the attachment cylinder 28 contracts. The bucket 24 is rotated in the opening direction with the rotation of the first and second links 41 and 42 in opposite directions. The excavation direction is a direction in which the cutting edge 25 of the bucket 24 approaches the ventral surface of the arm 22, and the ventral surface of the arm 22 is a surface facing downward when the arm 22 extends forward. Accordingly, the excavation direction is counterclockwise in FIG. 2. The opening direction is opposite to the excavation direction, which in FIG. 2 is clockwise.

FIG. 3 shows a portion of the hydraulic circuit installed in the hydraulic excavator that contributes to driving the attachment cylinder 28. The hydraulic circuit has a function of supplying hydraulic oil to each of the plurality of hydraulic actuators and controlling the direction and flow rate of the supply. Specifically, the hydraulic circuit includes a hydraulic pump 50, a control valve 52, and an attachment operating device (bucket operating device in this embodiment) 54 shown in FIG. 3 as elements for driving the attachment cylinder 28. .

The hydraulic pump 50 discharges hydraulic oil to be supplied to the attachment cylinder 28. Specifically, the hydraulic pump 50 is connected to the output shaft of the engine (not shown), and is driven by the engine to suck in hydraulic oil from the tank 51 and discharge it from a discharge port.

The control valve 52 is interposed between the discharge port of the hydraulic pump 50 and the attachment cylinder 28, and is configured to change the direction and flow rate of hydraulic oil supplied from the hydraulic pump 50 to the attachment cylinder 28. Opens and closes. Specifically, the control valve 52 according to this embodiment is constituted by a pilot-operated three-position directional switching valve having a first pilot port and a second pilot port (not shown), and has a neutral position shown in FIG. PN, has a first drive position P1 and a second drive position P2. The control valve 52 has a plurality of ports, and the plurality of ports are a pump port connected to the discharge port of the hydraulic pump 50 and a bottom chamber 36 of the attachment cylinder 28 via a bottom oil passage 56. and a rod side port connected to the rod chamber 38 of the attachment cylinder 28 via a rod side oil passage 58. Relief valves 57 and 59 are provided in the bottom side oil passage 56 and the rod side oil passage 58, respectively.

When pilot pressure is not supplied to either the first or second pilot port, the control valve 52 is maintained at the neutral position PN (center position in FIG. 3). The control valve 52 maintained at this neutral position PN blocks communication between the hydraulic pump 50 and the attachment cylinder 28 and forms an oil passage that directly communicates the discharge port of the hydraulic pump 50 with the tank 51. do. That is, the control valve 52 held at the neutral position PN is in a closed state that prevents the supply of hydraulic oil from the hydraulic pump 50 to the attachment cylinder 28.

When pilot pressure is supplied to the first pilot port, the control valve 52 shifts from the neutral position PN to the first drive position (left side position in FIG. 3) P1 with a stroke corresponding to the magnitude of the pilot pressure. In other words, the valve is opened. The control valve 52, which has been shifted to the first driving position P1, connects the discharge port of the hydraulic pump 50 and the bottom side oil passage 56 to each other, and also connects the rod side oil passage 58 to the tank 51. form a road. This oil passage has an opening area corresponding to the stroke (that is, corresponding to the magnitude of the pilot pressure). Therefore, the control valve 52 shifted to the first driving position P1 allows the hydraulic fluid discharged from the hydraulic pump 50 to flow into the bottom chamber 36 of the attachment cylinder 28 at a flow rate corresponding to the magnitude of the pilot pressure. At the same time, the hydraulic oil discharged from the rod chamber 38 of the attachment cylinder 28 is allowed to return to the tank 51, so that the attachment cylinder 28 is adjusted to the magnitude of the pilot pressure. Allows for expansion at a corresponding speed.

Conversely, when pilot pressure is supplied to the second pilot port, the control valve 52 moves from the neutral position PN to the second drive position (the right position in FIG. 3) with a stroke corresponding to the magnitude of the pilot pressure. The valve is shifted to P2, that is, the valve is opened. The control valve 52, which has been shifted to the second driving position P2, connects the discharge port of the hydraulic pump 50 and the rod-side oil passage 58 to each other, and also connects the bottom-side oil passage 56 to the tank 51. form a road. This oil passage has an opening area corresponding to the stroke (that is, corresponding to the magnitude of the pilot pressure). Therefore, the control valve 52 shifted to the second driving position P2 allows the hydraulic fluid discharged from the hydraulic pump 50 to flow into the rod chamber 38 of the attachment cylinder 28 at a flow rate corresponding to the magnitude of the pilot pressure. At the same time, the hydraulic oil discharged from the bottom chamber 36 of the attachment cylinder 28 is allowed to return to the tank 51, so that the attachment cylinder 28 is adjusted to the magnitude of the pilot pressure. Allows contraction at corresponding speed.

The attachment operation device (bucket operation device in this embodiment) 54 is capable of receiving an attachment operation (bucket operation in this embodiment) by an operator in the cab 16, and is capable of receiving an attachment operation (bucket operation in this embodiment) by an operator in the cab 16, and is capable of receiving an attachment operation (bucket operation in this embodiment) by an operator in the cab 16. The control valve 52 is configured to cause the control valve 52 to perform opening and closing operations. That is, the attachment operating device 54 allows the operator to operate the bucket 24 through the control valve 52.

Specifically, the attachment operating device 54 includes an attachment operating valve (in this embodiment, a bucket operating valve) 60, a first pilot line 61, and a second pilot line 62. The attachment operation valve 60 is constituted by a so-called remote control valve, and includes an operation lever 64 and a pilot valve 66. The first pilot line 61 is arranged to connect the pilot valve 66 and the first pilot port of the control valve 52 to each other. The second pilot line 62 is arranged to interconnect the pilot valve 66 and the second pilot port of the control valve 52.

The operating lever 64 is arranged in the cab 16 at a position near the driver's seat, more specifically at a position where it can receive an attachment operation by the operator sitting in the driver's seat. The attachment operation is, for example, an operation of lowering the operating lever 64 from a neutral position in which the operating lever 64 is upright in either a first direction or a second direction that are different from each other.

The pilot valve 66 is interconnected with the operating lever 64 so as to perform a valve opening operation corresponding to the attachment operation applied to the operating lever 64. The pilot valve 66 has an input port and a pair of output ports. The input port is connected to a pilot hydraulic power source (not shown). The pilot oil pressure source is, for example, a pilot pump, and the pilot pump is driven by the engine and discharges the hydraulic oil in the tank 51 as pilot oil. The pair of output ports are connected to the first and second pilot ports via the first and second pilot lines 61 and 62, respectively.

The pilot valve 66 receives pilot pressure from the pilot hydraulic pressure source to the first pilot port through the first pilot line 61 when the operating lever 64 is operated in the first direction. The valve opens to allow. Conversely, when the attachment operation in the second direction is applied to the operating lever 64, the pilot valve 66 inputs pilot pressure from the pilot hydraulic pressure source to the second pilot port through the second pilot line 62. The valve opens to allow the The degree of opening of the pilot valve 66 corresponds to the amount of attachment operation, which is the magnitude of the attachment operation. Therefore, a pilot pressure having a magnitude corresponding to the attachment operation amount is supplied from the pilot hydraulic pressure source to the first pilot port or the second pilot port.

The hydraulic excavator is further equipped with a held weight measuring device for measuring held weight. The held weight is a weight corresponding to the weight of the object held by the tip attachment. In this embodiment, the weight of earth and sand loaded into the bucket 24 by the excavation operation of the ground G by the bucket 24 corresponds to the held weight, that is, the weight to be measured.

Specifically, the holding weight measuring device according to this embodiment includes a holding pressure detector 68, a cylinder length detector 69, a pressure relief section 70, an operation lock switching section 72, and a controller 80 shown in FIG. .

The holding pressure detector 68 detects the holding pressure PH of the attachment cylinder 28. The holding pressure PH is the pressure of hydraulic oil in the holding side hydraulic chamber of the attachment cylinder 28. The holding side hydraulic chamber is one of the pair of hydraulic chambers of the attachment cylinder 28, and is supplied with hydraulic oil for holding the tip attachment against the weight of the tip attachment and the object to be held. This is a hydraulic chamber. The holding side hydraulic chamber according to this embodiment is operated to hold the bucket 24 against the gravity acting on the bucket 24 and its load (earth and sand) among the bottom chamber 36 and the rod chamber 38. This is a hydraulic chamber to which oil is supplied, that is, the bottom chamber 36. Therefore, the holding pressure detector 68 is arranged to detect the bottom pressure, which is the pressure of the hydraulic oil in the bottom chamber 36. The holding pressure detector 68 can be configured by, for example, a pressure sensor.

The cylinder length detector 69 detects the cylinder length, which is the length of the attachment cylinder 28 in the axial direction. The cylinder length detector 69 can be configured, for example, by a stroke sensor that detects the stroke of the attachment cylinder 28 in the expansion/contraction direction.

The cylinder length corresponds to a moment specific physical quantity according to the present invention. The moment specific physical quantity is a physical quantity necessary for specifying the radius R of the holding moment MH. The holding moment MH is a moment based on the holding pressure PH of the attachment cylinder 28, and is a moment around the attachment rotation axis that acts on the bucket 24, which is the tip attachment. For example, as shown in FIG. 2, the holding force due to the holding pressure PH of the attachment cylinder 28, that is, the holding force applied to the rod tip pin 44 and the ends of the first and second links 41, 42 connected thereto. Assuming that the thrust force in the extension direction of the attachment cylinder 28 is FH, the radius R of the holding moment MH corresponds to the distance between the holding force F and a straight line that is parallel to the holding force F and passing through the attachment rotation center axis. do. This radius R can be calculated geometrically based on the cylinder length.

The moment specific physical quantity is not limited to the cylinder length. The cylinder specific physical quantity may be, for example, an angle that the second link (idler link) 42 makes with respect to the arm 22. That is, it is possible to specify the radius R of the holding moment MH based on the angle as well. In this case, the physical quantity detector can be configured by, for example, an angle sensor that detects the angle.

The pressure relief section 70 is configured to perform a pressure relief operation. The pressure relief operation is performed by releasing a part of the hydraulic oil supplied to the bottom chamber 36, which is the holding-side hydraulic chamber, to the tank 51 through the throttle, thereby reducing the pressure of the hydraulic oil in the bottom chamber 36, that is, the bottom chamber. It is an action to release pressure.

In this embodiment, the pressure relief section 70 includes a pressure relief line 73 and a pressure relief switching valve 74.

The pressure relief line 73 is arranged so as to bypass the control valve 52 and communicate the bottom chamber 36 with the tank 51. Specifically, the pressure relief line 73 according to this embodiment branches from the middle of the bottom side oil passage 56 and reaches the tank 51.

The pressure relief switching valve 74 is provided in the pressure relief line 73 and is configured to be switchable between a closed position and an open position. In the closed position (the left position in FIG. 3), the pressure relief switching valve 74 blocks the pressure relief line 73 and prevents the pressure relief operation. In the open position (the right position in FIG. 3), the pressure relief switching valve 74 forms a throttle line that opens the pressure relief line 73 and includes the throttle, thereby enabling the pressure relief operation. do. The opening area of the throttle is set such that the bottom pressure decreases to a degree close to the true holding pressure, that is, the pressure that holds the bucket 24 against the weight of the earth and sand, due to the release of hydraulic oil through the throttle. , is set.

In this embodiment, the pressure relief switching valve 74 is constituted by an electromagnetic switching valve having a solenoid 75. The pressure release switching valve 74 maintains the closed position when the pressure release command is not input to the solenoid 75 (no excitation current is applied), and when the pressure release command is input to the solenoid 75 (excitation current is not applied). (when flushed) is switched to the open position.

The operation lock switching section 72 is incorporated into the attachment operation device 54 and can be switched between an operation lock state and an unlock state. The operation lock state is a state in which, among the attachment operations given to the attachment operating device 54, the attachment operation that causes the control valve 52 to perform a holding side valve opening operation is invalidated, and the control valve 52 is forcibly closed. It is. The holding side valve opening operation is an opening operation of the control valve 52 in the direction of increasing the pressure in the holding side hydraulic chamber (in this embodiment, the bottom chamber 36), and in this embodiment, the holding side valve opening operation is a valve opening operation of the control valve 52 in the direction of increasing the pressure in the holding side hydraulic chamber (in this embodiment, the bottom chamber 36). This is an operation in the direction of increasing the stroke from PN to the first drive position P1. The unlocked state is a state in which the attachment operating device 54 allows the control valve 52 to perform an opening/closing operation corresponding to the attachment operation, that is, a state in which the attachment operating device 54 is allowed to perform its original operation. , is.

The operation lock switching section 72 according to this embodiment includes an operation lock switching valve 76 and a pilot pressure relief line 78.

The operation lock switching valve 76 is provided in the middle of the first pilot line 61 and can be switched between an operation lock position and a lock release position. The operation lock switching valve 76 opens the first pilot line 61 in the lock release position (left side position in FIG. 3), and connects the first pilot line 61 from the attachment operation valve 60 to the first pilot line 61 of the control valve 52. A pilot pressure corresponding to the attachment operation in the first direction is allowed to be supplied to the pilot port. The operation lock switching valve 76 shuts off the first pilot line 61 in the operation lock position (the right position in FIG. 3) and communicates the first pilot port with the tank 51 through the pilot pressure relief line 78. This prevents the pilot pressure corresponding to the attachment operation from being supplied from the attachment operation valve 60 to the first pilot port of the control valve 52 through the first pilot line 61, and forcibly closes the control valve 52. valve, that is, keep it at the neutral position PN.

In this embodiment, the operation lock switching valve 76 is constituted by an electromagnetic switching valve having a solenoid 77. The operation lock switching valve 76 maintains the lock release position when the operation lock command is not input to the solenoid 77 (specifically, no excitation current is applied), and when the operation lock command is input to the solenoid 77. and (when the excitation current is applied) the operation is switched to the operation lock position.

The operation lock state may be a state in which at least the holding side valve opening operation is blocked, and the operation lock state may be a state in which at least the holding side valve opening operation is inhibited, and the opposite side valve opening operation (valve opening operation in the direction of increasing the pressure of the hydraulic oil in the rod chamber 38; neutral position PN) It does not matter whether or not the operation of increasing the stroke from the position P2 to the second drive position P2 is blocked. The operation lock switching section 72 according to this embodiment is configured to allow the valve opening operation on the opposite side.

The controller 80 can be composed of, for example, a microcomputer, and includes a measurement start timing determination section 82, a pressure release command section 84, and an operation lock as shown in FIG. 4 as elements for measuring the held weight. It includes a command section 86 and a retained weight calculation section 88.

The measurement start time determination unit 82 determines whether the measurement start time has arrived. The measurement start time is the time when the measurement of the held weight should be started, and specifically, the time when a preset measurement start condition is satisfied. That is, the measurement start time determining unit 82 determines whether the measurement opening condition is satisfied.

The measurement start condition is preferably set to a condition that makes it possible to determine that the attitude of the tip attachment (bucket 24) with respect to the arm 22 is in a stable state. Specifically, in the case of the hydraulic excavator shown in FIG. 1, after the excavation operation by the bucket 24 and the lifting operation by raising the boom 20 are completed, the upper revolving body 12 is rotated in the same posture, and the bucket Since the loading of earth and sand from the bucket 24 to the transport vehicle is performed when the bucket 24 reaches a position directly above the transport vehicle such as a dump truck, it is preferable that the holding weight is measured during the turning operation. . Therefore, the measurement start condition is preferably set to at least that the digging operation is completed, and more preferably that the lifting operation is completed and the turning operation is started.

The pressure relief command section 84 corresponds to a pressure relief control section according to the present invention, and controls the pressure caused by the pressure relief section 70 by inputting a pressure relief command to the pressure relief switching valve 74 at an appropriate timing. Controls the extraction operation. Specifically, the pressure release command unit 84 stops inputting the pressure release command and maintains the pressure release switching valve 74 at the closed position at least until the measurement start condition is satisfied. On the other hand, the pressure release command unit 84 inputs the pressure release command to the pressure release switching valve 74 after the time when the measurement start condition is satisfied (measurement start time), and inputs the pressure release command to the pressure release switching valve 74. Switch to the open position.

The operation lock command unit 86 corresponds to an operation lock control unit according to the present invention, and controls switching of the operation lock by inputting an operation lock command to the operation lock switching valve 76 at an appropriate timing. conduct. Specifically, the operation lock command unit 86 stops inputting the operation lock command and maintains the operation lock switching valve 76 at the unlocked position until the measurement start condition is satisfied. On the other hand, the operation lock command unit 86 inputs the operation lock command to the operation lock switching valve 76 at the time when the measurement start condition is satisfied (measurement start time), and switches the operation lock switching valve 76. Switch to the operation lock position.

The pressure release command section 84 sends the pressure release switching valve 74 to the pressure release switching valve 74 at the same time as the operation lock command is input from the operation lock command section 86 to the operation lock switching valve 76, or at a timing slightly delayed from the input. Start inputting the pressure release command. This allows the pressure relief operation to be performed in a state where the attachment operation for the holding side valve opening operation is reliably locked. In other words, when the attachment operation is performed during the pressure relief operation, the control valve 52 is prevented from actually performing the holding-side valve opening operation in response to the attachment operation.

The held weight calculation unit 88 calculates the held weight which is detected by the held pressure detector 68 and the cylinder length detector 69, respectively, at a time when preset measurement conditions are satisfied after the pressure release operation is started. The pressure PH and the cylinder length are acquired as the detected holding pressure and the detected cylinder length (detected physical quantities), respectively, and the held weight (in this embodiment, the bucket 24 is calculated based on the detected holding pressure and the detected cylinder length). Calculate the weight of the loaded earth and sand.

The measurement condition is set, for example, such that a preset pressure relief time elapses after the pressure relief operation is started. The pressure release time is set to a time required for the holding pressure (bottom pressure in this embodiment) PH to drop to a pressure corresponding to the weight of the earth and sand after the pressure release operation is started. The pressure release time is, for example, about 1 second, although it depends on the opening area of the throttle in the pressure release switching valve 74.

The retained weight calculation section 88 is connected to a display device 90. The display device 90 has a display screen. The display device 90 is arranged within the cab 16 so that the contents displayed on the display screen can be viewed by the operator.

Next, specific arithmetic and control operations performed by the controller 80 will be explained with reference to the flowchart of FIG.

The measurement start time determination unit 82 of the controller 80 determines whether the measurement start time has arrived, that is, whether preset measurement start conditions are satisfied (step S2). Until the measurement start condition is satisfied (NO in step S2), the holding weight measuring device is maintained in the initial state as shown in FIG. 3. Specifically, the pressure relief switching valve 74 of the pressure relief section 70 is kept in the closed position, and the operation lock switching valve 76 of the operation lock switching section 72 is kept in the unlocked position. Therefore, the pilot pressure corresponding to the attachment operation applied to the operation lever 64 of the attachment operation valve 60 is input to the control valve 52, and the hydraulic oil discharged from the hydraulic pump 50 is input to the bottom chamber 36 of the attachment cylinder 28. Supplied as usual.

When the measurement start time has arrived (YES in step S2), the operation lock command unit 86 of the controller 80 inputs an operation lock command to the operation lock switching valve 76 and sets the operation lock switching valve 76 to the operation lock position. (Step S4). As a result, the attachment operation for causing the control valve 52 to perform the holding side valve opening operation becomes invalid, and the control valve 52 is basically kept in the closed state. The time when the measurement start time has arrived is, for example, the time when the measurement start condition that the operation of the hydraulic excavator has shifted from the digging operation and the lifting operation to the turning operation is satisfied.

Disabling the attachment operation prevents the holding pressure PH from being increased by the attachment operation during subsequent measurement operations and preventing normal measurement of the held weight. In particular, after loading earth and sand into the bucket 24, the operator performs an operation to move the bucket 24 in the excavation direction (that is, corresponding to the holding side valve opening operation) in order to prevent earth and sand from spilling from the bucket 24 during the turning operation. Therefore, disabling such operations and closing the control valve 52 is effective in making accurate measurements.

Simultaneously with or following the input of the operation lock command, the pressure release command section 84 of the controller 80 inputs a pressure release command to the pressure release switching valve 74 of the pressure release section 70, thereby causing the pressure release switching. The valve 74 is switched to the open position, that is, the valve is opened (step S6). The pressure release switching valve 74 switched to the open position allows a part of the hydraulic oil in the bottom side oil passage 56 to escape to the tank 51 through the throttle, thereby causing the bottom chamber 36 of the attachment cylinder 28 to be released. This allows the bottom pressure to be released.

The pressure relief allows the bottom pressure to approach the pressure corresponding to the actual retained weight, thereby allowing a highly accurate measurement of the retained amount to be performed based on the bottom pressure. Specifically, in the excavation operation and the lifting operation, an attachment operation is often performed in which the attachment cylinder 28 makes a full stroke in the extension direction in order to rotate the bucket 24 in the excavation direction. In this case, the pressure in the bottom chamber 36 may reach a high pressure that exceeds the pressure corresponding to the retained weight (for example, the highest pressure corresponding to the relief pressure that is the set pressure of the relief valve 57). Furthermore, if the piston 32 of the attachment cylinder 28 has reached the full stroke position and does not move any further, the static friction force in the attachment cylinder 28 (the piston 32 and rod 34 are held stationary with respect to the cylinder body 30) (frictional force to be maintained) may significantly affect the measurement results. On the other hand, the pressure relief operation by the pressure relief section 70 allows the pressure in the bottom chamber 36 to drop to a pressure commensurate with the retained weight. At this time, the piston 32 and the rod 34 are displaced with respect to the cylinder body 30 while resisting dynamic frictional force, but since the variation in the dynamic frictional force is significantly smaller than the variation in the static frictional force, this also applies in this respect. It is expected that measurement accuracy will improve.

After the pressure relief operation is started, the retained weight calculation unit 88 of the controller 80 calculates the preset pressure from the start of the pressure relief operation in this embodiment, when preset measurement conditions are satisfied. When the extraction time has elapsed (YES in step S8), the holding pressure and cylinder length detected by the holding pressure detector 68 and the cylinder length detector 69 are respectively detected. (Step S10). Then, the held weight calculating section 88 calculates the held weight based on the detected holding pressure and the detected cylinder length (step S12).

In this embodiment, the retained weight is the weight of the earth and sand loaded in the bucket 24, and can be calculated, for example, according to the principle described below.

FIG. 2 shows the positions of the bucket gravity center G1 and the earth and sand gravity center G2. The bucket center of gravity G1 is the center of gravity of the bucket 24 when the bucket 24 is empty, with no earth and sand loaded therein, and the earth and sand center of gravity G2 is the center of gravity of the earth and sand estimated for the earth and sand loaded into the bucket 24. It is. The weight of the bucket 24 is W1, the weight of the earth and sand (in this embodiment, the weight equivalent to the holding weight) is W2, and the distance from the attachment rotation axis (the central axis of the attachment pin 23) to the bucket gravity center G1 and the earth and sand gravity center is Letting the horizontal distances to G2 be L1 and L2, respectively, the bucket weight moment MW1 and the weight moment MW2 during use, which are generated due to the bucket weight W1 and the earth and sand weight W2, are respectively expressed by the following equations.

MW1=W1×L1...(1)
MW2=W1×L1+W2×L2…(2)
The bucket weight moment MW1 is the moment around the attachment rotation axis due to the bucket weight W1 when the bucket 24 is empty and no soil is loaded, and the weight moment MW2 during use is the moment when the bucket 24 is actually loaded with earth and sand. This is the moment around the attachment rotation axis due to both the bucket weight W1 and the earth and sand weight W2 in a state where earth and sand are loaded. Both moments act on the bucket 24 in a direction that causes the bucket 24 to rotate in the opening direction, clockwise in FIG. 2 .

The horizontal distances L1 and L2 can be set based on the attitude that the bucket 24 is assumed to take with respect to the arm 22 when the measurement is performed and the shape of the earth and sand estimated in that attitude. be. Although there is a possibility that there is a deviation between the horizontal distance assumed in this way and the horizontal distance at the time of actual measurement, the deviation is small and has little effect on the measured value of the held weight.

By subtracting the above equation (1) from the above equation (2), the following equation for determining the earth and sand weight W2 corresponding to the retained weight is obtained.

W2=(MW2-MW1)/L2...(3)
On the other hand, the initial holding moment MH1 and the holding moment MH2 during use for holding the bucket 24 in the posture shown in FIG. 2 against the moments MW1 and MW2 due to the bucket weight W1 and the earth and sand weight W2 are calculated by the following formula It is expressed as

MH1=FH1×R1×μd…(4)
MH2=FH2×R2×μd…(5)
The holding moments MH1 and MH2 are both based on the holding force FH given by the attachment cylinder 28, and the holding forces FH1 and FH2 are based on the initial state when the bucket 24 is empty and when the bucket 24 is loaded with earth and sand. This corresponds to the thrust force in the extension direction of the attachment cylinder 28 in each of the usage conditions. Further, R1 and R2 are moment radii R of the initial holding moment MH1 and the holding moment MH2 during use, and μd is a kinetic friction coefficient that specifies the kinetic friction force generated in the attachment cylinder 28.

As described above, the moment radii R1 and R2 correspond to the distance between the holding forces FH1 and FH2 and a straight line that is parallel to the holding forces (cylinder thrust) FH1 and FH2 and passing through the attachment rotation center axis, It can be calculated geometrically based on the cylinder length.

The dynamic friction coefficient μd can be measured for the attachment cylinder 28 in advance. Although there is variation in the dynamic friction coefficient μd, the magnitude thereof is smaller than the variation in the static friction coefficient.

The thrust forces FH1 and FH2 are expressed by the following equations, assuming that the pressure receiving area of the piston 32 facing the bottom chamber 36 is Ap.

FH1=PH1×Ap…(6)
FH2=PH2×Ap…(7)
Here, PH1 is the holding pressure (bottom pressure) PH detected when the bucket 24 is empty, that is, the initial holding pressure. This initial holding pressure PH1 and the radius R1 of the initial holding moment MH1 can be detected in advance in a factory, for example, or can be acquired in an initial setting mode before measurement. Therefore, the initial holding moment MH1 (=FH1×R1×μd) can be stored in advance in the holding weight calculating section 88 as a known value. On the other hand, PH2 is the holding pressure detected by the holding pressure detector 68 when the bucket 24 is actually loaded with earth and sand, and is the holding pressure detected when the measurement conditions are satisfied. In other words, it is the detected holding pressure.

Since the initial holding moment MH1 and the holding moment MH2 in use are balanced with the bucket weight moment MW1 and the weight moment MW2 in use, respectively, the following equation is obtained.

MW1=MH1...(8)
MW2=MH2=FH2×R2×μd…(9)
By substituting equations (8) and (9) into equation (3) above, and further substituting equation (7) for FH2 in equation (9), the following equation is obtained.

W2=(PH2×Ap×R2×μd−MH1)/L2…(10)
Therefore, the retained weight calculation unit 88 calculates the amount of earth and sand corresponding to the retained weight based on the detected retained pressure PH2, the moment radius R2 corresponding to the detected cylinder length, and the initial retained moment MH1 stored in advance. It is possible to calculate the weight W2.

The retained weight calculation unit 88 generates display information that is information to be displayed to the operator based on the earth and sand weight (held weight) W2, and inputs this to the display device 90 to display it on the display screen. . In this embodiment, the display information is information about how much earth and sand can be loaded into the transport vehicle for which the total loaded weight has been set, for example, the remaining loaded weight and/or This is the number of loadings remaining. The display information can be obtained by integrating the earth and sand weight W2, which is measured every time earth and sand is loaded from the bucket 24 onto the transport vehicle.

After one measurement operation is completed as described above, the pressure release command unit 84 cancels the pressure release command and returns the pressure release switching valve 74 from the open position to the closed position (step S16). . Further, the operation lock command unit 86 releases the operation lock command and returns the operation lock switching valve 76 from the operation lock position to the lock release position (step S18). The measurement operation is performed every time the earth and sand excavated by the bucket 24 is loaded onto a transport vehicle.

The present invention is not limited to the embodiments described above. The present invention also includes, for example, the following embodiments.

(A) Regarding the holding pressure of the tip attachment and attachment cylinder The tip attachment according to the present invention is not limited to the bucket 24 described above. The present invention can be widely applied to various tip attachments that can hold an object at a specific holding position while being attached to the tip of a working device main body. Furthermore, the holding pressure of the attachment cylinder is not necessarily the bottom pressure, but is specified by the positional relationship between the attachment cylinder and the tip attachment.

Specifically, the present invention also includes, for example, a second embodiment and a third embodiment described below.

FIG. 6 shows the main parts of the working machine according to the second embodiment. This working machine is the hydraulic excavator according to the first embodiment, except that a lifting magnet 100 is attached to the tip of the arm 22 instead of the bucket 24. The lifting magnet 100 is a tip attachment that holds an object 92 containing a magnetic material by magnetic attraction.

Like the bucket 24, the lifting magnet 100 is attached to the arm 22 via an attachment pin 23 so as to be rotatable around the attachment rotation axis, which is the central axis thereof. The lifting magnet 100 is connected to the tip of the rod 34 of the attachment cylinder 28 via a drive transmission mechanism 40 so that the lifting magnet 100 can be rotated by the attachment cylinder 28 . The drive transmission mechanism 40 includes a first link 41 and a second link 42 similarly to the drive transmission mechanism 40 according to the first embodiment.

The lifting magnet 100 includes an attachment body 102, a connecting part 104, and an adsorption part 106. The attachment main body 102 has a built-in magnet (not shown), and the magnet generates magnetic force for attracting the object 92 to be held. The connecting portion 104 protrudes upward from the top surface of the attachment body 102 and is connected to the tip of the arm 22 and the drive transmission mechanism 40 . Specifically, the connecting portion 104 is rotatably connected to the arm 22 via the attachment pin 23 and rotatably connected to the first link 41 of the drive transmission mechanism 40 via a pin 46. is connected to. The suction section 106 has a suction surface that faces downward when in use, and attracts the object 92 onto the suction surface using the magnetic force generated by the magnet.

The suction surface of the suction section 106 has a shape that allows the holding position to be specified. The holding position is a position where the object to be held 92 is to be held on the suction surface (the position of the center of gravity of the object to be held 92). Specifically, the suction surface includes a pair of guide surfaces 107 and 108. The pair of guide surfaces 107 and 108 are arranged on both sides of the reference line 109, with the reference line 109 interposed therebetween. The reference line 109 is, for example, a straight line parallel to the attachment rotation axis (a straight line extending in the depth direction of the paper in FIG. 6), and the holding position is located directly below the reference line 109. The pair of guide surfaces 107 and 108 have a shape that guides the object to be held 92 that comes into contact with either of the guide surfaces 107 and 108 to the holding position, specifically, an upward slope toward the reference line 109. It has a shape. Alternatively, the suction surface may be an upwardly convex curved surface.

The holding position is a position away from the attachment rotation axis, and in this embodiment, it is set to the front side (on the left side in FIG. 6) of the attachment rotation axis in the posture during use as shown in FIG. 6. has been done. This allows a substantial increase in the working radius of the working machine.

The held weight measuring device according to the second embodiment has the same configuration as the measuring device according to the first embodiment, and measures the weight of the object to be held 92 as the held weight. . The measuring device according to this second embodiment also includes a holding pressure detector 68. However, contrary to the holding pressure detector 68 according to the first embodiment, this holding pressure detector 68 detects not the bottom pressure of the attachment cylinder 28 but the rod pressure, that is, the rod pressure in the rod chamber 38 of the attachment cylinder 28. The pressure of the hydraulic oil is arranged to be detected as the holding pressure PH. The reason is as follows.

Since the holding position is on the front side of the attachment rotating shaft, the moment MW2 that acts on the lifting magnet 100 during use due to the weight W2 of the object 92 held at the holding position causes the attraction surface of the lifting magnet 100 to The moment is in the backward direction, and in FIG. 6, the moment is in the counterclockwise direction. Therefore, the moment that the attachment cylinder 28 should apply to the lifting magnet 100 in order to hold the lifting magnet 100 in the posture shown in FIG. 6 against this moment MW2, that is, the holding moment MH2 during use, is in the clockwise direction in FIG. This is the moment due to the thrust of the attachment cylinder 28 in the contraction direction. The thrust in the contraction direction is generated by supplying hydraulic oil to the rod chamber 38 of the attachment cylinder 28. Therefore, in this second embodiment, the rod chamber 38 is a holding side hydraulic chamber, and the pressure of the hydraulic oil in the rod chamber 38 is the pressure to be detected as the holding pressure PH. In other words, the earth and sand weight of the first embodiment is determined based on the holding pressure PH which is the rod pressure and the moment specific physical quantity (for example, cylinder length) for specifying the radius of the holding moment MH2 in use. Similarly, the weight W2 of the object to be held 92 can be calculated as the held weight.

In this second embodiment, as shown in FIG. 6, for example, the possibility that the attachment cylinder 28 will be fully stroked during use is smaller than that of the bucket 24. However, even if the attachment cylinder 28 is not fully stroked in this way, the pressure relief operation before measurement can improve measurement accuracy by causing a small displacement in the attachment cylinder 28 and eliminating the static friction force that has large variations. It is possible to contribute.

FIG. 7 shows the main parts of the working machine according to the third embodiment. This working machine is the hydraulic excavator according to the first embodiment, except that a grapple 110 is attached to the tip of the arm 22 instead of the bucket 24. The grapple 110 is a tip attachment that grips and holds an object 92 such as wood.

The grapple 110 is also attached to the arm 22 via the attachment pin 23 so as to be rotatable around the attachment rotation axis, which is its central axis, and can be rotated by the attachment cylinder 28. It is connected to the tip of the rod 34 of the attachment cylinder 28 via a drive transmission mechanism 40.

The grapple 110 includes an attachment body 112, a connecting portion 114, a pair of gripping claws 116, and a gripping cylinder 118. Similar to the connecting portion 104 according to the second embodiment, the connecting portion 114 protrudes upward from the upper surface of the attachment main body 112 and is rotatably attached to the tip of the arm 22 via the attachment pin 23. At the same time, it is rotatably connected to the first link 41 of the drive transmission mechanism 40 via a pin 46 .

The pair of gripping claws 116 are driven by the gripping cylinder 118 in the opening and closing direction between an open position and a closed position shown in FIG. The pair of gripping claws 116 grip the object 92 in the closed position, and release the object 92 in the open position further apart from each other in the left-right direction than in the closed position. Specifically, each of the pair of gripping claws 116 has a proximal end and a claw end on the opposite side thereof, and a portion slightly shifted toward the distal end from the proximal end is connected to the rotating shaft 117. and is connected to the attachment main body 112. The pair of gripping claws 116 perform an opening/closing operation by respectively rotating in opposite directions about the rotation axis 117 and around an axis parallel to the attachment rotation axis.

The gripping cylinder 118 is constituted by a hydraulic cylinder, and is connected to the pair of gripping claws 116 so as to cause the pair of gripping claws 116 to open and close by expanding and contracting in its axial direction. The gripping cylinder 118 is housed in the attachment main body 112 in a horizontal position with its expansion and contraction direction being in the front-rear direction perpendicular to the attachment rotation axis. The gripping cylinder 118 has both ends in the axial direction, and the both ends are connected to the base ends of the pair of gripping claws 116 so as to be rotatable and relatively displaceable in the longitudinal direction of the gripping claws 116. ing.

The holding position where the grapple 110 holds the object 92 is the center of gravity of the object 92 held between the pair of gripping claws 116, as shown in FIG. Like the holding position according to the second embodiment, the holding position according to this embodiment is also located in front of the attachment rotation axis (the central axis of the attachment pin 23), and the holding moment MH by the attachment cylinder 28 is is based on the thrust of the attachment cylinder 28 in the contraction direction. Therefore, like the holding pressure detector 68 according to the second embodiment, the holding pressure detector 68 according to the third embodiment also detects the rod pressure of the attachment cylinder 28 as the holding pressure PH. is attached to the attachment cylinder 28.

Also in this third embodiment, the attachment cylinder 28 is not necessarily fully stroked in the contraction direction in the posture during use, but the pressure release operation before measurement causes a minute displacement in the attachment cylinder 28. Eliminating static friction force, which has large variations, can contribute to improving measurement accuracy.

(B) About retained weight and initial retained moment The retained weight, which is the object of measurement in the present invention, may be any weight that corresponds to the weight of the object to be held, and does not necessarily have to be the weight of the object itself. For example, for the purpose of diagnosing fatigue of an attachment cylinder or working equipment due to long-term use, the sum of the weight of the tip attachment and the object to be held (in the first embodiment, the sum of the bucket weight W1 and the earth and sand weight W2) is held. May be measured as weight. In this case, unlike the first embodiment, the holding weight calculation section does not necessarily need to store the initial holding moment. The initial holding moment is a moment for holding the tip attachment by the thrust of the attachment cylinder against its own weight when the tip attachment is not holding an object, and is a moment due only to the bucket weight W1. is the moment corresponding to .

On the other hand, in the embodiment in which the holding weight calculation section stores the initial holding moment in advance, the initial holding moment to be stored in the holding weight calculation section is limited to that calculated based on the initial holding pressure of the attachment cylinder. do not have. For example, the initial holding moment MH1 according to the first embodiment should be balanced with the opposite bucket weight moment MW1 caused by the bucket weight W1, and the bucket weight moment MW1 is equal to the bucket weight W1 and the attachment rotation. Since it is the product of the bucket center of gravity G1 and the horizontal distance L1 from the moving axis (MW1=W1×L1), the product may be stored in the held weight calculation unit as the initial holding moment MH1.

(C) Regarding pressure relief operation The timing at which the pressure relief operation according to the present invention is started can be set as appropriate. In the first embodiment, the operation is locked when the measurement start condition is met, and then the pressure relief operation is started, but the operation lock may be omitted or the pressure relief operation may be started. may be started when measurement start conditions are met. Moreover, the pressure relief operation does not necessarily have to be performed every time the object to be held is loaded. For example, as mentioned above, when the attachment cylinder makes a full stroke, the difference between the pressure in the holding side hydraulic chamber and the pressure corresponding to the actual weight being held becomes large. Control such as performing a pulling operation may be performed.

The measurement conditions, that is, the conditions for determining when to employ the detected holding pressure and the detected physical quantity after starting the pressure relief operation can also be set as appropriate. The measurement condition according to the first embodiment is that a predetermined pressure relief time has elapsed since the start of the pressure relief operation, but for example, the rate of decrease in the holding pressure detected by the holding pressure detector is constant. The following conditions may be set as measurement conditions.

(D) Regarding pressure relief The pressure relief operation according to the present invention is not limited to that performed by the combination of the pressure relief line 73 and the pressure relief switching valve 74. The pressure relief operation according to the present invention may be performed by slightly changing the stroke of the control valve 52. For example, the pressure relief operation may be performed by forcibly adjusting the pilot pressure input to the control valve 52 to an appropriate pilot pressure for measurement regardless of attachment operation. However, it is difficult to control the delicate stroke of the control valve 52, and in particular it is not easy to set the opening area of the throttle for pressure relief. This combination makes it possible to easily perform a pressure relief operation by opening and closing the pressure relief switching valve 74. Further, it is also easy to set the opening area of the throttle in the pressure release switching valve 74.

10 Lower traveling body (airframe)
12 Upper revolving body (airframe)
14 Working equipment 20 Boom (working equipment main body)
22 Arm (working device body)
23 Attachment pin 24 Bucket (tip attachment)
28 Attachment cylinder 36 Bottom chamber (hydraulic chamber)
38 Rod chamber (hydraulic chamber)
50 Hydraulic pump 52 Control valve 54 Attachment operating device 68 Holding pressure detector 69 Cylinder length detector (physical quantity detector)
70 Pressure relief section 72 Operation lock switching section 73 Pressure relief line 74 Pressure relief switching valve 76 Operation lock switching valve 80 Controller 82 Measurement start timing determination section 84 Pressure relief command section (pressure relief control section)
86 Operation lock command unit (operation lock control unit)
88 Holding weight calculation section 92 Object to be held 100 Lifting magnet (tip attachment)
110 Grapple (tip attachment)

Claims (8)

A working machine comprising a machine body and a working device connected to the machine body, wherein the working device includes a base end part connected to the machine body and a distal end part on the opposite side thereof. A working device main body that operates to relatively displace a tip portion, and a working device main body that is attached to the tip portion of the working device main body so as to be rotatable about an attachment rotation axis, and that is capable of holding an object to be held. an attachment cylinder that is provided between the working device body and the tip attachment and expands and contracts so as to rotate the tip attachment about the attachment rotation axis with respect to the working device body; , the attachment cylinder has a pair of hydraulic chambers located on opposite sides, and expands or contracts when hydraulic oil is supplied to one of the pair of hydraulic chambers to rotate the tip attachment. A held weight measuring method for measuring a held weight corresponding to the weight of the held object held by a working machine, the method comprising:
When a preset measurement start condition is satisfied with the tip attachment holding the object, one of the hydraulic chambers of the pair of hydraulic chambers is connected to the tip attachment and the object held by the object. A part of the hydraulic oil supplied to the holding-side hydraulic chamber, which is a hydraulic chamber to which hydraulic oil is supplied to hold the tip attachment against the weight of the object to be held, is released into the tank through the throttle. a pressure relief step of releasing the pressure of the hydraulic oil by
A holding pressure, which is the pressure of the hydraulic oil in the holding side hydraulic chamber of the attachment cylinder at a time when preset measurement conditions are met after the pressure relief step is started, and a holding pressure applied to the tip attachment by the holding pressure. a detection step of detecting a moment specific physical quantity, which is a physical quantity necessary for specifying a radius of a holding moment, which is a moment about the attachment rotation axis, as a detected holding pressure and a detected physical quantity, respectively;
A retained weight measuring method, comprising: a retained weight calculation step of calculating the retained weight based on the detected retained pressure and the detected physical quantity. 2. The held weight measuring method according to claim 1, wherein the held weight is the weight of only the held object, and the held weight measuring method is performed when the tip attachment is not holding the held object. The method further includes a storing step of measuring and storing an initial holding moment, which is a moment around the attachment rotation axis for holding the tip attachment, and in the holding weight calculation step, the initial holding moment and the detected holding pressure are measured. A retained weight measuring method, wherein the retained weight is calculated based on the detected physical quantity. A working machine comprising a machine body and a working device connected to the machine body, wherein the working device includes a base end part connected to the machine body and a distal end part on the opposite side thereof. A working device main body that operates to relatively displace a tip portion, and a working device main body that is attached to the tip portion of the working device main body so as to be rotatable about an attachment rotation axis, and that is capable of holding an object to be held. an attachment cylinder that is provided between the working device body and the tip attachment and expands and contracts so as to rotate the tip attachment about an attachment rotation axis with respect to the working device body; The attachment cylinder has a pair of hydraulic chambers located on opposite sides, and expands or contracts when hydraulic oil is supplied to one of the pair of hydraulic chambers to rotate the tip attachment. A held weight measuring device installed in a working machine for measuring a held weight corresponding to the weight of the object to be held held by the working machine,
One hydraulic chamber of the pair of hydraulic chambers of the attachment cylinder, which is supplied with hydraulic oil for holding the tip attachment against the weight of the tip attachment and the object to be held. a holding pressure detector that detects a holding pressure that is the pressure of hydraulic oil in a certain holding side hydraulic chamber;
a physical quantity detector that detects a moment specific physical quantity that is a physical quantity necessary for specifying a radius of a holding moment that is a moment around the attachment rotation axis that is applied to the tip attachment by the holding pressure;
a pressure relief part configured to perform a pressure relief operation to release the pressure of the hydraulic oil in the holding side hydraulic chamber by releasing a part of the hydraulic oil supplied to the holding side hydraulic chamber into a tank through a throttle;
a pressure relief control section that causes the pressure relief section to perform the pressure relief operation when a preset measurement start condition is satisfied with the tip attachment holding the object to be held;
Obtain the holding pressure and the moment specific physical quantities as the detected holding pressure and the detected physical quantity, respectively, at the time when the preset measurement conditions are satisfied after the pressure release operation is started, and obtain the detected holding pressure and the detected physical quantity. A retained weight measuring device comprising: a retained weight calculation section that calculates the retained weight based on the retained weight. 4. The held weight measuring device according to claim 3, wherein the held weight is the weight of only the held object, and the held weight calculation section measures the held weight in a state where the tip attachment does not hold the held object. An initial holding moment that is a moment around the attachment rotation axis for holding the tip attachment is stored, and the holding weight is calculated based on the initial holding moment, the detected holding pressure, and the detected physical quantity. A holding weight measuring device consisting of: 5. The holding weight measuring device according to claim 3, wherein the working machine includes a hydraulic pump discharging hydraulic oil to be supplied to the attachment cylinder, and a hydraulic pump interposed between the hydraulic pump and the attachment cylinder. further comprising a control valve that operates to change the flow rate of hydraulic oil supplied from the hydraulic pump to the tip attachment, and the pressure relief section bypasses the control valve to open the holding side hydraulic chamber. A pressure relief line is provided in the pressure relief line arranged to communicate with the tank, and is switchable between a closed position and an open position, and in the closed position, the pressure relief line is shut off, and the pressure relief line is connected to the pressure relief line. and a pressure relief switching valve that is a line that opens the pressure relief line and forms a throttle line that includes the throttle in the open position, and the pressure relief control section does not operate until the measurement condition is determined to be satisfied. holding the pressure relief switching valve in the closed position and controlling the operation of the pressure relief switching valve so as to switch the pressure relief switching valve to the open position after determining that the measurement condition is satisfied; Weight measuring device. 6. The holding weight measuring device according to claim 5, wherein the work machine includes an attachment operation device that receives an attachment operation for expanding and contracting the attachment cylinder and causes the control valve to perform an opening/closing operation corresponding to the attachment operation. The holding weight measuring device further includes an attachment operation that causes the control valve to perform a holding-side valve opening operation, which is a valve opening operation in the direction of increasing the holding pressure, among the attachment operations given to the attachment operating device. The control valve can be switched between an operation locked state in which the control valve is disabled and forcibly closed, and an unlocked state in which the attachment operating device allows the control valve to perform an opening/closing operation corresponding to the attachment operation. the operation lock switching section is kept in the unlocked state at least until the measurement start condition is satisfied, and the pressure relief section starts the pressure relief operation from the time when the measurement start condition is satisfied. an operation lock control section configured to switch the operation lock switching section to the operation lock state before starting the operation. 7. The holding weight measuring device according to claim 3, wherein the tip attachment is a bucket capable of excavating and loading earth and sand, and the holding pressure detector is configured to measure the holding pressure as the holding pressure. . A holding weight measuring device that detects a pressure in a hydraulic chamber to which hydraulic oil for rotating the bucket in the excavation direction is supplied, of the pair of hydraulic chambers of the attachment cylinder. 7. The held weight measuring device according to claim 3, wherein the tip attachment holds the object at a specific holding position away from the attachment rotation shaft, and the holding pressure The detector is configured to use the holding pressure to hold the tip attachment against a moment due to the weight of the object held at the holding position in the pair of hydraulic chambers of the attachment cylinder and the weight of the tip attachment. A holding weight measuring device that detects the pressure in the hydraulic chamber to which hydraulic oil for holding is supplied.

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