Working machinery

Abstract

To provide a work machine that can calculate the weight of an object being worked on with greater accuracy. [Solution] When the work device is in a predetermined measurement position, the controller controls the accumulator-side control valve so that the high-pressure side oil chamber of the boom cylinder is connected to the accumulator and the low-pressure side oil chamber is shut off from the hydraulic oil tank. It then controls the pump-side control valve so that the low-pressure side oil chamber of the boom cylinder is connected to the hydraulic pump and the high-pressure side oil chamber is shut off from the hydraulic oil tank. Finally, it shuts off the low-pressure side oil chamber from the hydraulic pump and controls the accumulator-side control valve so that the low-pressure side oil chamber is connected to the hydraulic oil tank, and then performs load calculation processing.

Description

[Technical Field]

[0001] This invention relates to a work machine for a work vehicle. [Background technology]

[0002] In construction machinery such as hydraulic excavators, there is a need to measure the weight of the workpiece when transporting it using the work device. This is done to prevent the machine from tipping over due to the weight of the workpiece, or to confirm the weight of the transported workpiece as part of the work volume. For this reason, it has been known that load calculations are performed by using the pressure of the hydraulic cylinder driving the work device and the posture of the work device to determine the load of the workpiece loaded in the bucket of the work device.

[0003] In a hydraulic cylinder, sealing members are interposed between the piston rod and the inner surface of the oil chamber, and at the outlet of the piston rod from the oil chamber. Static friction acts on the parts that come into contact with these sealing members. This static friction is a source of error in load calculations that measure the weight of the workpiece. Therefore, in order to reduce static friction, for example, Patent Document 1 discloses that, before performing load calculations, a directional control valve that controls the flow of pressurized oil supplied to the boom cylinder is switched by a controller to cause the boom cylinder to vibrate slightly to the extent that it does not extend or retract.

[0004] Furthermore, Patent Document 2 discloses a flow path switching means provided between the two oil chambers of a hydraulic cylinder and a hydraulic pump and a hydraulic fluid tank, and before performing load calculation, a controller controls the flow path switching means to switch the connection between the two oil chambers between the hydraulic pump and the hydraulic fluid tank, and after performing and stopping the raising operation of the boom of the work device holding the object to be measured, a boom lowering operation control means performs and stops the lowering operation of the boom, and then performs a further minute adjustment lowering operation. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2007-197133 [Patent Document 2] Japanese Patent Publication No. 2012-185006 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] The methods for reducing static friction force in load calculation described in Patent Documents 1 and 2 both control the extension and retraction of the hydraulic cylinder using a controller. Therefore, although the above-mentioned minute vibration and adjustment / downward movements performed immediately before executing the load calculation are important movements that directly relate to the reduction of static friction force, the control performance such as the calculation cycle and the output accuracy of the control signal of the controller affects the accuracy of the movement, making it difficult to make the movement even minute, and thus the static friction force cannot be sufficiently reduced, resulting in a problem of reduced accuracy in load calculation.

[0007] The object of the present invention is to provide a work machine that can calculate the weight of an object with greater accuracy. [Means for solving the problem]

[0008] To achieve the above objective, the present invention provides a work machine comprising: a work device having a boom and a boom cylinder for moving the boom up and down; a pressure detection device for detecting the pressure acting on each of the two oil chambers of the boom cylinder; a hydraulic pump capable of supplying hydraulic fluid to operate the boom cylinder to either of the two oil chambers; and a controller that performs load calculation processing to calculate the weight of a work object acting on the tip of the work device based on the pressure detected by the pressure detection device when the work device is in a predetermined measurement position, wherein the accumulator-side control valve connects one of the two oil chambers to an accumulator and connects or disconnects the other oil chamber to a hydraulic fluid tank, and connects one of the two oil chambers to the hydraulic pump The controller has a pump-side control valve that connects or disconnects the other oil chamber and connects or disconnects the other oil chamber to the hydraulic fluid tank, and when the work device is in the predetermined measurement position, the controller controls the accumulator-side control valve so that the high-pressure oil chamber of the two oil chambers of the boom cylinder is connected to the accumulator and the low-pressure oil chamber is disconnected from the hydraulic fluid tank, then controls the pump-side control valve so that the low-pressure oil chamber of the two oil chambers of the boom cylinder is connected to the hydraulic pump and the high-pressure oil chamber is disconnected from the hydraulic fluid tank, then disconnects the low-pressure oil chamber from the hydraulic pump, and further controls the accumulator-side control valve so that the low-pressure oil chamber is connected to the hydraulic fluid tank, and then performs the load calculation process. [Effects of the Invention]

[0009] According to the present invention, the weight of the workpiece can be calculated with greater accuracy. Other problems, configurations, and effects will be clarified by the following description of the embodiments. [Brief explanation of the drawing]

[0010] [Figure 1] This is a side view of a hydraulic excavator. [Figure 2] This is a diagram showing the hydraulic circuitry used in a hydraulic excavator. [Figure 3]It is a functional block diagram of a controller. [Figure 4] It is a side view of a working device provided in a hydraulic excavator. [Figure 5] It is a flowchart of load calculation processing.

Embodiments for Carrying out the Invention

[0011] [Configuration of Hydraulic Excavator 1] An embodiment of a working machine according to the present invention will be described with reference to the drawings. In this embodiment, a hydraulic excavator 1 will be described as an example of a working machine. Note that the working machine is not limited to the hydraulic excavator 1, and may be a wheel loader, dump truck, crane, or the like. Also, the front, rear, left, and right in this specification are based on the perspective of an operator who rides on and operates the hydraulic excavator 1, unless otherwise specified.

[0012] FIG. 1 is a side view of the hydraulic excavator 1. As shown in FIG. 1, the hydraulic excavator 1 includes a traveling body 2 and a revolving body 3 supported by the traveling body 2.

[0013] The traveling body 2 includes a pair of left and right crawlers 4 that are endless track belts. Then, by driving the traveling motor 5, the pair of left and right crawlers 4 rotate independently. As a result, the hydraulic excavator 1 travels. However, the traveling body 2 may be wheel-mounted instead of the crawlers 4.

[0014] The revolving body 3 is rotatably supported by the traveling body 2. Then, when a revolving device 6 such as a motor rotates, the revolving body 3 revolves with respect to the traveling body 2. The revolving body 3 mainly includes a revolving frame 7 as a base, a cab 8 disposed on the front left side of the revolving frame 7, a counterweight 9 disposed at the rear of the revolving frame 7, a working device 10 attached to the front center of the revolving frame 7 so as to be rotatable in the vertical direction, a machine room 20, and an accumulator 21. The counterweight 9 is a heavy object for taking a weight balance with the working device 10.

[0015] The working device 10 includes a boom 11 rotatably supported by a revolving body 3, an arm 12 rotatably supported at the tip of the boom 11, a bucket 13 (attachment) rotatably supported at the tip of the arm 12, a boom cylinder 14 for rotating the boom 11 with respect to the revolving body 3, an arm cylinder 15 for rotating the arm 12 with respect to the boom 11, and a bucket cylinder 16 for rotating the bucket 13 with respect to the arm 12. The boom cylinder 14, the arm cylinder 15, and the bucket cylinder 16 are all hydraulic actuators.

[0016] Angle sensors 34A to 34D are provided on the revolving body 3 and the working device 10 as attitude detection devices for detecting the attitude of the working device 10. An inclination angle sensor 34A for detecting the inclination angle of the revolving body 3 with respect to the horizontal level is attached to the revolving body 3. The inclination angle sensor 34A outputs a signal indicating the detected inclination angle to the controller 18.

[0017] A boom angle sensor 34B for detecting the angle of the boom 11 is provided at the connection point between the boom 11 and the revolving body 3 of the working device 10, an arm angle sensor 34C for detecting the angle of the arm 12 is provided at the connection point between the boom 11 and the arm 12, and a bucket angle sensor 34D for detecting the angle of the bucket 13 is provided at the connection point between the arm 12 and the bucket 13.

[0018] The boom angle sensor 34B is provided at the rotation center on the revolving body 3 side of the boom 11 rotatably provided on the revolving body 3, detects the angle of the boom 11 with respect to the revolving body 3, and outputs a signal indicating the detected angle to the controller 18.

[0019] The arm angle sensor 34C is provided at the rotation center on the boom 11 side of the arm 12 rotatably provided on the side of the boom 11 opposite to the revolving body, detects the angle of the arm 12 with respect to the boom 11, and outputs a signal indicating the detected inclination to the controller 18.

[0020] The bucket angle sensor 34D is mounted at the pivot point of the bucket 13, which is rotatably mounted on the opposite side (tip side) of the arm 12 from the boom 11. It detects the angle of the bucket 13 relative to the arm 12 and outputs a signal indicating the detected angle to the controller 18.

[0021] The posture of the work device 10 and any changes in posture are determined by the controller 18 based on the output of each angle sensor 34A to 34D.

[0022] The boom cylinder 14 is connected between the slewing body 3 and the boom 11, and rotates the boom 11 by extending and retracting. The arm cylinder 15 is connected between the boom 11 and the arm 12, and rotates the arm 12 by extending and retracting. The bucket cylinder 16 is connected between the arm 12 and the bucket 13, and rotates the bucket 13 by extending and retracting.

[0023] The driver's cab 8 includes a driver's seat where the operator sits, and an operating device 17 located near the driver's seat that enables the desired operation of each hydraulic actuator mounted on the slewing body 3, such as the slewing hydraulic motor, boom cylinder 14, arm cylinder 15, and bucket cylinder 16, and is operated by the operator gripping it from inside the driver's cab 8. Specific examples of the operating device 17 include an electric lever device, steering wheel, pedals, and switches.

[0024] Furthermore, the operator's cab 8 has a controller 18 that is connected to the operating device 17 and various sensors (described later) and processes information related to the hydraulic excavator 1. In addition, the operator's cab 8 is equipped with a display device 19 that is connected to the controller 18 and displays the status of the hydraulic excavator 1 to the operator.

[0025] The machine room 20 has an internal space that houses the engine 22, hydraulic pump 23, and the like. The engine 22 is an example of a drive source that burns fuel stored in a fuel tank to generate the driving force to operate the hydraulic excavator 1. The hydraulic pump 23 rotates due to the driving force of the engine 22 and discharges hydraulic fluid stored in the hydraulic fluid tank 24 (Figure 2) located outside the machine room 20.

[0026] The hydraulic fluid discharged from the hydraulic pump 23 is supplied to the hydraulic actuators (travel motor 5, slewing device 6, boom cylinder 14, arm cylinder 15, bucket cylinder 16) via a valve (not shown). This causes the hydraulic actuators to operate.

[0027] The operating device 17 is, for example, an operating lever, steering wheel, pedal, or switch, and receives operations from an operator to instruct the operation of the hydraulic excavator 1 (more specifically, the hydraulic actuator), and outputs an operation signal corresponding to the operator's operation to the controller 18. The controller 18 controls the operation of the engine 22 and the hydraulic pump 23 according to the operation signals output from the operating device 17.

[0028] <Configuration of a system for measuring the weight of an object being worked on> The weight of the workpiece is measured by detecting the operation of the boom cylinder 14 that drives the boom 11, and calculating the load based on the detection results of the load calculation process performed by the controller 18. As shown in Figure 2, the system for measuring the weight of the workpiece by the operation of the boom cylinder 14 consists of a hydraulic pump 23, a hydraulic oil tank 24, an accumulator 21, a first control valve 35, a fourth control valve 36, a second control valve 37, a third control valve 38, a fifth control valve 39, and a display device 19. The boom cylinder 14 is also equipped with pressure sensors 33A and 33B in the bottom oil chamber 14A and rod oil chamber 14B, respectively, as pressure detection devices. Here, the first control valve 35, the second control valve 37, and the third control valve 38 correspond to the pump-side control valves, and the fourth control valve 36 and the fifth control valve 39 correspond to the accumulator-side control valves.

[0029] Each pressure sensor 33A and 33B detects the pressure inside each oil chamber 14A and 14B and outputs a pressure signal indicating the detected pressure to the controller 18. Based on the pressure signals output from each pressure sensor 33A and 33B, the controller 18 can detect whether there is a pressure difference between the bottom oil chamber 14A and the rod oil chamber 14B (either one is higher or lower) or whether it is in a neutral state.

[0030] The accumulator 21 is housed in the machine room 20. The accumulator 21 can be connected to the boom cylinder 14 via a fourth control valve 36, which will be described later. In the load calculation process performed by the controller, which will be described later, the accumulator 21 is connected to or disconnected from the high-pressure side oil chamber of the boom cylinder 14 by switching the fourth control valve 36.

[0031] The gas-filled pressure of the accumulator 21 is determined so that, in the measurement position where the work device 10 begins its operation for load calculation processing (hereinafter referred to as the measurement operation), it can balance the pressure component due to the weight of the work device 10 among the pressure components of the high-pressure side oil chamber of the boom cylinder 14. Here, the measurement position is the position of the work device 10 during load calculation processing and is set in advance. The measurement position will be described in detail later.

[0032] Furthermore, the maximum operating pressure and gas volume of the accumulator 21 are determined so that the boom cylinder 14 does not reach the stroke end even when the measurement operation is performed with the maximum weight of the workpiece assumed to be included, taking into account the working device 10 and body specifications of the hydraulic excavator 1 and the operating conditions. These accumulator specifications may also be determined in conjunction with the measurement position, which is the position of the working device 10 when the measurement operation is started.

[0033] Figure 2 shows a hydraulic circuit relating to the present invention. In this embodiment, the hydraulic cylinder shown in Figure 2 is a boom cylinder 14. The first control valve 35 is provided on the hydraulic excavator 1 to control the posture of the work device 10 when the bucket 13 is performing normal work on the hydraulic excavator 1. The second control valve 37, third control valve 38, fourth control valve 36, and fifth control valve 39 are not used during the above-mentioned normal work of the hydraulic excavator 1, but are provided for use in the measurement operation in the present invention. Therefore, during normal work when the measurement operation is not being performed, the fourth control valve 36 is in a closed state, and the second control valve 37, third control valve 38, and fifth control valve 39 are in a connected state.

[0034] The first control valve 35 is located between the boom cylinder 14 and the hydraulic pump 23 and controls the direction and flow rate of the hydraulic fluid supplied from the hydraulic pump 23 to the boom cylinder 14. The first control valve 35 has three switching positions: a first switching position 351, a second switching position 352, and a neutral position 350.

[0035] The first switching position 351 connects the hydraulic pump 23 to the rod-side oil chamber 14B of the boom cylinder 14, and connects the bottom-side oil chamber 14A of the boom cylinder 14 to the hydraulic oil tank 24. Therefore, when the first control valve 35 is switched to the first switching position 351, the hydraulic oil discharged from the hydraulic pump 23 flows into the rod-side oil chamber 14B of the boom cylinder 14, and the hydraulic oil in the bottom-side oil chamber 14A of the boom cylinder 14 is discharged into the hydraulic oil tank 24. As a result, the rod of the boom cylinder 14 retracts, and the boom 11 rotates downward relative to the slewing body 3.

[0036] The second switching position 352 connects the hydraulic pump 23 to the bottom oil chamber 14A of the boom cylinder 14, and connects the rod-side oil chamber 14B of the boom cylinder 14 to the hydraulic oil tank 24. Therefore, when the first control valve 35 is switched to the second switching position 352, the hydraulic oil discharged from the hydraulic pump 23 flows into the bottom oil chamber 14A of the boom cylinder 14, and the hydraulic oil in the rod-side oil chamber 14B of the boom cylinder 14 is discharged into the hydraulic oil tank 24. As a result, the rod of the boom cylinder 14 extends, and the boom 11 rotates upward relative to the slewing body 3.

[0037] The neutral position 350 disconnects the connection between the hydraulic pump 23 and the boom cylinder 14, and the connection between the boom cylinder 14 and the hydraulic fluid tank 24. Therefore, when the first control valve 35 is switched to the neutral position 350, the inflow and outflow of hydraulic fluid into the boom cylinder 14 stops. As a result, the extension and retraction of the boom cylinder 14 rod stops, and the vertical rotation of the boom 11 relative to the slewing body 3 also stops.

[0038] The fourth control valve 36 is located between the boom cylinder 14 and the accumulator 21 and controls the direction and flow rate of the hydraulic fluid that is guided from the boom cylinder 14 to the accumulator 21. The fourth control valve 36 has three switching positions: a first switching position 361, a second switching position 362, and a neutral position 360.

[0039] The first switching position 361 connects the rod-side oil chamber 14B of the boom cylinder 14 to the accumulator 21, and connects the bottom-side oil chamber 14A of the boom cylinder 14 to the hydraulic oil tank 24. Therefore, when the fourth control valve 36 is switched to the first switching position 361, hydraulic oil flows from the accumulator 21 side into the rod-side oil chamber 14B of the boom cylinder 14, and the hydraulic oil in the bottom-side oil chamber 14A of the boom cylinder 14 is discharged into the hydraulic oil tank 24.

[0040] The second switching position 362 connects the bottom oil chamber 14A of the boom cylinder 14 to the accumulator 21, and connects the rod-side oil chamber 14B of the boom cylinder 14 to the hydraulic oil tank 24. Therefore, when the fourth control valve 36 is switched to the second switching position 362, hydraulic oil flows from the accumulator 21 side into the bottom oil chamber 14A of the boom cylinder 14, and the hydraulic oil in the rod-side oil chamber 14B of the boom cylinder 14 is discharged into the hydraulic oil tank 24.

[0041] Since the accumulator 21 is connected to the high-pressure oil chamber, the fourth control valve 36 is switched to either the first switching position 361 or the second switching position 362 depending on whether the high-pressure oil chamber is the bottom-side oil chamber 14A or the rod-side oil chamber 14B when the work device 10 is in the measurement position.

[0042] The neutral position 360 disconnects the connection between the accumulator 21 and the boom cylinder 14, and the connection between the boom cylinder 14 and the hydraulic oil tank 24, respectively. Therefore, when the fourth control valve 36 is switched to the neutral position 360, the accumulator 21 is disconnected from the hydraulic circuit that drives the work device 10.

[0043] The second control valve 37 is located between the first control valve 35 and the rod-side oil chamber 14B of the boom cylinder 14, and controls the connection and disconnection of the flow path of hydraulic fluid that is guided from the hydraulic pump 23 to the boom cylinder 14 via the first control valve 35. The second control valve 37 has a first switching position 371 that connects the first control valve 35 and the rod-side oil chamber 14B of the boom cylinder 14, and a neutral position 370 that disconnects the connection between the first control valve 35 and the rod-side oil chamber 14B of the boom cylinder 14.

[0044] The third control valve 38 is located between the first control valve 35 and the bottom oil chamber 14A of the boom cylinder 14, and controls the connection and disconnection of the flow path of hydraulic fluid that is guided from the hydraulic pump 23 to the boom cylinder 14 via the first control valve 35. The third control valve 38 has a first switching position 381 that connects the first control valve 35 and the bottom oil chamber 14A of the boom cylinder 14, and a neutral position 380 that disconnects the connection between the first control valve 35 and the bottom oil chamber 14A of the boom cylinder 14.

[0045] The fifth control valve 39 is located between the fourth control valve 36 and the hydraulic oil tank 24 and controls the connection and disconnection of the hydraulic oil flow path from the boom cylinder 14 to the hydraulic oil tank 24 via the fourth control valve 36. The fifth control valve 39 has a first switching position 391 that connects the fourth control valve 36 and the hydraulic oil tank 24, and a neutral position 390 that disconnects the connection between the fourth control valve 36 and the hydraulic oil tank 24.

[0046] The display device 19 displays information to the operator based on signals related to the load calculation results and measurement status output by the controller 18. The information displayed on the display device 19 may include, for example, information showing the results calculated by the load calculation unit 18B of the controller 18 based on the command signal of the load calculation unit 18B, information showing the status of load measurement notified based on the command signals of the condition determination unit 18C and the command signal output unit 18D, information indicating that load calculation processing is in progress notified while the load calculation processing by the command signal output unit 18D is being performed, and information indicating that load calculation processing is complete notified when the load calculation processing is completed.

[0047] Furthermore, the information indicating the load measurement status is intended to prompt the user to adjust the posture of the work device 10 to match the measurement posture when the condition determination unit 18C determines that the posture of the work device 10 does not match the measurement posture. This information may also be an image comparing the posture of the work device 10 at the time of display with the measurement posture.

[0048] Furthermore, the display device 19 is equipped with, for example, a touch panel, and by operating switches assigned to the touch panel, the operator can send input signals to the controller 18 to instruct it to perform a measurement operation.

[0049] <Controller 18 Configuration> The controller 18 is configured with a CPU, RAM, ROM, HDD, input interface, and output interface connected to each other via a bus. Various operating devices, as well as various sensors such as pressure sensors 33A and 33B and angle sensors 34A, 34B, 34C, and 34D, are connected to the input interface, and various control valves 35, 36, 37, 38, and 39 are connected to the output interface.

[0050] In this hardware configuration, the CPU reads the control program (software) stored in a recording medium such as ROM, HDD, or optical disc, expands it onto RAM, and executes the expanded control program. The control program and hardware then work together to realize the functions of the controller 18.

[0051] In this embodiment, the configuration of the controller 18 is described as a combination of software and hardware, but it is not limited to this, and may also be configured using an integrated circuit that realizes the functions of the control program executed on the hydraulic excavator 1.

[0052] <Functional blocks of controller 18> Figure 3 is a functional block diagram of the controller 18. As shown in Figure 3, the controller 18 includes a data acquisition unit 18A, a load calculation unit 18B, a condition determination unit 18C, and a command signal output unit 18D. The controller 18 functions as the data acquisition unit 18A, load calculation unit 18B, condition determination unit 18C, and command signal output unit 18D by, for example, the CPU 26 executing a program stored in memory 27.

[0053] The data acquisition unit 18A acquires data detected by each angle sensor (tilt angle sensor 34A, boom angle sensor 34B, arm angle sensor 34C, bucket angle sensor 34D) and each pressure sensor (bottom side pressure sensor 33A, rod side pressure sensor 33B).

[0054] The load calculation unit 18B executes a load calculation process for measuring the weight of a work object such as soil scooped up by the bucket 13 provided at the tip of the work device 10 as the load applied to the work device 10. FIG. 4 is a side view of the work device provided in the hydraulic excavator. The details of the load calculation will be described with reference to FIG. 4.

[0055] In the following description of the load calculation, the load applied to the work device 10 is indicated as W, and the self-weight of the work device 10 excluding the boom cylinder 14 is indicated as W1. Also, the horizontal length between the swing center P of the boom 11 and the load point is l bm , the length of the perpendicular line drawn from the swing center P of the boom 11 to the boom cylinder 14 is h bm , the horizontal length between the swing center P of the boom 11 and the center of gravity position of the work device 10 excluding the boom cylinder 14 is indicated as l1. Further, the bottom side pressure of the boom cylinder 14 is P 1b , the rod side pressure is P 1r , the bottom side pressure receiving area is A 1b , the rod side pressure receiving area is A 1r , and the static frictional force is indicated as R.

[0056] The thrust F of the boom cylinder 14 bm is expressed by the following formula 1. TIFF2026119961000002.tif13136 This thrust F bm balances the moment due to the load W and the moment due to the self-weight W1 of the work device 10, and formula 2 holds. TIFF2026119961000003.tif12136 Therefore, from formula 1 and formula 2, it is expressed as the following formula 3. TIFF2026119961000004.tif12136

[0057] Here, the bottom side pressure receiving area A 1b and the rod side pressure receiving area A 1r are determined by the specifications of the mounted boom cylinder 14, and the self-weight W1 of the work device 10 can also be obtained from the specifications. The bottom side pressure P 1b and the rod side pressure P 1rThese pressures are detected by the bottom-side pressure sensor 33A and the rod-side pressure sensor 33B of the boom cylinder 14, respectively, and output to the controller 18.

[0058] The static friction force R is output by the friction estimation device. The horizontal length l is the distance between the pivot center P of the boom 11 and the load point. bm The length of the perpendicular line drawn from the pivot center P of the boom 11 to the boom cylinder 14 is h. bm The horizontal length l1 between the pivot point P of the boom 11 and the center of gravity of the work device 10, excluding the boom cylinder 14, is calculated based on the detection results of the tilt angle sensor 34A, boom angle sensor 34B, arm angle sensor 34C, and bucket angle sensor 34D, respectively, and the dimensions of the boom 11, arm 12, and bucket 13 of the attached work device 10. Furthermore, the static friction force R can be ignored as it is reduced by the second minute movement of the boom cylinder, which will be described later. As explained above, the load W applied to the working device 10 is calculated by the load calculation unit for the boom cylinder 14 using the moment balance equations (equations 1-3) of the pivoting center P of the boom 11.

[0059] The condition determination unit 18C determines whether or not the posture of the work device 10 matches the measurement posture that has been set in advance as the posture at the start of the measurement operation, based on the angle signals output from each angle sensor 34A to 34D.

[0060] Here, we will explain the measurement posture. As mentioned above, the load W applied to the work device 10 is calculated for the boom cylinder 14 using the moment balance formula of the pivot center P of the boom 11. Therefore, the measurement posture should be such that the weight of the work object contained in the bucket 13 is easily transmitted to the boom cylinder 14, which is a hydraulic cylinder involved in load measurement. In other words, it should be such that the effect on the boom cylinder 14 due to differences in the weight of the work object, such as soil scooped up by the bucket 13, is more clearly expressed. For this reason, the measurement posture of the work device 10 should be such that the horizontal length l between the pivot center P of the boom 11 and the load point is bmThe position is set such that the range of motion is as long as possible, the boom cylinder 14 does not reach its stroke end during the measurement operation, and the work material such as soil in the bucket 13 does not spill out.

[0061] The values ​​from each angle sensor 34A to 34D when the work position is as described above are stored in the controller 18's memory 27 as measured position data. The memory 27 also stores the pressure value of the boom cylinder 14 when the bucket is empty while in the measured position.

[0062] The condition determination unit 18C detects that the measurement posture is met when the values ​​output from each angle sensor 34A to 34D match the measurement posture data stored in the memory 27, and outputs a command signal to the command signal output unit 18D. If the values ​​output from each angle sensor 34A to 34D do not match the measurement posture data stored in the memory 27, the condition determination unit 18C outputs a command signal to the measurement status output unit 19B of the display device 19, prompting the operator to adjust the posture of the work device 10 to match the measurement posture.

[0063] The command signal output unit 18D outputs a calculation execution signal to the load calculation unit 18B to perform load calculation processing, based on the execution command signal output from the condition determination unit 18C.

[0064] [Load calculation process] Figure 5 is a flowchart of the load calculation process. In the controller 18, first, the condition determination unit 18C determines whether or not the work device 10 is in a measurement position based on the measurement operation start signal from the switch provided on the display device 19 (step S1).

[0065] As described above, in the state before receiving the measurement operation start signal from the switch, that is, in the state where normal work other than measurement operation is possible, the fourth control valve 36 is set to the neutral position 360 and is disconnected from the hydraulic circuit that drives the boom cylinder 14, while the second control valve 37, the third control valve 38, and the fifth control valve 39 are all set to the first switching positions 371, 381, and 391 and are connected. In addition, hydraulic cylinders other than the boom cylinder 14 that are not involved in load calculation processing are kept inactive while the load calculation processing is being performed.

[0066] The condition determination unit 18C determines, based on the measurement operation start signal from the switch, whether the values ​​of each angle sensor 34A to 34D acquired by the data acquisition unit 18A match the measurement posture data stored in the memory 27. If the values ​​of each angle sensor 34A to 34D match the measurement posture data, the condition determination unit 18C determines that the work device 10 is in the measurement posture and outputs a signal to the command signal output unit 18D indicating that the work device 10 is in the measurement posture (step S1 / YES). On the other hand, if the values ​​of each angle sensor 34A to 34D do not match the measurement posture data, the condition determination unit 18C outputs a display signal to the display device 19 that prompts the work device 10 to match the measurement posture along with the values ​​of each angle sensor 34A to 34D (step S1 / NO, step S14).

[0067] If it is determined in step S1 that the work device 10 is in the measurement position (step S1 / YES), the command signal output unit 18D outputs a command signal to the first control valve 35 to switch to the neutral position 350. This command signal isolates both oil chambers of the boom cylinder 14 from the hydraulic pump 23 and the hydraulic oil tank 24 (step S2).

[0068] Next, the command signal output unit 18D outputs a command signal to the fourth control valve 36 to switch to the second switching position 362. This command signal connects the bottom oil chamber 14A, which is the high-pressure oil chamber of the boom cylinder 14, to the accumulator 21, and the rod oil chamber 14B, which is the low-pressure oil chamber, to the hydraulic oil tank 24 (step S3). At this time, the condition determination unit 18C determines whether the boom cylinder 14 is stationary or not based on the values ​​of each angle sensor 34A to 34D and each pressure sensor 33A and 33B acquired by the data acquisition unit 18A (step S4).

[0069] If it is determined in step S3 that the boom cylinder 14 is stationary (step S4 / YES), the command signal output unit 18D outputs a first command signal to the fifth control valve 39 to switch it to the neutral position 390. The first command signal isolates the rod-side oil chamber 14B from the hydraulic oil tank 24 (step S5).

[0070] Next, the command signal output unit 18D outputs a command signal to the third control valve 38 to switch it to the neutral position 380. This command signal shuts off the connection between the bottom oil chamber 14A, which is the high-pressure oil chamber of the boom cylinder 14, and the first control valve 35 (step S6). Note that the order of steps S5 and S6 may be reversed.

[0071] Next, the command signal output unit 18D outputs a command signal to the first control valve 35 to switch to the first switching position 351. This command signal connects the rod-side oil chamber 14B, which is the low-pressure oil chamber of the boom cylinder 14, to the hydraulic pump 23, and hydraulic fluid begins to flow into the rod-side oil chamber 14B of the boom cylinder 14 (step S7). As hydraulic fluid flows into the rod-side oil chamber 14B, the boom cylinder 14 begins to retract. Here, the designation signal output from the command signal output unit 18D in steps S6 and S7 corresponds to the second command signal.

[0072] The condition determination unit 18C determines whether the amount of contraction of the boom cylinder 14, which has begun to contract, has reached a preset amount of contraction, based on the values ​​of each angle sensor 34A to 34D acquired by the data acquisition unit 18A (step S8).

[0073] In step S8, if it is determined that the amount of contraction of the boom cylinder 14 has reached a predetermined amount (step S8 / YES), the command signal output unit 18D outputs a third command signal to the first control valve 35 to switch it to the neutral position 350. The third command signal isolates the rod-side oil chamber 14B from the hydraulic pump 23 (step S9).

[0074] Under the control of steps S7 to S9, the boom cylinder 14 is retracted by a predetermined amount (hereinafter referred to as the first minute movement). The amount of retraction at this time is set so that the amount of extension caused by the extension movement of the boom cylinder 14 that occurs when the pressure accumulated in the accumulator 21 is released during the first retraction movement is made as small as possible.

[0075] Next, the command signal output unit 18D outputs a fourth command signal to the fifth control valve 39 to switch to the first switching position 391. The fourth command signal connects the rod-side oil chamber 14B, which is the low-pressure oil chamber of the boom cylinder 14, to the hydraulic oil tank 24. When the rod-side oil chamber 14B and the hydraulic oil tank 24 are connected, the pressure accumulated in the accumulator 21 is released and hydraulic oil flows out into the hydraulic oil tank 24, and the boom cylinder 14 begins to extend (step S10). At this time, the boom cylinder 14 extends slightly as set, and the condition determination unit 18C determines whether the boom cylinder 14 is stationary or not based on the values ​​of each angle sensor 34A to 34D and each pressure sensor 33A and 33B acquired by the data acquisition unit 18A (step S11). The slight movement of the boom cylinder 14 in step S11 is hereinafter referred to as the second slight movement.

[0076] If it is determined in step S11 that the boom cylinder 14 is stationary (step S11 / YES), the command signal output unit 18D outputs a calculation execution signal to the load calculation unit 18B to perform load calculation processing, and the load calculation unit 18B performs the load calculation processing described above based on the command signal from the command signal output unit 18D (step S12). The load calculation unit 18B outputs the calculation result along with a command signal to display the result to the display device 19.

[0077] Finally, the command signal output unit 18D outputs a command signal to return the fourth control valve 36, the second control valve 37, and the third control valve 38 to their state before receiving the measurement operation start signal from the switch (step S13). That is, the fourth control valve 36 is set to the neutral position 360 and disconnected from the hydraulic circuit that drives the boom cylinder 14, and the second control valve 37, the third control valve 38, and the fifth control valve 39 are all set to the first switching positions 371, 381, and 391 and connected. With this command signal, the hydraulic excavator 1 becomes ready for normal operation, and the processing in the controller 18 is completed.

[0078] [Effects of the Embodiment] In the hydraulic excavator 1 of the above embodiment, when the boom cylinder 14 undergoes a first minute contraction before the controller 18 performs load calculation processing, the bottom-side oil chamber 14A, which becomes the high-pressure oil chamber, is connected to the accumulator 21, and the rod-side oil chamber 14B, which becomes the low-pressure oil chamber, is connected to the hydraulic pump 23 and isolated from the hydraulic oil tank 24. Since the hydraulic pump 23 supplies hydraulic oil, it is pressurized in the accumulator 21. After the accumulator 21 is pressurized, the rod-side oil chamber 14B is isolated from the hydraulic pump 23, so that just before the controller 18 performs load calculation processing, the pressure at which the boom cylinder 14 underwent the first minute contraction is maintained in the accumulator 21.

[0079] Subsequently, with the accumulator 21 pressurized, the rod-side oil chamber 14B is connected to the hydraulic oil tank 24, and the accumulated pressure is released. As a result, the boom cylinder 14 is pushed back by the pressure accumulated in the accumulator 21, and the hydraulic oil is pushed into the hydraulic oil tank 24, releasing the pressure in the accumulator 21. This causes a second minute movement in the boom cylinder 14, in which the rod is pushed back and extends.

[0080] Therefore, the second minute movement that occurs immediately before the load calculation process is a minute movement of the boom cylinder 14 rod caused by releasing the pressure in the pressurized accumulator 21. Unlike conventional methods where minute movements are actively performed by the hydraulic pump 23, the control performance of the controller 18, such as the calculation cycle and the output accuracy of the control signal, is less likely to affect the accuracy of the movement.

[0081] Furthermore, the amount of extension or retraction (in this embodiment, the amount of contraction) of the boom cylinder 14 during the first minute movement is set so that the amount of extension or retraction of the boom cylinder 14 caused by the pressure of the accumulator 21 accumulated during the first contraction movement is as small as possible. As a result, the second minute movement caused by the release of the pressure accumulated in the accumulator 21 is also a very small movement, making it possible to move the rod more slowly than when the rod is moved by the hydraulic pump 23. This makes it possible to reduce the amount of movement in the second minute movement compared to when the rod is moved by the hydraulic pump, thereby reducing the static friction force of the boom cylinder 14. As a result, by performing load calculation processing after the execution of the second minute movement, the effects of static friction become less pronounced, making it possible to calculate the weight of the workpiece more accurately.

[0082] Furthermore, in this embodiment, the hydraulic excavator 1 determines that the posture of the work device 10 is the measurement posture based on the outputs of the tilt angle sensor 34A, boom angle sensor 34B, arm angle sensor 34C, and bucket angle sensor 34D before executing the load calculation process. The measurement posture is such that the weight of the work object contained in the bucket 13 is easily transmitted to the boom cylinder 14, which is a hydraulic cylinder involved in load measurement. Therefore, the load calculation process can be performed in a situation that is less affected by error factors such as static friction force in the boom cylinder 14. As a result, the weight of the work object can be calculated with greater accuracy.

[0083] Furthermore, after connecting the bottom oil chamber 14A and the accumulator 21 in step S3, after connecting the rod-side oil chamber 14B and the hydraulic pump 23 in step S7, and after connecting the rod-side oil chamber 14B and the hydraulic oil tank 24 in step S10 (immediately before executing the load calculation process), it is determined whether the work device 10 has come to a standstill. After confirming that it has come to a standstill, the next process (steps S5, S9, and S12) is executed, so the pressure in the boom cylinder 14 is stable when each process is executed. Therefore, the results of each process executed are not affected by the process immediately preceding it, making it possible to calculate the weight of the workpiece more accurately.

[0084] In the above embodiment, an example was described in which the load calculation unit 18B of the controller 18 performs load calculation processing. However, the system is not limited to this, and for example, a load calculation unit may be provided separately from the controller 18, and the load calculation unit may perform load calculation processing based on command signals from the controller 18.

[0085] [Example 1] In the above embodiment, an accumulator 21 is provided solely to improve the accuracy of the load calculation process. However, the configuration is not limited to this. For example, if an accumulator is already provided in the hydraulic excavator 1 for purposes such as adding flexibility to the hydraulic cylinder to mitigate impacts to the work device 10, or for the purpose of regenerating hydraulic energy, that accumulator may be reused. In this case, it is necessary to determine the measurement posture according to the specifications of the accumulator.

[0086] [Differentiation 2] In the above embodiment, the control of each control valve 35 to 39 was described using an electrical signal as an example, but the configuration is not limited to this, and for example, control may be performed using a hydraulic signal. However, when control is performed using a hydraulic signal, the controllability is considered to be even lower than when control is performed using an electrical signal, so as in the above embodiment, by performing the final operation of the measurement operation by accumulating pressure in the accumulator 21, it is possible to obtain calculation results with higher accuracy.

[0087] [Difference 3] In the above embodiment, the working device posture is adjusted to match the measurement posture by operator operation. However, the controller 18 may also output command signals to each of the control valves 35-39 for hydraulic cylinder control, including the first control valve 35, to automatically control the posture of the working device 10 to match the measurement posture.

[0088] The embodiments described above are illustrative for explaining the present invention and are not intended to limit the scope of the invention to those embodiments only. Those skilled in the art can implement the present invention in various other forms without departing from the spirit of the invention. [Explanation of Symbols]

[0089] 1. Hydraulic excavator 2. Running body 3. Rotating body 4 Crawler 5. Driving motor 6. Swivel device 7. Swivel Frame 8. Driver's cab 9 Counterweight 10 Working equipment 11 Boom 12 arms 13 buckets 14 Boom Cylinder 14A Bottom oil chamber 14B Rod-side oil chamber 15 Arm Cylinder 16 Bucket Cylinder 17 Operating device 18 controllers 18A Load Calculation Unit 18B Condition judgment section 18C Command signal output section 19 Display device 19A Measurement Result Output Section 19B Measurement Status Output Unit 19C Load Measurement and Indicating Device 20 Machine room 21 Accumulator 22 Engine 23 Hydraulic pump 24. Hydraulic oil tank 26 CPU 27 memory 28. Proportional relief valve 33A Bottom-side pressure sensor 33B Rod-side pressure sensor 34A Tilt Angle Sensor 34B Boom Angle Sensor 34C Arm Angle Sensor 34D Bucket Angle Sensor 35. First control valve (pump-side control valve) 36. Fourth control valve (accumulator side control valve) 37. Second control valve (pump-side control valve) 38. Third control valve (pump-side control valve) 39. Fifth control valve (accumulator side control valve) P Oscillation center

Claims

1. A working device having a boom and a boom cylinder for moving the boom up and down, A pressure detection device for detecting the pressure acting on each of the two oil chambers of the boom cylinder, A hydraulic pump capable of supplying hydraulic fluid to either of the two oil chambers to operate the boom cylinder, A controller that performs load calculation processing to calculate the weight of the work object acting on the tip of the work device based on the pressure detected by the pressure detection device while the work device is in a predetermined measurement position, A work machine equipped with, An accumulator-side control valve connects one of the two oil chambers to the accumulator and connects or disconnects the other oil chamber to the hydraulic fluid tank, A pump-side control valve connects or disconnects one of the two oil chambers to the hydraulic pump and the other oil chamber to the hydraulic fluid tank, It has, When the work device assumes the predetermined measurement position, the controller controls the accumulator-side control valve so that the high-pressure side oil chamber of the boom cylinder's two oil chambers is connected to the accumulator and the low-pressure side oil chamber is isolated from the hydraulic fluid tank. After controlling the pump-side control valve so that the low-pressure oil chamber of the boom cylinder's two oil chambers is connected to the hydraulic pump and the high-pressure oil chamber is isolated from the hydraulic fluid tank, the low-pressure oil chamber and the hydraulic pump are isolated. Furthermore, the accumulator-side control valve is controlled so that the low-pressure side oil chamber is connected to the hydraulic fluid tank, and the load calculation process is executed. A work machine characterized by the following features.

2. A work machine according to claim 1, The pump-side control valve includes a first control valve provided between the two oil chambers of the boom cylinder and the hydraulic pump and the hydraulic oil tank, which switches the connection and disconnection between the oil chambers and the hydraulic pump and the hydraulic oil tank, and a second control valve provided between one of the two oil chambers of the boom cylinder and the first control valve, which switches the connection and disconnection. It consists of a third control valve provided between the other of the two oil chambers of the boom cylinder and the first control valve, which switches between connecting and disconnecting the oil chambers. The accumulator-side control valve is provided between the two oil chambers of the boom cylinder and the accumulator and the hydraulic fluid tank, and is a fourth control valve that switches the connection and disconnection between the oil chambers and the accumulator and the hydraulic fluid tank, The system includes a fifth control valve provided between the fourth control valve and the hydraulic fluid tank for switching between connection and disconnection. A work machine characterized by the following features.

3. A work machine according to claim 2, The aforementioned controller, Before the fifth control valve shuts off the high-pressure side oil chamber and the hydraulic fluid tank, and before the load calculation process is executed, the output of the pressure detection device is used to determine whether the boom cylinder is stationary or not. A work machine characterized by the following features.

4. A work machine according to claim 1, The device includes a posture detection device for detecting the posture of the work device, After the controller connects the low-pressure side oil chamber of the boom cylinder and the hydraulic pump using the pump-side control valve, when the extension or retraction of the boom cylinder is detected by the attitude detection device, the pump-side control valve shuts off the connection between the low-pressure side oil chamber of the boom cylinder and the hydraulic pump. A work machine characterized by the following features.

5. A work machine according to claim 4, The extension and retraction of the boom cylinder detected by the attitude detection device is set so that the amount of extension and retraction of the boom cylinder, which occurs when the connection between the low-pressure side oil chamber and the hydraulic pump is disconnected and then the low-pressure side oil chamber and the hydraulic oil tank are connected, is minimized. A work machine characterized by the following features.

6. A work machine according to claim 4, The controller, after connecting the low-pressure oil chamber and the hydraulic pump, determines whether the boom cylinder has extended or retracted by a predetermined amount based on the change in the posture of the work device. A work machine characterized by the following features.

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