Working machinery

Abstract

To reduce errors in the pressure sensor's detection results, prevent excessive temperature increases in the hydraulic fluid within the hydraulic cylinder. [Solution] The work machine comprises a machine body, a work device that operates by the extension and retraction of a hydraulic cylinder, an operating device that receives an operation to extend and retract the hydraulic cylinder, a posture sensor that detects the posture of the work device, a pressure sensor that detects the pressure of the hydraulic fluid in the hydraulic cylinder, a hydraulic circuit that controls the hydraulic fluid supplied to the hydraulic cylinder by the operation of the operating device, and a controller that measures the weight of the load lifted by the work device based on the posture of the work device detected by the posture sensor and the pressure of the hydraulic fluid detected by the pressure sensor. The controller limits the flow rate of hydraulic fluid supplied to the hydraulic cylinder by the hydraulic circuit when a stroke end operation is input to the operating device while the hydraulic cylinder has reached its stroke end, based on the detection result of the posture sensor.

Description

Technical Field

[0001] The present invention relates to a working machine for measuring the weight of a load.

Background Art

[0002] The upper limit of the loading capacity of the cargo bed of a dump truck is defined. Therefore, when loading earth and sand onto the cargo bed of a dump truck using a hydraulic excavator, it is necessary to manage the weight of the loaded earth and sand so that the loading capacity of the cargo bed does not exceed the upper limit.

[0003] Therefore, Patent Document 1 discloses a method for measuring the weight of a load lifted by a front working machine based on the posture of the front working machine and the pressure of the hydraulic oil in the boom cylinder. Further, it is known that an error occurs in the detection result of the pressure sensor due to a change in the temperature of the hydraulic oil, and temperature drift correction for correcting this error is disclosed in Patent Document 2.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Here, as shown by Equation 2 described later, the thrust Fbm is balanced by the self-weight W1 of the front working machine 10 and the weight W of the load and the moment around the rotation center X1. Note that the self-weight W1 of the front working machine 10 is sufficiently larger than the weight W of the load. Note that the measurement of the thrust Fbm is performed in a situation where the static frictional force R is infinitely close to 0.

[0006] For example, if the moment W1 × l1 of the front work implement 10's own weight W1 around the pivot center X1 is 140 [kN·m], and the moment W × lbm of the load weight W around the pivot center X1 is 20 [kN·m], then the moment Fbm × hbm of the thrust Fbm around the pivot center X1 should ideally be 160 [kN·m]. However, if a 1% error occurs in the thrust Fbm due to temperature drift caused by changes in the hydraulic fluid temperature, it may become 161.6 [kN·m] (i.e., including a 1% error of 1.6 [kN·m]).

[0007] However, the moment W1 × l1 of the front work implement 10's own weight W1 around the pivot center X1 is calculated from the design value and the attitude sensor, and therefore remains at 140 [kN·m] regardless of the change in hydraulic fluid temperature. As a result, this error (= 1.6 [kN·m]) is only reflected in the moment W × lbm of the load weight W around the pivot center X1 (= 21.6 [kN·m]), and its proportion is 8%. Since the moment arm is calculated from the design value and the attitude sensor, which are not affected by the change in hydraulic fluid temperature, this proportion is directly reflected in the error of the load weight W. Thus, even if the error in the pressure sensor detection result is small, the error in the measurement result of the load weight W becomes large.

[0008] This invention has been made in view of the above circumstances, and its purpose is to prevent an excessive rise in the temperature of the hydraulic fluid in a hydraulic cylinder in order to reduce errors in the detection results of a pressure sensor. [Means for solving the problem]

[0009] To achieve the above objective, the present invention provides a work machine comprising: a machine body; a work device supported by the machine body and operated by the extension and retraction of a hydraulic cylinder; an operating device that receives an operation to extend and retract the hydraulic cylinder; a posture sensor that detects the posture of the work device; a pressure sensor that detects the pressure of the hydraulic fluid in the hydraulic cylinder; a hydraulic circuit that controls the hydraulic fluid supplied to the hydraulic cylinder by the operation of the operating device; and a controller that measures the weight of the load lifted by the work device based on the posture of the work device detected by the posture sensor and the pressure of the hydraulic fluid detected by the pressure sensor, wherein the controller limits the flow rate of hydraulic fluid supplied to the hydraulic cylinder by the hydraulic circuit when a stroke end operation is input to the operating device to further extend or retract the hydraulic cylinder toward the stroke end when the hydraulic cylinder has reached the stroke end based on the detection result of the posture sensor. [Effects of the Invention]

[0010] According to the present invention, it is possible to prevent an excessive rise in the temperature of the hydraulic fluid in the hydraulic cylinder in order to reduce errors in the detection results of the pressure sensor. Other problems, configurations, and effects will be clarified by the following description of the embodiments. [Brief explanation of the drawing]

[0011] [Figure 1] This is a side view of a hydraulic excavator. [Figure 2] This is a hardware configuration diagram for a hydraulic excavator. [Figure 3] This is a functional block diagram of the controller according to this embodiment. [Figure 4] This diagram shows the relationship between the posture of the front work implement and the detection results of various sensors. [Figure 5] This is a flowchart of the boom cylinder extension / retraction process. [Figure 6] This is a functional block diagram of the controller in a modified example. [Modes for carrying out the invention]

[0012] [Configuration of Hydraulic Excavator 1] An embodiment of the hydraulic excavator 1 according to the present invention will be described with reference to the drawings. The hydraulic excavator 1 according to this embodiment is an example of a work machine. The specific example of a work machine is not limited to the hydraulic excavator 1, but can be any machine that can lift loads, such as a wheel loader or a crane. Also, unless otherwise specified, the front, back, left, and right directions in this specification are based on the viewpoint of the operator riding and operating the hydraulic excavator 1.

[0013] Figure 1 is a side view of a hydraulic excavator 1. As shown in Figure 1, the hydraulic excavator 1 comprises a lower traveling body 2 and an upper rotating body 3 supported by the lower traveling body 2. The lower traveling body 2 and the upper rotating body 3 are examples of the machine body.

[0014] The lower vehicle 2 is equipped with a pair of crawlers 4 on the left and right sides, which are continuous tracks. Driven by the travel motor 5, the pair of crawlers 4 rotate independently. As a result, the hydraulic excavator 1 moves. However, the lower vehicle 2 may be wheeled instead of having crawlers 4.

[0015] The upper slewing body 3 is rotatably supported by the lower traveling body 2. The upper slewing body 3 rotates relative to the lower traveling body 2 as the slewing motor 6 rotates. The upper slewing body 3 mainly consists of a base slewing frame 7, a cab (driver's seat) 8 located on the front left side of the slewing frame 7, a counterweight 9 located at the rear of the slewing frame 7, and a front work implement 10 (working device) mounted on the front center of the slewing frame 7 so as to be rotatable in the vertical direction.

[0016] The cab 8 is positioned adjacent to the front implement 10 in the left-right direction (the width direction of the vehicle body). More specifically, the cab 8 is positioned to the left of the front implement 10 (on one side in the left-right direction). However, the positioning of the cab 8 is not limited to the example described above; the cab 8 only needs to be positioned on one side of the front implement 10 in the left-right direction.

[0017] The cab 8 has a space for an operator who operates the hydraulic excavator 1 to board. Inside the cab 8, a seat on which the operator sits and an operating device 33 (see FIG. 2) operated by the operator sitting on the seat are arranged. The operating device 33 receives the operation of the operator for operating the hydraulic excavator 1. When the operating device 33 is operated by the operator, the lower traveling body 2 travels, the upper swing body 3 swings, and the front work implement 10 operates. Specific examples of the operating device 33 include a lever, a steering wheel, a pedal, a switch, and the like.

[0018] The front work implement 10 includes a boom 11 supported by the upper swing body 3 so as to be rotatable around a rotation center X1 (see FIG. 4), an arm 12 supported at the tip of the boom 11 so as to be rotatable around a rotation center X2 (see FIG. 4), a bucket 13 (attachment) supported at the tip of the arm 12 so as to be rotatable around a rotation center X3 (see FIG. 4), a boom cylinder 14 that rotates the boom 11 with respect to the upper swing body 3, an arm cylinder 15 that rotates the arm 12 with respect to the boom 11, and a bucket cylinder 16 that rotates the bucket 13 with respect to the arm 12. The counterweight 9 is for taking a weight balance with the front work implement 10 and is a heavy object having an arc shape in top view.

[0019] As shown in FIG. 4, the boom cylinder 14 is an example of a hydraulic cylinder including a cylinder tube 14a, a piston (not shown), and a cylinder rod 14b. The cylinder tube 14a is a cylindrical member having one end closed and the other end open. The piston is configured to be movable inside the cylinder tube 14a. Further, the piston partitions the internal space of the cylinder tube 14a into a bottom chamber and a rod chamber. The cylinder rod 14b has one end connected to the piston and the other end protruding from the open end of the cylinder tube 14a. The configurations of the arm cylinder 15 and the bucket cylinder 16 are also common.

[0020] In the internal space of the cylinder tube 14a, which is partitioned by a piston, the space opposite the cylinder rod 14b is referred to as the "bottom chamber," and the space on the cylinder rod 14b side is referred to as the "rod chamber." The closed end of the cylinder tube 14a is rotatably supported by the upper slewing body 3, and the tip of the cylinder rod 14b is rotatably supported by the boom 11. When hydraulic fluid is supplied to the bottom chamber and discharged from the rod chamber, the boom cylinder 14 extends (i.e., the boom 11 rises). Conversely, when hydraulic fluid is discharged from the bottom chamber and supplied to the rod chamber, the boom cylinder 14 retracts (i.e., the boom 11 collapses).

[0021] [Hardware configuration of hydraulic excavator 1] Figure 2 is a hardware configuration diagram of the hydraulic excavator 1. As shown in Figure 2, the hydraulic excavator 1 includes a controller 30 having a CPU 31 (Central Processing Unit) and memory 32. The memory 32 is composed of, for example, ROM (Read Only Memory), RAM (Random Access Memory), HDD (Hard Disk Drive), or a combination thereof. The controller 30 performs the processing described later by having the CPU 31 read and execute the program code stored in the memory 32.

[0022] However, the specific configuration of the controller 30 is not limited to this and may be implemented using hardware such as an ASIC (Application Specific Integrated Circuit) or FPGA (Field-Programmable Gate Array).

[0023] The controller 30 controls the operation of the entire hydraulic excavator 1. Based on various signals output from the operating device 33, measurement switch 34, temperature sensor 35, pressure sensors 36b, 36r, and angle sensors 37, 38, 39, the controller 30 controls the operation of hydraulic actuators (e.g., travel motor 5, slewing motor 6, boom cylinder 14, arm cylinder 15, bucket cylinder 16) through the hydraulic circuit 40 and displays various information on the display 41.

[0024] The operating device 33 receives an operator's command to instruct the operation of the hydraulic actuator and outputs an operation signal corresponding to the operator's command to the controller 30. For example, the operating device 33 receives an operation to extend or retract the boom cylinder 14, which is an example of a hydraulic actuator. More specifically, the operating device 33 receives an extension operation to extend the boom cylinder 14 and a retraction operation to retract the boom cylinder 14. The extension and retraction operations correspond, for example, to an operation to tilt the lever in the opposite direction.

[0025] The measurement switch 34 accepts input from the operator in the cab 8 and outputs a measurement signal to the controller 30 instructing it to measure the weight of the load scooped up by the bucket 13 (i.e., lifted by the front work machine 10).

[0026] The temperature sensor 35 detects the temperature of the hydraulic fluid inside the boom cylinder 14 and outputs a pressure signal indicating the detected temperature to the controller 30. The temperature sensor 35 may detect the temperature of both the bottom chamber and the rod chamber of the boom cylinder 14, or it may detect the temperature of either the bottom chamber or the rod chamber.

[0027] Pressure sensor 36b detects the hydraulic fluid pressure Pb in the bottom chamber of the boom cylinder 14 and outputs a pressure signal indicating the detected pressure Pb to the controller 30. Pressure sensor 36r detects the hydraulic fluid pressure Pr in the rod chamber of the boom cylinder 14 and outputs a pressure signal indicating the detected pressure Pr to the controller 30.

[0028] Angle sensor 37 detects the angle of the boom 11 with respect to the upper slewing body 3 (in other words, the mounting surface of the hydraulic excavator 1) (boom angle α) and outputs an angle signal indicating the detected boom angle α to the controller 30. Angle sensor 38 detects the angle of the arm 12 with respect to the boom 11 (arm angle β) and outputs an angle signal indicating the detected arm angle β to the controller 30. Angle sensor 39 detects the angle of the bucket 13 with respect to the arm 12 (bucket angle γ) and outputs an angle signal indicating the detected bucket angle γ to the controller 30. Angle sensors 37 to 39 are examples of attitude sensors that detect the attitude of the front work implement 10.

[0029] The hydraulic circuit 40 is a circuit that operates a hydraulic actuator (more specifically, supplies and discharges hydraulic fluid to the hydraulic actuator) according to the control of the controller 30. The hydraulic circuit 40 includes, for example, a hydraulic fluid tank for storing hydraulic fluid, a hydraulic pump for discharging the hydraulic fluid stored in the hydraulic fluid tank, a directional control valve for controlling the amount and direction of supply of hydraulic fluid discharged from the hydraulic pump to the hydraulic actuator, and a relief valve for discharging hydraulic fluid to the hydraulic fluid tank when the pressure of the hydraulic fluid supplied to the hydraulic actuator reaches a threshold. The configuration of the hydraulic circuit 40 is well known, so a detailed explanation is omitted.

[0030] The controller 30 operates the hydraulic actuator by controlling the hydraulic circuit 40 (more specifically, the directional control valve) according to the operation signal output from the operating device 33. More specifically, the controller controls the amount and direction of hydraulic fluid supply to the boom cylinder 14 according to the amount of tilt (operation amount) and the direction of tilt (operation direction) of the lever that rotates (raises) the boom 11. That is, the more the operating amount of the operating device 33 is increased, the more hydraulic fluid is supplied to the boom cylinder 14, and the less the operating amount of the operating device 33 is increased, the less hydraulic fluid is supplied to the boom cylinder 14. The relationship between the operating amount of the operating device 33 and the amount of hydraulic fluid supplied to the boom cylinder 14 is predetermined in the memory 32. The same applies to other hydraulic actuators.

[0031] Display 41 is an example of a notification device that informs the operator in cab 8 of information. Display 41 displays, for example, the weight W measured by the weight measuring means 52 (see Figure 3) described later, and notifies the operator that the amount of hydraulic fluid has been limited by the stroke end processing described later. However, the specific example of the notification device is not limited to display 41, and may also be an LED lamp, a speaker, or a combination thereof.

[0032] [Functional blocks of controller 30] Figure 3 is a functional block diagram of the controller 30 according to this embodiment. Figure 4 is a diagram showing the relationship between the posture of the front work machine 10 and the detection results of various sensors. As shown in Figure 3, the controller 30 includes a posture detection means 51, a weight measuring means 52, a stroke end determination means 53, a temperature determination means 54, and a flow rate control means 55. The controller 30 functions as the posture detection means 51, weight measuring means 52, stroke end determination means 53, temperature determination means 54, and flow rate control means 55 by, for example, the CPU 31 executing a program stored in the memory 32.

[0033] The posture detection means 51 detects the posture of the front work implement 10 based on the angles α, β, and γ detected by the angle sensors 37-39 and the various dimensions of the front work implement 10 (boom 11, arm 12, bucket 13). More specifically, as shown in Figure 4, the posture detection means 51 detects the horizontal length lbm from the pivot center X1 to the center position of the bucket 13 (in other words, the center of gravity of the load lifted by the bucket 13), the length hbm of the perpendicular line passing through the pivot center X1 to the boom 11, and the horizontal length l1 from the pivot center X1 to the center of gravity of the front work implement 10 excluding the boom cylinder 14. The posture detection means 51 detects the various lengths lbm, hbm, and l1 [m] by inputting the angles α, β, and γ [degrees] into a predetermined mathematical formula, for example. However, the specific method for detecting the various lengths lbm, hbm, and l1 is not limited to the example described above.

[0034] The weight measuring means 52 measures the weight W [kgf] of the load contained in the bucket 13 based on the posture (lbm, hbm, l1) of the front work machine 10 detected by the posture detection means 51 and the pressures Pb and Pr [Pa] detected by the pressure sensors 36b and 36r. For example, in response to the operation of the measurement switch 34, the weight measuring means 52 measures the weight W of the load using the following equations 1 to 3 and displays the measured weight W on the display 41. The operator should operate the measurement switch 34 when the static friction force R, described later, is as close to 0 as possible. In addition to being displayed on the display 41, the weight W measured by the weight measuring means 52 can also be used for the tipping prevention function. Fbm=Pb×Ab-Pr×Ar-R (Formula 1) Fbm×hbm=W×lbm+W1×l1 (Formula 2) W=(Fbm×hbm-W1×l1) / lbm (Formula 3)

[0035] Fbm[kgf] is the thrust in the direction of extending the boom cylinder 14, Ab[m 2 ] is the pressure-receiving area on the bottom chamber side of the piston, Ar[m 2 ] is the pressure-receiving area on the rod chamber side of the piston, R[kgf] is the static friction force of the boom cylinder 14, and W1[kgf] is the weight of the front work implement 10. The pressure-receiving areas Ab, Ar and the weight W1 are stored in memory 32 beforehand. Equation 1 is the formula for calculating the thrust Fbm of the boom cylinder 14 based on the pressures Pb and Pr detected by the pressure sensors 36b and 36r. Equation 2 is the formula showing the balance of moments around the front work implement 10. Equation 3 is the formula obtained by solving Equation 2 for weight W.

[0036] The stroke end determination means 53 determines that the corresponding hydraulic cylinder has reached its stroke end based on the detection results of the angle sensors 37 to 39. For example, for the boom cylinder 14, it is determined that the boom cylinder 14 has reached its stroke end based on the boom angle α detected by the angle sensor 37. The stroke end includes both the state in which the cylinder rod 14b is fully extended and the state in which the cylinder rod 14b is fully retracted. The boom angle α when the boom cylinder 14 reaches its stroke end is pre-stored in the memory 32. The same applies to other hydraulic cylinders.

[0037] The temperature determination means 54 determines whether the temperature T of the hydraulic fluid in the boom cylinder 14, as detected by the temperature sensor 35, is equal to or greater than the threshold temperature Tth. When the temperature of the hydraulic fluid in both the bottom chamber and the rod chamber is detected, the temperature determination means 54 may determine whether the temperature of the hydraulic fluid in both the bottom chamber and the rod chamber is equal to or greater than the threshold temperature Tth, or whether the temperature of the hydraulic fluid in either the bottom chamber or the rod chamber is equal to or greater than the threshold temperature Tth. The threshold temperature Tth is set to the hydraulic fluid temperature at which the temperature drift of the pressure sensors 36b and 36r is within an acceptable range. The threshold temperature Tth is assumed to be stored in the memory 32 in advance.

[0038] The flow rate control means 55 limits the flow rate of hydraulic fluid supplied to the hydraulic cylinder by controlling the hydraulic circuit 40 (more specifically, the directional control valve) in response to stroke end operations on the operating device 33. "Limiting the flow rate of hydraulic fluid" means making the flow rate of hydraulic fluid supplied to the hydraulic cylinder less than the supply amount corresponding to the operating amount stored in the memory 32. For example, setting the supply amount of hydraulic fluid to 0 regardless of the operating amount of the operating device 33 is one example of limiting the flow rate of hydraulic fluid. Another example of limiting the flow rate of hydraulic fluid is supplying a small amount of hydraulic fluid regardless of the operating amount of the operating device 33.

[0039] "Stroke end operation" refers to the operation of extending or retracting a hydraulic cylinder further toward the stroke end when it has reached its stroke end. For example, in a boom cylinder 14, extending the cylinder rod 14b when it is fully extended is an example of stroke end operation. Another example of stroke end operation is retracting the cylinder rod 14b when it is fully retracted.

[0040] When the stroke end operation is performed, more hydraulic fluid than necessary is supplied to the bottom chamber or rod chamber of the hydraulic cylinder. Also, if the pressure of the hydraulic fluid in the bottom chamber or rod chamber exceeds the upper limit, the relief valve opens and the hydraulic fluid is discharged into the hydraulic fluid tank. At this time, the temperature of the hydraulic fluid rises sharply. Furthermore, once the temperature of the hydraulic fluid rises, the high temperature state continues for a certain period of time. As a result, the error in the detection results of the pressure sensors 36b and 36r increases due to temperature drift, and the reliability of the weight measurement result of the weight measurement means 52 for weight W decreases.

[0041] [Boom cylinder extension / retraction process] Figure 5 is a flowchart of the boom cylinder extension / retraction process. The boom cylinder extension / retraction process controls the extension / retraction of the boom cylinder 14 (the amount and direction of hydraulic fluid supply to the boom cylinder 14) according to the operator's operation on the operating device 33. The controller 30 executes the boom cylinder extension / retraction process when it receives an operator's operation to extend or retract the boom cylinder 14 via the operating device 33. In this embodiment, the reference temperature for the cylinder extension / retraction process is the hydraulic fluid temperature of the boom cylinder 14 where the pressure sensors 36b and 36r are located. However, since the hydraulic fluid temperature also rises during the stroke end operation of the arm cylinder 15 and bucket cylinder 16, the process in Figure 5 is applied not only to the boom cylinder 14 but also to the arm cylinder 15 and bucket cylinder 16. However, the extension / retraction process for the arm cylinder 15 and bucket cylinder 16 is the same as that for the boom cylinder 14, and only the description of "boom cylinder 14" should be read as "arm cylinder 15" or "bucket cylinder 16", and the description of "boom angle α" should be read as "arm angle β" or "bucket angle γ", so a detailed explanation is omitted.

[0042] First, the temperature determination means 54 acquires the temperature T of the hydraulic fluid inside the boom cylinder 14 detected by the temperature sensor 35 (S11), and determines whether the acquired temperature T is equal to or greater than the threshold temperature Tth (S12).

[0043] Next, if the temperature determination means 54 determines that the hydraulic fluid temperature T is equal to or greater than the threshold temperature Tth (S12: Yes), the stroke end determination means 53 acquires the boom angle α detected by the angle sensor 37 (S13), and determines whether or not the boom cylinder 14 has reached the stroke end based on the acquired boom angle α (S14).

[0044] Next, if the stroke end determination means 53 determines that the boom cylinder 14 has reached the stroke end (S14: Yes), the flow rate control means 55 determines whether or not a stroke end operation has been performed based on the operation signal from the operating device 33 (S15).

[0045] Then, if the flow rate control means 55 determines that a stroke end operation is being performed (S15: Yes), it controls the hydraulic circuit 40 to limit the flow rate of hydraulic fluid supplied to the boom cylinder 14 by comparing it with the flow rate of hydraulic fluid corresponding to the amount of operation of the operating device 33 (S16).

[0046] On the other hand, if the temperature determination means 54 determines that the temperature T is less than the threshold temperature Tth (S12: No), if the stroke end determination means 53 determines that the boom cylinder 14 has not reached the stroke end (S13: No), or if the flow rate control means 55 determines that the stroke end operation has not been performed (S15: No), the flow rate control means 55 controls the hydraulic circuit 40 to supply the boom cylinder 14 with hydraulic fluid at a flow rate corresponding to the amount operated by the operating device 33 (S17).

[0047] [Effects of the Embodiment] According to the above embodiment, when the stroke end operation is performed, the flow rate of hydraulic fluid to the hydraulic cylinder is limited, thereby preventing the temperature of the hydraulic fluid in the boom cylinder 14 from rising excessively. This reduces the error in the detection results of the pressure sensors 36b and 36r due to temperature drift. As a result, the reliability of the weight measurement result of the weight measuring means 52 is improved.

[0048] Furthermore, according to the above embodiment, when the stroke end operation is performed, the flow rate of hydraulic fluid to the hydraulic cylinder is reduced to zero, which further prevents the temperature of the hydraulic fluid in the boom cylinder 14 from rising excessively. Note that if the flow rate of hydraulic fluid to the boom cylinder 14 is reduced too quickly, the load on the hydraulic circuit 40 will increase, so the flow rate may be reduced over a certain period of time.

[0049] Furthermore, in the above embodiment, if the stroke end operation is performed when the temperature T of the hydraulic fluid in the boom cylinder 14 is equal to or greater than the threshold temperature Tth, the flow rate of the hydraulic fluid to the hydraulic cylinder is restricted. In other words, if the temperature T of the hydraulic fluid is less than the threshold temperature Tth, the stroke end operation is permitted. This prevents unnecessary restriction of operation when the temperature T of the hydraulic fluid is low. However, the temperature determination means 54 and the processing in steps S11-S12 can be omitted.

[0050] [Modified examples of the above embodiments] Figure 6 is a functional block diagram of the controller 30A according to a modified example. Detailed explanations of the commonalities with the above embodiment will be omitted, and the explanation will focus on the differences. In addition, several modified examples will be described below, but some or all of them may be omitted.

[0051] First, the modified flow rate control means 55A may, in step S16, inform the operator via the display 41 that it is limiting the flow rate of the hydraulic fluid supplied to the boom cylinder 14.

[0052] Furthermore, the modified controller 30A may further include a pressure correction means 56. The pressure correction means 56 corrects the hydraulic fluid pressure detected by the pressure sensors 36b and 36r based on the hydraulic fluid temperature detected by the temperature sensor 35. For example, as in Patent Document 2, a correction table showing the correction amounts for pressures Pb and Pr corresponding to the hydraulic fluid temperature T may be stored in the memory 32. Then, the pressure correction means 56 corrects the pressures Pb and Pr based on the correction table stored in the memory 32.

[0053] Furthermore, although the above embodiment described an example of an electric operating device 33 that converts the operator's input into an electrical signal and outputs it to the controller 30, the present invention is also applicable to a hydraulic operating device that supplies pilot pressure corresponding to the operator's input to the pilot port of the directional control valve. In this case, the flow rate control means 55, 55A may limit the flow rate of hydraulic fluid supplied to the boom cylinder 14 by opening a solenoid valve that returns the hydraulic fluid passing through the oil passage from the hydraulic pump to the boom cylinder 14 to the hydraulic fluid tank.

[0054] Furthermore, the operating device 33 may include a changeover switch to switch whether or not to perform flow rate limiting (S16) of the hydraulic fluid supplied to the boom cylinder 14. That is, the flow rate control means 55, 55A may perform the process of step S16 when the changeover switch is in the first state "ON", and may not perform the process of step S16 when the changeover switch is in the second state "OFF".

[0055] 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]

[0056] 1: Hydraulic excavator 2: Lower running body 3: Upper rotating body 4: Crawler 5: Driving motor 6: Swivel motor 7: Swivel Frame 8: Cab 9: Counterweight 10: Front work machine 11: Boom 12: Arm 13: Bucket 14: Boom Cylinder 14a: Cylinder tube 14b: Cylinder rod 15: Arm Cylinder 16: Bucket Cylinder 30,30A: Controller 31: CPU 32: Memory 33: Operating device 34: Measurement switch 35: Temperature sensor 36b, 36r: Pressure sensors 37, 38, 39: Angle sensors 40: Hydraulic Circuit 41: Display 51: Posture detection means 52: Weight measurement means 53: Stroke end determination means 54: Temperature determination means 55, 55A: Flow rate control means 56: Pressure compensation means X1, X2, X3: Center of rotation

Claims

1. The aircraft and, A work device supported by the aforementioned machine body and operated by the extension and retraction of a hydraulic cylinder, An operating device that receives an operation to extend or retract the hydraulic cylinder, A posture sensor for detecting the posture of the work device, A pressure sensor for detecting the pressure of the hydraulic fluid in the hydraulic cylinder, A hydraulic circuit controls the hydraulic fluid supplied to the hydraulic cylinder by operating the aforementioned operating device, A work machine comprising a controller that measures the weight of a load lifted by the work device based on the posture of the work device detected by the posture sensor and the pressure of the hydraulic fluid detected by the pressure sensor, The controller is characterized in that, when a stroke-end operation is input to the operating device to further extend or retract the hydraulic cylinder toward the stroke end, based on the detection result of the attitude sensor, the hydraulic circuit limits the flow rate of hydraulic fluid supplied to the hydraulic cylinder.

2. In the work machine described in claim 1, The controller is characterized in that, when the stroke end operation is input to the operating device while the hydraulic cylinder has reached its stroke end, the flow rate of the hydraulic fluid supplied to the hydraulic cylinder by the hydraulic circuit is reduced to zero.

3. In the work machine described in claim 1, The hydraulic cylinder is equipped with a temperature sensor that detects the temperature of the hydraulic fluid inside the hydraulic cylinder. The controller is characterized in that, when the pressure of the hydraulic fluid detected by the temperature sensor is above a threshold temperature and the hydraulic cylinder has reached its stroke end, and the stroke end operation is input to the operating device, the hydraulic circuit limits the flow rate of the hydraulic fluid supplied to the hydraulic cylinder.

4. In the work machine described in claim 1, Equipped with a notification device to broadcast information, The work machine is characterized in that the controller notifies, through the notification device, that it is limiting the flow rate of the hydraulic fluid supplied to the hydraulic cylinder.

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