Work machine

Abstract

To provide a work machine capable of appropriately determining abnormality in a hydraulic cylinder that has a cushion throttle.SOLUTION: A work machine comprises: a sensor detecting a plurality of operating parameters of a work device; a memory storing a reference energy absorbed by a cushion throttle in correspondence with each combination of the a plurality of operating parameters of the work device; and a controller determining abnormality in a hydraulic cylinder. When detecting the generation of braking force due to the cushion throttle based on the operating parameters detected by the sensor, the controller measures actual energy absorbed by the cushion throttle, and obtains a reference energy corresponding to the combination of a plurality of operating parameters detected by the sensor, from memory. When determining that the actual energy is outside an allowable range including the reference energy, the controller executes an abnormality determination process to determine that the hydraulic cylinder is abnormal.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a work machine equipped with a hydraulic cylinder having a cushion restriction. [Background technology]

[0002] Conventionally, work machines equipped with a work device operated by a hydraulic cylinder have been known. The hydraulic cylinders mounted on work machines have the function of generating a braking force when fully extended, thereby absorbing the impact when the piston abuts on the cylinder cap, and in some cases are provided with a cushioning mechanism to absorb the impact.

[0003] If the shock absorption function does not function effectively and the shock is not absorbed properly, the energy generated when the hydraulic cylinder is fully extended will exceed the allowable range. This will result in damage to the hydraulic cylinder, which will require repair or replacement. Therefore, as in Patent Document 1, for example, it is conceivable to determine the abnormality from the peak pressure of the hydraulic cylinder. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-199895 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the energy absorbed by the cushion throttle varies greatly depending on the combination of operating parameters of the work tool (e.g., extension speed, extension direction, and hydraulic oil temperature). Therefore, it is difficult to accurately determine an abnormality in the hydraulic cylinder by simply measuring the peak pressure.

[0006] The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a work machine that can appropriately determine an abnormality in a hydraulic cylinder having a cushion restriction. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention provides a work machine equipped with a working device that operates by extending and retracting a hydraulic cylinder, the hydraulic cylinder having a cushion throttle that generates a braking force when it is extended to its maximum, a sensor that detects a plurality of operating parameters of the working device, a memory that stores reference energy absorbed by the cushion throttle in correspondence with each combination of the plurality of operating parameters of the working device, and a controller that determines an abnormality in the hydraulic cylinder, wherein when the controller detects the generation of a braking force by the cushion throttle based on the operating parameters detected by the sensor, the controller measures the actual energy absorbed by the cushion throttle and obtains from the memory the reference energy that corresponds to the combination of the plurality of operating parameters detected by the sensor, and executes an abnormality determination process that determines that the hydraulic cylinder is abnormal if it determines that the actual energy is outside an allowable range that includes the reference energy. [Effects of the Invention]

[0008] According to the present invention, it is possible to appropriately determine an abnormality in a hydraulic cylinder having a cushion restriction. Note that problems, configurations, and effects other than those described above will become apparent from the following description of the embodiments. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a side view of a hydraulic excavator. [Figure 2] FIG. 3 is a cross-sectional view of the arm cylinder. [Figure 3] FIG. 2 is a control block diagram of the hydraulic excavator. [Figure 4] FIG. 10 is a diagram illustrating an example of a reference energy table. [Figure 5]FIG. 10 is a diagram illustrating an example of a correction value table. [Figure 6] 10 is a flowchart of a process executed by a controller. [Figure 7] 4 is a flowchart of an abnormality determination process according to the first embodiment. [Figure 8] 10 is a flowchart of an abnormality determination process according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] [Configuration of Hydraulic Excavator 1] An embodiment of a hydraulic excavator 1 (work machine) according to the present invention will be described with reference to the drawings. However, specific examples of the work machine are not limited to the hydraulic excavator 1, and may be machines equipped with hydraulic cylinders with cushioned restrictions (for example, dump trucks, wheel loaders, and cranes). Furthermore, unless otherwise specified, the terms front, back, left, and right in this specification are based on the viewpoint of an operator who is riding on and operating the hydraulic excavator 1.

[0011] Fig. 1 is a side view of a hydraulic excavator 1. As shown in Fig. 1, the hydraulic excavator 1 includes 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 an example of a vehicle body.

[0012] The lower traveling body 2 is equipped with a pair of left and right crawlers 4, which are endless tracks. The pair of left and right crawlers 4 are rotated independently by driving a traveling motor 5. As a result, the hydraulic excavator 1 travels. However, the lower traveling body 2 may be of a wheeled type instead of the crawlers 4.

[0013] The upper rotating body 3 is rotatably supported on the lower traveling body 2. When the swing motor 6 rotates, the upper rotating body 3 swings relative to the lower traveling body 2. The upper rotating body 3 mainly comprises a swing frame 7 serving as a base, a cab (operator's seat) 8 disposed on the front left side of the swing frame 7, a counterweight 9 disposed at the rear of the swing frame 7, and a front work implement 10 (working device) attached to the front center of the swing frame 7 so as to be rotatable in the vertical direction.

[0014] The cab 8 is disposed adjacent to the front working implement 10 in the left-right direction (the width direction of the vehicle body). More specifically, the cab 8 is disposed to the left (one side in the left-right direction) of the front working implement 10. However, the location of the cab 8 is not limited to the example described above, and the cab 8 may be disposed on one side of the front working implement 10 in the left-right direction.

[0015] The cab 8 is formed with a space for an operator to ride in and operate the hydraulic excavator 1. Inside the cab 8, there is a seat on which the operator sits, and an operation device 41 (see FIG. 3) that is operated by the operator seated in the seat. The operation device 41 accepts operations by the operator to operate the hydraulic excavator 1, and outputs an operation signal indicating the content of the accepted operation to a controller 50 (see FIG. 3). When the operator operates the operation device 41, the lower traveling body 2 travels, the upper rotating body 3 rotates, and the front working implement 10 operates. Specific examples of the operation device 41 include a lever, a steering wheel, and a pedal.

[0016] The front work implement 10 includes a boom 11 supported on the upper rotating body 3 so that it can be raised and lowered, an arm 12 supported at the tip of the boom 11 so that it can rotate (crowd, dump), a bucket 13 supported at the tip of the arm 12 so that it can rotate (crowd, dump), a boom cylinder 14 that drives the boom 11, an arm cylinder 15 that drives the arm 12, and a bucket cylinder 16 that drives the bucket 13. Note that specific examples of the attachment are not limited to the bucket 13, and may include a grapple, cutter, crusher, breaker, etc. The counterweight 9 is a heavy object that has an arc shape when viewed from above and is used to balance the weight of the front work implement 10.

[0017] [Arm Cylinder 15 Configuration] FIG. 2 is a cross-sectional view of the arm cylinder 15. The arm cylinder 15 is a hydraulic cylinder with a so-called "cushion restriction" that generates a braking force when it is extended to its maximum. Note that the hydraulic cylinder with a cushion restriction is not limited to the arm cylinder 15, but may also be the boom cylinder 14 or the bucket cylinder 16. Furthermore, since the configuration of each hydraulic cylinder (14 to 16) is common, the arm cylinder 15 will be described in detail below. As shown in FIG. 2, the arm cylinder 15 mainly comprises a cylinder tube 21, a cylinder cap 22, a piston 23, a cylinder rod 24, and a restriction portion 25.

[0018] The cylinder tube 21 has a cylindrical outer shape with one axial end (hereinafter referred to as the "closed end") closed and the other axial end (hereinafter referred to as the "open end") open. The internal space of the cylinder tube 21 is liquid-tightly partitioned by the piston 23 into a bottom chamber 26 on the closed end side and a rod chamber 27 on the open end side. Furthermore, a supply / discharge port 28, which is a passage for supplying and discharging hydraulic oil to and from the bottom chamber 26, is formed on the closed end side of the cylinder tube 21.

[0019] The cylinder cap 22 closes the open end of the cylinder tube 21. The cylinder cap 22 is fixed to the open end of the cylinder tube 21 by, for example, bolts 29a and 29b. The cylinder cap 22 also has a through passage 30 through which the cylinder rod 24 passes, a supply / discharge port 31 which is a passage for supplying / discharging hydraulic oil to / from the rod chamber 27, and a hydraulic pressure detection port 32 for detecting the hydraulic pressure of the hydraulic oil in the rod chamber 27.

[0020] The through passage 30 penetrates the cylinder cap 22 in the extension direction of the cylinder tube 21 (in other words, the cylinder rod 24). In addition, the supply / discharge port 31 branches off from the through passage 30 and opens on the side surface of the cylinder cap 22. The oil pressure detection port 32 does not communicate with the through passage 30 and the supply / discharge port 31, but directly communicates the rod chamber 27 with the outside of the cylinder cap 22.

[0021] The piston 23 is housed in the internal space of the cylinder tube 21 and divides the internal space of the cylinder tube 21 into a bottom chamber 26 and a rod chamber 27. The piston 23 is configured to be movable within the internal space of the cylinder tube 21 in the axial direction of the cylinder tube 21.

[0022] The cylinder rod 24 is connected to the piston 23 via a throttle portion 25. The cylinder rod 24 passes through a rod chamber 27 from the piston 23 and protrudes to the outside of the arm cylinder 15 through a through passage 30. The cylinder rod 24 seals the through passage 30 liquid-tightly, and moves in and out of the cylinder tube 21 through the through passage 30 as the piston 23 moves.

[0023] 1, the closed end of the cylinder tube 21 is rotatably supported by the boom 11, and the protruding end of the cylinder rod 24 is rotatably supported by the arm 12. The arm cylinder 15 expands and contracts when hydraulic oil stored in a hydraulic oil tank (not shown) is supplied by a hydraulic pump (not shown). This causes the arm 12 to rotate relative to the boom 11.

[0024] More specifically, when hydraulic oil is supplied to the bottom chamber 26 through the supply / discharge port 28, the piston 23 moves toward the open end of the internal space of the cylinder tube 21. This causes the cylinder rod 24 to protrude from the cylinder tube 21 through the through passage 30 (i.e., the arm cylinder 15 extends), causing the arm 12 to crowd (rotate in a direction approaching the ventral surface of the boom 11). At this time, hydraulic oil in the rod chamber 27 is discharged through the supply / discharge port 31.

[0025] Meanwhile, hydraulic oil is supplied to the rod chamber 27 through the supply / discharge port 31, causing the piston 23 to move toward the closed end in the internal space of the cylinder tube 21. This causes the cylinder rod 24 to retract into the cylinder tube 21 through the through passage 30 (i.e., the arm cylinder 15 contracts), causing the arm 12 to dump (rotate in a direction away from the ventral surface of the boom 11). At this time, hydraulic oil in the bottom chamber 26 is discharged through the supply / discharge port 28.

[0026] The throttle portion 25 is disposed between the piston 23 and the cylinder rod 24. The throttle portion 25 has a truncated conical outer shape so that the area on the piston 23 side is large and the area on the cylinder rod 24 side is small. Furthermore, the throttle portion 25 enters the supply / discharge port 31 and suddenly reduces the opening area of ​​the supply / discharge port 31 when the arm cylinder 15 is fully extended (i.e., just before the piston 23 closes the supply / discharge port 31). As will be described below, the throttle portion 25 and the supply / discharge port 31 form a cushion throttle.

[0027] As shown in FIG. 2(A), when the piston 23 moves in region A where the throttle portion 25 does not enter the supply / discharge port 31, the opening area of ​​the supply / discharge port 31 is constant, so the flow rate of the hydraulic oil discharged from the supply / discharge port 31 when the arm cylinder 15 extends (in other words, the hydraulic pressure in the rod chamber 27) does not change significantly. On the other hand, as shown in FIG. 2(B), when the throttle portion 25 enters the supply / discharge port 31, the opening area of ​​the supply / discharge port 31 suddenly decreases. This causes a sudden decrease in the flow rate of the hydraulic oil discharged from the supply / discharge port 31 (in other words, a sudden increase in the hydraulic pressure in the rod chamber 27), and a braking force is generated that brakes the movement of the piston 23 toward the open end (i.e., the extension of the arm cylinder 15). In other words, the cushion throttle absorbs the energy that moves the piston 23 toward the open end, and generates a braking force that brakes the piston 23.

[0028] [Controller 50 Configuration] Fig. 3 is a control block diagram of the hydraulic excavator 1. As shown in Fig. 3, the hydraulic excavator 1 is equipped with a controller 50 having a CPU (Central Processing Unit) 51 and a memory 52. ​​The memory 52 is configured, for example, by a ROM (Read Only Memory), a RAM (Random Access Memory), an HDD (Hard Disk Drive), or a combination of these. The controller 50 realizes the processing described below by having the CPU 51 read and execute program code stored in the memory 52.

[0029] However, the specific configuration of the controller 50 is not limited to this, and may be realized by hardware such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field-Programmable Gate Array).

[0030] The controller 50 controls the overall operation of the hydraulic excavator 1. The controller 50 controls the operations of the traveling motor 5, swing motor 6, boom cylinder 14, arm cylinder 15, and bucket cylinder 16, for example, based on operation signals output from the operating device 41. The controller 50 also executes the processing shown in Fig. 6 based on stroke signals output from the stroke sensors 42a, 42b, and 42c, hydraulic pressure signals output from the hydraulic pressure sensors 43a, 43b, and 43c, and an oil temperature signal output from the oil temperature sensor 44. The stroke sensors 42a to 42c, the hydraulic pressure sensors 43a to 43c, and the oil temperature sensor 44 are examples of sensors that detect multiple operating parameters of the front working implement 10.

[0031] The stroke sensors 42a, 42b, 42c detect the extension amounts of the boom cylinder 14, arm cylinder 15, and bucket cylinder 16 (the protrusion amounts of the cylinder rods 24), and output stroke signals indicating the detected extension amounts to the controller 50. Then, the controller 50 identifies the extension directions of the boom cylinder 14, arm cylinder 15, and bucket cylinder 16 based on the stroke signals output from the stroke sensors 42a, 42b, 42c, and determines that the throttle section 25 has entered the supply / discharge port 31 (i.e., the cushion throttle has generated a braking force).

[0032] More specifically, the controller 50 determines whether the arm 12 is rotating in the direction of gravity or in the direction opposite to the direction of gravity (hereinafter referred to as the "anti-gravity direction") as the extension direction of the arm cylinder 15, depending on the combination of the extension amounts of the hydraulic cylinders (14, 15) detected by the stroke sensors 42a, 42b. Also, the controller 50 determines whether the bucket 13 is rotating in the direction of gravity or in the anti-gravity direction as the extension direction of the bucket cylinder 16, depending on the combination of the extension amounts of the hydraulic cylinders (14 to 16) detected by the stroke sensors 42a, 42b, 42c.

[0033] Furthermore, when the extension amount detected by the stroke sensors 42a, 42b, 42c reaches a predetermined threshold, the controller 50 determines that the cushion throttle of each hydraulic cylinder (14-16) generates a braking force. Furthermore, the controller 50 measures the extension speed of each hydraulic cylinder (14-16) based on the extension amount per unit time detected by the stroke sensors 42a, 42b, 42c.

[0034] The hydraulic pressure sensors 43a, 43b, 43c detect the hydraulic pressure of the hydraulic oil in the rod chamber 27 of each hydraulic cylinder (14-16) through the hydraulic pressure detection port 32, and output a hydraulic pressure signal indicating the detected hydraulic pressure to the controller 50. The oil temperature sensor 44 detects the temperature of the hydraulic oil supplied to each hydraulic cylinder (14-16), and outputs an oil temperature signal indicating the detected oil temperature to the controller 50. The installation location of the oil temperature sensor 44 is not particularly limited, and for example, the oil temperature sensor 44 may detect the temperature of the hydraulic oil stored in a hydraulic oil tank.

[0035] [Data structure of the reference energy table] Fig. 4 is a diagram showing an example of a reference energy table. The reference energy table shown in Fig. 4 is stored in the memory 52. ​​The reference energy table is a table that stores reference energies absorbed by the cushion throttle in association with each combination of a plurality of operating parameters. The reference energy is the magnitude of energy absorbed by the cushion throttle of the arm cylinder 15 when it is operating normally. The energy absorbed by the cushion throttle corresponds to, for example, a value obtained by integrating the pressure difference ΔP before and after the cushion throttle generates a braking force by the pressure receiving area of ​​the rod chamber 27 of the piston 23 over the time period during which the braking force is generated.

[0036] 4 stores reference energies in association with each combination of the extension speed of the arm cylinder 15 detected by the stroke sensor 42b (less than 1 m / s, 1 m / s or more but less than 2 m / s, 2 m / s or more), the extension direction of the arm cylinder 15 detected by the stroke sensors 42a and 42b (direction of gravity, direction against gravity), and the temperature of the hydraulic oil detected by the oil temperature sensor 44 (less than 30°C, 30°C or more but less than 40°C, 40°C or more but less than 50°C, 50°C or more). That is, the operating parameters according to this embodiment are the extension speed of the arm cylinder 15, the extension direction of the arm cylinder 15, and the temperature of the hydraulic oil supplied to the arm cylinder 15. However, specific examples of the operating parameters and the range of the values ​​of each parameter are not limited to the example in FIG. 4.

[0037] When the hydraulic excavator 1 is completed (or delivered), no reference energy is stored in the reference energy table. Then, the controller 50 sets the measured reference energy in the reference energy table by executing steps S11 to S13 in Fig. 6. This processing will be described later with reference to Fig. 6.

[0038] [Data structure of correction value table] Fig. 5 is a diagram showing an example of a correction value table. The memory 52 stores the correction value table shown in Fig. 5. The correction value table is a table in which correction values ​​are set to correct the reference energy set in the reference energy table shown in Fig. 4 to a reference energy corresponding to a specific combination of operating parameters (for example, an extension speed of 1 m / s to 2 m / s, an extension direction in the "anti-gravity direction," and an oil temperature of 40°C to 50°C). The memory 52 stores a plurality of correction value tables (24 types in this embodiment) corresponding to the respective cells in Fig. 4.

[0039] The correction value table contains correction values ​​determined through experiments or simulations. By multiplying the reference energy (e.g., Eth(3)) set in the reference energy table by the corresponding correction value (e.g., α4), the reference energy can be corrected to the reference energy corresponding to a specific combination of operating parameters (extension speed of 1 m / s to 2 m / s, extension direction "anti-gravity direction," and oil temperature of 40°C to 50°C).

[0040] Note that the reference energy tends to become larger as the extension speed of the arm cylinder 15 becomes faster. Therefore, in the example of FIG. 5, the correction value α13 becomes larger than 1, and α16 becomes smaller than 1. Also, the reference energy becomes larger when the arm cylinder 15 moves in the direction of gravity than when the arm cylinder 15 moves in the direction against gravity. Therefore, in the example of FIG. 5, the correction value α15 becomes smaller than 1. Furthermore, the reference energy does not change significantly depending on the temperature of the hydraulic oil. Therefore, in the example of FIG. 5, the correction values ​​α3, α9, and α20 become values ​​close to 1. Other correction values ​​are determined by combining these. However, specific examples of the correction values ​​and the method of correcting the reference energy are not limited to the above-mentioned examples.

[0041] [Processing by controller 50] Fig. 6 is a flowchart of the processing executed by the controller 50. As one example, the controller 50 executes the processing shown in Fig. 6 from the time the hydraulic excavator 1 is completed (or delivered) until an abnormality occurs in the arm cylinder 15. As another example, the controller 50 executes the processing shown in Fig. 6 from the time the arm cylinder 15 in which an abnormality has occurred is repaired or a part is replaced until an abnormality occurs again in the arm cylinder 15. It is assumed that at the start of the processing in Fig. 6, no reference energy has been set in the reference energy table.

[0042] First, the controller 50 waits to execute the processes in and after step S12 until the cushion throttling of the extended arm cylinder 15 generates a braking force (i.e., the throttling portion 25 enters the supply / discharge port 31) (S11: No). Next, when the controller 50 detects the generation of a braking force due to the cushion throttling of the arm cylinder 15 (S11: Yes), it measures the reference energy Eth(x) (S12). Furthermore, the controller 50 associates the reference energy Eth(x) measured in step S12 with the operating parameters detected by the stroke sensors 42a, 42b and the oil temperature sensor 44, and stores the reference energy Eth(x) in a reference energy table (S13).

[0043] More specifically, the controller 50 measures the reference energy Eth(1) by integrating over time a value obtained by multiplying the pressure difference ΔP before and after the cushion throttle generates a braking force by a pressure-receiving area (constant) of the rod chamber 27 of the piston 23 from the time when the extension amount detected by the stroke sensor 42b reaches a threshold value until the extension of the arm cylinder 15 stops (S12). Furthermore, the controller 50 stores the reference energy Eth(1) in a reference energy table in association with, for example, an extension speed (1 m / s to 2 m / s) determined from the extension amount detected by the stroke sensor 42b, an extension direction (anti-gravity direction) determined from the extension amount detected by the stroke sensors 42a, 42b, and an oil temperature (less than 30°C) detected by the oil temperature sensor 44 (S13).

[0044] Next, the controller 50 determines whether a predetermined termination condition has been met (S14). The termination condition is a condition for setting a reference energy in the reference energy table to an extent that allows the abnormality determination process, which will be described later, to be executed. As one example, the termination condition may be that a predetermined time has elapsed since the hydraulic excavator 1 was completed or delivered (or the arm cylinder 15 was repaired or parts were replaced). As another example, the termination condition may be that a reference energy has been set in all cells of the reference energy table.

[0045] Then, the controller 50 repeatedly executes the processing of steps S11 to S13 until the termination condition is satisfied (S14: No). In other words, until the termination condition is satisfied (S14: No), the controller 50 stores the reference energy in the memory 52 in association with the plurality of operation parameters detected by the sensors (42a to 42c, 44) every time it detects the generation of a braking force due to cushion squeezing of the arm cylinder 15. The processing of steps S11 to S14 may be executed when the manufacturer performs a test operation of the hydraulic excavator 1, or may be executed when the user who purchased the hydraulic excavator 1 actually operates the excavator. On the other hand, when the termination condition is satisfied (S14: Yes), the controller 50 executes the processing of step S15 and subsequent steps.

[0046] First, the controller 50 waits to execute the processes in step S16 and thereafter until the cushion throttle of the extended arm cylinder 15 generates a braking force (S15: No). Then, when the controller 50 detects the generation of a braking force due to the cushion throttle of the arm cylinder 15 (S15: Yes), it executes an abnormality determination process (S16). The abnormality determination process is a process for determining whether or not there is an abnormality in the arm cylinder 15 (more specifically, an abnormality in the cushion throttle). Details of the abnormality determination process will be described later with reference to Figs. 7 and 8.

[0047] Next, when the controller 50 determines in step S16 that there is no abnormality in the arm cylinder 15 (S17: No), it executes the processes from step S15 onwards again. That is, the controller 50 executes the abnormality determination process (S16) every time it detects the generation of a braking force due to cushion squeezing of the arm cylinder 15 (S15: Yes) until it determines that there is an abnormality in the arm cylinder 15 (S17: No).

[0048] On the other hand, if it is determined in step S16 that there is an abnormality in the arm cylinder 15 (S17: Yes), the controller 50 notifies the occurrence of the abnormality through an alarm device (S18), and ends the processing in Fig. 6. The alarm device is, for example, a display, monitor, or LED installed in the cab 8, or a management terminal connected to the hydraulic excavator 1 via a communication network. The content of the notification in step S18 may include, for example, that an abnormality has occurred in the arm cylinder 15, that use of the hydraulic excavator 1 should be stopped, or that repair or part replacement of the arm cylinder 15 is necessary.

[0049] [Abnormality determination process according to the first embodiment] 7 is a flowchart of the abnormality determination process according to the first embodiment. The abnormality determination process according to the first embodiment compares the measured energy Ec with a plurality of allowable ranges every time it detects the generation of braking force due to cushion squeezing of the arm cylinder 15, and determines that the arm cylinder 15 is abnormal if it is determined that the measured energy Ec is outside the plurality of allowable ranges.

[0050] First, the controller 50 measures the measured energy Ec (S21). The method for measuring the measured energy Ec is the same as the method for measuring the reference energy Eth(x) in step S12. Next, the controller 50 acquires, from a reference energy table, reference energies Eth(4), Eth(19) associated with an extension speed (e.g., 1 m / s to 2 m / s) determined from the extension amount detected by the stroke sensor 42b, an extension direction (e.g., antigravity direction) determined from the extension amount detected by the stroke sensors 42a, 42b, and an oil temperature (e.g., 40°C to 50°C) detected by the oil temperature sensor 44 (S22). The reference energies Eth(4), Eth(19) acquired in step S22 are examples of first reference energies.

[0051] Next, the controller 50 compares the actually measured energy Ec measured in step S21 with the allowable range including the reference energies Eth(4) and Eth(19) acquired in step S22 (S23). The allowable range is a numerical range having a predetermined width including the reference energy. That is, the allowable range is a numerical range specified by an upper limit value larger than the reference energy and a lower limit value smaller than the reference energy. Note that the allowable range including the first reference energy is an example of the first allowable range.

[0052] When there is one reference energy Eth acquired in step S22, the allowable range may be, for example, a range specified by a lower limit value (Eth - β1) and an upper limit value (Eth + β2). Note that β1 and β2 may be the same value or different values.

[0053] Also, when there are a plurality of reference energies Eth(4) and Eth(19) acquired in step S22, the allowable range may be, for example, a range including the plurality of reference energies Eth(4) and Eth(19). For example, when Eth(4) < Eth(19), the allowable range may be specified by a lower limit value (Eth(4) - β3) and an upper limit value (Eth(19) + β4). Note that β3 and β4 may be the same value or different values.

[0054] Furthermore, when there are a plurality of reference energies Eth(4) and Eth(19) acquired in step S22, the allowable range may be, for example, a range including the average value of the plurality of reference energies Eth(4) and Eth(19). That is, the allowable range may be specified by a lower limit value {Avg(Eth(4), Eth(19)) - β5} and an upper limit value {Avg(Eth(4), Eth(19)) + β6}. Note that β5 and β6 may be the same value or different values.

[0055] Next, when the controller 50 determines that the measured energy Ec is outside the first allowable range (S23: Yes), it acquires a reference energy (e.g., Eth(10)) associated with a combination of operation parameters different from the first reference energies Eth(4) and Eth(19) from the reference energy table (S24). The reference energy Eth(10) acquired in step S24 is an example of a second reference energy.

[0056] As one example, the controller 50 may acquire, as the second reference energy, a reference energy that has at least one of the plurality of motion parameters (in the above example, the extension speed and the extension direction) in common with the first reference energy. As another example, the controller 50 may acquire, as the second reference energy, a reference energy that was registered in the reference energy table after the first reference energy.

[0057] Next, the controller 50 corrects the second reference energy Eth(10) obtained in step S24 with the corresponding correction value α9 in the correction value table to calculate the corrected second reference energy Eth(10)' (S25). Next, the controller 50 compares the actual energy Ec measured in step S21 with an allowable range including the reference energy Eth(10)' corrected in step S25 (S26).

[0058] The allowable range including the corrected second reference energy is an example of the second allowable range. The method of specifying the second allowable range may be the same as that of the first allowable range. That is, the second allowable range may be specified by a lower limit value (Eth(10)'-γ1) and an upper limit value (Eth(10)'+γ2). Note that γ1 and γ2 may be the same or different. Furthermore, the widths of the first allowable range and the second allowable range may be the same or different. That is, β1 and γ1 may be the same value or different values. Furthermore, β2 and γ2 may be the same value or different values.

[0059] Next, if the controller 50 determines that the measured energy Ec is outside the second allowable range (S26: Yes), it determines that there is an abnormality in the arm cylinder 15 (S27) and ends the abnormality determination process. Also, if the controller 50 determines that the measured energy Ec is within the second allowable range (S26: No), it determines that there is no abnormality in the arm cylinder 15 (S28) and ends the abnormality determination process. Furthermore, if the controller 50 determines that the measured energy Ec is within the first allowable range (S23: No), it skips the processes of steps S24 to S27, determines that there is no abnormality in the arm cylinder 15 (S28), and ends the abnormality determination process.

[0060] [Effects of the first embodiment] According to the first embodiment, an abnormality in the arm cylinder 15 is determined by determining whether or not the actually measured energy when the cushion throttle generates a braking force is outside an allowable range specified from operation parameters detected at the same timing. This makes it possible to appropriately determine an abnormality in the arm cylinder 15 in accordance with the operating state of the hydraulic excavator 1. Note that the processes in Figs. 6 and 7 are applicable not only to the arm cylinder 15 but also to any hydraulic cylinder having a cushion throttle.

[0061] Furthermore, according to the first embodiment, if it is determined multiple times that the measured energy Ec is outside the allowable range (S23: Yes & S26: Yes), it is determined that the arm cylinder 15 is abnormal (S27). This reduces the possibility of erroneous determination due to temporary output abnormalities of the sensors (42a to 42c, 43a to 43c, 44). Note that the number of times the measured energy Ec is compared with the allowable range is not limited to two, and may be one, or three or more times.

[0062] Furthermore, according to the first embodiment, the measured energy Ec is compared with the second allowable range including the corrected second reference energy, so that an abnormality in the arm cylinder 15 can be appropriately determined in accordance with the operating state of the hydraulic excavator 1.

[0063] Furthermore, according to the first embodiment, by making the widths of the first allowable range and the second allowable range different, it is possible to more appropriately determine an abnormality in the arm cylinder 15. As one example, since the measured energy Ec is determined to be outside the first allowable range, by making the width of the second allowable range narrower than the first allowable range, it is possible to more precisely determine an abnormality in the arm cylinder 15. As another example, since the second reference energy has a different combination of corresponding operating parameters from the measured energy Ec, by making the width of the second allowable range wider than the first allowable range, it is possible to prevent erroneous determination due to this error.

[0064] Furthermore, according to the first embodiment, the reference energy table is created in the first half of the operation of the hydraulic excavator 1 (S11 to S14), and an abnormality in the arm cylinder 15 is determined in the second half of the operation of the hydraulic excavator 1 (S15 to S18), so that an abnormality in the arm cylinder 15 can be determined using a reference energy table that is tailored to the individual differences of the hydraulic excavator 1 (more specifically, the arm cylinder 15). As a result, an abnormality in the arm cylinder 15 can be determined more appropriately.

[0065] [Abnormality determination process according to the second embodiment] 8 is a flowchart of the abnormality determination process according to the second embodiment. Note that a detailed description of the commonalities with the first embodiment will be omitted, and the description will focus on the differences. The abnormality determination process according to the second embodiment compares one measured energy Ec with an allowable range each time it detects the generation of a braking force due to cushion squeezing of the arm cylinder 15, and determines that the arm cylinder 15 is abnormal if it is determined multiple times that the measured energy Ec is outside the allowable range.

[0066] In the second embodiment, the correction value table shown in Fig. 5 is omitted, and an abnormality flag is stored in memory 52. ​​The abnormality flag is a flag that indicates whether or not the arm cylinder 15 has been determined to be abnormal in a past abnormality determination process. The abnormality flag is set to a first value "OFF" that indicates that the arm cylinder 15 has not yet been determined to be abnormal, or a second value "ON" that indicates that the arm cylinder 15 has already been determined to be abnormal. The set value of the abnormality flag at the start of the process in Fig. 6 is the first value "OFF".

[0067] The processes of steps S21 to S23 and S26 to S27 in Fig. 8 are common to those in Fig. 7. Furthermore, when the controller 50 according to the second embodiment determines that the actual energy Ec measured in step S21 is within an allowable range including the reference energy acquired in step S22 (S23: No), it skips the processes of steps S31 to S32, determines that there is no abnormality in the arm cylinder 15 (S28), and ends the abnormality determination process.

[0068] On the other hand, when the controller 50 according to the second embodiment determines that the measured energy Ec is outside the allowable range (S23: Yes), it determines the set value of the abnormality flag (S31). Then, when the controller 50 determines that the first value "OFF" is set in the abnormality flag (S31: No), it sets the second value "ON" in the abnormality flag (S32), determines that there is no abnormality in the arm cylinder 15 (S28), and ends the abnormality determination process. On the other hand, when the controller 50 determines that the second value "ON" is set in the abnormality flag (S31: Yes), it determines that there is an abnormality in the arm cylinder 15 (S27), and ends the abnormality determination process.

[0069] According to the second embodiment, an abnormality in the arm cylinder 15 is determined using the reference energy Eth corresponding to the operating parameters when the actual energy Ec is measured, so that an abnormality in the arm cylinder 15 can be determined appropriately.

[0070] The above-described embodiments are merely illustrative examples of the present invention, and are not intended to limit the scope of the present invention to these embodiments. Those skilled in the art can implement the present invention in various other forms without departing from the spirit of the present invention. [Explanation of symbols]

[0071] 1: Hydraulic excavator 2: Lower running body 3: Upper rotating body 4: Crawler 5:Traction motor 6: Swing motor 7: Swivel frame 8: Cab 9: Counterweight 10: Front work equipment 11: Boom 12: Arm 13: Bucket 14: Boom cylinder 15: Arm cylinder 16: Bucket cylinder 21: Cylinder tube 22: Cylinder cap 23: Piston 24: Cylinder rod 25: Constriction section 26: Bottom chamber 27: Rod room 28: Intake / exhaust port 29: Bolt 30: Passage 31: Intake / exhaust port 32: Oil pressure detection port 41: Operating device 42: Stroke sensor 43: Oil pressure sensor 44: Oil temperature sensor 50: Controller 51: CPU 52: Memory

Claims

1. In a work machine equipped with a work device that operates by extension and contraction of a hydraulic cylinder, The hydraulic cylinder has a cushion throttle that generates a braking force when it is fully extended, a sensor for detecting a plurality of operational parameters of the working device; a memory that stores a reference energy absorbed by the cushion restrictor in association with each of a plurality of combinations of the operating parameters of the working device; a controller for determining an abnormality in the hydraulic cylinder, When the controller detects generation of a braking force due to the cushion squeezing based on the operation parameter detected by the sensor, measuring the actual energy absorbed by the cushion restriction; obtaining, from the memory, the reference energy corresponding to a combination of the plurality of operational parameters detected by the sensor; a hydraulic cylinder that is operated when the actual measured energy is determined to be outside an allowable range including the reference energy;

2. 2. The work machine according to claim 1, The working machine, wherein the controller determines that the hydraulic cylinder is abnormal when it determines multiple times that the measured energy is outside the allowable range.

3. 2. The work machine according to claim 1, Among the plurality of reference energies stored in the memory, The reference energy corresponding to a combination of the plurality of operation parameters detected by the sensor is defined as a first reference energy; When the reference energy associated with a combination of the plurality of operation parameters different from the first reference energy is set as a second reference energy, The controller when it is determined that the actual measured energy is outside a first allowable range including the first reference energy, correcting the second reference energy by a predetermined correction value between the first reference energy and the second reference energy; a hydraulic cylinder that is determined to be abnormal when the actual measured energy is determined to be outside a second allowable range that includes the corrected second reference energy;

4. 4. The work machine according to claim 3, A work machine, wherein the widths of the first allowable range and the second allowable range are different from each other.

5. 2. The work machine according to claim 1, The controller until a predetermined termination condition is satisfied, each time generation of a braking force due to the cushion squeezing is detected, the measured reference energy is associated with the plurality of operation parameters detected by the sensor and stored in the memory; a work machine that executes the abnormality determination process each time it detects generation of a braking force due to the cushion squeezing after the termination condition is satisfied;

6. 6. The work machine according to claim 5, a controller, in the abnormality determination process, when a plurality of reference energies corresponding to a plurality of the operation parameters detected by the sensor are stored in the memory, to determine whether the actual measured energy is outside the allowable range that includes the plurality of reference energies.

7. 2. The work machine according to claim 1, A work machine characterized in that the operating parameter is any one of an extension speed of the hydraulic cylinder, an extension direction of the hydraulic cylinder, and a temperature of hydraulic oil supplied to the hydraulic cylinder.

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