Work vehicles

Abstract

To provide a work vehicle which can quickly determine decrease in pressure accumulation performance of an accumulator.SOLUTION: A wheel loader 1 comprises: a brake circuit 301 and a fan circuit 302 that are connected to a hydraulic pump 31 in parallel; a priority valve 36 which flows a pressure oil, which is discharged from the hydraulic pump 31 provided on the brake circuit 301, in priority over the fan circuit 302; an accumulator 32 which is provided on the brake circuit 301, and accumulates the pressure oil discharged from the hydraulic pump 31; an accumulator pressure sensor 32A which detects an accumulator pressure P; and an abnormality determination device 5, 5A, 5B, 5C which determines abnormality of pressure accumulation performance of the accumulator 32. In the wheel loader, the abnormality determination device 5, 5A, 5B, 5C determines whether pressure accumulation performance of the accumulator 32 is normal or abnormal by characteristic parameters based on fluctuation of the accumulator pressure P that has been detected by the accumulator pressure sensor 32A.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a work vehicle in which an accumulator is provided on a pressure oil supply circuit that supplies pressure oil to a hydraulically driven device. [Background technology]

[0002] Brake control systems for vehicles, such as automobiles, including work vehicles and passenger cars, are equipped with accumulators that store hydraulic fluid discharged from a pump so that the brake system can be operated even if the pump that supplies hydraulic fluid to the brake system breaks down or the engine or motor that drives the pump stops. If an abnormality occurs in the accumulator and its performance deteriorates, it will no longer be able to store sufficient energy. Therefore, it is necessary to quickly determine the abnormality of the accumulator.

[0003] For example, Patent Document 1 discloses an accumulator pressure abnormality determination device including a motor that drives a pump, an accumulator pressure sensor that detects the accumulator pressure, which is the hydraulic fluid pressure of the accumulator, an accumulator pressure control unit that controls the operation of the motor so that the detected accumulator pressure is within a predetermined pressure range, and a low pressure abnormality determination unit that sets an upper limit time that serves as a criterion for determination, and determines that the accumulator pressure is abnormal if a state in which the accumulator pressure is equal to or lower than the predetermined pressure continues for more than the set upper limit time. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2008-105457 A Summary of the Invention [Problem to be solved by the invention]

[0005] In a work vehicle such as a wheel loader, pressure oil discharged from one hydraulic pump may be supplied to multiple hydraulic circuits. In this case, it is necessary to give priority to supplying pressure oil to hydraulic circuits related to the safety of the work vehicle, such as the pressure oil supply circuit related to the brake device and the pressure oil supply circuit related to the steering device. Therefore, a priority valve is provided on the pipe on the discharge side of the hydraulic pump, and when the circuit pressure is within a preset pressure range, pressure oil is supplied to the pressure oil supply circuit that should be given priority.

[0006] Therefore, in a work vehicle, if an accumulator is provided on a prioritized pressure oil supply circuit, pressure oil is always supplied to the accumulator with priority while the engine is running. Therefore, when the accumulator pressure abnormality determination device described in Patent Document 1 is adopted in the brake system of a work vehicle, the state in which the accumulator pressure is equal to or lower than a predetermined pressure is unlikely to continue for a set upper limit time or longer, and an abnormality in the accumulator cannot be accurately determined. Therefore, even if the pressure accumulation performance of the accumulator is degraded, it is difficult for the operator to notice the abnormality in the accumulator while the engine is running.

[0007] If a work vehicle continues to operate with the accumulator's pressure storage performance degraded, when the brake device is activated, the remaining amount of energy stored in the accumulator will rapidly decrease and quickly approach zero. This requires a constant supply of pressurized oil from the hydraulic pump to the accumulator, which increases the frequency of operation of various devices, including the hydraulic pump, and increases the load, causing the various devices to break down in a short period of time and worsening fuel efficiency.

[0008] SUMMARY OF THE PRESENT DISCLOSURE An object of the present invention is to provide a work vehicle that is capable of quickly determining a decrease in the pressure accumulation performance of an accumulator. [Means for solving the problem]

[0009] In order to achieve the above object, the present invention provides a work vehicle including a hydraulic pump driven by an engine and discharging pressurized oil, a first pressure oil supply circuit and a second pressure oil supply circuit connected in parallel to the hydraulic pump, a priority valve for causing the pressure oil discharged from the hydraulic pump to flow to the first pressure oil supply circuit in preference to the second pressure oil supply circuit, an accumulator provided on the first pressure oil supply circuit and storing the pressure oil discharged from the hydraulic pump, an accumulator pressure sensor for detecting the pressure of the accumulator, and an abnormality determination device for determining an abnormality in the pressure storage performance of the accumulator, wherein the abnormality determination device determines whether the pressure storage performance of the accumulator is normal or abnormal based on a characteristic parameter based on a fluctuation in the pressure of the accumulator detected by the accumulator pressure sensor. Effect of the Invention

[0010] According to the present invention, it is possible to quickly determine the deterioration of the pressure accumulation performance of the accumulator. Problems, configurations, and effects other than those described above will become apparent from the following description of the embodiments. [Brief description of the drawings]

[0011] [Figure 1] 1 is an external side view showing one configuration example of a wheel loader according to each embodiment of the present invention. FIG. [Diagram 2] 1 is a system configuration diagram showing a configuration example of a brake control system according to a first embodiment. [Diagram 3] 5 is a graph showing a change in accumulator pressure over time when the brake device is not in operation. [Figure 4] 1 is a functional block diagram showing functions of an abnormality determination device according to a first embodiment. [Diagram 5] 3 is a flowchart showing a flow of processing executed by the abnormality determination device according to the first embodiment. [Figure 6] 10 is a flowchart showing a flow of processing executed by an abnormality determination device according to a second embodiment. [Figure 7]10 is a flowchart showing a flow of processing executed by an abnormality determination device according to a third embodiment. [Figure 8] FIG. 13 is a functional block diagram showing functions of an abnormality determination device according to a fourth embodiment. [Figure 9] 10 is a flowchart showing a flow of processing executed by an abnormality determination device according to a fourth embodiment. [Figure 10] 4 is a graph showing a change in accumulator pressure over time when the brake device is operating. [Figure 11] FIG. 13 is a functional block diagram showing functions of an abnormality determination device according to a fifth embodiment. [Figure 12] 13 is a flowchart showing a flow of processing executed by an abnormality determination device according to a fifth embodiment. [Figure 13] FIG. 13 is a functional block diagram showing functions of an abnormality determination device according to a sixth embodiment. [Figure 14] 13 is a flowchart showing a flow of processing executed by an abnormality determination device according to a sixth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Below, as one aspect of the work vehicle according to each embodiment of the present invention, a wheel loader that performs loading and unloading work objects such as earth and sand or minerals and loading them onto a loading destination such as a dump truck will be described.

[0013] <Wheel loader 1 configuration> First, the configuration of the wheel loader 1 will be described with reference to FIG.

[0014] FIG. 1 is an external side view showing an example of the configuration of a wheel loader 1 according to each embodiment of the present invention.

[0015] The wheel loader 1 is an articulated work vehicle that is steered by bending the vehicle body near the center. Specifically, a front frame 1A forming the front part of the vehicle body and a rear frame 1B forming the rear part of the vehicle body are connected by a center joint 10 so as to be freely rotatable in the left-right direction, and the front frame 1A bends in the left-right direction relative to the rear frame 1B.

[0016] The vehicle body is provided with four wheels 11, two of which are front wheels 11A provided on both the left and right sides of the front frame 1A, and the remaining two wheels 11 are rear wheels 11B provided on both the left and right sides of the rear frame 1B. Of the four wheels 11, only the front wheel 11A and rear wheel 11B provided on the left side are shown in FIG. 1. There is no particular restriction on the specific number of wheels 11 provided on the vehicle body.

[0017] A hydraulically driven working device 2 for carrying out loading and unloading work is attached to the front of the front frame 1A. The working device 2 has a lift arm 21 attached to the front frame 1A so as to be rotatable in the vertical direction, two lift arm cylinders 22 as hydraulic cylinders for driving the lift arm 21, a bucket 23 attached to the tip of the lift arm 21 so as to be rotatable in the vertical direction, a bucket cylinder 24 as a hydraulic cylinder for driving the bucket 23, and a bell crank 25 rotatably connected to the lift arm 21 to form a link mechanism between the bucket 23 and the bucket cylinder 24. The two lift arm cylinders 22 are arranged side by side in the left-right direction of the vehicle body, but in FIG. 1, only the lift arm cylinder 22 arranged on the left side is shown by a dashed line.

[0018] When pressure oil is supplied to the bottom chambers of the two lift arm cylinders 22 and the rods 220 extend, the lift arms 21 rotate upward relative to the front frame 1A. On the other hand, when pressure oil is supplied to the rod chambers of the two lift arm cylinders 22 and the rods 220 retract, the lift arms 21 rotate downward relative to the front frame 1A.

[0019] When pressure oil is supplied to the bottom chamber of the bucket cylinder 24 and the rod 240 extends, the bucket 23 rotates upward relative to the lift arm 21 (tilt operation). On the other hand, when pressure oil is supplied to the rod chamber of the bucket cylinder 24 and the rod 240 retracts, the bucket 23 rotates downward relative to the lift arm 21 (dump operation). This allows the bucket 23 to scoop up and discharge (discharge) work objects such as soil and minerals.

[0020] The rear frame 1B is provided with a cab 12 in which an operator sits, a machine room 13 that houses various devices required to drive the wheel loader 1, such as the engine 30 (see FIG. 2), and a counterweight 14 for maintaining balance with the working implement 2 so that the vehicle body does not tilt. On the rear frame 1B, the cab 12 is located at the front, the counterweight 14 at the rear, and the machine room 13 between the cab 12 and the counterweight 14.

[0021] Next, the brake control system of the wheel loader 1 will be described for each embodiment.

[0022] First Embodiment A brake control system 3 according to a first embodiment of the present invention will be described with reference to FIGS.

[0023] (Schematic configuration of brake control system) First, the schematic configuration of the brake control system 3 will be described with reference to FIGS.

[0024] Fig. 2 is a system configuration diagram showing an example of the configuration of the brake control system 3 according to the first embodiment. Fig. 3 is a graph showing the change in accumulator pressure P over time when the brake device 33 is not in operation.

[0025] The brake control system 3 of the wheel loader 1 is composed of a hydraulic pump 31 driven by the engine 30 and discharging pressurized oil, an accumulator 32 that accumulates the pressurized oil discharged from the hydraulic pump 31, a brake device 33 that is driven by the pressurized oil supplied from the hydraulic pump 31 or the accumulator 32 and applies a braking force (braking force) to each of the four wheels 11 (see FIG. 1), a brake valve 34 that supplies control pressure to the brake device 33, and a check valve 35 that prevents reverse flow of pressurized oil from the accumulator 32 to the hydraulic pump 31 side.

[0026] The pressure oil discharged from the hydraulic pump 31 is supplied to the braking device 33 via a brake circuit 301 serving as a first pressure oil supply circuit. That is, the braking device 33 corresponds to a hydraulic drive device that is driven by the pressure oil supplied via the first pressure oil supply circuit. In the brake circuit 301, the brake valve 34 is disposed between the hydraulic pump 31 and the braking device 33, the accumulator 32 is disposed between the hydraulic pump 31 and the brake valve 34, and the check valve 35 is disposed between the hydraulic pump 31 and the accumulator 32.

[0027] Also provided on the brake circuit 301 are an accumulator pressure sensor 32A that detects the pressure P of the accumulator 32 (hereinafter simply referred to as "accumulator pressure P"), a brake pressure sensor 33A that detects the brake pressure (braking pressure) of the brake device 33, and a pressure switch 33B that serves as a brake lamp switch that turns on when the brake device 33 is activated.

[0028] The brake pressure sensor 33A can detect the operation of the brake device 33 by detecting a predetermined brake pressure, and the pressure switch 33B can detect the operation of the brake device 33 by switching to the side that turns on the brake lamp. Therefore, both the brake pressure sensor 33A and the pressure switch 33B correspond to an operation sensor that detects the operation of the brake device 33. Note that a potentiometer built into the brake valve 34 can also be used as the operation sensor.

[0029] In addition to the brake circuit 301, a fan circuit 302 serving as a second pressure oil supply circuit is connected to the hydraulic pump 31. That is, the brake circuit 301 and the fan circuit 302 are connected in parallel to the hydraulic pump 31, and pressure oil discharged from the hydraulic pump 31 is guided to both the brake circuit 301 and the fan circuit 302. The fan circuit 302 is a circuit for driving a cooling fan installed in the machine room 13 (see FIG. 1), and supplies pressure oil discharged from the hydraulic pump 31 to the hydraulic motor. The circuit pressure Pp of the fan circuit 302 is detected by a circuit pressure sensor 302A.

[0030] Because the brake circuit 301 is a circuit related to the safety of the traveling wheel loader 1, it is necessary for the pressurized oil discharged from the hydraulic pump 31 to flow through the brake circuit 301 with priority over the fan circuit 302. For this reason, a priority valve 36 is provided between the hydraulic pump 31 and the brake circuit 301 and fan circuit 302.

[0031] The priority valve 36 has a first valve 361 that guides the pressurized oil discharged from the hydraulic pump 31 to the fan circuit 302, and a second valve 362 that returns the pressurized oil discharged from the hydraulic pump 31 to the tank 31B when the accumulator pressure P becomes equal to or greater than the relief pressure.

[0032] An urging force set within a predetermined pressure range acts on the first valve 361. When the accumulator pressure P is equal to or lower than the predetermined pressure (when the accumulator pressure P is below the predetermined pressure range), the first valve 361 is maintained in a closed state by the action of the urging force, and the pressure oil discharged from the hydraulic pump 31 is guided to the brake circuit 301 side. On the other hand, when the accumulator pressure P is higher than the predetermined pressure (when the accumulator pressure P exceeds the predetermined pressure range), the first valve 361 switches to an open state against the urging force, and the pressure oil discharged from the hydraulic pump 31 is guided to the fan circuit 302 side.

[0033] Here, the "predetermined pressure range" refers to the pressure range in which pressure oil is accumulated in the accumulator 32, and is the pressure range (P1→P2) in which the pressure increases from the minimum operating pressure P1 to the maximum operating pressure P2 shown in Fig. 3. The accumulator 32 operates within a range between the minimum operating pressure P1 and the maximum operating pressure P2, and repeats accumulating the pressure oil discharged from the hydraulic pump 31 and discharging (consuming) the pressure oil accumulated in the accumulator 32.

[0034] Specifically, the accumulator 32 starts accumulating pressure when the accumulator pressure P falls below the minimum operating pressure P1 (P≦P1), and stops accumulating pressure when the accumulator pressure P rises to the maximum operating pressure P2 (P≧P2). Next, the accumulator 32, which is fully filled with pressure oil, starts discharging the accumulated pressure oil, and stops discharging the pressure oil when the accumulator pressure P falls to the minimum operating pressure P1 (P≦P1).

[0035] Therefore, the "minimum operating pressure P1" is a pressure set as the lowest pressure at which the accumulator 32 operates and starts accumulating pressure, and as the lowest pressure at which the accumulator 32 stops discharging pressure oil. The "maximum operating pressure P2" is a pressure set as the highest pressure at which the accumulator 32 stops accumulating pressure, and as the highest pressure at which the accumulator 32 starts discharging pressure oil.

[0036] Therefore, the pressurized oil discharged from the hydraulic pump 31 is guided to the brake circuit 301 side by the priority valve 36 when the accumulator pressure P drops to the minimum operating pressure P1, and is guided to the fan circuit 302 side by the priority valve 36 when the accumulator pressure P becomes higher than the maximum operating pressure P2, i.e., when there is no longer a need to supply pressurized oil to the accumulator 32.

[0037] 3, when the pressure accumulation performance of the accumulator 32 is normal, the accumulator 32 accumulates pressure oil at time T1 and discharges the pressure oil at time T2. In other words, the accumulator pressure P rises from the minimum operating pressure P1 to the maximum operating pressure P2 at time T1, and drops from the maximum operating pressure P2 to the minimum operating pressure P1 at time T2.

[0038] In the following description, the time during which the accumulator pressure P rises may simply be referred to as the "rise time," and the time during which the accumulator pressure P falls may simply be referred to as the "fall time." In addition, the rise time T1 when the pressure accumulation performance of the accumulator 32 is normal is referred to as the "first time T1," and the fall time T2 when the pressure accumulation performance of the accumulator 32 is normal is referred to as the "second time T2."

[0039] When the pressure accumulation performance of the accumulator 32 is degraded and abnormal, as shown by the dashed line in FIG. 3, the accumulator 32 rises from the minimum operating pressure P1 to the maximum operating pressure P2 in a time shorter than the first time T1, and drops from the maximum operating pressure P2 to the minimum operating pressure P1 in a time shorter than the second time T2.

[0040] In Fig. 3, it can be seen that the slope of the graph indicated by the dashed dotted line is steeper than the slope of the graph indicated by the solid line. In particular, the slope of the graph indicated by the dashed dotted line on the side where the accumulator 32 discharges pressure oil, i.e., on the side where the pressure drops from the maximum operating pressure P2 to the minimum operating pressure P1, is greater than the slope of the graph indicated by the solid line. In Fig. 3, while a normal accumulator 32 performs one operation cycle (first time T1+second time T2) from the start of pressure accumulation to the end of discharging pressure oil, an abnormal accumulator 32 performs about two cycles.

[0041] Note that FIG. 3 shows the change in accumulator pressure P over time when the braking device 33 is not operating. However, even when the braking device 33 is operating (see FIG. 10), while a normal accumulator 32 performs one cycle, an abnormal accumulator 32 will perform multiple cycles (approximately three cycles in FIG. 10).

[0042] Thus, when the pressure accumulation performance of the accumulator 32 is abnormal, the number of times the accumulator 32 operates increases compared to when it is normal, and the operation frequency of various devices including the hydraulic pump 31 increases, resulting in a larger load. Therefore, the brake control system 3 of the wheel loader 1 is equipped with an abnormality determination device 5 that determines whether there is an abnormality in the pressure accumulation performance of the accumulator 32, as shown in Figure 2.

[0043] Data relating to the accumulator pressure P detected by the accumulator pressure sensor 32A and the circuit pressure Pp detected by the circuit pressure sensor 302A, an operation signal output from the pressure switch 33B, etc. are input to the abnormality determination device 5. In addition, a monitor 4 serving as one form of an alarm device for alarming the result of the determination by the abnormality determination device 5 is electrically connected to the abnormality determination device 5.

[0044] (Configuration of Abnormality Determination Device 5) Next, the configuration of the abnormality determination device 5 will be described with reference to FIG.

[0045] FIG. 4 is a functional block diagram showing functions of the abnormality determination device 5.

[0046] The abnormality determination device 5 is configured by connecting a CPU, a RAM, a ROM, a HDD, an input I / F, and an output I / F via a bus. Various operating devices such as a pressure switch 33B and various sensors such as an accumulator pressure sensor 32A are connected to the input I / F, and the monitor 4 and the like are connected to the output I / F.

[0047] In such a hardware configuration, the CPU reads out a control program (software) stored in a recording medium such as a ROM, HDD, or optical disk, expands it on the RAM, and executes the expanded control program, whereby the control program and the hardware work together to realize the functions of the abnormality determination device 5.

[0048] In this embodiment, the abnormality determination device 5 is described as a computer configured by a combination of software and hardware, but this is not limited to the above. For example, as an example of another computer configuration, an integrated circuit that realizes the functions of a control program executed on the wheel loader 1 side may be used.

[0049] The abnormality determination device 5 includes a data acquisition unit 51, a time measurement unit 52, a time comparison unit 53, a performance determination unit 54, and a storage unit 55.

[0050] The data acquiring unit 51 acquires data relating to the accumulator pressure P detected by the accumulator pressure sensor 32A.

[0051] The time measurement unit 52 measures the rise time Tr of the accumulator pressure P. Specifically, the time measurement unit 52 starts measuring the rise time Tr when the accumulator pressure P acquired by the data acquisition unit 51 becomes equal to or lower than the minimum operating pressure P1 (P≦P1), and ends measuring the rise time Tr when the accumulator pressure P acquired by the data acquisition unit 51 becomes equal to or higher than the maximum operating pressure P2 (P≧P2).

[0052] The time comparison unit 53 compares the rise time Tr measured by the time measurement unit 52 with the first time T1. In this embodiment, the time comparison unit 53 compares the rise time Tr measured by the time measurement unit 52 with a time threshold Tth (Tth>T1) set to a time longer than the first time T1. Both the first time T1 and the time threshold Tth are stored in the storage unit 55 serving as a memory.

[0053] The performance determination unit 54 determines whether the pressure accumulation performance of the accumulator 32 is normal or abnormal based on a characteristic parameter based on the fluctuation of the accumulator pressure P detected by the accumulator pressure sensor 32A. In this embodiment, the "characteristic parameter" is the rise time of the accumulator pressure P.

[0054] Specifically, when the rise time Tr is determined in the time comparison unit 53 to be equal to or greater than the first time T1 and less than the time threshold Tth (T1 ≤ Tr < Tth), the performance determination unit 54 determines that the accumulation performance of the accumulator 32 is normal, and outputs a normal signal as a signal indicating the normality of the accumulator 32 to the monitor 4.

[0055] On the other hand, when the rise time Tr is determined in the time comparison unit 53 to be less than the first time T1 (Tr < T1), the performance determination unit 54 determines that the accumulation performance of the accumulator 32 is abnormal, and outputs an abnormal signal as a signal indicating the abnormality of the accumulator 32 to the monitor 4.

[0056] Also, in the present embodiment, when the rise time Tr is determined in the time comparison unit 53 to be equal to or greater than the time threshold Tth (Tr ≥ Tth), the performance determination unit 54 determines that there is an abnormality other than the accumulator 32 on the brake circuit 301, and outputs a circuit abnormality signal as a signal indicating an abnormality other than the accumulator 32 to the monitor 4.

[0057] (Processing in the abnormality determination device 5) Next, the specific processing flow executed by the abnormality determination device 5 will be described with reference to FIG. 5.

[0058] FIG. 5 is a flowchart showing the processing flow executed by the abnormality determination device 5.

[0059] The abnormality determination device 5 first causes the data acquisition unit 51 to acquire the accumulator pressure P detected by the accumulator pressure sensor 32A (step S501). Next, when the accumulator pressure P acquired in step S501 is equal to or less than the minimum operating pressure P1 (P ≤ P1) (step S502 / YES), the time measurement unit 52 starts measuring the rise time Tr (step S503). Note that when the accumulator pressure P is greater than the minimum operating pressure P1 in step S502 (step S502 / NO), the process does not proceed to step S503 until the accumulator pressure P becomes equal to or less than the minimum operating pressure P1.

[0060] Subsequently, the data acquisition unit 51 re-acquires the accumulator pressure P detected by the accumulator pressure sensor 32A (step S504). Then, when the accumulator pressure P re-acquired in step S504 is equal to or higher than the maximum operating pressure P2 (P ≥ P2) (step S505 / YES), the time measurement unit 52 ends the measurement of the rise time Tr (step S506).

[0061] On the other hand, when the accumulator pressure P is lower than the maximum operating pressure P2 (P < P2) in step S505 (step S505 / NO), it does not proceed to step S506 until the accumulator pressure P becomes equal to or higher than the maximum operating pressure P2.

[0062] Next, the time comparison unit 53 compares the rise time Tr measured by the time measurement unit 52 with the first time T1 and the time threshold Tth stored in the storage unit 55, and determines whether the rise time Tr is equal to or greater than the first time T1 and less than the time threshold Tth (step S507).

[0063] If it is determined in step S507 that the rise time Tr is equal to or greater than the first time T1 and less than the time threshold Tth (T1 ≤ Tr < Tth) (step S507 / YES), the performance determination unit 54 determines that the pressure accumulation performance of the accumulator 32 is normal, outputs a normal signal to the monitor 4 (step S508), and the processing in the abnormality determination device 5 ends.

[0064] On the other hand, if it is determined in step S507 that the rise time Tr is equal to or greater than the first time T1 and not less than the time threshold Tth (step S507 / NO), the time comparison unit 53 further determines whether the rise time Tr is less than the first time T1 (step S509).

[0065] If it is determined in step S509 that the rise time Tr is less than the first time T1 (Tr < T1) (step S509 / YES), the performance determination unit 54 determines that the accumulator performance of the accumulator 32 is abnormal, outputs an abnormal signal to the monitor 4 (step S510), and the processing in the abnormality determination device 5 ends.

[0066] If it is determined in step S509 that the rise time Tr is not less than the first time T1, that is, the rise time Tr is greater than or equal to the time threshold Tth (Tr ≧ Tth) (step S509 / NO), the performance determination unit 54 determines that a location other than the accumulator 32 in the brake circuit 301 is abnormal, outputs a circuit abnormal signal to the monitor 4 (step S511), and the processing in the abnormality determination device 5 ends.

[0067] In this way, when the accumulator performance of the accumulator 32 deteriorates, the abnormality determination device 5 determines the accumulator performance of the accumulator 32 based on the rise time Tr that characterizes the fluctuation of the accumulator pressure P that is easily directly affected by the deterioration. Therefore, it is possible to quickly determine the deterioration of the accumulator performance of the accumulator 32. And since the abnormality determination device 5 quickly determines the deterioration of the accumulator performance of the accumulator 32 and displays the abnormality on the monitor 4, it is possible to avoid an increase in the operating frequency of the accumulator 32 and suppress the deterioration of each device on the brake circuit 301 and the deterioration of fuel consumption.

[0068] Also, in the present embodiment, when the rise time Tr is greater than or equal to the time threshold Tth (Tr ≧ Tth), the abnormality determination device 5 determines that it is an abnormality in a location other than the accumulator 32 in the brake circuit 301, distinguishing it from an abnormality in the accumulator performance of the accumulator 32. Therefore, it is possible to more accurately determine an abnormality in the accumulator performance of the accumulator 32.

[0069] <Second Embodiment> Next, the abnormality determination device 5 according to the second embodiment of the present invention will be described with reference to FIG. 6.

[0070] FIG. 6 is a flowchart showing the flow of processing executed by the abnormality determination device 5 according to the second embodiment. In this embodiment, since the functional configuration of the abnormality determination device 5 is the same as that of the abnormality determination device 5 according to the first embodiment, the functional block diagram is omitted and only the flowchart shown in FIG. 6 will be described. In FIG. 6, components common to those described for the abnormality determination device 5 according to the first embodiment are denoted by the same reference numerals and their description is omitted.

[0071] In the first embodiment, the rise time Tr of the accumulator pressure P was used as the characteristic parameter, whereas in this embodiment, the fall time Td of the accumulator pressure P is used as the characteristic parameter. That is, the abnormality determination device 5 according to this embodiment determines whether the pressure accumulation performance of the accumulator 32 is normal or abnormal based on the fall time Td, which is the time taken for the discharge of the pressurized oil from the accumulator 32.

[0072] When the accumulator pressure P acquired in step S501 is equal to or higher than the maximum operating pressure P2 (P≧P2) (step S521 / YES), the time measurement unit 52 starts measuring the fall time Td (step S522). In step S521, when the accumulator pressure P is less than the maximum operating pressure P2 (P<P2) (step S521 / NO), the process does not proceed to step S522 until the accumulator pressure P becomes equal to or higher than the maximum operating pressure P2.

[0073] Next, when the accumulator pressure P reacquired in step S504 after step S522 becomes equal to or lower than the minimum operating pressure P1 (P≦P1) (step S523 / YES), the time measurement unit 52 ends the measurement of the fall time Td (step S524).

[0074] On the other hand, when the accumulator pressure P is greater than the minimum operating pressure P1 in step S523 (P>P1) (step S523 / NO), the process does not proceed to step S524 until the accumulator pressure P becomes equal to or lower than the minimum operating pressure P1.

[0075] Then, the time comparison unit 53 compares the drop time Td measured by the time measurement unit 52 with the second time T2 stored in the storage unit 55, and determines whether the drop time Td is equal to or greater than the second time T2 (step S525).

[0076] If it is determined in step S525 that the drop time Td is equal to or greater than the second time T2 (Td≥T2) (step S525 / YES), the performance determination unit 54 determines that the accumulation performance of the accumulator 32 is normal, outputs a normal signal to the monitor 4 (step S508), and the processing in the abnormality determination device 5 ends.

[0077] On the other hand, if it is determined in step S525 that the drop time Td is less than the second time T2 (Td<T2) (step S525 / NO), the performance determination unit 54 determines that the accumulation performance of the accumulator 32 is abnormal, outputs an abnormal signal to the monitor 4 (step S510), and the processing in the abnormality determination device 5 ends.

[0078] Also in this embodiment, the same operations and effects as those in the first embodiment can be achieved.

[0079] <Third Embodiment> Next, the abnormality determination device 5 according to the third embodiment of the present invention will be described with reference to FIG. 7.

[0080] FIG. 7 is a flowchart showing the flow of processing executed by the abnormality determination device 5 according to the third embodiment. Also in this embodiment, since the functional configuration of the abnormality determination device 5 is the same as that of the abnormality determination device 5 according to the first embodiment, the functional block diagram is omitted, and only the flowchart shown in FIG. 7 will be described. In FIG. 7, the same reference numerals are given to the components common to those described for the abnormality determination device 5 according to the first and second embodiments, and the description thereof is omitted.

[0081] In the first embodiment, the rise time Tr of the accumulator pressure P is used as the characteristic parameter, and in the second embodiment, the fall time Td of the accumulator pressure P is used as the characteristic parameter, whereas in this embodiment, both the rise time Tr and fall time Td of the accumulator pressure P are used as the characteristic parameters. That is, the abnormality determination device 5 according to this embodiment determines whether the pressure accumulation performance of the accumulator 32 is normal or abnormal based on the rise time Tr, which is the time it takes to accumulate pressure in the accumulator 32, and the fall time Td, which is the time it takes to discharge the pressure oil.

[0082] First, the abnormality determination device 5 performs the processes from step S501 to step S505 in the first embodiment. If the accumulator pressure P is equal to or higher than the maximum operating pressure P2 (P≧P2) in step S505 (step S505 / YES), the time measurement unit 52 ends the measurement of the rise time Tr and starts the measurement of the fall time Td (step S526).

[0083] Next, the data acquiring unit 51 reacquires the accumulator pressure P detected by the accumulator pressure sensor 32A (step S527). If the accumulator pressure P reacquired in step S527 is equal to or lower than the minimum operating pressure P1 (P≦P1) (step S528 / YES), the time measuring unit 52 ends the measurement of the decrease time Td (step S529).

[0084] Next, the time comparison unit 53 determines whether the rise time Tr measured by the time measurement unit 52 is greater than or equal to the first time T1 and less than the time threshold value Tth, and also determines whether the fall time Td measured by the time measurement unit 52 is greater than or equal to the second time T2 (step S530).

[0085] In step S530, when it is determined that the rise time Tr is equal to or greater than the first time T1 and less than the time threshold Tth (T1 ≤ Tr < Tth), and the fall time Td is equal to or greater than the second time T2 (Td ≥ T2) (step S530 / YES), the performance determination unit 54 determines that the accumulation performance of the accumulator 32 is normal, outputs a normal signal to the monitor 4 (step S508), and the processing in the abnormality determination device 5 ends.

[0086] On the other hand, in step S530, when it is not determined that the rise time Tr is equal to or greater than the first time T1 and less than the time threshold Tth, and the fall time Td is equal to or greater than the second time T2 (step S530 / NO), the time comparison unit 53 further determines whether the rise time Tr is less than the first time T1 and whether the fall time Td is less than the second time T2 (step S531).

[0087] In step S531, when it is determined that the rise time Tr is less than the first time T1 (Tr < T1) or the fall time Td is less than the second time T2 (Td < T2) (step S531 / YES), the performance determination unit 54 determines that the accumulation performance of the accumulator 32 is abnormal, outputs an abnormal signal to the monitor 4 (step S510), and the processing in the abnormality determination device 5 ends.

[0088] In step S531, when it is determined that the rise time Tr is not less than the first time T1 or the fall time Td is not less than the second time T2, that is, when it is determined that the rise time Tr is equal to or greater than the time threshold Tth (Tr ≥ Tth) (step S531 / NO), the performance determination unit 54 determines that a location other than the accumulator 32 in the brake circuit 301 is abnormal, outputs a circuit abnormality signal to the monitor 4 (step S511), and the processing in the abnormality determination device 5 ends.

[0089] Also in this embodiment, the same operations and effects as those in the first embodiment can be achieved.

[0090] <Fourth Embodiment> Next, an abnormality determination device 5A according to a fourth embodiment of the present invention will be described with reference to FIGS. 8 and 9.

[0091] FIG. 8 is a functional block diagram showing the functions of the abnormality determination device 5A according to the fourth embodiment. FIG. 9 is a flowchart showing the flow of processing executed by the abnormality determination device 5A according to the fourth embodiment. In FIGS. 8 and 9, components common to those described for the abnormality determination device 5 according to the first to third embodiments are denoted by the same reference numerals, and their description is omitted.

[0092] As shown in FIG. 8, the abnormality determination device 5A according to the present embodiment includes a data acquisition unit 51A, a time measurement unit 52, an operation state determination unit 56, a time comparison unit 53A, a performance determination unit 54, and a storage unit 55.

[0093] The data acquisition unit 51A acquires the circuit pressure Pp of the fan circuit 302 detected by the circuit pressure sensor 302A in addition to the accumulator pressure P detected by the accumulator pressure sensor 32A.

[0094] The operation state determination unit 56 determines whether or not the circuit pressure Pp acquired by the data acquisition unit 51A is lower than the minimum operating pressure P1. Here, when it is determined in the operation state determination unit 56 that the circuit pressure Pp is lower than the minimum operating pressure P1 (Pp < P1), the first valve 361 of the priority valve 36 is switched to the open state, and the pressure oil discharged from the hydraulic pump 31 is not supplied to the accumulator 32. In other words, this corresponds to a state in which the entire flow rate of the pressure oil discharged from the hydraulic pump 31 is supplied to the fan circuit 302 by the priority valve 36. Therefore, since the accumulator 32 is in a state of discharging pressure oil, the abnormality determination device 5A can accurately determine whether the accumulator performance of the accumulator 32 based on the decrease time Td is normal or abnormal.

[0095] As shown in Fig. 9, first, the data acquisition unit 51A acquires the circuit voltage Pp detected by the circuit voltage sensor 302A (step S532). Next, when the circuit voltage Pp acquired in step S532 is less than the minimum operating pressure P1 (Pp < P1) (step S533 / YES), the process proceeds to step S501, and thereafter, it is the same as the flow of the process executed by the abnormality determination device 5 according to the second embodiment.

[0096] On the other hand, when it is determined in step S532 that the circuit voltage Pp is greater than or equal to the minimum operating pressure P1 (Pp ≥ P1) (step S533 / NO), the process does not proceed to step S501 until the circuit voltage Pp becomes less than the minimum operating pressure P1.

[0097] Also in this embodiment, the same operations and effects as those in the first embodiment can be achieved.

[0098] <Fifth Embodiment> Next, the abnormality determination device 5B according to the fifth embodiment of the present invention will be described with reference to Figs. 10 to 12.

[0099] Fig. 10 is a graph showing the time change of the accumulator pressure P when the brake device 33 is operating. Fig. 11 is a functional block diagram showing the functions of the abnormality determination device 5B according to the fifth embodiment. Fig. 12 is a flowchart showing the flow of the process executed by the abnormality determination device 5B according to the fifth embodiment. In Figs. 10 to 12, for the components common to those described for the abnormality determination devices 5 and 5A according to the first to fourth embodiments, the same reference numerals are given and the description thereof is omitted.

[0100] The abnormality determination device 5B according to this embodiment determines whether the pressure accumulation performance of the accumulator 32 is normal or abnormal in consideration of the case where the brake device 33 is operating. When the brake device 33 operates, the accumulator pressure P drops suddenly. Therefore, as shown in Fig. 10, the graph showing the time change of the accumulator pressure P descends stepwise on the decreasing side.

[0101] When the pressure storage performance of the accumulator 32 is normal, when the braking device 33 is actuated once, the drop time of the accumulator pressure P is t1, when the braking device 33 is actuated twice, the drop time of the accumulator pressure P is t2, and when the braking device 33 is actuated three times, the drop time of the accumulator pressure P is t3.

[0102] These drop times t1, t2, and t3 are calculated by subtracting the time td during which the accumulator pressure P drops when the brake device 33 is operated once, multiplied by the number of times N the brake device 33 is operated, from the second time T2, which is the drop time when the pressure accumulation performance of the accumulator 32 is normal and the brake device 33 is not operating (t1=T2-td×1, t2=T2-td×2, t3=T2-td×3). Therefore, the drop time becomes shorter as the number of times the brake device 33 is operated increases (t1>t2>t3). In other words, the drop times t1, t2, and t3 of the accumulator pressure P when the pressure accumulation performance of the accumulator 32 is normal and the brake device 33 is operating are the second time T2 corresponding to the number of times the brake device 33 is operated.

[0103] Furthermore, as shown by the dashed dotted line in FIG. 10, even when the brake device 33 is activated, in the same manner as when the brake device 33 is not activated, when the pressure accumulation performance of the accumulator 32 is degraded, the change in the accumulator pressure P over time becomes smaller than when the pressure accumulation performance of the accumulator 32 is normal (shown by the solid line in FIG. 10), and the accumulator 32 operates more frequently.

[0104] In addition, when the pressure accumulation performance of the accumulator 32 is degraded, the amount of decrease ΔP in the accumulator pressure P when the brake device 33 is activated becomes larger than the amount of decrease when the pressure accumulation performance of the accumulator 32 is normal (P3 minus P4 shown in FIG. 10).

[0105] As shown in FIG. 11, the abnormality determination device 5B includes a data acquisition unit 51B, a time measurement unit 52, an operation number counting unit 57, a time comparison unit 53B, a performance determination unit 54, and a storage unit 55B.

[0106] The data acquiring unit 51B acquires the actuation signal output from the pressure switch 33B in addition to the accumulator pressure P detected by the accumulator pressure sensor 32A.

[0107] The activation counting unit 57 counts the number of activations of the braking device 33 based on the activation signal acquired by the data acquiring unit 51B. Note that, in this embodiment, the activation counting unit 57 counts the number of activations of the braking device 33 based on the activation signal (the light signal of the brake lamp) output from the pressure switch 33B, but is not limited thereto, and the activation number of the braking device 33 may be counted based on a data signal from the brake pressure sensor 33A or a potentiometer built into the brake valve 34.

[0108] The memory unit 55B stores second times t1, t2, t3, etc. corresponding to the number of times N1, N2, N3, etc. of operation of the braking device 33. The time comparison unit 53B compares the decrease time Td measured by the time measurement unit 52 with the second times t1, t2, t3, etc. corresponding to the number of times N1, N2, N3, etc. of operation of the braking device 33.

[0109] As shown in FIG. 12, when the accumulator pressure P becomes equal to or higher than the maximum operating pressure P2 (P≧P2) in step S502 (step S502 / YES), the abnormality determination device 5B causes the time measurement unit 52 to start measuring the decrease time Td, and also causes the operation counting unit 57 to start counting the number of operation times N of the brake device 33 (step S534).

[0110] Next, when the accumulator pressure P reacquired in step S504 becomes equal to or lower than the minimum operating pressure P1 (P≦P1) (step S505 / YES), the time measurement unit 52 stops measuring the decrease time Td, and the operation count unit 57 stops counting the number of operation times N of the brake device 33 (step S535).

[0111] Then, the time comparison unit 53B determines whether the number of operations N counted by the operation count unit 57 is less than or equal to N1 (=1 time) and whether the decrease time Td measured by the time measurement unit 52 is equal to or greater than the second time t1 corresponding to the number of operations N1 (step S536).

[0112] In step S536, when it is determined that the number of operations N is less than or equal to N1 (N≦N1) and the decrease time Td is equal to or greater than the second time t1 corresponding to the number of operations N1 (Td≧t1) (step S536 / YES), the performance determination unit 54 determines that the accumulation performance of the accumulator 32 is normal and outputs a normal signal to the monitor 4 (step S508), and the processing in the abnormality determination device 5B ends.

[0113] On the other hand, in step S536, when it is determined that the number of operations N is not less than N1 (N>N1) or the decrease time Td is less than the second time t1 corresponding to the number of operations N1 (Td<t1) (step S536 / NO), the time comparison unit 53B further determines whether the number of operations N is less than or equal to N2 (=2 times) and whether the decrease time Td is equal to or greater than the second time t2 corresponding to the number of operations N2 (step S537).

[0114] In step S537, when it is determined that the number of operations N is less than or equal to N2 (N≦N2) and the decrease time Td is equal to or greater than the second time t2 corresponding to the number of operations N2 (Td≧t2) (step S537 / YES), the process proceeds to step S508, and the performance determination unit 54 determines that the accumulation performance of the accumulator 32 is normal and outputs a normal signal to the monitor 4.

[0115] In step S537, when it is determined that the number of operations N is not less than N2 (N>N2) and the decrease time Td is less than the second time t2 corresponding to the number of operations N2 (Td<t2) (step S537 / NO), the performance determination unit 54 determines that the accumulation performance of the accumulator 32 is abnormal and outputs an abnormal signal to the monitor 4 (step S510), and the processing in the abnormality determination device 5B ends.

[0116] In this embodiment as well, it is possible to achieve the same effects and advantages as those in the first embodiment.

[0117] Sixth Embodiment Next, an abnormality determination device 5C according to a sixth embodiment of the present invention will be described with reference to FIGS.

[0118] Fig. 13 is a functional block diagram showing functions of an abnormality determination device 5C according to the sixth embodiment. Fig. 14 is a flowchart showing the flow of processing executed by the abnormality determination device 5C according to the sixth embodiment. In Figs. 13 and 14, components common to those described for the abnormality determination devices 5, 5A, and 5B according to the first to fifth embodiments are given the same reference numerals and description thereof will be omitted.

[0119] The abnormality determination device 5C according to the present embodiment, like the abnormality determination device 5B according to the fifth embodiment, determines whether the pressure accumulation performance of the accumulator 32 is normal or abnormal, taking into consideration the case where the brake device 33 is activated.

[0120] As described above, when the pressure accumulation performance of the accumulator 32 is degraded, the amount of decrease ΔP in the accumulator pressure P when the braking device 33 is activated becomes larger than the amount of decrease (P3 minus P4 shown in FIG. 10) when the pressure accumulation performance of the accumulator 32 is normal. Therefore, in the abnormality determination device 5C according to this embodiment, the characteristic parameter is set to the amount of decrease ΔP in the accumulator pressure P when the braking device 33 is activated.

[0121] As shown in FIG. 13, abnormality determination device 5C includes a data acquisition unit 51C, a decrease amount calculation unit 58, a decrease amount comparison unit 59, a performance determination unit 54C, and a storage unit 55C.

[0122] The data acquiring unit 51C acquires the actuation signal (brake actuation signal) output from the pressure switch 33B, in addition to the accumulator pressure P detected by the accumulator pressure sensor 32A.

[0123] The decrease amount calculation unit 58 calculates the amount of decrease ΔP of the accumulator pressure P based on the accumulator pressure P and the brake actuation signal acquired by the data acquisition unit 51C.

[0124] The decrease amount comparison unit 59 compares the decrease amount ΔP calculated by the decrease amount calculation unit 58 with the decrease amount ΔP1 (=P3-P4) when the pressure accumulation performance of the accumulator 32 is normal. The decrease amount ΔP1 is stored in advance in the storage unit 55C.

[0125] When the decrease amount comparison unit 59 determines that the decrease amount ΔP is equal to or less than ΔP1 (ΔP≦ΔP1), the performance determination unit 54C determines that the pressure accumulation performance of the accumulator 32 is normal, and outputs a normal signal to the monitor 4. On the other hand, when the decrease amount comparison unit 59 determines that the decrease amount ΔP is greater than ΔP1 (ΔP>ΔP1), the performance determination unit 54C determines that the pressure accumulation performance of the accumulator 32 is abnormal, and outputs an abnormality signal to the monitor 4.

[0126] 14, in the abnormality determination device 5C, first, the data acquisition unit 51C acquires the accumulator pressure P detected by the accumulator pressure sensor 32A (step S501). Next, when the data acquisition unit 51C acquires a brake actuation signal from the pressure switch 33B (step S538 / YES), the accumulator pressure P immediately before that (immediately before the data acquisition unit 51C acquires the brake actuation signal) is recorded (step S539). Note that, if the brake actuation signal is not output from the pressure switch 33B in step S538 (step S538 / NO), the process returns to step S501 and is repeated.

[0127] Subsequently, when the brake actuation signal is no longer output from the pressure switch 33B (step S538A / YES), the data acquisition unit 51C continues to reacquire the accumulator pressure P (step S540). On the other hand, when the brake actuation signal is being output from the pressure switch 33B in step S538A (step S538A / NO), the process does not proceed to step S540 until the brake actuation signal is no longer output.

[0128] Then, the decrease amount calculation unit 58 calculates the amount of decrease ΔP of the accumulator pressure P from the accumulator pressure P recorded in step S539 and the accumulator pressure P acquired in step S540 (step S541).

[0129] Next, the decrease amount comparison unit 59 determines whether or not the decrease amount ΔP calculated in step S541 is equal to or smaller than the decrease amount ΔP1 in the case where the pressure accumulation performance of the accumulator 32 is normal (step S542).

[0130] If it is determined in step S542 that the decrease amount ΔP is equal to or less than the decrease amount ΔP1 (ΔP≦ΔP1) (step S542 / YES), the performance determination unit 54C determines that the pressure accumulation performance of the accumulator 32 is normal and outputs a normal signal to the monitor 4 (step S508), and the processing in the abnormality determination device 5C ends.

[0131] On the other hand, if it is determined in step S542 that the decrease amount ΔP is greater than the decrease amount ΔP1 (ΔP>ΔP1) (step S542 / NO), the performance determination unit 54C determines that the pressure accumulation performance of the accumulator 32 is abnormal and outputs an abnormality signal to the monitor 4 (step S510), and the processing in the abnormality determination device 5C ends.

[0132] In this embodiment as well, it is possible to achieve the same effects and advantages as those in the first embodiment.

[0133] The embodiments of the present invention have been described above. Note that the present invention is not limited to the above-described embodiments, and various modified examples are included. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and are not necessarily limited to those having all of the configurations described. In addition, it is possible to replace a part of the configuration of this embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of this embodiment. Furthermore, it is possible to add, delete, or replace a part of the configuration of this embodiment with another configuration.

[0134] For example, in the above embodiment, a wheel loader 1 has been given as an example of one type of work vehicle, but the present invention is not limited to this and can be applied to any work vehicle equipped with a priority valve 36.

[0135] In addition, in the above embodiment, the brake device 33 has been described as an example of a hydraulic drive device driven by pressure oil supplied via the first hydraulic supply circuit, but the present invention is not limited to this and may be, for example, a steering device. [Explanation of symbols]

[0136] 1: Wheel loader (work vehicle) 5,5A,5B,5C: Abnormality determination device 30: Engine 31: Hydraulic pump 32: Accumulator 32A: Accumulator pressure sensor 36: Priority valve 301: Brake circuit (first pressure oil supply circuit) 302: Fan circuit (second pressure oil supply circuit) P: Accumulator pressure P1: Minimum operating pressure P2: Maximum operating pressure Tr: Rise time (characteristic parameter) Td: Decay time (characteristic parameter) T1: First Hour T2, t1, t2, t3: Second time ΔP: Amount of decrease (characteristic parameter)

Claims

1. A hydraulic pump driven by the engine to discharge pressure oil; a first pressure oil supply circuit and a second pressure oil supply circuit connected in parallel to the hydraulic pump; a priority valve that causes the pressure oil discharged from the hydraulic pump to flow to the first pressure oil supply circuit in preference to the second pressure oil supply circuit; an accumulator provided on the first pressure oil supply circuit and configured to accumulate pressure oil discharged from the hydraulic pump; an accumulator pressure sensor that detects the pressure of the accumulator; an abnormality determination device that determines an abnormality in the pressure accumulation performance of the accumulator; In a work vehicle equipped with The abnormality determination device includes: determining whether a pressure accumulation performance of the accumulator is normal or abnormal based on a characteristic parameter based on a fluctuation in the pressure of the accumulator detected by the accumulator pressure sensor; the characteristic parameter is a rise time of the pressure of the accumulator from a minimum operating pressure set as a minimum pressure at which the accumulator operates and starts accumulating pressure to a maximum operating pressure set as a maximum pressure at which the accumulator ends accumulating pressure; measuring the rise time based on the pressure of the accumulator detected by the accumulator pressure sensor; When the measured rise time is shorter than a first time, which is the rise time when the pressure accumulation performance of the accumulator is normal, it is determined that the pressure accumulation performance of the accumulator is abnormal; When the measured rise time is equal to or longer than a time threshold value set to a time longer than the first time, it is determined that an abnormality exists in a part of the first pressure oil supply circuit other than the accumulator. A work vehicle characterized by:

2. A hydraulic pump driven by an engine to discharge pressurized oil; a first pressure oil supply circuit and a second pressure oil supply circuit connected in parallel to the hydraulic pump; a priority valve that causes the pressure oil discharged from the hydraulic pump to flow to the first pressure oil supply circuit in preference to the second pressure oil supply circuit; an accumulator provided on the first pressure oil supply circuit and configured to accumulate pressure oil discharged from the hydraulic pump; an accumulator pressure sensor that detects the pressure of the accumulator; an abnormality determination device that determines an abnormality in the pressure accumulation performance of the accumulator; In a work vehicle equipped with a circuit pressure sensor for detecting a pressure in the second pressure oil supply circuit, The abnormality determination device includes: determining whether a pressure accumulation performance of the accumulator is normal or abnormal based on a characteristic parameter based on a fluctuation in the pressure of the accumulator detected by the accumulator pressure sensor; the characteristic parameter is a time period during which the pressure of the accumulator decreases from a maximum operating pressure set as the maximum pressure at which the accumulator operates and starts discharging pressure oil to a minimum operating pressure set as the minimum pressure at which the accumulator stops discharging pressure oil, measuring the decrease time based on the pressure of the accumulator detected by the accumulator pressure sensor; When the measured decrease time is shorter than a second time, which is the decrease time when the pressure accumulation performance of the accumulator is normal, it is determined that the pressure accumulation performance of the accumulator is abnormal; When the pressure in the second pressure oil supply circuit detected by the circuit pressure sensor is lower than the minimum operating pressure, it is determined whether the pressure accumulation performance of the accumulator is normal or abnormal based on the decrease time. A work vehicle characterized by:

3. The work vehicle according to claim 2, a hydraulic drive device that is driven by pressure oil supplied via the first pressure oil supply circuit; an operation sensor that detects operation of the hydraulic drive system and outputs an operation signal indicating that the hydraulic drive system has been operated to the abnormality determination device; The abnormality determination device includes: Counting the number of operations of the hydraulic drive device based on the operation signal output from the operation sensor; When the measured decrease time is shorter than the second time corresponding to the counted number of operations of the hydraulic drive device, it is determined that the pressure accumulation performance of the accumulator is abnormal. A work vehicle characterized by:

4. A hydraulic pump driven by an engine to discharge pressurized oil; a first pressure oil supply circuit and a second pressure oil supply circuit connected in parallel to the hydraulic pump; a priority valve that causes the pressure oil discharged from the hydraulic pump to flow to the first pressure oil supply circuit in preference to the second pressure oil supply circuit; an accumulator provided on the first pressure oil supply circuit and configured to accumulate pressure oil discharged from the hydraulic pump; an accumulator pressure sensor that detects the pressure of the accumulator; an abnormality determination device that determines an abnormality in the pressure accumulation performance of the accumulator; In a work vehicle equipped with a hydraulic drive device that is driven by pressure oil supplied via the first pressure oil supply circuit; an operation sensor that detects operation of the hydraulic drive system and outputs an operation signal indicating that the hydraulic drive system has been operated to the abnormality determination device; The abnormality determination device includes: determining whether a pressure accumulation performance of the accumulator is normal or abnormal based on a characteristic parameter based on a fluctuation in the pressure of the accumulator detected by the accumulator pressure sensor; The characteristic parameter is a pressure drop amount of the accumulator when the hydraulic drive device is operated, calculating the amount of decrease based on the actuation signal output from the actuation sensor and the pressure of the accumulator detected by the accumulator pressure sensor; When the calculated amount of decrease is greater than the amount of decrease when the pressure accumulation performance of the accumulator is normal, it is determined that the pressure accumulation performance of the accumulator is abnormal. A work vehicle characterized by:

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