Work vehicle

Abstract

To provide a work vehicle capable of preventing overheating in both a drive electric motor and a work electric motor.SOLUTION: A wheel loader 1 comprises: a work electric motor 31 and a drive electric motor 32 as drive sources; a first cooling pump 41; a second cooling pump 42; an electromagnetic switching valve 43 provided on a connecting pipe line 403 connecting a first pipe line 401 and a second pipe line 402 and switching between communication and cut-off between the first pipe line 401 and the second pipe line 402; and controllers 5, 5A for controlling the electromagnetic switching valve 43. The controllers 5, 5A determine whether the first cooling pump 41 and the second cooling pump 42 are each in an abnormal state, and depending on the result of an abnormal state determination, output to the electromagnetic switching valve 43 an open signal opening the electromagnetic switching valve 43 to a communication state or a close signal closing the electromagnetic switching valve 43 to a cut-off state.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a work vehicle equipped with a work device.

Background Art

[0002] In recent years, in work vehicles such as wheel loaders and hydraulic excavators, for the purpose of reducing the environmental load, electric drive vehicles using a battery as a power source instead of an engine and hybrid drive vehicles using both an engine and a battery as power sources have been developed. These work vehicles generally include a work electric motor for driving a hydraulic pump that supplies hydraulic oil to the work device, and a traveling electric motor for driving the wheels.

[0003] In electric work vehicles and hybrid work vehicles, it is required to appropriately perform temperature management of the battery, the work electric motor, and the traveling electric motor. Since the battery can generally supply power normally at a temperature of usually 15 to 35°C, it is necessary to always cool it so that this temperature range is maintained. On the other hand, since the work timing of heat generation of the work electric motor and the traveling electric motor differs depending on the work content performed by the work vehicle, it is necessary to perform appropriate cooling according to the heat generation timing of each.

[0004] For example, Patent Document 1 discloses a hybrid hydraulic excavator including a first electric motor that assists the driving of an engine, a second electric motor that is driven by the power of a power storage device, a first inverter that controls the driving of the first electric motor, a second inverter that controls the driving of the second electric motor, a cooling device that cools the power storage device, the first inverter, and the second inverter by circulating a coolant by a cooling pump, and a switching valve that switches the flow direction of the coolant to the first inverter and the second inverter according to the output of the first electric motor and the output of the second electric motor.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Japanese Patent No. 6112667 [Summary of the Invention] [Problems to be Solved by the Invention]

[0006] However, in the hydraulic excavator described in Patent Document 1, since the coolant discharged from one cooling pump is supplied to the first inverter and the second inverter via a switching valve, if the cooling pump fails, the coolant will not be led to either the first inverter or the second inverter. In this state, both the first electric motor and the second electric motor will overheat, so there is a risk that the hydraulic excavator will stop operating.

[0007] Therefore, an object of the present invention is to provide a work vehicle capable of avoiding the occurrence of overheating in both a traveling electric motor and a working electric motor. [Means for Solving the Problems]

[0008] In order to achieve the above object, the present invention provides a work vehicle including a vehicle body provided with wheels, a work device attached to the vehicle body, a work electric motor serving as a power source for driving the work device, and a traveling electric motor serving as a power source for driving the wheels. In the work vehicle, a first cooling pump is connected via a first pipeline to the upstream side of the work electric motor and discharges a refrigerant supplied to the work electric motor and the traveling electric motor; a second cooling pump is connected via a second pipeline to the upstream side of the traveling electric motor and discharges the refrigerant supplied to the work electric motor and the traveling electric motor; an electromagnetic switching valve is provided on a connection pipeline connecting the first pipeline and the second pipeline and switches between a communicating state in which the first pipeline and the second pipeline communicate with each other and a blocking state in which communication between the first pipeline and the second pipeline is blocked; and a controller for controlling the electromagnetic switching valve. The controller determines whether the first cooling pump and the second cooling pump are in an abnormal state respectively, and outputs an open signal for opening the electromagnetic switching valve to the communicating state or a close signal for closing the electromagnetic switching valve to the blocking state to the electromagnetic switching valve according to the determination results of the abnormal states of the first cooling pump and the second cooling pump respectively.

Advantages of the Invention

[0009] According to the present invention, it is possible to avoid the occurrence of overheating in both the traveling electric motor and the work electric motor. Problems, configurations, and effects other than those described above will be clarified by the description of the following embodiments.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Mode for Carrying Out the Invention

[0011] Hereinafter, as an aspect of a work vehicle according to each embodiment of the present invention, an electric drive wheel loader using a battery as a power source will be described as an example.

[0012] <Overall Configuration of Wheel Loader 1> First, the overall configuration of the wheel loader 1 according to each embodiment of the present invention will be described with reference to FIG. 1.

[0013] FIG. 1 is an external side view showing a configuration example of the wheel loader 1 according to each embodiment of the present invention.

[0014] The wheel loader 1 is an articulated work vehicle that is steered by the body folding in the vicinity of the center. Specifically, a front frame 1A that is the front part of the body and a rear frame 1B that is the rear part of the body are connected to be rotatable in the left - right direction by a center joint 10, and the front frame 1A bends in the left - right direction with respect to the rear frame 1B. In the following description, among the left - right direction (vehicle width direction) of the body, the direction on the left side with respect to the forward direction is defined as the "left direction", and the direction on the right side with respect to the forward direction is defined as the "right direction".

[0015] The vehicle body is provided with four wheels 11, two of which are front wheels 11A provided on both left and right sides of the front frame 1A, and the remaining two wheels 11 are rear wheels 11B provided on both left and right sides of the rear frame 1B, respectively. In FIG. 1, only the front wheel 11A and the rear wheel 11B provided on the right side among the four wheels 11 are shown.

[0016] The wheel loader 1 is a work vehicle that performs a loading operation of excavating a work object such as earth and sand or minerals and loading it into a dump truck or a hopper. At the front part of the front frame 1A, a hydraulically driven work device 2 for performing the loading operation is attached.

[0017] The work device 2 includes a lift arm 21 rotatably attached to the front frame 1A in the vertical direction, two lift arm cylinders 22 as hydraulic cylinders for driving the lift arm 21, a bucket 23 rotatably attached to the tip of the lift arm 21 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 and constituting a link mechanism between the bucket 23 and the bucket cylinder 24.

[0018] The two lift arm cylinders 22 are arranged side by side at a predetermined interval in the left - right direction of the vehicle body. In FIG. 1, only the right lift arm cylinder 22 is shown by a dashed line.

[0019] The lift arm 21 rotates upward with respect to the front frame 1A (lifting operation) when the rods 220 of the two lift arm cylinders 22 extend, and rotates downward with respect to the front frame 1A (lowering operation) when the rods 220 of the two lift arm cylinders 22 contract.

[0020] The bucket 23 rotates upward with respect to the lift arm 21 (tilting operation) as the rod 240 of the bucket cylinder 24 extends, and rotates downward with respect to the lift arm 21 (dumping operation) as the rod 240 of the bucket cylinder 24 contracts. Thereby, the bucket 23 can scoop up and discharge (excavate and dump) work objects such as earth and sand and minerals.

[0021] Note that the bucket 23 can be replaced with various attachments such as a blade or a plow. In addition to the cargo handling work using the bucket 23, the wheel loader 1 can also perform various operations such as snow removal work and earth pressing work.

[0022] The rear frame 1B is provided with a cab 12 for the operator to board, a machine room 13 for housing various devices necessary for driving the wheel loader 1 inside, and a counterweight 14 for maintaining the balance with the working device 2 so that the vehicle body does not tip over. In the rear frame 1B, the cab 12 is arranged at the front, the counterweight 14 is arranged at the rear, and the machine room 13 is arranged between the cab 12 and the counterweight 14.

[0023] <Configuration of the drive system 3 of the wheel loader 1> Next, the configuration of the drive system 3 of the wheel loader 1 will be described with reference to FIG. 2.

[0024] FIG. 2 is a system configuration diagram showing an example of the configuration of the drive system 3 of the wheel loader 1.

[0025] The drive system 3 of the wheel loader 1 is an electric drive type using the electric power output from a battery 30 mounted on the vehicle body as a power source, and includes a working drive device 301 for driving the working device 2 and a traveling drive device 302 for traveling the vehicle body.

[0026] The working drive device 301 includes a working electric motor 31 driven by the electric power output from the battery 30, a working inverter 33 that controls the working electric motor 31, a hydraulic pump 35 driven by the working electric motor 31, and hydraulic cylinders 22, 24 (two lift arm cylinders 22 and a bucket cylinder 24) driven by the supply of the hydraulic oil discharged from the hydraulic pump 35, and a direction control valve unit 37 that controls the flow (direction and flow rate) of the hydraulic oil led from the hydraulic pump 35 to the hydraulic cylinders 22, 24.

[0027] Based on the control signal output from the controller 5 described later, the working inverter 33 controls the rotational speed and output torque of the working electric motor 31, and also outputs these actual data to the controller 5.

[0028] The traveling drive device 302 includes a traveling electric motor 32 driven by the electric power output from the battery 30, a traveling inverter 34 that controls the traveling electric motor 32, and a transmission 36 that changes the output torque of the traveling electric motor 32 and transmits it to each wheel 11.

[0029] Similar to the working inverter 33, the traveling inverter 34 controls the rotational speed and output torque of the traveling electric motor 32 based on the control signal output from the controller 5, and also outputs these actual data to the controller 5.

[0030] The transmission 36 is an automatic transmission that switches the traveling direction (forward and backward) of the vehicle body and changes the rotational speed of the output shaft of the traveling electric motor 32. The rotational speed shifted by the transmission 36 is transmitted to each wheel 11 via the drive shaft 15 and the front axle 16A and the rear axle 16B, whereby the wheel loader 1 travels.

[0031] Here, V-shaped loading, which is one of the methods when the wheel loader 1 performs a loading and unloading operation, will be described with reference to FIG. 3.

[0032] FIG. 3 is an explanatory diagram for explaining V-shaped loading by the wheel loader 1.

[0033] The wheel loader 1 first advances toward the natural ground X and inserts the bucket 23 into the natural ground X. Subsequently, the bucket 23 performs a tilting operation to excavate earth and sand (arrow α1 shown in FIG. 3). When the excavation is completed, the wheel loader 1 temporarily retreats to the original position with the excavated earth and sand loaded in the bucket 23 (arrow α2 shown in FIG. 3).

[0034] Next, the wheel loader 1 advances while raising the working device 2 toward the dump truck Y which is the loading destination of the earth and sand in the bucket 23 (dump approach), and stops in front of the dump truck Y (arrow β1 shown in FIG. 3). In FIG. 3, the wheel loader 1 in the state of stopping in front of the dump truck Y is shown by a broken line. Subsequently, the bucket 23 performs a dumping operation to discharge the earth and sand onto the dump truck. When the discharging is completed, the wheel loader 1 retreats to the original position while lowering the working device 2 (arrow β2 shown in FIG. 3).

[0035] In this way, the wheel loader 1 performs a loading and unloading operation by operating the working device 2 while reciprocating in a V-shape between the natural ground X and the dump truck Y.

[0036] In this loading and unloading operation, for example, while the wheel loader 1 is advancing toward the natural ground X, since the working device 2 is not operating, mainly the traveling electric motor 32 is driven (the output on the traveling electric motor 32 side is large).

[0037] On the other hand, while the wheel loader 1 is stopped in front of the dump truck Y and discharging the earth and sand, since the wheel loader 1 is not traveling, mainly the working electric motor 31 is driven (the output on the working electric motor 31 side is large).

[0038] Also, while the wheel loader 1 is moving forward while raising the working device 2 toward the dump truck Y, since traveling and the operation of the working device 2 are performed simultaneously, both the working motor 31 and the traveling motor 32 are driven.

[0039] Among the components constituting the drive system 3 of the wheel loader 1, in particular, the battery 30, the working motor 31, the working inverter 33, the traveling motor 32, and the traveling inverter 34 are devices that tend to generate heat (generate a large amount of heat) when driven. Therefore, cooling water (refrigerant) is constantly supplied during driving so as not to overheat. Hereinafter, the configuration of the cooling circuit for cooling these heat-generating devices will be described for each embodiment.

[0040] <First Embodiment> The cooling circuit 4 according to the first embodiment of the present invention will be described with reference to FIGS. 4 to 6.

[0041] (Overall Configuration of Cooling Circuit 4) First, the overall configuration of the cooling circuit 4 will be described with reference to FIG. 4.

[0042] FIG. 4 is a schematic diagram showing a configuration example of the cooling circuit 4 according to the first embodiment of the present invention.

[0043] The battery 30, the working motor 31, the working inverter 33, the traveling motor 32, and the traveling inverter 34, which are heat-generating devices, are each cooled by the cooling water (refrigerant) circulating in the cooling circuit 4.

[0044] The cooling circuit 4 includes a cooling water tank 40 for storing cooling water, a first cooling pump 41 and a second cooling pump 42 for sucking up and discharging the cooling water from the cooling water tank 40, an electromagnetic switching valve 43 for switching the supply destinations of the cooling water discharged from the first cooling pump 41 and the cooling water discharged from the second cooling pump 42, respectively, and a heat exchanger 44 for cooling the heated cooling water.

[0045] The first cooling pump 41 is connected to the working motor 31 via the first pipeline 401. An inverter 33 for work is arranged on this first pipeline 401, that is, between the first cooling pump 41 and the working motor 31. Therefore, the cooling water discharged from the first cooling pump 41 and flowing in the first pipeline 401 cools by passing through the inverter 33 for work and the working motor 31 respectively.

[0046] Similarly, the second cooling pump 42 is connected to the traveling motor 32 via the second pipeline 402. A traveling inverter 34 is arranged in this second pipeline 402, that is, between the second cooling pump 42 and the traveling motor 32. Therefore, the cooling water discharged from the second cooling pump 42 and flowing in the second pipeline 402 cools by passing through the traveling inverter 34 and the traveling motor 32 respectively.

[0047] The first cooling pump 41 and the second cooling pump 42 are each electrically connected to a controller 5 described later. For example, when detecting the pressure, voltage, temperature, etc. inside the pump and the detected value does not become a value (not necessarily a single value, it may be a range) preset as the normal state of the pump, that is, when in an abnormal state, an abnormal signal is output to the controller 5.

[0048] The first cooling pump 41, the inverter 33 for work, and the working motor 31 connected to each other via the first pipeline 401, and the second cooling pump 42, the traveling inverter 34, and the traveling motor 32 connected to each other via the second pipeline 402 are connected in parallel.

[0049] The cooling water flowing in the first pipeline 401 and flowing out downstream of the working motor 31 and the cooling water flowing in the second pipeline 402 and flowing out downstream of the traveling motor 32 merge at the merging point P and flow in the merging pipeline 400 and return to the cooling water tank 40. A heat exchanger 44 and a battery 30 are arranged on the merging pipeline 400. The heated cooling water merged at the merging point P is cooled by passing through the heat exchanger 44, then passes through the battery 30 and then flows out to the cooling water tank 40.

[0050] The electromagnetic switching valve 43 is provided on a connection pipeline 403 that connects the first pipeline 401 and the second pipeline 402. Specifically, the connection point C1 between the first pipeline 401 and the connection pipeline 403 is between the first cooling pump 41 and the working inverter 33, and the connection point C2 between the second pipeline 402 and the connection pipeline 403 is between the second cooling pump 42 and the traveling inverter 34, respectively.

[0051] The electromagnetic switching valve 43 is controlled by a controller 5 described later, and switches between an open position where the connection pipeline 403 is communicated to put the first pipeline 401 and the second pipeline 402 in a communicating state, and a closed position where the connection pipeline 403 is blocked to block the communication between the first pipeline 401 and the second pipeline 402.

[0052] When the electromagnetic switching valve 43 is switched to the open position, the cooling water discharged from the first cooling pump 41 flows into each of the first pipeline 401 and the second pipeline 402 in the communicating state, and passes through all of the working inverter 33, the working motor 31, the traveling inverter 34, and the traveling motor 32 to cool them.

[0053] Similarly, when the electromagnetic switching valve 43 is switched to the open position, the cooling water discharged from the second cooling pump 42 flows into each of the first pipeline 401 and the second pipeline 402 in the communicating state, and passes through all of the working inverter 33, the working motor 31, the traveling inverter 34, and the traveling motor 32 to cool them.

[0054] On the other hand, when the electromagnetic switching valve 43 is switched to the closed position, since the between the first pipeline 401 and the second pipeline 402 is in a blocked state, the cooling water discharged from the first cooling pump 41 cannot flow into the second pipeline 402 side and flows through the first pipeline 401 to pass through and cool the two of the working inverter 33 and the working motor 31 respectively.

[0055] Similarly, when the electromagnetic switching valve 43 is switched to the closed position, the first pipeline 401 and the second pipeline 402 are in a blocked state. Therefore, the cooling water discharged from the second cooling pump 42 cannot flow into the first pipeline 401 side and flows through the second pipeline 402 to cool the traveling inverter 34 and the traveling motor 32 respectively.

[0056] Normally, the electromagnetic switching valve 43 is in the state of being switched to the closed position. The first cooling pump 41 discharges the cooling water for the working inverter 33 and the working motor 31, and the second cooling pump 42 discharges the cooling water for the traveling inverter 34 and the traveling motor 32. Note that the "normal time" refers to the normal state when both the first cooling pump 41 and the second cooling pump 42 are driving normally.

[0057] Among the working motor 31 which is the drive source for driving the working device 2 and the traveling motor 32 which is the drive source for traveling the vehicle body, since the traveling motor 32 consumes more power, in this embodiment, a pump with a capacity larger than that of the first cooling pump 41 is used for the second cooling pump 42.

[0058] (Configuration of the controller 5) Next, the configuration of the controller 5 will be described with reference to FIG. 5.

[0059] FIG. 5 is a functional block diagram showing the functions of the controller 5 according to the first embodiment.

[0060] As a hardware configuration, the controller 5 includes a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), an HDD (Hard Disk Drive), an input I / F (Interface), and an output I / F (Interface). These components are connected to each other via a common bus.

[0061] The CPU is an arithmetic means that controls the overall operation of the controller 5. The RAM is a volatile storage medium capable of high-speed reading and writing of information, and is used, for example, as a work area when the CPU processes management information. The ROM is a non-volatile storage medium for read-only, and programs such as firmware are stored therein.

[0062] The HDD is a non-volatile storage medium capable of reading and writing information and having a large storage capacity, and stores an OS (Operating System), control programs for executing various information processes described later, application programs, and the like. Note that the HDD can be substituted with, for example, an SSD (Solid State Drive) as long as it realizes the function of storing and managing information as a non-volatile storage medium, regardless of the type of device.

[0063] The input I / F is a connection interface between the input side communication network of the controller 5, and the first cooling pump 41, the second cooling pump 42, the work inverter 33, the traveling inverter 34, and the like are connected thereto.

[0064] The output I / F is a connection interface between the output side communication network of the controller 5, and the electromagnetic switching valve 43, the work inverter 33, the traveling inverter 34, and the like are connected thereto.

[0065] The controller 5 having such a hardware configuration is an information processing device that realizes a processing function by the arithmetic function of the CPU for control programs stored in the ROM and control programs and application programs loaded from a storage medium such as an HDD into the RAM.

[0066] By executing these information processes, a software control unit including various function modules in the controller 5 is configured. A function block that realizes the function of the controller 5 is configured by a combination of the software control unit configured in this way and the hardware resources including the above configuration.

[0067] In addition, in this embodiment, the configuration of the controller 5 is described by a combination of software and hardware. However, the present invention is not limited to this, and it may be configured using an integrated circuit that realizes the functions of the control program executed on the side of the wheel loader 1.

[0068] As shown in FIG. 5, the controller 5 includes a data acquisition unit 50, a pump abnormality determination unit 51, a working state determination unit 52, a traveling state determination unit 53, and a signal output unit 54.

[0069] When an abnormal state such as a failure occurs in the first cooling pump 41, the data acquisition unit 50 acquires the abnormal signal output from the first cooling pump 41. Similarly, when an abnormal state such as a failure occurs in the second cooling pump 42, the data acquisition unit 50 acquires the abnormal signal output from the second cooling pump 42. Further, the data acquisition unit 50 acquires data related to the rotational speed and output torque of the working motor 31 output from the working inverter 33, and the rotational speed and output torque of the traveling motor 32 output from the traveling inverter 34, respectively.

[0070] When the abnormal signal output from the first cooling pump 41 is acquired by the data acquisition unit 50, the pump abnormality determination unit 51 determines that the first cooling pump 41 is in an abnormal state. In other words, when the abnormal signal related to the first cooling pump 41 is not acquired by the data acquisition unit 50, the pump abnormality determination unit 51 determines that the first cooling pump 41 is in a normal state.

[0071] Similarly, when the abnormal signal output from the second cooling pump 42 is acquired by the data acquisition unit 50, the pump abnormality determination unit 51 determines that the second cooling pump 42 is in an abnormal state. In other words, when the abnormal signal related to the second cooling pump 42 is not acquired by the data acquisition unit 50, the pump abnormality determination unit 51 determines that the second cooling pump 42 is in a normal state.

[0072] The operation state determination unit 52 determines whether or not the work device 2 is operating based on the rotational speed and output torque of the work motor 31 acquired by the data acquisition unit 50. Specifically, when the rotational speed and output torque of the work motor 31 acquired by the data acquisition unit 50 are 0 or values close to 0, the operation state determination unit 52 determines that the work device 2 is stopped, that is, not operating. Conversely, when the rotational speed and output torque of the work motor 31 acquired by the data acquisition unit 50 are greater than 0 or values close to 0, the operation state determination unit 52 determines that the work device 2 is operating.

[0073] The traveling state determination unit 53 determines whether or not the wheel loader 1 is traveling based on the rotational speed and output torque of the traveling motor 32 acquired by the data acquisition unit 50. Specifically, when the rotational speed and output of the traveling motor 32 acquired by the data acquisition unit 50 are 0 or values close to 0, the traveling state determination unit 53 determines that it is in a stopped state, that is, not traveling. Conversely, when the rotational speed and output torque of the traveling motor 32 acquired by the data acquisition unit 50 are greater than 0 or values close to 0, the traveling state determination unit 53 determines that it is traveling.

[0074] The signal output unit 54 outputs an open signal for switching the electromagnetic switching valve 43 to the open position (bringing it into a communicating state in which the first pipeline 401 and the second pipeline 402 communicate) or a closed signal for switching the electromagnetic switching valve 43 to the closed position (bringing it into a blocking state in which the communication between the first pipeline 401 and the second pipeline 402 is blocked) to the electromagnetic switching valve 43 according to the determination result of the abnormal state for each of the first cooling pump 41 and the second cooling pump 42 determined by the pump abnormality determination unit 51, the operation state of the work device 2 determined by the operation state determination unit 52, and the traveling state of the vehicle body determined by the traveling state determination unit 53.

[0075] Further, when the pump abnormality determination unit 51 determines that both the first cooling pump 41 and the second cooling pump 42 are in a normal state, the signal output unit 54 outputs a closing signal to the electromagnetic switching valve 43. In this case, the signal output unit 54 outputs a closing signal to the electromagnetic switching valve 43 regardless of the operating state of the working device 2 and the traveling state of the vehicle body.

[0076] When both the first cooling pump 41 and the second cooling pump 42 are in a normal state, the first cooling pump 41 can supply a sufficient amount of cooling water to the working inverter 33 and the working motor 31, and the second cooling pump 42 can supply a sufficient amount of cooling water to the traveling inverter 34 and the traveling motor 32, respectively. Therefore, the controller 5 controls to switch the electromagnetic switching valve 43 to the closed position to block the connection pipeline 403.

[0077] On the other hand, when the pump abnormality determination unit 51 determines that both the first cooling pump 41 and the second cooling pump 42 are in an abnormal state, the signal output unit 54 outputs an opening signal to the electromagnetic switching valve 43 and outputs a limiting signal for limiting the output power of the working motor 31 to the working inverter 33 and a limiting signal for limiting the output power of the traveling motor 32 to the traveling inverter 34, respectively.

[0078] In this case, the signal output unit 54 outputs an opening signal to the electromagnetic switching valve 43 regardless of the operating state of the working device 2 and the traveling state of the vehicle body, and outputs a limiting signal to each of the working inverter 33 and the traveling inverter 34.

[0079] When both the first cooling pump 41 and the second cooling pump 42 are in an abnormal state, if the working motor 31 and the traveling motor 32 continue to be driven as they are, there is a very high possibility of overheating. Therefore, the controller 5 performs output limitation on the working motor 31 and the traveling motor 32. At this time, the controller 5 may output an alarm signal to a monitor, a speaker, etc. to alert the operator.

[0080] In addition, the "abnormal state" of each of the first cooling pump 41 and the second cooling pump 42 includes not only the state where the drive has stopped but also the state where the drive is excessive. Therefore, the signal output unit 54 outputs a stop signal for stopping the drive to the cooling pump determined to be in the abnormal state by the pump abnormality determination unit 51.

[0081] (Processing executed in the controller 5) Subsequently, the flow of the process executed in the controller 5 will be described with reference to FIG. 6.

[0082] FIG. 6 is a flowchart showing the flow of the process executed by the controller 5 according to the first embodiment.

[0083] In the controller 5, first, the pump abnormality determination unit 51 determines whether both the first cooling pump 41 and the second cooling pump 42 are in a normal state (step S501). That is, in step S501, it is determined whether an abnormal signal is not output from each of the first cooling pump 41 and the second cooling pump 42.

[0084] When it is determined in step S501 that both the first cooling pump 41 and the second cooling pump 42 are in a normal state (step S501 / YES), the signal output unit 54 outputs a close signal to the electromagnetic switching valve 43 (step S502), and the process in the controller 5 ends.

[0085] When it is determined in step S501 that both the first cooling pump 41 and the second cooling pump 42 are not in a normal state (step S501 / NO), subsequently, the pump abnormality determination unit 51 determines whether the first cooling pump 41 is in a normal state (step S503).

[0086] If it is determined in step S503 that the first cooling pump 41 is in a normal state, that is, if it is determined that the first cooling pump 41 is in a normal state and the second cooling pump 42 is in an abnormal state (step S503 / YES), the controller 5 determines what operation the wheel loader 1 is performing (step S504). In step S504, based on the determination result of the work state determination unit 52 and the determination result of the traveling state determination unit 53, the operation content of the wheel loader 1 is estimated.

[0087] If it is determined in step S504 that the wheel loader 1 is performing a dump approach (that is, an operation in which the working device 2 is in an operating state and the vehicle body is in a traveling state) (step S504 / dump approach), the signal output unit 54 outputs an open signal to the electromagnetic switching valve 43 (step S505), and the processing in the controller 5 ends.

[0088] In the dump approach, since the wheel loader 1 travels while operating the working device 2, both the working motor 31 and the traveling motor 32 are in a state of outputting power. Therefore, it is necessary to supply cooling water to both sides of the working motor 31 and the traveling motor 32. However, since the second cooling pump 42 that normally supplies cooling water to the traveling motor 32 is in an abnormal state, the controller 5 controls to switch the electromagnetic switching valve 43 to the open position to communicate the connection pipeline 403, so as to supply the cooling water from the first cooling pump 41 to the traveling motor 32 side as well.

[0089] If it is determined in step S504 that the wheel loader 1 is traveling (that is, the working device 2 is in a stopped state and the vehicle body is in a traveling state) (step S504 / traveling), similar to the case of the dump approach, the process proceeds to step S505, and the signal output unit 54 outputs an open signal to the electromagnetic switching valve 43.

[0090] When the wheel loader 1 is only traveling, only the traveling electric motor 32 is outputting power. Therefore, it is sufficient to supply cooling water to at least the side of the traveling electric motor 32. However, since the second cooling pump 42 that normally supplies cooling water to the traveling electric motor 32 is in an abnormal state, the controller 5 controls the electromagnetic switching valve 43 to switch to the open position to communicate the connection pipeline 403, so that the cooling water from the first cooling pump 41 is also supplied to the traveling electric motor 32 side.

[0091] If it is determined in step S504 that the wheel loader 1 is performing earth discharging (that is, an operation in which the working device 2 is in an operating state and the vehicle body is in a stopped state) (step S504 / earth discharging), the process proceeds to step S502, and the signal output unit 54 outputs a closed signal to the electromagnetic switching valve 43.

[0092] In earth discharging, since the wheel loader 1 operates only the working device 2 while stopped, only the working electric motor 31 is outputting power. Therefore, it is sufficient to supply cooling water to at least the side of the working electric motor 31. Since the first cooling pump 41 that normally supplies cooling water to the working electric motor 31 remains in a normal state, it is not necessary to communicate the connection pipeline 403, and the controller 5 controls the electromagnetic switching valve 43 to the closed position to cut off the connection pipeline 403.

[0093] Also, if it is determined in step S503 that the first cooling pump 41 is not in a normal state, that is, in an abnormal state (step S503 / NO), then subsequently, the pump abnormality determination unit 51 determines whether the second cooling pump 42 is in a normal state (step S506).

[0094] If it is determined in step S506 that the second cooling pump 42 is in a normal state, that is, if it is determined that the first cooling pump 41 is in an abnormal state and the second cooling pump 42 is in a normal state (step S506 / YES), the controller 5 determines what operation the wheel loader 1 is performing in the same manner as in step S504 (step S507).

[0095] When it is determined in step S507 that the wheel loader 1 is performing a dump approach (step S507 / dump approach), the process proceeds to step S505, and the signal output unit 54 outputs an open signal to the electromagnetic switching valve 43.

[0096] Similar to the case where it is determined as a dump approach in step S504, it is necessary to supply cooling water to both the working motor 31 and the traveling motor 32. However, since the first cooling pump 41 that normally supplies cooling water to the working motor 31 is in an abnormal state, the controller 5 performs control to switch the electromagnetic switching valve 43 to the open position to communicate the connection pipeline 403, thereby supplying the cooling water from the second cooling pump 42 to the working motor 31 side as well.

[0097] When it is determined in step S507 that the wheel loader 1 is traveling (step S507 / traveling), the process proceeds to step S502, and the signal output unit 54 outputs a close signal to the electromagnetic switching valve 43.

[0098] As described above, when the wheel loader 1 is traveling, it is sufficient to supply cooling water to at least the traveling motor 32 side. Since the second cooling pump 42 that normally supplies cooling water to the traveling motor 32 remains in a normal state, there is no need to communicate the connection pipeline 403, and the controller 5 controls the electromagnetic switching valve 43 to the closed position to block the connection pipeline 403.

[0099] When it is determined in step S507 that the wheel loader 1 is discharging soil (step S507 / discharging soil), the process proceeds to step S505, and the signal output unit 54 outputs an open signal to the electromagnetic switching valve 43.

[0100] As described above, in the case of the earth mover, it is only necessary to supply cooling water to at least the side of the working motor 31. However, since the first cooling pump 41 that normally supplies cooling water to the working motor 31 is in an abnormal state, the controller 5 controls the electromagnetic switching valve 43 to switch to the open position to communicate the connection pipeline 403, so that the cooling water from the second cooling pump 42 is also supplied to the side of the working motor 31.

[0101] Also, when it is determined in step S506 that the second cooling pump 42 is not in a normal state, that is, the second cooling pump 42 is in an abnormal state (step S506 / NO), both the first cooling pump 41 and the second cooling pump 42 are in an abnormal state. In this case, the signal output unit 54 outputs an open signal to the electromagnetic switching valve 43 and outputs a limit signal to each of the working inverter 33 and the traveling inverter 34 (step S508), and the processing in the controller 5 ends.

[0102] In this way, the wheel loader 1 is provided with two cooling pumps, namely, the first cooling pump 41 that normally supplies cooling water to the working motor 31 and the second cooling pump 42 that normally supplies cooling water to the traveling motor 32. When an abnormality occurs in either one of the cooling pumps, the controller 5 controls the electromagnetic switching valve 43 to the open position to communicate the connection pipeline 403, so that the cooling water discharged from the other normal cooling pump can be circulated in the cooling circuit 4. Thereby, it is possible to avoid the occurrence of overheating in both the working motor 31 and the traveling motor 32.

[0103] Furthermore, in the present embodiment, in addition to the abnormal states of the first cooling pump 41 and the second cooling pump 42, by considering the operation content of the wheel loader 1, the electromagnetic switching valve 43 switches so that the cooling water is supplied to the side of the motor that requires the cooling water. Therefore, even when an abnormality occurs in the first cooling pump 41 and the second cooling pump 42, it is possible to efficiently circulate the cooling water in the cooling circuit 4.

[0104] <Second Embodiment> Next, the cooling circuit 4A according to the second embodiment of the present invention will be described with reference to FIGS. 7 to 9.

[0105] FIG. 7 is a schematic diagram showing a configuration example of the cooling circuit 4A according to the second embodiment of the present invention. FIG. 8 is a functional block diagram showing the functions of the controller 5A according to the second embodiment. FIG. 9 is a flowchart showing the flow of processing executed by the controller 5A according to the second embodiment. In FIGS. 7 to 9, components common to those described in the first embodiment are denoted by the same reference numerals and their description is omitted.

[0106] As shown in FIG. 7, in the cooling circuit 4A according to the present embodiment, a first electromagnetic on-off valve 410 is provided on the downstream side of the working motor 31, and a second electromagnetic on-off valve 420 is provided on the downstream side of the traveling motor 32. More specifically, the first electromagnetic on-off valve 410 is provided on the third pipeline 401A between the working motor 31 and the confluence point P, and the second electromagnetic on-off valve 420 is provided on the fourth pipeline 402A between the traveling motor 32 and the confluence point P.

[0107] The first electromagnetic on-off valve 410 is controlled by the controller 5A and switches between an open position for communicating the third pipeline 401A and a closed position for blocking the third pipeline 401A. In a state where the first electromagnetic on-off valve 410 is switched to the closed position, since the third pipeline 401A is blocked, cooling water is no longer supplied to the working inverter 33 and the working motor 31 side.

[0108] The second electromagnetic on-off valve 420 is controlled by the controller 5A and switches between an open position for communicating the fourth pipeline 402A and a closed position for blocking the fourth pipeline 402A. In a state where the second electromagnetic on-off valve 420 is switched to the closed position, since the fourth pipeline 402A is blocked, cooling water is no longer supplied to the traveling inverter 34 and the traveling motor 32 side.

[0109] When the first electromagnetic on-off valve 410 and the second electromagnetic on-off valve 420 respectively acquire the opening command signal output from the controller 5A, they switch to the open position, and when they acquire the closing command signal output from the controller 5A, they switch to the closed position.

[0110] As shown in FIG. 8, in the present embodiment, the signal output unit 54A of the controller 5A outputs a signal to the electromagnetic switching valve 43 and outputs a command signal to each of the first electromagnetic on-off valve 410 and the second electromagnetic on-off valve 420.

[0111] As shown in FIG. 9, in the controller 5A, when it is determined in step S501 that both the first cooling pump 41 and the second cooling pump 42 are in a normal state (step S501 / YES), the signal output unit 54A outputs a closing signal to the electromagnetic switching valve 43, a first opening command signal to the first electromagnetic on-off valve 410, and a second opening command signal to the second electromagnetic on-off valve 420 respectively (step S512), and the processing in the controller 5A ends.

[0112] When it is determined in step S501 that both the first cooling pump 41 and the second cooling pump 42 are not in a normal state (step S501 / NO), the process proceeds to step 503. When it is determined in step S503 that the first cooling pump 41 is in a normal state, the process proceeds to step S504. When it is determined in step S503 that the first cooling pump 41 is not in a normal state (abnormal state), the process proceeds to step S506.

[0113] When it is determined in step S504 that the wheel loader 1 is performing a dump approach (step S504 / dump approach), the signal output unit 54A outputs an opening signal to the electromagnetic switching valve 43, a first opening command signal to the first electromagnetic on-off valve 410, and a second opening command signal to the second electromagnetic on-off valve 420 respectively (step S512), and the processing in the controller 5A ends.

[0114] When it is determined in step S504 that the wheel loader 1 is traveling (step S504 / traveling), the signal output unit 54A outputs an open signal to the electromagnetic switching valve 43, a first closing command signal to the first electromagnetic on-off valve 410, and a second opening command signal to the second electromagnetic on-off valve 420, respectively (step S513), and the processing in the controller 5A ends.

[0115] When the wheel loader 1 is traveling, it is sufficient to supply cooling water only to the side of the traveling motor 32. Therefore, it is more efficient if cooling water is not supplied to the side of the working motor 31 as much as possible. Thus, the controller 5A performs control to switch the first electromagnetic on-off valve 410 to the closed position to block the third pipeline 401A, so that all the cooling water discharged from the first cooling pump 41 is supplied to the side of the traveling motor 32.

[0116] When it is determined in step S504 that the wheel loader 1 is discharging soil (step S504 / discharging soil), the signal output unit 54A outputs a closed signal to the electromagnetic switching valve 43, a first opening command signal to the first electromagnetic on-off valve 410, and a second closing command signal to the second electromagnetic on-off valve 420, respectively (step S514), and the processing in the controller 5A ends.

[0117] Also, when it is determined in step S506 that the second cooling pump 42 is in a normal state, similar to the controller 5 according to the first embodiment, the process proceeds to step S507.

[0118] When it is determined in step S507 that the wheel loader 1 is approaching the dump truck (step S507 / approaching the dump truck), the process proceeds to step S512 in the same manner as when it is determined in step 504 that the wheel loader 1 is approaching the dump truck.

[0119] If it is determined in step S507 that the wheel loader 1 is traveling (step S507 / traveling), the signal output unit 54A outputs a close signal to the electromagnetic switching valve 43, a first close command signal to the first electromagnetic on-off valve 410, and a second open command signal to the second electromagnetic on-off valve 420, respectively (step S516), and the processing in the controller 5A ends.

[0120] If it is determined in step S507 that the wheel loader 1 is discharging soil (step S507 / discharging soil), the signal output unit 54A outputs an open signal to the electromagnetic switching valve 43, a first open command signal to the first electromagnetic on-off valve 410, and a second close command signal to the second electromagnetic on-off valve 420, respectively (step S517), and the processing in the controller 5A ends.

[0121] When the wheel loader 1 is discharging soil, since it is only necessary to supply cooling water to the side of the working motor 31, it is more efficient if cooling water is not supplied to the side of the traveling motor 32 if possible. Therefore, the controller 5A performs control to switch the second electromagnetic on-off valve 420 to the closed position to block the fourth pipeline 402A, so that all the cooling water discharged from the second cooling pump 42 is supplied to the side of the working motor 31.

[0122] Also, if it is determined in step S506 that the second cooling pump 42 is not in a normal state (abnormal state) (step S506 / NO), the signal output unit 54A outputs an open signal to the electromagnetic switching valve 43, a first open command signal to the first electromagnetic on-off valve 410, and a second open command signal to the second electromagnetic on-off valve 420, respectively, and outputs a limit signal to each of the working inverter 33 and the traveling inverter 34 (step S518), and the processing in the controller 5A ends.

[0123] Thus, in this embodiment, when the electromagnetic switching valve 43 is switched to the open position and the connection pipeline 403 is in communication, the controller 5A controls the opening and closing of the first electromagnetic on-off valve 410 and the second electromagnetic on-off valve 420 according to the operation content of the wheel loader 1, so that the cooling water can be supplied to the side of the motor that requires cooling water without waste.

[0124] In this embodiment, the first electromagnetic on-off valve 410 is arranged on the downstream side of the working motor 31, but it is not limited to this. For example, it may be arranged on the downstream side of the connection point C1 with the connection pipeline 403 on the first pipeline 401. Similarly, the second electromagnetic on-off valve 420 is arranged on the downstream side of the traveling motor 32, but it is not limited to this. For example, it may be arranged on the downstream side of the connection point C2 with the connection pipeline 403 on the second pipeline 402.

[0125] The above describes each embodiment of the present invention. It should be noted that the present invention is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments are described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Also, a part of the configuration of each embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of each embodiment. Furthermore, for a part of the configuration of each embodiment, addition, deletion, or replacement with other configurations is possible.

[0126] For example, in the above embodiment, the electric drive type wheel loader 1 is taken as an example of an aspect of the work vehicle for description. However, it is not limited to this. As long as it is a work vehicle adopting a drive system with an electric motor as the drive source, it may be an electric drive type or a hybrid type.

[0127] In the above-described embodiment, the controllers 5 and 5A determine the operating state of the working device 2 based on the rotational speed and output torque of the working motor 31. However, the present invention is not limited to this. For example, the determination may be made based on the posture of the working device 2 (angle with respect to the vehicle body), the operation amount output from the operating device for operating the working device 2, or the like.

[0128] In the above-described embodiment, the controllers 5 and 5A determine the traveling state of the vehicle body based on the rotational speed and output torque of the traveling motor 32. However, the present invention is not limited to this. For example, the determination may be made based on the depression amount of the accelerator pedal or the like.

[0129] In the above-described embodiment, the pump abnormality determination unit 51 makes an abnormality determination based on the abnormality signals acquired by the data acquisition unit 50, that is, the abnormality signals output from the first cooling pump 41 and the second cooling pump 42, respectively. However, the present invention is not limited to this. For example, pressure sensors may be provided on the first pipeline 401 and the second pipeline 402, respectively, and the abnormality determination may be made based on the fluctuations in the pressure values at each cooling pump 41, 42 and each pressure sensor.

Explanation of Reference Numerals

[0130] 1: Wheel loader (working vehicle) 1A: Front frame (vehicle body) 1B: Rear frame (vehicle body) 2: Working device 5, 5A: Controllers 11, 11A: Front wheels (wheels) 11, 11B: Rear wheels (wheels) 31: Working motor 32: Traveling motor 41: First cooling pump 42: Second cooling pump 43: Electromagnetic switching valve 401: First pipeline 402: Second pipeline 403: Connection pipeline 410: First electromagnetic on-off valve 420: Second electromagnetic on-off valve C1, C2: Connection points

Claims

1. A vehicle body provided with wheels, A working device attached to the vehicle body, A working electric motor serving as a power source for driving the working device, A traveling electric motor serving as a power source for driving the wheels, In a working vehicle equipped with: A first cooling pump connected via a first pipeline to the upstream side of the working electric motor and discharging a refrigerant supplied to the working electric motor and the traveling electric motor; A second cooling pump connected via a second pipeline to the upstream side of the traveling electric motor and discharging the refrigerant supplied to the working electric motor and the traveling electric motor; An electromagnetic switching valve provided on a connecting pipeline connecting the first pipeline and the second pipeline, and switching between a communicating state in which the first pipeline and the second pipeline communicate with each other and a blocking state in which the communication between the first pipeline and the second pipeline is blocked; A controller for controlling the electromagnetic switching valve, The controller: Determines whether the first cooling pump and the second cooling pump are each in an abnormal state, According to the determination results of the abnormal states for the first cooling pump and the second cooling pump respectively, outputs an open signal for opening the electromagnetic switching valve to the communicating state or a close signal for closing the electromagnetic switching valve to the blocking state to the electromagnetic switching valve. A working vehicle characterized by the above.

2. In the working vehicle according to Claim 1, The controller: Further determines the traveling state of the vehicle body and the operating state of the working device based on the operating state of the working electric motor and the operating state of the traveling electric motor, When it is determined that only the first cooling pump is in an abnormal state, the vehicle body is traveling, and the working device is operating, outputs the open signal to the electromagnetic switching valve, When it is determined that only the first cooling pump is in an abnormal state and only the vehicle body is traveling, outputs the close signal to the electromagnetic switching valve, When it is determined that only the first cooling pump is in an abnormal state and only the working device is operating, outputs the open signal to the electromagnetic switching valve, When it is determined that only the second cooling pump is in an abnormal state, the vehicle body is traveling, and the working device is operating, outputs the open signal to the electromagnetic switching valve, When it is determined that only the second cooling pump is in an abnormal state and only the vehicle body is traveling, outputs the open signal to the electromagnetic switching valve. When it is determined that only the second cooling pump is in an abnormal state and only the work device is operating, a close signal is output to the electromagnetic switching valve. A work vehicle characterized by the above.

3. In the work vehicle according to claim 1, the controller, when it is determined that both the first cooling pump and the second cooling pump are in abnormal states, an open signal is output to the electromagnetic switching valve, and the output power of the work motor and the output power of the traveling motor are each limited. A work vehicle characterized by the above.

4. In the work vehicle according to claim 1, a first electromagnetic on-off valve provided on the downstream side of the connection point with the connection pipeline on the first pipeline or on the downstream side of the work motor, a second electromagnetic on-off valve provided on the downstream side of the connection point with the connection pipeline on the second pipeline or on the downstream side of the traveling motor, and further has, the controller, according to the determination result of the abnormal state of each of the first cooling pump and the second cooling pump, an open signal or a close signal is output to the electromagnetic switching valve, and a first open command signal for opening the first electromagnetic on-off valve or a first close command signal for closing the first electromagnetic on-off valve is output to the first electromagnetic on-off valve, and a second open command signal for opening the second electromagnetic on-off valve or a second close command signal for closing the second electromagnetic on-off valve is output to the second electromagnetic on-off valve. A work vehicle characterized by the above.

5. In the work vehicle according to claim 4, the controller, further determines the traveling state of the vehicle body and the operating state of the work device based on the operating state of the work motor and the operating state of the traveling motor, when it is determined that only the first cooling pump is in an abnormal state and the vehicle body is traveling and the work device is operating, an open signal is output to the electromagnetic switching valve, a first open command signal is output to the first electromagnetic on-off valve, and a second open command signal is output to the second electromagnetic on-off valve, respectively. when it is determined that only the first cooling pump is in an abnormal state and only the vehicle body is traveling, a close signal is output to the electromagnetic switching valve, a first close command signal is output to the first electromagnetic on-off valve, and a second open command signal is output to the second electromagnetic on-off valve, respectively. When it is determined that only the first cooling pump is in an abnormal state and only the working device is operating, the open signal is output to the electromagnetic switching valve, the first open command signal is output to the first electromagnetic on-off valve, and the second close command signal is output to the second electromagnetic on-off valve, respectively. When it is determined that only the second cooling pump is in an abnormal state, the vehicle body is running, and the working device is operating, the open signal is output to the electromagnetic switching valve, the first open command signal is output to the first electromagnetic on-off valve, and the second open command signal is output to the second electromagnetic on-off valve, respectively. When it is determined that only the second cooling pump is in an abnormal state and only the vehicle body is running, the open signal is output to the electromagnetic switching valve, the first close command signal is output to the first electromagnetic on-off valve, and the second open command signal is output to the second electromagnetic on-off valve, respectively. When it is determined that only the second cooling pump is in an abnormal state and only the working device is operating, the close signal is output to the electromagnetic switching valve, the first open command signal is output to the first electromagnetic on-off valve, and the second close command signal is output to the second electromagnetic on-off valve, respectively. A working vehicle characterized by the above.

6. In the working vehicle according to claim 4, The controller is When it is determined that both the first cooling pump and the second cooling pump are in abnormal states, the open signal is output to the electromagnetic switching valve, the first open command signal is output to the first electromagnetic on-off valve, and the second open command signal is output to the second electromagnetic on-off valve, respectively, and the output power of the working motor and the output power of the traveling motor are each limited. A working vehicle characterized by the above.

7. In the working vehicle according to claim 1, The capacity of the second cooling pump is larger than the capacity of the first cooling pump. A working vehicle characterized by the above.

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