Work machine

Abstract

To provide a work machine capable of quickly lowering the temperature inside a building immediately after an engine is stopped without impairing rear visibility from a driver's cab.SOLUTION: A work machine comprises a changeover valve that can be switched to a steering drive position in which hydraulic oil pressurized a hydraulic pump is supplied to a steering cylinder when an engine is in an engine-stopped state and an operating device is in an operated operating state, and can be switched to a fan drive position in which hydraulic oil pressurized by the hydraulic pump is supplied to a fan motor when the engine is in a stopped state and the operating device is in a non-operated state and not operated.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a work machine equipped with an aftertreatment device. [Background technology]

[0002] Background Art Conventionally, there has been known a work machine that includes an engine building that houses an engine that generates driving force to operate a vehicle body, an aftertreatment device that purifies exhaust gas from the engine, and a cooling fan that generates cooling air using the driving force of the engine, and a driver's cab located in front of the engine building.

[0003] In such a work machine, when the cooling fan stops with the engine being stopped, the heat generated by the engine and the aftertreatment device remains in the engine building. As a result, the temperature inside the engine building becomes high, and the devices arranged inside the engine building, such as the electronic components mounted on the aftertreatment device, are damaged. Therefore, Patent Document 1 discloses a work machine equipped with an electric fan inside the engine building to cool the inside of the engine building after the engine is stopped. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2022-53252 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, since there is usually a limit to the width of the vehicle body, if the number of components accommodated in the engine building increases as in Patent Document 1, the height of the engine building must be increased, which results in a problem of poor rear visibility from the driver's cab located in front of the engine building.

[0006] The present invention has been made in consideration of the above-mentioned circumstances, and an object of the present invention is to provide a work machine that can quickly reduce the temperature inside the engine building after the engine is stopped, without impairing rear visibility from the driver's cab. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention provides a work machine comprising a vehicle body supporting a building, an engine housed in the building and generating a driving force for operating the vehicle body, a cooling fan housed in the building and generating cooling air, a driver's cab supported on the vehicle body forward of the building and equipped with an operating device operated to turn the vehicle body, a steering cylinder supplied with pressure oil generated by a hydraulic source driven by the driving force of the engine and turning the vehicle body, and a fan motor for rotating the cooling fan, the work machine comprising: an electric motor supplied with power from a battery mounted on the vehicle body and generating a driving force; The hydraulic system includes a controller that drives the electric motor, a hydraulic pump that is driven by the electric motor and pumps hydraulic oil, and a switching valve that switches the supply destination of the hydraulic oil pumped by the hydraulic pump, wherein the switching valve is switched to a steering drive position that supplies the hydraulic oil pumped by the hydraulic pump to the steering cylinder when the engine is in an engine stop state in which the engine is stopped and the operating device is in an operating state in which it is operated, and is switched to a fan drive position that supplies the hydraulic oil pumped by the hydraulic pump to the fan motor when the engine is in a stopped state and the operating device is in a non-operated state in which it is not operated. Effect of the Invention

[0008] According to the present invention, it is possible to obtain a work machine that can quickly reduce the temperature inside a building immediately after the engine is stopped without impairing the rear visibility from the driver's cab. Note that problems, configurations, and effects other than those described above will become apparent from the description of the embodiments below. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a side view of a wheel loader according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a circuit diagram of a drive circuit that drives the wheel loader. [Diagram 3] FIG. 2 is a hardware configuration diagram of the wheel loader. [Figure 4] 4 is a flowchart of a vehicle stopping process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Below, a wheel loader 10, which is an example of a work machine according to the present invention, will be described with reference to the drawings. In this specification, front, rear, left and right are based on the viewpoint of an operator who is riding on and operating the wheel loader 10, unless otherwise specified. In addition, specific examples of the work machine are not limited to the wheel loader 10, and may be a dump truck, a hydraulic excavator, a crane truck, etc.

[0011] [Overall configuration of the wheel loader 10] Fig. 1 is a side view of a wheel loader 10 according to this embodiment. As shown in Fig. 1, the wheel loader 10 has a vehicle body made up of a front frame 11 and a rear frame 12. The front frame 11 and the rear frame 12 are connected by a center pin 13 so as to be rotatable in the left-right direction. The front frame 11 and the rear frame 12 are also connected by a pair of left and right steering cylinders 14L, 14R. The pair of steering cylinders 14L, 14R extend and retract when supplied with hydraulic oil from a first hydraulic pump 32 and a third hydraulic pump 34 (see Fig. 2).

[0012] By extending one of the pair of steering cylinders 14L, 14R and retracting the other, the front frame 11 bends left and right relative to the rear frame 12 about the center pin 13. This changes the relative mounting angle between the front frame 11 and the rear frame 12, causing the vehicle body to bend and change direction. In other words, this wheel loader 10 is an articulate type in which the front frame 11 and the rear frame 12 bend about the center pin 13.

[0013] The front frame 11 supports a pair of left and right front tires 15L, 15R and a front working mechanism 16. The front working mechanism 16 has a lift arm 17, a bucket 18, a pair of lift arm cylinders 19, a bucket cylinder 20, and a bell crank 21.

[0014] The lift arm 17 extends in the front-rear direction. More specifically, the front end of the lift arm 17 is rotatably connected to a bucket 18, and the rear end of the lift arm 17 is rotatably connected to the front frame 11. The lift arm 17 rotates in the up-down direction (moves up and down) by the extension and contraction of a pair of lift arm cylinders 19.

[0015] The bucket 18 has a concave space capable of accommodating cargo (such as soil and sand). The bucket 18 is supported rotatably (tiltably or dumpably) at the front end of the lift arm 17. More specifically, the bucket 18 rotates in the vertical direction as a bell crank 21 rotates in conjunction with the extension and contraction of a bucket cylinder 20.

[0016] The rear frame 12 supports a pair of left and right rear tires 22L, 22R, a cab 23, an engine building 24 (building), and a counterweight 30.

[0017] The cab 23 defines an internal space for an operator to operate the wheel loader 10. Inside the cab 23, there is a seat (not shown) on which the operator sits, and an operation device (not shown) operated by the operator seated on the seat. When an operator in the cab 23 operates the operation device, the wheel loader 10 travels or turns, and the front work implement 16 operates. The operation device includes at least a key switch 23a (see Figure 3) that starts or stops the engine 25, and a steering wheel 23b (see Figures 2 and 3) that is operated to turn the front frame 11 (vehicle body).

[0018] The key switch 23a outputs an ON signal to a controller 50 (see FIG. 3), which will be described later, when operated by an operator to start the engine 25. The key switch 23a also outputs an OFF signal to the controller 50 when operated by an operator to stop the engine 25. The steering wheel 23b outputs a rotation signal indicating the direction and amount of rotation of the steering wheel 23b to the controller 50 when operated by an operator to rotate the steering wheel 23b clockwise or counterclockwise.

[0019] The cab 23 is supported by the rear frame 12 forward of the engine building 24. The cab 23 also includes a front window 23c provided on the front side, side windows 23d, 23e provided on the left and right sides (the right side window 23e is not shown in FIG. 1), and a rear window 23f provided on the rear side. The cab 23 (more specifically, at least a part of the rear window 23f) protrudes upward from the upper surface of the engine building 24. An operator in the cab 23 operates the operating devices while viewing the outside through the windows (23c to 23f) on each side.

[0020] 1 is a so-called "cab" type in which the seat and the operating devices are surrounded by walls and glass. However, the specific example of the operator's cab 23 is not limited to this, and may be a so-called "canopy" type in which the seat and the operating devices are partially uncovered.

[0021] The engine building 24 is supported by the rear frame 12 behind the operator's cab 23 and forward of the rearmost end of the counterweight 30. The engine building 24 has an internal space that houses components for driving the wheel loader 10 (for example, an engine 25, a radiator 26, a cooling fan 27, and an aftertreatment device 29).

[0022] A first vent 24a and a second vent 24b are formed in an outer wall (e.g., an exterior cover) that defines the internal space of the engine building 24. The first vent 24a and the second vent 24b penetrate the outer wall of the engine building 24 in the thickness direction to communicate the inside and outside of the engine building 24. In this embodiment, the first vent 24a is formed in the back surface (one example of a side surface) of the engine building 24, and the second vent 24b is formed in the front upper surface of the engine building 24. That is, the second vent 24b is formed forward and above the first vent 24a.

[0023] The engine 25 is housed in the engine building 24 forward of the radiator 26 and the cooling fan 27 and below the aftertreatment device 29. The radiator 26 is housed in the engine building 24 rearward of the engine 25 and the aftertreatment device 29 and forward of the cooling fan 27. The cooling fan 27 is housed in the engine building 24 rearward of the engine 25, the radiator 26, and the aftertreatment device 29. The aftertreatment device 29 is housed in the engine building 24 above the engine 25 and forward of the radiator 26 and the cooling fan 27.

[0024] The engine 25 generates driving force for operating the wheel loader 10. The driving force of the engine 25 is transmitted to rotate the front tires 15L, 15R and the rear tires 22L, 22R. This causes the wheel loader 10 to travel. Furthermore, the engine 25 generates heat and exhaust gas when generating driving force. As a result, when the engine 25 is driven, the temperature in the internal space of the engine building 24 rises.

[0025] The radiator 26 supplies cooling water to the engine 25, exchanges heat between the cooling water discharged from the engine 25 and cooling air, and returns the heat-exchanged cooling water to the engine 25. The cooling fan 27 supplies cooling air to the radiator 26. More specifically, the cooling fan 27 is configured to be capable of rotating forward and backward by the driving force of a fan motor 28 (see FIG. 2).

[0026] 1, the cooling fan 27 rotating in the forward direction generates cooling air that is drawn into the internal space of the engine building 24 through the first vent 24a, passes through the internal space of the engine building 24 toward the front, and is discharged upward from the internal space of the engine building 24 through the second vent 24b. The cooling fan 27 rotating in the reverse direction generates cooling air that is drawn into the internal space of the engine building 24 through the second vent 24b, passes through the internal space of the engine building 24 toward the rear, and is discharged backward (horizontally) from the internal space of the engine building 24 through the first vent 24a.

[0027] The aftertreatment device 29 purifies the exhaust gas discharged from the engine 25. The aftertreatment device 29 includes, for example, an EGR (Exhaust Gas Recirculation) device that recirculates a portion of the exhaust gas to the intake side, a DPF (Diesel particulate filter) that collects particulate matter in the exhaust gas, and a NOx catalyst that decomposes nitrogen oxides (NOx) into water and nitrogen.

[0028] The post-processing device 29 includes electronic components 29a. The electronic components 29a are mounted on, for example, a board attached to the post-processing device 29. The electronic components 29a include, for example, a sensor that detects the state of the post-processing device 29, and a controller that controls the operation of the post-processing device 29. The electronic components 29a are mounted on the post-processing device 29 on the flow path of the cooling air indicated by the dashed arrow (i.e., the cooling air generated by the cooling fan 27).

[0029] The electronic component 29a includes, for example, a temperature sensor that detects the temperature of the atmosphere in the engine building 24 (hereinafter referred to as "building temperature") and outputs a temperature signal indicating the detected building temperature to the controller 50. However, the temperature sensor may be installed in the engine building 24 separately from the electronic component 29a of the aftertreatment device 29.

[0030] [Drive circuit configuration] Figure 2 is a circuit diagram of a drive circuit that drives the wheel loader 10. The wheel loader 10 is equipped with the drive circuit shown in Figure 2. The drive circuit is a circuit for driving the hydraulic actuators (steering cylinders 14L, 14R, lift arm cylinder 19, bucket cylinder 20, and fan motor 28).

[0031] The drive circuit includes, as its main components, a hydraulic oil tank 31, a first hydraulic pump 32 (hydraulic source), a second hydraulic pump 33 (hydraulic source), a third hydraulic pump 34, an electric motor 35, a directional change valve 36, a steering valve 37, a fan valve 38, a priority valve 39 (changeover valve), check valves 40, 41, 42, 43, a pressure switch 44, and a pressure sensor 45.

[0032] The drive circuit mainly includes a first steering supply flow path L1, a second steering supply flow path L2 (supply flow path), a first fan supply flow path L3, a second fan supply flow path L4, a first pilot flow path L5, and a second pilot flow path L6. The flow paths (L1 to L6) are flow paths through which the hydraulic oil flows. The flow paths (L1 to L6) are configured, for example, by metal or resin piping, flexible hoses, or a combination of these.

[0033] The first steering supply flow path L1 is a flow path of hydraulic oil from the first hydraulic pump 32 to the steering valve 37 via the directional control valve 36 and the check valve 40. In other words, the first steering supply flow path L1 is a flow path that supplies hydraulic oil pumped from the first hydraulic pump 32 to the steering valve 37. The second steering supply flow path L2 is a flow path of hydraulic oil from the third hydraulic pump 34 to the steering valve 37 via the priority valve 39 and the check valve 41. In other words, the second steering supply flow path L2 is a flow path that supplies hydraulic oil pumped from the third hydraulic pump 34 to the steering valve 37. In addition, the first steering supply flow path L1 and the second steering supply flow path L2 join together downstream of the check valves 40 and 41 in the flow of hydraulic oil and reach the steering valve 37.

[0034] The first fan supply flow path L3 is a flow path for hydraulic oil that runs from the second hydraulic pump 33 to the fan valve 38 via the check valve 42. In other words, the first fan supply flow path L3 is a flow path that supplies the hydraulic oil pumped from the second hydraulic pump 33 to the fan valve 38. The second fan supply flow path L4 is a flow path for hydraulic oil that runs from the third hydraulic pump 34 to the fan valve 38 via the priority valve 39 and the check valve 43. In other words, the second fan supply flow path L4 is a flow path that supplies the hydraulic oil pumped from the third hydraulic pump 34 to the fan valve 38. In addition, the first fan supply flow path L3 and the second fan supply flow path L4 join together downstream of the check valves 42, 43 in the flow of hydraulic oil and lead to the fan valve 38.

[0035] The first pilot flow path L5 is a flow path for pilot pressure oil from the steering valve 37 to the first pilot port 39a of the priority valve 39. When the steering spool 37a described later is in the right turning position D or the left turning position E, the steering valve 37 communicates the second steering supply flow path L2 and the first pilot flow path L5. At this time, the hydraulic oil supplied from the second steering supply flow path L2 to the steering valve 37 is supplied to the first pilot port 39a as pilot pressure oil. On the other hand, when the steering spool 37a is in the neutral position C, the steering valve 37 blocks communication between the second steering supply flow path L2 and the first pilot flow path L5. At this time, the pilot pressure oil is not supplied to the first pilot port 39a.

[0036] The second pilot flow path L6 is a flow path for pilot pressure oil that branches off from the second steering supply flow path L2 downstream of the priority valve 39 and upstream of the check valve 41, and reaches the second pilot port 39b of the priority valve 39. When the steering spool 37a is in the neutral position C, the steering valve 37 closes the second steering supply flow path L2. As a result, the hydraulic oil supplied from the third hydraulic pump 34 to the second steering supply flow path L2 is supplied to the second pilot port 39b as pilot pressure oil. On the other hand, when the steering spool 37a is in the right turn position D or the left turn position E, the steering valve 37 communicates the second steering supply flow path L2 with the steering cylinders 14L, 14R and the first pilot flow path L5. At this time, the pilot pressure oil is not supplied to the second pilot port 39b.

[0037] The hydraulic oil tank 31 stores hydraulic oil to be supplied to the hydraulic actuators (14L, 14R, 19, 20, 28). The first hydraulic pump 32 is rotated by the driving force of the engine 25, and pressure-feeds the hydraulic oil stored in the hydraulic oil tank 31 to the first steering supply flow path L1. The second hydraulic pump 33 is rotated by the driving force of the engine 25, and pressure-feeds the hydraulic oil stored in the hydraulic oil tank 31 to the first fan supply flow path L3. The third hydraulic pump 34 is rotated by the driving force of the electric motor 35, and pressure-feeds the hydraulic oil stored in the hydraulic oil tank 31 to the second steering supply flow path L2 and the second fan supply flow path L4. The electric motor 35 is supplied with electricity stored in a battery 46 (see FIG. 3), and generates a driving force to rotate the third hydraulic pump 34.

[0038] The directional control valve 36 is disposed in the first steering supply flow passage L1, upstream of the check valve 40 in the flow of hydraulic oil. The directional control valve 36 is configured to be switchable between a steering position A where hydraulic oil pumped from the first hydraulic pump 32 is supplied to the steering cylinders 14L, 14R via the check valve 40 and the steering valve 37, and a lift arm position B where hydraulic oil is supplied to the lift arm cylinder 19 (not shown in FIG. 2). The directional control valve 36 is, for example, a priority valve that is switched to the steering position A when the steering spool 37a is in the right turning position D or the left turning position E, and is switched to the lift arm position B when the steering spool 37a is in the neutral position C.

[0039] The steering valve 37 is disposed in the joined first steering supply passage L1 and second steering supply passage L2. The steering valve 37 supplies hydraulic oil pumped from the first hydraulic pump 32 and the third hydraulic pump 34 to the steering cylinders 14L and 14R. The steering valve 37 has a steering spool 37a that moves to a neutral position C, a right turning position D, and a left turning position E in accordance with the operation of the steering wheel 23b by the operator. That is, the steering valve 37 is configured to be switchable between the neutral position C, the right turning position D, and the left turning position E. Note that the configuration of the steering valve 37 is well known, and therefore a detailed description thereof will be omitted.

[0040] The neutral position C is a position that blocks the first steering supply flow path L1 and the second steering supply flow path L2. As a result, the hydraulic oil pressure-fed from the first hydraulic pump 32 and the third hydraulic pump 34 is not supplied to the steering cylinders 14L, 14R. In addition, the neutral position C is a position that blocks communication between the second steering supply flow path L2 and the first pilot flow path L5. As a result, the hydraulic oil pressure-fed from the third hydraulic pump 34 is not supplied to the first pilot port 39a as pilot pressure oil. The steering spool 37a is located in the neutral position C when the steering wheel 23b is not operated.

[0041] The right turn position D communicates the first steering supply flow path L1 and the second steering supply flow path L2 with the bottom chamber of the steering cylinder 14L and the rod chamber of the steering cylinder 14R. As a result, the hydraulic oil pumped from the first hydraulic pump 32 and the third hydraulic pump 34 is supplied to the bottom chamber of the steering cylinder 14L and the rod chamber of the steering cylinder 14R. As a result, the steering cylinder 14L extends and the steering cylinder 14R retracts, causing the wheel loader 10 to turn right. The right turn position D is also a position that communicates the second steering supply flow path L2 and the first pilot flow path L5. As a result, the hydraulic oil pumped from the third hydraulic pump 34 is supplied to the first pilot port 39a as pilot pressure oil. The steering spool 37a is located at the right turn position D when the steering wheel 23b is rotated clockwise.

[0042] The left turning position E communicates the first steering supply flow path L1 and the second steering supply flow path L2 with the rod chamber of the steering cylinder 14L and the bottom chamber of the steering cylinder 14R. As a result, the hydraulic oil pumped from the first hydraulic pump 32 and the third hydraulic pump 34 is supplied to the rod chamber of the steering cylinder 14L and the bottom chamber of the steering cylinder 14R. As a result, the steering cylinder 14L contracts and the steering cylinder 14R expands, and the wheel loader 10 turns left. The left turning position E is also a position that communicates the second steering supply flow path L2 and the first pilot flow path L5. As a result, the hydraulic oil pumped from the third hydraulic pump 34 is supplied to the first pilot port 39a as pilot pressure oil. The steering spool 37a is located at the left turning position E when the steering wheel 23b is rotated counterclockwise.

[0043] Furthermore, the hydraulic pressure of the pilot pressure oil supplied from the steering valve 37 to the first pilot port 39a (i.e., pilot pressure) varies according to the operation amount (rotation amount) of the steering wheel 23b. More specifically, the pilot pressure decreases as the rotation amount of the steering wheel 23b decreases, and increases as the rotation amount of the steering wheel 23b increases.

[0044] The fan valve 38 is disposed in the first fan supply flow path L3 and the second fan supply flow path L4 where the flow paths are joined together. The fan valve 38 supplies the hydraulic oil pumped from the second hydraulic pump 33 and the third hydraulic pump 34 to the fan motor 28. The fan valve 38 has a fan spool 38a that moves to a forward rotation position F and a reverse rotation position G under the control of the controller 50. That is, the fan valve 38 is configured to be switchable between the forward rotation position F and the reverse rotation position G. The forward rotation position F is a position where the hydraulic oil pumped from the second hydraulic pump 33 and the third hydraulic pump 34 is supplied to the fan motor 28 in a direction that rotates the cooling fan 27 forward. The reverse position G is a position where the hydraulic oil pumped from the second hydraulic pump 33 and the third hydraulic pump 34 is supplied to the fan motor 28 in a direction that rotates the cooling fan 27 reversely. The configuration of the fan valve 38 is already known, so a detailed description thereof will be omitted.

[0045] The priority valve 39 is disposed in the second steering supply passage L2 and the second fan supply passage L4. The priority valve 39 switches the supply destination of the hydraulic oil pumped by the third hydraulic pump 34. More specifically, the priority valve 39 switches whether the hydraulic oil pumped from the third hydraulic pump 34 is supplied to the steering valve 37 through the second steering supply passage L2 or to the fan valve 38 through the second fan supply passage L4. The priority valve 39 is configured to be switchable between a steering drive position H and a fan drive position I. The priority valve 39 also includes a first pilot port 39a and a second pilot port 39b.

[0046] The steering drive position H is a position where the hydraulic oil pumped by the third hydraulic pump 34 is supplied to the steering cylinders 14L, 14R through the steering valve 37. The priority valve 39 is switched to the steering drive position H when pilot pressure oil is supplied to the first pilot port 39a through the first pilot flow path L5 (i.e., the steering wheel 23b is operated). The fan drive position I is a position where the hydraulic oil pumped by the third hydraulic pump 34 is supplied to the fan motor 28 through the fan valve 38. The priority valve 39 is switched to the fan drive position I when pilot pressure oil is supplied to the second pilot port 39b through the second pilot flow path L6 (i.e., the steering wheel 23b is not operated). The initial position of the priority valve 39 (i.e., the position when pilot pressure is not applied to the second pilot port 39b) is the steering drive position H.

[0047] Also, the priority valve 39 is a proportional valve that changes the distribution ratio of the hydraulic oil to the second steering supply flow path L2 (i.e., the steering cylinders 14L, 14R) and the second fan supply flow path L4 (i.e., the fan motor 28) according to the pilot pressure applied to the first pilot port 39a. That is, the priority valve 39 increases the flow rate of the hydraulic oil supplied to the steering cylinders 14L, 14R as the pilot pressure applied to the first pilot port 39a increases (i.e., the amount of rotation of the steering wheel 23b increases). In other words, the priority valve 39 supplies the amount of hydraulic oil corresponding to the amount of rotation of the steering wheel 23b to the steering cylinders 14L, 14R, and supplies the surplus hydraulic oil to the fan motor 28. On the other hand, when the pilot pressure is applied to the second pilot port 39b, the priority valve 39 supplies all of the hydraulic oil pumped from the third hydraulic pump 34 to the fan motor 28, and does not supply it to the steering cylinders 14L, 14R.

[0048] The check valve 40 is disposed in the first steering supply flow path L1 upstream of the joining position of the first steering supply flow path L1 and the second steering supply flow path L2. The check valve 40 allows the flow of hydraulic oil from the first hydraulic pump 32 toward the steering valve 37 through the directional control valve 36 and blocks the flow of hydraulic oil in the opposite direction. This prevents the hydraulic oil supplied from the third hydraulic pump 34 through the priority valve 39 and the check valve 41 from flowing back to the directional control valve 36.

[0049] The check valve 41 is disposed in the second steering supply passage L2 upstream of the joining position of the first steering supply passage L1 and the second steering supply passage L2. The check valve 41 allows the flow of hydraulic oil from the third hydraulic pump 34 toward the steering valve 37 through the priority valve 39, and blocks the flow of hydraulic oil in the opposite direction. This prevents the hydraulic oil supplied from the first hydraulic pump 32 through the directional control valve 36 and the check valve 40 from flowing back to the priority valve 39.

[0050] The check valve 42 is disposed in the first fan supply flow path L3, upstream of the joining position of the first fan supply flow path L3 and the second fan supply flow path L4. The check valve 42 allows the flow of hydraulic oil from the second hydraulic pump 33 toward the fan valve 38, and blocks the flow of hydraulic oil in the opposite direction. This prevents the hydraulic oil supplied from the third hydraulic pump 34 through the priority valve 39 and the check valve 43 from flowing back to the second hydraulic pump 33.

[0051] The check valve 43 is disposed in the second fan supply flow path L4 upstream of the joining position of the first fan supply flow path L3 and the second fan supply flow path L4. The check valve 43 allows the flow of hydraulic oil from the third hydraulic pump 34 toward the fan valve 38 through the priority valve 39, and blocks the flow of hydraulic oil in the opposite direction. This prevents the hydraulic oil supplied from the second hydraulic pump 33 through the check valve 42 from flowing back into the priority valve 39.

[0052] The pressure switch 44 is disposed in the first steering supply flow path L1 downstream of the directional control valve 36 and upstream of the check valve 40 in the flow of hydraulic oil. The pressure switch 44 outputs a detection signal to the controller 50 in response to the pressure in the first steering supply flow path L1 becoming less than a threshold value. The pressure sensor 45 is disposed in the second steering supply flow path L2 downstream of the priority valve 39 and upstream of the check valve 41 in the flow of hydraulic oil. The pressure sensor 45 detects the pressure value of the hydraulic oil flowing in the second steering supply flow path L2 and outputs a pressure signal indicating the detected pressure value to the controller 50.

[0053] [Controller 50 Configuration] FIG. 3 is a hardware configuration diagram of the wheel loader 10. The wheel loader 10 is equipped with a controller 50. The controller 50 is equipped with a CPU (Central Processing Unit) 51 and a memory 52. ​​The memory 52 is configured, for example, with a ROM (Read Only Memory), a RAM (Random Access Memory), a HDD (Hard Disk Drive), or a combination of these. The controller 50 realizes the processing described below by the CPU 51 reading and executing program code stored in the ROM or HDD. The RAM is used as a work area when the CPU 51 executes the program.

[0054] However, the specific configuration of the controller 50 is not limited to this, and may be realized by hardware such as an application specific integrated circuit (ASIC) or a field programmable gate array (FPGA).

[0055] The controller 50 controls the overall operation of the wheel loader 10. The controller 50 controls the operation of the engine 25, the electric motor 35, and the fan valve 38 based on various signals output from the key switch 23a, the steering wheel 23b, the electronic components 29a, the pressure switch 44, and the pressure sensor 45, and on the power stored in the battery 46.

[0056] First, when an ON signal is output from the key switch 23a, the controller 50 starts the engine 25. This causes the first hydraulic pump 32 and the second hydraulic pump 33 to rotate. The controller 50 also maintains the electric motor 35 in a stopped state. This causes the third hydraulic pump 34 to remain stopped. Furthermore, the controller 50 switches the fan valve 38 to the normal rotation position F. This causes the cooling fan 27 to rotate in the normal direction, generating cooling air in the engine building 24 from the first vent 24a to the second vent 24b.

[0057] When the steering wheel 23b is operated in this state, the position of the steering valve 37 is switched according to the direction of operation of the steering wheel 23b. As a result, hydraulic oil pumped from the first hydraulic pump 32 is supplied to the steering cylinders 14L, 14R, and the wheel loader 10 changes direction. Next, when an OFF signal is output from the key switch 23a, the controller 50 executes the vehicle stopping process shown in Fig. 4. Fig. 4 is a flowchart of the vehicle stopping process.

[0058] First, when an OFF signal is output from the key switch 23a, the controller 50 stops the engine 25 and drives the electric motor 35 using the power stored in the battery 46 (S11). As a result, the first hydraulic pump 32 and the second hydraulic pump 33 stop, and the third hydraulic pump 34 rotates. That is, the controller 50 drives the electric motor 35 when the engine 25 is stopped. The controller 50 also starts a timer that measures a predetermined time (for example, 60 seconds) after the engine 25 is stopped.

[0059] Here, if the steering wheel 23b has not been operated after the engine 25 has stopped, that is, if the engine is stopped and the operating device is not operated (S12: No), the steering valve 37 in the neutral position C closes the second steering supply flow path L2. As a result, the hydraulic oil supplied from the third hydraulic pump 34 to the second steering supply flow path L2 is supplied as pilot pressure oil to the second pilot port 39b through the second pilot flow path L6 branched off from the second steering supply flow path L2. As a result, the priority valve 39 is switched to the fan drive position I.

[0060] As a result, when the steering wheel 23b is not being operated, all of the hydraulic oil pumped from the third hydraulic pump 34 is supplied to the fan motor 28 through the priority valve 39 in the fan drive position I, the check valve 43, and the fan valve 38 in the normal rotation position F (S13). As a result, even after the engine 25 is stopped, the cooling fan 27 rotates in the normal direction, generating cooling air that flows from the first vent port 24a to the second vent port 24b inside the engine building 24.

[0061] On the other hand, when the steering wheel 23b is operated after the engine 25 is stopped, that is, when the engine is stopped and the operating device is in an operating state (S12: Yes), the steering spool 37a moves from the neutral position C to the right turn position D or the left turn position E according to the amount of operation of the steering wheel 23b, and opens the second steering supply flow path L2. In addition, by the steering valve 37 opening the second steering supply flow path L2, the pilot pressure oil that has been supplied to the second pilot port 39b flows back to the hydraulic oil tank 31 (i.e., the pilot pressure applied to the second pilot port 39b decreases). As a result, the priority valve 39 moves to the steering drive position H side, which is the initial position.

[0062] As a result, a portion of the hydraulic oil pumped by the third hydraulic pump 34 is supplied as pilot pressure oil from the steering valve 37 through the first pilot flow path L5 to the first pilot port 39a. As a result, the priority valve 39 distributes the hydraulic oil pumped by the third hydraulic pump 34 to the second steering supply flow path L2 and the second fan supply flow path L4 at a distribution ratio corresponding to the rotation amount of the steering wheel 23b.

[0063] As a result, when the steering wheel 23b is operated, some of the hydraulic oil pumped from the third hydraulic pump 34 is supplied to the steering cylinders 14L, 14R through the steering valve 37 (S14). As a result, the wheel loader 10 can be turned even after the engine 25 has stopped (a so-called emergency steering function is realized).

[0064] Furthermore, when the steering wheel 23b is in an operating state, another portion of the hydraulic oil pumped from the third hydraulic pump 34 (surplus hydraulic oil not supplied to the steering cylinders 14L, 14R) is supplied to the fan motor 28 through the fan valve 38 in the normal rotation position F (S15). As a result, even after the engine 25 is stopped, the cooling fan 27 rotates in the normal direction, generating cooling air in the engine building 24 from the first vent port 24a to the second vent port 24b.

[0065] Next, the controller 50 determines whether the building temperature detected by the electronic component 29a is equal to or higher than a threshold value (S16). The threshold value is set to a temperature (e.g., 60°C) that can suppress the discomfort felt by surrounding workers when the cooling air discharged to the outside of the vehicle hits the surrounding workers. If the controller 50 determines that the building temperature is lower than the threshold value (S16: Yes), the controller 50 switches the fan valve 38 to the reverse rotation position G (S17). On the other hand, if the controller 50 determines that the building temperature is equal to or higher than the threshold value (S16: No), the controller 50 skips the process of step S17 and maintains the fan valve 38 in the forward rotation position F.

[0066] Next, the controller 50 determines whether or not a predetermined time has elapsed (i.e., the timer has timed out) since the engine 25 was stopped (in other words, the electric motor 35 was started to be driven) (S18). If the controller 50 determines that the predetermined time has not elapsed since the engine 25 was stopped (S18: No), it executes the processes from step S12 onwards again. That is, the controller 50 repeatedly executes the processes from step S12 to S17 until the predetermined time has elapsed since the engine 25 was stopped (S18: No).

[0067] That is, during the first half of the period from when the engine 25 is stopped until a predetermined time has elapsed when the building temperature is equal to or above the threshold, the cooling fan 27 rotates in the forward direction to cool the inside of the engine building 24. Also, during the second half of the period when the building temperature is below the threshold, the cooling fan 27 rotates in the reverse direction to remove dust that has accumulated on the surface of the radiator 26. Furthermore, when the steering wheel 23b is operated, some of the hydraulic oil pumped from the third hydraulic pump 34 is supplied to the steering cylinders 14L, 14R to turn the wheel loader 10 (that is, the emergency steering function takes priority).

[0068] On the other hand, when the controller 50 determines that the predetermined time has elapsed since the engine 25 was stopped (S18: Yes), it stops the electric motor 35 (S19) and ends the vehicle stopping process. This stops the third hydraulic pump 34 and the cooling fan 27, and disables the emergency steering function.

[0069] According to this embodiment, for example, the following advantageous effects are obtained.

[0070] According to the above embodiment, by using the third hydraulic pump 34 to realize the emergency steering function and continuing to rotate the cooling fan 27 in the forward direction after the engine 25 is stopped, the temperature inside the engine building 24 can be quickly reduced immediately after the engine 25 is stopped.

[0071] In the above embodiment, the third hydraulic pump 34 and the electric motor 35 are components that have been conventionally installed to realize an emergency steering function, so the only major component that is newly required to realize the process of Fig. 4 is the priority valve 39. As a result, there is no need to increase the height of the engine building 24 to ensure the installation space for the additional components, so that it is possible to prevent the rear visibility from the operator's cab 23 from being deteriorated. Note that the specific configuration of the switching valve is not limited to the priority valve 39, and it may be a solenoid valve (electromagnetic proportional valve) that switches the supply direction of the hydraulic oil under the control of the controller 50.

[0072] According to the above embodiment, the electronic component 29a is disposed in the flow path of the cooling air from the first ventilation port 24a to the second ventilation port 24b, so that the temperature of the electronic component 29a can be prevented from increasing after the engine 25 is stopped. As a result, damage to the electronic component 29a can be prevented. However, the specific arrangement of the electronic component 29a is not limited to the example in FIG. 1 and may be any arrangement within the engine building 24.

[0073] Furthermore, according to the above embodiment, when the building temperature is equal to or higher than the threshold value, cooling air is discharged from the second vent 24b above the vehicle body (i.e., the cooling fan 27 rotates in the forward direction), and after the building temperature drops below the threshold value, cooling air is discharged from the first vent 24a on the side of the vehicle body (i.e., the cooling fan 27 rotates in the reverse direction). This makes it possible to remove dust that has accumulated on the surface of the radiator 26, thereby reducing the frequency of maintenance of the radiator 26. Furthermore, even if the cooling air discharged from the first vent 24a hits an operator around the wheel loader 10, discomfort can be reduced. However, the processing of steps S16 to S17 is not essential, and the cooling fan 27 may always rotate in the forward direction during the vehicle stop processing.

[0074] The above-described embodiments are illustrative examples of the present invention, and are not intended to limit the scope of the present invention to these embodiments. Those skilled in the art can implement the present invention in various other forms without departing from the gist of the present invention. [Explanation of symbols]

[0075] 10: Wheel loader 11: Previous frame 12: Rear frame 13: Center pin 14L, 14R: Steering cylinder 15L, 15R: Front tires 16: Front work machine 17: Lift arm 18: Bucket 19: Lift arm cylinder 20: Bucket cylinder 21: Bell crank 22L, 22R: Rear tires 23: Driver's cab 23a: Key switch 23b: Steering wheel 23c: Front window 23d: Side window 23e: Side window 23f: Rear window 24: Engine building 24a: First ventilation hole 24b: Second vent 25: Engine 26: Radiator 27: Cooling fan 28: Fan motor 29: Post-processing device 29a: Electronic components 30: Counterweight 31: Hydraulic oil tank 32: First hydraulic pump 33: Second hydraulic pump 34: 3rd hydraulic pump 35: Electric motor 36: Directional valve 37: Steering valve 37a: Steering spool 38: Fan valve 38a: Fun spool 39: Priority valve (switching valve) 39a: First pilot port 39b: 2nd pilot port 40-43: Check valve 44: Pressure switch 45: Pressure sensor 46: Battery 50: Controller 51: CPU 52: Memory

Claims

1. A vehicle body supporting the building; an engine housed in the building and configured to generate driving force for operating the vehicle body; A cooling fan that is housed in the building and generates cooling air; a cab supported on the vehicle body forward of the building and equipped with an operating device that is operated to turn the vehicle body; A working machine including a steering cylinder which is supplied with pressure oil generated by a hydraulic source driven by a driving force of the engine and which turns the vehicle body, and a fan motor which rotates the cooling fan, an electric motor that generates a driving force by receiving power from a battery mounted on the vehicle body; a controller that drives the electric motor when the engine is stopped; a hydraulic pump driven by the electric motor to pump hydraulic oil; A switching valve for switching a supply destination of the hydraulic oil pumped by the hydraulic pump, The switching valve is When the engine is stopped and the operating device is operated, the hydraulic pump is switched to a steering drive position for supplying hydraulic oil pressure-fed by the hydraulic pump to the steering cylinder. a fan drive position for supplying hydraulic oil pumped by the hydraulic pump to the fan motor when the engine is stopped and the operating device is in a non-operated state and not operated.

2. 2. The work machine according to claim 1, The controller: When the engine is stopped, the electric motor is driven. A working machine comprising: a driving mechanism for driving the electric motor, the driving mechanism for driving the electric motor being stopped after a predetermined time has elapsed since the start of driving the electric motor.

3. 2. The work machine according to claim 1, an electronic component that is housed in the building and is mounted on an aftertreatment device that purifies exhaust gas from the engine; A first ventilation opening and a second ventilation opening are formed in the building, The cooling fan generates cooling air that is sucked into the building through one of the first air vent and the second air vent and exhausted from the building through the other of the first air vent and the second air vent; The work machine, wherein the electronic component is disposed in a flow path of cooling air between the first ventilation port and the second ventilation port.

4. 2. The work machine according to claim 1, The building is formed with a first vent provided on a side surface of the building and a second vent provided on a top surface of the building, a fan valve that is switchable between a forward rotation position in which hydraulic oil pumped from the hydraulic pump is supplied to the fan motor in a direction that rotates the cooling fan so as to generate cooling air from the first vent port toward the second vent port, and a reverse rotation position in which hydraulic oil is supplied to the fan motor in a direction that rotates the cooling fan so as to generate cooling air from the second vent port toward the first vent port; A temperature sensor that detects a temperature inside the building, The controller: When the temperature detected by the temperature sensor is equal to or higher than a threshold value, the fan valve is in the forward rotation position; A work machine comprising: a fan valve that is in the reverse position when the temperature detected by the temperature sensor is lower than the threshold value.

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