Work machine

Abstract

To provide a technology for improving heating efficiency of a cab in an electric work machine.SOLUTION: A work machine includes a cab mounted on a vehicle body, a storage battery, an electric motor driven by power from the storage battery, a first hydraulic pump driven by power from the electric motor, a hydraulic actuator driven by hydraulic oil supplied from the first hydraulic pump, and an oil thermal heating device that heats the interior of the cab. The work machine further includes a hydraulic oil heater that heats the hydraulic oil supplied to and discharged from the hydraulic actuator. The oil thermal heating device heats the interior of the cab by heat exchange between the hydraulic oil heated by the hydraulic oil heater and air supplied to the cab.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an electric work machine. [Background technology]

[0002] In recent years, electric work machines that use an electric motor driven by electricity stored in a battery as a drive source instead of an engine have become popular. Some of these electric work machines use exhaust heat from hydraulic oil or a heater instead of engine heat as a heat source for heating the cab (see, for example, Patent Document 1).

[0003] In addition, when the temperature is low due to cold regions, etc., a warm-up operation is performed on work machines before work begins to warm the hydraulic oil until it reaches a viscosity that allows the hydraulic actuator to operate properly. During this warm-up operation, the hydraulic oil is warmed by circulating it within the drive circuit. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-96243 Summary of the Invention [Problem to be solved by the invention]

[0005] In the oil-fired heating system using hydraulic oil of Patent Document 1, it is difficult to heat the cab until the hydraulic oil is warmed up. Also, in the oil-fired heating system using hydraulic oil of Patent Document 1, when warming up and heating the cab are performed simultaneously, the hydraulic oil is heated by circulation in the drive circuit while being cooled by the oil-fired heating system, which makes it difficult to raise the temperature of the hydraulic oil, and there is a problem that it takes time to warm up and heat the cab.

[0006] The present invention has been made in consideration of the above-described circumstances, and its object is to provide a technique for quickly warming up an electric work machine and heating the interior of the cab. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention provides a work machine comprising a cab provided on a vehicle body, a storage battery, an electric motor driven by power from the storage battery, a first hydraulic pump driven by power from the electric motor, a hydraulic actuator driven by hydraulic oil supplied from the first hydraulic pump, and an oil-fired heating device that heats the interior of the cab, further comprising a hydraulic oil heater that heats the hydraulic oil supplied to and discharged from the hydraulic actuator, and the oil-fired heating device heats the interior of the cab by heat exchange between the hydraulic oil heated by the hydraulic oil heater and air supplied to the cab. [Effects of the Invention]

[0008] According to the present invention, it is possible to quickly warm up an electric work machine and heat the cab. Note that problems, configurations, and effects other than those described above will become apparent from the following description of the embodiment. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a side view of a wheel loader. [Figure 2] FIG. 2 is a circuit diagram of a drive circuit according to the first embodiment. [Figure 3] FIG. 2 is a hardware configuration diagram of the wheel loader. [Figure 4] 4 is a flowchart of a heating control process according to the first embodiment. [Figure 5] FIG. 10 is a circuit diagram of a drive circuit according to a second embodiment. [Figure 6] 10 is a flowchart of a heating control process according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] [First embodiment] Below, a wheel loader 10, which is an example of an electric 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. The term "electric work machine" refers to a work machine that operates using an electric motor as its drive source instead of an engine. More specifically, electric work machines include those that operate (travel, swing, work) directly using the driving force of an electric motor, and those that operate hydraulically by using the driving force of an electric motor to drive a hydraulic pump. Furthermore, specific examples of work machines are not limited to the wheel loader 10, and may include dump trucks, hydraulic excavators, crane trucks, etc.

[0011] [Overall configuration of wheel loader 10] FIG. 1 is a side view of a wheel loader 10. 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 38 (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 around 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 around 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-to-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-and-down direction (moves up and down) by extension and contraction of a pair of lift arm cylinders 19.

[0015] The bucket 18 has a recessed space capable of accommodating cargo (such as earth and sand). The bucket 18 is supported at the front end of the lift arm 17 so as to be able to rotate (tilt or dump). More specifically, the bucket 18 rotates in the vertical direction as a bell crank 21 rotates in accordance with the extension and contraction of the bucket cylinder 20.

[0016] The rear frame 12 supports a pair of left and right rear tires 22L, 22R, a cab 23 (operator's compartment), an engine building 24 (building), and a counterweight 25.

[0017] The cab 23 is supported by the rear frame 12 forward of the engine building 24. The cab 23 has an internal space formed therein for an operator to ride in and operate the wheel loader 10. Inside the cab 23, there are arranged a seat (not shown) on which the operator sits, an oil-fired heating device 26 (see FIG. 2) that heats the interior of the cab 23, and an operating device 27 and a heating selector switch 28 (see FIG. 3) that are operated by the operator seated in the seat.

[0018] Oil-fired heating device 26 is a device that uses the heat of hydraulic oil to supply warm air into cab 23, thereby maintaining (i.e., heating) the interior of cab 23 at a predetermined temperature. As shown in FIG. 2, oil-fired heating device 26 is composed of a warm air motor 36, a warm air fan 44, and a heater core 45. Details of oil-fired heating device 26 will be described later with reference to FIG. 2.

[0019] The operating device 27 accepts operations by the operator to operate the wheel loader 10 (more specifically, the hydraulic actuator). The operating device 27 includes, for example, an accelerator pedal for accelerating the wheel loader 10, a brake pedal for braking the wheel loader 10, a steering wheel for turning the front frame 11 (in other words, extending and retracting the steering cylinders 14L, 14R), and an operating lever for operating the front work implement 16 (in other words, extending and retracting the lift arm cylinder 19 and bucket cylinder 20). The operating device 27 outputs an operation signal corresponding to the operator's operation to the control device 60 (see FIG. 3).

[0020] The heating selector switch 28 receives an operator's operation to switch between on and off the heat exchange between the hydraulic oil in the oil-fired heating device 26 and the air supplied to the cab 23. The heating selector switch 28 is configured to be switchable between an on state in which heat exchange is performed and a off state in which heat exchange is stopped. The heating selector switch 28 outputs a heating signal corresponding to the operator's operation (i.e., the on state or the off state) to the control device 60.

[0021] The engine building 24 is supported by the rear frame 12 behind the cab 23 and forward of the rearmost end of the counterweight 25. The engine building 24 has an internal space that houses components for driving the wheel loader 10 (for example, an oil-fired heating device 26, a drive circuit 30, and a control device 60). The counterweight 25 is supported by the rear frame 12 behind the engine building 24. The counterweight 25 is a heavy object that is used to balance the front work implement 16.

[0022] [Configuration of drive circuit 30] Figure 2 is a circuit diagram of a drive circuit 30 according to the first embodiment. The wheel loader 10 is equipped with the drive circuit 30 shown in Figure 2. The drive circuit 30 mainly includes a high-voltage battery 31, a low-voltage battery 32 (see Figure 3), a first electric motor 33, a cooling motor 34, a second electric motor 35, a hot air motor 36, a hydraulic oil tank 37, a first hydraulic pump 38, a directional control valve 39, a cooling fan 40, a hydraulic oil cooler 41, a second hydraulic pump 42, a hydraulic oil heater 43, a hot air fan 44, a heater core 45, check valves 46 and 47, a first oil temperature sensor 48, and a second oil temperature sensor 49.

[0023] The high-voltage battery 31 and the low-voltage battery 32 are storage batteries that store electric power. The high-voltage battery 31 and the low-voltage battery 32 may store electric power supplied from an external power source, or may store regenerated electric power generated by the electric motors (33-36). The voltage of the high-voltage battery 31 (e.g., 400 V) is set higher than the voltage of the low-voltage battery 32 (e.g., 24 V). However, the storage batteries mounted on the wheel loader 10 are not limited to the above-mentioned examples, and only one type may be used.

[0024] The high-voltage battery 31 supplies power to, for example, a travel motor (not shown) that drives the wheel loader 10 (i.e., rotates the rear tires 22L, 22R), a first electric motor 33, and a hydraulic oil heater 43. The low-voltage battery 32 supplies power to, for example, a cooling motor 34, a second electric motor 35, a hot air motor 36, and a control device 60. However, the destinations to which the power of the high-voltage battery 31 and the low-voltage battery 32 is supplied are not limited to the examples described above.

[0025] The first electric motor 33 is an electric motor driven by power supplied from the high-voltage battery 31 via an inverter (not shown). The cooling motor 34, the second electric motor 35, and the hot air motor 36 are electric motors driven by power supplied from the low-voltage battery 32 via an inverter (not shown). The first electric motor 33, the cooling motor 34, the second electric motor 35, and the hot air motor 36 are, for example, three-phase AC motors.

[0026] The hydraulic oil tank 37 stores hydraulic oil for operating the hydraulic actuators. Note that while FIG. 2 shows only the bucket cylinder 20 as an example of a hydraulic actuator, hydraulic oil is similarly supplied to and discharged from the other hydraulic actuators. The drive circuit 30 also includes a first oil passage L1, a second oil passage L2, a third oil passage L3, a fourth oil passage L4, and a fifth oil passage L5 as oil passages through which the hydraulic oil passes. Each line (L1 to L5) is formed, for example, from a steel pipe, a hose, or a combination of these.

[0027] The first oil passage L1 is an oil passage that runs from the hydraulic oil tank 37 to the first hydraulic pump 38. The second oil passage L2 is an oil passage that runs from the first hydraulic pump 38 to the bucket cylinder 20 via the directional control valve 39. The third oil passage L3 is an oil passage that runs from the bucket cylinder 20 to the hydraulic oil tank 37 via the directional control valve 39, a check valve 47, and a hydraulic oil cooler 41. The fourth oil passage L4 branches off from the third oil passage L3 at a branching position P1, passes through a second hydraulic pump 42, a first oil temperature sensor 48, a hydraulic oil heater 43, and a heater core 45, and connects (converges) with the third oil passage L3 at a connection position (converging position) P2. The fifth oil passage L5 is an oil passage that runs from the hydraulic oil tank 37 to the check valve 46 and connects to the fourth oil passage L4 at a connection position P3.

[0028] That is, the first oil passage L1 is an oil passage through which hydraulic oil sucked from the hydraulic oil tank 37 by the first hydraulic pump 38 flows. The second oil passage L2 is an oil passage through which hydraulic oil discharged from the first hydraulic pump 38 flows toward the bucket cylinder 20. The third oil passage L3 is an oil passage through which hydraulic oil that has passed through the bucket cylinder 20 flows toward the hydraulic oil tank 37. The fourth oil passage L4 is an oil passage that branches off from the third oil passage L3 at a branching position P1 and connects back to the third oil passage L3 at a connecting position P2. However, the oil passage from which the fourth oil passage L4 branches and connects is not limited to the third oil passage L3, and may be the first oil passage L1 or the second oil passage L2. That is, the fourth oil passage L4 may branch off from any one of the first oil passage L1, the second oil passage L2, and the third oil passage L3 (hereinafter referred to as the "target oil passage") and connect back to the target oil passage. The fifth oil passage L5 is an oil passage that is connected to the hydraulic oil tank 37 at one end and to the fourth oil passage L4 at the upstream side of the first oil temperature sensor 48 in the flow of hydraulic oil at the other end.

[0029] The branch position P1 is a position in the third oil passage L3 that is downstream of the directional control valve 39 in the flow of hydraulic oil and upstream of the check valve 47 in the flow of hydraulic oil. The connection position P2 is a position in the third oil passage L3 that is downstream of the check valve 47 in the flow of hydraulic oil and upstream of the hydraulic oil cooler 41 in the flow of hydraulic oil. The connection position P3 is a position in the fourth oil passage L4 that is downstream of the branch position P1 in the flow of hydraulic oil and upstream of the second hydraulic pump 42 in the flow of hydraulic oil.

[0030] The first hydraulic pump 38 is disposed downstream of the hydraulic oil tank 37 in the flow of hydraulic oil and upstream of the direction switching valve 39 in the flow of hydraulic oil. The first hydraulic pump 38 is disposed in the first oil passage L1 and the second oil passage L2. The first hydraulic pump 38 is connected to the output shaft of the first electric motor 33. The first hydraulic pump 38 is driven by the power of the first electric motor 33. As a result, the first hydraulic pump 38 pumps hydraulic oil drawn from the hydraulic oil tank 37 through the first oil passage L1, and delivers the pumped hydraulic oil to the bucket cylinder 20 (direction switching valve 39) through the second oil passage L2. The first hydraulic pump 38 may be a variable displacement pump whose discharge capacity can be changed under the control of the control device 60.

[0031] The direction switching valve 39 is disposed in the second oil passage L2 downstream of the first hydraulic pump 38 in the flow of hydraulic oil and upstream of the bucket cylinder 20 in the flow of hydraulic oil. The direction switching valve 39 is also disposed in the third oil passage L3 downstream of the bucket cylinder 20 in the flow of hydraulic oil and upstream of the branch position P1 in the flow of hydraulic oil. The direction switching valve 39 controls the supply and discharge of hydraulic oil to and from the bucket cylinder 20. More specifically, the direction switching valve 39 supplies hydraulic oil pressure-fed from the first hydraulic pump 38 to the bucket cylinder 20 through the second oil passage L2, and discharges hydraulic oil discharged from the bucket cylinder 20 to the hydraulic oil tank 37 through the third oil passage L3.

[0032] The directional control valve 39 is configured to be switchable between an extended position and a retracted position under the control of the control device 60. The extended position is a position where the bucket cylinder 20 is extended by supplying hydraulic oil pressure-fed from the first hydraulic pump 38 to the bottom chamber of the bucket cylinder 20 and discharging hydraulic oil discharged from the rod chamber of the bucket cylinder 20 to the hydraulic oil tank 37. The retracted position is a position where the bucket cylinder 20 is retracted by supplying hydraulic oil pressure-fed from the first hydraulic pump 38 to the rod chamber of the bucket cylinder 20 and discharging hydraulic oil discharged from the bottom chamber of the bucket cylinder 20 to the hydraulic oil tank 37.

[0033] The cooling fan 40 is disposed in a position facing the hydraulic oil cooler 41. The cooling fan 40 is connected to the output shaft of the cooling motor 34. The cooling fan 40 generates cooling air by the driving force of the cooling motor 34. The volume of the cooling air generated by the cooling fan 40 is controlled by the control device 60. The hydraulic oil cooler 41 is disposed in the third oil passage L3 downstream of the connection position P2 (oil-heated heating device 26) in the hydraulic oil flow and upstream of the hydraulic oil tank 37 in the hydraulic oil flow. The hydraulic oil cooler 41 exchanges heat with (i.e., cools) the hydraulic oil passing through the third oil passage L3 with the cooling air generated by the cooling fan 40. The hydraulic oil cooled by the hydraulic oil cooler 41 returns to the hydraulic oil tank 37.

[0034] The second hydraulic pump 42 is disposed in the fourth oil passage L4 downstream of the connection position P3 in the flow of hydraulic oil and upstream of the first oil temperature sensor 48 in the flow of hydraulic oil. The second hydraulic pump 42 is connected to the output shaft of the second electric motor 35. The second hydraulic pump 42 is a hydraulic pump that, by power from the second electric motor 35, pressure-feeds at least one of the hydraulic oil that flows from the third oil passage L3 to the fourth oil passage L4 via the branch position P1 and the hydraulic oil that flows from the fifth oil passage L5 to the fourth oil passage L4 via the connection position P3, toward the hydraulic oil heater 43. The second hydraulic pump 42 may be a variable displacement pump whose discharge capacity can be changed under the control of the control device 60.

[0035] The hydraulic oil heater 43 is disposed in the fourth oil passage L4 downstream of the first oil temperature sensor 48 in the hydraulic oil flow and upstream of the heater core 45 in the hydraulic oil flow. The hydraulic oil heater 43 is, for example, a heating coil that generates heat using power from the high-voltage battery 31. The hydraulic oil heater 43 heats the hydraulic oil that is pressure-fed by the second hydraulic pump 42 (in other words, that passes through the fourth oil passage L4) out of the hydraulic oil supplied to and discharged from the bucket cylinder 20, and supplies the heated hydraulic oil to the heater core 45. The amount of heat generated by the hydraulic oil heater 43 is controlled by the control device 60.

[0036] The hot air fan 44 is disposed in a position facing the heater core 45. The hot air fan 44 is connected to the output shaft of the hot air motor 36. The hot air fan 44 generates a flow of air to be supplied to the cab 23 by the driving force of the hot air motor 36. The volume of air generated by the hot air fan 44 is controlled by the control device 60. The heater core 45 is disposed in the fourth oil passage L4 downstream of the hydraulic oil heater 43 in the hydraulic oil flow and upstream of the connection position P2 in the hydraulic oil flow. The heater core 45 exchanges heat between the hydraulic oil that has passed through the hydraulic oil heater 43 (i.e., passes through the fourth oil passage L4) and the air generated by the hot air fan 44. The air that has been heat exchanged (i.e., heated) by the heater core 45 is supplied to the cab 23 as hot air.

[0037] According to this embodiment, the first hydraulic pump 38, the cooling fan 40, the second hydraulic pump 42, and the hot air fan 44 are electrically driven by electric motors (33, 34, 35, 36). However, the cooling fan 40, the second hydraulic pump 42, and the hot air fan 44 are not limited to being electrically driven, and may be driven by other driving sources.

[0038] The check valve 46 is disposed in the fifth oil passage L5 downstream of the hydraulic oil tank 37 in the flow of hydraulic oil and upstream of the connection position P3 in the flow of hydraulic oil. The check valve 46 allows the flow of hydraulic oil from the hydraulic oil tank 37 toward the fourth oil passage L4 and blocks the flow of hydraulic oil from the fourth oil passage L4 toward the hydraulic oil tank 37. The check valve 47 is disposed in the third oil passage L3 downstream of the branch position P1 in the flow of hydraulic oil and upstream of the connection position P2 in the flow of hydraulic oil. The check valve 47 allows the flow of hydraulic oil from the branch position P1 toward the connection position P2 and blocks the flow of hydraulic oil from the connection position P2 toward the branch position P1.

[0039] The first oil temperature sensor 48 detects the temperature (hereinafter referred to as the "first oil temperature Th") of the hydraulic oil pressure-fed by the second hydraulic pump 42 (in other words, passing through the fourth oil passage L4 between the second hydraulic pump 42 and the hydraulic oil heater 43). The fourth oil passage L4 is provided with the second hydraulic pump 42, the first oil temperature sensor 48, the hydraulic oil heater 43, and the heater core 45, in this order from the upstream side of the hydraulic oil flow. That is, the first oil temperature sensor 48 detects the temperature of the hydraulic oil immediately before it flows into the hydraulic oil heater 43. The second oil temperature sensor 49 detects the temperature (hereinafter referred to as the "second oil temperature Tt") of the hydraulic oil stored in the hydraulic oil tank 37. The first oil temperature sensor 48 and the second oil temperature sensor 49 then output temperature signals indicating the detected hydraulic oil temperatures to the control device 60.

[0040] When the second hydraulic pump 42 is stopped, the hydraulic oil discharged from the bucket cylinder 20 to the third oil passage L3 does not flow into the fourth oil passage L4 through the branch position P1, but is discharged into the hydraulic oil tank 37 through the check valve 47 and the hydraulic oil cooler 41. Furthermore, when the second hydraulic pump 42 rotates, at least a portion of the hydraulic oil passing through the third oil passage L3 flows into the fourth oil passage L4 through the branch position P1. Furthermore, the amount of hydraulic oil flowing from the third oil passage L3 into the fourth oil passage L4 through the branch position P1 increases as the discharge capacity of the second hydraulic pump 42 (or the rotation speed of the second hydraulic pump 42) increases.

[0041] Furthermore, when the bucket cylinder 20 is operating, the hydraulic pressure of the hydraulic oil flowing from the third oil passage L3 to the fourth oil passage L4 is higher than the hydraulic oil supplied from the hydraulic oil tank 37 to the fourth oil passage L4 through the fifth oil passage L5. Therefore, the second hydraulic pump 42 preferentially pumps out the hydraulic oil flowing from the third oil passage L3 to the fourth oil passage L4, and draws in any deficiency from the fifth oil passage L5. On the other hand, when the bucket cylinder 20 is stopped, the second hydraulic pump 42 pumps out only the hydraulic oil flowing from the fifth oil passage L5 to the fourth oil passage L4 through the connection position P3.

[0042] Furthermore, the hydraulic oil that has exchanged heat with the air in the heater core 45 (i.e., its temperature has dropped) flows into the third oil passage L3 through the connection position P2, merges with the hydraulic oil that has passed through the check valve 47, is cooled in the hydraulic oil cooler 41, and returns to the hydraulic oil tank 37.

[0043] [Configuration of control device 60] FIG. 3 is a hardware configuration diagram of the wheel loader 10. The wheel loader 10 is equipped with a control device 60. The control device 60 is equipped with a CPU (Central Processing Unit) 61 and a memory 62. The memory 62 is configured, for example, from a ROM (Read Only Memory), a RAM (Random Access Memory), an HDD (Hard Disk Drive), or a combination of these. The control device 60 realizes the processing described below by having the CPU 61 read and execute program code stored in the ROM or HDD. The RAM is used as a work area when the CPU 61 executes the program.

[0044] However, the specific configuration of the control device 60 is not limited to this, and may be realized by hardware such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field-Programmable Gate Array).

[0045] The control device 60 receives a supply of power from the low-voltage battery 32 and controls the operation of the entire wheel loader 10. The control device 60 controls the first electric motor 33, the cooling motor 34, the second electric motor 35, the hot air motor 36, the directional control valve 39, and the hydraulic oil heater 43 based on an operation signal output from the operation device 27, a heating signal output from the heating selector switch 28, and temperature signals output from the first oil temperature sensor 48 and the second oil temperature sensor 49.

[0046] The control device 60 controls the first electric motor 33 and the directional control valve 39 based on an operation signal output from the operation device 27 (operation lever), thereby extending and retracting the bucket cylinder 20. Similarly, the control device 60 rotates the travel motor based on an operation signal output from the operation device 27, thereby extending and retracting the steering cylinders 14L, 14R and the lift arm cylinder 19. In other words, when the operator in the cab 23 operates the operation device 27, the wheel loader 10 travels or changes direction, and the front work implement 16 operates.

[0047] Furthermore, the control device 60 controls the cooling motor 34, the second electric motor 35, the hot air motor 36, and the hydraulic oil heater 43 based on the heating signal output from the heating selector switch 28 and the temperature signals output from the first oil temperature sensor 48 and the second oil temperature sensor 49. As a result, the inside of the cab 23 is maintained at a predetermined temperature by the hot air supplied to the cab 23. Details of this process will be described in detail with reference to FIG. 4.

[0048] [Heating control processing] Figure 4 is a flowchart of the heating control process according to the first embodiment. The control device 60 repeatedly executes the heating control process shown in Figure 4 at predetermined time intervals, for example, while the wheel loader 10 is operating (more specifically, while power is being supplied to the control device 60 from the low-voltage battery 32).

[0049] First, the control device 60 determines whether the heating switch 28 is in an active state (hereinafter, sometimes referred to as "heating ON") or a stopped state (hereinafter, sometimes referred to as "heating OFF") based on the heating signal output from the heating switch 28 (S11).

[0050] Next, when the control device 60 determines that the heating selector switch 28 is in the heating ON position (S11: Yes), the control device 60 drives the second electric motor 35 and the hot air motor 36 with the power stored in the low-voltage battery 32 (S12). As a result, the hydraulic oil in the fourth oil passage L4 is pressure-fed by the second hydraulic pump 42 toward the hydraulic oil heater 43. In addition, the hot air fan 44 rotates, and hot air that has exchanged heat with the hydraulic oil in the heater core 45 is supplied to the cab 23.

[0051] Next, the control device 60 compares the first oil temperature Th with a first threshold value Th0 based on the temperature signal output from the first oil temperature sensor 48 (S13). The first threshold value Th0 is set, for example, to a value that allows hot air of a predetermined temperature to be supplied to the cab 23. The first threshold value Th0 may be a predetermined fixed value (for example, 70°C) or a variable value that varies depending on the set temperature of the oil-fired heating device 26.

[0052] Then, when the first oil temperature Th is lower than the first threshold value Th0 (S13: Yes), the control device 60 supplies power from the low-voltage battery 32 to the hydraulic oil heater 43, heats the hydraulic oil passing through the fourth oil passage L4, and supplies the hydraulic oil to the heater core 45 (S14). On the other hand, when the first oil temperature Th is equal to or higher than the first threshold value Th0 (S13: No), the control device 60 stops the supply of power from the low-voltage battery 32 to the hydraulic oil heater 43, stops heating the hydraulic oil passing through the fourth oil passage L4, and supplies the hydraulic oil to the heater core 45 (S15).

[0053] The hydraulic oil discharged from the bucket cylinder 20 and flowing into the fourth oil passage L4 has a higher temperature than the hydraulic oil that flows from the hydraulic oil tank 37 through the fifth oil passage L5 and into the fourth oil passage L4. Therefore, the greater the proportion of hydraulic oil discharged from the bucket cylinder 20 among the hydraulic oil pumped by the second hydraulic pump 42, the more likely it is possible to stop the supply of power to the hydraulic oil heater 43, and the greater the proportion of hydraulic oil supplied from the hydraulic oil tank 37, the more likely it is necessary to supply power to the hydraulic oil heater 43.

[0054] Next, the control device 60 compares the second oil temperature Tt with a second threshold value Tton based on the temperature signal output from the second oil temperature sensor 49 (S16). The second threshold value Tton is set to a value (e.g., 90°C) that takes into account the amount of heat to be exchanged between the heater core 45 and the hot air fan 44, for example, in addition to the lower limit temperature Ttoff (e.g., 60°C) at which the hydraulic oil needs to be cooled by the hydraulic oil cooler 41.

[0055] Then, when the second oil temperature Tt is equal to or higher than the second threshold value Tton (S16: Yes), the control device 60 supplies power from the low-voltage battery 32 to the cooling motor 34 to rotate the cooling fan 40 (S17). This causes the hydraulic oil passing through the third oil passage L3 to be cooled and returned to the hydraulic oil tank 37. Note that the control device 60 may increase the rotation speed of the cooling fan 40 (increase the volume of cooling air) as the difference between the second oil temperature Tt and the second threshold value Tton increases (i.e., the second oil temperature Tt is higher).

[0056] On the other hand, if the second oil temperature Tt is lower than the second threshold value Tton (S16: No), the control device 60 stops the power supply from the low-voltage battery 32 to the cooling motor 34 and stops the cooling fan 40 (S18). As a result, the hydraulic oil passing through the third oil passage L3 returns to the hydraulic oil tank 37 without being cooled by the hydraulic oil cooler 41.

[0057] Furthermore, when the control device 60 determines that the heating selector switch 28 is in the heating OFF state (S11: No), it compares the second oil temperature Tt with a third threshold value Tt0 (S19) based on the temperature signal output from the second oil temperature sensor 49. The third threshold value Tt0 is set, for example, to a lower limit temperature (e.g., 50°C) at which the hydraulic oil has an appropriate viscosity (in other words, the hydraulic actuator can be operated appropriately).

[0058] When the control device 60 determines that the second oil temperature Tt is equal to or higher than the third threshold value Tt0 (S19: Yes), it stops the second electric motor 35 and the hot air motor 36 (S20). As a result, the second hydraulic pump 42 stops, and hydraulic oil does not flow from the third oil passage L3 and the fifth oil passage L5 to the fourth oil passage L4. In addition, the hot air fan 44 stops, and therefore hot air is not supplied to the cab 23. Furthermore, the control device 60 stops the supply of power from the low-voltage battery 32 to the hydraulic oil heater 43, and stops heating of the hydraulic oil (S21).

[0059] Next, the control device 60 compares the second oil temperature Tt with the lower limit temperature Ttoff based on the temperature signal output from the second oil temperature sensor 49 (S22). If the second oil temperature Tt is equal to or higher than the lower limit temperature Ttoff (S22: Yes), the control device 60 supplies power from the low-voltage battery 32 to the cooling motor 34 to rotate the cooling fan 40 (S23). On the other hand, if the second oil temperature Tt is lower than the lower limit temperature Ttoff (S22: No), the control device 60 stops the supply of power from the low-voltage battery 32 to the cooling motor 34 to stop the cooling fan 40 (S24).

[0060] On the other hand, when the control device 60 determines that the second oil temperature Tt is lower than the third threshold value Tt0 (S19: No), the control device 60 drives the second electric motor 35 with the power stored in the low-voltage battery 32 and stops the hot air motor 36 (S25). The control device 60 also supplies power from the low-voltage battery 32 to the hydraulic oil heater 43 to heat the hydraulic oil passing through the fourth oil passage L4 (S26). Furthermore, the control device 60 stops the power supply from the low-voltage battery 32 to the cooling motor 34 and stops the cooling fan 40 (S27).

[0061] As a result, the hydraulic oil pumped by the second hydraulic pump 42 is heated by the hydraulic oil heater 43 and returns to the hydraulic oil tank 37 without being cooled by the hydraulic oil cooler 41. This allows the temperature of the hydraulic oil to be rapidly raised to the third threshold value Tt0. Meanwhile, because the hot air fan 44 is stopped, no hot air is supplied to the cab 23.

[0062] [Effects of the first embodiment] According to the first embodiment, the hydraulic oil discharged from the bucket cylinder 20 is supplied to the heater core 45 via the hydraulic oil heater 43. In addition to circulating the hydraulic oil in the drive circuit, by heating the hydraulic oil with the hydraulic oil heater 43, the temperature of the hydraulic oil can be quickly raised (i.e., warm-up operation can be completed in a short time), and at the same time, the cab can be quickly heated using oil heat. Furthermore, when the hydraulic oil discharged from the bucket cylinder is hot, the amount of electricity supplied to the hydraulic oil heater 43 can be reduced to raise the temperature of the hydraulic oil to the temperature required for heat exchange with the air in the heater core 45.

[0063] Furthermore, according to the first embodiment, when the first oil temperature Th is equal to or higher than the first threshold value Th0 (S13: No), the power supply to the hydraulic oil heater 43 is stopped (S15), thereby reducing the power consumption of the hydraulic oil heater 43.

[0064] Furthermore, according to the first embodiment, the first oil temperature sensor 48 is located upstream of the hydraulic oil heater 43 in the flow of hydraulic oil. That is, the first oil temperature sensor 48 detects the temperature (first oil temperature Th) of the hydraulic oil immediately before it flows into the hydraulic oil heater 43. As a result, when it is determined whether to start or stop heating the hydraulic oil by the hydraulic oil heater 43 (S13 to S15), the start or stop of heating the hydraulic oil by the hydraulic oil heater 43 can be efficiently performed in accordance with the temperature of the hydraulic oil immediately before it flows into the hydraulic oil heater 43.

[0065] Furthermore, according to the first embodiment, when the amount of hydraulic oil supplied from the third oil passage L3 to the second hydraulic pump 42 is less than the required amount, the shortage can be made up for from the hydraulic oil tank 37 via the fifth oil passage L5. This makes it possible to supply the required amount of hydraulic oil to the second hydraulic pump 42 regardless of the operating state of the bucket cylinder 20 (hydraulic actuator).

[0066] Furthermore, according to the first embodiment, when the second oil temperature Tt is lower than the second threshold value Tton (S16: No), the cooling fan 40 is stopped, thereby preventing the temperature of the hydraulic oil from dropping too much. This eliminates the need to reheat the hydraulic oil cooled by the hydraulic oil cooler 41 with the hydraulic oil heater 43, thereby reducing the power consumption of the cooling fan 40 and the hydraulic oil heater 43.

[0067] Furthermore, according to the first embodiment, when the heater is OFF and the second oil temperature Tt is less than the third threshold value Tt0 (S11: No & S19: No), the second electric motor 35 is driven, the hot air motor 36 is stopped, the hydraulic oil heater 43 is energized, and the cooling fan 40 is stopped (S25 to S27). This makes it possible to rapidly raise the temperature of the hydraulic oil up to the third threshold value Tt0, so that when the wheel loader 10 is started in cold climates, for example, the warm-up time can be shortened. As a result, the productivity of the wheel loader 10 is improved.

[0068] [Second embodiment] 5 is a circuit diagram of a drive circuit 30A according to the second embodiment. Detailed descriptions of the commonalities with the first embodiment will be omitted, and differences will be mainly described. The drive circuit 30A according to the second embodiment differs from the drive circuit 30 in that it further includes a sixth oil passage L6 and a switching valve 50, but is otherwise the same as the drive circuit 30.

[0069] The sixth oil passage L6 is an oil passage that branches off from the fourth oil passage L4 at a branching position P5 and connects (merges) with the fourth oil passage L4 at a connection position (merging position) P6. The branching position P5 is a position in the fourth oil passage L4 that is downstream of the heater core 45 in the flow of hydraulic oil and upstream of the connection position P2 in the flow of hydraulic oil. The connection position P6 is a position in the fourth oil passage L4 that is downstream of the branching position P1 in the flow of hydraulic oil and upstream of the connection position P3 in the flow of hydraulic oil. In other words, the sixth oil passage L6 is an oil passage that returns the hydraulic oil that has passed through the heater core 45 (exchanged heat with air) to the upstream side of the flow of hydraulic oil from the second hydraulic pump 42.

[0070] The switching valve 50 is disposed in the fourth oil passage L4 downstream of the heater core 45 in the flow of hydraulic oil and upstream of the connection position P2 in the flow of hydraulic oil. More specifically, the switching valve 50 is disposed at a branching position P5 of the fourth oil passage L4 and the sixth oil passage L6. The switching valve 50 is configured to be switchable between a discharge position and a return position under the control of the control device 60.

[0071] The discharge position is a position where the hydraulic oil that has passed through the heater core 45 is discharged to the third oil passage L3 through the connection position P2. Furthermore, the switching valve 50 in the discharge position does not allow the hydraulic oil that has passed through the heater core 45 to return to the fourth oil passage L4 through the sixth oil passage L6. The return position is a position where the hydraulic oil that has passed through the heater core 45 is returned to the fourth oil passage L4 upstream of the second hydraulic pump 42 in the hydraulic oil flow direction through the sixth oil passage L6. Furthermore, the switching valve 50 in the return position does not discharge the hydraulic oil that has passed through the heater core 45 to the third oil passage L3.

[0072] 6 is a flowchart of the heating control process according to the second embodiment. The heating control process according to the second embodiment has steps S11 to S27 in common with the first embodiment, and further includes steps S28 to S31.

[0073] When the second oil temperature Tt is equal to or higher than the second threshold value Tton and the cooling fan 40 is rotated (S16: Yes → S17), the control device 60 according to the second embodiment switches the switching valve 50 to the discharge position (S28). As a result, the hydraulic oil that has been heat exchanged in the heater core 45 is cooled in the hydraulic oil cooler 41 and returned to the hydraulic oil tank 37. Furthermore, new hydraulic oil is supplied to the second hydraulic pump 42 from the third oil passage L3 or the fifth oil passage L5.

[0074] Furthermore, when the control device 60 according to the second embodiment stops the cooling fan 40 because the second oil temperature Tt is lower than the second threshold value Tton (S16: No → S18), it compares the second oil temperature Tt with a fourth threshold value Tt1 (S29) based on the temperature signal output from the second oil temperature sensor 49. The fourth threshold value Tt1 is set to, for example, a value (e.g., 55°C) that takes into account the amount of heat to be exchanged between the heater core 45 and the hot air fan 44 and the third threshold value Tt0 (e.g., 50°C).

[0075] Then, when the control device 60 according to the second embodiment determines that the second oil temperature Tt is equal to or higher than the fourth threshold value Tt1 (S29: Yes), it switches the switching valve 50 to the discharge position (S28). On the other hand, when the control device 60 according to the second embodiment determines that the second oil temperature Tt is lower than the fourth threshold value Tt1 (S29: No), it switches the switching valve 50 to the return position (S30). As a result, the hydraulic oil that has passed through the heater core 45 is supplied again to the second hydraulic pump 42. That is, the hydraulic oil circulates in the fourth oil passage L4 and the sixth oil passage L6, making it difficult for new hydraulic oil to be supplied to the oil-fired heating device 26.

[0076] Furthermore, when the control device 60 according to the second embodiment determines that the heating selector switch 28 is in the heating OFF state (S11: No), it switches the selector valve 50 to the discharge position (S31), thereby preventing the hydraulic oil from circulating in the fourth oil passage L4 and the sixth oil passage L6.

[0077] [Effects of the second embodiment] According to the second embodiment, when it is determined that the second oil temperature Tt is lower than the fourth threshold value Tt1 (S29: No), the switching valve 50 is switched to the reflux position (S30). This prevents the hydraulic oil in the fourth oil passage L4 and the sixth oil passage L6 from mixing with the low-temperature hydraulic oil in the hydraulic oil tank 37 and from being supplied to the oil-fired heating device 26. As a result, the heating efficiency of the oil-fired heating device 26 is improved.

[0078] On the other hand, according to the second embodiment, the switching valve 50 is switched to the discharge position (S28, S31) in cases other than step S30, thereby preventing the temperature of the hydraulic oil in the fourth oil passage L4 and the sixth oil passage L6 from rising too high.

[0079] The above-described embodiments are merely illustrative examples of the present invention, and are not intended to limit the scope of the present invention to these embodiments. Those skilled in the art can implement the present invention in various other forms without departing from the spirit of the present invention. [Explanation of symbols]

[0080] 10: Wheel loader 11: Previous frame 12: Rear frame 13: Center pin 14L, 14R: Steering cylinder (hydraulic actuator) 15L, 15R: Front tires 16: Front work equipment 17: Lift arm 18: Bucket 19: Lift arm cylinder (hydraulic actuator) 20: Bucket cylinder (hydraulic actuator) 21: Bell crank 22L, 22R: Rear tires 23: Cab 24: Engine building 25: Counterweight 26:Oil heating device 27: Operating device 28: Heating switch 30, 30A: Drive circuit 31: High-voltage battery (storage battery) 32: Low voltage battery (storage battery) 33: First electric motor 34: Cooling motor 35: Second electric motor 36: Hot air motor 37: Hydraulic oil tank 38: First hydraulic pump 39: Directional valve 40: Cooling fan 41: Hydraulic oil cooler 42: Second hydraulic pump 43: Hydraulic oil heater 44: Warm air fan 45: Heater core 46, 47: Check valve 48: First oil temperature sensor 49: Second oil temperature sensor 50: Switching valve 60: Control device 61: CPU 62: Memory

Claims

1. A cab provided on the vehicle body; A storage battery and an electric motor driven by the power of the storage battery; a first hydraulic pump driven by power of the electric motor; a hydraulic actuator driven by hydraulic oil supplied from the first hydraulic pump; an oil heating device that heats the inside of the cab by the heat of the hydraulic oil; In a work machine comprising: a hydraulic oil heater that heats the hydraulic oil supplied to and discharged from the hydraulic actuator; The oil-fired heating device heats the inside of the cab by heat exchange between the hydraulic oil heated by the hydraulic oil heater and air supplied to the cab. A work machine characterized by:

2. 2. The work machine according to claim 1, a control device for controlling the hydraulic oil heater; a first oil temperature sensor for detecting the temperature of the hydraulic oil; Furthermore, The control device When the temperature of the hydraulic oil detected by the first oil temperature sensor is lower than a first threshold value, heating of the hydraulic oil by the hydraulic oil heater is executed, and when the temperature of the hydraulic oil detected by the first oil temperature sensor is equal to or higher than the first threshold value, heating of the hydraulic oil by the hydraulic oil heater is stopped.

3. 3. The work machine according to claim 2, a hydraulic oil tank that stores the hydraulic oil; a first oil passage through which the hydraulic oil drawn by the first hydraulic pump from the hydraulic oil tank flows; a second oil passage through which the hydraulic oil discharged from the first hydraulic pump flows toward the hydraulic actuator; a third oil passage through which the hydraulic oil that has passed through the hydraulic actuator flows toward the hydraulic oil tank; Further provided is a fourth oil passage branching from a target oil passage which is any one of the first oil passage, the second oil passage, and the third oil passage and connecting to the target oil passage again; A work machine, wherein the fourth oil passage is provided with the first oil temperature sensor, the hydraulic oil heater, and the oil heating device in this order from the upstream side of the flow of the hydraulic oil.

4. 4. The work machine according to claim 3, The fourth oil passage branches off from the third oil passage and connects to the third oil passage again, a fifth oil passage having one end connected to the hydraulic oil tank and the other end connected to the fourth oil passage upstream of the first oil temperature sensor in the flow of the hydraulic oil; a second hydraulic pump that draws the hydraulic oil from the fifth oil passage into the fourth oil passage.

5. 4. The work machine according to claim 3, a second oil temperature sensor that detects the temperature of the hydraulic oil stored in the hydraulic oil tank; Further provided is a hydraulic oil cooler provided downstream of the oil-heated heating device in the third oil passage in the flow of the hydraulic oil, which cools the hydraulic oil, The control device When the temperature of the hydraulic oil detected by the second oil temperature sensor is equal to or higher than a second threshold value, cooling of the hydraulic oil by the hydraulic oil cooler is performed; When the temperature of the hydraulic oil detected by the second oil temperature sensor is lower than the second threshold value, cooling of the hydraulic oil by the hydraulic oil cooler is stopped. A work machine characterized by:

6. 5. The work machine according to claim 4, a second oil temperature sensor that detects the temperature of the hydraulic oil stored in the hydraulic oil tank; A heating selector switch that switches between performing and stopping heat exchange between the hydraulic oil and the air supplied to the cab by the oil-fired heating device, When the heat exchange between the working oil and the air supplied to the cab by the oil-fired heating device is stopped by the heating selector switch, The control device When the temperature of the hydraulic oil detected by the second oil temperature sensor is lower than a third threshold value, the second hydraulic pump is driven and the hydraulic oil is heated by the hydraulic oil heater; When the temperature of the hydraulic oil detected by the second oil temperature sensor is equal to or higher than the third threshold value, the second hydraulic pump is stopped and heating of the hydraulic oil by the hydraulic oil heater is stopped. A work machine characterized by:

7. 4. The work machine according to claim 3, a second oil temperature sensor that detects the temperature of the hydraulic oil stored in the hydraulic oil tank; a second hydraulic pump provided in the fourth oil passage upstream of the first oil temperature sensor in the flow of the hydraulic oil; A switching valve is provided in the fourth oil passage downstream of the flow of the hydraulic oil from the oil heating device, The switching valve is switched between a discharge position in which the hydraulic oil in the fourth oil passage is discharged to the target oil passage via the oil passage in which the oil heating device is provided, and a return position in which the hydraulic oil in the fourth oil passage is returned to the fourth oil passage upstream of the flow of the hydraulic oil from the second hydraulic pump via the oil passage in which the oil heating device is provided, The control device When the temperature of the hydraulic oil detected by the second oil temperature sensor is equal to or higher than a fourth threshold value, the switching valve is switched to the discharge position; When the temperature of the hydraulic oil detected by the second oil temperature sensor is lower than the fourth threshold value, the switching valve is switched to the reflux position. A work machine characterized by:

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