Transport vehicle

Abstract

A transport vehicle is provided with a heat exchanger for cooling a fluid to be cooled, a pump for circulating the fluid to be cooled, a temperature sensor for detecting the temperature of the fluid to be cooled, a fan for blowing air to the heat exchanger, and a hydraulic motor for driving the fan. When the temperature detected by the temperature sensor is between a first temperature and a second temperature, the rotational speed of the pump is increased from a first pump rotational speed to a second pump rotational speed according to an increase in the detected temperature, and when the detected temperature is between a third temperature and a fourth temperature, the rotational speed of the pump is increased from a first pump rotational speed to a second pump rotational speed according to an increase in the detected temperature. The rotation speed of the hydraulic motor is increased from a first motor rotation speed to a second motor rotation speed, the third temperature is set higher than the first temperature, and when the detected temperature is increased, the rotation speed of the pump starts to increase before the rotation speed of the hydraulic motor starts to increase, so that the driving frequency and the rotation speed of the fan can be suppressed, and the fan can be driven more stably. The fuel efficiency is improved, and noise is suppressed.

Description

Technical Field

[0001] The invention relates to a transport vehicle such as a dump truck. Background Art

[0002] The fan that supplies air to the heat exchanger such as the oil cooler mounted on the dump truck for mining, the excavator for mining, the truck traveling on the road, etc. is usually directly connected to the engine and driven. However, due to the large-scale cooling system, the limitation of the configuration of the heat exchanger and the engine, there are many cases where an electric drive fan or a hydraulic drive fan is used. In particular, there is a tendency to use a hydraulic drive fan for large fans that are not suitable for electric drive. As a cooling system using such a hydraulic drive fan, a cooling system is known, which has a plurality of fans and changes the number of driven fans according to the measured temperature of the fluid to be cooled (Patent Document 1).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 10-259728 Summary of the invention

[0006] Problems to be solved by the invention

[0007] However, in the system of Patent Document 1 that changes the number of rotating fans according to the required heat dissipation amount, the control of the heat dissipation amount depends only on the air flow rate, and at least one fan needs to be driven when heat dissipation is required.

[0008] As mentioned above, most hydraulically driven fans are large. The power required to drive a large fan is large, and if the fan drive frequency and speed become high, the fuel efficiency of the transport vehicle will deteriorate. In addition, the operating noise of the fan may also increase the fatigue of the operator and cause noise problems to neighbors.

[0009] An object of the present invention is to provide a transport vehicle capable of suppressing the driving frequency and rotation speed of a fan to achieve improved fuel efficiency and noise suppression.

[0010] Solutions to Solve Problems

[0011] In order to achieve the above-mentioned purpose, the present invention provides a transport vehicle, which has a frame and a cargo box that can be undulatingly arranged on the above-mentioned frame, wherein the transport vehicle has: a tank that stores a cooling object fluid; a heat exchanger that cools the above-mentioned cooling object fluid; a pump that circulates the above-mentioned cooling object fluid between the above-mentioned tank and the above-mentioned heat exchanger; a temperature sensor that detects the temperature of the above-mentioned cooling object fluid; a fan that sends air to the above-mentioned heat exchanger; a hydraulic motor that drives the above-mentioned fan; and a controller that controls the above-mentioned pump and the above-mentioned hydraulic motor according to the temperature detected by the above-mentioned temperature sensor, and the above-mentioned controller stores a first pump speed and a first temperature corresponding to the above-mentioned first pump speed, a second pump speed higher than the above-mentioned first pump speed, and a second temperature corresponding to the above-mentioned second pump speed. two temperatures, a first motor speed and a third temperature corresponding to the first motor speed, a second motor speed higher than the first motor speed and a fourth temperature corresponding to the second motor speed, when the detected temperature is between the first temperature and the second temperature, the speed of the pump is increased from the first pump speed to the second pump speed according to the increase of the detected temperature, when the detected temperature is between the third temperature and the fourth temperature, the speed of the hydraulic motor is increased from the first motor speed to the second motor speed according to the increase of the detected temperature, the third temperature is set higher than the first temperature, and when the detected temperature rises, the speed of the pump starts to rise before the speed of the hydraulic motor starts to rise.

[0012] Effects of the Invention

[0013] According to the present invention, it is possible to suppress the driving frequency and the rotation speed of the fan to achieve improved fuel efficiency and noise suppression. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a side view of a dump truck which is an example of a transport vehicle according to the first embodiment of the present invention.

[0015] Figure 2 It is a plan view of the vehicle frame of the transport vehicle according to the first embodiment of the present invention.

[0016] Figure 3 It is a side view of the vehicle frame of the transport vehicle according to the first embodiment of the present invention.

[0017] Figure 4 This is a hydraulic circuit diagram of a transport vehicle according to a first embodiment of the present invention.

[0018] Figure 5 This is a circuit diagram of a brake cooling oil cooling system provided in a transport vehicle according to a first embodiment of the present invention.

[0019] Figure 6 This is a diagram showing a control table for the fan rotation speed and the brake cooling oil flow rate of the controller included in the transport vehicle according to the first embodiment of the present invention.

[0020] Figure 7 This is a hydraulic circuit diagram of a transport vehicle according to a second embodiment of the present invention.

[0021] Figure 8 It is a diagram showing a hydraulic circuit diagram of a transport vehicle according to a comparative example. DETAILED DESCRIPTION

[0022] Hereinafter, embodiments of the present invention will be described using the drawings.

[0023] (First Embodiment)

[0024] -Transport vehicles-

[0025] Figure 1 FIG. 1 is a side view of a dump truck as an example of a transport vehicle according to the first embodiment of the present invention. Figure 1 The left and right in FIG. 8 are the front and rear of the dump truck 1 .

[0026] The dump truck 1 shown in the figure includes a frame 2 and a plurality of wheels rotatably provided on the frame 2. The wheels include left and right front wheels 3f and left and right rear wheels 3r. One front wheel 3f is disposed at each of the left and right ends of the front portion of the frame 2. Two rear wheels 3r are disposed at each of the left and right ends of the rear portion of the frame 2. The front wheels 3f are steering wheels that steer according to a steering angle input via a steering wheel or the like, and are driven wheels that are driven by the rear wheels 3r via the road surface on which the dump truck 1 travels. A travel motor (not shown) and a speed reducer 11 ( 12 ) for adjusting the rotation speed of the rear wheels 3r are individually connected to the rotation shafts of the left and right rear wheels 3r serving as drive wheels. Figure 2 ).

[0027] In addition, the dump truck 1 includes a deck 4, a cab 5, a control box 6, and a plurality of grid boxes 7. The deck 4 is a floor on which the operator walks, and is disposed above the front wheel 3f. The cab 5 is a cab in which the operator rides, and is disposed on the upper surface of the deck 4. In the cab 5, in addition to the driver's seat in which the operator sits, there are operating pedals (accelerator pedal, brake pedal, etc.) indicating the travel speed of the dump truck 1, and the above-mentioned steering wheel. The control box 6 is a room for storing various electrical equipment, and is mounted on the front part of the vehicle body. The grid box 7 is a device that dissipates the surplus energy generated based on the regenerative power generated during braking as heat, and is disposed on the right side of the control box 6.

[0028] The dump truck 1 further includes a cargo box 8 and a lifting cylinder 9. The cargo box 8 is a platform for loading cargo such as sand, ore, etc., and is connected to the vehicle frame 2 via a hinge pin 8p, and rises and falls relative to the vehicle frame 2. The lifting cylinder 9 connects the vehicle frame 2 and the cargo box 8 at a position forward of the hinge pin 8p, and extends and retracts to raise and lower the cargo box 8. Figure 1 In the embodiment, a prime mover 15 ( Figure 2 )、Generator 16( Figure 2 ) etc., and a control box 6 is mounted above each of these devices. The control box 6 contains a power control device 30 ( Figure 5 ). The power control device 30 is, for example, an inverter.

[0029] Figure 2 This is a top view of the frame. Figure 3 is a side view. Strictly speaking, Figure 2 express Figure 3 The cross-sectional view from the direction B in the figure is: Figure 3 express Figure 2 A cross-sectional view taken along the arrow A in FIG. Wet brakes 12 are mounted inside the left and right speed reducers 11 that support the left and right rear wheels 3r, respectively. The wet brakes 12 are brakes that use oil to cool the heat generated during braking. The dump truck 1 is equipped with a wet brake cooling system ( Figure 4 ).

[0030] Although not shown, the wet brake 12 includes a plate as a stationary body fixed to the vehicle body side and a plate rotating at the same speed as the speed reducer 11, and brakes the dump truck 1 by squeezing these two plates. A tank 13 storing brake cooling oil and operating oil is provided on the left side of the vehicle frame 2. The inside of the tank 13 is partitioned by a partition 14 so that the brake cooling oil and the operating oil are not mixed.

[0031] A prime mover 15 is mounted on the front part of the vehicle frame 2 with the output shaft facing forward and backward. In the present embodiment, the prime mover 15 is an engine (internal combustion engine). A generator 16, a hydraulic pump 17, and a pilot pump 18 are connected to the output shaft of the prime mover 15. A hydraulic pump 19 for cooling that circulates brake cooling oil between the tank 13 and the heat exchanger 24, and an electric motor 21 that drives the hydraulic pump 19 are provided on the upper side of the hydraulic pump 17. The power required to drive the hydraulic pump 19 is smaller than the power required to drive the hydraulic motor 25.

[0032] A control valve 22 is provided at the lower side of the hydraulic pump 17. A radiator 23 is provided on the front surface of the body of the dump truck 1. A heat exchanger (brake cooling oil cooler) 24 for cooling brake cooling oil as a cooling target fluid is mounted on the front side of the radiator 23. A hydraulic motor 25 is provided at the rear side of the radiator 23, and a fan 26 is connected to the output shaft of the hydraulic motor 25. The fan 26 is driven by the hydraulic motor 25 to send air to the radiator 23 and the heat exchanger 24.

[0033] A beam 27 extending in the left-right direction is provided on the upper portion of the vehicle frame 2 , and a control box 6 is provided on the upper portion of the beam 27 .

[0034] -Hydraulic circuit-

[0035] Figure 4 1 is a hydraulic circuit diagram of the dump truck 1. When the hydraulic pump 19 is driven by the electric motor 21, the brake cooling oil is sucked into the hydraulic pump 19 from the tank 13 via the suction pipe 31 and discharged to the discharge pipe 32 of the hydraulic pump 19. The brake cooling oil discharged from the hydraulic pump 19 is sent to the heat exchanger 24 via the discharge pipe 32, and after being cooled in the heat exchanger 24, it returns to the tank 13 via the wet brake 12. A safety valve 34 is provided in the discharge pipe 32. The maximum pressure of the discharge pipe 32 is determined by the safety valve 34. In addition, a temperature sensor 33 is provided in the suction pipe 31. The temperature of the brake cooling oil flowing in the suction pipe 31 is measured by the temperature sensor 33. The measured temperature of the brake cooling oil is output from the temperature sensor 33 and input to the controller 50 (described later).

[0036] On the other hand, the hydraulic pump 17 and the pilot pump 18 are driven by the prime mover 15. The hydraulic pump 17 sucks the hydraulic oil from the tank 13 via the suction pipe 36 and discharges the pressure oil to the discharge pipe 37. The pilot pump 18 sucks the hydraulic oil from the tank 13 via the suction pipe 38 and discharges the pressure oil to the discharge pipe 39. The maximum pressure of the discharge pipes 37 and 39 is also defined by the safety valve in the same manner as the safety valve 34.

[0037] The control valve 22 connects the hydraulic pump 17, the tank 13 (central bypass oil passage 35), and the hydraulic motor 25. The valve core of the control valve 22 is driven by the pilot pressure generated by the solenoid valve 41 with the pressure oil from the pilot pump 18 as the initial pressure. The working oil discharged from the hydraulic pump 17 is sent to the central bypass oil passage 35 and returns to the tank 13 via the central bypass oil passage 35. When the valve core of the control valve 22 moves, the central bypass oil passage 35 is throttled, and on the other hand, the connection opening (not shown) to the hydraulic motor 25 is opened according to the movement amount of the valve core, and the pressure oil is supplied to the hydraulic motor 25. The rotation speed of the hydraulic motor 25 is controlled according to the supply flow rate of the pressure oil, that is, the movement amount of the valve core. The pressure oil that drives the hydraulic motor 25 returns to the control valve 22 and returns to the tank 13 via the central bypass oil passage 35.

[0038] -Circuit-

[0039] Figure 5 Controller 50 is a vehicle-mounted computer equipped with a processing device such as a CPU and a storage device such as a memory, and has a function of controlling hydraulic pump 19 and hydraulic motor 25 according to the measured temperature T of the brake cooling oil. Controller 50 outputs a control signal to power control device 30 and solenoid valve 41 to control the circulation flow rate of the brake cooling oil at heat exchanger 24 and the rotation speed of fan 26.

[0040] The power control device 30 supplies the power supplied from the generator 16 to the electric motor 21 based on the control signal from the controller 50. In this way, the amount of power supplied to the electric motor 21 is controlled, and the amount of brake cooling oil circulated and supplied to the wet brake 12 is controlled according to the measured temperature of the brake cooling oil.

[0041] On the other hand, the solenoid valve 41 is driven based on a control signal from the controller 50, and the control valve 22 is driven according to the pilot pressure controlled by the solenoid valve 41. Thus, the supply flow rate of the pressurized oil to the hydraulic motor 25 is controlled, and the rotation speed of the fan 26 is controlled according to the measured temperature of the brake cooling oil.

[0042] -Control Table-

[0043] Figure 6 1 is a diagram showing a control table of the controller 50 for the fan speed and the brake cooling oil flow rate. Figure 6 The control table shown. As the values ​​of the prescribed control table, the pump minimum speed Pmin (first pump speed), the pump maximum speed Pmax (second pump speed), the motor minimum speed Mmin (first motor speed), the motor maximum speed Mmax (second motor speed), the first temperature T1, the second temperature T2, the third temperature T3 and the fourth temperature T4 are stored, and the relationship of the first temperature T1<second temperature T2<third temperature T3<fourth temperature T4 is present. In the present embodiment, the pump minimum speed Pmin is the minimum speed of the hydraulic pump 19, the pump maximum speed Pmax is the maximum speed of the hydraulic pump 19, the motor minimum speed Mmin is the minimum speed of the hydraulic motor 25, and the motor maximum speed Mmax is the maximum speed of the hydraulic motor 25. The first temperature T1 corresponds to the pump minimum speed Pmin, and the second temperature T2 corresponds to the pump maximum speed Pmax. The third temperature T3 corresponds to the motor minimum speed Mmin, and the fourth temperature T4 corresponds to the motor maximum speed Mmax. The controller 50 applies the measured temperature T of the brake cooling oil input from the temperature sensor 33 to the control table. Figure 6The rotation speeds of the hydraulic pump 19 and the hydraulic motor 25 are determined according to a control table, and control signals are output to the electric control device 30 and the solenoid valve 41.

[0044] In addition, the flow rate of the brake cooling oil (for example, the discharge flow rate of the hydraulic pump 19) and the rotation speed of the electric motor 21, which are proportional to the rotation speed of the hydraulic pump 19, can be treated as values ​​synonymous with the rotation speed of the hydraulic pump 19 in terms of control concept. Figure 6 In the control table, the rotation speed of the hydraulic pump 19 is specified by the relationship between the measured temperature T and the flow rate of the brake cooling oil. According to the control table of the rotation speed of the hydraulic pump 19, if the measured temperature T of the temperature sensor 33 is less than the first temperature T1 (T<T1), the controller 50 outputs a control signal to the electric control device 30 so that the hydraulic pump 19 is driven at the minimum rotation speed Pmin. When the measured temperature T is between the first temperature T1 and the second temperature T2 (T1≤T<T2), the controller 50 outputs a control signal to the electric control device 30 so that the rotation speed of the hydraulic pump 19 increases from Pmin to Pmax in accordance with the increase in T (for example, proportionally and linearly). When T1≤T<T2 and T decreases, the controller 50 also increases in accordance with the decrease in T. Figure 6 The control table reduces the rotation speed of the hydraulic pump 19. If the measured temperature T is equal to or higher than the second temperature T2 (T ≥ T2), the controller 50 outputs a control signal to the power control device 30 to drive the hydraulic pump 19 at the maximum rotation speed Pmax.

[0045] Regarding the rotation speed of the hydraulic motor 25, a value in a proportional relationship with the rotation speed of the fan 26 or the like can also be treated as a value synonymous with the control concept. Figure 6 In the control table of the rotation speed of the hydraulic motor 25, the relationship between the measured temperature T of the brake cooling oil and the rotation speed of the fan 26 is used to define the rotation speed of the hydraulic motor 25. According to the control table of the rotation speed of the hydraulic motor 25, if the measured temperature T of the temperature sensor 33 is less than the third temperature T3 (T<T3), the controller 50 outputs a control signal to the electric control device 30 so that the hydraulic motor 25 is driven at the minimum rotation speed Mmin. When the measured temperature T is between the third temperature T3 and the fourth temperature T4 (T3≤T<T4), the controller 50 outputs a control signal to the electric control device 30 so that the rotation speed of the hydraulic motor 25 increases from Mmin to Mmax in accordance with the increase in T (for example, proportionally and linearly). When T3≤T<T4 and T decreases, the controller 50 also increases in accordance with the decrease in T. Figure 6 The control table reduces the rotation speed of the hydraulic motor 25. If the measured temperature T is equal to or higher than the fourth temperature T4 (T≥T4), the controller 50 outputs a control signal to the power control device 30 to drive the hydraulic motor 25 at the maximum rotation speed Mmax.

[0046] -Pmin-

[0047] Here, a floating seal (not shown) is built into the wet brake 12 to prevent leakage of the brake cooling oil. The floating seal has low pressure resistance, and the pressure of the brake cooling oil applied to the wet brake 12 must be suppressed to be lower than the pressure resistance of the floating seal. When the temperature of the brake cooling oil is low, the viscosity increases, and the pressure inside the wet brake 12 is likely to increase due to the inflow of the brake cooling oil. Therefore, the minimum flow rate (the minimum rotation speed Pmin of the hydraulic pump 19) needs to be set so that the floating seal will not be damaged even at the lowest oil temperature assumed for the brake cooling oil. However, the minimum rotation speed Pmin of the hydraulic pump 19 is set to a value greater than 0. This is to ensure the circulation of the brake cooling oil whose temperature is measured by the temperature sensor 33.

[0048] -Pmax / Mmax-

[0049] The maximum pump speed Pmax and the maximum motor speed Mmax are values ​​that define the maximum cooling performance of the brake cooling oil. Therefore, it is necessary to assume the maximum heat generated by the wet brake 12 that may be generated by braking when the dump truck 1 is in operation, and set the maximum pump speed Pmax and the maximum motor speed Mmax in a manner that ensures sufficient cooling performance.

[0050] In addition, the pump minimum speed Pmin, the pump maximum speed Pmax, the motor minimum speed Mmin, and the motor maximum speed Mmax may be, for example, predetermined speeds or speed ranges determined in consideration of the above-mentioned aspects, or may be speeds of lower or upper limits determined by mechanical or electrical specifications. That is, for example, the pump maximum speed Pmax may be set to a speed of the hydraulic pump 19 that is higher than the pump minimum speed Pmin. In addition, for example, the motor maximum speed Mmax may be set to a speed of the hydraulic motor 25 that is higher than the motor minimum speed Mmin.

[0051] -T1, T2, T3, T4-

[0052] The settings of the first temperature T1, the second temperature T2, the third temperature T3, and the fourth temperature T4 are explained. If the first temperature T1, the second temperature T2, the third temperature T3, and the fourth temperature T4 are all set relatively low, the rotation speeds of the hydraulic pump 19 and the hydraulic motor 25 begin to increase when the measured temperature T has not risen that much. In this case, it is advantageous in maintaining the brake cooling oil at a low temperature, and the brake cooling oil is less likely to overheat during braking. However, on the other hand, the power consumption of the hydraulic pump 19 and the hydraulic motor 25 increases, and the fuel efficiency deteriorates. Therefore, from the perspective of the balance between cooling performance and fuel efficiency, it is preferred that the first temperature T1, the second temperature T2, the third temperature T3, and the fourth temperature T4 be set as high as possible within a range that can avoid overheating of the brake cooling oil.

[0053] At this time, if Figure 6 As shown in the control table, the third temperature T3 is set to be higher than the first temperature T1. Thus, when the measured temperature T rises from a temperature lower than the first temperature T1, before the rotation speed of the hydraulic motor 25 starts to rise from the minimum rotation speed Mmin, the rotation speed of the hydraulic pump 19 starts to rise from the minimum rotation speed Pmin. As described above, the minimum rotation speed Pmin of the hydraulic pump 19 is greater than 0, and when the dump truck 1 is in operation, the hydraulic pump 19 is continuously driven at a rotation speed greater than the minimum rotation speed Pmin, and the brake cooling oil continues to circulate. In contrast, the minimum rotation speed Mmin of the hydraulic motor 25 is 0, and if the measured temperature T is lower than the third temperature T3, the fan 26 stops. This setting is because if the measured temperature T is low, there is no need to air-cool the brake cooling oil.

[0054] Therefore, when the measured temperature T exceeds the first temperature T1 and rises, the rotation speed of the hydraulic pump 19 increases, and the flow rate of the brake cooling oil increases, but the measured temperature T does not reach the third temperature T3 and turns to decrease, the fan 26 is not driven. In particular, in the present embodiment, since the third temperature T3 is set higher than the second temperature T2, the control of the heat dissipation amount is tried only by controlling the circulation flow rate of the brake cooling oil within the temperature range in which the circulation flow rate of the brake cooling oil can be increased or decreased. In addition, in the present embodiment, the heat exchanger 24 is provided on the front surface of the dump truck 1, and the running wind blows to the heat exchanger 24. Therefore, even when the fan 26 is stopped, the heat dissipation amount is increased by synergizing with the increase in the circulation flow rate of the brake cooling oil, and the brake cooling oil is reasonably cooled.

[0055] -Comparative Example-

[0056] Figure 8 The hydraulic circuit shown in this figure includes a main fan 101 , a main hydraulic motor 102 , an auxiliary fan 103 , an auxiliary hydraulic motor 104 , a hydraulic pump 105 , a flow priority valve 106 , a thermal valve 107 , and a switching valve 108 .

[0057] The thermal valve 107 outputs an on signal if the temperature of the cooling target fluid (e.g., engine cooling water) is above a set value, and outputs an off signal if it is below the set value. The switching valve 108 is driven according to the signal from the thermal valve 107 to cut off and open the discharge pipeline of the hydraulic pump 105. The hydraulic pump 105 is driven by the engine. When the engine speed is low and the discharge flow rate of the hydraulic pump 105 is below a predetermined value, only the pressure oil is supplied to the main hydraulic motor 102 via the flow priority valve 106. On the contrary, when the engine speed is high and the discharge flow rate is greater than a predetermined value, the pressure oil is supplied to the main hydraulic motor 102 and the auxiliary hydraulic motor 104 via the flow priority valve 106.

[0058] In the comparative example of the above structure, when the temperature of the cooling target fluid is above the set value, the thermal valve 107 outputs a connection signal, and the discharge pipeline is opened through the switching valve 108. At this time, if the engine speed is below the predetermined value, the pressure oil is only supplied to the main hydraulic motor 102 through the flow priority valve 106, and only the main fan 101 participates in the cooling of the cooling target fluid. On the contrary, if the engine speed is greater than the predetermined value, the pressure oil is supplied to the main hydraulic motor 102 and the auxiliary hydraulic motor 104 through the flow priority valve 106, and the main fan 101 and the auxiliary fan 103 participate in the cooling of the cooling target fluid. Thus, it is switched to one or two according to the heat dissipation required for the cooling target fluid.

[0059] However, in the comparative example, when heat dissipation of the cooling target fluid is required, at least one fan needs to be driven. The power required to drive a large hydraulically driven fan is large, and if the configuration is such that when heat dissipation is required, one or more fans are always driven regardless of the required heat dissipation amount, the fuel efficiency of the transport vehicle deteriorates. In addition, the operating noise of the fan may also increase the fatigue of the operator and cause noise problems to neighbors.

[0060] -Effect-

[0061] (1) In the present embodiment, the hydraulic pump 19 for circulating brake cooling oil as a cooling target fluid is set to be motor-driven rather than engine-driven, so that the circulation flow rate of the cooling target fluid can be controlled regardless of the rotation speed of the prime mover (engine) 15. The hydraulic motor 25 driving the fan 26 can also be controlled regardless of the engine speed by adjusting the supply flow rate of the pressure oil by the control valve 22.

[0062] Furthermore, in the present embodiment, when the hydraulic pump 19 and the hydraulic motor 25 are controlled based on the measured temperature T of the brake cooling oil, when the measured temperature T rises, the rotation speed of the hydraulic pump 19 starts to increase before the rotation speed of the hydraulic motor 25 starts to increase ( Figure 6 ). That is, even if the measured temperature T starts to rise, the fan 26 is not driven first, and the heat dissipation is increased only by increasing the circulation flow rate of the brake cooling oil by the hydraulic pump 19. Only when the heat cannot be sufficiently dissipated by the control of the hydraulic pump 19 alone, the fan 26 is driven according to the required heat dissipation while the circulation flow rate of the brake cooling oil is increased. For example, when the measured temperature T rises, when the flow rate of the brake cooling oil is increased by the increase in the rotation speed of the hydraulic pump 19 but the third temperature T3 is not reached and the brake cooling oil turns to cooling, the fan 26 is not driven at all. In this way, the driving frequency and rotation speed of the fan 26 can be suppressed, the fuel efficiency of the dump truck 1 can be improved, the noise can be suppressed, and the fatigue of the operator can be reduced.

[0063] In addition, when the fan 26 is started, the circulation flow rate of the brake cooling oil in the heat exchanger 24 is always the largest, so the cooling efficiency of the brake cooling oil is high relative to the air supply volume of the fan 26, and the rotation speed of the fan 26 is difficult to increase. This is also an advantage of the coordinated control of the hydraulic pump 19 and the hydraulic motor 25.

[0064] (2) In particular, in the present embodiment, the third temperature T3 at which the fan 26 starts to rotate is set higher than the second temperature T2 at which the rotation speed of the hydraulic pump 19 reaches the maximum rotation speed Pmax. Therefore, as long as there is an increase in the rotation speed of the hydraulic pump 19 that can increase the heat dissipation amount of the brake cooling oil, the fan 26 does not rotate. As a result, the drive frequency of the fan 26 can be suppressed to a lower level.

[0065] (3) In addition, in the present embodiment, the heat exchanger 24 is provided on the front surface of the dump truck 1, and the running wind can be guided to the heat exchanger 24. When the brake cooling oil is heated up during braking, even when the fan 26 is stopped, the circulation flow rate of the brake cooling oil and the air cooling effect brought by the running wind can cooperate to reasonably cool the brake cooling oil.

[0066] (4) In addition, by setting the minimum rotation speed Pmin of the hydraulic pump 19 to a value greater than 0, it is possible to ensure the flow of the brake cooling oil whose temperature is measured by the temperature sensor 33. Thus, the temperature of the brake cooling oil, which is the basis for controlling the hydraulic pump 19 and the hydraulic motor 25, can be appropriately evaluated, and the reliability of the hydraulic pump 19 and the hydraulic motor 25 can be ensured.

[0067] (5) If the temperature sensor 33 is provided in the return pipe of the brake cooling oil (the pipe connecting the outlet of the wet brake 12 and the tank 13), the temperature of the brake cooling oil immediately after passing through the wet brake 12 is measured, and the increase and decrease of the measured temperature T becomes drastic. As a result, even if the temperature of the brake cooling oil in the tank 13 hardly increases, there is a possibility that the control of the hydraulic pump 19 and the hydraulic motor 25 functions too sensitively and wastes power.

[0068] In contrast, in the present embodiment, the temperature sensor 33 is provided in the suction pipe 31 of the hydraulic pump 19, thereby measuring the temperature of the brake cooling oil supplied to the wet brake 12 after the temperature change in the tank 13 is stabilized, and the above-mentioned overly sensitive control can be suppressed. In this way, it is also possible to avoid unnecessary driving of the fan 26 and the like and suppress waste of power.

[0069] (Second Embodiment)

[0070] Figure 7 2 is a hydraulic circuit diagram of a transport vehicle according to a second embodiment of the present invention. Figure 7In the embodiment, the same or corresponding elements as those in the first embodiment are marked with Figure 4 The same symbols are used and the description is appropriately omitted.

[0071] The present embodiment is different from the first embodiment in that the invention is applied to a cooling system for working oil. In the present embodiment, a heat exchanger (working oil cooler) 61 is provided in the central bypass oil passage 35. Like the heat exchanger 24, the heat exchanger 61 is also provided on the front surface of the dump truck 1, for example. The fan 26 blows air to the heat exchanger 24 and the heat exchanger 61. In addition, the hydraulic pump 17 is driven by an electric motor 62 instead of the prime mover (engine) 15. A temperature sensor 63 for measuring the temperature of the working oil is provided in the suction pipe 36 of the hydraulic pump 17.

[0072] In this embodiment, regarding the cooling system of the hydraulic oil, the controller 50 controls the rotation speed of the hydraulic pump 17 and the hydraulic motor 25 in the same manner as the control of the cooling system of the brake cooling oil. The control table related to the control of the hydraulic pump 17 and the hydraulic motor 25 is as follows: Figure 6 The control table shown in the figure can be similarly set so that the fan speed and the working oil circulation amount are shifted in association with the working oil temperature. That is, when the measured temperature T of the working oil from the temperature sensor 63 rises, the speed of the hydraulic pump 17 starts to rise from the minimum speed Pmin (>0) before the speed of the hydraulic motor 25 starts to rise from the minimum speed Mmin (=0). Therefore, when the working oil temperature rises, if the working oil circulation amount of the heat exchanger 61 increases due to the increase in the speed of the hydraulic pump 17 and the measured temperature T of the working oil decreases before reaching the third temperature T3, the fan 26 is not driven as long as it is related to the cooling of the working oil. With regard to other structures, this embodiment is the same as the first embodiment.

[0073] Therefore, the present invention can also be applied to a cooling system for hydraulic oil or the like other than brake cooling oil, and the same effects can be obtained.

[0074] also, Figure 7 Since the fan 26 is shared by the brake cooling oil cooling system and the working oil cooling system, the rotation speed of the fan 26 is controlled based on, for example, the maximum value of the measured temperatures T of the brake cooling oil and the working oil. If the heat exchangers 24 and 61 are configured to be blown with separate fans, the fan for cooling the brake cooling oil can be controlled independently of the measured temperature of the working oil, and the fan for cooling the working oil can be controlled independently of the measured temperature of the brake cooling oil.

[0075] (Variation Example)

[0076] In the above embodiment, the present invention is applied to the cooling system of brake cooling oil and working oil, but the present invention can also be applied to the cooling system of engine cooling water and engine oil, etc., and the same effect can be obtained. In addition, the electric motor 21 is illustrated as the driving device of the hydraulic pump 19, but as long as the rotation speed of the hydraulic pump 19 can be arbitrarily controlled, it can also be configured to, for example, drive the hydraulic pump 19 using a hydraulic motor.

[0077] Furthermore, although the case where the present invention is applied to the dump truck 1 is exemplified, the present invention can also be applied to other transport vehicles.

[0078] In addition, Figure 6 The example of setting the second temperature T2 to be lower than the third temperature T3 is described in the above, but the first temperature T1 (<T2) can be lower than the third temperature T3 (<T4) as long as the circulation flow rate of the heat exchanger is increased before the fan is started. Therefore, as long as T1 < T3, the second temperature T2 can also be higher than the third temperature T3. However, if the goal is to achieve a greater power reduction effect, it is preferred to Figure 6 As illustrated, the second temperature T2 is set lower than the third temperature T3.

[0079] In addition, in the above embodiment, the fan 26 is stopped when the measured temperature T is lower than the third temperature T3, but the fan 26 may be rotated at a low speed. That is, the minimum rotation speed Mmin of the hydraulic motor 25 may be set to be greater than 0. However, if a larger power reduction effect is desired, it is preferable to Figure 6 As shown in the example, Mmin=0.

[0080] In addition, a linear control table is exemplified for the control of the hydraulic pumps 17, 19, and the hydraulic motor 25, but a control table may be used that changes the rotation speed of the hydraulic pumps 17, 19, and the hydraulic motor 25 in a step-like or curve-like manner according to the measured temperature T. In the case of the step-like manner, in addition to simplifying the control, it is also expected that the change in the control of the hydraulic pumps 17, 19, and the hydraulic motor 25 will be reduced relative to the change in the measured temperature T. However, when the control table is set to be linear, the rotation speed of the hydraulic pumps 17, 19, and the hydraulic motor 25 follows the measured temperature T in real time, so it is reasonable that the required heat dissipation follows the measured temperature T and changes continuously.

[0081] Explanation of symbols

[0082] 1—dump truck (transport vehicle), 2—frame, 8—cargo box, 13—tank, 17—hydraulic pump, 19—hydraulic pump, 24—heat exchanger, 25—hydraulic motor, 26—fan, 31—suction pipe, 33—temperature sensor, 36—suction pipe, 50—controller, 61—heat exchanger, 63—temperature sensor, Mmax—maximum motor speed, Mmin—minimum motor speed, Pmax—maximum pump speed, Pmin—minimum pump speed, T—measured temperature, T1—first temperature, T2—second temperature, T3—third temperature, T4—fourth temperature.

Claims

1. A transport vehicle comprising a frame and a cargo box which is arranged on the frame in a manner that allows it to rise and fall. The transport vehicle is characterized by having: A tank storing a cooling object fluid; A heat exchanger for cooling the cooling object fluid; a pump that circulates the cooling target fluid between the tank and the heat exchanger; A temperature sensor for detecting the temperature of the cooling target fluid; a fan that supplies air to the heat exchanger; a hydraulic motor that drives the fan; and a controller that controls the pump and the hydraulic motor according to the temperature detected by the temperature sensor, As far as the controller is concerned, storing a first pump speed and a first temperature corresponding to the first pump speed, a second pump speed higher than the first pump speed and a second temperature corresponding to the second pump speed, a first motor speed and a third temperature corresponding to the first motor speed, a second motor speed higher than the first motor speed and a fourth temperature corresponding to the second motor speed, When the detected temperature is between the first temperature and the second temperature, the rotation speed of the pump is increased from the first pump rotation speed to the second pump rotation speed according to the increase of the detected temperature, When the detected temperature is between the third temperature and the fourth temperature, the rotation speed of the hydraulic motor is increased from the first motor rotation speed to the second motor rotation speed according to the increase of the detected temperature; The third temperature is set higher than the first temperature, and when the detected temperature rises, the rotation speed of the pump starts to increase before the rotation speed of the hydraulic motor starts to increase.

2. The transport vehicle according to claim 1, It is characterized in that The minimum speed of the pump is a value greater than 0, The minimum rotation speed of the hydraulic motor is 0.

3. The transport vehicle according to claim 1, It is characterized in that The third temperature is higher than the second temperature.

4. The transport vehicle according to claim 1, It is characterized in that The temperature sensor is provided on a suction pipe of the pump.

5. The transport vehicle according to claim 1, It is characterized in that The cooling target fluid is brake cooling oil.

6. The transport vehicle according to claim 1, It is characterized in that The cooling fluid is hydraulic oil.

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