Transportation vehicle

Abstract

The present invention provides a transportation vehicle comprising: a heat exchanger that cools a cooling target fluid; a pump that circulates the cooling target fluid; a temperature sensor that detects the temperature of the cooling target fluid; a fan that blows air to the heat exchanger; and a hydraulic motor that drives 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 raised from a first pump rotational speed to a second pump rotational speed in accordance with a rise in the detected temperature. When the detected temperature is between a third temperature and a fourth temperature, the rotational speed of the hydraulic motor is raised from a first motor rotational speed to a second motor rotational speed in accordance with a rise in the detected temperature. The first temperature is set higher than the third temperature. When the detected temperature rises, the raising of the rotational speed of the pump is commenced before the commencement of the raising of the rotational speed of the hydraulic motor. Thus, it is possible to suppress the rotational speed and the frequency of driving of the fan, to improve fuel consumption, and to suppress noise.

Description

Transport vehicle

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

[0002] Fans that blow air into heat exchangers such as oil coolers mounted on mining dump trucks, mining shovels, trucks that travel on public roads, and the like are generally driven by a direct connection to the engine. However, due to factors such as the increasing size of the cooling system and restrictions on the placement of the heat exchanger and engine, electrically or hydraulically driven fans are often used. In particular, hydraulically driven fans tend to be used for large fans that are not suitable for electrically driven operation. One known cooling system that uses hydraulically driven fans has multiple fans and changes the number of fans driven depending on the measured temperature of the fluid to be cooled (see Patent Document 1).

[0003] Japanese Patent Application Publication No. 10-259728

[0004] However, in the system of Patent Document 1, which changes the number of rotating fans according to the required amount of heat dissipation, the control of the amount of heat dissipation depends only on the airflow rate, and at least one fan must be driven when heat dissipation is required.

[0005] As mentioned above, hydraulically driven fans are often large. A large amount of power is required to drive such a large fan, and increasing the fan's operating frequency and rotation speed can worsen the fuel efficiency of the transport vehicle. Additionally, the operating noise of the fan can lead to increased operator fatigue and noise problems for neighbors.

[0006] An object of the present invention is to provide a transport vehicle that can reduce the driving frequency and rotation speed of the fan to improve fuel efficiency and reduce noise.

[0007] In order to achieve the above object, the present invention provides a transport vehicle having a body frame and a loading platform provided on the body frame in a manner that allows it to be raised and lowered, the transport vehicle comprising: a tank for storing a fluid to be cooled; a heat exchanger for cooling the fluid to be cooled; a pump for circulating the fluid to be cooled between the tank and the heat exchanger; a temperature sensor for detecting the temperature of the fluid to be cooled; a fan for blowing air to the heat exchanger; a hydraulic motor for driving the fan; and a controller for controlling the pump and the hydraulic motor in accordance with the temperature detected by the temperature sensor, the controller being configured to control a first pump rotation speed and a first temperature corresponding to the first pump rotation speed, a second pump rotation speed higher than the first pump rotation speed and a second temperature corresponding to the second pump rotation speed, a first motor rotation speed, a second pump rotation speed higher than the first pump rotation speed, a first motor rotation speed, a second pump rotation speed, a first motor rotation speed, a second motor ... second motor rotation speed, a first motor rotation speed, a second motor rotation speed, a second motor rotation speed, a first motor rotation speed, a second motor rotation speed, a second motor rotation speed, a first motor rotation speed, a and a third temperature corresponding to the first motor rotation speed, a second motor rotation speed higher than the first motor rotation speed, and a fourth temperature corresponding to the second motor rotation speed, wherein 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 in response to an increase in the detected temperature, and 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 in response to an increase in the detected temperature, wherein the third temperature is set higher than the first temperature, and when the detected temperature increases, the rotation speed of the pump starts to increase before the rotation speed of the hydraulic motor starts to increase.

[0008] According to the present invention, it is possible to reduce the driving frequency and rotation speed of the fan, thereby improving fuel efficiency and suppressing noise.

[0009] A side view of a dump truck, which is an example of a transport vehicle according to the first embodiment of the present invention. A plan view of a body frame of the transport vehicle according to the first embodiment of the present invention. A side view of a body frame of the transport vehicle according to the first embodiment of the present invention. A hydraulic circuit diagram of the transport vehicle according to the first embodiment of the present invention. An electrical circuit diagram of a cooling system for brake cooling oil provided in the transport vehicle according to the first embodiment of the present invention. A diagram showing a control table for fan rotation speed and brake cooling oil flow rate by a controller provided in the transport vehicle according to the first embodiment of the present invention. A hydraulic circuit diagram of a transport vehicle according to the second embodiment of the present invention. A diagram showing a hydraulic circuit diagram of a transport vehicle according to a comparative example.

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0011] (First embodiment) - Transport vehicle - Figure 1 is a side view of a dump truck, which is an example of a transport vehicle according to a first embodiment of the present invention. The left and right in Figure 1 are the front and rear of the dump truck 1.

[0012] The dump truck 1 shown in the figure includes a body frame 2 and a plurality of wheels rotatably mounted on the body frame 2. The wheels include left and right front wheels 3f and left and right rear wheels 3r. One front wheel 3f is disposed on each of the left and right ends of the front part of the body frame 2. Two rear wheels 3r are disposed on each of the left and right ends of the rear part of the body frame 2. The front wheels 3f are steered wheels that are steered according to a steering angle input via a steering handle or the like, and are driven wheels that are driven by the rear wheels 3r via the road surface of the road on which the dump truck 1 travels. A travel motor (not shown) and a reducer 11 ( FIG. 2 ) that adjusts the rotation speed of the rear wheels 3r are individually connected to the rotary shafts of the left and right rear wheels 3r, which are drive wheels.

[0013] The dump truck 1 is also equipped with a deck 4, a cab 5, a control cabinet 6, and multiple grid boxes 7. The deck 4 is the floor on which the operator walks, and is located above the front wheels 3f. The cab 5 is the driver's compartment in which the operator sits, and is installed on the top surface of the deck 4. The cab 5 is equipped with a driver's seat where the operator sits, as well as operation pedals (accelerator pedal, brake pedal, etc.) that control the traveling speed of the dump truck 1, and the steering handle mentioned above. The control cabinet 6 is a room that houses various types of power equipment, and is mounted at the front of the vehicle body. The grid box 7 is a device that dissipates surplus energy resulting from regenerative power generated during braking as heat, and is located on the right side of the control cabinet 6.

[0014] The dump truck 1 is further equipped with a bed 8 and a hoist cylinder 9. The bed 8 is a platform on which cargo such as earth, sand, ore, etc. is loaded. The bed 8 is connected to the body frame 2 via a hinge pin 8p and is raised and lowered relative to the body frame 2. The hoist cylinder 9 connects the body frame 2 and the bed 8 at a position forward of the hinge pin 8p and extends and retracts to raise and lower the bed 8. In FIG. 1 , a prime mover 15 ( FIG. 2 ), a generator 16 ( FIG. 2 ), etc. are disposed between the left and right front wheels 3 f of the body frame 2, and a control cabinet 6 is mounted above each of these devices. A power control device 30 ( FIG. 5 ) is housed inside the control cabinet 6. The power control device 30 is, for example, an inverter.

[0015] Figure 2 is a plan view of the body frame, and Figure 3 is a side view. Strictly speaking, Figure 2 is a cross-sectional view taken along arrow B in Figure 3, and Figure 3 is a cross-sectional view taken along arrow A in Figure 2. Wet brakes 12 are mounted inside left and right speed reducers 11 that individually support the left and right rear wheels 3r. The wet brakes 12 are brakes that use oil to cool the heat generated during braking, and the dump truck 1 is equipped with a wet brake cooling system (Figure 4) for cooling the heated oil.

[0016] Although not shown, the wet brake 12 is equipped inside with a plate that is a stationary body fixed to the vehicle body side and a plate that rotates at the same speed as the reducer 11, and the dump truck 1 is braked by pressing these two plates together. A tank 13 that stores brake cooling oil and hydraulic oil is installed on the left side of the vehicle body frame 2. The inside of the tank 13 is separated by a partition 14 so that the brake cooling oil and hydraulic oil do not mix.

[0017] A prime mover 15 is mounted on the front of the body frame 2 with its output shaft facing forward and backward. In this 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 cooling hydraulic pump 19 that circulates brake cooling oil between the tank 13 and a heat exchanger 24, and an electric motor 21 that drives the hydraulic pump 19 are installed above the hydraulic pump 17. The power required to drive the hydraulic pump 19 is less than the power required to drive the hydraulic motor 25.

[0018] A control valve 22 is provided below the hydraulic pump 17. A radiator 23 is provided on the front side of the body of the dump truck 1. A heat exchanger (brake cooling oil cooler) 24 that cools brake cooling oil, which is the fluid to be cooled, is mounted in front of the radiator 23. A hydraulic motor 25 is provided behind 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.

[0019] A beam 27 extending in the left-right direction is provided on the upper part of the body frame 2, and a control cabinet 6 is provided on the upper part of this beam 27.

[0020] -Hydraulic Circuit- Figure 4 is a hydraulic circuit diagram of the dump truck 1. When the hydraulic pump 19 is driven by the electric motor 21, 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, cooled in the heat exchanger 24, and then returned to the tank 13 via the wet brakes 12. A relief valve 34 is provided in the discharge pipe 32. The maximum pressure of the discharge pipe 32 is determined by the relief valve 34. A temperature sensor 33 is also provided in the suction pipe 31. The temperature sensor 33 measures the temperature of the brake cooling oil flowing through the suction pipe 31. The measured temperature of the brake cooling oil is output from the temperature sensor 33 and input to a controller 50 (described later).

[0021] Meanwhile, the prime mover 15 drives a hydraulic pump 17 and a pilot pump 18. The hydraulic pump 17 draws hydraulic oil from the tank 13 via a suction pipe 36 and discharges the pressurized oil to a discharge pipe 37. The pilot pump 18 draws hydraulic oil from the tank 13 via a suction pipe 38 and discharges the pressurized oil to a discharge pipe 39. The maximum pressures in the discharge pipes 37, 39 are also determined by relief valves, similar to the relief valve 34.

[0022] The control valve 22 connects the hydraulic pump 17, the tank 13 (center bypass oil passage 35), and the hydraulic motor 25. The spool of the control valve 22 is driven by pilot pressure generated by a solenoid valve 41 using pressurized oil from the pilot pump 18 as the source pressure. Hydraulic oil discharged from the hydraulic pump 17 is sent to the center bypass oil passage 35 and returns to the tank 13 via the center bypass oil passage 35. When the spool of the control valve 22 moves, the center bypass oil passage 35 is throttled, while a connection opening (not shown) to the hydraulic motor 25 opens in accordance with the amount of movement of the spool, and pressurized oil is supplied to the hydraulic motor 25. The rotation speed of the hydraulic motor 25 is controlled in accordance with the supply flow rate of pressurized oil, i.e., the amount of movement of the spool. The pressurized oil that drives the hydraulic motor 25 returns to the control valve 22 and then to the tank 13 via the center bypass oil passage 35.

[0023] 5 is an electrical circuit diagram of the brake cooling oil cooling system. The controller 50 is an on-board computer equipped with a processing device such as a CPU and a storage device such as a memory, and has the function of controlling the hydraulic pump 19 and the hydraulic motor 25 in accordance with the measured temperature T of the brake cooling oil. The controller 50 outputs control signals to the power control device 30 and the solenoid valve 41, and controls the circulating flow rate of the brake cooling oil in the heat exchanger 24 and the rotation speed of the fan 26.

[0024] The power control device 30 supplies the electric power from the generator 16 to the electric motor 21 based on a 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 brakes 12 is controlled in accordance with the measured temperature of the brake cooling oil.

[0025] 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 in response to the pilot pressure controlled by the solenoid valve 41. This controls the flow rate of pressure oil supplied to the hydraulic motor 25, and the rotation speed of the fan 26 in response to the measured temperature of the brake cooling oil.

[0026] —Control Table— Figure 6 is a diagram showing a control table for the fan rotation speed and brake cooling oil flow rate controlled by the controller 50. The control table shown in Figure 6 is stored in the memory of the controller 50. Values ​​that define the control table include a minimum pump rotation speed Pmin (first pump rotation speed), a maximum pump rotation speed Pmax (second pump rotation speed), a minimum motor rotation speed Mmin (first motor rotation speed), a maximum motor rotation speed Mmax (second motor rotation speed), a first temperature T1, a second temperature T2, a third temperature T3, and a fourth temperature T4, and the relationship is first temperature T1 < second temperature T2 < third temperature T3 < fourth temperature T4. In this embodiment, the minimum pump rotation speed Pmin is the minimum rotation speed of the hydraulic pump 19, the maximum pump rotation speed Pmax is the maximum rotation speed of the hydraulic pump 19, the minimum motor rotation speed Mmin is the minimum rotation speed of the hydraulic motor 25, and the maximum motor rotation speed Mmax is the maximum rotation speed of the hydraulic motor 25. The minimum pump rotation speed Pmin corresponds to a first temperature T1, and the maximum pump rotation speed Pmax corresponds to a second temperature T2. The minimum motor rotation speed Mmin corresponds to a third temperature T3, and the maximum motor rotation speed Mmax corresponds to a fourth temperature T4. The controller 50 applies the measured temperature T of the brake cooling oil input from the temperature sensor 33 to the control table in Figure 6 to determine the rotation speeds of the hydraulic pump 19 and the hydraulic motor 25, and outputs control signals to the power control device 30 and the solenoid valve 41.

[0027] In addition, the flow rate of the brake cooling oil (e.g., 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. In FIG. 6 , a control table for the rotation speed of the hydraulic pump 19 is defined by the relationship between the measured temperature T of the brake cooling oil and the flow rate. In accordance with this control table for the rotation speed of the hydraulic pump 19, the controller 50 outputs a control signal to the power control device 30 so that the hydraulic pump 19 is driven at the minimum rotation speed Pmin when the temperature T measured by the temperature sensor 33 is less than a first temperature T1 (T<T1). 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 power control device 30 so that the rotation speed of the hydraulic pump 19 increases from Pmin to Pmax in response to an increase in T (e.g., proportionally and linearly). When T decreases in the range of T1≦T<T2, the controller 50 also decreases the rotation speed of the hydraulic pump 19 in accordance with the control table in Fig. 6 in response to the decrease in T. 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 so that the hydraulic pump 19 is driven at the maximum rotation speed Pmax.

[0028] Regarding the rotation speed of the hydraulic motor 25, values ​​in a proportional relationship, such as the rotation speed of the fan 26, can also be treated as synonymous values ​​in terms of control. In FIG. 6 , a control table for the rotation speed of the hydraulic motor 25 is defined by the relationship between the measured temperature T of the brake cooling oil and the rotation speed of the fan 26. In accordance with this control table for the rotation speed of the hydraulic motor 25, the controller 50 outputs a control signal to the power control device 30 so that the hydraulic motor 25 is driven at the minimum rotation speed Mmin when the temperature T measured by the temperature sensor 33 is less than a third temperature T3 (T<T3). When the measured temperature T is between the third temperature T3 and a fourth temperature T4 (T3≦T<T4), the controller 50 outputs a control signal to the power control device 30 so that the rotation speed of the hydraulic motor 25 increases from Mmin to Mmax as T increases (e.g., proportionally and linearly). When T decreases and T3≦T<T4, the controller 50 also decreases the rotation speed of the hydraulic motor 25 in accordance with the control table of FIG. 6 as T decreases. If the measured temperature T is equal to or higher than a fourth temperature T4 (T≧T4), the controller 50 outputs a control signal to the power control device 30 so that the hydraulic motor 25 is driven at the maximum rotation speed Mmax.

[0029] -Pmin- Here, the wet brakes 12 are equipped with floating seals (not shown) that prevent leakage of brake cooling oil. These floating seals have low pressure resistance, so the pressure of the brake cooling oil applied to the wet brakes 12 must be kept below the pressure resistance of the floating seals. Brake cooling oil becomes more viscous at low temperatures, and the inflow of brake cooling oil is likely to increase the pressure inside the wet brakes 12. Therefore, the minimum flow rate (minimum rotation speed Pmin of the hydraulic pump 19) must be set so that the floating seals will not be damaged even at the lowest expected oil temperature of 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 flow of brake cooling oil, the temperature of which is measured by the temperature sensor 33.

[0030] -Pmax / Mmax- The maximum pump rotation speed Pmax and the maximum motor rotation speed Mmax are values ​​that define the maximum value of the cooling performance of the brake cooling oil. Therefore, it is necessary to assume the maximum amount of heat generated by the wet brake 12 due to braking when the dump truck 1 is in operation, and set the maximum pump rotation speed Pmax and the maximum motor rotation speed Mmax so that sufficient cooling performance is ensured.

[0031] The minimum pump rotation speed Pmin, the maximum pump rotation speed Pmax, the minimum motor rotation speed Mmin, and the maximum motor rotation speed Mmax may be predetermined rotation speeds or rotation speed ranges determined, for example, taking into consideration the above-mentioned points, or may be lower or upper limit rotation speeds determined by mechanical or electrical specifications. That is, for example, the maximum pump rotation speed Pmax may be set as a rotation speed of the hydraulic pump 19 that is higher than the minimum pump rotation speed Pmin. Also, for example, the maximum motor rotation speed Mmax may be set as a rotation speed of the hydraulic motor 25 that is higher than the minimum motor rotation speed Mmin.

[0032] -T1, T2, T3, T4- The settings of the first temperature T1, the second temperature T2, the third temperature T3, and the fourth temperature T4 will now be described. If the first temperature T1, the second temperature T2, the third temperature T3, and the fourth temperature T4 are all set low, the rotation speeds of the hydraulic pump 19 and the hydraulic motor 25 begin to increase before the measured temperature T rises significantly. This is advantageous for maintaining a low temperature of the brake cooling oil and makes it less likely for the brake cooling oil to overheat during braking. However, this increases the power consumption of the hydraulic pump 19 and the hydraulic motor 25, resulting in a deterioration in fuel efficiency. Therefore, from the perspective of balancing cooling performance and fuel efficiency, it is desirable to set the first temperature T1, the second temperature T2, the third temperature T3, and the fourth temperature T4 as high as possible within a range that avoids overheating of the brake cooling oil.

[0033] At this time, as shown in the control table of FIG. 6 , the third temperature T3 is set higher than the first temperature T1. As a result, when the measured temperature T rises from a temperature lower than the first temperature T1, the rotation speed of the hydraulic pump 19 begins to rise from the minimum rotation speed Pmin before the rotation speed of the hydraulic motor 25 begins to rise from the minimum rotation speed Mmin. 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 continues to operate at a rotation speed equal to or greater than the minimum rotation speed Pmin, and brake cooling oil continues to circulate. In contrast, if the minimum rotation speed Mmin of the hydraulic motor 25 is 0 and the measured temperature T is lower than the third temperature T3, the fan 26 is stopped. This setting is made because there is no need to air-cool the brake cooling oil when the measured temperature T is low.

[0034] Therefore, if the measured temperature T exceeds the first temperature T1, and the rotation speed of the hydraulic pump 19 increases, causing the brake cooling oil flow rate to increase, resulting in a decrease in the measured temperature T before reaching the third temperature T3, the fan 26 is not driven. In particular, in this embodiment, the third temperature T3 is set higher than the second temperature T2, so that, within the temperature range in which the circulating flow rate of the brake cooling oil can be increased or decreased, the heat dissipation amount is controlled solely by controlling the circulating flow rate of the brake cooling oil. Additionally, in this embodiment, the heat exchanger 24 is installed at the front of the dump truck 1, and is exposed to the wind from traveling. Therefore, even when the fan 26 is stopped, the heat dissipation amount increases synergistically with the increase in the circulating flow rate of the brake cooling oil, thereby rationally cooling the brake cooling oil.

[0035] 8 is a hydraulic circuit diagram of a transport vehicle according to a comparative example. The hydraulic circuit shown in the figure includes a main fan 101, a main hydraulic motor 102, a sub-fan 103, a sub-hydraulic motor 104, a hydraulic pump 105, a flow priority valve 106, a thermosensing valve 107, and a switching valve 108.

[0036] The thermosensing valve 107 outputs an ON signal when the temperature of the fluid to be cooled (e.g., engine coolant) is equal to or higher than a set value, and outputs an OFF signal when the temperature is equal to or lower than the set value. The switching valve 108 is driven by a signal from the thermosensing valve 107 to block and open the discharge line 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 equal to or lower than a predetermined value, pressurized oil is supplied only to the main hydraulic motor 102 via the flow priority valve 106. Conversely, when the engine speed is high and the discharge flow rate is greater than the predetermined value, pressurized oil is supplied to the main hydraulic motor 102 and the sub-hydraulic motor 104 via the flow priority valve 106.

[0037] In the comparative example having the above configuration, when the temperature of the fluid to be cooled reaches or exceeds a set value, an ON signal is output from the thermosensing valve 107, and the switching valve 108 opens the discharge line. At this time, if the engine speed is equal to or lower than a predetermined value, pressurized oil is supplied only to the main hydraulic motor 102 via the flow priority valve 106, and only the main fan 101 contributes to cooling the fluid to be cooled. Conversely, if the engine speed is higher than the predetermined value, pressurized oil is supplied to the main hydraulic motor 102 and the sub hydraulic motor 104 via the flow priority valve 106, and the main fan 101 and the sub fan 103 contribute to cooling the fluid to be cooled. As a result, switching is performed between one and two depending on the amount of heat radiation required for the fluid to be cooled.

[0038] However, in the comparative example, at least one fan must be driven when heat dissipation of the fluid to be cooled is required. Driving a large hydraulically driven fan requires a large amount of power, and if one or more fans are constantly driven when heat dissipation is required, regardless of the amount of heat dissipation required, the fuel efficiency of the transport vehicle will deteriorate. Furthermore, the operating noise of the fan can lead to increased operator fatigue and noise problems for neighbors.

[0039] -Effects- (1) In this embodiment, the hydraulic pump 19 that circulates the brake cooling oil, which is the fluid to be cooled, is driven by a motor rather than an engine, which makes it possible to control the circulation flow rate of the fluid to be cooled regardless of the rotation speed of the prime mover (engine) 15. The hydraulic motor 25 that drives the fan 26 can also be controlled regardless of the engine rotation speed by adjusting the supply flow rate of pressure oil with the control valve 22.

[0040] In this embodiment, when the hydraulic pump 19 and the hydraulic motor 25 are controlled in accordance with the measured temperature T of the brake cooling oil, the rotation speed of the hydraulic pump 19 begins to increase before the rotation speed of the hydraulic motor 25 begins to increase as the measured temperature T rises ( FIG. 6 ). In other words, even when the measured temperature T begins to rise, an attempt is made to improve the heat dissipation amount by simply increasing the circulating flow rate of the brake cooling oil by the hydraulic pump 19 without driving the fan 26. Only when control of the hydraulic pump 19 alone is sufficient to dissipate heat, is the fan 26 driven in accordance with the required heat dissipation amount while increasing the circulating flow rate of the brake cooling oil. For example, when the measured temperature T rises, the rotation speed of the hydraulic pump 19 increases, increasing the flow rate of the brake cooling oil. If this causes the temperature of the brake cooling oil to decrease without reaching the third temperature T3, the fan 26 is not driven at all. In this way, the driving frequency and rotation speed of the fan 26 can be reduced, improving the fuel efficiency of the dump truck 1, suppressing noise, and reducing operator fatigue.

[0041] Furthermore, when the fan 26 is activated, the circulating flow rate of the brake cooling oil in the heat exchanger 24 is always at a maximum, so the cooling efficiency of the brake cooling oil is high relative to the airflow rate of the fan 26, and it is difficult for the rotation speed of the fan 26 to increase. This is another advantage of cooperative control of the hydraulic pump 19 and the hydraulic motor 25.

[0042] (2) In particular, in this 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, the fan 26 does not rotate as long as there is room for an increase in the rotation speed of the hydraulic pump 19 that can improve the amount of heat dissipated by the brake cooling oil. This makes it possible to keep the driving frequency of the fan 26 low.

[0043] (3) In addition, in this embodiment, the heat exchanger 24 is installed on the front side of the dump truck 1, and traveling wind can be guided to the heat exchanger 24. When the temperature of the brake cooling oil rises during braking, even when the fan 26 is stopped, the increase in the circulating flow rate of the brake cooling oil is combined with the air-cooling effect of the traveling wind, and the brake cooling oil can be cooled rationally.

[0044] (4) Furthermore, since the minimum rotation speed Pmin of the hydraulic pump 19 is set to a value greater than 0, it is possible to ensure the flow of brake cooling oil whose temperature is measured by the temperature sensor 33. This makes it possible to properly evaluate the temperature of the brake cooling oil, which is the basis for controlling the hydraulic pump 19 and the hydraulic motor 25, and ensure the reliability of the hydraulic pump 19 and the hydraulic motor 25.

[0045] (5) If the temperature sensor 33 is provided in the brake cooling oil return pipe (the pipe connecting the outlet of the wet brakes 12 and the tank 13), the temperature of the brake cooling oil will be measured immediately after it has risen in the wet brakes 12, and the measured temperature T will fluctuate greatly. As a result, even in a situation where the temperature of the brake cooling oil inside the tank 13 has not risen significantly, the control of the hydraulic pump 19 and the hydraulic motor 25 may function too sensitively, resulting in a waste of power.

[0046] In contrast, in this embodiment, by installing the temperature sensor 33 in the intake pipe 31 of the hydraulic pump 19, the temperature of the brake cooling oil supplied to the wet brakes 12 is measured after the temperature fluctuations have settled in the tank 13, making it possible to suppress the above-mentioned overly sensitive control. This also makes it possible to avoid unnecessary driving of the fan 26, etc., and suppress waste of power.

[0047] Second Embodiment Fig. 7 is a hydraulic circuit diagram of a transporter vehicle according to a second embodiment of the present invention. In Fig. 7, elements that are the same as or correspond to those in the first embodiment are given the same reference numerals as in Fig. 4, and descriptions thereof will be omitted where appropriate.

[0048] This embodiment differs from the first embodiment in that the present invention is applied to a hydraulic oil cooling system. In this embodiment, a heat exchanger (hydraulic oil cooler) 61 is provided in the center bypass oil passage 35. Like the heat exchanger 24, the heat exchanger 61 is also installed, for example, on the front side of the dump truck 1. A fan 26 sends air to the heat exchanger 24 and the heat exchanger 61. In addition, the hydraulic pump 17 is driven by an electric motor 62 rather than the prime mover (engine) 15. A temperature sensor 63 that measures the temperature of the hydraulic oil is installed in the suction pipe 36 of the hydraulic pump 17.

[0049] In this embodiment, the controller 50 controls the rotation speed of the hydraulic pump 17 and the hydraulic motor 25 for the hydraulic oil cooling system in the same manner as the control of the brake cooling oil cooling system. The control table for controlling the hydraulic pump 17 and the hydraulic motor 25 may be set, similar to the control table shown in FIG. 6 , so that the fan rotation speed and the amount of hydraulic oil circulating change in conjunction with the hydraulic oil temperature. In other words, when the measured temperature T of the hydraulic oil from the temperature sensor 63 increases, the rotation speed of the hydraulic pump 17 begins to increase from the minimum rotation speed Pmin (>0) before the rotation speed of the hydraulic motor 25 begins to increase from the minimum rotation speed Mmin (=0). Therefore, when the hydraulic oil temperature increases, if the rotation speed of the hydraulic pump 17 increases and the amount of hydraulic oil circulating through the heat exchanger 61 increases, causing the measured temperature T of the hydraulic oil to drop without reaching the third temperature T3, the fan 26 is not driven as far as cooling the hydraulic oil is concerned. Other configurations of this embodiment are similar to those of the first embodiment.

[0050] In this way, the present invention can be applied to cooling systems for hydraulic oils other than brake cooling oil, and similar effects can be obtained.

[0051] 7 shows a configuration in which the fan 26 is shared by the brake cooling oil cooling system and the hydraulic oil cooling system, the rotation speed of the fan 26 is controlled, for example, in accordance with the maximum values ​​of the measured temperatures T of the brake cooling oil and the hydraulic oil. If separate fans are used to blow air to the heat exchangers 24, 61, it is possible to achieve a configuration in which the fan for cooling the brake cooling oil is controlled independently of the measured temperature of the hydraulic oil, and the fan for cooling the hydraulic oil is controlled independently of the measured temperature of the brake cooling oil.

[0052] (Modifications) In the above embodiment, the present invention has been described as being applied to a cooling system for brake cooling oil or hydraulic oil, but the present invention can also be applied to a cooling system for engine coolant or engine oil, for example, and similar effects can be obtained. Furthermore, although the electric motor 21 has been exemplified as the drive device for the hydraulic pump 19, the hydraulic pump 19 can also be driven by, for example, a hydraulic motor, as long as the rotation speed of the hydraulic pump 19 can be controlled as desired.

[0053] Furthermore, although the present invention has been exemplified as being applied to the dump truck 1, the present invention can also be applied to other transport vehicles.

[0054] 6 illustrates an example in which the second temperature T2 is set lower than the third temperature T3. However, in order to increase the circulation flow rate of the heat exchanger prior to starting the fan, it is sufficient that the first temperature T1 (< T2) is lower than the third temperature T3 (< T4). Therefore, as long as T1 < T3, the second temperature T2 may be equal to or higher than the third temperature T3. However, if a significant power reduction effect is desired, it is desirable that the second temperature T2 be lower than the third temperature T3, as illustrated in FIG. 6.

[0055] Furthermore, in the above embodiment, the fan 26 is stopped when the measured temperature T is lower than the third temperature T3. However, the fan 26 may be configured to rotate 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 significant power reduction effect is desired, it is desirable that Mmin = 0, as shown in FIG. 6.

[0056] Furthermore, although a linear control table has been exemplified for the control of the hydraulic pumps 17, 19 and the hydraulic motor 25, it is also possible to employ a control table that changes the rotation speed of the hydraulic pumps 17, 19 and the hydraulic motor 25 in a stepwise or curved manner according to the measured temperature T, for example. In the case of a stepwise manner, control is simplified and it is expected that fluctuations in the control of the hydraulic pumps 17, 19 and the hydraulic motor 25 will be reduced in response to changes in the measured temperature T. However, it is more rational to set the control table linearly, since the rotation speed of the hydraulic pumps 17, 19 and the hydraulic motor 25 will follow the measured temperature T in real time, and the required amount of heat dissipation will change continuously to follow the measured temperature T.

[0057] 1...Dump truck (transport vehicle), 2...Vehicle frame, 8...Loading platform, 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 rotation speed, Mmin...Minimum motor rotation speed, Pmax...Maximum pump rotation speed, Pmin...Minimum pump rotation speed, T...Measured temperature, T1...First temperature, T2...Second temperature, T3...Third temperature, T4...Fourth temperature

Claims

1. A transport vehicle including a vehicle body frame and a loading platform provided on the vehicle body frame in a foldable manner, A tank for storing a fluid to be cooled; a heat exchanger for cooling the fluid to be cooled; a pump for circulating the fluid to be cooled between the tank and the heat exchanger; a temperature sensor for detecting a temperature of the fluid to be cooled; A fan that blows air to the heat exchanger; A hydraulic motor that drives the fan; a controller for controlling the pump and the hydraulic motor in response to the temperature detected by the temperature sensor; The controller: a first pump rotation speed, a first temperature corresponding to the first pump rotation speed, a second pump rotation speed higher than the first pump rotation speed, a second temperature corresponding to the second pump rotation speed, a first motor rotation speed, a third temperature corresponding to the first motor rotation speed, a second motor rotation speed higher than the first motor rotation speed, and a fourth temperature corresponding to the second motor rotation speed; when the detected temperature is between the first temperature and the second temperature, increasing a rotation speed of the pump from the first pump rotation speed to the second pump rotation speed in response to an increase in the detected temperature; When the detected temperature is between the third temperature and the fourth temperature, increasing the rotation speed of the hydraulic motor from the first motor rotation speed to the second motor rotation speed in response to an increase in the detected temperature; The third temperature is set higher than the first temperature, and when the detected temperature reaches the first temperature from a temperature lower than the first temperature, the rotation speed of the pump starts to increase from the first pump rotation speed, and when the detected temperature rises above the first temperature, the rotation speed of the pump is increased from the first pump rotation speed without increasing the rotation speed of the hydraulic motor until the third temperature is reached, and when the detected temperature reaches the third temperature, the rotation speed of the hydraulic motor starts to increase from the first motor rotation speed. A transport vehicle characterized by:

2. 2. The transport vehicle according to claim 1, The minimum rotation speed of the pump is greater than 0; The minimum rotational speed of the hydraulic motor is 0. A transport vehicle characterized by:

3. 2. The transport vehicle according to claim 1, The transport vehicle, wherein the third temperature is higher than the second temperature.

4. 2. The transport vehicle according to claim 1, A transport vehicle, wherein the temperature sensor is installed in a suction pipe of the pump.

5. 2. The transport vehicle according to claim 1, 4. A transport vehicle, wherein the fluid to be cooled is brake cooling oil.

6. 2. The transport vehicle according to claim 1, 4. A transport vehicle, wherein the fluid to be cooled is hydraulic oil.