Transport 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

Technical Field

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

Background Art

[0002] Fans that blow air to heat exchangers such as oil coolers mounted on dump trucks for mines, shovels for mines, trucks running on public roads, etc. are generally directly connected to the engine and driven. However, due to reasons such as the enlargement of the cooling system and the constraints on the arrangement of the heat exchanger and the engine, electric drive fans or hydraulic drive fans are often adopted. In particular, hydraulic drive fans tend to be adopted for large fans that are not suitable for electric drive. As a cooling system adopting such a hydraulic drive fan, there is known one that 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).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] 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 volume, and it is necessary to drive at least one fan when heat dissipation is required.

[0005] As described above, many hydraulic drive fans are large. The power required to drive a large fan is large, and when the driving frequency and rotation speed of the fan increase, the fuel consumption of the transport vehicle deteriorates. In addition, the operating noise of the fan can also lead to an increase in the fatigue of the operator and noise problems in the neighborhood.

[0006] An object of the present invention is to provide a transport vehicle capable of improving fuel efficiency and suppressing noise by suppressing the driving frequency and rotational speed of a fan.

Means for Solving the Problems

[0007] In order to achieve the above object, the present invention provides a transport vehicle including a vehicle body frame and a loading platform provided on the vehicle body frame so as to be able to undulate, 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 according to the temperature detected by the temperature sensor. The controller stores 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, 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. 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. The third temperature is set higher than the first temperature. 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. When the detected temperature rises above the first temperature, the rotation speed of the pump is increased from the first pump rotation speed without causing the rotation speed of the hydraulic motor to start increasing until reaching the third temperature. 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 is provided.

Effect of the Invention

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

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Embodiments for Carrying Out the Invention

[0010] Embodiments of the present invention will be described below with reference to the drawings.

[0011] (First Embodiment) -Transport Vehicle- FIG. 1 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. The left and right in FIG. 1 are the front and rear of the dump truck 1.

[0012] The dump truck 1 shown in the figure includes a vehicle body frame 2 and a plurality of wheels rotatably provided on the vehicle body frame 2. The wheels include the left and right front wheels 3f and the left and right rear wheels 3r. The front wheels 3f are arranged one by one at both left and right ends of the front part of the vehicle body frame 2. The rear wheels 3r are arranged two by two at both left and right ends of the rear part of the vehicle body frame 2. The front wheels 3f are steering wheels steered according to the steering angle input via a steering wheel or the like, and are driven wheels driven by the rear wheels 3r via the road surface of the road on which the dump truck 1 travels. A traveling motor (not shown) and a speed reducer 11 (Fig. 2) for adjusting the rotational speed of the rear wheels 3r are individually connected to the respective rotation shafts of the left and right rear wheels 3r which are driving wheels.

[0013] In addition, the dump truck 1 is provided with a deck 4, a cab 5, a control cabinet 6, and a plurality of grid boxes 7. The deck 4 is a floor on which the operator walks and is arranged above the front wheels 3f. The cab 5 is a driver's cab in which the operator rides and is installed on the upper surface of the deck 4. The cab 5 is provided with an operator's seat, operation pedals (such as an accelerator pedal and a brake pedal) for commanding the traveling speed of the dump truck 1, and the above-described steering wheel. The control cabinet 6 is a room for housing various electric devices and is mounted on the front part of the vehicle body. The grid box 7 is a device that dissipates surplus energy generated by regenerative power during braking as heat and is arranged on the right side of the control cabinet 6.

[0014] The dump truck 1 is further equipped with a loading platform 8 and a hoist cylinder 9. The loading platform 8 is a platform for loading earth and sand, ore, etc., and is connected to the vehicle body frame 2 via a hinge pin 8p and undulates with respect to the vehicle body frame 2. The hoist cylinder 9 connects the vehicle body frame 2 and the loading platform 8 at a position in front of the hinge pin 8p, and expands and contracts to undulate the loading platform 8. In FIG. 1, at the position between the left and right front wheels 3f of the vehicle body frame 2, a prime mover 15 (FIG. 2), a generator 16 (FIG. 2), etc. are arranged, and a control cabinet 6 is mounted above each of these devices. Inside the control cabinet 6, a power control device 30 (FIG. 5) is stored. The power control device 30 is, for example, an inverter.

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

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

[0017] At the front of the vehicle body frame 2, the prime mover 15 is mounted with its output shaft oriented longitudinally. In the present embodiment, the prime mover 15 is an engine (internal combustion engine). The output shaft of the prime mover 15 is connected to a generator 16, a hydraulic pump 17, and a pilot pump 18. Above the hydraulic pump 17, a cooling hydraulic pump 19 for circulating the brake cooling oil between the tank 13 and the heat exchanger 24, and an electric motor 21 for driving the hydraulic pump 19 are installed. The power required to drive the hydraulic pump 19 is smaller than the power required to drive the hydraulic motor 25.

[0018] Below the hydraulic pump 17, a control valve 22 is installed. On the front surface of the vehicle body of the dump truck 1, a radiator 23 is installed. In front of this radiator 23, a heat exchanger (brake cooling oil cooler) 24 for cooling the brake cooling oil, which is the fluid to be cooled, is mounted. Behind the radiator 23, a hydraulic motor 25 is installed, 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 blow air to the radiator 23 and the heat exchanger 24.

[0019] On the upper part of the vehicle body frame 2, a beam 27 extending in the left - right direction is installed, and a control cabinet 6 is installed 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, the brake cooling oil is sucked from the tank 13 into the hydraulic pump 19 through the suction pipe 31 and discharged into the discharge pipe 32 of the hydraulic pump 19. The brake cooling oil discharged from the hydraulic pump 19 is sent into the heat exchanger 24 through the discharge pipe 32, cooled by the heat exchanger 24, and then returned to the tank 13 via the wet brake 12. A relief valve 34 is provided in the discharge pipe 32. The maximum pressure of the discharge pipe 32 is defined by the relief valve 34. Further, a temperature sensor 33 is installed in the suction pipe 31. The temperature of the brake cooling oil flowing through 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 a controller 50 (described later).

[0021] 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 through the suction pipe 36 and discharges the pressurized oil into the discharge pipe 37. The pilot pump 18 sucks the hydraulic oil from the tank 13 through the suction pipe 38 and discharges the pressurized oil into the discharge pipe 39. The maximum pressures of the discharge pipes 37 and 39 are also defined by relief valves in the same manner as 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 the pilot pressure generated by the solenoid valve 41 using the pressurized oil from the pilot pump 18 as the primary pressure. The hydraulic oil discharged from the hydraulic pump 17 is sent to the center bypass oil passage 35 and returned to the tank 13 through the center bypass oil passage 35. When the spool of the control valve 22 moves, the center bypass oil passage 35 is narrowed while the connection opening (not shown) to the hydraulic motor 25 opens according to the movement amount of the spool, and the pressurized oil is supplied to the hydraulic motor 25. The rotational speed of the hydraulic motor 25 is controlled according to the supply flow rate of the pressurized oil, that is, the movement amount of the spool. The pressurized oil that drives the hydraulic motor 25 returns to the control valve 22 and then returns to the tank 13 through the center bypass oil passage 35.

[0023] -Electrical Circuit- Figure 5 is an electrical circuit diagram of the brake cooling oil cooling system. The controller 50 is an in-vehicle computer equipped with a processing device such as a CPU and a storage device such as a memory, and has a function of controlling the hydraulic pump 19 and the hydraulic motor 25 according to the measured temperature T of the brake cooling oil. The controller 50 outputs a control signal to the power control device 30 and the solenoid valve 41, and controls the circulation 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 power supplied from the generator 16 to the electric motor 21 based on the control signal from the controller 50. In this way, the power supply amount to the electric motor 21 is controlled, and the supply amount of the brake cooling oil circulated and supplied to the wet brake 12 is controlled according to the measured temperature of the brake cooling oil.

[0025] On the other hand, the solenoid valve 41 is driven based on the control signal from the controller 50, and the control valve 22 is driven according to the pilot pressure controlled by the solenoid valve 41. Thereby, the supply flow rate of the pressure 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.

[0026] -Control Table- FIG. 6 is a diagram showing a control table for the fan rotation speed and the brake cooling oil flow rate by the controller 50. The control table shown in FIG. 6 is stored in the memory of the controller 50. As values defining the control table, a pump minimum rotation speed Pmin (first pump rotation speed), a pump maximum rotation speed Pmax (second pump rotation speed), a motor minimum rotation speed Mmin (first motor rotation speed), a motor maximum rotation speed Mmax (second motor rotation speed), a first temperature T1, a second temperature T2, a third temperature T3, and a fourth temperature T4 are stored, and they have a relationship of first temperature T1 < second temperature T2 < third temperature T3 < fourth temperature T4. In the present embodiment, the pump minimum rotation speed Pmin is the minimum rotation speed of the hydraulic pump 19, the pump maximum rotation speed Pmax is the maximum rotation speed of the hydraulic pump 19, the motor minimum rotation speed Mmin is the minimum rotation speed of the hydraulic motor 25, and the motor maximum rotation speed Mmax is the maximum rotation speed of the hydraulic motor 25. The first temperature T1 corresponds to the pump minimum rotation speed Pmin, and the second temperature T2 corresponds to the pump maximum rotation speed Pmax. The third temperature T3 corresponds to the motor minimum rotation speed Mmin, and the fourth temperature T4 corresponds to the motor maximum rotation 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 in FIG. 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] Incidentally, the flow rate of the brake cooling oil (e.g., the discharge flow rate of the hydraulic pump 19) and the rotational speed of the electric motor 21, etc., which are in a proportional relationship with the rotational speed of the hydraulic pump 19, can be treated as values synonymous with the rotational speed of the hydraulic pump 19 conceptually in terms of control. In FIG. 6, the control table for the rotational 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. According to this control table for the rotational speed of the hydraulic pump 19, when the measured temperature T by the temperature sensor 33 is less than the first temperature T1 (T < T1), the controller 50 outputs a control signal to the power control device 30 so that the hydraulic pump 19 is driven at the minimum rotational 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 power control device 30 so that the rotational speed of the hydraulic pump 19 increases from Pmin to Pmax in response to the increase in T (e.g., proportionally and linearly). Also when T decreases while T1 ≤ T < T2, the controller 50 decreases the rotational speed of the hydraulic pump 19 according to the control table in FIG. 6 in response to the decrease in T. When 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 rotational speed Pmax.

[0028] Regarding the rotational speed of the hydraulic motor 25 as well, a value in a proportional relationship such as the rotational speed of the fan 26 can be treated as a synonymous value in the control concept. In FIG. 6, the control table for the rotational speed of the hydraulic motor 25 is defined in relation to the measured temperature T of the brake cooling oil and the rotational speed of the fan 26. According to this control table for the rotational speed of the hydraulic motor 25, when the measured temperature T by the temperature sensor 33 is less than the third temperature T3 (T < T3), the controller 50 outputs a control signal to the power control device 30 so that the hydraulic motor 25 is driven at the minimum rotational 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 power control device 30 so that the rotational speed of the hydraulic motor 25 increases from Mmin to Mmax in response to the increase in T (for example, proportionally and linearly). Also when T decreases while T3 ≤ T < T4, the controller 50 decreases the rotational speed of the hydraulic motor 25 according to the control table in FIG. 6 in response to the decrease in T. When the measured temperature T is greater than or equal to the 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 rotational speed Mmax.

[0029] -Pmin- Here, the wet brake 12 incorporates a floating seal (not shown) that prevents leakage of the brake cooling oil. This floating seal has low pressure resistance, and the pressure of the brake cooling oil applied to the wet brake 12 must be kept below the pressure resistance of the floating seal. The viscosity of the brake cooling oil increases when the temperature is low, and the internal pressure of the wet brake 12 tends to increase due to the inflow of the brake cooling oil. Therefore, the minimum flow rate (the minimum rotational speed Pmin of the hydraulic pump 19) needs to be set so that the floating seal does not break even at the lowest oil temperature assumed for the brake cooling oil. However, the minimum rotational 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.

[0030] -Pmax / Mmax- Regarding the maximum pump rotation speed Pmax and the maximum motor rotation speed Mmax, they are values that define the maximum cooling performance of the brake cooling oil. Therefore, assuming the maximum heat generation amount of the wet brake 12 that can occur during braking when the dump truck 1 is in operation, it is necessary to set the maximum pump rotation speed Pmax and the maximum motor rotation speed Mmax so that sufficient cooling performance is ensured.

[0031] Note that 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 in consideration of points such as those described above, or may be the lower or upper limit rotation speeds defined by mechanical and electrical specifications. That is, for example, the maximum pump rotation speed Pmax may be set as a rotation speed of the hydraulic pump 19 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 higher than the minimum motor rotation speed Mmin.

[0032] -T1,T2,T3,T4- The setting of the first temperature T1, the second temperature T2, the third temperature T3, and the fourth temperature T4 will be described. If the first temperature T1, the second temperature T2, the third temperature T3, and the fourth temperature T4 are set low overall, the rotation speeds of the hydraulic pump 19 and the hydraulic motor 25 will start to increase before the measured temperature T rises much. In this case, it is advantageous for maintaining the brake cooling oil at a low temperature, and it becomes difficult for the brake cooling oil 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, it is desirable from the perspective of the balance between cooling performance and fuel efficiency to set the first temperature T1, the second temperature T2, the third temperature T3, and the fourth temperature T4 as high as possible within the range where overheating of the brake cooling oil can be avoided.

[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. Thereby, when the measured temperature T rises from a temperature lower than the first temperature T1, the rotational speed of the hydraulic pump 19 starts to rise from the minimum rotational speed Pmin earlier than the rotational speed of the hydraulic motor 25 starts to rise from the minimum rotational speed Mmin. As described above, the minimum rotational 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 be driven at a rotational speed equal to or higher than the minimum rotational speed Pmin, and the brake cooling oil continues to circulate. On the other hand, the minimum rotational 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 is set in this way because there is no need to forcibly air-cool the brake cooling oil when the measured temperature T is low.

[0034] Therefore, assuming that the measured temperature T has risen above the first temperature T1, and as a result of the rotational speed of the hydraulic pump 19 rising and the flow rate of the brake cooling oil increasing, if the measured temperature T turns downward without reaching the third temperature T3, 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, in the temperature range where the circulation flow rate of the brake cooling oil can increase or decrease, only the control of the circulation flow rate of the brake cooling oil is used to control the heat dissipation amount. In addition, in the present embodiment, the heat exchanger 24 is installed on the front surface of the dump truck 1, and the running wind hits the heat exchanger 24. Therefore, even when the fan 26 is stopped, the heat dissipation amount increases in cooperation with the increase in the circulation flow rate of the brake cooling oil, and the brake cooling oil is reasonably cooled.

[0035] - Comparative Example - FIG. 8 is a diagram showing 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 if the temperature of the fluid to be cooled (e.g., engine cooling water) is equal to or higher than a set value, and outputs an off-signal if it is 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 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 equal to or lower than a predetermined value, pressure 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, pressure 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 with the above configuration, when the temperature of the fluid to be cooled becomes equal to or higher than the set value, an on-signal is output from the thermosensing valve 107, and the discharge pipeline is opened by the switching valve 108. At this time, if the engine speed is equal to or lower than a predetermined value, pressure oil is supplied only to the main hydraulic motor 102 via the flow priority valve 106, and only the main fan 101 contributes to the cooling of the fluid to be cooled. Conversely, if the engine speed is greater than the predetermined value, pressure 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 the cooling of the fluid to be cooled. As a result, it switches between one or two according to the heat dissipation amount required for the fluid to be cooled.

[0038] However, in the comparative example, it is necessary to drive at least one fan when heat dissipation of the fluid to be cooled is required. The power required to drive a large hydraulic-driven fan is large. If it is configured to always drive one or more fans regardless of the required heat dissipation amount when heat dissipation is required, the fuel efficiency of the transport vehicle deteriorates. In addition, the operating noise of the fan can also lead to increased operator fatigue and noise problems in the neighborhood.

[0039] -Effect- (1) In this embodiment, by driving the hydraulic pump 19 that circulates the brake cooling oil, which is the fluid to be cooled, by a motor instead of by the engine, the circulation flow rate of the fluid to be cooled can be controlled regardless of the rotational speed of the prime mover (engine) 15. The hydraulic motor 25 that drives the fan 26 can also be controlled regardless of the engine rotational speed by adjusting the supply flow rate of the pressurized oil with the control valve 22.

[0040] Furthermore, in this embodiment, when controlling the hydraulic pump 19 and the hydraulic motor 25 according to the measured temperature T of the brake cooling oil, when the measured temperature T rises, the rotational speed of the hydraulic pump 19 starts to rise earlier than the rotational speed of the hydraulic motor 25 starts to rise (Fig. 6). That is, even when the measured temperature T starts to rise, first, only an increase in the circulation flow rate of the brake cooling oil by the hydraulic pump 19 is attempted without driving the fan 26, in order to improve the heat dissipation amount. Only when sufficient heat dissipation cannot be achieved by controlling only the hydraulic pump 19, the fan 26 is driven according to the required heat dissipation amount with the circulation flow rate of the brake cooling oil increased. For example, when the measured temperature T rises and the rotational speed of the hydraulic pump 19 rises and the flow rate of the brake cooling oil increases, if the brake cooling oil turns to temperature drop without reaching the third temperature T3, the fan 26 is not driven in the first place. In this way, the driving frequency and rotational 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 and the like can also be reduced.

[0041] Also, when the fan 26 starts, since the circulation flow rate of the brake cooling oil in the heat exchanger 24 is always maximum, the cooling efficiency of the brake cooling oil with respect to the air volume blown by the fan 26 is in a high state, and it is difficult for the rotational speed of the fan 26 to rise. This is also an advantageous point of the coordinated control of the hydraulic pump 19 and the hydraulic motor 25.

[0042] (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 rotational speed of the hydraulic pump 19 reaches the maximum rotational speed Pmax. Therefore, as long as there is an increase in the rotational speed of the hydraulic pump 19 that can improve the heat dissipation amount of the brake cooling oil, the fan 26 does not rotate. Thereby, the driving frequency of the fan 26 can be suppressed lower.

[0043] (3) Further, in the present embodiment, the heat exchanger 24 is installed on the front surface of the dump truck 1, and running air can be guided to the heat exchanger 24. When the brake cooling oil heats up during braking, even when the fan 26 is stopped, the increase in the circulation flow rate of the brake cooling oil can be synergistically combined with the air-cooling effect by the running air to reasonably cool the brake cooling oil.

[0044] (4) Also, since the minimum rotational speed Pmin of the hydraulic pump 19 is set to a value greater than 0, the flow of the brake cooling oil whose temperature is measured by the temperature sensor 33 can be ensured. Thereby, 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.

[0045] (5) If a 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 rising in the wet brake 12 is measured, and the increase and decrease of the measured temperature T become drastic. As a result, even in a situation where the temperature of the brake cooling oil inside the tank 13 has not risen so much, the control of the hydraulic pump 19 and the hydraulic motor 25 may function overly sensitively and waste power.

[0046] On the other hand, in the present embodiment, by installing the temperature sensor 33 in the suction pipe 31 of the hydraulic pump 19, the temperature of the brake cooling oil supplied to the wet brake 12 is measured after the temperature fluctuation has stabilized in the tank 13, and the above-mentioned overly sensitive control can be suppressed. Also by this, wasteful driving of the fan 26 and the like can be avoided, and waste of power can be suppressed.

[0047] (Second Embodiment) FIG. 7 is a hydraulic circuit diagram of a transport vehicle according to the second embodiment of the present invention. In FIG. 7, elements that are the same as or corresponding to those in the first embodiment are denoted by the same reference numerals as in FIG. 4, and the description thereof will be omitted as appropriate.

[0048] The difference between this embodiment and the first embodiment is that the invention is applied to the cooling system of the hydraulic oil. In this embodiment, a heat exchanger (hydraulic oil cooler) 61 is provided in the center bypass oil passage 35. Similar to the heat exchanger 24, the heat exchanger 61 is also installed, for example, on the front surface of the dump truck 1. The fan 26 blows air to the heat exchanger 24 and the heat exchanger 61. Further, 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 hydraulic oil is installed in the suction pipe 36 of the hydraulic pump 17.

[0049] In this embodiment, the controller 50 controls the rotational speeds of the hydraulic pump 17 and the hydraulic motor 25 with respect to the cooling system of the hydraulic oil in the same manner as the control of the cooling system of the brake cooling oil. The control table regarding the control of the hydraulic pump 17 and the hydraulic motor 25 may be set such that the fan rotational speed and the hydraulic oil circulation amount change in linkage with the hydraulic oil temperature in the same manner as the control table shown in FIG. 6. That is, when the measured temperature T of the hydraulic oil from the temperature sensor 63 rises, the rotational speed of the hydraulic pump 17 starts to rise from the minimum rotational speed Pmin (>0) earlier than the rotational speed of the hydraulic motor 25 starts to rise from the minimum rotational speed Mmin (=0). Therefore, when the rotational speed of the hydraulic pump 17 rises and the measured temperature T of the hydraulic oil drops without reaching the third temperature T3 due to an increase in the hydraulic oil circulation amount of the heat exchanger 61 when the hydraulic oil temperature rises, the fan 26 is not driven as far as the cooling of the hydraulic oil is concerned. Regarding other configurations, this embodiment is the same as the first embodiment.

[0050] Thus, the present invention can also be applied to a cooling system for hydraulic oil other than the brake cooling oil, and the same effects can be obtained.

[0051] Note that in FIG. 7, since the cooling system of the brake cooling oil and the cooling system of the hydraulic oil share the fan 26, the rotational speed of the fan 26 is controlled according to, for example, the maximum value of the measured temperatures T of the brake cooling oil and the hydraulic oil. If the configuration is such that separate fans blow air to the heat exchangers 24 and 61, the fan for cooling the brake cooling oil can be controlled without depending on the measured temperature of the hydraulic oil, and the fan for cooling the hydraulic oil can be controlled without depending on the measured temperature of the brake cooling oil.

[0052] (Modification example) In the above embodiments, the case where the present invention is applied to the cooling systems of the brake cooling oil and the hydraulic oil has been described. However, the present invention is also applicable to, for example, the cooling systems of engine cooling water and engine oil, and the same effects can be obtained. Further, although the electric motor 21 has been illustrated as the driving device of the hydraulic pump 19, if the rotational speed of the hydraulic pump 19 can be arbitrarily controlled, for example, a configuration in which the hydraulic pump 19 is driven by a hydraulic motor can also be adopted.

[0053] In addition, although the case where the present invention is applied to the dump truck 1 has been illustrated, the present invention is also applicable to other transport vehicles.

[0054] In FIG. 6, an example in which the second temperature T2 is set lower than the third temperature T3 has been described. However, in increasing the circulation flow rate of the heat exchanger prior to the start of the fan, it is sufficient that the first temperature T1 (<T2) is lower than the third temperature T3 (<T4). Therefore, if T1 < T3, the second temperature T2 may be equal to or higher than the third temperature T3. However, if aiming for a large power reduction effect or the like, it is desirable that the second temperature T2 is less than the third temperature T3 as illustrated in FIG. 6.

[0055] In the above embodiment, an example in which the fan 26 stops when the measured temperature T is less than the third temperature T3 has been illustrated. However, the fan 26 may be rotated at a low speed. That is, the minimum rotational speed Mmin of the hydraulic motor 25 may be set to be greater than 0. However, if aiming for a large power reduction effect or the like, it is desirable that Mmin = 0 as illustrated in FIG. 6.

[0056] Also, regarding the control of the hydraulic pumps 17 and 19 and the hydraulic motor 25, a linear control table has been exemplified. However, for example, a control table that changes the rotational speeds of the hydraulic pumps 17 and 19 and the hydraulic motor 25 stepwise or curvilinearly according to the measured temperature T can also be adopted. In the case of a stepwise change, not only is the control simplified, but it is also expected that the variation in the control of the hydraulic pumps 17 and 19 and the hydraulic motor 25 will decrease with respect to changes in the measured temperature T. However, it is more reasonable to set the control table linearly because the rotational speeds of the hydraulic pumps 17 and 19 and the hydraulic motor 25 follow the measured temperature T in real time, and the required heat dissipation continuously changes following the measured temperature T.

Description of Symbols

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

Claims

1. In a transport vehicle including a vehicle body frame and a loading platform provided on the vehicle body frame so as to be able to rise and fall, 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 according to the temperature detected by the temperature sensor, the controller stores 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, 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, 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, the third temperature is set higher than the first temperature, 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, when the detected temperature rises beyond 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 the following.

2. In the transport vehicle according to Claim 1, the minimum rotational speed of the pump is a value greater than 0, and the minimum rotational speed of the hydraulic motor is 0 A transport vehicle characterized by the following.

3. In the transport vehicle according to Claim 1, A transport vehicle characterized in that the third temperature is higher than the second temperature.

4. In the transport vehicle according to Claim 1, A transport vehicle characterized in that the temperature sensor is installed in the suction pipe of the pump.

5. In the transport vehicle according to Claim 1, A transport vehicle characterized in that the fluid to be cooled is brake cooling oil.

6. In the transport vehicle according to Claim 1, A transport vehicle characterized in that the fluid to be cooled is hydraulic oil.

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