A multi-cycle cooling system and a mine dump truck

Abstract

The utility model belongs to the vehicle cooling technical field, concretely relates to a kind of multi-cycle cooling system and dump truck for mine, including oil sump, main control valve, oil supply pump, first cooling valve, second cooling valve, hydraulic retarder, gearbox, pressure reducing valve, pressure-limiting cut-off valve, first oil cooler, second oil cooler and cooling water circulation loop;The utility model eliminates the oil temperature interference between hydraulic retarder and gearbox, realizes the precision management of the differentiation heat dissipation of both, and provides relatively independent, low-temperature cooling circuit for gearbox, guarantees its lubricating effect, prolongs service life, and establishes efficient self-circulation cooling circuit for hydraulic retarder, with the advantages of short cycle period and high heat dissipation efficiency, ensures sustained braking effect, and only relies on self-driving for circulation, thereby reducing the dependence on oil supply pump, and improving energy efficiency.

Description

Technical Field

[0001] This utility model belongs to the field of vehicle cooling technology, specifically relating to a multi-cycle cooling system and a mining dump truck. Background Technology

[0002] In the transmission system of mining dump trucks, the gearbox and hydraulic retarder are key components. The hydraulic retarder can effectively reduce the load on the service brakes in conditions such as long downhill slopes, thereby significantly improving driving safety. However, during its operation, it converts the vehicle's kinetic energy into heat energy, causing the working fluid temperature to rise sharply. Therefore, a matching cooling system is required to dissipate heat and ensure its continuous and stable operation.

[0003] Currently, to address the heat dissipation needs of transmissions, the industry generally adopts a shared single-channel cooling design. In this design, the oil in both the transmission and the hydraulic retarder flows through the same oil cooler for cooling before entering their respective working cycles.

[0004] However, since the oil temperature during the operation of a hydraulic retarder is typically much higher than the normal operating temperature of the transmission, sharing a cooling channel can cause the two different oil temperatures to interfere with each other during the cooling process. For the transmission, the abnormally high oil temperature can severely affect the lubrication of its internal gear pairs, thereby increasing the risk of equipment failure. For the hydraulic retarder, its actual cooling effect is limited by the overall oil temperature and cannot reach an ideal state, thus restricting its continuous braking effect. Utility Model Content

[0005] The purpose of this invention is to provide a multi-cycle cooling system and a mining dump truck, which solves the technical problems in the prior art where the transmission and hydraulic retarder share a cooling channel, causing two different types of oil to affect each other during the common cooling process, resulting in excessively high transmission oil temperature affecting lifespan and insufficient cooling of the hydraulic retarder reducing braking force.

[0006] In a first aspect, this utility model discloses a multi-cycle cooling system, comprising: Oil pan; The main control valve has a first port, a second port, a third port and a fourth port, and has a first position and a second position. In the first position, the second port and the fourth port are connected; in the second position, the first port and the third port are connected, and the second port and the fourth port are connected. The oil supply pump has its inlet connected to the oil pan via a pipeline, and its outlet connected to the first and second ports of the main control valve via a pipeline. The first cooling valve has a first port, a second port, a third port and a fourth port, and has a first station and a second station. In the first station, the first port and the second port are connected; in the second station, the first port and the third port are connected, and the second port and the fourth port are connected. The second cooling valve has a first port, a second port, a third port and a fourth port, and has a first station and a second station. In the first station, the first port and the third port are connected, and the second port and the fourth port are connected; in the second station, the first port and the second port are connected. The hydraulic retarder has its oil inlet connected to the second port of the first cooling valve via a pipeline, and its oil outlet connected to the first port of the first cooling valve via a pipeline. The gearbox has its oil inlet connected to the fourth port of the main control valve via a pipeline, and its oil outlet connected to the first port of the second cooling valve via a pipeline. The pressure reducing valve has its inlet connected to the third port of the main control valve via a pipeline, its outlet connected to the inlet of the hydraulic retarder via a pipeline, and its drain port connected to the oil pan via a pipeline. The pressure limiting shut-off valve has its inlet connected to the outlet of the hydraulic retarder via a pipeline, its outlet connected to the oil pan via a pipeline, and its pressure testing port connected to the inlet of the pressure reducing valve via a pipeline. The first oil cooler has its oil inlet connected to the third port of the first cooling valve and the third port of the second cooling valve via pipelines, and its oil outlet connected to the fourth port of the first cooling valve and the fourth port of the second cooling valve via pipelines. The second oil cooler has its oil inlet connected to the second port of the second cooling valve via a pipeline, and its oil outlet connected to the oil pan via a pipeline. The cooling water circulation loop has cooling water flowing through the first oil cooler and the second oil cooler for heat exchange with the oil. When the hydraulic retarder is closed, the main control valve, the first cooling valve, and the second cooling valve are all in the first position; when the hydraulic retarder is open, the main control valve, the first cooling valve, and the second cooling valve are all in the second position.

[0007] This application eliminates oil temperature interference between the hydraulic retarder and the transmission, achieving precise management of differentiated heat dissipation for both, and provides a relatively independent, low-temperature cooling circuit for the transmission, ensuring its lubrication effect and extending its service life. It also establishes an efficient self-circulating cooling circuit for the hydraulic retarder, which has the advantages of short cycle and high heat dissipation efficiency, ensuring continuous braking effect. Furthermore, it relies solely on its own drive for circulation, thereby reducing dependence on the oil supply pump and improving energy efficiency.

[0008] Based on the above technical solution, the solution of this application can be further improved as follows: Preferably, the cooling water circulation loop includes: Water source for the whole vehicle; The water supply pump has its inlet connected to the vehicle's water source via a pipeline, and its outlet connected to the inlets of the first oil cooler and the second oil cooler via pipelines respectively. In this design, the outlets of the first and second oil coolers are both connected to the vehicle's water source via pipelines. This solution, through a parallel design, allows cooling water to be delivered to the first and second oil coolers simultaneously and independently. Although this increases system complexity and cost, it ensures the consistency and controllability of the inlet water temperature of each oil cooler. This is beneficial for temperature-sensitive automatic transmissions, effectively preventing performance degradation due to poor cooling and ensuring reliable operation of the transmission system.

[0009] Preferably, the cooling water circulation loop includes: Water source for the whole vehicle; The water supply pump has its inlet connected to the vehicle's water source via a pipeline, and its outlet connected to the inlet of the second oil cooler via a pipeline. The outlet of the second oil cooler is connected to the inlet of the first oil cooler via a pipeline, and the outlet of the first oil cooler is connected to the vehicle's water source via a pipeline. This solution, with its series design, has the advantages of simple structure and low cost. Although it is less effective in temperature control, the manual transmission itself is not sensitive to temperature, so it can efficiently meet the core heat dissipation needs of the vehicle with the lowest manufacturing cost and system complexity while ensuring its reliable operation.

[0010] Preferably, it includes: A first check valve is connected in series between the oil outlet of the hydraulic retarder and the first port of the first cooling valve. The second one-way valve is connected in series between the oil inlet of the hydraulic retarder and the second port of the first cooling valve. This design forces the oil to flow in one direction, thereby providing positive guidance and reverse cut-off for the self-circulating cooling circuit of the hydraulic retarder, enhancing the stability and efficiency of the self-circulation.

[0011] Preferably, it includes: The third one-way valve is connected in series between the oil outlet of the transmission and the first port of the second cooling valve. This solution ensures that the hot oil of the transmission can be stably and reliably guided to the second cooling valve and subsequent cooling passages, preventing oil backflow that may be caused by factors such as pressure fluctuations or changes in vehicle posture, thereby ensuring the continuity of transmission lubrication and cooling.

[0012] Secondly, this utility model discloses a mining dump truck, including: the multi-cycle cooling system described in any one of the above claims.

[0013] Through the above technical solution, this utility model achieves the following beneficial effects: 1. This application eliminates oil temperature interference between the hydraulic retarder and the transmission, achieves precise management of differentiated heat dissipation between the two, and provides a relatively independent, low-temperature cooling circuit for the transmission, ensuring its lubrication effect and extending its service life. It also establishes an efficient self-circulating cooling circuit for the hydraulic retarder, which has the advantages of short cycle and high heat dissipation efficiency, ensuring continuous braking effect. Furthermore, it relies solely on its own drive for circulation, thereby reducing dependence on the oil supply pump and improving energy efficiency. 2. This application uses a first check valve and a second check valve to forcibly limit the unidirectional flow of oil, thereby providing positive guidance and reverse cut-off for the self-circulating cooling circuit of the hydraulic retarder, enhancing the stability and efficiency of self-circulation. Attached Figure Description

[0014] To more clearly illustrate the specific embodiments of this utility model or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0015] Figure 1 This is a schematic diagram of the multi-cycle cooling system described in a specific embodiment of this application; Figure 2 This is a schematic diagram of the multi-cycle cooling system described in specific embodiment two of this application; Explanation of reference numerals in the attached figures: 1. Oil pan; 2. Main control valve; 3. Oil supply pump; 4. First cooling valve; 5. Second cooling valve; 6. Hydraulic retarder; 7. Transmission; 8. Pressure reducing valve; 9. Pressure limiting shut-off valve; 10. First oil cooler; 11. Second oil cooler; 12. Cooling water circulation loop; 121. Vehicle water supply; 122. Water supply pump; 13. First check valve; 14. Second check valve; 15. Third check valve. Detailed Implementation

[0016] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings. These embodiments are merely illustrative of the present invention and should not be construed as limiting the scope of protection of the present invention.

[0017] The terms “first” and “second” are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as “first” or “second” may explicitly or implicitly include one or more of the stated features.

[0018] In this application, unless otherwise expressly specified and limited, the terms "installation" and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0019] To better understand the above technical solutions, the following will provide a detailed description of the technical solutions in conjunction with the accompanying drawings and specific embodiments.

[0020] Example 1: like Figure 1 As shown in the figure, this application discloses a multi-cycle cooling system for precise management of the differentiated heat dissipation requirements of the gearbox 7 and the hydraulic retarder 6. Its specific structure includes: an oil pan 1, a main control valve 2, an oil supply pump 3, a first cooling valve 4, a second cooling valve 5, a hydraulic retarder 6, a gearbox 7, a pressure reducing valve 8, a pressure limiting and shut-off valve 9, a first oil cooler 10, a second oil cooler 11, and a cooling water circulation loop 12.

[0021] Oil pan 1 is used to store working oil.

[0022] The main control valve 2 is used to determine the flow direction of the pressure oil. It has a first port, a second port, a third port and a fourth port, and a first position and a second position. In the first position, the second port and the fourth port are connected; in the second position, the first port and the third port are connected, and the second port and the fourth port are connected.

[0023] The oil supply pump 3 is used to draw oil from the oil pan 2 and provide oil with a certain pressure and flow rate for the entire cycle. Its oil inlet is connected to the oil pan 1 through a pipeline, and its oil outlet is connected to the first port and the second port of the main control valve 2 through a pipeline.

[0024] The first cooling valve 4 is responsible for switching the liquid-oil circuit. It has a first port, a second port, a third port and a fourth port, and a first station and a second station. In the first station, the first port and the second port are connected; in the second station, the first port and the third port are connected, and the second port and the fourth port are connected.

[0025] The second cooling valve 5 is responsible for switching the transmission oil circuit. It has a first port, a second port, a third port and a fourth port, and a first station and a second station. In the first station, the first port and the third port are connected, and the second port and the fourth port are connected; in the second station, the first port and the second port are connected.

[0026] The hydraulic retarder 6 is an auxiliary braking component that can convert the vehicle's kinetic energy into the heat energy of the oil. Its oil inlet is connected to the second port of the first cooling valve 4 through a pipeline, and its oil outlet is connected to the first port of the first cooling valve 4 through a pipeline.

[0027] The gearbox 7 is a transmission component that needs to operate at a suitable temperature to ensure lubrication. Its oil inlet is connected to the fourth port of the main control valve 2 through a pipeline, and its oil outlet is connected to the first port of the second cooling valve 5 through a pipeline.

[0028] The pressure reducing valve 8 is used to provide suitable oil pressure for the hydraulic retarder 6. Its oil inlet is connected to the third port of the main control valve 2 through a pipeline, its oil outlet is connected to the oil inlet of the hydraulic retarder 6 through a pipeline, and its oil drain port is connected to the oil pan 1 through a pipeline.

[0029] The pressure limiting shut-off valve 9 has its inlet connected to the outlet of the hydraulic retarder 6 via a pipeline, its outlet connected to the oil pan 1 via a pipeline, and its pressure test port connected to the inlet of the pressure reducing valve 8 via a pipeline.

[0030] The first oil cooler 10 removes heat from the oil through cooling water circulation and is mainly responsible for cooling the hydraulic retarder 6. It can be called ROC (Retarder Oil Cooler). Its oil inlet is connected to the third port of the first cooling valve 4 and the third port of the second cooling valve 5 through pipelines, and its oil outlet is connected to the fourth port of the first cooling valve 4 and the fourth port of the second cooling valve 5 through pipelines.

[0031] The second oil cooler 11 removes heat from the oil through cooling water circulation and is mainly responsible for cooling the gearbox 7. It can be called TOC (Transmission Oil Cooler). Its oil inlet is connected to the second port of the second cooling valve 5 through a pipeline, and its oil outlet is connected to the oil pan 1 through a pipeline.

[0032] The cooling water circulation loop 12 is used to provide cooling water, which flows through the first oil cooler 10 and the second oil cooler 11 for heat exchange with the oil.

[0033] The workflow of the above technical solution is as follows: Operating condition 1, when hydraulic retarder 6 is closed: Valve position status: Main control valve 2, first cooling valve 4 and second cooling valve 5 are all in the first working position; Oil flow direction: I. Transmission Circuit: Oil pan 1 → Oil supply pump 3 → Main control valve 2 (inlet at the second port, outlet at the fourth port) → Oil inlet of gearbox 7, providing lubricating and cooling oil to gearbox 7; Oil outlet of gearbox 7 (hot oil) → Second cooling valve 5 (inlet at the first port, outlet at the third port) → First oil cooler 10 → Second cooling valve 5 (inlet at the fourth port, outlet at the second port) → Second oil cooler 11 → Oil pan 1; It should be noted that although the third port of the first cooling valve 4 is connected to the oil inlet of the first oil cooler 10, and the fourth port of the first cooling valve 4 is connected to the oil outlet of the first oil cooler 10; however, when the first cooling valve 4 is in the first working position, its third and fourth ports are closed, so the oil circuit will only flow in the manner described above. II. Hydraulic buffer circuit: Oil pan 1 → Oil supply pump 3 → First port of main control valve 2. Since the main control valve 2 is in the first working position at this time, its first port and third port are the stop, so it is cut off here; It should be noted that since the pressure measuring port of the pressure limiting shut-off valve 9 is not subjected to the oil pressure from the oil supply pump 3, the pressure limiting shut-off valve 9 will be in the open state at this time. As a result, the oil in the hydraulic retarder 6 and the pipeline connected to it will be discharged back into the oil pan 1 through the pressure limiting shut-off valve 9. Under this condition, since the hydraulic retarder 6 is in the closed state, it does not need to be cooled. Therefore, the first oil cooler 10 and the second oil cooler 11 can work together to cool the gearbox 7 through the above design.

[0034] Operating Condition 2, when hydraulic retarder 6 is activated: Valve position status: Main control valve 2, first cooling valve 4 and second cooling valve 5 are all in the second working position; Oil flow direction: Transmission circuit: oil pan 1 → oil supply pump 3 → main control valve 2 (inlet at the second port, outlet at the fourth port) → oil inlet of gearbox 7, providing lubricating and cooling oil for gearbox 7; oil outlet of gearbox 7 (hot oil) → second cooling valve 5 (inlet at the first port, outlet at the second port) → second oil cooler 11 → oil pan 1; Hydraulic retarder circuit: Oil pan 1 → Oil supply pump 3 → Main control valve 2 (inlet at first port, outlet at third port) → Pressure reducing valve 8 → Oil inlet of hydraulic retarder 6, providing brake fluid to hydraulic retarder 6; Oil outlet of hydraulic retarder 6 (extremely hot oil) → First cooling valve 4 (inlet at first port, outlet at third port) → First oil cooler 10 → First cooling valve 4 (inlet at fourth port, outlet at second port) → Return to oil inlet of hydraulic retarder 6; It should be noted that, since the pressure measuring port of the pressure limiting shut-off valve 9 is subjected to the oil pressure from the oil supply pump 3, the pressure limiting shut-off valve 9 will be in the closed state at this time. Therefore, the oil in the hydraulic retarder 6 and the pipeline connected to it cannot be discharged into the oil pan 1 through the pressure limiting shut-off valve 9. It should be noted that during the initial startup of the hydraulic retarder 6, the oil supply pump 3 rapidly fills the hydraulic retarder 6 with oil through the pressure reducing valve 8. When the oil pressure inside the hydraulic retarder 6 and in its circulation pipeline is established and reaches the preset value, the pressure reducing valve 8 senses the oil pressure and will automatically close or greatly reduce its opening, thereby stopping the large-scale oil supply to maintain a constant oil pressure in the hydraulic retarder 6. At this time, the system will switch from "filling mode" to "circulation cooling mode". It should be noted that when the hydraulic retarder 6 is working, the rotation of its rotor will generate centrifugal force in the oil within the sealed cavity. This force will drive the oil to flow, thus forming a self-circulating cooling circuit: hydraulic retarder 6 oil outlet → first cooling valve 4 (inlet at the first port, outlet at the third port) → first oil cooler 10 → first cooling valve 4 (inlet at the fourth port, outlet at the second port) → back to hydraulic retarder 6 oil inlet. This circuit has a short circulation distance, resulting in a short circulation cycle and high heat exchange efficiency. It can quickly carry away hot oil and quickly return it after cooling, thereby enabling rapid heat exchange and effectively suppressing the rise in oil temperature inside the hydraulic retarder. After the self-circulation is established, the external oil supply pump 3 only needs to provide a very small amount of oil to maintain the system pressure, without the need to continuously provide a large flow to drive the circulation. This reduces the load on the oil supply pump 3, reduces the energy consumption of the entire vehicle, and improves economy. In addition, this self-circulating circuit allows the first oil cooler 10 to be dedicated to cooling the hydraulic retarder 6, thereby improving heat dissipation efficiency. Under this condition, since the hydraulic retarder 6 is in the open state, the first oil cooler 10 and the second oil cooler 11 can work independently through the above design, thereby cooling the hydraulic retarder 6 and the gearbox 7 respectively.

[0035] This invention eliminates oil temperature interference between the hydraulic retarder 6 and the transmission 7, achieving precise management of differentiated heat dissipation for both. It also provides a relatively independent, low-temperature cooling circuit for the transmission 7, ensuring its lubrication effect and extending its service life. Furthermore, it establishes an efficient self-circulating cooling circuit for the hydraulic retarder 6, which has the advantages of short cycle time and high heat dissipation efficiency, ensuring continuous braking effect. It also relies solely on its own drive for circulation, thereby reducing dependence on the oil supply pump 3 and improving energy efficiency.

[0036] In this embodiment, as Figure 1 As shown, the cooling water circulation loop 12 includes: The vehicle's water supply is 121. The water supply pump 122 is used to draw water from the vehicle water source 121 and provide sufficient pressure and flow. Its inlet is connected to the vehicle water source 121 through a pipeline, and its outlet is connected to the inlet of the first oil cooler 10 and the second oil cooler 11 through pipelines respectively. The outlets of the first oil cooler 10 and the second oil cooler 11 are both connected to the vehicle's water source 121 via pipelines.

[0037] It is understandable that the above-mentioned parallel water supply method ensures that the first oil cooler 10 and the second oil cooler 11 can obtain cooling conditions with the same inlet water temperature and basically the same water pressure.

[0038] The above-mentioned water circulation loop 12, through parallel design, can simultaneously and independently deliver cooling water to the first oil cooler 10 and the second oil cooler 11. Although it increases the complexity and cost of the system, it ensures the consistency and controllability of the inlet water temperature of each oil cooler. This is beneficial to temperature-sensitive automatic transmissions and can effectively prevent performance degradation due to poor cooling, thus providing a guarantee for the reliable operation of the transmission system.

[0039] In this embodiment, as Figure 1 As shown, it includes: The first one-way valve 13 is connected in series between the oil outlet of the hydraulic retarder 6 and the first port of the first cooling valve 4 to allow the oil to flow in one direction and to stop it in the opposite direction. The second one-way valve 14 is connected in series between the oil inlet of the hydraulic retarder 6 and the second port of the first cooling valve 4, and is used to make the oil flow in one direction and cut off in the opposite direction.

[0040] Through the above design, the unidirectional flow of oil is forcibly restricted, thereby providing positive guidance and reverse cut-off for the self-circulating cooling circuit of the hydraulic retarder 6, and enhancing the stability and efficiency of self-circulation.

[0041] In this embodiment, as Figure 1 As shown, it includes: The third one-way valve 15 is connected in series between the oil outlet of the gearbox 7 and the first port of the second cooling valve 5.

[0042] The above design ensures that the hot oil in the transmission 7 can be stably and reliably guided to the second cooling valve 5 and subsequent cooling passages, preventing oil backflow that may be caused by factors such as pressure fluctuations or changes in vehicle posture, thereby ensuring the continuity of lubrication and cooling of the transmission 7.

[0043] Example 2: like Figure 2 As shown, this application discloses a multi-cycle cooling system, which differs from Embodiment 1 in that the cooling water circulation loop 12 includes: The vehicle's water supply is 121. The water supply pump 122 has its inlet connected to the vehicle water source 121 via a pipeline, and its outlet connected to the inlet of the second oil cooler 11 via a pipeline. The outlet of the second oil cooler 11 is connected to the inlet of the first oil cooler 10 via a pipeline, and the outlet of the first oil cooler 10 is connected to the vehicle water source 121 via a pipeline.

[0044] Understandably, by allowing the cooling water to flow sequentially through the second oil cooler 11 and the first oil cooler 10, the maximum temperature difference can be used to fully cool the gearbox 7, ensuring that it operates within the optimal temperature range. Subsequently, the preheated cooling water flows through the first oil cooler 11. At this time, although the inlet water temperature rises, a sufficient temperature difference is still maintained between it and the extremely high-temperature sludge oil. This ensures efficient heat dissipation of the sludge while achieving tiered utilization and optimal configuration of the cooling water's cooling capacity.

[0045] The water circulation loop 12 described above has the advantages of simple structure and low cost through series design. Although it is less effective in temperature control, since the manual transmission itself is not sensitive to temperature, it can efficiently meet the core heat dissipation needs of the whole vehicle with the lowest manufacturing cost and system complexity while ensuring its reliable operation.

[0046] Example 3; This application discloses a mining dump truck, including the multi-cycle cooling system described in Embodiment 1 or Embodiment 2.

[0047] Numerous specific details are set forth in this specification. However, it will be understood that embodiments of this invention may be practiced without these specific details. In some instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this specification.

[0048] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and not to limit it. Although the utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this utility model, and they should all be covered within the scope of the claims and specification of this utility model.

Claims

1. A multi-cycle cooling system, characterized in that, include: Oil pan; The main control valve has a first port, a second port, a third port and a fourth port, and has a first position and a second position. In the first position, the second port and the fourth port are connected; in the second position, the first port and the third port are connected, and the second port and the fourth port are connected. The oil supply pump has its inlet connected to the oil pan via a pipeline, and its outlet connected to the first and second ports of the main control valve via a pipeline. The first cooling valve has a first port, a second port, a third port and a fourth port, and has a first station and a second station. In the first station, the first port and the second port are connected; in the second station, the first port and the third port are connected, and the second port and the fourth port are connected. The second cooling valve has a first port, a second port, a third port and a fourth port, and has a first station and a second station. In the first station, the first port and the third port are connected, and the second port and the fourth port are connected; in the second station, the first port and the second port are connected. The hydraulic retarder has its oil inlet connected to the second port of the first cooling valve via a pipeline, and its oil outlet connected to the first port of the first cooling valve via a pipeline. The gearbox has its oil inlet connected to the fourth port of the main control valve via a pipeline, and its oil outlet connected to the first port of the second cooling valve via a pipeline. The pressure reducing valve has its inlet connected to the third port of the main control valve via a pipeline, its outlet connected to the inlet of the hydraulic retarder via a pipeline, and its drain port connected to the oil pan via a pipeline. The pressure limiting shut-off valve has its inlet connected to the outlet of the hydraulic retarder via a pipeline, its outlet connected to the oil pan via a pipeline, and its pressure testing port connected to the inlet of the pressure reducing valve via a pipeline. The first oil cooler has its oil inlet connected to the third port of the first cooling valve and the third port of the second cooling valve via pipelines, and its oil outlet connected to the fourth port of the first cooling valve and the fourth port of the second cooling valve via pipelines. The second oil cooler has its oil inlet connected to the second port of the second cooling valve via a pipeline, and its oil outlet connected to the oil pan via a pipeline. The cooling water circulation loop has cooling water flowing through the first oil cooler and the second oil cooler for heat exchange with the oil. When the hydraulic retarder is closed, the main control valve, the first cooling valve, and the second cooling valve are all in the first position; when the hydraulic retarder is open, the main control valve, the first cooling valve, and the second cooling valve are all in the second position.

2. The multi-cycle cooling system according to claim 1, characterized in that, The cooling water circulation loop includes: Water source for the whole vehicle; The water supply pump has its inlet connected to the vehicle's water source via a pipeline, and its outlet connected to the inlets of the first oil cooler and the second oil cooler via pipelines respectively. The outlets of the first and second oil coolers are both connected to the vehicle's water source via pipelines.

3. The multi-cycle cooling system according to claim 1, characterized in that, The cooling water circulation loop includes: Water source for the entire vehicle; The water supply pump has its inlet connected to the vehicle's water source via a pipeline, and its outlet connected to the inlet of the second oil cooler via a pipeline. The outlet of the second oil cooler is connected to the inlet of the first oil cooler via a pipeline, and the outlet of the first oil cooler is connected to the vehicle's water source via a pipeline.

4. The multi-cycle cooling system according to claim 1, characterized in that, include: A first check valve is connected in series between the oil outlet of the hydraulic retarder and the first port of the first cooling valve. The second check valve is connected in series between the oil inlet of the hydraulic retarder and the second port of the first cooling valve.

5. The multi-cycle cooling system according to claim 1, characterized in that, include: A third one-way valve is connected in series between the oil outlet of the gearbox and the first port of the second cooling valve.

6. A mining dump truck, characterized in that, include: The multi-cycle cooling system according to any one of claims 1 to 5.

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