Underground lithium battery mine car double-loop hydraulic system and control method thereof

Abstract

A dual-circuit hydraulic system and its control method for an underground lithium battery mining vehicle are disclosed. The system includes a hydraulic tank, an electric pump, a filling valve, an accumulator, a dual-path foot brake valve, an electro-proportional pressure reducing valve, and a vehicle controller (VCU). The electric pump fills the accumulator via the filling valve. The accumulator is connected to both the electro-proportional pressure reducing valve and the dual-path foot brake valve. The output port of the electro-proportional pressure reducing valve is connected to the pilot control port of the dual-path foot brake valve. The VCU drives the electro-proportional pressure reducing valve based on the brake pedal travel signal, achieving stepless linear adjustment of the braking pressure. This invention employs a dual-redundant hydraulic circuit to ensure basic safety, achieves smooth and precise linear control braking through electro-proportional control, and integrates sensors for pressure and temperature monitoring and remote diagnostics. The parking brake also features an automatic parking function.

Description

Technical Field

[0001] This invention relates to the field of engineering machinery technology, and more specifically, to a hydraulic braking system and its control method for underground mining vehicles, particularly lithium battery-powered mining trucks. Background Technology

[0002] Underground mining trucks are core equipment for transporting materials underground. With the industry's shift towards electrification and intelligentization, higher demands are being placed on the safety, smoothness, and controllability of vehicle braking systems. The company's first-generation 20-ton pure electric underground dump truck uses a single-circuit hydraulic braking system, where the service brake and parking brake share the same hydraulic circuit. This system has inherent defects: firstly, the braking force and pedal travel lack a linear relationship, resulting in severe brake "nodding" and poor smoothness and ride comfort; secondly, the system is susceptible to single-point failure—if a leak occurs in the main circuit or a core component fails, the vehicle's braking force will be completely lost, posing a significant safety hazard.

[0003] Currently, the most advanced solution for downhole engineering machinery is to use a "dual-circuit hydraulic system" to drive a "hydraulic wet multi-disc brake." This solution achieves basic redundancy through independent or cross-arrangement of the front and rear axles, significantly improving failure safety. However, this solution still has the following shortcomings: Outdated control methods are incompatible with electrification platforms: relying on pure hydraulic or air-to-oil drive, braking commands depend on the physical characteristics of mechanical linkages and valve bodies, making it impossible to achieve precise, programmable brake-by-wire, difficult to deeply integrate with the vehicle's electronic control unit (VCU), and unable to coordinate intelligent functions such as regenerative braking.

[0004] Lack of intelligent and diagnostic capabilities: The system lacks comprehensive status sensing and remote monitoring capabilities, making it impossible to acquire key hydraulic parameters in real time. Troubleshooting relies on on-site experience, resulting in low maintenance efficiency and high costs associated with unplanned downtime.

[0005] The parking brake lacks intelligence: traditional mechanical or simple solenoid valve controlled parking brakes cannot be easily integrated into automated scenarios such as automatic start-stop and hill start assist. Summary of the Invention

[0006] The present invention aims to solve the problems existing in the prior art and provide an intelligent dual-circuit electro-hydraulic braking system and its control method specifically for underground lithium battery mining vehicles.

[0007] To solve the above-mentioned technical problems, the technical solution of the present invention is: a dual-circuit hydraulic system for underground lithium battery mining vehicles, comprising: The system comprises a hydraulic oil tank (1), an electric pump (2), a filling valve (4), an accumulator group (6), a dual-path foot brake valve (7), a relay valve (10), an electro-proportional pressure reducing valve (5), and a vehicle control unit (VCU). The inlet of the electric pump (2) is connected to the hydraulic oil tank (1), and the outlet is connected to the filling valve (4). The outlet of the filling valve (4) is connected to the accumulator group (6). The accumulator group (6) is connected to the inlet of the electro-proportional pressure reducing valve (5) and the inlet of the dual-path foot brake valve (7). The outlet of the electro-proportional pressure reducing valve (5) is connected to the pilot control port of the dual-path foot brake valve (7). The first outlet of the dual-path foot brake valve (7) is used to connect to the front axle brake, and the second outlet is connected to the middle and rear axle brakes through the relay valve (10). The relay valve (10) is used to shorten the response time of the rear axle brake circuit. The system also includes a sensor for acquiring brake pedal travel signals, the sensor being connected to the input of the vehicle controller (VCU); the output of the vehicle controller (VCU) is connected to the control of the electro-proportional pressure reducing valve (5), which generates a control current based on the travel signal, drives the electro-proportional pressure reducing valve (5) to steplessly adjust the pilot pressure output to the pilot control port, thereby linearly controlling the output braking pressure of the dual-path foot brake valve (7).

[0008] As an improvement, a manual pressure pump (8) is also included, which is connected between the filling valve (4) and the accumulator group (6) to provide emergency pressure; the filling valve (4), the parking brake solenoid valve (9), and the manual pressure pump (8) are integrated and installed on the hydraulic oil tank (1).

[0009] As an improvement, the sensor is an angle sensor, which is linked with the dual-path foot brake valve (7); the vehicle controller VCU is configured to: control the regenerative electric brake to intervene when the pedal is pressed at an angle within a first preset range; and control the electric proportional pressure reducing valve (5) to output hydraulic braking force when the pedal angle exceeds the first preset range.

[0010] As an improvement, a sensor group is also included, including at least a pressure sensor for monitoring brake circuit pressure, a temperature sensor for monitoring hydraulic oil temperature, and a contamination sensor for monitoring oil contamination level; all sensor groups are connected to the vehicle control unit (VCU) and the driver's cab display via a CAN bus.

[0011] As an improvement, a parking brake solenoid valve (9) is also included, the control end of which is connected to the vehicle controller VCU; the vehicle controller VCU is configured to automatically control the action of the parking brake solenoid valve (9) according to the received vehicle speed, gear and slope signals, so as to realize the automatic parking function.

[0012] As an improvement, the hydraulic tank (1) is an integrated structure with a total volume of 21L, used to integrate and install an electric pump (2), an accumulator group (6), a filling valve (4), a parking brake solenoid valve (9), a manual pressure pump (8), a temperature sensor, and a liquid level display.

[0013] As an improvement, the electric pump (2) is a dual-shaft electric pump, with one end driving a vane pump and the other end driving a cooling pump. The rated power of the motor is 5kW and the protection level is IP67.

[0014] As an improvement, the filling valve (4) is configured to start when the pressure of the accumulator group (6) is lower than 10 MPa, and fill it with liquid at a rate of 6 L / min until it reaches 12 MPa and then stops.

[0015] The control method of the present invention includes at least one of the following modes: Normal driving braking mode: The vehicle controller VCU receives the brake pedal travel signal and outputs control current to the electric proportional pressure reducing valve (5) according to the preset braking force distribution strategy. It linearly adjusts the pilot pressure output to the dual-path foot brake valve (7) to control the braking pressure output to the brake. Drive-by-wire active braking mode: The vehicle controller (VCU) operates independently of the driver's pedal according to the vehicle status and directly outputs control current to the proportional pressure reducing valve (5) to achieve active braking; Emergency braking mode: When the electric pump (2) or the filling valve (4) fails, operate the manual pressure pump (8) to establish emergency braking pressure; Automatic parking mode: After the vehicle comes to a complete stop, the vehicle controller (VCU) automatically controls the parking brake solenoid valve (9) to apply the parking brake, and automatically controls it to release the parking brake when it detects the intention to start.

[0016] The beneficial effects of this invention compared to the prior art are: 1. High safety redundancy: Adopting a dual-circuit hydraulic architecture, if any one circuit fails, the other circuit can still provide effective braking force; at the same time, the accumulator group provides emergency braking capability, and the manual pump provides mechanical redundancy. Multiple protections greatly improve the inherent safety of vehicle operation. 2. Smooth and precise braking: By introducing an electric proportional pressure reducing valve and an angle sensor, the braking intention is converted into an electrical signal control, realizing a linear relationship between braking force and pedal travel, eliminating the "nodding" phenomenon; in addition, intelligent coordination between electric braking and hydraulic braking is achieved, improving energy recovery efficiency. 3. High level of intelligence: The system integrates multi-dimensional sensing capabilities such as pressure, temperature, and pollution level, and realizes real-time status monitoring and remote fault diagnosis through CAN bus; 4. High integration and maintainability: Multiple hydraulic valves, sensors and manual pumps are integrated into the hydraulic oil tank, resulting in a compact structure; comprehensive status data can guide preventive maintenance, accurate fault location, and significantly reduce operation and maintenance costs. Attached Figure Description

[0017] Figure 1 This is a diagram of the hydraulic system piping.

[0018] Figure 2 This is a schematic diagram of the filling valve assembly.

[0019] Figure 3 This is a schematic diagram of a dual-way foot valve.

[0020] Figure 4 This is a schematic diagram of an electro-proportional pressure reducing valve.

[0021] Figure 5 This is a schematic diagram of a manual pressure pump.

[0022] Figure 6 This is a schematic diagram of the parking valve. Detailed Implementation

[0023] The present invention will now be further described with reference to the accompanying drawings.

[0024] like Figure 1 As shown, a dual-circuit hydraulic system for an underground lithium battery mining vehicle includes: a hydraulic oil tank 1, an electric pump 2, an emergency pump 3, a filling valve 4, an electro-proportional pressure reducing valve 5, an accumulator group 6, a dual-circuit foot brake valve 7, a manual pressurization pump 8, a parking brake solenoid valve 9, a relay valve 10, and a vehicle controller VCU.

[0025] The inlet of the electric pump 2 is connected to the hydraulic oil tank 1, and the outlet is connected to the filling valve 4; the outlet of the filling valve 4 is connected to the accumulator group 6; the accumulator group 6 is connected to the inlet of the electro-proportional pressure reducing valve 5 and the inlet of the dual-way foot brake valve 7 respectively; the outlet of the electro-proportional pressure reducing valve 5 is connected to the pilot control port of the dual-way foot brake valve 7; the first outlet of the dual-way foot brake valve 7 is used to connect to the front axle brake 11, and the second outlet is connected to the middle and rear axle brake 12 through the relay valve 10; the relay valve 10 is used to shorten the response time of the rear axle brake circuit; the manual pressure pump 8 is connected between the filling valve 4 and the accumulator group 6 to provide emergency pressure; the control terminal of the vehicle brake solenoid valve 9 is connected to the vehicle controller VCU; the vehicle controller VCU is configured to automatically control the action of the parking brake solenoid valve 9 according to the received vehicle speed, gear, and gradient signals to realize the automatic parking function.

[0026] The system also includes a sensor for acquiring brake pedal travel signals, which is connected to the input of the vehicle control unit (VCU). The output of the VCU is connected to the control of the electro-proportional pressure reducing valve 5, which generates a control current based on the travel signal to drive the electro-proportional pressure reducing valve 5 to steplessly adjust the pilot pressure output to the pilot control port, thereby linearly controlling the output braking pressure of the dual-path foot brake valve 7. The sensor is an angle sensor and is linked to the dual-path foot brake valve 7. The VCU is configured to: control regenerative braking to engage when the pedal is depressed within a first preset range; and control the electro-proportional pressure reducing valve 5 to output hydraulic braking force when the pedal angle exceeds the first preset range.

[0027] It also includes a sensor group, including at least a pressure sensor for monitoring brake circuit pressure, a temperature sensor for monitoring hydraulic oil temperature, and a contamination sensor for monitoring oil contamination level; all sensor groups are connected to the vehicle control unit (VCU) and the driver's cab display via a CAN bus.

[0028] Hydraulic oil tank 1 consists of a brake-steering oil tank and a cooling oil tank. The braking and steering systems share a single tank. The brake-steering oil tank, cooling oil tank, accumulator, pump bracket, and other components are assembled into a single unit. The overall dimensions of the brake-steering oil tank are 0.3m long x 0.2m wide x 0.3m high, with a total weight of approximately 15kg and a total volume of approximately 21L. The brake-steering pump, accumulator, filling valve, parking valve, manual pressure pump, temperature sensor, and level display are integrated into the oil tank. The brake-steering pump is a dual-shaft electric pump, with the brake-steering pump on the left end of the dual-shaft motor and the cooling pump on the right end. The electric pump motor has a rated power of 5KW, a maximum output power of 10KW, and an IP67 protection rating. The brake-steering pump uses a vane pump with a displacement of 14ml / r, a rated speed of 1500r / min, and a flow rate of 21L / min. According to the vehicle steering system calculation, this pump meets the flow and pressure requirements of the braking and steering systems.

[0029] like Figure 2As shown, the filling valve 4 and the parking valve assembly 9 form a valve group. The main function of the filling valve 4 is to replenish hydraulic oil to the system according to the pressure changes of the braking and steering system, maintain the system pressure stability, and ensure the stable and reliable operation of the vehicle's braking and steering system. When the vehicle brakes frequently, and the pressure of the accumulator 6 drops below 10 MPa, the filling valve 4 is activated. The A port of the filling valve 4 rapidly fills the accumulator 6 at a filling rate of 6 L / min. When the accumulator 6 reaches the pressure limit of 12 MPa, the filling stops. At this time, the system flow flows from the O port of the filling valve 4 to the steering gear and then back to the oil tank. When the steering gear is working, the power steering chamber will form a closed space, build up pressure, and provide steering assistance, making steering operation lighter and more flexible. The filling valve 4 is equipped with a pressure relief valve in the steering circuit. When the steering circuit pressure reaches 16.5 MPa, the system automatically relieves pressure to protect the circuit system components. In addition, the SW port of the filling valve 4 provides control pressure for the gearbox shifting and lifting directional valves.

[0030] The vehicle uses a total of three 4L accumulators 6, one for the front axle brake circuit and two for the rear axle brake circuit. The main function of accumulator 6 during normal operation is to store energy, provide braking pressure, and ensure stable brake circuit pressure. Upon initial vehicle start-up, accumulator 6 takes approximately 45 seconds to fill to normal operating temperature. In emergency situations, accumulator 6 can provide the pressure required for emergency braking. Under normal circumstances, the energy stored in accumulator 6 is sufficient to guarantee six braking maneuvers for the entire vehicle.

[0031] like Figure 3 As shown, the dual-way foot pedal valve 7 is a braking actuator, with separate circuits controlling the front and rear axle brakes. When the foot pedal valve is depressed, the output valve of the dual-way foot pedal valve 7 outputs a braking pressure of 7 MPa, and the braking pressure of the front and rear axle service brakes is also 7 MPa, achieving the braking effect. When the dual-way foot pedal valve 7 is released, hydraulic oil returns to the oil tank through the dual-way foot pedal valve 7, the brake disc pressure is unloaded, and the front and rear axle brakes stop working. The dual-way foot pedal valve 7 is equipped with an angle sensor, and the vehicle control can be adjusted according to the pedal angle. The vehicle control strategy is electric braking for the first 10° and hydraulic braking for the last 15°.

[0032] like Figure 4 As shown, the main function of the electro-proportional pressure reducing valve 5 is to achieve linear control of braking through an electrical signal, that is, to reserve an interface for the subsequent chassis to achieve drive-by-wire. The electro-proportional pressure reducing valve 5 can adjust the output pressure proportionally according to the magnitude of the electrical signal. The dual-way foot pedal valve 7 achieves linear output of braking pressure according to the change of the output pressure of the electro-proportional pressure reducing valve 5.

[0033] Because the foot pedal brake valve is located in the driver's cab, and the distance from the brake oil line to the rear axle is relatively long, under normal circumstances, when the foot pedal is pressed, the front axle brake disc will brake first. Due to the longer brake line, the braking response time of the rear axle will be delayed compared to the front axle. Under heavy load, the weight of the entire vehicle is concentrated on the cargo box. If the front axle brakes first, the inertial impact force of the fully loaded cargo box will impact the front axle. Therefore, a relay valve 10 needs to be installed before the rear axle brake line. By utilizing the fast response characteristic of the relay valve 10, the effect of prioritizing the rear axle or braking the front and rear axles simultaneously can be achieved.

[0034] like Figure 5 As shown, the function of the manual pressurization pump 8 is to manually pressurize the vehicle in the event of failure of the filling valve 4 or the pump. The manual pressurization range is between 0-30MPa, which meets the requirements for emergency braking. It can provide pressure for the accumulator, braking and lifting reversing control, and improve the emergency response capability of the vehicle.

[0035] like Figure 6 As shown, the filling valve 4 is connected to the parking valve 9. The parking valve 9 is equipped with a pressure reducing valve at the front end to reduce the pressure from 12MPa to 7.5MPa. The parking valve 9 mainly controls the rear axle parking brake. The parking valve is controlled by the VCU to achieve the functions of driving and parking, and releasing the parking brake.

[0036] The temperature sensor monitors the temperature of the brake steering fluid reservoir, promptly feeding back the data to the VCU (Vehicle Control Unit), detecting abnormal hydraulic fluid reservoir temperatures, and ensuring system stability. The brake steering fluid reservoir requires one temperature sensor, whose primary function is to monitor the temperature of the braking system circuit.

[0037] The hydraulic system monitors the pressure of each hydraulic circuit and feeds the pressure values ​​back to the VCU. Based on the pressure changes, the VCU outputs signals for braking and steering, enabling intelligent vehicle control. The hydraulic braking system requires three analog output pressure sensors: a front axle brake pressure sensor, middle and rear axle pressure sensors, and a system circuit pressure sensor.

[0038] The control method of the present invention includes at least one of the following modes: Normal service braking mode: The vehicle controller (VCU) receives the brake pedal travel signal and outputs control current to the electro-proportional pressure reducing valve 5 according to the preset braking force distribution strategy. This linearly adjusts the pilot pressure output to the dual-path foot brake valve 7, thereby controlling the braking pressure output to the brake. Drive-by-wire active braking mode: The vehicle controller (VCU) operates independently of the driver's pedal based on the vehicle status, directly outputting control current to the proportional pressure reducing valve 5 to achieve active braking; Emergency braking mode: When electric pump 2 or filling valve 4 fails, operate manual pressure pump 8 to establish emergency braking pressure; Automatic parking mode: After the vehicle comes to a complete stop, the vehicle controller (VCU) automatically controls the parking brake solenoid valve 9 to apply the parking brake, and automatically controls it to release the parking brake when it detects the intention to start.

[0039] The braking system provided by this invention combines high safety with intelligence. Its dual-circuit design ensures braking redundancy in the event of a single-point failure, significantly improving safety. Simultaneously, it employs electro-proportional control to achieve linear and precise adjustment of braking force, making the braking process smoother. Furthermore, the system integrates status monitoring and remote diagnostic functions, and realizes automatic control of the parking brake, significantly improving the vehicle's intelligence level and maintainability.

Claims

1. An underground lithium battery mule dual circuit hydraulic system, characterized by, include: Hydraulic oil tank (1), electric pump (2), filling valve (4), accumulator group (6), dual-way foot brake valve (7), relay valve (10), electric proportional pressure reducing valve (5) and vehicle controller VCU; The inlet of the electric pump (2) is connected to the hydraulic oil tank (1), and the outlet is connected to the filling valve (4); the outlet of the filling valve (4) is connected to the accumulator group (6); the accumulator group (6) is connected to the inlet of the electro-proportional pressure reducing valve (5) and the inlet of the dual-way foot brake valve (7); the outlet of the electro-proportional pressure reducing valve (5) is connected to the pilot control port of the dual-way foot brake valve (7); the first outlet of the dual-way foot brake valve (7) is used to connect to the front axle brake, and the second outlet is connected to the middle and rear axle brakes through the relay valve (10); the relay valve (10) is used to shorten the response time of the rear axle brake circuit. The system also includes a sensor for acquiring brake pedal travel signals, the sensor being connected to the input of the vehicle controller (VCU); the output of the vehicle controller (VCU) is connected to the control of the electro-proportional pressure reducing valve (5), which generates a control current based on the travel signal, drives the electro-proportional pressure reducing valve (5) to steplessly adjust the pilot pressure output to the pilot control port, thereby linearly controlling the output braking pressure of the dual-path foot brake valve (7).

2. The system of claim 1, wherein, It also includes a manual pressure pump (8), which is connected between the filling valve (4) and the accumulator group (6) to provide emergency pressure; the filling valve (4), the parking brake solenoid valve (9), and the manual pressure pump (8) are integrated and installed on the hydraulic oil tank (1).

3. The system according to claim 1, characterized in that, The sensor is an angle sensor, which is linked with the dual-path foot brake valve (7); the vehicle controller VCU is configured to: control the regenerative electric brake to intervene when the pedal is pressed at an angle within the first preset range; and control the electric proportional pressure reducing valve (5) to output hydraulic braking force when the pedal angle exceeds the first preset range.

4. The system according to claim 1, characterized in that, It also includes a sensor group, including at least a pressure sensor for monitoring brake circuit pressure, a temperature sensor for monitoring hydraulic oil temperature, and a contamination sensor for monitoring oil contamination level; all sensor groups are connected to the vehicle control unit (VCU) and the driver's cab display via a CAN bus.

5. The system according to claim 1, characterized in that, It also includes a parking brake solenoid valve (9), whose control terminal is connected to the vehicle controller VCU; the vehicle controller VCU is configured to automatically control the action of the parking brake solenoid valve (9) according to the received vehicle speed, gear and slope signals, so as to realize the automatic parking function.

6. The system according to claim 1, characterized in that, The hydraulic tank (1) is an integrated structure with a total volume of 21L. It is used to integrate and install an electric pump (2), an accumulator group (6), a filling valve (4), a parking brake solenoid valve (9), a manual pressure pump (8), a temperature sensor, and a liquid level display.

7. The system according to claim 1, characterized in that, The electric pump (2) is a twin-shaft electric pump, with one end driving a vane pump and the other end driving a cooling pump. The rated power of the motor is 5kW and the protection level is IP67.

8. The system according to claim 1, characterized in that, The filling valve (4) is configured to start when the pressure of the accumulator group (6) is lower than 10MPa, and fill it with liquid at a rate of 6L / min until it reaches 12MPa and then stops.

9. A braking control method for an underground lithium battery mining vehicle, applied to the system described in any one of claims 1 to 8, characterized in that, Includes at least one of the following modes: Normal driving braking mode: The vehicle controller VCU receives the brake pedal travel signal and outputs control current to the electric proportional pressure reducing valve (5) according to the preset braking force distribution strategy. It linearly adjusts the pilot pressure output to the dual-path foot brake valve (7) to control the braking pressure output to the brake. Drive-by-wire active braking mode: The vehicle controller (VCU) operates independently of the driver's pedal according to the vehicle status and directly outputs control current to the proportional pressure reducing valve (5) to achieve active braking; Emergency braking mode: When the electric pump (2) or the filling valve (4) fails, operate the manual pressure pump (8) to establish emergency braking pressure; Automatic parking mode: After the vehicle comes to a complete stop, the vehicle controller (VCU) automatically controls the parking brake solenoid valve (9) to apply the parking brake, and automatically controls it to release the parking brake when it detects the intention to start.

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