Mobile crane hybrid power system and gravitational potential energy closed-loop recovery method

Abstract

The invention discloses a mobile crane hybrid power system and a gravitational potential energy closed-loop recovery method, and belongs to the technical field of engineering machinery energy conservation. The system comprises an engine transmission system, an electric drive unit, a transmission clutch, a hydraulic pump clutch, a VCU intelligent controller, a power battery pack and a potential energy recovery system. The electric drive unit is a generator / motor all-in-one machine, can drive the hydraulic pump and can also assist in driving the drive axle. The potential energy recovery system converts gravitational potential energy of a heavy object or a cargo boom in hoisting operation into electric energy for storage through a hydraulic motor and a generator. The VCU integrates intelligent switching logic of eight working modes and a derating recovery algorithm based on a battery SOC, and the functions of driving electric auxiliary driving, kinetic energy recovery, electromagnetic retarding, parking power generation, oil-electricity hybrid and pure electric operation are achieved. By recovering kinetic energy, gravitational potential energy and standby mechanical energy and converting the kinetic energy, gravitational potential energy and standby mechanical energy into electric energy, energy conservation and emission reduction are achieved, meanwhile, braking safety is enhanced, the problem of DPF blockage is effectively solved, and the system is suitable for various mobile cranes.

Description

Technical Field

[0001] This invention relates to the field of energy-saving technology for engineering machinery, and in particular to a hybrid system for a mobile crane and a closed-loop method for recovering gravitational potential energy. Background Technology

[0002] Mobile lifting equipment such as truck cranes, vehicle-mounted cranes, and all-terrain cranes currently rely primarily on internal combustion engines to drive power take-off units that power hydraulic pumps, or external power sources for pure electric drive. This traditional approach has significant drawbacks: engine-driven mobile lifting equipment suffers from high fuel consumption and insufficient braking force due to its heavy weight; the engine operates at low power and low speed for extended periods during operation, resulting in wasted mechanical energy during idle and idle operation, low fuel efficiency, and a high risk of DPF clogging in China VI compliant engines due to insufficient exhaust temperature; external power sources and pure electric drive often lack access to external power and charging facilities in construction environments, limiting their application scenarios; more importantly, the significant gravitational potential energy generated during the descent of the load and boom is wasted through hydraulic throttling and heating, resulting in extremely low energy utilization.

[0003] Although some hybrid technologies have been applied to construction machinery, they are mostly focused on energy recovery during the driving phase. They lack a closed-loop recovery system for the unique energy flow during the operation phase, and the system mode is simple, failing to deeply integrate the lifting operation conditions with the vehicle's energy management, resulting in insufficient intelligence. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned defects of the prior art and provide a hybrid system for mobile cranes and a closed-loop method for recovering gravitational potential energy, which aims to achieve significant energy saving and consumption reduction, improve braking safety, solve the DPF blockage problem, and greatly improve energy utilization.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A hybrid system for a mobile crane includes an engine, a clutch, a gearbox, an electric drive unit, a transmission clutch, a hydraulic pump clutch, a VCU intelligent controller, a power battery pack, a bidirectional inverter, a hydraulic pump, and a potential energy recovery system.

[0007] The engine's power output is sequentially transmitted to the input end of the electric drive unit via a clutch and a gearbox. The electric drive unit is an integrated generator / motor unit with two power paths at its output end: the first path is connected to the vehicle drive axle via the transmission clutch for driving or energy recovery; the second path is connected to the hydraulic pump via the hydraulic pump clutch for providing hydraulic power. The electric drive unit is electrically connected to the power battery pack via the bidirectional inverter to achieve bidirectional flow of electrical energy.

[0008] The balance valve of the crane actuator is replaced with a high-flow gravity-feeding balance valve, which allows the oil in the working chamber to flow out smoothly at a larger flow rate during descent, achieving effective recovery of potential energy. The potential energy recovery system includes a first potential energy recovery subsystem and a second potential energy recovery subsystem. Both are composed of a control valve group, a potential energy recovery hydraulic motor, a recovery generator unit, and a one-way speed control valve. The oil inlet of the first potential energy recovery subsystem is connected to the oil circuit downstream of the balance valve of the rodless chamber of the crane luffing cylinder and / or the rodless chamber of the telescopic boom cylinder, for recovering the gravitational potential energy of the crane boom during luffing and / or boom retraction. The oil inlet of the second potential energy recovery subsystem is connected to the oil circuit downstream of the balance valve of the hoisting chamber of the crane's main winch motor and / or the hoisting chamber of the auxiliary winch motor, for recovering the gravitational potential energy of the load during the lowering of the main winch and / or auxiliary winch. The potential energy recovery system converts the recovered gravitational potential energy into electrical energy and stores it in the power battery pack.

[0009] The air circuit of the clutch slave pump is equipped with a normally closed two-position three-way solenoid valve and an adjustable throttle valve controlled by the VCU intelligent controller to realize the electronically controlled slow action of the clutch. The VCU intelligent controller, as the control core of the system, communicates with the engine ECU, transmission TCU, battery management system BMS, bidirectional inverter, ABS unit and sensors such as accelerator pedal, brake pedal and vehicle speed through the CAN bus. It is used to collect data from the above units in real time and execute intelligent decision-making and switching logic of eight working modes according to the preset control strategy.

[0010] This invention also provides a closed-loop method for recovering gravitational potential energy, characterized by comprising the following steps:

[0011] Detect action signals of crane boom descent and / or load descent;

[0012] The control valve group in the potential energy recovery system is turned on, so that the pressure oil drives the potential energy recovery hydraulic motor to rotate.

[0013] The potential energy recovery hydraulic motor drives the recovery generator unit to generate electricity.

[0014] The electrical energy generated by the recycling generator unit is rectified and regulated before being stored in the power battery pack.

[0015] The VCU intelligent controller prioritizes maintaining the stable descent speed of the actuator and dynamically adjusts the power generation of the recovery generator unit based on the real-time state of charge (SOC) of the power battery pack and according to a preset algorithm; thereby maximizing the recovery of gravitational potential energy while ensuring the normal operating speed of each mechanism.

[0016] The beneficial effects of this invention are as follows:

[0017] 1. Significant energy saving and consumption reduction: By using electric auxiliary drive and brake kinetic energy recovery, driving fuel consumption is effectively reduced; by recovering the gravitational potential energy of the load and the lowering of the crane arm during operation and the excess mechanical energy of the engine during standby, high-efficiency energy utilization under all working conditions is achieved, significantly improving energy utilization rate.

[0018] 2. Enhanced driving safety: Electric braking force is provided during vehicle braking, effectively compensating for the insufficient braking force caused by the vehicle's heavy weight; the VCU intelligent control of the clutch's smooth engagement and disengagement eliminates the impact of power transmission, protects the transmission system, and enhances operational safety and smoothness.

[0019] 3. Effectively solves environmental pain points: By using the parking generator mode when the vehicle is parked and the power take-off switch is on, the China VI diesel engine can continuously operate in the high-efficiency range, thereby increasing the exhaust temperature and fundamentally avoiding the DPF blockage problem caused by low-temperature operation, thus improving the vehicle's environmental reliability.

[0020] 4. Optimized Operation Performance and Comfort: By using the hybrid intelligent operation mode when the vehicle is parked and the power take-off switch is on, as well as the pure electric drive hydraulic pump operation mode, not only is the fuel efficiency improved, but also low-noise and zero-emission operation is achieved, thus improving the working environment.

[0021] 5. High level of intelligence and integration: Through intelligent VCU and adaptive switching strategy of eight working modes, the energy flow of the whole vehicle is optimized and managed globally, realizing efficient and smooth operation of the system and a high degree of intelligence.

[0022] 6. Excellent human-machine operation compatibility: By adding an adjustable throttle valve and an electronically controlled solenoid valve to the clutch slave pump air circuit, smooth clutch operation under VCU control is achieved, completely eliminating action shock, and ensuring that electronic control operation and driver mechanical operation do not interfere with each other, with excellent compatibility and reliability. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the overall architecture of the mobile crane hybrid system of the present invention.

[0024] Figure 2 This is a schematic diagram of the hydraulic principle of the potential energy recovery system of the present invention.

[0025] Figure 3 This is a flowchart illustrating the switching logic of the eight working modes of this invention.

[0026] Figure 4 This is a block diagram illustrating the control principle of the VCU intelligent controller of this invention.

[0027] Figure 5This is a schematic diagram of the air circuit principle for the implementation of the clutch electronic control modification of the present invention. Detailed Implementation

[0028] The preferred embodiments of the present invention will now be described in further detail with reference to the accompanying drawings.

[0029] To achieve intelligent electronic control and slow engagement of the clutch, the following modifications were made to the air circuit of the original clutch slave cylinder: An adjustable throttle valve was installed in series at the exhaust port of the clutch slave cylinder. The outlet of the adjustable throttle valve was connected to the working port (A port) of a normally closed two-position three-way solenoid valve. The inlet port (P port) of the solenoid valve was connected to the air source, and the exhaust port (R port) was open to the atmosphere. The control logic is as follows: When the VCU intelligent controller (8) controls the solenoid valve to be energized, the solenoid valve reverses, the inlet port (P port) and the working port (A port) are connected, and the compressed air is slowly throttled by the adjustable throttle valve and enters the slave cylinder, pushing the piston rod to slowly extend, thus achieving slow clutch disengagement; when the solenoid valve is de-energized, the solenoid valve resets, the working port (A port) and the exhaust port (R port) are connected, the compressed air in the clutch slave cylinder is slowly discharged into the atmosphere by the adjustable throttle valve, and the piston rod slowly retracts under the action of the reset spring, thus achieving slow clutch engagement. By adjusting the opening of the adjustable throttle valve, the airflow speed can be precisely controlled, thereby eliminating the impact of the operation. When the VCU intelligent controller (8) is de-energized, the solenoid valve remains de-energized, and the air path remains open to the atmosphere, ensuring that it does not affect the driver's normal operation.

[0030] To achieve efficient gravitational potential energy recovery, the original balance valves in the rodless chambers of the crane's luffing cylinder, telescopic boom cylinder, main winch motor lifting chamber, and auxiliary winch motor lifting chamber are replaced with large-diameter, high-flow gravity-lowering balance valves with lower opening pressure. This modification is a fundamental prerequisite for the system to achieve potential energy recovery. It ensures that when the boom and / or load descend, the pressure oil of the actuator can flow out smoothly with sufficient flow, thereby effectively driving the potential energy recovery hydraulic motor (15) to rotate, avoiding problems such as motion jamming or reduced recovery efficiency due to excessive back pressure in the oil circuit.

[0031] The hardware connections of the system of this invention are as follows: Figure 1As shown. Engine (1), clutch (2) (whose clutch slave pump has been modified by the above-mentioned electronic control), gearbox (3) (the original power take-off is removed), electric drive unit (4) (a high-power permanent magnet synchronous motor PMSM is selected as a generator / motor integrated unit), which is connected to the output flange of gearbox (3). The transmission clutch (5) adopts a normally closed electronic control clutch, which is integrated between the output end of electric drive unit (4) and the input flange of drive axle (6). The hydraulic pump clutch (11) adopts a normally open electronic control clutch, which is integrated between electric drive unit (4) and hydraulic pump (12). The VCU intelligent controller (8) uses a high-performance automotive-grade MCU as the main control chip. The VCU intelligent controller (8) exchanges data with nodes such as engine ECU, gearbox TCU, battery management system BMS, and ABS control unit through CAN bus network. The control valve group (14) of the potential energy recovery system adopts a hydraulically controlled two-position three-way directional valve, whose control oil circuit is drawn from the crane pilot control oil circuit. The one-way speed control valve (18) is installed on the return oil line of the potential energy recovery hydraulic motor (15). Its core safety function is: when the power battery pack (10) cannot recover energy due to being fully charged, or when the potential energy recovery system (including the generator (16), inverter (17) and related control system) experiences an electrical fault, the system will reduce or stop providing the generating counter torque. At this time, the one-way speed control valve (18) provides an independent and reliable safety back pressure to the return oil line with its inherent mechanical throttling characteristics, limiting the descent speed of the heavy object or the lifting arm, thereby preventing it from stalling and falling, and playing a role in mechanical safety redundancy protection. The valve allows free flow of oil when the lifting arm or heavy object is being lifted, and throttles and limits the speed when it is descending.

[0032] After the system is powered on and initialized, the VCU intelligent controller (8) continuously collects data from various sensors and network nodes. When the vehicle is in motion and the SOC value of the power battery is greater than 30%, it enters the electric auxiliary drive mode when the vehicle is in motion. When braking, deceleration, or downhill conditions are detected, it switches to the kinetic energy recovery mode or the electromagnetic deceleration mode when the vehicle is in motion. When the vehicle is in parking mode and the power take-off switch signal is valid, it intelligently enters the parking power generation mode, the hybrid electric intelligent operation mode, or the pure electric drive hydraulic pump operation mode when the vehicle is parked and the power take-off switch is on, based on the current SOC value.

[0033] The potential energy recovery process is shown in the attached figure. Figure 2The principle shown and the method described in the claims are performed automatically. Taking the lowering of the luffing cylinder as an example: when the luffing handle is lowered, the pilot control oil pressure causes the control valve group (14) to open. The pressure oil in the rodless chamber of the luffing cylinder enters the potential energy recovery hydraulic motor (15) through the control valve group (14), driving it to rotate. The oil then returns to the oil tank through the potential energy recovery hydraulic motor (15) via the one-way speed control valve (18) and the main valve. The rotational motion of the potential energy recovery hydraulic motor (15) drives the recovery generator unit (16) connected to it to generate electricity. The generated electrical energy is rectified, stabilized, and controlled by the inverter (17) and then stored in the power battery pack (10). The VCU intelligent controller (8) uses the real-time rotation speed of the recovery generator unit (16) as the main feedback signal and the real-time state of charge (SOC) of the power battery pack (10) as the core constraint. The VCU intelligent controller (8) dynamically adjusts the load (i.e., power generation) of the recovery generator unit (16) to precisely stabilize the rotation speed of the recovery generator unit (16) at a preset value, thereby indirectly controlling the descent speed of the crane operating mechanism (13). In this process, the VCU intelligent controller (8) dynamically limits and adjusts the power generation based on the SOC value through a preset derating algorithm, so as to achieve optimal recovery of gravitational potential energy under the premise of prioritizing the working speed of the equipment.

[0034] The intelligent switching logic for the eight working modes is calculated and decided by the VCU intelligent controller (8) based on the real-time collected vehicle status signals (including but not limited to vehicle speed, throttle opening, battery SOC value, power take-off switch status, etc.). The logic flow is shown in the attached figure. Figure 3 As shown, the eight modes specifically include: electric-assisted drive mode when the vehicle is driving; kinetic energy recovery mode when the vehicle is driving; electromagnetic deceleration mode when the vehicle is driving; pure fuel drive mode when the vehicle is driving; parking power generation mode when the vehicle is parked and the power take-off switch is on; hybrid electric intelligent operation mode when the vehicle is parked and the power take-off switch is on; pure electric drive hydraulic pump operation mode when the vehicle is parked and the power take-off switch is on; and external power charging mode when the vehicle is parked or stopped. The core control strategy of the VCU intelligent controller (8) is: to prioritize the use of the power battery pack (10) for electric-assisted drive mode and pure electric drive hydraulic pump mode; to intelligently start the engine (1) when the power is insufficient during operation and make it work in the high-efficiency range (parking power generation, hybrid electric intelligent operation mode); to prioritize energy recovery in all braking and gravity descent conditions; and finally to achieve global optimization management of the energy flow of the whole vehicle and achieve the goal of optimal system energy efficiency.

[0035] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A mobile crane hybrid system, characterized in that, include: The system includes an engine (1), clutch (2), gearbox (3), electric drive unit (4), transmission clutch (5), hydraulic pump clutch (11), VCU intelligent controller (8), power battery pack (10), bidirectional inverter (9), hydraulic pump (12), and potential energy recovery system; the electric drive unit (4) is an integrated generator / motor unit, whose input end is connected to the output end of the gearbox (3) via the main drive shaft, and whose output end is connected to the vehicle drive axle (6) via the transmission clutch (5); the electric drive unit (4) is also connected to the hydraulic pump (12) via the hydraulic pump clutch (11); the electric drive unit (4) is connected to the hydraulic pump (12) via the transmission clutch (11); the electric drive unit (4) is connected to the transmission clutch (5) via the transmission clutch (5). The bidirectional inverter (9) is electrically connected to the power battery pack (10); the potential energy recovery system includes a control valve group (14), whose oil inlet is connected to the pipeline downstream of the balance valve of the crane actuator (such as luffing cylinder, telescopic boom cylinder, winch motor), for recovering the gravitational potential energy of the boom and / or the load during operation and converting it into electrical energy for storage in the power battery pack (10); the VCU intelligent controller (8) is communicatively connected to the engine ECU, transmission TCU, bidirectional inverter (9), battery management system BMS, ABS control unit and various sensors, for intelligent control of the system's working mode switching.

2. The mobile crane hybrid system according to claim 1, characterized in that, The potential energy recovery system includes a control valve group (14), a potential energy recovery hydraulic motor (15), a recovery generator unit (16), and a one-way speed control valve (18). The oil inlet of the control valve group (14) is connected to the pipeline downstream of the balance valve of the rodless chamber of the crane luffing cylinder and the rodless chamber of the telescopic boom cylinder, and / or the pipeline downstream of the balance valve of the hoisting chamber of the main and auxiliary winch motors. Its oil outlet is connected to the oil inlet of the potential energy recovery hydraulic motor (15). The output shaft of the potential energy recovery hydraulic motor (15) drives the recovery generator unit (16). The output end of the recovery generator unit (16) is connected to the inverter (17). The inverter is connected to the power battery pack (10). The oil return port of the potential energy recovery hydraulic motor (15) is connected to the main valve return tank through the one-way speed control valve (18).

3. The mobile crane hybrid system according to claim 2, characterized in that, A one-way speed control valve (18) is connected in series on the return oil line of the potential energy recovery hydraulic motor (15); The installation direction of the one-way speed control valve (18) is configured as follows: • Its free flow direction is consistent with the hydraulic oil flow direction when the crane raises its boom or lifts a heavy object, and only minimal flow resistance is generated under this working condition; • Its throttling restriction direction is consistent with the hydraulic oil flow direction when the crane lowers its boom or the load descends; The one-way speed control valve (18) is used to provide an independent safety back pressure through its inherent mechanical throttling characteristics when the recovery generator unit (16) reduces or stops providing power generation counter-torque due to the power battery pack (10) being fully charged or a system failure. This limits the speed of the potential energy recovery hydraulic motor (15), thereby limiting the fastest descent speed of the boom and / or the load, and preventing it from stalling and falling. The potential energy recovery system is configured to throttle and restrict the return oil during the descent of the boom or load, while allowing free flow during lifting, serving as a mechanical safety redundancy for the system.

4. The mobile crane hybrid system according to claim 1, characterized in that, The transmission clutch (5) is a normally closed electronically controlled clutch located between the output end of the electric drive unit and the main reducer. The hydraulic pump clutch (11) is a normally open electronically controlled clutch located between the electric drive unit and the hydraulic pump.

5. The mobile crane hybrid system according to claim 1, characterized in that, The VCU intelligent controller (8) is configured to perform at least one of the following eight operating modes: - Electric assist drive mode when the vehicle is in motion: - Kinetic energy recovery mode during vehicle operation; - Electromagnetic deceleration mode when the vehicle is in motion. - Pure fuel-powered driving mode when the vehicle is in motion; - Parking power generation mode when the vehicle is parked and the power take-off switch is on. - Hybrid intelligent operation mode when the vehicle is parked and the power take-off switch is on; - Pure electric drive hydraulic pump operation mode when the vehicle is parked and the power take-off switch is on. - External power charging mode when the vehicle is parked or stopped.

6. A closed-loop method for recovering the gravitational potential energy of a crane, characterized in that, Applied to the mobile crane hybrid system as described in any one of claims 1-5, the method comprises the following steps: Detect the action signals of crane boom descent or load descent; The control valve group (14) in the control potential energy recovery system is turned on, and the potential energy recovery hydraulic motor (15) is driven to rotate by the pressure oil; The potential energy recovery hydraulic motor (15) drives the recovery generator unit (16) to generate electricity; The return oil flow from the control potential energy recovery hydraulic motor (15) passes through a one-way speed control valve (18) and then flows back to the oil tank via the main valve. The one-way speed control valve (18) is configured to throttle the return oil during the descent to provide mechanical safety back pressure. The electrical energy generated by the recycling generator unit (16) is rectified and regulated by the inverter (17) and then stored in the power battery pack (10). The VCU intelligent controller (8) controls the energy recovery power based on the real-time rotation speed of the regeneration generator unit (16) as the main feedback signal and the real-time state of charge (SOC) of the power battery pack (10) as the core constraint.

7. The energy consumption management method implemented by the mobile crane hybrid system according to claim 1, characterized in that, This includes the step of derating the energy recovery power based on the state of charge (SOC) value of the power battery pack (10): When the SOC value is in the first range, full-power energy recovery is enabled. When the SOC value is in the second range, the energy recovery power is derated according to the linear derating formula. Energy recovery stops when the SOC value reaches or exceeds the preset upper limit. The derating control is applicable to kinetic energy recovery during vehicle operation and gravitational potential energy recovery during lifting operations.

8. The method according to claim 7, characterized in that, When the power battery pack is a ternary lithium battery, the first range is 25% ≤ SOC < 83%, the second range is 83% ≤ SOC < 88%, and the preset upper limit is 88%. The linear derating formula is: P_rec = P_max × (88% - SOC) / 5%, where P_rec is the actual recovery power and P_max is the maximum allowable recovery power.

9. The method according to claim 7, characterized in that, When the power battery pack is a lithium iron phosphate battery, the first range is 25% ≤ SOC < 90%, the second range is 90% ≤ SOC < 95%, and the preset upper limit is 95%; the linear derating formula is: P_rec = P_max × (95% - SOC) / 5%.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the control method of the mobile crane hybrid system as described in claim 1.

Images