Method and system for protecting power system of methanol hybrid new energy hydraulic excavator

Abstract

The application discloses a protection method and system of a methanol hybrid new energy hydraulic excavator power system, which comprises obtaining an electronic handle operation signal, an engine torque signal and a motor torque signal; when the electronic handle signal decreases and a load sudden drop condition is met, a bypass cut-off valve gradient is controlled to be closed until the electronic handle signal is zero, a main pump target torque is calculated based on the engine torque signal and the motor torque signal, and a main pump actual torque is controlled to be not lower than the main pump target torque; when the electronic handle signal rises and a load sudden rise condition is met, a main pump allowable maximum torque is determined based on the engine torque signal and the motor torque signal, and the main pump actual torque is controlled to be not higher than the main pump allowable maximum torque. The application controls the load through the hydraulic system of the excavator, is linked with the methanol engine and the motor, guarantees smooth transition of the methanol engine torque, solves the load sudden change, and thus avoids the methanol engine in-cylinder misfire.

Description

Technical Field

[0001] This invention relates to the field of hydraulic system control technology for excavators, and in particular to a protection method and system for the power system of a methanol hybrid new energy hydraulic excavator. Background Technology

[0002] During the operation of a hydraulic excavator, sudden load changes refer to conditions where the digging resistance (such as the bucket cutting into hard soil or sudden unloading) changes drastically. This includes sudden load drops (such as the bucket suddenly leaving a high-resistance working surface) and sudden load increases (such as the bucket cutting into the working surface from its empty stroke). Under these conditions, the drastic fluctuations in hydraulic system pressure and flow will be directly transmitted to the power system (such as the engine and motor). If the torque response of the power system is not timely, it can easily lead to engine misfire, excessive speed fluctuations, or even engine stall, seriously affecting work efficiency and equipment reliability.

[0003] In large-tonnage methanol hybrid excavators, due to the power and responsiveness limitations of the methanol engine, sudden changes in high and low loads during excavator operation can cause misfires in the methanol engine cylinders (i.e., the methanol in the cylinder cannot burn properly to produce power). In severe cases, this can directly lead to engine shutdown. If this happens frequently, the fuel injectors will be damaged due to the corrosive nature of methanol and the inability to burn properly for a long time.

[0004] Pure hydraulic system protection uses components such as relief valves and unloading valves in the main oil circuit to force unloading when the pressure exceeds the threshold, which can prevent damage to hydraulic components. However, it is not linked to the torque control of the power system and cannot solve the problems of misfire and speed fluctuation caused by sudden load changes in the power system.

[0005] Traditional internal combustion engines use a governor or electronic control unit (ECU) to adjust the fuel injection quantity to adapt to load changes. While adjusting the fuel injection quantity in real time via the ECU to match the load is suitable for pure engine power systems, it does not incorporate the pressure-torque correlation logic of the hydraulic system and cannot adapt to the dual-power synergy scenario of "engine + electric motor" in methanol hybrid systems.

[0006] However, some solutions attempt to correlate hydraulic pressure with engine torque, calculating the main pump torque by detecting hydraulic pressure and feeding it back to the engine ECU to adjust the fuel injection quantity. However, these solutions lack adaptive protection logic for extreme conditions such as sudden load changes and do not address torque coordination with the electric motor in the methanol hybrid system. Therefore, in scenarios involving sudden load changes in methanol hybrid excavators, there remains a risk of torque mismatch in the power system and engine misfire.

[0007] In summary, existing technologies for methanol hybrid new energy hydraulic excavators face the following main technical challenges under sudden load changes: Existing technologies are prone to causing drastic fluctuations in engine fuel injection, resulting in a high risk of misfire in methanol engines. Incomplete combustion of methanol fuel can easily lead to knocking and misfire problems. Furthermore, existing technologies lack the ability to coordinate the maximum load capacity of methanol engines and electric motors, making it impossible to achieve "slow loading" without exceeding the maximum load capacity of the power system. This results in significant speed fluctuations in methanol engines due to their slow response (compared to diesel engines), affecting operational stability. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention provides a protection method and system for the power system of a methanol hybrid new energy hydraulic excavator. This invention uses the excavator's hydraulic system for load control, linking it with the methanol engine and motor to ensure a smooth torque transition of the methanol engine, resolve sudden load changes, and thus prevent misfires in the methanol engine cylinders.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a protection method for the power system of a methanol hybrid new energy hydraulic excavator, comprising: Acquire electronic handle operation signals, engine torque signals, and motor torque signals; When the electronic handle signal drops and the load drop condition is met, the bypass shut-off valve is controlled to close gradually until the electronic handle signal is zero. The target torque of the main pump is calculated based on the engine torque signal and the motor torque signal, and the actual torque of the main pump is controlled to be no less than the target torque of the main pump. When the electronic handle signal rises and the load surge condition is met, the maximum allowable torque of the main pump is determined based on the engine torque signal and the motor torque signal, and the actual torque of the main pump is controlled to not exceed the maximum allowable torque of the main pump.

[0010] As a further technical solution, the load drop condition is that the electronic handle signal is lower than a preset signal threshold and the electronic handle signal drops by more than a preset value within a unit cycle; the load rise condition is that the electronic handle signal rises from zero and is greater than the preset signal threshold.

[0011] As a further technical solution, when the electronic handle signal decreases, the engine torque signal is the minimum allowable torque value of the engine; the motor torque signal is the maximum torque value currently consumed by the motor.

[0012] As a further technical solution, when the electronic handle signal rises, the engine torque signal is the maximum load torque value that the engine can currently withstand; the motor torque signal is the maximum load torque value that the motor can currently withstand; the actual torque of the main pump is controlled not to exceed the allowable maximum torque, until the allowable maximum torque of the main pump exceeds the torque set in the original gear.

[0013] As a further technical solution, the calculation method for the target torque of the main pump is as follows: target torque of the main pump = minimum allowable torque value of the engine - maximum torque value currently consumed by the motor; the calculation method for the maximum allowable torque of the main pump is as follows: maximum allowable torque of the main pump = maximum load torque value that the engine can currently withstand + maximum load torque value that the motor can currently withstand.

[0014] As a further technical solution, the formula for calculating the actual torque of the main pump is as follows: ;in, The actual torque of the main pump Hydraulic oil pressure, The main pump displacement.

[0015] Secondly, the present invention provides a protection system for the power system of a methanol hybrid new energy hydraulic excavator, including: The vehicle hydraulic system controller, as well as the electronic handle, methanol engine, motor, main pump assembly, and hydraulic actuators that are connected to the vehicle hydraulic system controller; The main pump assembly includes a first main pump and a second main pump. The hydraulic actuator assembly includes a solenoid valve assembly and a bypass shut-off valve assembly. The solenoid valve assembly includes a first solenoid valve and a second solenoid valve. The bypass shut-off valve assembly includes a first bypass shut-off valve and a second bypass shut-off valve. The vehicle hydraulic system controller generates pilot pressure by outputting different current signals to the solenoid valve assembly, which drives the bypass shut-off valve assembly to close in a gradient manner.

[0016] As a further technical solution, the first solenoid valve and the second solenoid valve control the first bypass shut-off valve and the second bypass shut-off valve respectively; when the vehicle hydraulic system controller outputs a current signal to the first solenoid valve, the first solenoid valve generates different pilot pressures according to the magnitude of the current signal, causing the first bypass shut-off valve to gradually close; when the vehicle hydraulic system controller outputs a current signal to the second solenoid valve, the second solenoid valve generates different pilot pressures according to the magnitude of the current signal, causing the second bypass shut-off valve to gradually close.

[0017] As a further technical solution, the first bypass shut-off valve and the second bypass shut-off valve are respectively connected to the return oil circuit of the first main pump and the second main pump, and are used to control the degree of on / off of the return oil of the main pump.

[0018] As a further technical solution, the hydraulic actuator also includes a main relief valve, which is connected in parallel to the outlet main oil lines of the first main pump and the second main pump.

[0019] One or more technical solutions of the present invention have the following beneficial effects: This invention acquires electronic handle operation signals, engine torque signals, and motor torque signals. Under conditions of sudden load reduction, it first controls the bypass shut-off valve to gradually close to stabilize system pressure. Then, based on the engine and motor torque signals, it calculates the target torque of the main pump and controls the actual torque of the main pump to be no lower than this target torque. This process ensures a smooth transition of the main pump torque within the allowable range of the methanol engine, avoiding drastic changes in fuel injection volume due to sudden load drops. It fundamentally solves the problem of incomplete methanol combustion and knocking that cause misfires in the cylinder, while also preventing unburned methanol from corroding the injectors over time, thus extending the service life of critical engine components.

[0020] This invention determines the maximum allowable torque of the main pump based on engine torque and motor torque signals under conditions of sudden load increases, and controls the actual torque of the main pump to not exceed this allowable value. This design, through "dual-power torque coordination limitation," achieves "slow loading" of the hydraulic system without exceeding the maximum load capacity of the power system. This avoids significant speed fluctuations in the engine due to response lag when the load increases sharply, ensuring the stability of power output during excavator operation and improving operational smoothness and efficiency. Attached Figure Description

[0021] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0022] Figure 1 This is a simplified structural diagram of the protection system of the methanol hybrid new energy hydraulic excavator power system in this invention; Figure 2 This is a flowchart of the load drop control process of the present invention; Figure 3 This is a flowchart of the load surge control process of the present invention. Detailed Implementation

[0023] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0024] Example 1 This embodiment provides a protection system for the power system of a methanol hybrid new energy hydraulic excavator, such as... Figure 1 As shown, it includes: The vehicle hydraulic system controller (MCU) and the electronic handle, methanol engine, motor, main pump assembly and hydraulic actuators that communicate with the vehicle hydraulic system controller.

[0025] In this embodiment, the main pump group includes a first main pump and a second main pump, and the hydraulic actuator includes a solenoid valve group and a bypass shut-off valve group. The solenoid valve group includes a first solenoid valve and a second solenoid valve, and the bypass shut-off valve group includes a first bypass shut-off valve and a second bypass shut-off valve. The vehicle hydraulic system controller generates pilot pressure by outputting different current signals to the solenoid valve group, which drives the bypass shut-off valve group to close in a gradient manner.

[0026] Specifically: the first solenoid valve and the second solenoid valve control the first bypass shut-off valve and the second bypass shut-off valve respectively; when the vehicle hydraulic system controller outputs a current signal to the first solenoid valve, the first solenoid valve generates different pilot pressures according to the magnitude of the current signal, causing the first bypass shut-off valve to gradually close, thereby increasing the main oil circuit pressure of the first master pump; when the vehicle hydraulic system controller outputs a current signal to the second solenoid valve, the second solenoid valve generates different pilot pressures according to the magnitude of the current signal, causing the second bypass shut-off valve to gradually close, thereby increasing the main oil circuit pressure of the second master pump.

[0027] In this embodiment, the first bypass shut-off valve and the second bypass shut-off valve are respectively connected to the return oil circuits of the first main pump and the second main pump to control the degree of oil return from the main pump; and the hydraulic actuator also includes a main relief valve, which is connected in parallel to the outlet main oil circuits of the first main pump and the second main pump.

[0028] Example 2 This embodiment provides a protection method for the power system of a methanol hybrid new energy hydraulic excavator, based on the protection system for the power system of a methanol hybrid new energy hydraulic excavator provided in Embodiment 1, including: The electronic handle operation signal, engine torque signal, and motor torque signal are obtained through the vehicle hydraulic system controller (MCU).

[0029] When the electronic handle signal drops and the load drop condition is met, the bypass shut-off valve is controlled to close gradually until the electronic handle signal is zero. The target torque of the main pump is calculated based on the engine torque signal and the motor torque signal, and the actual torque of the main pump is controlled to be no less than the target torque of the main pump.

[0030] Specifically: When the excavator is under high load, if the handle is suddenly released significantly, the handle signal will decrease rapidly (the handle referred to is an electronic handle, with a signal range of 0-1000; the signal is 0 when the handle is not moved and 1000 when the handle is moved to its maximum). At this time, the valve core opening decreases, the flow to the working device decreases, and more hydraulic oil from the main pump returns directly to the hydraulic oil tank through the bypass shut-off valve, reducing the main pump pressure. It also decreased significantly, while the main pump displacement It also decreases, and the actual torque of the main pump is: Therefore, the sum of the torques of the first and second main pumps decreases.

[0031] In this embodiment, the load drop condition is that the electronic handle signal is lower than the preset signal threshold (e.g., lower than 10) and the electronic handle signal drops more than the preset value within a unit cycle (e.g., the drop exceeds 50%). The vehicle hydraulic system controller (MCU) controls the bypass shut-off valve to gradually close. When the handle signal is 0, the return oil circuit of the main pump is completely closed, and the system pressure is increased to the overflow pressure of the relief valve (usually 330 bar).

[0032] In this embodiment, when the electronic handle signal decreases, the engine torque signal is the minimum allowable torque value of the engine, and the motor torque signal is the maximum torque value currently consumed by the motor (the motor consumes a portion of the engine torque by charging the battery and replenishes the engine torque by discharging the battery). The main pump target torque is calculated as follows: main pump target torque = minimum allowable torque value of the engine - maximum torque value currently consumed by the motor. The load drop adjustment process ends when the main pump target torque is 0. Based on the main pump pressure and displacement, the torque value of the main pump is controlled to gradually decrease within the allowable range of the methanol engine, avoiding drastic changes in the engine's fuel injection quantity, thereby preventing misfire problems caused by incomplete methanol combustion and knocking.

[0033] When the electronic handle signal rises and the load surge condition is met, the maximum allowable torque of the main pump is determined based on the engine torque signal and the motor torque signal, and the actual torque of the main pump is controlled to not exceed the maximum allowable torque of the main pump.

[0034] Specifically: When the handle signal rises from 0, it indicates that the excavator has switched from standby to working state, and the load also rises from low load to high load. The condition for a sudden increase in load is that the electronic handle signal rises from zero and exceeds the preset signal threshold.

[0035] In this embodiment, when the electronic handle signal rises, the engine torque signal is the maximum load torque value that the engine can currently withstand; the motor torque signal is the maximum load torque value that the motor can currently withstand; the maximum allowable torque of the main pump = the maximum load torque value that the engine can currently withstand + the maximum load torque value that the motor can currently withstand; the MCU detects the hydraulic oil pressure P through the sensor, and controls the main pump q to ensure that the actual torque of the main pump does not exceed the maximum allowable torque, until the maximum allowable torque of the main pump exceeds the torque set in the original gear, indicating that the power system composed of the methanol engine and the motor has met the normal operating requirements of the hydraulic system.

[0036] Under conditions of sudden load increases, the maximum allowable torque of the main pump is determined based on the engine torque signal and the motor torque signal, and the actual torque of the main pump is controlled to not exceed this allowable value. This design achieves "slow loading" of the hydraulic system by "dual power torque coordination limitation" without exceeding the maximum load capacity of the power system. This avoids large fluctuations in engine speed due to response lag when the load increases suddenly, ensuring the stability of power output during excavator operation and improving operational smoothness and work efficiency.

[0037] Various modifications and variations of this invention will be apparent to those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A protection method for the power system of a methanol hybrid new energy hydraulic excavator, characterized in that, include: Acquire electronic handle operation signals, engine torque signals, and motor torque signals; When the electronic handle signal drops and the load drop condition is met, the bypass shut-off valve is controlled to close gradually until the electronic handle signal is zero. The target torque of the main pump is calculated based on the engine torque signal and the motor torque signal, and the actual torque of the main pump is controlled to be no less than the target torque of the main pump. The target torque of the main pump is calculated as follows: target torque of the main pump = minimum allowable torque value of the engine - maximum torque value consumed by the motor; the maximum allowable torque of the main pump is calculated as follows: maximum allowable torque of the main pump = maximum load torque value that the engine can currently withstand + maximum load torque value that the motor can currently withstand. When the electronic handle signal rises and the load surge condition is met, the maximum allowable torque of the main pump is determined based on the engine torque signal and the motor torque signal, and the actual torque of the main pump is controlled to not exceed the maximum allowable torque of the main pump.

2. The protection method for the power system of a methanol hybrid new energy hydraulic excavator as described in claim 1, characterized in that, The load drop condition is when the electronic handle signal is lower than a preset signal threshold and the decrease in the electronic handle signal within a unit cycle exceeds a preset value; the load rise condition is when the electronic handle signal rises from zero and exceeds the preset signal threshold.

3. The protection method for the power system of a methanol hybrid new energy hydraulic excavator as described in claim 1, characterized in that, When the electronic handle signal decreases, the engine torque signal is the minimum allowable torque value of the engine; the motor torque signal is the maximum torque value currently consumed by the motor.

4. The protection method for the power system of a methanol hybrid new energy hydraulic excavator as described in claim 1, characterized in that, When the electronic handle signal rises, the engine torque signal is the maximum load torque value that the engine can currently withstand; the motor torque signal is the maximum load torque value that the motor can currently withstand; control the actual torque of the main pump to not exceed the allowable maximum torque, until the allowable maximum torque of the main pump exceeds the torque set in the original gear.

5. The protection method for the power system of a methanol hybrid new energy hydraulic excavator as described in claim 1, characterized in that, The formula for calculating the actual torque of the main pump is as follows: ;in, The actual torque of the main pump Hydraulic oil pressure, The main pump displacement.

6. A protection system for the power system of a methanol hybrid new energy hydraulic excavator, based on the protection method for the power system of a methanol hybrid new energy hydraulic excavator according to any one of claims 1-5, characterized in that, include: The vehicle hydraulic system controller, as well as the electronic handle, methanol engine, motor, main pump assembly, and hydraulic actuators that are connected to the vehicle hydraulic system controller; The main pump assembly includes a first main pump and a second main pump. The hydraulic actuator assembly includes a solenoid valve assembly and a bypass shut-off valve assembly. The solenoid valve assembly includes a first solenoid valve and a second solenoid valve. The bypass shut-off valve assembly includes a first bypass shut-off valve and a second bypass shut-off valve. The vehicle hydraulic system controller generates pilot pressure by outputting different current signals to the solenoid valve assembly, which drives the bypass shut-off valve assembly to close in a gradient manner.

7. The protection system for the power system of the methanol hybrid new energy hydraulic excavator as described in claim 6, characterized in that, The first solenoid valve and the second solenoid valve control the first bypass shut-off valve and the second bypass shut-off valve respectively. When the vehicle hydraulic system controller outputs a current signal to the first solenoid valve, the first solenoid valve generates different pilot pressures according to the magnitude of the current signal, causing the first bypass shut-off valve to gradually close. When the vehicle hydraulic system controller outputs a current signal to the second solenoid valve, the second solenoid valve generates different pilot pressures according to the magnitude of the current signal, causing the second bypass shut-off valve to gradually close.

8. The protection system for the power system of the methanol hybrid new energy hydraulic excavator as described in claim 6, characterized in that, The first bypass shut-off valve and the second bypass shut-off valve are respectively connected to the return oil circuit of the first main pump and the second main pump, and are used to control the degree of oil return of the main pump.

9. The protection system for the power system of the methanol hybrid new energy hydraulic excavator as described in claim 6, characterized in that, The hydraulic actuator also includes a main relief valve, which is connected in parallel to the main oil outlet lines of the first main pump and the second main pump.

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