A negative flow electro-hydraulic system based on variable pressure control and its electric engineering machinery

Abstract

This invention provides a negative flow electro-hydraulic system based on variable pressure control and its associated electric engineering machinery. It relates to the technical field of negative flow electro-hydraulic systems, using a battery as a power source, a motor controller and a motor as the drive source, and a negative flow system as a hydraulic system (where the main pump is an electro-proportional pump). The hydraulic drive structure uses a constant speed variable displacement / variable speed constant displacement / variable speed variable displacement configuration, combined with an electronic control handle and a proportional pressure reducing valve for pilot control. The vehicle controller calculates the negative flow pressure setpoint based on signals from sensors and the electronic control pilot handle, executes a closed-loop control algorithm, and then adjusts the motor speed or main pump displacement to maintain the actual pressure before the bypass return oil throttle port at the negative flow pressure setpoint. This achieves negative flow pressure adjustment according to operating conditions (i.e., variable negative flow pressure), improving the energy efficiency and maneuverability of the entire machine.

Description

Technical Field

[0001] This invention relates to the field of negative flow electro-hydraulic system technology, specifically to a negative flow electro-hydraulic system based on variable pressure control and its electric engineering machinery. Background Technology

[0002] In traditional negative flow systems, the pressure before the bypass return oil throttling port (i.e., the negative flow pressure) is fixed once set and does not change with operating conditions. In actual use, it is difficult to balance the system's energy efficiency and rapid response capability when setting the negative flow pressure. If the negative flow pressure is set too high, the loss of bypass return oil will increase; if the negative flow pressure is set too low, the system response will be slow and the operation will have a strong lag.

[0003] In view of the above, this application is hereby submitted. Summary of the Invention

[0004] This invention provides a negative flow electro-hydraulic system based on variable pressure control and its electric engineering machinery, which can at least partially improve the above-mentioned problems.

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

[0006] A negative flow electro-hydraulic system based on variable pressure control includes: a vehicle controller, a signal sensing component, a power source component, a drive source component, a pump component, and a valve component. The input terminal of the vehicle controller is electrically connected to the output terminal of the signal sensing component, the output terminal of the power source component is connected to the input terminal of the drive source component, and the output terminal of the vehicle controller is electrically connected to the control terminals of the drive source component, the pump component, and the valve component.

[0007] The vehicle controller is configured to perform the following steps by executing a computer program stored internally:

[0008] The bypass throttle port pressure Pa, maximum load pressure Plmax, and handle input signal collected by the signal sensing component are acquired, and the handle input signal is normalized to obtain the equivalent pilot control signal and its rate of change x.

[0009] Based on the equivalent pilot control signal and the maximum load pressure signal, the variable pressure controller calculates the corresponding negative flow pressure setpoint Pt, and uses the negative flow pressure setpoint Pt as the target value. The pressure Pa before the bypass return oil throttle port is used as the actual feedback value. The output flow of the power source component and the drive source component is changed for closed-loop control, so that the pressure Pa before the bypass return oil throttle port is stabilized at the negative flow pressure setpoint Pt.

[0010] Preferably, the power source assembly includes a battery pack, a battery management system, and a high-voltage management unit. The output terminal of the battery pack is electrically connected to the input terminal of the battery management system, and the output terminal of the battery management system is electrically connected to the input terminal of the high-voltage management unit. The battery pack is a lithium iron phosphate battery.

[0011] Preferably, the drive source component includes a motor controller and a motor. The input terminal of the motor controller is connected to the vehicle controller and the high-voltage management unit, and the output terminal of the motor controller is connected to the motor. The motor is a permanent magnet synchronous motor.

[0012] Preferably, the pump assembly includes an electric proportional pump and a pilot pump, the electric motor, the electric proportional pump and the pilot pump are coaxially mechanically connected, the input end of the electric proportional pump and the input end of the pilot pump are used to connect to the hydraulic oil tank, and the output end of the vehicle controller is connected to the electric proportional pump.

[0013] Preferably, the valve assembly includes a first relief valve, a second relief valve, a first electro-proportional pressure reducing valve, a second electro-proportional pressure reducing valve, an open-center six-way proportional directional valve, a hydraulic cylinder, a shuttle valve, and a throttle valve. The C and P ports of the open-center six-way proportional directional valve are both connected to the outlet of the electro-proportional pump. The T port of the open-center six-way proportional directional valve is connected to the oil tank. The A port of the open-center six-way proportional directional valve is connected to the rodless chamber of the hydraulic cylinder. The B port of the open-center six-way proportional directional valve is connected to the rod chamber of the hydraulic cylinder. The shuttle valve is connected to the inlet and outlet ports of the hydraulic cylinder. The inlet ports of the throttle valve and the second relief valve are both connected to the open-center six-way proportional directional valve. The D port of the proportional directional valve, the outlet port of the throttle valve, and the outlet port of the second relief valve are all connected to the oil tank. The inlet port of the first relief valve, the inlet ports of the first electro-proportional pressure reducing valve, and the second electro-proportional pressure reducing valve are all connected to the outlet port of the pilot pump. The f port of the first relief valve, the first electro-proportional pressure reducing valve, and the j port of the second electro-proportional pressure reducing valve are all connected to the oil tank. The f port of the first electro-proportional pressure reducing valve and the j port of the second electro-proportional pressure reducing valve are respectively connected to the m and n ends of the open-center six-way proportional directional valve. The output terminal of the vehicle controller is connected to the input terminals of the first electro-proportional pressure reducing valve and the second electro-proportional pressure reducing valve.

[0014] Preferably, the signal sensing component includes a first pressure sensor, a second pressure sensor, and an electronically controlled pilot handle, wherein the output terminals of the first pressure sensor, the second pressure sensor, and the electronically controlled pilot handle are electrically connected to the input terminal of the vehicle controller.

[0015] Preferably, when it is determined that the rate of change of the handle input signal is greater than a preset value and the load condition is full-speed excavation, the negative flow pressure setting value is a first setting value; when it is determined that the rate of change of the handle input signal is less than a preset value and the load condition is light-load excavation or site preparation, the negative flow pressure setting value is a second setting value, wherein the first setting value is greater than the second setting value.

[0016] Preferably, the configuration of the drive source component is a constant speed motor driving a variable pump, a variable speed motor driving a fixed displacement pump, or a variable speed motor driving a variable pump. When the configuration of the drive source component is different, the output flow rate adjustment method is also different.

[0017] The present invention also provides an electric engineering machine, comprising: a mechanical body and a negative flow electro-hydraulic system based on variable pressure control as described above, wherein the negative flow electro-hydraulic system based on variable pressure control is disposed on the mechanical body.

[0018] In summary, the negative flow electro-hydraulic system based on variable pressure control uses a battery as the power source, a motor controller and a motor as the drive source, and a negative flow system as the hydraulic system (where the main pump is an electro-proportional pump). It employs a constant speed variable displacement / variable speed constant displacement / variable speed variable displacement hydraulic drive structure, combined with an electronic control handle and a proportional pressure reducing valve for pilot control. Specifically, the vehicle controller calculates the negative flow pressure setpoint based on signals from sensors and the electronic control pilot handle, executes a closed-loop control algorithm, and then adjusts the motor speed or main pump displacement to maintain the actual pressure before the bypass return oil throttle port at the negative flow pressure setpoint. This achieves negative flow pressure adjustment according to operating conditions (i.e., variable negative flow pressure), improving the overall energy efficiency and maneuverability of the machine. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the principle of the negative flow electro-hydraulic system based on variable pressure control provided in the embodiment of the present invention (taking a power source configuration with variable speed and variable displacement as an example).

[0020] Figure 2 This is a flowchart of the control strategy for a negative flow electro-hydraulic system based on variable pressure control provided in an embodiment of the present invention (taking a power source configuration with variable speed and variable displacement as an example).

[0021] Figure 3 This is a block diagram of motor speed control for a negative flow electro-hydraulic system based on variable pressure control, provided in an embodiment of the present invention.

[0022] Figure 4 This is a block diagram of the main pump displacement control of a negative flow electro-hydraulic system based on variable pressure control provided in an embodiment of the present invention.

[0023] Explanation of reference numerals in the attached diagram: 1-Battery pack; 2-Battery management system; 3-High voltage management unit; 4-Motor controller; 5-Motor; 6-Electric proportional pump; 7-Pilot pump; 8-Vehicle controller; 9-First relief valve; 10-First electro-proportional pressure reducing valve; 11-Second electro-proportional pressure reducing valve; 12-Electric pilot handle; 13-Open center six-way proportional directional valve; 14-Hydraulic cylinder; 15-Shuttle valve; 16-First pressure sensor; 17-Second pressure sensor; 18-Throttle valve; 19-Second relief valve. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0025] refer to Figures 1 to 4 As shown, the first embodiment of the present invention discloses a negative flow electro-hydraulic system based on variable pressure control, which includes: a vehicle controller 8, a signal sensing component, a power source component, a drive source component, a pump component, and a valve component. The input terminal of the vehicle controller 8 is electrically connected to the output terminal of the signal sensing component, the output terminal of the power source component is connected to the input terminal of the drive source component, and the output terminal of the vehicle controller 8 is electrically connected to the control terminal of the drive source component, the control terminal of the pump component, and the control terminal of the valve component.

[0026] The vehicle controller 8 is configured to perform the following steps by executing a computer program stored internally:

[0027] The bypass throttle port pressure Pa, maximum load pressure Plmax, and handle input signal collected by the signal sensing component are acquired, and the handle input signal is normalized to obtain the equivalent pilot control signal and its rate of change x.

[0028] Based on the equivalent pilot control signal and the maximum load pressure signal, the variable pressure controller calculates the corresponding negative flow pressure setpoint Pt, and uses the negative flow pressure setpoint Pt as the target value. The pressure Pa before the bypass return oil throttle port is used as the actual feedback value. The output flow of the power source component and the drive source component is changed for closed-loop control, so that the pressure Pa before the bypass return oil throttle port is stabilized at the negative flow pressure setpoint Pt.

[0029] In this embodiment, based on the overall scheme of the negative flow electro-hydraulic system with variable pressure control, the vehicle controller 8 calculates the negative flow pressure setpoint through signals fed back from sensors and the electronically controlled pilot handle, executes a closed-loop control algorithm, and then adjusts the motor speed or main pump displacement to maintain the actual pressure before the bypass return oil throttle port at the negative flow pressure setpoint. This achieves adjustment of the negative flow pressure according to operating conditions (i.e., variable negative flow pressure).

[0030] Preferably, the power source assembly includes a battery pack 1, a battery management system 2, and a high-voltage management unit 3. The output terminal of the battery pack 1 is electrically connected to the input terminal of the battery management system 2, and the output terminal of the battery management system 2 is electrically connected to the input terminal of the high-voltage management unit 3. The battery pack 1 is a lithium iron phosphate battery.

[0031] Preferably, the drive source component includes a motor controller 4 and a motor 5. The input terminal of the motor controller 4 is connected to the vehicle controller 8 and the high voltage management unit 3, and the output terminal of the motor controller 4 is connected to the motor 5. The motor 5 is a permanent magnet synchronous motor.

[0032] Preferably, the pump assembly includes an electric proportional pump 6 and a pilot pump 7. The electric motor 5, the electric proportional pump 6 and the pilot pump 7 are coaxially mechanically connected. The input end of the electric proportional pump 6 and the input end of the pilot pump 7 are used to connect to the hydraulic oil tank. The output end of the vehicle controller 8 is connected to the electric proportional pump 6.

[0033] Preferably, the valve assembly includes a first relief valve 9, a second relief valve 19, a first electro-proportional pressure reducing valve 10, a second electro-proportional pressure reducing valve 11, an open-center six-way proportional directional valve 13, a hydraulic cylinder 14, a shuttle valve 15, and a throttle valve 18. The C and P ports of the open-center six-way proportional directional valve 13 are both connected to the oil outlet of the electro-proportional pump 6. The T port of the open-center six-way proportional directional valve 13 is connected to the oil tank. The A port of the open-center six-way proportional directional valve 13 is connected to the rodless chamber of the hydraulic cylinder 14. The B port of the open-center six-way proportional directional valve 13 is connected to the rod chamber of the hydraulic cylinder 14. The shuttle valve 15 is connected to the inlet and outlet ports of the hydraulic cylinder 14. The inlet ports of the throttle valve 18 and the second relief valve 19 are both connected to... The D port of the open center six-way proportional directional valve 13, the oil outlet of the throttle valve 18, and the oil outlet of the second relief valve 19 are all connected to the oil tank. The oil inlet of the first relief valve 9, the oil inlet of the first electro-proportional pressure reducing valve 10, and the oil outlet of the second electro-proportional pressure reducing valve 11 are all connected to the oil outlet of the pilot pump 7. The f port of the first relief valve 9, the first electro-proportional pressure reducing valve 10, and the j port of the second electro-proportional pressure reducing valve 11 are all connected to the oil tank. The f port of the first electro-proportional pressure reducing valve 10 and the j port of the second electro-proportional pressure reducing valve 11 are respectively connected to the m and n ends of the open center six-way proportional directional valve 13. The output end of the vehicle controller 8 is connected to the input end of the first electro-proportional pressure reducing valve 10 and the second electro-proportional pressure reducing valve 11.

[0034] Preferably, the signal sensing component includes a first pressure sensor 16, a second pressure sensor 17, and an electronically controlled pilot handle 12, the output terminals of the first pressure sensor 16, the second pressure sensor 17, and the electronically controlled pilot handle 12 being electrically connected to the input terminal of the vehicle controller 8.

[0035] Preferably, when it is determined that the rate of change of the handle input signal is greater than a preset value and the load condition is full-speed excavation, the negative flow pressure setting value is a first setting value; when it is determined that the rate of change of the handle input signal is less than a preset value and the load condition is light-load excavation or site preparation, the negative flow pressure setting value is a second setting value, wherein the first setting value is greater than the second setting value.

[0036] Preferably, the configuration of the drive source component is a constant speed motor driving a variable pump, a variable speed motor driving a fixed displacement pump, or a variable speed motor driving a variable pump. When the configuration of the drive source component is different, the output flow rate adjustment method is also different.

[0037] In this embodiment, the drive unit of the negative flow electro-hydraulic system based on variable pressure control includes a power source component and a drive source component. The output signals of the first pressure sensor 16, the second pressure sensor 17, and the electronically controlled pilot handle 12 serve as input signals for the vehicle controller 8. The output signals of the vehicle controller 8 control the first electro-proportional pressure reducing valve 10, the second electro-proportional pressure reducing valve 11, the motor controller 4, and the electro-proportional pump 6.

[0038] It should be noted that in this embodiment, the battery pack 1 can be a lithium iron phosphate battery, but is not limited to this. The battery management system 2 has functions such as cell monitoring, current detection, insulation detection, charge / discharge process control, temperature detection, battery thermal management, and fault diagnosis. The high-voltage management unit 3 has an insulation resistance detection function and can also control the DC power distribution of the battery pack 1. The motor 5 can be a permanent magnet synchronous motor, but is not limited to this. The electro-proportional pump can be a swashplate variable displacement piston pump, but is not limited to this; the hydraulic drive structure can be one of constant speed variable displacement, variable speed constant displacement, and variable speed variable displacement.

[0039] The electrical energy of the battery pack 1 first passes through the battery management system 2, whose main relay controls the on / off of the high-voltage main circuit, and then connects to the high-voltage management unit 3, which in turn provides high-voltage DC power to the motor controller 4. The motor controller 4 inverts the DC power into three-phase power to power the motor 5, and the motor 5 drives the proportional pump 6 and the pilot pump 7 through a spline connection.

[0040] In this embodiment, the working principle of the negative flow electro-hydraulic system based on variable pressure control is as follows: First, the pressure Pa before the bypass throttle orifice and the maximum load pressure Plmax are detected by a pressure sensor and fed back to the vehicle controller 8. In addition, the signal from the electronically controlled pilot handle 12 is also fed back to the vehicle controller 8 and then normalized to obtain the equivalent pilot control signal and its rate of change x. Second, based on the received input signal, the variable pressure controller in the program calculates the corresponding negative flow pressure setpoint Pt. When the handle's rate of change is large and the load condition is full-speed excavation, the negative flow pressure setpoint is large (e.g., 8 MPa); when the handle's rate of change is small and the load condition is light-load excavation or site preparation, the negative flow pressure setpoint is small (e.g., 4 MPa). This significantly balances energy saving and driver operating comfort. Finally, using the negative flow pressure setpoint Pt as the target value and the pressure Pa before the bypass return oil throttle port as the actual feedback value, closed-loop control is performed by changing the output flow of the power source to stabilize the pressure Pa before the bypass return oil throttle port at the negative flow pressure setpoint Pt.

[0041] The adjustment of the power source output flow rate varies depending on the configuration of the power source. The power source can be a fixed-speed motor driving a variable-speed pump, a variable-speed motor driving a fixed-displacement pump, or a variable-speed motor driving a variable-speed pump.

[0042] Specifically, when the power source uses a constant-speed motor to drive a variable-displacement pump, the output flow rate of the power source is achieved by adjusting the displacement of the main pump; the vehicle controller 8 sends a PWM signal to the proportional electromagnet of the proportional pump 6, thereby adjusting the displacement to maintain the negative flow pressure at Pt. When the power source uses a variable-speed motor to drive a fixed-displacement pump, the output flow rate of the power source is achieved by adjusting the motor speed; the vehicle controller 8 sends a CAN signal to the motor controller 4, thereby adjusting the motor speed to maintain the negative flow pressure at Pt. When the power source uses a variable-speed motor to drive a variable-displacement pump, the output flow rate of the power source is achieved by adjusting the motor speed and the displacement of the main pump; the vehicle controller 8 sends a PWM signal to the proportional electromagnet of the main pump, thereby adjusting the displacement to maintain the negative flow pressure at Pt1, and at the same time, the vehicle controller 8 also sends a CAN signal to the motor controller 4, thereby adjusting the motor speed to maintain the negative flow pressure at Pt2. Where Pt1 > Pt2, the variable pump and motor 5 can adjust the negative flow pressure in stages without interfering with each other. Moreover, during system operation, the displacement of the variable pump is at the maximum value required by the system flow, which significantly improves the operating efficiency of the variable pump.

[0043] In summary, the negative flow electro-hydraulic system based on variable pressure control adjusts the pressure before the bypass return oil throttle port according to the operating conditions (i.e., variable negative flow pressure) through the program of the vehicle controller 8. This can significantly balance energy saving effect and driver's operating experience, achieving a good balance between energy saving and controllability of the whole machine.

[0044] A second embodiment of the present invention provides an electric engineering machine, including a mechanical body and a negative flow electro-hydraulic system based on variable pressure control as described above, wherein the negative flow electro-hydraulic system based on variable pressure control is disposed on the mechanical body.

[0045] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A negative flow electrohydraulic system based on variable pressure control, characterized in that, include: The system includes a vehicle controller, a signal sensing component, a power source component, a drive source component, a pump component, and a valve component. The input terminal of the vehicle controller is electrically connected to the output terminal of the signal sensing component, the output terminal of the power source component is connected to the input terminal of the drive source component, and the output terminal of the vehicle controller is electrically connected to the control terminals of the drive source component, the pump component, and the valve component. The valve assembly includes a first relief valve, a second relief valve, a first electro-proportional pressure reducing valve, a second electro-proportional pressure reducing valve, an open-center six-way proportional directional valve, a hydraulic cylinder, a shuttle valve, and a throttle valve. The C and P ports of the open-center six-way proportional directional valve are both connected to the outlet of the electro-proportional pump. The T port of the open-center six-way proportional directional valve is connected to the oil tank. The A port of the open-center six-way proportional directional valve is connected to the rodless chamber of the hydraulic cylinder. The B port of the open-center six-way proportional directional valve is connected to the rod chamber of the hydraulic cylinder. The shuttle valve is connected to the inlet and outlet ports of the hydraulic cylinder. The inlet ports of the throttle valve and the second relief valve are both connected to the open-center six-way proportional pump. For example, the D port of the directional control valve, the oil outlet of the throttle valve, and the oil outlet of the second relief valve are all connected to the oil tank. The oil inlet of the first relief valve, the oil inlet of the first electro-proportional pressure reducing valve, and the oil outlet of the second electro-proportional pressure reducing valve are all connected to the oil outlet of the pilot pump. The f port of the first relief valve, the first electro-proportional pressure reducing valve, and the j port of the second electro-proportional pressure reducing valve are all connected to the oil tank. The f port of the first electro-proportional pressure reducing valve and the j port of the second electro-proportional pressure reducing valve are respectively connected to the m end and the n end of the open-center six-way proportional directional control valve. The output end of the vehicle controller is connected to the input end of the first electro-proportional pressure reducing valve and the second electro-proportional pressure reducing valve. The vehicle controller is configured to perform the following steps by executing a computer program stored internally: The bypass throttle port pressure Pa, maximum load pressure Plmax, and handle input signal collected by the signal sensing component are acquired, and the handle input signal is normalized to obtain the equivalent pilot control signal and its rate of change x. Based on the equivalent pilot control signal and the maximum load pressure signal, the variable pressure controller calculates the corresponding negative flow pressure setpoint Pt, and uses the negative flow pressure setpoint Pt as the target value. The pressure Pa before the bypass return oil throttle port is used as the actual feedback value. The output flow of the power source component and the drive source component is changed for closed-loop control, so that the pressure Pa before the bypass return oil throttle port is stabilized at the negative flow pressure setpoint Pt. When it is determined that the rate of change of the handle input signal is greater than a preset value and the load condition is full-speed excavation, the negative flow pressure setting value is the first setting value. When it is determined that the rate of change of the handle input signal is less than a preset value and the load condition is light-load excavation or site preparation, the negative flow pressure setting value is the second setting value, wherein the first setting value is greater than the second setting value.

2. The negative flow electro-hydraulic system based on variable pressure control according to claim 1, characterized in that, The power source assembly includes a battery pack, a battery management system, and a high-voltage management unit. The output terminal of the battery pack is electrically connected to the input terminal of the battery management system, and the output terminal of the battery management system is electrically connected to the input terminal of the high-voltage management unit. The battery pack is a lithium iron phosphate battery.

3. The negative flow electro-hydraulic system based on variable pressure control according to claim 2, characterized in that, The drive source component includes a motor controller and a motor. The input terminal of the motor controller is connected to the vehicle controller and the high voltage management unit, and the output terminal of the motor controller is connected to the motor. The motor is a permanent magnet synchronous motor.

4. The negative flow electro-hydraulic system based on variable pressure control according to claim 3, characterized in that, The pump assembly includes an electric proportional pump and a pilot pump. The electric motor, the electric proportional pump, and the pilot pump are coaxially mechanically connected. The input end of the electric proportional pump and the input end of the pilot pump are used to connect to the hydraulic oil tank. The output end of the vehicle controller is connected to the electric proportional pump.

5. The negative flow electro-hydraulic system based on variable pressure control according to claim 1, characterized in that, The signal sensing component includes a first pressure sensor, a second pressure sensor, and an electronically controlled pilot handle. The output terminals of the first pressure sensor, the second pressure sensor, and the electronically controlled pilot handle are electrically connected to the input terminal of the vehicle controller.

6. The negative flow electro-hydraulic system based on variable pressure control according to claim 1, characterized in that, The configuration of the drive source component can be a constant speed motor driving a variable pump, a variable speed motor driving a fixed displacement pump, or a variable speed motor driving a variable pump. The output flow rate adjustment method is also different when the configuration of the drive source component is different.

7. An electric engineering machine, characterized in that, It includes a mechanical body and a negative flow electro-hydraulic system as described in any one of claims 1-6, wherein the negative flow electro-hydraulic system based on variable pressure control is disposed on the mechanical body.

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