A control method for fuel injection pressure of a diesel engine unit pump

Abstract

This application relates to a method for controlling the injection pressure of a diesel engine unit pump. The method is applied to a diesel engine unit pump, which includes: a plunger pump; a fuel injector; a servo motor; a pressure sensor; and an electronic control unit (ECU). The method further includes the following steps: S1: Setting a target injection pressure value via the ECU; S2: The ECU outputs a drive signal to control the servo motor to start until the pressure sensor detects that the actual pressure has reached the target value; S3: The ECU controls the injection solenoid valve to open, and the pressure sensor provides real-time feedback of the actual injection pressure value; S4: The ECU calculates the deviation between the actual injection pressure value and the target injection pressure value, and adjusts the rotation speed and angle of the servo motor accordingly; S5: After one injection is completed, the ECU controls the injection solenoid valve to fine-tune the servo motor, preparing for the next injection; S6: Repeating steps S1-S5. This application allows for flexible and precise adjustment of the diesel unit pump's injection pressure according to different operating conditions.

Description

Technical Field

[0001] This application relates to the technical field of diesel engine parts, and in particular to a method for controlling the injection pressure of a diesel engine unit pump. Background Technology

[0002] Diesel engines, with their advantages of high power density, good fuel economy, and high reliability, are widely used in commercial vehicles, construction machinery, marine power, and non-road mobile machinery. As a key component of a diesel engine, the fuel injection system's injection pressure control level directly affects the engine's power, fuel economy, and emissions performance. Especially under China VI and higher emission requirements, higher demands are placed on the speed of injection pressure build-up, control precision, and overall stability.

[0003] Unit pump fuel injection systems have become one of the mainstream injection solutions for medium and heavy-duty diesel engines due to their compact structure, strong adaptability, and low retrofit cost. Traditional diesel engine unit pumps mostly use a camshaft to mechanically drive the plunger to generate high-pressure fuel. The injection pressure is determined by the diesel engine speed and cam lift, making it difficult to achieve independent and precise control. At low speeds, insufficient injection pressure and poor fuel atomization are prone to occur, leading to incomplete combustion and increased harmful emissions. At high speeds, excessive pressure can cause fuel leakage and irregular injection patterns, affecting the stability of diesel engine operation.

[0004] When a diesel engine unit pump uses a camshaft to mechanically drive the plunger to reciprocate, the injection pressure is constrained by the diesel engine speed and cam lift, making it difficult to achieve flexible and precise adjustment according to different operating conditions. Summary of the Invention

[0005] In order to achieve flexible and precise adjustment of the injection pressure of the diesel unit pump according to different operating conditions, this application provides a method for controlling the injection pressure of the diesel unit pump.

[0006] The method for controlling the injection pressure of a diesel engine unit pump provided in this application adopts the following technical solution: A method for controlling the injection pressure of a diesel engine unit pump, applied to a diesel engine unit pump, the diesel engine unit pump comprising: a plunger pump; a fuel injector, the fuel injector being equipped with a fuel injection solenoid valve for controlling the opening or closing of fuel injection; a servo motor, the output shaft of the servo motor being drively connected to the plunger rod of the plunger pump, for driving the plunger rod to reciprocate; a pressure sensor disposed in the fuel injection channel of the fuel injector; and an electronic control component, electrically connected to the fuel injection solenoid valve, the pressure sensor, and the servo motor respectively; further comprising the following steps: S1: setting a target injection pressure value through the electronic control component; S2: the electronic control component outputting a drive signal to control the servo motor to start, driving the plunger rod of the plunger pump to reciprocate, thereby controlling the injection pressure of the unit pump ... S1: The fuel in the plunger pump is compressed to form high-pressure fuel, which enters the fuel injector until the pressure sensor detects that the actual pressure has reached the target value; S2: The electronic control unit controls the fuel injection solenoid valve to open, and the fuel injector begins to inject fuel. The pressure sensor provides real-time feedback on the actual fuel injection pressure value; S3: The electronic control unit calculates the deviation between the actual fuel injection pressure value and the target fuel injection pressure value, and dynamically adjusts the rotation speed and angle of the servo motor through the built-in PID feedback control algorithm; S4: After one fuel injection is completed, the electronic control unit controls the fuel injection solenoid valve to close, and fine-tunes the servo motor parameters to stabilize the actual pressure value in the fuel injector at the target fuel injection pressure value, preparing for the next fuel injection; S5: Repeat the above steps S1-S5.

[0007] By adopting the above technical solution, this method uses the actual pressure inside the fuel injector as the direct control object. A pressure sensor acquires the pressure changes in the injection channel in real time, and the electronic control component compares the actual injection pressure value with the target injection pressure value to form a closed-loop control quantity. The motion parameters of the servo motor are then adjusted to ensure that the piston pump's fuel injection action responds synchronously to pressure changes during the injection process. By utilizing the active control of the piston rod's reciprocating motion by the servo motor, the method replaces the reliance on mechanical speed or fixed cam lift to form injection pressure, thus freeing the injection pressure from being entirely limited by the diesel engine speed. This method can continuously maintain stable injection pressure during pressure build-up, injection, injection termination, and preparation for the next cycle, improving injection pressure control accuracy, enhancing fuel atomization consistency, and improving the injection stability of the diesel engine under different operating conditions.

[0008] Preferably, an inlet check valve is provided at the oil inlet of the plunger pump, and an outlet check valve is provided at the connection between the oil outlet of the plunger pump and the fuel injector; in S2, when the fuel pressure in the plunger pump reaches the opening pressure of the outlet check valve, the high-pressure fuel pushes open the outlet check valve and enters the fuel injector until the pressure sensor detects that the actual injection pressure value has reached the target injection pressure value, thus completing the pressure build-up.

[0009] By employing the above technical solution, the flow direction of fuel between the plunger pump and the injector is limited by the inlet and outlet check valves, ensuring unidirectional fuel flow during both intake and compression processes and preventing pressure loss caused by high-pressure fuel backflow. High-pressure fuel can only enter the injector when the pressure inside the plunger pump rises sufficiently to open the outlet check valve. Conversely, when the pressure is insufficient to open the valve or during the plunger's return stroke, the outlet check valve prevents fuel backflow onto the injector side. This structure improves the reliability of the pressure build-up process and the pressure holding capability, making the pressure sensor-detected injector pressure more stable and closer to the actual injection pressure, thus providing an accurate basis for subsequent closed-loop regulation.

[0010] Preferably, in step S4, when the actual fuel pressure is lower than the target injection pressure, the electronic control unit calculates the pressure compensation requirement based on the injection rate, controls the servo motor to increase its rotation speed and the number of rotations, drives the plunger rod to perform high-frequency reciprocating motion to compress the fuel, achieves rapid pressure replenishment, offsets the fuel pressure drop caused by injection, and maintains the fuel pressure in the injector channel within the target injection pressure range. The injection rate is calculated from the opening duration of the injection solenoid valve, the cross-sectional area of ​​the injector nozzle, and the current pressure, or obtained by looking up a table based on engine operating parameters. When the actual fuel pressure is higher than the target injection pressure, the electronic control unit controls the servo motor to stop, relying on the continuous injection of fuel to naturally reduce the actual injection pressure in the injector until the actual fuel pressure falls back to the target injection pressure range.

[0011] By adopting the above technical solution, when the pressure is below the target range, feedback adjustment is not only made based on the pressure deviation, but also the injection rate is introduced as a compensation basis, enabling the electronic control components to determine the amount of fuel injected per unit time and the resulting pressure drop trend. The higher the injection rate, the faster the fuel flows out of the injection channel, and the more significant the pressure drop. Therefore, it is necessary to increase the fuel replenishment capacity of the plunger pump by increasing the motion intensity of the servo motor. When the pressure is above the target range, the pressure replenishment is stopped, and the natural pressure relief generated by continued injection is used to lower the pressure. This method takes into account both pressure feedback and flow changes during the injection process, reducing pressure regulation lag, enhancing real-time compensation capabilities during injection, and maintaining the pressure in the injector's injection channel within a relatively stable target range.

[0012] Preferably, in S4, the number of rotations of the servo motor output shaft is proportional to the number of reciprocating motions of the plunger rod of the plunger pump, and the rotation speed of the servo motor output shaft is proportional to the reciprocating motion frequency of the plunger rod of the plunger pump. For every preset angle or preset number of rotations of the servo motor, the plunger pump completes one complete oil suction-pressure motion. By coordinating the adjustment of the rotation speed and number of rotations of the servo motor by the electronic control components, the reciprocating motion frequency and total stroke of the plunger rod of the plunger pump can be precisely controlled, thereby achieving precise compensation for oil pressure loss.

[0013] By adopting the above technical solution, the correspondence between the motion parameters of the servo motor and the oil pressure capacity of the plunger pump is clarified. This allows the electronic control components to control the movement frequency and stroke of the plunger rod by adjusting the rotational speed, number of rotations, rotation angle, or preset number of revolutions of the servo motor. The reciprocating frequency of the plunger rod affects the number of times oil is pressed per unit time, and the total stroke of the plunger rod affects the volume of fuel pressed into the injector. Therefore, changes in the servo motor parameters directly alter the pressure compensation speed and amount. This setting ensures that pressure compensation is not merely a general acceleration or shutdown, but rather establishes a correspondence with the actual oil pressure process of the plunger pump, which is beneficial for improving the controllability and accuracy of oil pressure loss compensation.

[0014] Preferably, in S5, when the fuel injection of the diesel engine unit pump reaches the preset injection duration or the operating condition requires to stop, the electronic control component sends a closing signal to the fuel injection solenoid valve, the fuel injection solenoid valve closes, and the fuel injector stops injecting fuel. Based on the residual pressure value signal in the fuel injector fed back by the pressure sensor, the electronic control component finely adjusts the rotation speed and number of rotations of the servo motor, drives the plunger rod of the plunger pump to make small reciprocating movements, so that the fuel pressure in the fuel injection channel of the fuel injector is stably maintained within the preset target injection pressure value range, preparing for the next injection action and ensuring the continuity and consistency of the fuel injection process.

[0015] By employing the above technical solution, the pressure recovery and pressure maintenance process after a single injection is controlled, ensuring that the injection channel of the injector maintains a suitable pressure for the next injection even after injection stops. At the end of injection, there may be residual low pressure or pressure fluctuations in the injection channel. The electronic control unit makes slight adjustments to the servo motor based on the residual pressure value fed back from the pressure sensor, causing the plunger pump to perform minor pressure replenishment or stabilize the pressure. This control method reduces pressure differences between adjacent injection cycles, shortens the pressure build-up response time for the next injection, and improves the consistency and stability during continuous injection.

[0016] Preferably, a crank-connecting rod mechanism for driving the piston rod to reciprocate is provided between the piston rod of the piston pump and the servo motor; an encoder for feeding back the rotation angle signal of the crank-connecting rod mechanism is also provided on the output shaft of the servo motor, and the encoder is electrically connected to the electronic control component.

[0017] By adopting the above technical solution, the rotational motion of the servo motor output shaft is converted into the linear reciprocating motion of the piston rod using a crank-connecting rod mechanism, and the rotational angle state of the crank-connecting rod mechanism is obtained through an encoder. A definite kinematic relationship exists between the motion position of the crank-connecting rod mechanism and the displacement and velocity of the piston rod. The electronic control components can determine in real time the specific state of the piston rod during oil pressure, oil suction, or reversing processes through encoder feedback. This structure helps improve the accuracy of piston rod motion control, allowing pressure regulation to be controlled in conjunction with the actual position of the mechanical mechanism, avoiding the problem of simply relying on motor speed control while ignoring the actual motion state of the piston rod.

[0018] Preferably, in S4, the electronic control component calculates the deviation between the actual injection pressure value and the target injection pressure value based on the actual injection pressure value fed back by the pressure sensor. At the same time, the electronic control component acquires the crank angle signal of the encoder on the servo motor in real time, determines the position and speed of the plunger rod of the plunger pump based on the kinematic characteristics of the crank-connecting rod mechanism, and dynamically adjusts the output torque or speed of the servo motor in combination with the calculated deviation.

[0019] By adopting the above technical solution, pressure feedback is combined with crank angle feedback, enabling the electronic control components to know whether the injection pressure deviates from the target value, as well as the current position and speed of the plunger rod. The output of the crank-connecting rod mechanism is not perfectly linear; the same servo motor speed will correspond to different plunger rod speeds and oil pressure capabilities at different crank angles. Therefore, it is necessary to correct the output torque or speed of the servo motor based on the kinematic characteristics of the crank-connecting rod mechanism. This control method can improve the matching degree between pressure regulation and plunger movement, reduce pressure fluctuations caused by mechanism nonlinearity, and make the closed-loop control of injection pressure more stable.

[0020] Preferably, in S4, when the electronic control component determines that the crank-connecting rod mechanism is about to enter the dead-point neighborhood, it controls the servo motor to perform short-term over-acceleration, increases the instantaneous angular velocity of the servo motor output shaft, realizes the smooth dead-point crossing of the crank-connecting rod mechanism, and restores the speed and torque output of the servo motor after the crossing is completed.

[0021] By adopting the above technical solution, the problem of insufficient driving arm that may occur in the vicinity of the dead point of the crank-connecting rod mechanism is proactively addressed. When the crank-connecting rod mechanism approaches the dead point, the ability of the servo motor output torque to transmit linear driving force to the plunger rod decreases, which can easily lead to motion lag or difficulty in crossing the dead point. Therefore, the electronic control components increase the instantaneous angular velocity of the servo motor output shaft in advance, allowing the mechanism to smoothly cross the dead point region with higher motion inertia. This control method can reduce the risk of jamming or pressure interruption in the crank-connecting rod mechanism near the dead point, improve the reliability of continuous oil pressure of the plunger pump, and ensure the smoothness of the oil injection pressure control process.

[0022] Preferably, when the diesel engine unit pump receives a shutdown command from the diesel engine or an abnormal shutdown occurs due to a circuit or hydraulic fault, the electronic control component first controls the fuel injection solenoid valve to close, and then drives the servo motor to rotate the crankshaft connecting rod mechanism at low speed. The specific starting area of ​​the non-dead point position is accurately located by the crank angle signal of the encoder. This starting area is the rotation range of the crank 30°-60° away from the dead point position. After the crank rotates to the specific starting area, the electronic control component controls the servo motor to stop running, completing the shutdown reset.

[0023] By adopting the above technical solution, the crankshaft and connecting rod mechanism is positioned for easy restarting when the engine stops or experiences abnormal stalling. If the crankshaft and connecting rod mechanism is stopped at or near dead center, the servo motor may have difficulty effectively driving the plunger rod during the next start, causing starting difficulties or delayed pressure build-up. Therefore, the electronic control unit first closes the fuel injection solenoid valve to stop fuel injection, then adjusts the crank position at low speed, and confirms that the crank has entered a specific starting zone through encoder feedback. This method can avoid drive failure due to unfavorable crank position during the next start, improving the recoverability of the diesel engine unit pump after shutdown and the reliability of restarting.

[0024] Preferably, in S1, the electronic control component dynamically sets the target injection pressure value of the fuel injector based on the current operating conditions of the diesel engine, such as the current speed and load, as a reference for closed-loop control.

[0025] By adopting the above technical solution, the target injection pressure value can be adjusted according to changes in the diesel engine's operating conditions, rather than using a fixed pressure setting. Different engine speeds and loads require different injection pressures, injection quantities, and atomization effects. The electronic control components dynamically set the control reference based on the current operating conditions, allowing the closed-loop control target to match the actual combustion requirements. This method improves the adaptability of injection pressure control to changes in operating conditions, avoiding excessive pressure at low speeds and low loads, and ensuring sufficient injection pressure at high speeds and high loads, thus balancing fuel economy, power, and emissions performance.

[0026] In summary, this application includes at least one of the following beneficial technical effects: 1. Using the actual injection pressure value in the injection channel of the injector as the direct feedback object, a closed-loop control is formed by pressure sensor, electronic control components and servo motor, so that the oil pressure action of the plunger pump can be adjusted in real time according to the actual pressure change, breaking the strong coupling relationship between injection pressure and diesel engine speed, and improving the injection pressure control accuracy and injection process stability. 2. During the injection process, dynamic compensation is performed based on pressure deviation and injection rate. By adjusting the rotation speed, angle, number of times or output torque of the servo motor, the reciprocating frequency and stroke of the plunger rod are controlled, thereby timely compensating for the oil pressure drop caused by injection, so that the fuel pressure in the injection channel of the injector is maintained within the target injection pressure range, improving fuel atomization consistency and continuous injection stability. 3. Through the crank-connecting rod mechanism, encoder feedback, dead-point pass-through control, and stop reset control, the electronic control components can adjust the pressure based on the actual position and speed of the piston rod, and perform targeted control when the crank-connecting rod mechanism approaches the dead point or stops, reducing the risk of mechanism jamming, starting difficulties, and pressure build-up delay, and improving the operational reliability and restart stability of the diesel engine unit pump. Attached Figure Description

[0027] Figure 1 This is a cross-sectional view of the overall structure of the control device for the injection pressure of the diesel engine unit pump, which is mainly reflected in Embodiment 1 of this application; Figure 2 This is a cross-sectional view of the overall structure of the control device for the injection pressure of the diesel engine unit pump, which is the main feature of Embodiment 2 of this application. Figure 3 This is a flowchart illustrating the control method of the diesel engine unit pump injection pressure control device in Embodiment 1 of this application. Figure 4 This is a flowchart illustrating the control method of the diesel engine unit pump injection pressure control device in Embodiment 2 of this application.

[0028] Reference numerals: 1. Piston pump; 11. Pump body; 12. Inlet check valve; 13. Outlet check valve; 2. Piston sleeve; 3. Piston rod; 4. Injector nozzle; 41. Pressure sensor; 5. Injection solenoid valve; 6. Servo motor; 7. Cam; 71. Roller; 72. Tappet; 73. Return spring; 8. Crank-connecting rod mechanism; 81. Drive rod; 82. Connecting rod; 9. Electronic control components. Detailed Implementation

[0029] The following is in conjunction with the appendix Figure 1-4 This application will be described in further detail.

[0030] This application discloses a method for controlling the injection pressure of a diesel engine unit pump.

[0031] Example 1 See Figure 1The diesel engine unit pump injection pressure control device includes a plunger pump 1, which includes a pump body 11. A fuel injector 4 is mounted on the upper side of the pump body 11, and a plunger sleeve 2 is embedded and fixed on the lower side of the pump body 11. A plunger rod 3 is housed inside the plunger sleeve 2, and the plunger rod 3 slides vertically against the plunger sleeve 2. The plunger head on the plunger rod 3 and the pump body 11 form a core pressure oil structure. An inlet check valve 12 is provided on one side of the pump body 11, and an outlet check valve 13 is provided between the outlet of the pump body 11 and the inlet of the fuel injector 4. This allows high-pressure fuel to enter the pump body 11 from one side and exit unidirectionally from the side fuel injector 4, preventing losses caused by fuel backflow.

[0032] An electronic control component 9 is also installed on one side of the pump body 11. This component 9 can be configured as a microcontroller, PLC controller, ECU, DSP controller, industrial control board, or other control module capable of signal acquisition, processing, and control output. The electronic control component 9 incorporates a PID feedback control algorithm. It is also electrically connected to the existing control system of the diesel engine. The current speed and load parameters of the diesel engine can be provided by the existing ECU, speed sensor, load sensor, or the overall control system.

[0033] The fuel injector 4 is equipped with a fuel injection solenoid valve 5 and a pressure sensor 41. The pressure sensor 41 is a piezoelectric sensor that is resistant to high temperature and high pressure. Its probe is embedded in the inner wall of the fuel injection channel inside the fuel injector 4 and is in direct contact with the fuel inside the fuel injection channel. The fuel injection solenoid valve 5 and the pressure sensor 41 are electrically connected to the electronic control assembly 9.

[0034] A servo motor 6 is also installed on the lower side of the pump body 11. The output shaft of the servo motor 6 is connected to the plunger rod 3 via a transmission. The servo motor 6 is electrically connected to the electronic control component 9, and the servo motor 6 is configured as a high-speed response servo motor. A cam 7 is fixed on the output shaft of the servo motor 6, and a tappet 72 is fixed to the lower end of the plunger rod 3. A roller 71 is rotatably connected to the tappet 72, and the circumferential side of the roller 71 abuts against the contour surface of the cam 7. A return spring 73 is also sleeved on the plunger rod 3. One end of the return spring 73 abuts against the pump body 11, and the other end abuts against the upper side of the tappet 72.

[0035] See Figure 1 , Figure 3 The control method of the diesel engine unit pump injection pressure control device includes the following steps: S1: Set the target injection pressure value through the electronic control component 9: The electronic control component 9 dynamically sets the target injection pressure value of the injector 4 according to the current operating conditions of the diesel engine, such as the current speed and load, as the reference for closed-loop control; S2: The electronic control component 9 outputs a drive signal to control the servo motor 6 to start. The output shaft of the servo motor 6 drives the cam 7 to rotate. The cam 7 pushes the plunger rod 3 to reciprocate linearly along the plunger sleeve 2 through the roller 71 and the tappet 72. During the downward or upward movement of the plunger rod 3, it forms a periodic volume change together with the pump body 11, thereby completing the intake and compression of fuel. In actual operation, fuel is drawn into the plunger pump 1 through the inlet check valve 12. After reaching the opening pressure during the oil compression process, high-pressure fuel is formed. The high-pressure fuel enters the injector 4 through the outlet check valve 13 until the pressure sensor 41 detects that the actual pressure has reached the target value. S3: Electronic control component 9 controls the opening of fuel injection solenoid valve 5, fuel injector 4 starts to inject fuel, and pressure sensor 41 provides real-time feedback of actual fuel injection pressure value. S4: The electronic control component 9 calculates the deviation between the actual injection pressure value and the target injection pressure value, and dynamically adjusts the rotation speed and angle of the servo motor 6 through the built-in PID feedback control algorithm of the electronic control component 9. When the actual fuel pressure is lower than the target injection pressure, the electronic control unit 9 calculates the pressure compensation requirement based on the injection rate, controls the servo motor 6 to increase its rotation speed and the number of rotations, drives the plunger rod 3 to perform high-frequency reciprocating motion to compress the fuel, achieves rapid pressure replenishment, and offsets the fuel pressure drop caused by injection, so that the fuel pressure in the injection channel of the injector 4 is maintained within the target injection pressure range. The injection rate is calculated from the opening duration of the injection solenoid valve 5, the cross-sectional area of ​​the nozzle 4, and the current pressure, or obtained by looking up the engine operating parameters in a table. When the actual fuel pressure is higher than the target injection pressure, the electronic control unit 9 controls the servo motor 6 to stop, and relies on the continuous injection of fuel to naturally reduce the actual injection pressure in the injector 4 until the actual fuel pressure falls back to the target injection pressure range. The number of rotations of the output shaft of the servo motor 6 is proportional to the number of reciprocating motions of the plunger rod 3 of the plunger pump 1. The rotation speed of the output shaft of the servo motor 6 is proportional to the reciprocating motion frequency of the plunger rod 3 of the plunger pump 1. For every preset angle or preset number of rotations of the servo motor 6, the plunger pump 1 completes one complete oil suction-oil pressure motion. By coordinating and adjusting the rotation speed and number of rotations of the servo motor 6 with the electronic control component 9, the reciprocating motion frequency and total stroke of the plunger rod 3 of the plunger pump 1 can be precisely controlled, thereby achieving precise compensation for oil pressure loss. S5: After one injection is completed, the electronic control component 9 controls the injection solenoid valve 5 to close, and fine-tunes the parameters of the servo motor 6 to stabilize the actual pressure value in the injector 4 at the target injection pressure value, in preparation for the next injection. When the fuel injection of the diesel engine unit pump reaches the preset injection duration or stops when the operating condition requires it to stop, the electronic control component 9 sends a closing signal to the fuel injection solenoid valve 5, the fuel injection solenoid valve 5 closes, and the fuel injector 4 stops injecting fuel. According to the residual pressure value signal in the fuel injector 4 fed back by the pressure sensor 41, the electronic control component 9 finely adjusts the rotation speed and number of rotations of the servo motor 6, drives the plunger rod 3 of the plunger pump 1 to make a small reciprocating motion, so that the fuel pressure in the fuel injection channel of the fuel injector 4 is stably maintained within the preset target injection pressure value range, preparing for the next fuel injection action and ensuring the continuity and consistency of the fuel injection process. S6: Repeat steps S1-S5 above.

[0036] Example 2 See Figure 2 The difference between this embodiment and Embodiment 1 is that the transmission structure between the output shaft of the servo motor 6 and the plunger rod 3 is set as a crank-connecting rod mechanism 8. The crank-connecting rod mechanism 8 includes a drive rod 81 and a connecting rod 82. One end of the drive rod 81 is rotatably connected to the connecting rod 82. The end of the drive rod 81 away from the connecting rod 82 is fixedly connected to the output shaft of the servo motor 6. The end of the connecting rod 82 away from the drive rod 81 is rotatably connected to the lower end of the plunger rod 3.

[0037] The servo motor 6 output shaft is also equipped with an encoder for feeding back the rotation angle signal of the drive rod 81. The encoder is electrically connected to the electronic control component 9.

[0038] See Figure 2 , Figure 4 The control method of the diesel engine unit pump injection pressure control device in this embodiment includes the following steps: S1: Set the target injection pressure value through the electronic control component 9: The electronic control component 9 dynamically sets the target injection pressure value of the injector 4 according to the current operating conditions of the diesel engine, such as the current speed and load, as the reference for closed-loop control; S2: The electronic control component 9 outputs a drive signal to control the servo motor 6 to start. The output shaft of the servo motor 6 drives the drive rod 81 to rotate. The drive rod 81 then drives the plunger rod 3 to reciprocate linearly along the plunger sleeve 2 through the connecting rod 82, thereby cooperating with the pump body 11 to complete the fuel intake and compression process. When the servo motor 6 drives the plunger rod 3 of the plunger pump 1 to compress the fuel entering the plunger pump 1, high-pressure fuel is formed. The high-pressure fuel enters the fuel injector 4 until the pressure sensor 41 detects that the actual pressure has reached the target value. S3: Electronic control component 9 controls the opening of fuel injection solenoid valve 5, fuel injector 4 starts to inject fuel, and pressure sensor 41 provides real-time feedback of actual fuel injection pressure value. S4: The electronic control component 9 calculates the deviation between the actual injection pressure value and the target injection pressure value, and dynamically adjusts the rotation speed and angle of the servo motor 6 through the built-in PID feedback control algorithm of the electronic control component 9. When the actual fuel pressure is lower than the target injection pressure, the electronic control unit 9 calculates the pressure compensation requirement based on the injection rate, controls the servo motor 6 to increase its rotation speed and the number of rotations, drives the plunger rod 3 to perform high-frequency reciprocating motion to compress the fuel, achieves rapid pressure replenishment, and offsets the fuel pressure drop caused by injection, so that the fuel pressure in the injection channel of the injector 4 is maintained within the target injection pressure range. The injection rate is calculated from the opening duration of the injection solenoid valve 5, the cross-sectional area of ​​the nozzle 4, and the current pressure, or obtained by looking up the engine operating parameters in a table. When the actual fuel pressure is higher than the target injection pressure, the electronic control unit 9 controls the servo motor 6 to stop, and relies on the continuous injection of fuel to naturally reduce the actual injection pressure in the injector 4 until the actual fuel pressure falls back to the target injection pressure range. The number of rotations of the output shaft of the servo motor 6 is proportional to the number of reciprocating motions of the plunger rod 3 of the plunger pump 1. The rotation speed of the output shaft of the servo motor 6 is proportional to the reciprocating motion frequency of the plunger rod 3 of the plunger pump 1. For every preset angle or preset number of rotations of the servo motor 6, the plunger pump 1 completes one complete oil suction-oil pressure motion. The electronic control component 9 calculates the deviation between the actual injection pressure value and the target injection pressure value based on the actual injection pressure value fed back by the pressure sensor 41. At the same time, the electronic control component 9 acquires the crank angle signal of the encoder on the servo motor 6 in real time, determines the position and speed of the piston rod 3 of the piston pump 1 based on the kinematic characteristics of the crank connecting rod mechanism 8, and dynamically adjusts the output torque or speed of the servo motor 6 in combination with the calculated deviation. By coordinating the adjustment of the rotation speed and number of rotations of the servo motor 6 with the electronic control component 9, the reciprocating frequency and total stroke of the plunger rod 3 of the plunger pump 1 can be precisely controlled, thereby achieving precise compensation for oil pressure loss. When the electronic control component 9 determines that the crank-connecting rod mechanism 8 is about to enter the dead point neighborhood, it controls the servo motor 6 to perform short-term over-acceleration, increases the instantaneous angular velocity of the output shaft of the servo motor 6, and realizes the smooth dead point crossing of the crank-connecting rod mechanism 8. After the crossing is completed, the speed and torque output of the servo motor 6 are restored. S5: After one injection is completed, the electronic control component 9 controls the injection solenoid valve 5 to close, and fine-tunes the parameters of the servo motor 6 to stabilize the actual pressure value in the injector 4 at the target injection pressure value, in preparation for the next injection. When the fuel injection of the diesel engine unit pump reaches the preset injection duration or stops when the operating condition requires it to stop, the electronic control component 9 sends a closing signal to the fuel injection solenoid valve 5, the fuel injection solenoid valve 5 closes, and the fuel injector 4 stops injecting fuel. According to the residual pressure value signal in the fuel injector 4 fed back by the pressure sensor 41, the electronic control component 9 finely adjusts the rotation speed and number of rotations of the servo motor 6, drives the plunger rod 3 of the plunger pump 1 to make a small reciprocating motion, so that the fuel pressure in the fuel injection channel of the fuel injector 4 is stably maintained within the preset target injection pressure value range, preparing for the next fuel injection action and ensuring the continuity and consistency of the fuel injection process. S6: Repeat steps S1-S5 above.

[0039] When the diesel engine unit pump receives a shutdown command from the diesel engine or experiences an abnormal stop due to a circuit or hydraulic fault, the electronic control unit 9 first controls the injection solenoid valve 5 to close, then drives the servo motor 6 to rotate the crankshaft connecting rod mechanism 8 at low speed. Using the crankshaft angle signal from the encoder, it precisely locates a specific starting zone outside the dead center position. This starting zone is the rotation range where the crankshaft deviates from the dead center position by 30°-60°. Once the crankshaft reaches this specific starting zone, the electronic control unit 9 controls the servo motor 6 to stop, completing the shutdown reset. This shutdown reset control is executed independently of the normal injection cycle and is triggered during shutdown or abnormal stop conditions.

[0040] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A method for controlling the injection pressure of a diesel engine unit pump, applied to a diesel engine unit pump, wherein the diesel engine unit pump comprises: Piston pump (1); The fuel injector (4) is provided with a fuel injection solenoid valve (5) for controlling the opening or closing of fuel injection. Servo motor (6), the output shaft of the servo motor (6) is connected to the piston rod (3) of the piston pump (1) for driving the piston rod (3) to reciprocate; A pressure sensor (41) is installed in the injection channel of the injector (4); The electronic control component (9) is electrically connected to the fuel injection solenoid valve (5), the pressure sensor (41), and the servo motor (6), respectively; Its characteristics include the following steps: S1: Set the target injection pressure value through the electronic control component (9); S2: The electronic control component (9) outputs a drive signal to control the servo motor (6) to start, which drives the plunger rod (3) of the plunger pump (1) to reciprocate, compressing the fuel entering the plunger pump (1) to form high-pressure fuel. The high-pressure fuel enters the fuel injector (4) until the pressure sensor (41) detects that the actual pressure has reached the target value. S3: The electronic control component (9) controls the injection solenoid valve (5) to open, the injector (4) starts to inject oil, and the pressure sensor (41) provides real-time feedback of the actual injection pressure value. S4: The electronic control component (9) calculates the deviation between the actual injection pressure value and the target injection pressure value, and dynamically adjusts the rotation speed and angle of the servo motor (6) through the built-in PID feedback control algorithm of the electronic control component (9); S5: After one injection is completed, the electronic control component (9) controls the injection solenoid valve (5) to close, and fine-tunes the parameters of the servo motor (6) to stabilize the actual pressure value in the injector (4) at the target injection pressure value, in preparation for the next injection. S6: Repeat steps S1-S5 above.

2. The method for controlling the injection pressure of a diesel engine unit pump according to claim 1, characterized in that: An inlet check valve (12) is provided at the inlet of the plunger pump (1), and an outlet check valve (13) is provided at the connection between the outlet of the plunger pump (1) and the injector (4). In S2, when the fuel pressure in the plunger pump (1) reaches the opening pressure of the outlet check valve (13), the high-pressure fuel pushes open the outlet check valve (13) and enters the injector (4) until the pressure sensor (41) detects that the actual injection pressure value reaches the target injection pressure value, and the pressure is built up.

3. The method for controlling the injection pressure of a diesel engine unit pump according to claim 1, characterized in that: In S4, when the actual fuel pressure is lower than the target injection pressure, the electronic control component (9) calculates the pressure compensation requirement based on the injection rate, controls the servo motor (6) to increase its rotation speed and the number of rotations, drives the plunger rod (3) to perform high-frequency reciprocating motion to compress the fuel, achieves rapid pressure replenishment, offsets the decrease in fuel pressure caused by injection, and keeps the fuel pressure in the injection channel of the injector (4) within the target injection pressure range. The injection rate is calculated by the opening duration of the injection solenoid valve (5), the cross-sectional area of ​​the nozzle (4) and the current pressure, or obtained by looking up the engine operating parameters in a table. When the actual fuel pressure is higher than the target injection pressure, the electronic control component (9) controls the servo motor (6) to stop, and relies on the continuous injection of fuel to naturally reduce the actual injection pressure in the injector (4) until the actual fuel pressure falls back to the target injection pressure range.

4. The method for controlling the injection pressure of a diesel engine unit pump according to claim 3, characterized in that: In S4, the number of rotations of the output shaft of the servo motor (6) is proportional to the number of reciprocating motions of the piston rod (3) of the piston pump (1). The rotation speed of the output shaft of the servo motor (6) is proportional to the reciprocating motion frequency of the piston rod (3) of the piston pump (1). For every preset angle or preset number of rotations of the servo motor (6), the piston pump (1) completes one complete oil suction-oil pressure motion. By coordinating the adjustment of the rotation speed and number of rotations of the servo motor (6) with the electronic control component (9), the reciprocating motion frequency and total stroke of the piston rod (3) of the piston pump (1) can be precisely controlled to achieve accurate compensation for oil pressure loss.

5. The method for controlling the injection pressure of a diesel engine unit pump according to claim 1, characterized in that: In S5, when the fuel injection of the diesel engine unit pump reaches the preset fuel injection duration or the operating condition requires to stop fuel injection, the electronic control component (9) sends a closing signal to the fuel injection solenoid valve (5), the fuel injection solenoid valve (5) closes, and the fuel injector (4) stops injecting fuel. The electronic control component (9) finely adjusts the rotation speed and number of rotations of the servo motor (6) according to the residual pressure value signal in the fuel injector (4) fed back by the pressure sensor (41), drives the plunger rod (3) of the plunger pump (1) to make a small reciprocating motion, so that the fuel pressure in the fuel injection channel of the fuel injector (4) is stably maintained within the preset target fuel injection pressure value range, preparing for the next fuel injection action and ensuring the continuity and consistency of the fuel injection process.

6. The method for controlling the injection pressure of a diesel engine unit pump according to claim 1, characterized in that: A crank-connecting rod mechanism (8) for driving the piston rod (3) to reciprocate is provided between the piston rod (3) of the piston pump (1) and the servo motor (6); an encoder for feeding back the rotation angle signal of the crank-connecting rod mechanism (8) is also provided on the output shaft of the servo motor (6), and the encoder is electrically connected to the electronic control component (9).

7. The method for controlling the injection pressure of a diesel engine unit pump according to claim 6, characterized in that: In S4, the electronic control component (9) calculates the deviation between the actual injection pressure value and the target injection pressure value based on the actual injection pressure value fed back by the pressure sensor (41). At the same time, the electronic control component (9) acquires the crank angle signal of the encoder on the servo motor (6) in real time, determines the position and speed of the piston rod (3) of the piston pump (1) based on the kinematic characteristics of the crank connecting rod mechanism (8), and dynamically adjusts the output torque or speed of the servo motor (6) in combination with the calculated deviation.

8. The method for controlling the injection pressure of a diesel engine unit pump according to claim 6, characterized in that: In S4, when the electronic control component (9) determines that the crank-connecting rod mechanism (8) is about to enter the dead point neighborhood, it controls the servo motor (6) to perform short-term over-acceleration, increases the instantaneous angular velocity of the output shaft of the servo motor (6), and realizes the smooth dead point crossing of the crank-connecting rod mechanism (8). After the crossing is completed, the speed and torque output of the servo motor (6) are restored.

9. The method for controlling the injection pressure of a diesel engine unit pump according to claim 6, characterized in that: When the diesel engine unit pump receives a shutdown command from the diesel engine or an abnormal shutdown occurs due to a circuit or hydraulic fault, the electronic control component (9) first controls the fuel injection solenoid valve (5) to close, and then drives the servo motor (6) to drive the crank connecting rod mechanism (8) to rotate at low speed. The specific starting area of ​​the non-dead position is accurately located by the crank angle signal of the encoder. The starting area is the rotation range of the crank 30°-60° away from the dead position. After the crank rotates to the specific starting area, the electronic control component (9) controls the servo motor (6) to stop running and completes the shutdown reset.

10. The method for controlling the injection pressure of a diesel engine unit pump according to claim 1, characterized in that: In S1, the electronic control component (9) dynamically sets the target injection pressure value of the injector (4) according to the current operating conditions such as the diesel engine speed and load, as the reference for closed-loop control.

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