CN104265474A - Highland starting oil quantity control method for car equipped with high supercharged diesel engine - Google Patents

Abstract

The invention discloses a method for controlling the starting fuel volume of a vehicle equipped with a high-pressure diesel engine. First, the driver's starting intention is identified by real-time detection of the vehicle speed signal and the shift command signal of the hydraulic automatic transmission; In the above, the diesel engine controller adds the feed-forward oil volume calibrated through the plateau start experiment and the base oil volume obtained through the PID closed-loop adjustment as the starting oil volume output; at the same time, the starting air-fuel ratio is limited for the output starting oil volume; finally, The diesel engine controller detects the starting time, and when the starting time exceeds the calibrated clutch engagement time, it is determined that the clutch is fully engaged, and the diesel engine exits the starting working condition. By accurately identifying the driver's starting intention and through coordinated control, the method can effectively improve the smoothness and speed of the vehicle's plateau starting, and avoid problems such as starting vibration and stalling.

Description

Method for controlling oil volume at plateau starting of vehicles equipped with high-pressure diesel engine

technical field

The invention relates to the field of electronic control of vehicles, in particular to a method for controlling the fuel quantity at plateau start of a heavy-duty vehicle equipped with a high-pressure diesel engine.

Background technique

The smoothness and rapidity of the vehicle starting process are important indicators for evaluating the driving comfort and power of the vehicle. In order to meet the evaluation indicators of the starting process as much as possible, it is generally expected that the diesel engine will run stably at a lower speed during the starting process, thereby reducing the speed of the starting process. shock and clutch wear. According to the dynamic principle of the vehicle starting process, during the starting process, the torque transmitted by the clutch is the driving torque of the vehicle on the one hand, and the load torque of the diesel engine on the other hand. In this process, if the torque transmitted by the clutch is greater than the maximum torque of the diesel engine The output torque will cause the diesel engine speed to drop, and its load capacity will further drop until the diesel engine speed and the hydraulic torque converter reach a suitable matching working point; if the diesel engine speed drops below the diesel engine’s minimum idle speed, it will The combustion in the diesel engine cylinder deteriorates, the cycle changes become larger, and even misfire occurs, which leads to unstable operation of the diesel engine and flameout. Therefore, during the starting process, the diesel engine speed cannot be lower than the minimum idle speed of the diesel engine. At present, in the start-up control technology of the vehicle, the ECU usually adjusts the throttle valve or the oil quantity automatically according to the external load when the diesel engine speed drops after the clutch is engaged, and increases the torque to remedy the diesel engine speed to prevent flameout.

However, for heavy-duty vehicles in a plateau environment, due to the high altitude, low atmospheric pressure, and thin air, the intake air volume of the diesel engine is significantly reduced. Yes, the large inertia of the diesel engine and the mechanical system of the heavy-duty vehicle makes the response of the intake and combustion links lag, causing the output torque of the diesel engine to drop significantly when the heavy-duty vehicle starts on a plateau, especially in the low-speed and low-load area. When the engine is not working, the output torque of the diesel engine drops more seriously. At this time, the usual starting oil control strategy is no longer suitable for the starting conditions of heavy-duty vehicles on plateaus. This is because the traditional starting fuel control method only adjusts when it detects that the diesel engine speed has dropped, and does not recognize the driver's starting intention in advance. It is a passive remedial measure, and the adjustment speed is correspondingly slow. At the same time, the traditional starting oil volume control technology usually uses PID feedback control alone. Compared with feedforward control, feedback control takes a longer time, because the control system can only issue corrections after receiving the feedback signal of the controlled object's activity. Therefore, the activities of the controlled object may fluctuate to a certain extent. Compared with other operating conditions, it is more difficult to control the start-up condition with independent feedback control. Especially, in the plateau environment, when the vehicle inertia When the load is large and the load changes suddenly, the diesel engine speed is likely to fluctuate, which will cause the diesel engine speed to drop or even stall.

The information disclosed in this Background section is only for enhancing the understanding of the general background of the present invention and should not be taken as an acknowledgment or any form of suggestion that the information constitutes the prior art that is already known to those skilled in the art.

Contents of the invention

The purpose of the present invention is to provide a method for controlling oil volume at plateau start of a vehicle equipped with a high-pressure diesel engine. The method of combining feedforward and feedback can quickly increase the energy of the turbocharger at plateau start, thereby improving the intake air. , increase the output torque of the diesel engine, and ultimately improve the smoothness and speed of vehicle starting.

In order to achieve the above object, the present invention provides a method for controlling the oil volume at plateau starting of a vehicle equipped with a high-pressure diesel engine, which is characterized in that it comprises the following steps: Step 1, starting the diesel engine to make it enter the idling condition, and in the idling condition In the process, the diesel engine controller detects the gear shift command signal and the vehicle speed signal of the hydraulic automatic transmission in real time, and the diesel engine controller recognizes the driver’s starting intention according to the gear shift command signal and the vehicle speed signal; step 2, when the diesel engine controller detects the hydraulic automatic transmission When the previous gear position of the transmission was neutral and the current gear position is 1st gear, and the current vehicle speed detected by the diesel engine controller is lower than the vehicle speed threshold for successful start, the diesel engine controller recognizes that the driver has the intention to start, and the diesel engine enters the starting mode. condition; step 3, in the starting working condition, the diesel engine controller will add the feed-forward oil quantity calibrated through the plateau starting experiment and the base oil quantity obtained through PID closed-loop adjustment as the starting oil quantity output; step 4, in the starting working condition In the condition, the diesel engine controller detects the starting time, and when the starting time exceeds the calibrated clutch engagement time, the clutch is deemed to be fully engaged, and the diesel engine exits the starting condition.

Preferably, when it is determined in step 4 that the clutch is fully engaged and the detected vehicle speed does not reach the vehicle speed threshold for successful start, the feed-forward fuel volume gradually decreases to 0 within 20 seconds, and the diesel engine slowly exits the start-up condition.

Preferably, the vehicle speed threshold for a successful start is 5 km/h.

Preferably, when it is determined in step 4 that the clutch is fully engaged, and it is detected that the vehicle speed is higher than the vehicle speed threshold for a successful start or when it is detected that the hydraulic automatic transmission leaves the first gear, the feed-forward oil volume is quickly reduced to 0 within 1 second, and the diesel engine The controller quickly exits the starting condition.

Preferably, in step 3, the diesel engine controller performs an external characteristic limit on the output start-up oil quantity, and the diesel engine controller can limit the start-up oil quantity within the range of the maximum required oil quantity of the diesel engine through the external characteristic limitation.

Preferably, in step 3, the diesel engine controller simultaneously limits the air-fuel ratio of the output start-up fuel quantity according to the calibrated start-up air-fuel ratio limit curve.

Preferably, the diesel engine controller detects the shift command signal and the vehicle speed signal of the hydraulic automatic transmission in real time through the CAN bus.

Preferably, the numerical value of the feed-forward oil quantity is obtained through a plateau start experiment.

Preferably, the starting oil quantity is output when an upshift signal is sent.

Preferably, the calibrated clutch engagement time is 1s.

Compared with the prior art, the present invention has the following beneficial effects:

1. Through the gear shift command signal and vehicle speed signal, the driver's starting intention can be accurately judged, and the upshift command signal is sent to the gear shift clutch to start combining this delay period to respond in advance, increase the energy of the supercharger, and improve the diesel engine Intake air, so as to actively compensate for the drop in speed and torque that will be generated during the start process, to ensure a smooth start and prevent flameout;

2. Feed-forward control can monitor disturbances or drivers in advance, and make adaptive responses in advance to prevent disturbances from disturbances. In this method, the starting intention is the motivation, the sudden change of the load at the start is the disturbance, and the feed-forward fuel volume is the adaptive response of the control system to the predicted disturbance, so the introduction of the feed-forward fuel volume can enhance the rapidity of control , quickly increase the oil volume to speed up the response of the supercharger, and at the same time, this method also maintains the stability of the PID closed-loop oil volume adjustment;

3. The ECU switches the air-fuel ratio limit oil quantity to the low limit mode, adopts the starting air-fuel ratio limit curve, appropriately releases the fuel quantity limit, and cooperates with the output of high fuel quantity, thereby increasing the energy of the turbocharger and effectively improving the low-speed and low-load area , especially the working conditions of the turbocharger in the plateau environment, speed up the response speed of the turbocharger, rapidly increase the turbine speed, increase the intake pressure, so as to achieve the increase of speed and torque, and finally improve the starting power.

Description of drawings

Fig. 1 is a schematic diagram of the starting oil quantity control strategy according to the present invention;

Fig. 2 is the flow chart of oil quantity control according to the starting process of the present invention;

Fig. 3 is a comparison diagram of the variation curves of feed-forward oil volume, base oil volume, total output oil volume, diesel engine speed and vehicle speed in the starting process according to the present invention.

Detailed ways

The specific embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments.

Unless expressly stated otherwise, throughout the specification and claims, the term "comprise" or variations thereof such as "includes" or "includes" and the like will be understood to include the stated elements or constituents, and not Other elements or other components are not excluded.

As shown in Fig. 1, the main idea of the plateau starting fuel quantity control method equipped with a highly boosted diesel engine vehicle according to a specific embodiment of the present invention is based on the PID closed-loop regulation of the idle speed target speed on the basis of the fuel quantity (base fuel quantity) In addition to the feed-forward oil volume, the control oil volume obtained by adding the two parts acts on the actuator unit pump, thereby changing the working state of the control object, that is, the diesel engine, and rapidly increasing the starting torque. In particular, the starting fuel quantity control method is suitable for plateau starting of a heavy-duty vehicle equipped with a high-pressure diesel engine.

As shown in Fig. 2, the method for controlling the oil volume at plateau starting of the high-pressure diesel engine vehicle of the present invention is described in detail with a kind of preferred embodiment, and this preferred embodiment has described the oil quantity in the whole process from the start to the end of the start. The specific implementation process of the quantity control method includes the following steps:

1. Identify the driver's starting intention, thereby triggering the starting coordinated control strategy, as follows:

(1) After the diesel engine is successfully started, it enters into an idling condition. At this time, the diesel engine controller performs PID closed-loop fuel quantity control based on the idle target speed (the prior art).

(2) In the idling condition, the diesel engine controller detects the gear shift command signal and the vehicle speed signal of the hydraulic automatic transmission in real time. Specifically, if the last gear is neutral and the current gear is 1st gear, and passed When the current vehicle speed detected by the vehicle speed sensor is less than 5km/h, it indicates that the driver has a starting intention, and the diesel engine enters the starting working condition (at this time, the position of the starting sign is set to 1), and the starting timing is started.

2. In the start-up execution stage, the fuel quantity control strategy based on the calibration-based feed-forward fuel quantity and the closed-loop PID adjustment is adopted, as follows:

(3) In the start-up condition, the diesel engine controller adopts the optimized start-up PID parameters to perform idle speed PID closed-loop adjustment, and calculates the base oil quantity Q _b .

(4) Add the feed-forward oil quantity Q _f required for plateau start calibrated in advance through the start-up experiment to the base oil quantity Q _b in the previous step, and output the obtained oil quantity as the final control oil quantity (starting oil quantity) , this part of the fuel is injected into the cylinder for combustion, and the upshift signal is sent to the delay period when the shift clutch starts to engage, so as to rapidly increase the energy of the turbocharger, increase the speed of the diesel engine, and compensate in advance to reduce the speed generated after the clutch is engaged. And the intake pressure drops to ensure a smooth start and prevent stalling.

3. The diesel engine controller limits the amount of starting oil output, as follows:

(5) First of all, limit the output start-up oil quantity by external characteristics, that is, compare the start-up oil quantity with the output oil quantity corresponding to the external characteristic torque point at the current engine speed, and take the smaller value to prevent excessive fuel injection beyond The maximum fuel demand of the diesel engine is reduced, thereby increasing fuel consumption and emissions.

(6) In particular, in this embodiment, the starting air-fuel ratio is limited to the output starting oil quantity. When the starting flag position 1 is detected in step (2), the ECU (diesel engine controller) will limit the air-fuel ratio to the oil quantity. Switch to the low limit mode, that is, use the start air-fuel ratio limit curve, cooperate with step (4) to increase the fuel output, so as to ensure the dynamic performance at start. The main purpose of using this low limit mode is to limit Insufficient amount, the mixture is too rich and exceeds the smoke limit of the diesel engine, resulting in worsening combustion and aggravating emissions.

Normally, it is enough to use the calibrated normal air-fuel ratio limit curve, but it will switch to the air-fuel ratio limit curve suitable for the start process during the start process. The start air-fuel ratio limit parameter is lower than the normal air-fuel ratio limit parameter, that is, priority Considering the power requirements of heavy-duty vehicles, the air-fuel ratio is properly released to limit the amount of fuel. In other working conditions in the non-starting state, the normal situation will be restored, and stricter restrictions on high air-fuel ratio will be adopted.

(7) Finally, the oil volume obtained in step (6) is further corrected and limited for final output, such as limiting the high oil volume of the diesel engine exhaust temperature, the low oil volume of the diesel engine oil pressure, etc., to complete the fast speed of the diesel engine speed and torque Lifting, when the shift clutch of the hydrodynamic automatic transmission starts to engage, the vehicle begins to move away.

4. Exit the start-up condition. At this stage, the diesel engine controller judges whether the clutch is fully engaged by detecting whether the start-up time exceeds the calibrated clutch engagement time. When the clutch is fully engaged, the diesel engine exits the start-up condition, specifically including slow exit and fast exit. Two situations:

(8) Slowly withdraw from the starting judgment: when the gear position is 1 and the vehicle speed has not reached the vehicle speed threshold for successful starting, in this embodiment, the vehicle speed threshold for successful starting is 5km/h, so that the feedforward fuel quantity Q _f gradually decreases with time Small, reduce to 0 within a certain period of time (20 seconds), and slowly exit the starting condition. During the process of slowly exiting and starting, the diesel engine controller has been adopting the strategy of slowly reducing the fuel volume until the 20s timer expires, the fuel volume is reduced to zero, and the start is over. After that, the ECU (diesel engine controller) will resume the normal fuel volume control strategy.

During this process, the process from the beginning of clutch engagement to full engagement is a process of dynamic friction changing into static friction. The torque demand is greater, and the diesel engine speed drops more. This process requires a large amount of feed-forward oil to increase the diesel engine speed in advance to prevent the speed from falling too much. When the clutch is fully engaged, the diesel engine speed is at the lowest state. If the diesel engine is not turned off, the speed will gradually rise after that. At this time, the feed-forward fuel volume can be gradually reduced. Slowly exiting the starting condition also leaves room for the driver. Step on the accelerator pedal to accelerate and start the space, thereby enhancing the maneuverability of the vehicle starting, this situation may occur in the process of starting uphill or turning at start.

(9) Quick exit start judgment: when the detected vehicle speed is greater than 5km/h, it is considered that the start is successful, or when the gear is not 1, it is considered that the driver chooses to exit the start. At this time, the start flag will be cleared to 0, so that the feed forward The quantity Q _f is quickly reduced to 0 in a relatively short time (1 second), and the smoothness of the transition of the working conditions is ensured while quickly exiting the start. After the start, the ECU will resume the normal fuel quantity control strategy.

In the above-mentioned technical scheme, the shift command signal and the vehicle speed signal in step (2) are obtained by the diesel engine ECU through the CAN bus; the feed-forward fuel quantity Q _f in the step (6) is passed through a specific plateau start experiment to optimize the rapidity of vehicle start and smoothness as the goal, specifically, Q _f is related to the atmospheric pressure value, which can be obtained by checking the one-dimensional MAP table according to the current atmospheric pressure at the start; The first stage delay period is agreed in advance by the diesel engine controller and the gearbox controller, and is related to the speed response of the diesel engine, and also affects the driver's operating experience when shifting gears. Considering the above two factors comprehensively, the delay period in this method Set it to 1S, the starting fuel volume is output when the upshift signal is sent out; the calibrated clutch engagement time in step (8), that is, the time t from the shift command to the complete engagement of the clutch, has multiple acquisition methods, and the clutch travel sensor can be used It can also be obtained through experimental calibration. The delay period in this embodiment is obtained by experimental calibration. The specific method is to analyze the change of the diesel engine speed from the maximum value point to the minimum value during the process from the beginning of the clutch to the completion of the coupling. The point change is 1S as measured by experiments.

Specifically, as shown in FIG. 3 , the vehicle plateau starting oil volume control method of the present invention feeds forward the real-time information of oil volume, base oil volume, total output oil volume (starting oil volume), diesel engine speed and vehicle speed in the process of actual action. The changes are as follows:

Before time t ₀ , the diesel engine is in the idling operation condition, the feed-forward oil volume is 0 and does not work, the total output oil volume is the PID closed-loop adjusted oil volume (base oil volume), the diesel engine speed maintains the idle speed target speed, and the vehicle speed is 0;

At time t ₀ , the ECU detects a shift instruction signal for shifting from neutral to first gear. At this time, the vehicle speed is 0 and less than 5 km/h, and thus enters the starting condition. The feed-forward fuel quantity Q _f required for start-up obtained from the calibration of the plateau start experiment starts to work, and changes from 0 to the calibration value, and is added to the closed-loop PID adjustment fuel quantity to obtain the final total fuel quantity of the diesel engine (starting fuel quantity), so the total The output oil volume also increases at time t ₀ ;

The time period from t ₀ to t ₀₊₁ is the delay period from when the upshift signal is sent to when the shift clutch starts to engage, and the time is 1S. During this period, since the clutch has not started to engage, and the total oil volume of the diesel engine has increased, the energy of the turbocharger increases rapidly, and the speed of the diesel engine will increase rapidly, which will compensate for the decrease in the speed of the diesel engine during the next clutch engagement process, and avoid the decrease in speed Too much will cause jitter and flameout; at this time, the controller actually performs a low air-fuel ratio curve switching operation to match the output of a large amount of fuel. At the same time, the base oil quantity Q _b adjusted by the PID closed-loop decreases because the actual speed of the diesel engine exceeds the target speed. Since the clutch is not engaged, the vehicle speed is still 0;

At time t ₀₊₁ , the shift clutch of the hydraulic automatic transmission begins to engage. During the period from t ₀₊₁ to t ₀₊₂ , the torque of the diesel engine begins to be transmitted to the wheels through the transmission system, and the vehicle speed increases from 0; the shift clutch engages During the process, the load of the diesel engine increases gradually, so the speed of the diesel engine will gradually decrease; the feed-forward oil quantity continues to act, and the total oil quantity is still obtained by adding the feedforward oil quantity Q _f and the PID closed-loop adjustment base oil quantity Q _b ;

At time t ₀₊₂ , the shifting clutch is fully engaged, and the state changes from dynamic friction to static friction. At this time, the diesel engine speed reaches the minimum, and then the diesel engine speed will gradually rise. At this time, the ECU sets the feed-forward oil volume at a certain rate to gradually increase within 20 seconds. Decrease to 0, when the vehicle speed does not reach 5km/h, the mode of slowly exiting the starting condition will be adopted; the total oil output will also decrease slowly, and the vehicle speed will further increase;

At time _t1 , it is detected that the vehicle speed is greater than 5km/h, which means that the start is successful. At this time, the controller will quickly reduce the feed-forward fuel volume to 0 within 1 second, quickly exit the starting condition, and then restore the normal fuel volume control strategy;

At time t ₁₊₁ , that is, 1 second after t ₁ , the feed-forward fuel volume is reduced to 0, the normal fuel volume control strategy is adopted, the total output fuel volume is adjusted by PID closed-loop, the diesel engine speed maintains the target idle speed, and the vehicle speed will be balanced at a certain value;

If the vehicle speed has been lower than 5km/h after starting, the controller will gradually reduce to 0 within 20 seconds after the clutch is fully engaged (time t ₀₊₂ ), that is, at time t ₀₊₂₂ , and slowly exit the starting condition. This situation may occur when a heavy-duty vehicle starts turning or starts uphill. In this case, the set time of 20 seconds reserves space for the driver to step on the accelerator pedal to assist acceleration and start, which enhances the possibility of starting the vehicle. operability.

In short, this method accurately identifies the driver's starting intention through the shift command signal and the vehicle speed signal, and uses the method of combining the calibrated feed-forward fuel quantity and the PID closed-loop adjustment based on the idle speed target speed to send out the shift command to the clutch to start engaging. In the previous time, the starting oil volume was rapidly increased, the turbocharger energy was rapidly increased, and the intake pressure drop and speed drop that would occur during the starting process were actively compensated; at the same time, the ECU switched the oil volume limiting strategy to coordinate the oil volume output, thus ensuring When the vehicle starts, especially when the heavy-duty vehicle starts on a plateau, the dynamic performance indicators such as smooth start and rapidity are improved.

The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. These descriptions are not intended to limit the invention to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teaching. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling others skilled in the art to make and use various exemplary embodiments of the invention, as well as various Choose and change. It is intended that the scope of the invention be defined by the claims and their equivalents.

Claims (10)

1. a plateau starting fuel-flow control method for highly supercharged diesel engine vehicle is housed, it is characterized in that, comprise the steps:

Step 1, starting diesel engine makes it enter idling operation, in idling operation, diesel engine controller detects shift command signal and the vehicle speed signal of hydraulic automatic speed variator in real time, and diesel engine controller is intended to according to the starting of described shift command signal and described vehicle speed signal identification driver;

Step 2, the upper moment gear detecting hydraulic automatic speed variator when diesel engine controller is neutral gear, current gear is 1 grade, and the current vehicle speed that diesel engine controller detects be less than starting the successful speed of a motor vehicle threshold value time, then diesel engine controller identification driver has starting intention, and diesel engine enters starting operating mode;

Step 3, in starting operating mode, diesel engine controller is using the feedforward oil mass gone out by plateau starting experimental calibration and be added as the output of starting oil mass by the basic oil mass that PID closed-loop adjustment obtains;

Step 4, in starting operating mode, diesel engine controller detects start-up time, and the clutch combination time exceeding demarcation when described start-up time then assert that clutch combines completely, and diesel engine exits starting operating mode.

2. the plateau starting fuel-flow control method that highly supercharged diesel engine vehicle is housed according to claim 1, it is characterized in that, after assert that clutch combines completely in described step 4, and the speed of a motor vehicle detected do not reach starting the successful speed of a motor vehicle threshold value time, described feedforward oil mass was reduced to 0 gradually in 20 seconds, and diesel engine slowly exits starting operating mode.

3. the plateau starting fuel-flow control method that highly supercharged diesel engine vehicle is housed according to claim 2, it is characterized in that, the successful speed of a motor vehicle threshold value that starts to walk is 5km/h.

4. the plateau starting fuel-flow control method that highly supercharged diesel engine vehicle is housed according to claim 1, it is characterized in that, after assert that clutch combines completely in described step 4, and detect the speed of a motor vehicle higher than starting successful speed of a motor vehicle threshold value or detect that hydraulic automatic speed variator leaves 1 grade time, described feedforward oil mass was reduced to 0 rapidly in 1 second, and diesel engine controller exits starting operating mode fast.

5. the plateau starting fuel-flow control method that highly supercharged diesel engine vehicle is housed according to claim 1, it is characterized in that, in described step 3, diesel engine controller carries out external characteristics restriction to the starting oil mass exported, and described starting oil mass can be limited within the scope of diesel engine greatest requirements oil mass by external characteristics restriction by diesel engine controller.

6. the plateau starting fuel-flow control method that highly supercharged diesel engine vehicle is housed according to claim 5, it is characterized in that, in described step 3, diesel engine controller carries out air fuel ratio restriction according to the starting air fuel ratio restrictive curve demarcated to the starting oil mass exported simultaneously.

7. the plateau starting fuel-flow control method that highly supercharged diesel engine vehicle is housed according to claim 1, it is characterized in that, diesel engine controller detects shift command signal and the vehicle speed signal of hydraulic automatic speed variator in real time by CAN.

8. the plateau starting fuel-flow control method that highly supercharged diesel engine vehicle is housed according to claim 1, it is characterized in that, the numerical value of described feedforward oil mass is obtained by plateau starting experiment.

9. the plateau starting fuel-flow control method that highly supercharged diesel engine vehicle is housed according to claim 1, it is characterized in that, described starting oil mass exports when upshift signal sends.

10. the plateau starting fuel-flow control method that highly supercharged diesel engine vehicle is housed according to claim 1, it is characterized in that, the clutch combination time of demarcation is 1s.