Control method of variable valve engine

Abstract

The invention discloses a control method of a variable valve engine, relates to a variable valve control method, and solves the technical problems of poor dynamic property, poor economic level and low transient responsiveness in steady-state operation of an existing variable valve control method. The method comprises the steps that the engine rotating speed and the circulating fuel injection quantity are obtained, the circulating fuel injection quantity change rate is obtained according to the circulating fuel injection quantity, and the circulating fuel injection quantity change rate threshold value is obtained according to the engine rotating speed; when the circulating fuel injection quantity change rate is larger than the circulating fuel injection quantity change rate threshold value, it is judged that the engine is in a transient acceleration state; when the circulating fuel injection quantity change rate is smaller than or equal to the circulating fuel injection quantity change rate threshold value, it is judged that the engine is in a steady-state operation state; when it is judged that the engine is in the transient acceleration state, an instantaneous acceleration control strategy is triggered; and when it is judged that the engine is in the steady-state operation state, a steady-state operation control strategy is triggered. The invention is beneficial to improving the economical efficiency and exhaust temperature of the engine and reducing the emission.

Description

Technical Field

[0001] The present invention relates to a variable valve control method, and more particularly, to a control method for a variable valve engine. Background Art

[0002] As my country's automobile population continues to grow, the problems associated with these vehicles are gradually becoming apparent. The energy consumption and emissions generated by this massive number of vehicles pose a significant challenge to building a resource-efficient and environmentally friendly society. Variable Valve Actuation (VVA) technology ensures optimal selection of the appropriate engine valve actuation technology for various operating conditions, effectively reducing fuel consumption and improving engine performance to a certain extent.

[0003] The two-stage variable intake cam technology can take into account two different valve lift curves at the same time. Under steady-state operation, it effectively reduces fuel consumption and the generation of pollutants such as NOx under a certain load of the engine, and also increases the exhaust temperature of the engine at low load, thereby improving charging efficiency and power performance.

[0004] But it is obvious that low-speed and low-load operating conditions increase exhaust temperature and improve catalyst efficiency. At the same time, its transient response deteriorates due to the decrease in air-fuel ratio, and the acceleration smoke density increases accordingly, making it difficult to meet user needs.

[0005] Therefore, how to achieve better results in terms of power, economy and transient response in steady-state operation through optimization control methods is an urgent problem to be solved in this application. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a control method for a variable valve engine in response to the shortcomings of the existing technology, so as to solve the technical problems of poor steady-state power, poor economy and low transient response of the existing variable valve control method.

[0007] A control method for a variable valve engine according to the present invention includes obtaining an engine speed and a cyclic fuel injection amount, obtaining a cyclic fuel injection amount change rate according to the cyclic fuel injection amount, and obtaining a cyclic fuel injection amount change rate threshold according to the engine speed;

[0008] When the cycle fuel injection amount change rate is greater than the cycle fuel injection amount change rate threshold, it is determined that the engine is in a transient acceleration state; when the cycle fuel injection amount change rate is less than or equal to the cycle fuel injection amount change rate threshold, it is determined that the engine is in a steady-state operation state;

[0009] When it is determined that the engine is in a transient acceleration state, a transient acceleration control strategy is triggered; when it is determined that the engine is in a steady-state operation state, a steady-state operation control strategy is triggered.

[0010] As a further improvement, the method for obtaining the cyclic injection amount change rate according to the cyclic injection amount is:

[0011] A unit time axis is set, and the cyclic fuel injection amount at each time point on the unit time axis is obtained. A change curve of the unit time-cyclic fuel injection amount is drawn based on the unit time axis and the cyclic fuel injection amount at each time point on the unit time axis. The slope of the change curve is calculated and used as the change rate of the cyclic fuel injection amount.

[0012] Furthermore, a method for obtaining a cyclic injection amount change rate threshold value according to the engine speed is as follows:

[0013] The cycle fuel injection amount change rate is calibrated according to the engine speed, and the cycle fuel injection amount change rate threshold is calibrated according to the cycle fuel injection amount change rate.

[0014] Furthermore, the instantaneous acceleration control strategy is:

[0015] When the engine speed is less than or equal to a preset speed switching value, the valve operating mode 1 is executed;

[0016] When the engine speed is greater than a preset speed switching value, valve operating mode 2 is executed.

[0017] Furthermore, the speed switching value is 1000rpm-1200rpm.

[0018] Furthermore, the steady-state operation control strategy includes:

[0019] The engine torque percentage is obtained by the engine speed and the cyclic injection amount. When the engine torque percentage is in the first area of ​​the preset MAP table, valve operating mode 1 is executed; when the engine torque percentage is in the second area of ​​the MAP table, valve operating mode 2 is executed.

[0020] Beneficial effects

[0021] The advantages of the present invention are:

[0022] The present invention obtains the engine speed and the cyclic injection amount, obtains the cyclic injection amount change rate according to the cyclic injection amount, obtains the cyclic injection amount change rate threshold according to the engine speed, and judges whether the engine is in a transient acceleration state or a steady-state operation state according to the cyclic injection amount change rate and the cyclic injection amount change rate threshold. When it is determined that the engine is in the transient acceleration state, the transient acceleration control strategy is triggered, and when it is determined that the engine is in the steady-state operation state, the steady-state operation control strategy is triggered; thereby, the variable valve working mode is selected according to the working requirements, which is beneficial to improving the economy and exhaust temperature of the engine and reducing emissions; in the transient acceleration state, the low-speed transient responsiveness of the engine is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a flow chart of the variable valve engine method of the present invention;

[0024] Figure 2 A logic diagram of the variable valve engine method process of the present invention;

[0025] Figure 3 A schematic diagram of the valve mechanism usage area when the engine of the present invention is in steady-state operation;

[0026] Figure 4 A schematic diagram of the valve mechanism usage area of ​​the engine of the present invention after transient acceleration activation;

[0027] Figure 5 This is the two-stage intake cam valve lift profile diagram of the present invention. DETAILED DESCRIPTION

[0028] The present invention will be further described below in conjunction with the embodiments, but this does not constitute any limitation to the present invention. Any limited number of modifications made by anyone within the scope of the claims of the present invention are still within the scope of the claims of the present invention.

[0029] See Figure 1-Figure 5 A control method for a variable valve engine of the present invention includes obtaining an engine speed and a cyclic fuel injection amount, and obtaining a cyclic fuel injection amount change rate based on the cyclic fuel injection amount. The method for obtaining the cyclic fuel injection amount change rate based on the cyclic fuel injection amount is as follows: setting a unit time axis, obtaining the cyclic fuel injection amount at each time point on the unit time axis, drawing a change curve of the unit time-cyclic fuel injection amount based on the unit time axis and the cyclic fuel injection amount at each time point on the unit time axis, calculating the slope of the change curve, and using the slope of the change curve as the cyclic fuel injection amount change rate.

[0030] A cycle-by-cycle fuel quantity change rate threshold is obtained based on the engine speed. The method for obtaining the cycle-by-cycle fuel quantity change rate threshold based on the engine speed is to calibrate the cycle-by-cycle fuel quantity change rate (CUR) based on the engine speed, and then calibrate the cycle-by-cycle fuel quantity change rate threshold based on the cycle-by-cycle fuel quantity change rate. The cycle-by-cycle fuel quantity change rate (CUR) is a preset cycle-by-cycle fuel quantity change rate threshold under different engine speed conditions.

[0031] When the cycle injection amount change rate is greater than the cycle injection amount change rate threshold, the engine is determined to be in a transient acceleration state; when the cycle injection amount change rate is less than or equal to the cycle injection amount change rate threshold, the engine is determined to be in a steady-state operation state.

[0032] When it is determined that the engine is in a transient acceleration state, the transient acceleration control strategy is triggered.

[0033] The instantaneous acceleration control strategy is:

[0034] When the engine speed is less than or equal to the preset speed switching value, valve operating mode 1 is executed; when the engine speed is greater than the preset speed switching value, valve operating mode 2 is executed. The speed switching value is 1000 rpm-1200 rpm. In this embodiment, the speed switching value is 1100 rpm.

[0035] Engine transient acceleration state:

[0036] The transient acceleration state refers to the state in which, when the driver steps deeply on the accelerator during the acceleration process, the electronic control unit (ECU) of the engine control system determines that the driver needs to accelerate based on the current vehicle speed, speed and gear position, and therefore appropriately increases the fuel injection amount to increase power to meet the acceleration requirements.

[0037] Since the transient response of the engine at low speed is poor, when the engine enters transient acceleration from steady state operation, the valve mechanism working mode will be as follows Figure 4 When the engine speed is less than or equal to 1100 rpm, the valve train implements valve operating mode 1; at other engine speeds, valve operating mode 2 is implemented to achieve better response characteristics.

[0038] When the engine is in a transient acceleration state, the valve train mode is executed as follows Figure 4The valve operating mode is defined as follows. When the initial acceleration condition is any operating condition between the lowest speed and 1100 rpm, the ECU receives pedal information to activate transient acceleration. During the acceleration process, the valve train will execute the operating instructions of valve operating mode 1 for all operating conditions between the lowest speed and 1100 rpm. Once the engine completes transient acceleration and exits the activated state, the valve train will operate in steady-state mode, with the valves switching accordingly. After transient acceleration exceeds 1100 rpm, the valve train will execute the operating instructions of valve operating mode 2.

[0039] When it is determined that the engine is in a steady-state operation state, the steady-state operation control strategy is triggered.

[0040] like Figure 3 As shown, the steady-state operation control strategy includes calculating the engine torque percentage through the engine speed and the cyclic injection amount. When the engine torque percentage is in the first area of ​​the preset MAP table, the valve operating mode 1 is executed; when the engine torque percentage is in the second area of ​​the MAP table, the valve operating mode 2 is executed.

[0041] When the engine is in steady-state operation: the engine speed is less than 1100rpm and the load rate is 40%, the valve mechanism executes valve working mode 1; the rest of the operating conditions execute valve working mode 2, such as Figure 3 shown.

[0042] When it is determined that the engine is in a steady-state operation state, the current engine torque percentage (load rate) is characterized by the speed and cyclic injection amount, and the VVA MAP table is interpolated to obtain the valve operating mode that the current working condition should be in. If the real-time torque percentage is in the "1" area of ​​the MAP table, valve operating mode 1 is executed; if the real-time torque percentage is in the "0" area of ​​the MAP table, valve operating mode 2 is executed.

[0043] The VVA MAP table uses speed and torque percentage (load rate) as coordinate XY axes. "0" and "1" in the MAP table represent the valve operating mode signal, which serves as a switching instruction.

[0044] This application provides two-stage valvetrain operating modes for steady-state operation and transient acceleration. In steady-state operation, the variable valve operating mode is selected according to operating requirements, which helps improve engine economy and exhaust temperature, and reduce emissions. In transient acceleration, it improves the engine's low-speed transient responsiveness.

[0045] The valve operating mode 1 and the valve operating mode 2 in the present invention are both existing technologies, and the present invention does not improve them.

[0046] The above is only a preferred embodiment of the present invention. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the structure of the present invention. These modifications and improvements will not affect the effect of the implementation of the present invention and the practicality of the patent.

Claims

1. A control method for a variable valve engine, characterized in that: The method comprises: obtaining an engine speed and a cyclic fuel injection amount, obtaining a cyclic fuel injection amount change rate according to the cyclic fuel injection amount, and obtaining a cyclic fuel injection amount change rate threshold according to the engine speed; When the cycle-by-cycle fuel injection amount change rate is greater than a cycle-by-cycle fuel injection amount change rate threshold, determining that the engine is in a transient acceleration state; When the cycle fuel injection amount change rate is less than or equal to the cycle fuel injection amount change rate threshold, it is determined that the engine is in a steady-state operation state; When the engine is in a transient acceleration state, the transient acceleration control strategy is triggered; when the engine is in a steady-state operation state, the steady-state operation control strategy is triggered.

2. The control method of a variable valve engine according to claim 1, characterized in that: The method for obtaining the cyclic injection amount change rate according to the cyclic injection amount is: A unit time axis is set, and the cyclic fuel injection amount at each time point on the unit time axis is obtained. A change curve of the unit time-cyclic fuel injection amount is drawn based on the unit time axis and the cyclic fuel injection amount at each time point on the unit time axis, and the slope of the change curve is used as the change rate of the cyclic fuel injection amount.

3. The control method of a variable valve engine according to claim 1, characterized in that: The method for obtaining the cyclic injection amount change rate threshold value according to the engine speed is: The cycle fuel injection amount change rate is calibrated according to the engine speed, and the cycle fuel injection amount change rate threshold is calibrated according to the cycle fuel injection amount change rate.

4. The control method of a variable valve engine according to claim 1, characterized in that: The instantaneous acceleration control strategy is: When the engine speed is less than or equal to the preset speed switching value, the valve operating mode 1 is executed; When the engine speed is greater than the speed switching value, valve operating mode 2 is executed.

5. The control method of a variable valve engine according to claim 4, characterized in that: The speed switching value is 1000 rpm-1200 rpm.

6. The control method of a variable valve engine according to claim 1, characterized in that: The steady-state operation control strategy includes: The engine torque percentage is obtained through the engine speed and the cyclic injection amount. When the engine speed and the torque percentage are both located in the first area of ​​the preset MAP table, valve operating mode 1 is executed; when the engine speed and the torque percentage are both located in the second area of ​​the MAP table, valve operating mode 2 is executed.

Images