Start-stop protection strategy for extended-range engine

Abstract

The invention discloses a start-stop protection strategy for an extended-range engine, and relates to an engine control technology, when the engine is shut down, the engine is dragged by an extended-range motor to continue to run at a set target rotating speed for a preset time so as to drive a water pump to rotate, so that cooling liquid in the engine keeps flowing after the engine is shut down. According to the invention, the heat generated by heat regeneration of the cylinder cover and the supercharger is taken away, the fatigue cracking fault of the cylinder cover caused by overheating or the clamping stagnation fault caused by coking of engine oil in the supercharger are effectively avoided, and the engine is well protected.

Description

Technical Field

[0001] The invention relates to engine control technology, and more particularly to a start-stop protection strategy for a range-extended engine. Background Art

[0002] like Figure 1 and Figure 2 As shown in the figure, the traditional engine start-stop protection strategy is to quickly decelerate the engine speed from the working speed to the shutdown after the engine is stopped, and the entire shutdown process takes less than 3 seconds. However, at this time, the engine coolant stops flowing due to the stop of the water pump, which can easily cause the temperature of the cylinder head and the supercharger to continue to rise under the effect of heat recovery, thereby causing overheating and fatigue cracking of the cylinder head or coking of the oil in the supercharger, resulting in a jamming failure. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a start-stop protection strategy for a range-extended engine in view of the deficiencies in the prior art, which plays the role of first removing the heat generated by the cylinder head and the supercharger during the shutdown process before shutting down.

[0004] The start-stop protection strategy of a range-extended engine described in the present invention is that when the engine is stopped, the engine is driven by the range-extended motor to continue to run at a set target speed for a predetermined time to drive the water pump to rotate, so that the coolant inside the engine keeps flowing after the engine is stopped.

[0005] As a further improvement, after the predetermined time is reached, the range extender motor stops dragging the engine, and the engine freely decelerates to a shutdown state.

[0006] Furthermore, a target water temperature and a target oil temperature of the engine are set, and a predetermined time is calibrated according to the temperature change rate of the coolant when cooling the engine water temperature and oil temperature, so that the engine water temperature and the oil temperature are the target water temperature and the target oil temperature when the range extender motor stops towing the engine.

[0007] As a further improvement, when the engine is stopped, the rotation speed at the moment of the engine stopping is used as the target rotation speed.

[0008] Furthermore, the predetermined time is 20 to 60 seconds.

[0009] As a further improvement, when the engine stops, the range extender motor is used to decelerate the engine to a preset intermediate speed, and the range extender motor is used to maintain the engine at the intermediate speed, with the intermediate speed being used as the target speed.

[0010] Furthermore, the predetermined time is greater than 60 seconds.

[0011] Furthermore, the intermediate speed is set in accordance with a principle to avoid the resonance speed region of the whole vehicle.

[0012] Beneficial Effects

[0013] The advantages of the present invention are as follows: the range-extended engine of the present invention adds a start-stop protection strategy, which delays the shutdown of the engine by dragging the range-extended motor, so that the heat generated by the heat recovery of the cylinder head and the supercharger is first taken away during the shutdown process before the engine is shut down, thereby effectively protecting high-temperature components such as the cylinder head and the supercharger. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the time curve of the start-stop control strategy of the traditional range-extended engine;

[0015] Figure 2 It is a time-operating condition comparison table of the traditional range-extended engine start-stop control strategy;

[0016] Figure 3 It is a schematic diagram of a time curve of the first embodiment of the start-stop protection strategy for the range-extended engine of the present invention;

[0017] Figure 4 A time-operating condition comparison table of the first embodiment of the range-extended engine start-stop protection strategy of the present invention;

[0018] Figure 5 It is a schematic diagram of a time curve of a second embodiment of the start-stop protection strategy for an extended-range engine of the present invention;

[0019] Figure 6 This is a time-operating condition comparison table of the second embodiment of the range-extended engine start-stop protection strategy of the present invention. DETAILED DESCRIPTION

[0020] The present invention will be further described below in conjunction with the embodiments, but it 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.

[0021] The start-stop protection strategy of the range-extended engine of the present invention, when the engine is stopped, the range-extended motor is used to drag the engine to continue to run at a set target speed for a predetermined time, so as to drive the water pump to rotate, so that the coolant inside the engine keeps flowing after the shutdown, thereby taking away the heat generated by the cylinder head and the supercharger heat recovery, effectively avoiding the cylinder head fatigue cracking failure caused by overheating or the sticking failure caused by the coking of the oil in the supercharger, and protecting the engine well.

[0022] In the present invention, the preset time for the range-extending motor to tow the engine is mainly controlled to ensure that the engine water temperature and oil temperature are within a safe range. Therefore, the present invention sets the target water temperature and target oil temperature of the engine, and calibrates the preset time according to the temperature change rate when the coolant cools the engine water temperature and oil temperature, so that the engine water temperature and oil temperature are the target water temperature and target oil temperature when the range-extending motor stops towing the engine. Since the engine does not work and generates heat during the process of the range-extending motor towing the engine, the preset time is calibrated directly by the temperature change rate, which can also effectively ensure the cooling rate of the water temperature and oil temperature after stopping towing without complicated calculations. When the preset time is over, it means that the water temperature and oil temperature of the engine have dropped to the target water temperature and target oil temperature. At this time, the range-extending motor stops towing the engine, and the engine decelerates freely to a shutdown state.

[0023] The start-stop protection strategy of the present invention proposes two implementation modes.

[0024] Embodiment 1

[0025] like Figure 3 and Figure 4 As shown, when the engine stops, the speed at the moment of engine stop is used as the target speed. That is, the engine is kept running at the working speed by the range extender motor, and continues to run until the predetermined time ends. In this embodiment, the predetermined time is between 20 and 60 seconds. When the predetermined time ends, the range extender motor stops running, and the engine is decelerated and stopped freely, and the stopping time is within 3 seconds.

[0026] Embodiment 2

[0027] like Figure 5 and Figure 6 As shown in the figure, when the engine stops, the range extender motor decelerates the engine to a preset intermediate speed, and the range extender motor maintains the engine at the intermediate speed, with the intermediate speed as the target speed. That is, the engine first decelerates to the intermediate speed, and maintains the intermediate speed for more than 60 seconds, and then the range extender motor stops towing, and the engine decelerates and stops freely. Among them, the time for the engine to decelerate to the intermediate speed is controlled within 1 to 3 seconds, and the time for the engine to decelerate and stop freely is within 3 seconds. In addition, the intermediate speed value is determined by actual vehicle calibration, and in principle, it only needs to avoid the resonance speed area of ​​the whole vehicle.

[0028] In the above two embodiments, after the engine stops, the range extender motor is used to delay the engine shutdown, and the coolant in the engine continues to flow to take away the heat generated by the heat recovery, effectively avoiding the cylinder head fatigue cracking failure caused by overheating or the oil coking in the supercharger causing the jamming failure. At the same time, the main energy consumption of the range extender motor is the energy consumption to overcome the friction work of the engine, and the power consumption of the towing is very small, which will not affect the user's concern about the power display.

[0029] 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, which will not affect the effect of the implementation of the present invention and the practicality of the patent.

Claims

1. A start-stop protection strategy for a range-extended engine, characterized in that: When the engine is stopped, the engine is driven by the range extender motor to continue running at a set target speed for a predetermined time to drive the water pump to rotate, so that the coolant inside the engine keeps flowing after the engine is stopped.

2. A start-stop protection strategy for a range-extended engine according to claim 1, characterized in that: After the predetermined time is reached, the range-extending motor stops dragging the engine, and the engine decelerates freely to a shutdown state.

3. A start-stop protection strategy for a range-extended engine according to claim 2, characterized in that: The target water temperature and the target oil temperature of the engine are set, and the predetermined time is calibrated according to the temperature change rate of the coolant when cooling the engine water temperature and the oil temperature, so that the water temperature and the oil temperature of the engine are the target water temperature and the target oil temperature when the range extender motor stops towing the engine.

4. A start-stop protection strategy for a range-extended engine according to any one of claims 1 to 3, characterized in that: When the engine is stopped, the rotation speed at the moment the engine is stopped is used as the target rotation speed.

5. A start-stop protection strategy for a range-extended engine according to claim 4, characterized in that: The predetermined time is 20 to 60 seconds.

6. A start-stop protection strategy for a range-extended engine according to any one of claims 1 to 3, characterized in that: When the engine is stopped, the range extender motor is used to decelerate the engine to a preset intermediate speed, and the range extender motor is used to maintain the engine at the intermediate speed, with the intermediate speed being used as the target speed.

7. A start-stop protection strategy for a range-extended engine according to claim 6, characterized in that: The predetermined time is greater than 60 seconds.

8. A start-stop protection strategy for a range-extended engine according to claim 7, characterized in that: The intermediate speed is set in accordance with the principle of avoiding the resonance speed region of the whole vehicle.

Images