Fuel injector switching device and method of electronic fuel injection gasoline engine

Abstract

The invention provides a fuel injector switching device and method for an electronic fuel injection gasoline engine, and relates to the technical field of engine control, and the method comprises the steps that when it is detected that the rotating speed of the electronic fuel injection gasoline engine exceeds the switching rotating speed, a downstream fuel injector is controlled to calculate the fuel injection quantity according to the target fuel quantity and the enrichment coefficient for fuel injection; the enrichment coefficient is attenuated once according to the attenuation step length after each working cycle of the electronic fuel injection gasoline engine, and then when the enrichment coefficient is not larger than a preset coefficient threshold value, the fuel injector switching device controls a downstream fuel injector to inject fuel according to the target fuel quantity, so that fuel injector switching is completed. The method has the beneficial effects that the required enrichment degree of the target oil quantity can be determined according to the opening degree of the throttle valve and is gradually reduced, so that the problems of over-enrichment, over-dilution, unstable combustion and the like in the process of switching the upstream oil injector into the downstream oil injector are solved, and an engine obtains an efficient and stable oil injector switching process; therefore, more accurate control and a better discharge level are obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of engine control, and in particular to a fuel injector switching device and method for an electronic fuel injection gasoline engine. Background Art

[0002] In order to adapt to the application of a wide speed range, the high speed and high load require the injector to complete the injection in an extreme time, requiring the injector to have a large flow characteristic; the low speed and small load require the injector to be precisely controlled, and the injector's flow characteristic cannot be too large. In order to meet the requirements of high and low speeds at the same time, so that the engine can take into account both performance and emissions, two sets of injectors are a common configuration, mainly used in motorcycle engines with higher maximum speeds.

[0003] There are several existing switching modes of two groups of injectors:

[0004] Simple and direct switching: After the ECU confirms that the switching conditions are met, it stops driving the upstream injector and drives the downstream injector. The problem is that it does not take into account that the injector that has just started is prone to lean due to factors such as temperature, and it is easy to cause unstable combustion and air-fuel ratio jump when switching between upstream and downstream, affecting power output and emission control.

[0005] Switching after overlapping injection: After the ECU confirms that the switching conditions are met, it starts using the downstream injector in advance before stopping driving the upstream injector, so that the two groups of injectors work simultaneously during the switching stage of the engine. The existing problem is that it is easy to burn too rich when switching between upstream and downstream, which is not good for emissions.

[0006] It can be seen that the current injector switching method still has major problems and disadvantages. Summary of the invention

[0007] In view of the problems existing in the prior art, the present invention provides an injector switching device for an electronic fuel injection gasoline engine, comprising:

[0008] A rotation speed sensor is provided in the electronic fuel injection gasoline engine and is used to detect the rotation speed of the electronic fuel injection gasoline engine;

[0009] An intake manifold, connected to the electronic fuel injection gasoline engine and the air filter, an upstream fuel injector is provided at one end of the intake manifold close to the air filter, and a downstream fuel injector is provided at one end of the intake manifold close to the electronic fuel injection gasoline engine;

[0010] A control unit is respectively connected to the speed sensor, the upstream injector and the downstream injector, and is used to switch the injection from the upstream injector to the downstream injector when the speed sensor detects that the speed of the electronic fuel injection gasoline engine exceeds the switching speed.

[0011] Preferably, the electronic fuel injection gasoline engine is a multi-cylinder engine, and comprises a plurality of intake manifolds, and both ends of each intake manifold are respectively connected to the air intake port of one of the cylinders of the multi-cylinder engine and the air filter.

[0012] Preferably, the electronic fuel injection gasoline engine comprises a plurality of exhaust manifolds, and both ends of each exhaust manifold are respectively connected to the exhaust port of a cylinder and the main exhaust pipe.

[0013] Preferably, a throttle body is provided on the intake manifold.

[0014] Preferably, the throttle body is arranged between the upstream injector and the downstream injector.

[0015] The present invention also provides a fuel injector switching method for an electronic fuel injection gasoline engine, which is applied to the fuel injector switching device as described above, and comprises:

[0016] Step S1, the injector switching device detects whether the speed of the electronic fuel injection gasoline engine exceeds the switching speed:

[0017] If yes, the upstream injector is controlled to stop injecting fuel, and the process goes to step S2;

[0018] If not, keep the upstream injector injecting fuel, and then return to step S1;

[0019] Step S2, the injector switching device controls the downstream injector to inject fuel according to the injection amount calculated based on the target fuel amount and the enrichment factor;

[0020] Step S3, the injector switching device decays the enrichment coefficient according to the decay step length after each working cycle of the electronic fuel injection gasoline engine, and then determines whether the enrichment coefficient is not greater than a preset coefficient threshold:

[0021] If yes, the injector switching device controls the downstream injector to inject fuel according to the target fuel quantity to complete the injector switching;

[0022] If not, return to step S2.

[0023] Preferably, the injector switching device comprises a storage unit, wherein a comparison table of standard throttle opening, enrichment coefficient and attenuation step length is stored in the storage unit;

[0024] Then, in step S2, the injector switching device matches the corresponding enrichment coefficient and the attenuation step length from the standard throttle opening, enrichment coefficient and attenuation step length comparison table according to the current throttle opening of the electronic fuel injection gasoline engine.

[0025] Preferably, one working cycle in step S3 is two rotations of the crankshaft of the electronic fuel injection gasoline engine.

[0026] The present invention also provides an injector switching method for an electronic fuel injection gasoline engine, which is applied to the injector switching device as described above. The electronic fuel injection gasoline engine is a multi-cylinder engine, and each cylinder of the multi-cylinder engine corresponds to a group of upstream injectors and downstream injectors. The injector switching method further includes:

[0027] Step A1, the injector switching device determines whether the speed of the electronic fuel injection gasoline engine exceeds the switching speed:

[0028] If yes, one of the cylinders is selected as the cylinder to be switched, the upstream fuel injector of the cylinder to be switched is controlled to stop fuel injection, and the upstream fuel injectors of the remaining cylinders are kept to inject fuel, and then the process goes to step A2;

[0029] If not, keep the upstream fuel injectors of all the cylinders to spray fuel, and then return to step A1;

[0030] Step A2, the injector switching device controls the downstream injector of the cylinder to be switched to inject fuel according to the injection amount calculated based on the target fuel amount and the enrichment coefficient;

[0031] Step A3, the injector switching device decays the enrichment coefficient according to the decay step length after each working cycle of the cylinder to be switched, and then determines whether the enrichment coefficient is not greater than a preset coefficient threshold:

[0032] If yes, the injector switching device controls the downstream injector of the cylinder to be switched to inject fuel according to the target fuel amount to complete the injector switching, and then turns to step A4;

[0033] If not, return to step A2.

[0034] Step A4, the injector switching device determines whether all cylinders have completed injector switching:

[0035] If yes, exit;

[0036] If not, a cylinder that has not completed injector switching is selected as the cylinder to be switched, and then the process returns to step A2.

[0037] Preferably, the injector switching device comprises a storage unit, wherein a comparison table of standard throttle opening, enrichment coefficient and attenuation step length is stored in the storage unit;

[0038] Then, in step A2, the injector switching device matches the corresponding enrichment coefficient and the attenuation step length from the standard throttle opening, enrichment coefficient and attenuation step length comparison table according to the current throttle opening of the cylinder to be switched.

[0039] The above technical solution has the following advantages or beneficial effects:

[0040] 1) Provides an injector switching device and a switching method, which can determine whether injector switching is required according to different engine speeds, clarify the injector switching timing, and switch different injectors to meet the injection requirements;

[0041] 2) The target fuel quantity can be enriched to a certain extent according to the throttle opening, and the concentration can be gradually reduced to solve the problems of over-enrichment, over-leanness, unstable combustion, etc. when the upstream injector is switched to the downstream injector, so that the engine can obtain an efficient and smooth injector switching process, thereby obtaining more precise control and better emission levels;

[0042] 2) The multi-cylinder engine switches sequentially, with only one cylinder in the switching state at a time, which solves the problem of the smoothness of the switching process. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a structural schematic diagram of a fuel injector switching device of an electronic fuel injection gasoline engine in a preferred embodiment of the present invention;

[0044] Figure 2 It is a flow chart of a method for switching the fuel injectors of an electronic fuel injection gasoline engine in a preferred embodiment of the present invention;

[0045] Figure 3 The figure is a flow chart of another method for switching the injectors of an electronic fuel injection gasoline engine in a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0046] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. The present invention is not limited to this embodiment, and other embodiments may also fall within the scope of the present invention as long as they conform to the gist of the present invention.

[0047] In a preferred embodiment of the present invention, based on the above problems existing in the prior art, a fuel injector switching device for an electronic fuel injection gasoline engine is provided. Figure 1 As shown, including:

[0048] The speed sensor 1 is provided in the electronic fuel injection gasoline engine 100 and is used to detect the speed of the electronic fuel injection gasoline engine;

[0049] An intake manifold 2 is connected to the electronic fuel injection gasoline engine 100 and the air filter 200. An upstream fuel injector 3 is provided at one end of the intake manifold 2 close to the air filter 200, and a downstream fuel injector 4 is provided at one end of the intake manifold 2 close to the electronic fuel injection gasoline engine 100.

[0050] The control unit 5 is connected to the speed sensor 1, the upstream injector 3 and the downstream injector 4 respectively, and is used to switch the injection from the upstream injector 3 to the downstream injector 4 when the speed sensor 1 detects that the speed of the electronic fuel injection gasoline engine 100 exceeds the switching speed.

[0051] In this embodiment, a throttle body 6 is provided on the intake manifold 2 , and the throttle body 6 is arranged between the upstream fuel injector 3 and the downstream fuel injector 4 .

[0052] Specifically, in this embodiment, a fuel injector switching device for an electronic fuel injection gasoline engine is provided, which uses a speed sensor 1 to detect the speed of the electronic fuel injection gasoline engine 100. When the electronic fuel injection gasoline engine 100 is at a low speed, the flow characteristics of the fuel injector are required not to be too large, so that the upstream fuel injector 3 can be accurately controlled, so the upstream fuel injector 3 is used for fuel injection; when the electronic fuel injection gasoline engine 100 is at a low speed, since the fuel injector needs to complete the fuel injection in an extreme time, the fuel injector is required to have a large flow characteristic. At this time, the control unit 5 stops the upstream fuel injector 3 from injecting fuel and switches to the downstream fuel injector 4 for fuel injection. And when just switching, the fuel injection amount of the downstream fuel injector 4 is increased according to the opening of the throttle body 6 (indicating the load of the engine), so as to avoid the problem of unstable combustion and air-fuel ratio jump when the upstream and downstream fuel injectors are switched, which affects the power output and emission control, and the fuel injection amount of the downstream fuel injector 4 is gradually adjusted during the switching process to avoid the problem of excessive fuel injection leading to over-rich combustion, which is unfavorable to emissions.

[0053] In a preferred embodiment of the present invention, Figure 1 As shown, the electronic fuel injection gasoline engine is a multi-cylinder engine, and includes a plurality of intake manifolds 2 , and both ends of each intake manifold 2 are respectively connected to the intake port of one of the cylinders 110 of the multi-cylinder engine 100 and the air filter 200 .

[0054] Specifically, in this embodiment, the injector switching device of the present invention is also applicable to multi-cylinder engines, and the upstream and downstream injectors between different intake manifolds 2 can be independently controlled to achieve a gradual adjustment effect, avoiding the problem of over-rich combustion caused by simultaneous adjustment of multiple injectors, which is unfavorable to emissions.

[0055] In a preferred embodiment of the present invention, the electronic fuel injection gasoline engine 100 includes a plurality of exhaust manifolds 7 , and both ends of each exhaust manifold 7 are respectively connected to an exhaust port of a cylinder 110 and a main exhaust pipe 8 .

[0056] The present invention also provides a method for switching the fuel injectors of an electronic fuel injection gasoline engine, which is applied to the fuel injector switching device as described above. Figure 2 As shown, including:

[0057] Step S1, the injector switching device detects whether the speed of the electronic fuel injection gasoline engine exceeds the switching speed:

[0058] If yes, the upstream injector is controlled to stop injecting fuel, and the process goes to step S2;

[0059] If not, keep the upstream injector injecting fuel, and then return to step S1;

[0060] Step S2, the injector switching device controls the downstream injector to inject fuel according to the injection amount calculated based on the target fuel amount and the enrichment factor;

[0061] Step S3, the injector switching device decays the enrichment coefficient according to the decay step length after each working cycle of the electronic fuel injection gasoline engine, and then determines whether the enrichment coefficient is not greater than a preset coefficient threshold:

[0062] If yes, the fuel injector switching device controls the downstream fuel injector to inject fuel according to the target fuel quantity to complete the fuel injector switching;

[0063] If not, return to step S2.

[0064] In this embodiment, the injector switching device includes a storage unit, in which a comparison table of standard throttle opening, enrichment factor and decay step length is stored;

[0065] In step S2, the fuel injector switching device matches the corresponding enrichment coefficient and attenuation step length from the standard throttle opening, enrichment coefficient and attenuation step length comparison table according to the current throttle opening of the electronic fuel injection gasoline engine.

[0066] In this embodiment, one working cycle in step S3 is two rotations of the crankshaft of the electronic fuel injection gasoline engine.

[0067] Specifically, the present invention provides a method for switching injectors of an electronic fuel injection gasoline engine. In this embodiment, the method is for a single-cylinder engine.

[0068] When the speed sensor detects that the engine is operating in a low speed region, the upstream injector is in a single-operation mode;

[0069] The control unit (ECU) determines based on the engine speed sensor whether the engine speed is higher than the switching speed RpmThr and remains for a period of time TimeThr;

[0070] If not satisfied, the current upstream injector injection mode is maintained;

[0071] If satisfied, the ECU enters the switching process from the upstream injector to the downstream injector. The steps are as follows:

[0072] Calculate the downstream injector enrichment coefficient and attenuation step length according to the current throttle opening of the electronic fuel injection gasoline engine; (The corresponding enrichment coefficient and attenuation step length are obtained by matching the standard throttle opening, enrichment coefficient and attenuation step length comparison table.)

[0073] The upstream fuel injector stops injecting fuel, and the downstream fuel injector injects fuel according to the target fuel quantity (which can be calculated by using the existing technology) × the fuel enrichment coefficient;

[0074] In each subsequent working cycle (two turns of the crankshaft of the electronic fuel injection gasoline engine), the enrichment coefficient decreases once according to the attenuation step length (the enrichment coefficient after this working cycle = the enrichment coefficient before this working cycle - the attenuation step length), and the downstream injector injects fuel according to the target fuel volume × the injection volume of the enrichment coefficient after this working cycle;

[0075] When the enrichment factor decreases to 1 or less than 1, the downstream injector injects fuel according to the target fuel quantity;

[0076] The switching process ends and the downstream injector enters a state where it works alone.

[0077] In this embodiment, when switching, the fuel injection amount of the downstream injector is increased according to the throttle opening of the throttle body (indicating the load of the engine) to avoid unstable combustion and air-fuel ratio jump when the upstream and downstream injectors are switched, which affects the power output and emission control. In addition, the fuel injection amount of the downstream injector is gradually adjusted during the switching process to avoid excessive fuel injection leading to over-rich combustion, which is unfavorable to emissions.

[0078] The present invention also provides an injector switching method for an electronic fuel injection gasoline engine, which is applied to the injector switching device as described above. The electronic fuel injection gasoline engine is a multi-cylinder engine, and each cylinder of the multi-cylinder engine corresponds to a group of upstream injectors and downstream injectors. Figure 3 As shown, the injector switching method also includes:

[0079] Step A1, the fuel injector switching device determines whether the speed of the electronic fuel injection gasoline engine exceeds the switching speed:

[0080] If yes, one of the cylinders is selected as the cylinder to be switched, the upstream injector of the cylinder to be switched is controlled to stop injecting fuel, and the upstream injectors of the remaining cylinders are kept injecting fuel, and then the process goes to step A2;

[0081] If not, keep the upstream fuel injectors of all cylinders spraying fuel, and then return to step A1;

[0082] Step A2, the injector switching device controls the downstream injector of the cylinder to be switched to inject fuel according to the injection amount calculated based on the target fuel amount and the enrichment coefficient;

[0083] Step A3: the injector switching device decays the enrichment coefficient according to the decay step length after each working cycle of the cylinder to be switched, and then determines whether the enrichment coefficient is not greater than a preset coefficient threshold:

[0084] If yes, the injector switching device controls the downstream injector of the cylinder to be switched to inject fuel according to the target fuel amount to complete the injector switching, and then goes to step A4;

[0085] If not, return to step A2.

[0086] Step A4, the injector switching device determines whether all cylinders have completed injector switching:

[0087] If yes, exit;

[0088] If not, a cylinder that has not completed injector switching is selected as the cylinder to be switched, and then the process returns to step A2.

[0089] In a preferred embodiment of the present invention, the injector switching device includes a storage unit, in which a comparison table of standard throttle opening, enrichment coefficient and attenuation step length is stored;

[0090] In step A2, the fuel injector switching device matches the corresponding enrichment coefficient and attenuation step length from the standard throttle opening, enrichment coefficient and attenuation step length comparison table according to the current throttle opening of the cylinder to be switched.

[0091] Specifically, this embodiment is directed to a multi-cylinder engine, including cylinders 1 to 4, each cylinder corresponding to an upstream injector, a downstream injector, and a throttle body between the upstream and downstream injectors;

[0092] When the speed sensor detects that the engine is operating in the low speed range, the upstream injectors of cylinders 1-4 are in a single working mode;

[0093] The control unit (ECU) determines based on the engine speed sensor whether the engine speed is higher than the switching speed RpmThr and remains for a period of time TimeThr;

[0094] If not satisfied, the current upstream injector injection mode is maintained;

[0095] If satisfied, the ECU enters the switching process from the upstream injector to the downstream injector. The steps are as follows:

[0096] First, for cylinder No. 1, the downstream injector enrichment factor and attenuation step length are calculated according to the current throttle opening of cylinder No. 1; (the corresponding enrichment factor and attenuation step length are matched from the standard throttle opening, enrichment factor and attenuation step length comparison table.)

[0097] The upstream injector stops injecting fuel (the upstream injectors of other cylinders maintain the original independent working mode), and the downstream injector injects fuel according to the injection amount of the target fuel amount (which can be calculated by the existing technology) × the enrichment factor (the downstream injectors of other cylinders have not been switched yet);

[0098] After each subsequent working cycle (two turns of the crankshaft of the electronic fuel injection gasoline engine), the enrichment coefficient is decreased once according to the attenuation step length (the enrichment coefficient after this working cycle = the enrichment coefficient before this working cycle - the attenuation step length), and the downstream injector injects fuel according to the target fuel volume × the injection volume of the enrichment coefficient after this working cycle;

[0099] When the enrichment factor decreases to 1 or less than 1, the downstream injector injects fuel according to the target fuel quantity;

[0100] The switching process is completed and cylinder No. 1 enters the state where the downstream injector works alone.

[0101] Then switch the remaining cylinders 2, 3, 4, etc. in turn according to the above steps until all cylinder injectors have completed the switch;

[0102] After the switching process is completed, all cylinders enter the state where the downstream injectors work alone.

[0103] In this embodiment, when switching, the fuel injection amount of the downstream injector is increased according to the throttle opening of the throttle body (indicating the load of the engine) to avoid unstable combustion and air-fuel ratio jump when the upstream and downstream injectors are switched, which affects the power output and emission control. In addition, the fuel injection amount of the downstream injector is gradually adjusted during the switching process to avoid excessive fuel injection leading to over-rich combustion, which is unfavorable to emissions.

[0104] The multi-cylinder engine switches sequentially, with only one cylinder in the switching state at a time, which solves the problem of the smoothness of the switching process.

[0105] The above are only preferred embodiments of the present invention, and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the contents of this specification and illustrations should be included in the protection scope of the present invention.

Claims

1. A fuel injector switching device for an electronic fuel injection gasoline engine, characterized in that: include: A rotation speed sensor is provided in the electronic fuel injection gasoline engine and is used to detect the rotation speed of the electronic fuel injection gasoline engine; An intake manifold, connected to the electronic fuel injection gasoline engine and the air filter, an upstream fuel injector is provided at one end of the intake manifold close to the air filter, and a downstream fuel injector is provided at one end of the intake manifold close to the electronic fuel injection gasoline engine; A control unit is respectively connected to the speed sensor, the upstream injector and the downstream injector, and is used to switch the injection from the upstream injector to the downstream injector when the speed sensor detects that the speed of the electronic fuel injection gasoline engine exceeds the switching speed.

2. The fuel injector switching device according to claim 1, characterized in that: If the electronic fuel injection gasoline engine is a multi-cylinder engine, it includes a plurality of intake manifolds, and both ends of each intake manifold are respectively connected to the air intake port of one of the cylinders of the multi-cylinder engine and the air filter.

3. The injector switching device according to claim 2, characterized in that: The electronic fuel injection gasoline engine comprises a plurality of exhaust manifolds, and both ends of each exhaust manifold are respectively connected to the exhaust port of a cylinder and the main exhaust pipe.

4. The injector switching device according to claim 1, characterized in that: A throttle body is arranged on the intake manifold.

5. The fuel injector switching device according to claim 4, characterized in that: The throttle body is arranged between the upstream fuel injector and the downstream fuel injector.

6. A method for switching the injectors of an electronic fuel injection gasoline engine, characterized in that: The fuel injector switching device as claimed in any one of claims 1 to 5 comprises: Step S1, the injector switching device detects whether the speed of the electronic fuel injection gasoline engine exceeds the switching speed: If yes, the upstream injector is controlled to stop injecting fuel, and the process goes to step S2; If not, keep the upstream injector injecting fuel, and then return to step S1; Step S2, the injector switching device controls the downstream injector to inject fuel according to the injection amount calculated based on the target fuel amount and the enrichment factor; Step S3, the injector switching device decays the enrichment coefficient according to the decay step length after each working cycle of the electronic fuel injection gasoline engine, and then determines whether the enrichment coefficient is not greater than a preset coefficient threshold: If yes, the injector switching device controls the downstream injector to inject fuel according to the target fuel quantity to complete the injector switching; If not, return to step S2.

7. The method for switching the fuel injector according to claim 6, characterized in that: The injector switching device comprises a storage unit, wherein a comparison table of standard throttle opening, enrichment coefficient and decay step length is stored in the storage unit; Then, in step S2, the injector switching device matches the corresponding enrichment coefficient and the attenuation step length from the standard throttle opening, enrichment coefficient and attenuation step length comparison table according to the current throttle opening of the electronic fuel injection gasoline engine.

8. The method for switching the fuel injector according to claim 6, characterized in that: One working cycle in step S3 is two rotations of the crankshaft of the electronic fuel injection gasoline engine.

9. A method for switching the fuel injectors of an electronic fuel injection gasoline engine, characterized in that: Applied to the injector switching device according to any one of claims 1 to 5, the electronic fuel injection gasoline engine is a multi-cylinder engine, and each cylinder of the multi-cylinder engine corresponds to a group of upstream injectors and downstream injectors, then the injector switching method further includes: Step A1, the injector switching device determines whether the speed of the electronic fuel injection gasoline engine exceeds the switching speed: If yes, one of the cylinders is selected as the cylinder to be switched, the upstream fuel injector of the cylinder to be switched is controlled to stop fuel injection, and the upstream fuel injectors of the remaining cylinders are kept to inject fuel, and then the process goes to step A2; If not, keep the upstream fuel injectors of all the cylinders to spray fuel, and then return to step A1; Step A2, the injector switching device controls the downstream injector of the cylinder to be switched to inject fuel according to the injection amount calculated based on the target fuel amount and the enrichment coefficient; Step A3, the injector switching device decays the enrichment coefficient according to the decay step length after each working cycle of the cylinder to be switched, and then determines whether the enrichment coefficient is not greater than a preset coefficient threshold: If yes, the injector switching device controls the downstream injector of the cylinder to be switched to inject fuel according to the target fuel amount to complete the injector switching, and then turns to step A4; If not, return to step A2. Step A4, the injector switching device determines whether all cylinders have completed injector switching: If yes, exit; If not, a cylinder that has not completed injector switching is selected as the cylinder to be switched, and then the process returns to step A2.

10. The fuel injector switching method according to claim 9, characterized in that: The injector switching device comprises a storage unit, wherein a comparison table of standard throttle opening, enrichment coefficient and decay step length is stored in the storage unit; Then, in step A2, the injector switching device matches the corresponding enrichment coefficient and the attenuation step length from the standard throttle opening, enrichment coefficient and attenuation step length comparison table according to the current throttle opening of the cylinder to be switched.

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