Method for suppressing rail pressure peak value when engine load is suddenly changed

Abstract

The application discloses a method for inhibiting rail pressure peak value when engine load mutates. When the rail pressure peak value inhibiting function is activated, the output torque of the current period is determined based on the original request torque of the current period and the output torque of the last period, and the actual injection oil quantity of the current period is determined according to the output torque of the current period. The theoretical injection oil quantity of the current period is determined based on the original request torque of the current period, and the corrected oil quantity is determined according to the theoretical injection oil quantity and the actual injection oil quantity. The injection oil quantity of the injector is controlled based on the output torque of the current period, and the high-pressure oil pump is controlled based on the corrected oil quantity, so that the rail pressure peak value inhibiting function is realized. The application identifies the mutation condition of the oil quantity by monitoring the change of the injection oil quantity, maintains the injection oil quantity of several injections to a certain extent, and leaves a certain response time for the high-pressure oil pump, so that the target of inhibiting the rail pressure peak value is realized.

Description

Technical Field

[0001] This invention belongs to the field of automotive technology, specifically relating to a method for suppressing rail pressure peaks when engine load changes abruptly. Background Technology

[0002] In the rail pressure control of a high-pressure common rail fuel system, to improve the dynamic response of the rail pressure, the feedforward flow rate of the high-pressure fuel pump is typically calculated based on the fuel injection quantity and leakage of the injectors. Then, based on the closed-loop regulation of the rail pressure, the flow rate of the high-pressure fuel pump is further adjusted to achieve precise control of the rail pressure.

[0003] The calculation of feedforward flow rate is later than the calculation of injection quantity. Furthermore, considering that high-pressure fuel pumping is a discrete event—that is, the high-pressure fuel pump starts pumping fuel after the fuel metering unit fills the required pumping flow rate into the high-pressure fuel pump plunger chamber—the high-pressure system cannot adjust the pumping flow rate again during this pumping phase. If a sudden change in injection quantity occurs at this time, it will cause an upward surge (sudden decrease in injection quantity) or a downward surge (sudden increase in injection quantity) in the actual rail pressure. The more drastic the change in injection quantity, the more severe the upward or downward surge in rail pressure, which will adversely affect the reliability of the high-pressure system and may even cause frequent opening of the high-pressure system's rail pressure relief valve. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the aforementioned background technology and provide a method for suppressing rail pressure peaks when engine load changes abruptly.

[0005] The technical solution adopted in this invention is: a method for suppressing rail pressure peak when engine load changes abruptly. When the rail pressure peak suppression function is activated, the output torque of the current cycle is determined based on the original requested torque of the current cycle and the output torque of the previous cycle, and the actual injection quantity of the current cycle is determined based on the output torque of the current cycle.

[0006] The theoretical injection quantity for the current cycle is determined based on the original requested torque for the current cycle, and the corrected injection quantity is determined based on the theoretical injection quantity and the actual injection quantity.

[0007] The system maintains and controls the injection quantity of the injector based on the output torque of the current cycle, and controls the high-pressure oil pump based on the corrected injection quantity to suppress rail pressure peaks.

[0008] Furthermore, the rail pressure peak suppression function is activated when the following conditions are met simultaneously:

[0009] 1) Engine speed is greater than the set speed;

[0010] 2) Faults lacking suppression function;

[0011] 3) The previous rail pressure peak suppression function has been completed or terminated;

[0012] 4) The fuel injection gradient is within the set range.

[0013] Furthermore, the fuel injection quantity gradient is the absolute value of the difference between the actual fuel injection quantity in the current cycle and the actual fuel injection quantity in the previous cycle.

[0014] Furthermore, the output torque for the current cycle is determined by the following formula:

[0015] C = B + (A - B) * Δ

[0016] A is the original requested torque for the current cycle, B is the output torque for the previous cycle, C is the output torque for the current cycle, and Δ is the torque limiting coefficient.

[0017] Furthermore, the corrected fuel quantity is the difference between the theoretical injection fuel quantity and the actual injection fuel quantity.

[0018] Furthermore, the process of maintaining the injection quantity of the injector is as follows: a set number of injections is set to maintain the injection quantity, and a count is made for each injection until the count reaches the required number of injections, at which point the injection quantity maintenance control ends. Within the count, the injection quantity of the injector remains unchanged.

[0019] Furthermore, after the rail pressure peak suppression function is activated, it will deactivate when any of the following conditions are met:

[0020] 1) Engine speed fluctuations exceed the calibration range;

[0021] 2) The number of times the injector maintains the injection quantity reaches the set injection number.

[0022] Furthermore, when the rail pressure peak suppression function is not activated or is deactivated, the corrected oil quantity is 0.

[0023] Furthermore, when the rail pressure peak suppression function is not activated or is deactivated, the output torque for the current cycle is determined based on the original requested torque for the current cycle.

[0024] Furthermore, when the rail pressure peak suppression function is not activated or is deactivated, the number of injections to maintain the oil quantity is 0.

[0025] The beneficial effects of this invention are:

[0026] This invention identifies sudden changes in fuel quantity by monitoring changes in fuel injection quantity. After activating the rail pressure peak suppression function, it maintains the actual injection quantity to a certain extent to allow the high-pressure oil pump a certain response time, thereby avoiding the occurrence of rail pressure peaks.

[0027] To avoid the problem of slow start-up fuel response caused by triggering the function when the engine is started, this invention introduces engine speed as the condition for function activation, which improves reliability. Attached Figure Description

[0028] Figure 1 This is a schematic diagram showing the location of the method of the present invention in the software.

[0029] Figure 2 This is an image showing the application effect when the rail pressure peak suppression function is not activated.

[0030] Figure 3 This is an image showing the effect of activating the rail pressure peak suppression function. Detailed Implementation

[0031] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings. It should be noted that these descriptions are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0032] like Figure 1 As shown, the present invention provides a method for suppressing rail pressure peak when engine load changes abruptly. When the rail pressure peak suppression function is activated, the output torque of the current cycle is determined based on the original requested torque of the current cycle and the output torque of the previous cycle, and the actual injection quantity of the current cycle is determined based on the output torque of the current cycle.

[0033] The theoretical injection quantity for the current cycle is determined based on the original requested torque for the current cycle, and the corrected injection quantity is determined based on the theoretical injection quantity and the actual injection quantity.

[0034] The system maintains and controls the injection quantity of the injector based on the output torque of the current cycle, and controls the high-pressure oil pump based on the corrected injection quantity to suppress rail pressure peaks.

[0035] When the rail pressure peak suppression function is activated, this invention identifies sudden changes in fuel quantity by monitoring changes in requested torque and fuel injection quantity, and maintains the fuel injection quantity for several injections to a certain extent, allowing the high-pressure fuel pump a certain response time, thereby achieving the goal of suppressing rail pressure peaks. This avoids rail pressure surges or plunges caused by drastic changes in fuel injection quantity, and improves the reliability of the high-pressure system.

[0036] In the above scheme, the rail pressure peak suppression function is activated when the following conditions are met simultaneously:

[0037] 1) Engine speed is greater than the set speed;

[0038] 2) Failure of the track pressure peak suppression function;

[0039] 3) The previous rail pressure peak suppression function has been completed or terminated;

[0040] 4) The fuel injection quantity gradient (the absolute value of the difference between the actual fuel injection quantity determined in the current cycle based on the original requested torque and the actual fuel injection quantity determined in the previous cycle based on the original requested torque) is within a set range. This set range can be greater than a speed-related calibration threshold or less than a speed-related calibration threshold. There is a corresponding conversion relationship between the requested torque and the fuel injection quantity, which is a conventional technique and will not be described in detail here.

[0041] In the above scheme, when the rail pressure peak suppression function is activated, it indicates a sudden change in the fuel injection quantity, and the corresponding torque will also change suddenly. To avoid torque sudden changes, this invention limits the torque. Therefore, the output torque of the current cycle is determined by the following formula:

[0042] C = B + (A - B) * Δ

[0043] A is the original requested torque for the current cycle, B is the output torque for the previous cycle, C is the output torque for the current cycle, and Δ is the torque limiting coefficient.

[0044] When the rail pressure peak suppression function is not activated or is deactivated, the torque limit is canceled, and the original requested torque of the current cycle is directly used as the output torque of the current cycle.

[0045] In the above scheme, when the rail pressure peak suppression function is activated, the corrected fuel quantity is the difference between the theoretical injection quantity and the actual injection quantity. When the rail pressure peak suppression function is not activated or is deactivated, the corrected fuel quantity is 0.

[0046] In the above scheme, the process of maintaining the injection quantity of the injector is as follows: A set injection number is set to maintain the injection quantity. This injection number is calibrated and distinguishes between two situations: a sudden increase in injection quantity and a sudden decrease in injection quantity. The calibration principle is that the set rail pressure and the required rail pressure can follow each other, and the vehicle's power response is not significantly affected. When the rail pressure peak suppression function is activated, the injector counts once for each injection, and the count is accumulated. When the accumulated count reaches the required injection quantity, the injection quantity maintenance control ends. Within the counted number (i.e., during the counting accumulation process), the injection quantity of the injector remains unchanged.

[0047] When the rail pressure peak suppression function is not activated or is deactivated, the number of injections to maintain the oil quantity is 0.

[0048] In the above scheme, after the rail pressure peak suppression function is activated, it will be deactivated when any of the following conditions are met:

[0049] 1) Engine speed fluctuations exceed the calibration range;

[0050] 2) The number of times the fuel injector maintains the fuel injection quantity reaches the above-set number of injections to maintain the fuel quantity.

[0051] Example

[0052] When the method of this invention is used on a certain 7.5L engine, a large sudden change in fuel quantity occurs during emergency upshifting or downshifting, triggering the rail pressure peak suppression function. For example... Figure 2 As shown. When the function is not activated, a sudden drop in engine load causes a sudden drop in demand rail pressure and a sudden drop in fuel injection quantity. The sudden drop in fuel injection quantity causes a surge in actual rail pressure. After the function is activated, as shown... Figure 3 As shown, a sudden drop in engine load causes a sudden drop in demand rail pressure, but the fuel injection quantity will continue to be maintained or increased for several cycles to avoid an increase in actual rail pressure.

[0053] It should be understood that the specific order or hierarchy of steps in the disclosed process is an example of an exemplary method. Based on design preferences, it should be understood that the specific order or hierarchy of steps in the process may be rearranged without departing from the scope of this disclosure. The appended method claims provide elements of various steps in an exemplary order and are not intended to limit the scope to the specific order or hierarchy described.

[0054] To make the description of this disclosure more detailed and complete, illustrative descriptions of the embodiments and specific examples of the present invention have been provided above; however, this is not the only form of implementing or utilizing the specific examples of the present invention. The embodiments cover the features of multiple specific examples and the method steps and their order for constructing and operating these specific examples. However, other specific examples may also be used to achieve the same or equivalent functions and order of steps.

[0055] In the above detailed description, various features are combined together in a single embodiment to simplify this disclosure. This approach to disclosure should not be construed as reflecting an intention that embodiments of the claimed subject matter require more features than are explicitly stated in each claim. Rather, as reflected in the appended claims, the invention is presented with fewer features than all of the features of the single disclosed embodiment. Therefore, the appended claims are hereby explicitly incorporated into the detailed description, wherein each claim stands alone as a preferred embodiment of the invention.

[0056] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Contents not described in detail in this specification belong to prior art known to those skilled in the art.

Claims

1. A method for suppressing rail pressure peaks during sudden changes in engine load, characterized in that: When the rail pressure peak suppression function is activated, the output torque of the current cycle is determined based on the original requested torque of the current cycle and the output torque of the previous cycle, and the actual injection quantity of the current cycle is determined based on the output torque of the current cycle. The theoretical injection quantity for the current cycle is determined based on the original requested torque for the current cycle, and the corrected injection quantity is determined based on the theoretical injection quantity and the actual injection quantity. The system maintains and controls the injection quantity of the injector based on the output torque of the current cycle, and controls the high-pressure oil pump based on the corrected injection quantity to suppress rail pressure peaks.

2. The method for suppressing rail pressure peaks during sudden engine load changes according to claim 1, characterized in that: The rail pressure peak suppression function is activated when the following conditions are met simultaneously: 1) Engine speed is greater than the set speed; 2) Faults lacking suppression function; 3) The previous rail pressure peak suppression function has been completed or terminated; 4) The fuel injection gradient is within the set range.

3. The method for suppressing rail pressure peaks during sudden engine load changes according to claim 2, characterized in that: The fuel injection quantity gradient is the absolute value of the difference between the actual fuel injection quantity in the current cycle and the actual fuel injection quantity in the previous cycle.

4. The method for suppressing rail pressure peaks during sudden engine load changes according to claim 1, characterized in that: The output torque for the current cycle is determined by the following formula: C = B + (A - B) × Δ A is the original requested torque for the current cycle, B is the output torque for the previous cycle, C is the output torque for the current cycle, and Δ is the torque limiting coefficient.

5. The method for suppressing rail pressure peaks during sudden engine load changes according to claim 1, characterized in that: The corrected fuel quantity is the difference between the theoretical injection quantity and the actual injection quantity.

6. The method for suppressing rail pressure peaks during sudden engine load changes according to claim 1, characterized in that: The process of maintaining and controlling the injection quantity of the injector is as follows: set the number of injections to maintain the injection quantity, count once for each injection, until the count reaches the injection quantity, then end the injection quantity maintenance control. Within the count, the injection quantity of the injector remains unchanged.

7. The method for suppressing rail pressure peaks during sudden engine load changes according to claim 6, characterized in that: After the rail pressure peak suppression function is activated, it will be deactivated when any of the following conditions are met: 1) Engine speed fluctuations exceed the calibration range; 2) The number of times the fuel injector maintains the fuel injection quantity reaches the set number of injections.

8. The method for suppressing rail pressure peaks during sudden engine load changes according to claim 7, characterized in that: When the rail pressure peak suppression function is not activated or is deactivated, the corrected oil quantity is 0.

9. The method for suppressing rail pressure peaks during sudden engine load changes according to claim 7, characterized in that: When the rail pressure peak suppression function is not activated or is deactivated, the output torque for the current cycle is determined based on the original requested torque for the current cycle.

10. The method for suppressing rail pressure peaks during sudden engine load changes according to claim 7, characterized in that: When the rail pressure peak suppression function is not activated or is deactivated, the number of injections to maintain the oil quantity is 0.

Images