Engine misfire diagnostic method and system for HEV

Abstract

The present invention discloses an engine misfire diagnosis method for HEV, which includes: comparing the engine roughness ER with the engine suspected misfire threshold A and the engine misfire threshold B. If the comparison result is ER ≤ A, it is considered that there is no engine misfire; if the comparison result is ER ≥ B, it is considered that there is an engine misfire; if the comparison result is A < ER < B, the driving mode of the HEV is switched to the engine single-drive mode or the motor single-drive mode, and whether there is an engine misfire is diagnosed in the engine single-drive mode or the motor single-drive mode. In the present invention, for HEV models, the engine suspected misfire threshold is introduced, and when the engine is suspected of misfiring, it is switched to the engine single-drive mode or the motor single-drive mode for misfire diagnosis, so as to eliminate the influence of the motor on the engine crankshaft when the engine is suspected of misfiring, in order to accurately diagnose whether there is an engine misfire.

Description

Technical Field

[0001] The present invention relates to the field of automotive electronics technology, and in particular to an engine misfire diagnosis method and system for an HEV (Hybrid Electric Vehicle). Background Art

[0002] Today's automotive electronics industry is developing rapidly, and many HEV models, such as PHEVs (Plug-in Hybrid Electric Vehicles), have already entered mass production. In HEVs, when the engine and motor are driven together, the output shafts of the engine and motor are rigidly connected via a clutch. Therefore, the motor's excellent speed control characteristics also affect the stability of the engine speed. Specifically, the engine speed is more stable when the motor is driven together than when the engine is driven alone.

[0003] For example, Figure 1 This is a schematic diagram of the HEV architecture of the P2 structure. Figure 1 As shown, the Hybrid Control Unit (HCU) connects to the Engine Control Unit (ECU), Motor Control Unit (MCU), and Transmission Control Unit (TCU) via the CAN (Controller Area Network) bus. It sends commands to each control unit and simultaneously controls clutch C0. The ECU controls the engine to achieve torque output. The MCU controls the motor to achieve torque output. The TCU controls clutch C1 and the transmission to achieve gear shifting and power output.

[0004] For P2 structure HEV, there are three driving modes according to the different power sources:

[0005] 1. Combined drive mode: Clutches C0 and C1 are both engaged, and both the engine and the motor have torque output;

[0006] 2. Engine-only drive mode: Clutches C0 and C1 are both engaged, but the HCU only controls the engine to output torque, the motor idles, and no power is output;

[0007] 3. Motor-only drive mode: Clutch C0 is disengaged, clutch C1 is engaged, the HCU controls the motor through the MCU to output torque, and the engine is turned off or in idle state.

[0008] In traditional engine misfire diagnosis methods, when misfire occurs in one or more cylinders, the engine speed fluctuation is relatively large, and there will be a relatively large difference in acceleration per revolution. Therefore, the roughness of the engine operation will increase abnormally. When the engine roughness ER (Engine Roughness) is greater than a certain threshold, the ECU diagnoses misfire. However, for HEVs, since the motor's speed control acts on the engine crankshaft, in the combined driving mode of the engine and the motor, when engine misfire occurs, the acceleration change rate of the engine crankshaft will decrease, that is, the roughness caused by engine misfire will be weakened by the motor. If the traditional engine misfire diagnosis method is used, it is very likely that misfire in this working condition cannot be detected, resulting in missed detection; and if the misfire diagnosis threshold is lowered, there will be a risk of misfire false alarms. Therefore, in order to meet the IUPR (In Use PeRformance, in-use detection rate) required by national regulations, an engine misfire diagnosis method suitable for HEVs needs to be developed. Summary of the Invention

[0009] The starting point of the present invention is to provide an engine misfire diagnosis method and system for HEVs, thereby solving the above problems existing in the prior art.

[0010] An embodiment of the present invention provides an engine misfire diagnosis method for HEVs, and the method includes:

[0011] Compare the engine roughness ER with the engine suspected misfire threshold A and the engine misfire threshold B.

[0012] If the comparison result is ER ≤ A, it is considered that there is no engine misfire.

[0013] If the comparison result is ER ≥ B, it is considered that there is engine misfire.

[0014] If the comparison result is A < ER < B, switch the driving mode of the HEV to the engine-alone driving mode or the motor-alone driving mode, and diagnose whether there is engine misfire in the engine-alone driving mode or the motor-alone driving mode.

[0015] Optionally, if the comparison result is A < ER < B, compare the battery power of the motor with the power threshold C.

[0016] If the comparison result is that the battery power ≤ C, switch to the engine-alone driving mode, and

[0017] If the comparison result is that the battery power > C, switch to the motor-alone driving mode.

[0018] Optionally, diagnosing whether there is an engine misfire in the engine sole drive mode or the motor sole drive mode includes:

[0019] In the engine sole drive mode or the motor sole drive mode, comparing the engine roughness ER with the engine misfire threshold B,

[0020] If the comparison result is ER < B, it is considered that there is no engine misfire,

[0021] If the comparison result is ER ≥ B, it is considered that there is an engine misfire.

[0022] An embodiment of the present invention further provides an engine misfire diagnosis system for a HEV, the system includes an HCU and an ECU, the HCU is connected to the ECU through a CAN bus,

[0023] The ECU is configured to compare the engine roughness ER with the engine suspected misfire threshold A and the engine misfire threshold B. If the comparison result is ER ≤ A, it is considered that there is no engine misfire; if the comparison result is ER ≥ B, it is considered that there is an engine misfire; if the comparison result is A < ER < B, a precise misfire diagnosis request is sent to the HCU,

[0024] The HCU is configured to, after receiving the precise misfire diagnosis request, switch the drive mode of the HEV to the engine sole drive mode or the motor sole drive mode, and

[0025] The ECU is further configured to diagnose whether there is an engine misfire in the engine sole drive mode or the motor sole drive mode.

[0026] Optionally, after receiving the misfire diagnosis request, the HCU compares the battery power of the motor with the power threshold C,

[0027] If the comparison result is that the battery power ≤ C, the HCU switches the drive mode of the HEV to the engine sole drive mode,

[0028] If the comparison result is that the battery power > C, the HCU switches the drive mode of the HEV to the motor sole drive mode.

[0029] Optionally, diagnosing whether there is an engine misfire in the engine sole drive mode or the motor sole drive mode includes:

[0030] In the engine sole drive mode or the motor sole drive mode, the ECU compares the engine roughness ER with the engine misfire threshold B,

[0031] If the comparison result is ER < B, the ECU considers that there is no engine misfire,

[0032] If the comparison result is ER≥B, the ECU considers that there is an engine misfire.

[0033] The engine misfire diagnosis method and system for HEV according to the embodiments of the present invention have at least the following advantages:

[0034] In the present invention, for HEV models, an engine suspected misfire threshold is introduced, and when the engine roughness is between the engine suspected misfire threshold and the engine misfire threshold (that is, the engine suspected misfire), the mode is switched to the engine alone drive mode or the motor alone drive mode for misfire diagnosis, thereby eliminating the influence of the motor on the engine crankshaft when the engine is suspected of misfire, so as to accurately diagnose whether there is an engine misfire. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Other details and advantages of the present invention will become apparent from the detailed description provided below. It should be understood that the following drawings are merely schematic and not drawn to scale, and therefore should not be considered as limiting the present application. The following detailed description will be given with reference to the accompanying drawings, in which:

[0036] Figure 1 This is a schematic diagram of the architecture of a P2-structured HEV.

[0037] Figure 2 A flow chart of an engine misfire diagnosis method for an HEV according to a specific embodiment of the present invention is shown.

[0038] Figure 3A and 3B A flow chart of an engine misfire diagnosis method for an HEV according to another embodiment of the present invention is shown. DETAILED DESCRIPTION

[0039] Embodiments of the present invention are described below with reference to the accompanying drawings. In the following description, many specific details are set forth to enable those skilled in the art to more fully understand and implement the present invention. However, it will be apparent to those skilled in the art that the present invention may be implemented without some of these specific details. Furthermore, it should be understood that the present invention is not limited to the specific embodiments described. Rather, it is contemplated that the present invention may be implemented with any combination of the features and elements described below, regardless of whether they relate to different embodiments. Therefore, the following aspects, features, embodiments, and advantages are provided for illustrative purposes only and should not be considered as elements or limitations of the claims unless expressly set forth in the claims.

[0040] Now refer to Figure 2 , shows a flow chart of an engine misfire diagnosis method for HEV according to a specific embodiment of the present invention. Figure 2As shown, the method includes:

[0041] Step S201, comparing the engine roughness ER with the engine suspected misfire threshold A and the engine misfire threshold B.

[0042] Step S202, if the comparison result is ER ≤ A, it is considered that there is no engine misfire; if the comparison result is ER ≥ B, it is considered that there is an engine misfire; if the comparison result is A < ER < B, switch the driving mode of the HEV to the engine-only driving mode or the motor-only driving mode, and diagnose whether there is an engine misfire in the engine-only driving mode or the motor-only driving mode.

[0043] Specifically, the ECU of the hybrid vehicle can compare the engine roughness ER with the engine suspected misfire threshold A and the engine misfire threshold B. If the comparison result is ER ≤ A, it is considered that there is no engine misfire; if the comparison result is ER ≥ B, it is considered that there is an engine misfire; if the comparison result is A < ER < B, send an accurate misfire diagnosis request to the HCU of the hybrid vehicle. After receiving the accurate misfire diagnosis request, the HCU switches the driving mode of the HEV to the engine-only driving mode or the motor-only driving mode. Then, the ECU diagnoses whether there is an engine misfire in the engine-only driving mode or the motor-only driving mode.

[0044] Specifically, the HCU can select to switch the driving mode of the HEV to the engine-only driving mode or the motor-only driving mode through the following strategy: if the battery power of the motor ≤ the power threshold C, switch to the engine-only driving mode; if the battery power of the motor > the power threshold C, switch to the motor-only driving mode. Using this strategy, when the battery power is sufficient, the motor can be used to drive the HEV vehicle during the accurate misfire diagnosis process, thus ensuring the smooth operation of the vehicle.

[0045] Specifically, in the engine-only driving mode or the motor-only driving mode, the ECU can diagnose whether there is an engine misfire through the following strategy: the ECU compares the engine roughness ER with the engine misfire threshold B. If the comparison result is ER < B, it is considered that there is no engine misfire; if the comparison result is ER ≥ B, it is considered that there is an engine misfire.

[0046] According to Figure 2 the principle of the engine misfire diagnosis method for HEV in Figure 3A and 3B a more specific flowchart of the engine misfire diagnosis method for HEV is disclosed. Among them, Figure 3A shows the first stage of misfire diagnosis (misfire pre-judgment process), Figure 3BShows the second stage of the misfire diagnosis that may need to be carried out (accurate misfire judgment process).

[0047] As Figure 3A shown, during the HEV driving process, the ECU compares the engine roughness ER with the engine suspected misfire threshold A and the engine misfire threshold B. If the comparison result is ER ≤ threshold A, it is considered that there is no engine misfire; if the comparison result is ER ≥ threshold B, it is considered that there is an engine misfire, and the misfire fault mode is entered and the fault light is lit; if the comparison result is A < ER < B, the ECU sends an accurate misfire diagnosis request to the HCU to request an accurate misfire diagnosis.

[0048] As Figure 3B shown, if the ECU requests an accurate misfire diagnosis, the HCU compares the battery charge of the motor with the charge threshold C. If the comparison result is that the battery charge ≤ threshold C, the HCU switches the driving mode of the HEV to the engine single-drive mode for accurate misfire diagnosis; if the comparison result is that the battery charge > C, the HCU switches the driving mode of the HEV to the motor single-drive mode, disconnects the clutch C0 and makes the engine idle for accurate misfire diagnosis.

[0049] Compared with the prior art, the engine misfire diagnosis method for HEV in the embodiments of the present invention has at least the following advantages:

[0050] In the present invention, for HEV models, an engine suspected misfire threshold is introduced, and when the engine roughness is between the engine suspected misfire threshold and the engine misfire threshold (i.e., engine suspected misfire), the driving mode is switched to the engine single-drive mode or the motor single-drive mode for misfire diagnosis, so as to eliminate the influence of the motor on the engine crankshaft when the engine is suspected of misfiring, in order to accurately diagnose whether there is an engine misfire.

[0051] It should be noted that the above description is only an example and not a limitation of the present invention. In other embodiments of the present invention, the method may have more, fewer or different steps, and the order, inclusion and function relationships between the steps may be different from those described and illustrated. For example, generally multiple steps can be combined into a single step, and a single step can also be split into multiple steps. For those of ordinary skill in the art, without creative efforts, the sequential changes of each step are also within the protection scope of the present invention.

[0052] The technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes a number of instructions for enabling a computer device (which can be a personal computer, server, or network device, etc.) or a processor or a microcontroller to execute all or part of the steps of the method described in each embodiment of the present invention.

[0053] Those skilled in the art will appreciate that all or part of the steps in the above-described method embodiments can be implemented using hardware associated with program instructions. The aforementioned program can be stored in a computer-readable storage medium. When executed, the program performs the steps of the above-described method embodiments. The aforementioned storage medium includes various media capable of storing program code, such as ROM, RAM, magnetic disks, or optical disks.

[0054] Although the present invention has been disclosed above with reference to preferred embodiments, the present invention is not limited thereto. Any changes and modifications made by those skilled in the art without departing from the spirit and scope of the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope defined by the claims.

Claims

1. A method for diagnosing engine misfire in HEV, characterized in that: The method includes: Comparing the engine roughness ER with the engine suspected misfire threshold A and the engine misfire threshold B; If the comparison result is ER ≤ A, it is considered that there is no engine misfire; If the comparison result is ER ≥ B, it is considered that there is an engine misfire; If the comparison result is A < ER < B, switch the driving mode of the HEV to the engine-only driving mode or the motor-only driving mode, and diagnose whether there is an engine misfire in the engine-only driving mode or the motor-only driving mode.

2. The method according to claim 1, wherein If the comparison result is A < ER < B, compare the battery power of the motor with the power threshold C; If the comparison result is that the battery power ≤ C, switch to the engine-only driving mode; If the comparison result is that the battery power > C, switch to the motor-only driving mode.

3. The method according to claim 1, wherein Diagnosing whether there is an engine misfire in the engine-only driving mode or the motor-only driving mode includes: In the engine-only driving mode or the motor-only driving mode, comparing the engine roughness ER with the engine misfire threshold B; If the comparison result is ER < B, it is considered that there is no engine misfire; If the comparison result is ER ≥ B, it is considered that there is an engine misfire.

4. An engine misfire diagnostic system for HEV, characterized in that: The system includes an HCU and an ECU, and the HCU is connected to the ECU via a CAN bus; The ECU is configured to compare the engine roughness ER with the engine suspected misfire threshold A and the engine misfire threshold B. If the comparison result is ER ≤ A, it is considered that there is no engine misfire; if the comparison result is ER ≥ B, it is considered that there is an engine misfire; if the comparison result is A < ER < B, send a precise misfire diagnosis request to the HCU; The HCU is configured to, after receiving the precise misfire diagnosis request, switch the driving mode of the HEV to the engine-only driving mode or the motor-only driving mode, and The ECU is further configured to diagnose whether there is an engine misfire in the engine-only driving mode or the motor-only driving mode.

5. The system according to claim 4, wherein: After receiving the misfire diagnosis request, the HCU compares the battery power of the motor with the power threshold C; If the comparison result is that the battery power ≤ C, the HCU switches the driving mode of the HEV to the engine-only driving mode; If the comparison result is that the battery power > C, the HCU switches the driving mode of the HEV to the motor-only driving mode.

6. The system according to claim 4, wherein: Diagnosing whether there is an engine misfire in the engine-only driving mode or the motor-only driving mode includes: In the engine-only driving mode or the motor-only driving mode, the ECU compares the engine roughness ER with the engine misfire threshold B; If the comparison result is ER < B, the ECU considers that there is no engine misfire; If the comparison result is ER ≥ B, the ECU considers that there is an engine misfire.

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