阅读说明：本技术 基于燃油箱泄露诊断模块的正压式脱附管路流量诊断方法 (Positive pressure type desorption pipeline flow diagnosis method based on fuel tank leakage diagnosis module ) 是由 郎晋平 吴俊峰 胡璋林 温敏 柯章俊 朱贺 陈瑞 于 2021-07-30 设计创作，主要内容包括：本发明公开了一种基于燃油箱泄露诊断模块的正压式脱附管路流量诊断方法,本发明的设计构思在于,利用了燃油箱泄露诊断模块的泵电流与泵气阻力的特性,将DMTL泵电流作为压力传感装置,以此来诊断脱附流量是否异常。具体地,在不增加额外的压力传感器的前提下,对DMTL泵的电流进行监控,根据泵电流以及泵电流频率的变化,来判断脱附管路中脱附流量的有无,从而完成对蒸发系统高低脱附管路脱附流量的监测诊断。本发明提出的脱附流量诊断方法使用已有的传感器、执行器完成诊断,无需在高脱附管路上增加压力传感器,简化了系统结构,降低成本。(The invention discloses a positive pressure type desorption pipeline flow diagnosis method based on a fuel tank leakage diagnosis module. Specifically, on the premise that an additional pressure sensor is not added, the current of the DMTL pump is monitored, and whether desorption flow exists in the desorption pipeline is judged according to the change of the pump current and the pump current frequency, so that the monitoring and diagnosis of the desorption flow of the high-low desorption pipeline of the evaporation system are completed. The desorption flow diagnosis method provided by the invention uses the existing sensors and actuators to complete diagnosis, and does not need to add a pressure sensor on a high desorption pipeline, thereby simplifying the system structure and reducing the cost.)

1. A positive pressure type desorption pipeline flow diagnosis method based on a fuel tank leakage diagnosis module is characterized by comprising the following steps:

after the engine is started, performing initial diagnosis on the fuel tank leakage diagnosis module;

triggering a heating unit of the fuel tank leakage diagnosis module to start after the initial diagnosis is passed;

the method comprises the steps of obtaining the current load of a carbon tank, closing a carbon tank electromagnetic valve after the current load is lower than a preset load threshold value, and executing the following low desorption flow diagnosis activation strategy or high desorption flow diagnosis activation strategy;

wherein the low desorption flow diagnostic activation strategy comprises: acquiring an intake manifold pressure, and triggering a pump unit of a fuel tank leakage diagnosis module to start to operate when the intake manifold pressure is smaller than a preset pressure threshold value; the high desorption flow diagnostic activation strategy includes: acquiring boost pressure and ambient pressure, and triggering a pump unit of a fuel tank leakage diagnosis module to start to operate when the ratio of the boost pressure to the ambient pressure is greater than a preset ratio threshold;

after the pump unit is started, detecting the current no-load current when the pump unit is in no-load; comparing the current no-load current with the historical no-load current of the pump unit correspondingly obtained in the previous low desorption or high desorption flow diagnosis;

when the deviation of the two is larger than a current deviation threshold value preset by corresponding low desorption or high desorption flow diagnosis, outputting a normally open fault of the carbon tank electromagnetic valve;

when the deviation between the two is smaller than the current deviation threshold value, opening a carbon tank electromagnetic valve, and detecting the change condition of the pump unit current after the preset operation time;

judging whether the current round of diagnosis is faulty or not according to the change condition and carrying out statistics;

and after repeated multi-round diagnosis, outputting a final flow diagnosis conclusion when the statistical number reaches a preset counting threshold value.

2. The positive pressure desorption pipeline flow diagnosis method based on the fuel tank leakage diagnosis module as claimed in claim 1, wherein the determining whether the current round of diagnosis is faulty and counting according to the variation comprises:

if the ratio of the current pump unit current to the current no-load current after the preset time is operated is larger than a current ratio threshold value preset for corresponding low desorption or high desorption flow diagnosis, adding 1 to the fault count;

and if the ratio of the current pump unit current to the current no-load current after the preset time is operated is smaller than the current ratio threshold, adding 1 to the no-fault count.

3. The positive pressure desorption pipeline flow diagnosis method based on the fuel tank leakage diagnosis module as claimed in claim 2, wherein the outputting of the final flow diagnosis conclusion after the statistical number reaches a preset counting threshold comprises:

outputting a desorption pipeline fault when the fault count is greater than a first count threshold;

and when the fault-free count is larger than a second count threshold value, the flow of the output desorption pipeline is normal.

4. The fuel tank leakage diagnosis module-based positive pressure desorption pipeline flow diagnosis method according to any one of claims 1 to 3, wherein the deviation is the difference between the historical no-load current and the current no-load current.

5. The positive pressure desorption pipeline flow diagnosis method based on the fuel tank leakage diagnosis module as claimed in any one of claims 1 to 3, wherein the triggering of the heating unit of the fuel tank leakage diagnosis module comprises: and starting and keeping the heating unit to work according to the preset duration, so that the ratio of the carbon tank load, the pressurization pressure and the environmental pressure meets the preset flow diagnosis condition.

Technical Field

The invention relates to the technical field of engines, in particular to a positive pressure type desorption pipeline flow diagnosis method based on a fuel tank leakage diagnosis module.

Background

The supercharged engine needs to monitor the flow of two desorption pipelines, namely a high desorption pipeline and a low desorption pipeline, when the engine runs under a small load, the pressure of an air inlet manifold is smaller than the ambient pressure, and fuel steam passes through a carbon tank electromagnetic valve from an evaporation system and enters the air inlet manifold through the low desorption pipeline; when the engine runs under a large load, the pressure of the air inlet manifold is greater than the ambient pressure, and fuel steam is pumped into the air inlet air filter through the venturi tube of the high desorption pipeline and then enters the air inlet manifold through the intercooler. The current monitoring requirement is to monitor the desorption flow, and if the desorption flow from the evaporation system to the engine is not detected, the desorption pipeline is damaged or fails, and the OBD system reports the corresponding failure.

The existing industry generally has two solutions to the above monitoring requirements: firstly, a carbon tank ventilation electromagnetic valve is closed actively, the connection between an evaporation system and the atmosphere is isolated, so that a closed system is formed, then a desorption pipeline is used for vacuumizing, and the desorption flow value is diagnosed according to the pressure drop of an oil tank pressure sensor; and secondly, judging the pressure change of the pipeline by utilizing a manifold pressure sensor and a high desorption pressure sensor when the carbon tank electromagnetic valve is opened.

However, the first scheme is a negative pressure type diagnosis scheme based on evaporative leakage, and hardware such as a fuel tank pressure sensor and a carbon tank vent valve is required to be used, and the scheme has the defect that for a hybrid vehicle, the leakage diagnosis scheme cannot be implemented due to the fact that an idling working condition is cancelled; the second scheme needs to additionally install a pressure sensor on a high-load desorption pipeline, so that the cost of the whole vehicle is increased.

Disclosure of Invention

In view of the above, the present invention aims to provide a positive pressure type desorption pipeline flow rate diagnosis method based on a fuel tank leakage diagnosis module, so as to solve the above-mentioned shortcomings of the existing desorption pipeline flow rate monitoring scheme.

The technical scheme adopted by the invention is as follows:

a positive pressure type desorption pipeline flow diagnosis method based on a fuel tank leakage diagnosis module comprises the following steps:

after the engine is started, performing initial diagnosis on the fuel tank leakage diagnosis module;

triggering a heating unit of the fuel tank leakage diagnosis module to start after the initial diagnosis is passed;

the method comprises the steps of obtaining the current load of a carbon tank, closing a carbon tank electromagnetic valve after the current load is lower than a preset load threshold value, and executing the following low desorption flow diagnosis activation strategy or high desorption flow diagnosis activation strategy;

wherein the low desorption flow diagnostic activation strategy comprises: acquiring an intake manifold pressure, and triggering a pump unit of a fuel tank leakage diagnosis module to start to operate when the intake manifold pressure is smaller than a preset pressure threshold value; the high desorption flow diagnostic activation strategy includes: acquiring boost pressure and ambient pressure, and triggering a pump unit of a fuel tank leakage diagnosis module to start to operate when the ratio of the boost pressure to the ambient pressure is greater than a preset ratio threshold;

after the pump unit is started, detecting the current no-load current when the pump unit is in no-load; comparing the current no-load current with the historical no-load current of the pump unit correspondingly obtained in the previous low desorption or high desorption flow diagnosis;

when the deviation of the two is larger than a current deviation threshold value preset by corresponding low desorption or high desorption flow diagnosis, outputting a normally open fault of the carbon tank electromagnetic valve;

when the deviation between the two is smaller than the current deviation threshold value, opening a carbon tank electromagnetic valve, and detecting the change condition of the pump unit current after the preset operation time;

judging whether the current round of diagnosis is faulty or not according to the change condition and carrying out statistics;

and after repeated multi-round diagnosis, outputting a final flow diagnosis conclusion when the statistical number reaches a preset counting threshold value.

In at least one possible implementation manner, the determining whether the current diagnosis is faulty and performing statistics according to the variation includes:

if the ratio of the current pump unit current to the current no-load current after the preset time is operated is larger than a current ratio threshold value preset for corresponding low desorption or high desorption flow diagnosis, adding 1 to the fault count;

and if the ratio of the current pump unit current to the current no-load current after the preset time is operated is smaller than the current ratio threshold, adding 1 to the no-fault count.

In at least one possible implementation manner, the outputting the final flow diagnosis result after the statistical number reaches a preset counting threshold includes:

outputting a desorption pipeline fault when the fault count is greater than a first count threshold;

and when the fault-free count is larger than a second count threshold value, the flow of the output desorption pipeline is normal.

In at least one possible implementation manner, the difference between the historical idle current and the current idle current is the difference between the historical idle current and the current idle current.

In at least one possible implementation, the triggering of the heating unit activation of the fuel tank leak diagnostic module includes: and starting and keeping the heating unit to work according to the preset duration, so that the ratio of the carbon tank load, the pressurization pressure and the environmental pressure meets the preset flow diagnosis condition.

The design concept of the invention is that the characteristics of pump current and pump resistance of a fuel tank leakage Diagnosis Module (DMTL) are utilized, and the DMTL pump current is used as a pressure sensing device so as to diagnose whether the desorption flow is abnormal or not. Specifically, on the premise that an additional pressure sensor is not added, the current of the DMTL pump is monitored, and whether desorption flow exists in the desorption pipeline is judged according to the change of the pump current and the pump current frequency, so that the monitoring and diagnosis of the desorption flow of the high-low desorption pipeline of the evaporation system are completed. The desorption flow diagnosis method provided by the invention uses the existing sensors and actuators to complete diagnosis, and does not need to add a pressure sensor on a high desorption pipeline, thereby simplifying the system structure and reducing the cost.

Drawings

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described with reference to the accompanying drawings, in which:

fig. 1 is a flowchart of a positive pressure desorption pipeline flow diagnosis method based on a fuel tank leakage diagnosis module according to an embodiment of the present invention.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative only and should not be construed as limiting the invention.

The invention provides an embodiment of a positive pressure desorption pipeline flow diagnosis method based on a fuel tank leakage diagnosis module, and specifically, as shown in fig. 1, the method may include the following steps:

step S1, after the engine is started, performing initial diagnosis on the fuel tank leakage diagnosis module;

step S2, after the initial diagnosis is passed, triggering a heating unit of the fuel tank leakage diagnosis module to start;

step S3, acquiring the current load of the carbon tank, closing the electromagnetic valve of the carbon tank after the current load is lower than a preset load threshold, and executing the following low desorption flow diagnosis activation strategy or high desorption flow diagnosis activation strategy;

wherein the low desorption flow diagnostic activation strategy comprises: step S100, acquiring pressure of an intake manifold, and triggering a pump unit of a fuel tank leakage diagnosis module to start to operate when the pressure of the intake manifold is smaller than a preset pressure threshold value; the high desorption flow diagnostic activation strategy includes: step S200, acquiring boost pressure and ambient pressure, and triggering a pump unit of a fuel tank leakage diagnosis module to start to operate when the ratio of the boost pressure to the ambient pressure is greater than a preset ratio threshold;

step S4, after the pump unit is started, detecting the current no-load current when the pump unit is in no-load;

step S5, comparing the current idle current with the historical idle current of the pump unit correspondingly obtained in the previous low desorption or high desorption flow diagnosis;

step S6, outputting a normally open fault of the carbon tank electromagnetic valve when the deviation between the two is larger than a current deviation threshold value preset by corresponding low desorption or high desorption flow diagnosis;

step S7, when the deviation between the two is smaller than the current deviation threshold value, opening a carbon tank electromagnetic valve, and detecting the change condition of the pump unit current after the operation for the preset time;

step S8, judging whether the current round of diagnosis has faults or not according to the change condition and carrying out statistics;

and step S9, after repeated multiple rounds of diagnosis, when the statistical number reaches a preset counting threshold value, outputting a final flow diagnosis conclusion.

Further, the determining whether the current round of diagnosis is faulty and counting according to the change condition includes:

if the ratio of the current pump unit current to the current no-load current after the preset time is operated is larger than a current ratio threshold value preset for corresponding low desorption or high desorption flow diagnosis, judging that the carbon tank electromagnetic valve is blocked or the high desorption pipeline falls off, and adding 1 to the fault count;

and if the ratio of the current pump unit current to the current no-load current after the preset time is operated is smaller than the current ratio threshold, indicating that the high desorption flow is normal, and adding 1 to the no-fault count.

Further, the outputting a final flow diagnosis conclusion after the statistical number reaches a preset counting threshold value includes:

when the fault count is greater than a first count threshold value, outputting a desorption pipeline fault, namely a carbon tank solenoid valve normal close-low desorption pipeline (or high desorption pipeline) fault;

when the no-fault count is greater than a second count threshold (which may not be limited to being the same as the first count threshold), the output desorption line flow is normal.

Further, the difference between the current idle current and the historical idle current is the difference of the current idle current and the historical idle current.

Further, the triggering of the heating unit activation of the fuel tank leak diagnostic module includes: and starting and keeping the heating unit to work according to the preset duration, so that the ratio of the carbon tank load, the pressurization pressure and the environmental pressure meets the preset flow diagnosis process starting condition.

In summary, the present invention is designed to utilize the characteristics of the pump current and the pumping resistance of the fuel tank leakage Diagnosis Module (DMTL) and use the DMTL pump current as a pressure sensing device to diagnose whether the desorption flow rate is abnormal. Specifically, on the premise that an additional pressure sensor is not added, the current of the DMTL pump is monitored, and whether desorption flow exists in the desorption pipeline is judged according to the change of the pump current and the pump current frequency, so that the monitoring and diagnosis of the desorption flow of the high-low desorption pipeline of the evaporation system are completed. The desorption flow diagnosis method provided by the invention uses the existing sensors and actuators to complete diagnosis, and does not need to add a pressure sensor on a high desorption pipeline, thereby simplifying the system structure and reducing the cost.

In the embodiments of the present invention, "at least one" means one or more, "a plurality" means two or more. "and/or" describes the association relationship of the associated objects, and means that there may be three relationships, for example, a and/or B, and may mean that a exists alone, a and B exist simultaneously, and B exists alone. Wherein A and B can be singular or plural. The character "/" generally indicates that the former and latter associated objects are in an "or" relationship. "at least one of the following" and similar expressions refer to any combination of these items, including any combination of singular or plural items. For example, at least one of a, b, and c may represent: a, b, c, a and b, a and c, b and c or a and b and c, wherein a, b and c can be single or multiple.

The structure, features and effects of the present invention have been described in detail with reference to the embodiments shown in the drawings, but the above embodiments are merely preferred embodiments of the present invention, and it should be understood that technical features related to the above embodiments and preferred modes thereof can be reasonably combined and configured into various equivalent schemes by those skilled in the art without departing from and changing the design idea and technical effects of the present invention; therefore, the invention is not limited to the embodiments shown in the drawings, and all the modifications and equivalent embodiments that can be made according to the idea of the invention are within the scope of the invention as long as they are not beyond the spirit of the description and the drawings.