阅读说明：本技术 尿素管路压力控制方法、发动机 (Urea pipeline pressure control method and engine ) 是由 李震 吕志华 耿宗起 仲昆 于 2021-08-12 设计创作，主要内容包括：本发明属于发动机技术领域,本发明提出了一种尿素管路压力控制方法和一种发动机,该方法用于控制车辆的后处理尿素喷射系统中尿素泵与尿素喷嘴之间的尿素管路的压力,包括以下步骤：获取所述尿素喷嘴的需求尿素喷射量和所述尿素管路的当前压力；根据所述需求尿素喷射量和所述当前压力查询关系表,所述关系表根据所述后处理尿素喷射系统的标定测试获得；根据查询所述关系表的结果对所述尿素泵的占空比进行前馈控制,使得所述尿素管路的压力达到预设压力值。该方法通过后处理系统模型计算的需求尿素喷射量,再根据尿素管路内的当前压力查询关系表作为压力控制的前馈输入,关系表由尿素喷射系统的标定测试获得,实现尿素喷射系统的管路压力稳定。(The invention belongs to the technical field of engines, and provides a urea pipeline pressure control method and an engine, wherein the method is used for controlling the pressure of a urea pipeline between a urea pump and a urea nozzle in an after-treatment urea injection system of a vehicle and comprises the following steps: acquiring the required urea injection quantity of the urea nozzle and the current pressure of the urea pipeline; inquiring a relation table according to the required urea injection quantity and the current pressure, wherein the relation table is obtained according to a calibration test of the post-treatment urea injection system; and performing feedforward control on the duty ratio of the urea pump according to the result of inquiring the relation table, so that the pressure of the urea pipeline reaches a preset pressure value. The method comprises the steps of calculating the required urea injection quantity through a post-processing system model, and using a current pressure query relation table in a urea pipeline as feed-forward input of pressure control, wherein the relation table is obtained through calibration test of the urea injection system, so that the pipeline pressure stability of the urea injection system is realized.)

1. A urea line pressure control method for controlling pressure in a urea line between a urea pump and a urea nozzle in an aftertreatment urea injection system of a vehicle, comprising the steps of:

acquiring the required urea injection quantity of the urea nozzle and the current pressure of the urea pipeline;

inquiring a relation table according to the required urea injection quantity and the current pressure, wherein the relation table is obtained according to a calibration test of the post-treatment urea injection system;

and performing feedforward control on the duty ratio of the urea pump according to the result of inquiring the relation table, so that the pressure of the urea pipeline reaches a preset pressure value.

2. The urea line pressure control method of claim 1, wherein the calibration test comprises the steps of:

controlling the urea pump and the urea nozzle to operate according to a preset working condition;

acquiring the duty ratio of the urea pump, the urea injection quantity of the urea nozzle and the pipeline pressure of the urea pipeline;

and establishing the relation table between the urea injection quantity and the duty ratio under the condition that the pipeline pressure is a set pressure value according to the duty ratio, the urea injection quantity and the pipeline pressure.

3. The urea line pressure control method of claim 2, wherein the controlling the urea pump and the urea nozzle to operate at a predetermined operating condition comprises:

controlling the urea pump to build pressure, enabling the pipeline pressure of the urea pipeline to reach a set pressure value, and recording the set pressure value;

controlling the urea injection quantity of the urea nozzle to be the minimum urea injection quantity, and recording the urea injection quantity;

controlling the duty ratio of the urea pump to enable the pipeline pressure of the urea pipeline to reach the set pressure value, and recording the duty ratio;

controlling the urea nozzle to increase the urea injection quantity;

and executing the control of the duty ratio of the urea pump to enable the pipeline pressure of the urea pipeline to reach a set pressure value until the urea injection quantity of the urea nozzle reaches the maximum urea injection quantity.

4. The urea circuit pressure control method of claim 1, wherein the obtaining a requested urea injection quantity of the urea nozzle and a current pressure of the urea circuit comprises:

establishing a post-processing system model;

obtaining a required urea injection amount according to the aftertreatment system model;

and receiving a current pressure signal of a urea pipeline pressure sensor.

5. The urea line pressure control method of claim 4, wherein the obtaining a requested urea injection amount based on an aftertreatment system model comprises:

establishing a catalyst chemical reaction model and an ammonia storage model;

receiving an upstream NOx concentration signal of a NOx concentration sensor;

the requested urea injection amount is obtained based on the upstream NOx concentration signal, the catalyst chemical reaction model, and the ammonia storage model.

6. An engine for performing the urea line pressure control method of any one of claims 1-5, comprising:

ECU and aftertreatment urea injection system, aftertreatment urea injection system with the ECU electricity is connected.

7. The engine of claim 6, further comprising a PID controller and a feedforward controller, the PID controller electrically connected to the ECU and the feedforward controller, respectively, the feedforward controller electrically connected to the aftertreatment urea injection system.

Technical Field

The invention belongs to the technical field of engines, and particularly relates to a urea pipeline pressure control method.

Background

This section provides background information related to the present disclosure only and is not necessarily prior art.

In the existing automobile-used post-treatment urea injection system, the problem of overlarge pressure fluctuation in a pipeline between a urea pump and a urea nozzle can occur when the urea injection amount is overlarge, and the existing feed-forward control is calibrated according to experience, so that the calibration difficulty and workload are increased, and the applicability to different injection systems is poor. In addition, the input of the existing feedforward control is the duty ratio and the period of the actual urea injection valve, the control lags behind one to two scheduling periods, and when the urea injection quantity is changed greatly, the pressure fluctuation is large, so that the feedforward control effect cannot be well played.

Disclosure of Invention

The invention aims to at least solve the problems of difficult calibration and control hysteresis of pipeline pressure control of an after-treatment urea injection system in the prior art, and the aim is realized by the following technical scheme:

a first aspect of the present invention proposes a urea line pressure control method for controlling a pressure of a urea line between a urea pump and a urea nozzle in an aftertreatment urea injection system of a vehicle, comprising the steps of:

acquiring the required urea injection quantity of the urea nozzle and the current pressure of the urea pipeline;

inquiring a relation table according to the required urea injection quantity and the current pressure, wherein the relation table is obtained according to a calibration test of the post-treatment urea injection system;

and performing feedforward control on the duty ratio of the urea pump according to the result of inquiring the relation table, so that the pressure of the urea pipeline reaches a preset pressure value.

The urea pipeline pressure control method provided by the invention uses the required urea injection amount calculated by a post-processing system model and then uses the current pressure query relation table in the urea pipeline as the feedforward input of pressure control to control the air-to-space ratio of the urea pump so as to realize the stable control of the pipeline pressure of the urea injection system. The relation table is obtained by a calibration test of a post-processing urea injection system, the relation between the urea injection amount and the duty ratio under constant urea pipeline pressure is tested and recorded in the test, the relation table is established according to the test result, and the relation table is input into a vehicle control system to control the duty ratio of the urea pump when the urea pipeline pressure fluctuation is large in the running process of a vehicle, so that the pressure stability of the urea pipeline is maintained.

In addition, the urea line pressure control method according to the present invention may further have the following additional technical features:

in some embodiments of the invention, the calibration test comprises the steps of:

controlling the urea pump and the urea nozzle to operate according to a preset working condition;

acquiring the duty ratio of the urea pump, the urea injection quantity of the urea nozzle and the pipeline pressure of the urea pipeline;

and establishing the relation table between the urea injection quantity and the duty ratio under the condition that the pipeline pressure is a set pressure value according to the duty ratio, the urea injection quantity and the pipeline pressure.

In some embodiments of the invention, the controlling the urea pump and the urea nozzle to operate at the preset operation condition comprises:

controlling the urea pump to build pressure, enabling the pipeline pressure of the urea pipeline to reach a set pressure value, and recording the set pressure value;

controlling the urea injection quantity of the urea nozzle to be the minimum urea injection quantity, and recording the urea injection quantity;

controlling the duty ratio of the urea pump to enable the pipeline pressure of the urea pipeline to reach the set pressure value, and recording the duty ratio;

controlling the urea nozzle to increase the urea injection quantity;

and executing the control of the duty ratio of the urea pump to enable the pipeline pressure of the urea pipeline to reach a set pressure value until the urea injection quantity of the urea nozzle reaches the maximum urea injection quantity.

In some embodiments of the present invention, the obtaining the required urea injection amount of the urea nozzle and the current pressure of the urea line comprises:

establishing a post-processing system model;

obtaining a required urea injection amount according to the aftertreatment system model;

and receiving a current pressure signal of a urea pipeline pressure sensor.

In some embodiments of the invention, said obtaining a requested urea injection amount from an aftertreatment system model comprises:

establishing a catalyst chemical reaction model and an ammonia storage model;

receiving an upstream NOx concentration signal of a NOx concentration sensor;

the requested urea injection amount is obtained based on the upstream NOx concentration signal, the catalyst chemical reaction model, and the ammonia storage model.

A second aspect of the invention proposes an engine for executing the urea line pressure control method as proposed in the first aspect of the invention, comprising:

ECU and aftertreatment urea injection system, aftertreatment urea injection system with the ECU electricity is connected.

The engine according to the second aspect of the present invention has the same advantages as the urea line pressure control method according to the first aspect of the present invention, and will not be described in detail herein.

In some embodiments of the invention, the engine further comprises a PID controller electrically connected to the ECU and the feedforward controller, respectively, and a feedforward controller electrically connected to the aftertreatment urea injection system.

Drawings

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Also, like parts are designated by like reference numerals throughout the drawings. In the drawings:

FIG. 1 schematically illustrates a flow diagram of a urea circuit pressure control method according to an embodiment of the invention;

FIG. 2 schematically illustrates a flow diagram of a calibration test of a urea circuit pressure control method according to an embodiment of the invention;

Detailed Description

Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

It is to be understood that the terminology used herein is for the purpose of describing particular example embodiments only, and is not intended to be limiting. As used herein, the singular forms "a", "an" and "the" may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms "comprises," "comprising," "including," and "having" are inclusive and therefore specify the presence of stated features, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order described or illustrated, unless specifically identified as an order of performance. It should also be understood that additional or alternative steps may be used.

Although the terms, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as "second" and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, an element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments.

For convenience of description, spatially relative terms, such as "inner", "outer", "inner", "side", "lower", "below", "upper", "above", and the like, may be used herein to describe one element or feature's relationship to another element or feature as illustrated in the figures. Such spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as "below" or "beneath" other elements or features would then be oriented "above" or "over" the other elements or features. Thus, the example term "below … …" can include both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

As shown in fig. 1 and 2, a first aspect of the present invention provides a urea line pressure control method for controlling a pressure of a urea line between a urea pump and a urea nozzle in an aftertreatment urea injection system of a vehicle, comprising the steps of:

acquiring the required urea injection quantity of a urea nozzle and the current pressure of a urea pipeline;

inquiring a relation table according to the required urea injection quantity and the current pressure, wherein the relation table is obtained according to a calibration test of a post-treatment urea injection system;

and performing feedforward control on the duty ratio of the urea pump according to the result of the query relation table to enable the pressure of the urea pipeline to reach a preset pressure value.

The required urea injection amount can be obtained through calculation of an after-treatment system model, the after-treatment system model calculates the required urea injection amount according to the upstream NOx concentration, a catalyst chemical reaction model and an ammonia storage model, and the principle is that gas concentration parameters are input to obtain data such as the required urea injection amount and the like based on a series of equations including a chemical reaction equation, an energy conservation equation, a mass conservation equation and the like.

The urea pipeline pressure control method provided by the invention uses the required urea injection amount calculated by a post-processing system model and then uses the current pressure query relation table in the urea pipeline as the feedforward input of pressure control to control the air-to-space ratio of the urea pump so as to realize the stable control of the pipeline pressure of the urea injection system. The relation table is obtained by a calibration test of a post-processing urea injection system, the relation between the urea injection amount and the duty ratio under constant urea pipeline pressure is tested and recorded in the test, the relation table is established according to the test result, and the relation table is input into a vehicle control system to control the duty ratio of the urea pump when the urea pipeline pressure fluctuation is large in the running process of a vehicle, so that the pressure stability of the urea pipeline is maintained.

As shown in FIG. 2, in some embodiments of the present invention, the calibration test includes the following steps:

controlling a urea pump and a urea nozzle to operate according to a preset working condition;

acquiring the duty ratio of a urea pump, the urea injection quantity of a urea nozzle and the pipeline pressure of a urea pipeline;

and establishing a relation table between the urea injection quantity and the duty ratio under the condition that the pipeline pressure is a set pressure value according to the duty ratio, the urea injection quantity and the pipeline pressure.

It can be understood that the calibration test may be a bench test, the urea injection amount of the urea nozzle may be controlled to change within an allowable range according to actual control requirements, the duty ratio of the urea pump is controlled to maintain the line pressure of the urea line at a constant value, and the relationship between the urea injection amount and the duty ratio is recorded during the test, so as to establish a relationship table between the urea injection amount and the duty ratio under the condition that the line pressure is a set pressure value.

The steps avoid calibration according to experience, reduce calibration workload and calibration difficulty, and increase the adaptability of the control system.

Specifically, controlling the urea pump and the urea nozzle to operate at the preset operating condition includes:

controlling a urea pump to build pressure, enabling the pipeline pressure of a urea pipeline to reach a set pressure value, and recording the set pressure value;

controlling the urea injection quantity of the urea nozzle to be the minimum urea injection quantity, and recording the urea injection quantity;

controlling the duty ratio of a urea pump to enable the pipeline pressure of a urea pipeline to reach a set pressure value, and recording the duty ratio;

controlling a urea nozzle to increase the urea injection amount;

and executing control on the duty ratio of the urea pump to enable the pipeline pressure of the urea pipeline to reach a set pressure value until the urea injection quantity of the urea nozzle reaches the maximum urea injection quantity.

The minimum urea injection amount and the maximum urea injection amount are determined according to the urea injection amount range of the urea injection nozzle.

In some embodiments of the present invention, obtaining the requested urea injection amount of the urea nozzle and the current pressure of the urea line comprises:

establishing a post-treatment system model, wherein the post-treatment system model is a Selective Catalytic Reduction (SCR) model, parametric modeling is carried out according to the specification and configuration of the device, and the model inputs the parameters of gas entering the SCR to obtain the data such as urea injection amount and the like;

obtaining a required urea injection amount according to the post-treatment system model;

and receiving a current pressure signal of a urea pipeline pressure sensor.

Specifically, obtaining the required urea injection amount according to the aftertreatment system model includes:

establishing a catalyst chemical reaction model and an ammonia storage model;

receiving an upstream NOx concentration signal of a NOx concentration sensor;

a requested urea injection amount is obtained based on the upstream NOx concentration signal, the catalyst chemical reaction model, and the ammonia storage model.

A second aspect of the invention proposes an engine for executing the urea line pressure control method as proposed in the first aspect of the invention, comprising:

ECU and aftertreatment urea injection system, aftertreatment urea injection system and with ECU electricity connection.

The aftertreatment urea injection system is preferably a Selective Catalytic Reduction (SCR), which is a currently used vehicle exhaust treatment device, and the SCR is provided with a urea nozzle, and when exhaust of a vehicle flows through the SCR, the urea nozzle injects urea to the exhaust according to a certain urea injection amount, so that ammonia gas volatilized from the urea reacts with nitrogen oxides (which can be generally expressed by a chemical formula NOx) in the exhaust to obtain harmless nitrogen and water, and the content of the nitrogen oxides in the treated exhaust is reduced.

The concrete implementation flow of the urea pipeline pressure control method is as follows:

firstly, a calibration test is carried out, a post-processing system of an engine is placed on a test bench, pressure build-up of a urea pump is controlled firstly, so that the pipeline pressure of a urea pipeline reaches a set pressure value, a urea injection valve of a urea nozzle is controlled to inject constant urea injection quantity, the pipeline pressure can change at the moment, the duty ratio of the urea pump is controlled so that the pipeline pressure is maintained near the set pressure value, and the duty ratio of the urea pump corresponding to the current urea injection quantity is recorded.

The urea injection amount at the beginning of the calibration test is the minimum urea injection amount of the urea nozzle, after the recording is completed, the urea injection amount is increased, and the duty ratio pressure regulation and the real-time urea injection amount and duty ratio recording are repeated until the urea nozzle reaches the maximum urea injection amount.

After the record of the duty ratio of the urea pump corresponding to the minimum urea injection amount to the maximum urea injection amount is finished, establishing a relation table of the urea injection amount and the duty ratio of the urea pump under the set pressure value, and inputting the relation table into a vehicle control system to finish the calibration test.

The urea injection quantity is adjusted according to the actual emission condition when the vehicle runs, the pressure in a urea pipeline can fluctuate too much when the urea injection quantity is too large, the vehicle control system calculates the required urea injection quantity according to the upstream NOx concentration obtained by the concentration sensor, the catalyst chemical reaction model and the ammonia storage model when the urea injection quantity is adjusted, the catalyst chemical reaction model and the ammonia storage model can be obtained by the SCR model of the SCR, the specific calculation method can refer to the related prior art and is not limited herein, then, a pipeline pressure signal is obtained according to a pressure sensor of the urea pipeline, when the pipeline pressure signal deviates from a set pressure value, the corresponding duty ratio of the urea pump is obtained by looking up a relation table through the required urea injection amount, the duty ratio of the urea pump is controlled in a feedforward mode, further, the pressure of the urea pipeline is adjusted to be close to the set pressure value, and the pressure of the urea pipeline is kept stable.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are also included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.