CN112031977B

CN112031977B - Control method for quickly warming engine

Info

Publication number: CN112031977B
Application number: CN202010900264.8A
Authority: CN
Inventors: 吴博; 王景智; 王世健; 张磊; 李俊峰; 李斯
Original assignee: Dongfeng Commercial Vehicle Co Ltd
Current assignee: Dongfeng Commercial Vehicle Co Ltd
Priority date: 2020-08-31
Filing date: 2020-08-31
Publication date: 2022-08-19
Anticipated expiration: 2040-08-31
Also published as: CN112031977A

Abstract

The invention discloses a control method for quickly warming up an engine, which comprises the following steps: step S1), judging whether the engine quick warm-up condition is met; step S2), obtaining an output torque demand according to the temperature change rate of the engine; step S3), setting a corresponding exhaust back pressure target according to the output torque demand; step S4), the engine controller adjusts the variable cross-sectional position of the VGT to obtain an exhaust back pressure target. The control method for quickly warming the engine of the invention properly increases the load of the engine by continuously and adjustably controlling the opening of the exhaust brake butterfly valve to quickly warm the engine; the engine temperature rate meeting the set requirement is realized through closed-loop control of exhaust back pressure; the exhaust backpressure target is corrected based on set values of the cooling liquid temperature and the atmospheric pressure, and the set temperature rise rate requirement can be met under the internal and external environments with different cooling liquid temperatures and atmospheric pressures.

Description

Control method for quickly warming engine

Technical Field

The invention relates to the technical field of vehicle control, in particular to a method for controlling quick engine warming.

Background

Conventional engines use natural aspiration, i.e. atmospheric pressure pushes air directly into the combustion chamber without any supercharger. The supercharging and inter-cooling technology of the invention utilizes the compressor to compress air, and then cools the compressed air through the heat exchanger (intercooler), thereby achieving the purpose of improving the air inlet density, the air inlet amount and the engine power of the engine. For the exhaust gas turbocharging which is widely adopted by a vehicle engine, a turbine arranged in an exhaust pipe is driven by exhaust gas to rotate at a high speed, and because a driving shaft of a compressor is the same as an output shaft of the turbine, the turbine can drive the compressor to rotate at a high speed, so that the compressor pressurizes air and then sends the air to a cylinder. Therefore, the higher the engine exhaust energy, the higher the turbine speed and the supercharger speed, and the higher the boost pressure.

However, the traditional fixed-section turbocharger usually takes medium and low speeds as an optimization area, so that the problems of overhigh supercharging pressure, overhigh rotating speed and the like occur during high-speed and high-load. The invention of VGT (Variable Geometry Turbocharger) technology successfully solves the problem. The angle of a turbine nozzle vane can be adjusted by the VGT system through an actuator, so that the utilization efficiency of waste gas is changed, and the supercharger can be well matched under various working conditions.

In the existing engine warming-up scheme, different engine idling speeds can be set according to the temperature of engine cooling liquid or engine oil, and the warming-up process is accelerated in a mode of increasing the idling speed.

Because the mode of increasing the idling speed does not obviously increase the load of the engine, the warming effect is very weak, the warming time is long, and obvious help cannot be provided for the urea thawing capacity of an after-treatment system and the warming effect of a cab. The engine is in a cold state for a long time, which results in low thermal efficiency of the engine, increased oil consumption and increased emission of pollutants. Moreover, the increase of the idle speed of the engine can increase noise, and the idle speed is different along with the difference of the temperature of the engine, thereby influencing the comfort feeling of a driver.

Disclosure of Invention

The invention aims to provide a quick warm-up control method for an engine, which has quick and obvious warm-up effect.

In order to achieve the purpose, the invention provides a control method for quickly warming up an engine, which comprises the following steps: step S1), judging whether the engine quick warm-up condition is met; step S2), obtaining an output torque demand according to the engine temperature change rate; step S3), setting a corresponding exhaust back pressure target according to the output torque demand; step S4), the engine controller adjusts the variable cross-sectional position of the VGT to obtain an exhaust back pressure target.

Preferably, in the step S1), the engine rapid warm-up condition includes an ambient temperature, a coolant temperature, a parking brake signal, a PTO state, and an engine torque.

Preferably, in step S2), the engine controller obtains the output torque request at each rotation speed by looking up a table according to the coolant temperature of the engine or the change rate request of the engine oil temperature.

Preferably, in step S3), an exhaust back pressure target corresponding to the output torque request is obtained according to a corresponding relationship between the exhaust back pressure and the output torque at the corresponding rotation speed.

Preferably, the method further comprises the following steps: step S5), the exhaust back pressure target is corrected based on the coolant temperature and the atmospheric pressure.

Preferably, the method further comprises the following steps: step S6), when the exhaust back pressure sensor fails, the engine controller adjusts the variable cross-sectional position of the VGT, controlling the duty opening.

The beneficial effects of the invention are: the control method for quickly warming the engine of the invention properly increases the load of the engine by continuously and adjustably controlling the opening of the exhaust brake butterfly valve to quickly warm the engine; the engine temperature rate meeting the set requirement is realized through closed-loop control of exhaust back pressure; the exhaust back pressure target is corrected based on set values of the cooling liquid temperature and the atmospheric pressure, and the set temperature rise rate requirement can be met under the internal and external environments with different cooling liquid temperatures and atmospheric pressures; in consideration of the countermeasure under the exhaust pressure sensor failure mode, the closed-loop control is switched to the open-loop control mode after the sensor fails, the controlled object is switched to the duty ratio opening from the exhaust back pressure, the open-loop control is adopted to ensure that the VGT opening is kept relatively stable, and the engine can be ensured to run stably while the exhaust pressure sensor is quickly warmed up.

Drawings

Fig. 1 is a flowchart of a method for controlling rapid warm-up of an engine according to a preferred embodiment of the present invention.

Detailed Description

The invention is described in further detail below with reference to the figures and the specific embodiments.

The invention designs a quick engine warming control method, which improves the idling warming effect of an engine by controlling a VGT (variable geometry turbine), and an automobile controller controls the variable section position of the VGT to realize the closed-loop control of the pressure of an exhaust main pipe, ensure the quick rise of the temperature of engine coolant, engine oil and exhaust gas and meet the warming requirements of the engine and a post-processing assembly.

Referring to fig. 1, the method for controlling rapid warm-up of an engine according to the present invention includes the following steps:

step S1), it is determined whether the engine quick warm-up condition is satisfied.

The starting and quick warming activation conditions are set with ambient temperature, coolant temperature, parking brake signals, PTO state, engine torque and the like, and the quick warming function is ensured to be activated only under the working condition of engine warming requirement.

Step S2), an output torque request is obtained according to the engine temperature change rate.

The engine controller obtains the output torque requirement under each rotating speed by looking up a table according to the change rate requirement of the engine temperature (the temperature of cooling liquid or engine oil).

Step S3), a corresponding exhaust back pressure target is set according to the output torque demand.

And obtaining an exhaust back pressure target corresponding to the output torque demand according to the corresponding relation between the exhaust back pressure and the output torque at the corresponding rotating speed.

Step S4), the engine controller adjusts the variable cross-sectional position of the VGT.

The exhaust back pressure target is obtained by continuously variable adjustment of the variable cross-sectional position of the VGT.

Step S5), the exhaust back pressure target is corrected based on the coolant temperature and the atmospheric pressure.

The closed-loop control exhaust back pressure ensures that the set temperature rise rate requirement can be realized under the internal and external environments with different cooling liquid temperatures and atmospheric pressures.

Step S6), the engine controller adjusts the variable cross-sectional position of the VGT to control the duty opening.

Aiming at the condition that the exhaust back pressure sensor fails, the controlled target can be switched to the duty ratio opening degree from the exhaust back pressure, the VGT opening degree is kept relatively stable through open-loop control, and the engine can be ensured to run stably while the engine is quickly warmed up.

In conclusion, the control method for quickly warming up the engine improves the idling warming-up effect of the engine by controlling the VGT, controls the pressure of the exhaust main pipe in a closed-loop manner by continuously and variably adjusting the position of the variable cross section increased by the VGT through the automobile controller, realizes the control of the heating rate at different engine temperatures according to the corresponding relation between the pressure of the exhaust main pipe and the output torque at the corresponding rotating speed, ensures that the temperatures of the coolant, the engine oil and the exhaust gas of the engine are quickly increased, and meets the warming-up requirements of the engine and an aftertreatment assembly.

Compared with the prior art, the control method for quickly warming up the engine has the advantages that:

(1) the engine is quickly warmed up by properly increasing the load of the engine through continuously and adjustably controlling the opening of an exhaust brake butterfly valve;

(2) the engine temperature rate meeting the set requirement is realized through closed-loop control of exhaust back pressure;

(3) the exhaust back pressure target is corrected based on set values of the cooling liquid temperature and the atmospheric pressure, and the set temperature rise rate requirement can be met under the internal and external environments with different cooling liquid temperatures and atmospheric pressures;

(4) in consideration of the countermeasure under the exhaust pressure sensor failure mode, the closed-loop control is switched to the open-loop control mode after the sensor fails, the controlled object is switched to the duty ratio opening from the exhaust back pressure, the open-loop control is adopted to ensure that the VGT opening is kept relatively stable, and the engine can be ensured to run stably while the exhaust pressure sensor is quickly warmed up.

The above-described embodiments of the present invention only represent some embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that various changes and modifications can be made by those skilled in the art without departing from the spirit of the invention, and these changes and modifications are all within the scope of the invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims

1. A method for controlling quick warm-up of an engine comprises the following steps:

step S1), judging whether the engine quick warm-up condition is met;

step S2), obtaining an output torque demand according to the engine temperature change rate;

step S3), setting a corresponding exhaust back pressure target according to the output torque demand;

step S4), the engine controller adjusting the continuously variable adjustment of the variable geometry position of the VGT to obtain an exhaust backpressure target;

step S5), correcting the exhaust back pressure target based on the coolant temperature and the atmospheric pressure;

step S6), when the exhaust back pressure sensor fails, the engine controller adjusts the variable section position of the VGT and controls the opening degree of the duty ratio;

wherein, in the step S1), the engine rapid warm-up condition includes an ambient temperature, a coolant temperature, a parking brake signal, a PTO state, and an engine torque;

in the step S2), the engine controller obtains the output torque demand at each rotation speed by looking up a table according to the coolant temperature of the engine or the change rate demand of the engine oil temperature;

in step S3), an exhaust back pressure target corresponding to the output torque request is obtained according to the corresponding relationship between the exhaust back pressure and the output torque at the corresponding rotation speed.