CN110566304B

CN110566304B - Valve train and control strategy for an engine having a low pressure EGR system

Info

Publication number: CN110566304B
Application number: CN201811454515.3A
Authority: CN
Inventors: 崔亚彬; 常进才; 李婧媛; 张帅; 张卫国
Original assignee: Great Wall Motor Co Ltd
Current assignee: Great Wall Motor Co Ltd
Priority date: 2018-11-30
Filing date: 2018-11-30
Publication date: 2022-04-22
Anticipated expiration: 2038-11-30
Also published as: WO2020108566A1; CN110566304A

Abstract

The invention discloses a valve train of an engine with a low-pressure EGR system and a control strategy, wherein the valve train comprises: the outer periphery of the cam is abutted against the rocker arm so as to push the rocker arm to move downwards when the cam rotates; the valve is disposed on the rocker arm to move with the rocker arm; and the rocker arm is also provided with a driving piece, and the driving piece is suitable for driving the valve to move relative to the rocker arm. Therefore, the opening time of the exhaust valve is prolonged, tail gas in the exhaust manifold is sucked into the cylinder, the hot atmosphere in the cylinder can be increased, and the combustion stability in the cylinder is ensured.

Description

Valve train and control strategy for an engine having a low pressure EGR system

Technical Field

The invention relates to the technical field of vehicles, in particular to a valve actuating mechanism of an engine with a low-pressure EGR system and a control strategy.

Background

In the related art, an engine EGR system is external EGR, which introduces exhaust gas after a catalyst into an intake supercharger before the exhaust gas enters an engine cylinder through the supercharger, an intake intercooler and a throttle valve.

Thus, when the engine is operated in a small load region or when the engine is operated in a large load region, once EGR suddenly enters the cylinder, combustion is unstable and there is a certain risk of engine misfire.

Disclosure of Invention

The present invention is directed to solving at least one of the problems of the prior art. To this end, it is an object of the present invention to propose a valve gear of an engine having a low-pressure EGR system, which can improve combustion stability of the engine at the time of cold start.

The invention also provides a control strategy of the valve train of the engine with the low-pressure EGR system.

The valve gear of the engine having the low-pressure EGR system according to the embodiment of the first aspect of the invention includes: the valve comprises a rocker arm, a cam and a valve, wherein the periphery of the cam is abutted with the rocker arm so as to push the rocker arm to move when the cam rotates; the valve is disposed on the rocker arm to move with the rocker arm; and the rocker arm is also provided with a driving piece, and the driving piece is suitable for driving the valve to move relative to the rocker arm.

According to the valve actuating mechanism of the engine with the low-pressure EGR system, the valve is driven by the driving piece to move relative to the rocker arm, when the rocker arm moves to the position where the valve is supposed to be closed, the valve still has a certain clearance, so that the opening time of the valve is prolonged, and at least part of EGR is extracted from an exhaust system through the low-pressure EGR system and is delivered into a cylinder during the prolonged opening time of the valve. Therefore, the opening time of the exhaust valve is prolonged, tail gas in the exhaust manifold is sucked into the cylinder, the hot atmosphere in the cylinder can be increased, and the combustion stability in the cylinder is ensured.

Furthermore, an oil cavity is formed in the rocker arm, the upper end of the valve is arranged in the oil cavity, and hydraulic oil can be selectively filled in the oil cavity to push the valve to move relative to the rocker arm.

Further, a movable pin is arranged at the upper end of the valve, and the movable pin is slidably arranged in the oil cavity.

Furthermore, a rocker arm oil duct is arranged on the rocker arm, one end of the rocker arm oil duct is communicated with the oil cavity, and the other end of the rocker arm oil duct is communicated with the oil inlet in the rocker arm.

Further, a tappet is arranged at the lower end of the rocker arm, and a hollow oil passage of the tappet is communicated with an oil inlet in the rocker arm.

Further, the hollow oil duct of the tappet is connected with an oil inlet pipe, and an electromagnetic valve for controlling hydraulic oil to enter and exit the oil cavity is arranged on the oil inlet pipe.

Furthermore, a rocker roller is arranged on the rocker arm, and the outer periphery of the cam is abutted against the rocker roller.

According to some embodiments of the invention, the rocker arm is provided with a pin hole, and two rocker arm rollers are symmetrically arranged on two sides of the pin hole.

According to the control strategy of the engine with the low-pressure EGR system of the second aspect of the invention, the valve mechanism is adopted, and the control strategy comprises a normal mode and a warm-up mode.

Further, the strategy for judging the warm-up mode includes: determining the current temperature of the engine oil and the ambient temperature; determining warm-up time according to the current temperature of the engine oil and the ambient temperature; when the accumulated time of the engine cold start is less than the warm-up time, the engine is in the warm-up mode.

Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

Drawings

The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

FIG. 1 is a schematic diagram of a low pressure EGR system, according to an embodiment of the present invention;

FIG. 2 is a schematic of a valve train according to an embodiment of the present invention;

FIG. 3 is a schematic illustration of a valve lift of a dispenser mechanism according to an embodiment of the present invention;

FIG. 4 is a schematic illustration of valve drop of a steam distribution mechanism according to an embodiment of the present invention;

FIG. 5 is a schematic of an operating position of a valve train according to an embodiment of the present invention;

FIG. 6 is a schematic view of a valve lash change corresponding to FIG. 5;

FIG. 7 is a schematic view of another operational position of a steam distribution mechanism according to an embodiment of the present invention;

FIG. 8 is a schematic view of a valve lash change corresponding to FIG. 7;

FIG. 9 is a schematic illustration of a control strategy according to an embodiment of the invention;

fig. 10 is a schematic top view of a rocker arm of a valve train according to an embodiment of the present invention.

Reference numerals:

100-a gas distribution mechanism, wherein,

110-rocker arm, 111-oil chamber, 112-rocker arm oil passage, 113-rocker arm roller, 120-cam, 130-valve, 140-movable pin, 150-tappet, 151-hollow oil passage, 160-oil inlet pipe, a-oil inlet,

200-a low-pressure GER system,

210-charge air intercooler, 220-fuel injector, 230, supercharger, 240-EGR cooler, 250-EGR valve, 260-throttle.

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 accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention.

As shown in fig. 1, the engine with the low-pressure EGR system 200 of the present embodiment first draws exhaust gas from a catalyst, enters the engine cylinder after passing through the supercharger 230, the charge air intercooler 210, the EGR cooler 240, the EGR valve 250, and the throttle valve 260, and is mixed with the oil gas sprayed from the injector in the cylinder.

The combustion stability of the engine under the cold engine starting working condition is poor, intermittent fire is possibly caused, the combustion efficiency is low, the oil consumption is high, and the TCH emission is high.

Based on the above problem of poor combustion stability, the inventors propose the valve actuating mechanism 100 of the present embodiment, and the valve actuating mechanism 100 effectively improves combustion stability, improves combustion efficiency, and reduces fuel consumption and TCH emission.

A valve gear 100 of an engine having a low-pressure EGR system 200 according to an embodiment of the present invention will be described with reference to fig. 1 to 10.

As shown in fig. 2 to 8, the valve gear 100 of the engine having the low-pressure EGR system 200 according to the embodiment of the first aspect of the invention includes: a rocker arm 110, a cam 120 and a valve 130, the outer periphery of the cam 120 being stopped against the rocker arm 110 to push the rocker arm 110 to move downward when the cam 120 rotates; the valve 130 is provided on the rocker arm 110 to move together with the rocker arm 110; wherein the rocker arm 110 is further provided with a driver adapted to drive the valve 130 to move relative to the rocker arm 110.

Specifically, the cam 120 rotates to push the rocker arm 110 to move, the rocker arm 110 drives the valve 130 to move, so that the valve 130 is opened and closed, when the valve 130 is opened, air is injected into the cylinder, so that oil gas in the cylinder is maintained to be combusted, and then the valve 130 is driven by the driving piece to move relative to the rocker arm 110, so that the opening time of the valve 130 is prolonged.

According to the valve train 100 of the engine with the low-pressure EGR system 200 provided by the embodiment of the invention, when the valve 130 is driven by the driver to move relative to the rocker arm 110, so that the rocker arm 110 moves to the position where the valve 130 should be closed, the valve 130 still has a certain clearance, thus the opening time of the valve 130 is prolonged, and at least part of EGR is extracted from the exhaust system by the low-pressure EGR system 200 and is delivered into the cylinder during the prolonged opening time of the valve 130. Therefore, the opening time of the exhaust valve is prolonged, tail gas in the exhaust manifold is sucked into the cylinder, the hot atmosphere in the cylinder can be increased, and the combustion stability in the cylinder is ensured.

As shown in fig. 3 and 4, an oil chamber 111 is provided in the rocker arm 110, an upper end of the valve 130 is provided in the oil chamber 111, and the oil chamber 111 is selectively filled with hydraulic oil to push the valve 130 to move relative to the rocker arm 110. That is, the hydraulic oil may flow into the oil chamber 111 or out of the oil chamber 111 so that the valve 130 may move toward the rocker arm 110 or away from the rocker arm 110, so that the valve 130 may be opened for a longer time when the valve 130 moves away from the rocker arm 110, the valve 130 may be gradually closed in a state of being opened for a longer time when the valve 130 moves toward the rocker arm 110, and the time during which the valve 130 moves toward the rocker arm 110 may coincide with the extended time during which the valve 130 is opened.

Thus, the structure for moving the driver control valve 130 relative to the rocker arm 110 is simpler, the operation stability is higher, and the response speed is faster.

As shown in fig. 5 and 7, the movable pin 140 is provided at the upper end of the valve 130, and the movable pin 140 is slidably provided in the oil chamber 111.

That is, FIG. 5 is a schematic illustration of the relative positions of the rocker arm 110 and the valve 130 during the normal start mode; fig. 7 is a schematic diagram illustrating the relative positions of the rocker arm 110 and the valve 130 in the cold start mode.

In the normal mode, no engine oil is in the oil chamber 111, the rocker arm 110 normally drives the valve 130 to open and close, in the cold machine starting mode, warming is needed, at the moment, the oil chamber 111 is filled with the engine oil, the engine oil pushes the movable pin 140 out of the valve 130 and props against the valve 130, so that in the ascending process of the rocker arm 110, the valve 130 can still be opened for a certain time, so that tail gas in an exhaust manifold is sucked into a cylinder when a piston descends, the in-cylinder hot atmosphere is increased, and the combustion stability is improved.

Further, the rocker arm 110 is provided with a rocker arm oil passage 112, one end of the rocker arm oil passage 112 is communicated with the oil chamber 111, and the other end of the rocker arm oil passage 112 is communicated with an oil inlet on the rocker arm 110. Thus, by arranging the rocker arm oil passage 112, hydraulic oil can circulate in the rocker arm oil passage 112, overflow of hydraulic oil in the process of flowing into or out of the valve 130 can be avoided, the working stability of the driving part can be improved, and the service life of the hydraulic oil is prolonged.

In the specific embodiment shown in fig. 2, the lower end of the rocker arm 110 is provided with a tappet 150, and the hollow oil passage of the tappet 150 is communicated with the oil inlet on the rocker arm 110. That is to say, the hollow oil duct is located one side of oil inlet, and rocking arm oil duct 112 is located the opposite side of oil inlet, and the three communicate to constitute the hydraulic oil return circuit, make things convenient for the circulation of hydraulic oil, and the position of hollow oil duct and rocking arm oil duct 112 is selected rationally, can reduce the space and occupy, and does not influence hydraulic oil transmission rate.

Further, the hollow oil passage of the tappet 150 is connected with an oil inlet pipe 160, and the oil inlet pipe 160 is provided with an electromagnetic valve for controlling the hydraulic oil to enter and exit the oil chamber 111. That is, the oil inlet pipe 160 is used to supply hydraulic oil to the oil chamber 111, and the above-described hollow oil passage, the rocker arm oil passage 112 is used to transport hydraulic oil, while by providing the solenoid valve, when the solenoid valve is opened and hydraulic oil flows toward the valve 130, an extended opening time of the valve 130 is achieved, and when the solenoid valve is opened and hydraulic oil flows out from the oil chamber 111, the opening of the valve 130 is switched to the normal mode.

Further, the rocker arm 110 is provided with a rocker arm roller 113, and the outer periphery of the cam 120 abuts against the rocker arm roller 113. Thus, during the rotation of the cam 120, the motion of the geometry shown in fig. 6 is a dynamic demonstration of the motion of the rocker roller 113, and further the dynamic demonstration of the opening clearance of the valve 130 is also the geometry shown in fig. 6, and when the movable pin 140 abuts against the valve 130, the dynamic demonstration of the motion of the cam 120 pushing the rocker 110 is consistent with fig. 8, and the dynamic demonstration of the opening clearance of the valve 130 is also consistent with the geometry shown in fig. 8 (i.e. the valve lift amount, the valve delay closing time and the valve delay closing angle are consistent with fig. 8).

As shown in fig. 10, the rocker arm 110 is provided with a pin hole, and two rocker arm rollers 113 are symmetrically arranged on both sides of the pin hole. In this way, the cam 120 drives the rocker roller 113 located at both sides of the pin hole simultaneously, so as to drive the rocker 110 to move, so that the forces applied to both sides during the movement of the rocker 110 are consistent, thereby effectively improving the stability of the movement of the rocker 110.

As shown in fig. 9, the control strategy of the engine having the low-pressure EGR system 200 according to the embodiment of the second aspect of the invention adopts the valve train 100 of the above embodiment, and includes a normal mode and a warm-up mode. The judgment strategy of the warming mode comprises the following steps: determining the current temperature of the engine oil and the ambient temperature; determining warm-up time according to the current temperature of the engine oil and the ambient temperature; when the accumulated time of the engine cold start is less than the warm-up time, the engine is in the warm-up mode.

Specifically, in the warm-up mode, the operation process of the valve train 100 is: the oil chamber 111 is filled with hydraulic oil to prop against the valve 130, and the valve 130 is still opened for a period of time in the process of ascending of the rocker arm 110, so that tail gas in the exhaust manifold is sucked into the cylinder when the piston descends.

The warm-up mode is judged by the following steps: and determining the current oil temperature and the ambient temperature, calculating reasonable warm-up time according to the oil temperature and the ambient temperature, and keeping the engine in a warm-up mode when the accumulated time of the cold start of the engine is less than the warm-up time.

That is, when the engine is in cold start, the ECU starts to execute the warming strategy, calculates the duration of the warming strategy, and drives the engine to enter the normal working mode when the duration is more than or equal to the warming time, otherwise, the engine continues to execute the warming mode. The warming time is calculated by an ECU, and the process is as follows: the ECU inputs the environmental temperature parameter and the engine oil temperature parameter into a warm-up time map according to the current engine oil temperature and the environmental temperature measured by the engine oil temperature sensor and the environmental temperature sensor, and the warm-up time map can be calibrated by an experiment, so that warm-up times corresponding to different environmental temperatures and different engine oil temperatures can be found.

The warm-up time map is obtained through a large amount of data after a plurality of tests by the inventor, the warm-up time can be obtained according to the environment temperature parameter, the engine oil temperature parameter and the warm-up time map, the warm-up time corresponding to the environment temperature parameter and the engine oil temperature parameter can also be obtained through other methods, and the method for obtaining the warm-up time is not limited.

Therefore, according to the control strategy of the engine with the low-pressure EGR system 200, the reasonable warm-up time is calculated, and after the engine is sufficiently warmed up, the normal working mode is switched back, so that the oil consumption of the engine can be effectively reduced, and the combustion stability is improved.

It can be understood that the engine control strategy of the low-pressure EGR system 200 and the valve train 100 of the present embodiment are both suitable for the engine of the vehicle, and the valve train 100 of the engine with the low-pressure EGR system 200 controlled by the control strategy can not only make the combustion medium (i.e. oxygen) content in the cylinder higher, but also raise the temperature in the cylinder, thereby improving the combustion stability in two directions of increasing the combustion medium content and raising the ambient temperature, so as to effectively improve the combustion stability in the cylinder, thereby reducing the fuel consumption, and enabling the vehicle under cold start to have abundant power.

In the description of the present invention, it is to be understood that the terms "central," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," and the like are used in the orientations and positional relationships indicated in the drawings for convenience in describing the invention and to simplify the description, and are not intended to indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and are not to be considered limiting of the invention.

In the description of the present invention, "the first feature" and "the second feature" may include one or more of the features.

In the description of the present invention, "a plurality" means two or more.

In the description of the present invention, the first feature being "on" or "under" the second feature may include the first and second features being in direct contact, and may also include the first and second features being in contact with each other not directly but through another feature therebetween.

In the description of the invention, "above", "over" and "above" a first feature in a second feature includes the first feature being directly above and obliquely above the second feature, or simply means that the first feature is higher in level than the second feature.

In the description herein, references to the description of the term "one embodiment," "some embodiments," "an illustrative embodiment," "an example," "a specific example," or "some examples" or the like mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

While embodiments of the invention have been shown and described, it will be understood by those of ordinary skill in the art that: various changes, modifications, substitutions and alterations can be made to the embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A valve train of an engine having a low pressure EGR system, comprising:

a rocker arm;

a cam having an outer periphery that abuts the rocker arm to urge the rocker arm to move when the cam rotates;

a valve provided on the rocker arm to move together with the rocker arm; wherein

The rocker arm is also provided with a driving piece, and the driving piece is suitable for driving the valve to move relative to the rocker arm;

the rocker arm is provided with a rocker arm oil duct, an oil cavity is formed in the rocker arm, one end of the rocker arm oil duct is communicated with the oil cavity, and the other end of the rocker arm oil duct is communicated with an oil inlet in the rocker arm;

a tappet is arranged at the lower end of the rocker arm, and a hollow oil duct of the tappet is communicated with an oil inlet on the rocker arm;

the hollow oil duct of the tappet is connected with an oil inlet pipe, and the oil inlet pipe is provided with an electromagnetic valve for controlling hydraulic oil to enter and exit the oil cavity.

2. The valve train of an engine having a low pressure EGR system of claim 1 wherein the upper end of the valve is disposed in the oil chamber, the oil chamber being selectively filled with hydraulic oil to urge the valve to move relative to the rocker arm.

3. The valve train of an engine having a low pressure EGR system of claim 2 wherein the upper end of the valve is provided with a movable pin that is slidably disposed within the oil cavity.

4. The valve train of an engine having a low pressure EGR system of claim 1 wherein the rocker arm has a rocker roller disposed thereon, and the cam has an outer periphery that abuts against the rocker roller.

5. The valve train of the engine with the low-pressure EGR system according to claim 4, wherein the rocker arm is provided with a pin hole, and two rocker arm rollers are symmetrically arranged on two sides of the pin hole.

6. A control strategy for an engine having a low pressure EGR system, wherein the valve train of any of claims 1-5 is employed, the control strategy comprising a normal mode and a warm-up mode.

7. The control strategy for an engine with a low-pressure EGR system according to claim 6, wherein said warm-up mode determining strategy comprises:

determining the current temperature of the engine oil and the ambient temperature;

determining warm-up time according to the current temperature of the engine oil and the ambient temperature;

when the accumulated time of the engine cold start is less than the warm-up time, the engine is in the warm-up mode.