阅读说明：本技术 发动机废气再循环装置及其控制方法 (Engine exhaust gas recirculation device and control method thereof ) 是由 陈欢 王绍明 程传辉 徐政 武涛 于 2019-08-27 设计创作，主要内容包括：本发明公开了一种发动机废气再循环装置及其控制方法,该装置包括与排气管连接的第一管路、第二管路以及与进气管连接的第三管路；第二管路上设有EGR阀和EGR冷却器；第一管路与催化器前侧的排气管连接；还包括连接催化器后侧的排气管与第二管路的第四管路；第二管路的出气端分出一条支路与三管路连接,支路上设有压气机；还包括第一、第二切换阀,第一切换阀能够在第一、第二管路导通且第四、第二管路截断的位置,和第一、第二管路截断且第四、第二管路导通的位置之间切换；第二切换阀能够在第二、第三管路导通且第三管路与支路截断的位置,和第二、第三管路截断且第三管路与支路导通的位置之间切换。该装置能够实现EGR收益最大化。(The invention discloses an engine exhaust gas recirculation device and a control method thereof, wherein the device comprises a first pipeline, a second pipeline and a third pipeline, wherein the first pipeline is connected with an exhaust pipe; an EGR valve and an EGR cooler are arranged on the second pipeline; the first pipeline is connected with an exhaust pipe on the front side of the catalyst; the fourth pipeline is used for connecting the exhaust pipe at the rear side of the catalyst with the second pipeline; the air outlet end of the second pipeline is divided into a branch which is connected with the three pipelines, and a compressor is arranged on the branch; the first switching valve can be switched between a position where the first pipeline and the second pipeline are communicated and the fourth pipeline and the second pipeline are cut off and a position where the first pipeline and the second pipeline are cut off and the fourth pipeline and the second pipeline are communicated; the second switching valve can be switched between a position where the second pipeline and the third pipeline are communicated and the third pipeline and the branch are cut off and a position where the second pipeline and the third pipeline are cut off and the third pipeline and the branch are communicated. The device can realize the maximization of EGR benefit.)

1. The engine exhaust gas recirculation device is characterized by comprising a first pipeline, a second pipeline and a third pipeline, wherein the first pipeline is connected with an exhaust pipe of an engine, the third pipeline is connected with an air inlet pipe of the engine, and the first pipeline is connected with the third pipeline through the second pipeline; an EGR valve and an EGR cooler are arranged on the second pipeline;

the connection point of the first pipeline and the exhaust pipe is positioned on the front side of a catalyst arranged on the exhaust pipe; the gas inlet end of the fourth pipeline is connected with the exhaust pipe on the rear side of the catalyst, and the gas outlet end of the fourth pipeline is connected with the gas inlet end of the second pipeline; a branch is divided from the air outlet end of the second pipeline and is connected with the three pipelines, and a compressor is arranged on the branch;

the first switching valve can be switched between a position where the first pipeline is communicated with the second pipeline and the fourth pipeline is cut off from the second pipeline and a position where the first pipeline is cut off from the second pipeline and the fourth pipeline is communicated with the second pipeline;

the second switching valve can switch between a position where the second pipeline is communicated with the third pipeline and the third pipeline is cut off from the branch, and a position where the second pipeline is cut off from the third pipeline and the third pipeline is communicated with the branch.

2. The engine exhaust gas recirculation apparatus according to claim 1, characterized in that a pressure stabilizing member for reducing fluctuations in the EGR gas flow is provided on the first pipe.

3. The engine exhaust gas recirculation apparatus according to claim 2, characterized in that the pressure-stabilizing member includes a tank storing water, an inlet of the tank communicating with the first pipe.

4. The engine exhaust gas recirculation device according to claim 3, wherein a drain hole is formed in a bottom wall of the box body, a float, a guide rod, a sealing element and an elastic element are arranged in the box body, a fixing plate is fixedly connected to an inner peripheral wall of the box body, the fixing plate is parallel to the bottom wall of the box body, the guide rod penetrates through the fixing plate and can slide relative to the fixing plate, the float is connected with the sealing element through the guide rod, and the float and the sealing element are located on two sides of the fixing plate; the elastic piece is sleeved on the guide rod, and two ends of the elastic piece are respectively abutted against the sealing piece and the fixing plate; the floater can drive the sealing element to move under the action of water buoyancy and the elastic element so as to open or close the drain hole.

5. The engine exhaust gas recirculation apparatus according to claim 4, wherein a heat radiating fin is attached to the outer peripheral wall of the case.

6. The engine exhaust gas recirculation apparatus according to claim 4, wherein the pressure stabilizing member further includes a partition plate having a plurality of vent holes, the partition plate being fixedly disposed in the third pipe and protruding into the case through an inlet of the case, the partition plate being disposed perpendicular to an axis of the third pipe.

7. Engine exhaust gas recirculation arrangement according to claim 1, characterized in that the compressor is embodied as an electric compressor or a constant volume pump.

8. The engine exhaust gas recirculation device according to any one of claims 1 to 7, further comprising a controller communicatively connected to the EGR valve, the first switching valve, the second switching valve, and the compressor, the controller configured to control an opening degree of the EGR valve, an operating position of the first switching valve, an operating position of the second switching valve, and a rotational speed of the compressor.

9. A control method of an engine exhaust gas recirculation apparatus according to any one of claims 1 to 8, characterized by comprising:

when the EGR demand of the engine is judged to be a first demand, the EGR valve is opened, and the opening degree of the EGR valve is adjusted to be in a first opening degree range; switching the first switching valve to a working position where the first pipeline and the second pipeline are cut off and the fourth pipeline and the second pipeline are communicated; switching the second switching valve to a working position where the second pipeline is communicated with the third pipeline and the branch are cut off;

when the EGR demand of the engine is judged to be a second demand, the EGR valve is opened, and the opening degree of the EGR valve is adjusted to be in a second opening degree range; switching the first switching valve to a working position at which the first pipeline is communicated with the second pipeline and the fourth pipeline is cut off from the second pipeline; switching the second switching valve to a working position where the second pipeline is communicated with the third pipeline and the branch are cut off;

when the EGR demand of the engine is judged to be a third demand, the EGR valve is opened, and the opening degree of the EGR valve is adjusted to a full-open position; switching the first switching valve to a working position at which the first pipeline is communicated with the second pipeline and the fourth pipeline is cut off from the second pipeline; switching the second switching valve to a working position where the second pipeline and the third pipeline are cut off and the third pipeline is communicated with the branch, and simultaneously starting the compressor;

wherein the first demand is less than the second demand, the second demand is less than the third demand, the first opening range is less than the second opening range, and the second opening range includes a fully open position.

10. The control method according to claim 9, characterized by further comprising:

when the transient fluctuation of the engine is judged to be larger than a set value, the EGR valve is opened, and the opening degree of the EGR valve is adjusted to a full-open position; switching the first switching valve to a working position where the first pipeline and the second pipeline are cut off and the fourth pipeline and the second pipeline are communicated; and switching the second switching valve to a working position where the second pipeline and the third pipeline are cut off and the third pipeline and the branch are communicated, and simultaneously starting the compressor.

Technical Field

The invention relates to the technical field of engines, in particular to an engine exhaust gas recirculation device and a control method thereof.

Background

The Exhaust Gas Recirculation (EGR) technology of the engine is used for increasing the specific heat capacity of the mixed Gas in the combustion chamber, reducing the highest combustion temperature, reducing the generation amount of nitrogen oxides in the tail Gas, and improving the oil consumption of part load, so that the EGR technology is increasingly applied.

The existing EGR technology can be divided into internal EGR and external EGR, wherein the EGR rate which can be realized by the internal EGR is very limited, and the external EGR technology drives the exhaust gas of an engine to flow back to an air inlet system by the pressure difference between exhaust and the air inlet system, so that the EGR rate is influenced by the operation condition of the engine, and the maximum utilization of the EGR rate under each operation condition is difficult to realize.

In view of this, how to improve the existing engine exhaust gas recirculation device to control the EGR rate according to the operation condition of the engine, so as to well match the EGR requirement of each operation condition of the engine, and to maximize the EGR yield is a technical problem that needs to be solved by those skilled in the art.

Disclosure of Invention

The invention aims to provide an engine exhaust gas recirculation device, which can control the EGR rate according to the operation working condition of an engine, well match the EGR requirement of each operation working condition of the engine and improve the utilization efficiency of the exhaust gas recirculation device.

Another object of the present invention is to provide a control method of the above engine exhaust gas recirculation apparatus.

In order to solve the technical problem, the invention provides an engine exhaust gas recirculation device, which comprises a first pipeline, a second pipeline and a third pipeline, wherein the first pipeline is connected with an exhaust pipe of an engine; an EGR valve and an EGR cooler are arranged on the second pipeline;

the connection point of the first pipeline and the exhaust pipe is positioned on the front side of a catalyst on the exhaust pipe; the gas inlet end of the fourth pipeline is connected with the exhaust pipe on the rear side of the catalyst, and the gas outlet end of the fourth pipeline is connected with the gas inlet end of the second pipeline; a branch is divided from the air outlet end of the second pipeline and is connected with the three pipelines, and a compressor is arranged on the branch;

the first switching valve can be switched between a position where the first pipeline is communicated with the second pipeline and the fourth pipeline is cut off from the second pipeline and a position where the first pipeline is cut off from the second pipeline and the fourth pipeline is communicated with the second pipeline;

the second switching valve can switch between a position where the second pipeline is communicated with the third pipeline and the third pipeline is cut off from the branch, and a position where the second pipeline is cut off from the third pipeline and the third pipeline is communicated with the branch.

The engine exhaust gas recirculation device provided by the invention has the advantages that the compressor is introduced into the EGR pipeline connected with the air inlet pipe, and meanwhile, a pipeline is respectively introduced from the front side and the rear side of the catalyst on the exhaust pipe of the engine to provide EGR exhaust gas for the air inlet pipe; after the arrangement, when the EGR demand of the engine is small, the pipeline at the rear side of the catalyst can be communicated with the air inlet pipe, the branch at which the air compressor is positioned is closed, the exhaust gas passing through the catalyst is relatively clean and has low temperature, when the EGR demand of the engine is medium, the pipeline at the front side of the catalyst can be communicated with the air inlet pipe, because the pressure at the front side of the catalyst is high, more exhaust gas can enter the air inlet pipe, when the EGR demand of the engine is high, the pipeline at the front side of the catalyst can be communicated with the air inlet pipe, the branch at which the air compressor is positioned is conducted, the air compressor is opened, the flow of the EGR exhaust gas is further increased under the action of the air compressor, so that the EGR rate is kept at relatively good strength, when the engine is in a working condition of large fluctuation of transient rapid acceleration or rapid deceleration, although the EGR demand is relatively small, the catalytic conversion efficiency of the catalyst is low, at the moment, EGR waste gas can be introduced from a pipeline at the rear side of the catalyst, and meanwhile, a branch where the compressor is located is conducted, so that the stable EGR rate is maintained by utilizing the supercharging supplementary effect of the compressor.

Therefore, the engine exhaust gas recirculation device can control the EGR rate according to different requirements of the engine, so that the EGR rate can be well matched with the EGR requirements of each operation condition of the engine, the utilization efficiency of the exhaust gas recirculation device is improved, and the benefit maximization of the exhaust gas recirculation device can be realized.

In the above-described engine exhaust gas recirculation apparatus, the first pipe is provided with a pressure stabilizing member for reducing fluctuations in the EGR gas flow.

The engine exhaust gas recirculation apparatus as described above, wherein the pressure stabilizing member includes a tank storing water, and an inlet of the tank communicates with the first pipe.

According to the engine exhaust gas recirculation device, the bottom wall of the box body is provided with the drain hole, the inside of the box body is provided with the floater, the guide rod, the sealing element and the elastic element, the inner peripheral wall of the box body is fixedly connected with the fixing plate, the fixing plate is parallel to the bottom wall of the box body, the guide rod penetrates through the fixing plate and can slide relative to the fixing plate, the floater is connected with the sealing element through the guide rod, and the floater and the sealing element are positioned on two sides of the fixing plate; the elastic piece is sleeved on the guide rod, and two ends of the elastic piece are respectively abutted against the sealing piece and the fixing plate; the floater can drive the sealing element to move under the action of water buoyancy and the elastic element so as to open or close the drain hole.

In the above engine exhaust gas recirculation apparatus, the outer peripheral wall of the case is connected with the heat radiation fins.

The engine exhaust gas recirculation device comprises a pressure stabilizing component, a third pipeline and a box body, wherein the pressure stabilizing component is arranged in the box body, the box body is provided with an inlet, the inlet of the box body is provided with a plurality of vent holes, the vent holes are arranged in the third pipeline, the baffle plate is fixedly arranged in the third pipeline and extends into the box body through the inlet of the box body, and the baffle plate is.

In the above engine exhaust gas recirculation apparatus, the compressor is specifically an electric compressor.

The engine exhaust gas recirculation device further comprises a controller, wherein the controller is in communication connection with the EGR valve, the first switching valve, the second switching valve and the compressor, and is used for controlling the opening degree of the EGR valve, the working position of the first switching valve, the working position of the second switching valve and the rotating speed of the compressor.

The present invention also provides a control method of an engine exhaust gas recirculation apparatus, which is the above exhaust gas recirculation apparatus, the control method comprising:

when the EGR demand of the engine is judged to be a first demand, the EGR valve is opened, and the opening degree of the EGR valve is adjusted to be in a first opening degree range; switching the first switching valve to a working position where the first pipeline and the second pipeline are cut off and the fourth pipeline and the second pipeline are communicated; switching the second switching valve to a working position where the second pipeline is communicated with the third pipeline and the branch are cut off;

when the EGR demand of the engine is judged to be a second demand, the EGR valve is opened, and the opening degree of the EGR valve is adjusted to be in a second opening degree range; switching the first switching valve to a working position at which the first pipeline is communicated with the second pipeline and the fourth pipeline is cut off from the second pipeline; switching the second switching valve to a working position where the second pipeline is communicated with the third pipeline and the branch are cut off;

when the EGR demand of the engine is judged to be a third demand, the EGR valve is opened, and the opening degree of the EGR valve is adjusted to a full-open position; switching the first switching valve to a working position at which the first pipeline is communicated with the second pipeline and the fourth pipeline is cut off from the second pipeline; switching the second switching valve to a working position where the second pipeline and the third pipeline are cut off and the third pipeline is communicated with the branch, and simultaneously starting the compressor;

wherein the first demand is less than the second demand, the second demand is less than the third demand, the first opening range is less than the second opening range, and the second opening range includes a fully open position.

The control method of the exhaust gas recirculation device has the same technical effects as those of the above-described exhaust gas recirculation device, and the discussion thereof will not be repeated.

The control method as described above, further comprising:

when the transient fluctuation of the engine is judged to be larger than a set value, the EGR valve is opened, and the opening degree of the EGR valve is adjusted to a full-open position; switching the first switching valve to a working position where the first pipeline and the second pipeline are cut off and the fourth pipeline and the second pipeline are communicated; and switching the second switching valve to a working position where the second pipeline and the third pipeline are cut off and the third pipeline and the branch are communicated, and simultaneously starting the compressor.

Drawings

FIG. 1 is a schematic block diagram of an embodiment of an engine exhaust gas recirculation apparatus according to the present invention;

fig. 2 is a schematic structural view of the voltage stabilization part shown in fig. 1;

fig. 3 is a schematic structural view of a diaphragm of the pressure stabilizing member of fig. 2.

Wherein, the one-to-one correspondence between component names and reference numbers in fig. 1 to 3 is as follows:

an engine 10, an intake pipe 11, an exhaust pipe 12, an air cleaner 13, a catalyst 14;

a first line 21, a second line 22, a third line 23, a fourth line 24, a branch line 25, an EGR valve 26, an EGR cooler 27, a compressor 28, a first switching valve 291, a second switching valve 292;

the pressure stabilizing member 30, the case 31, the drain hole 311, the float 32, the guide rod 33, the sealing member 34, the elastic member 35, the fixing plate 36, the partition plate 37, the vent hole 371, and the heat dissipating fin 38.

Detailed Description

In order that those skilled in the art will better understand the disclosure, the invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

For ease of understanding and brevity of description, the following description is provided in conjunction with an engine exhaust gas recirculation apparatus and a control method thereof, and the advantageous effects will not be repeated.

Referring to fig. 1, fig. 1 is a schematic structural diagram of an embodiment of an engine exhaust gas recirculation device according to the present invention.

An air cleaner 13 is arranged on an air inlet pipe 11 of the engine 10, a catalyst 14 is arranged on an exhaust pipe 12, and the catalyst 14 is usually a three-way catalyst and is used for purifying waste gas discharged by the engine 10.

The embodiment provides an exhaust gas recirculation arrangement comprising a first line 21, a second line 22, a third line 23, a fourth line 24 and a branch 25 from the second line 22.

The inlet end of the first pipeline 21 is connected with the exhaust pipe 12, the connection point is located at the front side of the catalyst 14, the first pipeline 21 is connected with the third pipeline 23 through the second pipeline 22, the outlet end of the third pipeline 23 is connected with the air inlet pipe 11, and the second pipeline 22 is provided with an EGR valve 26 and an EGR cooler 27.

The EGR valve 26 is used to open the second line 22 or block the second line 22, and the opening degree can be adjusted to determine whether to activate the exhaust gas recirculation device or to adjust the amount of exhaust gas entering the intake pipe 11 at the activation of the exhaust gas recirculation device.

In this embodiment, the inlet end of the fourth pipe 24 is connected to the exhaust pipe 12, and the connection point is located on the rear side of the catalyst 14, and the outlet end of the fourth pipe 24 is connected to the inlet end of the second pipe 22.

Hereinbefore, the front side of the catalyst 14 refers to the portion of the exhaust pipe 12 located in front of the inlet of the catalyst 14, and the rear side of the catalyst 14 refers to the portion of the exhaust pipe 12 located behind the outlet of the catalyst 14.

The exhaust gas recirculation device is provided with a first switching valve 291, the first switching valve 291 being switchable between two operating positions; when the first switching valve 291 is in its first operating position, the first line 21 is connected to the second line 22, and the fourth line 24 is disconnected from the second line 22, that is, at this time, the exhaust gas of the exhaust gas recirculation device is taken from the exhaust gas in the exhaust pipe 12 at the front side of the catalyst 14, that is, the exhaust gas directly discharged from the engine 10, and the exhaust gas that has not been catalytically converted by the catalyst 14; when the first switching valve 291 is in its second operating position, the first line 21 is blocked from the second line 22, and the fourth line 24 is open to the second line 22, i.e. when the exhaust gas of the exhaust gas recirculation device is taken from the exhaust gas in the exhaust pipe 12 behind the catalyst 14, i.e. from the relatively clean exhaust gas after catalytic conversion by the catalyst 14.

To simplify the piping arrangement, the first piping 21, the fourth piping 24, and the second piping 22 are in a three-way pipe structure, as shown in fig. 1, and the first switching valve 291 is a valve member and is disposed at the connection portion of the three piping.

It is understood that, in actual installation, the first pipeline 21 and the second pipeline 22 are separately connected, that is, the first pipeline 21 and the fourth pipeline 24 are not connected, and in this case, the first switching valve 291 may specifically include two valve elements for controlling on and off of the first pipeline 21 and the fourth pipeline 24.

In this embodiment, the outlet end of the second pipeline 22 is branched into a branch 25 to be connected with the third pipeline 23, and a compressor 28 is disposed on the branch 25.

The exhaust gas recirculation device is further provided with a second switching valve 292, the second switching valve 292 being switchable between two operating positions; when the second switching valve 292 is in its first operating position, the second line 22 is connected to the third line 23, and the third line 23 is disconnected from the bypass 25, i.e. the exhaust gas passing through the EGR cooler 27 and the EGR valve 26 flows directly to the third line 23 via the second line 22; when the second switching valve 292 is in its second operating position, the second line 22 is blocked from the third line 23, and the third line 23 is conducted to the branch line 25, i.e. the exhaust gas passing through the EGR cooler 27 and the EGR valve 26 flows to the third line 23 after passing through the second line 22 and the branch line 25 provided with the compressor 28.

To simplify the piping arrangement, the second piping 22, the third piping 23 and the branch 25 are also provided in a three-way pipe structure, as shown in fig. 1, and at this time, the second switching valve 292 is a valve member, which is disposed at the connection position of the three piping. Of course, the second switching valve 292 may also be two valve elements for controlling the on/off between the second pipeline 22 and the third pipeline 23, and between the branch 25 and the third pipeline 23, respectively.

In this embodiment, the exhaust gas recirculation apparatus further includes a controller connected in communication with the EGR valve 26, the first switching valve 291, the second switching valve 292, and the compressor 28, for controlling the opening degree of the EGR valve 26, the operating position of the first switching valve 291, the operating position of the second switching valve 292, and the rotational speed of the compressor 28. Specifically, the controller may be a vehicle controller, but may also be separately provided.

In this embodiment, the control method of the exhaust gas recirculation apparatus described above is based on the principle that the opening and closing of the EGR valve 26, the opening degree of the EGR valve 26, and the operating positions of the first switching valve 291 and the second switching valve 292 are controlled in accordance with the EGR demand of the engine 10.

It is understood that when the engine 10 does not require an exhaust gas recirculation device, the EGR valve 26 is controlled to be in a closed state, in which the exhaust gas discharged from the engine 10 cannot enter the intake pipe 11 through the corresponding line regardless of the operating positions of the first switching valve 291 and the second switching valve 292, and the EGR rate is zero. The EGR valve 26 may be normally closed and opened when needed.

The control method of the exhaust gas recirculation apparatus specifically includes:

when the EGR demand of the engine 10 is judged to be a first relatively low demand, the EGR valve 26 is opened, and the opening degree of the EGR valve 26 is adjusted to be in a first opening degree range; switching the first switching valve 291 to an operating position where the first line 21 and the second line 22 are blocked and the fourth line 24 and the second line 22 are connected; the second switching valve 292 is switched to a working position where the second pipeline 22 is communicated with the third pipeline 23, and the third pipeline 23 is cut off from the branch 25; at this time, since the EGR demand amount is relatively small, the opening degree of the EGR valve 26 can be adjusted within a relatively small first opening degree range, and the EGR exhaust gas taken from the exhaust gas on the rear side of the catalyst 14 is relatively clean and relatively low in temperature, enabling the combustion condition of the cylinders of the engine 10 to be effectively improved.

When the EGR demand of the engine 10 is judged to be a second medium demand, the EGR valve 26 is opened, and the opening degree of the EGR valve 26 is adjusted to be in a second opening degree range; switching the first switching valve 291 to an operating position where the first line 21 and the second line 22 are connected and the fourth line 24 and the second line 22 are disconnected; the second switching valve 292 is switched to a working position where the second pipeline 22 is communicated with the third pipeline 23, and the third pipeline 23 is cut off from the branch 25; at this time, the second demand is larger than the first demand, and more EGR gas is required, so the opening degree of the EGR valve 26 can be larger than that of the above regulation, that is, the second opening degree range is larger than the first opening degree range, and at the same time, the EGR gas is taken from the exhaust gas at the front side of the catalyst 14, and because the pressure at the front side of the catalyst 14 is larger, more exhaust gas can be cooled by the EGR cooler 27 and then enters the intake pipe 11 by using a larger pressure difference. Wherein the second opening range includes full opening, that is, within the second demand range, if the EGR demand of the engine 10 is large, the EGR valve 26 may be adjusted to full opening to meet the demand.

When it is judged that the EGR demand of the engine 10 is a third demand which is relatively high, the EGR valve 26 is opened, and the opening degree thereof is adjusted to the fully open position; switching the first switching valve 291 to an operating position where the first line 21 and the second line 22 are connected and the fourth line 24 and the second line 22 are disconnected; switching the second switching valve 292 to a working position where the second pipeline 22 and the third pipeline 23 are cut off and the third pipeline 23 and the branch 25 are communicated, and simultaneously starting the compressor 28; at this time, the third demand is larger than the second demand, the EGR valve 26 is adjusted to the full open position, the EGR exhaust gas is still taken from the exhaust gas on the front side of the catalyst 14, so that more exhaust gas is cooled by the EGR cooler 27 under a larger pressure difference and enters the intake pipe 11, and in this case, the exhaust gas flowing out from the second pipe 22 through the EGR cooler 27 and the EGR valve 26 flows to the third pipe 23 through the branch pipe 25, and the compressor 28 is operated to further increase the flow rate of the EGR exhaust gas, so that the EGR rate is maintained at a relatively better intensity.

When the compressor 28 is in operation, the rotation speed of the compressor can be changed according to the magnitude of the input voltage and the current, so as to meet the required EGR rate. Specifically, the compressor 10 is an electric compressor, and may be powered by a storage battery on the vehicle, and the input magnitude of the voltage and the current of the electric compressor may be controlled by the vehicle control unit.

Specifically, the compressor 10 may also be a constant volume pump, and on this basis, the lower band of the EGR flow rate may be known by measuring the rotation speed of the constant volume pump, so as to better control the EGR rate.

Obviously, the first demand is less than the second demand, which is less than the third demand; it is understood that the first requirement, the second requirement, and the third requirement are all range values.

The EGR demand of engine 10 is related to the operating conditions of engine 10, and the EGR demand versus operating conditions may be calibrated in advance.

Specifically, a relationship between the rotation speed and the load of the engine 10 and the EGR demand is formed with the goal of making the oil consumption and the performance of the engine 10 relatively optimal, and in practical application, the vehicle control unit monitors the current operating condition parameters (such as the rotation speed and the load) of the engine 10, and calls a pre-stored correspondence table to determine the EGR demand, and controls the valves of the exhaust gas recirculation device according to the EGR demand.

It will be appreciated that the first, second and third requirements are different for different models of engine 10, and are selected based on actual calibration.

Further, the control method further includes: when the transient fluctuation of the engine 10 is judged to be larger than a set value, the EGR valve 26 is opened, and the opening degree thereof is adjusted to a fully open position; switching the first switching valve 291 to an operating position where the first line 21 and the second line 22 are blocked and the fourth line 24 and the second line 22 are connected; the second switching valve 292 is switched to the working position where the second pipeline 22 and the third pipeline 23 are cut off and the third pipeline 23 and the branch 25 are communicated, and the compressor 28 is started at the same time.

The transient fluctuation of the engine 10 refers to a condition that the engine 10 is in transient rapid acceleration or rapid deceleration, the transient fluctuation can be represented by parameters such as acceleration, and the corresponding set value can be according toThe actual requirements. When the engine 10 is in a transient-fluctuating condition of rapid acceleration or rapid deceleration, the EGR demand is relatively small, the air-fuel ratio control of the engine 10 is unstable, the conversion efficiency of the catalyst 14 is reduced, and at this time, the exhaust gas passing through the catalyst 14 generates a large amount of gas pollutants which are not catalytically converted, such as HC, CO and NO_xWhen the gas is in a normal state, the EGR waste gas is controlled to be taken from the exhaust gas at the rear side of the catalyst 14, and the branch 25 is communicated, so that the compressor 28 works, the stable EGR rate can be maintained by matching the supercharging compensation function of the compressor 28, and the problem of dynamic delay of the differential pressure waste gas recirculation device is solved to a certain extent.

In this embodiment, a pressure stabilizing member 30 for reducing fluctuations in EGR gas flow is provided on the first pipe 21 directly connected to the intake pipe 11.

Referring to fig. 2 and fig. 3 in combination, fig. 2 is a schematic structural diagram of the voltage stabilizing component shown in fig. 1; fig. 3 is a schematic structural view of a diaphragm of the pressure stabilizing member of fig. 2.

In a specific embodiment, the pressure stabilizing member 30 includes a tank 31 storing water, and an inlet of the tank 31 is communicated with the third pipeline 23.

Thus, when the EGR gas flows to the tank 31 in the third pipeline 23, the flow space is increased due to the design of the tank 31, so that the EGR gas flow is buffered, the fluctuation of the EGR gas is reduced, and the function of stabilizing the pressure is achieved. Wherein the water stored in the tank 31 can prevent the EGR gas from leaking out.

In this embodiment, the pressure stabilizing component 30 is further provided with a drainage structure, specifically, a drainage hole 311 is formed in the bottom wall of the box 31, and a float 32, a guide rod 33, a sealing member 34 and an elastic member 35 are further arranged in the box 31, wherein the float 32 is connected with the sealing member 34 through the guide rod 33, and the float 32 can drive the sealing member 34 to move under the action of the water buoyancy and the elastic member 35 to open or close the drainage hole 311.

Obviously, the sealing member 34 corresponds to the position of the drain hole 311, and the float 32 can bring the sealing member 34 close to the drain hole 311 to close the drain hole 311 or far from the drain hole 311 to open the drain hole 311.

Specifically, a fixing plate 36 is fixedly connected to the inner peripheral wall of the box 31, the fixing plate 36 is parallel to the bottom wall of the box 31 and has a set distance with the bottom wall of the box 31, one end of the guide rod 33 close to the bottom wall is fixedly connected with a sealing element 34, the other end of the guide rod 33 penetrates through the fixing plate 36 and then is connected with the float 32, the guide rod 33 can slide relative to the fixing plate 36, the elastic element 35 can be a spring specifically and can be sleeved on the guide rod 33, and two ends of the elastic element 35 are respectively abutted to the sealing element 34 and the fixing plate 36.

More specifically, the outer peripheral wall of the tank 31 is connected with the heat dissipating fins 38, so that the EGR gas can flow into the intake pipe 11 after further heat exchange and cooling when flowing through the position of the tank 31, and condensed water generated by the heat exchange or condensed water carried in the EGR gas is retained in the tank 31.

In the orientation shown in fig. 2, when the water level in the tank 31 is high, under the action of the water buoyancy, the float 32 moves towards the inlet of the tank 31, and drives the guide rod 33 and the sealing member 34 to move upwards together, so as to open the drainage hole 311 to drain the condensed water in the tank 31, and the elastic member 35 is compressed in the process; when the water level drops, the buoyancy of the water applied to the float 32 is reduced, and at this time, the float 32, the guide rod 33 and the sealing member 34 are moved toward the bottom wall of the housing 31 by the restoring action of the elastic member 35, and the sealing member 34 blocks the water discharge hole 311 to prevent the EGR gas from leaking.

In a specific embodiment, the pressure stabilizing member 30 further includes a partition 37 having a plurality of vent holes 371, the partition 37 is fixedly disposed in the third pipeline 23 and extends into the tank 31 through an inlet of the tank 31, the partition 37 is perpendicular to an axis of the third pipeline 23, so that the EGR gas in the third pipeline 23 flows to the intake pipe 11 through the vent holes 371 of the partition 37, and the partition 37 prevents condensed water in the EGR gas from entering the intake pipe 11.

The engine exhaust gas recirculation device and the control method thereof provided by the invention are described in detail above. The principles and embodiments of the present invention are explained herein using specific examples, which are presented only to assist in understanding the method and its core concepts. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.