JP4247100B2 - Internal combustion engine with exhaust gas recirculation device - Google Patents

Description

  The present invention is applied to a diesel engine or the like, and includes an EGR passage that recirculates EGR (exhaust gas recirculation) gas obtained by extracting a part of exhaust gas from an exhaust passage of an engine (internal combustion engine) to an air supply passage. The present invention relates to an internal combustion engine with an exhaust gas recirculation (EGR) device.

An exhaust gas recirculation (EGR) device is an effective means for reducing nitrogen oxides (NOx) in exhaust gas in a diesel engine. The exhaust gas recirculation device is configured to recirculate EGR (exhaust gas recirculation) gas obtained by extracting a part of exhaust gas from the exhaust passage of the engine through the EGR passage to the air supply passage.
In such a diesel engine, in order to recirculate the exhaust gas smoothly as described above to exert the function of EGR, the exhaust pressure (exhaust gas pressure) in the exhaust passage where the EGR gas extraction portion of the EGR passage opens is set. It is necessary to increase the air supply pressure in the air supply passage where the EGR gas injection portion of the EGR passage opens.

As described above, as means for maintaining the exhaust pressure always higher than the supply air pressure, for example, on the exhaust turbine side of the supercharger as disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 11-62603). A variable displacement exhaust turbocharger is often used in which the nozzle area is reduced by the provided variable nozzle mechanism to increase the exhaust pressure upstream of the exhaust turbine.
In Patent Document 1, a nozzle vane that is rotatably supported by a nozzle mount attached to a turbine casing is provided, the driving force of an actuator is transmitted to a drive ring via a drive lever device, and the drive ring is rotated. By changing the capacity of the exhaust turbine by a variable nozzle mechanism configured to transmit to the nozzle vane via a ring assembly including a lever plate, rotate the nozzle vane, and change its blade angle, The exhaust pressure upstream of the exhaust turbine can be made higher than the supply pressure in the supply passage from the compressor.

  In Patent Document 2 (Japanese Patent Laid-Open No. 6-173781), a helical air supply port provided with a throttle for generating a swirl is provided, and an EGR passage is opened downstream of the throttle of the helical air supply port. Then, the EGR gas is recirculated into the supply port at the downstream portion of the throttle, the pressure of which is reduced by the throttle, and the pressure of the EGR gas injection part on the supply side is set to the pressure of the EGR gas extraction part on the exhaust side. Is always kept lower.

Japanese Patent Laid-Open No. 11-62603 Japanese Patent Application Laid-Open No. 6-173781

In an internal combustion engine with a variable displacement exhaust turbocharger having a variable nozzle mechanism disclosed in Patent Document 1, since there is a mechanical control operation part in high-temperature exhaust gas, the manufacture of the mechanical part Control errors are likely to occur due to tolerances, thermal deformation, and the like, and in an engine that performs EGR amount control by an exhaust gas recirculation (EGR) device, highly accurate EGR amount control is impossible.
In addition, when the exhaust pressure upstream of the exhaust turbine increases due to the variable nozzle mechanism, the turbocharger speed increases, and the intake air pressure on the downstream side of the compressor also increases accordingly, and the difference between the exhaust pressure and the supply air pressure is increased. The pressure is reduced, the increase in the amount of EGR is suppressed, and the desired EGR effect is difficult to obtain.

Further, in the internal combustion engine with an exhaust gas recirculation (EGR) device disclosed in Patent Document 2, a throttle for generating a swirl is provided in the air supply passage, and the pressure is reduced by installing the throttle in the air supply port. Since the opening of the EGR passage is formed in the part that has become, the throttle does not become a resistance to the EGR gas inflow, but the throttle causes an increase in the pressure loss of the supply air flow at the supply port, resulting in a decrease in engine performance To do.
In addition, since the throttle is installed in the air supply port, the structure of the air supply system becomes complicated and the engine manufacturing cost increases.
And so on.

  In view of the problems of the prior art, the present invention has a very simple structure without causing an increase in engine manufacturing cost, and without causing an increase in pressure loss of the supply air flow and a decrease in engine performance due to this. An object of the present invention is to provide an internal combustion engine equipped with an exhaust gas recirculation device capable of exhibiting a required EGR function by keeping the pressure of the EGR gas injection section always lower than the pressure of the EGR gas extraction section on the exhaust side. .

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The present invention achieves such an object, and the present invention includes an EGR passage that recirculates an EGR (exhaust gas recirculation) gas obtained by extracting a part of the exhaust gas from the exhaust passage of the engine to the supply passage. In an internal combustion engine with an exhaust gas recirculation device
The EGR passage is constituted by two EGR passages of a first and a second EGR passage, and each of the first and second EGR passages is a tangential port in which a low pressure is formed by a supply air flow in one supply port The first EGR passage opens in the vicinity of the rear wall surface of the vortex chamber, and the opening direction of the first EGR passage is set to a direction along the inner surface of the cylinder so as to promote swirl in the cylinder. the set in the direction toward the cylinder center so as to decelerate the swirl in the cylinder, the diameter of the opening of the first EGR passage (d _1), the diameter of the opening of the second EGR passage (d ₂ ) So that the swirl strength can be promoted during low engine speed or low load operation, and either one of the first and second EGR passages. In addition, an EGR control valve that adjusts the passage area of the EGR passage is provided on both sides, and the EGR control valve corresponds to the swirl strength in the combustion chamber that is set based on one or both of the engine speed and the load. It is characterized in that a controller for adjusting the opening degree of is provided .

According to such an invention, the pressure in the vicinity of the rear wall surface of the tangential port vortex chamber in the air supply port is reduced because the air supply air is separated from the air supply port wall surface. Therefore, since an opening on the air supply side through which the EGR gas is recirculated is provided on the rear wall surface of the tangential port vortex chamber where the low pressure is formed, the pressure of the EGR gas injection part on the air supply side is set on the exhaust side. It becomes possible to keep the pressure lower than the pressure of the EGR gas extraction portion.
Also, the first EGR passage in which the opening direction to the air supply port is set in a direction along the inner surface of the cylinder so as to promote the swirl in the cylinder, and the opening direction is directed to the cylinder center so as to decelerate the swirl in the cylinder. A second EGR passage set in the direction is also provided, and at the time of low-speed or low-load operation that requires swirling, EGR gas is ejected from the first EGR passage into the combustion chamber, and the EGR gas causes strong swirl. In the direction of reducing the swirl from the second EGR passage, the mixing of the air and the EGR gas and the injected fuel is promoted and the swirl needs to be decelerated. By jetting out and suppressing the swirl strength with the EGR gas and maintaining the proper swirl, stable fuel is maintained in the entire operation range. It is possible to occupy made the.

  That is, according to this invention, by using two EGR passages that are opened in two directions, a direction that promotes the swirl strength and a direction that decelerates the swirl strength, the NOx reduction effect and swirl that are the original functions of EGR are used. It is possible to achieve a combustion improvement effect by controlling the strength.

Further, the present invention, the diameter of the opening in the circumferential wall of the first EGR passage (d _1), larger than the diameter of the opening (d ₂₎ of the circumferential wall surface of the second EGR passage To do.
With this configuration, the amount of EGR gas is constant by the first EGR passage formed in the diameter (d ₁ ) of the opening and the second EGR passage formed in the diameter (d ₂ ) of the opening. And increasing the diameter (d ₁ ) of the opening portion of the first EGR passage opened in the direction of promoting the swirl strength in the cylinder, in particular, the swirl strength needs to be promoted. In the low rotation or low load operation, the effect of promoting the swirl strength by the ejection of the EGR gas from the first EGR passage can be further increased, and the mixing of the air and the EGR gas with the injected fuel can be promoted.

According to the present invention, an EGR control valve for adjusting the passage area of the EGR passage is provided in one or both of the first and second EGR passages, and engine operating conditions such as engine speed and engine load are provided. A controller for adjusting the opening degree of the EGR control valve corresponding to the swirl strength in the combustion chamber set based on
Specifically, the following configuration is preferable.
That is, an engine speed detector that detects the engine speed and a load detector that detects the engine load are provided, and the controller detects the engine speed value from the engine speed detector and the load. Based on one or both of the detected values of the engine load from the detector, the swirl strength corresponding to the detected value and the opening degree of the EGR control valve corresponding to the swirl strength are calculated, and the EGR control The valve is configured to be controlled to the calculated opening degree.

  If comprised in this way, the 1st EGR passage which set up the direction of opening to an air supply port in the direction which promotes the swirl strength in a cylinder, and the direction of opening in the direction which decelerates the swirl strength in a cylinder An EGR control valve is provided in one or both of the set second EGR passages, and the detected value of the engine speed or the engine load is set to the detected value of the engine speed or the engine load by a controller to which the detected value of the engine speed or the detected value of the engine load is input. Based on this, the swirl strength corresponding to the engine speed or the engine load is calculated, the proper opening of the EGR control valve corresponding to the swirl strength is calculated, and the EGR control valve is set to the proper opening. It is possible to control the amount of EGR gas and the swirl strength control by EGR gas with high accuracy depending on the engine operating conditions. Succoth can.

As described above, according to the present invention, the supply side EGR gas injection is provided by providing the supply side opening through which the EGR gas is recirculated on the rear wall surface of the tangential port vortex chamber where low pressure is formed. It is possible to keep the pressure of the part lower than the pressure of the EGR gas extraction part on the exhaust side.
This eliminates the need for a special device such as a swirl-generating throttle provided in the variable nozzle mechanism or the air supply passage, eliminates an increase in engine manufacturing cost with a very simple structure, and reduces the pressure loss of the air supply airflow. Therefore, the pressure of the EGR gas injection section on the supply side can be kept lower than the pressure of the EGR gas extraction section on the exhaust side, and the required EGR gas flow rate can be maintained. And the amount of NOx (nitrogen oxide) generated can be reduced.

  Further, according to the present invention, the first EGR passage in which the opening direction to the air supply port is set to a direction that promotes the swirl strength in the cylinder, and the opening direction is set to a direction in which the swirl strength in the cylinder is decelerated. By providing a set second EGR passage, it is possible to use two EGR passages that are open in two directions, a direction that promotes swirl strength and a direction that decelerates swirl strength. It is possible to combine the NOx reduction effect as a function and the combustion improvement effect by controlling the swirl strength.

Hereinafter, the present invention will be described in detail with reference to the embodiments shown in the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the component parts described in this example are not intended to limit the scope of the present invention only to specific examples unless otherwise specified. Only.
1 is a schematic cross-sectional view of a supply and exhaust system in a diesel engine with an exhaust gas recirculation device according to a reference example (schematic cross-sectional view taken along line AA in FIG. 2), and FIG. 2 is a schematic plan view of the supply and exhaust system. It is. FIG. 3 is a configuration diagram of an EGR system in a diesel engine with an exhaust gas recirculation device according to an embodiment of the present invention, and FIG. 4 is a control block diagram of the EGR system in the embodiment. FIG. 5 is a relationship diagram between the engine speed and engine load and the swirl strength in the embodiment, and FIG. 6 is a relationship diagram between the swirl strength and the EGR control valve opening in the embodiment.

1 and 2 showing the overall configuration of the air supply and exhaust system in the reference example, 9 is a combustion chamber of an engine (diesel engine), 5 is a cylinder, and 7 is provided in each cylinder (two may be one). It is an air supply valve. Reference numeral 6 denotes an air supply passage. As shown in FIG. 2, two air supply ports 2 opened and closed by the air supply valve 7 are branched from the air supply passage 6. 5a is the center of the cylinder.
Reference numeral 8 denotes an exhaust valve provided in each cylinder 5 by two (or one). Reference numeral 3 denotes two exhaust ports that are opened and closed by the exhaust valve 8. As shown in FIG. 2, the two exhaust ports 3 join to form an exhaust passage 4.

Reference numeral 1 denotes an EGR passage, which extracts a part of the exhaust gas branched from the EGR intake port 1e of the exhaust passage 4 and flowing through the exhaust passage 4 as EGR gas. As shown in FIG. 2, the EGR passage 1 is branched into two EGR passages 1a and 1b. The openings 1c and 1d of the EGR passages 1a and 1b are tangential ports of the two air supply ports 2 and 2, respectively. It is formed on the rear wall surface 2 a of the vortex chamber portion 14.
That is, in FIGS. 1 to 2, the tangential port vortex chamber portion 14 is a portion where the pressure decreases because the air supply air S is separated from the wall surface of the air supply port 2, and the air supply just above the air supply valve 7. The EGR passages 1 a and 1 b are formed in the rear wall surface 2 a that faces the tangential port vortex chamber portion 14.

  In this reference example, EGR gas which is a part of the exhaust gas taken in from the EGR intake port 1e of the exhaust passage 4 branches from the EGR passage 1 into two EGR passages 1a and 1b, and the tangential port vortex The tangential port vortex chamber portion 14 flows into the tangential port vortex chamber portion 14 through openings 1c and 1d formed in the rear wall surface 2a facing the chamber portion 14.

In the vicinity of the rear wall surface 2 a of the tangential port vortex chamber 14 in the air supply port 2, the pressure is low because the air supply air S is separated from the wall surface of the air supply port 2 as shown in FIG. 2.
Therefore, in such a reference example, the supply side opening 1c through which the EGR gas is recirculated through the EGR passages 1a and 1b to the rear wall surface 2a of the tangential port vortex chamber 14 where the low pressure is formed, and Since 1d is provided, it becomes possible to keep the pressure of the EGR gas injection portion on the supply air port 2 side lower than the pressure in the vicinity of the EGR intake port 1e on the exhaust passage 4 side, and constantly supply EGR gas at a required flow rate. Reflux to the side.

  Therefore, the supply wall side S has a very simple structure in which the supply side openings 1c and 1d through which the EGR gas is recirculated are provided on the rear wall surface 2a of the tangential port vortex chamber 14 where low pressure is formed. The pressure of the EGR gas injection part on the supply side can always be kept lower than the pressure of the EGR gas extraction part on the exhaust side without causing an increase in loss and a decrease in engine performance due to this. Thereby, the required EGR gas flow rate can be maintained and the amount of NOx (nitrogen oxide) generated can be reduced.

  Next, in FIG. 3 showing the configuration of the EGR system according to the embodiment of the present invention, the EGR passage 1 connected to the EGR intake port 1e (see FIG. 1) of the exhaust passage 4 has a single supply port. The EGR passage is branched into two EGR passages, one EGR passage 1f and a second EGR passage 1g. The first EGR passage 1f and the second EGR passage 1g are opened at positions as close as possible to the vicinity of the rear wall surface 2a of the tangential port vortex chamber portion 14 in the reference example.

Furthermore, the two EGR passage, the swirl intensity in the first EGR passage 1f opening direction of the cylinder 5 in clogging the combustion chamber 9 (see FIG. 1) in a direction which promotes as S ₁ in FIG. 2 set, is set in a direction for reducing the opening direction of the second EGR passage 1g as the combustion chamber 9 S ₂ in FIG. 2 the swirl strength in (see FIG. 1) within.

Further, the inner diameter d ₁ of the opening to the rear wall 2a of the which is the side that facilitates the swirl strength first EGR passage 1f, swirl strength on the side of deceleration is the second EGR passage larger form than the inner diameter d ₂ of the opening to the rear wall 2a.
According to this structure, holding the EGR gas amount constant by the second EGR passage 1g formed in the inner diameter d ₂ of the first EGR passage 1f an opening formed in the inner diameter d ₁ of the opening Te, by increasing the inner diameter d ₁ of the opened in a direction that promotes swirl strength openings of the first EGR passage 1f in the combustion chamber 9, low and require particular the promotion of swirl strength During rotation or low-load operation, the effect of promoting swirl strength due to the ejection of EGR gas from the first EGR passage 1f can be further increased, and mixing of air, EGR gas, and injected fuel can be promoted.

An EGR control valve (A) 10a is provided in the first EGR passage 1f to adjust the passage area of the first EGR passage 1f, and 10b is provided in the second EGR passage 1g. This is an EGR control valve (B) for adjusting the passage area of the EGR passage 1g. Reference numeral 11 denotes an EGR valve driving device that drives the EGR control valve (A) 10a and the EGR control valve (B) 10b to change their opening degrees.
12 is an engine speed detector for detecting the engine speed, and 13 is a load detector for detecting the engine load. Reference numeral 20 denotes an EGR valve drive device 11 by performing a calculation described later based on the detected value of the engine speed input from the engine speed detector 12 and the detected value of the engine load input from the load detector 13. A controller that outputs a control signal.

Next, the control operation by the controller 20 in this embodiment will be described with reference to FIGS.
The detected value of the engine speed from the engine speed detector 12 and the detected value of the engine load from the load detector 13 are input to the swirl strength calculator 21 of the controller 20.
Reference numeral 22 denotes a swirl strength setting unit, and as shown in FIG. 5, the relationship between the engine speed N, the engine load L, and the swirl strength F is set by mapping based on experimental results or simulation calculation results. . As shown in the figure, the swirl strength setting unit 22 is set to decrease as the swirl strength F, the engine speed N, or the engine load L increases.

In the swirl strength calculation unit 21, the swirl strength F corresponding to the detected value of the engine speed from the engine speed detector 12 and the detected value of the engine load from the load detector 13 is set as the swirl strength. Extracted from the map of the unit 22 and input to the EGR valve opening calculation unit 23.
Reference numeral 24 denotes a swirl strength / EGR valve opening setting unit. As shown in FIG. 6, the relationship between the swirl strength F and the opening E of the EGR control valve (B) 10b and the EGR control valve (A) 10a is The map is set based on the experimental result or the simulation calculation result.
As shown in FIG. 6, in the swirl strength / EGR valve opening setting section, the EGR control valve (B) 10b on the side for decelerating the swirl strength is operated in the region where the swirl strength F is reduced (decelerated). Thus, as the swirl strength F is increased, the opening degree of the EGR control valve (B) 10b is decreased, and in the region where the swirl strength F is increased (accelerated), the EGR control valve on the side where the swirl strength is increased. (A) It is set so that the opening degree of the EGR control valve (A) 10a is increased as the swirl strength F is increased by operating the 10a.

  In the EGR valve opening calculation unit 23, an EGR control valve (B) 10b and an EGR control valve (A) 10a corresponding to the swirl strength F calculated (extracted) by the swirl strength calculation unit 21. Is extracted from the map of FIG. 6 and input to the EGR valve drive device 11. The EGR valve driving device 11 drives the EGR control valve (B) 10b and the EGR control valve (A) 10a so as to have the proper opening.

  In this embodiment, either one of the EGR control valve (A) 10a or the EGR control valve (B) 10b is provided, and one EGR control valve is controlled by the controller 20 with the swirl strength F as described above. You may comprise so that EGR flow volume may be controlled.

  According to this embodiment, the first EGR passage 1f in which the opening direction to the air supply port 2 is set to a direction that promotes the swirl strength in the combustion chamber 9, and the swirl strength in the combustion chamber 9 is set to the opening direction. And a second EGR passage 1g set in a direction of decelerating the engine, and at the time of low rotation or low load operation that requires the promotion of swirl strength, EGR gas is discharged from the first EGR passage into the combustion chamber 9 The EGR gas is injected into the EGR gas to increase the swirl strength to promote the mixing of the air and the EGR gas with the injected fuel, and at the time of high rotation or high load operation that requires the swirl to be decelerated, the second EGR passage EGR gas is ejected from 1 g in the direction of decelerating the swirl (reducing the swirl strength), and the swirl strength is suppressed by the EGR gas to maintain an appropriate swirl. Ri, it is possible to occupy made stable combustion in all operating ranges.

  Further, according to this embodiment, the first EGR passage 1 f in which the opening direction to the air supply port 2 is set to a direction that promotes the swirl strength F in the combustion chamber 9, and the opening direction is set to the combustion chamber 9. The EGR control valve (A) 10a or the EGR control valve (B) 10b is provided in both or one of the second EGR passages 1g set in the direction in which the swirl strength F is decelerated, and the engine speed N is detected. Based on the detected value of the engine speed N or the engine load L, a swirl strength F corresponding to the engine speed N or the engine load L is calculated by the controller 20 to which the value or the detected value of the engine load L is input. Further, an appropriate opening degree of the EGR control valve (A) 10a or EGR control valve (B) 10b corresponding to the swirl strength F is calculated, and the EGR control The can be controlled to a proper degree according as it, and a control of the swirl strength by the EGR gas amount and the EGR gas can be made with high accuracy by the engine operating conditions.

  According to the present invention, the EGR gas injection part on the supply side is not increased without causing an increase in engine manufacturing cost with an extremely simple structure and without causing an increase in pressure loss of the supply air flow and a decrease in engine performance due to this. It is possible to provide an internal combustion engine including an exhaust gas recirculation device that can maintain the pressure always lower than the pressure of the EGR gas extraction portion on the exhaust side and exhibit the required EGR function.

It is a schematic sectional drawing (the AA line schematic sectional drawing of FIG. 2) of the air supply and exhaust system in the diesel engine with an exhaust-gas recirculation apparatus which concerns on the reference example of this invention. It is a schematic plan view of the air supply and exhaust system in the reference example. It is a block diagram of the EGR system in the diesel engine with an exhaust-gas recirculation apparatus based on the Example of this invention. It is a control block diagram of the EGR system in the embodiment. It is a relationship diagram of the engine speed in the said Example, an engine load, and swirl strength. It is a relationship diagram between the swirl strength and the EGR control valve opening degree in the embodiment.

Explanation of symbols

1, 1a, 1b EGR passage 1c, 1d opening 1e EGR inlet 1f first EGR passage 1g second EGR passage 2 air supply port 2a rear wall surface 3 exhaust port 4 exhaust passage 5 cylinder 6 air supply passage 7 air supply Valve 8 Exhaust valve 9 Combustion chamber 10a EGR control valve (A)
10b EGR control valve (B)
11 EGR valve drive device 12 Engine speed detector 13 Load detector 14 Tangential port vortex chamber 20 Controller

Claims (2)

In an internal combustion engine with an exhaust gas recirculation device provided with an EGR passage that recirculates EGR (exhaust gas recirculation) gas obtained by extracting a part of exhaust gas from an exhaust passage of an engine to an air supply passage,
The EGR passage is constituted by two EGR passages of a first and a second EGR passage, and each of the first and second EGR passages is a tangential port in which a low pressure is formed by a supply air flow in one supply port The first EGR passage opens in the vicinity of the rear wall surface of the vortex chamber, and the opening direction of the first EGR passage is set to a direction along the inner surface of the cylinder so as to promote swirl in the cylinder. the set in the direction toward the cylinder center so as to decelerate the swirl in the cylinder, the diameter of the opening of the first EGR passage (d _1), the diameter of the opening of the second EGR passage (d ₂ ) So that the swirl strength can be promoted during low engine speed or low load operation, and either one of the first and second EGR passages. In addition, an EGR control valve that adjusts the passage area of the EGR passage is provided on both sides, and the EGR control valve corresponds to the swirl strength in the combustion chamber that is set based on one or both of the engine speed and the load. An internal combustion engine with an exhaust gas recirculation device , characterized in that a controller for adjusting the opening of the exhaust gas is provided . An engine speed detector for detecting the engine speed and a load detector for detecting a load of the engine are provided, and the controller detects the detected value of the engine speed from the engine speed detector and the load detector. The swirl strength corresponding to the detected value and the opening degree of the EGR control valve corresponding to the swirl strength are calculated based on one or both of the detected value of the engine load from the engine load, and the EGR control valve 2. The internal combustion engine with an exhaust gas recirculation device according to claim 1, wherein the internal combustion engine is configured to control to the calculated opening degree .

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