Patent Publication Number: US-10316802-B2

Title: Exhaust gas recirculation device for vehicle

Description:
FIELD 
     The present disclosure relates to an exhaust gas recirculation (EGR) device for a vehicle and a method of recirculating exhaust gas. 
     BACKGROUND 
     The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
     In general, large amounts of harmful substances to humans such as carbon monoxide and nitrogen oxides are contained in exhaust gases emitted from a vehicle engine. Strict regulations are being enforced on nitrogen oxides because the nitrogen oxides are particularly harmful in that they contribute to acid rain, global warming, and respiratory problems. 
     The nitrogen oxides have the property that, as the combustion temperature of fuel in the engine increases, so does the amount of nitrogen oxides. 
     Many attempts have been made to reduce nitrogen oxide emissions, among which an exhaust gas recirculation (EGR) system is usually applied to vehicles. 
     The EGR system recirculates part of the exhaust gas emitted from the engine after fuel combustion to an intake system of the engine to direct it back to a combustion chamber of the engine. As a consequence, an air-fuel mixture decreases in density without a change in the air-fuel ratio of the air-fuel mixture, thus lowering the combustion temperature. 
     That is, the EGR system supplies a portion of exhaust gas to an intake manifold of the engine to direct it to the combustion chamber when there is a need to reduce nitrogen oxide emissions depending on the operating state of the engine. By doing so, exhaust gases help to decrease the density of the mixture to a lower level and therefore decrease the flame propagation velocity during fuel combustion. This suppresses an increase in combustion temperature and slows the fuel combustion, thereby suppressing the generation of nitrogen oxides. 
     Some EGR systems use a dedicated EGR cylinder type engine, where one engine cylinder supplies a high volume of exhaust gas to the EGR system at rates approaching 25% of exhaust gas being recirculated to the intake system of the engine. Such dedicated EGR systems can provide a slight supercharging effect. To attempt to control exhaust gas delivery to engine inlets equally and thereby increase engine stability, existing dedicated cylinder EGR systems attempt to restrict the exhaust gas recirculation flow and slow the passage of the EGR into the engine inlet stream. We have discovered that such existing dedicated cylinder EGR systems can be difficult to design and implement correctly, result in high pumping work and loss of fuel economy, and tend to be only effective at certain engine operating conditions due to varying gas flow rates. 
     SUMMARY 
     The present disclosure provides an exhaust gas recirculation (EGR) device for a vehicle and a method of recirculating exhaust gas from a dedicated cylinder of an engine. The EGR device and method use a mechanical device to capture, divide, and release EGR flow gas from a dedicated EGR cylinder in timed increments. 
     An Exhaust Gas Recirculation (EGR) mixer according to one form of the present disclosure includes a mixer tube, a first plate, and a second plate. The mixer tube has an outer wall extending between a first end and a second end. The outer wall of the mixer tube defines a central longitudinal axis about which the mixer tube rotates. The tube has a plurality of divider walls that extend radially between the longitudinal axis and the outer wall. The divider walls also extend longitudinally from the first end to the second end of the mixer tube. The divider walls define a plurality of mixing chambers therebetween. The first plate is rotatably disposed about the longitudinal axis at the first end of the mixer tube to selectively block off at least one chamber at the first end of the mixer tube. The first plate defines an opening therethrough sized to correspond to a first subset of the plurality of mixing chambers. The second plate is rotatably disposed about the longitudinal axis at the second end of the mixer tube to selectively block off at least one chamber at the second end of the mixer tube. The second plate defines an opening therethrough sized to correspond to a second subset of the plurality of mixing chambers. 
     According to one form, the first subset of the plurality of mixing chambers is approximately 25% of the plurality of mixing chambers, such that the first plate selectively blocks off approximately 75% of the chambers at the first end of the mixer tube. 
     In another form, the second subset of the plurality of mixing chambers is approximately 8% of the plurality of chambers, such that the second plate selectively blocks off approximately 92% of the chambers at the second end of the mixer tube. 
     According to one form of the present disclosure, rotation of the EGR mixer is driven by a timing belt that extends from an engine crankshaft. The mixer tube of the EGR mixer may be driven to rotate at a speed that is two times the operating speed of the engine crankshaft. The first plate of the EGR mixer may be driven to rotate at a speed that is half of the operating speed of the engine crankshaft. The second plate of the EGR mixer may be driven to rotate at a speed that is one and a half times the operating speed of the engine crankshaft. 
     In another form, the EGR mixer may also include an exhaust delivery tube configured to deliver exhaust gas from a dedicated cylinder of an engine to the first subset of the plurality of mixing chambers through the opening in the first plate. Exhaust gas may be delivered to the first subset of the plurality of mixing chambers only during an exhaust stroke of the dedicated cylinder of the engine. Additionally, the EGR mixer may also include an exhaust supply tube configured to supply exhaust from the second subset of the plurality of mixing chambers through the opening in the second plate to an intake manifold of an engine. 
     The present disclosure also provides an Exhaust Gas Recirculation (EGR) system for recirculating exhaust gas from a dedicated EGR cylinder of an engine to an intake manifold of the engine. The EGR system according to one form may include an EGR mixer having a mixer tube that has an outer wall extending between an inlet end and an outlet end and that defines a central longitudinal axis about which the mixer tube rotates. The tube has a plurality of divider walls that extend radially between the longitudinal axis and the outer wall and that extend longitudinally from the inlet end to the outlet end of the mixer tube. The plurality of divider walls define a plurality of mixing chambers therebetween. The EGR mixer also has a first plate rotatably disposed about the longitudinal axis at the inlet end of the mixer tube to selectively block off at least one chamber at the inlet end of the mixer tube. The first plate defines an opening therethrough sized to correspond to a first subset of the plurality of mixing chambers. The EGR mixer also has a second plate rotatably disposed about the longitudinal axis at the outlet end of the mixer tube to selectively block off at least one chamber at the outlet end of the mixer tube. The second plate defines an opening therethrough sized to correspond to a second subset of the plurality of mixing chambers. The EGR system also includes an exhaust delivery tube configured to deliver exhaust gas from the dedicated EGR cylinder of the engine to the first subset of mixing chambers through the opening in the first plate and an exhaust supply tube configured to supply exhaust from the second subset of mixing chambers to the intake manifold of the engine through the opening in the second plate. 
     According to one for, the exhaust gas may be delivered to the first subset of mixing chambers through the opening in the first plate only during an exhaust stroke of the dedicated cylinder of the engine. 
     In one form, the first subset of mixing chambers may include more mixing chamber than the second subset of mixing chambers. 
     In yet another form, the EGR system may also include at least one timing belt extending between a crankshaft of the engine and the EGR mixer to drive rotation of the mixer tube, the first block off plate, and the second block off plate based on an operating speed of the crankshaft. The mixer tube may be driven to rotate about the longitudinal axis at a first speed, the first plate may be driven to rotate about the longitudinal axis at a second speed, and the second plate may be driven to rotate about the longitudinal axis at a third speed. The first speed, the second speed, and the third speed may be correlated to the operating speed of the crankshaft by a fixed ratio. 
     The present disclosure also provides a method of recirculating exhaust gas from a dedicated cylinder of an engine to an intake manifold of the engine. In one form, the method includes providing an Exhaust Gas Recirculation (EGR) device having a tube having a plurality of chambers each having an inlet and an outlet; selectively blocking a first portion of the inlets of the plurality of chambers to store exhaust gas in selected chambers; and selectively blocking a second portion of the outlets of the plurality of chambers to control the supply of exhaust gas recirculated to the intake manifold of the engine. 
     In one form, the first portion of blocked inlets of the plurality of chambers is less than the second portion of blocked outlets of the plurality of chambers. 
     In another form, the first selectively blocking step may include rotating a first block off plate having a first opening at a first speed. Additionally, the second selectively blocking step may include rotating a second block off plate having a second opening at a second speed that is three times the first speed. The method may also include rotating the tube at a third speed that is four times the first speed. 
     Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       DRAWINGS 
       In order that the disclosure may be well understood, there will now be described various forms thereof, given by way of example, reference being made to the accompanying drawings, in which: 
         FIG. 1  is a schematic drawing of an engine having a dedicated cylinder exhaust gas recirculation system for a vehicle according to one form of the present disclosure; 
         FIG. 2  is an exploded isometric view of an exhaust gas recirculation mixer device for a vehicle according to one form of the present disclosure; 
         FIG. 3A  is a front view of exhaust gas recirculation mixer device of  FIG. 2 ; 
         FIG. 3B  is a rear view of exhaust gas recirculation mixer device of  FIG. 2 ; 
         FIG. 4  is a flowchart showing a method of recirculating exhaust gas from a dedicated cylinder of an engine to an intake system of the engine according to one form of the present disclosure; and 
         FIG. 5  is a schematic of a gearing system interconnecting the engine and the exhaust gas recirculation mixer of  FIGS. 1-3 . 
     
    
    
     The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
     DETAILED DESCRIPTION 
     The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. 
       FIG. 1  is a schematic drawing of an engine having a dedicated cylinder exhaust gas recirculation system  11  for a vehicle according to one form of the present disclosure. As shown in  FIG. 1 , a dedicated cylinder exhaust gas recirculation system  11  for a vehicle (not shown) includes an engine  12  having a plurality of cylinders  15 ,  14 . At least one of the engine cylinders is configured to be a dedicated exhaust gas recirculation cylinder  14 . Air is supplied to the cylinders  15 ,  14  by an intake manifold  16 , which generally receives air from an air inlet  18 . Combustion gasses are exhausted from the non-EGR cylinders  15  through a typical exhaust manifold  20  and exhaust  21 . 
     Combustion gas produced by the dedicated cylinder  14 , i.e. EGR gas, is provided to the EGR device  10  through an exhaust delivery tube  22 . EGR gas enters the EGR device  10  through an EGR inlet  24  at a first/inlet end  41  of the EGR device  10 . EGR gas exits the EGR device  10  through an EGR outlet  26  at a second/outlet end  43  of the EGR device  10 . Upon exiting the EGR device  10 , the EGR gas is supplied to the air inlet  18  and intake manifold  16  by an exhaust supply tube  28 . Thus, the dedicated EGR cylinder  14  of the engine  12  supplies a high volume of exhaust gas to the EGR system  11  at rates approaching approximately 25% of exhaust gas being recirculated to the intake  16  of the engine  12 . The EGR device  10  captures and equally distributes exhaust gas from less than all cylinders in the engine, and thus the exhaust gas recirculation flow is stretched temporally to deliver the EGR gas steadily or equally over time. 
     As will be described in further detail below, a crankshaft  30  of the engine  12  drives the operation of the EGR device  10  by a timing belt  32  which extends between the crankshaft  30  and the EGR mixer  10 . 
     Referring to  FIG. 2 , an Exhaust Gas Recirculation (EGR) mixer  10  according to one form of the present disclosure includes a mixer tube  40 , a first plate  42 , and a second plate  44 . The mixer tube  40  has an outer wall  46  extending between a first end  41  and a second end  43 . The outer wall  46  of the mixer tube  40  defines a central longitudinal axis X about which the mixer tube  40  rotates. The first plate  42  serves as an inlet plate or disc that allows entrance of exhaust gas only during the exhaust stroke of the dedicated cylinder (or cylinders), and is closed off thereafter. The second plate  44  serves as an outlet plate or disc that directs the captured exhaust gas to the intake manifold in a timed manner that temporally stretched to provide improved distribution. 
     The tube  40  has a plurality of divider walls  48  that extend radially between the longitudinal axis X and the outer wall  46 . The divider walls  46  may start at the center of the tube  40 , or may be offset from the center of the tube  40 , as shown. The divider walls  48  also extend longitudinally, or parallel to the longitudinal axis X, along the length of the tube  40  from the first end  41  to the second end  43  of the mixer tube  40 . 
     The divider walls  48  define a plurality of mixing chambers  50  therebetween. The mixing chambers  50  may have a generally triangular shape, as shown, or any other suitable shape. The chambers  50  may be equally sized. As shown in  FIG. 2 , the mixer tube  40  has twelve divider walls  48  which define twelve chambers  50 ; however, the size and number of chambers  50  may be increased or decreased based on design requirements. 
     As shown in  FIGS. 2 and 3A , the first plate  42  is rotatably disposed about the longitudinal axis X at the first end  41  of the mixer tube  40  to selectively block off at least one chamber  50  at the first end  41  of the mixer tube  40 . The first plate  42  defines an opening  24  therethrough sized to correspond to a first subset of the plurality of mixing chambers  50 . According to one form, the first subset of the plurality of mixing chambers is approximately 25% of the plurality of mixing chambers  50 . For example, when the mixer tube  40  includes twelve chambers  50  as shown, the first subset of mixing chambers  50  may be approximately three chambers  50 . In this case, the opening  24  through the first plate  42  is sized to correspond to three chambers  50 . The rest of the first plate  42  selectively blocks off approximately 75% of the chambers  50 , or the remaining nine chambers  50 , at the first end  41  of the mixer tube  40 . Stated another way, the opening  24  in the first plate  42  spans about 90 degrees radially, or relative to the crank angle degree (CAD) spans from 540 CAD to 720 CAD to correspond to the exhaust stroke of the selected cylinder used for exhaust recirculation. During 0 to 540 CAD, no exhaust is captured by the device  10 . 
     As shown in  FIGS. 2 and 3B , the second plate  44  is rotatably disposed about the longitudinal axis X at the second end  43  of the mixer tube  40  to selectively block off at least one chamber  50  at the second end  43  of the mixer tube  40 . The second plate  44  defines an opening  26  therethrough sized to correspond to a second subset of the plurality of mixing chambers  50 . In one form, the second subset of the plurality of mixing chambers  50  is approximately 8% of the plurality of chambers  50 . For example, when the mixer tube  40  includes twelve chambers  50  as shown, the second subset of mixing chambers  50  may be approximately one chamber  50 . In this case, the opening  26  through the second plate  44  is sized to correspond to one chamber  50 . The rest of the second plate  44  selectively blocks off approximately 92% of the chambers  50 , or the remaining eleven chambers  50 , at the second end  43  of the mixer tube  40 . Stated another way, the opening  26  in the second plate  44  spans about 20 degrees radially. 
     The first and second plates  42 ,  44  may be circular as shown or any other suitable shape. Generally, the first subset of mixing chambers  50  includes more mixing chambers  50  than the second subset of mixing chambers  50 . 
     Referring again to  FIG. 1 , rotation of the EGR mixer  10  may be driven by a timing belt  32  that extends from an engine crankshaft  30  to an input shaft  52  of the mixer. The rotation speed of each of the mixer tube  40 , the first plate  42 , and the second plate  44  are based on an operating speed of the crankshaft  30 . The mixer tube  40  of the EGR mixer  10  may be driven to rotate at a first speed, which in one example is about two times the operating speed of the engine crankshaft  30 . The first plate  42  (i.e inlet plate or disk) of the EGR mixer  10  may be driven to rotate at a second speed, which in one example is about half of the operating speed of the engine crankshaft  30 . The second plate  44  (i.e. outlet plate or disk) of the EGR mixer  10  may be driven to rotate at a third speed, which in one example is one and a half times the operating speed of the engine crankshaft  30 . In this way, the first speed, the second speed, and the third speed are correlated to the operating speed of the crankshaft  30  by a fixed ratio. Rotating the various parts  40 ,  42 ,  44  of the EGR mixer  10  at different speeds results in the first plate  42  and second plate  44  selectively blocking off and opening different chambers  50  as the plates  42  and  44  rotate. 
     Stated another way, the mixer tube  40  rotates one full revolution for each full dedicated cylinder exhaust stroke, thereby capturing the full volume of EGR gas in relatively equal volumes. The inlet or first plate  42  rotates to correspond to the exhaust stroke of the dedicated cylinder, while the outlet or second plate  44  rotates faster than the first plate  42 , but slightly slower than the mixer tube  40 , to release the exhaust gas in a given chamber of the tube  40  at equally spaced intervals. In this way, the mixer  10  is timed to the engine&#39;s exhaust port open timing to provide dedicated, controlled exhaust. 
     The relative rotation of the first plate  42 , mixer tube  40 , and second plate  44  at different speeds (e.g. at ½ times, 2 times, and 1.5 times of crankshaft speed, respectively) may be accomplished by using a gearing system such as a form of planetary gear system, or using belts and pulleys or the like, as well as co-axial shafts that surround the driven input shaft and connect to the three elements. One example of a geared system is shown in  FIG. 5 . The input shaft  52  is driven at one-half engine speed, e.g. through appropriately sized pulleys and belt  32  ( FIG. 1 ), although a geared connection could also be used to link the input shaft  52  to a shaft from the engine. The input shaft  52  is directly connected to first gear  54  for continuous rotation therewith, and is also directly connected to the first (inlet) plate  42  for continuous rotation therewith at about ½ crankshaft. 
     A second gear  54  and a third gear  56  float on the input shaft  52  for rotation relative thereto. The second gear  54  drives rotation of the mixer cylinder  40 , e.g. through a tubular sleeve fit over the input shaft, while the third gear  56  drives rotation of the second plate  44 , e.g. also through a tubular sleeve fit over the input shaft and the other tubular sleeve of the second gear  54 . The first gear  54  is operatively connected to the second gear  56  through gears  62  and  64  which are drivingly connected via a common shaft. Through sizing of the gears, the second gear  56 , and hence the mixer cylinder  40 , may be driven at a higher speed such as twice (2×) the engine crankshaft, or four times (4×) the speed of the first inlet plate  42 . 
     The first gear  54  is also operatively connected to the third gear  58  through gears  66  and  68  which are connected via a comment shaft. Through sizing of the gears, the third gear  58 , and hence the second outlet plate  44 , may be driven at a higher speed such as three times (3×) the speed of the first inlet plate  42 . In one representative example, for every two (2) revolutions of the engine crankshaft, the rotating elements of the mixer may have the following rotation: one (1) rotation of the first plate  42 , four (4) rotations of the mixer cylinder  40 , and three (3) rotations of the second plate  44 . For example, if the crankshaft is spinning at about 1000 RPM, the first plate  42  may spin at about 500 RPM, the mixer cylinder may spin at about 2000 RPM, and the second plate  44  may spin at about 1500 RPM. Different ratios of these rotating elements may be selected by the skilled artisan based on the size of the engine, the number of cylinders being recirculated, the size and number of chambers in the mixer cylinder  40 , and the size of the inlet and outlet openings in the first and second plates  42 ,  44 . 
     EGR gas may be delivered to the EGR mixer  10  through an exhaust delivery tube  22  configured to deliver exhaust gas from a dedicated cylinder  14  of an engine  12  to the first subset of the plurality of mixing chambers  50  through the opening  24  in the first plate, i.e. the mixer  10  inlet. EGR gas is delivered to the first subset, i.e. the open chambers  50 , of the plurality of mixing chambers  50  during an exhaust stroke of the dedicated cylinder  14  of the engine  12 . EGR gas is recirculated to the intake  18  and the intake manifold  16  from the EGR mixer  10  may by an exhaust supply tube  28  configured to supply exhaust from the second subset of the plurality of mixing chambers  50 , i.e. the open chambers  50  at the second end  43 , through the opening  26  in the second plate  44 . 
     Referring now to  FIG. 4 , a method  100  of recirculating exhaust gas from a dedicated cylinder of an engine to an intake manifold of the engine is shown. The method includes providing an Exhaust Gas Recirculation (EGR) device  10  having a tube  40  having a plurality of chambers  50  each having an inlet  41  and an outlet  43  at step S 110 . The method continues by selectively blocking a first portion of the inlets  41  of the plurality of chambers  50  to store exhaust gas in selected (open) chambers  50  at step S 120 , and selectively blocking a second portion of the outlets  43  of the plurality of chambers  50  to control the supply of exhaust gas recirculated to the intake manifold  16  of the engine  12  at step S 130 . The first portion of blocked inlets  41  of the plurality of chambers  50  may be less than the second portion of blocked outlets  43  of the plurality of chambers  50 . 
     The first selectively blocking step S 120  may include rotating a first block off plate  42  having a first opening  24  at a first speed. Additionally, the second selectively blocking step S 130  may include rotating a second block off plate  44  having a second opening  26  at a second speed that is three times the first speed. The method may also include rotating the tube  40  at a third speed that is four times the first speed. 
     While this present disclosure has been described in connection with what is presently considered to be practical exemplary forms, it is to be understood that the present disclosure is not limited to the disclosed forms. On the contrary, it is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the present disclosure.