Abstract:
In an exhaust gas recirculating device for an internal combustion engine, an EGR gas introduction port ( 32 ) for feeding EGR gas to an intake passage ( 20 ) includes an inlet end and an outlet end, and has a cross sectional area progressively increasing from the inlet end to the outlet end, the outlet end ( 49 ) opening out at an upper part of the intake passage. Because the EGR gas introduction port has a cross sectional area progressively increasing from the inlet end to the outlet end thereof, and the outlet end of the EGR gas introduction port opens out at an upper part of the intake passage, even when an intake flow is blown back from the engine main body, carbon and oil that may be contained in the EGR gas can be prevented from being deposited in the EGR gas introduction port, and this prevents the clogging of the EGR gas introduction port.

Description:
TECHNICAL FIELD 
     The present invention relates to a device for recirculating a part of exhaust gas of an internal combustion engine to an intake system thereof. 
     BACKGROUND OF THE INVENTION 
     Current internal combustion engines such as automotive internal combustion engines typically comprise an exhaust gas recirculating device (which is referred to as EGR device hereinafter) that recirculates a part of exhaust gas (which is referred to as exhaust gas recirculating gas or EGR gas hereinafter) to the intake system thereof for the purposes of improving fuel economy and reducing the NOx contents in the exhaust gas. 
     For such EGR devices, proposals have been made to prevent the clogging of an introduction port for introducing EGR gas into an intake passage. According to a proposal disclosed in Patent Document 1 (Japanese patent laid open publication No. 2008-75522), a distribution passage for EGR gas and blow-by gas is formed in a plate member provided between an intake manifold and a cylinder head in such a manner that a distribution passage outlet for blow-by gas (blow-by gas introduction port) is located downstream of a distribution passage outlet for EGR gas (EGR gas introduction port) with respect to the intake flow. Thereby, the structure around the intake passage of the engine can be simplified while the clogging of the distribution passage outlet for EGR gas with carbonized oil contents or the like that may be mixed in the blow-by gas can be avoided. 
     In a four-stroke engine, when an intake valve and an exhaust valve are simultaneously opened in an early part of an intake stroke (valve overlap), or when an intake valve is not fully closed in an early part of a compression stroke, a backflow of intake flow from the cylinder head to the intake manifold can occur. However, according to the proposal disclosed in Patent Document 1, because the distribution passage outlet for EGR gas is provided adjacent to the main part of the intake flow, when such a backflow occurs, carbon particles and oil contained in the blow-by gas may be deposited on an area surrounding the distribution passage outlet for EGR gas, and this could cause a clogging of the distribution passage outlet for EGR gas. 
     BRIEF SUMMARY OF THE INVENTION 
     In view of such problems of the prior art, a primary object of the present invention is to provide an exhaust gas recirculating device for internal combustion engines that can avoid the clogging of an EGR gas introduction port due to deposition of carbon and oil even when a backflow of intake from the main part of the engine occurs. 
     A second object of the present invention is to provide an exhaust gas recirculating device for internal combustion engines that allows the passages for EGR gas and blow-by gas to be formed in a convenient and economical manner. 
     According to the present invention, such an object can be accomplished by providing an exhaust gas recirculating device for an internal combustion engine, comprising: an EGR passage member interposed between a main body of an internal combustion engine and an intake pipe, and defining an intake passage for conducting an engine intake from the intake pipe to an intake port of a cylinder head of the engine, an EGR passage for conducting exhaust gas of the engine into the intake passage and an EGR gas introduction port for introducing the exhaust gas from the EGR passage into the intake passage; wherein the EGR gas introduction port includes an inlet end and an outlet end, and has a cross sectional area progressively increasing from the inlet end to the outlet end, the outlet end opening out at an upper part of the intake passage. 
     Because the EGR gas introduction port has a cross sectional area progressively increasing from the inlet end to the outlet end thereof, and the outlet end of the EGR gas introduction port opens out at an upper part of the intake passage, even when an intake flow is blown back from the engine main body, carbon and oil that may be contained in the EGR gas can be prevented from being deposited in the EGR gas introduction port, and this prevents the clogging of the EGR gas introduction port. 
     The EGR gas introduction port may comprise a small diameter section formed in an inlet part thereof and a large diameter section formed in an outlet part thereof. Alternatively, the EGR gas introduction port may comprise a tapered configuration having a progressively increasing diameter from an inlet end to an outlet end thereof. 
     The EGR gas introduction port may be provided adjacent to an interface between the EGR passage member and the intake pipe. When the EGR gas introduction port is placed in a part remote from the engine main body in this manner, the back flow of the engine intake is less likely to reach the EGR gas introduction port, and this contributes to the prevention of the clogging of the EGR gas introduction port. 
     According to a preferred embodiment of the present invention, the EGR gas introduction port has an axial line that passes across a part of an inner passage of the intake pipe. This allows the EGR gas introduction port to be easily formed by drilling or the like. 
     According to a certain aspect of the present invention, the passage member is additionally formed with a blow-by gas passage for conducting blow-by gas of the engine to an intake port of the engine, and an inlet of the blow-by gas passage is provided on a side of the passage member remote from the engine while an outlet of the blow-by passage is provided in a part of the intake passage adjacent to the engine. Thereby, the passage for blow-by gas can be formed without requiring any additional components. 
     Typically, the engine comprises a plurality of cylinders arranged in a row, and the EGR passage member comprises a plurality of intake passages corresponding to the different cylinders of the engine and an EGR chamber interposed between the EGR passage and the inlet ends of the EGR gas introduction ports. In such a case, the exhaust gas recirculating device of the present invention may comprise an EGR control valve attached to an outer end of the passage member remote from the engine and having an inlet port and an outlet port, and the EGR passage may include a first part extending across the passage member from the engine to the inlet port of the EGR control valve and a second part extending from the outlet port of the EGR control valve to the EGR gas introduction port via an EGR chamber formed in the passage member. 
     The EGR chamber enables the exhaust gas to be distributed evenly to the different intake passages, and this also contributes to the prevention of the clogging of the EGR gas introduction ports. 
     According to a particularly preferred embodiment of the present invention, the passage member comprises a first member adjacent to the engine, a second member remote from the engine and a gasket interposed between the first member and second member, the first member is provided with a groove extending in a direction of the cylinder row on a side of the first member remote from the engine and defining an elongated chamber in cooperation with the gasket, one end of the elongated chamber being communicated with the second part of the EGR passage, and the second member is formed with the EGR chamber, an opening being formed in the gasket for communicating the elongated chamber with the EGR chamber. The first member may be integrally formed with a cylinder head of the engine or formed as a separate member. 
     If the gasket is formed with two openings communicating the elongated chamber with the EGR chamber, and one of the openings adjacent to the one end of the elongated chamber communicating with an upstream part of the second part of the EGR passage is smaller than the other opening, the EGR gas can be distributed evenly to the different cylinders of the engine. 
     In a particularly preferred embodiment of the present invention, the passage member is additionally formed with a bifurcated blow-by gas passage for conducting blow-by gas of the engine, and an inlet of the blow-by gas passage is provided on a side of the passage member remote from the engine while each of bifurcated outlets of the blow-by gas passage is provided in a part of the corresponding intake passage adjacent to the engine. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Now the present invention is described in the following with reference to the appended drawings, in which: 
         FIG. 1  is an exploded perspective view of an EGR device embodying the present invention; 
         FIG. 2  is a front view of an EGR plate used in the EGR device; 
         FIG. 3  is a rear view of the EGR plate; 
         FIG. 4  is a sectional view taken along line IV-IV of  FIG. 3 ; 
         FIG. 5  is a front view of a gasket used in the EGR device; 
         FIG. 6  is a rear view of the gasket; 
         FIG. 7  is a fragmentary sectional view of the EGR device; 
         FIG. 8  is an enlarged fragmentary sectional view of an EGR gas introduction port of the EGR device; 
         FIG. 9  is a view similar to  FIG. 8  showing an alternate embodiment of the EGR gas introduction port; 
         FIG. 10  is an exploded perspective view of the EGR device illustrating the flow of EGR gas; and 
         FIG. 11  is an exploded perspective view of the EGR device illustrating the flow of blow-by gas. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the following description, for the convenience of description, orientations of various parts are indicated by the notation defined in  FIG. 1  although the actual orientation of the various parts may vary depending on the actual orientation of the engine. Also, the engine of the illustrated embodiment consists of a four-cylinder engine, and corresponding components of different cylinder are denoted by adding a suffix a-b. For instance, an intake port is generally denoted with numeral  10 , and an intake port of any particular cylinder is denoted with numeral  10   a - 10   d . However, the present invention is not limited by this particular example, but may be applicable to engines of different types, such as single cylinder engines, in-line multiple cylinder engines and V-type multiple cylinder engines. 
       FIG. 1  is an overall exploded perspective view of an EGR device embodying the present invention, and  FIGS. 2-4  show an EGR plate  4  of the EGR device.  FIGS. 5 and 6  show a gasket  5  of the EGR device. 
     Referring to  FIG. 1 , an automotive in-line four-cylinder engine is provided with an EGR device  1  for recirculating a part of the exhaust gas of the engine to the intake system of the engine. The EGR device  1  comprises an intake connecting member  3  attached to a side part of a cylinder head  2  of the engine defining intake ports and an EGR plate  4  attached to the outer side of the intake connecting member  3  via a gasket  5 . The intake connecting member  3  may be integrally cast with the cylinder head  2  as in the illustrated embodiment, but may also be a separate member that is attached to the cylinder head by using suitable means such as threaded bolts and welding. To the outer side of the EGR plate  4  is attached an intake manifold  51  ( FIG. 7 ). The EGR device  1  further comprises an EGR control valve  6  attached to the EGR plate  4  for controlling the flow of the EGR gas according to the operating condition of the engine in a per se known manner. 
     The intake connecting member  3  of the cylinder head  2  is provided with four intake ports  10   a - 10   d  arranged laterally in a row (or along the cylinder row) in a mutually spaced apart relationship so as to correspond to the four cylinders of the engine. The intake connecting member  3  is additionally formed with an EGR gas outlet hole  11  for ejecting EGR gas from the cylinder head  2  to the EGR control valve  6 , an EGR gas inlet hole  12  for receiving EGR gas metered by the EGR control valve  6  and an EGR gas inlet groove  13  extending linearly above the intake ports  10  in the lateral direction of the engine (along the cylinder row of the engine). Each intake port  10  has a substantially circular opening, and is provided with a blow-by gas introduction groove  14  on a lateral side of the intake port  10  to introduce blow-by gas into the engine intake. A peripheral part of the intake connecting member  3  is provided with a plurality of threaded mounting holes  15  for attaching the EGR plate  4  and gasket  5  onto the intake connecting member  3 . Some of the threaded mounting holes  16  are used for the additional purpose of attaching the EGR control valve  6  to the EGR plate  4 . 
     The EGR plate  4  is a metallic plate member which may be formed by casting for instance, and is formed with intake passages  20   a - 20   d  corresponding to the intake ports  10   a - 10   d  of the intake connecting member  3 , respectively, for passing the engine intake from the intake manifold  51  to the cylinder head  2 . The peripheral part of the EGR plate  4  is formed with through holes  21  and  22  corresponding to the EGR gas outlet hole  11  and EGR gas inlet hole  12  of the intake connecting member  3  and through holes  23  and  24  corresponding to the threaded mounting holes  15  and  16  of the intake connecting member  3 . A blow-by gas inlet pipe  25  extends from a lower middle part of the front face of the EGR plate  4  for connecting a hose or pipe (not shown in the drawings) for supplying blow-by gas thereto. 
     As shown in  FIG. 3 , a pair of EGR slots  30 L and  30 R each having a rectangular shape are formed in the rear surface of the EGR plate  4  at positions corresponding to the EGR gas inlet groove  13  of the intake connecting member  3 . The EGR slots  30 L and  30 R form inlets of an EGR chamber  31  formed in the EGR plate  4  as best shown in  FIG. 4 . The EGR chamber  31  has the shape of an elongated rectangular solid, and extends in the direction of the cylinder row above the intake passages  20   a  to  20   d . The EGR chamber  31  communicates with four EGR gas introduction ports  32   a  to  32   d  at a lower front part thereof. 
     As shown in  FIG. 3 , the rear surface of the EGR plate  31  is additionally formed with a blow-by gas distribution groove  35  communicating with the blow-by gas inlet pipe  25 . The blow-by gas distribution groove  35  defines a bifurcated passage in cooperation with the gasket  5 , and comprises an upstream section  36  extending laterally under the two middle intake passages  20   b  and  20   c  and a pair of downstream sections  37  and  38  communicating with the upstream section  36  and extending laterally between the intake passages  20   a  and  20   b  and between the intake passages  20   c  and  20   d , respectively. The downstream sections  37  and  38  are aligned with a central line of the intake passages  20   a  to  20   d . As seen in a front view, the lateral ends of the downstream section  37  coincide with the blow-by gas introduction grooves  14   a  and  14   b  of the intake connecting member  3 , and the lateral ends of the downstream section  38  coincides with the blow-by gas introduction grooves  14   c  and  14   d  of the intake connecting member  3 , via openings formed in the gasket  5  as will be described hereinafter. 
     The gasket  5  is a thin plate member made of metallic material, and is interposed between the intake connecting member  3  and EGR plate  4  as shown in  FIG. 1 . Referring to  FIGS. 5 and 6 , the gasket  5  is formed with intake openings  40   a  to  40   d  at positions corresponding to the intake ports  10   a  to  10   d  of the intake connecting member  3  and the intake passages  20   a  to  20   d  of the EGR plate  4 . The peripheral part of the gasket  5  is formed with EGR gas openings  41  and  42  corresponding to the EGR gas outlet hole  11  and EGR gas inlet hole  12 , respectively, and mounting openings  43  and  44  corresponding to the threaded mounting holes  15  and  16  of the intake connecting member  3 , respectively. The gasket  5  is further formed with EGR gas distribution openings  45 L and  45 R for distributing EGR gas at positions corresponding to the EGR slots  30 L and  30 R (indicated by double-dot chain-dot lines in  FIG. 5 ) of the EGR plate  4  and the EGR gas introduction groove  13  (indicated by double-dot chain-dot lines in  FIG. 6 ) the intake connecting member  3 . The opening area of the EGR gas distribution opening  45 L adjacent to the communication passage (not shown in the drawing between the EGR gas inlet hole  12  and EGR gas introduction groove  13  is greater than the EGR gas distribution opening  45 R remote from the communication passage so that an adequate amount of EGR gas is introduced into the EGR chamber  31 , and the EGR gas is evenly distributed between the different cylinders. 
     As shown in  FIG. 6 , the gasket  5  is formed with blow-by gas introduction openings  50   a  to  50   d  at positions corresponding to the blow-by gas introduction grooves  14   a  to  14   d  (indicated by double-dot chain-dot lines in  FIG. 6 ) of the intake connecting member  3 . The opening area of each blow-by gas introduction openings  50  is smaller than the corresponding blow-by gas introduction groove  14  so that the amount of blow-by gas introduced into the intake ports  10  can be appropriately adjusted. The positions of the blow-by gas introduction openings  50   a  and  50   b  correspond to the two terminal ends of the downstream section  37 , and the positions of the blow-by gas introduction openings  50   c  and  50   d  correspond to the two terminal ends of the downstream section  38 . 
       FIG. 7  is a simplified sectional view of the EGR device shown in  FIG. 7 , and  FIG. 8  is an enlarged sectional view of the EGR gas introduction port shown in  FIG. 7 . 
     As shown in  FIG. 7 , the EGR gas introduction port  32  extends from a lower part of the EGR chamber  31  adjacent to the intake manifold  51 , and opens out at an upper part of the intake passage  20  as denoted with numeral  49 . The intake manifold  51  comprises an intake pipe  52  defining an internal passage connected to the intake passage  20 . The EGR gas introduction port  32  has an axial line X directed toward the intake manifold  51  (or toward the upstream of the intake passage  20 ), and extends across a part of the internal passage of the intake pipe  52 . As shown in  FIG. 8 , the EGR gas introduction port  32  has a small diameter section  55  in an inlet end thereof and a large diameter section  56  in a outlet end thereof so that the cross sectional area of the EGR gas introduction port  32  progressively increases from the inlet end thereof to the outlet end thereof. 
       FIG. 9  shows an alternate embodiment of the EGR gas introduction port  32  which is given a tapered shape whose cross sectional area progressively increases from the inlet end thereof to the outlet end thereof In  FIG. 9 , the parts corresponding to those of the previous embodiment are denoted with like numerals without repeating the description of such parts 
       FIGS. 10 and 11  are views similar to  FIG. 1  showing the flows of EGR gas and blow-by gas, respectively, by arrows. 
     Referring to  FIG. 10 , the EGR gas released from the cylinder head  2  and expelled from the EGR outlet hole  11  of the intake connecting member  3  is introduced into the EGR control valve  6 . The EGR control valve  6  adjusts the flow of the EGR gas from the EGR outlet hole  11  according to the operating condition of the engine, and forwards an adjusted amount of the EGR gas to the EGR inlet hole  12 . Thereafter, the EGR gas flows into the EGR gas introduction groove  13 , and passes through the EGR gas distribution openings  45 L and  45 R of the gasket  5 , and the EGR slots  30 L and  30 R (See  FIG. 3 ) of the EGR plate  4 , before flowing into the EGR chamber  31 . The EGR gas in the EGR chamber  31  is fed into the intake passages  20  via the corresponding EGR gas introduction ports  32  (See  FIG. 5 ). 
     Because each EGR gas introduction port  32  opens out at an upper part of the corresponding intake passage  20 , even when a backflow of the intake from the cylinder head  2  should occur, heavier contents of the blow-by gas such as oil and carbon are allowed to flow in a lower part of the intake passage  20 , and is prevented from being deposited in a part adjacent to the EGR gas introduction port  32 . Because the axial line X of each EGR gas introduction port  32  is directed toward the intake manifold  51 , even when a backflow of the intake from the cylinder head  2  should occur, foreign matters such as carbon in the EGR gas and oil in the blow-by gas are prevented from flowing into the EGR gas introduction port  32 . 
     Because the cross sectional area of each EGR gas introduction port  32  progressively increases toward the outlet end thereof, even when foreign matters such as carbon and oil should be deposited in a part adjacent to the outlet end of the EGR gas introduction port  32 , an adequate opening area can be ensured for the EGR gas introduction port  32 , and the clogging of the EGR gas introduction port  32  can be effectively prevented. Also, the provision of a small diameter portion  55  in the inlet end of the EGR gas introduction port  32  (instead of reducing the diameter of the EGR gas introduction port  32  over the entire length thereof) allows the flow rate of the EGR gas to be appropriately adjusted. 
     Because the EGR chamber  31  having a relatively large volume is provided upstream of the EGR gas introduction ports  32 , the EGR gas can be evenly distributed to the different cylinders of the engine, and the clogging of the EGR gas introduction ports  32  can be effectively prevented. 
     When each EGR gas introduction port  32  opens out at a part of the intake passage  20  adjacent to the intake manifold  51 , and is therefore provided remote from the cylinder head  2  of the engine, the clogging of the EGR gas introduction port  32  can be effectively prevented because the engine backflow is prevented from reaching the EGR gas introduction port  32 . 
     When the axial line X of each EGR gas introduction port  32  passes across a part of the inner passage of the intake pipe  52  of the intake manifold  51 , the process of forming the EGR gas introduction port  32  can be simplified, and the manufacturing cost can be reduced. For instance, the EGR plate  4  is formed by casting, and the EGR gas introduction port  32  is formed by drilling. 
     Referring to  FIG. 11 , the blow-by gas received from the blow-by gas introduction pipe  25  flows into the upstream section  36  of the blow-by gas distribution groove  35  (See  FIG. 3 ) of the EGR plate  4 , and flows from the downstream sections  37  and  38  of the blow-by gas distribution groove  35  into the corresponding intake passages  20  via the corresponding blow-by gas introduction openings  50  and corresponding blow-by gas introduction grooves  14 . 
     In this case, because the blow-by gas distribution grooves  35  for introducing the blow-by gas into the intake passages  20  is formed in the rear surface of the EGR plate  4  facing the engine, the EGR gas introduction ports  32  can be spaced away from the blow-by gas introduction grooves  14  by using a simple structure. Thereby, the clogging of the EGR gas introduction ports  32  owing to the deposition of oil carried by the blow-by gas can be effectively avoided. 
     Although the present invention has been described in terms of a preferred embodiment thereof, it is obvious to a person skilled in the art that various alterations and modifications are possible without departing from the scope of the present invention which is set forth in the appended claims. 
     The contents of the original Japanese patent application on which the Paris Convention priority claim is made for the present application are incorporated in this application by reference.