DESC:FIELD OF THE INVENTION
[0001] The subject matter as described herein, relates generally to an internal combustion engine and more particularly, but not exclusively, to an exhaust gas recirculation system for use with an internal combustion engine, for purification of exhaust gases.
BACKGROUND OF THE INVENTION
[0002] A conventional automobile is powered by an internal combustion (IC) engine generally disposed at a lower half of the vehicle. This engine converts chemical energy into mechanical energy by combustion of air-fuel mixture within a combustion chamber of the engine. Upon combustion, the IC engine emits exhaust gases of various types into the environment. However, the control of these potentially hazardous emissions is necessary to limit the after-effects of the emissions, for enabling better air quality and adhere to emission norms of the respective territorial jurisdictions. With continous tightening in emission norms, controlling, cleaning and reducing harmful emissions in these engines has become an absolute necessity to meet the future legislative requirements.
[0003] Several emission control techniques are known in the prior art for preventing, controlling or minimizing the harmfulness of exhaust gases. These techniques vary based on target emissions such as carbon monoxide, hydrocarbons, smoke, various nitrogen oxides (NOx) and particulate matter among others. Conventionally, the NOx emissions are controlled by retarding the engine ignition timing which lead to a drop in fuel economy. So special control techniques were devised. Exhaust gas recirculation (EGR) is one such emission control technique mainly targeted to reduce NOx emissions where a portion of exhaust gases from the engine is recirculated back to the intake system to reduce the combustion temperature. Because NOx form primarily when a mixture of nitrogen and oxygen is subjected to high temperature, a lower combustion chamber temperature reduces the amount of NOx generated during the combustion.
[0004] The volume of recirculation of exhaust gas in the EGR systems as known in the available literature depends on various parameters specific to the engine design and intended reduction in NOx, and hence needs to be controlled for optimum performance of the engine. During routine engine operation, the exhaust port(s) emit exhaust gases with extremely high temperatures. Engines using EGR to lower their NOx emissions can attain lower emissions by cooling the recirculated exhaust gas. In a conventional EGR setup, several components are used which make the set up costly and space inefficient. For example, most EGR systems include at least one dedicated EGR cooler located between the exhaust manifold and the intake manifold of an engine. The EGR coolers cool the exhaust gas so that the exhaust gas has a lower latent heat content. The cooled exhaust gas and air mixture lowers the combustion temperatures in the combustion chamber, which results in less NOx produced from the engine.
[0005] However, this set up with atleast one EGR cooler is easy to implement in bigger liquid cooled engines in bigger vehicles like cars. But in smaller engines or small vehicles, it is difficult to implement because of space and layout constraints. The conventional setup also increases the number of components and thereby is not cost effective.

BRIEF DESCRIPTION OF THE DRAWINGS
[0006] The above and other features, aspects, and advantages of the subject matter will be better understood with regard to the following description and accompanying drawings where:
[0007] FIG. 1 shows a side view of a conventional three wheeled vehicle fitted with an IC engine according to the present invention.
[0008] FIG. 2(a) shows a side view of the IC engine in the installed condition with a cooling cowl.
[0009] FIG. 2(b) depicts a side view of the IC engine of FIG. 2(a) without cooling cowl.
[00010] FIG. 3 shows an illustrative top view of a portion of the cylinder head along the axis D-D’ of FIG. 2(b) according to an embodiment of the present invention.
[00011] FIG. 4 shows an exploded view of the EGR system installed in the cylinder head of the IC engine.
[00012] FIG. 5 shows a top perspective view of the IC engine along the axis D-D’ of FIG. 2(b) with the cooling cowl.
[00013] FIG. 6 shows a side perspective view of the IC engine to illustrate the cooling of the EGR system.
[00014] FIG. 7 shows the shows a top perspective view of the IC engine along the axis D-D’ with a carbon filter adopted in the EGR system.

DETAILED DESCRIPTION OF THE INVENTION
[00015] With NOx emission norms becoming stricter and now percolating to small engines, an EGR system to cater to these small engines is required subject to the aforementioned problems. Accordingly, it is an object of the present invention to provide a simple, fully mechanical, low cost EGR system usable in a small engine. It is another object of the present invention to reduce the temperature of exhaust gases before they are fed into the intake system without significantly altering the engine design and layout. The above system provides the following advantages such as a continuous EGR system without additional intercooler, it is easy to manufacture and cast the cylinder head, the carbon deposits are reduced and can be easily removed and serviced.
[00016] The present invention describes a port to port continuous exhaust gas recirculation system which re-circulates the cooled down exhaust gas from the exhaust system to reduce the NOx emissions. The cylinder head of the engine is configured to accommodate the EGR system according to the present invention. The EGR system is provided with a metering member and is routed in such a way that before entering the intake system, the exhaust gas is cooled down through the forced air cooling system of the engine. The cooled exhaust gas is then fed into the intake port. Thus, the air is cooled with the existing engine cooling system and without a conventional dedicated EGR intercooler. The EGR system according to the present invention uses the simple, low cost, metering member unlike a conventional EGR valve and hence recirculates the exhaust gas in a controlled way at a very low cost. The present EGR system reduces NOx emissions without affecting the engine’s fuel economy and rated engine specifications.
[00017] The present subject matter and its embodiments would now be described in greater detail in conjunction with the figures in the following description. The following description provides a convenient illustration for implementing exemplary embodiments of the invention. However, the description and the appended drawings are only used by those skilled in the art to understand the objects, features, and characteristics of the present invention and not to be used to confine the scope and spirit of the present invention. It is to be further noted that “front” and “rear”, and “left” and “right” wherever referred to in the ensuing description, refer to front and rear, and left and right directions as seen in a state of being seated on a seat of the vehicle and looking forward. In an embodiment, the vehicle is a three wheeled vehicle used as a passenger carrier. The internal combustion engine shown in ensuing drawings is a four stroke single cylinder IC engine with a rearwardly titled cylinder head mounted on the three wheeled vehicle. However, the concepts disclosed in the present invention can be practiced in other vehicles such as for a step-through type two wheeled scooter vehicle and other engines like a IC engine having horizontal axis.
[00018] FIG. 1 illustrates a side view of a conventional concerned three wheeled vehicle (hereafter referred to as vehicle) 100, and driven by an internal combustion (IC) engine (120). The vehicle can be used as a passenger carrier vehicle or a load carrier vehicle. It has a front cowl (101) supporting a windscreen (102). The lower portion of the front cowl (101) is connected to a front wheel (104) with a wheel cover (103) disposed in between. A handle bar assembly (109) is present behind the front cowl (101) which is used to operate the said three wheeled vehicle (100). The vehicle (100) is laterally divided into two halves along the line X-Y; an anterior portion (A) having a driver’s seat (107) while a posterior portion (P) having a long passenger seat (108) with a seating capacity of minimum three passengers. A rear compartment (106) is provided at a lower rear portion behind the passenger seat (108). The rear compartment (106) is positioned in the posterior portion (P) and is supported on a pair of rear wheels (105) located on either side of a longitudinal axis of the vehicle (100). The rear compartment (106) houses the IC engine (120) and other vehicular components.
[00019] FIG. 2(a) and 2(b) show a side view of the standalone IC engine (120) as installed in the vehicle (100). The IC engine (120) includes an engine casing (124), a cylinder block (121) coupled to the engine casing (124), and a cylinder head (122) coupled to an upper portion of the cylinder block (121). The cylinder head (122) is located above the cylinder block (121) and the engine casing (124) is located below the cylinder block (121), with the cylinder block (121) located between the cylinder head (122) and the engine casing (124). The cylinder block (121) has a centrally formed cylinder bore allowing a reciprocating piston to move slidably within the cylinder bore. A crankshaft (125) is rotatably supported in the engine casing (124). In an embodiment, the engine casing (124) covers a transmission system. The cylinder head (122) comprises of a valve train assembly and is covered by a cylinder head cover (123). The cylinder head cover (123) seals the components of the cylinder head (122). The IC engine (120) is made in a manner that the cylinder head cover (123), the cylinder head (122) and the cylinder block (121) are sequentially joined in a top to bottom direction and the cylinder head (122) is rearwardly titled according to frame layout of the vehicle (100). Accordingly, FIGs. 2(a) and 2(b) illustrates a vertical type engine where the cylinder block (121) is vertically oriented and disposed in such a way that the long axis of the cylinder block (121) is approximately perpendicular to the longitudinal axis of the crankshaft (125). However, the concepts disclosed herein are equally applicable on a horizontal engine.
[00020] The IC engine (120) is located in the closed rear compartment (106) of the vehicle (100). Hence, it is provided with a forced air cooling system to ensure optimum cooling of the IC engine (120) during its operation. The forced air cooling system comprises a cooling cowl (140) substantially covering the engine and a crankshaft operated cooling fan (126). In an embodiment, the cooling cowl (140) covers a substantial portion of the cylinder block (121) and the cylinder head (122) to keep the temperature in a combustion chamber (not shown) under control. The cooling cowl (140) comprises of a cowl inlet portion (141) facing one end portion of the crankshaft (125). The cooling fan (126) is rotatably disposed on said end portion of the crankshaft (125). The forced cooling air is channelized towards the cylinder head (122) through the profile of the cooling cowl (140).
[00021] FIG. 3 shows an exhaust gas recirculation system installed in the cylinder head (122) of the IC engine (120). In an embodiment, the cylinder head (122) comprises of at least two ports, namely an exhaust port (127) and an intake port (128) both of which communicate with the combustion chamber. The intake port (128) allows the combustible air-fuel mixture to enter the combustion chamber. After the mixture is combusted, the exhaust gases are taken out of the combustion chamber through the exhaust port (127). As shown in FIG. 5, the intake port (128) communicates with an inlet channel (130) in the cylinder head (122), and through an intake passage constituted therein the combustible mixture is supplied to the intake port (128) in the cylinder head (122). The exhaust port (127) communicates with an outlet channel (129) connected to a muffler through which the exhaust gases move out of the combustion chamber. To time the entry of combustible air-fuel mixture into the combustion chamber through the intake port (128) and the exit of exhaust gases from the combustion chamber through the exhaust port (127), the valve train assembly (not shown) having a plurality of valves is provided in the cylinder head (122).
[00022] The cylinder head (122) is further configured to receive and support the EGR system. It comprises of an exhaust removing opening (132) communicating with the outlet channel (129) and an intake introducing opening (133) communicating with the inlet channel (130). The exhaust removing opening (132) is formed laterally to the outlet channel (129) and the intake introducing opening (133) formed laterally to the inlet channel (130) when seen from a top view of the cylinder head (122). The intake introducing opening (133) and the exhaust removing opening (132) is casted integrally along with the rest of the cylinder head (122) during manufacturing of the same. The top view of the cylinder head (122) is the view as seen when the cylinder head (122) is cut across the axis D-D’ of the FIG. 2(b). The EGR system comprises of an EGR pipe (158), a first adapter (155-1), a second adapter (155-2), a first metering member (156-1) and a second metering member (156-2). In an embodiment, the EGR pipe (158) comprises of a first end portion (158A) functionally connected to the outlet channel (129), a second end portion (158B) functionally connected to the inlet channel (130) and a middle portion (158C) extending laterally outwardly of an outer peripheral surface (131) of the cylinder head (122) when seen in the top view along the D-D’ axis. In an embodiment, the first end portion (158A), the second end portion (158B) and the middle portion (158C) are integrally formed as one unit. The EGR pipe (158) is connected to the cylinder head (122) at the first end portion (158A) and the second end portion (158B).
[00023] The first adapter (155-1) and the second adapter (155-2) respectively functionally connect the exhaust port (127) and the intake port (128) of the cylinder head (122) to the EGR pipe (158). They provide support to the respective end portions of the EGR pipe. In an embodiment, the first adapter (155-1) is configured to be supported in the exhaust removing opening (132). The first end portion (158A) is received in the first adapter (155-1) and thus is connected to the exhaust removing opening (132). Similarly, the second adapter (155-2) is configured to be supported in the intake introducing opening (133). The second end portion (158B) is received in the second adapter (155-2) and connected to the inlet channel (130) through it. In a preferred embodiment, the first adapter (155-1) and the second adapter (155-2) include bosses. In an embodiment, the first adapter (155-1) and the second adapter (155-2) are casted along with the cylinder head (122) during manufacturing of the same. In another embodiment, the first adapter (155-1) and the second adapter (155-2) are separately inserted into the exhaust removing opening (132) and the intake introducing opening (133) respectively.
[00024] Further, the first metering member (156-1) is disposed between the first adapter (155-1) and the first end portion (158A) of the EGR pipe (158), and a second metering member (156-2) is disposed between the second adapter (155-2) and the second end portion (158B) of the EGR pipe. In an embodiment, the first metering member (156-1) and the second metering member (156-2) include a nozzle. The respective metering members have an orifice of predetermined diameter to control the flow of exhaust gas from the outlet channel (129) to the inlet channel (130).
[00025] The connection of one of the end portion, namely the first end portion (158A), of the EGR pipe (158) to the cylinder head (122) is now described in detail. The other end portion or the second end portion (158B) follows similar construction. The exhaust removing opening (132) extends inwardly from the outer peripheral surface (131) of the cylinder head (122) up to the outlet channel (129). Similarly, the intake introducing opening (133) extends inwardly from the outer peripheral surface (131) of the cylinder head (122) up to the inlet channel (130). One of the end portions of first adapter (155-1) is connected so as to be located close to the outlet channel (129) and at a location close to the exhaust port (127). As shown in FIG. 4, the first adapter (155-1) has a cylindrical cross section with a hollow inner construction. The end portion of the first adapter is connected to the outlet channel (129) protrudes out of an adapter body while the other end portion of the first adapter has a hollow opening to receive the first end portion (158A) of the EGR pipe (158). The first metering member (156-1) is located at endmost portion of the first end portion (158A). A first securing member (157-1) seals the first end portion (158A) of the EGR pipe to the other end portion of the first adapter. In an embodiment the first securing member includes a banjo bolt. Thus, the first end portion (158A) is connected to the exhaust removing opening (132) and hence to the outlet channel (129) through the first adapter (155-1). In an embodiment, the first metering member (156-1) has a one narrow end and a one other broad end. The first metering member (156-1) thus does not allow the full volume of exhaust gas leaving the exhaust port (127) to enter the EGR system. The volume of gas entering the EGR is metered according to the engine parameters and targeted emissions.
[00026] FIG. 5 shows a top perspective view of the IC engine (120) along the axis D-D’ of FIG. 2(b). The middle portion (158C) of the EGR pipe extends laterally outwardly of the outer peripheral surface (131) of the cylinder head (122) when seen in the top view along the D-D’ axis. Thus, the EGR pipe (158) is located at one side of the piston axis E-E’. According to an aspect of the present invention, the exhaust gas passing through the EGR pipe (158) is cooled down through the forced air cooling system of the engine (120). The cooling cowl (140) comprises of the cowl inlet portion (141), a cowl body (142) and a cowl outlet portion (143). In an embodiment, the cowl inlet portion (141) is located below the cowl body (142) and the cowl outlet portion (143) is located above the cowl body (142). When seen from the top view along the D-D’ axis, the cowl body (142) covers the engine substantially in a front to rear direction. The cowl outlet portion (143) further comprises of a front peripheral portion (143B) covering the front portion of the cylinder head (122) and a rear peripheral portion (143A) covering the rear portion of the cylinder head (122) in a front to rear direction of the vehicle (100).
[00027] According to an aspect, the EGR pipe (158) is positioned within the periphery of the cooling cowl (140) when seen in top view. More specifically, the middle portion of the EGR pipe (158) is positioned in the space between the cowl outlet portion (143) of the cooling cowl (140) and the outer peripheral surface (131) of the cylinder head (122). Thus, no portion of the EGR pipe (158) lies outside of the periphery of the cooling cowl in the front to rear direction of the vehicle. In an embodiment, the rear peripheral portion (143A) of the cowl outlet portion (143) is adjacent to the first end portion (158A) in the front to rear direction of the IC engine (120) and the front peripheral portion (143B) is adjacent to the second end portion (158B).
[00028] Further, the EGR pipe (158) is disposed downwardly or rearwardly of a spark plug socket (180) in said IC engine (120). In the engine as shown in FIG. 2(b), the EGR pipe is disposed downwardly of the spark plug socket.
[00029] FIG. 6 shows the cooling of the EGR pipe through the forced air cooling system of the engine. The incoming air (as shown by the arrows) is sucked into the cowl inlet portion (141) through the crankshaft operated cooling fan (126). In an embodiment, the cooling fan (126) is a centrifugal fan due to which the air after entering moves towards the cowl body (142) and then upwards to the cowl outlet portion (143). The forced air carries away the heat generated by the cylinder block (121), cylinder head (122) and cools the EGR pipe (158). The now hot air after cooling these components exits from the cowl outlet portion (143). Since the EGR pipe (158) is positioned within the periphery of the cooling cowl (140) right where the air enters from the cowl body to the cowl outlet portion (143), it is entirely cooled by the forced air. The forced air enables better cooling and leads to a temperature drop in the temperature of the exhaust gas passing within the EGR pipe before it reaches the inlet channel (130). The recirculated exhaust gas mixes with the incoming air mixture and dilutes the fresh mix which lowers the flame temperature and reduces the amount of excess oxygen. Since NOx is more readily formed at high temperatures, the EGR system limits the generation of NOx by keeping the temperatures low. Thus, without the need of any additional intercoolers or complex liquid cooling systems, the exhaust gas is cooled by the engine’s forced air cooling system.
[00030] In an embodiment, the first end portion (158A) of the EGR pipe (158) is connected to the outlet channel (129) close to the exhaust port (127) whereas the second end portion (158B) is connected to the inlet channel (130) substantially away from the intake port (128). This arrangement allows the exhaust gas being taken out from the outlet channel (129) to cover a long distance before reaching the inlet channel (130) thereby allowing it to cool sufficiently. It also increases the length of the EGR pipe so that it is optimally cooled to reduce the temperature of the exhaust gas flowing within the EGR pipe. FIG. 7 shows the shows a top perspective view of the IC engine (120) along the axis D-D’ of FIG. 2(b) with a carbon filter (160) on the first end portion (158A) of the EGR pipe (158) illustrating another embodiment. In another embodiment, the exhaust gas may contain carbon deposits so the carbon filter (160) may be provided in the first end portion of the EGR pipe to prevent them from depositing.
[00031] Further, as shown in FIG. 5, at least one stud hole (159) is provided between the exhaust removing opening (132) and the intake introducing opening (133) when seen from a top view of the cylinder head along the D-D’ axis. A stud passes through the at least one stud hole (159) to join the cylinder head (122) to the cylinder block (121). The stud hole (159) also allows the lubrication oil to pass through it so as to reach the valve train assembly in the cylinder head (122). More specifically, the at least one stud hole (159) is proximal to the intake introducing opening (133) and distal to the exhaust removing opening (132). This location prevents fouling of the exhaust removing opening (132) and the intake introducing opening (133) with the stud hole (159). Thus the chances of oil leak are minimized due to drilling of exhaust removing opening (132) and the intake introducing opening (133) in the cylinder head (122). The present invention also enables the proposed EGR system to be retrofitted in the cylinder head of the existing engines with minimal alterations.
[00032] The said EGR system is provided in an engine which is installed in a two wheeled and a three wheeled vehicle. The metering members are made of mild carbon steel and the adapter is made of a material from a group consisting of heat resistant plastic, alloy and metal.
[00033] From the foregoing description, it will be appreciated that the present invention offers many advantages including those described above. The exhaust gas tapped from the exhaust port is metered and its volume is controllable by changing the diameter of through hole of first metering member. The tapped exhaust gas is cooled through the forced air cooling system and is metered by the second metering member before it enters the inlet channel. The EGR gas flow can be controlled by changing the diameter of the metering members according to different engine requirements. The EGR system according to the present invention is simple, low cost and does not use a conventional costly and complex EGR valve and the dedicated EGR cooler. The EGR system is integrated with the cylinder head with minimum alterations to allow recirculation of exhaust gases in a controllable, low cost way. The EGR system uses the forced air cooling system of the engine to cool the exhaust gases rather than the costly intercooler arrangement. The EGR system in the present invention directly connects the exhaust port to intake port and hence does not require the present of a plenum chamber.
[00034] The present invention is thus briefly described. It will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the present invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the present invention.
,CLAIMS:We claim:
1. An internal combustion (IC) engine comprising:
a forced air cooling system to cool the IC engine (120);
a cylinder block (121), inside which the combustion of air-fuel mixture occurs and exhaust gases are generated as the result of the combustion;
a cylinder head (122) disposed above the cylinder block (121), said cylinder head (122) comprising:
an inlet channel (130) configured to allow entry of air-fuel mixture inside the cylinder block (121);
an outlet channel (129) configured to allow exit of exhaust gases out of the cylinder block (121);
wherein, the IC engine (120) comprising an EGR pipe (158), said EGR pipe having a first end portion (158A) connected to the outlet channel (129), a second end portion (158B) connected to the inlet channel (130), and a middle portion (158C) extending laterally outwardly of the outer peripheral surface (131) of the cylinder head (122), said EGR pipe (158) configured to continuously circulate at least a portion of the exhaust gases flowing through the outlet channel (129) back to the inlet channel (129); and said EGR pipe (158) is forced cooled through the forced air cooling system.
2. The IC engine (120) as claimed in claim 1, wherein the forced air cooling system comprises:
a cooling cowl (140) covering the cylinder head (122);
a crankshaft operated cooling fan (126) configured to admit atmospheric air inside the cooling cowl (140);
a cowl inlet portion (141) configured to receive atmospheric air from the crankshaft operated cooling fan (126);
a cowl body (142) surrounding one side of the IC engine (120) and the cylinder head (122) providing an air path for to circulate atmospheric air; and
a cowl outlet portion (143) located close to the cylinder head (122) to distribute the atmospheric air around the cylinder head (122).
3. The IC engine (120) as claimed in claim 2, wherein the EGR pipe (158) is positioned within the periphery of an upper portion of the cooling cowl (140) right where the atmospheric air enters from the cowl body (142) to the cowl outlet portion (143), and wherein the EGR pipe (158) is disposed downwardly and rearwardly of a spark plug socket (180) in said IC engine (120).
4. The IC engine (120) as claimed in claim 1, wherein the cylinder head (122) comprising:
an exhaust removing opening (132) formed laterally to the outlet channel (129);
an intake introducing opening (133) formed laterally to the inlet channel (130);
a first adapter (155-1) configured to be supported in the exhaust removing opening (132);
a second adapter (155-2) configured to be supported in the intake introducing opening (133);
said first end portion (158A) of the EGR pipe (158) is received in the first adapter (155-1) and connected to the exhaust removing opening (132);
said second end portion (158B) of the EGR pipe (158) is received in the second adapter (155-2) and connected to the intake introducing opening (133), and
said middle portion (158C) of the EGR pipe (158) extends laterally outwardly of the outer peripheral surface (131) of the cylinder head (122) when seen in the top view of the cylinder head (122).
5. The IC engine (120) as claimed in claim 4, wherein the first adapter (155-1) comprises a first nozzle (156-1) disposed between the first adapter (155-1) and the first end portion (158A) of the EGR pipe (158), and the second adapter (155-2) comprises a second nozzle (156-2) disposed between the second adapter (155-2) and the second end portion (158B) of the EGR pipe (158) to aid in circulation of metered quantity of exhaust gases through the EGR pipe (158).
6. The IC engine (120) as claimed in claim 4, wherein the first adapter (155-1) and the second adapter (155-2) is manufactured integrally with the cylinder head (122) by casting process.
7. The IC engine (120) as claimed in claim 4, wherein the first adapter (155-1) and the second adapter (155-2) is detachably attached to the cylinder head (122).
8. The IC engine (120) as claimed in claim 1, wherein at least one stud hole (159) is provided between the exhaust removing opening (132) and the intake introducing opening (133) when seen from a top view of the cylinder head (122), and wherein the at least one stud hole (159) is proximal to the intake introducing opening (133) and distal to the exhaust removing opening (132).
9. The IC engine (120) as claimed in claim 1, wherein a carbon filter (160) is inserted in the first end portion (158A) of the EGR pipe (158).
10. The IC engine (120) as claimed in claim 1, wherein the exhaust gas recirculation system is installed in a three wheeled vehicle (100) and a two wheeled vehicle.