Field of the invention
[0001] This invention relates to a device to vary a recirculated
exhaust gas (EGR) flow rate in a throat area of a venturi in a
vehicle.
Background of the invention
[0002] Exhaust Gas Recirculation (EGR) is widely used in diesel engine applications as a technically viable and cost effective technology for reducing Nitrogen oxides (NOx). There are different techniques to achieve this reduction. Aiding flow of exhaust from exhaust manifold (before turbocharger turbine) to intake manifold (after turbocharger compressor), is generally referred to as High Pressure EGR. If the exhaust flow is tapped after the turbocharger (turbine outlet) and led into the intake path before the turbocharger (compressor inlet), it qualifies as Low pressure EGR. For continuous flow of EGR, the exhaust pressure must always be higher than intake air pressure. This problem is not of much consequence with a low-pressure EGR technique, since turbocharger suction is always at a lower pressure than exhaust. With a high-pressure EGR technique, at some operating points of the engine, the exhaust pressure will be lower in comparison with the intake air pressure and hence there will be no EGR flow at such points.
[0003] Prior art patent application US20110185805 discloses a variable throat Venturi flow meter includes an upstream pipe section

having an upstream cross-sectional area, a throat section having a variable throat cross-sectional area that is smaller than the upstream cross-sectional area, and a plurality of section-varying elements adapted to temporarily vary the throat cross-sectional area to allow a downhole tool to pass through the throat section.
Brief description of the accompanying drawing
[0004] Different modes of the invention are disclosed in detail in the
description and illustrated in the accompanying drawing:
[0005] FIG. 1 illustrates a device to vary a recirculated exhaust gas
(EGR) in a throat area in accordance with one embodiment of the
invention;
[0006] FIG. 2 (a) illustrates a venturi connected to a throttle lever in
a vehicle in accordance with one embodiment of the invention;
[0007] FIG. 2 (b) illustrates a venturi connected to an accelerator
pedal in a vehicle in accordance with one embodiment of the
invention;
[0008] FIG. 3 illustrates a venturi connected to an intake manifold in
a vehicle in accordance with one embodiment of the invention; and
[0009] FIG. 4 illustrates a venturi connected to an electronic control
unit in a vehicle in accordance with one embodiment of the invention.
Detailed description of the embodiments

[0010] FIG. 1 illustrates a device 10 to vary a recirculated exhaust gas (EGR) flow rate in a throat area 16 of a venturi 18 in a vehicle according to one embodiment of the invention. The device 10 comprises a sliding piston 12 positioned in the throat area 16 above an exhaust gas recirculation inlet 20. The device 10 comprises an actuating unit 14 connected to the sliding piston 12. The actuating unit 14 connected to at least one component of the vehicle controls the movement of the piston 12 to vary the EGR flow rate in the throat area 16 via the EGR inlet 20.
[0011] Further the construction of the venturi 18 in an exhaust gas recirculation (EGR) system in the vehicle and the working of the exhaust gas recirculation is explained as follows. The venturi18 in the EGR system is divided into three portions. One being a convergent portion, the throat portion 16 and a divergent portion. In the throat portion/area, an EGR inlet 20 is made to redirect the exhaust gas that is existing from an exhaust manifold 21 of a vehicle. The area of the throat 20 is less when compared to the convergent and the divergent portions. The inlet pressure at the convergent portion experiences a drop in the throat 20, due to the smaller dimensions when compared to the convergent portion. The sliding piston 12 is positioned in the throat area by drilling a hole in the throat 16, above the EGR inlet 20, such that, the movement of the piston 12 above the EGR inlet 20 controls the EGR flow rate in the venturi 18 of the vehicle. The

actuating unit 14 is connected to the piston 12 and based on the working of the actuating unit 14, the piston 12 will be moved in the axial direction. At least one component of the vehicle that is connected to the actuating unit 14 is chosen from a group of components comprising an accelerator pedal 25, a throttle valve 24, an intake manifold 34 and an electronic control unit 38. According to one embodiment of the invention, the electronic control unit 38 is an engine control unit. However, it is not restricted to above disclosed engine control unit, but can be any control unit, which operates the actuating unit 14 of the device 10.
[0012] FIG. 2(a) illustrates a venturi 18 connected to a throttle lever 24 in a vehicle in accordance with one embodiment of the invention. The actuating unit 14 comprises a cable 26 and a control unit 28. The cable 26 is connected between the piston 12 and the throttle lever 24. The control unit 28 controls the functioning of the throttle lever 24. Based on the vehicle operating conditions, the position of the throttle lever 24 varies from a closed position to an open position. Depending on the movement of the throttle lever 24 (which operates based on the engine load and engine speed), the cable 26 moves the piston 12 in the axial direction in the throat 16. For instance, if the load on the engine is more, then the throttle lever 24 is in open position, the movement of the throttle lever 24 moves the piston 12 in the upward direction to allow a higher flow rate of the EGR from the exhaust

manifold 21. When the load on the engine is less, then the throttle lever 24 is moved to a closed position, which in turn moves the piston 12 downwards in the throat 16, via the cable 26, such that, the area where the EGR is directed to flow reduces. Thus, reducing the EGR flow rate into the throat 16.
[0013] FIG. 2 (b) illustrates a venturi 18 connected to an accelerator pedal 25 in a vehicle in accordance with one embodiment of the invention. The actuating unit 14 comprises a cable 26 and a control unit 28. The cable 26 is connected to an accelerator pedal 25. Based on the accelerator pedal press, the cable 26 moves the piston 12 in the throat 16 to vary the EGR flow rate from the exhaust manifold 21. The working of the device 10 when connected to the accelerator pedal 25 is same as disclosed above (similar to the throttle lever operation). For instance, the accelerator pedal 25 is pressed to the maximum position when the engine load is more, due to which the cable 26 pulls the piston 12 upwards in the throat 16, to allow maximum EGR flow rate from the exhaust manifold 21.
[0014] FIG. 3 illustrates a venturi 18 connected to an intake manifold 34 in a vehicle in accordance with one embodiment of the invention. The actuating unit 14 comprises a diaphragm 30 and a hose 36. The diaphragm 30 is force fitted onto the piston 12 and the hose 36 connected between the diaphragm 30 and the intake manifold 34.The

piston 12 is exposed to a differential pressure with boost on one side and ambient on the other. The connection of the boost pressure/intake pressure from the intake manifold 34 to the diaphragm 30 and the piston 12 (either at the topside or at the bottom side) will depend on the application. If the EGR is at higher loads and speeds (where the boost pressure is higher), the hose 36 is connected at the bottom side of the diaphragm 30 and the piston 12. If the EGR demand is at lower loads and speed, (where boost pressure is lower, then the hose 36/boost line is connected at the top side of the diaphragm 30 and the piston 12. With this kind of arrangement, when the device 10 experiences higher boost pressures, then the diaphragm 30 moves upwards, pushing the piston 12 upwards in the throat, thus increasing the EGR flow rate. In another scenario, when the loads are less on the engine , then the diaphragm 30 moves the sliding piston 12 closes the venturi throat area 16 completely, thereby cutting off EGR at lower loads and speeds.
[0015] FIG. 4 illustrates a venturi 18 connected to an electronic control unit 38 in a vehicle in accordance with one embodiment of the invention. The actuating unit 14 comprises a rack 39, a gear 40, a stepper motor 42 and the electronic control unit 38. The rack 39, gear 40 and the stepper motor 42 combination is connected to the electronic control unit 38. The electronic control unit 38 operates the stepper motor 42, which in turn operates the gear 40. The gear 40

moves the rack 39, that is connected to the piston 12 in a way, such that, the piston 12 moves up and down in the throat area 16. Based on the engine load and engine speed, and the requirement of the EGR flow, the piston 12 is moved upwards, to allow the EGR to flow into the throat area 16. The gear 40 as disclosed in this embodiment is a pinion gear.
[0016] with the above arrangement, the throat area 16 in the venturi 18 is varied with the movement of the piston 12 operated by at least one of the actuating units 14 (as disclosed above). The flow rate of the EGR will be increased at the higher engine loads, thus increasing the usage of the EGR system efficiency. The device 10 disclosed above provides a cost-effective solution as it involves a minimum number of components used , to maintain the exhaust pressure more than the inlet pressure at higher engine loads.
[0017] It should be understood that embodiments explained in the description above are only illustrative and do not limit the scope of this invention. Many such embodiments and other modifications and changes in the embodiment explained in the description are envisaged. The scope of the invention is only limited by the scope of the claims.

CLAIMS We Claim:
1. A device (10) to vary a recirculated exhaust gas (EGR) flow rate
in a throat area (16) of a venturi (18) in a vehicle, said device
(10) comprising :
- a sliding piston (12) positioned in said throat area (16) above an exhaust gas recirculation (EGR) inlet (20);
- an actuating unit (14) connected to said sliding piston (12), said actuating unit (14) connected to at least one component of said vehicle, adapted to control movement of said piston (12) to vary said EGR flow rate in said throat area (16) via said EGR inlet (20).

2. The device (10) as claimed in claim 1, wherein at least one component of said vehicle is chosen from a group of components comprising a throttle lever (16), an accelerator pedal (25), an intake manifold (34) and an electronic control unit (38).
3. The device (10) as claimed in claim 2, wherein said actuating unit (14) comprises a cable (26) and a control unit (28), said cable (26) connected between said piston (12) and said throttle lever (24) and said control unit (28) adapted to control functioning of said throttle lever (24).

4. The device (10) as claimed in claim 3, wherein said cable (26) adapted to move said piston (12) in an axial direction in said throat area (16) based on a movement of said throttle lever (24).
5. The device (10) as claimed in claim 2, wherein said actuating unit (14) comprises a cable (26) and a control unit (28), said cable (26) connected between said piston (12) and said accelerator pedal (25) and said control unit (28) adapted to control functioning of said accelerator pedal (25).
6. The device (10) as claimed in claim 2, wherein said actuating unit (14) comprises a diaphragm (30) and a hose (36), said diaphragm (30) mounted on said piston (12) and said hose (36) connected between said diaphragm (30) and said intake manifold (34).
7. The device (10) as claimed in claim 6, wherein a movement in said diaphragm (30) due to a differential pressure from said intake manifold (34) via said hose (36), adapted to move said piston (12) in said throat area (16) to vary said EGR flow rate.

8. The device (10) as claimed in claim 2, wherein said actuating unit (14) comprises a rack (39) and a gear (40) connected to said piston (12), a stepper motor (42) and said electronic control unit (38), said stepper motor (42) connected between said gear (40) and said electronic control unit (38).
9. The device (10) as claimed in claim 8, wherein said electronic control unit (38) adapted to operate said stepper motor (42), such that, said piston (12) adapted to move in axial direction in said throat area (16) based on movement of said gear (40) controlled by said stepper motor (42).
10. The device (10) as claimed in claim 1, wherein said EGR
flow rate is varied by movement of said piston (12) based on a
load on said engine and a speed of said engine.