Patent Application
20070261398
This invention relates generally to internal combustion engines and, more specifically, to intake and exhaust systems for such engines.
Power output and efficiency of internal combustion engines can be improved by tuning the properties of the intake and exhaust systems to take advantage of pressure waves propagating from the engine cylinders. In the exhaust system of a typical engine, exhaust gases are released into the exhaust system from the engine cylinder at high pressure. The resulting pressure wave travels at the speed of sound through the exhaust system. Part of the energy of the pressure wave is reflected back toward the cylinder in the form of a negative pressure wave when the pressure wave passes points where the air channel increases sharply in diameter. This typically occurs at a collector where exhaust pipes from the individual cylinders converge. In the intake system, the sudden intake of air during the intake stroke in four-stroke engines results in a negative wave, a portion of which is reflected toward the cylinder as a pressure wave by openings or dilations in the intake system.
If the return waves arrive at the cylinder at the appropriate time, they aid in the flow of gases in and out of the cylinder. If the exhaust system return wave arrives while the exhaust valve is still open, the negative pressure will help draw exhaust gases out of the cylinder. If the return wave strikes the exhaust port when both the exhaust valve and intake valve are open, the negative pressure aids in drawing a fresh charge of air and fuel into the cylinder. The return wave in the intake system aids in forcing the charge of air and fuel into the cylinder.
The return waves in the intake and exhaust system must be timed correctly in order to arrive at the intake and exhaust ports, respectively, at the appropriate times. In most engines, the air columns in the intake and exhaust systems are fixed. Since the speed of the return waves is substantially constant, the timing of the return waves is also constant. The engine therefore benefits from the return waves only for a small range of operating speeds where the opening of the exhaust and intake ports coincides with the return waves.
Some systems allow for manual adjustment of the length of the air column in the exhaust system in order to adjust engine operating speeds benefiting from the return wave. However, none of the prior systems provides a suitable means for accommodating the full range of operating speeds of the engine.
Accordingly, it would be an advancement in the art to provide a system and method for adapting the acoustic properties of an intake and exhaust systems according to the operating speed of the engine.
The present invention provides a system for tuning an intake and an exhaust system of an engine. The exhaust tuning system includes a plurality of upstream pipes connected to the exhaust ports of an engine and a downstream pipe. In one example of the invention, the upstream pipes and downstream pipe adjustably connect to a collector to create a fluid path. An actuator couples to the collector to adjust the collector position and vary the fluid path length from the exhaust ports to the collector. An engine control unit (ECU) is coupled to an engine speed sensor and adjusts the collector position in response to changes in the operating speed of the engine.
The collector may include a plurality of inlet tubes overlapping with the upstream tubes. An outlet tube secures to the collector and overlaps with the downstream tube. Sealing members maintain a sliding seal between the inlet tubes and the upstream tubes and between the outlet tube and the downstream tube. The sealing members engaging the inlet tubes may be offset from one another along a longitudinal direction corresponding to a direction of fluid flow within the inlet tubes.
An intake tuning system includes an upstream tube and a downstream tube. The downstream tube connects to the intake ports of an engine. A sliding tube slidably connects to the upstream tube and downstream tube. The upstream tube and downstream tube each include a straight portion oriented parallel to one another. The sliding tube is a U-shaped member and slides along the straight portions. An actuator engages the sliding tube to adjust its position relative to the upstream tube and downstream tube in order to vary the length of the fluid path followed by gases within the intake system. A speed sensor detects the operating speed of the engine provides the output to the ECU. The ECU causes the actuator to adjust the position of the sliding tube in response to sensed changes in the operating speed of the engine.
A sealing member suitable for use in the intake and exhaust system includes a first outer tube section having a first flange extending circumferentially outwardly therefrom and a second outer tube having a second flange extending circumferentially outward therefrom. An inner tube is slidably positioned within the first and second outer tubes sections having the first and second flanges facing one another. A fastener secures the first and second flanges together to capture a compressible seal between the flanges and the inner tube. In one embodiment, the fastener is embodied as first and second rings secured to one another having the first and second flanges positioned therebetween.
Preferred and alternative embodiments of the present invention are described in detail below with reference to the following drawings.
Referring to
An actuator 24 engages the collector 18 to change the location of the collector 18 relative to the exhaust ports. A controller 26 may be electrically coupled to the actuator 24 to cause the actuator 24 to move to a desired position. The controller 26 may translate directives regarding a desired location of the collector 18 into a quantity of electrical, hydraulic, pneumatic, or other power supplied to the actuator 24. The actuator 24 may provide feedback to the controller regarding the current location of the collector 18 to enable the controller 26 to meter power supplied to the actuator 24 to achieve an intended change in position.
The collector 18 includes a plurality of inlet tubes 28 overlapping with the upstream pipes 12. The upstream pipes 12 may include a straight portion 30 formed thereon or secured thereto for engaging the inlet tubes 28. The inlet tubes 28 are positioned either inside or outside the upstream pipes 12. The sealing members 20 typically secure to the outermost of the inlet tubes 28 and upstream pipes 12. An outlet tube 32 overlaps with the downstream pipe 16 and is positioned either in- or outside of the downstream pipe 16. The sealing member 22 secures to the outermost of the outlet tube 32 and downstream pipe 16.
A converging section 34, or funnel, couples the inlet tubes 28 to the outlet tube 32. The converging section 34 provides a dilation point within the air column thereby serving to reflect negative pressure waves toward the exhaust ports of the engine. Pressure waves propagating through the upstream pipes 12 will expand into adjacent upstream pipes 12 and the downstream pipe 16 upon reaching the converging section 34. This sudden dilation of the fluid path at the converging section 34 results in a negative pressure wave propagating back up the upstream pipe 12 that originated the pressure wave. The arrangement of the upstream pipes 12, inlet tubes 28, and converging section 34 provide a narrow fluid path up to the dilation point at the converging section 34.
The above described arrangement of upstream pipes 12, inlet tubes 28, and the converging section 34 ensures that the pressure waves from the different cylinders of the engine travel separate fluid paths up to the dilation point at the converging section 34. This avoids dissipation of the pressure wave and negative pressure wave. It further avoids interference between cylinders, enabling more predictable behavior and more precise tuning of the exhaust tuning system 10.
The converging section 34 may include an ear 36, or bracket, extending therefrom to engage the actuator 24. In one embodiment, the actuator 24 is embodied as a ball-screw, hydraulic, or pneumatic, cylinder 38 and piston 40. In the illustrated embodiment, the piston 40 secures to the ear 36 and the cylinder 38 secures to the downstream pipe 16 by means of a bracket 42. Alternatively, the cylinder 38 or piston 40 may secure to one or more of the upstream pipes 12.
Referring to
Referring to
Various embodiments of the actuator 24 are also possible. For example, the actuator 24 may drive a threaded rod 54 engaging a threaded aperture 56 formed in the converging section 34 or formed in an ear 58 secured to the converging section. The actuator 24 may secure to any fixed structure forming the engine or automobile in which the exhaust system is used. The actuator 24 may also secure to the downstream pipe 16, as illustrated, or to the upstream pipes 12. In the embodiment of
Referring to
The ECU 70 determines, based on the inputs received, a collector position suitable for coordinating pressure waves within the exhaust system with opening and closing of the exhaust ports. The ECU 70 may monitor the inputs and make substantially constant or regularly periodic adjustments to collector position. Alternatively, the ECU 70 may adjust the collector position only upon detection of a change in one or more of the inputs exceeding a specific threshold. The threshold may be proportional or otherwise related to operating speed or another parameter. The ECU 70 may map collector positions to specific values, or combinations of values, of one or more parameters such as operating speed, exhaust temperature, exhaust pressure and the like. In one embodiment, only operating speed is used. In other embodiments, changes in the speed of the waves due to temperature and pressure changes may be accommodated by mapping collector positions to values for operating speed, temperature, and/or pressure. Some engines may vary the timing of valve opening and closing relative to crankshaft position according to operating speed, load on the engine, and other parameters. Accordingly, the ECU 70 may adjust the collector position to coincide with these variations.
Mapping may be accomplished by various means. In one embodiment, tables map values, or ranges of values, of inputs to the ECU 70 to collector positions. In other embodiments, the ECU 70 accomplishes mapping according to a mathematical formula. In still other embodiments, the ECU 70 accomplishes mapping according to a plurality of mathematical formulae each corresponding to a range of input values for one or more inputs. Mathematical formulae and maps are typically generated by testing of a particular engine to determine which collector position provide the highest performance gains for a particular operating speed.
A formula for calculating collector position is L=((850*(360−EVO))/RPM)−3. Where L is the length of the fluid path from the engine 14 to the collector 18, EVO (exhaust valve opening) is the angular position at which the exhaust valve opens, and RPM (revolutions per minute) is the angular velocity of the crankshaft. A collector position achieving the desired length L may then be calculated.
In some embodiments, calculated values for L may be adjusted based on tracking of the exhaust gas pressure at the exhaust port. For example, where tracking of exhaust pressure shows that a return wave is arriving early or late, the ECU 70 may adjust the collector position to lengthen or shorten, respectively, the length L. In still other embodiments, feedback of exhaust gas pressure is the only means used to determine collector position. The ECU 70, for example, may determine whether the return wave is arriving early or late and adjust the collector position to lengthen or shorten, respectively, the length of the fluid path from the engine 14 to the collector. The ECU 70 may sample the arrival time of the return waves and adjust collector position substantially continuously or periodically in order to cause the collector position to track changes in engine operating speed.
Referring to
Referring to
The method 90 may optionally include detecting 104 arrival of the return wave, and recalculating 106 the collector position if the return wave arrives early or late. The collector position is then readjusted 108. The steps 104, 106, and 108 may be repeated multiple times for a single iteration of the method 90.
Referring to
An actuator 136 engages the sliding member 126 to adjust the length of the fluid path between the throttle 122 and the engine 14. A controller 138 may be coupled to the actuator and meter power supplied to the actuator 136 to achieve a desired change in position of the sliding member 126. In the illustrated embodiment, the actuator 136 is a ball-screw, hydraulic, or pneumatic cylinder 140 and piston 142 coupled to the sliding member 126 to cause translation thereof. A first end 146 of the cylinder 140 and piston 142 combination may engage the sliding member 126 by means of a cross member 144 extending between the legs of the U-shaped sliding member 126. Alternatively, the first end 146 secures directly to the sliding member 126.
A second end 148 of the cylinder 140 and piston 142 combination secures to the engine 14, such as to the head or block of the engine. In the illustrated embodiment, the second end 148 secures to the head of the engine 14 between the throttle tube 124 and intake tube 128. The second end 148 may secure to a bracket 150 secured to the head of the engine 14 proximate a valve cover 152. The throttle 122 or the throttle tube 124 may likewise secure to a bracket 154 secured to the head of the engine 14.
Referring to
The sliding member 126 may engage a guide 158 to ensure smooth changes in sliding member position. In the illustrated embodiment, the guide 158 is two grooved rails 160 extending parallel to the intake tubes 128. Struts 164 supporting the rails 160 secure to the block of the engine 14, or other structure within an engine compartment. In the illustrated embodiment, the struts 164 extend from a free end 166 of the rails 160 to the engine 14. The struts 164 may be arranged in the crossed configuration of
Referring to
Referring to
The ECU 70 determines, based on the inputs received, a sliding member position suitable for coordinating pressure waves within the intake tuning system 120 with opening and closing of the intake ports. The ECU 70 may monitor the inputs and make substantially constant or regularly periodic adjustments to sliding member position. Alternatively, the ECU 70 may adjust the sliding member position only upon detection of a change in one or more of the inputs exceeding a specific threshold. The threshold may be proportional or otherwise related to operating speed or another parameter. The ECU 70 may map sliding member positions to specific values, or combinations of values, of one or more parameters such as operating speed, exhaust temperature, intake pressure and the like. In one embodiment, only operating speed is used. In other embodiments, changes in the speed of the waves due to temperature and pressure changes may be accommodated by mapping collector positions to values for operating speed, temperature, and/or pressure. Some engines may vary the timing of valve opening and closing relative to crankshaft position according to operating speed, load on the engine, and other parameters. Accordingly, the ECU 70 may adjust the sliding member position to coincide with these variations.
Mapping may be accomplished by various means. In one embodiment, tables map values, or ranges of values, of inputs to the ECU 70 to sliding member positions. In other embodiments, the ECU 70 accomplishes mapping according to a mathematical formula. In still other embodiments, the ECU 70 accomplishes mapping according to a plurality of mathematical formulae each corresponding to a range of input values for one or more inputs. Mathematical formulae and maps are typically generated by testing of a particular engine to determine which sliding member position provide the highest performance gains for a particular operating speed. In some instances, particular combinations of sliding member position and collector position provide better performance for a particular operating speed than others. Accordingly, testing to determine mathematical formulae and maps may include identifying such combinations and developing maps and formulae to achieve them during engine operation.
In some embodiments, calculated values for sliding member position may be adjusted based on tracking of the intake gas pressure at the intake port. For example, where tracking of intake pressure shows that a return wave is arriving early or late, the ECU 70 may adjust the sliding member position to lengthen or shorten, respectively, fluid path length. In still other embodiments, feedback of intake pressure is the only means used to determine sliding member position. The ECU 70, for example, may determine whether the return wave is arriving early or late and adjust the sliding member position to lengthen or shorten, respectively, the length of the fluid path from the engine 14 to the throttle 122. The ECU 70 may sample the arrival time of the return waves and adjust sliding member position substantially continuously or periodically in order to cause the sliding member position to track changes in engine operating speed.
Referring to
Referring to
The method 200 may optionally include detecting 214 arrival of the return wave, and recalculating 216 the sliding member position if the return wave arrives early or late. The sliding member position is then readjusted 218. The steps 214, 216, and 218 may be repeated multiple times for a single iteration of the method 200.
The exhaust tuning system 10 and intake tuning system 120 and associated methods may be used to achieve a variety of objectives by controlling the timing of returning positive and negative waves. For example, the timing may be controlled to prevent reversion, in which exhaust gasses escape into the atmosphere through the intake or exhaust runners.
Timing may also be controlled to help the cylinder to achieve a higher percentage of volumetric efficiency by drawing in air during the valve overlap period, and then forcing an additional volume of air (or air-fuel mixture for carbureted engines) into the cylinder at the end of the intake cycle. In the intake-exhaust cycles, beginning with exhaust valve open (EVO), a positive pressure wave is generated when the exhaust valve opens and bow-down is in progress. If the length of the exhaust runner is correct for the RPM, then that wave will return to the cylinder as a negative pressure wave from the open end of the exhaust runner during the intake-exhaust valve overlap period to prevent reversion, draw off residual exhaust gas, and start the inflow of air by means of lowered cylinder pressure.
After the overlap period, the action of the piston moving down the cylinder and drawing in a fresh charge generates a strong suction wave. This wave is then reflected off the open end of the intake runner as a compression wave. If the intake runner is tuned to the proper length for a given RPM, the returning compression wave will force an additional charge of air into the cylinder just before the intake valve closes. This increases cylinder pressure and volumetric efficiency, and therefore torque. At the same time, reversion through the intake system is prevented by maintaining positive pressure at the intake port until the exhaust valve closes. The wave generated at intake valve close (IVC) will echo several times and will have become weaker by the time intake valve open (IVO) occurs. However, it appears to nonetheless provide a significant improvement.
The above benefits obtained by the tuning systems 10, 120 have particularly beneficial application in the field of lean-burn technology, in which emissions are reduced by using an extremely lean fuel/air mixture. This approach reduces the formation of Nitrous Oxides by reducing the temperature of combustion. Increasing cylinder pressure at IVC serves to increase the amount of fuel that can be added while still maintaining a high air/fuel ratio.
An engine may be dynamically tuned using one or both of the exhaust tuning system 10 and intake tuning system 120 to achieve all or part of these benefits. In addition to the methods described above, dynamic tuning may be accomplished by consulting an empirically derived map or curve fit of tuning system configurations and engine operating conditions. For example, incremental positions of a slider 126 and collector 18 may be mapped to one or more RPMs. In operation, a controller consults the map and sets the slider 126 and collector position to the position mapped to the present operating speed of the engine. Mappings may map tuning systems 10, 120 positions to multiple variables in addition to RPM such as throttle position, engine temperature, throttle position, and the like. Maps may be derived by connecting an engine or vehicle to a dynamometer and experimenting with tuning systems 10, 120 positions to determine which provides a preferred performance characteristic such as fuel efficiency, torque, horsepower, or the like.
The sealing members 20, 22, 132, 134, and 176 may be embodied as illustrated in
A retainer 242 maintains the flanges 230, 234 over the o-ring 238. The retainer 242 may force the flanges 230, 234 together to the extent that the o-ring 238 is pressed against the inner tube 240. In one embodiment, the retainer 242 is embodied as rings 244a, 244b abutting the flanges 230, 234, respectively. Fasteners, such as bolts 246 and nuts 248 may force the rings 244a, 244b together. In some embodiments, spacers 250 maintain a minimum separation between the rings 244a, 244b. The inner tube 240 may have a spacer 252 at an end thereof positioned within the outer tube 232. The spacer 252 may serve to reduce movement of the inner tube 240 within the outer tube 232 despite the difference in the diameters thereof and prevent complete removal of the inner tube 240 from the outer tube 232. The spacer 252 may also provide a partial seal between the outer tube 232 and the inner tube 240.
A felt ring 254 may be positioned between the extension 236 and the inner tube 240. The felt ring 254 serves to reduce the amount of contaminants reaching the o-ring 238. The felt ring 254 may also carry lubricant, which is deposited on the inner tube 240. An aperture 256, or zert, may be provided adjacent the felt ring 254 to facilitate application of lubricant thereto. Internal lands 258 formed in the extension 236 retain the felt ring 254.
Referring to
The embodiment of
Referring to
In some embodiments, an additional set of rings 302, 304 is provided within a groove 306. In one embodiment, rings 296 and 304 have an undeformed outer diameter slightly larger than their respective grooves 300, 306, whereas rings 198, 302 have undeformed inner diameters slightly smaller than the outer diameter of the inner tube 240. In this manner, as the inner tube 240 slides within the outer tube 232, at least one set of rings will be forced against one another to enhance sealing.
The rings 296, 298 may each have a gap 308 formed therein. The gap 308 facilitates deformation of the rings 296, 298, 302, 304 when positioning them into their respective grooves 300, 306 and around the inner tube 240. The gaps 308 of the rings 296, 298, 302, 304 are offset from one another to hinder leakage of gases therethrough. An aperture 310 may extend through the outer tube 232 to facilitate injection of lubricant over the rings 296, 298. A set screw 312 is threaded into the aperture 310 during operation to seal the aperture 310.
Referring to
Referring to
In the illustrated embodiment, the dampers 326 are embodied as pistons 328 and cylinders 330. The cylinders 330 may be spring loaded such that the pistons 328 are biased outwardly. Alternatively, the cylinders 330 may contain hydraulic fluid, or other means, exerting frictional force on the pistons 328 such that movement is resisted. In yet another alternative, the cylinders 330 both bias the pistons 328 outwardly and exert frictional force.
In the embodiment of
The cylinder 140 and piston 142, in the illustrated embodiment, are positioned between the throttle tubes 124. The intake manifold 332 securing to the throttle tubes 124 may have a gap 334 formed thereon suitable for receiving the cylinder 140. A mounting bracket 336 may likewise be positioned within the gap 334. The cylinder 140 may mount to the manifold 332.
While the preferred embodiment of the invention has been illustrated and described, as noted above, many changes can be made without departing from the spirit and scope of the invention. Accordingly, the scope of the invention is not limited by the disclosure of the preferred embodiment. Instead, the invention should be determined entirely by reference to the claims that follow.
