Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
  • F02B75/00—Other engines
  • F02B75/04—Engines with variable distances between pistons at top dead-centre positions and cylinder heads
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
  • F02B41/00—Engines characterised by special means for improving conversion of heat or pressure energy into mechanical power
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D15/00—Varying compression ratio
  • F02D15/04—Varying compression ratio by alteration of volume of compression space without changing piston stroke
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
  • F02B1/00—Engines characterised by fuel-air mixture compression
  • F02B1/02—Engines characterised by fuel-air mixture compression with positive ignition
  • F02B1/04—Engines characterised by fuel-air mixture compression with positive ignition with fuel-air mixture admission into cylinder

Definitions

• This invention relates to the internal combus- tion engine art and, more particularly, to an improved ar- rangement for controlling the compression ratio of the en- gine.
• This application is a continuation in part of a prior application filed 03/23/90 as serial number 07/497,666 by applicant Ahmed Syed, and which was aban- doned upon completion and acceptance of the filing of the CIP application and which was the subject of PCT applica- tion number PCT/US 91/01963 which was abandoned before issue.
• the CIP application being issued as a patent on 23 March 1993.
• Compression ratio is defined as the ratio of the total internal volume between the top surface of the piston and the bottom surface of the cylinder head of a cylinder when the piston is at bottom dead center (BDC) to the clearance volume of the cylinder when the piston is at top dead center (TDC) .
• BDC bottom dead center
• TDC top dead center
• the space between the piston and the cylinder head at TDC is also known as the combus- tion chamber.
• CR Total vol at BDC / Clearance vol at TDC There is always a clearance space enclosed by the piston top surface and the inner surface of the cylinder head when the piston is at TDC.
• CM compression pressure
• Typical compression ratios of modern spark ignition engines are anywhere from 8 to 9.5.
• the compression ratio for a particular spark ignition in- ternal combustion engine design is selected after a deter- mination of what safe compression pressures the engine can handle without the fuel mixture detonating prematurely.
• the CP at part throttle will be lower than at full throttle.
• CP is limited by the maximum (full throttle) CP. This limitation, a) hinders the use of very lean mixtures for emission control, and, b) places an un- desirable limitation on the theoretical efficiency of the engine. But an automobile is driven mostly at part throttle. During partial throttle operation, the CR may be safely increased without exceeding maximum safe CP.
• the '537 patent describes the inherent problem of a number of prior solution of the back-flow of the hydraulic fluid under the intense back pressure of the internal explosion of fuel and air.
• the prior art systems did not work as expected because the regulation of the compression ratio is accompanied by too large of an error imposed by the in- tense explosion pressure.
• the *537 patent attempts to solve the problems by only moving the sub-piston during the intake and ex- haust strokes of the engine. The opening and closing of a check valve is used to activate the movement of the sub- piston.
• '537 discloses that the sub-piston will be forced to a slightly rearward position during the in- tense power explosion. Such intermittent movement results in noise, vibration and control instability.
• the above and other objects of the present in- vention are achieved, according to a preferred embodiment thereof, by providing a control mechanism incorporating the geometry of an involute so that the moment of force generated by the shaft of the control piston is reduced to a very low value.
• the variable TDC clearance is generated by a movable secondary piston mounted within a secondary cylinder which opens upon the clearance space between the primary piston and the primary cylinder at TDC.
• the secondary piston is mounted with a spring.
• the return spring positions the secondary piston at a location most remote from the primary piston and firmly pressed against the surface of the involute.
• the position of the secondary piston is control- led by the rotational position of an involute mounted on a shaft and positioned to be in contact with the secondary piston cap extended above the secondary piston.
• the force vector of the secondary piston will be directed to the center of the shaft and involute arrangement reducing the moment around the shaft to almost zero.
• the end surface of the secondary piston cap may be formed in a wedge shape to conform to the shape of the surface of the involute.
• the involute may be the archimedian or the logarithmic involute shape.
• the main objective is to provide a control surface that is uniformly increasing/decreasing in diameter.
• the control device utilizes an electric motor acting on the shaft through a worm and gear arrangement.
• the worm and gear arrangement achieves a further reduction ratio in stability and further diminishes the reaction of the sys- tem to reverse torque.
• the involute is sup- ported by a shaft but driven by a sleeve surrounding the shaft.
• the sleeve communicates with the involute by means of a spring to advance the involute only during periods of low back pressure.
• the involute communicates with the shaft by means of a ratchet whereby the involute will ad- vance in only one direction and only during low pressure. The ratchet prevents movement in the other direction.
• the involute is repositioned by means of moving the shaft.
• Any such control device responding to the preselected variables of air temperature, pressure, octane rating of the fuel, engine temperature, etc. may be incor- porated in the algorithm used by the control device to determine the rotational position and achieve the preselected engine efficiency by changing the compression ratio.
• Figure 1 is a cross sectional view of an engine which shows a secondary cylinder positioned by an involute shaft according to the principles of the present inven- tion;
• Figure 2 illustrates the placement of the secon- dary piston;
• Figure 3 is a perspective view of the involute/shaft arrangement with control device;
• Figure 4 is a cross sectional view of an engine which illustrates the cap of the secondary cylinder as a wedge;
• Figure 5 is a perspective view of the shaped cap wedge arrangement;
• Figure 6 illustrates another embodiment of the present invention;
• Figure 7 illustrates a cross sectional view of the another embodiment of the present invention;
• Figure 8 illustrates another embodiment of the present invention;
• Figure 9 illustrates a block diagram of the position control;
• Figure 10 illustrates the ideal curve;
• Figure 11 illustrates another embodiment of the present invention;
• Figure 12 illustrates yet another embodiment of
• the purpose of this invention is to provide an arrangement which may be used to increase internal combus- tion engine thermal efficiency.
• the efficiency is a func- tion of the compression ratio and the fuel-air ratio.
• Unleaded gas and smog control devices have been introduced to reduce undesirable emissions.
• Higher octane gas is used to prevent knocking.
• the compression ratio of most engines is fixed at a range of 8 to 9.
• the quantities of fuel and air may be controlled to try to provide an ideal lean mixture which runs hotter. However, with low compression ratios, the lean mixture burns slower resulting in serious loss of power and some- times may even fail to ignite. If it is too slow, the burning is incomplete and creates pollutants.
• the engine controls may increase the fuel to create a richer mixture which burns faster. However, the rich mixture burns cooler and still creates pollutants.
• the desired control is to increase compression pressure to the maximum for the current load. With in- creased pressure, the mixture burns faster. Thus, the ideal mix may be used and pollutants reduced. Two distinct advantages are achieved at the same time, pollutants are reduced and economy of operation is improved.
• the theoretical efficiency is enhanced by reducing the combustion chamber volume with a correspond- ing rise in compression ratio. This also results in a fully compressed charge at all times. Enabling Leaner mixtures to burn faster and more completely.
• This inven- tion teaches an arrangement to control an increase in the pressure of an internal combustion engine while the engine is operating.
• the objective is to maintain a constant pressure of the charge in the combustion chamber prior to ignition regardless of engine load, speed or environmental condi- tions.
• the compression is varied by means of a secon- dary piston. Under part throttle conditions, the secon- dary piston moves down to increase the compression ratio. Under cruising conditions or part throttle con- ditions, the engine compression ratio is raised to run in a more fuel efficient manner. Since the charge density is made constant at all throttle conditions, it become pos- sible to use extremely lean mixtures reducing pollutants and improving economy. Under heavy load conditions or full throttle acceleration, the engine compression ratio is lowered. Another significant result of use of the ar- rangement of this invention is that the high charge den- sity attainable maintains a high flame propagation speed.
• FIG 10 is a graph showing the effect of com- pression ratio on the efficiency of a constant-volume en- gine.
• the fuel-air-cycle efficiency is seen to increase with compression, ratio.
• the ratio of fuel-air-cycle ef- ficiency to air-cycle efficiency is roughly constant for a given fuel-air ratio.
• Efficiency is increased as the com- pression ratio is increased.
• the objective of this inven- tion is to squeeze the maximum mileage from a given amount of fuel by running the engine at the highest possible com- pression ratio.
• FIG. 1 a cross sectional view of an inter- nal combustion engine generally designated 10.
• the engine has a primary cylinder 101, a cylinder head 102, and a primary piston 103.
• Other items necessary for the func- tion of the engine such as intake, exhaust valves, rocker arms, rocker arm camshaft, piston rings, crank shaft, con- necting rod, etc. are illustrated but not integral to this invention.
• a secondary cylinder 201 is formed in the cylinder head 102 and positioned so that the opening of the secondary cylinder 201 corresponds with a selected part of the volume which comprises the "clearance volume at TDC. As illustrated, the opening of the secondary cylinder 201 is fully enclosed within the upper portion of the cylinder head 102 which is opposite the upper surface of the primary piston 103.
• a secondary piston 203 is mounted within the secondary cylinder 201. The space within the secondary cylinder 201 and below the secondary piston 203 is added to the clearance volume of the engine 10 in computing the compression ratio. As the secondary piston 203 is lowered along the secondary cylinder 201, the clearance volume is reduced and the compression ratio is increased.
• Cooling of the secondary cylinder 201 and piston 203 may be provided by means of an oil flow which is well known in the art.
• a return spring 204 is attached to the secondary piston 203 to return the secondary piston 203 to the upper most position of the secondary cylinder 201 and keep it firmly pressed to the surface of the involute.
• the shaft of the actuator incorporates a spring return mechanism to rotate the shaft in the direction of minimum CR in case of loss of power or control signals to the actuator.
• the minimum CR position is the configura- tion utilized upon starting and stopping the engine.
• the secondary piston 203 must incorporate com- pression rings, lubrication channels, etc. to function but such items are well known in the art, are not part of the invention herein and therefore, not shown in detail.
• the spark plug 104 is illustrated as mounted within the secondary piston 203 with the spark gap between the electrodes ex- tending into the combustion chamber 110 of the primary cylinder 101, cylinder head 102 and primary piston 103.
• This configuration allows the secondary piston 203 to be as large as possible.
• This arrangement is more clearly shown by the diagram of Figure 2.
• the spark plug may be mounted else where given a different arrangement of the secondary cy] inder 201 and the intake and exhaust valves incorporated in the design. Multiple intake and exhaust valves may be used to increase the efficiency of the engine. But these items are well known in the art.
• Figure 4 shows the spark plug wire 105 from the distributor being connected to the spark plug 104 by means of a connector fitted on the camshaft cover.
• the size, placement and seal- ing requirements of the door to provide easy access to the spark plugs mounted inside the secondary piston is well known in the art.
• the camshaft cover could be fitted with cable connectors for passage of cables to the outside of the cover.
• the shaft 301 shown in perspective in Figure 3 may be mounted in bearings on towers and positioned so that the surface of a plurality of involutes 302 are in contact with a plurality of caps 205 for multicylinder en- gines.
• the shaft 301 is similar to a camshaft which is well known in the art.
• a control device is connected to one end of the shaft 301 and rotates the shaft 301 to a preselected posi- tion.
• the outside sur- face of the involute 302 will push down upon the cap 205 which lowers the secondary piston 203 thereby decreasing the clearance volume and increasing the compression ratio of the engine 10 to a preselected value for the present operating conditions.
• Fuel and air is input into the cylinder through the intake valve and ignited by the spark plug 104. The resulting explosion places an upward force upon the secon- dary piston 203 and the primary piston 103.
• the primary piston 103 will move down and transmit the force through the connecting rod 109 to the crankshaft of the engine 10.
• the secondary piston 203 will transmit its force through the cap 205 and the involute 302 to the shaft 301.
• the contact point between the involute 302 and the cap 205 is in-line with the axis of the shaft 301, there is very little, if any, torque applied to the shaft 301 to cause the shaft to change position. It is this stability which sets the arrangement of this inven- tion apart from the prior art.
• the prior art is very vul- nerable to the back pressure changing the control setting. The changes cause the system to vibrate between the desired position and the back pressure position resulting in noise, inefficiency, and wear on the arrangement.
• the servo control device 503 is illustrated to be an electric motor but may be a hydraulic drive device.
• the shaft 301 is rigidly mounted on bearings in towers to the cylinder head.
• Figure 4 is another embodiment of the present invention showing a shaped cap 405 mounted above the secondary piston 203.
• the secondary piston 203 is kept in rotational alignment within the secondary cylinder 201 by means of a guide 407 and key 406.
• FIG. 5 shows the detail of the wedge 408 and the alignment of the cap 408 on the surface of the in- volute 302.
• the control of the position of the shaft may utilize an electric servo motor.
• a hydraulic position control actuator may be used.
• the control means may utilize automatic braking to eliminate overshoot and backlash.
• the position of the control means may have a simple correspondence to the in- take manifold vacuum.
• the intake manifold butterfly may incorporate a dash pot to damp the throttle response to allow the con- trol system to follow the motion of the intake manifold butterfly valve.
• Figure 9 illustrates a block diagram of a con- trol method. Because it is impractical to measure the pressure in a cylinder while it is in operation, an in- direct method to compute the relative amount of charge present in a cylinder is used. A fairly accurate indica- tion is the inlet manifold vacuum. A vacuum manifold sen- sor produces a signal for input to the logic unit.
• Intake manifold vacuum is a direct parameter for establishing engine load and a fairly accurate means for determining the amount of charge entering the cylinders.
• the logic unit could combine in- puts from several variables such as atmospheric pressure, engine RPM, throttle position, engine temperature, etc. to evaluate current compression ratio.
• Figure 9 illustrates that RPM sensor 920 is another input which may be utilized by the logic unit.
• the position sensor 925 of the actuator 926 in- dicates to the logic unit 915 the present position of the involute 302 and thus the compression ratio of the engine.
• the reference 927 contains a table established for the engine and vehicle type to allow the logic unit 915 to compare current engine charge, RPM and compression ratio to the desired compression ratio established to produce top efficiency.
• the logic unit will then calcu- late a clockwise or counterclockwise position control sig- nal and communicate that signal to the actuator 926.
• the position sensor 925 provides the feed back to allow the logic unit 915 to determine when the actuator has turned the involute 302 to the position to achieve the desired compression ratio.
• the logic unit 915 Upon arrival at the desired position, the logic unit 915 will disengage the actuator 926.
• a switch may be provided to lock the actuator in its present position to further stiffen the tolerance of the system to backpressure. The objective is to maintain the compression ratio at the highest possible level for the conditions.
• preignition pressure not exceed a maximum tolerable value.
• This process of achieving the optimum compres- sion ratio for the present operation of the engine is es- sentially continuous.
• the position of the involute 302 may stay essentially the same for a period of time depend- ing upon the driving conditions.
• a damping mechanism may be utilized on the main throttle butterfly valve to ensure that it cannot be opened or closed too quickly.
• the damp- ing action should closely follow the response time of the actuator 926 to allow the system time to "catch up.”
• an additional throttle plate under the control of the logic unit may be utilized.
• con- trol systems are well known in the art.
• Figure 6 and 7 show another embodiment of threaded bolts 603 driven by a worm gear 502 moving a drive gear 501 on the shaft 301.
• the bolt 603 replaces the action of the involute 302.
• a second worm gear 602 mounted on the shaft 301 engages a second drive gear 601 formed in the top portion of the threaded bolt 603.
• the bolt 603 is rotated by the second drive gear 601, it pushes down on the cap 205 mounted on the secondary cylinder 203.
• the back pressure of the secondary cylinder 203 against the bolt 603 will create some torque force on the bolt 603 and tend to unscrew it.
• FIG. 8 illustrates yet another embodiment of the present invention in which the position of each in- volute 815 is independently controlled by a separate logic unit 816 or one channel of a multichanneled control unit.
• the control unit 816 is connected to the servo motor actuator 810 and directs it to rotate in the desired direction.
• a worm gear 813 is mounted on the shaft 817 of the servo motor actuator 810 and engaged with gear 814.
• Gear 814 is formed as part of the involute 815 and rotatably mounted to the cylinder head of the motor to be controlled.
• the servo motor position sensor 811 provides input to the logic unit 816. The control signal from the logic unit 816 to the servo motor actuator is terminated when the position sensed by the servo motor position sen- sor 811 indicates that the involute 815 has moved the secondary piston 203 to the preselected position.
• the servo limit switch 812 protects the control system from rotating beyond preselected limits by disengaging the servo motor actuator 810.
• the limit switch 812 may be incorporated into a fail safe position circuit to allow the servo motor actuator 810 to move the involute 815 to the minimum compression ratio position upon loss of the logic unit 816 or selected inputs to the logic unit 816.
• Figure 11 illustrates yet another embodiment of the present invention in which the position of each in- volute 1115 is independently controlled by a separate logic unit 1116 or one channel of a multichanneled control unit.
• the involute 1115 which controls the position of a cap 205 as described above is mounted on the shaft 1117 of the servo motor actuator 1110 in the same manner as described above.
• Figure 12 illustrates yet another embodiment of the present invention in which the position of each threaded bolt 1206 is independently controlled by a separate logic unit 1216 or one channel of a multichan- neled control unit.
• the rotated position of the threaded bolt 1206 which controls the position of the cap 205, as described above, corresponds to the rotation of the worm gear 1202 mounted on shaft 1217 of the servo motor ac- tuator 1210 in the same manner as described above.
• Figures 13 through 17 illustrate yet another em- bodiment of the .present invention in which the positioning of the involute is achieved with minimum power because the involute is advanced only during times of low pressure in the combustion chamber.
• Figure 13 depicts a base shaft 1301 on which is formed a ratchet 1302.
• Figure 15 depicts an involute 1501 in which a plurality of notches 1503 are formed at a preselected radius.
• a first wall 1504 is formed in the center of the involute and a click/lock mechanism 1502 is mounted in the inside surface of the first wall 1504.
• One involute 1501 with click/lock mechanism 1502 is mounted onto the base shaft 1301 over each ratchet 1302.
• the sleeve 1401 is formed with fingers 1402 which can be mounted through the notches 1503 of the involute 1501.
• a spring 1403 is mounted on the sleeve 1401 to com- municate torque from the sleeve 1401 to the involute 1501 upon the rotational movement of the sleeve 1401.
• the position of the sleeve 1401 is controlled by a servo motor actuator or hydraulic actuator as described above for other embodiments.
• a gear 1404 is formed on a selected portion of the sleeve 1401 to allow rotational information to be communicated between the actuator and the sleeve 1401 by such means as a worm gear or directly coupled gear transmission.
• the arrange- ment Upon movement of the shaft 1401 in the desired direction and the loading of the spring 1403, the arrange- ment is primed to have the involute move in the desired direction upon the occurrence of pressure in the combus- tion chamber as communicated to the involute 1301 by the secondary cylinder described above being lower than the spring 1403 coefficient.
• This movement of the involute 1501 relieves the tension on the spring 1403.
• the in- volute 1501 is prevented from rotating in the opposite direction by a click/lock 1502 mechanism mounted in the involute 1501 and engaging the ratchet 1302 on the base shaft 1301.
• the granularity of the teeth in the ratchet 1302 is of a preselected size.
• the granularity is small to allow the rotation of the involute 1501 to appear essentially continuous even though it is actually step wise.
• a "double" or two-stage bearing may be used in the middle for greater support.
• the bearing may be of the oil pressure type or a roller/ball bearing type.
• the bearing is comprised of a rotating inner bearing 1601 mounted within an outer bearing 1602 mounted on a journal 1603 which is positioned to support the arrangement.
• the inner bearing supports the base shaft 1301 while sections of the sleeve 1401 are attached to the outer bearing 1602.
• Figure 17 shows the entire embodiment assembled into arrangement 17.
• a stepper motor 1702 is depicted as having a transmission gear 1703 engaging the drive gear 1404 of the sleeve 1401.
• the involute 1501 is rotated into the desired forward position under a controller con- nected to the stepper motor 1702.
• a clutch mechanism 1701 at one end of the base shaft 1301 is released which will cause the base shaft 1301 to rotate in the direction of lower com- pression. Since certain change may be made in the above apparatus without departing from the scope of the inven- tion herein involved, it is intended that all matter con- tained in the above description, as shown in the accom- panying drawing, shall be interpreted in an illustrative, and not a limiting sense.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Output Control And Ontrol Of Special Type Engine (AREA)

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• 1993
  • 1993-03-19 EP EP93909156A patent/EP0700482B1/en not_active Expired - Lifetime
  • 1993-03-19 JP JP52098094A patent/JP3366332B2/ja not_active Expired - Fee Related
  • 1993-03-19 WO PCT/US1993/002728 patent/WO1994021908A1/en active IP Right Grant
  • 1993-03-19 DE DE69327408T patent/DE69327408T2/de not_active Expired - Fee Related

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