EP0191759A1 - Piston a taux de compression variable commande pour un moteur a combustion interne - Google Patents

Piston a taux de compression variable commande pour un moteur a combustion interne

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Publication number
EP0191759A1
EP0191759A1 EP19840903395 EP84903395A EP0191759A1 EP 0191759 A1 EP0191759 A1 EP 0191759A1 EP 19840903395 EP19840903395 EP 19840903395 EP 84903395 A EP84903395 A EP 84903395A EP 0191759 A1 EP0191759 A1 EP 0191759A1
Authority
EP
European Patent Office
Prior art keywords
piston
compression ratio
engine
fluid
hydraulic
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP19840903395
Other languages
German (de)
English (en)
Inventor
Dwight Allan Caswell
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Individual
Original Assignee
Individual
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Individual filed Critical Individual
Publication of EP0191759A1 publication Critical patent/EP0191759A1/fr
Withdrawn legal-status Critical Current

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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
    • F02B75/044—Engines with variable distances between pistons at top dead-centre positions and cylinder heads by means of an adjustable piston length
    • 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

  • the invention relates to a controlled variable compression spark-ignited internal combustion engine. More particularly, the invention relates to provision for adjusting the compression ratio of such an engine during operation, preferably by control external to the engine.
  • the invention is also directed to a system employing variable compression ratio apparatus in conjunction with a supercharger, with computerized control for maximizing efficiency and performance.
  • Lower compression engines suffer less from knock, and can burn lower octane fuels, such as unleaded gasoline.
  • low compression engines are less efficient than high compression engines because of the lower peak operating temperature and pressure. Usually combustion is less complete, with more unburned fuel exhausted from the engine.
  • variable compression ratio pistons 3,704,695, 3,656,412, 3,417,738, 3,403,662, 3,358,657, 3,303,831, 3,200,798, 3,161,112 and 2,376,214.
  • variable compression ratio engines controllable externally to the engine so that the compression ratio can be varied and optimized according to the prevailing conditions at any time, and to optionally provide, in conjunction with such an improved variable compression ratio engine, controlled supercharging so that a considerable smaller engine may be used in place of a larger engine, with compression ratio normally at a high value but reduced under conditions of heavy load, with the fuel supercharged under load conditions such that the smaller engine can be depended upon for substantially the same power output as the conventional larger engine, thereby realizing significant savings in fuel due to smaller displacement, lighter weight and more efficient combustion under most conditions.
  • the present invention provides an improved variable compression ratio engine as outlined above, with a compound piston connected by hydraulic conduits through the crankcase wall to an external control mechanism.
  • Computerized control of piston pressurization may be used, responsive to a number of input parameters so that the compression ratio is always at or near the maximum permissible ratio which will not cause knocking to occur.
  • an engine according to the invention may include a, supercharger, also controlled for maximum efficiency, to supplement the power output of the engine when required. This enable the use of a much smaller engine to perform the same work as a larger engine. Under conditions requiring more power, the combustion chamber size may be increased by reducing the compression ratio, and the fuel charge introduced may be increased by supercharging.
  • the internal cylinder pressure just before ignition can be substantially the same as for a conventional engine on the verge of knocking.
  • the maximum fuelair change that can be accommodated is in direct proportion to the size of the combustion chamber. For example, if the compression ratio of a variable compression ratio engine is reduced from a value of 9:1 to 7:1, the size of the combustion chamber is increased by one-third, assuming the piston stroke is constant. Thus, a one-third greater charge can be introduced into the engine when operating at the reduced 7:1 ratio. The operating efficiency of the engine will be reduced due to the lower compression ratio, but the maximum power output will be substantially increased.
  • an engine with the necessary maximum power output and torque characteristics is selected.
  • An engine of smaller displacement when measured at a conventional compression ratio, will be required if a supercharged, reduced compression ratio engine is used.
  • the power output of an automobile is, of course, considerably below the required maximum.
  • a variable compression ratio engine can be operated at a moderately high compression ratio, substantially higher than for a conventional fixed compression ratio engine, for the particular engine and for the octane of the fuel used. Because of the relatively smaller displacement of a variable compression ratio engine according to the invention, the engine will have less heat and friction loss than a conventional engine, so that engine efficiency will be improved under most driving conditions.
  • variable compression ratio engine When engine operating conditions are such that the required power output is minimal, the smaller variable compression ratio engine may be adjusted to a maximum compression ratio (i.e., the maximum ratio permissible without knocking under such optimum conditions), with further efficiency improvement.
  • an. internal combustion engine piston whose size can be controlled according to prevailing operating conditions. Changing the piston size changes the compression ratio of the engine.
  • the piston is controlled from a control means external to the engine block, through a special flexible control linkage which allows for movement of the piston and the connecting rod.
  • the piston can be controlled either externally or internally, and a supercharger is included on the engine to supplement power as described above, with compression ratio reduced.
  • the mechanism for adjusting the piston may take several forms, but a two-part piston is preferred with the upper part movable in response to changes in volume in an expansible fluid chamber contained in the piston.
  • hydraulic fluid is introduced to the piston via a special conduit or channel which is either wholly flexible or provided with flexible or rotatable joints such that one end of the conduit moves with the piston and one end is fixed relative to the engine block.
  • More than one fluid channel may be provided in the conduit to permit fluid circulation or to permit separate control of two control chambers or to facilitate transmission of information from sensing devices associated with the piston. 1
  • One or more hydraulic control chambers are provided
  • hydraulic fluids 11 other than engine oil can be used, but with an unsealed
  • control mechanism which
  • An analog or digital 33 computer may be connected to the control mechanism to re- 34 ceive and digest the large number of variables and to effect 35 the proper compression ratio for the existing conditions
  • the invention comprises a mechanism for varying the compression ratio of an internal combustion piston engine, involving the use of a piston having two portions movable relative to one another to change the height of the piston, through the introduction or removal of hydraulic fluid. Changes in the height of the piston result in changes in the compression ratio of the engine.
  • the hydraulic fluid is introduced into chambers of the hydraulically controlled piston through a special conduit separate from the connecting rod and comprising a movable duct connected to the piston at one end and fixed relative to the engine block at the other end.
  • the hydraulic conduit or duct preferably connects to a control mechanism outside the engine block.
  • a more specific object is to provide such control via hydraulic control, with a special conduit leading from a control device outside the engine block through the ⁇ rankcase and to the piston, with provisions for accommodating the recipical movement of the piston.
  • Another object of the invention is to provide for the use of a large number of parameters by the external control device, preferably through use of a computer for receiving input parameters relating to prevailing operating conditions and for instructing the control device accordingiy.
  • Another object of the invention is to provide an engine system utilizing variable compression ratio features, whether externally controlled or not, and also incorporating a supercharger so that under certain conditions, such as under heavy load, the compression ratio of the engine can be substantially reduced and the fuel supercharged, so that a high maximum power output is realized from a small engine.
  • the engine may under most conditions be operated at very high efficiency at a high compression ratio.
  • FIG. 1 is a block diagram indicating a system of the invention for an internal combustion engine, including a variable compression ratio piston and a supercharger, and a control system for optimizing efficiency and performance.
  • Fig. 2 is a schematic sectional view showing a variable compression ratio compound piston according to the invention, in an engine block cylinder, and with connected flexible hydraulic conduits in a helical arrangement for accommodating piston motion.
  • Fig. 3 is a view similar to Fig. 2, showing an alternate form of variable compression ratio piston and an alternate form of flexible conduit arrangement.
  • Fig. 4 is another view similar to Figs. 2 and 3, but showing another modified form of flexible conduit arrangement.
  • Fig. 5 is a schematic partial view of a piston similar to that of Fig. 2, but including a spring urging two piston sections together.
  • Fig. 6 is a partial view of a further modified form of piston including a flexible bellows acting as a hydraulic fluid chamber to control the separation of two piston portions, and also schematically indicating a hydraulic control arrangement that may be employed.
  • Fig. 7 is a schematic representation of another form of piston, with indication of a hydraulic control arrangement.
  • Fig. 8 is a schematic view of a modified, sealed hydraulic control system connected to a variable compression ratio piston.
  • Fig. 9 is a schematic view of a modified system wherein crankcase oil from the engine is used as hydraulic fluid and compression ratio is controlled by maintaining a generally constant peak pressure in the firing chamber, with supercharging to add power when needed.
  • Fig. 10 is a schematic view showing a modified form of variable compression ratio piston assembly wherein the position of a movable piston cap portion is controlled by an electric motor.
  • Fig. 1 shows in block diagram form a preferred system of the invention, indicating the arrangement of the control and operating mechanisms.
  • a computer 10 is preferably used to control both a hydraulic control mechanism 11 and a supercharger 12.
  • the hydraulic control mechanism is external to the piston and the engine block, being connected to the piston by a flexible hydraulic 13.
  • the hydraulic control mechanism 11 controls the amount of hydraulic fluid delivered through the flexible hydraulic conduit 13 to a hydraulic adjustable piston 14 capable of varying the compression ratio of the engine.
  • the computer 10 determines desirable compression ratio for the particular prevailing operating conditions of the engine and vehicle, delivers a signal to the hydraulic control mechanims 11 accordingly, and the control mechanism in turn pumps or withdraws fluid as appropriate until the desired compression ratio is obtained by the piston or pistons 14.
  • the computer 10 instructs a supercharger 12 at the intake manifold of the engine whether or not and to what extent the fuel charge should be supercharged.
  • engine power and efficiency levels are constantly regulated by the computer 10 and connected apparatus. Generally, maximum efficiency is achieved under low load or cruise conditions, and this is when the adjustable piston 14 can be set at the maximum compression ratio, the supercharger 12 being deactivated under these conditions. The power output of the engine under such conditions is relatively low, since little power is needed and efficiency is the chief concern.
  • Fig. 1 shows some of the important engine and vehicle operation inputs to be taken into consideration by the computer 10, according to a predetermined program, in controlling the compression ratio and the use of supercharging.
  • These inputs should include accelerator position and also accelerator movement, which may be used to determine the rate of change of accelerator position, both being relevant to the loading on the engine. Determining the rate of change of accelerator position helps anticipate loading slightly in advance.
  • Manifold vacuum level also a reflection of engine load, is input to the computer. Both vehicles speed and engine speed should be considered, and engine temperature may also be relevant, since detonation or knock often tends to occur more readily when an engine is hot.
  • Other dynamic variables relating to engine operating conditions may be input to the computer 10, if they are relevant to the tendency of knock to occur or to the maximum level at which compression ratio can be maintained without knocking.
  • Provisions may also be made for manually input and preset parameters relating to engine operation.
  • a setting may be provided for fuel octane, so that this adjustment may be made and left constant so long as the same fuel is being used.
  • Another preset input may be the allowable emission level for the particular vehicle or the geographical area in which it is being operated.
  • the thermal efficiency of the engine ! increases with increased compression ratio.
  • the heat loss and friction loss also increase with increased compression ratio.
  • a conventional engine modified by increasing the compression ratio only, i.e., without the reduced loss feature made possible by increasing the power with reduction of the compression ratio and supercharging, will have an efficiency improvement of only 37/32-1 16%, again using the Table II figures.
  • a subcompact car weighing 2500 pounds including a 400 pound load might be supplied with an engine with a peak power output of 70 HP. Good efficiency would probably be obtained up to about 55 HP.
  • this factor has been multiplied by the per-cylinder volume change factor for the particular compression ratio and by .75 for the reduced number of cylinders, to obtain a power factor (not listed).
  • the power factor has been multiplied by 55 HP to obtain the listed power output figures.
  • FIG. 2 shows in cross-section a head 20, engine block 21 including a combustion cylinder 22, and a variable compression ratio piston 23 according to the invention, as incorporated in an internal combustion engine.
  • two expansible fluid chambers 24 and 26 are included. These are formed by a piston base 27 connected by a wrist pin 28 in the usual way to a connecting rod 29, and a piston cap 31 configured as shown.
  • the base 27 includes a connecting yoke 32 at its lower end, through which the wrist pin 28 passes, only one side of the yoke 32 being shown in Fig. 2, and a wall portion 33 affixed thereto.
  • a cylindrical skirt 34 including some form of slidable sealing means, such as one or more O-rings 36 provided in appropriate grooves.
  • the sealing means 36 cooperates with the relatively movable piston cap 31, via a cylindrical outer wall 37 of the piston cap, similar to the cylindrical wall of a conventional piston.
  • a top end wall 38 again similar to that of a conventional piston, is secured to or integral with the cylindrical body 37, forming the upper expansible fluid chamber 24.
  • a lower wall 39 which may be generally annular in shape, with a central opening to accommodate slidably the connecting yoke 32 of the base portion as shown.
  • the slidable sealing means 41 are provided between the relatively movable surfaces, and the lower expansible fluid chamber 26 is formed between the walls 33 and 39 of the relatively movable piston portions, with the chamber surrounding the central yoke 32.
  • expansion of the upper fluid chamber 24 increases the height of the piston assembly and reduces the size of the firing chamber at top dead center piston position, thereby increasing the compression ratio of the piston and the engine.
  • the lower chamber 26 is being depleted of hydraulic fluid.
  • the upper chamber 24 is drained of fluid while fluid is pumped into the lower chamber 26, when the compression ratio is to be reduced.
  • the fluid supply to the chambers is controlled externally to the piston and to the engine block according to the invention, via hydraulic conduits 43 and 44, serving respectively the upper chamber 24 and the lower chamber 26. Communication of the conduits 43 and 44 with the chambers may be provided by channels 45 and 46 formed in the connecting yoke 32 of the piston base.
  • the flexible conduits 43 must of course reciprocate with the motion of the piston 23, and without interfering with the movement of the connecting rod 29, which ineludes side-to-side motion.
  • the conduits preferably have a considerable degree of flexibility and may be shaped in the form of a helix as illustrated, forming a helical path around the connecting rod and then passing to fittings 47 which conduct fluid through the engine block and to the hydraulic control mechanism 11 (Fig. 1).
  • This arrangement tends to minimize the amount of repeated flexure required at any one point on each hydraulic conduit 43 or 44, so that fatigue of the conduits does not cause a failure.
  • the helix shape absorbs the motion in the manner of a light spring.
  • the hydraulic conduits 43 and 44 may be made, for example, of such materials as beryllium-copper, monel or spring steel.
  • variable compression ratio piston assembly 23 illustrated in Fig. 2 has a pair of oppositelyacting expansible fluid control chambers
  • the helical hydraulie conduit arrangement shown may also be used for a single fluid control chamber embodiment, such as those discussed below and illustrated in Figs. 3, 4, 5 and 6. Similarily, additional conduits may serve the piston, such as for electrical wiring for monitoring sensors, so that more than two con ⁇ duits may be provided if desired.
  • Fig. 3 shows a different embodiment of a variable compression ratio piston 50, and a different arrangement for accommodating reciprocating motion in a hydraulic conduit 51. The piston 50, rather than including two relatively slidable portions as in Fig.
  • cap portion 52 which is a flexible diaphragm, corrugated as shown to accommodate differences in its configuration depending upon the volume of fluid in an expansible chamber 53 formed between the diaphragm 52 and a wall 54 of the piston base 56.
  • the diaphragm cap 52 may be formed. of a suitable material which will permit flexing without fatigue to the point of fracture, such as beryllium-copper.
  • the connecting rod 29 is connected to the piston base 56 in the conventional manner, by means of a wrist pin 57 passing through the cylindrical body 58 of the piston.
  • the modified form of hydraulic line arrangement of Fig. 3 includes a rigid tubular portion 59 extending downwardly from the piston base wall 54 as shown, in communication with the chamber 53, and the remaining hydraulic line 51 maybe flexible, formed into a loop and extending to connect with a fitting 61 communications with the exterior of the engine block 21.
  • a tension spring 62 is preferably ineluded, secured to the inside of the engine block 21 as shown, and connected to the flexible line 51 to continually urge it in an orientation which avoids the path of the connecting rod 29.
  • the lower looped portion 63 of the flexible line 51 remains in a U-shape, but the configuration changes to become a deeper or shallower loop with the reciprocation of the piston.
  • Fig. 4 shows another modified form of hydraulic line arrangement for a variable compression ratio piston assembly.
  • the type of piston cap 52 providing for variable compression ratio, is shown the same as that of Fig. 3.
  • a rigid tubular portion 65 of the conduit extends downwardly from the piston base wall 54 as in the Fig. 3 embodiment.
  • the remainder of the conduit is comprised of further rigid tubular portions 66 and 67, connected together and to an exit fitting 61 by pivotable, fluid-sealing joints 68, 69, and 71, respectively.
  • Fig. 5 shows another modified form of variable compression ratio piston assembly 75, with the cylinder, engine block and head omitted from this view.
  • a piston cap 76 of this form of the invention has a cylindrical body portion 77 and an end wall 78, with a central post structure 79 extending downwardly from the inside of the end wall 78, preferably integrally formed therewith.
  • At the lower end of the post structure 79 is an outwardly extending flange 81, against which a compression spring 82 bears, urging the flange 81 and the entire cap 76 downwardly with respect to a base 83 of the piston.
  • the base 83 of the piston also has a cylindrical body portion 84, secured to or integral with a base portion wall 86, which has a central opening 87 through which the post 79 passes, and appropriate sealing means 88 is provided.
  • sealing 89 is provided between the two telescopically fitted cylindrical bodies 84 and 77 of the base 83 and cap 76, respectively.
  • hydraulic fluid is sealed within an expansible chamber 91 formed between the base and the cap, and the chamber is in communication with a hydraulic conduit 92 which may take the form of a flexible, helical line as indicated for either of the other forms described above.
  • the spring 82 is included in the form of piston shown in Fig. 5 in order to urge the variable compression ratio piston assembly 75 toward the lower range of compression ratio, and to provide a resistance against inertia forces at the top of the stroke tending to lift the cap 76 off the base 83.
  • the hydraulics of the system also tend to retain the base and cap together, at least to the extent that cavitation would be required in the chamber 91 or the conduit 92 in order to enlarge the chamber 91 beyond the volume of hydraulic fluid present.
  • the spring provides additional restraint, and cavitation does not occur.
  • Fig. 6 shows a further modified form of variable compression ratio piston assembly 95, wherein a cap 96 and base 97 are telescopically fitted together as shown, each comprising generally a closed ended cylindrical body. No sealing need be provided between these relatively slidable bodies 96 and 97, since a flexible bellows 98 is secured within and between them and forms a fluid chamber 99.
  • the connecting rod 29 is connected by its wrist pin 28 to a rigid inner body 101 secured to the piston base 97 and extending upwardly, reducing the size of the chamber 99 and providing, along with the inner walls of the base portion 97 directly opposite, guidance for the reciprocal movement of the bellows 98.
  • the inner structure 101 provides space for receiving the end of the connecting rod 29, and forms a yoke for seating the wrist pin 28 to connect the piston base 97 and the connecting rod.
  • a form of hydraulic control assembly 102 is illustrated schematically in Fig. 6.
  • the system is shown as an open system, with hydraulic fluid stored in a sump 103 which may be open to the atmosphere and withdrawn therefrom by a pump 104, which delivers the fluid under pressure through a check valve 106 and a first hydraulic line 107 that may take the form of any of the types of conduit described above, passing through the engine block and up to the fluid chamber 99 in such a way as to avoid interference with the connecting rod 29.
  • a second hydraulic conduit 108 is provided, adjacent to and secured to the conduit 107, and serving as a return fluid conduit.
  • the check valve 106 serves the important function of preventing fluid backflow due to shock pressure at each explosion in the firing chamber of the engine cylinder.
  • a control valve 111 is provided in the line 108 just upstream of the fluid's return to the sump 103.
  • the valve 111 which is a simple on/off flow valve, is closed whenever the compression ratio of the piston is being increased or is maintained constant, and is opened when the compression ratio is to be reduced.
  • the pump 104 when the ratio is to be increased, the pump 104 is activated and the valve 111 is closed; when the ratio is maintained at a certain level, the pump 104 is inactive and the valve 111 remains closed; when compression ratio is to be reduced, the valve 111 is simply opened to return fluid to the sump, until the desired ratio is reached.
  • control functions can be governed by a computer 112, operably connected to the pump 104 and to the control valve 111 as indicated. For determining when the desired compression ratio is obtained, according to a predetermined program and according to some or all of the inputs discussed above in connection with Fig.
  • a pressure sensor 113 is included in the hydraulic delivery line 107 and operably connected to the computer 112, so that the pressure may be monitored at top dead center or other appropriate position of the piston's stroke, and this pressure will reflect the pressure in the firing chamber at that point and thus the compression ratio of the piston.
  • a third conduit 116 may be provided, following the same path as the other conduits 107 and 108, and this may lead to the computer 112 in place of or as a supplement to the pressure sensor 113 in the line 107.
  • a dashed line 117 indicates connection of the pressure transducer or sensor 114 to the computer 112, via the flexible conduit 116.
  • the bellows type variable compression ratio piston assembly 95 of Fig. 6 would be controlled with a single hydraulic line, in a closed system whereby fluid is simply moved into or out of the chamber 99 through the single hydraulic line, with pressure continually maintained on the fluid.
  • a control system will be described below in reference to Fig. 8.
  • the dual hydraulic line, open system 102 is shown in Fig. 6 for situations where circulation of fluid is desirable, as for cooling of the fluid and the piston assembly.
  • Fig. 7 schematically indicates a hydraulic control system 119 similar in many respects to the system of Fig. 6, connected to a dual-chamber variable compression ratio piston assembly 121, which may be similar to the piston assembly shown in Fig. 2.
  • dual hydraulie lines 122 and 123 to the piston assembly 121 with its upper, or increase-compression chamber 124 and its lower, or decrease-compression chamber 126 do not circulate fluid but act oppositely to one another. That is, when compression ratio is increased by a pumping of fluid through the line 122, fluid is at the same time being drained from the piston through the line 123.
  • valves 127 and 128 in the hydraulic lines 122 and 123, each of which has three positions: closed, so that fluid cannot pass through it in either direction; open, so that fluid is pumped into the hydraulic 122 or 123 by the pump 104; and a drain position, whereby the line 122 is connected directly to a drain line 129 into the sump 103, or the hydraulic line 123 is connected directly to a drain line 131 into the sump, as shown.
  • the pump 104 is valved off from that particular valve and associated hydraulic line.
  • Appropriate control of the valve 127, the valve 128, and the pump 104 is effected by the computer 112.
  • a pressure sensor 113 may be included in the hydraulic line 122, and one may additionally be provided in the line 123 (not shown) if needed.
  • the computer activates the pump 104 and opens the control valve 127 and moves the control valve 128 to the drain position. Therefore, the pump withdraws fluid from the sump 103 and delivers it through the valve 127 and the hydraulic line 122 to the upper chamber 124 of the piston, expanding it and increasing the compression ratio, while reducing the size of the lower chamber 126. Accordingly, fluid is drained from the chamber 126 through the line 123 and the valve 128 to the sump.
  • both control valves 127 and 128 are closed, and the pump 104 is deactivated. In this mode the pump 104 is isolated from the compression shock exerted on the piston 121 and its fluid chambers 124 and 126, since the valves 127 and 128 are both fully closed.
  • the pump 104 is again activated, but this time with the control valve 128 open to deliver fluid through the line 123, with the control valve 127 in the draining position.
  • the system 119 of Fig. 7 could be modified to a closed system, with fluid retained in the chambers, lines and pump and not circulated to an open sump.
  • the pump 104 is reversible, or appropriate valving is included, the sump 103 can be eliminated, with the valves 127 and 128 simple on/off valves, and when a change in the compression ratio of the piston 121 is desired the pump can simply withdraw fluid from one of the lines 122 or 123 and deliver it into the other.
  • the two on/off valves would both be open during changes in the compression ratio, and both closed under constant compression ratio to isolate the pump from compression shocks.
  • Fig. 8 shows a closed system hydraulic control arrangement 135 which can be used with any of the singlechamber type variable compression ratio pistons described above.
  • the system is closed in the sense that it is totally sealed with the fluid contained.
  • a piston assembly 50 similar to that of Fig. 3 is shown here.
  • an expandable control bellows 136 connects to the chamber 137 of the piston through a hydraulic line 138. Contraction of the control bellows 136 pushes fluid through the line 138 and expands the chamber 137.
  • the compression ratio is to be reduced.
  • the control system 135 illustrated in Fig. 8 is designed to develop a high pressure in the bellows 136 for control of the piston 50 by use of a relatively small motor 139. High pressures are required to add fluid to the chamber 137 during firing, and the illustrated system 135 is efficient for this purpose.
  • a bearing plate 140 at the rear of the control bellows 136 is borne against by a member 141 which is rigidly attached to a threaded shaft 142. Threadedly connected to the shaft 142 is a rotatable shaft 143, appropriately supported for rotation and against translation by bearings 144.
  • a worm gear 146 Threadedly connected to the shaft 142 is a rotatable shaft 143, appropriately supported for rotation and against translation by bearings 144.
  • Fig. 9 shows a modified variable compression ratio piston assembly and system which does not include external control of the compression ratio in the sense of the systerns described above.
  • a supercharger 151 is included and is operably connected to relevant engine/ vehicle operation inputs such as accelerator position and rate of change of position, manifold pressure and vehicle speed, so as to initiate supercharging when conditions demand greater power, under such conditions, the supercharger forces a pressurized charge into the combustion chamber 152, and pressure therein is accordingly increased. Peak pressure in the firing chamber 152 is therefore increased significantly, and this increase is also reflected in an expansible fluid chamber 153 between a movable cap portion 154 and a base portion 156 of the variable compression ratio piston 157.
  • the piston 157 may be a simple single chamber assembly, as also described above with reference to Fig. 5.
  • oil 158 from the engine's crankcase is preferably utilized for pressurizing the chamber 153 of the piston, so that the oil may be dumped directly back into the crankcase when the cap portion of 154 of the piston is to be retracted.
  • crankcase oil is drawn by a pump 159 through a line 161 from the crankcase, through an oil -filter 162, and delivered through a check valve 163 through the crankcase wall 164 and a flexible line 166 (which may take any of the forms described above) to the expansible fluid chamber 153.
  • the volume in the expansible fluid chamber 153 of the piston 157 be changed in small increments.
  • the pump 159 is more preferably adapted to be constantly operational in exerting pressure to push oil through the line 166 toward the fluid chamber 153. Fluid is moved by the pump into the chamber 153 not at peak pressure but at the lower cylinder pressures that occur between explosions in the cylinder. In the intake cycle (without supercharging) there is vacuum in the chamber 152, so that without a limitation on the pump 159, large increases in the fluid volume in the expansible chamber 153 could be expected to occur, only to be reversed when peak pressure occurs and the piston cap 154 is forced back downwardly.
  • both the pump 159 and the relief valve 167 are preferably structured to work in small increments.
  • the pump may advantageously be a reciprocating type pump, connected by linkage 168 which is illustrated only for example, operable directly from the rotation of the engine's crankshaft.
  • the mechanically operated reciprocal pump 159 therefore pumps incrementally.
  • the pumped increments of fluid are small so that the amount of increase in volume in the fluid chamber 153 of the piston, for each cycle, is limited to a definite quantity.
  • an increase in the compression ratio from an old value to a desired new value, based on conditions requires several cycles, perhaps even ten to fifteen cycles or more, to complete. In a given cycle therefore, only a very small increrment of increase in the fluid chamber volume occurs. This may occur even when the engine is operating under a steady state condition such as cruise; the small volume increase is reversed again at peak pressure by venting excess pressure (and volume) through the relief valve 167.
  • the relief valve 167 discharges fluid faster than it is admitted by the pump 159, and the piston cap 154 retracts to lower the compression ratio.
  • the compression ratio preferably is not lowered to its desired value in one or a few cycles. Instead, it should be lowered somewhat gradually, and this is accomplished by limiting the outflow of fluid from the relief valve 167 in each cycle.
  • Such limitation can be provided, for example, by an enclosure 169 below the relief valve, through which all fluid exiting the valve 167 must flow.
  • An orifice 171 in a wall of the enclosure limits the rate of flow of fluid out to the crankcase, but still has the effect of permitting somewhat higher outflow under higher pressures.
  • the relief valve 167 is operable to reduce compression ratio even without supercharging, under certain conditons. Thus, under load when peak pressure rises and ordinarily would cause knock, fluid is vented from the chamber 153 to lower the compression ratio somewhat, until conditions change again.
  • the pump 159 can be locate inside the engine's crankcase if desired, or mounted on the engine block in the same manner as a typical oil pump is mounted.
  • the relief valve 167 may optionally be a variable-threshold relief valve, with a control linkage line 173 leading from the valve alongside the hydraulic line 166 and out of the crankcase to an external control device 174.
  • the valve 167 may be pilot-pressure operated to provide the variable threshold, in which case the control line 173 would be a fluid conduit.
  • the valve may have a electrical pressure threshold control, as by a solenoid (not shown), and the line 173 would then be a conduit with electric wiring inside.
  • the control device 174 external to the engine block regulates the setting of the relief valve 167 according to engine and vehicle operation inputs as indicated in the drawing.
  • the control 174 may also regulate the operation of the supercharger 151. Adjustability of the pressure at which the relief valve vents fluid from the piston chamber 153 enables closer control of the compression ratio and better matching of the ratio to the wide variety of operating conditions encountered.
  • a variable compression ratio piston 176 has a movable cap portion 177 which is received in a s ⁇ rewthreaded connections on a base 178 as indicated schematically in the figure.
  • a long, shaft-like gear 179 is rigidly attached to and extends downwardly from the end wall 181 of the piston cap, and it is engaged by a motor and reduction gearing assembly 182 mounted on the top of the piston base portion 178 as shown.
  • Electrical wiring 183 from the motor assembly passes through base portion 178 and through a conduit 184 (which may be similar to any of those described above), out of the engine block to a computerized control device 186.
  • the control device 186 is connected to a power supply 187 for supplying power to the motor assembly 182.
  • the operation of this piston assembly is substantially as described above for the hydraulically operated embodiments.
  • a supercharger may be used with this system, also in the same manner as described earlier.
  • the invention encompasses several variations of engines and assemblies including an adjustable, variable compression ratio piston.
  • One principal feature of the invention is the provision of an adjustable piston with control external to the engine block, permitting complete adjustment for any variation of operating conditions. Supercharging may advantageously be used with such a system, but not necessarily.
  • the mechanism for adjusting the piston may take any of several forms.
  • Another very important feature of the invention is the use of supercharging in combination with any type of variable compression ratio piston, whether externally controlled or not, so that compression ratio may be lowered and supercharging introduced to increase power when needed. Under conditions requiring lower power, the compression ratio is maintained relatively high, without supercharging.
  • the invention includes methods, as well as apparatus, for performing these functions. Other important features of the invention include the specific preferred structures shown and described above.

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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)

Abstract

Le taux de compression d'un moteur est commandé afin d'optimiser son rendement et/ou sa performance en modifiant la longueur utile du piston (14), mesuré depuis le tourillon de crosse. La longueur du piston est hydrauliquement commandée par un ordinateur (10) qui commande un mécanisme extérieur (11) de commande hydraulique connecté à une extrémité de la conduite hydraulique (13); l'autre extrémité de la conduite (13) est connectée à une cavité de commande dans le piston (14). La conduite (13) s'ajuste au mouvement alternatif du piston (14), de préférence suivant une hélice souple. L'ordinateur (10) entre plusieurs paramètres de fonctionnement du moteur, tels que la position de l'étrangleur, la pression d'admission du collecteur, la température de l'air, la température d'échappement, et l'indice d'octane du carburant afin de calculer le taux de compression optimum dans toutes conditions de charge, même dans le cas d'un moteur surchargé, et d'obtenir un rendement maximal.
EP19840903395 1984-08-29 1984-08-29 Piston a taux de compression variable commande pour un moteur a combustion interne Withdrawn EP0191759A1 (fr)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/US1984/001397 WO1986001562A1 (fr) 1984-08-29 1984-08-29 Piston a taux de compression variable commande pour un moteur a combustion interne

Publications (1)

Publication Number Publication Date
EP0191759A1 true EP0191759A1 (fr) 1986-08-27

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EP19840903395 Withdrawn EP0191759A1 (fr) 1984-08-29 1984-08-29 Piston a taux de compression variable commande pour un moteur a combustion interne

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EP (1) EP0191759A1 (fr)
WO (1) WO1986001562A1 (fr)

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EP3748144A1 (fr) 2019-06-03 2020-12-09 Winterthur Gas & Diesel AG Procédé de fonctionnement d'un grand moteur ainsi que grand moteur

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DE3714762A1 (de) * 1987-05-04 1988-11-24 Bayerische Motoren Werke Ag Kolben mit variabler bauhoehe
AUPO904197A0 (en) * 1997-09-09 1997-10-02 Dixon, Michael Patrick Internal combusion engine
DE10220598B3 (de) * 2002-05-08 2004-03-04 Siemens Ag Verfahren zum Anpassen des Zündwinkels an das Verdichtungsverhältnis einer Brennkraftmaschine
DE10220597B3 (de) * 2002-05-08 2004-02-26 Siemens Ag Verfahren zum Anpassen einer Klopfregelung an das veränderliche Verdichtungsverhältnis einer Brennkraftmaschine
DE10220601C1 (de) * 2002-05-08 2003-12-18 Siemens Ag Verfahren zum Anpassen der Ladezeit einer Zündspule an das veränderliche Verdichtungsverhältnis einer Brennkraftmaschine
DE10220596B3 (de) * 2002-05-08 2004-01-22 Siemens Ag Verfahren zum Regeln des Verdichtungsverhältnisses einer Brennkraftmaschine
US6752105B2 (en) 2002-08-09 2004-06-22 The United States Of America As Represented By The Administrator Of The United States Environmental Protection Agency Piston-in-piston variable compression ratio engine
DE102010041103A1 (de) * 2010-09-21 2012-03-22 Bayerische Motoren Werke Aktiengesellschaft Kolben für eine Hubkolben-Brennkraftmaschine
CA2853748C (fr) 2011-10-05 2020-07-07 Engineered Propulsion Systems, Inc. Systeme de commande d'ensemble d'entrainement a compression-combustion aeronautique
KR101500386B1 (ko) 2013-12-20 2015-03-18 현대자동차 주식회사 가변 압축비 장치
JP6443408B2 (ja) * 2016-07-21 2018-12-26 トヨタ自動車株式会社 内燃機関の制御装置
EP3655635B1 (fr) 2017-07-21 2024-05-15 General Atomics Aeronautical Systems, Inc. Moteur diesel aéronautique amélioré
WO2019175696A1 (fr) * 2018-03-15 2019-09-19 King Abdullah University Of Science And Technology Commande sans fil de soupape actionnée dans un piston à taux de compression variable

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EP3748144A1 (fr) 2019-06-03 2020-12-09 Winterthur Gas & Diesel AG Procédé de fonctionnement d'un grand moteur ainsi que grand moteur

Also Published As

Publication number Publication date
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