Valve-arrangement for controlling gas in a piston-type internal-combustion engine

A valve arrangement for controlling gas exchange in a piston-type internal-combustion engine consisting of an arrangement of valves through which it is possible to optimize the filling of the combustion chamber of the cylinder with the fuel mixture as well as exhaust of the residual gases of combustion. The system includes (provides for) the transfer of the functions of the conventional intake and exhaust valves to additional valves located in the respective intake and exhaust conduits, each of the conduits being open to and communicated with the other in the cylinder head thereby creating a common chamber or chambers (plenum or plenums) through which the respective gas mixtures are directed, permitting a partial, controlled contact between the two gas mixtures, and using the conventional valve system opening directly to the combustion chamber for enhancing the speed and efficiency of charging the combustion chamber with working fluid, sealing the combustion chamber during the processes of compression of the combustible gas mixture and expansion of residual gases of combustion, and increasing the speed and efficiency of expulsion of gases of combustion from said combustion chamber.

BACKGROUND OF THE INVENTION
 This invention relates to an arrangement of valves for an internal
 combustion engine and more particularly to an improved arrangement of
 valves that permits better engine performance while, at the same time,
 affording a degree of exhaust emission control by simplifying the process
 of exhaust gas re-circulation (EGR). In addition, the invention provides
 for a simplification of systems known in the art that provide improved
 working fluid mixing (fuel+air) and better control of premature ignition
 through an automatic exhaust gas recycling (EGR) mechanism.
 It is well known that a variety of modifications have been incorporated
 over the years for improving the performance of internal combustion
 engines and for controlling exhaust gas emissions, and particularly for
 controlling the emission of hydrocarbons, carbon monoxide and NOx in the
 exhaust gases. Unfortunately, many of the innovations employed to provide
 exhaust emission control can deteriorate the fuel economy of an engine
 while performance enhancement often leads to greater complexity and cost
 in engine manufacture and maintenance.
 One way in which these objectives have been met is through the use of
 compound induction systems for the engine wherein low and mid-range
 performance operation is obtained by a single, relatively small intake
 passage to offer good turbulence in the combustion chamber, while high
 speed requirements are met by a larger effective passage so as to improve
 volumetric efficiency in the introduction of working fluid (the
 combustible gas mixture, fuel/air etc.). Normally this type of compound
 induction system incorporates at least two intake passages that serve each
 combustion chamber with a throttle valve arrangement for controlling the
 flow through one of the intake passages so that it will supply no charge
 under low and mid-range load conditions. However, the existence of this
 additional passage and its flow control valve can give rise to pumping
 losses that deteriorate the fuel economy of the engine when the control
 valve is closed.
 For the control of contaminating gas emissions, in particular NOx compounds
 that are major smog producing agents, the practice of exhaust gas
 recycling (EGR) is often incorporated. EGR is found to reduce the
 combustion temperature of the working fluid in the combustion chamber,
 thereby reducing the formation of NOx compounds and, at the same time,
 helping to prevent premature ignition of the combustible mixture which
 produces the well-known phenomenon knows as engine "knock." Premature
 ignition is conventionally controlled by adjusting the characteristics of
 the fuel by the addition of "anti-knock" agents, which are themselves
 known or suspected environmental contaminants.
 It is a principle object of this invention to provide a novel valve
 arrangement that improves engine performance by reducing the physical
 limitations placed on conventional valve arrangements in internal
 combustion engines by what is known in the art as "valve flotation," in
 which the rate of valve opening and closing is limited by the speed with
 which the valve actuating mechanisms known in the art can respond
 physically and thereby complete their intended function.
 It is a further principal object of this invention to provide a novel valve
 arrangement providing for common conduits leading to the combustion
 chamber of the engine through one or more pre-combustion chambers or
 plenums in which what may be considered conventional intake and exhaust
 chambers are openly and directly intercommunicated to form a chamber or
 chambers that communicate directly with the combustion chamber. Said
 communication between conventional conduits for induction and exhaust
 processes for an engine provide improved performance results under all
 running conditions, while at the same time providing improved exhaust
 emission control. These goals are achieved while simplifying the
 mechanical aspects of related current technology.
 It is a further object of this invention to provide an improved valve
 arrangement for induction and exhaust processes for an engine that permits
 the aforementioned results while, at the same time, eliminating or
 substantially reducing pumping losses under low and mid-range performance
 so as to improve fuel economy.
 One way in which NOx emissions are controlled is through the use of exhaust
 gas re-circulation (EGR). Re-circulating exhaust gases into the combustion
 chamber under at least some running conditions reduces the temperature of
 combustion and thereby the formation of NOx. However, the use of EGR can
 give rise to poor running characteristics when large quantities of exhaust
 gases are re-circulated, especially at high working loads.
 It is, therefore, a still further object of this invention to provide an
 improved system for permitting increased usage of EGR without
 deteriorating engine performance.
 It is a further object of this invention to provide an EGR system for an
 engine having a compound induction system wherein the EGR is employed to
 reduce pumping losses as well as controlling the emission of NOx.
 SUMMARY OF THE INVENTION
 The present invention relates to an arrangement of valves for single or
 multi-cylinder, piston-driven internal combustion engines, of the type
 comprising: a cylinder head comprised of at least one intake conduit and
 at least one exhaust conduit mutually communicated one with the other
 thereby forming one or more pre-combustion chambers or plenums, said
 plenum or plenums being communicated with the combustion chamber by one or
 more intake and exhaust valves, said valve or valves being of the
 conventional poppet-type with the respective valve actuation mechanisms
 well known in the art. The induction of working fluid into said plenum or
 plenums is controlled by: (a) one or more valves of the poppet type with
 the appropriate operating mechanisms well known in the art; (b) one or
 more rotary valves with the appropriate valve control mechanisms; or (c)
 an electronically controlled working fluid (fuel/air) mixture injection
 system or other suitable method for the controlled introduction of the
 required combustible gas mixture (working fluid) into one or more of said
 plenum or plenums. Said plenum or plenums being communicated with the
 combustion chamber of said cylinder by at least one intake valve and at
 least one exhaust valve for each cylinder, said valve or valves being of
 the conventional poppet-type with the respective valve actuation
 mechanisms suitable for simultaneously biasing all of said valves in the
 open position during both the intake and exhaust cycles of said engine.
 Internal combustion engines of various configurations have been developed
 and used for many years with many modifications intended to optimize the
 performance of the engine under all running condition. In such engines,
 various approaches have been proposed to overcome problems with engine
 performance, fuel combustion efficiency, and exhaust emissions. However,
 the solutions proposed heretofore are not fully satisfactory from the
 standpoint of simplicity and reliability of construction, and sometimes
 have caused problems due to poor combustion at high or low operating
 speeds and/or unacceptably high levels of nitrogen oxides in the exhaust
 gases under some operating conditions.
 In the current state of the art of piston-driven internal combustion
 four-cycle engines, several problems and limitations are encountered
 related to the cylinder head and the system or systems of valves employed
 to control the intake of the combustible fuel mixture (the working fluid)
 and the exhaust of residual gases of combustion. Among those disadvantages
 one can point out the following:
 a. Since the intake and exhaust ports and their respective valves are
 separate and isolated one from the other, except with respect to the
 combustion chamber, each function (intake and exhaust) utilizes only a
 fraction of the surface area or communication area available in the
 cylinder head leading to the combustion chamber for the entrance and exit
 of gases. That is, only approximately fifty per cent (50%) of the
 theoretically available opening into the combustion chamber is available
 for each of the intake and exhaust processes, thereby significantly
 limiting the efficiency of gas exchange (working fluid and exhaust gases).
 In many conventional engines the intake valve is larger than the exhaust
 valve because the gas flow into the cylinder, usually at or near
 atmospheric pressure, except where supercharging is involved, is slower
 than the exhaust flow out of the cylinder, which occurs under the pressure
 of the ascending piston in the exhaust cycle. In the current invention,
 since the intake and exhaust ports are communicated by one or more common
 pre-combustion chambers (plenums), each cycle of intake and exhaust takes
 full advantage of all valves opening to the combustion chamber, thereby
 making use of 100% of the theoretically available gas passage area and
 significantly improving both processes in terms of the rate of cylinder
 charging and evacuation that can be attained. By taking advantage of the
 opening produced by using the conventional exhaust valves during the
 intake cycle, it becomes possible to simplify the valve configuration by
 using all valves of the same size without sacrificing efficiency in the
 rate of fuel mixture aspiration or exhaust. It will be clear to one
 experienced in the art that such an arrangement should also significantly
 simplify the mechanism employed for the movement of said valves since all
 will be functioning in the same manner simultaneously.
 The use of a common pre-combustion plenum or plenums for both the intake
 and exhaust cycles gives the added advantages of allowing for the
 preheating (vaporization) of the working fluid by the residual heat of the
 exhaust gases remaining in the pre-combustion plenum or plenums and a more
 thorough mixing of said working fluid due to turbulence produced by said
 mixing and that produced by the influx of working fluid into the
 combustion chamber through the various ports provided by the conventional
 intake and exhaust valves.
 b. In the conventional four-cycle piston-driven internal combustion engine,
 a certain percentage of the energy provided by the combustion process is
 used (lost) as the motive force necessary for operating the essential
 mechanical functions of the engine, such as the opening and closing of
 valves. In the present invention, the ability of the system to aspirate
 (intake) the combustible fuel mixture (working fluid) and evacuate
 (exhaust) the residual gas mixture through an area much greater than that
 of a conventional engine, reduces engine power loss in the two processes
 significantly because the greater area available for gas passage into and
 out of the combustion chamber reduces resistance to flow due to gas
 viscosity.
 c. In a typical high technology, internal combustion engine in current
 production (for example, as used in the Fiat Tempra), the corresponding
 manual and automotive guide (February, 1994) states that during the intake
 cycle, the intake valves close 42.degree. in crank shaft rotation after
 the piston has passed the point of bottom-dead-center, being already in
 the ascending compression cycle, indicating that the intake valves are
 still open during the initiation of the compression cycle and full
 theoretical compression is not obtained. Likewise, as the exhaust cycle is
 beginning, the exhaust valves open 47.degree. before the piston reaches
 bottom-dead-center. That is, the expanding gases of combustion begin to
 escape before the expansion cycle is completed and useful potential work
 is lost. The sum of these two "overlaps" in the intake and exhaust cycles
 is 89.degree. of rotation of the crank shaft, directly translated in the
 movement of the piston in order to obtain the optimum equilibrium result
 in each of the cycles. Given the greatly enhanced rate of intake and
 exhaust provided by the current invention in terms of the filing and
 evacuating of the combustion chamber, a large part or all those 89.degree.
 of rotation of the crank shaft can be translated into useful, productive
 movement of the piston while still obtaining the optimum equilibrium in
 each cycle.
 d. The conventional piston-driven internal combustion engine is physically
 limited in the number of revolutions per minute that can be obtained by,
 among other things, the phenomenon know as "valve flotation." Valve
 flotation is the condition encountered at high rpm where the physical
 inertia of the valves and associated mechanisms makes it impossible for
 the mechanical apparatus involved to alternately open and close the valves
 in question at a faster rate. The result is a condition in which the
 valves effectively appear to be "floating" between their open and closed
 positions. The current invention, by reducing significantly the necessity
 to open and close the conventional valves to the combustion chamber, all
 of those valves being held open during both the intake and exhaust cycles,
 allows the engine to obtain much higher rpm's before the effect of valve
 flotation becomes apparent. In other words, a given theoretical engine
 design can obtain much higher rpm values resulting in much improved
 performance characteristics.
 e. In conventional high performance internal combustion engines the
 phenomenon known as premature ignition or engine "knock," due to high
 combustion chamber pressures and temperatures, necessitates the use of
 high octane fuels with added inhibitors (anti-knock agents), most of which
 are materials known or suspected to be damaging to the environment. In
 addition, the higher combustion temperatures obtained in high performance
 engines often leads to an increase in the amount of nitrogen oxides
 (NO.sub.x) produced in the combustion process, such compounds being
 principle smog-producing agents. On some conventional engines, the exhaust
 valve is allowed to stay open at the beginning of the intake cycle so that
 some exhaust gases are drawn back into the cylinder (internal recycling)
 or recycled using some external mechanism (external recycling) where they
 serve to lower the combustion temperature peaks and reduce NO.sub.x
 formation. The current invention, by creating and unifying one or more
 pre-combustion chambers, allows for an automatic, self-limited mixing of
 residual exhaust gases with the incoming combustible mixture (working
 fluid), thereby accomplishing the same favorable result desired in some
 conventional engines without sacrificing power due to late closing of the
 exhaust valve during the intake cycle and without the need to add complex
 operating mechanisms to control the extent of EGR according to the given
 running conditions. An additional advantage of the current invention may
 be seen in a reduced need for anti-knock components in the fuel.
 f. The use of overhead valves in conventional piston-driven internal
 combustion engines is necessitated primarily by the physical requirements
 of high performance engines related to the intake and exhaust cycles at
 high rpm and high compression ratios. The current invention, by
 significantly improving the speed and efficiency of each process, reduces
 the physical requirements leading to the necessity of using overhead
 valves. The replacement of overhead valve systems with simpler lateral
 valves could significantly reduce the cost of engine manufacture and
 maintenance.
 g. A recent innovation in high performance engines has been the
 introduction of variable distribution cam shaft operation which varies
 automatically the timing of the opening and closing of the intake and
 exhaust valves according to the operating conditions of the engine, said
 variability in operation being accomplished by the incorporation of
 complex centrifugal or other mechanisms that change the spatial
 relationships among the respective valve cams according to the operating
 speed or rpm's of the engine. A further important feature of the present
 invention is that the same effect is obtained automatically without the
 need for the addition of complex valve operating mechanisms.
 It is also to be pointed out that the engine according to the invention
 provides a better mixing of the residual gases and working fluid, so as to
 increase the percentage of residual gases which can be introduced into the
 cylinder without jeopardizing the efficiency of combustion.

DETAILED DESCRIPTION
 In a first preferred embodiment of the invention, an internal combustion
 engine is provided of the overhead valve type with one or more cylinders
 (only one of which is illustrated in the figures) formed in a cylinder
 block, said cylinder or cylinders having a piston adapted to be
 reciprocally moved in said cylinder, said cylinder or cylinders being
 sealed by attachment to the upper end of said cylinder or cylinders, and a
 cylinder head containing a disposition of valves according to the
 invention, said cylinder block and cylinder head cooperating in defining a
 combustion chamber.
 In FIGS. 1-9 reference numeral 10 generally designates the cylinder head of
 a single or multi-cylinder internal combustion engine comprising, for each
 cylinder, a cavity 11 formed by the bottom surface 12 of the cylinder head
 10, the top surface 13 of the piston, and the walls of the cylinder block
 23, thus defining the combustion chamber, into which there open one or
 more ports or conduits 14. In a conventional overhead valve internal
 combustion engine known in the art, said ports or conduits would be
 designated as "intake" and "exhaust" ports and would be opened and closed
 consecutively as required for the proper functioning of the engine by the
 respective valve actuating mechanisms. However, for the present invention,
 since all of said ports or conduits are employed for both intake and
 exhaust operations, said ports or conduits will be defined as "gas
 exchange ports" and their respective valve or valves "compression valves".
 The communication of said gas exchange port or ports 14 with the combustion
 chamber 11 is controlled by one or more compression valves 15, of the
 poppet-type or other type know to those skilled in the art and operated by
 mechanism well known in the art. Above the combustion chamber 11 and
 forming part of the cylinder head 10 is located one or more pre-combustion
 chambers or plenums 16, said plenums being communicated with one or more
 intake conduits 17 and one or more exhaust conduits 18. Communication of
 said intake conduit or conduits 17 with the pre-combustion chamber, plenum
 or plenums 16 is controlled by one or more intake valves 19, of the
 poppet-type, of the rotary-type, or of other types know to those skilled
 in the art. The opening and closing of said intake valve or valves 19
 being controlled by mechanisms well known in the art and schematically
 illustrated at 27. In a preferred embodiment of the invention, cylinder or
 combustion chamber compression valve(s) 15, pre-combustion chamber intake
 valves 19, and pre-combustion chamber exhaust valve(s) 20 will be operated
 by a single, unified cam mechanism.
 Communication of said exhaust conduit or conduits 18 with the
 pre-combustion chamber or chambers 16 is controlled by one or more exhaust
 valves 20, of the poppet-type, of the rotary-type or other type know to
 those skilled in the art. The opening and closing of said exhaust valve or
 valves 20 being controlled by mechanisms well known in the art. In a
 preferred embodiment of the invention, the internal combustion engine
 employing the valve arrangement of the invention will be of the spark
 ignition-type as illustrated by the presence of one or more spark plugs 21
 projecting into the combustion chamber 11.
 In FIG. 1, the working piston 22 is illustrated in its top-dead-center
 (TDC) position. In that position, the pre-combustion chamber intake
 valve(s) 17 and exhaust valve(s) 18 and the combustion chamber compression
 valves 15 are closed in preparation for the initiation of the intake
 cycle.
 In FIG. 2, the working piston 22 has begun its downward movement to begin
 the aspiration or induction of working fluid (fuel/air mixture) at which
 time the combustion chamber compression valve or valves 15 are opened
 simultaneously and the pre-combustion chamber intake valve or valves 19
 opens while pre-combustion chamber exhaust valve or valves 20 remains
 closed.
 In FIG. 3 induction of working fluid continues until the piston 22 reaches
 its position of bottom-dead-center (BDC) as illustrated in FIG. 4. At BDC
 the piston is in position to begin the compression cycle as illustrated in
 FIG. 5, at which time the combustion chamber compression valve or valves
 15 and the pre-combustion plenum(s) intake valve or valves 19 are closed.
 It should be noted that the timing of the valve opening and closing cycles
 is not in any way limited by the invention in that some overlapping of
 said operations may be desirable according to the needs of the engine to
 insure its most efficient operation.
 In FIG. 6 the compression cycle is completed, the piston 22 is located at
 TDC, and working fluid ignition occurs to initiate the power cycle as
 illustrated in FIG. 7. At the end of the power cycle the piston 22 reaches
 BDC as illustrated in FIG. 8 and the combustion chamber compression valve
 or valves 15 and the pre-combustion chamber exhaust valve or valves 20 are
 opened allowing the combustion gases to be expelled from the cylinder. In
 the process of exhausting combustion gases illustrated in FIG. 9, a
 portion of said combustion gases will remain in the pre-combustion chamber
 to be mixed with the working fluid inducted in the subsequent intake
 cycle.
 A further important feature of the invention lies in that the gas exchange
 ports 14 and the corresponding compression valves 15 associated with each
 cylinder combustion chamber may have specific shapes designed to optimize
 the mixing of fluid flows entering therein. In particular, the gas
 exchange ports 14 may be shaped so as to generate a high tumble of the
 fluid flow entering the combustion chamber. This can be obtained in any
 way known per se, by suitably designing the profile of said gas exchange
 ports.
 FIG. 10 illustrates an alternative embodiment of the invention wherein the
 intake and exhaust valves are rotary valves 24, 25 respectively. This
 embodiment is in all other respects identical in structure and function to
 the embodiment of FIGS. 1-9.
 FIG. 11 illustrates another alternative embodiment of the invention wherein
 the engine has a lateral-valve configuration. Cylinder valves 15 are
 positioned between pre-combustion chamber 16 and combustion chamber 11 as
 in the embodiments of FIGS. 1-10. The exhaust and intake valves are
 illustrated at 26, and operate as in the other embodiments so as to
 advantageously allow the entire volume of pre-combustion chamber 16 to be
 used for both fuel intake and exhaust outflow.
 Naturally, while the principle of the invention remains the same, the
 details of construction and the embodiments may widely vary with respect
 to what has been described and illustrated without departing from the
 scope of the present invention.