United States Patent [19]
`Worth et al.
`
`[54] METHOD OF OPERATING AN INTERNAL
`COMBUSTION ENGINE
`
`[75]
`
`Inventors: David Richard Worth, Shenton Park;
`Stephen James Watson, Greenwood;
`Jorge Manuel Pereira DaSilva. North
`Beach, all of Australia
`
`[73] Assignee: Orbital Engine Company (Australia)
`Pty. Limited, Balcatta, Australia
`
`[21] Appl. No.:
`
`446,739
`
`[22] PCf Filed:
`
`Jan.24, 1994
`
`[86] Per No.:
`
`PCT/AU94/00028
`
`§ 371 Date:
`
`Jun. 6, 1995
`
`§ 102(e) Date: Jun. 6, 1995
`
`[87] PCf Pub. No.: W094/17229
`
`PCf Pub. Date: Aug. 4, 1994
`
`[30]
`
`Foreign Application Priority Data
`
`[AU] Australia ................................. PL6972
`
`Jan. 25, 1993
`Int. Cl.6
`
`[51]
`
`................................ F01N 3/36; F01N 3/38;
`F02D 41/06; F02P 5/15
`[52] U.S. CI ............................ 60/285; 123m C; 123/305
`[58] Field of Search .................................. 123/73 C, 295,
`123/305, 425, 435, 676; 60/274, 276, 284,
`285
`
`[56]
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`I IIIII
`
`Ill IIIII IIIII IIIIi 1111111111111111111111111111111111111111111
`5,655,365
`Aug. 12, 1997
`
`US005655365A
`[11] Patent Number:
`[45] Date of Patent:
`
`3,813,877
`3,949,551
`4,023,359
`4,209,981
`4,276,745
`4,370,855
`5,050,551
`5,211,011
`5,303,168
`5,315,823
`
`6/1974 Hunt .......................................... 60/284
`4/1976 Eichler et al ......................... 60/285 X
`5/1977 Masaki et al. ............................ 60/277
`7/1980 Miyamori et al ......................... 60/274
`7/1981 Tabla et al ............................. 60/276
`2/1983 Tuggle ............................. 123/41.65 X
`9/1991 Morikawa ......................... 123n3 C X
`5/1993 Nishikawa et al. ....................... 60/284
`4/1994 Cullen et al ........................ 123/425 X
`5/1994 Nishikawa et al ........................ 60/286
`
`OTHER PUBLICATIONS
`
`Patent Abstracts of Japan, M-110, p. 1325, JP.A,4-183922,
`Jun. 30, 1992.
`Patent Abstracts of Japan, M-117. p. 1167, JP,AJ-164549,
`Jul. 16. 1991.
`Patent Abstracts of Japan, M-138, p. 949. JP,A,2-5740, Jan.
`10, 1990.
`Patent Abstracts of Japan, M-131, p. 588, JP,A,61-283735,
`Dec. 13, 1986.
`
`Primary Examiner-Tony M. Argenbright
`Attorney, Agent, or Finn-Nikaido, Marrnelstein, Murray &
`Orarn LLP
`
`[57]
`
`ABSTRACT
`
`A method of operating an internal combustion engine com(cid:173)
`prising retarding the ignition of a gas/fuel mixture within at
`least one cylinder of the engine to after top dead center
`(ATDC) in respect of the combustion cycle of said at least
`one cylinder of the engine. While the ignition is so retarded,
`the fuelling rate of said at least one cylinder is increased to
`a level higher than that required when the engine is operating
`nonnally.
`
`3,799,134
`
`3/1974 Griese ................................... 60/284 X
`
`18 Claims, 2 Drawing Sheets
`
`Cylinder
`Pressure
`
`Fuel
`
`BTDC
`
`60' 35"
`TDC
`Crankangle
`
`ATDC
`
`Cylinder
`Pressure
`
`Fuel
`Introduced
`
`BTDC
`
`20"
`TDC
`Crankangle
`
`ATDC
`
`BOSCH-DAIMLER EXHIBIT 1001
`
`Page 1 of 7
`
`

`
`U.S. Patent
`
`Aug. 12, 1997
`
`Sheet 1 of 2
`
`5,655,365
`
`Fig. 1
`
`Cylinder
`Pressure
`
`Fuel
`Introduced
`
`BTDC
`
`60° 35°
`TDC
`Crankangle
`
`ATDC
`
`Fig.2
`
`Cylinder
`Pressure
`
`Fuel
`Introduced
`
`BTDC
`
`60°
`
`20°
`TDC
`Crankangle
`
`ATDC
`
`Page 2 of 7
`
`

`
`U.S. Patent
`
`Aug. 12, 1997
`
`Sheet 2 of 2
`
`5,655,365
`
`Fig. 3
`
`t
`........... ~--v4
`-
`
`f
`
`I
`
`,.
`-r--- 2
`--;:t:::~\.~
`
`I
`
`6
`
`3
`
`5
`
`Page 3 of 7
`
`

`
`1
`METHOD OF OPERATING AN INTERNAL
`COMBUSTION ENGINE
`
`5,655,365
`
`This invention relates to a method of operating an
`internal combustion engine in order to produce high exhaust
`gas temperatures and is particularly useful for internal
`combustion engines incorporating a catalytic treatment
`means in the exhaust system for treatment of the exhaust
`gases to reduce undesirable contaminants therein.
`Although catalytic treatment of gases to reduce the level 10
`of undesirable emissions therein is effective, the catalytic
`material or catalyst of the catalytic treatment means has a
`minimum operating temperature (generally referred to as the
`"light off'' temperature and conventionally taken as the
`temperature at which the catalyst is 50% efficient), and is 15
`relatively ineffective until this required operating tempera(cid:173)
`ture has been reached, Thus, during such periods, increased
`levels of undesirable emissions are likely to issue from the
`exhaust system. Normally, at engine startup, particularly
`after a period of non-operation, the catalytic material is
`below its light-off temperature and in order to reduce the
`time, and therefore the amount of emissions output until
`light-off of the catalyst, it may be desirable to raise the
`temperature of the exhaust gases delivered from the com(cid:173)
`bustion chamber(s) of the engine to the exhaust system. 25
`However, at startup the engine typically will operate at a
`relatively low load and speed, such as is termed "engine
`idle", and therefore the amount of fuel being delivered to the
`engine is comparatively small and hence, only a relatively
`small amount of heat is available for raising the temperature 30
`of the exhaust gases and hence the temperature of the
`catalytic material to its "light-off'' temperature.
`Further, after catalyst light-off, when the engine is
`allowed to idle or operate at a low load condition for a
`significant period of time, particularly in low ambient tern- 35
`perature conditions, the exhaust gas temperature may drop
`to a value that is insufficient to maintain the catalytic
`material in the light-off condition and thus it will become
`ineffective in the treatment of contaminants and undesirable
`emissions in the exhaust gas.
`There have been proposals to heat the catalytic material
`by means of an afterburner device placed upstream of the
`catalytic treatment means. In such an arrangement, the
`afterburner device ignites the remaining combustible mix(cid:173)
`ture within the exhaust gases to raise the temperature of the 45
`catalytic material. This arrangement does however add sig(cid:173)
`nificantly to the cost and complexity of the engine installa(cid:173)
`tion.
`It is therefore the object of the present invention to
`provide a method of operating an internal combustion
`engine which will assist in maintaining high exhaust gas
`temperatures and thus, where appropriate, achieve rapid
`light-off of the catalytic material in the exhaust system and
`maintain such a light-off condition whilst the engine is
`operating.
`With this object in view, there is provided a method of
`operating an internal combustion engine comprising retard(cid:173)
`ing the ignition of a gas/fuel mixture within at least one
`cylinder of the engine to after top dead centre (.IXI'DC) in
`respect of the combustion cycle of said at least one cylinder
`of the engine. While said ignition is so retarded, the fuelling
`rate of said at least one cylinder is preferably increased to a
`level higher than that required when the engine is operating
`normally.
`Conveniently, ignition can be retarded up to about -30°
`BTDC (i.e 30° PJDC) and is preferably of the order of -zoo
`BTDC (i.e zoo PJDC). The ignition retardation may alter-
`
`2
`natively be variable, preferably between 15° .IXI'DC to 30°
`PJDC in the case of a multi cylinder engine such as a three
`cylinder engine. Preferably, the fuelling rate (measured in
`mgt cylinder/cycle) is greater than 50% of the fuelling rate at
`5 maximum load, and more preferably is up to about 80% of
`the fuelling rate at maximum load. However, if desired, the
`fuelling rate can be in excess of 100% of the fuelling rate at
`maximum engine load. However, the selected fuelling rate is
`·conveniently the minimum rate which will ensure that the
`desired exhaust gas temperature is achieved. The fuel may
`be introduced to the combustion chamber before top dead
`centre (BTDC) and most preferably at 60° to 80° BTDC in
`the case of a direct injected engine. It is however also
`envisaged that the fuel be introduced to the cylinder after top
`dead centre (PJDC) under certain conditions or situations.
`This method may conveniently be used in an engine
`including a catalytic treatment means provided in the
`exhaust system of the engine. A flame arrester may be placed
`between an exhaust port of the engine and the catalytic
`treatment means. This prevents the catalytic material held
`20 within the catalytic treatment means from directly contact(cid:173)
`ing any flame that may arise as a resulting of any still
`burning exhaust gases. Additional air may be introduced
`upstream of the catalytic treatment means. This additional
`air helps to promote the catalytic oxidation of the exhaust
`gases.
`The method can be operated during cold start of the
`engine. Alternatively or in addition, the method is operated
`when the temperature of the catalytic material is sensed or
`determined to be below a required operating temperature.
`The engine may conveniently be a two stroke internal
`combustion engine. The engine may preferably have piston
`operated exhaust ports.
`In the case of an air control system as disclosed in our
`copending Australian Patent Application No. 51065/90, the
`contents of which are hereby incorporated by reference, the
`by-pass air control valve under the control of the engine
`management system may be fully opened whilst the main
`manually controlled throttle valve remains in the closed
`position.
`The invention will be more readily understood from the
`following description of an exemplary embodiment of the
`. method of operating an internal combustion engine accord(cid:173)
`ing to the present invention as shown in the accompanying
`drawings.
`In the drawings:
`FIG. 1 is a graph showing the cylinder pressure(cid:173)
`crankangle characteristics for a typical direct injected two(cid:173)
`stroke internal combustion engine; and
`FIG. 2 is a graph showing the cylinder pressure-
`50 crankangle characteristics for a direct injected two-stroke
`internal combustion engine operated according to the
`method of the present invention, and
`FIG. 3 is a schematic view of an internal combustion
`engine and associated engine exhaust system.
`The method according to the invention can be used on a
`two stroke internal combustion engine having piston con(cid:173)
`trolled exhaust ports and the invention will be described in
`relation to this exemplary application.
`Referring initially to FIG. 1, in a typical direct injected
`60 two-stroke internal combustion engine, the fuel is intro(cid:173)
`duced to the cylinder at approximately 60° before top dead
`centre (BTDC) with ignition within the cylinder occurring
`prior to top dead centre at approximately 35° BTDC. The
`solid curve of the graph of FIG. 1 shows the cylinder
`65 pressure crankangle characteristics where ignition has
`occurred. The dashed curve shows the situation where
`ignition does not occur.
`
`40
`
`55
`
`Page 4 of 7
`
`

`
`5,655,365
`
`3
`In the method according to the invention and as shown in
`an exemplary embodiment in FIG. 2, while the fuel is
`introduced to the cylinder at between 60° and 80° BTDC, the
`ignition within the cylinder is retarded and occurs at up to
`about-30° BTDC, ie. 30° after top dead centre (ATDC). The
`curve of the graph of FIG. 2 shows the cylinder pressure
`crankangle characteristics where the fuel is introduced to the
`cylinder at 60° BTDC and ignition thereof occurs at -20°
`BTDC.
`The fuelling rate can also be varied such that it is greater 10
`than 50% of the fuelling rate at maximum load, and pref(cid:173)
`erably up to about 80% of the fuelling rate at maximum load.
`FIG. 3 shows an internal combustion engine 1 with an
`associated exhaust system 2 connecting the engine exhaust
`ports 6 to a catalytic treatment means 3. Catalytic material 15
`4 is supported within the catalytic treatment means 3. A
`flame arrester 5 is located upstream of the catalytic treatment
`means 3 between the exhaust ports 6 and the treatment
`means 3.
`The method according to the present invention can be 20
`varied depending on the number of cylinders of the engine.
`For example, in a three cylinder engine where only one or
`two cylinders are to be operated in accordance with said
`method, it is preferred that the fuelling rate thereto be kept
`constant and that the ignition be retarded a fixed amount, 25
`typically about 20° ATDC, for the cylinder(s) operating
`under ignition retard/high fuelling rate conditions. Under
`such operation, the other cylinder(s) still operates under
`normal conditions and the operation thereof may be such as
`to compensate for the temporary loss in torque while the 30
`other cylinder(s) operate(s) under said conditions. The
`cylinder(s) operating under normal conditions may also
`regulate the engine idle speed.
`By comparison, in a three cylinder engine where all
`cylinders are operating in accordance with said method it is 35
`preferred that a high fuelling rate be fixed for all of the
`cylinders and that all of the cylinders operate with retarded
`ignition. The degree of retardation for each of the cylinders
`may conveniently be the same during at least one combus-
`tion cycle of one light-off period.
`Further, it is preferable that the degree of ignition retard
`of the cylinders during the one light-off period be altered
`from cycle to cycle, typically between 15° ATDC to 30°
`ATDC, to control the engine idle speed. However, it is also
`envisaged that the degree of ignition retard could alterna- 45
`tively or in addition be controlled to differ between respec(cid:173)
`tive cylinders during the one light-off period.
`By virtue primarily of the retarded ignition and also to a
`lesser extent the high fuelling rate, the overall thermal
`efficiency (i.e the efficiency of conversion of energy pro- 50
`vided by combustion of the fuel into useful work) is quite
`low. Thus there is a high level of thermal energy available
`to heat the catalytic treatment means provided for treatment
`of the exhaust gases. In addition, extra heat is released to the
`engine coolant thereby rapidly increasing the coolant tern- 55
`perature which results in a lower engine output of HC
`emissions thereby reducing the dependence on the catalytic
`treatment means to maintain the required HC emissions
`level.
`The combustion preferably occurs under rich conditions 60
`with the overall air/fuel ratio being close to the stoichio(cid:173)
`metric ratio. Because of the inefficient combustion
`conditions, gases with lower oxidation temperatures such as
`H and CO will be produced. These gases can react with the
`catalytic material to increase its temperature and therefore 65
`aid the catalytic material in achieving its light-off tempera(cid:173)
`ture.
`
`4
`If desired, additional oxygen containing gas, such as air,
`may be introduced upstream of the catalytic treatment means
`provided in the exhaust system of the engine, for example,
`by use of an air pump, thus ensuring the introduction of
`5 excess oxygen to the exhaust system enabling catalytic
`conversion of any contaminants in the exhaust gas. In many
`cases, it will be desirable that the throttle or air control
`means for the air supply to the combustion chamber with
`retarded ignition be set at a ''wide open" or near "wide open"
`value such as to maximise air supply to that combustion
`chamber, thus allowing higher fuelling rates to be used.
`However, in the case that the air control system serves more
`than one cylinder, then the air flow rate must be established
`such that the combustion efficiency of the combustion
`chamber( s) without retarded ignition is not adversely
`affected.
`It has been found that maintaining the retarded ignition
`and high fuelling rate conditions for a "light-off' period only
`of the order of 30 seconds from engine startup is sufficient
`to bring the catalytic treatment means up to temperature to
`establish light-off of the catalytic material in the treatment
`means. In some cases, the level of thermal energy available
`is even greater thus shortening the above period to 5 seconds
`or so. Furthermore, and particularly in the case of two stroke
`engines, there may be insufficient time between the com(cid:173)
`mencement of ignition and the opening of the exhaust port
`for all of the fuel to be combusted within the combustion
`chamber. Thus, combustion may continue as the combustion
`gases flow from the combustion chamber into the exhaust
`system. In such a case, it may be beneficial to place a
`flameshield upstream of the catalytic treatment means to
`protect it from contact with any flames. Where necessary,
`and as alluded to hereinbefore, excess air may be introduced
`to the exhaust system to promote the catalytic oxidation of
`the exhaust gases.
`Further, it is to be understood that the high degree of
`retarding of the ignition resulting in the relatively short
`period between ignition and exhaust and the high fuelling
`rate may only produce a relatively low torque output
`Accordingly, at engine idle, the high fuelling rate does not
`result in the engine revving at a speed significantly different
`to the normal engine idle speed. In this regard, it may be
`preferable that in a multi-cylinder engine, only one or some
`of the cylinders are subjected to the highly retarded ignition
`and high fuelling rate thereby enabling the remaining
`cylinder(s) to provide the necessary control of engine idle
`speed as aluded to hereinbefore.
`It may be advantageous to "rotate" the cylinders such
`that each cylinder sequentially operates under the retarded
`ignition and high fuelling rate conditions. This rotation
`between cylinders may occur within a single light-off period.
`Alternatively, a different cylinder could be used for con(cid:173)
`secutive light-off periods. This helps to ensure that each
`cylinder is subjected to similar temperature and/or carbon
`formation conditions.
`The reduction in the time for the catalyst to reach its
`light-off temperature achieved by the use of the present
`invention also enables the catalytic treatment means to be
`located a greater distance downstream from the engine
`exhaust port than may otherwise be possible, thereby
`improving the durability of the catalytic treatment means.
`It will be appreciated that where an engine start-up
`occurs after only a short period of time after shut-down of
`the engine, the catalytic treatment means may still be at a
`sufficiently high temperature to immediately light-off on
`restarting the engine and hence it may be undesirable to
`further heat the catalytic treatment means by way of the
`
`40
`
`Page 5 of 7
`
`

`
`5,655,365
`
`10
`
`25
`
`5
`present invention. However, this condition can be deter(cid:173)
`mined by appropriate sensing of other engine parameters
`such as the temperature of the engine in general, cooling
`water temperature or the temperature of the exhaust system
`in the vicinity of the catalytic treatment means. Accordingly,
`sensing of these and/or other engine parameters may be
`effected and the specific ignition retarding and high fuelling
`rate conditions only implemented if for example, the sensed
`temperature condition of the engine and/or exhaust system
`indicates that the temperature of the catalytic treatment
`means is at a level which would necessitate assistance in
`achieving prompt light-off thereof.
`Further, where the engine is left idling for a considerable
`time, and particularly in low ambient temperature
`conditions, the exhaust system and particularly the catalytic
`treatment means may fall in temperature to a level at which
`the catalytic treatment means is below the light-off tempera(cid:173)
`ture. Similarly. appropriate sensors can be provided to detect
`this condition and the engine management system can be
`arranged to respond to the sensing of such conditions to
`implement the ignition retard and high fuelling rate condi(cid:173)
`tions to restore or maintain the catalytic treatment means in
`an acceptable operational condition.
`When the appropriate sensor or sensors detect that the
`engine parameter, for example the exhaust system
`temperature, is again above the acceptable value, the engine
`management system may then cease to effect the ignition
`retard and high fuelling rate conditions and return the
`cylinder to normal ignition timing and fuelling rates. Where
`more than one cylinder has been operating with retarded
`ignition and a high fuelling rate, the return to normal
`operation is preferably sequential, that is, one cylinder at a
`time is returned to normal operation and stabilised. This is
`particularly useful in the case where switching from a high
`to a lower fuelling rate causes fuel "hangup", that is,
`retention of fuel within the means used to deliver fuel to the
`cylinder, in which case the transient response of the engine
`may not be precise. However, if multiple cylinders are
`operating with retarded ignition and a high fuelling rate, they
`may be returned to normal operation simultaneously if there 40
`is a substantial increase in operator demand. The method of
`operating the engine according to the present invention can
`therefore be initiated, both during cold start of the engine,
`and when the temperature of catalytic material is sensed or
`determined to be below the required light-off operating 45
`temperature any time during the running of the engine.
`While the method of the present invention is particularly
`suitable for two-stroke engines, preferably those engines
`which are directly injected, the invention is not limited in its
`applicability to such engines. In a two-stroke three cylinder so
`1.2liter direct injected engine, the anticipated fuel per cycle
`at normal engine idle is 3 mg/cylinder/cycle whereas when
`retarded ignition and a high fuelling rate is enabled in
`accordance with the method of the present invention, the
`increased fuelling rate may be as high as 18 to 25 55
`mg/cylinder/cycle, i.e 85% to 115% of the fuelling rate at
`maximum engine load.
`In an air-assisted direct injected 2-stroke engine as
`described, for example, in the applicant's U.S. Pat. No.
`4,693,224, it may be convenient to control the speed of the 60
`engine by controlling the fuelling rate to the cylinders that
`are running under normal settings and by controlling the
`ignition timing of those cylinders that are operating with
`retarded ignition and increased fuelling rate according to the
`invention as described herein.
`
`6
`It will be appreciated that the invention is particularly
`beneficial for bringing the engine catalytic treatment means
`rapidly to its light-off temperature, and few if any additional
`components are required. This results in little to no addi-
`s tional costs to the piece price of the engine.
`The claims defining the invention are as follows:
`1. A method of operating an internal combustion engine
`comprising retarding the ignition of a gas/fuel mixture
`within at least one cylinder of the engine to after top dead
`centre (ATDC) in respect of the combustion cycle of said at
`least one cylinder of the engine and, while said ignition is so
`retarded, increasing the fuelling rate of said at least one
`cylinder to a level higher than that required when the engine
`15 is operating normally to thereby assist in increasing the
`exhaust gas temperature of the engine, the timing of the
`introduction of fuel into the at least one cylinder being
`maintained at before top dead centre (BTDC).
`2. A method according to claim 1 wherein the fuelling rate
`20 is greater than 50% of the fuelling rate at maximum load.
`3. A method according to claim 2, wherein the fuelling
`rate is about 80% of the fuelling rate at maximum load.
`4. A method according to claim 1 wherein the fuelling rate
`is greater than 100% of the fuelling rate at maximum load.
`5. A method according claim 1 wherein the ignition is
`retarded up to about 30° ATDC.
`6. A method according to claim 5, wherein the ignition is
`retarded to about 20° ATDC.
`7. A method according to claim 1 wherein the degree of
`30 ignition retardation differs between each of the cylinders of
`a multi-cylinder engine.
`8. A method according to claim 7 wherein the degree of
`ignition retardation differs between 15° ATDC and 30°
`35 ATDC.
`9. A method according to claim 1 wherein the fuel is
`introduced at between 60° to 80° BTDC.
`10. A method according to claim 1 wherein the engine
`includes in an exhaust system thereof a catalytic treatment
`means supporting a catalytic material therein.
`11. A method according to claim 10 wherein a flame
`arrester is inserted between an engine exhaust port and the
`catalytic treatment means.
`12. A method according to claim 10 wherein additional air
`is introduced upstream of the catalytic treatment means.
`13. A method according to claim 10 wherein the engine is
`operated according to said method during cold start of the
`engine.
`14. A method according to claim 10 wherein the engine is
`operated according to said method when the temperature of
`the catalytic material is sensed or determined to be below a
`required operating temperature.
`15. A method according claim 1 wherein the engine has
`piston controlled exhaust ports.
`16. A method according to claim 1 wherein the engine is
`a two stroke internal combustion engine.
`17. A method according to claim 1 wherein the engine is
`a multi-cylinder engine and at least one of said cylinders is
`operated without ignition timing retarded to after top dead
`centre.
`18. A method according to claim 1 wherein after a
`predetermined operating condition has been sensed or
`determined, said engine reverts back to normal operation.
`
`* * * * *
`
`Page 6 of 7
`
`

`
`UNITED STATES PATENT AND TRADEMARK OFFICE
`CERTIFICATE OF CORRECTION
`5,655,365
`
`PATENT NO.
`
`August 12, 1997
`DATED
`INVENTOR(S) : Worth et al.
`
`It is certified that error appears in the above-indentified patent and that said Letters Patent is hereby
`corrected as shown below:
`
`On t!1e title pae;e;
`Item [87], line 1, please delete" W094/17229" and insert therefor- W094117293 -
`
`Signed and Sealed this
`
`Fourteenth Day of October, 1997
`
`Attest:
`
`Attestinf? Officer
`
`Commis.\io11er nf Patents mu! TraJemad.s
`
`BRllCE LEHMAN
`
`Page 7 of 7