(12) United States Patent
`US 7,447,586 B2
`(10) Patent N0.:
`
`(45) Date of Patent: Nov. 4, 2008
`Idogawa et al.
`
`USOO7447586B2
`
`VALVE CHARACTERISTIC CONTROL
`APPARATUS FOR INTERNAL COMBUSTION
`ENGINE
`
`(56)
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`Inventors: Masanao Idogawa, Toyota (JP); Osamu
`Hosokawa, Toyota (JP)
`
`Assignee: Toyota Jidosha Kabushiki Kaisha,
`Toyota-shi (JP)
`
`5,293,741 A
`6,266,957 B1
`6,405,693 B2 *
`6,526,745 B1 *
`2002/0062800 A1
`
`3/1994 Kashiyama et al.
`7/2001 Nozawa et 31.
`
`123/9015
`6/2002 Yoeda et 31.
`3/2003 Ogiso ...................... 123/9015
`5/2002 Shimizu
`
`(54)
`
`(75)
`
`(73)
`
`(*)
`
`(22)
`
`(86)
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`(87)
`
`(65)
`
`(30)
`
`Notice:
`
`(21)
`
`Appl. No.:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 306 days.
`10/586,992
`
`FOREIGN PATENT DOCUMENTS
`
`EP
`JP
`JP
`JP
`
`1 167 734 A2
`2002—013419 A
`2002-161770 A
`2003-120348 A
`
`1/2002
`1/2002
`6/2002
`4/2003
`
`PCT Filed:
`
`Dec. 16, 2005
`
`PCT No.:
`
`PCT/IB2005/003800
`
`* cited by examiner
`
`§ 371 (0X1),
`(2), (4) Date:
`
`Jul. 21, 2006
`
`PCT Pub. No.: W02006/067581
`
`PCT Pub. Date: Jun. 29, 2006
`
`Prior Publication Data
`
`US 2008/0243363 A1
`
`Oct. 2, 2008
`
`Foreign Application Priority Data
`
`Dec. 20, 2004
`
`(JP)
`
`............................. 2004-367969
`
`Int. Cl.
`
`(51)
`
`(52)
`(58)
`
`(2006.01)
`F02D 13/02
`(2006.01)
`F02D 41/06
`US. Cl.
`.................................... 701/105; 123/9015
`Field of Classification Search ................. 701/105,
`701/102,101; 123/9015, 90.17
`See application file for complete search history.
`
`Primary ExamineriHieu T V0
`(74) Attorney, Agent, or FirmiKenyon & Kenyon LLP
`
`(57)
`
`ABSTRACT
`
`A valve characteristic control apparatus is provided in an
`internal combustion engine including a variable valve mecha-
`nism that can change at the least, among valve characteristics
`of an exhaust valve, a closing timing ofthe exhaust valve, and
`in which a number of injections of fuel is changed during one
`engine cycle. The valve characteristic control apparatus sets
`the closing timing of the exhaust valve to a retard side during
`an engine warming up operation. When setting to the retard
`side is performed, if two injections are performed, an exhaust
`side target displacement angle VTTex of the exhaust valve is
`calculated based on a dual injection use map. On the other
`hand, if one injection is performed, the exhaust side target
`displacement angle VTTex of the exhaust valve is calculated
`based on a single injection use map.
`
`6 Claims, 4 Drawing Sheets
`
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`OWNER Ex. 2036, page 1
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`

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`U.S. Patent
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`Nov. 4, 2008
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`Sheet 1 of 4
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`US 7,447,586 B2
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`US. Patent
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`Nov. 4, 2008
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`Sheet 2 of4
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`US 7,447,586 B2
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`FIG.2
`
`TARGET DISPLACEMENT
`
`ANGLE SETTING PROCESS
`
`
`
`
`READ COOLANT TEMP. THW.
`TIME-SlNCE-START ST, AND
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`EXTERNAL LOAD FACTOR A
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`DUAL INJECTION?
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`CALCULATE EXHAUST
`CALCULATE EXHAUST SIDE
`SIDE TARGET DISPLACEMENT
`TARGET DISPLACEMENT
`
`ANGLE V'lTex BASED
`ANGLE VTTex BASED
`
`
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`ON DUAL INJECTION MAP
`ON SINGLE INJECTION MAP
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`OWNER EX. 2036, page 3
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`US. Patent
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`Nov. 4, 2008
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`Sheet 3 of4
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`US 7,447,586 B2
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`Nov. 4, 2008
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`US 7,447,586 B2
`
`1
`VALVE CHARACTERISTIC CONTROL
`APPARATUS FOR INTERNAL COMBUSTION
`ENGINE
`
`INCORPORATION BY REFERENCE
`
`This is a 371 national phase application of PCT/IB2005/
`003800 filed 16 Dec. 2005, claiming priority to Japanese
`Patent Application No. 2004-367,969 filed 20 Dec. 2004, the
`contents of which are incorporated herein by reference.
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`
`The invention relates to a valve characteristic control appa-
`ratus for an internal combustion engine.
`2. Description of the Related Art
`I11 an internal combustion engine, exhaust gas components
`are purified by a catalyst. However, when a temperature ofthe
`catalyst is low when the engine is warming up, or the like, the
`catalyst is not able to provide adequate purification perfor-
`mance. To address this difficulty, various types of catalyst
`warming up control are performed in order to rapidly increase
`the temperature of the catalyst.
`For example, in an in-cylinder injection internal combus-
`tion engine that can directly inject and supply fuel to the
`combustion chamber, it is possible to increase a temperature
`of a combustion gas by, for example, (i) retarding an ignition
`timing, (ii) increasing an intake air amount to make an air fuel
`ratio leaner, and (iii) performing fuel injection in the latter
`half of the compression stroke. Accordingly, in this type of
`internal combustion engine, a fuel injection timing is set to be
`in the latter half of the compression stroke during engine
`warming up. As a result, an exhaust gas temperature
`increases, whereby the temperature of the catalyst increases
`rapidly.
`At the same time, various types of control are performed to
`reduce a discharge amount of hydrocarbon (HC) exhausted
`from the combustion chamber to an exhaust passage during
`engine warming up. In a device disclosed in Japanese Patent
`Laid-open Publication No. 2003-120348, for example, a clos-
`ing timing of an exhaust valve is set to a retard side during
`engine warming up in order to increase a valve overlap
`amount. As a result, exhaust gas discharged to an exhaust
`passage is
`intaken to the combustion chamber again.
`Unburned HC contained within the intaken exhaust gas are
`then combusted again in the following combustion stroke,
`whereby the HC discharge amount is reduced.
`However, in an internal combustion engine in which cata-
`lyst warming up control is performed in the manner described
`above, if a fuel injection amount injected in the latter half of
`the compression stroke increases excessively, the air fuel ratio
`in the vicinity of the spark plug becomes excessively rich,
`which causes the combustion condition ofthe air fuel mixture
`to deteriorate. In this case, as a countermeasure, the fuel
`injection can be separated and performed as a plurality of
`separated injections. This makes it possible to form a suitable
`air fuel ratio in the vicinity of the spark plug. However, if any
`one of the fuel injection amounts injected in the separated
`injections is less than a minimum injection amount of a fuel
`injection value (the minimum amount to which the fuel inj ec-
`tion amount can be controlled), the separated injections can-
`not be performed. Thus, non-separated inj ection is carried out
`and all of the fuel is injected in the latter half of the compres-
`sion stroke. Note that, the fuel injection amount is set based
`on engine load, engine rotational speed, or the like. When the
`fuel injection amount is not large enough to cause a rich air
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`fuel ratio to be formed in the vicinity of the spark plug,
`non-separated injection is performed.
`However,
`in an internal combustion engine like that
`described above, namely, in an internal combustion engine in
`which the number of times that fuel is injected during one
`engine cycle (the series of strokes including the intake stroke,
`compression stroke, combustion stroke and exhaust stroke) is
`changed, the combustion condition of the air fuel mixture
`changes depending on the number of injections. Therefore,
`when retard control of the closing timing of the exhaust valve
`is performed as described above, the retard amount that is
`optimal is different depending on the number of injections.
`However, with the above known retard control, the retard
`amount is not changed in accordance with the number of
`injections. As a result, there is need for further improvement
`in the retard control that is performed for the closing timing of
`the exhaust value in the above described internal combustion
`
`engine.
`
`SUMMARY OF THE INVENTION
`
`The invention has been conceived of in light of the above
`described circumstances, and it is the object thereof to pro-
`vide a valve characteristic control apparatus for an internal
`combustion engine performing control in accordance with a
`number of inj ections of fuel during one engine cycle, wherein
`a discharge amount ofhydrocarbon is reduced during a warm-
`ing up operation.
`According to a first aspect of the invention, a valve char-
`acteristic control apparatus is applied to an internal combus-
`tion engine which (i) includes a variable valve mechanism
`that is adapted to change at the least, among valve character-
`istics of an exhaust valve, a closing timing of the exhaust
`valve, and in which (ii) a number of injections of fuel during
`one engine cycle is changed. The valve characteristic control
`apparatus sets the closing timing to a retard side during a
`warming up operation of the internal combustion engine, and
`includes retard amount setting means for setting a retard
`amount of the closing timing based on the number of injec-
`tions during the warming up operation.
`According to the first aspect, even if the number of injec-
`tions of fuel is changed during the warming up operation, the
`retard amount ofthe closing timing of the exhaust valve is set
`based upon the number of injections of fuel. In other words,
`the retard amount is set to correspond with difference in a
`combustion condition that result from difference in the num-
`ber of injections. Accordingly, the retard amount of the clos-
`ing timing of the exhaust valve during the warming up opera-
`tion can be favorably controlled in accordance with the
`number of injections of fuel.
`In the first aspect, the retard amount setting means may set
`the retard amount such that, as the number of injections
`becomes fewer, the retard amount becomes smaller.
`Even if the fuel amount injected during one engine cycle is
`the same, the fuel amount injected in each injection becomes
`larger as the number of injections of fuel becomes fewer. As
`a result, an air fuel ratio in the vicinity of a spark plug is liable
`to become richer, which in turn causes a tendency for the
`combustion condition of the air fuel mixture to deteriorate
`
`more easily. Given this fact, according to the above described
`configuration, as the number of injections becomes fewer,
`namely, as the combustion condition becomes increasingly
`likely to deteriorate, a valve overlap amount is reduced and
`thus an internal EGR amount is reduced. As a result, even if
`the number of injections is changed, the combustion condi-
`tion can be maintained in a favorable state. Moreover, on the
`other hand, as the number of injections increases, namely, as
`
`OWNER Ex. 2036, page 6
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`

`

`US 7,447,586 B2
`
`3
`the combustion condition becomes more favorable, the retard
`amount of the exhaust valve closing timing becomes larger.
`Accordingly, the amount ofunburned HC intaken again to the
`combustion chamber can be increased, whereby the HC dis-
`charge amount can be reduced substantially.
`I11 the first aspect ofthe invention, the retard amount setting
`means may include retard amount setting maps for setting the
`retard amount of the closing timing in accordance with the
`number of injections. The retard amount may then be set
`based on the respective maps.
`With this configuration, the retard amount of the exhaust
`valve closing timing is set based upon the retard amount
`setting maps for setting the retard amount in accordance with
`the number of injections of fuel. Thus, it is possible to reliably
`set the retard amount of the closing timing based 011 the
`number of injections.
`I11 the first aspect, the retard amount may be set in accor-
`dance with an engine coolant temperature.
`When the retard amount of the closing timing of the
`exhaust valve is set larger,
`the amount of unburned HC
`intaken again to the combustion chamber is increased. At the
`same time, the internal EGR amount increases, which causes
`the combustion condition of the air fuel mixture to have a
`
`tendency to become more unstable. On the other hand, when
`the retard amount ofthe closing timing ofthe exhaust valve is
`set smaller, the amount of unburned HC intaken again to the
`combustion chamber reduces. However, since internal EGR
`amount reduces, a favorable air fuel mixture is formed that
`combusts more easily.
`Note that, the combustion of the air fuel mixture has a
`tendency to become more unstable when the coolant tempera-
`ture is low during the engine warming up operation. Accord-
`ingly, at such times, the retard amount may be set larger along
`with increase in the coolant temperature, thus enabling both
`(i) the combustion condition ofthe air fuel mixture to be made
`stable when the temperature is low, and (ii) the HC discharge
`amount to be reduced.
`
`On the other hand, when the coolant temperature is some-
`what high during the warming up operation, the HC discharge
`amount reduces because the catalyst is activated, and the
`temperature of the combustion gas is high. Accordingly, at
`such times, even if the retard amount is set smaller along with
`increase in the coolant temperature, the HC discharge amount
`can be adequately reduced, and a favorable air fuel mixture
`can be formed that is combusted more easily.
`As will be understood from the above description, the
`optimal value for the retard amount of the closing timing of
`the exhaust valve has a close relationship to the coolant tem-
`perature. Accordingly, the retard amount ofthe closing timing
`of the exhaust valve can be set in accordance with the engine
`coolant temperature in order to appropriately set the retard
`amount of the exhaust valve closing timing in accordance
`with the engine coolant temperature and the number of inj ec-
`tions of fuel. Further, by doing so, the HC discharge amount
`can be favorably reduced, and a favorable air fuel mixture can
`be formed that is combusted more easily.
`I11 the first aspect, the retard amount may be set in accor-
`dance with a degree of an engine external load.
`When engine external loads increase, such as when a com-
`pressor for an air conditioner is driven or when electrical load
`increases,
`the engine operating state has a tendency to
`become more unstable. If the retard amount of the exhaust
`
`valve closing timing is increased at such times, the internal
`EGR amount increases, which causes the combustion condi-
`tion of the air fuel mixture to have a tendency to deteriorate
`more easily. As a result, there is a possibility that the operating
`state will become even more unstable. To address this difii-
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`culty, according to the above described configuration, the
`retard amount is set in accordance with the number of injec-
`tions of fuel and the degree of the external load. Accordingly,
`it is possible to inhibit the operating state from becoming
`unstable in the above described manner. Note that, it is pref-
`erable that, in the above described configuration, the retard
`amount is set to become smaller as the degree of the engine
`external load increases.
`
`In the first aspect, the retard amount may be set in accor-
`dance with an elapsed time from engine start up.
`If the internal EGR amount is reduced so that a favorable
`
`air fuel mixture is formed that combusts more easily, namely,
`if the retard amount of the exhaust valve closing timing is set
`smaller, the HC discharge amount that is exhausted to the
`exhaust passage increases. Further, the temperature of the
`catalyst increases along with the elapse of time following
`engine start up, and the purification performance of the cata-
`lyst improves. Accordingly, in these circumstances, even if
`the retard amount is set smaller, the catalyst can purify HC.
`Given this, according to the above configuration, the retard
`amount of the exhaust valve closing timing is set in accor-
`dance with the elapsed time from engine start, whereby the
`retard amount is set is accordance with the purification per-
`formance of the catalyst. Thus, according to the above con-
`figurations, with the respective retard amounts set in accor-
`dance with the number of injections of fuel, it is possible to
`suppress increase in the HC discharge amount, and form a
`favorable air fuel mixture that can be combusted more easily.
`Note that, in the above configuration, it is preferable that the
`retard amount is set smaller as the elapsed time from engine
`start up increases.
`A valve characteristic control apparatus according to a
`second aspect of the invention includes a retard amount set-
`ting portion provided in an internal combustion engine which
`(i) includes a variable valve mechanism that can change at the
`least, among valve characteristics of an exhaust valve, a clos-
`ing timing of the exhaust valve, and in which (ii) a number of
`injections of fuel during one engine cycle is changed. The
`retard amount setting portion that sets a retard amount of the
`closing timing based on the number of injections during a
`warming up operation.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`The foregoing and further objects, features and advantages
`of the invention will become apparent from the following
`description of a preferred embodiment with reference to the
`accompanying drawings, wherein like numerals are used to
`represent like elements and wherein:
`FIG. 1 is a schematic configuration diagram showing an
`example in which a valve characteristic control apparatus
`according to the embodiment is applied to an internal com-
`bustion engine;
`FIG. 2 is a flow chart showing an operating procedure that
`is performed for setting a target displacement angle to an
`exhaust side in the above embodiment;
`FIG. 3A shows maps for setting a retard amount of a
`closing timing of an exhaust valve (that corresponds to an
`exhaust side target displacement angle) for a first injection
`and a second injection based on a temperature of a coolant;
`FIG. 3B shows maps for setting the retard amount of the
`closing timing of the exhaust valve (that corresponds to the
`exhaust side target displacement angle) for a first injection
`and a second injection based on an external load factor;
`FIG. 3C shows maps for setting the retard amount of the
`closing timing of the exhaust valve (that corresponds to the
`exhaust side target displacement angle) for a first injection
`
`OWNER Ex. 2036, page 7
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`US 7,447,586 B2
`
`5
`and a second injection based on a time that has elapsed since
`start up of the internal combustion engine; and
`FIG. 4 is a time chart showing change during an engine
`warming up operation of an actual exhaust side displacement
`angle that results from performance of the target displace-
`ment angle setting process.
`
`DETAILED DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`
`Hereinafter, an exemplary embodiment of a valve charac-
`teristic control apparatus for an internal combustion engine
`according to the invention will be described with reference to
`FIGS. 1 to 4.
`
`FIG. 1 shows a schematic diagram of a configuration of a
`gasoline engine 1 to which the valve characteristic control
`apparatus for the internal combustion engine according to the
`embodiment is applied.
`A cylinder block 2 ofthe gasoline engine 1 is provided with
`a plurality of cylinders 3. (Only one of the cylinders 3 is
`shown in FIG. 1. For the sake of simplicity the following
`explanation will focus on this cylinder 3, although the same
`description applies to the other cylinders 3). A piston 4 is
`provided in the cylinder 3 and is linked to a crank shaft 5 via
`a control rod 6. The control rod 6 converts reciprocal move-
`ment of the piston 4 to rotational movement ofthe crank shaft
`5. A coolant temperature sensor 43 for detecting an engine
`coolant temperature (coolant temperature THW) is attached
`to the cylinder block 2.
`A cylinder head 7 is attached to an upper portion of the
`cylinder block 2, and a combustion chamber 8 is formed in the
`cylinder 3 between an upper end of the piston 4 and the
`cylinder head 7. An injector 16 for directly injecting fuel into
`the combustion chamber 8 and a spark plug 11 are provided in
`the cylinder head 7. An intake port 12 and an exhaust port 13
`that respectively connect to an intake passage 14 and an
`exhaust passage 15 are provided in the cylinder head 7 at
`positions that correspond with the combustion chamber 8.
`The intake port 12 and the exhaust port 13 are respectively
`opened and closed by an intake valve 17 and an exhaust valve
`18 provided at positions that correspond with the combustion
`chamber 8. The intake valve 17 and the exhaust valve 18 are
`
`opened and closed along with rotation of an intake cam shaft
`31 and an exhaust cam shaft 32, and, more specifically, by
`rotation of respective cams provided on the intake cam shaft
`31 and the exhaust cam shaft 32. Timing pulleys 33 and 34 are
`provided at respective ends of the intake cam shaft 31 and the
`exhaust cam shaft 32. The timing pulleys 33 and 34 are
`coupled to and driven by the crank shaft 5 via a timing belt 35.
`When the crank shaft 5 rotates twice, each timing pulley 33
`and 34 rotates once. Further, when the gasoline engine 1 is
`operating, torque of the crank shaft 5 is transmitted to the
`intake cam shaft 31 and the exhaust cam shaft 32 via the
`timing belt 35 and the timing pulleys 33 and 34. Accordingly,
`the intake valve 17 and the exhaust valve 18 are driven to open
`and close synchronously with rotation of the crank shaft 5,
`namely, at a predetermined timing that corresponds with the
`reciprocal movement of the piston 4.
`A crank angle sensor 41 is provided in the vicinity of the
`crank shaft 5. This crank angle sensor 41 detects a rotational
`phase (crank angle) of the crank shaft 5, and uses this detec-
`tion result as a basis for detecting an engine rotational speed
`NE ofthe gasoline engine 1 (the crank shaft 5). An intake side
`cam angle sensor 421; is provided in the vicinity of the intake
`cam shaft 31. Output signals from the intake side cam angle
`sensor 42a and the crank angle sensor 41 are used as a basis
`for detecting a rotational phase (cam angle) ofthe intake cam
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`shaft 31. Similarly, an exhaust side cam angle sensor 42b is
`provided in the vicinity of the exhaust cam shaft 32. Output
`signals from the exhaust side cam angle sensor 42b and the
`crank angle sensor 41 are used as a basis for detecting a
`rotational phase (cam angle) of the exhaust cam shaft 32.
`A high voltage output from an igniter, not specifically
`shown, is applied to the spark plug 11. The ignition timing of
`the spark plug 11 is determined by the timing of the high
`voltage output from the igniter. In the gasoline engine 1,
`intake air from the intake passage 14 and fuel injected from
`the injector 16 are mixed to form an air fuel mixture that is
`ignited by the spark plug 11. The air fuel mixture is then
`combusted, and the resulting explosion in the combustion
`chamber 8 generates power of the gasoline engine 1. In addi-
`tion, combustion gas formed at that time is discharged to the
`exhaust passage 15, and purified by a catalyst 70.
`A surge tank 51 is provided in a portion of the intake
`passage 14 for suppressing pulsation of intake air. A throttle
`valve 53 whose opening degree is changed based on operation
`of an accelerator pedal, not shown, is provided at an upstream
`stream side of the surge tank 51. By changing the opening
`degree of the throttle valve 53 it is possible to adjust an air
`amount that is intaken to the combustion chamber 8. More-
`
`over, a throttle opening degree sensor 54 is installed in the
`vicinity ofthe throttle valve 53 and detects the opening degree
`thereof. An air flow meter 55 is disposed at an upstream side
`ofthe throttle valve 53 and generates an output in accordance
`with an intake air amount GA that is intaken to the gasoline
`engine 1.
`An intake valve variable timing mechanisms 6011 that acts
`as a variable valve mechanism is provided on the timing
`pulley 33 provided on the intake cam shaft 31. Further, an
`exhaust valve variable timing mechanisms 60b that acts as a
`variable valve mechanism is also provided on the timing
`pulley 34 provided on the exhaust cam shaft 32.
`The intake valve variable timing mechanism 60a continu-
`ously changes a valve timing ofthe intake valve 17 by chang-
`ing the relative rotational phase of the timing pulley 33 and
`the intake cam shaft 31 with respect to the crank shaft 5. The
`exhaust valve variable timing mechanism 60b continuously
`changes a valve timing of the exhaust valve 18 by changing
`the relative rotational phase of the timing pulley 34 and the
`exhaust cam shaft 32 with respect to the crank shaft 5.
`Various auxiliary devices 90 are attached to the gasoline
`engine 1 and driven using rotation of the crank shaft 5. These
`auxiliary devices 90 include a compressor 90a foruse in an air
`conditioner, not shown, an alternator 90/), an oil pump 900,
`and a water pump 90d.
`Various types of control of the gasoline engine 1 are per-
`formed by an electronic control unit (hereinafter referred to as
`“ECU”) 80. These controls include an ignition timing control,
`a fuel injection amount control, and valve timing control
`based on phase control of each valve timing mechanism. The
`ECU 80 is configured with a microcomputer as a main struc-
`tural element. The microcomputer includes a central process-
`ing unit (CPU). The ECU 80 is provided with, for example, a
`read-only memory (ROM) that stores various programs,
`maps, and the like, in advance, and a random access memory
`(RAM) that temporarily stores calculation results, or the like,
`of the CPU. The ECU 80 also includes a backup RAM that
`retains calculation results, pre-stored data, and the like, even
`when the gasoline engine 1 is stopped; an input interface; and
`an output interface. Output signals from the crank angle sen-
`sor 41, the intake side cam angle sensor 42a, the exhaust side
`cam angle sensor 42b, the coolant temperature sensor 43, the
`throttle opening degree sensor 54, and the air flow meter 55,
`etc. are input to the ECU 80 through the input interface. The
`
`OWNER Ex. 2036, page 8
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`US 7,447,586 B2
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`7
`ECU 80 is able to detect an operating state of the gasoline
`engine 1 based on the output signals from the sensors 41 to 43,
`54 and 55, etc.
`On the other hand, the output interface is connected to
`respective drive actuators for the injector 16, the igniter used
`by the spark plug 11, the intake valve variable timing mecha-
`nism 60a and the exhaust valve variable timing mechanism
`60b, etc., via respective corresponding drive circuits.
`The ECU 80 appropriately controls drive actuators of the
`injector 16,
`the igniter,
`the intake valve variable timing
`mechanism 60a and the exhaust valve variable timing mecha-
`nism 60b in accordance with control programs stored in the
`ROM and initial data based upon the output signals from the
`sensors 41 to 43, 54 and 55, and the like.
`The ECU 80 performs valve timing control of the intake
`valve 17 by driving and controlling the intake valve variable
`timing mechanism 60a. In the valve timing control of the
`intake valve 17, the intake valve variable timing mechanism
`60a is driven such that an actual valve timing of the intake
`valve 17 becomes a target valve timing that is set based on the
`engine operating state. In this control, as the actual valve
`timing of the intake valve 17, an intake side actual displace-
`ment angle VTin that is an actual displacement angle of the
`intake cam shaft 31 is employed. Further, as the target valve
`timing of the intake valve 17, an intake side target displace-
`ment angle VTTin that is a target displacement angle of the
`intake cam shaft 31 is employed. Drive of the intake valve
`variable timing mechanism 60a is feedback controlled in
`accordance with a deviation AVTin between the intake side
`
`actual displacement angle VTin and the intake side target
`displacement angle VTTin, whereby the valve timing of the
`intake valve 17 is adjusted to the target valve timing.
`Similarly, the ECU 80 performs valve timing control of the
`exhaust valve 18 by driving and controlling the exhaust valve
`variable timing mechanism 601). In the valve timing control of
`the exhaust valve 18,
`the exhaust valve variable timing
`mechanism 60b is driven such that an actual valve timing of
`the exhaust valve 18 becomes a target valve timing that is set
`based on the engine operating state. In this control, as the
`actual valve timing of the exhaust valve 18, an exhaust side
`actual displacement angle VTex that is an actual displacement
`angle ofthe exhaust cam shaft 32 is employed. Further, as the
`target valve timing of the exhaust valve 18, an exhaust side
`target displacement angleVTTex that is a target displacement
`angle of the exhaust cam shaft 32 is employed. Drive of the
`exhaust valve variable timing mechanism 60b is feedback
`controlled in accordance with a deviation AVTex between the
`
`exhaust side actual displacement angle VTex and the exhaust
`side target displacement angle VTTex, whereby the valve
`timing of the exhaust valve 18 is adjusted to the target valve
`timing.
`Note that, the respective displacement angles used in each
`of the above valve timing controls are values that indicate the
`relative rotational phase ofthe cam shaft 31 or 32 with respect
`to the crank shaft 5. These displacement angles are converted
`to a crank angle (0 CA). The intake side actual displacement
`angle VTin is derived based on the output signals from the
`crank angle sensor 41 and the intake side cam angle sensor
`42a. The intake side actual displacement angle VTin is “zero
`(0)0 CA” when the valve timing of the intake valve 17 is
`retarded to a maximum extent (hereinafter referred to as
`“maximum retard timing”). Accordingly,
`the intake side
`actual displacement angle VTin is a value that indicates how
`far the valve timing of the intake valve 17 has been advanced
`from the maximum retard timing.
`The exhaust side actual displacement angleVTex is derived
`based on the output signals from the crank angle sensor 41
`
`5
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`10
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`15
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`20
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`25
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`30
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`35
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`40
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`45
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`50
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`55
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`60
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`65
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`8
`and the exhaust side cam angle sensor 42b. The exhaust side
`actual displacement angle VTex is “zero (0)0 CA” when the
`valve timing of the exhaust valve 18 is advanced to a maxi-
`mum extent (hereinafter referred to as “maximum advance
`timing”). Accordingly, the exhaust side actual displacement
`angle VTex is a value that indicates how far the valve timing
`of the exhaust valve 18 has been retarded from the maximum
`
`advance timing, or, in other words, a value that indicates how
`far a closing timing of the exhaust valve 18 is retarded.
`In addition to the above controls, in the gasoline engine 1 of
`the embodiment, a catalyst rapid warming up control is per-
`formed so that the catalyst 70 can rapidly demonstrate its
`exhaust purification performance when the gasoline engine 1
`is started in cold conditions. In this catalyst rapid warming up
`control, (a) fuel injection is performed in the latter half of a
`compression stroke (for example, at 25° BTDC), (b) the fuel
`injection amount is increased by increasing the intake air
`amount, and (c) the ignition timing is retarded. As a result,
`increase of an exhaust gas temperature is promoted, whereby
`the catalyst 70 is activated rapidly.
`Note that, if the fuel injection amount injected in the latter
`half of the compression stroke increases excessively, an air
`fuel ratio in the vicinity of the spark plug 11 becomes exces-
`sively rich, which causes the combustion condition of the air
`fuel mixture to deteriorate. In this case, as a countermeasure,
`the fuel injection is separated and performed as a plurality of
`separated injections, whereby a suitable air fuel ratio is
`formed in the vicinity of the spark plug 11. For example, in
`this embodiment, the fuel injection may be performed as two
`injections, namely, one injection in the former half of the
`compression stroke (180° BTDC) and one injection during
`the latter half of the compression stroke (30° BTDC). How-
`ever, on some occasions, if a fuel injection amount of a certain
`size is divided into two fuel injection amounts, the divided
`fuel injection amounts may be smaller than a minimum inj ec-
`tion amount (the minimum amount to which the fuel injection
`amount can be controlled) of the injector 16. On such occa-
`sions, it is not possible to adjust the fuel injection amount. As
`a result, at these times, non-separated injec