Spark Ignition Type Internal Combustion Engine
A spark ignition type internal combustion engine comprises a variable compression ratio mechanism able to change a mechanical compression ratio, an actual compression action start timing changing mechanism able to change a start timing of an actual compression action, and an exhaust valve. At the time of engine low load operation, the mechanical compression ratio is maximized to obtain a maximum expansion ratio, and the actual compression ratio is set so that no knocking occurs. The maximum expansion ratio is 20 or more. The closing timing of the exhaust valve at the time of engine low load operation is made substantially intake top dead center. Due to this, even if operating the internal combustion engine in a state of a large expansion ratio, the temperature of the exhaust purification catalyst can be maintained at a relatively high temperature.
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The present invention relates to a spark ignition type internal combustion engine.
BACKGROUND ARTKnown in the art is a spark ignition type internal combustion engine provided with a variable compression ratio mechanism able to change a mechanical compression ratio and a variable valve timing mechanism able to control a closing timing of an intake valve, performing a supercharging action by a supercharger at the time of engine medium load operation and engine high load operation and, in the state holding an actual compression ratio fixed at the time of engine medium and high load operation, increasing the mechanical compression ratio and retarding the closing timing of the intake valve as the engine load becomes lower (for example, see Japanese Patent Publication (A) No. 2004-218522).
However, in general, in an internal combustion engine, the larger the expansion ratio, the longer the period in an expansion stroke where a downward force acts on the piston, therefore the larger the expansion ratio, the more the heat efficiency is improved. Therefore, to raise the heat efficiency at the time of engine operation, it is preferable to make the mechanical compression ratio as high as possible and make the expansion ratio α large one.
However, if increasing the expansion ratio in this way, most of the heat energy produced in the combustion chamber is converted to kinetic energy, so the exhaust gas falls in temperature. Further, along with this, the pressure of the exhaust gas in the combustion chamber at the end of the expansion stroke also becomes lower and accordingly the exhaust gas becomes harder to exhaust from the combustion chamber. This tendency appears particularly remarkably when the expansion ratio is made 20 or more.
On the other hand, if the engine exhaust purification catalyst provided in the engine exhaust passage is not raised to a certain temperature or more, generally it cannot exhibit its excellent exhaust purification action. For this reason, in most internal combustion engines, the heat of the exhaust gas exhausted from the engine body is used to maintain the exhaust purification catalyst at a high temperature.
However, as explained above, if increasing the expansion ratio, the exhaust gas falls in temperature, so the temperature by which the exhaust purification catalyst is raised per unit flow rate becomes lower. Further, if increasing the expansion ratio, the exhaust gas becomes harder to be exhausted from the combustion chamber, so the flow rate of the exhaust gas flowing into the exhaust purification catalyst becomes smaller. For this reason, if operating the internal combustion engine in the state of a large expansion ratio, maintaining the exhaust purification catalyst at a high temperature becomes difficult.
DISCLOSURE OF INVENTIONTherefore, an object of the present invention is to provide a spark ignition type internal combustion engine able to maintain an exhaust purification catalyst at a relatively high temperature even when operating the internal combustion engine in the state of a large expansion ratio.
The present invention provides a spark ignition type internal combustion engine described in the claims of the claim section as means for realizing the above object.
In an aspect of the present invention, there is provided a spark ignition type internal combustion engine comprising a variable compression ratio mechanism able to change a mechanical compression ratio, an actual compression action start timing changing mechanism able to change a start timing of an actual compression action, and an exhaust valve, wherein at the time of engine low load operation the mechanical compression ratio is maximized to obtain a maximum expansion ratio and the actual compression ratio is set so that no knocking occurs, wherein the maximum expansion ratio is 20 or more, and wherein the closing timing of the exhaust valve at the time of engine low load operation is made substantially intake top dead center.
In another aspect of the present invention, there is provided a spark ignition type internal combustion engine comprising a variable compression ratio mechanism able to change a mechanical compression ratio, an actual compression action start timing changing mechanism able to change a start timing of an actual compression action, and an exhaust variable valve timing mechanism able to change the closing timing of the exhaust valve, wherein at the time of engine low load operation the mechanical compression ratio is maximized to obtain a maximum expansion ratio and the actual compression ratio is set so that no knocking occurs, wherein the maximum expansion ratio is 20 or more, and wherein a settable region of the closing timing of the exhaust valve at the time of engine low load operation is limited more to an intake top dead center side than that at the time of engine high load operation.
In another aspect of the present invention, at the time of engine low load operation, the closing timing of the exhaust valve is made substantially intake top dead center.
In another aspect of the present invention, the engine further comprises an intake variable valve timing mechanism able to change the opening timing of the intake valve, and the closing timing of the exhaust valve and the opening timing of the intake valve are controlled so that at the time of engine low load operation a period where the opening of the intake valve and the opening of the exhaust valve overlap is made minimum.
In another aspect of the present invention, the engine further comprises an intake variable valve timing mechanism able to change the opening timing of the intake valve, and the closing timing of the exhaust valve and the opening timing of the intake valve are controlled so that at the time of engine low load operation the period where the opening of the intake valve and the opening of the exhaust valve overlap, becomes zero.
In another aspect of the present invention, the engine further comprises an intake valve opening timing changing mechanism able to change the opening timing of the intake valve and, and at the time of engine low load operation, the opening timing of the intake valve is made substantially intake top dead center.
In another aspect of the present invention, the actual compression ratio at the time of engine low load operation is made substantially the same as the actual compression ratio at the time of engine medium and high load operation.
In another aspect of the present invention, at the time of engine low speed, regardless of the engine load, the actual compression ratio falls within a range of 9 to 11.
In another aspect of the present invention, the higher the engine speed, the higher the actual compression ratio.
In another aspect of the present invention, the actual compression action start timing changing mechanism is comprised of an intake variable valve timing mechanism able to change the closing timing of the intake valve.
In another aspect of the present invention, the amount of intake air fed into the combustion chamber is controlled by changing the closing timing of the intake valve.
In another aspect of the present invention, the closing timing of the intake valve is shifted as the engine load becomes lower to a direction away from intake bottom dead center until a limit closing timing enabling control of the amount of intake air fed into the combustion chamber.
In another aspect of the present invention, in a region of a load higher than the engine load when the closing timing of the intake valve reaches the limit closing timing, the amount of intake air fed into the combustion chamber is controlled without regard to a throttle valve arranged in an engine intake passage by changing the closing timing of the intake valve.
In another aspect of the present invention, in a region of a load higher than the engine load when the closing timing of the intake valve reaches the limit closing timing, the throttle valve is held at the fully opened state.
In another aspect of the present invention, in a region of a load lower than the engine load when the closing timing of the intake valve reaches the limit closing timing, a throttle valve arranged in an engine intake passage is used to control the amount of intake air fed into the combustion chamber.
In another aspect of the present invention, in a region of a load lower than the engine load when the closing timing of the intake valve reaches the limit closing timing, the lower the load, the larger the air-fuel ratio is made.
In another aspect of the present invention, in a region of a load lower than the engine load when the closing timing of the intake valve reaches the limit closing timing, the closing timing of the intake valve is held at the limit closing timing.
In another aspect of the present invention, the mechanical compression ratio is increased as the engine load becomes lower to the limit mechanical compression ratio.
In another aspect of the present invention, in a region of a load lower than the engine load when the mechanical compression ratio reaches the limit mechanical compression ratio, the mechanical compression ratio is held at the limit mechanical compression ratio.
According to the present invention, since as much exhaust gas as possible is discharged from the combustion chamber to the exhaust purification catalyst, even if operating the internal combustion engine in the state of a large expansion ratio, the exhaust purification catalyst can be maintained at a relatively high temperature.
The present invention will be more clearly understood from the description as set forth below with reference to the accompanying drawings, in which:
Referring to
The surge tank 12 is connected via an intake duct 14 to an outlet of the compressor 15a of the exhaust turbocharger 15, while an inlet of the compressor 15a is connected through an intake air amount detector 16 using for example a heating wire to an air cleaner 17. The intake duct 14 is provided inside it with a throttle valve 19 driven by an actuator 18.
On the other hand, the exhaust port 10 is connected through the exhaust manifold 20 to the inlet of the exhaust turbine 15b of the exhaust turbocharger 15, while an outlet of the exhaust turbine 15b is connected through an exhaust pipe 21 to a catalytic converter 22 housing an exhaust purification catalyst. The exhaust pipe 21 has an air-fuel ratio sensor 23 arranged in it.
Further, in the embodiment shown in
The electronic control unit 30 is comprised of a digital computer provided with components connected with each other through a bidirectional bus 31 such as a ROM (read only memory) 32, RAM (random access memory) 33, CPU (microprocessor) 34, input port 35, and output port 36. The output signal of the intake air amount detector 16 and the output signal of the air-fuel ratio sensor 23 are input through the corresponding AD converter 37 to the input port 35. Further, an accelerator pedal 40 is connected to a load sensor 41 generating an output voltage proportional to the amount of depression of the accelerator pedal 40. The output voltage of the load sensor 41 is input through a corresponding AD converter 37 to the input port 35. Further, the input port 35 is connected to a crank angle sensor 42 generating an output pulse every time the crankshaft rotates by for example 30°. On the other hand, the output port 36 is connected through the drive circuit 38 to the spark plug 6, fuel injector 13, throttle valve drive actuator 18, variable compression ratio mechanism A, and intake variable valve timing mechanism B.
As shown in
When the circular cams 56 fastened to the cam shafts 54, 55 are rotated in opposite directions from each other as shown by the solid line arrows in
As will be understood from a comparison of
As shown in
Further,
First, explaining the cam phase changer B1 of the intake variable valve timing mechanism B, this cam phase changer B1 is provided with a timing pulley 71 made to rotate by an engine crank shaft through a timing belt in the arrow direction, a cylindrical housing 72 rotating together with the timing pulley 71, a shaft 73 able to rotate together with a cam shaft 70 and rotate relative to the cylindrical housing 72, a plurality of partitions 74 extending from an inside circumference of the cylindrical housing 72 to an outside circumference of the shaft 73, and vanes 75 extending between the partitions 74 from the outside circumference of the shaft 73 to the inside circumference of the cylindrical housing 72, the two sides of the vanes 75 formed with advancing use hydraulic chambers 76 and retarding use hydraulic chambers 77.
The feed of working oil to the hydraulic chambers 76, 77 is controlled by a working oil feed control valve 78. This working oil feed control valve 78 is provided with hydraulic ports 79, 80 connected to the hydraulic chambers 76, 77, a feed port 82 for working oil discharged from a hydraulic pump 81, a pair of drain ports 83, 84, and a spool valve 85 for controlling connection and disconnection of the ports 79, 80, 82, 83, 84.
To advance the phase of the cams of the cam shaft 70, the spool valve 85 is made to move to downward in
As opposed to this, to retard the phase of the cam of the cam shaft 70, the spool valve 85 is made to move upward in
When the shaft 73 is made to rotate relative to the cylindrical housing 72, if the spool valve 85 is returned to the neutral position shown in
Next, explaining the cam actuation angle changer B2 of the intake variable valve timing mechanism B, this cam actuation angle changer B2 is provided with a control rod 90 arranged in parallel with the cam shaft 70 and made to move by an actuator 91 in the axial direction, an intermediate cam 94 engaging with a cam 92 of the cam shaft 70 and slidably fitting with a spline 93 formed on the control rod 90 and extending in the axial direction, and a pivoting cam 96 engaging with a valve lifter 24 for driving the intake valve 7 and slidably fitting with a spline 95 extending in a spiral formed on the control rod 90. The pivoting cam 96 is formed with a cam 97.
When the cam shaft 70 rotates, the cam 92 causes the intermediate cam 94 to pivot by exactly a constant angle at all times. At this time, the pivoting cam 96 is also made to pivot by exactly a constant angle. On the other hand, the intermediate cam 94 and pivoting cam 96 are supported not movably in the axial direction of the control rod 90, therefore when the control rod 90 is made to move by the actuator 91 in the axial direction, the pivoting cam 96 is made to rotate relative to the intermediate cam 94.
When the cam 92 of the cam shaft 70 starts to engage with the intermediate cam 94 due to the relative rotational positional relationship between the intermediate cam 94 and pivoting cam 96, if the cam 97 of the pivoting cam 96 starts to engage with the valve lifter 24, as shown by a in
When the pivoting cam 96 is made to rotate relative to the intermediate cam 94 in the arrow Y-direction of
The cam phase changer B1 can be used to freely change the opening timing of the intake valve 7 and the cam actuation angle changer B2 can be used to freely change the opening time period of the intake valve 7 in this way, so both the cam phase changer B1 and cam actuation angle changer B2, that is, the intake variable valve timing mechanism B, may be used to freely change the opening timing and opening time period of the intake valve 7, that is, the opening timing and closing timing of the intake valve 7.
Note that the intake variable valve timing mechanism B shown in
Further, the exhaust variable valve timing mechanism C also basically has a configuration similar to the intake variable valve timing mechanism B and can freely change the opening timing and opening time period of the exhaust valve 9, that is, the opening timing and closing timing of the exhaust valve 9.
Next, the meaning of the terms used in the present application will be explained with reference to
Next, the most basic features of the present invention will be explained with reference to
The solid line in
On the other hand, under this situation, the inventors strictly differentiated between the mechanical compression ratio and actual compression ratio and studied the theoretical thermal efficiency and as a result discovered that in the theoretical thermal efficiency, the expansion ratio is dominant, and the theoretical thermal efficiency is not affected much at all by the actual compression ratio. That is, if raising the actual compression ratio, the explosive force rises, but compression requires a large energy, accordingly even if raising the actual compression ratio, the theoretical thermal efficiency will not rise much at all.
As opposed to this, if increasing the expansion ratio, the longer the period during which a force acts pressing down the piston at the time of the expansion stroke, the longer the time that the piston gives a rotational force to the crankshaft. Therefore, the larger the expansion ratio is made, the higher the theoretical thermal efficiency becomes. The broken line in
If the actual compression ratio is maintained at a low value in this way, knocking will not occur, therefore if raising the expansion ratio in the state where the actual compression ratio is maintained at a low value, the occurrence of knocking can be prevented and the theoretical thermal efficiency can be greatly raised.
Referring to
As explained above, generally speaking, in an internal combustion engine, the lower the engine load, the worse the heat efficiency, therefore to improve the heat efficiency at the time of vehicle operation, that is, to improve the fuel efficiency, it becomes necessary to improve the heat efficiency at the time of engine low load operation. On the other hand, in the superhigh expansion ratio cycle shown in
Now, as explained above, at the time of engine high load operation, the normal cycle shown in
On the other hand, as shown in
In this way, when the engine load becomes lower from the engine high load operating state, the mechanical compression ratio is increased along with the fall in the amount of intake air under a substantially constant actual compression ratio. That is, the volume of the combustion chamber 5 when the piston 4 reaches compression top dead center is reduced proportionally to the reduction in the amount of intake air. Therefore the volume of the combustion chamber 5 when the piston 4 reaches compression top dead center changes proportionally to the amount of intake air. Note that at this time, the air-fuel ratio in the combustion chamber 5 becomes the stoichiometric air-fuel ratio, so the volume of the combustion chamber 5 when the piston 4 reaches compression top dead center changes proportionally to the amount of fuel.
If the engine load becomes further lower, the mechanical compression ratio is further increased. When the mechanical compression ratio reaches the limit mechanical compression ratio corresponding to the structural limit of the combustion chamber 5, in the region of a load lower than the engine load L1 when the mechanical compression ratio reaches the limit mechanical compression ratio, the mechanical compression ratio is held at the limit mechanical compression ratio. Therefore at the time of engine low load operation, the mechanical compression ratio becomes maximum, and the expansion ratio also becomes maximum. Putting this another way, in the present invention, so as to obtain the maximum expansion ratio at the time of engine low load operation, the mechanical compression ratio is made maximum. Further, at this time, the actual compression ratio is maintained at an actual compression ratio substantially the same as that at the time of engine medium and high load operation.
On the other hand, as shown by the solid line in
In the embodiment shown in
Note that to prevent such pumping loss from occurring, in the region of a load lower than the engine load L2 when the closing timing of the intake valve 7 reaches the limit closing timing, in the state holding the throttle valve 17 fully opened or substantially fully opened, the air-fuel ratio may be made larger the lower the engine load. At this time, the fuel injector 13 is preferably arranged in the combustion chamber 5 to perform stratified combustion.
As shown in
On the other hand, as explained above, in the superhigh expansion ratio cycle shown in
Further, in the example shown in
On the other hand, as shown by the broken line in
Next, the closing timing of the exhaust valve 9 will be explained focusing on the low load operation where the superhigh expansion ratio cycle shown in
In general, at the time of low load operation where a superhigh expansion ratio cycle is executed, the amount of heat generated due to combustion of the air-fuel mixture in the combustion chamber 5 itself is small, so the temperature of the exhaust gas exhausted from the combustion chamber 5 easily becomes low. In addition to this, in an internal combustion engine, the larger the expansion ratio, the longer the period during which a force pushing down the piston acts at the time of an expansion stroke, so most of the heat energy produced by combustion of the air-fuel mixture in the combustion chamber is converted to kinetic energy of the piston. Along with this, the temperature of the combustion gas in the combustion chamber at the end of the expansion stroke becomes lower. For this reason, when the superhigh expansion ratio cycle shown in
On the other hand, in most internal combustion engines, the harmful ingredients contained in exhaust gas (for example, HC, CO, NOx, etc.) are removed by providing inside the engine exhaust passage a three-way catalyst, NOx storing and reducing catalyst, or other exhaust purification catalyst. Such an exhaust purification catalyst cannot effectively remove the harmful ingredients in the exhaust gas unless its temperature becomes the activation temperature or more. Here, in most internal combustion engines, the temperature of the exhaust gas is considerably higher than the activation temperature, so the exhaust gas is made to flow into the exhaust purification catalyst to maintain the temperature of the exhaust purification catalyst at the activation temperature or more.
However, if the superhigh expansion ratio cycle shown in
Here, referring to
As shown in
On the other hand, as shown in
In particular, when the superhigh expansion ratio cycle is executed, at the time of the expansion stroke, the combustion gas in the combustion chamber 5 considerably expands, so the pressure of the combustion gas at the end of the expansion stroke will be relatively low. For this reason, the strength of the exhaust gas flowing out from the combustion chamber 5 to the exhaust port 10 at the exhaust stroke will be weak. Therefore, if the piston 4 descends after reaching intake top dead center, part of the exhaust gas flowing out into the exhaust port 10 will again easily flow into the combustion chamber 5.
In this way, when closing the exhaust valve 9 after intake top dead center, the exhaust gas flowing out once into the exhaust port 10 will again return to the inside of the combustion chamber 5, so the exhaust gas in the combustion chamber 5 will not be able to be sufficiently exhausted to the exhaust manifold 20 and the flow rate of exhaust gas flowing into the exhaust purification catalyst will be small.
Therefore, in the present embodiment, when the superhigh expansion ratio cycle shown in
As shown in
Alternatively, when the superhigh expansion ratio cycle shown in
In this way, when the mechanical compression ratio is high, by limiting the region in which the closing timing of the exhaust valve 9 can be set to the intake top dead center side or making the closing timing of the exhaust valve 9 substantially intake top dead center, it is possible to sufficiently exhaust the exhaust gas in the combustion chamber 5 to the exhaust manifold 20 and make the flow rate of exhaust gas flowing into the exhaust purification large.
That is, the exhaust valve 9 is made to close near intake top dead center, so as shown in
Note that the “substantially intake top dead center” indicates within 10° before and after intake top dead center, preferably within 5° before and after intake top dead center.
Further, if raising the mechanical compression ratio, the combustion chamber volume at intake top dead center becomes smaller and accordingly depending on the closing timing of the exhaust valve 9, the exhaust valve 9 will end up interfering with the piston 4.
As opposed to this, according to the present embodiment, when the mechanical compression ratio is high, the region in which the closing timing of the exhaust valve 9 can be set is limited to the intake top dead center side, in particular the amount of maximum retardation by which the closing timing of the exhaust valve 9 can be set is made smaller. For this reason, as shown in
However, when there is a valve overlap where the opening time period of the intake valve 7 and the opening time period of the exhaust valve 9 overlap, the amount of exhaust gas exhausted from inside of the combustion chamber 5 to the exhaust manifold 20 changes even during that period. Below, referring to
In general, when the intake valve 7 and exhaust valve 9 are simultaneously opened, part of the exhaust gas in the combustion chamber 5 and part of the exhaust gas once flowing out from the combustion chamber 5 to the exhaust port 10 will sometimes flow into the intake port 8. In this way, when part of the exhaust gas flows into the intake port 8, the exhaust gas exhausted from the combustion chamber 5 to the exhaust manifold 20 will become smaller by that amount.
Therefore, when the overlap period is large as shown in
Therefore, in this embodiment, when the superhigh expansion ratio cycle shown in
In this way, when the mechanical compression ratio is high, by minimizing the overlap period, the exhaust gas flowing into the intake port 8 becomes smaller, so the exhaust gas exhausted from the combustion chamber 5 to the exhaust manifold 20 becomes great and accordingly the flow rate of the exhaust gas flowing into the exhaust purification catalyst becomes greater.
Note that the overlap period when the mechanical compression ratio is high need not necessarily be made the minimum so long as it is shorter than the overlap period when the mechanical compression ratio is low. Therefore, for example, the overlap period when the mechanical compression ratio is high need only be 10° or less of the settable range even at the minimum.
Further, as explained above, if raising the mechanical compression ratio, the combustion chamber volume at intake top dead center becomes smaller. Accordingly, depending on the opening timing of the intake valve 7, the intake valve 7 will end up interfering with the piston 4.
As opposed to this, according to the present embodiment, when the mechanical compression ratio is high, the overlap period is made the minimum, so the opening timing of the intake valve 7 is made substantially intake top dead center or less. For this reason, as shown in
Further, the closing timing IC of the intake valve 7 required for feeding the required amount of intake air into the combustion chamber 5 is stored as a function of the engine load L and engine speed Ne in the form of a map as shown in
Next, at step 105, it is judged if the engine load L is smaller than a predetermined value L3. Here, this predetermined value L3 is, for example, made a value equal to the engine load at which when the engine load becomes smaller, the drop in the temperature of the exhaust gas may be accompanied with a drop in the temperature of the exhaust purification catalyst to below the activation temperature. When it is judged at step 105 that the engine load L is smaller than the predetermined value L3, the routine proceeds to step 106. At step 106, the closing timing EC of the exhaust valve 9 is made substantially intake top dead center. Next, at step 107, the overlap period ΔOL is made the minimum and the routine proceeds to step 110.
On the other hand, when it is judged at step 105 that the engine load is the predetermined value L3 or more, the routine proceeds to step 108. At step 108, the map shown in
At step 110, the mechanical compression ratio is made the mechanical compression ratio CR by controlling the variable compression ratio mechanism A, while the closing timing of the intake valve 7 is made the closing timing IC and the overlap period is made the overlap period ΔOL by controlling the intake variable valve timing mechanism B. Further, the closing timing of the exhaust valve 9 is made the closing timing EC by controlling the exhaust variable valve timing mechanism C.
While the invention has been described by reference to specific embodiments chosen for purposes of illustration, it should be apparent that numerous modifications could be made thereto by those skilled in the art without departing from the basic concept and scope of the invention.
Claims
1. A spark ignition type internal combustion engine comprising a variable compression ratio mechanism able to change a mechanical compression ratio, an intake variable valve timing mechanism able to change the closing timing of the intake valve, and an exhaust valve,
- wherein at the time of engine low load operation, the variable compression ratio mechanism controls the mechanical compression ratio so as to be maximized to obtain a maximum expansion ratio and the intake variable valve timing mechanism controls the closing timing of the intake valve so that the actual compression ratio is set so that no knocking occurs,
- wherein said maximum expansion ratio is 20 or more, and
- wherein the closing timing of the exhaust valve at the time of engine low load operation is made substantially intake top dead center.
2. A spark ignition type internal combustion engine comprising a variable compression ratio mechanism able to change a mechanical compression ratio, an intake variable valve timing mechanism able to change the closing timing of the intake valve, and an exhaust variable valve timing mechanism able to change the closing timing of the exhaust valve,
- wherein at the time of engine low load operation, the variable compression ratio mechanism controls the mechanical compression ratio so as to be maximized to obtain a maximum expansion ratio and the intake variable valve timing mechanism controls the closing timing of the intake valve so that the actual compression ratio is set so that no knocking occurs,
- wherein said maximum expansion ratio is 20 or more, and
- wherein a settable region of the closing timing of the exhaust valve at the time of engine low load operation is limited more to an intake top dead center side than that at the time of engine high load operation.
3. A spark ignition type internal combustion engine as set forth in claim 2, wherein at the time of engine low load operation, the closing timing of the exhaust valve is made substantially intake top dead center.
4. A spark ignition type internal combustion engine as set forth in claim 2, wherein the closing timing of the exhaust valve and the opening timing of the intake valve are controlled so that at the time of engine low load operation a period where the opening of the intake valve and the opening of the exhaust valve overlap is made minimum.
5. A spark ignition type internal combustion engine as set forth in claim 2, wherein the closing timing of the exhaust valve and the opening timing of the intake valve are controlled so that at the time of engine low load operation the period where the opening of the intake valve and the opening of the exhaust valve overlap becomes zero.
6. A spark ignition type internal combustion engine as set forth in claim 1, wherein at the time of engine low load operation, the opening timing of the intake valve is made substantially intake top dead center.
7. A spark ignition type internal combustion engine as set forth in claim 1, wherein the actual compression ratio at the time of engine low load operation is made substantially the same actual compression ratio as at the time of engine medium and high load operation.
8. A spark ignition type internal combustion engine as set forth in claim 7, wherein, at the time of engine low speed, regardless of the engine load, said actual compression ratio falls within a range of 9 to 11.
9. A spark ignition type internal combustion engine as set forth in claim 8, wherein the higher the engine speed, the higher the actual compression ratio.
10. (canceled)
11. A spark ignition type internal combustion engine as set forth in claim 1, wherein the amount of intake air fed into the combustion chamber is controlled by changing the closing timing of the intake valve.
12. A spark ignition type internal combustion engine as set forth in claim 11, wherein the closing timing of the intake valve is shifted as the engine load becomes lower to a direction away from intake bottom dead center until a limit closing timing enabling control of the amount of intake air fed into the combustion chamber.
13. A spark ignition type internal combustion engine as set forth in claim 12, wherein in a region of a load higher than the engine load when the closing timing of the intake valve reaches said limit closing timing, the amount of intake air fed into the combustion chamber is controlled without regard to a throttle valve arranged in an engine intake passage by changing the closing timing of the intake valve.
14. A spark ignition type internal combustion engine as set forth in claim 13, wherein in a region of a load higher than the engine load when the closing timing of the intake valve reaches said limit closing timing, the throttle valve is held at the fully opened state.
15. A spark ignition type internal combustion engine as set forth in claim 12, wherein in a region of a load lower than the engine load when the closing timing of the intake valve reaches said limit closing timing, a throttle valve arranged in an engine intake passage is used to control the amount of intake air fed into the combustion chamber.
16. A spark ignition type internal combustion engine as set forth in claim 12, wherein in a region of a load lower than the engine load when the closing timing of the intake valve reaches said limit closing timing, the lower the load, the larger the air-fuel ratio is made.
17. A spark ignition type internal combustion engine as set forth in claim 12, wherein in a region of a load lower than the engine load when the closing timing of the intake valve reaches said limit closing timing, the closing timing of the intake valve is held at said limit closing timing.
18. A spark ignition type internal combustion engine as set forth in claim 1, wherein said mechanical compression ratio is increased as the engine load becomes lower to the limit mechanical compression ratio.
19. A spark ignition type internal combustion engine as set forth in claim 18, wherein in a region of a load lower than the engine load when said mechanical compression ratio reaches said limit mechanical compression ratio, the mechanical compression ratio is held at said limit mechanical compression ratio.
Type: Application
Filed: Apr 9, 2007
Publication Date: Jul 16, 2009
Applicant: TOYOTA JIDOSHA KABUSHIKI KAISHA (TOYOTA-SHI)
Inventors: Daisuke Akihisa (Susono-shi), Daisaku Sawada (Gotenba-shi), Eiichi Kamiyama (Mishima-shi)
Application Number: 12/227,601
International Classification: F01L 1/34 (20060101);