Early closing miller cycle internal combustion engine

Abstract

The present invention mitigates restriction due to the fact that the opening period (angular working range) of the intake valve becomes smaller in the early closing Miller cycle operation, in which the intake valve closing timing occurs before the bottom dead center. The crankshaft center O1 is offset on one side from the cylinder central axis X. The top dead center and the bottom dead center of the piston occur when the three points, namely the crankshaft center O1, the crankpin center O2, and the piston pin center O3 are aligned in one line. At this time, the connecting rod and the crank arm are inclined relative to the axis X. The inclination angle &thgr;bdc at the bottom dead center is greater than the inclination angle &thgr;tdc at the top dead center. Therefore, as the crankshaft rotates in the direction of arrow &ohgr;, the intake process and the expansion process become greater than 180° CA, while the compression process and the exhaust process become smaller than 180° crank angle. Accordingly, the angular working range of the intake valve is enlarged. Therefore, the restriction to the valve lift curve is mitigated.

Description

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention generally relates to an early closing Miller cycle internal combustion engine. More specifically, the present invention relates an early closing Miller cycle internal combustion engine, in which Miller cycle is achieved by advancing the angular timing of the closing of an intake valve relative to the intake bottom dead center.

[0003] 2. Background Information

[0004] A Miller cycle internal combustion engine has a greater expansion rate than compression rate in order to improve the fuel consumption rate. Thus, the Miller cycle internal combustion engine has recently been drawing more interest in the automotive field. Miller cycle internal combustion engines are broadly divided into late closing Miller cycle engines and early closing Miller cycle engines. In the late closing Miller cycle engines, the intake valve closing timing is delayed relative to the intake bottom dead center, such that the air that has been inhaled is partially pushed back. In the early closing Miller cycle engines, the intake valve closing timing is advanced relative to the intake bottom dead center, such that the intake process is effectively shortened. An early closing Miller cycle engine is disclosed in Japanese Laid-Open Patent H7-310565.

[0005] Typically, the intake valve of an internal combustion engine is mechanically driven via a camshaft. However, there various types of valve activation devices have been suggested, in which an electromagnetic actuator is provided in each intake valve. In such case, each valve can be opened and closed separately. Also, there is more flexibility in the control of the opening and closing timings. An valve activation device is disclosed in Japanese Laid-Open Patent Application H8-189315.

[0006] In view of the above, there exists a need for an early closing Miller cycle engine which overcomes the problems in the prior art. This invention addresses this need in the prior art as well as other needs, which will become apparent to those skilled in the art from this disclosure.

SUMMARY OF THE INVENTION

[0007] In an early closing Miller cycle engine, since the intake valve closing timing is before the intake bottom dead center, as long as the intake valve opening timing is set at an appropriate position from the point of view of valve overlap, the intake valve opening period (or the valve angular working range) becomes very short. Accordingly, the intake valve has to be opened and closed abruptly. As a result, an impact due to momentum of the valve becomes large. Therefore, the durability of the valve is likely to decrease. Also, the valve lift curve has to be designed such that the valve does not fall out of the valve lift curve in the high-speed region. As a result, flexibility of the valve design decreases.

[0008] It has been discovered that it is possible to use a movable valve mechanism that utilizes an electromagnetic or hydraulic actuator to operate an engine in a Miller cycle only under certain conditions. In such valve driving device that does not depend on a crankshaft, the minimum length of the valve opening period is uniquely determined based on the responsiveness of the actuator or the applied voltage, regardless of the rotations of the mechanism. Therefore, when early closed Miller cycle engine is combined with this type of valve driving device, it is difficult to adjust the valve timing in the high-speed region, in which the actual period of time that corresponds to the valve opening period becomes shorter. In other words, operation in high-rotation region of the engine in a Miller cycle is restricted. Otherwise, a larger actuator will be necessary, or more electric power will be necessary to further increase the responsiveness.

[0009] On the other hand, with regard to a late closing Miller cycle engine, in which the intake valve closing timing is delayed until after the bottom dead center, the valve opening period is longer than that of a regular Otto cycle engine. Therefore, such problem does not occur.

[0010] In accordance with one aspect of the present invention, an early closing Miller cycle internal combustion engine is provided. The early closing Miller cycle internal combustion engine comprises a piston slidably disposed in a cylinder to reciprocate along a cylinder central axis, an intake valve disposed in an intake opening of the cylinder to open and close the intake opening, an exhaust valve disposed in an exhaust opening of the cylinder to open and close the exhaust opening, a movable valve mechanism arranged to close the intake valve before a bottom dead center to achieve the Miller cycle operation, a crankshaft operatively coupled to the piston to move the piston in the cylinder, the crankshaft having a crankshaft center axis of rotation offset from the cylinder central axis in such a direction that an intake process and an expansion process have greater than 180° crank angle.

[0011] These and other objects, features, aspects and advantages of the present invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses a preferred embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Referring now to the attached drawings which form a part of this original disclosure:

[0013] FIG. 1 is a diagrammatic structural view of an early closing Miller cycle internal combustion engine in accordance with the present invention;

[0014] FIG. 2 is a characteristics graph showing the valve lift characteristics of intake valve in accordance with the present embodiment; and

[0015] FIG. 3 is a diagrammatic view of a crankshaft having a connecting rod and piston coupled thereto at top dead center, wherein the crankshaft center is offset from the from the piston pin center in accordance with the present invention;

[0016] FIG. 4 is a diagrammatic view of a crankshaft having a connecting rod and piston coupled thereto at bottom dead center, wherein the crankshaft center is offset from the from the piston pin center in accordance with the present invention;

[0017] FIG. 5 is a diagrammatic view of a crankshaft having a connecting rod and piston coupled thereto at top dead center, wherein the crankshaft center is aligned with the piston pin center;

[0018] FIG. 6 is a diagrammatic view of a crankshaft having a connecting rod and piston coupled thereto at bottom dead center, wherein the crankshaft center is aligned with the piston pin center;

[0019] FIG. 7 is a valve timing diagram showing opening and closing timings of the intake valve during an early closing Miller cycle operation, where the crank offset is zero such as shown in FIGS. 5 and 6;

[0020] FIG. 8 is a valve timing diagram showing opening and closing timings of the intake valve during early closing Miller cycle operation in the case of the present invention, where the crankshaft center is offset from the from the piston pin center such as shown in FIGS. 3 and 4;

[0021] FIG. 9 is a diagrammatic structural view of an alternate embodiment of the present invention in which a hydraulic valve driving device is used; and

[0022] FIG. 10 is a diagrammatic structural view of an early closing Miller cycle internal combustion engine in accordance with another embodiment of the present invention;

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Selected embodiments of the present invention will now be explained with reference to the drawings. It will be apparent to those skilled in the art from this disclosure that the following description of the embodiments of the present invention is provided for illustration only, and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.

[0024] Referring initially to FIG. 1, an early closing Miller cycle internal combustion engine is diagrammatically illustrated to explain a first embodiment of the present invention. Basically, the early closing Miller cycle internal combustion engine embodiment of the present invention has an engine control unit 1 that controls an electromagnetic actuator controller 6 to open and close a plurality of intake valves 17 (only one shown) and a plurality of exhaust valve 19 (only one shown) by an intake valve driving actuator 16 and an exhaust valve driving actuator 18, respectively, such that the valves 17 and 19 independently open and close intake openings 17a and exhaust openings 19a.

[0025] In the present invention, “Miller cycle internal combustion engine” is not limited to internal combustion engines that always operate as a Miller cycle internal combustion engine. It also includes internal combustion engines that operate as a Miller cycle internal combustion engine only under certain operative circumstances by varying the closing period of the intake valves 17 through the use of a movable valve device. In this case, a target closure timing of the intake valves 17 are calculated in accordance with one or more engine operating conditions, and the movable valve device is controlled so that the closure timing of the intake valves 17 meets the calculated target closure timing. The target closure timing includes at least a timing set before the bottom dead center.

[0026] As seen in FIG. 1, a piston 13 is slidably disposed within a cylinder 12. Of course, the internal combustion engine of the present invention is preferably a multi-cylinder engine with a plurality of pistons 13 that are slidably disposed within a corresponding number of cylinders 12. Moreover, while only one intake valve 17 and one exhaust valve 19 is shown per cylinder 12, it will be apparent from this disclosure that more than one intake valve and more than one exhaust valve can be used per cylinder in carrying out the present invention. The center O1 of the crankshafts (not shown in the FIG. 1) is disposed at a position offset on one side from the central axis X of the cylinder 12 as seen in FIGS. 3 and 4. Accordingly, as described below, the intake process and the expansion process have greater than 180° of crank angle (CA) allocated thereto. As seen in FIG. 1, an ignition plug 20 is disposed on an approximate center of the cylinder 12. A fuel injection valve 15 is disposed on an intake manifold. The intake valve 17 and the exhaust valve 19 are operatively coupled to the intake valve driving actuator 16 and the exhaust valve driving actuator 18, respectively, such that the valves 17 and 19 are opened and closed independently. The intake valve driving actuator 16 and exhaust valve driving actuator 18 are preferably electromagnetically operated actuators that have substantially the same structures.

[0027] The electromagnetic actuator controller 6 together with the intake valve driving actuator 16 and exhaust valve driving actuator 18 form an electromagnetic valve driving device. The electromagnetic valve driving device of the present invention can be, for example, the one disclosed in of Japanese Patent Application No. 2000-1453525 (U.S. patent application Ser. No. 09/438,499). The entire disclosures of Japanese Patent Application No. 2000-1453525 and U.S. patent application Ser. No. 09/438,499 are hereby incorporated herein by reference, especially with regard to the electromagnetic valve driving device disclosed therein. Instead of using the electromagnetic valve driving device, a hydraulic valve driving device such as the one shown in FIG. 9 can be used.

[0028] The electromagnetic actuator controller 6, the intake valve driving actuator 16 and exhaust valve driving actuator 18 are conventional components that are well known in the art. Since electromagnetic actuator controllers, electromagnetic actuators, such as electromagnetic actuator controller 6, the intake valve driving actuator 16 and exhaust valve driving actuator 18, are well known in the art, these structures will not be discussed or illustrated in detail herein. Moreover, the electromagnetic valve driving device forms “valve control means” which as utilized in the claims should include any structure that can be utilized to carry out the function of opening and closing the valves 17 and 19 of an engine in accordance with present invention.

[0029] The intake valves 17 and the exhaust valves 19 are each maintained at neutral positions by a pair of springs (not shown) in a conventional manner. The springs are axially aligned with the valves 17 and 19, respectively, with each of the valves 17 and 19 being positioned between a pair of springs. Also, two electromagnetic coils are disposed on each of the valves 17 and 19. The electromagnetic coils bias the springs in the opening direction and the closing direction, respectively. Since electrification and stoppage of the electromagnetic coils are controlled by the electromagnetic actuator controller 6, each of the valves 17 and 19 is opened and closed based on the lift property shown in FIG. 2. Since the moving speeds of the valves 17 and 19 are determined by the natural frequency of the spring-mass system, the movement of the valves become relatively slow with respect to the crank angle as the mechanism starts high-speed rotation and actual period per unit crank angle becomes shorter. Therefore, in the valve lift property relative to the crank angle, the inclinations of the opening timing and closing timing vary depending on the rotations of the mechanism.

[0030] As seen in FIG. 1, the aforementioned internal combustion engine includes a crank angle sensor 11 that outputs a unit crank angle signal, and a cylinder detection sensor 9 that outputs a cylinder detection signal. These detection signals are inputted into an the engine control unit 1, along with other signals such as intake air amount signal, throttle opening signal, and water temperature signal. The engine control unit 1 controls the opening and closing timings of the intake valves 17 and the exhaust valves 19 through the aforementioned electromagnetic actuator controller 6, the intake valve driving actuator 16 and exhaust valve driving actuator 18 based on these detection signals. In one embodiment, the valve driving device closes the intake valves 17 at a predetermined closure timing that corresponds to at least one engine operating condition detected from these detection signals so that the predetermined timing is set before bottom dead center at least under the detected engine operating condition. Thus, the valve driving device is controllably arranged to vary and control the closure timing of the intake valves 17 to a target closure timing of the intake valves 17 that is determined based on the detected engine operating conditions. The target closure timings of the intake valves 17 include at least one timing set before bottom dead center. A battery 7 is provided to supply electrical power to the electromagnetic actuator controller 6.

[0031] The control unit I preferably includes a microcomputer with a control program that controls the electromagnetic actuator controller 6 as discussed above. The control unit 1 can also include other conventional components such as an input interface circuit, an output interface circuit, and storage devices such as a ROM (Read Only Memory) device and a RAM (Random Access Memory) device. The control unit 1 is operatively coupled to the electromagnetic actuator controller 6 in a conventional manner. The internal RAM of the control unit 1 stores statuses of operational flags and various control data. It will be apparent to those skilled in the art from this disclosure that the precise structure and algorithms for the control unit 1 can be any combination of hardware and software that will carry out the functions of the present invention. In other words, “means plus function” clauses as utilized in the specification and claims should include any structure or hardware and/or algorithm or software that can be utilized to carry out the function of the “means plus function” clause.

[0032] In an early closing Miller cycle internal combustion engine in which a Miller cycle operation is achieved by closing the intake valve 17 before a bottom dead center position, the crankshaft center O1 is offset from a cylinder central axis X, in such a direction that an intake process and an expansion process have greater than 180° crank angle.

[0033] As shown in FIGS. 5 and 6, the situation is illustrated in which the center O1 of the crankshaft is positioned on a cylinder central axis X. In other words, the center O1 of the crankshaft is aligned with the central axis X of the cylinder. This arrangement has a crank offset of zero (0°) with three basic reference points (i.e., the crankshaft center O1, a crankpin center O2, and a piston pin center O3). In this arrangement, the piston pin center O3 is aligned on the central axis X, at both top dead center (TDC) position as shown in FIG. 5 and the bottom dead center (BDC) position as shown in FIG. 6. Accordingly, the four processes (i.e., intake, compression, expansion, and exhaust) each has 180° of crank angle (CA) allocated thereto. In the FIGS. 5 and 6, the length 1 of a connecting rod and the rotational radius r of the crankpin are shown.

[0034] On the other hand, as shown in FIGS. 3 and 4, when the crankshaft center O1 is offset from the central axis X of the cylinder 12, the bottom dead center position and the top dead center position of the piston 13 still occur when the three reference points (i.e., the crankshaft center O1, the crankpin center O2, and the piston pin center O3) are aligned along a single reference line. At this time, as shown in FIGS. 3 and 4, the connecting rod and the crank arm are inclined relative to the central axis X of the cylinder 12. Where the offset amount of the crankshaft center O1 from the cylinder center axis X is H, the inclination angle &thgr;tdc at the top dead center position is &thgr;tdc=sin−1{H/(r+1)} as shown in FIG. 3. On the other hand, the inclination angle &thgr;bdc at the bottom dead center position is &thgr;bdc=sin−1{H/(1−r)} as shown in FIG. 4. Therefore, based on these equations, the inclination angle &thgr;tdc at the top dead center position is less than the inclination angle &thgr;bdc at the bottom dead center position, i.e., &thgr;tdc<&thgr;bdc. If the rotational direction of the crankshafts is in the direction of the arrow&ohgr;) in FIGS. 3 and 4, the intake process and the expansion process, during which the piston 13 moves from the top dead center position to the bottom dead center position in this rotational direction, becomes greater than 180° crank angle, while the compression process and the exhaust process become less than 180° crank angle. More specifically, the crank angular range during which the intake process and the expansion process occur is 180+(&thgr;bdc-&thgr;tdc), which is greater by (&thgr;bdc-&thgr;tdc) than the case where there is no crank offset.

[0035] Referring now to FIGS. 7 and 8, valve timing diagrams show examples of opening/closing timings of the intake valves for the early closing Miller cycle engine. FIG. 7 shows the case where there is no crank offset, while FIG. 8 shows the case where there is a crank offset in accordance with the present invention. When there is no crank offset, the intake process and the expansion process both have 180° crank angle, as described above. The intake valve opening timing (IVO) is set at shortly before the intake top dead center, while the intake valve closing timing (IVC) is set at an angle that is advanced relative to the intake bottom dead center. The effective intake process capacity is determined by this intake valve closing timing.

[0036] On the other hand, where there is a crank offset, the intake process becomes longer than 180° crank angle as described above. In FIG. 8, the valve timing diagram is drawn with respect to the position of its top dead center (TDC) in order to make an easy comparison with FIG. 7. In this manner, the range of crank angle that corresponds to the intake process is enlarged. Therefore, when the intake process capacity during Miller cycle engine is secured in the similar manner as in the case of FIG. 7, the position of the intake valve closing timing (IVC) relative to the top dead center (TDC) needs to be at a relatively delayed position in comparison with the case of FIG. 7. Accordingly, the angular working range of the intake valve (crank angle between IVO and IVC) is enlarged. Therefore, more flexibility is allowed in the design of the valve lift curve. Also, when the identical valve working angle is to be obtained, the intake valve closing timing can be set at an angle that is significantly advanced from the bottom dead center. Accordingly, the intake process capacity can be further decreased during the Miller cycle operation.

[0037] Next, FIG. 9 shows an example of a structure in which a hydraulic valve driving device is utilized to drive the intake valves 17 and the exhaust valves 19. Since the intake valves 17 and the exhaust valves 19 basically have the same structure, the intake valves 17 and the exhaust valves 19 are controlled in the same manner. Thus, the hydraulic valve driving device will only be illustrated as operating a pair of intake valves 17. The hydraulic valve driving device replaces the electromagnetic actuator controller 6, the intake valve driving actuator 16 and exhaust valve driving actuator 18 of the first embodiment shown in FIG. 1 to open and close the intake valves 17 and the exhaust valves 19.

[0038] This hydraulic valve driving device basically includes a reserve tank 901, a hydraulic pump 902, a hydraulic adjusting valve 903, an accumulator 904, a high pressure line 905, a valve opening hydraulic switching valve 906, a plurality of hydraulic cylinders 907, a valve closing hydraulic switching valve 911, a plurality of valve springs 909, and a drain line 912. A hydraulic actuator is formed by the valve opening hydraulic switching valve 906, the hydraulic cylinders 907, the valve closing hydraulic switching valve 911, the valve springs 909. The valve opening hydraulic switching valve 906 opens and closes the high pressure line 905, while the valve closing hydraulic switching valve 911 opens and closes the drain line 912. In this structure, the hydraulic pump 902 and the accumulator 904 always generate a high hydraulic pressure. As the valve opening hydraulic pressure switching valve 906 is opened while valve closing hydraulic switching valve 911 is closed by a control signal from the engine control unit 1 (not shown in the FIG. 9), the hydraulic pressure acts on the hydraulic pressure cylinders 907. Accordingly, the valves 17 open. Then, as the valve opening hydraulic switching valve 906 is closed while the valve closing hydraulic switching valve 911 is opened, the hydraulic pressure of the hydraulic cylinders 907 is immediately released. Accordingly, the valves 17 close due to the spring force of the valve springs 909.

[0039] Thus, each intake valve 17 is preferably driven through an electromagnetic or hydraulic actuator. By providing either an electromagnetic or a hydraulic actuator for each intake valves 17 to open and close the intake valves 17, as disclosed in Japanese Laid-Open Patent Application H8-189315, the intake valves 17 can be opened/closed at any desired timing. In this manner, an early-closing Miller cycle operation can be performed easily. In this type of device, the shortest period of time in which the valve 17 is open is uniquely determined based on the responsiveness of the actuator or the applied voltage, regardless of the rotations of the mechanism. However, in this invention, the valve angular working range during the early closing Miller cycle operation is enlarged due to the crank offset. Therefore, even if the actual period of time during which the valve 17 is open is the same, the early closing Miller cycle operation can be performed in a higher-speed region. Also, if the maximum rotation speed during the Miller cycle operation is the same, the valve opening period (actual period of time) becomes longer because the valve angular working range during the early closing Miller cycle operation is enlarged due to the crank offset. Therefore, it is possible to utilize, for instance a small actuator, which does not have high responsiveness, or to decrease the consumption of electric power. In the case of a hydraulic actuator, the responsiveness is always determined by the hydraulic pressure. Therefore, the control is possible with lower hydraulic pressure.

[0040] In the early closing Miller cycle internal combustion engine according to the present invention, the intake valve closing timing, which is on the advanced angle side relative to the intake bottom dead center, can be effectively delayed while maintaining the same intake process capacity. Therefore, if the intake valve opening timing is on the same position, the requisite valve angular working range is relatively enlarged. Accordingly, there is more flexibility in design of valve lift curve. Also, if restrictions from the valve lift curve of the intake valve are the same, the intake valve closing timing can be positioned further toward the advance angle side from the bottom dead center. Accordingly, the intake process capacity can be further decreased in the Miller cycle operation.

[0041] Particularly, when the Miller cycle engine is combined with the electromagnetic or hydraulic valve driving device, the operable limit of the early closing Miller cycle operation in the high-speed region can be extended to a higher rotation side. The operable limit is set by the shortest open period that is determined by the responsiveness of the actuator. Furthermore, the size of the actuator can be decreased, and the electric power consumption and/or hydraulic power pressure to be supplied can also be decreased.

[0042] As another embodiment, the intake valves can be driven by a mechanical valve driving device that is mechanically driven along with a movement of the crankshaft and this can be achieved by a regular camshaft having static cam lift property and driven mechanically along with a movement of the crankshaft.

[0043] Referring to FIG. 10, the a mechanical valve driving device can further include the actuator controller and one or more electromagnetic or hydraulic actuators 16 and 18 to control the opening and closing timings of the intake valves 17 and the exhaust valves 19 based on the aforementioned detection signals. This can be achieved by a regular camshaft having static cam lift property and changing the phase of the opening and closing timings of the intake valves 17 and the exhaust valves 19, or a mechanical valve driving device that can change the cam lift property continuously or step by step. For instance, U.S. Pat. No. 5,988,125 discloses a mechanical valve driving device that can continuously change the valve angular working range. The entire disclosure of U.S. Pat. No. 5,988,125 is hereby incorporated herein by reference, especially with regard to the movable valve mechanism disclosed therein. Early closing Miller cycle operation can be achieved by combining this type of device and a mechanism that changes the phase of the center of the angular working range with respect to the crankshaft, and by advancing the angle of the center of the angular working range, while narrowing the angular working range. In this invention, the valve angular working range is enlarged due to the crank offset, as described above, when early closing Miller cycle operation is performed. Therefore, more flexibility is allowed in designs of, for instance, the cam profile.

[0044] The terms of degree such as “substantially”, “about” and “approximately” as used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed. For example, these terms can be construed as including a deviation of at least ±5% of the modified term if this deviation would not negate the meaning of the word it modifies.

[0045] This application claims priority to Japanese Patent Application No. 2000-266725. The entire disclosure of Japanese Patent Application No. 2000-266725 is hereby incorporated herein by reference.

[0046] While only selected embodiments have been chosen to illustrate the present invention, it will be apparent to those skilled in the art from this disclosure that various changes and modifications can be made herein without departing from the scope of the invention as defined in the appended claims. Furthermore, the foregoing description of the embodiments according to the present invention are provided for illustration only, and not for the purpose of limiting the invention as defined by the appended claims and their equivalents. Thus, the scope of the invention is not limited to the disclosed embodiments.

Claims

1. An early closing Miller cycle internal combustion engine, comprising;

a piston slidably disposed in a cylinder to reciprocate along a cylinder central axis;

an intake valve disposed in an intake opening of said cylinder to open and close said intake opening;

an exhaust valve disposed in an exhaust opening of said cylinder to open and close said exhaust opening;

a valve driving device arranged to close said intake valve before bottom dead center to achieve the Miller cycle operation;

a crankshaft operatively coupled to said piston to move said piston in said cylinder, said crankshaft having a crankshaft center axis of rotation offset from said cylinder central axis in such a direction that an intake process and an expansion process have greater than 180° crank angle.

2. The early closing Miller cycle internal combustion engine as set forth in claim 1, wherein

said valve driving device mechanically drives said intake valve by moving along with a movement of said crankshaft.

3. The early closing Miller cycle internal combustion engine as set forth in claim 1, wherein

said valve driving device includes a hydraulic actuator which hydraulically drives said intake valve.

4. The early closing Miller cycle internal combustion engine as set forth in claim 1, wherein

said valve driving device includes an electromagnetic actuator which drives said intake valve.

5. The early closing Miller cycle internal combustion engine as set forth in claim 1, wherein

said valve driving device closes said intake valve at a predetermined closure timing that corresponds to a detected engine operating condition, and said predetermined timing is set before said bottom dead center at least under said detected engine operating condition.

6. The early closing Miller cycle internal combustion engine as set forth in claim 1, wherein

said valve driving device is controllably arranged to vary a closure timing of said intake valve, said valve driving device controls said closure timing of said intake valve to a target closure timing of said intake valve that is determined based on a detected engine operating condition, and said target closure timing of said intake valve includes a timing set before said bottom dead center.

7. The early closing Miller cycle internal combustion engine as set forth in claim 4, wherein

said valve driving device closes said intake valve at a predetermined closure timing that corresponds to a detected engine operating condition, and said predetermined timing is set before said bottom dead center at least under said detected engine operating condition.

8. The early closing Miller cycle internal combustion engine as set forth in claim 4, wherein

said valve driving device is controllably arranged to vary a closure timing of said intake valve, and controls said closure timing of said intake valve to a target closure timing of said intake valve that is determined in accordance with a detected engine operating condition and said target closure timing of said intake valve includes a timing set before said bottom dead center.

9. An early closing Miller cycle internal combustion engine, comprising;

a piston slidably disposed in a cylinder to reciprocate along a cylinder central axis;

intake valve means for opening and closing an intake opening of said cylinder;

an exhaust valve means for opening and closing an exhaust opening of said cylinder;

valve control means for closing said intake valve before a bottom dead center to achieve the Miller cycle operation;

crank means for moving said piston in said cylinder, said crank means having a center crank axis offset from said cylinder central axis in such a direction that an intake process and an expansion process have greater than 180° crank angle.