JP2000170559A - 6-cycle internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the thermal fatigue of a piston and the overcooling of an internal combustion engine while avoiding a reduction in engine efficiency as much as possible in a 6-cycle internal combustion engine. SOLUTION: When a particular running state where the thermal load of an internal combustion engine is low is determined by a running state detecting means 3A (e.g. the low load of the internal combustion engine, the temperature TEX of the internal combustion engine being lower than a specified temperature, or the rotational speed of the same being lower than a specified rotational speed is detected), among first intake, compression, expansion, first exhaustion, second intake and second exhaustion, the operations of the intake and exhaust valves of the second intake and second exhaustion processes are stopped to prevent the overcooling of the internal combustion engine while efficiently operating the internal combustion engine). If not, the first intake, the compression, the expansion, the first exhaustion, the second intake and the second exhaustion are sequentially executed to cool the internal combustion engine.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a six-cycle internal combustion engine suitable for use in a direct injection internal combustion engine.

[0002]

2. Description of the Related Art Generally, the upper surface of a piston constituting an engine (internal combustion engine) is exposed to the high temperature and high pressure of combustion while repeatedly reciprocating at a high speed inside a cylinder, so that thermal fatigue tends to occur. In particular, in a direct injection gasoline engine (a direct injection internal combustion engine), the piston upper surface is formed with irregularities in order to optimize the flow of intake air in the combustion chamber. It is more susceptible to heat load than injection engine.

[0003] Similarly to the piston, the cylinder exposed to combustion also has a high temperature, so that the air taken into the combustion chamber in the first half of the intake stroke is immediately heated and expanded by the high-temperature cylinder, and the subsequent air is expanded. From flowing into the cylinder. For this reason, the amount of oxygen drawn into the cylinder is reduced, which may cause a decrease in engine output and a deterioration in fuel consumption rate.

Further, before ignition by the spark plug, the fuel ignites spontaneously from the vicinity of the inner wall surface of the high-temperature cylinder, and abnormal combustion (knocking) accompanied by vibration and noise occurs. There is a risk of causing thermal fatigue. Therefore, between the exhaust stroke for discharging the combustion gas and the intake stroke for sucking the combustion air, a cold intake stroke for sucking air for cooling the piston and the cylinder, and a cold exhaust stroke for discharging the cooling air And newly established,
An internal combustion engine that cools the piston and cylinder,
That is, a six-stroke internal combustion engine that sequentially executes the steps of intake, compression, expansion, exhaust, cold intake, and cold exhaust has been conventionally proposed. For example, Japanese Patent Application Laid-Open No. 2-264120 discloses such a six-stroke internal combustion engine. A six-cycle internal combustion engine that runs constantly is disclosed.

[0005]

However, such a conventional six-stroke internal combustion engine has the following problems. That is, in a general four-cycle internal combustion engine, the crankshaft makes two revolutions in one combustion, whereas in a six-cycle internal combustion engine, six strokes, that is, three revolutions of the crankshaft, in one combustion. become. Therefore,
For a four-stroke internal combustion engine, the newly added two strokes of cold intake and cold exhaust are essentially negative work (pumping loss) that consumes energy serving as the driving force of the engine.

On the other hand, in the prior art, even when there is no need to cool the piston and the cylinder, the respective steps of cold intake and cold exhaust are always performed, so that pumping loss is large and engine efficiency is reduced. Problem. Further, in the related art, there is also a problem that the engine is excessively cooled since each process of the cold intake and the cold exhaust is always performed.

[0007] The present invention has been made in view of the above-described problems, and it is possible to avoid a decrease in engine efficiency as much as possible.
It is an object of the present invention to provide a six-cycle internal combustion engine capable of preventing thermal fatigue of a piston and preventing overcooling of the internal combustion engine.

[0008]

Therefore, in the six-stroke internal combustion engine according to the present invention, when the operating state detecting means detects a specific operating state in which the heat load of the internal combustion engine is reduced, control is performed. The operation of the valve operation switching means is controlled by the means. For example, when it is detected that the internal combustion engine has a low load, the temperature of the internal combustion engine is lower than a predetermined temperature, or the rotation speed of the internal combustion engine is lower than a predetermined rotation speed, as the specific operation state, , The second of the first intake, compression, expansion, first exhaust, second intake, and second exhaust.
By halting the operation of the intake valve and the exhaust valve in each of the intake and second exhaust strokes, the internal combustion engine is efficiently operated and the supercooling of the internal combustion engine is prevented. Compression, expansion, first exhaust, second
The internal combustion engine is cooled by sequentially executing the intake and second exhaust strokes.

[0009]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a six-stroke internal combustion engine according to an embodiment of the present invention; FIG.
This will be described with reference to FIG. Six-cycle internal combustion engine in the present embodiment (hereinafter simply referred to as internal combustion engine or engine)
Is configured as an in-cylinder injection internal combustion engine (in-cylinder injection gasoline engine) in which fuel is directly injected into a cylinder and combustion is performed by spark ignition as shown in FIG. As a direct injection gasoline engine.

An intake passage 2 and an exhaust passage 3 are connected to the combustion chamber 1, and the intake passage 2 and the exhaust passage 3 are controlled to communicate with the combustion chamber 1 by an intake valve 4B and an exhaust valve 4A, respectively. ing. The intake passage 2 is provided with an air cleaner and a throttle valve (not shown), and the exhaust passage 3 is provided with an exhaust gas purifier 6 for removing harmful components in the exhaust gas and a muffler (muffler) (not shown). I have.

An injector (fuel injection valve) 8
Is arranged so that its opening faces the combustion chamber 1 in order to directly inject fuel toward the combustion chamber 1 in the cylinder 32. Further, the injector 8 is controlled based on a signal from an electronic control unit (ECU) 20 as control means.
The operation is controlled. In addition, the present engine has an exhaust valve 4A so that the engine cycle can be selected from a normal cycle and a cooling cycle.
And a variable valve mechanism (VVT) 60 as valve operation switching means for switching the operation state of the intake valve 4B. The variable valve mechanism 60 is used when the internal combustion engine is not in a specific operation state with a low heat load, for example, when the temperature of the engine is equal to or higher than a predetermined temperature, the engine load is equal to or higher than a predetermined load, or the engine speed is equal to or higher than a predetermined rotation speed. The operation of the engine can be switched from the normal cycle to the cooling cycle. In the present embodiment, the exhaust gas temperature is detected as a temperature relating to the engine, and when the exhaust gas temperature is higher than a predetermined temperature, the operation of the engine can be switched by the variable valve mechanism 60 assuming that the engine is not in the specific operation state. ing.

Here, the cooling cycle refers to the piston 31
In the cooling cycle, the engine is operated for intake (first intake), compression, expansion, exhaust (first exhaust), cold intake (second intake), and cold exhaust (second exhaust). 6) during one cycle.
Further, the normal cycle is different from the cooling cycle in that the exhaust valve 4A and the intake valve 4 in each of the cold intake and cold exhaust strokes.
B is in an idle state, that is, during a normal cycle, the engine is operated for intake, compression, expansion,
Six strokes of exhaust, cold intake stop, and cold exhaust stop are performed in one cycle.

The switching between the normal cycle and the cooling cycle by the variable valve mechanism 60 will be described later. The engine is provided with an EGR 9, and a part of the exhaust gas (EG) discharged from the combustion chamber 1 to the exhaust passage 3.
The R gas is recirculated to the intake passage 2 by opening an exhaust gas recirculation valve (EGR valve) 9A.

The engine has an exhaust gas temperature sensor (operating state detecting means) 3A and a cooling water temperature sensor 7A.
1, various sensors such as an accelerator position sensor 72, a crank angle sensor 73 (or a cam angle sensor 75), and a pressure sensor 74 are provided. Detection signals from the sensors are sent to the ECU 20, and these detection signals are sent to the ECU 20. Based on this, control of the injector 8 and the like is performed.

The exhaust gas temperature sensor 3A is provided in the exhaust passage 3 on the upstream side of the exhaust gas purifying device 6, and detects the exhaust gas temperature T _EX immediately before the exhaust gas purifying device 6. The cooling water temperature sensor 71 is inserted into a water jacket 30B provided in a cylinder block between the right bank and the left bank, and detects a cooling water temperature T _{W of the} engine. Furthermore, an accelerator position sensor 72 is for detecting the accelerator opening theta _A as an engine load. Also, the crank angle sensor 7
3 is provided in the crank shaft 5, and detects the engine speed number Ne, the pressure sensor 74 is provided in the intake passage 2, and detects the pressure P _b of the intake pipe (intake passage) 2.

The engine will be further described. When the engine is running at a low rotation speed and a low load, the fuel is injected from the injector 8 during the compression stroke, and the intake air flowing into the combustion chamber 1 from the intake passage 2 is transferred to the piston 31. A small amount of fuel is collected only in the vicinity of the ignition plug 7 while generating a vertical vortex (reverse tumble flow) in the concave portion 31A. Thus, stable stratified combustion (stratified super-lean combustion) is performed to suppress fuel consumption.

When the engine is running at a medium to high speed and a medium to high load, the fuel injected from the injector 8 is homogenized throughout the combustion chamber 1, and the interior of the combustion chamber 1 is made to have a stoichiometric air-fuel ratio or a rich air-fuel ratio. Mixed combustion is performed. Next, an operation mode of the engine according to the present embodiment and an operation mode of a general four-stroke engine will be described with reference to an acupressure diagram shown in FIG.

First, in a general four cycles, FIG.
As shown in (A), in the intake stroke A1, the in-cylinder pressure becomes P
₁While keeping the cylinder volume substantially constant,₁(piston
Is at the top dead center) to V_Two(Piston is down
Change to the volume at the dead center) and burn in the cylinder
Inhale air. And, in the compression stroke A2,
Is a closed space, and the in-cylinder volume is V_TwoTo V₁Do not compress until
The pressure in the cylinder is P₁To P _ThreeUp to And
In the expansion stroke A3, the fuel in the cylinder is ignited and
Volume is V₁To V_TwoAs well as the pressure in the cylinder
P_ThreeTo P_TwoAnd in the exhaust stroke A4,
In-cylinder pressure is P_TwoWhile maintaining the cylinder volume approximately constant_Two
To V₁The burned gas into the cylinder.
And returns to the intake stroke A1 again.

Here, the portion surrounded by the stroke traveling in the counterclockwise direction shown by the dashed line in FIG. 3A represents negative work (pumping loss) not used as the driving force of the engine. The smaller the area of the part, the better the efficiency of the engine. Next, a cooling cycle consisting of six strokes will be described. The cooling cycle is shown in FIG.
As shown in (B), an intake stroke B1, a compression stroke B2, an expansion stroke B3, an exhaust stroke B4, a cold intake stroke B5, and a cold exhaust stroke B7 are sequentially performed. Intake stroke B1, compression stroke B
2, the expansion stroke B3, exhaust stroke B4 are performed in the same manner as 4 cycles, the cold intake stroke B5, similarly to the intake stroke B1, while maintaining the cylinder pressure substantially constant in P _1, the cylinder volume V varied from ₁ to V _2, inhale the air for cooling in the cylinder.

Then, the process proceeds to a cold exhaust stroke B7. At the beginning of the cold exhaust stroke B7, the inside of the cylinder is sufficiently cooled by the air taken in by the cold intake stroke B5.
A state B6 for sealing the inside of the cylinder is provided. During this time, the piston 31 is rising, the volume cylinder, cylinder pressure with decreases from V ₂ to V _C rises from P ₁ to P ₂ '. Then, after the middle stage of the cold exhaust stroke B7, the exhaust valve 4A is opened to reduce the in-cylinder volume from V _C to V ₁ , thereby discharging the cooling air from the inside of the cylinder and returning to the intake stroke B1. Return. In addition, such a closed state B
By opening the exhaust valve 4A from 6, the in-cylinder pressure becomes P
It will be slightly lower than ₂ '.

Therefore, when the engine is operated in such a six-stroke cycle, two strokes for cooling the inside of the engine are added, as compared with a normal four-stroke engine. It can be reduced. However, in such a cooling cycle, in addition to the pumping loss caused by the intake stroke B1 and the exhaust stroke B4, as shown by the one-dot chain line in FIG. 3B, the cold intake stroke B5 and the cold exhaust stroke B7 (in the closed state). B
6), the pumping loss (cooling pumping loss) is caused, and the efficiency is reduced by four minutes for four cycles.

On the other hand, in the normal cycle, the operations of the exhaust valve 4A and the intake valve 4B in the cold intake stroke B5 and the cold exhaust stroke B7 of the above-described cooling cycle are stopped. That is, as shown in FIG. 3C, the intake stroke C1, the compression stroke C2, the expansion stroke C3, and the exhaust stroke C
4 is performed in the same manner as 4 cycles and the cooling cycle,
In the next cold intake stop process C5, the exhaust valve 4A and the intake valve 4
When both B are closed, the piston 31 moves from the top dead center (in-cylinder volume V ₁ ) to the bottom dead center (in-cylinder volume V ₂ ). Valve 4B
Are closed, the piston 31 rises from bottom dead center (cylinder volume V ₂ ) to top dead center (cylinder volume V ₁ ), and again,
The process returns to the intake stroke C1.

Therefore, in the normal cycle, as shown by the one-dot chain line in FIG. 3C, a portion corresponding to the cooling pumping loss in the cooling cycle becomes small, and the efficiency of the engine is substantially equal to four cycles. More efficient than a cooling cycle. Therefore, as shown in the functional block diagram of FIG. 1, the ECU (control means) 20 provided in the six-cycle internal combustion engine according to the present embodiment receives the exhaust gas temperature T _EX from the exhaust gas temperature sensor (operating state detecting means) 3A. Is entered. Then, this exhaust gas temperature T _EX becomes a predetermined temperature T
If it is higher than _EX0, it is determined that the heat load is high and the engine needs to be cooled, and the variable valve mechanism (valve operation switching means) 60 is controlled by the ECU 20.
Basically, it is operated by a cooling cycle. On the other hand, if the exhaust gas temperature T _EX is equal to or lower than the above-described predetermined temperature T _EX0 , it is determined that cooling of the engine is not necessary because the engine is in the specific operation state with a low heat load, and the operation of the variable valve mechanism 60 is controlled. The engine is operated by an efficient normal cycle.

If the exhaust gas temperature T _EX does not become lower than the above-mentioned predetermined temperature T _EX0 even after the predetermined time t _{0 has} elapsed since the switching of the engine cycle to the cooling cycle, the engine cycle becomes the normal cycle. At the same time, fuel injection (cooling fuel injection) is performed almost simultaneously with the start of the cold intake stop process, and the piston 31 and the cylinder 32 are cooled using the latent heat of vaporization of the fuel.

The switching control between the cooling cycle and the normal cycle will be described later in detail. Next, the variable valve mechanism 60 will be described.
Has the same configuration as that disclosed, for example, in JP-A-6-33719. Specifically, as shown in FIG. 4, the variable valve mechanism 60 according to the present embodiment includes an exhaust valve 4A.
And a variable valve mechanism 60A on the intake valve 4B side (intake side).

The variable valve mechanism 60 includes exhaust-side cams 12A, 12A provided on exhaust-side and intake-side camshafts 11A, 11B which rotate in response to rotation of the crankshaft 5 (see FIG. 2) of the engine. 13A, the intake side cams 12B, 13B, and these cams 12A, 13A, 12B.
B, 13B driven by rocker arms 14A, 1B
5A, 14B, and 15B.

Here, the cams 12A and 12B always operate the exhaust valve 4A and the intake valve 4B (hereinafter simply referred to as the valve 4A) regardless of the above-mentioned normal cycle and cooling cycle.
A, 4B), while the cams 13A, 13B are sub-cams (cold intake / exhaust cams) that can drive the valves 4A, 4B only during the engine cooling cycle.

Here, in order to perform the cooling cycle and the normal cycle shown in FIGS. 6A and 6B, each of the camshafts 11A and 11B is, for example, one-third via a chain or gear (not shown). At the rotation speed ratio, the rotation is performed in conjunction with the crankshaft 5. The main cam 12A of the exhaust valve 4A and the main cam 1A of the intake valve 4B
The phase difference from 2B is set to about 180 ° in the cam angle.

As for the exhaust valve 4A, the main cam 12A and the sub-cam 13A are mounted so as to have a predetermined phase difference (for example, about 130 °) on the camshaft 11A, and for the intake valve 4B, the sub-cam 13B
The main cam 12B and the main cam 12B are attached so as to have a predetermined phase difference (for example, about 120 °) in the camshaft 11B.

For example, in the first cylinder shown in FIGS. 6A and 6B, during one cycle of a cooling cycle, six strokes of expansion, exhaust, cold intake, cold exhaust, intake, and compression are sequentially performed. In order to execute the six strokes at this timing, the crank angle must be between θ _A1 and θ _A2 (exhaust stroke) and between θ _C1 and θ _C2 (cold exhaust stroke). The exhaust valve 4A must be in the open state, and the intake valve 4B must be in the open state when the crank angle is between θ _B1 and θ _B2 (cool intake stroke) and between θ _D1 and θ _D2 (intake stroke).

When the exhaust gas temperature T _EX is _{equal to} or lower than the predetermined temperature T _EX0 (in a specific operating state),
Since the operation of the exhaust valve 4A and the intake valve 4B is stopped during the cold intake and cold exhaust strokes and the operation is performed in the normal cycle, the crank angle is between θ _C1 and θ _C2 (cool exhaust stroke) and between θ _B1 and θ _B2. Up to (cold intake stroke), the exhaust valves 4A,
It is necessary to stop the operation of the intake valve 4B.

Accordingly, the exhaust valve 4A is provided by the main cam 12A when the crank angle is between θ _A1 and θ _A2 (exhaust stroke), and by the sub cam 13A when the crank angle is between θ _C1 and θ _C2 (cool exhaust stroke). Is set to be driven to open the valve. The sub cam 13B is used when the crank angle is between θ _B1 and θ _B2 (the cold intake stroke), and the main cam 1 is used when the crank angle is between θ _D1 and θ _D2 (the intake stroke).
2B, the intake valves 4B are set to be driven to open.

That is, to satisfy the above conditions, the main cam 12A of the exhaust valve 4A and the main cam 1A of the intake valve 4B
2B is about 540 ° in crank angle (θ _D1 −θ _A1 ,
Or, a phase difference of about θ _D2 −θ _A2 ) (about 180 at the cam angle)
°), the intake valve 4B and the exhaust valve 4A are opened and closed. And the main cam 12A of the exhaust valve 4A
And the sub cam 13A are approximately 390 ° in crank angle.
With the phase difference of (θ _C1 −θ _A1 or θ _C2 −θ _A2 ) (the cam angle is about 130 °), the main cam 12A
A is set to open and close the exhaust valve 4A earlier than A.

The main cam 12B and the sub-cam 13B of the intake valve 4B have a crank angle of about 360 ° (θ
_D1 - [theta] _B1, or, with a phase difference of θ _D2 -θ _B2) (approximately 120 ° in the cam angle), the sub-cam 13B is set so as to open and close the early intake valve 4B than the main cam 12B.
In addition, during the period from the crank angle θ _B2 to θ _C1 , the exhaust valve 4A
The intake valve 4B and the intake valve 4B are both closed, and are provided to allow the air taken in during the cold intake stroke to stay and sufficiently cool the inside of the cylinder.

The exhaust valve 4A and the intake valve 4B are not driven by the sub-cams 13A and 13B by using the variable valve mechanism 60, so that the intake angle between the crank angle θ _B1 and θ _B2 is reduced. The normal cycle shown in FIG. 6B can be performed by closing both the valve 4B and the exhaust valve 4A when the crank angle is between θ _C1 and θ _C2 .

The camshafts 11A and 11B only need to make one rotation while the crank angle rotates 1080 ° (three rotations).
Are interlocked with the crankshaft 5 at a rotation speed ratio of 1/3. The variable valve mechanism 60 will be described in more detail with reference to FIGS. 5 (A), 5 (B) and 5 (C). Here, as shown in FIG. 4, the exhaust-side and intake-side variable valve mechanisms 60A and 60B are substantially the same in terms of mechanism, and therefore only the exhaust-side variable valve mechanism 60A will be described.

As shown in FIG. 5A, the exhaust valve 4A
The variable valve mechanism 60A that drives the exhaust valves 4A, 4A includes cams 12A, 13A provided on a camshaft 11A, and the cams 12A, 1A.
Rocker arms 14A and 15A driven by 3A are provided. The rocker arms 14A and 15A are both rocker arms with rollers.
A is in contact with the exhaust valves 4A, 4A and
A main rocker arm directly related to the opening and closing drive of A,
The rocker arm 15A is a sub rocker arm that does not contact the exhaust valves 4A, 4A and is indirectly involved in opening and closing the exhaust valves 4A, 4A.

The main rocker arm 14A is shown in FIG.
As shown in (B) and (C), it is provided integrally with the rocker shaft 16. The rocker shaft 16 is pivotally supported by a bearing portion 30A provided on a cylinder head 30 (see FIG. 4) of the engine or the like.
A is configured to be able to turn around the rocker shaft 16.

At the intermediate portion of the main rocker arm 14A,
A main roller 18 that can contact the main cam 12A is provided. The main roller 18 is rotatably supported by a shaft 18A that is supported by an intermediate portion of the main rocker arm 14A so that the main roller 18 can smoothly rotate. With such a structure, the main cam 12A rotates with the camshaft 11A while rotating the main roller 1A at a predetermined rotation position.
8, the exhaust valves 4A, 4A are driven constantly via the main rocker arm 14A.

On the other hand, the sub rocker arm 15A is rotatably supported at its cylindrical base 62 so as to be rotatable with respect to the rocker shaft 16 (that is, the main rocker arm 14A). And a sub-roller 19 which can abut the roller. The sub-roller 19 is also pivotally supported by a shaft 19A supported by the swinging end 61 of the sub-rocker arm 15A, so that it can rotate smoothly.

Between the sub-rocker arm 15A and the rocker shaft 16, a mode in which the sub-rocker arm 15A is rotatable with respect to the rocker shaft 16 and does not operate in cooperation with the main rocker arm 14A (non-coupling mode).
A hydraulic piston mechanism 17 is provided as mode switching means for switching between a mode in which the sub rocker arm 15A rotates integrally with the rocker shaft 16 and operates in cooperation with the main rocker arm 14A (coupling mode).

As shown in FIGS. 5B and 5C, the hydraulic piston mechanism 17 as the mode switching means is movably disposed in a piston chamber formed in the rocker shaft 16 in the diameter direction of the rocker shaft 16. The installed piston 17A
Is provided. Then, when hydraulic oil is guided from an oil passage 16A formed in the axial center portion of the rocker shaft 16, the piston 17A is moved to the distal end side as shown in FIG. 5C [FIGS. 5B and 5C]. 5B, while the supply of the hydraulic oil is cut off, the piston 17A moves toward the base end side as shown in FIG. 5B [downward in FIGS. 5B and 5C]. To be driven.

That is, when hydraulic oil is supplied, the sub-rocker arm 15
A rotates integrally with the rocker shaft 16 to operate in cooperation with the main rocker arm 14A (cooperation mode) (see FIG. 5C). When the supply of the hydraulic oil is cut off, the piston 17A separates from the tip of the piston 17A. The sub rocker arm 15 is set to be in a mode in which the sub rocker arm 15 is rotatable with respect to the rocker shaft 16 and does not operate in cooperation with the main rocker arm 14A (non-coupling mode) (see FIG. 5B).

The hydraulic oil is supplied from the rocker shaft 1.
The operation is performed through a hydraulic oil supply system (not shown) via an oil passage 16 </ b> A in the inside 6. The supply state in which the hydraulic oil is supplied and the supply stop state in which the hydraulic oil is not supplied are switched by controlling the opening and closing of the solenoid valve provided in the hydraulic oil supply system by the ECU 20. In the present embodiment, the solenoid valve is controlled in accordance with the exhaust gas temperature T _EX from the exhaust gas temperature sensor 3A to operate the exhaust valve 4A by the cooling cycle sub cam 13A (and the intake valve 4B by the sub cam 13B). By switching the non-operation, the normal cycle and the cooling cycle of the engine cycle can be switched.

The six-cycle internal combustion engine according to one embodiment of the present invention is configured as described above.
An engine cooling cycle and a normal cycle as shown in (A) and (B) can be performed. Hereinafter, FIG.
With reference to FIGS. 2 and 4 together with (A) and (B),
The cooling cycle and the normal cycle of the engine will be described. Note that the engine of the present embodiment is configured as a V-type six-cylinder engine in which each cylinder is alternately inclined left and right (see FIG. 2), and as shown in FIGS. 6A and 6B,
A cylinder row inclined to the right is called a right bank, and a cylinder row inclined to the left is called a left bank.

First, the cooling cycle (when the cold intake / exhaust cam is operated) will be specifically described. Here, focusing on the first cylinder (cylinder), as shown in FIG.
During one cycle, six steps of expansion, exhaust, cold intake, cold exhaust, intake, and compression are sequentially executed. In addition, FIG.
As for the crank angle shown in (B), the angle at which the piston 31 is located at the top dead center at the start of the expansion stroke is the reference angle (0 °).
And

First, in the expansion stroke, the top dead of the piston 31
Immediately before the point (crank angle 0 °) (compression stroke), the ignition
The mixture ignited by the lug 7 is ignited in the combustion chamber 1.
It burns and expands rapidly, pushing down the piston 31. this
At this time, the force due to the expansion of the mixed gas acts on the piston 31.
Thus, the exhaust valve 4A and the intake valve 4B are closed. Soshi
The piston 31 is at the bottom dead center (crank angle 180 °)
Previous crank angle θ _A1Descends to the position corresponding to
And the main cam 12A of the exhaust valve 4A is the main rocker arm.
The exhaust valve 4A is opened by pushing down the system 14A. And
The piston 31 moves down to the bottom dead center (crank angle 180 °).
Then, it starts to rise again, and the exhausted gas
Push to Road 3 (exhaust stroke).

Next, the piston 3 raised by the exhaust stroke
When the first cam 1 moves to a position corresponding to the crank angle θ _A2 after the top dead center (crank angle 360 °), the main cam 1
2A and the main rocker arm 14A are separated from each other and the exhaust valve 4
A is closed. On the other hand, at the crank angle θ _B1 before the piston 31 reaches the top dead center (crank angle 360 °), the intake valve 4B is moved by the sub rocker arm 15 by the sub cam 13B.
B is pushed down to be in an open state, and air for cooling the piston 31 and the cylinder 32 is supplied into the cylinder 32 which has become negative pressure by the piston 31 which has started to descend after reaching the top dead center (crank angle 360 °). The intake air is sucked into the combustion chamber 1 from the intake passage 2 by the negative pressure (cold intake stroke).

It is to be noted that the crank angle θ _{A2 is obtained} from the crank angle θ _B1.
, The exhaust valve 4A and the intake valve 4B are both open (overlap).
The exhaust flowing from the exhaust passage 3 into the exhaust passage 3 also has inertia, so the intake valve 4B is opened early to take advantage of this inertia,
They are trying to inhale a lot of air quickly.

Then, the piston 31 has the crank angle θ _B2
At the time when the sub cam 13B and the sub rocker arm 15B are separated from each other, the intake valve 4B is closed. On the other hand, the exhaust valve 4A is pushed down by the sub cam 13A via the sub rocker arm 15A and opened when the piston 31 has risen to a position corresponding to the crank angle θ _C1 after passing the bottom dead center (crank angle 540 °). In this state, the air in the combustion chamber 1 is pushed out to the exhaust passage 3 by the ascending piston 31 (cold exhaust stroke).

Therefore, between the crank angle θ _B2 and the crank angle θ _C1 , the exhaust valve 4A and the intake valve 4B are both closed, and during this time the air (cooling air) sucked in the cold intake stroke is It will stay in the cylinder 32.
That is, the cooling air is not discharged immediately, but is kept in the cylinder 32 for a predetermined period (the crank angle is θ _B2 to θ _C1 ), so that the piston 31 and the cylinder 32 are sufficiently cooled by the cooling air. They try to cool.

When the piston 31 which has risen to the top dead center (crank angle 720 °) starts to descend, the cylinder 3
The pressure in the interior 2 is reduced by the lowering of the piston 31. Intake valve 4
B is pushed down by the main cam 12B via the main rocker arm 14B at the crank angle θ _D1 before the piston 31 rises to the top dead center (crank angle 720 °), so that B is open. Due to this pressure reduction, combustion air is drawn into the cylinder 32 from the intake passage 2 (intake stroke).

Then, the piston 31 is moved to the top dead center (crank).
Angle 720 °) and the crank angle θ _C2In a position equivalent to
When moved, the sub-cam 13A that was in contact with it until then
And the sub rocker arm 15A are separated from each other,
The exhaust valve 4A is closed. Where the crank angle θ_D1From
Crank angle θ_C2, The exhaust valve 4A and the intake
The valves 4B are both opened (overlap).
This is similar to the overlap during the cold intake stroke described above,
This is because the intake is efficiently performed by utilizing the inertia of the air.

The piston 31 descended during the intake stroke
Starts rising again when it reaches the bottom dead center (crank angle is 900 °). When the piston 31 moves to a position corresponding to the crank angle θ _D2 , the intake valve 4
B, the main cam 12B and the main rocker arm 14B are separated from each other, the intake valve 4B is closed, and the exhaust valve 4A is closed.
Is also closed, the air in the cylinder 32 is compressed by the rising piston 31 (compression stroke).

Then, in the compression stroke, the raised piston 31 is moved to the top dead center (crank angle is 1080 °, ie,
0 °), and thereafter, the same process as described above is repeated. Although the detailed description of the fuel injection timing is omitted in the description of the cooling cycle, the fuel is appropriately injected during the intake stroke or the compression stroke depending on the operation state of the engine.

For other cylinders, see FIG.
As shown in (A), the crank angle is 1 in the order of the cylinder number.
Each stroke is performed with a shift of every 80 °. Next, the normal cycle will be described. Note that the expansion stroke and the exhaust stroke in this normal cycle are the same as those in the above-described cooling cycle, and the description is omitted. By the way, in the latter half of the exhaust stroke, when the piston 31 rises to the crank angle θ _B1 before the top dead center (crank angle 360 °), the sub cam 13 of the intake valve 4B
The sub rocker arm 15B is pushed down by B,
Since the sub rocker arm 15B is in the non-coupling mode with the main rocker arm 14B, the intake valve 4B is not driven by the sub cam 13B and remains closed.

On the other hand, the exhaust valve 4A is closed when the piston 31 moves to a position corresponding to the crank angle θ _A2 after passing the top dead center (crank angle 360 °), so that the exhaust valve 4A and the intake valve 4B are simultaneously closed (cold intake stop process). Eventually, the piston 31 passes the bottom dead center (crank angle is 540 °), and the crank angle θ _C1
Is reached, the sub cam 1 of the exhaust valve 4A
3A pushes down the sub rocker arm 15A, but the sub rocker arm 15A
The exhaust valve 4A is kept in the closed state without being driven by the sub-cam 13A because of the non-coupling mode with A (the cold exhaust stop process).

Then, when the piston 31 reaches a position corresponding to the crank angle θ _D1 near the top dead center (crank angle 720 °), the intake valve 4B is opened, and after the top dead center (crank angle 720 °). Piston 31 which started to descend again
Accordingly, combustion air is sucked into the combustion chamber 1 from the intake passage 2 (intake stroke). The subsequent intake and compression strokes are the same as those in the above-described cooling cycle, and thus description thereof is omitted.

The operation mode of the engine is switched according to, for example, a flowchart shown in FIG. First, in step S10, the exhaust gas temperature sensor 3A
It is determined whether or not the engine is in a high temperature state based on the exhaust gas temperature T _EX input from FIG. 2 (see FIG. 2). If the exhaust gas temperature T _EX is higher than a predetermined temperature (exhaust gas reference temperature) T _EX0 , the engine is in a high temperature state and the piston 31
Thermal fatigue, engine output reduction, fuel consumption rate deterioration,
After it is determined that knocking is likely to occur and the timer is started in step S15,
Proceed to 20 to execute a cooling cycle.

On the other hand, the exhaust gas temperature T _EX is equal to the exhaust gas reference temperature T.
_{If EX0} or less, the engine is in the specific operation state with a low heat load, that is, the engine is not in the high temperature state, and it is determined that there is no risk of thermal fatigue on the piston 31 and the cylinder 32. The operation of the engine is performed in a cycle. Note that, at this time, specifically, the electromagnetic valve which is a component of the hydraulic oil supply system of the variable valve mechanism 60 is closed.

In step S20, the solenoid valve of the hydraulic oil supply system of the variable valve mechanism 60 is driven to open, the variable valve mechanism 60 is switched, and a cooling cycle is executed. Next, in step S30, the exhaust gas temperature T _EX again
Determines whether the engine is in a high temperature state,
If the exhaust gas temperature T _EX is higher than the exhaust gas reference temperature T _EX0 , it is determined that the engine is still in a high temperature state, and the process proceeds to step S40.

On the other hand, when the exhaust gas temperature T _EX is equal to the exhaust gas reference temperature T
If it is less than _EX0 , it is determined that the engine has been cooled by the effect of the cooling cycle, the process proceeds to step S100, the solenoid valve of the hydraulic oil supply system of the variable valve mechanism 60 is closed, and the normal cycle is started. At the same time, the cooling cycle elapsed time t is reset in step S110.

[0063] At step S40, the cooling cycle elapsed time t, whether exceeds a predetermined time t ₀ is determined, if not exceeded, the process returns to step S20, the operation is performed subsequently in the cooling cycle, cooling cycle elapsed time If t exceeds the reference time t ₀ , the process proceeds to step S45 to reset the cooling cycle elapsed time t and to execute step S45.
The process proceeds to 50, and switches to the normal cycle.

That is, during the predetermined time t ₀ , the exhaust gas temperature T
_It is determined at any time whether or not _EX falls below a predetermined temperature T _EX0 . If the exhaust gas temperature T _EX does not fall below the predetermined temperature T _{EX 0} even after the predetermined time t _{0 has} elapsed, the combustion chamber 1 is heated by the latent heat of vaporization of the fuel. The fuel is injected (cooled fuel injection) by the injector 8 so that is cooled (step S60),
Thereafter, the process proceeds to step S70.

It is to be noted that the cooling fuel injection is performed substantially simultaneously with the start of the cold intake stop process (when the cylinder 31 is located near the top dead center). Also, the fuel injected at this time is
It is also for generating a predetermined engine output while cooling the combustion chamber 1. In the present embodiment, when cooling fuel injection is performed, the entire amount of fuel required for engine output is injected as cooling fuel, and combustion is performed using this fuel at the end of the next compression stroke. Therefore, when cooling fuel injection is performed, normal fuel injection during the compression stroke or the intake stroke is not performed.

In step S70, the exhaust gas temperature T
_EX determines whether the engine is in a high temperature state. If the exhaust gas temperature T _EX is equal to or higher than the exhaust gas reference temperature T _EX0, it is determined that the engine is still in a high temperature state, and the process returns to step S60 and returns to step S60. Then, cooling fuel injection is performed. On the other hand, the exhaust gas temperature T _EX is
_If it is lower than _EX0, it is determined that the engine has been cooled, the cooling fuel injection is stopped, and fuel injection (normal fuel injection) is performed in the latter half of the compression stroke or in the intake stroke as usual (step S80). And return.

When the switching from the cooling fuel injection to the normal fuel injection is performed between the time when the cooling fuel is injected (immediately after the start of the cold intake stop process) and the time when the fuel is ignited (immediately before the expansion stroke). Until the ignition is performed once, the injection of the injector 8 is stopped. That is, the normal fuel injection is not performed in the latter stage of the compression stroke or the intake stroke immediately after the cooling fuel injection, but after the ignition is performed once, the normal fuel injection in the latter stage of the compression stroke or the intake stroke is performed thereafter. Thereby, when switching from the cooling fuel injection to the normal fuel injection is performed, it is possible to prevent both the cooling fuel injection and the normal fuel injection from being performed and excessive injection of the fuel.

Therefore, according to the six-cycle internal combustion engine of the present embodiment, the engine cycle can be switched between a cooling cycle capable of cooling the engine and a normal cycle more efficient than the cooling cycle. When the engine temperature is high (when the thermal load of the engine is high), the engine is cooled by a cooling cycle to prevent thermal fatigue of the piston, decrease in engine output, deterioration of fuel consumption rate, and knocking. When a load is applied (in a specific operation state in which the heat load of the engine is low), there is an advantage that the operation can be more efficiently performed in a normal cycle.

If the engine is not cooled within a predetermined time even if the engine cycle is set to a cooling cycle, there is an advantage that the engine can be cooled to a predetermined state by cooling fuel injection having a higher cooling effect. . Further, when the engine is sufficiently cooled in the cooling cycle, the mode is switched to the normal cycle, so that the engine is not overcooled.

It should be noted that the six-cycle internal combustion engine of the present invention is not limited to the above-described embodiment, and can be implemented with various modifications. For example, in the six-stroke internal combustion engine according to the above-described embodiment, a case has been described in which a direct injection gasoline engine is applied. However, the present invention is not limited to this, and is applied to a general port injection engine. Is also good. Further, the present invention may be applied to a diesel engine as well as a gasoline engine.

The cooling fuel injection may be performed not during the cold intake / exhaust stop process of the normal cycle but during the cold intake process of the cooling cycle. In this case, the injected fuel is discharged into the exhaust passage 3 during the cold exhaust stroke without being burned. Therefore, the EGR valve 9A is controlled to a predetermined opening degree, and the fuel is returned to the engine by the EGR 9 again. You may make it burn and burn. Further, an ignition device may be provided in the exhaust passage 3 so that the fuel discharged to the exhaust passage 3 is burned by the ignition device to promote an increase in the catalyst temperature at a cold start.

In this embodiment, the exhaust gas temperature T _EX
The switching between the cooling cycle and the normal cycle is determined by using only the cooling cycle. For example, the operating state detecting means includes a cooling water temperature sensor 71, an accelerator position sensor 72, a crank angle sensor 73, a pressure sensor 74, and the like. Then, based on these outputs, it is possible to detect or estimate whether or not the internal combustion engine is in a specific operation state with a low heat load, and to switch between the cooling cycle and the normal cycle.

Specifically, when the cooling water temperature T _W detected by the cooling water temperature sensor 71 is higher than a predetermined temperature (condition 1), the accelerator opening θ _A detected by the accelerator position sensor 72 becomes smaller than the predetermined opening. When it is determined that the internal combustion engine is in a high load state (condition 2), when the engine speed Ne detected by the crank angle sensor 73 and the cam angle sensor 75 is larger than a predetermined speed (condition 3),
Alternatively, if the intake pipe pressure P _b detected by the pressure sensor 74 other than the lean operating region is higher than a predetermined pressure (condition 4) or the like, because of the high thermal load of the internal combustion engine performs a cooling cycle of the internal combustion engine heat In order to prevent fatigue and thermal degradation of the exhaust gas purifying device 6, in other specific operating states where the heat load is low, the normal cycle may be executed to make the operating state more efficient than the cooling cycle. The normal cycle and the cooling cycle may be switched by combining the above conditions 1 to 4.

When performing the cooling fuel injection, all the fuel required for the engine output is injected during the cold intake / exhaust stop process in the normal cycle, and the normal fuel injection is not performed. The fuel injection and the normal fuel injection may be performed together. However, it is necessary to make the sum of the fuel injected by the cooling fuel injection and the normal fuel injection equal to the fuel amount required for the engine output. In this case, the amount of fuel required for the cooling fuel injection may be stored in the ECU 20 as a function of the exhaust gas temperature T _EX , and a predetermined amount of the fuel may be used for the cooling fuel injection according to the stored amount.

Further, instead of using the variable valve mechanism 60, the exhaust valve 4A and the intake valve 4B are constituted by solenoid valves so that they can be opened and closed at an arbitrary timing. In addition to the cooling and cooling cycles, a general cycle including four strokes of intake, compression, expansion, and exhaust may be performed.

[0076]

As described above in detail, according to the six-stroke internal combustion engine of the present invention, it is possible to minimize the efficiency of the internal combustion engine while minimizing the thermal fatigue, the output reduction, the deterioration of the fuel consumption rate, and the like. Advantageously, knocking and the like can be prevented, and overcooling of the engine can be prevented.

[Brief description of the drawings]

FIG. 1 is a block diagram schematically showing a configuration of control means in a six-cycle internal combustion engine as one embodiment of the present invention.

FIG. 2 is a schematic diagram showing an overall configuration of a six-cycle internal combustion engine as one embodiment of the present invention.

FIG. 3 is a diagram of acupressure for explaining the effectiveness of cycle switching in a six-cycle internal combustion engine as one embodiment of the present invention, wherein (A) is a diagram of a general four-stroke internal combustion engine; FIG. 3B is a diagram of a finger pressure of a cooling cycle in a six-cycle internal combustion engine, and FIG.

FIG. 4 is an overall configuration diagram schematically showing valve operation switching means in a six-cycle internal combustion engine as one embodiment of the present invention.

FIG. 5 is a schematic diagram of a valve operation switching means in a six-cycle internal combustion engine as one embodiment of the present invention, and FIG.
Is a perspective view showing the entire configuration, (B) is a cross-sectional view taken along the line AA of (A), showing a state where the sub rocker arm does not operate in cooperation with the main rocker arm, and (C) is an arrow AA of (A). FIG. 5 is a view showing a state in which a sub rocker arm operates in cooperation with a main rocker arm in a sectional view as viewed.

FIG. 6 is a timing chart of each stroke in a six-cycle internal combustion engine as one embodiment of the present invention.

FIG. 7 is a flowchart showing control in a six-cycle internal combustion engine as one embodiment of the present invention.

[Explanation of symbols]

 3A Exhaust gas temperature sensor (operating state detecting means) 4A Exhaust valve 4B Intake valve 20 ECU (control means) 60 Variable valve mechanism (valve operation switching means)

Continued on the front page F-term (reference)

Claims (1)

[Claims] 1. A first intake, compression, expansion, first exhaust, second
A six-stroke internal combustion engine capable of sequentially executing each of intake and second exhaust strokes, comprising: valve operation switching means capable of switching an operation state of an intake valve and an exhaust valve; and an operation state for detecting an operation state of the internal combustion engine. When the specific operating state in which the thermal load of the internal combustion engine is reduced is detected by the detecting means and the operating state detecting means, the operation of the intake valve and the exhaust valve in each stroke of the second intake and the second exhaust is stopped. And a control means for controlling the operation of the valve operation switching means so as to perform the operation.