JP2022076373A - Six stroke internal combustion engine - Google Patents

Abstract

To achieve an internal combustion engine capable of generating a satisfactory air-fuel mixture by securing a sufficient time for mixing of intake air and fuel before an expansion stroke.SOLUTION: A six stroke internal combustion engine is configured to perform: an intake stroke in which a piston in a cylinder is moved from a top dead center to a bottom dead center and an intake valve of the cylinder is opened; a temporary compression stroke in which the piston in the cylinder is moved from the bottom dead center to the top dead center; a temporary expansion stroke in which the piston in the cylinder is moved from top dead center to bottom dead center, intake air and fuel filled in the cylinder are mixed, but the fuel is not combusted; a compression stroke in which the piston in the cylinder is moved from the bottom dead center to the top dead center; an expansion stroke in which the piston in the cylinder is moved from the top dead center to the bottom dead center and the fuel is combusted in the cylinder; and an exhaust stroke in which the piston in the cylinder is moved from the bottom dead center to the top dead center and an exhaust valve of the cylinder is opened.SELECTED DRAWING: Figure 2

Description

The present invention relates to a new type 6-stroke (6-cycle) internal combustion engine as a reciprocating engine.

Most of the internal combustion engines mounted on vehicles and the like are 4-stroke (4-cycle) reciprocating engines that repeatedly execute a series of intake stroke-compression stroke-expansion stroke-exhaust stroke in a cylinder (for example, the following patent documents). reference).

A good air-fuel mixture that can obtain ideal combustion is a mixture that is evenly and evenly mixed so that the entire air-fuel ratio becomes the target air-fuel ratio (the theoretical air-fuel ratio in the case of a spark ignition engine that burns gasoline or the like). .. In order to obtain such an air-fuel mixture, it is necessary to secure sufficient time for the intake air and the fuel to mix.

However, in the current 4-stroke internal combustion engine, the period from fuel injection to ignition combustion is short, and there is a limit to vaporizing the fuel and sufficiently mixing it with the intake air. The intake air and the fuel are mixed in the intake stroke or the compression stroke. In the compression stroke, the pressure inside the cylinder increases and the boiling point of the fuel component rises. Fuel contains multiple components, some of which originally have a high boiling point and are difficult to vaporize.

The fuel component that cannot be vaporized by the end of the compression stroke and remains as droplets is vaporized and burned with a delay after the temperature inside the cylinder becomes high in the expansion stroke. This can be a factor that reduces the thermomechanical conversion efficiency of the internal combustion engine.

Further, if the concentration of the fuel in the air-fuel mixture before combustion is uneven and the combustible portion and the non-combustible portion are mixed, abnormal combustion typified by knocking is caused in the combustible portion. In addition, the hazardous substance NO _x is generated in the portion where the air-fuel ratio is locally lean.

Japanese Unexamined Patent Publication No. 2011-247107

An object of the present invention is to realize an internal combustion engine capable of producing a good air-fuel mixture by ensuring a sufficient time for the intake air and the fuel to mix before the expansion stroke.

In the present invention, an intake stroke in which the piston of the cylinder moves from top dead center to bottom dead center and the intake valve of the cylinder opens, a temporary compression stroke in which the piston of the cylinder moves from bottom dead center to top dead center, and the cylinder. Temporary expansion stroke in which the fuel is mixed with the intake air filled in the cylinder from the top dead center to the bottom dead center, but the fuel does not burn, and the piston of the cylinder moves from the bottom dead center to the top dead center. The compression stroke toward which the cylinder's piston moves from top dead center to bottom dead center and the expansion stroke in which fuel burns in the same cylinder, and the cylinder's piston moves from bottom dead center to top dead center and the exhaust valve of the same cylinder. A 6-stroke internal engine was constructed to perform a dead center and a dead center opening.

If it is an in-cylinder direct injection type that directly injects fuel into the cylinder, it is preferable to inject fuel into the cylinder during the provisional expansion stroke.

According to the present invention, it is possible to realize an internal combustion engine capable of producing a good air-fuel mixture by securing a sufficient time for the intake air and the fuel to mix before the expansion stroke.

The figure which shows the schematic structure of the internal combustion engine for a vehicle of one Embodiment of this invention. The figure which shows the content of the cycle executed in the cylinder of the internal combustion engine of the same embodiment. The figure which shows the position of the piston and the lift amount of an intake / exhaust valve during a cycle executed in the cylinder of the internal combustion engine of the same embodiment.

An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an outline of an internal combustion engine for a vehicle according to the present embodiment. The internal combustion engine of the present embodiment is an in-cylinder direct injection type (direct injection) spark ignition engine, and has a plurality of cylinders 1 (one of which is illustrated in FIG. 1). Each cylinder 1 is provided with an injector 11 for directly injecting fuel into the combustion chamber of the cylinder 1. Further, a spark plug 12 is attached to the ceiling of the combustion chamber of each cylinder 1. The spark plug 12 receives the application of the induced voltage generated by the ignition coil and causes a spark discharge between the center electrode and the ground electrode. The ignition coil is integrally built in the coil case together with the igniter which is a semiconductor switching element.

The intake passage 3 for supplying intake air takes in air from the outside and guides it to the intake port of each cylinder 1. An air cleaner 31, an electronically controlled throttle valve 32 as an intake throttle valve, a surge tank 33, and an intake manifold 34 are arranged on the intake passage 3 in this order from the upstream.

The exhaust passage 4 for exhausting the exhaust guides the exhaust generated as a result of burning the fuel in the cylinder 1 to the outside from the exhaust port of each cylinder 1. An exhaust manifold 42 and a three-way catalyst 41 for purifying exhaust gas are arranged on the exhaust passage 4. In addition, an exhaust bypass passage 43 that bypasses the exhaust turbine 52 and a wastegate valve 44 that is a bypass valve that opens and closes the inlet of the bypass passage 43 are provided.

The exhaust turbocharger 5 is configured so that the exhaust turbine 52 and the impeller 51 of the compressor are coaxially connected via a shaft 53 and interlocked with each other. Then, the turbine 52 and the impeller 51 are rotationally driven by using the energy of the exhaust, and the compressor is made to perform a pumping action by the rotational force, whereby the intake air is pressurized and compressed (supercharged) and sent to the cylinder 1.

The exhaust gas recirculation device 2 opens and closes the external EGR passage 21 connecting the exhaust passage 4 and the intake passage 3, the EGR cooler 22 provided on the EGR passage 21, and the EGR passage 21 to open and close the EGR passage 21. The element is an EGR valve 23 that controls the flow rate of EGR gas flowing through the passage 21. The inlet of the EGR passage 21 is connected to a predetermined position downstream of the catalyst 41 in the exhaust passage 4. The outlet of the EGR passage 21 is connected to a predetermined position (particularly, the surge tank 33 or the intake manifold 34) downstream of the throttle valve 32 in the intake passage 3.

The variable valve timing mechanism 6 changes the opening / closing timing of the intake valve by changing the rotation phase of the intake camshaft that drives the opening / closing of the intake valve of each cylinder 1 with respect to the crankshaft of the internal combustion engine. Is.

The electronic control unit (Electronic Control Unit) 0 that controls the operation of the internal combustion engine of the present embodiment is a microcomputer system having a processor, a memory, an input interface, an output interface, and the like. The ECU 0 may be a plurality of ECUs or controllers connected to each other so as to be communicable with each other via a telecommunication line such as CAN (Control Area Network).

The input interface of ECU 0 has a vehicle speed signal a output from a vehicle speed sensor that detects the actual vehicle speed of the vehicle, a crank angle signal b output from a crank angle sensor that detects the rotation angle of the crank shaft of the internal combustion engine and the engine rotation speed. , Accelerator opening signal c output from a sensor that detects the amount of depression of the accelerator pedal by the driver as the accelerator opening (so to speak, the engine load factor or engine torque required for the internal combustion engine), intake passage 3 (particularly). , Intake temperature / intake pressure signal d output from the temperature / pressure sensor that detects the intake air temperature and intake pressure in the surge tank 33 or the intake manifold 34), and cooling output from the water temperature sensor that detects the cooling water temperature of the internal combustion engine. Water temperature signal e, brake depression amount signal f output from a sensor that detects the depression amount of the brake pedal, cam angle signal g output from the cam angle sensor at a plurality of cam angles of the intake cam shaft of the internal combustion engine, atmospheric pressure. The atmospheric pressure signal h or the like output from the atmospheric pressure sensor that detects the above is input.

From the output interface of ECU 0, the ignition signal i for the igniter of the ignition plug 12, the fuel injection signal j for the injector 11, the opening operation signal k for the throttle valve 32, and the opening operation for the EGR valve 23. The signal l, the control signal m of the opening / closing timing of the intake valve, and the like are output to the VVT mechanism 6.

The processor of ECU 0 interprets and executes a program stored in the memory in advance, calculates an operation parameter, and controls the operation of the internal combustion engine. The ECU 0 acquires various information a, b, c, d, e, f, g, h necessary for the operation control of the internal combustion engine via the input interface, obtains the engine speed and the accelerator opening, and cylinder 1 Estimate the amount of air sucked into the engine. Then, based on them, the required fuel injection amount (necessary to realize the target air-fuel ratio at or near the theoretical air-fuel ratio) and the fuel injection timing (number of fuel injections in one cycle of cylinder 1) corresponding to the intake air amount. , Fuel injection pressure, ignition timing (including the number of spark ignitions in one cycle of cylinder 1), required EGR rate (or EGR gas amount), opening / closing timing of the intake valve, and various other operating parameters are determined. The ECU 0 applies various control signals i, j, k, l, n corresponding to the operation parameters via the output interface.

As shown in FIGS. 2 and 3, the internal combustion engine of the present embodiment has a series of intake stroke-temporary compression stroke-temporary expansion stroke-compression stroke-expansion stroke-exhaust stroke as one cycle, and this is each cylinder. It is a 6-stroke reciprocating engine that is repeatedly executed in 1. FIG. 3 shows the position of the piston of one cylinder (first cylinder) 1 and the lift amount of the intake / exhaust valve. In FIG. 3, the process in which fuel can be injected from the injector 11 into the combustion chamber of the cylinder 1 is drawn by a thick broken line. Hereafter, each process will be supplemented.

[1] Intake stroke: The piston of cylinder 1 moves from top dead center to bottom dead center. During the intake stroke, the intake valve of the cylinder 1 opens, and the intake air is sucked into the cylinder 1 from the intake passage 3. The exhaust valve may be open early in the intake stroke (causing valve overlap in which both the intake and exhaust valves open), but is basically closed.

[2] Temporary compression stroke: The piston of cylinder 1 moves from bottom dead center to top dead center. From the early to mid-term of this tentative compression stroke, the intake valve of cylinder 1 may still be open, as in the so-called Miller cycle, but the intake valve closes during the tentative compression stroke. The exhaust valve of cylinder 1 is closed. During the tentative compression stroke, only the intake air is present in the combustion chamber of the cylinder 1, and the fuel is not yet present.

[3] Temporary expansion stroke: The piston of cylinder 1 moves from top dead center to bottom dead center. During the tentative expansion stroke, the intake valve and the exhaust valve of the cylinder 1 are closed. Then, during the temporary expansion stroke, fuel is injected into the combustion chamber from the injector of the cylinder 1. The tentative expansion stroke plays a role of mixing the fuel injected in the cylinder 1 with the intake air. In this tentative expansion stroke, the ignition is not yet performed and the fuel is not burned.

[4] Compression stroke: The piston of cylinder 1 moves from bottom dead center to top dead center. During the compression stroke, the intake valve and the exhaust valve of the cylinder 1 are closed. In the compression stroke, the intake air and the fuel are sufficiently mixed in the cylinder 1 and then compressed.

[5] Expansion stroke: The piston of cylinder 1 moves from top dead center to bottom dead center. During the expansion stroke, the intake valve and the exhaust valve of the cylinder 1 are closed. At the end of the compression stroke or the beginning of the expansion stroke, spark ignition is performed by the spark plug 12 of the cylinder 1, and the fuel is ignited and burned. As a result, the engine torque is output.

[6] Exhaust stroke: The piston of cylinder 1 goes from bottom dead center to top dead center. During the exhaust stroke, the exhaust valve of the cylinder 1 opens, and the exhaust gas from the cylinder 1 is discharged to the exhaust passage 4. The intake valve may be open at the end of the exhaust stroke, but is basically closed.

In a 6-stroke internal combustion engine, one cycle of one cylinder 1 includes the above six strokes. That is, since the piston reciprocates three times in one cycle, the crankshaft makes three rotations and 1080 ° CA (crank angle) completes one cycle. On the other hand, the intake valve of the cylinder 1 is opened once in one cycle, and the exhaust valve is also opened once in one cycle. For this reason, the intake camshaft that opens and closes the intake valve of the cylinder 1 and the exhaust camshaft that opens and closes the exhaust valve make one rotation every 1080 ° CA, respectively. In short, the rotational speed of the intake camshaft and the exhaust camshaft is 1/3 of the rotational speed of the crankshaft.

As shown in FIG. 2, the 6-stroke internal combustion engine of the present embodiment can be configured as an internal combustion engine having two cylinders 1 as a set and one or a plurality of the sets. For example, an internal combustion engine such as an in-line two-cylinder engine, an in-line four-cylinder engine, or an in-line six-cylinder engine can be configured. The distance between the expansion strokes of the two cylinders 1 in a set is 540 ° CA, which is a so-called evenly spaced explosion.

The advantage of the 6-stroke internal combustion engine of the present embodiment is that when the piston of one of the two cylinders 1 rises from the bottom dead center to the top dead center, the piston of the other cylinder 1 dies. It is possible to descend from the point toward the bottom dead center. In a known in-line two-cylinder 4-stroke internal combustion engine, the piston of one cylinder 1 and the piston of the other cylinder 1 both rise and fall, resulting in increased vibration and the amount of blow-by gas leaking from the crankcase. There is a tendency to increase. With 6 strokes, the rise of the piston of one cylinder 1 and the fall of the piston of the other cylinder 1 cancel each other out the vibration and the pressure fluctuation in the crankcase. Therefore, it is advantageous for forming an in-line two-cylinder internal combustion engine.

The increase / decrease adjustment of the engine load factor, in other words, the intake amount to be charged in the cylinder 1 and the fuel injection amount can be performed via the intake VVT mechanism 6. If the opening / closing timing of the intake valve of the cylinder 1 is retarded, the intake amount and the fuel injection amount are reduced by that amount, and the engine torque is reduced. If the opening / closing timing of the intake valve of the cylinder 1 is advanced, the intake amount and the fuel injection amount increase by that amount, and the engine torque increases.

If the displacement of the cylinder 1 and the engine speed are the same, the output of the 6-stroke internal combustion engine is 2/3 of that of the 4-stroke internal combustion engine. In order to compensate for this, it is preferable to supercharge the intake air with the supercharger 5. However, the turbocharger 5 is not essential.

In addition, by increasing the number of strokes by two from the 4-stroke internal combustion engine, the mechanical loss (mechanical loss) per cycle of one cylinder 1 increases 1.5 times in theory. On the other hand, by adopting the Miller cycle method that delays the closing timing of the intake valve and keeps the intake valve open until the early to middle of the temporary compression stroke, pumping loss is reduced and thermomechanical conversion efficiency is improved. Can be planned.

In addition, if the engine speeds are the same, it can be expected that the rotation speed of the camshaft will be 2/3 as compared with the 4-stroke internal combustion engine, the wear of the camshaft and the cam journal will be reduced, and the life will be extended.

In the present embodiment, an intake stroke in which the piston of cylinder 1 moves from top dead center to bottom dead center and the intake valve of the cylinder 1 opens, and a provisional compression stroke in which the piston of cylinder 1 moves from bottom dead center to top dead center. Then, the piston of the cylinder 1 moves from the top dead center to the bottom dead center, and the intake air filled in the cylinder 1 and the fuel are mixed, but the fuel does not burn. The compression stroke from dead center to top dead center, the expansion stroke in which the piston of cylinder 1 moves from top dead center to bottom dead center and fuel burns in the same cylinder 1, and the piston of cylinder 1 starts from bottom dead center. A 6-stroke internal combustion engine was configured to execute an exhaust stroke in which the exhaust valve of the same cylinder 1 opens toward top dead center.

According to the present embodiment, in an in-cylinder direct injection type internal combustion engine, a temporary expansion stroke and a compression stroke for mixing intake air and fuel are executed before the expansion stroke for burning the fuel, and the fuel is vaporized. You can have enough time to let it mix with the intake air. In the tentative expansion stroke, the pressure inside the cylinder 1 is lowered and the boiling point of the fuel component is lowered, so that the fuel injected at this time can be effectively vaporized. In particular, the amount of vaporized components that originally have a high boiling point increases.

Then, a good air-fuel mixture that is evenly and uniformly mixed so that the whole becomes the target air-fuel ratio (the theoretical air-fuel ratio in a spark ignition engine that burns gasoline or the like) can be obtained, which improves the thermomechanical conversion efficiency and is harmful. It is possible to reduce the amount of material emissions.

Further, if the amount of the fuel component vaporized before combustion increases, the latent heat (heat of vaporization) causes the temperature in the combustion chamber (combustion end temperature) of the cylinder 1 to become lower at the end of the compression stroke (compression top dead point). This leads to a reduction in the risk of causing abnormal combustion such as knocking.

The 6-stroke internal combustion engine of the present embodiment can also be applied to an HCCI engine that performs premixed compression ignition combustion in which the air-fuel mixture is compressed and self-ignited in the cylinder 1.

The present invention is not limited to the embodiment described in detail above. For example, the internal combustion engine of the above embodiment is an in-cylinder direct injection type, but it is also possible to make a port injection type internal combustion engine that injects fuel from an injector toward the intake port of each cylinder into a 6-stroke engine. be.

If it is a port injection type internal combustion engine, fuel is injected at the end of the exhaust stroke or the beginning of the intake stroke. The injected fuel is sucked into the cylinder 1 together with the intake air in the intake stroke. Then, the fuel is vaporized and sufficiently mixed with the intake air during the intake stroke, the provisional compression stroke, the provisional expansion stroke, and the compression stroke.

In addition, the specific configuration of each part can be variously modified without departing from the spirit of the present invention.

The present invention can be applied to an internal combustion engine mounted on a vehicle or the like.

1 ... Cylinder 11 ... Injector 12 ... Spark plug 3 ... Intake passage 4 ... Exhaust passage 5 ... Exhaust turbocharger 6 ... Intake VVT mechanism

Claims (2)

The intake stroke in which the piston of the cylinder moves from top dead center to bottom dead center and the intake valve of the same cylinder opens.
A temporary compression stroke in which the piston of the cylinder moves from bottom dead center to top dead center,
A temporary expansion stroke in which the piston of the cylinder moves from top dead center to bottom dead center and the intake air filled in the cylinder and the fuel are mixed but the fuel does not burn.
The compression stroke from the bottom dead center to the top dead center of the piston of the cylinder,
The expansion stroke in which the piston of the cylinder moves from top dead center to bottom dead center and fuel burns in the cylinder.
A 6-stroke internal combustion engine that executes an exhaust stroke in which the piston of the cylinder moves from the bottom dead center to the top dead center and the exhaust valve of the cylinder opens. It is an in-cylinder direct injection type that injects fuel directly into the cylinder.
The 6-stroke internal combustion engine according to claim 1, wherein fuel is injected into the cylinder during the provisional expansion stroke.

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