JP3039147B2 - 2-4 stroke switching engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a turbocharger driven by exhaust energy of an engine.
It relates to a four-stroke switching engine.

[0002]

2. Description of the Related Art In general, the operation of an engine is such that the operation of an explosion stroke, that is, an expansion stroke, an exhaust stroke, a suction stroke, and a compression stroke is sequentially repeated, and two types of a four-stroke engine and a two-stroke engine are available. is there. A two-stroke engine, i.e., a two-stroke engine, has an exhaust port formed in a cylinder head or a lower part of a cylinder, a scavenging port provided in a lower part of a cylinder, and one cycle is completed in two strokes of a piston. Power can be obtained. A four-stroke engine, that is, a four-stroke engine, is an engine that requires four strokes of the piston, that is, two rotations of the crankshaft, to complete the one cycle by performing the above four operations for each stroke of the piston.

Conventionally, in an engine having a turbocharger driven by exhaust energy and an energy recovery turbine, a turbocharger, an energy recovery turbine, and the like are connected downstream of an exhaust pipe such as an exhaust manifold connected to an exhaust port to generate the engine. The exhaust energy is recovered by a turbocharger, an energy recovery turbine, or the like, and is driven by a compressor, or is recovered as electric energy by a power generator / motor by a battery or the like.

Further, as the cycle switching engine, Japanese Patent Application Laid-Open Nos. Hei 3-279632 and Hei 3-27963 are known.
No. 3 discloses a technique disclosed in Japanese Patent Laid-Open Publication No. Hei. In these cycle switching engines, the intake and exhaust valves are made of a lightweight material such as a ceramic material, and the intake and exhaust valves are opened and closed by electromagnetic force to control the operation state, so that the intake and exhaust valves are independent of the crank rotation. focuses to be freely controlled, also with two-cycle engine is large, the output torque in the low speed region than four-stroke engine, and focusing on the effect of suppressing the effects i.e. NO _X generation of EGR can be expected, the operation of the engine It is configured to be switchable between two cycles or four cycles, and is configured to be switchable between a direct injection type and a sub chamber type.

When the engine is running at a low speed and a high load, the engine is operated in two cycles and switched to a direct injection type to reduce the volume of the combustion chamber, burn the fuel in a fuel-rich state at a high compression ratio, and perform EGR. Ensure high output. Further, at the time of low-speed part-load and high-speed part-load, it switched to direct injection by operating the engine in four cycles, to reduce the volume of the combustion chamber is burned in a fuel-rich state at a high compression ratio suppress of the NO _X I do. Further, at high speed and high load, the engine is operated in four cycles and switched to the sub-chamber type, the combustion in the sub-chamber type is performed, the volume of the combustion chamber is increased, a large amount of air is introduced, and a low compression ratio and a low compression ratio are obtained. the generation of the NO _X is suppressed by primary combustion in the fuel-rich at room, thereby suppressing the generation of the NO _X in any of the operating region of the engine, provides a cycle switching engine capable of obtaining an efficient high-power engine That is.

The cycle switching engine includes an intake valve disposed at an intake port formed in a cylinder head, an exhaust valve disposed at an exhaust port, an intake valve disposed at an intake port formed at a lower portion of a cylinder, and a sub-chamber provided at a cylinder head. An opening / closing switching valve arranged in a communication hole communicating the main chamber with each other, each electromagnetic valve driving device for opening and closing each of the valves by electromagnetic force, a detecting means for detecting an operating state of the engine,
And a controller for controlling the operation state of each valve in response to a detection signal from the detection means. The detection means detects the operation state of the engine speed, load, and the like, and outputs the detection signal to the controller. , The controller can control the opening and closing of each of the valves in response to the operating state of the engine,
The engine can be switched to two or four cycles, and can be switched to a direct injection type or sub-chamber type combustion state. In particular, control is performed to suppress the generation of NO _X over the entire operation range of the engine. be able to.

[0007]

In a two-stroke engine, when a turbocharger is provided, it is impossible to make the exhaust pressure higher than the scavenging pressure due to the principle of two-stroke operation. However,
The in-cylinder pressure immediately before the exhaust stroke is several kg / cm ² or more,
If the high in-cylinder pressure is used, exhaust energy can be effectively recovered by the exhaust turbine. However, in reality, the pressure once expands to the pressure before the exhaust turbine, and the pressure expands to the atmospheric pressure. Only the pressure difference can be recovered by the exhaust turbine. In addition, when considering increasing the pressure in front of the exhaust turbine to increase the amount of recovery, in a two-stroke engine, it is necessary to increase the scavenging pressure to a level higher than the pressure in front of the exhaust turbine, and the energy required for this increases. However, the total recovery efficiency is not improved.

Particularly, in an engine having a turbocharger provided with a turbine and a compressor, the turbocharger has a problem that exhaust gas energy becomes small at low speed and low load, and it is difficult to secure a sufficient supercharging pressure. I have.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and to provide a turbocharger having a generator / motor driven by exhaust energy, and to provide a scavenging port used in two-stroke operation during four-stroke operation. In the exhaust stroke, the intake air is introduced and the exhaust gas in the cylinder is pushed out, and the exhaust gas in the cylinder is forcibly scavenged at the beginning of the exhaust stroke in the cylinder. An object of the present invention is to provide a 2-4 stroke switching engine in which fresh air receives heat from a cylinder wall surface to obtain thermal energy, recovers energy by a turbocharger or an energy recovery turbine, and improves thermal efficiency.

[0010]

The present invention is configured as follows to achieve the above object. That is,
According to the present invention, an intake port and an exhaust port formed in a cylinder head, an exhaust valve disposed in the exhaust port, and the intake port are closed and held during a two-stroke operation, and are opened and closed during a four-stroke operation to compress from near the end of the exhaust stroke. A turbocharger having an intake valve disposed at the intake port for performing intake during an initial stroke, a scavenging port formed at a lower portion of a cylinder, a generator / motor driven by exhaust energy, and the turbocharger at an early stage of an exhaust stroke during four-stroke operation. And a check valve provided at the scavenging port, which is opened to scavenge the inside of the cylinder with fresh air from the engine.

In the 2-4 stroke switching engine, at low speed and low load, the generator / motor of the turbocharger is operated by an electric motor to secure a supercharging pressure by supercharging from the turbocharger.

Further, in this 2-4 stroke switching engine, the opening timing of the exhaust valve is set such that the exhaust valve is opened earlier in the two stroke operation than in the four stroke operation.

[0013]

The 2-4 stroke switching engine according to the present invention is constructed as described above and operates as follows. That is, in the 2-4 stroke switching engine, the intake valve arranged in the intake port of the cylinder head is kept closed during the two-stroke operation, opened and closed during the four-stroke operation to perform intake, and during the four-stroke operation, in the early stage of the exhaust stroke. The check valve provided in the scavenging port at the bottom of the cylinder opens and scavenges fresh air from the turbocharger driven by exhaust energy into the cylinder, so that the inside of the cylinder is forcibly scavenged during the exhaust stroke and remains in the cylinder. The gas becomes extremely small, and the fresh air receives heat from the wall surface during scavenging in a four-stroke operation and is recovered by a turbocharger or a power generation turbine to improve thermal efficiency. Further, by scavenging the inside of the cylinder with the check valve, it is possible to delay the opening timing of the exhaust valve during the four-stroke operation as compared with the two-stroke operation. Can be adjusted.

Further, since the generator / motor of the turbocharger is operated by an electric motor at a low speed and a low load, a sufficient boost pressure can be ensured even at a low speed and a low load by supercharging the compressor of the turbocharger.

[0015]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
One embodiment of the four-stroke switching engine will be described. FIG.
FIG. 1 is a schematic sectional view showing an embodiment of a 2-4 stroke switching engine according to the present invention, and FIG. 2 is a schematic explanatory view showing an example of a turbocharger having a generator / motor incorporated in the 2-4 stroke switching engine of FIG. , And FIG.
FIG. 4 is a schematic explanatory view showing an example of the energy recovery turbine incorporated in the four-stroke switching engine, and FIG. 4 is an explanatory view showing the operation of the 2-4 stroke switching engine in FIG.

This 2-4 stroke switching engine has a turbocharger 5 driven by the exhaust energy of the engine and, in some cases, an energy recovery turbine 6. In this embodiment, both are provided. The 2-4 stroke switching engine includes a cylinder block 2, a cylinder head 1 fixed to the cylinder block 2, a cylinder liner 13 forming a cylinder 10 fitted in a hole formed in the cylinder block 2,
A piston 7 reciprocating in the cylinder 10, that is, in the cylinder;
And a connecting rod and a crankshaft for converting a reciprocating motion of the piston 7 into a rotary motion. An exhaust port 8 is formed in the cylinder head 1 and a fuel injection nozzle 29 for injecting fuel into the cylinder is disposed. Further, a scavenging port 12 is formed below the cylinder 10. Exhaust port 8 formed in cylinder head 1
Are connected to the exhaust manifold via a manifold gasket. Exhaust manifold is turbocharger 5
The energy recovery turbine 6 is connected to an exhaust passage 16 on the upstream side of the turbocharger 5 and an exhaust passage 17 on the downstream side of the turbocharger 5.

This 2-4 stroke switching engine particularly holds the intake port 3 and the exhaust port 8 formed in the cylinder head 1, the exhaust valve 9 arranged in the exhaust port 8, and the intake port 3 closed during the two-stroke operation. In addition, an intake valve 4 disposed at an intake port 3 for opening and closing during a four-stroke operation and performing intake from near the end of an exhaust stroke to an early stage of a compression stroke, a scavenging port 12 formed at a lower portion of the cylinder 10, and power generation driven by exhaust energy A turbocharger 5 having an electric motor 21 and a check valve 2 provided at a scavenging port 12 capable of scavenging fresh air from the turbocharger 5 into a cylinder, that is, into the cylinder 10 at an early stage of an exhaust stroke during four-stroke operation.
Eight. Further, the exhaust port 8 is connected to the turbine scroll 14 of the turbine 20 in the turbocharger 5.
It is connected to. The compressor 19 of the turbocharger 5 has the intake port 3 through the intake passage 24 and the scavenging port 12 through the scavenging passage 11 branched from the intake passage 24.
It is connected to.

As shown in FIG. 2, the turbocharger 5 incorporated in the 2-4 stroke switching engine is provided on a turbine 20, a compressor 19 connected to a shaft 23 fixed to the turbine 20, and the shaft 23. Power generator / motor 21. The turbine scroll 14 on the inlet side of the turbine 20 communicates with the exhaust passage 16. The exhaust passage 17 on the outlet side of the turbine 20 is
The energy recovery device 6 shown in FIG. 3 communicates with a turbine scroll 26 on the inlet side of the power generation turbine 25. The exhaust passage 18 on the outlet side of the power generation turbine 25 is open to the atmosphere through, for example, an exhaust gas purification device. The energy recovery turbine 6 is configured such that a generator 27 is provided for a shaft 22 fixed to a power generation turbine 25, and the generator 27 recovers exhaust energy.

The operation of the 2-4 stroke switching engine configured as described above will be described with reference to FIG.
FIG. 4 is a diagram illustrating an embodiment of the operation of the 2-4 stroke switching engine. In FIG. 4, the piston 7
Represents the displacement of the piston 7 when it reciprocates in the cylinder 10, the upper dead center is shown by TDC, and the lower dead center is shown by B.
Indicated by DC. In this 2-4 stroke switching engine, the upper stage shows the time of 4-stroke operation, and the lower stage shows the time of 2-stroke operation. The open period of the check valve 28 provided in the scavenging port 12 is denoted by EV, the open period of the intake valve 4 is denoted by IV, and the open period of the exhaust valve 9 is denoted by EV. Also,
The 2-4 stroke switching engine includes a compression stroke CS, a combustion stroke or expansion stroke ES, an exhaust stroke ES, and an intake stroke IS.
(In the two-stroke operation, the scavenging and intake strokes) are sequentially repeated.

In the 2-4 stroke switching engine, a sensor (not shown) detects an operating state of the engine such as an engine speed and an engine load, and in response to the detection signal, a command from a controller (not shown) is issued. Control the opening / closing timing of the intake valve 4 and the exhaust valve 9 by two stroke operation or 4
It switches to stroke operation. In the 2-4 stroke switching engine, the scavenging port 1 provided at the lower part of
2, scavenging and intake are performed, and an exhaust valve 9 provided in an exhaust port 8 formed in the cylinder head 1 is opened / closed to perform exhaust through the exhaust port 8. Further, at the time of the four-stroke operation, after scavenging the inside of the cylinder with fresh air from the scavenging port 12, the intake valve 4 provided in the intake port 3 formed in the cylinder head 1 is opened and closed to perform intake through the intake port 3, An exhaust valve 9 provided in an exhaust port 8 formed in the cylinder head 1 is opened and closed to perform an exhaust operation through the exhaust port 8.

During the two-stroke operation, the intake valve 4 provided on the cylinder head 1 is kept closed, and fresh air supplied from the compressor 19 of the turbocharger 5 passes through the scavenging passage 11 and from the scavenging port 12. The gas is scavenged in the cylinder, that is, in the cylinder 10, and the gas in the cylinder is exhausted from the cylinder through the exhaust port 8 when the exhaust valve 9 is opened. The combustion gas in the cylinder is exhausted to the upstream side of the turbine 20 of the turbocharger 5 through the exhaust port 8, and the exhaust gas is driven by the energy recovery turbine 6 from the outlet side of the turbine 20, that is, the exhaust passage 17 after driving the turbine 20. Turbine 2
The exhaust gas is exhausted to the outside after driving the power generation turbine 25. The turbine 20 of the turbocharger 5 can be driven, the compressor 19 can be driven, and the electric power can be recovered as electric energy by the power generation / motor 21 provided in the turbocharger 5.

During a four-stroke operation, the intake valve 4 provided on the cylinder head 1 opens and closes, and intake air is supplied into the cylinder, that is, into the cylinder 10 through the intake port 3 of the cylinder head 1, and exhausted through an expansion stroke. During the exhaust stroke, the in-cylinder gas is exhausted from the interior of the cylinder through the exhaust port 8 when the exhaust valve 9 is opened, and at the beginning of the exhaust stroke, the check valve 28 of the scavenging port 12 is opened, forcibly scavenged, and the residual gas in the cylinder is left. The gas is very low. Further, the exhaust gas is supplied to the exhaust port 8
Then, the gas energy is sent to the turbocharger 5 through the exhaust passage 16, and the gas energy is recovered by the turbocharger 5, and then sent to the energy recovery turbine 6 to recover the energy.

In this 2-4 stroke switching engine,
The exhaust valve 9 is set to open earlier in the two-stroke operation than in the four-stroke operation. Also, when the piston 7 comes close to the top dead center TDC in the compression stroke and the in-cylinder air is compressed to a high temperature and a high pressure, the fuel injection nozzle 2
From 9, fuel is injected into the cylinder, mixed with compressed air and burned, and the piston 7 descends in the combustion stroke, that is, the expansion stroke. When the piston top surface 15 of the piston 7 reaches the upper end of the scavenging port 12 and the in-cylinder pressure becomes lower than the pressure in the scavenging passage 11, the check valve 28 opens.

Further, in this 2-4 stroke switching engine, the inside of the cylinder 10 is scavenged by the check valve 28 so that
The opening timing of the exhaust valve 9 at the time of the stroke operation can be delayed as compared with the time of the two-stroke operation, and can be adjusted to the optimal timing for the four-stroke operation. That is, by providing the check valve 28 in the scavenging port 12, for example, if the exhaust valve 9 is configured to be electromagnetically driven by an electromagnetic force, the opening timing of the exhaust valve 9 in the four-stroke operation and the two-stroke operation, that is, The release timing can be set separately. Generally, the opening timing of the exhaust valve 9 is set earlier during the two-stroke operation than during the four-stroke operation. However, if the opening timing of the exhaust valve 9 is not set earlier during the two-stroke operation, blowdown cannot be used and scavenging cannot be performed well. On the other hand, at the time of four-stroke operation, the exhaust valve 9
Unless the opening timing of the valve is set as late as possible, there is a problem that the work of the expansion stroke cannot be effectively utilized.

Therefore, in the 2-4 stroke switching engine, the opening timing of the exhaust valve 9 during the four stroke operation is adjusted to be later than the stroke opening timing during the two stroke operation. In the 2-4 stroke switching engine, the opening timing of the exhaust valve 9 is set earlier during the two-stroke operation, and the scavenging is favorably performed by effectively using the blowdown. The opening timing of the exhaust valve 9 is set as late as possible so that the work of the expansion stroke can be effectively utilized.

[0026]

The 2-4 stroke switching engine according to the present invention is configured as described above and has the following effects. That is, in the 2-4 stroke switching engine, an intake valve provided in an intake port formed in a cylinder head is closed and held in two strokes, and opened and closed in four strokes to perform intake air. A check valve is provided to scavenge fresh air from the turbocharger into the cylinder at the beginning of the four-stroke operation exhaust stroke.
During the exhaust stroke, the inside of the cylinder is forcibly scavenged, and the residual gas in the cylinder can be extremely reduced. Also, at the time of scavenging in the four-stroke operation, fresh air receives heat from the wall surface and is recovered in energy by the turbocharger or the power generation turbine, thereby improving thermal efficiency. Further, by scavenging the inside of the cylinder with the check valve, the opening timing of the exhaust valve at the time of four-stroke operation can be adjusted to the optimal timing for four-stroke operation by delaying the opening timing to the last minute, so that work can be effectively utilized.

Further, in the 2-4 stroke switching engine, the switching between the two stroke operation and the four stroke operation can be performed simply by providing the check valve in the scavenging port formed in the lower portion of the cylinder, and special control is performed. It is only necessary to control the operation timing of the intake valve and the exhaust valve, and the structure is extremely simple.

Further, in this 2-4 stroke switching engine, the opening timing of the exhaust valve during the 4-stroke operation is adjusted so that the stroke opening timing is delayed as compared with the 2-stroke operation. ,
By setting the opening timing of the exhaust valve earlier, the scavenging can be performed well by effectively using the blowdown.
At the time of the stroke operation, the opening timing of the exhaust valve can be set as late as possible so that the work of the expansion stroke can be effectively utilized.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an embodiment of a 2-4 stroke switching engine according to the present invention.

FIG. 2 is a schematic explanatory view showing an example of a turbocharger having a generator / motor installed in the 2-4 stroke switching engine of FIG. 1;

FIG. 3 is a schematic explanatory view showing an example of an energy recovery turbine incorporated in the 2-4 stroke switching engine of FIG. 1;

FIG. 4 is a diagram showing an example of the operation of the 2-4 stroke switching engine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylinder head 2 Cylinder block 3 Intake port 4 Intake valve 5 Turbocharger 6 Energy recovery turbine 7 Piston 8 Exhaust port 9 Exhaust valve 10 Cylinder 11 Scavenging passage 12 Scavenging port 21 Generator / motor 28 Check valve

Claims (3)

(57) [Claims] An intake port and an exhaust port formed in a cylinder head, an exhaust valve disposed in the exhaust port, the intake port is closed and held during a two-stroke operation, and is opened and closed during a four-stroke operation to close from the end of the exhaust stroke. An intake valve disposed at the intake port for performing intake during an early stage of a compression stroke, a scavenging port formed at a lower portion of a cylinder, a turbocharger having a generator / motor driven by exhaust energy, and the turbocharger at an early stage of an exhaust stroke during four-stroke operation. A 2-4 stroke switching engine comprising: a check valve provided at the scavenging port which is opened to scavenge the inside of the cylinder with fresh air from a charger. 2. The two- to four-stroke switching engine according to claim 1, wherein at a low speed and a low load, the generator / motor is operated by an electric motor to secure a supercharging pressure by supercharging from the turbocharger. 3. The two- to four-stroke switching engine according to claim 1, wherein an opening timing of the exhaust valve is set so as to open earlier in a two-stroke operation than in a four-stroke operation.