JPH0610694A - 2-4 stroke switching engine - Google Patents

Abstract

PURPOSE:To obtain a 2-4 strokes switching engine which performs scavenging through a check valve of a scavenging port during 4-stroke operation, and improves heat efficiency. CONSTITUTION:An intake valve 4 arranged on an intake port 3 of a cylinder head 1 is held in a blocked condition during 2-stroke operation, and opened/ closed during 4-stroke operation, for performing intake. A check valve 28 provided on a scavenging port on a lower side of a cylinder 10 is opened in an initial period of an exhaust process of the 4-stroke operation. New air is sent into a cylinder for scavenging from a turbocharger 5 driven by an exchaust energy. The space inside the cylinder is forcibly scavenged in an exhaust process of the 4-stroke operation, so that an amount of the residual gas in the cylinder gets extremely small. The new air receives heat from a wall surface at the scavenging time in the 4-stroke operation, and energy is recovered by the turbocharger 5 and the like, and thus the heat efficiency is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a turbocharger driven by the exhaust energy of an engine.
It relates to a 4-stroke switching engine.

[0002]

2. Description of the Related Art Generally, regarding the operation of an engine, the operations of an explosion stroke, that is, an expansion stroke, an exhaust stroke, an intake stroke, and a compression stroke are sequentially repeated, and there are two methods, a 4-cycle engine and a 2-cycle engine. is there. A two-cycle engine, that is, a two-stroke engine, has an exhaust port formed in the cylinder head or the lower part of the cylinder, a scavenging port provided in the lower part of the cylinder, and one cycle is completed by two strokes of the piston. The power of can be obtained. A four-cycle engine, that is, a four-stroke engine is an engine that requires four strokes of the piston, that is, two rotations of the crankshaft, in order to complete one cycle by performing the above four operations for each stroke of the piston.

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

Further, as a cycle switching engine, Japanese Patent Application Laid-Open No. 3-279632 and Japanese Patent Application Laid-Open No. 3-27963.
There is one disclosed in Japanese Patent No. In these cycle switching engines, the intake / exhaust valve is made of a lightweight ceramic material, and the intake / exhaust valve is opened / closed by electromagnetic force to control the operating state and independent of 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 can be switched to 2 cycles or 4 cycles, and can be switched to a direct injection type or a sub chamber type.

When the engine is operating at a low speed and a high load, the engine is operated in two cycles and is switched to the direct injection type to reduce the volume of the combustion chamber so that the fuel is burned in a fuel rich state at a high compression ratio to perform EGR. Ensure high output. Also, at low speed partial load and high speed partial load, the engine is operated in 4 cycles to switch to the direct injection type, and the volume of the combustion chamber is reduced to burn at a high compression ratio in a fuel rich state to suppress the generation of NO _X. To do. Furthermore, at high speed and high load, the engine is operated in 4 cycles and switched to the sub-chamber type to perform the sub-chamber type combustion to increase the volume of the combustion chamber and introduce a large amount of air to achieve the low compression ratio and the sub-type. 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 above cycle switching engine includes an intake valve arranged in an intake port formed in a cylinder head, an exhaust valve arranged in an exhaust port, an intake valve arranged in an intake port formed in a lower portion of a cylinder, and a sub chamber provided in a cylinder head. An opening / closing switching valve arranged in a communication hole that communicates with the main chamber, each electromagnetic valve drive device that opens and closes each of the valves by electromagnetic force, detection means for detecting an operating state of the engine,
And a controller for controlling the operating state of each valve in response to a detection signal from the detecting means, wherein the detecting means detects the operating state of the engine speed and load, and the controller outputs the detected signal. Input to the controller to control the open / closed state of each of the valves in response to engine operating conditions, thus:
It is possible to switch the engine to two-cycle or four cycle, can be switched to the combustion state of the direct injection type or pre-combustion chamber, in particular, performs a control that can suppress the occurrence of the NO _X with respect to the total operating range of the engine be able to.

[0007]

By the way, in a two-stroke engine, when a turbocharger is provided, it is impossible from the principle of two-stroke operation to make the exhaust pressure higher than the scavenging pressure. However,
The cylinder pressure immediately before the exhaust stroke is several kg / cm ² or more,
By utilizing the high in-cylinder pressure, it is possible to effectively recover the exhaust energy by the exhaust turbine. However, in reality, it expands once to the pressure before the exhaust turbine and then expands to atmospheric pressure. Only the pressure difference can be recovered by the exhaust turbine. In addition, in the case of considering increasing the pressure before the exhaust turbine and increasing the amount of recovery thereof, in a two-stroke engine, it is necessary to raise the scavenging air pressure to be equal to or higher than the pressure before 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 equipped 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. There is.

Therefore, an object of the present invention is to solve the above-mentioned problems, and a turbocharger having a generator / motor driven by exhaust energy is provided and a scavenging port used in two-stroke operation during four-stroke operation. Is configured to introduce intake air in the exhaust stroke to push out the exhaust gas in the cylinder, forcibly scavenging at the beginning of the exhaust stroke in the cylinder, extremely reducing the residual gas in the cylinder, and scavenging in four-stroke operation, It is an object of the present invention to provide a 2-4 stroke switching engine in which fresh air receives heat from a cylinder wall surface to obtain heat energy and energy is recovered by a turbocharger or an energy recovery turbine to improve thermal efficiency.

[0010]

In order to achieve the above object, the present invention is configured as follows. That is,
According to the present invention, an intake port and an exhaust port formed in a cylinder head, an exhaust valve arranged in the exhaust port, and the intake port are held closed during a two-stroke operation and opened and closed during a four-stroke operation to compress near the end of the exhaust stroke. An intake valve arranged in the intake port for intake during the early stage of the stroke, a scavenging port formed in the lower part of the cylinder, a turbocharger having a generator / motor driven by exhaust energy, and the turbocharger at the early stage of the exhaust stroke during 4-stroke operation. 2-4 stroke switching engine having a check valve provided at the scavenging port for opening the inside of the cylinder with fresh air from

Further, in this 2-4 stroke switching engine, at low speed and low load, the generator / motor of the turbocharger is operated as an electric motor to ensure supercharging pressure by supercharging from the turbocharger.

Further, in this 2-4 stroke switching engine, the opening timing of the exhaust valve is set so as to open earlier in the 2-stroke operation than in the 4-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 this 2-4 stroke switching engine, the intake valve arranged in the intake port of the cylinder head is held closed during the 2-stroke operation, and opened / closed during the 4-stroke operation to intake air, and at the early stage of the exhaust stroke during the 4-stroke operation. The check valve provided in the scavenging port at the bottom of the cylinder opens to scaveng the fresh air from the turbocharger driven by exhaust energy into the cylinder, so the cylinder is forcibly scavenged during the exhaust stroke and remains in the cylinder. As the gas becomes extremely small, the fresh air receives heat from the wall surface at the time of scavenging in four-stroke operation, and the energy is recovered by the turbocharger or the power generation turbine to improve the 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 at the time of 4-stroke operation as compared with that at the time of 2-stroke operation. It can be adjusted.

Further, since the generator / motor of the turbocharger is operated by the electric motor at low speed and low load, the supercharging of the compressor of the turbocharger ensures sufficient supercharging pressure even at low speed and low load.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings,
An embodiment of the 4-stroke switching engine will be described. Figure 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. , FIG. 3 is 2-
FIG. 4 is a schematic explanatory diagram showing an example of an energy recovery turbine incorporated in a 4-stroke switching engine, and FIG. 4 is an explanatory diagram showing the operation of the 2-4 stroke switching engine of FIG. 1.

This 2-4 stroke switching engine has a turbocharger 5 which is driven by the exhaust energy of the engine and optionally also an energy recovery turbine 6. In this embodiment, both are assumed to be provided. This 2-4 stroke switching engine includes a cylinder block 2, a cylinder head 1 fixed to the cylinder block 2, a cylinder liner 13 constituting a cylinder 10 fitted in a hole formed in the cylinder block 2,
A piston 7 that reciprocates in the cylinder 10, that is, in the cylinder,
And a connecting rod and a crankshaft for converting the 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 is arranged to inject fuel into the cylinder. Further, a scavenging port 12 is formed on the lower portion of 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
Is connected to the exhaust passage 16 on the upstream side, and the energy recovery turbine 6 is connected to the exhaust passage 17 on the downstream side of the turbocharger 5.

In this 2-4 stroke switching engine, in particular, the intake port 3 and the exhaust port 8 formed in the cylinder head 1, the exhaust valve 9 disposed in the exhaust port 8 and the intake port 3 are closed and held during the 2-stroke operation. In addition, the intake valve 4 disposed in the intake port 3 that performs the intake and exhaust during the period from the end of the exhaust stroke to the beginning of the compression stroke by opening and closing during the 4-stroke operation, the scavenging port 12 formed below the cylinder 10, and the power generation driven by exhaust energy -The turbocharger 5 having the electric motor 21 and the check valve 2 provided in the scavenging port 12 capable of scavenging the fresh air from the turbocharger 5 into the cylinder, that is, the cylinder 10 in the early stage of the exhaust stroke during the 4-stroke operation.
Have eight. Further, the exhaust port 8 is connected to the turbine scroll 14 of the turbine 20 of the turbocharger 5.
Are linked to. The compressor 19 of the turbocharger 5 has the scavenging port 12 through the intake port 3 and the scavenging passage 11 branched from the intake passage 24 through the intake passage 24.
Are linked to.

As shown in FIG. 2, the turbocharger 5 incorporated in the 2-4 stroke switching engine is provided on the turbine 20, the compressor 19 connected to the shaft 23 fixed to the turbine 20, and the shaft 23. It has a 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
It communicates with the turbine scroll 26 on the inlet side of the power generation turbine 25 of the energy recovery device 6 shown in FIG. 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 purifying device. The energy recovery turbine 6 is configured such that a power generator 27 is provided on a shaft 22 fixed to a power generation turbine 25, and exhaust energy is recovered by the power generator 27.

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 example of the operation of the 2-4 stroke switching engine. In FIG. 4, the piston 7
Indicates the displacement of the piston 7 when the cylinder reciprocates in the cylinder 10, the top dead center is TDC, and the bottom dead center is B.
Shown as DC. In this 2-4 stroke switching engine, the 4-stroke operation is shown in the upper stage and the 2-stroke operation is shown in the lower stage. The open period of the check valve 28 provided in the scavenging port 12 is shown by a symbol EV, the open period of the intake valve 4 is shown by a symbol IV, and the open period of the exhaust valve 9 is shown by a symbol EV. Also,
A 2-4 stroke switching engine has 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 / intake stroke) is sequentially repeated.

In this 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 a command of a controller (not shown) in response to the detection signal. Controls the opening / closing timing of the intake valve 4 and the exhaust valve 9 with the 2-stroke operation or 4
It is for switching to stroke operation. In the 2-4 stroke switching engine, the scavenging port 1 provided at the lower portion of the cylinder 10 is operated during the 2 stroke operation.
Scavenging and intake are performed from 2, and the exhaust valve 9 provided in the exhaust port 8 formed in the cylinder head 1 is opened / closed to perform exhaust through the exhaust port 8 to operate. In addition, during the 4-stroke operation, after the inside of the cylinder is scavenged by the 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 / closed to perform intake through the intake port 3, The exhaust valve 9 provided in the exhaust port 8 formed in the cylinder head 1 is opened and closed to perform exhaust through the exhaust port 8 to operate.

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

During the 4-stroke operation, the intake valve 4 provided on the cylinder head 1 is opened and closed so that the intake air is supplied into the cylinder, that is, the cylinder 10 through the intake port 3 of the cylinder head 1, and is exhausted through the expansion stroke. In the stroke, when the exhaust valve 9 is opened, the in-cylinder gas is exhausted from the inside of the cylinder through the exhaust port 8, and at the beginning of the exhaust stroke, the check valve 28 of the scavenging port 12 is opened and forcibly scavenged to remain in the cylinder. The gas is extremely low. Furthermore, exhaust gas is exhaust port 8
And, it is sent to the turbocharger 5 through the exhaust passage 16 and the gas energy is recovered by the turbocharger 5, and then is sent to the energy recovery turbine 6 to recover energy.

In this 2-4 stroke switching engine,
The exhaust valve 9 is set to open earlier in two-stroke operation than in four-stroke operation. Further, when the piston 7 becomes close to the top dead center TDC in the compression stroke and the in-cylinder air is compressed and becomes high temperature and high pressure, the fuel injection nozzle 2
Fuel is injected from the cylinder 9 into the cylinder, mixed with the compressed air and burned, and in the combustion stroke, that is, the expansion stroke, the piston 7 descends. 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 the 2-4 stroke switching engine, the check valve 28 scavenges the inside of the cylinder 10 so that 4
The opening timing of the exhaust valve 9 at the time of stroke operation can be delayed as compared with that at the time of 2-stroke operation, and can be adjusted to the optimum time for 4-stroke operation. That is, by providing the check valve 28 in the scavenging port 12, for example, when the exhaust valve 9 is configured to be electromagnetically driven by electromagnetic force, the opening timing of the exhaust valve 9 in the 4-stroke operation and the 2-stroke operation, that is, The opening timing can be set separately. Generally, the opening timing of the exhaust valve 9 is set earlier in the 2-stroke operation than in the 4-stroke operation. However, if the opening timing of the exhaust valve 9 is not set early during the two-stroke operation, blowdown cannot be used and scavenging cannot be performed satisfactorily. On the other hand, at the time of 4-stroke operation, the exhaust valve 9
There is a problem that the work of the expansion stroke cannot be effectively used unless the opening timing of is set to the latest.

Therefore, in this 2-4 stroke switching engine, the opening timing of the exhaust valve 9 during the 4-stroke operation is adjusted to be later than the stroke opening timing during the 2-stroke operation. In the 2-4 stroke switching engine, the opening timing of the exhaust valve 9 is set early during the 2-stroke operation so that the blowdown is effectively used to perform the scavenging satisfactorily. The opening timing of the exhaust valve 9 is set as late as possible, and is adjusted to effectively use the work of the expansion stroke.

[0026]

The 2-4 stroke switching engine according to the present invention is constructed as described above and has the following effects. That is, in this 2-4 stroke switching engine, the intake valve provided in the intake port formed in the cylinder head is held closed during 2 strokes, and is opened and closed during 4 strokes to intake air, and the scavenging port formed under the cylinder is used. Since a check valve is provided, the fresh air from the turbocharger is scavenged into the cylinder at the beginning of the exhaust stroke of the 4-stroke operation.
The inside of the cylinder is forcibly scavenged during the exhaust stroke, and the residual gas in the cylinder can be made extremely small. Further, during the scavenging operation of the 4-stroke operation, the fresh air receives heat from the wall surface and the energy is recovered by the turbocharger or the power generation turbine, and the thermal efficiency is improved. Further, by scavenging the inside of the cylinder with the check valve, the opening timing of the exhaust valve at the time of 4-stroke operation can be delayed to the last minute and adjusted to the optimum timing for 4-stroke operation, so that work can be effectively utilized.

Further, in this 2-4 stroke switching engine, switching between 2-stroke operation and 4-stroke operation is simply performed by providing the check valve at the scavenging port formed in the lower portion of the cylinder, and special control is required. There is no need to do so, 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 as to be later than that during the 2-stroke operation, so during the 2-stroke operation. ,
By setting the opening timing of the exhaust valve early, it is possible to effectively use blowdown to perform good scavenging.
During stroke operation, the exhaust valve opening timing can be set to the last minute to effectively utilize the work of the expansion stroke.

[Brief description of 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 incorporated in the 2-4 stroke switching engine of 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.

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

[Explanation 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 Power Generation / Motor 28 Check Valve

Claims (3)

[Claims] 1. An intake port and an exhaust port formed in a cylinder head, an exhaust valve arranged in the exhaust port, the intake port is held closed during a 2-stroke operation and opened and closed during a 4-stroke operation from near the end of the exhaust stroke. An intake valve arranged in the intake port for intake during the initial stage of the compression stroke, a scavenging port formed in the lower part of the cylinder, a turbocharger having a generator / motor driven by exhaust energy, and the turbo at the early stage of the exhaust stroke during 4-stroke operation. A 2-4 stroke switching engine having a check valve provided at the scavenging port for opening the inside of the cylinder with fresh air from the charger. 2. The 2-4 stroke switching engine according to claim 1, wherein at low speed and low load, the generator / motor is operated as an electric motor to ensure supercharging pressure by supercharging from the turbocharger. 3. The 2-4 stroke switching engine according to claim 1, wherein the opening timing of the exhaust valve is set so that the exhaust valve is opened earlier during a 2-stroke operation than during a 4-stroke operation.