JP2000329009A - Diesel engine with EGR device - Google Patents

Abstract

(57) [Problem] To provide a large amount of EGR gas to a combustion chamber, this diesel engine is configured with an EGR port and an intake port in separate systems, and an electromagnetic force driving device controls the EGR valve in an open state. The space for the drive mechanism is made small. The diesel engine cools exhaust gas passing through a turbocharger by a cooling device,
At the beginning of the suction stroke, the EGR valve 6 is lifted by the EGR gas pressure, and the open state of the EGR valve 6 is determined by the electromagnet 42 and the magnetically permeable member 4.
The EGR gas is supplied to the combustion chamber 1 while being maintained by the electromagnetic driving device composed of the fuel cell 1, and then the intake valve 7 is lifted to supply the compressed air to the combustion chamber 1 and a part of the fuel to the combustion chamber 1. Promotes the mixing of EGR gas, fuel and compressed air,
At the compression top dead center, fuel for ignition is injected to ignite and burn the air-fuel mixture to prevent NOx, black smoke and knocking.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diesel engine provided with an EGR device for supplying a part of exhaust gas to a combustion chamber.

[0002]

2. Description of the Related Art In general, a diesel engine has a large compression ratio near the top dead center and a large combustion rate, and therefore has the advantage of high thermal efficiency. However, in a diesel engine, when fuel is injected from a fuel injection nozzle into compressed high-temperature, high-pressure air in a cylinder, an ideal air-fuel mixture cannot be formed in a process in which the fuel is dispersed and vaporized and burns. Black smoke is generated. Therefore, for a diesel engine, if there is sufficient time in the mixing process of air and fuel, the injection of fuel into the compressed air will sufficiently mix the air and fuel and disperse and mix well. NOx and black smoke are not generated. Also, for a diesel engine, when fuel is injected from a fuel injection nozzle into a combustion chamber, for example, at the beginning of a compression stroke or at a later stage of a suction stroke, the mixing period of air and fuel becomes sufficient, and premixing is performed satisfactorily. Although the generation of NOx and black smoke is reduced, knocking occurs due to self-ignition.

[0003] To prevent knocking in a diesel engine, an EGR that can reduce the oxygen concentration in intake air is conceivable. As a diesel engine equipped with an EGR device, for example, Japanese Patent Application Laid-Open No. 10-103
No. 160 discloses a technique disclosed in Japanese Patent Application Laid-open No. 160-160. The multi-cylinder engine equipped with the EGR device performs the EGR by opening the exhaust valve during the intake stroke and sending the exhaust gas into the cylinder, but the amount of the EGR gas is small, at most 20 to 30%. It is about.

[0004]

In the case of a diesel engine, when the EGR is performed in a large amount of 50% or more during the intake stroke to reduce the O ₂ concentration, the fuel is injected from the fuel injection nozzle into the combustion chamber at the beginning of the compression stroke. The fuel was O ₂
Since the concentration is low, the fuel cannot be ignited and burnt, and the vaporization of the fuel, the diffusion of the fuel in the combustion chamber, and the mixing of the air and the fuel progress. Among fuels, light oil is easy to ignite, and when the temperature reaches about 500 ° C., the fuel ignites and burns in a short period of time. However, the fuel according to the O ₂ concentration is made thinner hardly ignited, the O ₂ concentration is 15% or less, 80
If the temperature does not rise above 0 ° C, the fuel will not ignite and burn.

Usually, the O ₂ concentration in the air is 21%. However, in an engine in which the excess air ratio is set to about 1.2, for example, when the EGR of 50% is performed, the O ₂ concentration becomes 1%.
It can be reduced to 7%. Also, if the fuel content in the normal O ₂ concentration of 21% is too high, the fuel will spontaneously ignite and knock, so that even at full load, the flow rate of the fuel mixed into the intake is 50% or less, ie, equivalent The ratio must be less than 0.5. However, the O ₂ concentration is 17% to 15%.
%, The premixing rate can be increased to about 80%. Further, in the diesel engine, the temperature of the exhaust gas to be used for EGR is too high, the less amount of gas can be enclosed in the cylinder, in addition to generating energy is reduced, the compression end pressure is increased, the generation of NO _X causes and will, therefore adversely affecting the combustion, it is necessary to suppress the generation of the NO _X by cooling the exhaust gas to be used for EGR.

However, when a diesel engine is configured to supply exhaust gas used for EGR to an intake pipe for feeding compressed air, it is not easy to execute a large amount of EGR. When the exhaust gas and air are compressed together by the turbocharger compressor, the amount of work to blow the fresh air of the turbocharger is reduced and the total work is increased, or compressed air is supplied by the turbocharger compressor. There is a problem that a powerful pump is required to feed the exhaust gas for EGR into the intake pipe that is turned on. Therefore, in a diesel engine, in order to suppress the generation of NOx and black smoke and to prevent the occurrence of knocking and to improve the performance, that is, the fuel efficiency, a large amount of EGR is performed to produce a large amount of premixed air in the combustion chamber. It is necessary to ignite and burn the premixed gas near the top dead center of the compression stroke.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide an EGR system for performing EGR to solve the above-mentioned problem.
The valve is opened using the EGR gas pressure without providing a cam-type valve operating mechanism, and is kept open by electromagnetic force.
The driving mechanism of the EGR valve configured in a small space with properly controlling the amount of R, to thin adjust the O ₂ concentration to suppress the occurrence of the NO _X is prevented knocking by performing a large amount of EGR, further EGR Most of the fuel is supplied to the combustion chamber during the intake stroke to cool the exhaust gas and increase the premixing amount to lower the maximum compression pressure and to improve the mixing of fuel, compressed air and cooling exhaust gas. , An intake port for supplying compressed air to the combustion chamber by a turbocharger and an EGR port for supplying exhaust gas for EGR to the combustion chamber, and a large amount of EGR exhaust gas from the EGR port to the combustion chamber during the intake stroke. Then, compressed air is supplied from the intake port to the combustion chamber, and a part of fuel is injected from the fuel injection nozzle into the combustion chamber to generate a good premixed gas.
In the vicinity of top dead center compression stroke by injecting ignition fuel into the combustion chamber is ignited and burned, to provide a diesel engine with HC, and EGR system to improve the thermal efficiency and prevent the occurrence of such NO _X.

According to the present invention, there is provided a cylinder block to which a cylinder head is fixed, a piston reciprocating in a cylinder provided in the cylinder block, and fuel injection for injecting fuel into a combustion chamber formed by the piston and the cylinder. A nozzle, a turbocharger provided in an exhaust pipe for discharging exhaust gas from the combustion chamber, an intake port formed in the cylinder head communicating with an intake pipe communicating with a compressor of the turbocharger, and a turbocharger. An intake valve, an EGR pipe branched from a discharge pipe downstream of the turbocharger, and an EG for supplying EGR gas comprising a part of the exhaust gas to the combustion chamber through the EGR pipe.
An R pump, an EGR port formed in the cylinder head communicating with the EGR pipe, and an EG seated on a valve seat of the EGR port and receiving an EGR gas pressure to lift.
An R-valve, an electromagnetic driving device for holding the EGR valve in an open state, and the EGR in a direction to close the EGR port.
The present invention relates to a diesel engine provided with an EGR device comprising a valve spring for biasing a valve.

The electromagnetic force driving device comprises an electromagnet disposed around the valve stem of the EGR valve on the cylinder head, and a magnetically permeable member attached to an end of the EGR valve and attracted to the electromagnet. It is configured. Furthermore,
The magnetically permeable member constitutes a valve spring retainer serving as a seating surface of the valve spring for returning the EGR valve.

The electromagnet includes an attraction core fixed to the cylinder head around the valve stem of the EGR valve and a coil wound around the attraction core. The attracting core attracts the magnetically permeable member by the generated electromagnetic force, and
The GR valve keeps the valve open.

The intake valve lifts from about 70 ° after the top dead center of the intake stroke to about 50 ° after the bottom dead center of the compression stroke to supply the compressed air compressed by the compressor to the combustion chamber. The valve is used to supply the exhaust gas to the combustion chamber from the beginning of the intake stroke to 90 after the top dead center of the intake stroke.
Lift to ° position.

In this diesel engine, the EGR
The pump can apply a pressure so as to divide the exhaust gas from the discharge pipe to the EGR pipe and open the EGR valve. Also, this diesel engine
The exhaust gas diverted to the EGR pipe is cooled by a cooling device.

In response to the engine load, the EGR rate of the exhaust gas supplied from the EGR port to the combustion chamber becomes 50% at full load and 70% at half load or less. Controlled.

In this diesel engine, fuel is injected from the fuel injection nozzle into the combustion chamber near the top dead center of the compression stroke when the engine is started, and during the operation other than the start of the engine, the fuel is injected from the late stage of the intake stroke to the initial stage of the compression stroke. In the step, a part of the fuel is injected from the fuel injection nozzle into the combustion chamber, and then the remaining amount of fuel is injected near the top dead center of the compression stroke to perform ignition combustion.

In the diesel engine, the EGR pipe connected to the EGR port has an exhaust pipe provided downstream of a branch portion connected to the exhaust pipe to control an amount of EGR sent to the EGR port. A valve is provided.

The EGR port is formed as a tangential port, and the intake port is formed as a helical port, and the tangential port of the EGR port in a state in which a part of the fuel supplied to the combustion chamber is wrapped. The compressed air supplied from the helical port of the intake port is supplied to the outer periphery of the cooling exhaust gas supplied from the port, thereby promoting the mixture generation.

In this diesel engine, as described above, when the EGR rate of the exhaust gas is gradually increased as the load decreases, and the exhaust gas amount relative to the air amount, that is, the EGR gas amount is set to 70% at 1/2 load. , O ₂ concentration is about 1
It becomes about 5%, and even if the premixed gas has a high compression ratio, it does not ignite and knocking does not occur near the compression top dead center. Therefore, near the compression top dead center, the remaining amount of ignition fuel is injected from the fuel injection nozzle into the combustion chamber.
The mixture is ignited and burned in the combustion chamber, and the flame is diffused into the combustion chamber at a stretch to promote combustion. In addition, since it is difficult for the diesel engine to ignite the air-fuel mixture at start-up, the controller injects the entire amount of fuel injection near the compression top dead center, and injects fuel during rated operation when combustion is stable. Injection is performed during the period from the latter half of the stroke to the early stage of the compression stroke, and the control is switched to injection of ignition fuel near the compression top dead center. Further, in this diesel engine, the fuel injected into the combustion chamber for premixing with air is about 80 to 60%, and the fuel injected into the combustion chamber near the compression top dead center is about 20 to 40%. Is set.

Since this diesel engine is constructed as described above, the EGR is provided above the cylinder head.
No need for a cam-operated valve mechanism consisting of a cam or camshaft that operates the valve, a small space with only an electromagnetic force drive unit can be realized, and the intake mechanism is composed of two systems consisting of an EGR port and an intake port. Since the supply timings at which the EGR gas is supplied in the first half of the intake stroke and then the compressed air is supplied in the second half of the intake stroke and the first half of the compression stroke, a large amount of EGR can be carried out, and knocking may occur. without, by exhaust gas to be used for EGR is cooled by the cooling device it is possible to suppress the occurrence of NO _X, there is no possibility of adversely affecting the combustion, moreover EG
Ensuring sufficient time for the mixing of the R gas and the fuel promotes good mixing of the EGR gas, a portion of the fuel and the compressed air. By configuring this diesel engine in the combustion system described above, NOx contained in exhaust gas can be suppressed to 50 ppm or less, and particulate matter can be reduced to 0.05 gr / KW · h or less. In a conventional diesel engine, NOx contained in exhaust gas is about 500 ppm, and particulate matter is about 0.22 gr / KW · h.

This diesel engine has an EGR
The compressed air and the compressed air are supplied to the combustion chamber by separate supply systems, respectively, and the supply timing to both the combustion chambers is supplied first by the EGR gas, so that the work of the turbocharger does not increase. Further, since the exhaust gas is sucked into the combustion chamber at a low pressure through the cooling device, the work of increasing the pressure of the EGR gas becomes unnecessary, and then the air compressed to the high pressure is discharged from the middle position of the intake stroke. Since the air is supplied to the combustion chamber when the intake valve is opened, the compressed air gives the piston work that pushes down the piston in the latter half of the intake stroke, so that the work loss is reduced. If the intake valve is opened to about 50 degrees after the bottom dead center of the piston in the first half of the compression stroke, sufficient air is supplied to the combustion chamber.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a diesel engine having an EGR device according to the present invention will be described below with reference to the drawings. A diesel engine equipped with this EGR device can be applied to an engine such as a cogeneration system or an automobile engine. FIG. 1 is a schematic sectional view showing an embodiment of a diesel engine according to the present invention, and FIG. 2 is an EG in the diesel engine shown in FIG.
FIG. 3 is a plan view showing the relationship among an R port, an intake port, a fuel injection nozzle, and an exhaust port. FIG. 3 is a diagram illustrating lift timings of an EGR valve, an intake valve, an exhaust valve, and a control valve in the diesel engine of FIG. FIG. 5 is a schematic explanatory view showing an injection state of the premixing fuel into the combustion chamber at an early stage of the intake stroke.
6 is a schematic explanatory view showing the state of injection of the ignition fuel into the combustion chamber near the compression top dead center, and FIG. 6 is a graph showing the relationship between the load and the EGR rate in the diesel engine of FIG.

As shown in FIG. 1, this diesel engine comprises a cylinder head 3 attached to the cylinder block 4, a cylinder liner 28 constituting the cylinder 15 fitted in a hole 29 of the cylinder block 4, and a cylinder inside the cylinder 15. The piston 5 reciprocates. Combustion chamber 1
Is formed in cooperation with the piston 5 and the cylinder 15, and is formed by a region surrounded by the cylinder 15 and the piston 5 and a cavity 34 formed in the center of the piston 5. The cylinder head 3 has a cam 2
4, an intake port 9 provided with a valve seat on which an intake valve 7 driven to open and close is disposed, and an EGR provided with a valve seat provided with an EGR valve 6 driven to be opened and closed by an electromagnetic force driving device
Exhaust port 27 provided with port 8 and a valve seat in which an exhaust valve 35 (FIG. 2) that is driven to open and close by a cam system is arranged.
Are formed. The intake port 9 communicates with the intake pipe 12, the EGR port 8 communicates with the EGR pipe 11, and the exhaust port 27 communicates with the exhaust pipe 13.

At the center of the cylinder 15 of the cylinder head 3, a fuel injection nozzle 2 having an injection hole 32 for injecting fuel such as light oil into the combustion chamber 1 is arranged. In addition, the intake valve 7
Is closed by the spring force of the valve spring 26 disposed between the upper surface 39 of the cylinder head 3 and the valve spring retainer 36 attached to the end of the valve stem 22. Although not shown, a headliner that forms the combustion chamber 1 is arranged in the cylinder head 3 so as to form a heat-insulating air layer, and the combustion chamber 1 can be configured to have a heat-insulating structure. The piston 5 includes, for example, a piston head formed of a heat-resistant material such as ceramics such as Si ₃ N ₄ or a heat-resistant alloy, and a piston skirt formed of a metal material such as an Al alloy or an Fe alloy fixed to the piston head. Can be configured.

This diesel engine cools exhaust gas that has passed through a turbocharger 14 provided in an exhaust pipe 13 that discharges exhaust gas discharged from the combustion chamber 1 and a turbine (not shown) of the turbocharger 14. The cooling device 17 provided in the EGR pipe 11 branched at the branch portion 40 of the exhaust pipe 45 downstream of the turbocharger 14, and the cooling exhaust gas cooled by the cooling device 17 is sent to the EGR pipe 11 for sending it to the combustion chamber 1. An EGR pump 20 is provided. The EGR pipe 11 communicates with an EGR port 8 formed in the cylinder head 3. The compressed air compressed by the compressor (not shown) of the turbocharger 14 is supplied to the combustion chamber 1 through the intake pipe 12 and the intake port 9 communicating with the compressor (not shown) of the turbocharger 14. The intake pipe 12 is connected to an intake port 9 formed in the cylinder head 3.

The EGR pump 20 divides exhaust gas from the exhaust pipe 45 to the EGR pipe 11 and
The cooling device 17 operates to apply a pressing force so as to open the valve 6, and the cooling device 17 increases the amount of EGR supplied to the combustion chamber 1 by reducing the temperature expansion of the exhaust gas.
To reduce the compression end pressure, the exhaust gas diverted to the EGR pipe 11 is cooled. The exhaust pipe 12 downstream of the turbocharger 14 is provided with an exhaust muffler 16 to reduce noise generated by the flow of exhaust gas. Cooling device 17
Although not shown in detail, for example, it is configured as a kind of heat exchanger having a structure for removing heat from exhaust gas by cooling air supplied by a cooling fan or the like or cooling water supplied by a cooling pump or the like. ing.

This diesel engine is particularly suitable for EGR
The electromagnetic force driving device for driving the valve 6 is characterized. The electromagnetic driving device includes an electromagnet 4 disposed on the upper surface 39 of the cylinder head 3 around the valve stem 21 of the EGR valve 6.
2 and a magnetically permeable member 41 attached to the end 43 of the valve stem 21 of the EGR valve 6 and attracted to the electromagnet 42. The magnetically permeable member 41 constitutes a valve spring retainer 44 serving as a seating surface of the valve spring 25 for returning the EGR valve 6. The valve spring 25 is disposed between the upper surface 39 of the cylinder head 3 and the magnetically permeable member 41 of the valve spring retainer 44. The electromagnet 42 is attached to the suction core 3 fixed to the upper surface 39 of the cylinder head 3 around the valve stem 21 of the EGR valve 6.
7 and a coil 38 wound around the suction core 37. Coil 38 by command of controller 10
Due to the electromagnetic force generated in the attraction core 37 due to the power supply to the attraction core 37, the attraction core 37 attracts the magnetically permeable member 41 and the EGR valve 6 is maintained in the open state.

As shown in FIG. 3, the EGR valve 6 lifts from the initial stage of the intake stroke to about 90 ° after the top dead center of the intake stroke to supply exhaust gas to the combustion chamber 1. In addition, the intake valve 7
Lifts from about 70 ° after the top dead center of the intake stroke to about 50 ° after the bottom dead center of the compression stroke to supply the compressed air compressed by the compressor to the combustion chamber 1. Therefore, in this diesel engine, the EGR valve 6 lifts up to about 90 ° after the top dead center of the intake stroke from the beginning of the intake stroke to supply the cooling exhaust gas for EGR to the combustion chamber 1, and then the intake valve 7 operates the intake stroke The intake port 9 is communicated with the combustion chamber 1 by lifting from about 70 ° after top dead center to about 50 ° after bottom stroke of the compression stroke, and compressed air is supplied to the combustion chamber 1 and the injection hole of the fuel injection nozzle 2 is formed. 32
A part of the fuel is injected into the combustion chamber 1 from the combustion chamber. Further, the fuel injection nozzle 2 is operated by an electromagnetic drive device or the like in a period from the latter half of the suction stroke to the first half of the compression stroke according to a command from the controller 10 to open the injection hole 32 and supply fuel from the fuel source to the combustion chamber 1 through the fuel passage to the combustion chamber 1. Supply. Further, the exhaust valve 35 (FIG. 2) lifts in the exhaust stroke to lift the combustion chamber 1 and the exhaust port 2.
7 through which the exhaust gas existing in the combustion chamber 1 is exhausted.
Discharge to 3.

This diesel engine has an EGR pipe 11
An exhaust pressure control valve 18 is provided in the exhaust pipe 45 downstream of the branch 40 connected to the exhaust pipe 45 to adjust the amount of EGR sent to the EGR pipe 11. Exhaust pressure control valve 18
Is operated by an actuator 19 so as to adjust the amount of EGR cooling exhaust gas supplied to the combustion chamber 1 in accordance with an engine operating state such as an engine load in accordance with a command from the controller 10. Further, the controller 10 can be configured to control the operation of the fuel injection nozzle 2 in order to adjust the amount of fuel supplied to the combustion chamber 1 according to the engine operating state such as the engine load. That is, the controller 10
Is a flow rate of fuel injected from the fuel injection nozzle 2 into the combustion chamber 1 in response to a detection signal of an engine operation state from a load sensor 30 for detecting an engine load, a rotation sensor 31 for detecting an engine speed, and the like. The operation state of the motor / generator provided in the charger 14, the opening / closing amount of the exhaust control valve 18, the operation of the motor provided in the EGR cooling device 17,
The operation of the GR pump 20 can be appropriately controlled.

The controller 10 controls the amount of exhaust gas supplied to the combustion chamber 1 by the EGR device, that is, the amount of EGR, reduces the amount of exhaust gas supplied to the intake from a low load to a high load, and exhausts the exhaust gas at full load. It is set to perform control to reduce the gas amount. Therefore, the controller 10 performs control to increase the intake air amount by an amount commensurate with the reduction of the EGR amount in order to perform control to appropriately increase the air amount as the engine load increases. In this diesel engine, for example, as shown in FIG. 6, the EGR rate of the exhaust gas supplied from the EGR port 8 to the combustion chamber 1 becomes 50% in a full load state and becomes less than 1/2 load in a load state. It is controlled by the engine load to be 70%. EGR pipe 1 connected to EGR port 8
1 is connected to a branch portion 40 of a discharge pipe 45 downstream of the turbocharger 14. An exhaust muffler 16 is provided in a discharge pipe 45 downstream of the branch 40, and the exhaust pipe 45 downstream of the exhaust muffler 16 is provided with an EG to be sent to an EGR port.
An exhaust control valve 18 is provided to adjust the R amount.

As shown in FIG. 2, the EGR port 8 communicating with the EGR pipe 11 is formed as a tangential port, and the intake port 9 communicating with the intake pipe 12 is formed as a helical port. Therefore, the cooling exhaust gas supplied from the EGR pipe 11 to the combustion chamber 1 through the EGR port 8 and the combustion chamber 1 from the intake pipe 12 through the intake port 9.
The compressed air supplied to the combustion chamber 1 intersects with each other in a pattern in which the compressed air exists on the outer periphery of the cooling exhaust gas in the combustion chamber 1 to promote mixing, thereby generating a uniform mixture.

Since this diesel engine is configured as described above, it is operated as follows. This diesel engine has, for example, a suction stroke, a compression stroke,
It is driven by repeating four cycles of an expansion stroke and an exhaust stroke. In this diesel engine, as shown in FIG. 3, the controller 10 injects fuel from the fuel injection nozzle 2 into the combustion chamber 1 near the top dead center of the compression stroke at the time of engine start, and from the latter half of the intake stroke at the time of driving other than the engine start. A part of the fuel is injected from the fuel injection nozzle 2 into the combustion chamber 1 in the initial period of the compression stroke (FIG. 4), and then the remaining fuel is injected near the top dead center of the compression stroke to perform ignition combustion. (FIG. 5). When the engine is in the rated operation state after the start of the engine, the controller 10 controls the operation of the exhaust control valve 18 and supplies EGR to the combustion chamber 1 through the cooling device 17 as shown in FIG. Control of the amount of cooling exhaust gas for
% Of the cooling exhaust gas is supplied to the combustion chamber 1. When the engine load exceeds 1/2 load, the controller 10
While reducing the amount of cooling exhaust gas, the amount of intake air is increased and the supply of O ₂ accompanying the load is controlled. At a full load of 4/4 load, the amount of cooling exhaust gas is reduced to about 50% and suction is performed. Control is performed to reduce the amount of air to 50%.

The operation of this diesel engine is, for example, as follows. In the suction stroke in which the piston 5 descends in the cylinder 15, the exhaust valve 35
7 is closed, when EGR gas is sent from the EGR pipe 11 to the EGR port 8 in the first half of the suction stroke, the EGR gas pressure acts on the surface of the valve head of the EGR valve,
The EGR valve 6 lifts against the spring force of the valve spring 25, the EGR port 8 opens to the combustion chamber 1, and the magnetically permeable member 41 of the valve spring retainer 44 descends toward the adsorption core 37. Controller 10
The coil 38 is energized by the command (1), and an electromagnetic force is generated in the suction core 37. Therefore, the suction core 37 sucks the magnetically permeable member 41 of the valve spring retainer 44 that has been lowered, and holds the EGR valve 6 in the open state. Therefore, cooling exhaust gas for EGR is supplied from the discharge pipe 45 to the combustion chamber 1 through the EGR pipe 11 and the EGR port 8. Then,
When the piston 5 is lowered and the latter half of the suction stroke, the energization of the coil 38 is stopped by a command from the controller 10,
The EGR valve 6 is returned by the spring force of the valve spring 25 to close the EGR port 8, and the intake valve 7 is lifted from the middle of the intake stroke to the beginning of the compression stroke, so that the compressed air flows from the compressor of the turbocharger 14 to the intake pipe 12 and Compressed air is supplied to the combustion chamber 1 through the intake port 9, while the fuel injection nozzle 2 is operated and the combustion chamber 1
Injected to

In the compression stroke, the piston 5 moves up in the cylinder 15 and the cooling exhaust gas for EGR, a part of the fuel and the compressed air supplied to the combustion chamber 1 are compressed while being mixed. Until near the top dead center of the compression stroke, the O ₂ concentration is low, the temperature in the cylinder is still low, and the fuel is not supplied to the equivalent ratio, so that the mixture does not self-ignite and knocking does not occur. Near the top dead center of the compression stroke,
When the fuel injection nozzle 2 is actuated and fuel is injected from the injection hole 32, a mixture of cooling exhaust gas, a part of fuel, and compressed air compressed in the combustion chamber 1 promotes mixing and ignites. Burn. Therefore, while the piston 5 is pushed down by the combustion gas pressure of the combustion chamber 1, the combustion in the combustion chamber 1 of the fuel is promoted, NO _X, together with the combustion is completed in a state of suppressing the occurrence of HC, piston 5 The combustion cycle ends by lowering the cylinder 15 and then the piston 5
Reaches the bottom dead center and shifts to the exhaust stroke. The exhaust valve 35 opens the exhaust port 27, the exhaust gas is exhausted from the exhaust pipe 13 through the exhaust port 27, and the exhaust heat energy of the exhaust gas is recovered by the turbine of the turbocharger 14.

[0033]

The diesel engine according to the present invention
As described above, since the system is configured as the two-system intake supply system of the compressed air and the EGR gas, a large amount of the EGR gas can be supplied to the combustion chamber, and the premixing of the EGR cooled exhaust gas, the fuel, and the compressed air is performed. By accelerating and injecting the fuel for ignition, the ignition combustion can be reliably performed, the work of the turbocharger compressor can be reduced by the amount of the EGR exhaust gas, and the supply amount of the cooling exhaust gas and the compressed air can be reduced. The ratio can be easily and properly controlled, and EG
By cooling the R exhaust gas and supplying it to the combustion chamber, the O ₂ supply amount can be reduced to prevent knocking, and the compression end pressure can be reduced to reduce the generation of NO _X.
Further, by supplying the exhaust gas to the combustion chamber by the EGR device, the O ₂ concentration can always be controlled to an appropriate level, and knocking does not occur.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing one embodiment of a diesel engine according to the present invention.

FIG. 2 is a plan view showing a relationship among an EGR port, an intake port, a fuel injection nozzle, and an exhaust port in the diesel engine of FIG.

FIG. 3 shows an EGR valve,
FIG. 3 is a diagram illustrating lift timings of an intake valve, an exhaust valve, and a control valve.

FIG. 4 is a schematic explanatory diagram showing an injection state of premixing fuel into a combustion chamber at an early stage of a suction stroke.

FIG. 5 is a schematic explanatory view showing an injection state of ignition fuel to a combustion chamber near a compression top dead center.

FIG. 6 is a graph showing a relationship between an EGR rate and a load in the diesel engine of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Combustion chamber 2 Fuel injection nozzle 3 Cylinder head 4 Cylinder block 5 Piston 6 EGR valve 7 Intake valve 8 EGR port 9 Intake port 10 Controller 11 EGR pipe 12 Intake pipe 13 Exhaust pipe 14 Turbocharger 15 Cylinder 17 EGR cooling device 18 Exhaust control Valve 20 EGR pump 21 Valve stem 25 Valve spring 37 Adsorption core 38 Coil 39 Cylinder head upper surface 40 Branch portion 41 Magnetically permeable member 42 Electromagnet 43 Valve stem end 44 Valve spring retainer 45 Discharge pipe

Claims (10)

[Claims] A cylinder block to which a cylinder head is fixed, a piston reciprocating in a cylinder provided in the cylinder block, a fuel injection nozzle for injecting fuel into a combustion chamber formed by the piston and the cylinder, A turbocharger provided in an exhaust pipe for discharging exhaust gas from the combustion chamber, an intake port formed in the cylinder head communicating with an intake pipe communicating with a compressor of the turbocharger, and an intake port arranged in the intake port; A valve, an EGR pipe branched from a discharge pipe downstream of the turbocharger, an EGR pump for supplying EGR gas comprising a part of the exhaust gas to the combustion chamber through the EGR pipe,
An EGR port formed in the cylinder head communicating with the EGR pipe, an EGR valve seated on a valve seat of the EGR port and lifted by receiving EGR gas pressure, and an electromagnetic force driving for holding the EGR valve in an open state A diesel engine comprising an EGR device comprising: a device and a valve spring for urging the EGR valve in a direction to close the EGR port. 2. An electromagnet disposed on the cylinder head around a valve stem of the EGR valve, and a magnetically permeable member attached to an end of the EGR valve and attracted to the electromagnet. A diesel engine provided with the EGR device according to claim 1, comprising: 3. The diesel engine according to claim 2, wherein the magnetically permeable member constitutes a valve spring retainer serving as a seating surface of the valve spring for returning the EGR valve. 4. The electromagnet includes an attraction core fixed to the cylinder head around the valve stem of the EGR valve, and a coil wound around the attraction core.
2. The EGR device according to claim 1, wherein the attraction core attracts the magnetically permeable member and the EGR valve is kept open by an electromagnetic force generated in the attraction core by energizing the coil. Equipped diesel engine. 5. The intake valve lifts from about 70 ° after the top dead center of the suction stroke to about 50 ° after the bottom dead center of the compression stroke to supply the compressed air compressed by the compressor to the combustion chamber. The EGR valve supplies the exhaust gas to the combustion chamber from the beginning of the intake stroke to 90 after the top dead center of the intake stroke.
2. The EG according to claim 1, comprising lifting to a degree.
Diesel engine with R device. 6. The EGR pump divides the exhaust gas from the discharge pipe to the EGR pipe,
2. A diesel engine equipped with an EGR device according to claim 1, wherein a pressure can be applied so as to open the R valve, and the exhaust gas diverted to the EGR pipe is cooled by a cooling device. 7. The exhaust gas supplied from the EGR port to the combustion chamber has an EGR rate of 50% at full load.
2. The diesel engine provided with the EGR device according to claim 1, wherein the engine is controlled in response to the engine load so that the load becomes 70% under a load condition of less than 1/2 load. 8. When starting the engine, fuel is injected from the fuel injection nozzle into the combustion chamber near the top dead center of the compression stroke, and at the time of driving other than the start of the engine, the fuel is injected in the late stage of the intake stroke and in the early stage of the compression stroke. 2. The EGR device according to claim 1, wherein a part of the fuel is injected from a fuel injection nozzle into the combustion chamber, and then the remaining amount of fuel is injected near a top dead center in a compression stroke to perform ignition combustion. Equipped diesel engine. 9. The EGR connected to the EGR port
2. The EGR according to claim 1, wherein an exhaust control valve is provided in the exhaust pipe downstream of a branch connected to the exhaust pipe to adjust an amount of EGR sent to the EGR port. Diesel engine with equipment. 10. The EGR port is formed as a tangential port, the intake port is formed as a helical port, and the EGR port of the EGR port in a state in which a part of the fuel supplied to the combustion chamber is wrapped. 2. The EGR device according to claim 1, wherein the compressed air supplied from the helical port of the intake port is supplied to an outer periphery of the cooling exhaust gas supplied from a tangential port to promote the generation of an air-fuel mixture. 3. Equipped diesel engine.