JP2002155765A - White smoke prevention device of diesel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a white smoke prevention device of a diesel engine capable of promoting a temperature raising of an air compressed in a combustion chamber without using a specific heater such as an electric heater and preventing a discharge of a white smoke accompanying an incomplete combustion. SOLUTION: The diesel engine 1 is provided with a combustion chamber 6 for compressing a suction air between a piston 4 and the combustion chamber 6; a fuel injection valve 9 for injecting a pressurized fuel to the combustion chamber; and an exhaust manifold 24 continuously laid on the combustion chamber. A butterfly valve 30 for reducing a passage area of an exhaust port 27 only at the time of low temperature starting is installed on the exhaust manifold.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diesel engine, and more particularly to a device for preventing the emission of white smoke due to poor combustion at a low temperature start.

[0002]

2. Description of the Related Art In a diesel engine, air taken into a combustion chamber is compressed at a high compression ratio, and fuel is injected into high-temperature, high-pressure air due to the compression. The fuel particles injected into the combustion chamber rise in temperature by being heated by the compressed air and evaporate to become an ignitable air-fuel mixture when mixed with air at an appropriate temperature and filled in the combustion chamber.

[0003] Therefore, when the fuel is burned by the heat of air compression as in a diesel engine, the ignitability of the fuel is determined by the ignition delay time from when the fuel is actually injected into the combustion chamber until combustion starts. Has a close relationship with
It has a great effect on the startability of diesel engines.

[0004] Specifically, when the diesel engine is started at a low temperature, the temperature of the air compressed into the combustion chamber is relatively low because the temperature (initial temperature) of the air taken into the combustion chamber is low. And the ignition delay increases. As a result, the ignitability of the fuel at the time of low temperature start is deteriorated, and a problem such as emission of white smoke accompanying incomplete combustion particularly during low load operation including idling occurs.

[0005] As a countermeasure, a diesel engine in which an electric heater is installed in a suction path for guiding air to a combustion chamber is known. In this conventional diesel engine,
By energizing the electric heater at the time of low temperature start and forcibly heating the intake air, the initial temperature of the air taken into the combustion chamber is raised, the temperature rise of the compressed air is promoted, and the ignition delay of the fuel is shortened. I have.

[0006]

However, according to this conventional structure, a special electric heater for heating the air sucked into the combustion chamber is required, so that the structure of the intake system becomes particularly complicated and the cost is increased. It may cause. In addition, during operation of the electric heater, a large current flows through the electric heater, so that an external power supply such as a large-capacity battery must be prepared, and there is still room for improvement in this respect.

The present invention has been made in view of such circumstances, and can promote the temperature rise of air compressed in a combustion chamber without using a special heating device such as an electric heater. It is an object of the present invention to provide a white smoke prevention device for a diesel engine that can prevent the emission of white smoke accompanying incomplete combustion.

[0008]

According to a first aspect of the present invention, there is provided a diesel engine white smoke prevention apparatus for compressing intake air between a piston and a combustion chamber. A fuel injection valve for injecting fuel pressurized into the combustion chamber, and a throttle means provided in an exhaust passage connected to the combustion chamber to reduce a passage area of the exhaust passage at a low temperature start.

According to a fourth aspect of the present invention, there is provided an apparatus for preventing white smoke from a diesel engine, comprising: a combustion chamber for compressing intake air between the piston and a fuel injection for injecting pressurized fuel into the combustion chamber; A throttle valve installed in an exhaust passage connected to the combustion chamber, the throttle valve being operated over an open position that opens the exhaust passage, and a closed position that partially closes the exhaust passage. A drive unit for selectively operating either the open position or the closed position, and detecting whether or not the engine temperature at the time of starting is lower than a predetermined temperature, and when the engine temperature is lower than a specified value, Control means for operating the throttle valve to the closed position via a driving means.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIGS. 1 to 3 disclose a four-cycle three-cylinder diesel engine 1 used for general-purpose machines such as industrial machines, construction machines, and generators. In FIGS. 1 and 3, the cylinder block denoted by reference numeral 2 has three cylinders 3 (only one is shown).
have. The cylinders 3 are arranged at intervals in the axial direction of a crankshaft (not shown), and the pistons 4 are housed inside the cylinders 3.

A cylinder head 5 is connected to an upper end of the cylinder block 2. The cylinder head 5 forms a main combustion chamber 6 in cooperation with the top of the piston 4. A vortex chamber 7 is formed inside the cylinder head 5. The vortex chamber 7 is connected to the main combustion chamber 6 through an injection port 8, and pressurized fuel is injected into the vortex chamber 7 through a fuel injection valve 9.

A water jacket 10 is formed inside each of the cylinder block 2 and the cylinder head 5. The water jacket 10 surrounds the cylinder 3, the main combustion chamber 6, and the vortex chamber 7, and the engine coolant flows through the water jacket 10.

As shown in FIG. 2, the cylinder block 2 supports a single fuel injection pump 11. The fuel injection pump 11 has three discharge ports 12a, 12b, 1
2c. These outlets 12a, 12b, 12
“c” is connected to the fuel injection valve 9 of each cylinder 3 via an injection pipe 13.

As shown in FIGS. 1 and 3, the cylinder head 5 has an intake port 15 and an exhaust port 16 for each cylinder 3. The intake port 15 and the exhaust port 16 are open to the main combustion chamber 6, and the openings 15a, 16 of these ports 15, 16 to the main combustion chamber 6 are provided.
a are arranged in the radial direction of the cylinder 3.

The cylinder head 5 supports an intake valve 17 for opening and closing the opening 15a of the intake port 15 and an exhaust valve 18 for opening and closing the opening 16a of the exhaust port 16. Intake valve 17 and exhaust valve 18
Are arranged parallel to each other along a bore center line O1 of the cylinder 3. The intake valve 17 and the exhaust valve 18 are linked to a cam shaft 22 for intake and exhaust via a rocker arm 19, a push rod 20, and a tappet 21, respectively.

Therefore, when the camshaft 22 is driven to rotate by the transmission of power from the crankshaft, the rocker arm 19 swings via the tappet 21 and the push rod 20, and the rocker arm 19 causes the intake valve 17 to swing.
And the exhaust valve 18 is driven to open and close.

As shown in FIG. 1, the intake port 15 and the exhaust port 16 extend in opposite directions with respect to the bore center line O1 of the cylinder 3 and are opened on the side surfaces of the cylinder head 5, respectively. The upstream end of the intake port 15 is connected to an intake pipe 23, and the downstream end of the exhaust port 16 is connected to an exhaust manifold 24 as an exhaust passage.

The exhaust manifold 24 is connected to the exhaust port 16.
Branch pipe parts 25a, 25b, 25c connected to the downstream end of
And one collecting pipe 26 to which the downstream ends of the branch pipes 25a, 25b, 25c are joined. The collecting pipe section 26 has one exhaust outlet 27 opened upward. The passage of the exhaust outlet 27 has a circular cross section, and an exhaust pipe 28 is connected to the exhaust outlet 27.

At the exhaust outlet 27 of the exhaust manifold 24, a butterfly valve 30 as a throttle valve (throttle means) is provided. The butterfly valve 30 includes a disk-shaped disk 31 and a pivot shaft 32 fixed to the disk 31.
And The pivot shaft 32 passes through the center of the disk 31 and penetrates the disk 31 in the radial direction. Both ends of the pivot shaft 32 are rotatably supported by the collecting pipe portion 26 of the exhaust manifold 24. ing.

Therefore, the disk 3 of the butterfly valve 30
1 is a closed position for closing the exhaust outlet 27 as shown in FIG. 4A, and an exhaust outlet 27 as shown in FIG.
Is rotated by 90 ° over a closed position where the shutter is opened.

The disk 31 has a circular through hole 33 at a position avoiding the pivot shaft 32. Through hole 33
When the disk 31 is turned to the closed position, the upstream side and the downstream side of the disk 31 communicate with each other. Therefore, due to the presence of the through hole 33, the disk 31 only partially closes the exhaust outlet 27 even when rotated to the closed position. In the case of the present embodiment, the disk 31 is turned to the closed position. When moved, the passage area of the exhaust outlet 27 is reduced to 1/6.

As shown in FIGS. 4 and 5, one end of the pivot shaft 32 projects outside the exhaust manifold 24. One end of the pivot shaft 32 is linked to a valve driving device 35 as driving means. Valve drive 35
Is for selectively holding the disk 31 of the butterfly valve 30 at either the closed position or the open position. The valve drive device 35 includes an electromagnetic solenoid 36 as a drive source, and a link mechanism 37 that transmits the movement of the electromagnetic solenoid 36 to the pivot shaft 32.

The electromagnetic solenoid 36 has an armature (not shown) which is linearly reciprocated by an electromagnet. Further, the link mechanism 37 is connected to the control lever 3.
8 and a relay rod 39. The control lever 38 has one end fixed to the pivot shaft 32 and the other end connected to a relay rod 39 via a pin 40.
It is connected to the tip of. The base end of the relay rod 39 is connected to the armature of the electromagnetic solenoid 36.

Therefore, when the electromagnetic solenoid 36 is excited, the movement of the armature is transmitted from the relay rod 39 to the pivot shaft 32 of the butterfly valve 30 via the control lever 38, and the disk 31 of the butterfly valve 30 is opened. To the closed position. When the excitation of the electromagnetic solenoid 36 is released, the relay rod 39 is pushed back by a return spring (not shown) incorporated in the electromagnetic solenoid 36, and the disk 31
Are rotated from the closed position to the open position.

As shown in FIG. 5, the electromagnetic solenoid 36
Is excited based on a signal output from a controller 43 as a control means. The controller 43 controls the electromagnetic solenoid 36 when the diesel engine 1 is started at a low temperature.
A signal S1 indicating the temperature of the diesel engine 1 is input to the controller 43. In the present embodiment, the temperature of the engine cooling water flowing through the water jacket 10 is detected by the water temperature sensor 44,
The temperature of the engine cooling water is used as the signal S1.

The controller 43 determines that the diesel engine 1 is in a low temperature starting state when the temperature of the engine cooling water at the time of starting the engine is lower than 50 ° C., and sends an excitation signal S 2 to the electromagnetic solenoid 36. ing.

That is, as shown in the flowchart of FIG. 6, the controller 43 sets the main switch (not shown) of the diesel engine 1 in the first process P1.
When it is turned ON, the actual temperature of the engine cooling water is detected via the water temperature sensor 44 in a second step P2. The temperature of the engine cooling water is a value (50 ° C.) determined as a reference of the engine temperature at the time of starting the engine in the third process P3.
Is compared to And the temperature of the actual engine cooling water
When the temperature is lower than 50 ° C., it is determined that the diesel engine 1 is in the low temperature starting state, and the process shifts to the fourth step P4.
In this fourth step P4, the excitation signal S2 is
From the electromagnetic solenoid 36 to the electromagnetic solenoid 3
6 is excited. Therefore, the disk 31 of the butterfly valve 30 is rotated from the open position to the closed position via the link mechanism 37, and the exhaust outlet 27 of the exhaust manifold 24 is
Passage area is reduced to 1/6.

In the third step P3, if the temperature of the engine cooling water exceeds 50 ° C., the controller 43
Determines that the diesel engine 1 is in a warm state, and stops sending the excitation signal S2 to the electromagnetic solenoid 36.
Shifts to step P5. Therefore, the butterfly valve 30 rotates from the closed position to the open position, and the passage area of the exhaust outlet 27 is maximized.

In the diesel engine 1 having such a configuration, the air drawn into the main combustion chamber 6 from the intake port 15 is compressed by the piston 4 during the compression stroke, and a part of the air is drawn from the injection port 8 to the vortex chamber 7. Into the vortex chamber 7
Generates a strong swirl inside. When the pressurized fuel is injected into the vortex chamber 7 through the fuel injection valve 9, most of the fuel is mixed with the compressed air and burns in the vortex chamber 7, and includes some unburned fuel. The combustion gas is blown out from the injection port 8 into the main combustion chamber 6 and completely burns in the main combustion chamber 6.

Then, the burned gas whose combustion has been completed is discharged from the exhaust manifold 24 to the atmosphere via the exhaust pipe 28 when the exhaust port 16 is opened in the exhaust stroke.

When the diesel engine 1 is started at a low temperature, since the temperature of the air taken into the main combustion chamber 6 is low as described in the background art, the air is compressed in the main combustion chamber 6 and the vortex chamber 7 is compressed. The temperature of the compressed air flowing into the tank decreases, and the ignitability of the fuel deteriorates.

However, in the diesel engine 1 having the above-described configuration, the temperature of the diesel engine 1 at the time of starting is detected from the temperature of the engine cooling water.
When the temperature does not reach ℃, the butterfly valve 30 is rotated to the closed position to release the exhaust outlet 27 of the exhaust manifold 24.
Passage area is reduced to 1/6.

Therefore, during the start-up process of the diesel engine 1, the high-temperature burned gas discharged from the main combustion chamber 6 to the exhaust manifold 24 becomes difficult to escape, and a part of the high-temperature burned gas is removed from the main combustion chamber. 6 and exhaust manifold 24
To stay in.

As a result, the temperature of the cylinder head 5 including the main combustion chamber 6 rises in a short time due to the thermal influence of the burned gas, and the air sucked into the main combustion chamber 6 from the intake port 15 during the intake stroke. Is heated. At the same time, the volume efficiency of the intake air decreases due to the retention of the burnt gas, and the excess air ratio decreases.

Therefore, the initial temperature of the intake air is increased by an amount corresponding to the influence of the heat of the burned gas on the intake air, so that the temperature of the compressed air compressed during the compression stroke rises, and the fuel actually enters the vortex chamber 7. The ignition delay time from the injection to the start of combustion is reduced. Therefore, even at the time of the low temperature start, the ignitability of the fuel can be maintained satisfactorily, and the emission of white smoke accompanying incomplete combustion can be prevented.

It should be noted that the inventor of the present invention has proposed a four-cycle three-cylinder diesel engine having a bore of 70 mm, a stroke of 70 mm, and a displacement of 808 cc, in a case where the butterfly valve 30 is installed in the exhaust manifold 24 and in a case where the butterfly valve 30 is not installed. The generation status of white smoke at low temperature start was verified. As a result, in the standard diesel engine, it took 90 seconds from the start of the engine to the disappearance of the white smoke. On the other hand, in the diesel engine 1 of the present invention in which the butterfly valve 30 was installed in the exhaust manifold 24, It was confirmed that white smoke disappeared 18 seconds after the engine 1 was started.

As is clear from the verification results, by narrowing the exhaust outlet 27 of the exhaust manifold 24 at the time of low temperature starting, the temperature rise of the air taken into the main combustion chamber 6 due to the thermal influence of the burned gas is reduced. It can be seen that the ignitability of the fuel is enhanced by being promoted.

Further, according to the above configuration, a part of the burned gas is retained in the main combustion chamber 6 and the exhaust manifold 24, so that the temperature of the intake air at the time of low temperature starting can be increased. It is not necessary to install an electric heater in
Even if an electric heater is dared to be installed, the electric heater need only generate a small amount of heat. Therefore, there is an advantage that the power supply capacity of the electric heater can be reduced, which is advantageous in terms of cost.

In the above-described embodiment, the butterfly valve is provided in the collecting pipe of the exhaust manifold. However, the present invention is not limited to this. For example, the butterfly valve is provided in each of a plurality of branch pipes of the exhaust manifold. And the butterfly valves may be linked to each other, or a butterfly valve may be installed in an exhaust pipe connected to the collecting pipe section of the exhaust manifold.

The throttle means for opening and closing the exhaust passage of the diesel engine is not limited to the butterfly valve, but may be another type of valve.

Further, in the diesel engine according to the present invention, the type of the combustion chamber is not limited to a sub-chamber type having a vortex chamber, but may be, for example, a pre-combustion chamber type or a type in which fuel is transferred to a piston head and a cylinder head. Single-chamber type that directly injects air between the two.

[0042]

According to the present invention described in detail above, since the passage area of the exhaust passage is forcibly reduced only at the time of low-temperature start, the high-temperature combustible discharged from the combustion chamber to the exhaust passage during the exhaust stroke. Gas escape becomes worse, and a part of the burned gas stays in the combustion chamber and the exhaust passage. Therefore, the temperature of the combustion chamber rises in a short time due to the thermal influence of the burned gas,
The temperature rise of the air sucked into the combustion chamber during the suction stroke is promoted, and the volume efficiency of the suction air is reduced due to the retention of the burned gas, and the excess air ratio is reduced.

As a result, the temperature (initial temperature) of the air taken into the combustion chamber can be increased without having to install a special heating device such as an electric heater in the intake system, and accordingly, the compression during the compression stroke can be increased. The temperature of the compressed air thus generated rises, and the ignition delay time from when fuel is actually injected into the combustion chamber to when combustion starts is shortened. Therefore, there is an advantage that the ignitability of the fuel can be favorably maintained even at the time of a low temperature start, and the emission of white smoke accompanying incomplete combustion can be prevented.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a diesel engine having an exhaust manifold incorporating a butterfly valve.

FIG. 2 is a sectional view of the diesel engine taken along the line 2F-2F in FIG. 1;

FIG. 3 is a plan view of a diesel engine.

FIG. 4A is a plan view of an exhaust manifold showing a state where a butterfly valve is turned to a closed position. (B) is a top view of an exhaust manifold showing a state where a butterfly valve was turned to an open position.

FIG. 5 is a block diagram schematically showing a drive path of a butterfly valve.

FIG. 6 is a flowchart showing the opening / closing timing of a butterfly valve.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Diesel engine 4 ... Piston 6 ... Combustion chamber (main combustion chamber) 9 ... Fuel injection valve 24 ... Exhaust passage (exhaust manifold) 30 ... Throttle means, throttle valve (butterfly valve) 35 ... Drive means (valve drive device) 43 ... Control means (controller)

Claims (5)

[Claims] A combustion chamber for compressing intake air between the piston and a piston; a fuel injection valve for injecting fuel pressurized into the combustion chamber; and an exhaust passage connected to the combustion chamber; A white smoke prevention device for a diesel engine, comprising: throttle means for reducing a passage area of an exhaust passage. 2. A butterfly valve according to claim 1, wherein said throttle means has a disk-shaped disk rotatable between a closed position for closing said exhaust passage and an open position for opening said exhaust passage. Wherein the disk of the butterfly valve has a through hole for communicating the upstream side and the downstream side of the disk when rotated to the closed position, wherein the white smoke prevention device for a diesel engine is provided. . 3. The method according to claim 1, wherein
The exhaust passage is an exhaust manifold having a plurality of branch pipes connected to the plurality of combustion chambers, and a single collecting pipe section in which the downstream ends of the branch pipes are merged with each other. An apparatus for preventing white smoke of a diesel engine, wherein the above-mentioned throttling means is provided in a collecting pipe portion. 4. A combustion chamber for compressing intake air with a piston, a fuel injection valve for injecting fuel pressurized into the combustion chamber, and an exhaust passage installed in an exhaust passage connected to the combustion chamber. A throttle valve that is operated over an open position to open the throttle valve, a closed position that partially closes the exhaust passage, and a drive unit that selectively operates the throttle valve to either the open position or the closed position. Detecting whether or not the engine temperature at the time of starting is lower than a predetermined temperature, and controlling the throttle valve to the closed position via the driving means when the engine temperature is lower than a predetermined value. And a means for preventing white smoke of a diesel engine. 5. The control means according to claim 4, wherein said control means includes a sensor for detecting an actual engine temperature from a temperature of the engine cooling water, and based on the temperature of the engine cooling water, the throttle valve closes or closes. A white smoke prevention device for a diesel engine, wherein the driving unit is controlled so as to be located at one of the open positions.