JP2995427B2 - Secondary combustion chamber diesel 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 sub-combustion chamber type diesel engine for reducing the emission of nitrogen oxides (NOx) contained in exhaust gas in all load ranges.

[0002]

2. Description of the Related Art In a conventional auxiliary combustion chamber type diesel engine, the amount of air in the auxiliary combustion chamber at the time of compression is set to be about 50% of the air amount in the entire combustion chamber. And
At the end of the compression stroke, the fuel injected into the sub-combustion chamber mixes with the air in the sub-combustion chamber and starts combustion, so that the inside of the sub-combustion chamber is in a high temperature and high pressure state. The combustion gas and the unburned gas in the sub-combustion chamber are ejected to the main combustion chamber via the injection holes, and secondary mixed with the air in the main combustion chamber to continue combustion. When the combustion continues in the main combustion chamber, the combustion temperature is maintained at a low temperature because the piston is in the process of lowering and the volume of the main combustion chamber is expanding.

[0003] Therefore, since only 50% of the total air is present in the sub-combustion chamber in which fuel is injected, the equivalence ratio (the ratio of fuel to the amount of air) in the sub-combustion chamber increases, and the amount of fuel in the main combustion chamber increases. Since the combustion is continued in a low temperature state, compared with a direct injection diesel engine having no auxiliary combustion chamber, NO
The generation of x is suppressed, and the emission amount of NOx contained in the exhaust gas is significantly reduced.

In such a conventional auxiliary combustion chamber type diesel engine, when the load is high, that is, when the fuel injection amount is large, the emission amount of NOx is reduced as described above. At the time of load, that is, when the fuel injection amount is small, the equivalent ratio in the sub-combustion chamber does not become large, and therefore, the effect of suppressing the generation of NOx is not exhibited.
There is a problem that the emission amount of NOx does not decrease.

A method of reducing the amount of NOx emission by recirculating a part of exhaust gas from the engine to the intake side (exhaust gas recirculation: EGR) is known. Although the emission amount of NOx decreases, the emission amount of hydrocarbons (HC) and black smoke increases.

The present invention has been made in view of the above problems, and effectively suppresses the generation of NOx even when the load is not high.
It is an object of the present invention to provide a sub-combustion chamber type diesel engine which aims to reduce NOx emission in all load regions.

[0006]

SUMMARY OF THE INVENTION To solve the above problems, the present invention relates to a sub-combustion chamber type diesel engine having a sub-combustion chamber which communicates with a main combustion chamber via an injection hole. Opening / closing valve, injection amount detecting means for detecting that the amount of fuel injected into the sub-combustion chamber is equal to or more than a predetermined value, and top dead when the rotational phase of the engine shifts from the compression stroke to the expansion stroke. A phase detecting means for detecting that the position is within a predetermined range including a point, and a valve opening / closing means for opening / closing the opening / closing valve when inputting a detection signal from at least one of the two detecting means. When the fuel injection amount is lower than a predetermined value, and the position detection means detects that the fuel injection amount is not within a predetermined range including the top dead center at the time of transition from the compression stroke to the expansion stroke, the valve opening / closing means sets the injection hole. Shut off Providing auxiliary combustion chamber type diesel engine, characterized in that allowed to seal the exhaust gas to the auxiliary combustion chamber.

[0007]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a partial sectional view showing a structure around a cylinder head of a diesel engine for a sub-combustion chamber according to the present invention.

Reference numeral 1 denotes an engine body. Inside the engine body 1, a cylinder sleeve 11 made of a heat-resistant and heat-insulating material such as silicon nitride is provided. Above the cylinder sleeve 11, an intake valve 12 for opening and closing an intake port is provided. And an exhaust valve 13 for opening and closing the exhaust port.

An inner peripheral surface of an exhaust pipe, which is a passage of exhaust gas discharged through the exhaust valve 13, has a port liner 14 made of aluminum titanate or the like having excellent heat insulation.
Covered by

Reference numeral 2 denotes a piston slidably provided inside the cylinder sleeve 11. The head surface of the piston 2 is covered with the same heat insulating material as that of the cylinder sleeve 11. Sleeve 11
The main combustion chamber 21 is formed by this space.

Reference numeral 3 denotes a sub-combustion chamber formed of the same heat insulating material as that of the cylinder sleeve 11;
1 is communicated via an injection hole 32, and the injection hole 32 is opened and closed by an opening / closing valve 31. Reference numeral 33 denotes a fuel injection nozzle for injecting fuel into the sub-combustion chamber 3. The open / close valve 31 is formed of a ceramic such as silicon nitride, which is a high-strength material having excellent heat resistance.

Reference numeral 4 denotes a valve driving device, which is an open / close valve 3
The opening / closing valve 31 is connected to the shaft end of the shaft 1 and freely driven to open and close by a control signal from the controller 5.

The controller 5 includes an input / output interface for controlling the input and output of signals to and from the outside, a ROM for storing programs and various data in advance, a CPU for performing calculations based on the programs stored in the ROM, the calculation results and input data. , A control memory for controlling the flow of signals inside the controller 5, and the like. The valve drive device 4 and the flow sensor 51 are connected to the input / output interface.

The flow sensor 51 detects a fuel injection amount Q injected from the fuel injection nozzle 33 into the sub-combustion chamber 3 and inputs the detected fuel injection amount Q to the controller 5. A phase sensor 52 detects the rotation phase T of the engine and inputs the detected rotation phase T to the controller 5.

FIG. 2 is a view showing an example of the structure of the valve driving device 4. Referring to FIG. 2, the structure will be described. A movable magnetic pole 41 made of a magnetic material is provided above the shaft of the opening / closing valve 31.
Is installed. A fixed electromagnet 42 is provided at a position corresponding to the lower surface of the movable magnetic pole 41,
As the movable magnetic pole 41 is attracted by the fixed electromagnet 42, the opening / closing valve 31 is driven in the opening direction.

The movable magnetic pole 41 is biased in the closing direction by a spring 44 via a sleeve 43. When the fixed electromagnet 42 is de-energized by a control signal from the controller 5, the bias force of the spring 44 acts. The opening / closing valve 31 is driven in the closing direction.

Reference numeral 45 denotes a damper, which is an open / close valve 3
Immediately before the seat 1 is closed, air is blocked by the shaft end of the opening / closing valve 31 to reduce seating shock. Since the sealed air is discharged from the pipe 47 through the variable throttle 46, the variable throttle By adjusting the throttle amount of 46, the amount of relaxation of the seating impact can be adjusted. Further, when the open / close valve 31 is opened, the air flows backward through the check valve 48, so that there is no resistance to the opening operation.
This figure shows a state in which the open / close valve 31 is open.

FIG. 3 is a diagram showing a change in the pressure in the combustion chamber and the timing of opening and closing the valve. FIG. 4 is a diagram showing a control flow of the opening and closing valve. The operation of the present embodiment will be described with reference to these drawings.

When the control flow starts as shown in FIG. 4, first, in step 1, the fixed electromagnet 42 is excited, and the open / close valve 31 is opened. Next, in step 2, the fuel injection amount Q is detected by the flow rate sensor 51, and in step 3, the detected fuel injection amount Q is compared with a predetermined value Q1.
In the case of Q1, that is, in the case of a low load, the process proceeds to step 4. In the case of Q ≧ Q1, ie, in the case of a high load, the process returns to step 1 above. Operates as a diesel engine.

If the load is lower than the predetermined load, the rotational phase T of the engine is detected in step 4 and if the rotational phase T is after the closing timing Tc of the on-off valve 31 or before the opening timing To of the on-off valve 31, Step 7
Then, the fixed electromagnet 42 is de-energized, and the on-off valve 31 is closed. Then, the process returns to step 4 to keep the open / close valve 31 in the closed state until T becomes between To and Tc. When T reaches between To and Tc, the process returns to step 1 to open the on-off valve 31.

The pressure in the combustion chamber when the load is lower than the above-mentioned predetermined load will be described with reference to FIG. 3.
Is reached Tc, the open / close valve 31 is closed. Then, the combustion gas remains closed in the sub-combustion chamber 3 and the internal pressure is maintained at Ps.

After the opening and closing valve 31 is closed, the exhaust gas and the intake gas are exchanged by the normal operation of the exhaust valve 13 and the intake valve 12, and the process shifts to the compression stroke. When the rotation phase T reaches To in the middle of the compression stroke, the on-off valve 31 is opened and the air in the main combustion chamber 21 flows into the sub-combustion chamber 3.

Since the exhaust gas remains in the sub-combustion chamber 3, the amount of air flowing into the sub-combustion chamber 3 is limited. Therefore, the equivalence ratio inside the sub-combustion chamber 3 does not decrease even when the load is low. The on-off valve 31 has a rotation phase T
Is held open until the next Tc timing.

The above To is 1 before the top dead center of the piston.
Between 40 and 40 degrees, Tc is between 14 and 60 degrees after top dead center.
Each is set between 0 degrees.

Further, in the engine according to the present embodiment, the main combustion chamber 21, the sub-combustion chamber 3, and the exhaust pipe are insulated from the outside, so that the temperature of the exhaust gas becomes high and the energy of the exhaust gas becomes high. Is effectively collected by a turbocharger (not shown) or the like.

Although the above embodiment employs an electromagnetically driven on-off valve as shown in FIG. 2, the operation of the on-off valve is selectively controlled by a hydraulic control valve using a mechanical cam or rocker arm. It is also possible.

In the above, the embodiments of the present invention have been described in detail, but unless departing from the spirit of the present invention,
Since various different embodiments can be readily constructed, the invention is not limited to any particular embodiment except for the limitations set forth in the appended claims.

[0029]

As described above, according to the present invention,
Since the exhaust gas remains in the sub-combustion chamber when the load is lower than the predetermined load, the equivalence ratio in the sub-combustion chamber is not reduced, so that the NOx emission can be reduced.

Since the opening / closing valve 31 is driven by electromagnetic force so that the opening / closing timing can be freely changed, the opening / closing timing can be changed by changing the load, and the amount of residual exhaust gas can be increased or decreased.

Further, since the exhaust gas immediately after the combustion remains, the temperature inside the sub-combustion chamber 3 rises and the startability is improved, so that the compression ratio can be set low. In particular, in the case of an insulated engine with a combustion chamber insulated, it is necessary to increase the amount of intake air to suppress the rise in combustion temperature. The advantage that the startability is improved by applying the invention is obtained.

Further, since the exhaust gas remains only in the sub-combustion chamber 3 and does not remain in the main combustion chamber 21, the effect of suppressing the generation of HC and black smoke can be obtained.

[Brief description of the drawings]

FIG. 1 is a partial sectional view of an engine according to the present invention.

FIG. 2 is a structural view of a valve driving device.

FIG. 3 is a diagram showing a change in pressure in a combustion chamber and opening / closing timing of a valve.

FIG. 4 is a diagram showing a control flow of an opening / closing valve.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Engine main body 2 ... Piston 3 ... Sub combustion chamber 4 ... Valve drive device 5 ... Controller 21 ... Main combustion chamber 31 ... Open / close valve 32 ... Injection hole 51 ... Flow rate sensor 52 ... Phase sensor.

Claims (4)

(57) [Claims] 1. A sub-combustion chamber type diesel engine having a sub-combustion chamber communicating with a main combustion chamber via an injection hole, an opening / closing valve for opening and closing the injection hole, and injection of fuel injected into the sub-combustion chamber. Injection amount detection means for detecting that the amount is equal to or more than a predetermined value, and phase detection means for detecting that the rotational phase of the engine is within a predetermined range including the top dead center at the time of transition from the compression stroke to the expansion stroke. Valve opening / closing means for opening / closing the opening / closing valve at the time of inputting a detection signal from at least one of the two detection means, the valve opening / closing timing being variable. When the fuel injection amount is lower than a predetermined value, the position detection is performed. When the means detects that it is not within the predetermined range including the top dead center at the time of transition from the compression stroke to the expansion stroke, the valve opening / closing means closes the injection hole and seals the exhaust gas into the sub-combustion chamber. Feature Combustion chamber diesel engine. 2. The sub-combustion chamber diesel engine according to claim 1, wherein said on-off valve is made of heat-resistant ceramic and can be freely opened and closed. 3. The sub-combustion chamber diesel engine according to claim 1, wherein the inner walls of the sub-combustion chamber and the main combustion chamber are formed of a heat insulating material or a heat-resistant material. 4. A predetermined range including the top dead center is one before the top dead center.
The auxiliary combustion chamber type diesel engine according to claim 1, wherein the temperature is 40 degrees to 140 degrees after the top dead center.