JPH0436011A - Exhaust gas purifying device for cylinder gasoline injection type internal combustion engine - Google Patents

Abstract

PURPOSE:To restrict the discharge amount of nitrogen oxides-elements to prevent contamination of a catalytic converter by detecting an excess air factor, thereafter introducing exhaust gas to the catalytic converter when the excess air factor is in a specified range, and allowing exhaust gas to bypass the catalytic converter when the excess air factor is out of the specified range. CONSTITUTION:When an excess air factor sensor 108 detects an excess air facter lambda, and lambda<lambda0 or lambda>lambda1 is established, a solenoid valve 100 is turned off, and a bypass valve 94 closes a bypass passage 92. Thus, the total amount of exhaust gas is introduced to a catalytic converter 23. When lambda0<=lambda<=lambda1 is established, the solenoid valve 100 is turned on, and the bypass valve 94 opens the bypass passage 92. Thus, the total amount of exhaust gas is introduced to the bypass passage 92, but not introduced to the catalytic converter 23. As a result, purification of exhaust gas is efficiently performed to enhance the durability of the catalytic converter.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to an exhaust gas purification device for a cylinder gasoline internal combustion engine that uses light oil as an auxiliary fuel for ignition and gasoline as a main fuel.

[Conventional technology]

The present applicant has previously filed an application for a dual-fuel diesel engine that uses gasoline as the main fuel and light oil as an auxiliary fuel for ignition (see Japanese Patent Application No. 1-97416). Compression ignition of gasoline is difficult and normally cannot be used in diesel engines, but light oil is first injected to ignite it, which becomes the spark that combusts the injected gasoline.

[Problem to be solved by the invention]

In-cylinder injection also uses a catalytic converter to purify exhaust gas, just as in normal spark ignition systems. However, in a direct injection internal combustion engine that uses gasoline as fuel, black smoke is produced significantly more on the high load side where the excess air ratio is small. When exhaust gas containing a large amount of black smoke is passed through a catalytic converter, the black smoke components cause unfavorable results in terms of durability of the catalytic converter.

This invention efficiently purifies exhaust gas using a catalytic converter in a dual fuel cylinder injection internal combustion engine that uses gasoline as the main fuel and light oil for ignition, and also uses black smoke contained in the exhaust gas to catalyze the The purpose is to prevent the durability of the converter from being impaired.

[Means to solve the problem]

According to this invention, in a direct injection internal combustion engine that uses diesel as a secondary fuel for ignition and gasoline as the main fuel, and that has a catalyst device installed in the exhaust pipe, it is possible to selectively bypass the catalyst device. It includes a switching means, a means for detecting an excess air ratio, and a driving means for operating the switching means according to the excess air ratio, and the exhaust gas is passed through the catalyst device when the excess air ratio is within a predetermined range, and when the excess air ratio is within a predetermined range, the exhaust gas is An exhaust gas purification device for a direct gasoline injection internal combustion engine is provided, wherein the exhaust gas is bypassed through a catalyst device at an excess air ratio.

[Effect]

The excess air ratio detection means detects the excess air ratio, and the driving means guides the exhaust gas to the catalytic converter when the detected excess air ratio is within a predetermined range, and when the detected excess air ratio is outside the predetermined range. Allow exhaust gases to bypass the catalytic converter.

〔Example〕

Fig. 1 shows a diesel engine, where lO is a cylinder block, 12 is a piston, and 14 is a cylinder head. 1
6 is an intake valve, 18 is an intake boat, 20 is an exhaust valve, 22 is an exhaust boat, and 23 is a catalytic converter.

The fuel injection valve 24 is provided in the cylinder head 14, is configured as a dual fuel injection device, and is capable of injecting light oil for ignition and gasoline as the main fuel.

The fuel injection valve 24 includes a main body 26 fixed to the cylinder head 14 and a needle 28 slidably provided on the main body 26.
and. A nozzle 30 is formed at the lower end of the main body 26 and communicates with the combustion chamber 34 via a passage 32 in the cylinder head 14 . Main body 26 and needle 28
An annular fuel chamber 36 is formed between the fuel chamber 36 and
The main fuel passage 38 opens. Further, an auxiliary fuel passage 40 for ignition is formed in the needle 28, and this auxiliary fuel passage 40
communicates with the lower part of the fuel chamber 36 near the nozzle 30.

The auxiliary fuel from the auxiliary fuel passage 40 is stored in the fuel chamber 36 prior to fuel injection, and at the time of main injection, the auxiliary fuel stored in the fuel chamber 36 is first injected, and then the auxiliary fuel is injected into the main fuel passage 38.
The main fuel from is injected.

In this embodiment, the fuel injection pump 50 is a sub-type fuel injection pump, and has a fuel discharge part 52 and a fuel introduction part 53 to the fuel injection valves of each cylinder. The fuel introduction part 53 is connected to the main fuel pump 54, and gasoline, which is the main fuel, from the main fuel tank 56 is introduced into the fuel injection pump 50, and is pumped from each fuel discharge part 52 to the fuel injection valve 24 of each cylinder. be done.

An auxiliary fuel filling device 60 is connected to the fuel discharge portion 52 of each cylinder. The auxiliary fuel filling device 60 operates to fill auxiliary fuel into the fuel injection valve of a cylinder whose phase is different from that of the cylinder during the fuel injection process of the cylinder to which it is connected. For example, in the case of a four-cylinder engine, if the fuel injection valve 24 shown in the figure is installed in the first cylinder, the auxiliary fuel filling device 60 of the first cylinder will inject three times before the third cylinder. The function is to fill the fuel injection valve with auxiliary fuel. (It may be configured to be filled once or twice before.) The same applies to the fuel injection valves of other cylinders. The auxiliary fuel filling device 60 consists of a main body 62, a plunger 64 provided within the main body 62, and check valves 66 and 68. The plunger 64 responds to the pressure of the main fuel in the pipe 70 that connects the fuel discharge portion 52 to the main fuel passage of the fuel injection valve 24 of that cylinder, and directs the auxiliary fuel to the fuel injection valve of the cylinder whose phase is different from that of the cylinder. It acts as a filler. That is, the pump chamber 72 is located on one side of the plunger 64.
The pump chamber 72 is connected to an auxiliary fuel pump 80 and an auxiliary fuel tank 82 via a check valve 66. Further, the pump chamber 72 is connected to the auxiliary fuel passage 40 via the check valve 68.
It is connected to piping 84 to.

A check valve 86 is provided in this pipe 84, and this check valve 86 prevents the main fuel from flowing back into the auxiliary fuel filling device 60 side.

The catalytic converter 23 is an exhaust pipe 90 from the exhaust boat 22
connected to. An exhaust bypass passage 92 is connected to the exhaust pipe 90 on the inlet side of the catalytic converter 23 .

The bypass valve 94 is provided so as to be switchable between a solid line position where the exhaust pipe 90 is connected to the catalytic converter 23 and a broken line position where the exhaust pipe 90 is connected to the exhaust bypass passage 92. The diaphragm actuator 96 is for driving the bypass valve 94, and its rod 96a is connected to the bypass valve 94, and by introducing negative pressure or atmospheric pressure to the diaphragm 96b, the bypass valve 94 is moved between the solid line position and the broken line position. Driven by switching. The solenoid valve 100 introduces atmospheric pressure or negative pressure from a negative pressure pump 102 into the actuator 96.

The solenoid 100a of the electromagnetic valve 100 is connected to the drive transistor 104, and turns the transistor 104 ON and OFF.
The solenoid valve 100 can be selectively driven by F. The first comparator 106 has two inputs, one of which is connected to the excess air ratio sensor 108 and the other to a resistive voltage divider, for a predetermined excess air ratio λ. sensor 1 at
The voltage corresponding to the voltage generated by 08 is selected. Here, the excess air ratio sensor 108 may be a so-called lean sensor type oxygen concentration sensor in which an electrode is formed on the surface of a solid electrolyte such as zirconia, and a porous diffusion control layer is provided on the electrode surface. .

The second comparator 110 has two inputs, one of which is connected to the excess air rate sensor 108 and the other to a resistive voltage divider, so that at a given excess air rate λ1 the sensor 108
The voltage is selected to correspond to the voltage generated. An AND gate 114 connects the first and second comparators 106 , 110 to transistor 104 . As shown in Figure 2,
The first comparator 106 has λ≧λ.

It turns on at λ〈λ. It turns off. On the other hand, the second comparator 110 is turned off when λ>λ1, and λ≦λ.

turns on. Therefore, the gate 114 is λ0≦λ≦λ1
It turns on at λ〈λ. Or it is turned off when λ>λ1.

The operation of this dual fuel injection device will be described with respect to the fuel injection operation of the first cylinder, but the same applies to the operation of the other cylinders. The fuel injection valve 24 of the first cylinder executes fuel injection 54
When fuel injection is performed in the third cylinder before 0° CA, the main fuel (gasoline) is sent under pressure from the fuel discharge part 52 of the third cylinder to the fuel injection valve (not shown) of the third cylinder via the pipe 70-3. However, at this time, the plunger 643 is moved to the right in the figure by the pressure of the main fuel against the spring 65-3, and the plunger 643 is moved to the right in the figure by the pressure of the main fuel.
The auxiliary fuel (light oil) in 2-3 is pressurized and passed through the check valve 68-
3 is pushed open, and the auxiliary fuel is filled into the fuel chamber 36 through the conduit 84, the check valve 86, and the auxiliary fuel filling passage 40. When the discharge pressure decreases due to the completion of fuel injection in the third cylinder, the plunger 64-3 moves to the left due to the bias of the spring 65-3, and the pressure in the pump chamber 72-3 decreases, causing the check valve 66-3 to open. The auxiliary fuel from the auxiliary fuel pump 80 is supplied to the pump chamber 92-3 in preparation for the next filling of the auxiliary fuel.

In the injection stroke of the first cylinder, the fuel discharge part 5 of the first cylinder
The main fuel from No. 2 is fed under pressure to the fuel chamber 36 via the main fuel passage 38 of the fuel injection valve 24 of the first cylinder via the piping 70,
This pressure causes the needle 28 to be lifted against a spring (not shown), and fuel is injected from the nozzle 30 toward the combustion chamber 34. During this fuel injection, the fuel chamber 36
The auxiliary fuel previously filled in the tank is first injected, and then the main fuel is injected.

Light oil, which is first injected as auxiliary fuel, is ignited, and then the flame propagates to gasoline, which is injected as main fuel, to cause combustion.

Next, the switching operation of the bypass valve 94 will be explained. The excess air ratio sensor 108 detects the excess air ratio λ,
. Or, when λ>λ, comparator 106 or 1
10 is turned off, gate 114 is turned off, and solenoid valve 10 is turned off.
0 is turned off, the rod 96a moves to the left in order to apply atmospheric pressure to the diaphragm 96b, and the bypass valve 94 assumes a position that closes the bypass passage 92. Therefore, the entire amount of exhaust gas is introduced into the catalytic converter 23.

λ. When ≦λ≦λ1 holds, comparator I06゜110
are both turned on, the gate 114 is turned on, the solenoid valve 100 is turned on, the rod 96a moves to the right to apply negative pressure to the diaphragm 96b, and the bypass valve 94 is turned on.
takes a position that opens the bypass passage 92. Therefore,
The entire amount of exhaust gas is introduced into the bypass passage 92 and is not introduced into the catalytic converter 23.

FIG. 3 shows the excess air ratio λ and the emissions of nitrogen oxide NOx, hydrocarbon HCl-carbon oxide CO1, and black smoke (SB) components. Hydrocarbon HCl for excess air ratio λ
- The trends in the emissions of carbon oxide CO1 and black smoke (SB) components are similar; the emissions are small in the region where the excess air ratio λ is large, and the emissions are large in the region where the excess air ratio λ is small. The trends in the amount of nitrogen oxide NOx emissions are completely different; the amount of emissions is small in both the large and small regions of excess air ratio λ, and the amount of emissions is large in the region of intermediate excess air ratio λ. λ of the predetermined values for switching the opening and closing of the bypass valve 94 in the apparatus shown in FIG. The value of is determined corresponding to the value of the excess air ratio λ at which the amount of black smoke (SB) component discharged increases rapidly when the excess air ratio λ decreases. Also λ. also corresponds to the region where the amount of nitrogen oxide NOx emissions begins to increase toward the peak of the amount of emissions when the excess air ratio increases. The value of λ1 increases when the excess air ratio λ increases beyond the peak of NOx emissions.
It is determined in accordance with a region where the amount of Ox discharged is small. Furthermore, in a region where the excess air ratio is large, the catalytic converter is not active, so it is not very meaningful to pass the exhaust gas through the catalytic converter.

In the example, the excess air rate is measured using a lean sensor type oxygen sensor 1.
08, but instead of this, the amount of fuel,
The excess air ratio can be determined by measuring the intake air amount and its ratio, and it is also possible to indirectly determine the excess air ratio by the throttle valve opening or the ratio of the intake air amount to the engine speed.

[Effects] According to the present invention, the excess air ratio is detected in a dual-fuel diesel engine using light oil as a pilot flame and gasoline as the main fuel, and exhaust gas is guided to the catalytic converter within a predetermined range, and outside the predetermined range, the catalytic converter is By bypassing the catalytic converter, it is possible to suppress the amount of nitrogen oxide components discharged and prevent the catalytic converter from being contaminated by black smoke components.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of the present invention. FIG. 2 is a diagram showing the operation of the comparator of FIG. 1. FIG. 3 is a diagram showing the relationship between the excess air ratio and the emissions of hydrocarbon IC1-carbon oxide CO1 black smoke (SB) and nitrogen oxide NOx in exhaust gas. 10... Cylinder block, 12... Piston, 1
4... Cylinder head, 16... Intake valve, 18...
・Intake port, 20...Exhaust valve, 22...Exhaust port, 23...Catalytic converter, 24...Fuel injection valve, 2
6...Body, 28...Needle, 30...Nozzle,
36.Fuel chamber, 38.. Main fuel passage, 40.. Sub-fuel passage, 50.. Fuel injection pump, 52.. Fuel discharge section, 54.. Main fuel pump, 56.. Main fuel Tank, 60...Auxiliary fuel filling device, 62...Main body, 64.
...Plunger, 66, 68...Check valve, 80.
- Sub fuel pump, 82... Sub fuel pump, 86... Check valve, 90... Exhaust pipe, 94... Bypass valve,
96... Actuator, 100... Solenoid valve, 104
...Transistor, 106...Comparator, 108.
...Air excess rate sensor, 110...Comparator. λ0 λ1 Figure 2 Figure 3

Claims (1)

[Claims] In a direct-injection internal combustion engine that uses diesel as an auxiliary fuel for ignition and gasoline as the main fuel, and that has a catalyst device installed in the exhaust pipe, there is provided a switching means that can selectively bypass the catalyst device, and a switch that can prevent excess air. comprising means for detecting the excess air ratio and driving means for operating the switching means in accordance with the excess air ratio;
An exhaust gas purification device for a direct gasoline injection internal combustion engine, characterized in that exhaust gas is allowed to pass through a catalyst device when the excess air ratio is within a predetermined range, and the exhaust gas is bypassed through the catalyst device at other excess air ratios.