JPH0422705A - Exhaust processing equipment for internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent a fuel for regeneration from leaking outward as white smoke by returning the exhaust gas, which has passed a filter, to combustion chamber of an engine, at the time of regeneration of the filter, on which particulates collected are burnt, by means of fuel supply to the upper stream of the filter. CONSTITUTION:An exhaust filter 4, which is forced to carry an oxiding catalyzer and used for collecting particulates, is interposed in an exhaust passage 3. A fuel injection valve 5, which supplies fuel (hydrocarbon, carbon monoxide, etc.) into the exhaust gas is provided upstream from this filter 4. In addition, an exhaust throttling valve 7 is installed on downstream from the filter 4, while an exhaust return passage 8, which is branched off from between the filter 4 and the exhaust throttling valve 7, is connected to the lower stream of an intake throttling valve 9 of an intake passage 2. At the same time, a by-path passage 11 is provided in such a manner that it makes a detour round both the filter 4 in the exhaust passage 3 and the exhaust throttling valve 7. In addition, a by-path valve 12 is installed in the midst of the by-path passage 11. At the time of regeneration of the filter 4, the gas which has passed the filter 4 is circulated again through the intake system of the engine.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is mainly applied to an exhaust treatment device for a diesel engine.

(Prior Art) In order to prevent particulates (fine particles) in the exhaust gas of a diesel engine from being released into the atmosphere, a filter for trapping the particulates is sometimes installed in the exhaust passage. In this case, if the exhaust pressure increases with the amount of particulates collected by the filter, it will have a negative effect on engine performance, so the filter can be regenerated by periodically burning the trapped particulates. Is going.

For this reason, as stated in Japanese Patent Application Laid-Open No. 59-122721, when the regeneration time determined from the integrated value of engine rotation speed is reached, an appropriate amount of unburned fuel such as hydrocarbons and carbon oxide is supplied upstream of the filter. The collected particulates are burned.

The fuel introduced into the exhaust gas functions as a combustion aid to combust the particulates containing carphone as a main component, which are trapped in the filter, and the particulates are automatically combusted due to the temperature rise after ignition.

(Problem to be Solved by the Invention) However, when fuel is supplied to the exhaust gas during filter regeneration, a portion of the supplied fuel may be completely drained, depending on the exhaust temperature at that time, the amount of oxygen in the exhaust gas, etc. It may not be combusted and may be emitted as is, producing white smoke.

In terms of exhaust countermeasures, reducing this white smoke is one of the challenges for filter regeneration.

The present invention is an exhaust treatment device for an internal combustion engine that completely burns unburned fuel in the engine combustion chamber and prevents the emission of white smoke by circulating the gas that passes through the filter during regeneration into the engine intake system again. The purpose is to provide

(Means for Solving the Problems) As shown in FIG. 1, the present invention includes a collection filter 51 interposed in an exhaust passage 50 of an engine, and means 52 for supplying fuel upstream of the filter during filter regeneration. , an exhaust gas recirculation passage 54 that branches from downstream of the filter and connects to the intake passage 53 of the engine, an exhaust throttle valve 55 interposed in the exhaust passage 50 downstream of this branching point, and an exhaust throttle valve 55 during filter regeneration.
6 (Function) When the filter is regenerated, fuel is supplied upstream of the filter,
Burns the particulates collected in the filter.
At this time, since the exhaust throttle valve is narrowed down, the exhaust pressure downstream of the filter becomes higher than the pressure in the intake passage, and the gas that has passed through the filter is recirculated into the intake air.

This reflux gas may contain unburned fuel components that have passed through the filter, but these are combusted in the engine combustion chamber, thereby reliably preventing the generation of white smoke during regeneration.

(Example) Embodiments of the present invention will be described below based on the drawings.

In Figure 2, 1 is the main body of the diesel engine;
2 is an intake passage, 3 is an exhaust passage, and the exhaust passage 3 is interposed with an exhaust filter 4 for collecting particulates carrying an oxidation catalyst.

A fuel injection valve 5 is provided upstream of the filter 4 to supply fuel (hydrocarbon, carbon oxide, etc.) into the exhaust gas. The amount of fuel injected from the fuel injection valve 5 is controlled by the control unit 6 as described later when the filter 4 is regenerated.

An exhaust throttle valve 7 is provided downstream of the filter 4, and an exhaust gas recirculation amount #! is branched from between the filter 4 and the exhaust throttle valve 7. 8 is connected downstream of the intake throttle valve 9 in the intake passage 2 .

Note that an exhaust gas recirculation valve 10 is interposed in the middle of the exhaust gas recirculation passage 8 to control the amount of exhaust gas recirculation according to the operating state during normal operation.

A bypass passage 11 is provided to bypass the filter 4 and exhaust throttle valve 7 of the exhaust passage 3.
A bypass valve 12 is provided that opens and closes.

The exhaust throttle valve 7, intake throttle valve 9 and bypass valve 12 are driven by diaphragm devices ff7g, 9m and 12g, respectively, and three-way solenoid valves 7b, 9b and 12 control the operating pressure introduced into these diaphragm devices 7a9a12m.
b is provided.

Then, the operation of each of these solenoid valves 7b, 9b, 12b is as follows.
Along with the operation of the fuel injection valve 5, the controller +l-i
7, +t h heather) (1 store o A) The control unit 6 receives the rotation speed signal Ne from the engine rotation speed sensor 15 in order to detect the operating state of the engine.
, a fuel injection amount signal Q to the lever opening sensor 17 of the fuel injection pump 16, a water temperature signal Tw from the engine cooling water temperature sensor 18, and an exhaust temperature signal T1 from the exhaust temperature sensor 19 disposed near the filter 4. , the differential pressure signal ΔP from the front and rear differential pressure sensor 20 of the filter 4 are respectively input.

The control unit 6 determines the regeneration time based on the degree of clogging of the filter 4 based on the signal from the differential pressure sensor 20, and when it is the regeneration time, the control unit 6 bypasses While opening the valve 12,
The exhaust throttle valve 7 is throttled, the intake throttle valve 9 is throttled, the exhaust recirculation valve 10 is fully opened, and fuel injection is started from the fuel injection valve 5 to regenerate the filter 4.

At the same time, the electric heater 13 placed immediately before the filter 4 is energized to reduce the temperature immediately before the filter.The fuel introduced upstream of the filter 4 is ignited in the high-temperature atmosphere and collected by the filter 4. While promoting the combustion of particulates, the gas that has passed through the filter 4 is recirculated to the intake passage 2 via the exhaust gas recirculation passage 8 because the exhaust throttle valve 7 is throttled.

In this case, even if some of the supplied fuel is incompletely combusted, in a diesel engine, even when no fuel is injected, the cylinder air temperature rises to a level sufficient for ignition due to compression alone; It is reburned in the chamber.

At this time, since the bypass valve 12 is open, a portion of the exhaust gas is discharged via the bypass passage 11, and therefore, the exhaust gas containing an appropriate amount of oxygen to burn particulates flows into the filter 4. .

Note that regeneration is performed during deceleration because if the injection amount into the cylinder is zero, it is possible to return the entire amount of exhaust gas to the intake system, and even if there is a partial load, when the injection amount is small, This is because the occurrence of smoke and the like is extremely small, and the exhaust gas can be passed through the filter 4 as a bus pass.

FIG. 3 shows a control routine for the regeneration operation executed by the control unit 6. To explain it according to this routine, each detection signal Ne, Q, Tw, T, .DELTA.P is
is read, and first, it is checked whether the differential pressure ΔP across the filter 4 has reached a predetermined value, and the regeneration timing is determined. Since the differential pressure increases according to the amount of particulates accumulated on the filter 4, the time when this pressure reaches a predetermined value is determined as the time to regenerate the filter 4.

In S3, it is determined from the engine speed Ne and the fuel injection amount Q whether or not the engine is in a deceleration state. Note that during deceleration, the rotational speed is high despite the small amount of fuel injected (no injection).

If neither of these is the case, in S12 the bypass valve 1 is
2, open the exhaust throttle valve 7 and intake throttle valve 9, turn off the heater 13, and return to the original state.

On the other hand, if it is the regeneration time and the deceleration state has been entered, it is determined in S4 whether the exhaust gas temperature T is higher than a predetermined value, and in order to perform the regeneration operation when the exhaust gas temperature is high, first, Turn on the heater 13 (energize) and turn on the bypass valve 1.
2 is opened, the exhaust throttle valve 7 is throttled, the exhaust gas recirculation valve 10 is further opened, and the intake throttle valve 9 is throttled (35 to S7).

As a result, during deceleration after the exhaust gas temperature has risen sufficiently, a portion of the exhaust gas is discharged from the bypass passage 11, and an appropriate amount of exhaust gas (oxygen) flows into the filter 4, and further passes through the exhaust gas recirculation passage 8. It flows back into the intake passage 2.

In step S8, the amount of fuel required for regeneration is injected from the fuel injection valve 5. The fuel injected in a high-temperature atmosphere contacts the heater 13 and ignites, and further serves as a combustion aid for the particulates collected in the filter 4, promoting combustion of the particulates.

The exhaust gas that has passed through the filter 4 is directly recirculated from the exhaust gas recirculation passage 8 to the intake passage 2 and combusted again in the engine combustion chamber.

Therefore, even if the fuel introduced into the exhaust gas for regeneration is not completely combusted in the filter 4 and passes through the filter 4 as unburned fuel, it will be sent to the engine combustion chamber again together with the exhaust gas, and will be compressed and It burns completely by going through a combustion process. Most of the gas after this re-combustion will be discharged from before the filter 4 via the bypass valve 12, but the problem of unburned fuel becoming white smoke and being released to the outside during regeneration will definitely be solved. Ru.

The playback time is counted in S9 and SIO, and the above operations are continued until the playback time reaches a predetermined time.

When the predetermined reproduction is completed, the reproduction determination timing data is erased in the Sll, everything is returned to the initial state, and preparation is made for the next reproduction operation.

When the filter 4 is not in the regeneration period, the bypass valve 12 is closed and the exhaust throttle valve 7 is fully open.
The entire amount of exhaust gas flows into the filter 4, and particulates in the exhaust gas are captured by the filter 4.

In addition, a part of the exhaust gas after passing through the filter is transferred to the exhaust gas recirculation valve]
(At this time, in order to ensure a predetermined amount of exhaust gas recirculation, the intake throttle valve 9 is
), suppressing the generation of NOx.

Incidentally, in this embodiment, the regeneration timing of the filter 4 is determined based on the differential pressure ΔP across the filter 4, but it can also be determined based on the integrated value of the rotational speed Ne. Furthermore, without providing the bypass passage 1-1 and the bypass valve 12, it is also possible to allow a portion of the exhaust gas to flow downstream without fully closing the exhaust throttle valve 7 during regeneration. is not necessarily an essential requirement.

Therefore, in this case, the means for supplying fuel into the exhaust gas is not limited to the fuel injection valve 5 downstream of the branching point of the bypass passage 11, but for example, from a fuel injection valve provided in the engine combustion chamber during the engine exhaust stroke. It is also possible to inject fuel and use this unburned fuel discharged into the exhaust passage as fuel for regeneration.

Furthermore, in this example, the conditions for regeneration were limited to when no particulates are generated and regeneration can be performed efficiently in a short time, during deceleration and when the exhaust temperature is high; It is possible to perform playback at any time.

(Effects of the Invention) As described above, according to the present invention, when the filter is regenerated, the exhaust gas that has passed through the filter is regenerated by 8! Since it is designed to flow back into the inter-combustion chamber, even if the fuel supplied to the exhaust gas during regeneration is incompletely combusted, it will be reliably combusted in the engine combustion chamber, and the regenerated fuel will not be released outside as white smoke. You can prevent this from happening.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the present invention, FIG. 2 is a schematic block diagram showing an embodiment thereof, and FIG. 3 is a flowchart of control operations executed by a control unit. DESCRIPTION OF SYMBOLS 1... Engine body, 2... Intake passage, 3... Exhaust passage, 4... Filter, 5... Fuel injection valve, 6...
Control unit, 7... Exhaust throttle valve, 8...
Exhaust recirculation passage, 9... Intake throttle valve, 11... Bypass passage, 12... Bypass valve. Patent applicant Nissan Motor Co., Ltd.

Claims (1)

[Claims] 1. A collection filter installed in the exhaust passage of the engine, a means for supplying fuel upstream of the filter during filter regeneration, an exhaust recirculation passage branching from the downstream of the filter and connecting to the intake passage of the engine, and An exhaust gas treatment device for an internal combustion engine, comprising an exhaust throttle valve interposed in a downstream exhaust passage, and a control means for throttling the exhaust throttle valve during filter regeneration.