JPH0486319A - Exhaust emission control device for diesel engine - Google Patents

Abstract

PURPOSE:To obtain high efficiency in filter regeneration and to prevent a crack and fusing damage of a filter by raising an exhaust temperature by means of exhaust throttle and acceleration control, and introducing the resultant high temperature exhaust entirely to a filter without bypassing at the time of filter regeneration. CONSTITUTION:A warning lamp (regeneration lamp) 10 is turned on when an integrated value L of input signals from a car speed sensor 11 exceeds a prescribed value L0 and a trap filter 3 is thereby judged to be at the time of regeneration. Then, a driver, in a state of vehicle stopping, turns on a regeneration switch 9 to start a timer together with a throttle valve actuator 5 and an acceleration actuator 6 so that an exhaust throttle valve 4 throttles an exhaust passage 2 to a predetermined opening degree and a fuel injection pump 7 is held at a predetermined acceleration opening degree. Accordingly, engine speed is increased and an exhaust temperature is raised rapidly to a temperature sufficient for re-combustion of particulates so as to regenerate the filter 3 efficiently.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an improvement in an exhaust purification device for a diesel engine.

(Prior art) In diesel engines, in order to remove and purify particulates (carbon particles) contained in the exhaust, a particulate trap filter is provided in the exhaust passage, and the collected particulates are periodically removed. It is well known to regenerate filters by combustion treatment.

Among these, JP-A-62-58007 discloses trap filter regeneration means that includes an electric heater that heats the inside of the filter, an exhaust throttle valve that throttles the exhaust passage upstream or downstream of the filter, and bypasses the filter and exhaust throttle valve. When the filter is regenerated, the exhaust gas is throttled to raise the filter temperature, and an electric heater burns the collected particulates, and most of the exhaust flows downstream from the bypass passage to prevent excessive exhaust pressure. Some proposals have been made to suppress the rise in .

According to this, there is an advantage that the power consumption of the electric heater can be reduced as much as possible while preventing a decrease in engine power performance etc. even during filter regeneration.

(Problems to be Solved by the Invention) However, in this conventional example, during filter regeneration, the introduction of exhaust gas into the filter is limited to a small amount by the exhaust throttle, so the combustion of the collected particulates 1 to 1 proceeds slowly. As a result, heat builds up in the center of the filter, creating a large temperature gradient with respect to the outer periphery, making cracks and melting damage more likely to occur.Furthermore, it is difficult to burn the collected particulates at the outer periphery, making the regeneration of the filter inefficient. There was a problem that the value was low.

Furthermore, the structure of the exhaust system becomes complicated due to the provision of a bypass passage, which is disadvantageous in terms of vehicle mountability.

This invention aims to solve these problems.

(Means for Solving the Problem) Therefore, the present invention includes a trap filter that collects particulates in the exhaust gas discharged from the exhaust passage l\ from a diesel engine, and an exhaust passage downstream of the wrap filter. A valve that throttles the valve to its opening, a device that drives the exhaust throttle valve, a device that drives the accelerator lever of the fuel injection pump to a predetermined opening, and a device that drives the accelerator lever of the fuel injection pump to a predetermined opening, and when the manual switch is turned on during trap filter regeneration, the vehicle is stopped. The throttle valve drive device and the accelerator lever drive device are provided with control means for operating the throttle valve drive device and the accelerator lever drive device for a predetermined period of time.

(Function) During filter regeneration, when the vehicle is stopped and the manual switch is turned on, the accelerator lever drive device operates the accelerator lever of the fuel injection pump to a predetermined opening degree, and at the same time, the throttle valve drive device opens the exhaust throttle valve. The exhaust passage downstream of the filter is narrowed to a predetermined opening degree through the filter.

As a result, the engine speed increases and exhaust throttling is performed, so that the exhaust temperature quickly rises to a temperature sufficient to re-burn particulates.

All of this high-temperature exhaust gas is introduced into the filter, flows almost evenly throughout the filter, and is discharged downstream.
Therefore, the combustion process of the collected particulates is promoted in the filter by a large amount of high-density oxygen, and the temperature distribution throughout the filter is made uniform.

As a result, high regeneration efficiency of the filter is obtained, and
It is also possible to effectively prevent cracks and melting of the filter.

Furthermore, after a predetermined period of time has elapsed from the start of the regeneration process, the operation of the throttle valve drive device and the accelerator lever drive device is released, the exhaust throttle valve is returned to the fully open state, and the accelerator lever of the fuel injection pump is returned to the no-load position. .

(Example) In Fig. 1, 1 is a diesel engine, in which an exhaust passage 2 has a trap filter 3 with a catalyst that collects particulates, and an exhaust throttle valve that throttles the exhaust passage 2 downstream to a predetermined opening degree. 4 is interposed.

Reference numeral 5 denotes an actuator that opens and closes the exhaust throttle valve 4. The actuator 5 is driven and controlled via a control valve (not shown) that selectively supplies operating pressure and atmospheric pressure.

On the other hand, 6 is an accelerator actuator attached to the fuel injection pump 7 of the engine 1. The actuator 6 is driven by the operating pressure supplied through a control valve (not shown) during filter regeneration, which will be described later, and the accelerator lever
is held at a predetermined opening degree, and when the control valve is released to the atmosphere, the accelerator lever is released.

The controller 8 controls the drive of the throttle valve actuator 5 and the accelerator actuator 6.
is provided with a manual regeneration switch 9 and a lamp 10 that warns when it is time to regenerate the filter 3. Reference numeral 11 denotes a vehicle speed sensor that detects vehicle speed from, for example, propeller shaft rotation, and this detection signal is input to the controller 8 .

FIG. 2 is a flowchart illustrating the control operation performed within the controller 8. When the input signals from the vehicle speed sensor 11 are integrated, and the integrated value (the distance traveled by the vehicle) exceeds a specified value I-o, a trap is detected. It is determined that it is time for the filter 3 to be regenerated, and the warning lamp 10 is turned on (steps 20 to 22).

When the driver turns on the regeneration switch 9 while the vehicle is stopped (the accelerator pedal opening is 0% and the transmission is in neutral), the regeneration switch ON flag is set and the timer is started, and at the same time, the throttle valve actuator 5 and The accelerator actuator 6 is operated together (steps 23 to 26).As a result, the exhaust throttle valve 4 throttles the exhaust passage 2 to a predetermined opening degree, the fuel injection pump 7 is held at a predetermined accelerator opening degree, and the engine rotation is reduced. As a result, the exhaust temperature quickly rises to a temperature sufficient to re-burn the particulates and regenerate the filter.

When the count value TM of the timer reaches the specified value TM, it is determined that the regeneration process has ended, and the accelerator actuator 6
The throttle valve actuator 5 is deactivated to stop the exhaust throttle and accelerator control, and at the same time, the regeneration lamp 10 is cleared so that the cumulative value of the vehicle speed and the count value TM of the timer do not return to zero (Stella 127 to 32). ).

When the vehicle starts moving during filter regeneration, in order to prevent deterioration of engine power performance and driving feeling, the exhaust throttle and accelerator control are stopped, the timer count value TM is returned to zero, and the regeneration switch ON flag is cleared. (Steps 33 to 37) a Although it is possible to provide the exhaust throttle valve 4 upstream of the trap filter 3, as is clear from the experimental results shown in FIG. With this configuration, the effect of regenerating the filter is greater when the filter is regenerated, so the exhaust gas temperature rises due to the exhaust throttling and accelerator control during filter regeneration. All of this high-temperature exhaust gas is introduced into the filter 3, flows almost uniformly through the filter 3, and is discharged downstream. Therefore, inside the filter 3, the combustion process of the collected particulates is carried out by a large amount of high-density oxygen. In addition, the temperature distribution throughout the filter 3 is also made uniform.

As a result, high regeneration efficiency of the filter 3 can be obtained, and cracks and melting damage of the filter 3 can be effectively prevented.

In addition, all of the exhaust gas is introduced into the filter 3 even during filter regeneration, so particulates contained in the exhaust gas are not directly released into the atmosphere even during filter regeneration. The system configuration can be simplified, which is advantageous in terms of vehicle mountability and cost.

FIG. 4 shows another embodiment in which an intake throttle valve 15 is provided in addition to the exhaust throttle valve 4. During filter regeneration, the controller 8 controls the intake throttle valve 15 in the same way as the exhaust throttle valve 4.
By controlling the temperature, the exhaust temperature can be raised more effectively, and therefore, it is effective for filter regeneration processing in cold weather, for example.

(Effects of the Invention) In summary, according to the present invention, the exhaust gas temperature is increased by exhaust throttle and accelerator control during filter regeneration, and all of this high-temperature exhaust gas is introduced into the filter without being bypassed. In addition to obtaining regeneration efficiency, it is possible to obtain effects such as effectively preventing cracks and melting damage of the filter.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram showing an embodiment of the present invention, Fig. 2 is a flowchart explaining the control contents in the controller, and Fig. 3 is a flow chart showing the exhaust throttle valve on the upstream side of the filter and the same on the downstream side. FIG. 4 is a characteristic diagram showing the difference in filter regeneration effect depending on the arrangement, and FIG. 4 is a configuration diagram of another embodiment. 2... Exhaust passage, 3... Trap filter, 4...
・Exhaust throttle valve, 5... Throttle valve actuator, 6...
・Accelerator actuator, 7...fuel injection pump,
8... Controller, 9... Playback switch. Patent applicant Nissan Diesel Industries (mg/f)

Claims (1)

[Claims] 1. A trap filter that collects particulates in the exhaust discharged from the diesel engine into the exhaust passage;
A valve that throttles the exhaust passage on the downstream side of the trap filter to a predetermined opening, a device that drives this exhaust throttle valve, a device that drives the accelerator lever of the fuel injection pump to a predetermined opening, and a manual 1. An exhaust gas purification device for a diesel engine, comprising a control means that operates a throttle valve drive device and an accelerator lever drive device for a predetermined period of time when a vehicle is stopped when a switch is turned on.