JPS58222907A - How to regenerate diesel engine exhaust particulate trap - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for regenerating a trap in a diesel engine in which particulates, particles, and troughs are provided in the exhaust pipe.

A technique has been proposed in which a particulate trap is provided in an exhaust pipe to remove particulates from exhaust gas emitted from a diesel engine. During engine operation rC) Particulates are collected on the lap. In order to avoid an increase in the pressure loss in the exhaust pipe due to the collection of particulates in the trap, the collected particulates in the trap are incinerated every time the vehicle travels. The regeneration of traps through incineration poses an extremely critical problem in selecting the timing. That is, unless a certain amount of fine particles are collected in the trap, ignition will not occur or good combustion will not occur. On the other hand, if the temperature exceeds a certain level, combustion will proceed too much and the amount of traps will become extremely high, which may lead to not only melting but also deterioration of the trap function. The negative particulate matter collected in the trap has a serious impact on regeneration control as described above, but as a practical matter, it is difficult to accurately adjust the needle of the particulate matter collected in the trap at the start of the regeneration process. It is difficult to know. Traditionally, the regeneration timing has been decided by calculating the engine speed or by detecting an increase in back pressure with a pressure sensor in the exhaust pipe, but the integrated rotation speed and back pressure are only used to determine the regeneration timing. This is just a guide as a starting point. If the number of particulates is small, it is not a big problem because no combustion reaction occurs, but if there is a large amount of particulates, over-twisting must be avoided from the viewpoint of safety measures.

In order to avoid such drawbacks of the prior art, it is an object of the present invention to provide a complete method that can prevent over-twisting and deterioration of the trap by continuously detecting the combustion state within the trap during regeneration. In order to achieve this object, the present invention detects the temperature of the exhaust pipe downstream of the trap and reduces the amount of air introduced into the trap when the temperature is above a predetermined value. Therefore, over-twisting of the trap can be reliably detected and the incineration process can be stopped.

To explain with reference to the drawings below, in FIG. 1, 10 is the main body of the diesel engine, 12 is an intake pipe, 14 exhaust pipes, 1
6 is an exhaust gas recirculation passage f which connects the exhaust pipe 14 to the intake pipe 12. A rice control valve (EGR valve) 18 to the recirculated exhaust gas is provided in the exhaust gas recirculation @16. Exhaust pipe 14
A particulate trough f20 is provided therein. The particulate trap 20 includes a filter material 24 (made of cordierite foam ceramic, for example) provided within a case 22 . A heater 26 is provided upstream of the filter material 24 as means for starting ignition and incineration at the start of the regeneration process.

An exhaust throttle valve 28 is provided upstream of the heater 26 and the exhaust pipe 1
4 and a bypass passage 32 that guides the exhaust gas from the trap 20 to the filter material 24 and the trap 20, respectively.
It is arranged so that it can be switched between the two positions.

34 is a control circuit as a programmable microcomputer system that performs regeneration control of the trough f24, and a drive signal to the actuator 28' of the flow rate control valve 18, the heater 26, and the exhaust throttle valve 28 is connected to the line t1 s 12.
Output via s 1m.

In order to detect the start of the regeneration process, in this embodiment, the engine rotational speed is integrated. That is, the pulse generator 40 is located close to the crankshaft 10' and generates 0 pulses per engine revolution.

It is connected to the via counter 42. The counter 42 outputs one pulse to the line 1 . via control circuit 34
to be introduced. Further, in order to detect the temperature inside the trap during regeneration, a temperature sensor 46 is provided downstream of the filter material 24 and is connected to the control circuit 34 via a line t.

In the illustrated embodiment, the regeneration timing of the trap is detected based on the integrated value of the rotational speed from the self-generator 40, and the filter material 24 is activated by operating the exhaust throttle valve 28 and the heater 26.
Incineration is started by increasing the temperature of Exhaust gas flow rate increase (i.e. trap 20
It is controlled to reduce the air noise in the exhaust gas. Such control is performed by a program stored in the control circuit 34, and an example of the routine will be explained with reference to FIGS. 2 to 5.

When the cumulative value of the engine rotational speed reaches a predetermined value, the counter 42 applies a pulse to one interrupt port of the MPU (not shown) in the control circuit 34, and an interrupt routine 50 is started. At 62, the heater 26 is actuated.Then, at 64, the actuator 28' is moved counterclockwise in FIG.
8 to make the exhaust gas flow rate to the trough f20 almost zero.

As a result, the temperature inside the trap 20 increases and the filter material 2
Ignition and combustion of the particulates collected at step 4 begin. 66
Set timer 1 to a time sufficient to cause ignition and combustion of the particulates. This interrupt routine ends at 68.

When the time t has elapsed, an interrupt routine is started at 70 in FIG. 3, energization to the heater 26 is stopped at 72, and the actuator 28' is driven to rotate the exhaust throttle valve 28 clockwise in the figure at 74. Excess air contained in the exhaust gas continues to burn the collected particulates in the trap 20.

76 indicates the reset of timer 1), and 78ij indicates the main routine.

If combustion of particulates within the trap occurs excessively during the regeneration process, the temperature within the trap exceeds a predetermined value and the interrupt routine of FIG. 4 is initiated at 80.

At 82, the control valve 18 is driven in the opening direction to reduce the amount of air occupying the engine intake pipe 12.

As a result, the combustion reaction in the trap 20 is suppressed. At step 84, timer 2 is set to a time t' sufficient to lower the temperature inside the trap 20. 86iJ Indicates the end of this interrupt routine.

88 in FIG. 5 indicates the start of the interrupt routine starting at time t', 90 returns the flow rate control valve 18f to its original position #, 92 resets the timer 2, and 94 indicates the end of this interrupt routine. show.

In the embodiments described above, the entire temperature rise in the trap is detected and the flow rate of the recirculated exhaust gas is increased. Therefore, the amount of air in the exhaust gas is suppressed, thereby preventing over-twisting of the trap and the resulting deterioration in the function of the trap.

As another embodiment within the scope of the present invention, a throttle valve may be provided in the intake pipe 12 instead of the recirculated exhaust gas flow rate control valve 18, and the throttle valve may be activated when the temperature rises. By suppressing the amount of air, over-twisting is prevented. Further, by the method of driving the exhaust throttle valve 28 shown in FIG. 1 when the temperature rises, the amount of air flowing into the trough 7° 20 is reduced, so that the temperature rise can be suppressed.

In order to detect the regeneration timing of the trough 7'20, instead of calculating the Enson rotational speed, a pressure increase in the exhaust pipe can be detected by a pressure sensor. Further, instead of using the heater 26 and the exhaust throttle as the ignition means at the start of regeneration, it is optional to use the exhaust throttle alone, the intake throttle, or the ignition burner.

[Brief explanation of drawings]

FIG. 1 is an overall schematic diagram of a diesel engine that implements the method of the present invention, and the five stripes in FIG. 2 are flowcharts showing the method of the present invention. 10...Engine body, 12...Intake pipe, 14...
・〃 is trachea, 18...EGR valve, 20...trap, 26...°-'・zs-mRt6i″lF・°
・"°°゛control mu o 屹"° 1゜...Temperature sensor 1, Fig. 4 Fig. 5

Claims (1)

[Claims] In a diesel engine equipped with a trap for exhaust particulates in the exhaust pipe, by detecting the regeneration time of the trap, ignition and incineration of the particulates collected in the trap is started,
Means for reducing the total amount of air introduced into the drag when the temperature in the exhaust pipe downstream of the trap exceeds a predetermined value'
fr: A method for regenerating an exhaust particulate trap of a diesel engine that is driven.