JPS59147814A - Regenerating burner control device for trap collecting exhaust fine particle in internal-combustion engine - Google Patents

Abstract

PURPOSE:To improve the ignition characteristic so as to prevent a trap from being burnt out by increasing the amount of fuel supply for correction for a prescribed period from burning initiation of a burner used for trap regeneration and further decreasing said amount of fuel supply when a changing speed of exhaust temperature exceeds a prescribed value during said fuel amount increasing correction. CONSTITUTION:An exhaust air purifying device collects fine particles in exhaust gas by means of a trap 4 provided in an exhaust passage 1, and regenerates the trap 4 by operating a burner 5 for its burning in response to the pressure difference obtained from outputs of pressure sensors 18, 19 located across the trap 4. In this case, a temperature sensor 23 is provided between the burner 5 and the trap 4, and until its detected value T1 reaches a prescribed lower limit value (about 550 deg.C), a fuel amount increasing correction means 32 is operated based on a command issued from a comparison means 36, and a basic injection amount retrieved by means of a basic injection amount retrieving means 31 is increased for correction. Further, during said situation, the exhaust temperature T1 is differentiated by a differential means 37, and when the differentiated value exceeds a prescribed value, a fuel amount decreasing correction means 33 is operated, allowing a fuel injection amount to be decreased for correction.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control device for a burner for regenerating an exhaust particulate trap used as an exhaust purification device for an internal combustion engine, and more particularly to a device for controlling the amount of fuel supplied to the burner.

As a conventional exhaust gas purification device for an internal combustion engine for an automobile, there is one disclosed in, for example, Japanese Patent Laid-Open No. 115809/1983. This is done by setting up a trap in the middle of the exhaust passage to collect particulates whose main component is carbon in the exhaust.
It is also equipped with a trap regeneration burner upstream of the trap, and when it is detected that a predetermined amount of fine particles have been collected in the trap, the burner is operated for a predetermined period of time to remove the fine particles. Incinerates and regenerates traps.

However, such conventional trap regeneration burner control devices do not particularly control the amount of fuel supplied to the burner during regeneration, but instead supply a constant amount of fuel. There were some problems.

In other words, in order to burn exhaust particulates, it is necessary to maintain the exhaust temperature at the trap inlet side at approximately 600°C, but there is a period from the start of fuel supply to the rise in exhaust temperature due to ignition combustion, and the period when the exhaust temperature reaches the predetermined exhaust temperature. The required amount of fuel supply differs depending on the amount of fuel supplied, and even when the amount of fuel supplied is constant, and even when the amount of fuel supplied is controlled according to engine operating conditions such as rotation speed and load, ignitability may be affected. No improvement or reduction in start-up time can be expected.

For this reason, it has been considered to increase the amount of fuel supplied during the start-up period.

However, if the rate of temperature rise is too fast, the temperature will continue to rise even after reaching the target value, as shown by the broken line in Figure 1, and there is a risk of problems such as burnout or melting of the trap due to overtemperature. there were.

In view of these circumstances, the present invention aims to improve ignition performance and shorten the rise time of exhaust gas temperature, while also preventing overshoot due to an excessive temperature rise rate, as shown by the solid line in Figure 1. The purpose is to obtain such characteristics.

For this reason, the present invention includes a decorative air temperature detection means for detecting the exhaust temperature on the trap inlet side downstream of the burner, a differential calculation means for differentiating the detected value, and a detection means for detecting the exhaust temperature by ignition combustion from the start of fuel supply to the burner. increasing correction means for increasing the amount of fuel supplied to the burner for a period until the value reaches a predetermined value; A weight loss correction means is provided to correct the weight increase correction value to a smaller value.

Examples will be described below.

In FIG. 2, a trap case 2 is interposed in the middle of an exhaust passage 1 of a diesel engine, and a honeycomb type trap 4 is installed inside the trap case 2 with a buffer material 3 interposed therebetween. This trap 4 is constructed by opening the inlet side of some of the holes in the honeycomb and closing the outlet side, and closing the inlet side and opening the outlet side of the other holes, so that the exhaust gas passes through the wall of the hole. This is used to collect fine particles.

A burner 5 for trap regeneration is provided upstream of the trap 4 in the trap case 2.

The burner 5 includes a combustion tube 6 having a large number of exhaust gas introduction holes 6a on the peripheral wall, a backflow type evaporator tube 7 located inside the combustion tube 6 and having a flame jetting lower a, and a mixture conduit facing into the backflow type evaporator tube 7. 8, and a glow plug 9 for ignition that faces near the flame outlet 1a of the reverse flow type evaporator tube 7 within the combustion tube 6.

A discharge port of an air pump 1o is connected to the inlet side of the air-fuel mixture conduit 8 via an electromagnetic switching valve 11.

The air pump 10 is driven by an engine, and its suction port is connected to an air cleaner (not shown).

The switching valve 11 connects the discharge port and the suction port of the air pump 1o in a non-energized state, and is switched to supply air from the air pump 1° to the mixture conduit 8 in a energized state. Further, on the inlet side of the air-fuel mixture conduit 8, an electromagnetic fuel injection valve 14 is provided that injects fuel guided from the fuel tank 12 by an electromagnetic fuel pump 13.

In particular, the glow plug 9, the air supply switching valve 11
, the fuel pump 13 and the fuel injection valve 14 are controlled by a control device 15.
It is designed to be driven by a signal current from.

However, the glow plug 9 and fuel pump 13 are connected to the battery 1.
These relays L'-9a and 13a are connected to the control device 1 through normally open relays 9a and 13a, respectively.
5. Further, the glow plug 9, the air supply switching valve 11, and the fuel pump 13 are controlled on and off, but the fuel injection valve 14 is controlled by duty.

A power supply voltage is applied to the control device 15 from the battery 16 via the engine key switch 1T, and signals from various sensors are also input.

That is, a pressure sensor 18 for detecting the trap inlet exhaust pressure Pl is provided at the exhaust inlet to the trap 4 (downstream of the burner 5), and a pressure sensor 18 is provided at the exhaust outlet from the trap 4 to detect the trap outlet exhaust pressure P2. A pressure sensor 19 is provided for this purpose.

These pressure sensors 1B and 19 are composed of piezoelectric elements, for example. Signals from these pressure sensors 18 and 19 are then input to the control device 15.

It's the engine speed sensor 20 that detects the engine speed.
and a load sensor 21 for detecting the load of the engine. The rotation speed sensor 20 is constituted by a crank angle sensor, and the load sensor 21 is constituted by a potentiometer interlocked with a control lever 22a of the fuel injection pump 22.

Signals from the rotation speed sensor 20 and the load sensor 21 are also input to the control device 15.

Furthermore, for example, C is installed at the exhaust gas inlet to the trap 4 (downstream of the burner 5) to detect the trap inlet side exhaust gas temperature Tl.
A temperature sensor 23 consisting of an A thermocouple is provided. The signal from this temperature sensor 23 is also input to the control device 15.

The control device 15 is mainly composed of a microcomputer, and as shown in the functional block diagram of FIG. 3, it detects whether or not it is the regeneration time (limit collection amount) and indicates that the regeneration time has come. a regeneration time detection means 25 that sometimes issues a regeneration start signal; and an output control means 26 that issues an output signal to each device for the burner 5 to operate each device when receiving the regeneration start signal from the regeneration time detection means 25. Equipped with.

Here, the regeneration timing detection means 25 is the pressure sensor 18.1.
(PIP2)/Pt is calculated from the signal No. 9, and compared with a predetermined value. When the value exceeds the predetermined value, it is determined that it is time to reproduce, and a reproduction start signal is issued.

The output control means 26 has a built-in delay circuit, etc.
When operating the burner 5, first the glow plug 9 is operated, then the air supply switching valve 11 and the fuel pump 1 are operated.
3 and the fuel injection valve 14 are operated.

In particular, for the fuel injection valve 14, as shown in FIG. a basic injection amount search means 31 for searching for the basic injection amount (proportional to the load and inversely proportional to the load), an increase correction means 32 and a reduction correction means 33 and 34 for appropriately correcting the basic injection amount found by the basic injection amount search means 31. , and a pulse signal output means 35 for outputting a pulse signal having a duty ratio (pulse width) corresponding to the injection amount obtained by passing through these correction means 32, 33, and 34.

Here, the increase correction means 32 adjusts the trap inlet side exhaust gas temperature TI based on a command from the comparison means 36 that compares the trap inlet side exhaust gas temperature TI with a predetermined lower limit value (for example, 550 degrees Celsius) with respect to the target value (for example, 600 degrees Celsius). Temperature Ill! is less than a predetermined lower limit value, an increase correction is performed. Further, the weight loss correction means 33 performs the following operations based on a command from the comparison means 38, which compares the differential value by the differential calculation means 3T, which differentiates the exhaust gas temperature when the trap inlet side exhaust gas temperature T1 is less than a predetermined value, with a predetermined value. Weight loss correction is performed when the differential value is greater than or equal to a predetermined value.

Further, the weight loss correction means 34 reduces the trap inlet side exhaust gas temperature fT.
Based on a command from the comparison means 39 that compares + with a predetermined upper limit value (for example, 650° C.), a reduction correction is performed when the trap inlet side exhaust gas temperature WTt exceeds the predetermined upper limit value.

Next, the effect will be explained.

The honeycomb trap 4 has the characteristics of a laminar flow meter.
If the amount of collected exhaust particulates (flow path resistance) is constant, the trap inlet side exhaust pressure P+ (proportional to the gas amount) and the differential pressure between the inlet side exhaust pressure P1 and the outlet side pressure P2, p, -p, are linearly proportional, and their ratio (PI F2)/PI is constant. Of course, the ratio increases as the amount of collected water increases.

Therefore, the regeneration timing detection means 25 of the control device 15,
From the signals of pressure sensors 18 and 19, (PIF2)/PI
is calculated, and it is determined whether or not this is greater than or equal to a predetermined value, that is, whether or not the limit collection amount has been reached and it is time for regeneration.

As a result, when it is determined that it is the regeneration time, the regeneration time detection means 25 issues a regeneration start signal, and the output control means 26 operates each device for the burner 5 to regenerate the trap 4.

Specifically, first, the relay 9a is closed, the glow plug 9 is activated, and the temperature is raised to a temperature necessary for ignition.

After a certain period of time, the air supply switching valve 11 is switched, the injection valve 14 is operated, and fuel supply is started.

As a result, a mixture of air and fuel is ejected from the air-fuel mixture conduit 8 of the burner 6, flows through the reverse flow type evaporator cylinder I, and is sent into the combustion cylinder 6 through its flame ejection lower a. At this time, the heat of the glow plug 9 ignites and burns. Incidentally, the glow plug 9 activates the relay 9a after a certain period of time from the start of fuel supply.
is deactivated by opening.

When the combustion of the bar 1--5-71' starts, the combustion heat heats the exhaust gas introduced from the numerous exhaust gas introduction holes 6a of the combustion tube 6. Then, as the heated exhaust gas passes through the trap 4, the particulates collected in the trap 4 are combusted and incinerated by excess oxygen in the exhaust gas.

Here, the amount of fuel supplied to the burner 5 is determined by the output control means 2
The basic injection amount search means 31 in 6 searches the basic injection amount according to the current rotation speed and load from the signals of the rotation speed sensor 20 and the load sensor 21, and the pulse signal output means 35 searches for this basic injection amount. By outputting a corresponding pulse signal and controlling the operation of the fuel injection valve 14, the operation is controlled according to the rotation speed and load. 5, where the trap inlet side exhaust temperature T+ detected by is the predetermined lower limit value.
During the period until the temperature reaches 50°C, the increase correction means 32 operates based on the command from the comparison means 36, increases the basic injection amount retrieved by the basic injection amount search means 31, and outputs the pulse signal output means 35. By sending the fuel to the fuel tank, the amount of fuel supplied is increased. Therefore, ignition can be performed quickly, and the rise time of the exhaust gas temperature vTl on the trap inlet side can be shortened. In this period, comparison means 3
Based on the command from 6, the differential calculation means 3T differentiates the trap inlet side exhaust temperature T1 and visually observes the change.
When the differential value is equal to or greater than a predetermined value, that is, when the temperature increase correlation becomes excessive, the reduction correction means 33 is activated based on a command from the comparison means 38. At this time, the injection amount corrected by the increase correction means 32 is changed to the injection amount corrected by the reduction correction means 33.
Therefore, the amount of fuel supplied does not have to be corrected and sent to the pulse signal output means 35, and therefore the degree of increase in the amount of fuel supplied becomes small. Therefore, an excessive temperature rise (overshoot) can be prevented, and a smooth transition to the target value of 600''C can be achieved as shown by the solid line in FIG.

Further, even if the trap inlet side exhaust gas temperature TI reaches around the target value and then decreases by 550'C, which is the predetermined lower limit value, the increase correction means 32 performs an increase correction, and conversely, when the trap inlet side exhaust gas temperature TI reaches the target value, the increase correction means 32 performs an increase correction. When a certain 650'C is exceeded, the weight loss correction means 39 is operated based on a command from the comparison means 39, and a weight loss correction is performed accordingly. In this way, the trap inlet side temperature T is feedback-controlled to the target value, and proper combustion is maintained.

Then, after a certain period of time has elapsed from the start of combustion, the operation of the fuel injection valve 14 is stopped, the relay 138 is opened, and the operation of the fuel pump 13 is stopped. After this, the switching valve 11 is switched and the supply of air is also stopped. This ends playback.

Next, a specific example using the control device 150 microcomputer will be explained.

Figure 5 shows the hardware configuration, in addition to the CPU 41, memory 42, and PIO 43 for interface, there is an A/D on the input side that converts analog data to digital data.
A converter 44 and selectively converting one of the plurality of input signals to A.
, /D converter 440 input multiplexer 45
and is provided.

The input signals include analog voltages (P+, P2) from the pressure sensors 18 and 19, a pulse signal from the rotation speed sensor 2o, an analog voltage from the load sensor 21, and ? The analog voltage (T1) from the quality sensor 23 is input to the multiplexer 45. However, rotation speed sensor 2
The pulse signal from O is converted to analog voltage by F/
It is input to multiplexer 45 via V converter 46.

The CPU 41 operates according to a program based on the flowchart shown in FIG.
After giving a channel instruction to the multiplexer 45 and a start instruction to the A/D converter 44, and receiving an EOC signal indicating the end of conversion from the A/D converter 44, digitally converted data is input. ing. The flowchart will be described later.

On the output side, switch circuits 47, 48, and 49 are provided for operating the glow plug relay 9a, switching valve 11, and fuel pump relay 13a, respectively, in response to an output command from the CPU 41 via the PIO 43.

Further, in order to operate the fuel injection valve 14 and control the pulse width of the driving pulse signal (duty control),
A triangular wave oscillator 50, a gate 51, a D/A converter 52, a comparator 53, and an amplifier 54 are provided. Here, the gate 51 opens in synchronization with the operation of the fuel pump 13 according to an output command from the CPU 41 via the PIO 43, and functions to input the output (triangular wave) of the triangular wave oscillator 50 to the comparator 53. /'A converter 52 functions to convert the control value (digital value) of the injection amount calculated within the CPU 4j and output via the PIO 43 into an analog voltage and input it to the comparator 53. As shown in FIG. 7, the comparator 53 compares the triangular wave with an analog voltage (slice level), forms a pulse signal whose pulse width is controlled by the analog voltage, and sends this pulse signal through an amplifier 54. It functions to output the fuel to the fuel injection valve 14.

To explain the flowchart of FIG. 6, in Sl, it is determined whether or not it is reproduction time. Specifically, the exhaust pressure P+ and P2 are read, (PIP2)/PI is calculated, and this is compared with a predetermined value to make a determination.

If it is determined that it is the reproduction time, the process advances to S2 and thereafter to start reproduction.

In S2, the glow plug 9 is turned on via the switch circuit 47 and the relay 9a. After delaying for a predetermined time (for example, 30 seconds) in S3, the switch circuit 48 is activated in S4.
The supply of p-air is started by turning on the switching valve 11 via the switch circuit 49 and the relay 138, and the fuel pump 13 is turned on via the switch circuit 49 and the relay 138, and the gate 51 is opened to turn on the fuel injection valve 14. Activation starts supplying fuel. Although omitted in the flowchart from now on,
Read the rotation speed and load, look up the basic injection amount in the table, and if you do not perform the correction described later, change the control value of the basic injection amount to that! In the case of correction, the injection amount by the fuel injection valve 14 is controlled by outputting the corrected injection amount control value to the D/A converter 52. Furthermore, although omitted in the flowchart, the glow plug 9 is turned off after a predetermined time from the start of fuel supply, or when the exhaust gas temperature Tt on the trap inlet side rises to a certain extent.

The next steps 86 to S8 form a loop, and in S6 it is determined whether the exhaust gas temperature Tl on the trap inlet side is 550°C or higher, and if it is less than 550°C, then step S9. SIO,
...Execute the subroutine.

In S7, it is determined whether the exhaust gas temperature T1 on the trap inlet side is below 650°C, and if it exceeds 650°C, S7
16. The subroutine of S17 is executed. In S8, it is determined whether a predetermined time (for example, 10 minutes) has elapsed since the start of reproduction, and if the time has elapsed, the process returns to S6 and repeats these steps.

In the subroutine when the temperature is less than 550°C, the basic injection amount is reduced in S9, and the trap inlet side exhaust temperature WTt is adjusted in S10.
is read and stored in register A, a minute time delay is performed in 811, the trap inlet side exhaust gas temperature TI is read again in S12 and stored in register B, and in S13 the difference between the value in register B and the value in the register (B -A) is greater than or equal to a predetermined value. 1 when B-A is less than the specified value
- Return to the main routine. Therefore, in this case, S9
The operation of the fuel injection valve 14 is controlled based on the injection amount corrected to increase in step , and the injection amount is increased. Also, when B-A is greater than a predetermined value, the temperature rise rate is excessive, so S1
Proceed to step 4 and correct the injection amount that was corrected to increase in S9 by decreasing it.
After a minute delay in S15, the process returns to the main routine. Therefore, in this case, after the increase is corrected in S9, S1
The operation of the fuel injection valve 14 is controlled based on the injection amount corrected for reduction in step 4, and the degree of increase in the injection amount becomes smaller.

In the subroutine when the temperature exceeds 650° C., the basic injection amount is corrected to decrease in S16, and after a minute delay is performed in S17, the process returns to the main routine. Therefore, in this case, S16
The operation of the fuel injection valve 14 is controlled based on the injection amount corrected to reduce the injection amount, and the injection amount is reduced.

If a predetermined period of time has elapsed from the start of regeneration, the process proceeds from S8 to 818 to terminate the regeneration, turn off the fuel pump 13, close the gate 51, stop the operation of the fuel injection valve 14, and stop the supply of fuel. do. After a delay of a predetermined time (for example, 30 seconds) in S19, the switching valve 11 is turned off in S20 to stop the air supply.

As explained above, according to the present invention, the amount of fuel supplied to the burner is increased during the period from the start of fuel supply to the burner until the trap inlet exhaust temperature reaches a predetermined value due to ignition combustion. In addition, when the differential value between the exhaust gas temperatures exceeds a predetermined value within the above-mentioned period, further weight loss correction is performed to reduce the temperature rise rate. By preventing the trap from becoming too large, it is possible to prevent burnout and melting of the trap due to overshoot.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the transition of exhaust gas temperature on the trap inlet side after the start of regeneration, Fig. 2 is a functional block diagram of the fuel injection valve control section in an embodiment of the present invention, and Fig. FIG. 6 is a flow chart of the control device in FIG. 6, and FIG. 7 is a signal waveform diagram of the same. 1...Exhaust passage 4...Trap 5...Burner 9...Glow plug 10-...Air pump 11...Switching valve 13...Fuel pump 1
4...Fuel injection valve 15...Control device 18.
19...Pressure sensor 20...Rotation speed sensor
21...Load sensor 23...Temperature sensor 2
5... Regeneration timing detection means 26... Output control means 31... Basic injection amount search means 32... Increase correction means 33° 34... Reduction correction means 35.
...Norculus signal output means 3T...Differential calculation means Patent Applicant: Nissan Motor Co., Ltd. Representative Patent Attorney Fujio Sasashima Figure 1 Ntoku 1 Return 1

Claims (1)

[Claims] A trap installed in the exhaust passage to collect particulates in the exhaust, a trap regeneration burner installed upstream of the trap, and a control that activates the burner when it detects that a predetermined amount of particulates have been collected in the trap. an internal combustion engine comprising: an exhaust temperature detection means for detecting the exhaust temperature between the burner and the trap; a differential calculation means for differentiating the detected value of the exhaust temperature detection means; increasing correction means for increasing the amount of fuel supplied to the burner for a period until the detected value by the exhaust temperature detecting means reaches a predetermined value; 1. A control device for a burner for regenerating an exhaust particulate trap in an internal combustion engine, comprising a reduction correction means for reducing the amount of fuel supplied to the burner to a value smaller than the value corrected for the increase.