JPS59158310A - Regenerative burner controller for micro exhaust particle catching trap for internal-combustion engine - Google Patents

Abstract

PURPOSE:To improve firing performance of burner by controlling at least one of fuel or air supply to burner thereby making air-fuel ratio immediately after starting of burner thick then making gradually thin to transfer to optimal air- fuel ratio. CONSTITUTION:Upon detection of regeneration timing by means of regenerating timing detecting means 31, an output control means 32 will operate each machinery for burner to start regeneration of trap 3. Here drive pulse having constant duety ratio is provided to fuel control valve 12 to control fuel supply constant, but drive pulse having duty ratio controlled in accordance to predetermined pattern is provided to an air relief valve to control relief air flow or air supply. Air supply is controlled to be constant as time elapses to provide optimal air- fuel ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control device for a regeneration burner of an exhaust particulate trap used as an exhaust purification device for an internal combustion engine.

As a conventional exhaust purification device for internal combustion engines for automobiles, a trap is installed in the middle of the exhaust passage to collect particulates whose main component is carbon in the exhaust, and a predetermined amount of particulates are collected in the trap. At this stage, a burner installed upstream of the trap is activated to heat the exhaust gas, and the heated exhaust gas incinerates particulates to regenerate the trap.

By the way, when operating a burner, the glow plug or heater for ignition is made red hot and then the supply of fuel and air is started to ignite and burn, but it is necessary to ensure ignition and combustion. Gansho 57-1070
As proposed in No. 39, the arrangement structure of the combustion tube and evaporator tube has been devised.

However, until the burner starts combustion, the temperature of the evaporator tube is low, and the fuel in the mixture is not sufficiently atomized before it is discharged, and the glow plug is easily cooled by air, making ignition difficult. This tendency is particularly noticeable under low speed and low load conditions with low exhaust temperature.

In view of these circumstances, the present invention aims to improve the ignition performance at the start of burner operation by controlling the air-fuel ratio of the mixture of fuel and air supplied to the burner. Control at least one of the fuel supply amount or the air supply amount to the burner during the ignition period immediately after the start of operation of the burner, so that the air-fuel ratio at the beginning of the period becomes richer and becomes thinner as time passes to shift to an appropriate air-fuel ratio. The ignitability is improved by providing an air-fuel ratio control means.

Examples will be described below.

In FIG. 1, a honeycomb trap 3 for collecting exhaust particulates is interposed in the middle of an exhaust passage 2 of a diesel engine 1, and a burner 4 for L-lap regeneration is provided upstream thereof.

The burner 4 includes a combustion tube 5 having a large number of exhaust flow holes,
It includes a mixture conduit 6 facing into the combustion tube 5, a reverse flow type evaporator tube 7 surrounding the outlet end of the mixture conduit 6, and a glow plug 8 for ignition.

The inlet side of the mixture conduit 6 is connected to a fuel supply pipe 9 and an air supply pipe 10.
The fuel supply pipe 9 is connected to an electromagnetic fuel pump 1 that sucks fuel from a fuel tank (not shown) and pumps it.
1, and a fuel control valve 12 that controls the amount of fuel supplied. A discharge port of an air pump 13 is connected to the air supply pipe 10 via an electromagnetic switching valve 14, and a check valve 15 is provided in the middle thereof.

The air pump 13 is driven by a pulley by an engine, and its suction port is connected to an air cleaner (not shown).

The switching valve 14 connects the discharge port and the suction port of the air pump 13 in a non-energized state, and connects the discharge port of the air pump 13 and the air supply pipe 10 in a energized state.

An air release pipe 16 is provided which branches from between the switching valve 14 and the check valve 15 of the air supply pipe 10 and connects to the intake port of the air pump 13, and this air release pipe 16 controls the amount of air released. An electromagnetic air relief valve 17 is provided.

Here, a rotation speed sensor 18 for detecting the rotation speed of the engine, and a load sensor 1 for detecting the load of the engine.
9 is provided. The rotation speed sensor 18 is constituted by an electromagnetic pink amplifier placed close to the drive gear 20H of the fuel injection pump 20, and is constituted by a potentiometer linked to the control lever 20b of the fuel injection pump 20.

Further, a differential pressure sensor 21 is provided, and this differential pressure sensor 21
The upstream exhaust pressure P1 and the downstream exhaust pressure P2 of the trap 3 are respectively guided by pressure conduits 22,23. Further, a temperature sensor 24 is provided upstream of the burner 4 for detecting the upstream exhaust gas temperature To, and a temperature sensor 24 is provided downstream of the burner 4 for detecting the downstream exhaust temperature T1.
5 is provided. These rotation speed sensor 18, load sensor 19, differential pressure sensor 21, temperature sensors 2i, 25
The signal is input to the control device 30, and the control device 30 controls the glow plug 8, fuel pump 11, and fuel control valve 12.
, controls the operation of the air supply switching valve 14 and the air relief valve 17.

The control device 30 is composed of a microcomputer, and as shown in the functional block diagram of FIG. ΔP(-P+
P2), a regeneration time detection means 31 detects the regeneration time (the amount of collected particles is equal to or greater than a predetermined amount) and issues a regeneration start signal; The presence or absence of ignition of the burner 4 is detected based on the temperature difference T+To between the exhaust temperature To and TI detected by the output control means 32 that operates each device for the burner 4 and the temperature sensor 24° 25 after a predetermined time from the start of regeneration. ignition detection means 33 that issues a regeneration stop signal to the output control means 32 when no ignition occurs, and a regeneration stop that monitors the regeneration time and issues a regeneration stop signal to the output control means 32 when a predetermined regeneration time has elapsed. and a timer 34.

The output control means 32 has a delay function, etc., and when operating the burner 4 to start regeneration, it first operates the glow plaque 8, and then operates the fuel pump 11, fuel control valve 12, and air supply switching valve. 14 and air relief valve 17
It is designed to operate.

A drive pulse with a constant duty ratio (pulse width) is output to the fuel control valve 12 in order to control the fuel supply amount to a predetermined value, but a drive pulse with a constant duty ratio (pulse width) is output to the air relief valve 17 immediately after the start of regeneration. The duty of the drive pulse is set such that the air supply amount is decreased (increases the air release amount) during the ignition period, and the air supply amount is gradually increased (the air release amount is gradually decreased) during that period to a predetermined value. - Control the ratio. That is, as shown in the functional block diagram of FIG. 3, the output control means 32 includes air release amount setting means 35,
It has a timer 36, an increase correction means 37, and a drive pulse output means 38, and during the ignition period, the timer 36 operates the increase correction means 37 to set the air release amount setting means 35.
The amount of air escaping set by is corrected by increasing the amount of air escaping, and the amount of air escaping is corrected by decreasing the correction coefficient over time to gradually decrease the amount of air escaping, and the control value of the corrected amount of air escaping is sent to the drive pulse output means 38. Then, drive pulses having a control pattern as shown in FIG. 4 are outputted to the air relief valve 17. Note that the air relief valve 17 opens when it is ON and closes when it is OFF.

The actual hardware configuration of the control device 30 is as shown in FIG. 5, where 40 is a CPU, 41 is a memory, and 42 is a CPU.
is the PI3 for the interface.

On the input side, there is an A/D converter 43 that converts analog data into digital data, and a multiplexer 4 that selectively inputs one of a plurality of input signals to the A/D converter 43.
4 is provided. The input signals are a pulse signal from the rotation speed sensor 18, an analog voltage from the load sensor 19, an analog voltage from the differential pressure sensor 21, and an analog voltage from the temperature sensors 24 and 25, which are input to the multiplexer 44. .

However, the pulse signal from the rotation speed sensor 18 is input to the multiplexer 44 via the F/V converter 45 in order to convert it into an analog voltage.

The CPU 40 operates according to a program based on flowchart 1 in FIG.
After receiving the EOC signal indicating the end of conversion from the A/D converter 43, the digitally converted data is read. Note that the flowchart will be described later.

On the output side, switch circuits 46, 47, and 48 are provided for controlling on/off the glow plug 8, fuel pump 11, and air supply switching valve 14, respectively, based on output commands from the CPU 40 via the PIO 42.

Further, in order to operate the fuel control valve 12, a square wave oscillator 49, a gate 50, and an amplifier 51 are provided.

Here, the gate 50 is opened in synchronization with the operation of the fuel pump 11 by an output command from the CPU 40 via the PI 042, and the rectangular wave from the rectangular wave oscillator 49 is input to the amplifier 51 and amplified, and the duty ratio is constant. A driving pulse is applied to the fuel control valve 12. Further, in order to operate the air relief valve 17, a triangular wave oscillator 52, a gate 53, a D/A converter 54, a comparator 55 and an amplifier 56 are provided. Here, the gate 53 opens in synchronization with the operation of the air supply switching valve 14, and the triangular wave from the triangular wave oscillator 52 is inputted to the comparator 55. Further, the D/A converter 54 converts the digital data of the air release amount control value outputted from the CPU 40 via the PIO 42 into an analog voltage, and inputs the analog voltage to the comparator 55 . As a result, as shown in FIG. 6, the comparator 55 outputs a signal whose pulse width is controlled by the analog voltage (slice level) from the D/A converter 54, and the signal is sent to the air relief valve via the amplifier 56. A driving pulse is given to 17.

Next, the operation will be explained with reference to the flowchart in FIG.

The function of the regeneration time detection means 31 corresponds to 31 in the flowchart, and determines whether the amount of particles collected in the trap 3 has reached a predetermined amount and it is time for regeneration. For details, read the rotation speed N, load and differential pressure ΔP, and set the rotation speed N.
The limit value of the differential pressure f (N.

L) is table-look-amplified and the differential pressure ΔP and limit value f
(N, L), it is determined that it is time for regeneration when the differential pressure ΔP is equal to or greater than the limit value f (N, L).

In this way, when the regeneration time detection means 31 detects that it is the regeneration time, a regeneration start signal is issued, and the output control means 32 starts regeneration of the trap 3 by operating each device for the burner. do. This corresponds to S2 to S4 in the flowchart. For details, first turn on the glow plug 8 (S2), and then wait for a certain period of time (S3).
) to raise the temperature to the level required for ignition, the fuel pump 11 and fuel control valve 12 are operated to start supplying fuel, and the air supply switching valve 14 and air relief valve 1 are activated.
7 to start supplying air (S4).

As a result, a mixture of fuel and air is ejected from the mixture conduit 6 of the burner 4 and passes through the backflow type evaporator tube 7 to the combustion tube 5.
sent inside. At this time, the heat of the glow plug 8 ignites and starts combustion.

At this time, a driving pulse with a constant duty ratio is applied to the fuel control valve 12, and the fuel supply amount is controlled to be constant, but the duty ratio is applied to the air relief valve 17 in a predetermined pattern. A controlled drive pulse is given, and based on this, the amount of air escape and therefore the amount of air supplied is controlled.

That is, the air release amount setting means 35 of the output control means 32
Immediately after the start of regeneration, the set value of the air release amount is increased by the increase correction means 37 for a time specified by the timer 36, and is corrected so that it gradually decreases as time passes within that time, and the drive pulse output means Drive pulses are output from 38 to the air relief valve 17 in a control pattern as shown in FIG. This is S5 of flowchar 1-
．． Corresponds to S6.

Therefore, the amount of air released by the air release valve 17 immediately after the start of regeneration becomes large, and gradually decreases with time.

Conversely, the amount of air supplied is small immediately after the start of regeneration, and gradually increases over time. Looking at the air-fuel ratio, it is rich right after the start of regeneration, and becomes leaner over time until it reaches an appropriate value.

In this way, by increasing the air-fuel ratio immediately after the start of regeneration, ignition can be performed reliably and quickly. Furthermore, when the air supply amount decreases, cooling by air decreases, and this also improves ignition performance.

Then, when a predetermined period of time has elapsed from the start of playback, the timer 3
The operation of the increase correction means 37 according to step 6 is completed, and thereafter the air supply amount is also controlled to be constant, and the air supply becomes appropriate. Also,
The glow plug 8 is turned off (S7 in the flowchart).
).

When the burner 4 is ignited and combustion starts in this way, the combustion heat heats the exhaust gas flowing into the combustion tube 5. Then, this heated exhaust gas
By passing through the knob 3, the particulates collected in the trap 3 are combusted and incinerated.

During this period, the ignition detection means 33 detects whether or not there is ignition, and the regeneration stop timer 344 monitors the regeneration time. This is 38.39 of the flowchart
corresponds to the exhaust temperature T o in S8.

Read T1 and find out that the temperature difference TI-Tθ is, for example, 10
It is determined whether or not the temperature is 0°C or higher, and if it is 100°C or higher, it is assumed that the ignition has occurred, and the process proceeds to the next G. In S9, it is determined whether or not a predetermined regeneration time has elapsed, and the If it is, the process returns to S8 and these determinations are repeated.

If the temperature difference T + To does not reach 100℃ (yo,
The ignition detection means 33 determines that there is no ignition or misfire,
A regeneration stop signal is issued from the ignition detection means 33 to the output control means 32, and as a result, the fuel pump 11 and the fuel control valve 1
2. The operation of the air supply switching valve 14 and the air relief valve 17 is stopped. This corresponds to Sll in the flowchart.

When a predetermined playback time has elapsed, a playback stop signal is issued from the playback stop timer 34 to the output control means 32,
As a result, the operation of the fuel pump 11, fuel control valve 12, air supply switching valve 14, and air relief valve 17 is stopped.

This corresponds to SIO in the flowchart. This ends the playback.

In this embodiment, the fuel supply amount is kept constant and the air supply amount is decreased to make the air-fuel ratio richer. However, it is also possible to keep the air supply amount constant and increase the fuel supply amount to make the air-fuel ratio richer. You can also do this. However, reducing the amount of air supplied is more suitable for improving ignitability since cooling by air is reduced.

In addition, when controlling the fuel supply amount and air supply amount according to operating conditions such as rotation speed and load, it is sufficient to correct the fuel supply amount or air supply amount determined according to the operating conditions. .

As explained above, according to the present invention, the initial air iJt is concentrated during the ignition period immediately after the start of burner operation, and is controlled to become thinner with the passage of time to shift to the appropriate air-fuel ratio. The effect is that the process can be performed reliably and quickly.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, and FIG.
FIG. 3 is a functional block diagram of the air relief valve control section in the output control means in FIG. 2, FIG. 4 is a signal waveform diagram of the drive pulse to the air relief valve, and FIG. The figure is a hardware configuration diagram of the same control device as above, and Figure 6 is a signal waveform diagram of the air relief valve control section in Figure 5.
FIG. 7 is a flowchart of the above control device. 1...Diesel engine 2...Exhaust passage 3...
Trap 4... Burner 8... Glow plug 11... Fuel pump 12... Fuel control valve 13... Air pump 14... Air supply switching valve 17... Air relief valve 3o... Control device patent applicant Nissan Motor Co., Ltd. Patent attorney Fujio Sasashima

Claims (1)

[Claims] In an internal combustion engine that is equipped with a trap that is installed in an exhaust passage to collect particulates in the exhaust, a burner for regenerating the trap that is installed upstream of the trap, and a control device that controls the operation of the burner, An air-fuel ratio in which at least one of the fuel supply amount or air supply amount to the burner is controlled during the ignition period immediately after the start of the operation, so that the air-fuel ratio at the beginning of the period is enriched and becomes thinner with the passage of time to shift to an appropriate air-fuel ratio. 1. A control device for a burner for regenerating a trap for collecting exhaust particulates in an internal combustion engine, characterized in that the control device is provided with a control means.