JPH0726934A - Exhaust emission control device for diesel engine - Google Patents

Abstract

PURPOSE:To provide an exhaust emission control device for a diesel engine which can precisely calculate a trapped volume of particulates. CONSTITUTION:A filter 7 for trapping particulates is located in the exhaust system of a diesel engine 1. An electronic circuit 19 is provided on the sensor signal input side of a CPU 18, and the responsivenesses of output signals from an engine speed sensor 13, a pressure sensor 14 and a pressure sensor 15 is adjusted to the responsiveness of an output signal from a temperature sensor 16 which is the most slow-responsive of the signals 13, 14, 15, 16. The CPU 18 calculates a trapped volume of particulates in the filter 7 from received signals from the sensors, and carries current to an electrical heater 8 so as to burn the particulates trapped in the filter 7 while driving a motor driven air pump 11. Thus, the trapped particulate are burnt so as to regenerate the filter 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust emission control device for a diesel engine.

[0002]

2. Description of the Related Art D as a measure against black smoke in diesel engines
A PF (diesel particulate filter) system is adopted. As shown in FIG. 5, the diesel engine 31 has an exhaust system provided with a DPF 32 for collecting particulates, and a CPU is used during filter regeneration.
By energizing the electric heater 33 at 35, the DPF 3
The particulate matter collected in 2 is ignited and the air pump 34 is driven to supply secondary air to the DPF 32 to incinerate the particulate matter collected in the DPF 32. At this time, in order to determine whether or not to perform the reproduction, the CPU 35 determines that the rotation speed sensor 3
6, pressure sensor 37, pressure sensor 38, temperature sensor 39
Signal from the pressure sensor 37 and the pressure sensor 38.
The exhaust gas temperature from the temperature sensor 39, the engine speed from the rotation speed sensor 36, and the like are added to the differential pressure before and after the filter 32 obtained from the above, and the amount of collected particulate matter of the filter 32 is calculated. Then, when the amount of collected particulates becomes equal to or more than a predetermined value, regeneration is performed.

[0003]

In order for the DPF system to operate effectively, it is necessary to accurately know the trapped amount of particulates. However, when calculating the amount of trapped particulates, as shown in FIG. 6, since there is a difference in responsiveness among the sensors, an incorrect trapping may occur depending on the processing timing (for example, the timing of t1 in FIG. 6). There was a risk that the total amount would be calculated. That is, in general, the rotation speed sensor 36
The pressure sensors 37 and 38 have good responsiveness, but the temperature sensor (thermocouple) 39 has poor responsiveness. Therefore, as shown in FIG. 6, when the operating state changes stepwise at the timing of t0, each sensor signal also changes as shown in the figure. However, when the processing of the CPU 35 is performed at the timing of t1, the temperature sensor 39 is responding, so the CPU 3
In the case of 5, an incorrect value is taken in, and an error occurs in the collection amount calculation.

Therefore, an object of the present invention is to provide an exhaust emission control device for a diesel engine, which can accurately calculate the amount of particulates trapped.

[0005]

According to the present invention, there is provided a filter provided in an exhaust system of a diesel engine for collecting particulates, and for burning the particulates collected by the filter to regenerate the filter. Regenerating means, a plurality of collection amount calculation sensors for calculating the collection amount of particulates in the filter, and signals from the collection amount calculation sensor are input to the particulates in the filter. In a diesel engine exhaust gas purification apparatus including a control circuit that regenerates a filter by the regenerating means when the collected amount is calculated to be a predetermined value or more, the plurality of collected amount calculation sensors The exhaust gas purifying device for a diesel engine, in which the responsiveness of the output signal of the other sensor is combined with the responsiveness of the output signal of the sensor having the slowest responsiveness, is the gist thereof.

[0006]

In the control circuit, the signal from the collection amount calculation sensor is input to calculate the collection amount of particulates in the filter. At this time, the response of the plurality of collection amount detection sensors is the highest. The responsiveness of the output signals of other sensors is combined with the output signals of the slower sensor. As a result, the responsiveness deviations of the plurality of trapping amount detection sensors are eliminated.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an overall configuration diagram of an exhaust emission control device for a diesel engine.

The vehicle is equipped with a diesel engine 1. The diesel engine 1 has an intake pipe 2 and an exhaust pipe 3
And are connected. The intake pipe 2 is provided with an engine air cleaner 4. Also, diesel engine 1
The exhaust pipe 3 is provided with a housing 6 of an exhaust emission control device 5. The housing 6 communicates with the exhaust pipe 3, and the exhaust gas of the diesel engine 1 passes through the housing 6. A filter (DPF) 7 is provided in the housing 6, and the filter 7 collects particulates discharged from the diesel engine 1. Further, an electric heater 8 is provided at the upstream end of the filter 7, and when the electric heater 8 is energized, the electric heater 8 generates heat to ignite the particulates collected by the filter 7.

A secondary air supply pipe 9 is branched on the upstream side of the housing 6 in the exhaust pipe 3, and an electromagnetic valve 10 is arranged in the middle of the secondary air supply pipe 9. The electromagnetic valve 10 is for preventing exhaust gas from flowing back into the secondary air supply path during normal operation. The discharge side of the electric air pump 11 is connected to the tip of the secondary air supply pipe 9. Further, an air cleaner 12 for an air pump is provided on the intake side of the electric air pump 11. Then, when the electromagnetic valve 10 is opened, the secondary air is supplied to the intake pipe 3 of the diesel engine 1 by driving the electric air pump 11.

Further, the diesel engine 1 is provided with a rotation speed sensor 13, which detects the engine rotation speed. A pressure sensor 14 is provided on the upstream side of the filter 7, and the sensor 14 detects the pressure (absolute pressure) on the upstream side of the filter 7. A pressure sensor 15 is provided on the downstream side of the filter 7, and the sensor 15 detects the pressure (absolute pressure) on the downstream side of the filter 7. A temperature sensor 16 is provided in the exhaust pipe 3, and the sensor 16 detects the temperature of exhaust gas flowing into the filter 7. A thermocouple is used for the temperature sensor 16.

The electronic control unit (ECU) 17 has a CP
A U 18 and an electronic circuit 19 are provided. And C
The PU 18 is connected to the electric heater 8 via a semiconductor relay 20, and the energization of the electric heater 8 is controlled according to a control signal from the CPU 18. The CPU 18 is connected to the electric air pump 11 via a semiconductor relay 21,
The drive of the electric air pump 11 is controlled according to a control signal from 18.

The rotation speed sensor 13, the pressure sensor 14, the pressure sensor 15 and the temperature sensor 16 are connected to the CPU 18 through an electronic circuit 19, and the rotation speed sensor 13, the pressure sensor 14 and the pressure sensor 15 are connected through the electronic circuit 19. The output signal from the temperature sensor 16 is fetched by the CPU 18.

A primary delay circuit (CR circuit) shown in FIG. 2 is connected to each sensor input line in the electronic circuit 19. That is, the input signal line 22 has a resistor 2
3 is connected and a capacitor 25 is connected between the input signal line 22 and the ground line 24. Here, the temperature sensor 16 has the slowest response among the respective sensors 13, 14, 15, 16 and, with respect to the response time constant τ of the temperature sensor 16, the remaining sensors 13,
The resistance (resistance value; R) 23 and the capacitor (capacitance; C) 25 in 14 and 15 are set to values such that τ = C · R holds. Therefore, on the output side of the electronic circuit 19, as shown in FIG. 3, the responsiveness of the respective sensors 13, 14, 15, 16 is the same even if the operating state changes.

In the present embodiment, the electric heater 8 and the electric air pump 11 constitute a regeneration means, and the rotation speed sensor 13
The pressure sensor 14, the pressure sensor 15, and the temperature sensor 16 constitute a trapping amount calculation sensor, and the CPU 18 constitutes a control circuit.

Next, the operation of the exhaust gas purifying apparatus for a diesel engine thus constructed will be described. CPU during playback
The operation in 18 will be described with reference to the flowchart of FIG.

First, while the diesel engine 1 is in operation, the CPU 18 determines in step 100 the rotational speed sensor 1
3, pressure sensor 14, pressure sensor 15, temperature sensor 16
Each sensor signal of is acquired. Then, the CPU 18 determines in step 101 whether the reproduction condition is established. That is, the CPU 18 determines the temperature sensor 1 with respect to the differential pressure across the filter 7 obtained from the pressure sensor 14 and the pressure sensor 15.
The exhaust gas temperature from 6 and the engine speed from the speed sensor 13 are corrected, and the trapped amount of the particulates of the filter 7 is calculated. At this time, as shown in FIG. 3, since the responsiveness of each of the sensors 13, 14, 15, 16 is the same, the trapped amount of particulates is accurately calculated.
That is, even when the operating state changes stepwise at the timing of t0 in FIG. 3, each sensor signal having the same response delay is input to the CPU 18.

When it is determined that the particulate collection amount is less than the predetermined value and the regeneration is not necessary, the CPU 18 ends this routine. On the other hand, when the amount of collected particulates becomes equal to or larger than a predetermined value and the regeneration is required, the regeneration is started.

When the regeneration is started while the diesel engine 1 is stopped, the CPU 18 opens the electromagnetic valve 10 in step 102 so that air (oxygen) can be supplied from the electric air pump 11. Furthermore, CPU1
Step 8 determines the regeneration condition for performing the regeneration control of the exhaust emission control device 5 in step 103. Here, the target control flow rate of the electric air pump 11 and the target control power of the electric heater 8 are determined.

Next, the CPU 18 controls the energization of the electric heater 8 and the drive control of the electric air pump 11 in step 104. That is, when the electric heater 8 is energized, the particulates collected in the filter 7 are ignited, the secondary air is supplied by driving the electric air pump 11, the particulates are incinerated, and the filter 7 is regenerated.

Then, the CPU 18 judges the elapsed time after the start of reproduction in step 105, and terminates the reproduction if the set time has elapsed. Thus, in this embodiment,
An electronic circuit 19 is provided on the sensor signal input side of the CPU 18,
Rotation speed sensor 13, pressure sensor 14, pressure sensor 15,
The output signal of the temperature sensor 16 having the slowest response of the temperature sensors 16 (a plurality of trapping amount detection sensors) is matched with the response of the output signals of the other sensors 13, 14, and 15. As a result, in the CPU 18 (control circuit), the sensor 1
Filters 7 by inputting signals from 3, 14, 15 and 16
At this time, the amount of collected particulates is calculated. At this time, the output signal of the temperature sensor 16 having the slowest response of the plurality of sensors 13, 14, 15, 16 is used as the output signal of the other sensor 1.
The responsiveness of the output signals of 3, 14, and 15 are combined, and the responsiveness deviation of the plurality of sensors 13, 14, 15, and 16 is eliminated. Therefore, the trapped amount of particulates can be accurately calculated.

The present invention is not limited to the above-mentioned embodiment. For example, in the above-mentioned embodiment, the electronic circuit 19 is provided when the first-order delay element is inserted in the sensor signal processing. Sensors 13, 14,
The signals of 15 and 16 are directly input to the CPU 18 and the CPU 18
First-order delay elements may be included in the software according to.

[0022]

As described above in detail, according to the present invention,
It has an excellent effect that the amount of collected particulates can be accurately calculated.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an exhaust emission control device for a diesel engine of an embodiment.

FIG. 2 is an electrical configuration diagram of an electronic circuit.

FIG. 3 is a timing chart.

FIG. 4 is a flowchart for explaining the operation.

FIG. 5 is an overall configuration diagram of a conventional diesel engine exhaust emission control device.

FIG. 6 is a timing chart.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Diesel engine 7 Filter 8 Electric heater which constitutes regenerating means 11 Electric air pump which constitutes regenerating means 13 Rotation speed sensor which constitutes a trapping amount detection sensor 14 Pressure sensor 15 which constitutes a trapping amount detection sensor 15 Pressure sensor 16 that constitutes the amount detection sensor Temperature sensor 18 that constitutes the trapped amount detection sensor CPU as control circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Keiichi Kato 1-1, Showa-cho, Kariya city, Aichi Prefecture Nihon Denso Co., Ltd. (72) Inventor Naoji Morita 1-1-1, Showa-cho, Kariya city, Aichi prefecture Nidec Within the corporation

Claims (1)

[Claims] 1. A filter provided in an exhaust system of a diesel engine for collecting particulates, a regeneration means for burning the particulates captured by the filter to regenerate the filter, and the filter. A plurality of collection amount calculation sensors for calculating the collection amount of particulates, and a signal from the collection amount calculation sensor is input to calculate the collection amount of particulates in the filter. In a diesel engine exhaust gas purification device provided with a control circuit that regenerates a filter by the regenerating means when the collected amount becomes a predetermined value or more, the slowest response of the plurality of collected amount calculation sensors An exhaust emission control device for a diesel engine, characterized in that the output signal of a sensor is combined with the response of the output signals of other sensors.