JPH0734856A - Regenerrating device for diesel exhaust gas filter - Google Patents

Abstract

PURPOSE:To prevent generation of any crack on a filter by reducing the temperature difference in a filter inside, and burning collected particulates, during burning regeneration of the filter. CONSTITUTION:Voltages of electric heaters 7a, 7b and 7c and the air flow rates of air flow rate control valves 10a, 10b and 10c are controlled in order to lower the temperature difference in radial direction of a filter 1. After ignition is confirmed, only the air flow rates of the air flow amount control valves 10a, 10b and 10c are controlled in order to suppress rapid temperature rise and a maximum temperature after ignition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention collects particulates in exhaust gas discharged from a diesel engine by a physical means on a filter and periodically incinerates this with an electric heater to regenerate the filter. The present invention relates to a regeneration device for a diesel exhaust gas filter suitable for.

[0002]

2. Description of the Related Art Generally, a diesel engine has a low exhaust gas temperature. Therefore, in order to incinerate the collected particulates and regenerate the filter, the exhaust gas temperature is raised by some method or the ignition temperature of the particulates is lowered. Have to burn. As this method, a method has been proposed in which an electric heater is provided upstream of the filter and the heat raises the particulates to the ignition temperature.

[0003]

However, in the conventional method, the amount of particulates adhering to the vicinity of the upstream end face of the filter is small and the ignition becomes unstable. Also, once ignited, combustion begins rapidly and the heat inside the filter is
The temperature rises above 000 ° C. On the other hand, in the vicinity of the outer circumference of the filter, a heat insulating material is generally wound around the outer circumference of the filter to reduce the heat conduction loss with the container, but the temperature is still kept low by heat radiation. .
Therefore, the temperature gradient is large at a distance from the outer circumference of the filter in the radial direction, and as a result, the outer circumference of the filter is subjected to tensile as thermal stress. The filter cannot withstand this stress, and a ring-shaped crack called ring-off occurs on the outer peripheral portion.

Therefore, the present invention is a diesel engine which ignites easily and stably, reduces the temperature difference in the radial direction of the filter, and burns to maintain the original shape of the structure and to withstand long-term use. An object is to provide a regeneration device for an exhaust gas filter.

[0005]

To achieve this object, the present invention provides a plurality of electric heaters in the radial direction of the filter near the exhaust gas downstream of the filter and a plurality of air heaters corresponding to the electric heaters. A nozzle tube is provided and the timing of ignition of particulates on the filter is controlled by a temperature gradient.

[0006]

The operation of the technical means of the present invention is as follows.

That is, by controlling the voltages of a plurality of electric heaters and the flow rates of a plurality of air nozzle pipes arranged in the radial direction in the vicinity of the exhaust gas downstream end surface of the filter having a large amount of particulates adhered, the flow rate during regeneration is controlled. The temperature difference in the filter can be reduced.

As a result, the thermal stress applied to the inside of the filter is small, and there is no large displacement that causes cracks in the outer peripheral portion. Further, the timing of the particulate ignition is surely judged by the temperature gradient, and after the ignition, the voltage of the electric heater is set to 0, and the air flow rate is controlled only to prevent a rapid temperature increase after the ignition. It is possible.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a diesel exhaust gas filter regenerating apparatus according to the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a diesel exhaust gas filter regenerator with a partial block diagram added. Reference numeral 1 is a ceramic filter having a large number of cells 2a and 2b therein. One end of each of the cells 2a and 2b is alternately closed by a plug 3 to form a filter. The filter 1 is formed by winding a sealing material 5 which is made of ceramic fibers into a sheet shape with an organic binder and has an excellent heat insulating property, and is housed in a cylindrical container 6 made of stainless steel.

Reference numerals 7a, 7b and 7c denote electric heaters arranged in the vicinity of the exhaust gas downstream end surface of the filter 1 and in the radial direction of the filter 1, respectively, and relays 21a, 21b and relays 21a, 21b, which operate based on the output signal of the controller 20, respectively. 21c is connected. 8a, 8b and 8c are
The air nozzle tubes are arranged so as to correspond to the electric heaters 7a, 7b and 7c, respectively. 9a, 9a ', 9
Reference numerals b, 9b ', 9c and 9c' are thermometers for detecting the internal temperature of the filter 1 and are connected to the controller 20, respectively, and their detection signals are respectively supplied to the controller 20.
It is designed to be input to. Reference numerals 10a, 10b and 10c are air flow rate control valves for controlling the auxiliary combustion and the temperature inside the filter 1 which are connected to the air nozzle tubes 8a, 8b and 8c, respectively, and are operated by an output signal of the controller 20.

An exhaust pipe 11 connected from a diesel engine (not shown) is branched into an exhaust gas introduction pipe 12 and an exhaust gas bypass pipe 13 in front of the container 6, and the exhaust gas bypass pipe 13 is again provided in the container 6. The muffler connecting pipes 14 are connected so as to join in the middle in the rear. Reference numeral 15 is a combustion gas exhaust pipe at the time of regeneration. The exhaust gas introduction pipe 12, the exhaust gas bypass pipe 13, the muffler connection pipe 14, and the combustion gas discharge pipe 15 are used for switching between the time of collection and the time of regeneration.
Are provided with shutter valves 16, 17, 18 and 19, respectively.

The operation of the diesel exhaust gas filter regenerating apparatus of the present invention constructed as above will be described.

In this case, the shutter valves 16, 17,
The open and closed positions of 18 and 19 are in the positions shown in FIG.
That is, 16 and 18 are open and 17 and 19 are closed. Exhaust gas from the diesel engine reaches the upstream end surface of the filter 1 via the exhaust gas introduction pipe 12. From here, the exhaust gas enters the cell 2b which is open to the upstream side. At this time, the particulates contained in the exhaust gas cannot pass through the cell wall 4 and accumulate in the cell 2b. On the other hand, the exhaust gas that has been cleaned by removing the particulates enters the muffler connection pipe 14, and is discharged to the atmosphere through the exhaust muffler. Then, the particulate accumulation amount in the filter 1 is detected (not shown) by the differential pressure before and after the filter 1, and the operation at the time of regeneration is performed according to the flowchart shown in FIG.

The operation during reproduction is as follows: First, the shutter valve 1
The open / close positions of 6, 17, 18 and 19 are opposite to those in FIG. That is, 16 and 18 are closed, and 17 and 19 are switched to the open position. Combustion control during regeneration is performed in two stages with the particulate ignition timing before and after (step 1).

In the first stage until ignition, the electric heaters 7a, 7b and 7c are instructed by the controller 20.
To the air nozzle pipes 8a, 8b and 8c for a predetermined set time, and the regenerating air having a flow rate controlled by the air flow rate control valves 10a, 10b and 10c, respectively, is supplied for a certain set time (step 2). When that period is completed, the thermometer 9a,
The respective data measured by 9b and 9c are input to the controller 20, and the temperature difference between the thermometers 9a, 9b and 9c is maximum 2 according to the instruction from the controller 20.
The controller 20 controls the voltage applied to the electric heaters 7a, 7b, and 7c so that the temperature does not exceed 00 ° C., and the air flow control valves 10a and 1c.
The supply amount of regeneration air is individually controlled by 0b and 10c. When one of the thermometers 9a, 9b and 9c records a certain set temperature gradient, the filter 1
It is judged that the particulates have ignited (step 3),
The signal shifts to the second stage (step 4).

In the second stage, in order to suppress a rapid temperature rise after ignition, all the voltages of the electric heaters 7a, 7b and 7c are set to 0 and only the air flow control valves 10a, 10b and 10c are used for regeneration air. Control only the flow rate. Specifically, in this stage, thermometers 9a, 9a ', 9b, 9b', 9c and 9c '
All are controlled so that the maximum temperature does not exceed 900 ° C.

All the thermometers 9a, 9a ', 9
Under the condition that b, 9b ′, 9c and 9c ′ are 400 ° C. or less, the operation at the time of regeneration is completed, and at the same time, the shutter valves 16, 17, 18 and 19 are switched to the position at the time of collection (step 5).

As described above, when the particulate matter deposited on the filter 1 is incinerated and regenerated, the electric heater 7a is divided into three parts in the radial direction of the filter 1 near the exhaust gas downstream end surface of the filter 1 having a large particulate deposit amount. , 7b and 7c and their corresponding air nozzle tubes 8a, 8b
And 8c are provided, the ignition timing of the particulates is surely grasped by the temperature gradient at the time of combustion, and in order to reduce the temperature difference in the filter 1, the ignition is divided into two stages, that is, a front stage and a second stage. Filter 1 on stage
The temperature difference in the radial direction is controlled to be small, and in the second stage, a rapid temperature rise after ignition is suppressed, and the temperature is controlled so as not to exceed a certain set maximum temperature. As a result, the thermal stress generated in the filter 1 can be reduced.

[0020]

According to the present invention, the timing of ignition can be reliably detected, and the control of combustion regeneration is divided into two stages before and after the timing of ignition, and in the first stage, the temperature difference in the radial direction of the filter is adjusted. The temperature is controlled to be small, and the second stage is controlled so as to suppress the rapid temperature rise and the maximum temperature. As a result, the thermal stress generated in the filter can be suppressed to a small level, and the filter is prevented from cracking. Therefore, the regeneration device for a diesel exhaust gas filter of the present invention ensures durability that is approximately equivalent to the service life of the diesel engine.

[Brief description of drawings]

FIG. 1 is a sectional view of a diesel exhaust gas filter regenerating apparatus according to an embodiment of the present invention.

FIG. 2 is a flowchart showing an operation during regeneration of the diesel exhaust gas filter regeneration device according to the embodiment of the present invention.

[Explanation of symbols]

1 Filter 2a, 2b Cell 3 Plug 4 Cell wall 5 Sealing material 6 Container 7a, 7b, 7c Electric heater 8a, 8b, 8c Air nozzle pipe 9a, 9a ', 9b, 9b', 9c, 9c 'Thermometer 10a, 10b , 10c Air flow rate control valve 11 Exhaust pipe 12 Exhaust gas introduction pipe 13 Exhaust gas bypass pipe 14 Muffler connection pipe 15 Combustion gas exhaust pipe 16, 17, 18, 19 Shutter valve 20 Controller 21a, 21b, 21c Relay

Claims (2)

[Claims] 1. A diesel engine installed in an exhaust gas passage,
A filter for collecting particulates contained in the exhaust gas, a plurality of electric heaters provided in the vicinity of the exhaust gas downstream end surface of the filter and provided in the radial direction of the filter, and an air nozzle corresponding to each of the electric heaters. Regeneration device for diesel exhaust gas filter characterized by having a pipe. 2. The regeneration device for a diesel exhaust gas filter according to claim 1, wherein the ignition timing of the particulates on the filter is judged and output based on the temperature gradient during heating and incineration.