JPH07233720A - Exhaust gas particulate purifier - Google Patents

Abstract

PURPOSE:To improve efficiency of filter recovery by setting the filter recovering period of a device in accord with a period of time required for the actual filter recovery in an exhaust gas particulate purifier wherein a filter to catch particulates in exhaust gas is provided thereto and the filter is recovered by combustively removing the particulates caught by the filter. CONSTITUTION:A filter temperature detecting means 9 which is connected to a recovery control means 8 is provided in an exhaust gas particulate purifier having such basic constitution that a filter 3 is provide on one of exhaust gas passages of the branch part 2 of an exhaust pipe 1 so that the exhaust gas is run in the exhaust gas passage during particulates catching period and run to the exhaust gas passage 2B during filter recovering period by switching valves 5A, 5B to be controlled by means of a filter recovery control means 8. Further, this purifier is built up in such a manner that the period of time required for the filter recovery is calculated from filter temperature before starting the filter recovery by means of the recovery control means 8, and timing is made to match a recovery end so as to making switching control to valves 5A, 5B.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas fine particle purification apparatus for collecting fine particles contained in exhaust gas of a vehicle engine, especially a diesel engine, and burning and removing the fine particles.

[0002]

2. Description of the Related Art FIG. 6 shows a typical example of this type of exhaust gas fine particle purification apparatus, and one exhaust gas passage 2A of a branch portion 2 formed in the middle of an exhaust pipe 1 of an engine (not shown).
Is provided with a filter 3 for collecting fine particles containing carbon as a main component contained in exhaust gas, and a heater 4 is provided on one end face of the filter 3 (end face on the wake side in the illustrated example). Valves 5A and 5B are provided at the front and rear positions of the branch portion 2. A differential pressure gauge 6 for detecting a differential pressure before and after the filter 3 is provided in one exhaust gas passage 2A of the branch portion 2, and an air pump 7 communicating with the differential pressure gauge 6 is provided in the downstream of the filter 3. . And the valves 5A, 5B and the heater 4
The air pump 7 is controlled by the reproduction control means 8 built in the computer.

At the time of collecting fine particles, one exhaust gas passage 2A is selectively opened by the valves 5A and 5B, and the filter 3
As a result, the fine particles in the exhaust gas are collected. When the collection of fine particles progresses and the differential pressure across the filter 3 reaches a predetermined value, the regeneration control means 8 controls the valves 5A and 5B.
The exhaust gas flows through the other exhaust gas passage 2B, the heater 4 is energized, and the air is supplied from the air pump 7 to the filter 3. The air passes through the filter 3 and is discharged from the air discharge pipe 20. The fine particles collected by the filter 3 are ignited by the heater 4, and the collected fine particles are burned and removed by the propagation of the flame to regenerate the filter 3. After the regeneration, by switching the valves 5A and 5B, the exhaust gas again flows through the one exhaust gas passage 2A provided with the filter 3, and the particulates are collected.

[0004]

By the way, the filter 3
The time required to complete the regeneration of No. 1 varies depending on the regeneration conditions based on the engine operating conditions and the like. Therefore, when the regeneration time of the regeneration control means 8 for controlling the valves 5A, 5B and the like is set to a constant value, the regeneration mode ends in a shorter time than the actual regeneration time depending on the regeneration condition, and many filters 3 are included in the filter 3. The collection will be started again with the fine particles left. On the contrary, if the regeneration mode is continued even though the regeneration of the filter 3 is actually completed, there is a problem that the air pump 7 is operated and unnecessary power is consumed.

In view of such circumstances, it is an object of the present invention to set the filter regeneration time in the exhaust gas fine particle purification apparatus to a value which is as close as possible to the actual filter regeneration time so that the filter regeneration can be performed efficiently. It was made as.

[0006]

The temperature of the filter changes from 100 ° C to 500 ° C depending on the load condition of the engine. As a result of many experiments conducted by the inventors, there is a large correlation between the time required for filter regeneration and the filter temperature (filter preheat temperature) before the start of filter regeneration, and as shown in FIG. 4, the regeneration time is equal to the filter preheat temperature. It was confirmed that it shortened in proportion to.

The present invention has been made on the basis of this finding, and as shown in FIG. 1, temperature detection means 9 for detecting the filter temperature is provided in the vicinity of the filter 3 of the exhaust gas fine particle purification apparatus, and regeneration control is performed. The means 8 receives the input from the temperature detection means 9, calculates the time required for filter regeneration from the filter temperature before the start of filter regeneration, and is set to control the filter regeneration time.

Specifically, the regeneration control means 8 is set to calculate the filter regeneration temperature in a proportional relationship between the filter temperature before starting the filter regeneration and the time required for filter regeneration. More specifically, the above proportional relationship is set so that the time required for filter regeneration becomes linearly shorter than the filter temperature before the start of filter regeneration.

A filter 3 provided in at least one of the branch exhaust gas passages 2A and 2B of the exhaust pipe 1, a heater 4 which is controlled by the regeneration control means 8 and burns and removes fine particles captured by the filter 3 and regeneration control means 8 The basic structure provided with the valves 5A and 5B that are controlled by the above-mentioned method to switch the exhaust gas passages 2A and 2B between the time of collecting the particulates and the time of regenerating the filter is substantially the same as the conventional device.

[0010]

The valve 5 is controlled by the regeneration control means 8 at the timing which coincides with the timing of completion of the regeneration of the filter.
A and 5B are switched, and the apparatus shifts to the particulate collection mode. Therefore, the fine particles hardly remain, the power consumption is not wasted, and the filter is efficiently regenerated.

[0011]

EXAMPLE Exhaust gas passages 2A, 2 of a branch 2 of an exhaust pipe 1
On one side 2A of B, a filter 3 having a honeycomb structure, which is made of porous cordierite and has a large number of cells penetrating front and back.
Is installed. The openings in front of and behind the cell are closed alternately. An electric heater 4 is attached to the end surface on the downstream side of the filter 3. On the upstream side of the filter 3 in one exhaust gas passage 2A, an air exhaust pipe 20 is branched, and the passage 2A and the exhaust pipe 20 are selectively opened and closed by a valve 5A provided in the passage 2A. There is. At the rear end of the filter 3 of the one exhaust gas passage 2A, a valve 5 that selectively opens and closes the rear end of the passage 2A and the other exhaust gas passage 2B.
B is provided. A differential pressure gauge 6 for detecting a differential pressure ΔP before and after the filter 3 is provided in one exhaust gas passage 2A. An air pump 7 is connected to the exhaust gas passage 2A on the downstream side of the filter. Further, a temperature sensor 9 is provided on the downstream side of the filter in the passage 2A so as to detect the filter temperature from the exhaust gas temperature passing through the filter 3. Valves 5A, 5B, heater 4, differential pressure gauge 6,
The air pump 7 and the temperature sensor 9 are connected to an electronic control unit 8 equipped with a microcomputer as a filter regeneration control means, and the electronic control unit 8 receives an input from the differential pressure gauge 6 and the temperature sensor 9 to energize the heater 4. In addition, the operation of the valves 5A and 5B and the air pump 7 is controlled by a predetermined tanning.

Next, the basic operation of this apparatus will be described. The valve 5A is controlled by the electronic control unit 8 so that the valve 5A opens the inlet of the exhaust gas passage 2A provided with the filter 3 and closes the air discharge pipe 20, and the valve 5B. When the outlet of the exhaust gas passage 2A is opened and the outlet of the exhaust gas passage 2B is closed, the exhaust gas flows through the exhaust gas passage 2A, and the fine particles in the exhaust gas pass through the filter 3
Captured in.

When the collection progresses and the electronic control unit 8 detects that the particulate collection amount has reached a predetermined amount by the input from the differential pressure gauge 6, the valves 5A and 5B close both ends of the exhaust gas passage 2A to exhaust the gas. The gas is discharged through the exhaust gas passage 2B.
At this time, the heater 4 is energized under the control of the electronic control unit 8,
The air pump 7 operates and air is supplied to the filter 3.

As a result, the collected particulates at the downstream end of the filter 3 are ignited, the flame propagates to the upstream side, the collected particulates are burned and removed, and the filter 3 is regenerated. The air is discharged from the air discharge pipe 20.

When the filter regeneration is completed, the valves 5A, 5
B is again controlled so that the exhaust gas flows through the exhaust gas passage 2A, and the collection of fine particles is started.

By the way, this apparatus is equipped with a temperature sensor 9 for detecting the temperature of the filter 3, and the operation timing of the valves 5A and 5B for terminating the filter regeneration depends on the filter temperature (preheating temperature) before the start of the filter regeneration. It is decided each time. Prior to describing the details, the experiments conducted by the inventors will be described.

The experiment is made of cordierite, and the size is φ140 ×.
It was carried out using a filter having a tubular honeycomb body of 130 mm.
In this experiment, the amount of collected fine particles at the start of filter regeneration was measured directly from the weight of the filter before and after collection. The collection amount at the start of regeneration was 9.2 g / I, and the air flow rate during regeneration was 0.1 m.
/ S, heater power 2 Kw, energizing time 3 minutes, the experiment was conducted.

The results are shown in FIG. It was found that the time required for filter regeneration shortened linearly in proportion to the preheating temperature. Also, the time is about 3 at a preheating temperature of 0 to 500 ° C.
It was found that the value greatly changed from minutes to 6.5 minutes.

The present invention has been made on the basis of the knowledge obtained by experiments. A temperature sensor 9 is provided as a filter preheating temperature detecting means, and an electronic control unit 8 is provided every time the filter is regenerated.
Calculate the time required for regeneration from the preheating temperature with
This is to control A and 5B.

That is, as shown in the flow chart of FIG. 2, when the differential pressure ΔP across the filter 3 exceeds a predetermined value, the electronic control unit 8 calculates and sets the filter regeneration time t from the preheating temperature T. At the same time, the valves 5A and 5B are switched to filter regeneration. Then, after the lapse of t time, valves 5A and 5B
To switch to particulate collection.

Thus, as shown in FIG. 5B, in the conventional device, the regeneration time is set to 6.5 minutes so that the collected particulates are not left unburned when the filter is regenerated. As shown in FIG. 5A, the reproduction time can be set to the time actually required for reproduction. Therefore, the particles are not left unburned, the consumption of electric power required for regeneration can be suppressed as much as possible, and the regeneration efficiency of the filter can be greatly improved.

According to the present invention, as shown in FIG. 3, filters 3A and 3 are provided in both exhaust gas passages 2A and 2B of a branch portion 2 of an exhaust pipe 1.
It can also be applied to an exhaust gas purification device provided with B.

In this device, by switching the valves 5A and 5B, the exhaust gas selectively flows through both passages 2A and 2B,
When the fine particles are collected by one filter, the other filter is regenerated. Each exhaust gas passage 2A, 2B is provided with a temperature sensor 9A, 9B and an air exhaust pipe 20A, 20B, and the differential pressure across the filters 3A, 3B is a common differential pressure gauge 6.
Is detected by the air filter 7 and is supplied from the common air pump 7 when the filter is regenerated. The other structure is substantially the same as that of the previous embodiment shown in FIG. 1 and its explanation is omitted. Also in this device, the same operational effects as those of the above-described embodiment can be obtained.

[0024]

According to the exhaust gas particle purification apparatus of the present invention,
Since the filter regeneration time is set to the time actually required for filter regeneration, there is no unburned particulates left behind due to excessive regeneration time, and there is no waste of power consumption due to excessive regeneration time. Done.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a first embodiment device of the present invention.

FIG. 2 is a flowchart showing the operation of the above embodiment.

FIG. 3 is a diagram showing a configuration of a second embodiment device of the present invention.

FIG. 4 is a diagram showing an experimental result regarding a relationship between a filter preheating temperature and a filter regeneration time.

FIG. 5 is a model view showing control of filter regeneration time of the device of the present invention (A) and the device of the related art (B).

FIG. 6 is a diagram showing a configuration of a conventional device.

[Explanation of symbols]

 1 Exhaust Pipe 2 Branches 2A, 2B Exhaust Gas Passage 3, 3A, 3B Filter 4 Heater 5A, 5B Valve 6 Collection Amount Detection Means (Differential Pressure Gauge) 7 Air Pump 8 Regeneration Control Means (Electronic Control Section) 9, 9A, 9B Filter temperature detection means (temperature sensor)

Claims (3)

[Claims] 1. A filter installed in at least one exhaust gas passage of a branch formed in the middle of an exhaust pipe of an engine to collect fine particles contained in exhaust gas, and a filter for collecting fine particles collected by the filter. A collection amount detecting means for detecting the collection amount, a heater for burning and removing fine particles collected by the filter to regenerate the filter, and switching of the exhaust gas passage at the time of selection of the particulate collection and the filter regeneration Valve and
In an exhaust gas fine particle purification apparatus having a regeneration control means for controlling energization of a heater and switching of a valve, a temperature detection means for detecting a filter temperature is provided, and the regeneration control means receives an input from the temperature detection means. An exhaust gas fine particle purification device, characterized in that a time required for filter regeneration is calculated from a filter temperature before the start of filter regeneration and the filter regeneration time is controlled. 2. The exhaust gas fine particle purification apparatus according to claim 1, wherein the regeneration control means is set to calculate the time required for filter regeneration by making the filter temperature before starting filter regeneration and the time required for filter regeneration proportional to each other. 3. The exhaust gas fine particle purification device according to claim 2, wherein the proportional relationship is such that the time required for filter regeneration decreases linearly with respect to the filter temperature before the start of filter regeneration.