JP3146870B2 - Particulate filter regeneration device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a particulate filter regenerating apparatus for removing particulates from exhaust gas of a diesel engine.

[0002]

2. Description of the Related Art Diesel engine exhaust gas contains
A particulate trap containing particulate filters is installed on the exhaust gas flow path of the diesel engine to collect particulates without releasing them to the atmosphere. It is effective to be.

[0003] This type of particulate trap increases the trapping amount as the vehicle travels. Flow resistance of the exhaust gas passage of this for the vehicle increases with the increase in the exhaust gas flow rate and running time, so that the suppressed obtain output. Therefore, in a normal particulate trap, the collected particulates are burned by an electric heater arranged on the exhaust gas inflow side inside the particulate trap to regenerate the particulate trap.

There are the following two methods for determining the timing of regeneration of the particulate trap.

[0005] 1. Normally, between the pressure loss (Δp) of a particulate filter (hereinafter referred to as a filter) and the exhaust flow rate (αNe), the deposition amount of the particulate (PM) increases as the exhaust flow rate increases, and There is a characteristic that pressure loss increases. Therefore, the pressure loss of the filter is detected, and the amount of the particulate PM deposited based on the pressure loss is determined.
A method of starting regeneration of a filter when the amount of the filter reaches a predetermined value.

[0006] 2. As shown in FIG. 6, between the running time and the amount of accumulated particulate PM, there is a characteristic that as the running time becomes longer, the amount of accumulated particulate PM increases. In the figure, reference symbol A represents a city area traveling pattern, B represents a medium speed pattern, and C represents a relationship between the traveling time of the high speed pattern and the accumulation amount of the particulate PM. Therefore, a method of measuring the running time and starting regeneration of the filter at regular intervals.

[0007]

SUMMARY OF THE INVENTION One of the above-mentioned methods includes:
There is a problem that the amount of particulates deposited at the time of low rotation of the engine varies widely, and detection cannot be performed with sufficient accuracy.

In the second method, the amount of particulate PM deposited in a certain period of time varies depending on the running pattern. For example, in the traveling pattern A, it takes time ta for the deposition amount of the particulate PM to become a (g), but in the traveling pattern C, it takes t to reach a (g).
It takes i hours. Assuming that the time is set to start the regeneration of the filter at ta, in the traveling pattern C, the particulate PM accumulates in c (g).

As shown in FIG. 7, between the filter maximum temperature Tmax and the amount of deposited particulate PM, there is a characteristic that as the amount of deposited particulate PM increases, the filter maximum temperature Tmax increases. When the temperature of the filter exceeds the allowable value shown in the figure, the filter is cracked or melted and damaged. Therefore, the particulate PM is c
(G) When the regeneration of the filter is started after the deposition, there is a problem that the filter is damaged.

The second method is suitable for a vehicle running in a fixed pattern such as a route bus, but has a problem that it is not suitable for a vehicle running in various patterns such as a truck.

An object of the present invention is to provide a reliable and durable particulate regenerating apparatus which can be applied to all operating conditions, does not damage the filter when regenerating the filter, and has a high reliability.

[0012]

According to the first aspect of the present invention,
A filter for trapping particulates in the exhaust,
Regenerating means for heating the filter to burn the trapped particulates, particulate amount detecting means for detecting the amount of particulates trapped in the filter, and measuring the running time since the previous filter regeneration processing a travel time detection means, response to driving conditions of the engine
The output of the particulate amount detection means and the travel
A control for selecting one of the outputs of the time detecting means and activating the reproducing means when the output of the particulate amount detecting means exceeds a set value or when the output of the traveling time detecting means exceeds a set time. Means.

According to a second aspect of the present invention, in the particulate filter regenerating apparatus according to the first aspect, the particulate amount detecting means detects a pressure difference between before and after the filter.

[0014]

According to the present invention, the control means selects either the output of the particulate quantity detection means or the output of the travel time detection means in accordance with the operating condition of the engine, and the output of the particulate quantity detection means sets the set value. When the time exceeds the predetermined time or when the output of the travel time detecting means exceeds the set time, the regenerating means is operated to burn the particulates.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, reference numerals 10A and 10B denote particulate traps (hereinafter, traps 10A and 10B, respectively).
B). The trap 10A is provided with a main exhaust pipe 8 connected to an exhaust manifold 7 of the diesel engine E.
Meanwhile, the traps 10B are provided in the branch pipes 9 that are branched from the main exhaust pipe 8, respectively.

Since the traps 10A and 10B have the same configuration, the configuration will be described as a representative of the trap 10A. The configuration of the trap 10B is the same as that of the trap 10B.
In the figure, B is added to the end of the reference numeral used for A. As shown in FIG. 2, the trap 10A is housed via a wire mesh 12A inside a bulging portion 2Aa at the center of the casing 2A, and a metal particulate filter 1A that collects particulates in exhaust gas. (Hereinafter referred to as a filter), an electric heater 6A disposed on the exhaust gas inflow side of the filter 1 and heating the filter 1A to burn the trapped particulates, and a heat reflecting plate 11A disposed further forward of the electric heater 6A. It is mainly composed of

The casing 2A is made of stainless steel,
Before and after the central bulging portion 2Aa, a front and rear cone portion 3 is provided.
A and 4A are integrally formed to extend. Front cone 3
A is connected to the main exhaust pipe 8, and the rear cone 4 is connected to an exhaust pipe to a muffler (not shown).

As shown in FIG. 2, the filter 1A is made of ceramic having a honeycomb structure in which a large number of narrow paths 28A are stacked in the same direction, and is made of particulates from exhaust gas passing through the side walls of the narrow paths 28A. Is configured to be filtered.

As shown in FIG. 1, the electric heaters 6A and 6B are connected to an engine control unit 14 (hereinafter referred to as ECU) as control means and a battery 26 via switches SA and SB, which will be described later. An alternator 27 is connected to the battery 26.

The main exhaust pipe 8 and the branch pipe 9 are connected to a trap 10
A and 10B are connected upstream of the exhaust gas inflow side by a communication pipe 5, and filters 1 </ b> A and 1 </ b> B are connected to the center of the communication pipe 5.
An air pump P for supplying air to the traps 10A and 10B when reproducing B is provided. Normally closed valves 18 and 19 are arranged on both sides of the air pump P of the communication pipe 5. The air pump P and the valves 18 and 19 are connected to the ECU 14, and when the filters 1A and 1B are regenerated, the ECU
14, based on the signal from 14 and traps 10A,
Supply secondary air to 10B. Here, the electric heater 6
A and 6B and the air pump P constitute a regeneration unit.

The connecting portion between the main exhaust pipe 8 and the branch pipe 9 has E
A switching valve 13 that is selectively oscillated between a position where the main exhaust pipe 8 is closed and a position where the branch pipe 9 is closed by an actuator (not shown) connected to the CU 14 is disposed. The switching valve 13 closes the main exhaust pipe 8 when the trap 1A is at the time of regeneration, and closes the branch pipe 9 when the trap 1B is at the time of regeneration, in response to a signal from the ECU 14.

A pressure sensor 21 for detecting exhaust pressure is disposed in the main exhaust pipe 8 on the upstream side of the switching valve 13, and pressure sensors 22 and 23 for detecting exhaust pressure are also provided downstream of the traps 10A and 10B. Each is arranged. The pressure information from each of the pressure sensors 21, 22, and 23 is input to the particulate amount detection means 20.

When the switching valve 13 is located at a position where the branch pipe 9 is closed,
Based on the pressure information from the pressure sensors 21 and 22, the pressure difference before and after the trap 10A is calculated, and when the switching valve 13 is located at the position where the main exhaust pipe 8 is closed, the pressure difference from the pressure sensors 21 and 23 is calculated. Based on the pressure information, the trap 10B
Is calculated, and the amount of particulate trapped in the filters 1A and 1B is detected.

As shown in FIG. 3, the filters 1A and 1B have a characteristic that the combustion temperature becomes higher as the amount of particulates (PM) increases during filter regeneration. In this example, the value is set to a (g) within a range not exceeding the filter durability temperature.

As shown in FIG. 4, between the running time (running time from the previous filter regeneration process) and the amount of accumulated particulate PM discharged from the engine E, as the running time increases, the particulate PM increases. There is a characteristic that the amount of deposits increases. In the figure, the reference symbol A denotes a pattern with many zones where the engine speed is low when traveling in an urban area, B is a medium speed pattern, and C is the travel time and particulate PM of a pattern where there are many zones where the engine speed is high and the engine speed is high.
Respectively with respect to the amount of deposition. In this example, when the running pattern is A, the above-mentioned reproducing means is operated when the running time reaches ta. In addition, the travel time ti in the travel pattern C
It represents the time when the amount of particulates deposited on the filter becomes a (g).

As shown in FIG. 5, there is a characteristic between the pressure loss before and after the filters 1A and 1B and the exhaust flow rate (αNe) that the pressure loss increases as the exhaust flow rate increases. However, as shown in the figure, when the vehicle travels after depositing a certain amount of particulates, when the exhaust gas flow rate is small, the variation is large and the deposition amount cannot be measured with an accuracy of ± 10%.
On the other hand, when the exhaust flow rate is large, it is possible to measure with an accuracy of ± 10%. Therefore, only the pressure loss in the high rotation region where the exhaust gas flow rate is large is used for detecting the amount of accumulated particulates. However, for example, in a vehicle traveling in an urban area where many operations are performed in a low rotation range, it is impossible to determine the amount of accumulated particulates based on the filter pressure loss. Such travel patterns into account, the vehicle can not determine the particulate matter deposit amount in the filter pressure loss is so as to implement the regeneration process reaches the fixed time.

The main part of the ECU 14 is constituted by a microcomputer, and stores maps and programs shown in FIGS. Here, the ECU 14 takes in the information from the particulate amount detecting means 20 or the traveling time detecting means 25 and drives the air pump P, energizes the electric heaters 6A and 6B, and switches the valves 18, 19 and the switching valve 13. It has a function to control.

The operation of the particulate filter reproducing apparatus according to the present invention will be described below. First, when the starter switch is operated, the engine E, the ECU 14 and various sensors are operated, and the exhaust gas from the engine E is supplied to the main exhaust pipe 8.
, The particulates are trapped by the filter 1A and discharged into the atmosphere.

Here, the ECU 14 measures the filter pressure loss and the exhaust flow rate only when the engine speed is high, and starts the regeneration process when the pressure loss exceeds the set value input on the map.

When the pressure loss is lower than the set value according to the map of FIG. 5, the ECU 14 keeps the electric heater 6A and the air pump P inactive. When the pressure loss eventually becomes higher than the set value, the ECU 14 operates the actuator to swing the switching valve 13 from the position for closing the branch pipe 9 shown in FIG. The valve 19 is opened, the valve 18 is closed, and the exhaust gas is led to the trap 10B. The electric heater 6A is turned on to heat the filter 1A, and after a predetermined time, the air pump P is turned on to send secondary air into the trap 10A, and the particulates deposited on the filter 1A are burned and regenerated. You. After a predetermined time has elapsed, the operation of the electric heater 6A is stopped, and thereafter, the operation of the air pump P is also stopped.

Next, when the engine speed during running is too low to measure the pressure loss, the ECU 14 activates the actuator and closes the switching valve 13 to close the main exhaust pipe 8 at the running time ta. Swinging from the position to the position where the branch pipe 9 shown in FIG. 1 is closed, the valve 19 of the communication pipe 5 is closed, the valve 18 is opened, and the exhaust gas is guided to the trap 10A.
The electric heater 6B is turned on to heat the filter 1B, and after a predetermined time, the air pump P is turned on to send the secondary air into the trap 10B, and the particulates deposited on the filter 1B are burned and regenerated. You. After a lapse of a predetermined time, the operation of the electric heater 6B is stopped, and thereafter,
The operation of the air pump P is also stopped.

[0032]

According to the present invention, the control means controls the output of the particulate amount detecting means in accordance with the operating condition of the engine.
Alternatively, one of the outputs of the traveling time detecting means is selected, and when the output of the particulate amount detecting means exceeds the set value or when the output of the traveling time detecting means exceeds the set time, the reproducing means is operated to activate the particulate. Since the curate is burned, it can be applied to all operating conditions, and there is no damage to the filter at the time of regeneration of the filter, and a reliable and durable particulate regeneration apparatus can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a particulate filter reproducing apparatus according to an embodiment of the present invention.

FIG. 2 is a sectional view of the particulate trap shown in FIG.

FIG. 3 is a graph showing a relationship between a filter maximum temperature of the particulate filter shown in FIG. 1 and a particulate deposition amount.

FIG. 4 is a graph showing a relationship between a particulate accumulation amount and a traveling time of the particulate filter shown in FIG.

FIG. 5 is a graph showing a relationship between a pressure loss of the particulate filter shown in FIG. 1 and an exhaust flow rate.

FIG. 6 is a graph showing a relationship between a particulate accumulation amount and a traveling time of a conventional particulate filter.

FIG. 7 is a graph showing the relationship between the maximum filter temperature of a conventional particulate filter and the amount of accumulated particulates.

[Explanation of symbols]

 Reference Signs List 1A, 1B particulate filter 2A, casing 2Aa bulging part 3A front cone part 4B rear cone part 6A, 6B electric heater 7 exhaust manifold 8 main exhaust pipe 9 branch pipe 10A, 10B particulate trap 11A, 11B heat reflecting plate DESCRIPTION OF SYMBOLS 13 Selection valve 14 ECU as a control means 18, 19 Valve 20 Particulate amount detection means 21, 22, 23 Pressure sensor 25 Traveling time detection means

Claims (2)

(57) [Claims] 1. A filter for trapping particulates in exhaust gas, regenerating means for heating the filter to burn the trapped particulates, and a particulate quantity for detecting an amount of the particulates trapped in the filter. Detecting means, running time detecting means for measuring the running time since the previous filter regeneration processing, and engine
The output of the particulate amount detection means depends on the operating condition.
Force or the output of the travel time detecting means, and when the output of the particulate amount detecting means exceeds a set value or when the output of the travel time detecting means exceeds a set time, the reproducing means And a control means for operating the particulate filter. 2. The particulate filter regenerating apparatus according to claim 1, wherein said particulate amount detecting means detects a pressure difference between before and after the filter.