JPH07310532A - Diesel particulate filter - Google Patents

Abstract

PURPOSE:To make the trapping and burning of particulate more effectual by concentrically arranging three kinds of conductive filter elements, and providing a shut-off valve in the upstream of the central filter element, a pressure sensor for exhaust pressure and a clogging sensor. CONSTITUTION:A coarse mesh metal filter 33 is arranged in the inner cylinder 20 of a filter case 1, and an extremely fine mesh outer filter 31 and a fine mesh middle filter 32 are arranged in the peripheral part of the metal filter 33 for forming the filters in a triple layer structure, and a shut-off valve 22 actuated according to the exhaust pressure of an engine is attached to an intake 22 in the upstream of the cylinder 20. In order to make the outer filter 31 and the middle filter 32 conductive, a heat resisting metal heater is united with ceramics fiber, and moreover a clogging sensor 43 functioning on the detection of the variation of resistance value is attached to the metal filter 33, and three kinds of filter screening based on the trapping of the particulate and the supplying of electric current are controlled according to the exhaust pressure depending upon the operating condition of the engine and a clogging state.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Since a diesel engine injects fuel into high-pressure high-pressure air and mixes it, the fuel is often not completely mixed and carbonized at the time of ignition, carbonized, and often mixed in exhaust gas and discharged. .

The compound of carbon and hydrocarbon contained in the exhaust gas is called particulate, which is one of the causes of urban pollution that pollutes the atmosphere.

In order to prevent the particulates discharged from the diesel engine from being released into the atmosphere,
A particulate filter has been developed that attaches a filter to the exhaust flow path and filters to purify the exhaust gas.
Usually, a filter made of a porous material made of ceramics is used.

Since it is difficult to remove the collected particulates with a filter made of this type of ceramics, an ignition source is arranged in a part of the filter, and the particulates collected by the ignition source are ignited and incinerated. Removes particulates from the filter.

[0006]

In the method of igniting and removing the particulates by the ignition source arranged in the filter as described above, the ignited particulates are partially burned without progressive combustion. However, abnormal heat is generated and the temperature becomes high, causing a melting damage accident of the ceramic filter.

The present invention seeks to remedy such conventional problems, and its object is to provide an ignition source in a part of a filter element for collecting particulates,
The filter itself is made to have conductivity, and a filter element is arranged according to the size of the particulate matter contained in the exhaust flow passing through the filter to efficiently collect it, and also according to the clogging state of the filter element. An object of the present invention is to provide a diesel particulate filter that energizes itself to heat the clogged filter to burn the particulates evenly.

[0008]

In order to achieve the above object, according to the present invention, the exhaust gas of a diesel engine is guided to a filter element having a ceramic or metal fiber laminated filter and a conductive incineration material. In a diesel particulate filter that incinerates the collected particulate by energizing the filter element by energizing the filter element, and a coarse filter element arranged in the central portion of the gas flow passing through the filter, Diesel particulates that have a filter that combines fine and extremely fine filter elements arranged on the outer periphery of the coarse filter and an on-off valve that opens and closes according to the exhaust pressure of the engine and that allows a gas flow to flow to the coarse filter element A filter is provided.

Two kinds of filter elements are provided in the peripheral part, that is, a filter element having an extremely fine outer side and a filter element having a finer inner side, both of which are made of ceramic long fiber material and a metal heater. One is used, and a diesel particulate filter using a metal filter or a porous metal plate with a wire mesh in the center part is provided,
Further, the filter areas of the respective filter elements arranged from the peripheral portion toward the central portion are configured to be successively reduced, but the filter area of the metallic filter in the central portion is 10 times or more the exhaust pipe cross-sectional area. A diesel particulate filter is provided in which the diameter of the bypass pipe is equal to or larger than the diameter of the exhaust pipe.

[0010]

[Function] A coarse metal filter is arranged in the central portion of the gas flow passing through the filter, a fine filter in which ceramics fibers and a metal heater are combined is arranged on the outside thereof, and an extra fine filter of the same kind as the fine filter material is arranged on the outside thereof. However, an opening / closing valve that opens according to the exhaust pressure is installed at the inlet of the coarse filter in the center, so that the gas flow is guided to an appropriate filter according to the exhaust pressure from the engine to efficiently collect particulates. In addition, since each filter is made conductive, the filter itself uniformly generates heat when the heating power is applied, and the filter is screened.

[0011]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a configuration block diagram showing an embodiment of a diesel particulate filter according to the present invention. Reference numeral 1 in the figure is a filter case, which is formed in a cylindrical shape with its upstream and downstream directions narrowed, a flange 11 connected to the exhaust pipe of the engine at the upstream end, and a mounting plate for the tail pipe at the downstream end. A filter block 2 is housed in the central case 10 with a block outer wall 21 supported by a layer of a heat insulating material 13 inscribed in the case.

A concentric cylinder 20 having an intake 22 in the upstream direction is attached to the center of the filter block 2, and a long fiber material of ceramics is laminated on the outer periphery of the cylinder 20.
A cylindrical outer filter 31 in which a partially locked filter and a heat-resistant metal mesh heater are combined;
The fine middle filter 32 is concentrically and doubly arranged. Then, the upstream direction of the outer filter 31 and the block outer wall 21 are closed, and the outer filter 31 and the middle filter 3 are closed.
The downstream side of 2 is closed with a similar conductive filter material, and the upstream side of the middle filter 32 and the intake 22 side of the cylinder 20 are closed. The outer filter 31 has a filter mesh of 20 μm to 60 μm, which is extremely dense, and the middle filter 32 has a filter mesh of 60 μm to 150 μm.

Next, inside the cylinder 20, a metal filter 33 having a bottomed cylindrical metal mesh made of porous heat-resistant metal is laminated or a metal filter 33 made of a metal porous plate has its opening in the upstream direction, that is, the intake port 22. Is normally biased in the closing direction by a spring 25 and the on-off valve 23 is offset, so that the intake port 22 is opened in response to an increase in exhaust gas exhaust pressure, and ,
Actuator 24 responding to a signal from a pressure sensor described later
The on-off valve 23 opened by is attached. Since the on-off valve 23 is attached by the offset support shaft, it automatically opens when the exhaust pressure increases. Further, the filter mesh of the metal filter 33 is coarser than the above-mentioned and medium filters, and is formed to 200 μm to 300 μm, and the filter area is 10 times or more of the exhaust pipe cross-sectional area, and the cross-sectional area of the intake port 22 is The diameter is larger than the diameter of the exhaust pipe, and the inner filter 32 and the outer filter 31 are sequentially formed in a large area.

Reference numeral 41 is a battery, which serves as a power source for supplying power for incineration to a controller, which will be described later, or a clogged filter, 42 is a pressure sensor for detecting exhaust pressure from the engine, and 43 is a clogging sensor. With metal filter 3
3 is provided to detect the change in electric resistance value due to the accumulation of particulates to detect the clogging state of the filter. 34 and 35 are energizing terminals for energizing the outer filter 31 and the middle filter 32, and 36 and 37 is an energizing terminal for energizing the metal filter 33, and lead wires from these sensors and energizing terminals are connected to a predetermined port of the controller.

The controller 4 is composed of a microcomputer and is provided with a central control unit for performing arithmetic processing, various memories for storing arithmetic processing procedures and control procedures, input ports and output ports, etc. When a signal is input, predetermined arithmetic processing is performed, and based on the stored control procedure, a command to the actuator 24,
It is configured to issue a power supply command to the energizing terminal.

Explaining the operation of this embodiment thus constructed, the exhaust gas is pressure-fed to the filter block 2 via the flange 11 to the filter case 1 connected to the exhaust pipe of the engine.

Here, the on-off valve 23 of the intake port 22 is closed by the elastic force of the spring 25 when the exhaust pressure from the engine is low, but when the exhaust pressure increases, the on-off valve 2 is unbalanced.
Since the spindle of No. 3 is designed to be opened by applying torque, when the engine is running at high speed and a large amount of exhaust gas is emitted, the exhaust pressure of exhaust gas increases only by passing through the outer filter 31 and the middle filter 32. The on-off valve 23 is opened. Therefore, of the exhaust gas particulates that emit a large amount,
Fine particles that often float are extra fine outer filter 3
1, medium particles with little floating are medium filters 32
Further, the larger particles are filtered by the central metal filter 33, and the particulate-removed clean gas is discharged from the tail pipe to the atmosphere via the downstream mounting plate 12.

Next, in a normal operating condition where the engine is running at low speed, the on-off valve 23 has a spring 25 because the exhaust pressure is low.
The outer filter 31 and the middle filter 32 on the outer side cleanse the exhaust gas by the spring force of. During this time, when the signal from the clogging sensor 43 provided on the metal filter 33 is the resistance value in a state in which the incineration of the deposit is required, the controller 4 sends the power from the battery 41 to the energizing terminals 36 and 37 to open and close. Screening of the metal filter 33 with the valve 23 closed is performed.

Also, the outer filter 3 located outside even during normal operation.
When the 1 and the medium filter 32 are clogged due to the accumulation of particulates, the exhaust pressure becomes high.
Is opened and the exhaust gas is guided to the metal filter 33, and power is supplied to the energizing terminals 34 and 35 in response to a command from the controller to heat the outer filter 31 and the middle filter 32, and the screening of these filters is performed. become.

As described above, in this embodiment, three kinds of filters for collecting the particulates are used, the outer filter 31 having extremely fine outer portions, the medium filter 32 having finer outer portions, and the central portion controlled by exhaust pressure upstream. The coarse metal filter 33 housed in the cylinder 20 provided with the opening / closing valve 23 is arranged,
The exhaust pressure sensor 42 controls the exhaust flow to the central metal filter 33, and the clogging sensor 43 detects the clogging state of the filter. Therefore, when the engine is running at high speed and the displacement is large, the outer filter The exhaust pressure rises too much with only two types of filters, 31 and the medium filter 32, and the exhaust flow is guided to all the filters. Therefore, the particulates having a large particle size, which are mostly distributed in the central portion of the exhaust flow, are collected by the coarse metal filter 33, and the fine particles in the peripheral portion of the exhaust flow have a fine medium filter 32 or a very fine filter. The particulates are efficiently collected by the respective filter elements according to the size of the particle size floating in the outer filter 31.

In the incineration of the collected particulates, since each filter element is electrically conductive, each filter element uniformly generates heat instead of partial heating when electric power is supplied. Therefore, the deposits are also averaged. It is incinerated to prevent the filter element itself from being melted.

[0022]

As described above, according to the present invention, a coarse filter element is provided at the center of the gas flow passing through the filter.
The peripheral part is divided into two layers, the outer layer is extremely fine, the inner layer is a fine filter element, and an on-off valve controlled according to the exhaust pressure from the engine is provided upstream of the filter element in the central portion. Since the peripheral part is composed of a filter element in which fibrous ceramics and a metal heater are combined, and the central part is composed of a wire mesh filter element, when collecting particulates, it is efficient according to the size of the particulates distributed in the gas flow. Since the filter element has conductivity as well as being collected, it is possible to obtain uniform heat generation instead of partial heating at the time of energization, and the effect of uniformly burning the deposit can be obtained.

Further, in the present invention, since the pressure sensor for detecting the exhaust pressure and the clogging sensor for detecting the clogging are provided, the gas flow path control and the filter are controlled according to the operating state of the engine and the accumulated state of particulates. The advantage is that the device can be properly screened.

[Brief description of drawings]

FIG. 1 is a configuration block diagram showing an embodiment of a diesel particulate filter according to the present invention.

[Explanation of symbols]

 1 ... Filter case 2 ... Filter block 10 ... Central case 20 ... Cylindrical 22 ... Intake 23 ... Open / close valve 24 ... Actuator 31 ... Outer filter 32 ... Medium filter 33 ... Metal filter 4 ... Controller 42 ... Pressure sensor 43 ... Clogging sensor

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location F01N 3/02 B 321 K

Claims (6)

[Claims] 1. A diesel engine exhaust gas is guided to a filter element provided with a filter in which ceramic or metal fibers are laminated and a conductive incinerator to collect particulates, and the filter element is energized and collected. In a diesel particulate filter that incinerates particulates, a coarse filter element arranged in the central portion of the gas flow passing through the filter and a fine and extremely fine filter element arranged in the outer peripheral portion of the coarse filter are combined. Diesel particulate filter, characterized in that it has a filter and an opening / closing valve that opens and closes according to the exhaust pressure of the engine, and allows a gas flow to flow to the coarse filter element. 2. The fine filter element is arranged in parallel in a flow path divided into an outer layer and an inner layer, and an extremely fine filter element is used for the outer layer and a fine filter element is used for the inner layer, both of which are long ceramics. The fibers are laminated, and a partially sewn filter and a mesh-shaped heater made of a heat-resistant metal are laminated and combined, and the coarse filter is a wire mesh made of a heat-resistant metal or ceramics or a porous metal plate. The diesel particulate filter according to claim 1, which is a metal filter laminated and ceramic-coated on the surface. 3. The extremely fine filter element is 20 μm.
m to 60 μm, finer filter element is 60 μm to 150
The diesel particulate filter according to claim 2, wherein the filter element having a size of μm and a coarse filter element has a size of 200 μm to 300 μm. 4. The filter area of the coarse filter element is 10 times or more the exhaust pipe cross-sectional area of the engine, and the cross-sectional area of the bypass pipe having an on-off valve is set to be equal to or larger than the exhaust pipe diameter. The diesel particulate filter according to claim 2. 5. The opening / closing valve of the opening / closing valve is offset with respect to the central axis of the pipe and is biased in the closing direction by the elastic force of the spring, and is automatically opened as the exhaust pressure from the engine increases under a predetermined load or more. The diesel particulate filter according to claim 1, wherein a valve of the diesel particulate filter is opened by a signal of a pressure sensor that detects exhaust pressure due to clogging of a fine filter to energize the fine filter side. 6. The coarse filter element is provided with a clogging sensor for detecting a change in electric resistance value due to accumulation of particulates, and heating of the filter element is performed in response to a signal of the sensor and a load signal below a predetermined level of the engine. The diesel particulate filter according to claim 1, wherein electric power is supplied.