JP3073375B2 - Exhaust gas purification device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purifying apparatus for collecting and regenerating particulate components (particulates) contained in exhaust gas of a diesel engine.

[0002]

2. Description of the Related Art In a conventional exhaust gas purifying apparatus, a heater (a so-called end face heater) is provided along an upstream end face of a particulate filter for collecting and collecting particulates which is provided in a case and has a large number of cells having both ends opened. It is known that a particulate is ignited upstream of a filter.

As an example of this end face heater, a type in which a bare heating wire is formed in a spiral shape in the vicinity of an upstream end face of a filter (hereinafter referred to as a spiral heater) has been proposed.
As another example of the end face heater, Japanese Utility Model Publication No. 61-40893 is used.
The publication discloses a heating wire having a large number of U-shaped bent portions inserted into each cell of a honeycomb-shaped ceramic filter and disposed along an end face of the filter, and a cell having each bent portion inserted therein. (Hereinafter referred to as an embedded heater) comprising a blind plug made of a ceramic material, which is filled with a heater and fixes each bent portion of the heater to each cell.

[0004]

However, the above-mentioned spiral heater has the following problems. That is,
Since the naked heating wire is arranged in a spiral shape, if the heating wire is extended to increase its surface area, lower the heat transfer resistance between the two and increase the heating power, the heating wire will obstruct the air flow. As a result, the flow velocity is reduced, and thereby, the heat transfer between the air flow and the heating wire or the filter or the burning of the particulates is hindered.

On the other hand, in the above-described embedded heater, the heating wire is embedded in the filter cell by a blind plug, so that when the filter is replaced because ash or the like is deposited on the filter or the filter is damaged, it is not inexpensive. There was a major problem that the embedded heater had to be discarded at the same time. The present invention has been made in view of the above problems,
Particulate from heating wire while suppressing increase in fluid resistance
It is an object of the present invention to provide an exhaust gas purifying apparatus which reduces the thermal resistance to the exhaust gas and does not require simultaneous disposal when replacing the filter.

[0006]

SUMMARY OF THE INVENTION An exhaust gas purifying apparatus according to the present invention comprises a plurality of cells having openings at both ends and a honeycomb filter for collecting particulates provided in an exhaust passage of a diesel engine. An exhaust gas purifying apparatus comprising: a heater disposed along an end face of the filter and configured to burn the particulate by energization.
The heater, while being arranged to be separated from the filter, provided with a heating wire naked having multiple bend formed into a U-shape in the axial direction of the filter, further, the heating
The filter has a large number of cells open at both ends and the filter
Honeycomb inside the exhaust path on the upstream side of the filter
Wherein the bent portion of the heating wire is the holder
Of cells.

[0007] In a preferred embodiment, a part of the bent portion
Is a ceramic filler to be filled in some of the cells
Is fixed to the holder.

[0008] In a preferred aspect, the distal end of each of the bent portions is detachably inserted into each of the cells of the filter.

[0009]

The heater according to the present invention includes a bare heating wire disposed separably from the filter, and the heating wire has a large number of bent portions formed in a U-shape in the axial direction of the filter. Therefore, the following effects can be obtained. First
In addition, each bent portion is moved in the axial direction of the filter, that is,
Because it is extended in the shape of a letter, the contact area (heat transfer area) between the heating wire and the airflow can be increased significantly compared to the conventional spiral heater, while suppressing the increase in the resistance of the airflow. Thus, the heating power can be increased while avoiding a rise in temperature, and the entire airflow can be uniformly heated.

Second, the heater of the present invention is configured to be separated from the filter as compared with an embedded heater having a similar shape (ie, a large number of bent portions formed in a U-shape in the axial direction of the filter). Therefore, there is an advantage that it is not necessary to discard the filter at the same time when replacing the filter. Also,
Since the heater of the present invention is exposed to the air stream naked and the air stream is not blocked by the blind plug or the like of the embedded heater, the heating wire quickly spreads the particulate on the upstream end face of the filter through the air stream. And it can be heated uniformly.

As a result, the heater of the present invention has
It is possible to suppress the increase in the fluid resistance of the air flow, to reduce the thermal resistance from the heating wire to the particulates, and to obtain an excellent effect that the filters do not have to be discarded at the same time in replacement. In addition, each bent portion of the heating wire has many openings at both ends of the holder.
Adjacent bends because they are individually housed in a number of cells
Keep them stable without touching each other or vibrating.
You can have. The cells of this holder are open at both ends.
And its fluid resistance is much smaller than the cell of filter 2.
No. In addition, for the reasons described above, the cells in the holder
-It is difficult to accumulate, so particulate combustion
High temperature has little effect on the holder and heating wire.
Can also increase the lifespan.

[0012]

(Embodiment 1) An embodiment of the exhaust gas purifying apparatus of the present invention is shown in FIG. This exhaust gas purifying device has a filter housing case 1 sealed at both ends.
And an upstream pressure sensor 7 for detecting exhaust pressure, a temperature sensor 6, a heater 9, a filter 2, and a downstream pressure sensor for detecting pressure downstream of the filter in the filter housing case 1 from the upstream side to the downstream side. 17 are arranged in order. An exhaust pipe 3 on the upstream side of the diesel engine 20 is disposed on an upstream end wall of the filter housing case 1.
The air supply pipe 10 branches off in the middle of the process. The air supply pipe 10 is connected to an outlet of an air supply blower 13 through an electromagnetic valve 14, and an inlet of the air supply blower 13 is opened to the outside through an air flow sensor 15. 4 is a downstream exhaust pipe.
You.

On the other hand, the drive of the motor M of the heater 9 and the blower 13 is controlled by the controller 8, and the output signal of the rotation speed sensor 18 mounted on the diesel engine 20 is output to the controller 8. The controller 8 is provided with an A / D converter microcomputer (not shown), both the switch 55 and 56 open and close control to control the heater 9, the blower 13 turns on the abnormal alarm lamp 90 when an abnormality occurs . Note that the controller 8
A voltage applied to the blower 13 based on a signal from the air flow sensor 15 is precisely controlled to a target level by a duty ratio control (feedback control) to a supply flow rate of the blower 13.

A power supply device 5 includes a plug 51 connected to a commercial ground power supply (not shown), a step-down transformer 52,
The DC voltage output from the full-wave rectifier 53 is supplied to the heater 9 and the blower driving motor M through the semiconductor power switches 55 and 56. The filter 2 is a honeycomb ceramic filter (manufactured by Nippon Insulator KK, diameter: 5.66 inches × length: 6 inches), which is fired in a cylindrical shape using cordierite as a material. The filter 2 has a large number of air holes (cells in the present invention) penetrating both end surfaces, one of the adjacent air holes is sealed at the upstream end, and the other is sealed at the downstream end. Exhaust gas passes through the porous partition between adjacent vents, and only particulates are trapped in the vents. Both end faces of the filter 2 face both end faces of the case 1 at a predetermined distance.

The heater 3 is made of an electrothermal resistor made of a Kanthal wire as will be described later, and is arranged close to an end face which is on the upstream side during regeneration of the filter 2. Hereinafter, the operation of this device will be described. (Particle collection operation) Diesel engine 20
The exhaust gas discharged from the exhaust pipe is introduced into the case 1 through the exhaust pipe 3, particulates in the exhaust gas are collected by the filter 2, and the purified exhaust gas is discharged from the tail pipe 4 to the outside.

(Filter Regeneration Operation) Next, the regeneration operation of the filter 2 will be described with reference to the flowchart of FIG. In this device, it is assumed that the filter regeneration operation is started by manual operation after receiving power from an external power supply during the engine stop period. Immediately before the start of regeneration, the solenoid valve 14 is opened.

FIG. 2 shows a filter regeneration routine consisting of a filter regeneration determination routine (steps 100 to 111) executed during engine operation and a filter regeneration execution routine (steps 112 to 116) executed while the engine is stopped. . First, a filter regeneration determination routine is started when the engine 20 is started.
At 00, the exhaust pressure P detected by the pressure sensors 7 and 17
1, P2, the engine speed n detected by the speed sensor 18 and the exhaust gas temperature T detected by the temperature sensor 6 are used to calculate a particulate collection amount based on a memory map.

Next, at step 108, it is checked whether or not the collected amount of collected particulate G exceeds a predetermined threshold value Gt. If not, the process returns to step 100, and if it does, the process returns to step 111. move on. In step 111, the lamp 91 for instructing the filter regeneration is turned on, and the routine ends.

Thereafter, when the driver visually recognizes the lighting of the lamp 91 for instructing the filter regeneration and turns on the regeneration switch (not shown) while the engine is stopped, the filter regeneration execution routine is started. In this routine, first, the blower 13 is started in step 112, then a built-in timer is started (114), and a timer control subroutine is executed to energize the motor M and the heater 9 in a predetermined order ( 116), and end the reproduction (118).

The detailed structure of the heater 9 will be described below with reference to FIGS. The heater 9 has a case 90, a honeycomb-shaped holder 91 housed in the case 90, and a heating wire 92 (see FIG. 5) held by the holder 91 as main components. The case 90 includes a cylinder 901 made of stainless steel and having both ends opened, and wheel plates 902 and 903 welded to both ends of the cylinder 901. Wheel plates 902, 9
Through holes 904 are opened around the periphery of the filter 03, and the through holes 904 are formed by through bolts (not shown) penetrating through holes 905 of the upstream exhaust pipe 3 and through holes 906 of the filter housing case 20. It is interposed between the side exhaust pipe 3 and the filter housing case 20.

The holder 91 is made of a thick disk-shaped ceramic honeycomb formed of the same process and the same material as the filter 2, and has a large number of cells (holes) having openings at both ends. The holder 91 is accommodated at the downstream end of the cylinder 901 via a mat 911 made of expandable ceramic, and the downstream end surface of the mat 911 (and the outer peripheral portion of the holder 91) is in contact with the wheel plate 903. . On the other hand, the cylinder 901 has the wheel plate 9
07 is fixed by welding, and the wheel plate 907 is
0 3 sandwiching the mat 911 and the holder 91 together.

The heating wire 92, as shown in FIG. 5, full I Le
Consists bare Kanthal wire having a plurality of bent portions 920 which extends in a U-shape to the other downstream, are inserted individually into each cell 912 from the upstream side end face of each of the bent portions 920 holder 91. Of course, each bent portion 920 may be individually inserted into each cell 912 from the downstream end surface of the holder 91.

FIG. 4 shows an upstream end surface of the holder 91. The heating wires L1 to L15 extend in the horizontal direction in the figure along the upstream end surface of the holder 91, respectively.
L15 has a large number of U-shaped bent portions 920 which are individually accommodated in the respective cells 912 of the holder 91 as shown in FIG. The heating wires 92 are formed by connecting the heating wires L1 to L15 in series.

Further, as shown by a black dot in FIG.
A part of the cells 912a of the cells 912 containing the “0” is filled with a ceramic heat-resistant sealing material (trade name: Sumiceram, manufactured by Sumitomo 3M Limited), and the heating wire 92 is formed by the hardened ceramic heat-resistant sealing material. Fixed. On the other hand, a holding plate 908 is disposed radially upstream of the wheel plate 907 by a predetermined distance, and both ends of the holding plate 908 are fixed to the inner peripheral surface of the cylinder 901.
Further, a plate 93 including an insulator is fixed to the opening of the cylinder 901, and a pair of screw holes (not shown) of the insulator 93 has a male screw shape for individually fixing one end of each of the electrode bars 94 and 95. Electrode terminals 96, 96 (one shown) are individually screwed.

Further, the other end of each of the electrode bars 94 and 95 is fixed to a holding plate 908 by screws 98 via an insulator tube 97. The electrode bars 94 and 95 and both ends of the heating wire 92 are connected to electric wires 99 and 99, respectively. Are connected individually. The heater 9 of the present embodiment configured as described above has the following effects. First, the heater 9 is provided so as to be separable from the filter 2 and includes a naked heating wire 92 having a large number of bent portions 920 formed in a U-shape in the axial direction of the filter 2.

Therefore, the contact area (heat transfer area) between the heating wire and the air flow can be increased remarkably while suppressing the increase in the resistance of the air flow, and the heating power can be reduced while avoiding a decrease in the supply flow rate and a rise in the temperature of the heating wire. It can increase and uniformly heat the entire airflow. Further, since the heater 9 is configured separately from the filter 2, it is not necessary to discard the filter 2 at the same time when the filter 2 is replaced.

Further, since each bent portion 920 of the heating wire 92 is individually accommodated in a large number of cells 912 at both ends of the holder 91, adjacent bent portions 920 may come into contact with each other or vibrate. And can be stably held. The cells 912 of the holder 91 are open at both ends,
Its fluid resistance is much smaller than that of the filter 2 cell.
Although the holder 91 is made of porous cordierite in this embodiment, it may be made of dense ceramic.

Further, the cell 91 of the holder 91 for the above-described reason.
Since the particulates hardly accumulate in 2, the high temperature due to the particulate combustion hardly affects the holder 91, the heating wire 92 and the ceramic heat-resistant sealing material, and the life thereof can be increased. FIG. 6 shows this holder 91.
The result of examining the heating capability of the contained heating wire 92 is illustrated.

In the experiment, the downstream end of the heating wire 92 and the filter 2
5 shows the maximum temperatures of the radial center portion a and the outer peripheral portion b of the upstream end surface of the filter 2 when the gap d between the upstream end surface of the filter 2 is variously changed. In addition, the supply air flow rate is about 60 liters / minute,
The diameter of the filter 2 is 143.8 mm and the heating power is 2 kW
And

This experiment shows that the gap d is preferably 15 mm or less, more preferably 10 mm or less. However, if the inner peripheral surface of the cylinder 901 in this gap is insulated by a ceramic mat, the temperature drop is small even if the gap d is further extended. Next, under the same conditions as in the experiment of FIG. 6, a change in temperature at the radial center portion a of the upstream end face of the filter 2 was examined when the preheating power was 0.8 kW, 7 minutes, the ignition power was 1.3 kW, and 23 minutes. . The result is shown by a solid line. Further, a conventional example using an embedded heater is shown by a dotted line.

From this experiment, it can be seen that this embodiment can raise the temperature quickly. (Embodiment 2) Another embodiment is shown in FIG. In this embodiment, the heating wire 92 is inserted from the upstream end surface 91a of the holder 91, and each bent portion 920 is greatly elongated. Further, each bent portion 920 is connected to each cell (not shown) of the filter 2 (not shown). Cells are sealed at the downstream end)
Has been inserted.

In this way, the particulates collected in each cell of the filter 2 (these cells are sealed at the downstream end) come into direct contact with the heating wire 92, so that the ignitability is improved. Significantly improved. (Embodiment 3) FIG. 9 shows another embodiment.

In this embodiment, the heating wire 92 is
Is inserted from the downstream end face 91b of the
(Only one end is shown) 92a penetrates the upstream end surface of the holder 91. By doing so, the heating wire 92 can be fixed to the holder 91 by fixing both ends (only one end is shown) 92 a of the heating wire 92. (Embodiment 4) Another embodiment is shown in FIG.

In this embodiment, the heating wire 92 is
Every other cell 912. Further, the tip of each bent portion 920 projects from the holder 91, and a ceramic rod 92 b is inserted into the tip of each bent portion 920, and the heating wire 92 is fixed to the holder 91. In this way, the fixing of the heating wire 92 is simplified. (Embodiment 5) Another embodiment is shown in FIG.

In this embodiment, the heating wire 92 is
Are inserted line by line in each cell 912. By doing so, the insertion step becomes complicated, but the heating wire 92 can be fixed to the holder 91 without adding a step of fixing the heating wire 92. In each of the above-described embodiments, the radial cross-sectional area of the cell 912 of the holder 91 may not be the same as that of each cell of the filter 2. In short, the smooth flow of the supply air flow and the stable holding of the heating wire 92 It is sufficient that heat transfer from the heating wire 92 to the supply air flow can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of an exhaust gas purification device of the present invention;

FIG. 2 is a flowchart showing the reproducing operation;

FIG. 3 is a cross-sectional view of one embodiment of a heater.

FIG. 4 is a front view of a holder that is a part of the heater.

FIG. 5 is a partially enlarged sectional view of the heater of FIGS. 3 and 4;

FIG. 6 is a temperature change diagram obtained by examining the heating capacity of the heater of FIG. 3;

FIG. 7 is a temperature change diagram obtained by examining the heating capacity of the heater of FIG. 3;

FIG. 8 is a sectional view showing another embodiment of the heater.

FIG. 9 is a cross-sectional view showing another embodiment of the heater.

FIG. 10 is a cross-sectional view showing another embodiment of the heater.

FIG. 11 is a sectional view showing another embodiment of the heater.

[Explanation of symbols]

2 is a filter, 6 is a temperature sensor, 7 and 17 are pressure sensors, 8 is a controller, 9 is a heater, 13 is a blower, 9
1 is a holder of the heater 9, 92 is a heating wire of the heater 9, 90
Denotes a case of the heater 9.

Continued on the front page (72) Inventor Kenji Arakawa 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Co., Ltd. (72) Inventor Terutaka Kageyama 1-1-1 Showa Town, Kariya City, Aichi Prefecture Japan Denso Co., Ltd. (56 ) References JP-A 4-105921 (JP, U) JP-A 61-40893 (JP, Y2) JP-A 63-35151 (JP, Y2) JP-A 2-18276 (JP, Y2) (58) Field surveyed (Int. Cl. ⁷ , DB name) B01D 46/00-46/54 F01N 3/02-3/038

Claims (3)

(57) [Claims] 1. A semiconductor device comprising a large number of cells having openings at both ends, and
Particulates installed in the exhaust path of diesel engines
A honeycomb-shaped filter for collecting sheets,
It is arranged along the end face,
Exhaust gas purifier equipped with a heater for burning
Wherein the heater is provided so as to be separable from the filter.
WithBeforeMany U-shaped in the axial direction of the filter
Equipped with a naked heating wire having a bent part,  The heater has a large number of cells with openings at both ends.
C that is provided in the exhaust path on the upstream side of the filter.
It has a honeycomb-shaped holder,  The bent portion of the heating wire is housed in a cell of the holder.
ToCharacterized byExhaust gas purification device. The bent portion of wherein in part, an exhaust gas purification device according to claim 1, wherein the ceramic filler is filled in a part of the cell is fixed to the holder. Wherein the distal ends of the bent portion, detachably exhaust gas purifying device according to claim 1, wherein are inserted into each cell of the filter.