JPH0442487Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] This invention relates to a reburning device for capturing and burning unburned particles such as carbon contained in the exhaust gas of automobiles, etc. This invention relates to an exhaust gas re-combustion device for internal combustion engines, etc., which has an improved particle combustion structure.

[Prior Art] Automobiles equipped with internal combustion engines, especially diesel engines, contain unburned particulates such as carbon in the exhaust gas from the engine, which poses a major problem in terms of environmental pollution. To deal with this, a honeycomb filter for capturing unburned particles is disposed in the exhaust path of the engine, and the exhaust gas is allowed to pass through this filter. According to this, carbon adheres to the filter during the flow of exhaust gas, and since the adhered carbon is exposed to high-temperature exhaust gas, the carbon is combusted. This carbon adhesion and combustion are repeated as appropriate to remove particulate carbon from the exhaust gas.

However, the temperature required for the carbon attached to the filter to burn is generally 600℃ or higher.
Even if the filter is coated with platinum, the temperature is over 400℃, but there is no guarantee that the exhaust gas temperature will always reach the above combustion temperature or higher, and the amount of carbon deposited on the filter will only increase. There is a risk that the combustion removal function will not work.

To prevent this, for example, a separate electric heater for preheating is prepared, the electric heater is placed upstream of the filter relative to the exhaust gas, and the electric heater is periodically energized as the car is driven. The idea is to raise the temperature in advance and then send it into a filter to ensure that the carbon is burned.

[Problems with the Prior Art] An example of this electric heater is a sheathed glow plug type as shown in FIG. 7, which includes 5 to 12 rod-shaped glow plugs 50 (8 in FIG. 7).
They are prepared and arranged radially at equal angular intervals on a ring-shaped frame 50a.

By the way, in this electric heater, the heat generation state of the glow plug 50 inside the frame body 50a is large at the center, gradually decreases toward the outside, and becomes smaller at the outermost periphery, so that the heating distribution state is not uniform but biased. be. Therefore, the exhaust gas that has passed through the frame is sent to the filter with an uneven temperature rise that is highest in the center and lower in the outer periphery, so carbon in the filter is heated earlier in the center and later. Each burns at the outer periphery.

For this reason, there is a large temperature difference between the center and the outer periphery of the filter, and since the filter is generally made of ceramic, there is a disadvantage that the difference in thermal expansion can cause the filter to crack or break. It has also been considered to provide a gas burner to heat the exhaust gas itself; however, since the gas burner generates a large amount of heat, there is a risk that the filter may melt.

[Purpose of the invention] This invention was made in view of the above circumstances.
The purpose of this is not only to burn and remove unburned particles in the exhaust gas, but also to preheat the exhaust gas almost uniformly before sending it to the filter, so the filter does not melt, and when it is burned and removed, the center and outer periphery of the filter It is an object of the present invention to provide a practically excellent exhaust gas reburning device for an internal combustion engine, etc., which does not cause a large temperature difference between the parts and the filter, and does not cause cracking or damage to the filter due to the amount of thermal expansion.

[Means to solve the problem] This idea adopted the following configuration.

1. An exhaust passage for leading exhaust gas from an internal combustion engine to the outside, and a filter made of fire-resistant ceramic that is provided in the exhaust passage so that the exhaust gas can pass therethrough and that captures unburned particles in the exhaust gas. ,
a preheating heater disposed close to the filter on the upstream side of the exhaust passage; The electrical resistor is formed from a plurality of electrical resistors whose tips are bent at approximately right angles in a predetermined direction, and the electrical resistors are arranged at approximately equal angular intervals in the same plane and at approximately right angles to the flow of the exhaust gas. It is arranged so that it is oriented in the direction, and is energized as appropriate during operation.

2. The electrical resistance wires are made of sheathed heaters, and three or more electrical resistance wires are provided at equal angular intervals on a ring-shaped frame.

3. An exhaust path for leading exhaust gas from an internal combustion engine to the outside, and a filter made of fire-resistant ceramic that is provided in the exhaust path so that the exhaust gas can pass through and that captures unburned particles in the exhaust gas. ,
a preheating heater disposed close to the filter on the upstream side of the exhaust passage; A pair of electrical resistors are formed by bending their tips at approximately 45 degrees in a predetermined direction. It is arranged so that it is oriented toward the direction of the motor, and is energized as appropriate during operation.

[Operations and Effects] The present invention configured as described above exhibits the following operations and effects.

1. A preheating heater is made of a plurality of electrical resistors formed by bending an electrical resistance wire into a substantially U-shape from the outside toward the center, and bending the arc-shaped tip at a substantially right angle in a predetermined direction. By forming the two heaters and locating them in the same plane, a substantially uniform temperature distribution can be obtained from the center of the heater to the outer circumference, and the exhaust gas passing through the heater is almost uniform between the center and outer circumference. A substantially uniform state with no temperature difference is achieved, and a large temperature difference does not occur between the center and outer circumference of the filter during combustion and removal, and cracking and damage of the filter due to thermal expansion can be prevented.

Further, the electrical resistance wires are made of sheathed heaters, and three or more electrical resistance wires are provided at equal angular intervals on the ring-shaped frame, so that a uniform temperature distribution can be easily obtained.

Therefore, it is possible to provide an exhaust gas reburning device for an internal combustion engine or the like that exhibits excellent effects such as no melting, unlike devices using gas burners.

2 A plurality of electrical resistors made by bending a preheating heater into a substantially U-shape from the outside toward the center using electrical resistance wires, and bending the arc-shaped tips at approximately 45 degrees in a predetermined direction. By forming the wires and locating them on the same plane, the above-mentioned effect of not creating a temperature difference is hardly reduced, and the installation of electrical resistance wires and energization are easy. equipment can be provided.

[Embodiment] A first embodiment in which the present invention is applied to an automobile equipped with a diesel engine will be described below with reference to the drawings.

First, in FIGS. 1 and 2, 1 is a preheating heater, which connects an electric resistor 1a (see FIG. 4) to a tubular sheath 1b through a powdered insulating material such as magnesia (MgO). (See FIG. 4) is a well-known sheathed heater. This heater 1 is disposed in a circular ring-shaped frame 2, and an electric resistance wire 1a has one end a passed through the frame 2 in the thickness direction and fastened with a nut 3, with the middle part directed toward the center. The other end b is passed through the frame body 2 in the thickness direction, and is fastened with a nut 4 at a position close to the aforementioned one end a, and the electric resistor 5a is It consists of

A total of four such electrical resistors 5a are arranged on the same plane at equal angular intervals of 90 degrees on the frame 2,
The arc-shaped tip end portion of each electrical resistance wire 1a is bent at a substantially right angle in a predetermined direction, so that the overall external shape is boot-shaped.

In this case, the preheating heater 1 is in a state parallel to the opening surface of the frame body 2, and is controlled at predetermined time intervals of, for example, 30 to 60 minutes, taking into consideration the amount of carbon adhesion, which will be described later, when driving the car. A circuit (not shown) periodically energizes it. Furthermore, the portions of the frame 2 where the nuts 3 and 4 are fastened to the heater 1 are cut in the tangential direction to facilitate fastening of the flat nuts 3 and 4.

The heater 1 is disposed in a predetermined exhaust path between an exhaust manifold 6 and a muffler 7 of a diesel engine 5 in an automobile shown in FIG. That is, as shown in FIG. 4, the exhaust manifold 6 and the exhaust pipe 8 have flanges 6a and 8a formed at their joints, respectively, and the frame 2 is sandwiched between these flanges 6a and 8a in a sandwich-like manner. In this state, the flange portion 6a,
The aforementioned three members are fastened together by bolts 9 that pass through the frame body 2 and the flange portion 8a in a substantially horizontal direction. 10 is a honeycomb filter made of ceramic, as shown in Fig. 2.
It is constructed by partitioning the inside of a cylindrical body into a rectangular lattice shape with partition walls oriented in the axial direction. As shown in FIG.
, and one end of the opening is located close to the heater 1 .

Thus, when the automobile is operated, exhaust gas from the engine 5 is discharged to the outside through the exhaust manifold 6, the heater 1, the honeycomb filter 10, the exhaust pipe 8, and the muffler 7 in this order.

At this time, unburned particulates such as carbon powder contained in the exhaust gas are captured and adhered inside the honeycomb filter 10, but when the amount of carbon adhesion reaches a predetermined value, the heater 1 is turned on by the control circuit. Since the exhaust gas is energized and generates heat, it is heated in the process of passing through the heater 1 as shown by the white arrow in FIG. Therefore, the adhered carbon comes into contact with the exhaust gas in the high temperature atmosphere, so the carbon is burned and removed from the honeycomb filter 10, and the carbon is prevented from being emitted outside as fine particles. This is extremely convenient in terms of preventing environmental pollution.

Moreover, in the above configuration, when constructing the preheating heater 1, the electrical resistance wire 1a is bent into a substantially U-shape, and the arc-shaped tip is bent at a substantially right angle in a predetermined direction to align the electrical resistance wire 1a. , electric resistors 5a having a boot-like shape as a whole are provided, and four of these electric resistors 5a are arranged in the same plane as shown in the above embodiment, so that a glow plug type heater can be used radially. Unlike the conventional arrangement, the temperature distribution state from the center to the outer periphery of the preheating heater 1 is even and substantially uniform. As a result, the exhaust gas passing through the heater 1 has a temperature distribution state with a small temperature difference between the center and the outer periphery. Therefore, the adhered carbon that has come into contact with this exhaust gas burns simultaneously at the center and the outer periphery of the honeycomb filter 10 with almost no time difference, and the temperature of the center and outer periphery of the honeycomb filter 10 also varies. There is no large difference, and the temperature distribution is generally uniform, and there is no fear that cracks or cracks will occur in the honeycomb filter 10 due to the difference in the amount of thermal expansion caused by the temperature difference.Moreover, unlike a gas burner, the filter 10 will not be melted. This contributes to a longer lifespan.

Further, as the carbon burns almost simultaneously in the center and the outer periphery of the honeycomb filter 10, a secondary effect such as rapid recovery of the function of the filter 10 can be obtained.

Incidentally, FIGS. 5 and 6 show the center part A and the outer peripheral part B near the entrance of the honeycomb filter 10.
It also shows how the temperature distribution state between the central part C and the outer peripheral part D (marked with an asterisk * in Fig. 4 for convenience) near the exit of the same filter 10 changes over time. Figure 5 shows the present invention, and Figure 6 shows the conventional case. In both cases, the vertical axis shows temperature (℃),
The elapsed time (min) is plotted on the horizontal axis.

In both FIG. 5 and FIG. 6, the center A, the outer periphery B, and the center C and outer periphery D of the honeycomb filter 10 are indicated by a narrowly spaced broken line, a solid line, a dashed-dotted line, and a widely spaced broken line, respectively. There is.

According to this, the conventional maximum temperature difference between the center part A and the outer peripheral part B is 700, as shown by the symbol Lj in Fig. 6.
While the difference between ℃ and 420℃ is approximately 280℃, the difference in this invention is 680℃ as shown by symbol Lh in Figure 5.
The temperature is only 90℃, which is the difference between 590℃ and 590℃, and the duration is only 30 seconds to 1 minute.

Furthermore, the conventional maximum temperature difference between the center C and the outer periphery D is 980°C and 580°C, as shown by the symbol Mj in Figure 6.
℃, which is about 400℃, but in this invention, it is 980℃ as shown by symbol Mh in
The difference from 680℃ is 300℃, which is 100℃ compared to 400℃ above.
℃ is also a small value, and the duration is only an extremely short time of about 1 minute.

Except for the part with the maximum temperature difference mentioned above, the temperature differences between the center A, the outer periphery B, and between the center C and the outer periphery D of the honeycomb filter 10 are significantly smaller than the conventional one shown in FIG. This clearly shows that the present invention has significantly improved the temperature distribution within the honeycomb filter 10 during carbon combustion by making it more uniform.

Next, an embodiment (a second embodiment of the present invention) corresponding to claim 3 will be described with reference to FIG. 8 (see also FIGS. 2, 3, and 4).

The preheating heater 1 has a pair of electrical resistors 5a disposed within a ring-shaped frame 2, each part of which is symmetrical with respect to the center 11 of the frame 2.
The frame body 2 is point symmetrical with respect to the frame body 2 at the upper and lower parts of the diagram.
It is electrically connected to two sets of nuts 3 and 4 that penetrate through the thickness direction and are screwed together.

The electric resistor 5a has straight portions 51, 5 of different lengths.
2, straight portions 53, 54 of approximately equal length, and curved portions 55, 56, 57 that engage with these portions. The straight parts 51 and 52 first extend a predetermined length toward the center of the frame body 2, and approximately extend in the direction of extension.
It is bent to the right by 45 degrees to form curved parts 55 and 56, followed by straight parts 53 and 54, the tips of which are closed by a curved part 57.

In this embodiment, the temperature distribution from the center to the outer periphery of the preheating heater 1 is substantially uniform with almost no significant difference compared to the above embodiment. Furthermore, since only four nuts and two electrical resistors 5a are required, the arrangement of the electrical resistors 5a and the energization thereof are easy.

The present invention includes the following embodiments.

In the first embodiment, the four electrical resistors 5a in the preheating heater 1 are provided at equal angular intervals, but the number is not limited to this, and the number may be three or six.

When setting the opening width interval dimension that indicates the degree of expansion of the electric resistance wire 1a in the preheating heater 1, take into consideration the diameter dimension of the filter 10, the required power, the cross-sectional area of the exhaust path, etc. determined.

Furthermore, in the first embodiment, the preheating heater 1
The electricity was applied periodically at 30- to 60-minute intervals;
Of course, the time is not limited to 60 minutes, and heater 1
The timing of energization can be changed as appropriate.
In this case, for example, a suitable sensor for detecting carbon deposits may be separately provided and the heater 1 may be energized every time the amount of carbon deposit reaches a predetermined value.

Further, the preheating heater 1 is not limited to a sheathed heater, but may be constructed of a ceramic heater in which a helical heating element is provided on or inside the ceramic and sintered together.

Furthermore, the mounting position of the heater and filter is not limited to the joint between the exhaust manifold 6 and the exhaust pipe 8 as in the first embodiment, but is essentially located in the exhaust path of the exhaust gas from the engine. It's fine if it's inside.

Furthermore, the filter for capturing unburned particles is not limited to a honeycomb filter, but may be a refractory ceramic filter.

In addition, various changes may be made in the specific implementation without departing from the gist of the present invention.

[Brief explanation of the drawing]

Figures 1 to 5 show an embodiment of the present invention, in which Figure 1 is a front view of a preheating heater, Figure 2 is an exploded perspective view of the heater and honeycomb filter, and Figure 3 is an exploded perspective view of the heater and honeycomb filter.
The figure is a partially cutaway front view of an automobile, Figure 4 is a vertical cross-sectional view of the main parts, Figure 5 is a graph showing the temperature distribution state versus elapsed time, and Figure 6 is a graph showing the temperature distribution state versus elapsed time in the conventional technology. 7 is a front view of a preheating heater showing a conventional example, and FIG. 8 is a front view of a preheating heater showing a second embodiment of the present invention. In the figure, 1... Heater for preheating, 5a... Electric resistor, 10... Honeycomb filter.

Claims (1)

[Scope of Claim for Utility Model Registration] 1) An exhaust passage for leading exhaust gas from an internal combustion engine to the outside, and an exhaust passage provided in the exhaust passage so that the exhaust gas can pass therethrough, and unburned particles in the exhaust gas. and a preheating heater installed close to the filter on the upstream side of the exhaust passage, the heater being directed from the outside toward the center by an electric resistance wire. It is formed from a plurality of electrical resistors that are bent into a substantially U-shape, with their arcuate tips bent at a substantially right angle in a predetermined direction, and the electrical resistors are arranged at substantially equal angular intervals in the same plane, and An exhaust gas reburning device for an internal combustion engine or the like, characterized in that it is arranged so as to be oriented substantially perpendicular to the flow of the exhaust gas, and is energized as appropriate during operation. 2) The exhaust gas reburning device for an internal combustion engine or the like according to claim 1, wherein the electric resistance wires are made of sheathed heaters, and three or more are provided at equal angular intervals on a ring-shaped frame. . 3) An exhaust passage for leading exhaust gas from the internal combustion engine to the outside, and a fire-resistant ceramic filter installed in the exhaust passage so that the exhaust gas can pass therethrough, and that captures unburned particles in the exhaust gas. and a preheating heater installed close to the filter on the upstream side of the exhaust passage, the heater being bent into a substantially U-shape from the outside toward the center by an electric resistance wire. , is formed from a pair of electrical resistors whose tip portions forming an arc shape are bent at approximately 45 degrees in a predetermined direction, and the electrical resistors are opposed to each other in the same plane and are approximately oriented with respect to the flow of the exhaust gas. An exhaust gas reburning device for an internal combustion engine, etc., characterized in that it is arranged so as to be oriented in a right angle direction, and is energized as appropriate during operation.