JPS59194019A - Purifier for exhaust particulate of diesel engine - Google Patents

Abstract

PURPOSE:To readily perform extensive burning of a trap for restoration by providing both a bypass pipe which contains an opening and closing control valve and bypasses a particulate trap disposed in an exhaust gas passage and a gas flow deflection means in said exhaust gas passage. CONSTITUTION:A trap container 12 is attached to a main exhaust pipe 5 at the lower site of an exhaust manifold and contains trapping substance 20. An electric heater 16 is mounted in the trap container 12 at the upstream end thereof, having the positive pole terminal connected via a relay 21 to a battery 22 and the negative pole terminal connected to the trap container 12. A bypass pipe 6 which connects the upper end and the lower end of the trap 12 to each other is joined with the main exhaust pipe 5 and involves a constantly closed control valve 31 which is opened only when the trapping substance 20 is burnt for restoring the trap by the heater 16. A fin 25, namely, a means for deflecting gas flow is disposed at the inlet part 41 of the main exhaust pipe 5 so as to reduce the rate of exhaust gas which flows into the trap container 12 when said valve 31 is opened.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exhaust gas treatment device for a diesel engine. Suitable for collecting fine particles (called particulates or particulates) on a suitable trapping material (trap material) such as a filter element by a physical method, periodically incinerating the collected exhaust particulates, and regenerating the trapping material. The present invention relates to an exhaust particulate purification device.

Most of these types of exhaust particles are flammable, such as carbon particles, and these flammable particles are collected,
Various types of diesel particulate cards are known that regenerate the collection material by incinerating the collected particulates. An electric heater is generally used as a means for burning the collected particulates and regenerating the trap. That is,
An electric heater is attached to the entire surface of the collection material, and this heater burns the exhaust particulates adhering to the surface of the collection material, using it as a heat source to make the downstream particulates natural.

However, if the flow velocity of the exhaust gas flowing through the trap at the time of heater ignition is too high, the trapped particulates near the heater that are heated by the heater will lose heat and be cooled by the exhaust gas flow, resulting in poor ignition. Therefore, in the past, the regeneration range of the trap was limited to fluorine, and efficient regeneration was not possible.

The object of the present invention is to solve this problem by expanding the trap reproducible area and easily controlling the regeneration.

In order to achieve the above object, the present invention provides a particulate matter 1 having a trap material for collecting exhaust particulates and an electric heater for igniting and burning the exhaust particulates collected by the trap material. - A diesel engine exhaust particulate purification device in which a lamp is provided in the exhaust gas path of the diesel engine, wherein a control valve for controlling opening and closing of the bypass pipe passage is provided in the bypass pipe that bypasses the particulate trap, and the particulate trap is provided with a control valve for controlling opening and closing of the bypass pipe passage. The present invention is characterized in that a gas flow deflection means is provided in the upstream exhaust gas path to prevent the flow of exhaust gas from directly hitting the heater.

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

The trap container 12 is attached to the main exhaust pipe 5 downstream of the exhaust manifold. Inside the trap 12 there is a collection material (trap material) 20. As the trapping material 20, a known foamed ceramic or a similar material can be used. That is, the trapping material 20 has a three-dimensional mesh structure, through which the exhaust gas can flow, and exhaust particulates contained in the exhaust gas can be collected between the meshes.

An electric heater 16 is attached to the upstream end of the trap container 12. The heater 16 may be, for example, a plurality of heater wires bent in a zigzag pattern so as to span the entire passage of the main exhaust pipe, or a known ceramic heater. The terminal is connected to the trap container 12 (ground voltage).

By energizing the electric heater 16, the particulates collected in the trap material 20 near the heater are first ignited, and then the flame is propagated downstream by the exhaust gas flow to regenerate the entire trap by combustion. As is well known, the timing of energizing the heater 16 (regeneration timing) is controlled by a microcomputer under predetermined operating conditions based on detection signals such as engine speed, engine load, engine water temperature, exhaust gas pressure, exhaust gas salt, etc. .

The main exhaust pipe 5 is provided with a bypass pipe 6 that connects the upstream and downstream sides of the trap 12. A normally closed control valve 31 of a simple ON-OFF operation type is provided in the bypass pipe 6 to open the passage of the bypass pipe 6 only at predetermined times. As an actuator for the control valve 31, for example, a diaphragm device 33 can be used which is linked thereto. The negative pressure working chamber of the diaphragm device 33 is selectively connected to the atmosphere or to a vacuum pump via a negative pressure switching valve (νSV) 35. That is, when the diaphragm device 33 is connected to a vacuum pump or other negative pressure region, the on-off valve 31 opens and the passage of the bypass pipe 6 is opened. As a result, most of all the exhaust gas flowing toward the trap 12 when the control valve 31 is closed flows through the bypass pipe 6 when the control valve 31 is opened. In this way, in order to cause most of the exhaust gas to flow to the bypass side rather than to the trap side when the control valve 31 is closed, it is preferable to use a bypass pipe when looking at the flow of exhaust gas from the exhaust manifold (arrow X). 6 is preferably on the smooth extension of the flow path (arrow Y). That is, when the main exhaust pipe 5 is viewed as a flow of exhaust gas, its population 41 and the angle of the outlet 43 are the same as the bypass pipe 6.
It has changed more than that. By doing so, most of the exhaust gas flows into the bypass pipe 6 when the control valve 31 is opened. Further, the control valve 31 is normally in the closed position, but at that time, substantially all of the exhaust gas flows to the trap 12 side, and its particulates are transferred to the trap material 2.
effectively captured by o.

Switching control of the VSV 35 is performed in the following manner using an output signal S from a microcomputer (not shown). That is, when the heater 16 starts igniting the particulates 1, as described above, if the flow velocity of the exhaust gas is too high, ignition failure will occur. Therefore, when starting ignition, the control valve 31 is opened so that almost no exhaust gas flows into the trap 12. After the ignition is completed, the control valve 31 is quickly closed again to allow the exhaust gas to flow into the trap 12, causing the ignition flame to propagate to the collected particulates downstream of the trap.

In this way, the control valve 31 is controlled by the actuator 33 to open only when the heater starts ignition.

In an exhaust gas particulate purification device such as a dual-unit system, when the on-off valve 31 is in the open position, the amount of exhaust gas flowing to the trap 12 side is desired to be zero, as described above. However, since there is a pressure difference in the exhaust gas between the inlet portion 41 and the outlet gl143, it is inevitable that a certain amount of exhaust gas will flow to the trap side even when the on-off valve 31 is opened. Therefore, the present invention provides gas flow deflection means on the inlet side of the trap to prevent the flow of exhaust gas from directly hitting the heater. In the embodiment shown in FIG. 1, this deflection means is formed by a fin 25 provided at the inlet section 41. In the embodiment shown in FIG.

The fins 25 smoothly deflect the flow of exhaust gas toward the bypass pipe 6, and therefore preferably exhibit the same curvature as the upstream end 5a of the exhaust pipe 5. A heater portion 16a is formed downstream of the fin 25 and is not directly exposed to exhaust gas.

In the embodiment shown in FIG. 2, the deflection means is constructed as a part 26 of the wall of the branching portion between the main exhaust pipe 5 and the bypass pipe 6. The wall portion 26 also mainly directs the flow of exhaust gas through the bypass pipe 6.
A heater portion 16a is formed downstream of the heater portion 16a, which is shaped to face toward the side and is not directly exposed to exhaust gas. In addition, in FIG. 2, 23 indicates a wire net that holds the trap material 20.

By providing the exhaust gas deflection means in this way, a part of the exhaust gas that is about to flow to the trap side when the on-off valve 31 is opened is forcibly directed to the bypass pipe side, so that the exhaust gas flowing to the trap side is forced to flow toward the trap side. The gas amount, ie the exhaust gas flow rate, can be reduced.

Preferably, energization is started from a portion where the exhaust gas flow rate is slow, as shown by the spiral 27 in FIGS. 1 and 2, that is, from the heater portion 16a. Therefore, for example, as the heater 16, as disclosed in Japanese Patent Application Laid-Open No. 57-210115,
By using a ceramic heater in which a plurality of ceramic heater elements each having an electric heating element coated with ceramic are distributed and arranged, the ignition order of the heater elements can be arbitrarily controlled, so that it is possible to energize the heater element present in the heater portion 16a first. can. By doing so, ignition occurs at a location where the flow velocity of the exhaust gas is almost zero, which is more effective.

As described above, according to the present invention, the flow rate (amount) of exhaust gas flowing to the trap side when the control valve in the bypass pipe is opened is
Since the regeneration combustion of the trap can be reduced, regenerative combustion of the trap can be reliably performed under a wide range of operating conditions.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the overall configuration of an exhaust particulate purification device according to the present invention, and FIG. 2 is an enlarged sectional view of main parts showing a different embodiment from FIG. 1. 5... Main exhaust pipe, 6... Bypass pipe, 12... Trap container, 20... Trap material, 25... Fin, 26... Wall portion, 31... Control valve. Patent applicant Toyota Motor Corporation Patent application agent Akira Aoki Patent attorney Kazuyuki Nishidate Patent attorney Kyosuke Donakayama Patent attorney Akira Yamaguchi Figure 1 Figure 2

Claims (1)

[Claims] In an exhaust particulate purification device for a diesel engine in which a particulate trap having a trap material for collecting exhaust particulates and an electric heater for igniting and burning the exhaust particulates collected by the trap material is provided in the exhaust gas path of the diesel engine. A bypass pipe is provided to bypass the particulate trap, and a control valve for controlling opening and closing of the bypass pipe passage is provided in the bypass pipe, and the flow of exhaust gas is directly directed into the exhaust gas path upstream of the particulate trap. 1. An exhaust particulate purification device for a diesel engine, characterized in that a gas flow deflection means is provided to prevent the gas flow from falling below i%.