JPS6319533Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to an exhaust gas treatment device for a diesel engine, and more specifically, it uses a physical method to remove carbon particles and similar particulates (hereinafter referred to as exhaust particles) contained in exhaust gas. The present invention relates to an exhaust particulate purification device suitable for collecting exhaust particulates on a suitable trap such as a filter element, periodically incinerating the collected exhaust particulates, and regenerating the trapping material.

Most of these types of exhaust particulates are flammable, such as carbon particles, and diesel particulates collect these flammable particulates and incinerate them to regenerate the collection material. Various traps are known. An electric heater is generally used as a means for burning the collected particulate and regenerating the trap. That is, an electric heater is attached to the upstream end of the collection material, and the heater burns the exhaust particulates adhering to the surface of the collection material, which is used as a heat source to cause the downstream particulates to self-combust.

In order to improve the ignition performance of the electric heater, an opening/closing control valve is preferably provided in the exhaust pipe on the upstream or downstream side of the trap to control the flow rate of exhaust gas flowing through the trap. This opening/closing control valve is closed during trap regeneration to reduce the flow rate (ie, flow velocity) of exhaust gas flowing into the trap to almost zero, thereby improving the ignition of exhaust particles by the electric heater. In fact, when the exhaust gas flow velocity is high, it is almost impossible to ignite and burn the exhaust particulates even if the electric heater is energized. In this type of exhaust particulate purification device, a bypass pipe is provided to bypass the trap so that exhaust gas can be discharged even when the on-off control valve is closed.

However, in the heater-ignited particulate trap as described above, combustion regeneration of the trap is performed with the on-off valve closed to reduce the exhaust gas flow velocity, so that the particulates collected at the downstream end of the trap are combusted. There was a problem that it took too long for the information to be completely propagated. That is, there was a problem that the trap playback time was too long.

An object of the present invention is to provide an exhaust particulate purification device with a simple structure that eliminates the above-mentioned drawbacks and can be regenerated in a short period of time.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

A trap container 12 provided in an exhaust pipe 1 of a diesel engine is filled with a trap material 3. As the trap material 3, known foamed ceramic or similar materials can be used. That is, trap material 3
has a three-dimensional mesh structure through which exhaust gas (arrow) can flow, and exhaust particulates contained in the exhaust gas are collected between the meshes. An electric heater 5 is attached to the upstream end of the trap container 12 for igniting and burning the particulate collected by the trapping material 3. 7 is a bypass pipe that bypasses the trap container 12, and the upper part of the exhaust gas is always discharged through this bypass pipe 7. An on-off control valve 9 is provided downstream of the trap container. The on-off control valve 9 is for closing the exhaust passage as necessary and controlling the flow rate of exhaust gas flowing into the trap, and is provided upstream of the trap container (but downstream of the inlet port 7A of the bypass pipe 7). Good too.
The on-off valve 9 is connected to an actuator 11 via a link system 10. The actuator 11 may be, for example, a negative pressure actuated diaphragm device as shown in the figure, and can be selected from the atmosphere or a negative pressure area (e.g., the intake negative pressure area of an intake manifold or intake pipe) via a negative pressure switching valve (VSV) 13. The opening/closing valve 9 is connected to the opening/closing valve 9 to operate the opening/closing valve 9.

As is well known, the timing of energizing the heater 5 (trap regeneration timing) is determined and controlled by the computer unit CPU 20 based on various parameter signals S such as engine speed, engine load, engine water temperature, trap material internal temperature, back pressure, etc. be done.

According to the present invention, a temperature detecting element for exhaust particulates is provided in the trap member 3, for example, comprising a pair of thermocouples 15A and 15B. This temperature detection element detects the temperature of exhaust particulates ignited by the heater 5, and is therefore disposed downstream from the heater 5 by a predetermined distance l. That is, if it is too close to the heater 5, the temperature of the heater 5 will be directly detected, but the temperature detection element is not for detecting the temperature of the heater, but for detecting the fact that exhaust particles are ignited. It is something. Normally, exhaust particulates can self-combust due to propagation when they reach about 600°C, so by selecting the set temperature of the temperature detection element to, for example, 600°C, the exhaust particulates at a distance l from the heater 5 can reach 600°C. This can be detected when it is reached. The fact that the temperature of the exhaust particulates at a distance l downstream from the heater 5 has reached 600°C means that the exhaust particulates are completely ignited. It has been experimentally confirmed that, for example, l≈20 [mm] is suitable for l.

According to the present invention, at the same time that the thermocouples 15A and 15B detect the set temperature, the VSV is detected via the CPU 20.
13 to the atmosphere side, and the actuator 11 quickly opens the on-off valve 9. As mentioned above, the on-off valve 9 is almost fully closed immediately after the start of energization to the heater 5 in order to reduce the exhaust gas flow velocity and improve the ignitability of the heater (actually, it is closed slightly to prevent the valve body from sticking to the exhaust pipe wall). (open) position
Controlled by CPU 20.

As soon as the on-off valve 9 is fully opened, the flow rate and hence the flow velocity of the exhaust gas passing through the trap increases rapidly, and the combustion that has been propagated to the vicinity of a distance l is transmitted all at once to the downstream end of the trap material. At this time, if there is a large amount of exhaust gas flowing into the trap, there is a possibility that the ignition fire will be blown out, but since a portion of the exhaust gas always flows into the bypass pipe, the amount of exhaust gas flowing into the trap is relatively small. Therefore, the combustion propagates without the ignition fire being blown out.

In this way, according to the present invention, when the trap is regenerated, as soon as the heater ignites the exhaust particles collected in the trap material, the valve is closed for the purpose of reducing the exhaust gas flow velocity. The on-off valve is quickly fully opened to allow combustion, which would otherwise propagate slowly, to propagate all at once to the downstream of the trap material, thereby shortening the trap regeneration time.

Furthermore, according to the present invention, the heater is energized by the on-off valve 9.
Since the heater can be stopped at the same time as the valve is opened, power consumption can be reduced, and the number and capacity of the heaters themselves can also be reduced.

[Brief explanation of drawings]

The drawing is a diagram schematically showing an exhaust particulate purification device according to the present invention. 1... Exhaust pipe line, 3... Trap material, 5... Electric heater, 7... Bypass pipe, 9... Open/close valve, 1
1... Actuator, 15A, 15B... Thermocouple.

Claims (1)

[Scope of utility model registration request] A particulate trap that collects exhaust particulates is provided in the exhaust pipe of a diesel engine, and an electric heater is installed at the upstream end of the particulate trap to ignite and burn the collected exhaust particulates. An on-off valve that controls the flow rate of exhaust gas flowing into the particulate trap is installed in the exhaust pipe on the upstream or downstream side of the trap, and exhaust gas can be discharged even when the on-off valve is closed. Exhaust gas is constantly flowing in order to
In an exhaust particulate purification device provided with a bypass pipe that detours around a particulate trap, a temperature detection element for detecting the temperature of combustion exhaust particulates is provided in the particulate trap at a predetermined distance downstream from the electric heater; An exhaust particulate purification device for a diesel engine, comprising an actuator that opens the on-off valve in response to an output signal from the temperature detection element.