JPH0143456Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a diesel engine for vehicles, particularly for automobiles.

Diesel engines that are equipped with a dust collection filter and are regenerated by periodically burning off the dust accumulated by this filter are known, for example, from West German Publication No. 2655932 and European Patent No. 10384. It is. As an example, the regenerator has a heating system with an ignition device and an air suction device, but this can only be activated if no exhaust gas is passed through the filter. Therefore, two filters are placed side by side to allow exhaust gas from the engine to pass through them alternately, and while passing exhaust gas through one filter, the other is cleaned.

Other regenerators incinerate the dust by placing a special shutoff valve in the engine's intake system that closes and increases the temperature of the diesel engine's exhaust gas to the point where it ignites the dust collected on the filter. There is.

Both known regenerators require additional equipment that is not itself necessary for the operation of the engine and is expensive.

Therefore, an object of the present invention is to periodically regenerate a dust collection filter at a low cost.

In this invention, a layer with a catalytic effect is provided on the filter, and in order to increase the temperature of the dust collection filter,
We are considering operating the exhaust gas return device in a special manner. Note that the exhaust gas return device may be a conventionally provided device depending on the case. In this case, a large amount of exhaust gas is returned to the intake pipe of the engine by the exhaust gas return device, so that carbon monoxide and hydrocarbons rapidly increase in the engine. These undesirable components resulting from incomplete combustion are however catalytically oxidized in the dust filter. However, due to the exothermic reaction in this case, the temperature inside the dust collecting filter during operation rises to such an extent that the soot particles accumulated within the filter are ignited. In order to obtain a sufficiently high filter temperature, for example 400-500 DEG C., it may be necessary to return more exhaust gas in a shorter period of time. It is especially necessary to reduce NO _x (nitrogen oxides).

Further, in the present invention, the exhaust gas return device is continuously changed from the closed state to the open state while such a cleaning operation is being performed. In other words, the process in which exhaust gas is introduced constantly alternates with the process in which exhaust gas is not introduced, and the alternating processes in which exhaust gas is not introduced are necessary to supply air to burn the soot that has accumulated in the filter. be. That is, while the exhaust gas is being returned, there is only a small amount of air, or in other words, excess oxygen, necessary to burn the soot particles accumulated in the filter.

Hereinafter, a description will be given based on one embodiment of the present invention.
The figure schematically shows a diesel engine based on the present invention. Symbol 1 indicates a diesel engine for vehicles, especially passenger cars, and its exhaust pipe 3 has a pipe that separates solid dust components contained in the exhaust gas of the engine. A filter 2 is arranged for this purpose. This dust is essentially soot, or unburned carbon, which accumulates on the filter over extended periods of operation.

In order to avoid the inconvenience of having to replace the filter at predetermined intervals, the present invention regenerates the filter by periodically igniting the soot particles. However, this requires a high temperature of 400 to 500°C in the dust collecting filter 2, which cannot be achieved during normal operation of a diesel engine. In the present invention, the high temperature required for this operation is achieved by using a special method of exhaust gas return equipment used to reduce nitrogen oxides in diesel engines, which in some cases has already been installed. This has been achieved by This exhaust gas return device includes a return pipe 5 for returning part of the exhaust gas from the engine 1 to the intake pipe 4, and a valve 6 arranged in this pipe and controlled by a control device 7.

This exhaust gas return device operates in the following special manner. That is, the valve 6 is activated while the exhaust gas return device is operating to regenerate the dust collection filter.
It constantly alternates opening and closing in a pulse-operated manner. In other words, in a series of operations, the process of introducing exhaust gas and the process of not introducing exhaust gas are repeatedly alternated in a short period of time. In the process of introducing exhaust gas, the concentration of carbon monoxide and hydrocarbons in the exhaust gas increases due to the lack of air, that is, oxygen, and in the process of not introducing excess air, the exhaust gas usually contains excess air.

When the concentration of carbon monoxide and hydrocarbons in the exhaust gas increases, the operating temperature of the dust collection filter 2 can be increased. For this purpose, the filter is provided with a catalytically active layer on the side facing the exhaust gas, so that a catalytically exothermic oxidation reaction takes place within the filter. This heat generation significantly increases the temperature in the dust collection filter. This increases the temperature inside the filter to the extent necessary to ignite the soot particles.
Therefore, the introduction of exhaust gas must be regulated so that the amounts of carbon monoxide and hydrocarbons are sufficient.

In order to regenerate the dust filter, exhaust gas may be introduced at high rates in some cases, in which case valve 6 must be opened wide, which also reduces nitrogen oxides. This is also necessary above. In such a process, the surplus of air, that is, oxygen, in the exhaust gas of the engine 1 is extremely reduced and is no longer sufficient for the combustion of soot particles. Therefore, in order to improve the temperature in the filter 2, The necessary exhaust gas introduction process must be replaced by a process in which sufficient oxygen is present in the exhaust gas. Therefore, during operation of the exhaust gas introduction device, the valve 6 is constantly opened and closed in a pulsed manner to interrupt the introduction of exhaust gas and maintain sufficient oxygen for the combustion of soot.

Assume that the time required to regenerate the dust collection filter 2 is approximately 90 seconds. During this time, the valve 6 opens and closes many times, but the "opening" and "closing" processes can be performed at the same time. For example, the valve 6 is opened and closed for 1/2 second each, and during the "opening" process, approximately 60% of the exhaust gas is released from the exhaust pipe 3.
~70% is returned into the fresh air intake pipe 4. As a result, the exhaust gas emitted by the engine 1 is, for example, 2
% carbon monoxide and only 3% oxygen. A process without the introduction of exhaust gas, which can also be for 1/2 second as described above, results in an exhaust gas with approximately 14% oxygen and no carbon monoxide.
This excess oxygen is sufficient to oxidize the soot particles accumulated on the dust collection filter.

The means (medium) by which the dust filter accumulates oxygen
It is possible to improve the combustion of soot particles by maintaining the oxidizing effect even in the process of introducing exhaust gas, and it is preferable from the viewpoint of the purpose of the present invention.

The periodic operation of the filter cleaning device according to the invention can depend on the engine or on the specific operating conditions of the vehicle. Therefore, the above-mentioned cleaning operation can be performed every predetermined mileage, and the fact that the exhaust gas pressure has increased due to the clogging of the filter 2 can also be used as a direct criterion for activating the cleaning device. can.

This is important, especially if the diesel engine is originally equipped with an exhaust gas recirculation system to reduce nitrogen oxides in the exhaust gas. There is no need to spend a lot of money on cleaning and refurbishing. It is only necessary to provide the filter with a known catalytic layer and to set the exhaust gas recirculation device in a special mode of operation, that is to say in a pulsating manner, with short alternations between introduction and non-intake of exhaust gas.

It is an objective of the present invention to operate the cleaning device under driving conditions that do not interfere with or adversely affect other operations in the vehicle. For this purpose, the control device 7 can be designed to initiate the periodic exhaust gas introduction operation for regeneration only during selected specific operating conditions of the engine.

[Brief explanation of the drawing]

The figure schematically shows an engine part to explain the present invention. DESCRIPTION OF SYMBOLS 1... Diesel engine, 2... Dust collection filter, 3... Exhaust pipe, 4... Intake pipe, 5... Inlet pipe, 6... Valve, 7... Control device.

Claims (1)

[Scope of Claim for Utility Model Registration] 1. A heat-resistant filter installed in the exhaust pipe for the purpose of removing soot from exhaust gas in a diesel engine for a vehicle, especially for an automobile, and for adjusting the operating state of the engine. The filter 2 has a layer with a catalytic effect on the surface exposed to the exhaust gas, and a device that operates periodically to burn off the dust collected by the filter. a device consisting of exhaust gas return devices 5 to 7 for returning the exhaust gas to the intake pipe 4;
The above-mentioned diesel engine is characterized in that during operation, this device alternately switches between a state in which exhaust gas is introduced and a state in which exhaust gas is not introduced in a short period of time. 2. A diesel engine as set forth in claim 1 of the utility model registration claim, in which the exhaust gas return device is provided with an introduction pipe 5 that guides the exhaust gas to the intake pipe 4 of the engine 1, and this introduction pipe is equipped with a valve 6. The above-mentioned diesel engine is characterized in that the opening and closing operations are alternately performed by the control device 7. 3 Utility model registration claims The diesel engine described in claim 1 or 2, in which the exhaust gas return devices 5 to 7 are used for a predetermined running period (distance)
Diesel engine is characterized by being operated every time. 4 Utility Model Registration Scope of Claims The diesel engine described in claim 1 or 2 is characterized in that the exhaust gas return devices 5 to 7 are activated when the exhaust gas pressure exceeds a predetermined value. Diesel engine.