Patent Application
20080163615
1. Field of the Invention
The present invention relates to filtration systems for internal combustion engines.
2. Description of the Prior Art
With any internal combustion engine, it is desirable to treat the exhaust before emission to the atmosphere. In many engines, one of the operating problems is the presence of gaseous pollutants (CO, NOx, CO2, etc.) and fine solid particles in the exhaust. Many different types of filtration systems have been proposed for filtering the impurities from the exhaust.
Problems have been encountered when filters, such as carbon filters become saturated or clogged, thus diminishing their effectiveness and in some instances building up back pressure which may be deleterious to the continued operation of the engine.
Efforts have been made in the past to address issues involving warm up or overheating of an internal combustion engine exhaust filters. One such effort led to the proposal of a control valve downstream of the filter and responsive to cold temperatures to close and divert the exhaust from a bypass path through the filter. When the engine heats up the valve is opened to allow the exhaust to bypass the filter. A device of this type is shown in U.S. Pat. No. 5,223,009 to Schuster. While effective to direct control through the filter during warm up, such devices suffer the shortcoming that, in the event of the filter becoming clogged, flow directed through the filter itself may create a back pressure which, over a period of time could damage the engine.
Other efforts to control exhaust flow through a filter have focused on diesel engines where the exhaust may, under certain conditions, reach upwards of 1,100° F. These efforts have led to proposal of a system including a filter bed of steel wool or the like where carbon particles are collected during warm up and wherein flow from the engine is divided to divert a minor part while some is re-circulated from downstream of the filter to balance the fuel and oxygen content in effort to maintain the desired temperature in the filter bed.
A system of this type is shown in U.S. Pat. No. 4,217,757 to Crone. While having utility to control the temperature in the filter bed, such systems suffer the shortcoming that pressure build up from the filter clogging or the like can lead to a high back pressure against the engine.
Other efforts have focused on burning of the soot produced by diesel engines. These efforts have led to a proposal that a particulate filter be connected with a diesel engine to collect soot which may be oxidized by introducing forced air to the filter. A valve controls exhaust flow to a filter bypass in response to the engine speed. A system of this type is shown in Japanese Patent No. JP404183917 to Shimoda. While having advantages for controlling the flow of exhaust from a diesel engine, systems of this type are extremely complicated, expensive to make, complicated to control and pose the problem that, should flow through the filter be hindered when the bypass valve is closed backpressure can build up at the engine exhaust manifold.
The exhaust filtration system of the present invention is characterized by an opening between the engine exhaust pipe and filter inlet pipe sized to, under normal operating conditions, induce flow to the filter, but responsive to a pressure build up in the filter, vent exhaust directly to the atmosphere.
Other features and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings which illustrate, by way of example, the features of the invention.
Referring to
An internal combustion engine typically incorporates an exhaust pipe 31 leading to a filter for filtering hydrocarbon residue from the exhaust prior to emission to the atmosphere. It is of concern that, when the filter becomes plugged raising resistance to flow, damage can be done to the engine from build up of back pressure.
The present invention incorporates a space defining the gap 33 between the terminal end of the exhaust pipe 31 and inlet end to the inlet pipe 29 leading to the filter 25 to, upon elevation of pressure at the inlet to the filter exhaust to atmosphere ahead of the filter.
Outlet from the filter 25 is typically exhausted through a tail pipe or the like to atmosphere. In the preferred embodiment, my invention includes the blower 37 driven by an electric motor 40, and which may be connected in electric circuit with the engine system and in some embodiments includes a speed control responsive to different engine conditions, such as RPM's, for adjusting the speed of the blower 37 to increase the blower speed at heavier loads and greater exhaust flow.
As will be appreciated by those skilled in the art, an exhaust pipe may have a diameter of about 2½ inches and the gap 33 should be at least 1/16th of an inch or more long to afford sufficient cross sectional for escape of the exhaust flow where in the event the filter becomes clogged and may, in fact, take many different forms. In one embodiment, the gap may be from about 1 to 2 inches in length, it being appreciated that the gap need only be sufficiently great to allow for substantially full transfer of flow from the exhaust pipe 31 to the inlet pipe 29 during normal operation. In the event of a back up from the filter resulting in pressure in the inlet pipe 29 being increased above a certain range the gap will allow for escape of exhaust from the gap. The length of the gap will be selected to match the operating characteristics of the engine but must be sufficiently short so the negative pressure in the inlet pipe 29 under normal operating conditions will draw substantially all the exhaust into such pipe to flow through the filter. Those of skill in the art will select the size and shape for the particular engine exhaust characteristics. A negative pressure device, such as the blower 37, will draw exhaust flow from the filter at 39 to generate a negative pressure to increase the pressure differential across the gap 33 during normal operation to thereby capture substantially the entire flow from the exhaust pipe 31 to the inlet pipe 29.
Referring to
As noted, in this configuration, should the pressure build up in the inlet pipe 29 above a normal range the gap forming the relief device will allow for escape of exhaust from the exhaust pipe 31 as depicted by the directional arrow 55 in
As it will be appreciated by those skilled in the art, during normal operation, the lower 37 will be actuated to draw a negative pressure on the downstream side of the filter bed 39 to facilitate a relatively high rate of flow through the inlet pipe 29 and through the filter bed 39. Under normal engine operating conditions, the blower 37 provides sufficient flow rate to afford a negative pressure in the inlet pipe 29, preferably of about 1 psi, to combine with the several psi positive pressure in the exhaust pipe 31 to afford a pressure differential across the gap 33 of several psi such that the rather forceful ejection of exhaust from the pipe 31, combined with the negative pressure drawing that exhaust into the inlet pipe 29, provides for substantially full transfer of exhaust flow from the exhaust pipe 31 to the inlet pipe 29. This then provides for substantially complete flow of the exhaust into the filter 25 and across the filter bed 39 through the blower 37 and out the tail pipe 34. Preferably the flow is balanced to the point where a quantity of atmospheric air, typically about 10% of the full flow stream, is drawn into the inlet pipe to facilitate cooling of the filter. It is also noted that the air gap 33 acts as a thermal barrier to limit transfer of heat from the high temperature exhaust pipe to limit heating of the filter.
As the engine conditions vary, the speed controller in the motor 41 will adjust the speed of the blower 37 to correspondingly adjust the flow rate through the pipe 29 and filter 25 to control magnitude of negative pressure drawn within the inlet pipe 29. For instance, as the engine is revved up, the speed 41 will proportionally increase the speed of the blower 37 to increase the negative pressure drawn on the downstream side of the filter bed 39, the consequent pressure differential across the filter bed 39 and thus the magnitude of negative pressure in the inlet pipe 29 will further increase the pressure differential across the gap 33 to further enhance the tendency of the system to draw the exhaust expelled from the exhaust pipe into the inlet pipe 29.
As will be appreciated by those skilled in the art, the blower 37 may take the form of any desirable negative pressure device for drawing a negative pressure in the inlet pipe to induce exhaust flow from the exhaust pipe, across the pressure relief exemplified by the gap 33 and through the filter, it only being important that the pressure be reduced, as by a venture or partial vacuum device.
As will be further appreciated by those skilled in the art, should the filter bed 39 become clogged or flow there through be otherwise obstructed, the exhaust being expelled into the inlet pipe 29 will tend to build pressure up therein and as such pressure increases above a normal operating range, the pressure differential across the gap 33 will be decreased and even reversed to the point where the pressure is greater in the inlet pipe thereby tending to spill the exhaust from the exhaust pipe 31 out through the gap 33 to escape to atmosphere thereby avoiding excessive pressure on the filter bed 39 to thereby avoid unwanted high pressure in the exhaust pipe 31, which could result in unwanted back pressure against the exhaust from the internal combustion engine. Malfunctioning of the filter will quickly be detected and, when time permits, repairs may be made to return the system to its normal operating condition. In the meantime, the system will be protected against over pressurizing in a relatively foolproof manner.
It will be appreciated by those skilled in the art that the construction of the pressure release device shown in
In some instances, the exhaust pipe 31 will be telescoped sufficiently far into the inlet pipe 51 to provide approximately a 4″ inch linear overlap.
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From the foregoing, it will be appreciated that the engine exhaust filtration system of the present invention provides an economical and reliable means for avoiding excessive back pressure on the engine system.
As will be appreciated by those skilled in the art, the pressure release configuration of the present invention is relatively independent of original equipment exhaust systems and thus does not detract from the operation thereof. It can be readily retrofitted into original equipment exhaust system. In many embodiments, the pressure release device provides for an air gap between the exhaust and tail pipes which acts as a thermal barrier limiting the rate of heat transfer from the exhaust pipe to the intake pipe. In some embodiments, the pressure release device provides for the introduction of a small quantity of ambient air to be mixed with the exhaust gases and actually facilitates cooling of the exhaust gases passing through the filter.
