Patent Publication Number: US-2003230076-A1

Title: Filter regeneration system for eliminating particulate matter generated in a diesel engine

Description:
FIELD OF THE INVENTION  
       [0001] The present invention relates to a filter regeneration system for eliminating particulate matter generated by a diesel engine. More particularly, the invention relates to a filter regeneration system adapted to accurately detect the time to regenerate for the filter used for collecting particulate matter, and to increase the discharge gas temperature via a secondary injection of fuel, and to incinerate the particulate matter collected by the filter, thereby promoting an effective regeneration of the filter.  
       BACKGROUND OF THE INVENTION  
       [0002] Generally, although a diesel engine has advantages over a gasoline engine in fuel combustion efficiency and output, the diesel engine is disadvantageous in that it creates more NOx, a hazardous material. To overcome this disadvantage, the diesel engine has adopted an exhaust gas recirculation (EGR) device for re-supplying the unburned exhaust gas to the diesel intake system, allowing the unburned exhaust gas to be re-burnt in the combustion chamber.  
       [0003] But there is a problem in the EGR device thus described in that, although the amount of the NOx contained in the exhaust gas after combustion can be effectively reduced, other polluting materials, such as particulate matter from the re-burning of exhaust gas, are discharged in large quantities. It has been reported that particulate matter is a major source of pollution. As a result, many efforts are being made to decrease the harmful materials, such as particulate matter. Various technologies and methods for reducing particulate matter have been developed. One such method uses a diesel particulate filtering system.  
       [0004] The diesel particulate filtering system is a technique by which particulate matter, discharged after combustion, is collected by a filter in an exhaust system. This matter is removed by incineration using the high temperature of the exhaust gas discharged after combustion.  
       [0005] Although some of the particulate matter collected by the filter is incinerated by the high temperature of the exhaust gas, there is a problem because exhaust gas discharged from the diesel engine after combustion is approximately 200° C.˜300° C. in temperature. This is much lower than the 550° C.˜600° C. temperature range necessary for completely incinerating the particulate matter.  
       [0006] To cope with this problem, research has been conducted to increase the temperature of exhaust gas. This has resulted in methods using a secondary injection of fuel after the main injection of fuel in a common rail engine, adding an oxidation catalyst, using fuel additives, and the like. However, these methods are all under development and are not yet practical.  
       [0007] The problem with the secondary injection of fuel is that it is difficult for a diesel engine particulate matter eliminating system to determine the necessary time to regenerate. There is another problem in that the control logic of a control unit becomes complicated and should precede the development of a control unit capable of performing an accurate control. Accurate control is necessary to safely control the amount of fuel injected during secondary injection for filter regeneration, even following the determination of a time to regenerate and an injection timing. There is still another problem in that even if a control unit is developed, the fuel combustion efficiency, along with the output, can be decreased by the frequency of secondary injection of fuel.  
       SUMMARY OF THE INVENTION  
       [0008] The present invention provides a filter regeneration system for eliminating particulate matter generated in a diesel engine from the filter. A preferred embodiment of the invention is adapted to accurately detect when to regenerate the filter and to inject a level of fuel adequate to incinerate the particulate matter, thereby eliminating the particulate matter collected by the filter in an effective and timely manner.  
       [0009] In accordance with an embodiment of the present invention, a filter regeneration system for eliminating particulate matter generated in a diesel engine from a filter comprises: a collected amount detecting unit for detecting the amount of particulate matter collected by a filter disposed in an exhaust system; a control unit for determining the time to regenerate of the filter based on the amount of collected particulate matter detected by the collected amount detecting unit and for controlling the injection of fuel for incinerating the particulate matter; and a fuel injection unit mounted on the exhaust system for injecting the fuel into the exhaust system in response to the control of the control unit.  
       [0010] A further preferred embodiment of the invention is a method for regenerating a filter in an exhaust system of an engine, comprising: determining when to regenerate the filter; measuring the temperature of the exhaust; and increasing the temperature of the exhaust to regenerate the filter.  
       [0011] Another preferred embodiment of the invention is a system for regenerating a filter in an exhaust system of an engine, comprising: a detection system for detecting filter blockage and for determining when to regenerate the filter including a pressure sensor or a flow sensor; and an exhaust temperature increasing system, including an injector for injecting a combustible material into the exhaust system. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0012] For fuller understanding of the nature and objects of the invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings, in which:  
     [0013]FIG. 1 is a block diagram of a filter regeneration system for eliminating particulate matter generated in a diesel engine according to a preferred embodiment of the present invention; and  
     [0014]FIG. 2 is a schematic drawing of the system of FIG. 1. 
    
    
     [0015] Like numerals refer to similar elements throughout the several drawings.  
     DETAILED DESCRIPTION OF THE INVENTION  
     [0016] In FIG. 1, the filter regeneration system for eliminating particulate matter generated in a diesel engine includes a collected amount detecting unit  12  for detecting the amount of particulate matter collected in a filter and a temperature detecting unit  14  for detecting the temperature of exhaust gas discharged after combustion.  
     [0017] A control unit  16  determines the time to regenerate the filter based on the collected volume of particulate matter detected by the collected amount detecting unit  12 . The control unit  16  also controls the time to inject the fuel and injection duration and amount necessary for incinerating the particulate matter collected in the filter  10  (FIG. 2) based on the time to regenerate and the temperature of the exhaust gas detected by the temperature detecting unit  14 . A fuel supply unit  20  injects high-pressurized fuel into the exhaust system of a diesel engine  18  (FIG. 2) to promote combustion of the particulate matter. Control unit  16  preferably comprises a processor and memory, and other associated hardware and software as may be selected and programmed by a person of ordinary skill in the art to execute the control functions as described herein.  
     [0018] In FIG. 2, the collected amount detecting unit  12  monitors a filter  10  in an exhaust pipe  22  using pressure sensors  10   a  and  24   a . Pressure sensors  10   a  and  24   a  are mounted upstream of an oxydation catalyst  24   a  and downstream of the filter  10 , respectively. Oxidation catalyst  24  reacts with the exhaust gas to raise the temperature of the exhaust gas, thereby contributing to combustion of the particulate matter. The control unit  16  determines the amount of particulate matter gathered at the filter  10  from the input values detected by the pressure sensors  10   a  and  24   a  and accurately determines a time to regenerate the filter  10  based on the amount of particulate matter collected by the filter  10 . When the filter  10  has collected excessive particulate matter, the control unit  16  determines this time to regenerate the filter  10  by the increase in pressure between the pressure sensors  10   a  and  24   a . One of ordinary skill in the art will know how to choose the pressure differential between sensors  10   a  and  24   a  that is used to trigger a regeneration.  
     [0019] The fuel supply unit  20  is composed of a fuel tank  28  filled with fuel with a fuel pump  30  mounted within for sending the fuel at a high pressure, and a secondary injector  34  connected via the fuel pump  30  and supply pipe  32 , and mounted before the oxidation catalyst on the exhaust pipe  22 . Intake air cooling device  42  cools intake air for diesel engine  18 . A main supply pipe  44  provides fuel from the fuel tank  28  to the primary injector  36 .  
     [0020] The temperature detecting unit  14  (FIG. 1) is a temperature sensor  26  mounted in the exhaust pipe  22  of the diesel engine  18  that detects the temperature of the exhaust gas. The control unit  16  determines the optimal amount of fuel necessary for incinerating the particulate matter accumulated in the filter from the temperature value of the exhaust gas detected by the temperature sensor  26 .  
     [0021] Based on the difference between the temperature of the exhaust gas and the appropriate temperature for incinerating the particulate matter, the control unit  16  sends an appropriate signal to the fuel supply unit  20  so that unit  20  injects the amount of fuel necessary to raise the temperature of the exhaust gas to an optimal level for an optimal duration for incinerating the particulate matter. The control unit  16  causes the fuel supplied to the secondary injector  34  through the supply pipe  32  to be injected into the exhaust pipe  22 . As a result, the fuel injected into the exhaust pipe  22  is ignited by the temperature of the exhaust gas and raises the temperature of the exhaust gas from 200° C.˜300° C. as much as 100° C.˜200° C., initially. The exhaust gas thereafter reacts with oxidation catalyst  24  and is heated to 550° C.˜600° C., which is an appropriate and preferable temperature for incinerating the particulate matter collected at the filter  10 .  
     [0022] The control unit  16  increases the injected amount of fuel from the secondary injector  34 , if the temperature of the exhaust gas circulating in the exhaust pipe  22  is low. If the temperature of the exhaust gas is high, the control unit  16  decreases the amount of the fuel injected, thereby preventing unnecessary fuel waste or decrease of the fuel combustion efficiency and engine output.  
     [0023] The control unit  16  is dedicated to the filter regeneration system and eliminating particulate matter generated in a diesel engine and is separate from a main control unit  40 . Main control unit  40  is for controlling the operation of a primary injector  36 , which is the injector mounted within the diesel engine for driving the engine. It is preferable to construct the control unit  16  as the exclusive control system for controlling the regeneration frequency, the amount of fuel injected to control incinerate temperature, and the injection duration. The purpose of this unique construction is to prevent the main control unit  40  from participating in the control of the filter regeneration system. This simplifies the control of the vehicle. Another purpose is to allow the filter regeneration system according to a preferred embodiment of the present invention to be installable separately from the existing construction, thereby enabling it to be an aftermarket installation without changing the existing main control unit  40 .  
     [0024] As apparent from the foregoing, an advantage of the filter regeneration system according to the present invention, is that it accurately detects the time to regenerate and determines the amount of fuel to inject to eliminate particulate matter, thereby maximally reducing the amount of particulate matter discharged after combustion.  
     [0025] Furthermore, another advantage is that only a secondary fuel injection is used when regenerating the filter  10  and the control unit  16  is separate from the main engine control unit  41  thus simplifying the control logic and facilitating installation in a wider range of applications and thereby simplifying the control logic, dispensing with the development of an additional control unit for controlling an accurate control and providing an easy application.  
     [0026] The foregoing descriptions of specific embodiments of the present invention are presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously many modifications and variations are possible in view of the above teachings. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents.