Diesel Exhaust System Reversible Particulate Filter

Abstract

The invention concerns a diesel particulate filter in an exhaust system of a vehicle having a diesel engine. The particulate filter may have soot burned out via a regeneration process, and may be serviced for ash buildup by selectively reversing the diesel particulate filter, or its brick, in the exhaust system.

Description

BACKGROUND OF INVENTION

The present invention relates generally to an exhaust system in a vehicle having a diesel engine.

Recent emissions regulations for vehicles employing diesel engines limit the amount of soot that the vehicles may emit. The soot is produced as a by-product of the combustion of the diesel fuel and is emitted with the vehicle exhaust. Diesel particulate filters (also called traps) added to the exhaust system limit the soot emissions sufficiently to meet the regulations.

Diesel particulate filters work by collecting the soot while allowing the exhaust gases to pass through. As the vehicle operates, then, the soot builds up in the filter. This soot needs to be periodically eliminated from the filter in order to assure that the filter does not become clogged. A clogged filter can potentially cause damage to itself or the engine. The soot that builds up in the filter can be removed through a process called regeneration. Regeneration is performed by heating the diesel particulate filter to a temperature where the soot will burn away, thus cleaning out the filter.

Unfortunately, ash also tends to collect in the diesel particulate filter. Ash is different than soot. During engine operation, the lubrication oil used in diesel engines works its way into the engine cylinders. This lubrication oil includes additives. While the oil is burned during combustion events, the additives exit the engine cylinders and flow into the exhaust system as ash—along with the soot. A diesel oxidation catalyst, which is typically employed in a diesel exhaust assembly, is a flow through catalyst and so the ash and soot do not build up in it. But the ash, along with the soot, do collect in the honeycomb structure of the diesel particulate filter. The soot can be burned away through the regeneration process, as discussed above, but the ash cannot be burned away under this process. After many miles of driving the vehicle, then, the ash buildup in the diesel particulate filter will make the backpressure in the exhaust system too high.

The diesel particulate filter must be repaired (if serviceable) or replaced when it is no longer functioning properly. The diesel particulate filter is expensive to replace, and so this is undesirable if it is possible to service the filter. But servicing by disassembling a diesel particulate filter assembly and cleaning the ash from the brick (the honeycomb structure) is also a time-consuming and costly solution that is less than desirable.

It is desirable, therefore, to provide an exhaust system employing a diesel particulate filter with a means for continuing the use of the diesel engine exhaust system for as many miles of vehicle use as possible, while minimizing the cost of replacement or servicing of the filter due to ash buildup.

SUMMARY OF INVENTION

An embodiment contemplates an exhaust system for a vehicle having a diesel engine. The exhaust system may comprise a diesel particulate filter having a first end and an opposed second end, a first pipe, located upstream of the diesel particulate filter, for directing exhaust gases into the diesel particulate filter, and a second pipe, located downstream of the diesel particulate filter, for receiving exhaust gases from the diesel particulate filter. The exhaust system may also comprise a first mounting flange mounted on the first end of the diesel particulate filter, mountable on either of the first pipe and the second pipe, and mounted on one of the first pipe and the second pipe, and a second mounting flange mounted on the second end of the diesel particulate filter, mountable on either of the first pipe and the second pipe, and mounted on the other of the first pipe and the second pipe.

An embodiment contemplates a method of monitoring and servicing a diesel particulate filter that may become loaded with ash, in an exhaust system of a vehicle having a diesel engine, the method comprising the steps of: monitoring at least one parameter indicative of a buildup of the ash in the diesel particulate filter; determining from the at least one parameter if action is required due to the ash buildup in the diesel particulate filter; indicating that diesel particulate filter servicing is needed when it is determined that action is required; and reversing a direction of exhaust flow through a brick in the diesel particulate filter when servicing is needed and if reversal is desirable.

An embodiment contemplates a method of regenerating and servicing a diesel particulate filter in an exhaust system of a vehicle having a diesel engine, the method comprising the steps of: (a) operating the diesel engine and exhaust system in a normal operating mode; (b) monitoring at least one soot parameter indicative of soot buildup in the diesel particulate filter while operating in the normal operating mode; (c) monitoring at least one ash parameter indicative of a buildup of the ash in the diesel particulate filter; (d) determining from the at least one soot parameter when the diesel particulate filter needs regenerating; (e) operating the vehicle in a regeneration mode, if it is determined in step (d) that the diesel particulate filter needs regenerating; (f) determining from the at least one ash parameter if action is required due to the ash buildup in the diesel particulate filter; and (g) reversing a direction of exhaust flow through a brick in the diesel particulate filter when step (f) determines that action is required.

An advantage of an embodiment is that the useful life of a diesel particulate filter is significantly increased.

An advantage of an embodiment is that the cost to extend the useful life of the diesel particulate filter is minimized.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic illustration of a vehicle with a diesel engine, and a portion of an exhaust system for the vehicle.

FIG. 2 is a side view of a diesel particulate filter.

FIG. 3 is a section view taken along line 3-3 in FIG. 2.

FIG. 4 is a flow chart illustrating the diesel particulate filter monitoring and reversal process.

FIG. 5 is a flow chart similar to FIG. 4, but illustrating an alternative embodiment.

DETAILED DESCRIPTION

FIG. 1 illustrates a vehicle 20 having an engine compartment 22, with a diesel engine 24 mounted therein. The diesel engine 24 drives a transmission 26, which, in turn, drives a vehicle driveline 28, and, ultimately, vehicle wheels 30. A controller 32 operatively engages the diesel engine 24 and transmission 26. The controller 32 may be made up of one or more discrete controllers, and may be formed from various combinations of software and hardware, as is known to those skilled in the art.

An exhaust system 34 receives exhaust gases 36 from the diesel engine 24, treats the exhaust gases 36, and directs them into the atmosphere away from the vehicle 20. More specifically, an exhaust pipe 42 connects at an upstream end to conventional exhaust system hardware (not shown), such as, for example, a turbocharger (not shown), that receives exhaust from exhaust manifolds (not shown) on the engine 24. The exhaust pipe 42 directs the exhaust gases 36 into a diesel oxidation converter 44 (also known as a diesel oxidation catalyst). The diesel oxidation converter 26 treats the exhaust gases 36 in order to reduce the amounts of certain constituents that will be emitted into the atmosphere. Such constituents may be, for example, carbon monoxide (CO) and unburned hydrocarbons (HC). The vehicle and its components discussed above are known to those skilled in the art and so will not be discussed or shown in more detail herein.

A first intermediate pipe 38 connects to the downstream end of the diesel oxidation converter 44 and directs the exhaust gases 36 into a diesel particulate filter 50 (also called a diesel particulate trap). The diesel particulate filter 50 is basically a filter for collecting (i.e., trapping) soot (also called diesel particulate matter) from the exhaust in order to minimize the amount of soot in the exhaust gases 36. Downstream of the diesel particulate filter 50 is a second intermediate pipe 40. The second intermediate pipe 40 directs the exhaust gases 36 into a muffler 46. The muffler directs the exhaust flow into a tailpipe 48, which extends to an open downstream end where the exhaust gases 36 are emitted into the atmosphere away from the vehicle 20.

The exhaust system 34 may also include an upstream pressure sensor 80, which is mounted just prior to exhaust gas entry into the diesel particulate filter 50 in order to measure the pressure in the exhaust gas stream just prior to entry into the filter 50. A downstream pressure sensor 82 may be mounted in the exhaust system 34 just after the exhaust exit from the diesel particulate filter 50 in order to measure the pressure in the exhaust gas stream after exit from the filter 50. Both the upstream and downstream pressure sensors 80, 82 are in communication with the controller 32. The controller 32 may also be in communication with various components of the diesel engine 24 and transmission 26, as is known to those skilled in the art. The controller 32 may also be connected to an indicator light 33 mounted, for example, on an instrument panel (not shown).

The diesel particulate filter 50 will now be discussed in more detail with reference to FIGS. 1-3. The particulate filter 50 includes a housing (also called a can) 52, which has a generally cylindrical shell 54 mounted between an inlet cone 56 on an upstream end and an outlet cone 58 on a downstream end. Brick support material 60 is mounted around the inside of the shell 54 and supports a brick 62. The brick 62 may be a wall-flow honeycomb structure, with an upstream end 64 facing an inlet channel 66 defined by the inlet cone 56, and a downstream end 68 facing an outlet channel 70 defined by the outlet cone 58. A support ring 72 may also mount around a portion of the brick 62. The diesel particulate filter 50 may be catalyzed or uncatalyzed. If catalyzed, then a catalyst wash coat should be applied evenly to both the inlet and outlet channels.

The diesel particulate filter 50 includes a first mounting flange 74 on an upstream end and a second mounting flange 76 on a downstream end. Both of the mounting flanges 74, 76 can be attached to either of the first and second intermediate pipes 38, 40. These flanges 74, 76 are also preferably of the type that allow for removal and reinstallation of the diesel particulate filter 50. The mounting flanges 74, 76 may be, for example, a V-bend type of flange. This is just one example, since there are many types of mounting flanges 74, 76 that can be employed to allow for removal, reversal and reinstallation of the diesel particulate filter 50. Moreover, the term mounting flange as used herein is to be interpreted broadly to include many known exhaust pipe joints that can be used to mount the diesel particulate filter 50.

FIG. 4 illustrates a method for prolonging the useful life of the diesel particulate filter 50, as illustrated in the exhaust system 34 of FIGS. 1-3. As the diesel engine 24 operates, the exhaust gases 36 flow from the engine 24, through the diesel oxidation converter 44, the diesel particulate filter 50, the muffler 46, and through the tailpipe 48 into the atmosphere. As exhaust gases flow through the exhaust system 34, soot and ash are collected in the brick 62 of the diesel particulate filter 50, and build up over time. A determination, then, needs to be made as to when the soot and when the ash have built up to a level where action needs to be taken. Accordingly, one or more parameters for determining the amount of soot buildup are monitored, step 100, and one or more parameters for determining the amount of ash buildup are monitored, step 102.

A comparison is made between the soot buildup parameter(s) and predetermined threshold(s) to determine if soot regeneration is required, step 104. If not, then a comparison is made between the ash buildup parameter(s) and predetermined threshold(s) to determine if action needs to be taken due to ash buildup, step 108. If not, then the monitoring continues.

At some point, a determination is made (step 104) that the soot needs to be burned off (i.e., the filter regenerated) in order to avoid clogging the diesel particulate filter 50. The determination of when the regeneration mode will be initiated can be based on one or more of several factors (parameters). For example, the controller 32 may keep track of engine run time, vehicle mileage or fuel consumption since the last regeneration process occurred, and initiate the regeneration process after a predetermined amount of engine run time, vehicle mileage or fuel consumption, as the case may be. For another example, the controller 32 may determine the pressure drop across the particulate filter 50 by calculating the difference in measured pressure between the upstream pressure sensor 80 and the downstream pressure sensor 82, with the regeneration process initiated when a predetermined pressure difference across the particulate filter 50 is reached. Or, the controller 32 may employ a soot regeneration algorithm that estimates an amount of soot buildup based upon some combination of two or more of the previous listed factors, or other factors.

When the determination is made that regeneration of the particulate filter 50 is needed, the controller 32 begins the regeneration process, step 106. The controller 32 will cause the regeneration process to occur by various known means. The particular actions taken by the controller 32 may depend upon the engine and vehicle operating conditions as well as the ambient conditions. The temperature of the diesel particulate filter 50 is raised sufficiently to cause soot to burn off. The controller 32 continues with the process until the desired amount of regeneration is achieved. This may be based, for example, on a predetermined pressure drop across the particulate filter 50 being achieved, a predetermined length of regeneration time, or a soot regeneration algorithm that estimates the amount of soot burn-off achieved.

At some point, a determination is made (step 108) that the ash buildup is sufficient that action needs to be taken. One will note that it is contemplated that the regeneration for soot occurs far more frequently than any action needed to account for ash buildup. For example, soot regeneration may happen as often as every fuel tank fill, while action take for ash buildup may not be required until around 200,000 kilometers of vehicle travel. The determination that action is required for ash buildup may be based on, for example, measuring the pressure drop across the diesel particulate filter 50—in particular if the pressure drop is above a predetermined threshold even after soot regeneration. Examples of other possible determining factors may be reaching a certain mileage with the diesel particulate filter in the same orientation, or an increase in fuel consumption by the diesel engine 24. Or, a combination of two or more of these factors, or others, may be employed to make this determination. The particular factors and thresholds used may depend upon the particular vehicle, engine and exhaust system to which this method is applied.

If the ash buildup requires action, then an indication is provided that diesel particulate filter reversal or replacement is needed, step 110. This indication may be, for example, the light 33 that illuminates on an instrument panel (not shown), or a wireless data transmission to a computer network (not shown) that will email an operator of this need. Of course, other types of indicators that will notify a vehicle operator of the need to take action for ash buildup can also be employed instead, if so desired.

With the wall-flow honeycomb structure of the brick 62 in the filter 50, the ash that builds up will tend to build up near the upstream end 64 of the brick 62. Thus, turning the entire filter 50 (or just the brick 62) around will locate the part of the brick 62 with the most ash buildup (the end that was originally upstream) on the downstream end facing the outlet channel 70. This will allow the built-up ash to be blown out in the exhaust stream 36 as it passes from the brick 62 into the outlet channel 70. As noted above, the first and second mounting flanges 74, 76 can each connect to either the first intermediate pipe 38 or the second intermediate pipe 40, and allow for removal and reinstallation of the diesel particulate filter 50.

Accordingly, a determination is made as to whether reversal is desirable, step 112. If it is not desirable to reverse the filter 50, then the diesel particulate filter 50 is replaced, step 116. If it is desirable to reverse the filer 50, then it is removed from the exhaust system 34, reversed (i.e., rotated 180 degrees from its original orientation), and then reinstalled in the exhaust system 34, step 114. The controller 32 can then be reset and the process starts over again.

Reasons to replace instead of reverse the filter 50 may be, for example, that it has already been reversed previously at least once and, for this particular vehicle, engine and filter combination, it is not desirable to reverse it an additional time. Another reason may be that, for example, this particular filter 50 is clogged, rather than just fully loaded with ash. A fully-loaded filter 50 signifies that it is time to take some action relative to the ash buildup—the engine and exhaust system will still function though somewhat less efficiently. Clogged signifies that the filter 50 is no longer functioning—the engine and exhaust system will run very poorly or maybe not at all for this condition. Of course, where possible, the filter 50 is preferably reversed since this will generally cost significantly less than replacement.

FIG. 5 illustrates an alternative method to that in FIG. 4. In this embodiment, steps that are similar to those in FIG. 4 will be similarly designated, but using 200-series numbers. This method essentially separates the process for dealing with ash buildup from the process for dealing with soot buildup. Such a separate process may be desirable since soot regeneration occurs relatively frequently, while ash buildup is something that may only need attention once or twice during the entire life of the vehicle.

The parameter(s) for ash buildup are monitored, step 202. A comparison is made between the ash buildup parameter(s) and predetermined threshold(s) to determine if action needs to be taken due to ash buildup, step 208. If not, then the monitoring continues. If the ash buildup requires action, then an indication is provided that diesel particulate filter reversal or replacement is needed, step 210. A determination is made as to whether reversal is desirable, step 212. If it is not desirable to reverse the filter 50, then the diesel particulate filter 50 is replaced, step 216. If it is desirable to reverse the filer 50, then it is removed from the exhaust system 34, reversed (i.e., rotated 180 degrees from its original orientation), and then reinstalled in the exhaust system 34, step 214.

For the processes described above, there may be alternative ways to accomplish some of the steps. For example, this process comprehends the technique of servicing a diesel particulate filter 50 that is loaded with ash by reversing it, but reinstalling it on another vehicle. As another alternative, this process can include ash removal before reinstallation. As yet another alternative, this process can include the diesel particulate filter 50 being removed, the housing 52 being opened, the brick 62 removed and reinstalled in the housing 52 in the reverse direction, and then reinstalling the housing 52 in the exhaust system 34 in the same direction. Or, as a further alternative, the housing 52 may remain attached to the exhaust system 34 while being opened, the brick 62 removed, reversed and reinserted, and the housing 52 closed again.

While certain embodiments of the present invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention as defined by the following claims.

Claims

1. An exhaust system for a vehicle having a diesel engine comprising:

a diesel particulate filter having a first end and an opposed second end;

a first pipe, located upstream of the diesel particulate filter, for directing exhaust gases into the diesel particulate filter;

a second pipe, located downstream of the diesel particulate filter, for receiving exhaust gases from the diesel particulate filter;

a first mounting flange mounted on the first end of the diesel particulate filter, mountable on either of the first pipe and the second pipe, and mounted on one of the first pipe and the second pipe; and

a second mounting flange mounted on the second end of the diesel particulate filter, mountable on either of the first pipe and the second pipe, and mounted on the other of the first pipe and the second pipe.

2. The exhaust system of claim 1 wherein the diesel particulate filter includes a brick that has a wall-flow honeycomb structure.

3. The exhaust system of claim 1 including a diesel oxidation converter connected to an upstream end of the first pipe.

4. The exhaust system of claim 1 including a muffler connected to a downstream end of the second pipe.

5. The exhaust system of claim 1 wherein the diesel particulate filter includes a housing having an inlet channel and a brick mounted in the housing having a first end and an opposed second end, with the brick selectively mountable in the housing in a first orientation with the first end facing the inlet channel and in a second orientation with the second end facing the inlet channel.

6. The exhaust system of claim 1 including a controller, an upstream pressure sensor located adjacent to the first pipe and operable to measure an upstream pressure in the exhaust gases, and a downstream pressure sensor located adjacent to the second pipe and operable to measure a downstream pressure in the exhaust gases, with the upstream and downstream pressure sensors in communication with the controller.

7. The exhaust system of claim 1 wherein the first mounting flange is removable from one of the first pipe and the second pipe and reinstallable on the other of the first pipe and the second pipe, and the second mounting flange is removable from the other of the first pipe and the second pipe and reinstallable on the one of the first pipe and the second pipe to thereby allow for reversal of the diesel particulate filter in the exhaust system.

8. The exhaust system of claim 7 including a controller operable to detect at least one parameter correlating to an ash buildup in the diesel particulate filter and operable to determine a reversal or replacement of the diesel particulate filter is needed.

9. The exhaust system of claim 1 including a controller operable to detect at least one parameter correlating to an ash buildup in the diesel particulate filter and operable to determine a reversal or replacement of the diesel particulate filter is needed.

10. A method of monitoring and servicing a diesel particulate filter that may become loaded with ash, in an exhaust system of a vehicle having a diesel engine, the method comprising the steps of:

(a) monitoring at least one parameter indicative of a buildup of the ash in the diesel particulate filter;

(b) determining from the at least one parameter if action is required due to the ash buildup in the diesel particulate filter;

(c) indicating that diesel particulate filter servicing is needed when it is determined in step (b) that action is required; and

(d) reversing a direction of exhaust flow through a brick in the diesel particulate filter when step (c) indicates the servicing is needed and if the reversal is desirable.

11. The method of claim 10 wherein step (a) is further defined by the at least one parameter including at least vehicle mileage.

12. The method of claim 10 wherein step (a) is further defined by the at least one parameter including at least detecting a difference in pressure between an upstream end and a downstream end of the diesel particulate filter.

13. The method of claim 10 wherein step (d) is further defined by removing the brick from a housing of the diesel particulate filter and reinstalling the brick in a reverse direction.

14. The method of claim 10 wherein step (d) is further defined by removing the diesel particulate filter from the exhaust system, and reinstalling the diesel particulate filter into the exhaust system in an opposite orientation.

15. The method of claim 10 wherein step (d) is further defined by the reversal being desirable if the direction of exhaust flow through the brick in the diesel particulate filter has not been previously reversed.

16. The method of claim 10 including the step of: (e) replacing the diesel particulate filter in the exhaust system when step (c) indicates that servicing is needed and reversal of the direction of exhaust flow through the brick is not desirable.

17. The method of claim 10 wherein step (c) is further defined by the indication that servicing is needed including lighting an indicator light on the vehicle.

18. A method of regenerating and servicing a diesel particulate filter in an exhaust system of a vehicle having a diesel engine, the method comprising the steps of:

(a) operating the diesel engine and exhaust system in a normal operating mode;

(b) monitoring at least one soot parameter indicative of soot buildup in the diesel particulate filter while operating in the normal operating mode;

(c) monitoring at least one ash parameter indicative of a buildup of the ash in the diesel particulate filter;

(d) determining from the at least one soot parameter when the diesel particulate filter needs regenerating;

(e) operating the vehicle in a regeneration mode, if it is determined in step (d) that the diesel particulate filter needs regenerating;

(f) determining from the at least one ash parameter if action is required due to the ash buildup in the diesel particulate filter; and

(g) reversing a direction of exhaust flow through a brick in the diesel particulate filter when step (f) determines that action is required.

19. The method of claim 18 wherein step (g) is further defined by removing the brick from a housing of the diesel particulate filter and reinstalling the brick in a reverse direction.

20. The method of claim 18 wherein step (g) is further defined by removing the diesel particulate filter from the exhaust system, and reinstalling the diesel particulate filter into the exhaust system in an opposite orientation.