Patent Grant
8397557
The subject invention relates to a method and apparatus for identifying a component failure within a thermal regenerator system for a vehicle exhaust system.
Untreated engine emissions, such as those generated by a diesel engine for example, include hydrocarbons, carbon monoxide, and other carbon based particulate matter which is also referred to as “soot.” Vehicle exhaust systems include exhaust after-treatment devices that filter these contaminants. These devices include emission abatement components such as filters/traps that collect the contaminants. Periodically, the filter or trap is regenerated with a fuel-fired burner which burns off the collected matter.
State and federal regulations require that diesel engine exhaust after-treatment devices include diagnostics to detect system problems, and also require that these diagnostics be able to identify which component within the system is faulty.
A vehicle exhaust system includes a burner control unit that controls a thermal regenerator system and detects one or more system failures at a component level.
A method for identifying a component failure within the thermal regenerator includes the following steps. The burner control unit monitors at least one of a fuel pump characteristic for a fuel pump in the thermal regenerator system and an ignition system characteristic for an ignition system in the thermal regenerator system. The fuel pump is used to supply fuel to a fuel-fired burner and the ignition system is used to ignite fuel supplied to the fuel-fired burner. The fuel pump characteristic is communicated to the burner control unit which compares the fuel pump characteristic to a predetermined fuel pump criteria. The ignition system characteristic is communicated to the burner control unit which compares the ignition system characteristic to a predetermined ignition system criteria. The burner control unit identifies a fuel pump failure when the fuel pump characteristic does not meet the fuel pump criteria, and identifies an ignition system failure when the ignition system characteristic does not meet the ignition system criteria.
In one example, the burner control unit generates a warning indication with a corresponding specified component fault code to an end user in response to identification of any fuel pump and ignition system failures.
These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.
A thermal regenerator (TR) system 10 is shown in
Exhaust gas from the engine 12 flows through an exhaust tube 28 and enters an inlet 30 to the fuel-fired burner 14. The fuel-fired burner 14 includes a combustion chamber 32 with a plurality of openings 34. Some of the exhaust gas flows from the inlet 30 and into the combustion chamber 32 via the openings 34, while a remainder of the exhaust gas flows around the combustion chamber 32 and exits at an outlet 36 from the fuel fired burner 14. The outlet 36 directs exhaust gases into filter or trap that is located immediately downstream of the fuel-fired burner 14.
The combustion chamber 32 includes a chamber inlet 38 that receives combustion air from the combustion air path 24 in combination with a mix of air/fuel supplied via an atomization module 40. The atomization module 40 receives fuel from the fuel supply system 18 and air from the air supply system 20. The atomization module 40 atomizes the fuel/air mixture which is sprayed from a nozzle 42 into the combustion chamber 32.
The ignition system 16 includes one or more igniter plugs 44, such as electrodes for example, and an ignition coil 46 which is used to boost the voltage supplied to the plugs 44. When the atomized fuel/air mixture is sprayed into the combustion chamber 32, it mixes with the combustion air and is ignited via a spark generated from the igniter plugs 44. This activates the fuel-fired burner to increase heat for filter regeneration as known.
The fuel supply system 18 includes a fuel injector 48, a fuel tank 50, a fuel filter 52, and a fuel pump 54. A fuel pressure sensor 56 and pressure regulator 58 monitor and control the amount of fuel pumped from the fuel tank 50 to be atomized within the atomization module 40. The air supply system 20 includes an air tank 60, a control valve 62, and an air pressure sensor 64 which operate together to delivered a desired amount of air to be atomized with the fuel delivered by the fuel injector 48 within the atomization module 40.
In addition to the fuel pressure sensor 56 and the air pressure sensor 64, the TR system 10 includes a plurality of other sensors which monitor/measure various system characteristics. For example, the TR system 10 includes a combustion air temperature sensor 70 located near the chamber inlet 38 of the fuel-fired burner 14 and a flame temperature sensor 72 that measure the flame temperature within the combustion chamber 32. An exhaust inlet temperature sensor 74 is located at the inlet 30 and an exhaust outlet temperature sensor 76 is located at the outlet 36. A voltage sensor 78 is used to measure battery voltage of the fuel pump 54 and a current sensor 80 is used to measure current flowing through the fuel pump 54. Another voltage sensor 82 measures the voltage of the ignition coil 46. Each of these sensors, and any additional sensors that may be required, communicate measurements/data to a burner control unit (BCU) 90 of a control system. The control system then uses this information to identify any of various specific component failures within the TR system 10.
As shown at step 110, the system initiates a fuel pump check which includes monitoring the fuel pump characteristic and communicating this characteristic to the BCU 90. The BCU 90 then compares the fuel pump characteristic to a predetermined fuel pump criteria and identifies a fuel pump failure when the fuel pump characteristic does not meet the fuel pump criteria.
As shown at step 150, the system initiates an ignition system check which includes monitoring the ignition system characteristic and communicating this characteristic to the BCU 90. The BCU 90 then compares the ignition system characteristic to a predetermined ignition system criteria and identifies an ignition system failure when the ignition system characteristic does not meet the ignition system criteria.
Once a failure is identified, the BCU 90 communicates any fuel pump and ignition system failures to an end user via a warning signal 200 (
In one example, as shown at step 120 in
The resistance of the fuel pump 54 is significantly lower when the fuel pump 54 is stationary (non-rotating) as compared to when the fuel pump 54 is rotating. As discussed above, the BCU 90 continuously determines the resistance over time and if the resistance is too low, then a “fuel pump current over limit” fault will be activated. In one example, the resistance threshold is set within a range of 1-2 ohms; however, other values could also be used.
In one example, as shown at step 130 in
Further, if the fuel pressure is lower than expected yet not close to zero, the BCU 90 must be able to distinguish between a failed fuel pressure regulator and a failure due to worn vanes. If the fuel pressure is low due to worn vanes, then when fuel is injected through a fuel injector, the fuel pressure will decrease significantly, such as more than 15% for example.
As discussed above, at step 150 the system initiates an ignition system check which includes monitoring the ignition system characteristic and communicating this characteristic to the BCU 90. In one example, as indicated at step 160, the predetermined ignition system criteria comprises a voltage threshold and the step of monitoring the ignition system characteristic includes measuring a voltage of the ignition coil 46. As known, the ignition coil 46, which is used to boost voltage for ignition, has a primary side and a secondary side that has a higher voltage than the primary side. The voltage sensor 82 measures voltage at the secondary side and the BCU 90 compares this voltage to the voltage threshold and identifies an ignition system failure if the voltage of the ignition coil 46 falls below the voltage threshold.
The voltage output by the ignition coil 46 is monitored by the BCU 90 via a feedback circuit. The feedback circuit produces a voltage that is proportional to the igniter voltage. If the feedback voltage is not within an acceptable range when the ignition system is activated, then the ignition system has failed.
In one example, as indicated at step 170, the predetermined ignition system criteria comprises a combustion air temperature threshold and the step of monitoring the ignition system characteristic includes measuring a temperature of combustion air communicated from the engine 12 to the combustion chamber 32 of the fuel-fired burner 14 with the combustion air temperature sensor 70. The BCU 90 compares the temperature of combustion air entering the combustion chamber 32 to the combustion air temperature threshold and identifies that the combustion air valve 26 is stuck open if the temperature of the air entering the combustion chamber 32 falls below the combustion air temperature threshold by a predetermined amount.
Combustion air from the turbocharger 22 is combined with the atomized fuel/air mixture from the atomization module 40 in the combustion chamber 32 in order to produce a good, stable flame. The BCU 90 monitors the combustion air temperature as the combustion air enters the chamber, and when the engine 12 is running, this temperature should be relatively close to an exhaust gas temperature of the engine exhaust gases. If the combustion air temperature is not within a certain threshold range during this type of engine condition then it is an indication of a problem with the combustion air valve 26. If the temperature is too low, it is an indication that the combustion air valve 26 is stuck open.
If the combustion air valve is stuck closed, then the temperature will not decrease when the valve receives an activation command. To determine whether the combustion air valve 26 is stuck closed, the BCU 90 determines an initial combustion temperature when the engine is on and then monitors the temperature over a period of time as indicated at step 180. If the combustion air temperature does not decrease by a certain percentage, such as by 25% for example, it is an indication that the combustion air valve 26 is stuck closed.
Next, the control system determines if any additional checks are needed as indicated at step 190. If so, the BCU 90 continues with the additional checks. If not, the BCU 90 then initiates a start-up cycle.
Although a preferred embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.
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