# US 8,769,928 B2 · Exhaust system having cross-sensitive sensor

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- Number: US 8,769,928 B2
- Document ID: US8769928B2
- Status: Granted
- Kind: B2
- Application number: 12/891,264
- Filed: 2010-09-27
- Published: 2012-03-29
- Granted: 2014-07-08
- Earliest claimed: 2010-09-27
- Assignees: Caterpillar Inc.
- Applicants: Mary L. Yeager; Christopher L. Wynkoop; Amit Jayachandran
- Inventors: Mary L. Yeager; Christopher L. Wynkoop; Amit Jayachandran
- Web page: https://patentgrep.com/patent/US8769928B2

## CPC

- F01N 3/208: {Control of selective catalytic reduction [SCR], e.g. by adjusting the dosing of reducing agent}
- F01N 3/106: {Auxiliary oxidation catalysts}
- F01N 13/009: {having two or more separate purifying devices arranged in series}
- F02D 41/1463: {of the exhaust gases downstream of exhaust gas treatment apparatus}
- F01N 2560/02: the means being an exhaust gas sensor
- F01N 2560/021: for measuring or detecting ammonia NH3
- F01N 2560/06: the means being a temperature sensor
- F01N 2560/07: the means being an exhaust gas flow rate or velocity meter or sensor, intake flow meters only when exclusively used to determine exhaust gas parameters
- F01N 2610/02: the substance being ammonia or urea
- F02D 2041/1468: {the characteristics being an ammonia content or concentration of the exhaust gases}
- F02D 2250/14: Timing of measurement, e.g. synchronisation of measurements to the engine cycle
- Y02T 10/12: Improving ICE efficiencies
- F01N: GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES (arrangements in connection with gas exhaust of propulsion units in vehicles B60K13/00; combustion-air intake silencers specially adapted for, or arranged on, internal-combustion engines F02M35/00; protecting against, or damping, noise in general G10K11/16)
- F02D: CONTROLLING COMBUSTION ENGINES (vehicle fittings, acting on a single sub-unit only, for automatically controlling vehicle speed B60K31/00; conjoint control of vehicle sub-units of different type or different function, road vehicle drive control systems for purposes other than the control of a single sub-unit B60W)
- Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION

## Abstract

An exhaust system for use with a combustion engine is disclosed. The exhaust system may have an exhaust passage, a reduction catalyst disposed within the exhaust passage, and an injection device configured to inject reductant into the exhaust passage. The exhaust system may also have a sensor configured to generate a signal indicative of a concentration of an exhaust constituent and the reductant, and a controller in communication with the sensor and the injection device. The controller may be configured to make a comparison of a value indicative of a rate of change of the signal for a period of time with a threshold amount, and make a determination of whether the sensor is sensing a concentration of the exhaust constituent or the reductant based on the comparison. The controller may also be configured to adjust operation of the injection device based on the determination.

## Claims

### Claim 1

An exhaust system for a combustion engine, comprising:
an exhaust passage;
a reduction catalyst disposed within the exhaust passage;
an injection device configured to inject reductant into the exhaust passage upstream of the reduction catalyst, the reductant selected to facilitate within the reduction catalyst a reduction of an exhaust constituent;
a sensor configured to generate a signal indicative of a concentration of the exhaust constituent and the reductant within the exhaust passage; and
a controller in communication with the sensor and the injection device, the controller being configured to:
calculate a value indicative of a rate of change of the signal for a period of time as a cumulative sum of time weighted based on an absolute value of the rate of change of the signal and a flow rate of exhaust through the reduction catalyst;
make a comparison of the value indicative of the rate of change of the signal for the period of time with a threshold amount;
make a determination of whether the sensor is sensing a concentration of the exhaust constituent or the reductant based on the comparison; and
adjust operation of the injection device based on the determination.

### Claim 2 (depends on 1)

The exhaust system of claim 1, wherein the threshold amount is fixed and based on a desired concentration of reductant sensed downstream of the reduction catalyst.

### Claim 3 (depends on 1)

The exhaust system of claim 1, wherein the controller is further configured to monitor a speed and a load of the combustion engine, and determine a feedforward control parameter for the injection device based on the speed and load.

### Claim 4 (depends on 3)

The exhaust system of claim 3, wherein the controller is further configured to determine a feedback control parameter for the injection device based on the signal when it is determined that the sensor is sensing the concentration of the exhaust constituent.

### Claim 5 (depends on 4)

The exhaust system of claim 4, wherein the controller is further configured to inhibit use of the feedback control parameter and reduce the feedforward control parameter when it is determined that the sensor is sensing the concentration of the reductant.

### Claim 6 (depends on 5)

The exhaust system of claim 5, wherein the controller is configured to reduce the feedforward control parameter based on a control map stored in a memory of the controller.

### Claim 7 (depends on 6)

The exhaust system of claim 6, wherein the controller is configured to only partially reduce the feedforward control parameter.

### Claim 8 (depends on 6)

The exhaust system of claim 6, wherein the controller is further configured to reset the feedforward control parameter from the reduced feedforward control parameter when it is determined that the sensor is again sensing the concentration of the exhaust constituent.

### Claim 9 (depends on 1)

The exhaust system of claim 1, wherein the controller is further configured to:
track a frequency of the sensor sensing the reductant; and
trigger a diagnostic procedure when the frequency exceeds a threshold frequency.

### Claim 10

A power system, comprising:
an internal combustion engine configured to combust fuel and generate a flow of exhaust;
an exhaust passage leading from the internal combustion engine to the atmosphere;
an SCR catalyst disposed within the exhaust passage;
an injector configured to inject a urea solution into the exhaust passage upstream of the SCR catalyst, the urea solution selected to facilitate within the SCR catalyst a reduction of NOx;
a sensor disposed within the exhaust passage downstream of the SCR catalyst and configured to generate a signal indicative of a concentration of NOx and NH3 within the exhaust passage; and
a controller in communication with the sensor and the injector, the controller being configured to:
calculate a value indicative of a rate of change of the signal for a period of time as a cumulative sum of time weighted based on an absolute value of the rate of change of the signal and a flow rate of exhaust through the SCR catalyst;
determine that the sensor is sensing a concentration of NOx when the value indicative of the rate of change of the signal for the period of time is less than a threshold amount;
determine that the sensor is sensing a concentration of NH3 when the value of the rate of change of the signal is greater than the threshold amount; and
adjust operation of the injector differently depending on whether the sensor is sensing a concentration of NOx or NH3.

### Claim 11

A method of operating an exhaust system, comprising:
directing a flow of exhaust from a combustion engine through a reduction catalyst;
injecting reductant into the flow of exhaust to reduce a constituent of the exhaust;
sensing a concentration of the constituent and the reductant and generating a corresponding signal;
calculating a value indicative of a rate of change of the signal for a period of time as a cumulative sum of time weighted based on an absolute value of the rate of change of the signal and a flow rate of exhaust through the reduction catalyst;
making a comparison of the value indicative of the rate of change of the signal for the period of time with a threshold amount;
making a determination of whether the concentration of the constituent or the reductant is currently being sensed based on the comparison; and
adjusting the injecting based on the determination.

### Claim 12 (depends on 11)

The method of claim 11, wherein the threshold amount is fixed and based on a desired concentration of reductant sensed downstream of the reduction catalyst.

### Claim 13 (depends on 11)

The method of claim 11, further including;
monitoring a speed and a load of the combustion engine; and
determining a feedforward injection control parameter based on the speed and load.

### Claim 14 (depends on 13)

The method of claim 13, further including determining a feedback injection control parameter based on the signal when it is determined that the concentration of the constituent is currently being sensed.

### Claim 15 (depends on 14)

The method of claim 14, further including inhibiting use of the feedback injection control parameter and reducing the feedforward injection control parameter when it is determined that the concentration of the reductant is being sensed.

### Claim 16 (depends on 15)

The method of claim 15, wherein reducing the feedforward injection control parameter further includes reducing the feedforward injection control parameter based on a relationship map.

### Claim 17 (depends on 15)

The method of claim 15, wherein reducing the feedforward injection control parameter further includes only partially reducing the feedforward injection control parameter.

### Claim 18 (depends on 15)

The method of claim 15, further including resetting the feedforward injection control parameter from the reduced feedforward injection control parameter when it is determined that the concentration of the constituent is currently being sensed.