Urea-SCR System and Control Method Thereof

• US 20090217644A1
• Filed: 02/25/2009
• Published: 09/03/2009
• Est. Priority Date: 03/03/2008
• Status: Active Grant

• Current Assignee: Kia Motors Corporation (Kia Corp.)
• Original Assignee: Hyundai Motor Company (Hyundai Motor Group)
• Inventors: JUNG, Jaeyoon
• Granted Patent: US 8,079,209 B2
• Time in Patent Office: Days
• US Class Current: 60/276
• CPC Class Codes: B01D 2251/2062 Ammonia
• CPC Class Codes: F01N 11/00 Monitoring or diagnostic devices for exhaust-gas treatment apparatus , e.g. for catalytic activity safety, indicating or supervising devices for internal combustion engines F02B77/08; testing of machines G01M13/00
• CPC Class Codes: F01N 2550/05 Systems for adding substances into exhaust
• CPC Class Codes: F01N 2560/026 for measuring or detecting NOx
• CPC Class Codes: F01N 2570/14 Nitrogen oxides
• CPC Class Codes: F01N 2610/02 the substance being ammonia or urea
• CPC Class Codes: F01N 2900/0421 using an increment counter when a predetermined event occurs
• CPC Class Codes: F01N 2900/0422 measuring the elapsed time
• CPC Class Codes: F01N 2900/102 Travelling distance
• CPC Class Codes: F01N 2900/1402 Exhaust gas composition
• CPC Class Codes: F01N 2900/1808 Pressure
• CPC Class Codes: F01N 3/0231 using special exhaust apparatus upstream of the filter for producing nitrogen dioxide, e.g. for continuous filter regeneration systems [CRT]
• CPC Class Codes: F01N 3/208 Control of selective catalytic reduction [SCR], e.g. dosing of reducing agent
• CPC Class Codes: F02N 11/101 for preventing engine starter actuation or engagement
• CPC Class Codes: Y02A 50/20 Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

A method for controlling an urea-SCR system may include a first step for calculating a target urea injection amount, a second step that uses urea injection pressure and urea injection time to calculate a real urea injection amount, a third step that calculates a difference value between the target urea injection amount and the real urea injection amount, and monitors the difference value at a predetermined time interval, a fourth step that accumulates difference values for a determined time when the difference value exceeds a predetermined level, and transfers an alarm signal to a driver when the average value thereof exceeds a predetermined level, and/or a fifth step that starts to accumulate a number of engine starts and driving distance after transferring the alarm signal, and when the number of engine starts is larger than a predetermined value or the driving distance is longer than a predetermined value, if the difference value does not become lower than a predetermined level, executes urea recharging means for a driver to charge a urea tank with a urea solution. The urea consumption amount may be continuously monitored, the remained urea amount may be accurately detected, and the urea recharging may be induced in time such that the nitrogen oxide exhaust is prevented.

Claims

1. A method for controlling a urea-SCR system comprising:

a first step of calculating a target urea injection amount;

a second step of using urea injection pressure and urea injection time to calculate a real urea injection amount;

a third step of calculating a difference value between the target urea injection amount and the real urea injection amount, and monitoring the difference value at a predetermined time interval;

a fourth step of accumulating difference values for a determined time when the difference value exceeds a predetermined level, and transferring an alarm signal to a driver when the average value thereof exceeds a predetermined level; and

a fifth step of starting to accumulate a number of engine starts and driving distance after transferring the alarm signal, and when the number of engine starts is larger than a predetermined value or the driving distance is longer than a predetermined value, if the difference value does not become lower than a predetermined level, recharging a urea tank with a urea solution.

2. The method for controlling a urea-SCR system of claim 1, wherein;

engine speed and fuel supply amount are measured and an initial NO;

NO₂ ratio value of initial NO_x is detected;

an NO₂ increment is estimated through temperature of a diesel oxidation catalyst (DOC) and an NO₂ decrement is analyzed through a pressure difference change amount through a catalytic particulate filter (CPF);

temperature and continuous regeneration trap (CRT) effectiveness are compared to the initial NO;

NO₂ ratio value to calculate a final NO;

NO₂ ratio value; and

whereby a reaction molecular ratio with an NH₃ and NO_x purification efficiency of the SCR catalyst is determined to calculate the target urea injection amount in the first step.

3. The method for controlling an urea-SCR system of claim 1, wherein the real urea injection amount value is displayed on an instrument cluster in real time for the driver to check the real urea injection amount in the second step.

4. The method for controlling a urea-SCR system of claim 1, wherein the fourth step further includes a step of updating the average difference value at a predetermined cycle based on the accumulation value of the driving distance if the difference value between the target urea injection amount and the real urea injection amount is less than the predetermined value.

5. The method for controlling an urea-SCR system of claim 1, wherein the recharging is accomplished with an output reduction logic that reduces the output of the engine and a restarting restriction logic that causes the engine to not be restarted in the fifth step.

6. The method for controlling an urea-SCR system of claim 5, wherein the output restriction logic is operated if the number of engine starts after transferring the alarm signal is larger than a predetermined value, and the restarting restriction logic is operated if the accumulation value of the driving distance is longer than a predetermined value and the difference value between the target urea injection amount and the real urea injection amount is larger than a predetermined value.

7. A selective catalyst reduction device control system, comprising:

a selective catalyst reduction device that is mounted on an exhaust pipe so as to eliminate nitrogen oxide that is included in exhaust gas;

a urea tank in which a urea solution is stored;

an injector that injects the urea solution supplied from the urea tank; and

a control portion that calculates a target injection amount and a real injection amount that is to be injected from the injector, and that generates an alarm signal if the difference value between the target injection amount and the real injection amount is larger than a predetermined value;

wherein the control portion includes;

a counting portion that counts a number of engine starts after generating the alarm signal;

an accumulating portion that accumulates the driving distance after generating the alarm signal; and

a recharging induction portion that generates a recharging signal for recharging the urea tank with a urea solution if the difference value is larger than the predetermined value, if the number of engine starts or the accumulated driving distance is larger than the predetermined value.

8. The selective catalyst reduction device control system of claim 7, wherein the recharging induction portion prevents the engine from being started.

9. The selective catalyst reduction device control system of claim 7, wherein the recharging induction portion restricts the engine output so that the amount of exhaust gas is decreased.

10. The selective catalyst reduction device control system of claim 7, wherein the control portion updates the average of the difference value at a predetermined cycle, when the difference value between the target injection amount and the real injection amount is less than the predetermined value.

11. The selective catalyst reduction device control system of claim 7, wherein an alarm lamp or an alarm sound (voice) is turned on by the alarm signal.

12. The selective catalyst reduction device control system of claim 7, wherein a recharging lamp or a recharging sound (voice) is turned on by the recharging signal.