KR100774718B1 - Oxygen control method of catalytic converter for vehicle - Google Patents

Abstract

An oxygen control method of catalytic converter for vehicle is provided to remove oxygen stored in WCC and UCC and to reduce nitrogen oxides by obtaining oxygen storage capacities when a state of fuel is changed from Rich to Lean or from Lean to Rich, and obtaining exact fuel spray amount by multiplying oxygen storage capacity when the state of fuel is changed from Rich to Lean by fuel addition/reduction factor. An oxygen control method of catalytic converter for vehicle includes the steps of determining whether fuel cut occurs, (a)determining whether air amount of a warm-up catalytic converter(WCC) is larger than oxygen storage capacity(OSC) of the WCC, (b)determining whether air amount of under-flower UCC is larger than oxygen storage capacity(OSC) of the UCC when air amount of the WCC is larger than OSC of the UCC in the step(b), spraying fuel to the WCC and UCC with a value obtained by multiplying the OSC by fuel addition/reduction factor when the air amount of UCC is larger than OSC of the UCC in the step(c), the OSC is the value when the state of fuel is changed from Rich to Lean, receiving a sense signal from an oxygen sensor provided between the WCC and UCC and spraying fuel until an oxygen output value becomes higher than a reference value.

Description

Oxygen control method of catalytic converter for vehicle}

1 is a device configuration diagram showing a catalytic converter for a vehicle,

2 is a graph showing the effect of reducing NOx in the actual exhaust mode,

3 is a flowchart illustrating an oxygen control method of the catalytic converter according to the present invention;

4 is a flowchart illustrating an oxygen control method of a catalytic converter according to the prior art.

<Description of the symbols for the main parts of the drawings>

10: Warm up Catalytic Converter (WCC)

11: UCC (Under floor Catalytic Converter)

12,13: oxygen sensor

The present invention relates to an oxygen control method for a catalytic converter for a vehicle, and more particularly, the oxygen emission after the fuel cut is effective in reducing NOx, but due to inaccuracy of fuel reinjection time, there is a problem in that CO or NOx is generated. The OSC (oxygen storage capacity) of the catalysts WCC and UCC is different from when the fuel is cut off from the lean to the lean and when the fuel is re-injected from the lean to the rich. The present invention relates to an oxygen control method for a catalytic converter for a vehicle capable of reducing NOx by injection.

The injection operation of the fuel which is variable in the state change of the vehicle is changed in accordance with the state change of the vehicle.

That is, when the driver suddenly accelerates the speed due to the operation of the accelerator pedal, the asynchronous injection method increases the injection amount of the fuel for a separate injection time in addition to the basic injection time, and suddenly rotates the engine in a steady state maintaining a constant speed. There is a method of stopping the injection operation of the fuel for a predetermined time when the number is suddenly decelerated above the set value.

In addition, there is a basic injection method capable of executing a deceleration or acceleration operation by adjusting the basic injection time according to the speed of the variable vehicle while the engine speed changes below a set value.

Therefore, when the injection amount of the fuel is adjusted according to the driving state of each vehicle as described above, the injection operation of the fuel is stopped for a predetermined time so that the driving can be performed in a state suitable for the driving state.

In general, when the vehicle is decelerated, fuel cut-off is generated to reduce fuel consumption.

During this period, the catalyst is filled with oxygen, which makes it vulnerable to nitrogen oxide (NOx) emissions for some time during subsequent operation, so the closed loop lambda is controlled to purify the oxygen present in the catalyst. During control, a method of shifting lambda control richly using a delay delay (P_Jump Delay) is used.

However, when using the above method, conventionally, in order to cope with the North American enhanced exhaust (E / M) regulation, it is difficult to contribute to catalytic purging simply by rich lambda shift. , It exposes the limit of NOx emission.

In order to solve such a problem, conventionally, the apparatus which reduces NOx by artificially draining oxygen by injecting fuel into a catalyst is proposed.

1 is a device configuration diagram showing a catalytic converter for a vehicle, in which a warm-up catalytic converter 10 (hereinafter referred to as WCC) and an under-floor catalytic converter 11 (hereinafter referred to as UCC) are installed back and forth. Oxygen sensors 12 and 13 are provided in front and rear of the warm-up catalytic converter 10.

When the fuel cut occurs while driving, the fuel is changed from the RICH to the LEAN atmosphere so that the oxygen sensor detects the lean state of the fuel.

Since the amount of air introduced into the WCC 10 exceeds WCC OSC (OXYGEN STORAGE CAPACITY) and only the air enters the fuel cut state, oxygen is stored in the WCC 10.

Subsequently, when the WCC 10 is filled with oxygen, an oxygen sensor installed at the rear of the WCC 10 detects a lean state and oxygen is stored in the UCC 11 to generate NOx.

In order to prevent the generation of NOx, after the fuel cut, if the amount of air inflow to the WCC 10 exceeds OSC, fuel is injected by draining oxygen by the time until the OSC exceeds OSC to reduce NOx.

However, if a large amount of fuel is injected as described above, the air-fuel ratio is rich to 12.5: 1, and CO is generated. If too little is injected, NOx is generated.

The fuel injection amount is injected as determined by the target fuel addition amount according to the air amount, but it is not accurate because the injection time is determined by the OSC.

In addition, the fuel injection time is determined by the OSC, but the time from the rich to lean and the time from the lean to the rich is different, there is a problem that can not accurately oxygen drain with the same fuel injection.

That is, if the OSC is 2g, the OSC when going from rich to lean and the OSC when going from lean to rich are different. For example, if the OSC is 2g and the WCC is full of oxygen and wants to remove the oxygen by injecting fuel, the fuel injection amount is insufficient and NOx is generated when the fuel is injected for the time until the OSC 2g is filled.

The present invention has been made in view of the above, and when the oxygen storage capacity when the lean to the lean in the fuel and the oxygen storage capacity when the lean to lean in the fuel is accurately calculated It is an object of the present invention to provide an oxygen control method for a catalytic converter for a vehicle that can reduce NOx by removing oxygen stored in WCC and UCC by multiplying the oxygen storage capacity by the fuel derating factor.

In the present invention for achieving the above object in the oxygen control method of a catalytic converter for a vehicle,

Determining whether a fuel cut has occurred; Determining whether a warm-up catalytic converter (hereinafter referred to as WCC) air amount is greater than the WCC oxygen storage capacity (OSC); Determining whether the under-floor UCC air amount is larger than the UCC OSC when the WCC air amount is larger than the WCC OSC in the step; Injecting fuel into the WCC and the UCC by multiplying the fuel decay factor by the OSC when the UCC air volume is greater than the UCC OSC in the rich to lean state (from Rich to Lean); And injecting fuel until the oxygen output value is greater than or equal to a reference value by receiving a detection signal from an oxygen sensor installed between the WCC and the UCC.

In a preferred embodiment, the fuel derating factor is (OSC when lean to rich) ÷ (OSC when lean to lean).

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The present invention relates to an oxygen control method of a catalytic converter for reducing NOx after fuel cut.

The present invention accurately calculates the OSC (Oxygen Storage Capacity) when the fuel is cut off from the rich to lean after the fuel cut and the fuel is re-injected to reduce the lean to rich, thereby reducing NOx by fuel injection according to the OSC. One point is to make sure.

As described above, the fuel is injected to the WCC 10 and the UCC 11 after the fuel cut in order to improve fuel efficiency and reduce the NOx.

The WCC 10 and the UCC 11 are installed side by side in the exhaust line connected to the exhaust manifold to collect and burn environmental pollutants such as CO and NOx in the exhaust gas discharged from the vehicle and burn them.

Oxygen sensors 12 and 13 are installed at the front and rear ends of the WCC 10 to detect the amount of oxygen in the introduced air.

Here, the test accurately calculates the OSC when the fuel is cut off and becomes lean to lean after the fuel cut, and the OSC when the fuel is re-injected and becomes lean to lean.

Equation 1 is a formula for calculating the OSC, Δλ is the fuel injection amount deceleration coefficient, V is the air flow rate per hour (g / s), T is the time (sec).

OSC = Δλ × V × T × 0.23 × 1000

The test result in the test difference according to Equation 1 is shown in Table 1 below.

Referring to the oxygen control method of the catalytic converter according to the present invention.

1) When the vehicle decelerates, after detecting the fuel, the detection signal is input from the oxygen sensor installed in front of the WCC 10 to detect the lean state in the reach.

2) It is determined whether the amount of air introduced into the WCC 10 is greater than the WCC OSC value obtained through the test.

When the amount of WCC air exceeds WCC OSC, only air enters the fuel cut state, so that only oxygen is stored in the WCC 10.

3) It is determined whether the air amount introduced into the UCC 11 is larger than the UCC OSC value.

At this time, since the UCC 11 cannot obtain a test result, the UCC 11 is decremented by the volume VOLUME of the WCC 10.

When the amount of UCC air exceeds the UCC OSC, oxygen is stored in the UCC 11.

4) In order to remove oxygen stored in the WCC 10, the OSC at the time of becoming lean (L) from lean (L) obtained in Table 1 is divided by the OSC at the time of becoming lean (L) from rich (R). That is, (L → R OSC) ÷ (R → L OSC), and the fuel derating factor F is obtained.

5) The value of (R → L OSC) multiplied by the fuel decay factor is the fuel injection amount for removing oxygen.

For example, in Table 1, when the APS (Excel Opening Sensor) and the TPS (Throttle Opening Sensor) are 5% and 3%, respectively, the OSC at Rich → Lean is 784.3mg, and the OSC at Lean → Rich is 3.8 times, which is 2973mg. .

That is, in order to remove oxygen stored in the WCC 10, the fuel injection amount should be injected 3.8 times more than that of Rich → Lean OSC.

6) In order to remove the oxygen stored in the UCC (11), as in the WCC (10) to obtain a fuel derating factor, and then fuel is injected by the value of the fuel → the Rich → Lean OSC.

As described above, the fuel injection due to the accurate OSC calculation during the fuel re-injection can reduce the NOx by removing oxygen as shown in FIG. 2.

While the invention has been shown and described with respect to certain preferred embodiments thereof, the invention is not limited to these embodiments, and has been claimed by those of ordinary skill in the art to which the invention pertains. It includes all the various forms of embodiments that can be carried out without departing from the spirit.

As described above, according to the oxygen control method of the vehicle catalytic converter according to the present invention, the OSC of the WCC and the UCC is different from the case of the RICH → LEAN in which no fuel is used and the LEAN → RICH in which the fuel is re-injected. By using the concept, it is possible to improve the conventional occurrence of CO or NOx due to inaccuracy of fuel reinjection time, and to reduce NOx by fuel injection by accurate OSC calculation during fuel reinjection.

In addition, if only the OSC calculation result is obtained experimentally, it can be used universally in other models.

Claims (2)

In the oxygen control method of a vehicle catalytic converter, Determining whether a fuel cut has occurred; Determining whether a warm-up catalytic converter (hereinafter referred to as WCC) air amount is greater than the WCC oxygen storage capacity (OSC); Determining whether the under-floor UCC air amount is larger than the UCC OSC when the WCC air amount is larger than the WCC OSC in the step; Injecting fuel into the WCC and the UCC by multiplying the fuel decay factor by the OSC when the UCC air volume is greater than the UCC OSC in the rich to lean state (from Rich to Lean); Injecting fuel until an oxygen output value is greater than or equal to a reference value by receiving a detection signal from an oxygen sensor installed between the WCC and the UCC; Oxygen control method of a catalytic converter for a vehicle, characterized in that made. The method according to claim 1, And said fuel derating factor is (OSC when lean to lean) ÷ (OSC when lean to lean).

Images