KR100427291B1 - Method of controlling feedback for o2 sensor heater in a vehicle - Google Patents

Abstract

An oxygen sensor heater feedback control method of a vehicle is disclosed. The disclosed oxygen sensor heater feedback control method of a vehicle comprises the steps of: (a) applying heating for temperature rise so that the sensor is activated at the beginning of the vehicle startup; (b) determining an early entry condition of a close loop and determining an exhaust test condition; (c) controlling a heater temperature below the sensor crack damage temperature when the condition in step (b) is satisfied; (d) determining whether a dewpoint is completed; (e) determining the heating duty by using the driving condition (RPM) and the exhaust gas model of the vehicle when the duty point is completed in the step (d). According to the present invention, it is possible to effectively activate the sensor, there is an advantage that can prevent crack damage that is a problem in durability.

Description

Oxygen sensor heater feedback control method of vehicle {METHOD OF CONTROLLING FEEDBACK FOR O2 SENSOR HEATER IN A VEHICLE}

The present invention relates to an O2 sensor heater feedback control method of a vehicle, and more particularly, an oxygen sensor within a dew point using a FLO (Fast Light Off) oxygen sensor. The present invention relates to an oxygen sensor heater feedback control method of a vehicle for preventing damage and activating an oxygen sensor.

In order to prevent oxygen sensor crack damage and activate the oxygen sensor in the cold section before passing through the dew point, there is a gap between the sensor crack damage temperature and the sensor active temperature (the difference between the sensor specifications is generally Min. 50 ℃ ~ Max. 150 ℃) is not big, so precise temperature control is required.

If the sensor temperature is out of the control temperature range, the risk of sensor crack damage and the inability to close-loop control due to sensor inactivity can occur. This problem causes problems in emission control. This is the LSH_POW_CTRL state in FIG. 3 to be described later.

However, if the heater control in the dew point section is controlled only by the cooling water temperature and the driving conditions (RPM, load), it is difficult to control the temperature within the control temperature band due to the deviation between the vehicles and the oxygen sensor heater resistance deviation. have.

An object of the present invention is to provide an oxygen sensor heater feedback control method of a vehicle which prevents damage to an oxygen sensor and activates an oxygen sensor in a dew point section.

1 and 2 are schematic flowcharts sequentially showing a method of controlling a feedback sensor of an oxygen sensor heater of a vehicle according to the present invention.

Figure 3 is a graph showing a heater control method and a closed loop entry time point to which the present invention is applied.

4 is a graph showing a change in the internal resistance of the sensor according to the temperature change of the sensor.

5 is a graph showing the change in VLS_ecu amplitude according to the temperature change of the sensor.

Figure 6 is a proven graph applied to the oxygen sensor heater feedback control method of the vehicle according to the present invention.

Oxygen sensor heater feedback control method of the vehicle of the present invention for achieving the above object, (a) the step of applying a heating for the temperature rise so that the activation of the sensor at the initial start of the vehicle; (b) determining an early entry condition of a close loop and determining an exhaust test condition; (c) controlling a heater temperature below the sensor crack damage temperature when the condition in step (b) is satisfied; (d) determining whether a dewpoint is completed; (e) determining the heating duty by using the driving condition (RPM) and the exhaust gas model of the vehicle when the duty point is completed in the step (d).

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

1 and 2 are schematic flowcharts sequentially showing a method of controlling a feedback sensor of an oxygen sensor heater of a vehicle according to the present invention.

Referring to each of the drawings, the oxygen sensor heater feedback control method of the vehicle according to the present invention, first, the heating (heating) is applied to increase the temperature so that the sensor is activated at the initial start of the vehicle (step 110).

Step 110 is an LSH_POW_RISE (State) state, as shown in FIG. 3, which is an initial heating state immediately after starting. This is to raise the temperature to around 300 ° C, which is an active temperature of the FLO oxygen sensor, and determines the heating duty and heating duration by using the cooling water temperature condition and the intake temperature condition at the start-up.

Next, an early entry condition of the close loop is determined, and an exhaust test condition is determined (step 120).

If the condition in step 120 is satisfied, the heater temperature is controlled to be equal to or less than the sensor crack damage temperature.

As shown in FIG. 3, if only the oxygen sensor readiness bit is confirmed even before the completion of the dew point, the closed loop enters the LSH_POW_CTRL state. And to take advantage of the early activation characteristics of the FLO sensor at low temperatures.

Then, it is determined whether the dewpoint is completed (step 140).

When the duty point is completed in step 140, the heating duty is determined using the vehicle driving condition (RPM) and the exhaust gas model (step 150).

As illustrated in FIG. 3, the step 150 corresponds to a heater control section for controlling to a sensor heater temperature (about 700 ° C.) which exhibits the most stable signal output characteristic in the LSH_POW_CTL state.

In addition, the main factor for determining the heater temperature is self heating by the heater applied voltage (heating duty) and heating by the exhaust gas temperature. Therefore, the heater control in the LSH_POW_CTL state is based on the driving condition (RPM condition) and the OBD of the vehicle. The heating duty is determined using the exhaust gas model temperature used for monitoring. Ie heating duty = f (RPM, exhaust model temperature)

If the condition in step 120 is not satisfied, it is determined whether a due point is completed.

If the dew point is completed in step 210, the heater temperature is increased to apply the full heating to activate the sensor (step 220).

The above step 220 corresponds to a heating section for raising the temperature to around 700 ° C. which is a general heater control temperature after checking the completion point of the end point section in the LSH_POW_RED state described later in the LSH_POW_MAX state.

Subsequently, the full heating duty is reduced to the heater control heating duty to allow the closed loop to be entered, and the step 150 is performed (step 230).

Step 230 corresponds to a section for reducing from the maximum heating duty of the LSH_POW_MAX state to the heater control heating duty of the LSH_POW_CTL state in the LSH_POW_FALL state. This slows down by introducing a change limit to prevent sudden changes in the heating duty.

In this LSH_POW_FALL state, since the sensor activation is completed, it is possible to enter the closed loop after checking the oxygen sensor readiness bit indicating whether the sensor signal is output.

On the other hand, if the duty point is not completed in step 210, a reduction heating duty is applied and the step 210 is performed again (step 310). The step 310 is in the LSH_POW_RED state.

On the other hand, in FIG. 3, the LSH_OFF state is an engine stop condition.

If the dupoint is not completed in step 140, step 130 is performed again.

In addition, in step 130, the concept of the feedback point oxygen sensor heater feedback is introduced to determine whether the system is in a closed loop early entry state and a state for using an early active characteristic at a low temperature of the sensor (step 131).

When the condition of step 131 is satisfied, the filtered oxygen sensor average amplitude VLS_MMV_DIF is calculated (step 132).

In step 132, the filtered oxygen sensor average amplitude VLS_MMV_DIF is calculated by Equation 1 below.

VLS_MMV_DIF_n + 1 = VLS_MMV_DIF_n + FAC_1 × {abs (VLS_DIF_n + 1) -VLS_MMV_DIF_n}

Where VLS_MMV_DIF is the average amplitude of the filtered oxygen sensor,

FAC_1 is a filtering constant.

Next, the oxygen sensor heating duty of the duty point control section is calculated (step 133).

In step 133, the oxygen sensor heating duty of the duty point control section is calculated by Equation 2 below.

Heating duty = f (cooling water temperature, RPM, Load) x FAC_2 (VLS_MMV_DIF)

Here, the heating duty is the oxygen sensor heating duty of the duty point control interval,

f (cooling water temperature, RPM, Load) is the pilot heating duty (3D map), which is mapped to the target temperature according to the engine operating conditions in the duty point section,

FAC_2 (VLS_MMV_DIF) is a feedback factor that uses the filtered sensor signal average amplitude (VLS_MMV_DIF) in the duty point interval as a dependent variable.

As described above, the oxygen sensor heater feedback control method of the vehicle according to the present invention is to perform feedback heater control for precise temperature control of the closed loop early entry section before passing the dew point.

That is, the ECU generally filters the sensor output using an internal circuit to prevent distortion of the sensor output. The sensor signal output value changes due to a change in the internal impedance of the sensor that changes with temperature. The sensor temperature is predicted using this to feedback control the heating duty to prevent the sensor from rising above the crack damage temperature of the sensor and to control feedback using the sensor output value so as not to fall below the active temperature.

In addition, the present invention is a part for detecting the sensor impedance change according to the heater temperature and the resulting amplitude change of the sensor signal and the part for predicting the temperature of the sensor heater using this to feedback control the heater power within the dew point temperature control range Divided into

First, the heater temperature prediction using the sensor signal will be described. In order to prevent disturbance of the sensor signal, the ECU of the vehicle filters a sensor signal by applying a large resistance inside the ECU as shown in Equation 3 below.

VLS_ecu = VLS_Sensor × R_ecu / (R_ecu + R_Sensor)

Here, VLS_ecu is the oxygen sensor signal filtered from the ECU,

VLS_Sensor is Oxygen Sensor Raw Signal,

R_ecu is the ECU's internal resistance (512Ω) for filtering the sensor output.

R_ sensor is the internal resistance of the oxygen sensor.

Referring to Equation 3, when the ECU internal resistance R_ecu is infinitely large compared to the R_sensor, it can be seen that the sensor signal is converted to 1: 1 without distortion at all.

However, when the resistance of the sensor has a value that is not relatively small compared to the internal resistance of the ECU, the ECU internal oxygen sensor signal calculated by Equation 3 may be reduced and distorted in amplitude.

And the internal resistance of the sensor has a resistance value as shown in Figure 4 according to the sensor temperature, the sensor resistance value corresponding to the heater control temperature (300 ~ 350 ℃) in the dew point control section is 60 ~ 600Ω level of the internal resistance of the ECU This becomes a relatively large value, which reduces the sensor signal.

On the other hand, in the section of 500 ℃ or higher where the oxygen sensor is fully heated, the sensor resistance is less than 5Ω, which is negligible compared to the internal resistance of the ECU, and the sensor signal is converted to 1: 1 without any distortion.

For example, it is assumed that the output value of the oxygen sensor signal is 0 to 1 V, which is an ideal value, and the amplitude at this time is regarded as 100%. And when the ECU internal resistance is 500Ω, the resistance value at the heater temperature 300 ℃ 500Ω, the resistance value at 350 ℃ to 50Ω, as shown in Figure 5, VLS_ecu amplitude at 300 ℃ 50%, 350 ℃ The VLS_ecu amplitude of is shown at 90% level.

Therefore, using the characteristics of these signals in the dew point control section, it is possible to estimate the sensor temperature inversely, to prevent the damage of the sensor cracks, and to effectively control the heater.

Secondly, in the dew point control section heater control using the oxygen sensor signal amplitude, the variation range of the sensor signal is monitored as VLS_DIF_n of FIG. 5 based on 0.5 V, which is a neutral value, to estimate the oxygen sensor heater temperature. to monitor.

In addition, the average amplitude is calculated by filtering VLS_DIF_n to calculate a more stable signal amplitude in response to unexpected noise of the sensor signal. This is referred to Equation 1 above.

The heater duty in the duty point control section is applied by multiplying a base map value based on the cooling water temperature and an operating condition by a feedback factor defined using the VLS_MMV_DIF value calculated in Equation 1 above. In other words, if the VLS_MMV_DIF value decreases below 50% of the basic amplitude, the sensor temperature can be lowered below the active temperature.Increasing the heater duty and showing 90% or more amplitude reduces the heating amount because there is a risk of crack damage due to excessive sensor heating. .

Since the sensor resistance value is different according to the temperature between the new sensor and the old sensor, the control factor is set to 60 ~ 80% amplitude to map the feedback factor in the direction of reducing the deviation due to sensor aging.

On the other hand, Figure 6 is a proven graph applied to the oxygen sensor heater feedback control method of the vehicle according to the present invention.

As described above, the oxygen sensor heater feedback control method of the vehicle according to the present invention has the following effects.

Precise temperature control within the dewpoint area required for early entry into the closed loop using FLO oxygen sensors enables effective sensor activation and prevents crack damage that is a problem in durability.

In addition, maintenance cost can be reduced by securing the sensor durability, and precise emission control can be precisely controlled in the cold section through more accurate sensor active temperature control, thereby improving cold emission.

Although the present invention has been described with reference to one embodiment shown in the drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent embodiments are possible. Therefore, the true scope of protection of the present invention should be defined only by the appended claims.

Claims (7)

(a) applying heating to increase the temperature so that the sensor is activated at the start of the vehicle; (b) determining an early entry condition of a close loop and determining an exhaust test condition; (c) controlling a heater temperature below the sensor crack damage temperature when the condition in step (b) is satisfied; (d) determining whether a dewpoint is completed; (e) determining the heating duty by using the driving condition (RPM) and the exhaust gas model of the vehicle when the duty point is completed in the step (d). Oxygen sensor heater feedback control method. The method of claim 1, (f) if the condition in step (b) is not satisfied, determining whether a due point is completed; (g) if the dew point is complete in step (f), raising the heater temperature and applying it to full heating to activate the sensor; (h) reducing the full heating duty to the heater control heating duty to allow a closed loop entry, and performing step (e); and the oxygen sensor heater feedback control of the vehicle further comprising: Way. The method of claim 2, If the duty point is not completed in step (f), applying a reduction heating duty and causing the step (f) to be performed again. Heater feedback control method. The method of claim 1, In the step (c) by introducing the concept of the feedback point oxygen sensor heater feedback, (i) determining a closed loop early entry state and whether to use the early activation characteristics at low temperatures of the sensor; (j) calculating the filtered oxygen sensor average amplitude (VLS_MMV_DIF) when the condition of step (i) is satisfied; and (k) calculating an oxygen sensor heating duty of the duty point control section. The method of claim 4, wherein The oxygen sensor heater feedback control method of the vehicle, characterized in that in step (j) the filtered oxygen sensor average amplitude (VLS_MMV_DIF) is calculated by the following equation (1). [Equation 1] VLS_MMV_DIF_n + 1 = VLS_MMV_DIF_n + FAC_1 × {abs (VLS_DIF_n + 1) -VLS_MMV_DIF_n} Where VLS_MMV_DIF is the average amplitude of the filtered oxygen sensor, FAC_1 is a filtering constant. The method of claim 4, wherein Oxygen sensor heating duty in the step (k) is the oxygen sensor heater feedback control method of the vehicle, characterized in that calculated by the following equation (2). [Equation 2] Heating duty = f (cooling water temperature, RPM, Load) x FAC_2 (VLS_MMV_DIF) Here, the heating duty is the oxygen sensor heating duty of the duty point control interval, f (cooling water temperature, RPM, Load) is the pilot heating duty (3D map), which is mapped to the target temperature according to the engine operating conditions in the duty point section, FAC_2 (VLS_MMV_DIF) is a feedback factor that uses the filtered sensor signal average amplitude (VLS_MMV_DIF) in the duty point interval as a dependent variable. The method of claim 1, The method of controlling the oxygen sensor heater feedback of the vehicle, characterized in that the step (c) is performed again if the dew point is not completed in the step (d).