JPH0670618B2 - Control O ▲ Lower 2 ▼ Sensor automatic correction method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is for control in the air-fuel ratio automatic control of a gas engine in which methane is the main combustion component and a three-way catalyst is installed in the exhaust system.
The present invention relates to an O ₂ sensor automatic correction method.

[Conventional technology]

The three-way catalyst can remove NOx, CH, and HC in the exhaust gas at the same time, but the purification characteristics change greatly depending on the set air-fuel ratio of the engine, so strict control of the air-fuel ratio is required. FIG. 2 shows this, and both NOx and CO are removed only in a narrow range such as around the air-fuel ratio of 1.0, and NOx or CO is not removed at an air-fuel ratio outside of that range. The range where both of these are removed is called the window. In order to control the air-fuel ratio within this range, the output characteristics shown by Ao → A ₁ → A ₂ in Fig. 2 are shown for the air-fuel ratio of the engine. It is known to utilize a zirconia-type O ₂ sensor having. That is, the air-fuel ratio is controlled so that the output (voltage) of the O ₂ sensor becomes the value Vp corresponding to the window on the output characteristic curve. A typical example is shown in FIG. In FIG. 3, the O ₂ sensor (1) is installed in front of the catalyst layer (4) in the exhaust gas line (3) of the engine (2). The mixer (5) roughly determines the mixing ratio of gas and air, that is, the air-fuel ratio, and is provided with the air bypass line (6) for air-fuel ratio fine adjustment. If the output of the O ₂ sensor (1) is lower than Vp, the control valve (7) installed in the air bypass line (6)
Is operated in the closing direction via the controller (8) to adjust the air-fuel ratio in the gas rich direction, and if the output of the O ₂ sensor (1) is higher than Vp, the control valve (7) is operated in the opening direction. Then, the air-fuel ratio is adjusted in the gas lean direction.

By the way, the output Vp of the control O ₂ sensor (1) with the control O ₂ sensor at a point corresponding to the window on the output characteristic curve of the (1) called slush level, if methane-based fuel, the second As shown in the figure, the control O ₂ sensor (1) is located in a flat portion on the left side of the falling portion (A ₁ ) of the control O ₂ sensor (1), and its relative relationship with the window changes with the load and the rotational speed of the engine (2). Therefore, it is usually dealt with by creating a table in the memory of the controller (8), which gives Vp as a function of the load and speed of the engine (2).

However, when the control O ₂ sensor (1) deteriorates due to the influence of heat or poisonous substances, the output characteristics deteriorate as shown by the dotted line in FIG. 2, so the output of the control O ₂ sensor (1) When feedback is applied to Vp, the air-fuel ratio is out of the window, which has the drawback of causing a large increase in NOx or CO.

In order to cope with the deterioration (output decrease) of the control O ₂ sensor (1), as shown in FIG. 3, the exhaust gas line (3)
An exhaust gas bypass line (10) is provided in the exhaust gas heat exchanger (9) installed downstream of the catalyst layer (4) inside, and an O ₂ sensor for verification (1
1) is installed, and compressed air is supplied to the upstream side of the verification O ₂ sensor (11) in the exhaust gas bypass line (10) except during the verification to prevent the verification O ₂ sensor (11) from deterioration. aside action to prevent, occasionally (e.g., about once in several weeks, etc., periodically or when necessary) for controlling O ₂ sensor (1) and the calibrating O ₂ sensor (11) and control O ₂ by comparing the If the sensor (1) is deteriorated, its feedback set value is corrected from Vp to Vp 'in FIG. 2 to prevent the air-fuel ratio from falling out of the window.

[Problems to be Solved by the Invention]

Conventionally, an operator compares the outputs of the control O ₂ sensor (1) and the verification O ₂ sensor (11) to determine the presence or absence of deterioration of the control O ₂ sensor (1) and the degree of deterioration, The output of the controller (8) is corrected according to the degree of the deterioration. However, for causing the correction during the control of the control O ₂ sensor (1), during control Control O ₂ sensor (1)
Output is hunted and it is difficult to correct, and there is a problem that the deviation of the sentiment cannot be corrected accurately.

The present invention has been proposed in view of the above problems of the related art, and an object of the present invention is to prevent the deviation of sensing by automatically correcting the control O ₂ sensor in the controller. It is intended to provide an O ₂ sensor automatic correction method.

[Means for Solving the Problems]

To achieve the above object, the present invention is an engine at initialization control O ₂ sensor and calibrating O ₂ by gradually changing the air-fuel ratio
Sensor outputs are input at the same time, an output relation table for both sensors is created by this input and stored in the memory of the controller, feedback control of the control O ₂ sensor is terminated during verification, and the air-fuel ratio is gradually changed. For control
The O ₂ sensor and the output of the calibrating O ₂ sensors to create a correction table by comparing the value of the memory, and corrects the feedback set value of the control O ₂ sensor based on the correction table.

[Action]

When the control O ₂ sensor is deteriorated, the feedback setting value of the control O ₂ sensor can be automatically corrected in the memory of the controller based on the correction table.

〔Example〕

FIG. 1 is a schematic diagram of a supply / exhaust system of a gas engine for carrying out the method of the present invention, in which (1) is an O ₂ sensor for control,
(2) is an engine, (3) is an exhaust gas line, (4) is a catalyst layer, (5) is a mixer, (6) is an air bypass line for fine adjustment of air-fuel ratio, (7) is a control valve, (8). Shows a controller, (9) shows an exhaust gas heat exchanger, (10) shows an exhaust gas bypass line, and (11) shows an O ₂ sensor for verification. These have the same configuration as the conventional one.

First, according to the present invention, when the engine is initialized, the air-fuel ratio is gradually changed and the control O ₂ sensor (1) and the verification O ₂ sensor (1
Input the detection of 1) at the same time, and by these inputs, Table 1
A sensor output relation table as shown in (1) is created and fixedly stored in the memory of the controller (8).

The control O ₂ sensor (1) and the verification O ₂ sensor (11) are occasionally compared by the controller (8) at regular intervals (for example, once every few weeks, or when necessary), and the difference is displayed. Deterioration of the control O ₂ sensor (1) is detected because it is different from 1, and the feedback set value of the control O ₂ sensor (1) is corrected from Vp to Vp ′ in FIG. To do. That is, the controller (8) operates under the condition that the engine load and the rotation speed are constant (when the load controller is present,
The request may be sent to the load controller)
When the feedback control of the O ₂ sensor (1) is terminated and the output range of the verification O ₂ sensor (11) in Table 1 is covered, the control valve (7) is opened or closed or closed. The air-fuel ratio is gradually changed by operating at a speed slow enough to open. Then, input the outputs of the control O ₂ sensor (1) and the verification O ₂ sensor (11) during that period as stable values by means such as nozzle filtering and moving average, and compare this input with Table 1. Then, a correction table as shown in Table 2 is created and stored in the memory of the controller (8). For example, when the output of the verification O ₂ sensor (11) is 0.85V and the output of the control O ₂ sensor (1) is 0.869V, ΔVp (Vp of 0.
The position of 87V) becomes -0.01V.

Therefore, Kotorora (8) for controlling O ₂ by adding ΔVp to Vp
The feedback set value of the sensor (1) is corrected from Vp to Vp 'in FIG. 2 and the feedback control is restarted. When the control O ₂ sensor (1) is further deteriorated when the next test is performed, ΔVp is added to the feedback set value of the control O ₂ sensor (1) to correct it.
In this way, ΔVp is added to the set value Vp for correction.
The outputs of the control O ₂ sensor (1) and the test O ₂ sensor (11) for each test are created in the test table shown in Table 3 and stored in the memory of the controller (8). Based on this, the next time at the time of verification, the presence or absence of deterioration will be detected from the previous time, and if there is deterioration, a correction operation will be entered, and if there is no deterioration, a confirmation display will be displayed to indicate whether or not there is a correction operation. You can also let it.

In the above explanation, the outputs of the control O ₂ sensor (1) and the verification O ₂ sensor (11) at each verification time are created in a verification table as shown in Table 3 and stored in the memory of the controller (8). Although the case of storing is illustrated, the output of the control O ₂ sensor in the sensor output relation table of Table 1 may be rewritten and stored for each test.

〔The invention's effect〕

According to the present invention, in a state in which broke off feedback control of the control O ₂ sensor, since by comparing the output of the calibrating O ₂ sensors and the control O ₂ sensor, it is possible to perform the test in a stable manner As a result, it is possible to provide a highly reliable automatic air-fuel ratio control means for a gas engine by preventing the sensing deviation.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a supply / exhaust system of a gas range for carrying out the control O ₂ sensor automatic control method of the present invention, and FIG. 2 is a NOx and CO sensor output with respect to an air-fuel ratio (horizontal axis) of a gas engine (vertical axis). ) Is a graph showing the relationship, and the output characteristic curve of the zirconia O ₂ sensor is shown in the graph. FIG. 3 is a schematic diagram showing an example of a gas supply / exhaust system of a gas engine. (1) …… Control O ₂ sensor, (2) …… Engine, (3) …… Exhaust gas line, (4) …… Catalyst layer, (5) …… Mixer, (6) …… Fine air-fuel ratio Adjustment bypass line, (7) …… Control valve, (8) …… Controller, (9) …… Exhaust gas heat exchanger, (10) …… Exhaust gas bypass line, (12) …… Verification O ₂ sensor.

Claims (1)

[Claims] 1. At the time of initial setting of the engine, the air-fuel ratio is gradually changed and the outputs of the control O ₂ sensor and the verification O ₂ sensor are simultaneously input, and the output of both sensors is created by this input to create a controller It is stored in the memory and the feedback control of the control O ₂ sensor is terminated at the time of verification, and the air-fuel ratio is gradually changed to control O ₂ sensor and verification.
The O ₂ sensor output to generate a correction table by comparing the value of the memory, the correction control for O ₂ sensors automatic correction and correcting the feedback set value of the control O ₂ sensor based on the table Method.