JP3890830B2 - O2 sensor diagnostic device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an O2 sensor diagnostic apparatus, and more particularly to an O2 sensor diagnostic apparatus capable of accurately diagnosing an abnormal state of an O2 sensor that detects an oxygen concentration in exhaust gas.
[0002]
[Prior art]
Some engines mounted on vehicles and the like are provided with an air-fuel ratio control device that controls the air-fuel ratio to a target value. In the air-fuel ratio control device, an O2 sensor is provided in the middle of the exhaust passage, and the fuel is controlled so that the air-fuel ratio becomes the target value by correcting the feedback control amount calculated from the output signal of this O2 sensor with the feedback correction amount. There is.
[0003]
Thereby, the air-fuel ratio control device optimizes the air-fuel ratio of the engine by the output signal from the O2 sensor to improve the combustibility, improve the exhaust gas purification efficiency by the catalyst body, and reduce the exhaust harmful component value to be discharged. I am trying.
[0004]
An example of the O2 sensor diagnostic apparatus is disclosed in Japanese Patent Laid-Open No. 10-141122. An oxygen sensor deterioration diagnosis device disclosed in this publication is a sensor that is provided in an exhaust passage of an engine and whose output changes in response to oxygen concentration in exhaust gas, and is a heater for heating a sensor element Is a deterioration diagnosis device for an oxygen sensor, and a deterioration diagnosis means for performing a deterioration diagnosis of the oxygen sensor on the condition that the elapsed time after the start of energization to the heater is equal to or longer than a predetermined delay time, Delay time in the deterioration diagnosis means when the engine cold state is determined by the cooler / complete warming determination means for determining whether the engine temperature state is the cold state or the fully warmed state. As a result, the engine is fully warmed by means of a cold time delay time setting means that sets a delay time that is set in advance according to the cold air condition, and a cold / complete warming determination means. When determined, the delay time in the deterioration diagnosis means is configured to include a delay time setting means for complete warming that sets a delay time previously set in conformity with the warmed state, and is provided with a heater. The sensor deterioration diagnosis is frequently executed based on the accurate determination of the active state.
[0005]
[Problems to be solved by the invention]
By the way, in the conventional O2 sensor diagnostic apparatus, many prior applications already exist as control for diagnosing characteristic abnormality due to abnormality and deterioration of the O2 sensor.
[0006]
The deterioration diagnosis control method in the prior application is for diagnosing output characteristic abnormality mainly caused by poisoning or exposure to high temperatures.
[0007]
In addition to the above, there is a control method for diagnosing a trouble, short circuit, or disconnection state of the O2 sensor, but the output characteristics of the O2 sensor are shown in FIG. Unstable during the hour or predetermined time after startup.
[0008]
For this reason, diagnosis is prohibited only for a predetermined time after the engine is started and when the engine coolant temperature is low.
[0009]
If water or the like enters the O2 sensor connector or the O2 sensor, the heater power supply for the O2 sensor leaks to the O2 sensor signal line, the O2 sensor element insulation resistance decreases, or the atmosphere of the O2 sensor As a result, as shown in FIG. 7, the output of the O2 sensor becomes abnormal and the fuel control is not performed accurately, resulting in a drivability failure or an engine stall. There is a concern that there is a concern and it is disadvantageous in practice.
[0010]
Further, as shown in FIG. 7, when the abnormal state continues for a long time, such as the abnormality of the O2 bank 1 which is the first O2 sensor output voltage disposed in the exhaust system on the first cylinder bank side which is one side of the engine. As shown in O2 bank 2, which is the second O2 sensor output voltage disposed in the exhaust system on the second cylinder bank side, which is the other side of the engine, can determine the abnormal state by the current abnormality diagnosis control. In addition, the second O2 sensor output voltage is in an abnormal state only for a while after the start, and if it returns to the normal state after that, it becomes impossible to detect the abnormality of the O2 sensor.
[0011]
The number of seconds after which the engine is in an abnormal state varies depending on the degree of penetration of water or the like and does not take a fixed value.
[0012]
If the above-mentioned problems occur during actual use, engine stall may occur after starting, or drivability defects such as idle malfunction or acceleration failure may occur. Therefore, the abnormal state of the O2 sensor cannot be detected and various parts such as the engine controller, throttle, ISC (idle speed control) valve, and AFS are not abnormal. However, it is exchanged at the time of repair work at a dealer or the like, requiring a lot of time, which is disadvantageous for practical use, has a high repair cost, and is disadvantageous economically.
[0013]
[Means for Solving the Problems]
Therefore, in order to eliminate the above-described disadvantages, the present invention is provided with an O2 sensor for detecting the oxygen concentration in the exhaust gas in the middle of the exhaust passage of the engine, and an O2 sensor having control means for controlling the diagnosis of the O2 sensor. In the diagnostic apparatus, the control means sets the O2 sensor abnormality diagnosis time after the engine is started at an engine cooling water temperature that is equal to or lower than a predetermined engine cooling water temperature, and an engine whose O2 sensor abnormality diagnostic voltage width is equal to or lower than a predetermined engine cooling water temperature. While setting is made for each cooling water temperature, the elapsed time after engine start is within the O2 sensor abnormality diagnosis time, and the detected O2 sensor output voltage is based on the O2 sensor abnormality diagnosis voltage width with respect to the design voltage of the O2 sensor. That the engine is idling and that the engine is idling is set as an abnormality determination condition. But it detects a prior to the start of the fuel feedback control and the O2 activity prior to the O2 sensor output voltage of the sensor of the engine, and having a function of performing diagnosis of the O2 sensor by the abnormality determination condition.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
By inventing as described above, the O2 sensor output voltage is detected before the activation of the O2 sensor, and the O2 sensor is diagnosed according to a predetermined abnormality determination condition. An abnormal state of the O2 sensor that was difficult to diagnose is accurately diagnosed.
[0015]
【Example】
Embodiments of the present invention will be described below in detail with reference to the drawings.
[0016]
1 to 5 show an embodiment of the present invention. In FIG. 2, 2 is an engine, 4 is an intake passage, and 6 is an exhaust passage.
[0017]
The engine 2 has a first cylinder bank 8 on one side and a second cylinder bank 10 on the other side arranged in a V shape.
[0018]
An air cleaner 12, an intake air temperature sensor 14, a mass air flow sensor 16, and a throttle valve 18 are sequentially arranged in the intake passage 4 from the upstream side. The first branch intake passage 4-1 is connected to a combustion chamber (not shown) on the first cylinder bank 8 side, and the second branch intake passage 4-1, 4-2 is branched. A branch intake passage 4-2 is provided connected to a combustion chamber (not shown) on the second cylinder bank 10 side.
[0019]
The throttle valve 18 is provided with a throttle opening sensor 20 for detecting the throttle opening of the throttle valve 18 and a bypass passage 22 for bypassing the throttle valve 18. An air control valve 24 is provided.
[0020]
Further, the exhaust passage 6 is provided with its upstream side branched into two first and second branch exhaust passages 6-1 and 6-2, and the first branch exhaust passage 6-1 is provided in the first cylinder bank 8. A second branch exhaust passage 6-2 is provided connected to a combustion chamber (not shown) on the second cylinder bank 10 side.
[0021]
The first catalytic converter 26-1 is provided in the middle of the first branch exhaust passage 6-1, and the second catalytic converter 26-2 is provided in the middle of the second branch exhaust passage 6-2. A first front-side O2 sensor 28-1 for detecting the oxygen concentration in the exhaust gas is provided at a position upstream of the first catalytic converter 26-1 in the middle of the first, and the first halfway in the first branch exhaust passage 6-1. A first rear O2 sensor 30-1 is provided at a downstream side of the catalytic converter 26-1.
[0022]
A second front side O2 sensor 28-2 is provided upstream of the second catalytic converter 26-2 in the middle of the second branch exhaust passage 6-2, and a second catalytic converter in the middle of the second branch exhaust passage 6-2. A second rear-side O2 sensor 30-2 is provided at a site downstream of 26-2.
[0023]
Furthermore, the first and second branch exhaust passages 6-1 and 6-2 are merged at the downstream side of the first and second rear O2 sensors 30-1 and 30-2. Also, a three-way catalytic converter 32 is disposed in the middle of the exhaust passage 6 on the downstream side.
[0024]
The engine 2 is provided with a fuel injection valve 34 directed to each combustion chamber (not shown). The fuel injection valve 34 communicates with a fuel tank 38 through a fuel supply passage 36. The fuel in the fuel tank 38 is pumped by the fuel pump 40, dust is removed by the fuel filter 42, and the fuel is supplied to the fuel injection valve 34 by the fuel supply passage 36.
[0025]
In the middle of the fuel supply passage 36, a fuel pressure adjusting unit 44 for adjusting the fuel pressure is provided in communication. The fuel pressure adjusting unit 44 adjusts the fuel pressure to a constant value by the intake pressure introduced from the pressure guiding passage 46 communicating with the intake passage 4, and returns excess fuel to the fuel tank 38 through the fuel return passage 48. The fuel tank 38 is provided with a fuel level sensor 50 and a pressure sensor 52.
[0026]
The fuel tank 38 communicates with the intake passage 4 on the downstream side of the throttle valve 18 through the evaporated fuel passage 54, and a canister 56 is interposed in the middle of the evaporated fuel passage 54.
[0027]
The engine 2 is provided with EGR control means 58. The EGR control means 58 is provided with an EGR valve 60 that adjusts the EGR amount of the exhaust gas recirculated from the exhaust system to the intake system. The EGR valve 60 includes a second branch exhaust passage 6-2 upstream of the second front-side O2 sensor 28-2 of the exhaust system and first and second branch intake passages 4-1 and 4-2 of the intake system. Is provided in an EGR passage 62 communicating with the merging portion, and the operation is electronically controlled to adjust the EGR amount.
[0028]
Reference numeral 64 denotes a PCV valve.
[0029]
The intake air temperature sensor 14, the mass air flow sensor 16, the throttle opening sensor 20, the idle air control valve 24, the first front side O2 sensor 28-1, and the first rear side O2 sensor 30-1. The second front side O2 sensor 28-2, the second rear side O2 sensor 30-2, the fuel injection valve 34, the fuel pump 40, the pressure sensor 52, and the EGR valve 60 are controlled by a control means (“ECM It is also connected to 66).
[0030]
The control means 66 includes a camshaft position sensor 68, an intake pressure sensor 70, an ignition coil assembly 72, a water temperature sensor 74, a crank angle sensor 76, an indicator lamp 78, a connection terminal 80, a power steering pressure. Switch 82, heater blower fan switch 84, cruise control module 86, vehicle speed sensor 88, combination meter 90, A / D capacitor fan relay 92, A / C controller 94, and data link connector 96 ABS controller module 98, main relay 100, ignition switch 102, P / N position switch 104, battery 106, starter switch 108, O / D off lamp 110, power lamp 112, light lamp 112, Switch 114, stop lamp switch 116, O / D cut switch 118, power / normal change switch 120, 4WD LOW switch 122, transmission range switch 124, first solenoid valve 126, and second solenoid valve. 128, a TCC solenoid valve 130, an A / T input speed sensor 132, and an A / T output speed sensor 134 are connected to each other.
[0031]
The control means 66 performs diagnosis of the first front O2 sensor 28-1, the first rear O2 sensor 30-1, the second front O2 sensor 28-2, and the second rear O2 sensor 30-2. Although it has a function, the control means 66 is configured to add a function of detecting the O2 sensor output voltage before the activation of the O2 sensor and diagnosing the O2 sensor according to a predetermined abnormality determination condition.
[0032]
Specifically, the predetermined abnormality determination condition is
(1) Within O2 sensor abnormality diagnosis time TO2T from the elapse of time ta after engine start (2) Design voltage other than 0.3 ± O2 sensor abnormality diagnosis voltage width Va (* Design voltage varies depending on the system)
(3) Idle switch is ON
When all of (1) to (3) are established, it is determined that the O2 sensor is abnormal.
[0033]
Further, the O2 sensor abnormality diagnosis time TO2T on the front side is set at the engine coolant temperature as shown by the hatched lines in FIG. As shown in FIG. 4, the O2 sensor activation time KO2T from the rear side engine start is also obtained at the engine coolant temperature.
[0034]
Further, the O2 sensor abnormality diagnosis voltage width Va is set for each engine coolant temperature as shown in FIG.
[0035]
Next, the operation will be described along the control flowchart of FIG.
[0036]
When the engine 2 is started (200) and the control program is started, the engine cooling water temperature is measured (202) after starting, and the O2 sensor abnormality diagnosis time TO2T on the front side is obtained from the engine cooling water temperature and set according to FIG. 204).
[0037]
Then, the abnormality diagnosis voltage width Va is obtained and set from the engine coolant temperature in FIG. 5 (206), and the O2 sensor output voltage O2V before activation is measured (208).
[0038]
Further, the O2 sensor output voltage O2V before activation is within the design voltage 0.3 ± O2 sensor abnormality diagnosis voltage width Va, that is,
(0.3-Va) <O2V <(0.3 + Va)
Is determined (210), and if this determination (210) is YES, the process proceeds to determination (212) as to whether or not the O2 sensor abnormality diagnosis time TO2T has elapsed. If 210) is NO, it is diagnosed that the O2 sensor is abnormal, lamp lighting or the like is performed to notify the user of the abnormality (214), and the process proceeds to an end (218) described later.
[0039]
In the determination (212) of whether or not the O2 sensor abnormality diagnosis time TO2T has passed, if this determination (212) is NO, the process returns to the measurement process (208) of the O2 sensor output voltage O2V before activation, If the determination (212) is YES, the O2 sensor is diagnosed as normal (216), and the process proceeds to the end (218).
[0040]
Thus, the O2 sensor output voltage is detected before the activation of the O2 sensor, and the control means 66 to which the function of diagnosing the O2 sensor according to a predetermined abnormality determination condition is added. It is possible to accurately diagnose the condition, which is advantageous in practical use, can eliminate the occurrence of drivability failure due to the O2 sensor failure, and has also failed to diagnose the abnormality of the O2 sensor. There is no need for repair work, and there is no need to replace various parts such as engine controllers, throttles, ISC (idle speed control) valves, and AFS. is there.
[0041]
Further, by setting the O2 sensor abnormality diagnosis time TO2T based on the engine coolant temperature, an appropriate O2 sensor abnormality diagnosis time TO2T according to the engine state can be obtained, and the time required for pursuing the cause of the malfunction of the O2 sensor. Can be shortened, and usability can be improved.
[0042]
Furthermore, by setting the O2 sensor abnormality diagnosis voltage width Va for each engine coolant temperature, an appropriate O2 sensor abnormality diagnosis voltage width Va corresponding to the engine state can be obtained, and the reliability of abnormality diagnosis control can be improved. .
[0043]
The present invention is not limited to the above-described embodiments, and various application modifications are possible.
[0044]
For example, in the embodiment of the present invention, the O2 sensor abnormality diagnosis time and the O2 sensor abnormality diagnosis voltage width after engine start are set according to the engine cooling water temperature, but the detection signal from the intake air temperature sensor is also used together. A special configuration is also possible.
[0045]
That is, as apparent from FIG. 2, the intake air temperature sensor is disposed in the vicinity of the air cleaner, and a detection signal close to the outside air temperature can be obtained by the intake air temperature sensor.
[0046]
In this case, the detection signal from the intake air temperature sensor enables appropriate control according to the outside air condition such as season and weather, which is practically advantageous.
[0047]
In the embodiment of the present invention, when an abnormality of the O2 sensor is diagnosed, the lamp is turned on to notify the user, but the O2 sensor is excluded from engine control at the time of abnormality diagnosis. It is also possible to do.
[0048]
That is, when the abnormality of the O2 sensor is diagnosed, the engine control by the signal of the O2 sensor is stopped by preventing the signal from the O2 sensor from being used by the control means. Alternatively, a measure for stopping the engine itself may be considered in order to stop the engine control.
[0049]
Then, the O2 sensor diagnosed as abnormal can be excluded from the engine control, accurate engine control can be performed, and the reliability of the control can be improved.
[0050]
【The invention's effect】
As described above in detail, according to the present invention, it is possible to accurately diagnose the abnormal state of the O2 sensor, which has been difficult to diagnose in the past, which is practically advantageous and also has a drivability defect due to a problem with the O2 sensor. Occurrence can be eliminated, and repair work at the dealer, etc. caused by the failure to diagnose the abnormality of the O2 sensor becomes unnecessary, and there are no abnormal engine controllers, throttles, ISC (idle speed control) valves, AFS, etc. Therefore, it is possible to greatly reduce the repair cost without replacing various parts of the apparatus, which is economically advantageous.
[Brief description of the drawings]
FIG. 1 is a control flowchart of an O2 sensor diagnostic apparatus showing an embodiment of the present invention.
FIG. 2 is a schematic configuration diagram of an O2 sensor diagnostic device.
FIG. 3 is a time chart showing a fuel hood back (F / B) correction value, a rotation speed, a front O2 output, a rear O2 output, and a vehicle speed.
FIG. 4 is a diagram showing a relationship between engine (E / G) cooling water temperature and O2 sensor activation time from engine (E / G) startup.
FIG. 5 is a diagram showing a relationship between engine (E / G) cooling water temperature and a diagnostic voltage width over an O 2 sensor.
FIG. 6 is a time chart of the O2 sensor output voltage showing the prior art of the present invention.
FIG. 7 is a time chart showing a fuel hoodback (F / B) correction value and an O2 sensor output voltage.
[Explanation of symbols]
2 Engine 4 Intake passage 4-1 First branch intake passage 4-2 Second branch intake passage 6 Exhaust passage 6-1 First branch exhaust passage 6-2 Second branch exhaust passage 8 First cylinder bank 10 Second cylinder bank 12 Air Cleaner 14 Intake Air Temperature Sensor 16 Mass Air Flow Sensor 18 Throttle Valve 20 Throttle Opening Sensor 24 Idle Air Control Valve 26-1 First Catalytic Converter 26-2 Second Catalytic Converter 28-1 First Front Side O2 Sensor 28- 2 2nd front side O2 sensor 30-1 1st rear side O2 sensor 30-2 2nd rear side O2 sensor 32 Three way catalytic converter 34 Fuel injection valve 38 Fuel tank 44 Fuel pressure adjustment part 52 Pressure sensor 56 Canister 58 EGR control Means 60 EGR valve 66 Control means 70 Intake pressure sensor 74 Water temperature sensor 7 Crank angle sensor

Claims (2)

In an O2 sensor diagnostic apparatus having an O2 sensor for detecting oxygen concentration in exhaust gas in the exhaust passage of an engine, and having a control means for controlling the O2 sensor to perform diagnosis, the control means includes O2 after engine start. The sensor abnormality diagnosis time is set at the engine cooling water temperature that is equal to or lower than the predetermined engine cooling water temperature, and the O2 sensor abnormality diagnosis voltage width is set for each engine cooling water temperature that is equal to or lower than the predetermined engine cooling water temperature. Is within the O2 sensor abnormality diagnosis time, the detected O2 sensor output voltage deviates from the O2 sensor abnormality diagnosis voltage width with respect to the design voltage of the O2 sensor, and the engine is idling. This is set as an abnormality determination condition, and this control means starts the fuel feedback control of the engine. In it and the prior activities of the O2 sensor to detect the O2 sensor output voltage, the O2 sensor diagnostic apparatus characterized by having a function of performing diagnosis of the O2 sensor by the abnormality determination condition. The O2 sensors are provided upstream and downstream of the catalyst in the middle of the exhaust passage, respectively, and the upstream O2 sensor and the downstream O2 sensor are set to the O2 sensor abnormality diagnosis time after starting the engine, respectively. 2. The O2 sensor diagnosis apparatus according to claim 1, wherein the O2 sensor abnormality diagnosis time after engine startup is set longer for the same engine coolant temperature than that of the upstream O2 sensor .

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