JPH11218044A - Heating control device of oxygen sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To quickly raise the temperature of an oxygen sensor up to a proper range at the time of starting a cooling machine, suppress the temperature within a proper range during a traveling and stabilize exhaust gas by performing a duty control for a heater according to elapsed time from time when an ignition switch starting energizing to engine load and the heater is turned on. SOLUTION: When an engine is started, a basic duty value O2HSTD is set according to engine load made of intake air amount, fuel injection amount, intake manifold pressure and charging efficiency (Step 212). A correction coefficient CTHA according to an intake air temperature is determined and a duty value = O2HSTD×CTHA is calculated (Step 214) and the duty value of a heater is controlled according to the intake air temperature. Correction time after an ignition switch is turned on is set by the temperature of cooling water (Step 216), a correction (AFT) according to elapsed time after the ignition switch is turned on is enforced; and the duty value = O2HSTD×CTHA×AFT is calculated (Step 218).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating control device for an oxygen sensor, and more particularly, to a heating control device for an oxygen sensor having a heater so as to maintain an active state.

[0002]

2. Description of the Related Art In an engine of a vehicle, an oxygen sensor is provided in an exhaust system in order to detect an oxygen concentration in exhaust gas and perform feedback control of an air-fuel ratio based on the oxygen concentration.
Some oxygen sensors have a built-in heater so as to maintain an active state. The heater is duty-controlled by the control means, and is heated to the maximum when the duty value is 100%, while the energization is stopped when the duty value is 0%.

That is, in controlling the heater of the oxygen sensor, as shown in FIG. 15, the heater is set to a duty value for a set time (t ₁ ) (indicated by S ₂ ) from the start of the engine (indicated by S ₁ ). Control at 100% to accelerate the activity of the oxygen sensor, and after the lapse of the set time (t ₁ ), reduce the duty value to a fixed value (duty value is about 40%) and allow the heater temperature to so as not to 800 ° C. maximum temperature, further, when the engine is in a high rotation (indicated by S _3), the duty value of the heater stops power supply to the heater as 0%, the heater is not heated to a high temperature Like that.

The purpose of duty control of the heater of the oxygen sensor is as follows. First, the temperature of the oxygen sensor is rapidly increased from the time of engine cooling to speed up the feedback control of the air-fuel ratio to reduce the exhaust gas. Secondly, the oxygen sensor and the heater are damaged at high temperatures and their characteristics are deteriorated. Therefore, the oxygen sensor and the heater are prevented from exceeding the allowable upper limit temperature (800 ° C.). Third, the temperature of the heater is stabilized. This is to stabilize the exhaust gas by keeping the output characteristics of the oxygen sensor constant.

As a heating control apparatus for such an oxygen sensor equipped with a heater, for example, Japanese Patent Application Laid-Open No. Hei 8-22691 is disclosed.
No. 2, Japanese Unexamined Patent Publication No. Hei.
No. 202,785 and Japanese Patent Publication No. 7-89105.

Japanese Unexamined Patent Publication No. Hei 8-226912 discloses a method of reducing the power supplied to a heater so that activation of an air-fuel ratio sensor is completed when an air-fuel ratio feedback control start condition is satisfied after the internal combustion engine is started. By controlling, that is, controlling the duty value to the heater by the resistance value of the heater and the water temperature, eliminating unnecessary power consumption by the heater, and suppressing the deterioration of the heater and the air-fuel ratio sensor due to excessive energization of the heater. It is. Japanese Patent Application Laid-Open No. Hei 8-220059 discloses that the heater element is activated early by controlling the heater duty value in accordance with the heater resistance value, the air-fuel ratio feedback control is started early, and the air-fuel ratio feedback control is started. When the operation shifts from the high load operation to the bottom load operation after the completion of the fuel ratio sensor warm-up, the deterioration of the heater and the sensor element is prevented, and the efficiency of power supply to the heater is improved. Japanese Patent Laying-Open No. 5-202785 discloses an engine temperature detecting means for detecting an engine temperature of a surrounding environment of a gas concentration detecting section of a cooling water temperature or an intake air temperature of an internal combustion engine, and an operation of the internal combustion engine before starting. A pre-start state detecting means for detecting a preparatory operation; and, when the pre-start state detecting means detects the operation preparatory operation, when the engine temperature detected by the engine temperature detecting means is high, the gas generated by heating the heater is used. Target temperature setting means for setting the target temperature until the start of the concentration detection unit at a low temperature, while increasing the target temperature when the engine temperature is low, is provided with a target temperature setting means for reducing the power consumption and the idle time when the internal combustion engine is started. This allows the fuel ratio control to be properly performed. In the device described in Japanese Patent Publication No. Hei 7-89105, the power supplied to the heater is usually controlled so that the heater resistance value becomes a predetermined target resistance value. Only during the period, the power supplied to the heater is controlled, so that immediately after the start of the heater energization control, the heater located near the oxygen sensor detection unit due to the difference in heat capacity between the oxygen sensor detection unit and the mounting unit. This is to prevent the temperature of the distal end portion from rising sharply and the detecting portion of the sensor from excessively rising above the target temperature, and to improve the accuracy of detecting the air-fuel ratio by the oxygen sensor.

[0007]

Conventionally, however, in controlling the temperature of the heater of the oxygen sensor, if the vehicle is to be driven at a rapid acceleration and a high speed immediately after the engine is started, as shown in FIG.
As shown in FIG. 5, there was a problem that the temperature of the heater exceeded the allowable upper limit temperature (800 ° C.) within the set time (t ₁ ).

If the set time (t ₁ ) is set to a short value in order to solve this problem, the duty value for the heater becomes smaller than a required value. Has become unstable and the exhaust gas has deteriorated.

Further, when the temperature of the oxygen sensor changes, the characteristics of the oxygen sensor change, and the amount of exhaust gas also increases. Therefore, if the temperature of the heater is not stabilized, there is a disadvantage that stable exhaust gas control cannot be performed. Was.

[0010]

SUMMARY OF THE INVENTION In order to eliminate the above-mentioned disadvantages, the present invention detects an oxygen concentration in the exhaust gas of a vehicle engine and controls the temperature of the oxygen by a heater whose duty is controlled. In an oxygen sensor heating control device provided with a sensor, control means is provided for starting energization of the heater when an ignition switch is turned on, and performing duty control of the heater based on an engine load and an elapsed time from when the ignition switch is turned on. It is characterized by having.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention provides a duty control of a heater from the start of an engine cold start to quickly raise the temperature of an oxygen sensor to an appropriate range to stabilize exhaust gas, The duty of the heater is appropriately controlled in accordance with the operating state of the engine so that the temperature of the oxygen sensor does not increase, and the temperature of the oxygen sensor can be suppressed within an appropriate range to stabilize the exhaust gas.

[0012]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention; 1 to 14 show an embodiment of the present invention. 14, 2 is an engine mounted on the vehicle, 4 is an intake manifold, 6 is an intake passage,
8 is a surge tank, 10 is a throttle body, 12 is a throttle valve, 14 is an intake pipe, 16 is an air cleaner, 18
Is an exhaust manifold, 20 is an exhaust passage, 22 is an exhaust pipe, 2
4 is a catalytic converter.

A bypass air passage 28 that bypasses the throttle valve 12 communicates with the intake passage 6 so as to constitute an idle speed control system (ISC system) 26 that controls the intake air flow during idling operation of the engine 2. Is provided. An idle air adjusting screw 30 is provided in the bypass air passage 28. Further, the idle air adjusting screw 3 is provided in the bypass air passage 28.
An idle air passage 32 is provided so as to communicate with it so as to bypass 0. The idle air passage 32 is provided with an electromagnetically operated idle control valve (ISC valve) 34.

A pressure introducing passage 36 communicates with the surge tank 8. A pressure sensor 38 is provided in the pressure introduction passage 36.

A fuel injection valve 40 is mounted on the engine 2.

The fuel injection valve 40 constitutes a fuel supply system 42, and is connected to a fuel tank 46 through a fuel supply passage 44. This fuel supply passage 44
Is provided with a fuel filter 48. Further, a fuel return passage 50 is connected to the fuel supply passage 44. The fuel return passage 50 is provided with a fuel pressure regulator 52. This fuel pressure regulator 52
Is connected to a regulator pressure passage 54 for introducing the intake pipe pressure from the surge tank 8. A fuel pump 56 is connected to the fuel tank 46 by the fuel supply passage 44.
And a fuel level sensor 58 are provided.

The engine 2 is provided with a PCV valve 60. A blow-by gas passage 62 communicating with the surge tank 8 is connected to the PCV valve 60.

Between the engine 2 and the fuel tank 46, first and second evaporation systems 64 and 66 are provided as an evaporation system for controlling the amount of fuel vapor (purge amount) to the intake system according to the operating state of the engine 2. Is provided.

In the first evaporation system 64, a first canister 72 is provided between a first evaporation passage 68 communicating with the fuel tank 46 and a first purge passage 70 communicating with the surge tank 8. The first evaporative passage 68
A tank pressure control valve 74 is provided, and a first purge valve 76 that is electromagnetically operated is provided in the first purge passage 70.

In the second evaporation system 66, a second canister 82 is provided between a second evaporation passage 78 communicating with the fuel tank 46 and a second purge passage 80 communicating with the first purge passage 70. The second evaporating passage 78 is provided with a second tank internal pressure control valve 84, and the second tank internal pressure control valve 84 is provided with an operating pressure passage 86 communicating with the pressure introduction passage 36, and the operating pressure passage 86 is provided with a solenoid vacuum valve 88 are provided. The second purge passage 80 is provided with a second purge valve 90 that operates electromagnetically. Further, in the second purge passage 80 between the second canister 82 and the second purge valve 90, a diagnostic communication passage 92 communicating with the intake passage 6 on the upstream side of the throttle valve 12 is provided. An evaporative diagnosis valve 94 is provided in the diagnosis communication passage 92. The second canister 82 is provided with a canister air valve 96. In the second evaporation system 66, the fuel tank 46
Is provided with a tank internal pressure sensor 98.

Between the surge tank 8 and the exhaust passage 20, there is provided an EGR passage 102 of the EGR system 100 that recirculates a part of the exhaust gas of the engine 2 to the intake system. This E
An EGR control valve 104 is provided in the GR passage 102.

The pressure sensor 38, the fuel pump 56, the fuel level sensor 58, the first purge valve 76, the solenoid vacuum valve 88, the second purge valve 90, and the canister air valve 96
The tank internal pressure sensor 98 and the EGR control valve 104 are in communication with a control means (ECM) 106.

The control means 106 includes a timer 1
06a, an intake air temperature sensor 108 provided on the air cleaner 16, an intake air amount sensor 110 provided on the intake pipe 14, a throttle sensor 112 provided on the throttle body 10, and a coolant temperature sensor provided on the engine 2. 1
14, a front oxygen sensor 116 with a heater provided in the exhaust manifold 18, and a rear oxygen sensor 118 with a heater provided in the exhaust pipe 22 downstream of the catalytic converter 24.
, A crank angle sensor 120, a range position switch 122 for an automatic transmission, an air conditioner system 124, a vehicle speed sensor 126, a power steering pressure switch 128, a diagnostic switch terminal 130, and a test switch terminal 132.
, Ignition switch 134, shift switch 1
36, starter switch 138 and main fuse 1
40 and the battery 142 are in communication. Further, an ignition coil 148 of an ignition timing control system 146 attached to an ignition plug 144 provided in the engine 2 is connected to the control means 106.

Front and rear oxygen sensors 116, 118
The built-in duty control (0 to 10) detects the oxygen concentration in the exhaust gas and maintains the active state.
0%) is controlled by a heater (not shown).

The control means 106 inputs various signals, starts energization of the heater when the ignition switch 134 is turned on, and controls the engine load (see FIGS. 3 and 4) and the elapsed time from when the ignition switch 134 is turned on (FIG. 7). ) To control the duty of the heater.

The control means 106 starts energizing the heater when the ignition switch 134 is turned on, and maps the engine speed and the engine load (FIG. 3, FIG. 3).
4) and duty control of the heater based on the elapsed time from when the ignition switch 134 is turned on.

Further, the control means 106 sets a correction time after the ignition switch 134 is turned on based on the cooling water temperature when the ignition switch 134 is turned on (see FIG. 6).
The duty of the heater is controlled in accordance with the correction time.

Further, as shown in FIG. 5, the control means 106 sets a correction coefficient according to the intake air temperature, and performs duty control of the heater according to the correction coefficient (see FIG. 5).

The control means 106 stops power supply to the heater when the engine 2 does not start even after the set time (t ₁ ) has elapsed after the ignition switch 134 is turned on.

Next, the operation of this embodiment will be described with reference to the flowchart of FIG. 1 and the time chart of FIG.

When the program starts in the control means 106 (step 202), it is first determined whether or not the ignition switch 134 is turned on (step 20).
4).

If this step 204 is NO, this determination is continued.

If step 204 is YES, the timer 106a and the heater are started (step 20).
6) Then, it is determined whether or not the engine 2 has started (step 208).

As described above, by starting the timer 106a and the heater by turning on the ignition switch 134, the temperature of the heater can be increased quickly, and the exhaust gas can be stabilized more quickly.
The temperature of the front and rear oxygen sensors 116 and 118 can be prevented from deteriorating.

If step 208 is NO, if the engine 2 is not started within the set time (t ₁ ) from the time when the ignition switch 134 is turned on, the power supply to the heater is stopped (cut) (step 210). Return to step 204. This prevents wasteful use of the voltage of the battery 142, prevents unnecessary heating of the heater, and protects the battery 142 and the heater.

If step 208 is YES, a basic duty value (O2HSTD) corresponding to the engine load is set as shown in FIGS.
2). The above-described engine load includes an intake air amount, a fuel injection amount, an intake pressure, a charging efficiency, and the like. In other words, as shown in FIGS. 8 and 12, even when the engine speed is constant, the temperature of the exhaust gas varies depending on the engine load, and thus the temperatures of the front and rear oxygen sensors 116 and 118 also differ. In the case where a map of the engine speed and the engine load (see FIGS. 3 and 4) or an engine load table is set, the control is performed based on the intake air amount, the charging efficiency, and the fuel injection amount.

Then, as shown in FIG. 5, a correction coefficient (CTHA) based on the intake air temperature is obtained, and a duty value (O2HD
TY) is calculated by O2HDTY = O2HSTD × CTHA (step 214). That is, the temperature of the exhaust gas varies depending on the intake air temperature, and the front and rear oxygen sensors 11
Since the temperatures 6 and 118 also change, the duty value of the heater is controlled according to the intake air temperature.

Further, as shown in FIG. 6, the correction time (AFT1, AFT2) after the ignition switch 134 is turned on.
Is set as the cooling water temperature (step 216).

Then, as shown in FIG. 7, a correction (AFT) based on the elapsed time after the ignition switch 134 is turned on.
, That is, O2HDTY = O2HSTD × CTH
A × AFT is calculated (step 218), and the program ends (step 220).

As shown in FIG. 13, the temperature rise of the front and rear oxygen sensors 116 and 118 varies depending on the duty value of the heater, and also varies depending on the engine speed and the engine load. 6 and 7, the duty value is controlled in accordance with the water temperature at that time, thereby increasing the amount of power supply and increasing the power supply time in the cooler. On the contrary, it is possible to control the temperature of the front and rear oxygen sensors 116 and 118 so as not to exceed the allowable upper limit temperature by reducing the amount of power supply and shortening the power supply time in the fully warm-up machine. .

Therefore, after the engine 2 is started, the temperature of the front and rear oxygen sensors 116 and 118 is increased as shown in FIGS.
As shown by 0, the appropriate range (RITemp) can be quickly achieved, and thereafter, the duty value can be controlled according to the engine load state, and the temperature can be maintained in the appropriate range.

As a result, the heater is turned on when the ignition switch 134 is turned on, so that the temperature of the front and rear oxygen sensors 116 and 118 rises quickly, and the exhaust gas can be stabilized.

Further, since the heater is controlled by the engine load, the temperatures of the front and rear oxygen sensors 116 and 118 can be accurately controlled to a target appropriate temperature (RITemp).

Further, by controlling the power supply time to the heater by the water temperature, the front and rear oxygen sensors 11
6, 118 can be quickly raised and controlled so as not to exceed the allowable temperature.

Further, although the temperature of the exhaust gas changes depending on the intake air temperature, the correction coefficient is calculated in accordance with the intake air temperature, so that the temperatures of the front and rear oxygen sensors 116 and 118 can be accurately controlled to an allowable range. .

Further, since the amount of current supplied to the heater is increased for a certain period of time after the start of the engine 2, the temperature of the front and rear oxygen sensors 116 and 118 can be increased quickly.

Further, if the engine 2 does not start after the ignition switch 134 is turned on, the energization of the heater is stopped, so that the battery 142 is prevented from rising and the battery 142 is protected. It is possible to prevent the durability of 116 and 118 from decreasing.

That is, by appropriately controlling the temperatures of the front and rear oxygen sensors 116 and 118 from the start of the cold operation of the engine 2, the front and rear oxygen sensors 116 and 118 are controlled.
The temperature of the exhaust gas 18 can be quickly raised to an appropriate range to stabilize the exhaust gas (see FIG. 11).

Also, while the vehicle is running, the duty of the heater is appropriately controlled in accordance with the operation state, and the front and rear oxygen sensors 116 and 118 are protected from high temperatures, and the temperatures are kept within an appropriate range. By controlling, the exhaust gas can be stabilized.

[0050]

As is apparent from the above detailed description, according to the present invention, the heater is energized by turning on the ignition switch, and the duty of the heater is controlled by the engine load and the elapsed time from when the ignition switch is turned on. Control means to appropriately control the duty of the heater from the time of cold start of the engine to quickly raise the temperature of the oxygen sensor to an appropriate range to stabilize the exhaust gas. The duty of the heater is appropriately controlled in accordance with the operation state of the above to prevent the temperature of the oxygen sensor from rising, and the temperature of the oxygen sensor can be suppressed within an appropriate range to stabilize the exhaust gas.

[Brief description of the drawings]

FIG. 1 is a flowchart of heating control of a heater.

FIG. 2 is a time chart of heating control of a heater.

FIG. 3 is a diagram for setting a duty value according to an engine load.

FIG. 4 is a diagram for setting a duty value according to an engine speed and an engine load.

FIG. 5 is a diagram for setting a correction coefficient according to an intake air temperature.

FIG. 6 is a diagram for setting a correction time according to a water temperature.

FIG. 7 is a diagram for setting a correction coefficient according to an elapsed time after turning on an ignition switch.

FIG. 8 is a diagram showing a relationship between an engine speed and a heater temperature.

FIG. 9 is a diagram showing the relationship between the temperature of the oxygen sensor and the allowable temperature.

FIG. 10 is a diagram showing a relationship between an output voltage of an oxygen sensor and an air-fuel ratio.

FIG. 11 is a diagram showing a relationship between a change in an air-fuel ratio and an exhaust gas amount.

FIG. 12 is a diagram illustrating a relationship between an engine speed and a duty value.

FIG. 13 is a diagram showing a relationship between the temperature of the oxygen sensor and time.

FIG. 14 is a system configuration diagram of a heating control device.

FIG. 15 is a time chart of a conventional heating control.

[Explanation of symbols]

 2 Engine 106 Control means 116 Front oxygen sensor 118 Rear oxygen sensor 134 Ignition switch

Claims (5)

[Claims] 1. An oxygen sensor heating control device provided with an oxygen sensor whose temperature state is controlled by a heater whose duty is controlled while detecting an oxygen concentration in exhaust gas of an engine of a vehicle, wherein the heater is turned on when an ignition switch is turned on. A heating control device for an oxygenase sensor, further comprising a control unit that starts energization of the heater and controls duty of the heater based on an engine load and an elapsed time from when the ignition switch is turned on. 2. A heating control apparatus for an oxygen sensor, comprising: an oxygen sensor for detecting an oxygen concentration in exhaust gas of an engine of a vehicle and controlling a temperature state by a heater which is duty-controlled. And heating means for controlling the duty of the heater according to the map of the engine speed and the engine load and the elapsed time from the time when the ignition switch is turned on. . 3. The control means sets a correction time after the ignition switch is turned on based on a cooling water temperature when the ignition switch is turned on, and performs duty control of the heater in accordance with the correction time. The heating control device for an oxygen sensor according to claim 1 or 2, wherein 4. The control unit according to claim 1, wherein a correction coefficient is set according to an intake air temperature, and duty control of the heater is performed according to the correction coefficient.
3. The heating control device for an oxygen sensor according to claim 1. 5. The control device according to claim 1, wherein the control unit stops energizing the heater when the engine does not start even after a set time has elapsed after the ignition switch is turned on. Item 3. A heating control device for an oxygen sensor according to Item 2.