JPH0544985B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a means for detecting and controlling the concentration of oxygen contained in exhaust gas for feedback control of an internal combustion engine. The present invention relates to an oxygen concentration detection control device that controls heating power to a heater that heats and sets a concentration detection sensor.

[Background technology] For example, in the case of an internal combustion engine installed in a vehicle, in order to purify and control the exhaust gas, the concentration of oxygen contained in the exhaust gas is detected and the stoichiometric air-fuel ratio is determined based on the detected information. It is known to perform feedback control of the air-fuel ratio by calculating, for example, controlling the fuel injection amount.

That is, in such a control device for an internal combustion engine, an oxygen concentration detection device is installed in the exhaust gas passage of the engine in order to detect the oxygen concentration in the exhaust gas. As an oxygen concentration sensor constituting such a detection device, a zirconia-based limiting current type sensor is known, as disclosed in, for example, Japanese Patent Laid-Open No. 57-48648.

In the case of such an oxygen concentration sensor, since a detection current corresponding to the oxygen concentration can be obtained, for example, the air-fuel ratio is controlled to the lean side when the engine is operating at low load to improve fuel efficiency. This makes it possible to perform air-fuel ratio control in a more precise manner. However, in order to perform such precise air-fuel ratio control, it is necessary to set the oxygen concentration sensor to an activated state, and for this purpose, the sensor is heated and controlled using a heater. There is.

In order to activate such an oxygen concentration sensor, it is sufficient to heat the sensor to a predetermined temperature or higher, but if the heating temperature rises too much, the heater will break, In addition, there is a risk that a failure may occur that destroys the sensor, and the sensor temperature must be set within a specified temperature range, e.g.
It is being considered to carry out control to set the temperature between 650°C and 750°C. For example, as shown in Japanese Utility Model Application Publication No. 58-112958, power supply to the heater is controlled to be cut off when the internal combustion engine has a high output or when the exhaust gas is in a high temperature state. This prevents the heater and sensor from becoming too high, thereby preventing disconnection of the heater and destruction of the sensor due to a rise in exhaust gas temperature.

However, no particular countermeasures have been taken for cases where the exhaust gas temperature drops and the sensor temperature also drops when the engine enters a fuel cut operation state, for example. In this case, the oxygen concentration sensor may not be activated, and a good detection signal cannot be obtained. Normally, during the fuel cast operation state as described above, feedback control is not being executed, and the rise of the oxygen concentration detection signal does not pose much of a problem. However, when feedback control is restarted, the oxygen If the temperature of the concentration sensor is low, air-fuel ratio control cannot be restarted in a good condition.

[Problems to be Solved by the Invention] This invention has been made in view of the above points, and even when the internal combustion engine enters a fuel cut operation state, the temperature of the oxygen concentration sensor remains unchanged. An object of the present invention is to provide an oxygen concentration detection control device that allows a sensor to be set to an activated state so that a good oxygen concentration detection signal can always be obtained. be.

[Means for Solving the Problems] That is, in the oxygen concentration detection control device according to the present invention, an oxygen concentration sensor is installed in the exhaust system of an internal combustion engine, and this sensor has a heating The heater is set for
The heating power for this heater is controlled by a control means, and this control means V is set to be supplied with a detection signal from a detection means for detecting the fuel cut operation state of the internal combustion engine, and a signal from this detection means. It is controlled by instructions from the calculation means.

In this case, when the fuel cut operation state is detected by the detection means, the heating power corresponding to the amount of air flowing around the sensor is set to be supplied to the heater, and the fuel cut operation state is set. When the internal combustion engine is not in this state, the heating power is set and controlled in accordance with the operating state of the internal combustion engine.

[Operation] In other words, in the device configured as described above, first, based on the operating state of the internal combustion engine, it is determined by the detection means whether or not it is in the fuel cut operating state. In this case, a command is given to the control means V to control and set the heating power to the heater, for example, based on information corresponding to the rotation speed of the internal combustion engine. Then, the temperature of the oxygen concentration sensor during the fuel cut operation is set to the activated state. Further, when the internal combustion engine is not in the fuel cut operation state, the calculation means generates a control command to the control means based on the detection signal of the engine operation state, and sets and controls the heating power of the heater.

Therefore, in the fuel cut operation state,
The oxygen concentration sensor is heated and controlled by a heater, and the activation state of this sensor is controlled to be maintained reliably. In the normal fuel supply control state, the oxygen concentration sensor is heated and set to a predetermined temperature state, and air-fuel ratio feedback control is effectively executed.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 shows its configuration, and shows the internal combustion engine 11 equipped with an oxygen concentration detection device and in which feedback control is executed, and its surroundings.

That is, this internal combustion engine 11 is provided with an intake pipe 12 that takes in air from an air cleaner portion (not shown).
2, a throttle valve 13 whose drive is controlled by an accelerator pedal or the like, and a surge tank 14 are installed.
A bypass passage 15 is formed in which the air flow rate is controlled and set in a state where three portions are bypassed. Here, an intake temperature sensor 16 for detecting the temperature state of intake air is attached to the intake pipe 12, and an intake pressure sensor 17 is attached to the surge tank 14. A throttle position sensor generates a signal corresponding to the opening degree of the throttle valve 13, and also generates an idle switch signal that is activated when the throttle valve 13 is set to an idle operating state. 18 will be provided.

An oxygen concentration detection device 20 is installed and set to the exhaust pipe 19 of the internal combustion engine 11,
The oxygen concentration sensor portion of the detection device 20 is set inside the exhaust pipe 19 and is set in contact with the exhaust gas flowing through the exhaust pipe 19.

In the head portion of the internal combustion engine 11,
A spark plug 21 is installed and set in a state corresponding to each cylinder, and a water temperature sensor 22 is set to detect the cooling water temperature of the engine 11.

The operating state of the internal combustion engine 11 is detected by detection signals from the intake temperature sensor 16, intake pressure sensor 17, throttle position sensor 18, water temperature sensor 22, and oxygen concentration detection device 20. Yes, these detection signals are sent to the control circuit 23.
The supply is set for. This control circuit 23 is further required to receive information corresponding to the rotational speed of the internal combustion engine 11, and this information is detected from a rotational speed sensor 25 set for the distributor 24. It is. For this distributor 24, the control circuit 23
An ignition signal from an igniter 26 controlled by a command from the igniter 26 is set to be supplied.

That is, the control circuit 23 calculates the fuel injection amount, ignition timing, etc. in accordance with the operating state of the internal combustion engine 11, and the control circuit 23 calculates the fuel injection amount, ignition timing, etc.
The ignition control for the spark plug 21 is performed by controlling the igniter 26 and the igniter 26.

FIG. 3 shows a specific configuration of the control circuit 23, in which the oxygen concentration sensor 20 includes a detection element 20a whose current amount is set according to the state of the oxygen concentration contained in the exhaust gas, and A power source 31 is set for the detection element 20a. The current value flowing through the detection element 20a is converted into a voltage value by the circuit of the resistor 32, appropriately amplified by the amplifier 33, and converted into digital data by the A/D converter 34, which is used as one of the input detection signals. It is something to do.

Detection signals from an intake temperature sensor 16, an intake pressure sensor 17, a throttle position sensor 18, a water temperature sensor 22, and a rotational speed sensor 25 are also coupled to the A/D converter 34. In this case, the A/D converter 34 is configured to include a multiplexer function, and the detection signals from each sensor are sequentially converted into digital data and supplied to the microcomputer 35 as input data. become. This microcomputer 35 calculates, for example, the fuel injection amount, ignition timing, etc. based on the input data from each of the above-mentioned sensors, and controls the drive circuit 36 based on the calculation results corresponding to the above-mentioned fuel injection amount, thereby controlling the injection valve. 27
The valve opening time, that is, the fuel injection amount is set and controlled. Further, the calculated ignition timing signal is supplied to the igniter 26 to control the distributor 24 and the spark plug 21.

The heater 20b of the oxygen concentration sensor 20 is connected to the power supply 3 by an energization control circuit 37 controlled by a command from the microcomputer 35.
The heating power supplied to the heater 20b is detected by the heater voltage detection circuit 39 and the heater current detection circuit 40, and this detection output is set to be supplied to the microcomputer 35. Ru. And heater 2
The temperature of 0b is set to the set temperature state.

In the case of the control circuit 23 configured in this way, in addition to the calculation control of the fuel injection amount, ignition timing, etc., as described above, the heater 20 of the oxygen concentration sensor 20
b, but also performs heating power control for the heater 20b corresponding to the operating state of the internal combustion engine. FIG. 4 shows the state of the control flow.

This control routine is executed at predetermined time intervals, for example, 100 m.
This is executed every S, and the power supply from the power source 38 to the heater 20b is controlled by, for example, a duty ratio corresponding to the operating state of the internal combustion engine 11.

When the process for this purpose is started, first, in step 101, various parameters related to the operating state of the internal combustion engine 11, that is, the rotation speed, are
Ne, intake pressure Pm, detection current of oxygen concentration sensor 20
Is, idle switch signal Id indicating the idling state of the engine 11, voltage Vh of heater 20b, heater 2
Read the current Ih etc. flowing through 0b.

When various parameters are read and set in this way, in the next step 102, from the heater voltage Vh and heater current Ih read above,
The amount of power when the heater 20b is energized for a predetermined period of time, for example, 100 mS, that is, the amount of power A at a duty ratio of 100% is calculated. After the process of calculating the electric energy A is executed in this way, the process proceeds to the next step 103, where it is determined whether the internal combustion engine 11 is in fuel cut operation. Here, all the above-mentioned electric power values are expressed in terms of electric power per 100 mS.

If it is determined in step 103 that the fuel cut operation is in progress, the process proceeds to step 104, and if it is determined that the fuel cut operation is not in progress, the process proceeds to step 105.

Here, the internal combustion engine 1 in step 103 above
1, whether or not fuel cut operation is in progress can be performed, for example, by looking at fuel injection amount data in fuel injection amount calculation control in another control routine not shown in the figure. Idle switch signal read in step 101 above
The determination may be made based on Id and the rotational speed Ne of the engine 11. That is, when the idle switch signal Id is on and the fuel cut condition in which the winning rotational speed Ne is equal to or higher than a predetermined rotational speed is satisfied, it is determined that the internal combustion engine 11 is in a fuel cut operation.

If it is determined in step 103 that the fuel cut operation is not in progress, then in step 105 the target power amount C of the heater 20b is determined based on the rotational speed Ne and the intake pressure Pm. Specifically, a map as shown in FIG. 5 is stored in a storage device set corresponding to the microcomputer 35, and the electric energy C is calculated from this map M1 in accordance with the parameters Ne and Pm. The electric power amount C is calculated by reading or using a predetermined calculation formula.

In the map M1 shown in FIG. 5, the target power amount C is set in advance using the rotational speed Ne of the internal combustion engine 11 and the intake pressure Pms as parameters.
Here, if the intake pressure Pm is large, or the rotation speed
When Ne is large, the amount of fuel injected into the engine 11 increases, the exhaust temperature rises and heats the oxygen concentration sensor 20, so the detection element 20a is heated by this exhaust temperature. The power supplied to the heater 20b can be reduced. In addition, in a state opposite to the above case, the power supplied to the heater 20b is set to be large, and the map M1 has a target power amount C set corresponding to the rotation speed Ne and the intake pressure Pm. It's becoming like that.

Once the target power amount C is calculated in step 105, the process proceeds to the next step 106. This step 106
calculates the duty ratio D for supplying the target power amount C to the heater 20b using the power amount C and the power amount A at the duty ratio of 100% obtained in step 102 as parameters. This duty ratio D is calculated by the following formula.

D=(C/A)×100 Then, in the next step 107, the pulse-like signal with the duty ratio D obtained above is applied to the energization control circuit 3.
7 and executes processing for controlling the power supplied to the heater 20b.

In such a control state, for example, the duty ratio
If the 100% power amount A is 50W/100mS, and the target power amount C obtained from the map M1 from the rotation speed Ne of the engine 11 and the intake pressure Pm is 25W/100mS, the duty ratio D is 50%, and the energization The pulsed control signal supplied to the control circuit 37 is as shown by the solid line in FIG.

If it is determined in step 103 that the internal combustion engine 11 is in fuel cut operation, the process proceeds to step 104 as described above. This step 104 is the seventh
Based on the map M2 shown in the figure, the rotation speed Ne at this time
Find the target power amount C for. During this fuel cut operation, there is no combustion state of fuel in the engine 11, and the temperature of the exhaust gas is in a state of decreasing. The degree of this exhaust gas temperature drop corresponds to the flow velocity of the exhaust gas (air in the fuel cut state), which changes depending on the rotation speed of the engine 11, and is influenced by the rotation speed Ne of the engine 11. state. Therefore, as shown in FIG. 7, the target electric power amount C during the fuel cut is determined by representing the gas flow rate by the rotational speed, and the higher the rotational speed Ne of the engine 11, the larger the target electric power amount C becomes.
The process then proceeds from step 104 to step 106, where the power supplied to the heater 20b is controlled in accordance with the calculated target power amount C.

That is, for example, the fuel cut operation state is set in a state where the throttle valve is closed and the rotational speed Ne is large, for example, in a deceleration operation state, but even during such a fuel cut operation, the oxygen concentration sensor 20 is Electric power for heating control is set to be supplied to the heater 20b in response to the temperature drop caused by the exhaust gas. Therefore, the temperature of the detection element 20a is set and controlled so that the detection element 20 is maintained in an activated state even in such a fuel cut operation state. Even when the system returns to the feedback control state, the operation for detecting the oxygen concentration in the exhaust gas continues to perform well, and precise air-fuel ratio control is executed in response to the operating conditions. It is something.

In the above embodiment, the power control means using the duty ratio is shown as the power control means for the heater 20b, but this may be done by controlling the voltage applied from the heater power source, for example. It is something.

In addition, the target power amount in the fuel cut state is
In the case where the basic injection amount of fuel is determined in accordance with the amount of intake air, the target power amount C during fuel cut operation may be determined in accordance with this amount of intake air. good. Furthermore, the target power amount may be determined based on vehicle speed or the like.

[Effects of the Invention] As described above, according to the oxygen concentration detection control device according to the present invention, the detection element of the oxygen concentration sensor constituting the detection device is adjusted according to the operating state of the internal combustion engine for which this detection device is set. The temperature of the sensor is set and controlled to a state that activates this detection element, and especially when the internal combustion engine is in a fuel cut operation state, the temperature of the detection element is set and controlled in response to the air flow velocity state around the sensor. The heating of the element becomes controlled. Therefore, during the fuel cut operation, the temperature of the detection element is set and controlled so as to reliably maintain the activated state, and even when the fuel cut state shifts to the feedback control state, The oxygen concentration in exhaust gas can be accurately measured and detected, and air-fuel ratio control of an internal combustion engine can be stably executed.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram illustrating an oxygen concentration detection control device according to the present invention, and FIG. 2 shows a control mechanism portion of an internal combustion engine illustrating the oxygen concentration detection device according to an embodiment of the present invention. 3 is a block diagram explaining the control circuit shown in FIG. 2, FIG. 4 is a flowchart explaining the operation of the control circuit portion, and FIG. 5 is used in the control flow described above. FIG. 6 is a diagram showing the state of the control pulse obtained in the above control, and FIG. 7 is a diagram showing the second map used in the above control. 11...Internal combustion engine, 12...Intake pipe, 13...
Throttle valve, 16... Intake temperature sensor, 17...
Intake pressure sensor, 18...Throttle position sensor, 19...Exhaust pipe, 20...Oxygen concentration sensor, 20a...Detection element, 20b...Heater, 2
1...Spark plug, 22...Water temperature sensor, 23...
...control circuit, 24...distributor, 25
...Rotational speed sensor, 27...Fuel injection valve, 35...
...Microcomputer, 37...Electrification control circuit.

Claims (1)

[Scope of Claims] 1. Heater control means for controlling supply heating power to a heater for heating and controlling an oxygen concentration sensor set in an exhaust passage of an internal combustion engine, and a fuel cut operation by detecting the operating state of the internal combustion engine. means for determining whether or not the internal combustion engine is in the operating state; and a first heater power for calculating the heating power of the heater corresponding to the operating state of the internal combustion engine when the determining means determines that the fuel cut operation is not in progress. a calculating means, a detecting means for detecting information corresponding to air circulation around the oxygen concentration sensor in a state where the determining means determines that the fuel cut operation is in progress, and a detecting means corresponding to the information detected by the detecting means. a second heater power calculation means for calculating heating power of the heater, and the first and second heater power calculation means control the heater control means to set the heating power for the heater. An oxygen concentration detection control device characterized by: 2. The oxygen concentration detection control device according to claim 1, wherein the detection means comprises means for detecting information corresponding to the rotational speed of the internal combustion engine. 3. The oxygen concentration detection control device according to claim 1, wherein the detection means is constituted by means for detecting information corresponding to the intake air amount for the internal combustion engine.