JPH0473098B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a control device that controls power supplied to a heater provided in an oxygen concentration sensor that detects the oxygen concentration in exhaust gas from an internal combustion engine.

[Prior art] Conventionally, a three-way catalytic converter has been used as an air-fuel ratio control device for vehicle internal combustion engines to reduce CO,
In order to efficiently purify the three components of HC and NOx,
It is known that an exhaust system is equipped with an oxygen concentration sensor to detect the oxygen concentration in the exhaust gas, and the air-fuel ratio of the internal combustion engine is controlled to be the stoichiometric air-fuel ratio, which performs so-called feedback control. In recent years, a zirconia-based limiting current sensor that can obtain a detection current corresponding to the oxygen concentration has been developed as an oxygen concentration sensor used in this type of control device. In addition to controlling the air-fuel ratio near the air-fuel ratio, for example, when the internal combustion engine is operating at low load, the air-fuel ratio is controlled to the lean side to improve fuel efficiency, which is called lean burn control. It has become possible to implement it.

By the way, in order to obtain a detection current corresponding to the oxygen concentration in this type of oxygen concentration sensor, it is necessary to activate the detection element by maintaining the temperature of the detection element at a predetermined temperature, for example, a high temperature of 650°C or higher. In addition to the detection element, the oxygen concentration sensor usually has a built-in heater for heating the detection element. During operation of the internal combustion engine, a predetermined voltage is applied to this heater so that the oxygen concentration sensor can always provide good detection results.

In addition, in order to activate the detection element and obtain good detection results with the oxygen concentration sensor, it is sufficient to heat the detection element to a predetermined temperature or higher using a heater, etc., but if the detection element is heated too much, Problems such as heater disconnection and detection element destruction may occur due to abnormal overheating of the exhaust gas.
If the heater of the oxygen concentration sensor is disconnected, the detection result of the air-fuel ratio sensor becomes unreliable, making it impossible to control the air-fuel ratio properly.
As shown in the publication, when the heater of the oxygen concentration sensor is disconnected, feedback control of the air-fuel ratio is stopped and open-loop control is performed to fix the air-fuel ratio to a preset value. .

However, if the heater breaks, repairs such as sensor replacement are required, and feedback control cannot be performed until repairs are made.
Eliminating disconnection of the oxygen concentration sensor heater was an important issue.

[Object of the Invention] Therefore, the present invention prevents disconnection of the heater of the oxygen concentration sensor or destruction of the detection element due to abnormal overheating of the exhaust gas of an internal combustion engine, etc., and also maintains the detection element at an optimal temperature at all times to activate it. It is an object of the present invention to provide a control device for a heater for an oxygen concentration sensor that can be used to control a heater for an oxygen concentration sensor.

[Configuration of the Invention] As shown in FIG. 1, the configuration of the present invention to achieve the above object controls a heater provided in an oxygen concentration sensor installed in the exhaust system of an internal combustion engine to detect the oxygen concentration in exhaust gas. A control device comprising: a temperature sensor that detects an ambient temperature of the internal combustion engine; an operating state detection means that detects a predetermined operating state of the internal combustion engine; and a control device that controls the heater according to the detected operating state. basic power setting means for setting the basic power to be supplied; target power determining means for correcting the set basic power according to the detected ambient temperature and determining a target power to be supplied to the heater; The present invention provides a control device for a heater for an oxygen concentration sensor, comprising: a control means for controlling the power supplied to the heater according to a set target power.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

First, FIG. 2 is a schematic system diagram showing a vehicle internal combustion engine (hereinafter abbreviated as engine) in which the oxygen concentration sensor heater control device of this embodiment is mounted and its peripheral devices.

In the figure, 1 is an engine, 2 is a piston, 3 is a cylinder, and 4 is a cylinder head.The exhaust port 5 of each cylinder in the cylinder head 4 has an exhaust manifold 6, and the intake port 7 of each cylinder in the cylinder head 4 has an exhaust manifold 6. Intake manifolds 8 are connected to each other. The intake manifold 8 is also provided with a surge tank 9 to prevent pulsation of intake air.
The surge tank 9 is equipped with an intake pressure sensor 10 that detects the pressure inside the intake manifold 8, that is, the intake pipe pressure Pm.

Next, 11 is a throttle valve that controls the amount of intake air sent to each cylinder via the surge tank 9;
12 is an intake air bypass path that bypasses the throttle valve 11; 13 is an intake air temperature sensor that detects the intake air temperature;
Throttle position sensor 14 includes a throttle valve opening sensor that outputs a signal corresponding to the opening of the throttle valve 11 and an idle switch that is turned on when the engine 1 is idling.
are directly connected. Further, 15 is an oxygen concentration sensor attached to the exhaust manifold 6 and includes a detection element for detecting the oxygen concentration in the exhaust gas and a heater for heating, 16 is a water temperature sensor for detecting the cooling water temperature of the engine 1, and 17 is a water temperature sensor for detecting the engine 1. A distributor 20 applies a high voltage output from an igniter 19 to the spark plug 18 of the engine 1 at a predetermined timing; each represents.

Various detection signals from the intake pressure sensor 10, intake temperature sensor 13, throttle position sensor 14, oxygen concentration sensor 15, water temperature sensor 16, and rotational speed sensor 20 are output to the control circuit 25. Based on the detection signal, fuel injection valve 2
Various control processes such as fuel injection control of 6, ignition timing control of the spark plug 18, or heater control of the oxygen concentration sensor 15 are executed.

Next, FIG. 3 shows a block diagram showing the configuration of the above-mentioned control circuit 25. In the figure, 31 is an application power source for applying a predetermined voltage to the detection element 15a of the oxygen concentration sensor 15, 32 is a resistor for detecting the current flowing through the detection element 15a, and 33 is a resistor 32.
34 is an output signal from the amplifier circuit 33, that is, an analog signal corresponding to the oxygen concentration in the exhaust gas;
This is an A/D converter that receives analog signals detected by the intake pressure sensor 10, intake temperature sensor 13, throttle position sensor 14, water temperature sensor 16, etc., and converts them into digital signals. Further, 35 represents a drive circuit which is controlled by a control signal calculated and outputted by the microcomputer 37, and which is driven by the fuel injection valve 26 and injects the desired amount of fuel calculated by the microcomputer 37. This circuit outputs a drive signal to be supplied to the engine 2. Igniter 19 is also microcomputer 3
At 7, the high voltage is controlled to be output to the distributor 17 at a predetermined timing.

Next, 38 is the heater 15b of the oxygen concentration sensor 15.
This is an energization control circuit for controlling the power supplied to the heater, and controls energization from the heater power source 39 in accordance with a control signal from the microcomputer 37. Further, 40 is a heater voltage detection circuit that detects the heater voltage when the heater 15b is energized, and 41 is a heater current detection circuit that similarly detects the heater current.

In the control circuit of this embodiment configured in this way, various controls such as fuel injection amount control, ignition timing control, oxygen concentration sensor heater control, etc. are executed as described above. Next, the heater control of the oxygen concentration sensor, which is the main control process related to the present invention, will be explained in detail according to the control program shown in FIG.

The heater control of the oxygen concentration sensor shown in Fig. 4 is as follows:
It is executed at predetermined time intervals, for example, every 100 [m sec.], and the power supply from the heater power supply 39 to the heater 15b is performed based on the operating state of the engine 1 and the oxygen concentration sensor 15.
This is done by controlling the duty of heater energization according to the detection result.

When the process starts, first in step 101, the engine rotation speed Ne, intake pipe pressure Pm, intake air temperature Ti,
Various parameters such as heater voltage Vh and heater current Ih are read, and the process moves to the following step 102.

In step 102, from the heater voltage Vh and heater current Ih read in step 101, the amount of power when the heater 15b is energized for a predetermined period of time, for example, 100 [m sec.], that is, the duty ratio is 100. % of the electric energy A is executed, and the process moves to step 103. Hereinafter, all electric power amounts are per 100 [m sec.].

Next, in step 103, the above step 101 is performed.
For example, the heater 15 can be determined from a map M1 as shown in FIG.
The basic power amount B of b is determined and the process moves to the following step 104. Here, in the map M1, as is clear from Fig. 5, the basic electric energy B when the intake air temperature Ti is 20°C is set using the engine speed Ne and the intake pipe pressure Pm as parameters. This is because when the intake pipe pressure Pm is large or when the engine speed Ne is large, the amount of fuel injected into the engine 1 naturally increases, the exhaust temperature rises, and the detection element 15a can be heated by the exhaust gas. , the power supplied to the heater 15b is decreased, and on the other hand, when the engine speed Ne is low or the intake pipe pressure Pm is low, the exhaust temperature decreases and the detection element cannot be heated, so the power supplied to the heater 15b is increased. is set to.

Next, in step 104, the above step 101 is performed.
A process is executed to obtain the corrected electric energy b for the basic electric energy B from the map M2 using the intake air temperature Ti obtained in step 105 as a parameter.
to move to.

Then, in step 105, the basic power amount B
Processing is performed to calculate the target amount of power C to actually be supplied to the heater 15b using the following equation C=B+b using the corrected amount of power b as parameters.

Here, the map M2 used in step 104 is as shown in FIG. 6, for example, where Ti >
In the case of 20 [℃], the corrected electric energy b becomes a negative value, and Ti
In the case of <20[° C.], the corrected power amount b is set to be a positive value. This is in contrast to the above explanation where map M1 is set under the condition of Ti = 20 [℃], and the value of map M1 can be used as is when Ti = 20 [℃]. Set the correction power amount b to "0" and Ti>20
In the case of [° C.], if the value of map M1 is used as it is, the oxygen concentration sensor 15 will become too hot, so a negative correction value is set.

When the target power amount C is determined in this way,
In the following step 106, a target power is set for the heater 15b using the following equation D=(C/A)×100, which uses this target power amount C and the power amount A at a duty ratio of 100% obtained in step 102 as parameters. A duty ratio D for supplying the electric energy C is calculated.

Then, in the following step 107, the pulse signal of the duty ratio D obtained above is sent to the energization control circuit 38.
A process for controlling the power supplied to the heater 15b is executed, and the present control process ends.

Here, for example, the amount of electricity A at a duty ratio of 100% is
50 [w・100m sec.], target power amount is 25 [w.100m
sec.], the duty ratio D is 50[%]
Therefore, the pulse signal sent to the energization control circuit 38 is as shown by the solid line in FIG.

As explained above, in the oxygen concentration sensor heater control device of this embodiment, the engine rotational speed is
The target electric energy C is calculated from the basic electric energy B obtained according to Ne and the intake pipe pressure Pm, and the corrected electric energy b obtained according to the intake air temperature Ti, and according to the obtained target electric energy C. According to this control device, the heating of the detection element 15a by the heater 15b is precisely controlled according to the operating state of the engine 1, and the heating of the detection element 15a is controlled precisely according to the operating state of the engine 1. The temperature can always be maintained within a predetermined temperature range, and the engine 1
The detection element can be activated at all times during operation. In addition, the intake air temperature Ti increases,
Even if the temperature of the exhaust becomes high as a result, the target amount of electric power C to be supplied to the heater 15b is reduced according to the intake air temperature Ti, so there is no risk of the heater 15b breaking or the detection element 15a being destroyed. It can be prevented. Furthermore, since more power than necessary is not supplied to the heater 15b, energy can be saved.

Here, in the above embodiment, the intake temperature sensor 13 corresponds to the temperature sensor V described above.
The intake pressure sensor 10 and the rotation speed sensor 20 correspond to the operating state detection means, and the basic power amount B corresponds to the basic power setting means.
The process in step 103 for determining the corrected electric energy b and the process in step 105 for determining the target electric energy C correspond to the target power determining means, and the process in step 105 to determine the target electric energy C corresponds to the heater. Steps to execute energization control
107 processing and energization control circuits 38 are listed.

In the above embodiment, the engine speed Ne and the intake pipe pressure Pm are used to calculate the basic power amount B, but other factors such as the intake air amount and the opening degree of the throttle valve 11 are also used. It is also possible to simply use one of engine speed Ne, intake pipe pressure Pm, etc.

Further, in the above embodiment, the corrected power amount b is determined according to the intake air temperature Ti, but any temperature other than the intake air temperature Ti may be used as long as it corresponds to the ambient temperature of the engine 1, for example, the outside air temperature. But that's fine.

Further, in the above embodiment, the basic power amount B is corrected by (B+b) using the corrected power amount b, but the correction coefficient K is obtained using a map with the intake air temperature Ti as a parameter as shown in FIG. 8, for example. , the basic power amount B may be corrected by (K×B).

Further, in the above embodiment, the power supply control of the heater 15b is performed by duty control based on the power supply time per 100 [m sec.], but in addition to this, for example, the power supplied to the heater 15b is determined, The voltage applied to the heater 15b may be controlled.

[Effects of the Invention] As detailed above, in the oxygen temperature sensor heater control device of the present invention, the basic power is first set according to the operating state of the internal combustion engine, and then this basic power is set depending on the ambient temperature of the internal combustion engine. The target power is determined by correcting the power according to the target power, and the power supplied to the heater is controlled in accordance with the target power. Therefore, the detection element of the oxygen concentration sensor can always be heated above a predetermined temperature, and the temperature can be kept at a temperature that does not cause disconnection of the heater or destruction of the detection element, allowing the oxygen concentration sensor to always provide stable and good detection. You will be able to get results. Furthermore, since disconnection of the heater and destruction of the detection element can be prevented, replacement work in the event of a defective sensor can be reduced, and furthermore, since no more power than necessary is supplied to the heater, energy can be saved.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing the configuration of the present invention, Figure 2 is a block diagram showing the configuration of the present invention.
The figure is a schematic system diagram showing the engine and its peripheral equipment equipped with the oxygen concentration sensor heater control device according to the embodiment of the present invention, FIG. 3 is a block diagram showing the configuration of the control circuit 25, and FIG. 4 is the control circuit. A flowchart showing the heater control process of the oxygen concentration sensor executed in the circuit 25, FIG. 5 is a graph showing the map M1 for determining the basic power amount B, and FIG. 6 is a map for determining the corrected power amount b. 7 is a time chart showing the control signal output to the energization control circuit 38, and FIG. 8 is a graph showing a map for determining the correction coefficient K in place of the correction power amount b. 1...Engine, 6...Exhaust manifold, 1
0...Intake pressure sensor, 13...Intake temperature sensor, 1
5...Oxygen concentration sensor, 20...Rotation speed sensor,
25...Control circuit, 37...Microcomputer, 38...Electrification control circuit.

Claims (1)

[Scope of Claims] 1. A control device for controlling a heater included in an oxygen concentration sensor installed in an exhaust system of an internal combustion engine to detect the oxygen concentration in exhaust gas, the temperature detecting the ambient temperature of the internal combustion engine. a sensor; an operating state detecting means for detecting a predetermined operating state of the internal combustion engine; a basic power setting means for setting a basic power to be supplied to the heater according to the detected operating state; Target power determining means for correcting basic power according to the detected ambient temperature and determining a target power to be supplied to the heater; and control for controlling the power to be supplied to the heater according to the determined target power. 1. A control device for a heater for an oxygen concentration sensor, comprising: means. 2. The control device for an oxygen concentration sensor heater according to claim 1, wherein the temperature sensor is an intake temperature sensor that detects the temperature of intake air of the internal combustion engine.