JPS60125553A - Temperature controller of oxygen sensor - Google Patents

Abstract

PURPOSE:To control the temperature of an oxygen sensor by calculating a calorific value of the oxygen sensor on a basis of operation state detection data of an internal combustion engine. CONSTITUTION:Various parameters such as the intake of air, the injection quantity, the temperature of cooling water, the rotation number of the engine, etc. which indicate the operation state of the internal combustion engine are read into a microcomputer 37. A power supply control circuit 53 consisting of a thyristor or a transistor is controlled on a basis of this operation state to supply a current to a heater part 52. The control output at this time is performed by a pulse signal of a duty D, and the quantity of power supply of the heater part 52 is controlled by the proportion of the duty D. The amount of heat flowed from an oxygen concentration detecting part 51 is proportional to the square of the difference between the temperature of discharged air and a prescribed temperature of activation of the detecting part 51 and a gas flow rate. Then, the same amount of heat as the amount of heat flowed out from the detecting part 51 is supplied to hold the detecting part 51 at a prescribed temperature, and it is possible that the detecting part 51 has not a temperature lower than the temperature of activation. The duty D is operated by the compute 37, and the circuit 53 is controlled by the proportion of the duty D, thereby holding the detecting part 51 at this temperature.

Description

[Detailed Description of the Invention] [Industrial Application Field J] The present invention is directed to the temperature IIJ Ij ik M of an oxygen sensor.
In particular, the present invention relates to an 81 degree control device that maintains the activation temperature of an oxygen sensor that detects the oxygen concentration in the exhaust gas of internal combustion engine 1IIrlJ.

[Prior art J] Among these, a limiting current type oxygen concentration detector using a solid electrolyte such as zirconia is particularly attracting attention as a sensor for precise combustion control in internal combustion engines due to its linear output characteristics.

Incidentally, it is important that the oxygen concentration be detected by the oxygen 1 degree detector in a region where the detector output is stable and at a substantially constant temperature. For example, in internal combustion engines for automobiles, the exhaust temperature of the internal combustion engine is controlled, or when the exhaust temperature is low, the oxygen concentration detector is activated by a heater (Japanese Patent Laid-Open No. 57-48648), and the heater also serves as a concentration sensor. The device was installed in an oxygen concentration detector, and the amount of heat generated by the heater was controlled so that the temperature remained almost constant (Japanese Patent Laid-Open No. 192852/1983).

However, among the above-mentioned conventional techniques, the method of controlling the exhaust gas temperature greatly restricts the operation of the internal combustion engine, and the method of simply heating the heater when the exhaust temperature is low is useful for quickly bringing the temperature of the oxygen concentration detector to a normal level. is difficult to maintain at a constant temperature. Furthermore, if the oxygen concentration detector is equipped with a temperature detection device, the structure of the sensor itself will be complicated, making it difficult to mass produce and increasing the possibility of failure. However, there was also a situation where the oxygen concentration detection part was still at a low temperature, which could cause problems in precise internal combustion engine control.

[Object of the Invention] An object of the present invention is to provide a temperature control device for an oxygen sensor that accurately controls the temperature of the oxygen concentration detection section of the oxygen sensor without complicating the structure of the oxygen concentration detector.

[Structure of the Invention] The gist of the present invention is as shown in the basic configuration diagram of FIG. Based on the operating state of the internal combustion engine M1 detected by the heat generating means M4 that heats the sensor M3 and the operating state detecting means M2, the calorific value of the heat generating means M4 becomes the temperature that the oxygen sensor M3 targets. A concentration control device for an oxygen sensor is provided, comprising: a calorific value control means M5 that adjusts the amount of heat so as to adjust the concentration of the oxygen sensor.

Next, embodiments of the present invention will be described with reference to the drawings.

[Embodiment] FIG. 2 shows an electronic fuel injection system for an automobile engine and an air-fuel ratio control device incorporated therein. That is, 1
is a cylinder of the engine 2, 3 is an exhaust manifold connected to the exhaust boat 5 of each cylinder of the cylinder head 4, 6 is an intake manifold connected to the intake boat 7 of the cylinder head 4, and the intake manifold 6 has a surge tank. 8 are connected. An air 70 meter 9 that detects the amount of intake air from an air cleaner (not shown) is connected to the surge tank 8, and 1f of intake air is connected near the air 70 meter 9.
An intake air temperature sensor 10 is installed to detect m[. 1
1 is an intake air bypass passage that bypasses the throttle valve 12 that controls the amount of intake air sent to each cylinder via the surge tank 8; 13 is a fuel injection provided near the tip of the intake manifold 6 on the side of the intake boat 7; The fuel injection valve 14 is a throttle opening sensor that detects the opening of the throttle valve 12, and the former fuel injection valve 13
is driven and controlled by the control circuit 15, and the latter throttle sensor 14 sends a signal corresponding to the throttle opening to the control circuit 1.
It is connected to output to 5. Reference numeral 16 denotes an air-fuel ratio sensor 1 which is attached to the exhaust manifold 3 and includes an oxygen S degree detection section as an oxygen sensor for detecting the oxygen concentration in the exhaust gas and a part of a heater as a heat generating means for heating the detection section.
7 is a water temperature sensor that detects the cooling water temperature of the engine 2; 18;
20 is a distributor that applies a high voltage output from the igniter 19 to each spark plug 18a of the engine 2 at a predetermined timing, and 20 is a rotation speed sensor that is attached to the distributor 18 and generates a pulse signal corresponding to the rotation speed of the engine 2. , the air-fuel ratio sensor 16 , the water temperature sensor 17 , and the rotational speed sensor 20 . Each detection signal is output to the control circuit 15 . Among the above configurations, air flow meter 9
, intake temperature sensor 10. Throttle opening sensor 14. The water temperature sensor 171 and the rotation speed sensor 20 correspond to the operating state detection means of the internal combustion engine. Further, the control circuit 15 also serves as a heat generation amount control means.

The structure of the air-fuel ratio sensor 16 described above is shown in FIG.
).

In FIG. 3(A), reference numeral 168 denotes an oxygen concentration detection section, which forms a sheath body having a U-shaped cross section. This oxygen concentration detection section 1
Electrode layers are provided on the inner and outer surfaces of the exhaust manifold 6a, and by applying a predetermined voltage between the lead wires 31a and 31b electrically connected to the electrode layers, the current flowing between the two electrode layers is measured. 3. Detect the oxygen concentration of the exhaust gas flowing through the system. Further, a heater 16b is inserted into the sheath of the #I elementary concentration detection section 16a, and a lead wire 32
By applying a voltage to a and 32b, heat is generated, and the amount of heat is supplied to the oxygen concentration detection section 16a.

The oxygen concentration detection section 16a and the heater 16b are combined in an insulated state. In addition, the hood 160 covers the lI elementary concentration detection section, and the through hole 16C formed therein
1, the exhaust air diffuses onto the surface of the oxygen 11 degree detection section 16a.
is configured to be supplied by an elephant. This food 1
6c is for protecting the oxygen concentration detecting section 16a and equalizing the concentration of oxygen that diffuses and flows into the hood 16C from the exhaust gas flowing through the exhaust manifold 3.

Oxygen concentration detection section 16a of the air-fuel ratio sensor 16.

The heater 16b and the hood 16c are fixedly integrated by a mounting pedestal 16°d and fixed to the exhaust manifold 3.

The hood 1.6c of the air-fuel ratio sensor 16 was a single-layer hood, but as shown in FIG.
A double hood 16e, 16f with 6f 1 may be provided. Of course, these configurations can also be used with a suitable mounting base 16.
It is attached to the exhaust manifold 3 by a.

Next, FIG. 4 shows a block diagram showing the configuration of the above-mentioned control circuit 15. In the figure, 31 is an application power source for applying a predetermined voltage to the oxygen concentration detecting section 16a of the air-fuel ratio sensor 16, 32 is a resistor for detecting the current flowing to the detecting section 16a, and 33 is a predetermined voltage drop across the resistor 32. An amplifier circuit 34 is used to amplify the output signal from the amplifier circuit 33, that is, an analog signal corresponding to the oxygen concentration in the exhaust gas, an air flow meter 9, an intake air temperature sensor 10. This is an A/D converter that receives analog signals detected by the throttle opening sensor 14, water temperature sensor 17, etc., and converts them into digital signals. Reference numeral 35 represents a drive circuit controlled by a control signal calculated and outputted by the microcomputer 37, which drives the fuel injection valve 13 and supplies the desired amount of fuel pumped by the microcomputer 37 to the engine 2. This is a circuit that outputs a drive signal for supplying the power. The igniter 19 is also controlled by the microcomputer 37 so as to output a high voltage to the distributor 18 at a predetermined timing.

38 is similarly controlled by the microcomputer 37, and controls energization to the heater IBI 6b of the air-fuel ratio sensor 16;
For example, it is an energization control circuit that controls the amount of energization and the energization time. The power consumed by the heater portion 16b is detected by a power consumption detection circuit 39 and becomes data in a RAM (random access memory) of the microcomputer 37.

In this embodiment, among the above configurations, air flow meter 9°, intake temperature sensor 10. Throttle opening sensor 14° Water temperature sensor 1
Based on the output signal from the 79 rotation speed sensor 20, the control circuit 15 controls the amount of power supplied to the heater portion 16b of the air-fuel ratio sensor 16.

In FIG. 5, the energization control circuit 38 and the power consumption detection section 39 shown in FIG. 4, which control the heat generation of the heater part 16b, which is the main part of this practical example, will be explained in more detail. Here, 51 represents an oxygen 1 degree detection section, and 52 represents a part of a heater. Reference numeral 53 represents a switching circuit consisting of a thyristor or transistor corresponding to the current-carrying 11m circuit, and supplies a predetermined amount of current to the heater portion 52 based on the output from the microcomputer 37 side. The output from the microcomputer 37 is a pulse signal with a duty D as shown in FIG.
The amount of electricity applied to the heater portion 52 is controlled.

Further, 54 is an A/D conversion circuit corresponding to the power consumption detection circuit, which converts the applied voltage difference between points P1 and P2 in FIG. 5 into a digital quantity and outputs it to the microcomputer 37. . 56 is a voltage detection resistor, and Tm indicates a terminal to which a voltage is applied from a power source.

In such a configuration, when a voltage of value ■1 is applied to one point P1 and a voltage of value ■2 is applied to point P2, the voltage detected by the A/D converter 54 is Vl-V2.
It is. From this, in order to realize the necessary power IW to be supplied to the heater part 52 calculated from the operating state of the internal combustion engine, the resistance during operation of the switching circuit 53 must be 52° compared to the resistance 56 of the heater part 52. If it can be ignored, the following formula (1)
It is sufficient to output a pulse signal of duty D that satisfies the above from the microcomputer 37 to the switching circuit 53.

W −(Vl−Vz) ・'・−””−(1)j
(o.

In the above configuration, if the resistance of the switching circuit 53 cannot be ignored, the point P2 may be between the heater part 52 and the resistor 56.

As another example, a constant current circuit 71 may be provided as shown in FIG. 7, and energization to the heater portion 52 may be controlled by a switching circuit 72. In this case, the heater part 52
The relationship between the power supplied to the switching circuit 72 and the duty D of the output pulse from the microcomputer 37 to the switching circuit 72 is as shown in the following equation (2), where io is the current flowing under the control of the constant current circuit 71.

W= (Vl-V2) ・i 0-! A! 42,-
, (2)00 As another example, as shown in FIG.
It is also possible to set the voltage v2 after the voltage drop due to the voltage drop at the point P3. Here, 83 is a switching circuit, and 84 is a voltage detection resistor having a resistance value r. The relationship between W and D in this case is as shown in the following equation.

Next, in the above-described configuration, the amount of heat generated by a portion of the heater is controlled based on input signals from each operating state detection means. In this case, a flowchart of a program executed by the microcomputer 37 that controls the amount of power supplied to a portion of the heater will be described.

FIG. 9 is a flowchart showing a first example of the program. Here, 110 is various variables.

Represents the step of initializing flags. 120 does not represent a step of determining whether the air-fuel ratio sensor 16 is in an active state. Whether or not the air-fuel ratio sensor 16 is active can be determined by applying two types of voltage to the solid electrolyte element of the oxygen concentration detection unit 16a, and determining that it is active if the difference in current flowing at that time is less than a predetermined value. It is also possible to determine whether the sensor is active by reversing the positive and negative voltages on a similar solid electrolyte element and comparing the difference in the current flowing at that time, or by measuring the oxygen concentration in the exhaust gas during fuel cut. . 13
0 is the preset duty and heater section 16
represents the step of controlling b. Reference numeral 140 indicates various parameters representing the operating state of the internal combustion VA system, such as intake air amount,
Fuel injection amount, cooling water temperature.

Represents the step of reading engine speed, etc. 150 represents a step of measuring and calculating the exhaust flow rate.

n [The air flow rate is the intake air I determined in step 140 above.
Since it is parallel to Qo, it can be determined by multiplying the QO by a certain coefficient. 160 represents a step of calculating the expected value T of the exhaust gas temperature from the data determined in steps 140 and 150 above. This calculation is performed from a map based on the various parameters mentioned above, for example, through experiments.

170 represents a step of determining whether the exhaust gas temperature T determined in step 160 is less than 10, which is the target temperature of the oxygen concentration detection section 16a. 180 is heater part 1
6b represents the step of calculating the duty of a control signal that determines the amount of electric power to be heated. The duty D of this needle bar is set by the following method. First, the amount of heat flowing out from the oxygen concentration detection section 16a at the temperature TO is the atmosphere ml*
Since it is proportional to the square of the difference with T and proportional to the gas flow IQ, it is expressed as the following equation (3) above.

= A-Q (T-To) = (3) where A is a constant of proportionality. Furthermore, by supplying the same amount of heat m from the heater 16b as the amount of heat flowing out from the oxygen concentration detection section 16a, the temperature of the oxygen concentration detection section 16a can be set constant to the target temperature To.
The heat IKo received from the heater part 16b is proportional to the electric power W given to the heater part 16b, and has a relationship as shown in the following equation (4).

Ko=B-W=K'-(4) Here B is a proportionality constant.

From the above equations (3) and (4), the electric power W supplied to the heater portion 16b is expressed by the following equation (5).

W=A/B-Q・(T-To)' ・=(5) Here, if we use the circuit shown in FIG. -p-=A/
The relationship B-Q ・(T-To)2 is 1o.

Therefore, if the switching circuit 53 is controlled using the calculation result of this duty D, the oxygen concentration detection section 51 will be maintained at the predetermined temperature To.

Next, 190 does not represent a switch that sets the duty to 0.

This is because since the ambient temperature T is higher than the target temperature To, it is no longer necessary to energize the heater portion 16b. 200 represents the step of controlling the heater portion 16b using the duty D determined in steps 180 and 190 above.

When the program as described above is started, initial settings are first made in step 110, and then step 120 is performed.
It is determined whether the air-fuel ratio sensor 16 is active or not, and if it is not active, step 130 is executed and the heater 16b is controlled with a preset duty D. This is because, since the air-fuel ratio sensor 16 is still in a cooled state, the heater 16b is controlled with the duty D set for raising the temperature, and the temperature of the oxygen WA degree detection section 16a is quickly raised. Meanwhile, the sensor 16 is activated and step 12
If rYEsJ is determined in step 140, various parameters are read in step 140, and then step 150
The exhaust flow rate is calculated.

Next, in step 160, the exhaust gas temperature is determined, and then in step 170, it is determined whether the exhaust gas temperature T is less than 2 degrees To. Here, if T<To, T
The duty calculation of step 180 is performed to maintain o, while T≧T.

If so, it is determined that it is rNOJ, and there is no longer a need for heating, so the duty is set to 0 in step 190. Next, in step 200, the heater is controlled by duty D, and the process returns to step 120 again.

With this embodiment, the temperature of the oxygen II detection section 16a can be kept constant at or above the activation temperature even without having an RM detection section in the air-fuel ratio sensor 16. It is something that can be done. Therefore, the air-fuel ratio sensor 16 does not need to have a complicated structure, but can be used with a simple structure, resulting in high manufacturing yields, fewer failures, and fewer parts, which contributes to resource saving.

Next, a flowchart as a second example of the control program is shown in FIG. Assume that the temperature control device uses the configuration shown in Figure 'W45.

Here, 210 represents a step for initializing various variables and flags. 220 does not represent a step of determining whether the operating conditions are medium load steady.

This medium load steady state means that the engine rotational speed is within a certain value range, for example, 1.500 to 3.0OOr, l).

This refers to an operating state in which the engine rotates at a speed of 1/2 m, and the fluctuation rate is small, and the fluctuation is small within a certain range of intake air amount, for example, about 1/10 to 1/8 of the full load. If it is determined that the operating state is not a steady state but rNOJ, the processing in this routine ends.

On the other hand, when the operating state becomes a medium load steady state, it is determined in step 220 that rYEsJ, and in step 23
0, the switching circuit 53, which is a heater drive circuit composed of, for example, a transistor, starts to be energized, and the value of the timer counter at that time is stored in the RAM of the microcomputer 37. Then step 240
Read the value of V1+■2 at step 250.
The total power W expected to be required in the Katamaro atmosphere where the exhaust temperature has reached a medium load steady state in advance (this may also be a map of W with the rotation speed and intake air amount as parameters) and the above Duty D is calculated from Vl and V2 taken in step 240.

Next, in step 260, the energization time T1 is calculated from the set cycle T2 for energizing the switching circuit 53 and the duty D determined in step 250 above. This calculation is given by T1=T2 xD/100. This set cycle T2 means that when electricity is energized or de-energized according to this cycle, the heater part 52, oxygen Il! The temperature is set so that the pulsation of the temperature change in the temperature detection section 51 can be ignored. Then step 270
Then, the energization stop time 70+TI is calculated from the energization start time To and the energization time T1, and in the next step 280, the energization to the switching circuit 53 is stopped when the timer counter and To+T1 match. Next, in step 290, the energization start time is calculated from the energization start time TO and the period T2,
Return to step 220.

By having the present embodiment configured in this way, the exhaust gas temperature can be almost predicted, especially in a steady medium load state where the exhaust gas temperature is relatively low and there is a risk that the oxygen 11 degree detection section 51 may be inactivated. In this state, the temperature of the oxygen II detection unit 51 is maintained in a substantially constant state by setting the expected amount of heat generation required and predicting and supplying the amount of power to the heater part 52. It is possible to do so.

In this way, in the air-fuel ratio sensor that simply has the heater part 52, the temperature of the oxygen III degree detection part 51 can be kept constant with a simple structure.

[Effects of the Invention] The present invention calculates the amount of heat generated by the heat generating means for heating the oxygen sensor based on data detected by the operating state detecting means of the internal combustion engine, thereby eliminating the need for making the oxygen sensor a particularly complicated structure. This makes it possible to maintain the temperature of the oxygen sensor at a constant temperature higher than the activation temperature, making it easy to apply the oxygen sensor to internal combustion engines. Such a simple structure reduces failures, is easy to manufacture, has a high yield, and does not require special parts, contributing to resource conservation.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the basic configuration of the present invention, FIG. 2 is a schematic configuration diagram of the first embodiment of the present invention, and FIG. 3 (A) is a main part showing the structure of the air-fuel ratio sensor used therein. 3(b) is a sectional view of the main part of an air-fuel ratio sensor with another structure, FIG. 4 is a block diagram of the I control circuit used in the first embodiment, and FIG. 5 is a heater of the air-fuel ratio sensor. A block diagram showing the details of the control, Fig. 6 is a one-pulse waveform diagram showing the pulse waveform of the control signal, Fig. 7 is a block diagram showing another example of heater control of the air-fuel ratio sensor, and Fig. 8 is a heater control diagram. FIG. 9 is a block diagram showing the configuration of yet another example, FIG. 9 is a flowchart of one control example, and FIG. 10 is a flowchart of another control example. 2... Internal combustion engine 3... Exhaust manifold 9... Air flow meter 10... Intake temperature sensor 13... Fuel injection valve 14... Throttle opening sensor 15... Control circuit 16... Air-fuel ratio sensor 16a, 51...Oxygen ll1r! I detection section 16b, 5
2...Heater is partially represented by one patent attorney, Tsutomu Sadatetsu, Figure 5, Figure 6, Figure 7, Figure 8, Figure 1.

Claims (1)

[Scope of Claims] 1. Internal combustion *tm operating state detection means, heating means for heating an oxygen sensor for detecting oxygen m degrees in the exhaust gas of the internal combustion engine, and internal combustion*tm operating state detection means detected by the operating state detection means. An oxygen sensor m-degree control device comprising: a calorific value control means that adjusts the calorific value of the heat generating means so that the oxygen sensor reaches its target temperature based on the operating state of the engine. . 2. The operating state detection means includes an intake air amount detection section and an exhaust ms detection section of an internal combustion engine, and the heat generation means supplies electric power to a resistance heating element attached to the oxygen sensor and the resistance heating element. and a power supply for controlling the amount of heat supplied from the power supply to the intake air amount detected by the intake air amount detection section and the exhaust m degree detected by the exhaust air amount detection section. 2. The temperature control device for an oxygen sensor according to claim 1, wherein the temperature control device for an oxygen sensor is configured to adjust the amount of heat generated by the heat generating means by controlling based on . 3. The temperature control device for an oxygen sensor according to claim 1, which maintains the amount of heat generated from the heat generating means at a predetermined amount when the fluctuation in the operating state detected by the operating state detecting means is within a predetermined range. .