JPS60214251A - Controller of heater for oxygen concentration sensor - Google Patents

Abstract

PURPOSE:To maintain the heater of an oxygen concn. sensor at an optimum temp. by setting basic electric power corresponding to the operating condition of an internal combustion engine, correcting the basic electric power according to ambient temp., setting the target electric power and controlling the heater of said sensor by the target power. CONSTITUTION:The basic electric energy of the heater IV of an oxygen concn. sensor IIIis determined from the calculation equation in which the engine speed and the pressure of an intake pipe detected by a means VI for detecting the operating condition are used as a parameter. The intake air temp. is measured by a temp. sensor V and the process for determining the corrected electric energy for the basic electric energy is executed according to said temp. The target electric energy to be supplied to the heater IV is calculated from the basic electric energy and corrected electric energy. When the target electric energy is determined, a duty ratio to be conducted to the heater IV is calculated and the pulse signal of the duty ratio is supplied to the heater VIIby a controlling means IX. If the heater is constituted in the above-mentioned way, the heating of the oxygen concn. sensor to the prescribed temp. or above at all times is made possible and the heater is kept at the temp. at which disconnection and the breakdown of the detecting element do not arise.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] The present invention is directed to an oxygen concentration sensor that detects the oxygen concentration in the exhaust gas of an internal combustion engine.
This relates to a control device.

[Prior art] Conventionally, a three-way catalyst [converter] has been used as an air-fuel ratio control device for internal combustion engines for vehicles to reduce CO1I'c, NOx in exhaust gas.
In order to efficiently purify the three components of
There is a known system that is equipped with an I sensor to detect the oxygen concentration in the exhaust gas and performs so-called feedback control in which the air-fuel ratio of the internal combustion I is controlled so that it becomes the stoichiometric air-fuel ratio. In recent years, zirconia-based or titania-based limiting current sensors that can obtain a detection current corresponding to the oxygen degree have been developed as oxygen degree sensors used in this type of control device. In addition to simply controlling the air-fuel ratio of the engine to near the stoichiometric air-fuel ratio, for example, when the internal combustion engine is operating at low load, the air-fuel ratio is controlled to the 1st level to improve fuel efficiency, such as so-called lean burn control. It has become possible to execute air-fuel ratio control more precisely.

By the way, in order to obtain a detection current corresponding to the oxygen concentration with the oxygen 11 degree sensor of this scale, 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 degrees Celsius or higher. Oxygen concentration sensors usually have a built-in heater for heating the detection element in addition to the detection element.

During operation of the internal combustion engine, a predetermined voltage is applied to this heater so that the oxygen II degree sensor can always obtain good detection results.

In addition, in order to activate the detection element and obtain good detection results with the oxygen m degree sensor, it is sufficient to heat the detection element to a predetermined temperature or higher using a heater, etc. However, if it is heated too much, the exhaust gas Problems such as heater disconnection or detection element destruction may occur due to abnormal overheating.

If the heater of the oxygen concentration sensor is disconnected,
Since the detection results of the air-fuel ratio sensor become unreliable and good air-fuel ratio control is no longer possible, as a countermeasure, conventionally, as shown in Japanese Patent Application Laid-open No. 57-140539, the m depth sensor is used. When the heater Ili is on, feedback control of the air-fuel ratio is stopped and A-pun loop control is performed to fix the air-fuel ratio to a preset value.
= Control was being carried out.

However, if the heater is disconnected, repairs such as sensor replacement are required, and feedback control cannot be performed until the heater is repaired, so eliminating the disconnection of the oxygen concentration sensor heater is an issue for vehicle equipment. O [Purpose 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 optimum temperature at all times. It is an object of the present invention to provide a control device for a heater for an oxygen concentration sensor, which can be activated by the oxygen concentration sensor.

[Structure of the Invention] In order to achieve the above object, the present invention is directed to the following: As shown in Fig. 1, the Vi
This is a control device that controls the heater 1V installed in the oxygen concentration sensor 4'' which outputs a temperature of 447, and is equipped with a temperature sensor that detects the ambient temperature of the internal combustion engine.
■ and an operating state detection means Vl for detecting a predetermined operating state of the internal combustion lever; and a basic power setting means vH for setting the basic power to be supplied to the heater v according to the detected operating state. , target power determining means (3) for correcting the set basic power according to the detected local till temperature and determining a target power to be supplied to the heater; The gist of the present invention is a control device for a heater for an oxygen concentration sensor 1), characterized in that it is equipped with a tl+1 control means IX for controlling the electric power supplied to the oxygen concentration sensor 1).

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

First, Fig. 2 is a schematic system diagram showing the internal combustion capacity (hereinafter referred to as engine) for a vehicle equipped with the acid-based temperature sensor heater control device of this embodiment and its peripheral equipment. be.

In the figure, 1 is an engine, 2 is a piston, 3 is a cylinder, and 4 is a cylinder head. An exhaust manifold 6 is attached to the exhaust boat 5 of each cylinder of the cylinder head 4, and an exhaust manifold 6 is attached to the intake board of each cylinder of the cylinder head 4. The intake manifolds 8 are connected to each other. The intake manifold 8 is also provided with a surge tank 9 for preventing pulsation of intake air, and the first surge tank 9 has an intake pressure sensor 10 that detects the pressure inside the intake manifold 8, that is, the intake pipe pressure [m].
is provided.

Next, 11 is a throttle valve that controls the amount of intake air sent to each cylinder via the nozzle tank 9; 12 is an intake air bypass path that bypasses the throttle valve 11;
Reference numeral 3 designates an intake temperature sensor 1 which detects the intake air temperature i, and a throttle valve 11 has a throttle valve 11 which outputs tri A throttle position sensor 14 is directly connected to the throttle position sensor 14, which has an idle switch that is turned on when the engine 1 is idling. Further, 15 is an oxygen concentration sensor installed in the exhaust manifold 6 and equipped with a detection element for detecting the oxygen concentration in the exhaust gas and a heater for heating, and 16 is a water temperature sensor for detecting the cooling water temperature of the engine 1. , 17 is a distributor that applies a high voltage output from one igniter at a predetermined timing to the spark plug 18 of the engine 1, and 20 is attached to the distributor 17 and generates a pulse signal corresponding to the rotation speed of the engine 1. Each represents a rotation speed sensor.

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 fuel injection valve 26, the fuel injection IJJmi! III group,
Various control 11 processes such as ignition timing control of the spark plug 18 or control of the heater 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 a power supply 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 voltage drop across the resistor 32. An amplifier circuit 34 is used to amplify the signal by a predetermined value, and 34 is an output signal from the amplifier circuit 33, that is, an analog signal corresponding to the degree of oxygen in the exhaust gas, an intake pressure sensor 10, an intake temperature sensor 13, and a throttle position. It is a Δ/D converter that receives analog signals detected by the lens υ 14, water temperature sensor 16, etc. and converts them into digital signals. This circuit represents a drive circuit controlled by a control signal, which is driven by the fuel injection valve 26 and outputs a drive signal for supplying the engine 2 with the fuel of 1=desired m calculated by the microcomputer 37. The igniter 196 is controlled by the microcomputer 37 to output a high voltage to the distributor 17 at a predetermined timing.

Next, 38 controls the power supply to the heater 15b7\ of the oxygen ia melon 15 +-! It is an energization control circuit for J
, the power supply from the heater power source 39 is controlled according to the control signal of the micro combi coater 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,
As mentioned above, various controls such as fuel injection control, ignition timing control, and oxygen concentration sensor heater control are executed. Regarding sensor heater control, Part 4
A detailed explanation will be given according to the control program shown in the figure.

The heater control of the oxygen sensor shown in FIG. 4 is executed every predetermined time interval, for example, 100 [m sec, This is carried out by the heater energization control 11 according to the detection result of step 15.

When the process starts, first in step 101, various information such as engine rotation speed Ne, intake pipe pressure Pn+, intake air temperature 111 (heater voltage V1), heater current 11+, etc. The parameters are read and the process moves to the following step 102.

In step 102, the heater voltage Vl+ and heater current 1 h read in step 101 are used for a predetermined period of time, for example, 100 m sec.

], a process is executed to extract the amount of electric power when the heater 15b is energized, that is, the electric power ff1A with a DuVui ratio of 100%, and the process moves to step 103. Hereinafter, all references to electric energy are assumed to be electric energy per 100 [m sec,].

Next, in step 103, the step 101 described above is performed.
Engine speed Ne and intake pipe pressure PIl determined by
The basic power 11 of the heater 15b is determined from a map M1 or a sieve formula as shown in FIG.
13, and the process moves to the following step 104. Here, in the map M1, as is clear from FIG. 5, the engine speed Ne and the intake pipe pressure IPI11 are used as parameters, and the basic power ff1 when the intake air conditioning -1゛i is 20℃.
B is set, which is the intake pipe pressure PM
is large, or when the engine speed Ne is large, naturally the amount of fuel injected into the engine 1 increases, the exhaust temperature rises, and the detection element 15a can be heated by the exhaust gas, so the power supplied to the heater 15b is reduced. Make it smaller;
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 151) is set to be increased.

Next, in step 104, a process is executed to calculate a correction power 1b for the basic power IB from a map M2 in which the intake air temperature 1-i obtained by 1q in step 101 is used as a parameter, and the process proceeds to step 105.

Then, in step 105, the target power amount C to be actually supplied to the heater 15b is calculated using the following formula 〇=B+b, which uses the basic power amount B and the corrected power mb as parameters.
A process is carried out to deceive the person.

Here, the map M2 used in step 104 is as shown in FIG. 6, for example, and when the intake air temperature Ti is 20°C, the correction power mb is negative when Ti>20[°C]. For the value of 7'i < 20 [℃
In the case of J, the correction power mb is set to be positive 1ho1. This is because map M1 is Ti = 2 in the above explanation.
0 ["This is based on the setting under CI conditions, and in the case of T'1-20 [℃], the value of map M1 can be used as is, so the correction power mb is set to 1-0." In the case of Ti>20["CI, if 1ifI of map M1 is used as it is, the oxygen m degree sensor 15 becomes too high temperature, so a negative correction value must be set.

When the target power amount C is determined in this way, the target power amount C and the above-mentioned stainless steel 1102 are determined in the following step 106.
The duty jfJ, lSD for supplying the target power interval C to the heater 5b is calculated using the following formula (%) in which the electric power amount △ at the duty ratio of 100% determined by is used as a parameter.

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

For example, the power mA at 100% duty is 50
[w ・100m5ec,], target electric power is 25 [w
If J is 100 m5ec, ]r, the Tutee ratio will be 50%, and the pulse signal sent to the energization control circuit 38 will be as shown by the solid line in FIG.

As explained above, in the control device for the oxygen temperature sensor heater of this embodiment, the basic power amount B is set according to the engine speed Ne and the intake pipe pressure pm, and the basic power amount B is set according to the intake air temperature 1-i. According to this control device, the target electric power amount C is calculated from the determined corrected electric power ff1b, and the heater energization control is executed by duty control according to the determined target electric power amount C. Heater 15b
The heating of the detection element 15a by
lt range, and the detection element can be constantly activated while the engine 1 is running. Furthermore, even if the intake air temperature 1-i increases and the exhaust gas temperature increases accordingly, the heater 15. Since the target power IC to be supplied to J
It is possible to prevent such things from happening. (2) Since more power than necessary is not supplied to the heater 15b, energy is saved.

In the above embodiment, it is assumed that the intake air temperature sensor 13 corresponds to the temperature sensor V described above, and the operating state detection means v1 corresponds to the intake pressure sensor 10 and the rotational speed sensor 20, and the basic power Equivalent to setting means v1
In step 103, the basic power ff1B is calculated.
The processing of step 104 for calculating the corrected power ib and the processing of step 105 for calculating the target power amount C correspond to the target power determining means (■), and the processing of step 105 for determining the target electric power C corresponds to the heater energization The process of step 107 and the energization control circuit 38 that override the execution of the control are listed.

In the above embodiment, when calculating the basic electric power IB, the engine speed Ne and the intake pipe pressure Pm are used, but in addition to these, the intake air amount and the throttle valve 1
1 colleague, etc. may be used, or simply one of engine rotation speed Ne, intake pipe pressure pm, etc. may be used.

In addition, in the above embodiment, the correction power fib is set to the intake air temperature T.
In addition to the intake air temperature Ti, any temperature may be used as long as it corresponds to the ambient temperature of the engine 1. For example, it may be set depending on the outside air mixture.

Furthermore, in the above embodiment, the basic power amount B is corrected using the compensation power amount (B+b>), but for example, the correction coefficient K is calculated using a map with intake air temperature - [i as a parameter as shown in FIG. Therefore, the basic power MB may be corrected by (KXB).

In addition, in the above embodiment, the power supply control of the heater 15b is carried out by duty control based on the power supply time per 100 [m Sec,], but in addition to this, for example, the power supply to the heater 15b is controlled. Therefore, the voltage applied to the heater 15b may be controlled.

[Effects of the Invention] As described in detail above, in the control device for the heater for oxygen heating according to the present invention, first the main power is set according to the operating state of the internal combustion engine, and then this basic power is set. The target electric power is determined by correcting the electric power according to the ambient temperature of the internal combustion engine, and the electric horn supplied to the heater is controlled according to this target electric 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, and the oxygen concentration sensor always provides stable and good detection results. You will be able to do 1q.

In addition, since it prevents the heater from breaking and the detection element from being destroyed, the need to replace the sensor when it is defective can be reduced.
Furthermore, since no more power than necessary is supplied to the heater, energy can be saved.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of the present invention, and FIG. 2 is a block diagram showing an engine and its peripheral equipment equipped with a control device for an oxygen concentration sensor heater according to an embodiment of the present invention.
System diagram, Figure 13 is a block diagram showing the configuration of the control circuit 25, and Figure 4 is a flowchart 1-1 showing the heater control of the oxygen temperature sensor executed by the control circuit 25. is a graph showing the map M1 for calculating the basic power amount B, FIG. 6 is a graph showing the map M2 for calculating the corrected power mb, and FIG. The time chart shown in FIG. 8 is a graph showing a map for determining the correction coefficient K in place of the correction power. 1... Engine 6... Exhaust manifold 10...
・Intake pressure sensor 13... Intake temperature sensor →) - 15... Oxygen concentration sensor 20... Rotation speed sensor 25)... Control circuit 37... ...Microcomputer 38...
・Electrification control circuit agent Patent attorney Tsutomu Sadatsu et al. 1 person Figure 1 Figure 4 Figure 5 0 70 20 30 40 -tzoe (x700) (rpm) Figure 6-TI t'Cノ

Claims (1)

[Claims] 1. Control I'r of a heater provided in an oxygen concentration sensor installed in the exhaust system of an internal combustion engine and detecting the oxygen concentration in the exhaust gas.
A control device comprising: a temperature sensor that detects the ambient temperature of the internal combustion engine; an operating state detection means that detects a predetermined operating state of the internal combustion engine; basic type horn setting means for setting the basic power to be supplied to the heater; and target power determining means for correcting the set basic type horn according to the detected ambient temperature and determining the target power to be supplied to the heater. And, it has been decided! A control device for a heater for an oxygen concentration sensor, comprising: a control means for controlling electric power supplied to the heater according to a target electric power. 2. The control device for a heater for an oxygen concentration sensor according to claim 1, wherein the ambient temperature is an intake air temperature of an internal combustion engine, and the temperature sensor is an intake temperature sensor. 3. The power obtained by the basic power setting means and the target power determining means is the amount of power supplied to the heater per predetermined time, and the control means determines the target power per predetermined time determined by the target power determining means. A control device for a heater for an oxygen concentration sensor according to claim 1 or 2, wherein the control device is configured to control energization of the heater according to a duty ratio according to the amount of electricity.