JPH01265148A - Electric power control device for heater provided to oxygen concentration sensor - Google Patents

Abstract

PURPOSE:To improve the reliability of an oxygen concn. sensor by opening and closing an suction passage control valve in accordance with the operating condition of an internal combustion engine and determining the target electric power to be supplied to the heater of the oxygen concn. sensor. CONSTITUTION:Heater control of the oxygen concn. sensor 15 is executed at prescribed time intervals, for example, at every 100ms and the energization to the heater 15b from a power supply 33 for heater is executed by the duty control of the heater energization according to the operating condition of the engine 1 and the detection result of the sensor 15. Namely, the target electric energy C is calculated from the basic electric energy B determined according to the rotating speed Ne of the engine and the suction pipe pressure Pm and the correction electric energy (b) determined according to a target air-fuel ratio and the energization control of the heater 15b is executed by the duty control according to the results of the calculation. The detecting element temp. is, therefore, maintained at all times in a prescribed temp. range and the detecting element 15a is activated at all times during the operation of the engine 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] This invention is attached to the exhaust pipe of an internal combustion engine and is provided for maintaining the detection element of an oxygen concentration sensor for detecting the oxygen concentration in exhaust gas at an activation temperature. The present invention relates to a power control device for a heater, and more particularly to a power control device for a heater provided in an oxygen concentration sensor of an internal combustion engine having an intake passage control valve in an intake passage.

[Prior Art] Conventionally, in devices that control the air-fuel ratio of the air-fuel mixture supplied to an internal combustion engine to a desired air-fuel ratio that is thinner (lean) than the stoichiometric air-fuel ratio, an oxygen concentration sensor that can detect a lean air-fuel ratio has been used. It is being This sensor is equipped with a detection element for detecting oxygen concentration, and a zirconia-based limiting current type detection element is generally used as this detection element.

In order to be able to accurately detect the oxygen concentration with this detection element, the temperature of the detection element must be kept at 650°C or higher and kept in an active state. A heater is provided for this purpose.

As the temperature control device mentioned above, for example, JP-A-60
As shown in Japanese Patent No. 125553, a system has been proposed in which the exhaust temperature is estimated from the load condition such as the intake air amount of the internal combustion engine and the electric power supplied to the heater is controlled.

[Problems to be Solved by the Invention] However, in recent years, in order to improve the combustion efficiency and output of internal combustion engines, an increasing number of internal combustion engines are equipped with variable intake passage areas using intake passage control valves. Controlling the area of the intake passage in this way changes the volumetric efficiency and combustion rate in the combustion chamber of the internal combustion engine, which in turn changes the exhaust temperature. Therefore, the conventional temperature control device described above, which estimates the exhaust temperature from the load condition such as the intake air amount of the internal combustion engine, causes an error in the estimated exhaust gas temperature of the internal combustion engine, making it impossible to accurately control the power supplied to the heater. As a result, there was a problem in that the detection element could not be maintained at a temperature higher than the activation temperature.

This invention was made to solve the above problems, and its purpose is to accurately control the power supplied to the heater depending on the state of the intake passage control valve, and to maintain the detection element at a temperature above the activation temperature. An object of the present invention is to provide a power control device for a heater included in an oxygen concentration sensor.

[Means for Solving the Problems 1] In order to achieve the above object, the present invention detects the oxygen concentration in the exhaust gas of an internal combustion engine and adjusts the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine, as shown in FIG. It is equipped with a detection element that outputs a corresponding signal and a heater that heats the detection element, and changes the volumetric efficiency or combustion speed in the combustion chamber of the internal combustion engine depending on the oxygen concentration sensor installed in the exhaust system and its open/closed state. An intake passage control valve provided in the intake passage of an internal combustion engine, a driving means for opening and closing the intake passage control valve, and an operating state of the internal combustion engine are detected, and a signal is output according to the detected operating state. a drive control means for controlling a drive means to open and close the intake passage control valve based on an output signal from the operation state detection means; an output signal from the operation state detection means and the drive control means; target power determining means for determining power to be supplied to the heater of the oxygen 1 degree sensor based on an output signal of the control means; and power to be supplied to the heater in accordance with the target power determined by the target power determining means. The gist of the present invention is a power control device for a heater included in an oxygen concentration sensor, which is equipped with power supply control means for controlling the power supply.

[Operation] Therefore, the drive control means drives and controls the drive means based on the operating state of the internal combustion engine determined by the operating state detection means, and the intake passage control valve is opened and closed. Further, the target power determination means determines the target power to be supplied to the heater of the oxygen concentration sensor based on the output signal from the operating state detection means and the output signal from the drive control means, and the supply power control means adjusts the target power to the target power. The corresponding power is supplied to the heater.

[Example] An example embodying the present invention will be described below with reference to FIGS. 2 to 12.

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

A piston 2 is housed in the cylinder 3 of the engine 1 so as to be able to move up and down, and an exhaust manifold 6 is attached to the exhaust boat 5 for each cylinder, which is formed on the cylinder head 4 fixed to the upper part of the cylinder 3. An intake manifold 8 is connected to each intake boat 7 formed for each cylinder. Further, the intake manifold 8 is connected to a surge tank 9 for preventing pulsation of intake air, and 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. It is provided.

The surge tank 9 is connected to an air cleaner (not shown) via an intake pipe 11, and the intake pipe 11 is provided with a throttle valve 12 that controls the amount of intake air sent to each cylinder according to the amount of operation of an accelerator pedal (not shown). ,
An intake air temperature sensor 13 is provided to detect intake air temperature. The throttle valve 12 is equipped with an opening sensor 14a (see FIG. 3) that outputs a signal corresponding to the opening of the throttle valve 12, and an idle switch 14b (see FIG. 3) that is turned on when the engine 1 is idling. A position sensor 14 is directly connected.

The exhaust manifold 6 includes a detection element 15a (see FIG. 3) that detects the oxygen concentration in the exhaust gas and outputs a signal corresponding to the air-fuel ratio of the air-fuel mixture supplied to the engine 1, and a platinum heater 15b for heating. An oxygen concentration sensor 15 is attached to the cylinder 3, and a water temperature sensor 16 for detecting the temperature of the cooling water of the engine 1 is provided in the cylinder 3. Further, a distributor 17 is connected to the spark plug 18 provided for each cylinder in the cylinder head 4 to apply a high voltage outputted from an igniter 19 at a predetermined timing. A rotation speed sensor 20 is provided which generates a pulse signal.

Further, in the cylinder head 4, a swirl control valve (hereinafter referred to as SC■) 21 as an intake passage control valve protrudes into the intake boat 7 and is in a "closed" state shown by a solid line and "open" shown by a two-dot chain line. When the 5CV 21 is closed, a swirl (swirling flow) is generated in the combustion chamber. This 5CV21 is opened and closed by a diaphragm actuator 22, and the pressure in the negative pressure chamber of this diaphragm actuator 22 is controlled by a vacuum switch notching valve (hereinafter referred to as ■S■) 2.
3 selectively switches between atmospheric pressure and the pressure in the surge tank 9, and when atmospheric pressure is introduced by VSV23, 5CV21 is activated by the diaphragm actuator 22.
is set in the "open" state, and when the intake pipe pressure Pm in the surge tank 9 is introduced, the 5CV 21 is set in the "closed" state by the diaphragm actuator 22. In this embodiment, the diaphragm actuator 22 and the VSV 23 constitute driving means for the 5CV 21. Note that a check valve 24 is provided in the pipeline between the VSV 23 and the surge tank 9.

Furthermore, the intake manifold 8 is provided with an electrically controlled fuel injection valve 25 .

The operating state B of the internal combustion engine is determined by the intake pressure sensor lO1, the intake temperature sensor 13, the throttle position sensor 14, the oxygen concentration sensor 15, the water temperature sensor 16, and the rotation speed sensor 20.
The output signals of the respective sensors are input to a control circuit (hereinafter referred to as ECU) 26 as a drive control means, a target power determination means, and a supply power control means.
Based on the above output signals, the CU 26 controls the fuel injection amount of the fuel injection valve 25, the ignition timing control of the spark plug 18, and 5C.
Various control processes such as opening/closing control of V21 or control of the heater of oxygen concentration sensor 15 are executed.

Next, the ECU 26 mentioned above will be explained in detail based on FIG.

An application power supply 27 for applying a predetermined voltage is connected to the detection element 15a of the oxygen concentration sensor 15, and a resistor 28 for detecting the current flowing through the element 15a is connected. An amplifier circuit 29 for amplifying the voltage drop at 28 by a predetermined factor is connected.

An A/D converter 30 is connected to the amplifier circuit 29.
The converter 30 converts the output signal from the amplifier circuit 29, that is, an analog signal corresponding to the oxygen concentration in the exhaust gas, into a digital signal. Further, the A/D converter 30 is connected to the intake pressure sensor 10, the intake temperature sensor 13, the opening sensor 14a of the throttle position sensor 14, the water temperature sensor 16, etc., and converts the output signals from these sensors into gibtal signals. It is supposed to be converted.

The A/D converter 30 includes a central processing unit (CPU) 31a,
A read only memory (ROM) 31b, a random access memory (RAM) 31c, etc. are connected to the microcomputer 31 having such a configuration. The microcomputer 31 also includes an energization control circuit 3 for controlling the power supplied to the heater 15b of the oxygen concentration sensor 15.
2 is connected, and the energization from the heater type aiaa is controlled based on a control signal output from the micro combinator 31. Furthermore, the microcomputer 31 includes a heater voltage detection circuit 34 that detects the heater voltage when the heater 15b is energized by the energization control circuit 32.
is connected, and a heater current detection circuit 35 for detecting the heater current is also connected.

The fuel injection valve 25 is connected to the microcomputer 31 via a drive circuit 36, and a drive circuit 37
The VSV 23 is connected via. Drive circuit 3
Reference numeral 6 opens the fuel injection valve 25 based on a control signal output from the microcomputer 31 to supply a desired amount of fuel to the engine 1. Drive circuit 37
operates the VSV 23 based on a control signal output from the microcomputer 31 to switch between atmospheric pressure and the intake pipe pressure Pm, that is, to open and close the 5CV 21. Furthermore, an igniter 19 is connected to the microcomputer 31, and this igniter 19 also outputs a high voltage to the distributor 17 at a predetermined timing based on a control signal from the microcomputer 31.

In the control circuit of this embodiment configured in this way,
As mentioned above, fuel injection amount control, ignition timing control, 5CV2
Various controls such as opening/closing control of 1 and heater control of oxygen concentration sensor 15 will be executed.
Opening/closing control of No. 1 and heater control of oxygen concentration sensor 15 will be explained.

Lean feedback control in fuel injection amount control is known, for example, in Japanese Unexamined Patent Publication No. 14443/1983, and will therefore be briefly explained here.

When the detection element 15a of the oxygen concentration sensor 15 is in the active state and it is determined that the operating state is to execute lean feedback control based on each sensor signal, the data is stored in the ROM 31b as shown in FIG. A target air-fuel ratio is determined based on the engine speed Ne and intake pipe pressure Pm from a pre-stored map, and this target air-fuel ratio is equal to the stoichiometric air-fuel ratio (1
4, 7) Only when the air-fuel ratio is on the lean side, the actual air-fuel ratio obtained from the output signal from the detection element 15a is compared with this target air-fuel ratio, and the air-fuel ratio correction amount is integrally processed based on the comparison result. and ask.

In addition, the basic injection amount is calculated based on the engine speed Ne and the intake pipe pressure Pm, and the basic injection amount is corrected based on the correction amount obtained from the cooling water temperature, intake air temperature, etc. and the air-fuel ratio correction amount to perform effective injection. Find the quantity. Then, a time width signal is formed by adding the power supply voltage correction to the time width signal corresponding to this effective injection amount, and this signal is output to the drive circuit 36 at a timing synchronized with the engine rotation, and the fuel injection valve 25 is opened. Let me speak.

Further, although the detection element 15a of the oxygen concentration sensor 15 is in the active state, acceleration is detected and the stoichiometric air-fuel ratio (A/F=14.
7>, the stoichiometric air-fuel ratio is used as the target air-fuel ratio, and the actual air-fuel ratio obtained from the output signal from the detection element 15a is determined as in the lean feedback control process for correction. The basic injection amount is corrected by calculating the air-fuel ratio correction amount by comparing it with the fuel ratio to determine the effective injection amount. Then, the time width signal corresponding to this effective injection amount is corrected by the power supply voltage, and the fuel injection valve 25 is driven by the corrected time width signal.

By the way, the 5CV 21 is controlled to open and close according to the intake pipe pressure Pm and the engine speed Ne, and is controlled to have hysteresis characteristics as shown in FIGS. 5 and 6. That is, in this example, the 5CV2 t
As shown in FIG.
or the rotation speed sensor 2 as shown in FIG.
It is designed to be output when the engine rotational speed Ne at 0 becomes 3200 rpm or more. Also, 5CV21 is “
The control signal for setting the "closed" state is determined when the intake pipe pressure Pm measured by the intake pressure sensor 10 is approximately 560 mmHg or less as shown in FIG. The following will be output. Note that the target air-fuel ratio is the air-fuel ratio read out from the map in Figure 4 according to the engine speed Ne and intake pipe pressure Pm at that time (Figures 5 and 6 show the case where the target air-fuel ratio is 20). ) is set.

Next, control of power supply to the heater 15b of the oxygen concentration sensor 15 will be explained based on the control program shown in FIG.

The heater control of the oxygen concentration sensor 15 shown in FIG. This is done by controlling the duty of heater energization accordingly.

When the process starts, first step 1 (hereinafter simply 8
1), various parameters such as engine rotational speed Ne, intake pipe pressure Pm, heater voltage vh, heater current 1h, etc. are read based on the signals from the sensors and detection circuits, and the process proceeds to S2.

In S2, the heater voltage vh and heater current Ih read in S1 are used for a predetermined period of time, for example, 100
+nsO, a process is executed to calculate the amount of power when the heater 15b is energized, that is, the power IA at a duty ratio of 100%, and the process moves to S3. Hereinafter, all electric power amounts are per 100+na.

Next, at 83, a flag
Determine the status of scv. Note that this flag xscv is set to X5CV when 5CV21 is in the "closed" state as described above.
=rlJ, and when 5CV21 is in the "open" state, xscv=rOJ is set.

Then, if X5CV=rlJ, in S4, the corrected power 1b is obtained from a map set as shown in FIG. 8, using engine speed Ne and intake pipe pressure Pm as parameters, and If so, the correction power amount is set to 0 in S5.

Next, in step 86, the basic power amount B to be supplied to the heater 15b is determined from the map shown in FIG. 9, for example, using the engine speed Ne and intake pipe pressure Pm determined in S1 as parameters, to move to. here this ninth
The value of the basic power amount B in the map in the figure shows that 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, and the exhaust temperature rises. This setting takes into consideration both the fact that the further the air-fuel ratio is from the stoichiometric air-fuel ratio, the lower the exhaust gas temperature becomes.

Then, in S7, the basic power iB and the corrected power 1b
Using the following equation with parameters, the target amount of electric power C actually supplied to the heater 15b
A process is performed to calculate .

When the target power amount C is determined in this way, '1rj
For supplying the target power amount C to the heater 15b at t < 38, the following formula % is used, which uses this target power amount C and the power i1A with a duty ratio of 100% obtained in S2 as parameters. A duty ratio is calculated.

Then, when m<39, a pulse signal corresponding to the reduced duty ratio is sent to the energization control circuit 32, and the heater 15b is
The process of controlling the power supplied to the controller is executed, and the main control process ends.

For example, the power iA at a duty ratio of 100% is 50
[W・100LI], target power amount is 25 [W・Loo
ms), the duty ratio is 50%, and the pulse signal sent to the energization control circuit 32 is
It becomes as shown by the solid line in the figure.

Figure 11 shows how the heater 1
5b is a time chart showing changes in the heater salt, element temperature, and exhaust temperature when the air-fuel ratio changes in a conventional configuration in which the power supplied to the power supply unit 5b is not corrected. According to the same figure, 5CV2
1 changes from open to closed, the exhaust temperature decreases, and the element temperature of the detection element 15a falls below the lowest activation temperature.

FIG. 12 shows 5CV21 in the configuration of this embodiment described above.
3 is a time chart showing changes in heater salt, element temperature and exhaust temperature, and heater power when the state of the heater changes. According to the figure, when the 5CV21 changes from open to closed, the power supplied to the heater 15b is corrected to increase through the above process, so that the exhaust temperature increases as the 5CV21 changes to the "closed" state. Even if the temperature drops, the element temperature of the detection element 15a will not fall below the lowest activation temperature.

As explained above, in the heater control device included in the oxygen concentration sensor of this embodiment, the engine speed N
Basic power amount B determined according to e and intake pipe pressure Pm
The target power amount C is calculated from the corrected power amount S determined according to the target air-fuel ratio, and the calculated target power ff1
It is configured to control the energization of the heater 15b by duty control according to C. Therefore, according to the present 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 detection element temperature can always be maintained within a predetermined temperature range.
The detection element tSa can always be activated while the engine 1 is operating.

Also, 5CV21 is the engine speed Ne and the intake pipe pressure Pm
Even if the state changes from "closed" to "open" and the exhaust temperature increases accordingly, this 5CV2
Since the target power Ic to be supplied to the heater 15b is lowered in accordance with the change in the state of the heater 15b, disconnection of the heater 15b,
It is possible to prevent thermal damage to the detection element 15a.

Furthermore, since more power than necessary is not supplied to the heater 15b, energy can be saved.

In the above embodiment, the engine speed Ne and the intake pipe pressure Pm were used when determining the basic power amount B, but instead of the intake pipe pressure Pm, the intake air amount or the opening degree of the throttle valve 12, etc. may be used, or simply one of the engine rotational speed Ne, intake pipe pressure Pm, etc. may be used.

Furthermore, in the above embodiment, the target power amount C is determined by adding the corrected power amount S to the basic power amount B, but for example, as shown in FIG. 13, the engine rotation speed Ne and the intake pipe pressure Pm may be used as parameters. The correction coefficient K may be determined using the map, and the target power 1tC may be calculated by multiplying the basic power 51B by the correction coefficient K.

Furthermore, in the above embodiment, the power supply control of the heater 15b is executed by duty control based on the power supply time per too (ms), but in addition to this, for example, the power supplied to the heater 15b is determined, and the power supplied to the heater 15b is The applied voltage may be controlled.

In addition, in the above embodiment, the target power amount is determined by correcting the basic power amount B according to the open/closed state of the 5CV21, but the map that determines the target power amount when the 5CV21 is "open" is used. It is also possible to separately provide a map that defines the target power amount when the 5CV is closed, and determine the target power amount from either map depending on the state of the 5CV 21.

In addition, considering the delay in 5CV21 (7) operation when switching 5CV21 open/close, a delay is added to the correction change or map switching.
Alternatively, the power before switching may be gradually changed to the power after cutting.

Furthermore, in the above embodiment, the electric power amount is corrected according to the opening/closing state of the 5CV21 that generates a swirl in the combustion chamber, but the present invention can change the length of the intake passage according to the operating state of the internal combustion engine. The present invention can also be applied to a system that changes the volumetric efficiency within the combustion chamber, and the amount of electric power may be corrected depending on the state of a valve that changes the length of the intake passage.

[Effects of the Invention] As detailed above, according to the present invention, the power supplied to the heater is accurately controlled depending on the state of the intake passage control valve, and
The detection element can be maintained at a temperature higher than the activation temperature, and the heater temperature can be prevented from rising to a temperature that would cause heater deterioration or falling to a point where the activation state of the detection element cannot be maintained; This has the excellent effect of being able to always obtain a stable output signal from the detection element and improving the reliability of the oxygen concentration sensor.

[Brief explanation of the drawing]

Fig. 1 is a diagram corresponding to the claims of this invention, and Fig. 2 is a schematic system diagram showing an engine and its peripheral equipment equipped with a heater control device included in an oxygen concentration sensor according to an embodiment of the invention. , Fig. 3 is a block diagram showing the configuration of the control circuit, Fig. 4 is a map for determining the target air-fuel ratio, Fig. 5 is a characteristic diagram showing the H closed state of the swirl control valve with respect to intake pipe pressure, Fig. 6 7 is a characteristic diagram showing the opening/closing state of the swirl control valve with respect to the engine speed, FIG. 7 is a flowchart showing the heater control process of the oxygen 4 degree sensor executed in the control circuit, and FIG. Fig. 9 is a map for determining the basic electric energy, Fig. 10 is a time chart showing the control output to the energization control circuit (No. 3), and Fig. 11 is a time chart showing the control output to the energization control circuit (No. 3). Supply power, heater temperature. Time chart showing changes in element temperature and exhaust temperature, 1st
Figure 2 is a time chart showing changes in power supplied to the heater, heater temperature, element temperature, and exhaust temperature with respect to changes in air-fuel ratio according to the configuration of the embodiment of the present invention, and Figure 13 is a time chart showing a correction coefficient in place of the correction power amount. This is a map for In the figure, l is the engine, 6 is the exhaust manifold, 10 is the intake pressure sensor, 15 is the oxygen concentration sensor, 15a is the detection element, 15b is the heater, 20 is the rotation speed sensor, 21 is the swirl control valve, and 22 is the drive means. A diaphragm actuator 23 also constitutes a driving means, and a control circuit 26 serves as a drive control means, a target power determining means, and a power supply control means. Figure 1 Ne (X100) (rpnI) Nc (xtoo
) (rpnQ - 111 Kahagiben time □ Elapsed time Figure 18 Correction coefficient K Ne (11000) (rprn)

Claims (1)

[Scope of Claims] 1. A device comprising a detection element that detects the oxygen concentration in the exhaust gas of an internal combustion engine and outputs a signal corresponding to the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine, and a heater that heats the detection element. , an oxygen concentration sensor installed in the exhaust system; an intake passage control valve installed in the intake passage of the internal combustion engine for changing the volumetric efficiency or combustion speed in the combustion chamber of the internal combustion engine according to its opening/closing state; a driving means for opening and closing the passage control valve; an operating state detecting means for detecting the operating state of the internal combustion engine and outputting a signal according to the detected operating state; drive control means for controlling a drive means to open and close the intake passage control valve; and electric power supplied to the heater of the oxygen temperature sensor based on an output signal from the operating state detection means and an output signal from the drive control means. An oxygen concentration sensor comprising: a target power determining means for determining the power; and a power supply control means for controlling the power supplied to the heater according to the target power determined by the target power determining means. Equipped with heater power control device.