JPH0277640A - Power control device of heater in oxygen concentration sensor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a power control device for a heater provided in an oxygen concentration sensor, and more specifically, to a heater in an oxygen concentration sensor that detects the oxygen concentration in the exhaust gas of an internal combustion engine. The present invention relates to a device for controlling the amount of electric power.

[Prior Art] Conventionally, as an oxygen concentration sensor for detecting the oxygen concentration in the exhaust gas of an internal combustion engine, a sensor using a solid electrolyte such as zirconia is known. In this type of oxygen concentration sensor, in order to obtain a stable detection signal, it is necessary to set the detection element at a nearly constant activation temperature, but the temperature of the detection element changes due to changes in the amount of heat received from the exhaust gas. Control is performed to maintain the temperature of the detection element at a predetermined temperature by controlling the amount of power supplied to the heater.

As an example of such control, for example, JP-A-60-12
As described in Japanese Patent No. 5553 and Japanese Patent Publication No. 63-1540, the exhaust temperature is indirectly predicted based on the load condition such as the amount of intake air of the internal combustion engine, and the amount of current applied to the heater is controlled. There is.

[Problem to be solved by the invention] However, such a fall device for controlling the amount of heater power cannot be used.
Exhaust gas recirculation (EG) is an effective means of reducing NOx.
It's called R. ), the following problems arise when applied to an internal combustion engine.

That is, in this type of internal combustion engine, when EGR is turned on, the maximum combustion temperature decreases due to the heat capacity of the inert gas, and the exhaust temperature also changes.

For this reason, in conventional control devices that estimate the exhaust gas temperature from the load state of the internal combustion engine, an error occurs in the estimated exhaust gas temperature of the internal combustion engine, and therefore it is not possible to perform control to precisely maintain the element temperature at a predetermined temperature.

In particular, when lean control is performed using an air-fuel ratio sensor that can detect the air-fuel ratio in the lean region, the problem is that the air-fuel ratio cannot be controlled accurately because the limit current changes greatly depending on the temperature of the detection element. occurs.

The present invention has been made to solve the problems of the conventional technology described above, and maintains the temperature of the detection element of the oxygen concentration sensor at a predetermined temperature regardless of whether EGR is ON or OFF to accurately detect oxygen concentration. An object of the present invention is to provide a power control device for a heater provided in an oxygen concentration sensor.

[Means for Solving the Problems] As shown in FIG. 1, the present invention, which has been made to solve the above problems, recirculates exhaust gas to the intake pipe M3 through a passage M2 having a flow control valve M1. an oxygen concentration sensor M7 having an exhaust gas recirculation means M4, an oxygen concentration detection section M5 for detecting the oxygen concentration in the exhaust gas, and a heater M6 for heating the detection section M5;
and an operating state detection means M8 for detecting the operating state of the internal combustion engine, including at least the load state, and the flow control valve M1 is opened based on the detection signal from the oxygen concentration sensor M7 and the operating state of the operating state detection means M8. degree control and fuel injection! In an internal combustion engine that controls the quantity -j, a flow control valve drive means M9 drives and controls the flow control valve M1 to open and close the flow control valve M1 based on the operating state from the operating state detection means M8; Detection means M
Target power determining means MIO determines the power to be supplied to the heater M6 of the oxygen concentration sensor M7 based on the operating state from 8 and the output signal of the flow control valve driving means M9; A power supply control means Mll that controls power supplied to the heater M6 according to a target power.

[Operation] According to the configuration of the present invention, the flow control valve driving means M9 performs the following operations based on the operating state output from the operating state detecting means M8.
It is determined whether the flow rate control valve M1 is open or closed, and when a predetermined condition is met, the flow rate control valve M1 is opened to direct the exhaust gas to the passage M.
Exhaust gas recirculation control is performed to recirculate the exhaust gas to the intake pipe M3 through the exhaust gas. Further, the oxygen concentration in the exhaust gas of the internal combustion engine is detected by the oxygen concentration detection section M5 of the oxygen concentration sensor M7, and fuel injection amount control is performed based on this detection signal and the like.

This oxygen concentration sensor M7 is provided with a heater M6 for heating the detection section M5.
The power is controlled by the following means.

That is, the operating state from the operating state detecting means M8 is manually input to the target power determining means MIO, and this operating state is used as a parameter for determining the target power to be supplied to the heater M6. An output signal indicating the open/closed state from the flow control valve driving means M9 is also used as a parameter for determining the target power. The target power determined based on the operating state and the opening/closing state of the flow rate control valve M1 is manually input to the power supply control means Mll, and the power supply to the heater M6 is controlled by this means Mll. Therefore, in the present invention, the oxygen concentration sensor M7
Since the electric power supplied to the heater M6 is calculated based not only on the operating state of the internal combustion engine but also on the operating state of the exhaust gas recirculation means M4, even if the exhaust temperature changes due to the recirculation of the exhaust gas, the amount of recirculation of the exhaust gas remains unchanged. The reflected power flows to heater M6.

Therefore, since the temperature of the oxygen/agricultural product detection section M6 is maintained constant, the oxygen concentration sensor 7 can accurately detect the oxygen concentration.

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

FIG. 2 is a configuration diagram showing the configuration of an internal combustion engine 2 and its peripheral devices in an embodiment to which the present invention is applied.

In the figure, reference numeral 4 denotes an intake pipe that sucks air through an air cleaner 6, and this intake pipe 4 includes an intake temperature sensor 8 that detects the intake air temperature, a throttle valve 10, and a sensor that detects the opening degree of the throttle valve 10. A throttle position sensor 12 is provided. In addition, a surge tank 14 is formed in the intake pipe 4 to suppress intake pulsation.
This surge tank 14 has internal pressure (intake pipe pressure)
An intake pressure sensor 16 is provided to detect the intake pressure.

On the other hand, the intake pipe is equipped with an oxygen concentration sensor 20 that detects the air-fuel ratio of the fuel mixture supplied to the internal combustion engine 2 from the oxygen concentration in the exhaust gas, and a three-way catalytic converter 22 that purifies the exhaust gas. It is being

Also, on the first day of the exhaust pipe, an exhaust gas recirculation device 24 is used to return the exhaust gas to the surge tank 14 for exhaust gas recirculation (EGR).
is provided.

The exhaust gas recirculation device 24 includes an exhaust pipe and a surge tank 14.
an EGR valve 26 that opens and closes the exhaust passage connecting the EGR valve 26, a pressure regulating valve 26 that controls the EGR operation by regulating the negative pressure applied to the EGR valve 26, and a pressure regulating valve 26 that adjusts the negative pressure applied to the EGR valve 26 and applies the pressure to the EGR valve 26. Open and close the negative pressure passage,
Prohibiting or permitting EGR operation of GR valve 26゛E
It consists of a GR permission valve 30.

That is, the constant pressure chamber 26a of the EGR valve 26 and the exhaust pipe 1
The diaphragm chamber 26d, which is connected to the valve chamber 26b and the surge tank 14 via the valve chamber 26b and the diaphragm 26c, is connected to the upper chamber 28a of the pressure regulating valve 28 via the EGR permission valve 30. By connecting, the valve element 26e provided between the chamber 26'a and the valve chamber 26b and connected to the diaphragm 26c
is moved vertically in the figure in response to the negative pressure transmitted from the pressure regulating valve 28 via the EGR permission valve 30, thereby opening and closing the passage between the intake pipe 18 and the surge tank 14. There is.

Note that on the second day of the pressure regulating valve, the EGR permission valve 30
An upper chamber 28a, EG that communicates with the diaphragm chamber 26d of the GR valve 26 and also communicates with the surge tank 14.
Constant pressure chamber 28b communicating with constant pressure chamber 26a of R valve 26
, and a diaphragm chamber 28c that communicates with the EGR bow 4a formed slightly upstream of the installation position of the throttle valve 10 in the intake pipe 4, and the opening degree of the throttle valve 10 corresponds to the position of the EGR bow 4a. When the pressure is smaller, the pressure in the diaphragm chamber 28c becomes as high as atmospheric pressure, communicating the upper chamber 28a and the diaphragm chamber 28c, and conversely, the opening degree of the throttle valve 10 increases (EGR bow).
When the pressure becomes larger than the position 4a, the pressure in the diaphragm chamber 28c decreases due to the negative pressure in the intake pipe 4, and the upper chamber 28a and the diaphragm chamber 28c are cut off.

Therefore, the EGR permission valve 30 operates and the upper chamber 28
a communicates with the diaphragm chamber 26d of the EGR valve 26 (exhaust gas recirculation control is permitted), and if the throttle valve 10 is at a predetermined opening or higher, then the FGR
The negative pressure of the surge tank 14 is transmitted to the diaphragm chamber 26d of the valve, and the valve body 26e operates in response to this.
The amount of recirculation of exhaust gas, that is, the amount of EGR is controlled.

The internal combustion engine 2 also includes the above-mentioned intake air temperature sensor 8, throttle position sensor 12, intake pressure sensor 16,
and a rotation speed sensor 34 that detects the rotation speed of the internal combustion engine from the rotation of the rotor 32a of the distributor 32;
A cylinder discrimination sensor 36 outputs a pulse signal once every two rotations of the crankshaft of the internal combustion engine 2 in accordance with the rotation of the cylinder, and a water temperature sensor 38 detects the temperature of the cooling water of the internal combustion engine 2. The distributor 32 is for distributing the high voltage output from the igniter 40 to the spark plugs 42 of each cylinder in synchronization with the crank angle of the internal combustion engine 2, and the ignition timing of the spark plugs 42 is determined by the high voltage output from the igniter 40. Determined by voltage output timing.

Detection signals from each of the sensors are output to an electronic control unit 44 configured as a logic operation circuit centered on a microcomputer.

As shown in FIG. 3, the electronic control device 44 includes CPtJ,
It is mainly composed of a one-chip microcomputer 46 that has built-in ROM, RAM, etc., and is equipped with a human output board. A rotation speed sensor 34, a cylinder discrimination sensor 36, and an igniter 40 are directly connected to the human output boat of this one-chip microcomputer 46.
The D conversion input circuit 4 is connected to a heater energization control circuit 52 that controls the power supplied to the heater 20b of the agricultural sensor 20 using the battery 50 as a power source, and a drive circuit 54 that drives the fuel injection valve 53. There is.

Note that a voltage application circuit 56 is connected to the detection element 20a of the oxygen concentration sensor 20, and applies a predetermined voltage US for detection to the detection element 20a.

The A/D conversion input circuit 4 has an intake pressure sensor 16,
Sensors that output analog signals, such as a throttle position sensor 12, an intake air temperature sensor 8, and a water temperature sensor 38, are connected. Therefore, the CPU can read various parameters reflecting the operating state of the internal combustion engine 2 through the A/D conversion input circuit 4 and can know them one by one. In addition, on the 4th day of this A/D conversion input circuit, the output of the heater energization control circuit 52 that applies voltage to the heater 20b of the oxygen concentration sensor 20, and the terminal voltage of the current detection resistor on the 5th day are output to the amplifier 60. The terminals of the output and current detection resistor 62 are connected, and the applied voltage JnVn of the heater 20b,
The current flowing through the detection element 20a and the current In flowing through the heater 20b can be detected.

The electronic control device 44 controls the fuel injection amount from the fuel injection valve 53, the ignition time via the igniter 40, and EGR permission control that determines whether the operating state satisfies exhaust gas recirculation conditions and, when the exhaust gas recirculation conditions are satisfied, drives the EGR permission valve 30 to operate the exhaust gas recirculation device 24; and the oxygen concentration sensor 20.
Control of the amount of electric power to the heater 20b, etc. is executed.

Hereinafter, the EGR control executed by the electronic control device 44 will be described using FIG. 4, and the oxygen concentration sensor 20
Control of the amount of electric power to the heater 20b will be explained using FIG. 5.

First, the EGR control routine shown in FIG. 4 will be explained. This process is repeatedly executed at predetermined time intervals. First step 100 and subsequent step 1
05 is a process for determining whether or not the current operating state of the internal combustion engine satisfies the EGR condition, in which the cooling water temperature THW based on the detection signal from the water temperature sensor 38 is a predetermined value Kl (for example, 35 It is determined whether the intake pipe pressure PM based on the detection signal from the intake pressure sensor 16 is equal to or greater than a predetermined value by 2 (for example, 35 KPa).

If an affirmative determination is made in each of the determination processes in step 100 and step 105, it is assumed that the EGR condition has been established, and the process proceeds to step 110, where a flag F indicating an EGR ON command is issued.
Set EGR to 1, and then press E at step 115.
The GR permission valve 30 is turned on/on to operate EGR. On the other hand, if a negative determination is made in any of the determination processes (steps 100 and 105), it is determined that the EGR condition is not satisfied, and the process proceeds to step 120. The flag FEGR is reset to 0, and then the process proceeds to step 125, where the EΩR permission valve 30 is set to 0FFL to stop the EGR operation.

In other words, the 4th L! ] In the process, EGR is turned on and off by a known EGR control process, and
Depending on the operating state of EGR, a flag FEGR used for controlling the heater power of the oxygen moisture sensor shown in FIG. 5 is set or reset.

The routine of FIG.
5i, and the amount of electric power from the heater power supply to the heater 20b is controlled by duty according to the operating state of the engine and the operating state of EGR.

That is, when processing starts, the first step 20
0, the engine rotation speed Ne based on the detection signal of the rotation speed sensor 34, the intake pipe pressure PM based on the intake pressure sensor 16, and various parameters such as the heater voltage Vn and the heater current In are read.

In the following step 205, based on the heater voltage Vn and heater current In read in step 200, the heater 20b is activated for a predetermined period of time, for example, 100 m5.
The amount of electricity when energized, that is, the duty ratio is 10
Calculate the electric energy A at 0%. Note that all electric power amounts are calculated per 100 m5 (see Ttl- in FIG. 6).

In the subsequent step 210, the engine speed Ne and intake pipe pressure PM obtained in step 200 are used as parameters, and the basic power amount B in a state in which EGR is not operating is determined from the engine. Here, since the detection element 20a of the oxygen concentration sensor 20 is heated by the exhaust gas, the value of the basic power consumption value of the map is set according to changes in the exhaust gas temperature in order to maintain the element temperature at a predetermined value. Note that the actual exhaust temperature does not respond immediately to changes in operating conditions such as intake pipe pressure PM and engine speed Ne, but changes with a slight delay and is smoothed to some extent. It is desirable to search using a method of smoothing the intake pipe pressure PM or the engine speed Ne, and a map using the smoothed intake pipe pressure PM' or the engine speed Ne' as parameters (Japanese Patent Application Laid-Open No. (See Japanese Patent Publication No. 60-235049, Japanese Patent Publication No. 59-87244).

In the next step 215, it is determined whether EGR is operating or not based on the flag FEGR that is set and reset in steps 110 and 120 in FIG. If FEGR=1 in this step 215, the engine speed Ne and the intake pipe pressure P are determined in step 220.
The corrected power amount S is calculated using a map using M as a parameter. On the other hand, if FEGR=0 in step 225, the corrected power amount S is set to 0 in step 225.

In the subsequent step 230, the basic power amount B determined in the step 210 and the corrected power amount S calculated in step 220 or 225 are added to calculate the target power amount C actually supplied to the heater 20b.

In the next step 235, the duty ratio to be sent to the heater energization control circuit 52 is calculated using the calculation formula D=(C/A) Calculate the difference. Thereafter, in step 240, a pulse signal corresponding to the duty ratio is sent to the heater energization control circuit 52, that is, as shown in FIG.
), the current is applied for a time t corresponding to the duty ratio, and the present control process is completed.

Therefore, in this embodiment, the basic power amount B is determined based on the intake pipe pressure PM and the engine speed Ne (step 210), and when it is determined that F'GR is ON (step 215), the EGR A corrected power amount C is calculated according to the exhaust gas recirculation amount (step 220), and a target power amount C is obtained by adding this corrected power amount C (step 230).
The amount of power supplied to the heater 20b is controlled based on the duty ratio based on (steps 235 and 240).

To explain the state of such control using FIG. 7, when EGR is switched from OFF to ON at time ti, the exhaust temperature decreases, but at the same time, the correction power is added to the basic power B. The amount of electricity added to the heater 20
b is energized. As a result, the temperature of the heater 20b increases, so that the heater 20b supplies the detection element 20a with an amount of heat that compensates for the decrease in the amount of heat received due to the decrease in exhaust gas temperature, and the temperature of the detection element 20a is maintained at a predetermined temperature. Therefore, a stable detection value can be obtained from the oxygen concentration sensor 20.

Hereinafter, the present invention can be realized by other embodiments in which some of the constituent elements of the above-described embodiments are replaced or new constituent elements are added within the scope of not changing the gist of the present invention. .

■ In step 220 of Fig. 5, a map was used in which the intake pipe pressure PM and the engine speed Ne were used as parameters for the corrected electric energy, but if precise temperature control is not required, the corrected electric energy may be set to a constant value, thereby reducing the memory capacity.

■ In the above embodiment, the engine speed Ne and the intake pipe pressure PM were used as the parameters used in the map for determining the basic electric energy B and the corrected electric energy S, but instead of the intake pipe pressure PM, the throttle opening TA Alternatively, it is also possible to simply use one of these parameters, such as the engine speed Ne or the intake pipe pressure PM.

■Also, the target power amount C is calculated by adding the correction power amount S to the basic power amount B, but the correction coefficient K is calculated using a map with intake pipe pressure PM and engine speed Ne as parameters. The target power amount C may be calculated by multiplying the basic power amount B by this correction coefficient
It is also possible to have two basic types that correspond to ON and OFF of R and use intake pipe pressure PM and engine rotational speed Ne as parameters, and calculate based on these.

■ Control the power supply to the heater per 100m5.

Instead of duty control based on power time, the voltage applied to the heater may be variably controlled using chopper control or the like.

(2) Since the exhaust gas temperature does not drop immediately when EGR is turned on, but gradually drops, a delay time may be provided or correction may be made gradually in order to cope with this.

[Effects of the Invention] As described above, according to the present invention, the power supplied to the heater of the oxygen concentration sensor is controlled according to the operating state, and the power supplied to the heater is roughly controlled depending on the operating state of EGR. It is being corrected. Therefore, even when EGR is switched from OFF to ON, power is supplied to the heater according to the amount of exhaust gas recirculated, so the detection element temperature can be maintained above the activation temperature, and the heater can prevent deterioration. It is possible to prevent the temperature from rising to such a level as to cause such a problem, or from falling to such a level that the active state of the detection element cannot be maintained. Therefore,
A stable output signal can always be obtained from the detection element, and the reliability of the oxygen moisture sensor can be improved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the basic structure of the present invention, FIG. 2 is a block diagram showing an internal combustion engine and its peripheral equipment according to an embodiment of the present invention, and FIG. 3 is a control circuit diagram of the same embodiment. FIG. 4 is a flowchart showing the EGR control process according to the same embodiment, FIG. 5 is a flowchart showing the heater power amount control process according to the same embodiment, FIG. 6 is an explanatory diagram explaining the energization state to the heater, and FIG. It is a time chart explaining the effect|action of the same Example. Ml...Flow rate control valve M2...Passage M3...Intake pipe M4...Exhaust gas recirculation means M5...Oxygen) seismic intensity detection unit M6...Heater M7...Oxygen concentration sensor M8... - Operating state detection means M9...Flow rate control valve drive means MIO...Target power determination means Mll...Supply power control means 2...Internal combustion engine 4...Intake pipe 16...Intake pressure sensor 20 ...Oxygen concentration sensor 2
0a...Detection element 20b...Heater 26...
EGR valve 30...EGR permission valve 34...
Rotation speed sensor 44...Electronic control device 52...Heater energization control circuit Agent Patent attorney Tsutomu Ashioki (and 2 others) Fig. 1 Ml Fig. 4

Claims (1)

[Scope of Claims] Exhaust gas recirculation means for recirculating exhaust gas to the intake pipe through a passage having a flow rate control valve, an oxygen concentration detection section for detecting the oxygen concentration in the exhaust gas, and a heater for heating this detection section. and an operating state detecting means for detecting an operating state including at least a load state of the internal combustion engine, the flow control valve is controlled based on the detection signal from the oxygen concentration sensor and the operating state from the operating state detecting means. In an internal combustion engine that controls opening degree and fuel injection amount, a flow control valve driving means drives and controls the flow control valve to open and close the flow control valve based on the operating state from the operating state detection means; target power determining means for determining the power to be supplied to the heater of the oxygen concentration sensor based on the operating state from the detection means and the output signal of the flow rate control valve driving means; A power control device for a heater provided in an oxygen concentration sensor, comprising: power supply control means for controlling power supplied to the heater.