JP2633641B2 - Exhaust gas concentration detector - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an exhaust gas concentration detecting device, and more particularly to an exhaust gas concentration detecting device having a heater resistor for heating.

(Problems to be Solved by the Prior Art and the Invention) In order to improve the exhaust characteristics and fuel efficiency of an internal combustion engine, the exhaust gas concentration is detected, and the mixture of the air-fuel mixture supplied to the engine is detected in accordance with the detection result. A technique for performing feedback control of an air-fuel ratio (supply air-fuel ratio) to a target air-fuel ratio is well known.
In this case, as an oxygen concentration sensor for detecting the oxygen concentration in the exhaust gas, a sensor having a built-in heating heater is known. (JP-A-61-35347). In this device, the accuracy of the air-fuel ratio detection is ensured by maintaining the temperature of the sensor unit at a required temperature by controlling the heater resistance to a constant value using a bridge circuit.

However, in this type of sensor with a heater, the heater temperature, and hence the sensor temperature, changes due to the variation in the heater resistance, and as a result, the detection output of each sensor used tends to be different. There is. That is, the heater resistance varies in the resistance value in the manufacturing process, and when such variation occurs, the heater temperature changes. Particularly, in the case of a proportional output type sensor having an output characteristic proportional to the so-called oxygen concentration, the above-described variation in the heater resistance has a large effect, and the pump current, and thus the air-fuel ratio output value, also changes due to a temperature change. Therefore, such variations cannot be corrected by the same control system (a control device having the same specification combined with the sensor) (for example, individual differences cannot be corrected using the same control program).

The present invention has been made in view of the above points,
It is an object of the present invention to provide an exhaust gas concentration detecting device capable of preventing individual differences in heater element temperature caused by such fluctuations even if the heater resistance of the exhaust gas concentration detecting device varies.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides an exhaust gas concentration detecting element having a built-in heater, and a heater for keeping the temperature of the heater within a predetermined range. A power supply control device for controlling the amount of power supplied to the exhaust gas concentration detection device, and an exhaust gas concentration detection device comprising a coupler connecting the power supply control device and the exhaust gas concentration detection device, wherein the power supply control device includes a power supply for heating the heating heater; A switch for controlling a heating current applied from the power supply to the heating heater, a power supply for detecting a temperature of the heating heater, and a differential amplifier circuit. A bridge circuit comprising a first resistor connected in series with the heater and a circuit in which a second resistor and a third resistor connected in series with the series circuit are provided, When the switch for controlling the current is off, a power supply for detecting the temperature of the heating heater is applied to the bridge circuit, and a voltage at a connection point between the heating heater and the first resistor and the second voltage are applied to the bridge circuit. And a voltage at a connection point between the third resistor and the third resistor is input to the differential amplifier circuit, and the heating current is controlled based on an output of the differential amplifier circuit.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is an overall configuration diagram of a fuel supply control device including an exhaust gas concentration detection device according to the present invention.

In FIG. 1, reference numeral 1 denotes an oxygen concentration sensor (hereinafter, referred to as an “O ₂ sensor”) as an exhaust concentration sensor with a heater, which is a part of the exhaust concentration detection device, and is attached to an exhaust pipe 3 of the internal combustion engine 2. I have. In this embodiment, the O ₂ sensor 1 is of a proportional output type, and has a configuration described later,
An electronic control unit (hereinafter referred to as “ECU”) 4 detects the oxygen concentration of the exhaust gas and outputs a signal corresponding to the detected value.
To supply.

O ₂ electrical connection of the sensor 1 and ECU4, including the heater control is performed by the coupler 100 for middle interposed connection of the wire harness from the sensor body. Details of the structure of the coupler 100 and the heater control will be described later.

A three-way catalyst 5 is mounted on the exhaust pipe 3 downstream of the O ₂ sensor 1, and purifies components such as HC, CO, and NO _X in the exhaust gas.

The engine 2 is, for example, a four-cylinder four-cycle engine,
The intake air is supplied via the air cleaner 6 and the intake pipe 7. The air cleaner 6 is attached an intake air temperature (T _A) sensor 8, an electric signal indicative of the sensed intake air temperature T _A
Supply to ECU4. A throttle valve 9 is provided in the intake pipe 7. A throttle valve opening (θ _TH ) sensor 10 is connected to the throttle valve 9, and outputs an electric signal corresponding to the opening θ _TH of the throttle valve 9 and supplies it to the ECU 4.

The fuel injection valve 11 is provided for each cylinder between the engine 2 and the throttle valve 9 and slightly upstream of the intake valve (not shown) of the intake pipe 7. Each injection valve 11 is connected to a fuel pump (not shown). The ECU 4 is electrically connected to the ECU 4, and the valve opening time of the fuel injection is controlled by a signal from the ECU 4.

On the other hand, an intake pipe absolute pressure (P _BA ) sensor 12 is provided immediately downstream of the throttle valve 9, and the intake pipe absolute pressure P _BA
The ECU 4 supplies the ECU 4 with an electric signal corresponding to

Engine cooling water temperature (T
w) The sensor 13 includes a thermistor or the like, detects the engine cooling water temperature Tw, and supplies a corresponding electric signal to the ECU 4. The engine speed (Ne) sensor 14 is mounted around a camshaft (not shown) of the engine 2 or around a crankshaft.
The engine speed sensor 14 is connected to the crankshaft 18 of the engine 2.
A pulse (TDC signal pulse) is output at a predetermined crank angle position at every 0-degree rotation and supplied to the ECU 4.

FIG. 2 is a configuration diagram of an air-fuel ratio control apparatus comprising a O ₂ sensor 1 of the sensor body O ₂ sensor 1 and ECU4 like shown including the configuration of (sensor element portion).

The sensor body 20 of the O ₂ sensor 1 has a substantially cubic shape and is made of a solid electrolyte material having oxygen ion conductivity (for example, ZrO ₂ (zirconium dioxide)). The sensor main body 20 is a one-element type (a type including one oxygen concentration detecting element having one battery element and one oxygen pump element) in the case shown in FIG. The two wall portions 21 and 22 are formed in parallel with each other, and a gas diffusion chamber (gas diffusion limited region) 23 is defined between the two wall portions 21 and 22. The gas diffusion chamber 23 communicates with the inside of the exhaust pipe 3 through the introduction hole 24,
Exhaust gas is introduced through 24. Also, the first wall 21 and an outer wall formed on the wall 21 side
A gas reference chamber 26 is formed between the gas reference chamber 25 and the air reference chamber 25.

On both side surfaces of the first wall portion 21, one electrode pair 27a, 27b made of Pt (platinum) is provided so as to face each other to form a battery element 28, and both side surfaces of the second wall portion 22 are formed. Is similarly provided with the other electrode pair 29a, 29b and the oxygen pump element 30
Has made. On the other hand, the outer wall 25 is provided with a heater (heating element) 31 for heating the battery element 28 and the oxygen pump element 30 to promote their activation.

The outer electrode 27a of the battery element 28 of the electrodes is a coupler 1
It is connected to the inverting input terminal of the differential amplifier circuit 32 via “00”.

On the other hand, each inner electrode of the battery element 28 and the oxygen pump element 30
27b and 29b are grounded in this embodiment. The electrodes 27b, 2
Regarding the grounding of 9b, in the case shown, this is done by connecting to the sensor body, but as in the case of the outer electrode 27a, the lead wire is drawn out to the coupler 100.
The ECU 4 may perform grounding (GND).

The differential amplifier circuit 32 includes a reference voltage source 33 connected to its non-inverting input terminal and a switch 34 connected to the output terminal, and a current supply circuit (pump current supply means) of the O ₂ sensor 1.
35. The reference voltage of the reference voltage source 33
Vso is set to a voltage (for example, 0.4 V) generated in the battery element 28 when the supply air-fuel ratio is equal to the stoichiometric mixture ratio.

The switch 34 is controlled in accordance with the activation and deactivation of the sensor body 20, and is switched off when in the inactive state and on when it is activated.
In the case of the present embodiment, the switch 34 is connected to one end of a current detection resistor 36 for detecting a pump current, and the other end of the resistor 36 is connected to the outer electrode 29a of the oxygen pump element 30 via a coupler 100.
It is connected to the.

The current supply circuit 35 and the current detection resistor 36 are integrated into the ECU 4, and the voltage between both ends of the current detection resistor 36 is used as a detection output of the O ₂ sensor 1 for detecting the air-fuel ratio.
It is supplied to the A / D converter 401 of U4.

The coupler 100 also connects the heating heater 31 and an energization control device that controls energization of the heater 31 so that the resistance value of the heater 31 becomes a target resistance value. That is, the heater
The ECU 31 is provided with a heater system input / output circuit 413 for heater control and activity (temperature) detection, which is connected to the coupler 100. The circuit 413 functions as an energization control circuit that performs operations such as sending out an applied voltage (heater power) to the heater 31 and taking in heater resistance. Specifically, the circuit 413 controls the heater 31 so that the heater resistance becomes a target value. ON / OFF control.

Coupler 100 consists of an O ₂ sensor side of the connector 100a and the ECU side connector 100b. As the coupler 100, use O ₂
The sensor has a structure capable of accommodating a resistance for adjusting and correcting a variation in manufacturing among the sensors and the like, in particular, a variation in a built-in heater resistor. When incorporating this type of resistor into the coupler 100, of the two connectors 100a and 100b, the connector 100a on the sensor side is used.
It is a more convenient structure to dispose it on the side.

When employing a configuration to place a resistor in the sensor side of the connector 100a, are those the connector 100a is used as the used O ₂ sensor pair, the connector in the assembly or the like 10
0a and O ₂ sensor 1 can be handled as one unit. Therefore,
Above units the resistance value in accordance with the individual difference so as to be able to absorb the variations with a selected and resistance to the required ones, that is if so as to advance a number fabricate a unit consisting of the connector 100a and the O ₂ sensor 1 , the use O ₂ sensor
When combining with the ECU 4 side, even if there is a variation in the O ₂ sensor side to be combined at the time of manufacturing, etc., it is possible to compensate for the variation of the individual difference of the used O ₂ sensor only by connecting the two connectors 100 a and 100 b of the coupler 100. In this state, the air-fuel ratio control device shown in FIG. 2 can be assembled. In this case, the ECU 4 side, the O ₂ whether those variations of the sensor is how not considered individually being combined use, ECU 4 and the connector 100b internal structure of the ECU 4 (eg, ECU program), including the The same configuration and structure on the side can be used, and the connector 100b and the ECU 4 are connected to one.
Units having the same specification and configuration can be mass-produced as a unit, which contributes to an improvement in productivity even during mass production.

In addition, when the O ₂ sensor 1 fails or is repaired, a new O ₂
When the sensor needs to be replaced, the connector 10
It is sufficient to replace the unit part on the 0a and O ₂ sensor side with a completely new one, and even in such a case, the work such as repair does not spread to the connector 100b and the ECU 4 side (built-in resistor is connected to the connector 100b on the ECU side New O ₂
With the replacement of the sensor, since the resistance becomes possible to change to one of the resistance value corresponding to the variation of the exchange O ₂ sensor, as described above, the only exchange of up to O ₂ sensor and the connector 100a moiety enough Absent).

In particular, as will be described later, when the resistance for adjustment according to individual differences for adjusting individual differences is molded with resin from the viewpoint of ensuring waterproofness inside the coupler, it is no longer necessary to use the built-in resistor alone. Therefore, it is required to replace the entire coupler 100 including the O ₂ sensor and the connector 100b on the ECU side, and the connector 100 is not replaced.
Work such as removing and reconnecting multiple wiring cords between b and the ECU 4 is also necessary, but as described above, if built in the connector 100a, productivity may be reduced. In addition, since such inconvenience can be avoided, it is convenient.

Therefore, it is desirable that the built-in resistor in the coupler 100 be provided on the connector 100a side, but is not limited to such a structure.

3 to 5 show one specific example of the structure of a waterproof type coupler 100 that can incorporate different correction resistors for each O ₂ sensor. In the case shown in the figure, the installation position of the built-in resistor is set to the connector 100a on the sensor side from the above viewpoint.

As shown in FIGS. 3 and 5, the connector on the sensor side
100a is a resin case 101 (for example, made of polyester)
And a coupling portion 102 which is a detachable portion with the connector 100b on the ECU side. The coupling portion 102 is integrally attached to a front portion of the case 101 via a lock portion 103. ECU side connector 10
Reference numeral 0b denotes a housing 104 (for example, made of polyester) formed with an insertion portion 105 protruding from the front side of the coupling portion 102 on the connector 100a side, and a seal protection cap 106 (for example, made of polyester) from the rear end side. ), A required number (for example, 11) of wiring cords 107 are drawn out.

At the end of each wiring cord 107, a terminal 108 as shown in FIG. 4 is fixed as a female connection terminal. Each terminal 108 is housed and fixed in the connector 100b. Is provided with a seal 109 (for example, silicone rubber) (FIG. 5). Connector 100b
The wiring cord 107 drawn out from the side is guided to the ECU 4 side and connected to the heater system input / output circuit 413 and other necessary circuit parts.

On the inner surface of the coupling portion 102 of the sensor-side connector 100a,
A seal protection cap 111 (for example, made of polyester) for a seal 110 (for example, silicone rubber) shown in FIG. 5 is provided as shown in FIG. Further, a wafer 112 (for example, made of polyester) (see FIG. 5) constituting the bonding portion 102 has an ospin as shown in FIG.
113 is implanted as a male connection terminal corresponding to each terminal 108 on the connector 100b side. As shown in FIG. 5, when the two connectors 100a and 100b are connected, the male pin 113 and the terminal 108 are connected to each other. Makes an electrical connection.

As shown in FIG. 3, on both side walls of the case 101 of the connector 100a, pillar portions 115 having sleeves 114 (for example, galvanized) are formed, and O ₂ is formed from the rear wall side. The harness 116 from the sensor 1 is introduced. Because of this, the harness is
A seal 117 (for example, neoprene rubber) and a seal protection cap 118 (for example, made of polyester) through which the 116 passes are attached, and a harness 116 from the O ₂ sensor 1 is attached.
Is waterproofed by the seal 117 and the seal protection cap 118 and is drawn into the connector 100a of the coupler 100.

A wiring board (printed board) 119 is provided in the connector 100a.
And a wafer 120 (for example, made of polyester). The leg of each male pin 113 described above is
It is attached to 19 by soldering and connected to the wiring pattern on the substrate 119.

On the other hand, a board-in terminal 122 is attached to the end of each wiring cord 121 of the harness 116 from the O ₂ sensor 1 drawn into the coupler 100 as a terminal terminal. 122 is attached by soldering and connected to the wiring pattern on the substrate 119, so that variations in the terminal processing of the harness 116 can be absorbed. Thus mounted, the other end of the wiring cord 121 of the connected harness 116 is guided to the O ₂ sensor 1 side as shown in FIG. 3, the O ₂
Since it is connected to the above-described heater 31 of the sensor 1 and each electrode section, as described above, the connector 100a of the coupler 100
It will be assembled together as a one unit and to the use O ₂ sensor.

As shown in FIGS. 3 and 5, a plurality of sets of round pins 123 are implanted through the connector wafer 120.
The upper end and the lower end of each round pin 123 project up and down, respectively. The lower end of each round pin 123 is attached to the wiring board 119 by soldering, and is connected to a wiring pattern on the board 119.

Resistance to internal to the coupler 100, i.e. in the illustrated example for accommodating the connector 100a side resistance, the target resistance when the resistance value of the heater 31 Using O ₂ sensor is energized the heater 31 so that the target resistance It includes an individual difference adjusting resistor corresponding to the individual difference of the value, and an inactive discriminating resistor used when judging the activity and inactivity of the O ₂ sensor by the magnitude of the heater resistance value. There are two types of built-in resistors: a solid resistor and a chip resistor. The solid resistor 124 is fixed to the upper end of the round pin 123 protruding above the wafer 120 by soldering.
Fixed on 119 and connected to the wiring pattern.

In the case of the structure shown in FIG. 3, four sets of round pins 123 are provided. Therefore, as shown by an arrow 125 in FIG.
There are four resistance mounting positions where can be mounted. One of the mounting position for the solid resistance of these four locations are used for the label attachment of resistors for obtaining a correction coefficient of the element output using the O ₂ sensor.

The O ₂ sensor 1 of the present embodiment is a sensor on the proportional output side. In particular, in this type of sensor, an air-fuel ratio (A) detected by an individual difference due to a variation in the diameter of an introduction hole (diffusion hole) at the time of manufacturing. / F) may vary, but the resistance value of the label resistor is set to a value corresponding to the variation of the characteristic value when compared with a standard sensor body, for example. , Used for sensor output correction.

The above-described label resistor is stored, and one end of the label resistor is connected to the wiring pattern of the wiring board 119, the male pin 113, the terminal 108, and the wiring cord 107 in accordance with the electrical connection with the ECU 4 side. If it is configured to be connected to a power supply voltage (for example, a 5V voltage for a label resistor), the ECU 4 can input the individual difference correction information corresponding to the resistance value with the voltage or current value from the other end of the label resistor. it can. Therefore, in the case of this example, the ECU side connector 100
The connection function in b also includes a connection function for applying the label resistance voltage and capturing the individual difference correction value information. The information includes a wiring code and an input port (not shown) in FIG. It is read as output correction data by the control system in the ECU 4 via the ECU.

The remaining mounting positions of the four resistance mounting positions are the heater control of the O ₂ sensor 1 (HHR: heater high reference, HTR: heater trigger reference,
Used for mounting solid resistors used for HLR (heater low reference). HH of these three
For those for R and for the HLR, when controlling the temperature of the element used O ₂ sensor is used to set the heater activation temperature when controlling the heater 31 to the target activation temperature, Moreover, for the HTR It is used to set a heater target temperature that is the control center temperature.

The connection function of the ECU-side connector 100b is, for the heater control system, in addition to the above-mentioned information regarding HHR, HTR, and HLR, and the voltage applied to both ends of the heater 31 for driving the heater.
HPWR (heater power), that is, the supply of a heater ON / OFF drive voltage, which will be described later, the acquisition of information on the actual heater resistance, and thus the HBS (heater base) representing the heater temperature, and the detection of the heater resistance It has a connection function for applying a predetermined voltage RPWR (reference power) used for the above.

After the required electrical assembly of the sensor-side connector 100a, such as connection to the harness 116 and connection of a resistor, is performed, the internal space 126 is filled with resin. That is, coupler 100
Is a harness from one end wall (the rear wall of the connector 100a)
In addition, a wiring cord 121 of 116 is introduced, and the other side has a waterproof type connector structure, and a wiring board 119 and a resistor are embedded in a resin case 101 having one side open widely. The resin is molded inside, thereby ensuring reliable waterproofness, preventing corrosion of the internal printed wiring board, and improving the vibration resistance of the printed wiring board and the soldered portion.

In general, for the purpose of waterproofing, a structure in which a resin cover is attached to the coupler and the outer periphery is welded, or an O (O) ring is attached to the cover is conceivable, but as described above, the wafer 120 in the connector 100a of the coupler 100 is considered. The printed wiring board 119 is provided at the lower part of the wafer 120, and the storage processing of the built-in resistance such as soldering the correction resistance at the upper part of the wafer 120 is performed.
The waterproofing of the printed wiring board and the correction resistor, etc. is made by filling the resin and solidifying it integrally, so that the individual difference in the heater resistance of each O ₂ sensor can be controlled by the adjustment resistance in the connector 100a of the coupler 100. It can be absorbed, and by molding the resin without gaps inside, it is possible to improve the waterproof and vibration resistance, it is possible to block the air, and the corrosion of the printed wiring board part can be prevented .

The resistance circuit portion including the target resistance value adjustment resistance of the heater resistance incorporated in the coupler 100 is provided with a predetermined resistance value, and if maintained in a state of a predetermined resistance value, an intended function such as prevention of individual variation in heater element temperature. Where it is possible to keep
If a change in the contact resistance at the connection point occurs due to infiltration or vibration of rainwater during use, as a result, the initial adjustment and correction state may be deviated. However, when using the above-described mold structure, such a risk can be eliminated, and the resistance value can be maintained and secured at the initially set value for a long time, so that higher reliability and higher stability can be achieved. it can.

In the configuration of FIG. ₂ , the O2 sensor 1 and the ECU 4 are connected and connected by the coupler 100 having the structure shown in FIGS.

The ECU 4 has the following processing device in addition to the A / D converter 401, the heater input / output circuit 413, and the like described above.

That is, the ECU 4 includes a level conversion circuit 404, and the intake air temperature sensor 8, the throttle valve opening sensor 10, the intake pipe absolute pressure sensor 1
2 and the output signals from the engine coolant temperature sensor 13 are corrected to a predetermined voltage level by a level conversion circuit 404, and then sequentially output to an A / D converter 406 by a multiplexer 405.
Supplied to A / D converters 401 and 406 sequentially convert the supplied analog signals into digital signals and convert them into data buses.
Central processing unit (hereinafter referred to as “CPU”) 40 via 407
Supply 8

The output signal from the engine speed sensor 14 is subjected to waveform shaping by a waveform shaping circuit 409, and then is converted into a TDC signal pulse by the CPU 408.
And also supplied to the counter 410.
The counter 410 measures the time interval from the previous input of the TDC signal pulse from the engine speed sensor 14 to the current input thereof, and the count value Me is proportional to the reciprocal of the engine speed Ne. The counter 410 transfers the count value Me to the data bus 407.
To the CPU 408 via the.

The CPU 408 is further connected to a read-only memory (hereinafter referred to as “ROM”) 411, a random access memory (hereinafter referred to as “RAM”) 412, and drive circuits 414 and 415 via a data bus 407. RAM412 temporarily stores the calculation results in the CPU 408, ROM 411 stores a control program executed by the CPU 408, the map for calculating the fuel injection time T _OUT of the fuel injection valve 11 or the like.

The CPU 408 is also supplied with a later-described heater activation signal HACT (heater act) generated by the heater system input / output circuit 413. The drive circuit 414 sends a switching drive signal to the switch 34 to turn ON / OFF the power supply to the O ₂ sensor 1 element based on the heater activation signal.

Further, the CPU 408 determines an engine operation state such as a feedback operation area based on the above-described various engine parameter signals including a detection signal of the O ₂ sensor 1 and, in accordance with the engine operation state, according to a control program (not shown). The fuel injection time _TOUT of 11 is calculated, and a drive signal based on the calculation result is supplied to the fuel injection valve 11 via the drive circuit 415. Thus, during the feedback operation of the engine 2, the supply air-fuel ratio is feedback-controlled to the target air-fuel ratio.

During the air-fuel ratio feedback control, the oxygen concentration is detected by the O ₂ sensor 1 on the lean side and the rich side of the air-fuel ratio as follows.

That is, with the operation of the engine 2, the exhaust gas is
When introduced into the gas diffusion chamber 23 through the
An oxygen concentration difference occurs between the inside and the inside of the gas reference chamber 26 into which outside air is introduced. When the battery element 28 is in an active state, a voltage Vs is generated between the electrodes 27a and 27b of the battery element 28 according to the oxygen concentration difference, and this voltage Vs is applied to the harness shown in FIGS. Wiring code 121 and coupler in 116
The signal is supplied to the inverting input terminal of the differential amplifier circuit 32 via the board-in terminal 122 in 100, the wiring pattern on the printed wiring board 119, the male pin 113, the terminal 108, and one wiring code 107. As described above, the reference voltage Vso supplied to the non-inverting input terminal of the differential amplifier circuit 32 is set to the voltage Vs generated in the battery element 28 when the supplied air-fuel ratio is equal to the stoichiometric mixture ratio.

Therefore, when the supply air-fuel ratio is on the lean side,
When the voltage Vs of the battery element 28 becomes smaller than the reference voltage Vso, the output level of the differential amplifier circuit 32 becomes a positive level.

Here, when the temperature of the heater 31 for heating is within an activation temperature range that is set at a predetermined width above and below the target control temperature as described later, the switch 34 is turned on. The positive level voltage is applied to the oxygen pump element 30 through the switch 34 and the current detection resistor 36, and further through an energizing path via the coupler 100 according to the above.
By the application of the positive level voltage, when the oxygen pump element 30 is in an active state, oxygen in the gas diffusion chamber 23 is ionized and released through the electrode 29b, the second wall 22, and the electrode 29a. , O ₂ sensor 1 and pump current flows from electrode 29a to electrode 29b.

On the other hand, when the supply air-fuel ratio is on the rich side by the voltage Vs of the battery element 28 becomes greater than the reference voltage Vso, the output level of the differential amplifier circuit 32 becomes a negative level, by the action described above and the reverse, O ₂ Oxygen outside the sensor 1 is pumped into the gas diffusion chamber 23 via the oxygen pump element 30, and a pump current flows from the electrode 29b toward the current 29a. When the supply air-fuel ratio is equal to the stoichiometric mixture ratio, the voltage Vs of the battery element 28 becomes equal to the reference voltage Vso, so that the output level of the differential amplifier circuit 32 becomes 0, and oxygen is not pumped or pumped. Therefore, no pump current flows.

Thus, pumping and汲込oxygen is performed so that the oxygen concentration in the gas diffusion chamber 23 becomes constant, since the pump current flows, the pump current I _P is lean and rich feed air On the side, they are respectively proportional to the oxygen concentration of the exhaust gas. This pump current value _IP is a current detection resistor
The voltage drop appearing across 36, is supplied to ECU4 as a detection signal of the O ₂ sensor 1 as described above, the air-fuel ratio is detected based on this.

Air-fuel ratio detection based on the O ₂ sensor output is performed when in the active state as described above. In Figure 6 and below,
An example of the configuration and operation of a sensor heater control circuit including a temperature control using a heater resistance value and an activation / inactivation discrimination process is shown.

As shown in FIG. 6, the heater control system includes an input / output circuit 413 in the ECU 4, a resistance network formed by built-in resistors in the coupler 100, and a heater 31 on the sensor body side. The input / output circuit 413 has a heater activation signal HACT (FIG. 7A).
And a P.MO for the main drive of the heater / power HPWR (FIG. 8 (a)) system.
An SFET 451, first and second transistors 452 and 453 for applying a reference power (FIG. 8B) system, and first and second transistors used to determine the heater temperature from the value of the heater resistance _RH . Second and third differential amplifier circuits (operation amplifiers) 454, 455, and 456, and first, second, and third differential amplifier circuits 454 to 456 in which outputs are supplied to one input terminal.
AND gates 457, 458 and 459 are provided.

Control processing circuit 450, an output terminal 450 ₁ for applying a clock CK generated at a constant period to the first to the other input terminal of the third AND gate 457 to 459 as a timing pulse for capturing heater base HBS , Each AND gate 457 ~ 459
Input terminals 450 ₂ , 450 ₄ , 450 _{5 to} which the output of the clock CK is supplied, and an output terminal 450 ₃ for transmitting an on / off control signal synchronized with the clock CK to the first and second transistors 452, 453.
Output terminal for sending heater ON / OFF signal (Fig. 7 (b))
450 _6, and an output terminal 450 ₇ for sending a heater activation signal HACT.

Wherein between the source and the drain of the FET451 for the main drive, a power supply V _B, it is inserted between the wiring cord 107 ₁ connecting end, its gate, the control for delivering heater ON / OFF signal It is connected to the output terminal 450 ₆ processing circuit 450. Further, the wiring cord 107 _first connection end, the circuit 41
3 is grounded via a resistor 460 (resistance value is, for example, 10 KΩ).

The first transistor 452, the emitter is grounded, whose base is connected on synchronized with a clock CK having a predetermined period, the output terminal 450 ₃ of the control processing circuit 450 for delivering off-control signal Have been. The collector of the first transistor 452 is connected to the base of the second transistor 453, the emitter-collector of the second transistor 453 is inserted between the power source V _B, a wiring cord 107 ₂ connecting end ing. By the first and second transistors 452 and 453 are switched by the signal from the output terminal 450 _third control processing circuit 450, RPWR a constant voltage for detecting the heater resistor (for example 10V) is through wiring cord 107 ₂ The voltage is applied to the resistance network in the coupler 100 at a constant period.

One input terminal of the first differential amplifier circuit 454 (the inverting input), along with being connected to the connection end of the wire cord 107 ₃ via an input resistor 461 (e.g., resistance 1K ohm), the second and third also one input terminal of the differential amplifier circuit 455, 456 of which is connected to the connection end of the wire cord 107 ₃ via the resistor 461 as well. The other input terminal of the first differential amplifier circuit 454 (non-inverting input terminal) via an input resistor 462 (e.g., resistance 1K ohm) is connected to the connection end of the wiring cord 107 _4, also the second and third the other input terminal of the differential amplifier circuit 455, 456 of the 3 is connected to the wire cord 107 _5, 107 ₆ connecting end through an input resistor, respectively 463 and 464 (e.g., resistance 1K ohm).

The circuit configuration of the interior of the coupler 100 side, as shown in Figure 6, first connection end wiring cord 107 ₁ which is connected to the FET451 for the main drive is on the direct in the coupler 100 printed circuit board 119 a wiring pattern It is configured to be connected to the heater board in terminal 122 ₁ through.

The board-in terminal 122 ₁ is connected to O ₂ via a wiring cord 121 _1.
It is connected to one end of the heater 31 of the sensor 1. Heater 31
Is connected to a heater board-in terminal 122 ₂ of the coupler 100 via a wiring cord 121 ₂ , and the board-in terminal
122 ₂ is connected to the connection end of the wire cord 107 ₇ to the output circuit 413 side through the wiring pattern on the substrate 119. The illustrated case, the wiring cord 107 ₇ output circuit 413
Grounded inside. Such heater ground HG
Regarding the ND, in addition to the above-described configuration, the ND may be performed by connecting to the sensor body as in the case of the electrodes 27b and 29b of the sensor body 20 described above, or the ND may be a coupler case ground as shown by a broken line. It is also possible to adopt a simple configuration.

The heater 31 is provided with the FET 451 by the above-described configuration.
The heater power HPWR is applied according to the ON / OFF control of.

In the coupler 100, in addition to the above HPWR system, built-in resistors R _{1 to} R
₁₁ is formed. reference·
The connection end of power RPWR system wiring cord 107 ₂ is
Connected to one end of each of the resistors R ₁ , R ₂ , R ₃ and R ₄ . The resistance R ₁ (for example, a resistance value of 5.2 KΩ) is a resistance that supplies a current for detecting the heater resistance R _H to the heater 31.
The other end is connected to a connection point A. The connection point A is connected to the board-in terminal 122 ₁ described above directly, thus the heater 31 is connected to the resistor R ₁ in series.

On the other hand, the connection point A is connected to a resistor R ₈ (for example, a resistance value of 4.0K).
Omega) is branched to the side, the input-output circuit via the resistor R ₈
It is also connected to a wiring cord 107 ₃ connecting end for HBS system to the 413 side.

The other ends of the resistors R ₂ (for example, a resistance value of 5.2 KΩ), R ₄ (for example, a resistance value of 5.4 KΩ), and R ₆ (for example, a resistance value of 5.2 KΩ) are respectively a resistor R ₃ , a resistor R _5, and a resistor R _7. is connected to each one end of these resistors R _3, the other ends of the resistor R ₅ and the resistor R ₇ is connected to the ground wiring pattern of the above-described board-in terminal 122 _2. Therefore, the above resistors R ₂ and R ₃
A series circuit, and the resistance of the series circuit, the resistor R ₄ and the resistor R ₅ and
A series circuit of the R ₆ and the resistor R ₇ is connected in parallel with the series circuit composed of the heater 31 from the resistor R _1, to constitute a bridge circuit respectively.

Furthermore, the connection point B between the resistor R ₂ and the resistor R ₃ in each bridge circuit, a connection point D of the connection point between the resistor R ₄ and the resistor R ₅ C, and a resistor R ₆ and the resistor R ₇ are respectively the resistance R ₉ (for example, resistance 1.4K
Omega), the resistance R ₁₀ (for example, resistance 1.3Keiomega), and a resistor R ₁₁ via (e.g. resistance 1.5 k), for HTR system to the output circuit 413 side, the wiring cord for HHR for systems, and the HLR system It is connected to a 107 _{4-107 6} connecting end.

The resistors R ₃ , R ₅ , and R ₇ are solid resistors 124 mounted at three of the four resistor mounting positions set by the set of round pins 123 described with reference to FIGS. 3 and 5. in a those composed, when performing heater control, the resistance R ₃ controlled central temperature, also the resistor R ₅ is the maximum temperature of the activation temperature range, a further resistor R ₇ is lower limit temperature, to set each used, the heater 31 respectively using the O ₂ sensor
Is set to a predetermined resistance value in accordance with the fixed difference so as to absorb the variation of.

Note that the resistors R ₂ , R ₄ , R ₆ and the resistors R _{8 to} R ₁₁ branched from the connection points A, B, C, D and connected in series to the respective branch points.
Is composed of a chip resistor.

Since a constant voltage is applied as the reference power RPWR, when the RPWR is applied, the connection points B, C, and D generate a predetermined divided voltage determined according to the resistance value of each resistor of each series circuit, On the other hand, since a divided voltage (accordingly, a voltage representing the heater temperature at that time) is generated at the connection point A in accordance with the magnitude of the heater resistance _RH , the actual heater temperature is reduced by using these voltages. Each of the differential amplifier circuits 454 to 4 has three points: whether the temperature is higher or lower than the target control temperature, whether the temperature exceeds the upper limit of the activation temperature, and whether the temperature is lower than the lower limit.
A comparison can be made by 56 (FIG. 7 (d)).

As described above, in this embodiment, the correction resistor is incorporated in the O ₂ sensor side, that is, in the connection coupler 100 in accordance with the individual difference, and not only at the control circuit side in the ECU 4 but also at one point of the target control temperature. In order to have a function to determine the upper and lower limits of the activation temperature as well as the control of the control temperature, the sensor has _three correction resistors R ₃ , R ₅ and R ₇ for the control center temperature, the upper limit and the lower limit, and the heater of each sensor element. It is possible to perform temperature control appropriately by eliminating 31 variations.

Further, when the sensor element has upper and lower correction resistances unique to the sensor element, even when the relationship between the heater resistance and the temperature is not necessarily linear, it can be easily dealt with and appropriate determination can be performed. by the heater 31 to the target activation temperature suitable for the used sensor elements to the duty control as described later, O ₂ sensor output stability can also be achieved, in particular, variations in the heater temperature pumping current, therefore the air-fuel ratio detected It becomes suitable for heater control of the proportional output type O ₂ sensor 1 which affects the value.

In the configuration of FIG. 6, for example, the control center temperature is 700 ° C.,
The temperature is controlled by setting the upper limit temperature to 800 ° C. and the lower limit temperature to 600 ° C. The following is a setting example of the relationship between temperature, resistance, and voltage in that case.

800 ° C / 5.625Ω / 6.2356V (2.356mV / ° C) 700 ° C / 5.2Ω / 6.0V (4.25mΩ / ° C) 600 ° C / 4.775Ω / 5.7444V (2.55mV / ° C) The above resistors R ₃ , R ₅ , each of the resistance values of R _7, R ₃ is 5.2K
Omega, R ₅ is 5.625KΩ, R ₇ is set at 4.775Keiomega.

In the above configuration, the input / output circuit 413 sends out a heater power HPWR that is turned on / off in accordance with a heater on / off signal as shown in FIG. 7B. HPWR is in between time _{t 10 ~t 12, t 14 ~t} 15 shown in FIG. 7, the heater ON / O
FF signal is ON only tau _ON time at every predetermined period tau (e.g. 16.384msec), since the OFF tau-tau _ON time (e.g. 256μsec), a voltage is applied to the heater 31 over tau _ON time Correspondingly You. On the other hand, during the time corresponding to the τ−τ _ON time,
The reference power RPWR closes with the heater circuit. The RPWR Since dispatched in synchronism with the clock CK having a constant period as described above, the OFF state is continuously heater ON / OFF signal as between time t ₁₂ ~t ₁₄ shown in FIG. 7 Even when continuing, a constant voltage is applied to the resistor network on the coupler 100 side as RPWR.

FIG. 8 is a timing chart of the HPWR OFF timing, RPWR application timing, and CK for explaining the heater response (F characteristic).
The following shows the specific relationship of the occurrence timing. FIG.
As shown in (b), the HPWR OFF time T ₁ (T ₁ = τ−
τ WR) is applied for T ₂ + T ₃ times (T ₁ = T ₂ + T ₃ ) during the time period (τ _ON ). On the other hand, the clock CK, as shown in FIG. (C), is generated in accordance with the latter half portion T ₂ of the pulse applied RPWR.

The reason for setting the control cycle as described above is as follows.

The heater 31 is ON the HPWR, but is duty-controlled (when OFF time T ₁ of the HPWR is 256μsec as described above, the maximum ON duty ratio is 97%) by OFF, the HPWR
ON and OFF are performed by the drive MOSFET 451, and there is a delay in switching the FET 451 from ON to OFF. On the other hand, the control of the RPWR is performed by turning on and off the transistor 453, and there is a delay in switching the transistor 453 from OFF to ON. In order to detect the heater resistance _RH stably and with high accuracy, the overlapping periods of both the HRWR and RPWR must not match (if they overlap, the detection when the heater temperature is calculated as a voltage conversion value) The power supply voltage itself will fluctuate. Therefore, in order to avoid this, that is, to ensure that a constant voltage is always applied as RPWR,
The HPWR must not overlap), and a clock CK must be generated as a timing pulse for taking in the heater resistance during the voltage stabilization period after the application of the RPWR.

Therefore, and be provided with a T ₂ hours of the first half portion of the applied pulse of RPWR, this OFF delay FET451, the bridge voltage of the resistor circuit of the coupler 100 to ON delay and actually voltage of the transistor 453 is applied For example, T ₂ is set to 192 μsec in consideration of the stabilization time, while T _{3 in} the latter half is set to T ₁ −T ₂ = 64 μsec. The T ₃ is the minimum pulse width of the clock CK, when latching the heater base HBS level indicating heater resistor by such pulses, allows the detection of stable and high precision.

That is, when the RPWR and the clock CK are generated as described above, when the RPWR is applied, the seventh point from the connection point A in the coupler 100
Voltage corresponding to the heater resistance value at time t ₁₀ ~t ₁₆ as shown in (d) of FIG retrieved, the heater resistance R _H at each time point
Is latched on the circuit as HBS. On the other hand, at the same time, a predetermined divided voltage obtained by dividing RPWR by the respective resistors R ₂ and R ₃ is generated at the connection point B, and this is taken out as a heater trigger reference HTR. Since HBS represents the heater resistance R _H , and thus the actual temperature of the heater 31, while HTR represents the resistance value corresponding to the heater target temperature, and thus the control center temperature, the respective signals correspond to the first differential amplifier circuit 454. , The output corresponding to whether the actual temperature of the heater 31 is higher or lower than the control center temperature is compared with the first AN.
It is supplied to D gate 457. Since the clock CK is applied to the AND gate 457, the output is given to the control processing circuit 450 through the AND gate 457, and the circuit 450 forms a heater ON / OFF signal according to the comparison result described above. , HPWR ON
/ OFF.

In the case of the operation example shown in FIG. 7, the time _{t 10, t 11, t 14} , t
_At each of the timings _{15, since} the temperature is below the target control temperature, the HPWR is turned on, and the times t ₁₂ , t ₁₃ , t ₁₆
At each of the timings, the control is performed so as to be turned off.

Further, when RPWR is applied, in addition to the above-mentioned control, a process of discriminating between active and inactive is simultaneously executed.

When RPWR is applied, a predetermined voltage divided by the resistors R ₄ , R ₅ , and R ₆ , R ₇ is generated at the connection points C and B in the coupler 100, respectively, and the heater high reference The signals are taken out as the HHR and the heater low reference HLR, and the respective signals are supplied to the second and third differential amplifier circuits 455 and 456. On the other hand, these differential amplifier circuits 455 and 456 are also supplied with the signals for the HBS described above. HHR and HLR
Indicate the upper and lower limits of the heater activation temperature, respectively. Therefore, in each of the differential amplifier circuits 455 and 456,
By comparison with the above, an output corresponding to whether the actual temperature of the heater 31 exceeds the upper limit value of the activation temperature and an output corresponding to whether the actual temperature of the heater 31 is lower than the lower limit value are taken out and controlled through the respective AND gates 458, 459. It is supplied to the processing circuit 450. AN
The signal provided to the circuit 450 via the D gates 458 and 459 is
Active temperature range represents the temperature of the heater 31 when viewed as a reference, the control processing circuit 450 forms a heater activation signal HACT as shown in FIG. 7 on the basis of this (a), the output terminal 450 ₇ Sent from.

Namely, speaking in the case of Figure 7, since below the lower limit temperature at time t _10, and determines that the inert, outputs a low level to indicate an inactive state. O ₂ sensor 1 is not in the active state, thus the heater resistance R _H is low heater temperature
Is smaller, it can be determined that the O ₂ sensor 1 is inactive. In this manner, the inactivity of the O ₂ sensor 1 can be determined by checking the magnitude of the heater resistance R _H , and the state where the HPWR for heating is not actually added to the heater 31, that is, RP
Just by supplying the WR application pulse, accurate determination can be made by sampling.

For Figure 7 at time t _13, the state heater temperature is higher than the upper limit, thus the heater resistance R _H is small (low temperature inactive)
However, it outputs a low level because it is in a high temperature state (high temperature inactive). The reason why the low-level signal indicating inactivity is transmitted at a high temperature exceeding the upper limit is to avoid over-energization of the sensor element as described later.

As described above, when the heater 31 is out of the active temperature range between the upper and lower limits and the heater 31 is in the low temperature state or the high temperature state, the heater activation signal HACT is set to the low level. As shown at times t ₁₁ , t ₁₂ , t _{14 to} t ₁₆ , it is determined that it is in the active state, and a high level indicating this is output.

With the heater activation signal HACT formed in this way,
Turns ON / OFF the power supply to the O ₂ sensor 1 element part. That is, when the heater resistance R _H is larger than the resistance value corresponding to the lower limit temperature and smaller than the resistance value corresponding to the upper limit temperature, therefore, when the heater 31 is not in the low temperature state or the high temperature state,
Based on the HACT as described above, a command to supply the pump current of the O ₂ sensor 1 is generated.
Is turned on so that the pump current _IP can flow.
As a result, it is possible to prevent element destruction such as blackening due to over-current at a low temperature or a high temperature in the O ₂ sensor 1 element portion, and to stabilize the output of the O ₂ sensor 1 and accurately measure the oxygen concentration. The air-fuel ratio feedback control can be performed when the air-fuel ratio can be detected. That is, the resistance value of the heater 31 reflects the temperatures of the battery element 28 and the oxygen pump element 30, and the output of the O ₂ sensor 1 is affected by the temperature change of these elements as described above. O ₂ due to this effect is determined by using the magnitude of the heater resistance R _H
A change in the output of the sensor 1 is also prevented.

As described above, whether the O ₂ sensor 1 is active or inactive is determined. The heater control circuit shown in FIG. 6 has a high detection accuracy of the heater temperature. Therefore, the accuracy of the deactivation determination using the heater resistance _RH is further improved by the high-precision heater temperature detection. _{2 After} sensor 1 is activated,
Even when the engine's low load state continues and the temperature of the sensor body drops due to the temperature of the exhaust gas and becomes inactive due to this, the inactive state after such activation determination is properly determined. It is possible.

The present invention is not limited to the above embodiment, and various modifications are possible. For example, applicable sensor elements are not limited to those of the proportional output type. In addition, even if it is a proportional output type, the element structure is not limited to that shown in FIG.

(Effects of the Invention) According to the present invention, an exhaust gas concentration detecting element having a built-in heating heater, and the amount of electricity supplied to the heating heater controlled by the heating heater so as to keep the temperature of the detecting element within a predetermined range. In the exhaust gas concentration detecting device comprising a power supply control device and a coupler connecting the exhaust gas concentration detecting element and the power supply control device, the exhaust gas is detected by detecting the temperature of the heating heater separately from the heating circuit of the heating heater. A circuit that detects the temperature of the concentration detection element is provided, so that the temperature of the exhaust concentration detection element as a control target can be accurately measured, and multiple resistors that constitute the bridge circuit of the temperature detection circuit are provided in the coupler. Therefore, when replacing the exhaust gas concentration detection element, it is not necessary to adjust the energization control device one by one by performing it integrally with the coupler, and it is one of the resistors that constitute the bridge circuit in the coupler. May be set to a predetermined resistance value according to the individual difference so as to absorb the variation of the heater for heating. Since the amount of current supplied to the heating heater is controlled using the temperature detected by the temperature detection circuit as an index, it is possible to relatively easily prevent individual differences in the heater element temperature.

Also, by providing three bridge circuits and three correction resistors for the control center temperature, the upper limit, and the lower limit, it is possible to provide a function of determining the upper and lower limits of the activation temperature of the exhaust gas concentration detection element. Having.

[Brief description of the drawings]

1 shows an embodiment of the present invention, FIG. 1 is an overall configuration diagram of a fuel supply control device, FIG. 2 is a configuration diagram of an air-fuel ratio control device including the structure of a sensor main body of an O ₂ sensor, 3 is a perspective view showing a configuration of a coupler for connection, FIG. 4 is a diagram showing connection terminals for coupling of the coupler, FIG. 5 is a sectional view showing an internal structure of the coupler, and FIG. 6 is a configuration of a heater control circuit. FIG. 7 is a timing chart for explaining the operation and the like of the control processing circuit in FIG. 6, and FIG. 8 is an explanatory diagram showing an example of a control cycle on the control processing circuit side. 1 ...... O ₂ sensor, 4 ...... electronic control unit (EC
U), 20 ...... sensor body (sensor element), 31 ...... heater, 100 ...... coupler, 124 ...... solid resistance, 413 ...... heater system input-output circuit, 450 ...... control processing circuit, R ₁ to R ₁₁ ......
resistance.

Claims (3)

(57) [Claims] An exhaust concentration detecting element having a built-in heating heater; an energization control device for controlling an energization amount of the heating heater so as to keep the temperature of the heating heater within a predetermined range; In an exhaust gas concentration detection device including a coupler that connects an element and a conduction control device, the conduction control device includes a power supply for heating the heating heater,
A switch for controlling a heating current applied from the power supply to the heating heater; a power supply for detecting a temperature of the heating heater; and a differential amplifier circuit, wherein the heating heater is provided inside the coupler. A bridge circuit consisting of a first resistor connected in series with the first resistor, and a circuit in which a second resistor and a third resistor are connected in series with the series circuit, When the switch for controlling the heater is off, a power supply for detecting the temperature of the heater for heating is applied to the bridge circuit, and the heater for heating and the first
The voltage at the connection point with the resistor and the voltage at the connection point between the second resistor and the third resistor are input to the differential amplifier circuit, and the heating current is calculated based on the output of the differential amplifier circuit. An exhaust gas concentration detection device characterized by controlling a switch to be controlled. 2. A circuit according to claim 1, wherein at least one of a plurality of resistors constituting a bridge circuit with a heater for heating formed in said coupler is provided as a solid resistor on a wiring board provided in said coupler. 2. The exhaust gas concentration detecting device according to claim 1, wherein the exhaust gas concentration detecting device is fixed to a terminal and the other resistor is directly fixed on the wiring board as a chip resistor. 3. A bridge circuit with a heater for heating formed in the coupler includes a first resistor connected in series with the heater for heating, and a first resistor connected in parallel with the series circuit.
, And a voltage at a connection point between the heater and the first resistor, and a voltage at a connection point between the heater and the first resistor. The first resistor and the third resistor connected in parallel with
2. The exhaust gas concentration detecting device according to claim 1, wherein three differential amplifier circuits for connecting a voltage at a connection point of the resistor to an input terminal are provided in the conduction control device.