JPH0224550A - Controlling device of heater power of oxygen concentration sensor with heater - Google Patents

Abstract

PURPOSE:To obtain a stable output signal from a detecting element by curbing the lowering of the temperature of the detecting element of an oxygen concentration sensor immediately after the transition from an idle state to a non-idle state. CONSTITUTION:A target power to be supplied to a heater M3 in accordance with a state of operation detected by an operating state detecting means M5 is determined by a target power determining means M6, and a power supplied to the heater M3 is controlled in accordance with the determined target power by a supply power control means M7. Moreover, from the result of detection by an idle state detecting means M8, the time of continuation of an idle state is calculated by an idle time calculating means M9, while a change in the state, i.e. the transition from the idle state to a non-idle state, is detected by a state change detecting means M10. When the change in the state is detected, the target power is corrected by a target power correcting means M11.

Description

Detailed Description of the Invention [Industrial Application Fields] The present invention controls the amount of power supplied to a heater provided in an oxygen concentration sensor that detects the oxygen concentration in exhaust gas between internal combustion engines. The present invention relates to a heater power control device for an oxygen concentration sensor with a heater.

[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 seismic intensity sensor, in order to obtain a stable detection signal, it is necessary to set the detection element to a nearly constant activation temperature, but the temperature of the detection element changes depending on the amount of heat received from the exhaust gas. So,
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 Publication No. 5553 and Japanese Patent Publication No. 63-1540, there is a device that indirectly predicts the exhaust temperature based on the load condition such as the intake air amount of the internal combustion engine and controls the amount of current applied to the heater. There is.

By the way, in such a device, during transient operation of the internal combustion engine (during sudden acceleration, etc.), the exhaust temperature rises later than the change in the load condition of the internal combustion engine, so the heater energization is adjusted according to the actual exhaust temperature. Although there are inconveniences such as the inability to control the amount, as a solution to these inconveniences,
As described in Japanese Unexamined Patent Publication No. 169755/1983, a device has also been proposed that attempts to control the amount of current to the heater based on the rate of change in the load of the internal combustion engine during transient operation.

[Problems to be Solved by the Invention] However, when a vehicle equipped with an internal combustion engine equipped with such a conventional device starts and accelerates after idling due to a traffic stop, etc., the exhaust pipe of the internal combustion engine may open during idling. As it cools down, the temperature of the detection element of the oxygen concentration sensor decreases. Particularly when the idling state continues for a long time, the temperature of the detection element decreases markedly. However, the detection element temperature could not be raised to the desired activation temperature. Therefore, by controlling the air-fuel ratio based on the detection results of this oxygen concentration sensor, the A/F
becomes overrich, and as a result, CO in the exhaust
This resulted in problems such as increased generation of HC, exhaust odor, and deterioration of drivability.

The present invention has been made in view of the above-mentioned problems, and suppresses the decrease in the temperature of the detection element of the oxygen concentration sensor immediately after the transition from idle state to load operation, thereby reducing the generation of CO and HC and the generation of exhaust odor. An object of the present invention is to provide a heater power control device for an oxygen concentration sensor equipped with a heater, which prevents this and improves drivability.

Structure of the Invention [Means for Solving the Problems] In order to achieve the above object, the present invention has the following structure as a means for solving the problems. That is, the heater power control device for the heater-equipped oxygen concentration sensor of the present invention, as illustrated in FIG. an oxygen concentration sensor M4 having a heater M3 that detects the internal combustion engine; an operating state detecting means M5 that detects the operating state including at least the load state of the internal combustion engine M1; Target power determining means M6 that determines the target power to be supplied to the heater M3; Supply power control means M7 that controls the power to be supplied to the heater M3 according to the target power determined by the target power determining means M6; A heater power control device for an oxygen concentration sensor with a heater, comprising: idle state detection means M8 for detecting the idle state of the internal combustion engine M1; and based on the detection result of the idle state detection means M8, Idle time calculation means M9 that calculates the duration of the idle state and state change detection that detects a state change in which the internal combustion engine M1 shifts from an idle state to a non-idle state based on the detection results of the idle state detection means M8. means MIO, and when the state change is detected by the state change detection means MIO, the target power determination means M6 determines the duration of the idle state calculated by the idle time calculation means M9. The present invention is characterized in that it is provided with target power correction means MIX for correcting the target power.

[Operation] The heater power control device for the oxygen concentration sensor with a heater of the present invention configured as described above has the target power determining means M6 controlling the heater M3 according to the operating state detected by the operating state detecting means M5. The target power to be supplied is determined, and the power supply control means M7 controls the power to be supplied to the heater M3 according to the determined target power. The idle time calculation means M9 calculates the duration of the idle state of the internal combustion engine M1, and the state change detection means MIO detects a state change in which the internal combustion engine M1 shifts from an idle state to a non-idle state. and,
When the state change is detected, the target power determining means M
6, the target power determined by the target power correction means M
It works to correct according to the duration of the idle state calculated by ll.

Therefore, the longer the idle state continues, the more power can be supplied to the heater M3 at the time of transition to the non-idle state, increasing the temperature rise of the oxygen concentration detection unit M2 immediately after the transition.

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

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

As shown in the figure, the intake pipe 4 of the internal combustion engine 2 is provided with a throttle valve 8 that opens and closes in conjunction with an accelerator pedal 6. On the upstream side of the throttle valve 8, the flow rate is adjusted by opening and closing the throttle valve 8. The internal combustion engine 2 is equipped with an air flow meter 10 that detects the intake air amount of the internal combustion engine 2, and an intake temperature sensor 12 that detects the temperature of the intake air. Further, the intake pipe 4 is provided with a throttle position sensor 14 that includes an opening sensor that detects the opening of the throttle valve 6 and an idle switch that is turned on when the internal combustion engine 2 is idling.

On the other hand, in the exhaust pipe of the internal combustion engine 2, there is 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 ternary sensor for purifying the exhaust gas. A catalytic converter 22 is provided.

The internal combustion engine 2 also includes the above-mentioned air flow meter 10 as an operating state detection means for detecting its operating state.
In addition to the intake temperature sensor 12, throttle position sensor 14, and oxygen concentration sensor 20, the distributor 21
The rotation speed sensor 26 detects the rotation speed of the internal combustion engine from the rotation of the L/L 24a of 1, and also the distributor 2
A cylinder discrimination sensor 28 that outputs a pulse signal once every two revolutions of the crankshaft of the internal combustion engine 2 in response to 40 rotations, and a water temperature sensor 30 that detects the temperature of the cooling water of the internal combustion engine 2 are provided. The distributor 24 is for distributing the high voltage output from the igniter 32 to the spark plugs 34 of each cylinder in synchronization with the crank angle of the internal combustion engine 2, and the ignition timing of the spark plugs 34 depends on the high voltage output from the igniter 32. Determined by voltage output timing.

Detection signals from each of the sensors are output to an electronic control unit 4o configured as a logic operation circuit centered on a microcomputer.

As shown in FIG. 3, the electronic control device 40 includes a CPU, R
It is mainly composed of a one-chip microcomputer 42 that has a built-in OM5 RAM, etc., and is equipped with a human output board. A rotation speed sensor 26, a cylinder discrimination sensor 28, and an igniter 32 are directly connected to the human output boat of this one-chip microcomputer 42.
The D conversion input circuit 44 is connected to a heater energization control circuit 4 which uses the battery 46 as a power source to control the power supplied to the heater 20b of the oxygen concentration sensor 20, and a drive circuit 52 which drives the fuel injection valve 50. .

Note that a voltage application circuit 54 is connected to the detection element 20a of the oxygen temperature sensor 20, and applies a predetermined voltage VLS for detection to the detection element 20a.

The A/D conversion input circuit 44 includes an air flow meter 1o.
, intake temperature sensor 12, throttle position sensor 14
, a water temperature sensor 30, and other various sensors that output analog signals are connected. Therefore, the CPU can read various parameters reflecting the operating state of the internal combustion engine 2 via the A/D conversion input circuit 44 and know them one by one. The A/D conversion input circuit 44 also includes the output of a heater energization control circuit PI4B that applies voltage to the heater 20b of the oxygen concentration sensor 20, and the output of an amplifier 60 that amplifies the terminal voltage of the current detection resistor 5. , current detection resistor 62
and the positive terminal of the battery 46 are connected to each other, and the applied voltage Vn of the heater 20b and the detection element 2 are connected to each other.
Is the current flowing to 0a, the current flowing to heater 20b? M.I.
n, the output voltage vb of the battery battery 46 can be detected.

The electronic control device 44 controls the fuel injection amount from the fuel injection valve 53, the ignition timing via the igniter 32, and the oxygen concentration sensor according to the operating state of the internal combustion engine 2 detected using various sensors. Control of the amount of electric power to the heater 20b of No. 20 is executed.

The heater power amount control routine according to the present invention executed by the electronic control unit 24 will be explained below using the flowchart of FIG. 4. Note that this routine is executed at predetermined time intervals, for example, every 4 ms, and is performed to supply energy from the battery 46 to the heater 20 of the seismic intensity sensor 20.
The amount of electric power supplied to the engine b is duty-controlled according to the operating state of the engine, particularly the duration of the idle state.

When the process is started, the process first moves to step 100, where the engine rotation speed Ne based on the detection signal of the rotation speed sensor 26, the intake air amount Q based on the detection signal of the air flow meter 10, and the throttle position sensor 14 are determined. Various data such as the detection signal of the idle switch and the battery output voltage vb are read.

In the subsequent step 110, based on the intake air amount Q read in step 100, a smoothed air amount Q is calculated.
Calculate t. Specifically, it is calculated by the following equation (1) using the annealed air amount Qt-1 obtained when this routine was executed last time.

Qt = (63Qt-1+Q)/64...(
1) In the following step 120, the pace duty ratio DUTYQ, which is the basis for heater power amount control, is calculated based on the calculated smoothed air amount Qt. In detail, map A as shown in Fig. 5 is used to
YQ is calculated, but according to this map A, the annealed air f
As f1Qt increases, the value of DUTYQ is decreased.

In the following step 130, it is determined from the detection signal of the idle switch of the throttle position sensor 14 whether the internal combustion engine 2 is in an idle state. here,
If it is determined to be idle, the process proceeds to step 1.
40, and the corrected duty ratio D in the idle state
Calculate UTY,L. Specifically, the DUTYL is calculated based on the duration of the idle state using map B as shown in FIG. Note that the horizontal axis in the figure is an idle counter (iCLL) indicating the duration of the idle state, but this counter (fflcLL
is determined by executing the CLL count routine shown in FIG. Note that this routine takes 1 sec.
It is executed by an interrupt every time.

In FIG. 7, when the process is started, it is first determined from the detection signal of the idle switch of the throttle position sensor 14 whether or not it is in the idle state (step 14).
1). Here, if it is determined that it is in the idle state, the process moves to step 142, and the idle counter (i
It is determined whether CL L is (+M 160) (step 142). If it is determined that it is not (m 160), CLL'jir: is incremented by the value 1 (step 143), and it is determined that the value is 160. If so, the process of step 143 is skipped.On the other hand, step 14
1, if it is determined that it is not in the idle state, it is determined whether the idle counter (fiCLL) is 0 (step 144).Here, if it is determined that it is not in the idle state (step 144),
Decrement CLL by the value 1 (step 145),
If it is determined that the value is 0, the process of step 145 is skipped. In this way, the processing of this routine is temporarily terminated. That is, according to this routine, the idle state is 16.
While it lasts 0 seconds, CLL is incremented by 1, and after that, CL I is kept at the value 160. Then, when transitioning from the idle state to the non-idle state, the value of CLL is sequentially decremented by 1 from 160.

Note that the corrected duty ratio DU during the idle state is determined based on the idle counter value CLL calculated in this way.
As can be seen from map B shown in FIG. 6, TYL gradually increases until the idle duration time is 160 seconds, and after that, it becomes idle! 1IiIi value 10% when duration is 160 seconds
I take the.

Returning again to the heater power amount control routine in FIG. 4, after executing step 140, a flag F, which will be described later, is cleared to the value 0 (step 150).

On the other hand, if it is determined in step 130 that the vehicle is in a non-idle state, the process proceeds to step 160, and it is determined whether the flag F is the value 0 or not. This flag F is a flag indicating whether it is in an idle state or a non-idle state.
If fffiO is determined in step 60, the acceleration correction duty ratio DUTYA is calculated (step 170), and the flag F is set to (direct 1) (step 180).
The corrected duty ratio DUTYL during the idle state calculated in step 140 is cleared to the value O (step 190
). On the other hand, if flag F is determined to have a value of 1 in step 160, the process skips steps 170 to 190. That is, when the idle state is switched to the non-idle state, the acceleration correction duty ratio DUTYA is calculated in step 170, and further steps 180 and 19 are performed.
0 processing will be executed. This DUTYA calculation process is, in detail, the duration of the idle state before switching to the non-idle state (idle counter value CLL)
Based on this, the DUTYA is calculated using a map C as shown in FIG. That is, DUTYA
is a counter (i CL L increases in proportion to the value of CLL up to a predetermined value C1, CLL takes a constant value from a predetermined value C2 to a predetermined value C2, and CLL increases from a predetermined value [C2 to a value 160) increases in proportion to

Note that the acceleration correction duty ratio D U calculated in this way
T Y A is attenuated by a separate routine executed every 2 seconds as shown in Fig. 9, but in detail, as shown in Fig. 9, it is decremented by 1 per shift until DUT\A reaches a slope of O. (Steps 191 and 192).

On the other hand, after executing step 150 or 190, or if it is determined that the flag F is 0 in step 160, the process moves to step 200, and the voltage correction duty ratio DUT
Calculate YB. Specifically, based on the output voltage vb of the battery 46 that supplies power to the heater 20b, DUTYB is calculated using a map D as shown in FIG. 10. According to this map D, the output voltage of the battery 46 is v
If b is small, DUTYB is made to be large.

In the following step 210, the base duty ratio DU
A process of calculating another correction duty ratio α, which is a correction coefficient of TYQ, is executed. This process is performed by executing the flowchart shown in FIG. First, it is determined whether or not fuel cut is in progress to cut off fuel injection from the fuel injection valve 50 (step 211). If fuel cut is in progress, the corrected duty ratio α is incremented by a predetermined value a; If not, it is determined whether the engine is in an idle state (step 213), and if it is in an idle state and the cooling water temperature THW is a predetermined temperature (for example, 70° C.) or higher (step 214).
), the corrected duty ratio α is decremented by a predetermined value (step 215). Further, in the case of a non-idling state or when the cooling water temperature TE (W) is lower than 70° C. in an idling state, the corrected duty ratio α is cleared to the value O (step 216).

In this way, the pace duty ratio DUTYQ, the corrected duty ratio DUTYL during the idle state, the acceleration corrected duty ratio DUTYA, the voltage corrected duty ratio DUTYB, and other corrected duty ratios α are calculated. In the following step 220, these duty ratios are calculated. The duty ratio D sent to the heater energization control circuit 52 based on
UTY is calculated using the following equation (2).

DUTY= (DUTYQ+DUTYL+DUTYA+
α) x DUTYB ... (2) Furthermore, if the duty ratio DUTY calculated in this way is 100% or more, (
Step 230), and suppress the upper limit to 100% (Step 240).

Then, in step 250, the duty ratio DUT
A pulse signal of Y is sent to the heater energization control circuit 52, that is, as shown in FIG.
In c), the current is applied for a time t corresponding to the duty ratio DUTY, and the processing of this routine ends -1.

Therefore, in this embodiment, the pace duty ratio DU, which is the base for controlling the heater power amount, is based on the intake air amount Q.
TYQ is determined (step 120), and when the internal combustion engine 2 shifts from an idle state to a non-idle state (step 130.160), acceleration correction is performed according to the idle counter value CLL indicating the duration of the idle state. Duty ratio DUTYA is calculated (step 170), DUTYA is added to DUTYQ, and various correction duty ratios DUTYL, α, D are calculated.
The amount of power supplied to the heater 20b is controlled by the duty ratio DUTY, which is calculated by taking UTYB into consideration.
220).

As a result of such control, as shown in FIG. 13, when the idle state becomes longer, the duty ratio DUTY sent to the heater energization control circuit 52 at time t1 immediately after acceleration changes depending on the duration Ta of the idle state. Therefore, in the conventional device, the temperature of the detection element 20a decreases significantly as shown by the broken line in the figure, but this decrease can be suppressed. For this reason, the temperature of the detection element 20a is maintained at a predetermined activation temperature, so that a stable detection value can be obtained from the oxygen concentration sensor 20. Therefore, immediately after the transition from the idle state to the non-idle state, the generation of CO and HC is reduced, the generation of exhaust odor is also prevented, and furthermore, drivability can be improved.

Further, in this embodiment, the acceleration correction duty ratio DU is used as the correction duty ratio of the pace duty ratio DUTYQ.
Not a T YA scale, but a correction duty ratio DUTYL in an idle state, a voltage correction duty ratio DUTYB,
Other corrected duty ratios α are used, so that emissions and drivability can be improved not only immediately after acceleration from an idling state but also in various operating states of the internal combustion engine 2.

Incidentally, in the above embodiment, the idle switch of the throttle position sensor 14 is used as the state change detection means MIO, but instead of this, the intake air amount Q detected by the air flow meter 10 or the pressure sensor is used. The state change may be detected based on the detected intake pipe negative pressure P, or may be based on the fuel injection amount TP that determines the fuel injection amount of the fuel injection valve 50.

Furthermore, the configuration may be such that a change in state is detected directly based on the intake air amount Q, the intake pipe negative pressure P, or the fuel injection amount TP.

[Effects of the Invention] As detailed above, the heater power control device for the oxygen intensity sensor with a heater of the present invention suppresses the decrease in the temperature of the detection element of the oxygen concentration sensor immediately after transition from the idle state to the non-idle state. It is possible to obtain a stable output signal from the detection element. Therefore, the generation of CO and HC is reduced, the generation of exhaust odor is also prevented, and furthermore, drivability can be improved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram illustrating the basic configuration of the present invention, FIG. 2 is a schematic 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 of the same embodiment. FIG. 4 is a flowchart showing a heater power amount control routine executed by the electronic control device, and FIG.
The figure is a graph showing map A used in the control routine, FIG. 6 is a graph showing map B, FIG. 7 is a flowchart showing the CLL count routine that is executed by interrupting the control routine, and FIG. The figure is a graph showing map C used in the heater power amount control routine, FIG. 9 is a flowchart showing the DUTYA damping routine that is executed by interrupting the heater power amount control routine, and FIG.
The figure shows map D used in the heater power amount control routine.
11 is a flowchart showing the α calculation routine which is a subroutine of a predetermined step of the heater power amount control routine, FIG. 12 is an explanatory diagram explaining the energization state to the heater, and FIG. It is a timing chart explaining an effect|action. Ml...Internal combustion engine M2...Oxygen concentration detection unit M3...Heater M4...Oxygen concentration sensor M5...Operating state detection means M6...Target power determination means Ml...Supply power control means M8...Idle state detection means M9...Idle time calculation means MIO...State change detection means Mll...Target power correction means 2...Internal combustion engine 10...Air flow meter 14...Throttle position Sensor 20...Oxygen concentration sensor 20a...Detection element 20b...Heater 40
...Electronic control device 4th day...Heater energization control circuit representative Patent attorney Tsutomu Sadatsu (and 2 others) Fig. 1 Fig. 5 Fig. 6 Fig. 7 Fig. 8 ○ CI C2 Fiddle counter available LL Fig. 9 Fig. 10 Battery output voltage Vl) (V) Fig. 11 Fig. 12 ---> Fig. 13

Claims (1)

[Scope of Claims] An oxygen concentration sensor having an oxygen concentration detection section that detects the oxygen concentration in exhaust gas of an internal combustion engine and a heater that heats this detection section; and an oxygen concentration sensor that detects an operating state including at least a load state of the internal combustion engine. an operating state detecting means; a target power determining means for determining a target power to be supplied to the heater according to the operating state detected by the operating state detecting means; A heater power control device for an oxygen concentration sensor with a heater, comprising: supply power control means for controlling power supplied to the heater in accordance with the above, and idle state detection means for detecting an idle state of the internal combustion engine; and an idle state detection means for detecting an idle state of the internal combustion engine. an idle time calculation means for calculating the duration of the idle state of the internal combustion engine based on the detection result of the detection means; and an idle time calculation means for calculating the duration of the idle state of the internal combustion engine based on the detection result of the idle state detection means; a state change detection means for detecting a transitional state change; and when the state change detection means detects the state change, the target power is adjusted according to the duration of the idle state calculated by the idle time calculation means. A heater power control device for an oxygen concentration sensor with a heater, comprising: target power correction means for correcting the target power determined by the determination means.