JPH0515910B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an engine temperature sensor correction device that corrects the engine temperature directly detected by a temperature sensor.

(Prior technology) Air-fuel ratio sensor (O ₂ sensor) installed in the exhaust system
While the air-fuel ratio of the air-fuel mixture is feedback-controlled based on the output of Engines in which deterioration of combustibility is prevented by stopping combustion are conventionally known (for example, Japanese Patent Publication No. 52-26284).

By the way, when determining the air-fuel ratio feedback control region based on the engine temperature as in this known example, conventionally the engine temperature was directly detected from the engine cooling water temperature or the engine wall temperature using a temperature sensor. Ta.

However, temperature sensors such as water temperature sensors or wall temperature sensors are prone to detection errors due to variations in accuracy during manufacture or changes over time. Therefore, if the engine temperature is detected by a temperature sensor that is prone to such detection errors, and if air-fuel ratio feedback control is performed based on this, the reliability of the control may be impaired. be.

(Object of the Invention) The present invention provides an engine temperature sensor correction device that improves the reliability of control in a control system using a temperature sensor by correcting the detection error of the temperature sensor. It was done for a purpose.

(Structure of the Invention) The engine temperature sensor correction device of the present invention includes:
As shown in FIG. 1, a temperature sensor 20 that directly detects the engine temperature from engine cooling water, etc.
, an air-fuel ratio sensor 21 that detects the air-fuel ratio of the air-fuel mixture supplied to the engine, and the air-fuel ratio sensor 2
air-fuel ratio control means 22 for feedback-controlling the air-fuel ratio of the air-fuel mixture to a predetermined air-fuel ratio in response to the output of
Then, during feedback control by the air-fuel ratio control means 22, the actual air-fuel ratio detected by the output of the air-fuel ratio sensor 21 changes from leaner to richer than the predetermined air-fuel ratio, or richer than the predetermined air-fuel ratio. a time measuring means 23 for measuring at least one of the times until the change from the side to the lean side; and a temperature sensor correction that receives the output of the time measuring means 23 and corrects the output of the temperature sensor 20 based on the time. It is characterized by comprising means 24.

(Example) The engine temperature sensor correction device of the present invention includes:
In an engine that performs feedback control of the air-fuel ratio of the air-fuel mixture according to the output of an air-fuel ratio sensor, the better the vaporization and atomization state of the fuel, the better the
In other words, we focused on the fact that the higher the engine temperature, the shorter the time from when fuel system control starts until the air-fuel ratio of the air-fuel mixture actually changes, that is, the feedback cycle becomes shorter. The purpose is to correct the output of the temperature sensor using the correlation with the engine temperature, compensate for the detection error of the temperature sensor, and improve control accuracy (reliability).

Hereinafter, a case will be described as an example in which the temperature sensor correction device of the present invention is applied as an output correction device for a temperature sensor that determines the control range of air-fuel ratio feedback control.

FIG. 2 shows a control system diagram of the four-cylinder automobile engine 1. As shown in FIG. The intake passage 2 of the engine 1 includes an air cleaner 6 and an air flow meter 5.
and fuel injector 12 and throttle valve 4
are installed sequentially from the intake upstream side to the intake downstream side. Further, an O ₂ sensor 8 functioning as an air-fuel ratio sensor and an exhaust purification catalyst 7 are sequentially installed in the exhaust passage 3 from the upstream side of the exhaust gas toward the downstream side of the exhaust gas. Further, a temperature sensor 9 is attached to the cylinder wall of the engine 1 to detect the engine temperature from the engine cooling water temperature, and a crank angle sensor 10 is attached to a position near a crank pulley (not shown) of the engine 1.

In this engine 1, the air flow meter 5
According to the outputs of the O ₂ sensor 8 and the crank angle sensor 10, the controller 11 performs feedback control of the air-fuel ratio. The control range of the air-fuel ratio feedback control is determined according to the engine temperature detected by the temperature sensor (water temperature sensor) 9. In other words, the engine temperature is set to a predetermined temperature (feedback control start temperature).
The air-fuel ratio is feedback-controlled only when the temperature is lower than Tw _F/B ), and the feedback control is stopped when the temperature is lower than a predetermined temperature.

Below, the control system by the controller 13 will be explained based on the control flowchart shown in _FIG .
1 is initialized, the intake air amount Q _A is read (step S ₂ ), and the basic fuel injection amount T _FB is calculated from the intake air amount Q _A and the engine speed (step S ₃ ). Next, the cooling water temperature Tw is read (step S ₄ ), and the water temperature correction value Twofs = 0 for the first time.
Therefore, the water temperature after correcting this cooling water temperature Tw is
Tw′ (step S ₅ ). Water temperature after this correction
Tw' is compared with a preset feedback control start water temperature Tw _F/B to determine whether the current engine temperature is within or outside the feedback control range.

If Tw′<Tw _F/B , it is a non-feedback control region, so in step _S7 , the fuel injection amount T _F is set to the basic injection amount T _FB (C _F/B =
1) Fuel injection is performed from the position T.D.C for a period of time _TFB (step _S8 , step _S9 ), and the process returns to step _S2 . The above control is Tw′＞Tw _F/B
It is repeated until .

On the other hand, if the engine temperature gradually rises as the operating time passes and Tw′>Tw _F/B , air-fuel ratio feedback control is started, and first, O ₂
The current air-fuel ratio is determined from the output of the sensor 8 (step S ₆ ).

First, assuming that the air-fuel ratio is currently lean,
In this case, it is necessary to increase the fuel injection amount, so the feedback correction coefficient C _F/B is increased by ΔC _F/B (step S ₁₁ ), and the fuel injection amount T _F is set to this feedback correction coefficient C _F/B. Based on this calculation (step _S7 ), fuel injection is performed at the T, D, and C positions (step _S8 , step _S9 ). At this time, set the ₀₂ flag to the lean side, that is, 0 (step
_SS12 ). This flowchart from step _S10 through step _S11 and step _S12 and back to step _S2 is repeatedly executed while the air-fuel ratio is on the lean side, and each time the feedback correction coefficient C _F/B is _ΔF/B
The ₀₂ flag is cleared.

On the other hand, this is a case where the air-fuel ratio is reversed from the lean side to the rich side, but for the sake of explanation here, the air-fuel ratio is reversed once from the lean side to the rich side, and then shifts to the lean side again, and the flow at the time of lean is described above. To explain the case where the chart is reversed from the lean side to the rich side (that is, when F0 ₂ = 0 in step _S13 ), in this case, first step
In steps _S14 to _S20 , the engine temperature is calculated from the feedback cycle, and a correction value for the output of the temperature sensor 9 is calculated based on this engine temperature.
After that, the feedback correction coefficient of the fuel injection amount is corrected. That is, first, read the output reversal time _t2 of the timer 1 to ₀₂ sensor (step _S14 ).
At the same time, the feedback period T _F/B (=t ₂ −t ₁ ) is calculated from the time t ₂ and the time t ₁ when the output of the previous 0 ₂ sensor reversed from the lean side to the rich side (step ₁₅ ). . Also, at this time, the previous reversal time _t1 is updated to the current reversal time _t2 (step _S16 ).

Next, the water temperature found in step _S5 from memory.
The reference feedback period _TF/Bref corresponding to Tw' is read (step _S17 ). That is, as shown in Fig. 4, the memory stores a correlation curve between the cooling water temperature Tw and the reference feedback period (T _F/B ), which was determined in advance through experiments, and this correlation curve Read the feedback cycle T _F/Bref corresponding to the water temperature detected by temperature sensor 9 (which has already been corrected last time) from . (replaced by the feedback period).

Next, the reference feedback period T _F/Bref obtained by replacing the water temperature Tw' is compared with the actual feedback period T _F/B obtained in step _S15 (step S15).
S ₁₈ ), as a result, if T _F/B > T _F/Bref , it means that the output of temperature sensor 9 deviates to the high temperature side, so the water temperature correction value T _wpfs is corrected to the low temperature side by ΔT _wpfs . On the other hand, if T _F/B < T _F/Bref , it means that the output of the temperature sensor 9 deviates to the low temperature side, so the water temperature correction value T _wpfs is corrected to the high temperature side by ΔT _wpfs (Step S ₁₉ , Step S ₂₀ ). This water temperature correction value T _wpfs is used for water temperature correction in step _S5 in the next control cycle.

After calculating the water temperature correction T _wpfs , the feedback correction coefficient C _F/B is reduced by ΔC _F/B in order to reduce the fuel injection amount (step S ₂₁ ), and the fuel The injection amount T _F is calculated (step S ₇ ), fuel is injected for a time T _F at the T, D, and C positions (step S ₈ , step S ₉ ), and the process returns to step S ₂ again. At this time, the 0 ₂ flag is set to the rich side, that is, F0 ₂ =1 (step S ₂₂ ).

In addition, if the air-fuel ratio is on the rich side and feedback control continues, the step
Control is performed according to a flowchart from _S13 directly to step _S7 via step _S21 and step _S22 . At this time, the water temperature sensor T _W detected by the temperature sensor 9 is corrected by the water temperature correction value T _wpfs every time step _S5 is passed.

As mentioned above, if the output of the temperature sensor 9 is corrected according to the actual feedback cycle, even if the output characteristics of the temperature sensor 9 differ from the time of manufacture due to aging, the actual engine temperature ( Accurate output corresponding to the cooling water temperature can be obtained, further improving the reliability of feedback control.

In this embodiment, the water temperature T _W detected by the temperature sensor (water temperature sensor) 9 is
(T _W ′) is replaced with the reference feedback period T _F/Bref , and this reference feedback period T _F/Bref is compared with the actual feedback period T _F/B to determine the water temperature correction value.
However, in other embodiments of the _invention , the actual feedback period T _F/B is first replaced by the water temperature T _WO using a memory correlation curve. , this displacement water temperature T _WO and the water temperature T _W detected by the temperature sensor 9
(T _W ′), and based on this, the water temperature correction value can be determined.

(Effects of the Invention) The engine temperature sensor correction device of the present invention has the following features:
The engine temperature detected by the temperature sensor is compared with the engine temperature calculated based on the air-fuel ratio feedback cycle, and the output of the temperature sensor is corrected according to the difference. Even if the sensor ages and its output characteristics differ from when it was manufactured, the temperature sensor will still provide an accurate output corresponding to the actual engine temperature, making it easier to use conventional control devices (e.g. This has the effect that the reliability of the control is improved compared to the case where the detected value of the temperature sensor is directly used for controlling the air-fuel ratio, as in the case of Publication No. 52-26284.

[Brief explanation of the drawing]

FIG. 1 is a functional block diagram of an engine temperature sensor correction device according to the present invention, FIG. 2 is a control system diagram of an engine equipped with a temperature sensor correction device according to an embodiment of the present invention, and FIG. The control flowchart of the controller shown in FIG. 4 is a correlation diagram between the engine cooling water temperature and the reference feedback period. DESCRIPTION OF SYMBOLS 1... Engine, 2... Intake passage, 3... Exhaust passage, 4... Throttle valve, 5... Air flow meter, 6... Air cleaner, 7... Catalyst, 8...
...0 ₂ sensor, 9...temperature sensor, 10...crank angle sensor, 11...controller, 12
...fuel injector.

Claims (1)

[Claims] 1 A temperature sensor that directly detects the engine temperature from engine cooling water, etc., an air-fuel ratio sensor that detects the air-fuel ratio of the air-fuel mixture supplied to the engine,
an air-fuel ratio control means for feedback-controlling the air-fuel ratio of the air-fuel mixture to a predetermined air-fuel ratio in response to the output of the air-fuel ratio sensor; a time measuring means for measuring at least one of the time until the actual air-fuel ratio changes from a leaner side to a richer side than the predetermined air-fuel ratio or from a richer side to a leaner side than the predetermined air-fuel ratio; An engine temperature sensor correction device comprising: temperature sensor correction means for receiving the output of the temperature sensor and correcting the output of the temperature sensor based on the time.