JPH0531245Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention relates to a fuel supply system for an engine, particularly for an engine that uses a specific fuel mixed with different types of fuel.

(Prior art) An air-fuel ratio control device for an engine that uses gasoline (specific fuel)
A method has been proposed that can also be applied to fuels in which a mixture of

To explain this regarding an electronically controlled fuel injection system adapted for gasoline-only fuel, according to the L-dietronic system, the fuel injection pulse width Ti expressed by the following equation (1) is It is output to the fuel injection valve twice per rotation in synchronization with the ignition timing.

Ti＝Tp×COEF×α＋Ts…(1) However, each symbol in the formula is as follows.

Tp...The basic pulse width gives the injection amount determined by the intake air amount Qa detected by the intake air amount sensor and the engine rotation speed N detected by the crank angle sensor, and according to this injection amount, the air-fuel ratio is approximately stoichiometric. A mixture of

COEF...The sum of various correction coefficients (for example, water temperature increase correction coefficient K _TW , post-start increase correction coefficient K _AS , etc.) temporarily enriches the air-fuel ratio at startup or at low water temperature, improving drivability.

α: Air-fuel ratio feedback correction coefficient, calculated based on the deviation between the actual air-fuel ratio and the theoretical air-fuel ratio. Note that when feedback control is stopped to improve driveability (during open loop control), it is set to 1.00.

Ts...This is a voltage correction coefficient for compensating for the delay in the operation of the injection valve.

When a fuel mixed with alcohol is used in such a fuel injection device, the stoichiometric air-fuel ratio of alcohol is smaller than that of gasoline, so open-loop control of the air-fuel ratio is necessary, for example when the air-fuel ratio is cold or when the throttle valve is fully open. If this is done, the air-fuel ratio shifts to leaner than the stoichiometric air-fuel ratio, increasing the amount of harmful components released and deteriorating drivability. This means that during feedback control, the deviation from the stoichiometric air-fuel ratio is absorbed by α (a value larger than 1), but during open-loop control, α is uniformly 1.00, and the air-fuel ratio that had been absorbed until then is This is because deviations come to the surface.

In order to maintain the stoichiometric air-fuel ratio even when fuel mixed with alcohol is used, a sensor is provided that outputs an output according to the alcohol mixture ratio, and the fuel is adjusted according to the sensor output (V). The goal is to increase the amount of injection.

Therefore, ALC0 (≧1.00) is introduced as an increase correction coefficient according to the alcohol mixing ratio, and in the following formula (2),
By calculating Ti, the air-fuel ratio is maintained at the stoichiometric air-fuel ratio even during open-loop control.

Ti=Tp×COEF×α×ALC0+Ts (2) According to the equation (2), the increase in amount is corrected in advance at ALC0 even during open loop control.

In addition, if the sensor output V and the alcohol mixing ratio are proportional, the increase correction coefficient ALC0 can be set in advance in a table with a value that increases as V increases, for example, and read it out using a table search, etc. Good.

(Problem to be solved by the invention) By the way, in such a device, even if the sensor output is correct, when refueling fuel with a different alcohol mixture ratio, the fuel before refueling near the fuel injection valve is replaced by the fuel after refueling. During this period, the amount of fuel supplied cannot be controlled at an appropriate mixture ratio, and the engine may not be able to operate stably.

This is because the ALC0 given according to the sensor output is given for the equilibrium state where the alcohol mixture ratio does not change, so the period between the sensor and the fuel injection valve until the fuel before refueling is replaced by the fuel after refueling. This is because an appropriate value will not be given during a transient period when the alcohol mixing ratio of the fuel near the fuel injection valve changes moment by moment. This problem becomes more pronounced as the sensor and fuel injector are spaced apart and the fuel path between them becomes longer, and there is a correspondingly larger delay in the change in mixture ratio at the fuel injector position compared to the sensor position. become. Therefore, unless an increase correction coefficient is calculated in response to the transient, the air-fuel ratio will deviate from the target air-fuel ratio and become rich or lean, which will not only prevent smooth startup and warm-up. There may also be cases where the engine cannot be operated continuously.

This invention was made with a focus on these conventional problems, and the purpose is to provide a device that can calculate an appropriate fuel injection amount even during transitions when the alcohol mixture ratio changes. shall be.

(Means for solving the problem) This invention, as shown in Fig.
means 3 for calculating according to operating conditions (for example, engine load and rotation speed), a sensor 4 for outputting (V) according to the mixing ratio of a different type of fuel (for example, alcohol) to a specific fuel, and means 5 for measuring the change (dV/dt) in the sensor output;
Value of sensor output after finishing rapid change (V _H )
means 6 for measuring, and means 7 for calculating the target value of the increase correction amount (ALC _H ) according to the measured value V _H
and a means 8 for calculating a predicted value (ALCn) of the increase correction amount using the calculated target value ALC _H and the first-order lag coefficient (K ₁ ), and a means 8 for calculating the basic injection amount Tp using the calculated predicted value ALCn. Means 9 for calculating the fuel injection amount after a sudden change in the fuel mixture ratio for the mixed fuel of different types of fuel by correcting the above, and a predicted value similarly calculated.
Means 10 is provided for calculating the first-order lag coefficient K ₁ based on the deviation between ALCn and the target value ALC _H and the change dV/dt in the sensor output.

Note that 1 is the engine load (for example, the amount of intake air
A sensor 2 detects the rotation speed (N).

(Operation) In the present application, a predicted value ALCn that changes with a first-order response delay is calculated as a transient change amount with respect to a target value ALC _H obtained from the value of the sensor output after the rapid change ends. In addition, the degree of response of the predicted value ALCn is determined by the degree of change in the alcohol mixture ratio due to refueling (according to dV/dt) and the degree of change in the alcohol mixture ratio during the transition.
It can change depending on the amount of deviation of ALCn from ALC _H , but if the first-order lag coefficient K ₁ is calculated according to these values, ALCn will change in response to transient changes in the alcohol mixing ratio that vary. Appropriately given.
As a result, even during a transition period when the fuel between the sensor and the fuel injection valve is switched from the fuel before refueling to the fuel after refueling, an appropriate mixture ratio can be obtained in response to changes in the alcohol mixture ratio.

(Embodiment) Fig. 2 is a block diagram of a control system according to an embodiment, in which a fuel injection device that uses only gasoline as fuel and an L-dietronic system for the injection device are adopted as is. . Therefore, there is no difference in the configuration from the conventional device except for the control portion performed based on the output V of the methanol mixture ratio detection sensor 14.

11 is a crank angle sensor that generates a signal for each unit crank angle and a signal for each crank angle reference position (for example, a predetermined position before compression top dead center), and the engine rotation speed (N) is measured from the unit crank angle signal. be done. 12 is a sensor (air flow meter) that detects the load (for example, intake air amount Qa);
From Qa and N, the basic pulse width Tp (=K×Qa/N, where K is a constant that determines the value of the air-fuel ratio) for gasoline-only fuel is calculated. 13 is a water temperature sensor.

14 is a sensor that is installed in a fuel supply system such as a fuel tank or fuel pipe and outputs an output according to the mixing ratio of methanol. For example, when the mixing ratio is changed, the capacitance or refractive index of the fuel mixed with methanol changes. Since the resulting physical property values differ, these are detected electrically or optically. Here, it is assumed that the sensor output V also increases as the mixing ratio increases.

Reference numeral 15 denotes an oxygen sensor, which has a characteristic of rapidly changing from rich to lean or vice versa, centering on a target air-fuel ratio (stoichiometric air-fuel ratio) for gasoline-only fuel. The signal from this sensor 15 becomes an air-fuel ratio feedback signal.

21 is a control unit into which various signals from sensors are input, I/O 22, CPU 2
3, a ROM 24 and a RAM 25, and information is exchanged between them via a bus 27. In the control unit 21, operating condition signals (load signal, crank angle signal), sensor output V
The operation shown in Figures 3 and 4 is performed based on the air-fuel ratio feedback signal, and the fuel injection pulse width (Ti) for the methanol-mixed fuel is determined by the following formula (3): Ti = Tp x COEF x α x ALC + Ts ...Set in (3). A drive pulse is created from this pulse width Ti, and the drive pulse is output toward the fuel injection valve 28 provided at the intake port of each cylinder.

Furthermore, the meaning of each symbol in equation (3) is as follows:
Except for the difference in the contents of ALC, it is the same as that used in the L-dietronic method for injection control using gasoline (Tp is the basic pulse width, COEF is the sum of various correction coefficients, α is the air-fuel ratio Feedback correction coefficient, Ts is voltage correction coefficient). Therefore, since this example is configured for a methanol mixed fuel,
There is no need to perform new matching to obtain various quantities (Tp and correction coefficients), and the Tp and correction coefficients conventionally used for gasoline-only fuel can be used as they are.

Now, ALC is an increase correction amount (or increase correction coefficient) given according to the methanol mixture ratio, but because fuel with a different methanol mixture ratio is refueled, the fuel before refueling is replaced by the fuel after refueling. During this period (transient period), the ALC must be determined in accordance with the gradually changing mixing ratio.

For example, if we refuel gasoline-only fuel with methanol-mixed fuel, during the transition period until gasoline between the sensor and the fuel injection valve is replaced with methanol-mixed fuel, the seventh As shown in the figure, the sensor output V increases exponentially from the value for gasoline fuel,
Sensor output for methanol mixed fuel (V _HO )
It calms down. Here, since the mixture ratio near the fuel injection valve changes with a delay with respect to the mixture ratio at the sensor position, the increase correction coefficient ALC is adjusted according to the increase in V.
Must increase exponentially.

In this case, if we consider the change in ALC shown in Figure 7 to be a first-order delayed response, then
Using the ALC value (ALC _H ) and the first-order lag coefficient _K1 ,
The value on the curve (transient value) can be calculated using the following equation (4).

ALCn=ALC _H (1/K ₁ )+ALC _o-1 (1-1/
_K1 ) However, the same equation (4) is a formula for calculating at a constant cycle, and "n-1" and "n" appended to ALC are the (n-1)th calculated value and the nth calculated value, respectively. means a calculated value. According to the same formula, we calculated this time
The next ALC (ALCn) is cyclically determined from the ALC (ALC _o-1 ). That is, ALCn here
gives the value that will occur next at the present moment, and has the meaning of a predicted value. This is to deal with response delays during transient times.

Figure 3 shows a program that calculates the value after the rapid change in the sensor output V (V _H ) and the change (differential value) dV/dt in the sensor output per unit time during the transient period. Executed at regular intervals.

First, V is within the set time _T1 (for example, 500 msec
dV/dt (= _{ΔV/T 1 ,} where ΔV is V
It means the change amount. ) is calculated. ΔV≧V ₁
The reason for this condition is that when the mixing ratio changes significantly, the deviation between the equilibrium value and the transient value becomes a problem. Furthermore, the purpose of determining dV/dt is to determine the degree of change in the mixing ratio.

To execute this with the program shown in Figure 3, the current V (Vn) must change by more than a predetermined value (C ₁ ) compared to the previous value (V _o-1 ), and the number of times the change has occurred (n).
Determine whether or not is greater than or equal to a predetermined number of times (C ₂ ),
If this is determined, a flag (differential flag) instructing to calculate a differential value may be turned on (steps 32 to 35). Note that if the calculation period is T ₀ , then T ₁ = T ₀ ×C ₂ , |ΔV| = |Vn−V _o-1 |×C ₂
Determine C ₁ and C ₂ so that

On the other hand, when the change in V becomes less than the set value and continues to be less than the set value for the set time, it is determined that the state is in a quasi-steady state, and the subsequent V is determined as the value of the sensor output after the rapid change (V _H ) (steps 32, 37, 39).

Finally, turn on the flag for performing ALC correction (step 42).

Figure 4 shows a program to set the basic pulse width for fuel mixed with methanol.In step 55, the sensor output value _VH after the rapid change is completed.
ALC corresponding to , that is, ALC _H is calculated (step 55). Here, since ALC _H is the equilibrium value,
It can be determined in advance by matching, and is the same as that required by conventional devices.
In other words, ALC _H (≧1.00) is the equilibrium value of the increase correction amount determined according to the sensor output, for example, a one-dimensional table (number of grid points 16) with V _H as a parameter.
It can be found by referring to. This table can be built into the ROM 24, and its contents are shown in _Figure 5.
16 grid points (from "00" to "F0") are taken, and each grid point has ALC _H data (from "80" to "F8").
) are stored. In addition, the values in the same figure are
It is displayed in hexadecimal.

Next, regarding the first-order lag coefficient _K1 , this is a value that determines the degree to which the predicted value approaches the target value. The larger the value, the faster the predicted value approaches the target value.

Therefore, the deviation ΔALC (=ALC _H −ALC _o-1 ) between ALC _H as the target value and the current predicted value (ALC _o-1 )
Determine K ₁ according to the above-mentioned dV/dt (step
56, 57). For example, as shown in Figure 6, ΔALC
A two-dimensional table (number of lattice points: 8×8) with parameters dV/dt and dV/dt is stored in advance in the ROM 24, and the value can be determined by referring to the table.
Note that the value of ΔALC in FIG. 6 is expressed in hexadecimal notation, and the value on the grid point represents 1/K ₁ .

Here, since ALC _H and K ₁ are determined, the above formula
The next predicted value (ALCn) is obtained in (4) (step 58). That is, _ALCH and _K1 are predetermined values, and using these values, a predicted value that gives a value during a transient period is cyclically determined.

And the predicted value ALC _o-1 that was found last time
is again set as ALC, and the basic pulse width Tp for gasoline-only fuel is corrected in this ALC (steps 59 and 61).

Ti set in this case is Ti=(Tp×ALC)×COEF+Ts...(3A). This is because the time when the fuel before refueling is replaced by the fuel after refueling appears to occur immediately after starting, and the feedback control of the air-fuel ratio is stopped. Therefore, according to the same equation (3A), the air-fuel ratio accuracy is greatly affected by how ALC is determined, but the corresponding predicted value is
Since it is given as ALC, air-fuel ratio accuracy is also maintained well.

Also, when calculating the predicted value ALCn, the correction flag is ON.
Therefore, the delay time τ (for example, about 10 to 20 seconds)
It is performed after the time has elapsed (steps 53 and 54). This is because the values of ALC _H and ALCn are for the fuel at the position where the sensor 14 is installed, so if there is a considerable distance between the sensor installation position and the injection valve 28 installation position, the actual injection valve 2
This is because a response delay occurs from the time when the fuel is injected. Therefore, the delay time τ is predetermined in consideration of the mounting position of the sensor 14 and the discharge amount of the fuel pump.

Finally, change ALCn again for the next calculation.
Store it as ALC _o-1 (step 60). Note that the elapsed time after the correction flag turns ON is handled by turning the soft timer ON (steps 53 and 62).On the other hand, when the sensor output V changes from a quasi-steady state to a steady state, , the predicted value is calculated using the first-order lag coefficient K ₁ (32 in FIG. 6) that makes the change in the predicted value the most gradual. The same applies when the sensor output changes gradually so as not to exceed the set value within the set time even after refueling. however,
In these cases, no delay time is provided, and the calculations in steps 56 to 58 are performed immediately when ΔALC exceeds the set value (C ₃ ) (steps 64 and 66).

Next, to explain the effect of this example in the case where the methanol mixture ratio changes in the direction of increasing after refueling, as the fuel remaining in the fuel pipe near the injection valve is consumed due to startup, the Since the fuel gradually changes from the fuel before refueling to the fuel after refueling, the sensor output V increases from the value for the residual fuel as shown in FIG. 7, and changes to the value for the fuel after refueling ( _VH )
approach.

In this case, even though the sensor 14 is provided, if the ALC given according to the sensor output V is used, it will not be possible to use the appropriate ALC during the transition from the fuel before refueling to the fuel after refueling. It cannot be a value. This is because the ALC determined according to V is a value set for a state at equilibrium, that is, after the sensor output has stabilized, and is therefore inappropriate as a value during a transient state.

Therefore, as shown in Fig. 7, if V _H responds with a first-order lag with V _HO as the target value, then
Regarding ALC, a value on a curve that responds with a first-order lag should be calculated using ALC _H as a target value.

Therefore, in this example, a predicted value ALCn that changes with a first-order response delay is calculated using the above equation (4) using ALC _H corresponding to V _H as a target value. Here,
ALCn differs from ALC _H (equilibrium value) and gives the amount of change during a transient period.

In addition, the degree of response of the predicted value ALCn may vary depending on the degree of change in the methanol mixing ratio due to refueling (according to dV/dt) and the amount of deviation of ALCn from ALC _H during the transition (ΔALC). ,
Since the first-order lag coefficient K ₁ is calculated according to these values, the predicted value ALCn can be appropriately provided in response to transient changes in the methanol mixing ratio that vary.

As a result, even during the transition period when the fuel before refueling is switched to the fuel after refueling, an appropriate mixture ratio can be obtained in response to changes in the methanol mixture ratio, thereby preventing rotational instability from startup to warm-up. The engine runs smoothly without any problems.

Further, if the sensor mounting position and the injection valve position are far apart, the change in the sensor output, that is, the mixture ratio change, reaches the injection valve 28 with a delay. in this case,
Since the mixture ratio change that occurs at the sensor installation position also occurs with a delay at the injector installation position, there is not much error, so the predicted value calculated with a response delay does not reflect the actual supply from the injector. This is a good reflection of the fuel properties.

Finally, although methanol was used in the examples, it goes without saying that the invention is not limited to this.

(Effects of the invention) As explained above, this invention introduces a predicted value of the increase correction amount as a transient change amount when the mixing ratio of different fuels changes, and uses this predicted value to determine the basics for a specific fuel. Since the injection amount is corrected, even if the mixture ratio changes moment by moment during the process of changing from the fuel before refueling to the fuel after refueling, an appropriate mixture ratio can be obtained in response to the change in the mixture ratio. The engine can be operated smoothly from startup to warm-up without any instability in rotation.

[Brief explanation of drawings]

Fig. 1 is a claim correspondence diagram of this invention, Fig. 2 is a system diagram of a control system of an embodiment of this invention, and Fig. 3 is a system diagram of a control system of an embodiment of this invention.
Figures 5 and 4 are flowcharts for explaining the control contents of this embodiment, and Figures 5 and 6 are characteristic diagrams showing the contents of ALC _H and 1/K ₁ used in this embodiment, respectively. . FIG. 7 is a waveform diagram for explaining the transient operation of this embodiment. 1... Engine load detection sensor, 2... Rotation speed detection sensor, 3... Basic injection amount calculation means, 4...
Mixing ratio detection sensor, 5... Change measuring means, 6...
... Value measuring means at the time of change completion, 7... Target value calculating means, 8... Predicted value calculating means, 9... Means for calculating transient fuel injection amount, 10... Delay coefficient calculating means, 11
... Crank angle sensor, 12 ... Air flow meter, 14 ... Mixing ratio detection sensor, 21 ... Control unit, 23 ... CPU, 24 ...
ROM, 28...Fuel injection valve.

Claims (1)

[Scope of utility model registration request] A means for calculating the basic injection amount for a specific fuel according to operating conditions, and a means for providing an output in accordance with the mixing ratio of different fuels to the specific fuel, which is installed in a fuel tank or fuel pipe separated from a fuel injection valve. A sensor, a means for measuring a change in the sensor output per unit time, a means for measuring the value of the sensor output after the rapid change has ended, and a means for measuring the value of the sensor output after the measured rapid change has ended. a means for calculating a target value of the increase correction amount according to the amount, a means for calculating a predicted value of the increase correction amount using the calculated target value and the first-order lag coefficient, and a means for calculating the basic injection amount using the calculated predicted value. means for correcting the amount of fuel to be injected after a sudden change in the fuel mixture ratio for the mixed fuel of different types of fuel; 1. A fuel supply device for an engine, comprising: means for calculating a first-order lag coefficient.