JPS6213503B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel control device for an internal combustion engine, and more particularly to a safety function in the event of a failure of a sensor that measures the amount of intake air.

In currently used fuel control devices, such as electronically controlled fuel injection devices, the basic fuel injection amount is calculated based on the intake air amount and the engine speed.

To measure the amount of intake air mentioned above, an air flow sensor is generally used that converts the amount of movement of a flap installed in the intake system into a voltage signal using a sliding resistance, but the signal line of this air flow sensor is disconnected or shorted. In this case, the fuel injection amount cannot be calculated normally, which may cause the engine to stop. Especially in the case of vehicular engines,
From the standpoint of safety, it is not desirable to stop the engine while the vehicle is running.

The present invention was made in order to solve the problems of the prior art as described above, and an object of the present invention is to provide a fuel control device that can safely continue operation even when the intake air amount sensor fails. do.

In order to achieve the above object, in the present invention,
a first means for detecting whether the output of the intake air amount sensor is within a predetermined normal operating range of the engine;
If the signal of the means indicates that the sensor output is outside the predetermined normal range, the output of the sensor is changed to a pseudo signal that continuously corresponds to the throttle valve opening or continuously corresponds to the throttle valve opening. A second means for calculating the fuel supply amount by a normal calculation process except for switching to a pseudo signal calculated from the corresponding signal and the signal corresponding to the engine speed, and using the pseudo signal instead of the sensor output. It is configured to have the following.

Note that the first means corresponds to, for example, the abnormality detection circuit 7 in the embodiment described later, and the second means corresponds to the arithmetic device 1.

The present invention will be explained in detail below based on the drawings.

FIG. 1 is a block diagram of one embodiment of the present invention.

In FIG. 1, 1 is an arithmetic unit, which is composed of a microcomputer and an analog circuit. Further, 2 is an intake air amount sensor, 3 is a rotation sensor that detects the engine speed, 4 is a throttle sensor that detects the throttle valve opening, and 5 is an exhaust gas sensor that detects the concentration of exhaust gas components (for example, oxygen concentration in exhaust gas). It is a sensor.

The calculation device 1 calculates the basic injection amount based on the intake air amount signal _S1 of the intake air amount sensor 2 and the signal of the rotation sensor 3, and calculates the basic injection amount based on the intake air amount signal S1 of the above-mentioned intake air amount sensor 2 and the signal of the rotation sensor 3. The injection amount is determined by adding a correction amount based on the signal (cooling water temperature, air temperature, atmospheric pressure, etc.), and an injection pulse with a pulse width corresponding to the amount is output. This injection pulse drives the injection valve 6 to supply an appropriate amount of fuel to an engine (not shown).

On the other hand, the abnormality detection circuit 7
When the magnitude of the intake air amount signal S ₁ deviates from a predetermined range, it is determined that the intake air amount signal S ₁ is abnormal, and an abnormal signal S ₂ is output.

When the arithmetic unit 1 receives the abnormality signal _S2 , it cuts off the intake air amount signal _S1 and switches it to a predetermined pseudo signal. This switching operation can be easily performed by a program if the arithmetic unit 1 is composed of a microcomputer. In addition, if it is configured by an analog circuit or the like, a switching circuit may be provided that switches between the intake air amount signal S ₁ and the pseudo signal when the abnormal signal S ₂ is applied.

Next, the above pseudo signal will be explained.

To control the air-fuel ratio of the air-fuel mixture supplied to the engine to be constant, basically, if the intake air amount is Q, the rotation speed is N, and the correction coefficient is K, the fuel supply amount F = KQ/ N …………(1) fuel should be supplied.

In equation (1), Q is given by the intake air amount signal _S1 .

A throttle opening signal is most suitable as a pseudo signal for this intake air amount signal _S1 . In other words, since the amount of intake air has a corresponding relationship with the throttle opening, if the throttle opening signal is used as a pseudo signal, operation can be continued without major problems. Incidentally, if the throttle sensor 4 shown in FIG. 1 outputs a signal proportional to the throttle opening, that signal can be used as it is as a pseudo signal.

Furthermore, it is even more effective to comprehensively calculate the signals from the rotation sensor 3 and throttle sensor 4, calculate a value that most closely approximates the intake air amount, and use it as a pseudo signal.

As described above, the present invention provides that when an abnormality occurs in the sensor that measures the intake air amount, the output of the sensor is sent to a pseudo signal that continuously corresponds to the throttle valve opening or to a pseudo signal that continuously corresponds to the throttle valve opening. The system is configured to switch to a pseudo signal calculated from a signal corresponding to the engine speed and a signal corresponding to the engine speed, and to use the pseudo signal instead of the sensor output to calculate the fuel supply amount using the normal calculation process. This is what I did.

Therefore, in the present invention, when an abnormality occurs in the intake air amount sensor, a pseudo signal is simply used instead of the sensor output, and the content of calculation of the fuel supply amount does not change.

Therefore, the basic fuel supply amount is calculated from the intake air amount Q and the rotational speed N using the above equation (1), as is used for calculating the general fuel supply amount,
When calculating the fuel supply amount by making various corrections based on the cooling water temperature, air temperature, atmospheric pressure, etc., the various corrections are performed in the same way as in normal times, only Q being replaced by a pseudo signal. In addition, in the present invention, as the above-mentioned pseudo signal, a throttle valve opening that always shows a value that closely corresponds to the intake air amount even if the operating state of the engine changes, or a throttle valve opening that corresponds even more closely to the intake air amount is used. Therefore, a pseudo signal calculated from the throttle valve opening and engine speed is used.

Therefore, for example, a configuration may be adopted in which several types of operating conditions are determined from the opening degrees of several locations of the throttle valve, and one of several predetermined fixed injection amounts is selected and used accordingly. In comparison, the fuel supply amount can be controlled much more precisely when the intake air amount sensor fails, and good drivability can be maintained under a wide range of operating conditions.

Next, FIG. 2 is a circuit diagram of an embodiment of the intake air amount sensor 2 and the abnormality detection circuit 7.

In FIG. 2, the intake air amount sensor 2 includes a sliding resistance R ₁ that is linked to a flap (not shown) that moves in accordance with the intake air amount, and a resistance R ₂ that is connected in series with the sliding resistance R ₁ . A constant voltage V _B is applied to one end of the resistor R ₂ .

Voltage difference V D between the voltage V ₀ (constant value) at the connection point between the resistor R ₂ and the sliding resistor R ₁ and the voltage V _S at the output terminal of the sliding resistor R ₁ ( _{V D =} V ₀ − V _S ) changes according to the displacement of the flap, and V _D takes a value corresponding to the amount of intake air.

The value of V _D during normal operation is configured so that it does not fall below the minimum value V _Dnio due to the movable range of the slider of sliding resistance R ₁ .

On the other hand, in the abnormality detection circuit 7, the terminal for inputting the voltage V _S is connected to the power supply voltage V _CC via the resistor R ₃ , and the terminal for inputting the voltage V ₀ is connected to the resistor R ₄
grounded via. Further, the voltages V _S and V ₀ are respectively applied to two input terminals of a differential amplifier circuit composed of an operational amplifier OP ₁ and resistors R ₅ to R ₈ . Note that the values of resistors R ₃ and R ₄ are sufficiently large compared to R ₁ and R ₂ , and V _CC > V ₀ and V ₀ > V _S (that is, V _D > V _D
nio > 0).

The output of the above differential amplifier circuit is given to the negative input terminal of comparator _COM1 . Also comparator COM ₁
The above-mentioned V is applied as a reference voltage to the positive input terminal of
The same voltage V ₁ as _Dnio (created by dividing V _CC with resistors R ₉ and R ₁₀ ) is applied.

When the intake air amount sensor 2 is normal, as mentioned above, since V _D > V _Dnio = V ₁ > 0, the output of the operational amplifier OP ₁ becomes a value larger than V ₁ , and therefore the output of the comparator COM The output of ₁ is at a low level.

However, if one or both of the two signal lines from the intake air amount sensor 2 are disconnected,
The input of the differential amplifier circuit is connected to V _CC by resistors R ₃ and R ₄ .
Or it is pulled to 0V, so its output becomes a low level value. Further, when the two signal lines are short-circuited, V ₀ =V _S and the output of the differential amplifier circuit becomes 0. Therefore, in either case of disconnection or short circuit, the level of the negative input terminal of comparator COM ₁ becomes V ₁ or less, and the output of comparator COM ₁ becomes high level. The output of this comparator COM ₁ is sent as an abnormality signal S ₂ to the arithmetic unit 1 shown in FIG.

As explained above, in the present invention, if an abnormality occurs in the sensor that measures the amount of intake air,
The output of the above sensor is always switched to a pseudo signal that corresponds well to the intake air amount even if the engine operating condition changes, and the pseudo signal is used instead of the intake air amount sensor output. Since the fuel supply amount is calculated, various correction calculations can be performed in the same way as normal, and even if the intake air amount sensor fails, good drivability can be maintained under a wide range of operating conditions. . Therefore, even if a breakdown occurs while the vehicle is running, the vehicle can be driven to the nearest safe place or repair shop under its own power, improving driving safety and serviceability. Furthermore, since the signal of an existing sensor can be used as the pseudo signal, there is no need to add a new sensor, so there is an effect that it can be realized at low cost.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of one embodiment of the present invention, and FIG.
The figure is a circuit diagram of an embodiment of an intake air amount sensor and an abnormality detection circuit. <Explanation of symbols> 1... Arithmetic device, 2... Intake air amount sensor, 3... Rotation sensor, 4... Throttle sensor, 5... Exhaust sensor, 6... Injection valve,
7... Abnormality detection circuit, OP ₁ ... Operational amplifier,
COM ₁ ... Comparator.

Claims (1)

[Claims] 1. In a fuel control device that calculates the amount of fuel supplied to the engine using the output of a sensor that measures the intake air amount of the engine as at least one calculation element, and controls the amount of fuel supplied based on the result, the output of the sensor a first means for detecting whether or not the output of the sensor is within a predetermined service range of the engine; switching the output to a pseudo signal that continuously corresponds to the throttle valve opening or a pseudo signal calculated from a signal that continuously corresponds to the throttle valve opening and a signal that corresponds to the engine speed,
A fuel control device for an internal combustion engine, comprising: second means for calculating a fuel supply amount using a normal calculation process except for using the above-mentioned pseudo signal instead of the above-mentioned sensor output.