JPS5898638A - Fuel control apparatus - Google Patents

Abstract

PURPOSE:To enable to operate an engine without any trouble, by using a fixed correction value when some trouble is caused with a microcomputor (MPU) which calculates and gives a correction value for the datum amount of fuel to be supplied according to the operational conditions of the engine. CONSTITUTION:Output signals of various sensors attached to an engine 50 are afforded to a microcomputor 20, which in turn calculates and gives a correction value for the amount of fuel to be supplied according to the operational conditions of the engine. The correction value thus obtained is furnished to an adder 23 via a switching circuit 21, and a by-pass flow controller 32 is controlled by an electromagnetic solenoid driving circuit 30 on the basis of the signal obtained by adding the above correction value to the output of a datum-value output circuit 24. Resultantly, the output signal of an air-flow meter 4 is feedbacked to the solenoid driving circuit 30, and the amount of fuel and the amount of air to be supplied are determined. In case that some trouble is caused with a trouble detector 22 for the MPU, the switching circuit 21 gives a datum correction value stored in the circuit 21 to the adder 23.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel control device, and more particularly, to a fuel control device that controls a bypass air flow rate and fuel in conjunction with each other using an electromagnetic solenoid. Regarding a control device.

Generally, when driving an automobile engine, it is most efficient to perform combustion at a stoichiometric air-fuel ratio (hereinafter referred to as A/F) of 14.7, which is the ratio between the amount of air and the amount of fuel. Therefore, during normal driving, the air amount and fuel amount are controlled to maintain the stoichiometric air-fuel ratio.

However, during acceleration or due to changes in load, a large amount of fuel may be required, or for deceleration it may be necessary to reduce the amount of fuel compared to the amount of air. Furthermore, since the fuel amount does not change linearly with changes in the air cover, a ramp correction is always required, and this correction 1'1 has conventionally been output from a microcomputer (hereinafter referred to as MPU). This correction value changes depending on the amount of air, so it is output from the MPU, but it is not limited. However, if the MPU fails, fuel control becomes impossible.

SUMMARY OF THE INVENTION An object of the present invention is to provide a fuel control device that can perform fuel control without causing any trouble to the vehicle even if the microcomputer malfunctions.

The present invention includes means for detecting an abnormality in the microcomputer and means for outputting a fixed correction value, and when an abnormality in the microcomputer is detected, the fixed correction value is switched to and output. The aim is to ensure that this does not cause any hindrance to driving.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows an intake pipe of an internal combustion engine according to the present invention, in which a bypass passage 3 is provided in parallel with a main passage 1. As shown in FIG. This main passage Ml is provided with an orifice 2 and a throttle valve 5 on the downstream side. A hot wire flowmeter 4 is provided in the bypass passage 3,
An air flow rate control nozzle 7 is provided downstream. This air flow rate control nozzle 7 is configured to be slid by an electromagnetic solenoid 6, and the amount of air is controlled in the gap formed by the air flow rate control nozzle 7 by this sliding movement. A fuel supply control nozzle 8 is formed opposite to the air flow control nozzle 70 and operates in conjunction with the air flow control nozzle 7. That is, increasing the air flow rate decreases the supplied fuel amount, and decreasing the air flow rate increases the supplied fuel amount. The most downstream side of the bypass passage 3 is located at a location where the orifice 2 of the throttle chamber is formed.

Further, the electromagnetic solenoid 6 that drives the nozzle 7.8 is
It is driven by an electromagnetic solenoid drive circuit 30. There are two types of electromagnetic lens drive circuits: one using a proportional solenoid and the other using a duty solenoid.

FIG. 2 shows an electromagnetic solenoid drive circuit using a specific solenoid. That is, electromagnetic solenoid 6
A transistor 10 is connected in series. The emitter of this transistor 10 is grounded, and the base is connected to the output terminal of the operational amplifier 9. The negative input terminal of the operational amplifier 9 is configured to receive the output of the hot wire type air flow meter 4, and the positive input terminal is configured to receive a value obtained by adding a reference value and a correction value, which will be described later. has been done.

FIG. 3 shows an electromagnetic solenoid drive circuit using a duty solenoid. That is, a transistor 10 is connected in series to the electromagnetic solenoid 6.
The emitter of this transistor 10 is grounded. Further, the output terminal of a comparator 13 is connected to the base of this transistor 10. Further, the triangular wave oscillator 11 is connected to the negative input terminal of the comparator 13, and the output terminal of the error amplifier 12 is connected to the positive input terminal.

The error amplifier 12 is configured such that the output of the hot wire air flow meter 4 is input to the negative input terminal, and a ratio value obtained by adding a reference value and a correction value, which will be described later, is input to the positive input terminal. ing. In a good electromagnetic solenoid drive circuit using this duty solenoid, the triangular wave oscillator 11 outputs a signal as shown in FIG. 4, and the differential amplifier 12 outputs a signal as shown in FIG. It is compared in the comparator 13, and as shown in FIG.
f neat pulse is output. This ON duty pulse turns on the transistor 10.

The average fct flow after turning OFF is the electromagnetic solenoid 6
will flow.

In such a configuration, the throttle valve 5 in FIG.
When opened, more air flows into the main passage l. As the amount of air flowing into the main passage 1 increases, the negative pressure in the orifice 2 increases and the amount of air flowing into the bypass passage 3 increases. As the air flow rate increases, the output of the hot wire type air flow meter 4 increases. When the output of the air flow meter 4 increases, current is supplied to the 1aMi solenoid 6 in the direction of decreasing the flow rate of the bypass passage 3 to match the control value input to the electromagnetic solenoid drive circuit, and the air am control nozzle 7 is drive When the air flow rate control nozzle 7 is driven, the opening area of the fuel supply control nozzle 8 that determines the amount of fuel increases, and the amount of fuel increases.

Further, when the throttle valve 5 is closed, the amount of air t flowing into the main passage 1 decreases. When the amount of air flowing into the main passage 1 decreases, the negative pressure in the orifice 2 decreases, and the amount of air flowing into the bypass passage 3 also decreases. Bypass passage 3
When the air flow to the lid decreases, the air flow 111! The output of lt4 becomes smaller. When the output of this air flow 1tlTt4 becomes smaller, the flow of air 1 supplied to the electromagnetic solenoid 6 is controlled in the direction of increasing the flow rate of the bypass passage 3 so as to match the control Kl value inputted to the electromagnetic solenoid drive circuit 30, The air flow rate control nozzle 7 is driven. When the air cover control nozzle 7 is driven, the fuel supply control nozzle 8, which determines the amount of fuel, has a small opening area and the amount of fuel decreases.

In this way, the electromagnetic solenoid drive circuit 3o maintains the amount of air flowing into the bypass passage 3 constant, controls the nozzle so that the output of the air flow meter 4 is equal to the control mK, and adds the fuel that is rare to the air flow rate of the main passage 1. It's something we can supply.

FIG. 5 shows an example M of the fuel control device according to the present invention.

In the figure, an adder 23 is connected to a microcomputer (MPU J20) via a switching circuit 21. On the other hand, this MPU20KFi failure detector 22 is connected, and the output of this failure detector 22 is Switching circuit 21
1sg is set so that it is input to . This switching port j13
21 is an output from the MPU 20 and a switching circuit 21 to be described later.
The basic value output circuit 24 is connected to the adder 23, and this addition 623 is connected to the basic value output circuit 24.
In addition to the basic flk output from , the output is shown below.

This addition 523 includes the electromagnetic solenoid drive circuit 30!
& controlled. This electromagnetic solenoid drive circuit'#763
The bypass flow controller 32 is controlled by the drive of 0. The measured value of the air flow meter 4 provided in the bypass i-lid controller 32 is fed back to the electromagnetic lunoid drive circuit '1630. This 'tkii solenoid drive time lol! The fuel lid and air lid are determined by the drive &C of 130 and supplied to the engine 50. The configuration is such that output from a sensor attached to this engine 50 is input to the MPU 20. This electromagnetic solenoid drive circuit 30, bypass flow rate control circuit 32, and air flow rate 1F
4 constitute a solenoid valve circuit 31.

The failure detector 22 of the fuel control system constructed in this way has a construction as shown in FIG.

That is, the output from the MPU 20 is the transistor Tr.
applied to the base of i. A power supply voltage (2) is applied to the collector of the transistor Tr1 via a resistor R1. The emitter of this transistor Trl is grounded. Furthermore, the cathode of a diode D1 and the anode of a diode D2 are connected to the collector of the transistor Tr1 via a capacitor C1. Diode D
The anode of the diode D2 is grounded, and the cathode of the diode D2 is grounded via the capacitor D2. Also,
A resistor R3 and an input terminal of the operational amplifier 25 are connected to the cathode of the diode D2. The other end of this resistor R3 is grounded. Further, the (g) input terminal of this operational amplifier 25 is configured so that the set value Vast is inputted thereto. Further, the output terminal and the input terminal of this operational amplifier 25 are bridged via a resistor R2. Further, the output from the output terminal of the operational amplifier 25 serves as a failure signal and lights up the switching circuit 21 and a failure lamp (not shown).

When the fault detector 22 configured in this manner is outputted from the MPU 20 as a signal shown in FIG. is input manually to the (c) input terminal of the operational amplifier 25,
(g) A set voltage Vtxzy as shown in b in FIG. 7 is input to the input terminal. Since this operational amplifier 25 (g) outputs a signal when the input voltage is large, no output signal is output from the output terminal of the operational amplifier 25 as long as the signal shown in the seventh prisoner is output from the MPU 20. . However, when the MPU 20 no longer outputs the signal shown in the seventh prisoner, the discharge voltage causes the seventh prisoner to
The set voltage Vmxr shown in the figure becomes larger, and the set voltage Vmxr shown in Fig. 7 (Q
A signal is output as shown in FIG. When this output signal from the operational amplifier 25 is output, it indicates that the MPU 20 is out of order. This fault detector 22 is commonly referred to as a watchdog.

Further, the switching circuit 21 of the fuel control device shown in FIG. 5 has a configuration as shown in FIG. That is, the output from the MPU 20 is input to one terminal of the AND circuit 60. One input terminal of an OR circuit 61 is connected to the output terminal of this AND circuit 60, and the output terminal of an AND circuit 62 is connected to the other input terminal of this OR circuit 61. The AND circuit 62 is configured such that a correction value from a reference correction value output circuit 63 is input to one input terminal thereof. Further, the other input terminal of the AND circuit 62 is configured to receive an output signal from the failure detection circuit 22 . The output from this failure detection circuit 22 is connected to the other input terminal of an AND circuit 60 via an inverter 64.

The adder 23 is connected to the output terminal of the OR circuit 61. This AND circuit 60°62, OR circuit 61, reference correction value output circuit 63, and inverter 64
A switching circuit 21 is configured by these.

This switching circuit 21 always outputs no output from the failure detector 22 (when the MPU 20 is normal (a state where the signal shown in the seventh prisoner continues to be output)). In order to receive input via the inverter 64,
The output from the MPU 20 is connected to an AND circuit 60 and an OR circuit 6.
1 to the switching circuit 23. If MPU2
0 fails, there is an output from the failure detector 22, and AN
No signal is input to the D circuit 60 via the inverter 64t, a signal is input to the AND circuit 62, and the correction value output from the reference correction value output circuit 63 is output to the AND circuit 62, O.
R and is output to the switching circuit 23 via the circuit 61.

In this way, when the MPU 20 is operating normally,
The correction value output from the MPU 20 is added to the basic value by the adder 23 and output to the electromagnetic solenoid drive direction l#630. Furthermore, when the MPU 20 fails, it is switched by the switching circuit 21, and the reference correction value provided in the switching circuit 21 is output to the adder 23, where it is added to the basic value to change the electromagnetic solenoid drive direction w130. is output to.

The basic value output from the basic value output circuit 24 shown in FIG. 5 is a value corresponding to the stoichiometric air-fuel ratio.

Therefore, according to the present embodiment, even if a failure occurs in the microcomputer, the reference correction value is added to the basic value for control, so that the vehicle can be driven without any problems.

Another embodiment of the invention is shown in FIG. This embodiment uses digital values, whereas the embodiment shown in FIG. 5 uses analog values.

In the drawings, parts with the same reference numerals as those in the embodiment shown in FIG. 5 are the same parts and have the same functions.

In the figure, both the switching circuit 40 and the failure detector 41 are digitally processed. That is, it is output as a pulse signal. This pulse signal is integrated by an integrating circuit 43 and processed as an analog voltage, and the rest is the same as in the embodiment shown in FIG.

Therefore, according to this embodiment, the same effects as the embodiment shown in FIG. 5 can be obtained.

As explained above, according to the present invention, even if a failure occurs in the microcomputer, there is no problem in driving.

[Brief explanation of the drawing]

Figure 1 is a partial configuration diagram of the intake pipe of an internal combustion engine, Figure 2 is an electromagnetic solenoid drive circuit diagram using a proportional solenoid, 144
Figure 3 is an electromagnetic solenoid drive circuit diagram using a duty solenoid, and Figure 4 is #! 3 is a time chart, FIG. 5 is a circuit diagram showing an embodiment of the present invention, FIG. 6 is a circuit diagram of the fault detector shown in FIG. 5, FIG. 7 is a time chart of FIG. 6,
FIG. 8 is a detailed circuit diagram of the switching circuit shown in FIG. 5, and FIG. 9 is a circuit diagram showing another embodiment of the present invention. 20...MPU, 21.40...Switching circuit, 22°4-1...Failure detector, 23...Adder, 24...
・Basic value output circuit, 30...Electromagnetic solenoid drive circuit, 63''V

Claims (1)

[Claims] 1. Means for detecting the operating state of the engine, and means for detecting the intake air i.
an air flow rate needle for detecting t; a means for outputting a basic value that determines the constant value of the supplied fuel and air volume; A correction value output from the microcomputer is added to the basic value to drive an electromagnetic solenoid as a control value, and the monthly output from the air flow rate needle is added to the control value. A fuel control device for controlling the fuel so as to match the microcomputer includes a first means for detecting a difference in the microcomputer, a second means for constantly outputting a smoothed and determined fixed correction value, and a second means for always outputting a smoothed fixed correction value, 2. A fuel control device comprising: third means for switching and outputting an output value from the second means as a correction value in place of the correction value output from the microcomputer according to a detection signal. In the invention as set forth in claim 1, the fuel control device is characterized in that the basic value is a value that is compatible with the stoichiometric air-fuel ratio.3.411fIII! 3. The fuel control device according to the invention, wherein the first means is a watchdog circuit.