JPS5867963A - Air-fuel ratio controller - Google Patents

Abstract

PURPOSE:To control a flow of fuel to an adequate quantity without cuasing the necessity for a signal from an oxygen sensor, by directly detecting the fuel in a fuel passage. CONSTITUTION:A controller is constituted in such a manner that a hot-wire flow meter 30, having a thermally sensing resistor 31, is set between an opening-closing valve 5 in a fuel passage 26 and a control valve 6, and a signal from the hot-wire flow meter 30 is input to a control circuit 33 to control a flow of fuel. The flow meter 30 measures a flow quantity by flowing an electric current, heating the resistor 31, placing the resistor in a flow of fluid, cooling the resistor and utilizing a change of resistance, and the flow quantity can be measured from passage sectional area of a place, in which the resistor 31 is placed, and a flow speed. In this way, the flow of fuel can be directly further continuously detected by a simple detecting means.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air-fuel ratio control device that controls the air-fuel ratio of an air-fuel mixture supplied to an engine using a feedback control system.

Fuel supply systems for automobile engines require oxygen sensors, electronic control circuits, and electromagnetic drives because when a three-way catalyst is used for exhaust purification, the air-fuel ratio must be controlled within an extremely narrow range around the stoichiometric air-fuel ratio. The air-fuel ratio control device is comprised of a combination of control valves. If the fuel supply device is a carburetor, the R and il of the fuel or bleed air are adjusted with a control valve, and in the case of a fuel injection device, the fuel flow rate is adjusted with a control valve.

In addition to the oxygen sensor, suitable elements among various factors such as throttle valve opening, engine temperature, engine rotational speed, intake air temperature, intake air amount, and engine intake negative pressure are used as means for generating signals input to the control circuit. It is common to use a combination of detectors. In a fuel supply system equipped with an air-fuel ratio control device such as C, the fuel flow rate is set by the effective cross-sectional area of the fuel passage and the opening time of the control valve, but the actual flow rate is determined by the effect on the nozzle opening into the intake passage. negative pressure, fuel pump discharge pressure.

Due to the influence of fluctuations in fuel temperature, etc., fuel is not supplied according to the scheduled setting value, which disturbs the air-fuel ratio and causes the oxygen sensor to generate signals more frequently than planned, which affects its lifespan.

SUMMARY OF THE INVENTION An object of the present invention is to provide an air-fuel ratio control device that can adjust the fuel to an appropriate level without using a signal from an oxygen sensor by directly detecting the fuel flow rate in a fuel passage. According to the investigation, a hot edge flow meter was installed in the fuel passage, and the signal from this meter was input to the control circuit to adjust the fuel flow rate.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
A downwardly opened injection lower is installed, and a throttle valve 8 is arranged below it. The control valve 6 includes a valve main body 12 having a jet-shaped valve port 11 built in and fixed to a cylindrical support 10 connected to the body 2 and connected to the main body 2;
The valve body 13 is inserted into the valve body 12 and has a needle-shaped valve body 13 whose tip reaches the valve port 11. A force is applied to the valve body 13 in the direction of pulling it out from the valve port 11, and the jet lower is formed at the tip of the valve body 12 protruding from the support lO, and at the narrowest part of the venturi-shaped air metering part 15. A bleed air hole 17 is provided in a portion of the valve body 12 between the valve port 11 and the injection lower that is open and introduces air sucked from the air bleed jet 16.

A step motor is used as the prime mover 18 that moves the valve body 13 of the control valve 6. The step motor is composed of a rotor 19 made of a cylindrical permanent magnet and a stator 2o made of a plurality of electromagnets arranged around the rotor 19 at equal intervals in the circumferential direction. is sequentially supplied to move the magnetic flux generation point of the fixed lock 2o in the circumferential direction to generate a repulsive force between it and the rotor 19, thereby causing the rotor 191 to rotate. The rotation angle of 19 is determined by the circumferential spacing of the electromagnets.

The rotor 19 has a housing 21 mounted on a support lO.
A core member 23 is rotatably supported by a bearing 22.
The output shaft 24 is fixed to the screw hole in the center of this core material 23.
The female thread part 24m is screwed.

The output @24 is movably coupled to the housing 21 in the axial direction by a detent 25 consisting of a key and a keyway, and its tip is in contact with the proximal end of the valve body 13. Therefore, when the two rotors 19 rotate, the output shaft 24 is moved in the axial direction by a distance determined by the rotation angle of the rotor 190 and the thread pitch of the threaded portion 24m, and the direction of movement is determined by the order in which the coils are energized. The valve body 13 is the output shaft 24
or by the spring 14, the effective cross-sectional area of the valve port 11 decreases or increases steplessly. There is no problem even if the body 13 is moved in the axial direction while rotating.

Fuel is supplied from the fuel tank 3 to the fuel pump 4. It has a magnetically driven on-off valve 5 and passes through the bowl 9 to connect the support 10 and the valve body 1.
The fuel passes through a fuel passage 26 that reaches an annular inlet chamber 27 between the inlet chamber 27 and the valve chamber 29 in the valve body 12 through a through hole 28, and from there through the valve port 11. It is supplied from the injection lower to the intake passage l.

A hot wire flow meter 30 is installed between the on-off valve 5 and the control valve 6 of the fuel passage 26, and its heat-sensitive resistor 31 is connected to the fuel passage 26.
is installed inside. The hot wire flowmeter 30 measures the flow rate by applying a current to a heat-sensitive resistor 31 such as a platinum wire to heat it, and then placing it in a fluid stream to cool it and using the change in resistance to measure the flow rate. There are two methods: one that keeps the sensibility of the heat-sensitive resistor 31 constant and expresses the current as a function of fi speed, and the other that keeps the current constant and expresses the resistance as a function of flow velocity. The flow rate can be determined from the cross-sectional area of the passage where the heat-sensitive resistor 31 is placed and the flow velocity.The resistance change of the heat-sensitive resistor 31 is generally measured by a bridge circuit 32, and the measured value is converted into a continuous signal and transmitted to an electronic system. Control circuit 3
3.

In addition to the exhaust oxygen sensor 34 and the fuel temperature detector 35, the means for generating signals input to the control circuit 33 include the throttle valve opening, the engine speed, the engine speed, the intake air width, and the intake air cover.

Engine intake negative pressure and atmospheric pressure detectors 36, 37゜38
．． 39, 40, 41.42 are used, and an ignition switch 43. An air conditioner activation switch 44 is connected to the control circuit 33. The output signal from the control circuit 33 is the IfA motor 1g, the fuel pump 4. A driving current is applied to each of the on-off valves 5, and the fuel pump 4 is driven while the engine is operating. The on-off valve 5 remains open while the engine is running, but? yi, the valve may be closed at speed. The prime mover 18 is the state of engine operation.

The valve body 13 of the control valve 6 is actuated by the drive flow given according to the conditions, and the fuel flow rate is adjusted so that the desired air-fuel ratio can be obtained.

Starting, warming up, idling, acceleration, 11th overall.

When decelerating or when using an air conditioner, the amount of fuel a is corrected so that the required air-fuel ratio can be obtained.

In the illustrated embodiment, the fuel flow rate is adjusted by changing the opening degree of the control valve 60 steplessly using a step motor.
Even in the case where the fuel flow rate is adjusted by changing the P time, the object of the present invention can be achieved by installing the hot wire flow meter 30 at an appropriate location in the fuel passage from the fuel pump or constant oil level chamber to the control valve.

As described above, in the present invention, the hot wire flowmeter is installed in the fuel passage to measure the fuel flow rate based on the fact that the resistance of the heat-sensitive resistor changes depending on the fuel flow rate, that is, the flow rate. The fuel flow rate can be detected directly and continuously using detailed means. In addition, in a feedback control system that adjusts the fuel flow rate by detecting one of the few elements that should be used to control the air-fuel ratio according to engine operating conditions in addition to fuel temperature, the actual fuel flow rate is input to the control circuit. Since it is an input, even if the negative pressure acting on the nozzle, the discharge pressure of the fuel pump, the oil level in the tU oil level chamber, the fuel temperature, etc. fluctuate, the actual flow rate can be detected and the air-fuel ratio controlled to be appropriate. It generates a drive current for the control valve to adjust the flow of sludge to an appropriate level, reducing the burden on the m-element sensor and performing appropriate air-fuel ratio control.

[Brief explanation of the drawing]

The drawings are longitudinal sectional views showing embodiments of the present invention. l...Intake path, 4...Fuel pump, 6
... Control valve, 7 ... Nozzle, 8 ...
...Edge valve, 11...Valve mouth, 12...
Valve body, 13...Valve body, 18...Motor, 26...Fuel passage, 30...Heat*
gtmt. 33...Control circuit, 34...Oxygen sensor, 35-42...Detector. Agent Mutsuaki Nozawa

Claims (1)

[Claims] In an air-fuel ratio control device in which the flow rate of fuel supplied from a nozzle to an intake passage is adjusted by a control valve driven by a drive current from a feedback control system, one of means for generating a signal input to a control circuit of the control system. An air-fuel ratio control device characterized in that the air-fuel ratio control device includes a thermal helix flow meter installed in a fuel passage that sends fuel to the nozzle.