JPS58176446A - Air-fuel ratio controlling apparatus used at starting engine - Google Patents

Abstract

PURPOSE:To enable to start an engine always in a stable manner, by supplying mixture of an optimal air-fuel ratio to cylinders of the engine at the time of starting the same. CONSTITUTION:The amount of auxiliary air supplied to an intake manifold or the amount of bleed air supplied to a carburetor is controlled by an electromagnetic control valve 28. An electronic control unit 70 controls operation time of the electromagnetic control valve 28 on the basis of the output signals of a starter switch 100 and a temperature sensor 98 for detecting the engine temperature. The duty ratio of continuous pulses impressed on the control valve 28 is increased as the engine temperature is raised. Therefore, the amount of bleed air or auxiliary air supplied at the time of starting an engine is also increased as the engine temperature is raised.

Description

[Detailed description of the invention] The present invention relates to an air-fuel ratio control device for starting an engine.

If the engine is stopped while the engine temperature is high, the fuel in the carburetor float chamber will continue to evaporate even after the engine has stopped.
This evaporated fuel flows into the intake passage and accumulates in the intake manifold. Therefore, when the engine is restarted, the fuel vapor accumulated in the intake manifold is supplied into the engine cylinders together with the fuel supplied from the carburetor, so that the air-fuel mixture supplied into the engine cylinders becomes rich. This creates the problem that it becomes difficult to start the engine.

In order to solve this problem, an air-fuel ratio control device has been known that supplies auxiliary air into the intake manifold while the starter motor is being driven to start the engine.

However, if auxiliary air is supplied into the intake manifold while the starter motor is driven in this way, if the amount of fuel vapor accumulated in the intake manifold is small, the air-fuel mixture supplied to the engine cylinders will be overflowed. It becomes thinner and as a result it becomes difficult to start the engine.

An object of the present invention is to provide an air/fuel ratio control device that can supply an air-fuel mixture with an optimal air-fuel ratio into an engine cylinder when starting an engine, thereby ensuring stable starting at all times.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

Referring to Fig. 1, 1 is the carburetor main body, 2 is an intake passage that sharpens in the vertical direction, 3 is a piston that moves laterally within the intake passage 2, and 4 is a piston that is attached to the tip of the piston 3. needle, 5 is sakshi, piston 3
A spacer 6 is fixed on the inner wall surface of the intake passage 2 facing the tip surface of the intake passage 2 downstream of the suction piston 3.
A throttle valve 7 provided in the interior indicates the float chamber of the carburetor, and the tip surface of the suction piston 3 and the suction piston 5 are connected to each other.
A pliers part 8 is formed between them. A hollow cylindrical casing 9 is fixed to the carburetor body 1, and a guide sleeve 10 extending in the axial direction of the casing 9 inside the casing 9 is attached. A bearing 12 with a number of goals 11 is inserted into the guide sleeve 10, and the outer end of the guide sleeve 10 is closed by a blind cover 13. On the other hand, suction piston 3 has a plan (3
) The inner rod 14 is fixed, and this guide rod 14 is connected to the bearing 1.
2 so as to be movable in the axial direction of the guide rod 14. Since the suction piston 3 is thus supported by the casing 9 via the bearing 12, the suction piston 3 can move smoothly in its axial direction.

The interior of the casing 9 is divided by the suction piston 3 into a negative chamber 15 and an atmospheric pressure chamber 16, and a compression spring 17 is inserted into the negative chamber 15 to constantly press the suction piston 3 toward the venturi section 8. The negative pressure chamber 15 is connected to the bench part 8 through a suction vent hole 18 formed in the suction piston 3, and the atmospheric pressure chamber 16 is connected to the suction piston through an air hole 19 formed in the carburetor body 1. 3” is connected within the second-flow intake passage.

On the other hand, a fuel passage 20 extending in the axial direction of the needle 4 is formed in the carburetor body 1 so that the needle 4 can enter therein, and a metering shed 21 is provided within the fuel passage 20. The fuel passage 20 upstream of the metering jet 21 is connected to the float chamber 7 via a downwardly extending fuel pipe 22 (4), and the fuel in the float chamber 7 is sent into the fuel passage 20 via this fuel pipe 22. It will be done. Furthermore, a hollow cylindrical nozzle 23 arranged coaxially with the fuel passage 20 is fixed to the spacer 5 .

This nozzle 23 protrudes from the inner wall surface of the sweeper 4-5 into the venturi portion 8, and the upper half of the tip of the nozzle 23 further protrudes from the lower half toward the suction piston 3.

The needle 4 extends through the nozzle 23 as well as the metering jet 21, and the fuel is supplied from the nozzle 23 into the intake passage 2 after being squeezed through the annular gap formed between the needle 4 and the metering jet 21.

As shown in FIG. 1, an intake passage 2 is provided at the upper end of the spacer 5.
A raised wall 24 is formed that projects inward in the horizontal direction,
Flow rate control is performed between this raised wall 24 and the tip of the suction piston 3. When engine operation is started, air flows downward in the intake passage 2. At this time, the air flow is constricted between the suction piston 3 and the raised wall 24, so that negative pressure is generated in the venturi portion 8, and this negative pressure is guided into the negative pressure chamber 15 through the suction hole 18. The suction piston 3 is arranged so that the pressure difference between the self-pressure chamber 15 and the atmospheric pressure chamber 167 remains at a substantially constant pressure determined by the spring force of the compression spring 17, that is, so that the negative pressure within the venturi portion 8 remains substantially constant. Moving.

As shown in FIG. 1, the carburetor main body 1 is mounted on an intake manifold 25, and an exhaust manifold 26 is arranged below the intake manifold 25. Intake manifold 2
5 is formed with an auxiliary air supply hole 27, and an electromagnetic control valve 28 is attached to this auxiliary air supply hole 27. This electromagnetic control valve 28 has a valve chamber 30 connected to an air cleaner (not shown) via an air supply conduit 29, and an auxiliary air supply hole 27.
a valve port 31 that communicates with the valve port 31, a valve body 32 that controls opening and closing of the valve port 31, and a blanker 33 that is connected to the valve body 32.
and a solenoid 34 for suctioning the syringe 33, and the solenoid 34 is connected to an output terminal of an electronic control unit 70. On the other hand, an oxygen concentration detector 69 is attached to the exhaust manifold 26, and this oxygen concentration detector 6
The output signal of 9 is connected to an input terminal of an electronic control unit 70.

FIG. 2 shows a circuit diagram of the electronic control unit 7o.

Note that in FIG. 2, VB indicates the power supply voltage. Referring to FIG. 2, the oxygen concentration detector 69 shown in FIG. 1 is shown. As shown in FIG. 3, this oxygen concentration detector 69 detects a temperature of about 0.1 tert when the exhaust gas is in an oxidizing atmosphere, that is, when the air-fuel ratio of the mixture supplied into the engine cylinder is larger than the stoichiometric air-fuel ratio. On the other hand, when the exhaust gas is in a reducing atmosphere, that is, when the air-fuel ratio of the air-fuel mixture supplied into the engine cylinder is smaller than the stoichiometric air-fuel ratio, an output of approximately 0.09 gelt is generated. In FIG. 3, the vertical axis V shows the output voltage of the oxygen concentration detector 69, and the horizontal axis shows the air-fuel ratio of the air-fuel mixture supplied into the engine cylinder. Note that on this horizontal axis, S
indicates the stoichiometric air-fuel ratio, L indicates the lean side, and R indicates the rich side.

Referring again to FIG. 2, electronic control unit 701dl
lf-J* o controller 71, AGC circuit 72, (7) first converter 73, integral circuit 74, proportional circuit 75 consisting of an inverting amplifier, addition circuit 76, and second It includes a converter 2 regulator 77, a harmonic generation circuit 78, an analog switch 79, and a transistor 80. An output terminal of the oxygen concentration detector 69 is connected to a non-inverting input terminal of a Gertezo follower 71, and an output terminal of the Virtezo follower 71 is connected to an input terminal of an AGC circuit 72. On the other hand, the output terminal of the AGC circuit 72 is connected to the first
It is connected to the non-inverting input terminal of the comparator 73, and a reference voltage of about 0.4 < 1st Con
The output terminal of the rotator 73 is connected on the one hand to the input terminal of an integrating circuit 74 and on the other hand to the input terminal of a proportional circuit 75. Further, the output terminal of the integrating circuit 74 is connected to the adding circuit 7.
The output terminal of the proportional circuit 75 is connected to the second input terminal of the adding circuit 76. 7J
The output terminal of the rl calculating circuit 76 is connected to the non-inverting input terminal of the second comparator 77 via a resistor 83, while (8) the inverting input terminal of the second comparator 77 is connected to the harmonic generation circuit 78 via a resistor 84. Connected. In addition, the second con 9
The output terminal of the regulator 77 is connected to the base of a transistor 80 via an analog switch 79 and a resistor 85. The emitter of transistor 80 is grounded, while the collector of transistor 80 is connected to solenoid 34 of electromagnetic control valve 28 (FIG. 1). Note that a surge current absorbing diode 86 is connected in parallel to the solenoid 34.

The output signal of the oxygen concentration detector 69 is transmitted through the gelteno follower 71.
The signal is supplied to the AGC circuit 72 via.

The AGC circuit 72 is an amplifier configured to increase the gain when the average value of the output signal of the oxygen concentration detector 69 decreases. Therefore, the output terminal of the AGC circuit 72 is connected to the oxygen concentration detector 69. An output voltage is generated that varies proportionally to the output voltage of the output voltage and whose average value is maintained at a constant level. FIG. 4(,) shows the output voltage of this AGC circuit 72. In FIG. 4(a), "1 voltage vr" indicates the reference voltage applied to the inverting input terminal of the first converter/lator 73. The output voltage of the first comparator 73 becomes high level when the output voltage of the AGC circuit 72 becomes larger than the reference voltage Vr, and thus the output voltage of the first comparator 73 becomes as shown in FIG. The output voltage of the first comparator 73 is integrated in the integration circuit 74, and an output voltage as shown in FIG. 4(e) is generated at the output terminal of the integrated integration circuit 74.
The output voltage is inverted and amplified in the proportional circuit 75, and as a result, output electrons as shown in FIG. 4(d) are generated at the output terminal of the proportional circuit 75. The output voltage of the integrating circuit 74 and the output voltage of the proportional circuit 75 are added in the adding circuit 76, and as a result, the output terminal of the adding circuit 76 has the voltage shown in FIG.
) is generated. On the other hand, the harmonic generation circuit 78 generates an output voltage of a constant frequency as shown in FIG. 4(f). The output voltage of this harmonic generation circuit 78 is compared with the output voltage of the adder circuit 76 in a second comparator 77 as shown in FIG. 4(g).
The output voltage of the controller 77 becomes high level when the output voltage of the adder circuit 76 becomes higher than the output voltage of the harmonic generation circuit 78. Therefore, a continuous pulse as shown in FIG. Assuming that the analog switch 79 is in a conductive state, the solenoid 34 is energized by this continuous pulse. 34 energization time increases. The valve body 32 of the electromagnetic control valve 28 shown in FIG. 1 opens the valve port 31 when the solenoid 34 is energized, and closes the valve port 31 when the solenoid 34 is deenergized. Therefore, as shown in Figure 1, A
When the output of the GC circuit 72 reaches a high level, that is, when the air-fuel ratio of the air-fuel mixture supplied into the engine cylinder becomes smaller than the stoichiometric air-fuel ratio, a The pulse width of continuous pulses becomes wider,
As a result, the opening time of the control valve 28 becomes longer. As the opening time of the electromagnetic control valve 28 becomes longer, the amount of auxiliary air supplied from the auxiliary air supply hole 27 into the intake manifold 25 increases, so that the air-fuel ratio of the air-fuel mixture supplied into the engine cylinder increases. On the other hand, when the air-fuel ratio of the air-fuel mixture supplied into the engine cylinder becomes larger than the stoichiometric air-fuel ratio, the output voltage of the AGC circuit 72 becomes a low level 1, and as a result, a continuous pulse is generated at the output terminal of the second controller 77. i+
The loop width becomes narrower, and the opening time of the electromagnetic control valve 28 becomes shorter. In this way, the amount of auxiliary air 1 supplied into the intake manifold 25 from the auxiliary air supply hole 27 decreases, and the air-fuel ratio of the air-fuel mixture supplied into the engine cylinder becomes smaller.

In this way, the air-fuel ratio of the air-fuel mixture supplied into the engine cylinders is made to substantially match the stoichiometric air-fuel ratio.

On the other hand, as shown in FIG. 2, the electronic control unit 70 includes a dinotal computer 90.

This digital computer 90 includes a microprocessor (CPU) 91 that performs various calculation processes, a random access memory (RAM) 92, and a read-only memory (R) in which control zolograms, calculation constants, etc. are stored in advance.
OM) 93, input port 94, output port 95f,
It is equipped with a CPU91 and a RAM92.

ROM 93, input port 94 and output port 95
are interconnected via bidirectional paths 96. Furthermore, a clock generator 97 is provided within the digital computer 90 to generate various clock signals. On the other hand, a water temperature sensor 98 for detecting engine cooling water temperature is connected to the input port 94 via an AD converter 99, for example.
connected to.

This water temperature sensor 98 is composed of, for example, a thermistor, and generates an output voltage proportional to the engine cooling water temperature. Water temperature sensor 9
The output voltage of 8 is converted into a corresponding binary number in an AD converter 99, and this binary number is sent to an input port 94 and a path 9.
6 to the CPU 91. Further, a starter switch 100 for operating a starter motor for starting the engine is connected to the input port 94, and the opening/closing signal of this starter switch 100 is transmitted to the input port 94 and the bus 9.
6 to the CPU 91.

On the other hand, the output port 95 is connected to a set input terminal S and a reset input terminal R of a pair of S-R fritsuno frogs 101 and 102. Further, in the electronic control unit 70, there is provided an AND r-t 103 which takes the inverted output terminal G of the flip-flop 70 F101 as one input and the output terminal Q of the flip-flop 102 as the other input. -4 output terminal is analog switch 79 and resistor 8
5 connection point 104. Further, the analog switch 79 is connected to the true output terminal Q of the flip 70 f101 and is controlled by the output of the flip F101 (N).

Next, the operation of the air-fuel ratio control device according to the present invention will be explained with reference to the flowchart shown in FIG. Referring to FIG. 5, first, in step 120, it is determined whether starter switch 100 is on. When the starter switch 100 is on, the process proceeds to step f121 and the count number of the counter C is incremented by one. Note that the count value of the counter C is zero when passing through step 121 for the first time, so when the starter switch 100 is turned on, the counting action of the counter C is started. Next, the steg 122 calculates the air bleed time C8, that is, the operating time of the electromagnetic control valve 28, based on the output signal of the water temperature sensor 98 from the relationship shown in FIG. FIG. 6 shows the relationship between the engine cooling water temperature T and the air bleed time CO, and it can be seen that the higher the engine cooling water temperature T, the longer the air bleed time CO.

Note that the relationships shown in FIG. 6 are stored in advance in the ROM 93 in the form of functions or data tables. Next, in the Stella f123, it is determined whether the count value of the counter C is larger than the air bleed time co, and the counter C
If the count value is greater than the air bleed time CO, the process advances to Stella f124. In Stella f124, a start control flag is set. When the start control flag is set, the output voltage of the true output terminal Q of the flip-flop 101 becomes a low level, and the analog switch 79 becomes non-conductive. Therefore, when the startup control flag is set, the flap control by the oxygen concentration detector 69 is stopped.
The output voltage between the inverting output terminals becomes a high level sim. Next, in Stella 7' 125, the duty ratio of the continuous pulse applied to the electromagnetic control valve 28 is calculated based on the output signal of the water temperature sensor 98 from the relationship shown in FIG. Figure 7 shows the relationship between engine cooling water temperature T and duty ratio. It can be seen that the duty ratio increases as MT increases. The relationships shown in FIG. 7 are stored in the ROM 9 in advance in the form of functions or data tables.
It is stored in 3. A set signal and a reset signal are inputted to the set input terminal S and the reset input terminal R of the flip-flop 102 according to this duty ratio, and the output terminal Q of the flip-flop f102 receives a continuous duty ratio.・Grus occurs. Anne r
The output voltage of the r-t 103 becomes high level every time a pulse is generated at the output terminal Q of the flip flora f102, and thus the solenoid 34 of the electromagnetic control valve 28 has a duty voltage.
A ratio drive of 9 pulses is applied. On the other hand, Stella 7'1
20'', when it is determined that the starter switch 100 is turned off, the process advances to step 126 and the counter C is turned off.
is reset to zero, and then in step 127 the starting control flag is cleared. Further, when the count value of the counter C becomes larger than the air bleed time co in Stellar f123, the process proceeds to Stellar f127 and the start control flag is lowered.

When the start control flag is lowered, the flip-flop 10
Since the output voltage of the growth output terminal Q of No. 1 becomes a high level, the analog switch 79 becomes conductive, and feedback control by the oxygen concentration detector 69 is started. At this time, the output voltage of the inverted output terminal of the flip roller f101 becomes low, so that the output voltage of the AND dart 103 is maintained at a low level.

FIG. 8 shows a time chart, in which H indicates the output signal of the starter switch 100, ■ indicates the state of the start flag, and J indicates the continuous pulse supplied to the solenoid 34. As mentioned above, the air bleed time C
o1j: The higher the engine cooling water temperature T becomes, the longer it becomes, and the duty ratio of the continuous pulses applied to the electromagnetic control valve 28 at this time becomes larger as the engine cooling water temperature T becomes higher.

Therefore, the supply time and amount of the auxiliary air supplied from the auxiliary air supply hole 27 during aircraft startup increases as the engine cooling water temperature T increases. This is because the higher the engine cooling water temperature T at startup, the more easily the fuel supplied from the carburetor body evaporates, and therefore the air-fuel mixture supplied into the engine cylinders becomes richer. Therefore, by increasing the supply time and supply amount of auxiliary air as the engine cooling water temperature T rises, it is possible to supply a mixture with an optimal air-fuel ratio into the engine cylinders at the time of starting the aircraft, thus ensuring a constant stable air-fuel mixture. It is possible to ensure the start of the engine.

On the other hand, if the machine Q is restarted immediately after stopping the engine, there will not be much fuel vapor accumulated in the intake manifold 25, and if auxiliary air is supplied in such a case, the mixture supplied to the engine cylinders will be reduced. There is a risk that you will become discouraged and have difficulty starting the engine.

A low chart considering this situation is shown in Fig. 9. This flowchart is the same as that of FIG. 5 except that step 128 is inserted between stela 7 degrees 120 and 121 in the flowchart of FIG. 5, and therefore the explanation of steps 120 to 127 will be omitted. Referring to FIG. 9, when it is determined in Stella f120 that the starter switch 100 is on, the process proceeds to Stella 7'128, where it is determined whether or not the oxygen concentration detector 35 is emitting an output signal. If it is determined in step 128 that the oxygen concentration detector 35 is not emitting an output signal, the process proceeds to Stella f127, after which the electromagnetic control valve 28 is operated based on the engine cooling water temperature T as described above. on the other hand,
When it is determined in the Stellar f128 that the oxygen concentration detector 35 is emitting an output signal, the process proceeds to step 126. The oxygen concentration detector 35 does not generate an output signal unless its own temperature exceeds a certain temperature. Therefore, if the engine is restarted immediately after the engine is stopped, the oxygen concentration detector 35
The oxygen concentration detector 35 is emitting an output signal because the temperature of This can prevent the engine from becoming difficult to start.

Another embodiment is shown in FIG. In this embodiment, an air bleed passage 40 connecting the intake passage 2 upstream of the suction piston 3 and the metering jet 21 is formed in the carburetor body 1, and an electromagnetic control valve 41 is arranged within this air bleed passage 40. In this embodiment, the air-fuel ratio is made to substantially match the stoichiometric air-fuel ratio by controlling the amount of air supplied from the air bleed passage 40 into the fuel passage 20 after engine warm-up is completed. Furthermore, when starting the engine, the amount of air supplied from the air bleed passage 40 into the metering jet 21 is controlled, as in the embodiment shown in FIG. 1, so that a mixture with an optimal air-fuel ratio is formed. The amount of fuel supplied from the main nozzle 23 is controlled.

As described above, according to the present invention, the supply time and amount of the auxiliary air supplied into the intake manifold when the engine starts, or the air supplied from the air bleed passage into the fuel passage, changes as the engine cooling water temperature increases. Since the engine cooling water temperature is increased, a mixture with an optimum air-fuel ratio can be supplied into the engine cylinders regardless of the engine cooling water temperature, and thus good engine starting can be ensured at all times.

[Brief explanation of the drawing]

Figure 1 is a side sectional view of the intake and exhaust system of an internal combustion engine, and Figure 2 is
A circuit diagram of the electronic control unit, FIG. 3 is a diagram showing the output voltage of the oxygen concentration detector, FIG. 4 is a time chart showing the operation of the electronic control unit, and FIG. 5 is a flow chart showing the operation of the air-fuel ratio control device. Figure 6 is a diagram showing the relationship between engine cooling water temperature and air bleed time, Figure 7 is a diagram showing the relationship between engine cooling water temperature and duty ratio, and Figure 8 is the operation of the air-fuel ratio control device when starting the engine. FIG. 9 is a flowchart showing the operation of another embodiment of the air-fuel ratio control device, and FIG. 10 is a side sectional view of another embodiment of the carburetor. 1... Carburetor body, 25... Intake manifold, 26
...Exhaust manifold, 27...Auxiliary air supply hole, 2
8゜41...Solenoid control valve, 35...Oxygen concentration detector, 70...Electronic control unit. Bee〉 Q box C mouth ■Import
：Liangguchii＼ Sheng

Claims (1)

[Claims] In an air-fuel ratio control device in which an electromagnetic control valve is inserted into an auxiliary air supply passage that supplies auxiliary air into an intake manifold or an air bleed passage of a carburetor, and the air-fuel ratio is controlled by the electromagnetic control valve. , comprising a starter switch that operates a starter motor of the engine, a temperature sensor that detects the engine temperature, and an electronic control unit that controls the operating time of the electromagnetic control valve based on output signals of the starter switch and the temperature sensor. . An air-fuel ratio control device for engine starting, wherein the electronic control unit is provided with an operating time increasing means for increasing the operating time as the engine temperature increases.