JPH0232843Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) The present invention aims to improve the air-fuel ratio of the air-fuel mixture produced by the carburetor installed in the engine's intake system to a target value. The present invention relates to a fuel control device for a carburetor that controls a fuel supply system in the carburetor based on a signal obtained from an exhaust sensor installed in the carburetor.

(Prior art) In an engine equipped with a carburetor in the intake system, an oxygen vaporizer installed in the exhaust system is used to converge the air-fuel ratio of the air-fuel mixture provided for combustion in the combustion chamber to a target value (usually the stoichiometric air-fuel ratio). A fuel control device that controls a fuel supply system of a carburetor based on a signal obtained from an exhaust sensor such as a _2- sensor is known, for example, as disclosed in Japanese Patent Laid-Open No. 53-22929. It is being Various fuel control devices that control the fuel supply system of the carburetor have been proposed in the past. There is a type that uses a solenoid valve to open and close the fuel passage and the slow system air passage for feeding air into the slow system fuel passage, thereby controlling the fuel flow rate guided to the intake passage in the carburetor. .

An example of a fuel control device for a carburetor having such a structure will be described with reference to FIG. The fuel ratio control solenoid valve 2 is
It has a solenoid 3 and a rod-shaped valve member 4, and when the solenoid 3 is excited, a first valve part 4a formed at one end (lower end) of the valve member 4 is connected to the main system fuel passage 5A. At the same time, the second valve part 4b formed at the other end (upper end) of the valve member 4 closes the main system correction fuel passage 5B provided in Conversely, when the solenoid 3 is not energized, the first valve portion 4a is operated by the elasticity of the return spring 7 to correct the main system. While opening the fuel passage 5B, the second valve portion 4b closes the slow system air passage 6.

Therefore, the control circuit section connected to this air-fuel ratio control solenoid valve 2 is connected to an exhaust sensor such as an _O2 sensor.
Based on the detection signal S obtained from the OS, the air-fuel ratio of the air-fuel mixture used for combustion is set to a target value (stoichiometric air-fuel ratio).
When feedback control of the air-fuel ratio is performed, for example, by forming a control pulse signal P and supplying it to the solenoid 3 of the air-fuel ratio control solenoid valve 2, in order to converge the air-fuel ratio, for example,
Valve member 4 according to the duty of control pulse signal P
is reciprocated, and the above-mentioned main system correction fuel passage 5B
and the slow system air passage 6 are alternately opened and closed. As a result, during feedback control, the fuel flow rate guided from the float chamber 8 of the carburetor 1 to the intake passage via the main system fuel passage 5A and the main system correction fuel passage 5B, and the slow system flow rate through the slow system air passage 6. The amount of mixed air in the slow system guided to the fuel passage 9 is adjusted to obtain an appropriate air-fuel ratio.

However, the fuel control device for a carburetor configured as described above and configured to perform feedback control of the air-fuel ratio has the following problems.

That is, in an engine equipped with such a carburetor fuel control device, when the fuel consumption is relatively low, for example, when idling continues for a relatively long period of time, the float chamber 8 or because the flow of fuel in the fuel passages such as the main system fuel passage 5A and the main system correction fuel passage 5B is small, the fuel stays in the float chamber 8 or the fuel passage for a relatively long time, and therefore the fuel inside the carburetor 1 can easily become hot. When the fuel temperature inside the carburetor 1 is relatively high and the control pulse signal P is supplied to the air-fuel ratio control solenoid valve 2 to cause the valve member 4 to reciprocate, as shown in FIG. As shown, the first valve portion 4a of the valve member 4
Bubbles are generated in the fuel at the portion where the first valve portion 4a of the main system correction fuel passage 5B, which is opened and closed by the main system correction fuel passage 5B, is located. When such bubbles are generated, fuel is not supplied sufficiently from the float chamber 8 through the main system correction fuel passage 5B, and as a result, the air-fuel ratio shifts to the lean side (lean side). For example, when the vehicle shifts from an idling state to a running state, the acceleration response of the vehicle deteriorates, resulting in problems such as a failure to obtain a smooth running state.

(Purpose of the invention) In view of the above, _the present invention aims to converge the air-fuel ratio of the air-fuel mixture provided for combustion in the combustion chamber to a target value. Based on the signal obtained from the sensor, the air-fuel ratio control valve located in the carburetor controls the opening and closing of the main system correction fuel passage of the carburetor and the slow system air passage that supplies air to the slow system fuel passage. It is designed to perform feedback control of
It is an object of the present invention to provide a fuel control device for a carburetor that can avoid deviation of the air-fuel ratio toward the lean side due to the generation of bubbles in the fuel due to the operation of an air-fuel ratio control valve.

(Structure of the invention) In order to achieve the above object, the fuel control device for a carburetor according to the invention detects the fuel temperature inside the carburetor, and when the detected temperature is less than a predetermined value, Then, when the air-fuel ratio control valve is in a state where it is difficult to generate bubbles in the fuel, feedback control is performed that involves the operation of the air-fuel ratio control valve in response to the signal obtained from the exhaust sensor, and the carburetor is activated. The main system correction fuel passage is opened and closed. In addition, when the detected temperature of the fuel inside the carburetor exceeds a predetermined value, in other words, when the air-fuel ratio control valve is activated and bubbles are likely to be generated in the fuel, the exhaust sensor Feedback control, which involves operating the air-fuel ratio control valve in response to the obtained signal, is stopped to maintain the carburetor's main system correction fuel passage in an open state. Since a larger amount of fuel is supplied than during feedback control, and there is a risk that the air-fuel ratio may shift to the rich side, the main correction fuel passage should be kept open and the throttle valve in the intake passage should be kept open. Supplemental air is supplied to the downstream section to maintain the proper air/fuel ratio.

For this reason, the fuel control device for a carburetor according to the present invention, as shown in its basic configuration in FIG. a temperature sensor that detects fuel temperature or a temperature related thereto; a fuel passage that is provided in the carburetor and communicates between the float chamber and the intake passage; and a correction fuel passage that communicates between the middle of the fuel passage and the float chamber; an air-fuel ratio control valve arranged in the correction fuel passage to control opening and closing of the correction fuel passage; and a supplementary air supply section arranged to supply supplementary air to a position downstream of the throttle valve in the intake passage of the carburetor. , receives the output of the exhaust sensor and the temperature sensor, and when the temperature detected by the temperature sensor is less than a predetermined value, opens and closes the air-fuel ratio control valve based on the output of the exhaust sensor to bring the air-fuel ratio of the mixture to the predetermined value. an air-fuel ratio control valve control means that controls the air-fuel ratio control valve and continuously causes the air-fuel ratio control valve to take a position in which the correction fuel passage is opened when the temperature detected by the temperature sensor is equal to or higher than a predetermined value; and replenishment air control means for causing the replenishment air supply unit to perform a replenishment air supply operation when the temperature detected by the temperature sensor is equal to or higher than a predetermined value.

This configuration prevents bubbles from forming in the fuel due to the operation of the air-fuel ratio control valve, and eliminates the problem of the air-fuel ratio shifting toward the lean side when idling continues. It will be resolved.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 2 shows an example of a fuel control device for a carburetor according to the present invention together with the main parts of a carburetor to which the device is applied.

In FIG. 2, a carburetor 10 provided in an intake system of an engine has a float chamber 12, and a float 14 is disposed within the float chamber 12 to maintain a constant fuel level. A main system fuel passage 16 has one end connected to an intake passage 30 and the other end opens at the bottom of the float chamber 12, and a main jet 18 is provided in the main system fuel passage 16. Further, a main system correction fuel passage 20 is opened at the side of the float chamber 12 on the intake passage 30 side, and a correction jet 22 is provided in this main system correction fuel passage 20. The main system fuel passage 16 and the main system correction fuel passage 2 merge, and a main air bleed 26 is provided downstream from the junction, and
The main air bleed 26 causes air to be mixed into the fuel that is led from the main system fuel passage 16 and the main system correction fuel passage 20 to the main nozzle 28 via the main air bleed 26 .
The main nozzle 28 opens into the inner wall of the small bench lily 32 in order to supply fuel to the intake passage 30 in which the small bench lily 32 and the large bench lily 34 are arranged. These main system fuel passage 16, main jet 18, main system correction fuel passage 20, correction jet 22, main air bleed 26, main nozzle 28, small bench lily 32, and large bench lily 34
The main system of the carburetor 10 is composed of the following.

Furthermore, the starting end of the slow system fuel passage 36 is open downstream of the confluence between the main system fuel passage 16 and the main system correction fuel passage 20, and the fuel in the float chamber 12 is supplied to the main system fuel passage 16 and the main system correction fuel passage 20. Through the main system correction fuel passage 20, the slow jet 44
The intake passage 3 is also connected to the slow port 38 and the idle port 42 whose effective opening area is adjusted by the idle adjustment screw 41 through the slow system fuel passage 36 provided with the slow air bleed 46.
0. Further, a correction air passage 40 for adjusting the amount of air mixed into the fuel is opened in the slow system fuel passage 36. These slow system fuel passage 36, slow port 38, correction air passage 40, idle adjustment screw 41, idle port 42, slow jet 44, slow air bleed 46, etc. constitute the slow system of the carburetor 10.

Inside the carburetor 10 having the above-described configuration, there is an air-fuel ratio control solenoid valve that is operated to converge the air-fuel ratio of the air-fuel mixture generated by the carburetor 10 to a target value (for example, the stoichiometric air-fuel ratio). 50
is included. This air-fuel ratio control solenoid valve 5
0 includes a rod-shaped valve member 52 in which a first valve part 52a is formed at one end (lower end) and a second valve part 52b is formed at the other end (upper end), and this valve member 52.
The solenoid 54 is driven in response to a control pulse signal Pc supplied from a control unit 100, which will be described later, and a meturn spring 56 acts on the valve member 52. When the control pulse signal Pc is supplied to the solenoid 54, the valve member 52 opens and closes the main correction fuel passage 20 with the first valve part 52a, and the correction air passage 40 with the second valve part 52b of the valve member 52. When the solenoid 54 is reciprocated to open and close, and when the control pulse signal Pc is not supplied to the solenoid 54, the biasing force of the return spring 56 causes the first valve portion 52a of the valve member 52 to move toward the main system correction fuel passage 20. is opened, and the second valve portion 52b is placed in a position to close the correction air passage 40.

Further, a replenishment air supply passage 70 for introducing replenishment air from the air cleaner 72 to a portion of the intake passage 30 downstream of the throttle valve 60 is provided. A normally closed type electromagnetic switching valve 74 that opens and closes is provided.

Solenoid 5 of the above-mentioned air-fuel ratio control solenoid valve 50
The control unit 100 that supplies the control pulse signal Pc to the intake passage 30 has a control unit 100 that controls the opening degree of the throttle valve 60 disposed in the intake passage 30, that is, the throttle opening degree θ.
A detection signal St corresponding to the throttle opening θ is sent from the throttle opening _sensor 62 that detects Detection signal So, detection signal Sn corresponding to engine rotation speed Ne from an engine rotation speed sensor 66 provided in connection with the crank mechanism of the engine (not shown), and fuel temperature inside the carburetor 10 are detected. A detection signal Ss from a temperature sensor 68 attached to the float chamber 12 is supplied. Then, the control unit 100 forms the above-mentioned control pulse signal Pc based on the above-mentioned detection signals St, So, Sn, Ss, etc., and supplies it to the solenoid 54 of the air-fuel ratio control solenoid valve 50. A drive signal Cf is supplied to a normally closed type electromagnetic switching valve 74 provided in the supplementary air supply passage 70.

Based on the configuration as described above, such a vaporizer 10
When the engine equipped with the engine is in a normal operating state including an idling operating state, the control unit 100 performs an air-fuel ratio feedback control operation based on the detection signal So obtained from the O ₂ sensor 64. In this case, the control unit 100 determines that when the oxygen concentration in the exhaust gas indicated by the detection signal So obtained from the O ₂ sensor 64 is lower than a predetermined value, that is, when the air-fuel ratio of the air-fuel mixture provided for combustion at that time is When the air-fuel ratio is lower than the air-fuel ratio (the mixture is rich), the duty of the control pulse signal Pc supplied to the air-fuel ratio control solenoid valve 50 is increased to increase the time for closing the main system correction fuel passage 20, and the correction air passage 40 is increased. Reduce opening time. As a result, the amount of fuel flowing out from the float chamber 12 through the main correction fuel passage 20 is reduced, and the amount of air introduced into the slow system fuel passage 36 is increased, making the air-fuel mixture for combustion leaner. be done. On the contrary, when the air-fuel ratio indicated by the detection signal So becomes larger than the stoichiometric air-fuel ratio (the mixture is lean), the control unit 100 changes the control pulse signal Pc to be supplied to the solenoid 54 of the air-fuel ratio control solenoid valve 50. By reducing the duty, the time for closing the main correction fuel passage 20 is reduced, and the time for opening the correction air passage 40 is increased. As a result, the amount of fuel flowing out from the float chamber 12 through the main system correction fuel passage 20 increases, and the amount of air introduced into the slow system fuel passage 36 decreases, making the air-fuel mixture for combustion richer. be done. In this way, control unit 1
By changing the duty of the control pulse signal Pc supplied to the solenoid 54 of the air-fuel ratio control solenoid valve 50 based on the detection signal So obtained from the O ₂ sensor 64, The fuel ratio can be made to converge to the stoichiometric air-fuel ratio, and harmful components in the exhaust gas can be reduced.

By the way, for example, when the engine is in an idling state where the fuel consumption is relatively low for a long time, the air-fuel ratio control electromagnetic valve 5
Due to the reciprocating movement of the valve member 52 of the main system correction fuel passage 20, bubbles are generated in the fuel in the portion where the first valve part 52a of the main system correction fuel passage 20 is located, and the main system correction fuel passage 20 is removed from the float chamber 12. Then, the amount of fuel that flows out becomes insufficient and the air-fuel ratio deviates to the lean side.As a result, there is a risk that the acceleration response of the vehicle will deteriorate when the vehicle transitions from an idling state to a running state.

In order to prevent the air-fuel ratio from shifting to the lean side,
In this example, the control unit 100 first detects that the throttle valve 60 is in a substantially fully closed state (throttle opening θ) based on the detection signal St obtained from the throttle opening sensor 62 and the detection signal Sn obtained from the engine speed sensor is at the idling opening θ ₀ ) and the engine rotational speed Ne is at a predetermined rotational speed (idling rotational speed N ₁ ), that is, the engine is in an idling operating state and fuel consumption is relatively small. determine whether the condition is
Furthermore, a detection signal obtained from the temperature sensor 68
Based on Ss, it is determined whether the fuel temperature Tm inside the carburetor 10 is equal to or higher than a predetermined temperature _T1 . As a result, when the engine is in an idling state and it is detected that the fuel temperature Tm inside the carburetor 10 is equal to or higher than the predetermined temperature _T1 , a control pulse is applied to the solenoid 54 of the air-fuel ratio control solenoid valve 50. signal
At the same time as stopping the supply of PC, the electromagnetic switching valve 74
A drive signal Cf is supplied to the As a result, the operation of the air-fuel ratio control solenoid valve 50 is stopped, the main system correction fuel passage 20 is kept open, the correction air passage 40 is kept closed, and the electromagnetic The switching valve 74 is opened and the replenishment air supply passage 70 is brought into communication, and the intake passage 3
Supplementary air is now supplied to the downstream portion of the throttle valve 60 at 0. At this time, the fuel from the float chamber 12 flows out through the main correction fuel passage 20 without being blocked by the valve member 52, and the amount of fuel sucked into the intake passage 30 from the idle port 42 and the like increases. Since replenishment air is supplied to the downstream side of the throttle valve 60 of the intake passage 30 via the replenishment air supply passage 70, the air-fuel ratio does not deviate to the rich side and remains at an appropriate value (near the stoichiometric air-fuel ratio). maintained.

Thereafter, when the vehicle shifts from the idling state in which the operation of the air-fuel ratio control solenoid valve 50 is stopped as described above to the running state of the vehicle, the control unit 100 detects signals from the throttle opening sensor 62 and the engine rotation speed sensor 66. This is detected based on the detection signals St and Sn, and the air-fuel ratio feedback control is started and the electromagnetic switching valve 74
The supply of replenishment air is stopped by cutting off the supply of the drive signal Cf to. At this time, since the operation of the air-fuel ratio control solenoid valve 50 had been stopped and the valve member 52 of the air-fuel ratio control solenoid valve 50 was in a stationary state, the fuel in the carburetor 10 was at a relatively high temperature. Even if the main system correction fuel passage 20
No bubbles are generated in the portion of the valve member 52 where the first valve portion 52a is located. That is, by stopping the operation of the air-fuel ratio control solenoid valve 50 and keeping the valve member 52 in a stationary state, air bubbles are removed in the portion of the main system correction fuel passage 20 where the first valve portion 52a of the valve member 52 is located. This prevents the occurrence of Therefore, as the vehicle transitions from idling to running, fuel can flow out smoothly from the float chamber 12 through the main system correction fuel passage 20, causing the air-fuel ratio to deviate from the stoichiometric air-fuel ratio to the lean side. As a result, the acceleration response of the vehicle is improved.

The above-mentioned control is mainly performed by the operation of a microcomputer built into the control unit 100, and an example of a program executed by such a microcomputer will be explained with reference to the flowchart shown in FIG.

In this program, after starting, in process 101, the throttle opening θ indicated by the detection signal St obtained from the throttle opening sensor 62 and the engine rotation speed Ne indicated by the detection signal Sn obtained from the engine rotation speed sensor 66 are read. In the subsequent decision 102, the throttle opening θ and engine speed Ne read in process 101 are
Based on this, it is determined whether the throttle opening θ is at the idling opening θ ₀ and the engine speed Ne is at the idling speed N ₁ , that is, whether the engine is in an idling operating state. do. If it is determined that the idling operation is not in progress, the flow of fuel in the carburetor 10 is relatively active and bubbles are less likely to be generated in the fuel, so the process proceeds to process 103, as described above. Similarly, the detection signal So obtained from the O ₂ sensor 64
The solenoid 5 of the air-fuel ratio control solenoid valve 50
The duty of the control pulse signal Pc supplied to the control pulse signal Pc is changed to perform feedback control of the air-fuel ratio.
In such feedback control, it is not necessary to supply replenishment air through the replenishment air supply passage 70, so the process proceeds to process 104, where the sending of the drive signal Cf to the electromagnetic switching valve 74 is stopped, and the replenishment air is supplied through the replenishment air supply passage 70. The supply of supplementary air through the supply passage 70 is shut off.

On the other hand, if it is determined at decision 102 that the vehicle is in an idling state, the process proceeds to process 105 where the fuel temperature Tm indicated by the detection signal Ss obtained from the temperature sensor 68 is read. Predetermined temperature
Whether it is T ₁ or more, that is, the air-fuel ratio control solenoid valve 50
It is determined whether or not the temperature is higher than the temperature at which bubbles are generated in the fuel as the valve member 52 reciprocates, causing the above-mentioned problems. Here, fuel temperature
If it is determined that Tm is not equal to or higher than the predetermined temperature _T1 , the above-described processes 103 and 104 are sequentially executed to perform normal feedback control.

Further, if it is determined in the decision 106 that the fuel temperature Tm is equal to _or higher than the predetermined temperature T1, the process proceeds to process 107 to stop the operation of the air-fuel ratio control solenoid valve 50. The control pulse signal Pc is not supplied to the solenoid 54, and the feedback control is stopped. As a result, the main correction fuel passage 20 is kept open, and the correction air passage 40 is kept closed. And the following process 1
At 08, a drive signal Cf is supplied to the electromagnetic switching valve 74 to open it, and the replenishment air supply passage 7 is opened.
0 is connected. As a result, the intake passage 30
Replenishment air is supplied (inhaled) to the downstream side of the throttle valve 60, and the air-fuel ratio of the air-fuel mixture used for combustion is maintained at an appropriate value (near the stoichiometric air-fuel ratio).

In the above-mentioned example, the fuel temperature inside the carburetor is detected by the temperature sensor 68 provided in the float chamber, but in the fuel control device for a carburetor according to the present invention, this is not necessarily the case. It is not necessary to directly detect the fuel temperature inside the carburetor; for example, by detecting a temperature related to the fuel temperature inside the carburetor, such as the ambient temperature in the float chamber, it is possible to indirectly detect the fuel temperature inside the carburetor. Temperature may also be detected.

(Effect of the invention) As is clear from the above explanation, according to the fuel control device for a carburetor according to the present invention, when the vehicle is in a normal running state, the air-fuel ratio control valve is controlled based on the signal obtained from the exhaust sensor. On the other hand, when the engine is idling and the fuel temperature inside the carburetor exceeds a predetermined value, the operation of the air-fuel ratio control valve is stopped to control the carburetor. The main system correction fuel passage is opened, the air passage that supplies air to the slow system fuel passage is closed, and supplementary air is supplied to the downstream part of the intake passage from the throttle valve, so the idling Even when the operating state continues for a long time, the generation of bubbles in the fuel due to the operation of the air-fuel ratio control valve can be prevented. Therefore, it is possible to avoid a shift in the air-fuel ratio toward the lean side due to the generation of bubbles in the fuel, which may occur immediately after idling continues for a long time, and it is possible to prevent the vehicle from idling. It is possible to solve problems such as the vehicle not being smoothly accelerated or the acceleration response being deteriorated when transitioning to the state.

[Brief explanation of the drawing]

FIG. 1 is a basic configuration diagram of a fuel control device for a carburetor according to the present invention, and FIG. 2 is a schematic configuration diagram showing an example of a fuel control device for a carburetor according to the present invention together with a carburetor to which it is applied. FIG. 3 is a flowchart showing an example of a program executed by a microcomputer used in the control unit shown in FIG. 2, and FIGS. 4 and 5 show the configuration and operation of a conventional fuel control device for a carburetor. FIG. 2 is a partial schematic configuration diagram used for explanation. In the figure, 10 is a carburetor, 16 is a main system fuel passage, 20 is a main system correction fuel passage, 30 is an intake passage, 36 is a slow system fuel passage, 40 is a correction air passage, and 50 is a solenoid valve for air-fuel ratio control. , 64 is an O ₂ sensor, 68 is a temperature sensor, 70 is a supplementary air supply passage, and 74 is an electromagnetic switching valve.

Claims (1)

[Scope of utility model registration request] An exhaust sensor installed in the engine exhaust system,
a temperature sensor that detects the fuel temperature inside the carburetor provided in the intake system of the engine or a temperature related thereto; a fuel passage provided in the carburetor that communicates the float chamber and the intake passage; a correction fuel passage communicating between the middle of the fuel passage and the float chamber; an air-fuel ratio control valve disposed in the correction fuel passage to control opening and closing of the correction fuel passage; and a throttle valve of the intake passage in the carburetor. A replenishment air supply section arranged to supply replenishment air at a position on the downstream side receives the outputs of the exhaust sensor and the temperature sensor, and when the temperature detected by the temperature sensor is less than a predetermined value, the air-fuel mixture is The air-fuel ratio control valve is controlled to open and close based on the output of the exhaust sensor to bring the air-fuel ratio to a predetermined value, and when the temperature detected by the temperature sensor is equal to or higher than a predetermined value, the air-fuel ratio control valve is an air-fuel ratio control valve control means for continuously keeping the corrected fuel passage in an open position; A fuel control device for a carburetor, comprising a replenishment air control means for causing a replenishment air supply operation to be performed.