JPH0330613Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a variable bench lily type carburetor for use in an internal combustion engine.

[Conventional technology]

When the engine is started at a low temperature, the temperature of the intake manifold is low, so the fuel supplied from the variable bench lily type carburetor and attached to the inner wall of the intake manifold does not easily vaporize, resulting in the air-fuel mixture supplied into the engine cylinders being too lean. There is a problem with getting used to it.
Furthermore, in order to ensure good acceleration during engine acceleration, it is necessary to increase the amount of fuel supplied from the variable bench lily type carburetor, whether the engine is at low temperature or high temperature.

Therefore, an accelerator pump that is activated during acceleration operation is provided, and the pump chamber of the accelerator pump is connected to the intake passage upstream of the bench lily section via the acceleration fuel supply passage to accelerate the engine regardless of whether the engine is at low temperature or high temperature. When the pump is activated, additional fuel is supplied into the intake passage upstream of the bench lily, while a starting fuel supply passage is branched from the acceleration fuel supply passage, and this starting fuel supply passage is connected to the intake passage downstream of the bench lily. A variable bench lily type carburetor is known (see Utility Model Application No. 55-98362), which is provided with an on-off valve that opens when the suction piston is fully closed in the starting fuel supply passage.

In this variable bench lily type carburetor, the on-off valve is opened when the engine is started when the suction piston is fully closed, so if the accelerator pump is activated at this time, the fuel in the pump chamber will flow through the starting fuel supply passage to the vent lily. It is supplied into the intake passage downstream of the engine.

[Problem that the invention attempts to solve]

However, with this variable bench lily type carburetor, fuel is not supplied from the starting fuel supply passage unless the accelerator pump is activated, and when the engine starts running on its own and the suction piston opens, the on-off valve is closed. Therefore, no additional fuel is supplied unless the accelerator pump is activated. In other words, additional fuel is supplied in this variable ventilator carburetor only when the accelerator pump is activated.

However, the fuel adhering to the intake manifold does not easily vaporize until the engine temperature rises and the temperature of the intake manifold rises, and unless additional fuel is continuously supplied during this period, the fuel will not be easily vaporized into the engine cylinders. The air-fuel mixture becomes too lean.

Therefore, if additional fuel is supplied only when the accelerator pump is activated, as in the case of the above-mentioned variable bench lily type carburetor, the air-fuel mixture that is supplied into the engine cylinder unless the accelerator pump is activated. There is a problem in that the fuel becomes too lean and good combustion cannot be achieved continuously until the engine temperature rises sufficiently.

[Means for solving problems]

In order to solve the above problems, the present invention is equipped with an accelerator pump, and the fuel in the float chamber is passed through the pump chamber through a first check valve that can flow only from the float chamber to the pump chamber of the accelerator pump. In a variable bench lily type vaporizer designed to supply
The pump chamber of the acceleration pump is connected to the bench lily portion via an acceleration fuel supply passage, and a second check valve is provided in the acceleration fuel supply passage that allows flow only from the pump chamber to the bench lily portion. An air bleed passage is connected to the atmosphere from the acceleration fuel supply passage located between the stop valve and the bench lily, and a control valve that responds to the engine temperature and closes when the engine temperature is below a predetermined temperature is connected to the air bleed passage. Provided in the bleed passage, when the control valve is closed and the acceleration pump is not operating, the negative pressure generated in the bench lily part drains the fuel in the float chamber to the first check valve and the second check valve. Accelerating fuel is continuously sucked out from the accelerating fuel supply passage into the bench lily section through the valve, and when the control valve is closed and the accelerating pump is operated, the fuel in the pump chamber is accelerated through the second check valve. The fuel is supplied from the fuel supply passage into the bench lily, and when the control valve is open and the acceleration pump is not operating, the suction of fuel from the acceleration fuel supply passage to the bench lily is stopped and the control valve is opened. and when the accelerator pump is activated, the fuel in the pump chamber is
The acceleration fuel is supplied into the bench lily portion from the acceleration fuel supply passage through the check valve.

〔Example〕

Referring to FIG. 1, 1 is a carburetor main body, 2 is an intake passage extending vertically, 3 is a suction piston that moves laterally within the intake passage 2, and 4 is attached to the tip surface of the suction piston 3. 5 indicates the inner wall surface of the intake passage 2 facing the tip surface of the suction piston 3, 6 indicates a throttle valve provided in the intake passage 2 downstream of the suction piston 3, and 7 indicates a float chamber of the carburetor. A bench lily portion 8 is formed between the distal end surface of the suction piston 3 and the inner wall surface 5 of the intake passage. 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 large number of balls 1 are contained within the guide sleeve 10.
1 is inserted, and the outer end of the guide sleeve 10 is closed by a blind cover 13.
On the other hand, the suction piston 3 has a guide rod 14.
is fixed, and the guide rod 14 is inserted into the bearing 12 so as to be movable in the axial direction of the guide rod 14. Inside the casing 9 is a suction piston 3
The negative pressure chamber 15 is divided into a negative pressure chamber 15 and an atmospheric pressure chamber 16, and a compression spring 17 is installed in the negative pressure chamber 15 to constantly pressurize the suction piston 3 toward the bench lily portion 8.
is inserted. The negative pressure chamber 15 is connected to the bench lily section 8 through a suction hole 18 formed in the suction piston 3, and the atmospheric pressure chamber 16 is connected to the suction piston 3 upstream through an air hole 19 formed in the carburetor body 1. The intake passage 2 is connected to the inside of the intake passage 2.

On the other hand, a main fuel passage (not shown) 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 jet that cooperates with the needle 4 is formed in the main fuel passage. (not shown) is provided. The main fuel passage upstream of this metering jet is connected to the float chamber 7.

As shown in FIG. 1, a raised wall 20 that projects horizontally into the intake passage 2 is formed on the inner wall surface 5 of the intake passage facing the upstream end of the suction piston 3. sion piston 3
Flow rate control is performed between the tips of the . When engine operation is started, air flows downward in the intake passage 2. At this time, since the air flow is restricted between the suction piston 3 and the raised wall 20, negative pressure is generated in the bench lily portion 8, and this negative pressure is guided into the negative pressure chamber 1 through the suction hole 18. The suction piston 3 has a negative pressure chamber 15 and an atmospheric pressure chamber 16.
The bench lily portion 8 moves so that the pressure difference therebetween becomes a substantially constant pressure determined by the spring force of the compression spring 17, that is, the negative pressure within the bench lily portion 8 becomes substantially constant.

On the other hand, an acceleration pump 21 is provided within the carburetor main body 1. This acceleration pump 21 includes a piston 23 that can be moved up and down within a cylinder 22, and a pump chamber 24 defined by the piston 23. On the one hand, the pump chamber 24 has a check valve 25 that allows flow only from the float chamber 7 into the pump chamber 24.
It is connected to the inside of the float chamber 7 via an acceleration fuel supply passage 26 and a fuel supply port 27 on the other hand. A fuel supply port 27 is provided in the acceleration fuel supply passage 26 from the pump chamber 24.
A check valve 28 is inserted that allows flow only towards the direction. A piston 23 of the acceleration pump 21 is connected to, for example, a throttle valve 6, and when the throttle valve 6 is opened, the piston 23 is lowered. When the piston 23 is lowered, the fuel in the pump chamber 24 is supplied into the bench lily portion 8 from the fuel supply port 27 via the acceleration fuel supply passage 26. When the piston 23 rises, the fuel in the float chamber 7 is sent into the pump chamber 24.

On the other hand, the acceleration fuel supply passage 26 downstream of the check valve 28
A jet 29 is inserted therein, and the acceleration fuel supply passage 26 between the jet 29 and the fuel supply port 27 is communicated with the atmosphere via an air bleed passage 30 and an air filter 31. Air bleed passage 3
A control valve 32 is disposed within 0. One terminal of the solenoid 33 of the control valve 32 is connected to a power source 35 via an ignition switch 34, and the other terminal is grounded via a timer 36 and a temperature sensitive switch 37. The temperature sensitive switch 37 is turned on when the engine temperature is lower than a predetermined temperature.
On the other hand, after the timer 36 is energized,
It remains on for a certain period of time, for example several minutes.

Therefore, when the engine is started when the engine temperature is lower than a predetermined temperature, the temperature sensitive switch 37 and the timer 36 are both turned on, so the solenoid 33 is energized, and as a result, the control valve 32 is closed. I am forced to do it. At this time, since a negative pressure is generated in the bench lily portion 8, the fuel in the float chamber 7 flows from the fuel supply port 27 via the check valve 25, the pump chamber 24, the check valve 28, and the acceleration fuel supply passage 26. It is sucked out into the bench lily section 8. In this way, after the engine is started at a low temperature, fuel is additionally supplied from the fuel supply port 27 in addition to the fuel supplied from the main fuel passage (not shown), so that the air-fuel mixture supplied into the engine cylinders becomes too lean. can be prevented.
Of course, if the acceleration pump 21 is operated at this time, a larger amount of fuel will be additionally supplied.

When the timer 36 turns off after a certain period of time has passed after the engine has started, or when the engine temperature becomes higher than a predetermined temperature and the temperature-sensitive switch 37 turns off, the solenoid 33 is deenergized, and as a result, the control valve 32 is turned off.
opens. Therefore, at this time, the inside of the acceleration fuel supply passage 26 downstream of the jet 29 communicates with the atmosphere, so only air is supplied from the fuel supply port 27, and the supply of fuel is stopped. Note that at this time, the acceleration pump 21 is not activated. If forced to do so, the fuel in the pump chamber 24 is supplied to the fuel supply port 27 via the acceleration fuel supply passage 26.
Supplied from.

Another embodiment is shown in FIG. In this embodiment, a temperature-sensitive control valve 40 is disposed within the air bleed passage 30. A temperature sensing portion 41 of the control valve 40 is disposed within an engine cooling water passage 42, and a bimetal element 43 for controlling opening and closing of the air bleed passage 30 is disposed within the temperature sensing portion 41. When the engine cooling water temperature is lower than a predetermined temperature, bimetal element 4
3 is curved to close the valve port 44 as shown in FIG.
The fuel inside is sucked out into the bench lily portion 8 from the fuel supply port 27 via the acceleration fuel passage 26. On the other hand, when the engine cooling water temperature is higher than a predetermined temperature, the bimetal element 43 bends in the opposite direction to that shown in FIG. 2 to open the valve port 44.
As a result, only air is supplied from the fuel supply port 27, and the supply of fuel is thus stopped.

[Effect of the invention] Additional fuel is continuously supplied into the vent lily while the engine temperature rises to a predetermined temperature, so that the engine cylinders are kept cool until the engine temperature rises to the predetermined temperature. The air-fuel mixture supplied to the engine does not become too lean, and thus good combustion can be achieved during this period. In addition, since the acceleration fuel supply passage is used to increase the amount of fuel after the engine starts at a low temperature without providing a starting fuel passage, the structure of the carburetor can be simplified and the carburetor can be manufactured easily. can do.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view of a variable bench lily type carburetor, and FIG. 2 is a side sectional view of a variable bench lily type carburetor showing another embodiment. 3... Suction piston, 4... Needle,
8... Bench lily part, 21... Acceleration pump, 24
... Pump chamber, 26 ... Acceleration fuel supply passage, 27
... Fuel supply port, 30 ... Air bleed passage, 3
2...Control valve.

Claims (1)

[Scope of utility model registration request] In a variable bench lily type carburetor equipped with an accelerator pump, the fuel in the float chamber is supplied into the pump chamber via a first check valve that allows flow of fuel only from the float chamber to the pump chamber of the accelerator pump, A pump chamber of the acceleration pump is connected to the bench lily portion via an acceleration fuel supply passage, and a second check valve is provided in the acceleration fuel supply passage allowing flow only from the pump chamber to the bench lily portion, and the second check valve is provided in the acceleration fuel supply passage. A control valve that branches an air bleed passage communicating with the atmosphere from the acceleration fuel supply passage located between the check valve and the bench lily, and closes when the engine temperature is below a predetermined temperature in response to the engine temperature. is provided in the air bleed passage, and when the control valve is closed and the acceleration pump is not operating, the negative pressure generated in the bench lily portion drains the fuel in the float chamber to the first check valve and The fuel in the pump chamber is continuously sucked out from the acceleration fuel supply passage into the bench lily section through the second check valve, and when the control valve is closed and the acceleration pump is operated, the fuel in the pump chamber is Fuel is supplied from the acceleration fuel supply passage into the bench lily through a stop valve, and when the control valve is open and the acceleration pump is not operating, the action of sucking out fuel from the acceleration fuel supply passage into the bench lily is stopped. At the same time, when the control valve is open and the acceleration pump is operated, the fuel in the pump chamber is supplied from the acceleration fuel supply passage into the bench lily portion via the second check valve. vessel.