JP2010048232A - Fuel supply device of engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a simple and inexpensive automatic drain technology, in a fuel supply device of an engine having drain passages for pulling out fuel from a float chamber of a carburetor. <P>SOLUTION: A drain valve 50 closing when rotating a crankshaft 19 and opening when stopping the crankshaft 19, is interposed in the drain passages 35 and 36 up to a fuel tank 31 from the float chamber 32 of the carburetor 13. The drain valve 50 opens based on pressure of a crankcase 23 without depending on electric-electronic control. When stopping the engine, the drain valve automatically opens. As a result. the fuel stored in the carburetor returns to the fuel tank by the gravitational action. Since the drain valve is opened and closed by the pressure of the crankcase without using the electric-electronic control, the fuel supply device of the engine is simplified and reduced in cost. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel supply device for an engine having a drain passage for removing fuel from a float chamber of a carburetor.

In an engine equipped with a carburetor, fuel mist is mixed with air by the carburetor and supplied to the fuel chamber of the engine.
The carburetor includes a fuel reservoir portion called a float chamber, and sucks fuel from the float chamber and mixes it with air. Therefore, fuel is always stored in the float chamber.

  This is not a problem for vehicles with a relatively short stoppage period, but the following problems occur when the period of use is limited as in the case of agricultural machines, and most of the year is suspended. That is, the fuel accumulated in the float chamber deteriorates and changes quality during the suspension. Altered fuel induces clogging of the carburetor nozzle.

As a countermeasure, it has been proposed to remove fuel from the float chamber of the carburetor (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 10-227263 (FIG. 1)

Patent document 1 is demonstrated based on the following figure.
FIG. 8 is a diagram for explaining the basic principle of the prior art. The first fuel supply path 101 is extended from the fuel tank 100 and connected to the D port of the switching cock 103 of the pump 102. The A port of the switching cock 103 is shown in FIG. The second fuel supply path 104 is extended from the upper part of the float chamber 106 of the carburetor 105.

  A first fuel return passage 107 extends from the bottom of the float chamber 106 of the carburetor 105 and is connected to the C port of the switching cock 103 of the pump 102, and a second fuel return passage 108 extends from the B port of the switching cock 103. It is extended and connected to the fuel tank 100.

  Normally (for example, an operation period of an agricultural machine), the D port and the A port are communicated using the cock lever 109. When the pump 102 is started, the fuel in the fuel tank 100 can be supplied to the vaporizer 105. Since the first fuel return passage 107 is closed by the switching cock 103, the fuel does not return from the carburetor 105 to the fuel tank 100.

  At the time of storage (for example, when the agricultural machine is idle), the cock port 109 is used to connect the C port and the B port. When the pump 102 is started, the fuel in the float chamber 106 of the vaporizer 105 is returned to the fuel tank 100.

The cock lever 109 is operated by an operator's hand. If the operator forgets to do this artificially, fuel remains in the float chamber 106 in the vaporizer 105. In order to avoid this problem, it is conceivable that the operating state of the engine is detected by electric / electronic technology, and the drain valve is opened when the engine enters the idle period. However, electric / electronic control is expensive and difficult to implement.
Therefore, a simple automatic drain technology that does not depend on electric / electronic control is required.

  It is an object of the present invention to provide a simple and inexpensive automatic drain technique in an engine fuel supply apparatus having a drain passage for extracting fuel from a float chamber of a carburetor.

  According to a first aspect of the present invention, in the fuel supply apparatus for an engine having a drain passage for drawing fuel from the float chamber of the carburetor, the drain passage is connected to a fuel tank disposed below the carburetor in the direction of gravity. The drain passage is provided with a drain valve that automatically closes when the engine is in an operating state and automatically opens when the engine is in a stopped state.

  The invention according to claim 2 is characterized in that the drain valve is closed by receiving a positive pressure generated in the crank chamber of the engine, and is opened when the positive pressure cannot be received when the engine is stopped.

  The invention according to claim 3 is characterized in that the drain valve is closed by receiving the discharge pressure of the fuel pump that pumps the fuel in the fuel tank to the vaporizer, and opens when the discharge pressure of the fuel pump cannot be received.

  In the invention according to claim 1, when the engine stops, the drain valve automatically opens. As a result, the fuel accumulated in the carburetor returns to the fuel tank by gravity.

  In the invention according to claim 2, the drain valve is opened and closed based on the internal pressure of the crank chamber of the engine. Since the drain valve is opened and closed by the pressure in the crank chamber without using electric / electronic control, the fuel supply device of the engine is simple and inexpensive.

  In the invention according to claim 3, the drain valve is opened and closed based on the discharge pressure of the fuel pump. Since the drain valve is opened / closed by the discharge pressure of the fuel pump without using electric / electronic control, the fuel supply device of the engine becomes simple and inexpensive.

The best mode for carrying out the present invention will be described below with reference to the accompanying drawings. The drawings are viewed in the direction of the reference numerals.
FIG. 1 is a principle diagram of an engine fuel supply apparatus according to the present invention. An engine 10 controls the flow rate of air sucked through an air cleaner 11 by a throttle valve 12 and supplies fuel to the controlled air by a carburetor 13. The mixture is mixed, sent to the combustion chamber 15 through the intake passage 14, compressed by the piston 16, and ignited / exploded by the spark plug 17 to rotate the crankshaft 19 through the connecting rod 18, and the exhaust gas passes through the exhaust passage 21 and the muffler 22. It is an internal combustion engine whose operating principle is that it is discharged.

  The fuel supply device 30 for supplying fuel to the engine 10 is arranged below the carburetor 13 in the direction of gravity and stores the fuel tank 31 and the fuel tank 31 to the upper part of the float chamber 32 of the carburetor 13. An extended fuel supply passage 33, a fuel pump 34 provided in the fuel supply passage 33 for sending fuel to the float chamber 32, drain passages 35, 36 extending from the bottom of the float chamber 32 to the fuel tank 31, and these drains A drain valve 50 (details will be described later) provided between the passages 35 and 36, a pressure guiding pipe 37 extending from the drain valve 50 to the crank chamber 23 of the engine 10, and a check valve 38 provided in the pressure guiding pipe 37. Become.

The check valve 38 includes a ball 39 and a spring 41. When the pressure in the crank chamber 23 is higher than the pressure on the drain valve 50 side, the ball 39 moves to the right in the figure, and the high pressure is drained. Guided to valve 50. When the pressure in the crank chamber 23 is lower than the pressure on the drain valve 50 side, the ball moves to the left in the figure and the valve is closed.
The fuel pump 34 is preferably a trochoid pump or a gear pump, and is driven by the crankshaft 19 via a chain or belt 42, for example.

  FIG. 2 is a configuration diagram of the drain valve. The drain valve 50 includes a container-like valve box 53 having a bottom portion 51 and a peripheral wall portion 52 and an open surface, and a diaphragm 54 that blocks the open surface of the valve box 53. The cup 54 covers the diaphragm 54, the drain passage 35 is inserted from the bottom 51 of the valve box 53, and the diaphragm 54 is urged to the right in the figure, the valve A connection port 57 for connecting the drain passage 36 to the peripheral wall portion 52 of the box 53, an insertion port 58 for connecting the pressure guiding tube 37 to the lid 55, and an outside air communication hole 59 for communicating the inside of the lid 55 with the outside. .

  When high-pressure air is supplied into the lid body 55 through the pressure guiding pipe 37, the diaphragm 54 is pushed to close the drain passage 35 as indicated by the white arrow. Although air always leaks from the outside air communication hole 59, since the amount of air supplied through the pressure guiding tube 37 is superior, the pushing action indicated by the white arrow is maintained.

  FIG. 3 is an operation diagram of the drain valve. When supply of high-pressure air into the lid 55 is interrupted, air leaking out from the outside air communication hole 59 becomes obvious. When air leaks, the internal pressure of the lid 55 decreases with time. Then, the diaphragm 54 moves to the right in the figure by the pushing action of the return spring 56. As a result, the tip of the drain passage 35 is opened, and the drain passage 35 and the drain passage 36 are connected.

The operation of the fuel supply apparatus having the above configuration will be described next.
4A and 4B are diagrams for explaining the operation of the fuel supply apparatus according to the present invention. FIG. 4A shows when the engine is operating, and FIG. 4B shows when the engine is stopped.
When the engine is operated, as shown in (a), the crankshaft 19 rotates, the fuel pump 34 rotates, and the fuel in the fuel tank 31 is sent to the float chamber 32 of the carburetor 13 via the fuel supply passage 33.

  At this time, in the crank chamber 23, when the piston 16 descends, the air is compressed and becomes positive pressure. This positive pressure is guided to the drain valve 50 via the pressure guiding pipe 37. Then, as shown in FIG. 2, the drain passage 35 is closed and the fuel in the float chamber 32 does not return to the fuel tank 31. When the pressure in the crank chamber 23 repeats positive pressure and negative pressure (or zero pressure), only the positive pressure component is sent to the drain valve 50 by the action of the check valve 38.

When the engine is stopped, positive pressure air is not sent from the crank chamber 23 to the drain valve 50. Then, as shown in FIG. 3, the drain passage 35 and the drain passage 36 are connected.
As a result, as shown in FIG. 4B, the fuel remaining in the float chamber 32 is returned to the fuel tank 31 via the drain passages 35 and 36.

  In other words, the present invention is characterized in that the drain valve 50 is closed by receiving a positive pressure generated in the crank chamber, and is opened when the positive pressure cannot be received as the engine stops. Since the drain valve 50 is opened and closed by the pressure in the crank chamber 23 without using electric / electronic control, the fuel supply device 30 of the engine is simple and inexpensive.

  Note that the drain valve 50 was also considered to be opened and closed using the negative pressure of the crank chamber 23, but was not adopted for the following reason. That is, when the pressure guiding tube 37 shown in FIG. 1 is used for a long time, the joint or the like may be loosened. According to the present invention, since the pressure guiding tube 37 has a positive pressure, air blows out of the tube. Air blowout can be detected by simply holding your hand over the relevant part, and if you apply soap water just in case, bubbles will be generated and leaks will be detected.

  On the other hand, if the inside of the pressure guiding tube 37 has a negative pressure and a crack is generated, air enters the tube from the outside. This intrusion cannot be detected by holding your hand, and it cannot be detected by applying soapy water. If a crack is left without being generated, the drain valve 50 cannot be opened and closed as intended. For example, the drain valve 50 remains open, causing a problem that fuel returns from the float chamber to the fuel tank even during engine operation. If the pressure guiding tube 37 is positive pressure, such a problem does not occur.

Next, another embodiment will be described.
FIG. 5 is a diagram showing another embodiment of FIG. 1. Elements common to those in FIG. That is, the fuel supply device 30B is characterized in that the structure of the drain valve is changed with respect to the fuel supply device 30 of FIG.

  FIG. 6 is a diagram showing another embodiment of FIG. 2, and the drain valve 60 includes a spool valve body 64 having a small diameter portion 63 interposed between a first large diameter portion 61 and a second large diameter portion 62, and the spool valve body 64. The valve body 65 movably accommodates the valve body 64, a lid body 66 that closes the opening of the valve body 65, and a return spring 67 that pushes the spool valve body 64 toward the lid body 66. A drain passage 35 and a drain passage 36 are connected to each other at 64, and a pump pressure guiding pipe 68 branched from the fuel supply passage 33 on the discharge side of the fuel pump 34 shown in FIG.

  When the engine is operating, the fuel pump discharges high-pressure fuel. This discharge pressure is supplied to the left side of the spool valve body 64 in the figure through the pump pressure guiding pipe 68. Then, the spool valve body 64 is pushed as indicated by a white arrow and hits the first stopper 69 to stop. The first large diameter portion 61 closes the drain passage 35 at this stop position. As a result, fuel does not return from the carburetor to the fuel tank when the engine is operating.

  FIG. 7 is an explanatory diagram of operation. In FIG. 5, when the fuel pump 34 is stopped along with the engine stop, the fuel in the fuel supply passage 33 returns to the fuel tank 31 by the action of gravity. At the same time, the pressure of the pump pressure guiding pipe 68 decreases. Then, in FIG. 7, the spool valve body 64 moves to the left in the figure by the pushing action of the return spring 67, hits the second stopper 71 and stops. At this stop position, the small diameter portion 63 connects the drain passage 35 and the drain passage 36. As a result, when the engine is stopped, the fuel automatically returns from the carburetor to the fuel tank.

  In this alternative embodiment, high-pressure fuel is used as the drive source for the drain valve 60. Since the pressure is high, the pressure receiving area can be reduced and the outer diameter of the spool valve body 64 can be reduced. Therefore, the drain valve 60 can be easily reduced in size and weight.

  The present invention is suitable for a general-purpose engine mounted on an agricultural machine or the like, but may be employed for such an internal combustion engine.

  The present invention is suitable for a general-purpose engine having a long idle period.

It is a principle figure of the fuel supply apparatus of the engine concerning the present invention. It is a block diagram of a drain valve. It is an effect | action figure of a drain valve. It is a figure explaining the effect | action of the fuel supply apparatus which concerns on this invention. It is a figure which shows another Example of FIG. It is another Example figure of FIG. It is an operation explanatory view. It is a figure explaining the basic principle of the prior art.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Engine, 13 ... Vaporizer, 23 ... Crank chamber, 30, 30B ... Engine fuel supply device, 31 ... Fuel tank, 32 ... Float chamber, 34 ... Fuel pump, 35, 36 ... Drain passage, 37 ... Impulse pipe 50, 60 ... drain valve, 68 ... pump pressure guiding tube.

Claims (3)

In a fuel supply device for an engine having a drain passage for extracting fuel from a float chamber of a carburetor,
The drain passage is connected to a fuel tank disposed below the carburetor in the direction of gravity. The drain passage is automatically closed when the engine is in operation and the engine is stopped. A fuel supply device for an engine, characterized by a drain valve that automatically opens sometimes.   The engine fuel supply according to claim 1, wherein the drain valve is closed by receiving a positive pressure generated in a crank chamber of the engine, and is opened when the positive pressure is not received as the engine is stopped. apparatus.   2. The engine according to claim 1, wherein the drain valve is closed by receiving a discharge pressure of a fuel pump that pumps fuel in the fuel tank to the carburetor and opens when the discharge pressure of the fuel pump cannot be received. Fuel supply system.

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