JPH1018931A - Fuel supplying device for crank case compressing type two-cycle engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a lightweight, miniatured, and inexpensive fuel supplying device utilizing to the utmost the qualities of a carburetor and an injection nozzle, by noticing the characteristics of a crank case compressing type two-cycle engine, in particular the fact of expectable good fuel sypplying performance even in low pressure such as a crank case compressor. SOLUTION: A fuel pump is composed of a diaphragm type fuel pump 1 operated by driving a diaphragm 11 by active and negative pressure generated in the crank case of a crank case compressing type two-cycle engine. Since the diaphragm 11 is operated in a direction for expanding a fuel chamber 12 which case pressure is negative, a suction valve (one-way valve) 13 communicated with a fuel tank is closed. Next, since the diaphragm 11 is operated in a direction for compressing the fuel chamber 12 when the case pressure becomes active, the suction valve 13 is closed to open an exhaust valve 15, to perform action for sending fuel, in the fuel chamber 12, to a pressure accumulating chamber 31. Fuel which is pressure accumulated in the pressure accumulating chamber 31 drives a needle 21 to control the opening/closing of a nozzle hole 22.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel supply device suitable for supplying fuel to a small general-purpose engine in a composite stratified scavenging type crankcase compression type two-cycle engine for supplying fuel and air to cylinders separately.

[0002]

2. Description of the Related Art There are the following three types of known fuel supply devices used in engines, and the configuration thereof will be briefly described. First, a carburetor shown in FIG. 4 is used in a fuel supply device of a general-purpose small two-cycle engine. To briefly explain the configuration, a fuel pump 110 pumps fuel from a fuel tank (not shown) and supplies the fuel to a main diaphragm chamber 107. The supplied fuel is sucked out through the gap between the needle jet 103 and the jet needle 104 and the main jet 106 due to the negative pressure generated in the venturi 102 during the intake process of the engine, and flows in from outside through the venturi 102. It has the function of being mixed with air and being sucked out by the engine. 101 is a slot valve, 105 is a main adjust screw, 10
8 is a main diaphragm.

FIG. 5 shows an example of a fuel injection device for an automobile gasoline engine which supplies only fuel to the gasoline engine fuel supply device. FIG. 5 shows only the injection nozzle, which is the main part of the fuel injection device. However, other components such as a fuel pump for supplying fuel, a controller for controlling the injection period, and a power supply for operating the controller and the excitation coil in the injection nozzle are provided. is there. The function of the injection nozzle is to supply the fuel to the engine by opening the injection port 121 by operating the spacer (stopper) 114 for a necessary period of time for the fuel fed from the fuel pump (not shown) and fed to the injection nozzle. When the exciting coil is excited by a power source (not shown) through a controller (not shown), the core 116 operates, and the connected spacer (stopper) 114 operates in a direction to open the injection port 121, and fuel is supplied to the engine. You. The fuel amount is adjusted by controlling the excitation time of the excitation coil by a controller (not shown). 111 is a sleeve, 112 is a valve body, 113 is a valve needle, 115 is a housing, 1
17 is a spring, 118 is an adjustment pipe, 119 is an excitation coil, and 120 is a connector pipe.

Further, FIG. 6 shows an example of an injection device of a diesel engine which injects fuel into a cylinder at a high pressure. In the figure, the injection pump 131 pressurizes the fuel and sends it to the injection nozzle 139. The needle valve 140 in the injection nozzle 139 is opened by the pressure of the pressurized fuel itself to open the injection port and supply fuel to the cylinder. The injection pump 131 is a plunger-type displacement pump, and has a structure in which the fuel flowing into the cylinder from the inlet port 136 is compressed by driving the plunger 133 by the cam of the camshaft 132. Reference numeral 134 denotes a spill port, 135 denotes a delivery valve, 137 denotes an inlet gallery, and 138 denotes a control rod.

[0005]

However, the above three prior arts have the following problems and problems. First, in the fuel supply device for a general-purpose small two-stroke engine shown in FIG. 4, the carburetor has a simple structure, has excellent features capable of simultaneously supplying the air amount and the fuel amount required by the engine, and is inexpensive. Although having the advantage, the ability to provide air and fuel simultaneously is a drawback in a composite stratified scavenging crankcase compression two-stroke engine that supplies fuel and air separately to cylinders. That is, a vaporizer which cannot supply air and fuel separately cannot be used.

Further, the injection nozzle of the fuel injection device for a gasoline engine shown in FIG. 5 can electrically control the amount of fuel, so that a good amount of fuel can be supplied to the entire operation range of the engine.
It can also be used in a composite stratified scavenging type crankcase compression type two-stroke engine that supplies fuel and air separately to cylinders. However, compared to a conventional fuel supply system that uses a carburetor and has no power supply, It has the disadvantage of double cost and weight. In particular, it is often used in hand-held type working machines and is not suitable for a fuel supply device for a general-purpose small two-stroke engine which requires light weight, small size and low cost.

Further, the injection device for a diesel engine shown in FIG. 5 can be used also for a composite stratified scavenging type crankcase compression type two-cycle engine in which fuel and air are separately supplied to a cylinder, but compared with a conventional fuel supply device. There are drawbacks such as the necessity of a new cam and the high precision required to control a very small amount of fuel, which makes it expensive and heavy. Therefore, a composite stratified scavenging type crankcase compression type two-stroke engine that separately supplies fuel and air to cylinders is a general-purpose small two-stroke engine that is required to be lightweight, small and inexpensive. A fuel supply mechanism having a function of achieving both light weight, small size, and low cost does not exist in the above-described related art.

In view of such technical problems, the present invention pays attention to the properties of a composite stratified scavenging type crankcase compression type two-stroke engine, and particularly to the fact that good fuel supply performance can be expected even at a low pressure like a crankcase compressor. It is another object of the present invention to provide a lightweight, small, and inexpensive fuel supply device that makes the most of the properties of the vaporizer and the injection nozzle.

[0009]

According to the present invention, in order to attain the above technical object, the pressure in the crankcase of a crankcase compression type two-cycle engine is repeatedly switched between positive pressure and negative pressure. The pressure used in the motive power and the pressure in the crankcase is calculated based on the supply ratio (intake air amount) with respect to the time during which the positive pressure is generated, and the half of the time during which the positive pressure is generated and the maximum value of the positive pressure. By focusing on the fact that the product has a property that is approximately proportional to the product, the above-described problem is solved by utilizing the knowledge for controlling the fuel supply amount.

That is, in the first aspect of the present invention,
In a fuel supply device for a crankcase compression type two-stroke engine, a membrane fuel pump that is operated by pressure generated in a crankcase and supplies fuel from a fuel tank, and is connected to the membrane fuel pump, And an injection nozzle which is opened and closed at an appropriate timing by a pressure generated in the inside, and injects fuel supplied from the membrane fuel pump into a combustion chamber.

[0011] In this case, the membrane fuel pump and the injection nozzle are integrally formed with each other to reduce the weight, while the membrane fuel pump and the injection nozzle are connected to each other. And the structure around the cylinder head is simplified even if only the injection nozzle is provided on the cylinder head side. Further, it is preferable that a pressure accumulating chamber for adjusting fuel to a constant pressure is provided between the membrane fuel pump and the injection nozzle. Further, as described in claim 4,
The injection nozzle may be configured as a needle type injection nozzle having a needle for opening and closing an injection port, and the needle may include a film that is operated by a pressure generated in the crankcase. In this case, a hinge may be interposed between the membrane and the needle.

According to a second aspect of the present invention, there is provided a fuel supply device for a crankcase compression type two-cycle engine.
A fuel pump for supplying fuel from a fuel tank; and a fuel pump connected to the fuel pump, which is opened and closed at an appropriate timing by a pressure generated in the crankcase to inject fuel supplied from the fuel pump into a combustion chamber. And an injection nozzle. That is, in the present invention, the fuel pump is not limited to the membrane fuel pump. Also in this case, it is preferable that a pressure accumulating chamber for adjusting the fuel from the fuel pump to a constant pressure is provided integrally with the injection nozzle.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be illustratively described in detail below with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, and are merely illustrative examples. Only. FIG. 1 shows a fuel supply device according to a first embodiment of the present invention, which comprises a membrane pressure type fuel pump 1 and an injection nozzle 2 connected to the pump 1.
6, the pressure in the crankcase (hereinafter referred to as case pressure) is received, and a diaphragm 11 forming a diaphragm chamber 17, a fuel chamber 12 provided below the diaphragm 11, and fuel from a fuel tank (not shown) are supplied to the inlet. A suction valve 13 for supplying fuel to the fuel chamber 12 through the passage 14, a discharge valve 15 for supplying fuel in the fuel chamber 12 to the pressure accumulating chamber 31, a pressure regulating valve 32 for bypassing between the pressure accumulating chamber 31 and the inlet passage 14, and a pressure regulating spring. 33. The injection nozzle 2 transfers the fuel in the pressure accumulation chamber 31 to the injection port 2 through the fuel passage 26.
A needle 21 for controlling supply (opening / closing control) to the second, a needle chamber 24 for receiving a crankcase pressure through the diaphragm chamber 11 through the second pulse passage 23, and a needle chamber 24 provided in the needle chamber 24. It comprises a needle piston 25 for controlling opening and closing of the needle 21 and a needle spring 27.

To explain the operation of this embodiment, a fuel pump 1 for pumping fuel from a fuel tank (not shown) and sending it to a pressure accumulating chamber 31 is provided in a crankcase (not shown) of a compression type two-cycle engine. The positive / negative pressure generated
This is performed by driving the diaphragm 11. That is, in this embodiment, when the pressure of the crankcase is a negative pressure, a negative case pressure acts on the diaphragm 11 via the pulse passage 16 and the diaphragm chamber 17, and the diaphragm 11 works in a direction to expand the fuel chamber 12. Therefore, the intake valve 13 (one valve) is opened, and fuel flows from the fuel tank (not shown) into the fuel chamber 12 through the inlet passage 14. At this time, the discharge valve 15 (one valve) communicating with the accumulator 31 is closed. Next, when the case pressure becomes positive, the diaphragm 11 acts in the direction of compressing the fuel chamber 12, so that the suction valve 13 is closed, the discharge valve 15 is opened, and the fuel in the fuel chamber 12 is sent to the pressure accumulating chamber 31. ing. The pressure in the pressure accumulating chamber 31 is kept constant by a pressure regulating valve 32 (one valve). That is, when the pressure of the pressure accumulating chamber 31 exceeds the force of the pressure adjusting spring 33, the pressure adjusting valve 32
Is opened, and the fuel in the accumulator 31 is discharged to the inlet passage 14. Naturally, when the pressure in the pressure accumulating chamber 31 is lower than the force of the pressure adjusting spring 33, the pressure adjusting valve 32 is closed. The injection nozzle 2 sends the accumulated fuel to the engine (not shown).
Then, the needle 21 is driven with a positive case pressure to
Open and do. In this embodiment, when the case pressure is a positive pressure, the pulse passage 16, the diaphragm chamber 17 and the pulse second passage 23
, The case pressure guided to the needle chamber 24 acts on the needle piston 25 to drive the needle 21 in the direction in which the nozzle 22 opens, so that the nozzle 22 opens and the pressure accumulating chamber 31
The fuel inside is supplied to the engine from the nozzle 22 through the fuel passage 26. The timing for driving the needle 21 is adjusted by the force of the needle spring 27.

Therefore, according to the present embodiment, the fuel pump 1 for pumping fuel from a fuel tank (not shown) and sending it to the accumulator 31 is provided with a positive pressure generated in the crankcase of the crankcase compression type two-cycle engine. And the membrane fuel pump 1 driven by driving the diaphragm 11 with negative pressure. When the pressure in the crankcase (hereinafter, referred to as case pressure) is a negative pressure, the diaphragm 11 works in a direction to expand the fuel chamber, so that the suction valve (one-way valve) 13 communicating with the fuel tank is provided.
Is closed. Next, when the case pressure becomes positive, the diaphragm 11 acts in the direction of compressing the fuel chamber 12, so that the suction valve 13 closes, the discharge valve 15 opens, and the fuel in the fuel chamber 12 is sent to the pressure accumulating chamber 31. I have. And the accumulator chamber 31
The fuel stored in the nozzle drives the needle 21 with the case pressure to control the opening and closing of the nozzle 22. In this embodiment, when the case pressure is positive, this pressure is applied to the needle 21 in the direction in which the nozzle 22 opens.
, The nozzle 22 is opened, and the fuel in the pressure accumulation chamber 31 is supplied from the nozzle 22 to the engine (in the cylinder). When the supply time increases and the intake air volume increases,
The magnitude of the positive pressure in the case and the connection time become longer and longer, so that the fuel supply amount becomes larger. In this case, in order to reduce the weight, the fuel pump 1 and the injection nozzle 2 have an integral structure.

FIG. 2 shows another embodiment of the present invention. Although an example in which the fuel pump of FIG. 1 is provided with a fuel pressure accumulating function is described in the embodiment in which the fuel pump is separated, the pressure accumulating function of this embodiment may be omitted when a fuel pump having a pressure accumulating function is used. . In FIG. 2, the injection nozzle 2 includes a needle 21, an injection port 22, a pulse second passage 23 for guiding case pressure, a needle chamber 24, a needle piston 25, and a needle spring 2.
7 and the fuel passage 26 from the pressure accumulating chamber 31 is the same as in the previous embodiment. A fuel passage 34 for taking in fuel from a fuel pump (not shown) and a drain 3
Pressure regulating valve 32 and pressure regulating spring 3 for maintaining a constant pressure in pressure accumulating chamber 31 by bypassing between pressure accumulating chamber 31 and pressure accumulating chamber 31.
3 are provided.

The operation of the embodiment will be described. Fuel sent from a fuel pump (not shown) is stored in the accumulator 31 from the fuel passage 34. The pressure accumulating chamber 31 includes the pressure regulating valve 3
The pressure is kept constant at 2 (one valve). That is, when the pressure in the pressure accumulating chamber 31 becomes equal to or greater than the force of the pressure adjusting spring 33, the pressure adjusting valve 32 is opened and returned from the drain 35 to a fuel tank (not shown) or a fuel pump (not shown). Naturally, when the pressure in the pressure accumulating chamber 31 is lower than the force of the pressure adjusting spring 33, the pressure adjusting valve 32 is closed. The injection nozzle 2 sends the accumulated fuel to the engine (not shown) by driving the needle 21 with a positive case pressure to open the injection port 22. In this embodiment, when the case pressure is a positive pressure, the pulse passage 23
Then, the case pressure guided to the needle chamber 24 acts on the needle piston 25 to drive the needle 21 in the direction in which the nozzle 22 opens, so that the nozzle 22 opens, and the fuel in the accumulator 31 passes through the fuel passage 26. The fuel is supplied from the nozzle 22 to the engine. The timing for driving the needle 21 is adjusted by the force of the needle spring 27.

Therefore, in this embodiment, since the fuel pump is separated and the injection nozzle can be used alone, the fuel supply unit attached to the cylinder head can be made as compact as possible, and the whole engine can be made more compact.

FIG. 3 shows an embodiment in which the structure of the injection nozzle is different from that of FIG. 1 and a new function is added to the injection nozzle 2. The fuel pump 1 includes a diaphragm 11, a fuel chamber 12, a suction valve 13, an inlet passage 14, an exhaust valve 15, a pulse passage 16, a diaphragm chamber 17, a pressure accumulating chamber 31, and a pressure regulating valve 32 as in the embodiment shown in FIG. And the pressure adjusting spring 33 are the same as in the previous embodiment. The injection nozzle 2 includes a needle 21, an injection port 22, a pulse second passage 2,
3, the fuel passage 26 is the same as that of the previous embodiment, except that the main diaphragm chamber 37 receives the case pressure from the pulse second passage 23, and the main diaphragm chamber 37 swings by the main diaphragm chamber 37 and has a projection 37a. 3
8. a hinge 39 which comes into contact with the projection 37a and is displaced about the fulcrum 39a in response to the swing of the main diaphragm 38;
The hinge includes a hinge spring 41 for causing the hinge 39 to follow the main diaphragm 38, and the other end of the hinge is engaged with the needle 21.

The operation of this embodiment is as follows. It is the injection nozzle 2 that sends the fuel stored in the pressure storage chamber 31 to the engine (not shown), and drives the needle 21 with the positive case pressure to open the injection port 22. In this embodiment, when the case pressure is a positive pressure, the main diaphragm chamber 37 passes through the pulse passage 16, the diaphragm chamber 17 and the pulse second passage 23.
The case pressure guided to the main diaphragm 38 drives the needle 21 via the hinge 39 in the direction in which the injection port 22 opens so that the injection port 22 is opened, and the fuel in the accumulator 31 passes through the fuel passage 26 and the injection port 22 From the engine.
The timing for driving the needle 21 is adjusted by the force of the hinge spring 41.

Therefore, according to this embodiment, the injection nozzle 2 which sends the fuel stored in the pressure storage chamber 31 to the engine drives the main diaphragm 38 in the nozzle case 20, and furthermore, the main diaphragm 38 is substantially connected to the main diaphragm 38 via the hinge 39. The spout 22 is opened and closed by driving the needle 21 which is connected to the nozzle 21. In this embodiment, when the case pressure is positive, the main diaphragm 38 pushes up the nozzle 21 in the opening direction of the nozzle 22. That is, since the main diaphragm 38 is substantially connected to the needle 21 via the hinge 39, When the diaphragm 38 is pushed, the fuel in the pressure accumulation chamber 31 is supplied from the injection port 22 to the engine. The reason why the needle 21 is driven by the main diaphragm 38 via the hinge 39 is to allow the operation of the needle 21 to be performed more smoothly and at a lower pressure.

[0022]

As described above, according to the invention shown in FIG. 1, since the fuel pump and the injection nozzle are driven by the pressure of the crankcase of the two-stroke engine of the crankcase compression type, no extra auxiliary equipment is required. Can be provided at low cost. The operating pressure can be a crankcase pressure, that is, a low pressure, so that the structure is simple and the thickness of the structure can be reduced, and a lightweight material can be used. Further, since the fuel pump and the injection nozzle have an integral structure, they can be made inexpensive, small, and lightweight. Further, according to the invention shown in FIG. 2, the injection nozzle can be made compact in addition to the effect shown in FIG. 1, so that the entire area around the cylinder head can be made compact and the entire engine can be made compact. According to the invention shown in FIG. 3, since the needle is driven by the diaphragm through the hinge together with the effect shown in FIG. 1, the operation of the needle can be performed more smoothly and even at a low pressure, so that the reliability is improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a fuel supply device according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a fuel supply device according to a second embodiment of the present invention.

FIG. 3 is a sectional view of a fuel supply device according to a third embodiment of the present invention.

FIG. 4 is a sectional view showing a conventional carburetor-type fuel supply device for a general-purpose small two-cycle engine.

FIG. 5 is a sectional view showing a conventional fuel injection type fuel supply device for a gasoline engine.

FIG. 6 is a sectional view showing a conventional fuel injection type fuel supply device for a diesel engine.

[Explanation of symbols]

 Reference Signs List 1 fuel pump 2 injection nozzle 11 diaphragm 12 fuel chamber 13 suction valve 14 inlet passage 15 discharge valve 16 pulse passage 17 diaphragm chamber 21 needle 22 injection port 23 pulse second passage 24 needle chamber 25 needle piston 26 fuel passage 27 needle spring 31 accumulator 32 Pressure adjusting valve 33 Pressure adjusting spring 34 Fuel passage 35 Drain 37 Main diaphragm chamber 38 Main diaphragm 39 Hinge 41 Hinge spring

Claims (7)

[Claims] 1. A fuel supply system for a crankcase compression type two-stroke engine, comprising: a membrane fuel pump that is operated by pressure generated in a crankcase and supplies fuel from a fuel tank; and is connected to the membrane fuel pump. And an injection nozzle which is opened and closed at an appropriate timing by pressure generated in the crankcase and injects fuel supplied from the membrane fuel pump into a combustion chamber. A fuel supply device for a compression type two-cycle engine. 2. The fuel supply system for a crankcase compression type two-stroke engine according to claim 1, wherein said membrane fuel pump and said injection nozzle are integrally formed. 3. A compression type crankcase according to claim 1, wherein a pressure accumulating chamber for adjusting fuel to a constant pressure is provided between said membrane fuel pump and said injection nozzle. Fuel supply device for two-cycle engine. 4. The method according to claim 1, wherein the injection nozzle is a needle type injection nozzle having a needle for opening and closing an injection port, and a film that operates the needle by a pressure generated in the crankcase. The fuel supply device for a crankcase compression type two-stroke engine according to any one of claims 1 to 3. 5. The fuel supply device for a crankcase compression type two-stroke engine according to claim 4, wherein a hinge is interposed between the membrane and the needle. 6. A fuel supply device for a crankcase compression type two-stroke engine, comprising: a fuel pump for supplying fuel from a fuel tank; and a fuel pump connected to the fuel pump, and at an appropriate timing by a pressure generated in the crankcase. An injection nozzle that is opened and closed to inject fuel supplied from the fuel pump into a combustion chamber. 7. A fuel supply device for a crankcase compression type two-stroke engine according to claim 6, wherein a pressure accumulating chamber for adjusting fuel from a fuel pump to a constant pressure is provided integrally with said injection nozzle.