JPS6132118Y2 - - Google Patents

Description

[Detailed description of the invention] This invention is a two-cycle engine, in particular, a fuel pump is driven by the pulsating pressure generated in the crankcase, and the fuel discharged from the pump is supplied into the float chamber of the carburetor. This device is related to a carburetor starting device installed in a type of engine that controls the positive pressure transmitted from the inside of the crankcase to the upper space in the carburetor float chamber to start the engine from a low temperature state. The process can be performed smoothly and automatically from beginning to end from the time of cranking to the end of instantaneous operation, and the magnitude of the positive pressure can be accurately corrected for complete explosion using the discharge fuel pressure of the fuel pump. An object of the present invention is to provide a starting device having a simple structure.

In order to achieve this purpose, the present invention
In the two-cycle engine of the above type, the upper space in the float chamber and the inside of the crankcase are connected via a positive pressure extraction device that transmits only positive pressure of the pulsating pressure generated in the crankcase to the float chamber side. , the upper space in the float chamber and the atmosphere are communicated independently through first and second atmosphere introduction passages, and the first atmosphere introduction passage includes a jet and a valve that opens and closes the first atmosphere introduction passage. A normally closed on-off valve is interposed in series between the on-off valve and the fuel pump, and the discharge fuel pressure of the pump is applied to the valve so as to open the valve at the time of a complete engine explosion. A fuel pressure transmission device is provided in the second atmosphere introduction passage, and the second atmosphere introduction passage is further provided with a temperature sensing valve that closes the second atmosphere introduction passage when the engine atmosphere temperature is below a predetermined value and opens when the engine atmosphere temperature exceeds a predetermined value. do.

An embodiment of the present invention will be described below with reference to the drawings. An intake hole of a two-stroke engine 1 is connected to the downstream end of an intake path 3 of a carburetor 2. The carburetor 2 consists of a carburetor body 4 through which an intake passage 3 passes, and a float chamber 5 disposed at the bottom of the carburetor body 4.
A throttle valve 6 for controlling the amount of air flowing through the intake passage 3 is disposed in the intake passage 3, and a main nozzle 9 connected to a main jet 8 opens in a bench lily portion 7 of the intake passage 3. Inside the float chamber 5, a float 10 is attached to a shaft 11.
A float arm 12 at the end of the float 10 is rotatably supported by a rotatable shaft and is disposed corresponding to a float valve 15 disposed opposite to a valve seat 14 in the fuel inlet passage 13 . Fuel is supplied to the fuel inlet passage 13 from a fuel pump 17 driven by pulsating pressure within the crankcase 1a of the engine 1, and this fuel is supplied into the float chamber 5 via the valve seat 14. , the float 10, the float valve 15, and the valve seat 14 cooperate to form and maintain a constant liquid level XX in the float chamber 5. The fuel pump 17 has a pressure chamber 17A with a diaphragm 18.
The pressure chamber 17A is divided into a pump chamber 17B and a pump chamber 17B.
The pump chamber 17B is connected to the suction side check valve 2.
0 to the fuel tank 21 and to the fuel inlet passage 13 via the discharge side check valve 22. The above structure is a structure commonly used in the past.

The inside of the crankcase 1a and the upper space 5A in the float chamber 5 are communicated with each other via a communication path 23 branched from the pulsating pressure 19,
In the middle of the communication path 23, there is a
A check valve 24 is interposed as a positive pressure take-off device that transmits only the positive pressure of the pulsating pressure in the float chamber 5 to the upper space 5A in the float chamber 5, and this valve 24 forms a part of the communication path 23. A casing 25 in which a valve passage is formed, and a valve seat 2 provided in the casing 25.
a valve body 27 that can come into contact with and separate from 6 to open and close the valve passage;
It is comprised of a valve spring 28 that springs it in the closing direction.

The upper chamber 5A in the float chamber 5 is communicated with the atmosphere through first and second atmospheric air introduction passages 29 and 38, which are independent of each other. A jet 47 and an on-off valve 50 are provided in series. The on-off valve 50 includes a valve hole 48 formed in the casing 31 and forming a part of the first atmosphere introduction path 29, a valve body 33 that can open and close this valve hole 48, and this valve body 3.
3 in the closing direction via a valve rod 49, the valve body 33 is normally closed.
is connected to the fuel pump 17 via a fuel pressure transmission device 30, which will be described below. That is, the device 30 includes a fuel pressure introduction path 51 branched from the fuel inflow path 13 and a diaphragm 36 connected to the valve rod 49 and stretched over the casing 31.
It is composed of an atmospheric chamber 35 defined on one side of the diaphragm 36, and a pressure receiving chamber 34 defined on the other side of the diaphragm 36 and communicating only with the fuel pressure introduction path 51. The fuel pump 1 is then passed through the fuel pressure introduction passage 51 into the pressure receiving chamber 34.
When a discharge fuel pressure equal to or higher than a predetermined value of 7 is applied, the fuel pressure can move the valve body 33 in the opening direction via the diaphragm 36.

Further, a temperature sensing valve 39 is installed in the second atmospheric air introduction passage 38, which closes the passage 38 when the engine ambient temperature is below a predetermined value (for example, 20° C.) and opens when it exceeds a predetermined value. This temperature sensing valve 39 includes a valve body 42 facing a valve seat 41 of a valve body 40, and this valve body 42 is connected to an operating rod 44 having one end opened in a sealed expansion/contraction chamber 43. Ru. In addition, 45 is the expansion chamber 4
3 is a heat-expandable material such as ether or paraffin sealed in the chamber, and 46 is a spring that presses the operating rod 44 to the left in the figure so as to bring the valve body 42 into contact with the valve seat 41. In the case where the thermal expansion material 45 in the expansion/contraction chamber 43 expands, the operating rod 44 moves to the right in the figure against the pressing force of the spring 46, and the valve body 42 is separated from the valve seat 41. Atmospheric air is introduced into the upper space 5A in the float chamber 5. On the other hand, when the engine atmosphere temperature is below a certain temperature, the operating rod 44 is pressed by the spring 46 as the thermal expansion material 45 contracts. The valve body 42 moves to the left and comes into contact with the valve seat 41 to block the introduction of the atmosphere from the second atmosphere introduction path 38 into the space 5A.

Next, the operation of the above embodiment will be explained. First of all, when starting when the engine ambient temperature exceeds a certain temperature (for example, 20°C), the pulsating pressure generated in the crankcase 1a due to engine cranking is transferred to the positive pressure extraction device from the communication passage 23. 24, so by appropriately selecting the spring 28, the valve body 27 is separated from the valve seat 26 by positive pressure, and only positive pressure is taken out to the downstream side of the communication passage 23, and the float chamber Positive pressure is introduced into the upper space 5A in the 5. On the other hand, at this time, the thermal expansion material 45 of the temperature sensing valve 39 disposed in the second atmosphere introduction path 38 expands and increases its volume, so that the operating rod 44 and the valve body 42 resist the spring force of the spring 46. It moves to the right in the figure, opens the valve seat 41, and introduces the atmosphere into the upper space 5A from the second atmosphere introduction path 38.

Therefore, in such a temperature state, the float chamber 5
Positive pressure is introduced from the communication passage 23 into the upper space 5A, but since the positive pressure is released to the atmosphere from the second atmosphere introduction passage 38, the inside of the upper space 5A is maintained at atmospheric pressure. Since a relatively thin starting air-fuel mixture is supplied to the engine at the time of starting, smooth operation can be achieved at the time of starting in a state where the engine ambient temperature is high or at the time of hot restart.

Next, the engine ambient temperature is set to a constant temperature (e.g. 20
℃) and below will be explained.

The temperature sensing valve 39 in the second atmosphere introduction path 38 is operated by the operating rod 44 because the thermal expansion material 45 in the expansion/contraction chamber 43 contracts and reduces its volume due to the engine ambient temperature.
is moved to the left in the figure by the spring force of the spring 46, thereby causing the valve body 42 to close the valve seat 41 and block the second atmosphere introduction path 38, thereby cutting off the upper space 5A in the float chamber 5 from the atmosphere. do.

On the other hand, since the fuel pump 17 is inactive, no fuel pressure acts within the pressure receiving chamber 34 of the fuel pressure transmission device 30, and the diaphragm 36
The valve element 33 contacts the valve seat 32 and closes the first atmosphere introduction passage 29, thereby cutting off the upper space 5A in the float chamber 5 from the atmosphere.

When the engine is cranked in such a state, the pulsating pressure generated in the crankcase 1a acts on the valve body 27 of the positive pressure take-off device 24, and as described above, only the positive pressure of the pulsating pressure is released. is transmitted into the upper space 5A in the float chamber 5 via the communication path 23. This positive pressure causes the upper space 5
As soon as the pressure is transmitted into the upper space 5A, the atmospheric pressure is immediately converted to positive pressure (at this time, the first and second atmospheric air introduction passages 29 and 38 are blocked), and the main nozzle The pressure difference acting on the fuel nozzles 9, etc. is large, and a large amount of fuel can be supplied into the intake passage 3 from these fuel nozzles, and a rich mixture for starting suitable for low-temperature starting can be supplied to the engine. Good engine startability can be obtained.

Next, when the engine completely explodes, the engine speed increases and the negative pressure in the intake passage 3 increases, so if you continue to supply positive pressure to the upper space 5A in the float chamber 5 as during cranking, As described above, as the negative pressure in the intake tract increases, an excessively rich air-fuel mixture is supplied to the engine, which may exceed the flammability limit of the engine and cause the engine to stop.

However, the present invention focuses on the point that when the engine completely explodes and the engine speed increases, the frequency of the diaphragm 18 of the fuel pump 17 increases and the fuel discharge pressure increases as the engine speed increases. , this fuel discharge pressure is transferred to the pressure receiving chamber 3 of the fuel pressure transmission device 30.
It was designed to be introduced into 4. That is, when the engine completely explodes, the rapidly increased fuel discharge pressure is introduced into the pressure receiving chamber 34, so that the diaphragm 3
6 moves to the left in the figure with this increased pressure,
The valve body 33 is moved against the valve seat 32 against the valve closing force of the valve spring 37.
The upper space 5A in the float chamber 5 and the atmosphere are communicated through the first atmosphere introduction path 29 with more difficulty.

According to this, the positive pressure in the upper space 5A is the first
It is gradually released to the atmosphere from the atmosphere introduction passage 29 via the jet 47, and the pressure value of the positive pressure can be gradually brought closer to the atmospheric pressure side, so that the mixture concentration supplied to the engine is corrected to tend to be diluted. This makes it possible to achieve good engine complete explosion operability.
The amount of positive pressure released to the atmosphere is controlled by the jet 4.
This can be achieved by appropriately selecting the effective diameter of 7.

Next, as the instantaneous operation of the engine progresses and the engine ambient temperature rises above a certain temperature, the thermal expansion material 45 in the expansion and contraction chamber 43 expands and increases its volume, so that the operating rod 44 is moved by the spring 46. The valve body 42 moves to the right in the figure against the force, opens the valve seat 41, communicates the upper space 5A in the float chamber 5 with the atmosphere through the second atmosphere introduction passage 38, and enlarges the space 5A. The pressure is returned to atmospheric pressure and the atmospheric pressure is maintained thereafter. Therefore, the air-fuel mixture can be controlled to tend to be more diluted, and the operation of the engine can be stabilized.

As described above, according to the present invention, the fuel pump is driven by the pulsating pressure generated in the crankcase,
In a two-cycle engine in which the fuel discharged from this pump is supplied into a float chamber of a carburetor, the upper space of the float chamber and the inside of the crankcase are controlled to have a positive pressure out of the pulsating pressure generated within the crankcase. The upper space in the float chamber is connected to the atmosphere through a positive pressure take-out device that transmits only the air to the float chamber side, and the upper space in the float chamber and the atmosphere are independently communicated via first and second atmosphere introduction passages, and the first atmosphere A jet and a normally-closed on-off valve capable of opening and closing the first atmosphere introduction path are interposed in series in the inlet passage, and the valve is inserted between the on-off valve and the fuel pump when the engine is completely detonated. A fuel pressure transmission device is provided for applying the discharge fuel pressure of the pump to the valve so as to open the valve, and the second atmosphere introduction passage is further provided with a fuel pressure transmission device that applies the discharge fuel pressure of the pump to the valve so as to open the valve. A temperature sensing valve that closes and opens when it exceeds a predetermined value is installed, so when the engine is cranking when the engine ambient temperature is below a predetermined value, the positive pressure in the crankcase is directly supplied to the upper space in the float chamber, and the carburetor is activated. The concentration of the air-fuel mixture generated in the engine can be controlled to a high level that is optimal for starting, and then when the engine reaches a complete explosion state, the opening/closing valve is opened using the rapidly increasing discharge fuel pressure of the fuel pump. By opening the upper space of the float chamber to the atmosphere to some extent through the jet of the first atmosphere introduction passage, the positive pressure acting on the upper space is reduced, and the above-mentioned mixture concentration is optimized for instantaneous operation after complete detonation. When the engine's instantaneous operation progresses and the engine atmosphere temperature exceeds a predetermined value, the temperature sensing valve opens and the float passes through the second atmosphere introduction path. By greatly opening the upper space of the interior to the atmosphere, it is possible to place the upper space under atmospheric pressure and control the above-mentioned mixture concentration to a lower value that is optimal for normal operation of the engine, thereby reducing the low temperature of the engine. Starting operation from a state can be smoothly and automatically performed from beginning to end from the time of cranking to the time of completion of instantaneous operation. In particular, the complete explosion correction means for the positive pressure has a simple structure that simply causes the discharge fuel pressure of the existing fuel pump to act on the opening/closing valve, so it can contribute to cost reduction, and also The discharge fuel pressure of the fuel pump reliably shows an upward change from engine cranking to complete explosion, and pressure fluctuations are relatively small in the instantaneous operation state after complete explosion, so the above-mentioned complete explosion correction is performed accurately. At the same time, fluctuations in the mixture concentration during instantaneous engine operation can be suppressed.

[Brief explanation of the drawing]

The drawing is a system diagram including a vertical sectional view of essential parts showing an embodiment of the carburetor starting device for a two-cycle engine according to the present invention. 1a... crankcase, 2... carburetor, 5...
...Float chamber, 5A... Upper space, 17... Fuel pump, 24... Check valve as a positive pressure extraction device,
29...First atmosphere introduction path, 30...Fuel pressure transmission device, 38...Second atmosphere introduction path, 39...Temperature sensing valve, 47...Jet, 50...Opening/closing valve.

Claims (1)

[Scope of utility model registration request] In a two-cycle engine in which a fuel pump is driven by pulsating pressure generated in the crankcase, and the fuel discharged from the pump is supplied into a float chamber of a carburetor, an upper air barrier in the float chamber and a crankcase The upper space in the float chamber is connected to the atmosphere through a positive pressure take-out device that transmits only positive pressure of the pulsating pressure generated in the crankcase to the float chamber, and the upper space in the float chamber is connected to the atmosphere in the first and second The first atmosphere introduction passages are connected to each other independently through the atmosphere introduction passages, and the first atmosphere introduction passages are interposed in series with a jet and a normally-closed on-off valve capable of opening and closing the first atmosphere introduction passages. A fuel pressure transmission device is provided between the opening/closing valve and the fuel pump, and the fuel pressure transmission device applies the discharge fuel pressure of the pump to the valve so as to open the valve when the engine completely explodes, and the fuel pressure transmission device is further provided in the second atmospheric air introduction path. 2 is characterized in that the second atmosphere introduction passage is provided with a temperature sensing valve that closes when the engine atmosphere temperature is below a predetermined value and opens when it exceeds a predetermined value.
Carburetor starter for cycle engines.