JPH0466773A - Fuel injection equipment of internal combustion engine - Google Patents

Abstract

PURPOSE:To surely stop compressed air from entering into a fuel injection valve by providing a compressed air pressure regulating valve which is opened and allows the compressed air n a compressed air passage to escape when pressure of fuel supplied to a fuel injection valve becomes lower than compressed air pressure. CONSTITUTION:An air blast valve 9 comprises a switching valve 33 whose end portion is formed into a nozzle opening 32 located inside a combustion chamber 4 and which is disposed in a compressed air passage 31. A diagonally extending compressed air passage 39 branches off from the compressed air passage 31 and is connected to a compressed air supply opening 40 and is equipped with a fuel injection valve 41 for injecting fuel toward the inside of the compressed air passage 39. Compressed air is supplied to the compressed air supply opening 40 of each cylinder via a compressed air passage 19 and a compressed air distribution chamber 20 by means of actuation of a vane pump 18. A compressed air pressure regulating valve 21 for maintaining compressed air pressure inside the compressed air distribution chamber 20 at fixed pressure is interposed in the compressed air passage 19 so as to prevent the compressed air from flowing into the fuel injection valve 41.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a fuel injection device for an internal combustion engine.

[Conventional technology]

a nozzle port; a compressed air passageway with one end connected to the nozzle port and the other end connected to a compressed air source; an on-off valve for controlling opening and closing of the nozzle port; and a fuel injection valve for injecting fuel into the compressed air passageway. The fuel injection valve has a nozzle whose opening and closing are controlled by a spring-biased needle, and the fuel injected into the compressed air passage from the nozzle of the fuel injection valve is ejected from the nozzle port together with the compressed air. A fuel injection device is known (see Japanese Patent Publication No. Hei 1-503554). In this fuel injection device, as mentioned above, fuel is injected into the compressed air passage from the nozzle of the fuel injection valve, so the fuel injection amount is determined by the pressure of the fuel supplied to the fuel injection valve and the compressed air pressure in the compressed air passage. Determined by differential pressure and fuel injection time.

This fuel injection device controls the fuel injection amount by controlling the fuel injection time. Therefore, in order to perform accurate injection control, it is necessary to maintain a constant differential pressure between the fuel pressure and compressed air pressure. need to be maintained. Therefore, in this fuel injection system, when the fuel pressure becomes higher than the compressed air pressure by more than a predetermined pressure, the valve is opened and some of the fuel is returned to the fuel tank, thereby reducing the difference between the fuel pressure and the compressed air pressure. Equipped with a fuel pressure regulating valve to maintain constant pressure.

[Problem to be solved by the invention]

Incidentally, in this fuel injection device, the needle of the fuel injection valve is structured to be held in a closed state by fuel pressure and spring force, and the valve-closing force of the needle due to only the spring force is set to be quite small.

However, even if the valve closing force of the needle due to spring force alone is set to be quite small, the fuel pressure is usually higher than the compressed air pressure, so compressed air does not flow into the fuel injection valve through the nozzle. . In addition, in such a fuel injection system, the fuel supply system usually has better sealing than the compressed air supply system, so when the engine stops, the compressed air pressure decreases earlier than the fuel pressure. The fuel does not flow into the fuel injection valve through the nozzle.

However, if the fuel pressure drops earlier than the compressed air pressure for some reason when the engine is stopped, the compressed air will flow into the fuel injection valve through the injection port. In other words, the fuel pressure regulating valve mentioned above controls the fuel pressure so that the differential pressure between the fuel pressure and the compressed air pressure does not exceed a certain pressure, so even if the fuel pressure falls below the compressed air pressure, the compressed air pressure will not increase accordingly. The structure is not designed to allow the temperature to deteriorate. That is,
Even if the fuel pressure decreases, the compressed air pressure will remain high. Therefore, when the fuel pressure decreases and the valve-opening force of the needle due to compressed air pressure becomes greater than the valve-closing force of the needle due to fuel pressure and spring force, the compressed air pressure forces the needle to open, and as a result, the fuel injection valve Compressed air will flow inside. If compressed air flows into the fuel injection valve in this way, when the engine is started, the fuel injection amount not only decreases until the compressed air is completely driven out by the fuel, but also becomes unstable. This results in the problem that not only is it not possible to start the engine properly, but even if the engine is started, stable combustion cannot be obtained for a while.

[Means to solve the problem]

In order to solve the above-mentioned problems, the present invention includes a nozzle opening, a compressed air passage whose one end is connected to the nozzle opening and the other end connected to a compressed air source, an on-off valve for controlling opening and closing of the nozzle opening, a fuel injection valve for injecting fuel into the air passage; the fuel injection valve has a nozzle whose opening and closing are controlled by a spring-biased needle; In a fuel injection device in which injected fuel is ejected from a nozzle port together with compressed air, the pressure of the fuel is higher than the compressed air pressure in response to the pressure of the fuel supplied to the fuel injection valve and the compressed air pressure in the compressed air passage. It is equipped with a compressed air pressure regulating valve that opens to release the compressed air in the compressed air passage when the pressure becomes low or lower than a predetermined pressure.

[For production]

When the pressure of the fuel becomes lower than the compressed air pressure, or becomes lower than a predetermined pressure, the compressed air pressure regulating valve opens and the compressed air in the compressed air passage is released. the result,
Since the compressed air pressure is reduced, the needle is not opened by the compressed air pressure.

〔Example〕

FIG. 1 shows an overall diagram of a two-stroke internal combustion engine.

Referring to FIG. 1, 1 is a cylinder block, 2 is a piston that reciprocates within printer block 1, 3 is a cylinder head fixed on cylinder block 1, and 4 is formed between piston 2 and cylinder head 3. combustion chamber,
5 is an air supply valve, 6 is an air supply boat, 7 is an exhaust valve, 8 is an exhaust port, and 9 is an air blast valve that injects fuel together with compressed air into the combustion chamber 4. Although not shown in the drawings, an ignition plug is arranged at the center of the inner wall surface of the cylinder head 3. The air supply boat 6 is connected to a surge tank 11 via an air supply branch pipe 10, and the surge tank 11 is connected to an engine-driven mechanical supercharger 12, an air supply duct 13, and an air flow meter 1.
It is connected to the air cleaner 15 via 4. A throttle valve 16 is arranged within the air supply duct 13.

FIG. 2 shows an enlarged sectional view of the air blast valve 9.

Referring to FIG. 2, the housing 30 of the air blast valve 9
A compressed air passage 31 extending straight is formed inside.
A nozzle port 32 located within the combustion chamber 4 (FIG. 1) is formed at the tip of this compressed air passage 31. An on-off valve 33 is disposed within the compressed air passage 31, and a valve body 34 for controlling opening and closing of the nozzle port 32 is integrally formed at the outer end of the on-off valve 33. Inside the housing 30, a movable core 36 which is disposed coaxially with the on-off valve 33 and is biased toward the on-off valve 33 by a compression spring 35, and a solenoid 37 for attracting the movable core 36 are arranged. . The inner end of the on-off valve 33 is brought into contact with the end surface of the movable core 36 by a compression spring 38, and the spring force of the compression spring 38 is
Since the spring force is stronger than the spring force of 5, the nozzle port 32 is normally used as the on-off valve 3.
It is closed by a valve body 34 of No. 3. solenoid 37
When the movable core 36 is energized, the movable core 36 moves toward the on-off valve 33, and as a result, the valve body 34 of the on-off valve 33 opens the nozzle port 32.

On the other hand, a compressed air passage 39 that extends obliquely from the compressed air passage 31 branches off from the compressed air passage 31, and this compressed air passage 39 is connected to a compressed air supply port 40.

A fuel injection valve 41 is attached to the housing 30.

The fuel injection valve 41 includes a nozzle 42 that is controlled to open and close by a spring-biased needle 43, and fuel is injected into the compressed air passage 39 from the nozzle 42.

As shown in FIG. 1, an air blasting air passage 17 is branched from the air supply duct 13 between the air flow meter 14 and the throttle valve 16.
7 is an engine-driven vane pump 18 and a compressed air passage 1
It is connected via 9 to a compressed air distribution chamber 20 . This compressed air distribution chamber 20 is connected to a compressed air supply port 40 of an air blast valve 9 provided for each cylinder. A compressed air pressure regulating valve 21 is attached to the compressed air passage 19 to maintain the compressed air pressure in the compressed air distribution chamber 20 at a predetermined constant pressure, for example, 3 kg/cffl. On the other hand, the fuel injection valve 41 is connected to the fuel tank 24 via the fuel passage 22 and the engine-driven fuel pump 23, so that fuel discharged from the fuel pump 23 is supplied to the fuel injection valve 41 via the fuel passage 22. Ru. The fuel pressure supplied to the fuel injection valve 41 is set in the fuel passage 22 at a predetermined constant pressure, for example, 2.5 kg/Cn!, which is lower than the compressed air pressure. In other words, the fuel pressure supplied to the fuel injection valve 41 is maintained at a predetermined constant pressure, for example, 5.5 kg.
A fuel pressure regulating valve 25 is installed to maintain the pressure at /Crl.

The compressed air pressure regulating valve 21 has a movable valve body 5 supporting a ball 50.
1, a bellows 52, and a diaphragm 53, and a plate 54 is fixed to the ball 50. One end of the bellows 52 is fixed to the peripheral edge of the movable valve body 51.
The other end of 2 is fixed to the inner wall surface of the housing. The movable valve body 51 and the bellows 52 form a movable valve 55, and the inside of the compressed air pressure regulating valve 21 includes a diaphragm 53 and a movable valve 55.
is divided into three chambers: an atmospheric pressure chamber 56 located above the diaphragm 53, a fuel chamber 57 formed between the diaphragm 53 and the movable valve 55, and a compressed air chamber 58 formed below the movable valve 55. be done. Atmospheric pressure chamber 56
is open to the atmosphere through an atmosphere communication hole 59, the fuel chamber 57 is connected to the fuel passage 22 through a fuel passage 60, and the compressed air chamber 58 is connected to the compressed air passage through a compressed air inlet port 61. It is connected to 19. Further, a compressed air outlet port 62 is opened in the compressed air chamber 58, and the opening and closing of this compressed air outlet port 62 is controlled by the plate 54. This compressed air outlet port 62 is connected to the air supply duct 13 via a compressed air return passage 63.

A compression spring 64 is inserted into the atmospheric pressure chamber 56 to press the diaphragm 53 toward the movable valve 55.
A compression spring 65 is also inserted between the valve body 3 and the movable valve body 51. Furthermore, the diaphragm 53 and the movable valve body 51 are connected to each other by a loose connection mechanism 6.
They are connected to each other via 6. This play connection mechanism 6
6 consists of a hollow sleeve 67 fixed to the movable valve body 51 and a rod 69 having an enlarged head 68 and connected to the diaphragm 53. The enlarged head 68 is movable within the hollow sleeve 67 and is connected to the hollow sleeve 67. It is arranged so as to be able to engage with the inner wall surface of the distal end portion of 67.

On the other hand, the fuel pressure regulating valve 25 includes a movable valve body 71 supporting a ball 70 and a diaphragm 72 supporting the movable valve body 71.
A plate 73 is fixed to the ball 70. The interior of the fuel pressure regulating valve 25 is divided by the diaphragm 72 into two chambers: a compressed air chamber 74 located above the diaphragm 72 and a fuel chamber 75 located below the diaphragm 72. The compressed air chamber 74 is the compressed air passage 7
6 to the compressed air passage 19, and the fuel chamber 75 to the fuel passage 22 via a fuel inlet port 77. Further, a fuel outlet port 78 is open in the fuel chamber 75, and the opening and closing of this fuel outlet port 78 is controlled by a plate 73. This fuel outlet boat 78 is connected to the fuel tank 24 via a fuel return passage 79. A compression spring 80 that presses the diaphragm 72 toward the fuel chamber 75 is inserted into the compressed air chamber 74 .

During engine operation, the fuel chamber 57 of the compressed air pressure regulating valve 21 is filled with fuel at a fuel pressure of approximately 5.5 kg/cfIt.

At this time, the movable valve body 51 and the diaphragm 53 are held in a position farthest from each other, that is, in a state where the enlarged head 868 of the rod 69 of the loose coupling mechanism 66 and the inner wall surface of the distal end portion of the hollow sleeve 67 are engaged. Therefore, at this time, the fuel chamber 5
If the fuel pressure in the compressed air chamber 58 is higher than the compressed air pressure in the compressed air chamber 58, the movable valve body 51 and the diaphragm 53 move up and down together. That is, at this time, when the compressed air pressure in the compressed air chamber 58 increases, the movable valve body 51 and the diaphragm 53 rise against the spring force of the compression spring 64, and the plate 54 opens the compressed air outlet port 62. As a result, the compressed air pressure in the compressed air chamber 58 and the compressed air passage 19 decreases as the compressed air in the compressed air chamber 58 is released into the air supply duct 13 via the compressed air return passage 63. on the other hand,
When the compressed air pressure in the compressed air chamber 58 decreases, the movable valve body 5
1 and diaphragm 53 are lowered against the spring force of compression spring 64, and plate 54 closes compressed air outlet port 62. As a result, the compressed air pressure within the compressed air chamber 58 and the compressed air passage 19 gradually increases. In this way, the compressed air pressure in the compressed air chamber 58 and the compressed air passage 19 is maintained at a constant pressure determined by the spring force of the compression spring 64. In the embodiment shown in FIG. 1, the spring force of the compression spring 64 is determined so that the compressed air pressure in the compressed air chamber 58 and the compressed air passage 19 is 3.0 kg/crl.

On the other hand, in this way, the compressed air pressure in the compressed air passage 19 is 3.
．． When maintained at 0 kg/crl, the fuel pressure regulating valve 25
The compressed air pressure in the compressed air chamber 74 is also 3.0 kg/crl.
will be maintained. In this fuel pressure regulating valve 25, when the differential pressure obtained by subtracting the compressed air pressure in the compressed air chamber 74 from the fuel pressure in the fuel chamber 75 becomes 2.5 kg/cr1 or more, the plate 73 opens the fuel outlet port 78, and this difference pressure is 2.5
kg/cI11 or less, plate 73 closes fuel outlet port 78. Therefore, the fuel pressure regulating valve 25 reduces the pressure difference between the fuel pressure in the fuel passage 22 and the compressed air pressure by 2.
．． 5 kg/cm, i.e. the fuel pressure in the fuel passage 22 is maintained at 5.5 kg/cm. In this way, when the engine is running, the compressed air pressure is 3.0 kg/c.
fuel pressure is maintained at 5.5 kg/crl.

FIG. 3 shows the opening period of the intake valve 5 and the exhaust valve 7, the period of fuel injection from the fuel injection valve 41, and the valve body 34 of the on-off valve 33.
In other words, the valve opening period of the air blast valve 9 is shown.

As shown in FIG. 3, in the embodiment shown in FIG. 1, the exhaust valve 7 opens before the intake valve 5 and closes before the intake valve 5. Also,
As shown in FIG. 3, before the valve element 34 of the on-off valve 33 opens, that is, before the air blast valve 9 opens, the fuel injection valve 41 directs the compressed air into the compressed air passage 39. Fuel is injected. Next, when the air blast valve 9 opens, the injected fuel is injected from the nozzle port 32 into the combustion chamber 4 together with compressed air. On the other hand, as shown in FIG.
A mask wall 26 is formed on the inner wall surface of the cylinder head 3 to cover the opening of the side air supply valve 5 during the period when the air supply valve 5 is fully open. Therefore, when the air supply valve 5 opens, fresh air flows to the air supply port 6.
The air is supplied into the combustion chamber 4 through the opening of the intake valve 5 on the side opposite to the exhaust valve 7. As a result, the fresh air flows along the peripheral wall surface of the combustion chamber 4 as shown by arrow S, thus achieving good loop scavenging.

When the engine stops, vane pump 18 and fuel pump 2
3 is stopped. At this time, the fuel pump 23
Since the sealing performance of the vane pump 18 is better than that of the vane pump 18, the compressed air pressure in the compressed air passage 19 is normally applied to the fuel passage 19.
The fuel pressure drops before the internal fuel pressure.

When the compressed air pressure in the compressed air passage 19 decreases, the fuel in the fuel passage 22 descends by the action of the fuel pressure regulating valve 25 while maintaining a pressure 2.5 kg/cffl higher than the compressed air pressure. Therefore, at this time, the fuel injection valve 4
Since the fuel pressure in the compressed air passage 39 is maintained higher than the compressed air pressure in the compressed air passage 39, the needle 43 is opened by the compressed air in the compressed air passage 39, whereby the compressed air is injected through the nozzle 42. No intrusion into the valve 41 occurs.

On the other hand, when the engine is stopped, for some reason the fuel passage 22
When the fuel pressure within the fuel chamber 57 of the compressed air pressure regulating valve 21 decreases before the compressed air pressure within the compressed air chamber 58, the fuel pressure within the fuel chamber 57 of the compressed air pressure regulating valve 21 decreases before the compressed air pressure within the compressed air chamber 58. At this time, if the spring force of the compression spring 65 provided in the fuel chamber 57 is extremely weak, the fuel pressure in the fuel chamber 57 decreases to 3 kg/cnf or less, and the fuel pressure in the fuel chamber 57 decreases to the compressed air chamber 58.
When the pressure becomes lower than the compressed air pressure within, the enlarged head 68 of the rod 69 of the idle connection mechanism 66 separates from the inner wall surface of the distal end portion of the hollow sleeve 67, and the movable valve body 51 rises. As a result, the compressed air pressure in the compressed air chamber 58 decreases because the plate 54 opens the compressed air outlet boat 62. Next, when the compressed air pressure in the compressed air chamber 58 becomes lower than the fuel pressure in the fuel chamber 57, the plate 54 closes to the compressed air outlet boat 62.
will be closed. In this way, if the spring force of the compression spring 65 is extremely weak, and the fuel pressure decreases before the compressed air pressure, the compressed air pressure in the compressed air chamber 58 and the compressed air passage 19 will increase while maintaining almost the same pressure as the fuel pressure. Decrease with pressure. By the way, the fuel injection valve 41 controls the fuel pressure and the needle 4.
A force in the valve closing direction is applied to the needle 43 due to the biasing spring force on the needle 43, and even if the fuel pressure and the compressed air pressure become approximately equal, the needle 43 is held in the valve closed state by the biasing spring force on the needle 43. Ru. Therefore, as described above, when the compressed air pressure decreases with the fuel pressure while maintaining almost the same pressure as the fuel pressure, the needle 43 of the fuel injection valve 41 is held in the closed state, and the compressed air is injected into the fuel via the nozzle 42. No intrusion into the valve 41 occurs.

On the other hand, if the spring force of the compression spring 65 provided in the fuel chamber 57 is strengthened, when the fuel pressure decreases before the compressed air pressure, the compressed air pressure will increase by a certain differential pressure determined by the spring force of the compression spring 65. decreases with fuel pressure. Even in this case, as long as the force in the needle valve opening direction acting on the needle 43 due to this differential pressure is weaker than the force in the needle valve closing direction due to the biasing spring of the needle 43, compressed air flows into the fuel injection valve 41 through the nozzle 42. will be prevented from entering. In other words, the compression spring 65 of the compressed air pressure regulating valve 21
The spring force can be made as strong as desired as long as the force in the needle valve opening direction acting on the needle 43 due to the above-mentioned differential pressure is weaker than the force in the needle valve closing direction due to the biasing spring force of the needle 43.

〔Effect of the invention〕

To prevent compressed air from entering the fuel injection valve not only when the compressed air pressure drops before the fuel pressure when the engine is stopped, but also when the fuel pressure drops before the compressed air pressure. I can do it.

[Brief explanation of drawings]

Figure 1 is an overall view of a two-stroke internal combustion engine, Figure 2 is an enlarged side sectional view of the air blast valve, and Figure 3 is a line diagram showing the opening periods of the supply and exhaust valves, the opening periods of the air blast valve, etc. be. 9... Air blast valve, 21... Compressed air pressure regulating valve, 25... Fuel pressure regulating valve, 41... Fuel injection valve.

Claims (1)

[Claims] a nozzle port; a compressed air passageway with one end connected to the nozzle port and the other end connected to a compressed air source; an on-off valve for controlling opening and closing of the nozzle port; and a fuel injection valve for injecting fuel into the compressed air passageway. The fuel injection valve has a nozzle whose opening and closing are controlled by a spring-biased needle, and the fuel injected into the compressed air passage from the nozzle of the fuel injection valve is ejected from the nozzle port together with the compressed air. In a fuel injection device, when the pressure of the fuel becomes lower than the compressed air pressure or lower than a predetermined pressure in response to the pressure of the fuel supplied to the fuel injection valve and the compressed air pressure in the compressed air passage. A fuel injection device for an internal combustion engine equipped with a compressed air pressure regulating valve that opens to release compressed air in a compressed air passage.