EP0377784B1

EP0377784B1 - A fuel supply device of an engine

Info

Publication number: EP0377784B1
Application number: EP19890116036
Authority: EP
Inventors: Yuichi C/O Toyota Jidosha Kabushiki Kaisha Takano; Takahiro Toyota Jidosha Kabushiki Kaisha Kushibe; Naotaka Shirabe
Original assignee: Toyota Motor Corp; NipponDenso Co Ltd
Current assignee: Denso Corp; Toyota Motor Corp
Priority date: 1989-01-12
Filing date: 1989-08-30
Publication date: 1992-08-12
Anticipated expiration: 2009-08-30
Also published as: AU608997B2; EP0377784B2; DE58902044D1; DE58902044T2; AU4087389A; EP0377784A1

Description

The present invention relates to a fuel supply device of an engine, according to the preamble of claim 1.
In a known "air blast" valve, the opening and closing operation of the nozzle opening is electromagnetically controlled by a needle, to cause an injection of fuel by pressurized air. A pressurized air passage extending from the nozzle opening along'the needle is formed around the needle and connected to a pressurized fuel source, a nozzle chamber open to the pressurized air passage is provided, and the nozzle of the fuel injector is arranged deep in the interior of the nozzle chamber. The needle has a guide portion formed thereon, this guide portion having three equally spaced lobes which are in slidable contact with the inner wall of the pressurized air passage, to support and guide the needle. Because of the provision of the lobes to support and guide the needle, passages formed between the lobes for the fuel-air charge must have a relatively large cross sectional area, to reduce flow resistance.
After fuel is injected from the fuel injector toward the needle, the needle opens the nozzle opening and the thus injected fuel is injected together with pressurized airfrom the nozzle opening of the air blast valve according to the teaching of WO-A87 005837.
Where, however, passages formed between the lobes for the fuel-air charge have a relatively large cross sectional area, as in the above-mentioned air blast valve, when fuel is injected from the fuel injector toward the needle, most of the fuel injected from the fuel injector passes through passages formed between the lobes and collects in the pressurized air passage, near the nozzle opening, and as a result, the fuel collected near the nozzle opening is forced out as liquid fuel by the pressure of the pressurized air when the needle opens the nozzle opening, and thus a problem arises in that fuel injected from the nozzle opening is not fully atomized and is not completely mixed with the air.
Furthermore in document US-A-1 615 457 there has been disclosed a generic fuel supply device comprising a guide member of approximately rectangular shape in cross section being enclosed in a circular member, thereby providing longitudinal passages which are supplied with oil. The circular membercom- prises tangential passages for supplying fuel from said longitudinal passages to the pressurized air passage thereby maintaining a whirling motion of the body of fuel. In this manner the mixing of fuel and air should be improved. Despite of the very complicated construction of such a fuel supply device, the fuel cannot be fully atomized and completely mixed with the air by means of this device.
An object of the present invention is to provide a fuel supply device capable of injecting fuel which has been fully atomized and completely mixed with the air, from the nozzle opening.
According to the present invention, there is provided a fuel supply device of an engine, comprising: a pressurized air passage; a nozzle opening formed at a tip end of the pressurized air passage for injecting fuel and pressurized air; a valve means for controlling the opening of the nozzle opening; a fuel supply means for supplying fuel to the pressurized air passage; and a guide member arranged in the pressurized air passage between the nozzle opening and the fuel supply means and having at least three contacting faces in contact with a cylindrical inner wall of the pressurized air passage. The guide member having at least three substantially flat faces each extending in an approximately straight line between the contacting faces which are located on each side of the flat face to form a fuel and air passage between the cylindrical inner wall of the pressurized air passage and the substantially flat face.
The present invention may be more fully understood from the description of preferred embodiments of the invention set forth below, together with the accompanying drawings.
In the drawings:

Fig. 1 is an enlarged cross-sectional side view of a portion of an air blast valve denoted by an arrow K in Fig. 2;
Fig. 2 is a partly cross-sectional side view of the air blast valve;
Fig. 3 is an enlarged cross-sectional view of the guide member, taken along the line III - III in Fig. 1;
Fig. 4 is a bottom view of the innerwall of the cylinder head of a two-stroke engine;
Fig. 5 is a cross-sectional side view of the two-stroke engine;
Fig. 6 illustrates the relationship between an amount of fuel supplied by the fuel injector and an amount of air injected from the nozzle opening;
Fig. 7 is a partly cross-sectional side view of another embodiment of the air blast valve;
Fig. 8 is an enlarged cross-sectional side view of a tip portion of the air blast valve illustrated in Fig. 7;
Fig. 9 is an enlarged cross-sectional view of the guide member, taken along the line IX - IX in Fig. 8;
Fig. 10 is perspective view of the guide member;
Fig. 11 is a diagram illustrating the opening timing of the intake valve and the exhaust valve;
Fig. 12 is an enlarged cross-sectional side view of another embodiment of a tip portion of the air blast valve;
Fig. 13 is an enlarged cross-sectional side view of a further embodiment of a tip portion of the air blast valve; and
Fig. 14 is an enlarged cross-sectional side view of a still further embodiment of a tip portion of the air blast valve.

DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to Figs. 4 and 5, reference numeral 1 designates a cylinder block, 2 a piston, 3 a cylinder head, and 4 a combustion chamber; 5 designates a pair of intake valves, 6 intake ports, 7 a pair of exhaust valves, 8 exhaust ports; and 9 designates a spark plug. Masking walls 10, each masking the valve opening formed between the valve seat and the peripheral portion of the intake valve 5, which is located on the exhaust valve side, for the entire time for which the intake valve 5 is open, are formed on the inner wall of the cylinder head 3. Consequently, when the intake valves 5 open, fresh air flows into the combustion chamber 4 from the valve opening which is located at a position opposite to the exhaust valves 7, as illustrated by the arrow A in Fig. 5. An air blast valve 20 is arranged on the inner wall of the cylinder head 3 between the intake valves 5.
Figures 1 and 2 illustrate a first embodiment of the air blast valve 20. Referring to Figs. 1 and 2, a straight needle insertion bore 22 is formed in the housing 21 of the air blast valve 20, and a needle 23 having a diameter smaller than that of the needle insertion bore 22 is inserted into the needle insertion bore 22. A nozzle opening 24 is formed at one end of the needle insertion bore 22, and the opening and closing operation of the nozzle opening 24 is carried out by the valve head 25 formed on the tip of the needle 23. In this embodiment, as shown in Fig. 2, the nozzle opening 24 is arranged in the combustion chamber 4, a spring retainer 26 is mounted on the needle 23, and a compression spring 27 is inserted between the spring retainer 26 and the housing 21. The nozzle opening 24 is normally closed by the valve head 25 of the needle 23 due to the spring force of the compression spring 27. A movable core 28 continuously abuts against the end portion of the needle 23, which is positioned opposite to the valve head 25, due to the spring force of the compression spring 29, and a solenoid 30 and a stator 31 are arranged in the housing 21 to attract the movable core 28. When the solenoid 30 is energized, the movable core 28 moves toward the stator 31, and at this time, since the needle 23 moves toward the nozzle opening 24 against the compression spring 27, the nozzle opening 24 is opened.
A nozzle chamber 32 having a cylindrical shape is formed in the housing 21. The nozzle chamber 32 has an air inlet 32a and an air outlet 32b separately formed from and spaced from the air inlet 32a. The air inlet 32a is connected to a pressurized air source 34 via a pressurized air inflow passage 33, and the air outlet 32b is connected to the needle insertion bore 22 via a pressurized air outflow passage 35. The nozzle 37 of a fuel injector 36 is arranged in the nozzle chamber 32 at a position between the air inlet 32a and the air outlet 32b.
As can be seen from Figs. 1 and 2, the pressurized air outlet passage 35 extends in a straight line. The nozzle 37 of the fuel injector 36 is arranged on the axis of the pressurized air outlet passage 35, and fuel having a small spread angle is injected from the nozzle 37 along the axis of the pressurized air outflow passage 35. The pressurized air outlet passage 35 extends obliquely to the needle insertion bore 22 toward the nozzle opening 24 and is obliquely connected to the needle insertion bore 22 at a connecting portion 38, at an angle of 20 to 40 degrees with respect to the axis of the needle insertion bore 22.
Referring to Figure 1, the needle 23 has an enlarged portion 42 formed thereon and sl idably fitted into the nozzle insertion bore 22 at a position opposite to the nozzle opening 24 with respect to the connecting portion 38 of the pressurized air outlet passage 35 and the needle insertion bore 22, whereby a flow of pressurized air and fuel toward the solenoid 30 (Fig. 2) is prevented. Also, the needle 23 has a guide member 39 integrally formed thereon at a position midway between the nozzle opening 24 and the connecting portion 38 of the pressurized air outlet passage 35 and the needle insertion bore 22.
Figure 3 is an enlarged cross-sectional plan view of the guide member 39. Referring to Fig. 3, the guide member 39 has four cylindrical portions 39a in slidable contact with the cylindrical inner wall of the needle insertion bore 22, and four flat faces 39b each extending in a straight line between the cylindrical portions 39a which are located on each side of the flat face 39b to form a narrow passage 40 between the cylindrical inner wall of the needle insertion bore 22 and the flat face 39b. The cylindrical portion 39a has approximately the same radius as the cylindrical inner wall of the needle insertion bore 22. The cross section of the guide member 39 is shaped approximately as a square inscribed in the cylindrical inner wall of the needle insertion bore 22 at the cylindrical portion 39a. The sum of the cross-sectional areas of the four narrow passages 40 is considerably smaller than the cross-sectional area of the passage 43 (Fig. 1) formed between the needle 23 and the needle insertion bore 22. The cross-sectional area of the narrow passage 40 is constant along the axis of the needle 23.
Returning to Figs. 1 and 2, the needle insertion bore 22, the nozzle chamber 32, and the pressurized air outflow passage 35 are connected to the pressurized air source 34 via the pressurized air inflow passage 33, and thus are filled with pressurized air. Fuel is injected into the pressurized air from the nozzle 37 along the axis of the pressurized air outflow passage 35. The injected fuel impinges on the needle 23 and the inner wall of the needle insertion bore 22, and at this time, a part of the fuel is instantaneously atomized and another part of the fuel forms an emulsion. As the cross-sectional area of the narrow passage 40 is relatively small, most of the injected fuel adheres to the inner and outer wall of the narrow passage 40 and collects in the needle insertion bore 22 upstream of the narrow passage 40, and only a very small amount of the fuel reaches the interior of the needle insertion bore 22 around the needle 23 near the valve head 25. Therefore, when the solenoid 30 is energized, the needle 23 opens the nozzle opening 24, and at this time, as soon as the needle 23 opens the nozzle opening 24, the very small amount of fuel in the needle insertion bore 22 near the valve head 25 is injected into the combustion chamber4 (Fig. 2) from the nozzle opening 24. Further, when the needle 23 opens the nozzle opening 24, the pressurized air flows into the nozzle chamber 32 from the pressurized air inflow passage 33 via the air inlet 32a, and then flows toward the nozzle opening 24 via the pressurized air outflow passage 35 and the needle insertion bore 22. At this time, the injected fuel in the narrow passage 40 and the needle insertion bore 22 upstream of the narrow passage 40 is atomized by the pressurized air blowing within the needle insertion bore 22 and the narrow passage 40 and is carried away toward the nozzle opening 24 by the pressurized air, while being mixed with the pressurized air. Then, the fuel and the pressurized air are injected together from the nozzle opening 24 into the combustion chamber 4 (Fig. 2). Also the fuel stuck to the inner wall of the pressurized air outflow passage 35, the inner wall of the nozzle chamber 32, and the innerwall of the needle insertion bore 22 is carried away by the pressurized air and injected from the nozzle opening 24.
As mentioned above, when the needle 23 opens the nozzle opening 24, an extremely small amount of the fuel existing in the needle insertion bore 22 near the valve head 25 is initially injected from the nozzle opening 24, but immediately thereafter, fuel fully atomized and fully mixed with the air is injected from the nozzle opening 24. Consequently, the fuel fully atomized and fully mixed with the air is injected from the nozzle opening 24 from the beginning of the air-fuel injection, and thus it is possible to form a good air-fuel mixture in the combustion chamber 4 (Fig. 2).
In addition, as soon as the needle 23 opens the nozzle opening 24, the entire amount of injected fuel is injected from the nozzle opening 24 and, after the injection of the entire injected fuel is completed, only the pressurized air is injected from the nozzle opening 24. Then the solenoid 30 is deenergized, and thus the needle 23 closes the nozzle opening 24. Consequently, only the pressurized air is injected from the nozzle opening 24 immediately before the needle 23 closes the nozzle opening 24.
If fuel is still injected from the nozzle opening 24 immediately before the needle 23 closes the nozzle opening 24, when the flow area of the nozzle opening 24 becomes small due to the closing by the needle 23, and the velocity of the pressurized airflowing from the nozzle opening 24 becomes low, the fuel is not atomized, and thus the liquid fuel adheres to the wall around the nozzle opening 24; if the liquid fuel adheres to the wall around the nozzle opening 24, carbon accumulates on the wall around the nozzle opening 24 and affects the injecting operation. Nevertheless, in the embodiment illustrated in Fig. 2, since only the pressurized air is injected from the nozzle opening 24 immediately before the needle 23 closes the nozzle opening 24, the liquid fuel does not adhere to the wall around the nozzle opening 24, and therefore, carbon will not accumulate on the wall around the nozzle opening 24.
Figure 5 illustrates the case where the air blast value 20 is used for a two-stroke engine, and the injection of fuel by the air blast valve 20 is started just before the intake valves 5 close. When the engine is operating under a light load, since the velocity of the fresh air A flowing into the combustion chamber 4 is low, the fuel injected from the air blast valve 20 is collected around the spark plug 9, and thus a good ignition can be obtained. When the engine is operating under a heavy load, since the velocity of the fresh air A flowing into the combustion chamber 4 is high, a strong loop scavenging operation is carried out. In addition, since the fuel injected from the air blast valve 20 is carried downward along the inner wall of the combustion chamber 4 by the fresh air A flowing in a loop shape, a homogenous air-fuel mixture is formed in the combustion chamber 4, and as a result, a high output power of the engine can be obtained.
Figure 6 illustrates a relationship between an amount of fuel supplied by the fuel injector 36 and an amount of air injected from the nozzle opening 24. In the conventional air blast valve, as most of the fuel supplied by the fuel injector is collected in the needle insertion bore 22 near the valve head 25, the fuel is forced out of the nozzle opening 24 as liquid fuel by the pressure of the pressurized air. Therefore the fuel injected from the nozzle opening 24 is not fully atomized and completely mixed with the air. Since the pressurized air is not injected from the nozzle opening 24 before the fuel is forced out of the nozzle opening 24, the amount of air injected from the nozzle opening 24 is reduced in accordance with the increase of an amount of fuel supplied by the fuel injector 36. In this embodiment, an extremely small amount of fuel in the needle insertion bore 22 near the valve head 25 is ini- i-tially injected from the nozzle opening 24, and then the fuel fully atomized and completely mixed with the air is injected from the nozzle opening 24. Accordingly, as shown in Fig. 6, since the amount of air injected from the nozzle opening 24 is not charged by the charge of the amount of fuel supplied by the fuel injector 36, the maximum amount of air injected from the nozzle opening 24 can be reduced as shown by a phantom line in Fig. 6.
Figure 7 illustrates a second embodiment of the present invention. Referring to Fig. 7, a housing 51 of an air blast valve 50 comprises a nozzle portion 51a a and a body portion 51b. The nozzle portion 51a extends through the cylinder head 3, and the body portion 51 b is fixed to the upper end of the nozzle portion 51a. A fuel injector 52 and an air injector 53 are arranged at the body portion 51 b. A straight fuel and air supply bore 54 is formed in the nozzle portion 51a, and a nozzle opening 52a of the fuel injector 52 is arranged at the upper end of the fuel and air supply bore 54. Fuel having a small spread angle is injected from the nozzle opening 52a along the axis of the fuel and airsupply bore 54. An airsupply air bore 55 is connected to the upper end of the fuel and air supply bore 54 and a nozzle opening 53a of the air injector 53 is arranged at the end of the air supply bore 55. Pressurized air injected from the air injector 53 is supplied to the fuel and air supply bore 54 via the air supply bore 55. A nozzle opening 56 is formed at the lower end of the nozzle portion 51a and is arranged in the combustion chamber 4. An automatic opening and closing valve 57 for the opening and closing the nozzle opening 56 is arranged in the nozzle portion 51 a.
Referring to Figures 8 through 10, the automatic opening and closing valve 57 comprises a mushroom- shaped valve head 58, a valve shaft 59 extending in and along the axis of the fuel and air supply bore 54, a spring retainer 60 arranged at the top of the valve shaft 59, and a compression spring 61 constantly urging the spring retainer 60 upward. As shown in Fig. 8, the nozzle opening 56 is normally closed by the valve head 58 due to the spring force of the compression spring 61. The fuel and air supply bore 54 comprises a small diameter portion 54a having a constant cross-sectional area and extending from near the spring retainer 60 to the fuel injector 52 (Fig. 7), and a large diameter portion 54b formed around the valve shaft 59 and extending upward. The small and the large diameter portions 54a, 54b are formed coaxially. The spring retainer 60 is arranged in the large diameter portion 54b. An upper end 54c of the large diameter portion 54b is formed into a conical shape by which the cross-sectional area thereof is gradually reduced upward, and the upper end 54c of the large diameter portion 54b is connected to the lower end of the small diameter portion 54a. A guide member 62 having a diameter larger than that of the spring retainer 60 is fitted into and fixed to the large diameter portion 54b. The guide member 62 has a base portion 63 and a head portion 64.
The head portion 64 is formed into a conical shape by which the cross-sectional area thereof is gradually reduced upward and is coaxial with the large diameter portion 54b. The base portion 63 has four cylindrical portions 63a in contact with the cylindrical innerwall of the large diameter portion 54b, and four flat faces 63b each extending between the cylindrical portions 63a which are located on each side of the flat face 63b. A narrow passage 65 having a constant cross-sectional area is formed between the flat face 63b and the large diameter portion 54b. Also, a narrow passage 66 having a constant cross-sectional area is formed between the head portion 64 and the upper end 54c of the large diameter portion 54b.
Figure 7 illustrates the case where the air blast valve 50 is used for a two-stroke engine, and Figure 11 illustrates an example of the opening timing of the intake valves 5 and the exhaust valves 7, the fuel injection timing of the fuel injector 52, and the air injection timing of the air injector 53. As shown in Fig. 11, the air injection is started immediately before the closing of the intake valves 5, and the fuel injection from the fuel injector 52 is carried out at any time after the air injection is completed but before the next air injection is started.
Fuel is injected from the fuel injector 52 toward the guide member 62. As the cross-sectional area of the narrow passages 65, 66 is relatively small, a large part of fuel injected from the fuel injector 52 adheres to the inner walls and the outer walls of the narrow passages 65, 66, and thus a very small amount of the fuel reaches the valve head 58. Then, when pressurized air is injected from the air injector 53, the valve head 58 opens the nozzle opening 56 as illustrated by the phantom line in Fig. 8. At that time, as the cross-sectional area of the narrow passages 65, 66 is small, air flows in the narrow passages 65, 66 at a high speed, and thus the fuel stuck to the inner and outer walls of the narrow passages 65, 66 is atomized and carried away by the pressurized air. Accordingly, the injection of the atomized fuel from the nozzle opening 56 is started as soon as pressurized air is injected from the nozzle opening 56. In this embodiment, the first stage of the atomization of the fuel is carried out in the narrow passages 65, 66, and the second stage of the atomization of fuel is carried out when fuel is injected from the nozzle opening 56. Namely, in this embodiment, as two stages of the atomization of the fuel are carried out, fuel that is fully atomized and completely mixed with the air is injected from the nozzle opening 56 from the beginning of the air-fuel injecting operation.
Note, when air and fuel are injected from the nozzle opening 56, as the exhaust valves 7 are already closed, fuel injected from the nozzle opening 56 does not flow into the exhaust ports 8.
Figures 12 through 14 illustrate another embodiment wherein the shape of the head portion 64 of the guide member 62 is changed.
In the embodiment illustrated in Fig. 12, the apical angle 8₁ of the head portion 64 formed in a conical shape is larger than the apical angle 0₂ of the upper end 54c of the large diameter portion 54b, which is also formed in a conical shape. Accordingly, in the embodiment illustrated in Fig. 12, the cross-sectional area of the narrow passage 66 gradually becomes smaller in the downstream direction.
In the embodiment illustrated in Fig. 13, the head portion 64 is formed into the shape of a truncated cone.
In the embodiment illustrated in Fig. 14, the head portion 64 is formed into the shape of a sphere.
Note, the air blast valve according to this invention can be used for four-stroke engine, and fuel may be injected to the intake port.
While the invention has been described with reference to specific embodiments chosen for purposes of illustration, it should be apparent that numerous modifications could be made thereto by those skilled in the art.

Claims

1. A fuel supply device of an engine, comprising: a pressurized air passage (33, 35, 55, 54);

a nozzle opening (24, 56) formed at a tip end of said pressurized air passage (33, 35, 55, 54) for injecting fuel and pressurized air;

a valve means (23, 25, 30, 58, 59, 60, 61) for controlling an opening of said nozzle opening (24, 56);

a fuel supply means (36, 52) for supplying fuel to said pressurized air passage (33, 35, 55, 54); and

a guide member (39,62) having at least three contacting faces (39a, 63a) in contact with a cylindrical inner wall and said guide member (39, 62) having at least three substantially flat faces (39b, 63b) each extending approximately in a straight line between said contacting faces (39a, 63a) which are located on each side of said flat face (39b, 63b),
characterized in that

said guide member (39, 62) is arranged in said pressurized air passage (35, 54) between said nozzle opening (24, 56) and said fuel supply means (36, 52) to form a fuel and air passage (40, 65) between said cylindrical inner wall of said pressurized air passage (35, 54) and said flat face (39b, 63b).

2. A fuel supply device according to claim 1, characterized in that said contacting face (39a, 63a) is formed by a part of a cylindrical face having approximately a same radius as that of said cylindrical inner wall.

3. A fuel supply device according to claim 1, characterized in that said guide member (39, 62) has four contacting faces (39a, 63a) and four substantially flat faces (39b, 63b).

4. A fuel supply device according to claim 3, characterized in that a cross section of said guide member (39, 62) has a shape of approximately a square inscribed in said cylindrical inner wall at said contacting face (39a, 63a).

5. A fuel supply device according to claim 1, characterized in that said valve means (23, 25, 30) comprises a needle (23) arranged in a needle insertion bore (22) having a diameter larger than that of said needle (23) to electromagnetically control the opening operation of said nozzle opening (24), and pressurized air is continuously supplied in said pressurized air passage (33, 35).

6. A fuel supply device according to claim 5, characterized in that said needle insertion bore (22) is merged into said pressurized air passage (35) at a merging portion (38) and extends toward said nozzle opening (24), said guide member (39) being an enlarged portion formed on said needle (23) between said nozzle opening (24) and said merging portion (38).

7. A fuel suppyl device according to claim 6, characterized in that said guide member (39) is formed at a position midway between said nozzle opening (24) and said merging portion (38).

8. A fuel supply device according to claim 6, characterized in that said guide member (39) is integrally formed with said needle (23) and is slidable against said cylindrical inner wall.

9. A fuel supply device according to claim 6, characterized in that said needle insertion bore (22) extends in a straight line, and said pressurized air passage (35) is obliquely merged with said needle insertion bore (22) at said merging portion (38).

10. A fuel supply device according to claim 6, characterized in that said needle (23) has a second enlarged portion (42) formed thereon and slidably fitted into said needle insertion bore (22) at a position opposite to said nozzle opening (24) with respect to said merging portion (38) of said pressurized air passage (35) and said needle insertion bore (22).

11. A fuel supply device according to claim 10, characterized in that said second enlarged portion (42) has an end face positioned adjacent to said merging portion (38) of said pressurized air passage (35) and said needle insertion bore (22).

12. A fuel supply device according to claim 11, characterized in that said end face of said second enlarged portion (42) has a conical shape.

13. A fuel supply device according to claim 5, characterized in that said valve means (23, 25, 30) further comprises a solenoid (30) actuating said needle (23) and a valve head (25) formed on said needle (23) to control the opening of said nozzle opening (24).

14. A fuel supply device according to claim 5, characterized in that said fuel supply device further comprises a nozzle chamber (32) arranged in said pressurized air passage (33, 35) and having an air inlet (32a) connected to a pressurized air source (34), and said nozzle chamber (32) having an air outlet (32b) separately formed and spaced from said air inlet (32a) and connected to said nozzle opening (24), wherein said fuel supply means (36) is arranged in said nozzle chamber (32).

15. A fuel supply device according to claim 14, characterized in that said nozzle chamber (32) has an inner circumferential wall circumferentially extending about an axis of said nozzle chamber (32), and said air inlet (32a) is formed on the circumferential wall of said nozzle chamber (32), said air outlet (32b) being formed on the axis of said nozzle chamber (32).

16. A fuel supply device according to claim 15, characterized in that said fuel supply means (36) comprises a nozzle (37) arranged on the axis of said nozzle chamber (32) to inject fuel from said nozzle (37) along the axis of said nozzle chamber (32).

17. A fuel supply device according to claim 15, characterized in that said pressurized air passage (33, 35) has a pressurized air outflow passage (35) which is connected to said air outlet (32b) and extends in a straight line along the axis of said nozzle chamber (32) and said fuel supply means (36) comprises a nozzle (37) arranged on the axis of said nozzle chamber (32) to inject fuel from said nozzle (37) into said pressurized air outflow passage along the axis of said nozzle chamber (32).

18. A fuel supply device according to claim 17, characterized in that said valve means comprises a needle (23) arranged in a needle insertion bore (22) having a diameter larger than that of said needle (23) to electromagnetically control the opening of said nozzle opening (24) and said needle insertion bore (22) extends toward said nozzle opening (24), said pressurized air outflow passage (35) being connected to said needle insertion bore (22).

19. A fuel supply device according to claim 1, characterized in that said fuel supply device further comprises an air injection means (53) arranged in said pressurized air passage (55, 54) at a position opposite to said nozzle opening (56) with respect ot said fuel supply means (52) to inject pressurized air into said pressurized air passage, wherein said valve means opens said nozzle opening (56) due to the pressure of pressurized air in said pressurized air passage when said air injection means (53) injects pressurized air into said pressurized air passage (55, 54).

20. A fuel supply device according to claim 19, characterized in that said pressurized air passage (54) has a straight passage, and said nozzle opening (56) is formed at one end of said straight passage, said fuel supply means (52) being arranged at the other end of said straight passage.

21. A fuel supply device according to claim 20, characterized in that said fuel supply means (52) comprises a nozzle arranged on the axis of said straight passage to inject fuel from said nozzle along the axis of said straight passage.

22. A fuel supply device according to claim 19, characterized in that said pressurized air passage (54) has an upstream passage (54a) and an enlarged passage (54b) downstream of said upstream passage, which has a cross-sectional area larger than that of said upstream passage (54a), and said valve means is arranged in said enlarged passage (54b), said guide member (62) being fitted into and fixed to said enlarged passage (54b) upstream of said valve means.

23. A fuel supply device according to claim 22, characterized in that said enlarged passage (54b) and said upstream passage (54a) are in the form of a coaxial cylinder, and said enlarged passage (54b) and said upstream passage (54a) are connected by a conical passage (54c), said guide member (62) further comprising a head portion (64) arranged in said conical passage (54c) to form a further fuel and air passage between the inner face of said conical passage (54c) and the outer face of said head portion (64).

24. A fuel supply device according to claim 23, characterized in that said head portion (64) is in the form of a cone which is coaxial with an axis of said conical passage (54c) and said head portion (64) is tapered toward said upstream passage (54a).

25. A fuel supply device according to claim 24, characterized in that an apical angle of said head portion (64) is larger than an apical angle of said conical passage (54c).

26. A fuel supply device according to claim 23, charaterized in that said head portion (64) is in the form of a truncated cone which is coaxial with an axis of said conical passage (54c) and said head portion (64) is tapered toward said upstream passage (54a).

27. A fuel supply device according to claim 23, characterized in that said head portion (64) has a spherical shape.

28. A fuel supply device according to claim 22, characterized in that said valve means comprises a valve shaft (59), a valve head (58) formed at one end of said valve shaft (59) to open and close said nozzle opening (56), and a spring retainer (60) formed at the other end of said valve shaft (59) to retain a spring (61) which forces said valve head (58) to close said nozzle opening (56), and said guide member (62) faces said spring retainer (60) and covers an entire face of said spring retainer (60) which faces said guide member (62).

29. A fuel supply device according to claim 19, characterized in that said valve means comprises a valve head (58) urged by a spring (61) to close said nozzle opening (56).