EP1486665A1

EP1486665A1 - Fuel injector

Info

Publication number: EP1486665A1
Application number: EP03710360A
Authority: EP
Inventors: Yoshiaki Bosch Automotive Systems Corp TAKASHIMA; Takahisa Bosch Automotive Systems Corp. SUDA; Yoshikazu Bosch Automotive Systems Corp. SUZUKI
Original assignee: Bosch Automotive Systems Corp
Current assignee: Bosch Corp
Priority date: 2002-03-15
Filing date: 2003-03-14
Publication date: 2004-12-15
Also published as: KR100597760B1; CN1323238C; CN1507537A; WO2003078829A1; KR20040012819A; EP1486665A4

Abstract

In a fuel injector (1) whose injector body (2) is equipped with a magnetic valve (4) for fuel injection control that has a magnet unit (6) composed of multiple components assembled into a fixed sleeve (61), escape passages (67B) is formed inside the fixed sleeve (61) for allowing air trapped in gaps of the components in the fixed sleeve (61) by pressurized fuel sent to the magnet unit (6) to escape outside the fixed sleeve (61) and be replaced by fuel. The trapped air present in the gaps between the components in the magnet unit (6) of the magnetic valve (4) is rapidly replaced with fuel at the start of operation so that stable control of the quantity of injected fuel can be reliably established in a short time.

Description

TECHNICAL FIELD

The present invention relates to a fuel injector for directly injecting fuel into a cylinder of an internal combustion engine.

BACKGROUND ART

As an injector for directly injecting fuel into a cylinder of an internal combustion engine, such as in the common rail system, there is known, for example, the type of fuel injector disclosed in Japanese Unexamined Patent Publication No. Hei 7(1995)-310621. This fuel injector is configured to open a magnetic valve upon application of electric current so as to communicate a control chamber in the injector body with a low-pressure section, thereby removing valve piston backpressure to enable a nozzle needle to lift and start fuel injection, and after elapse of a prescribed time period, to stop application of current to the magnetic valve so as to interrupt the communicating state between the control chamber and low-pressure section, thereby causing a prescribed backpressure to act on the valve piston so as to press down the nozzle needle and terminate the fuel injection.

The magnetic valve for fuel injection control that is attached to the injector body and opened/closed by a control signal applied from the outside is an assembly obtained by coaxially disposing and fastening a backflow tube and a cylindrical fixed core wound with an exciting coil within a fixed sleeve that serves as a housing, and further inserting a bush at the inner surface of the fixed core.

The components installed inside the fastening sleeve as described above are fabricated to a prescribed dimensional precision and assembled so that gaps do not arise between adjacent components. In actuality, however, slight gaps do occur between the components and become filled with air immediately after assembly. When a fuel injector in this condition is installed in a cylinder, for example, and operated to inject fuel, the air in the gaps is gradually replaced with fuel as the temperature of the fuel and magnetic valve rises following start of operation. However, the fact that air remains in the gaps until they are all completely filled with fuel makes it impossible to obtain sufficient valve closing force. As a result, changes arise in the amount of bouncing in the attraction/repulsion action of the armature effected in response to the on-off of current supply to the magnetic valve conducted for controlling the communicating state between the control chamber and low-pressure section. This gives rise to the problem that immediately after injector installation fluctuation occurs in the speed of the internal combustion engine because the quantity of injected fuel cannot be stably controlled. One way to avoid this problem would be to continue test running until the trapped air is driven out, but as this requires otherwise unnecessary running time and fuel consumption, it leads to another problem, namely, inefficiency.

An object of the present invention is to provide a fuel injector capable of overcoming the foregoing problems of the prior art.

Another object of the present invention is to provide a fuel injector that enables stable fuel injection operation from immediately after installation.

Another object of the present invention is to provide a fuel injector that does not require otherwise unnecessary running time.

Another object of the present invention is to provide a fuel injector enabling efficient fuel injection operation.

DISCLOSURE OF THE INVENTION

One feature of the present invention resides in the point that:

in a fuel injector whose injector body is equipped with a magnetic valve for fuel injection control that has a magnet unit composed of a hollow cylindrical fixed core fitted in a fixed sleeve and a bush fitted in a center hollow portion of the fixed core, the magnet unit being installed between a control chamber for accumulating high-pressure fuel for controlling a lift operation of a nozzle needle and a low-pressure section so that high-pressure fuel in the control chamber escapes through the bush to the low-pressure section when the magnetic valve is open,

oil-tight seals are installed between components housed in the fixed sleeve to prevent high-pressure fuel in the control chamber from infiltrating into gaps between components.

Another feature of the present invention resides in the point that:

in a fuel injector whose injector body is equipped with a magnetic valve for fuel injection control that has a magnet unit composed of multiple components assembled in a fixed sleeve,

an escape passage is provided for enabling air trapped in gaps of the components in the fixed sleeve by pressurized fuel sent to the magnet unit to escape outside the fixed sleeve and be replaced by fuel.

When the fuel injector is operated in a state with trapped air present in the gaps in the fixed sleeve, pressurized fuel enters the gaps and the pressure of the pressurized fuel rapidly drives the trapped air out through the escape passage to fill the gaps with fuel instead of the trapped air. Stable control of the quantity of injected fuel can therefore be reliably established in a short time immediately after injector installation.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a sectional view showing an embodiment of the present invention.

Fig. 2 is an enlarged sectional view of a magnet unit of a magnetic valve shown in Fig. 1.

Fig. 3 is a sectional view showing an enlargement of an essential portion of the magnet unit shown in Fig. 2.

Fig. 4 is a sectional view showing an essential portion of another embodiment of the present invention.

Fig. 5 is a front view with the right half of an exciting coil in another embodiment of the present invention shown in section.

Fig. 6 is a view for explaining an oil-tight seal in the case of providing the exciting coil shown in Fig. 5 in a fixed core.

Fig. 7 is a front view with the right half of an exciting coil in still another embodiment of the present invention shown in section.

Fig. 8 is a view for explaining an oil-tight seal in the case of providing the exciting coil shown in Fig. 7 in a fixed core.

Fig. 9 is a sectional view of an essential portion for explaining still another embodiment of the present invention.

Fig. 10 is sectional view showing an essential portion of another embodiment of the present invention.

Fig. 11 is a perspective view of a sleeve shown in Fig. 10.

Fig. 12 is a perspective view of a fixed core shown in Fig. 10.

Fig. 13 is a perspective view of a backflow tube shown in Fig. 10.

BEST MODE OF CARRYING OUT THE INVENTION

In order to clarify the present invention in greater detail, it will now be explained with reference to the attached drawings.

Fig. 1 is a sectional view showing an embodiment of the present invention. Represented by reference numeral 1 is a fuel injector used in a common rail system for injecting fuel in a diesel internal combustion engine. The fuel injector 1 is installed in a cylinder of a diesel internal combustion engine (not shown) for injecting a prescribed amount of high-pressure fuel supplied from a common rail (not shown) into the cylinder at prescribed timing. It comprises an injector body 2 equipped with a magnetic valve 4.

The injector body 2 is equipped with a hollow body 23 having an axial recess 22 within which a valve piston 21 slides. The hollow body 23 is connected to a nozzle body 26 whose terminal end is a nozzle orifice 25 closed by the tip of a nozzle needle 24 connected to the valve piston 21.

The hollow body 23 is formed with a hollow appendage 28 surrounding an inlet coupling 27 connected with a high-pressure fuel supply pump (not shown). Fuel is led into a fuel reservoir 29 through an internal passage and the nozzle body 26 is formed with a shoulder section 30 on which the pressurized fuel in the fuel reservoir 29 acts. A nozzle spring 31 acts to press the valve piston 21 and the nozzle needle 24 downward.

Therefore, when the valve piston 21 is pressed downward to compress the nozzle spring 31 and hold the nozzle needle 24 at a position where it closes the nozzle orifice 25 of the nozzle body 26, no fuel is injected from the fuel injector 1. When the force of the nozzle spring 31 moves the valve piston 21 upward to hold the nozzle needle 24 at a position where the nozzle orifice 25 is open, fuel is injected by the fuel injector 1.

The hollow body 23 is formed with a head 33 provided with a downward facing drain chamber 32 that extends in the axial direction of the hollow body 23 coaxially with the axial recess 22. The head 33 is formed with a control chamber 37 in communication with a radial feed passage 34 and an axial drain passage 35. The feed passage 34 communicates with the inlet coupling 27 through a radial passage 36 in the hollow body 23 and the bottom of the control chamber 37 is formed at the upper face of the valve piston 21.

The fuel reservoir 29 is supplied with high-pressure fuel using a passage 38. The control chamber 37 is also supplied with high-pressure fuel but the configuration is such that the fuel pressure of the control chamber 37 becomes lower than the fuel pressure of the fuel reservoir 29 when the drain passage 35 is communicated with a fuel low-pressure section by the magnetic valve 4 as explained later. The upper surface of the valve piston 21 is formed to have a larger area than the upper surface of the shoulder section 30 and, therefore, when the drain passage 35 is closed by the magnetic valve 4 so that the control chamber 37 is filled with high-pressure fuel, the nozzle needle 24 is held in the position of closing the nozzle orifice 25 and no fuel is injected.

On the other hand, when the magnetic valve 4 is opened, the fuel pressure of the control chamber 37 escapes to the fuel low-pressure section through the drain passage 35, and since the fuel pressure of the control chamber 37 therefore becomes lower than the fuel pressure of the fuel reservoir 29, the nozzle needle 24 retracts to be held at a position that opens the nozzle orifice 25, whereby fuel injection is conducted.

The magnetic valve 4 for controlling the fuel pressure of the control chamber 37 to control the start and termination of fuel injection is provided integrally with the injector body 2. The magnetic valve 4 includes a magnet unit 6, which is shown in an enlarged sectional view in Fig. 2. The magnet unit 6 comprises a backflow tube 62 and a fixed core 63 installed in a fixed sleeve 61 and an exciting coil 64 is provided in the fixed core 63. An O-ring 65 is provided between the fixed sleeve 61 and the backflow tube 62 to form a structure such that fuel does not leak to the exterior from between the fixed sleeve 62 and the backflow tube 62.

A drain connector 62A for connection with a fuel tank is formed integrally with the backflow tube 62. A bush 67 with a small hole 67A formed at one end is provided in an axial hole 66 of the fixed core 63. The bush 67 is attached to pass through the fixed core 63 so that its small hole 67A and the drain connector 62A are coaxial. Thus, the backflow tube 62, fixed core 63 and bush 67 are coaxially installed in the fixed sleeve 61. The components installed in the fixed sleeve 61 in the aforesaid manner are fabricated to a prescribed dimensional precision and assembled so that gaps do not arise between adjacent components.

A disk-shaped armature 41 made of magnetic iron is provided to face the fixed core 63 in the magnet unit 6, and a ball 42 (Fig. 1) that operates as a valve body is retained at the tip of a pillar-shaped portion 41A extending integrally from the armature 41. The armature 41 is pushed downward by the force of a valve spring (not shown) to form a structure such that the ball 42 is pressed onto the open end of the drain passage 35 to seal the drain passage 35.

Therefore, when the magnet unit 6 is not energized, the open end of the drain passage 35 is sealed by the ball 42, whereby the control chamber 37 is filled with high-pressure fuel and, as a result, the valve piston 21 causes the nozzle needle 24 to close the nozzle orifice 25 so that fuel is not injected.

When the magnet unit 6 is energized, the armature 41 is drawn onto the magnet unit 6 overcoming the force of the valve spring, the ball 42 separates from the open end of the drain passage 35, the high-pressure fuel in the control chamber 37 escapes to the low-pressure section through the bush 67 and the drain connector 62A, and fuel is injected owing to the decreasing pressure in the control chamber 37.

When energization of the magnet unit 6 is stopped, the nozzle needle 24 again returns to the position of closing the nozzle orifice 25 so that fuel injection is terminated.

In the magnetic valve 4, however, a gap G1 occurs at the contact surface between the backflow tube 62 and fixed core 63 owing to the surface roughness and assembly of the two components, and slight gaps G2 and G3 are formed between the fixed sleeve 61 and fixed core 63 and between the fixed core 63 and bush 67 owing to dimensional error occurring in the production process.

At the initial stage following assembly of the magnetic valve 4, these gaps G1 - G3 are filled with air. Therefore, if the fuel injector 1 should be operated in this state, the difference in the damping forces of the air and fuel in the gaps G1 - G3 will, until the gaps are completely filled with fuel, cause changes in the amount of bouncing in the attraction/repulsion action of the armature effected in response to the on-off of current supply to the magnetic valve 4 conducted for controlling the communicating state between the control chamber 33 and low-pressure section. As a result, a condition will arise that makes it impossible to conduct stable control of the quantity of injected fuel immediately after installation of the fuel injector 1. In order to avoid this problem, the fixed sleeve 61 and bush 67 are provided with seal members S1 and S2 for establishing oil-tight sealing so that fuel does not infiltrate into the fixed sleeve 61.

Fig. 3 is a sectional view showing an enlargement of an essential portion of the unit shown in Fig. 2 in detail. The oil-tight seals provided on the fixed sleeve 61 and bush 67 will be explained with reference to Fig. 3.

An annular groove 61B is formed in the circumferential direction on the inner peripheral surface 61A of the fixed sleeve 61 and the seal member S1 is installed in the groove 61B to establish an oil-tight seal between the fixed sleeve 61 and fixed core 63. Further, an annular groove 67C is formed in the circumferential direction on the outer peripheral surface 67B of the bush 67 and the other seal member S2 is installed in the groove 67C to establish an oil-tight seal between the bush 67 and the fixed core 63. The seal members S1 and S2 are both formed as annular members composed of a resin material having elasticity. Therefore, when the fixed core 63 is installed in the fixed sleeve 61, the seal members S1 and S2 are elastically forced in contact with the associated wall of the of the fixed core 63 to establish an oil-tight seal between the fixed core 63 and the exciting coil 64. As a result, fuel trying to infiltrate into a gap G4 from the side of the armature 41 can be stopped by the seal members S1 and S2, and fuel can be prevented from infiltrating into the gaps G1 to G3. In addition, by installing the seal members S1 and S2 to be positioned as far toward the armature 41 side as possible, fuel can be almost totally prevented from infiltrating into the gaps G1 to G3.

As a result, high-pressure fuel can be effectively prevented from entering the fixed sleeve 61 when control of the communicating state of the control chamber 33 and the low-pressure section is effected in response to the on-off of current supply to the magnetic valve 4, and even if trapped air is present in the gaps G1 - G3, changes in the amount of bouncing in the attraction/repulsion action of the armature can be suppressed to enable stable control of the quantity of injected fuel from immediately after installation of the fuel injector 1. It is worth noting that if the seal members S1 and S2 are installed to be positioned as far toward the armature 41 side as possible, fuel can be almost totally prevented from infiltrating into the fixed sleeve 61.

Fig. 4 is a sectional view showing an essential portion of another embodiment of the present invention. Here the contact regions C1 of the fixed sleeve 61 and fixed core 63 are formed with a tapered contact portion 61C and a tapered contact portion 63A, respectively, and the fixed core 63 is pressed downward by swaging the upper portion of the fixed sleeve 61 so as to form an oil-tight seal at a linear region of contact at the contact region C1 for preventing infiltration of fuel into the gap G2 from the armature 41 side, thereby obtaining a structure that omits the seal member S1.

In other words, the outer edge of the fixed core 63 is brought into forced contact with the fixed sleeve 61 along its inner peripheral surface to establish a structure that forms an oil-tight seal with respect to the annular gap arising between the fixed sleeve 61 and fixed core 63.

As shown in Figure 2, the magnetic valve 4 has, aside from the gaps G1 - G3, a slight gap G4 between the fixed core 63 and the exciting coil 64. The air trapped in the gap G4 causes the same problems as those caused by the air trapped in the gaps G1 - G3. They can, if desired, be avoided by providing an oil-tight seal between the fixed core 63 and exciting coil 64.

Figs. 5 and 6 show another embodiment in which an oil-tight seal is provided between the fixed core 63 and exciting coil 64. Fig. 5 is a front view with the right half of the exciting coil 64 shown in section, and Fig. 6 is a view for explaining the oil-tight sealing state when the exciting coil 64 shown in Fig. 5 is provided in the fixed core 63. In the embodiment shown in Fig. 5, the exciting coil 64 is covered by a coating layer 641 formed by molding with a coating material composed of a resin material having elasticity. Further, the outer surface 641a and inner surface 641b of the coating layer 641 are integrally formed and provided with seal members S31 and S32 in the manner of annular ridged members that extend along the associated surfaces in triangular shape as viewed in cross-section, whereby the seal members S31 and S32 have appropriate elasticity as seal members.

Since the seal members S31 and S32 are provided on the exciting coil 64 to have appropriate elasticity as seal members in the foregoing manner, an oil-tight seal is established between the fixed core 63 and exciting coil 64 when the exciting coil 64 is attached to the fixed core 63 as shown in Fig. 6 because the seal members S31 and S32 are elastically forced in contact with the associated walls of the fixed core 63. As a result, fuel trying to infiltrate into the gap G4 from the side of the armature 41 can be stopped by the seal members S31 and S32, and fuel can be prevented from infiltrating into the gap G4. In addition, when the seal members S31 and S32 are provided to be positioned as far toward the armature 41 side as possible, fuel can be almost totally prevented from infiltrating into the gap G4.

Fig. 7 shows a modification of the exciting coil 64 shown in Fig. 5. In the embodiment of Fig. 7, the exciting coil 64 differs from that shown in Fig. 5 in the point that the seal members S31 and S32 are replaced by seal members S41 and S42 each formed integrally in the manner of a ridge member of hemispherical shape as viewed in cross-section.

Since the seal members S41 and S42 are provided on the exciting coil 64 to have appropriate elasticity as seal members in the foregoing manner, an oil-tight seal is established between the fixed core 63 and exciting coil 64 when the exciting coil 64 is attached to the fixed core 63 as shown in Fig. 8 because the seal members S41 and S42 are elastically forced firmly in contact with the associated walls of the fixed core 63. As a result, fuel trying to infiltrate into the gap G4 from the side of the armature 41 can be stopped by the seal members S31 and S32, and fuel can be prevented from infiltrating into the gap G4.

Fig. 9 shows still another embodiment of the present invention. Here the fixed core 63 is covered by a coating layer 631 formed by molding with a coating material composed of a resin material having elasticity. Further, the outer surface 631a and inner surface 631b of the coating layer 631 are integrally formed and provided with seal members S51 and S52 in the manner of annular ridged members that extend along the associated surfaces in hemispherical shape as viewed in cross-section, whereby the seal members S51 and S52 have appropriate elasticity as seal members.

Since the seal members S51 and S52 are provided on the fixed core 63 to have appropriate elasticity as seal members in the foregoing manner, an oil-tight seal is established between the fixed core 63 and fixed sleeve 61 when the fixed core 63 is attached to the fixed sleeve 61 because the seal members S51 and S52 are elastically forced in contact with the associated walls of the fixed core 63. As a result, fuel trying to infiltrate into the gaps G1 to G3 from the side of the armature 41 can be stopped by the seal members S51 and S52, and fuel can be prevented from infiltrating into the gaps G1 to G3.

As set out in the foregoing, the fuel injector 1 is provided with oil-tight seals between components housed in the fixed sleeve to prevent high-pressure fuel in the control chamber from infiltrating into gaps between the components and, therefore, when the fuel injector 1 is installed in a cylinder, for example, and operated to inject fuel, the amount of bouncing in the attraction/repulsion action of the armature effected in response to the on-off of current supply to the magnetic valve conducted for controlling the communicating state between the control chamber and low-pressure section does not change for the reason that sufficient valve closing force cannot be obtained because of air remaining in the gaps. As a result, the quantity of injected fuel can be stably controlled from immediately after installation of the fuel injector and fluctuation in the internal combustion engine speed can be decreased. Moreover, since there is no need to continue test running until the trapped air is driven out, efficiency is very high because no otherwise unnecessary running time or fuel consumption arises.

An essential part of another embodiment of the fuel injector according to this invention is shown in Fig. 10. Like the magnetic valve 4, the magnetic valve 104 shown in Fig. 10 is attached to the injector body 2 shown in Fig. 1 to configure a fuel injector. The magnetic valve 104 includes a magnet unit 106. The magnet unit 106 comprises a backflow tube 162 and a fixed core 163 installed in a fixed sleeve 161 and an exciting coil 164 is provided in the fixed core 163. An O-ring 165 is provided between the fixed sleeve 161 and the backflow tube 162 to form a structure such that fuel does not leak to the exterior from between the fixed sleeve 161 and the backflow tube 162.

A drain connector 162A for connection with a fuel tank is formed integrally with the backflow tube 162. A bush 167 formed with a small hole 167A at one end is provided in an axial hole 166 of the fixed core 163. The bush 167 is attached to pass through the fixed core 163 so that its small hole 167A and the drain connector 162A are coaxial. Thus, the backflow tube 162, fixed core 163 and bush 167 are coaxially installed in the fixed sleeve 161. The components installed in the fixed sleeve 161 in the aforesaid manner are fabricated to a prescribed dimensional precision and assembled so that gaps do not arise between adjacent components.

A disk-shaped armature 141 made of magnetic iron is provided to face the fixed core 163 in the magnet unit 106, and a ball (not shown) that operates as a valve body is retained at the tip of a pillar-shaped portion 141A extending integrally from the armature 141. The mechanism by which movement of the armature 141 controls injection of fuel from the injector body is the same as that in the case of the previous embodiment described with reference to Fig. 1.

In the magnet unit 106, however, a gap G5 occurs at the contact surface between the backflow tube 162 and fixed core 163 owing to the surface roughness and assembly of the two components, and a slight gap G6 is formed between the fixed sleeve 161 and fixed core 163 owing to dimensional error occurring in the production process. Further, a slight gap G7 is also formed between the bush 167 and fixed core 163 owing to dimensional error occurring in the production process.

At the initial stage following assembly, these gaps G5, G6 and G7 are filled with air. Therefore, the bush 167 is formed with trapped air escape passages in order to rapidly discharge the trapped air in the gaps G5, G6 and G7 to outside the magnetic valve 104 and replace it with fuel immediately after operation of the fuel injector 101 following assembly.

Fig. 11 is a perspective view of the bush 167. As can be seen from Fig. 11, the bush 167 is formed with four round hole-like escape passages 167B at locations of the same height as that of the gap G5 between the backflow tube 162 and the fixed core 163. Therefore, when the magnet unit 106 is energized to allow high-pressure fuel in the control chamber 137 to escape to the low-pressure section through the bush 167 and the drain connector 162A, the fuel pressure acting on the gap G5 can cause the air trapped in the gaps G5, G6 and G7 to escape into the bush 167 through the escape passages 167B. As a result, the trapped air in the gaps G5, G6 and G7 occurring in the magnetic valve 104 can be rapidly discharged and simultaneously replaced with fuel.

Although the escape passages 167B are formed at four locations, the number of locations is not limited to this and can be one or any larger number of locations. Moreover, the shape thereof need not be round and passages of rectangular or other desired shapes can be provided in appropriate sizes at appropriate locations.

Moreover, auxiliary passages for promoting passage of trapped air are provided in the fixed core 163 and backflow tube 162 so as to enable still more rapid discharge of the trapped air in the magnetic valve 104 from the gaps G5, G6 and G7 to the outside.

Fig. 12 is a perspective view of the fixed core 163 and Fig. 13 is a perspective view of the backflow tube 162. The auxiliary passages formed in these will be explained with reference to Figs. 12 and 13.

The fixed core 163 is formed on its outer peripheral surface 163A facing the fixed sleeve 161 with four groove-like auxiliary passages 163B. Each of the auxiliary passages 163B is formed from the top surface 163C to the bottom surface 163D of the fixed core 163. The auxiliary passages 163B allow trapped air present at the bottom surface 163D side of the fixed core 163 and in the gap G6 to be rapidly passed to the top surface 163C of the fixed core 163.

Although the auxiliary passages 163B are formed at four places to have an angular U-like cross-sectional shape here, they can be formed at any number of locations and can be of other appropriate shapes.

Further, the bottom surface 162B of the backflow tube 162 facing the fixed core 163 is grooved with auxiliary passages 162C. The auxiliary passages 162C extend to a hole at the center part of the backflow tube 162. The auxiliary passages 162C therefore enable trapped air present in the slight gaps among the fixed sleeve 161, backflow tube 162 and fixed core 163, and/or the trapped air that has passed through the auxiliary passages 163B to between the top surface 163B of the fixed core 163 and the fixed sleeve 161 to be rapidly passed to and discharged from the escape passages 167B (see Fig. 11), and to be replaced by fuel. Auxiliary passages similar to the auxiliary passages 162C can, for the same purpose, be formed on the end of the fixed core 163 facing the backflow tube 162.

It is worth noting that if the auxiliary passages 162C and auxiliary passages 163B are formed at locations where they communicate with each other, the trapped air present at the bottom surface 163D side of the fixed core 163 and in the gap G6 can be still more rapidly passed to the top surface 163C of the fixed core 163 and the trapped air passed to the top surface 163C can be passed through the auxiliary passages 162C to the gap G5, so that the trapped air can be rapidly discharged from the gap G5 through the escape passages 145B.

Although the auxiliary passages 162C are formed at four locations in this embodiment, this is not limitative and they can be formed at one or an appropriate larger number of locations, while the shape and the like thereof can be appropriately decided. In addition, the auxiliary passages 162C can be machined in the surface of the fixed core 163 that contacts the backflow tube 162.

As set out in the foregoing, the fuel injector 101 has the bush 167 formed with the escape passages 167B for enabling air trapped in the gaps between components in the fixed sleeve 161 by the pressurized fuel sent from the magnet unit 106 to escape to the outside of the fixed sleeve 161 and be replaced by fuel, and therefore, even if the fuel injector 101 is installed, for example, in a cylinder and made to conduct fuel injection operation, the trapped air can be rapidly replaced with fuel after the start of operation.

Since this results in the gaps being completely filled with fuel in a short time, sufficient valve closing force can be obtained. By this, the amount of bouncing in the attraction/repulsion action of the armature effected in response to the on-off of current supply to the magnetic valve conducted for controlling the communicating state between the control chamber and low-pressure section does not change for the reason that sufficient valve closing force cannot be obtained because of air remaining in the gaps, so that the quantity of injected fuel can be stably controlled even from immediately after fuel injector installation and fluctuation in the internal combustion engine speed can be suppressed. Therefore, since there is no need to continue test running until the trapped air is driven out, efficiency is very high because no otherwise unnecessary running time or fuel consumption arises.

INDUSTRIAL APPLICABILITY

As set out in the foregoing, the fuel injector according to the present invention helps to ensure running stability immediately after its installation.

Claims

A fuel injector whose injector body is equipped with a magnetic valve for fuel injection control that has a magnet unit composed of a hollow cylindrical fixed core fitted in a fixed sleeve and a bush fitted in a center hollow portion of the fixed core, the magnet unit being installed between a control chamber for accumulating high-pressure fuel for controlling a lift operation of a nozzle needle and a low-pressure section so that high-pressure fuel in the control chamber escapes through the bush to the low-pressure section when the magnetic valve is opened, which fuel injector is characterized in that:

oil-tight seals are installed between components housed in the fixed sleeve to prevent fuel escaping from a high-pressure section to a low-pressure section in the control chamber from infiltrating into gaps between components.
A fuel injector as claimed in claim 1, wherein a seal member is provided in an annular gap arising between the fixed sleeve and the fixed core and another seal member is provided in an annular gap arising between the fixed core and the bush.
A fuel injector as claimed in claim 1, wherein an oil-tight seal is formed with respect to an annular gap arising between the fixed sleeve and the fixed core by bringing an outer edge of the fixed core into forced contact with the fixed sleeve along its inner peripheral surface.
A fuel injector as claimed in claim 1, 2 or 3, wherein an exciting coil fitted in the fixed core is molded in a coating material having elasticity and the coating material elastically presses against the fixed core to establish an oil-tight seal between the fixed core and the exciting coil.
A fuel injector as claimed in claim 1, 2 or 3, wherein an exciting coil fitted in the fixed core is molded in a coating material having elasticity and a portion of the coating material elastically presses against the fixed core to establish an oil-tight seal between the fixed core and the exciting coil.
A fuel injector as claimed in claim 1, wherein the fixed core is molded in a coating material having elasticity and the coating material establishes a required oil-tight seal.
A fuel injector whose injector body is equipped with a magnetic valve for fuel injection control that has a magnet unit composed of multiple components assembled in a fixed sleeve, which fuel injector is characterized in that:

an escape passage is provided for enabling air trapped in gaps of the components in the fixed sleeve by fuel sent to the magnet unit to escape outside the fixed sleeve and be replaced by fuel.
A fuel injector whose injector body is equipped with a magnetic valve for fuel injection control that has a magnet unit composed of a hollow cylindrical fixed core fitted in a fixed sleeve and a bush fitted in a center hollow portion of the fixed core, the magnet unit being installed between a control chamber for accumulating high-pressure fuel for controlling a lift operation of a nozzle needle and a low-pressure section so that high-pressure fuel in the control chamber escapes through the bush to the low-pressure section when the magnetic valve is opened, which fuel injector is characterized in that:

an escape passage for enabling air trapped in gaps of the components in the fixed sleeve by fuel sent to the magnet unit to escape outside the fixed sleeve and be replaced by fuel is formed in the bush.
A fuel injector as claimed in claim 8, wherein the escape passage is formed to allow air in gaps arising between components installed between the fixed sleeve and the bush to escape inward of the bush.
A fuel injector as claimed in claim 8 or 9, wherein an auxiliary passage for allowing the trapped air to escape to outside the fixed sleeve is formed in a peripheral surface of the fixed core.
A fuel injector as claimed in claim 8 or 9, wherein an auxiliary passage for allowing the trapped air to escape to outside the fixed sleeve is formed in an end surface of the fixed core.