JP2003269288A - Fuel injector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To ensure stability of control on a fuel injection quantity by preventing an intrusion of fuel into a gap between parts in a magnet unit of a solenoid valve. <P>SOLUTION: A fuel injector 1 is so designed that an injector body 2 has the solenoid valve 4 having the magnet unit 6 comprising a hollow cylindrical fixed core 63 fitted in a fixed sleeve 61 and a bush 67 fitted in the fixed core 63, the magnet unit 6 is arranged between a control chamber 37 for storing high pressure fuel and a low pressure part, and when the solenoid valve 4 is opened, the high pressure fuel in the control chamber 37 escapes to the low pressure part via the bush 67. Seal members S1 and S2 are disposed between parts contained in the fixed sleeve 61 to prevent an intrusion of the high pressure fuel in the control chamber 37 into gaps between the parts. <P>COPYRIGHT: (C)2003,JPO

Description

Description: BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a fuel injector for directly injecting and supplying fuel into a cylinder of an internal combustion engine. 2. Description of the Related Art As an injector for directly injecting and supplying fuel into a cylinder of an internal combustion engine as in a common rail system, for example, a fuel injector of the type disclosed in JP-A-7-310621 is known. is there.
The fuel injector communicates the control chamber in the injector body with the low-pressure section by energizing and opening the solenoid valve, thereby removing the back pressure of the valve piston and lifting the nozzle needle to start fuel injection, After a lapse of a predetermined time, the solenoid valve is de-energized to release the communication between the control chamber and the low-pressure section, and a predetermined back pressure is applied to the valve piston to depress the nozzle needle, thereby terminating the fuel injection. Is configured. The solenoid valve for fuel injection control, which is mounted on the injector body and opened and closed according to a control signal given from the outside, has a backflow tube and an exciting coil wound around a fixing sleeve serving as a housing. A cylindrical fixed core is coaxially arranged and fixed, and a bush is fitted on the inner peripheral surface of the fixed core. [0004] Each component disposed in the fixing sleeve as described above is manufactured and assembled with a predetermined dimensional accuracy so that no gap is formed between adjacent components. I have. However, in practice, some gaps are formed between the components, and these gaps are filled with air immediately after assembly. When the fuel injector in such a state is assembled into a cylinder to perform a fuel injection operation, the air in the gap is gradually replaced by the fuel as the temperature of the fuel and the solenoid valve increases after the start of driving. As a result, a sufficient valve closing force cannot be obtained because the gap is filled with air until the gap is completely filled with fuel, so that the energization of the solenoid valve is turned on and off. The amount of bouncing in the suction and separation operations of the armature for controlling the state of communication between the control chamber and the low-pressure section, which is executed accordingly, changes, and the fuel injection amount is controlled stably immediately after the assembly of the injector. This causes a problem that the rotation of the internal combustion engine is fluctuated. In order to avoid this problem, it is conceivable to perform a test operation until the filled air is removed, but this consumes unnecessary operation time and fuel, and causes another problem of inefficiency. . An object of the present invention is to provide a fuel injector which can solve the above-mentioned problems in the prior art. According to the present invention, to solve the above problems, according to the present invention, a hollow cylindrical fixed core is fitted into a fixing sleeve, and a bush is fitted into a hollow portion of the fixed core. An electromagnetic valve for fuel injection control having a combined magnet unit is provided in the injector body, and is provided between a control chamber for storing high-pressure fuel for controlling the lift operation of the nozzle needle and the low-pressure section. In the fuel injector, wherein the magnet unit is disposed, and the high-pressure fuel in the control chamber escapes to the low-pressure section through the bush when the solenoid valve is opened, the high-pressure fuel in the control chamber is An oil-tight seal is provided between the components to prevent the components from entering the gaps between the components housed in the fixing sleeve. Is proposed. An embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a sectional view showing an example of an embodiment of the present invention. Reference numeral 1 denotes a fuel injector used in a common rail system for injecting and supplying fuel to a diesel internal combustion engine. The fuel injector 1 is mounted on a cylinder of a diesel internal combustion engine (not shown), and injects a high-pressure fuel supplied from a common rail (not shown) into the cylinder at a required timing and in a required amount. Solenoid valve 4
Is provided. The injector body 2 has a hollow body 23 having an axial recess 22 in which a valve piston 21 slides.
It has. The hollow body 23 is connected to a nozzle body 26 terminating at an injection orifice 25 which is normally closed at the bottom by a tip of a nozzle needle 24 connected to a valve piston 21. The hollow body 23 forms a hollow attachment 28 surrounding an intake 27 connected to a high-pressure fuel supply pump (not shown). The fuel is guided to the injection chamber 29 via an internal conduction path, and the nozzle body 26 is formed with a shoulder 30 on which the pressurized fuel inside the injection chamber 29 acts. The nozzle spring 31 acts to push the valve piston 21 and the nozzle needle 24 downward. Accordingly, the valve piston 21 is pushed downward, the nozzle spring 31 is compressed, and the nozzle needle 24 is moved to the injection orifice 2 of the nozzle body 26.
When the fuel injector 5 is held at the closed position, the fuel is not injected from the fuel injector 1. Further, when the valve piston 21 moves upward by the force of the nozzle spring 31 and the nozzle needle 24 is held at the position where the injection orifice 25 is opened, the fuel is injected from the fuel injector 1. The hollow body 23 is provided with a head 33 having a downwardly extending drain chamber 32 coaxial with the axial recess 22 and extending in the axial direction of the hollow body 23. A control chamber 37 is formed in the head 33 and communicates with the radial supply channel 34 and the axial drain channel 35. The supply channel 34 communicates with the intake 27 via a radial channel 36 in the hollow body 23, and the bottom of the control chamber 37 is formed by the upper surface of the valve piston 21. The injection chamber 29 is supplied with high-pressure fuel through a conduction path 38. On the other hand, high-pressure fuel is also supplied to the control chamber 37. However, when the drain communication path 35 is communicated with the low-fuel portion by the solenoid valve 4 as described later,
The fuel pressure in the control chamber 37 is lower than the fuel pressure in the injection chamber 29. Since the area of the upper surface of the valve piston 21 is formed larger than that of the upper surface of the shoulder portion 30, the drain communication path 35 is closed by the solenoid valve 4, and the control chamber 37 is filled with high-pressure fuel. If so, the nozzle needle 24 is held at the position where the injection orifice 25 is closed, and no fuel injection is performed. On the other hand, when the solenoid valve 4 is opened, the control room 37 is opened.
The fuel pressure in the control chamber 37 escapes to the low-pressure part through the drain conduction path 35, and the fuel pressure in the control chamber 37 becomes lower than the fuel pressure in the injection chamber 29. Therefore, the nozzle needle 24 retreats and the injection orifice 25 is opened. Since the fuel pressure is maintained, fuel injection is performed. An electromagnetic valve 4 for controlling the fuel pressure in the control chamber 37 to control the start and end of fuel injection is provided integrally with the injector body 2. The solenoid valve 4 includes a magnet unit 6, and FIG. 2 is an enlarged sectional view of the magnet unit 6. The magnet unit 6 includes a backflow tube 62 and a fixed core 63 in a fixed sleeve 61, and an excitation coil 64 is provided on the fixed core 63. An O-ring 65 is provided between the fixed sleeve 61 and the backflow tube 62 so as to prevent fuel from leaking from between the fixed sleeve 62 and the backflow tube 62 to the outside. The back flow tube 62 is integrally formed with a drain mounting portion 62A connected to the fuel tank. A bush 67 having a small hole 67A formed at one end is provided in the axial hole 66 of the fixed core 63. The bush 67 has the small hole 67A and the drain mounting portion 6
It is attached through the fixed core 63 so as to be coaxial with 2A. Thus, the backflow tube 62, the fixed core 63, and the bush 67 are coaxially arranged in the fixed sleeve 61. Fixing sleeve 61
Each of the components arranged as described above is manufactured and assembled with a predetermined dimensional accuracy so that no gap is generated 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 valve is provided at the tip of a columnar portion 41A integrally extended with the armature 41. A ball 42 (see FIG. 1) serving as a body is held. Armature 41
Is pressed down by the force of a valve spring (not shown), so that the ball 42 is pressed against the open end of the drain conduction path 35 and closes the drain conduction path 35. Therefore, when the magnet unit 6 is not energized, the open end of the drain conduction path 35 is closed by the ball 42, whereby the control room 3 is closed.
7 is filled with high-pressure fuel, the nozzle needle 24 is moved by the valve piston 21 to the injection orifice 2.
5 is closed, and no fuel injection is performed. When the magnet unit 6 is energized, the armature 41 is attracted to the magnet unit 6 by overcoming the force of the valve spring, the ball 42 separates from the open end of the drain conduction path 35, and the high-pressure fuel in the control chamber 37 is released. The fuel escapes to the low-pressure portion through the bush 67 and the drain attachment portion 62A, and the pressure in the control chamber 37 drops, so that fuel injection is performed. When the energization of the magnet unit 6 is stopped, the nozzle needle 24 is returned to the position where the injection orifice 25 is closed again, so that the fuel injection ends. In the solenoid valve 4, the back flow tube 62 has a gap G 1 on the surface that comes into contact with the fixed core 63 due to the surface roughness and assembly of the two components. 63 and between the fixed core 63 and the bush 67 due to dimensional errors occurring during the manufacturing process.
Is formed. Since the gaps G1 to G3 are filled with air in the initial stage immediately after the assembly of the solenoid valve 4, if the fuel injector 1 is operated in this state, the gaps G1 to G3 Due to the large damping force of the filled air, the communication state between the control chamber 33 and the low-pressure section, which is executed according to the turning on and off of the energization of the solenoid valve 4, until the gap is completely filled with fuel. The amount of bouncing in the armature suction and separation operations for control changes, and a situation arises in which the fuel injection amount cannot be controlled stably immediately after the fuel injector 1 is assembled. In order to avoid this inconvenience, seal members S1 and S1 for oil-tightly sealing the fixed sleeve 61 and the bush 67 so that fuel does not enter the fixed sleeve 61.
2 are provided. FIG. 3 is an enlarged cross-sectional view showing a main part of FIG. An oil-tight seal provided on the fixed sleeve 61 and the bush 67 will be described with reference to FIG. An annular groove 61B is formed on the inner peripheral surface 61A of the fixed sleeve 61 along the circumferential direction.
Inside B, a seal member S1 for providing an oil-tight seal between the fixed sleeve 61 and the fixed core 63 is provided. An annular groove 67C is formed on the outer peripheral surface 67B of the bush 67 along the circumferential direction, and another seal for oil-tight sealing between the bush 67 and the fixed core 63 is formed in the groove 67C. A member S2 is provided. Seal member S
1 and S2 are both formed as annular members made of a resin material having elasticity. As a result, the fixed core 6
3 is attached to the fixed sleeve 61, the sealing member S
1, S2 is elastically pressed against the corresponding wall surface of the fixed core 63, and an oil-tight seal is provided between the fixed core 63 and the exciting coil 64. As a result, the fuel that is going to enter the gap G4 from the armature 41 side is
1, it is possible to stop at S2, and it is possible to prevent fuel from entering the gaps G1 to G3. If the seal members S1 and S2 are provided as close to the armature 41 as possible, it is possible to prevent almost no fuel from entering the gaps G1 to G3. As a result, when the control of the communication state between the control chamber 33 and the low-pressure section is executed in accordance with the on / off of the energization of the solenoid valve 4, the high-pressure fuel is effectively prevented from entering the fixed sleeve 61. However, even if there is filled air in the gaps G1 to G3, it is possible to suppress a change in the bouncing amount in the armature suction and separation operations, and to stably control the fuel injection amount immediately after the fuel injector 1 is assembled. . If the seal members S1 and S2 are provided so as to be located as close to the armature 41 as possible, it is possible to prevent almost no fuel from entering the fixed sleeve 61. FIG. 4 is a sectional view showing a main part of another embodiment of the present invention. Here, a tapered contact portion 61C and a contact portion 63A are formed at respective contact portions C1 between the fixed sleeve 61 and the fixed core 63, and the fixed core 63 is pressed downward by caulking the upper portion of the fixed sleeve 61, and the contact is made. An oil-tight seal for preventing fuel from entering the gap G2 from the armature 41 side at the linear portion contacting at the portion C1 is formed, whereby the seal member S1 is omitted. As shown in FIG. 2, the solenoid valve 4 has a small gap G4 between the fixed core 63 and the exciting coil 64 in addition to the gaps G1 to G3. Since certain filled air causes a problem similar to that caused by the filled air in the gaps G1 to G3, an oil-tight seal is provided between the fixed core 63 and the exciting coil 64 in order to avoid this. It may be. FIGS. 5 and 6 show another embodiment of the present invention in which an oil-tight seal is provided between the fixed core 63 and the exciting coil 64. FIG. FIG. 5 shows the excitation coil 6.
4 is a front view showing a cross section of the right half of FIG. 4, and FIG. 6 is a view for explaining an oil-tight sealing state when the exciting coil 64 shown in FIG. In the embodiment shown in FIG. 5, the exciting coil 64 is covered with a coating layer 641 formed by molding with a coating material made of an elastic resin material. The outer peripheral surface 641a and the inner peripheral surface 641b of the coating layer 641 each have a seal member S3 in the form of an annular ridge member having a triangular cross section and extending along the corresponding peripheral surface.
1, S32 are integrally formed and provided, whereby the sealing members S31, S32 have appropriate elasticity as a sealing member. As described above, the sealing member S3 having appropriate elasticity as a sealing member for the exciting coil 64 is provided.
As shown in FIG. 6, when the excitation coil 64 is attached to the fixed core 63, the sealing members S31 and S32 are elastically pressed against the corresponding wall surfaces of the fixed core 63, as shown in FIG. An oil-tight seal is provided between the fixed core 63 and the exciting coil 64. As a result, the fuel that tries to enter the gap G4 from the armature 41 side can be stopped by the seal members S31 and S32, and the fuel can be prevented from entering the gap G4. If the seal members S31 and S32 are provided so as to be as close to the armature 41 as possible, the gap G4
The fuel can hardly enter the inside. FIG. 7 shows a modification of the exciting coil 64 shown in FIG. In the embodiment shown in FIG. 7, instead of the seal members S31 and S32, the excitation members 64 and the excitation coil 64 shown in FIG. Is different. As described above, the sealing member S4 having appropriate elasticity as a sealing member for the exciting coil 64 is provided.
As shown in FIG. 8, when the excitation coil 64 is attached to the fixed core 63, the seal members S41 and S42 are firmly pressed against the corresponding wall surface of the fixed core 63 with elasticity. Then, an oil-tight seal is provided between the fixed core 63 and the exciting coil 64. As a result, the fuel that tries to enter the gap G4 from the armature 41 side can be stopped by the seal members S31 and S32, and the fuel can be prevented from entering the gap G4. FIG. 9 shows still another embodiment of the present invention. Here, the fixed core 63 is covered with a coating layer 631 formed by molding with a coating material made of an elastic resin material. The outer peripheral surface 631a and the inner peripheral surface 631b of the coating layer 631 are integrally formed with sealing members S51 and S52 in the form of annular ridge members extending along the corresponding peripheral surfaces with a semicircular cross section. Is provided,
Thereby, the sealing members S51 and S52 have appropriate elasticity as a sealing member. As described above, the sealing member S5 having appropriate elasticity as a sealing member on the fixed core 63.
1. Since S52 is provided, when the fixed core 63 is attached to the fixed sleeve 61, the sealing member S51,
S52 is elastically pressed against the corresponding wall surface of the fixed core 63, and an oil-tight seal is provided between the fixed core 63 and the fixed sleeve 61. As a result, the fuel that tries to enter the gap G3 from the gap G1 from the armature 41 side can be stopped by the seal members S51 and S52, and the gap G
It is possible to prevent fuel from entering from 1 to G3. As described above, the fuel injector 1 is provided with an oil-tight seal between the components in order to prevent the high-pressure fuel in the control chamber from entering the gaps between the components housed in the fixing sleeve. Fuel injector 1
Even if the fuel injection operation is performed by assembling the cylinder into the cylinder, after the start of driving, the valve is closed to the solenoid valve because it is not possible to obtain sufficient valve closing force because air is filled in the gap. The amount of bouncing in the attraction and separation operations of the armature for controlling the communication between the control chamber and the low-pressure section, which is executed in accordance with the on / off of the current supply, does not change.
As a result, the control of the fuel injection amount can be stably performed immediately after the assembly of the injector, and the rotation fluctuation of the internal combustion engine can be reduced. In addition, since it is not necessary to perform the test operation until the filled air is eliminated, it is very efficient without wasting the operation time and the fuel. According to the present invention, as described above, in order to prevent the high-pressure fuel in the control chamber from entering the gaps between the components housed in the fixing sleeve, oil-tightness is established between the components. Since the seal is provided, even if the fuel injector 1 is mounted on a cylinder to perform a fuel injection operation, a sufficient valve closing force can be obtained because the gap is filled with air after the start of driving. The bouncing amount in the armature suction / separation operation for controlling the communication between the control chamber and the low-pressure section, which is executed according to the on / off state of energization of the solenoid valve, is changed because it cannot be obtained. There is no. As a result, it is possible to stably control the fuel injection amount immediately after the assembly of the injector, and reduce the rotation fluctuation of the internal combustion engine. In addition, since it is not necessary to perform the test operation until the filled air is eliminated, it is very efficient without wasting the operation time and the fuel.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view illustrating an example of an embodiment of the present invention. FIG. 2 is an enlarged sectional view of a magnet unit of the solenoid valve shown in FIG. FIG. 3 is an enlarged sectional view showing a main part of the magnet unit shown in FIG. 2; FIG. 4 is a cross-sectional view of a main part showing another embodiment of the present invention. FIG. 5 is a front view showing a cross section of a right half of an exciting coil according to another embodiment of the present invention. FIG. 6 is a view for explaining an oil-tight seal when the exciting coil shown in FIG. 5 is provided on a fixed core. FIG. 7 is a front view showing a cross section of a right half of an exciting coil in still another embodiment of the present invention. FIG. 8 is a view for explaining an oil-tight seal when the exciting coil shown in FIG. 7 is provided on a fixed core. FIG. 9 is an essential part cross-sectional view for explaining still another embodiment of the present invention. [Description of Signs] 1 Fuel injector 2 Injector body 4 Solenoid valve 6 Magnet unit 21 Valve piston 24 Nozzle needle 25 Injection orifice 29 Injection chamber 37 Control room 41 Armature 42 Ball 61 Fixed sleeve 62 Backflow tube 63 Fixed core 64 Exciting coil 67 Bush G1, G2, G3, G4 Gap S1, S2, S31, S32, S41, S42, S5
1, S52 sealing member

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Takahisa Suda             Saitama Prefecture Higashi Matsuyama City             Formula company Bosch Automotive System             Higashimatsuyama factory (72) Inventor Kaichi Suzuki             Saitama Prefecture Higashi Matsuyama City             Formula company Bosch Automotive System             Higashimatsuyama factory F term (reference) 3G066 AA01 AA02 AA07 AB02 AC09                       BA19 BA22 BA36 BA51 CC01                       CC06U CC14 CD10 CE23                       CE25

Claims (1)

Claims: 1. An electromagnetic valve for fuel injection control having a magnet unit formed by fitting a hollow cylindrical fixed core into a fixing sleeve and fitting a bush into a hollow portion of the fixed core. Is provided in the injector body, the magnet unit is disposed between a control chamber for storing high-pressure fuel for controlling the lift operation of the nozzle needle and the low-pressure section, and the electromagnetic valve is opened. A fuel injector configured to cause high-pressure fuel in the control chamber to escape to the low-pressure section via the bush when the fuel escapes from the high-pressure section to the low-pressure section in the control chamber. A fuel injector characterized in that an oil-tight seal is provided between the components to prevent the components from entering the gaps between the components.