JP2005016528A - Fuel injection valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection valve which does not increase cost, enables improvement of a degree of parallelization and accuracy between an armature 45 and a magnet core 24, and is inexpensive and has small unevenness in performance. <P>SOLUTION: A sliding part of the armature 45 is arranged inside the magnet core 24. The point is aimed at improving a supporting structure for the sliding of the armature 45, and a guided part 45C of the sliding, extending on the magnet core 24 side, is formed at the armature 45. Then the guided part 45C of the sliding is made possible to be guided on the inner radius side(an armature guide part 41C of a core-mounting body 41) of the magnet core 24. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a fuel injection valve, and more particularly to a fuel injection valve that injects high-pressure fuel supplied from a pressure accumulator (common rail) or the like at a predetermined timing.

A conventional fuel injection valve will be outlined with reference to FIG.
4 is an enlarged cross-sectional view of a main part of the fuel injection valve 1. The fuel injection valve 1 includes an injector housing 2, a nozzle body 3, a nozzle needle 4, a valve piston 5, a valve body 6, and a back. Pressure control unit 7.

The injector housing 2 is provided with a nozzle body 3 at its tip and a high-pressure fuel introduction part 8 at the upper part thereof. The back pressure control unit 7 is provided above the high pressure fuel introduction unit 8.
The fuel from the fuel tank 9 is made high pressure by the fuel pump 10 and stored in the common rail 11 (pressure accumulator), and the high pressure fuel is supplied from the high pressure fuel introduction part 8 to the fuel injection valve 1.
That is, a fuel passage 12 is formed from the high pressure fuel introduction part 8 to the injector housing 2 and the nozzle body 3 so that the high pressure fuel can be supplied to the pressure receiving part 4A of the nozzle needle 4. Further, a part of the fuel passage 12 is extended upward in FIG. 4 from the high-pressure fuel introduction part 8 to form a fuel return passage 13 from the back pressure control part 7 so that the fuel can be returned to the fuel tank 9.

    The nozzle body 3 is formed with an arbitrary number of fuel injection holes 14 at the tip thereof, and the tip of the nozzle needle 4 is seated on the sheet portion 15 connected to the injection hole 14 to close the injection hole 14. When the needle 4 is lifted from the seat portion 15, the injection hole 14 is opened and fuel can be injected.

    A nozzle spring 16 that urges the nozzle needle 4 in the seat direction toward the seat portion 15 is provided above the nozzle needle 4, and a valve piston 5 that is integral with the nozzle needle 4 extends further upward.

The valve body 6 forms a control pressure chamber 17 at the upper center portion thereof, and the tip end portion of the valve piston 5 is made to face the control pressure chamber 17 from below.
The control pressure chamber 17 communicates with an introduction-side orifice 18 formed in the valve body 6. The introduction side orifice 18 communicates with the fuel passage 12 and supplies the introduction pressure from the common rail 11 to the control pressure chamber 17.

The control pressure chamber 17 communicates with an opening / closing orifice 19, and the opening / closing orifice 19 can be opened and closed by a valve ball 20 (control valve body) of the back pressure control unit 7.
Note that the pressure receiving area of the top portion 5 </ b> A of the valve piston 5 in the control pressure chamber 17 is larger than the pressure receiving area of the pressure receiving portion 4 </ b> A of the nozzle needle 4.

    The back pressure control unit 7 controls the lift operation of the nozzle needle 4 by controlling the pressure in the control pressure chamber 17 (that is, the back pressure of the nozzle needle 4). An integral armature 21, an armature guide 22, a magnet 23, a magnet core 24, a core mounting body 25, a valve spring 26, a gap adjustment collar 27, a connector 28, and the control pressure chamber 17 described above are included. Have.

    The armature 21 has its rod portion 21A guided in the axial direction by an armature guide 22 and a predetermined parallelism between the plate portion 21B orthogonal to the rod portion 21A and the tip portion 27A of the gap adjusting collar 27. And the first gap L1 (lift amount) is opened, and the second gap L2 is opened while maintaining a predetermined parallelism with the attraction surface 24A of the magnet core 24.

    The magnet 23 is housed in the magnet housing portion 24B of the magnet core 24, generates a predetermined magnetic flux in the magnet core 24, and can attract the armature 21 (plate portion 21B).

The magnet core 24 is composed of a magnetic material.
The outer edge portion of the attracting surface 24A of the magnet core 24 is brought into contact with the inner step portion 29A of the fixing body 29 made of steel or the like, and the core mounting body 25 is disposed on the upper portion of the magnet core 24, thereby the inner step portion 29A. The magnet core 24 and the core mounting body 25 are integrated by pressing between the crimping portion 29B of the fixing body 29 and the retaining nut 30 engaged with the outward projecting portion 29C of the fixing body 29 is injected into the injector. By fastening to the housing 2, the core mounting body 25 and the magnet core 24 are mounted.
The core mounting body 25 is made of a non-magnetic material, and the upper open portion thereof is closed by the plug 31.

The gap adjusting collar 27 is inserted into the center hole 24 </ b> C of the magnet core 24.
A shim 32 is provided between the gap adjustment collar 27 and the valve spring 26 and the core mounting body 25 to enable adjustment of the first gap L1 (lift amount) and the second gap L2.

    The connector 28 is connected to an external control circuit (not shown) and supplies a drive signal to the magnet 23 at a predetermined timing.

In the fuel injection valve 1 having such a configuration, the high-pressure fuel from the common rail 11 is supplied from the high-pressure fuel introduction portion 8 to the pressure receiving portion 4A of the nozzle needle 4 via the fuel passage 12 and is controlled via the introduction-side orifice 18. The pressure chamber 17 is supplied to the top 5 </ b> A of the valve piston 5.
Therefore, the nozzle needle 4 receives the back pressure of the control pressure chamber 17 via the valve piston 5, seats on the seat portion 15 of the nozzle body 3 together with the urging force of the nozzle spring 16, and closes the injection hole 14. ing.

By supplying a drive signal from the connector 28 to the magnet 23 at a predetermined timing, the magnet 23 attracts the armature 21 against the urging force of the valve spring 26 and the valve ball 20 lifts to release the opening / closing orifice 19. Since the high pressure in the control pressure chamber 17 returns to the fuel tank 9 through the fuel return passage 13 via the opening / closing orifice 19, the high pressure acting on the top 5A of the valve piston 5 in the control pressure chamber 17 is released, The nozzle needle 4 is lifted from the seat portion 15 against the urging force of the nozzle spring 16 due to the high pressure of the pressure receiving portion 4A, and the injection hole 14 is released to inject fuel.
When the valve ball 20 closes the opening / closing orifice 19 by demagnetizing the magnet 23, the pressure in the control pressure chamber 17 causes the nozzle needle 4 to seat at its seat position (seat portion 15) via the valve piston 5. Then, the injection hole 14 is closed and the fuel injection is terminated.

Thus, in order to stabilize the magnetic characteristics of the magnet core 24, the internal magnetism generated by cutting or other mechanical processing is removed by annealing (magnetic annealing) before assembling, and then mechanically. Ideally used as a product without force.
However, in actuality, at the time of assembling, a tightening force or a compressive force is applied to the magnet core 24 from the outside by a caulking operation by the fixing body 29, a tightening operation by the retaining nut 30, and the like, so that distortion (compression strain) is generated inside the magnet core 24. There is a problem that the magnetic characteristics are deteriorated and the solid difference occurs.

That is, as the mounting structure of the magnet core 24, the entire magnet core 24 is integrated with the fixing body 29 (product case) via the core mounting body 25. Change is inevitable. Although illustration is omitted, although the magnet core 24 is separated, when there is a caulking process or the like at the time of assembly, internal stress is generated in the magnet core 24, and most of them change magnetically. Met.
Further, in any case, since the magnet core 24 facing the armature 21 (plate portion 21B) is in contact with the inner step portion 29A of the fixing body 29, for example, the inner core portion 29A is interposed via this inner step portion 29A. In addition to inevitable magnetic leakage and magnetic loss from the magnet core 24, there is a problem that the magnetic leakage itself tends to vary.

As a magnetic material for the magnet core 24, the sintered material has an advantage that it is easy to prevent the generation of eddy currents because of the presence of minute voids therein, but the cost is high, and high-pressure and high-precision fuel injection is possible. In the valve, the occurrence of the above-described magnetostriction due to the action of external force cannot be ignored.
Pure iron material is easy to process at low cost and can be thermally strong to ensure magnetic performance. On the other hand, it does not have microscopic voids inside like sintered material, so it needs a structure to prevent eddy currents. At the same time, there is a problem that magnetostriction due to the action of an external force is likely to occur and efficiency is likely to be lowered. For any material, there is a great demand for reducing the influence of external force during processing and assembly.
Further, in the fuel injection valve 1 connected to the common rail 11, it is necessary to control the fuel injection amount per single stroke with very high accuracy, but there is also a demand for enabling this to be performed at low cost.
Furthermore, in addition to injecting high-pressure fuel according to the demands of the fuel injection system, in addition to pilot injection (pre-injection) and main injection, post-injection may be required. When excitation and demagnetization are performed, there is a problem that distortion caused by generated heat and magnetic change cannot be ignored.

Next, the parallelism between the armature 21 and the gap adjusting collar 27 and the magnet core 24 will be described. The first gap L1 between the plate portion 21B of the armature 21 and the tip end portion 27A of the gap adjusting collar 27, The parallelism in the second gap L2 between the magnet core 24 and the suction surface 24A of the magnet core 24 is as follows: the magnet core 24, the core mounting body 25, the fixing body 29, the shim 32, the gap adjustment collar 27, the armature guide 22, Furthermore, it is created by accumulating the accuracy of each component such as the armature 21, but since there are multiple components related, it is difficult to improve the accuracy of the gap, and there are many components that require high accuracy, There is a problem of high costs.
In particular, in order to stabilize the characteristics of the magnet 23 and reduce the difference between the solids, the air gap (second gap L2) between the armature 21 and the magnet core 24 is minimized or optimized, and the accuracy of the parallelism. However, there is a problem that the cost of the portion of the back pressure control unit 7 is increased by assembling a plurality of parts as described above.

    Furthermore, since the armature 21 is guided by the armature guide 22 at the rod portion 21A located on the opposite side to the first gap L1, the second gap L2, etc., the parallelism and accuracy of the gap are improved. There is a problem that it is difficult.

JP-A-8-165965 JP-A-11-82228

    The present invention has been made in view of the above problems, and an object thereof is to provide a fuel injection valve having an improved armature sliding support structure.

    Another object of the present invention is to provide a fuel injection valve capable of improving the parallelism and accuracy between the armature and the magnet core.

    Another object of the present invention is to provide a fuel injection valve having an armature and a magnet core that are inexpensive and have little variation in performance.

    That is, the present invention focuses on improving the armature sliding support structure by providing an armature sliding portion inside the magnet core, and controls the back pressure of the nozzle needle that can open and close the fuel injection hole. A control valve body for opening and closing the control pressure chamber, an armature for driving the control valve body, and a magnet core and a magnet for attracting the armature, and the pressure of the control pressure chamber is A fuel injection valve controlled by a control valve body and capable of opening and closing the injection hole by the nozzle needle, wherein a sliding guided portion extending toward the magnet core is formed in the armature, and the sliding The fuel injection valve is characterized in that the guided part can be guided on the inner peripheral side of the magnet core.

    The sliding guided portion can be formed so as to be orthogonal to a plate portion facing in parallel with the attraction surface of the magnet core.

    The magnet core is fixed to the core mounting body, and the sliding guided portion can be guided by an armature guide portion formed on the core mounting body on the inner peripheral side of the magnet core. it can.

    The magnet core may be provided with a slight annular gap between a member located on the outer peripheral side thereof, for example, an injector housing to which the core mounting body is attached.

    The magnet core may be provided with a slight annular gap between the core mounting body (for example, an armature guide portion formed on the core mounting body) located on the inner peripheral side of the magnet core.

    The magnet core may be formed with radial grooves in the radial direction.

In the fuel injection valve according to the present invention, by improving the armature sliding support structure, the parallelism or accuracy of the magnet core and the armature is maintained at a predetermined level, thereby ensuring low cost and reliable performance. Can do.
In particular, the sliding guided part extending to the magnet core side is formed on the armature, and the sliding guided part is guided inside the magnet core, so that the parallelism between them is closer. And can be obtained between members that are more directly combined.
Thus, the parallelism and accuracy between the armature and the magnet core are improved to improve the performance, the number of parts is reduced, the individual differences or variations in cost and performance are reduced, and the durability and reliability are improved. Can do.
Furthermore, by providing a certain annular gap between the magnet core and a member on the outer peripheral side thereof, for example, the injector housing, the magnet core and the center of the armature opposed to the magnet core within the range of the annular gap with respect to the injector housing side. It is possible to make adjustment of the feeding and contribute to improvement of assembly accuracy.

    In the present invention, since the sliding guide structure extending to the magnet core side is formed in the armature to improve the sliding support structure of the armature, the parallelism or accuracy of the magnet core and the armature is maintained at a predetermined level, and the cost is reliable. A fuel injection valve that can ensure reliable performance has been realized.

Next, the fuel injection valve 40 according to the first embodiment of the present invention will be described with reference to FIGS. However, the same parts as those in FIG. 4 are denoted by the same reference numerals, and detailed description thereof will be omitted.
1 is an enlarged cross-sectional view of a main part of the fuel injection valve 40, and FIG. 2 is a cross-sectional view of a magnet core 24 portion taken along line II-II in FIG. The magnet core 24 is integrated under the core mounting body 41 corresponding to the above by laser welding or the like.
That is, by welding the upper circumferential portion 24D (fixed end) of the magnet core 24 at the lower circumferential portion 41A of the core mounting body 41, the core mounting body 41 and the magnet core 24 are integrated with each other. As the integration means, a technique such as welding using a frictional action or the like can be employed.

The core mounting body 41 is attached to the injector housing 2 by a retaining nut 42 that engages with the outward projecting portion 41B, and an O-ring 43 is disposed between the upper projecting portion 2A of the injector housing 2 and the core mounting body 41. The shim 44 is interposed between the injector housing 2 and the main body.
Further, the core mounting body 41 integrally has an armature guide portion 41C as a skirt portion at a portion corresponding to the gap adjusting collar 27 as a stopper portion of the armature 45.

The armature 45 includes a rod portion 45A having the valve ball 20, a plate portion 45B orthogonal to the rod portion 45A, and a sliding guided portion 45C orthogonal to the plate portion 45B. The guide portion 45C can be slidably guided in the axial direction within the armature guide portion 41C of the core mounting body 41.
The armature guide portion 41C is simply fitted into the center hole 24C of the magnet core 24, rather than being press-fitted.

    As described above, the magnet core 24 is cantilevered with the core mounting body 41 at the upper circumferential portion 24D, and the suction surface 24A opposite to the upper circumferential portion 24D is a free end. The armature 45 (plate portion 45B) faces the free end (suction surface 24A) in parallel.

    A first annular gap 46 is formed between the magnet core 24 and the injector housing 2 located on the outer peripheral side of the magnet core 24, and the core mounting body 41 is fitted into the upper projecting portion 2 </ b> A of the injector housing 2. It is possible to secure a radial adjustment margin when setting the central axis.

    A portion of the outer peripheral surface of the armature guide portion 41C is cut in the radial direction to make this portion thin, and a second annular gap 47 is formed between the central hole 24C of the magnet core 24, and the armature guide portion 41C is In addition, it is possible to reduce the magnetic leakage from the magnet core 24 through which the armature guide portion 41 </ b> C expands due to processing heat.

    The second gap L2 is formed between the attraction surface 24A of the magnet core 24 and the plate portion 45B of the armature 45, and the first gap L1 (lift amount) is equal to that of the armature guide portion 41C. This is formed between the tip portion 41D and the plate portion 45B.

    As shown in FIG. 2, the magnet core 24 is formed with a radial groove 24E in the radial direction thereof, and the core mounting body 41 is formed with a communication passage 48 communicating with the radial groove 24E. .

    In the fuel injection valve 40 having such a configuration, the magnet core 24 is only fixed to the lower circumferential portion 41A of the core mounting body 41 at the upper circumferential portion 24D, and faces the plate portion 45B of the armature 45. The suction surface 24A is an open free end not in contact with any member, and the first annular gap 46 is provided between the injector housing 2 and the armature guide portion 41C. Since the annular gap 47 is formed, the magnet core 24 is attached in a cantilever manner in a suspended state, and no external force acts on the magnet core 24.

    Accordingly, not only during processing or assembly, but also when an external force acts on the fuel injection valve 40 or the injector housing 2 after assembly, no stress distortion occurs in the magnet core 24, and its magnetic characteristics do not change. At the same time, there is little possibility of differences in properties between solids.

    Further, the armature 45 is guided in the axial direction by the armature guide portion 41C of the core mounting body 41 at the sliding guided portion 45C on the magnet core 24 side, and parallel between the armature 45 and the suction surface 24A of the magnet core 24. The degree of accuracy can be ensured more easily and relatively easily, and the performance can be improved and the number of parts can be reduced, and the cost can be reduced.

Since the radial groove portion 24E formed in the magnet core 24 and the communication passage 48 formed in the core mounting body 41 communicate with each other, the fuel in the upstream and downstream directions of the armature 45 accompanying the reciprocating motion of the armature 45 in the axial direction. Can be easily moved, and the response speed of the armature 45 can be maintained at a predetermined level.
Even when a pure iron material is used, the magnet core 24 can prevent the generation of eddy current in the circumferential direction due to the presence of the radial groove 24E.

    FIG. 3 is an enlarged cross-sectional view of the main part of the fuel injection valve 50 according to the second embodiment of the present invention. The fuel injection valve 50 is attached to the core mounting body 41 in the same manner as the fuel injection valve 40 (FIG. 1). The corresponding integrated structure of the core mounting body 25 (FIG. 4) and the magnet core 24 (magnet core mounting structure) is an upper circumferential portion 24D (fixed end) of the magnet core 24 and a lower circumferential surface of the core mounting body 25. The part 25A is integrated with each other by welding or the like, and the armature guide part 25B of the core mounting body 25 guides the sliding guided part 45C of the armature 45 in the axial direction even when the armature sliding support structure is used.

    However, in the fuel injection valve 50, the fixing body 29 and the retaining nut 30 having a caulking structure are used when the core mounting body 25 is mounted on the injector housing 2.

The magnet core 24 forms the first annular gap 46 between the magnet core 24 and the fixing body 29 located on the outer peripheral side thereof.
The second gap L2 is formed between the tip portion 25C of the armature guide portion 25B and the plate portion 45B.

Also in the fuel injection valve 50 having such a configuration, the magnet core 24 is cantilevered as described above with respect to the core mounting body 25, thereby obtaining good magnetic characteristics without giving distortion to the magnet core 24. be able to.
Further, by performing the guide of the armature 45 by the armature guide portion 25B of the core mounting body 25, the parallelism and accuracy between the armature 45 and the magnet core 24 can be obtained at a predetermined level, and stable performance can be obtained. Can be secured.
Furthermore, most of the parts of the conventional fuel injection valve 1 (FIG. 4) can be used as they are, and an increase in cost can be suppressed.

As described above, according to the present invention, the armature is guided on the magnet core side, so that it is possible to manufacture at a reduced cost while ensuring the parallelism and accuracy between the parts, and the stability and Reliability can be improved.

It is a principal part expanded sectional view of the fuel injection valve 40 by 1st Example of this invention. It is sectional drawing of the magnet core 24 part in the II-II line | wire of FIG. It is a principal part expanded sectional view of the fuel injection valve 50 by the 2nd Example of this invention. It is a principal part expanded sectional view of the conventional fuel injection valve.

Explanation of symbols

1 Fuel injection valve (Fig. 4)
2 Injector housing 2A Upper protrusion of injector housing 2 (FIG. 1)
DESCRIPTION OF SYMBOLS 3 Nozzle body 4 Nozzle needle 4A Pressure receiving part of nozzle needle 4 5 Valve piston 5A Top part of valve piston 5 6 Valve body 7 Back pressure control part 8 High pressure fuel introduction part 9 Fuel tank 10 Fuel pump 11 Common rail (pressure accumulator)
12 Fuel passage 13 Fuel return passage 14 Injection hole 15 Seat portion 16 Nozzle spring 17 Control pressure chamber 18 Introducing orifice 19 Opening / closing orifice 20 Valve ball (control valve body)
21 Armature 21A Rod portion 21B of armature 21 Plate portion 22 of armature 21 Armature guide 23 Magnet 24 Magnet core 24A Attraction surface (free end) of magnet core 24
24B Magnet housing portion 24C of magnet core 24 Center hole 24D of magnet core 24 Upper circumferential portion of magnet core 24 (fixed end, FIG. 1)
24E Radial groove of magnet core 24 (FIG. 2)
25 Core mounting body (Figs. 3 and 4)
25A Lower circumference of core mounting body 25 (FIG. 3)
25B Armature guide part of core mounting body 25 (FIG. 3)
End of 25C armature guide 25B (Fig. 3)
26 Valve spring 27 Gap adjustment collar 27A Tip end portion 28 of gap adjustment collar 27 Connector 29 Fixing body 29A Inner step portion 29B of fixing body 29 Caulking portion 29C of fixing body 29 Outward protruding portion 30 of fixing body 29 Retaining nut 31 Plug 32 Shim 40 Fuel injection valve (first embodiment, FIG. 1)
41 Core mounting body 41A Lower circumferential portion 41B of core mounting body 41 Outward projecting portion 41C of core mounting body 41 Armature guide portion 41D of core mounting body 41 Tip 42 of armature guide portion 41C Retaining nut 43 O-ring 44 Shim 45 Armature 45A Rod portion 45B of armature 45 Plate portion 45C of armature 45 Sliding guided portion 46 of armature 45 First annular gap 47 Second annular gap 48 Communication passage 50 Fuel injection valve (second embodiment, FIG. 3)
L1 First gap (lift amount)
L2 Second gap

Claims (6)

A control valve body for opening and closing a control pressure chamber for controlling a back pressure of a nozzle needle capable of opening and closing a fuel injection hole;
An armature for driving the control valve body;
A magnet core and a magnet for attracting the armature;
A fuel injection valve that controls the pressure of the control pressure chamber with the control valve body and enables the nozzle needle to open and close the injection hole;
While forming a sliding guided portion extending to the magnet core side in the armature,
A fuel injection valve characterized in that the sliding guided portion can be guided on the inner peripheral side of the magnet core. 2. The fuel injection valve according to claim 1, wherein the sliding guided portion is formed so as to be orthogonal to a plate portion facing in parallel with the attraction surface of the magnet core. The magnet core is fixed to the core mounting body,
2. The fuel injection valve according to claim 1, wherein the sliding guided portion can be guided by an armature guide portion formed in the core mounting body on the inner peripheral side of the magnet core. 2. The fuel injection valve according to claim 1, wherein the magnet core is provided with a slight annular gap between the magnet core and a member located on the outer peripheral side thereof. 4. The fuel injection valve according to claim 3, wherein the magnet core is provided with a slight annular gap between the magnet core and the core mounting body located on the inner peripheral side thereof. 2. The fuel injection valve according to claim 1, wherein a radial groove is formed in the radial direction of the magnet core.