EP1399667B1 - Fuel injection device for an internal combustion engine - Google Patents

Description

The invention relates to a fuel injection device for a Internal combustion engine according to the preamble of claim 1.

Such a fuel injection device is characterized by the US-A1-5829413 known. This fuel injector has a solenoid valve for controlling the fuel injection, wherein the solenoid valve by an electrical control device is controlled. The solenoid valve has a solenoid and a movable piston-shaped armature, through the one Valve member against a force acting on the valve member return spring is movable between two positions. It also shows that Solenoid valve on a magnetic disk, through which the armature at current-carrying solenoid is tightened. Furthermore, the Solenoid valve a cup-shaped capsule into which the magnet armature dips in and the magnet armature over its outer jacket slidably guided. The armature and the valve member are while firmly connected or integrally formed, wherein the valve member in a housing part of Fuel injector is guided while the armature guided in the capsule. This can be due to Manufacturing and assembly tolerances Problems in ensuring to give an accurate guide. In addition, the capsule is made several separate components, resulting in a complex structure of the solenoid valve results.

By US-A-5732888 is an electromagnetically actuated valve in which the electromagnet is a magnetic coil and a having movable piston-shaped armature. The magnet armature is at an abutment portion, with which the armature with open Valve comes into contact with a stop, with one Wear-resistant coating provided. On his outer coat, with the armature is slidably guided, is the armature not coated.

Advantages of the invention

The fuel injection device according to the invention with the Features according to claim 1 has the advantage that the Solenoid valve has a simple structure and that the Valve member and the armature can be performed separately and thus an accurate guidance of these parts is possible.

In the dependent claims are advantageous Embodiments and developments of the invention Fuel injector specified. By the Training according to claims 2 to 7 is a Wear of the armature avoided.

drawing

Several embodiments of the invention are in the Drawing shown and in the following description explained in more detail. FIG. 1 shows a Fuel injection device for an internal combustion engine with a solenoid valve in a simplified representation, Figure 2 the solenoid valve in an enlarged view and Figure 3 a magnet armature of the solenoid valve in enlarged Representation according to a modified embodiment.

Description of the embodiments

In Figure 1 is a fuel injection device for a Internal combustion engine, in particular of a motor vehicle shown. The fuel injector has a Fuel pump 10 and a fuel injection valve 12, which are combined to form a common unit and form a so-called pump-nozzle unit, which in a Drilled hole used in the cylinder head of the internal combustion engine is, wherein the fuel injection valve 12 into the combustion chamber a cylinder of the internal combustion engine protrudes. The Fuel pump 10 has one in a cylinder bore 14 a pump body 16 guided axially displaceable Pump piston 18, in the cylinder bore 14 a Pump working space 20 limited in which the delivery stroke of Pump piston 18 fuel is compressed under high pressure. The pump working chamber 20 is at the suction stroke of the pump piston 18 supplied fuel from a fuel tank. The pump piston 18 is not closer by a illustrated cam drive of the internal combustion engine against the Force of a return spring 22 in a lifting movement driven.

The fuel injection valve 12 has a valve body 26 on, which can be designed in several parts, and with the Pump body 16 is connected. In the valve body 26 is in a bore 30 an injection valve member 28th guided longitudinally displaceable. The bore 30 extends at least approximately parallel to the cylinder bore 14 of the pump body 16, but may also be inclined to this. Of the Valve body 26 has at its the combustion chamber of the cylinder facing end region at least one, preferably a plurality Injection openings 32. The injection valve member 28 has at its the combustion chamber end facing a For example, about conical sealing surface 34, which with one in the valve body 26 in the combustion chamber facing End region trained, for example, also about conical valve seat 36 cooperates, from or after the discharge the injection openings 32.

In the valve body 26 is between the injection valve member 28th and the bore 30 to the valve seat 36 toward an annular space 38th present, in its the valve seat 36 facing away End region by a radial extension of the bore 30 in a pressure chamber 40 surrounding the injection valve member 28 passes. The injection valve member 28 has the height of the Pressure chamber 40 by a cross-sectional reduction to the Valve seat 36 facing pressure shoulder 42 on. At the Combustion chamber facing away from the injection valve member 28th engages a prestressed closing spring 44, through which the Injection valve member 28 with its sealing surface 34 for Valve seat 36 is pressed down. The closing spring 44 is in a spring chamber 46 which is located on the bore 30th followed. The pressure chamber 40 is a through the Valve body 26 and the pump body 16 extending channel 48 connected to the pump working chamber 20.

For controlling the fuel injection by the Fuel injection device has these in Figure 2 enlarged illustrated solenoid valve 50, which by a electronic control device 52 is driven. By the solenoid valve 50 will be a connection of the Pump workspace 20 controlled with a discharge space, with open solenoid valve 50, the connection of the Pump work space 20 is opened with the discharge space, so that build up in the pump working chamber 20 no high pressure can and no fuel injection takes place. If that Solenoid valve 50 is closed, so is by this the Pump working space 20 separated from the discharge space, so that in the pump working chamber 20 high pressure corresponding to the stroke build the pump piston 18 and a Fuel injection can be done. The solenoid valve 50 is for example arranged laterally on the pump body 16 and has a in a bore 54 of the pump body 16th guided valve member 56 on. The bore 54 is transverse, For example, at least approximately perpendicular to Cylinder bore 14. The bore 54 has a radial Extension 55, from which a connection bore 58 discharges into the pump working chamber 20.

The bore 54 opens into a cross-section opposite this enlarged annular space 59 in the pump body 16, wherein the mouth of the bore 54, for example, approximately conical expanded and forms a valve seat 60. The valve member 56 has in his from the bore 54 in the annular space 59th projecting end portion on a larger cross-section than in the bore 54, whereby the valve member 56 a to Valve seat 60 pointing, for example, approximately conical Sealing surface 61 is formed, with the valve seat 60th interacts. In the annular space 59 opens a Connecting bore 62 to a relief space when the at least indirectly the Fuel tank is used. When the valve member 56 with its sealing surface 61 rests against the valve seat 60, so is the Pump workspace 20 separated from the discharge chamber and when the valve member 56 with its sealing surface 61 to the valve seat 60 is spaced, then the pump working chamber 20 with the Relief room connected. In the open position of the Valve member 56 is the suction stroke of the pump piston 18th Fuel through the connecting hole 62 in the Pump workspace 20 sucked. In the open position the valve member 56 may be in the pump working chamber 20 and in the associated with this via the channel 48 pressure chamber 40th of the fuel injection valve 12 do not build up high pressure, so that the fuel injection valve 12 due to the Closing spring 44 through which the injection valve member 28 with its sealing surface 34 held in contact with the valve seat 36 will, is closed and no fuel injection he follows. In the closed position of the valve member 56th builds up in the pump working chamber 20 and in the pressure chamber 40 High pressure corresponding to the stroke of the pump piston 18. When the pressure in the pressure chamber 40 is so high that the through this on the pressure shoulder 42 on the Injector member 28 generates force in the opening direction 29 is greater than that by the closing spring 44 on the Injection valve member 28 exerted closing force, so that lifts Injection valve member 28 with its sealing surface 34 from Valve seat 36 and releases the injection openings 32, through which fuel is injected into the combustion chamber. When the pressure in the pressure chamber 40 drops again so far that the generated by this on the pressure shoulder 42 Pressing force is less than the force of the closing spring 44, so the fuel injection valve 12 closes again and the Fuel injection is finished.

At the end of the solenoid valve 50 facing away from the Valve member 56 engages a preloaded compression spring 64, through which the valve member 56 in its opening direction that is in a direction from the valve seat 60 way. The spring 64 is supported on the one hand at least indirectly on the valve member 56 and on the other hand at a Bore 54 occlusive lid 65 from, in the Pump body 16 is inserted. In his in the annular space 59 projecting end portion, the valve member 56 has a in Cross-section enlarged flange 66 and to these in axial Direction away from the sealing surface 61 cylindrical section 67, at the distance to the flange 66 an enlarged in cross section annular collar 68 is formed is. The annular space 59 is multiply in diameter stepped bore 69 of the pump body 16 and formed in axial direction away from the pump body 16 through one in one opposite the annulus 59 in diameter slightly larger Section of the bore 69 inserted stop plate 70th limited. The stop disk 70 has a bore 71, through which the cylindrical portion 67 of the valve member 56th protrudes. The bore 71 in the stop plate 70 is only slightly larger in diameter than the annular collar 68 of the valve member 56 disposed in the bore 71 is. The bore 71 in the stop plate 70 is in Diameter smaller than the flange 66 of the Valve member 56, thus not in the bore 71st can dive. The stop plate 70 is in axial Direction to the pump body 16 toward a stop shoulder 72 in the bore 69 on the pump body 16 at. The valve member 56 is with its annular collar 68 in the bore 71 of the Stop disc 70 performed with little play.

At the stop disc 70 receiving portion of Bore 69 closes another in diameter enlarged portion of the bore 69, in as Part of the solenoid valve 50, a magnetic disk 74th is used. The magnetic disk 74 has a bore 75 into which the cylindrical portion 67 of the valve member 56 protrudes. Between the magnetic disk 74 and an am Pump body 16 formed, the stopper plate 70th surrounding annular shoulder 76 is an elastic sealing ring 77th clamped.

The solenoid valve 50 has a movable armature 80 on, on which the valve member 56 with the end face of his the bore 75 of the magnetic disk 74 protruding end rests. The armature 80 is at least approximately cylindrical piston formed and in one cup-shaped capsule 81 at least approximately coaxial with Valve member 56 slidably disposed. The magnet armature 80 is about his outer sheath in the capsule 81 with low Game slidably guided. The magnet armature 80th facing end face of the magnetic disk 74 and the Magnetic disk 74 facing end face of the armature 80th are parallel to each other with the highest possible accuracy arranged and the armature 80 is moved with highest possible accuracy perpendicular to this facing end face of the magnetic disk 74. The magnet armature 80 may include one or more axial through holes 79 exhibit. The end face of the valve member 56 is located on the the magnetic disk 74 facing the front side of the magnet armature 80 on. Between the end facing away from the magnetic disk 74 the capsule 81 arranged with this one-piece, bottom 82 of the capsule 81 and the the magnetic disk 74 facing away from the end face of the armature 80 is a prestressed compression spring 83 is arranged, through which the armature 80 is applied to the magnetic disk 74 towards is. The by the compression spring 83 to the armature 80th applied force is less than that by the compression spring 64th on the valve member 56 exerted force. By on the Valve member 56 acting compression spring 64 and on the Magnetic armature 80 acting compression spring 83 is a system of Valve member 56 secured to the armature 80 without these two parts are interconnected.

Between the capsule 81 and the magnetic disk 74 is a ring 85 arranged on the one hand with the capsule 81 and on the other hand connected to the magnetic disk 74, in particular welded. The ring 85 is not made magnetizable material. The magnetic disk 74 forms so to speak a capsule 81 closing lid and the Magnetic armature 80 is in through the capsule 81 and the Magnetic disk 74 limited interior arranged. The capsule 81 is in an approximately hollow cylindrical support 86th used, which has an outer diameter, the at least approximately the same size as the outer diameter the magnetic disk 74. The carrier 86 faces the magnetic disk 74 has a radial recess 87 in its inner circumference, in which a magnetic coil 88 is inserted. The magnetic coil 88 is in the recess in the axial direction between the Carrier 86 and the magnetic disk 74 fixed. With the Carrier 86 is preferably made of plastic Terminal body 89 connected in the electrical Conductor elements are arranged, on the one hand with the Magnetic coil 88 and on the other hand with plug contacts 90th are connected, with which a not shown Plug part of leading to the control device 52 electrical lines is connectable.

The bore 69 is in an approximately hollow cylindrical neck 91 of the pump body 16 formed at its Outer circumference is provided with an external thread. On the Carrier 86 of the solenoid valve 50 is a union nut 92nd slid on the external thread of the neck 91 of the Pump body 16 is screwed on and thus the Solenoid valve 50 is attached to the pump body 16. The Union nut 92 engages the carrier 86, which is located on the Magnetic disk 74 is supported, which in turn at the Stop disc 70 is supported, which at the stop shoulder 72 of the pump body 16 is present. The sealing ring 77 is through the magnetic disk 74 is elastically compressed when this comes to the stop plate 70 to the plant.

Hereinafter, the function of the solenoid valve 50 explained. When the solenoid coil 88 is de-energized, so does on the armature 80 no magnetic force. By the Force of the compression spring 64, the valve member 56 in his held open position, since the force of the compression spring 64th is greater than the force of the magnet armature 80th acting compression spring 83. The armature 80 is thus with axial distance from the magnetic disk 74 is arranged. The Movement of the valve member 56 and thus the armature 80th in the opening direction is limited by the fact that the Valve member 56 with its flange 66 on the stop plate 74 comes to the plant. When the solenoid valve 50 is closed is to be, so by the controller 52, the Magnetic coil 88 is energized, so that through the magnetic coil 88, the magnetic disk 74 and the armature 80 a closed magnetic circuit is created and the Magnetic armature 80 is attracted by the magnetic disk 74. The by the compression spring 83 and the magnetic disk 74 on the Magnetic armature 80 applied force is greater than that through the Compression spring 64 on the valve member 56 force applied, so that by the armature 80, the valve member 56 in his closed position is moved in this with his Sealing surface 61 rests against the valve seat 60. The hub that the Valve member 56 between its open position and executes its closed position, is sized to that the armature 80 is also in the closed position still arranged at an axial distance to the magnetic disk 74 is. By the existing residual air gap is prevents the armature 80 on the magnetic disk 74th adheres after the solenoid coil 88 is de-energized and the armature 80 is again moved away from the magnetic disk 74 must become. The stroke h, the valve member 56 between his open position and his closed position is carried out by the distance between the valve seat 60, on which the valve member 56 with its sealing surface 61 for Appendix comes, on the one hand and the stop plate 74, at the the valve member 56 comes to rest with its flange 66, on the other hand. The residual air gap s between the Magnetic armature 80 and the magnetic disk 74 can by Using a stopper plate 74 with an adapted Thickness can be adjusted to the required level. The Stopping disc 74 can, for example, by stamping be prepared.

The magnet armature 80 is preferably made of an alloy, which contains at least iron and cobalt, wherein the proportion of cobalt is between 10 and 50%. Preferably the proportion of cobalt is between 15 and 20%, especially advantageous is a proportion of cobalt of about 17%. The Percentages of the cobalt content are by weight based. The armature 80 is particularly characterized advantageous magnetic properties. By the Control device 52 is the time course of the Current flow detected by the magnetic coil 88 and evaluated. The magnet armature 80 provides a movable Part of the magnetic circuit, during the movement the inductance of the magnetic circuit is changed, resulting in a certain time course of the current flow through the solenoid 88 leads. If the armature 80 is not moves more, so the inductance no longer changes and This results in a characteristic change of the time course of the current flow through the solenoid coil 88. For fuel injection control especially the time of importance if that Solenoid valve 50 is closed, so that in Pump work room 20 builds up high pressure and the Fuel injection begins. From the characteristic Change of the current flow through the solenoid coil 88 can are determined when the armature 80 and thus the Valve member 56 has reached the closed position. at the manufacture of the armature 80 from the above given material results in a pronounced Change in the current flow through the solenoid coil 88, when the armature 80 stops moving, so that the Closing time of the solenoid valve 50 and thus the Time of injection start with high accuracy determine.

The hardness of the material from which the magnet armature 80 for Achieving the favorable magnetic properties, is opposite to the hardness of the material that makes up the Valve member 56 is lower. To prevent by the system of the valve member 56 on the armature 80 at This is an inadmissible heavy wear occurs preferably provided that the surface hardness of Magnetic anchor 80 at least in the area of the system Valve member 56 is increased.

To prevent the magnet armature 80 and / or on the Capsule 81 due to the leadership of the armature 80 a Inadmissible heavy wear occurs, are on the armature 80 and / or on the capsule 81 according to FIG 3 measures for Increased surface hardness provided. In Figure 3 are the armature 80 and the capsule 81 from Clarity in an exploded view shown. It can be provided here that the Magnetic anchor 80 at least partially a coating 94th made of a material opposite to the material, the is the iron-cobalt alloy from which the magnet armature 80th exists, has a higher hardness. As material for the Coating 94, a metal may be used in particular nickel or chromium. It can be a Surface hardness of the armature 80 of, for example, about 700 HV can be achieved. The coating 94 can only on Outer jacket of the magnet armature 80, about this in the Capsule 81 is guided, or at the end face of the Magnetic armature 80 may be applied, on which the valve member 56th is applied, or over the entire surface of the magnet armature 80. It can also be provided that the capsule 81 at her the magnet armature 80 leading inner circumference with a Coating 94 is provided. The coating 94 is preferably at least at the part of magnet armature 80 and capsule 81 applied, which has the lower hardness.

Instead of the coating 94, the magnet armature 80 and / or the capsule 81 also wholly or partially with a method for increasing its surface hardness be treated. The magnet armature 80 and / or the capsule 81 can be subjected to a heat treatment process and for example, be case hardened by Gas nitrocarburizing or treated by carbonitriding be. The surface hardness of the magnet armature 80 and / or the Capsule 81 can only on the outer shell or at the Be increased inner circumference, at which the leadership of the armature 80 takes place. Alternatively, the surface hardness also over a larger area of the surface or over the entire Surface of the armature 80, in particular at the End face of the armature 80, on which the valve member 56th is increased, be increased. The capsule 81 may for example consist of plasma nitrided steel.

Furthermore, the magnet armature 80 and / or the capsule 81 completely or partially a cold work hardening process be subjected and, for example, by ball irradiation or impact strengthening. These too Treatment of the armature 80 and / or the capsule 81 may only on the outer jacket of the magnet armature 80 or on the inner circumference the capsule 81 take place, where the leadership of the armature 80th he follows. Alternatively, the work hardening can also over a larger area of the surface or over the entire Surface of the armature 80 done.

The use of the above-described solenoid valve 50 with the guided in the capsule 81 armature 80 is not to the described embodiment of Fuel injection device in the form of the pump-nozzle unit limited but can also be any other Embodiments of fuel injectors provided become.

Claims (8)

1. Fuel injection device for an internal combustion engine having at least one solenoid valve (50) for controlling the injection of fuel, the solenoid valve (50) being actuated by means of an electric control device (52) and having a solenoid (88), a movable piston-shaped armature (80) by means of which a valve element (56) can be moved between at least two positions counter to the force of a restoring spring (64) which acts on the valve element (56), a magnet disc (74) by means of which the armature (80) is attracted when current flows through the solenoid (88), and a pot-shaped capsule (81) into which the armature (80) dips, the armature (80) being displaceably guided in the capsule (81) by means of its outer surface, characterized in that the capsule (81) has a base (82) which is embodied in one piece with the latter, and in that a compression spring (83), by means of which the armature (80) is loaded in the direction of the magnet disc (74), is clamped between the base (82), the armature (80), the armature (80) and the valve element (56) not being connected to one another.
2. Fuel injection device according to Claim 1, characterized in that at least the outer surface of the armature (80) and/or the inner surface of the capsule (81) are provided with a coating (94) made of a metal with a greater level of hardness than the material from which the armature (80) or the capsule (81) is composed.
3. Fuel injection device according to Claim 2, characterized in that the coating (94) is composed of chromium or nickel.
4. Fuel injection device according to Claim 1, characterized in that at least the outer surface of the armature (80) and/or the inner surface of the capsule (81) are treated with a method for increasing the surface hardness.
5. Fuel injection device according to Claim 4, characterized in that the armature (80) and/or the capsule (81) are case-hardened.
6. Fuel injection device according to Claim 4, characterized in that the armature (80) and/or the capsule (81) are treated with a nitriding process, in particular with a gas nitrocarburizing process or a carbonitriding process.
7. Fuel injection device according to Claim 4, characterized in that the armature (80) and/or the capsule (81) is treated with a strain-hardening process, in particular a shot peening process or an impact-consolidating process.
8. Fuel injection device according to one of the preceding claims, characterized in that the armature (80) is composed at least essentially of an alloy which contains at least iron and cobalt, the proportion of cobalt being between 10% and 50%.

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