The present invention relates to a valve for metering a fluid, in particular to a fuel injector for internal combustion engines. Specifically, the present invention relates to the field of injectors for fuel injection systems of motor vehicles, in which preferably a direct injection of fuel into combustion chambers of an internal combustion engine takes place.
A valve for metering fluid is known from German Published Patent Application No. 10 2013 222 613. The known valve includes a solenoid for actuating a valve needle controlling a metering opening. The solenoid is used to actuate an armature movable on a valve needle. The armature has a borehole which abuts the valve needle and forms a spring receptacle for a prestroke spring.
This design has the disadvantage that a guidance between the armature and the valve needle is only implemented over a short guide length.
The valve according to the present invention has the advantage that an improved design and functionality are enabled. In particular, an improved guidance between the armature and the valve needle and of the valve needle along a longitudinal axis of the housing may be implemented.
On the valve for metering the fluid, the armature serving as a solenoid armature is not fixedly connected to the valve needle, but is overhung between stops. Such a stop may be formed on a stop element, which may be implemented as a stop sleeve and/or stop ring. The stop element, however, may also be designed in one piece with the valve needle. With the aid of a spring, the armature, in the resting state, is adjusted to a stop which is stationary with respect to the valve needle, so that the armature rests against it. When the valve is activated, the entire armature free travel is then available as an acceleration distance, the spring being shortened during the acceleration. The armature free travel may be predefined via the axial play between the armature and the two stops.
The present invention has the advantage that the guide length between the armature and the valve needle is increased. For example, the armature may be guided on its outer side in the valve housing along the longitudinal axis. Accordingly, the guidance of the valve needle along the longitudinal axis then improves over the increased guide length between the armature and the valve needle. One embodiment in which the valve needle is guided via the stop element, for example, on an inner pole situated in the housing in a stationary manner accordingly results in an improved guidance of the armature relative to the housing.
The present invention has the advantage that an additional extension of the guide length may be achieved, which is independent of the design of the spring receptacle. In this way, it is possible, for example, for the spring receptacle to directly abut the valve needle. In this way, in particular, a robust design is possible in which the guide extension is able to absorb stop forces.
The present invention has the advantage that the guide extension, in particular, may be designed with an outside diameter which is situated within openings of through-openings of the armature used to conduct a fluid through the armature. This has a favorable effect on the operating behavior.
The present invention has the advantage that a guidance may be achieved which is as good as or even better than in the case of an armature without spring receptacle.
The present invention has the advantage that the spring, during actuation, is able to immerge completely into the spring receptacle, so that an optimal compromise with respect to multiple disadvantages of a conventional design may be achieved.
The disadvantages of a conventional design first relate to the manufacturability, the costs and the assembly when a design without spring receptacle is implemented in which an additional component for accommodating the spring and its connection to the armature is required. Secondly, disadvantages result when a pole surface between the armature and the inner pole is reduced since then a lower magnetic force occurs. This relates specifically to one possible embodiment in which a stepped borehole is formed on the inner pole to create space for a spring.
A third disadvantage relates to a magnetic short circuit via the spring and the loss of magnetic force associated therewith, which results in a slower force build-up and a lower holding force in the opened state. In general, this relates to the used magnetic spring steels, which represent a bypass for the magnetic flux between the armature and the inner pole. A fourth disadvantage relates to the smaller contact surface between the armature and a stop ring in one variant, in which the stop ring immerges into the spring receptacle formed on the armature. This may cause increased wear and reduced hydraulic damping.
In a fifth disadvantage, a lever arm may result between the upper needle guide and the armature, which relates, in particular, to the above-mentioned embodiment in which the stop ring immerges into the spring receptacle. This may result in large bending of the needle, which leads to increased wear, an oblique impact and the like. A sixth possible disadvantage relates to embodiments in which a large spring diameter becomes necessary. Due to the limited radial installation space, lower spring forces are then achievable, which is bad for fast armature settling after the first injection, in particular with respect to multiple injections. At the same spring force, a larger spring diameter moreover means a larger tilting moment onto the armature, which is also disadvantageous for the injector function and, in particular, may result in a tilted armature impact. A seventh and last disadvantage relates to the risk of the spring bulging under load and to the resultant contact with the inner pole and/or the stop ring due to a relatively long spring length and small radial spatial conditions. This causes an undefined friction which, in addition to possible wear and the development of particles, results in considerable variances of the injection behavior.
In this way, as a result of the complete immergence of the spring into the spring receptacle of the armature, an optimal compromise with respect to the above-described possible disadvantages may be achieved. The stop element may be manufactured from a non-magnetic material, whereby it is able to separate the inner pole from the armature from a magnetic point of view. Furthermore, the lever arm may be kept short. Both a pole surface and a stop surface between the armature and the stop element, in particular stop ring, may be selected to be sufficiently large. Furthermore, a relatively small inside diameter of the spring may be implemented, so that it is possible to achieve relatively high spring forces, even with a comparatively thin wire gauge of the spring. Moreover, the spring may also have a relatively short design, so that the risk of bulging and accordingly occurring wear is reduced, and a tilting moment introduced onto the armature in this regard remains within acceptable limits.
The present invention enables an advantageous flow through the armature. In this way, a guidance of the armature in the housing may be achieved in one possible embodiment. Furthermore, in one further possible embodiment, an annular gap between the armature and the housing may be minimized. With respect to predefined housing dimensions, this results in a faster force build-up and a great holding force. Due to the combination of the through-openings with the spring receptacle, moreover the end face of the armature facing the inner pole can be designed to be larger than when separate through-openings are implemented.
The present invention has the further advantage that the flow cross section may be increased disproportionately in relation to the resultant reduction of the surface area of the end face of the armature.
The present invention has the advantage that an advantageous fuel flow may be achieved in the area of the stop element, without having to increase the internal borehole of the inner pole.
Valve 1 includes a housing (valve housing) 2 in which an inner pole 3 is situated in a stationary manner. A longitudinal axis 4, which serves as a reference for the guidance of a valve needle 5 situated inside housing 2 here, is determined by housing 2. This means that, during operation, an orientation of valve needle 5 along longitudinal axis 4 is to take place.
An armature (solenoid armature) 6 is situated on valve needle 5. Moreover, a stop element 7 and a further stop element 8 are situated on valve needle 5. Stops 7′,8′ are formed on stop elements 7, 8. Armature 6 may be moved between stop elements 7, 8 during an actuation, an armature free travel 9 being predefined. Armature 6, inner pole 3 and a solenoid coil, which is not shown, are integral parts of an electromagnetic actuator 10.
A valve closing body 11, which cooperates with a valve seat surface 12 to form a seal seat, is formed on valve needle 5. During an actuation of armature 6, it is accelerated in the direction toward inner pole 3. When armature 6 strikes against stop 7′ of stop element 7 and thereby actuates valve needle 5, fuel may be injected via the opened seal set and at least one nozzle opening 13 into a chamber, in particular a combustion chamber.
Valve 1 includes a return spring 14, which adjusts valve needle 5 via stop element 7 into its initial position in which the seal seat is closed.
Armature 6 is based on a cylindrical basic shape 20 including a through-borehole 21, armature 6 being guided on valve needle 5 at through-borehole 21. Basic shape 20 of armature 6 has a length L between an end face 22 facing inner pole 3 and an end face 23 facing away from inner pole 3.
Armature 6 includes a spring receptacle 25. Spring receptacle 25 is open on end face 22 of armature 6. Along longitudinal axis 4, spring receptacle 25 has a length f between end face 22 and a spring support surface 26 of armature 6. Spring support surface 26 represents bottom 26 of spring receptacle 25. In the initial state, in which the seal seat is closed, a spring 27 situated partially in spring receptacle 25 has a spring length F. Spring length F is spring length F of spring 27 in the non-actuated initial state here. Spring 27 is supported on spring support surface 26 of armature 6 on the one hand, and on stop 7′ of stop element 7 on the other hand. Spring length F is greater than length f of spring receptacle 25. During an actuation of armature 6, however, spring 27 is shortened compared to its initial length F, it being able to immerge completely into spring receptacle 25.
A guide web 28 is formed on armature 6 in this exemplary embodiment. Between spring support surface 26 and end face 23, armature 6 has a (shortened) length l along longitudinal axis 4. Without guide web 28, only this shortened length l would be available as the guide length. As a result of guide web 28, length l is extended by length s of guide web 28 along longitudinal axis 4. This results in guide length l+s in this exemplary embodiment. Length s of guide web 28 is preferably selected to be as large as or even greater than length f of spring receptacle 25. Guide length l+s of armature 6 on valve needle 5 is thus equal to or even greater than length L of armature 6 between its end faces 22, 23.
The guidance of valve needle 5 with respect to longitudinal axis 4 or with respect to housing 2 in this exemplary embodiment is derived with the aid of stop element 7. Stop element 7 is guided in a guidance area 30 on an internal borehole 31 of inner pole 3. Possible embodiments of stop element 7 which enable an advantageous through-conduction of the fluid, in particular fuel, are described based on
In one modified embodiment, the guidance of valve needle 5 may, in addition or as an alternative, also be implemented via armature 6. Outer side 32 of armature 6 extends at least partially to inner side 33 of housing 2. Instead of guidance area 30, in this embodiment an annular gap may then be implemented between stop element 7 and inner pole 3.
In this way, an advantageous guidance of valve needle 5 along longitudinal axis 4 may be implemented. At the same time, this results in an advantageous guidance between armature 6 and valve needle 5 over a guide length l+s, which preferably is not smaller than length L.
It is thus possible, in this exemplary embodiment, for spring receptacle 25 to directly abut valve needle 5. This facilitates, in particular the manufacture of armature 6 since spring receptacle 25 may be implemented by a cylindrical recess oriented on longitudinal axis 4. However as a result, only length l, which is shortened compared to length L of armature 6 which the armature has between end faces 22, 23, is available directly on basic shape 20 of armature 6. This shortened length l is thus extended to a certain extent by length s′ via guide extension 40. Specifically, length s′ may be predefined in such a way that guide length s′+1 is as large as or even greater than length L of armature 6 between its end faces 22, 23.
Moreover, guide extension 40 has a sleeve-shaped design. This means that an outside diameter 41 on guide extension 40 is selected to be considerably smaller than an outside diameter 42 on outer side 32 of armature 6.
Furthermore, spring 27 is designed with ground spring ends 43, 44 in this exemplary embodiment. This results in an even better support. Furthermore, it results in reduced wear and a more uniform force introduction into armature 6 on spring support surface 26 on the one hand, and on stop 7′ of stop element 7 on the other hand.
In the exemplary embodiment described based on
To conduct the fuel past stop element 7, recesses 61 through 64 are provided. Proceeding from a hollow cylindrical basic shape 65, which is characterized by an outside diameter D, stop element 7 may be modified by such recesses 61 through 64. This results in both the option of a guidance on the outside diameter D and a fuel conduction through recesses 61 through 64.
Recesses 61 through 64 are designed in such a way here that, as viewed from longitudinal axis 4, they extend maximally up to a diameter d. This means that a circular ring-shaped surface area 66 remains from valve needle 5 up to diameter d.
Preferably, diameter d is predefined in such a way that it is between outer line 60A and inner line 601. As a result, spring 27 at least partially rests against support area 60, namely at least against circular ring-shaped surface area 66, even in the area of recesses 61 through 64. This results in a compromise between a good contact of spring 27 on support area 60 and preferably large recesses 61 through 64 and, simultaneously, in the option of a guidance on outside diameter D.
The present invention is not limited to the described exemplary embodiments.
Number | Date | Country | Kind |
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102016225776.5 | Dec 2016 | DE | national |
Filing Document | Filing Date | Country | Kind |
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PCT/EP2017/076701 | 10/19/2017 | WO | 00 |
Publishing Document | Publishing Date | Country | Kind |
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WO2018/114088 | 6/28/2018 | WO | A |
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