EP2330288A1 - Fuel injector valve - Google Patents

Abstract

The fuel injector (1) has housing (2) and an actuator (3) that is arranged in the housing, where the housing has a housing part (4) which is made of an alloy that has iron, nickel and cobalt. The housing has another housing part (5) which is formed from steel. The former housing part and the latter housing part are connected with each other.

Description

State of the art

The invention relates to a fuel injection valve for fuel injection systems of internal combustion engines. Specifically, the invention relates to an injector for fuel injection systems of air-compressing, self-igniting internal combustion engines or mixture-compression, spark-ignited internal combustion engines.

From the DE 103 36 327 A1 is an injector for injection systems of internal combustion engines, in particular direct injection diesel engines, known. The known injector has a piezoelectric actuator arranged in an injector body, which is held in abutment via spring means on the one hand with the injector and on the other hand with a sleeve-like booster piston. Furthermore, a nozzle body connected to the injector body is provided, which has at least one nozzle outlet opening. In the nozzle body, a nozzle needle is guided axially displaceable.

The from the DE 103 36 327 A1 known injector has the disadvantage that in operation temperature-induced changes of the piezoelectric actuator and the injector lead to a relative displacement of the booster piston, which must be compensated. This represents an additional requirement for the design of the booster piston.

Advantages of the invention

The fuel injection valve according to the invention with the features of claim 1 has the advantage that temperature-induced changes in length are at least partially compensated. Specifically, the requirements for a hydraulically realized, for example, temperature compensation are reduced, whereby the chain of effects of the actuator for actuating a valve closing body is optimized.

The measures listed in the dependent claims advantageous developments of the fuel injection valve specified in claim 1 are possible.

It is advantageous that the alloy from which the housing part is formed, at least substantially based on iron, nickel and cobalt. Specifically, it is advantageous in this case that the alloy from which the housing part is formed has at least approximately 54% by mass of iron, at least approximately 29% by mass of nickel and at least approximately 17% by mass of cobalt. Thus, especially the alloy Fe54Ni29Co17 can be used. Here, there is the advantage that a temperature compensation is possible over a very wide temperature range.

The coefficient of thermal expansion represents an individual material property. However, the coefficient of thermal expansion is generally not constant over a wide temperature range. As a rule, the temperature-related expansion increases disproportionately with increasing temperature, since the coefficient of thermal expansion also increases. Temperature compensation can therefore usually be carried out effectively only in a narrow temperature range. Outside this temperature range, the compensation of the change in length due to the different increases in the coefficients of thermal expansion is only insufficiently possible. For example, materials made of Invar or having the Invar effect can minimize the thermal expansion, as these materials experience only minimal strain as a function of temperature, but even with these materials, the change in length can only be in a limited temperature range be compensated. Outside this temperature range, however, there are length changes.

Due to the design of the housing part made of the alloy with iron, nickel and cobalt, in particular Fe54Ni29Co17 temperature compensation can be achieved over a very wide temperature range. It can be achieved here that the temperature expansion coefficient decreases with increasing temperature and thus behaves contrary to the usual property of materials. Due to the nickel and cobalt content, the decrease in the coefficient of thermal expansion can be achieved with increasing temperature. Here, a design for the respective application is possible. For example, from slightly below room temperature to a temperature of 400 ° C. Thus, in the field of operating temperatures occurring in fuel injection valves, an advantageous compensation of temperature-induced changes in length can take place. By using the housing part formed from the alloy, in addition to the compensation of the change in length with temperature change Also, the dependence of the coefficient of thermal expansion of the temperature can be compensated. Thus, in particular, a fuel injection valve with a piezoelectric actuator can be provided in which a uniform temperature expansion over a wide temperature range is achieved. As a result, an advantageous switching behavior is made possible.

Advantageously, a further housing part of the housing is provided, which is formed at least substantially of steel and which is connected to the housing part of the alloy. Furthermore, it is advantageous that a transitional foot is provided, that the transitional foot between the actuator and the housing is arranged and that the actuator is supported on the transitional foot on the housing. This allows an advantageous adaptation to the length of the preferably piezoelectric actuator. Specifically, the housing part made of the alloy along a longitudinal direction of the actuator may be designed to be longer or shorter than this.

It is also possible that a transition head is provided, which is based on aluminum, that the transition head between the actuator and a valve closing body is arranged and that the actuator acts on the transition head on the valve closing body. Here, both a transition foot and a transition head made of aluminum can be provided. The expansion of the aluminum acts as a change in length in the section of the moving components. In contrast, the housing of the alloy and optionally the steel are to be regarded as immobile components. A change in length between the moving and the stationary components can be largely compensated by a design of the components.

Specifically, it is advantageous that at least one length of the housing part along a longitudinal axis of the actuator is predetermined so that a temperature-induced change in length between the housing and an actuatable by the actuator element is at least substantially compensated. Here, it is also advantageous that the temperature-induced change in length between the housing and the actuatable by the actuator element in a range of about -40 ° C to about 180 ° C are at least substantially compensated. For example, such a temperature-induced change in length can be reduced by the compensation to approximately + -1 μm. Thus, with respect to the function of the fuel injection valve, an almost complete compensation of the temperature-induced changes in length can take place. This is especially advantageous for direct needle control. In this case, advantageously, a valve seat surface configured on a nozzle body can interact with the valve closing body to form a sealing seat, wherein the preferably piezoelectric actuator directly actuates the valve closing body.

Brief description of the drawings

• Fig. 1 ein Ausführungsbeispiel eines Brennstoffeinspritzventils der Erfindung in einer schematischen, axialen Schnittdarstellung;
• Fig. 2 ein Diagramm, das die Differenz einer Längenänderung von bewegten und unbewegten Bauteilen eines Brennstoffeinspritzventils im nicht kompensierten Zustand veranschaulicht und
• Fig. 3 ein Diagramm, das eine Differenz der Längenänderung von bewegten und unbewegten Bauteilen des Brennstoffeinspritzventils im kompensierten Zustand veranschaulicht.

Preferred embodiments of the invention are explained in more detail in the following description with reference to the accompanying drawings, in which corresponding elements are provided with identical reference numerals. It shows:

• Fig. 1 an embodiment of a fuel injection valve of the invention in a schematic, axial sectional view;
• Fig. 2 a diagram illustrating the difference of a change in length of moving and stationary components of a fuel injection valve in the uncompensated state and
• Fig. 3 a diagram illustrating a difference in the change in length of moving and stationary components of the fuel injection valve in the compensated state.

Embodiments of the invention

Fig. 1 shows an embodiment of a fuel injection valve 1 in a schematic, axial sectional view. The fuel injection valve 1 can serve in particular as an injector for fuel injection systems of air-compressing, self-igniting internal combustion engines or mixture-mixing, spark-ignited internal combustion engines. Specifically, the fuel injection valve 1 is suitable for commercial vehicles or passenger cars. A preferred use of the fuel injection valve 1 is for a fuel injection system with a common rail, the diesel fuel under high pressure leads to a plurality of fuel injection valves 1. However, the fuel injection valve 1 according to the invention is also suitable for other applications.

The fuel injection valve 1 has a multi-part housing 2 and a piezoelectric actuator 3 arranged in the housing 2. The housing 2 has a housing part 4, a further housing part 5, a housing cover 6 and a guide part 7. In addition, a nozzle body 8 is provided, which is connected in a suitable manner, for example by means of a nozzle lock nut, with the housing 2.

In the interior of the housing 2, an actuator chamber 9 is formed, in which the piezoelectric actuator 3 is arranged. Between the piezoelectric actuator 3 and the housing cover 6, a transition foot 10 is disposed within the actuator chamber 9, which is added in this embodiment to the actuator 3 and configured as an actuator base 10. In addition, a transitional head 11 is provided, which is added in this embodiment to the actuator 3 and configured as an actuator head 11. The actuator head 11 is guided in this case in the guide part 7.

The piezoelectric actuator 3 can be charged and discharged to operate the fuel injection valve 1. In this case, the piezoelectric actuator 3 expands along a longitudinal axis 15 during loading and accordingly it contracts again during unloading. This results in a stroke of the actuator head 11, which transmits to a nozzle needle 16. Depending on the configuration of the fuel injection valve 1, a suitable operative connection exists between the actuator head 11 and the nozzle needle 16, which is illustrated by the double arrow 17. The nozzle needle 16 has in this embodiment, a valve closure member 18 which cooperates with a formed on the nozzle body 8 valve seat surface 19 to a sealing seat. According to the actuation of the piezoelectric actuator 3, an opening and closing of the sealing seat formed between the valve closing body 18 and the valve seat surface 19 takes place in order to inject fuel from a fuel chamber 20 via one or more nozzle openings 21.

The housing cover 6, the housing part 4, the further housing part 5 and the guide part 7 constitute stationary components 4, 5, 6, 7 of the fuel injection valve 1 during operation. The components 10, 3, 11 are parallel to the components 4, 5, 7 , namely, the actuator base 10, the piezoelectric actuator 3 and the actuator head 11, arranged. The components 3, 11 represent components of the moving chain for actuating the valve closing body 18.

During operation of the fuel injection valve 1, there may be temperature-induced changes in length of individual components, in particular the components 4, 5, 7 of the housing 2 and the components 10, 3, 11 come. Due to different materials and thus different coefficients of thermal expansion in this case the actuator head 11 can be adjusted relative to the guide member 7 in an initial state of the piezoelectric actuator 3. In the Fig. 1 an end face 2 of the actuator head 11 is shown as a reference point relative to a side 23 of the guide part 7. In an initial state, for example at room temperature, the fuel injection valve 1 can be configured, for example, such that the end face 22 of the actuator head 11 with respect to the longitudinal axis 15 Page 23 concludes. A change in length δL of the moving and unmoved components of the fuel injection valve 1 disappears in this case, that is, δL = 0.

The configuration of the fuel injection valve 1 is described below with reference to FIGS FIGS. 2 and 3 described in further detail.

Fig. 2 FIG. 12 is a graph illustrating the change in length ΔL as a function of the temperature of the fuel injection valve 1 in a conventional embodiment. In contrast, the shows Fig. 3 a diagram in which the change in length δL as a function of the temperature in a possible embodiment of the fuel injection valve 1 is shown according to the invention.

If the housing 2 and thus in particular the housing part 4 and the further housing part 5 are made of steel, then it can for example in the Fig. 2 shown course of the change in length δL come. Here, the housing 2 is designed such that at a temperature of 0 ° C, there is no difference in length between the end face 22 and the side 23, so that the change in length δL is equal to zero. The actuator base 10 may be configured, for example, of aluminum. The piezoelectric actuator 3 consists of piezoceramic layers and electrode layers arranged therebetween. The actuator head 11 may be made of steel. Due to the different coefficients of thermal expansion, starting from a temperature of 0 ° C., when the temperature is lowered, negative changes in length ΔL occur. For example, at temperatures that are slightly lower than -20 ° C, a change in length δL of more than -2 microns. Furthermore, at temperatures of more than 40 ° C for a certain range length changes δL of more than 2 microns. If the temperature continues to rise, a reduction of the change in length ΔL occurs again at a temperature of slightly more than 60 ° C. At about 135 ° C, the change in length δL disappears again, that is to say δL = 0, and this leads to negative length changes δL. The Indian Fig. 2 shown course serves to illustrate that due to different temperature dependence of the thermal expansion coefficients both increases and decreases in the change in length δL with increasing temperature are possible. Even with the use of Invar steel, due to the large temperature range, significant length changes δL continue to occur.

Fig. 3 shows a diagram in which the materials of the fuel injection valve include, inter alia, an alloy having iron, nickel and cobalt. For example, the housing part 4 is formed from an alloy which is at least approximately 54 % By mass of iron, at least approximately 29% by weight of nickel and at least approximately 17% by weight of cobalt. Specifically, the alloy Fe54Ni29Co17 can be selected. The further housing part 5 may be formed of a stainless steel. The guide member 7 may also be formed of stainless steel. The actuator base 10 may be formed of aluminum, while the actuator head 11 is formed of stainless steel. The piezoelectric actuator 3 again consists of piezoceramic layers and electrode layers arranged therebetween.

The design of the housing part 4 of Fe54Ni29Co17 results in an advantageous course of the thermal expansion coefficient. In this case, the coefficient of thermal expansion continues to decrease with increasing temperature. This effect exists at least for a certain temperature range. For Fe54Ni29Co17, this temperature range extends from just below room temperature to a temperature of about 400 ° C. Specifically, this can cover a temperature range of about -40 ° C to about 180 ° C. By using Fe54Ni29Co17 as an alloy for the housing part 4 not only the change in length with temperature change can be compensated, but also the dependence of the temperature expansion coefficient of the temperature can be compensated. Thus, a uniform temperature expansion on the one hand, the stationary components and on the other hand, the components of the moving chain can be achieved. Here, the change in length δ L varies only slightly over the range of -40 ° C to 180 ° C. For example, the fuel injection valve 1 may be designed so that at the temperature of 0 ° C, the change in length δL disappears. At temperatures lower than 0 ° C, positive changes in length ΔL occur. However, these are small, in particular smaller than 1 micron. At temperatures greater than 0 ° C first negative length changes δL occur, the magnitude of which are also significantly smaller than 1 micron. At about 140 ° C, the change in length δL disappears again and at temperatures greater than 140 ° C again positive length changes δL occur. Over the entire range of -40 ° C to +180 ° C, however, the amount of change in length δL remains smaller than 1 μm, in particular significantly smaller than 1 μm.

The Indian Fig. 3 can be achieved, inter alia, by a suitable choice of a length 25 of the housing part 4 made of the alloy, which is given by Fe54Ni29Co17 in this embodiment, along the longitudinal axis 15 of the piezoelectric actuator 3 illustrated favorable temperature profile of the change in length. As a result, temperature-induced changes in length ΔL between the housing 2 and the actuator head 11 that can be actuated by the piezoelectric actuator 3 are at least substantially compensated. In this embodiment, such temperature-induced changes in length between the housing 2 and that of the piezoelectric actuator 3 actuatable element 11, namely the actuator head 11, illustrated by the change in length δL between the end face 22 of the element 11 and the side 23 of the guide member 7.

Specifically, a direct needle control of the nozzle needle 16 can be realized by the piezoelectric actuator 3. In this case, the actuator head 11 can act directly on the nozzle needle 16. By loading the piezoelectric actuator 3, for example, the sealing seat between the valve closing body 18 and the valve seat surface 19 can be closed. By discharging the piezoelectric actuator 3 then injecting fuel is possible. Here, there is the advantage that with temperature-induced changes in length δL, the nozzle needle 16 is neither excessively pressed against the valve seat surface 19, whereby an opening behavior slows down, nor that there is an undesirable gap between the valve closing body 18 and the valve seat surface 19.

Further measures for temperature compensation, for example, with a hydraulic coupler, thereby simplify or even completely eliminated.

The invention is not limited to the described embodiments.

Claims (11)

Fuel injection valve (1) having a housing (2) and an actuator (3) arranged in the housing (2), wherein the housing (2) has at least one housing part (4) which is formed from an alloy comprising iron, nickel and Cobalt has. Fuel injection valve according to claim 1,
characterized,
that the alloy is formed from the housing part (4) at least substantially on iron, nickel and cobalt based. Fuel injection valve according to claim 1 or 2,
characterized,
that comprises the alloy of which the housing part (4) is formed, at least approximately 54 mass percent of iron, at least approximately 29 mass percent of nickel and at least approximately 17 percent by mass cobalt. Fuel injection valve according to one of claims 1 to 3,
characterized,
that the housing (2) comprises a further housing part (5) which is formed at least substantially of a steel, and that the housing part (4) and the further housing part (5) are interconnected. Fuel injection valve according to one of claims 1 to 4,
characterized,
in that a transition foot (10) is provided which is based on aluminum, that the transition foot (10) between the actuator (3) and the housing (2) is arranged and that the actuator (3) via the transition foot (10) on the housing (2) is supported. Fuel injection valve according to one of claims 1 to 5,
characterized,
in that a transition head (11) based on aluminum is provided, in that the transition head (11) is arranged between the actuator (3) and a valve closing body (18) and that the actuator (3) via the transitional head (11) acts on the valve closing body (18). Fuel injection valve according to one of claims 1 to 6,
characterized,
in that at least one length (25) of the housing part (4) along a longitudinal axis (15) of the actuator (3) is predetermined so that a temperature-induced change in length between the housing (2) and an actuatable by the actuator (3) element (11) is at least substantially compensated. Fuel injection valve according to claim 7,
characterized,
in that temperature-induced changes in length between the housing (2) and the element (11) which can be actuated by the actuator (3) are at least substantially compensated in a range from about -40 ° C to about 180 ° C. Fuel injection valve according to claim 8,
characterized,
that temperature-induced changes in length between the housing (2) and an element (11) which can be actuated by the actuator (3) are reduced by the compensation to approximately + -1 μm. Fuel injection valve according to one of claims 1 to 9,
characterized,
in that a valve seat surface (19) configured on a nozzle body (8) and a valve closing body (18) are provided, that the valve closing body (18) cooperates with the valve seat surface (19) to form a sealing seat and that the actuator (3) holds the valve closing body (18). directly drives. Fuel injection valve according to one of claims 1 to 10,
characterized,
that the actuator (3) as a piezoelectric actuator (3) is designed.

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