EP1276984A2

EP1276984A2 - Valve for controlling the flow of fluids

Info

Publication number: EP1276984A2
Application number: EP01913616A
Authority: EP
Inventors: Patrick Mattes
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2000-04-20
Filing date: 2001-02-13
Publication date: 2003-01-22
Also published as: CZ20014521A3; KR20020023239A; DE10019764B4; WO2001081752A3; US20030098428A1; DE10019764A1; US6698711B2; JP2003532001A; HUP0202459A2; WO2001081752A2

Abstract

The invention relates to a valve for controlling the flow of fluids. Said valve comprises an actuator unit (4) for actuating a valve element (3), which has a first plunger (9) and a second plunger (11) that is separated therefrom by a hydraulic chamber (13), and which actuates a valve closing element (12) that separates a low pressure area (16) with system pressure from a high pressure area (17). A filling device (24), which has a cavity (25) and which can be connected to the high pressure area (17), is provided for compensating for leakage. A flow restrictor (26) is arranged in said cavity in such a manner that a line (33) leading to the high pressure area (17) opens into the cavity (25) at one end of the flow restrictor (26), and a system pressure line (28) leading to the hydraulic chamber (13) branches off at the other end of the flow restrictor (26). The system pressure is built up, according to a pressure existing in the high pressure area, due to the geometric determination of a flow restricting borehole (27) located in the flow restrictor (26) and of the dimensions of the plunger (9), along which the system pressure (p_sys) is reduced.

Description

Valve for controlling liquids

State of the art

The invention relates to a valve for controlling

Liquids according to the kind defined in claims 1 and 2. Valves of this type for controlling liquids, in which a valve closing member separates a low-pressure area in the valve from a high-pressure area, are known in practice, for example in fuel injectors, in particular common-rail injectors, or in pumps of motor vehicles in a wide variety of designs.

Such a valve is also known from EP 0 477 400 A1, the valve described therein being operable via a piezoelectric actuator and having an arrangement for a displacement transformer of the piezoelectric actuator acting in the stroke direction. The actuator deflection is transmitted via a hydraulic chamber, which acts as a hydraulic transmission and Tolerance compensation element is used. The hydraulic chamber closes a common one between two pistons delimiting it, of which one piston is designed with a smaller diameter and is connected to a valve closing element to be controlled, and the other piston is designed with a larger diameter and is connected to the piezoelectric actuator Working volume. The hydraulic chamber is clamped between the pistons in such a way that the actuating piston makes a stroke that is increased by the ratio of the piston diameter when the larger piston is moved by a certain distance by the piezoelectric actuator. In addition, tolerances can be compensated for via the working volume of the hydraulic chamber, for example due to different coefficients of thermal expansion of the materials used, and any setting effects without the valve closing member experiencing a change in its position.

To ensure the function of such valves, the hydraulic system in the low pressure range, in particular the hydraulic coupler, requires a system pressure. This will drop due to leakage if there is insufficient hydraulic fluid refill.

The filling of the system pressure range is achieved, for example, in common rail injectors known from practice, in which the system pressure is expediently generated in the valve itself and is kept as constant as possible even when the system is started of hydraulic fluid from the high pressure area of the fuel to be controlled into the low pressure area in which system pressure is to be realized. Filling is often carried out with the help of leak gaps, which are represented by leak or filling pins. The system pressure is usually set by means of a valve, whereby the system pressure can also be kept constant for several common rail valves, for example.

However, this is problematic in the case of an essentially constant system pressure in the hydraulic chamber, which is at least largely independent of the prevailing high pressure in the high-pressure region, since at high pressure values a large actuator force is required to open the valve closing element against the high-pressure direction, which requires a correspondingly large and costly dimensioning of the actuator unit due. Furthermore, at high pressure in the high-pressure area, the displacement of hydraulic volume from the hydraulic chamber via the gaps surrounding the adjacent pistons is correspondingly increased, whereby the refilling time for building up and maintaining the counterpressure on the low-pressure side may be extended in such a way that lack of complete refilling in the event of a short subsequent actuation of the valve, a shorter valve lift is carried out, which may have a negative influence on the opening behavior of the entire valve. Advantages of the invention

The valve according to the invention for controlling liquids with the features of claim 1 or 2 has the advantage that a system pressure dependent on the pressure level in the high pressure range is provided for refilling the hydraulic chamber, with which the safe function of the hydraulic chamber is ensured as a hydraulic translator. In the case of a valve according to the invention, an increase in the system pressure at a high pressure level in the high-pressure area in the hydraulic chamber is possible, as a result of which the opening of the valve-closing member is supported against the high pressure present. In this way, a reduced control voltage of the actuator unit, which is preferably designed as a piezoelectric unit, is sufficient compared to a valve with a constant system pressure. The valve according to the invention can therefore be equipped with a smaller and less expensive actuator unit.

Furthermore, the invention enables a defined refilling of the low pressure area, in particular the hydraulic chamber. A very precise adjustment of the system pressure can take place through flow changes on the throttle body, which are carried out in a particularly preferred manner by hydroerosive rounding during assembly. The valve according to the invention is thus characterized in addition to the reliable provision of the required system pressure in the entire engine map and also by low costs in manufacture and assembly. This is mainly due to the constructively simple before the design of the valve, which allows the variable system pressure in the hydraulic chamber to be defined by easily adjustable geometric parameters such as the throttle flow and the dimensions of the body along which the system pressure is reduced to low pressure.

Further advantages and advantageous configurations of the subject matter of the invention can be gathered from the description, the drawing and the patent claims.

drawing

Some exemplary embodiments of the valve according to the invention for controlling liquids are shown in the drawing and are explained in more detail in the following description. Show it

FIG. 1 shows a schematic, partial illustration of a first exemplary embodiment of the invention in a fuel injection valve for internal combustion engines in longitudinal section,

FIG. 2 shows a simplified, partial illustration of a further exemplary embodiment of the invention in longitudinal section, and FIG. 3 shows a simplified schematic diagram of an addition to the embodiments shown in FIGS. 1 and 2. Description of the embodiments

The embodiment shown in Figure 1 shows a use of the valve according to the invention in a fuel injection valve 1 for internal combustion engines of motor vehicles. In the present embodiment, the fuel injection valve 1 is designed as a common rail injector for the injection of preferably diesel fuel, the fuel injection being controlled via the pressure level in a valve control chamber 2 which is connected to a high pressure supply. In order to set an injection start, an injection duration and an injection quantity via the force relationships in the fuel injection valve 1, a valve member 3 is controlled via an actuator unit designed as a piezoelectric actuator 4, which is arranged on the side of the valve member 3 facing away from the valve control chamber and combustion chamber. The piezoelectric actuator 4 is constructed in a conventional manner from a plurality of layers and has an actuator head 5 on its side facing the valve member 3 and an actuator base 6 on its side facing away from the valve member 3, which is supported on a wall of a valve body 7. A first piston of the valve member 3, which is also referred to as an actuating piston, bears against the actuator head 5 via a support 8. The valve member 3 is arranged axially displaceably in a longitudinal bore 10 of the valve body 7 and, in addition to the first piston 9, comprises a further second piston 11 which actuates a valve closing member 12 and is therefore also referred to as an actuating piston. The pistons 9 and 11 'are coupled to one another by means of a hydraulic transmission, which is designed as a hydraulic chamber 13 and transmits the deflection of the piezoelectric actuator 4. The hydraulic chamber

13 includes between the two pistons 9 and 11 delimiting them, in which the diameter Al of the second piston 11 is smaller than the diameter A0 of the first piston 9, a common compensation volume in which there is a system pressure p_sys. The valve member 3, its pistons 9 and 11 and the piezoelectric actuator 4 lie one behind the other on a common axis, the second piston 11 making a stroke increased by the ratio of the piston diameter when the larger first piston 9 by the piezoelectric actuator 4 by a certain one Distance is moved.

The compensation volume of the hydraulic chamber 13 allows compensation of tolerances due to temperature gradients in the component or different coefficients of thermal expansion of the materials used as well as any setting effects without influencing the position of the valve closing element 12 to be controlled.

At the end of the valve member 3 facing the valve control chamber 2, the ball-like valve closing member 12 cooperates with valve seats 14, 15 formed on the valve body 7, the valve closing member 12 having a low pressure region 16 with the system pressure p_sys from a high pressure region 17 with a high pressure or

Rail pressure p_R separates. The valve seats 14, 15 are in a valve chamber 18 formed by the valve body 7, from which a leakage drain channel 19 leads away on the side of the valve seat 14 facing the piezoelectric actuator 4. On the high pressure side, the valve chamber 18 can be connected to the valve control chamber 2 of the high pressure region 17 via the second valve seat 15 and an outlet throttle 20. The valve control chamber 2 is only indicated in FIG. 1. A movable valve control piston, not shown, is arranged in it. By means of its axial movements, the injection behavior of the fuel injection valve 1 is controlled in a manner known per se, the valve control chamber 2 being usually connected to an injection line which is connected to a high-pressure storage chamber (common rail) common to several fuel injection valves.

At the piezo-side end of the bore 10, a further valve chamber 21 is provided, which is delimited by the valve body 7, the first piston 9 and a sealing element 22 connected to this and the valve body 7. The sealing element 22, which is designed here as a bellows-like membrane, prevents the piezoelectric actuator 4 from coming into contact with the fuel contained in the low-pressure region 16. A leakage line 23 branches off from the valve chamber 21 in order to discharge leakage liquid.

In order to compensate for leakage losses in the low-pressure region 16 when the fuel injection valve 1 is actuated, a filling device 24 is provided. which is connected to the high pressure region 17. The filling device 24 is formed with a channel-like cavity 25, in which a pin-like throttle body 26 with a continuous throttle bore 27 is pressed. At the high-pressure end of the throttle body 26, a line 27 leading to the high-pressure region 17 opens into the cavity 25, while a system pressure line 28 leading to the hydraulic chamber 13 branches off from the cavity 25 at the opposite end of the throttle body 26.

In the preferred solutions shown in the drawing, the system pressure line 28 opens into a gap 29 surrounding the first piston 9, via which the system pressure opposes the valve chamber 21 and

Leakage line 23 is reduced. However, it can also be provided that the system pressure line 28 alternatively or additionally opens into a gap 30 surrounding the second piston 11, as is indicated by the line 28 'in dashed lines in the figures. The indirect filling of the hydraulic chamber 13 serves in any case to improve the pressure holding capacity in the hydraulic chamber 13 during the control, but it is of course also possible to fill the hydraulic chamber 13 directly via the system pressure line 28.

The system pressure p_sys in the fuel injection valve 1 according to the invention shown in FIG. 1 is determined by geometrically fixing the throttle bore 27 in the throttle body 26 and the dimensions, ie the length and the diameter A0, of the first piston 9. As long as the system pressure p_sys is reduced towards the low pressure region 16, it is built up in the high pressure region 17 as a function of the present pressure p_R.

By changing the flow cross section of the throttle bore 27 e.g. By means of hydroerosive rounding, the coupler pressure or system pressure p__sys in the assembly can be set so that it varies depending on the pressure p_R prevailing in the high pressure region 17. The system pressure p_sys, which is reached after an injection after a certain refilling time, must not exceed a maximum permissible static system pressure or coupler pressure, which would lead to the valve opening independently without actuation of the piezoelectric unit 4. Accordingly, the gap dimensions on the pistons 9 and

11 dimensioned. The diameter A0 of the first piston 9 and the diameter AI of the second piston 11 are thus parameters for the geometric definition of the throttle body 26 and the first piston 9. Further parameters for their geometric definition include the diameter ratio of the pistons 9 and 11 and a seat diameter A2 of the first valve seat 14 and a spring force F_F of a spring 31, which in the present case is arranged between the valve closing member 12 and the second valve seat 15 and the valve closing member

12 holds the first valve seat 14 in the closed position when the high pressure region 17 is relieved.

Referring to FIG. 2, a section of a further exemplary embodiment of the fuel injection valve is tils shown, which works in principle like the fuel injector described for Figure 1. For reasons of clarity, functionally identical components are identified by the reference numerals used in FIG. 1.

Compared to the embodiment according to FIG. 1, in which the high pressure p_R is reduced to the low-pressure region 16 via a series connection of the throttle body 26 and the first piston 9, the function of reducing the pressure along the piston 9 is alternatively realized here by a further throttle body 32. This throttle body 32, which is also designed like a sleeve with a throttle bore 34, is pressed into the cavity 25, which also receives the first throttle body 26, being connected upstream of a leakage line 35 branching off directly from the cavity 25. Between the throttle bodies 26 and 32, the system pressure p_sys builds up in the cavity 25 and in the system pressure line 28 and the hydraulic chamber 13 as a function of the present pressure p_R in the high-pressure region 17. The system pressure p_sys is reduced here along the second throttle body 32 to the low pressure region 16. In the solution shown in FIG. 2, there is also the possibility of adjusting the system pressure in the hydraulic chamber 13 in a simple manner by specifically matching the throttle bores 27 and 34, which is implemented, for example, by hydroerosive rounding. If the first throttle body 26 cavitates, the system pressure p_sys and the leakage occurring are limited to a maximum value. FIG. 3 shows a basic illustration of a supplement to the embodiments according to FIG. 1 and FIG. 2, with the cavity 25 accommodating at least the first throttle body 26 being provided on the high pressure side

Cavity 36 is connected upstream with a solid 37 arranged therein. This solid 37, which in the advantageous embodiment shown is piston-like, is axially movable in the cavity 36 and is arranged with play, whereby it serves at least primarily as a filter for throttling the downstream first throttle body 26. Filtering the high-pressure flow flowing to the first throttle body 26 is particularly advantageous in the case of a small throttle diameter of the first throttle body 26, as is often required in passenger cars. So that dirt particles do not clog the throttle bore 27 of the throttle body 26 here, these dirt particles, which are larger than a predefined gap dimension, are retained by the piston 37. Due to the preferably large gap dimension around the piston 37, this causes only a very small throttling. The pressure divider function for setting the system pressure p_sys thus only takes place via the first throttle body 26 and the first piston 9 or the second throttle body 32.

The axial mobility of the piston 37 serving as a filter also ensures that its gap dimension, which can be, for example, 10 μm to 15 μm, is not clogged by the dirt particles becomes. In order to ensure at least one axial movement of the piston 37 under pressure fluctuations, a spring device 39 is provided between the solid body or piston 37 and a throttle-side stop 38, by means of which the piston 37 can be displaced to a high-pressure side stop 40 in the high-pressure region 17 when the high pressure p_R drops is. Thus, the piston 37 is moved at every start-up and shut-down phase, which frees the piston gap automatically. To set the system pressure p_sys, the piston 37 is geometrically fixed as a function of the parameters already listed with regard to the throttle body dimensioning.

The fuel injection valve according to Figure 1, 2 or 3 operates in the manner described below.

When the fuel injector 1 is closed, i.e. If no voltage is present at the piezoelectric actuator 4, the valve closing member 12 is located on the upper valve seat 14 assigned to it and is pressed against the first valve seat 14 by the spring 31 with the spring preload F_F and mainly by the rail pressure p_R.

In the event of slow actuation, for example as a result of temperature-related changes in length of the piezoelectric actuator 4 or further valve components, the first piston 9, which serves as an actuating piston, penetrates into the compensation volume of the hydraulic chamber 13 when the temperature rises and pulls out of it Temperature reduction back without the overall closing and opening position of the valve closing member 12 and the fuel injection valve 1 being affected.

When the valve is to be opened and an injection is to take place through the fuel injection valve 1, the piezoelectric actuator 4 is acted on by voltage, as a result of which it suddenly expands axially. The piezoelectric actuator 4 is supported on the valve body 7 and builds up an opening pressure in the hydraulic chamber 13. Only when the valve 1 is in equilibrium in the hydraulic chamber 13 due to the system pressure p_sys, does the second piston 11 drive the valve closing member 12 out of its upper valve seat 14 into a central position between the two valve seats 14 and 15. At high rail pressure p_R, a greater force is exerted on the piezo side required to reach the equilibrium pressure in the hydraulic chamber 13. In the case of the filling device 24 according to the invention, however, the pressure in the hydraulic chamber 13 is also correspondingly increased when the rail pressure p_R is high. In this way, the piezo-side force on the valve closing member 12 is increased with the same voltage on the piezoelectric actuator 4. This increase in force corresponds to a substantially higher voltage which would have to be applied to the piezoelectric actuator 4. The power reserve obtained can be used in the design of the valve, for example, to reduce the size of the piezoelectric actuator. In order to move the valve closing member 12 against the rail pressure p_R backwards into a central position after reaching its second lower valve seat 15 and to achieve a fuel injection again, the energization of the piezoelectric actuator 4 is interrupted. Simultaneously with the return movement of the valve closing member 12, the hydraulic chamber 13 is refilled to the system pressure p_sys via the filling device 24.

The described embodiments each relate to a so-called double-seat valve, but the invention can of course also be applied to single-switching valves with only one valve seat.

Likewise, it is not imperative that the line 33 of the filling device 24 leading to the high-pressure region 17 is connected, as in the preferred embodiments shown, to the valve chamber 18, in which the valve closing member 12 can be moved between the valve seats 14 and 15. In alternative embodiments, it can also be provided that the line 33 is connected in terms of flow to a high-pressure inlet from a high-pressure pump, for example to the valve control chamber 2 in the high-pressure region 17 or to the outlet throttle 20.

It is also understood that the invention can be used not only in the common rail injectors described here as a preferred area of application, but generally in fuel injectors or also in other environments such as pumps can be realized.

Claims

Expectations

1. Valve for controlling liquids with an actuator unit (4), in particular with a piezoelectric unit, for actuating a valve member (3) axially displaceable in a valve body (7), to which a valve closing member (12) is assigned, which with at least one valve seat (14, 15) for opening and

Closing the valve (1) cooperates and separates a low-pressure area (16) with system pressure from a high-pressure area (17), the valve member (3) having at least a first piston (9) and a second piston (11), between which one The hydraulic chamber (13) is designed as a hydraulic transmission, a filling device (24) which can be connected to the high-pressure region (17) being provided to compensate for leakage losses, characterized in that the filling device (24) is designed with at least one channel-like cavity (25) , in which at least one throttle body (26) is arranged such that ^' in the cavity (25) at one end of the throttle body (26) opens a line (33) leading to the high pressure region (17), and that at the opposite end of the Throttle body (26) leading to the hydraulic chamber (13) rende system pressure line (28) branches, whereby a system pressure (p_sys) by geometrically defining a throttle bore (27) in the throttle body (26) and the dimensions of the piston (9), along which the system pressure (p_sys) to the low pressure area (16) is reduced, builds up as a function of an existing pressure (p_R) in the high-pressure region (17).

2. Valve for controlling liquids with an actuator unit (4), in particular a piezoelectric unit, for actuating a valve member (3) which is axially displaceable in a valve body (7) and which is assigned a valve closing member (12) which is associated with at least one valve seat (14, 15) cooperates to open and close the valve (1) and separates a low pressure area (16) with system pressure from a high pressure area (17), the valve member (3) having at least a first piston (9) and a second one Piston (11), between which a hydraulic chamber (13) working as a hydraulic transmission is formed, a filling device (24) which can be connected to the high-pressure region (17) being provided to compensate for leakage losses, characterized in that the filling device (24) also includes at least one channel-like cavity (25) is formed, in which a first throttle body (26) is arranged such that in the cavity (25) on one At the end of the throttle body (26) a line (33) leading to the high pressure region (17) opens, and that at the opposite end of the throttle body (26) branches off to the hydraulic chamber (13) leading system pressure line (28), whereby yourself a system pressure (p_sys) in by geometrically defining a throttle bore (27) in the first throttle body (26) and a throttle bore (34) of a second throttle body (32) which is connected upstream of a leakage line (35) branching off from the cavity (25) Dependency of an existing pressure (p_R) builds up in the high pressure area (17), which is reduced along the second throttle body (32) to the low pressure area (16).

3. Valve according to claim 1 or 2, characterized in that the cavity (25) receiving the at least one throttle body (26, 32) on the high-pressure side is preceded by a further cavity (36) with a solid body (37) arranged therein, the solid

(37) is arranged therein with a play with which it serves at least primarily as a filter for throttling the downstream throttle body (26).

4. Valve according to claim 3, characterized in that the solid body (37) is arranged axially movable, wherein preferably between the piston-like solid body (37) and a throttle-side stop (38) a spring device (39) is provided, by means of which the solid body if the pressure (p_R) drops in the high-pressure region (17), it can be moved to a high-pressure side stop (40).

5. Valve according to one of claims 1 to 4, characterized in that the geometric definition of the at least one throttle body (26, 32) and / or Piston (9) along which the system pressure (p_sys) is reduced towards the low-pressure region (16), depending on at least the parameters seat diameter (A2) and ratio of the diameter (A0) of the first piston (9) to the diameter (AI) of the second piston (11) is selected.

6. Valve according to one of claims 1 to 5, characterized in that a spring force (F_F) of a spring (31) which is arranged between the valve closing member (12) and a high pressure region (17) facing the second valve seat (15) and that Valve closing element (12) holds the first valve seat (14) in the closed position when the high pressure region (17) is relieved, a parameter for geometrically determining the at least one throttle body (26, 32) and / or the piston (9) along which the system pressure ( p_sys) is reduced towards the low-pressure region (16) and / or the solid body (37) upstream of the throttle body (26).

7. Valve according to one of claims 1 to 6, characterized in that the geometric definition is carried out such that the system pressure (p_sys) in the hydraulic chamber (13) is always less than a maximum permissible system pressure, the maximum permissible system pressure Hydraulic chamber (13) preferably corresponds to a pressure at which an automatic valve opening occurs without actuation of the actuator unit (4).

8. Valve according to one of claims 1 to 7, characterized in that the at least one throttle body (26, 32) is sleeve-shaped.

9. Valve according to one of claims 1 to 8, characterized in that the system pressure line (28) leading to the hydraulic chamber (13) into this via an adjacent to the hydraulic chamber (13), the first piston (9) surrounding gap ( 29) and / or the gap (30) surrounding the second piston (11), preferably over the gap (29) surrounding the first piston (9).

10. Valve according to one of claims 1 to 5, characterized in that the line leading to the high-pressure region (17) flows in terms of flow with a high-pressure inlet from a high-pressure pump to a valve control chamber (2) in the high-pressure region (17) or with an outlet throttle ( 20) between the at least one valve seat (15) and the valve control chamber (2) in the high pressure region (17) or preferably with a valve chamber (18) in which the valve closing member (12) between a first valve seat (14) and a second Valve seat (15) is movable, is connected.

11. Valve according to one of claims 1 to 10, characterized by its use as a component of a fuel injection valve for internal combustion engines, in particular a common rail injector (1).