WO2005095784A1 - Pressure-compensated, directly controlled valve - Google Patents

Abstract

The invention relates to a valve, especially a valve for high-pressure hydraulics, which comprises a valve bore (3) provided in a valve housing (2). In said valve bore, at least one valve seat (5; 19; 23) is located and separates a guide (8) on the high-pressure side of the valve bore (3) from a guide (12) on the low-pressure side of the valve bore (3). The valve also comprises a valve needle (1), directly actuated by an actuator (4) and guided in the valve bore (3) and having at least one sealing face (9; 28) that cooperates with the at least one valve seat (5; 19; 23). The valve needle (1) is complex and comprises, in the area of the guide (12) on the low-pressure side, at least one sleeve (13; 21, 22; 24, 25).

Description

Pressure balanced, direct operated valve

Technical field

To supply fuel to combustion chambers in internal combustion engines, injection systems are used to inject fuel, the injectors or valves of which are exposed to extremely high pressures. The valves in the area of diesel injection technology in particular are designed so that they can hold tight at high hydraulic pressures. Such diesel valves operate either according to the inward opening principle or according to the outward opening principle and are extremely fast switching. The function, which ensures a sealing hold is determined at such a diesel valves in the closed state ^'by a minimum leakage and by minimal hydraulic forces acting on the valve needle.

When such a valve is used for a distributor type fuel injection pump, it serves to connect a pump work space to a low pressure area through which fuel is supplied. In this way, the valve controls both the supply of fuel to the pump work space during suction and the end of injection, in which the valve, by opening, prevents further pressure from being built up in the pump work space.

State of the art

In the case of diesel injection valves, it is generally known to minimize the hydraulic forces acting in the opening direction by reducing the pressure application areas by making the sealing diameter equal to the guide diameter of the valve bore.

In the open state, however, such valves are not, or at least only partially, pressure balanced. The result of this is that pressure waves which build up when the valves are switched subsequently generate hydraulic forces on the valve needle. The switching behavior of the valve may be changed by these undefined forces, which may result in a scattering behavior in the injection quantities. In addition, the occurrence of so-called cavitation erosions is well known. When the valve is opened to terminate the fuel requirement or to determine the fuel injection quantity, the pressure in the pump work space is reduced, which was previously at a very high level, for example 1000-1200 bar via the valve opening to the low-pressure area, in which fuel flows out. With this outflow, flow separations and so-called flow recirculation zones can occur because of the high pressure difference between the high-pressure area and the low-pressure area of the valve. Gas and vapor bubbles are formed in the fuel in these. The reason for this is that the static pressure drops below the vapor pressure of the fuel. As soon as the pressure rises again, namely during a subsequent implosion, the vapor condenses in the vapor bubbles and the fuel strikes the valve housing and the valve member at high speed. This effect is all the more pronounced the more turbulence is in the flow. Such turbulence arises in particular from the sudden widening of the cross-section after the valve seat, since the flow there breaks off with strong eddy and vapor bubble formation.

In particular in the vicinity of the surrounding walls, this can lead to material damage, the so-called cavitation erosion, which occurs in particular directly behind the valve seat. If this erosion extends to the valve seat itself, this leads to long-term malfunctions in the valve.

From the prior art, for example from DE 197 17 494 AI, it is known to reduce the risk of cavitation damage by forming a narrow cross section in the outflow channel from the chamber behind the valve seat. Such a narrowed cross section is intended to ensure that when the medium flows into the chamber, it can quickly build up pressure, so that possible eddy currents and the resulting bubble formation effects are at least reduced. However, the valve known from this document suffers from the disadvantage that additional machining steps are required to form this diameter constriction in the fuel connection line, which is formed in the valve housing, which increase the costs of the production process.

In addition, from DE 199 40 296 AI a valve for a fuel injection pump of the distributor type is known, in which the cavitation effects are avoided in that the valve needle has at least one guide surface, which has at least one guide surface provided in the valve bore of the valve housing in the open state of the valve cooperates in such a way that a flow channel is formed which extends in the flow direction, starting from a minimal cross section in the area of the valve seat, expanded with a constant gradient. This gradient has the effect that the pressure increase is limited to a value that the flow boundary layer at this guide surface is still able to absorb without any signs of detachment of gas bubbles. However, the valve of this type is not able to completely eliminate the cavitation effects and, moreover, requires complex and detailed fluidic evaluations. In connection with this, the valve has a complicated shape, which can only be accomplished with increased costs and time.

Presentation of the invention

With the solution proposed according to the invention, cavitation effects, on the one hand, and undefined forces on the valve needle, on the other hand, can be completely avoided, such a valve being able to be produced with a significantly reduced production outlay. Since, as a result of the complete low pressure compensation that can be achieved with this valve, the hydraulic forces are greatly reduced when the valve is opened, the switching behavior and thus the injection quantity accuracy of the valve is considerably improved.

In general, the invention is characterized in that the valve needle to be used has a multi-part structure, in particular in such a way that at least one sleeve is provided in the region of the guide of the valve bore of the valve on the medium pressure side. This sleeve is pushed onto a reduced diameter of the valve needle with a narrow element play, preferably 1-2 μm, so that it can easily perform axial movements. Compared to the valve bore, the sleeve is itself guided with a small element play, also preferably 1-2 μm. The sleeve is axially braced against the valve needle by means of at least one elastic element.

In a further embodiment of the invention, the valve needle on the high-pressure-side guide of the valve bore has the same diameter as on the medium-pressure-side guide of the valve bore, where the sleeve is mounted in a leading manner. This has the effect that the guide diameter and the sealing diameter are of the same size, which ensures complete high-pressure compensation and low-pressure compensation.

The valve constructions proposed in this way are particularly suitable for diesel injection valves of the 2/2 or 3/2 valve type. It becomes clear that the simple manufacture of a multi-part construction of the valve needle makes it easy to determine the individual diameters, so that the effects of pressure equalization in the high pressure and low pressure range can be achieved both with the valve open and closed. The invention uses functional principles and components that are technically simple to implement.

Drawing;

The invention is described in more detail below with reference to the drawing.

It shows:

FIG. 1 shows an embodiment variant of the solution of a 2/2 valve type proposed according to the invention,

FIG. 2 shows a first embodiment variant of a 3/2 valve type,

3 shows a second embodiment variant of the solution of a 3/2 valve type proposed according to the invention, and

Figure 4 shows a third embodiment of the solution proposed according to the invention of a 3/2 valve type.

variants

FIG. 1 shows a 2/2 valve according to the solution proposed according to the invention, in particular a 2/2 diesel injector. This comprises a valve needle 1, which is guided axially in the valve bore 3 of a valve housing 2. The valve needle 1 is actuated directly by an actuator 4, not shown. It is possible for the valve needle 1 to be firmly connected to the actuator on the assembly side, it being possible to use all of the design variants known from the prior art, such as, for example, a magnetic actuator, piezo actuator, etc.

The valve bore 3 has an inward opening valve seat 5 (I-valve seat). The valve shown in FIG. 1 is shown in its open position. The I-valve seat 5 separates the valve bore 3 into a high pressure area and a control pressure or low pressure area.

The high-pressure region has a first channel 6, through which fuel is fed into a high-pressure chamber 7 under the intended high pressure. The valve bore 3 of the high-pressure area forms a guide 8 for the valve needle 1 on the high-pressure side.

The sealing edge 9 of the valve needle 1 on the valve needle 1 results from the seat angle difference of the cone angle relative to the valve housing 2 or the valve bore 3.

The low pressure area of the 2/2 valve has a second channel 10 for the control pressure, which opens into a control chamber 11. The valve bore 3 forms a guide 12 on the low pressure side in the low pressure region.

The valve needle 1 has a smaller diameter in this low pressure area than in the high pressure area. A sleeve 13 with a very small amount of play is pushed onto this section of smaller diameter of the valve needle 1, so that minimal relative movements of the sleeve 13 can be carried out. The sleeve 13 is mounted on a shoulder 14 of the valve needle 1 by means of an elastic element 15, for example a spring washer. Opposite this elastic element 15, the sleeve 13 is supported on a snap ring 16 which is enclosed in a groove in the valve needle 1. For this purpose, the sleeve 13 has a chamfer 17, so that the snap ring 16 is received by the latter in such a way that the sleeve 13 is axially braced, on the one hand the spring force of the elastic element 15 and on the other hand a pressure which may prevail in the control chamber 11 this axial bracing cause.

It can be seen that for the high-pressure compensation in a closed state of the 2/2 valve, the sealing edge 9 of the I-valve seat 5 has the same diameter as the guide diameter of the high-pressure-side guide 8 of the valve needle 1 in the valve bore 3, whereas for a low-pressure compensation in When the 2/2 valve is open, the valve needle 1 has the same diameter on the high-pressure guide 8 and on the medium-pressure guide 12. The latter is accomplished by fixing the sleeve 13 with appropriate dimensions for this.

Due to the fact that the sleeve 13 in the pressure side guide 12 of the valve bore 3 and on the corresponding section of the valve needle 1 with a very tight element play is performed, a seal of the pressure prevailing in the control chamber 11 is ensured to a return 18.

The valve needle 1 can be inserted into the valve bore 3 from the actuator side, with the elastic element 15, the sleeve 13 and the snap ring 16 then being mounted from the return side, so that the overall arrangement of the 2/2-way valve is easily assembled can be.

FIGS. 2-4 show different design variants of a 3/2 valve type, in particular a 3/2 diesel injection valve. Identical reference numerals are used for features of the different design variants that have the same function.

Figure 2 shows a first embodiment of a 3/2 valve type. This valve has a second valve seat in the form of a slide seat 19 in the low pressure range. As a result, the opening cross section is composed of the total stroke of the valve needle 1 minus the overlap of the slide seat 19 in a closed state. A third channel 20 for the return flow into the control chamber 11 opens into the low pressure area of the valve.

In the section on the pressure side of the medium, the valve needle 1 has an elongated diameter. A first sleeve 21 is pushed onto this section directly abutting the rounded portion 14. Furthermore, a second sleeve 22 is provided, the elastic element 15, the spring washer, being inserted between the first sleeve 21 and the second sleeve 22. The second sleeve 22 in turn has a chamfer 17 at the end opposite the elastic element 15, in which the snap ring 16, which is framed in a groove, is received on the valve needle 1.

The first sleeve 21 and the second sleeve 22 have the same outer diameter and are pushed onto the portion of smaller diameter of the valve needle 1 with a very narrow element play, preferably 1-2 μm. The first sleeve 21 can in turn be guided in the bore of the slide 19 with a very narrow element play. The second sleeve 22 is also fitted with an element clearance that is just as narrow in the low-pressure side guide 12 of the valve bore 3. The leakage of the closed slide seat 19 is determined by the axial overlap of the sleeve 21 in the bore of this slide seat 19 and by the very small element play. For complete high-pressure compensation on the one hand and low-pressure compensation on the other hand of the slide seat 19, the outer diameter of the sleeve 21 is equal to the diameter of the guide 8 of the valve needle 1 on the high-pressure side and equal to the outer diameter of the second sleeve 22.

Of course, this embodiment variant of a 3/2 valve is also conceivable with only a single sleeve, as was described in connection with the embodiment of a 2/2 valve described in FIG.

FIG. 3 shows a second embodiment variant of a 3/2 valve which, instead of a slide seat, has an outwardly opening valve seat 23 (A valve seat) in the low-pressure region of the valve.

On a portion of the valve needle 1 with a reduced diameter, a first sleeve 24 is guided with a tight guide play. On the outside, this first sleeve 24 is also with a very narrow guide play in the guide 12 on the medium pressure side

Valve bore 3 fitted. Outside the valve bore 3, a second sleeve 25 is provided, which in turn has a chamfer 17 for receiving the on the valve needle 1 in a

Groove snap ring 16 is used. A U-shaped disk 26 is inserted between this first sleeve 24 and this second sleeve 25 and is axially guided in a bushing 27. The bushing 27 is provided as a separate component to the valve housing 2, but can also be part of the valve housing 2. So that the snap ring 16 can be mounted at a valve needle stroke that is smaller than the length of the chamfer 17, the sleeves 24 and 25 are pushed onto the valve needle 1, the snap ring 16 is mounted and then between the first sleeve 24 and the second Sleeve 25, the U-shaped disc 26 inserted. Thus the dimension of this U-shaped serves

Disc 26 especially the setting of the valve lift.

The valve bore 3 has a section with a sealing diameter 29 which is identical to the diameter of the guide 8 of the valve needle 1 on the high-pressure side, so that complete A high-pressure compensation can follow when the A-valve seat 23 is closed. For the purpose of low pressure compensation when the A valve seat 23 is closed, the first sleeve 24 has the same diameter as the sealing seat of the A valve seat 23.

As can be seen in FIG. 3, the first sleeve 24 has a slightly larger diameter than the diameter of the guide 8 on the high-pressure side. For this reason, with a closed A-valve seat 23 there is only partial low-pressure compensation possible since the diameter of the first sleeve 24 is consequently also somewhat larger than the sealing diameter of the I-valve seat 5.

The pressure in a chamber 30, from which the third channel branches off for the return and which is connected to the control chamber 11 when the A valve seat 23 is open, presses the first sleeve 24 and thus also the second sleeve 25 together with the U-fb The disk 26 is always against the snap ring 16. When the A valve seat 23 is closed, this is brought about by the counterforce on this A valve seat 23. The embodiment variant of the 3/2 valve shown in FIG. 3 can be designed with or without an elastic element 15. In the embodiment variant shown in FIG. 3, complete hydraulic pressure compensation is achieved on the high-pressure side when the A-seat 23 is closed, since the sealing diameter of the A-seat 23 is equal to the diameter of the guide 8 on the high-pressure side. At the same time, an at least partially hydraulic low-pressure compensation can be achieved in that the diameter of the A-seat 23 essentially corresponds to the diameter of the guide 12 on the pressure side.

FIG. 4 shows a third embodiment variant of a 3/2 valve, the essential features of which correspond to the embodiment variant described in FIG. 3, with the difference that the first sleeve 24 has the same diameter as the guide 8 on the high-pressure side, i.e. the same diameter as the sealing seat of the I-valve seat 5 and the A-valve seat 23. In this way, both a full high-pressure compensation and a complete low-pressure compensation are guaranteed with such a 3/2 valve.

The proposed design variants can be used with all fast-switching and high-pressure valves that are used in self-igniting internal combustion engines. The valve variants shown in FIGS. 1 to 4 are all distinguished by the fact that they can all be mounted from the side of the high-pressure guide 8. As a result, an actuator which is firmly connected to the valve needle 1 can be used, which can be both a pre-assembled magnet armature assembly and a piezo actuator. The design variants of a valve for use in high-pressure hydraulics shown in FIGS. 1 to 4 are hydraulically pressure-balanced, ie the diameter of, for example, an inward-opening valve seat 5 corresponds to a diameter of the guide 8 on the high-pressure side with respect to the high-pressure side. To achieve hydraulic low pressure compensation, the diameters of a slide seat 19 correspond or, depending on the design variant of an A-seat 23, the diameter of a guide 12 of the valve needle 1 on the pressure side.

LIST OF REFERENCE NUMBERS

valve needle

valve housing

valve bore

Actuator inward opening valve seat (I-valve seat) first channel

High pressure chamber guide on the high-pressure side

Sealing edge of the second channel

Control room on the low-level side

shell

Rounding of heel elastic element

snap ring

phase

returns

Slider seat third channel (return) first sleeve second sleeve outward opening valve seat (A valve seat) first sleeve second sleeve

U-shaped disc

Rifle

sealing edge

Sealing diameter

chamber

Claims

claims 1. Valve for high-pressure hydraulics with a valve bore (3) provided in a valve housing (2), in which at least one valve seat (5; 19; 23) is formed, which guides the high-pressure side (8) of the. Separates the valve bore (3) from a medium pressure-side guide (12) of the valve bore (3), and with a valve needle (1) which can be operated directly by an actuator (4) and which is guided in the valve bore (3) and has at least one sealing surface (9; 28) which can interact with the at least one valve seat (5; 19; 23), characterized in that the valve needle (1) is constructed in several parts and in the region of the guide (12) on the low-pressure side at least one sleeve (13; 21, 22 ; 24, 25). 2. Valve according spoke 1, characterized in that the at least one sleeve (13; 21, 22; 24, 25) in the low-pressure guide (12) and on the valve needle (1) is guided with a tight element play. 3. Valve according spoke 2, characterized in that the at least one sleeve (13; 21, 22; 24, 25) is axially braced on a rounded portion (14) of the valve needle (1) by means of an elastic element (15). 4. Valve according spoke 3, characterized in that the at least one sleeve (13; 21, 22; 24, 25) opposite the elastic element (15) has a chamfer (17) into which a in a groove on the valve needle ( 1) arranged snap ring (16) is received. 5. Valve according to one of claims 1-4, characterized in that two sleeves (21, 22) are provided which are separated from one another by means of an elastic element (15) and are axially clamped together. Valve according to one of claims 1-4, characterized in that two sleeves (23, 24) are provided which are separated from one another by means of a U-shaped disc (26), the U-shaped disc (26) being in one with the Valve housing (2) in the connected socket (27) is guided. Valve according to one of claims 1-6, characterized in that the valve is designed as a 2/2 valve with an inwardly opening valve seat (5). 8. Valve according to one of claims 1-6, characterized in that the valve is designed as a 3/2 valve with an inwardly opening valve seat (5) and with a slide seat (19). 9. Valve according to one of claims 1-6, characterized in that the valve is designed as a 3/2 valve with an inwardly opening valve seat (5) and with an outwardly opening valve seat (23). 10. Valve according spoke 7, 8 or 9, characterized in that to compensate for the hydraulic forces acting on the valve needle (1) in the opening direction, the valve needle (1) on the high-side guide (8) and on the low-pressure guide (12) the same diameter having. 11. Valve according spoke 9, characterized in that for the partial compensation of the hydraulic forces acting on the valve needle (1) in the opening direction, the valve needle (1) on the high-pressure side guide (8) has a smaller diameter than on the low-pressure side guide (12) , 12. Valve according to claim 1, characterized in that the valve needle is mountable from the high-pressure side guide side (8). 13. Valve according spoke 1, characterized in that a diameter at the inward opening valve seat (5) corresponds to the diameter of the valve needle (1) within the high-pressure guide (8), whereby the valve needle is pressure balanced. 14. Valve according spoke 1, characterized in that when the slide seat (19) is closed, a full hydraulic high-pressure compensation due to the matching diameter of the slide seat (19) and the diameter of the high-pressure guide (8) on the one hand and a complete hydraulic low-pressure compensation due to the correspondence of the diameter of the Slider seat (19) with the diameter of the low-pressure guide (12) is reached. 15. Valve according to claim 1, characterized in that with a closed, outwardly opening valve seat (23) a full hydraulic high-pressure compensation due to the correspondence of the diameter of the outwardly opening valve seat (23) with the diameter of the high-pressure side Guide gear (8) on the one hand and a complete hydraulic low-pressure compensation is achieved due to the correspondence of the diameter of the valve seat opening outwards with the diameter of the guide (12) on the low-pressure side. 16. Valve according to claim 6, characterized in that the sleeves (24, 25) are positioned via the pressure load or closing forces when the outwardly opening valve seat (23) is closed and are set against a snap ring (16).