EP1135591A1

EP1135591A1 - Valve for controlling fluids

Info

Publication number: EP1135591A1
Application number: EP00972589A
Authority: EP
Inventors: Wolfgang Stoecklein
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1999-09-30
Filing date: 2000-09-09
Publication date: 2001-09-26
Also published as: DE19946828C1; WO2001023741A1; CZ20011880A3; KR20010101057A; JP2003510504A; US6427968B1

Abstract

The invention relates to a valve (1) for controlling a fluid, comprising a piezoelectric unit (3) for actuating an axially displaceable valve member (2) which can be positioned in the bore (8) of a valve body (9).One end of the bore (8) borders on a valve system pressure chamber (18) which is limited by a sealing element (25). The other end of said bore (8) borders on a valve low pressure chamber (16) having a run-off channel (17) for spillage. Said channel (17) is connected via a compensating channel (19) including a pressure limiting element (20, 23`) and a filling device (23, 23`) and comprising a valve system pressure chamber (18), to a valve low pressure chamber (16). A valve closing member (13) is connected to a valve member (2) which cooperates with at least two valve seats (14, 15), located in the valve low pressure chamber (16) and designed for opening and closing the valve (1), in such a way that said valve low pressure chamber (16) is separated from a high pressure valve control room (12). In an intermediate position between the valve seat (14, 15), said member fluidically connects the valve low pressure chamber (16) to the valve control chamber (12), whereby at least one damping element (20, 23`, 24) which generates a temporary opposing hydraulic force is provided in order to dampen the controlling movements of the valve member (2).

Description

Valve for controlling liquids

State of the art

The invention is based on a valve for controlling fluids according to the type defined in more detail in patent claim 1.

DE 197 328 02 discloses a fuel injection device for internal combustion engines with a high-pressure fuel source. The fuel injector has two valve seats with sealing surfaces on a closing body

Actuation by means of a piezo drive interact in a movement sequence, the closing body initially being in the closed position on the first valve seat, then being brought into an intermediate position between the valve seats in order to then return to the second valve seat in a closed position.

In this way, a short-term relief of a valve control chamber is achieved through the movement sequence of the closing body from one valve seat to the other

Pressure level determines an opening or closing position of a valve needle in the force-balanced designed fuel injection device and thus the fuel injection is controlled. The fuel injection is made possible while the closing body is in an intermediate position between the two valve seats. In this way, fuel injection is implemented by means of a single excitation of the piezo drive.

Since a time-consuming reversal of the movement of the closing body during the fuel injection is not necessary, the loss times in the control of the known fuel injection device are advantageously relatively short.

However, it has been shown that overshoots of the closing body occur when it is to be brought into a central position between the two valve seats. As soon as the closing body swings too far in the direction of the first or the second valve seat, this can disadvantageously lead to inaccuracies in the metering of the injection quantity.

It is possible to stabilize the central position of the closing body between the valve seats by means of spring force, but this has the disadvantage that the piezo drive had to be moved into its closed position on the second valve seat against the spring force. As a result, the piezo drive had to be dimensioned correspondingly large, as a result of which the manufacturing costs and the structural dimensions of the injection device are negatively influenced.

The invention has for its object to provide a valve for controlling liquids, with which the aforementioned disadvantages, in particular overshoots in the central position of the valve closing member, are avoided. Advantages of the invention

The valve according to the invention for controlling liquids with the features of claim 1 has the advantage that the actuating movements of the valve member are damped by means of steaming elements in such a way that the valve closing member is stabilized in its central position between the two valve seats. As a result, high-frequency injections of liquids, in particular fuel, can also be carried out exactly by the valve according to the invention, without there being any fluctuations in the injection quantity due to overshoots of the valve closing element in an unfavorable intermediate position.

In the valve according to the invention, hydraulic forces are generated by the damping organs, which act briefly against the direction of movement of the valve closing member and thus brake it accordingly into a central position between the two valve seats. Accordingly, the valve closing member can reach its stable middle position without the occurrence of overshoots.

A significant advantage of the invention is further that the hydraulic counter forces generated by the damping elements only act for a short time, so that the piezoelectric unit does not move the valve closing member against these damping forces m the closed position to the second valve seat. The piezoelectric unit can thus be dimensioned correspondingly small, as a result of which the production costs are reduced.

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

Two 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

Figure 1 is a schematic, partial representation of a first embodiment of the invention in a fuel injection valve for internal combustion engines in longitudinal section, Figure 2 is a schematic, partial illustration of a second embodiment in a fuel injection valve in longitudinal section with a hollow drilled leakage pin, and

FIG. 3 shows a diagram with diagrams for a leakage pin, a gap pressure and a gap width being plotted over a length of the pin.

Description of the exemplary embodiments

The first exemplary embodiment shown in FIG. 1 shows the use of the valve according to the invention in a fuel injection valve 1 for internal combustion engines of motor vehicles. The fuel injection valve 1 is designed here as a common rail injector, the fuel injection being controlled via the pressure level in a valve control chamber 12, 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 2 is controlled via a piezoelectric unit designed as a piezoelectric actuator 3, which is arranged on the side of the valve member 2 facing away from the valve control chamber and combustion chamber. The piezoelectric actuator 3 is made up of several layers and has an actuator head 4 on its side facing the valve member 2 and an actuator foot 5 on its side facing away from the valve member, which is supported on a wall 26. An actuator piston 7 of the valve member 2 is in contact with the actuator head 4 via a support 6, the piston being of stepped diameter.

The valve member 2 is axially displaceable in a bore 8 of a valve body 9 designed as an elongated bore and, in addition to the actuating piston 7, also comprises an actuating piston 10 actuating a valve closing member 13, the actuating piston 7 and the actuating piston 10 having different diameters. The actuating piston 7 and the actuating piston 10 are coupled to one another by means of a hydraulic transmission.

The hydraulic transmission is designed as a hydraulic chamber 11, which transmits the deflection of the piezoelectric actuator 3. The hydraulic chamber 11 encloses a common compensation volume between the two pistons 7 and 10 delimiting it, of which the actuating piston 10 is designed with a smaller diameter and the actuating piston 7 with a larger diameter.

The hydraulic chamber 11 is clamped between the actuating piston 7 and the actuating piston 10 in such a way that the actuating piston 10 of the valve member 2 makes a stroke which is increased by the ratio of the piston diameter when the larger actuating piston 7 is moved by the piezoelectric actuator 3 by a certain distance. The valve member 2, the

The actuating piston 7, the actuating piston 10 and the piezoelectric actuator 3 lie one behind the other on a common axis. The filling of the hydraulic chamber 11 is not shown in FIG. 1. Tolerances based on temperature gradients in the component or different coefficients of thermal expansion of the materials used and any setting effects can be compensated for via the compensation volume of the hydraulic chamber 11, without a change in the position of the valve closing element 13 to be controlled thereby occurring.

At the valve control chamber end of the valve member 2, the spherical valve closing member 13 is provided. The valve closing member 13 cooperates with valve seats 14, 15 formed on the valve body 9, the lower valve seat 15 being assigned a spring 27 which holds the valve closing member 13 on the upper valve seat 14 when the valve control chamber 12 is relieved.

The valve seats 14, 15 are formed in a valve low-pressure chamber 16 formed by the valve body 9, which is connected to a leakage drain channel 17 and to a compensation channel 19 leading to a valve system pressure chamber 18. The leakage drain channel 17 has a damping element designed as a throttle 20. In addition, the valve low-pressure chamber 16 has a connection, formed by the lower valve seat 15, to the valve control chamber 12, which is only indicated in FIG. 1, and a filling channel 21 which flows into the equalization channel 19.

A movable valve control piston, which is not shown in the drawing, is arranged in the valve control chamber 12. An injection nozzle of the fuel injection valve 1 is controlled in a manner known per se by axial movements of the valve control piston in the valve control chamber 12. An injection line, which supplies the injection nozzle with fuel, usually also flows into the valve control chamber 12. The injection line is one for multiple fuel injectors common high-pressure storage space (common rail) connected. The high-pressure storage space is fed in a known manner from a high-pressure fuel pump with high-pressure fuel from a storage tank.

The compensation channel 19 leading to the valve system pressure chamber 18 has a spring-loaded pressure relief valve 22 regulating the system pressure in the valve system pressure chamber 18 on the valve low pressure chamber side and is equipped with a damping element designed as a throttle 24. The filling channel 21 is connected to the compensation channel 19 via a leakage pin 23 regulating the filling, which is fitted into a bore and enables a predetermined leakage. The leakage pin 23 enables the realization of a small flow cross-section in a simple manner, however, of course, a precision bore can of course also serve as a filling device.

In a very advantageous embodiment, it can also be provided that the material of the leakage pin 23 has a greater coefficient of thermal expansion than the material of the

Valve body 9 has that, with increasing temperature, a viscosity-related increase in the volume flow flowing around the leakage pin 23 is severely limited, an almost constant volume flow with temperature changes being achievable with an optimal choice of material.

The valve system pressure chamber 18 connects to the piezo-side end of the bore 8 and is delimited on the one hand by the valve body 9 and on the other hand by a sealing element 25 connected to the actuating piston 7 of the valve member 2 and the valve body 9. The sealing element is designed as a bellows-like membrane 25 and prevents the piezoelectric actuator 3 from coming into contact with the fuel contained in the valve system pressure chamber 18. Of course, the sealing element can be used in others Versions can also be designed as a corrugated tube or the like.

The fuel injection valve 1 according to FIG. 1 operates in the manner described below.

When the fuel injection valve 1 is closed, i.e. when the piezoelectric actuator 3 is not energized, the valve closing member 13 of the valve member 2 is held in contact with the upper valve seat 14 assigned to it, so that none

Fuel can get into the valve low pressure chamber 16 from the valve control chamber 12 connected to the high pressure storage chamber and can then escape through the leakage drain channel 17.

As the spring rate of the hydraulic spring increases with increasing

Diameter of the actuating piston 7 projecting into the hydraulic chamber 11 increases proportionally, the biasing force of the piezoelectric actuator 3 can be adjusted via the diameter of the actuating piston 7, with the largest possible piston diameter being advantageous. Values adapted to the individual case can be selected by the person skilled in the art.

In the case of slow actuation, as occurs when the length of the piezoelectric actuator 3 or other valve components such as e.g. of the valve member 2 or

Valve body 9 occurs, the control piston 7 penetrates into the compensating volume of the hydraulic chamber 11 with an increase in temperature or withdraws from it when the temperature drops without this having any effect on the closed and open position of the valve member 2 and the fuel valve 1 as a whole.

If an injection is to take place through the fuel injection valve 1, the piezoelectric actuator 3 is energized, as a result of which its axial expansion increases abruptly. With such a rapid actuation of the piezoelectric actuator 3, it is supported on the wall 26, as a result of which the actuating piston 10 with the valve closing member 7 of the valve member 2 moves from its upper valve seat 14 into a central position between the two valve seats 14, 15. Due to the actuating movement of the valve member 2, the volume of the valve system pressure chamber 18 is reduced due to the moving membrane 25, as a result of which the system pressure in the valve system pressure chamber 18 increases accordingly. This pressure increase cannot be reduced immediately by the pressure relief valve 22, since the

Throttle 24 briefly builds up the system pressure. As a result, a hydraulic counterforce acts on the diaphragm 25 against the actuating movement of the valve member 2. The actuating movement is accordingly damped, so that the valve closing member 13 is stabilized in the central position between the two valve seats 14, 15.

After the system pressure has been reduced by the pressure relief valve 22, the valve closing member 13 can be moved into its closed position on the lower valve seat 15, as a result of which fuel can no longer penetrate from the valve control chamber 12 into the valve low pressure chamber 16. The fuel injection is then ended.

Thereafter, the current supply to the piezoelectric actuator 3 is interrupted, as a result of which the valve member is brought back into the middle position between the two valve seats 14, 15 and fuel injection takes place. Fuel can penetrate into the valve low-pressure chamber 16 through the lower valve seat. Due to the throttle 20 arranged in the leakage discharge channel 17, the pressure cannot be reduced immediately. The brief pressure increase in the valve low pressure chamber 16 causes a hydraulic counterforce which brakes the actuating movement of the valve member 2 in such a way that the valve closing member 13 in its central position between the two valve seats 14, 15 is stabilized and fuel injection is realized again. After the pressure in the valve low-pressure chamber 16 has been reduced by the leakage drain anal 17, the valve closing member 13 moves into its closed position to the upper valve seat 14. Thus, each activation (energizing or stopping the energizing) of the piezoelectric unit enables fuel injection.

Referring to FIG. 2, a second exemplary embodiment of fuel injector 1 is shown, in which:

For the sake of clarity, functionally identical components are designated with the reference numerals used in FIG. 1.

Compared to the embodiment according to FIG. 1, the fuel injection valve 1 shown here differs in that the throttle 24 arranged in the compensating channel 19 is replaced by a leakage pin 23, which is at least partially drilled hollow, for filling the valve system pressure chamber. The leakage pin 23 has a throttle area a and a leakage area b. The bore in which the leakage pin 23 ^{λ is} arranged has an annular groove 28 which is connected to the pressure relief valve 22. The throttle 24 in the first exemplary embodiment is replaced here by a gap throttling, so that the mode of operation of the damping element of the fuel injector does not change. Of course, other are constructive

Embodiments of the leakage pin 23 ^λ possible. In addition, the throttle 20 arranged in the leakage discharge channel 17 was also dispensed with in the second exemplary embodiment.

With regard to the choice of material for the leakage pin 23 ^{Λ, it} can also be provided here that it has a substantially greater coefficient of thermal expansion than the material of the valve body 9 in order to limit a viscosity-related increase in the temperature as the temperature increases. Of course, the damping elements designed as throttles 20, 24 or leakage pin 23 can alternatively or also be used side by side in the valve according to the invention. The operation of the valve can be further stabilized if several steaming elements are used side by side.

3 shows a diagram with diagrams, in which on the one hand a gap width s (x) and a gap pressure p (x) over the gap height or pin length x of the leakage pin 23 "can be seen. The pressure decrease takes place in the gap between the leakage pin 23 ^Λ and the surrounding bore linear if the bore and the leakage pin 23 ^Λ fitted into the bore are cylindrical, the maximum pressure corresponds to an internal pressure p_0 in the leakage pin 23 ^λ and there is a minimum pressure in the gap at a maximum gap width s_0 ,

As can be seen from the middle diagram, the internal pressure p_0 in the hollow leakage pin 23 ^{Λ is} constant over the pin length x.

Both together leads to the fact that the wall of the hollow drilled leakage pin 23 ^{λ is} widened and the leakage becomes smaller or increases more slowly. This ensures that adequate filling of the valve system pressure range is ensured at relatively low common rail pressures, while the leakage at high common rail pressures is limited.

In both embodiments described, the hydraulic medium for filling the hydraulic chamber 11 is the fuel, which is also injected into a combustion chamber of an internal combustion engine. With a suitable separation between the fuel supply and the discharge of the exiting in the hydraulic chamber 11 Hydraulic medium and a tracking of leakage losses, it is also possible to use separate 01 such as Motorol as the hydraulic medium.

Claims

Expectations

1. Valve for controlling liquids, with a piezoelectric unit (3) for actuating a valve member (2) which is axially displaceable in a bore (8) of a valve body (9) and which is used as a tolerance compensation element for compensating

Elongation tolerances of the piezoelectric unit (3) formed hydraulic ratio (11), wherein at one end of the bore (8) a valve system pressure chamber (18) delimited by a sealing element (25) and at its other end a leakage drain channel (17) Valve low pressure chamber (16), which is connected to the valve system pressure chamber (18) via a compensating channel (19), which has a pressure limiting member (20, 23 ~) and a filling device (23, 23 '), the valve member (2) Valve closing member (13) is assigned, which with at least two in the valve low pressure chamber

(16) arranged valve seats (14, 15) for opening and closing the valve (1) cooperate in such a way that in a closed position it separates the valve low pressure chamber (16) from a high pressure valve control chamber (12) and in an intermediate position between the valve seats ( 14, 15) connects the valve low pressure chamber (16) with the valve control chamber (12) in terms of flow, at least one damping element (20, 23 ^* , which briefly generates hydraulic counterforces), 24) is provided for steaming the actuating movements of the valve member (2).

2. Valve according to claim 1, characterized in that at least one first damping element (23 ^' , 24) is arranged in the compensation channel (19).

3. Valve according to claim 1 or 2, characterized in that at least a second damping element (20) is arranged in the leakage drain channel (17).

4. Valve according to one of claims 1 to 3, characterized in that the damping element is a throttle (20, 24).

5. Valve according to one of claims 2 to 4, characterized in that the first damping element is a leakage pin (23) with a throttle area (a) and a leakage area (b) for filling the valve system pressure chamber (18).

6. Valve according to claim 5, characterized in that the leakage pin (23 ^Λ ) is partially drilled.

7. Valve according to one of claims 1 to 6, characterized in that the pressure limiting member is a spring-loaded pressure relief valve (22) for adjusting the system pressure in the valve system pressure chamber (18).

8. Valve according to one of claims 1 to 7, characterized in that the filling device is formed with a leakage pin (23, 23 ^λ ) by means of which the valve control chamber (12) can be connected in terms of flow to the valve system pressure chamber (18).

9. Valve according to claim 8, characterized in that the material of the leakage pin (23, 23 ^λ ) such a larger one Thermal expansion coefficient as the material of the valve body (9), that with increasing temperature a viscosity-related increase in the volume flow flowing around the leakage pin (23, 23 ^λ ) is at least partially limited.

10. Valve according to one of claims 1 to 9, characterized in that the sealing element which delimits the valve system pressure chamber (18) is designed as a bellows-like membrane (25) which is connected in this way to the valve member (2) and to the valve body (9), that the piezoelectric unit (3) is protected from contact with the liquid to be controlled.

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).