CZ20013358A3 - Valve for liquid control - Google Patents

Abstract

The invention relates to a valve (1) for controlling liquids that is provided with a piezoelectric unit (4) that actuates a valve member (3) that is axially slidable within the bore (10) of a valve housing (7). The valve member (3) is configured as a multiple component consisting of at least one adjusting piston (9) adjoining the piezoelectric unit (4) and one actuation piston (12) adjoining the valve closing member (11), a hydraulic chamber (13) being disposed in between the two pistons. The bore (10) opens into a valve chamber (17) in which the valve closing member (11) can be displaced between a first valve seat (14) limiting a low-pressure zone (18) and a second valve seat (15) leading to a high-pressure zone (19). In its intermediate position, the valve closing member (11) is stabilized by a spring device (20) which interacts with a tapered section (21) of the valve member (3). Said tapered section (21) and the spring device (20) engage with each other when the valve closing member (11) is in its intermediate position.

Description

Technical field

BACKGROUND OF THE INVENTION The present invention relates to a fluid control valve having a piezoelectric unit for actuating a valve member axially displaceable in a borehole of the valve housing, which is formed as a multi-part valve for the control of a valve member. Q 1 £ i »

unit and with at least one actuating piston bordering a shut-off valve member between which is arranged a hydraulic chamber operating as a hydraulic transmission and a tolerance compensating element, the end of the bore facing away from the piezoelectric unit bordering the valve space in which the shut-off valve is arranged a member movable between a first valve seat formed at the end of the bore and delimiting the low pressure region and a second valve seat facing the valve control space of the high pressure region for opening and closing the valve, flowing in the intermediate position between the valve seats valve control space.

BACKGROUND OF THE INVENTION

DE 197 328 02 discloses a valve of this type for a fuel injection device of a high-pressure internal combustion engine. The fuel injector has two valve seats which, in sequence, interact with the sealing surfaces of the shut-off valve member when actuated by a piezoelectric actuator, the shut-off valve member initially in the closed position on the first valve seat then occupying an intermediate «♦» ♦ · · · · · 9 • • <9j * ·.

the position between the valve seats and then returns to the closing position on the second valve seat. The piezoelectric actuator is subjected to a pressure-dependent voltage in the common reservoir, which causes the actuator to extend and result in movement of the shut-off valve member to the second valve seat. The reverse movement of the shut-off valve member in the direction of the first valve seat is accomplished by interrupting the voltage in the actuator.

In this way, during the movement of the shut-off valve member from one valve seat to the other, a short-term relief of the valve control space, which is located under high pressure and over whose pressure level the opening or closing position of the valve needle is controlled, is thereby controlled. of fuel in the injection device, which is designed to be force-balanced. Fuel injection is thereby possible when the shut-off valve member is in the intermediate position between the two valve seats. In this way, it is possible to realize dual fuel injection, such as pre-injection and main injection, by a single excitation of the piezoelectric drive.

However, it has been shown that overshoot of the shut-off valve member may occur if the shut-off valve member is to be brought into an intermediate position between the two valve seats. If the shut-off valve member oscillates too far in the direction of the first or second valve seat, this may lead to disadvantages in the dosing inaccuracies in the injected quantities. This problem arises especially at high pressures in a common reservoir.

Furthermore, at high voltages on the piezoelectric actuator, depending on the operating points or the pressure in the common reservoir, and thus the very rapid adjusting movements, the time at which the shut-off valve member is in the intermediate může may be.

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position so short that the member is not sufficient to act on the valve needle and fuel injection is not performed.

Attempts have been made to stabilize the intermediate position of a valve closure member between valve seats by appropriately dimensioning a spring that is often disposed between the second valve seat and the valve closure member to maintain this member at the first valve seat when the valve control space is pressure relieved. However, this is disadvantageous in that the shut-off valve member

it must move along its entire adjustment path from p; r r; ť i k A Q O Η 1 Q l in 14 A li W Owwiv *

the valve to its closing position on the second valve seat against the spring force. As a result, the piezoelectric drive must be sized to the appropriate size, which can negatively affect the manufacturing cost and design dimensions of the injection device.

There is also the possibility of regulating the piezoelectric actuator such that when the closing valve member moves from the first to the second valve seat, the voltage is so high that the closing time of the closing valve member is so short that it does not affect the opening behavior valve. Injection can be achieved by returning to the first valve seat, the voltage at the piezoelectric actuator is reduced in a stepwise manner, the injection time and thus the amount injected is controlled by the duration of the effect of the mean voltage on the piezoelectric actuator. However, the effect of the double-connection valve is lost in a disadvantageous manner. Furthermore, this solution is energy problematic, especially with respect to power consumption and lost power, at least at high rotational speed and multiple injections.

SUMMARY OF THE INVENTION

These problems are overcome by a fluid control valve having a piezoelectric unit for actuating a valve member axially displaceable in the bore of the valve housing, which is formed as a multi-piece with at least one adjusting piston. bordering a piezoelectric unit and at least one actuating piston bordering a shut-off valve member between which a hydraulic chamber operating as a hydraulic transmission and a tolerance compensation element is disposed, the end of the bore facing away from the piezoelectric unit bordering the valve space; a shut-off valve member is movable between a first valve seat formed at the end of the bore and delimiting the low pressure region and a second valve seat facing the valve control space of the high pressure region for opening and closing the valve, wherein in the intermediate position between the seats, it connects the low pressure region with the valve control space according to the invention, which is characterized in that the spring device stabilizing the shut-off valve member in its intermediate position cooperates with the valve member constriction; that they are engaged with each other when the shut-off valve member is in its intermediate position.

The liquid control valve according to the invention has the advantage that the adjusting movements of the shut-off valve member are damped by the spring device according to the invention in such a way that the shut-off valve member is stabilized in its intermediate or central position between the two valve seats by simple and cost-effective means.

The invention allows a safe realization of the middle valve stroke, independently of the high pressure prevailing on the second valve seat, wherein the valve can be operated in principle with the possibility of dual

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energy-efficient regulation. Precise high-frequency injection of liquids, in particular of fuel, can also be provided by the valve according to the invention, without varying the injection quantity due to overshooting of the shut-off valve member or completely omitting the injections.

Further advantages and advantageous embodiments of the subject matter of the invention will be apparent from the description, drawings and claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION FIG. 1 is a schematic representation of a first exemplary embodiment of a fuel injector for internal combustion engines in a cut-out and in a longitudinal section, wherein the shut-off valve member is in an intermediate position between the first Fig. 2 shows a schematic cross-section along line II in Fig. 1, Fig. 3 a graph of a qualitative course of the force that dampens the movement of the shut-off valve member in its intermediate position; and Fig. 4 a schematic sectional view of another embodiment longitudinal section of the fuel injector for internal combustion engines.

DETAILED DESCRIPTION OF THE INVENTION

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The first embodiment shown in FIG.

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and 2 shows the use of a valve according to the invention in a fuel injector 1 for automotive internal combustion engines. The fuel injection valve 11 is designed as a common rail injector, the fuel injection being controlled via a pressure level in the valve control space 2, which is connected to a high pressure supply.

To set the start of injection, injection duration and VCfrenching XKa nrac ςίΙ / Λχ / Λnmž u and resistingVxzarim 1

V. A A A W A W A W A W A A A A 4 A 1 A - LS A W h? The valve member 3 is controlled by a piezoelectric unit formed by the piezoelectric actuator 4, which is arranged on the side of the valve member 3 facing away from the control and combustion chamber.

The piezoelectric actuator 4 is assembled in a known manner from a plurality of layers and has an actuator head 5 on its side facing the valve member 3 and an actuator foot 6 on its side facing away from the valve member, which rests on the valve housing 7. An adjusting piston 9 of the valve member 3, which is of graduated diameter, abuts the head 5 of the actuator.

The valve member 3 is axially displaceable in a borehole 10 formed as a longitudinal bore disposed in the valve housing 7 and includes, in addition to the adjusting piston 9, an actuating piston 12 controlling the spherical shut-off valve member 11. The adjusting piston 9 and the actuating piston 12 are mutually connected by a hydraulic converter.

The hydraulic transducer is designed as a hydraulic chamber 13 which transmits the deflections of the piezoelectric actuator 4. The hydraulic chamber 13 encloses between the two pistons 9 and 12 which limit it, of which the control piston 12 is formed with a smaller diameter and the adjustment piston 9 with a larger diameter equalizing volume.

The hydraulic chamber 13 extends between the adjustment piston 9 and the control piston 12 such that the control piston 12 performs an increased stroke based on the transmission ratio given by the piston diameters if the larger adjustment piston 9 is moved a certain distance by the piezoelectric actuator 4. The adjusting piston 9, the actuating piston 12 and the piezoelectric actuator 4 lie in succession on a common axis.

Through the equalizing volume of the hydraulic chamber 13, in addition to the hydraulic transmission of forces, tolerances due to temperature gradients in the structural element or different coefficients of thermal expansion of the materials used can also compensate for possible settling effects without changing the position of the shut-off valve member 11. be regulated. The filling of the hydraulic chamber 13 is not shown in FIG.

At the end of the valve control side of the valve member 3 and the actuating piston 12 respectively, the spherical shut-off valve member 11 in the valve space 17 interacts with the valve seats 14, 15 formed on the valve housing 7, the first and upper valve seats 14 respectively facing the low pressure. and the second or lower valve seat 15 respectively to the valve control space 2 in which the pressure is high. The lower valve seat 15 is associated with a spring 16 that holds the shut-off valve member 11 while relieving the control valve space 2 at the upper valve seat 14.

A movable valve control piston, not shown further in the figure, is disposed in the control space 2 of the high pressure region valve 19. The fuel injector 1 is controlled in a known manner by the axial movements of the valve control piston in the valve control space 2. The injection chamber 2 usually also opens into the valve control space 2, which supplies fuel to the injection nozzle. The injection line is connected to a common high-pressure supply space (common rail). The high-pressure storage space is fed in a manner known per se by the high-pressure delivery pump with high-pressure fuel from the storage tank.

To stabilize the shut-off valve member 11 in its central position, a spring device 20 is disposed in the region between the hydraulic chamber 13 and the valve space 17 in which the shut-off valve member 11 is arranged. on the actuating piston 12, wherein the constriction 21 and the spring device 20 are arranged to engage with each other when the shut-off valve member 11 is in its intermediate position.

As can be seen from FIGS. 1 and 2, the spring device 20 is formed in the illustrated embodiment with a tension spring 22 which, with its end facing away from the valve member 3 and the actuating piston 12, bears against the valve housing 7, and has a sliding device 23 at its second end facing the actuating piston 12.

In the present embodiment, the sliding device 23 is formed by three spheres 24 uniformly distributed around the circumference of the actuating piston 12 which interact with the geometry of the constriction 21 on the actuating piston 12 in such a way that the shut-off valve member 11 is braked in its central position during adjustment. The position of the balls 24 and the geometry of the constriction 21 of the actuating piston 12 are adapted by the skilled person according to the desired braking of the shut-off valve member 11.

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At the end of the bore 10 on the piezoelectric side is a system pressure valve space 25. This is bounded on the one hand by the valve housing 7 and on the other by the sealing element

26. connected to the adjusting piston 9 of the valve member 3 and the valve housing 7. The sealing element 26 is designed in the design as a diaphragm in the form of a pleated bag and prevents the piezoelectric actuator 4 from coming into contact with the fuel contained in the system pressure valve space 25. The filling device 27 for replenishing the low pressure area 18 is schematically indicated.

The fuel injector 1 of FIGS. 1 and 2 operates in the following manner.

In the closed state of the fuel injector 1 and with the piezoelectric actuator 4 de-energized, the shut-off valve member 11 of the valve member 3 is held in contact with the associated valve seat 14 so that the low pressure region 18 with high pressure storage space, can not get any fuel.

In the case of a slow actuation, such as occurs with a temperature-dependent length change in the piezoelectric actuator 4 or other components, such as the valve housing 7, the adjusting piston 9 enters the equalizing volume of the hydraulic chamber 13 with temperature increase or retracts without temperature in total, it has affected the closing and opening positions of valve member 3 and fuel valve 1.

If the fuel injection valve 1 is to be injected, the piezoelectric actuator 4 is energized so that its axial expansion suddenly increases. Via the adjusting piston 9 and the hydraulic chamber 13, this extension of the piezoelectric actuator 4 is transmitted to the actuating piston 12, thereby raising the shut-off valve member 11 from its first upper valve seat 15 and moving against the common reservoir pressure to the second lower valve seat 15 . If the actuating piston 12 now reaches the region in which the balls 24 of the sliding device 23 are located by its narrowing 21, a braking force directed against the direction of movement of the shut-off valve member is applied to the control valve, which leads to stabilization in this position.

FIG. 3 shows in a simplified manner the course of this braking force, which occurs more than the engagement between the constriction 21 of the actuator 12 and the spring device 20 and its maximum is in the central position h Mitte of the shut-off valve member 11. from its center position due to the piezoelectric force of the corresponding size, the constriction 21 moves out of the sphere of balls 24 compressed to the actuating piston 12, with the force against the direction of movement of the valve gradually decreasing. The shut-off valve member 11 can thus be moved without counteracting by the spring device 20 to its maximum stroke position h max, i.e. to the second valve seat 15.

When the electric current is applied to the piezoelectric actuator 4, the shut-off valve member 11 is now moved in the opposite direction with pressure in the reservoir, and by engaging the spring device 20 into the constriction 21 of the piston 12 again, the shut-off valve member 11 is stabilized. its central position.

The setting of the piezoelectric actuator takes place essentially in such a way that the medium voltage level acts on or does not act on the injection actuator. The actuator stroke thus set ensures that the control valve can be positioned approximately in the middle position between the seats. The device according to the invention ensures that the center position can be set up securely and with high accuracy.

FIG. 4 shows a further embodiment of a fuel injector 1 according to the invention in which, for the sake of clarity, functionally identical components are indicated by reference numerals already used.

In contrast to the embodiment of FIG.

and FIG. 2 is shown

A spring 28 is provided in the V11L1 VV Vf 111 of the shut-off valve member 11 and is supported on one side by the end of the valve space 17 associated with the second valve seat 15 and on the other by a stop 29 in the region between the first valve seat 14 and the second seat 15. valve. By appropriately positioning the stopper 29, the spring 28 is also positioned such that its spring force dampens the adjusting movement of the shut-off valve member 11 from the first valve seat 14 to the second valve seat 15 from reaching its intermediate position.

The described embodiments can of course be used alternatively or also simultaneously with the valve according to the invention. In the combined use of the spring device, the method of operation or the central position of the shut-off valve member can be further stabilized.

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Claims (8)

PATENT CLAIMS Liquid control valve, having a piezoelectric unit (4) for actuating a valve member (3) axially displaceable in a borehole (10) of a valve housing (7), which is formed as a multi-piece with at least one adjusting piston (9) bordering with a piezoelectric unit (4) and with at least one actuating piston (12) bordering a shut-off valve member between which a hydraulic chamber is arranged. 13). operating as a hydraulic transmission ά tolerance compensation element, wherein the end of the borehole (10) facing away from the piezoelectric unit (4) borders the valve space (17) in which the shut-off valve member (11) is movable between the first seat (14) a valve formed at the end of the bore (10) and delimiting the low pressure region (18) and the second valve seat (15) facing the control space (2) of the high pressure region valve (19) for opening and closing the valve (1); and which, in the intermediate position between the seats (14, 15), fluidically connects the low pressure region (18) with the valve control space (2), characterized in that the spring device (20) stabilizing the shut-off valve member (11) in its intermediate position interacting with the constriction (21) of the valve member (3), wherein the constriction (21) and the spring device (20) are arranged to engage one another The valve member (11) is in its intermediate position. Valve according to claim 1, characterized in that the constriction (21) is formed on the control piston (12). Valve according to claim 1 or 2, characterized in that the spring device (20) is formed with a tension spring (22) which, with its end facing away from the valve member (3), bears against the housing (0). 7) of the valve and, at its end, facing the valve member (3), has a sliding device (23). Valve according to claim 3, characterized in that the sliding device (23) is formed by spheres (24), in particular three spheres (24) are provided with uniform spacing. Valve according to one of Claims 1 to 4, characterized in that the spring device (20) is arranged in the region between the hydraulic chamber (13 ') and the valve chamber (17). Liquid control valve, in particular according to one of claims 1 to 6 5, characterized in that the spring device (20) is arranged with a spring (28) in the valve space (17) of the closing valve member (11), which on one side bears against the end of the valve space (17) facing the other seat (15) and on the other hand a stop (29) in the region between the first valve seat (14) and the second valve seat (15), the stop (29) being arranged in such a way that the spring force dampens the adjusting movement of the shut-off valve member 11) from the first valve seat (14) to the second valve seat (15) from reaching its intermediate position. Valve according to one of Claims 1 to 6, characterized in that a further spring element (16) is provided between the end of the valve space (17) facing the second valve seat (15) and the shut-off valve member (11). under tension, the shut-off valve member (11) is held at the first valve seat (14) while relieving pressure in the valve control space (2). Valve according to one of Claims 1 to 7, characterized by its use as part of a fuel injection valve for internal combustion engines, in particular an injector (1) with a common pressure reservoir.