DE19504689A1 - Micro-mechanical seat valve with outlet plate - Google Patents

Abstract

In the outlet plate (1) is formed at least one fluid outlet (11) with a valve seat (12). The monocrystalline semiconductor layer contains a stationary part (23) and at least one closure member (22), with the stationary part coupled to the outlet plate. Each closure member in the valve seat section is movable orthogonally to the outlet plate. Each closure member is moved by switchable magnetic fields for fluid flow control. At least one recess (24) is formed in each semiconductor closure member, with each recess filled with a solid ferromagnetic material (3), at least partly. Between the latter and the semiconductor is a positive connection.

Description

The invention relates to a micromechanical seat valve according to the preamble of Claim 1 and a method for its production.

So far, a number of micromechanical seat valves are known, which are electro static, piezoelectric or thermomechanical drives. These drive principles have the disadvantage that only small valve lifts and ratios moderately small actuating forces can be achieved. This has the consequence that such valves only very much can switch small pressure differences and is only suitable for extremely small flow rates are not.

To the advantages of microfabrication for areas of conventional fine to be able to use mechanically manufactured valves, d. H. for pressure differences larger than 1 bar and valve strokes above 50 µm, micro valves with electromagnetic be provided with drives. The microstructure proves to be difficult tion of the highly conductive or ferro necessary for the electromagnetic drive magnetic materials. In particular, problems arise from occurring paa such materials with silicon.

From DE-OS 39 14 031 a micromechanical actuator is known in which the Forces from electromagnetic fields can be used for deflection. In doing so Movable actuator parts are provided with conductor tracks through which electrical currents decrease flow right to the field of a permanent magnet. As a result of the Lorentz force, the movable actuator parts deflected. These actuators are made of silicon provides, the electrical conductors usually by vapor deposition of thin gold layers are generated on the silicon. The Lorentz force that can be achieved is here limited by the thickness of these conductor tracks (approx. 1 µm). Structural Dic would be desirable the current conductor in the area of the thickness of the silicon structures (greater than 100 μm). This cannot be achieved with thin-film technology. Another disadvantage is that the conductor tracks are connected to the movable silicon parts by adhesion are. Due to the different thermal expansion of silicon and the  Conductor material leads to mechanical with increasing thickness of the conductor tracks Structural tensions and unreliable liability.

From the scientific publication "Microfabricated actuator with moving permanent magnet "from the Proceedings MEMS workshop, Nara, 1991, pp. 27-32 a micromechanical actuator is known in which a movable silicon part small permanent magnet is glued on. Sufficient actuating forces are thereby he targetable. In this case too, the glue gives disadvantages due to thermi tensions. This actuator principle also requires individual assembly of the Magnets on the many silicon structures of a wafer, which is unfavorable in terms of cost is.

The object of the present invention is to provide a micromechanical seat valve electromagnetic drive to indicate that

• - is suitable for pressures above 1 bar and valve strokes above 50 µm;
• - has driving forces of more than 1 N;
• - Can be inexpensively manufactured using standard methods of silicon micromechanics;
• - works in a wide temperature range;
• - has a particularly high level of reliability.

One example of the use of the valve is fuel injection at Ottomo thought gates. Here, a high level of atomization comes as additional requirements training quality and high dosing accuracy.

This task is accomplished by a valve with the characteristic features of Pa claim 1 solved. It has one or more movable locking members, for example from microstructured silicon, facing the outlet openings of the valve are ordered. Ferromagnetic armature structures are integrated into these closing elements. The closing elements are relatively fixed by switchable magnetic fields The valve seats move and control the flow of fluid through the outlet openings. The Connection between the anchor structures and the silicon parts of the Locking elements are not adhesive but form-fitting. This has the advantage that a Interruption of power transmission between anchor structures and locking members and a related failure of the valve can only occur if that Monocrystalline silicon ensures positive locking. This case is due to This design is practically avoidable since the strength of the single crystal does not age.  

If you provide the form fit with a defined small game (claim 2), it can advantageously be avoided that the thermal expansion of the anchor structure leads to mechanical stresses in the silicon closing element. This in turn he leaves anchor structures with very large structure thicknesses, which correspondingly high Stell powers enabled.

The claims 4 to 7 represent advantageous modifications of the Invention appropriate valve for use as a fuel injector. By Mi crostructuring can be made in the said locking members Establish stroke limitation. Due to the high precision of the structuring process a very high dosing accuracy of the valve is guaranteed. An individual comparison of the Thurs In contrast to conventionally manufactured injection valves, the quantity to be added is not necessary. With the same structuring methods, membrane-shaped closures can be used in the locking elements Form the sealing lips. This enables an extremely high tightness of the ge closed valve. Also the outlet plate of the valve with outlet openings and Valve seats generated micromechanically, so swirling can be done easily and inexpensively til be displayed. This allows the fuel and atomization to be very effective a defined beam angle. By appropriate shaping of the stop surfaces and the outlet plate is end position damping of the valve without further effort, in both end positions.

In claim 8 and the associated claims, a method for Manufacture of the valve according to the invention specified. It is advantageous that the ferromagnetic armature structures with the precision of silicon micromechanics ge be manufactured. A single assembly is not necessary. All process steps for structuring the locking elements and the anchor structures are parallel to one Variety of valve elements running on a wafer.

The following are preferred embodiments of the invention with reference to Drawings explained. Show it

Figure 1 is a schematic sectional view of an embodiment of the valve according to the inven tion.

Fig. 2 is an illustration of an embodiment of the outlet plate of the valve according to the invention;

Fig. 3a to 3e are schematic sectional views for one embodiment of the manufacturing method according to the invention.

The embodiment according to FIG. 1 shows a valve outlet plate 1 , which is produced from a silicon single crystal wafer, the main surfaces of which are formed by the index [100] surface. An outlet opening 11 and a valve seat 12 are formed in it by means of anisotropic etching. A fixed part 23 and a closing member 22 are structured out of a second [100] silicon wafer. The fixed part 23 is firmly connected to the outlet plate 1 . The closing member 22 has a resilient connec tion by means of a bending beam 25 to the fixed part and is thereby pressed against the valve seat 12 , so that the valve is closed in the de-energized state. Recesses 24 in the closing member 22 made of silicon are filled with a most soft magnetic material 3 . The positive connection between the closing member 22 and the ferromagnetic fillings 3 is ensured at the top by the [111] etching facets of the recesses 24 , at the bottom by suitable silicon bridges spanning the recesses 24 at the bottom. The two silicon wafers are integrated in a fluid-tight manner into a component made of ferromagnetic material, which has the function of a magnetic circuit 61 . If the excitation coil 62 is energized, the magnetic circuit closes via the fillings 3 , which therefore have the function of a magnetic armature. The closing member 22 is consequently drawn to the magnetic circuit 61 , releases the valve seat 12 and enables the fluid to flow out. Another feature of this embodiment is the etched out stop surface 26 , which together with the counterpart 261 results in an exact limitation of the valve lift. A ausgeätz te membrane 27 with stiffened core 28 is pressed by the fluid pressure inside the Ven valve on the valve seat 12 and closes the valve particularly tight. The membrane 27 , the spring bars 25 and the silicon bridges under the recesses 24 are to be produced in a common manufacturing step from an n-doped epitaxial layer by means of electrochemical etching technology.

Fig. 2 shows an embodiment of the valve outlet plate 1 , also micromechanically made of [100] silicon, with a downwardly narrowing outlet 11 , the valve seat 12 and channels 13 , via which the fluid is guided to the valve seat 12 . The eccentric shape of these channels gives the inflow into the outlet area 11 a swirl component. This swirl component is accelerated by the increasing narrowing of the outlet 11 . This improves the atomization of the emerging fluid jet. The size of the area between the channels 13 determines the end position damping when the valve closes.

Fig. 3 shows schematically the manufacturing process for another form of the valve according to the inven tion. A wafer 2 made of single-crystal [100] silicon 21 is provided with through openings 241 by double-sided anisotropic etching ( FIG. 3a). The surface of the wafer is coated with a dielectric thin layer 242 , in particular in the area of the through openings 241 ( FIG. 3b). The wafer is then joined together with a contact structure 4 which has electrically conductive areas 5 in the area of the through openings 241 ( FIG. 3c). These are connected to the negative pole of a current source and a ferromagnetic material 3 is galvanically deposited through the through openings 241 ( FIG. 3d). After the end of the galvanic step, the contact structure is detached, the galvanic fillings 3 remaining in the silicon due to the positive connection ( FIG. 3e). The dielectric thin film 242 is removed from the gap between the metal and silicon in order to set a defined play. The silicon is further processed by means of anisotropic etching in order to form the closing element 22 and the spring bars 25 . All process steps are carried out in parallel at u. U. executed several hundred valve members on a wafer.

Claims (18)

1. Micromechanical seat valve with the following known features (generic term):

• - In an outlet plate ( 1 ) at least one fluid outlet ( 11 ) with at least one valve seat ( 12 ) is formed;
• - In a layer structure ( 2 ), which consists of at least one single-crystalline semiconductor layer ( 21 ), a fixed part ( 23 ) and at least one closing member ( 22 ) is formed, the fixed part ( 23 ) being connected to the outlet plate ( 1 ) is and each closing member ( 22 ) in the region of at least one valve seat ( 12 ) - substantially perpendicular to the outlet plate ( 1 ) - is movable;
• - Each movable closing member ( 22 ) is moved under the influence of switchable magnetic fields, whereby the fluid flow through each associated outlet ( 11 ) is controlled;

and the following new features ( characteristic part ):

• - in the group consisting of semiconductor (21) portion of each closure member (22) at least one recess (24) is formed;
• - Each recess ( 24 ) of the closing member ( 22 ) is at least partially filled with a solid ferromagnetic material ( 3 );
• - The connection between each ferromagnetic filling ( 3 ) and the semi-conductor ( 21 ) existing part of the closing member ( 22 ) is positive.

2. Micromechanical seat valve according to claim 1, characterized in that the connection between each ferromagnetic filling ( 3 ) and the semiconductor ( 21 ) part of the closing member ( 22 ) is positively with play. 3. Micromechanical seat valve according to claim 1 or 2, characterized in that each movable closing member ( 22 ) with the fixed part ( 23 ) via bars ( 25 ) or membranes is resiliently connected. 4. micromechanical seat valve according to one of claims 1 to 3, characterized in that in each movable closing member ( 22 ) of the layer structure ( 2 ) Ver recesses ( 26 ) are formed, which together with a counterpart ( 261 ) Be the movement of the closing member ( 22 ) limit. 5. Micromechanical seat valve according to one of claims 1 to 4, characterized in that in each movable closing member ( 22 ) at least one membrane ( 27 ) is formed with a stiffened core ( 28 ), each membrane ( 27 ) - with GE closed switching position of the valve - is pressed by the pressure of the fluid on a valve seat ( 12 ) and tightly closes the associated outlet ( 11 ). 6. micromechanical seat valve according to one of claims 1 to 5, characterized in that in the outlet plate ( 1 ) fluid channels ( 13 ) are worked out, through which the fluid flows when the valve is open to each valve seat ( 12 ), the fluid channels ( 13 ) have an eccentric geometry, whereby the flow in each outlet ( 11 ) is imparted with a swirl movement. 7. Micromechanical seat valve according to one of claims 1 to 6, characterized in that each fluid outlet ( 11 ) narrows in the flow direction, whereby a swirl movement of the flow is accelerated in the flow direction. 8. A method for producing a micromechanical seat valve, in particular according to one of claims 1 to 7, in which in a layer structure ( 2 ) movable closing members ( 22 ) are produced with positively connected ferromagnetic fillings ( 3 ), with the following - variable in order - procedural steps:

• - The layer structure ( 2 ), which consists essentially of a single-crystal layer or of a plurality of single-crystal layers of a semiconducting material ( 21 ), is provided with at least one through opening ( 241 ) in that the single-crystalline semiconducting material ( 21 ) is anisotropically etched;
• - The surface of the layer structure ( 2 ), at least in the area of each existing opening ( 241 ), is coated with a dielectric coating ( 242 );
• - The layer structure ( 2 ) is assembled with a contact structure ( 4 ) which is at least in the area ( 5 ) of each through opening ( 241 ) of the layer structure ( 2 ) is electrically conductive;
• - It is a ferromagnetic metal ( 3 ) or a ferromagnetic alloy, star tend from each of the electrically conductive areas ( 5 ) of the contact structure ( 4 ), through each through opening ( 241 ) of the layer structure ( 2 ) through galvanically separated and thus each through opening ( 241 ) at least partially completed to form the positive connection;
• - By means of selective etching of the semiconducting material ( 21 ) of the layer structure ( 2 ), the fixed part ( 23 ) and the movable closing members ( 22 ) are worked out, the ferromagnetic fillings ( 3 ) being integrated into the closing members ( 22 ).

9. The method according to claim 8, characterized in that after the galvanic deposition, the dielectric coating ( 242 ) from the space between the galvanic fillings ( 3 ) and the semiconducting material ( 21 ) of the layer structure ( 2 ) is released. 10. The method according to any one of claims 8 or 9, characterized in that the layer structure ( 2 ) is made of silicon. 11. The method according to any one of claims 8 to 10, characterized in that the layer structure ( 2 ) is formed from a plurality of single-crystalline silicon layers. 12. The method according to claim 11, characterized in that the different sili Zium layers have different doping. 13. The method according to claim 11, characterized in that the different sili Zium layers are joined together using silicon wafer bonds. 14. The method according to any one of claims 8 to 13, characterized in that the through openings ( 241 ) in the layer structure ( 2 ) are spatially structured using electrochemical etching stop techniques. 15. The method according to any one of claims 8 to 14, characterized in that the dielectric coating ( 242 ) is produced by means of thermal oxidation. 16. The method according to any one of claims 8 to 14, characterized in that the dielectric coating ( 242 ) is produced by means of a PVD method. 17. The method according to any one of claims 8 to 14, characterized in that the dielectric coating ( 242 ) is produced by means of the CVD method.