Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16K—VALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING
  • F16K31/00—Actuating devices; Operating means; Releasing devices
  • F16K31/004—Actuating devices; Operating means; Releasing devices actuated by piezoelectric means
  • F16K31/005—Piezoelectric benders
  • F16K31/006—Piezoelectric benders having a free end
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
  • F15C—FLUID-CIRCUIT ELEMENTS PREDOMINANTLY USED FOR COMPUTING OR CONTROL PURPOSES
  • F15C3/00—Circuit elements having moving parts
  • F15C3/10—Circuit elements having moving parts using nozzles or jet pipes
  • F15C3/14—Circuit elements having moving parts using nozzles or jet pipes the jet the nozzle being intercepted by a flap

Definitions

• the invention relates to a fluidic valve, in particular for switching or controlling relatively large volume flows, preferably using a piezoelectric drive.
• the invention finds preferred application in 3/2 valves.
• Solenoid valves are widely used for switching volume flows.
• the main disadvantages of these solenoid valves are that they require a constant supply of energy to hold the magnet in one position, they have relatively long switching times and a large construction volume.
• Valves of the generic type are also known and are preferably used in electrovalve technology as an alternative to solenoid valves (see data sheet PLEZO 2000 A5P023D61KO30 ⁇ from Hoerbiger Pneumatic).
• these valves contain a piezoelectric bending actuator, which can be switched in at least two positions by applying an electrical voltage. Depending on the application, such bending actuators are selected or optimized with regard to the achievable adjustment path, the force, size and electrical operating voltage.
• the invention has for its object to provide a fluidic valve, in particular for switching or controlling relatively large volume flows, which preferably includes a piezoelectric drive.
• a piezoelectric drive in particular a piezoelectric bender with predeterminable voltage, driving force and bending deflection and the prevailing fluidic pressure, as well as the valve lift according to the invention, can create valves which control or switch larger volume flows through a defined configuration of at least one valve opening to let. If the switching of larger volume flows is not the main concern of the user, the invention can be used to create simplified and thus more cost-effective valve designs by using smaller piezoelectric actuators with less drive force and / or less stroke.
• at least one nozzle is given a shape deviating from a circular geometry such that its circumference, with an otherwise identical nozzle cross-sectional area, is at least 1.5 times the comparison nozzle circumference of a circular nozzle geometry.
• Fig. 1 shows a 3/2 valve in side section as an example of the
• Fig. 3 shows a possibility of an additional application of force to the piezoelectric drive by means of a spring.
• a valve housing 1 contains a piezoelectric drive 2, which in the example is designed as a bimorph bender. Furthermore, the valve is designed as a 3/2 valve, wherein it has openings P, R and a connecting path A. In the illustration shown, the 3/2 valve is closed; the broken line representation of the bender stands for the open valve position, a flow path for the medium present at the opening P to the connecting path A being released in this switching position. In the closed switching position, the bender is subjected to a fluidic pressure force F p .
• the medium flowing through the connecting path A in the open valve position causes the adjustment of an adjusting piston 3 which is shown by way of example and which, in the closed position, undergoes an opposite movement along a double arrow, for example by a spring (not shown).
• an adjusting piston 3 which is shown by way of example and which, in the closed position, undergoes an opposite movement along a double arrow, for example by a spring (not shown).
• the predeterminable valve lift is designated by s.
• the openings of P and R are circular; see. Fig. 2a.
• the cross-sectional areas Ap of the opening P and Ao of the opening R are each approximately 1.3 mm 2 .
• fluidic forces Fp or FQ in the open valve position
• a multilayer bimorph bender intended for operating the valve should have a maximum stroke of 0.7 mm and exert a maximum force F ⁇ of 1.3 N.
• valve stroke s usable in the valve is only 0.2 mm.
• valve housing 1 Based on the described reference example, two openings P and R with the same opening cross-sectional areas are in turn in a first exemplary embodiment in the valve housing 1
• Opening cross-sectional design as shown in Fig. 2b, assumed.
• a s 0.82 mm 2
• This means that the same conditions are already achieved here with a valve stroke s 0.1 mm.
• piezoelectric drive only has to overcome 62% of the force difference.
• the additional external force can be generated as in the first embodiment and should be about 0.3 N here.
• a further advantage here is that the resonant frequency of the bender increases by a factor of 2.25 to approximately 820 Hz, which means that valve switching processes can be implemented much faster.
• a valve as in example 2 is to be considered equipped with a geometry of the opening as in example 1 and provided with a piezoelectric drive as in the reference example. There is an additional external force of approximately 0.3 N, as provided in the second embodiment.
• Such a valve can be operated with voltages of 50 V if the bender width is increased to 12.5 mm or the operating pressure is reduced to 4.5 bar. With such a requirement, the valve can be connected to standard 24 V voltage supplies by means of a simple voltage doubler circuit or can be supplied via 24 V bus lines.
• Fb 0.4 N can still be actuated safely if an additional spring generates a static preload of 0.1 N.
• the bender can then be given the following dimensions, for example, length: 20 mm, width:
• This opening cross section enlarged by a factor of 2.75 compared to the reference example, results in values of ⁇ min ⁇ 1.0 N, ⁇ F ⁇ 0.6 N and a static preload of ⁇ 0.7 N.
• this valve can even switch a volume flow that is about 3 times as large as in the reference example with a slightly weaker bender, e.g. by reducing its width to 8 mm.
• FIG. 2c shows a last exemplary embodiment in which the opening cross-sectional areas of P and R are to be of different sizes.
• the flow cross sections Ag of both openings are the same size.
• the static preload force of an additional spring that engages the bender is set at 0.7 N.
• slot-shaped openings with a rectangular cross-section have been described in the context of the description, they represent a particularly preferred embodiment, since they can be more easily closed in one plane by the bender, but do not limit the invention to this.
• Essential within the scope of the invention is the defined choice of openings with a cross-section that deviates from a circular cross-section and thus make it possible for the first time to mutually adapt the mutually influencing opening and bending parameters to the respective application.
• elliptical openings, slot openings or the like as indicated in FIG. 2d, also fall under the invention.
• the invention is also not limited to the use of piezoelectric drives in the form of benders. While maintaining the above considerations, piezoelectric stack drives can also be used, as described, for example, in P 44 45 642.5.

Landscapes

• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Theoretical Computer Science (AREA)
• Physics & Mathematics (AREA)
• Fluid Mechanics (AREA)
• Electrically Driven Valve-Operating Means (AREA)

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Publications (1)

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Citations (4)

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• 1995
  • 1995-12-16 DE DE1995147149 patent/DE19547149A1/de not_active Ceased
• 1996
  • 1996-11-29 WO PCT/EP1996/005286 patent/WO1997022824A1/de active Application Filing

Patent Citations (4)

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