Microelectromechanical apparatus, microelectromechanical speaker, and method for operating a microelectromechanical apparatus

Abstract

The invention relates to a microelectromechanical apparatus (1) for generating a pressurized fluid flow (2), comprising: a pressure chamber (4) which surrounds a chamber volume (3); and a displacement unit (5) arranged on the pressure chamber (4), for compressing and conveying a fluid volume located in the chamber volume (3), wherein: the displacement unit (5) has a first diaphragm (5a) and a second diaphragm (5b) which can be moved relative to one another; the microelectromechanical apparatus (1) has a first drive device (10) designed to cause a first oscillation of the first diaphragm (5a) at a first frequency (f1) and to cause a second oscillation of the second diaphragm (5b) at a second frequency (f2) different from the first frequency (f1); and the pressure chamber (4) comprises a largely closed chamber boundary (6) and a fluid equalization device (7) for the exchange of fluid between the chamber volume (3) and surroundings (8) of the pressure chamber (4). The invention also relates to a microelectromechanical speaker (20) and to a method (100) for operating a microelectromechanical apparatus (1).

Description

[0001] Description

[0002] title

[0003] Microelectromechanical device, microelectromechanical loudspeaker and method for operating a microelectromechanical device

[0004] The invention relates to a microelectromechanical device for generating a pressurized fluid flow. The invention further relates to a microelectromechanical loudspeaker and a method for operating a microelectromechanical device for generating a pressurized fluid flow.

[0005] State of the art

[0006] Microelectromechanical devices, also known as microelectromechanical systems under the term “MEMS”, are known from the state of the art.

[0007] For example, US 2022 / 0 315412 A1 discloses a MEMS device for in-ear headphones with two membrane sections which, in order to avoid occlusion effects, are controlled in such a way that a vent opening is formed by a difference between their respective displacement.

[0008] Disclosure of the invention

[0009] According to the features of independent claim 1, a microelectromechanical device for generating a pressurised fluid flow is proposed, comprising a pressure chamber enclosing a chamber volume and a displacement unit arranged on the pressure chamber for compressing and conveying a fluid volume located in the chamber volume, wherein the displacement unit has a first membrane and a second membrane which are movable relative to one another, wherein the microelectromechanical device has a first drive device which is configured to excite the first membrane to a first oscillation at a first frequency and to excite the second membrane to a second oscillation at a second frequency deviating from the first frequency,and wherein the pressure chamber has a predominantly closed chamber boundary and a fluid compensation device for exchanging fluid between the chamber volume and an environment of the pressure chamber.,

[0010] In simple terms, the proposed microelectromechanical device makes it possible to deliberately utilize different phase positions of the oscillating membranes to generate a fluid flow by oscillating the first and second membranes at different frequencies. Due to the relative mobility of the first and second membranes to one another, the membranes can, for example, oscillate past one another depending on the phase position, thereby forming a fluid opening for sucking in the fluid contained in the chamber volume, or oscillate in the same direction to displace the sucked-in fluid and thereby generate a fluid flow. By appropriately exciting the first and second membranes, the oscillation sequences can be influenced, and thus various parameters for generating the fluid flow can be easily varied.Such variable fluid flow generation can be used in particular for sound signal generation, for example by varying phase shift.

[0011] By providing a pressure chamber with a predominantly closed chamber boundary, it is possible to generate a pressurized fluid flow, so that, for example, a desired minimum fluid pressure can be generated with the device. The chamber boundary can act as a counterpressure surface for the fluid volume to be compressed, thus enabling an effective pressure buildup. A predominantly closed chamber boundary can be understood here as a boundary structure enclosing the pressure chamber and having predominantly closed surface sections. The boundary structure can, for example, have temporarily formed and / or permanently present openings, particularly in the area of ​​the displacement unit and the fluid compensation device.A cumulative opening area of ​​temporary and / or permanent openings of the boundary structure can, for example, occupy a surface area of ​​at most 15%, in particular at most 10% or at most 5% of the boundary structure in order to form a predominantly closed chamber boundary. Conversely, the closed surface sections of the boundary structure can occupy a surface area of ​​at least 85%, in particular at least 90% or at least 95% of the boundary structure in order to form a predominantly closed chamber boundary. The chamber boundary can have, at least in sections, a substantially rigid chamber wall. The displacement unit and the fluid compensation device can be considered part of the chamber boundary and, for example, enclose the chamber volume together with the rigid chamber wall.

[0012] A fluid flow can be a moving volume of gas and / or liquid and can be described, for example, by means of a volume or mass flow. The fluid can in particular be a gas mixture, in particular air. Accordingly, the fluid flow can in particular be designed as an air flow and can be used, for example, to generate a sound signal. A pressurized fluid flow can be understood as a fluid flow with a pressure that is higher than the ambient pressure. A sound signal can be understood as a variable fluid pressure signal. The pressurized fluid flow can therefore be used to generate sound signals that are perceptible to the human auditory organ and can be specifically controlled by varying the sound pressure. The sound pressure can be described by a sound pressure level (SPL).

[0013] Particularly in acoustic applications of microelectromechanical devices, generating a sufficient sound pressure level, especially at low frequencies, is considered a technical challenge due to the very small dimensions of the sound-generating structures. With the proposed microelectromechanical device, it is possible to generate a high sound pressure level even at low frequencies, particularly due to the specially designed displacement unit and the provided pressure chamber. The pressurized fluid flow can, for example, be conveyed into a target volume, where the target volume can, in particular, be a limited spatial volume such as an ear canal.

[0014] A displacement unit can be a micromechanical structure of the microelectromechanical device, with which an enclosed fluid can be pressurized by means of movable structural elements and a fluid flow can be generated with the pressurized fluid. Such movable structural elements can be formed by the proposed first and second membranes, which can be excited at different frequencies. In principle, it is conceivable for the displacement unit to have further movable structural elements, in particular also further membranes, in addition to the first and second membranes. A membrane can be a substantially flat, deflectable structural element with a height and length several times greater than its width. The first membrane and the second membrane can each be connected to a fixed support structure of the device and held by it so that they can move in space.A fluid opening can be formed between the first membrane and the second membrane by a relative movement of the membranes to one another. The displacement unit can in particular be configured to generate a fluid flow directed from the pressure chamber into an area surrounding the pressure chamber. According to some embodiments, which can in particular comprise microelectromechanical devices with multiple pressure chambers, a displacement unit of at least one pressure chamber can also be configured to generate a fluid flow directed from an area surrounding the pressure chamber into the pressure chamber. The displacement unit can also be configured to selectively generate a fluid flow directed from the pressure chamber into an area surrounding the pressure chamber or a fluid flow directed from an area surrounding the pressure chamber into the pressure chamber, i.e. have an adjustable fluid conveying direction.

[0015] The environment of the pressure chamber can in principle be a substantially unlimited ambient volume, for example an atmospheric environment. The environment can also be formed by a limited ambient volume, for example a device housing. It is also conceivable for the pressure chamber to be arranged between a limited target volume, for example a human ear canal, and a substantially unlimited ambient volume, such as the atmospheric environment. Furthermore, it is possible for the pressure chamber to be arranged between two limited ambient volumes of different sizes, for example between an ear canal and a device housing. The generated fluid flow can, for example, be directed into a target volume such as an ear canal. The displacement unit can face the target volume.Fluid equalization can be achieved, for example, via fluid exchange with a base ambient volume, such as the atmosphere or a housing interior. The fluid equalization device can face the base ambient volume.

[0016] The microelectromechanical device can, for example, be manufactured using semiconductor technology as a layered structure on a substrate and have one or more functional layers, wherein, for example, the first and second membranes can form a first functional layer and the drive device can form a second functional layer. To manufacture the device, for example, a membrane layer can be applied to the substrate and a drive structure can be applied to the membrane layer. The membrane layer can be structured such that a first and a second membrane are formed which are movable relative to one another. The pressure chamber can, for example, be formed in the substrate or in a further intermediate layer applied between the membrane layer and the substrate. It is clear that the described microelectromechanical device can be manufactured very easily.

[0017] The first drive device can be a controllable microelectromechanical unit for actuating the first and second diaphragms. The first and / or the second diaphragm can, for example, be assigned a drive element of the drive device which is configured to excite vibrations on the diaphragm, for example is mechanically coupled to the diaphragm. Depending on the embodiment, for example, one drive element per diaphragm can be provided on the drive device for excitation, or a common drive element can be provided for the first or second diaphragm, wherein the excitation of the respective other diaphragm can occur, for example, through a superimposed drive signal and a mechanical coupling of the first and second diaphragms to one another. The drive element can be configured to compress and / or stretch the respective diaphragm in certain regions and thereby cause a deflection of the diaphragm.Depending on the embodiment, the drive element can be bidirectional, i.e., configured to selectively deflect the respective membrane in a first deflection direction and in a second deflection direction opposite the first deflection direction, or unidirectional, i.e., configured to deflect the respective membrane in only one predetermined deflection direction. The drive element can, in particular, be a piezoelectric drive element. In principle, it is also conceivable to design the drive element as a capacitive drive element or to use alternative drive concepts for electromechanical actuation of the membrane.According to the proposed features, the first drive device is configured to excite the first membrane to a first oscillation at a first frequency and to excite the second membrane to a second oscillation at a second frequency deviating from the first frequency. The first oscillation at the first frequency and the second oscillation at the second frequency can be regarded as mechanical, for example at least approximately sinusoidal oscillations of the membranes. The second frequency of the second oscillation can be regarded as a frequency deviating from the first frequency of the first oscillation. In particular, the second frequency can be higher than the first frequency. The first frequency and the second frequency can, in particular, deviate from a frequency of the generated fluid flow signals, since the fluid flow generation depends on the oscillation behavior of the membranes and not directly on the excitation frequency.Due to this frequency decoupling, low-frequency sound signals with high sound power can be generated, for example, despite the very small dimensions of the microelectromechanical device. To generate different frequencies, it is generally possible to apply different excitation frequencies to the membranes using different drive elements of the drive device. Alternatively or additionally, it is conceivable to vary the natural frequencies of the membranes through appropriate geometric design and dimensioning of the membranes. Even small deflections of the membranes are effective and effective for generating a fluid flow, allowing the microelectromechanical device to be operated efficiently and with low energy consumption.

[0018] Depending on the embodiment, a fluid compensation device can be a passive or active device for supplying fluid into the chamber volume or for discharging fluid from the chamber volume. The fluid compensation device can, in particular, enable a targeted fluid exchange between the chamber volume and the surroundings of the pressure chamber, for example, to maintain a substantially constant fluid volume in the chamber volume. Depending on the embodiment, the fluid compensation device can temporarily or permanently fluidically connect the chamber volume to the surroundings of the pressure chamber.Due to the microelectromechanical device's ability to generate a pressurized fluid flow by means of the displacement unit, in particular a fluid flow directed out of the pressure chamber, the fluid volume in the chamber volume can decrease during operation of the device, resulting in a pressure drop in the delivered fluid flow over time. In order to keep the fluid volume at least approximately constant and thus continue to deliver a pressurized fluid flow with a predetermined minimum pressure, the proposed concept allows for fluid to be fed from the environment of the pressure chamber by means of the fluid compensation device.According to some applications, which may, for example, comprise a multi-chamber system with at least two pressure chambers (as explained below), fluid can also be conveyed into the pressure chamber by means of the displacement unit instead of out of it, for example, to enable pressure equalization between a limited target volume, such as a human ear canal, and a substantially unlimited ambient volume, such as an atmospheric environment or a comparatively larger limited ambient volume. In this case, the fluid equalization device can be configured to discharge fluid from the chamber volume into the larger or unlimited ambient volume.A passive fluid compensation device can, for example, be a substantially immutable mechanical-structural component of the pressure chamber that enables fluid exchange, in particular, a directed fluid withdrawal from the environment of the pressure chamber or a directed fluid release into the environment of the pressure chamber. An active fluid compensation device can, for example, be a controllable component of the pressure chamber that can be varied, for example, in an opening cross-section, which enables a controllable fluid supply into the chamber volume or a controllable fluid release into the environment.

[0019] According to one embodiment, the fluid compensation device can comprise a fluid channel. A fluid channel can be a permanent through-channel that fluidically connects the chamber volume to the environment of the pressure chamber. A fluid channel can be considered a passive fluid compensation device, as it can form an unchangeable mechanical-structural component of the pressure chamber. The fluid channel, in particular a cross-section of the fluid channel, can be designed depending on the average or maximum fluid flow rate achievable with the displacement unit in order to ensure sufficient fluid replenishment or fluid discharge through the fluid channel to maintain a specified or required fluid quantity in the chamber volume.A fluid channel can be used to provide a particularly simple fluid compensation device, so that a microelectromechanical device with a simple and cost-effective structure can be achieved.

[0020] According to one embodiment, the fluid compensation device can comprise a passive valve. The passive valve can, in particular, form a direction-dependent flow valve. This can promote a directed fluid withdrawal from the environment of the pressure chamber or a directed fluid discharge into the environment of the pressure chamber without having to provide an active control or moving parts on the fluid compensation device. A passive valve can, for example, be a fluid channel or a fluid channel system with a specific channel shape or channel arrangement that allows or promotes a higher fluid flow in a first flow direction compared to a fluid flow in an opposite second flow direction.According to a simple design option, the passive valve can be designed as a fluid channel with a conically widening or conically tapering channel cross-section, or, simply put, it can be formed by a funnel-shaped fluid channel. The passive valve can be designed as a nozzle fluid channel with a tapered channel cross-section in the direction from the environment into the pressure chamber. The passive valve can be designed as a diffuser fluid channel with a widening channel cross-section in the direction from the environment into the pressure chamber. It is also conceivable to choose a complex passive valve shape. For example, the passive valve can be designed as a so-called Tesla valve.A Tesla valve uses a branched channel system in which different flow resistances are generated in the channel branches by means of geometrically differently designed channels in order to form a passive, direction-dependent flow valve.

[0021] According to one embodiment, the fluid compensation device can have an active valve. An active valve can be an electrically actuated device with microstructural moving parts. With an active valve, controlled fluid compensation can be achieved, for example, through a targeted, temporarily formed fluid compensation opening and / or through a controllable flow direction into or out of the pressure chamber. This can, in particular, prevent pressure loss via a permanent fluid compensation device during a compression and pumping process of the displacement unit. An active valve can, for example, be formed by actuated membranes that are movable relative to one another, as explained below.

[0022] According to one embodiment, the fluid compensation device can have a third membrane and a fourth membrane that are movable relative to one another, and the microelectromechanical device can have a second drive device for exciting the third membrane and the fourth membrane. This can provide a specifically actuatable fluid compensation device and enable precisely adjustable fluid supply or fluid release. In particular, a temporary fluid compensation opening to enable fluid exchange can be formed by the membranes that are movable relative to one another. The second drive device can basically have a similar structure and function to the first drive device. However, it is also conceivable to use differently designed drive devices for the displacement unit and for the fluid compensation device.

[0023] According to a further development, the second drive device can be configured to excite the third membrane to a third oscillation at a third frequency and to excite the fourth membrane to a fourth oscillation at a fourth frequency that differs from the third frequency. By exciting the third and fourth membranes at different frequencies, a temporary fluid equalization opening, which can be formed periodically, for example, can be specifically created between the third and fourth membranes in order to enable fluid exchange between the chamber volume and the environment of the pressure chamber. Such a temporary formation of the fluid equalization opening can, in particular, be temporally coordinated with a temporary formation of a fluid opening by means of the displacement unit. In particular, the fluid equalization opening can be formed at a time at which no fluid opening is formed between the first and second membranes.According to one possible embodiment, the second drive unit can be configured to excite the fourth membrane to a fourth oscillation at a fourth frequency that is substantially twice as high as the third frequency. For example, the fourth frequency can correspond substantially to twice the third frequency plus or minus a maximum of 25 percent of the third frequency. The fourth membrane can therefore go through approximately two periods during one period of the third membrane, i.e. oscillate at least approximately twice as fast as the third membrane. This makes it possible to achieve a favorable phase relationship between the membranes, which enables effective fluid equalization in the pressure chamber. According to one possible embodiment, the third frequency and / or the fourth frequency can be at least 20 kHz (kilohertz).This allows excitation of the third and / or fourth membrane outside the humanly audible frequency range, enabling device operation without disruptive harmonics. According to one possible embodiment, the third frequency of the third membrane can correspond to the first frequency of the first membrane. Furthermore, the fourth frequency of the fourth membrane can correspond to the second frequency of the second membrane.

[0024] According to one embodiment, the first drive device and the second drive device can be configured for coordinated excitation of the first, second, third, and fourth membranes. This enables coordinated excitation of the first and second membranes of the displacement unit and the third and fourth membranes of the fluid compensation device. In particular, a temporary formation of a fluid compensation opening by means of the fluid compensation device can be temporally coordinated with a temporary formation of a fluid opening by means of the displacement unit. This ensures that a substantially constant fluid volume in the pressure chamber is maintained at all times during operation of the microelectromechanical device. Furthermore, at least approximately continuous fluid flow generation can be achieved.The first drive device and the second drive device can, for example, be connectable or connected in terms of signal technology to a common higher-level signal processing unit or have signal paths coupled to one another in order to enable coordinated control for implementing coordinated excitation of the membranes.

[0025] According to one embodiment, the first membrane and the third membrane can be designed essentially identically and / or the second membrane and the fourth membrane can be designed essentially identically. The third membrane can in particular have a shape and dimensions comparable to those of the first membrane. Accordingly, the third membrane can have properties comparable to those of the first membrane, for example an at least approximately identical natural frequency. The fourth membrane can in particular have a shape and dimensions comparable to those of the second membrane. Accordingly, the fourth membrane can have properties comparable to those of the second membrane, for example an at least approximately identical natural frequency.By providing a substantially similar structure for the fluid equalization device and the displacement unit with membranes that are movable relative to one another, it is conceivable that the displacement unit and the fluid equalization device can be selectively operated with interchangeable functionality. Accordingly, the first and second membranes can form a fluid equalization device during reverse operation of the microelectromechanical device, and the third and fourth membranes can form a displacement unit during reverse operation of the microelectromechanical device. This enables versatile and flexible use of the electromechanical device, for example, with regard to flexible positioning of the device relative to a target volume.

[0026] According to one embodiment, the first drive device can have a drive element arranged on the first membrane and on the second membrane and / or the second drive device can have a drive element arranged on the third membrane and on the fourth membrane. This allows a very targeted and individual excitation of the said membranes independently of one another. As described above, however, it is generally also conceivable to provide a common drive element for the first and second membranes, to mechanically couple the first and second membranes to one another, and to excite both using a superimposed drive signal. Furthermore, it is generally also conceivable to provide a common drive element for the third and fourth membranes, to mechanically couple the third and fourth membranes to one another, and to excite both using a superimposed drive signal.The drive element can be configured to compress and / or stretch the respective membrane in certain regions, thereby causing a deflection of the membrane. Depending on the embodiment, the drive element can be bidirectional, i.e., configured to selectively deflect the respective membrane in a first deflection direction and in a deflection direction opposite to the first deflection direction, or unidirectional, i.e., configured to deflect the respective membrane in only one predetermined deflection direction. The drive element can, in particular, be a piezoelectric drive element.

[0027] According to a further development, at least one drive element can be arranged on a side of the first, second, third and / or fourth membrane facing the chamber volume, and at least one drive element can be arranged on a side of the first, second, third and / or fourth membrane facing away from the chamber volume. In other words, the drive elements can be arranged alternately on different sides of the membrane. This makes it possible to construct the microelectromechanical device with a simply designed drive device, in particular with unidirectionally acting drive elements. The unidirectionally acting drive elements define a predetermined deflection direction of the respectively assigned membrane, and the membranes can be deflected relative to one another in their respective predetermined deflection direction upon actuation of the respective drive elements and can swing back automatically when the actuation is discontinued.By virtue of the mutual arrangement, a fluid opening between the first and second membranes and / or a fluid equalization opening between the third and fourth membranes can be efficiently formed.

[0028] According to one embodiment, at least one drive element can be configured to selectively deflect the first, second, third, and / or fourth membrane in opposite directions. In other words, at least one drive element can be bidirectionally effective, i.e., configured to selectively deflect the respective membrane in a first deflection direction and in a deflection direction opposite the first deflection direction. This makes it possible to provide a particularly flexible microelectromechanical device. For example, a change in the flow direction or the volume flow of the pressurized fluid flow conveyed by the displacement unit can be implemented in a simple manner.

[0029] According to one embodiment, the second membrane may have a natural frequency that is substantially twice the natural frequency of the first membrane, and / or the fourth membrane may have a natural frequency that is substantially twice the natural frequency of the third membrane. For example, the natural frequency of the second membrane may be substantially twice the natural frequency of the first membrane plus or minus a maximum of 25 percent of the first frequency. For example, the natural frequency of the fourth membrane may be substantially twice the natural frequency of the third membrane plus or minus a maximum of 25 percent of the third frequency.As a result, when the membranes are excited in the range of their natural frequency or close to their natural frequency, a favorable phase relationship can be achieved between the first and second membranes and / or between the third and fourth membranes, which enables efficient fluid flow generation and / or fluid tracking or fluid release. In the range of the natural frequencies of the membranes, larger amplitudes can be generated with the same excitation energy than outside the natural frequency range. The natural frequencies of the membranes can be influenced, for example, by their geometric design and dimensions. For example, the second membrane can be designed to be narrower, shorter, or thinner than the first membrane, for example essentially half as wide, half as long, or half as thick as the first membrane.For example, the fourth membrane may be designed to be narrower, shorter, or thinner than the third membrane, for example, substantially half as wide, half as long, or half as thick as the third membrane.

[0030] According to one embodiment, the displacer unit can be arranged on a first side of the pressure chamber, and the fluid compensation device can be arranged on a second side of the pressure chamber opposite the first side. This makes it possible to provide a compact, energy-efficient microelectromechanical device with direct fluid flow paths. In principle, it is not excluded to arrange the fluid compensation device on a third side of the pressure chamber, wherein the third side can be directly adjacent to the first side of the pressure chamber. According to one embodiment, the displacer unit and the fluid compensation device can be arranged on the same side of the pressure chamber. In other words, the displacer unit and the fluid compensation device can be arranged next to one another instead of, for example, opposite one another.A microelectromechanical device with the described arrangement of the displacement unit and the fluid compensation device can be manufactured particularly easily, since the displacement unit and the fluid compensation device can be processed in a common process step, for example, without having to rotate the device between processing steps. If the displacement unit and the fluid compensation device are essentially identical in design, they can be produced simultaneously alongside one another, particularly in common process steps, for example, built up layer by layer and structured as needed, for example, through etching steps.

[0031] According to one embodiment, the microelectromechanical device can have at least two pressure chambers, each with a displacement unit and a fluid compensation device. This allows multiple pressurized fluid flows to be generated, which can be generated, for example, in the same direction or in different directions, or, for example, in a time-related sequence or simultaneously, thus enabling parallel or serial operation of the pressure chambers. The microelectromechanical device can have a first drive device associated with the displacement unit for each pressure chamber and / or a second drive device associated with the fluid compensation device for each pressure chamber.The second drive device can be provided, in particular, for controlling an active valve of the fluid compensation device, wherein the active valve can be formed, for example, by a third and a fourth membrane, as described above. The first and / or second drive devices of different pressure chambers can, in particular, be controllable in a coordinated manner. Alternatively, it is conceivable, for example, to provide a common first drive device for a plurality of pressure chambers with respective drive elements for the first and second membranes of the displacement units of the pressure chambers and / or to provide a common second drive device for a plurality of pressure chambers with respective drive elements for the third and fourth membranes of the fluid compensation devices of the pressure chambers.

[0032] According to a further development, the displacement units of the at least two pressure chambers can each be configured to generate a pressurized fluid flow with opposing flow directions. This allows, in particular, a fluid pressure signal, in particular a sound pressure signal, to be generated complementarily to one another, and, in particular, fluid exchange and / or pressure equalization between two separate ambient volumes of the microelectromechanical device to be enabled. In simple terms, a first displacement unit of a first pressure chamber can be configured for a pumping process into a target volume, and a second displacement unit of a second pressure chamber can be configured for a pumping process out of the target volume.

[0033] According to one embodiment, the displacement unit and / or the fluid compensation device can be operated bidirectionally. In other words, the displacement unit and / or the fluid compensation device can be configured to convey fluid in a first conveying direction and in a second conveying direction opposite to the first conveying direction. Accordingly, a fluid flow direction through the microelectromechanical device is reversible, in particular through control technology, without the need to make structural changes to the microelectromechanical device to reverse the flow direction. For example, a flow direction through the displacement unit can be reversible through control technology adaptation of the vibration behavior of the first and second membranes.Depending on the embodiment of the fluid compensation device, for example, a fluid channel can enable fluid exchange in opposite flow directions, or for example, a third and fourth membrane as a fluid compensation device can be adapted with regard to their vibration behavior such that a reversal of the flow direction can be effected. According to a further embodiment, the first membrane and / or the third membrane can have a recess and / or the second membrane and / or the fourth membrane can have a stiffening structure. A natural frequency can therefore also be influenced by changing the stiffness of the membranes. For example, a stiffening structure, for example in the form of a stiffening lip, can be formed onto the second or fourth membrane in order to increase the stiffness and thus the natural frequency.For example, a recess can be introduced into the first or third membrane to reduce stiffness and thus the natural frequency. Stiffening structures or recesses can also be used to specifically influence the movement pattern of the membranes, for example, to move a larger volume of fluid.

[0034] According to a further embodiment, the natural frequency of the first membrane, the second membrane, the third membrane, and / or the fourth membrane can be at least 20 kHz. This allows efficient excitation of the membrane or membranes outside the humanly audible frequency range. Accordingly, operation of the device without audible pumping noise or disruptive harmonics is enabled. Furthermore, at such high frequencies, many oscillations can be generated per unit of time, so that the proposed device can achieve a high energy conversion per unit of time and, for example, a high pumping or sound power.

[0035] According to a further embodiment, a sealing lip can be provided between the first diaphragm and the second diaphragm and / or between the third diaphragm and the fourth diaphragm. This can achieve favorable sealing for improved pumping behavior of the displacement unit and for more efficient pressurization without impairing the mechanical behavior of the diaphragms. Alternatively or additionally, it can be provided, for example, that the first diaphragm and the second diaphragm and / or the third diaphragm and the fourth diaphragm are thinned at their mutually facing ends or at their transition region in order to influence the pumping and vibration behavior. Such thinning can have an advantageous effect, for example, depending on the properties of the fluid to be pumped or depending on a basic thickness of the diaphragm.

[0036] According to a further embodiment, the first membrane and the second membrane can be mechanically coupled to one another, and / or the third membrane and the fourth membrane can be mechanically coupled to one another. This makes it possible to at least partially transmit vibrational movements of one membrane to the other coupled membrane.

[0037] According to a further embodiment, the first membrane and the second membrane can be configured for excitation by a superimposed drive signal of a drive element assigned to the first membrane or the second membrane, and / or the third membrane and the fourth membrane can be configured for excitation by a superimposed drive signal of a drive element assigned to the third membrane or the fourth membrane. This makes it possible to provide an efficient and simply constructed device. Furthermore, a high fluid volume can be conveyed with just one drive element for the first and second membranes and / or for the third and fourth membranes, thus achieving high pumping or sound power or sufficient fluid compensation.

[0038] According to a further embodiment, the device can have at least two first membranes that are configured to be excited by the first oscillation at the first frequency by means of the drive device, and / or at least two second membranes that are configured to be excited by the second oscillation at the second frequency by means of the first drive device. Alternatively or additionally, the device can have at least two third membranes that are configured to be excited by the third oscillation at the third frequency by means of the drive device, and / or at least two fourth membranes that are configured to be excited by the fourth oscillation at the fourth frequency by means of the second drive device. This makes it possible to provide an efficient device that is suitable, for example, for generating high pump or sound power levels and / or for sufficient fluid compensation.The first and second membranes can, for example, be arranged alternately next to one another in order to optimally utilize the dynamic relative vibration behavior of the first and second membranes. The third and fourth membranes can, for example, be arranged alternately next to one another in order to optimally utilize the dynamic relative vibration behavior of the third and fourth membranes.

[0039] According to a further embodiment, two second membranes can be mechanically coupled to a first membrane arranged between the two second membranes, wherein the second membranes and the first membrane are configured for excitation by a superimposed drive signal from drive elements of the drive device assigned to the second membranes. This forms a rocker structure with which an efficient device can be provided. The second membranes can be designed to be excited at a frequency approximately twice as high as the first membrane; for example, through suitable geometric design and dimensioning, the second membranes can have a natural frequency twice as high as that of the first membrane.Alternatively or additionally, according to a further embodiment, two fourth membranes can be mechanically coupled to a third membrane arranged between the two fourth membranes, wherein the fourth membranes and the third membrane are configured to be excited by a superimposed drive signal from drive elements of the drive device assigned to the fourth membranes. This forms a rocker structure with which an efficient device can be provided. The fourth membranes can be designed to be excited at a frequency approximately twice as high as the third membrane; for example, through suitable geometric design and dimensioning, the fourth membranes can have a natural frequency twice as high as that of the third membrane.

[0040] The invention further relates to a microelectromechanical loudspeaker comprising a microelectromechanical device according to one of the above-described features, wherein the displacement unit of the microelectromechanical device is configured to generate a sound signal, and a signal processing unit for applying and processing signals from the microelectromechanical device. Due to the above-described design of the device, the proposed microelectromechanical loudspeaker enables efficient and powerful sound pressure generation despite the very small dimensions of the device, since the sound energy and sound frequency of the generated fluid flow do not depend directly on the excitation frequency at the membranes, but rather on their relative vibration behavior to one another, which can be easily and dynamically controlled.In particular, the proposed loudspeaker can also generate low-frequency sound signals with high sound power. Accordingly, an efficient and powerful use of the loudspeaker as a bass loudspeaker is conceivable, for example. The sound signal generated by the first and second diaphragms can be regarded as quasi-beat, since no actual beat is generated in the narrow acoustic sense, but is simulated by the interaction of the diaphragm vibrations. By providing a pressure chamber with a predominantly closed chamber boundary, it is possible to generate a pressurized fluid flow so that a desired minimum sound pressure can be generated with the loudspeaker. The chamber boundary can act as a counterpressure surface for the fluid volume to be compressed, thus enabling effective pressure buildup.According to one possible embodiment, the microelectromechanical loudspeaker can be an in-ear headset that can be worn in a human ear. In this case, the displacement unit can be oriented toward an auditory canal, and the fluid equalization device can be oriented toward an atmospheric environment and / or a housing accommodating the device and the signal processing unit. It can be advantageous if the microelectromechanical device has at least two pressure chambers, each with a displacement unit and a fluid equalization device, and if the displacement units of the at least two pressure chambers are each configured to generate a pressurized fluid flow with opposing flow directions. This enables fluid exchange and / or pressure equalization between the auditory canal and the atmospheric environment.In simple terms, a first displacement unit of a first pressure chamber can be configured to emit a sound signal toward the ear canal, and a second displacement unit of a second pressure chamber can be configured to return fluid from the ear canal to the atmospheric environment. The signal processing unit can be implemented, for example, as an ASIC.

[0041] The invention further relates to a method for operating a microelectromechanical device for generating a pressurised fluid flow with a pressure chamber enclosing a chamber volume and a displacement unit arranged on the pressure chamber for compressing and conveying a fluid volume located in the chamber volume, wherein the displacement unit has a first membrane and a second membrane which are movable relative to each other,The pressure chamber has a predominantly closed chamber boundary and a fluid equalization device for exchanging fluid between the chamber volume and the surroundings of the pressure chamber. To generate the pressurized fluid flow, the first membrane is excited to a first oscillation at a first frequency, and the second membrane is excited to a second oscillation at a second frequency deviating from the first frequency, by means of a first drive device of the microelectromechanical device. The proposed method can also achieve the above-described advantages of efficient and powerful fluid flow generation with a desired minimum pressure. The microelectromechanical device can be designed, in particular, according to one of the above-described features.

[0042] According to one embodiment, the fluid compensation device can have an active valve, and the active valve can be actuated in coordination with the excitation of the first membrane and the second membrane. This can enable a coordinated excitation of the first and second membranes of the displacement unit and the active valve of the fluid compensation device. In particular, a temporary formation of a fluid compensation opening by means of the active valve can be temporally coordinated with a temporary formation of a fluid opening by means of the displacement unit. This can ensure the maintenance of a substantially constant fluid volume in the pressure chamber at all times during operation of the microelectromechanical device. Furthermore, an at least approximately continuous fluid flow generation can be achieved.

[0043] According to one embodiment, the fluid compensation device can comprise a third membrane and a fourth membrane that are movable relative to one another, and the third membrane and the fourth membrane can be excited by a second drive device of the microelectromechanical device. This can provide a specifically actuatable fluid compensation device and enable precisely adjustable fluid supply or fluid discharge to maintain a substantially constant fluid volume in the chamber volume. In particular, a temporary fluid compensation opening can be formed by the relatively movable membranes to enable fluid exchange.

[0044] According to one embodiment, the third membrane can be excited to a third oscillation at a third frequency and the fourth membrane to a fourth oscillation at a fourth frequency different from the third frequency by means of the second drive device. By exciting the third and fourth membranes at different frequencies, a temporary fluid equalization opening, which can be formed periodically, for example, can be specifically created between the third and fourth membranes in order to enable fluid exchange between the chamber volume and the environment of the pressure chamber. Such a temporary formation of the fluid equalization opening can, in particular, be temporally coordinated with a temporary formation of a fluid opening by means of the displacement unit. According to one possible embodiment, the third frequency of the third membrane can correspond to the first frequency of the first membrane.In addition, the fourth frequency of the fourth membrane may correspond to the second frequency of the second membrane.

[0045] According to a further development, the second frequency of the second oscillation can be substantially twice as high as the first frequency of the first oscillation and / or the fourth frequency of the fourth oscillation can be substantially twice as high as the third frequency of the third oscillation. For example, the second frequency can correspond substantially to twice the first frequency plus or minus a maximum of 25 percent of the first frequency. The second membrane can therefore go through approximately two periods during one period of the first membrane, i.e. oscillate at least approximately twice as fast as the first membrane. This makes it possible to achieve a favorable phase relationship between the first and second membranes, which enables effective fluid flow generation. For example, the fourth frequency can correspond substantially to twice the third frequency plus or minus a maximum of 25 percent of the third frequency.The fourth membrane can therefore oscillate for approximately two periods during one period of the third membrane, meaning it can oscillate at least approximately twice as fast as the third membrane. This allows a favorable phase relationship between the third and fourth membranes to be achieved, enabling effective fluid balance.

[0046] According to one embodiment, the first frequency, the second frequency, the third frequency, and / or the fourth frequency can be at least 20 kHz. This allows the membranes to be excited outside the humanly audible frequency range, enabling operation of the device without disruptive harmonics. It is conceivable, for example, to select frequency ranges from 50 to 400 kHz for the first, second, third, and / or fourth frequency. This allows very small and rigid microelectromechanical structures to be used for the device. This results in high efficiency and space utilization of the microelectromechanical device.

[0047] According to one embodiment, the excitation of the first membrane and the excitation of the third membrane can be carried out such that the first oscillation and the third oscillation have a substantially constant phase shift, and the excitation of the second membrane and the excitation of the fourth membrane can be carried out such that the second oscillation and the fourth oscillation are substantially in phase. This allows a favorable phase relationship to be established between the membranes, enabling efficient fluid flow generation and a temporally coordinated fluid compensation.For example, this can enable a comparatively small fluid equalization opening to be formed by the third and fourth membranes of the fluid equalization device during the formation of a maximum fluid opening at the displacement unit by means of the first and second membranes, so that there is essentially negligible leakage into a base ambient volume, such as an atmospheric environment of the device. Furthermore, a maximum fluid equalization opening can be formed by the third and fourth membranes of the fluid equalization device when a pumping operation of the displacement unit is completed and the first and second membranes swing back to their initial position.

[0048] According to one embodiment, the microelectromechanical device can have at least two pressure chambers, each with a displacement unit and a fluid equalization device, and a pressurized fluid flow with opposing flow directions can be generated by the displacement units of the at least two pressure chambers. This allows, in particular, a fluid pressure signal, in particular a sound pressure signal, to be generated complementarily to one another, and, on the other hand, fluid exchange and / or pressure equalization between two separate ambient volumes of the microelectromechanical device can be enabled. Put simply, a pumping process into a target volume can be carried out by a first displacement unit of a first pressure chamber, and a pumping process out of the target volume can be carried out by a second displacement unit of a second pressure chamber.

[0049] According to one embodiment, the first, second, third, and / or fourth membranes of the at least two pressure chambers can be simultaneously excited in the same direction. This allows parallel operation of the pressure chambers of the device, thus increasing the performance of the device and, for example, providing a stronger fluid pressure signal. Simultaneous, rectified excitation can be understood to mean that the first membrane of the first pressure chamber is simultaneously deflected in the same direction as the first membrane of the second pressure chamber, the second membrane of the second pressure chamber is simultaneously deflected in the same direction as the second membrane of the second pressure chamber, and so on.

[0050] According to one embodiment, the first, second, third, and / or fourth membranes of the at least two pressure chambers can be excited simultaneously or sequentially in opposite directions. This enables counter-rotating operation of the pressure chambers of the device, so that, for example, a pumping-in process and a pumping-out process can be implemented in a coordinated manner using the device, as described above.A simultaneous or successive opposite excitation can be understood here as meaning that the first membrane of the first pressure chamber is deflected in a first direction and the first membrane of the second pressure chamber is deflected at the same time or subsequently in a second direction opposite to the first direction, the second membrane of the first pressure chamber is deflected in a first direction and the second membrane of the second pressure chamber is deflected at the same time or subsequently in a second direction opposite to the first direction, et cetera.The opposite deflections can be realized, for example, by means of bidirectionally effective drive elements with corresponding counter-rotating control or by means of unidirectional drive elements arranged alternately on the membranes, for example by arranging a drive element on the first membrane of the first pressure chamber on a side of the first membrane facing the chamber volume and by arranging a drive element on the first membrane of the second pressure chamber on a side of the first membrane facing away from the chamber volume.

[0051] According to one embodiment, a fluid flow direction, a fluid flow rate, and / or a differential pressure of the pressurized fluid flow can be controlled by controlling the phases, frequencies, and / or amplitudes of the oscillations of the first, second, third, and / or fourth membranes. Accordingly, the properties of the generated fluid flow can be specifically influenced by targeted, individual excitation of the membranes with different oscillation characteristics. In particular, precise fine adjustment of the desired fluid flow can be achieved using continuously variable drive signals for the membranes. For example, it can be provided that a phase change is controlled in such a way that, starting from two identical oscillations, a phase shift of +90° or -90° or of +180° or -180° is achieved between at least two of the first, second, third, and fourth membranes.

[0052] According to one embodiment, the phase relationship between the first vibration of the first membrane and the second vibration of the second membrane can be varied to generate a sound signal. As a result, the generated fluid flow can be varied and used to generate a sound signal. This can enable advantageous use of the microelectromechanical device in a loudspeaker. The first frequency of the first vibration and the second frequency of the second vibration can, in particular, deviate from a frequency of the generated fluid flow signals, since the generation of fluid flow depends on the vibration behavior of the membranes and not directly on the excitation frequency. Due to this frequency decoupling, according to the proposed method, low-frequency sound signals with high sound power, for example, can be generated despite the very small dimensions of the microelectromechanical device.Accordingly, for example, an efficient use of the device as a bass loudspeaker is conceivable, whereby, when applying the proposed method, high sound energy can be generated at low sound frequencies. The sound signal generated by the first and second membranes can be regarded as quasi-beat, since no actual beat is generated in the narrow acoustic sense, but is simulated by the interplay of the membrane vibrations. In principle, it can be advantageous for a start-up phase of the operation of the device in a loudspeaker to initially maintain a constant phase relationship until the device has reached the desired operating pump power, and then to begin varying the phase relationship to generate acoustic signals.

[0053] According to one embodiment, a sound frequency of the sound signal can be controlled via a frequency difference between the first frequency of the first oscillation and the second frequency of the second oscillation, and / or a sound intensity of the sound signal can be controlled via the amplitude of the first oscillation and / or the second oscillation. Accordingly, for example, when the device is used in a loudspeaker, a frequency and / or volume of the sound signal can be continuously adjusted by appropriately influencing the relative oscillation behavior of the membranes to one another, for example, via their relative phase relationship.

[0054] According to a further embodiment, the excitation of the third membrane and the fourth membrane by means of the second drive device can be coordinated with the excitation of the first membrane and the second membrane by means of the first drive device. This allows fluid compensation to be achieved by means of the fluid compensation device, which is tailored to the fluid flow generation.

[0055] According to a further embodiment, the first membrane and the second membrane can each be excited by a drive element of the drive device. Furthermore, it is conceivable that the third membrane and the fourth membrane are each excited by a drive element of the drive device.

[0056] According to a further embodiment, the first membrane and the second membrane can be excited by a common drive element, wherein the first membrane and the second membrane can be mechanically coupled to one another. For example, the first membrane and the second membrane can be excited by a superimposed drive signal from a drive element assigned to the first membrane or the second membrane. Furthermore, it is conceivable for the third membrane and the fourth membrane to be excited by a common drive element, wherein the third membrane and the fourth membrane can be mechanically coupled to one another. For example, the third membrane and the fourth membrane can be excited by a superimposed drive signal from a drive element assigned to the third membrane or the fourth membrane.

[0057] In general, in the context of this application, the words “a / an”, unless expressly defined otherwise, are not to be understood as a number, but as an indefinite article with the literal meaning of “at least one”.

[0058] The invention permits various embodiments and is explained in more detail below using exemplary embodiments and the accompanying drawings. They show schematically:

[0059] Fig. 1 - a basic principle of a microelectromechanical device according to a first embodiment in a side view;

[0060] Fig. 2 - a basic principle of a microelectromechanical device according to a second embodiment in a side view;

[0061] Fig. 3-7 - a schematic flow chart of a method for operating the microelectromechanical device according to the second embodiment based on an oscillation cycle;

[0062] Fig. 8 - a basic principle of a microelectromechanical device according to a third embodiment in a side view;

[0063] Fig. 9 - a basic principle of a microelectromechanical device according to a fourth embodiment in a side view;

[0064] Fig. 10 - a basic principle of a microelectromechanical device according to a fifth embodiment in a side view;

[0065] Fig. 11 - a basic principle of a microelectromechanical device according to a sixth embodiment in a side view;

[0066] Fig. 12 - a schematic diagram of a microelectromechanical loudspeaker with a microelectromechanical device;

[0067] Fig. 13 - a simplified flow diagram of a method for operating the microelectromechanical device;

[0068] Fig. 14 - a simulation diagram illustrating a fluid pressure that can be generated with the microelectromechanical device;

[0069] Fig. 15 - a simulation diagram illustrating a sound signal that can be generated with the microelectromechanical device.

[0070] Fig. 1 shows a simplified schematic diagram of a microelectromechanical device 1 for generating a pressurized fluid flow 2 according to a first embodiment. The device 1 has a pressure chamber 4 that encloses a chamber volume 3. A fluid volume (not shown in detail) is located in the chamber volume 3, which can be, for example, an air volume. A displacement unit 5 is arranged on the pressure chamber 4 for compressing and conveying the fluid volume located in the chamber volume 3 into a target volume 9. The displacement unit 5 has a first membrane 5a and a second membrane 5b, which are movable relative to one another and can form a fluid opening 13 between them.

[0071] The microelectromechanical device 1 further comprises a first drive device 10. According to the exemplary embodiment shown, the first drive device 10 has a drive element 10a for each of the first membrane 5a and the second membrane 5b. This means that a drive element 10a of the first drive device 10 is arranged on each of the first membrane 5a and the second membrane 5b and is configured to actuate the respective membrane 5a, 5b. The drive elements 10a can be, for example, piezoelectric drive elements. According to the embodiment shown, the drive elements 10a of the first drive device 10 are each arranged on a side of the first and second membranes 5a, 5b facing away from the chamber volume 3.The drive elements 10a of the first drive device 10 can be configured to deflect the first membrane 5a, in particular alternately in opposite directions, and to deflect the second membrane 5b, in particular alternately in opposite directions. The first drive device 10 is configured to excite the first membrane 5a to a first oscillation at a first frequency f1 and the second membrane 5b to a second oscillation at a second frequency f2, wherein the second frequency f2 deviates from the first frequency f1. The second membrane 5b can have a natural frequency that is essentially twice as high as the natural frequency of the first membrane 5a.

[0072] As can be seen in Fig. 1, the pressure chamber 4 has a predominantly closed chamber boundary 6 with a rigid chamber wall 6a. In addition, the pressure chamber 4 has a fluid compensation device 7 for the exchange of fluid between the chamber volume 3 and an environment 8 of the pressure chamber 4. With the microelectromechanical device 1 shown as an example in Figs. 1 to 11, it is possible to deliberately use different phase positions of the vibrating membranes 5a, 5b to generate a fluid flow 2 by oscillating the first and second membranes 5a, 5b at different frequencies f 1 , f 2 . The predominantly closed chamber boundary 6 makes it possible to achieve a desired minimum fluid pressure, since the chamber boundary 6 acts as a counterpressure surface for the fluid volume to be pumped, thereby enabling effective pressure build-up.

[0073] According to the embodiment shown in Fig. 1, the fluid compensation device 7 has a fluid channel 7', so that a permanent fluidic connection exists between the chamber volume 3 and the environment 8 and a simply constructed fluid compensation device 7 with a permanent fluid compensation opening 14 is provided. The environment 8 can in particular form a basic environmental volume such as an atmospheric environment. A fluid compensation flow 11 can flow through the fluid channel 7' between the environment 8 and the chamber volume 3. In particular, after a certain portion of the fluid volume located in the chamber volume 3 has been displaced by the displacement unit 5, a compensation fluid volume can flow into the chamber volume 3 via the fluid channel 7'.

[0074] As can be seen in Fig. 1, the displacement unit 5 is arranged on a first side of the pressure chamber 4 and the fluid compensation device is arranged on a second side of the pressure chamber 4 opposite the first side, so that direct fluid flow paths are present and a compact device 1 can be provided.

[0075] Fig. 2 shows a simplified schematic diagram of a microelectromechanical device 1 for generating a pressurized fluid flow 2 according to a second embodiment. The pressure chamber 4 and the displacement unit 5 essentially correspond in their basic structure and mode of operation to the pressure chamber 4 and the displacement unit 5 of the microelectromechanical device 1 according to the first embodiment. As can be seen from Fig. 2, the pressure chamber 4 of the microelectromechanical device 1 according to the second embodiment has a fluid compensation device 7, which is designed as an active valve 7'".With such an active valve 7'", a temporary fluidic connection can be formed between the chamber volume 3 and the environment 8, so that a targeted control of the fluid compensation is possible and any pressure losses can be minimized via a permanent fluid compensation opening 14 during a compression process by the displacement unit 5.

[0076] According to the exemplary embodiment shown, the fluid compensation device 7 has a third membrane 7a and a fourth membrane 7b, which are movable relative to one another. This makes it possible to provide a fluid compensation device 7 that can be actuated in a targeted manner. In addition, the microelectromechanical device 1 has a second drive device 12 for exciting the third membrane 7a and the fourth membrane 7b. According to the exemplary embodiment shown, the second drive device 12 has a drive element 12a for each of the third membrane 7a and the fourth membrane 7b. This means that a drive element 12a of the second drive device 12 is arranged on each of the third membrane 7a and the fourth membrane 7b and is configured to actuate the respective membrane 7a, 7b. The drive elements 12a can be piezoelectric drive elements, for example.According to the embodiment shown, the drive elements 10a of the first drive device 10 and the drive elements 12a of the second drive device 12 are each arranged on a side of the membranes 5a, 5b, 7a, 7b facing away from the chamber volume 3. The drive elements 10a of the first drive device 10 can be configured to deflect the first membrane 5a, in particular alternately in opposite directions, and to deflect the second membrane 5b, in particular alternately in opposite directions. The drive elements 12a of the second drive device 12 can be configured to deflect the third membrane 7a, in particular alternately in opposite directions, and to deflect the fourth membrane 7b, in particular alternately in opposite directions. As can be seen in Fig. 2, the second.

[0077] Drive device 12 is configured to excite the third membrane 7a to a third oscillation at a third frequency f3 and to excite the fourth membrane 7b to a fourth oscillation at a fourth frequency f4 that differs from the third frequency f3. The third frequency f3 of the third membrane 7a can correspond to the first frequency f1 of the first membrane 5a, and the fourth frequency f4 of the fourth membrane 7b can correspond to the second frequency f2 of the second membrane 5b. This makes it possible to specifically create a periodically formable temporary fluid equalization opening 14 between the third membrane 7a and the fourth membrane 7b. The second membrane 5b can have a natural frequency that is essentially twice as high as the natural frequency of the first membrane 5a. In addition, the fourth membrane 7b can have a natural frequency that is essentially twice as high as the natural frequency of the third membrane 7a.

[0078] The first membrane 5a and the third membrane 7a can be designed essentially identically. Furthermore, the second membrane 5b and the fourth membrane 7b can be designed essentially identically. An identical design can in particular refer to a comparable shape and dimensions of the respective membranes 5a, 5b, 7a, 7b. This makes it conceivable that the displacement unit 5 and the fluid compensation device 7 can be operated with interchangeable functionality. The first drive device 10 and the second drive device 12 are designed according to the second embodiment for a coordinated excitation of the first, second, third and fourth membranes 5a, 5b, 7a, 7b. As can be seen in Fig. 1, the displacement unit 5 is arranged on a first side of the pressure chamber 4 and the fluid compensation device 7 is arranged on a second side of the pressure chamber 4 opposite the first side.

[0079] 3 to 7, a method 100 for operating the microelectromechanical device 1 according to the second embodiment will be explained below with reference to an oscillation cycle, as shown schematically in FIG. 13. A period of the first oscillation of the first membrane 5a, which corresponds to a complete oscillation cycle, is denoted by T hereinafter. According to the exemplary embodiment shown, the second membrane 5b and the fourth membrane 7b are excited with a second frequency f2 and a fourth frequency f4 corresponding to the second frequency f2, which frequency essentially corresponds to twice a first frequency f1 and a third frequency f3 corresponding to the first frequency f2, with which the first membrane 5a and the third membrane 7a are excited. The third membrane 7a is excited with a relative phase shift of TT TO the first membrane 5a.The second membrane 5b and the fourth membrane 7b are excited with a relative phase shift of 14 TT to the first membrane 5a.

[0080] In Fig. 3, which depicts a state of the device 1 at a time 0, an excitation of the membranes 5a, 5b, 7a, 7b begins, by which the second membrane 5b is deflected toward the chamber volume 3 and the fourth membrane 7b toward the environment 8 as shown in Fig. 3. At the time 0 shown in Fig. 2, no pressure buildup and no fluid flow generation takes place.

[0081] Fig. 4 shows a state of the device 1 at 14 T. Here, the first membrane 5a, the third membrane 7a and the fourth membrane 7b are deflected in the direction of the chamber volume 3, so that the volume of the chamber volume 3 is reduced and a pressure build-up is caused. The second membrane 5b is deflected in the direction of the target volume 9, so that a fluid opening 13 is formed. This can generate a pressurized fluid flow 2 into the adjacent target volume 9. Since the third membrane 7a and the fourth membrane 7b are deflected in the same direction in the direction of the chamber volume 3, a resulting opening between the third membrane 7a and the fourth membrane 7b according to the state shown can be regarded as a negligible leakage opening into the environment 8.

[0082] Fig. 5 shows a state of the device 1 at 14 T. The first membrane 5a and the third membrane 7a are returned to their initial position. The second membrane 5b is deflected toward the chamber volume 3, and the fourth membrane 7b is deflected toward the environment 8. The resulting openings between the first membrane 5a and the second membrane 5b, as well as between the third membrane 7a and the fourth membrane 7b, can be considered negligible leakage openings, so that no significant fluid exchange with the target volume 9 and the environment 8 and, accordingly, no significant change in the fluid volume in the chamber volume 3 occurs.

[0083] Fig. 6 shows a state of the device 1 at % T. The first membrane 5a and the second membrane 5b are deflected in the direction of the target volume 9, with a resulting opening between the first membrane 5a and the second membrane 5b forming a negligible leakage opening into the target volume 9. The third membrane 7a is deflected into the environment 8 and the fourth membrane 7b is deflected in the direction of the chamber volume 3, whereby a fluid compensation opening 14 is formed between the third membrane 7a and the fourth membrane 7b. As a result, a fluid compensation flow 11 can flow from the environment 8 into the chamber volume 3, so that the fluid volume in the chamber volume 3 is increased again after being reduced by the generated fluid flow 2 by means of the displacement unit 5 and a new displacement process can take place with a sufficient fluid pressure.

[0084] In Fig. 7, a complete period T has been reached, and the membranes 5a, 5b, 7a, 7b are again in the starting position shown in Fig. 3, so that the fluid flow generation process and fluid equalization can take place again as described above. As can be easily understood from the method 100 described above, a reversal of the flow direction that is easy to implement in terms of control technology can be achieved, for example, by adapted excitation of the first membrane 5a, the second membrane 5b, the third membrane 7a, and the fourth membrane 7b, so that the displacement unit 5 and the fluid equalization device 7 can be considered bidirectionally operable.

[0085] Fig. 8 shows a simplified schematic diagram of a microelectromechanical device 1 for generating a pressurized fluid flow 2 according to a third embodiment. The pressure chamber 4, the displacer unit 5, and the fluid compensation device 7 essentially correspond in their basic structure and mode of operation to the aforementioned components of the microelectromechanical device 1 according to the second embodiment. As can be seen from Fig. 8, according to the third embodiment, the displacer unit 5 and the fluid compensation device 7 are arranged on the same side of the pressure chamber 4, i.e., next to one another instead of opposite one another as in the other embodiments shown. This enables simplified manufacture of the device 1, since the displacer unit 5 and the fluid compensation device 7 can be manufactured in common process steps.

[0086] Fig. 9 shows a simplified schematic diagram of a microelectromechanical device 1 for generating a pressurized fluid flow 2 according to a fourth embodiment. The pressure chamber 4, the displacer unit 5, and the fluid compensation device 7 essentially correspond in their basic structure and mode of operation to the aforementioned components of the microelectromechanical device 1 according to the second embodiment. As can be seen from Fig. 9, the microelectromechanical device according to the fourth embodiment has two pressure chambers 4, each with a displacer unit 5 and a fluid compensation device 7. According to the embodiment shown, the displacer units 5 of the pressure chambers 4 are each configured to generate a pressurized fluid flow 2 with synchronized flow directions, thereby enabling parallel operation of the pressure chambers 4.In this way, an amplified fluid pressure signal can be introduced into the target volume 9 with the fluid flows 2.

[0087] Fig. 10 shows a simplified schematic diagram of a microelectromechanical device 1 for generating a pressurized fluid flow 2 according to a fifth embodiment. The pressure chambers 4, the displacement units 5, and the fluid compensation devices 7 essentially correspond in their basic structure and mode of operation to the aforementioned components of the microelectromechanical device 1 according to the fourth embodiment. As can be seen from Fig. 10, the displacement units 5 of the pressure chambers 4 are each configured to generate a pressurized fluid flow 2 with opposing flow directions. This enables a pumping process into the target volume 9 and a complementary pumping process into the environment 8.If it is sufficient for the desired application to specify fixed flow directions of the generated fluid streams 2 for the pressure chambers 4, this embodiment can be easily implemented using unidirectionally acting drive elements 10a, 12a. As schematically illustrated in Fig. 10, the drive elements 10a, 12a can be arranged alternately, depending on a predetermined main deflection direction of the membranes 5a, 5b, 7a, 7b, on a side of the membranes 5a, 5b, 7a, 7b facing toward the chamber volume 3 and on a side of the membranes 5a, 5b, 7a, 7b facing away from the chamber volume 3. For example, as shown in Fig. 10, the drive elements 10a, 12a of the first membrane 5a and the fourth membrane 7b can be arranged on a membrane side facing the chamber volume 3 in a first pressure chamber 4, while the drive elements 10a, 12a of the second membrane 5b and the third membrane 7a are arranged on a membrane side facing away from the chamber volume 3.Furthermore, as shown in Fig. 10, the drive elements 10a, 12a of the first membrane 5a and the fourth membrane 7b can be arranged on a membrane side facing away from the chamber volume 3 in a second pressure chamber 4, while the drive elements 10a, 12a of the second membrane 5b and the third membrane 7a are arranged on a membrane side facing the chamber volume 3.

[0088] Fig. 11 shows a simplified schematic diagram of a microelectromechanical device 1 for generating a pressurized fluid flow 2 according to a sixth embodiment. The pressure chambers 4 and the displacement units 5 essentially correspond in their basic structure and mode of operation to the aforementioned components of the microelectromechanical device 1 according to the fifth embodiment. As can be seen from Fig. 11, the displacement units 5 of the pressure chambers 4 are each configured to generate a pressurized fluid flow 2 with opposing flow directions. According to the illustrated embodiment, the drive elements 10a of the first drive device 10 are again arranged on a side of the first and second membranes 5a, 5b facing away from the chamber volume 3. As shown in Fig.11, the fluid equalization devices 7 of the microelectromechanical device 1 according to the sixth embodiment have a passive valve 7". The passive valves 7" each form a direction-dependent flow valve which, in the pressure chamber 4 shown on the left in Fig. 11, promotes fluid entry from the environment 8 into the chamber volume 3 through a conical channel shape tapering in the direction of the chamber volume 3, and in the pressure chamber 4 shown on the right in Fig. 11, promotes fluid exit from the chamber volume 3 into the environment 8 through a channel shape conically widening in the direction of the chamber volume 3. This makes it possible to achieve improved fluid extraction from the environment 8 and improved fluid discharge into the environment 8 compared to a straight through-channel, without having to provide active control or moving parts on the fluid equalization device 7.The passive valves 7" each form a permanent fluidic connection between the chamber volume 3 and the environment 8 and provide a permanent fluid equalization opening 14.

[0089] Fig. 12 shows a simplified schematic diagram of a microelectromechanical loudspeaker 20. The loudspeaker 20 has a microelectromechanical device 1, which can be configured according to one of the features described above, in particular according to one of the embodiments described above. The displacement unit 5 or the displacement units 5 of the microelectromechanical device 1 are configured to generate a sound signal. The loudspeaker 20 also has a signal processing unit 21 for applying and processing signals from the microelectromechanical device 1. The signal processing unit 21, which can be implemented, for example, as an ASIC, is connected to the microelectromechanical device 1 via a suitable signal connection 22. The loudspeaker 20 can, in particular, be designed as an in-ear headphone that can be worn in a human ear.

[0090] Fig. 13 shows a simplified schematic diagram of a method 100 for operating a microelectromechanical device 1 for generating a pressurized fluid flow 2. The microelectromechanical device 1 can be designed according to one of the features described above, in particular according to one of the embodiments described above.In a step 110, a microelectromechanical device 1 is provided with a pressure chamber 4 enclosing a chamber volume 3 and a displacement unit 5 arranged on the pressure chamber 4 for compressing and conveying a fluid volume located in the chamber volume 3, wherein the displacement unit 5 has a first membrane 5a and a second membrane 5b that are movable relative to one another, wherein the pressure chamber 4 has a predominantly closed chamber boundary 6 and a fluid compensation device 7 for exchanging fluid between the chamber volume 3 and an environment 8 of the pressure chamber 4. In addition, the microelectromechanical device 1 has a first drive device 10.To generate a pressurized fluid flow 2, it is provided that, according to a sub-step 120, the first membrane 5a is excited to a first oscillation with a first frequency f1 and, in a parallel sub-step 130, the second membrane 5b is excited to a second oscillation with a second frequency f2 deviating from the first frequency f1 by means of the first drive device 10 of the microelectromechanical device 1.

[0091] Here, the fluid compensation device 7 can have an active valve 7'", as shown in Figs. 2 to 10, which is actuated in coordination with the excitation of the first membrane 5a and the second membrane 5b.

[0092] In particular, the fluid compensation device 7, as shown in Figs. 2 to 10, can have a third membrane 7a and a fourth membrane 7b, which are movable relative to one another, wherein the third membrane 7a and the fourth membrane 7b are excited by means of a second drive device 12 of the microelectromechanical device 1. The third membrane 7a can be excited to a third oscillation with a third frequency f3 and the fourth membrane 7b can be excited to a fourth oscillation with a fourth frequency f4 that differs from the third frequency f3 by means of the second drive device 12. According to one possible embodiment, the second frequency f2 of the second oscillation can be substantially twice as high as the first frequency f1 of the first oscillation and / or the fourth frequency f4 of the fourth oscillation can be substantially twice as high as the third frequency f3 of the third oscillation.The first frequency f1, the second frequency f2, the third frequency f3 and / or the fourth frequency f4 may be at least 20 kHz.

[0093] As illustrated in Figs. 3 to 7, the excitation of the first membrane 5a and the excitation of the third membrane 7a can be performed such that the first oscillation and the third oscillation have a substantially constant phase shift. Furthermore, the excitation of the second membrane 5b and the fourth membrane 7b can be performed such that the second oscillation and the fourth oscillation are substantially in phase.

[0094] In this way, a favorable phase relationship can be established between the membranes 5a, 5b, 7a, 7b for the successive formation of a fluid opening 13 and a fluid compensation opening 14.

[0095] As indicated in Fig. 9, the first, second, third and / or fourth membranes 5a, 5b, 7a, 7b of the at least two pressure chambers 4 can be excited simultaneously in the same direction.

[0096] As illustrated in Figs. 10 and 11, the microelectromechanical device 1 can have at least two pressure chambers 4, each with a displacement unit 5 and a fluid compensation device 7, and a pressurized fluid flow 2 with opposing flow directions can be generated by the displacement units 5 of the at least two pressure chambers 4. For this purpose, for example, the first, second, third, and / or fourth membranes 5a, 5b, 7a, 7b of the at least two pressure chambers 4 can be excited simultaneously or sequentially in opposite directions.

[0097] Within the scope of the method 100 for operating the microelectromechanical device 1, it is conceivable to control a fluid flow direction, a fluid flow quantity and / or a differential pressure of the pressurized fluid flow 2 by controlling the phases, the frequencies f1, f2, f3, f4 and / or the amplitudes of the oscillations of the first, second, third and / or fourth membrane 5a, 5b, 7a, 7b. Furthermore, it is conceivable to vary the phase relationship between the first oscillation of the first membrane 5a and the second oscillation of the second membrane 5b in order to generate a sound signal. In this case, for example, a sound frequency of the sound signal can be controlled via a frequency difference between the first frequency f1 of the first oscillation and the second frequency f2 of the second oscillation and / or a sound intensity of the sound signal can be controlled via the amplitude of the first oscillation and / or the second oscillation.

[0098] Fig. 14 shows a simulation diagram illustrating a fluid pressure P that can be generated with the microelectromechanical device 1 over time t according to a non-limiting exemplary embodiment. For this exemplary embodiment, a microelectromechanical device 1 according to the second embodiment was selected, in which the second frequency f2 of the oscillation of the second membrane 5b is substantially twice as high as the first frequency f1 of the oscillation of the first membrane 5a. The third frequency f3 of the oscillation of the third membrane 7a can substantially correspond to the first frequency f1, and the fourth frequency f4 of the oscillation of the fourth membrane 7b can substantially correspond to the second frequency f2.With suitable dimensioning of the membranes 5a, 5b, 7a, 7b and with suitable selection of the frequencies f1, f2, f3, f4, it is possible, as shown, to achieve a fluid pressure above a pressure of 200 Pa, which corresponds to a sound pressure of 121 dB for a sinusoidal sound wave with a frequency of 1 kHz.

[0099] Fig. 15 shows a simulation diagram illustrating a sound signal that can be generated with the microelectromechanical device 1 by superimposing the generated fluid flow Q and the fluid pressure P over time t. The flow direction reversal of the fluid flow 2 illustrated in the diagram can be achieved in particular by reversing the deflection direction of the membranes 5a, 5b, 7a, 7b or by reversing their phase relationship. By varying the phase relationship, different sound signals can be generated, as illustrated, for example, by the sinusoidal sound wave shown.

Claims

Claims 1. A microelectromechanical device (1) for generating a pressurized fluid flow (2) comprising a pressure chamber (4) enclosing a chamber volume (3) and a displacement unit (5) arranged on the pressure chamber (4) for compressing and conveying a fluid volume located in the chamber volume (3), wherein the displacement unit (5) has a first membrane (5a) and a second membrane (5b) that are movable relative to one another, wherein the microelectromechanical device (1) has a first drive device (10) configured to excite the first membrane (5a) to a first oscillation at a first frequency (f1) and to excite the second membrane (5b) to a second oscillation at a second frequency (f2) that differs from the first frequency (f1),and wherein the pressure chamber (4) has a predominantly closed chamber boundary (6) and a fluid compensation device (7) for exchanging fluid between the chamber volume (3) and an environment (8) of the pressure chamber (4).

2. Microelectromechanical device (1) according to claim 1, wherein the fluid compensation device (7) has a fluid channel (7').

3. Microelectromechanical device (1) according to claim 1 or 2, wherein the fluid compensation device (7) comprises a passive valve (7").

4. Microelectromechanical device (1) according to one of the preceding claims, wherein the fluid compensation device (7) comprises an active valve (7").

5. Microelectromechanical device (1) according to one of the preceding claims, wherein the fluid compensation device (7) comprises a third membrane (7a) and a fourth membrane (7b) which are movable relative to one another, and wherein the microelectromechanical device (1) has a second drive device (12) for exciting the third membrane (7a) and the fourth membrane (7b).

6. Microelectromechanical device (1) according to claim 5, wherein the second drive device (12) is configured to excite the third membrane (7a) to a third oscillation at a third frequency (f3) and to excite the fourth membrane (7b) to a fourth oscillation at a fourth frequency (f4) deviating from the third frequency (f3).

7. Microelectromechanical device (1) according to claim 5 or 6, wherein the first drive device (10) and the second drive device (12) are arranged for a coordinated excitation of the first, second, third and fourth membranes (5a, 5b, 7a, 7b).

8. Microelectromechanical device (1) according to one of claims 5 to 7, wherein the first membrane (5a) and the third membrane (7a) are formed substantially identically and / or wherein the second membrane (5b) and the fourth membrane (7b) are formed substantially identically.

9. Microelectromechanical device (1) according to one of the preceding claims, wherein the first drive device (10) has a drive element (10a) arranged on the first membrane (5a) and on the second membrane (5b) and / or wherein the second drive device (12) has a drive element (12a) arranged on the third membrane (7a) and on the fourth membrane (7b).

10. Microelectromechanical device (1) according to claim 9, wherein at least one drive element (10a, 12a) is arranged on a side of the first, second, third and / or fourth membrane (5a, 5b, 7a, 7b) facing the chamber volume (3) and at least one drive element (10a, 12a) is arranged on a side of the first, second, third and / or fourth membrane (5a, 5b, 7a, 7b) facing away from the chamber volume (3).

11. Microelectromechanical device (1) according to claim 9 or 10, wherein at least one drive element (10a, 12a) is configured to selectively deflect the first, second, third and / or fourth membrane (5a, 5b, 7a, 7b) in mutually opposite directions.

12. Microelectromechanical device (1) according to one of the preceding claims, wherein the second membrane (5b) has a natural frequency which is substantially twice as high as the natural frequency of the first membrane (5a) and / or wherein the fourth membrane (7b) has a natural frequency which is substantially twice as high as the natural frequency of the third membrane (7a).

13. Microelectromechanical device (1) according to one of the preceding claims, wherein the displacement unit (5) is arranged on a first side of the pressure chamber (4) and wherein the fluid compensation device (7) is arranged on a second side of the pressure chamber (4) opposite the first side.

14. Microelectromechanical device (1) according to one of claims 1 to 12, wherein the displacement unit (5) and the fluid compensation device (7) are arranged on the same side of the pressure chamber (4).

15. Microelectromechanical device (1) according to one of the preceding claims, wherein the microelectromechanical device (1) has at least two pressure chambers (4), each with a displacement unit (5) and a fluid compensation device (7).

16. Microelectromechanical device (1) according to claim 15, wherein the displacement units (5) of the at least two pressure chambers (4) are each configured to generate a pressurized fluid flow (2) with mutually opposite flow directions.

17. Microelectromechanical device (1) according to one of the preceding claims, wherein the displacement unit (5) and / or the fluid compensation device (7) are bidirectionally operable.

18. A microelectromechanical loudspeaker (20) comprising a microelectromechanical device (1) according to one of claims 1 to 17, wherein the displacement unit (5) of the microelectromechanical device (1) is configured to generate a sound signal, and a signal processing unit (21) for applying and processing signals of the microelectromechanical device (1).

19. Method (100) for operating a microelectromechanical device (1) for generating a pressurised fluid flow (2) with a pressure chamber (4) enclosing a chamber volume (3) and a displacement unit (5) arranged on the pressure chamber (4) for compressing and conveying a fluid volume located in the chamber volume (3), wherein the displacement unit (5) has a first membrane (5a) and a second membrane (5b) which are movable relative to one another,wherein the pressure chamber (4) has a predominantly closed chamber boundary (6) and a fluid compensation device (7) for exchanging fluid between the chamber volume (3) and an environment (8) of the pressure chamber (4), and wherein, in order to generate the pressurised fluid flow (2), the first membrane (5a) is excited to a first oscillation at a first frequency (f1) and the second membrane (5b) is excited to a second oscillation at a second frequency (f2) deviating from the first frequency (f1) by means of a first drive device (10) of the microelectromechanical device (1).

20. The method (100) according to claim 19, wherein the fluid compensation device (7) comprises an active valve (7"), and wherein the active valve (7") is actuated in coordination with the excitation of the first membrane (5a) and the second membrane (5b).

21. The method (100) according to claim 19 or 20, wherein the fluid compensation device (7) comprises a third membrane (7a) and a fourth membrane (7b) which are movable relative to one another, and wherein the third membrane (7a) and the fourth membrane (7b) are excited by means of a second drive device (12) of the microelectromechanical device (1).

22. Method (100) according to claim 21, wherein the third membrane (7a) is excited to a third oscillation with a third frequency (f3) and the fourth membrane (7b) is excited to a fourth oscillation with a fourth frequency (f4) deviating from the third frequency (f3) by means of the second drive device (12).

23. The method (100) according to any one of claims 19 to 22, wherein the second frequency (f2) of the second oscillation is substantially twice as high as the first frequency (f1) of the first oscillation and / or wherein the fourth frequency (f4) of the fourth oscillation is substantially twice as high as the third frequency (f3) of the third oscillation.

24. The method (100) according to any one of claims 19 to 23, wherein the first frequency (f1), the second frequency (f2), the third frequency (f3) and / or the fourth frequency (f4) are at least 20 kHz.

25. The method (100) according to any one of claims 21 to 22, wherein the excitation of the first membrane (5a) and the excitation of the third membrane (7a) are carried out such that the first oscillation and the third oscillation have a substantially constant phase shift, and wherein the excitation of the second membrane (5b) and the excitation of the fourth membrane (7b) are carried out such that the second oscillation and the fourth oscillation are substantially in phase.

26. Method (100) according to one of claims 19 to 25, wherein the microelectromechanical device (1) has at least two pressure chambers (4), each with a displacement unit (5) and a fluid compensation device (7), and wherein a pressurized fluid flow (2) with mutually opposite flow directions is generated by the displacement units (5) of the at least two pressure chambers (4).

27. Method (100) according to one of claims 19 to 26, wherein the first, second, third and / or fourth membranes (5a, 5b, 7a, 7b) of the at least two pressure chambers (4) are simultaneously excited in the same direction.

28. Method (100) according to one of claims 19 to 26, wherein the first, second, third and / or fourth membranes (5a, 5b, 7a, 7b) of the at least two pressure chambers (4) are excited simultaneously or successively in opposite directions.

29. Method (100) according to one of claims 19 to 28, wherein a fluid flow direction, a fluid flow quantity and / or a differential pressure of the pressurized fluid flow (2) are controlled by controlling the phases, the frequencies (f 1 , f2, f3, f4) and / or the amplitudes of the oscillations of the first, second, third and / or fourth membrane (5a, 5b, 7a, 7b).

30. The method (100) according to any one of claims 19 to 29, wherein the phase relationship between the first vibration of the first membrane (5a) and the second vibration of the second membrane (5b) is varied to generate a sound signal.

31. The method (100) according to claim 30, wherein a sound frequency of the sound signal is controlled via a frequency difference between the first frequency (f1) of the first oscillation and the second frequency (f2) of the second oscillation and / or wherein a sound intensity of the sound signal is controlled via the amplitude of the first oscillation and / or the second oscillation.

32. Method (100) according to one of claims 19 to 31, wherein the microelectromechanical device (1) is designed according to one of claims 1 to 17.

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