阅读说明：本技术 用于材料检测的一维超声换能器单元 (One-dimensional ultrasonic transducer unit for material detection ) 是由 R·奥根施泰因 T·凯因德尔 于 2019-05-23 设计创作，主要内容包括：一种用于材料监测的一维超声换能器单元(10)包括具有用于固定在表面处的固定器件的壳体(14)以及设计用于将具有在20kHz与400kHz之间的一致工作频率的声波耦合输出至气态介质中的至少三个分立的超声换能器(12)和设计用于单独控制每个超声换能器(12)的控制单元,其中,每两个彼此直接相邻的超声换能器(12)具有间距(A1),一维超声换能器单元(10)在每个超声换能器(12)上具有声通道(22),声通道分别具有恰好一个分配给超声换能器的输入开口(24)和输出开口(26),输出开口(26)沿直线布置,直接相邻的输出开口(26)的间距(A2)最高对应于气体介质中的全或半波长并且小于相应的间距(A1),输出开口(26)的面积与输入开口(24)的面积之商位于0.30与1.2之间,并且每个声通道(22)都具有至少对应于输入开口(24)的直径的长度。(A one-dimensional ultrasonic transducer unit (10) for material monitoring comprises a housing (14) with fixing means for fixing at a surface and at least three separate ultrasonic transducers (12) designed for coupling out sound waves with a uniform operating frequency of between 20kHz and 400kHz into a gaseous medium and a control unit designed for individually controlling each ultrasonic transducer (12), wherein each two ultrasonic transducers (12) directly adjacent to one another have a spacing (A1), the one-dimensional ultrasonic transducer unit (10) has on each ultrasonic transducer (12) a sound channel (22) which has exactly one input opening (24) and output opening (26) assigned to the ultrasonic transducer, respectively, the output openings (26) are arranged in a straight line, the spacing (A2) of the directly adjacent output openings (26) corresponds at most to a full or half wavelength in the gaseous medium and is smaller than the respective spacing (A1), the quotient of the area of the output opening (26) and the area of the input opening (24) lies between 0.30 and 1.2, and each acoustic channel (22) has a length which corresponds at least to the diameter of the input opening (24).)

1. A one-dimensional ultrasound transducer unit (10) for material detection, comprising a housing (14), at least three ultrasound transducers (12) and a control unit, wherein,

-the control unit is designed for individually steering each ultrasonic transducer (12),

-the housing (14) has a fixing means (11) for fixing on a surface,

-the control unit is arranged at least partially in the housing (14),

-the housing has a communication interface,

-each ultrasonic transducer (12) having a transducer housing (18), a piezoelectric body (18) arranged in the transducer housing (18), and an acoustic outcoupling layer (20) arranged at an open end of the transducer housing (18) for outcoupling into a gaseous medium, respectively, and each ultrasonic transducer being arranged at one fixed position in the housing (14),

each ultrasonic transducer (12) being designed for emitting and/or receiving sound waves having a uniform operating frequency,

-the operating frequency of the sound waves is in the range of 20kHz to 400kHz,

it is characterized in that the preparation method is characterized in that,

-every two ultrasound transducers (12) directly adjacent to each other have a spacing (A1) of at most 10cm or at most 5cm or at most 2cm in the housing (14) from the center of the sound-coupling-out layer (20) to the center of the sound-coupling-out layer (20),

-the one-dimensional ultrasound transducer unit (10) has an acoustic channel (22) on each ultrasound transducer (12),

-each acoustic channel (22) has an input opening (24) and an output opening (26),

exactly one of the input openings (24) is associated with each sound coupling-out layer (20),

-the output openings are arranged along a straight line,

the output openings are respectively arranged in a wall of the housing or the acoustic channel passes through the wall of the housing,

-the distance (A2) from the center of one of the output openings (26) to the center of the immediately adjacent output opening (26) corresponds at most to a wavelength in the gaseous medium or at most to half a wavelength in the gaseous medium,

-wherein the spacing (A2) between two directly adjacent output openings (26) is respectively smaller than the spacing (A1) between the ultrasound transducers (12) assigned to the respective input openings (24),

-the quotient of the area of the output opening (26) and the area of the input opening (24) has a value between 0.30 and 1.2, and

-each acoustic channel (22) has a length at least corresponding to the diameter of the input opening (24).

2. One-dimensional ultrasound transducer unit (10) according to claim 1, characterized in that the housing has a movable cover device (32), wherein the cover device (32) is designed for closing the output openings (26) of all acoustic channels (22).

3. The one-dimensional ultrasound transducer unit (10) of claim 1 or 2, characterized in that a quotient of an area of the output opening (26) and an area of the input opening (24) has a value between 0.5 and 1.5 or between 0.9 and 1.1.

4. The one-dimensional ultrasound transducer unit (10) of any of claims 1 to 3, wherein each acoustic channel (22) has a length (L1) from the acoustic outcoupling layer (20) of each ultrasound transducer (12) to the output opening (26) of the associated acoustic channel (22), and the length (L1) is an integer multiple of one-eighth of the wavelength of a sound frequency or an integer multiple of one-half of the wavelength of a sound frequency.

5. The one-dimensional ultrasound transducer unit (10) of any of claims 1 to 4, wherein the output openings (26) of all acoustic channels (36) are located in a common flat plane (E1) or in a curved plane (F1).

6. The one-dimensional ultrasound transducer unit (10) of any of claims 1 to 5, wherein each acoustic channel (22) consists of or comprises metal or plastic.

7. The one-dimensional ultrasound transducer unit (10) of any of claims 1 to 6, wherein each ultrasound transducer (12) has an acoustic decoupling layer between the acoustic coupling-out layer (20) and the transducer housing (22).

8. The one-dimensional ultrasound transducer unit (10) of any of claims 1 to 7, characterized in that the control unit is arranged completely or partially in the housing (14).

9. The one-dimensional ultrasound transducer unit (10) of any of claims 1 to 8, characterized in that the housing (14) of the one-dimensional ultrasound transducer unit (10) is constructed at least corresponding to the IP 40 protection class.

10. The one-dimensional ultrasound transducer unit (10) of any of claims 1 to 9, wherein the communication interface is configured for wireless data transfer.

Technical Field

The invention relates to a one-dimensional ultrasound transducer unit for material detection, having at least three separate and individually steerable ultrasound transducers for detecting objects, contours or spacings.

Background

Ultrasonic or ultrasonic transducers are used in a wide variety of measurement arrangements. Depending on the application, the ultrasound is coupled out into a liquid medium or a gaseous medium.

An ultrasound transducer array for applications in gaseous media is known from WO 2008/135004 a 1. The array has a layer structure consisting of a layer of electrets between two electrode structures, wherein the one electrode structure comprises a plurality of independently addressable electrode elements, thereby generating local thickness vibrations of the electret layer.

A 1.5D array of ultrasound transducers with improved near field resolution is known from US 2013/0283918 a 1. Phased (phased) ultrasound transducer arrays and adaptive or compensatory control methods are described in US 2014/0283611 a1 and US 6,310,831B 1.

For use in an industrial environment, the ultrasound transducers used must be able to guarantee a stability of the measured temperature from-40 ℃ to partly over +100 ℃ and an electromagnetic compatibility with other technical equipment. Furthermore, ultrasound transducers must be robust against harsh environmental influences (e.g. dust, moisture, corrosive chemicals) as well as against mechanical shocks or both requiring mechanical scraping.

To achieve a high detection action pitch, piezoelectric ceramics such as lead zirconate titanate (PZT) are used, which have a high coupling coefficient compared to other piezoelectric materials, such as quartz, electret or PVFD. Here, the coupling coefficient represents a measure of the conversion efficiency between mechanically stored energy and electrically stored energy. For PZT, these coupling coefficients lie, for example, in the range of 0.3 to 0.75, depending on the excitation direction.

Depending on the polarization direction of the piezoelectric material, resonant mechanical vibrations can be generated in the piezoelectric body by means of an alternating voltage, which vibrations are referred to as planar vibrations, thickness vibrations or shear vibrations depending on the geometrical propagation. For these vibrations, the typical dimensions of the piezoelectric body, which are necessary for resonant vibrations at a predetermined frequency, can be estimated from the material-specific frequency constants. For PZT, these frequency constants are typically between 1300kHz mm and 2600kHz mm, depending on the type of vibration.

Thus, a thin disk composed of PZT suitable for use in a sensing device has a diameter of about 4mm to 100mm in planar mode for an excitation frequency of 20kHz to 500 kHz. Due to the capacitive properties of such a thin plate, a low excitation voltage can be achieved well at the corresponding polarization.

A greater thickness of the piezoelectric disc is not desirable. On the one hand, as the thickness of the piezoelectric material increases, higher voltages (even rapidly in the kV range) have to be applied for the same frequency range, which means higher safety overhead. On the other hand, the rigidity of the piezoelectric body also changes with the thickness of the piezoelectric body, which has a direct influence on the reception of the acoustic wave.

When applying a plurality of ultrasound transducers in a phased at least one-dimensional array (phased array), it should also be noted that the spacing between adjacent ultrasound transducers should not be greater than the wavelength of the ultrasound waves or preferably should not be greater than half the wavelength.

The structural size of the individual transducers or the frequency range which can be achieved by means of a defined structural configuration/size of the ultrasonic transducers is correspondingly limited by this spacing condition.

For example, for a frequency range between 20kHz and 500kHz and coupling out into air, it follows that the maximum spacing between adjacent transducers is in the order of about 8.5mm to 0.3 mm.

However, due to the piezoelectric disc diameter, the transducers previously described with thin discs composed of PZT suitable for use in sensing devices have a diameter that is on average more than ten times larger.

Disclosure of Invention

On this background, the object of the invention is to specify a device which expands the prior art.

This object is achieved by a one-dimensional ultrasound transducer unit for hazard recognition of material detection having the features of claim 1. Advantageous embodiments of the invention are the subject matter of the dependent claims.

According to the subject matter of the present invention, a one-dimensional ultrasound transducer unit for material detection is provided, comprising a housing, at least three ultrasound transducers and a control unit, wherein the control unit is designed for individually operating each ultrasonic transducer, the housing has fixing means for fixing on a surface, the control unit is arranged at least partially in the housing, which has a communication interface, each ultrasonic transducer has a transducer housing, a piezoelectric body arranged in the transducer housing and an acoustic outcoupling layer arranged at the open end of the transducer housing for coupling out into a gaseous medium, and the ultrasonic transducers are arranged at fixed positions in the housing, each ultrasonic transducer being designed for emitting and/or receiving sound waves having a uniform operating frequency, and the operating frequency of the sound waves being in the range of 20kHz to 400 kHz.

Every two ultrasound transducers directly adjacent to one another have a distance of at most 10cm or at most 5cm or at most 2cm in the housing from the center of the sound-coupling-out layer to the center of the sound-coupling-out layer. The one-dimensional ultrasound transducer unit has an acoustic channel on each ultrasound transducer, wherein each acoustic channel has an input opening and an output opening, exactly one of the input openings is assigned to each acoustic outcoupling layer, the output openings are arranged along a straight line, and the output openings are arranged in the wall of the housing or the acoustic channel penetrates the wall of the housing, respectively. The distance from the center of one of the output openings to the center of the immediately adjacent output opening corresponds at most to a wavelength in the gaseous medium or at most to half a wavelength in the gaseous medium, wherein the distance between two immediately adjacent output openings is smaller than the distance of the ultrasonic transducers assigned to the respective input opening, respectively, the quotient of the area of the output opening and the area of the input opening has a value between 0.30 and 1.2, and each acoustic channel has a length at least corresponding to the diameter of the input opening.

It should be understood that the ultrasound transducers of these one-dimensional ultrasound transducer units relate to a single discrete component, wherein each ultrasound transducer is arranged in and connected with the housing and thus has a fixed spacing from all other ultrasound transducers. Two ultrasound transducers arranged next to one another without a further ultrasound transducer arranged between them are here ultrasound transducers directly adjacent to one another.

It should also be understood that the individual sound channels are tubular or rod-shaped, wherein, for example, the tube diameter is reduced and/or the shape of the cross section is changed and/or the course of the channels is arched. Advantageously, the sound channel has no edges over its entire length from the sound outcoupling layer to its output opening.

The acoustic channel directs sound waves generated by each ultrasonic transducer out of the housing or directs reflected sound waves back to the ultrasonic transducer. As a result, a wave front is generated at the output opening on the housing wall or outside the housing as a result of the superposition.

By means of a plurality of individually steerable ultrasonic transducers, a wave front with an adjustable main propagation direction can be generated by temporally offset or phase offset steering. A large measurement region can thereby be scanned at least in one dimension by means of only one-dimensional ultrasound transducer unit. Furthermore, the surface structure of the object and/or the shape of the object may be detected. Thus, for example, a material type and/or an object type may be determined.

By arranging the sound channels in front of the respective ultrasonic transducers, the respective sound sources are arranged at the respective ends of the sound channels or at the output openings, when or for superimposing the common wave front. This enables the spacing between individual sound sources to be adjusted independently of the size (e.g. diameter) of the individual ultrasound transducers or independently of the spacing between the individual ultrasound transducers. The spacing between sound sources may be particularly reduced compared to the spacing between individual transducers.

In the case of a housing diameter of the respective ultrasonic transducer of, for example, 7mm, the spacing between the two transducers is at least 14 mm. Accordingly, in the absence of an acoustic channel, only wavefronts with frequencies up to 22kHz (λ ≧ 14mm) or up to 11kHz (λ/2 ≧ 14mm) can be realized. With the acoustic channel according to the invention, it is possible to generate wave fronts with higher frequencies (i.e. shorter wavelengths) with the same ultrasonic transducer, since the spacing between the individual "sound sources" during superposition is not determined by the dimensions of the transducer housing, but only by the dimensions and spacing of the output openings of the acoustic channel.

Accurate, directional detection is also ensured by the acoustic channel.

The transmission aperture of the piezoelectric transducer (for example, a circular aperture having a diameter predetermined by the piezoelectric body) is changed by means of the acoustic channel in such a way that it meets the requirements of the desired array arrangement in at least one dimension. This enables the use of robust, reliable and/or cost-effective discrete ultrasound transducers in a phased array arrangement. The phased array arrangement enables a large viewing angle with only one-dimensional ultrasound transducer unit and thus a reliable monitoring of, for example, the filling height. Surface structures and/or objects or object shapes can also be recognized.

It is not necessary to use particularly small, for example integrated, ultrasonic transducers, for example MEMS. It is also not necessary to install, read out and, if necessary, coordinate a plurality of converter units with one another.

According to one embodiment, the housing has a movable cover device, wherein the cover device is designed to close the outlet openings of all the sound channels. As long as the one-dimensional ultrasonic transducer unit is not used, the acoustic channel can be closed by means of the cover device, whereby the entry of foreign objects/contaminants can be prevented. For opening and closing the acoustic channel or for moving the cover device, the one-dimensional ultrasonic transducer unit comprises, for example, an actuator.

According to one embodiment, the quotient between the area of the second cross section and the area of the first cross section has a value between 0.5 and 1.5 or between 0.9 and 1.1. According to the invention, the area of the input area can be increased, decreased or kept constant, while at least the width of the output opening is reduced compared to the input opening.

According to a further embodiment, each acoustic channel has a length from the sound outcoupling layer of each ultrasonic transducer to the output opening of the associated acoustic channel, wherein the length is an integer multiple of one eighth of the wavelength of a sound frequency or an integer multiple of one half of the wavelength of a sound frequency.

According to another embodiment, the output openings of all acoustic channels are located in a common flat plane or in a curved surface. By being arranged in a curved surface (e.g. a concave surface), for example, a focused wavefront can be generated.

In another embodiment, each acoustic channel is composed of metal or plastic. Alternatively, each acoustic channel comprises metal or plastic.

According to a further embodiment, each ultrasonic transducer has an acoustic decoupling layer between the acoustic decoupling layer and the transducer housing.

In another embodiment, the control unit is arranged completely or partially in the housing.

According to a further embodiment, the housing of the one-dimensional ultrasound transducer unit is constructed at least corresponding to the IP 40 protection class.

In a further embodiment, the communication interface is designed for wireless data transmission, for example as a bluetooth interface. Thus, for example, control and/or measurement signals may be exchanged wirelessly between the one-dimensional ultrasound transducer unit and, for example, an external control unit or an analysis processing unit. Alternatively, the one-dimensional ultrasound transducer units communicate via a cable by means of a communication interface, for example by means of a bus system or protocol.

According to a further embodiment, each ultrasonic transducer projects with an acoustic coupling-out layer forward into the associated input opening, wherein, in one embodiment, each acoustic channel receives at least a part of the associated ultrasonic transducer in a precisely matched manner. In other words, according to this embodiment, the inner shape of the acoustic channel corresponds as exactly as possible to the outer shape of the respective ultrasonic transducer in the region of the input opening.

In another embodiment, the housing of each ultrasonic transducer has a diameter of at least 7 mm. The housing of each ultrasonic transducer is configured, for example, as a cylindrical metal cup. According to one development of this embodiment, the surface of the acoustic decoupling layer, the edge of the metal cup and the acoustic decoupling layer arranged between them, for example of each individual ultrasonic transducer, each lie in a flat plane.

In another embodiment, each ultrasound transducer has an electromagnetic shield at a reference potential. It should be understood that the electromagnetic shield may also be constructed completely or at least partially from the housing, in particular the metal cup used as housing. Alternatively, the one-dimensional ultrasound transducer unit may also have a common shielding for all ultrasound transducers, for example a common housing.

In another embodiment, each acoustic channel has a wall thickness of at least 0.5mm or at least 1 mm. According to a further embodiment, each two sound channels have a distance of at least 0.5mm or at least 1mm from each other over the entire length of the two sound channels.

According to another embodiment, the housing comprises a flat rear wall and a front wall extending parallel to the rear wall. The mounting and orientation of the one-dimensional ultrasound transducer unit on a surface can thereby be realized particularly simply and reliably. The ultrasonic transducer is preferably mounted on the rear wall, while the acoustic channel preferably ends at or in the front wall. Particularly preferably, not only the output opening of the acoustic channel but also the ultrasonic transducer and the input opening of the acoustic channel are arranged along a straight line. The straight line which is developed through the input of the acoustic channel is for example significantly longer than the straight line which is developed through the output opening.

Drawings

The invention will be further elucidated with reference to the drawing. Here, the same type of portions are denoted by the same reference numerals. The illustrated embodiment is highly schematic, i.e. the spacing and the lateral and vertical extension are not to scale and, unless otherwise stated, do not have any mutually derivable geometrical relationship. Shown here are:

figure 1A shows a view according to a first embodiment of the invention of a one-dimensional ultrasound transducer unit for fill level detection,

figure 1B shows a view of a second embodiment according to the invention of a one-dimensional ultrasound transducer unit for object detection,

figure 2 shows a cross-sectional view of an embodiment according to the invention of a housing of a one-dimensional ultrasound transducer unit,

figure 3 shows a view of another embodiment according to the invention of the acoustic channel,

figure 4 shows a view of another embodiment according to the invention of the acoustic channel,

figure 5 shows a view of another embodiment of a single acoustic channel,

fig. 6 shows a schematic view of a different embodiment of the output face of the acoustic channel.

Detailed Description

The image of fig. 1A shows a view of a first embodiment of a one-dimensional ultrasound transducer unit 10 according to the invention for fill level detection. The one-dimensional ultrasonic transducer unit has a housing 14 which is mounted on a ceiling 102 of a container 102 for bulk material 104 by means of a fixing means 11. The acoustic waves 11 are generated by a one-dimensional ultrasound transducer unit 10. The acoustic wave 11 has a main propagation direction which is swingable in the image plane (dashed line, dotted line, or dashed line), whereby the entire container 102 can be reliably scanned. Bulk material 104 and/or the bottom of container 102 and/or the side walls of container 102 reflect acoustic waves 11. By means of the one-dimensional ultrasonic transducer unit, not only the height or amount of bulk material 104, but also the surface structure of bulk material 104 can be detected, from which the type of bulk material 104 can be inferred.

A second embodiment according to the present invention of a one-dimensional ultrasound transducer unit 10 is shown in the image of fig. 1B. The one-dimensional ultrasonic transducer unit 10 is mounted on a building roof 106 above a conveyor belt 108 by means of a fixing device 11, so that an object 110 on the conveyor belt can be detected by means of ultrasonic waves. By the oscillation of the emitted ultrasonic waves, a large area of the conveyor belt 108 can be monitored and the shape or surface structure of the objects 110 lying on the conveyor belt 108 can be identified.

A cross-sectional view of the housing 14 of the ultrasound transducer unit 10 is shown in the image of fig. 2. In the housing 14, five discrete ultrasound transducers 12 are arranged along a flat rear wall 16 of the housing 14. Each ultrasonic transducer 12 has its own transducer housing 18 and acoustic coupling-out layer 20. Each ultrasonic transducer 12 has a spacing a1 from the center of the acoustic coupling-out layer 20 to the center of the acoustic coupling-out layer 20 with respect to the immediately adjacent ultrasonic transducer or transducers 12.

An acoustic channel 22 is associated with each ultrasonic transducer 12, wherein each acoustic channel 22 has an input opening 24 and an output opening 26. The input openings 24 are each arranged in front of or around one of the ultrasonic transducers 12 in such a way that each ultrasonic transducer 12 emits into the corresponding acoustic channel 22. The output opening 26 of the acoustic channel 22 is arranged along a flat front wall 30 of the housing 14 opposite the rear wall or through the front wall 30.

Each two adjacent output openings 26 have a spacing a2 from the center of the output opening 26 to the center of the output opening 26. According to the invention, the distance a2 of the output openings 26 is smaller than or equal to the distance a1 of the associated or associated ultrasound transducer 12.

The length L1 of the output opening 26 from each acoustic outcoupling layer 20 up to the associated acoustic channel 22 is an integer multiple of one eighth of the wavelength of the acoustic frequency.

The housing 14 also includes a movable cover device 32. In the illustrated embodiment, the lid device 32 is in a closed state. For this purpose, the cover device is arranged in front of a front wall 30 of the housing 14 with the output opening 26, thereby closing the acoustic channel 22. In the open state, the cover device 32 is no longer in front of the front housing wall 30 and the output opening 26, for example by being flipped or moved, and the output opening 26 is exposed.

In the embodiment shown in fig. 3, the acoustic channels 22 extend such that the output openings 26 of all the acoustic channels 22 lie in a common flat plane E1. In the embodiment shown, the front wall 30 of the housing 14 of the one-dimensional ultrasound transducer unit 10 extends in a plane E1. The region 34 of each sound channel 22, which is still in front of the input opening 24 of the respective sound channel 22, is designed in such a way that the respectively associated ultrasonic transducer 12 fits into the sound channel 22 in a precisely fitting manner. For this purpose, each sound duct 22 has an inner diameter in this region corresponding to the outer diameter D1 and an edge 36 serving as a stop.

A control unit, not shown, is designed for individually operating each ultrasonic transducer 12. By actuating the individual ultrasonic transducers 12 in a time-staggered or phase-staggered manner, the one-dimensional ultrasonic transducer unit 10 generates a planar ultrasonic wave having a main propagation direction (arrow), wherein the angle between the main propagation direction or main propagation direction and the first plane E1 can be adjusted by means of the phase offset between the sound waves emerging from the output openings 26 of the individual sound channels.

In the embodiment shown in fig. 4, the output openings 40 of all acoustic channels 36 are located in the concave curved surface F1.

The individual sound channels 22 are schematically illustrated in the image of fig. 5, wherein the differences with respect to fig. 1 to 4 are explained next.

The input opening 24 has a cross-section with a width x1 and a height y1, and the output opening 26 has a cross-section with a width x2 and a height y 2.

The input opening 24 is configured to be circular, i.e. the width x1 and the height y1 of the cross-section have the same value. Conversely, the output opening 26 has an elliptical shape, and thus the width x2 of the cross-section is less than the width y 2.

The width x2 of the output opening 26 is preferably smaller than the width x1 of the input opening 26. Conversely, the height y2 of the output opening 26 is preferably greater than the height y1 of the input opening 24. Particularly preferably, the increase in the height of the acoustic channel 22 compensates for the decrease in the width of the acoustic channel 22 in such a way that the area of the cross section of the input opening 24 corresponds to the area of the cross section of the output opening 26.

It should be understood that the width x2 of each output opening 26 must be less than the wavelength of the sound frequency in order to enable the spacing of the wavelength of the highest sound frequency from the center of the output opening 26 to the center of the immediately adjacent output opening 26.

A number of embodiments according to the invention of the cross section of the output opening 26 are schematically shown in the image of fig. 6. In order to make the cross-sectional area of the outlet opening 26 correspond to the cross-sectional area of the inlet opening 24, the following shapes are particularly suitable: the shape has a ratio of width x2 to height y2 of about 1.5.