EP1565905B1 - Method and device for cooling ultrasonic transducers - Google Patents

Abstract

The cooling device has a cooling fluid which is under pressure passed through at least one flow channel (7) in each ultrasonic transducer block (6) obtained by combining at least 2 transducer bodies (5), the pressure of the cooling fluid selected for reducing or preventing cavitation.

Description

The invention relates to a method and a device for cooling of ultrasonic transducers with the features mentioned in the preambles of claims 1 and 6.

In the operation of ultrasonic transducers, power losses occur in the form of heat. The cause for this are, on the one hand, electrical losses and, moreover, internal friction losses in the piezoelectric elements, which arise in the conversion of the electrical energy into mechanical energy. The derivation of the resulting amounts of heat under the application of different active principles is well known. The operation of the known cooling systems is based on the principles of heat transfer by conduction or by convection. Mostly a combination of both principles of action is used.

The difficulty in the cooling of high-power ultrasound transducers, which naturally have large vibration amplitudes, is to dissipate the resulting large amounts of heat without additional burden in the form of friction or additional heat generation. By applying the effective heat dissipation by convention, this is so far only possible with gaseous media, since the use of cooling liquids, a high additional power input by cavitation, which can lead to damage to the transducer. When using gaseous coolant large amounts of gas at high pressure for cooling are required, making this cooling process is very uneconomical. Furthermore, the cooling gas must be free of solid or liquid contaminants, so in particular Due to the high voltages occurring in high power ultrasound transducers, no short circuits due to bridge formation occur.

Out EP 0553804 A2 For example, a cooling system for a high-frequency ultrasound transducer is known, which is based on the principle of heat conduction. Located behind the ultrasonic transducer is a heat sink in the form of a heat sink. The heat sink is in turn connected by means of a thermally conductive resin to a housing. The heat is first transferred from the converter into the heat sink and from there via the resin into the surrounding housing, where the heat is ultimately dissipated to the surrounding air. This type of cooling is insufficient for high performance and not applicable for high amplitudes of several micrometers, because it is a high energy input into the resin.

In many cases, the operation of ultrasonic transducer cooling systems is based solely on heat removal through the openings of a housing surrounding the transducer by convection (e.g., SONOPULS HD 60, BANDELIN electronic GmbH & Co. KG). This type of cooling is not sufficient for high performance.

Furthermore, numerous variants of these cooling systems are known in which additional cooling is achieved by fans or by compressed air, for example WO 9959378 , A disadvantage of this type of cooling is that dust or moisture can be increasingly transported into the housing, wherein the risk of electrical short circuit increases by bridge formation by means of electrically conductive impurities. Even closed systems with fans and heat exchange from the inside to the outside are known, but they are technically complicated and also allow only a limited heat dissipation.

Out EP 0782125 A2 Furthermore, an arrangement for cooling a high-frequency ultrasonic transducer is known in which a liquid-conducting heat pipe is connected to a heat sink arranged behind the converter. The cooling liquid is supplied and removed via supply lines. The heat dissipation from the heat sink is thus by convection. In a special embodiment of this cooling system, the heat conduction tube is formed as a channel completely or partially in the material surrounding the transducer in order to realize the largest possible contact surface. The cooling liquid does not flow through the sound transducer but rather through a cooling system in contact with the sound transducer. Again, the heat dissipation for high performance is insufficient.

In addition, is off WO 0008630 A1 an arrangement for heat dissipation, in particular for ultrasonic transducer high power known. The heat dissipation is based on the combination of heat conduction and convection. Here, the surface of the transducer body is provided with a vibration-absorbing layer, which reduces the mechanical friction losses during heat transfer. Above it is a layer of thermally conductive material. On this layer, a cooling body is arranged, from which the heat can be dissipated by means of a coolant by convection. The disadvantage of this arrangement is that the temperature gradients created by the layer transitions cause a reduction in the efficiency of heat dissipation. Furthermore, the maximum possible common contact surface between the transducer and cooling device is limited to the transducer surface, whereby the continuous operation of high-power ultrasound transducers can be ensured only by supplying large amounts of coolant, resulting in a low cost of the process results.

With the US 5,936,163 Finally, an ultrasonic transducer is described, which is used in high-temperature environment such as reactors and steam lines used. For discharging the heat introduced from the environment into the transducer, the body of the ultrasonic transducer is cooled by means of a circulating cooling medium.

The disadvantage of all known solutions is that the continuous operation of ultrasonic transducers at high power can not be guaranteed or not without great effort and / or without a deterioration of the efficiency.

The invention is based on the object to provide a method and a device for cooling of ultrasonic transducers, which are characterized by a more effective heat dissipation of heat generated by power losses than previously known and thus reliably and economically ensure the continuous operation of ultrasonic transducers at high power.

According to the invention this object is achieved by a method having the features mentioned in claim 1 and a device having the features mentioned in claim 6. The inventive method for cooling of ultrasonic transducers is characterized in that the body of the ultrasonic transducer flows through a introduced under pressure cooling fluid and / or flows around. In this way, it is advantageously achieved that the heat generated in the transducers is dissipated directly by convection. No heat transfer via cooling elements is required. By flowing through the transducer body, a large common contact surface between transducers and coolant is realized. The achieved heat dissipation is much more effective than in the known methods, so that can be ensured with the inventive compositions of the continuous operation of ultrasonic transducers high performance.

In the context of the method according to the invention, it is preferably provided that the pressure of the cooling liquid is dimensioned such that the cavitation is reduced or avoided. In this case, the pressure is preferably set in a range from 200 to 2000 kPa (2 to 20 bar). Particularly preferred 500 kPa (5 bar) are provided. This advantageously ensures that the risk of damage to the device is significantly reduced by cavitation and that an additional power input is reduced or avoided by cavitation.

The pressure of the cooling liquid can be generated by the dimensioning of flow channels and / or by gas pressure.

Furthermore, it is preferably provided in the context of the method according to the invention that the flow through the body of the ultrasonic transducer from the inside to the outside, wherein the liquid pressure is built up in the interior and the cooling liquid flows through the housing, or from the outside to the inside, wherein the pressure is built up in the outdoor area and the cooling liquid flows over the inner area, is realized. In this way, a particularly effective dissipation of heat from the transducers is achieved. In addition, it is particularly preferably provided that the flow takes place in such a way that pressure is built up to prevent cavitation both in the interior and in the exterior, wherein a pressure gradient between the interior and exterior is required for the flow of the cooling liquid.
It is furthermore preferably provided that the body of the ultrasonic transducer is flowed around in the interior and / or in the outer area, since in this way heat is removed from the converter surface by convection.

The interior is in this case in particular the cavity between the tension rod and transducer body, the outside area, in particular the space between the transducer body and housing.

Furthermore, it is preferably provided in the context of the method according to the invention that the cooling liquid is an electrically non-conductive liquid, as this electrical short circuits are avoided.

The inventive device for cooling ultrasonic transducers is characterized in that the device consists of at least one piezo package and at least two cylindrical transducer bodies, which together with the piezo packet form a λ / 2 oscillator, wherein in multiple arrangements of transducers each two transducer body to a common transducer body can be combined and wherein at least one of the at least two transducer body has at least one flow passage through which introduced under pressure cooling liquid can be flowed. In this way, it is advantageously achieved that the heat generated in the transducers can be dissipated directly by convection. No heat transfer via cooling elements is required. Furthermore, a large common contact surface between transducers and cooling liquid can be realized with the agents according to the invention. The achieved heat dissipation is much more effective than in the known methods, so that can be ensured with the inventive compositions of the continuous operation of ultrasonic transducers high performance.

In a preferred embodiment of the invention it is preferably provided that the pressure of the cooling liquid is dimensioned such that the cavitation is reducible or avoidable. In this case, the pressure is preferably set in a range from 200 to 2000 kPa (2 to 20 bar). Particularly preferred 500 kPa (5 bar) are provided. This will be advantageous achieved that the risk of damage to the device is significantly reduced by cavitation and that an additional power input by cavitation generation is reduced or avoided.

Furthermore, it is provided in a preferred embodiment of the invention that at least one flow channel is slit-shaped, as a result, a large common contact surface between the converter body and the cooling liquid can be realized. This leads to a higher efficiency in heat dissipation.

In a preferred embodiment of the invention it is further provided that the device comprises a arranged in a cavity of the at least two transducer body tension rod having at least two openings and at least one guide channel through which the introduced under pressure cooling liquid can be flowed. As a result, a particularly easy to implement and uniform feeding possibility of the cooling liquid is achieved in the cavity.

In addition, in a preferred embodiment of the invention, it is provided that the cooling liquid can be supplied via the at least one guide channel and can be discharged via the at least one throughflow channel. It is furthermore preferably provided that the cooling fluid can be supplied via the at least one flow channel and can be discharged via the at least one guide channel in the tension rod. In this way, a particularly easy-to-handle and realizable possibility of the flow through the transducer body from the inside to the outside or from the outside to the inside is given.

In addition, it is preferably provided in one embodiment of the invention that the device comprises a liquid-tight housing. The housing serves on the one hand to protect the active elements of the transducer and also offers a particularly favorable possibility of receiving and guiding the coolant.

Moreover, it is provided in a preferred embodiment of the invention that the device comprises a flange which is connected to the housing and / or a horn and / or an end mass. Through the flange a particularly easy to be realized mounting option of the housing is achieved. Furthermore, a particularly favorable possibility of connection with a sonotrode is given by the horn.
In a preferred embodiment of the invention, it is further provided that the device has at least one connection device for a coolant line, through which the cooling fluid can be discharged into the cavity of the transducer body and / or can be discharged from the cavity. By this means, a particularly easy to handle connection possibility of the cavity to a cooling liquid supply device and a supply possibility of the cavity with cooling liquid is realized.

In a preferred embodiment of the invention it is further provided that the device has at least one connection device for a coolant line, through which the cooling liquid in the at least one guide channel is flowable and / or discharged from the at least one guide channel. By this means, a particularly easy to handle connection possibility of the at least one guide channel to a cooling liquid supply device and a supply possibility of the at least one guide channel with cooling liquid is realized.

Furthermore, in a particularly preferred embodiment of the invention, it is provided that the device has at least one connection device for a coolant line through which the coolant can flow into the housing and / or can be discharged from the housing. By this means, a particularly easy to handle connection possibility of the housing to a cooling liquid supply device and a supply possibility of the at least one guide channel with cooling liquid is realized.

Finally, it is provided in a preferred embodiment of the invention that at least one of the at least two transducer body is at least partially flowed around on the inner surface and / or at least partially on the outer surface of the cooling liquid. As a result, an effective dissipation of heat from the transducer bodies is achieved by convection.

In a further embodiment variant of the invention, the transducer bodies have no through-flow channels. In this embodiment variant, the converter bodies are merely flowed around, with the interior space being connected to the outside space by a connecting channel.

Further preferred embodiments of the invention will become apparent from the remaining, mentioned in the dependent claims characteristics.

Figur 1

eine schematische Schnittdarstellung eines Ultraschallwandlers mit einer Vorrichtung zur Kühlung mit einem axial angeordneten Zulauf für Kühlflüssigkeit

Figur 2

eine schematische Schnittdarstellung eines Ultraschallwandlers mit einer Vorrichtung zur Kühlung mit zwei radial angeordneten Zuläufen für Kühlflüssigkeit

Figur 3

eine schematische Schnittdarstellung eines Ultraschallwandlers mit einer Vorrichtung zur Kühlung ohne Durchströmkanäle und mit Verbindungskanal.

The invention will be explained in more detail in embodiments with reference to the accompanying drawings. Show it:

FIG. 1

a schematic sectional view of an ultrasonic transducer with a device for cooling with an axially arranged inlet for cooling fluid

FIG. 2

a schematic sectional view of an ultrasonic transducer with a device for cooling with two radially arranged inlets for cooling fluid

FIG. 3

a schematic sectional view of an ultrasonic transducer with a device for cooling without flow channels and with connecting channel.

In FIG. 1 is shown schematically the longitudinal section of an ultrasonic transducer with an embodiment of the device according to the invention for cooling the ultrasonic transducer. The ultrasonic transducer is composed of cylindrical transducer bodies 5, 6, each having piezoelectric packages 4 arranged on the front side between two transducer bodies 5, 6, some of the transducer bodies 5, 6 being designed as common transducer bodies 6, on the front sides of which in each case a piezoelectric package 4 is arranged. In each case a piezo package 4 forms with one of the transducer body 5 and half of the common transducer body 6 or with each half of two common transducer body 6 a λ / 2 oscillator. The transducer bodies 5, 6 have flow-through channels 7 in the radial direction. Transducer body 5, 6 and 4 piezo packages are alternately lined up on a tension rod 3 with end threads. With the help of two arranged at opposite ends of the tension rod 3 end masses 10 with thread, which are each screwed onto a threaded end of the tension rod 3, the arrangement is fixed and tensioned. The tension rod 3 has a guide channel 13 for cooling liquid, wherein at one end of a connecting device for a coolant line 1 is attached, which forms the inlet 1 for the cooling liquid. The tension rod has an outlet opening for the coolant flowing out of the guide channel into the cavity 11 of the transducer body. The opposite end mass 10 is connected to a horn 8, which is the connection option with a sonotrode and serves to transmit the mechanical vibrations generated by the transducer. The device is provided with a liquid-tight housing 12 for receiving the cooling liquid, which is connected to a flange 9, which offers a possibility for mounting in an external plant. The flange 9 is connected to the horn 8. The flange 9 has a connection device for a coolant line 2, which forms the outlet 2 for the cooling liquid from the housing 12. The coolant line for the inlet 1 is guided through the housing 12. The cooling liquid is introduced via the inlet 1 under pressure into the guide channel 13 of the tension rod 3. Via the guide channel 13, the cooling liquid is supplied to the cavity 11 of the transducer body, where the transducer body are flowed through by the cooling liquid to ultimately flow through the flow channels 7 of the transducer body 5, 6. The heat generated by the transducers is transferred in this way directly by convection to the cooling liquid. The exiting from the flow channels 7 cooling liquid is collected in the housing 12 and discharged via the outlet 2 from the device. In this way, a more effective cooling of the ultrasonic transducer is achieved than in the known methods. With the aid of the means according to the invention, the continuous operation of high-power ultrasonic transducers is also ensured.

To increase the service life of the transducer body and / or to realize an effective flow through the passage formed as slots 7 7 openings, for example, circular holes can be attached to the ends of the flow channels. The diameter of the bores is expediently greater than the width of the slots.

FIG. 2 shows schematically the longitudinal section of the structure of an ultrasonic transducer with a further embodiment of the device according to the invention for cooling the ultrasonic transducer, which substantially the in FIG. 1 shown corresponds. Unlike the build in FIG. 1 are two inlets 1 for the cooling liquid present, which are each arranged radially and are guided from the outside through the housing 12 and the end masses 10 into the cavity 11 between the tension rod 3 and transducer body 5, 6. The connection means 1 for the connection of the cooling liquid lines to the cavity 11 are thus arranged at the opposite ends of the transducer. In this way, the cooling liquid is introduced from the opposite ends under pressure into the cavity 11 and discharged through the flow channels 7. This results in a more uniform heat dissipation over the entire length of the device as in FIG. 1 , It is thus an even more effective cooling of the ultrasonic transducer as with in FIG. 1 achieved embodiment shown.

FIG. 3 shows a further embodiment of the invention, in which the transducer body 5, 6 have no flow channels 7. However, the inner space 11 is connected to the outer space 14 via a connecting channel 15. In a first variant, the cooling liquid is supplied via the inlet 1, passes through the guide channel 13 into the interior 11, flows around and cools the transducer body 5, 6, leaves the interior 11 via the connection channel 15 and is discharged via the exterior space 14 and the outlet 2 dissipated. In this variant, only the inside of the transducer body 5, 6 is cooled.
Alternatively, it is possible in a second variant, only to cool the outside of the transducer body 5, 6, 17 is supplied via the housing inlet 1a and a ring line 17 cooling liquid. The over the housing inlet 1a supplied coolant is uniformly supplied and distributed through the ring line 17 and now flows around the outside of the converter 5, 6 or at least here forms a coolant film and is discharged via the outlet 2. In a third variant, it is possible to cool both the inner sides and the outer sides of the transducer bodies 5, 6 by supplying coolant to the outer space 14 both via the inlet 1 into the inner space 11 and via the housing inlet 1a.
The discharge of the over the inlet 1 for cooling the inner sides and the over the housing inlet 1a for cooling the outer sides of the transducer elements 5, 6 supplied coolant via the flow of the second
To avoid cavitation, a gas pressure is generated in the present embodiment via the gas pressure port 6 in the housing 12, which is 6 bar in this embodiment.

The invention is not limited to the embodiment shown here. Rather, it is possible to realize by combining the described means and features of further embodiments without departing from the scope of the invention.

LIST OF REFERENCE NUMBERS

1

Connection device for coolant lines, inlet

1a

housing supply

2

Connection device for coolant lines, drain

3

tie rod

4

piezo package

5

transducer body

6

common transducer body

7

flow-through

8th

horn

9

flange

10

final mass

11

Cavity, interior

12

liquid-tight housing

13

guide channel

14

outer space

15

connecting channel

16

Gas discharge nozzle

17

loop

Claims (10)

1. Method for cooling ultrasonic transducers by removing heat generated by power losses, characterized in that

   - a cooling fluid flows through and/or around the body of the ultrasonic transducer,

   - a pressure is generated in the cooling fluid is adjusted in a range from 200 to 2000 kPa, wherein the pressure is dimensioned so as to reduce or prevent cavitations, and

   - the pressure is generated by dimensioning the flow-through channels and/or by a gas pressure.
2. Method according to claim 1, characterized in that the pressure of the cooling fluid is preferably 500 kPa.
3. Method according to claim 1 or 2, characterized in that the cooling fluid flows through the body of the ultrasonic transducer from the interior region to the exterior region or from the exterior region to the interior region.
4. Method according to one of the claims 1 to 3, characterized in that cooling fluid flows around the interior region and/or the exterior region of the body of the ultrasonic transducer.
5. Method according to one of the claims 1 to 4, characterized in that the cooling fluid is an electrically non-conducting fluid.
6. Device for cooling ultrasonic transducers, comprising at least one piezo stack (4) and at least two cylindrical transducer bodies (5), which together with the piezo stack (4) form a λ/2 oscillator, wherein two corresponding transducer bodies can be combined as multiple transducer arrangements to form a unitary transducer body (6), characterized in that the transducer bodies (5, 6) are surrounded by an interior space (11) and an exterior space (14), and that at least one of the at least two transducer bodies (5,6) includes at least one flow-through channel (7), through which a cooling fluid introduced under pressure can flow, and/or that at least one connecting channel (15) is arranged between the interior space (11) and the exterior space (14), wherein the pressure is dimensioned so as to reduce or prevent cavitations, and that the pressure is adjusted in a range from 200 to 2000 kPa , and preferably is 500 kPa .
7. Device according to claim 6, characterized in that at least one flow-through channel (7) is formed as a slit and that the device comprises a tensioning rod (3) arranged in a hollow space (11) formed by at least two transducer bodies (5, 6) and having at least one opening and at least one guide channel (13), through which the cooling fluid introduced under pressure can flow, and that the cooling fluid can be supplied through the at least one guide channel (13) and removed through the at least one flow-through channel (7), and that the cooling fluid can be supplied through the at least one flow-through channel (7) and removed through the at least one guide channel (13) disposed in the tensioning rod (3).
8. Device according to one of the claims 6 to 8, characterized in that the device includes a fluid-tight housing (12) and a flange, which is connected with the housing (12) and with a horn (8), and that the device includes at least one corresponding connection (1, 2) for a cooling liquid line through which the cooling liquid can flow into the hollow space (11) and/or be removed from the hollow space (11), or that the device includes at least one corresponding connection (1, 2) for a cooling fluid line, through which the cooling fluid can flow into the at least one guide channel (13) and/or be removed from the at least one guide channel (13), or that the device includes at least one corresponding connection (1a,2) for a cooling fluid line, through which the cooling fluid can flow into the housing (12) and/or be removed from the housing (12).
9. Device according to one of the claims 6 to 8, characterized in that the cooling fluid can flow at least around a portion of the inner surface and/or at least around a portion of the outer surface of at least one of the at least two transducer bodies (5, 6).
10. Device according to one of the claims 6 to 9, characterized in that openings are disposed on the ends of the flow-through channels (7), which openings have a diameter that is greater than the width of the flow-through channels (7).

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