WO2012171823A2

WO2012171823A2 - Device for transmitting and/or receiving sound signals

Info

Publication number: WO2012171823A2
Application number: PCT/EP2012/060510
Authority: WO
Inventors: Michael Helmle; Andre Gerlach
Original assignee: Robert Bosch Gmbh
Priority date: 2011-06-15
Filing date: 2012-06-04
Publication date: 2012-12-20
Also published as: DE102011077558A1; WO2012171823A3

Abstract

The invention relates to a device for transmitting and/or receiving sound signals, in particular ultrasound, comprising an electromechanical film (3) which is connected to at least one front side electrode (7) and at least one rear side electrode (11), wherein the electromechanical film (3) is thermally conductively connected to a substrate. The invention further relates to a use of the device as an ultrasound sensor for registering an environment, in particular for registering the environment of a motor vehicle.

Description

description

title

The invention relates to a device for transmitting and / or receiving sound signals

Acoustic signals, in particular ultrasound, comprising an electromechanical foil, which is connected to at least one front-side electrode and at least one rear-side electrode. Furthermore, the invention also relates to a use of the device. State of the art

Devices for transmitting and / or receiving sound signals, in particular

Ultrasound, for example, are used as ultrasonic sensors for environment detection. For this purpose, a signal is sent by a transmitter, which is an object in the

Detection range of the sensor is reflected. The reflected echo is from a

Receiver received and determined from the runtime the distance to the object. Here it is possible to use separate components as transmitter and receiver or a sensor which first sends a sound pulse and receives the echo after swinging. Such sensors are also referred to as transceivers.

Such ultrasonic sensors are used, for example, to monitor the surroundings of a motor vehicle, for example for automatic parking systems or for blind spot monitoring. In addition to use in motor vehicles, such sensors can also be used in robots, for example in driverless transport systems, automatic

Lawnmowers or vacuum cleaners or the like.

Usually ultrasonic sensors are currently being built which operate on a piezoelectric basis. As an alternative to these, however, it is also known to use so-called electromechanical foils for transmitting and / or receiving sound signals. The construction and production of such films are described, for example, in US 4,654,546. Due to the high frequency of an ultrasonic signal and the associated

Movement in the electromechanical foil arises when sending and receiving the signals heat. This leads to an undesirable heating of the sensor. Alternatively, it can also come from the outside to a heat on the sensor element.

In order to remove heat from a circuit arrangement, it is known from DE-A 10 2007 037 543 to provide a heat dissipation unit between individual chips and to couple them to a heat dissipation device. However, such a unit can be found in

Ultrasonic sensors are not used because with appropriate heat-dissipating layers, the vibrations of the sensor are attenuated. An appropriate one

Ultrasonic sensor would thus not work reliably.

Disclosure of the invention

A device according to the invention for transmitting and / or receiving sound signals, in particular ultrasound, comprises an electromechanical film which is connected to at least one front-side electrode and at least one rear-side electrode, wherein the electromechanical film is connected to a carrier in a heat-conducting manner.

Due to the heat-conductive connection with a carrier, heat from the

removed electromechanical film, thus ensuring that the film at

Essentially constant temperature and thus works reliably. In the case of temporary heat input from the outside, this heat is dissipated faster and the temperature of the sensor element is lowered faster to working temperature.

An electromechanical film according to the present invention comprises a membrane of a so-called ferroelectret material. As Ferroelektret materials in particular closed-cell polymer foams are referred to, in which at the

Interface of individual pores positive and negative electrostatic charges are permanently localized. Due to the impressed electrostatic charges, the individual pores expand upon application of an electrical voltage or contract with reverse polarization. This makes it possible, by appropriate excitation to generate a vibration that can be sent as a sound pulse. Accordingly, upon impact of sound waves by the mechanical change in the size of the pores, a voltage can be generated which can be tapped.

As polymer materials for the production of the foams, in particular fluorine-based polymers, for example polytetrafluoroethylene, polyfluoroethylene propylene and

Polyvinylidene fluoride. Also suitable, for example, polyethylene terephthalate. In addition to the polymers mentioned, copolymers of these polymers are also suitable.

In order to use the electromechanical film as a transmitter or receiver for sound signals, one side of the film is generally metallized over the entire surface. This layer serves as a ground electrode. On the opposite side of the full metallized side electrodes are applied in each case at the positions at which the respective transmitter and / or receiver are to be located. Both the full-surface ground electrode and the electrodes at the positions, which each serve as transmitter and / or receiver, are applied, for example, by electroless and / or galvanic deposition, chemical deposition methods or physical deposition methods. Particularly suitable for applying the metallization for the electrodes are methods in which the metal is vapor-deposited on the electromechanical film, for example CVD (Chemical Vapor Deposition) method or PVD (Physical Vapor Deposition) method.

Alternatively, it is also possible to form none of the electrodes over the entire surface, but to make both the front side electrode and the rear side electrode opposite to each other. However, it is preferred to design either the front-side electrode or the rear-side electrode over the entire surface. If the front-side electrode and / or the rear-side electrode is a full-surface metal layer, this can be achieved in a first embodiment according to the invention

Embodiment for heat dissipation are connected to the carrier. For this purpose, it is possible, for example, to apply the electrode formed over the entire area to a portion of the carrier which conducts heat well. Alternatively, it is also possible to make the entire-area electrode in a greater thickness, preferably in a thickness of at least 100 μηη, in order to dissipate the heat via laterally mounted thermal bridges, with which the heat-conducting layer is connected to the carrier. In an alternative embodiment, an insulating layer is applied to the electromechanical foil and the at least one front-side electrode or the at least one rear-side electrode, and a heat-conductive layer on the insulating layer for heat removal. The applied insulating layer serves in particular as electrical insulation. Suitable materials for the insulating layer are any dielectric materials,

in particular polymers. Suitable polymers are, for example, polyethylene, polypropylene, polyvinyl chloride, polyamide, polyester, or polyurethanes.

In the context of the present invention, a "good heat-conducting" is understood as meaning a material having a thermal conductivity which is so great that during operation of the device a thermal conductivity is achieved

formed electromechanical film formed sensor element heat can be removed without the sensor element to temperatures above the

Working temperature heated and the sensor element can be operated at substantially constant temperature.

The good heat-conducting layer applied to the insulating layer is preferably a metallic layer. The good heat-conducting layer can, as well as the electrodes by electroless and / or galvanic deposition or by chemical or

physical deposition, such as vapor deposition can be applied. Heat generated during operation of the sensor is transported by heat conduction through the insulating layer to the good heat-conducting layer and dissipated by this to the carrier. For this purpose, the good heat-conducting layer is thermally conductively connected to the carrier.

As a material for the good heat-conducting layer are, for example, copper, aluminum, silver, brass or steel.

As a material for the electrodes, in particular if they are used as a heat-conducting layer, are suitable, for example, copper, silver, gold or aluminum. In order to be able to conduct the heat from the electromechanical film to the carrier, it is preferred for the carrier to contain a material which conducts heat well. The heat from the electromechanical film is then passed through the heat-conductive connection via the good heat-conducting layer to the good heat-conducting material of the carrier. It is both possible that the entire carrier is made of a good heat conducting material or only parts of the carrier of a good heat conducting material and the base of the Carrier made of a poorly heat-conductive material. The electromechanical foil is then connected to the good heat-conducting sections of the carrier.

In the context of the present invention, a "poorly heat-conducting" is a

Thermal conductivity understood that is so small that the heat generated during operation of a sensor element can not be dissipated and therefore the sensor element heats up.

As a basis for the carrier are then, for example, plastics, which may also have a low heat transfer coefficient. As well heat-conducting sections, for example, metallic sections can be used.

Alternatively, it is also possible to make the carrier for example of a material with a good heat storage capacity. In this case, heat is transferred from the sensors to the heat-storing material when the sensors are heated, and heat is transferred from the heat-storing material back to the sensor as the sensors cool. This makes it possible to operate the sensor at a substantially constant temperature. In order to avoid current flowing into the carrier when a voltage is applied to the electromechanical foil, it is advantageous if an insulating layer is accommodated between the carrier and the electrode of the electromechanical foil is. Any electrically insulating material is suitable for the insulating layer, in particular plastic materials are suitable.

The device according to the invention for transmitting and / or receiving sound signals is suitable, for example, for detecting the surroundings of driver assistance systems in motor vehicles. Furthermore, the device can also be used to detect the environment in autonomously moving systems. Such autonomously moving systems are, for example, robots, for example, driverless lawnmowers or vacuum cleaners, or even driverless transport systems, such as those used in industry.

When the device for transmitting and / or receiving sound signal in a

Motor vehicle is used, it is particularly preferred if the carrier is a bumper of the motor vehicle. The electromechanical foil is in this case with the bumper of the motor vehicle connected in such a way that in each case at the positions at which

Ultrasonic sensors are to be located, an electrode or an array is formed. Alternatively, it is also possible to apply each foil sections at the positions at which sensors are to be located. These positions have a good connection to

Airborne field, but need not be in the bumper.

In order to dissipate the heat from the electromechanical film, either a full-surface electrode of the device is thermally conductively connected to the carrier or the separate provided heat-dissipating layer.

Brief description of the drawings

Embodiments of the invention are illustrated in the figures and are explained in more detail in the following description.

Show it:

Figure 1 A device according to the invention for transmitting and / or receiving

Sound signals in a first embodiment, Figure 2 A device according to the invention for transmitting and / or receiving

Sound signals in a second embodiment.

Embodiments A device 1 for transmitting and / or receiving sound signals comprises an electromechanical film 3, which is provided on one side with a metallic coating 5. The metallic coating 5 acts as a ground electrode 7. The metallic

Coating 5 can, as shown in Figure 1, the full surface on the

be applied electromechanical film 3 or in each case at the points at which individual transducers 9 are to be formed on the electromechanical film 3. Each transducer 9 further comprises a transducer electrode 1 1. The transducer electrode 1 1 is the shape and size of the transducer 9 again. If not the entire surface of the electromechanical film 3 is coated with a metallic coating 5 to form the ground electrode 7, but only the one

Transducer electrodes 1 1 opposite points, it is preferred if the Ground electrode has the same shape as the transducer electrode 1 1. Alternatively, it is also possible to provide the ground electrode slightly larger than the transducer electrode 1 1.

In the embodiment shown in FIG. 1, the converter electrodes 11 are formed on a printed circuit board 13. The circuit board 13 can be made of any known to the expert material for printed circuit boards. It is preferred to form the printed circuit board 13 from a flexible material.

On the transducer electrodes 1 1, which are formed on the circuit board 13, an adhesive layer 15 is applied. With the adhesive layer 15, the electromechanical film 3 is attached to the circuit board 13 and the transducer electrodes 1 1. As adhesive for the adhesive layer 15, any adhesive with which the electromechanical film 3 can be mounted on the circuit board 13 is suitable. It is important to ensure that an adhesive is used that does not damage the electromechanical film 3.

On the ground electrode 7 further protective layers 17 may be applied. As a protective layer 17 is for example a polymer layer with which the device 1 is protected for transmitting and / or receiving sound signals against mechanical effects. In addition, the entire device 1 for sending and / or

Receiving sound signals from another protective layer 19 to be enclosed. The further protective layer 19, like the protective layer 17, serves to protect the device 1 for transmitting and / or receiving sound signals against external influences, for example against weather influences or mechanical influences. In order to dissipate heat generated during operation of the device 1, which is

Device 1 according to the invention connected to a heat-dissipating carrier 21. The heat-dissipating carrier 21 is preferably made of a metallic material that is good heat-conducting. In order to remove the heat from the heat-dissipating carrier 21, this is, for example, when using the device for transmitting and / or

Receiving sound signals as a distance sensor in a motor vehicle connected to other body parts of the vehicle. Here, the heat-dissipating carrier 21 is preferably thermally connected to the body. This can be done for example by a welded joint. The heat-dissipating carrier 21 is preferably made of a metal, for example steel, aluminum, brass or copper. At the same time, the heat-dissipating carrier 21, if it is formed from a metal and thus also can easily conduct an electric current, serve as a ground electrode for an electrical shielding of the device 1 for transmitting and / or receiving sound signals.

The heat-dissipating carrier 21, on which the circuit board 13 is fixed to the sound transducers 9, may be, for example, a body component. The further protective layer 19 may be, for example, a vehicle paint in this case, which also represents a protection against environmental influences. Alternatively, it is also possible, for example, to apply a metal layer on a body component made of a plastic material, which serves as a heat conducting layer and thus as a heat dissipating carrier 21. So it is possible, for example, on a bumper made of a plastic material, a metal layer for

Apply heat conduction and on this metal layer, the circuit board with the device 1 for transmitting and / or receiving sound signals. When the circuit board is made of a flexible material, this has the advantage that the entire device for transmitting and / or receiving sound signals is flexible and can be adapted to the surface on which it is applied. The attachment of the device for transmitting and / or receiving sound signals is effected, for example, by gluing the printed circuit board on the heat-dissipating carrier 21st In addition to sticking any other type of attachment can be selected. Essential in the attachment is a heat-dissipating attachment. When the circuit board is bonded to the heat-dissipating carrier 21, it is particularly advantageous when a thermally conductive adhesive is used.

FIG. 2 shows a device for transmitting and / or receiving sound signals in a second embodiment.

The construction of the embodiment shown in FIG. 2 essentially corresponds to that shown in FIG. Also in FIG. 2, the device for transmitting and / or receiving sound signals comprises an electromechanical film 3, a ground electrode 7 applied as metallic coating 5 on the electromechanical film 3, two transducer electrodes 1 1, each defining a sound transducer 9. Also in the embodiment shown in Figure 2, the transducer electrodes 1 1 are formed as conductor tracks on a printed circuit board 13. The electromechanical foil with the applied on it Metallic coating 5 is fixed with an adhesive layer 15 on the circuit board 13 with the transducer electrodes 1 1 applied thereto. In contrast to the embodiment shown in FIG. 1, in the embodiment shown in FIG. 2, the heat dissipating carrier 21 is designed to have a surface whose dimensions are the size of the device 1 for transmitting and / or receiving

Sound signals corresponds. Parts of the circuit board 13 on which there is no more electromechanical film 3, are placed around the heat-dissipating carrier 21 and thus abut against this. In this way, heat can be released to the heat-dissipating carrier 21 over the entire printed circuit board 13.

To operate the transducer, a voltage is applied between transducer electrode 1 1 and ground electrode 7. By applying the voltage, the electromechanical film 3 is excited to vibrate by applying electric charges impressed on pores 23 of the electromechanical film by applying the voltage to the electromechanical film

Repulsion or attraction of the opposite sides lead. The vibrations thus applied are emitted as a sound signal from the transducer 9.

When a sound signal impinges on the sound transducer 9, the electromechanical film 3 begins to vibrate and due to the charges on the pores 23, a voltage is generated. This can be tapped via the conversion electrodes 1 1. Based on the sound propagation time between emitted signal and received echo, the distance to an object can be determined.

In addition to the embodiments shown in Figures 1 and 2 with only two

Sound transducers 9, it is also possible to have more than two transducers on the

provide electromechanical film 3, which can be used for example as ultrasonic sensors as distance sensors on motor vehicles. It is also possible to provide only one transducer electrode 1 1. Furthermore, it is also possible, the heat-dissipating carrier 21 on the side of

Provide ground electrode. In this case, the ground electrode can also be connected in a heat-conducting manner to a carrier and dimensioned such that the ground electrode simultaneously serves as a heat-dissipating carrier. However, an arrangement of the

heat dissipation carrier 21 on the side of the transducer electrodes 1 1, as shown in Figures 1 and 2.

Claims

claims

1 . Device for transmitting and / or receiving sound signals, in particular

Ultrasound comprising an electromechanical foil (3) which is connected to at least one front-side electrode (7) and at least one rear-side electrode (11), characterized in that the electromechanical foil (3) has a heat-conducting effect

Carrier (21) is connected.

2. Device according to claim 1, characterized in that the

Front side electrode (7) and / or the back side electrode (1 1) is a full-surface metal layer, which is connected to the heat dissipation to the carrier (21).

3. Device according to claim 1, characterized in that on the

electromechanical film (3) and the at least one front-side electrode (7) or the at least one rear-side electrode (1 1) an insulating layer is applied and on the insulating layer, a good heat-conducting layer for heat dissipation.

4. The device according to claim 3, characterized in that the insulating layer comprises a layer of a polymer.

5. Apparatus according to claim 3 or 4, characterized in that the well

thermally conductive layer is a metal layer, for example copper, aluminum, silver, brass or steel.

6. Device according to one of claims 1 to 5, characterized in that the carrier (21) contains a good heat-conducting material.

7. Device according to one of claims 1 to 6, characterized in that the carrier has a base made of a poor thermal conductivity material and a good heat-conducting portion with which the electromechanical film is thermally conductively connected.

8. Device according to one of claims 1 to 7, characterized in that between the carrier (21) and the electromechanical film (3) an insulating layer is added.

Device according to one of claims 1 to 8, characterized in that the carrier (21) is a bumper, a body part or other attached to the outer shell part of a motor vehicle or an autonomously moving system.

Apparatus according to claim 9, characterized in that the autonomously moving system is a robot.

1 1. Use of the device according to one of claims 1 to 9 as an ultrasonic sensor for environment detection, in particular for detecting the environment of a motor vehicle or an autonomously moving system.