Manufacturing process for producing a diaphragm pot of an ultrasonic transducer, diaphragm pot and injection moulding tool

Abstract

A manufacturing process for producing a diaphragm pot of an ultrasonic transducer, comprising the following steps: injecting (120) a polymer melt (340) into at least one cavity (310) of the injection moulding tool (300) by means of at least one nozzle (320), the cavity (310) of the injection moulding tool (300) being larger than the diaphragm pot (200) to be manufactured; closing (130) the nozzle (320), in particular by means of a needle valve (321); compressing (140) the polymer melt (340) by reducing the volume of the cavity of the injection moulding tool (300); cooling (150) the polymer melt (340); and removing (160) the diaphragm pot (200) from the injection moulding tool (300), wherein the removed diaphragm pot (200) comprises at least one region (210) which is capable of vibrating and which at least on the outer contour (220) has a wall thickness (230) of less than 100 μm.

Description

[0001] Description

[0002] Manufacturing process for the production of a diaphragm cup of an ultrasonic transducer, diaphragm cup and injection molding tool

[0003] The present invention relates to a manufacturing method for producing a diaphragm cup of an ultrasonic transducer, wherein a plastic melt is injected into a cavity of an injection mold and subsequently compacted. The present invention also relates to the manufactured diaphragm cup obtained by the manufacturing method. The invention further relates to the injection mold for producing the diaphragm cup.

[0004] State of the art

[0005] The document DE 10 2010 027 780 A1 discloses a method for controlling an ultrasonic sensor and an ultrasonic sensor.

[0006] The document DE 10 2014 110 179 A1 discloses an ultrasonic sensor device for a motor vehicle.

[0007] The document EP 3 414 796 B1 discloses a method for forming a contact element.

[0008] The document DE 10 2017 205 375 A1 discloses methods for producing a functional group of a sound transducer.

[0009] In ultrasound-based parking assistance systems, the ultrasonic sensors or ultrasonic transducers are located on the vehicle bumpers. They operate according to the well-known echo sounder principle and emit short ultrasonic pulses in the 40 kHz range, which are reflected by any obstacles. A control unit determines the distance to the obstacle from the propagation time of the echo signals received by the sensor. The diaphragm cups or sensor heads of the ultrasonic sensors are typically made of metallic materials and are therefore limited in their shape to specific contours. Signal conversion via vibrating surfaces is not feasible with these materials. The object of the present invention is to improve an injection molding process for a dimensionally stable diaphragm cup for an ultrasonic transducer.

[0010] Disclosure of the invention

[0011] The above object is achieved according to the invention according to the independent claims 1, 10 and 11.

[0012] The present invention relates to a manufacturing method for producing a diaphragm cup of an ultrasonic transducer. The method advantageously comprises optionally heating an injection mold to a temperature greater than 100°C, in particular by means of heating elements of the injection mold. A plastic melt is then injected into at least one cavity of the injection mold using at least one nozzle, wherein the cavity of the injection mold is larger than the diaphragm cup to be manufactured. Advantageously, several cavities with the same geometry are provided in the injection mold for the parallel production of several identical diaphragm cups. In a further step, the nozzle is sealed or closed, in particular by means of a needle or a needle valve.Subsequently, according to the invention, the plastic melt is compacted by reducing the volume of the respective cavity, in particular the compaction takes place by means of at least one movable die and / or by bringing the tool parts closer together. The plastic melt is then cooled, in particular heating elements are switched off and water cooling is activated. Finally, the at least one manufactured diaphragm pot is removed from the injection molding tool, in particular by means of ejector pins and / or a robot arm. The removed, manufactured diaphragm pot comprises at least one oscillatable region, wherein the oscillatable region has a wall thickness of less than 100 μm at least on the outer contour. The method enables the cost-effective production of a warpage and stress-free, very flat diaphragm pot with a low wall thickness of less than 100 μm using the injection molding process.

[0013] The manufactured diaphragm cup preferably comprises at least four oscillatable regions. This allows the diaphragm cup to be advantageously used to manufacture a sensor array. In other words, the ultrasonic transducer or ultrasonic sensor in this embodiment can advantageously comprise four ultrasonic sensor elements or ultrasonic transducer elements, thereby improving the spatial assignment to the origin of the ultrasonic echo or the determination of the reflection point in the horizontal and / or vertical direction.

[0014] In a particularly preferred embodiment, the plastic melt comprises polycarbonate. This results in a membrane cup that is paintable, water-resistant, resistant to chemical cleaning agents, ultraviolet radiation (UV radiation), and stable at temperatures up to at least 100 °C.

[0015] In an advantageous embodiment, the plastic melt comprises UV stabilizers and heat stabilizers. This embodiment improves stability against ultraviolet radiation (UV radiation) and high temperatures exceeding 100°C.

[0016] In one embodiment, it is preferably provided that the plastic melt is injected or sprayed into the cavity at a location that represents a component shoulder of the diaphragm cup. In other words, the nozzle or a needle valve nozzle is arranged at a location in the cavity that represents a component shoulder of the diaphragm cup, for example, on the underside or on a cantilever edge of the diaphragm cup. This advantageously avoids a sprue and subsequent processes for removing the sprue.

[0017] In a preferred embodiment, the nozzle for injecting the plastic melt is a needle-valve nozzle. This advantageously eliminates the need for a sprue and subsequent processes for removing the sprue. Furthermore, it advantageously prevents backflow of the plastic melt during compaction.

[0018] It can be provided that the compaction is carried out in at least two compaction stages with increasing compaction levels. Each compaction stage is advantageously realized or carried out using at least one different die, which is moved into the cavity. In other words, the compaction is carried out in two steps, with the pressure of the plastic melt increasing gradually. In this further development of the invention, the pressure on the plastic melt can advantageously be increased. This advantageously reduces the roughness of the diaphragm cup and material stresses inside the diaphragm cup.

[0019] Advantageously, a rest period is provided between the compression stages. This allows for the pressure distribution in the plastic melt to be homogenized.

[0020] In another embodiment, different temperatures of the injection mold are generated or adjusted during the different compression stages. This advantageously optimizes the material properties of the diaphragm cup as well as its stability.

[0021] The invention also relates to the diaphragm pot as a product which is obtained by a manufacturing method according to the invention.

[0022] The invention further relates to an injection molding tool for producing the diaphragm cup for an ultrasonic transducer. The injection molding tool comprises at least one cavity, wherein the cavity of the injection molding tool is larger than the diaphragm cup to be produced. The injection molding tool has at least one closable nozzle for injecting the plastic melt. Furthermore, the injection molding tool comprises, in particular, at least one, in particular cylindrical, embossing die. The optional embossing die is designed to be inserted into the cavity of the injection molding tool and to reduce the volume of the cavity. This advantageously allows a plastic melt injected into the cavity through the nozzle to be compressed.

[0023] Further advantages will become apparent from the following description of embodiments with reference to the figures.

[0024] Figure 1 : Flowchart of the manufacturing process of a diaphragm pot

[0025] Figure 2: Diaphragm pot in cross section Figure 3: Injection molding tool in a first variant

[0026] Figure 4: Injection molding tool in a second variant

[0027] Figure 5: Injection molding tool in a third variant

[0028] Examples of implementation

[0029] Figure 1 shows a flow chart for the manufacturing process for a diaphragm pot, schematically as a block diagram. The process comprises optionally heating 110 an injection mold to a temperature greater than 100°C, in particular by means of heating elements of the injection mold or an injection molding machine. Subsequently, in step 120, a plastic melt is injected into at least one cavity of the injection mold using at least one nozzle, wherein the cavity of the injection mold in step 120 is larger than the diaphragm pot to be manufactured. The plastic melt advantageously comprises polycarbonate and additives, for example UV stabilizers and heat stabilizers. The nozzle is particularly preferably a needle valve nozzle. In step 120, the plastic melt is preferably injected into the cavity at a location which represents a component shoulder or an underside or a cantilever edge of the diaphragm pot.In the further step 130, the nozzle is closed, in particular by means of a needle valve. Subsequently, in step 140, the plastic melt in the cavity is compacted by reducing the cavity volume of the injection molding tool using at least one movable die. The compaction takes place, for example, in at least two compaction stages with increasing compaction levels or increasing pressures, with an additional die being moved into the cavity for each compaction stage. A rest period can be provided between the compaction stages. During the various compaction stages, the injection molding tool is regulated or adjusted, in particular, to different temperatures in step 140, with the temperature advantageously increasing with increasing pressure or higher compaction level. In step 150, the plastic melt is cooled.Cooling is achieved in particular by active water cooling, meaning that cold water is pumped through the cavities of the injection mold. Subsequently, in step 160, the molded or manufactured diaphragm cup is removed from the injection mold. The removed diaphragm cup comprises at least one oscillatable region, which has a wall thickness of less than 100 μm, at least along the outer contour. The diaphragm cup preferably comprises at least four oscillatable regions.

[0030] Figure 2 shows a schematic cross-section of the oscillating region 210. The diaphragm cup 200 comprises polycarbonate or is made of polycarbonate. The diaphragm cup 200 can advantageously comprise additives, in particular UV stabilizers and heat stabilizers. The diaphragm cup 200 has an oscillating region 210 or a diaphragm, which has a wall thickness 230 of less than 100 μm at least on the outer contour 220. The diaphragm cup can comprise a plurality of oscillating regions 210, which are arranged in particular on the front side 260 of the diaphragm cup 200 (not shown here). The plastic melt is injected using a nozzle in an injection mold, preferably on the underside 270 of the diaphragm cup 200 or on a cantilever edge 250 of the diaphragm cup 200. The diaphragm cup 200 further comprises an advantageously cylindrical outer surface 240.The diaphragm cup 200 is configured to accommodate at least one ultrasonic sensor element within its interior, wherein the ultrasonic sensor element is in particular contacted with the oscillatable region 210, for example, by a material-to-material contact, in particular a welded and / or adhesive connection. The oscillatable region 210 or the diaphragm can comprise an oscillating mass 280.

[0031] Figure 3 shows a schematic cross-sectional view of an injection molding tool 300 in a first variant. The injection molding tool 300 comprises a first tool part 301 and a second tool part 302. The first tool part 301 and the second tool part 302 can be detached or separated from one another in the direction 390. In the contacted state, at least one cavity 310 or hollow space is formed between the first tool part 301 and the second tool part 302. In the exemplary embodiment from Figure 1, a first cavity 310a and a second cavity 310b are formed, wherein each cavity 310, 310a, 310b can be used to produce a diaphragm cup 200 by injection molding. Each cavity 310, 310a, 310b represents a negative mold of the diaphragm cup 200 to be produced.Once the first tool part 301 and the second tool part 302 are connected to one another and the cavity 310 is formed, a plastic melt can be injected into each cavity 310 by means of a hot runner 325 and a respective nozzle 320 connected to the cavity 310. The injected plastic melt 340 is distributed in the respective cavity 310. The nozzle 320 is then closed, for example, by means of a needle 321. According to the invention, the plastic melt injected into the respective cavity 310 through the hot runner 325 and the nozzle 320 is (post-)compacted after injection by moving or retracting or extending dies into the cavity or by bringing the first and second material parts 301, 302 closer together.In the example of Figure 3, the plastic melt 340 injected into the cavity 310 is compacted 140 by reducing the joining gap 330 by bringing the first and second material parts 301, 302 closer together in the direction 390, see Figures 3a and 3b. After the compacted plastic melt 340 has cooled in the (reduced in volume) cavity 310, the first tool part 301 and the second tool part 302 are separated from one another in the direction 390, and the finished membrane pot 200 or the finished membrane pots 200 are removed.

[0032] Figures 4 and 5 schematically show a cross-sectional view of a second and third variant of the injection molding tool 300. The injection molding tool 300 from Figures 4 and 5 is essentially constructed like the injection molding tool from Figure 3, or corresponds to it, except for the arrangement of a respective die 350 for each cavity 310; see the description, including the reference numerals, for Figure 3. According to the invention, the plastic melt injected into the respective cavity 310 through the hot runner 325 and the nozzle 320 is compressed after injection by retracting or extending the die 350 in the direction 395 in the respective cavity 310. In the example from Figures 4 and 5, a compression 140 of the plastic melt 340 injected into the cavity 310 takes place by moving the stamping die in the respective direction 395 into the cavity 310, compare Figures 4a and 4b or 5a and 5b.

Claims

Claims 1 . Manufacturing method for producing a diaphragm cup of an ultrasonic transducer, comprising the steps • Injecting (120) a plastic melt (340) into at least one cavity (310) of the injection molding tool (300) by means of at least one nozzle (320), wherein the cavity (310) of the injection molding tool (300) is larger than the membrane pot (200) to be manufactured, • Closure (130) of the nozzle (320), in particular by means of a needle closure (321), • Compression (140) of the plastic melt (340) by reducing the cavity volume of the injection mold (300), • Cooling (150) of the plastic melt (340), and • Removing (160) the diaphragm pot (200) from the injection molding tool (300), wherein the removed diaphragm pot (200) comprises at least one oscillatable region (210) which has a wall thickness (230) of less than 100 pm at least on the outer contour (220).

2. Manufacturing method according to claim 1, wherein the diaphragm pot (200) has at least four vibratable regions (210).

3. Manufacturing method according to one of the preceding claims, wherein the plastic melt (340) comprises polycarbonate.

4. Manufacturing method according to one of the preceding claims, wherein the plastic melt (340) comprises UV stabilizers and heat stabilizers.

5. Manufacturing method according to one of the preceding claims, wherein the plastic melt (340) is injected into the cavity (310) at a location which represents a component shoulder or a bottom side (270) or a cantilever edge (250) of the diaphragm pot (200).

6. Manufacturing method according to one of the preceding claims, wherein the nozzle (320) is a needle valve nozzle.

7. Manufacturing method according to one of the preceding claims, wherein the compaction (140) takes place in at least two compaction stages with increasing compaction levels, wherein for each compaction stage an additional stamping die (350) is moved into the cavity (310).

8. Manufacturing method according to claim 7, wherein a rest period is provided between the compaction stages.

9. Manufacturing method according to one of claims 7 or 8, wherein different temperatures of the injection molding tool (300) are set during the different compression stages.

10. Membrane cup (200) for an ultrasonic transducer, obtained by a manufacturing method according to one of claims 1 to 9. 11 . Injection molding tool (300) for producing a diaphragm cup (200) for an ultrasonic transducer by a manufacturing method according to one of claims 1 to 9, comprising at least • a cavity (310), wherein the cavity (310) is larger than the membrane pot (200) to be manufactured, • at least one closable nozzle (320), and • in particular at least one stamping die (350) which is designed to be inserted into the cavity (310) of the injection molding tool (300) and to reduce the volume of the cavity (310) so that a plastic melt (340) injected into the cavity (310) through the nozzle (320) is compressed.

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