Particle collecting unit for a radiation-based control device

Abstract

The invention relates to a collecting unit for maintaining the particle-free nature of a closed cavity (14) of a radiation-based control device (10), characterised in that the collecting unit comprises an electrostatically charged needle, bundles of needles, e.g. also carbon fibres (22), and a collecting tank (24a) which is arranged therebelow in the vertical direction. A strong and inhomogeneous electrical field is generated in the cavity (14) in the vicinity of the needle tip (23), as a result of which particles floating in the cavity (14) are drawn towards the needle tip and are deposited thereon. In phases of currentless pauses in operation of the transmitter or receiver (10), the adhering particles detach from the needle tip (23) and sink into the collecting tank (24a) due to gravity, as a result of which settling on the sensitive surface of the transmitter or receiver (10) is prevented.

Description

[0001] Particle capture unit for a radiation-based control unit

[0002] The invention relates to a capture unit for maintaining the particle-free status of a sealed cavity of a radiation-based control device.

[0003] With radiation-based environmental sensing devices such as lidar, cameras, or radar, a challenge lies in keeping the cavity inside the transmitter and / or receiver free of particles during assembly and throughout their operational lifespan. As the structures in the transmitting and receiving areas become increasingly smaller, the systems become more susceptible to interference from ever smaller particles. Microparticles can be carried into the cavity of the control device during assembly or can detach during assembly, for example, through joining processes, or during operation. These particles can then settle from the surrounding cavity onto the transmitter or receiver, creating blind spots that can reduce the safety and / or functionality of the device.While it is largely possible to ensure a particle-free cavity during manufacturing and to keep the cavity absolutely sealed against the environment, this becomes increasingly difficult and complex for particle sizes below 100 µm, thus complicating the manufacturing process. It is also possible that such small particles could detach during operation of the control unit, for example, due to vigorous movements of the unit during operation, and settle on the radiation-sensitive surfaces.

[0004] From US patent 2009 / 0183322 A1, it is known to clean a substrate using an electrostatically charged needle by passing the needle tip over the substrate surface and thereby electrostatically attracting particles from the substrate surface. The object of the invention is to keep the cavity of a radiation-based control device as particle-free as possible throughout its operating time and to provide a radiation-based control device with a particle-free cavity. For the purposes of this invention, a control device is understood to be a transmitter or receiver of electromagnetic radiation, in particular laser light or radar radiation.

[0005] The invention is defined by the features of the independent claims. Advantageous further developments and embodiments are the subject of the dependent claims.

[0006] The problem is solved according to claim 1 in that the capture unit comprises an electrostatically charged needle and / or a bundle of several electrostatically charged needles, e.g. also carbon fibers, as well as a collection tray arranged vertically below it.

[0007] The invention generates a strong and inhomogeneous electric field in the cavity surrounding the needle tip. This causes particles suspended in the cavity to experience a charge displacement, attracting them to the needle tip and depositing them there, as in US 2009 / 0183322 A1. During periods of power-off inactivity of the transmitter or receiver, or when the needle's power supply is switched off, the adhering particles detach from the needle tip and sink into the collection tray due to gravity, thus preventing them from settling on the transmitter or receiver. This allows even very small particles, measuring 100–300 pm, to be effectively removed from the cavity.

[0008] According to an advantageous embodiment of the invention, the needle is directed vertically downwards, thus extending vertically downwards from a needle attachment, in order not to impair the accessibility of the needle tip from all sides.

[0009] According to an advantageous embodiment of the invention, the collection tray is funnel-shaped in order to collect the sunken particles in the bottom of the funnel.

[0010] According to an advantageous embodiment of the invention, the collection tray has a collection chamber above which a funnel with an opening to the collection chamber is arranged. The upper funnel thus serves to feed settled particles through the opening into the collection chamber below, from which they can hardly escape again, since the opening should preferably be kept relatively small.

[0011] According to an alternative advantageous embodiment of the invention, the collection tray has the form of a multi-funnel with a funnel-shaped collection chamber, above which a further funnel with an opening to the funnel-shaped collection chamber is arranged, the axes of the two funnels being offset from each other. This design forms a labyrinth for the trapped particles, since the particles arranged in the funnel base of the collection chamber do not escape from the collection chamber through the opening when the transmitter or receiver is tipped over by 180°.

[0012] According to an advantageous embodiment, the collection chamber is manufactured as a drilled blind hole, and the funnel arranged above it is formed as a mountable attachment, preferably made of plastic. Thus, the collection chamber can be drilled into the housing as a funnel- or cylindrical-shaped blind hole, and the upper funnel is attached to it as an attachment, for example, by gluing.

[0013] According to an advantageous embodiment of the invention, the base of the collection tray is coated with a long-lasting adhesive material. This is preferably a silicone-based adhesive or a polymer adhesive that does not outgas and remains tacky over the long term. Since particles tend to detach during the initial phase of operation, it is particularly important that the adhesive remains usable for approximately one year. In the case of a funnel-shaped collection tray, the adhesive will be applied to the tip of the funnel. In the case of a cylindrical collection chamber, the adhesive will be applied to the entire base.

[0014] According to an advantageous embodiment of the invention, the needle is attached to a circuit board. This makes it structurally simple to electrostatically charge it using the power supply of the control electronics.

[0015] According to an advantageous embodiment of the invention, the power supply to the needle can be switched off periodically. If the transmitter or receiver is designed to be switched off periodically, as is the case, in particular, with environmental sensors in vehicles, the periods without power are sufficient to allow particles adhering to the tip to sink into the collection tray. However, if the transmitter or receiver is designed for continuous operation, a circuit must be provided that periodically switches off the power supply to the needle tip to allow the particles adhering to the needle tip to sink into the collection tray.

[0016] The problem is further solved by a radiation-based transmitter or receiver that includes a capture unit of one of the aforementioned designs. The transmitter or receiver is preferably a laser or radar transmitter or receiver.

[0017] Further advantages, features, and details will become apparent from the following description, in which – possibly with reference to the drawings – at least one embodiment is described in detail. Identical, similar, and / or functionally equivalent parts are identified by the same reference numerals.

[0018] They show:

[0019] Figure 1: a schematic representation of a control unit;

[0020] Figure 2: a schematic representation of a second collection tray shape; Figure 3: a schematic representation of a third collection tray shape.

[0021] Figure 1 schematically depicts a radiation-based control unit 10, preferably an optical or radio wave-based transmitter or receiver. This unit comprises a dustproof housing 12 with a dustproof cavity 14 containing a printed circuit board 16 with an optical transmitter and / or receiver 18. A lens holder 20 with a lens is mounted on the housing 12. A needle 22 is mounted on the underside of the circuit board 16 and is electrically coupled to the board 16 to electrostatically charge it. Instead of a single needle 22, a bundle of several needles can also be used. If, in particular, the control unit is a LiDAR sensor, several hundred volts from a required APD array (“avalanche photodiode”) are available. The needle 22 preferably has a length of approximately 0.3–1 cm, and the tip radius of the needle tip 23 is preferably 1–100 pm.

[0022] Directly below the needle 22, a collection tray 24a is arranged, preferably at a distance of 0.2–2 cm from the needle tip. In the embodiment shown in Figure 1, the collection tray 24a is designed as a funnel, preferably with a depth of 0.2–0.5 cm. Adhesive 26 is provided in the base of the funnel to retain fallen particles long-term. The funnel-shaped collection tray 24a is preferably drilled or integrally formed as a blind hole in the housing 12, which is preferably manufactured as a casting.

[0023] Figure 2 shows a first alternative collection tray 24b, in which the collection tray 24b consists of two funnel elements arranged one above the other. The lower funnel element forms a collection chamber 28a, which is generally shaped like the collection tray 24a of Figure 1, and a second funnel element 30 is offset onto it. An opening 32 with the smallest possible cross-section is formed between the collection chamber 28a and the second funnel element 30. This opening is located directly below the needle tip 23, allowing particles falling from the needle tip 23 to fall as directly as possible into the lower collection chamber 28a through this opening. The axes of the two funnels are spaced a distance a of preferably 1–3 mm apart, thus preventing particles lying in the bottom of the collection chamber 28a from being thrown back through the opening 32 into the cavity 14 when the control unit 10 tilts.

[0024] Figure 3 shows a further embodiment of the collection tray 24c, which has a cylindrical collection chamber 28b. In the collection chamber 28b as well, the entire bottom is preferably covered with adhesive 26.

[0025] The funnel element 30 is preferably made of plastic and was glued over the collecting chamber 28a or 28b after drilling.

[0026] In operation, the needle 22 is electrostatically charged, so that, due to the point effect in the vicinity of the needle tip 23, particles are attracted to it due to charge displacement and collect on the needle 22, thus keeping the rest of the cavity 14 free of particles. As soon as the power supply to the needle 22 is switched off, either by switching off the control unit 10 entirely or by a circuit (not shown) that only periodically switches off the power supply to the needle 22, some of the particles adhering to the needle 22 fall downwards and thus into the collection tray 24a, 24b, 24c. In the collection tray 24a, these then slide along the funnel wall to the bottom and are held in place by the adhesive 26 located there.In the configurations shown in Figures 2 and 3, the particles either fall directly through the opening 32 or first slide along the wall of the funnel element 30 and then through the opening 32 to reach the collection chamber 28a or 28b below and be fixed to the bottom by the adhesive 26 located there.

[0027] Although the invention has been further illustrated and explained in detail by means of preferred embodiments, the invention is not limited by the disclosed examples, and other variations can be derived from them by a person skilled in the art without departing from the scope of protection of the invention. It is therefore clear that a multitude of possible variations exist. It is also clear that the embodiments mentioned as examples are truly only examples and are not to be understood in any way as limiting, for example, the scope of protection, the possible applications, or the configuration of the invention.Rather, the preceding description and the description of the figures enable the person skilled in the art to implement the exemplary embodiments in concrete terms, whereby the person skilled in the art, with knowledge of the disclosed inventive concept, can make various changes, for example with regard to the function or the arrangement of individual elements mentioned in an exemplary embodiment, without leaving the scope of protection defined by the claims and their legal equivalents, such as further explanations in the description.

Claims

Patent claims 1. Capture unit for maintaining the particle-free status of a closed cavity (14) of a radiation-based control device (10), characterized in that it comprises an electrostatically charged needle and / or a bundle of electrostatically charged needles (22), as well as a collection tray (24a, 24b, 24c) arranged vertically below it.

2. Catching unit according to claim 1, characterized in that the needle (22) and / or the bundle of needles is directed vertically downwards.

3. Catching unit according to claim 1 or 2, characterized in that the collection tray (24a) is funnel-shaped.

4. Catching unit according to claim 1 or 2, characterized in that the collecting tray (24b, 24c) has a collection chamber (28a, 28b) above which a funnel (30) with an opening (32) to the collection chamber (28a, 28b) is arranged.

5. Collection unit according to claim 1 or 2, characterized in that the collection tray (24b) has the form of a multiple funnel with a funnel-shaped collection chamber (28a), above which a further funnel (30) with an opening (32) to the funnel-shaped collection chamber (28a) is arranged, wherein the axes of the two funnels (28a, 30) have an offset (a) relative to each other.

6. Capture unit according to claim 4 or 5, characterized in that the collection chamber (28a, 28b) is manufactured as a drilled or molded blind hole, and the funnel (30) arranged above it is formed as an attachment, preferably made of plastic.

7. Collection unit according to one of the preceding claims, characterized in that the bottom of the collection tray (28a, 28b) is coated with a long-term adhesive (26).

8. Catching unit according to one of the preceding claims, characterized in that the needle (22) and / or the bundle of needles is attached to a circuit board (16); or characterized in that the power supply of the needle (22) and / or the bundle of needles can be switched on and off.

9. Radiation-based transmitter (10), preferably a laser or radar transmitter, comprising a capture unit according to any of the preceding claims.

10. Radiation-based receiver (10), preferably a laser or radar receiver, comprising a capture unit according to any of the preceding claims.

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