Vehicle camera with surface heating

Abstract

A camera (20) for a vehicle, in particular a commercial vehicle, has a housing (22), at least one optical element (24) arranged in or on the housing (22), and a circuit board (10) with at least one image sensor (16) and a surface heater (17) for heating the optical element (24).

Description

Field of the invention

[0001] The present invention relates to a camera with a surface heating system, in particular a camera for a vehicle, e.g., a commercial vehicle. State of the art

[0002] For some time now, camera systems or image recording systems have been used in vehicles, particularly commercial vehicles, alongside conventional mirrors as devices for indirect vision, either as a supplement to or as a replacement for these mirrors. The camera systems usually have an image recording unit, such as a camera, which continuously records the vehicle's surroundings as (video) data. The (video) data recorded by the image recording unit is transmitted, possibly after processing, to a playback unit located in the driver's cab, which displays the (video) data to the driver continuously and in real time and, if necessary, displays additional information, such as collision warnings, distances and the like, for the recorded surrounding area.

[0003] The cameras of camera systems are typically mounted on the exterior of a vehicle. Accordingly, the cameras are exposed to all weather conditions at the vehicle's location. Particularly at low temperatures, the formation of frost or condensation on the optical element or the optical element's cover glass can impair the camera's image capture function. Furthermore, there is a risk that components repeatedly exposed to low temperatures will experience material changes and thus wear out more quickly.

[0004] To prevent the formation of frost or condensation on the optical element of a camera, it is known to heat the camera. To this end, heating elements, e.g., in the form of discrete resistors, are arranged at specific positions on the circuit board, as disclosed in DE 10 2013 020 894 B3. However, these heating elements require a relatively large amount of space within the camera. This either results in a lack of space within the camera for other components, or, if the other components are installed anyway, the camera becomes larger overall, which in turn has a negative impact on the required installation space in the vehicle. Object of the invention

[0005] Based on this, it is the object of the invention to provide a camera which has a compact heater which, on the one hand, reliably counteracts the formation of frost and condensation and, on the other hand, requires little installation space in the camera. Description of the invention

[0006] This object is achieved with a camera having the features of claim 1 and a vehicle having the features of claim 18. Preferred embodiments are specified in the dependent claims.

[0007] The invention is based on the idea of ​​providing a camera for a vehicle, in particular a commercial vehicle, with a surface heater. The surface heater is at least partially applied to the circuit board, which also carries the image sensor. The surface heater is made of a heat-conducting material and extends over a certain area of ​​the circuit board. In this case, a surface is understood to be a geometric shape, more precisely an area that is flat in length and width. In particular, the surface heater is defined by the fact that its length and width are many times greater than its extension in a thickness direction. The length and width directions of the surface heater are defined such that they span a plane that, when arranged on the circuit board, is essentially parallel to the plane spanned by the length and width directions of the circuit board.

[0008] With panel heating, heat is evenly distributed over a larger area into the camera's optical element, as the heat radiation surface is larger than with conventional heating elements. At the same time, the very small extension of the panel heating in the thickness direction of the panel heating requires very little installation space in the longitudinal direction of the camera. The longitudinal direction of the camera is defined as the direction in which a connector, one or more circuit boards, and an optical element of the camera are arranged one behind the other.

[0009] For example, the surface heating can be formed from a thin metal sheet that is glued to the circuit board. Alternatively, the surface heating can also be a thin metal layer that is sprayed, cast, vapor-deposited, or electroplated onto the circuit board. Preferably, however, the surface heating is formed from a conductor track. The conductor track can be made of copper, aluminum, or a copper or aluminum alloy. Alternatively, the conductor track can also be made of another heat-conducting material. To provide surface heating, the conductor track is laid such that individual sections of the conductor track, or in the case of multiple conductor tracks, the individual conductor tracks, are arranged next to one another on the circuit board. Adjacent to one another means that there is no further element between the individual sections of the conductor track(s), but the sections do not touch one another.For example, the conductor track can be laid in a meandering pattern. In this context, "meandering" means that the conductor track is laid in loops or windings such that it changes direction by approximately 180 degrees at two predefined end positions. The conductor track thus has several conductor track sections that run approximately parallel to each other without interruption. A meandering arrangement has the advantage that—in contrast to a spiral arrangement of the conductor track—an antenna effect of the conductor track is avoided, thus ensuring that neither the camera's electronics nor neighboring devices are disturbed by emitted interference, thus ensuring electromagnetic compatibility.

[0010] The heating output of a surface heating system formed by a conductor track is determined by the cross-section and length of the conductor track, as well as its arrangement, hereinafter referred to as the geometry of the surface heating system. A resistance can be generated based on the specific thermal conductivity of the material used for the conductor track, as well as the length and cross-section of the conductor track. Thus, a resistance can be calculated for a given current or voltage, as well as a given heating output, which can then be converted into a suitable conductor track geometry.

[0011] To effectively heat the optical element, it is preferable for the conductor track to extend partially around the image sensor. Alternatively, the conductor track can also completely surround the image sensor.

[0012] Since heating the camera primarily serves to prevent the formation of frost and condensation, it is advantageous if the conductor track is located on the side of the circuit board where the image sensor is located, thus pointing toward the optical element. Alternatively, the conductor track can also be located on the side facing away from the optical element, or a conductor track can be located on both sides of the circuit board.

[0013] According to a preferred embodiment, the outer boundary of the planar conductor track on the circuit board essentially corresponds to the outer dimensions of the optical element. This ensures efficient heat input into the optical element.

[0014] Preferably, the conductor track is arranged on a specific circuit board layer, more preferably on the circuit board layer on which the image sensor is also arranged. Alternatively, the conductor track can also be arranged on another, for example, internal, circuit board layer or on a circuit board layer on the side of the board opposite the side with the image sensor. Because the conductor track is arranged on only one circuit board layer, the conductor track further preferably has a substantially two-dimensional, planar shape in which the conductor track has an extension in a length and width direction, but hardly any extension in a thickness direction.

[0015] Alternatively, the conductor track can extend across several substantially parallel circuit board layers. This means that the conductor track is arranged such that, while in a plan view of the board, it has a planar arrangement of adjacent conductor track sections or conductor tracks, in a sectional view of the board, it alternates between different parallel circuit board layers. In other words, in a section through the board, conductor tracks are present on several circuit board layers that alternate between the circuit board layers.The term “surface heating” is therefore also to be understood as an arrangement whose individual sections are flat and thus have only a very small extension in the thickness direction of the conductor track, but which as a whole, in a sectional or side view, does not have a flat design, but rather a design which assumes different heights with respect to the thickness direction of the board, while maintaining a dimension which extends only very slightly in one thickness direction.

[0016] To prevent the image sensor from heating up and thus causing image noise, the circuit board layer on which the image sensor is arranged can be removed between the image sensor and the conductor track. This means that there is no heat-conducting material between the image sensor and the conductor track. This prevents the heat from the conductor track from being transferred to the image sensor, which in turn promotes reliable function of the image sensor. This effect can be further enhanced by filling the space left free by the heat-conducting material with a heat-insulating material. Alternatively or in addition to removing the circuit board layer, a heat barrier can also be provided between the image sensor and the conductor track. The heat barrier can either be made of a heat-insulating material and serve for heat insulation, or it can be made of a heat-conducting material, e.g. the material of the conductor track, and serve to store or dissipate heat.serve as a heat buffer. In order to be able to absorb or buffer sufficient heat, the thermal barrier has a certain thermal capacity. The term "thermal capacity" in this context refers to the ability to absorb and store heat. For example, the thermal barrier can be designed as a ring with a certain extension in the longitudinal direction of the camera or the thickness direction of the conductor track, so that the thermal barrier has a certain accumulation of material for storing thermal energy.

[0017] The camera preferably contains at least a second conductor track for targeted control depending on the heating power requirement. For example, the camera can have two conductor tracks, both of which can be designed as described above and can be arranged either concentrically to one another or next to one another around the image sensor. During operation of the heater, one of the two conductor tracks can only be connected to the other conductor track when a higher heating power is required, as is the case, for example, at temperatures below freezing. Alternatively or in addition to adjusting the heating power, the cross-section of the conductor track can change over the extent of the conductor track. For example, the conductor track can have a continuously varying cross-section or only vary in terms of cross-section in certain sections.

[0018] To secure the optical element in or to the camera housing, a heat-conducting element can be provided between the optical element and the housing. The heat-conducting element is preferably formed by a potting compound that fixes the optical element in the housing and is made of a heat-conducting material. This allows the heat from the conductor track to be introduced not only directly into the optical element, but also indirectly into the optical element via the potting compound, by first introducing the heat into the camera housing and then via the camera housing into the optical element. This promotes even more efficient and rapid heating of the optical element.

[0019] Alternatively or additionally, the optical element can be attached to the circuit board using an adhesive. The adhesive is preferably also made of a thermally conductive material, ensuring reliable heat transfer from the conductor track to the optical element.

[0020] The camera preferably contains at least one temperature sensor for adjusting the heating output and / or for adjusting the heating duration. The temperature sensor serves to determine temperature conditions inside the camera housing and / or on the optical element which require either an adjustment of the heating output and / or an adjustment of the heating duration. For this purpose, the sensor is preferably arranged inside the camera housing, e.g. embedded in the potting compound and / or the adhesive, preferably on or near the optical element. If the temperature sensor determines, for example, that the temperature inside the camera housing has exceeded a certain, predetermined value, this result can be forwarded via a central control unit (ECU) to a control unit which then reduces the heating output or switches it off completely.Conversely, the control unit can also start or increase the heating output if the temperature sensor detects that the temperature inside the camera housing has fallen below a predefined temperature threshold. Monitoring of the temperature inside the camera housing can additionally or alternatively be initiated by an operator, e.g. the driver of the vehicle. For this purpose, an operator button / knob, such as an operator interface with an on / off switch, is provided inside the vehicle, via which the operator can start or stop the operation of the surface heating. Alternatively or additionally, the temperature inside the camera housing can also be controlled by specifying a heating duration.

[0021] In principle, the surface heating can be operated via the ECU in conjunction with a control unit. Temperature sensors detect and report temperature values. If the temperature falls below or exceeds specified values, the surface heating is activated or deactivated. Alternatively or additionally, the surface heating can also be started by an operator, e.g., via specific control devices provided for this purpose in the passenger compartment of the vehicle, if the operator is unable to obtain sufficiently clear camera images due to low temperatures and the resulting formation of condensation or frost.

[0022] In addition to or alternatively to the at least one temperature sensor, at least one current sensor can be provided which determines the current strength in the conductor track and, if necessary, adjusts the heating output or heating duration via a control unit if the current strength in the conductor track exceeds a permissible value or falls below a required value. The current sensor can be provided in the heat barrier or on the circuit board. Here, too, the heating output or heating duration can be manually adjusted by an operator depending on the current strength. For this purpose, the operator is informed of the current strength and can adjust it accordingly. In the event of adjustments by the operator that are detrimental to the heating, the control unit can override the operator input in order to avoid possible damage to the surface heating and the camera.

[0023] The at least one conductor track is preferably used not only to heat the optical element, but also as a power supply line for components located on the circuit board, such as the image sensor. The simultaneous use of the conductor track as a supply line results in a voltage drop that must be taken into account when designing the conductor track. Short description of the characters

[0024] The invention is described below by way of example with reference to the accompanying figures, in which: Fig. 1 shows a longitudinal section through a camera according to the invention with a surface heating according to a first embodiment, Fig. 2 shows a perspective view of a circuit board with a conductor track and an optical element, Fig. 3 shows a top view of a circuit board with a conductor track, image sensor and thermal barrier, and Fig. 4 shows a perspective view of a circuit board with a surface heater according to a second embodiment. Description of preferred embodiments

[0025] Fig. 1 shows a longitudinal section through a camera 20 for a vehicle, which has a central axis aa'. The camera 20 has a housing 22. An optical element 24 and a plurality of circuit boards 10 are arranged inside the housing 22. The optical element 24 consists of a lens and a cover glass for protecting the lens. On the circuit board 10 closest to the optical element 24, an image sensor 16 for recording images of the environment around the vehicle is arranged centrally on the side facing the optical element 24. On the opposite side, i.e. the side of the circuit board 10 facing away from the optical element 24, electronic components 14 are arranged which are required to carry out a camera function. The electronic components 14 can alternatively or additionally also be arranged on the side of the circuit board 10 facing the optical element.The circuit board furthest from the optical element 24 is provided with a connector 30 for supplying power to the camera and for data transmission. The circuit boards are conductively connected to one another (not shown). The direction along the longitudinal axis a-a', in which the circuit boards, the image sensor 16, and the optical element 24 are arranged one behind the other, is referred to herein as the longitudinal direction.

[0026] A surface heater 17, designed as a conductor track 18, is arranged around the image sensor 16, i.e., on the side of the circuit board 10 facing the optical element 24. The external dimensions of the conductor track 18 essentially correspond to the external dimensions of the surface of the optical element 24 facing the circuit board 10.

[0027] The optical element 24 is connected to the housing 22 and the circuit board 10 via a potting compound 28. The potting compound 28 is made of a thermally conductive material, such as a polyurethane-based material.

[0028] Fig. 2 shows a perspective view of the circuit board 10 with the optical element 24. As in Fig. As shown in Figure 2, an end face of the optical element 24 facing the circuit board 10 is bonded to the circuit board 10, more precisely to the conductor track 18, by means of an adhesive 26, such as a superglue, a two-component adhesive, or the like. Like the potting compound 28, the adhesive 26 is also made of a thermally conductive material. Fig. 2, the conductor track 18 is meander-shaped around the image sensor 16 (in Fig. 2 not shown), wherein the individual windings or conductor track areas change their direction of travel by approximately 180 degrees at a specific position with respect to the image sensor 16.

[0029] Fig. 3 shows a top view of the circuit board 10 from Fig. 1. As in Fig. 3, the image sensor 16 is arranged approximately in the center of the circuit board. However, the position of the image sensor 16 on the circuit board 10 can also be off-center and is generally selected such that the optical element 24 can at least partially project images of the vehicle's surroundings onto the image sensor 16. This means that it is not necessary, but nevertheless possible, for the optical element 24 to be arranged exactly above the image sensor 16. The conductor track 18 is arranged around the image sensor 16. The conductor track 18 is laid in a meandering shape around the image sensor 16 in order to prevent an antenna effect of the conductor track 18. The connection ends 19 of the conductor track 18 are also provided on the circuit board 10 and are conductively connected to a power source (not shown). The image sensor 16 and the conductor track 18 are applied to a circuit board layer 12. The circuit board layer 12 is formed of a heat-conducting metal, e.g. copper, and forms a copper layer.

[0030] A thermal barrier 13 is provided between image sensor 16 and conductor track 18. The thermal barrier 13 is designed as a closed barrier, e.g., as a ring, and completely surrounds the image sensor 16. The thermal barrier 13 can be formed from a heat-insulating material or can be formed from a metal, for example, the same material as the circuit board layer 12. Alternatively or in addition to the thermal barrier 13, the circuit board layer 12 between the image sensor 16 and conductor track 18 can also be omitted. This—optionally in addition to the thermal barrier 13—prevents the heat from the conductor track 18 from being transferred via the circuit board layer 12 to the image sensor 16.

[0031] To heat the camera 20, current is applied to the conductor track 18, which causes the conductor track 18 to heat up. Due to the spatial proximity of the conductor track 18 to the optical element 24, the heat from the conductor track 18 is transferred to the optical element 24 by thermal convection via the air. In addition, the thermal energy of the conductor track 18 is transferred directly via the thermally conductive adhesive 26, i.e. from the conductor track 18 without any element other than the adhesive 26, to the optical element 24. In addition, the heat from the conductor track 18 is also transferred to the housing 22 via the thermally conductive potting compound 28 and from the housing 22 via thermal convection via the air to the optical element 24. In this way, the formation of condensation or frost on the optical element can be avoided, or an already existing frost or condensation can be removed.

[0032] It is conceivable that the current intensity or voltage of the current flowing through the conductor varies depending on the desired heating power. Additionally or alternatively, in order to vary the heating power, it is conceivable that not just one conductor track 18, but several conductor tracks 18 are provided on the circuit board 10, which can be operated individually or together. It is also conceivable that the conductor track 18 does not have the same cross-section over its entire length, but that this can change over the extent of the conductor track 18. For example, the conductor track 18 can have a continuously varying cross-section or only vary in terms of cross-section in certain sections. In general, the smaller the cross-section and the longer the conductor track, the higher the resistance, and vice versa.Thus, based on a desired heating power and a given current or voltage as well as the specific thermal conductivity of the selected material for the conductor track 18, a cross-section and a length of the conductor track 18 can be calculated.

[0033] The thermal barrier 13 acts as a type of protective ring to prevent heat from being transferred from the conductor track 18 to the image sensor 16. The thermal barrier 13 either prevents heat transfer to the image sensor 16 by being made of a thermally insulating material and isolating the image sensor 16 from the conductor track 18. Or the thermal barrier 13 is made of a thermally conductive material and stores the heat from the conductor track 18 so that it is not transferred to the image sensor 16 or only transfers after a considerable time. The thermal insulation effect is further supported by the fact that the printed circuit board layer 12 between the image sensor 16 and the conductor track 18 can be omitted or kept free. The omission of the printed circuit board layer 12 between the image sensor 16 and the conductor track 18 can also be provided as the sole measure (i.e., without the provision of a thermal barrier 13) for thermally insulating the image sensor 16.

[0034] Fig. 4 shows a perspective view of a circuit board 10 in which the conductor track 18 is not only arranged on one circuit board layer 12, but in which the conductor track 18 extends over several circuit board layers.

[0035] At the Fig. In the embodiment of the surface heater 17 designed as a conductor track 18 shown in Figure 4, this is essentially formed from two conductor track regions 18a and 18b. The first conductor track region 18a runs on a first circuit board layer 12a, whereas the second conductor track region 18b runs on a second circuit board layer 12b that is essentially parallel to the first circuit board layer (not shown). The two conductor track regions 18a and 18b are conductively connected to one another by a conductor track web 18c. Since the conductor track web 18c establishes a connection between the first conductor track region 18a, which is located on the first circuit board layer 12a, and the second conductor track region 18b, which is located on the further circuit board layer 12b, it extends in a further spatial direction, and the conductor track 18 is formed three-dimensionally at the position of the conductor track web 18c.In principle, however, the conductor track 18 is predominantly two-dimensional and thus over large sections due to the conductor track areas 18a and 18b.

[0036] Even if Fig.4 shows an essentially exact overlap or identical design of the two conductor track regions 18a and 18b, it is possible for the conductor track regions 18a and 18b to be of identical design in terms of their areal extent, but to be offset in the transverse direction to the longitudinal direction of the camera. Alternatively or additionally, it is also conceivable for the conductor track regions 18a, 18b to be of different design in terms of their areal extent. For example, it is conceivable for the conductor track region 18a located closer to the optical element 24 to have a larger area than the conductor track region 18b, which is arranged further away from the optical element 24 than the conductor track region 18a. The cross-section and material of the conductor track regions 18a, 18b can also differ.A suitable change of the cross-section and / or the material would be at the conductor track bridge 18c, but can also be made at any other point in the conductor track areas 18a and 18b. List of reference symbols 10 circuit boards 12, 12a, 12b PCB layer 13 Thermal barrier 14 electronic component 16 image sensor 17 Surface heating 18 conductor track 18a, 18b Conductor track areas 19 power connections 20 Camera 22 housings 24 optical element 26 adhesives 28 Potting compound 30 plugs aa' central axis QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2013 020 894 B3

[0004]

Claims

[1] Camera (20) for a vehicle, in particular a commercial vehicle, comprising: a housing (22), at least one optical element (24) arranged in or on the housing (22), and a circuit board (10) with at least one image sensor (16) and a surface heater (17) for heating the optical element (24). [2] Camera (20) according to claim 1, wherein the surface heating (17) is formed from at least one conductor track (18), wherein conductor track sections of the conductor track (18) are arranged adjacent to one another to form a planar arrangement on the circuit board (10). [3] Camera (20) according to claim 2, wherein the conductor track (18) is arranged in a meandering shape. [4] Camera (20) according to claim 2 or 3, wherein the conductor track (18) is arranged at least partially around the image sensor (16). [5] Camera (20) according to one of claims 2 to 4, wherein the conductor track (18) is arranged on the side of the circuit board (10) which is directed towards the optical element (24). [6] Camera (20) according to one of claims 2 to 5, wherein the outer boundary of the conductor track (18) on the circuit board substantially corresponds to the outer dimension of the surface of the optical element (24) directed towards the conductor track (18). [7] Camera (20) according to one of claims 2 to 6, wherein the conductor track (18) is arranged on a specific printed circuit board layer (12) of the circuit board (10). [8] Camera (20) according to claim 7, wherein the conductor track (18) has a substantially two-dimensional shape. [9] Camera (20) according to one of claims 2 to 6, wherein the conductor track (18) extends over a plurality of substantially mutually parallel circuit board layers (12). [10] Camera (20) according to claim 9, wherein the conductor track (18) has a three-dimensional shape. [11] Camera (20) according to one of claims 5 to 10, wherein the printed circuit board layer (12) is kept free in a region between the image sensor (16) and the conductor track (18). [12] Camera (20) according to one of claims 2 to 11, wherein a heat barrier (13) is provided between the image sensor (16) and the conductor track (18). [13] The camera (20) of claim 12, wherein the thermal barrier (13) is formed of a thermally conductive material and is configured to have a thermal capacity. [14] Camera (20) according to one of claims 2 to 13, comprising at least one second conductor track (18) for targeted control depending on the heating power requirement. [15] Camera (20) according to one of claims 1 to 14, further comprising a thermally conductive potting compound (28) arranged between the circuit board (10), the housing (22) and the optical element (24). [16] Camera (20) according to one of claims 1 to 15, further comprising at least one temperature sensor for determining a temperature inside the housing (22) for adjusting the heating power and / or for adjusting the heating duration. [17] Camera (20) according to one of claims 2 to 16, wherein the at least one conductor track (18) is adapted for use as a power supply line for the image sensor (16) and / or further components (14) on the circuit board (10). [18] Vehicle with a camera (20) according to one of claims 1 to 17.

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