Optoelectronic sensor for detecting objects in a monitored area

Abstract

Optoelectronic sensor (S) for detecting objects in a monitored area, comprising - a rotating optical unit (1) with at least one light transmitter (4) for emitting transmitting light beams (SL), at least one light receiver (5) for receiving received light (EL) reflected from objects in the monitored area, and associated electronics (6) for controlling the optical unit (1), - a drive unit (2) for rotating the optical unit (1), - a static housing (3) for enclosing at least the optical unit (1), wherein the housing (3) has at least one transmitting light beam and receiving light (SL and EL) transparent window area (3C), and heat exchange elements (8) which are provided on the outside of the optical unit (1) and are arranged such that the heat exchange elements (8) rotate with the optical unit (1) and flat sides (8A) of the heat exchange elements (8) are at a defined distance (A) from an inner side (I) of the housing (3) in order to provide convective heat exchange with the housing (3), wherein the heat exchange elements (8) are designed such that the flat sides (8A) run parallel to the inner side (I) of the housing (3).

Description

[0001] The invention relates to an optoelectronic sensor for detecting objects in a surveillance area according to claim 1.

[0002] Laser scanners are particularly well-suited for distance measurements that require a large horizontal angular range within a surveillance area. A light beam generated by a light transmitter, in the form of a laser, periodically sweeps the surveillance area as the transmitted light beam. The transmitted light beam is reflected off objects in the surveillance area and received by a light receiver. The received light, referred to below as the received light, is evaluated electronically in the laser scanner.

[0003] The light transmitter, the light receiver, and the associated electronics are combined in a rotating optical unit. The angular position of a rotating shaft of the sensor, to which the optical unit is attached, is used to determine the angular position of the object. The light travel time, using the speed of light, is used to determine the distance of the object from the sensor.

[0004] With the angle and distance information, an object is detected in the surveillance area.

[0005] Due to the increasing performance of electronics and the more compact design of the sensor, significant heat generation within the sensor is occurring. This cannot be satisfactorily addressed by passive cooling, such as heat pads, making it difficult to maintain a permissible operating temperature for the sensor. A higher device temperature also negatively impacts the sensor's service life and performance.

[0006] In known laser scanners, in which the electronics are arranged in static housing parts, the heat can be dissipated directly to the housing of the laser scanner, thus enabling heat exchange between the laser scanner and the environment.

[0007] If the electronics are located in the rotating optical unit (rotor), direct dissipation of the electronics' heat to the housing is not possible without considerable design effort. The use of mechanical components made of metal to improve heat conduction has a negative impact on the rotor, as this requires a larger motor with a higher load-bearing capacity, which reduces robustness against environmental stress (shock / vibration). This also leads to higher power consumption of the device and thus, in turn, higher energy consumption and heat input. Heat dissipation via the bearing, the bearing shaft, and the motor is severely limited due to the low heat dissipation of these components. The heat could also be dissipated by the air surrounding the rotor, but the constant rotation creates a stable radial flow, so that the relative velocity of the air near the heat sources is very low.Although the air heats up, there is hardly any turbulence, thus reducing heat transfer. Mechanical elements, especially optics, also create areas that are shaded from the airflow. Pockets form from which almost no convective heat transfer occurs. Overall, the heat exchange between the rotating electronics and the static housing, and thus the environment, is inadequate.

[0008] DE 102018214598 A1 discloses an assembly for an environmental sensor, wherein the assembly comprises a housing and a rotor rotating in the housing, the rotor having cooling fins against which air flows by forced convection. DE 102017216241 A1 describes a LiDAR arrangement in which a rotating optical unit also comprises a cooling device for generating a cooling air flow for cooling the optoelectronic components.

[0009] It is an object of the present invention to provide an optoelectronic sensor that enables improved heat exchange between the heat-generating components of the sensor's electronics and the environment.

[0010] This object is achieved according to the invention by an optoelectronic sensor having the features of claim 1.

[0011] The optoelectronic sensor for detecting objects in a surveillance area includes: - a rotating optical unit with at least one light transmitter for emitting transmitted light beams, at least one light receiver for receiving received light remitted by objects in the surveillance area, and associated electronics for controlling the optical unit, - a drive unit for rotating the optical unit, - a static housing for enclosing at least the optical unit, wherein the housing has at least one window area permeable to the transmitted light beam and to the received light, and - Heat exchange elements which are provided on the outside of the optical unit and are arranged such that the heat exchange elements rotate with the optical unit and flat sides of the heat exchange elements are located at a defined, as small as possible distance from an inside of the housing in order to provide a convective heat exchange with the housing, wherein the heat exchange elements are designed such that the flat sides run parallel to the inside of the housing.

[0012] As the heat exchange elements move along the inside of the static housing during rotation, the air is swirled between the flat sides of the heat exchange elements and the inside of the housing, resulting in improved heat transfer. This ensures optimal convective heat transfer. The resulting mixing of the air layers allows for significantly higher heat transfer between the heat exchange elements and the housing, and thus ultimately the sensor's environment.

[0013] Preferably, the defined distance is in the single-digit millimeter range, in particular between two and nine millimeters. This advantageously leads to increased heat convection between the heat exchange elements and the housing.

[0014] The heat exchange elements are designed so that the flat sides run essentially parallel to the inside of the housing, in order to achieve turbulence and thus good convection over a larger area, i.e., over the entire flat side of a heat exchange element. The housing can be cylindrical, conical, or dome-shaped. The flat sides move parallel to the inside of the static housing at a defined, small distance.

[0015] Furthermore, the heat exchange elements preferably have a large surface area to form wall sections on the circumference of the optical unit. In particular, a heat exchange element can cover a quarter of the circumference of the optical unit. This provides a larger surface area for heat transfer. Furthermore, the heat exchange elements, as components of the rotor, can contribute to improving the structural stability of the optical unit.

[0016] According to a preferred embodiment, at least two heat exchange elements are arranged diametrically opposite each other on the circumference of the optical unit. This allows for easy balancing and, at the same time, leaves room for the optical unit's light transmitters and light receivers to be arranged between them, providing a clear field of view while still maintaining a compact design.

[0017] The heat exchange elements are made of a material with high thermal conductivity, preferably aluminum or copper. In conjunction with the large-surface design of the heat exchange elements, this enables high and rapid heat absorption from the interior of the optical unit and rapid heat dissipation to the sensor housing.

[0018] Advantageously, the heat exchange elements are connected to the heat sources of the optical unit's electronics in a heat-conducting manner, for example, using heat-conducting materials such as heat-conducting plates. The heat generated inside the optical unit is thus conducted more quickly to the heat exchange elements, further improving heat dissipation from the optical unit.

[0019] Since heat-conducting components in the motor, such as the bearing shaft and bearings, are no longer necessary, these components can now be made of plastic and thus be lighter. This reduces the weight of the rotor and saves drive energy.

[0020] According to a preferred embodiment, the optoelectronic sensor is designed as a scanner, in particular a laser scanner, which can detect the position of the object based on its distance and angle to the object. In particular, the optical unit is designed to cover an angle of 360° with the transmitted light beam.

[0021] Preferred embodiments and further developments as well as further advantages of the invention can be found in the dependent claims, the following description and the drawings.

[0022] The invention will be explained in detail below using exemplary embodiments with reference to the drawings. The drawings show: Fig. 1 is a schematic perspective view of a preferred embodiment of a sensor according to the invention; Fig. 2 a schematic view of an optical unit of the sensor according to the invention; and Fig. 3 a detailed view of a preferred embodiment of the heat exchange elements of the sensor according to the invention.

[0023] The Fig. 1 shows a schematic perspective view of a preferred embodiment of a sensor S according to the invention, which is designed to detect objects in a monitoring area.

[0024] The sensor S shown comprises, roughly divided, a rotating optical unit 1, a drive unit 2, and a static housing 3. In the illustrated embodiment, the housing 3 consists of a first housing part 3A and a second housing part 3B. The first housing part 3A houses the rotating optical unit 1 and has at least one light-permeable window area 3C that extends over 360° and is thus rotationally symmetrical. The second housing part 3B houses the drive unit 2, which is connected to the optical unit 1 and rotates it about a longitudinal axis (not shown) of the sensor S.

[0025] The optical unit 1 comprises at least one light transmitter 4, which is preferably formed from a laser. The light transmitter 4 generates a transmitted light beam SL, which is preferably emitted into the monitored area in the form of light pulses. If the transmitted light beam SL strikes an object in the monitored area, a corresponding light beam is remitted to the sensor S as received light EL. The transmitted light beam SL and the received light EL pass through the window area 3C of the first housing part 3A.

[0026] Furthermore, the optical unit 1 comprises at least one light receiver 5, which preferably consists of a detector array and receives the received light EL. The received light beam EL is converted into an electrical received signal.

[0027] Furthermore, electronics 6, in particular at least one circuit board (not shown) with corresponding electronic and optoelectronic components, are provided in the optical unit 1. The electronics 6 serve to control or regulate the optical unit 1. The light transmitter 4, the light receiver 5, and the electronics 6 form heat sources of the optical unit 1, with the heat from the heat sources being conducted from the interior of the optical unit 1 to the housing 3, where it is intended to be dissipated to the environment.

[0028] A first and second structural part 7A and 7B are provided, to which the light transmitter 4, the light receiver 5 and the electronics 6 are mounted. As shown in the Fig. As shown in Figure 1, the first and second structural parts 7A and 7B are screwed together by screws 7C. The structural parts 7A and 7B of the optical unit 1 are preferably made of a material with a low weight, preferably plastic or composite, so that the optical unit 1 can be designed to be lightweight overall.

[0029] According to the invention, heat exchange elements 8 are provided on the outside of the optical unit 1 and arranged on the circumference in such a way that the heat exchange elements 8 rotate with the optical unit 1 and flat sides 8A of the heat exchange elements 8 are at a defined distance A from an inner side I of the housing 3, as in the Fig. 2, in order to effect a convective heat exchange with the housing 3.

[0030] The heat exchange elements 8 are preferably shaped as rectangular cover parts with large, curved flat sides 8A. The curvature of the curved flat side 8A approximately corresponds to the curvature of the first housing part 3A. Attached to the first and second structural parts 7A and 7B, the heat exchange elements 8A form, so to speak, wall sections of the optical unit 1 on the circumference of the optical unit 1. As a result, the heat exchange elements 8 can contribute to the mechanical stability of the optical unit.

[0031] In the Fig. Figure 2 shows a schematic view of the optical unit 1 of the preferred embodiment of the sensor S, showing the light transmitter 4, the light receiver 5, and the heat exchange elements 8. The first housing part 3A encloses these parts.

[0032] The at least two heat exchange elements 8 are arranged diametrically on the circumference of the optical unit 1. Optical elements of the light transmitter 4 and the light receiver 5 are arranged between them in such a way that the optical elements protrude between the two heat exchange elements 8. This allows the transmitted light beam SL and the received light EL to be emitted and received unhindered by the heat exchange elements 8.

[0033] The defined distance A is provided between the flat sides 8A of the heat exchange elements 8 and the inner side I of the first housing part 3A. Advantageously, the defined distance A is in a single-digit range of millimeters, in particular from two to nine millimeters.

[0034] During operation of the sensor S, i.e., when the optical unit 1 rotates, the heat exchange elements 8 are surrounded by the hot air generated inside the optical unit 1. A flow develops at the defined distance A between the flat sides 8A of the heat exchange elements 8 and the inner side I of the first housing part 3A, resulting in a significantly higher convective heat exchange between the heat exchange elements 8 and the housing 3, and thus the environment.

[0035] Advantageously, the flat sides 8A of the heat exchange elements 8 are arranged approximately parallel to the inner side I of the housing 3 or the first housing part 3A, so that the defined distance A is approximately the same across the entire surface of the flat sides 8A. The first housing part 3A can have a cylindrical, conical, or dome-shaped form.

[0036] The heat exchange elements 8 are made of a material with high thermal conductivity, preferably aluminum or copper. This material also allows for a reduction in the weight of the heat exchange elements 8.

[0037] The Fig. Figure 3 shows a schematic perspective view of the heat exchange elements 8, with an inner side 8B of a heat exchange element 8 being shown in detail. The inner side 8B of the heat exchange element 8 has ribs 8C to reduce weight. Additionally, heat-conducting pads 8D may be provided, which are attached to the inner side 8B of the heat exchange elements 8.

[0038] In the preferred embodiment shown, a heat sink 8E is preferably arranged between two halves of a heat exchange element 8. The body 8E or the heat exchange elements 8 are connected directly to heat sources, in particular the electronics 6 (not shown), of the optical unit 1 via heat-conducting lines (not shown).

[0039] Furthermore, heat conducting plates (not shown) provided inside the optical unit 1 can be arranged in such a way that they guide the warm air towards the heat exchange elements 8, so that the heat is conducted more quickly and directly to the heat exchange elements 8.

[0040] Due to the above-mentioned configurations of the heat exchange elements 8 inside the optical unit 1, the dissipation of heat from inside the optical unit 1 is greatly improved.

[0041] The described preferred embodiment of the sensor S according to the invention comprises a scanner, in particular a laser scanner, which is designed to detect a distance between the object (not shown) and the scanner and an angle of the object relative to a zero angle of the scanner. In the scanner, the optical unit 1 is designed to cover an angle of 360° with the transmitted light beam SL. List of reference symbols 1 optical unit 2 drive unit 3 housings 3A first housing part 3B second housing part 4 light transmitters 5 light receivers 6 Electronics 7A first structural part 7B second structural part 7C screws 8 Heat exchange element 8A Flat side of the heat exchange element 8B Inside of the heat exchange element 8C ribs 8D heat pads 8E heat sink A defined distance EL reception light I Inside the housing S optoelectronic sensor SL transmitted light beam

Claims

[1] Optoelectronic sensor (S) for detecting objects in a surveillance area, comprising - a rotating optical unit (1) with at least one light transmitter (4) for emitting transmitted light beams (SL), at least one light receiver (5) for receiving received light (EL) remitted by objects in the surveillance area, and associated electronics (6) for controlling the optical unit (1), - a drive unit (2) for rotating the optical unit (1), - a static housing (3) for enclosing at least the optical unit (1), wherein the housing (3) has at least one window region (3C) permeable to transmitted light beams and received light (SL and EL), and heat exchange elements (8) which are provided on the outside of the optical unit (1) and are arranged such that the heat exchange elements (8) rotate with the optical unit (1) and flat sides (8A) of the heat exchange elements (8) are at a defined distance (A) from an inner side (I) of the housing (3) in order to provide a convective heat exchange with the housing (3), wherein the heat exchange elements (8) are designed such that the flat sides (8A) run parallel to the inner side (I) of the housing (3). [2] Optoelectronic sensor (S) according to claim 1, wherein the heat exchange elements (8) each have a large area to form wall sections on the circumference of the optical unit (1). [3] Optoelectronic sensor (S) according to one of the preceding claims 1 to 2, wherein at least two heat exchange elements (8) are arranged diametrically on the circumference, so that optical elements of the light transmitter (4) and the light receiver (5) are arranged between the heat exchange elements (8). [4] Optoelectronic sensor (S) according to one of the preceding claims, wherein the defined distance (A) is in a single-digit millimeter range, preferably two to nine millimeters. [5] Optoelectronic sensor (S) according to one of the preceding claims, wherein the heat exchange elements (8) consist of a material with high thermal conductivity, preferably aluminum or copper. [6] Optoelectronic sensor (S) according to one of the preceding claims, wherein the heat exchange elements (8) are connected via heat-conducting lines to heat sources, in particular the electronics (6), of the optical unit (1). [7] Optoelectronic sensor (S) according to one of the preceding claims, wherein supporting structural parts (7A, 7B) of the optical unit (1) consist of a material with low inherent weight, preferably plastics or composite materials. [8] Optoelectronic sensor (S) according to one of the preceding claims, wherein heat conducting plates provided in the interior of the optical unit (1) are arranged such that they guide hot air in the direction of the heat exchange elements (8). [9] Optoelectronic sensor (S) according to one of the preceding claims, wherein the sensor (1) is a scanner, in particular a laser scanner, which is designed to detect a position of an object. [10] Optoelectronic sensor (S) according to one of the preceding claims, wherein the optical unit (1) is designed to cover an angle of 360° with the transmitted light beam (SL).

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