Vehicle roof structure and conductive plate

Abstract

To improve the transmission efficiency of wireless signals. [Solution] In a vehicle roof structure in which a space is formed between a roof panel and a roof lining for a communication module having a first antenna and a base substrate and a second antenna, a non-conductive roof panel cover is placed above the space, a conductive plate to which the communication module and the second antenna can be attached is placed below the space, and an opening is provided in at least a portion of the conductive plate that faces the base substrate.

Description

Technical Field

[0001] The present invention relates to wireless communication.

Background Art

[0002] A system in which an in-vehicle computer performs wireless communication has become widespread. In relation to this, for example, Patent Document 1 discloses a technique regarding the arrangement position of an in-vehicle communication antenna.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present disclosure aims to improve the transmission efficiency of wireless signals.

Means for Solving the Problems

[0005] One aspect of an embodiment of the present disclosure is a roof structure of a vehicle, having a communication module having a first antenna and a base substrate between a roof panel and a roof lining, and forming a space in which a second antenna is disposed, wherein a non-conductive roof panel cover is disposed above the space, a conductive plate to which the communication module and the second antenna can be attached is disposed below the space, and an opening is provided in at least a part of a portion of the conductive plate facing the base substrate.

[0006] One aspect of an embodiment of the present disclosure is A conductive plate is provided between the roof panel and roof lining of a vehicle, to which a communication module having a first antenna and a base board and a second antenna can be attached, and to which an opening is provided in at least a portion of the portion facing the base board. [Effects of the Invention]

[0007] According to this disclosure, the transmission efficiency of wireless signals can be improved. [Brief explanation of the drawing]

[0008] [Figure 1] A schematic diagram showing an example of the configuration of a vehicle system in an embodiment. [Figure 2] A schematic diagram showing an example of the configuration of the DCM10 and the in-vehicle device 20. [Figure 3] A block diagram illustrating an example of the functional configuration of DCM10. [Figure 4] Hardware external view of the DCM10. [Figure 5] A perspective view illustrating the arrangement of the DCM10. [Figure 6] A cross-sectional view illustrating the arrangement of the DCM10. [Modes for carrying out the invention]

[0009] The number of vehicles equipped with communication terminals is increasing. Furthermore, in recent years, with improvements in vehicle functionality, the amount of communication data has tended to increase, making it essential to maximize communication efficiency.

[0010] In communication modules that utilize high-frequency radio waves with high directivity, it is necessary to ensure sufficient ground clearance. Therefore, antennas are often placed on the upper part of the vehicle (for example, near the roof).

[0011] The roof structure according to the embodiment of this disclosure forms a space between the roof panel and the roof lining in which a communication module having a first antenna and a base substrate and a second antenna are arranged. A roof panel is a component that makes up the upper surface of a vehicle's roof. A roof lining, on the other hand, is an interior component located on the underside of a vehicle's roof.

[0012] The vehicle-mounted communication module inputs and outputs wireless signals via a first antenna. By creating a space between the roof panel and the roof lining and positioning the communication module and antenna within this space, high gain can be achieved. The second type of antenna is typically one that is not used for data communication, such as a broadcast receiving antenna or a GPS antenna.

[0013] In such roof structures, the upper surface of the space is often covered with a non-conductive material (e.g., a resin plate), while the other surfaces (sides and bottom) are covered with conductive plates (e.g., metal). This protects the antenna from electromagnetic noise generated inside the vehicle and suppresses the loss of gain caused by noise.

[0014] However, covering the space within the roof with a conductive material can cause cavity resonance due to electromagnetic waves generated both inside and outside the structure. If this resonance frequency is close to the frequency at which communication is attempted, it may interfere with the communication. Furthermore, if the base substrate and conductive plate of the communication module are in close proximity, a high-frequency current with opposite phases may flow between the base substrate and the conductive plate. This can act like noise, potentially degrading the radiation performance of the first antenna.

[0015] Therefore, in the roof structure according to the present disclosure, a non-conductive roof panel cover is arranged above the space, and a conductive plate to which the communication module and the second antenna can be attached is arranged below the space, and an opening is provided in at least a part of the portion of the conductive plate that faces the base substrate.

[0016] That is, while covering the space inside the roof with a conductor plate, an opening (such as a notch) is provided in a portion of the conductor plate close to the base substrate. This can suppress the generation of the above-mentioned inverse-phase current while having a certain role of shielding electromagnetic waves generated inside the vehicle, and can improve the radiation performance of radio waves. Furthermore, by adjusting the size of the opening, it becomes possible to suppress resonance or control the resonance frequency.

[0017] Note that the conductor plate may have a rising portion surrounding the side of the space. That is, the conductor plate may cover the four side directions and the bottom surface.

[0018] Also, the first antenna may be an antenna for cellular communication, and the second antenna may be an antenna for broadcast reception. The second antenna can be, for example, an antenna for TV reception, an antenna for radio reception, etc. The frequency band of broadcast is lower than the frequency band of cellular communication and is more susceptible to noise, so there is a benefit in shielding by the conductor plate.

[0019] The maximum length of the opening (for example, the diagonal length) can be determined based on the frequency of the noise to be suppressed. When the size of the opening is X, from the operating principle of the slot antenna, the upper limit wavelength λ of the radio wave passing through the opening is represented by X = λ / 2. For example, when the maximum length of the opening is 200 millimeters or less, radio waves of less than 750 MHz can be shielded, and radio waves of frequencies of 750 MHz or more can be transmitted. In other words, resonance occurring at frequencies of 750 MHz or more can be reduced. The maximum length of the opening may be appropriately set according to the frequency of the noise to be suppressed as described above and the pitch of the screw holes for fixing the communication module.

[0020] The following describes specific embodiments of this disclosure with reference to the drawings. Unless otherwise specified, the hardware configurations, module configurations, functional configurations, etc., described in each embodiment are not intended to limit the technical scope of the disclosure to those configurations alone.

[0021] (First embodiment) An overview of the vehicle system according to the first embodiment will be described with reference to Figure 1. The vehicle system according to this embodiment is configured to include a vehicle 1.

[0022] Vehicle 1 is a connected car that has a communication function with external devices. Vehicle 1 is composed of a DCM (Data Communication Module) 10 and an in-vehicle device 20. An external device is a device located outside of Vehicle 1. An external device may be, for example, a server device connected to the Internet, or it may be a terminal or roadside device (installed on another vehicle) located near Vehicle 1 that can communicate directly with DCM 10.

[0023] The DCM10 is a device that communicates wirelessly with other devices (or external networks) over a network. The DCM10 functions as a gateway for connecting components of vehicle 1 (hereinafter referred to as vehicle components) to an external network or external devices.

[0024] The DCM10 can provide communication (cellular communication) to a mobile communication network. The mobile communication network is connected to a wide-area network such as the Internet, which allows various components of vehicle 1 to communicate with any external device.

[0025] The in-vehicle device 20 is installed in the vehicle 1 and provides information to the occupants of the vehicle 1. The in-vehicle device 20 is also called a car navigation system, infotainment system, or head unit. The in-vehicle device 20 can provide navigation and entertainment to the occupants of the vehicle. The in-vehicle device 20 may also have the function of receiving television and radio broadcasts. Furthermore, the in-vehicle device 20 may be a device that can be linked with a smartphone or the like.

[0026] The amount of communication data handled by in-vehicle DCMs is expected to increase in the future as vehicle functions improve. Therefore, there is a need to improve the communication efficiency of DCMs. Therefore, in this embodiment, the DCM10 installs both the antenna and the communication module inside the roof of the vehicle 1. This ensures a clear line of sight and allows the cable connecting the antenna and the communication module to be as short as possible. The specific arrangement method will be described later. Furthermore, in this embodiment, an antenna for receiving broadcasts, used by the on-board device 20, is located inside the roof of the vehicle 1. That is, both a cellular communication antenna (first antenna) and a broadcast reception antenna (second antenna) are located inside the roof of the vehicle 1.

[0027] The interior of the roof is shielded with conductive material to improve noise immunity. This can improve the reception sensitivity of television and radio broadcasts. On the other hand, shielding the inside of the roof with a conductor may cause cavity resonance within the roof, potentially interfering with communication. Furthermore, placing the base substrate of the DCM10 and the conductor close together may result in the flow of out-of-phase high-frequency currents, which can become noise and degrade the antenna's radiation performance. Therefore, in this embodiment, these problems are addressed by giving the conductor placed inside the roof a specific shape. Details will be described later.

[0028] Figure 2 is a diagram illustrating the components of the DCM10 and the in-vehicle device 20 according to this embodiment. The DCM10 according to this embodiment is composed of a control device 11, a storage device 12, a cellular antenna 13, a cellular communication module 14, and an auxiliary battery 15. The in-vehicle device 20 comprises a control device 21, a storage device 22, a broadcast receiving antenna 24, and a broadcast receiving module 25.

[0029] First, let me explain DCM10. The control device 11 is a calculation unit that realizes various functions of the DCM 10 by executing a predetermined program.

[0030] The control device 11 performs the function of mediating communication between an external device and components of the vehicle 1 (vehicle components). Vehicle components are, for example, one or more in-vehicle devices mounted on the vehicle 1. The external device may be, for example, a server device that provides information. For example, if a vehicle component requires communication with an external device, the control unit 11 performs a function to relay data transmitted from that vehicle component to the external device (or external network). It also performs a function to receive data transmitted from the external device (or external network) and forward that data to the appropriate vehicle component.

[0031] Furthermore, the control device 11 can perform functions specific to its own device. For example, the control device 11 is configured to perform security system monitoring and communication functions, and can make security alerts, emergency alerts, etc., based on triggers that occur inside the vehicle.

[0032] The storage device 12 is a memory device that includes main memory and auxiliary storage. The auxiliary storage device stores the operating system (OS), various programs, various tables, etc., and by loading the programs stored therein into the main memory and executing them, various functions that match the predetermined purpose, as described later, can be realized.

[0033] The cellular antenna 13 is an antenna element that performs input and output of wireless signals. In this embodiment, the cellular antenna 13 is compatible with cellular communication (for example, mobile communication such as 3G, LTE, and 5G). The cellular antenna 13 may be composed of multiple physical antennas. For example, when using mobile communication via high frequency, multiple antennas may be distributed to stabilize communication. The cellular communication module 14 is a communication module for performing mobile communication.

[0034] The auxiliary battery 15 is a battery that supplies backup power to the DCM 10. The DCM 10 operates using power supplied from the vehicle 1, but the power supply may be interrupted due to traffic accidents, illegal activities, etc. In such cases, the auxiliary battery 15 supplies power to the DCM 10. This allows the DCM 10 to continue operating even in emergencies. The auxiliary battery 15 may also be charged while receiving power from the vehicle 1.

[0035] Next, we will describe the functions performed by the control device 11. Figure 3 is a diagram illustrating the functional modules of the control device 11. The illustrated functional modules can be realized by the control device 11 executing programs stored in a storage means such as ROM.

[0036] The data relay unit 111 relays data transmitted and received between vehicle components. For example, it receives a message sent by a first device connected to the in-vehicle network and, if necessary, performs the process of forwarding the message to a second device connected to the in-vehicle network. Furthermore, when the data relay unit 111 receives a message from a vehicle component destined for an external device, it relays the message to the external network. It also receives data transmitted from the external network and forwards that data to the appropriate vehicle component.

[0037] The emergency call unit 112 makes an emergency call to an operator outside the vehicle when an abnormal situation occurs in the vehicle 1. Examples of abnormal situations include traffic accidents and vehicle breakdowns. The emergency call unit 112 initiates a connection with an operator when a predetermined trigger occurs, such as pressing a call button located inside the vehicle or the deployment of an airbag, enabling communication between the vehicle occupant and the operator. In addition, the emergency call unit 112 may transmit the vehicle's location information to the operator when making an emergency call. In this case, the emergency call unit 112 may obtain the location information from the GPS module 26.

[0038] The security management unit 113 performs security monitoring processing. For example, based on data received from the ECU that manages the vehicle's electronic lock, the security management unit 113 detects that the vehicle has been unlocked without following the proper procedure and sends a security alert to a predetermined device. The security alert may include the vehicle's location information. In this case, the security management unit 113 may obtain the location information from the GPS module 26. If the security management unit 113 determines that a security problem has occurred with its own vehicle, it may obtain the location information and periodically transmit the obtained location information to a pre-specified external device.

[0039] Next, the in-vehicle device 20 will be described. The in-vehicle device 20 is a device that provides information to the occupants of the vehicle.

[0040] The control device 21 is a calculation unit that realizes various functions of the in-vehicle device 20 by executing a predetermined program.

[0041] The control device 21 is configured to provide, for example, the following functions: • Navigation function This function searches for the vehicle's route and provides guidance to the occupants. • Terminal link function This function connects to devices (such as smartphones) carried by the vehicle's occupants, enabling playback of music and videos, screen mirroring, and other similar functions. • Audio function This function allows you to play music stored on a storage device. • TV / radio function This function allows you to receive radio broadcasts and digital television broadcasts. These functions can be provided, for example, via the input / output unit 23 (e.g., a touch panel display), which will be described later.

[0042] The storage device 22 is a memory device that includes main memory and auxiliary storage. The auxiliary storage device stores the operating system (OS), various programs, various tables, etc., and by loading the programs stored therein into the main memory and executing them, various functions that match the predetermined purpose, as described later, can be realized.

[0043] The input / output unit 23 is a means for receiving input operations performed by the user and presenting information to the user. Specifically, the input / output unit 23 consists of a touch panel and its control means, and a liquid crystal display and its control means. In this embodiment, the touch panel and liquid crystal display consist of a single touch panel display. The input / output unit 23 may also include a unit for outputting audio (amplifier or speaker), a unit for inputting audio (microphone), etc.

[0044] The broadcast receiving antenna 24 is an antenna element that receives radio waves for television and radio broadcasts. The broadcast receiving antenna 24 may also be composed of multiple physical antennas. For example, multiple antennas facing different directions can be used as the broadcast receiving antenna 24. The broadcast receiving antenna 24 may be built into the in-vehicle device 20 or it may be located outside the in-vehicle device 20. In this case, the broadcast receiving antenna 24 may be connected to the in-vehicle device 20 via a cable or the like.

[0045] The broadcast receiving module 25 is a module for receiving television and radio broadcasts.

[0046] The in-vehicle device 20 can be configured as a computer having a processor such as a CPU or GPU, main memory such as RAM or ROM, and auxiliary storage such as EPROM, disk drive, or removable media, similar to the DCM 10.

[0047] Furthermore, the DCM10 and the in-vehicle device 20 have interface units for connecting to the in-vehicle network. Furthermore, in this embodiment, multiple vehicle components, including the DCM10 and the in-vehicle device 20, are interconnected via the network bus 30. For example, CAN (Controller Area Network) can be used as an example of an in-vehicle network standard. If a network utilizes multiple standards, the communication interface may have multiple interface devices that conform to the standards of the communication destination. Examples of communication standards other than CAN include Ethernet (registered trademark).

[0048] The network bus 30 is a communication bus that constitutes the in-vehicle network. In this example, one bus is shown as an example, but vehicle 1 may have two or more communication buses. Multiple communication buses may be connected to each other by the DCM 10 or a gateway that coordinates multiple communication buses.

[0049] Figure 4 shows the external appearance of the DCM10 hardware. The DCM10 hardware consists of a main board (base board) and various components mounted on the main board. The main board is a board on which a control device 11, a storage device 12, a cellular antenna 13, a cellular communication module 14, and an auxiliary battery 15 are mounted. In this example, the cellular antenna 13 is mounted on the main board, but the cellular antenna 13 may be connected to the main board via an external port.

[0050] The DCM10 may also include multiple connectors for external connections. One of the connectors is compatible with in-vehicle network buses such as CAN and Ethernet. The other connector can be used as an expansion connector. Examples of such expansions include a port for connecting an external antenna to the DCM10, and a USB port for connecting external devices (e.g., maintenance terminals) to the DCM10.

[0051] The illustrated hardware is located inside the roof of vehicle 1. Figure 5 illustrates the integration of the DCM 10 shown in Figure 4 into vehicle 1.

[0052] As shown in the diagram, the roof panel 2 of vehicle 1 has an opening. A roof lining 3 (interior material) is placed at the bottom of the opening. First, the DCM10 is mounted on the fixing plate 5. In this embodiment, the fixing plate 5 is a metal plate (conductor). The fixing plate 5 has fastening parts (e.g., screw holes) for connecting to the main board of the DCM10, and is fastened to the main board by these fastening parts. The fixing plate 5 is also provided with an opening of a predetermined size, and the DCM10 is mounted so as to straddle this opening (described later). Note that components other than the DCM10 may be attached to the fixing plate 5. For example, the in-vehicle device 20 or the broadcast receiving antenna 24 connected to the in-vehicle device 20 may be fastened to the fixing plate 5. In the illustrated example, the broadcast receiving antenna 24 is fastened to the fixing plate 5 together with the DCM10.

[0053] The fixing plate 5, to which the DCM10 and broadcast receiving antenna 24 are attached, is inserted through an opening in the roof panel 2 and fixed in the space between the roof panel 2 and the roof lining 3 (hereinafter referred to as the storage space). The fixing plate 5 may also be fixed to the roof panel 2 via conductive members such as screws. This allows the fixing plate 5 to be grounded. Finally, the roof panel opening is closed with the roof panel cover 4. The roof panel cover 4 is made of a non-conductive material (e.g., resin).

[0054] Next, the detailed shape of the fixing plate 5 will be described with reference to Figure 6(A). Figure 6(A) is a cross-sectional view (AA section) of the fixing plate 5 when it is attached to the vehicle 1.

[0055] As shown in Figure 5, the fixing plate 5 has an opening, and the DCM 10 is mounted so as to straddle the opening. When the DCM 10 is connected to the fixing plate 5 by multiple screws, the length of one side of the opening is designed to be shorter than the distance between the screws. The fixing plate 5 consists of a surface that contacts the roof lining 3, that is, a surface located at the bottom of the storage space, and four vertically rising surfaces (referred to as "rising sections" in this disclosure; shown by dotted lines in Figure 6). The rising sections surround all four sides of the storage space.

[0056] Previously, it was known that the DCM10 and the broadcast receiving antenna24 were placed in a storage space surrounded by the roof panel and roof lining. In this configuration, the cross-sectional view is as shown in Figure 6(B). However, in this case, five of the six surfaces forming the storage space will be surrounded by a conductive material, which may cause cavity resonance due to electromagnetic waves generated inside and outside the storage space. The resonant frequency may vary depending on the size of the storage space and the fixing plate, but if the resonant frequency is close to the frequency used by the DCM10 for communication, it may interfere with that communication. Furthermore, because the base board and fixing plate (i.e., the conductive material) of the communication module are in close proximity, a high-frequency current with opposite phases may be generated between the base board and the fixing plate, which may become noise and similarly interfere with communication.

[0057] On the other hand, in this embodiment, as shown in Figure 6(A), an opening is provided in the fixing plate 5, and the DCM 10 is positioned across this opening. With this configuration, the base substrate and the fixing plate can be separated, so the generation of reverse-phase current can be suppressed. In other words, it becomes possible to improve antenna performance. Furthermore, by adjusting the size of the opening, the frequency of the transmitted electromagnetic waves can be controlled, so resonance that occurs in the storage space can be suppressed.

[0058] For example, if the longest side of the storage space is slightly less than 2 meters, it is known that the resonant frequency will be in the UHF band (around 1 GHz). This frequency band can affect cellular communications and GNSS signals. Furthermore, if higher-order resonances occur in the SHF band (e.g., several GHz), they can affect communications such as Wi-Fi. Therefore, in order to suppress these resonances, the size of the opening should be adjusted so that electromagnetic waves in the relevant frequency band can pass from the inside to the outside of the storage space.

[0059] If the maximum length of the aperture (for example, the length of the diagonal) is X, then, according to the operating principle of a slot antenna, the upper limit wavelength λ of radio waves that can pass through the aperture is given by X = λ / 2. Here, for example, if the noise frequency (resonant frequency) is 1150 MHz, its wavelength is 260 mm, so if the maximum length of the aperture is 130 mm or more, electromagnetic waves of that frequency can be transmitted, and resonance can be reduced.

[0060] (modified version) The embodiments described above are merely examples, and the present invention may be modified as appropriate without departing from its spirit.

[0061] For example, in this embodiment, a cellular communication antenna (first antenna) and a broadcast reception antenna (second antenna) are placed in the storage space, but the second antenna is not limited to one for broadcast reception. Furthermore, the storage space may also contain antennas for receiving positioning signals transmitted from positioning satellites (also known as GNSS satellites). These antennas are an example of a second antenna. By providing openings in the fixing plate, resonance can be reduced, thereby improving the reception performance of these antennas as well.

[0062] Furthermore, Vehicle 1 may be equipped with a terminal (V2X terminal) that communicates with other vehicles located in the vicinity of Vehicle 1 or with roadside equipment. The V2X terminal communicates using centimeter-wave or millimeter-wave radio waves. Functions provided by V2X terminals include, for example, functions to prevent collisions between vehicles by exchanging data with other vehicles through vehicle-to-vehicle communication, and functions to acquire data related to traffic signals through vehicle-to-infrastructure communication. V2X functionality may also be included as part of the autonomous driving function. The V2X terminal performs functions such as generating predefined messages and periodically broadcasting them outside the vehicle, and receiving messages sent by other V2X terminals and controlling the vehicle's movement based on those messages. In this case, additional antennas for V2X communication may be placed in the storage space.

[0063] Furthermore, while the description of the embodiment illustrates a communication module and antenna that utilize cellular communication, the DCM10 may be equipped with multiple sets of communication modules and antennas that support other communication standards. Examples of such communication methods include Wi-Fi® and Bluetooth®. [Explanation of Symbols]

[0064] 1. Vehicle 10··DCM 20...In-vehicle equipment 30...Network bus 11,21...Control device 12,22...Storage device 13. Cellular antenna 14. Cellular communication module 15. Auxiliary battery 23...Input / output section 24... Broadcast receiving antenna 25...Broadcast receiving module

Claims

1. A vehicle roof structure that forms a space between the roof panel and the roof lining in which a communication module having a first antenna and a base board and a second antenna are arranged, A non-conductive roof panel cover is positioned above the aforementioned space. Below the aforementioned space, a conductive plate on which the communication module and the second antenna can be mounted is arranged. An opening is provided in at least a portion of the conductive plate that faces the base substrate. Vehicle roof structure.

2. The conductive plate has a rising portion that surrounds the sides of the space. The roof structure of a vehicle according to claim 1.

3. The first antenna is an antenna for cellular communication. The roof structure of a vehicle according to claim 1.

4. The aforementioned second antenna is an antenna for receiving broadcasts. The roof structure of a vehicle according to claim 1.

5. A conductive plate is provided, which is positioned between the roof panel and the roof lining of a vehicle, and to which a communication module having a first antenna and a base board and a second antenna can be attached, respectively. An opening is provided in at least a portion of the part facing the base substrate. Conductive plate.

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