On-vehicle antenna

Abstract

To improve a performance of an on-vehicle antenna.SOLUTION: An on-vehicle antenna 100 comprises: a ground conductive board 34; an antenna element 20 that is connected to the ground conductive board 34, and is provided on a windshield 10 side of a vehicle with respect to the ground conductive board 34; and a reflective conductor 54 that includes a front surface facing the antenna element 20 side from a position of a vehicle chamber side with respect to the windshield 10. The reflective conductor 54 is positioned on the vehicle chamber side with respect o the antenna element 20, is expanded toward a direction to be separated away from the windshield 10, and has a shape that is warped toward a side approaching to the antenna element 20.SELECTED DRAWING: Figure 12

Description

Technical Field

[0001] The present invention relates to an in-vehicle antenna, and particularly to an antenna disposed on the passenger compartment side of an automobile glass.

Background Art

[0002] Automobiles are equipped with various wireless devices such as radios, ETCs, and car navigation systems. These wireless devices are connected to in-vehicle antennas having characteristics corresponding to the operating frequency bands. Some in-vehicle antennas are attached to spoilers, roofs, window glasses, window frames, etc. according to their shapes and required characteristics.

[0003] The following Patent Documents 1 to 4 respectively describe antennas attached to spoilers, roofs, window glasses, and window frames of automobiles.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0005] Generally, the characteristics of in-vehicle antennas vary depending on the shape of the automobile body and the positional relationship between the in-vehicle antenna and the automobile body. Therefore, depending on the shape of the body and the mounting position on the body, etc., good characteristics may not be obtained for the in-vehicle antenna.

[0006] The object of the present invention is to improve the performance of an in-vehicle antenna.

Means for Solving the Problems

[0007] The in-vehicle antenna according to the present invention includes a ground conductor plate, an antenna element connected to the ground conductor plate and provided on the glass side of the vehicle rather than the ground conductor plate, and a reflection conductor having a surface facing the antenna element side from a position on the passenger compartment side of the glass. It is characterized by including.

[0008] In one embodiment, the reflection conductor has a region that spreads in a direction away from the glass on the passenger compartment side of the antenna element.

[0009] In one embodiment, a cover that covers the passenger compartment side of the substrate including the ground conductor plate is provided, and the reflection conductor is disposed on the cover.

[0010] In one embodiment, a case that supports the substrate including the ground conductor plate is provided, and the case is fixed to a reinforcement near the upper side of the glass.

[0011] In one embodiment, the antenna element includes a linear conductor extending in a direction along the ground conductor plate, a ground wire connecting the linear conductor to the ground conductor plate, and a power supply line connected to the linear conductor.

[0012] In one embodiment, the antenna element has a linear conductor extending in a direction along the ground conductor plate, the length of the ground conductor plate in the direction in which the linear conductor extends is longer than the linear conductor, and the length of the ground conductor plate in a direction intersecting the direction in which the ground conductor plate extends is 0.19 times or more the wavelength of the electromagnetic wave transmitted or received.

[0013] In one embodiment, the length of the ground conductor plate in the direction in which the linear conductor extends is 0.3 times or more the wavelength of the electromagnetic wave.

Effects of the Invention

[0014] According to the present invention, the performance of the in-vehicle antenna can be improved.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

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Figure 4

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Figure 8

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Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Embodiments for Carrying Out the Invention

[0016] An in-vehicle antenna according to an embodiment of the present invention will be described with reference to each figure. The same reference numerals are given to the same components shown in a plurality of drawings to simplify the description. Terms such as "upper", "lower", "right", "left", "passenger compartment side", and "outside" in this specification are for convenience in explaining the structure and do not limit the posture of each component when assembling the in-vehicle antenna.

[0017] FIG. 1 shows an in-vehicle antenna 100 attached near the upper side of the windshield 10 of an automobile. On the passenger compartment side of the body 12, a reinforcement 14, which is a reinforcing member, is located above the windshield 10. A cross-section of the reinforcement 14 is shown in FIG. 1. The reinforcement 14 extends obliquely downward and forward from the upper side, then is recessed toward the passenger compartment side to form a U shape, and at the tip of the U shape, it further extends obliquely downward and forward. The in-vehicle antenna 100 is attached to a flange region 16 that extends obliquely downward and forward from the region where the U shape is formed.

[0018] FIGS. 2 and 3 show the configuration of the main part of the in-vehicle antenna 100. The main part of the in-vehicle antenna 100 includes an antenna element 20, a substrate 22, and a case 18. The antenna element 20 includes a linear conductor 21 that extends in the left-right direction shown in FIGS. 2 and 3, a feeding line 24 that extends from the right end of the linear conductor 21 toward the passenger compartment, and a ground line 26 that extends from a midpoint between the feeding line 24 and the left end of the linear conductor 21 toward the passenger compartment. The linear conductor 21 is formed from a first strip region 23 that extends in a strip shape in the left-right direction on a plane intersecting the direction toward the passenger compartment, and a second strip region 25 that extends in a strip shape in the lateral direction on a plane that spreads from the rear of the first strip region 23 toward the passenger compartment side.

[0019] Note that the antenna element 20 may have a structure in which the ground line 26 extends from the right end of the linear conductor 21 toward the passenger compartment, and the feeding line 24 extends from a midpoint between the ground line 26 and the left end of the linear conductor 21 toward the passenger compartment. Also, the antenna element 20 may be a folded antenna element from which the ground line 26 is removed.

[0020] The substrate 22 includes an insulating board 32, a ground conductor plate 34 provided on the outer surface of the insulating board 32, and a power supply pattern conductor line 36 provided on the vehicle interior side surface of the insulating board 32. The tip of the power supply line 24 of the antenna element 20 is connected to the power supply pattern conductor line 36 provided on the vehicle interior side surface through an antenna mounting hole 38 formed in the substrate 22. The tip of the ground line 26 of the antenna element 20 is connected to the ground conductor plate 34 provided on the outer surface while passing through the antenna mounting hole 38 formed in the substrate 22.

[0021] An antenna connector 40 is fixed to the vehicle interior side surface of the substrate 22. One end of the power supply pattern conductor line 36 provided on the vehicle interior side surface of the substrate 22 is connected to the tip of the power supply line 24 of the antenna element 20. The antenna connector 40 is connected to the other end of the power supply pattern conductor line 36. The power supply pattern conductor line 36 forms a transmission line connecting between the tip of the power supply line 24 of the antenna element 20 and the antenna connector 40. Note that a multilayer substrate may be used for the substrate 22. In this case, the ground conductor plate 34 and the power supply pattern conductor line 36 may be formed in the inner layer of the multilayer substrate. A cable drawn from a wireless device mounted on the vehicle is connected to the antenna connector 40. Note that the cable drawn from the wireless device may be directly connected to the substrate 22 without using the antenna connector 40.

[0022] The case 18 has an uneven shape to facilitate attachment to the vehicle and has a structure in which the rear upper diagonal side is bent toward the vehicle interior side. The case 18 may be formed, for example, by pressing a metal plate. As will be described later, the substrate 22 is fixed to the case 18 from the vehicle interior side. Also, the antenna element 20 is fixed to the case 18 by a resin member described later.

[0023] FIG. 4 shows an exploded perspective view of the in-vehicle antenna 100. The terms "right", "left", "front diagonally downward", "front diagonally upward", "passenger compartment side", and "outside" shown in FIG. 4 are for convenience in explaining the structure and do not limit the postures of the respective components when assembling the in-vehicle antenna 100. As shown in FIG. 4, the in-vehicle antenna 100 includes an antenna element 20, a substrate 22, an antenna connector 40, a case 18, a resin base 50, a cover 52, a reflective conductor 54, and a temporary fixing plate 56. FIG. 5 shows a perspective view of the assembled in-vehicle antenna 100.

[0024] The in-vehicle antenna 100 will be described with reference to FIG. 4. The substrate 22 is provided with fixing holes 60 for fixing the substrate 22 to the case 18. The case 18 is provided with fixing claws 62 protruding toward the passenger compartment side for fixing the substrate 22. The substrate 22 is fixed to the case 18 by inserting the fixing claws 62 into the fixing holes 60 of the substrate 22 from the outside toward the passenger compartment side. The fixing claws 62 may be soldered to the ground conductor plate 34 of the substrate 22. The region of the substrate 22 where the antenna mounting holes 38 are provided does not overlap the case 18 at the front diagonally lower side of the case 18, and the outer surface of the region outside the region where the antenna mounting holes 38 are provided faces outside the case 18.

[0025] The antenna element 20 is fixed to the substrate 22 from the outside with the tip portions of the power supply line 24 and the ground line 26 inserted into the antenna mounting holes 38 of the substrate 22 from the passenger compartment side.

[0026] In this way, the antenna element 20 is fixed to the substrate 22, and the substrate 22 is fixed to the case 18. Thereby, the antenna element 20 is fixed to the case 18 via the substrate 22. In order to increase the mechanical strength of the antenna element 20, the antenna element 20 is fixed to the case 18 by a resin base 50 as described below.

[0027] The antenna element 20 is covered by the resin base 50 from the front lower diagonal side, and the antenna element 20 is fixed to the resin base 50. From the front lower diagonal edge of the case 18, two fixing pieces 64 project downward in the front lower diagonal direction. On the left and right side surfaces of the resin base 50, grooves 51 into which the left and right fixing pieces 64 are inserted are formed. The resin base 50 is fitted from the front lower diagonal side between these two fixing pieces 64 so that the left and right fixing pieces 64 are inserted into the left and right grooves 51, and is attached to the case 18. Thereby, the antenna element 20 is fixed to the case 18 via the resin base 50.

[0028] Figures 6 and 7 show an antenna element - case portion 102 extracted from the in - vehicle antenna 100 with only the antenna element 20, the case 18, the resin base 50, and the temporary fixing plate 56. These drawings show a state in which the resin base 50 is fixed between the two fixing pieces 64. Figure 6 is a view of the antenna element - case portion 102 seen from the front lower diagonal side, and Figure 7 is a view of the antenna element - case portion 102 seen from the rear upper diagonal side.

[0029] On the left side of each of Figures 8 and 9, a view of the main body portion 104 formed by combining the antenna element 20, the resin base 50, the substrate 22, and the case 18 is shown as seen from the passenger compartment side. On the right side of Figure 8, a cross - section along line AA of the main body portion 104 is shown, and on the right side of Figure 9, a cross - section along line BB of the main body portion 104 is shown.

[0030] As shown on the right side of Figure 7 and Figures 8 and 9 respectively, between the power supply line 24 and the ground line 26 of the antenna element 20, an engaging protrusion 70 of the resin base 50 enters from the front lower diagonal side toward the rear upper diagonal side. The engaging protrusion 70 catches on the rear - side surface of the antenna element 20 and fixes the antenna element 20 to the resin base 50.

[0031] Also, as shown in FIG. 7, on the left side of the ground line 26 in the linear conductor 21 of the antenna element 20, the sub-engagement protrusion 72 of the resin base 50 enters from the front lower diagonal side toward the rear upper diagonal side. The sub-engagement protrusion 72 catches on the rear surface of the antenna element 20 and fixes the antenna element 20 to the resin base 50.

[0032] Here, although the embodiment in which the antenna element 20 and the resin base 50 are separate parts is shown, a part of the antenna element 20 may be formed by a conductive paint or the like applied to the resin base 50.

[0033] Returning to FIG. 4 for explanation. The cover 52 has a first region 80 that spreads in a plate shape from the outside toward the passenger compartment side. Also, the cover 52 bends at the leading edge of the first region 80 so that a ridge line extends laterally toward the rear, and has a second region 82 that spreads in a plate shape toward the rear. The cover 52 further bends at the leading edge of the second region 82 so that a ridge line extends laterally toward the rear upper diagonal, and has a third region 84 that spreads in a plate shape toward the rear.

[0034] The reflection conductor 54 is fixed to the passenger compartment side surface of the cover 52. The reflection conductor 54 is formed in a plate shape that bends along the first region 80 and the second region 82 of the cover 52. The reflection conductor 54 is fixed to the passenger compartment side surface of the cover 52 so as to match the surface of the cover 52. As shown in FIG. 5, the cover 52 is attached to the main body portion 104 so as to cover the substrate 22 and the antenna connector 40. Here, an example in which a plate-shaped reflection conductor 54 is used is shown, but the reflection conductor 54 may be replaced with a conductive paint or the like. Also, the first region 80 and the second region 82 of the cover 52 may have a gently bent shape, and the reflection conductor 54 may also have a gently bent shape along the first region 80 and the second region 82.

[0035] FIG. 10 shows a view of the main body 104 of the vehicle-mounted antenna 100 fixed to the reinforcement 14 by bolts 90 and nuts 92 as viewed from the passenger compartment side. On the right side of FIG. 10, a CC cross-sectional view of the main body 104 is shown. A bolt hole 19 is provided in the left region of the case 18, and a temporary fixing plate 56 is attached around the bolt hole 19 from the passenger compartment side. The temporary fixing plate 56 is a plate-like member with a temporary fixing hole 57 sized such that the thread groove of the bolt 90 catches. The temporary fixing plate 56 is attached to the case 18 so that the temporary fixing hole 57 and the bolt hole 19 of the case 18 coincide.

[0036] The case 18 is overlapped with the reinforcement 14 so that the bolt hole 19 of the case 18 and the fixing hole 15 provided in the reinforcement 14 coincide, and then the bolt 90 is inserted into the bolt hole 19 of the case 18 and the fixing hole 15 of the reinforcement 14 from the outside. Also, a nut 92 is attached to the bolt 90 from the passenger compartment side. Thereby, the case 18 and the reinforcement 14 are fastened by the bolts 90 and nuts 92. The temporary fixing plate 56 prevents the main body 104 from falling after the bolt 90 is inserted into the bolt hole 19 of the case 18 and the fixing hole 15 of the reinforcement 14.

[0037] As described above, the vehicle-mounted antenna 100 according to the present embodiment includes a ground conductor plate 34, an antenna element 20 connected to the ground conductor plate 34 and provided on the front glass 10 side of the vehicle more than the ground conductor plate 34, and a reflection conductor 54 having a surface facing the antenna element 20 from a position on the passenger compartment side of the front glass 10.

[0038] The vehicle-mounted antenna 100 includes a cover 52 that covers the passenger compartment side of the substrate 22 including the ground conductor plate 34, and the reflection conductor 54 is disposed on the cover 52.

[0039] The vehicle-mounted antenna 100 includes a case 18 that supports the substrate 22 including the ground conductor plate 34, and the case 18 is fixed to the reinforcement 14 near the upper side of the front glass 10.

[0040] The antenna element 20 includes a linear conductor 21 extending in a direction along the ground conductor plate 34, a ground wire 26 connecting the linear conductor 21 to the ground conductor plate 34, and a feeding wire 24 connected to the linear conductor 21.

[0041] In FIG. 11, the visible range 94 of the in-vehicle antenna 100 is shown by a dashed line. Also, the direct transmission / reception range 96 where electromagnetic waves are directly radiated from the in-vehicle antenna 100 and directly arrive at the in-vehicle antenna 100 is shown by a filled pattern. In the in-vehicle antenna 100 according to the present embodiment, the antenna element 20 is provided on the front glass 10 side rather than the ground conductor plate 34 of the substrate 22. As a result, the direct transmission / reception range 96 is formed in front of the in-vehicle antenna 100.

[0042] FIG. 12 shows an enlarged cross-sectional view of an automobile near the in-vehicle antenna 100. In this figure, the reflection conductor 54 is drawn in a thick line exaggeratedly. The reflection conductor 54 spreads in a direction away from the front glass 10 on the passenger compartment side rather than the antenna element 20 and has a shape warped toward the side approaching the antenna element 20. In the example shown in FIG. 12, the reflection conductor 54 spreads in a direction away from the front glass 10 below the antenna element 20. As shown by the arrow 98, a part of the electromagnetic waves radiated from the antenna element 20 is reflected by the reflection conductor 54, propagates through the passenger compartment, and is radiated to the rear of the automobile through the rear glass. Also, the electromagnetic waves arriving from the rear of the automobile propagate through the passenger compartment through the rear glass, are reflected by the reflection conductor 54, and are received by the antenna element 20. As a result, electromagnetic wave transmission and reception are performed not only in front of the automobile but also in the rear.

[0043] Note that depending on the position where the in-vehicle antenna 100 is attached and the body 12 and the reinforcement 14, the reflection conductor 54 may have a non-warped shape having a region that spreads in a direction away from the front glass 10 on the passenger compartment side rather than the antenna element 20.

[0044] FIG. 13 shows an example of the sizes of the antenna element 20 and the substrate 22. In the example shown in FIG. 13, the lateral length of the substrate 22 is 0.3144λ, and the longitudinal length (in the direction from the front lower diagonal to the rear upper diagonal) is 0.1976λ. Here, λ is the wavelength of the electromagnetic wave transmitted or received. The antenna element 20 is disposed at a position that is 0.0249λ obliquely upward from the front edge of the substrate 22. The height from the ground conductor plate 34 of the substrate 22 to the upper surface of the linear conductor 21 is 0.0939λ.

[0045] The lateral length of the substrate 22 may exceed 0.3144λ, and the longitudinal length may also exceed 0.1976λ. The antenna element 20 may be disposed at a position that is obliquely upward by a distance longer than 0.0249λ from the front edge of the substrate 22.

[0046] FIG. 14 shows the experimental results of the antenna gain [dBi] when the lateral length of the substrate 22 is fixed at 0.3144λ and the longitudinal length of the substrate 22 is changed. The horizontal axis represents the longitudinal length, and the vertical axis represents the antenna gain. The antenna gain is defined as the radiation level in a specific direction when the radiation level from an omnidirectional antenna is set to 0 dB. When the lateral length of the substrate 22 is longer than the linear conductor 21 of the antenna element 20, the longitudinal length of the substrate 22 may be 0.19λ or more in order to ensure a sufficient radiation level in a specific direction. Also, the lateral length of the substrate 22 may be 0.3λ or more.

[0047] In the above, an example of attaching the in-vehicle antenna 100 above the front glass 10 was shown. The in-vehicle antenna 100 may be attached around other glasses in the automobile, such as above the rear glass.

[0048] The in-vehicle antenna 100 according to this embodiment may be used in a wireless device that conforms to standards such as Wi-Fi, LTE (Long Term Evolution), 5G (5th Generation), DAB (Digital Audio Broadcasting), and DTV (Digital TeleVision).

[0049] [Configuration of the Present Invention] Configuration 1: A ground conductor plate, An antenna element connected to the ground conductor plate and provided on the glass side of the vehicle rather than the ground conductor plate, A reflection conductor having a surface facing the antenna element side from a position on the passenger compartment side rather than the glass, and an in-vehicle antenna characterized by comprising. Configuration 2: The in-vehicle antenna according to Configuration 1, The reflection conductor is, An in-vehicle antenna characterized by having a region that spreads in a direction away from the glass on the passenger compartment side rather than the antenna element. Configuration 3: The in-vehicle antenna according to Configuration 1 or Configuration 2, A cover that covers the passenger compartment side of the substrate including the ground conductor plate, An in-vehicle antenna characterized in that the reflection conductor is disposed on the cover. Configuration 4: The in-vehicle antenna according to any one of Configurations 1 to 3, A case that supports the substrate including the ground conductor plate, An in-vehicle antenna characterized in that the case is fixed to a reinforcement near the upper side of the glass. Configuration 5: The in-vehicle antenna according to any one of Configurations 1 to 4, The antenna element is, A linear conductor extending in a direction along the ground conductor plate, A ground wire that connects the linear conductor to the ground conductor plate, An in-vehicle antenna characterized by comprising a feeding wire connected to the linear conductor. Configuration 6: The in-vehicle antenna according to any one of Configurations 1 to 5, The antenna element has a linear conductor extending in a direction along the ground conductor plate, The length of the ground conductor plate in the direction in which the linear conductor extends is longer than that of the linear conductor. The length of the ground conductor plate in the direction intersecting the direction in which the ground conductor plate extends is 0.19 times or more the wavelength of the electromagnetic wave transmitted or received, and the vehicle-mounted antenna is characterized by this. Configuration 7: The vehicle-mounted antenna according to Configuration 6, The length of the ground conductor plate in the direction in which the linear conductor extends is 0.3 times or more the wavelength of the electromagnetic wave, and the vehicle-mounted antenna is characterized by this.

Explanation of Signs

[0050] 10 Front glass, 12 Body, 14 Reinforcement, 16 Flange region, 18 Case, 19 Bolt hole, 20 Antenna element, 21 Linear conductor, 22 Substrate, 23 First strip region, 24 Feeding line, 25 Second strip region, 26 Ground line, 32 Insulating plate, 34 Ground conductor plate, 36 Pattern conductor line, 38 Antenna mounting hole, 40 Antenna connector, 50 Resin base, 51 Groove, 52 Cover, 54 Reflective conductor, 56 Temporary fixing plate, 57 Temporary fixing hole, 60 Fixing hole, 62 Fixing claw, 64 Fixing piece, 70 Engaging protrusion, 72 Sub-engaging protrusion, 80 First region, 82 Second region, 84 Third region, 90 Bolt, 92 Nut, 94 Visible range, 96 Direct transmission / reception range, 98 Arrow, 100 Vehicle-mounted antenna, 102 Antenna element / case part, 104 Main body part.

Claims

1. A ground conductor plate, an antenna element connected to the ground conductor plate and provided on the glass side of the ground conductor plate with respect to the vehicle, and a reflection conductor having a surface facing the antenna element side from a position on the passenger compartment side of the glass, wherein the vehicle-mounted antenna is characterized by comprising the same.

2. The vehicle-mounted antenna according to claim 1, wherein the reflection conductor has a region that spreads in a direction away from the glass on the passenger compartment side of the antenna element, and the vehicle-mounted antenna is characterized by the same.

3. The vehicle-mounted antenna according to claim 1 or claim 2, comprising a cover that covers the passenger compartment side of a substrate including the ground conductor plate, wherein the reflection conductor is disposed on the cover, and the vehicle-mounted antenna is characterized by the same.

4. The vehicle-mounted antenna according to claim 1 or claim 2, comprising a case that supports a substrate including the ground conductor plate, wherein the case is fixed to a reinforcement near the upper side of the glass, and the vehicle-mounted antenna is characterized by the same.

5. The vehicle-mounted antenna according to claim 1 or claim 2, wherein the antenna element comprises a linear conductor extending in a direction along the ground conductor plate, a ground wire connecting the linear conductor to the ground conductor plate, and a feeding wire connected to the linear conductor, and the vehicle-mounted antenna is characterized by the same.

6. The vehicle-mounted antenna according to claim 1 or claim 2, wherein the antenna element has a linear conductor extending in a direction along the ground conductor plate, the length of the ground conductor plate in the direction in which the linear conductor extends is longer than the linear conductor, and the length of the ground conductor plate in a direction intersecting the direction in which the ground conductor plate extends is 0.19 times or more the wavelength of an electromagnetic wave to be transmitted or received, and the vehicle-mounted antenna is characterized by the same.

7. The vehicle-mounted antenna according to claim 6, wherein the length of the ground conductor plate in the direction in which the linear conductor extends is 0.3 times or more the wavelength of the electromagnetic wave, and the vehicle-mounted antenna is characterized by the same.

Images