JP2018133792A - Vehicle antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vehicle antenna ensuring reception performance equivalent to that of a short pole antenna provided on the roof made of a sheet metal, even if it is installed on the roof made of resin.SOLUTION: A vehicle antenna 1 includes a monopole 2 disposed on the surface side of a resin roof 21 of a vehicle and having an electric length of 1/4 wavelength, conductors 3 disposed radially at equal angular intervals in at least three directions from one end of the monopole 2 on the back side of the resin roof 21, and an antenna attachment part 24 consisting of a monopole connection 24a to be connected with one end of the monopole 2 on the surface side of the resin roof 21, and a base 24b to be connected with one end of the conductor 3 on the back side of the resin roof 21, where the base 24b is grounded to the body of the vehicle 20, and is electrically open for the body over the full length excepting one end of the conductor 3, thus realizing a vehicle antenna 1 having good reception performance and omnidirectionality even on the resin roof 21.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a vehicular antenna, and more particularly to a mounting structure for a vehicular antenna installed on a resin roof of a vehicle (hereinafter referred to as a resin roof).

  In a conventional vehicle antenna, a short pole antenna provided on a sheet metal roof is known. The pole antenna is also called a monopole antenna. In the short pole antenna, the roof surface acts as a reflector, and non-directional reception performance such as FM broadcasting can be secured. A loop antenna is known as an antenna that does not use the roof surface as a reflector.

Patent Document 1 discloses a loop antenna as an omnidirectional vehicle antenna installed on a roof.
FIG. 11 is a configuration diagram of the antenna device disclosed in Patent Document 1, and FIG. 12 is a circuit diagram of a power feeding switch of the antenna device of FIG.
As shown in FIGS. 11 and 12, the loop antenna element 100 includes a plurality of power feeding elements 111a, 111b, 111c, and 111d and a plurality of power feeding elements 111a, 111b, 111c, and 111d that are switched by a switch device 122n. The power supply switching unit 120 for selecting an element and a coaxial cable 114 connected to the power supply switching unit 120 are configured. According to the loop antenna described in Patent Document 1, the loop antenna element 100 is provided on the back surface of the resin roof of the vehicle and disposed on the inner periphery of the vehicle body structure (metal frame), so that the radiation / reception antenna element is efficient. It describes that it is possible to emit and receive good radio waves.

FIG. 13 is a diagram showing two loop antennas 210 and 210 disclosed in Patent Document 2 as vehicle antennas installed on a resin roof and applicable to diversity reception and the like. FIG. 14 shows the configuration of the loop antenna 210. FIG.
As shown in FIG. 13, the loop antenna 210 is an in-vehicle antenna that can be disposed on the resin roof 221 of the vehicle, and the two loop antennas 210 and 210 are disposed for application to diversity reception or the like. .

  As shown in FIG. 14, this loop antenna 210 has a substantially inverted triangular loop structure with the vicinity of the feeding point downward, and a short-circuit stub 221 that adjusts the loop length of the approximately inverted triangle according to its own line length. The loop structure is inserted in series near one vertex of the substantially inverted triangle. As a result, the position of the midpoint of the loop and the position of the apex substantially coincide with each other, and the current flowing in the lateral direction can be effectively radiated, so that it is possible to eliminate the drop in reception sensitivity in the front-rear direction of the automobile. Has been.

JP 2003-243922 A JP 2004-96618 A

  However, the antenna described in Patent Document 1 requires a new power supply switching device 120 that switches a plurality of loop antennas 100 provided on the resin roof by the switch device 122n, and costs are increased to establish an antenna that satisfies directivity. There is a problem of hanging.

  In addition, the antenna described in Patent Document 2 attempts to improve the directivity on the premise that the antenna is diversified as compared with the conventional loop antenna, and ensures the directivity as compared with the short pole antenna mounted on the roof. Therefore, there is a problem that costs are increased.

A conventional short pole antenna provided on a resin roof has a problem in that reception performance cannot be ensured because there is nothing equivalent to a ground plate.
Therefore, an object of the present invention is to provide a vehicular antenna that can obtain reception performance equivalent to that of a short pole antenna provided on a sheet metal roof even when installed on a resin roof.

  In order to achieve the above object, a vehicle antenna of the present invention includes a monopole portion disposed on the front side of a resin roof of a vehicle and having an electrical length of 1/4 wavelength, and at least from one end of the monopole portion on the back side of the resin roof. Conductors arranged in three directions, preferably radially and having an electrical length of ¼ wavelength, a monopole connecting portion to which one end of the monopole portion is connected on the front side of the resin roof, and a conductor on the back side of the resin roof An antenna mounting portion including a base portion to which one end of the portion is connected, the base portion of the mounting portion is grounded to the body portion of the vehicle, and the entire length excluding one end of the conductor portion is electrically opened to the body portion. It is characterized by.

In the above configuration, the conductor portions are preferably arranged in three directions at equal intervals of 120 degrees on the back side of the resin roof.
Preferably, a loading coil is inserted into the monopole part and / or the conductor part in order to shorten the monopole part and / or the conductor part.
A receiver mounted on the vehicle and a monopole connecting portion are connected by a coaxial cable, an inner conductor of the coaxial cable is connected to the monopole connecting portion, and an outer conductor is connected to the base portion.

  According to the vehicle antenna of the present invention, it becomes possible to realize a pole antenna having a good reception performance even with a resin roof, and the conductor portion is almost the same as that of a vehicle roof made entirely of sheet metal. By deploying radially at equal intervals and using it as a wave reflector for a monopole antenna, it is possible to improve reception sensitivity and omnidirectionality even with a resin roof.

It is a perspective view which shows typically the structure of the vehicle antenna of this invention. It is an expansion perspective view which shows the structural example of the antenna 1 for vehicles of this invention. It is sectional drawing along the AA line of FIG. It is a perspective view of the location B shown with a dotted line in FIG. It is a top view which shows the antenna for vehicles of Example 1. FIG. It is a figure which shows the result of having simulated the directivity of the vehicle antenna of Example 1. FIG. It is a figure which shows the result of having simulated the directivity of the vehicle antenna of a comparative example. FIG. 6 is a plan view showing a vehicle antenna according to a second embodiment. FIG. 6 is a plan view showing a vehicle antenna according to a third embodiment. It is a top view which shows the antenna for vehicles of Example 4. 1 is a configuration diagram of an antenna device disclosed in Patent Document 1. FIG. FIG. 12 is a circuit diagram of a power feeding switch of the antenna device of FIG. 11. It is a figure which shows the two loop antennas currently disclosed by patent document 2 as an antenna for vehicles which is installed in a resin roof and can be applied to diversity reception. It is a block diagram of the loop antenna of FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the scope of the present invention is not limited to the embodiments and can be appropriately changed. In particular, the shape, dimensions, positional relationship, and the like of each member described in the drawings merely show conceptual matters, and can be changed according to the application scene. In the drawings, the same or corresponding members are denoted by the same reference numerals.
FIG. 1 is a perspective view schematically showing a configuration of a vehicle antenna 1 according to an embodiment of the present invention, and FIG. 2 is an enlarged perspective view showing a configuration example of the vehicle antenna 1. FIG. 3 is a cross-sectional view taken along the line AA in FIG. 2 and shows an attachment structure in which the vehicle antenna 1 is attached to the resin roof 21 of the vehicle 20. 4 is a perspective view of a portion B indicated by a chain line in FIG.

  As shown in FIGS. 1 and 2, a vehicle antenna 1 according to an embodiment of the present invention includes a monopole portion 2 having an electrical length of ¼ wavelength and disposed on the front side of a resin roof 21 of a vehicle 20. On the back side of the resin roof 21, for example, on the back side, the conductor portion 3 having an electrical length of ¼ wavelength that is radially arranged at an equiangular interval in at least three directions from one end of the monopole portion 2, and the resin roof 21 An antenna mounting portion 24 including a monopole connection portion 24a to which one end of the monopole portion 2 is connected on the front side and a base portion 24b to which one end of the conductor portion 3 is connected on the back side of the resin roof 21, and the base portion 24b has The vehicle 20 is grounded to the body portion, and the entire length excluding one end of the conductor portion 3 is electrically open to the body portion.

  In the case of illustration, the conductor part 3 consists of three conductors 3a, 3b, and 3c, and the length thereof is set to an electrical length that is ¼ wavelength of the wavelength of FM broadcast, like the monopole part 2. The conductor portion 3 is also called a ground wire or a counterpoise conductor wire, and acts as a ground wire, that is, a ground, with respect to the monopole portion 2. In the vehicular antenna 1 of the present invention, at least three conductor portions 3a, 3b, and 3c are preferably arranged radially in three directions at equiangular or nearly equiangular intervals, like a so-called ground plane antenna. It operates as an omnidirectional antenna.

  The monopole portion 2 is composed of a conductor composed of a conductor pattern formed on a wire, a bar, a printed circuit board, a flexible printed circuit (also referred to as FPC), or the like. The monopole part 2 may be coat | covered with insulators, such as resin. The monopole portion 2 may be arranged perpendicularly or at an angle to the surface of the resin roof 21.

  A loading coil may be inserted into the monopole part 2 in order to shorten the length of the monopole part 2. You may adjust to the length of 1/4 wavelength of the wavelength of the FM broadcast to receive by inserting a coil in the middle or the edge part side of the conductor which consists of an above-mentioned line | wire, a rod, a printed circuit board, and FPC. This coil is referred to as a monopole loading coil in this specification. By inserting the monopole loading coil, the actual length of the monopole 2 can be made shorter than the length of the quarter wavelength, which is the electrical length. Thereby, the vehicle antenna 1 is reduced in size.

  When the radio wave to be received is FM broadcast, the frequency of Japanese FM broadcast is about 76 MHz to 90 MHz, so the length of the quarter wavelength is about 99 cm to 83 cm, which is about 1 m. When the received radio wave is an FM complementary relay station that relays medium wave (AM) broadcasting, the frequency is about 90 MHz to about 95 MHz, so the length of the quarter wavelength is about 83 cm to 79 cm. . By inserting a monopole portion loading coil into the monopole portion 2, the length of the monopole portion 2 is equivalently set to a quarter wavelength which is an electrical length, for example, the actual length of the monopole portion 2. Can be shortened to, for example, about 1 to 20 cm.

  Each conductor part 3a, 3b, 3c is comprised with the conductor which consists of a conductor pattern formed in the line | wire, the rod, and the printed circuit board. As the conductor, roof reinforcement (also referred to as roof reinforcement or R / F) disposed to reinforce the resin roof 21 may be used. The shape of the conductor to be the conductor portions 3a, 3b, and 3c can be a straight line or a shape obtained by bending a straight line.

  Here, the loading coil may be inserted not only in the monopole part 2 but also in the conductor part 3. In other words, a coil may be inserted between or at the ends of the conductors 3a, 3b, and 3c of the conductors 3a, 3b, and 3c to adjust the length to a quarter wavelength of the wavelength of the FM broadcast to be received. In this specification, this coil is called a radial loading coil. By inserting the radial loading coil, the actual length of each of the conductor portions 3a, 3b, 3c can be made shorter than the length of the quarter wavelength that is the electrical length. Thereby, it can be set as the vehicle antenna 1 which can be mounted in the small vehicle 20 with the area of the resin roof 21 small.

  The conductor portion 3 shown in FIG. 2 includes three conductor portions 3a, 3b, and 3c. The conductor portions 3a, 3b, and 3c are arranged at predetermined angular intervals with the adjacent conductor portions 3a, 3b, and 3c. . For example, when the number of conductor portions is three, the angle can be set to 120 degrees. The number of conductor portions 3 may be four or more. In this case, the interval between the conductor portions 3 may be an equal interval of 90 degrees, for example.

  Next, an attachment structure for attaching the vehicle antenna 1 according to the embodiment of the present invention to the resin roof 21 of the vehicle 20 will be described with reference to FIG. The monopole portion 2 and the conductor portions 3a, 3b, and 3c are connected to an antenna mounting portion 24 disposed on the resin roof 21. The antenna mounting portion 24 includes a monopole connection portion 24a connected to the monopole portion 2, a base portion 24b connected to the conductor portions 3a, 3b, and 3c, and an insulation that insulates the monopole connection portion 24a and the base portion 24b. Part 24c. The insulating part 24c is made of air, fluororesin, or the like.

  The monopole connecting portion 24 a is made of a conductor and has, for example, a hollow tube shape, and an upper portion thereof opens on the front side of the resin roof 21, and a lower portion thereof protrudes on the back side of the resin roof 21. For example, one end of a rod-shaped monopole portion 2 is inserted into the upper portion of the monopole connecting portion 24 a and fixed on the resin roof 21. For waterproofing and dustproofing, it is desirable that after one end of the monopole part 2 is inserted into the monopole connecting part 24a, the lower part of the monopole part 2 is covered with a seal part 28 made of resin or rubber.

  The base portion 24 b is made of a conductor and has a thread on the outer peripheral portion. The base portion 24 b is inserted into an opening portion 21 a for mounting a vehicle antenna provided on the resin roof 21, and fastened to the resin roof 21 with a nut 27 via a washer 26. Is done.

  As shown in FIG. 4, the conductor portions 3 a, 3 b, and 3 c are connected to the washer 26, and the base portion 24 b together with the washer 26 is connected to a body portion (not shown) serving as a ground. A roof reinforcement can be used as each conductor part 3a, 3b, 3c. In this case, the roof reinforcement is grounded by being electrically connected to the body portion. When one end of the roof reinforcement is connected to the washer 26, the length of the roof reinforcement is set to a quarter wavelength of the FM broadcast receiving wavelength, and the total length excluding the one end connected to the base 24b of the roof reinforcement is It is electrically open to the body part. That is, the roof reinforcement as the conductor portion is electrically opened or floated, and the other end side opposite to one end of the roof reinforcement is insulated from the body portion.

  The lowermost part of the monopole connecting part 24a and the lowermost part of the base part 24b are connected to the FM receiver via a transmission line. A coaxial cable 31 can be used as the transmission line. Thereby, the receiver mounted on the vehicle 20 and the monopole connecting portion 24a are connected by the coaxial cable 31, and the inner conductor 31a at one end of the coaxial cable 31 is connected to the lowermost portion of the monopole connecting portion 24a. The outer conductor 31b of the coaxial cable 31 is connected to the lowermost part of the base 24b. Then, the other end (not shown) of the coaxial cable 31 connected to the vehicle antenna 1 is connected to an FM receiver disposed on the instrument panel. Here, an amplifier may be connected between the vehicle antenna 1 and the coaxial cable 31.

  According to the vehicle antenna 1 of the present invention, it can be installed on the resin roof 21, the monopole part 2 functions as a quarter wavelength antenna, the conductor part 3 functions as a reflector, and is omnidirectional like a so-called ground plane antenna. Directional characteristics and reception sensitivity equivalent to that of a short pole antenna provided on a sheet metal roof can be realized.

  According to the vehicle antenna 1 of the present invention, omnidirectionality can be realized with a simple structure, so that a plurality of antennas for diversity and parts and circuits for switching between the plurality of antennas are unnecessary, and the cost is low. Can be manufactured.

  Furthermore, according to the vehicle antenna 1 of the present invention, it can be installed not on the sheet metal roof but on the resin roof 21 and the vehicle 20 can be reduced in weight. Can be considered. Specific examples of the vehicular antenna of the present invention are shown below.

Next, a first embodiment in which the vehicle antenna of the present invention is disposed on a resin roof of the vehicle will be described.
FIG. 5 is a plan view illustrating the vehicle antenna 1 </ b> A according to the first embodiment. As shown in FIG. 5, the vehicle antenna 1 </ b> A is disposed on the resin roof 21 on the rear side of the vehicle, and the monopole portion 2 is disposed in the direction perpendicular to the surface of the resin roof 21 to become the conductor portion 3. The first to third roof reinforcements 3d, 3e, and 3f are disposed on the back side of the resin roof 21 at an equal angle, that is, an angular interval of 120 degrees.

  The first roof reinforcement 3 d is disposed on the resin roof 21 at approximately the center in the width direction of the vehicle 20 and along the front-rear direction of the vehicle 20. The first roof reinforcement 3d has a length of about 1 m as a quarter wavelength of the wavelength of the FM broadcast to be received.

  One end of the first roof reinforcement 3d is connected to the base portion 24b of the antenna mounting portion 24 via the washer 26, and the base portion 24b and the washer 26 are electrically connected to a body portion serving as a ground. It is fixed.

  The other end of the first roof reinforcement 3d is not electrically connected to the body part, but is floated with respect to the body part. In the first embodiment, the other end of the first roof reinforcement 3d is inserted into a connection member such as a resin, and an adhesive or the like is attached to another roof reinforcement (not shown) or a roof cross member that is another reinforcing member. It is fixed by. As a result, the other end of the first roof reinforcement 3d is not electrically connected to the body portion by the insulator, but is fixed to another roof reinforcement, so that the resin roof 21 is fixed to the first roof reinforcement 3d. It will be reinforced by the reinforcement 3d.

  The second roof reinforcement 3e is disposed at the right rear of the vehicle 20 at an angle of 120 degrees from the first roof reinforcement 3d in the resin roof 21 and is a reinforcement member at the rear end of the resin roof 21. The header 41 is disposed toward the one end side. Similarly to the first roof reinforcement 3d, the second roof reinforcement 3e has a length of about 1 m.

  One end of the second roof reinforcement 3e is connected to the base 24b of the antenna mounting portion 24 via the washer 26, similarly to one end of the first roof reinforcement 3d, and the base 24b and the washer 26 are connected to the ground. It is fixed to be electrically connected to the body part.

  The other end side of the second roof reinforcement 3e is not electrically connected to the body portion but is in a floating state with respect to the body portion. The other end of the second roof reinforcement 3e is inserted into a connecting member such as a resin and is fixed to one end of the rear header 41 with an adhesive or the like. As a result, the other end of the second roof reinforcement 3e is not electrically connected to the body portion by the insulator, but is fixed to the rear header 41. Therefore, the resin roof 21 is provided with the second roof reinforcement 3e. Ment 3e.

  Further, the third roof reinforcement 3f is a reinforcing member at the rear end of the resin roof 21 disposed on the left rear side of the vehicle 20 at an angle interval of 120 degrees from the second roof reinforcement 3e in the resin roof 21. The rear header 41 is disposed toward the other end side. Similarly to the first roof reinforcement 3d, the third roof reinforcement 3f has a length of about 1 m.

  One end of the third roof reinforcement 3f is connected to the base 24b of the antenna mounting portion 24 via the washer 26, similarly to one end of the first roof reinforcement 3d, and the base 24b and the washer 26 are grounded. It is fixed to be electrically connected to the body part.

  The other end side of the third roof reinforcement 3f is not electrically connected to the body portion but is in a floating state with respect to the body portion. The other end of the third roof reinforcement 3f is inserted into a connecting member such as a resin and fixed to the other end of the rear header 41 with an adhesive or the like. Thereby, the other end side of the third roof reinforcement 3f is not electrically connected to the body portion by the insulator, but is fixed to the other end portion of the rear header 41. 3 roof reinforcement men 3f.

(Comparative example)
A vehicle antenna configured in the same manner as in Example 1 was used as a comparative example, except that the number of conductor portions was two and that the two were arranged left and right from the center in the vehicle width direction.

FIG. 6 is a diagram illustrating a result of simulating the directivity of the vehicle antenna 1A of Example 1, and FIG. 7 is a diagram illustrating a result of simulating the directivity of the vehicle antenna of the comparative example. 6 and 7, the vehicle 20 is indicated by a dotted line, the X direction is the front-rear direction of the vehicle 20, and Y is the vehicle width direction.
As shown in FIG. 6, it can be seen that the directivity of the vehicle antenna 1A of the present invention is almost omnidirectional, and the sensitivity of the vehicle antenna 1A of the present invention is a short pole antenna provided on a sheet metal roof. It was found that the reception performance equivalent to
On the other hand, as shown in FIG. 7, it was found that the vehicle antenna of the comparative example has high directivity that the sensitivity is high in the left-right direction of the vehicle, but the sensitivity is deteriorated in the front-rear direction of the vehicle.

Next, a second embodiment of the vehicle antenna of the present invention will be described.
FIG. 8 is a plan view in which the vehicular antenna 1B of the second embodiment is disposed on the resin roof of the vehicle. As shown in FIG. 8, the vehicle antenna 1B of the second embodiment is disposed on a resin roof 21 on the rear side of the vehicle 20, and the monopole portion 2 is disposed in a direction perpendicular to the surface of the resin roof 21, The first to third roof reinforcements 3g, 3h, 3i are different from the first to third roof reinforcements 3d, 3e, 3f of the first embodiment in FIG. It is installed.

  The first roof reinforcement 3g is disposed in the resin roof 21 at approximately the center in the width direction of the vehicle 20 and along the front-rear direction of the vehicle 20 in the same manner as the first roof reinforcement 3d of the first embodiment. Has been. The first roof reinforcement 3g has a length of about 1 m as a quarter wavelength of the wavelength of the FM broadcast to be received.

  One end of the first roof reinforcement 3g is connected to the base 24b of the antenna mounting portion 24 via the washer 26, as in the first roof reinforcement 3d of the first embodiment, and the base 24b and the washer 26 are connected to each other. It is fixed so as to be electrically connected to the body part that is grounded.

  Similarly to the first roof reinforcement 3d of the first embodiment, the other end of the first roof reinforcement 3g is not electrically connected to the body part but is floated with respect to the body part. Yes. In the second embodiment, the other end of the first roof reinforcement 3g is inserted into a connecting member such as resin, and another roof reinforcement (not shown) or a roof cross member that is another reinforcing member is attached with an adhesive or the like. Fixed. As a result, the other end of the first roof reinforcement 3g is not electrically connected to the body portion by the insulator, but is fixed to another roof reinforcement. It will be reinforced by the roof reinforcement 3g.

  Unlike the second roof reinforcement 3f of the first embodiment, the second roof reinforcement 3h is disposed at the right rear of the vehicle 20 at an angle of about 90 degrees, and the rear end of the resin roof 21 is reinforced. The member is disposed in the direction of one end of the rear header 41, but is bent in a substantially L shape. In FIG. 8, as an example, the second roof reinforcement 3h extends linearly from the monopole portion 2 side to the right end portion of the resin roof 21, and further, the rear header is at an angle of about 90 degrees with respect to this straight line. It has a substantially L-shape extending to 41. Similarly to the first roof reinforcement 3g, the second roof reinforcement 3h has a length of about 1 m.

  One end of the second roof reinforcement 3h is connected to the base 24b of the antenna mounting portion 24 via the washer 26, similarly to one end of the first roof reinforcement 3g, and the base 24b and the washer 26 are grounded. It is fixed to be electrically connected to the body part.

  The other end side of the second roof reinforcement 3h is not electrically connected to the body portion but is in a state of floating with respect to the body portion. The other end of the second roof reinforcement 3h is inserted into a connecting member such as a resin, and fixed to the left end of the rear header 41 with an adhesive or the like. As a result, the other end of the second roof reinforcement 3h is not electrically connected to the body portion by the insulator, but is fixed to the rear header 41. Therefore, the resin roof 21 is provided with the second roof reinforcement 3h. It will be reinforced by 3h.

  Further, unlike the third roof reinforcement 3f of the first embodiment, the third roof reinforcement 3i is disposed on the left rear side of the vehicle 20 at an angle of about 90 degrees, and the rear end of the resin roof 21 The reinforcing member is bent in a substantially L shape toward the other end side of the rear header 41. In FIG. 8, as an example, the third roof reinforcement 3i extends linearly from the monopole part 2 side to the left end part of the resin roof 21, and further, at an angle of about 90 degrees with respect to this straight line, the rear header It has a substantially L-shape extending to 41. Similarly to the first roof reinforcement 3g, the third roof reinforcement 3i has a length of about 1 m.

  One end of the third roof reinforcement 3i is connected to the base 24b of the antenna mounting portion 24 via the washer 26, similarly to one end of the first roof reinforcement 3g, and the base 24b and the washer 26 are connected to the ground. It is fixed to be electrically connected to the body part.

  The other end side of the third roof reinforcement 3i is not electrically connected to the body portion but is in a state of floating with respect to the body portion. The other end of the third roof reinforcement 3i is inserted into a connecting member such as a resin and is fixed to the other end of the rear header 41 with an adhesive or the like. Thereby, the other end side of the third roof reinforcement 3i is not electrically connected to the body portion by the insulator, but is fixed to the other end portion of the rear header 41. 3 roof reinforcement 3i.

Next, a third embodiment of the vehicle antenna of the present invention will be described.
FIG. 9 is a plan view illustrating a state in which the vehicle antenna 1 </ b> C according to the third embodiment is disposed on the resin roof of the vehicle. As shown in FIG. 9, the vehicle antenna 1 </ b> C is disposed on a resin roof 21 on the rear side of the vehicle 20, and the monopole portion 2 is disposed in a direction perpendicular to the surface of the resin roof 21. The three conductor portions 3a, 3b, 3c are arranged on the back side of the resin roof 21 at an equal angle, that is, at an angular interval of 120 degrees.
The vehicle antenna 1C of the third embodiment is different from the vehicle antenna 1A of the first embodiment in that the first to third conductor portions 3a, 3b, 3c are replaced with the first to third roof reinforcement portions 3d, 3e. This is a point constituted by an electric wire made of copper or the like instead of 3f.

  As a material other than copper, a low resistance material such as aluminum is desirable. The copper or aluminum wires used as the first to third conductor portions 3a, 3b, and 3c can use a single core or a stranded wire, and are insulated and coated with a resin or the like except for one end connected to the base portion 24b. It is desirable. Moreover, you may use the conductor pattern body which consists of copper formed in the board | plate material, the printed circuit board, and FPC for the 1st-3rd conductor parts 3a, 3b, 3c.

  The first conductor portion 3 a is disposed in the resin roof 21 at approximately the center in the width direction of the vehicle 20 and along the front-rear direction of the vehicle 20. The length of the 1st conductor part 3a has a length of about 1 m as a quarter wavelength length of the wavelength of FM broadcast to receive.

  One end of the first conductor portion 3a is connected to the base portion 24a of the antenna mounting portion 24 through the washer 26, and is fixed so that the base portion 24b and the washer 26 are electrically connected to a body portion serving as a ground. ing. Here, it is desirable that the body part is connected directly and at the shortest distance to a roof reinforcement or the like which is one of the body parts closest to the antenna mounting part 24.

  The other end side, which is the entire length excluding one end of the first conductor portion 3a, is not electrically connected to the body portion but is in a floating state with respect to the body portion. The floating state with respect to the body portion can be realized relatively easily by using an electric wire or the like that is insulated and coated on the first conductor portion 3a and second and third conductor portions 3b and 3c described later. The other end of the first conductor portion 3a is inserted into a connecting member such as resin and is fixed to a roof reinforcement (not shown) or a roof cross member that is another reinforcing member by an adhesive or the like. Thereby, the other end side of the 1st conductor part 3a is fixed to a roof reinforcement etc., without being electrically connected to a body part by an insulator.

  The arrangement and dimensions of the second and third conductor portions 3a and 3b are the same as in the first embodiment. Further, one end of each of the second and third conductor portions 3a and 3b is connected to the base portion 24b of the antenna mounting portion 24 via the washer 26, like the one end of the first roof reinforcement 3d of the first embodiment. At the same time, the base 24b and the washer 26 are fixed so as to be electrically connected to the body portion serving as a ground.

  The other end sides of the second and third conductor portions 3a and 3b are not electrically connected to the body portion but are floated with respect to the body portion. Similar to the other ends of the second and third roof reinforcements 3d and 3e of the first embodiment, the other ends of the second and third conductor portions 3a and 3b are inserted into a connecting member such as a resin, and the rear It is fixed to one end of the header 41 with an adhesive or the like. Thus, the other end sides of the second and third conductor portions 3a and 3b are fixed to the rear header 41 without being electrically connected to the body portion by the insulator.

Next, a fourth embodiment of the vehicle antenna of the present invention will be described.
FIG. 10 is a plan view illustrating the vehicle antenna 1D according to the fourth embodiment. As shown in FIG. 10, the vehicle antenna 1D is disposed on a resin roof 21 on the rear side of the vehicle 20, the monopole portion 2 is disposed in a direction perpendicular to the surface of the resin roof 21, and a radial loading coil is provided. The first to third conductor portions 3a, 3b, and 3c into which 45 is inserted are disposed radially on the back surface side of the resin roof 21 at equal angles, that is, at an angular interval of 120 degrees.
The vehicle antenna 1D of the fourth embodiment is different from the vehicle antenna 1C of the third embodiment in that a radial loading coil 45 is inserted into the first to third conductor portions 3a, 3b, and 3c. Since other configurations are the same as those of the third embodiment, the description thereof is omitted.

The first to third conductor portions 3a, 3b, and 3c into which the radial loading coil 45 is inserted will be described.
As shown in FIG. 10, all of the first to third conductor portions 3a, 3b, 3c into which the radial loading coil 45 is inserted can have the same configuration. The first to third conductor portions 3a, 3b, and 3c, into which the radial loading coil 45 is inserted, have the loading coil 45 disposed at the intermediate portion or the tip portion of the conductor pattern made of copper formed on the printed circuit board or the FPC. It is formed by.

  The radial loading coil 45 is, for example, a coil obtained by winding an enamel wire at a predetermined number of times, and when connected to a conductor pattern made of copper formed on a printed circuit board or FPC, the radial loading coil 45 is ¼ of the reception frequency of FM broadcasting. It is fabricated so as to have a predetermined inductance with a wavelength. The first to third conductor portions 3a, 3b, 3c, into which the radial loading coil 45 is inserted, can be manufactured by soldering to a conductor pattern formed on a printed circuit board or FPC. The radial loading coil 45 is soldered to a conductor pattern, and then the inductance is adjusted by changing the pitch of the winding, or a variable capacitor is further provided in parallel or in series with the radial loading coil 45 to adjust the inductance. May be. As a result, it is possible to select, that is, tune, the reception frequency of FM broadcasting.

  The arrangement and dimensions of the first to third conductor portions 3a, 3b, and 3c are the same as those in the third embodiment. Furthermore, one end of the first to third conductor portions 3a, 3b, and 3c is connected to the antenna mounting portion via the washer 26, similarly to the one end of the first to third conductor portions 3a, 3b, and 3c of the third embodiment. The base 24b and the washer 26 are fixed to be electrically connected to a body portion serving as a ground.

  The other end sides of the first to third conductor portions 3a, 3b, and 3c are not electrically connected to the body portion but are floated with respect to the body portion. The other ends of the first to third conductor portions 3a, 3b, and 3c are inserted into a connecting member such as a resin similarly to the other ends of the first to fourth conductor portions 3a, 3b, and 3c of the third embodiment. Then, it is fixed to one end of the rear header 41 with an adhesive or the like. Thus, the other end sides of the first to third conductor portions 3a, 3b, and 3c are fixed to the rear header 41 without being electrically connected to the body portion by the insulator.

  According to the vehicle antenna 1D of the fourth embodiment, since the radial loading coil 45 is inserted, there is an advantage that the vehicle antenna 1D is reduced in size.

  The present invention is not limited to the above embodiment, and various modifications are possible within the scope of the invention described in the claims, and it goes without saying that these are also included in the scope of the present invention. Nor.

X Vehicle longitudinal direction Y Vehicle width direction 1, 1A, 1B, 1C, 1D: Vehicle antenna 2: Monopole portion 3: Conductor portions 3a, 3b, 3c: First to third conductor portions 3d, 3g: First Roof reinforcement 3e, 3h: second roof reinforcement 3f, 3i: third roof reinforcement 20: vehicle 21: resin roof 24: antenna mounting portion 24a: monopole connecting portion 25b: base portion 24c: insulating portion 26 : Washer 27: Nut 28: Seal part 31: Coaxial cable 31a: Inner conductor 31b: Outer conductor 41: Rear header 45: Radial loading coil

Claims (4)

A monopole portion disposed on the front side of the resin roof of the vehicle and having an electrical length of ¼ wavelength;
A conductor portion having an electrical length of ¼ wavelength disposed in at least three directions from one end of the monopole portion on the back side of the resin roof;
An antenna mounting portion comprising a monopole connection portion to which one end of the monopole portion is connected on the front side of the resin roof and a base portion to which one end of the conductor portion is connected on the back side of the resin roof;
With
The base is grounded to the body of the vehicle;
A vehicular antenna that is electrically open to the body part over the entire length excluding one end of the conductor part.   The vehicle antenna according to claim 1 or 2, wherein the conductor portions are radially arranged in three directions at equal intervals of 120 degrees on the back side of the resin roof.   The vehicle antenna according to claim 1 or 2, wherein a loading coil is inserted into the monopole part and / or the conductor part in order to shorten the monopole part and / or the conductor part.   A receiver mounted on the vehicle and a monopole connecting portion are connected by a coaxial cable, and an inner conductor of the coaxial cable is connected to the monopole connecting portion and an outer conductor is connected to the base portion, respectively. The vehicle antenna according to any one of the above.