JP2006279302A - On-vehicle antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology of suppressing production of a wind noise at an antenna rod without impairing the outer appearance of the antenna rod. <P>SOLUTION: A rod support section 3 freely revolvably supports the antenna rod 2, the antenna rod 2 is placed by an elastic member at an initial position in a way of being erected or tilted backward with respect to an axis 5 in a forward backward direction of a vehicle, when a wind pressure directed from the front of the vehicle toward the backward is exerted to the antenna rod 2, the elastic member is elastically deformed to tilt the antenna rod 2 backward from the initial position. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a vehicle-mounted antenna.

  Conventionally, an in-vehicle antenna attached to a roof of a vehicle body has an antenna rod, and this antenna rod is generally attached in a standing state with respect to the vehicle body. In a vehicle-mounted antenna having such a structure, wind noise is generated at the antenna rod portion when traveling at high speed, which may cause discomfort to the passenger.

In order to deal with such a problem, Patent Document 1 discloses a structure in which a spiral conductor is spirally wound in a region from a front end portion to a base end portion of an antenna rod (antenna element in Patent Document 1). According to this structure, it is said that the wind noise generated by the antenna rod generated during traveling can be suppressed by disturbing the air with the spiral conductor and diffusing the low pressure region that is about to occur in the lee of the antenna rod. ing.
JP-A-7-193418

  However, the structure disclosed in Patent Document 1 has a problem that the appearance of the antenna rod is impaired because the spiral conductor is spirally wound around the region from the front end portion to the base end portion of the antenna rod.

  The objective of this invention is suppressing generation | occurrence | production of the wind noise in an antenna rod, without impairing the external appearance of an antenna rod.

  The present invention provides a rod support portion that rotatably supports an antenna rod so as to undulate with respect to a vehicle longitudinal axis, and is provided on the rod support portion. An elastic member positioned at an initial position that is inclined backward, and when the wind pressure acting from the front of the vehicle to the rear acts on the antenna rod, the elastic member is elastically deformed to cause the antenna rod to move according to the wind pressure. The main feature is to tilt backward from the initial position.

  According to the present invention, when a wind pressure from the vehicle front to the rear acts on the antenna rod, the elastic member is elastically deformed to tilt the antenna rod backward from the initial position according to the wind pressure. The area (projected area) of the antenna rod facing the air flow direction is reduced in accordance with the wind pressure. This reduces the pressure drag on the antenna rod, thereby suppressing the generation of wind noise on the antenna rod. The Therefore, since it is not necessary to provide a member such as a spiral conducting wire on the antenna rod in order to suppress the generation of wind noise in the antenna rod, the appearance of the vehicle-mounted antenna is not impaired.

  An embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a side view showing an in-vehicle antenna 1 of the present embodiment. As shown in FIG. 1, the vehicle-mounted antenna 1 includes a columnar antenna rod 2 and a rod support portion 3, and is attached to the vehicle body 4. Here, examples of the vehicle body 4 to which the vehicle-mounted antenna 1 is attached include a roof panel and a fender panel.

  In the vehicle-mounted antenna 1, the antenna rod 2 is rotatably supported by the rod support portion 3 so as to rise and fall with respect to the vehicle longitudinal axis 5 with the standing direction as the vehicle upper direction, and the antenna rod 2 is supported by the torsion spring 15 (FIG. 4)). That is, the antenna rod 2 is provided with a variable mounting angle.

Here, the initial position is a position where the antenna rod 2 is erected in an upright or rearward tilted state with respect to the vehicle longitudinal axis 5 and is a position where reception performance is high. In the present embodiment, the position where the antenna rod 2 stands in a rearward tilted state with respect to the vehicle longitudinal axis 5 is applied as the initial position. Note that the rising angle of the antenna rod 2 with respect to the vehicle longitudinal axis 5 (the angle from the vehicle longitudinal axis 5 to the antenna rod 2 counterclockwise in FIG. 1) θ is called the rod angle θ, and the rod at the initial position. Assume that the angle θ is θ ₀ .

  2 is a longitudinal side view showing the vehicle-mounted antenna 1, FIG. 3 is a plan view thereof, FIG. 4 is a longitudinal rear view thereof, and FIG. 5 is a perspective view showing a torsion spring 15. 4 is a cross-sectional view taken along line AA in FIG.

  A hollow cylindrical portion 2 b having an axial direction in the vehicle width direction is formed at the base end portion 2 a of the antenna rod 2.

  The rod support 3 includes an antenna base 11 and a rubber protector member 12 attached to the lower portion of the antenna base 11. The protector member 12 covers the lower portion of the side edge portion of the rod support portion 3, and the lower surface of the protector member 12 abuts on the upper surface 4 a of the vehicle body 4. As a result, direct contact between the antenna base 11 and the vehicle body 4 is avoided. Then, the antenna base 11 is attached to the upper surface 4a of the vehicle body 4 via a protector member 12 with bolts and nuts (not shown).

  The antenna base 11 has a pair of side wall portions 11a facing each other in the vehicle width direction, and the space between the side wall portions 11a is opened forward, rearward and upward. Between these side wall portions 11a, a support shaft 13 having an axial direction in the vehicle width direction is installed. A cap member 14 is interposed between the support shaft 13 and the side wall portion 11a. The support shaft 13 is connected to the antenna rod 2 while penetrating the cylindrical portion 2 b of the antenna rod 2, and supports the antenna rod 2 so as to be rotatable around the support shaft 13.

  A torsion spring 15 is fitted on both sides of the antenna rod 2 on the support shaft 13. One end portion 15 a of these torsion springs 15 is supported by a support portion 11 b formed on the antenna base 11, while the other end portion 15 b of the torsion spring 15 is supported on a lower portion of the antenna rod 2. It is supported by. In this way, the torsion spring 15 is connected to the antenna base 11 and the antenna rod 2. The torsion spring 15 positions the antenna rod 2 at the initial position when the spring displacement amount (torsion amount) is zero.

  Moreover, the vehicle-mounted antenna 1 is provided with the lock mechanism 16 which locks the antenna rod 2 in the position along the vehicle body 4, as shown in FIG. In the present embodiment, the antenna rod 2 is positioned along the vehicle body 4. The first position of the antenna rod 2 along the vehicle body 4 with the tip 2 c of the antenna rod 2 facing the front of the vehicle, and the tip of the antenna rod 2. The antenna rod 2 is set at two positions, the second position along the vehicle body 4 with the portion 2c facing the rear of the vehicle. In the first position, the rod angle θ = 180 °, and in the second position, the rod angle θ = 0 °. Further, with this structure, the range in which the antenna rod 2 is rotated by the wind pressure is restricted to 0 ° <θ <180 °. Note that the antenna rod 2 located at the first position and the antenna rod 2 located at the second position are represented by phantom lines in FIG. 2 and denoted by 2 ′ and 2 ″, respectively.

  The lock mechanism 16 includes a ball plunger 17 provided at the bottom of the antenna base 11 and first and second convex portions 18 a and 18 b formed on the outer peripheral surface of the cylindrical portion 2 b of the antenna rod 2. . The ball plunger 17 is slidably disposed on the outer peripheral surface of the cylindrical portion 2 b of the antenna rod 2. The first and second convex portions 18a and 18b are provided in series in the circumferential direction of the cylindrical portion 2b.

  In the lock mechanism 16, the antenna rod 2 is rotated forward by a predetermined force and the ball plunger 17 gets over the convex portion 18a, whereby the ball plunger 17 and the convex portion 18a are engaged, and the antenna The rod 2 'is locked in the first position. Similarly, when the antenna rod 2 is rotated rearward with a predetermined force or more and the ball plunger 17 gets over the convex portion 18b, the ball plunger 17 and the convex portion 18b are engaged, and the antenna rod 2 ' Is locked in the second position. These locks are released by rotating the antenna rod 2 backward or forward with a predetermined force or more to release the engagement between the ball plunger 17 and the convex portion 18a or 18b.

  In such a configuration, the displacement of the antenna rod 2 when the vehicle travels will be described with reference to FIG. Here, FIG. 6 is an explanatory diagram for explaining the displacement of the antenna rod 2 during traveling of the vehicle.

When the vehicle moves forward, air (wind) flows relative to the vehicle-mounted antenna 1 in the direction b opposite to the vehicle traveling direction a, and wind pressure from the vehicle front to the rear acts on the antenna rod 2. This wind pressure acts on the torsion spring 15 as a rotational force in a direction in which the antenna rod 2 is tilted backward. Here, in this embodiment, when the wind speed V with respect to the vehicle-mounted antenna 1 is Vs or less, the spring constant k of the torsion spring 15 is set so that the antenna rod 2 is positioned at the initial position. That is, the wind speed V _S is a threshold value of the wind speed at which the antenna rod 2 rotates.

  When the speed of the vehicle increases and the wind speed V becomes higher than Vs, the torsion spring 15 is elastically deformed by the wind pressure, and the antenna rod 2 tilts backward from the initial position according to the wind pressure. Then, the antenna rod 2 is positioned at a position where the wind pressure and the restoring force of the torsion spring 15 are balanced.

  Here, in general, the force (drag) acting on an object moving in a fluid such as air includes a pressure drag due to a pressure difference between the front and back of the object and a friction drag due to friction between the object surface and the fluid. When the value is large, the wind noise tends to increase. As described above, in the present embodiment, the torsion spring 15 is elastically deformed by the wind pressure, and the antenna rod 2 is tilted backward from the initial position according to the wind pressure. Therefore, the area of the antenna rod 2 facing the air flow direction ( (Projected area) is reduced in accordance with the wind pressure, and the pressure drag on the antenna rod 2 is thereby reduced, so that the generation of wind noise at the antenna rod 2 is suppressed. At this time, as the vehicle speed increases and the wind speed V increases and the wind pressure on the antenna rod 2 increases, the antenna rod 2 tilts backward and the projected area of the antenna rod 2 facing the air flow direction becomes smaller. Therefore, even if the wind pressure with respect to the antenna rod 2 increases, the generation of wind noise is suppressed accordingly.

  When the vehicle speed decreases and the wind speed decreases, the wind pressure applied to the antenna rod 2 decreases, so that the antenna rod 2 rotates toward the initial position by the restoring force of the torsion spring 15, and the wind speed V ≦ Vs is satisfied. If this happens, the torsion spring 15 returns to its original shape, and the antenna rod 2 returns to the initial position.

  Here, a specific method for setting the spring constant of the torsion spring 15 for realizing the displacement of the antenna rod 2 according to the wind pressure as described above to an optimum value will be described. In the following description, the torsion spring 15 is simply described as a spring. Here, FIG. 7 is a graph showing the relationship between the drag coefficient and the Reynolds number.

  The spring constant k of the spring may be determined so that the relationship between the flow resistance D of the antenna rod 2 and the reverse force D ′ by the spring satisfies D> D ′. Here, D ′ can be expressed as D ′ = D ′ (k, θ) as a function of the rod angle θ.

The diameter of the antenna rod 2 is d, the length is L, the air kinematic coefficient is ν, the density is ρ, the projected area of the antenna rod 2 in the air flow direction is S, the drag coefficient is C _D , and the wind speed is the same as the above V Then, the drag D caused by the air flow is
D = (C _D · ρ · V ² · S) / 2 (1)
It is represented by However, a V> threshold _{V S.}

The drag coefficient C _D is expressed as a function of the Reynolds number R _e , and may be strictly determined by a bench test or the like, but when L / d> 100, the Reynolds is as follows: it can be determined simply by using the number _{R e} (reference: Kato Hiroshihen, "learning point of the flow dynamics", Maruzen Co., Ltd., p. 71 table 6.1).

The Reynolds number _Re is
R _e = v · d / ν (2)
It can be expressed as

When R _e <4 × 10 ⁵ , C _D ˜1.20
When R _e > 4 × 10 ⁵ , C _D ˜0.34
And R _ec ≡4 × 10 ⁵ , the Reynolds number R _e can be obtained using the equation (2), and the magnitude of R _ec can be determined, thereby obtaining C _D. D is required.

Assuming D ′ to k · L · θ ₀ (when θ = θ ₀ ), in order to satisfy D> D ′,
^{_{k <(C D · ρ ·}} V 2 · S) / (2 · L · θ 0) (3)
Finding k that becomes

Also, if the L / d> 100 following condition does not hold, the C _D as described above as a function of R _e, for example, as shown in FIG. 7, previously obtained by experiment (reference: for example, parity edit Committee edition, “Familiar Fluid Mechanics”, Maruzen Co., P. 66, Fig. 3).

Then, by obtaining the Reynolds number _{R e} by Equation (2), _{C D} is determined, D is determined by equation (1). Therefore, k in the same manner as in Equation (3) is determined using the C _D.

  As described above, in the present embodiment, it is possible to suppress the generation of wind noise in the antenna rod 2 without providing the antenna rod 2 with a member such as a spiral conductive wire that impairs the appearance of the antenna rod 2. That is, according to the present embodiment, the rod support portion 3 that rotatably supports the antenna rod 2 so as to undulate with respect to the vehicle longitudinal axis 5, and the rod support portion 3 is provided with the antenna rod 2. A torsion spring 15 positioned at an initial position inclined backward with respect to the vehicle longitudinal axis 5, and when the wind pressure from the vehicle front to the rear acts on the antenna rod 2, the torsion spring 15 is elastically deformed to By tilting the antenna rod 2 backward from the initial position according to the wind pressure, it is possible to suppress the generation of wind noise in the antenna rod 2 without impairing the appearance of the antenna rod 2.

  Further, since it is not necessary to provide a member such as a spiral conducting wire to the antenna rod 2 in order to suppress the generation of wind noise in the antenna rod 2, the antenna rod can be used in common in different vehicle types, and thus the antenna An increase in the type of rod 2 is prevented.

  Moreover, in this embodiment, the rod support part 3 has the antenna base 11 attached to the vehicle body 4, and the spindle 13 provided in the antenna base 11 with the vehicle width direction as an axial direction and connected to the antenna. The antenna rod 2 is rotatably supported around the support shaft 13, and the elastic member is a torsion spring 15 that is connected to the antenna base 11 and the antenna rod 2 and is externally fitted to the support shaft 13. Since the support shaft 13 is located inside the torsion spring 15, the component arrangement is integrated, and the in-vehicle antenna 1 can be downsized.

  In the present embodiment, the locking mechanism 16 that locks the antenna rod 2 at a position along the vehicle body 4 is provided, so that, for example, when the car is washed or the carrier is mounted on the roof, the anten rod is moved along the vehicle body 4. It can be locked, improving convenience. Furthermore, in this embodiment, since the antenna rod 2 is set along the vehicle body 4, the two positions of the first position and the second position described above are set, and only one of them is the antenna rod. Compared with the case where 2 is not set as the position along the vehicle body 4, the convenience is improved.

  The present invention is not limited to this embodiment, and various other embodiments can be adopted without departing from the gist of the present invention. For example, the initial position of the antenna rod 2 may be a position where the antenna rod 2 stands upright (θ = 90 °) with respect to the vehicle longitudinal axis 5.

It is a side view which shows the vehicle-mounted antenna of one Embodiment of this invention. It is the vertical side view. FIG. FIG. It is a perspective view which shows a torsion spring. It is explanatory drawing for demonstrating the displacement of the antenna rod at the time of vehicle travel. It is a graph which shows the relationship between a drag coefficient and Reynolds number.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vehicle-mounted antenna 2 Antenna rod 3 Rod support part 4 Car body 5 Vehicle front-back direction axis | shaft 11 Antenna base 13 Support shaft 15 Torsion spring (elastic member)
16 Locking mechanism

Claims (3)

An antenna rod,
A rod support portion that rotatably supports the antenna rod so as to undulate with respect to the vehicle longitudinal axis;
An elastic member that is provided in the rod support portion and positions the antenna rod at an initial position that is upright or backwardly inclined with respect to the vehicle longitudinal axis;
With
When a wind pressure from the front of the vehicle to the rear acts on the antenna rod, the elastic member is elastically deformed to tilt the antenna rod backward from the initial position according to the wind pressure. The rod support portion includes an antenna base attached to a vehicle body, and a support shaft provided on the antenna base with the vehicle width direction as an axial direction and coupled to the antenna, and the antenna rod is rotated around the support shaft. To freely support,
The in-vehicle antenna according to claim 1, wherein the elastic member is a torsion spring that is connected to the antenna base and the antenna rod and is externally fitted to the support shaft. The vehicle-mounted antenna according to claim 1, further comprising a lock mechanism that locks the antenna rod at a position along the vehicle body.

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