JPH0924774A - Antenna for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure sufficient receiving sensitivity without problems such as necessity of a countermeasure for wind noise and degradation of vehicle design properties. SOLUTION: In a vehicle provided with a control device operating on-vehicle equipment based on receiving/transmitting of signal electric waves exchanged with the outside, a loop antenna 1 receiving/transmitting signal electric waves is provided for a side surface faced to the cabin side of a front pillar part B1, and a loop surface of the loop antenna is laid along a side surface of the front pillar part B1 so as to be fixed. A polarized wave of the loop antenna 1 in receiving/transmitting electric waves is normal to the loop surface, and is in the direction perpendicularly intersected with the longitudinal direction of the front pillar part B1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle antenna,
In particular, the present invention relates to a vehicle antenna that can be suitably used in a keyless entry system or the like that locks and unlocks a vehicle door based on a signal radio wave from an external transmitter.

[0002]

2. Description of the Related Art In recent years, a keyless entry system for automatically locking and unlocking a door by receiving a code signal by a weak radio wave from a transmitter has become popular in place of a conventional door lock device using a key. In recent years, various functions have been added such as not only door locking / unlocking operation but also opening / closing of a trunk room or window glass, alarm output for theft and the like.

As a receiving antenna of this type of keyless entry system, there is one that shares a radio receiving antenna, but the radio receiving antenna is adjusted around a broadcasting FM band different from the frequency used by the keyless entry system. However, there is a problem that sufficient reception sensitivity cannot be obtained because it is necessary to divide the received signal of the receiving antenna from the radio tuner.

[0004]

Therefore, it is conceivable to provide an antenna dedicated to the keyless entry system, but an antenna protruding outside the vehicle causes a problem of wind noise when the vehicle is running, and a dedicated antenna pattern is provided on the window glass. Forming it is not preferable because it impairs the design and visibility of the vehicle.

In order to avoid this, for example, as shown in FIG. 5, a monopole antenna 5 or a wire antenna 6 having a polarization parallel to the longitudinal direction of the antenna is installed along the inner surface of the pillar B1 of the vehicle. Is being tried,
There was a problem that the radio wave reception sensitivity was significantly inferior to that of an antenna protruding outside the vehicle. The present invention solves such a problem, and provides a vehicle antenna capable of obtaining sufficient reception sensitivity without causing problems such as measures against wind noise and deterioration of vehicle design. To aim.

[0006]

According to the present invention, the electric field strength of a radio wave entering a vehicle body formed of a frame or panel made of a conductive metal material is orthogonal to the longitudinal direction of the pillar portion rather than the longitudinal direction thereof. The present invention has been made based on a new finding by the inventors that the size becomes sufficiently large.
In the invention described in (1), in a vehicle provided with a control device (2) for operating an in-vehicle device based on transmission and reception of a signal radio wave with the outside, an antenna (1) for transmitting and receiving the signal radio wave
Is provided along the surface of the pillar portion (B1) of the vehicle, and the polarized wave of the antenna is set in a direction orthogonal to the longitudinal direction of the pillar portion.

According to a second aspect of the invention, in the vehicle antenna according to the first aspect, the loop antenna (1) is used as the antenna, and the loop surface of the loop antenna is aligned with the surface of the pillar portion (B1). The feature is that it is fixed to this. In addition, the code | symbol in parenthesis of each said means shows the correspondence with the concrete means of the Example described later.

[0008]

According to the invention of claim 1, since the antenna is provided along the surface of the pillar portion of the vehicle,
It does not project outside the vehicle and produce no wind noise,
There is no problem that the visibility of the occupant and the appearance of the vehicle are impaired as compared with the case where the window glass is formed. Further, since the polarized wave of this antenna is set in the direction orthogonal to the longitudinal direction of the pillar portion where the electric field strength of the external radio wave becomes sufficiently large, sufficient sensitivity is guaranteed when transmitting and receiving the signal radio wave.

According to the second aspect of the present invention, since the loop antenna has the polarization in the direction perpendicular to the loop surface, the loop antenna is provided by aligning the loop surface with the surface of the pillar portion. It is possible to easily realize an antenna in which polarized waves are set in a direction orthogonal to the longitudinal direction of the pillar portion.

[0010]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG. 1 shows the overall configuration of a keyless entry system for remotely locking and unlocking vehicle doors. A lock / unlock signal radio wave transmitted from a mobile transmitter (not shown) is received by an antenna 1 (described later) provided in the vehicle, filtered and amplified by a reception circuit 31 in a vehicle-mounted receiver 3, and then demodulated. Input to the circuit 32. The demodulated lock / unlock signal is input to the CPU 22 via the input circuit 21 of the control device 2, and the CPU 22 causes the door lock motor 4 to rotate normally and reversely via the actuator drive circuit 23 according to the result of decoding the signal.

As shown in FIG. 2, the antenna 1 is provided along the side surface of the front pillar B1 on the driver's seat D side that faces the passenger compartment. That is, the antenna 1 is a loop antenna having a rectangular loop portion 11 having the long side in the longitudinal direction of the front pillar portion B1, and the side surface of the front pillar portion B1 is attached by a mounting method such as double-sided tape that does not affect the antenna characteristics. Is fixed along.

Since the polarized wave of the loop antenna 1 is in the direction perpendicular to the loop plane, the antenna 1 has a front pillar portion B1.
It has good sensitivity in the inward and outward directions perpendicular to the side surface of the. The antenna 1 is actually covered with a pillar garnish so as not to impair the design of the vehicle interior. Now, as shown in FIG. 3, the longitudinal direction of the front pillar portion B1 is defined as an x-axis, and axes perpendicular to each other are defined as a y-axis and a z-axis, respectively. Then, a transmitting antenna was provided outside the vehicle, the vehicle was turned, and the electric field strength of the signal radio wave entering the vehicle interior was measured. The results are shown in FIG. 4, where (a), (b), and (c) are the x-axis and y, respectively.
It is the electric field intensity of polarized waves parallel to the axis and the z-axis.

As is clear from the figure, regarding the electric field strength of the signal radio wave, the polarized wave parallel to the x-axis is the smallest over the entire circumference of the vehicle, and the polarized wave parallel to each axis in the plane orthogonal to the x-axis is anyway. Also has a larger electric field strength than the polarized wave parallel to the x-axis. It is considered that the reason why the electric field strength of the polarized wave parallel to the x-axis becomes small is that the electric wave is absorbed by the metal front pillar portion B1 extending in parallel to cause a loss.

Here, as described above, the loop antenna 1 has the polarization in the direction perpendicular to the side surface of the front pillar portion B1, that is, in the direction in which the electric field strength of the signal radio wave is large and the direction orthogonal to the x axis. , Sufficiently large reception sensitivity can be obtained. As described above, according to the vehicle antenna of the present embodiment, the locking / unlocking operation of the vehicle door can be reliably performed by receiving the signal radio wave from the remote location without causing the wind noise and the deterioration of the design. It can be carried out.

In the above embodiment, the antenna is not limited to the loop antenna and, for example, an inverted F antenna can be used. In the end, the polarization of the antenna provided along the side surface of the front pillar portion is the length of the front pillar portion. Anything that is perpendicular to the hand direction will do. Further, the antenna is not limited to reception only as in the above-described embodiment, and the same effect can be obtained even if the antenna is transmitted from the vehicle side to the portable reception device or the like via the antenna.

Further, the pillar portion provided with the antenna is not limited to the front, but may be either the center or the rear.
Needless to say, the application target of the present invention is not limited to the keyless entry system.

[Brief description of drawings]

FIG. 1 is a schematic block configuration diagram of a keyless entry system according to an embodiment of the present invention.

FIG. 2 is a perspective view of the interior of a vehicle having an antenna provided on a front pillar portion according to an embodiment of the present invention.

FIG. 3 is a perspective view of a vehicle front portion according to an embodiment of the present invention.

FIG. 4 is a radar chart showing the electric field strength of a signal radio wave that has entered the vehicle according to an embodiment of the present invention.

FIG. 5 is a schematic perspective view of a vehicle front pillar portion according to a conventional example.

[Explanation of symbols]

1 ... Loop antenna, 11 ... Loop part, 2 ... Control device,
B1 ... Front pillar part.

Claims (2)

[Claims] 1. In a vehicle provided with a control device for operating an in-vehicle device based on transmission / reception of a signal radio wave to / from the outside, an antenna for transmitting / receiving the signal radio wave is provided along a surface of a pillar portion of the vehicle, and A vehicle antenna characterized in that the polarization of the antenna is set in a direction orthogonal to the longitudinal direction of the pillar portion. 2. The vehicle antenna according to claim 1, wherein a loop antenna is used as the antenna, and the loop surface of the loop antenna is fixed along the pillar surface along the surface of the pillar portion.