JP2007228601A - Hot-wire pattern structure of defogger formed on vehicle-use rear glass and vehicle-use rear glass - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hot-wire structure for reducing the effect of defogger hot-wires on a TV-use antenna, especially a digital TV-use antenna, installed on rear glass. <P>SOLUTION: In one hot wire 43 which is the closest to a dipole antenna 40, a part opposing the dipole antenna 40 is linear, and both sides of the linear part 44 are in meandering forms 46 and 48 by being bent into rectangular shapes at equal intervals. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a structure of a defogger provided on a rear glass of a vehicle and a vehicle rear glass, and more particularly to a structure of a heat ray pattern of a defogger of a rear glass provided with a glass antenna and a vehicle rear glass.

  TV antennas installed on the rear glass of vehicles, especially glass antennas for terrestrial digital TV broadcasting (frequency 470 to 710 MHz), directivity is controlled so as to be directed to the desired wave direction, and there is no need to come from directions other than the desired wave direction. The performance of suppressing the interference of waves and improving the picture quality of the television is required. Especially when traveling at high speed, the reception performance is degraded by Doppler shift, so it is considered that the sensitivity difference (FB ratio; front-back ratio) between the desired wave and the unwanted wave is required to be 10 dB or more.

For this purpose, it is known that it is effective to use a directional antenna having a reflector and a director, as disclosed in, for example, Japanese Patent Application Laid-Open No. 2002-135025. Further, as disclosed in Japanese Patent Laid-Open No. 2003-283405, it is known that directivity in a desired wave direction is obtained by operating a roof portion (metal) of a vehicle body as a reflector (reflector).
JP 2002-135025 A JP 2003-283405 A

  When the conventional antenna is provided on the rear glass, the following problems occur. That is, it is difficult to control the directivity in the desired wave direction due to the influence of heat rays. That is, there is a situation where it is difficult to ensure the FB ratio. This is because the directivity of the rear glass antenna changes in a direction perpendicular to the rear glass surface due to the influence of heat rays, as indicated by a dotted line 2 in FIG. In addition, 4 in the figure has shown the directivity of the antenna when there is no heat ray.

  In addition, due to the influence of the heat rays, it is difficult to control directivity in the desired wave direction even if a reflector and a director, which are parasitic elements, are used.

  An object of the present invention is to provide a structure of a heat ray pattern that reduces the influence of heat rays of a defogger on an antenna installed on a rear glass, especially a TV antenna, particularly a digital TV antenna.

  Another object of the present invention is to provide a rear glass including an antenna and a defogger having the heat ray pattern structure.

  The heat ray pattern structure of the present invention is a defogger heat ray pattern structure formed opposite to an antenna formed on a rear glass of a vehicle. At least one heat ray of the defogger adjacent to the antenna has a meander shape. is doing.

According to the first aspect, the portion having the meander shape faces the antenna. Thus, by making the portion facing the antenna into a meander shape, the distance of the heat ray of the meander portion to the antenna is substantially increased, and the synergistic effect is that the impedance of the meander shape portion becomes high in frequency. This reduces the influence of the meander-shaped part on the antenna.
According to the second aspect, the portion of the at least one heat ray facing the antenna has a linear shape, and both sides or one side of the linear portion have a meander shape. As described above, since the meander portion has a high frequency impedance, the linear portion facing the antenna functions as a director, so that the directivity characteristics of the antenna can be improved.

  The vehicle rear glass according to the present invention is an antenna formed on the rear glass and a defogger formed on the rear glass so as to face the antenna, and at least one heat ray adjacent to the antenna has a meander shape. And a defogger having a heat ray pattern structure.

  According to the present invention, since the heat ray close to the antenna on the rear glass has a shape that reduces the influence of the heat ray on the antenna, the directivity in the desired wave direction can be controlled.

  Hereinafter, the present invention will be described in detail based on examples. In the following description, λ represents the wavelength of the received wave of the digital TV antenna, and k represents the wavelength shortening rate (0.6 to 0.7 in glass).

  FIG. 2 is a diagram showing an embodiment of the heat ray pattern structure of the defogger of the present invention provided on the rear glass. The hot wire pattern of the defogger is symmetrical, and only the left end portion is shown to simplify the drawing.

  A monopole antenna 16 for digital TV is provided between the defogger 12 on the rear glass 10 of the vehicle and the roof 14 of the vehicle body (body), close to the pillar 17. In this specification, the monopole antenna has a single linear shape, a single strip shape (wider than the linear shape), and a single strip shape in a loop shape. Including FIG. 2 shows a loop-shaped monopole antenna.

  When the wavelength of the received wave (600 MHz) is λ and the wavelength short-circuit rate is k, the monopole antenna 16 has a length A of (¼) λk and a width B of about 10 mm. Reference numeral 18 denotes a feeding point (feeding position) of the monopole antenna. In this case, the power feeding position 18 is on the pillar side, but the same effect can be obtained even on the roof side. Therefore, the feeding point (feeding position) may be on the pillar side or on the roof side.

  The defogger 12 and the monopole antenna 16 are made of a silver printed wire formed by printing and baking a silver paste on the rear glass.

  The defogger 12 is configured by arranging hot wires between the bus bars 20 on both sides. The uppermost portion of the hot wire 12-1 adjacent to the monopole antenna 16 is bent into a rectangular shape at equal intervals to have a meander shape. A distance L between the meander-shaped heat ray portion 22 and the monopole antenna 16 is (1/4) λk.

  One transverse heat wire 13 extends below the meander-shaped heat wire portion 22, and this heat wire is connected to the vertical heat wire 15. Four hot wires 12-2, 12-3, 12-4, and 12-5 extending in the horizontal direction are commonly connected to the vertical heat wire 15. The transverse heat wire 13 is at the same transverse position as the heat wire 12-5. The hot wires 12-6 and thereafter are normal-shaped hot wires extending between both bus bars.

  Since the heat ray of the meander-shaped heat ray portion 22 meanders, the portion becomes longer than the straight heat ray, so that the resistance increases. For this reason, since total resistance becomes large compared with the normal heat wire 12-6 extended between the bus bars linearly in the horizontal direction, the current flowing through the heat wire 12-1 having meander-shaped heat wire portions at both ends is reduced. For this reason, Joule heat generated by the hot wire 12-1 is reduced, and the anti-fogging effect is reduced. In order to prevent this, the width of the hot wire of the meander-shaped hot wire portion 22 may be increased to reduce the resistance of that portion. In this case, the width of the hot wire of the meander-shaped hot wire portion 22 is adjusted so that the antifogging effect in the vicinity of the hot wire 12-1 is approximately the same as that of the normal hot wire 12-6. For example, when the line width of the hot wire 12-1 is 1 mm, the width of the hot wire of the meander hot wire portion 22 is preferably 1 to 4 mm.

  Further, since all of the currents flowing through the four heat wires 12-2, 12-3, 12-4, and 12-5 flow through the heat wires 13 and 15, it is preferable to increase the width of the wires and reduce the resistance. . This is because if the heat wires 13 and 15 have the same width as the normal heat wires, the amount of heat generated in the heat wires 13 and 15 may increase, resulting in abnormal heat generation. Therefore, for example, when the width of a normal hot wire is 1 mm, the width of the hot wires 13 and 15 needs to be 3 to 4 mm.

  The transverse dimension of the meander-shaped heat ray portion 22 is W, the longitudinal dimension is H, and the equally spaced width of the longitudinal heat ray is D. As a result of the experiment, the transverse dimension W of the meander-shaped portion 22 is (1/4) λk to (1/2) λk, the longitudinal dimension H is (1/8) λk to (1/4) λk, and the longitudinal heat ray. It was found that the equal interval D of (1/40) λk to (3/40) λk is suitable.

  The experiment was performed as follows. First, a normal type hot wire 30 shown in FIG. 3 was formed on the rear glass of the vehicle as a reference heat ray, and the monopole antenna 16 was formed at a position (1/4) λk from the uppermost heat ray. The monopole antenna 16 has a length of (1/4) λk and a width of 10 mm.

  In the anechoic chamber, the vehicle is irradiated with a radio wave with a frequency of 600 MHz from one direction while rotating the vehicle 360 ° horizontally, and the reception sensitivity of the monopole antenna 16 in each direction of the vehicle is measured. A characteristic value (directional characteristic) is obtained.

Based on the measurement results, desired direction sensitivity (average sensitivity in a region with an angular width of 180 degrees centered on the rear of the vehicle on the horizontal plane of the vehicle when glass is mounted on the rear window of the vehicle) The sensitivity in the reverse direction (average sensitivity in a region with an angular width of 180 degrees centered on the front of the vehicle on the horizontal plane of the vehicle) and the FB ratio were calculated. Here, the FB ratio is a value represented by a difference in sensitivity between the desired direction sensitivity and the desired direction, and is obtained by the following formula.
FB ratio (dB) = desired direction sensitivity (dB) −sensitivity in the direction opposite to the desired direction (dB)

  Next, as shown in FIG. 4, the hot wire 30 is separated from the bus bar 20, and the separation distance W is set to (1/8) λk, (1/4) λk, (3/8) λk, (1/2) λk. , (5/8) λk, respectively, and the reception sensitivity was measured in an anechoic chamber, and the desired direction sensitivity, the reverse direction sensitivity and the FB ratio were calculated based on the measurement results. In addition, these measurement and calculation were performed by the same method as the measurement and calculation of a reference | standard heat ray. The hot wire 30 is separated from the bus bar 20, and the separation distance W is changed to (1/8) λk, (1/4) λk, (3/8) λk, (1/2) λk, (5/8) λk, respectively. Table 1 shows the results of the desired direction sensitivity and the FB ratio in the case of the above, expressed as differences with respect to the sensitivity and the FB ratio obtained with the reference heat ray.

  FIG. 5 is a graph of Table 1. It can be seen that the sensitivity and the FB ratio are improved as the distance W is increased. However, if the distance W is excessively widened, an antifogging effect as a defogger cannot be obtained in a portion where there is no heat ray. Therefore, the distance W is preferably selected from (1/4) λk to (1/2) λk in view of anti-fogging.

  Returning to FIG. 2, in order to obtain the optimum meander shape, the horizontal dimension W is fixed to (3/8) λk, the vertical dimension H and the width D are changed, and the radio wave of frequency 600 MHz is irradiated in the anechoic chamber. The reception sensitivity of the monopole antenna 16 was measured, and the desired direction sensitivity and the FB ratio were calculated based on the measurement results. These measurements and calculations were performed in the same manner as the measurement and calculation of the reference hot wire. The longitudinal dimension H is changed to (3/40) λk, (6/40) λk, (9/40) λk, (12/40) λk, and the width D is (1/40) λk, It was changed to (3/40) λk and (5/40) λk. Table 2 shows the result of the measured desired direction sensitivity as a difference with respect to the sensitivity obtained with the reference hot wire.

  FIG. 6 is a graph of Table 2. In the case of D = (5/40) λk, no improvement in sensitivity is observed. Therefore, it is understood that the width D is preferably (1/40) λk to (3/40) λk, and the longitudinal dimension H is preferably (1/8) λk to (1/4) λk.

  Table 3 shows a result of the obtained FB ratio expressed as a difference with respect to the FB ratio obtained with the reference heat ray.

  FIG. 7 is a graph of Table 3. In the case of D = (5/40) λk, the FB ratio is not improved. Therefore, it is understood that the width D is preferably (1/40) λk to (3/40) λk, and the longitudinal dimension H is preferably (1/8) λk to (1/4) λk.

  From the above results, the transverse dimension W of the meander-shaped hot wire portion 22 in FIG. 2 is (1/4) λk to (1/2) λk, and the longitudinal dimension H is (1/8) λk to (1/4). ) Λk and the width D is preferably (1/40) λk to (3/40) λk.

  FIG. 8 is an example of a meander shape obtained by inverting the meander shape of FIG. In the shape of FIG. 2, the hot wire 12-1 of the meander-shaped portion is connected to the uppermost end of the bus bar 20, but in the case of FIG. 8, the hot wire 12-1 of the meander-shaped portion is a distance from the uppermost end of the bus bar 20. Connected to a position lowered by H. The effect is the same as that of the meander shape in FIG.

  FIG. 9 shows another modification of the meander-shaped part. This modification is a case where the longitudinal dimension H is (3/16) λk in the meander shape of FIG. The same effect as the meander shape of FIG. 2 was obtained.

  FIG. 10 shows a meander-shaped hot wire portion composed of two meander-shaped heat wires 32 and 34, unlike the meander-shaped hot wire portion of FIG. It is preferable that the longitudinal dimension H, the lateral dimension W, and the width D of the meander-shaped hot wire portion are in the same ranges as in the example of FIG. In this case, the meander-shaped heat wires 32 and 34 meandering are approximately 2 W in length, and the two meander-shaped heat wires are connected in parallel. Therefore, the combined resistance is a straight line having a lateral dimension of approximately W. Equivalent to the resistance of the conductor. Therefore, the width of the meander-shaped heat wires 32 and 34 may be the same as the width of a normal heat wire.

In each of the above embodiments, the antenna is a monoball antenna, but in this embodiment, a dipole antenna is used.
FIG. 11 shows a heat ray pattern structure of this example. The structure which made the part which opposes the dipole antenna 40 among the one heat ray 43 nearest to the diball antenna 40 the meander shape part is shown. Of one heat ray close to the dipole antenna 40, the portion facing the dipole antenna 40 is a meander-shaped portion.

  The dipole antenna 40 has a total length of 18 cm and is provided with a feeding point 42 in the center. The meander-shaped portion has a lateral dimension W of 24 cm, a longitudinal dimension H of 4.2 cm, and an equal interval D of 1.2 cm.

  In a anechoic chamber, while rotating the vehicle 360 ° horizontally, the vehicle is irradiated with radio waves with a frequency of 500 MHz from one direction, the reception sensitivity of the dipole antenna 40 in each direction of the vehicle is measured, and the characteristics of the reception sensitivity of the entire circumference A value (directional characteristic) was obtained. FIG. 12 shows the directivity characteristics. It can be seen that the directivity gain in the rear direction of the vehicle is improved.

  This embodiment uses the characteristic that the heat ray in the meander-shaped part exhibits high impedance to the high frequency, so that the part facing the antenna of one heat ray closest to the antenna functions as a waveguide as a linear part. It is a thing.

  FIG. 13 shows the heat ray pattern structure of the present embodiment. The antenna is a dipole antenna as in the fifth embodiment. The dipole antenna 40 has a total length of 18 cm and is provided with a connection point 42 in the center. The one heat wire 43 closest to the dipole antenna 40 has a straight portion facing the dipole antenna 40, and meander-shaped portions 46 and 48 on both sides of the straight portion 44. The transverse dimension W1 of the meander portion 46 is 4.8 cm, the transverse dimension W2 of the meander portion 48 is 18 cm, and the length W3 of the linear portion 44 is 12 cm. The height H of the meander portion is 4.2 cm, and the equidistant width D is 1.2 cm.

The directivity characteristics of the heat ray pattern structure of this example were obtained in the same manner as in Example 5. FIG. 14 shows the directivity characteristics. It can be seen that the directivity gain in the rear direction of the vehicle is improved.
In the example of FIG. 13, the meander-shaped portion 46 can be omitted when the antenna 40 is provided so as to be close to the pillar 17.

  In each of the above examples, the meander shape is a rectangular bent shape, but is not limited thereto. You may round the corner | angular part of a bend, ie, you may give R (R). An example of the meander-shaped heat ray portion is shown in FIG. The meander-shaped bent corner shown in FIG. 2 is rounded. A meander shape meandering in a sine wave shape is also possible.

  In the above embodiments, the case where the antenna is a digital TV antenna has been described. However, the present invention is not limited to this, and can be applied to general TV antennas including analog TV antennas, and other FM antennas. It is clear that this can also be applied.

FIG. 1 is a diagram showing how the directivity of a rear glass antenna changes in a direction perpendicular to the surface of the rear glass due to the influence of heat rays. FIG. 2 is a diagram showing Example 1 of the heat ray pattern structure of the defogger of the present invention provided on the rear glass. FIG. 3 is a diagram showing a normal type heat ray. FIG. 4 is a diagram illustrating a state in which the heat ray is separated from the bus bar in FIG. 3. FIG. 5 is a graph of Table 1. FIG. 6 is a graph of Table 2. FIG. 7 is a graph of Table 3. FIG. 8 is a diagram showing a second embodiment which is a modification of the meander shape of FIG. FIG. 9 is a diagram showing a third embodiment which is another modification of the meander shape of FIG. FIG. 10 is a diagram showing Example 4 having a meander-shaped heat ray portion composed of two meander-shaped heat rays. FIG. 11 is a diagram illustrating a fifth embodiment in which the antenna is a bipolar antenna. FIG. 12 is a diagram illustrating antenna directivity characteristics according to the fifth embodiment. FIG. 13 is a diagram illustrating Example 6 in which a part of heat rays is a waveguide. FIG. 14 is a diagram illustrating the directivity characteristics of the antenna according to the sixth embodiment. FIG. 15 is a diagram showing a meander-shaped hot wire portion with rounded corners.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Rear glass 12 Defogger 14 Roof 17 Pillar 40 Bipole antenna 42 Feeding point 20 Bus bar 44 Linear hot wire part 46, 48 Meander-shaped hot wire part

Claims (5)

A heat ray pattern structure of a defogger formed to face an antenna formed on a rear glass of a vehicle,
At least one hot wire of the defogger adjacent to the antenna has a meander shape;
The at least one heat ray has a heat ray pattern structure in which a portion facing the antenna has a linear shape, and both sides or one side portions of the linear shape portion have a meander shape.   2. The heat ray pattern structure according to claim 1, wherein the heat rays in the meander-shaped portion are bent at equal intervals in a rectangular shape in a vertical direction and a horizontal direction.   The heat ray pattern structure of Claim 2 with which the corner | angular part of the bending of the heat ray of the said meander shape part is rounded. A rear glass for a vehicle,
An antenna formed on the rear glass;
A defogger having a heat ray pattern structure according to claim 1, 2 or 3, formed on the rear glass so as to face the antenna.
A vehicle rear glass comprising:   The vehicle rear glass according to claim 4, wherein the antenna is a monopole antenna or a dipole antenna.

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