EP1898675A2

EP1898675A2 - Rear window glass for vehicles

Info

Publication number: EP1898675A2
Application number: EP07253570A
Authority: EP
Inventors: Yoshinobu c/o Nippon Sheet Glass Company Ltd. Tsurume
Original assignee: Nippon Sheet Glass Co Ltd
Current assignee: Nippon Sheet Glass Co Ltd
Priority date: 2006-09-11
Filing date: 2007-09-10
Publication date: 2008-03-12
Also published as: JP2008067300A

Abstract

There is provided a rear window (30) for vehicles, in which a broad defogging and deicing area is provided for a driver, and on which an antenna (16,18) having a preferable performance for a high frequency band of 170MHz or more is formed. The rear window comprises two bus bars (24,26) each provided on both sides of a glass sheet; a first heating section (21) composed of a plurality of lateral heating lines (5) arranged between bus bars, a second heating section (20) provided above the first heating section and on a central portion in a lateral direction of the glass sheet, and composed of a plurality of lateral heating lines (4) and two vertical heating lines (2a,2b) each thereof connecting ends of the lateral heating lines, respectively; and meander-shaped heating lines (32,34) arranged between the bus bars and the second heating section, respectively, for connecting the bus bars to the vertical heating lines.

Description

BACKGROUND OF HE INVENTION

1. Field of the invention

The present invention relates to a rear window for vehicles, particularly to a rear window for vehicles for providing an effective defogging and deicing in an antenna setting small area for a driver, the rear window comprising an antenna for preferably receiving a broadcast wave of 170MHz or more.

2. Description of Related Art

A rear window of a vehicle such as a compact car, a minivan, and a van is usually upright, so that the vertical dimension of a window is short. In such a window, a defogging and deicing performances are required for a substantially entire surface of the window, so that heating lines are broadly spread, resulting in the difficulty in securement of an area required for setting an antenna. Such an antenna provided on a rear window is limited to an antenna for a low frequency band (76MHz - 108MHz) such as a radio FM band, etc. , while an antenna for receiving a band of 170MHz or more is generally provided on another glass such as a built-in glass at the side portion of a vehicle.
This is due to the fact that the heating lines of a defogger serve as an antenna for receiving a low frequency band of 76 - 108MHz used for an FM radio broadcast, etc., so that an antenna provided near to the heating lines functions not as an antenna suitable for reception of a high frequency (170MHz or more) but as an antenna suitable for reception of a low frequency due to the capacitive coupling with the heating lines.
As a solution for above-described problems, Japanese Patent Publication No.2005/101809 discloses an example in which an antenna for receiving a high frequency band is provided on a rear window. FIG. 1 slows a rear window 6 disclosed in the Japanese Patent Publication. Areas 12, 14 are secured on both sides of a glass sheet 8 by removing both sides of the upper portion of a defogger 10 provided on the glass sheet 8. In these areas, there are provided monopole antennas 16 and 18 for the band of 170MHz or more. Reference numerals 17 and 19 designate feeding points of the antennas, respectively. Hereinafter, a normal heating line section of the lower portion of the defogger 10 is referred to as a first heating section 21, and a convex heating line section of the upper portion thereof as a second heating section 20.
The second heating section 20 comprises two vertical heating lines 2a and 2b on both sides, and a plurality of lateral heating lines 4 arranged therebetween. In the figure, reference numerals 24 and 26 designate a bus bar of the defogger 10, respectively.
It is also known in PCT International Publication No. WO 2006/001486 that the effect of the heating lines to the antenna may be reduced by forming each of heating lines near to the antenna in a meander shape.
On both sides of the second heating section in order to provide an antenna for preferably receiving a high frequency of 170MHz or more in the rear window 6 shown in FIG. 1, it is required to secure an antenna area spaced from a window frame of a vehicle body and a lateral heating line. Therefore, in the antenna area, there are no heating lines for defogging and deicing, then there are problems such that defogging and deicing performances are not realized in that antenna area and an effective sight through region may not be obtained. Accordingly, a conventional heating line pattern is not suitable for use in an upright window.

BRIEF SUMMARY OF THE INVENTION

An object of the present invention is to provide a rear window for vehicles, in which a broad defogging and deicing area is provided for a driver, and on which an antenna having a preferable performance for a high frequency band of 170MHz or more is provided.
A rear window for vehicles according to the present invention comprises a glass sheet; two first bus bars provided on both sides of the glass sheet; a first heating section composed of a plurality of first lateral heating lines arranged between the two first bus bars; a second heating section, provided above the first heating section and on a central portion in a lateral direction of the glass sheet, and composed of a plurality of second lateral heating lines and two vertical heating lines each there of connecting ends of the plurality of second lateral heating lines, respectively; meander-shaped heating lines, arranged between each of the first bus bars and the second heating section, respectively, for connecting the first bus bars to the vertical heating lines of the second heating section, respectively; and an antenna element provided on a surface of the glass sheet in at least one of areas on both sides of the second heating section; wherein the second heating section is arranged so as to be extended above the meander-shaped heating lines.
In accordance with the present invention, it is preferable that the rear window further comprises two second bus bars, each provided in the areas on both sides of the second heating section, for connecting each of the two vertical heating lines to a corresponding one of the two vertical heating lines, respectively, to supply an electric power to the second heating section.
It is preferable that at least one coil is inserted in the second bus bar in the area where the antenna element is provided. In this case, the inductance of the one coil is selected at high impedance for a frequency of 80MHz or more. Concretely, the inductance of the coil is in the range of 0.1 - 2.0 µ H. It is preferable that the length of the second heating section extended above the topmost portion of the meander-shaped heating lines is in the range of 30 - 100 mm. When it is larger than 30 mm, an area enough for an antenna element may be secured, the area being above the meander-shaped heating line and on the side of the second heating section. When it is smaller than 100 mm, an area where an antenna element is not provided may be suppressed in its size.
When a window is mounted to a vehicle, the distance between the uppermost heating line of the second heating section and the upper edge portion of the vehicle body may be 20 mm. Therefore, it is preferable that the vertical dimension of each of the areas on both sides of the second heating section is in the range of 50 - 120 mm.
In the rear window in accordance with the present invention, an area where there is no heating line due to the setting of an antenna element is only a small area on the upper portion of the window, so that other area is occupied by heating lines, resulting in a broad area for defogging and deicing. It is also possible that a preferable performance of an antenna may be provided by causing the shape of a heating line just below the antenna to be a meander-shape.
In accordance with a rear window of the present invention, an antenna having a preferable receiving performance in the band of 170MHz or more may be implemented. Therefore, it becomes possible that an antenna for all media may be provided to a vehicle such as a light vehicle having no built-in glass at the side portion thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view illustrating the structure of a conventional rear window.

FIG 2 is a schematic view illustrating the structure of a rear window of a first embodiment according to the present invention.
FIG 3 is a schematic view illustrating measured results of the sensitivity of an antenna.
FIG 4 is a schematic view illustrating the structure of a rear window of a second embodiment according to the present invention.
FIG 5 is a schematic view illustrating the structure of a rear window of a third embodiment according to the present invention.
FIG 6 is a schematic view illustrating the structure of a rear window of a fourth embodiment according to the present invention.
FIG 7 is a schematic view illustrating measured results of the sensitivity of an antenna.
FIG 8 is a schematic view illustrating an example in which a coil is inserted in a bus bar.
FIG 9 is a schematic view illustrating the mounting of a coil.
FIG 10 is a schematic view illustrating the structure of a conventional rear window having no second heating section.
FIG 11 is a schematic view illustrating an example of heating lines having no meander-shaped heating lines.
FIG 12 is a schematic view illustrating measured results of the sensitivity of an antenna.
FIG 13A is a schematic view illustrating an example of an antenna pattern.
FIG 13B is a schematic view illustrating an example of an antenna pattern.
FIG 14 is a schematic view illustrating an example of an antenna pattern.
FIG 15 is a schematic view illustrating an example of an antenna pattern.
FIG 16 is a schematic view illustrating an example of an antenna pattern.
FIG 17 is a schematic view illustrating an example of an antenna pattern.
FIG 18 is a schematic view illustrating an example of an antenna pattern.
FIG 19 is a schematic view illustrating an example of an antenna pattern.
FIG 20 is a schematic view illustrating an example of an antenna pattern.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will now be described with reference to preferable embodiments.

Embodiment 1

Referring to FIG 2, there is shown a rear window 30 according to a first embodiment of the present invention, in which same reference numerals are used for same components in FIG. 1.
The rear window 30 comprises a first heating section 21 composed of a plurality of lateral heating lines 5 arranged between first bus bars 24 and 26 provided on both sides of a glass sheet 8; a second heating section 20 composed of a plurality of lateral heating lines 4 and two vertical heating lines 2a and 2b to connect the ends of the plurality of lateral heating lines 4, respectively, and provided on a central portion in a lateral direction and above the first heating section 21; and meander- shaped heating lines 32 and 34, arranged between each of the first bus bars 24 and 26 and the second heating section 20, respectively, for connecting the first bas bars to the vertical heating lines 2a and 2b.
The second heating section 20 is arranged so as to be extended above the meander- shaped heating lines 32 and 34. Monopole antennas 16 and 18 are provided on the glass sheet surface in areas 12 and 14 on both sides of the second heating section 20, respectively.
The pattern of each of monopole antennas 16 and 18 is structured so as to comprise an optimized pattern for 200MHz. The length of each antenna element of the monopole antennas 16 and 18 from each of feeding points 17 and 19 to the corresponding end thereof, is 1/4 λ·κ=225 mm (the wavelength λ at 200MHz is equal to 150 mm, and κ is a velocity of propagation (a wavelength shortening factor) of the glass, for example 0.6 in the present embodiment).
The height A (the distance between the upper edge portion of a vehicle body and the uppermost portion of the meander-shaped heating line) is 50mm.
The second heating section 20 extends above the uppermost portion of the meander-shaped heating lines 32 and 34 by one interval (approximately 35mm) between adjacent lateral heating lines.
The distance between the uppermost lateral line portion of each meander-shaped heating line 32 and 34 and the lateral antenna element of each monopole antenna 16 and 18 is approximately 3 mm, but not limited thereto.
The respective widths of the lateral heating line 5 of the first heating section 21 and the lateral heating line 4 of the second heating section 20 are approximately 2 mm, and respective widths of the meander-shaped heating lines 32 and 34 are approximately 5-6 mm. The width of the meander-shaped heating line is made thick in this manner, so that the amount of a current to be supplied to the second heating section 20 becomes large, resulting in an enough heating performance of the second heating section 20.
The rear window 30, the structure thereof being described above, was provided on a vehicle in an anechoic chamber to measure the sensitivity of the antenna. The measured results are shown in FLG 3 in which the abscissa axis designates frequency (MHz) and the ordinate axis the sensitivity of the antenna. An average sensitivity of the antenna is shown in Table 1. Herein, the sensitivity is represented by a ratio to the sensitivity of a dipole antenna, which is referred to as a dipole ratio. TABLE 1

Average Sensitivity

170MHz-217MHz 471MHz-771MHz

-6.5dBd -10.2dBd
While the monopole antennas 16 and 18 are provided on the glass sheet surface in areas 12 and 14 on both sides of the second heating section 20, respectively, one monopole antenna may be provided in only one area on the glass sheet surface.

Embodiment 2

The second embodiment is an example in which a second bus bar is further provided in the first embodiment. FLG. 4 shows the structure of the second embodiment. The second bus bar is composed of a bus bar 36 connecting the first bus bar 24 to the upper end of the vertical heating line 2a of the second heating section 20, and a bus bar 38 connecting to the second bus bar 26 to the upper end of the vertical heating line 2b of the second heating section 20. These second bus bars serve to supply an electric power to the second heating section 20 for heating it like the meander-shaped heating line. It is preferable that the width of the second bus bar is thick in order to supply most of an electric power to the second heating section. In the present embodiment, respective widths of these bus bars 36 and 38 are 4 - 5 mm. Corresponding to this, even if the respective widths of the meander-shaped heating lines 32 and 34 are thinned to 1 - 2 mm, the second heating section 20 may have an enough heating performance. In this case, a rearward visibility through the rear window 30 may be preferably obtained for a driver, because the width of the meander-shaped heating line is thin such as 1 - 2 mm.
The rear window 30, the structure thereof being described above, was provided on a vehicle in an anechoic chamber to measure the sensitivity of the antenna. The measured results are shown in FLG 3 for comparison with the embodiment 1. An average sensitivity is shown in Table 2. TABLE 2

Average Sensitivity

170MHz - 217MHz 471 MHz - 771MHz

-9.1dBd -11.0dBd
It is appreciated that the sensitivity is reduced and is shifted toward a low frequency due to the effect on the antenna from the second bus bars 36 and 38 provided to cover the portion above the antenna. This is because the meander-shaped heating lines 32 and 34, and second bus bars 36 and 38 surrounding the antennas 16 and 18, respectively, make loops which capacitively couple to the antennas 16 and 18 to function as antennas for receiving a low frequency band. In the second present embodiment, the width of the meander-shaped heating line may be thin compared with that in the first embodiment, so that a preferable rearward visibility through the rear window 30 may be obtained as described above.

Embodiment 3

In the third embodiment, the second heating section 20 extends upward from the uppermost portions of the meander-shaped heating lines 32 and 34 by two intervals (approximately 70 mm), one interval being determined by adjacent lateral heating lines of the heating section 20, compared with the first embodiment. In the present embodiment, respective heights A of the areas 12 and 14 provided with the antennas 16 and 18 are 80 mm.
FIG. 5 shows a rear window according to the present embodiment Measured sensitivity (average sensitivity) of the antenna in the present embodiment is shown in Table 3. TABLE 3

Average Sensitivity

91 MHz-103MHz 170MHz- 217MHz 471NIHz- 771MHz

-6.2dBd -5.9dBd -10.1dBd
It is appreciated that the sensitivity of an antenna is improved compared with that in the first embodiment.

Embodiment 4

The fourth embodiment is an example in which a second bus bar is further provided in the third embodiment. FIG 6 shows the structure of the fourth embodiment. As in the second embodiment, respective widths of the second bus bars 36 and 38 are 4 - 5 mm, and respective widths of the meander-shaped heating lines 32 and 34 are 1 - 2 mm. Measured sensitivity of the antenna in the present embodiment is shown in FLG.7, and an average sensitivity thereof in Table 4. TABLE 4

Average Sensitivity

91MHz-103MHz 170MHz-217MHz 471MHz-771MHz

-11.8dBd -7-OdBd -10.4dBd
As illustrated in the second embodiment, it is appreciated that the sensitivity is shifted toward a low frequency by providing the second heating section 20 with the second bus bars 36 and 38. This is because the frequency received by the antenna is shifted toward a low frequency by an effect of the second bus bars and meander-shaped heating lines 32 and 34.

Embodiment 5

As illustrated in the second and fourth embodiments, the sensitivity is shifted toward a low frequency by providing the second heating section 20 with the second bus bars 36 and 38.
In the present embodiment, the structure of a rear window having no shift toward a low frequency in the fourth embodiment will now be described. FIG. 8 shows the structure of the present embodiment. In the figure, only the portion neighbored to an antenna on left side is shown for simplicity, because both sides of the rear window are identical. A coil 40 is inserted in the second bus bar 36. The position where the coil is inserted in the second bus bar may be arbitrarily selected. As an example, the position where the coil is inserted may be selected to be 1/4 λ· κ far from the connecting point 41 of the bus bar 36 to the second heating section 20. Herein, κ is a velocity of propagation of the glass. The width of the second bus bar 36 is 4 - 5 mm, and the width of the meander-shaped heating line 32 is 1 - 2 mm.
FIG 9 shows an illustration for mounting the coil 40. A portion of the second bus bar 36 is opened, and the open ends of which are provided with pads 42, respectively. The coil 40 is mounted with their ends being connected to the pads 42 by soldering etc., respectively. The coil 40 conducts an electric power to the second heating section 20, but serves to cut a high frequency component to be received by the antenna. For this purpose, the coil is required to be a high impedance for a high frequency component of 80 MHz or more. To this end, it is preferable that the impedance of the coil is selected to be 0.1 - 2.0 µH.
The sensitivity of the antenna was measured to confirm the effect of the coil 40. Measured sensitivity of the antenna is shown in FIG. 7 for comparison with the embodiment 4 and an average sensitivity thereof in Table 5. TABLE 5

Average sensitivity

91MHz-103MHz 170MHz-217MHz 471MHz-771MHz

-15.8dBd -5.4dBd -10.5dBd
It is appreciated from the measured results that the second bus bar is cut in a high frequency by inserting the coil there in, so that the performance equivalent to that where there are no second bus bars may be obtained.
In case that a coil is not inserted in the second bus bar, the second bus bar serves as an extended portion of the heating section, so that the second bus bar is a part of the antenna functioning in a low frequency band. Therefore, the antenna is effected by the second bus bar to receive a low frequency.
On the contrary, if the coil is inserted in the second bus bar, a part of the second bus bar is cut in a high frequency to deprive the function of an antenna operating in a low frequency, causing the receiving performance to be the original one.
In the embodiments described above, the monopole antennas 16 and 18 are provided on the surface the glass window in both side areas 12 and 14 of the second heating section 20, respectively, one monopole antenna may be provided in only one area on the glass sheet surface. In this case, a coil is inserted in the second bus bar 36 in an area where the monopole antenna is provided.

Comparative Example 1

In order to confirm an advantageous effect of the window according to the present invention, the sensitivity (average sensitivity) of an antenna of the window was measured, in which monopole antennas 16 are provided above the defogger having no a second heating section and meander-shaped heating lines as shown in FIG. 10. Measured results are shown in Table 6. TABLE 6

Average Sensitivity

170MHz- 217MHz 471MHz- 771MHz

-17.7dBd -17.3dBd
As apparent from the comparison with the average sensitivity in each embodiment, it is appreciated that the sensitivity is lower than that of the present invention.

Comparative Example 2

In order to confirm an advantageous effect of the meander-shaped heating lines 32 and 34, the rear window shown in FIG. 11 in which the meander-shaped heating line is replaced by a linear heating line 33 is prepared to measure the sensitivity of an antenna. In this case, the distance between the monopole antenna 16 and the heating line 33 is approximately 108 mm. Measured results are shown in FIG 12, and an average sensitivity thereof in Table 7. TABLE 7

Average Sensitivity

170MHz - 217MHz 471MHz-771MHz

-9.1dBd -10.2dBd
It is apparent from the above measured results that the antenna of the window comprising meander-shaped heating lines has a performance superior to that of the antenna of the window comprising no meander-shaped heating lines. It is also appreciated that the performance of the antenna of the window comprising meander-shaped heating lines is rather excellent because a defogging capability is also superior due to the exothermic heat by the meander-shaped lines.

Embodiment 6

In the first-fifth embodiments, a meander shape is rectangular, but is not limited thereto. FIGS. 13A and 13B show modified examples. In FIG 13A, there is shown a triangular meander-shaped heating line 44, and in FIG. 13B a sawtooth meander-shaped heating line 46. These types of meander-shaped heating lines have advantageous effects equivalent to that of the rectangular meander-shaped heating lines.

Embodiment 7

In each embodiment described above, the case where an antenna pattern is a monopole type with its feeding point being on the upper edge portion of a window has been described, but is not limited thereto. Various types of antenna patterns may be designed, for example an antenna of rectangular loop, and an antenna with its ground point formed on the surface of the window, other than an antenna of monopole type composed of one element or a plurality of elements. FIGS. 14 - 20 show various modified examples of antenna patterns.
In FIG 14, there is shown a monopole antenna 52 with its feeding point 50 provided near to the side edge portion of the window.
In FIG 15, there is shown an inverted T-shaped antenna 54 with its feeding point 50 provided near to the upper edge portion of the window.
In FIG 16, there is shown an antenna composed of a plurality of antenna elements 56 and 58 with its feeding point 50 provided near to the upper edge portion of the window.
In FIG 17, there is shown a rectangular type of antenna 60 with its feeding point 50 provided near to the upper edge portion of the window.
In FIG 18, there is shown two monopole antennas 62 and 64 extending from respective feeding points 50 and 51 with feeding points provided near to the upper edge portion of the window.
In FIG 19, there is shown a coaxial cable connected type of antenna composed of a hot element 66 extending from a feeding point 50 and a ground element 68 extending from a feeding point 51 with the feeding points 50 and 51 provided near to the upper edge portion of the window. In this case, a central wire of the cable is connected to the feeding point 50 of the hot element 66, and the outer wire to the feeding point 51 of the ground wire 68.
In FIG. 20, there is shown a loop antenna 70 structured between the feeding points 50 and 51 provided near to the upper edge portion of the window.

Claims

A rear window for vehicles, comprising:
a glass sheet;

two first bus bars each provided on both sides of the glass sheet;

a first heating section composed of a plurality of first lateral heating lines arranged between the two first bus bars;

a second heating section, provided above the first heating section and on a central portion in a lateral direction of the glass sheet, and composed of a plurality of second lateral heating lines and two vertical heating lines each thereof connecting ends of the plurality of second lateral heating lines, respectively;

meander-shaped heating lines, arranged between each of the first bus bars and the second heating section, respectively, for connecting the first bus bars to the vertical heating lines of the second heating section; and

an antenna element provided on a surface of the glass sheet in at least one of areas on both sides of the second heating section;
wherein the second heating section is arranged so as to be extended above the meander-shaped heating lines.
A rear window according to claim 1, further comprising two second bus bars, each provided in the areas on both sides of the second heating section, for connecting each of the two vertical heating lines of the second heating section to a corresponding one of the first bus bars, respectively, to supply an electric power to the second heating section.
A rear window according to claim 2, wherein at least one coil is inserted in the second bus bar in the area where the antenna element is provided.
A rear window according to claim 3, wherein the inductance of the coil is in the range of 0.1-2.0 µH.
A rear window according to any one of claims 1-4, wherein the length of the second heating section extended above the topmost portion of the meander-shaped heating lines is in the range of 30 - 100 mm.
A rear window according to any one of claims 1 - 4, wherein the width in a vertical direction of each of the areas on both sides of the second heating section is in the range of 50-120 mm.