WINDOW GLASS FOR AUTOMOBILE

Abstract

 Window glass for vehicles by which a highly-sensitive DTV antenna can be obtained even if an AM antenna is installed under the DTV antenna and the sensitivity of the AM antenna can be secured is provided. The heating wire pattern of a defogger (14) is a shape having a convex heating wire pattern portion (30) being raised in a middle part toward a metal part (24) of a vehicle roof, and a non-heat generating area is provided on both sides of the convex heating wire pattern portion. DTV antennas (32a, 32b) are disposed on the upper portion of the space and near the metal part of the vehicle roof, a part of an element of the AM antenna is disposed in the non-heat generating area while keeping a distance relative to the DTV antenna, and an FM antenna is disposed along the convex heating wire pattern portion in the non-heat generating area.

Description

BACKGROUND OF THE INVENTION

Field of the Invention

[0001] The present invention relates to a window glass for vehicles, particularly to a window glass for vehicles provided with a defogger for preventing fogging and antennas.

Description of the Related Art

[0002] When antennas are mounted on a rear window provided with a defogger, the antennas are provided in a narrow space between the defogger and a metal part of a vehicle body roof. Mounted antennas include an AM antenna and an FM antenna, as disclosed in Japanese Unexamined Patent Application Publication No. 2003-500870.

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

[0003] Recently, attempts have been made to provide a DTV antenna with an AM antenna and an FM antenna to receive digital terrestrial television (DTV) broadcasting.

[0004] When a DTV antenna, an AM antenna and an FM antenna, specifically, a DTV antenna and an AM antenna are provided in a narrow space between a defogger and a vehicle body roof, the AM antenna is located near the DTV antenna. Thus the sensitivity of the DTV antenna is reduced. In particular, when a horizontal antenna element is installed under the DTV antenna, the sensitivity of the DTV antenna is reduced. This is because the directionality of the elevation angle of the DTV antenna relative to the horizontally-polarized wave is changed from the horizontal to the zenith direction due to the influence of the horizontal antenna element, which is disadvantage to reception of the terrestrial wave and results in reduction in the sensitivity.

[0005] For the reason mentioned above, if the AM antenna cannot be provided close to and under the DTV antenna, a footprint of the antenna element cannot be ensured and as a result, the sensitivity of the AM antenna cannot be ensured sufficiently.

[0006] Thus, it is the purpose of the present invention to provide a window glass for vehicles by which a highly-sensitive DTV antenna can be obtained even if the AM antenna and the FM antenna are installed under the DTV antenna and the sensitivity of the AM antenna and the FM antenna can be ensured.

Solution to the Problems

[0007] According to the present invention, the following means are employed. (1) The heating wire pattern of the defogger has a shape having a convex heating wire pattern portion, the upper middle portion of the convex heating wire pattern portion being raised in the state where a window glass is mounted on a vehicle. Both sides of the convex heating wire pattern portion recede and a non-heat generating area is ensured between the DTV antenna and the heating wire pattern portion that recedes downwardly. The AM antenna has a plurality of first elements facing the convex heating wire pattern portion and being parallel to the heating wire that forms the convex heating wire pattern portion and a second element disposed in the non-heat generating area. Thus the distance is kept between the DTV antenna and the second element of the AM antenna located under the DTV antenna, thereby reducing the influence of the AM antenna to the reception of horizontally-polarized wave by the DTV.

[0008] (2) The pattern of the second element of the AM antenna disposed under the DTV antenna has a meandering shape or a comb shape, thereby further reducing the influence of the AM antenna to the reception of horizontally-polarized wave by the DTV. In addition, although the AM antenna requires a footprint, the second element of the AM antenna can be disposed in the non-heat generating area. Thus the footprint can be ensured, thereby ensuring the sensitivity of the AM antenna.

[0009] (3) When an FM antenna is provided, an element of the FM antenna disposed under the second element of the AM antenna has a pattern that is formed along the convex heating wire pattern portion. Thus the distance between the DTV antenna and the FM antenna located under the DTV antenna can be kept, thereby reducing the influence of the FM antenna to the reception of horizontally-polarized wave by the DTV. Further, a footprint of the FM antenna can be ensured, thereby ensuring the sensitivity of the FM antenna.

[0010] (4) Power feeding terminals for the AM antenna and the FM antenna are provided on the sides of the rear window.

Effects of the Invention

[0011] According to the present invention, a window glass for vehicles by which a highly-sensitive DTV antenna can be obtained even if an AM antenna is installed under the DTV antenna, and the sensitivity of the AM antenna can be ensured is realized. Further, since power can be fed to the AM antenna from the sides of the rear window, an AM amplifier can be mounted on a vehicle, thereby enhancing a degree of freedom in designing a vehicle.

BRIEF DESCRIPTION OF DRAWINGS

[0012] 

FIG.1 is a diagram showing one embodiment of a window glass for vehicles according to the present invention;

FIG.2 is a diagram showing a comparative example of the window glass for vehicles;

FIG.3 is a diagram showing another embodiment of the window glass for vehicles according to the present invention; and

FIG.4 is a partial enlarged view of the left side portion including a convex heating wire pattern portion of a defogger.

DETAILED DESCRIPTION OF THE INVENTION

[0013] Embodiments of the present invention will be described below based on the drawings.

(Embodiment 1)

[0014] FIG.1 is a diagram showing one embodiment of a window glass for vehicles according to the present invention. The window glass for vehicles 10 of the present embodiment has a defogger 14 formed on the vehicle interior surface of a rear window 12. The defogger 14 consists of a plurality of heating wires 18 connected laterally between bus bars 16a and 16b provided on both sides of the rear window 12. The pattern of these heating wires has a convex heating wire pattern portion in which the upper middle portion rises and both sides thereof recede downwardly in the sate where the window glass for vehicles 10 is mounted on a vehicle. The convex portion (convex heating wire pattern portion) 30 includes five lateral heating wires 18 and both sides of the convex heating wire pattern portion are provided with vertical heating wires 20a and 20b to which these five lateral heating wires 18 are connected. Lower portions of the vertical heating wires 20a and 20b are connected respectively to the upper end portions of the bus bars 16a and 16b through lateral heating wires 22a and 22b.

[0015] The heating wires 20a and 22a, and 20b and 22b that connect the convex heating wire pattern portion 30 to the bus bars carry current for the five lateral heating wires. Therefore, if they have the same wire width as that of the lateral heating wire 18, the heat generating amount will be greater than that generated by other portions. To avoid this, wire width of these heating wires should be greater than that of the lateral heating wire 18.

[0016] A non-heat generating area where antennas can be provided stretches out between the defogger 14 in a shape of such convex heating wire pattern and the upper hem 24 of the glass adjacent to the metal part of the vehicle body roof. In particular, on both sides of the convex heating wire pattern portion 30, a wide non-heat generating area stretches out under the upper hem 24 of the glass. In such non-heat generating area, a DTV antenna, an AM antenna and an FM antenna formed respectively by conductive lines are disposed.

[0017] DTV antennas are provided respectively on both sides of the upper portion of the vehicle interior surface of the rear window 12, and consist respectively of U-shaped DTV antenna elements 32a and 32b that are disposed near the upper hem 24 of the window glass. These DTV antenna elements are disposed in the upper portion of the wide non-heat generating area that stretches out on both sides of the convex heating wire pattern portion 30. Power feeding terminals 34a and 34b are connected respectively to these DTV antenna elements.

[0018] FM antennas are provided respectively on both sides of the defogger along the convex heating wire pattern portion 30 thereof and consist respectively of L-shape antenna elements 26a and 26b. Power feeding terminals 28a and 28b are connected respectively to these FM antenna elements.

[0019] As described above, the DTV antennas and the FM antennas are disposed symmetrically so that they can constitute diversity.

[0020] The AM antenna is disposed above the defogger 14 and the FM antenna and under the DTV antenna. As shown in FIG.1, the AM antenna consists of a rectangular antenna element (first element) 36 that is formed by arranging a plurality of conductive lines in parallel in a lateral direction and disposed above the convex heating wire pattern portion 30 of the defogger 14, and meander-shaped antenna elements (second elements) 38a and 38b disposed respectively on both sides of the rectangular antenna element. The second elements 38a and 38b meander vertically and laterally in a rectangular pattern, and each one end of the elements is connected to the first element 36, other end of the second element 38a is connected to the power feeding terminal 40 and other end of the second element 38b is open.

[0021] As shown in FIG.1, the second elements 38a and 38b of the AM antenna are disposed respectively under the DTV antenna elements 32a and 32b in the non-heat generating area formed on both sides of the convex heating wire pattern portion. In this manner, since the second elements located respectively under the DTV antenna elements 32a and 32b meander, the influence to the sensitivity of the DTV antenna is reduced.

[0022] Further, the non-heat generating area that is sufficient to dispose the FM antenna elements and the AM antenna elements is ensured on both sides of the convex heating wire pattern portion 30 of the defogger 14. Thus the distances between the DTV antenna element 32a and the AM antenna second element 38a, and between 32b and 38b can be kept respectively, thereby further reducing the influence of the second element of the AM antenna to the sensitivity of the DTV antenna.

[0023] The meandering shape of the second element of the AM antenna is not limited to the rectangular meandering shape as shown in the diagram, and it can be a sinusoidal meandering shape. Further, the vertical meander width does not have to be constant, and may vary depending on the meandering. Moreover, the shape of the second element located under the DTV antenna element is not limited to a meandering shape, and can be, for example, a comb shape. It does not have to be a meandering shape to keep a predetermined distance between the AM antenna and the DTV antenna and, thus the influence of the AM antenna to the sensitivity of the DTV antenna can be reduced.

(Comparative example)

[0024] As shown in FIG.2, in order to confirm the effect of the non-heat generating area of the embodiment I, a window glass for vehicles provided with AM antenna elements 36, 38a and 38b having a meandering shape and DTV antenna elements 32a and 32b located above a normal type defogger 60 forming no convex heating wire pattern portion is prepared as a comparative example, and average sensitivity of each of the AM antenna and DTV antenna is measured with respect to the embodiment 1 and the comparative example.
Table 1 shows measured values of the average sensitivity of each AM antenna.

[0025] 

(Table 1)

Average	Comparative example	Embodiment 1
value (dBuV)	41.5	47.5

Table 2 shows the average sensitivity of each DTV antenna.

[0026] 

(Table 2)

	Comparative example	Embodiment 1
Average value in the band (dBd)	-9.66	-4.3
Lowest value of priority band (dBd)	-10.8	-5.8
Lowest value of non priority band (dBd)	-10.8	-8.5

Tables show that embodiment 1 is superior to the comparative example in average sensitivity in terms of both of the AM antenna and the DTV antenna.

(Embodiment 2)

[0027] FIG.3 shows another embodiment of a window glass for vehicles where the second elements of the AM antennas located under DTV antenna elements have a comb shape. The comb shaped second elements are indicated as 42a and 42b. The second elements are shaped like a comb with teeth facing upward. Other structures are the same as the embodiment shown in FIG.1. Thus the components that are the same as those in FIG.1 are assigned with the same reference numerals.

(Embodiment 3)

[0028] In the above mentioned two embodiments, when a convex heating wire pattern portion is formed at the upper portion of the defogger, both ends of the five lateral heating wires 18 in the convex heating wire pattern portion are connected respectively to the heating wires 20a and 22a, and the heating wires 20b and 22b. For example, when the wire width of the lateral heating wire 18 is 1mm, abnormal heat generation occurs if each of the heating wires of 20a, 22a, 20b and 22b is 8mm in width. Thus, the wire width is set to be 15.5mm. In this case, since the wire width is large, it lacks design aesthetics.

[0029] Another example of a convex heating wire pattern portion with improved design aesthetics is described below. FIG.4 is a partial enlarged view of the left side of the defogger including a convex heating wire pattern portion 50. The defogger is symmetric, thus only the left side portion is described.

[0030] In this example, the five lateral heating wires 18 constituting the convex heating wire pattern portion 50 are divided into three wires on the upper side and two wires on the lower side. The three lateral heating wires on the upper side are connected to the vertical heating wire 20a of large wire width, which is connected to the lateral heating wire 22a. The two lateral heating wires on the lower side are connected to the lateral heating wire 46a of large wire width. The lateral heating wires 22a and 46a of large wire width are connected respectively to the bus bar 16a.

[0031] When the wire width of the lateral heating wire 18 is 1mm, wire width of each of the heating wires 20a and 22a generating no abnormal heat is 7.7mm and wire width of the heating wire 46a generating no abnormal heat is 6.5mm. Thus, since the wire width can be reduced compared to the case where five lateral heating wires 18 are connected to one heating wire of large wire width, design aesthetics can be improved.

[0032] In the above example, five lateral heating wires are divided into three on the upper portion and two on the lower portion, and this can be two on the upper portion and three on the lower portion. Further, when the number of lateral heating wires constituting the convex heating wire pattern portion is four, they may be divided into two on the upper portion and two on the lower portion. In addition, when the number of lateral heating wires constituting the convex heating wire pattern portion is six, they may be divided into three on the upper portion and three on the lower portion.

Claims

1. A window glass for vehicles comprising a defogger, a DTV antenna and an AM antenna provided above the defogger, the defogger, the DTV antenna and the AM antenna being formed on a surface of a rear window, wherein
a heating wire pattern of the defogger has a shape having a convex heating wire pattern portion, an upper middle of the convex heating wire pattern portion being raised in a state where the window glass is mounted on a vehicle, and a non-heat generating area is provided on both sides of the convex heating wire pattern portion;
the DTV antenna is disposed in an upper portion of the non-heat generating area and near a metal part of a roof of the vehicle; and
a part of an element of the AM antenna is disposed in the non-heat generating area while keeping a distance relative to the DTV antenna.

2. The window glass for vehicles according to claim 1, wherein the AM antenna comprising:

a plurality of first elements facing to the convex heating wire pattern portion and parallel to a heating wire forming the convex heating wire pattern portion; and

a second element disposed in the non-heat generating area.

3. The window glass for vehicles according to claim 1, wherein the second element of the AM antenna disposed in the non-heat generating area has a meandering shape.

4. The window glass for vehicles according to claim 1, wherein the second element of the AM antenna disposed in the non-heat generating area has a comb shape.

5. The window glass for vehicles according to claim 1, wherein four or more lateral heating wires constituting the convex heating wire pattern portion are divided into two, which are connected respectively to a heating wire of width greater than the lateral heating wire, and the heating wires are connected to a bus bar of the defogger.

6. The window glass for vehicles according to claim 1, wherein a power feeding terminal of the AM antenna is provided on a side of the rear window.

Drawing