Vehicular discharge lamp

Abstract

 A vehicular discharge lamp includes a lamp body that has an outer tube, an arc tube, and a pair of electrodes; a first lead wire and a second lead wire that are connected to the pair of electrodes, and of which respective end portions are provided as power supply terminal portions; a plug that is formed from a resin material, and has a first terminal cover portion and a second terminal cover portion that respectively cover the power supply terminal portions of the pair of lead wires in a state of close contact therewith from the outer circumferential side; a case body to which the plug is joined; and a starting device that is arranged inside the case body, and applies a starting voltage to the power supply terminal portion when starting the lamp body. A gap is formed between the first terminal cover portion and the second terminal cover portion. A partition is provided on the case body and arranged in the gap, and separates the first terminal cover portion and the second terminal cover portion.

Description

[0001] The present invention relates to a vehicular discharge lamp. More specifically, the present invention relates to a technical field wherein a gap is formed between a pair of terminal cover portions that respectively covers a pair of power supply terminal portions, and a partition is arranged in the gap to secure insulation between the pair of power supply terminal portions.

[0002] There are various types of vehicular headlamps. For example, there is a type that uses an incandescent lamp (incandescent bulb) or a halogen lamp (halogen bulb) as a light source, a type that uses a discharge lamp (discharge bulb) as a light source, and a type that uses a light emitting diode (LED) as a light source.

[0003] A discharge lamp has more light output than an incandescent lamp, a halogen lamp, and a light emitting diode. Therefore, a vehicular headlamp that uses a discharge lamp as a light source is advantageous for its ability to achieve a higher intensity.

[0004] The discharge lamp has a double tube structure in which an arc tube, which holds a pair of electrodes and has a metal halide and a gas such as a noble gas sealed inside, is arranged inside an outer tube. The arc tube has a light emitting portion in which discharge occurs.

[0005] The pair of electrodes has end portions that project to inside the arc tube, and other end portions that are respectively connected to a pair of lead wires through a molybdenum foil. The lead wires each lead out from the outer tube to outside, and end portions of the lead wires on sides opposite the sides connected to the electrodes are each provided as power supply terminal portions to which a starting voltage is applied when starting lighting of the lamp.

[0006] In the discharge lamp, a predetermined starting voltage is applied to the pair of electrodes held in the arc tube, and lighting of the lamp is started by discharge occurring in the light emitting portion of the arc tube.

[0007] The discharge lamp described above has a starting device, also called a starter, for applying the starting voltage to an end side in the lengthwise direction of the outer tube (see Patent Document 1, for example).

[0008] In the discharge lamp, in order to apply a high voltage of 20 kV, for example, as the starting voltage to one of the power supply terminal portions from the starting device when starting lighting of the lamp, it is necessary to secure insulation between the pair of power supply terminal portions.

[0009] The discharge lamp described in Patent Document 1 attempts to provide insulation between the pair of power supply terminal portions by using a resin material to cover the power supply terminal portions.

[Patent Document 1]

[0010] Japanese Patent Application Laid-Open (Kokai) No. 2008-159509

[0011] According to the discharge lamp described in Patent Document 1, the resin material fills between the pair of power supply terminal portions. The thickness of the resin material between the pair of power supply terminal portions is thick, and parts to be formed by the resin material are prone to voids (air holes) during molding. The occurrence of a void may generate a spark and lead to an insulation breakdown.

[0012] Further, since the resin material fills between the pair of power supply terminal portions, the creeping distance between the pair of power supply terminal portions is short, and an insufficient creeping distance may make it difficult to secure an adequate insulated condition.

[0013] Hence, it is an object of a vehicular discharge lamp according to the present invention to secure insulation between a pair of power supply terminal portions.

[0014] In order to solve the above problem, a vehicular discharge lamp includes: a lamp body that has an outer tube, an arc tube arranged inside the outer tube, and a pair of electrodes arranged inside the arc tube; a first lead wire and a second lead wire that are respectively connected to the pair of electrodes, and of which end portions on sides that are opposite sides connected to the pair of electrodes are respectively provided as power supply terminal portions; a plug that is formed from a resin material, and has a first terminal cover portion and a second terminal cover portion that respectively cover the power supply terminal portions of the pair of lead wires in a state of close contact therewith from an outer circumferential side; a case body, to which the plug is joined, inside which the first terminal cover portion and the second terminal cover portion are arranged; and a starting device that is arranged inside the case body, and applies a starting voltage to the power supply terminal portion when starting the lamp body. A gap is formed between the first terminal cover portion and the second terminal cover portion in a direction orthogonal to an optical axis of light radiated from the lamp body. A partition is provided on the case body and arranged in the gap, and separates the first terminal cover portion and the second terminal cover portion.

[0015] Accordingly, in the vehicular discharge lamp, the existence of the gap reduces a thickness of the resin material between the pair of power supply terminal portions.

[0016] A vehicular discharge lamp according to the present invention is characterized by including: a lamp body that has an outer tube, an arc tube arranged inside the outer tube, and a pair of electrodes arranged inside the arc tube; a first lead wire and a second lead wire that are respectively connected to the pair of electrodes, and of which end portions on sides that are opposite sides connected to the pair of electrodes are respectively provided as power supply terminal portions; a plug that is formed from a resin material, and has a first terminal cover portion and a second terminal cover portion that respectively cover the power supply terminal portions of the pair of lead wires in a state of close contact therewith from an outer circumferential side; a case body, to which the plug is joined, inside which the first terminal cover portion and the second terminal cover portion are arranged; and a starting device that is arranged inside the case body, and applies a starting voltage to the power supply terminal portion when starting the lamp body. A gap is formed between the first terminal cover portion and the second terminal cover portion in a direction orthogonal to an optical axis of light radiated from the lamp body. A partition is provided on the case body and arranged in the gap, and separates the first terminal cover portion and the second terminal cover portion.

[0017] Accordingly, since the gap is formed between the first terminal cover portion and the second terminal cover portion, voids (air holes) are not prone to occur during molding of the plug, and an insulation breakdown of the discharge lamp caused by the occurrence of a void can be prevented.

[0018] In addition, forming the gap enables an increase in the creeping distance between the power supply terminal portion of the first lead wire and the power supply terminal portion of the second lead wire. By increasing the creeping distance, an adequate insulated condition can be secured between the power supply terminal portions.

[0019] Further, the partition is arranged in the gap. Therefore, the surrounding thickness of the resin material (insulating material) around the power supply terminal portion increases, making it possible to achieve sufficient insulation between the power supply terminal portions.

[0020] In a preferred embodiment, the power supply terminal portion of the first lead wire and the power supply terminal portion of the second lead wire are positioned separated in the optical axis direction.

[0021] Consequently, there is a long distance between the power supply terminal portions, and an insulation property between the power supply terminal portions can be improved.

[0022] In a further preferred embodiment, an outer arranging portion is provided on the plug and arranged on an outer side of the case body, and closes an end portion on the plug side of the lamp body from the outer circumferential side. A thickness of the first terminal cover portion and the second terminal cover portion is less than a thickness of the outer arranging portion, and the thickness of the first terminal cover portion and the second terminal cover portion is from 0.5 mm to 2.0 mm.

[0023] Therefore, both an insulation property can be secured between the power supply terminal portions and a holding state of each of the power supply terminal portions can be stabilized.

[0024] According to a further preferred embodiment, a support wall portion and a retainer wall portion, each generally shaped as a cylinder extending in the optical axis direction, are provided on the case body. The first terminal cover portion is inserted into the support wall portion, and the second terminal cover portion is inserted into the retainer wall portion.

[0025] Consequently, the support wall portion and the retainer wall portion enable an improved insulation property between the power supply terminal portions, and the plug can be easily and reliably joined to the case body.

[0026] Hereinafter, a preferred embodiment for carrying out a vehicular discharge lamp of the present invention will be described with reference to the accompanying drawings. The vehicular discharge lamp is provided in a vehicular headlamp.

[0027] A vehicular headlamp 1 is arranged and installed in both right and left end portions of a front end portion of a vehicle body.

[0028] The vehicular headlamp 1, as FIG. 1 shows, includes a lamp housing 2 that has a concave portion opening forward, and a cover 3 that closes the opening face of the lamp housing 2. The lamp housing 2 and the cover 3 configure a lamp outer case 4. An internal space of the lamp outer case 4 is formed as a lamp chamber 5.

[0029] A rear end portion of the lamp housing 2 is formed with an insertion hole 2a that runs front to back therethrough, and the insertion hole 2a is closed by a back cover 6. A lower end portion of the lamp housing 2 is formed with an arranging hole 2b that runs top to bottom therethrough.

[0030] In the lamp chamber 5, a reflector 7 is tiltably supported by a light axis adjustment mechanism not shown in the drawing. A rear end portion of the reflector 7 is formed with an attachment hole 7a that runs front to back therethrough.

[0031] A discharge lamp (vehicular discharge lamp) 8 is attached to the attachment hole 7a of the reflector 7.

[0032] An extension 9 blocks a portion of a structure arranged in the lamp chamber 5 and is disposed in a front end portion of the lamp chamber 5.

[0033] A discharge lamp lighting device 10 is attached to the arranging hole 2b of the lamp housing 2. The discharge lamp lighting device 10 is formed by accommodating a lighting circuit not shown in the drawing inside a circuit case 11. An input connector 12 is provided on a rear surface of the circuit case 11, and an output connector 13 is provided on an upper surface of the circuit case 11. The output connector 13 is connected to an end portion of a power supply cord 14. The input connector 12 is connected to a power supply circuit not shown in the drawing.

[0034] The discharge lamp 8 has a lamp body 15, a plug 16, and a starting circuit portion 17 (see FIGS. 1 to 3).

[0035] The lamp body 15 has an outer tube 18 and an arc tube 19 that is arranged inside the outer tube 18. The outer tube 18 and the arc tube 19 are integrally formed using silica glass, for example.

[0036] As shown in FIG. 2, the outer tube 18 is formed by a closing portion 18a that covers the arc tube 19 and the like, a front holding portion 18b that projects forward from a front end portion of the closing portion 18a, and a rear holding portion 18c that projects rearward from a rear end portion of the closing portion 18a.

[0037] The arc tube 19 is formed by a light emitting portion 20, and pinch seal portions 21, 21 that respectively continue from both front and rear ends of the light emitting portion 20. Electrodes 22, 22 are respectively held inside the pinch seal portions 21, 21.

[0038] The pinch seal portions 21, 21 respectively seal molybdenum foils 23, 23, and end portions of the molybdenum foils 23, 23 are respectively connected to the electrodes 22, 22.

[0039] The molybdenum foil 23 rearwardly positioned has a rear end portion that is connected to a first lead wire 24 that longitudinally extends. The first lead wire 24 projects rearward from the rear holding portion 18c of the outer tube 18 and the pinch seal portion 21 on the rear side of the arc tube 19. A rear end portion of the first lead wire 24 is provided as a power supply terminal portion 24a.

[0040] The molybdenum foil 23 forwardly positioned has a front end portion that is connected to a second lead wire 25. The second lead wire 25 is formed from a first part 26 that longitudinally extends and projects forward from the front holding portion 18b of the outer tube 18 and the pinch seal portion 21 on the forward side, and a second part 27 that is connected to a front end portion of the first part 26 and curved into an L shape.

[0041] An intermediate portion of the second part 27 is positioned directly below the outer tube 18, and the intermediate portion is overlaid with an insulating sleeve 28. In the second lead wire 25, a rear end portion of the second part 27 is provided as a power supply terminal portion 25a.

[0042] The power supply terminal portion 24a of the first lead wire 24 and the power supply terminal portion 25a of the second lead wire 25 are fixed separate from each other in the longitudinal direction, and the power supply terminal portion 24a is positioned more rearward than the power supply terminal portion 25a.

[0043] In the discharge lamp 8, a rear end portion of the closing portion 18a of the outer tube 18 is held by holding brackets 29, 30.

[0044] The plug 16 has a front end portion that is attached to the holding brackets 29, 30. The plug 16 is formed from a resin material such as polyphenylene sulfide resin (PPS) that has a high heat resistance, for example.

[0045] The plug 16 is integratedly formed from an outer arranging portion 31 that is positioned forward of the starting circuit portion 17, a projecting portion 32 that is generally cylindrical and projects rearward from a center portion of the outer arranging portion 31, a first terminal cover portion 33 that is cylindrical and continues from a rear end of the projecting portion 32, and a second terminal cover portion 34 that projects rearward from a lower end portion of the outer arranging portion 31.

[0046] The plug 16 has a center portion that is formed with an arranging recess portion 16a opening forward. The arranging recess portion 16a is formed on a part that spans from the outer arranging portion 31 to the projecting portion 32.

[0047] The plug is formed with a gap 16b between the first terminal cover portion 33 and the second terminal cover portion 34.

[0048] A rear end portion of the lamp body 15 is inserted and arranged in the arranging recess portion 16a of the plug 16.

[0049] In the lamp body 15, the power supply terminal portion 24a of the first lead wire 24 except for a rear end portion thereof is held in a state of close contact to the first terminal cover portion 33 from the outer circumferential side, and the rear end portion of the power supply terminal portion 24a projects rearward from the first terminal cover portion 33. Further, in the lamp body 15, the power supply terminal portion 25a of the second lead wire 25 except for a rear end portion thereof is held in a state of close contact to the second terminal cover portion 34 from the outer circumferential side, and the rear end portion of the power supply terminal portion 25a projects rearward from the second terminal cover portion 34.

[0050] The plug 16 is joined to a case body 35. The case body 35 is formed from a resin material such as polybutylene terephthalate resin (PBT) that has a high voltage resistance performance, for example. The case body 35 is formed by joining a case portion 36 and a cover portion 37 in the longitudinal direction (see FIGS. 2 and 3).

[0051] The case portion 36 is formed into a generally oblong box shape opening rearward, and has a front surface portion that is formed with a shallow positioning recess portion 36a opening forward. A first insertion hole 36b opening to the positioning recess portion 36a is formed at a generally center portion of the front surface portion of the case portion 36. A second insertion hole 36c opening to the positioning recess portion 36a is formed at a position toward a lower end of the front surface of the case portion 36. An arranging notch 36d opening upward and downward is formed on a rear end portion of a lower surface portion of the case portion 36.

[0052] A connecting wall portion 38 that longitudinally extends is provided inside the case portion 36. A front end of the connecting wall portion 38 is provided at a position that connects with an upper opening edge of the first insertion hole 36b. The connecting wall portion 38 is formed with a connecting hole 38a opening rearward.

[0053] A retainer wall portion 39 that has a cylindrical shape and longitudinally extends is provided inside the case portion 36, and a front end of the retainer wall portion 39 is connected to an opening edge of the second insertion hole 36c.

[0054] The cover portion 37 is integrally formed from a closing surface portion 40 that faces in the longitudinal direction and shaped as an oblong plate, and a support wall portion 41 that projects forward from a general center portion of the closing surface portion 40. The support wall portion 41 has a notch 41a that is generally shaped as a cylinder and opens sideward. A lower end portion of the support wall portion 41 is provided as a partition 41b.

[0055] The cover portion 37 is joined to the case portion 36 by inserting a portion of the support wall portion 41 into the connecting hole 38a of the connecting wall portion 38 from behind, and the opening on the rear side of the case portion 36 is closed by the closing surface portion 40 of the cover portion 37.

[0056] In a state where the case body 35 is configured by joining the case portion 36 and the cover portion 37, three spaces, namely, an upper space 35a, an intermediate space 35b, and a lower space 35c, are formed inside the case body 35 (see FIG. 2). The intermediate space 35b is an internal space of the support wall portion 41 of the cover portion 37, the upper space 35a is a space on the upper side of the support wall portion 41, and the lower space 35c is a space on the lower side of the support wall portion 41.

[0057] A starting transformer 42 that functions as a starting device is arranged in the upper space 35a of the case body 35.

[0058] A circuit unit 43 is arranged in the lower space 35c of the case body 35. The circuit unit 43 is connected to the starting transformer 42 inside the case body 35.

[0059] The circuit unit 43 has electronic components 44, 44, ..., and a connector 45. The connector 45 is formed from a connector case 45a, and a connector terminal 45b that is provided inside the connector case 45a. The connector case 45a is formed with a connecting hole opening downward, and a portion of the connector terminal 45b is arranged in the connecting hole.

[0060] In the circuit unit 43, a portion of the connector case 45a projects downward from the arranging notch 36d of the case body 35.

[0061] The plug 16 to which the lamp body 15 is attached is joined to the case body 35 by inserting the projecting portion 32 and the first terminal cover portion 33 into the first insertion hole 36b from the front, and inserting the second terminal cover portion 34 into the second insertion hole 36c from the front. At such time, a portion of the plug 16 is fitted into the positioning recess portion 36a to perform positioning of the plug 16 with respect to the case body 35.

[0062] In a state where the plug 16 is joined to the case body 35, the projecting portion 32 and the first terminal cover portion 33 of the plug 16 are inserted into the support wall portion 41 of the case body 35 to respectively position the connecting wall portion 38 and the partition 41b of the support wall portion 41 above and below the first terminal cover portion 33. Further, in the state where the plug 16 is joined to the case body 35, the second terminal cover portion 34 of the plug 16 is inserted and arranged in the lower space 35c while fitted to the retainer wall portion 39 of the case body 35. At such time, the partition 41b of the support wall portion 41 of the case body 35 is arranged in the gap 16b of the plug 16.

[0063] A part that projects rearward from the first terminal cover portion 33 of the power supply terminal portion 24a of the first lead wire 24 is connected to a first connecting terminal 46, and the first connecting terminal 46 is connected to the starting transformer 42.

[0064] A part that projects rearward from the second terminal cover portion 34 of the power supply terminal portion 25a of the second lead wire 25 is connected to a second connecting terminal 47, and the second connecting terminal 47 is connected to the circuit unit 43.

[0065] Another end portion of the power supply cord 14, which is connected to the output connector 13 of the discharge lamp lighting device 10, is connected to the connector terminal 45b of the connector 45.

[0066] Lighting of the discharge lamp 8 is performed as follows. A power supply voltage of the power supply circuit is increased and transformed by the lighting circuit of the discharge lamp lighting device 10, and used as a lighting voltage (starting voltage) that is a high-voltage alternating current or a pulsing voltage. The starting voltage is applied to the power supply terminal portion 24a of the first lead wire 24 through the power supply cord 14, the circuit unit 43, and the starting transformer 42, whereby discharge is started in the light emitting portion 20.

[0067] As described above, in the discharge lamp 8, a gap 16b is formed between the first terminal cover portion 33 that covers the power supply terminal portion 24a of the first lead wire 24 in a state of close contact therewith, and the second terminal cover portion 34 that covers the power supply terminal portion 25a of the second lead wire 25 in a state of close contact therewith. Accordingly, voids (air holes) are not prone to occur during molding of the plug 16, and an insulation breakdown of the discharge lamp 8 caused by the occurrence of a void can be prevented.

[0068] In addition, forming the gap 16b enables an increase in the creeping distance between the power supply terminal portion 24a of the first lead wire 24 and the power supply terminal portion 25a of the second lead wire 25. By increasing the creeping distance, an adequate insulated condition can be secured between the power supply terminal portions 24a, 25a.

[0069] Further, the partition 41b provided on the case body 35 is arranged in the gap 16b. Therefore, the arrangement of the partition 41b increases the surrounding thickness of the resin material (insulating material) around the power supply terminal portion 24a by a corresponding amount, making it possible to achieve sufficient insulation between the power supply terminal portions 24a, 25a.

[0070] The power supply terminal portion 24a of the first lead wire 24 and the power supply terminal portion 25a of the second lead wire 25 are positioned separate from each other in the longitudinal direction. Therefore, the distance between the power supply terminal portion 24a and the power supply terminal portion 25a is increased by a corresponding amount, and an insulation property between the power supply terminal portions 24a, 25a can be improved.

[0071] Note that the thickness (wall thickness) of the first terminal cover portion 33 and the second terminal cover portion 34 provided in the cover portion 36 of the case body 35 is less than the thickness (wall thickness) of the outer arranging portion 31, and may be from 0.5 mm to 2.0 mm, for example.

[0072] By forming the first terminal cover portion 33 and the second terminal cover portion 34 to have such a thickness, both an insulation property can be secured between the power supply terminal portions 24a, 25a and a holding state of the power supply terminal portion 24a and the power supply terminal portion 25a can be stabilized.

[0073] In the discharge lamp 8, the support wall portion 41 and the retainer wall portion 39 are each generally shaped as cylinders extending in the longitudinal direction and provided on the case body 35. The first terminal cover portion 33 is inserted into the support wall portion 41, and the second terminal cover portion 34 is inserted into the retainer wall portion 39.

[0074] Accordingly, the support wall portion 41 and the retainer wall portion 39 enable an improved insulation property between the power supply terminal portions 24a, 25a, and the plug 16 can be easily and reliably joined to the case body 35.

[0075] Further, in the discharge lamp 8, the case body 35 and the plug 16 to which the lamp body 15 is attached are configured as separate. Therefore, portions on the lamp body 15 side can be assembled separate from portions on the case body 35 side, and manufacturing of the discharge lamp 8 can be simplified.

[0076] Note that the plug 16 may also be integrally formed with the case body 35.

[0077] The shapes and structures of the respective portions in the above preferred embodiment are all but mere examples for carrying out the present invention.

[0078] 

FIG. 1 shows together with FIGS. 2 and 3 a best mode of a vehicular discharge lamp according to the present invention, and is a schematic cross-sectional view of a vehicular headlamp.

FIG. 2 is a side view of the discharge lamp that shows a cross section of a portion of the discharge lamp.

FIG. 3 is a perspective view that shows a portion of the discharge lamp.

[Description of the Reference Numerals]

[0079] 

8

DISCHARGE LAMP (VEHICULAR DISCHARGE LAMP)

15

LAMP BODY

16

PLUG

16b

GAP

18

OUTER TUBE

19

ARC TUBE

22

ELECTRODE

24

FIRST LEAD WIRE

24a

POWER SUPPLY TERMINAL PORTION

25

SECOND LEAD WIRE

25a

POWER SUPPLY TERMINAL PORTION

31

OUTER ARRANGING PORTION

33

FIRST TERMINAL COVER PORTION

34

SECOND TERMINAL COVER PORTION

35

CASE BODY

39

RETAINER WALL PORTION

41

SUPPORT WALL PORTION

41b

PARTITION

42

STARTING TRANSFORMER (STARTING DEVICE)

Claims

1. A vehicular discharge lamp, comprising:

a lamp body (15) that has an outer tube (18), an arc tube (19) arranged inside the outer tube (18), and a pair of electrodes (22) arranged inside the arc tube (19);

a first lead wire (24) and a second lead wire (25) that are respectively connected to the pair of electrodes (22), and of which end portions on sides that are opposite sides connected to the pair of electrodes (22) are respectively provided as power supply terminal portions (24a,25a);

a plug (16) that is formed from a resin material, and has a first terminal cover portion (33) and a second terminal cover portion (34) that respectively cover the power supply terminal portions (24a,25a) of the pair of lead wires (24,25) in a state of close contact therewith from an outer circumferential side;

a case body (35), to which the plug (16) is joined, inside which the first terminal cover portion (33) and the second terminal cover portion (34) are arranged; and

a starting device (42) that is arranged inside the case body (35), and applies a starting voltage to the power supply terminal portion when starting the lamp body (15), wherein

a gap (16b) is formed between the first terminal cover portion (33) and the second terminal cover portion (34) in a direction orthogonal to an optical axis of light radiated from the lamp body (15), and

a partition (41b) is provided on the case body (35) and arranged in the gap (16b), and separates the first terminal cover portion (33) and the second terminal cover portion (34).

2. The vehicular discharge lamp according to claim 1,
characterized in that
the power supply terminal portion (24a) of the first lead wire (24) and the power supply terminal portion (25a) of the second lead wire (25) are positioned separated in the optical axis direction.

3. The vehicular discharge lamp according to claim 1 or 2,
characterized in that
an outer arranging portion (31) is provided on the plug (16) and arranged on an outer side of the case body (35), and closes an end portion on the plug side of the lamp body (15) from the outer circumferential side,
a thickness of the first terminal cover portion (33) and the second terminal cover portion (34) is less than a thickness of the outer arranging portion (31), and
the thickness of the first terminal cover portion (33) and the second terminal cover portion (34) is from 0.5 mm to 2.0 mm.

4. The vehicular discharge lamp according to claim 1, 2, or 3,
characterized in that
a support wall portion (41) and a retainer wall portion (39), each generally shaped as a cylinder extending in the optical axis direction, are provided on the case body (35), and
the first terminal cover portion (33) is inserted into the support wall portion (41), and the second terminal cover portion (34) is inserted into the retainer wall portion (39).

Drawing