EP3088794A1

EP3088794A1 - Led lamp

Info

Publication number: EP3088794A1
Application number: EP14874999.7A
Authority: EP
Inventors: Yasuhisa Matsumoto; Kanae Matsumoto; Masayuki Matsuzaki
Original assignee: Iwasaki Denki KK
Current assignee: Iwasaki Denki KK
Priority date: 2013-12-26
Filing date: 2014-11-20
Publication date: 2016-11-02
Also published as: EP3088794A4; JP2015125849A; WO2015098383A1; JP6261119B2

Abstract

The purpose of the present invention is to provide an LED lamp comprising a novel cooling/radiation means. This LED lamp comprises: a plurality of LED elements; a plurality of light-source supporting bodies having each of the plurality of LED elements mounted thereon and extending along the lamp axial line; and a hermetically sealed glass container encasing the light-source supporting bodies. The plurality of light-source supporting bodies are arranged so as to form an n-angle shape (n = a natural number such as 3, 4, ....), as viewed from a cross-section perpendicular to the lamp axial line, such that a gas flow path is formed that flows along the lamp axial line between both end sections thereof. The light-source supporting bodies have a ventilation structure that penetrates between an LED element mounting surface and a rear surface, such that an inflow and outflow of gas in the gas flow path is formed.

Description

TECHNICAL FIELD

The present invention relates to an LED lamp.

BACKGROUND ART

Generally, lighting lamps have been successively developed as incandescent light bulbs, fluorescent lamps, HID (High Intensity Discharge) lamps, and LED (Light Emitting Diode) lamps, and have been put to practical use. An LED lamp is a lamp using a light-emitting diode element as a light source. LED lamps have enabled the white light emission by the development of a blue LED element, and have been recently spread to be used as lighting lamps.
Figs. 1A to 1C are diagrams illustrating an example of currently widely sold LED lamps. These LED lamps 100 are generally lamps having the output of 10 watts or less (typically about 7 watts). As shown in Figs. 1A to 1C, the lamps have various shapes, and basically include a base 102, a heat radiating portion 104, and a globe 106. The heat radiating portion 104 is formed of aluminum die-casting, and in most cases heat radiation fins are formed on the outer peripheral surface. The globe 106 is made of translucent resin.
Unlike the incandescent light bulb, the fluorescent lamp, the HID lamp and the like, and an LED element is not fundamentally needed to be disposed in a vacuum atmosphere or a predetermined gas atmosphere since it is a semiconductor element. Therefore, the aluminum die-cast portion 104 and the globe 106 become fixed with a suitable adhesive. Thus, the internal space formed by the aluminum die-cast portion 104 and the globe 106 is not hermetically sealed from the external space of the lamp.
The present inventors know that the following patent literatures related to the present invention is present.

Citation List

Patent Literature

Patent Literature 1: JP 2012-156036 A , "LED LAMP" (Publication Date: 2012/08/16), Applicant: Iwasaki Electric Co., Ltd.
Patent Literature 2: WO 2011/004798 A1 , "ELEMENT MOUNTING CERAMIC SUBSTRATE, LED MOUNTING CERAMIC SUBSTRATE, LED LAMP, AND HEAD LIGHT, AND ELECTRONIC COMPONENT" (International Publication Date: 2011/01/13), Applicant: Toshiba Corporation
Patent Literature 3: JP 2013-8721 A , "MOUNTING BOARD AND LIGHT EMITTING MODULE" (Publication Date: 2013/01/10), Applicant: Panasonic Corporation
Patent Literature 4: JP 2006-147333 A , "LED-MOUNTING PRINTED CIRCUIT BOARD" (Publication Date: 2006/06/08), Applicant: Toyoda Gosei Co., Ltd.

SUMMARY OF INVENTION

Technical Problem

The LED element is a semiconductor element, and the temperature of the semiconductor junction and the element lifetime are closely related to each other. That is, when the temperature of the junction during operation is relatively low, the element life is a long term, however the element lifetime is suddenly shortened as the temperature becomes high. Thus, when the temperature of the LED element is high in the LED lamp, the lamp lifetime is shortened and the lamp illuminance is also deteriorated. Therefore, a cooling and heat radiation means is an important matter in the LED lamp.
The present applicant has suggested the following LED lamp based on Patent Literature 1. That is, the cooling gas (low molecular weight gas) is encapsulated in the lamp in hermetically sealed lamp configurations. A light-source support body having a shape longer in the lamp axial line direction is disposed inside the lamp and a plurality of LEDs is mounted on its periphery. Inside the light-source support body, a through hole is formed along the lamp axial line as a cooling gas flow path to efficiency cool also the rear surface of the LEDs. With respect to this idea, a certain cooling effect is confirmed to be present, and the effect is shown in the graph of Fig. 6 in Patent Literature 1.
After filing Patent Literature 1, the present inventors have continued to research and develop the LED lamp configuration with an improved cooling and heat radiation means, based on the idea.
Based on the results of this research and development, the present invention has an object to provide an LED lamp with a novel cooling and heat radiation means.

Solution to Problem

An LED lamp of the present invention comprises: a plurality of LED elements; a plurality of light-source support bodies each mounting thereon a plurality of LED elements, extending along a lamp axial line; and a glass sealed container encasing therein said light-source support bodies to hermetically seal, wherein said plurality of light-source support bodies are arranged to form a n-gon (n is a natural number larger than two) as viewed in a cross section perpendicular to the lamp axial line, so as to form a flow path for gas flowing along the lamp axial line between both end sections, and a ventilation structure penetrating between a LED element mounting surface and a rear surface is formed in each of said light-source support bodies so as to form an inflow and an outflow with respect to a gas in said gas flow path.
Further, in the above LED lamp, wherein said light-source support body may be made of a metal core substrate.
Further, in the above LED lamp, wherein said ventilation structure formed in each of said light-source support bodies may include a groove, a circular opening, or a plurality of through holes.
Further, in the above LED lamp, wherein said ventilation structure formed in each of said light-source support bodies may be formed in a region between adjacent LED elements.
Further, in the above LED lamp, wherein said adjacent light-source support bodies may be spaced a gap apart to be held so as to form an inflow and an outflow with respect to a gas in said gas flow path.

Advantageous Effects of Invention

According to the present invention, it is possible to provide an LED lamp with a novel cooling and heat radiation means.

BRIEF DESCRIPTION OF DRAWINGS

Fig. 1A is a diagram illustrating an example of currently widely sold LED lamps.
Fig. 1B is a diagram illustrating another example of currently widely sold LED lamps.
Fig. 1C is a diagram illustrating further example of currently widely sold LED lamps.
Fig. 2A is a front view of a LED lamp according to the present embodiment.
Fig. 2B is a right side view of the LED lamp shown in Fig. 2A.
Fig. 3 is an enlarged perspective view of the LED lamp according to the present embodiment.
Fig. 4A is an outline diagram of a light-source support body used in the LED lamp according to the present embodiment.
Fig. 4B is a cross-sectional view of the X-X place shown in Fig. 4C.
Fig. 4C is a diagram illustrating a light-source support body mounting LED elements.
Fig. 4D is an alternative example of grooves formed in the light-source support body.
Fig. 5A is a diagram illustrating a flow of the cooling flow when the LED lamp is vertically lit according to the present embodiment.
Fig. 5B is a diagram illustrating a flow of the cooling flow when the LED lamp is horizontally lit according to the present embodiment.
Figs. 5C(A) and 5C(B) are diagrams illustrating flows of the cooling flow as viewed in the cut surface of the Y-Y place shown in Fig. 5B, and Figs. 5C(A) and 5C(B) are caused by the difference of the engaging state upon screwing the lamp into the base.
Fig. 6 is a flowchart illustrating a method of manufacturing the LED lamp according to the present embodiment.

DESCRIPTION OF EMBODIMENTS

After this, the embodiment of an LED lamp according to the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the same elements will be denoted by the same reference numerals in the figures, and an overlapping explanation will be omitted. In addition, it should be understood that the embodiments described below are exemplary, and are not intended to limit the scope of the present invention.

(Overall Configuration of LED Lamp)

Fig. 2A is a front view of a LED lamp according to the present embodiment, and Fig. 2B is a right side view thereof This LED lamp 10 is primarily directed to a higher output LED lamp of 20 to 50 watts class, typically of 25 watts, rather than a lower output LED lamp of about 7 watts which is currently widely advertised and sold as described in Fig. 1. Therefore, the cooling and heat radiation means becomes a furthermore important consideration.
The LED lamp 10 includes a plurality of LED elements 18 disposed inside the outer bulb 6 one end of which is hermetically sealed at the base 2. The plurality of LED elements 18 are mounted on the light-source support body 14 at appropriate intervals and are fixed thereto.
The light-source support body 14 is typically made of a metal core board. The light-source support body 14 is positioned and supported at an appropriate place inside the outer bulb 6, by using the two metal bands 28 at the upper and lower portions of the support column 20 extending from the stem 8 which is adhered to one end of the outer bulb 6. Therefore, the recesses 14n for holding the metal bands (see Fig. 4A) are formed in the light-source support body 14. Optionally, a part of the support column 20 adjacent to the light-source support body 14 is covered with an insulating tube (not shown), whereby the electrical insulation between the light-source support body 14 and the support column 20 is secured.
Furthermore, a heat shield member 30 (see Fig. 3) may be disposed inside the outer bulb 6 near the base 2. The heat shield member 30 is formed of, for example, ceramics, a metal plate, a mica plate, and the like. The function of the heat shield member 30 will be described below in relation to the manufacturing method shown in Fig. 6.
Preferably, a low molecular weight gas is encapsulated in the internal space 22 of the outer bulb 6. In the present application document, "a low molecular weight gas" means a gas of high specific heat and good thermal conductivity, typically helium gas. The present inventors empirically know that the discoloration occurring in a sealing member (typically, silicone layer) used in the LED element mounting can be suppressed by mixing a small amount of oxygen when helium gas is used. Therefore, when helium gas is used, a mixed gas having the volume ratio of helium : oxygen = 93 : 7 (units: %) is preferred to be used.

(Description of Each Component of LED Lamp)

Fig. 3 is an enlarged perspective view of the LED lamp according to the present embodiment. The base 2 may be a screw type (E type) or a plug type used in incandescent light bulbs and HID lamps.
The outer bulb 6 is, for example, a BT tube made of translucent hard glass such as borosilicate glass. However, it may be any shape. The outer bulb 6 may be any one of transparent type or diffusing type (frosted glass type).
As with the known incandescent lamp and HID lamp, the outer bulb 6 is hermetically sealed at the portion of the base 2, and the boundary between the outer bulb internal space and the external space is in a hermetically sealed state.
The LED lamp 10 includes four light-source support bodies 14, nine LED elements 18 are mounted on each of the light-source support bodies, and 36 LED elements in total complete the LED lamp of 25 watts.
The four light-source support bodies 14 are arranged so as to generally form a rectangle as viewed in the cross section in the direction perpendicular to the lamp axial line. Furthermore, preferably, the adjacent light-source support bodies are not connected in-between, and are spaced the gap 26 apart to be disposed. It should be noted that although the four light-source support bodies 14 are arranged so as to form a rectangle, the disposition is not limited thereto. That is, three light-source support bodies may be disposed spaced a gap apart so as to form a triangle, and any number n (n is a natural number larger than two) of light-source support bodies may be disposed spaced a gap apart so as to form an n-gon.

(Light-Source Support Body)

Fig. 4A is an outline diagram of a light-source support body 14 used in the LED lamp according to the present embodiment, Fig. 4B is a cross-sectional view of the X-X place shown in Fig. 4C, Fig. 4C is a diagram illustrating a light-source support body mounting LED elements, and Fig. 4D is an alternative example of grooves (slits) formed in the light-source support body.
The light-source support body 14 shown in Fig. 4A is preferably made of a metal core board, and is, for example, a plate-like body about 100 mm long, 20 mm wide, and 2 mm thick. The LED element mounting place is indicated by reference numeral 18a. A groove (slit) 14b cutting from the edge of the light-source support body 1 is formed so as to disconnect between adjacent LED element mounting places 18a.
As shown in Fig. 4B, in the light-source support body 14, a thin insulating layer 14i is formed on a relatively thick main body portion 14a, and further conductor patterns 14g and 14e typically made of copper are formed on the insulating layer, and further a thin resist layer 14j made of resin and the like is formed thereon. The main body portion 14a is made of a material having good thermal conductivity, such as copper, aluminum, and a thermal conductivity resin. A high coefficient of thermal conductivity is realized in the thermal conductivity resin by mixing a resin with the metal powder, or metal piece. Here, the material having the best thermal conductivity, workability, economy, and the like as the light-source support body 14 is aluminum.
As shown in Fig. 4C, the LED elements 18 are sequentially connected in series in the leftward direction from the first electrode 14d through the upper side pattern 14e, and through the upper and lower connection pattern 14f, and further are sequentially connected in series in the rightward direction to the electrode 14h through the lower side pattern 14g. The four light-source support bodies 14 are connected sequentially in series through lead wires (not shown). Eventually, all the 36 LED elements are connected in series.
See Fig. 4D. In Fig. 4A, although the groove (slit) 14b of the light-source support body 14 is described to have the shape cutting from the edge thereof, the groove (slit) 14b is not limited thereto. It is satisfactory as long as the groove (slit) 14b has a ventilation structure (vent hole) that penetrates the light-source support body 14.
Therefore, it may be a rectangular opening 14k instead of the groove (slit) 14b. The rectangular opening 14k is preferable to be formed in a region between the adjacent LED elements 18.
Alternatively, it may be a circular opening 141. The circular opening 141 is also preferable to be formed in a region between the adjacent LED elements 18. In this case, a plurality of through holes 14m may be formed in a region between the adjacent LED elements 18.

(Method of Manufacturing LED Lamp)

Fig. 6 is a flowchart illustrating a method of manufacturing the LED lamp according to the present embodiment.
In the mount assembly process in step S1, the LED element 18 is mounted on the light-source support body 14, and the light-source support body is attached to the support column 20 to form a mount, and then the mount is attached to the stem 8.
In the sealing process in step S2, the mount is inserted inside the outer bulb 6, and the stem 8 attached to the mount and the outer bulb 6 are sealed by heating with a burner to seal hermetically.
In the exhausting process in step S3, the inside of the outer bulb already sealed is once evacuated to a vacuum state through an exhaust pipe. Then, a mixed gas of helium and oxygen is encapsulated, and the exhaust pipe is chipped off (to seal by fusing the exhaust pipe with a burner).
In the base-attaching process in step S4, the base 2 are soldered at the top portion and the side portion thereof.
Through the lighting test and inspection in step S5, the LED lamp 10 is completed.
Here, in steps S2 to S4, the sealing portion, the stem, and the like of the outer bulb are heated to a high temperature of near 1000°C by a burner. The heat shield member 30 (see Fig. 3) is disposed between the base attaching portion of the outer bulb and the LED elements 18 so that this heat is not transferred to the LED elements 18 inside the outer bulb so as not to damage.

(Advantages and Effects of the Present Embodiment)

The LED lamp 10 according to the present embodiment has the advantages and effects as follows.

(1) As described in relation to Fig. 4D, the ventilation structure (vent hole) penetrating the light-source support body 14 is formed, whereby the weight reduction of the light-source support body 14 can be achieved. As a result, the weight reduction of the LED lamp 10 can be achieved.
(2) The ventilation hole penetrating the light-source support body 14 is formed, whereby the surface area of the light-source support body 14 increases to improve the heat dissipation effect. That is, the cooling effect of the LED element 18 is improved.
(3) Details of Cooling Effect

The cooling effect considering the lamp lighting direction (vertical lighting or horizontal lighting) will be described with reference to Figs. 5A to 5C. It should be noted that although the base is positioned on the upper side in the vertical lighting shown in Fig. 5A, the same effect can be expected even when the base is positioned on the lower side.
As shown in Fig. 5A, the rectangular space extending along the lamp axial line formed by the four light-source support bodies 14 forms the flow path of cooling flow Ca from the bottom to the top by the chimney effect. Furthermore, the gap 26 between the light-source support bodies forms the flow path of inflow and outflow Cb with respect to the cooling flow Ca to enhance the cooling effect.
Furthermore, the groove (slit) 14b formed in the light-source support body 14 shown in Fig. 4A, the rectangular opening 14k, the circular opening 141, and the plurality of through holes 14m formed in the region between the adjacent LED elements shown in Fig. 4D (hereinafter referred to as "groove 14b and the like") will be described. As shown in Fig. 4A, the thermal influence is reduced by the groove 14b and the like because the linear thermal conduction (arrow b) between the adjacent LED elements is blocked or reduced while the thermal conduction path in the length direction (arrow a) of the light-source support body is secured.
In the LED lamp in the vertical lighting shown in Fig. 5A, the groove 14b and the like of the light-source support body 14 forms the flow path of inflow and outflow Cb with respect to the cooling flow Ca in the same manner as the gap 26 between the light-source support bodies 14, and blocks or reduces the linear thermal conduction between the adjacent LED elements to reduce the thermal influence while securing the thermal conduction path in the length direction of the light-source support body.
Fig. 5B is in a case of the horizontal lighting, Figs. 5C(A) and 5C(B) are cut surfaces taken along line Y-Y, and Figs. 5C(A) and 5C(B) are caused by the difference of the engaging state upon screwing the lamp into the base. That is, Fig. 5C(A) is a diagram showing a case where the four light-source support bodies are positioned so as to form a square, and Fig. 5C(B) is a diagram showing a case where the four light-source support bodies are positioned so as to form a rhombus.
In the case of the horizontal lighting, the cooling flow Ca by the chimney effect described with reference to Fig. 5A is relatively decreased. However, the cooling flow Cb passing through the gap 26 between the light-source support bodies is relatively increased. Furthermore, the groove 14b and the like of the light-source support body 14 forms the flow path of cooling flow Cc, and blocks or reduces the linear thermal conduction between the adjacent LED elements to reduce the thermal influence while securing the thermal conduction path in the length direction of the light-source support body.
By these, with respect to the high-output LED lamp, sufficient cooling effects are confirmed even in the horizontal lighting.

(Conclusion)

As described above, although the embodiments of the LED lamp according to the present invention are described, these are exemplary and are not intended to limit the scope of the present invention. The technological scope of the present invention is determined by the appended claims.

Reference Signs List

2: base, 6: outer bulb, 8: stem, 10: LED lamp, lamp, 14: light-source support body, 14a: main body portion, 14b: groove, slit, 14d: electrode, 14f: upper and lower connection pattern, 14h: electrode, 14i: insulating layer, 14j: resist layer, 14k: opening, 14k: rectangular opening, 141: circular opening, opening, 14m: through holes, 14n: recess, 18:LED element, 18a:element mounting place, 20:support column, 22:internal space, 26:gap, 28:metal band, 30:heat shield member, 100:LED lamp, lamp, 102:base, 104: aluminum die-cast portion, heat radiating portion, 106:globe,
a: arrow, b: arrow, Ca, Cb, Cc: cooling flow

Claims

An LED lamp comprising:
a plurality of LED elements;

a plurality of light-source support bodies each mounting thereon a plurality of LED elements, extending along a lamp axial line; and

a glass sealed container encasing therein said light-source support bodies to hermetically seal,

wherein said plurality of light-source support bodies are arranged to form a n-gon (n is a natural number larger than two) as viewed in a cross section perpendicular to the lamp axial line, so as to form a flow path for gas flowing along the lamp axial line between both end sections, and

a ventilation structure penetrating between a LED element mounting surface and a rear surface is formed in each of said light-source support bodies so as to form an inflow and an outflow with respect to a gas in said gas flow path.
The LED lamp according to claim 1,
wherein said light-source support body is made of a metal core substrate.
The LED lamp according to claim 1,
wherein said ventilation structure formed in each of said light-source support bodies includes a groove, a circular opening, or a plurality of through holes.
The LED lamp according to any one of claims 1 to 3,
wherein said ventilation structure formed in each of said light-source support bodies is formed in a region between adjacent LED elements.
The LED lamp according to any one of claims 1 to 4,
wherein said adjacent light-source support bodies are spaced a gap apart to be held so as to form a flow of an inflow and an outflow with respect to a gas in said gas flow path.
The LED lamp according to any one of claims 1 to 5,
wherein said gas is a low molecular weight gas.
The LED lamp according to claim 6,
wherein said low molecular weight gas is at least a mixed gas containing helium and oxygen.