The present invention relates to an LED lamp and an illumination device, in particular to an LED lamp suitable as a substitute for an incandescent light bulb.
Due to a recent demand for resource saving, LED lamps, which have a longer life and require less electricity to work, have been commercialized, and additional research studies are in progress.
Such a bulb-type LED lamp generally has a single mounting substrate and a plurality of LED chips mounted on the mounting substrate, and a circuit unit for lighting the LED chips is housed in an inner space of a housing provided between the back side of the mounting substrate and a base.
When used as a substitute for an incandescent light bulb, the bulb-type LED lamp is required to present the closest possible light distribution characteristics to the incandescent light bulb. Specifically, assume the case where the bulb-type LED lamp is placed to face downward. In this case, the bulb-type LED lamp is required to emit light in a broad range, namely, obliquely backward and laterally, in addition to downward.
However, the light distributed by the bulb-type LED lamp exhibits Lambertian characteristics to be directed strongly along a specific direction, and, by its nature, illuminates a limited area right under the lamp and its neighborhood. To address the problem, a bulb-type LED lamp which includes a globe having an opening near the mounting substrate and covering the entire mounting substrate has been conceived (Patent Literature 1). This LED lamp is designed to yield the broadest possible light distribution range, by making the globe from a translucent milk-white material or the like so that the light emitted from the LEDs (i.e. LED chips) is diffused while it passes through the globe.
According to the above technology, however, the light emitted from the LEDs mostly passes through some sections of the globe ahead of the LEDs due to the Lambertian direction characteristics, and the diffusion can only produce a limited effect.
In view of the above problems, the applicant of the present application previously filed an application for an improved LED lamp in which a light diffusing member is provided between the front side of the mounting substrate and the globe.
According to the invention previously filed, a portion of the light emitted from the LEDs is diffused (i.e. scattered) by the light diffusing member positioned ahead of the LEDs and radiated after passing through broader sections of the inner surface of the globe than before. As a result, the light distribution characteristics is improved.
[Patent Literature 1] Japanese Patent Application Publication No. 2009-037995.
[Patent Literature 2] Japanese Patent Application Publication No. 2010-086713.
Although the previous invention provides an effect of improving the light distribution characteristics to a certain degree, there is still a need for further improvement. Accordingly, an objective of the present invention is to provide an LED lamp that is capable of producing an even more broader light distribution region. Another objective of the present invention is to provide an illumination device that includes such a LED lamp.
In order to achieve the above objective, an aspect of the present invention provides an LED lamp an LED lamp for emitting light outward through a globe, comprising: a plurality of LED modules composed of one main LED module and one or more auxiliary LED modules, each of the plurality of LED modules having a mounting substrate and LEDs mounted on the mounting substrate; a base through which power is supplied to the LEDs for light emission; and a light diffusing member, wherein the main LED module is positioned on an imaginary extension of a central axis of the base, and the light diffusing member is positioned inside the globe such that the main LED module emits light towards the light diffusing member, and the one or more auxiliary LED modules are positioned in a vicinity of the main LED module, with at least one of the one or more auxiliary LED modules tilted to face the light diffusing member.
According to the aspect of the present invention directed to an LED lamp, the LED lamp may be modified as follows. The main LED module is positioned such that the imaginary extension of the central axis of the base passes through a center of the main LED module, and the one or more auxiliary LED modules comprise at least two auxiliary LED modules which are arranged in rotational symmetry about the central axis of the base when viewed in a direction along the central axis.
Furthermore, the main LED module may emit a larger amount of light than any of the one or more auxiliary LED modules.
Furthermore, the light diffusing member may have a polyhedron shape.
Alternatively, the light diffusing member may be ring-shaped, positioned such that the imaginary extension of the central axis of the base passes through a center of the ring-shaped light diffusing member.
Moreover, LED lamp may further comprise a mount, wherein the plurality of LED modules are mounted on the mount, and the light diffusing member is supported by the mount via a supporting member.
Alternatively, the light diffusing member may be fixed to the globe.
In order to achieve the other objective, another aspect of the present invention provides an illumination device comprising: a lighting fixture; and an LED lamp according to claim 1 which is coupled to the lighting fixture.
According to the LED lamp with the above structure, not only the main LED module positioned on the imaginary extension of the central axis of the base but also at least one of the one or more auxiliary LED modules face the light diffusing member. Accordingly, compared to a case where only a single LED module is provided (i.e. where all the LEDs emit light to a same direction), the amount of light diffused by the light diffusing member becomes larger. As a result, light passes through broader sections of the globe. Consequently, the light distribution range of the LED lamp becomes even more broader.
The following describes an embodiment of the present invention with reference to the drawings.
As shown in
The casing 12 includes a metal portion 18 and a insulating portion 20. The metal portion 18 is made of, for example, aluminum, and doubles as a heat sink for dissipating heat emitted by LED modules 22, 24, 26, 28, 30 which are described later. The insulating portion 20 is made of epoxy resin or another kind of synthetic resin material.
The metal portion 18 has a circular truncated cone shape that is hollow. As shown in
The LED module 22, which is arranged in the middle among the five LED modules 22, 24, 26, 28, 30, has a square-shaped mounting substrate 22A on which nine blue LED chips 22B (not shown in
Regarding the other LED modules 24, 26, 28, 30, the structure of these modules is basically the same as that of the LED module 22, except for a difference in the shape of mounting substrates 24A, 26A, 28A, 30A and the number of LED chips mounted thereon. Specifically, on each of the rectangle-shaped mounting substrates 24A, 26A, 28A, 30A, six blue LED chips (not shown) are arranged in a matrix of 2 rows and 3 columns, and respective green phosphor films 24C, 26C, 28C, 30C are formed to cover the six blue LED chips.
The LED module 22 is positioned such that the imaginary extension of a later-described central axis X passes through a center of the LED module 22, and the other LED modules 24, 26, 28, 30 are arranged in rotational symmetry about the central axis X when viewed in a direction along the central axis X.
Now, referring back to
Referring to
The base 14 complies with the E26 base standards defined in JIS (Japanese Industrial Standards), for example, and is attachable to a socket (not shown) for conventional incandescent light bulbs.
The base 14 includes a shell 50, which is also referred to as a cylindrical body, and an eyelet 52 having a circular dish-like shape. The shell 50 and the eyelet 52 are integrated together, with a first insulating part 54 therebetween. The first insulating part 54 is made of a glass material. This integrated body is fit into a second insulating part 56 which extends from the casing 12 and has a cylindrical shape.
The second insulating part 56 is provided with a through hole 56A, and the first lead line 48 extends from the inside of the second insulating part 56 to the outside, via the through hole 56A.
The internal lead of the first lead line 48 at one end thereof is sandwiched between the internal surface of the shell 50 and the external surface of the second insulating part 56. Thus, the first lead line 48 and the shell 50 are electrically connected.
The eyelet 52 has a through hole 52A which is provided around the center thereof. The internal lead of the second lead line 49 extends to the outside through the through hole 52A, and connected to the external surface of the eyelet 50 by soldering.
Inside the globe 16A, a light diffusing member 58 is provided.
In the present example, the light diffusing member 58 is positioned on the imaginary extension of the central axis of the base 14 (note that the imaginary extension of the central axis is also referred to as central axis X below), and the middle LED module 22 among the five LED modules 22, 24, 26, 28, 30 is also positioned on the central axis X. In the present example, the LED module 22 is positioned such that the central axis X passes through the center (i.e. a point where two diagonal lines cross on a rectangular main surface, that is, a light-emitting surface of the green phosphor film 22C) of the LED module 22.
From among light that has been emitted by the LED module 22 and reached the light diffusing member 58, which is positioned face-to-face with the LED module 22, some light portions are reflected off the light diffusing member 58. The reflected light partly passes though some sections of the globe 16 near an opening thereof before being radiated outward. Accordingly, compared with a case without the light diffusing member 58, the LED lamp 10 is capable of distributing light over a broader range. Furthermore, the remaining portions of the light which has reached the light diffusing member 58 pass through the light diffusing member 58 and are radiated outward through the globe 16 as scattered light. Thus, with the light diffusing member 58 formed with the light-transmissive material, a shadow is prevented from being formed on an object to be lit to the maximum extent practicable.
Now, unlike the present example in which the plurality of LED modules are provided, assume a case where only a single LED module is provided (note that a total number of the LED chips remains same as the present example). Specifically, suppose that the single LED module (referred to below as a “comparative LED module”) has a single mounting substrate on which LED chips are arranged in a matrix. In this case, light distributed by each LED chip exhibits the Lambertian characteristics to be directed strongly along a specific direction. Accordingly, only some of the LED chips arranged around the center of the mounting substrate can emit such intensive light that reaches the light diffusing member, and most of the light emitted by other LED chips mounted close to a periphery of the mounting substrate hits an inner surface of the globe without reaching the light diffusing member. As a result, the light emitted by the LED chips mounted around the periphery of the mounting substrate fails to contribute to production of a broader light distribution range of the LED lamp.
In contrast to the above case, in the present example, auxiliary LED modules are provided instead of the LED chips supposed to be mounted around the periphery of the mounting substrate in the comparative LED module. Furthermore, the auxiliary LED modules are arranged in a vicinity of (i.e. around) the LED module that is positioned to intersect the central axis X (i.e. positioned on the central axis X), while titled to face the light diffusing member. Note that the LED modules 24, 26, 28, 30 correspond to the auxiliary LED modules.
In order to tilt the LED modules 24, 26, 28, 30 as described above, the external bottom surface of the metal portion 18 is provided with inclined portions. A description is given of the LED module 24 as an example with reference to
The exterior bottom surface of the metal portion 18 is provided with an inclined portion 66 gradually sloping up towards the central axis X, and the LED module 24 is mounted on the inclined portion 66. Regarding a degree of inclination, the inclined portion 66 does not necessarily need to be inclined sufficiently such that the light diffusing member 58 is positioned exactly in front of the LED module 24. It is only necessary to incline the LED module 24 to let the light diffusing member 58 be within an angle of the light distribution range, providing that a normal to the mounting substrate 24A, which passes through the center of the LED module 24, forms an angle of 0 degree. With the above structure, the amount of light delivered to the light diffusing member 58 becomes larger compared to the case in the comparative LED module.
Note that the other LED modules 26, 28, 30 are also provided with inclined portions 68, 70, 72, respectively, and the LED modules 26, 28, 30 are mounted on the inclined portions 68. 70, 72, respectively.
Regarding a relative size of the light diffusing member 58 with respect to the LED module 22, it is preferable that in the plan view the light diffusing member 58 is smaller than the main light-emitting surface (i.e. an upper surface of the phosphor film 22C in
According to the LED lamp 10 with the above structure, since the light diffusing member 58 is positioned face-to-face with the main LED module 22 which emits light in the direction of the central axis X, and the LED modules 24, 26, 28, 30 are provided around the LED module 22 to be titled to face the light diffusing member 58, the amount of light delivered to the light diffusing member 58 becomes larger compared to the case in the above-described comparative LED module due to presence of the LED modules 24, 26, 28, 30. Consequently, the amount of light reflected off the light diffusing member 58 and bounced obliquely backward towards the base 14 is increased, whereby the light distribution range of the LED lamp 10 becomes broader.
Note that not all the LED modules 24, 26, 28, 30 need to be tilted, and the light distribution characteristics can be improved than the comparative LED module by making at least one of the LED modules 24, 26, 28, 30 tilted.
The present invention is described above based on the embodiment. However, of course the present invention is not limited to the embodiment above. For example, the following modifications can be made.
In the above embodiment, as can be seen from
That is to say, the light diffusing member 73 may be positioned closer to the LED module 22 relative to the globe center C.
Adopting the above structures helps prevent a decrease in the amount of light passing through the central axis X and some sections of the globe 16 around the central axis X.
However, in some cases, the mounting substrate is so thick that the rectangular main surface (i.e. light-emitting surface) of the phosphor film 22C is at an unnecessarily far distance from the surface of the metal portion 18 (i.e. the surface on which the LED modules are mounted). In such a case, the globe center may be defined to be a central point on the central axis .X located between the rectangular main surface of the phosphor film 22C and the inner surface of the globe 16.
Although in the above embodiment the main portion of the light diffusing member 58 is shaped in the heptagonal pyramid, the present invention is not limited to the above embodiment. For example, the following modifications are considered.
As shown in
As shown in
As shown in
Alternatively, as shown in
Note that as shown in
Although in the above embodiment the light diffusing member 58 is supported by the four legs 64 on the metal portion 18 within the globe 16, the light diffusing member 58 may be provided within the globe 16 according to another method.
For example, as shown in
Furthermore, as shown in
Moreover, as shown in
Moreover, as shown in
In addition to the case of
Note that the number of the LED modules arranged around the middle LED module is not limited to four (as in
(1) Although in any of the above modification examples the LED modules are made to face the light diffusing member, LED modules positioned near opening edges of the globe may be tilted towards the opening edges.
In an example of
With the above structure, the amount of light directly delivered from the LED modules 124, 126 to the opening edges of the globe 16 is increased, and accordingly the amount of light diffused by the opening edges and radiated from the globe 16 is increased. As a result, the light distribution range of the LED lamp 120 becomes even more broader.
(2)
Here, as shown in
The lighting fixture 152 can be ceiling-mounted small-size lighting fixture that is attachable to a ceiling, wall, and the like.
The lighting fixture 152 includes an outer frame 154, a shell bearing 156 housed in the outer frame 154, and an eyelet piece 158.
The outer frame 154 is made of an insulating material such as heat-resistant plastic, and shaped in a cylinder partitioned almost in the middle in a longitudinal direction of the outer frame 154.
The bearing shell 156 includes a cylindrical female screw, and fixed to a partition wall 154A of the outer frame 154 by a screw 160.
The eyelet piece 158 is formed by bending a strip of metal, and fixed to the partition wall 154A by a screw 162 as well.
By screw-fitting the base 14 (of
A bulb-type LED lamp according to the present invention is suitable as a substitute for an incandescent light bulb, for example.
10 bulb-type LED lamp
14 base
16 globe
22, 24, 26, 28, 30, 90, 92, 94, 96, 100, 102, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115 LED module
58, 74, 80, 82, 84, 86, 88 light diffusing member
Number | Date | Country | Kind |
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2010-114870 | May 2010 | JP | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/JP2011/001626 | 3/18/2011 | WO | 00 | 12/22/2011 |