WO2008093359A2

WO2008093359A2 - A solid light guide for uniform illumination of dial, a dial background luminous system and a method thereof

Info

Publication number: WO2008093359A2
Application number: PCT/IN2008/000058
Authority: WO
Inventors: Dharmaraj Prasad; Mohamed Kaja Aliar Husain
Original assignee: Pricol Limited
Priority date: 2007-02-01
Filing date: 2008-01-30
Publication date: 2008-08-07
Also published as: WO2008093359A3

Abstract

The present invention relates to background luminous for mechanical and/or electrical and/or electronic systems, more specifically related to a light guide (1) of an indicating device for uniform illumination of dial (2) comprises a printed circuit board [PCB (3)] at its center with built-in light emitting diodes [LED(4)].

Description

A SOLID LIGHT GUIDE FOR UNIFORM ILLUMINATION OF DIAL, A DIAL BACKGROUND LUMINOUS SYSTEM AND A METHOD THEREOF

FIELD OF THE INVENTION

The present invention relates to background luminous for mechanical and/or electrical and/or electronic systems, more specifically related to a light guide (1) of an indicating device for uniform illumination of dial (2) comprises a printed circuit board [PCB (3)] at its center with built-in light emitting diodes [LED (4)].

BACKGROUND OF THE INVENTION AND PRIOR ARTS

The existing trends of instrument cluster dials are illuminated by incorporating one or more candescent lamp below the dial or by using light conducting transparent material optically coupled to a near-by light source. In the case of the lamp on the dial, it is expensive to provide a lamp that is sufficiently small and yet not sufficiently bright to illuminate the dial, this lamp consumes more current and generate more heat.

The techniques for illuminating dials, indicators and instrument face plates have become increasingly popular over the last decade because they offer opportunities to mask the light source from the viewer or operator and also flexibility in positioning the light source, and if properly utilized, can defuse and spread light evenly over the- surface to be illuminated.

This invention relates to a method and apparatus for illuminating a dial display with a light source and light guide with matt-finish surfaces to increase the light efficiency for an instrument dial display. An instrument cluster for a vehicle is located on a vehicle dashboard and includes several gauges or dials that indicate various vehicle-operating conditions. For example, an instrument cluster may include a speedometer, a tachometer, an engine oil temperature indicator, oil pressure indicator etc, and other known types of gauges. These gauges are illuminated to facilitate reading of the information by the vehicle occupants.

Improvements in the area of optics over the years have resulted in a significant increase in light output from light sources. This has significantly increased the number of light sources needed to adequately illuminate an instrument display. However, this increased light output has also made it more difficult to evenly or uniformly distribute luminance over the display without requiring some form of compensation. Compensation usually involves the addition of coatings or layers of material applied to at least one of the gauge components to absorb light in certain areas. In one example, an additional layer of black dots is applied to the dial bottom in the areas of bright illumination, i.e. the areas closest to the light source. This layer of dots is typically placed on top of the white paint layer, which is applied to the bottom surface of the dial. While this configuration provides for more even illumination, it is disadvantage because light efficiency is decreased due to the light absorption.

Thus, there is a need for an instrument gauge and/or dial display that provides a more even/uniform and brighter illumination in order to overcome the other above-mentioned problems.

One way to improve the illumination on the dial of an instrument cluster is by providing light emitting diodes rather the use of any sort of lamps. For example, US Patent Number 6, 979, 094 describes the use of light emitting diodes, wherein reflector provides different-colored backlighting to indicia and a background field of an instrument dial. The dial is mounted on a reflector, forming an interior space. The reflector is assembled on a printed circuit board (PCB). A recessed section of the reflector has an opening exposing a portion of the PCB) to the interior space. Another section of the reflector provides a short tube having an inner cavity suspended over the opening. A first group of light emitting diodes is mounted on the exposed portion of the PCB under the tube such that light from the first group is reflected through the inner cavity to light a pointer. A second group of light emitting diodes having a different color is mounted outside the tube and backlights the indicia of the dial. A gap between the exposed portion of the PCB and an end of the tube enables light to leak from the inner cavity and backlight the background field of the dial a different color than the indicia.

However the above document discloses the illumination of the instrument cluster with

PCB, the document US 6, 979, 094 is no where related to instant invention. In case of instant invention the dial is uniformly illuminated with the use of miniature light emitting diodes and the light guide. The light guide in instant invention is a solid section for uniform illumination of the dial, whereas in the prior art there is an interior space provided for reflection of light beams emitted from a light source. This interior space will raise a problem of spot light brightness of the dial and occupies more space within the system of instrument cluster.

Thus in the instant invention the use of light guide made as transparent solid section to get uniform illumination for the background of dial makes the entire system simple in construction, robust in design and economical. In addition the instant invention overcomes the spot light section illumination on the dial.

Yet another existing way for providing automobile instrument cluster illuminated is by providing light sources producing different colours of light. For example US 5, 975, 728 provides for an automobile instrument cluster being illuminated by different colours of light. It provides for a method and apparatus for providing user selectable multi-color illumination to automotive instrument panel instruments. In one embodiment, an instrument panel or individual instrument is supplied with a plurality of differently colored illumination sources. The intensity of each color is individually controllable, allowing the user to select both intensity and hue of instrument illumination. In one embodiment, an instrument panel illumination system comprises ^■ three light sources that produce nominally white light and three associated diffusing filters, one red, one green, one blue. In other embodiment different colors of illumination are provided by light sources producing different colors of light, such as, for example, a plurality of high intensity red, green, and blue light emitting diodes ("LED's"). In one embodiment, a plurality of triplets of red, green and blue high- intensity LED's are mounted above a white diffusing filter. In one embodiment, a plurality of colored light sources is mounted in instrument housing behind the instrument's bezel.

However the above US 5, 975, 728 document discloses the use of LED's with specific in their colours. There are number of sets of LED's with red, green, and blue colours with a white diffusing filter. Thus the US document is no where related to instant invention whereas in the instant invention the dial is uniformly illuminated with the use of miniature light emitting diodes and the light guide. The light guide in instant invention is a solid section for uniform illumination on the dial, whereas in the prior art there is an interior space provided for reflection of light beams emitted from a light source. This interior space will raise a problem of spot light brightness of the dial and occupies more space within the system of instrument cluster. Thus the problem of spot light illumination on the dial of an instrument cluster is completely solved by the instant invention.

BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS

Figure 1: Shows cross section view of a light guide (1) with interior space for reflection of light beams emitted from LEDs (4).

Figure 2: shows the assembly sequence of the system, wherein the dial (2) is mounted on the top of the light guide (1 ) and the PCB (3) with LEDs (4) is mounted on the bottom side of the light guide (1).

Figure 3:

(a) shows the top view of the light guide (1). (b) shows the side view of the light guide (1).

Figure 4:

(a) shows the bottom view of the light guide (1).

(b) shows the cross section view of the light guide (1).

Figure 5:

(a) shows the top view of the dial (2) of the system.

(b) shows the section view of the light guide (1) showing the reflection of light beams. Figure 6: shows the reflection of the emitted light beams inside the light guide (1) of solid section and uniform illumination.

OBJECTS OF THE INVENTION

The principal object of the invention is to develop a solid light guide (1) for uniform illumination of dial (2). Yet another object of the present invention is to develop printed circuit board [PCB (3)] carrying Light Emitting Diodes [LED (4)] for multi-colour illumination of the dial (2).

Still another object of the invention is to develop a light guide (1) of about 5 mm thickness at center and about 2 mm at its periphery.

Still another object of the invention is to develop a light guide (1) having bottom surface as angular surface with slope of about 5 degrees.

Still another object of the invention is to develop a method for illuminating the dial (2) background for uniform illumination.

STATEMENT OF THE INVENTION

Accordingly the invention relates to a solid light guide (1) for uniform illumination of dial (2) having, a flat top surface for placing the dial (2), an angular bottom surface for reflecting light beams, and Printed Circuit Board [PCB (3)] assembly space at center of the angular bottom surface; a dial (2) background luminous system comprising solid light guide (1) for uniform illumination of dial (2) having, a flat top face for placing the dial (2), an angular bottom surface for reflecting light beams, Printed Circuit Board assembly space at center of the angular bottom surface; and printed circuit board [PCB (3)] having Light Emitting Diodes [LED (4)] for emitting light beams for illuminating the dial (2); and a method for uniform illumination of dial (2) comprises steps of, emitting light beams from light emitting diodes, and reflecting the emitted light through angular bottom surface of light guide (1) for uniform illumination of the dial (2).

DETAILED DESCRIPTION OF THE INVENTION

The present invention is in relation to a solid light guide (1) for uniform illumination of dial (2) having, a flat top surface for placing the dial (2), an angular bottom surface for reflecting light beams, and Printed Circuit Board [PCB (3)] assembly space at center of the angular bottom surface.

In yet another embodiment of the present invention the light guide (1) is matt finished for reflecting the light beams. In still another embodiment of the present invention the light guide (1) is transparent and is preferably made of acrylic plastic material.

In still another embodiment of the present invention the light guide (1) has a thickness of about 5 mm at center and about 2 mm at its circumference.

In still another embodiment of the present invention the bottom angular surface of the light guide (1) has slope of about 5°.

In still another embodiment of the present invention the light guide (1) has a cut-out for

Liquid Crystal Display (LCD) mounting at its bottom semicircle segment.

In still another embodiment of the present invention the top surface of the light guide (1) has pointer axle hole at center surrounded by two dial (2) mounting pinches placed 180° apart.

In still another embodiment of the present invention the light guide (1) has system mounting counter holes extending from the top surface to the bottom surface.

In still another embodiment of the present invention the light guide (1 ) has system mounting pinches (Ic) at its angular bottom surface.

In still another embodiment of the present invention the light guide (1) has PCB mounting pinches (Ib) inside the PCB mounting assembly space (2a) extending from the top surface to the angular bottom surface.

The present invention is in relation a dial (2) background luminous system comprising solid light guide (1 ) for uniform illumination of dial (2) having, a flat top face for placing the dial (2), an angular bottom surface for reflecting light beams, Printed Circuit Board PCB assembly mounting space (2a) at center of the angular bottom surface; and printed circuit board [PCB (3)] having Light Emitting Diodes [LED (4)] for emitting light beams for illuminating the dial (2).

In yet another embodiment of the present invention the light guide (1) is matt finished for reflecting the light beams. In still another embodiment of the present invention the light guide (1) is transparent and is preferably made of plastic material.

In still another embodiment of the present invention the light guide (1) has a thickness of about 5 mm at center and about 2 mm at its circumferential end.

Liquid Crystal Display (LCD) mounting at its bottom semicircle segment.

In still another embodiment of the present invention the top face of the light guide (1) has pointer axle hole (Ie) at center surrounded by two dial mounting pinches (Ia) placed 180° apart.

In still another embodiment of the present invention the light guide (1) has system mounting counter holes (Id) extending from the top face to the bottom face.

In still another embodiment of the present invention the light guide (1) has system mounting pinches (Ic) at its angular bottom surface.

In still another embodiment of the present invention the light guide (1) has PCB mounting pinches (Ib) inside the PCB mounting assembly mounting space (2a) extending from the top surface to the angular bottom surface.

In still another embodiment of the present invention the PCB (3) is inserted into the PCB assembly mounting space (2a) of the light guide (1) and heat sealed with PCB mounting pinches (I b) for preventing the PCB (3) from coming out of the light guide (I)-

In still another embodiment of the present invention the light emitting diodes (4) are preferably 5 in number, mounted onto the PCB (3) and are miniature type LEDs (4) of cuboidal in shape. In still another embodiment of the present invention rectangular face of the LEDs (4) facing outwards emits light beams of multi-colours for illuminating the dial (2).

The present invention is in relation to a method for uniform illumination of dial (2) comprises steps of, emitting light beams from light emitting diodes, and reflecting the emitted light through angular bottom surface of light guide (1) for uniform illumination of the dial (2).

In yet another embodiment of the present invention the light emitting diodes (4) emits multi-colour light beams for illumination.

In still another embodiment of the present invention the light beams enter the light guide (1) from its PCB assembly mounting space (2a) in side ways direction.

Figure 1 illustrates section view of a light guide with interior space for reflection of light beams emitted from LEDs. Here the light beams emitted from the LEDs will directly hit the dial background; this raises a problem of spot illumination of the dial. The light guide will have an interior space for the light beams reflection. This space within the light guide will increase the problem of space within the system that is the space occupied by the light guide is more.

Figure 2 illustrates the assembly sequence of the system, wherein the dial (2) is mounted onto the light guide (1) and the PCB (3) with LEDs (4) is mounted into the light guide (1). The light guide (1) here is a solid section light guide (1) wherein there is no interior space in the light guide (1) the light beams emitted from the LEDs (4) of PCB (3) will reflect within the light guide (1) and these will help us in creating uniform illumination of the dial (2).

Figure 3 (a) illustrates the top view of the light guide (1) wherein the system mounting counter holes (Id), pointer hole (Ie) at the center, dial (2) mounting pinches adjacent exterior to the pointer hole (Ie), and the cut-out for liquid crystal display (LCD) with logo illuminating projection (If). The system mounting counter holes (Id) made on the light guide (1) is used to assemble the light guide (1) on to the instrument cluster or indicating instrument using screws. The pointer hole (Ie) is made at center for pointer axle to pass through the light guide (1). The dial mounting pinches (Ia) of the light guide (1) helps in mounting the dial (2) onto the light guide (1) wherein, these dial mounting pinches (Ia) prevents the angular misalignment of the dial (2) with respect to the light guide (1) and keeps the dial (2) always in desired position.

3 (b) illustrates the side view of the light guide (1) wherein the thickness of the light guide (1) is of about 5mm at center and at periphery the thickness is about 2 mm with the slope of angular bottom surface is 5 degrees.

Figure 4(a) illustrates the bottom view of the light guide (1) wherein the angular bottom surface has PCB Assembly mounting space (2a), system mounting pinches (Ic) and PCB mounting pinches (I b). The PCB Assembly mounting space (2a) is the space provided for placing the PCB (3) with the LEDs (4). This PCB (3) assembly is aligned with the PCB mounting pinches (Ib) before mounting in to the space of the light guide (1). The PCB mounting pinches (Ib) are then heat sealed which will prevent the PCB (3) assembly from coming out of the light guide (1). The light guide (1) has the system mounting pinches (Ic) which will help the light guide (1) assembly having the dial (2) on top, PCB (3) assembly at its bottom inner space or PCB Assembly mounting space (2a) to mount onto the instrument cluster.

4 (b) illustrates the cross section view of the light guide (1), wherein the light guide (1) is a solid section having PCB mounting pinches (Ib), PCB assembly mounting space (2a), and system mounting pinches (Ic) at its angular bottom surface and dial mounting pinches (Ia), system mounting counter holes (Id) extending from top surface to the angular bottom surface and a pointer axle hole (Ie) at center. The angular bottom surface has a slope of about 5 degrees with respect to horizontal.

Figure 5 (a) illustrates the top view of the dial (2) of the instrument cluster system. The dial (2) on top of the light guide (1) is illuminated by the reflecting light beams emitted from the light emitting diodes LEDs (4) which are mounted onto the PCB (3) assembly. The LEDs (4) emits the light beams in side rectangular surface wherein the rest all the faces of the LEDs (4) are blocked. The emitted light from the LEDs (4) enter the light guide (1) for reflection within the light guide (1). This reflection within the light guide (1) will increase the intensity of the light beams and in turn increases the brightness of the background of the dial (2) uniformly.

5 (b) illustrates the section view of the light guide (1) showing the reflection of light beams within the light guide (I). The light beams emitted from the LEDs (4) of the PCB (3) will enter the light guide (1) in side way direction at an angle of about 120 degrees. These light beams will hit the angular bottom surface of the light guide (1). The surfaces of the light guides (1) are given with the fine matt finish which will increase the reflecting property of the light guide (1) and hence reduces the loss of light beams from the light guide (1). The reflected light beams will hit the dial (2) background for uniform illumination.

Figure 6 illustrates the reflection of the emitted light beams inside the light guide (1) for uniform illumination. The dial (2) is uniformly illuminated by the emitted light from the LEDs (4). These LEDs (4) is miniature in size and are able to emit multi-color. The light beams emitted from the LEDs (4) enter the light for reflection in a direction wherein the beams should hit the angular bottom surface of the light guide (1). These light beams will reflect back through the fine matt finished surface and increases the light beam intensity within the light guide (1). Hence the dial (2) background is illuminated uniformly using the light guide (1) which is a solid section in nature.

Solid-section

Light guide (1) which is in solid portion without any group of flutes is known as solid- section. This light guide (1) consists of an angular cross sectional wall thickness in circular shape. This type of solid-section light guide (1) is used to reduce spot light while illuminating condition and to gain a uniform distribution of the output light. The backlight unit has circle shape; An LED attached at the side face of the light guide (1) plate is used as a light source.

Close view of the microstructure distribution:

The microstructure consists of a lot of pyramidal elements that works as lens to control the light propagation inside the LGP. Microstructure elements are aligned to form concentric arcs. Each element is oriented toward the LED light source.

Overview of the backlight unit with an LED in the circular portion of light guide:

A microstructure is formed on a bottom face of a light guide (1) plate (LGP). Five LED's attached in circular path with soldering in the PCB (3) of the light guide plate illuminates the whole emitting area of the backlight unit. Scheme of the microstructure distribution:

The microstructure elements are aligned to form concentric arcs, orientation of each element can be different to control light propagation inside the LGP.

Shapes and distributions of microstructure elements:

Initial shape and distribution of the microstructure. Dimensions and orientation of the elements are designed to vary while their coordinates are fixed. Initial microstructure and luminance distributions. All geometrical properties of the microstructure elements are exactly the same. The luminance near the LED is high and the output light is not uniform.

Final microstructure and luminance distributions: Sizes of the microstructure elements near the LED are reduced according to the distance from the LED. Uniformity of the output luminance distribution has been improved.

Matt finish

It is the Texture finish for light guide (1); it is used to increase the scatter light. The reflection is based on the below mentioned texture size.

Different texture size: coarse, medium, fine

Course texture finish: The brightness is low and uniform.

Medium: The brightness is moderate.

Fine: The brightness is very high and uniform. Surface texture (finish) on precision-machined parts is dependent upon three factors.

First, the material specified must be able to produce the surface texture required.

Second, the surface texture is dependent upon the tools and process used to produce the surface. Third, the surface texture specified should be consistent with the function of or use for the surface.

Industrial Applicability

The disclosed solid light guide (1) for uniform illumination of dial (2) having, a flat top surface for placing the dial, an angular bottom surface for reflecting light beams, and Printed Circuit Board assembly mounting space (2a) at center of the angular bottom surface.

The dial (2) is placed onto the solid light guide (1) for uniform illumination finds potential application in any instrument cluster or any indicating instrument. The disclosed light guide (1) finds particular applicability in instrument clusters used in automobiles.

Other industrial advantages includes, eliminates the space occupied by the light guide (1) having interior space for reflection of light beams and non desirable spot light illumination on the dial. This further makes the system of instrument cluster having solid light guide (1) as simple in construction, robust in design and provides the commercial need of uniform illumination.

It will be apparent to those skilled in the art that various modifications and variations can be made to the light guide (1 ) of the present disclosure. Other embodiments of light guide (1) will be apparent to those skilled in the art from consideration of the specification of the light guide (1) disclosed herein. It is intended that the specification and multiple alternatives be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents.

Claims

We claim:

1. A solid light guide (1) for uniform illumination of dial (2) having, a. a flat top surface for placing the dial, b. an angular bottom surface for reflecting light beams, and c. Printed Circuit Board (PCB) assembly mounting space (2a) at center of the angular bottom surface.

2. The solid light guide (1) as claimed in claim 1, wherein the light guide (1) is matt finished for reflecting the light beams.

3. The solid light guide (1) as claimed in claim 1, wherein the light guide (1) is transparent and is preferably made of acrylic plastic material.

4. The solid light guide (1) as claimed in claim 1, wherein the light guide (1) has a thickness of about 5 mm at center and about 2 mm at its circumference.

5. The solid light guide (1) as claimed in claim 1, wherein the bottom angular surface of the light guide (1) has slope of about 5°.

6. The solid light guide (1) as claimed in claim 1, wherein said light guide (1) has a cut-out for Liquid Crystal Display (LCD) mounting at its bottom semicircle segment.

7. The solid light guide (1) as claimed in claim 1, wherein the top surface of the light guide (1) has pointer axle hole (Ie) at center surrounded by two dial mounting pinches (Ia) placed 180° apart.

8. The solid light guide (1) as claimed in claim 1, wherein the light guide (1) has system mounting counter holes (Id) extending from the top surface to the bottom surface.

9. The solid light guide (1) as claimed in claim 1, wherein the light guide (1) has system mounting pinches (Ic) at its angular bottom surface.

10. The solid light guide (1) as claimed in claim 1, wherein the light guide (1) has PCB mounting pinches (Ib) inside the PCB assembly mounting space (2a) extending from the top surface to the angular bottom surface.

1 1. A dial (2) background luminous system comprising a. solid light guide (1) for uniform illumination of dial (2) having, i. a flat top face for placing the dial (2), ii. an angular bottom surface for reflecting light beams, iii. Printed Circuit Board (PCB) assembly mounting space (2a) at center of the angular bottom surface; and b. printed circuit board (PCB (3)) having Light Emitting Diodes [LED (4)] for emitting light beams for illuminating the dial (2).

12. The dial (2) background luminous system as claimed in claim 11, wherein the light guide (1) is matt finished for reflecting the light beams.

13. The dial (2) background luminous system as claimed in claim 11 , wherein the light guide (1) is transparent and is preferably made of acrylic plastic material.

14. The dial (2) background luminous system as claimed in claim 11, wherein the light guide (1) has a thickness of about 5 mm at center and about 2 mm at its circumferential end.

15. The dial (2) background luminous system as claimed in claim 11, wherein the bottom angular surface of the light guide (1) has slope of about 5°.

16. The dial (2) background luminous system as claimed in claim 11, wherein said light guide (1) has a cut-out for Liquid Crystal Display (LCD) mounting at its bottom semicircle segment.

17. The dial (2) background luminous system as claimed in claim 1 1, wherein the top face of the light guide (1) has pointer axle hole (Ie) at center surrounded by two dial mounting pinches (Ia) placed 180° apart.

18. The dial (2) background luminous system as claimed in claim 1 1, wherein the light guide (1) has system mounting counter holes (Id) extending from the top face to the bottom face.

19. The dial (2) background luminous system as claimed in claim 1 1, wherein the light guide (1) has system mounting pinches (Ic) at its angular bottom surface.

20. The dial (2) background luminous system as claimed in claim 11, wherein the light guide (1) has PCB mounting pinches (Ib) inside the PCB assembly mounting space (2a) extending from the top surface to the angular bottom surface.

21. The dial (2) background luminous system as claimed in claim 1 1, wherein the PCB (3) is inserted into the PCB assembly mounting space (2a) of the light guide (1) and heat sealed with PCB mounting pinches (Ib) for preventing the PCB (3) from coming out of the light guide (1).

22. The dial (2) background luminous system as claimed in claim 1 1, wherein the light emitting diodes (4) are preferably 5 in number, mounted onto the PCB (3) and are miniature type LEDs (4) of cuboidal in shape.

23. The dial (2) background luminous system as claimed in claim 1 1, wherein rectangular face of the LEDs (4) facing outwards emits light beams of multi-colours for illuminating the dial (2).

24. A method for uniform illumination of dial (2) comprises steps of, a. emitting light beams from light emitting diodes (4), and b. reflecting the emitted light through angular bottom surface of light guide (1) for uniform illumination of the dial (2).

25. The method as claimed in claim 24, wherein the light emitting diodes (4) emits multi-colour light beams for illumination.

26. The method as claimed in claim 24, wherein the light beams enter the light guide (1) from its PCB assembly mounting space (2a) in side ways direction.