Measuring instrument

A measuring instrument includes a light source, a dial plate with a scale design, and a light guide member. The light guide member includes a receiving portion for receiving the light from the light source, and a flat plate portion for irradiating the light transmitted from the receiving portion to the dial plate. The flat plane portion includes a thick wall section located close to the scale design, and a thin wall section extending from the thick wall section in a direction away from the light source. The thick wall section is thicker than the thick wall section. A boundary end face connected to a region of the thick wall section and a region of the thin wall section in the second face of the light guide member reflects the light transmitted in the light guide member from the light receiving portion to irradiate the image design.

TECHNICAL FIELD

The present invention relates to a measuring instrument.

BACKGROUND ART

FIG. 5is an exploded perspective view showing a schematic structure of a conventional measuring instrument for a vehicle which is disclosed in Patent Literature 1,FIG. 6is a plan view showing a light guide member in the measuring instrument which is taken out therefrom,FIG. 7is a sectional view as seen in a direction of arrow marks VII-VII inFIG. 6, andFIG. 8is a sectional view as seen in a direction of arrow marks VIII-VIII inFIG. 6.

This measuring instrument for a vehicle is a combination meter in which a speed meter section, a fuel meter section, a water temperature meter section, a gear position section, etc. are integrated, and includes, as shown inFIG. 5, a body case110, a light guide member120which is provided at a surface side of the body case110, a dial plate130which is arranged at a surface side of this light guide member120, and a pointer140which rotates on the surface of this dial plate130. Moreover, this meter has a movement150which is arranged at a back face side of the body case110for rotating the pointer140, a circuit board160, a light source L which is mounted on the circuit board160, and so on.

In the speed meter section of the dial plate130, there are provided a scale design131which is formed in a circular arrangement along a rotation direction of the pointer140, a warning design133, and so on. These designs131,133are so adapted as to be lit up with an illuminating light from the back face side.

The light guide member120mainly illuminates the scale design131of the dial plate130. As shown in detail inFIG. 6, the light guide member120has a flat plate portion121in a shape of a semicircular disc corresponding to the speed meter section of the dial plate130, a pointer shaft insertion hole125arranged at a center of the semicircular shape, light receiving portions122in a shape of conical wall arranged near the pointer shaft insertion hole125, which will be described below, a through hole123provided corresponding to the warning design133, three triangular holes126arranged between the pointer shaft insertion hole125and the light receiving portions122, and light guide paths127interposed between two of the three triangular holes126thereby to guide the light which has been reflected by the light receiving portions122to a reflecting face129around the pointer shaft insertion hole125. The reflecting face129around the pointer shaft insertion hole125performs a function of lighting up the pointer140, by introducing an incident light to a light receptive face in a base part of the pointer140, as its light path is shown inFIG. 8.

The light receiving portion122is a part for performing a function of receiving a light from a spot-like light source L (hereinafter referred to as a point light source=LED) which is arranged so as to be opposed to the light receiving face122aat a back face side thereof, and radially diffusing the light toward the flat plate portion121. As shown inFIG. 7, the light receiving portion122includes a projected part in a truncated conical shape which is projected toward the back face side of the flat plate portion121, and a recess in a conical shape is concentrically formed inside the truncated conical shape to be dented from a surface side of the flat plate portion121. In this manner, the light receiving face122ais formed on a top face of the projected part in the truncated conical shape, and reflecting faces122b,122c,122d,122eare formed on conical faces outside and inside the projected part. In this prior art, an angle θ1of an inside conical face and an angle θ2of an outside conical face are set to be stepwise varied in such a manner that inclination angles of the reflecting faces122b,122c,122d,122emay approach to that of the flat face plate121, as approaching to the flat plate portion121.

Moreover, as shown inFIG. 5, the body case110is provided with a light guide member containing part111for containing the light guide member120at a surface side thereof. Dented parts112for containing the light receiving portions122, a triangular tube part113to be fitted to the through hole123in the light guide member120, and a pointer shaft hole115for passing the pointer shaft therethrough are formed in the light guide member containing part111. Then, the back face of the light guide member120is contained in the light guide member containing part111, the light receiving portions122of the light guide member120are contained in the dented parts112, and the triangular tube part113to which a light of another point light source is introduced is fitted into the through hole123in the light guide member120.

Because the measuring instrument is constructed as described above, the light R1from the point light source L enters into the light guide member120from the light receiving face122aof the light receiving portion122, as shown inFIG. 8, and then, radially guided to the flat plate portion121sequentially repeating reflections on the reflecting faces122b,122c,122d,122e, whereby the scale design131of the dial plate130is illuminated from the back face side.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

The above described conventional light guide member120is provided with the light receiving portion122in a shape of conical wall, and the light from the point light source L is radially diffused from the light receiving portion122toward the flat plate portion121. However, there are some cases where unevenness in brightness and luminance is observed particularly in a peripheral edge part of the flat plate portion121, and in such cases, it has been desired to improve the light guide member. Also, it is desired that some characters at specified positions in the scale design131are brightly illuminated to enhance an appearance of the measuring instrument, and there has been a request to improve the light guide member so that such desire can be realized.

The invention has been made in view of the above described circumstances, and it is an object of the invention to provide a light guide member of a measuring instrument for a vehicle, in which brightness of a peripheral edge part of the light guide member which is particularly important in case of illuminating a scale design can be sufficiently enhanced, and at the same time, unevenness of brightness and luminance can be improved, and to provide the measuring instrument for a vehicle employing the light guide member.

Solution to Problem

In order to achieve the above object, according to the present invention, there is provided a measuring instrument, comprising

a light source;

a dial plate which has a scale design; and

a light guide member which is provided between the light source and the dial plate, and guides a light received from the light source to the dial plate, wherein the light guide member having a first face that faces to the dial plate and a second face that is opposite to the first face,

wherein the light guide member includes a light receiving portion for receiving the light from the light source, and a flat plate portion for irradiating the light transmitted from the light receiving portion to the dial plate;

wherein the scale design is arranged in a circular shape around the light source in view from an opposite side of the light source with respect to the dial plate;

Wherein the flat plane portion includes a thick wall section that is positioned at a vicinity of the scale design, and a thin wall section that is provided so as to be extended from the thick wall section in a direction away from the light source, the thick wall section is greater in thickness than the thin wall section in a direction perpendicular to the dial place; and

Wherein a boundary end face which is connected to a region of the thick wall section and a region of the thin wall section in the second face of the light guide member reflects the light transmitted in the light guide member from the light receiving portion to irradiate the scale design.

Preferably, a plane which is defined by the region of the thin wall section in the second face of the light guide member and the boundary end face has a substantially triangular shape. An apex of the substantially triangular shape is set at one position of a peripheral edge of the thick wall section, and a bottom side of the substantially triangular shape is set at a peripheral edge of the thin wail section.

Preferably, a hole in a substantially triangular shape is formed in vicinity of the light receiving portion. One apex of the triangular shape of the hole is positioned between a side of the triangular shape connecting two other apexes and the light source.

Preferably, a hole is formed in the thick wall section of the light guide member, the hole passing through from the first face to the second face of the light guide member. A side face which connects the first face and the second face for defining the hole reflects the light transmitted in the light guide member from the light receiving portion to irradiate the scale design.

According to the light guide member of the measuring instrument having the above structure, the light from the point light source can be radially diffused toward the flat plate portion by the light receiving portion. Moreover, a part of the light diffused in the flat plate portion can be guided to the thin wall section, and at the same time, the remaining light is reflected by the reflecting face defined by the boundary end face, whereby the light can be guided toward the designs on the dial plate which is positioned near the thick wall section. In short, it is possible to increase an amount of the light around the thick wall section by the reflecting face defined by the boundary end face, while an amount of the light in the thin wall section is reduced. As the results, according to specification of the light guide member, a position to be brilliantly illuminated can be easily and brilliantly illuminated, and sensuous unevenness of brightness and luminance can be improved. Moreover, it is possible to regulate unevenness of luminance, by changing a thickness of the thin wall section and an angle of the reflecting face defined by the boundary end face.

According to the light guide member of the measuring instrument having the above structure, it is possible to adjust the brightness around the thick wall section, by appropriately changing the shape of the boundary end face.

According to the light guide member of the measuring instrument for a vehicle having the above structure, it is possible to adjust the brightness around the thick wall section, by appropriately changing the shape of the boundary end face.

Advantageous Effects of Invention

According to the invention, it is possible to sufficiently enhance the brightness in the peripheral edge part of the light guide member which is important particularly in case of illuminating the scale design, and at the same time, it is possible to improve unevenness of brightness and luminance.

The invention has been briefly described, hereinabove. Details of the invention will be further made clear, by reading the “Description of Embodiments” section which will be described below, referring to the attached drawings.

DESCRIPTION OF EMBODIMENTS

Now, a preferred embodiment according to the invention will be described in detail, referring to the drawings.

FIG. 1is a plan view showing a structure of a light guide member as seen from a surface side (a side where a dial plate of a measuring instrument for a vehicle, which will be described below, is positioned),FIG. 2Ais a sectional view as seen in a direction of arrow marks IIa-IIa inFIG. 1,FIG. 2Bis a sectional view as seen in a direction of arrow marks IIb-IIb inFIG. 1,FIG. 3Ais a perspective view of the structure of the light guide member as seen from a back face side (a side where a light source of the measuring instrument for a vehicle, which will be described below, is positioned),FIG. 3Bis an enlarged view of an encircled part IIIb inFIG. 3A,FIGS. 4A and 4Bare views showing a manner how a light advances in case where a triangular hole is not present.FIG. 4Ais a perspective view of the structure of the light guide member as seen from the surface side, andFIG. 4Bis an enlarged view of an encircled part IVb inFIG. 4A.

The measuring instrument for a vehicle to which a light guide member20is applied is a speed meter section of a combination meter as shown inFIG. 5. The measuring instrument for a vehicle includes a case (not particularly shown), a dial plate130(SeeFIG. 2) provided at a surface side of the case and having a scale design131(SeeFIG. 3) which is arranged in a circular shape around a light source L, a pointer which rotates around the light source L for indicating the scale design131in a circular arrangement at the surface side of the dial plate130, a light guide member which is provided between the case and the dial plate130, a circuit board which is arranged at a back face side of the case, and a light source L which is mounted on the circuit board for entering an illumination light to a light receiving face of the light guide member through an opening formed in the case. In this description, the light guide member20in the embodiment of the invention, which will be described below, is used as the light guide member, and an LED is used as the spot-like light source (a point light source).

As shown inFIGS. 1 and 2, the light guide member20is positioned between the light source L and the dial plate130, and guides a light received from the light source L to the back face of the dial plate130. The light guide member20includes light receiving portions22for receiving the light from the point light source L which is arranged so as to be opposed to a light receiving face22aat a back face side of the light guide member itself, and a flat plate portion21in a circular shape which is arranged near a back face of the scale design131of the dial plate130in a circular arrangement. The light transmitted from the point light source L to the light receiving portions22is radially diffused toward the flat plate portion21, and further, the light traversing the flat plate portion21is irradiated to the back face of the dial plate130. A face of the flat plate portion21in contact with the back face of the dial plate is formed as a delustered face, for example, for enabling the light to be easily diffused.

The light receiving portion22is arranged on an inner peripheral part of the flat plate portion21in a circular shape. As shown inFIG. 2, The light receiving portion22has a projected part in a truncated conical shape projected toward the back face side of the flat plate portion21, and a recess in a conical shape concentrically formed inside the truncated conical shape from a surface side of the flat plate portion21. The light receiving face22ais formed on a top face of the projected part in the truncated conical shape, and reflecting faces22b,22d,22e,22fare formed on conical faces outside and inside the recess. In this embodiment, the outside conical face (the reflecting face22b) is at a constant angle, but an angle of the inside conical face (the reflecting faces22d,22e,22f) is stepwise varied so as to gradually approach to an angle of the flat plate portion21.

As shown inFIG. 1, a plurality of the light receiving portions22each having the above described structure are provided on an inner periphery of the flat plate portion21in the circular shape, at an interval in a circumferential direction. These light receiving portions22are formed by cutting off those regions of the flat plate portion21in the circular shape which are positioned at the inner peripheral side toward the center, and planes of the regions which have been cut off serve as the reflecting faces22d,22e,22f.

Because the light receiving portion22having the above described structure is formed in the light guide member20, the light from the point light source L is received by the light receiving face22aof the light receiving portion22, and radially guided to the flat plate portion21, while being repeatedly reflected by the reflecting faces22b,22d,22e,22f. In this manner, the scale design131of the dial plate130can be illuminated from the back face side.

In this light guide member20, as shown inFIG. 1andFIG. 2A, cut-outs25in a planar shape are formed in a peripheral edge area of the flat plate portion21, by cutting off the back face of the flat plate portion21toward the peripheral edge area. Consequently, the flat plate portion21has thick wall sections25qwhich are positioned near the inner periphery of the flat plate portion21, and thin wall sections25phaving a thinner wall thickness than the thick wall sections and positioned near the outer periphery of the flat plate portion21. The thick wall sections25qare positioned near the scale design131of the dial plate130, while the thin wall sections25pare formed so as to extend from the thick wall sections25qin a direction away from the point light source L.

Because the thin wall section25pand the thick wall section25qare different in thickness from each other, an inclined face is formed in a boundary which connects a back face of the thin wall section25pand a back face of the thick wall section25q. This inclined face (sometimes referred to as a boundary end face25a) serves as a reflecting face for reflecting the light which has been transmitted from the light receiving portion22to the thick wall section25qof the flat plate portion21. Inclination or a shape of the boundary end face25ais appropriately designed so that the light reflected by the reflecting face may be favorably irradiated to the scale design. For example, in this embodiment, a plane including the thin wall section25pand the boundary end face25awhich are formed by the cut-out25in the planar shape has a substantially triangular shape, setting an apex at one position of a peripheral edge of the thick wall section25q, and setting a base at a peripheral edge of the thin wall section25p. The boundary end face25ain the triangular shape serves as the reflecting face. In this embodiment, a plurality of the cut-outs25as described above are provided on the outer periphery of the flat plate portion21at an interval in the circumferential direction.

Moreover, triangular holes26,27are formed in the flat plate portion21. Inner faces which define the holes26,27serve as reflecting faces for changing a direction of the light which is transmitted through the flat plate portion21to other directions. In this case, the hole26is formed in a shape of a substantially triangular pyramid in the flat plate portion21in such a manner that one apex of a bottom face of the hole26in a triangular shape which is formed on the same plane as the back face of the thick wall section25qso as to be positioned between a bottom side connecting the remaining two apexes of the bottom face of the hole26and the point light source L. Moreover, the hole27in a substantially triangular shape is formed near the light receiving portion22in such a manner that one apex of the triangular shape of the hole27is positioned between a side connecting the remaining two apexes and the light source L corresponding to the light receiving portion22.

According to the light guide member20having the above described structure, the light R from the point light source L can be radially diffused to the flat plate portion21by the light receiving portion22. Particularly, because a plurality of the light receiving portions22are provided at an interval in the circumferential direction of the flat plate portion21in the circular shape, the light can be evenly supplied to an entirety of the flat plate portion21in the circular shape. In addition, because those areas of the light receiving portions22positioned at the inner peripheral side of the flat plate portion21are cut out, the light receiving portions22are formed in such a shape that only a part of an angular range in the circumferential direction is left, and the planes which have been cut serve as the reflecting faces. Therefore, most of the light which is reflected toward the inner peripheral side of the flat plate portion21can be reflected again to the peripheral edge area of the flat plate portion21, and hence, it is possible to increase brightness of an object part to be illuminated, while useless light is decreased.

Moreover, a part of the light which is diffused in the flat plate portion21can be guided to the thin wall sections25p, as shown inFIG. 2A, and the remaining light is reflected by the reflecting face defined by the boundary end face25a, as shown inFIGS. 3A and 3B, whereby the light can be guided toward the design131.

It is possible to increase an amount of the light in the thick wall section25qby the reflecting face defined by the boundary end face25a, while an amount of the light to be transmitted to the thin wall section25pis reduced. As the results, according to specification (shape, quality of material) of the light guide member20, a position to be brilliantly illuminated (for example, the position where the design is provided) can be effectively brightly lit up, and sensuous unevenness of brightness and luminance can be improved. Moreover, it is possible to regulate unevenness of luminance, by changing a thickness of the thin wall section25pand an angle of the reflecting face defined by the boundary end face25a.

Further, according to this light guide member20, it is possible to adjust the brightness at a desired position of the dial plate, by appropriately designing a shape of the planar cut-out25(a triangular shape in this embodiment), and by adjusting the amount of the light which is reflected by the reflecting face, according to the shape of the cut-out25.

Still further, according to this light guide member20, it is possible to convert the light which is advancing in a radial direction inside the light guide member20to other directions, due to presence of the holes26,27. For example, in case where the holes are not present, as shown inFIG. 4, the light from the light receiving portion22advances only to the peripheral edge area of the flat plate portion21. On the other hand, in case where the hole26is present as shown inFIG. 3, the light can be converted to other directions, because the inner face of the hole26serves as the reflecting face, and hence, the required scale design can be brightly illuminated.

Particularly, because the holes26,27are formed in a substantially triangular shape in section, the light can be reflected in a plurality of directions, and hence, the required design can be brightly illuminated.

Therefore, by incorporating this light guide member20into the measuring instrument, it is possible to brightly illuminate specified portions of the dial plate130which are likely to be dark, and hence, it is possible to improve unevenness of the brightness and luminance, and to enhance an appearance.

It is to be noted that the invention is not limited to the above described embodiment, but various modifications, improvements and so on can be appropriately made. Further, material, shape, size, number, positions to be arranged and so on of the respective constituent elements in the above described embodiment are not limited, but can be optionally selected, provided that the invention can be achieved.

The present application is based on Japanese Patent Application No. 2008-295911 filed on Nov. 19, 2008, the contents of which are incorporated herein for reference.

REFERENCE SIGNS LIST