Color wheel unit

Abstract

A color wheel unit includes: a color wheel including a plurality of color regions; a motor adapted to rotate the color wheel and including a rotor with a rotary shaft; and a case adapted to house the color wheel and the motor and including a heat radiating means disposed at the outer surface of the case. In the color wheel unit, a first protrusion structure extending radially outwardly is disposed at the outer circumferential surface of the rotor, and a second protrusion structure extending radially inwardly is disposed at the inner surface of the case, wherein the projection area of the second protrusion structure on the plane orthogonal to the rotary shaft of the rotor is overlapped at least partly with the projection area of the first protrusion structure on the plane orthogonal to the rotary shaft of the rotor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partly cross sectional side view of a color wheel unit according to one embodiment of the present invention;

FIG. 2 is a side view of a color wheel assembly incorporated in the color wheel unit of FIG. 1;

FIG. 3 is a rear view of the color wheel assembly seen when a color wheel case is cross-sectioned along line B-B in FIG. 1;

FIG. 4 is a schematic view of a conventional projection display device;

FIG. 5 is a perspective view of a conventional color wheel unit;

FIG. 6 is a partly cross sectional view of the conventional color wheel units of FIG. 5; and

FIG. 7 is a side view of a conventional color wheel assembly.

DETAILED DESCRIPTION OF THE INVENTION

An exemplary embodiment of the present invention will be described with reference to the accompanying drawings.

Referring to FIG. 1, a color wheel unit 30 includes a color wheel 3, a motor 10, and a case 42 to house the color wheel 3 and the motor 10. The color wheel 3 is composed of a plurality of sector-shaped color filter segments put together in a disk configuration. Each of the color filter segments is structured such that a dielectric multilayer film to transmit a light having a specific (red/green/blue) wavelength is formed on a sector-shaped substrate made of a light transmittable material such as optical glass.

Referring also to FIG. 2, the motor 10 is an outer rotor brushless DC motor principally including a stator core (not shown), and a rotor 31 having a rotor magnet opposing the outer circumference of the stator core, wherein a flange 33 is fixedly attached to a hub (not shown) which is fixed to a rotary shaft (not shown) of the rotor 31. The color filter segments constituting the color wheel 3 are fixedly attached to the motor 10 such that the color filter segments are adhesively fixed onto the flange 33 and then a support member 34 is placed on the color filter segments and engaged with the hub on the motor 10 so as to press the color filter segments toward the flange 33, whereby a color wheel assembly 20 is built up in which the color wheel 3 is fixedly coupled to the motor 10 so as to rotate with the rotation of the motor 10.

Referring additionally to FIG. 3, the motor 10 includes a first protrusion structure which is composed of four first blades 32 arranged equiangularly on the outer circumferential surface of the rotor 31 so as to extend radially outwardly. The first blades 32 are oriented to slant with respect to a plane orthogonal to the rotary shaft (its center is indicated by A in FIGS. 1 to 3) of the rotor 31.

The case 42 is composed of a base section 36 having a double cylindrical framework with major and minor cylinder portions and a lid section 39, and the color wheel unit 30 is built up such that the color wheel assembly 20 is fixed to the base section 36 with a boss 35 of the motor 10 engaging with a circular bottom wall 36b of the base section 36 and then the lid section 39 is attached to the base section 36.

On the case 42, radiation fins 37 are provided at the outer surface of the base section 36 (specifically, the circular bottom wall 36b in FIG. 1), and a plurality of openings 40 and 41 for allowing airflow are formed respectively at an annular rear wall 36a of the base section 36 opposing the color wheel 3 and at the circular bottom wall 36b of the base section 36.

The axial direction position and dimension of the first blades 32 disposed on the outer circumferential surface of the rotor 31 of the motor 10 are determined such that a certain clearance distance is provided from the first blades 32 to the inner surface of the circular bottom wall 36b of the base section 36 as shown in FIG. 1 when the color wheel assembly 20 is fixed to the base section 36 of the case 42. In an open space defined by the aforementioned clearance distance, a second protrusion structure is provided which is composed of four second blades 38 arranged equiangularly on the inner circumferential surface of the minor cylinder portion of the base section 36 so as to extend radially inwardly toward the outer circumferential surface of the rotor 31. The second blades 38 are oriented also to slant with respect to the plane orthogonal to the rotary shaft of the rotor 31.

Since the radial distal end (outermost portion) of the first blades 32 of the first protrusion structure provided at the outer circumferential surface of the rotor 31 is positioned farther from the shaft center A than the radial distal end (innermost portion) of the second blades 38 of the second protrusion structure provided at the inner circumferential surface of the minor cylinder portion of the base section 36 as shown in FIG. 3, when the first blades 32 revolve with the rotation of the rotor 31, a portion of each first blade 32 becomes located behind each second blade 38, whereby the projection area of the first blade 32 on the plane orthogonal to the rotary shaft of the rotor 31 becomes partly overlapped with the projection area of the second blade 38 on the aforementioned same plane.

In the present embodiment, the circumferential dimension of the second blade 38 is slightly smaller than the circumferential distance between adjacent two of the four first blades 32 disposed equiangularly, and therefore it can happen that the first blade 32 is positioned so as not to overlap with any portion of the second blade 38 (refer to FIG. 3). In the present embodiment, the color wheel assembly 20 is preferably fixedly attached to the base section 36 of the case 42 at a disposition position shown in FIG. 3.

In the present embodiment, the rotor 31 is made of a metallic material such as aluminum alloy, the first blades 32 are formed integrally with the rotor 31 by aluminum die-casting, or like methods, the base section 36 and the lid section 39 of the case 42 are made of a metallic material such as aluminum alloy, and the radiation fins 37 and the second blades 38 are formed integrally with the base section 36 by aluminum die-casting, or like methods.

Description will now be made on the operation of the color wheel unit 30 described above, and also the structure of the color wheel unit 30 will be further described in conjunction with the operation. While the following description will refer to the directions (or positions), left and right, with respect to the color wheel unit 30 in line with FIG. 1, the directions do not limit the actual disposition arrangement.

While the color wheel unit 30 operates, the first blades 32 of the first protrusion structure are caused to oppose portions of the second blades 38 of the second protrusion structure with respect to the direction along the rotary shaft of the rotor 31 except at the time of the disposition state shown in FIG. 3, whereby heat at the rotor 31 can be conducted to the case 42 via the first blades 32 and the second blades 38 thus enhancing the heat conduction performance from inside the case 42 to the outer surface of the case 42, and so the heat generated inside the case 42 can be efficiently released into the outside air from the radiation fins 37 provided on the outer surface of the case 42.

Referring again to FIG. 1, on the assumption that the rotor 31 rotates in a direction indicated by an arrow C (see FIGS. 1 and 3), the first blades 32 are each slanted relative to the rotation direction of the rotor 31 such that a leading edge 32a is positioned leftward and a trailing edge 32b is positioned rightward in the figure, that is to say, the first blades 32 are each oriented at a certain inclination angle with respect to the direction of an airflow moving from the leading edge 32a toward the trailing edge 32b, whereby a positive pressure is generated at the right side of each of the first blades 32 while a negative pressure is generated at the left side of each of the first blades 32, thereby causing an airflow including an axial flow component directed rightward in the figure (from the color wheel 3 toward the circular bottom wall 36b).

Accordingly, the plurality of openings 40 formed at the annular rear wall 36a of the base section 36 of the case 42 function mainly as air inlets into the inside of the case 42 while the plurality of openings 41 formed at the circular bottom wall 36b of the base section 36 function mainly as air outlets from the inside of the case 42, whereby air taken inside the case 42 through the openings 40 is caused to flow along the color wheel 3, then axially toward the circular bottom wall 36b, and to exit the case 42 through the openings 41. With the airflow caused as described above, heat generated inside the case 42 can be efficiently released outside.

In this connection, the first blades 32 of the first protrusion structure provided at the outer circumferential surface of the rotor 31 and the second blades 38 of the second protrusion structure provided at the inner surface of the case 42 not only constitute heat transmission paths from the inside of the case 42 to the outer surface of the case 42 as described above but also function as radiation fins for dissipating the heat of the rotor 31 and the heat of the case 42, respectively, thus increasing the heat radiation area of the color wheel unit 30 and also effectively cooling the color wheel unit 30 from inside the case 42.

Further, the first blades 32 are each configured such that the left side (negative pressure side) surface is curved convex, whereby the thickness at the leading edge 32a and the trailing edge 32b is smaller than the thickness at the middle portion, thus forming an airfoil profile. As a result, the amount of airflow in the axial direction is increased, and at the same time the separation flow of the airflow along the surface of the blade 32 is reduced lowering the wind noises.

The second blades 38 are also preferably configured to form an airfoil profile so that the wind noises attributable to the airflow running along the cascade of the second blades 38 can be reduced. The orientation of the second blades 38 is determined appropriately in consideration of the characteristics of the airflow generated by the rotor vanes and the stator vanes constituted respectively by the first blades 32 to move round with the rotation of the rotor 31 and the second blades 38 fixed to the case 42.

The present invention has been explained with reference to the exemplary embodiment but is not limited to the configuration described above. For example, the color wheel unit of the present invention may incorporate a color wheel assembly in which a color wheel fixedly attached to the rotary shaft of the rotor 31 is, as described in the explanation of the conventional projection display device shown in FIG. 4, structured such that a plurality of sector-shaped dielectric multilayer filters adapted to transmit respective lights having red, green and blue wavelengths are formed on a disk-like plate made of a light transmittable material, such as optical glass.

Also, the first blades 32 provided at the outer circumferential surface of the rotor 31 are formed integrally with the rotor 31 in the embodiment but may alternatively be produced discretely are fixedly attached to the rotor 31 by an appropriate fixing means or method, for example such that the first blades 32 are engaged in holes or slits formed in the rotor 31, or it may be arranged such that a mounting ring provided integrally with the first blades 32 is engagingly attached to the rotor 31. The alternative arrangements allow the first blades 32 to be made of a resin material, but a metallic material is preferable in view of radiation performance.

In the same way, the radiation fins 37 provided at the outer surface of the case 42 and the second blades 38 provided at the inner surface of the case 42 may be produced separately from the case 42 and fixedly attached to the case 42 by an appropriate means or method.

Further, the first and second blades 32 and 38 are not limited in number, size, shape, orientation angle and position to the configuration of the embodiment described with reference to FIGS. 1 to 3, but those design and layout particulars are to be appropriately determined according to the heat transference between the first blades 32 and the second blades 38, to the respective heat radiation performances of the first and second blades 32 and 38, and to the desired characteristic of the airflow generated by the revolving of the first blades 32. In consideration of the above conditions, the first blades 32 and/or the second blades 38 may be made of a thin sheet of a uniform thickness arranged in an appropriate profile, or made of a flat plate without curving.

In addition, the first blades 32 and/or the second blades 38 may be arranged in multiple arrays. For example, the first blades 32 may be arranged in two arrays with respect to the axial direction, and the second blades 38 may be arranged in one array between the two arrays of the first blades 32.

And, in the embodiment described above, the first and second blades 32 and 38 are configured and arranged to generate an airflow for which the openings 40 formed at the annular rear wall 36a of the case 42 function as air inlets while the openings 41 formed at the circular bottom wall 36b of the case 42 function as air outlets, but the first and second blades 32 and 38 may alternatively be configured and arranged to generate an airflow for which the openings 40 function as air outlets and the openings 41 function as air inlets.

Claims

1. A color wheel unit comprising: a color wheel comprising a plurality of color regions;a motor to rotate the color wheel, the motor comprising a rotor with a rotary shaft, wherein a first protrusion structure extending radially outwardly is disposed at an outer circumferential surface of the rotor; anda case to house the color wheel and the motor, the case comprising a heat radiating means disposed at an outer surface of the case, wherein a second protrusion structure extending radially inwardly is disposed at an inner surface of the case, and a projection area of the second protrusion structure on a plane orthogonal to the rotary shaft of the rotor is overlapped at least partly with a projection area of the first protrusion structure on the plane orthogonal to the rotary shaft of the rotor.

2. A color wheel unit according to claim 1, wherein the first and second protrusion structures each comprise a surface oriented slant with respect to the plane orthogonal to the rotary shaft of the rotor.

3. A color wheel unit according to claim 1, wherein the case comprises a first opening functioning as an air inlet for an airflow generated by revolving of the first protrusion structure, and a second opening functioning as an air outlet for the airflow.

4. A color wheel unit according to claim 2, wherein the first and second protrusion structures each comprise a plurality of blades.

5. A color wheel unit according to claim 2, wherein the case comprises a first opening functioning as an air inlet for an airflow generated by revolving of the first protrusion structure, and a second opening functioning as an air outlet for the airflow.