Patent Application
20100052496
This application claims the benefit of Japanese Patent Application No. 2008-223391, filed Sep. 1, 2008.
The present invention relates to a discharge lamp with a reflective mirror that is used in a projector.
Currently, an alternating-current (AC) discharge lamp with a reflective mirror (hereinafter, referred to as a lamp), particularly when combined with an elliptical reflective mirror, has an increase in the temperature of the electrode on the opening part side of the elliptical reflective mirror due to the reflected light from the optical system. Consequently, a temperature difference develops between the two electrodes, and the normal halogen cycle no longer functions. As a result, sometimes, the electrode tip on the opening part side of the elliptical reflective mirror erodes, and the lamp characteristics cannot be maintained. In addition, the electrode shape deforms and an offset of the arc spot is produced by the erosion of the electrode. Generally, for an AC high-pressure mercury lamp, spot offset in each cycle gives the impression of “flickering.”
As a remedy, PCT Application PCT/IB95/00392 shows a method that adds a pulse superimposed on the current waveform in each cycle, increases the temperature of the electrode tip, and optimizes the halogen cycle. However, in the proposed method, a constant current pulse is always generated, and the halogen cycle is optimized, conversely, substantial damage to the electrode is possible.
The present invention solves the above problems and provides a discharge lamp with a reflective mirror which suppresses the temperature increase in the electrode on the opening part side of the reflective mirror and has little erosion of the electrode.
The discharge lamp with a reflective mirror related to the present invention comprises a reflective mirror having an opening part and a neck part opposite the opening part, an F electrode welded to an F molybdenum foil which is welded to an F lead wire, an R electrode welded to an R molybdenum foil which is welded to an R lead wire, and a light discharge tube having a roughly spherical light discharge part in the center which seals in mercury, wherein each of the F electrode and the R electrode has a coil having the specified wire diameter and the specified number of windings wound around the end of a core wire having the specified wire diameter, where the core wires are positioned to place the F electrode opposite the R electrode, next, the tips of the F electrode and the R electrode are melted to form melt electrodes having a curved surface, furthermore, electrode tips are formed on the tips of the melt electrodes by aging, and the shapes of the F electrode and the R electrode before forming the melt electrodes satisfy any one of conditions (a) to (c) shown below or any combination of conditions (a) to (c) shown below: (a) let the diameter of the core wire of the F electrode be d1f, and the diameter of the core wire of the R electrode be d1r, then d1f>1.2×d1r; (b) let the wire diameter of the coil of the F electrode be d2f, and the wire diameter of the coil of the R electrode be d2r, then d2f>1.2×d2r; (c) let the number of windings of the coil of the F electrode be nf, and the number of windings of the coil of the R electrode be nr, then nf>1.2×nr.
In the discharge lamp with a reflective mirror related to the present invention, the surface area of the F electrode can be larger than the surface area of the R electrode, and the temperature increase of the F electrode on the opening part side of the reflective mirror caused by the reflected light from the optical system of the projector can be suppressed by having the shapes of the F electrode and the R electrode before forming the melt electrodes satisfy any one of conditions (a) to (c) shown below or any combination of conditions (a) to (c) shown below. Thus, the halogen cycle functions normally, and the lamp characteristics can be maintained.
(a) Let the diameter of the core wire of the F electrode be d1f, and the diameter of the core wire of the R electrode be dir, then d1f>1.2×d1r;
(b) let the wire diameter of the coil of the F electrode be d2f, and the wire diameter of the coil of the R electrode be d2r, then d2f>1.2×d2r;
(c) let the number of windings of the coil of the F electrode be nf, and the number of windings of the coil of the R electrode be nr, then nf>1.2×nr.
The embodiment features the electrodes positioned inside of the light discharge tube (1). Therefore, the entire structure of the discharge lamp with a reflective mirror (100) is briefly explained.
The structure of the discharge lamp with a reflective mirror (100) is explained based on
The light discharge tube (1) has an F electrode (12) welded to an F molybdenum foil (15) which is welded to an F lead wire (17), an R electrode (13) welded to an R molybdenum foil (16) which is welded to an R lead wire (18), and a roughly spherical light discharge part (11) sealing mercury (14) in the center (center part).
The elliptical reflective mirror (3) forms a portion of a rotational elliptical shape. The material of the elliptical reflective mirror (3) is glass.
The light discharge tube (1) positions the F electrode (12) on the opening part (3a) side and the R electrode (13) on the neck part (3b) side of the elliptical reflective mirror (3).
The structure incorporates the light discharge tube (1) in the elliptical reflective mirror (3) so that the center axis of the light discharge tube (1) is aligned to the center axis which connects the opening part (3a) and the neck part (3b) of the elliptical reflective mirror (3), and the center of the light discharge part (11) coincides with the focal point of the elliptical reflective mirror (3).
The ceramic ring (2) has a roughly cylindrical shape with an outer peripheral surface (2a) and an inner peripheral surface (2b). The ceramic ring (2) provides a fitting (22) which fits onto the edge on the side fixed to the elliptical reflective mirror (3) to cover the neck part (3b) of the elliptical reflective mirror (3).
The ceramic ring (2) provides a contact part (21) which places the edge in the axial direction of the neck part (3b) of the elliptical reflective mirror (3) in contact with the edge on the side fixed to the elliptical reflective mirror (3). The contact part (21) is roughly orthogonal to the direction of the center line of the light discharge tube (1).
The ceramic ring (2) is fixed to the elliptical reflective mirror (3) by cement (4a). The main component of the cement (4a) is silica.
Furthermore, the ceramic ring (2) provides a cut-out part (23) cut from the fitting (22) on the edge on the side fixed to the elliptical reflective mirror (3). The cut-out part (23) functions as a vent hole. In the discharge lamp with a reflective mirror (100), the cut-out part (23) is open in the state where the ceramic ring (2) is fixed to the elliptical reflective mirror (3). If the light discharge tube (1) explodes for some reason, a mesh (7) is provided on the cut-out part (23), as shown in
The assembly procedure of the discharge lamp with a reflective mirror (100) is briefly explained.
First, the ceramic ring (2) is fixed to the elliptical reflective mirror (3). The fitting (22) of the ceramic ring (2) is fitted onto the neck part (3b) of the elliptical reflective mirror (3) to cover the neck part (3b), and the contact part (21) of the ceramic ring (2) is placed in contact with the edge in the axial direction of the neck part (3b).
In this state, the elliptical reflective mirror (3) and the ceramic ring (2) are bonded by the cement (4a). The main component of the cement (4a) is silica.
Next, the light discharge tube (1) is inserted inside of the elliptical reflective mirror (3) and the ceramic ring (2). Then, while the light discharge tube (1) is lit, the position is adjusted in three dimensions in the light discharge tube (1) (referred to as the axis adjustment).
Thus, the center axis of the light discharge tube (1) is aligned with the center axis connecting the opening part (3a) and the neck part (3b) of the elliptical reflective mirror (3), and the center of the light discharge part (11) becomes the focal point of the elliptical reflective mirror (3).
Then, the cement (4b) is injected into the gap between the light discharge tube (1) and the inner peripheral surface (2b) of the ceramic ring (2) and dries (
Furthermore, the light discharge tube (1) which projects from the ceramic ring (2) is cut off. The R lead wire (18) is not cut.
The R lead wire (18) and a trigger wire (9) are crimped by a crimping member (not shown, made of metal). The R lead wire (18) and the trigger wire (9) pass through the ring-shaped crimping member, and the ring-shaped crimping member appears to be crushed and crimped.
The crimping member which crimps the R lead wire (18) and the trigger wire (9) is welded to a first terminal (6).
The cap (5) covers the ceramic ring (2). There is a cut-off part (not shown) in the side wall of the cap (5), and the first terminal (6) is fitted in the cut-off part.
The F lead wire (17) on the opening part (3a) side of the elliptical reflective mirror (3) of the light discharge tube (1) is connected to a second terminal (31) installed on the outer peripheral surface of the elliptical reflective mirror (3).
The first terminal (6) and the second terminal (31) are connected to a power supply.
Next, the structures of the F electrode (12) and the R electrode (13) are explained. Although the sizes thereof differ, the basic structures of the F electrode (12) and the R electrode (13) are the same. Therefore, the F electrode (12) is explained.
As shown in
For example, the F electrode (12) shown in
The material of the core wire (12a) is tungsten. The diameter (d1f) of the core wire (12a) is approximately 0.5 mm.
The material of the coil (12b) is tungsten. The wire diameter (d2f) of the coil (12b) is approximately 0.25 to 0.3 mm.
The F electrode (12) (the same applies to the R electrode (13)) has the shape in
The melt electrode (12c) is formed by a current flowing in the F electrode (12) and the R electrode (13) to melt the tungsten. The melting point of tungsten is approximately 3407° C.
The melt electrode (12c) may be formed before the F electrode (12) and the R electrode (13) are incorporated into the light discharge tube (1), or after the F electrode (12) and the R electrode (13) are incorporated into the light discharge tube (1).
Furthermore, after the lamp is completed, when aging (the lamp is lit), an electrode tip (12d) smaller than the melt electrode (12c) is formed on the tip of the melt electrode (12c) of the F electrode (12) (the same applies to the R electrode (13)).
The dimensions of the electrode tip (12d) are, for example, approximately 0.1 to 0.2 mm for the length in the axial direction and the maximum diameter.
The F electrode (12) and the R electrode (13) in this embodiment have shapes before forming the melt electrodes (12c, 13c) which satisfy any one of conditions (a) to (c) shown below or any combination of conditions (a) to (c) shown below:
As shown in
The distance L between the F electrode (12) and the R electrode (13) is, for example, approximately 1.0 mm. The dimensions of the electrode tip (12d) are, for example, approximately 0.1 to 0.2 mm for the length in the axial direction and the maximum diameter. Consequently, when the electrode tip (12d) of the F electrode (12) erodes, the distance L between the F electrode (12) and the R electrode (13) changes to approximately 1.1 to 1.2 mm
By making the surface area of the F electrode (12) larger than the surface area of the R electrode (13), a temperature increase in the F electrode (12) on the opening part side of the elliptical reflective mirror (3) due to the reflected light from the optical system of the projector is suppressed. The resulting temperature difference between the two electrodes is smaller compared to the case of the same surface area of the F electrode (12) as the surface area of the R electrode (13); the halogen cycle functions normally; and the erosion of the F electrode (12) can be suppressed.
The halogen cycle refers to when the tungsten, which is the electrode material vaporized from the electrode, for example, returns to the electrode tip and maintains the electrode shape by increasing the electrode tip to the appropriate temperature by a current waveform in every cycle.
Next, the results of an examination of the energy of the reflected light returned from the optical system of the projector to the lamp by a simulation are presented.
The front glass (30) is inclined at the angle θ1 with respect to the line orthogonal to the center wire (100a) of the discharge lamp with a reflective mirror (100). For example, the angle θ1 is no more than 10°. At the front glass (30), the light discharged from the light discharge tube (1) is fully transmitted (example).
A UV/IR filter (40) (ultraviolet light/infrared light filter) which reflects ultraviolet light and infrared light is provided in front of the front glass (30). The UV/IR filter (40) is inclined at the angle θ2 with respect to the line orthogonal to the center line (100a) of the discharge lamp with a reflective mirror (100). For example, the angle θ2 is 10°.
The UV/IR filter (40) is inclined at the angle θ2 because the ultraviolet light/infrared light returned from the UV/IR filter (40) misses the discharge lamp with a reflective mirror (100), and the energy returned to the light discharge tube (1) is smaller than when not inclined.
A color wheel (50) is provided in front of the UV/IR filter (40). The light is radiated forward from the color wheel (50). However, energy also returns from the color wheel (50).
As is clear from
(1) the energy returned to the F electrode (12) (ratio [%] to the total discharge energy) is approximately 6.5 to 8 [%];
(2) the energy returned to the R electrode (13) (ratio [%] to the total discharge energy) is approximately 1 to 2 [%].
Compared to the R electrode (13), the energy returned to the F electrode (12) is overwhelmingly large. Therefore, when the temperature of the F electrode (12) increases and a temperature difference is produced with the R electrode (13), sometimes, the electrode tip (12d) of the F electrode (12) erodes, and the lamp characteristics can no longer be maintained. In addition, the electrode shape deforms and an offset of the arc spot is produced by the erosion of the electrode tip (12d). For an AC discharge lamp with a reflective mirror (100), the spot offset in each cycle gives the impression of “flickering.”
An example of the temperature data of the F electrode (12) and the R electrode (13) in the above simulation (structure in
(1) Temperature of the F electrode (12): approximately 2900° C.
(2) Temperature of the R electrode (13): approximately 2800° C.
A difference between the two of approximately 100° C. is seen. Although these are only reference data, an example of the temperature data of the F electrode (12) and the R electrode (13) when the discharge lamp with a reflective mirror (100) is removed from the projector, the data are as follows.
(1) Temperature of the F electrode (12): approximately 2815 to 2820° C.
(2) Temperature of the R electrode (13): approximately 2811 to 2817° C.
Almost no difference between the two is seen. Thus, the temperature increase of the F electrode (12) on the opening part side of the elliptical reflective mirror (3) by the reflected light from the optical system of the projector when the discharge lamp with a reflective mirror (100) is incorporated into the projector is understood. A temperature difference between the F electrode (12) and the R electrode (13) is produced, and the normal halogen cycle no longer functions. As a result, sometimes, the electrode tip (12d) of the F electrode (12) on the opening part side of the elliptical reflective mirror (3) erodes, and the lamp characteristics can no longer be maintained.
As described above, according to the embodiment, the shapes of the F electrode (12) and the R electrode (13) before forming the melt electrodes (12c,13c) satisfy any one of conditions (a) to (c) shown below or any combination of conditions (a) to (c) shown below:
From the above, the surface area of the F electrode (12) can be greater than the surface area of the R electrode (13), and the temperature increase of the F electrode (12) on the opening part side of the elliptical reflective mirror (3) caused by the reflected light from the optical system of the projector can be suppressed. Thus, the halogen cycle functions normally, and the lamp characteristics can be maintained.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2008-223391 | Sep 2008 | JP | national |
