JP5203574B2 - High pressure discharge lamp lighting device - Google Patents

Description

  The present invention relates to a lighting device for a high-pressure discharge lamp, a high-pressure discharge lamp device, a projection-type image display device, and a high-pressure discharge lamp lighting method, and more particularly to a high-pressure discharge lamp lighting device that turns on the high-pressure discharge lamp by passing an alternating current.

Among the high-pressure discharge lamps, the high-pressure mercury lamp is used as a light source for a projection-type image display device such as a liquid crystal projector, and has attracted attention in recent years.
In general, a high-pressure mercury lamp has a pair of electrodes opposed to each other in an arc tube in which a halogen substance, a rare gas, and mercury are sealed. In the high pressure discharge lamp lighting device, a predetermined high voltage pulse voltage is applied to the high pressure discharge lamp to break the insulation between the electrodes, and then an alternating current having a predetermined fixed period is supplied to light the lamp.

The lamp life of such a high-pressure mercury lamp is about 2000 to 3000 hours.
The electrodes used in this type of high-pressure mercury lamp have a short distance between the electrodes of, for example, 0.5 mm to 2.0 mm, and the temperature during lighting is very high. Therefore, the tip of the electrode melts during lighting. At this time, when the same electrode having a tungsten coil attached to the tip of a tungsten electrode shaft is used as the electrode, the tip is melted irregularly and the shape of the electrode is not stable. As a result, the distance between the electrodes may be difficult to stabilize. Therefore, if the tip of the electrode is made into a substantially hemispherical or substantially cone-shaped lump in advance, the molten state during lighting can be stabilized. As an example of such an electrode, a tungsten rod formed into a desired shape by machining is known (see, for example, Patent Document 2).
JP-A-4-303592 JP 2002-175890 A

Conventionally, liquid crystal projectors have been mainly used in school classrooms and conference rooms, but in recent years, they are becoming popular.
The liquid crystal projector uses light generated by causing discharge between short electrodes, that is, a point light source, as the light source. For this reason, the stability of the image depends on the stability of the discharge. For this reason, in order to ensure the discharge stability of the discharge lamp, the following lamp configuration and lighting method have been conventionally used.

  In general, high-pressure mercury lamps for liquid crystal projectors currently used contain a halogen substance in addition to mercury as an enclosure. This is to prevent the blackening of the lamp that occurs when tungsten, which is the material of the electrode, evaporates during lighting by using the halogen cycle action of the enclosed halogen substance. This halogen cycle action is very effective in preventing the blackening of the lamp, but at the same time, tungsten transferred to the tip of the electrode is deposited by this action and forms protrusions on the electrode. JP-A-2001-312997 and JP-A-2003-338394 disclose that the growth of this protrusion can be controlled by changing the frequency of the alternating current supplied. According to this method, the distance between the electrodes is shortened by forming appropriate protrusions, and the luminance is stabilized by using a point light source.

  Japanese Patent Laid-Open No. 2003-338394 discloses that protrusion growth can be suppressed by changing the frequency of an alternating current to be supplied with respect to protrusion growth that occurs in the initial period of 100 to 500 hours. . By this method, excessive growth of protrusions occurring in the first 100 to 500 hours at the beginning of the life can be suppressed, and luminance can be stabilized. That is, a method has been adopted in which the discharge voltage is detected, feedback control is performed based on the voltage change, and the electrode tip is repaired.

  However, in recent years, new problems have arisen when the use range of liquid crystal projectors is used as displays for home theaters and the like that can realize television screens and large screens. Projectors mainly used in school classrooms and conference rooms have many still images, and their usage time is at most several hours a day. On the other hand, when it is used as a television display or a home theater, a moving image display is the center and it is continuously used. For this reason, it is premised on long-time use that cannot be compared with conventional use. Furthermore, television images and images displayed in home theaters are more demanding than color images and subtle changes in brightness compared to computer images. For this reason, the lamp is required to be stable for a long time. As a result, the lifespan of liquid crystal projectors that have been mainly used in classrooms and conference rooms in conventional schools, which is inadequate from 2000 hours to 3000 hours, is required to be several times that of conventional lamps. Moreover, extremely stable color reproduction and brightness have been demanded during this long lifetime.

  However, when these conventional lighting methods are used as a display such as a home theater capable of realizing a television screen and a large screen, the above-mentioned long life (for example, 6000 hours) and stable color reproduction and brightness cannot be obtained. As a result of analyzing the cause, the following was clarified. At the electrode tip of the lamp, the growth of the protrusions is noticeable in the early stage of driving. However, in the subsequent 2000 to 3000 hours, the decrease progresses more slowly than the growth of the protrusions, and the electrode interval gradually increases. For this reason, the discharge area is enlarged, and the luminance in the optical device is lowered. In the conventional lamp lighting method, the discharge voltage is detected and control is performed by changing the frequency of the supplied AC current. In this process, the change in the discharge voltage is gradual, and this control method works effectively. do not do. In addition, since the electrical characteristics of the lamp gradually change with the lapse of the driving time, the optimum conditions for controlling the growth and reduction of the protrusions also change. For these reasons, it has been difficult to maintain the electrode shape at the start of lamp use sufficiently in the control method in which control is performed under the same drive frequency conditions in the time period from the initial driving of the lamp to 2000 hours or 3000 hours. . In particular, an electrode cut out from a tungsten rod as described above (cut-out electrode) among electrodes may be inferior in heat dissipation compared to an electrode in which a tungsten electrode coil is similarly attached to a tungsten electrode shaft. Therefore, during lighting, the temperature of the electrode is excessively increased, and the amount of tungsten, which is an electrode material, is scattered, which makes it difficult to control the formation of protrusions. However, it is conceivable to increase the electrode and increase the surface area and mass to avoid the above problem. However, the increase in the size of the electrode leads to the increase in the size of the lamp. It is unsuitable.

  Furthermore, there is stability against color reproduction of the displayed image and subtle changes in brightness. As described above, a display such as a home theater capable of realizing a television screen and a large screen requires stability for a long time. As a result of analysis on this problem, it was found that maintaining the shape of the electrode tip is necessary to maintain stability. The light emission center of the light source is located between the electrodes of the lamp. The brightness and color reproduction of the projector depends on the size of the light emission center, and the position is also important in relation to the optical axis of the optical system. As a result, if the shape of the tip of the electrode is maintained, stability against color reproduction of the image and subtle changes in brightness can be maintained.

  The present invention can improve the life characteristics determined by a decrease in luminance even when a cut-out electrode is used as an electrode, and can maintain stability against color reproduction over a lifetime and subtle changes in brightness. An object of the present invention is to provide a high pressure discharge lamp lighting device, a high pressure discharge lamp device, a projection type image display device, and a high pressure discharge lamp lighting method.

  In order to achieve the above object, a high pressure discharge lamp lighting device according to the present invention has an arc tube in which a halogen substance is enclosed and a pair of electrodes are arranged, and the tip of the electrode is cut out. A lighting circuit that is formed into a substantially pyramid shape by processing, and that supplies an alternating current to a high-pressure mercury lamp that has a projection formed on the tip portion of the substantially cone-shaped lamp, A high-pressure mercury lamp and a high-pressure mercury lamp, comprising: frequency control means for changing the frequency of the alternating current without depending on operation data that changes with the lighting elapsed time of the high-pressure mercury lamp.

Here, the apex of the “substantially pyramid shape” in the present invention may be sharply pointed, visually rounded, or truncated (for example, a truncated cone or a truncated pyramid). Also good. In addition, the term “substantially” as used in the present invention means not only that the shape is a true cone but also a case where the shape is not a true cone but is substantially a cone. .
The “projection” referred to in the present invention refers to a high-pressure discharge lamp that is formed during the aging of the high-pressure discharge lamp, particularly during the aging of the manufacturing process, and in the initial lighting of the finished product (within 100 hours of lighting elapsed time). In addition, the “operation data that changes with the elapsed lighting time” in the present invention refers to the voltage value and current value of the high-pressure discharge lamp, the brightness in the optical device, the distance between the electrodes (arc length), and the temperature of the arc tube (particularly the lighting). It is measurable operation data that changes as the lighting time of the high-pressure discharge lamp elapses, such as the temperature of the upper part of the arc tube that becomes a medium-high temperature. Further, the “machining process” in the present invention is to be interpreted in a broad sense and includes mechanical removal processes such as cutting, grinding, and polishing.

Further, the frequency control means changes the frequency regularly or irregularly for a certain period of time without depending on the operation data that changes with the lighting elapsed time of the high-pressure mercury lamp. A high-pressure mercury lamp characterized in that the control is repeated continuously or intermittently as a cycle.
Further, the frequency control means alternately repeats a change period in which the frequency is continuously changed without depending on operation data that changes with a lighting elapsed time of the high-pressure mercury lamp, and a fixed period in which the frequency is fixed. A high-pressure mercury lamp that is controlled.

Further, the frequency control means performs control to intermittently switch the frequency to at least two different values.
Furthermore, the frequency control means performs a control to constantly change the frequency regularly or irregularly without depending on operation data that changes with the lighting elapsed time of the high-pressure mercury lamp. Mercury lamp.

The high-pressure discharge lamp lighting device according to the present invention includes an arc tube in which a halogen substance is enclosed and a pair of electrodes are arranged, and the tip of the electrode is substantially conical by machining. A lighting circuit that supplies an alternating current to a high-pressure mercury lamp that has a protrusion formed on the tip portion that has a substantially conical shape and is lit.
Frequency control means for controlling the frequency of the alternating current to change regularly or irregularly for a certain period, and to repeat this intermittent period as one cycle, or to continue intermittently. High pressure mercury lamp characterized by

  The high-pressure discharge lamp lighting device according to the present invention includes an arc tube in which a halogen substance is enclosed and a pair of electrodes are arranged, and the tip of the electrode is substantially conical by machining. And a lighting circuit for supplying an alternating current to the high pressure mercury lamp having a protrusion formed on the substantially cone-shaped tip, and lighting the alternating current. A high-pressure mercury lamp, comprising: a frequency control unit that performs control to alternately repeat a change period in which a frequency is continuously changed according to a predetermined rule and a fixed period in which the frequency is fixed.

  The high-pressure discharge lamp lighting device according to the present invention includes an arc tube in which a halogen substance is enclosed and a pair of electrodes are arranged, and the tip of the electrode is substantially conical by machining. And a lighting circuit for supplying an alternating current to the high pressure mercury lamp having a protrusion formed on the substantially cone-shaped tip, and lighting the alternating current. A high-pressure mercury lamp comprising frequency control means for constantly changing the frequency according to a predetermined rule.

Furthermore, the frequency control means continuously changes the frequency during the certain period.
The frequency control means may change the frequency by switching the frequency intermittently to at least two or more values during the predetermined period.
Further, the fixed period includes a change period in which the frequency continuously changes and a fixed period in which the frequency is fixed.

Further, the frequency control means changes the frequency between a predetermined maximum frequency and a minimum frequency, and the minimum frequency is 70 Hz or more.
The high-pressure discharge lamp device according to the present invention has an arc tube in which a halogen substance is enclosed and a pair of electrodes are disposed, and the tip of the electrode is formed into a substantially conical shape by machining. A high-pressure mercury lamp having a projection formed on the substantially cone-shaped tip, and the high-pressure discharge lamp lighting device for lighting the high-pressure mercury lamp. It is characterized by having.

In addition, a projection type image display device according to the present invention includes the high-pressure discharge lamp device.
A lighting method for a high-pressure discharge lamp according to the present invention includes an arc tube in which a halogen substance is enclosed and a pair of electrodes is disposed, and the tip of the electrode is formed into a substantially conical shape by machining. And a high pressure discharge lamp lighting method in which an alternating current is supplied to a high pressure mercury lamp having a projection formed on the substantially cone-shaped tip. A high-pressure mercury lamp, a high-pressure mercury lamp, wherein the frequency of the alternating current is changed without depending on operation data that varies with the lighting elapsed time of the high-pressure mercury lamp.

Further, the frequency is changed regularly or irregularly for a certain period without depending on the operation data that changes with the lighting elapsed time of the high-pressure mercury lamp, and this constant period is defined as one cycle. It repeats automatically, or it is characterized by continuing this intermittently.
Further, the present invention is characterized by alternately repeating a change period in which the frequency continuously changes without depending on operation data that changes with the lighting elapsed time of the high-pressure discharge lamp, and a fixed period in which the frequency is fixed. To do.

Furthermore, the frequency is intermittently switched to at least two different values.
Further, the frequency is constantly changed regularly or irregularly without depending on operation data changing with the lighting elapsed time of the high-pressure discharge lamp.
Further, the lighting method of the high pressure discharge lamp according to the present invention includes an arc tube in which a halogen substance is enclosed and a pair of electrodes are arranged, and the tip of the electrode is formed into a substantially conical shape by machining. A high pressure discharge lamp lighting method in which an alternating current is supplied to a high pressure mercury lamp that is formed in a body shape and has a protrusion formed on the tip end having a substantially conical shape. The frequency of the alternating current is changed regularly or irregularly for a certain period, and this constant period is set as one cycle, and this is continuously repeated or continued intermittently. Mercury lamp.

  Further, the lighting method of the high pressure discharge lamp according to the present invention includes an arc tube in which a halogen substance is enclosed and a pair of electrodes are arranged, and the tip of the electrode is formed into a substantially conical shape by machining. A high pressure discharge lamp lighting method in which an alternating current is supplied to a high pressure mercury lamp that is formed in a body shape and has a protrusion formed on the tip end having a substantially conical shape. A high-pressure mercury lamp characterized by alternately repeating a change period in which the frequency of the alternating current is continuously changed according to a predetermined rule and a fixed period in which the frequency is fixed.

  Further, the lighting method of the high pressure discharge lamp according to the present invention includes an arc tube in which a halogen substance is enclosed and a pair of electrodes are arranged, and the tip of the electrode is formed into a substantially conical shape by machining. A high pressure discharge lamp lighting method in which an alternating current is supplied to a high pressure mercury lamp that is formed in a body shape and has a protrusion formed on the tip end having a substantially conical shape. A high-pressure mercury lamp characterized by constantly changing the frequency of the alternating current according to a predetermined rule.

According to the present invention, even when a shaved electrode is used as an electrode, the life characteristics determined by a decrease in luminance are improved, and the stability of color reproduction and subtle changes in brightness over the lifetime is maintained. It is possible to provide a high-pressure discharge lamp lighting device, a high-pressure discharge lamp device, a projection-type image display device, and a high-pressure discharge lamp lighting method that can be realized.
In addition, a change in luminance due to a change in the shape of the protrusion at the tip of the electrode during steady lighting is suppressed, and a lifetime exceeding 2000 hours to 3000 hours that cannot be achieved with a conventional lamp can be realized. Accordingly, the lifetime is limited by other factors such as a decrease in light transmittance due to white turbidity of the lamp outer tube or a decrease in light transmittance due to deformation of the lamp outer tube.

(Embodiment 1)
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
1. Configuration of High-Pressure Mercury Lamp The configuration of a high-pressure mercury lamp as an example of a high-pressure discharge lamp will be described.
FIG. 1 is a diagram showing a schematic configuration of a high-pressure mercury lamp 100 (hereinafter simply referred to as “lamp”) having a rated power of 130 W.

As shown in FIG. 1, the arc tube 101 is made of quartz glass as a constituent material of the envelope, and includes a light emitting part 101a and sealing parts 101b and 101c provided at both ends of the light emitting part 101a. Yes.
The light emitting unit 101a has a substantially spheroid shape, and inside the discharge space (light emitting space) 108, mercury 109, which is a light emitting substance, and argon (Ar), krypton (Kr), A rare gas such as xenon (Xe) and a halogen substance such as iodine (I) or bromine (Br) are enclosed. A pair of tungsten (W) electrodes 102 and 103 are disposed substantially opposite to each other inside the light emitting unit 101a.

The sealed amount of mercury 109 is set in the range of 150 to 650 mg / cm ³ per inner volume of the arc tube 101, and the sealed pressure of the rare gas during lamp cooling is set in the range of 0.01 MPa to 1 MPa.
The halogen substance has a function of performing a so-called halogen cycle action in which tungsten, which is an electrode material evaporated from the electrodes 102 and 103 due to a high temperature during lighting, is returned to the electrodes 102 and 103. In order to make the above action function effectively, the bromine encapsulation amount is preferably set in the range of 1 × 10 ⁻¹⁰ to 1 × 10 ⁻⁴ mol / cm ³ , more preferably 1 × 10 ^−9. mol / cm ³ to 1 × 10 ⁻⁵ mol / cm ³ .

The distance between the tip portions of the electrodes 102 and 103, that is, the interelectrode distance De is set in the range of 0.5 to 2.0 mm. In addition, in the electrodes 102 and 103 of the present embodiment, when the product is completed, a certain amount of protrusions 102d and 103d (see FIG. 2) are formed at the tips, so the interelectrode distance De is the protrusion 102d. , 103d shows the distance between the tips.
The electrodes 102 and 103 are electrically connected to the external molybdenum lead wires 106 and 107 via the molybdenum foils 104 and 105. The external molybdenum lead wires 106 and 107 are connected to the end surfaces of the sealing portions 101b and 101c. It is led out of the arc tube 101.

FIG. 2 is a perspective view showing an appearance of the electrode 102 according to the present embodiment.
The electrode 102 includes an electrode rod portion 102a, a tip portion 102c connected to the electrode rod portion 102a, and a coil portion 102b disposed at the tip of the electrode rod portion 102a. The tip portion 102c is formed in a substantially conical shape by machining, and a protrusion 102d is formed at the apex of the substantially conical body.

  In the example shown in FIG. 2, the apex of the “substantially conical body” is not sharply pointed but truncated (conical frustum). Further, the protrusion 102d is formed at the apex of the substantially conical body, but may be formed on the inclined surface of the approximately conical body as long as it is a position near the apex (if it can be the starting point of the arc). Good.) Moreover, if it is a cone, it is not restricted to a shape to a substantially cone, For example, a substantially pyramid may be sufficient.

The coil portion 102b is formed by winding a tungsten wire about 6 times and is in contact with the tip portion 102c. For this reason, the coil part 102b has a heat radiation effect of the tip part 102c, which becomes particularly hot during lighting.
The other electrode 103 has the same structure as that of the electrode 102, and includes an electrode rod portion 103a, a coil portion 103b, a tip portion 103c, and a protruding portion 103d (not shown).

Here, the dimension of each part of the electrode 102 will be described. The following dimensions are examples and are not limited to these.
Diameter of electrode rod portion 102a φ3 ... 0.45mm
Diameter φ2 of the bottom surface of the conical tip 102c... 1.05 mm
Diameter of the base portion at the apex of the conical tip portion 102d φ1... 0.10 mm
Height e of the conical tip 102c 1.0 mm
Length f of coil portion 102c in the longitudinal direction ... 1.8 mm
2. Configuration of Lamp Unit FIG. 3 is a partially cutaway perspective view showing the configuration of the lamp unit (high pressure mercury lamp apparatus) 200.

The lamp unit 200 includes a lamp 100, a lighting device (not shown) for lighting the lamp 100, and a concave reflecting mirror 203 as a reflector (reflecting material) that reflects light emitted from the lamp 100.
A base 201 is attached to one end of the arc tube 101 (see FIG. 1), and the lamp 100 is attached to the concave reflecting mirror 203 via a spacer 202. This attachment is adjusted so that the central axis in the longitudinal direction of the arc tube 101 and the optical axis of the concave reflecting mirror 203 are substantially parallel, and the position of the discharge arc of the lamp 100 is substantially coincident with the focal position of the concave reflecting mirror 203. It is done.

Electric power is supplied to the lead wire 107 (see FIG. 1) on the base 201 side of the lamp 100 via a terminal 204. Electric power is supplied to the other lead wire 106 through a lead wire 205 that passes through a through-hole 206 formed in the concave reflecting mirror 203 and is drawn to the outside.
3. Configuration of Lighting Device FIG. 4 is a block diagram showing a configuration of a lighting device 300 that lights the lamp 100.

As shown in the figure, the lighting device 300 includes a DC power source 302, a DC / DC converter 304, a DC / AC inverter 306, a high voltage generator 308, a control unit 310, a current detector 312, a voltage detector 314, and a programmable oscillator 316. Composed.
The DC power supply 302 includes, for example, a rectifier circuit, and generates a DC voltage from household AC 100V.

The DC / DC converter 304 supplies a direct current having a predetermined magnitude to the DC / AC inverter 306.
The DC / AC inverter 306 generates a rectangular wave alternating current having a predetermined frequency based on the control signal sent from the control unit 310 and sends it to the high voltage generator 308.
The high voltage generator 308 includes, for example, a transformer, generates a high voltage, and applies it to the lamp 100.

The control unit 310 comprehensively controls the DC / DC converter 304, the DC / AC inverter 306, and the like.
The current detector 312 detects the current of the lamp 100, and the voltage detector 314 detects the voltage of the lamp 100.
The programmable oscillator 316 generates a rectangular wave alternating current having a predetermined frequency based on a predetermined program. Control unit 310 refers to this waveform and sends a control signal to DC / AC inverter 306.

By changing the set value of the program, it is possible to change the frequency of the rectangular alternating current in a desired pattern. That is, in the present embodiment, the configuration including the control unit 310 and the programmable oscillator 316 corresponds to a frequency control unit that changes the frequency of the alternating current.
When a lighting switch (not shown) of the lamp 100 is turned on, the lighting device 300 applies a high-pressure pulse to the lamp 100. When the dielectric breakdown occurs between the electrodes of the lamp 100 and an arc discharge current starts flowing between the electrodes, the current detector 312 sends a detection signal to the control unit 310, and the lighting determination circuit in the control unit 310 “lights start”. Judging.

  After “lighting start”, control unit 310 performs constant current control until the voltage increases and reaches the rated power. And after a voltage reaches | attains a predetermined value, it transfers to constant power control. That is, the control unit 310 compares the product of the current value detected by the current detector 312 and the voltage value detected by the voltage detector 314 with the power reference value stored in the internal memory of the control unit 310. The output current of the DC / DC converter 304 is controlled so as to be constant power.

Note that a switch for communicating with a control unit 402 (see FIG. 11) provided outside the lighting device 300 is connected to the control unit 310.
4). Background to the Invention of the Present Invention In the case of using a cut-out electrode, the present invention is a rectangular wave alternating current that flows during conventional lighting in response to the problem that it is very difficult to control the protrusion formed at the tip of the electrode. Since it arrived with the consideration of the lighting test result using the method of fixing the frequency of the current and the conventional method of controlling the protrusion at the tip of the electrode, these will be described in order below.

(1) Consideration of lighting test result when frequency is fixed The inventors of the present invention set the fixed frequency of the rectangular wave alternating current that flows during the lighting of the lamp 100 to a different value, and the luminance maintenance rate of the lamp 100 and the lamp A lighting test was conducted to investigate changes in voltage over time.
This test was performed with the lamp 100 with a rated power of 130 W attached to the high-pressure mercury lamp apparatus 200 and the fixed frequency of the rectangular wave current that flows during steady lamp operation set to a value different from 85 Hz, 170 Hz, 340 Hz, and 510 Hz. It was.

FIG. 5 shows a graph of the test results. In this test, five lamps are used for each frequency, and the average value for the five lamps is drawn on the graph.
In the graph of FIG. 5, the luminance maintenance rate represents a relative value when the luminance at the beginning of lighting is 100%. This luminance is obtained based on ANSIlm measurement (ancillary measurement: the screen illuminance projected from the optical system is measured at nine points determined on the screen, and the luminous flux is calculated from the average illuminance). It was. Moreover, the graph of FIG. 5 is a semilogarithmic graph, and represents the cumulative lighting time on the horizontal axis logarithmically. This is to make it easier to grasp the dynamic change in the initial lighting stage.

  As shown in the graph of FIG. 5, in the lamp set at a fixed frequency of 85 Hz, the luminance increases considerably immediately after the start of lighting, but the luminance decreases sharply after peaking around the lighting time of 20 hours. Yes. This decrease in luminance is due to excessive growth of electrode protrusions and blackening of the inner wall of the arc tube 101 in a short time. The lamp with a fixed frequency of 85 Hz was stopped from the lighting test after the characteristic deterioration due to blackening became significant.

In the lamps with fixed frequencies set to 340 Hz and 510 Hz, the brightness decreased immediately after the start of lighting, and after 100 hours and before 1000 hours, the brightness maintenance rate was below 50%, which is the standard for lamp life. .
In a lamp with a fixed frequency of 170 Hz, although the luminance gradually increased immediately after the start of lighting, the luminance gradually decreased after reaching about 20 hours of lighting time, and the lifetime was about 3000 hours.

In the lighting test, when the tip portions of the electrodes 102 and 103 in the lamp having the longest life and the fixed frequency of 170 Hz are observed, the sizes of the protrusions 102d and 103d of the electrodes 102 and 103 change. I found.
FIG. 6 is a schematic diagram showing changes over time of the protrusions 102d and 103d of the electrodes 102 and 103 when the lamp 100 is set at a fixed frequency of 170 Hz as in the lighting method according to the prior art.

  As shown in FIG. 6A, before the lighting test is started, the protrusions 102d and 103d of the electrodes 102 and 103 are kept at an appropriate length, but as shown in FIG. After several tens of hours after the start of lighting in the initial stage, the protrusions 102d and 103d of the electrodes 102 and 103 grew excessively. Then, as shown in FIG. 6C, it was found that the protrusions 102d and 103d of the electrodes 102 and 103 almost disappeared at the late stage of life (2000 to 3000 hours). In FIG. 6C, it is schematically shown as completely disappearing.

  The reason for the excessive growth and disappearance of the protrusions 102d and 103d can be estimated as follows. That is, as described above, a halogen substance is enclosed in the arc tube 101 of the lamp 100 in order to realize a halogen cycle action. When tungsten, which is the material of the electrodes 102 and 103, evaporates during lighting, the tungsten combines with halogen, returns to the arc plasma by convection in the arc tube 101, and dissociates into positive ions. Tungsten that has become positive ions is attracted to a region centering on an arc spot that is an electric field concentration point at the tip of the electrode on the cathode phase side of the electrodes 102 and 103, and is deposited there. Next, when the electrode on the cathode phase side is inverted to the anode phase, electrons collide with the electrode tip, the temperature of the electrode tip rises, and tungsten deposited in the cathode phase evaporates again.

If the balance between deposition and evaporation is maintained, the protrusions 102d and 103d at the tips of the electrodes 102 and 103 can be maintained at an appropriate size without growing or disappearing. In other words, if this balance is not achieved, the sizes of the protrusions 102d and 103d at the tips of the electrodes 102 and 103 change.
The reason why the protrusions 102d and 103d grew excessively at the early stage of the life is considered to be that a large amount of tungsten was deposited on the protrusions 102d and 103d serving as the starting points of the arc.

The overgrowth of the protrusions 102d and 103d leads to a reduction in the interelectrode distance De. Therefore, the protrusions 102d and 103d are closer to the point light source, and the light collection efficiency when the lamp 100 is combined with the concave reflecting mirror 203 is improved and the luminance is increased.
In the lamp with a fixed frequency of 170 Hz in the lighting test [see FIG. 5B], the increase in luminance until about 20 hours after starting lighting is due to the shortened distance between the electrodes.

Since the lamp is controlled with constant power, the current value increases and the voltage value decreases as the distance between the electrodes decreases. In the lighting test, the voltage value is particularly low in the vicinity of about 20 hours after the start of lighting because the distance between the electrodes is shortened in this time zone.
Next, from the middle stage to the late stage of the life, recrystallization of the electrodes 102 and 103 starts and the composition of the electrodes 102 and 103 changes, so that evaporated tungsten is difficult to return to the tips of the electrodes 102 and 103. For this reason, the protrusions 102d and 103d are shortened and eventually disappear. Even after the protrusions 102d and 103d disappear, the tungsten at the electrode tip portions 102c and 103c continues to evaporate, so that the electrode tip portions 102c and 103c are gradually scraped.

The disappearance of the protrusions 102d and 103d leads to an increase in the interelectrode distance De (an increase in the arc length), which gradually shifts from the ideal point light source. Therefore, the lamp 100 is combined with the concave reflecting mirror 203. When the light collection efficiency is reduced, the luminance is also reduced.
In the lamp with a fixed frequency of 170 Hz in the lighting test [see FIG. 5 (b)], the luminance decreases monotonically during and after the lifetime because the tips of the electrodes 102 and 103 are shaved and the distance between the electrodes is long. It is because it became.

(2) Consideration of the method for controlling the protrusion at the electrode tip The problems of the conventional method for controlling the protrusion at the electrode tip are as follows.
First, Japanese Patent Laid-Open No. 2001-312997 discloses that the growth of protrusions is intentionally promoted by selecting the frequency of an alternating current supplied in the manufacturing stage. In this method, the distance between the electrodes is shortened by forming appropriate protrusions, and the luminance at the time of shipment can be stabilized by using a point light source. Currently used high-pressure mercury lamps are designed to actively apply the growth of electrode protrusions by the halogen cycle and concentrate the discharge arc by forming the protrusions to increase the lamp brightness. .

  Japanese Patent Application Laid-Open No. 2003-338394 discloses that the growth can be suppressed by changing the frequency of the supplied alternating current with respect to the excessive growth of the protrusions occurring from about 100 hours to 500 hours, which is the initial stage of the life. Is disclosed. By this method, excessive growth of protrusions occurring from about 100 hours to about 500 hours at the beginning of the life can be suppressed, the luminance can be stabilized, and it has been used to solve such problems.

Since the protrusion control method during the lifetime is controlled by detecting the discharge voltage of the lamp during steady driving, the change in frequency is not started unless there is a change in the discharge voltage. That is, after the electrode tip of the lamp is deformed from the initial state of the start of lamp use, the control of the frequency change is started afterwards.
In other words, the frequency change is controlled after excessive growth of the protrusions, and the control is performed by evaporating the already grown protrusions and returning them to the original state. This is a method based on repair control after the protrusions are deformed.

  As a problem of this method, it has been difficult to control effectively in the process in which the electrode protrusion of the lamp gradually decreases with the driving time. In this process, the conventional control method performs control based on the value of lamp operation data that changes over time, such as lamp voltage. However, when the detected operation data changes slowly, it becomes difficult to control effectively. Furthermore, since the electrical characteristics of the lamp change gradually with the lapse of driving time, the optimum conditions for controlling the growth and reduction of the protrusions also change. In other words, the drive frequency, control time, and other control conditions set initially for control may deviate from the optimum conditions. For these reasons, there is a problem that the protrusion control method during the lifetime cannot be effectively controlled.

In the present invention, in response to this new problem, the lamp is formed at the time of manufacturing the lamp by constantly changing the frequency of the alternating current supplied to the lamp, regardless of the operation data value of the lamp which changes as the driving time elapses. The shape of the electrode protrusion was stabilized and the life could be extended.
It has been empirically found that the optimum conditions for promoting the growth and disappearance of the protrusions at the tip of the electrode change depending on the lamp design conditions, and also change depending on the cumulative lighting time when the lamp is steadily lit. ing. In consideration of this, an experiment was attempted by constantly changing the frequency at which lighting was possible, and it was found that there was an effect of maintaining the initial shape.
5. FIG. 7 shows a rectangular wave alternating current generated by the lamp lighting device according to the present embodiment, and the upper graph shows the temporal change of the rectangular wave alternating current, The graph corresponds to the upper graph, and shows the temporal change in the frequency of the rectangular wave alternating current.

In the present embodiment, during the steady lighting of the lamp, the frequency of the rectangular wave alternating current is switched stepwise between the frequencies of 340 Hz, 255 Hz, 170 Hz, 128 Hz, and 85 Hz for each period of the rectangular wave.
When the frequency is gradually reduced from 340 Hz, which is the maximum frequency to be switched, to 85 Hz, which is the minimum frequency, the frequency is increased stepwise to 340 Hz, and this frequency switching is repeated.

As shown in FIG. 7, a cycle (cycle) at which frequency switching is repeated is referred to as a variable cycle. During lighting, the frequency switching during the variable period is always repeated. This variable period is about 50.0 ms per period.
Using the lamp lighting method according to the present invention, a lighting test was performed using the lamp 100 as described above.

FIG. 8 shows a graph of the test results. In the figure, a graph of a conventional 170 Hz frequency fixing method is also shown for convenience of comparison.
As shown in the graph of FIG. 8 (a), the variable method lighting method according to the present embodiment does not increase the luminance at the initial stage of the life unlike the conventional frequency fixing method, and from the start of lighting to 100 hours. Has a substantially constant luminance. In general, the lamp is required to have a constant luminance during its lifetime, but according to the variable method, the luminance during the lifetime can be stabilized more than before.

Then, it can be seen that in the late stage of the lifetime, the brightness has decreased more gradually than before, and a long lifetime of 6000 hours or more has been realized.
Thus, in the lighting method of the present invention, the lifetime can be extended by maintaining the balance between the above-described deposition and evaporation, so that the protrusions 102d at the tips of the electrodes 102 and 103 in the initial state of the lamp use start are provided. , 103d can be maintained for a longer time than before.

9 and 10 are tables showing the results of the luminance transition and the voltage transition in the lighting test described above, respectively.
(About switching frequency)
(1) In the present embodiment, the frequency is not directly changed between 340 Hz and 85 Hz, but there are three frequencies of 255 Hz, 170 Hz, and 128 Hz between the frequencies of 340 Hz and 85 Hz, 340 Hz, 255 Hz, It is changed stepwise to 170 Hz, 128 Hz, and 85 Hz. This is because, due to the characteristics of the lighting circuit, if the frequency is rapidly changed, the rectangular wave may be distorted. In this way, it is possible to suppress the distortion of the rectangular wave by changing the frequency stepwise.

  (2) In the present embodiment, the frequency is changed between 340 Hz and 85 Hz so as to sandwich the frequency of 170 Hz that has the longest lifetime at a fixed frequency. If the frequency is changed across 170 Hz, which is the optimum in terms of lifetime within a fixed frequency, the above-described balance between deposition and evaporation can be maintained as compared with the conventional one, and the lifetime of the lamp can be reliably increased. . Here, “optimal in terms of lifetime” means that a luminous flux having no practical problem can be obtained at the beginning of the lifetime, and that the luminous flux maintenance factor is unlikely to decrease for a long time.

Which pattern should be used to change the frequency of the rectangular wave alternating current during steady lamp operation depends on the lamp specifications (such as the arc tube volume, the composition of the substance enclosed in the tube, the distance between the electrodes, etc.) and is suitable from experiments. Can determine the correct pattern.
(3) Lower limit of frequency to be changed The minimum frequency when the lamp 100 is driven to be steadily lit can be driven from several Hz. However, when it is driven at 50 Hz or 60 Hz, which is currently used as a commercial frequency, the lighting device blinks and the projector display screen blinks with the phase change, and the display screen blinks. It becomes. In order to avoid such a problem, 60 Hz or more is required as a minimum frequency in order to avoid interference with a commercial frequency. According to the experiment, such a flashing was less noticeable when shifted by 10 Hz. Therefore, considering the margin to the maximum frequency currently used as a commercial frequency, 70 Hz or higher can be selected as a safe frequency. It has been confirmed that the protrusions at the tip of the electrode grow at this frequency.

(4) Upper limit of frequency to be changed It has been confirmed that when the 130 W lamp 100 is driven at 130 W, steady driving is possible at each of fixed frequencies of 300 Hz, 400 Hz, 500 Hz, and 550 Hz. Experiments were also performed for other power conditions, but a fixed frequency of 300 Hz to 500 Hz can be used as the maximum frequency. Even in consideration of the inherent variation of the lamp, the maximum driving frequency capable of steady driving is in the range of 300 Hz to 500 Hz. At this time, the electrode protrusions of the lamp were also evaluated. The electrode protrusions of the lamp do not grow at this frequency, and there is a tendency to decrease. This is also confirmed from the discharge voltage of the lamp. That is, this frequency is a driving frequency at which the growth of the protrusion generated at the electrode tip is the least or the distance between the electrodes is increased.

(5) The maximum frequency to be changed is preferably at least three times the minimum frequency. This is because it is considered that it is easy to maintain the distance between the electrodes appropriately by providing such a difference between the maximum and minimum frequencies.
(6) In the present embodiment, the three frequencies of 340 Hz, 170 Hz, and 85 Hz are switched and changed, but only two frequencies may be switched. In that case, in order to lengthen the period during which the distance between the electrodes is properly maintained, a larger one of the two frequencies is set to a frequency at which the tip of the electrode recedes at the initial stage of life, and The smaller frequency is preferably set to a frequency at which the tip of the electrode grows at the initial stage of life.
6). Image Display Device The lamp unit 200 including the lamp lighting device 300 according to the present invention can be applied to a projection type image display device.

FIG. 11 is a schematic diagram showing a configuration of a liquid crystal projector 400 using the above-described lamp unit 200 as an example of a projection type image display apparatus.
As shown in FIG. 11, a transmissive liquid crystal projector 400 includes a power unit 401, a control unit 402, a condenser lens 403, a transmissive color liquid crystal display panel 404, a lens unit 405 incorporating a drive motor, and a cooling unit. Fan device 406 for use.

The power supply unit 401 converts commercial AC input (100 V) into a predetermined DC voltage and supplies it to the control unit 402.
The control unit 402 displays the color image by driving the color liquid crystal display panel 404 based on the image signal input from the outside. In addition, a driving motor in the lens unit 405 is controlled to execute a focusing operation or a zoom operation.

The light emitted from the lamp unit 200 is collected by the condenser lens 403, passes through the color liquid crystal display plate 404 disposed in the middle of the optical path, and is formed on the liquid crystal display plate 404 via the lens unit 405. Is projected onto a screen outside the figure.
By using a lamp unit having a longer life than the conventional lamp unit comprising a high-pressure mercury lamp and a lighting device according to the present invention, a liquid crystal projector having a high commercial value can be provided.

Note that the lamp unit 200 including the lamp lighting device 300 according to the present invention includes a DLP (registered trademark) projector using a DMD (digital micromirror device), and a liquid crystal using other reflective liquid crystal elements. The present invention can also be applied to other projection type image display devices such as a projector.
7). Modifications As described above, the present embodiment has been described. However, the present invention is not limited to the above-described form, and can be appropriately changed without departing from the spirit of the invention.

(1) Various variations of the frequency switching pattern of the rectangular wave alternating current are conceivable. The said modification is shown in FIGS. In any figure, it is the figure made the same expression as the graph of the upper part of FIG.
The switching pattern shown in FIG. 12 is similar to the first embodiment in that when the frequency is reduced stepwise from the maximum frequency to the minimum frequency, the frequency is increased stepwise again to the maximum frequency. The frequency is changed every time. For example, in one variable cycle, the frequency is sequentially switched every half cycle from 340 Hz, 255 Hz, 170 Hz, 128 Hz, 85 Hz, 128 Hz, 170 Hz, and 255 Hz.

In the switching pattern shown in FIG. 13, a cycle in which the frequency is switched stepwise for each cycle of the rectangular wave from the maximum frequency to the minimum frequency is defined as one variable cycle. For example, one variable cycle switches the frequency to 340 Hz, 255 Hz, 170 Hz, 128 Hz, and 85 Hz for each cycle of the rectangular wave.
The switching pattern shown in FIG. 14 switches the frequency every half cycle of the rectangular wave from the maximum frequency to the minimum frequency. For example, in the variable 1 period, the frequency is sequentially switched between 340 Hz, 255 Hz, 170 Hz, 128 Hz, 85 Hz, 128 Hz, 170 Hz, and 255 Hz for each half period of the rectangular wave.

  The switching pattern shown in FIG. 15 is a cycle in which three variable frequencies of fixed periods a, b, and c with a fixed frequency every fixed time are sequentially switched as one variable cycle (one cycle). For example, the fixed frequency of the fixed period a (first period) is 340 Hz, the fixed frequency of the fixed period b (second period) is 170 Hz, and the fixed frequency of the fixed period c (third period) is 85 Hz.

Further, as shown in FIG. 15, each of the fixed periods a, b, and c has a length including a plurality of fixed frequencies, the fixed period a is 7.5 periods, and the fixed period b is 6.5 periods. The fixed period c includes 2.5 cycles.
In the switching pattern shown in FIG. 16, a cycle in which a fixed period in which the frequency is fixed every fixed time and a variable period in which the frequency is changed are alternately switched is defined as one variable cycle. For example, one variable period is composed of two periods, a fixed period in which the fixed frequency is 340 Hz, and a variable period in which the same switching as the frequency switching in the variable period shown in FIG. 13 is performed.

(2) In the present embodiment, the frequency is changed stepwise (jumping), but the frequency may be changed linearly.
A lighting device for realizing a linear change in frequency will be described. FIG. 17 is a block diagram illustrating a configuration of a lighting device 301 according to a modification. Since the lighting device 301 shown in FIG. 17 has basically the same configuration as the lighting device 300 according to the embodiment (see FIG. 4), the differences will be mainly described.

The oscillator a318 generates a modulated signal, and the oscillator b320 generates a modulated signal.
The frequency determination circuit 316 modulates the modulated signal with a modulation signal and generates a modulated rectangular wave.
The control unit 310 sends a predetermined control signal to the DC / AC inverter 306 with reference to the rectangular wave.

According to such a lighting device 301, it is possible to constantly change the frequency of the rectangular wave alternating current supplied to the lamp with a simple circuit configuration, and to finely control the change in frequency.
A known frequency modulation circuit may be used in place of the frequency determination circuit 316 and the oscillators 318 and 320.

(3) Various variations of the frequency change are possible. The said modification is shown in FIGS. In each of the graphs in FIGS. 18 to 21, the time (t) is taken on the horizontal axis and the frequency (f) is taken on the vertical axis.
(A) Regular change and irregular change The frequency may be changed regularly, that is, according to a fixed interval, or may be changed irregularly. The graph in FIG. 18 conceptually shows regular changes and irregular changes. As shown in FIG. 18, the change in the frequency in the period A ₁ whereas a regular change of the frequency in the period A ₂ is irregular. In the period A _2, to say that irregular changes, set maximum frequency and (fmax) a minimum (fmin), so that changing between the two.

(B) Intermittent change and continuous change The frequency may be changed intermittently, or may be changed continuously, that is, constantly. The graphs in FIGS. 19A and 19B conceptually show an intermittent change and a continuous change.
In the graph in FIG. 19 (a), a fixed period of frequency is followed by a fixed period of changing the frequency, and the fixed period of the frequency change continues from time to time.

On the other hand, in the graph in FIG. 19B, the frequency changes continuously.
(C) Combination of intermittent change and continuous change The period of intermittent change and the period of continuous change described in (B) above may be combined. For example, as shown in the graph in FIG. 20, the period of intermittent change and the period of continuous change may be alternately repeated.

(D) Grouping of change period and fixed period Although not particularly shown, a period in which both a period in which the frequency is continuously changed and a period in which the frequency is fixed may be grouped may be repeated as one cycle. For example, two periods of a continuously changing period and a subsequent fixed period may be grouped and handled as one cycle, and this may be repeated.

(E) Irregular repetition As shown in the graph in FIG. 21, two periods of a continuous change and a frequency fixed period may be prepared, and both periods may be irregularly repeated. That is, the order of both may not be determined in advance, and it may be undefined which period is set after a certain period.

(F) Combination with frequency change depending on operation data (discharge voltage, etc.) In the above (A) to (E), there are a period for changing the frequency without depending on the operation data and a period for fixing the frequency. Although the combination has been described, a period in which the frequency is changed depending on operation data may be used instead of the period in which the frequency is fixed.
8). Others (1) The shape of the cut electrode is not limited to the electrode 102 described above, and a cut electrode having the following shape can also be used.

FIG. 22 is a perspective view showing the appearance of the shaved electrode 122. The electrode 122 includes an electrode rod portion 122a and a tip portion 122b connected to the tip of the electrode rod portion. The tip portion 122b is composed of a cylindrical portion having a diameter larger than that of the electrode rod portion 122a and a conical portion following the cylindrical portion, and a protrusion 122d is formed near the top of the conical portion. Since the electrode 122 has a small surface area and is slightly inferior in heat dissipation as compared with the electrode 102, the shape of the protruding portion changes with time. For this reason, it is particularly effective to control the size of the protrusions by frequency modulation.
(2) In the above embodiment, the high-pressure mercury lamp in which mercury is enclosed as the luminescent material has been described as an example. However, the present invention can also be applied to other high-pressure discharge lamps such as a metal halide lamp.

  Since the high-pressure discharge lamp lighting device according to the present invention has a longer life than before, it can be applied to a liquid crystal display device or the like.

1 is a diagram showing a schematic configuration of a high-pressure mercury lamp 100. FIG. 2 is a perspective view illustrating an appearance of an electrode 102. FIG. 1 is a partially cutaway perspective view showing a configuration of a lamp unit 200 using a high-pressure mercury lamp 100. FIG. 3 is a block diagram showing a configuration of a lighting device 300. FIG. (A) is a graph which shows the relationship between the accumulation lighting time at the time of using the conventional system in a lighting test, and a luminance maintenance factor.

(B) is a graph which shows the relationship between the cumulative lighting time of a lighting test result at the time of using a conventional system in a lighting test, and a lamp voltage.
It is a schematic diagram which shows the time-dependent change of the protrusion of an electrode in the conventional lamp | ramp with a fixed frequency of 170 Hz, (a) shows the shape of the protrusion of the electrode before a lighting start, (b) is the electrode of the initial stage of a lifetime. The shape of the protrusion is shown, and (c) shows the shape of the protrusion of the electrode at the later stage of the lifetime. The upper graph shows the temporal change in the waveform of the rectangular alternating current. The lower graph corresponds to the upper graph and shows the temporal change in the frequency of the rectangular wave alternating current. (A) is a graph which shows the relationship between the cumulative lighting time of the lighting test result using the conventional system, and a luminance maintenance factor.

(B) is a graph showing the relationship between the cumulative lighting time of the lighting test result using the conventional method and the lamp voltage;
It is a table | surface which shows the result of the brightness transition in a lighting test. It is a table | surface which shows the result of the voltage transition in a lighting test. It is a block diagram which shows the structure of a liquid crystal projector. It is a figure which shows the time change of the waveform of the rectangular wave alternating current which concerns on one modification. It is a figure which shows the time change of the waveform of the rectangular wave alternating current which concerns on one modification. It is a figure which shows the time change of the waveform of the rectangular wave alternating current which concerns on one modification. It is a figure which shows the time change of the waveform of the rectangular wave alternating current which concerns on one modification. It is a figure which shows the time change of the waveform of the rectangular wave alternating current which concerns on one modification. It is a block diagram which shows the structure of the lighting device 301 which concerns on a modification. It is a figure which shows the time change of the frequency of the rectangular wave alternating current which concerns on one modification. It is a figure which shows the time change of the frequency of the rectangular wave alternating current which concerns on one modification. It is a figure which shows the time change of the frequency of the rectangular wave alternating current which concerns on one modification. It is a figure which shows the time change of the frequency of the rectangular wave alternating current which concerns on one modification. 3 is a perspective view showing an appearance of a shaved electrode 122. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 High pressure mercury lamp 101 Light emission tube 101a Light emission part 101b, 101c Sealing part 102,103,122 Electrode (cut-out electrode)
102c, 122b Tip portion 102d, 122d Protrusion 200 Lamp unit (high pressure discharge lamp device)
300, 301 lighting device 400 liquid crystal display device

Claims (1)

An arc tube in which a pair of tungsten electrodes in which a halogen substance is enclosed and a projection for stabilizing brightness is formed by a halogen cycle action is disposed at the tip is disposed at the tip of the electrode The part is equipped with a lighting circuit that supplies an alternating current to a high-pressure mercury discharge lamp that is formed in a substantially conical shape by machining, and turns on the lamp.
The lighting circuit is configured to change the frequency of the alternating current multiple times to two or more different values without depending on the operation data that changes with the lighting elapsed time of the high-pressure mercury discharge lamp during continuous lighting, maximum frequency to be changed, a 300Hz～500Hz, and I 3 times der the minimum frequency,
The maximum frequency is a frequency at which the protrusion of the tip of the electrode recedes at the initial stage of life,
The high-pressure discharge lamp lighting device according to claim 1, wherein the minimum frequency is a frequency at which a protrusion at the tip of the electrode grows at an early stage of life .

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