JPH0443383B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field of the Invention) The present invention relates to a lighting device that can be applied from general lighting to office machines such as document reading devices.

(Background Art) Conventionally, lighting devices such as document reading devices use light sources such as fluorescent lamps and halogen lamps.

However, in recent years, there has been a demand for a light source with high brightness and long life in order to more reliably obtain document information.

Based on such requirements, light sources that do not have a filament for discharging inside the light source have been considered.

FIG. 13 is a cross-sectional view of this light source. 4 is a lamp, and the inner surface of this lamp 4 has a phosphor 3.
is coated with mercury and inert gas. A protruding cylindrical portion 7 is formed in the lamp 4 so as to include the transformer 2. The transformer 2 consists of a core 6 and a coil 5, and both ends of the coil 5 wound around the core 6 are connected to the high frequency lamp power source 1.

By applying a high frequency voltage to the coil 5 from the high frequency lamp power source 1, the area around the coil 5 is
A high frequency electromagnetic field is generated. The electrical energy of this electromagnetic field excites the mercury gas in the lamp 4, and the ultraviolet rays of the mercury caused by this excitation are converted into visible light by the phosphor 3 applied to the surface of the lamp 4.

In this configuration, energy is applied to the gas inside the lamp from the outside to cause it to discharge, so it takes a long time for the lamp to rise until it reaches a predetermined amount of light, and it requires less frequent on/off switching than in lighting devices such as document reading devices. It is not suitable for applications where it is desired to reach a predetermined amount of light in a short period of time due to a high amount of light. Furthermore, there is a problem in that the discharge state is difficult to stabilize due to temperature unevenness within the lamp, and it takes more time to achieve a stable luminescence distribution.

(Objective) The present invention solves the above-mentioned problems and provides a lighting device that has high brightness, long life, reaches a predetermined amount of light in a short time, and has excellent start-up characteristics.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a discharge tube that generates visible light using a high-frequency electromagnetic field, and a discharge tube provided in contact with or near the outer wall of the discharge tube. In a lighting device having an electrode and a voltage applying means capable of applying a high frequency voltage to the discharge electrode, the voltage applying means applies a first voltage to the discharge electrode that causes the discharge tube to discharge. an application means, and a second application means that applies an output that does not cause the discharge tube to discharge to the discharge electrode, and during standby, heating the discharge electrode by the second application means This method is characterized by preheating the discharge tube.

(Example) Hereinafter, an example of the present invention will be described based on the drawings.

In the figures, the same members are given the same numbers.

FIG. 12 is a sectional view of an image forming apparatus equipped with a document reading section to which the illumination device of the present invention is applied.

In the figure, 21 is a document placement cover, 22 is a document exposure device to which the illumination device of the present invention is applied, 23 is a first mirror, 24 is a second mirror, 25 is a lens mirror lens, and 26 is a third mirror. , an optical image is projected onto the photosensitive drum 27 by subjecting the document to slit exposure. Reference numeral 28 denotes primary and secondary chargers for forming a latent image on a photoreceptor having an insulating layer on its surface, which are integrally constructed here. Note that the above optical image is exposed simultaneously with the secondary charging. Furthermore, an electrostatic latent image is formed on the surface of the drum 27 by the full-surface exposure lamp 29. 30 is a developing device for visualizing the latent image thus formed.

On the other hand, cut paper as a recording material in the paper feed stacker 31 is fed by a pick-up roller 32, passed through a paper feed guide 33, and a visible image on the drum 27 is transferred by a transfer charger 34. It is conveyed by the conveyance section 35 and is transferred to the fixing device 36.
The fixed image is made into a fixed image and the paper is ejected to a paper ejection stacker 37.

After the developing agent remaining on the drum 27 during the transfer process is removed by a cleaner 38, the drum 27 is neutralized by a neutralizing lamp 39 and a neutralizing lamp 40 to erase the electrical image remaining on the photoreceptor. Return to state. Note that 41 is a blank exposure lamp which forms a bright latent image in order to prevent development from occurring when the optical system is back up. In the figure, E,
E ₂ and E ₃ indicate exposed areas.

Of course, in this embodiment, the illumination device of the present invention can be used not only as the document illumination device but also as the static elimination lamp 40 and the blank exposure lamp 41.

Next, a lighting device according to an embodiment of the present invention will be described.

FIG. 1 is a simplified diagram showing one embodiment of the present invention.

In the figure, 1 indicates a high-frequency lamp power supply, 10 is a long discharge lamp, and the glass is ordinary soda glass or Pyrex glass, and the inner surface is coated with a prescribed phosphor. There is. Furthermore, the discharge lamp is filled with mercury and an inert gas.

A discharge electrode 11 is connected to a high-frequency lamp power supply and applies a high-frequency electromagnetic field to the inside of the discharge tube, and covers the circumferential surface of the lamp on the longitudinal end side of the lamp. The material may be any ordinary conductor, but copper, stainless steel, etc., which are less prone to deterioration due to oxidation, are preferable.

Before the lighting device 22 is turned on, that is, during standby, Sw. 1 and Sw. There is.

When a lighting signal is applied in this state, Sw,1 and Sw,2 are in contact with terminal B, and a high frequency is applied to the electrodes. The mercury gas inside the discharge tube is brought into an excited state by the high-frequency electric field, and the generated ultraviolet rays are converted into visible light by the phosphor.

FIG. 2 is a block diagram illustrating the outline of this embodiment. Input power is applied from the input power supply to the high frequency oscillation circuit to generate a high frequency, and then the voltage is amplified by the amplifier circuit and applied to the electrodes via the transmission line.

According to this embodiment, since the gas in the discharge tube is heated during standby and kept in a state where it is easy to excite, the start-up time can be shortened.

FIG. 3 shows another embodiment of the invention.

Here, the discharge tube is the same as that shown in FIG. 1, but the electrode is in contact with the discharge tube and is wound in a coil shape a plurality of times in the longitudinal direction of the discharge tube.

Hereinafter, the electrodes of the embodiments of the present invention will be explained using those shown in FIG. 1 and those shown in FIG. 3, but the embodiments are not limited to the shape of the electrodes, and either shape of the electrodes may be used.

The coil-shaped electrode shown in FIG. 3 is preferable because it can supply a larger amount of power than the electrode having the shape shown in FIG. 1, and therefore can provide even higher brightness.

FIG. 4, FIG. 6, and FIG. 8 are block diagrams of different embodiments for explaining the outline of the embodiment of FIG. 3.

First, the embodiment shown in FIG. 4 will be explained. Input power is applied to the high frequency oscillation circuit from an input power source.
The high frequency oscillator circuit is provided with a terminal a that outputs a high frequency wave with a voltage high enough to discharge the discharge tube via an amplifier circuit, and a terminal b that outputs the same frequency wave with a voltage high enough to discharge the discharge tube.

During standby, terminal b and the amplifier circuit are in a conductive state, and a voltage sufficient to cause a discharge is applied to the electrode via the transmission line, so the discharge tube does not discharge, and the electrode is heated and the gas inside is also It is easily excited at about 30°C.

When a lighting signal is input in this state, the terminal a and the amplifier circuit are brought into conduction by the switching means, and a voltage sufficiently high to discharge the discharge tube is applied to the electrode, so that the discharge tube enters the discharge state.

FIG. 5 shows the power applied to the electrodes. As shown in the figure, it is small during standby and large when turned on, and it is possible to switch between the heating state and the lighting state by changing the voltage state like this.

In this embodiment, as in the embodiments shown in FIGS. 6 and 8, which will be described later, the gas in the discharge tube is in a state where it is easy to excite, so the rise time until discharge is short, and furthermore, the rise time is short in the longitudinal direction of the discharge tube. Since the battery is heated uniformly, there is no temperature unevenness in the longitudinal direction, and a uniform light emission distribution in the longitudinal direction can be obtained almost at the same time as discharge, which is particularly preferable in document reading devices.

Another embodiment will be explained with reference to the block diagram of FIG.

During standby, a sufficiently low frequency output is applied to the electrodes through terminal d, which does not cause discharge, and the discharge tube is in a heated state (approximately 30°C), and when a lighting signal is input in this state. The switching means makes the terminal c conductive, and an output with a frequency sufficiently high to cause the discharge tube to discharge is applied to the electrode, so that the discharge tube is turned on.

According to this embodiment, since the discharge is controlled by frequency, the output voltage used for preheating can be set high, and the heating capacity is increased.

FIG. 7 shows the output applied to the electrodes. As shown in the figure, by setting the frequency during preheating to a sufficiently lower frequency than during lighting, it is possible to switch between the heating state and the discharging state.

Still another embodiment will be explained with reference to the block diagram of FIG.

During preheating, a low voltage is input from the input power source to the voltage controlled oscillator. Here, the voltage controlled oscillator has an output frequency that changes as the input voltage changes, and can control both the frequency and voltage.

When a lighting signal is input, a high voltage is input from the input power source to the voltage controlled oscillator, and an output with a sufficiently high voltage and high frequency is applied to the electrodes to discharge the discharge tube, and the discharge tube enters the discharge state. becomes.

FIG. 9 shows the output applied to the electrodes.

In this way, by lowering both the voltage and the frequency during preheating, it is possible to further ensure that no discharge occurs during preheating.

Further, according to the configuration shown in FIG. 3, there is no need to provide a special power source, and the cost and size can be reduced, which is preferable.

Next, the preheating temperature will be explained using FIG. 10. The horizontal axis shows the temperature of the discharge tube, and the vertical axis shows the rise time. Moreover, this result was measured based on the example shown in FIG.

As can be seen from the figure, the rise time is shortest near 30°C, and increases as you move away from this point.
From this, it can be seen that preheating of 20° C. to 40° C. is preferable since the rise characteristics are excellent.

FIG. 11 shows the effects of the present invention.

The solid line shows the rise characteristics without preheating, and the dashed line shows the rise characteristics with preheating (30°C).

It can be seen that when preheating is performed, the rise characteristic is significantly shortened to about 1/3.

It was also found that preheating quickly stabilized the discharge. This is thought to be due to the fact that fine temperature unevenness in the discharge tube was reduced by preheating.

Next, the high frequency used for discharge will be explained.

The inventors of the present invention carried out experiments with consideration to improving brightness and power efficiency, and found that 10 ⁶ to ^{10 8} Hz is preferable. Furthermore, in the embodiments of FIGS. 6 and 8, it has been found that the frequency used for preheating is preferably 10 ⁶ Hz or less in view of increasing heating efficiency.

The present invention is not limited to the shape of the electrodes in the embodiments, and any shape may be used as long as the shape allows a high-frequency electromagnetic field to be applied to the discharge tube.

Further, the electrode may be separated from the discharge tube, but it is preferable that the electrode be close to the discharge tube, and particularly preferably that it is in contact with the discharge tube.

(Effects) The lighting device of the present invention has excellent effects such as high brightness, long life, short start-up time, and easy to stabilize the amount of light.

[Brief explanation of drawings]

FIG. 1 is a simplified diagram of one embodiment of the present invention, FIG. 2 is a block diagram illustrating the outline of the embodiment of FIG. 1, and FIG.
The figures are simplified diagrams of alternative embodiments of the invention, Figures 4 and 6.
8 are different embodiments applied to FIG. 3, FIG. 5 is an explanatory diagram of the embodiment of FIG. 4, FIG. 7 is an explanatory diagram of the embodiment of FIG. 6, and FIG. 9 is an explanatory diagram of the embodiment of FIG. FIG. 8 is an explanatory diagram of an embodiment, FIGS. 10 and 11 are explanatory diagrams of the present invention, FIG. 12 is a sectional view of an image forming apparatus to which the present invention can be applied, and FIG. 13 is an explanation for comparison with the present invention. It is a diagram. In the figure, 1 is a high-frequency lamp power supply, 10 is a discharge tube,
11 is an electrode.

Claims (1)

[Claims] 1. A discharge tube that generates visible light using a high-frequency electromagnetic field, a discharge electrode provided in contact with or near the outer wall of the discharge tube, and a high-frequency voltage to which a high-frequency voltage can be applied. a first voltage applying means that applies an output to the discharge electrode to cause the discharge tube to discharge; and a first voltage application means to apply an output to the discharge electrode that causes the discharge tube to discharge; a second application means for applying an electric voltage to the discharge electrode, and preheats the discharge tube by heating the discharge electrode with the second application means during standby. .