JPH06289504A - Exposure lamp lighting device - Google Patents

Abstract

PURPOSE:To prevent an exposure device used for a digital copying machine from being continuously turned on when the abnormality occurs without providing a special heat detecting element. CONSTITUTION:As to the exposure lamp lighting device provided with a switching means whose on/off is controlled in accordance with a lighting control signal and which is installed between an exposure lamp 14 and a power source 11, and the on/off of the switching means 13 is periodically controlled in response to the light control signal, a timer circuit 12 is installed between the switching means 13 and the power source 11, and the timer circuit 12 is set when the power is supplied to the exposure lamp and the circuit 12 is reset when a voltage equal to or below a prescribed voltage is supplied from the power source to the exposure lamp, and the timer circuit is provided with a switching means 12 for disconnecting between the power source and the exposure lamp when the timer is up.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure lamp lighting device used in an exposure device such as a high speed digital PPC, a fax machine or a scanner.

[0002]

2. Description of the Related Art In recent years, digital copying machines utilizing digital technology have been developed and put into practical use. That is, an image from a document is read by a CCD (charge coupled device) type line sensor, and a signal from the line sensor is quantized and processed. A halogen lamp is used as an exposure device of such a digital copying machine. This halogen lamp is controlled to be turned on / off (lighting / lighting off) by a lighting control signal from the main control unit of the digital copying machine.

[0003]

As described above, in the digital copying machine, assuming that the halogen lamp cannot be turned off due to some trouble, a heat such as a thermal fuse is provided around the halogen lamp. A detection element is provided to protect the halogen lamp from continuous lighting. However, the above-described heat detecting element has a problem that it is difficult to design an optimum operating point because the variable elements depending on the environmental temperature and the ambient conditions become large.

The present invention has been made in view of the above points, and it is an object of the present invention to reliably prevent continuous lighting of an exposure device used in a digital copying machine when an abnormality occurs, without providing a special heat detecting element. The present invention relates to an exposure lamp lighting device that can be used.

[0005]

An exposure lamp lighting device according to a first aspect of the present invention is provided with a switch means which is on / off controlled according to a lighting control signal between an exposure lamp and a power supply, and a lighting control signal. In the exposure lamp lighting device in which the switch means is periodically turned on / off in response to
A timer circuit is provided between the switch means and the power supply, and the timer circuit is set when the power is supplied to the exposure lamp, and the exposure lamp is supplied with a voltage equal to or lower than a predetermined voltage lower than the power supply. Then, it is reset, and a switch means is provided for disconnecting the power supply and the exposure lamp when the timer is up.

In the exposure lamp lighting device according to a second aspect of the present invention, the timer time set in the timer circuit of the first aspect is set to be longer than the period in which the switch means is periodically turned on / off. .

In the exposure lamp lighting device according to a third aspect of the present invention, the lamp is connected to the lamp lighting device, and the built-in timer circuit supplies power to the lamp for a set time in response to an ON signal input thereto. In the exposure lamp lighting device configured as described above, the control unit outputs the reset signal in a time shorter than the set time set in the timer circuit and turns on the lamp for a time longer than the set time.

[0008]

The present invention has the timer circuit which is set when the power is supplied to the exposure lamp as described above and is reset when the terminal voltage of the exposure lamp is equal to or lower than the predetermined voltage. Even when the exposure lamp cannot be turned off, the exposure power can be surely turned off by cutting off the power supply by the timer circuit.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An exposure lamp lighting device according to a first embodiment of the present invention will be described below with reference to the drawings. Figure 1
(A) is a lighting device of an exposure lamp for a digital copying machine as shown in FIG. In FIG. 1A, 11 is a DC power supply. The anode of the DC power supply 11 is the timer circuit 12
It is connected to one end of a halogen lamp 14 used in an exposure device of a digital copying machine through a switch 12s and a switch 13 therein. When the timer circuit 12 counts the time T after being reset, the switch 12s is turned off (opened).
To do.

One end of the halogen lamp 14 is connected to the timer circuit 12 via the line a. Halogen lamp 14
When the voltage at one end drops below a certain voltage (including zero),
A reset signal for resetting the timer circuit 12 is input.

As shown in FIG. 1B, the switch 13 is composed of a transistor, and the on / off control of the transistor 13 is performed by a control circuit C. By a lighting control signal C from the control circuit C, The transistor 13 may be on / off controlled. Returning to FIG. 1A, the switch 13 is on / off controlled by a lighting control signal C from a control unit for a digital copying machine (not shown).
The other end of the halogen lamp 14 is connected to the cathode of the DC power supply 11 and the timer circuit 12.

Here, the lighting control signal C is a pulse having a cycle Tc as shown in FIG. 3C, and the timer circuit 12 receives Tt (Tc <Tt <2T after the reset signal is input.
When it becomes c), the switch 12s is turned off (opened). Further, the off time is set to about 50 msec, for example.

A digital copying machine in which the present lighting device is used will be described with reference to FIG. FIG. 2 is a schematic configuration diagram showing the internal structure of the digital copying machine. In FIG. 2, the digital copying machine 21 includes a scanner unit (reading unit) 22 for optically reading image information of an original, and a scanner unit 22 for reading the image information, or is supplied from an external device described later. An image forming section (image forming means) 23 for outputting image information on a recording material, that is, a copy sheet, is included in accordance with the image signal.

The scanner unit 22 includes an original placing table 24 on which an original to be copied is placed, the halogen lamp 14 shown in FIG. 1 for illuminating the original placed on the placing table 24, and the halogen lamp 14. It has a CCD sensor 15 that converts the reflected light into an image information signal by photoelectrically converting the reflected light from the document D illuminated via the above.

A reflector for efficiently focusing the illumination light from the halogen lamp 14 on the original is disposed on the side of the halogen lamp 14. Further, between the halogen lamp 14 and the CCD sensor 25, a plurality of mirrors for bending an optical path through which the light traveling from the document toward the CCD sensor 25, that is, the reflected light from the document passes, and the above-mentioned The reflected light is the above CC
A lens or the like for focusing is arranged on the light collecting surface of the D sensor 25.

On the upper part of the document placing table 24, there is arranged a document retainer for bringing the document into close contact with the document placing table 24. This document retainer can be replaced with, for example, an SDF, a semi-automatic document feeder, or an ADF, an automatic document feeder, depending on the size or copying ability of the digital copying machine 21.

The image forming section 23 has a cylindrical shape,
A photoelectric conversion element that is formed rotatably in a desired direction via a motor (not shown), is charged to a desired potential, and changes the potential of a region irradiated with the light beam by being irradiated with the light beam, that is, It has a photosensitive drum 26.

Around the photosensitive drum 26, a charging device 27 for applying a desired electric potential to the drum 26, and an image signal or a print signal from the image processing section, which will be described later, to the photosensitive drum 26, that is, copying or output. A laser unit 28 that outputs a laser beam that is turned on / off according to image information to be supplied, and a visualization agent, that is, toner is supplied to the electrostatic latent image formed on the photoconductor 26 by the laser beam from the laser unit 28. The developing device 29 for developing the toner image and the toner image on the photoconductor 26 developed via the developing device 29 are used as a recording material fed from a recording material feeding portion described later, that is, a copy. A transfer device 30 for transferring onto a sheet is arranged in order.

After the transfer device 30 around the photoconductor 26, the toner remaining on the surface of the photoconductor 26 is removed, and the potential generated on the photoconductor 26 by the laser beam is removed. A cleaner unit 31 for erasing the change for the next image formation is arranged.

Between the developing device 29 and the transfer device 30, the copy sheet for transferring the toner image formed on the photoconductor 26 is fed toward the transfer device 30. A recording material feeding unit 32 is arranged.

Further, in the direction subsequent to the transfer device 30 and in the direction in which the copy paper on which the toner image is transferred via the transfer device 30 is separated from the photoconductor 26, the toner is added to the copy paper. A fixing device 33 for fixing an image, and a conveying device 34 arranged between the fixing device 33 and the transfer device 30 for conveying the copy sheet toward the fixing device 33 are arranged. There is.

Next, the operation of the first embodiment will be described. First, when copying is started in the digital copying machine, a lighting control signal C as shown in FIG. Therefore, the switch 13 is repeatedly turned off for 50 msec at every Tc time. Therefore, the light quantity of the halogen lamp 14 is instantly dimmed every Tc time as shown by D in FIG. Here, since the off time is set to 50 msec, the amount of light does not affect the exposure function of the copying machine because of the light emitted by the Jule heat.

Further, as shown in FIG.
The applied voltage of is also reduced to zero in synchronization with each Tc time. This signal is used as a reset signal for the timer circuit 12, and the timer time Tt is set to Tc <Tt <2Tc. Therefore, the timer circuit 12 is reset before the timer circuit 12 counts up. .

By the way, due to some trouble, FIG.
As shown in (C), when the lighting control signal F is output to the switch 13 but the switch is not turned off, the terminal voltage of the halogen lamp 14 does not drop to zero as shown in G. Therefore, since the reset signal is not output to the timer circuit 12, the timer circuit 12 continues the clock operation, and when the timer circuit 12 measures Tt, the switch 12s
Turn off. Therefore, the lamp voltage drops to zero as indicated by H in FIG. Therefore, the halogen lamp 1
4 is turned off, and the light amount falls to zero as indicated by I in FIG. 4 (B).

In this way, even if the halogen lamp 14 used in the exposure apparatus of the digital copying machine is continuously turned on due to some trouble, it can be surely turned off by the timer circuit 12 without using the heat detecting element. .

Next, a second embodiment of the present invention will be described with reference to FIGS. In FIG. 5, reference numeral 41 is a halogen lamp used as an exposure lamp for a digital copying machine. Both ends of the halogen lamp 41 are connected to the halogen lighting device body 43 in the lamp lighting device 42. An outlet plug 44 is connected to the halogen lighting device body 43.

Reference numeral 45 is a controller which controls the digital copying machine as a whole. This controller 45 has a built-in timer circuit 45t.
Outputs a reset signal to the lighting device 42 as a control signal C every set time Tb. This controller 45 performs the processing shown in FIG. Further, the timer circuit 45u continues the counting operation after the timer circuit 45t first starts the counting operation (the count value is Tu).

The control signal C from the controller 45 is output to the ON / OFF circuit 46 in the lighting device 42. A reset circuit 47 is connected to the ON / OFF circuit 46. Further, the reset circuit 48 includes a timer circuit 48.
Are connected. The timer circuit 48 is a reset circuit 47.
When Ta is counted after the reset signal from is input, the switch (not shown) of the halogen lighting device body 43 is turned off (opened), the power supply to the halogen lamp 41 is cut off, and the halogen lamp 41 is turned off. Where T
It is set to a> Tb.

Next, the operation of the second embodiment will be described. First, the time Th during which the halogen lamp 41 is continuously turned on.
Is set in the controller 45. When copying is started in the digital copying machine, the halogen lamp 41 is turned on and the scanning process is started. At the same time, the time counting operation of the timer circuits 45t, 45u and 48 is started. By the way, the controller 45 outputs a reset signal as the control signal C to the ON / OFF circuit 46 every time the timer circuit 45t measures the time Tb. As a result, the reset circuit 47 outputs a reset signal to the timer circuit 48. Here, since Ta> Tb is set, the timer circuit 48 is reset before measuring the time Ta, and then continues the time counting operation. Therefore, the switch (not shown) in the halogen lighting device main body 43 is not turned off even after the time Ta has passed, so that the halogen lamp 41 is continuously turned on.

When Th-Tu <Tb, the reset signal is not output from the controller 45 to the lighting device 42 as the control signal C. Therefore, when the timer circuit 48 measures the time Ta, the reset signal is output to the switch (not shown) of the halogen lighting device main body 43, so that the halogen lamp 41 is turned off. Therefore, the halogen lamp 41 is turned off as shown by G in FIG. 7 (B).

As described above, this is an effective device when it is desired to control ON / OFF of the halogen lamp 41 at a cycle longer than the timer time Ta set in the timer circuit 48. When the halogen lamp 41 is controlled to be turned on / off at a cycle longer than the cycle of the normal timer circuit 48, a timer circuit having the long cycle may be used. However, such a long timer circuit requires a long inspection time to confirm the operation. There is a problem of becoming. However, even if the timer time Ta of the timer circuit 38 is short as in the second embodiment, T smaller than Ta
By resetting the timer circuit 38 every b, it is possible to control the lighting of the halogen lamp 41 for an appropriate time. In this case, the inspection time for checking the operation of the timer circuit 48 can be shortened. In the above embodiment, the lighting control of the exposure lamp of the digital copying machine is described, but the invention can be similarly applied to the facsimile and the scanner.

[0032]

As described above in detail, according to the present invention, it is possible to prevent continuous lighting of an exposure apparatus used in a digital copying machine when an abnormality occurs, without providing a special heat detecting element. Moreover, it is possible to provide an exposure lamp lighting device capable of lighting the exposure lamp for a long time even if a short timer circuit is used.

[Brief description of drawings]

FIG. 1 is a block diagram of a lighting device for an exposure lamp according to a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram showing an internal structure of the digital copying machine according to the first embodiment.

FIG. 3 is a timing chart for explaining the operation of the first embodiment.

FIG. 4 is a timing chart for explaining the operation of the first embodiment.

FIG. 5 is a block diagram of a lighting device for an exposure lamp according to a second embodiment of the present invention.

FIG. 6 is a flowchart showing the operation of the controller according to the second embodiment.

FIG. 7 is a flowchart for explaining the operation of the second embodiment.

[Explanation of symbols]

11 ... DC power supply, 12 ... Timer circuit, 12s ... Switch, 14, 41 ... Halogen lamp, 42 ... Lamp lighting device, 43 ... Halogen lighting device body, 44 ... Outlet plug, 45 ... Controller, 45t, 48 ... Timer circuit.

Claims (3)

[Claims] 1. A switch means is provided between the exposure lamp and a power source, the switch means being on / off controlled according to a lighting control signal,
The switch means is periodically turned on / off in response to the lighting control signal.
In the exposure lamp lighting device controlled to be off, a timer circuit is provided between the switch means and a power source, and the timer circuit is set when the power source is supplied to the exposure lamp, An exposure lamp lighting device comprising switch means for resetting when a voltage lower than a predetermined voltage smaller than the power supply is supplied and for disconnecting the power supply and the exposure lamp when a timer is up. 2. The exposure lamp according to claim 1, wherein a timer time set in the timer circuit is set longer than a cycle in which the switch means is periodically turned on / off. Lighting device. 3. An exposure lamp lighting device, wherein a lamp is connected to the lamp lighting device, and the built-in timer circuit supplies power to the lamp for a set time in response to an ON signal input to the lamp lighting device. 2. An exposure lamp lighting device, comprising: a control unit that outputs a reset signal in a time shorter than a set time set in the timer circuit and turns on the lamp for a time longer than the set time.