JPS5832698B2 - Exposure control device in scanning copying machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrophotographic copying machine, and particularly to an exposure control device.

Generally, when a scanning electrophotographic copying machine is turned on, a document is placed on a document table made of a transparent plate such as glass, and an exposure lamp is used to illuminate the document surface from the bottom of the document table. Scanning the surface of the original by moving an optical system included therein, successively projecting and exposing the scanned image onto the surface of a photoreceptor,
An electrostatic latent image corresponding to the brightness and darkness of the original image is formed on the photoreceptor.

In this type of scanning electrophotographic copying machine, since the exposure lamp uses a high-intensity one, it also emits a large amount of heat rays, causing a problem of temperature rise on the document table, especially on the glass surface on which the document is placed.

Such a temperature rise on the glass surface is caused especially when the so-called scanning means for moving the document table or the optical system is configured so that its scanning distance changes in accordance with the length of the document, and when the button on the copying machine is pressed. This becomes more noticeable as the scanning distance becomes shorter.

That is, an example of a copying machine whose scanning distance changes depending on the length of the original is a copying machine that uses roll copying paper and cuts it into lengths that correspond to the length of the original. .

This type of copying machine has an index set on the side of the document placement glass that is set according to the length of the document, and integrally with this index, a movable switch for cutting the roll paper and returning the scanning system is provided. This switch is actuated by the movement of the scanning system to cut the roll paper according to the length of the document and return the scanning system.

Therefore, if the original is short and a large number of sheets are continuously copied using the scanning return method as described above, the time required for the exposure lamp to return to the starting position after it is turned off at the end of scanning is extremely short. , because the next exposure/scanning process starts immediately, the temperature of the original glass surface increases significantly.

As a means to prevent the temperature of the document placement glass from rising, heat ray-absorbing glass may be installed between the exposure lamp and the document placement glass, or an air blower may be provided to cool the surface of the document placement glass. measures are being taken.

However, the higher the heat absorption efficiency of heat ray absorption glass, the better the heat insulation effect, but on the other hand, it also reduces the amount of light required for exposure, so the input voltage to the exposure lamp must be reduced in order to obtain a predetermined amount of light. This necessitates measures such as raising the lamp height, which adversely affects the life of the exposure lamp.

Cheap casings with low heat absorption efficiency have very weak heat insulation effects.

In addition, when a blower is provided to cool the original glass, special means such as a fan or a duct are required for blowing air, and the cooling effect is extremely weak when used alone.

The present invention has been made with attention to the above points, and is one of the features of a scanning electrophotographic copying machine in which the moving distance of the scanning means is variable. By providing a control means that regulates the minimum time from turning off the light after turning it on to turning on 1 accompanying the next scanning movement so that the temperature rise of the document placing table due to the lighting of the exposure lamp is below a predetermined value, the document placing glass An object of the present invention is to provide an exposure control device that prevents an abnormal temperature rise.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view schematically showing an electrostatic latent image transfer type copying machine M using roll copying paper as an example of a scanning type electrophotographic copying machine to which the present invention is applied.

First, an outline of the copying operation will be explained.

An original (not shown) placed on the original placing glass 1 (hereinafter simply referred to as original glass) is irradiated with an exposure lamp L, and is exposed to a first reflecting mirror m1, a second reflecting mirror m2, a third reflecting mirror m3, The image is projected onto the photosensitive drum 4 via the lens 2, the fourth reflecting mirror m4, and the slit portion 3.

The exposure lamp L and the first reflecting mirror m1 are supported by the supporting portion 5 and are movable in one direction, and when scanning an original, the exposure lamp L is turned on and moved at a constant speed 2 in the direction of the arrow a.

Further, the second and third reflecting mirrors rn2 s 1713 are supported by the support member 6 and are movable in one direction, and are moved at a constant speed (V/
2).

At 10,000, the copy paper P is stocked in a roll, pulled out from the stock position by a paper feed roller 7, and cut by a cutter 8 activated by a cutter activation signal, which will be described later.

The original image scanned by the scanning system S including the above-mentioned exposure lamp and reflecting mirrors m1 to m4 is projected onto the surface of the photosensitive drum 4 charged by the charger 9 to become an electrostatic latent image. The image is transferred to the copying machine P by the transfer section 10.

After the transfer, the copy paper P is separated from the surface of the photosensitive drum 4 by a separating claw 11, passes through a developing device to be developed, and is fixed by a drying and fixing device H to complete copying.

Further, after the transfer, residual charges are removed from the photosensitive drum 4 by the eraser 12, and the photosensitive drum 4 enters the next copying process.

Copy machine 1 like the above! Using the vHC, the return of the scanning system S and the cutting of the copy paper P are performed as follows.

That is, as shown in FIG. 2, the original 20 placed on the original glass 1 has its negative side aligned with the reference side 1a of the original glass 1, and the upper cover 21 of the copying machine Align the slidable index 22.

As shown in FIG. 3, a switch mounting plate 23 is fixed to the index 22 so as to protrude from the bottom of the upper cover 21, and a button is attached to the switch mounting plate 23. Furthermore, a cutter operation switch SW1 and a return switch are mounted on this switch mounting plate 23. SW2 is fixedly installed.

On the other hand, a switch actuation piece 24 is fixedly attached to the support part 5 that supports the exposure lamp L, etc., and is set so that the cutter actuation switch SW1 and the return switch SW2 can be energized and actuated, respectively. be done.

Furthermore, a switch actuation piece 25 is further fixed to the support portion 5, and is capable of energizing and operating the return position regulation switch SW3 fixed to a predetermined position inside the copying machine M. It is set as follows.

As mentioned above, this return position regulation switch SW3 is
It is set at a position where the exposure lamp L can heat the original glass 1 to an acceptable degree, and is connected to the return switch SW2 by a circuit configuration described later, so that it can perform the scanning shown by the solid line in FIG. 3 or FIG. 1. The distance l from the starting position of the system S until the switch actuating piece 25 energizes the switch SW3 is a predetermined shortest movement distance of the scanning system S, and the scanning system S does not return at a distance less than this. It is for the purpose of

With such a configuration of the switch and switch actuating piece,
The cutter operation returns as the scanning system S moves, and the index 22 is made to be able to slide freely according to the size of the original 20, and the copy paper P is moved to the cutter 8 according to the size of the original 20. Mechanisms for cutting are generally known, and therefore the details thereof will be omitted.

Next, Fig. 4 shows one of the circuit configurations in which each of the above switches is arranged.
Give an example.

The power supply lines 30 and 31 are from a control power supply whose voltage is appropriately rectified and stepped down from a power supply circuit (not shown) of the copying machine M.

Here, relay RY1 for control power supply is contact point 1 of starting switch S''w4 such as a printed switch and relay RYI.
parallel circuit of a1 and relay RY2. RY3 contact 2bl
, 3b1 are connected to the power supply line 30.31 through a parallel circuit.

The aforementioned return switch SW2 is connected in series with a relay RY3 having a self-holding contact 3al, and the return position regulating switch SW3 is connected in series with a relay RY2 having a self-holding contact 2a1, so that the above-mentioned starting switch SW4 and Each relay RY2 . RY3 is connected to the power supply line 31.

Further, the contact point 1a2 of the relay RYI serves as a power switch for the scanning system drive circuit 32 and the control circuit 33 for exposure, charging, erasure, etc.;
It is connected via the normally closed contact 3b2 of Y3.

The operation of the above circuit will be explained with reference to FIG.

To explain the case where the return switch SW2 is located closer to the starting position of the scanning system S than the return position regulation switch SW3 as shown in FIG. 3, when the starting switch SW4 such as a print switch is closed, the relay RY1 is closed. is relay RY2. It is turned on via the normally closed contacts 2b1 and 3bl of RY3, and is self-held by the contact 1a1.

As a result, the contact 1a2 is closed, the circuits 32 and 33 are energized, the scanning system S and the exposure lamp start operating, and the charger 9, eraser 12, etc. start operating.

By the way, at this time, the conveyance of the copy paper P is also started, but therefore the control circuit, cutter control circuit, etc. will be omitted.

As the scanning system S moves, the cutter activation switch SW1 is first pressed by the switch activation piece 24, and the cutter 8 is activated by a known mechanism to cut the copy paper P into a length corresponding to the original document 20. Paper feed roller 7 stops.

The scanning system S continues to move, and when the switch operating piece 24 presses the return switch SW2, the relay RY3 turns ONL and the contact 3a through the self-holding contact 1a'l of the relay RY1.
Self-hold at 1 and open contact 3bL 3b2.

By opening the contact 3b2, the exposure lamp 1 charger 9 and the eraser 12 are turned OFF at this point, and the scanning is essentially completed, but the relay RY1 is connected to the contact 2' of the relay RY2.
D1 continues ONL for 1, and when the switch operating piece 25 pushes the return position regulation switch SW3 and the relay RY2 is turned on, the relay RY1 is turned off due to the opening of the contact 2b1, and the contacts 1a1 and 1a2 are opened, and the scanning system S
movement is stopped.

At this point, the return of the scanning system S is started, but the return drive mechanism is such that, for example, the electromagnetic clutch for scanning movement is turned off.
A mechanism that pulls it back by a spring etc. after it has been F, or
Appropriate means may be employed, such as activating another clutch mechanism that drives in the return direction.

Next, when the return switch SW2 is located on the left side of the return position regulation switch SW3 in FIG. The order, that is, the order of operation of relays RY2 and RY3 is reversed, but the rest is the same.

Therefore, the relay RY1 becomes 0FFK when the return switch SW2 is pressed and the relay RY3 is turned on.

In this case, stop the scanning system S and turn off the exposure lamp L etc.
F is performed at the same time.

Therefore, if you do the above, return switch SW2
is far from the starting position of the scanning system S with respect to the return position regulation switch SW3, the scanning system S is returned according to the length of the document, but the document becomes shorter and the return position regulation switch SW3 When the scanning system S reaches the starting position, the scanning system S does not return when the return switch SW2 is activated, but returns only when the return position regulating switch SW3 is activated.

This is illustrated in the graph of FIG.

In Figure 5, the vertical axis represents the time required for one copying operation.
The horizontal axis shows the size (length) of the document, where a indicates the case where the document is simply returned according to the document size, and b indicates the shortest length of the scanning system S, as shown in the embodiments of FIGS. 3 and 4. When the moving distance l is set, even after the actual scanning such as cutting and exposure is completed for a document whose size is smaller than the document size l corresponding to the distance l, only the movement of the scanning system S is performed. It shows.

In this case, the time required for one copying operation is constant T regardless of the original size, and the original glass 1 is prevented from being overheated even in continuous repeated operations.

Next, another embodiment of the present invention will be described with reference to FIGS. 6 and 7.

In the configurations shown in FIGS. 6 and 7, those having basically the same functions as those in FIGS. 3 and 4 are designated by the same reference numerals, and the description thereof will be omitted.

The switch mounting plate 23 that moves together with the index 22 is provided with a cutter operating switch SW1 and a switch 'sw for turning off the exposure/charging circuit 33, which are set to be energized and operated by the switch operating piece 24. .

In addition, so as to be biased and operated by the switch operating piece 25,
The return switches Rotake to SW are arranged at appropriate intervals, and together with the switch SW, a circuit as shown in FIG. 7 is constructed.

Regarding the circuit shown in Figure 7, start switch SW.

is the self-holding contact of relay RY1, as well as the relay RY
It is connected to the relay RY1 via the normally closed contact of No. 4.

The normally open contact 1a3 of relay RYI is the circuit 33 OFF switch SW, and the self-holding switch 5a1 of relay RY5
This switch SW5 is also connected to relay RY5.
and between the connection point J of relay RY5 and the power line 31,
A capacitor C is connected through the series connection of the return switches SW6 to SW9, and the a of each switch SW6 to SW is
A state on the contact side normally indicates a state in which the switch actuation piece 25 is not actuated, and when pushed by the switch actuation piece 25, it switches to the b contact side.

The b contact of each switch SW6 to SW9 is a relay R.
Connected to Y4.

Oh, contact 1a2 of relay RYI is scanning system 1 drive circuit 3
2 and the exposure/charging/eraser control circuit 33, and is connected to the circuit 33 via the normally closed contact 5bl of the relay RY5.

The operation of the above circuit will be explained with reference to FIG.

As mentioned above, the index 22 is slidably installed on the top cover 21 of the copying machine main body, and its maximum movement position from the reference side 1a is the same as when the exposure OFF switch SW5 is moved between the return switches SW8 and SW9. It is set in a position between the

Here, as the position of index 22, exposure O
FF switch SW5 is return switch SW6 and SW7
Consider the case between.

In this state, when the start switch SW4 is pressed, the relay RY1 is turned ON via the normally closed contact 4bl of the relay RY4.
, is self-held at the contact point 1a1.

As a result, the contacts 1a3 and 1a2 are closed, and the driving of the scanning system S is started by the circuit 32, and the circuit 33 is energized via the normally closed contact 5b1 of the relay →■5. etc. are turned on.

As described above, as the scanning system S moves, the operation of the cutter 8 and paper feed roller 7 is controlled by the switch SW1.

After that, the scanning system S continues to move, and the first return switch SW6 is pressed by the switch actuation piece 25, but at this time, the switch actuation piece 24 turns the exposure OFF switch SW5.
Return switches SW6 to SW9 are not pressed because
The return operation does not occur unless the circuit containing it is energized.

The scanning system S further moves, and the switch actuating piece 24 is exposed to light.
When FF switch SW5 is pressed, relay RY5 switches to relay R.
ONL via contact 1a3 of Y1 and self-holding at contact 5a1.

The exposure circuit 33 is turned off by opening the contact 5b1 in conjunction with the operation of the relay RY5, and the capacitor C is charged via the a contacts of the return switches SW6 to SW9 by closing the contact 5a1.

[At this time, the switching behavior described above has returned to the a contact side.

In this way, the switch actuating piece 25 connects each switch SW6 to
SW9 is set to be energized for only a short period].

After the capacitor C is charged, when the switch operating piece 25 presses the return switch SW7, the contact point changes from a to b, and the charge in the capacitor C flows, turning relay RY4 ON.
L, the contact 4b1 is opened, the relay RY1 is set to 0FFL, and the contact 1a2 is opened, so the scanning system S is stopped and returned as described above.

In this way, according to the embodiment shown in FIGS. 6 and 7, the exposure OF
It is returned by the return switch that is activated next to the F switch SW5. If the exposure OFF switch SW5 and the return switch were to be turned on at the same time, the capacitor C would not be charged at that time. , the scanning system S is returned by the next return switch.

As is clear from the above description, in this embodiment, the first return switch SW6 determines the shortest moving distance of the scanning system S, for example, in the state shown in FIG. In the case where the index 22 is located to the right in the figure, the return is not performed even if the exposure OFF switch SW is used to complete the actual scanning process, the return switch SW6 is activated.

The relationship between document size and return in this case is shown in FIG. 8 using a graph similar to that of FIG. 5 described above.

That is, the distance between each return switch SW6 to SW9 is the same return position, that is, SW7. SW8. SW
It will return at the operating position of 9, and all switches shorter than return switch SW6
This is to prevent the original glass 1 from overheating.

As described above, by determining the shortest moving distance l of the scanning system S and regulating the shortest time that the exposure lamp is turned off, the heating of the original glass 1 by the exposure lamp L during scanning can be adjusted to the shortest scanning moving distance. It was confirmed that even if the product was not used for a long time, it was sufficiently cooled during return and overheating was prevented.

That is, as a result of an experiment using the copying machine shown in the above embodiment without using heat-insulating glass or cooling air blowing means, when the shortest moving distance l was set to the length of A4 size for an A5 size document, Compared to the case of direct return with A5 size, the temperature rise of document glass 1 is approximately 2
08C, it got low.

It was confirmed that this was almost the same effect as using a 3-5 mm blue glass filter, and there was no significant difference in the results compared to using a heat shielding filter.

For reference, the temperature drop was approximately 5° C. when an air flow was generated on the lower surface of the document platen glass using air blowing from an internal fan.

The setting of the shortest extinguishing time is determined in consideration of the material of the document glass, the performance of the exposure lamp, and the like.

Therefore, if the return speed is slowed down, the specified time can be obtained even if the return distance is shortened.

Further, the present invention may be used in combination with heat-insulating glass and air blowing means, and the combined use has advantages such as reducing the weight and cost of the heat-insulating glass and making it possible to use a much simpler air blowing means.

Among these, in the case where roll copy paper is not used, that is, standard sheet copy paper is used, and when it is possible to make copies of a plurality of sizes, a configuration as shown in FIGS. 6 and 7 can be adopted.

In this case, the cutter activation switch SW1 is not required, and the configuration allows the use of non-standard short copy paper.

Furthermore, the present invention is not limited to the moving optical system type and electrostatic latent image transfer type copying machines shown in the above embodiments, but may also be of the moving document table type, and also to so-called FAX machines.
It can also be applied to the image transfer type.

As described above, the present invention relates to a scanning type copying machine in which the moving distance of the scanning means during scanning is variable, and the present invention is applicable to a scanning copying machine in which the moving distance of the scanning means is variable. This exposure control device is equipped with a regulating means that regulates the minimum time for lighting 1 so that the temperature rise on the document table due to lighting of the exposure lamp is below a predetermined value. This has the effect that it is possible to prevent overheating of the original glass, and that overheating can be sufficiently prevented without using special heat-insulating means such as heat-insulating glass or air blowing means.

In addition, when used in combination with the above-mentioned heat-insulating glass, air blowing means, etc., it also has the effect of reducing the cost and simplifying the structure.

[Brief explanation of drawings]

Fig. 1 is a general board diagram showing an example of a scanning electrophotographic copying machine, Fig. 2 is a top view thereof, Fig. 3 is a diagram showing the relationship between the switch arrangement of the return mechanism and the scanning system, and Fig. 4. 5 is a graph showing the relationship between the conventional return mechanism and the return mechanism of the present invention. FIG. 6 is a diagram showing another embodiment. FIG. 7 is a diagram of the circuit configuration. It is a graph showing its operation. 1... Document placement glass, 2... Lens, 20...
Original, 22... Index, 24.25... Switch actuation piece, 30.31... Power line, 32...
Scanning system 1 drive circuit, 33... Exposure, charger, eraser control circuit, SWl... Cutter operation switch, SW
2...Return switch, SW3...Return position regulation switch, 8w4...Starting switch, SW,・
...Exposure OFF switch, SW -8W9...Return switch, L...Exposure lamp, m, ~m4.
...Reflector, P...--Copy paper.

Claims (1)

[Scope of Claims] 1. A document placement table, an exposure lamp that illuminates the document placed on the document placement table, and scanning movement while illuminating the surface of the document via the document placement table with the exposure lamp. and a scanning means for performing the above scanning movement, and when the scanning movement distance of the scanning means is variable and a plurality of copies are obtained by continuous copying operations from the same original, C1 from one lighting of the exposure lamp accompanying the scanning movement. A scanning copying machine in which the time during which lighting 1 accompanies the next scanning movement is variable includes means for setting the scanning movement distance of the scanning means; A control means for regulating the minimum time from turning off the lamp after an operation associated with a scanning movement of the lamp to turning it on during the next scanning movement so that a temperature rise in the document mounting table due to the lighting of the exposure lamp is below a predetermined value. An exposure control device comprising: . 2. The setting means makes the moving distance of the scanning means variable in accordance with the length of the copy paper used,
The control means controls the shortest time so that the exposure lamp is turned off for a longer time than the time when the exposure lamp is turned off during continuous copying when the smallest usable copy paper is used. Exposure control device according to scope 1. 3. When the control means has means for regulating the shortest movement distance of the scanning means, and the scanning movement distance set by the setting means is shorter than the shortest movement distance, at least the exposure is controlled by the operation of the setting means. 3. The exposure control device according to claim 1, wherein the exposure control device controls to turn off the lamp but not to return the scanning means.