JPH0776827B2 - Document size detector - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a document size detecting device, and more specifically, to a document size detection device for closely fixing a document on a contact glass so that the document is sucked and sucked. The present invention relates to a novel document size detection device capable of simultaneously detecting the size of a document.

<Prior Art> It has been strongly demanded to automatically detect the size of an original set on a contact glass. To satisfy this requirement, a light-emitting body and a light-receiving body are provided below the contact glass. There is provided a document size detecting device which utilizes the fact that the amount of light received by the light receiver changes depending on the presence or absence of a document.

Therefore, with the document size detecting device having this configuration,
By selecting the positions of the light emitter and the light receiver, it is possible to determine which standard size original is set on the contact glass, and especially for a copying machine having a variable magnification automatic setting function. For example, the copying operation can be efficiently performed by automatically setting the scaling ratio based on the copy paper size selected in advance and the detected document size.

<Problems to be Solved by the Invention> With the document size detecting device having the above configuration, it is possible to perform reliable size detection as described above.
The required number of light emitters and light receivers must be mounted below the contact glass, which complicates the structure and must be considered so as not to hinder the movement of the optical system during document exposure. There is an inconvenience that the possible range is limited. Further, there is also a problem that the document setting position is displaced by closing the document retainer after setting the document on the contact glass.

Of these, only the latter problem can be dealt with by generating an electrostatic attraction force on the document retainer (see Japanese Patent Laid-Open No. 60-11832), but the former problem is nothing. It cannot be resolved.

This invention has been made in view of the above problems,
Even when the document holder is closed, there is no misalignment of the document,
Moreover, it is an object of the present invention to provide an original size detecting device which does not cause any complicated structure below the contact glass.

<Means for Solving the Problems> The document size detecting apparatus of the present invention for achieving the above-mentioned object is provided with a plurality of pairs of conductors at predetermined positions of a document retainer for closely fixing the document on the upper surface of the contact glass. Are mounted close to each other, the above-mentioned multiple pairs of conductors are covered with a high dielectric surface adsorption layer, and a high voltage is applied between the conductors of each pair, and the voltage of one conductor of each pair is also applied. It is characterized by comprising a detecting means for detecting a change.

However, it is preferable that each of the pair of conductors is attached to a region corresponding to the set position of a fixed-size document, and the detecting means is the voltage of one of the conductors of each pair at the beginning of power-on. Is maintained and the voltage of one conductor of each pair at the time of the detection operation is compared with the above-mentioned sustain voltage.

<Operation> In the above configuration, since a high voltage is applied between each pair of conductors attached to the document holder, an electrostatic attraction force is uniformly generated in the surface attraction layer covering the conductors. . As a result, the original can be fixed in a close contact without being displaced.

As a result of diligent research conducted by the inventor of the present case, it was found that the leakage current between each pair of conductors changes depending on whether the original is adsorbed or not adsorbed. By detecting the voltage change of one of the conductors of each pair, it is possible to detect the original adsorption area, that is, the original size.

When the pair of conductors are attached to the area corresponding to the set position of the standard document, it is possible to detect which standard size the document is, and the detection means , If the voltage of one conductor of each pair at the time of power-on is maintained and the voltage of one conductor of each pair at the time of detection operation is compared with the above-mentioned sustain voltage, it will be affected by deterioration over time. It is possible to detect the document size without fail.

<Example> Hereinafter, detailed description will be given with reference to the accompanying drawings illustrating an example.

FIG. 3 is an external perspective view showing an embodiment of a copying machine equipped with the document size detecting device of the present invention, in which a contact glass (2) is attached to the center of the upper surface of the copying machine main body (1). A document holder (3) that can be opened and closed is attached. The paper feed cassette (4) is detachably attached to one side surface at a predetermined position, and the discharge tray (5) is attached to the other side surface at a predetermined position. still,
(6) is an operation panel attached to the front part of the upper surface of the copying machine body.

FIG. 1 is an electric circuit diagram showing an embodiment of a document size detecting device.

A pair of conductors (7a) and (7b) are arranged at predetermined positions of the document retainer (3) so as to correspond to standard size document setting areas of A3 size, A4 size, B4 size and B5 size. , A pair of one conductor (7a) is connected to the positive voltage terminal of the DC high-voltage power supply (8), and the other conductor (7b) is connected to the DC high-voltage power supply (8) via a resistor (9). Connected to the negative voltage terminal of. Then, the voltage at the connection point between each conductor (7b) and the resistor (9) is directly applied to the amplifier (10) and is also applied to the amplifier (12) via the holding circuit (11). (10) Apply the output signal from (12) to the comparator (13) as a detection means, and generate the comparison output signal from the comparator (13) to CPU, RAM, ROM, I / O port, clock It is applied to a microcomputer (14) having a container and the like.

A cassette size detection signal is applied to the microcomputer (14), and a control signal from the microcomputer (14) is applied to the paper feed clutch (15) and the optical system (16). There is.

The document retainer (3) will now be described in more detail. As shown in FIG. 2, an insulating layer (17) (for example, a thickness of 2 to 4 mm) made of an insulating plastic or the like is separated from each other by a predetermined distance. In this state, conductors (7a) and (7b) made of conductive plastic or the like are provided, and the conductors (7a) and (7b) provided above are surfaces made of high dielectric plastic or the like. Adsorption layer (18) (For example, thickness 0.5m
m). Then, both conductors (7a), (7
A high DC voltage of 500 to 3000 V is applied during b). Therefore, in the surface adsorption layer (18), an electrostatic adsorption force with a shear peel strength of 3 to 5 kg on A4 size paper is uniformly generated.

With the above configuration, if the copying machine is made operable by turning on a power switch (not shown), a high DC voltage is applied between each pair of conductors (7a) and (7b) The voltage at the connection point between the conductor (7b) and the resistor (9) corresponding to the leakage current generated between the conductors (7a) and (7b) (in the state where the copy paper is not adsorbed) in It is kept held by 11) and is applied to the comparator (13) via the amplifier (12). And the other amplifier (1
At 0), the connection point voltage at each time point is applied.

Therefore, the output signals from the amplifiers (10) and (12) are equal when the original is not adsorbed, and the output signals from the amplifier (10) are large when the original is adsorbed. (10) Based on the comparison output signal from the comparator (13) which is determined by the magnitude relationship of the output signals of (12), it is possible to determine whether or not the original is adsorbed in the microcomputer (14). . Then, if the original is adsorbed, for example, if the original is adsorbed only in the area corresponding to the smallest original size by the comparison output signals from the plurality of comparators (13), then the corresponding comparator (13) only. Outputs the suction state signal, the size of the sucked document can be detected.

Then, by controlling the driving of the paper feed clutch (15) according to the detected document size, for example, a copy sheet corresponding to the document size can be conveyed, and the optical system (16)
It is possible to reliably prevent the exposure operation over an unnecessarily wide range, for example, by controlling the driving of the.

In this case, if the copying machine has an automatic scaling function, the scaling ratio can be automatically set based on the detected original size and the preset copy paper size, and the efficiency is improved. A copying operation can be performed.

Further, when the original is set on the contact glass (2), since the electrostatic attraction force is uniformly generated in the surface attraction layer (18) formed on the surface of the original retainer (3), the original retainer ( The document retainer (3) can be closed while the document is attracted to the predetermined position of 3). Therefore, it is possible to set the original in a close contact with the contact glass (2) at a predetermined position without causing positional deviation. On the contrary, even when the original is taken out, the electrostatic attraction force is generated in the surface attraction layer (18), so that it does not fly. For this reason, the contact glass (2) is attached to the document retainer (3) while being attracted to it.
Can be lifted from.

Further, since the electrostatic adsorption force generated in the surface adsorption layer (18) is evenly generated, even if the edge of the document is rolled up, for example, the part should be flattened and the entire surface should be adsorbed. You can

The present invention is not limited to the above-described embodiment, and for example, by finely setting the arrangement state of the conductors (7a) and (7b), it is possible to detect the size of the original document other than the standard size. In addition to the above, it is possible to omit the holding circuit (11) and apply a preset constant value to the comparator (13). It is possible to change the design of.

<Effects of the Invention> As described above, according to the present invention, since the size of the original is detected based on the voltage change of the conductor attached to the original holder, the light emitting element and the light receiving element are provided below the contact glass. The original size can be detected with a simple configuration.

Moreover, since the conductors of each pair attached to the document holder to which a high voltage is applied are covered with the surface adsorption layer, a uniform electrostatic adsorption force can be generated. Therefore,
The original can be surely adsorbed. Therefore, even if the edge of the document is rolled up, that part can be flattened and the entire surface can be adsorbed, so that good copying can be achieved.

[Brief description of drawings]

FIG. 1 is an electric circuit diagram showing an embodiment of a document size detecting device, FIG. 2 is a longitudinal sectional view showing the structure of a document pressing device, and FIG. 3 is a copying machine equipped with the document size detecting device of the present invention. FIG. 3 is an external perspective view showing an example. (2) ... contact glass, (3) ... document holder, (7a) (7b) ... conductor, (11) ... holding circuit, (13) ... comparator as detection means,

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Masuo Kawamoto 1-2-2 Tamatsukuri, Higashi-ku, Osaka City, Osaka Prefecture Mita Industrial Co., Ltd. (72) Katsumi Nagata 1-2-2 Tamatsukuri, Higashi-ku, Osaka City, Osaka Prefecture No. Sanda Kogyo Co., Ltd. (56) Reference JP-A-56-64363 (JP, A) Actually opened 58-31552 (JP, U) Actually opened 56-145059 (JP, U) Actually opened 60- 140948 (JP, U)

Claims (3)

[Claims] 1. A plurality of pairs of conductors are attached in close proximity to each other at a predetermined position of a document holder for closely fixing a document on the upper surface of a contact glass, and the plurality of pairs of conductors are attracted to the surface of a high dielectric material. A document size detecting apparatus, which is covered with a layer, applies a high voltage between the conductors of each pair, and is provided with detection means for detecting a voltage change of one conductor of each pair. 2. A document size detecting apparatus according to claim 1, wherein each pair of conductors is attached to an area corresponding to a set position of a standard size document. 3. The detecting means maintains the voltage of one conductor of each pair at the beginning of power-on, and compares the voltage of one conductor of each pair at the time of detection operation with the sustain voltage. The document size detecting device according to claim 1.