JPS58217948A - Copying machine - Google Patents

Abstract

PURPOSE:To prevent copy deviation due to an impact generated during returning operation, by controlling the starting of the return of an optical system in accordance with the length of copying paper in a paper feeding direction. CONSTITUTION:The optical system 42 moves forth as shown by an arrow B to make a scan on an original and the distance of this forward movement is controlled by counting a reference pulse signal. For example, when the forward movement of the optical system 42 is detected by a sensor 50, in other words, once a paper feeding roll 15 starts rotating, the counting of the reference pulse signal is started. When the counted value of a pulse signal generated until a sensor 17 detects the rear end of copying paper is greater than a specific value, namely, when the length of the copying paper in the paper feeding direction is longer than the conveyance path length between the transfer position and fixing and clamping part of a photosensitive drum 3, the backward movement of the optical system 42 is inhibited for a specific time corresponding to the detected length of the copying paper. Therefore, transfer deviation due to an impact during the backward movement of the optical system 42 is not caused.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method in which the length of the transfer material conveyance path between the transfer position of the image bearing drum and the fixing pressure section is shorter than the length of the copyable transfer material, such as copy paper, in the paper feeding direction. The present invention relates to a copying apparatus having a paddle configuration.

An outline of the copying process in the above-mentioned copying apparatus will be described.

When a copy document is placed on the document table and a copy button is pressed, an exposure lamp illuminates the document and travels in a predetermined direction together with an optical system including a reflecting mirror. Reflected light corresponding to the density of the original is uniformly irradiated onto the charged image carrier drum, that is, the photosensitive drum, through the optical system, and an electrostatic latent image is formed on the image carrier drum. . Furthermore, a toner image corresponding to the density of the document is formed on the photoreceptor drum by the developer.

On the other hand, copy paper (transfer material) is fed from the paper feeder so as to match the position of the toner image on the photoreceptor drum.
(They come into contact with each other.) Then, the toner image formed on the surface of the photoreceptor doshim is transferred to the copy paper by the transfer electrode.

During this time, the photosensitive drum continues to rotate in a predetermined direction, and the toner image is gradually transferred onto the copy paper. After that, the copy paper with the toner image transferred is separated from the photoreceptor drum,
The copy paper is sent to a roller fusing device. The roller fixing device includes two rollers, at least one of which is a heated roller, and heats and fixes an image formed by a developer onto copy paper.

Thereafter, the copy paper is ejected out of the main body of the copying apparatus.

In the above-described copying process, a document is copied onto copy paper, but during this process, so-called transfer deviation may occur. The cause of transfer misalignment is that the leading edge of the copy paper is clamped by the fixing roller and the other end (rear end) is still in contact with the photoreceptor drum, and the optical system travels in a predetermined direction and then returns. This tends to occur when transitioning to operation.

Therefore, if the length of the copy paper is shorter than the length of the conveyance path between the position of the fixing roller and the photosensitive drum, the above-mentioned transfer deviation hardly occurs.

That is, in a typical copying apparatus, a single drive motor moves the optical system, rotates the photosensitive drum, feeds paper, and so on. When the length of the copy paper in the paper feeding direction is longer than the length of the transport path, in other words, when copy paper larger than a certain size is used, the impact caused by the impact when the optical system shifts to the return operation, etc. , it is thought that the above-mentioned transfer deviation occurs.

The present invention is intended to correct the above-mentioned defects, and is designed to control the start of the return movement (return travel) of the optical Iz control system in accordance with the size of the transfer material, for example, copy paper. By preventing the optical system from starting the return movement while the leading edge of the copy paper is being pinched by the fixing roller and the trailing edge is in contact with the photoreceptor drum, the optical system can be It was possible to prevent so-called copying misalignment from occurring on the transfer material due to the impact generated during the moving operation.

Next, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic sectional view of essential parts of an example of an electrophotographic copying machine to which the present invention is applied.

A copy original (not shown) is placed on the original glass 1 . A photosensitive drum 3 is provided at the center of the interior of the body housing 2 and is driven to rotate in the direction of arrow A. A charger 4, a developing device 5, a transfer electrode 6, a separating electrode 7, a static eliminating electrode 8, and a cleaning device 9 are provided on the outer circumference of the photosensitive drum 3, respectively.

Reference numerals 11 and 12 denote paper feed cassettes, which store copy sheets of different sizes. Reference numerals 13 and 14 are paper feed rollers, and 15 and 16 are feed rollers 2.

Further, numeral 17 is a sensor for detecting the leading edge and trailing edge of the copy paper.

Reference numeral 21 includes a conveyor mechanism 461, including a drive roller 22, a driven roller 23, and a conveyor belt (24) wrapped around these rollers. Reference numeral 31 denotes a fixing device, which is composed of a heating roller 32, a pressure roller 233, etc. 0. The upper part of the photosensitive drum 3 is guided by a guide member 41 and moves forward in the direction of arrow B. An optical system 42 that doubles in the direction is provided. optics. In the system 42, the light from the exposure lamp 43 passes through the document table glass 1 and illuminates the copy document. The light reflected from the copy original is then
The light is reflected by the reflecting mirror 44 , the second reflecting mirror 45 , the third reflecting mirror 46 , and the fourth reflecting mirror 47 to irradiate the photosensitive drum 3 .

Note that 48 is a lens. 5o is a sensor for detecting the position of the optical system (the position of the center of the optical axis).0 In the copying machine configured as described above, when copying, the paper feed cassette is moved by an operation switch (not shown). specified, and the specified signal is supplied to the microconbeater. Therefore, which of the paper feed rows 213, 14 is rotated is specified. Then, by operating a copy button (not shown), the optical system 42 moves in the direction of arrow B, and the photosensitive drum 3 rotates. ``Furthermore, the photosensitive drum 3 is brought into a charged state by the charger 4.

Further, for example, the lower cassette 12 is selected, and the paper feed roller 1
4 rotates to feed the copy paper into the conveyance path C, and when the leading edge of the copy paper is detected by the sensor 17, the paper feed roller 14 is brought to a stopped state.

On the other hand, while the optical system 42 is moving in direction B, it is detected by the sensor, and this causes the paper feed roller 15 to rotate and feed the copy paper toward the photoreceptor drum 3. The copy paper comes into contact with the visible image (toner image) formed on the surface of the copy paper, and the transfer electrode 6 transfers the visible image onto the copy paper. Thereafter, the copy paper separated from the photoreceptor drum 3 by the separation electrode 7 is fed into the fixing device 31 from the conveyance path.

Incidentally, the optical system 42 moves forward in the direction of arrow B to scan the document, but the distance of this forward movement is controlled by counting the reference pulse signal in this embodiment.

The reference pulse signal is obtained by a reference pulse generation mechanism as shown in FIG. This reference pulse signal is used as the basis for various control timings, and for example, counting starts when the forward movement of the optical system 42 is detected by the sensor 50, in other words, when the paper feed roller 15 starts rotating. do. That is, when motor M rotates,
If the optical system 42 and the photosensitive drum 3 are configured to rotate in synchronization with the belt 60, the belt 60
The encoder plate 61, which has grooves cut at equal intervals on its periphery, rotates, and in accordance with the rotation, a reference pulse signal is generated by a detector 62, such as a photointerrupter, which is composed of a light emitting diode 621 and a phototransistor 622. is detected. Note that the time of one cycle of the reference pulse signal obtained from the detector 62 varies depending on the precision of control, but is generally about several m5ec.

This reference pulse signal is supplied to a microcomputer as a control section. Therefore, by counting the reference pulse signals generated while the sensor 17 detects the copy paper after the paper feed rollers 15 and 16 start rotating, the size of the copy paper can also be detected as the number of reference pulses. . That is, if the trailing edge of the copy paper is detected by the sensor 17 and the count value of the pulse signal at that time is larger than a predetermined value, in other words, the length of the copy paper in the feeding direction is the same as the transfer position of the photoreceptor drum and the fixing position. If it is longer than the conveyance path length with the pinching part, the control signal from the microcomputer will
The return movement of the optical system 42 is prohibited for a predetermined period of time depending on the detected length of the copy paper. The above prohibited operations are
The time corresponding to the number of pulse signals is stored in advance in the storage device in the control unit. 31. Therefore, even if the optical system 42 moves back after the prohibition is canceled, the rear end of the copy paper remains detached from the photosensitive drum 3. Therefore, no transfer deviation occurs due to impact when the optical system 42 moves back.Of course, if the length of the copy paper is shorter than the conveyance path length, there is no need to temporarily prohibit the back movement of the optical system 42. .

In the fixing device 31, the copy paper is heated by being sandwiched between a heating roller 32 and a pressure roller 33. The transferred visible image is then printed onto copy paper. Thereafter, the copy paper is discharged outside the main body 2, and the series of copying steps is completed.

Since copying is performed as described above, even if the optical system 42 moves back (in the direction of arrow B'), no transfer deviation will occur due to the impact at that time.

Note that in this embodiment, a transfer material detection means is provided in the conveyance path,
This method detects the length of the transfer material, but another method is to detect the size of the transfer material using a paper cassette and store it in advance in the microcopier/peter. A similar effect can be obtained by controlling the timing of the backward movement of the optical system without detecting the trailing edge.As described above, the present invention provides that the optical system, which has moved forward in a predetermined direction for the copying operation, The timing of backward and backward movement can be controlled. Therefore, even if one end of the copy paper is clamped by the fixing clamping unit, transfer misalignment will not occur.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a copying machine showing an embodiment of the present invention, and FIG. 2 is an explanatory diagram of pulse signal generating means for detecting the timing when the optical system moves backward. Note that the symbols used in the drawings are 3......Photosensitive drum 13.14...Roller 17.50...・・・・・・Sensor 21・・・・・・・・・・・・・・・・Transport device 31・
・・・・・・・・・・・・・・・Fixing device 42...
・・・・・・・・・・・・・・・It is an optical system.
Agent: Hiroshi Aisaka, patent attorney @1 country! @Figure 2

Claims (1)

[Scope of Claims] 1. In a copying apparatus configured such that the length of the transfer material conveyance path between the transfer position of the image carrier drum and the fixing pressure section is shorter than the length of the copyable transfer material in the sheet feeding direction. 1. A copying apparatus characterized in that the start of the backward movement of the optical system is controlled according to the length of the transfer material in the sheet feeding direction. 2. A transfer material detection means is provided on the upstream side of the transfer position in the conveyance path of the transfer material, and after the forward movement of the optical system is stopped according to the length of the transfer material in the paper feeding direction detected by this detection means, The optical system is configured to start a backward movement operation after a predetermined time.
A copying apparatus according to claim 1.