JPH02304580A - Image forming device - Google Patents

Abstract

PURPOSE:To make the whole of an image forming device simple, small-sized, and low-cost by using a surface area corresponding to the image area part to be subjected to trimming processing and masking processing as a non- electrification part and using only a required surface area as an electrification part and selectively performing the electrification processing. CONSTITUTION:A contact electrifying member 2 is formed to a one-dimensional array body of plural small electrifying members 21, 22 to 2n divided in the longitudinal direction, and these electrifying members have front end parts brought into contact with the surface of a photosensitive drum 1 with a prescribed pressing force in the drum generating line direction. A voltage is selectively applied to them through electric wires individually connected them. An area designating means 30 is provided which designates coordinates of the image part area to be subjected to trimming, masking, or the like out of the image surface of an original to be copied, and for example, a digitizer which discriminates the position by a pen type marker 30a is used. Thus, the whole of the device is made simple, small-sized, and low-cost because only the required surface area is selectively electrified as the electrification part.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to an image forming apparatus.

More specifically, the present invention relates to an image forming apparatus that performs image formation by applying an image forming process that includes a step of charging the surface of an image carrier such as an electrophotographic photoreceptor or an electrostatic recording dielectric material.

(Prior Art) Conventionally, image forming apparatuses such as electrophotographic copying machines equipped with image trimming processing functions and masking processing functions are known. Specifically, the surface of the photoreceptor as an image carrier is uniformly charged by a charging means, and then the area of the photoreceptor surface corresponding to the image area to be trimmed or masked is charged using a laser scanning method, an LED array method, or a liquid crystal display. An exposure/optical system such as a shutter array type is used to selectively expose and eliminate static electricity, that is, to make the area into a non-image area.

(Problems to be Solved by the Invention) However, the exposure/optical system used as the static elimination exposure means itself requires a complicated and expensive exposure device, its drive circuit, etc., and as a result, the image forming apparatus becomes complicated and large in size. This was one of the reasons for the high cost.

The present invention selectively uses the charging means of the image bearing member itself to selectively change the surface area of the image bearing member corresponding to the image area portion to be trimmed or masked into a non-charging part, and to make only the required surface area a charging part. The purpose is to provide a solution that solves the above-mentioned problems by making it possible to process tFi[.

(Means for Solving the Problems) The present invention is an image forming apparatus that executes image formation by applying an image forming process to the surface of an image carrier, including a step of charging the surface of the image carrier. The charging means is a contact charging device that charges the surface of the image carrier by bringing a charging member to which a voltage is applied into contact with the surface of the image carrier.

The charging member of the contact charging device is an array of small charging members divided into a plurality of parts along a direction substantially perpendicular to the direction of relative movement with the image carrier surface and electrically insulated from each other.

It has a contact charging device control means for selectively controlling the applied voltage to each of the small charging members of the charging member, and has a contact charging device control means for selectively controlling the voltage applied to each of the small charging members, and the voltage applied to each of the small charging members is adjusted to an arbitrary value on the surface of the image carrier by selecting the selected image side σ-. An image forming apparatus is characterized in that it is possible to selectively charge a surface area of the image forming apparatus.

(Function) Corona dischargers such as corotrons and scorotrons, which have good uniformity of charge, are widely used as a means for charging the surface of the image bearing member, which is the object to be charged. However, corona dischargers require expensive high-voltage power supplies. It requires space for itself and a shield space for the high-voltage power supply, and it often generates corona products such as ozone, which requires additional means and mechanisms to deal with them, which makes the device larger and more expensive. There are problems such as the factors being equal.

Therefore, in recent years, consideration has been given to using contact charging means (direct charging means) instead of corona dischargers, which have many problems. In contact charging, a voltage (
For example, by contacting a conductive member (charging member) to which a DC voltage of about 1 to 2 KV, or a superimposed voltage of DC voltage and AC voltage, etc. is applied, charges are directly injected into the surface of the image carrier to carry the image. This device charges the body surface to a predetermined potential, and includes roller charging type (JP-A-58-91253) and blade charging type (JP-A-51194349 and JP-A-6G-14775).
Publication No. 8), combined charging and cleaning type (Unexamined Japanese Patent Publication No. 1983-
No. 185188) etc. have been devised.

This contact charging means is extremely effective even if corona products are generated.
It is a trace amount. It has the characteristics that the applied voltage can be lowered, the charging width is narrow, the charging process starts quickly after applying the voltage, and conversely, the charging process can be abruptly stopped by stopping the voltage application or lowering the applied voltage level, etc. It has the following characteristics.

The present invention uses this contact zone 'I as a charging means for the f#l carrier.
T! , r one stage is used. Then, as described above, the charging member of the contact charging means is divided into a plurality of parts along the direction perpendicular to the direction of relative movement with the image carrier surface, and the small charging members are arranged in an electrically insulated manner. (a one-dimensional array of small charging members) and selectively controlling the applied voltage to the individual small charging members, i.e., the individual small charging members.
By having a configuration in which the electrical member is selectively controlled between a belt-centered state and an uncharged state with respect to the image carrier surface, for example, an LED
- Individual LE of dimensional array or liquid crystal shutter dimensional array
Selectively turn on and off the D or liquid crystal shutter in the main scan to selectively write and expose the surface of the image carrier that moves in the sub-scanning direction, or turn on and off the individual heat generating elements of the one-dimensional array individually in the main scan. In the same way as when selectively heating the surface of a thermal recording paper that moves in the sub-scanning direction to form a desired image information pattern, the contact charging device itself serves as a means for uniformly charging the surface of the image carrier. , the surface area corresponding to the part to be trimmed or masked specified in advance is unbanded. , and only the necessary surface area can be selectively charged as a charging section.

Therefore, it is no longer necessary to provide an exposure/optical system as a means for selectively forming a charged area portion and an uncharged head portion on the surface of an image carrier, which is required in the past, and the overall image forming apparatus can be simplified, miniaturized, and Cost reduction becomes possible. Furthermore, since the surface of the image carrier is charged by a contact charging method rather than a corona discharger,
Advantages specific to the contact charging method, such as lower voltage and suppression of the generation of corona products, can also be achieved. (Example) Example 1 FIG. 1 shows a schematic configuration of an image forming apparatus according to an example of the present invention.

(1) Overall configuration of the apparatus 1 is a drum-shaped electrophotographic photoreceptor (hereinafter referred to as a photoreceptor drum) as an image carrier, and is rotated clockwise around a support shaft 1a at a predetermined circumferential speed (process speed).

Reference numeral 2 denotes a charging member of a contact charging device for charging the surface of the photoreceptor drum. This contact charging device will be described in detail later. The contact charging member 2 charges the entire surface of the photosensitive drum 1 or selectively a designated partial area thereof to a predetermined potential.

0 is an original to be copied, which is set on a reciprocating type original table glass (not shown) with the image surface facing downward.

Alternatively, in a sheet document conveyance device 2i (ADF) (not shown), 1
The iQIJJ section 3 is moved from one side to the other side, and the downward image section is illuminated and scanned by the lamp 4, and the light reflected from the document surface of the illumination light is used by the short focus lens array 5 (SLA) to illuminate the charged image at the exposure section 6. Image forming exposure 7 is performed on one surface of the photoreceptor drum. Through this exposure 7, a static latent image corresponding to the exposure pattern is formed on the surface of the photoreceptor drum.

The Hq image is developed as a toner image by a developing device 8 and reaches the position of a transfer roller 9 as a transfer means.

On the other hand, a transfer material P fed from a paper feed section (not shown) is fed to a transfer section between the photoconductor drum I and the transfer roller 9 via a pair of registration rollers 1O in synchronization with the rotation of the photoconductor drum I. The toner image on the first surface of the photoreceptor drum is sequentially transferred to the surface of the fed transfer material at the transfer section.

The transfer material that has undergone the image transfer is separated from the surface of the photoreceptor drum and introduced into the fixing device 11, where it undergoes image fixing processing.
After the image has been transferred, the surface of the photosensitive drum is cleaned by a cleaning device 12 and is repeatedly used for image formation.

(2) The contact charging member 2 of the contact charging device in this example is generally perpendicular to the rotational direction of the photoreceptor drum 1 (in the direction of the line of the drum 14).
The blade-shaped contact charging member 2 of this example is a blade-shaped conductive member (made of conductive rubber, etc.) having a long length.
As shown in the front view in FIG. 2(a) and in the plan view in FIG.・0 individual small charging members 2I in the form of a one-dimensional array of 2n ・2
2...2n are made of a one-dimensional array of small electrically charged members of the whole wood by overlapping and fixing the side parts one after another with an insulating adhesive 2o (alpha should be glued). The small electrically charged members of are electrically insulated from each other and non-conductive,
The tip portions of the individual small charging members 21, 22, .

In addition, each small charging member 2I, 22...2n is connected to the electric wire 21.
22...2n are connected, and each small charging member receives a voltage selectively through the connected electric wire. As shown in the third diagram, each small charging member 2
The power supply 22 that applies voltage to I 22...2n is 1
and its output side and each small charging member 21
2...Electric wires 21+ and 212... connected to 2n
21n is one tree connected through the switching circuit 23, and each switch element F23+ ・232...2
3n is selectively controlled by a drive circuit 24. The drive circuit 24 includes a first buffer 24a and a second buffer 24b.

(3) Area Designation Means In FIG. 1, numeral 30 is an area designation means for specifying the coordinates of a partial image area to be trimmed or masked on the image surface of the original to be copied. In this example, a digitizer is used that identifies the position using a pen-shaped marker 30a. Since this digitizer itself is conventionally known, detailed explanation thereof will be omitted.

When creating a copy by trimming or masking a desired partial image area on the image surface of the original to be copied, set the original in a predetermined position on the original holding plate (coordinate plate) of the digitizer 30 and perform the trimming or masking process. The desired image partial area is designated by operating the mode keys 31a to 31d and the marker 30a, and is stored in the memory 33.

Specifically, this is done in two ways. One is when the image partial area to be specified is a rectangle, press the mode key 31c and use the marker 30a to specify the coordinate positions of two points on the diagonal line of the area and read it. . The other is mode key 31d
is pressed to specify and read the coordinate position of the edge portion of the desired area using the marker 30a. After specifying an area in this way, the first step is to press the mode key 31a if you want to trim the specified area, or press the mode key 31b if you want to mask it.This operation will display the coordinate position information of the specified area and the trimming or Masking selection designation information is stored in the memory 33. Specifically, a matrix of position coordinates is sequentially arranged with the longitudinal direction (generating force surface) of the photoreceptor drum l as the line direction, and one-dimensionally stored as "1" or "0" depending on whether it is an image area or a non-image area. be done.

(4) After performing voltage application control to the charging member and specifying the image area as described in h, the original is removed from the digitizer 30 and set on the original platen glass of the image forming apparatus or the sheet original transport device.

When a copy start signal is input to the control circuit by pressing the copy start button, etc., the contact charging device first records one line at the leading end of the memory stored in the memory 33 as described above. The memory of the 0th line read into the buffer 24a is shifted and registered to the second buffer 24b, and the memory of the next line is transferred to the first line instead.
The data is read into the buffer 24a. If the memory of each unit area corresponds to the image area, that is, rlJ, then the energization switching element for the small charging member corresponding to that position is driven by the drive circuit 24 and turned on. Otherwise, it remains off. Then the photoreceptor drum
According to the rotation of , a potential is applied to the column to which a voltage is applied to the small charging member. When the photoreceptor drum l further rotates to the position corresponding to the next line, the small charging member at the part "l" in the memory stored in the second buffer 24b turns on. Become. "
0" is off. In this way, only the photoreceptor drum surface area corresponding to the designated image area is selectively charged to a predetermined uniform potential, and the steps of image exposure 7 and development 8 are applied to that drum surface. Also, by executing the transfer and fixing, an image copy is output in a form in which trimming processing and masking processing have been performed as the area was initially specified.

The voltage applied to each small charging member 2I, 22, . . . 2n to charge the surface of the photoreceptor drum is, for example, 1 to 2K.
For example, - By applying a DC voltage of 1.3 KV, a charging potential of about -700 is applied. In the case of applying an oscillating voltage, the charging potential can be controlled to the voltage value of the DC voltage component, for example, 150
A charging potential of -700V is applied at 0VPP and -700VDC. In the case of a method that applies an oscillating voltage, charging/uncharging control is performed by turning on and off a superimposed voltage of AC and DC components for each small charged member, and also by turning only the DC component on and off. Example 2 In Example 1, in order to obtain one image, the number of photoreceptor drums l is 1. If the drum must be rotated more than once, or if there is a part of the drum that was charged in one revolution but should not be charged in the same place in the next revolution, the voltage applied to the small charging member corresponding to that part Static electricity cannot be removed simply by turning off the application, so the charging member 2
It is necessary to eliminate static electricity by pre-exposure or the like on the upstream side in the direction of movement of the drum surface. Therefore, in this embodiment, in order to eliminate the charge removal process such as pre-exposure, the direction of the voltage applied to the band':rL member 2 is changed.

First, the applied voltage is AC,! Note that -DC is superimposed 1 For example, by applying 1500VPP, -7000(:), a charged potential of -700V can be obtained.Here, if this application method is used, the DC voltage will be approximately Ov. By doing this, the drum potential can be neutralized to approximately Ov. Therefore, as a power supply, two types of DC voltage outputs, 1700V and approximately Ov, are prepared in advance, and in Example 1, band 1 is turned off. The switch is changed so that the DC voltage becomes approximately Ov.

Embodiment 3e (FIG. 4) In this example, a blade-shaped contact charging member 2 is supported by a horizontally long insulating thin plate 25, and small charging members 211, 122, .・Arrange 2n in a staggered pattern and glue and fix the whole - wooden small 1? It is constructed in the form of a one-dimensional array of main members.

In comparison with the example shown in the m2 diagram above, the strength of this example is improved overall, and there is no need for the overlapping adhesion α between adjacent small charged members as in the example shown in Figure 2, so the adhesive is not required. It is possible to reduce the overlap of charging widths between adjacent small charging members to almost zero, and to reduce the convergence of each small charging member, it is possible to increase the number of divisions and perform more precise area-specific charging processing. Become.

Embodiment 4 (FIG. 5) Charging blade pieces 211122, which are individual small charging members of the blade-shaped adhesive charging member 2 as shown in FIGS. 2 and 4.
When selectively applying a voltage to 2n to selectively charge one surface of the photoreceptor drum, which is an image carrier, the adjacent charging blade pieces 21, 22, . . . 2n move in the direction of movement of the drum 1 surface. Because the relationship is shifted back and forth, Figure 5 (
As shown in b), the region boundary line between the upstream side and the downstream side in the drum surface movement direction of the charged region a becomes a jagged line.

This jagged line condition can be resolved by shifting the driving timing of the switch that applies voltage to the front and rear charging blade pieces in the drum surface movement direction of each charging blade piece, as shown in Figure 5 Cm). .

Example 5 (Figure 6).

In this example, charging blade pieces 21 and 22 are used as small charging members.
... 2n are lined up in a horizontal line without shifting back and forth in the direction of movement of the drum surface, and adjacent charging blade pieces are electrically insulated from each other and glued together to form a single small 4n"i.
The blade-like contact charging member 2 is constructed in the form of an ri member-dimensional array. Reference numeral 25a is a support (insulating) that is commonly attached to each small charging member.In the case of this charging member 2, the jaggedness of the charging area boundary line as shown in FIG. 5(b) does not occur.

By setting the spacing between adjacent charging blade pieces to 50 gm or less, there is almost no occurrence of slit lines on the image surface due to poor charging in adjacent parts of the charging blade pieces (A
(in case of C+DC application).

Note that the charging blade pieces 2+*, which are individual small charging members of the blade-shaped contact charging member 2 of the example in FIG. 2, the example in FIG. 4, and the example in FIG.
2z...2n may be made of a conductive material (10'Ω・Cm or less) and exposed, as long as the adjacent ones are insulated to be non-conductive.
It may be coated with a resistance layer of 10/2" to 10/2" Ωcm (to prevent leakage).

Embodiment 6 (Fig. 7) In this example, as shown in the enlarged vertical cross-sectional view of Fig. 7 (b), a rectangular insulating frame cover is made of a large number of conductive wires 26 whose outer peripheral surfaces are coated with a resistive coating 26a. 27, each of the bundled conductive thin wires 26 is provided with a common electrode portion 28 to constitute a unit charging brush unit 29, and the brush unit 29 is used as a small charging member, and a plurality of the brush units 29+ and 29z”-29n are connected to a seventh As shown in Figure (a), the small charging members are arranged horizontally in a line to form a single small charging member-dimensional array, and this is used as the contact charging member 2.0Individual unit charging brush unit y
29 (+~n) is the charging blade piece 2 (!~
Corresponding to n), electric wires 21 (1 to n) for voltage application are connected to each electrode portion 28 of each brush unit 29 (+ to n).

This type of contact charging member 2 is less likely to cause streaks on the image surface due to charging failure in the adjacent portions of each brush unit, and it is also less likely to cause jagged charging area boundaries as shown in FIG. 5(b). Don't let it happen.

Note that the contact charging member 2 may have a configuration other than those shown in each of the above embodiments. A similar configuration can be considered using electric rollers.

Further, in the above embodiments, a trimming process or a masking process is used as an example to selectively charge a desired surface area of the image carrier surface, but in other cases, for example, the width of the transfer material P to be fed may be changed. Detect it and respond to it to control the charging motion.

The contact charging member 2 can also be controlled to create a binding margin.

(Effects of the Invention) As described above, according to the present invention, unlike the conventional image Jjl
It is no longer necessary to provide an exposure/optical system as a means to selectively form a charged region Φ uncharged region in body blood.
The entire image forming apparatus can be simplified, downsized, and lowered in cost. Furthermore, since the surface of the image carrier is charged by a contact charging method rather than by a corona discharger, advantages unique to the contact charging method such as lower voltage and suppression of the generation of corona products can be enjoyed.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment. Fig. 2(a) is an enlarged front view of the contact charging member with parts omitted, Fig. 3(b) is its plan view, Fig. 3 is a block diagram of the switching circuit and drive circuit system, and Figs. 4(a) and (b). ) is a partially omitted enlarged front view and a plan view of another configuration example of a contact charging member, and FIGS. 5(a) and 5(b) are an example in which the charging sphere boundary line is not a jagged line and an example in which it is a jagged line, respectively. FIG. 6 is a partially omitted perspective view of yet another configuration example of the contact charging member, FIG. 7(a) is a partially omitted perspective view of a contact charging member in the form of a charging brush, and FIG. 7(b) is an enlarged vertical cross-sectional view of the brush and its constituent thin lines. 1 is a photosensitive drum as an image carrier, 2 is a contact charging member, 21 to n·29+xn are charging blade pieces or unit charging brush units as divided small charging members, 22 is a voltage application source, 23 is a switching circuit, 24 is a drive circuit, 30
33 is a digitizer as a charging processing area designation means; and 33 is a memory.

Claims (1)

[Claims] (1) An image forming apparatus that performs image formation by applying an image forming process that includes a step of charging the image bearing surface, and the charging means for the image bearing surface charges a charging member to which a voltage is applied to form an image. This is a contact charging device that charges the surface of the image carrier by bringing it into contact with the surface of the image carrier, and the charging member of the contact charging device is divided into a plurality of pieces along a direction substantially perpendicular to the direction of relative movement with the surface of the image carrier. It is an array of small charging members electrically insulated from each other, and has a contact charging device control means for selectively controlling the voltage applied to each of the small charging members, An image forming apparatus characterized in that it is possible to selectively charge an arbitrary surface area of an image carrier surface by selectively controlling a voltage applied to a member.