JPS63136063A - Image formation control method for copying machine - Google Patents

Abstract

PURPOSE:To switch developing bias voltages in units of electrostatic latent images by delaying the start point of a copying process after switching by a specific time and equalizing this delay time to the time up to the complete exit from a state in a developing area. CONSTITUTION:When an operator switches developing bias voltages by a switching means, the time of image formation is delayed by the specific time to produce a state wherein there is no electrostatic latent image in the development area L in a next copying process, and the developing bias voltages are switched in this period. The developing bias voltages are not switched in real time, but switched in a next developing process. When the interval between the rear end of an electrostatic latent image 26 and the front end of an electrostatic latent image 28 is (l) and the speed of a photosensitive body 1 is (v), the specific delay time T is T>=t1-t2 (where t1=L/v and t2=l/v). Namely, the delay time is as long as the time required for the precedent electrostatic latent image to exit completely from the state in the development area L. Consequently, an optimum copy can be taken.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an image formation control method in a copying machine.

(Prior Art) A continuous copying process is possible in which the electrostatic latent image on the photoreceptor is continuously visualized, and the electrostatic latent image is sent to the development area,
2. Description of the Related Art A copying machine that visualizes an electrostatic latent image under application of a developing bias voltage is known.

Particularly in high-speed copying machines, in order to increase the copying speed, the spacing between transfer sheets is reduced, and therefore the spacing between electrostatic latent images carried on the photoreceptor is also set small. Therefore, there is a possibility that a plurality of electrostatic latent images exist simultaneously in the development area and are visualized.

For this reason, even if it becomes necessary to adjust the density of one image, the developing bias value cannot be changed for each electrostatic latent image. There is a problem in that it is necessary to visualize the image with a developing bias of .

Additionally, many copiers require the operator to
An image density control method is adopted in which the developing bias value is switched by operating a density adjustment key. In such a copier.

Since the bias value changes immediately upon operation, there is a problem in that the bias value changes even during the development of the electrostatic latent image, resulting in visible images with different densities within the image.

As a means to solve these problems, in copying machines where the developing area is formed by a developing device consisting of multiple developing sleeves, a dedicated bias power source is provided for each developing sleeve, and the application timing is controlled for each. However, since it is necessary to provide a dedicated bias power source for each of the plurality of sleeves, there is a problem of increased cost.

(Objective) Therefore, the object of the present invention is to make it possible to switch the developing bias voltage for each electrostatic latent image without providing a dedicated bias power supply for each of a plurality of sleeves. i! An object of the present invention is to provide an improved method of controlling image formation in a copying machine that can obtain optimal development corresponding to a latent image.

(Structure) In order to achieve the above object, the present invention provides a system in which when the leading edge of an electrostatic latent image is at the entrance of the developing area, the trailing edge of the immediately preceding electrostatic latent image is still in the developing area. When the developing bias voltage is switched during continuous copying under the electrostatic latent image spacing condition of
It is characterized in that the time required for the preceding image to completely leave the development area from the state in which it is present in the development area is taken as the time.

A detailed description will be given below based on one embodiment of the present invention.

In FIG. 1 illustrating the developing device according to the present invention, developing sleeves 2A, 2B, and 2C are sequentially arranged from upstream of a belt-shaped photoreceptor 1 that moves in the direction of the arrow, and the developing area is defined by the area in which these sleeves are arranged. is set. Each developing sleeve rotates in the direction of the arrow, and performs a developing function by forming developer in the shape of a magnetic brush on its circumferential surface by the magnetic force of a magnet immovably provided inside. Although not shown, a developing bias voltage is applied to each developing sleeve.

This developing bias voltage is used to make the electrostatic latent image on the photoconductor 1 visible using toner, which is a developer on each developing sleeve, and to prevent the background part of the electrostatic latent image from becoming visible. applied.

In high-speed copying machines, the linear velocity of the photoreceptor 1 is high, and accordingly, in order to improve the developing ability, the rotational speed of each developing sleeve is increased or the number of developing sleeves is increased.

Reference numeral 6 indicates a paddle, which smoothly transports the developer to the developing sleeve 2A. The developer sent to the developing sleeve 2A is sequentially transferred to the other developing sleeves 2B and 2C, is used for development, and then falls, passes through the coil bobbin 8, and is sent to the stirring spring 1.
It reaches 0.

The stirring spring 10 has the function of stirring the developer to facilitate frictional electrification, and also having the function of making the toner supplied from the toner supply roller 12 uniform.

Reference numeral 14 designates a toner stirring member, which is provided to send the toner supplied from the toner cartridge 16 to the toner supply roller 12 side and to prevent toner from accumulating at the toner near-end sensor 18.

The toner near-end sensor 18 here uses a piezoelectric element, and converts the pressure difference between when there is toner on the sensor surface and when there is no toner on the sensor surface into a voltage. has some toner, so
It is used as a near-end sensor.

Reference numeral 20 indicates a control printed board provided with a control circuit for keeping the toner concentration constant, and the inductance of the developer passing through the coil bobbin 8 is compared with the inductance of a reference coil in the printed board. When the toner concentration is low, the toner replenishment motor is activated and toner is replenished by rotation of the toner replenishment roller 12. At this point, if the toner density does not increase even after replenishment, it is determined that the toner is completely empty, and
- It is the end of the story.

Reference numeral 22 indicates a power supply for developing bias, and the DC voltage is l.
It can be switched to O number of stages.

It is desirable that the surface of the photoreceptor 1 facing the developing sleeves 2A, 2B, and 2C has a flatness with an appropriate gap, and a backup roller 2 is used as a means to ensure the above state.
4A, 24B, and 24C are provided.

Each arrow shown in Fig. 1 indicates the rotation direction of the member to which the arrow is attached, and since the advancing direction of the photoreceptor and the rotation direction of each developing sleeve are the same, the forward three-stage development method is used. It can be said to be a developing device.

In the above configuration, in the case of high-speed copying, the interval between the electrostatic latent images on the photoreceptor 1 is reduced, so that the electrostatic latent image 26 is formed on the developing sleeve 2C1 and the electrostatic latent image 2 as shown in FIG.
8 may be simultaneously developed on the developing sleeve 2A.

If the developing bias is switched under such conditions, the density will differ within one electrostatic latent image, which is not preferable.

Therefore, when switching the developing bias voltage, it is necessary to prevent the electrostatic latent image 26 and the electrostatic latent image 28 from being developed at the same time.

In this example, when the operator switches the bias voltage by means of switching the developing bias voltage, by delaying the image forming timing by a certain predetermined delay time, static electricity is generated in the developing area in the next copying process. A state is created in which no latent image exists, and the developing bias voltage is switched while this state is absent.

Therefore, the developing bias voltage is not changed in real time, but is changed in the first developing process.

The predetermined delay time T is between the rear end of the electrostatic latent image 26 and the electrostatic latent image 2.
If the distance from the tip of photoreceptor 8 is Q, and the speed of photoreceptor 1 is V, then T≧1. -12 (however, t = L / V
+ tz = 12/V) - That is, the delay time T is the time required for the preceding electrostatic latent image to completely leave the development area from being in the development area.

As shown in the timing chart of FIG. 2, in the copying machine of this example, the copy process is performed in the following order: start of transfer paper feeding, start of charging of the photoreceptor, start of exposure, and start of development. In other words, the transfer paper feed signal, charging signal, exposure signal,
Each process is controlled in order of development bias voltage to obtain a copy.

For example, if the bias voltage switching command v1 is issued while the developing bias voltage is being applied in the first copy process, the bias voltage cannot be switched in real time because an electrostatic latent image is already present in the developing area.

Also, since the second copy process has already started,
The distance between the electrostatic latent image in the first copy process and the electrostatic latent image in the second copy process is also set smaller than the development area. Therefore, the interval between the electrostatic latent image formed by the second copying process and the electrostatic latent image formed by the third copying process is made larger than the developing area, so that a state in which no electrostatic latent image exists in the developing area is achieved. During this process, the developing bias voltage is changed. Therefore, the transfer paper feed signal is delayed by a delay time T in real time with the development bias voltage switching command Vt. As a result, the paper feed signal for the transfer paper in the third copy process is delayed by the delay time T. Similarly, in the third copy process, the iF electric double signal exposure signal,
The timing at which the developing bias voltage is generated is delayed by a delay time T.

Therefore, the electrostatic latent image in the second copying process (however,
When the trailing edge (which has already been visualized) leaves the developing area, the leading edge of the electrostatic latent image in the third copy process has not yet reached the developing area, so the developing bias should be adjusted at this time. Switching is performed based on voltage switching command v1.

By switching the developing bias voltage in this manner, development is performed using the switched bias voltage after development in the third copy process.

Furthermore, after the fourth copy process, the process returns to the normal process start timing.

Note that when the bias voltage switching command v2 is issued during development in the third copy process, each start timing of the fifth copy process is controlled to be delayed by the delay time T according to the above example, and the fourth copy process ends. The bias voltage is switched before starting the development process in the fifth copy process.

By controlling in this way, the developing bias voltage is not switched while the two electrostatic latent images are being developed simultaneously, and therefore the density does not differ from the middle of the copied image.

Although omitted in the timing chart of FIG. 2, it goes without saying that the transfer and separation processes are also controlled to be delayed by the delay time T (see FIG. 3).

As mentioned above, the bias voltage may be switched manually by the operator after checking the copying status, but in copying machines that can select the automatic density adjustment mode, the automatic density adjustment mode allows the machine to read the document information and switch the bias voltage manually. Automatically switches to the optimal developing bias voltage.

In that case, a document reading optical system is placed near the imaging lens 104 (see FIG. 5), and the developing bias voltage is automatically set based on the document information read by the optical system. ).

In this case as well, the copy process is controlled by considering the selection of the automatic density adjustment mode in the same manner as the timing of the bias voltage switching commands Vl, V2, etc. in the above example.

FIG. 5 shows the configuration of a copying apparatus suitable for carrying out the present invention.

The reference numeral 100 indicates the main body of the copying machine, the reference numeral 200 indicates a recycled automatic document feeder (hereinafter referred to as "R"), and the reference numeral 300 indicates a finisher.

First, regarding the configuration of the copying machine, reference numeral 101 indicates a flash exposure lamp and a power supply accommodating unit, and the light from there is irradiated onto the original on the contact glass 102 and the first mirror 1
03, the photoreceptor 1 is exposed through the imaging lens 104 and the second mirror 105. Reference numeral 106 indicates a regulating member for preventing unnecessary portions of the photoreceptor 1 from being exposed.

Since the photoreceptor 1 is uniformly charged in advance by the charger 108, an electrostatic latent image is carried thereon by exposure. The non-image area of this electrostatic latent image is removed by an eraser 109 and made into a visible image by toner in a developing section 110. The transfer paper is fed from any one of the first paper feed tray 113, the second paper feed tray 114, and the third paper feed tray 115, and is transferred to the registration roller 1.
16, the movement starts in synchronization with the toner image on the photoreceptor. The toner image is transferred onto a transfer paper by a transfer charger 111, and the transfer paper is separated from the photoreceptor 1 by a separation charger 112.

The transferred and separated transfer paper passes through a transport tank 117 and reaches a fixing device 118, where the toner image is fixed.

The behavior of the transfer paper after this differs depending on the copying mode.

In the mode of discharging the transfer paper to the main body tray 123, the duplex switching claw 120 is at a different position from that shown in the figure, and the advancing direction is determined so that the transfer paper does not advance to the duplex tray 124. At this time, the copy surface of the transfer paper is turned downward by the turning section 122. Therefore, the pages are arranged in descending page order.

On the other hand, in the mode of ejecting the paper to the finisher 300, the paper ejection claw 121 moves and the paper is ejected in the direction of the insertion slot 301.

The above is the conveyance path of the transfer paper in the mode in which the transfer paper is discharged from the main body 100, but the route is different in the mode in which double-sided copying is performed.

The transfer paper that has been copied on the front side is stored in the duplex tray 124 by the duplex switching claw 120. Therefore, the pages are arranged in order from the bottom with the front copy side facing upward.

The lower side of the transfer paper stored in the duplex tray 124 is fed by the duplex paper feed belt 125, and then transferred to the paper feed tray 1.
It travels along the same transport path as the transfer paper fed from 13, 114, and 115, and passes through the registration rollers 116.

It is copied onto the back side and discharged from the main body tray 123 to the finisher 300.

The RDF 200 consists of a document tray, an intermediate tray, a document reversing section, etc., and is capable of ADF mode and RDF mode.

In the ADF mode, documents are sequentially fed, exposed for the required number of documents, and then sequentially discharged onto the document discharge tray 211.

In the RDF mode, one original is exposed to light once, and by repeating this exposure, copies are made one by one to obtain the required number of copies.

The finisher 300 perforates or binds copies in units of a predetermined number of copies.

FIG. 4 shows a control block diagram for controlling the copying apparatus shown in FIG.

The copy process described above is carried out by the illustrated central processing unit (
CPU), read-only memory (ROM), read/write memory (RAM), non-volatile memory (NV
, RAM), various timers (TIMER), RDF
Protocol controller (P
R.O.T.

C0NT, ), key matrix such as numeric keypad (MTRx
l) Display LED, matrix (MTRX2), I10 port (Ilo POR) that inputs or outputs these
T), each sensor (SENS, ) and load (LOA) in the machine
A driver (1')) that drives the DS), ■10 ports that input or output these (Ilo PORT
), bias power supply (B-AS), exposure lamp regulator (EXP), charging high-voltage power supply (CH), and I10 boat (ILO FOR) that outputs the signals that operate these.
T) etc.

(Effects) According to the present invention, even when the interval between electrostatic latent images is small during high-speed copying, problems such as differences in density within one image do not occur by switching the developing bias voltage, and each electrostatic latent image can be Advantageously, an appropriate bias voltage can be applied to obtain optimal copying.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a developing device suitable for carrying out the present invention, Fig. 2
The figure is a timing chart explaining one embodiment of the present invention.
FIG. 3 is a flowchart explaining one embodiment of the present invention;
FIG. 4 is a control block diagram relating to control of a copying apparatus suitable for implementing the present invention, and FIG. 5 is a configuration diagram of the copying apparatus corresponding to the same figure. 26.28... Electrostatic latent image, T... Delay time.

Claims (1)

[Scope of the Claims] A continuous copying process is possible in which a latent electrostatic image on a photoreceptor is continuously visualized, the latent electrostatic image being conveyed to a development area,
In a copying machine that visualizes an electrostatic latent image under the application of a developing bias voltage, when the leading edge of the electrostatic latent image is at the entrance of the developing area, the trailing edge of the immediately preceding electrostatic latent image is When the development bias voltage is switched during continuous copying under the condition that the electrostatic latent image is still in the development area, the start of the copy process after switching is delayed by a predetermined delay time. is at least the time required for the preceding image to completely leave the developing area from the state in which it is present.