JPH0332795B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cleaning device for a copying machine, and more particularly to control of contact and release of a blade that sweeps residual toner from a photoreceptor drum surface with respect to the drum surface.

A copying machine having a photosensitive drum has a structure as shown in FIG. 1, for example. The document surface on the document table 1 is illuminated by a light source 2, and due to the relative movement between the document table 1 and the light source 2, an image of the document surface passes through an optical system of reflecting mirrors 3, 4, 5 and a lens 6 to a photoreceptor drum. The image is formed on the peripheral surface of 7. The photosensitive drum 7 is driven to rotate in the direction of the arrow in the figure, and as the photosensitive surface rotates, the peripheral photosensitive surface is charged by the charging electrode 8, and then passes through the optical system to form an original image as an electrostatic latent image. is developed with toner at the developing device 9 position, and this toner image is adhered to the copy paper 11 fed from the paper feed cassette 10 and transferred to the copy paper 11 by the transfer electrode 12.
The copy paper 11 is separated from the photoreceptor drum 7 by a separation electrode 13, the image is fixed by a fixing roll 14, and the copy paper 11 is taken out of the machine.

Here, a cleaning device 15 is provided between the separation electrode 13 and the charging electrode 8 in the rotation direction of the photoreceptor drum 7 to sweep away toner and paper dust remaining on the surface of the photoreceptor drum 7 from the photoreceptor surface. This cleaning device 15 includes a blade 15A that is pressed against the photosensitive surface of the drum 7 in a direction opposite to the direction in which the photosensitive surface is transported, and when the blade 15A is pressed against the photosensitive surface, the toner and Sweep up paper dust. This blade 15A is made of a material that is softer than that so as not to damage the photosensitive surface, and has appropriate elasticity so as to be able to reliably sweep away the toner.
For example, it is made of hard resin. However, blade 1
5A should be made of an appropriate material, but if it is left in pressure contact with the drum surface, it will tend to wear out, the photosensitive surface will wear out, deteriorate, and the drum surface will warp in areas that are strongly hit by the blade. Become. Therefore, conventionally, the blade 15A is provided with a control device that presses the blade 15A against the photosensitive drum surface only during the copying operation and releases the blade 15A from the drum surface when the copying is completed. For example, as shown in the figure, this control device reciprocates the pressing and releasing of the blade 15A against the drum surface using a motor 16 and a gear mechanism 17 whose operation is controlled based on ticing signals for starting and ending copying, and a clutch mechanism. configured to switch.

However, as in the past, when copying starts, blade 1
In the control in which the blade 15A is brought into pressure contact with the drum surface and released almost simultaneously with the completion of copying, the number of times the blade 15A is brought into contact with and released the pressure is as frequent as the number of copies, requiring frequent control of the control mechanism. .
In addition, when the blade 15A is pressed against the drum surface from the released state, the blade 15A has the effect of hitting the drum surface with toner and paper powder remaining on the photoreceptor drum surface and the blade itself, which may cause damage to the drum surface. It can cause wear and tear, and it can also cause poor cleaning.

The present invention has been made in view of the above-mentioned circumstances, and by minimizing the amount of pressure contact and release of the blade against the drum surface, it eliminates blade fatigue and reduces damage and wear on the drum surface. The purpose of the present invention is to provide a cleaning device that enables reliable cleaning.

FIG. 2 is a configuration diagram of a control device showing an embodiment of the present invention. The microcomputer 20, which is the control center of the entire copying machine, sends and receives copy button operation signals, copy number setting signals, copy size setting signals, copy number display signals, etc., to and from the operation display section 21 of the copying machine.
The microcomputer 20 performs charging, developing, paper feeding,
Controls a series of copying controls such as transfer, separation, and cleaning. The microcomputer 20 provides a drive start signal to the motor control unit 22 of the cleaning device 15, and also provides a timer 23 with a clock start signal.
This drive start signal is generated, for example, at the timing of an operation signal of a copy start button. The motor control unit 22 is
When the drive start signal is given, the motor 16 is driven in normal rotation, and when the motor 16 has driven the blade 15A to a state where it comes into pressure contact with the drum surface, the normal rotation of the motor 16 is stopped. A timing start signal is given to the timer 23 when copying is completed and cleaning of the entire circumferential surface of the drum 7 is completed. This timing start signal is generated when one copy is completed in a single copy setting, and is generated when the last copy is completed in a multiple copy setting.

Note that when the timer 23 is given a timekeeping start signal again during the timekeeping, the timer 23 restarts the timekeeping from the beginning.

The timer 23 starts counting time from the time when the timing start signal is given, and gives a blade release command to the motor control unit 22 when the set time limit is reached. Based on this command, the motor control unit 22 drives the motor 16 in the reverse direction, and stops the reverse drive of the motor 16 when the motor 16 has been driven to a state where the blade 15A is released from the drum surface.

Therefore, at the start of copying, the blade 15A touches the drum 7.
unless a timing start signal is given again within the time set in the timer 23 after copying is completed, that is, unless copying is restarted during timing.
After the time set by the timer 23 has elapsed, the blade 15A is released from the drum surface.

Here, the set time of the timer 23 varies depending on the copying machine model and size, but it is set so as to minimize the pressure contact and release of the blade against the drum surface, and at least the time required to replace the original and the replacement of the copying operator. The time is set to be sufficiently longer than the time required for With these settings, as illustrated in FIG. 3, the period T ₁ during which copying operations are repeated
In this case, the blade remains in pressure contact even during the time t _N from the end of copying to the start of the next copy, reducing the frequency of repetition of pressure contact and release, and copying ends during period T ₂ during which copying operations are performed accidentally. The blade is immediately released after the timer setting time T _w has elapsed, thereby eliminating blade fatigue. Further, at the start of copying, the blade is pressed against the blade regardless of the time limit of the timer, and cleaning failures do not occur.

Although the embodiment shows a case in which the blade is pressed and released by driving the motor 16 in forward and reverse directions, it is possible to switch between pressing and releasing only by driving the motor 16 in the normal rotation using an appropriate link or cam mechanism.

Further, although the time limit of the timer 23 is shown as being fixed, more appropriate blade control is possible by adjusting the program by the microcomputer 20 according to the copying operation history of the copying machine and the time of day. For example, the microcomputer 20 calculates the average number of copies from the current time up to a predetermined time (for example, 10 minutes), and when the average number of copies is large, the time limit of the timer 23 is set to a large value, and when the average number of copies is small, the time limit is set to a small value. do. moreover,
In the above embodiments, a cleaning blade was used as an example of the cleaning means, but the present invention is not limited to the cleaning blade, and cleaning means such as a roller brush may be used.

As described above, according to the present invention, since the pressure contact and release of the blade against the drum surface is kept to the necessary minimum, it is possible to prevent the blade from becoming worn out and to reduce scratches and wear on the drum surface.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a copying machine, FIG. 2 is a block diagram showing an embodiment of the present invention, and FIG. 3 is a time chart showing an example of pressing and releasing a blade in the present invention. 7... Photosensitive drum, 15... Cleaning device,
15A...Blade, 16...Blade motor, 17
...Gear mechanism, 20...Microcomputer, 21
...Operation display unit, 22...Control unit, 23...Timer.

Claims (1)

[Claims] 1. In a copying machine in which a cleaning device for sweeping up residual toner on an image forming drum is provided with a pressure contact/release mechanism that brings a cleaning means into pressure contact with the surface of the drum, the pressure contact/release mechanism does not contact the cleaning means during copying. A copying machine comprising: a control means for pressing the cleaning means against the drum surface and separating the cleaning means from the drum surface when copying is not resumed until a set time has elapsed from the completion of copying a set number of copies. .