JPS6155675A - Transfer type printer - Google Patents

Abstract

PURPOSE:To perform transfer printing well by obtaining the difference between a toner density before transfer of a transfer device and that after transfer by a detector and detecting the abnormality of the transfer device on the basis of the difference value and controlling a transfer voltage on the basis of the difference value to adjust the transfer efficiency. CONSTITUTION:Outputs of amplifying circuits 13-1 and 13-2 corresponding to the toner density before transfer and that after transfer in the same position on a photosensitive drum 1 are held in peak holding circuits 14-1 and 14-2. The output of an AD converter 16 is stored in a register 17 by a timing signal supplied thereafter. A control circuit 19 calculates the transfer efficiency eta of a transfer device 5 on the basis of the value stored in the register 17 and compares this transfer efficiency with a reference transfer efficiency etath. If the calculated transfer efficiency eta is lower than (etath-5)% as the comparison result, the voltage of the transfer device is raised; and if it is higher than (etath+5)%, the voltage of the transfer device is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to improvements in transfer printing devices such as electrostatic or electrophotographic.

FIG. 2 is a schematic diagram illustrating the configuration of an electrophotographic transfer printing apparatus, in which 1 is a photosensitive drum whose cylindrical surface is coated with a photosensitive member as a toner image forming body, and 2 is a photosensitive drum 1 that is formed by charging the photosensitive drum 1. A charger that imparts photosensitivity to the cylindrical surface; 3 an exposure device that forms an electrostatic latent image on the cylindrical surface of the photosensitive drum 1 imparted with photosensitivity by exposure to light modulated by recorded information; 4 a photosensitive device; a developing device 5 that develops the electrostatic latent image formed on the drum 1 with toner to form a toner image;
is a transfer device that transfers the toner image formed on the photosensitive drum 1 onto the recording paper 6.

The photosensitive drum 1 rotates at a constant speed in the direction of arrow A.
After charging and exposure P by the charger 2, exposure by r3, development by the developer 4, and transfer by the transfer device 5, residual charges are removed by the static eliminator 7, and residual toner is removed by the cleaning brush 8 and cleaning fleece 9. undergoes removal.

On the other hand, the recording paper 6 travels in the direction of arrow B, receives the toner image, is fixed by heating and melting in two fixing devices (not shown), and is discharged to a stacker (not shown).

Such transfer printing devices are widely used as output devices for electronic computers, but the printing speed is extremely high, so detecting printing defects based on the print results will result in a large number of printing defects. This is automatically detected and an alarm is issued to immediately stop printing. Or it is necessary to take measures.

Relatively many printing defects appear as an increase or decrease in toner density, and the causes include abnormalities in the developing device 4 or transfer device 5, or changes in the thickness, width, electrical resistance, or other properties of the recording paper. Therefore, it is necessary to clarify the cause and take appropriate measures.

[Conventional technology]

3 and 4 are schematic diagrams illustrating the configurations of a first conventional example and a second conventional example of a transfer printing device, respectively, and the same reference numerals as in FIG. 2 indicate the same objects. In addition to showing
In FIG. 3, 10 is a detector for detecting the density of the toner image on the photosensitive drum 1 between the developing device 4 and the transfer device 5;
Reference numeral 11 in the figure is a detector that detects the toner density on the recording paper 6 after the toner image has been transferred by the transfer device 5.

In this way, an alarm is issued when the toner concentration detected by the detector 10 or the detector 11 exceeds a predetermined range. Or this.

The amount of toner supplied to the developing device 4 is controlled so that the amount falls within a predetermined range.

[Problem that the invention seeks to solve]

Both of the above configurations have the problem that they cannot deal with printing defects due to abnormalities in the transfer device, and in the second conventional example, the amount of toner supplied to the developing device 4 is controlled. When the toner concentration decreases due to a temporary failure of the transfer device, there is a problem in that after the failure is recovered, the toner concentration increases until the amount of toner in the developing device returns to an appropriate value.

[Means for solving problems]

The transfer printing apparatus according to the present invention includes a first detector that detects the toner concentration on the toner image forming body before transfer, and a second detector that detects the toner concentration on the toner image forming body after transfer. The above problem is solved by providing a means for detecting an abnormality in the transfer device based on the output of the first detector and the output of the second detector.

[Effect]

That is, the detection means determines the difference in toner concentration before and after the transfer device, and based on this, an abnormality in the transfer device is detected and an alarm is issued. Alternatively, the transfer efficiency is controlled by controlling the transfer voltage.

It should be noted that, until now, there has been a method that detects the thickness and width of the transfer material, that is, the recording paper, using a detection means to maintain constant transfer efficiency in the transfer device.
0061 r transfer device"), one that detects the electrical resistance of the transfer material and changes the input to the transfer charging accordingly (February 12, 1981: JP 56-14271 r Transfer material separation method"), A resistance detection means for detecting the resistance value of the transfer paper is provided, and an optimum transfer current is applied to the transfer paper based on the detection result.June 2, 1981: Japanese Patent Application Laid-Open No. 1981-1986
The present invention can achieve both of these objects.

〔Example〕

The gist of the present invention will be specifically explained below with reference to an embodiment shown in FIG.

FIG. 1(a) is a block diagram showing the configuration of one embodiment of the present invention, in which the same reference numerals as in FIG. 2 refer to the same objects.
A first detector 0 detects the density of the toner image on the photosensitive drum 1 between the developing device 4 and the transfer device 5.

A second detector 12 detects the density of the toner image on the photosensitive drum 1 between the transfer device 5 and the static eliminator 7.

13-1 and 13-2 are respectively the first detector 1
an amplifier (
AMP"), 14-1 and 14-2 are peak holding circuits that hold the peak values of the outputs of the amplifier 10 and the amplifier 14-2, respectively, and 15 is the peak holding circuit 14.
-1 and a differential amplifier (D-AMP) that amplifies the difference between the outputs of the peak holding circuit 14-2, and 16 is an odor device (80) that digitally converts the output of the differential amplifier 15.
, 17 is a register for storing the output of the converter 16, 1
8 is a D^ converter (D^) that converts the output of the register 17 into analog; and 19 is a control circuit that controls the voltage of the transfer device 5 in accordance with the output of the DΔ converter 18.

FIG. 1 (bl is a time chart of signals in each part of the above configuration.

■ is the output signal of amplifier 13-1.

2 is a sampling signal supplied to the peak holding circuit 14-1.

2 is a reset signal supplied to the peak holding circuit 14-1.

■ is the output signal of the peak holding circuit 14-1.

■ is the output signal of amplifier 13-2.

(2) is a sampling signal supplied to the peak holding circuit 14-2.

2 is a reset signal supplied to the peak holding circuit 14-2.

■ is the output signal of the peak holding circuit 14-2.

■ is the output signal of the differential amplifier 15.

[Phase] is a timing signal supplied to the register 17.

The sampling signal ■, reset signal ■, sampling signal ■, reset signal ■, and timing signal [phase] are supplied from a host control unit (not shown), and the sampling signal ■
is supplied when the photosensitive drum 1 rotates from the position where the first detector 10 is provided to the position where the second detector 12 is provided after the sampling signal ■ is supplied, while the reset signal ■ and the reset signal Signal (2) is supplied prior to sampling signal (2) and sampling signal (2), respectively.

As a result, the outputs of the amplifier circuits 13-1 and 13-2 corresponding to the toner densities before and after transfer at the same position on the photosensitive drum 1 are respectively output to the peak holding circuit 14-1.
and 14-2.

Further, the timing signal [phase] is supplied thereafter, and the output of the AD converter 16 is stored in the register 17 by this timing signal [phase], and the control circuit 19 calculates the transfer efficiency of the transfer device 5 from the value stored in the register 17. Calculate η and compare this with the standard transfer efficiency ηth (e.g. 80%),
When 77 is lower than (ηth-5)%, the voltage of the transfer device 5 is increased, and when it is higher than (ηth+5)%, the voltage of the transfer device 5 is controlled to be lowered.

Although the above embodiment controls the transfer efficiency in the transfer device 5, it is also possible to issue a warning for printing defects simply by means of a display or the like.

〔Effect of the invention〕

As explained above, according to the present invention, printing defects caused by the transfer device can be reliably detected and appropriate countermeasures can be taken.

In addition, it is possible to deal with not only abnormalities in the transfer device itself but also printing defects caused by abnormalities 2 in the printing paper, such as changes in thickness, width, or electrical resistance.

[Brief explanation of drawings]

FIG. 1 (al is a block diagram of an embodiment of the present invention. FIG. 1 (bl is a time chart explaining the functions of the embodiment) FIG. 2 is a schematic diagram explaining the structure of an electrophotographic transfer printing apparatus 3 and 4 are configuration diagrams of the conventional example. In the figure: 1 is a photosensitive drum, 5 is a transfer device, 6 is a recording paper, 10 is a first detector, 12 is a second detector , 13-1 and 13-2 are amplifiers. 14-1 and 14-2 are peak holding circuits. 15 is a differential amplifier, 16 is an AD converter, 17 is a register, 18 is a DA converter, and 19 is a control circuit. . Kyou 1 tail (~ ■ ■

Claims (1)

[Claims] In a printing device including a toner image forming body on which a toner image is formed and a transfer device that transfers the formed toner image to a recording medium, a first step detecting the toner concentration on the toner image forming body before the transfer. a second detector that detects the toner concentration on the toner image forming body after the transfer, and a second detector that detects the toner concentration on the toner image forming body after the transfer, and a 1. A transfer printing device characterized by comprising means for detecting an abnormality in the container.