JPS61118781A - Flash fixing device - Google Patents

Abstract

PURPOSE:To take a copy without unevenness even when image density varies by detecting an inflow current from a transfer corotron device to a photosensitive body and detecting the density of an image to be copied, and controlling a flash input current according to the detection output of the image density. CONSTITUTION:An electrostatic charging device 2, exposing device 3, developing device 4, transfer corotron 5, and cleaning device 6 are arranged at the periphery of a photosensitive drum 1. A form 7 after transfer is conveyed to under a flash fixing device 9 by a conveyor belt 8. The device 9 consists of a flash discharge tube 10, a reflecting mirror 11, and a housing 12 and flash energy is supplied to the form 7 at a specific period to fix an image. The inflow current from the device 5 to the drum 1 is detected by a constant current detecting circuit 4 and the mean value of the image density on the form 7 in the axial direction of the drum is detected. The output of the circuit 14 is compared with the reference voltage of a reference circuit 18 and an input current control circuit 20 controls flash light input electric power to the discharge tube 10. Thus, a copy having no unevenness is taken even when the image density varies.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a copying machine that controls f11 the energy supplied to a flash fixing device according to the density of an image.

[Conventional technology]

A flash fixing device using a flash discharge tube is known as a fixing device for a copying machine. This flash fixing device has a problem in that the amount of flash light reflected from the paper surface varies depending on the density of the image to be copied, and the energy absorbed by a portion of the toner becomes uneven, resulting in uneven fixing and uneven density. For example, when comparing the case of image density of 30% and the case of 100% (full black), it has been found by staining that the energy absorbed by the toner is 30% less (11N) in the latter case.

Furthermore, if the fixing energy is set high to reliably fix an image with a high image density, the energy will be too much when the W4@density is low, which may cause problems such as deterioration of image quality due to toner scattering, increase in noise, etc. Ta.

As a means to solve these problems, (1) Unexamined Japanese Patent Publication No. 56
As in Publication No. 1074, the surface potential of the photoreceptor is detected by using a latent image potential detection electrode for auto bias or by providing a dedicated latent image potential detection electrode to control the flash power ( ii) Black information, which detects the amount of black information by determining the true signal contained in recorded data in an electrostatic recording facsimile, etc., or by using a field sensor in a copying machine, as disclosed in Japanese Patent Application Laid-Open No. 56-114977. Document information can be detected by providing a quantity detection means and controlling the flash timing by the detection output, or (iii) by counting the number of P, picture: T, in the picture signal as in Japanese Patent Application Laid-Open No. 57-23984. There is a known device that detects the concentration of light and controls the light emission time of a flash discharge tube.

[Problem that the invention seeks to solve]

However, any of these configurations could not be used unless the detection means were complicated and expensive, or the image information was supplied in the form of an electrical signal, such as in a facsimile.

Means and operation for solving problem c] The present invention detects the image density by detecting the current flowing from the transfer corotron to the photoreceptor in a copying machine using a flash fixing device, and uses this detection output to detect the image density. By controlling the flash energy accordingly, it is possible to perform uniform copying even when the image density changes with a simple configuration without providing any special detection means.

[Embodiment] FIG. 1 shows a schematic configuration diagram of a copying machine to which the present invention is applied.

1st rI! In J, reference numeral 1 indicates a photoreceptor drum, and around this photoreceptor drum 1, a charging device 2, an exposure device 3, a developing device 4, a transfer corotron 5, and a cleaning device 6 are arranged as usual. After the transfer, the paper 7 is conveyed to below a flash fixing device 9 by a conveyor belt 8 . This flash fixing device 9 includes a flash discharge tube 101, a reflecting mirror 11, and a housing 12, and performs fixing by applying flash energy to the paper 7 being conveyed at a predetermined period.

Here, the current flowing through the photosensitive drum 1 in the copying machine shown in FIG. 1 will be considered. FIG. 2 shows a circuit for measuring the current flowing through the photoreceptor drum 1, and 13 is a high voltage power supply circuit;
Reference numeral 14 indicates a current detection circuit.The positive electrode of the high voltage electric S circuit 13 is connected to the corotron wire 15 of the transfer corotron 5, and the negative electrode is connected to the shield 16 of the transfer corotron 5, and the current detection circuit 14 is connected to the negative electrode. Grounded. Now, if the drum inflow current flowing from the transfer corotron 5 to the photosensitive drum l is 401, the current flowing to the shield 16 of the transfer corotron 5 is S, and the total current flowing from the high voltage power supply circuit 13 is also T, then 47=43+4J.

becomes. Therefore, the drum inflow current L6 can be detected by measuring the current flowing into the high voltage power supply circuit 13 from the ground.

Next, the potential V of the photosensitive drum l and the drum inflow current 15!
When considering the relationship with 0, as shown in Figure 3,
It is inversely proportional. In other words, when the image density is high, such as solid black, and the photoreceptor potential is high, the drum inflow current 4
．． is small as shown in Ll, and when the image density is low like a white background and the photoreceptor potential is low, the drum inflow current becomes large as shown in 4J2. Therefore, if the drum inflow current is detected, the drum axis on the paper The average value of the image density in the direction can be known moment by moment.

FIG. 4 shows a control circuit for controlling the flash fixing device according to the present invention.

The output of the current detection circuit 14 is sent to the reference circuit 1 by the comparison circuit 17.
The output of the comparison circuit 17 is supplied to the input current control circuit 20 via a delay circuit 19 having a delay time corresponding to the distance between the transfer corotron 5 and the flash fixing bag VT9. This input terminal control circuit 20
The output of is supplied to a discharge circuit 21 which supplies a high voltage for discharge to the flash discharge tube IO. When the image density is high, that is, when the black area is large, the drum inflow current detected by the detection circuit 14 decreases, so by controlling the discharge circuit 19 accordingly and increasing the flash input current, Increases the luminous energy of flash discharge tubes. This makes it possible to irradiate appropriate flash energy according to the image density.

[Effects of the Invention] As explained above, according to the present invention, in a copying machine using a flash fixing device, image density is detected by detecting the current flowing from the transfer corotron to the photoreceptor, and this detection output is used to detect the image density. By controlling the full length of the flash accordingly,
The present invention has the advantage that even when the image density changes, uniform copying can be performed with a simple configuration without providing any special detection means.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram of a copying machine to which the present invention is applied;
The figure is a circuit diagram for measuring the current flowing through the photoconductor drum of the copying machine shown in FIG. 1 shows a control circuit diagram for controlling the flash fixing device. l: Photosensitive drum 2: Charging device 3: N-light device 24: gA @ device 5: Transfer corotron 6: Cleaning device 7: Paper 8: Conveyor belt 9: Flash fixing device
10: Flash discharge tube Il: Reflector 12: Housing 13: High voltage @ source circuit 14: 111 flow detection circuit 15: Corotron wire 16: Shield 17: Comparison circuit 18: M quasi-circuit 11a extension circuit
20: Input current-control circuit 2/1; Discharge circuit patent applicant Fuji Xerox Co., Ltd. agent
Masu Tebori (and 1 other person) Fig. 1 Fig. 2 Uki3I71 L21ro

Claims (1)

[Claims] 1. In a flash fixing device that controls the amount of flash light emitted during flash fixing, an image density detection device that detects the density of an image to be copied by detecting the current flowing from the transfer corotron device to the photoreceptor; A flash fixing device comprising: a control circuit for controlling flash input power in accordance with the output of the image density detection device.