JPS59152471A - Electrostatic copying machine - Google Patents

Abstract

PURPOSE:To obtain stable transfer and sepn. irrespectively of the condition of an original by detecting the density of the image formed on a photosensitive drum or the density of the original and controlling the voltage on one or both of a transfer charger and a sepn. charger. CONSTITUTION:A photosensitive drum 2 which is electrostatically charged by an electrostatic charger 1 is exposed through a slit 3 and the image thereon is developed to a sensible image by a developing device. The transfer paper fed from rollers 5, 5' contacts the sensible image surface on the drum 2 and is subjected to transfer with a transfer charger 6 then to destaticization with a sepn. charger 7. A reflection type photoelectric sensor 17 which detects the amt. of the toner adhered on the sensible image surface is attached to a developing device 4 in the lower part thereon on the downstream side with respect to the rotating direction of the drum 2. The output from the sensor 17 is inputted to a control circuit 20, and is supplied to an arithmetic circuit 23 after amplification 21 and integration 22. The circuit 23 calculates said output in such a way that the density of the image and the sepn. voltage are inversely proportional to each other and that the density of the image and the transfer voltage are directly proportional to each other. The voltages for the chargers 6, 7 are thus set optimum. The stable transfer and sepn. are made possible irrespectively of the original condition in the above-mentioned way.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an electrostatic copying machine that can always stably perform 9-separation transfer depending on the density of a document, etc.

Conventional Structures and Problems In recent years, when copying with a copying machine, it has become essential to be able to faithfully copy the entire original without missing parts in the copied image. In order to achieve this, it is a prerequisite that image transfer to copy paper and separation from the photosensitive drum can be performed reliably.

FIG. 1 is a schematic diagram of a conventional electrostatic copying machine. In the figure, a latent image is formed on a photoreceptor drum 2 charged by a charger 1 by exposure light from a slit 3, and a developed image is formed by a developer 4. be converted into Furthermore, the copy paper fed from a pair of rollers 6.5 comes into contact with the developing surface on the photosensitive drum 2 in synchronization, and is transferred by the transfer charger 6. Next, a separation charger 7 is used to weaken the electrostatic adhesion force between the copy paper and the photoreceptor drum 2.
The static electricity is removed by the copy paper, and the copy paper is separated from the photoreceptor drum 2 by utilizing its rigidity. 8 is a cleaning part.

In such a configuration, the voltage applied to the transfer charger 6 and the separation charger 7 and their positional relationship can only have a fixed correlation, and the voltage may vary depending on factors such as image density that affect transfer and separation. Experimentally find the correlation between and jiγ position,
It was constructed to be positioned at the most favorable point.

Set the entire surface heat and the entire surface self-separation area 12 as shown in Figure 2.
In order to do this, under certain conditions, in the correlation between the transfer voltage and the separation voltage, the completely transferable range 14 is determined by experiment, and then the full black separable range 11 is set, and the full white separable range 13 is set. The setting voltages for transfer and separation were determined by obtaining a completely black-and-white, full-scale self-separated area 12 so that both partially overlap.Then, the above procedure was repeated under various environments. An average optimum value was obtained by performing the test. Note that 15.16 indicates the non-transferable range.

However, even if the transfer and separation voltages are limited in this way, it will not be possible to adequately respond to changes in the original density, changes in the density of mixed images, and environmental changes due to differences in the region and location of use. However, these methods often have the disadvantage of causing poor transfer and separation. For this reason, it has had the disadvantage that it is extremely difficult to set conditions for transfer and separation voltages.

OBJECTS OF THE INVENTION The present invention aims to eliminate the drawbacks of the above-mentioned conventional examples, and it is an object of the present invention to provide an electrostatic copying machine that enables stable transfer and separation operations.

Structure of the Invention In order to achieve the above object, the present invention provides a detection means for detecting the image density of an image formed on a photoreceptor drum or the original density, and detects the image density or the original density detected by the detection means. The device is configured to control the voltage of both or either of the transfer charger and the separation charger using a control signal corresponding to the density, thereby ensuring stable transfer and separation regardless of the document condition or environmental conditions. There are five skills.

Description of Embodiment Fig. 3 d5 Outline of an electrostatic copying machine according to an embodiment of the present invention) is omitted.

In this series of configurations, the present invention provides a reflective photoelectric sensor for detecting the amount of toner adhesion of a toner image formed on the surface of the photoreceptor drum at the lower downstream side of the photoreceptor drum 2 of the developing device 4 in the rotating direction. I have been able to obtain 17.

Detected by this reflective photoelectric sensor 17 during close-up photography /ζ
The amount of toner adhesion, that is, the image density, is detected by a circuit configuration as shown in the block diagram of FIG. That is, the transfer charger 6 and the separation charger 7 are connected to high-voltage power supplies 18 and 19, respectively, and the cylinder pressure's source 18, 19 is
is connected to the control 1 channel 20 via a remote terminal. The control circuit 20 includes an amplifier 21 that amplifies the detection output of the reflective photoelectric sensor 17, an integrator 22 that integrates the output,
and an arithmetic circuit 23 whose inputs are the output voltage of the integrator 22.
The calculation circuit 23 performs calculations so that the image density and the separation voltage are inversely proportional to the separation voltage, and furthermore, the image density and the transfer voltage are directly proportional to the transfer voltage. The configuration is such that independent control signals are generated for 18 and 19, and separation and transfer voltages optimal for the image density at that time are set.

Note that the transfer voltage may be set to a constant value and the separation voltage may be controlled to be set to an optimal value.

As described above, according to this embodiment, stable transfer and separation operations can be realized by detecting the image density and setting the optimum transfer and separation voltage for the density in the high voltage power supply 18.19. Can be done.

In the above embodiment, the image density is detected by monitoring the surface of the photoreceptor immediately after development using a reflective photoelectric sensor, but this method is not particularly limited, and any function that can detect the image density or document density may be used. Anything is fine as long as it has the following. For example, when detecting the state before development, a surface potential sensor for detecting the surface potential of the photoreceptor drum may be provided between the slit and the developing device. Alternatively, a document density detection sensor arranged to directly detect the document density may be used.

Effects of the Invention The present invention includes a detection means for detecting image density or original density, and a control signal corresponding to the image density or original density detected by this detection means, so that both the transfer voltage and the separation voltage are always optimized. Alternatively, since the copying operation is performed while one of the voltages is set to 1 on the open side, an excellent effect can be obtained in that stable transfer and separation can be obtained regardless of the state of the document. Additionally, the effect of the environment in which the electrostatic copying machine is used is reduced, and the range of paper selection available is expanded.

[Brief explanation of drawings]

91;, Figure 1 is a configuration diagram of the main parts of a conventional electrostatic copying machine, Figure 2
The figure is a correlation diagram showing transfer voltage and separation voltage, FIG. 3 is a diagram showing the eastern configuration of an electrostatic copying machine in an embodiment of the present invention, and FIG. 4 is a block diagram of the main parts of this embodiment. ...Charger, 2...Photoreceptor drum, 4
...Developer, 6...Transfer charger, 7.
... Separation charger, 17 - ... Reflective photoelectric sensor, 18, 19 ... High voltage power supply, 20 ...
...Control circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person 1st
Figure 2 Figure 4, / 4-. 2 43 44 4-5
((,,y)Summary U- Figure 3, Figure 4, 2θ!

Claims (2)

[Claims] (1) A photoreceptor drum, a charger, a developer, a transfer charger, and a separate charger are provided around the photoreceptor drum to detect the image density of the image formed on the photoreceptor drum or the original density. A detection means is provided, and the voltage of either the transfer charger or the separation charger is controlled by a control number corresponding to the Ij image density or original density detected by the detection means. An electrostatic copying machine characterized by: (2) A reflective photoelectric sensor is used as a detection means, and a high-voltage power source is provided in each of the transfer chargers and the 9 separate chargers.
Claim 1, characterized in that each of the high-voltage power supplies or one of the high-voltage power supplies is controlled by a control signal corresponding to the image density or document density detected by the reflective photoelectric sensor. Electrostatic copying machine described in Section 1.