JPH04335383A - Image forming device - Google Patents

Abstract

PURPOSE:To impress a transferring voltage neither too much nor too little, to make the transferring efficiency high without adversely influencing a developing process, and to faithfully transfer a toner image on the surface of a photosensitive body by impressing the transferring voltage corresponding to toner amount detected. CONSTITUTION:The data on the toner amount transmitted from a toner amount detecting means 5 is inputted to a voltage controlling part 9; and based on this data, an impressed voltage corresponding to the toner amount detected, which is impressed on a transferring roller 7 is decided; and this voltage is impressed on the transferring roller 7 which the transferring material 12 carried in synchronism with the image part of the photosensitive drum 2 takes a transferring position, while relation between the rotating speed of the photosensitive drum 2 and a distance (s) between the toner amount detecting means 5 and a transferring area to be transferred by the transferring roller 7 is taken into consideration. In this case, when toner adhering amount, reflected light intensity, and the output at a light receiving part are high, the impressed voltage is set to be low; conversely, as the former three are low, the impressed voltage is set to be high.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to an image forming apparatus having an image carrier for holding a developed toner image, and a transfer means for electrostatically transferring the toner image on the image carrier onto a transfer material. Regarding.

0002

BACKGROUND OF THE INVENTION In image formation by the above-mentioned image forming apparatus, the quality is influenced by the working conditions in the developing step and the transfer step. In particular, in the transfer step, the toner image developed on the image carrier is It is desirable that the transfer efficiency is high so that the image is completely transferred onto the transfer material, and if the transfer efficiency decreases, the image quality will deteriorate and the burden on the cleaning means for the image bearing member will increase. By the way, when performing electrostatic transfer, the toner is moved by electrical force, so
The following problems occur due to excess or deficiency of electrostatic force or van der Waals force between the toner and the photoreceptor. (1) When the transfer potential is insufficient, non-transferred toner remains on the photoreceptor. (2) If the transfer potential is too large, charge leaks to the photoreceptor and toner is not transferred. (3) The optimum transfer potential (supplied charge amount) differs depending on the amount of toner attached. Due to the combination of (1) to (3), the amount of toner developed on the photoreceptor is not proportional to the amount of toner transferred onto the transfer material. Such problems are also influenced by the electrical resistivity, dielectric constant, and charge retention of the transfer material, as well as the amount of charge, low efficiency, and dielectric constant of the toner. Since a normal image has a different amount of toner attached to each location on the image carrier, it is common to set the optimum transfer potential at which the entire image is transferred in the best condition. Moreover, theoretically, 100% transfer is possible by applying to the transfer material a charge equal to or greater than the total amount of charge of the toner present on the image carrier.

However, electrostatic transfer of toner images potentially has the problems described above, and therefore
% toner transfer is difficult to achieve. FIG. 6 shows an OPC (Or
The relationship between the transfer efficiency and the transfer bias is shown when a sheet of conductive polycarbonate is used as the transfer material, and the transfer method in this case is a general roller transfer method. . This figure shows that as the amount of toner adhesion on the photoreceptor increases, the bias that provides the highest transfer efficiency increases, and that an optimum transfer voltage exists depending on the amount of toner adhesion.

0004

Currently, as a transfer method, a corona charge method or a bias roller method is generally used in which a transfer voltage is applied uniformly to the conveyance of a transfer material. However, in these methods,
There is a problem in that different transfer voltages cannot be simultaneously applied to portions perpendicular to the transfer direction of the transfer material. In addition, as a method of increasing the transfer efficiency of toner images, there is a method of adding fine particles that focuses not only on electrostatic attraction force but also on the physical fluidity between powders (Japanese Patent Application Laid-Open No. 129866/1986). It is publicly known. However, this method has the problem that the amount of charge of the developer tends to change due to the influence of additives, and while the transferability is improved, it has a negative effect on the development process.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above-mentioned problems of conventional image forming apparatuses, to apply transfer voltage to the transfer means in an appropriate amount, and to transfer toner without adversely affecting the developing process. An object of the present invention is to provide an image forming apparatus that can increase efficiency and faithfully transfer a toner image on the surface of a photoreceptor.

[0006]

[Means for Solving the Problems] In order to achieve the above-mentioned object, the invention of claim 1 includes an image bearing member that holds a developed toner image, and a toner image on the image bearing member. In an image forming apparatus having a transfer means for electrostatically transferring onto a transfer material, a toner amount detection means for detecting the amount of toner on an image carrier and a transfer voltage corresponding to the detected amount of toner are applied to the transfer means. The device is characterized in that it has a voltage applying member that applies a voltage. Further, the invention of claim 2 provides an image forming apparatus having an image bearing member that holds a developed toner image, and a transfer means that electrostatically transfers the toner image on the image bearing member onto a transfer material. The toner amount detecting means detects the amount of toner on the body for each region, and the voltage applying member independently applies a transfer voltage to each region according to the amount of toner in the detected region. It is something to do. The toner amount detection means is composed of a reflective sensor.

[0007]

According to the first aspect of the invention, when the amount of toner detected by the toner amount detection means is large, the voltage applied by the voltage applying member is lowered, and on the contrary, when the amount of toner is small, A transfer voltage corresponding to the amount of toner is applied to the transfer means by increasing the applied voltage, and in this way, a good transferred image is obtained. Further, in the invention of claim 2, the amount of toner in the transfer means is detected for each transfer area by the toner amount detection means, and when the amount of toner is large,
The voltage applied by the voltage applying member to the transfer area is lowered, and on the other hand, when the amount of toner is small, the voltage applied to the transfer area is increased, and the transfer voltage is applied to each area according to the amount of toner. The voltage is applied to the transfer means, and in this way a good transferred image is obtained.

[0008]

[Embodiment] In an embodiment of the invention of claim 1 shown in FIGS. 1 and 2, reference numeral 1 denotes a scanner section having a halogen lamp, a mirror, etc. In this scanner section 1, the light irradiated onto a document and reflected is further The surface of the photosensitive drum 2 charged by the charger 3 is exposed to light through a mirror lens or the like, and this operation is continuously performed as the scanner section 1 moves. The electrostatic latent image formed by this exposure is transferred to a developing section 4 having a stirring roller, a developing roller, etc.
to create a visible image using toner. The electrostatic latent image changes according to the amount of exposure, and the amount of toner on the photoreceptor drum 2 after development is controlled according to the potential distribution. A toner amount detecting means 5 for detecting the amount of toner adhering to the photosensitive drum 2 is provided downstream of the developing section 4, and a transfer roller 7 and a cleaning means 8 are sequentially arranged downstream of the developing section 4. The amount detection means 5 and the transfer roller 7 are connected to a voltage control section 9, and the voltage control section 9 is connected to a power source 10. Note that 12 indicates a transfer material.

The toner amount detecting means 5 is composed of a reflective sensor, and its light emitting section is composed of a long infrared LED array, which illuminates the surface of the photosensitive drum 2 perpendicularly to its rotation direction. is possible. The light-receiving part has the same length as the light-emitting part, and has a counter electrode, an amorphous silicon photoelectric conversion layer, and a surface transparent electrode formed on a glass substrate as a base. A current is output according to the amount of light incident on the part. The intensity (amount) of reflected light from the surface of the photoreceptor drum 2 is maximum when no toner is present, decreases as the amount of toner adhesion increases, and when the amount of toner adhesion exceeds a predetermined value, the reflected light The intensity approaches a constant value. Figure 3 shows this relationship, but since this relationship changes depending on the LED emission wavelength, toner type (color, constituent material, etc.), and type of photoreceptor, it is important to understand the conditions for each system in advance. The current output from the light receiving section is converted into a voltage signal by a photoamplifier.

In the above-mentioned device, the toner amount data transmitted from the toner amount detection means 5 is transmitted to the voltage control section 9.
Based on this input data, an applied voltage corresponding to the detected toner amount applied to the transfer roller 7 is determined, and this voltage is determined based on the rotational speed v of the photosensitive drum 2, the toner amount detection means 5, and the transfer roller. Considering the relationship with the distance s between the transfer area and the transfer area according to 7, the voltage is applied to the transfer roller 7 when the transfer material 12, which is conveyed in synchronization with the image area of the photoreceptor drum 2, reaches the transfer position. It has become. In this case, the toner adhesion amount (mg/cm2) and the reflected light intensity (ph
Figure 4 shows the correlation between the photodetector output (mA), the photoamplifier output (U), and the voltage applied to the transfer roller 7 (V). When the former three are high, the applied voltage ( V) is low, and as the former three become low, the applied voltage (V
) is becoming higher.

In the embodiment of the invention of claim 2 shown in FIG. 5, the transfer roller 7 is divided into a plurality of parts in the axial direction, and toner is applied to each of the divided roller parts 7-1 to 7-n, respectively. Amount detection means 5-1 to 5-n are provided, and these roller portions 7-1 to 7-n and toner amount detection means 5-1 to 5-n,
There is no difference from the embodiment of the invention according to claim 1 except that each of them is connected to the voltage control section 9 separately. Therefore, in this embodiment, each roller portion 7-1 to n
The amount of adhering toner is detected by the corresponding toner amount detection means 5-1 to 5-n, and an appropriate voltage is applied from the voltage control section 9 to each of the roller sections 7-1 to 7-n based on the detection signal. becomes.

0012

Effects of the Invention The present invention is as described above, and the invention according to claim 1 has a toner amount detection means for detecting the amount of toner on an image bearing member and a voltage application means, and the toner amount detection means When the amount of toner detected is large, the voltage applied by the voltage applying means is lowered, and on the contrary, when the amount of toner is small, the applied voltage is increased, and in this way, the voltage applied by the voltage applying means is increased depending on the amount of toner detected. Since the transfer voltage is applied to the transfer means, an appropriate transfer voltage can always be applied in the conveying direction of the transfer material, and excess or deficiency of the transfer voltage can be effectively prevented. This has the effect that the toner image on the surface of the photoreceptor can be faithfully transferred. Further, in the invention of claim 2, the amount of toner in the transfer means is detected by the detection means for each transfer area, and in the transfer area where the amount of toner is large, the voltage applied by the voltage application means is lowered. The applied voltage is increased in transfer areas where the amount of toner is small, and a transfer voltage corresponding to the amount of toner is applied to the transfer means for each area. In this way, the overall transfer voltage is always appropriate for the transfer direction of the transfer material. This effectively prevents excessive or insufficient transfer voltage, allowing the toner image on the surface of the photoreceptor to be faithfully transferred, increasing the toner transfer efficiency, and improving overall performance. This has the effect that a transferred image can be obtained. Since the toner amount detection means is composed of a reflective sensor, it is possible to accurately detect the toner amount.

[Brief explanation of drawings]

FIG. 1 is a front view of an embodiment of the invention according to claim 1.

FIG. 2 is a control system diagram of the main parts of the same as above.

FIG. 3 is a correlation diagram between the amount of toner adhesion on the photoreceptor and the intensity of reflected light.

[Figure 4] Toner adhesion amount and reflected light intensity on the photoreceptor as above,
FIG. 4 is a correlation diagram between a light receiving unit output, a photoamplifier output, and a transfer roller voltage.

FIG. 5 is a perspective view of a main part of an embodiment of the invention according to claim 2;

FIG. 6 is a correlation diagram between the amount of toner adhering to a photoreceptor and transfer efficiency in an image forming apparatus.

[Explanation of symbols]

2 Photoreceptor drum 3　Electrical charger 4 Developing section 5 Toner amount detection means 7 Transfer roller 9 Voltage control section 10 Power supply

Claims (3)

[Claims] Claim 1. An image forming apparatus comprising an image bearing member that holds a developed toner image and a transfer means that electrostatically transfers the toner image on the image bearing member onto a transfer material. 1. An image forming apparatus comprising: a toner amount detecting means for detecting a toner amount; and a voltage applying member applying a transfer voltage to the transfer means according to the detected toner amount. 2. An image forming apparatus comprising an image bearing member that holds a developed toner image and a transfer means that electrostatically transfers the toner image on the image bearing member onto a transfer material. An image characterized by having a toner amount detection means for detecting the amount of toner in each region, and a voltage application member that independently applies a transfer voltage to each region according to the amount of toner in the detected region. Forming device. 3. The image forming apparatus according to claim 1, wherein the toner amount detection means comprises a reflective sensor.