JPH03288174A - Image forming device - Google Patents

Abstract

PURPOSE:To always perform stable electrostatic charging for whatever environment by utilizing a means for heating an electrostatic charging means. CONSTITUTION:The electrostatic charging means 2 is provided with the heating means 7 for heating the means 2. For example, it is assumed that an electrostatic charging roller 2 press-contacts with an image carrier 1 which is formed in a cylindrical shape and rotates and travels in a direction shown by an arrow, and the surface of the image carrier is uniformly electrostatically charged by impressed bias by a power source 5. Then, a temperature detector is provided in a proper part near the end of the hollow metallic pipe 6 of the roller 2. When a detected temperature is lower than a reference value, the power is supplied to the heater 7 inside the pipe 6 so as to raise the temperature of the roller 2, and when it is higher than the reference value, the power supply to the heater 7 is cut. Thus, the image carrier 1 is always stably electrostatically charged without receiving the effect of the environment.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Object of the Invention (Field of Industrial Application) The present invention relates to an image forming apparatus using an electrostatic transfer process, such as an electrostatic copying machine and a printer thereof.

(Prior art and problems to be solved) In the well-known image forming apparatus as described above, a charging means is used to uniformly charge the surface of the image carrier, and a toner image formed on the surface of the image carrier is transferred to a transfer material. It is preferable to use a roller-shaped charging means or transfer means that comes into contact with the image bearing member as a transfer means for the image carrier, as compared to a known method using a corona discharger, this type of device has a lower ozone It is gradually being used because it has advantages such as no generation of electricity and no need to use a very high voltage power source.

FIG. 5 is a schematic side view of a known image forming apparatus showing only the rotating cylindrical image bearing member 1 and the charging roller 2 disposed in contact with the image bearing member 1, and parts other than the charging roller are omitted. be.

The charging roller 2 consists of a core metal 4 and a conductive outer layer 3 made of an elastic material such as rubber adjusted to an appropriate volume resistivity value, and is brought into contact with the image carrier with an appropriate pressing force by a spring member (not shown). , a charging bias is applied by the power source 5 through the core metal 4, and the surface of the image carrier is uniformly charged.

In the case of transfer, a transfer roller having a mechanical configuration similar to that in the above case is in contact with the image carrier, and the transfer material is guided to the transfer site that is the nip between the two, and transfer is performed. It is a thing (as it is known).

However, the impedance of the conductive elastic material 3 used as a charging means and a transfer means increases (changes) due to changes in the environment, and the applied voltage of the power source 5 and the charging current
Since the V-I characteristic indicating the relationship changes as shown in FIG. 6, this causes various problems in actual image formation.

-Next, when using a charging roller as a charging means, in order to uniformly charge the surface of the image carrier, it is sufficient to apply a constant voltage to the nip with the charging roller; , a constant voltage power source may be used as the power source, but as mentioned above, as the impedance of the charging roller changes, the charging current also changes, and the voltage at the nip also changes, so the surface potential of the image carrier also changes. This causes an inconvenience in that the image formation is affected and the line width of the image changes.

When using a transfer roller as a transfer means, if the power source that applies the transfer bias is a constant voltage power source, as mentioned above, the impedance of the transfer roller changes greatly depending on the environment, so it is difficult to obtain appropriate transfer performance at room temperature. Even if the impedance of the transfer roller increases in a low-temperature, low-humidity environment, there will be an insufficient supply of charge, resulting in transfer defects. Depending on the presence or absence of the charge memory, charging memory appears on the image carrier, leading to problems such as deterioration of image quality.

In addition, if a constant current power source is used as a power source, the transfer bias voltage will rise too much at low temperatures and low humidity, charging the toner with the opposite polarity to the original charging polarity and causing image disturbances, and the applied voltage will decrease at high temperatures and high humidity. This may cause problems such as poor transfer.

The present invention has been made in order to cope with such a situation, and in an image forming apparatus that uses a charging means and a transfer means that come into contact with an image carrier, by using a means for heating the charging or transfer means. It is an object of the present invention to provide an image forming apparatus that can perform stable charging and transfer at all times, regardless of the environment.

(2) Structure of the invention (technical means for solving the problem and its operation) In order to achieve the above object, the present invention comprises an image bearing member and a contact type charging means and (or transfer means) that are brought into pressure contact with the image bearing member. The image forming apparatus is characterized in that the charging means and (or the transfer means) include a heating means for heating the charging means and (or the transfer means).

With this configuration, the image bearing member can be stably charged and (or transferred) at all times without being affected by the environment.

(Description of Embodiments) FIG. 1 is a side sectional view showing an embodiment of the present invention, and FIG. 2 is a front sectional view thereof, in which an image carrier 1 is formed in a cylindrical shape and rotates in the direction of the arrow in the figure. The charging roller 2 is pressed against the
It is assumed that the surface of the image carrier is uniformly charged by the bias applied by the power source 5, as in the above-mentioned known case.

The elastic outer layer 3 of the charging roller 2 is formed on the surface of a hollow metal vibro, and a charging bias is applied to this vibro by a power source 5.

As can be seen from Figure 2, a temperature detector 8 is placed at a suitable location near the end of the metal vibro, and its temperature signal is sent to a comparator 9, where the temperature is compared and the detected temperature is determined. If it is lower than the reference value, the output signal of the comparator 9 is turned on, the switch 10 is closed, and the power supply 11 is turned on.
As a result, the heater 7 inside the vibro is energized to raise the temperature of the charging roller 2.

On the other hand, when the temperature of the vibro is higher than the reference value of the comparator 9, the switch 10 is turned off and the electricity to the heater 7 is cut off.

If the reference temperature is set to a value higher than the upper limit of the operating environment temperature of the device, the temperature of the vibro is maintained at the reference temperature by controlling the power supply to the heater 7 as described above, and the temperature of the outer layer 3 and the drying temperature are maintained. Since the state can be maintained constant regardless of the environment, the impedance of the charging roller 2 can be kept almost constant, the charging characteristic curve can also be maintained almost constant regardless of the environmental conditions, and a stable charging function can be obtained.

Next, an experimental example will be explained.

Experimental Example-1 An aluminum cylinder with a diameter of 30 mm on which an OPC photosensitive layer was formed on the surface was used as an image carrier, and a stainless steel pipe with an outer diameter of 8 mm was used as a charging roller, and carbon was dispersed in EPDM to make it conductive. 6m of elastomer layer
A material formed to a thickness of m and an outer diameter of 20 mm was used.

As a heater, 100 nichrome wire sealed with an insulator is used.
W was used, a thermistor was used as the temperature detection element, and the reference temperature was set at 40°C.

For the power supply, use a -3000V DC constant voltage power supply, (15℃, 10%RH), (23℃, 60%RH),
Charging was performed in various environments (35° C., 80% RH) at a circumferential speed of the image carrier of 50 m+o/sec, and the results shown in the table below were obtained.

In the above table, the values in parentheses are when the heater is turned off all the time.
This corresponds to a known one.

From this result, it can be seen that the above-mentioned example device has excellent stability against the environment.

-After the next charging, exposure, reversal development, transfer, cleaning, and fixing were performed using well-known methods and compared, and compared to the same work as a known device in which the heater was always turned off, this example It was confirmed that stable charging characteristics could be obtained at all times, with no problems such as image fogging or line width thinning in high-temperature environments.

FIG. 3 shows another embodiment, in which the illustrated device shows the vicinity of the transcription site.

A transfer roller 2 consisting of a core bar 4 and an elastic conductive layer 3 disposed outside the core bar 4 is attached to an image carrier 1 rotating and traveling in the direction of the arrow shown in the figure.
' are in pressure contact with each other, and when the transfer material is supplied to the transfer area formed as a nip between the two, a transfer bias is applied to the transfer roller 2° by the power supply 12, and the toner formed on the surface of the image carrier is Image 18 is transferred to the transfer material.

In this device, the heating roller 13 is in contact with the transfer roller 2°.

The heating roller 13 can be formed by forming a well-known self-heating control type planar heating element (for example, Ceramic (registered trademark)) 14 into a cylindrical shape, and forming an insulating layer 15 on the surface thereof.

By applying a voltage to this heating roller 13 from a power supply (not shown), it is possible to maintain the temperature at a predetermined temperature, so that by appropriately setting and maintaining the temperature of the transfer roller, the impedance of the roller can be kept constant. keep,
It is possible to always obtain stable transferability regardless of changes in the environment.

Further, by applying a voltage even when the apparatus is stopped, the transfer roller 2° can be maintained at a higher temperature than the environment and in a dehumidified state, so that the impedance of the conductive layer 3 of the roller can be kept approximately constant.

Furthermore, by appropriately selecting the material of the insulating layer 15, it is possible to promote the transfer of toner to the heating roller 13 while being kept at a high temperature, and by disposing a scraper 16 on the roller 13, By configuring the toner to be removed, the transfer roller 2° can be kept clean and transfer performance can be improved.

Experimental Example 2 Using the same image carrier as in Experimental Example 1, an elastic conductive layer 3 made of urethane rubber was molded to a thickness of 5 mm on a stainless steel core with a diameter of 6 mm as the transfer roller 2. An outer diameter of 16 mm was used, and this was pressed against the image carrier 1 with a force of 800 gr.

As the heating roller 13, 15 μm of silicon is coated on the surface of a self-heating control type planar heating element 14 formed into a cylindrical shape.
A film formed to a thickness of m and an outer diameter of 12 mm was used.

AC 100V is constantly applied to the heating roller 13, and the surface temperature is self-controlled within the range of 40 to 45°C.

The circumferential speed of the image carrier was set to 90 mm/sec, and a voltage of +3000 V was applied to the core metal of the transfer roller 2.
℃, 10%RH), (23℃, 60%RH), (35℃
, 80% RH).Transferability was examined in each environment. The transfer current at this time was as shown in the table below.

The figures in parentheses in the above table are for the case where the heating roller is always turned off, which is the same as in a known device. However, in the device of this example, it was confirmed that the increase in transfer current was suppressed and the environmental dependence was small.

FIG. 4 shows a third embodiment of the present invention, in which parts corresponding to those of the apparatus of each of the above embodiments are denoted by the same reference numerals.

Reference numeral 19 denotes a planar heater, which is spread on the inner surface of the aluminum base of the image carrier 1. A power supply (not shown) is controlled by a temperature detection element 8 to adjust the surface temperature of the aluminum cylinder according to the environment. It is maintained several degrees higher than the temperature. Charging roller 2
As shown in the figure, the transfer roller 2° is heated by the heater 19 via an aluminum cylinder, and the temperature is kept almost constant regardless of the environment. Stable charging characteristics and transferability can be maintained.

Moreover, by configuring in this way, the charging roller,
There is no need to provide a special heater to the transfer roller.

Furthermore, in the case of the above-mentioned embodiment, if the image carrier has a large heat capacity, the surface potential of the portion of the image carrier that was in contact with the charging and transfer rollers decreases while the apparatus is at rest due to the temperature characteristics of the OPC. However, in the case of this embodiment, since the image bearing member is heated uniformly and then each roller is heated, there is no deterioration of the image. A device with stable charging characteristics and transfer characteristics can be obtained.

(3) Detailed Description of the Invention As described above, the present invention provides an image forming apparatus that uses a charging roller and/or a transfer roller that come into contact with an image carrier, by heating the roller to maintain a substantially constant temperature at all times. Since the structure is configured to maintain impedance, it is possible to prevent the environmental dependence of charging characteristics and transfer characteristics, and to perform stable charging and/or transfer at all times, which has a remarkable effect on obtaining high-quality images. .

[Brief explanation of drawings]

FIG. 1 is a schematic explanatory diagram of a main part of an image forming apparatus showing an embodiment of the present invention, an end sectional view of No. 61 No. 2 same as above, and FIGS. 3 and 4 are main parts showing other embodiments, respectively. FIG. 5 is a schematic side view showing the structure of a charging portion of a known image forming apparatus, and FIG. 6 is a graph showing the voltage-current characteristics of the same. DESCRIPTION OF SYMBOLS 1... Image carrier, 2 Charging roller, 2°... Transfer roller, 3... Elastic conductive layer, 4... Core bar, 5... Power supply, 6... Pipe, 7... - Heater, 13... Heating roller, 19... Planar heating element 1. Figure 3 Figure 3 Departure =

Claims (8)

[Claims] (1) An image forming apparatus comprising an image bearing member and a contact type charging means that presses against the image bearing member, wherein the charging means includes a heating means for heating the charging means. (2) The image forming apparatus according to claim 1, wherein the heating means is a heat source disposed inside the charging means. (3) The image forming apparatus according to claim 1, wherein the heating means is a heat source disposed outside the charging means. (4) The image forming apparatus according to claim 1, wherein the heating means is a heat source disposed inside the image carrier. (5) An image forming apparatus comprising an image bearing member and a contact type transfer means that presses against the image bearing member, the image forming apparatus comprising a heating means for heating the transfer means. (6) The image forming apparatus according to claim 5, wherein the heating means is a heat source disposed inside the transfer means. (7) The image forming apparatus according to claim 5, wherein the heating means is a heat source disposed outside the transfer means. (8) The image forming apparatus according to claim 5, wherein the heating means is a heat source disposed inside the image carrier.