JPH01179180A - Image forming device - Google Patents

Abstract

PURPOSE:To always stably separate a transfer material regardless of the kinds of the transfer material and environment by controlling a separation current based on the change of the driving current of a photosensitive drum. CONSTITUTION:The number of rotation of the photosensitive body is detected by a device 6 at the time of passing paper and kept constant by a control unit 61. The photosensitive body driving current value is monitored by a device 7 in such a state and inputted in a control unit 71 to detect the difference of said value from a specified value. By feeding back the difference to a high voltage unit 8, the separation discharge current of a separation electrifier 4 is controlled so that the photosensitive body driving current becomes the specified value. Thus, the transfer material can be stably separated by giving proper separation discharge current to various kinds of transfer materials.

Description

DETAILED DESCRIPTION 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 or a printer, and particularly to a transfer material separation device thereof.

[Conventional technology]

A transferable toner image is formed using charged powder toner on a photosensitive layer on the surface of an image carrier that runs in an endless manner, and a transfer material, mainly paper, is brought into contact with the toner image. After the toner image is electrostatically transferred to the transfer material by applying a charge of opposite polarity, the transfer material is separated from the image carrier and the toner image is fixed and fixed on the transfer material. Image forming apparatuses configured to repeat the process of removing toner and residual charges are conventionally well known.

In such an image forming apparatus, when a toner image is transferred to a transfer material, the transfer material is electrostatically attracted to the image carrier after the transfer due to the influence of the electric charge applied to the toner image, making it easy to separate the two. Therefore, after the transfer, an AC corona discharge with a polarity opposite to that of the charge at the time of transfer is applied to the transfer material to neutralize the charge at the time of transfer. Those configured to be separated from the image carrier are widely used.

[Problem that the invention is trying to solve] However,
Paper, which is most commonly used as a transfer material, changes significantly in its elasticity and stiffness depending on its type, and even on the same type of paper depending on the environment and humidity. It is not always easy to always achieve a stable separation effect by using only this alone.

Furthermore, when separation is performed using the above-mentioned separation charger, the separation performance deteriorates as the number of sheets increases, and scattered toner, paper dust generated from the transfer material, and other foreign matter get onto the discharge wire of the charger. It is known that due to adhesion, the discharge current decreases or becomes unstable, which reduces the static elimination function.

The present invention focuses on the fact that the load applied to the image bearing member by the transfer material increases when the static elimination function decreases and separation failure occurs due to the reasons mentioned above, and the amount of load is monitored as a drum current, and It is an object of the present invention to provide a transfer material separation device that can perform a stable separation operation at all times by feeding back the separation current value to a separation current controller and changing the separation current value as needed.

[Means (and effects) for solving the problem] According to the studies conducted by the present inventors, when the drum drive speed is kept constant and the drum drive current value is monitored by varying the separation current, the results shown in Fig. 2 are obtained. It turned out as shown.

A in the figure shows that as the separation current value 1sep increases,
Since the winding force of the transfer material around the image carrier becomes weaker, the load on the image carrier becomes smaller, and the drum drive current value 1d becomes smaller. As the current value decreases and finally reaches the point shown in the figure, a jam phenomenon occurs in which the transfer material is completely wrapped around the image carrier and is not separated from the image carrier, thereby increasing the load of the transfer material on the image carrier. increases rapidly, and the drum drive current value increases as shown in C in the figure.On the other hand, if l5ep becomes too large (too much), it is assumed that a retransfer phenomenon will occur.The threshold value is shown in the figure. d, l5ep, and latitude is e in the figure.

In addition, as mentioned above, when the separation static elimination function gradually deteriorates due to durability etc., the transfer paper starts to wrap around the drum, and the load on the drum increases (Idr increases accordingly). This is as shown in Fig. 3. In this graph, a is the value of Idr when the initial separation charge removal is in a good state. In the present invention, this a is used as a means to detect separation failure. I thought of setting the value of Idr in advance if the separation static electricity removal is not good (the value of Idr increases as it becomes better), and if this value is set as b, then (b-a) means that the separation static electricity removal is not good. Since this is the drum driving current increased due to failure, the structure is characterized in that l5ep is increased so that it always becomes a.

[Embodiment 1] Fig. 1 is a side view of the main parts of an embodiment in which the present invention is applied to a copying machine equipped with a rotating cylindrical image bearing member (photoreceptor), which rotates in the direction indicated by the arrow. The transferable toner image formed on the surface of the photoreceptor l is placed on the conveyance path 21 and transferred to a transfer site equipped with a transfer charger 3 in synchronization with the transfer material waiting at the position of the registration rollers 2. At this point, the transfer material comes into contact with the transfer material, and at this position, the back surface of the transfer material is given a charge with a polarity opposite to that of the toner, and the toner image on the photoreceptor side is transferred to the transfer material.

At this time, the transfer material adheres to the surface of the photoconductor by electrostatic adsorption force, so the separation charger 4 applies a charge of opposite polarity to that in the transfer charger to the transfer material to remove the previous charge and transfer The material is separated from the photoreceptor due to its stiffness and weight, and is transported to the next fixing site by means such as the transport belt 5.

Said photoreceptor! Around the , there is a primary charger to uniformly charge the surface, a part to which an image signal is applied to form an electrostatic latent image, a developer to visualize the latent image, and a part to remove residual toner. Of course, cleaners and the like are provided for cleaning, but since these are not directly related to the present invention, a description thereof will be omitted.

In the above-described copying machine, the present invention includes a device 6 for monitoring the torque of the motor that drives the photoconductor as a current value, and a device 7 for detecting the rotation speed of the photoconductor.
will be established.

On the other hand, in the case of the electrostatic separation method, an AC corona discharge whose polarity is opposite to that of the transfer current is used for the discharge current, and the static elimination ability is determined by the amount of current directed toward the transfer material, and by passing the paper.
In particular, a decrease in the DC component was observed. It has been confirmed that this direct current component has an appropriate value depending on the configuration of the apparatus, and it has been confirmed that if it is too small, separation failure will occur, and if it is too large, retransfer will occur.

With this configuration, the number of rotations of the photoreceptor can be detected by the device 6 during paper passing, and the number of rotations can be kept constant by the control unit 61. In this state, when paper is fed, the photoreceptor drive current value Idr is monitored at 7, inputted to the control unit 71, the difference from a shown in FIG. 3 is calculated, and this is applied to the high voltage unit 8. The photoreceptor driving current Idr.

The DC component of the 1sep is increased so that Idr becomes the normal value a. One way to do this is to input the relationship shown in Figure 2 into the control unit in advance, and set Idr, l5 which can be increased by the value of
One example is to determine the value of ep.

In this way, the transfer body always has an appropriate separation discharge current of 1 s.
EP, it was possible to obtain good copies with few jams.

[Example 2] In the copying machine described in the previous section, as the number of sheets passing increased, scattered toner and other foreign matter adhered to the discharge wire of the separation charger, causing wire contamination, and the wire was periodically cleaned. There is a need to.

Therefore, in addition to the above embodiment, the limit of wire contamination is determined in advance, the photoconductor drive current value at that time is set as the wire contamination latitude, and the photoconductor drive current value monitored in step 7 every time the paper passes is set to the latitude. It is preferable to adopt a configuration in which when the wire reaches this value, the operator is notified that it is time to clean the wire and is prompted to clean it.

[Example 3] As another example, assume that a jam occurs when paper is passed and the transfer paper wraps around the photoreceptor. In this state, the load of the transfer paper on the photoreceptor increases rapidly, and the Idr
takes a value as shown in FIG. 2C. Therefore, we used this to create a jam detection device that would immediately stop the operation of the machine and notify the operator that there is a jam if the Idr is monitored using the device 7 during paper feeding and reaches the value of C. It is preferable to take this configuration.

〔Effect of the invention〕

Since the present invention has the above configuration, in an image forming apparatus using a separation charger, the function is maintained by detecting separation failure and controlling the discharge current value.
Additionally, in the event of a jam, the machine can be stopped immediately and functionality can be restored quickly. In this way, a good separation effect can be maintained over a long period of time, resulting in the effect of obtaining high-quality images. It is also possible to notify when it is the best time to clean the wires, making it suitable for maintenance and the like.

[Brief explanation of the drawing]

FIG. 1 is a side view of essential parts showing an embodiment in which the present invention is applied to a copying machine. Figure 2 shows the separation current value 1sep and the drum drive current value Id.
Graph showing the relationship between r. FIG. 3 is a graph showing the relationship between the number of sheets passed and the drum drive current value 1dB. l... Photoconductor 2... Registration roller 3.
...Transfer charger 4...Separation charger 5...Transport belt 6...Drum rotation speed detection device 7...Drum drive current detection device 8...High voltage unit 61...Control unit 71.・Control unit general control unit

Claims (4)

[Claims] (1) After transferring the toner image onto the transfer material by bringing a synchronously running sheet-like transfer material into contact with or close to the toner image on the surface of the moving image carrier, the transfer material is separated from the image carrier. In an image forming apparatus configured to be conveyed, a rotation control means detects the number of rotations of the image carrier and drives the image carrier while keeping this number of rotations constant, and a driving force detection device detects the magnitude of the driving force of the image carrier. An image forming apparatus comprising a separation control means for controlling a separation current applied to a transfer material by the means. (2) The image forming apparatus according to claim 1, wherein the separation control means controls a DC component of the separation current. (3) The image forming apparatus according to claim 1, wherein automatic cleaning of the separation charging electrode is controlled based on the driving force detection means. (4) The image forming apparatus according to claim 1, wherein a jam of the transfer material is detected based on the driving force detection means.