JP2003076234A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of inexpensively erase detecting disconnection of an LED lamp for discharge, a wiring failure, or the like which will cause a serious damage to the device once it occurs. SOLUTION: A circuit for detecting a failure of a discharge lamp 5 is arranged in a main board of a picture forming device main body. An ON-OFF signal of the discharge LED comes into a port output from a pot of a CPU. An input to the port is high when the discharge lamp 5 is connected with the circuit in a normal state, while it is low when a disconnection or faulty wiring occurs. Abnormality of the discharge lamp 5 is detected by the signal inputted to this port.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to removing static electricity from a photoconductor.
The present invention relates to a two-component image forming apparatus using an ED lamp.

[0002]

2. Description of the Related Art In an electrophotographic process using a two-component type developer, an extremely large role is given to charge removal of a photoconductor in front of a charging device. This is because if the charge removal does not function sufficiently, the potential on the surface of the photoconductor rises, causing a problem of carrier adhesion. That is, when the carrier adheres to the photoconductor, the carrier may damage the edge of the cleaning blade, or the carrier transferred to the recording paper may damage the surface of the fixing roller, causing serious damage to the machine. .

In the technique disclosed in Japanese Unexamined Patent Publication No. 10-161368, when a faulty lighting of the static elimination light source occurs,
A surface potential sensor that measures the surface potential on the surface of the photoconductor detects an increase in the surface potential, and changes the control of the charging device to avoid problems such as carrier adhesion.

However, the potential sensor for measuring the potential on the surface of the photoconductor is an expensive one, and it is not realistic to adopt such an expensive component in view of the recent market situation where cost competition is intense.

According to the present invention, it is possible to inexpensively detect a problem such as a disconnection of the LED lamp for static elimination, a connection failure, etc., which would cause a great deal of damage to the device when it occurs, and to minimize damage to the device body. It is an object of the present invention to provide an image forming apparatus that can be stopped as much as possible.

[0006]

In order to achieve the above object, an image forming apparatus according to claim 1 of the present invention uses a two-component type developer composed of a toner and a carrier, and the rotational direction of a photoconductor. In the image forming apparatus by the electrophotographic process in which the static eliminating device is provided upstream from the charging device and the static eliminating device uses the LED lamp, the disconnection detection circuit of the LED lamp of the static eliminating device is provided in the main board of the image forming apparatus main body. It is characterized by

According to a second aspect of the present invention, in order to achieve the above object, in the image forming apparatus according to the first aspect, when the disconnection of the LED lamp is recognized by a signal from the disconnection detection circuit, the image is displayed. It is characterized in that it has means for stopping the image recording operation in the main body of the forming apparatus.

According to a third aspect of the present invention, in order to achieve the above object, the image forming apparatus according to the first or second aspect has means for constantly monitoring the signal of the detection circuit circuit when the LED lamp is turned on. Is characterized by.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing an outline of an image forming unit of an image forming apparatus that carries out a two-component electrophotographic process. In the figure, reference numeral 1 is a photosensitive drum, around which a developing roller 2, a developing doctor 3, a charging roller 4, a discharging lamp 5, a cleaning blade 6, a transfer roller 7, a P sensor 8 and the like are arranged, and further, a developing device. Conveying screws 9 and 10 and a toner concentration sensor 11 are provided to configure the above, and a charging roller cleaner 12 is attached to the charging roller 4.

The charging of this device will be described. The charging roller 4 uniformly charges the surface of the photosensitive drum 1. As the charging means, there are a scorotron method and a corotron method which are wire charging as a non-contact charging, and a contact roller method using a medium resistance rubber roller as a contact charging. In the illustrated example, the roller charging method is used.

The scorotron method has been widely used in the past when the photosensitive drum 1 was negatively charged, but since ozone is generated during discharge, it is currently limited from the viewpoint of environmental protection. It is used only in the model group. In addition, the corotron method is one in which the photoconductor is positively charged, and the generation of ozone is small, but it is not generally used. Recently, since the unit price of the charging roller capable of suppressing the generation of ozone has become low, the contact type roller charging method is the most general charging means.

This contact type roller charging method also has a method of superimposing an alternating current on a direct current and a method of applying only a direct current. In the former, by controlling the alternating current with a constant current,
Although it has the advantage that it is not affected by the change in the resistance value of the charging roller due to the change in the environment with respect to the surface potential, the cost of the high-voltage power supply is high, and AC high-frequency sound is a problem. The latter is directly affected by the change in the resistance value of the charging roller due to the change in the environment with respect to the surface potential, so that some means for correcting the applied voltage is necessary for the change in the environment. As a correction method, means for detecting the temperature in the vicinity of the charging roller 4 and switching the applied voltage, and the photosensitive drum 1
There is a means for periodically detecting the above ground stain and switching the applied voltage. By adopting these methods, the surface of the photosensitive drum 1 is charged to about -900V.

Writing will be described. A latent image is formed by irradiating the portion of the photosensitive drum 1 to which the toner is attached with a laser beam by an exposing unit (not shown).
The portion not irradiated with laser light is about −900V, whereas the portion irradiated with laser light is −100V.
The potential drops to about V to -200V. Toner adhesion is controlled by this potential difference.

The development will be described. The two-component developer comprises a non-magnetic toner and a magnetic carrier. The main component of this carrier is iron, which is held on the developing sleeve by the magnetic force of the developing roller 2 which is a magnet roller, and electrically has a polarity (+) opposite to the developing bias.
have. Therefore, the surface potential of the photosensitive drum 1 is normally about -900V and the developing bias is -600V.
In some cases, there is no problem, but when this potential difference becomes large, the electric force becomes stronger than the magnetic force, and the carrier adheres to the photosensitive drum 1. When the developing bias is set, if the difference from the surface potential of the photosensitive drum 1 is large, the carrier adheres, and if it is small, the toner adheres to the background, resulting in background stain.

The transfer will be described. In the transfer device, an electric charge having a polarity opposite to that of the toner is applied from the back surface of the recording paper. Due to this electric charge, the toner is attracted to the recording paper. Previously,
The non-contact wire system was generally used, but recently, the roller transfer system is generally used. In addition to cost, this is because transfer wires are generally used from the viewpoint of safety, because a considerable amount of voltage is applied to wires and the risk of fire if the recording paper touches the wires. It has become to.

The cleaning will be described. The most commonly used method is a cleaning blade method in which a cleaning blade 6 made of urethane rubber is brought into contact with the surface of the photosensitive drum 1 in the counter direction and the residual toner after transfer is scraped off at the edge portion thereof. In the case of the illustrated example, the toner scraped off by the cleaning blade 6 is conveyed by the screw 13 in the direction perpendicular to the paper surface of the drawing and returned to the developing device for reuse.

The static elimination will be described. Again, before the electric potential is applied by the charging roller 4, the electric charge of the photosensitive drum 1 is set to a certain value or less. By this static elimination, it is necessary to bring the surface potential of the photosensitive drum 1 as close as possible to GND (0V). Actually, the surface potential of the photosensitive drum 1 is lowered to about -150V by removing the charge. As this static elimination means, the static elimination lamp 5 using an LED lamp, which is inexpensive in cost and sufficiently satisfies the required function, is most commonly used, but the static elimination functions due to the failure of the LED lamp. When it disappears, it will be further charged above the potential of -900V, and the photosensitive drum 1
When the surface potential of -is 1000 V or higher, the risk of carrier adhesion increases.

FIG. 2 is a diagram showing an example of a failure detection circuit of the static elimination lamp 5. This circuit is provided in the main board of the main body of the image forming apparatus. In the case of this example, the ON / OFF signal of the static elimination LED comes into the port output from the port of the CPU. When it is ON, a high signal is input, and when it is OFF, a low signal which is the opposite of the high signal is input. If the static elimination lamp 5 is in normal condition and connected to the circuit,
The input to the port becomes High when it is ON. However,
When disconnection or connection error has occurred, the input to the port is a Low signal. The signal input to this port is used to detect an abnormality in the static elimination LED.

FIG. 3 is a control flowchart of the embodiment of the present invention. After the plotter operation starts, the main motor starts to rotate and the static elimination lamp 5 is also turned on (step 1). Although they are turned on at the same time in the flowchart, they are not necessarily turned on at the same time. Simultaneously with turning on the static elimination lamp 5, judgment of failure detection is started (step 2). During the recording operation (step 3), the failure detection is in operation, and when the failure is detected, the machine is stopped and an error message is displayed (step 4). Of course, when an image is formed without any error and a predetermined number of sheets have been output (steps 5 and 6), the main motor is stopped and the static elimination lamp 5 is turned off (step).

In the case of an error, the operation that the user can easily perform (press the button on the operation panel, turn on the power
It is desirable that the machine does not recover with FF / ON etc.).
Also, the time from the detection of a failure to the stop of the machine should be as short as possible, but the distance between charging and development on the photoconductor: A [mm], the linear velocity of the photoconductor: B [mm / sec], failure detection From the time until the stop: T [sec], if the time T <A ÷ B is not satisfied, some damage may be done to the machine, so be careful.

FIG. 4 is a diagram showing the relationship of each potential. Under normal conditions, the surface of the photosensitive drum 1 is about -90 due to charging.
The area exposed to light during writing, which was charged to 0V, was about −
It goes down to 150V. The developing bias is -600V, and by maintaining these relationships, the toner adheres to the portion that drops to -150V and the toner does not adhere to the portion that -900V. In the figure, VD is the surface potential of the photosensitive drum 1, VL is the potential of the writing portion, VB is the developing bias, and VD-VB> -300. In this case, depending on the value (VD-VB> -400 in this example), the carrier tends to be easily attached. Conversely, VD-VB <-3
When it becomes 00, it depends on the value (in the case of this example, V
D-VB <-200), and the possibility of occurrence of scumming increases.

[0022]

As described above, the image forming apparatus according to the present invention uses a two-component developer composed of toner and carrier, and is a static eliminator upstream of the charging device in the rotation direction of the photoconductor. In the image forming apparatus by the electrophotographic process using the LED lamp,
Since the disconnection detection circuit of the LED lamp of the static eliminator is provided in the main board of the main body of the image forming apparatus, it is possible to detect the failure of the static eliminator LED without cost.

In the image forming apparatus according to the second aspect, the recording operation is stopped when the disconnection of the LED lamp of the static eliminator is recognized by the signal from the detection circuit. Therefore, the failure of the static elimination LED can be detected without cost. At the same time, there is an effect that damage to the machine can be suppressed.

In the image forming apparatus of claim 3, since the signal of the detection circuit is constantly monitored when the LED lamp of the static eliminator is turned on, the failure of the static elimination LED can be detected without cost and damage to the machine. The effect is that you can minimize the.

[Brief description of drawings]

FIG. 1 is a cross-sectional view illustrating an outline of an image forming unit of an image forming apparatus that executes a two-component electrophotographic process.

FIG. 2 is a diagram showing an example of a failure detection circuit for a static elimination lamp.

FIG. 3 is a control flowchart of the embodiment of the present invention.

FIG. 4 is a diagram showing a relationship between potentials.

[Explanation of symbols]

1 photoconductor drum 2 developing roller 3 Development Doctor 4 charging roller 5 Static elimination lamp 6 cleaning blade 7 Transfer roller 8 P sensor 9,10 Transport screw 11 Toner density sensor 12 Charge roller cleaner 13 screws

Claims (3)

[Claims] 1. An image formation by an electrophotographic process using a two-component developer comprising a toner and a carrier, and a static eliminator provided upstream of a charging device in the rotation direction of a photoconductor, the static eliminator using an LED lamp. In the apparatus, the disconnection detection circuit for the LED lamp of the static eliminator is provided in the main board of the main body of the image forming apparatus. 2. The image forming apparatus according to claim 1, further comprising means for stopping an image recording operation in the main body of the image forming apparatus when the disconnection of the LED lamp is recognized by a signal from the disconnection detecting circuit. A characteristic image forming apparatus. 3. The image forming apparatus according to claim 1, further comprising means for constantly monitoring the signal of the detection circuit circuit when the LED lamp is lit.