JP4424808B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus having a member or an apparatus configured to come into contact with or separate from an image carrier in response to power on or off, and more particularly to an electrostatic latent image formed on an image carrier. The present invention relates to an image forming apparatus including a developing device that develops an image by pressing or contacting a developing roller.
[0002]
[Prior art]
In general, in an image forming apparatus such as a copying machine, a printer, or a plotter using an electrophotographic method, an electrostatic latent image of a desired image is formed on an image carrier such as a photosensitive member, and the electrostatic latent image is applied to the electrostatic latent image. A developer is supplied by a developing device and development is performed to form a visible image. As the developer, a two-component developer composed of toner and carrier, a magnetic one-component developer composed only of toner, a non-magnetic one-component developer, and the like are well known, and various development systems suitable for these developers have been developed. Proposed.
[0003]
Above all, the non-magnetic one-component developer has various advantages but has been delayed in use in the actual machine, but in recent years it has been further improved in performance such as polymerized toner with excellent image reproducibility and transferability. As new or improved developers are developed, their use in actual machines is rapidly expanding.
[0004]
As an example of a developing device using a non-magnetic one-component developer, an elastic developing roller having a conductive or moderate electric resistance is used as a developer carrying member for supplying the developer to the image carrying member. There has been proposed a contact-type developing device in which development is performed by forming a thin layer of developer on the surface and then bringing the roller into contact with the surface of the image carrier at an appropriate pressure. Such a contact-type developing device does not require an edge enhancement effect, such as a digital printer in which an image is composed of black and white binary, and development that requires the development characteristics of the line image and the surface image to be the same. It is known that it can be preferably used.
[0005]
Conventionally, the developing roller of the developing device described above is continuously pressed against the image carrier at the same place even when image formation is not performed for a long time. Or deforms or adversely affects electrical characteristics such as charging and transfer at a portion pressed by the developing roller of the image bearing member, thereby deteriorating the quality of the output image. In addition, a cleaning roller, a cleaning blade, or a charging roller provided so as to act in contact with the image carrier has the same problem.
[0006]
For this reason, when the device is not used for a long time by the cam mechanism, the power is turned off and the cam mechanism is operated by a timer provided so that the cam mechanism is activated after a predetermined time has elapsed, or by manually operating the cam mechanism. The developed member, for example, the developing device is moved away from the image carrier to release the pressing force of the developing roller from the image carrier. However, the timer control does not deal with accidents such as a power failure or a paper jam, and the manual control causes complicated work.
[0007]
[Problems to be solved by the invention]
The present invention has been made in view of the above points, and a member that is pressed against the image carrier with a simple configuration, for example, the developing roller can be separated from the image carrier, and the development roller can be deformed by pressing for a long time. It is an object of the present invention to provide an image forming apparatus capable of preventing a negative effect on an image carrier and obtaining a stable output image.
[0008]
[Means for Solving the Problems]
In order to solve such a problem, the present invention provides a member that contacts or presses against the image carrier when the power is turned on by rotation of the cam by driving the driving means and moves away from the image carrier when the power is turned off. An image forming apparatus having a spring means for biasing a member in a direction away from the image carrier and a capacitor for charging when the power is turned on and the capacitor is driven when the power is turned off. It is characterized in that the member is moved in a direction away from the image carrier by switching the switching means so as to be a power source of the means and rotating the cam.
[0009]
Further, the developing device includes a developing roller that makes contact with or presses against the image carrier and develops it, and abuts against a part of the developing device and rotates when the power is turned on to turn the developing roller to the image carrier. In an image forming apparatus including a developing device having a cam to be contacted or pressed, a spring means for urging the developing roller in a direction away from the image carrier, a driving means for rotating the cam, and a power source are turned on. A capacitor that is sometimes charged is provided, and when the power is turned off, the capacitor is switched to become the power source of the driving means, and the cam is rotated to move the developing roller away from the image carrier. Features.
[0010]
Further, the cam has a shape in which the outer peripheral surface gradually becomes a small diameter from a large diameter and has a step from the maximum diameter to the minimum diameter, and the position of the outer peripheral surface in the vicinity of the minimum diameter of the cam and the developing device. The position where the part abuts was the first position, the position of the outer peripheral surface in front of the maximum diameter of the cam and the part where the part of the developing device abuts was the second position, and the power was turned on. Sometimes the drive means operates to rotate the cam from the first position to the second position, charge the capacitor, and the capacitor drives the cam when the power is turned off. Switching is performed by the switching means so as to be a power source for the driving means, and the cam is rotated from the second position to the first position through the step by driving the driving means by the electricity stored in the capacitor. Characterized by
[0011]
Still further, the capacitor is charged when the position of the cam that contacts the developing device reaches the second position, and the member includes a cleaning roller or a cleaning blade. The member is a charging roller .
[0012]
With this configuration, when the apparatus main body is turned on, it receives driving from the driving means for driving the cam and rotates from the first position to the second position while the outer peripheral surface of the cam abuts a part of the developing device. Move. The developing device is gradually moved by the rotation of the cam, and the developing roller is pressed against the image carrier to form a predetermined nip width.
Next, when the power is turned off, the switching means including the relay is switched so as to connect to the driving means for driving the cam by the capacitor, and the driving means is driven by the electricity charged in the capacitor. The cam is rotated by a predetermined angle to the position of 1. As the cam rotates, the developing device instantaneously moves away from the image carrier through the step of the cam, and the pressing force of the developing roller is relaxed or separated.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of a developing device of an electrophotographic apparatus to which the present invention is applied.
In the figure, reference numeral 1 denotes a drum-shaped image carrier that rotates in the direction indicated by the arrow A, that is, clockwise, and has a configuration in which an electrophotographic photosensitive member is provided on the surface of a drum-shaped substrate such as aluminum. As the photoreceptor, a known photoreceptor such as an OPC photoreceptor or an amorphous silicon photoreceptor can be used.
[0014]
Although not shown, the image carrier 1 is provided around the image carrier 1 in contact with the surface of the image carrier, an eraser lamp for erasing residual charges of the image carrier along the rotation direction A. A charging roller that uniformly charges the body with a specific polarity, an exposure device such as an LED head that forms an electrostatic latent image on the image carrier by entering digital light information on the surface of the charged image carrier, and an image carrier The toner is supplied to the electrostatic latent image for reversal development, that is, the toner is attached to the exposed portion to form a toner image, and the surface of the image carrier carrying the toner image is uniformly exposed. A post lamp for uniformly eliminating the charge of the image carrier and the toner to help improve the transfer efficiency of the toner, a paper provided in contact with the surface of the image carrier and inserted between the image carrier and the like. A transfer roller that transfers the toner image on the image carrier onto the transfer material is placed It has been. As the configuration around the image carrier, a well-known configuration can be adopted except for the developing device 2. Further, a cleaning device including a cleaning roller or a cleaning blade may be provided so as to contact the image carrier in order to remove toner remaining on the image carrier in the order of the transfer roller.
[0015]
In such an arrangement, the developing device 2 is arranged in contact with the developing container 3 containing a developer made of, for example, insulating non-magnetic one-component toner, the developing roller 4 made of an elastic body, and the developing roller 4 with an appropriate pressure. A layer thickness regulating member 5 that regulates the thickness of the toner layer formed on the developing roller 4, a supply roller 6 that is provided in contact with the developing roller 4 and supplies toner to the developing roller 4, and disposed behind the supply roller 6. The developing roller 4, the supply roller 6, and the layer thickness regulating member 5 are connected to an appropriate bias power source and a predetermined bias voltage is applied to each of them. For example, a toner having the same polarity as the charging polarity of the image carrier is used for reversal development. Reference numeral 24 denotes a toner cartridge.
[0016]
The developing roller 4 has a configuration in which an elastic intermediate layer 9 is formed around a central axis 8 made of a conductive rigid body such as stainless steel, and an elastic surface layer 10 is formed on the outer periphery of the intermediate layer 9. The intermediate layer 9 is elastically deformed and is disposed so as to come into pressure contact with the surface of the image carrier 1 with a nip width of 0.2 mm or more, preferably 0.2 to 4 mm. That is, it rotates in the counterclockwise direction B.
[0017]
Further, a spring 13 is provided on the outer surface of the developing container 3 of the developing device 2 so as to abut a cam described later. Reference numeral 14 denotes a support member that restricts the movement of the developing device 2 and supports the developing device 2. In order to move the developing device 2, a driving unit 11 such as a stepping motor and a cam 12 connected directly or indirectly to the driving unit 11 are provided. A spring 13 interposed between the cam 12 and the developing container 3 buffers the sudden movement of the developing device 2.
[0018]
The cam 12 is fixed to the shaft 15 and can be rotated by driving of the driving means 11. The cam 12 is provided so that a part of its outer peripheral surface comes into contact with a part of the developing device 2 (in the embodiment, a spring 13), and the outer peripheral surface has a shape gradually increasing from a small diameter to a large diameter. In addition, there is a stepped portion 16 that becomes the smallest diameter from the largest diameter. The height of the step 16 is set corresponding to the nip width of the developing roller to be obtained, and has a height of 3 to 7 mm in the embodiment. The cam has a width of 20 to 30 mm, and two cams are provided so as to be paired in a direction perpendicular to the drawing.
In the embodiment, even if the dimensional accuracy is deviated through the spring 13 that is harder than the hardness of the developing roller 4, the developing roller 4 does not apply an excessive load to the image carrier 1.
[0019]
The operation of the cam 12 will be described. The driving means 11 operates in conjunction with the turning on of the power of the apparatus, and the cam 12 is in the first position 17 (as shown in FIG. 1). The position of the outer surface near the minimum diameter of the cam and the position where a part of the developing device comes into contact with the second position 18 (the position of the outer peripheral surface in front of the maximum diameter of the cam as shown in FIG. 2) The developing device is gradually moved in the direction of the arrow C toward the position (a position where a part of the developing device comes into contact) and gradually moves in the direction of the image carrier (left side in the drawing).
As shown in FIG. 2, the cam 12 stops when the second position 18 is reached, and a predetermined nip width is formed between the image carrier 1 and the developing roller 4. The first and second positions are detected by controlling the rotation time of the cam 12, that is, the operation time of the driving means 11, or by detecting the position of the mark attached to the cam by a photo sensor or the like. The stop timing is determined.
The support member 14 is positioned so as to press the upper frame, and the upper frame of the developing device 2 is guided along the lower side thereof. By the movement of the developing device 2 toward and away from the image carrier, Is also supported so as not to be displaced in the vertical direction of the developing device 2.
[0020]
FIG. 3 shows a circuit for operating the driving means 11 of the developing device 2 of the electrophotographic apparatus according to the present invention.
The illustrated circuit includes a driving unit 11 such as a stepping motor, a switching unit 19 including a relay, a capacitor 20, a motor control unit 21 that operates the driving unit 11 from a power source, and a charging control unit 22 that charges the capacitor 20. Have
A switch A and a switch B are provided in the switching means 19, and when the power is turned on by a relay (not shown), the switch A is connected to the contact a and the contact e as shown in FIG. The switch B is provided so that the contact c and the contact f are connected. Further, in the state where the power is not turned on, the contact of the switch A is connected to the contact b and the contact e and the switch B is connected to the contact d and the contact f as shown in FIG. It is provided as follows.
The driving means 11 is connected to the cam 12 indirectly or directly via a gear.
FIG. 3 shows a state when the power is turned on, and the switching unit 19 operates to drive the driving unit 11 for a predetermined time by a signal from the driving control unit 21. In addition, charging of the capacitor 20 is started by a signal from the charging control means 22 that charges the capacitor 20.
[0021]
FIG. 4 shows a state when the power is turned off. The two switches A and B of the switching means 19 are switched by a relay (not shown) so that the capacitor 20 is connected as a power source. As a result, the driving means 11 is driven by the electricity charged in the capacitor 20. Regarding the driving time of the driving means 11, the electric capacity of the capacitor 20 is appropriately selected, and the cam 12 is rotated from the second position 18 to the first position 17. When the cam 12 is located at the first position, the developing device 2 is operated so as to move away from the image carrier due to the repulsion of the elastic developing roller 9. Alternatively, a spring means such as a tension spring may be provided in advance and the developing device may be urged in a direction away from the image carrier to assist movement in such a separation direction.
[0022]
The operation of the image forming apparatus having the developing device having such a configuration will be described.
When power is supplied to the apparatus main body, the driving means 11 is driven based on a signal from the motor control means 21, and the cam 12 rotates from the first position 17 of the cam 12 that contacts a part of the developing device 2. By rotating to the second position 18, the developing device located at the position shown in FIG. 1 is located at the position shown in FIG. As a result, the developing roller 4 can form a predetermined nip width with respect to the image carrier 1. Further, when the power is turned on, a signal is output from the capacitor charging control means, and the capacitor is charged by electricity from the power source.
[0023]
When the power supply of the apparatus main body is cut off, the switching means 19 is in the state shown in FIG. 4, a circuit that handles the capacitor 20 as a power supply is formed, the driving means 11 is driven by the electricity discharged from the capacitor 20, and the cam 12 is From the position 18 to the first position 17. In the embodiment, the rotational direction of the cam is one direction.
The cam moves so that the developing device moves in a direction in which the developing roller moves away from the image carrier by an amount corresponding to the step 16 that passes from the second position to the first position. The amount of charge required for the capacitor 20 to rotate the cam 12 may be about 10 to 60 degrees as an angle of rotation of the cam in consideration of safety. In the embodiment, 3000 to 5000 microfarads may be used. It was rotated about 45 degrees using a capacitor. Although FIG. 1 shows a state in which the image carrier 1 and the developing roller 4 are slightly in contact with each other, the image carrier 1 and the developing roller 4 may be completely separated from each other.
[0024]
In the embodiment, the capacitor is charged when the power is turned on. However, it is preferable to start charging when the cam reaches the second position. That is, when the cam is turned from the first position to the second position and the power is cut off, and the cam stops halfway, the turning angle by the capacitor is almost the same, so it does not pass through the step. The cam rotates within the range, and the developing roller is stopped without being separated from the image carrier.
For example, it is preferable that the cam is stopped when the contact with the developing device reaches the second position, and the capacitor is charged based on the stop signal.
[0025]
Further, in the embodiment, the cam is rotated by turning on and off the main power, but the rotation of the cam may be controlled based on the jam detection signal.
Furthermore, in the embodiment, the developing device is moved by a cam having a step, but an eccentric cam may be used.
[0026]
In the description of the present invention, the image forming apparatus provided with the developing device has been described. However, the present invention is not limited to this, and a cleaning roller, a cleaning blade, or a charging roller provided so as to act on the image carrier, This can be applied to a transfer roller or the like, and has the same effect.
[0027]
【The invention's effect】
As described above, according to the present invention, a capacitor such as a developing roller that is in contact with the image carrier in conjunction with the disconnection of the power supply is obtained by charging the capacitor when the power is turned on and using this electricity instead of the power supply. Can be automatically separated from the image carrier.
Further, even when power is not supplied due to a power failure, the cam can be rotated by the electricity of the capacitor to separate members such as the developing roller from the image carrier.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing a state in which a developing roller of a developing device according to the present invention is positioned in a direction away from an image carrier.
FIG. 2 is a schematic cross-sectional view showing a state in which a developing roller of a developing device according to the present invention is pressed against an image carrier.
FIG. 3 shows an example of a circuit diagram for operating the driving means.
FIG. 4 shows a circuit diagram in which driving means is connected to a capacitor.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Image carrier 2 Developing device 3 Developing container 4 Developing roller 5 Layer thickness regulating member 6 Supply roller 7 Stirring member 8 Central shaft 9 Intermediate layer 10 Elastic surface layer 11 Driving means 12 Cam 13 Spring 14 Support member 15 Shaft 16 Step 17 First step 1 position 18 second position 19 switching means 20 capacitor 21 motor control means 22 charge control means 23 power supply

Claims (6)

In the image forming apparatus, the image bearing member includes a member that contacts or presses when the power is turned on by rotation of a cam by driving of the driving unit and moves in a direction away from the image carrier when the power is turned off. Spring means for urging in a direction away from the image carrier and a capacitor for charging when the power is turned on are provided, and the capacitor becomes a power source for the drive means when the power is turned off. As described above, the image forming apparatus is characterized in that the member is moved in a direction away from the image carrier by rotating the cam and switching the cam. A developing device provided with a developing roller that contacts or presses against an image carrier to develop the image bearing member, and abuts against a part of the developing device and rotates when the power is turned on to move the developing roller to the image carrier In the image forming apparatus having a developing device having a cam that contacts or presses, a spring means for urging the developing roller in a direction away from the image carrier, a driving means for rotating the cam, and a power source A capacitor that is charged when the power is turned on, and when the power is turned off, the capacitor is switched to be a power source for the driving means, and the cam is rotated to move the developing roller to the image carrier. An image forming apparatus, wherein the image forming apparatus is moved in a direction away from the image forming apparatus.   The cam has a shape in which the outer peripheral surface is gradually increased from a small diameter to a large diameter and has a step from the maximum diameter to the minimum diameter, and the position of the outer peripheral surface in the vicinity of the minimum diameter of the cam and a part of the developing device When the power is turned on, the first contact position is the first position, the second front position is the position of the outer peripheral surface that is the maximum diameter of the cam and the part of the developing device. Driving means for driving the cam when the driving means is operated to rotate the cam from the first position to the second position, charge the capacitor, and turn off the power supply. It is switched by the switching means so as to be a power source of, and the drive means is driven by the electricity stored in the capacitor to rotate the cam through the step from the second position to the first position. Claim The image forming apparatus according.   4. The image forming apparatus according to claim 2, wherein the capacitor is charged when the position of the cam contacting the developing device reaches a second position. 5.   2. The image forming apparatus according to claim 1, wherein the member is a cleaning device provided with a cleaning roller or a cleaning blade.    The image forming apparatus according to claim 1, wherein the member is a charging roller.

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