JP3785818B2 - Image recording device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrophotographic image recording apparatus including, for example, a roller brush charger.
[0002]
[Prior art]
Conventionally, in an electrophotographic image recording apparatus, a charging corona that performs corona discharge is generally used as a charging means for a photosensitive drum. Then, after setting the surface potential of the photosensitive drum to a constant value by discharging the charged corona, an electrostatic latent image is created by irradiating light according to the image, and toner is applied to the electrostatic latent image. By supplying, a visible image as a toner image is created. The toner image is transferred to a sheet using a transfer corona at an image transfer position, and the sheet carrying the toner image is fixed through a fixing device and discharged as a recording sheet. However, in an image recording apparatus using a corona, there is a problem that ozone is generated by high-pressure discharge from the corona. For this reason, it is necessary to provide an ozone filter in exhaust means such as an exhaust fan, which increases the size of the apparatus.
[0003]
Therefore, for a small image recording apparatus, a charger for charging a photosensitive drum and a transfer member for transferring a toner image onto a sheet (brush charger) or A roll-shaped member made of sponge is used. For example, by using a brush charger, the configuration of the image forming apparatus can be simplified, the discharge voltage is set to a relatively low voltage, and the generation of ozone is eliminated, so that the configuration of the exhaust means and thus the entire configuration of the apparatus is achieved. It becomes possible to demonstrate the feature that can be simplified.
[0004]
[Problems to be solved by the invention]
However, in the conventional image recording apparatus as described above, since the brush charger is composed of conductive fibers, the cross-sectional shape of the brush roller in the direction perpendicular to the axis is not a perfect circle, and the circumferential surface Has subtle irregularities. For this reason, when the bristles of the roller brush are always rotated in contact with the peripheral surface of the photoconductor drum, the length of the bristles of the brush that contacts the photoconductor drum, the pressure contact force, and the like are not constant, and the photoconductor drum There was a problem that the charging of the ink was uneven and the print quality was deteriorated. Further, due to the inconsistent brush length and pressure contact force, load fluctuations are applied to the rotational drive system, and the charging unevenness of the photosensitive drum is deteriorated, resulting in a further deterioration in print image quality. However, when the roller-like brush is always stopped, toner and paper powder easily enter between the brush hairs and adhere to the brush, resulting in brush stains. When the brush becomes dirty, the charging performance of the photosensitive drum is lowered. When the brush is affected by environmental conditions (changes in humidity), the resistance value changes and the surface of the photosensitive drum becomes uniform. This causes a problem that it cannot be charged.
[0005]
In particular, in an image forming apparatus of a method (cleanerless method) in which a toner image is transferred from a photosensitive drum to a sheet, and the remaining toner is not collected by a cleaning device but returned to a developing device (cleanerless method). Since the toner remaining on the body drum is not removed before charging, the brush charger is more easily soiled than the system using the cleaning device, and the contamination of the brush charger has a great influence on the charging performance of the photosensitive drum. Is.
[0006]
The object of the present invention is to eliminate such drawbacks of the prior art, to stabilize the pressure contact force of the brush that contacts the photosensitive drum, to prevent fluctuations in the rotational drive load, to stabilize the charging of the photosensitive drum, An object of the present invention is to provide an image recording apparatus capable of improving printing quality.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, an invention according to claim 1 is an image recording apparatus in which a charger is disposed on the surface of a photosensitive member and uniform charging is performed before an electrostatic latent image is formed on the photosensitive member. In addition, the charger is composed of a roller brush charger, and the brush charger starts rotating before the photosensitive member changes from stop to rotation, and when the photosensitive member starts rotating, the brush charger stops rotating. To do. According to a second aspect of the present invention , the brush charger starts rotating after the photosensitive member changes from rotating to stopping, and rotates for a predetermined time. Further, the invention of claim 3 is an angle at which the rotation angle of the intermittent rotation of the roller brush charger is not an integral multiple of 360 °.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an image recording apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a front view showing an image recording apparatus according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing a configuration of a scanning apparatus used by being incorporated in the apparatus of FIG. FIG. 3 is a cross-sectional view of a process apparatus unit disposed on the main body frame of FIG. FIG. 4 is an explanatory diagram showing the configuration of the process apparatus of FIG. FIG. 5 is an explanatory diagram showing a configuration of the photosensitive unit of the process apparatus of FIG. FIG. 6 is a timing chart showing a driving operation in the photosensitive unit of FIG.
[0009]
The configuration of the image recording apparatus of the present invention will be described with reference to the illustrated example. The example shown in FIG. 1 shows a case in which a facsimile apparatus and a copying machine are combined, and the image recording apparatus 1 has two paper feed cassettes 3 and 3a arranged at the lower part thereof. A main body frame 2 provided with an electrophotographic recording unit on the upper part and a scanning unit frame 20 provided so as to be swingable via a fulcrum 21 provided on one side of the main body frame 2 are combined. In the scanning unit frame 20, a platen is disposed on the upper surface of the frame, and a scanning device as an FBS (Flatbed Scanner) that scans a document of a book set on the platen, and the upper surface of the platen cover are used as a document discharge tray 28. A moving document scanning unit that scans a document to be inserted from the document tray 27 while moving it in a document transport unit 40 as an automatic document transport device and performs an operation as an automatic document transport device (ADF) is provided. In the image recording apparatus 1, as shown by a broken line in FIG. 1, the scanning unit frame 20 is configured to be openable and closable with respect to the main body frame, and the scanning unit frame 20 is opened via a fulcrum 21. In the state, the upper surface of the main body frame 2 is opened.
[0010]
By disposing each component and the frame opening / closing mechanism, the image recording apparatus of the present invention can perform sheet replenishment to the sheet feeding cassette and control of the apparatus from the front side, and a manual feed tray is used. The paper supply and copy take-out operations can be performed from both sides. In addition, the upper part of the main body frame is opened by opening and closing the scanning unit frame 20 so that the maintenance of the process apparatus of the image recording unit can be performed. Furthermore, the operation of setting the original of the book on the platen can be performed by opening and closing the upper opening / closing frame 25 on the scanning unit frame 20, and transmitting the image information while scanning the original set on the platen. Can be easily performed.
[0011]
The paper feed cassettes 3 and 3a accommodated in the lower part of the main body frame 2 are capable of accommodating paper of an arbitrary size and are provided so as to be pulled out to the front side of the apparatus. Also, as shown in FIG. 3, a manual insertion slot 5 is arranged on the other side of the main body frame so that the manual feed tray 6 can be mounted. A copy can be made using a small number of sheets that are not accommodated in the printer, and when the manual feed tray is not mounted, the side of the main body frame does not protrude. Further, as shown in FIG. 1, a discharge tray 7 for storing a copy is disposed on one side of the main body frame 2, and an auxiliary tray 8 can be pulled out corresponding to a large size sheet. In the state where the auxiliary tray 8 is not pulled out, the discharge tray 7 does not protrude from the end portion of the scanning unit frame 20 to the side portion, so that the paper is accommodated in a state where the paper slightly protrudes from the tray.
[0012]
In the image recording apparatus 1, the scanning unit frame 20 disposed on the upper part of the main body frame 2 is provided with a scanning device 30 configured as shown in FIG. 2. The scanning device 30 includes a full rate carriage 31 provided with a lamp 32 and one mirror m1, and two opposing mirrors m2 and m3, similar to those used in a reading device of a general copying machine or image recording device. Provided in combination with the half-rate carriage 33 to be arranged, the scanning information of the original is transmitted to the CCD 38 via the lens device 37, the optical signal is converted into an electric signal, and is transmitted to the image information processing unit arranged on the main body frame. . In order to drive the full-rate carriage 31 and the half-rate carriage 33, in this embodiment, drive pulleys 35 and 35a having a diameter of 2: 1 are arranged coaxially and wound around the respective drive pulleys. A mechanism is provided for moving the two carriages in conjunction with each other via belts 36 and 36a.
[0013]
A book original is placed on the upper end of the scanning unit frame 20, and a platen 23 corresponding to the operation as the FBS and a platen 24 disposed below the original conveying unit 40 corresponding to the operation as the ADF are provided. Provided. For the platen 23, the upper open / close frame 25 is opened to set the original, and the upper open / close frame is closed, whereby the platen cover 26 presses the image surface of the original on the upper surface of the platen, and the original is set at the fixed position. Scan. For the document set on the platen 23, the full rate carriage 31 of the scanning device 30 reciprocates by the length in the scanning direction of the document in accordance with detection information of a sensor (not shown), and the half rate carriage 33 is moved. Image information is read while moving at half the speed of the full-rate carriage 31, and an image signal is output via the CCD 38. Further, when scanning a document on a sheet using the document tray 27, the document is transported through a U-shaped transport path 44 provided in a document transport unit 40 as an ADF (automatic document transport device), and a portion of the platen 24 is scanned. The image reading operation is performed in a state where the scanning device is fixed.
[0014]
The U-shaped conveyance unit 44 provided in the document conveyance unit 40 is provided with a pickup roller 42 of a document front insertion unit, a sheet separating device 43, and a conveyance roller device 45 that conveys the document inside the U-shaped conveyance path. . The conveying roller device 45 includes a large-diameter driving roller 46 that forms a guide surface on the inner surface of the turn portion of the document and two pinch rollers 47 and 47a. The platen 24 is positioned downstream of the pinch roller 47a. I am letting. In addition, a discharge roller device 48 is disposed at the end of the U-shaped conveyance path 44 to discharge the scanned document toward the discharge tray 28.
[0015]
The document transport unit 40 is provided with an open / close frame 41 integrally provided with a paper guide outside the U-shaped transport path 44 so as to be openable / closable via a support shaft 40a. A roller of the device 43 and pinch rollers 47 and 47a are arranged. Then, by opening the opening / closing frame 41, the U-shaped conveyance path 44 is opened so that jammed paper can be processed. Although not shown, the frame including the guide plate inside the U-shaped conveyance path 44, the driving roller 46, and one roller of the discharge roller device 48 can be opened and closed with respect to the lower frame of the document conveyance unit. In the case where the platen 24 is provided, maintenance such as cleaning for the platen 24 can be easily performed.
[0016]
When the original set on the original tray 27 is scanned using the original conveying section 40, the fact that the original has been set on the original tray is activated by a detection signal from a detection means (not shown). This is done by inputting an image reading command to the control panel using the document feeder. In response to the signal, the full-rate carriage 31 of the scanning device 30 is stopped at a position corresponding to the platen 24, the half-rate carriage 33 is moved to the left end of the scanning unit frame 30, and the document is removed from the document tray 27. The sheets are conveyed one by one in the U-shaped conveyance path 44, and the original image is read by the platen 24. Therefore, in the scanning device arranged in the scanning unit frame 20, the scanning device can be set in correspondence with the two platens 23 and 24, and an operation of reading an arbitrary document can be performed, and the transmission function of the image recording device can be achieved. The image information can be transmitted by using it.
[0017]
The main body frame 2 arranged at the lower part of the document conveying section 40 includes a process device 50 using an electrophotographic method as shown in FIGS. 3 and 4, and a sheet conveying mechanism from the paper feed cassette to the discharge tray. Is provided. The process device 50 is a combination of the developing unit 51 and the photosensitive unit 60, and the developing roller 55 of the developing unit 50 is arranged with respect to the photosensitive drum 62 provided in the photosensitive unit 60. A transfer roller 17 is provided at the lower portion of the sheet so as to sandwich the paper path. As will be described later, the two units 51 and 60 constituting the process apparatus 50 are detachably provided from the upper part of the main body frame while being combined together, and are fixedly held in the operating position with the intermediate lid 10 closed. . Reference numeral 63 denotes a drum shaft of the photosensitive drum 62. In this embodiment, a photosensitive drum is used as the photosensitive member, but a photosensitive belt can also be used.
[0018]
In the paper feed cassette 3 disposed in the lower part of the process apparatus of the main body frame, the paper is fed one by one by the paper feed roller 13 disposed on the paper feed side, and is conveyed through the paper conveyance path 14 via the image transfer unit. Then, the toner is fed into the fixing device 18 and discharged toward the discharge tray via the discharge roller device 19. Conveying roller devices 15 and 16 are provided in the sheet conveying path 14, and when the leading end of the sheet is nipped by the conveying roller device 15, the feeding operation by the sheet feeding roller 13 is interrupted, and the conveying roller device 15 causes the sheet to be conveyed. Will be sent. Thereafter, according to the timing of the toner image formed on the photosensitive drum 62, the conveyance roller device 16 is driven to convey the paper, and the toner image on the photosensitive drum 62 is applied by applying a voltage from the transfer roller 17. Is transferred to the paper. The sheet on which the toner image has been transferred is guided to the fixing device 18 by the sheet feeding action by the photosensitive drum 62, is fixed between the heat roller and the pressure roller of the fixing device 18, and the copy is discharged. The device 19 is discharged to a discharge tray.
[0019]
In the apparatus shown in FIG. 1, two paper feeding cassettes are arranged in the paper feeding unit. However, the paper feeding from the paper feeding cassette 3a below the paper feeding cassette 3 through the paper feeding path 14a shown in FIG. Sent to the road. Further, the paper supplied via the manual feed tray provided in the manual insertion slot 5 shown in FIG. 1 is sent to the transport roller device 16 via the manual feed roller device 5a shown in FIG. 3, and the image is transferred. . The vertical paper transport path 14a of the main body frame is provided with a means for opening the paper transport path with the side plate 4 opened. Paper processing can be performed in the paper transport path. For the side plate 4, a lock mechanism and detection means are provided in the main body frame so that the sheet can be conveyed only when the side plate is closed.
[0020]
As shown in FIG. 3, in the process device 50 disposed above the horizontal portion of the paper transport path 14, a writing device 70 is disposed above the photosensitive drum 62 of the photosensitive unit 60, and the writing device 70 is intermediate. It is provided so as to be positioned with respect to the photosensitive drum 62 with the lid 10 closed. The process device 50 is configured as a cleaner-less device, and after the cleaning device is disposed on the photosensitive drum 62 and the toner image is transferred onto the paper, it remains attached to the photosensitive drum 62. It has a different configuration from the conventional one that collects toner. The two units of the developing unit 51 and the photosensitive unit 60 constituting the process apparatus are detachably attached to the holding unit of the main body frame while the two units are combined.
[0021]
As shown in FIG. 4, a stirring member 53 for supplying the toner to the paper feed roller 54 while stirring the toner is disposed in the container portion 52 that accommodates the nonmagnetic one-component toner of the developing unit 51. . A supply roller 54, a developing roller 55 in contact with the photosensitive drum 62, and a layer thickness regulating member 56 in contact with the developing roller 55 are provided in the toner discharge portion from the container portion 52. The stirring member 53 supplies the toner toward the supply roller 54 while stirring the toner, and can be configured as a member provided with an arbitrary blade member or a rod-shaped member. The supply roller 54 can be configured as an elastic roller having a sponge-like elastic elastic body having a shaft or a flocking body having conductive fibers provided at a predetermined thickness. A bias voltage having a value of about −400 to −600 V, preferably about −500 V is applied to the shaft of the supply roller 54 from a power supply member (not shown).
[0022]
The developing roller 55 is composed of a roller shaft made of metal such as stainless steel and a conductive rubber (silicon rubber, urethane rubber, NBR) coated at a predetermined thickness, and the roller surface is smooth. Configure as a thing. A bias voltage having a value of about −200 to −400 V, desirably about −300 V is applied to the developing roller 55. The layer thickness regulating member 56 disposed with respect to the developing roller 55 is for setting a thin layer of toner formed on the surface of the developing roller 55 to a uniform thickness, and is made of a urethane resin sheet or stainless steel. It is configured as a spring having a plate member. A bias voltage in the range of −300 V to −500 V, preferably around −400 V is applied to the layer thickness regulating member 56.
[0023]
The distance between the shaft centers of the supply roller 54 and the developing roller 55 is set to be slightly smaller than the sum of the radii of the two rollers, and by rotating both rollers in the same direction (arrow X direction), The contact portion is slid in the opposite direction while being pressed. The toner is charged between the two rollers due to the frictional action of both rollers and the voltage applied to each roller, and the toner adheres to the surface of the developing roller 55. Further, the toner attached to the surface of the developing roller 55 is formed to a uniform thickness by the layer thickness regulating member 56 and exposed toward the photosensitive drum 62, and the toner is applied to the latent image formed on the photosensitive drum 62. Transfer to form a toner image.
[0024]
As shown in FIGS. 4 and 5, the photosensitive unit 60 arranged in combination with the developing unit 51 is charged with a photosensitive drum 62 supported by a unit frame 61 and a surface by a flocking member or the like. A brush charger 65 such as a brush roller is provided. Then, the writing unit 70 is arranged on the photosensitive drum 62 to write an image, and the toner image formed on the photosensitive drum 62 is transferred onto the sheet by the discharge of the transfer roller 17. The writing device 70 is constituted by an LED head array. Based on information from the image information output device, the writing device 70 emits an LED to irradiate the photosensitive drum 62 with light. The surface of the photoconductive drum 62 is made of a grounded photoconductor, charged at −780 V by the brush charger 65, and irradiated with light from the writing device 70, that is, the portion of the image information corresponding to black. The potential is about −80 V, and a potential difference is generated between the light irradiated portion and the non-irradiated portion (portion corresponding to white in the image information), and an electrostatic latent image corresponding to the image information is formed.
[0025]
When the negatively charged toner adhering to the surface of the developing roller 55 comes into contact with the electrostatic latent image formed on the photosensitive drum 62, the toner is applied to the light irradiation portion on the surface of the photosensitive drum 62. As a result, the toner image is formed on the surface of the photosensitive drum 62 (reversal development). At the transfer position of the toner image, a bias voltage of 600 V to 3.5 kV is applied from the back surface of the paper by the transfer roller 17, whereby the toner image is transferred to the paper. The sheet on which the toner image is transferred is sent toward the fixing device 18 by the rotation of the photosensitive drum 62.
[0026]
Further, after the toner image is transferred to the paper, the toner remaining on the surface of the photosensitive drum 62 is disturbed by the memory removal brush 66 disposed on the downstream side of the transfer roller 17 so as to contact the drum surface, Dispersed on the surface of the photosensitive drum 62. A predetermined voltage (preferably +300 V) is applied to the memory removal brush 66 in order to effectively disturb the toner on the drum surface. Then, at a position where the photosensitive drum 62 is in contact with the developing roller 55, the toner is transferred to the developing roller 55 side due to the potential difference between the two, and is mixed with the toner newly supplied from the container portion and reused. Therefore, it is configured as a cleanerless system.
[0027]
The photosensitive drum 62 and the brush charger 65 are driven independently in the direction of the arrow X1 in the figure when performing a printing operation in which a toner image is formed on the photosensitive drum 62 and transferred to a sheet. The surface of the photosensitive drum 62 is charged by the potential applied to the brush charger 65 (for example, driven by separate motors).
[0028]
Next, the operation of the above-described photoreceptor unit 60 will be described with reference to the timing chart shown in FIG. As shown in FIG. 6, ON / OFF of the printing operation, rotation and stop of the photosensitive drum 62, and ON / OFF of the charger potential are performed at the same timing. However, the brush charger starts rotating ts seconds before the printing operation and the charger potential change from OFF to ON, or the photosensitive drum changes from stop to rotation, and rotates for the time ts. When the printing operation or the like is turned from OFF to ON, the brush charger stops. Next, when the printing operation changes from ON to OFF, the brush charger starts rotating and rotates for a time t. As described above, during the printing operation, since the brush charger does not rotate, charging irregularities and the like do not occur on the photosensitive drum. Furthermore, since the brush charger is rotated for a predetermined time before and after the printing operation, the brush charger does not have a standby waiting time. Thus, since the brush charger is intermittently rotated, good print quality is maintained.
[0029]
During the time ts, the brush charger is controlled to rotate at an angle θs that is not an integral multiple of 360 °. In addition, during the time t, the brush charger rotates by an angle θ that does not become an integral multiple of 360 °. Although the angles θs and θ may be the same or different, it is desirable that θs + θ is not an integral multiple of 360 °. By controlling in this way, the portion where the brush charger contacts the photoconductor is different each time, and the deformation of the brush due to the standby rod can be prevented.
[0030]
In the image recording apparatus according to the above-described embodiment, the case where the brush charger is rotated before and after the printing operation has been described. However, it is possible to rotate only one of the brush charger before and after the printing operation. .
[0031]
【The invention's effect】
As described above, according to the first aspect of the present invention, even if the brush of the brush charger does not have a perfect circle shape, it is not always rotated, so that the photosensitive drum cannot be charged unevenly and the print quality is reduced. there is no problem. Further, load fluctuation does not occur in the rotational drive system, the charging of the photoconductor is further stabilized, and the printing image quality is improved. In addition, since the brush charger does not stop at all times, toner or paper powder gets in between the hairs of the brush and adheres to the brush. It is also possible to prevent the problem that the battery cannot be charged. By incorporating the above unit into a cleanerless system, the characteristics of the image recording apparatus can be effectively utilized, and the action of charging the photosensitive drum can be performed under favorable conditions, and printing can be performed. Can maintain good image quality.
[0032]
According to the second aspect of the present invention, the pressure contact force of the brush during the printing operation becomes constant, the photoreceptor is not unevenly charged, and the printing quality is improved. Further, since the brush charger is rotated outside the printing operation, the user does not feel uncomfortable.
[0033]
According to the third aspect of the present invention, the portion where the photoconductor and the brush charger are in contact with the photoconductor when the intermittent rotation is stopped is not at the same position, so that the deformation of the brush due to the standby rod is mitigated.
[Brief description of the drawings]
FIG. 1 is a front view showing an image recording apparatus according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view showing a configuration of a scanning device used by being incorporated in the device of FIG.
FIG. 3 is a cross-sectional view of a process apparatus unit disposed on the main body frame of FIG. 1;
4 is an explanatory diagram showing a configuration of the process apparatus of FIG. 3;
FIG. 5 is an explanatory diagram showing a configuration of a photoreceptor unit of the process apparatus of FIG. 3;
6 is a timing chart illustrating a driving operation in the photosensitive unit of FIG.
[Explanation of symbols]
1 image recording device 50 process device 60 photoconductor unit 62 photoconductor drum 65 brush charger X1 rotation direction ts time t time

Claims (3)

An image recording apparatus in which a charger is disposed on the surface of a photosensitive member and uniformly charged before an electrostatic latent image is formed on the photosensitive member, and the charger is constituted by a roller brush charger. An image recording apparatus , wherein the brush charger starts rotating before the photosensitive member changes from stop to rotation, and the brush charger stops rotating when the photosensitive member starts rotating . 2. The image recording apparatus according to claim 1, wherein the brush charger starts rotating after the photosensitive member changes from rotation to stop, and rotates for a predetermined time .   3. The image recording apparatus according to claim 1, wherein a rotation angle of the intermittent rotation of the roller brush charger is an angle that is not an integral multiple of 360 °.

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