JP2002287601A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable even an operator to easily clean and replace a developer toner density detecting sensor, and moreover to improve positioning accuracy of the toner density detecting sensor with regard to a photoreceptor, in an image forming apparatus provided with the two-component developing device consisting of upper/lower units openable/closable by using a paper sheet carrier path as a border. SOLUTION: In this image forming apparatus, the toner density detecting sensor is provided integrally with a transfer charger on a unit other than a unit incorporating the photoreceptor. The positioning accuracy is further improved, in the case that the positioning of the toner density detecting sensor with respect to the photoreceptor is directly performed with regard to the photoreceptor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus which comprises an upper and lower unit which can be opened and closed at a paper path and uses a two-component developer.

[0002]

2. Description of the Related Art In an image forming apparatus such as a small-sized copying machine or a printer, for the purpose of facilitating maintenance such as clearing of a jam in a paper transport path, replacement of parts, and inspection, the paper transport path is divided into two parts. A so-called clamshell-type configuration that is pivotally connected to one end at one end and is largely openable is often employed.

FIG. 5 is a diagram showing the configuration of an example of this type of copying machine. The copier further uses a substantial portion of the document transport path for reading the document and the recording paper transport path for image formation, thereby simplifying the configuration and reducing the size of the apparatus.

At the bottom of the apparatus, there is provided a cassette paper feeder 1 on which a recording paper 2 is placed. Timing is taken, the photosensitive drum 4
Transported to the top of Around the photosensitive drum 4, a charging charger 5 and a laser writing optical system 6 are arranged in the order of their rotation.
An incident position of writing light carrying image information emitted from the printer, a two-component developing device 7, a transfer charger 8, and a cleaning device 11 are arranged, and these devices form a photosensitive member 3 on the photosensitive member 3 by a known electrophotographic process. The formed toner image is transferred to the recording paper 2 under the action of the transfer charger 8, and the recording paper is fixed by the fixing device 9, and
Discharged to zero. The recording paper 13 is also stored in the manual paper feeder 1.
Feeding is also possible from 2.

In order to read a document image, a read timing roller pair 14 and a read timing roller pair 14 are provided in a sheet transport path between a confluence point of a transport path from the paper feed cassette 1 and a transport path from the manual paper feeder and the registration roller pair 3. A reading sensor 15 is provided, and a branch guide 16 for selectively switching between a path to a document discharge section 17 and a path to a transfer section is provided immediately downstream of the registration roller pair 3.

At the time of reading an original, the original is fed from the cassette paper feeder 1 or the manual paper feeder 12, and after timing is set by the timing roller pair 14, the original is conveyed to the reading sensor 15 and the image information is read. It is read and discharged to the discharge unit 17 by the branch guide 16.

In this copying apparatus, the apparatus transports the sheet from near the confluence of the sheet transport path from the cassette sheet feeder 1 and the sheet transport path from the manual sheet feeder 12 to the discharge section of the fixing device 9. Upper unit 20 and lower unit 3 on the road
0, and these two units are connected to each other by a pivot 21 provided near the axis of the lower roller of the discharge roller pair of the fixing device 9. As shown by the chain line in the figure, the right end of the figure can be flipped up to open a wide mouth.

The upper unit 20 includes an upper roller of the reading timing roller pair 14, an upper roller of the registration roller pair 3,
The branch guide 16, the transfer charger 8, the upper roller of the fixing device 9, and the upper roller of the discharge roller pair are provided. The lower unit 30 is provided with the remaining devices such as the photosensitive drum 4, the developing device 7, and the like.

Therefore, when a paper jam occurs in the paper transport path, the upper unit 20 is flipped up and the lower unit 30 is raised.
By opening the gap between them, the jammed paper can be easily removed, and maintenance and replacement of parts can be easily performed.

[0010] Incidentally, the two-component developing apparatus used
A component developer is composed of a toner and a carrier. As the development is repeated, the toner is consumed, and the toner density decreases with time, and the density of the developed image does not become a normal density. Each time the operation is performed, the toner is supplied or the toner concentration of the developer is detected. When the toner concentration is lower than a predetermined value, the toner is supplied so that the toner concentration is always maintained in a certain range. One of the toner density detection methods is to form a reference potential latent image pattern on a photoreceptor every time a predetermined number of developments are performed, and to determine the density of the toner image pattern obtained by developing the pattern with a developing device. There is known a method in which a signal is detected by a photoelectric sensor, the signal is compared with a value for normal toner, and when the signal falls below a predetermined range, toner is supplied.

The sensor used in this method is configured to irradiate light from a light emitting element such as a light emitting diode onto a toner image pattern on a photoreceptor, and to receive reflected light thereof by a light receiving element such as a photo sensor. Therefore, the sensor must be provided at a position close to the peripheral surface of the photosensitive drum between the developing device and the transfer device. However, floating toner and the like are always present near the photoconductor in this portion, and there is a fatal defect that the light emitting surface and the light receiving surface of the sensor are stained and a detection error occurs. The only solution is to periodically clean the sensor. Also, since the sensor is an electrical component, it has a limited life and must be replaced when the life expires. However, there is usually a gap of about 5 mm between the light emitting / receiving surface of the toner density detection sensor and the surface of the photoconductor, and cleaning is not easy. As for the replacement, other parts had to be removed and the operator could not do it himself, and he had to ask a specialized service person.

Therefore, there is a demand that the operator can easily clean and replace the toner concentration detecting sensor for the developer and that the sensor can be accurately positioned with respect to the photosensitive member when the sensor is replaced.

[0013]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances regarding a developer toner concentration detecting sensor of an image forming apparatus using a two-component developer, and the apparatus has been divided into upper and lower units with a paper transport path as a boundary. It is an object of the present invention to provide an image forming apparatus in which a toner concentration detection sensor for a developer can be easily cleaned and replaced, and when replaced, the positioning can be easily performed with high accuracy on a photoconductor.

[0014]

According to the present invention, in order to solve the above-mentioned problems, in an image forming apparatus comprising the above-mentioned upper and lower units, the toner density detecting means is provided on a unit different from the unit including the photosensitive member. It is characterized by having been provided.

[0015]

According to the above construction, if the upper and lower units are widely opened, the light emission and light receiving surfaces of the toner density detection sensor are far away from the photoreceptor, so that cleaning and replacement become easy.

Further, if the toner concentration detecting sensor has the same life and is integrally formed with the transfer means which needs to be replaced, it can be replaced together with the transfer means, which saves trouble and reduces The positioning of the sensor is simplified.

Further, if the positioning of the detection sensor with respect to the photoconductor is performed directly with respect to the photoconductor, it is effective in improving the positioning accuracy.

[0018]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a perspective view showing a state in which an upper unit 20 of an embodiment in which the present invention is applied to a clamshell type copying machine comprising upper and lower units 20 and 30 described in FIG. 5 is opened.

Although the photosensitive drum 4 is included in the lower unit 30, the transfer charger 8 is detachably provided at a position of the upper unit 20 facing the upper portion of the photosensitive drum 4 when the upper unit is closed. I have.

As shown in FIGS. 1 and 2, a toner density detecting sensor 23 is integrally mounted on the transfer charger 8 near the longitudinal center of the casing 8a and on the upstream side in the transfer paper transport direction. Positioning holes 8 are provided in end blocks 8b provided at both ends of the casing 8a of the transfer charger 8.
c is drilled, and as shown in FIG.
Is closed, the positioning pins 2 projecting from the photoconductor unit 19 attached to the lower unit 30 and supporting the photoconductor are supported.
4, the transfer charger 8 is pressed against the positioning surface of the frame of the photoconductor unit 19 by the urging force of the positioning spring 25 provided between the casing 8a of the transfer charger and the upper unit frame, and It is positioned with respect to the drum 4.

Since the toner density detecting sensor 23 is integrally fixed and attached to the casing 8a of the transfer charger, it is exchanged together when exchanging the transfer charger, so that it is possible to save time and effort. Positioning is performed with respect to the photosensitive drum 4 via the transfer charger, and it is not necessary to separately provide a positioning unit for the transfer charger and a positioning unit for the toner density detection sensor, thereby simplifying the configuration.

If the right end of the upper unit 20 is flipped up to open the space between the upper and lower units, the transfer charger 8 and the toner density detecting sensor 28 provided integrally therewith are separated from the photoreceptor, and the jam of the transfer paper is removed. Density detection sensor 28
Cleaning and replacement of the transfer charger integrally including the toner concentration detection sensor can be easily performed.

As a clamshell type image forming apparatus,
In some cases, the transfer path of the transfer paper is below the photoconductor, the photoconductor is provided in the upper unit, and the transfer charger is provided in the lower unit. In this case, it goes without saying that the developer toner concentration detection sensor may be provided in a lower unit separate from the unit including the photoconductor. Also in this case, by forming the toner density detection sensor integrally with the transfer charger, it is possible to replace the toner density detection sensor integrally with the transfer charger. At the same time, it can be positioned with respect to the photoconductor.

However, as described above, if the transfer charger casing is interposed to position the toner density detection sensor with respect to the surface of the photoreceptor, assembling errors among the members accumulate, resulting in high positioning. It is difficult to obtain accuracy. As a result, there is a problem that the detection capability is reduced and the reliability is reduced.

FIG. 4 shows a configuration of an embodiment for preventing this problem. In this embodiment, the toner density detection sensor 23
2 is provided in the upper unit 20 different from the lower unit 30 including the photosensitive drum 4 in the same manner as the embodiment described above with reference to FIG. Can be easily cleaned and replaced as in the previous embodiment, but the detection sensor 23 is not fixed to the transfer charger.
If the life of the transfer charger is different, it can be replaced separately. The detection sensor 23 is slidably provided on a frame of the upper unit 20 along a guide 28 provided in a direction to approach and separate from the photoconductor.
6 is urged in the direction toward the photoconductor. A rotating body 29 is attached to a tip of a bracket provided at an end of the toner concentration detection sensor 23 facing the photoconductor so as not to obstruct the optical path for detection.

When the upper unit 20 and the lower unit 30 are closed, the toner density detecting sensor 23 slides on the inner surface of the guide 28 while keeping the rotating body 29 pressed against the photosensitive member by the force of the spring 26, and The body 4 is positioned at a predetermined position. The rotator 29 is driven as the photoconductor 4 rotates, and the rotation of the photoconductor 4 does not displace the detection sensor 23. With this configuration,
Even when there is a displacement between the upper and lower units 20 and 30, the toner density detection sensor can accurately position the photoconductor.

[0028]

As described above, according to the present invention, the cleaning and replacement of the toner concentration detection sensor of the two-component developer of the image forming apparatus including the upper and lower units which can be opened and closed with the paper conveyance path as the boundary is performed. But it can be done easily,
Detection errors can be prevented. Further, even when the detection sensor is replaced, the positioning can be easily performed with high accuracy with respect to the photoconductor, so that the detection accuracy is improved and the effect of improving reliability is obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view of an embodiment of an image forming apparatus to which the present invention is applied.

FIG. 2 is a side view showing a configuration of a mounting portion of the toner density detection sensor of the embodiment.

FIG. 3 is an explanatory diagram for explaining the operation.

FIG. 4 is a side view illustrating a configuration of a mounting portion of a toner density detection sensor according to another embodiment of the present invention.

FIG. 5 is a cross-sectional view illustrating an overall configuration of an example of a clamshell type image forming apparatus including a two-component developing device to which the present invention is applied.

[Explanation of symbols]

 Reference Signs List 4 photosensitive drum 7 developing device 8 transfer charger (transfer unit) 20 upper unit 21 pivot shaft 23 toner density detection sensor 24 positioning pin 25 positioning spring 26 positioning spring 28 guide 29 rotating body

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] March 6, 2002 (2002.3.6)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction contents]

[0013]

SUMMARY OF THE INVENTION The present invention is directed to an image forming apparatus comprising two units which can be opened and closed in view of the above-mentioned situation regarding a developer toner concentration detecting sensor of an image forming apparatus using a two-component developer. , The toner contamination of the toner concentration detecting means of the developer can be remarkably suppressed, the concentration detecting means can be easily cleaned and replaced, and the removal of jammed paper can be satisfactorily performed while avoiding the danger of touching the detection surface of the concentration detecting means. The task is to be able to do so.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction contents]

[0014]

According to the present invention, in order to solve the above-mentioned problems, a photoconductor is provided in a first unit, and a density detecting means for detecting the density of a toner image formed on the photoconductor is provided in a second unit. The image forming apparatus is provided on the unit, and when the image forming apparatus is opened between the two units, the detecting surface of the density detecting unit is exposed, and the paper conveying path is positioned on the opposite side to the photoconductor so that the sheet is conveyed. As viewed in the direction, of the roller pairs on the upstream side of the transfer position, one roller of the most downstream roller pair is provided in the first unit, and the other roller is provided in the second unit. While keeping parallel to each other
The opening of the image forming apparatus is realized.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0015

[Correction method] Change

[Correction contents]

[0015]

With the above construction, if both units are opened widely, the light emission and light receiving surfaces of the toner density detection sensor are far away from the photoreceptor, so that cleaning and replacement become easy.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0019

[Correction method] Change

[Correction contents]

FIG. 1 is a perspective view showing a state in which an upper unit 20 of an embodiment in which the present invention is applied to a clamshell type copying machine comprising upper and lower units 20 and 30 described in FIG. 5 is opened. Lower unit 30 is the first unit, upper unit 20
Becomes the second unit.

[Procedure amendment 6]

[Document name to be amended] Statement

[Correction target item name] 0028

[Correction method] Change

[Correction contents]

[0028]

As described above, according to the present invention, when the toner image on the photoreceptor passes through the detecting means, the recording paper exists between the photoreceptor and the detecting means for a long time, and the toner of the detecting means has a long time. Contamination is significantly reduced, and contamination of the detection means during image formation can be prevented. In addition, since both units open the roller pair on the upstream side of the transfer position while maintaining their axes parallel (an aspect in which the fulcrum axis of the opening operation is parallel to the roller axis), one end side of the roller pair The opening is wider in the range of the transfer position from the roller pair as compared with the case where the other end side is opened at the center (an aspect in which the fulcrum axis of the opening operation is orthogonal to the roller axis), and the cleaning of the detecting means and the removal of jammed paper can be performed. Can be performed well. In addition, since the jammed paper can be removed satisfactorily, it is possible to prevent a hand from touching the detection surface of the detection means.

 ──────────────────────────────────────────────────続 き Continued on front page F term (reference) 2H027 DA10 EC03 HB16 HB18 HB20 ZA10 2H071 AA02 AA08 BA03 BA14 BA27 BA29 DA09 DA15 DA23 DA32 EA04 2H200 FA01 GA23 GA45 HA12 HB03 HB32 JA02 JA30 PB18 PB39

Claims (4)

[Claims] 1. A reference potential latent image pattern formed on a photoreceptor is developed by a developing device using a two-component developer composed of a toner and a carrier. An image forming apparatus having a toner density detecting means for detecting the toner density of the two-component developer by detecting the density of the toner image obtained as described above, wherein the toner density detecting means is different from the unit including the photoreceptor. An image forming apparatus provided on a unit side of the image forming apparatus. 2. The image forming apparatus according to claim 1, wherein the paper transport device is located above the photoconductor, and the toner image formed on the photoconductor provided in the lower unit is transferred over the paper transport path above the photoconductor. 2. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus that is transferred to paper by a transfer unit provided in the upper unit, and wherein the toner density detecting unit is provided in the upper unit. 3. An image forming apparatus according to claim 1, wherein said toner density detecting means is integrated with a transfer means. 4. The image forming apparatus according to claim 1, wherein the positioning of the toner density detecting means with respect to the photoconductor is performed directly with respect to the photoconductor.