JP2003066776A - Electrophotographic apparatus and method of detecting opening or closing of cover of the apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic apparatus and a method of detecting opening or closing of a cover of the apparatus capable of preventing various troubles caused by an incompletely closed state of a door by detecting the incompletely closed state of the door by the toner density detection sensor or a registration sensor. SOLUTION: A toner density detection sensor 23 for detecting a toner image formed on an image carrier 1 by a development unit 4 is provided. The toner density detection sensor 23 is arranged at the door 20 for opening and closing the neighborhood of the image carrier 1 and detects the toner image on the image carrier 1 in a state where the door 20 is closed. A density detection value detected by the toner density detection sensor 23 before the door 20 is opened and a density detection value detected by the toner density sensor 23 after the door 20 is opened and closed are compared with each other, and determination is made on the basis of a difference between the detection values about whether or not the closed position of the door after the opening and closing operations of the door is in a regular closing position. In stead of the toner density sensor 23, the registration sensor can also be used to discriminating the closed position of the door.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic apparatus and, more particularly, to a defective transfer of a toner image or conveyance of a transfer sheet due to incomplete closing of the door after opening and closing the door for maintenance or the like. The present invention relates to an electrophotographic apparatus and a cover open / close detection method that can prevent defects and toner concentration control abnormality due to erroneous detection of a toner concentration detection sensor.

[0002]

2. Description of the Related Art In a conventional electrophotographic apparatus such as a copying machine, a printer, and a facsimile machine, a transfer sheet conveying path is provided in the lower part of the main body of the apparatus, and the transfer sheet is conveyed horizontally along the conveying path. At the transfer position, however, the transfer paper is brought into contact with the image carrier made of a photoconductor to transfer the toner image formed on the surface of the image carrier to the transfer paper.

However, with the downsizing of the apparatus, it is necessary to effectively use the space inside the apparatus body, and accordingly, the transport path for the transfer paper has to be devised. Therefore, the developing device is arranged below the image carrier composed of a photosensitive drum, and the transfer device is arranged at a position substantially horizontal to the image carrier.
An electrophotographic apparatus is also used in which a transfer paper conveyance path is set in the vertical direction and a layout is performed so that a toner image is transferred to the transfer paper conveyed in the vertical direction.

Therefore, for example, in an electrophotographic apparatus in which the transfer device and the registration driven roller are separated from the image carrier by opening the door for maintenance, the transfer paper conveying path is provided in the vertical direction. A method is used in which a transfer portion is brought into contact with an image carrier at a conveying path portion in a direction to transfer a toner image onto a transfer sheet.

In this type of apparatus, a developing device is provided on the upstream side in the rotational direction of the image carrier as viewed from the transfer section and below the image carrier, and the toner image formed on the image carrier by this developing device is provided. Is transferred by the transfer unit onto the transfer paper fed from the registration rollers along the substantially vertical transport path. A toner density detection sensor that detects the toner density on the image carrier is disposed between the transfer unit and the developing device, and the density of the toner image developed on the image carrier is detected by the developing device. The toner concentration detection sensor is arranged on the door side so as not to block the transfer paper conveyance path, and is separated from the image carrier together with the door when the door is opened. Since the toner concentration detection sensor uses a photo sensor, it is necessary to position the sensor light in the direction normal to the tangent line of the image carrier in order to irradiate the sensor light vertically to the surface of the image carrier. Therefore, in the case where the toner concentration detection sensor is attached to the door side, the door positioning means is required so that the door is closed at the proper position, and the confirmation means is also required.

Further, in order to transfer the toner image to a predetermined position on the transfer paper, the electrophotographic apparatus positions the front end of the transfer paper and synchronizes the transfer paper with the toner image formed on the image carrier. It has a registration roller for sending out. And
A registration sensor for detecting the presence or absence of the transfer paper is arranged on the upstream side of the registration roller, that is, the paper feed roller side. The registration roller is managed by managing the time after the leading edge of the transfer paper passes the position of the registration sensor. The amount of slack in the transfer paper on the upstream side is determined. The registration sensor has a light emitting element and a light receiving element. The registration sensor and the reflection plate are arranged so as to face each other across the transfer paper conveyance path, and the transfer paper shields the light flux from the light emitting element and changes the output of the light receiving element to detect the passage of the front end of the transfer paper. It is supposed to do.

As described above, in the electrophotographic apparatus of the type in which the toner image is transferred while the transfer paper is conveyed in the substantially vertical direction, the reflection plate combined with the registration sensor does not block the transfer paper conveyance path. It is arranged on the door side and is configured to be separated from the registration sensor at the same time when the door is opened. Since the resist sensor uses a photo sensor as a light receiving element, in order to irradiate the reflection plate with the sensor light perpendicularly, it is necessary to position it in the direction normal to the tangent line of the reflection plate. Therefore, when the door is closed, it is necessary to determine whether the closed position of the door is in the regular closed position, and if it is not in the regular closed position, it is necessary to reclose the door to the regular closed position.

[0008]

As described above, in the electrophotographic apparatus configured so that the toner image is transferred while the transfer sheet is conveyed in the substantially vertical direction, the transfer apparatus and the registration driven roller are provided on the door side. And is pressed against the image bearing member and the registration driving roller by a compression spring, respectively. Therefore, when the door is closed, immediately before the door is closed to the regular position, resistance is applied by the reaction force due to the pressurization. If the door lock means closes the door with enough force to get over the convex portion on the main body side, it is possible to fit the door in the proper position. However, if the door is closed slowly, the door lock means cannot get over the convex portion, the door does not close to the proper position, and the door is in the incompletely closed state. If the door is incompletely closed,
In the electrophotographic apparatus of the type in which the toner concentration sensor is attached to the door, the toner concentration sensor is also not in the proper position, so the light emitted from the sensor to the image bearing member does not sufficiently return to the sensor, and the sensor erroneous detection occurs. There is a problem that it is not possible to obtain a high quality image composed of toner density. Further, in an electrophotographic apparatus of a type in which a reflection plate combined with a registration sensor is attached to the door side, if the door is in an incompletely closed state, a transfer paper leading edge detection error occurs. Further, in the above-mentioned electrophotographic apparatus in which the transfer device and the registration driven roller are separated from the image carrier by opening the door for maintenance, the transfer paper is positioned if the door is not closed to the proper position. Is inaccurate, and the transfer of the toner image on the surface of the image carrier to the transfer paper is incomplete, so that a high quality image cannot be obtained.

The present invention has been made in order to solve the above-mentioned problems of the prior art, and erroneously detects the toner density detection sensor due to the incomplete closing of the door after opening and closing the door, and the front end of the transfer paper. Detection error or transfer paper positioning error,
Furthermore, it prevents incomplete transfer of the toner image to the transfer paper,
An object of the present invention is to provide an electrophotographic apparatus capable of obtaining a high quality image and a cover open / close detection method thereof.

In Japanese Patent Laid-Open No. 11-228223, the image carrier is irradiated with light across the transfer paper transport path.
A density sensor that detects the toner density by detecting the amount of light reflected from a standard image formed on an image carrier is described. This density sensor also serves as a jam detection sensor for the transfer paper, because it can be known whether or not the transfer paper has been conveyed through the above-mentioned conveyance path. Further, an embodiment is described in which the concentration sensor is arranged on a manual feed table that can be opened and closed with respect to the apparatus main body. However, the invention described in the above publication is not an idea of using the toner concentration sensor or the registration sensor to determine whether or not the closed position of the door is the regular closed position.

Further, Japanese Patent No. 2661941 discloses an electrophotographic apparatus in which a toner image formed on an image carrier is once transferred onto a transfer belt, and this image is further transferred onto transfer paper. A density sensor for detecting the density of the toner image on the transfer belt is described. The density sensor also serves as a sensor for detecting the transfer belt when it is moved for maintenance. In addition, it has a door switch that detects whether the door is open or closed, and the image is displayed only when it is detected that the door is closed and the transfer belt is in the proper transfer position. The forming operation is performed. However, the invention described in the above publication is also not based on the idea of using the toner concentration sensor or the registration sensor to determine whether or not the closed position of the door is the regular closed position.

[0012]

In order to achieve the above-mentioned object, the present invention according to claims 1 and 9 provides a developing device arranged in the vicinity of the image carrier, and the developing device on the image carrier. A transfer device that transfers the toner image formed on the transfer paper to a transfer paper, and a toner density sensor that detects the density of the toner image formed on the image carrier, and the toner density sensor opens and closes the vicinity of the image carrier. An electrophotographic apparatus which is arranged on a door and is capable of detecting the density of a toner image on an image carrier in a state where the door is closed, wherein the image detected by the toner density sensor before the opening operation of the door is performed. The density detection value on the surface of the carrier is compared with the density detection value on the surface of the image carrier detected by the toner density sensor after the door is opened and closed, and the door opening / closing operation is performed based on the difference between the detected values. Door closed position Characterized in that it has a door position determining means for determining whether the closed position of normal.

The toner density detection value of the image bearing member upper background portion of the toner density detection sensor detected after the previous image forming operation, that is, the toner density detection value of a portion without any toner, and the toner density detection sensor after the door is opened and closed. By comparing the detected value of the upper surface of the image carrier detected by the above, it is possible to determine whether the position of the toner concentration detection sensor when the door is closed is a normal position based on the difference between the detected values. Can
This makes it possible to determine whether the door is in the proper closed position.

Whether the door closed position is the proper closed position is determined by first holding the detection value of the background portion of the image bearing member previously detected by the toner density detection sensor, and then after opening and closing the door. The detection is performed again by detecting the background portion on the image bearing member and comparing both detection values. If the door closed position is not in the regular closed position but in the incomplete closed state, the toner concentration detection sensor deviates from the regular position, and the light flux emitted from the toner concentration detection sensor is reflected by the curvature of the image carrier surface. Light does not sufficiently return to the toner concentration detection sensor, and the detection value also decreases. Therefore, the door position determination means can determine whether or not the door is incompletely closed based on the difference between the toner density detection values. When it is determined that the door is incompletely closed, for example, the operation unit, the display panel, or the like is displayed, and the door is urged to be surely closed to the regular closed position.

The invention according to claim 2 or 10 is the invention according to claim 1 or 9, wherein the toner concentration sensor is
It is characterized in that the density of the background portion of the image carrier is detected.

According to a third aspect of the present invention, in the first aspect of the invention, the door has a transfer roller, and when the door is closed, the transfer roller is above the developing device and is in pressure contact with the photosensitive member. In addition, it is arranged so as to be in pressure contact with the downstream side of the position detected by the toner density sensor in the rotational direction of the image carrier.

According to a fourth aspect of the invention, in the invention of the first aspect, the door has one of the pair of registration rollers, and when the door is closed, the door is in pressure contact with the other of the pair of registration rollers. It is arranged in.

According to a fifth aspect of the invention, in the first aspect of the invention, the door has a transfer roller and one of a pair of registration rollers, and the toner is provided between the transfer roller and one of the registration rollers. It is characterized by having a density sensor.

According to the ninth and eleventh aspects of the present invention, there is provided an electrophotographic apparatus having a reflecting plate which is arranged at a door portion facing a registration sensor and which moves toward and away from the registration sensor according to a door opening / closing operation. The detection value of the reflected light from the reflector detected by the resist sensor before the opening operation is performed, and the detected value of the reflected light from the reflector detected by the resist sensor after closing the door is compared, It is characterized in that whether or not the closed position of the door after the door opening / closing operation is at the regular position is determined based on the difference between the detected values.

When determining whether the closed position of the door is at the proper position, the registration sensor holds the detection value of the reflected light on the reflection plate detected last time. Then, after the door is opened and closed, the reflected light on the reflector is detected again. If the closed position of the door is not in the proper position, the registration sensor will be out of the proper position. Then, the light emitted from the light emitting element of the resist sensor and reflected by the reflecting plate does not sufficiently return to the resist sensor, and the detection value by the light receiving element of the resist sensor also decreases. Whether or not the closed position of the door is at the regular position is determined based on the difference between the detected values. In that case, it is possible to display that the door is not properly set on the operation unit to prompt the user to surely close the door.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of an electrophotographic apparatus and a cover open / close detection method according to the present invention will be described below with reference to the drawings. FIG. 1 is a vertical sectional view showing an overall configuration of an embodiment of the present invention in a door open state and a door closed state, FIG. 2 is a vertical sectional view showing the same in a door closed state, and FIG.
It is an appearance perspective view showing an example of the electrophotographic device which adopted the door opening and closing detection device concerning the present invention. The electrophotographic apparatus shown here is configured as a copying machine. In the present invention, the electrophotographic apparatus may be considered as an image forming apparatus using an electrophotographic process.

1 and 2, the image forming apparatus has an image carrier 1 made of a drum-shaped photoconductor. The image carrier 1 is rotationally driven counterclockwise in the figure. Around the image carrier 1, the charging roller 2 is located on the upper left of the image carrier 1, the optical writing device 3 is located substantially on the left side of the image carrier 1, and the developing unit 4 is located directly below the image carrier 1. Transfer rollers 6 are arranged substantially on the right side of the carrier 1, and roller pairs 7a and 8b forming a fixing device 7 are arranged above the image carrier 1 and, more accurately, obliquely above the right. Further, below the image carrier 1 and below the developing unit 4, there are paired registration rollers 5a and 5b, further below the sheet feed roller 12, and diagonally below the sheet feed cassette 10. Are arranged. The transfer sheets P are drawn out one by one from the sheet feeding cassette 10, and the registration roller pair 5a,
5b, the toner image on the image carrier 1 is transferred by the transfer roller 6 to the transfer portion, further transferred to the fixing device 7 and the toner image is fixed on the transfer paper in the fixing device 7, and the discharging roller 11 Then, the sheet is discharged to the sheet discharge tray 9. As can be understood from the above description, the transfer path of the transfer paper P from the paper feed roller 12 to the fixing device 7 is a transfer path oriented in the vertical direction.

1 and 2 of the image forming apparatus, a door 20 is horizontally provided at the lower end portion on the right side of the image forming apparatus in order to remove a jam of the transfer paper or to perform other maintenance. The right side surface is mounted so that it can be opened and closed by rotating in a vertical plane about the axis 26 of the direction. A hook 13 is attached to the upper end of the door 20 so as to be rotatable about a shaft 13a in a vertical plane. When the door 20 is closed, the hook 13 is rotationally biased so as to be caught by the projection 27 on the apparatus main body side, and when the door 20 is closed, the hook 13 gets over the projection 27.
Further, it is possible to open the door 20 by rotating the hook 13 against the urging force by an external operation to release the hook with the protrusion 27.

The transfer roller 6 is rotatably attached to the door 20, and one of the pair of registration rollers 5b is rotatably attached to the door 20. The transfer roller 6 and the registration roller 6b serve as the image carrier 1 and the other registration roller 5 when the door 20 is closed.
It is urged by springs 14 and 15 so as to be pressed against a. A toner concentration sensor 23 is attached to the door 20 between the transfer roller 6 and the registration roller 5b. The transfer roller 6 is smaller than the developing unit 4, and a space is formed between the transfer roller 6 and the registration roller 5b, and the toner density sensor 23 is arranged in this space. The toner concentration sensor 23 has a light emitting portion and a light receiving portion, and when the door 20 is closed to a regular position, the toner concentration sensor 23 faces the image carrier 1 from diagonally lower right to diagonally upper left, and A light beam is emitted from a direction normal to the tangent line of the surface, and reflected light from the surface of the image carrier 1 is received. In addition,
In FIG. 1, “A” is added to the end of the reference numerals indicating the door and the members attached to the door when the door 20 is open.

Next, the cover opening / closing detecting method will be described together with the operation of the above-described embodiment. In FIG. 1 and FIG. 2, the leading edge of the transfer paper P fed one by one from the paper feed cassette 10 by the paper feed roller 12 hits against the nip of the registration roller pair 5 (5a, 5b) whose rotation is stopped. To form a predetermined loop and stop the movement once. By forming this loop, the skewed state of the sheet P is corrected.
On the other hand, the image carrier 1, which is a rotatably supported drum-shaped photosensitive member, is rotationally driven counterclockwise in FIG. The surface of the image carrier 1 is uniformly charged to a predetermined polarity by the charging roller 2, and the charged surface is irradiated with the light-modulated laser light L emitted from the optical writing device 3, whereby the image carrier is carried. A predetermined electrostatic latent image is formed on the surface of 1. This electrostatic latent image is visualized by toner when passing through the position of the developing unit 4.

The registration roller pair 5 (5a, 5b) starts rotating at a timing aligned with the tip of the electrostatic latent image on the image carrier 1 which is rotating counterclockwise, and is in a skewed state. The transfer paper P that has been corrected is conveyed to a transfer portion (nip portion) between the image carrier 1 and the transfer roller 6. The toner images on the image carrier 1 are sequentially transferred by the transfer roller 6 onto the transfer paper P conveyed to the transfer section. The transfer paper P on which the toner image is transferred is sent to the nip portion of the fixing roller 7a and the pressure roller 8b of the fixing device 7, and the toner image is fixed on the transfer paper P here. After the toner image is fixed, the transfer paper P is ejected to the outside of the machine by the paper ejection roller pair 11, and the paper ejection tray 9
Stacked on top.

In the illustrated embodiment, before the operation of opening the door 20, the density of the background portion of the image carrier 1 is detected by the toner density sensor and the detected value is stored. Then, for example, when the transfer paper is jammed and the jam is released and the door is closed, or when the door is opened and closed for other maintenance, the toner concentration detection sensor 23 is activated. The density of the background portion of the image carrier 1 is detected. A door position determination means is provided for determining whether or not the closed position of the door is the regular closed position depending on whether or not there is a level difference between the detected value and the stored detected value, and, A control unit is provided to stop the image forming operation by issuing a display indicating that the door is in the incompletely closed state when the door is not in the regular closed position.

That is, in the embodiment shown in the figure, the toner concentration detection sensor of the toner replenishment control device for controlling the toner replenishment by detecting the toner concentration of the reference image formed on the image carrier 1 The incompletely closed state is detected.

FIG. 3 shows an example of a drive circuit of the toner concentration detecting sensor, and FIGS. 4 and 5 show an example of the detecting operation of the toner concentration detecting sensor. In FIG. 3, reference numeral 23 is a toner concentration detection sensor, 24 is a constant current circuit, 26 is a CPU including door position determination means, 27 is a resistor, 30 is a D / A converter, 3
Reference numeral 1 denotes an A / D converter, respectively. As shown in FIG. 3, a D / A converter 30 is connected to the CPU 26, and a control signal from the CPU 26 is input to the D / A converter 30 and converted into an analog signal. D /
A constant current circuit 24 including an operational amplifier 24a, a transistor 24b, and a resistor is connected to the A converter 30, and the constant current circuit 24 allows the toner concentration sensor 2 to operate.
The LED 23a on the light emitting side of No. 3 is driven by a constant current.

The light flux from the LED 23a is applied to the image carrier 1, and the reflected light from the image carrier 1 is incident on the phototransistor 23b of the toner density detection sensor 23 and is applied to the resistor 27 connected to the phototransistor 23b. A current flows according to the amount of light reflected from the image carrier 1. Therefore, a voltage proportional to the current is input to the A / D converter 31 connected to the resistor 27. This voltage is A / D converted by the A / D converter 31 and input to the CPU 26 connected to the A / D converter 31.

As shown in FIG. 4, the light quantity from the LED 23a is controlled so that the background voltage of the image carrier 1 is 2.5V. Such control such that the background voltage of the image carrier 1 becomes 2.5 V and the toner density control by detecting the toner density of the reference image are performed immediately after the main switch is turned on and every 500 sheets. Is performed at the end of image formation.

However, when the door is opened / closed in order to eliminate the jam when the transfer paper is jammed during image formation or for other maintenance, the toner concentration detection sensor 23 is driven by the control means, Toner concentration is detected. More specifically, after the door switch has changed from off to on, i.e. after closing the open door,
The toner concentration detection sensor 23 is driven by the control means,
The voltage of the background portion of the image carrier 1 is detected. This detected value is
As shown in Fig. 5, the background voltage before opening and closing the door is 2.5V
Compare with. As a result, if the detection level difference ΔV exists, the determination unit determines that the door is in the incompletely closed state, and the operation unit or the display unit displays that the door is in the incompletely closed state to form an image. It is configured to stop the operation.

As described above, immediately after the main switch of the apparatus is turned on and immediately after the completion of image formation for every 500 sheets, control is performed so that the background voltage of the image carrier 1 becomes 4V, and the toner of the reference image is used. The control of the toner density so that the density becomes constant is performed by the CPU 26 shown in FIG.

FIG. 6 is a flow chart showing the operation of the control means when the door opening / closing operation occurs. When the operator opens the door at time t1 shown in FIG. 5, step S
At 1, the toner concentration detection sensor (P sensor) 23 detects the voltage of the background portion of the image carrier 1, and the detected value V1 is stored in a memory (not shown). When the operator closes the door in step S2, the process proceeds to step S3, and at time t2 shown in FIG.
Thus, the voltage of the background portion of the photoconductor 1 is detected again, and the detected value V2 is obtained. Next, in step S4, the detection value V1 stored in the memory in step S1 is compared with the detection value V2 detected in step S3. Step S
If V1-V2> 0.5 in the determination of 4, the door is determined to be in the incompletely closed state, the process proceeds to step S5, the door warning is displayed on the operation unit by the control unit, and the image formation of the apparatus is performed. The operation cannot be started. If the determination in step S4 is V1 = V2, normal image processing operation becomes possible.

Therefore, when the control means determines that the door is in the incompletely closed state, a message to that effect is displayed and the image forming operation of the apparatus is disabled.
There is no erroneous detection of toner density due to the fact that 3 is not in the proper position, and formation of an image of poor quality due to erroneous detection of toner density is prevented.

FIG. 7 is a block diagram showing an example of the control device of the copying machine according to this embodiment, and the reference numeral 39 is a CPU.
, A memory in which a control program is recorded, a microprocessor, and the like. Reference numeral 23 is a toner concentration detection sensor, 40 is a door switch of the front door, I1 is an input terminal of the door switch 40, and I2 is an input terminal of the toner concentration detection sensor 23. As is apparent from this configuration, only when the door switch 40 is opened and closed, the toner density detection sensor 23 and the CPU 39 detect the incompletely closed state of the door and the control based on the detection.

FIG. 8 is a flow chart of the incompletely closed state check control of the door, and FIG. 9 is an external view showing the open state of the door of the copying machine. In FIG. 8, it is checked whether the copying machine has finished copying 500 sheets, and if 500 sheets have been copied, the measured value of the reflected light obtained by turning on the LED 23a after the copying is stored in the memory as DATA1 (step S
0). Next, the occurrence of a jam is detected (step S1).
When the occurrence of a jam is detected, the copy operation is stopped (step S2). Next, it is determined whether the right door 20 is open (step S3). When the jam generated in step S1 can be processed by opening the door other than the right door 20, for example, when a jam occurs in the ADF, the jam is AD.
Since it can be processed by opening only the F door 21a, step S
After 4, the check of whether the door is in the incompletely closed state is completed (step S11).

When the opening of the right door 20 is detected in step S3, the right door 20 is not always closed last after the jam treatment, so that all the doors, that is, the front door 21b, the ADF door 21a, and the supply door are supplied. It is checked whether the paper device door 21c is closed (step S6). If closed,
The toner concentration detection sensor 23 is turned on once, and the measured value is stored in the memory as DATA2 (step S7).
Next, it is confirmed whether the stored value of DATA2 is 2.0V or less (step S8).
The value of DATA2 is subtracted from the value of A1 (step S9).
If the value is 0.5 V or more, it is determined that the door is in the incompletely closed state, a warning is displayed on the copier operation unit 32, and the user is notified. Further, for example, by connecting to the communication line, it becomes possible to notify the maintenance person of the copying machine that the door is incompletely closed (step S10).

Next, another embodiment of the present invention will be described with reference to FIGS. This embodiment is characterized in that it is configured to determine whether or not the door is at a predetermined closed position by attaching to the door a reflector that is combined with a resist sensor that the electrophotographic apparatus has. The configuration is substantially the same as the configuration described above. Therefore, the same reference numerals are given to the same components as those of the above-described embodiment.

In FIG. 10, around the image carrier 1,
A charging roller 2, an optical writing device 3, a developing unit 4, and a transfer roller 6 are arranged. Transfer paper P on the bottom of the device
There is a paper feed cassette 10 that accommodates. A pair of registration rollers including a sheet feed roller 12, a registration driving roller 8a, and a registration driven roller 8b are provided along the transfer sheet conveyance path. A registration sensor 23 and a reflection plate 50 are provided on the upstream side of the pair of registration rollers with the transfer sheet conveyance path interposed therebetween. The fixing roller pair 7 is provided on the downstream side of the transfer section, and the paper discharge roller pair 11 is provided further on the downstream side thereof. The upper part of the apparatus is a paper discharge tray 9.

A right door 20 for opening and closing the right side surface of the apparatus main body is provided so as to be rotatable around a lower fulcrum 26. A lock portion 13 that rotates around a fulcrum 13a is provided on the upper end of the right door 20, and a locked portion 27 that engages with the lock portion 13 is provided on the apparatus body side. Transfer roller 6,
The registration driven roller 6a and the reflection plate 50 are fixed to the right door 20 and move as the right door 20 opens and closes. The reflection plate 50 also has a function as a guide plate for guiding the transfer of the transfer paper P. The reflection plate 50 has a curved surface that is curved in the transfer paper conveyance direction, and is in point contact or line contact with the transfer paper that is conveyed. The transfer paper P pulled out from the paper feed cassette 10 and fed by the paper feed roller 12 passes through the registration sensor 23, and its leading end abuts on the nip portion of the registration roller pair which is not rotating to form a predetermined loop. Stop once. By forming this loop, the skewed state of the transfer sheet P is corrected.

On the other hand, while the image carrier 1 is rotated counterclockwise in FIG. 10, the surface of the image carrier is uniformly charged to a predetermined polarity by the charging roller 2, and the charged surface is optically written. The light-modulated laser light L emitted from the device 3 is irradiated and scanned, whereby a predetermined electrostatic latent image is formed on the surface of the image carrier. This electrostatic latent image is visualized by the toner when passing through the developing unit 4. After the correction of the skewed state is completed, the transfer sheet P is rotated by a registration roller pair which starts rotation at a timing of aligning with the tip of the electrostatic latent image on the image carrier 1 rotating counterclockwise. Image carrier 1 and transfer roller 6
And is sent to a transfer section having a nip section between

The transfer roller 6 sequentially transfers the toner images on the image carrier 1 onto the transfer paper P sent to the transfer section.
The transfer paper P on which the toner image is transferred is sent to the nip portion of the fixing roller pair 7, and the toner image is fixed on the transfer paper P here. After the toner image is fixed, the transfer paper P is a discharge roller pair 1
It is discharged to the outside of the machine by 1 and is stacked on the discharge tray 9.

Registration sensor 23 comprising a photo sensor
Detects the passage of the transfer paper P, irradiates the sensor light toward the reflection plate 50, and receives the reflected light. Therefore, since the received light output level is different when the transfer sheet P is present in the conveyance path and when it is not present, the presence or absence of the transfer sheet,
In other words, it is possible to detect the passage of the transfer paper in the transport path.

FIG. 11 shows a drive circuit diagram of the registration sensor. In FIG. 11, the CPU 26 includes a door position determining means for determining whether the door closed position after the door opening / closing operation is the regular closed position, and the control signal from the CPU 26 is sent to the D / A converter 30. It is input and converted into an analog signal. The output of the D / A converter 30 is input to the operational amplifier 24a, and the output of the operational amplifier 24a is input to the constant current circuit 24 including a transistor 24b and a resistor, and the constant current circuit 24 causes the LED 23a, which is a light emitting element of the registration sensor 23. Are driven by a constant current to emit a constant amount of light.

The light of the LED 23a is applied to the reflecting plate 50, and the reflected light from the reflecting plate 50 enters the phototransistor 23b which is the light receiving element of the resist sensor 23 and is reflected by the resistor 27 connected to the phototransistor 23b. An electric current flows according to the amount of reflected light from the plate 50. Therefore, a voltage proportional to the current is input to the A / D converter 31 connected to the resistor 27. This voltage is A / D converted by the A / D converter 31 and input to the CPU 26.

12 and 13 are explanatory views of the detection operation of the registration sensor. As shown in FIG. 12, when the reflected light from the reflection plate 50 is received, the voltage output from the phototransistor 23b becomes 2.5V.
The amount of light emitted from the ED 23a is controlled. The control such that the output voltage of the phototransistor 23b by the reflected light of the reflection plate 50 becomes 2.5V is performed immediately after the main switch (not shown) is turned on and at the time of completing the image formation for every N sheets.

However, when the transfer paper P is jammed at the time of image formation or during maintenance, the right door 20 is opened.
When is closed, the resist sensor 23 is driven under the control of the CPU 26, and the voltage value of the phototransistor 23b by the reflected light from the reflection plate 50 is measured. As described in FIG. 5, the measured value V1 (2.5V) before opening the door
And the detection level difference ΔV from the value V2 measured after opening and closing the door is a predetermined value or more, it means that the door is not closed to the regular closed position on the operation unit or the display. Is displayed and the image forming operation is stopped. During the normal copying operation, when the transfer paper P passes through the position of the registration sensor 23, the light emitted from the LED 23a is reflected on the transfer paper P,
The CPU 26 shown in FIG. 11 controls the output voltage of the phototransistor 23b to 4V.

FIG. 13 is a flowchart of the control operation when the door opening / closing operation occurs. In FIG. 13, when the operator opens the right door 20 at time t1 shown in FIG. 5,
In step S1, the light emitted from the light emitting element of the registration sensor 23 and reflected by the reflection plate 50 is reflected by the registration sensor 23.
The value of the voltage output by the light receiving element of (1) receives the detected value V1, and this is stored in the memory. When it is detected in step S2 that the right door 20 is closed by the operator, the process proceeds to step S3, and at time t2 shown in FIG. 5, the light emitted from the light emitting element of the resist sensor 23 is reflected by the reflection plate 50 again. Registration sensor 2
The value of the voltage output when the light receiving element of No. 3 receives light is detected, and this is set as the detected value V2. Next, in step S4, the detected value V1 stored in the memory in step S1 is compared with the detected value V2 in step S3.

In the determination of step S4, V1-V2> 0.5
If so, the CPU 26 proceeds to step S5 to display a warning indicating that the door is not completely closed on the operation unit, prohibits the start of the image forming operation, and prompts a serviceman call. The determination in step S4 is V1-
If V2> 0.5, for example V1 = V2,
A normal image forming operation becomes possible. As described above, when the door is not completely closed, the CPU 26 controls that the right door 20 is not set properly, and the image forming operation of the apparatus is disabled. Therefore, the right door 20 is in the normal position. It is possible to prevent transfer failure and transfer paper conveyance failure due to the absence of the above.

The connection between the CPU, the door switch and the registration sensor is the same as the connection in the above-described embodiment shown in FIG. Only when the door switch is opened / closed, the registration sensor 23 and the CPU 26 execute detection control as to whether or not the door is in the regular closed position. The detection control operation of whether or not the door is in the regular closed position is the same as the detection control operation of the above-described embodiment shown in FIG. 8, and therefore the description of the detection control operation will be omitted.

According to the embodiment described above, the registration sensor 23 can be used to determine whether the closed position of the door 20 is the regular closed position, so that the incompletely closed state of the door 20 is detected. It is possible to prevent the operator from performing the image forming operation while overlooking the transfer failure due to the incomplete closing of the door or the transfer sheet transfer failure without adding a new device or component for performing the operation.

Further, since the reflecting plate 50 combined with the registration sensor 23 has a function as a transfer paper guide plate in the transfer paper conveying path, the number of guide plates can be reduced and the cost can be reduced. it can. Further, the surface of the reflection plate 50 does not deposit toner or paper powder on contact with the transfer paper, and it is possible to always return the light emitted from the resist sensor to the resist sensor with a constant reflectance. In addition, since the reflection plate 50 has a function as a transfer paper guide plate and has a curved surface, the transfer paper can be smoothly guided.

[0054]

According to the present invention, the detection value of the image carrier upper surface detected by the toner density detecting sensor during the previous image forming operation and the image carrier upper surface detected by the toner density detecting sensor when the door is opened and closed. The incompletely closed state of the door is determined by comparing the detection values of the parts and the detected values based on the difference between the detection values. It is possible to prevent the operator from performing an image forming operation while overlooking the transfer failure due to the incomplete closing of the door or the transfer paper transfer failure without adding a new device or a part for detecting the error. it can. Further, it is possible to prevent the image forming operation from being performed while overlooking the toner concentration control abnormality due to the toner concentration detection sensor erroneous detection.

[Brief description of drawings]

FIG. 1 is a front sectional view showing an embodiment of an electrophotographic apparatus and a cover opening / closing detection method according to the present invention.

FIG. 2 is a front cross-sectional view showing another operation mode of the above embodiment according to FIG.

FIG. 3 is a circuit diagram showing an example of a control circuit applicable to the present invention.

FIG. 4 is a graph showing a difference in voltage level between a background portion and a visible portion on an image carrier in an electrophotographic apparatus.

FIG. 5 is a graph showing a difference in toner concentration sensor output when the door is opened and when the door is closed in the above embodiment.

FIG. 6 is a flowchart showing the operation of the control means when the door opening / closing operation is performed in the above embodiment.

FIG. 7 is a block diagram showing an example of a control device applicable to the present invention.

FIG. 8 is a flowchart showing a half-door check control operation in the above embodiment.

FIG. 9 is a perspective view showing an example of various doors of a copying machine and an open / closed state thereof.

FIG. 10 is a front sectional view showing another embodiment of the electrophotographic apparatus and the cover open / close detection method according to the present invention.

FIG. 11 is a circuit diagram showing an example of a control circuit applicable to the above embodiment.

FIG. 12 is a graph showing a difference in voltage level when the reflected light from the transfer paper and the reflected light from the reflection plate are received in the above embodiment.

FIG. 13 is a flowchart showing the operation of the control means when the door opening / closing operation is performed in the above embodiment.

[Explanation of symbols]

1 Image carrier 2 charging roller 3 Optical writing device 4 developing roller 6 Transfer roller 7 Fixing device 20 doors 23 Toner concentration detection sensor 50 reflector

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2H027 DA10 DA26 DA41 DC14 DE02                       DE07 DE09 EC06 EC07 EC09                       ED17 ED24 EE07                 2H071 AA03 AA06 AA08 AA19 AA42                       BA04 BA14 BA16 BA17 BA20                       DA08 DA09 DA15 DA22 DA32                 2H200 GA23 GA44 GB41 HA01 HB12                       HB22 JA01 JA08 JB10 JB20                       JB32 LA03 LA17 LA23

Claims (11)

[Claims] 1. A developing device arranged in the vicinity of an image carrier, a transfer device for transferring a toner image formed on the image carrier by the developing device onto a transfer sheet, and a developing device on the image carrier. A toner density sensor for detecting the density of the formed toner image, wherein the toner density sensor is arranged on a door that opens and closes the vicinity of the image carrier, and the toner image on the image carrier is in a closed state. Is an electrophotographic apparatus capable of detecting the density of the image carrier surface density detected by the toner density sensor before the door opening operation is performed, and the door is opened and closed. After that, the density detection value on the surface of the image carrier detected by the toner density sensor is compared, and based on the difference between the detection values, it is determined whether the door closing position after the door opening / closing operation is the regular closing position. Judgment Electrophotographic apparatus characterized in that it has a door position determining unit that. 2. The electrophotographic apparatus according to claim 1, wherein the toner density sensor detects the toner density of the background portion of the image carrier. 3. The door has a transfer roller, and when the door is closed, the transfer roller is above the developing device so as to come into pressure contact with the image carrier, and the toner is arranged in the rotational direction of the image carrier. The electrophotographic apparatus according to claim 1, wherein the electrophotographic apparatus is arranged so as to come into pressure contact with a downstream side of a position detected by the density sensor. 4. The door has one pair of registration rollers, and when the door is closed, one of the registration rollers is arranged so as to be in pressure contact with the other of the pair of registration rollers. Item 1. The electrophotographic apparatus according to Item 1. 5. The electrophotographic apparatus according to claim 1, wherein the door has a transfer roller and one of a pair of registration rollers, and a toner concentration sensor between the transfer roller and one of the registration rollers. apparatus. 6. An image forming apparatus having a reflector arranged at a door portion facing a registration sensor and moving toward and away from the registration sensor according to a door opening / closing operation, wherein the registration is performed before a door opening operation is performed. The detection value of the reflected light from the reflector detected by the sensor and the detected value of the reflected light from the reflector detected by the resist sensor after closing the door are compared, and the difference between the detected values is calculated. An electrophotographic apparatus, comprising: a door position determining means for determining whether or not the closed position of the door after the door opening / closing operation is a regular closed position. 7. The electrophotographic apparatus according to claim 6, wherein the reflection plate has a function of a transfer guide plate in the transfer paper conveyance path. 8. The electrophotographic apparatus according to claim 6, wherein the reflection plate has a curved surface. 9. A developing device arranged in the vicinity of the image carrier, a transfer device for transferring the toner image formed on the image carrier by the developing device to a transfer paper, and a developing device on the image carrier. A toner density sensor for detecting the density of the formed toner image, wherein the toner density sensor is arranged on a door that opens and closes the vicinity of the image carrier, and the toner image on the image carrier is in a closed state. Is a method for detecting the opening / closing of a cover of an electrophotographic apparatus, which is capable of detecting the density of the toner on the surface of the image carrier by the toner density sensor before the operation of opening the door is performed. After opening and closing, the toner density sensor detects the toner density on the surface of the image carrier, and the toner density detection value before opening the door and the toner density detection value after opening and closing the door Comparison, the cover closing detection method of an electrophotographic apparatus wherein the closed position of the door after the door opening and closing operation on the basis of a difference between these detected values to determine whether the closed position of normal. 10. The cover open / close detection method for an electrophotographic apparatus according to claim 9, wherein the toner density sensor detects the toner density of the background portion of the image carrier. 11. A cover open / close detection method for an electrophotographic apparatus, which has a reflection plate disposed at a door portion facing a registration sensor and moving toward and away from the registration sensor according to a door opening / closing operation. While detecting the reflected light from the reflection plate by the registration sensor before the operation is performed, after detecting the reflected light from the reflection plate by the registration sensor after closing the door, the detection value before opening the door And a detection value after the door is opened and closed, and based on the difference between the detection values, it is determined whether or not the door closing position after the door opening / closing operation is the regular closing position. Method for detecting cover open / close of electrophotographic device