JPH0738082B2 - Image forming device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus having a spare process unit built therein.

(Prior Art) Personalization is progressing in the field of image forming apparatuses such as laser printers and electrophotographic copying machines. Therefore, there is a tendency to use a part of the image forming unit integrated as a replaceable process unit so that the user can easily perform maintenance work.

In such an image forming apparatus employing a process unit, it is possible to return to the used state by a simple operation of replacing a unit whose life has expired with a new unit, and it is very easy to maintain and manage. Has become.
However, although it has such advantages, it also has the following drawbacks.

For example, if toner is consumed during continuous copying and the life of the process unit is reached, the copying machine body detects the life and stops the copying operation. Alternatively, the set number of copies may be made, but the copy may have a low image density from the middle.

Even in such a case, if the spare process unit is always bought back, the copying process can be restarted with a short interruption by replacing it with this new process unit. However, if there is no spare unit, the copying operation cannot be resumed until a new one is purchased.
As a result, I can't get the copy I need, so I'm happy. Generally, when you are in a hurry, you don't have a spare unit, and you often experience a lot of inconvenience. In particular, such a situation is more likely to occur because the service person does not regularly show his face to the user due to personalization.

(Technical problem to be solved by the present invention) An object of the present invention is to eliminate the above-mentioned inconvenience, and for example, in the case where toner is consumed and the process unit reaches the end of its life. Also, it is an object of the present invention to provide an apparatus capable of continuously performing an image forming operation.

(Structure of the Invention) The present invention has the following structure in order to achieve the above object, that is, an image forming apparatus including a process unit in which a latent image carrier and at least a developing unit or a cleaning unit are integrally formed, The image forming apparatus further comprises a spare process unit in a state capable of forming an image, which is a structural feature of the first invention.

Further, in the present invention, in relation to the provision of at least two process units in an image formable state, which is a characteristic of the above configuration, an image forming reference position when performing image formation using the first process unit. Further, it is a structural feature of the second invention that an image forming reference position for forming an image by using the second process unit is provided in one image forming apparatus.

In a third aspect of the present image forming apparatus, the life of the process means included in the process unit that uses the switching from one of the process units in the image formable state to the other is detected. A structural feature is that it is performed by the switching means provided in the image forming apparatus based on the signal from the detection means.

(Examples of the Invention) Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram for explaining the structure of a copying machine as an aspect of the image forming apparatus of the present invention.

In a copying machine indicated by 2 as a whole, a document placing table 4 for placing a document on an upper portion, a paper feed mechanism 6 for supplying a copy sheet to the right side in the drawing, and a transfer sheet on the copy sheet on the left side in the figure. A fixing device 8 for fixing the toner is provided, and a copy paper conveying path 10 is formed as a path from the paper feeding mechanism 6 to the fixing device 8.

Inside the copying machine 2 and above the copy paper transport path 10, two process units are provided along the transport path 10.
12,14 are installed side by side in a detachable manner.

The process units 12 and 14 have the same configuration, and have the following configurations. The process unit 12 has an electrostatic latent image holding drum 16 (hereinafter sometimes referred to as a drum), which has a photosensitive layer on its surface and is rotatable by being driven by a drive source (not shown) of the copying machine main body, A main charger 18, an image exposure opening 20, a developing device 22, and a cleaning device 23 are integrally formed in the unit housing 24 in this order around the main charger 18. An opening 26 is formed on the lower side of the unit housing 24 in the figure, that is, on the side facing the conveyance path 10, and a toner image is formed on the copy sheet that has moved on the conveyance path 10 at the position of the opening 26. Is to be transcribed.

Further, between the process units 12 and 14 and the document placing table 4, at a position corresponding to the exposure openings 20 and 20 'provided in the housings 24 and 24' of the units 12 and 14, an optical system unit ( For example, SELFOC lenses 28, 28 'are provided so that the original image on the original table 4 illuminated by the lamp 30 or 30' is projected onto the drums 16, 16 '.

Next, the operation of the copying machine 2 will be described taking the case where the process unit 12 is now contributing to image formation as an example.

When a copy start command is issued by pressing the copy button or the like, the power from the main body drive source causes the drum, developing device, etc. to start rotating or operating. At this time, the document platen 4 on which the document is placed is It moves to the right side in the figure, and stands by at the position corresponding to the optical system unit 28 with the left side of the mounting table 4 as the leading edge of the document. On the other hand, the paper feed roller that started to rotate due to the copy start command
The copy sheet whose feeding has been started by 32 stands by at the position of the registration roller pair 33 which has not rotated yet.

Next, when a signal indicating the standby state of the document table 4 is issued, the lamp 30 is turned on and the main charger 18 starts discharging. A latent image is formed on the drum 16 as the document table 4 moves to the left side in the drawing, and a toner image is formed by the developing device.

On the other hand, by the time the leading edge of the toner image reaches the transfer area, that is, the area 34 where the drum 16 projects from the opening 26 of the housing 24, the leading edge of the copy sheet moves on the transport path 10 as described above. After a required time elapses based on the waiting signal of the document table, the registration roller pair 33 starts to rotate and the sheet is conveyed.

Then, the leading edge of the toner image and the leading edge of the copy sheet are synchronized with each other, and the toner image is transferred onto the sheet in the transfer area 34 by the action of the transfer charger 36 provided on the back side of the sheet on the conveying path.

The toner image transferred onto the copy sheet is fixed by the fixing device 8, and the copy sheet is discharged to the discharge tray 38. On the other hand, after the transfer, the cleaning device 23 removes the residual toner from the drum 16 and contributes to the next image formation. Further, the document table 4 that has moved to the left and has completed image exposure moves to the right and stops at the original position.

One of the features of the present invention in such a copying machine is that it has two process units. Moreover,
Since both of these two process units are arranged on the conveyance path 10 in a state capable of forming an image, for example, even if all the toner in the developing device of the process unit 12 in FIG. 1 is completely consumed. The process unit 14 can still be used. Therefore, even if one of the process units reaches the end of its life, the other process unit can continue to perform the remaining copy.

Then, by replacing the process unit that has reached the end of its life with a new unit by using the time during which copying is not performed, etc., when the life of the spare unit reaches the end, the image is formed using the unit that was replaced earlier. You can do it.

In the image forming apparatus of the present invention, two process units are provided side by side in a usable state, and are appropriately switched according to the life of any one of the process units to be used. That is, the copying machine body 2
Since there is only one conveyance path 10 in the above, a process unit is provided in a usable state here, and in order to form the final copy in conformity with the original regardless of which process unit is used, No matter which process unit is used, the operation of the image forming means and the conveyance of the copy sheet must be synchronized with each other.

The present inventor has devised the simplest method to provide the reference position for image formation in accordance with the number of process units provided therein so as to surely satisfy the above requirements. That is, referring to the copying machine shown in FIG. 1, the process unit 12 is provided with a reference position corresponding to the unit, and the process unit 14 is provided with a reference position corresponding to a unit 14 different from the reference position. .

Here, the term reference position means the following contents in this specification. That is, based on a copy start (image formation start) command, the operation of the exposure optical system when a series of image forming mechanisms starts to operate, and the image formed by the operation is transferred onto a copy sheet at an accurate position. It means a time position at which a signal to be a reference is output in order to synchronize with a paper feeding operation for performing the operation. To explain with a specific example, in the case of the copying machine shown in FIG. 1, the document table 4 is initially moved to the right side,
When the leading edge of the document comes to a position corresponding to the optical system unit 28 (or 28 '), a signal indicating that the standby state of the document table 4 is completed is issued here, and is used as the basis for the start command for each operation. . Therefore, at this time or the position of the document table 4 in the copying machine becomes the reference position S or S '.

In addition to this, the copy paper is first conveyed to the position of the registration roller by the rotation start of the paper feed roller, and at this position, a signal indicating a standby state for starting image formation is issued On the other hand, in the case of the copying machine shown in FIG. 1 which is referred to as a moving platen type), this registration end time or end position can be the reference position.

In the present invention, it is an important feature that there are a plurality of reference positions corresponding to the number of process units. The following example can be given as the setting mechanism of the reference position. Referring to FIG. 2, the document table 4 is provided with information transmitting means (for example, a protrusion or a magnet) 50 for allowing the detector on the main body side to recognize the leading edge of the document. Then, on the main body side, a detection means (for example, a microswitch or a hall element) 52 for detecting the arrival of the transmission means 50 in the vicinity of the optical system units 28 and 28 'provided corresponding to the units 12 and 14, respectively. , 52 ', 53, 53' are provided.
Now consider the use of process unit 12. In this case, the document table first moves to the right side in response to the instruction to start copying, and the information transmission means 50 first passes the detection means 52. In this case, the detection unit 52 is installed in the microcomputer that controls the main body of the copying machine.
It is programmed to determine to move the platen in the opposite direction by the signal from the. Therefore, the driving means of the document table 4 is temporarily stopped by the signal from the detection means 52 which has detected the passage of the information transmission means 50, so that the document table 4 is stopped.
Also stop. At this time, the copy sheet that has been fed by the previous copy start command is also stopped at the position of the registration roller 33.

On the other hand, since the stop position of the document table 4 is received by a signal from the detecting means 52 and is operated by a braking means (not shown), a predetermined time lag occurs and the position is set at a predetermined distance from the detecting means 52. . Another detection means 53 is provided at this predetermined position and issues a signal for confirming that the platen is stopped.

This signal becomes a reference signal when the process unit 12 is used, and this stop position becomes the image formation reference position S.

Next, based on the reference signal emitted from the detection means 53,
The charger 18 in the process unit 12 and the lamp 30 for the process unit 12 provided in the main body are turned on. Then, when the document table driving means is started to reverse, the document table 4 starts moving to the left and image exposure is started. At this time, detection is performed so that the timing at which the exposure start position on the drum circumference reaches the transfer area 34 as the drum 16 rotates and the timing at which the copy sheet reaches the transfer area 34 as the registration roller 33 rotates. Reversing start timing RT12 of the platen drive means based on the reference signal issued from the means 53 and the registration roller 33
By inputting the rotation start timing ST12 of the above into the microcomputer provided in the main body in advance, the movement of the document table 4 and the conveyance of the copy sheet can be synchronized.

Next, the case where all the developer in the process unit 12 is consumed and the life of the process unit 12 is reached will be described.
The end-of-life detecting unit of the process unit 12 may be, for example, a toner sensor provided in the developing device (in the case of two components, a toner concentration detecting unit or the like, and in the case of one component, a Hall element or a Hall element for detecting the presence or absence thereof). The signal indicating that the toner is zero is performed by the signal from the electrostatic capacity detection element). Alternatively, since the developer filling amount is generally determined in accordance with the printing durability of the drum 16, a signal indicating that the printing durability has been reached from a counter indicating the number of times of copying.

By this detection signal, the operation control means (microcomputer) provided in the main body of the copying machine causes the process unit 12 to form an image.
Make a decision at 12 '. Therefore, the stop position for exposing the document table 4 is also changed to the position corresponding to the process unit 14. In the example shown in FIG. 2, as in the case described above based on the copy start command, first, the document table (2B
(Fig.) Moves to the right, and when the information transmission means 50 passes the detection means 52 and reaches the position 52 ', the stop command is the detection means.
It is emitted from 52 'and stops on the detection means 53'. Then, the stop confirmation signal is continuously issued from the detecting means 53 '. This signal serves as a reference signal for the process unit 14.
This position becomes the reference position S '.

Therefore, based on this reference signal, the process unit 14
The rotation start timing RT14 of the platen drive means and the rotation start timing ST14 of the registration roller 33 corresponding to
If separately defined, the movement of the platen and the conveyance of the copy paper can be performed in synchronization with the process unit 14 as well.

By thus performing electrical control using the detection means 52, 52 ', 53, 53', the reference position can be easily changed, and the process units can be switched easily and reliably.

By adopting a belt conveying means, the toner image before fixing can be surely conveyed without disturbing the downstream side of the conveying path from the transfer area 34 'of the process unit 14.

In the above, the switching by the electrical switching means (control means by the microcomputer) based on the life of the process unit has been described. However, the concept of the present invention is not limited to this range, and various modifications can be considered.

For example, when the main charger or the developing device in the process unit being used becomes unusable due to disconnection or short circuit, the abnormality is detected and the spare process unit is switched based on this detection signal. It is also possible.
In this case, it is useful to provide the display board (operation panel) of the image forming apparatus with a display unit for informing the operator whether the reason for switching is due to life or abnormality.

Alternatively, one of the two process units is set as a reference unit and the other is set as an emergency unit, and the emergency unit has the same components as the reference unit, but is a low-cost unit lower in cost than the reference unit. Put on. And only use this unit in an emergency,
It is also effective to always form an image on the reference unit side when the reference unit can form an image by replacement.

(Effect) According to the present invention, since the spare process unit is provided in the main body of the image forming apparatus in an image formable state,
Even if one of the process units reaches the end of its life, image formation can be continued without interruption.

Further, according to the present invention, since the image forming reference positions are provided as many as the number of built-in process units, complicated work is not required when switching process units. Moreover, since the switching is electrically controlled by the life detecting means, it is automatically and reliably performed.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the construction of a copying machine which is one embodiment of the present invention, and FIG. 2 is a schematic diagram showing a reference position detecting operation for the copying machine shown in FIG. The reference numbers in the figure indicate the following contents. 2 ... Copier 12, 14 ... Process unit 50 ... Information transmission means 52, 52 ', 53, 53' ... Detection means S, S '... Image formation reference position

Claims (3)

[Claims] 1. An image forming apparatus comprising a process unit in which a latent image carrier and at least a developing unit or a cleaning unit are integrally formed, wherein the image forming apparatus is a spare process unit in a state in which an image can be further formed. An image forming apparatus comprising: 2. An image forming apparatus comprising a process unit integrally formed with a latent image carrier and at least a developing means or a cleaning means, the image forming apparatus comprising at least two process units, a first process unit and a second process unit. In addition, the image forming apparatus has a first image forming reference position corresponding to the first unit and a second image forming reference position corresponding to the second unit when forming an image. 3. An image forming apparatus comprising a process unit integrally formed with a latent image carrier and at least a developing means or a cleaning means, wherein the image forming apparatus comprises at least first and second process units. , When any one of the process means reaches the end of its life due to a signal from the detecting means for detecting the life of each process unit or a signal from the detecting means for detecting the abnormality of each process unit, another process unit forms an image. An image forming apparatus having a switching means for continuing the operation.