JPH08305118A - Image forming device - Google Patents

Abstract

PURPOSE: To prevent image defect resulting from the use of a wrong developing unit in development, in an image forming device which rotates a group of developing units, thereby shifting required one into a developing position. CONSTITUTION: Grooves 200a are made in the tube 200 of a rotary type developing device, one for each developing unit, and the main body of the device is provided with a photosensor 201 which detects each groove 200a. In case the photosensor 201 do not recognize the groove 200a, which is intended to be recognized, at particular timing after the start of the rotation of the rotary type developing device during printing, a microprocessor stops the printing operation of the device.

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 such as a copying machine, a facsimile and a printer.

[0002]

2. Description of the Related Art Conventionally, as an image forming apparatus of this type, a developing device unit having a plurality of developing devices arranged around a rotation center line, and an arbitrary developing device at a developing position facing a latent image carrier. There is known an image forming apparatus provided with a developing device unit rotating means for rotating the developing device unit about the rotation center line in order to move the developing device unit (for example, Japanese Laid-Open Patent Publication No. 63-316068). See Japanese Patent Publication No. 52-89046). In this image forming apparatus, as a plurality of developing devices, a black developing device for forming a black toner image, a yellow developing device for forming a yellow toner image, a magenta developing device for forming a magenta toner image, and a cyan forming a cyan toner image. Using a developing device, the developing device unit rotating means moves a desired developing device to a position facing the latent image carrier (hereinafter referred to as a developing position), and the developing device sequentially forms a toner image to obtain a full color image. An image can be formed.

[0003]

However, in such a conventional image forming apparatus, when the developing unit rotating means is vibrated due to a person hitting the apparatus body during image formation, the developing unit rotating means is rotated. May not work well, and the latent image formed on the latent image carrier may be developed by a developing device different from the originally used developing device.

An image forming apparatus in which, for example, a black developing device, a cyan developing device, a magenta developing device, and a yellow developing device are moved in this order to a developing position and each developing device forms a toner image at that position. In the above, when the cyan developing device is moved to the developing position, the developing device unit rotating means malfunctions, and the cyan developing device may be pulled out after the black developing device and the magenta developing device may move to the developing position. is there. In this case, unlike the original order shown above, each developing device moves to the developing position in the order of the black developing device, the magenta developing device, the yellow developing device, and the black developing device, and the toner image is formed at that position. It will be. Therefore, the latent image to be developed with cyan toner is magenta toner, the latent image to be developed with magenta toner is yellow toner, and the latent image to be developed with yellow toner is black toner.
Each latent image is developed with toner of a color different from the toner that should be used originally.

As described above, as a cause of the developing unit rotating means not rotating properly, in a device provided with a motor driven electrically such as a stepping motor, when the load applied to the motor is rapidly changed due to vibration or the like. There is a so-called step-out, which is a phenomenon in which the synchronization from the input from the power source cannot be maintained because the input cannot respond to the change.

Further, when images are continuously formed on a plurality of recording papers, not only the recording papers to be image-formed when an operation failure occurs in the developing unit rotating means, but also the image forming operation thereafter is performed. Defects also occur in images formed on all target recording sheets. For example, in the example of the rotation operation failure of the developing device unit described above, the developing operation for forming an image on the recording paper when the failure occurs is completed by the black developing device. Therefore, in the developing operation for forming an image on the next recording sheet, the cyan developing device is first used although the developing device which should be originally used is the black developing device. As a result, in the developing operation for forming an image on the recording paper, all the latent images are developed by using a developing device different from the developing device that should be originally used. Further, in the subsequent developing operation for forming an image on the recording paper, the developing operation is performed by the developing device different from the originally used developing device.

Incidentally, the above-mentioned Japanese Patent Laid-Open No. 63-31606.
No. 8 and Japanese Utility Model Application Laid-Open No. 52-89046 do not disclose or suggest any of the above-mentioned harmful effects resulting from the poor operation of the developing device unit rotating means, and solve the adverse effects. There is no disclosure or suggestion of means for doing so.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a developing device unit having a plurality of developing devices and the developing device for moving an arbitrary developing device to a developing position. In an image forming apparatus provided with a developing device unit rotating means for rotating a developing device unit, a malfunction occurs in the developing device unit rotating means, so that a latent image is developed by a developing device different from the originally used developing device. An object of the present invention is to provide an image forming apparatus capable of forming an excellent image by preventing the occurrence of an image defect caused by the above.

[0009]

In order to achieve the above object, an image forming apparatus according to a first aspect of the present invention includes a developing device unit having a plurality of developing devices arranged around a rotation center line, and an arbitrary developing device. Developing device unit rotating means for rotating the developing device unit about the rotation center line in order to move the developing device to a developing position facing the latent image carrier, and each of the plurality of developing devices in the developing device unit. At a predetermined timing after the developing unit is started to rotate, the detecting unit fixed to the apparatus main body to detect the detecting unit fixed to the main body of the apparatus. And a control unit that stops the image forming operation when the detection unit does not detect the detected portion.

An image forming apparatus according to a second aspect is the image forming apparatus according to the first aspect, further comprising display means for displaying the occurrence of an abnormality when an abnormality occurs in the image forming operation, and the control means comprises: It is characterized in that the display means is operated when the detecting means does not detect the detected portion at a predetermined timing after the developing unit is started to rotate.

An image forming apparatus according to a third aspect of the present invention is the image forming apparatus according to the first aspect, wherein the detected portion and the detecting means are used for identifying the plurality of developing devices. is there.

An image forming apparatus according to a fourth aspect of the present invention is the image forming apparatus according to the first aspect, in which the operation unit is operated to bring the apparatus main body in a state in which the image forming operation is stopped into a state capable of forming an image. And a home position detection part provided in the developing device unit for moving the developing device unit to a home position, which is a position serving as a reference for the rotation operation of the developing unit, and fixed to the apparatus main body. Home position detecting means for detecting the home position detected portion, and the developing device unit rotating means for controlling the developing device unit when the operating portion is operated while the image forming operation is stopped. It is characterized by including a control means for moving to a home position.

An image forming apparatus according to a fifth aspect of the present invention is the image forming apparatus according to the first aspect, wherein the control means causes the detection means to detect the detected object at a predetermined timing after the developing device unit starts rotating. It is characterized in that the apparatus main body is rendered inoperable when a situation in which no part is detected occurs a plurality of times in succession.

[0014]

In the image forming apparatus according to any one of claims 1 to 5, the control means performs the image forming operation when the detecting means does not detect the detected portion at a predetermined timing after the developing unit starts rotating. Stop. As a result, it is possible to prevent the image formation from being continued in a developing device other than the originally used developing device which is in a state used for developing the latent image due to the defective rotation of the developing unit rotating means.

Particularly, in the image forming apparatus according to the second aspect, the control means activates the display means when the detecting means does not detect the detected portion at a predetermined timing after the developing unit starts rotating. Display the occurrence of abnormalities.

Further, particularly in the image forming apparatus of the third aspect, the detection means fixed to the main body of the apparatus detects the detected portion provided in the developing device unit in a one-to-one correspondence with each developing device. Then, the detection result is used to control the developing device unit rotating means for moving an arbitrary developing device to the developing position facing the latent image carrier.

Further, particularly in the image forming apparatus of claim 4, when the operation portion for making the apparatus main body capable of forming an image is operated while the image forming operation is stopped, the image forming apparatus is provided in the developing device unit. The home position detection means, which fixes the home position detected part to the main body of the apparatus, detects it. Then, using the detection result, the control means controls the developing device unit rotating means to move the developing device unit to the home position.

Further, particularly in the image forming apparatus according to the fifth aspect, when a situation in which the detecting means does not detect the detected portion occurs a plurality of times at a predetermined timing after the developing device unit starts rotating, Not only does the image forming operation of the apparatus main body be stopped, but the apparatus main body is made inoperable.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a color electrophotographic printer (hereinafter referred to as a printer) which is an image forming apparatus will be described below. FIG. 1 is a schematic configuration diagram of a printer according to this embodiment. First, an outline of the entire printer will be described. In FIG. 1, a photosensitive drum 1 serving as a latent image carrier is uniformly driven by a charging charger 2 serving as uniform charging means while being rotationally driven in the direction of arrow A, and then image information is generated by a laser optical device 3. Scanning exposure is performed on the basis of the above to form an electrostatic latent image on the surface. Here, the image information to be exposed is image information of a single color obtained by separating a desired full-color image into color information of yellow, magenta, cyan, and black. The electrostatic latent image formed on the photoconductor drum 1 is developed with yellow, magenta, cyan, and black toners as predetermined developers by a rotary developing device 4 as a developing device unit, which will be described later. An image of each color is formed on the photoconductor drum 1.

Each color image formed on the photoconductor drum 1 is formed on the intermediate transfer belt 5 which rotates in the direction of arrow B in the figure in synchronization with the photoconductor drum 1 for each color of yellow, magenta, cyan and black. The primary transfer charger 6 sequentially performs the superimposed transfer. The yellow, magenta, cyan, and black images that are superposed on the intermediate transfer belt 5 are transferred from the automatic paper feed cassette 7 for double-sided copying or the manual paper feed tray 7a through the paper feed rollers 8 and 8a and the registration rollers 9. The secondary transfer charger 11 collectively transfers the transferred sheet 10 onto the transfer sheet 10. After the transfer is completed, the toner image is fixed on the transfer paper 10 by the fixing device 12, and the transfer paper 10 is discharged outside the machine as a full-color print.

The toner on the photoconductor drum 1 that has not been transferred onto the intermediate transfer belt 5 is removed by the photoconductor cleaner 13.
Is removed from the photosensitive drum 1 by the
The toner on the intermediate transfer belt 5 that has not been transferred onto the
It is removed from the intermediate transfer belt 5 by the intermediate transfer belt cleaner 14.

Next, the developing device 4 will be described. 2 is an exploded perspective view of the developing device, FIG. 3 is a cross-sectional view showing the internal structure of the developing device unit 40 of the developing device, and FIG. 4 includes the central shaft 52 of the vertical conveying screws 86, 91 of the black developing device. It is a longitudinal cross-sectional view by a surface.

In FIG. 2, the rotary developing device is provided with a developing device for each of four colors, for example, black, cyan, yellow and magenta, and rotates around a central axis (not shown) as a rotation center line in the printer body. A developing unit 40 having a substantially cylindrical outer periphery that is rotatably attached by
Four toner containers 4 corresponding to the developing devices one-to-one and containing black, yellow, magenta, and cyan toners, respectively.
1, 42, 43, 44 are attached and mounted so as to be substantially coaxial with the front side of the developing unit 40 in the central axis direction, and the developing unit 4 is provided around the central axis.
0, a toner container unit 45 that rotates together with the developing device unit 40 and the toner container unit 45.
In the state of carrying (hereinafter referred to as a revolver developing unit), a storage stand 46 slidable in the printer main body substantially in parallel with the central axis line, and a non-rotatably provided cover 47 for covering the rotation supply unit. .

The revolver developing unit is provided with a receiving table 46.
The disk-shaped front end wall 5 of the developing device unit 40 includes, for example, two supporting rollers 49 rotatably attached to the front supporting plate 48 of the developing device unit 40.
0, and a central axis 52 of the tip end taper protruding from the center of the disk-shaped rear end wall 51 of the developing device unit 40.
Is rotatably supported by a central shaft insertion hole 54 formed in the rear plate 53 of the main body, so that the rotation axis of the main body is substantially the same as the rotation axis of the photosensitive drum 1 in the printer main body as shown in FIG. They are positioned so as to be parallel to each other in the same horizontal plane and are rotatable.

Next, a mechanism for rotatably supporting the revolver developing unit will be described with reference to FIG. The housing base 46 has front and rear end portions fixed to the front support plate 48, the rear support plate 55, and both support plates, and has connecting rods 56, 5
And a side cover 59 reinforced with 7, 58. An insertion hole 60 into which the revolver developing unit can be inserted is formed in the front support plate 48, and in addition to the support roller 49, a motor 61 for driving a toner replenishing roller provided in the toner container unit 45 and the motor 61. A gear train driven by a motor 61 is attached. Also, the rear support plate 55
An intermediate plate 63 is attached to the connecting rods 56 and 57 in the vicinity thereof, and a positioning pin 63b that fits into a positioning hole 63a formed in the rear plate of the main body is provided on the intermediate plate 63 so as to project. A bracket 64 holding a rotary positioning roller 66 at a positioning pin portion between the intermediate plate 63 and the rear support plate 55.
The base end of is attached swingably. This bracket 64 attaches the roller 66 to the rear end wall 51 of the developing unit.
A spring 67 is biased in a direction to fit a total of four concave portions 65 formed for positioning each developing device at a predetermined position on the peripheral surface of the developing device.

The front plate 68 of the main body is formed with an insertion hole 69 or the like into which the storage stand 46 carrying the revolver developing unit can be inserted, and between the front plate 68 of the main body and the rear plate 53 of the main body. Upper and lower guides 70, 71 for slidably supporting the storage base 46 are hung. Guided portions 72 and 73 are provided at the upper end and side portions of the storage table side cover 59 as the receiving table portion guided by these guides 70 and 71, and the lower surface portion of the guided portion 73 on the side of these is provided. A guide pin groove 75 into which the guide pin 74 that is planted upward in the guide 71 is inserted is formed in the.

In the support mechanism of the revolver developing unit described above, when the storage base 46 is inserted into the main body, the tapered tip end of the positioning pin 63b protruding from the intermediate plate 63 is provided just before the completion of insertion of the storage base into the printer main body. , Body rear side plate 53
When the insertion is completed, the rear support plate 55 of the accommodating base 46 and the bracket 63 are inserted.
Positioning roller 6 held by the intermediate plate 64 via
Position 6 correctly in the body. Meanwhile, storage 46
In the pulled-out state, the rear end portion of the revolver developing unit supported by the rear side plate 53 of the accommodating base 46 has the tapered central axis 52 in the central axis insertion hole 54 immediately before the main body of the accommodating stand 46 is completely inserted. When the insertion is completed, the rear support plate 55 is completely lifted.
Emerge from. Then, the front support plate 48 of the storage table 46 is fixed to the front plate 68 of the main body with screws 76 or the like after the insertion of the storage table 46 into the main body is completed. As a result, the revolver developing unit has its front end supported by the support roller 49 of the housing stand front support plate 48 accurately positioned on the main body, and the central shaft 5
The rear end portion is rotatably positioned on the rear plate 53 of the main body via 2 and is rotatable.

Next, the developing unit 40 will be described with reference to FIGS. In FIG. 2, a revolver output gear 78 driven by a revolver rotation motor (not shown) such as a stepping motor is attached to the main body rear side plate 53 as a developing device unit rotating means for rotating the revolver developing unit. This engages a revolver input gear 79 having a diameter substantially the same as that of the rear end plate 51 fixed to the rear surface of the rear end plate of the developing device unit 40 by screwing or the like, and rotationally drives the revolver developing unit. There is. A development output gear 81 driven by a development driving motor (not shown) for driving a development roller and the like in the developing device unit 40 described later is also attached to the main body rear side plate 53.

As shown in FIG. 3, the developing device unit 4 is used.
Reference numeral 0 includes the above-mentioned substantially disc-shaped front and rear end plates and a partition wall provided between the front and rear end plates. This partition wall has a hollow cylindrical portion 82 into which a cylindrical black toner bottle containing black toner can be inserted, and a partition wall extending radially from the hollow cylindrical portion 82 so that the space around the hollow cylindrical portion 82 is substantially in the circumferential direction. Developing device casing portion 8 divided into four developing chambers of the same type
3, 83C, 83M, and 83Y. Each of these developing chambers contains a carrier as a developer and a two-component developer including toner of each color. In the illustrated example, the developing position facing the photoconductor drum is the developing chamber of the black developing device containing the black toner and the carrier, and in the counterclockwise order in the figure, the yellow developing device containing the yellow toner and the carrier is arranged. A developing chamber, a developing chamber of a magenta developing unit containing magenta toner and a carrier, and a developing chamber of a cyan developing unit containing cyan toner and a carrier.

Since the internal structures of the four developing chambers are exactly the same, the internal structure will be described below by taking the black developing chamber in the developing position in FIG. 3 as an example, and the internal structures of the other developing chambers. Are the same reference numerals as the corresponding reference numerals in the black developing chambers, but with the suffixes Y, M, and C added to distinguish the yellow, magenta, and cyan developing chambers from each other. To do.

In the black developing device at the developing position in the figure, an opening portion facing the photosensitive drum 1 is formed in the developing device casing portion 83, and a part is exposed through the opening portion in the developing chamber. A developing roller 84 is provided. Further, in the developing chamber, a doctor blade 85 which is carried by the developing roller 84 and regulates the amount of the developer conveyed to the portion facing the photoconductor drum 1, and the development which is regulated by the doctor blade 85 and pressed into the developing chamber An upper conveying screw 86 for conveying a part of the developer along the central axis direction from the front to the front and a guide 87 therefor, and a stirring paddle 88 for stirring the developer in the developing chamber are provided. The stirring paddle 88 has a plurality of developer discharge holes 89a across the width of the developing roller 84.
And a plurality of stirring plate portions 90 radially extending from the peripheral surface of the hollow cylindrical portion 89. The hollow cylindrical portion 89 is provided with the above-mentioned upper transfer along the central axis direction. A lower carrying screw 91 for carrying the developer in the opposite direction to the screw 86 is housed. The developer casing below the lower transport screw 91 is provided with a developer discharge port used as a discharge port for a deteriorated developer or an input port for unused developer (toner mixed) when a developer is replaced due to deterioration of development in the developing chamber. An outlet 92 is formed. The discharge port 92 is covered from the outside by a cap 93 attached with a screw 94. (Hereinafter, margin)

In FIG. 4, the upper and lower conveying screws 86,
The front end of 91 is outside the effective width region of the developing roller 84 (in the example shown, outside the front end wall 50 of the developing unit).
A drop portion 96 for extending the developer conveyed by the upper conveying screw 86 to the lower conveying screw 91 by its own weight is provided at this extending portion. The front end of the lower conveying screw 91 extends further to the front side than the drop portion 96, and extends to the communication chamber below the toner supply roller 97 provided corresponding to each developing chamber of the toner container unit 45. ing.

Then, the developer discharged from the developer discharge port of the hollow cylindrical portion 82 of the stirring paddle 88 to the developer pool at the lower portion of the developing chamber is so-called vertical stirring by the rotation of the stirring paddle 88 on the stirring plate portion. Further, the toner dropped on the lower conveying screw 91 in the communication chamber by the rotation of the replenishing roller 97 is dropped by the lower conveying screw 91 to the dropping portion 9
6 is carried into the developer dropped from the upper carrying screw 86 and mixed with each other, and the mixed developer enters the developing chamber through the developer discharge port, whereby the developer in the developing chamber is discharged. Increase the toner density of.

Incidentally, the rear end wall 51 of the developing device unit 40.
Part, specifically, the development output gear 8 on the main body side, behind the revolver input gear 79 fixedly mounted on the rear end wall 51.
A developing input gear on the revolver developing unit side (not shown) that meshes with 1 is rotatably provided, and the developing roller 84 and the shafts of the upper and lower conveying screws 86 and 91 protruding through the rear end wall 51 and the like. Gears are fixed at the ends. With these, each rotating body (developing roller, etc.) is driven via the developing input gear and the like.

The toner container unit 45 has a disk-shaped unit face plate 107 (see FIG. 4) as shown in FIG.
And a total of four toner receiving cases 110 mounted on the front surface of the face plate in a one-to-one correspondence with each developing device.
It has Y, M, C, and 110, and a toner replenishing roller 97 provided in each toner receiving case. The toner replenishing roller is located almost directly above the extending portion of the lower conveying screw 91 into the case when the corresponding developing chamber is located at the developing position. Is supported by.

Also, as shown in FIG. 4, the unit face plate 107 has a circular through hole through which a cylindrical black toner container can pass, formed in the central portion thereof, and the toner receiving case 110Y, M, C and 110 are attached by escaping the through holes. Further, the unit face plate 107 has a lower transport screw 91 extending from the developing chamber of each developing unit.
Through holes are also formed, and the lower conveying screws extend through the through holes into the toner receiving cases 110Y, M, C, 110 on the front surface of the unit face plate 108. .

The unit face plate 107 bears the shaft of the toner replenishing roller 97, and a gear is fixed to the end of the shaft which penetrates the face plate 107 and projects toward the developing unit 40. There is. Then, the unit face plate 107
On the surface of the developing unit side, a supply input gear for drive input (not shown) that meshes with the gear 197 is rotatably provided. Of the replenishment input gears provided for each toner replenishment roller, the replenishment input gear of the toner replenishment roller 97 in the case corresponding to the developing device at the developing position is provided on the front support plate 48 (see FIG. 2) of the accommodating base. The replenishment motor 61 (see FIG. 2) attached is meshed with a gear to be driven and rotated by the motor 61. The toner replenishment control is performed by the drive control of the replenishment motor 61.

As shown in FIG. 2, among the four toner receiving cases 110Y, M, C, 110, all three color toner receiving cases 110Y, M, C corresponding to each color developing device are all. It has a similar shape. That is, the toner replenishing roller 97 is enclosed when the inner extending portion of the lower conveying screw 91 and the toner replenishing roller 97 are surrounded and the corresponding developing chamber is located at the developing position.
Has a peripheral wall portion in which a toner receiving port is formed at a position above. Around this toner receiving port, color toner containing containers 42 to 44 of the same shape for each color containing color toner are attached by sliding in the direction of the rotation center line of the revolver developing unit with the toner discharge port facing downward. A toner container mounting portion is formed.

On the other hand, as shown in FIG. 2, the black toner receiving case 110 corresponding to the black developing device is arranged in the color toner receiving cases 109Y, M, C as shown in FIG.
It has a peripheral wall shape that is substantially the same as the overall peripheral wall shape of both with 2, 43 and 44 attached. Further, a toner receiving opening having a shape corresponding to the toner discharging opening of the black toner container 41 is formed at a portion of the peripheral wall portion having a shape similar to that of the color toner receiving case and facing the center line of the revolver developing unit. .

The black toner container 41 has a cylindrical shape,
A toner discharge port is formed on the peripheral wall portion at one end in the longitudinal direction, and a ridge portion for feeding toner is formed in a spiral shape on the inner peripheral surface portion from the other end portion to the toner discharge port side. With this spiral protrusion, the stored toner is sent from the rear end portion to the front end portion where the toner discharge port is formed by the rotation integrally with the revolver developing unit attached to the unit. Has become. Such a black toner container 41 has a rear end portion which is formed in the cover 47 shown in FIG.
0 into the hollow cylindrical portion 82 (see FIG. 3), and is set in a state in which the leading end is inserted to be substantially flush with the front surface of the front end wall of each case of the toner container unit 45. It

Here, in the printer of this embodiment, the front and rear end wall portions that support the developing roller 84Y and the doctor blade 85Y are separated from the other front and rear end wall portions as shown in the yellow developing device in FIG. The possible small end wall portion 104 is configured, and is fixed by screwing or the like in a state of being fitted to the other front and rear end wall portions. As a result, when cleaning the interior of the developing chamber or replacing parts, the developing roller 84Y and the doctor blade 85Y together with the small end wall portion 104.
It is easy to access to the developing room by removing.

Further, in this embodiment, as schematically shown in FIG. 5A, the tubular portion 200 is provided on the front side of the front end wall 50 of the revolver developing unit 40. Note that the tubular portion 200 is not shown in FIGS. 2 and 4. The tubular portion 200 may be formed integrally with the front end wall 50, or may be formed by separately attaching a tubular member to the front portion of the front end wall. Then, as shown in FIG. 5B, the outer peripheral surface of the tubular portion 200 is received by the support roller 49 attached to the support plate 48 at the front of the receiving stand by the shaft 49a.

Further, as shown in FIG. 5C and FIG. 6A which is a sectional view of the tubular portion 200, the tubular portion 200 includes:
Grooves 200a are formed as detected portions in a one-to-one correspondence with the respective positions of the developing devices of the revolver developing unit. As shown in FIG. 6B, the groove portion 200a has a different shape for each of the developing devices. That is, the black groove portion 200a corresponding to the black developing device is 1.5 mm.
, And the cyan groove portion 200aC corresponding to the cyan developing device is composed of two 1.5 mm grooves. In addition, the magenta groove portion 200aM corresponding to the magenta developing device has 1.5
The yellow groove portion 200aY corresponding to the yellow developing device includes four 1.5 mm grooves. Note that, for example, the yellow groove portion 200aY and the black groove portion 200a
The angles formed by the groove portions provided adjacent to each other as described above are all set to 90 degrees.

Further, as shown in FIG. 6A, the tubular portion 20
At a position between the cyan groove portion 200aC and the black groove portion 200a of 0, a home position provided for moving the rotary developing device to a home position which is a reference position of the rotary operation of the rotary developing device 4. A home position groove portion 200b is provided as a detection target portion. As shown in FIG. 6B, the home position groove portion 200b is 5 mm different from any shape of each groove portion 200a.
It consists of a groove.

Further, FIG. 5 (b) and FIG.
As shown in (a), an optical sensor 201 that functions as a detection unit and a home position detection unit that detects each groove 200a and the home position groove 200b.
Has been fixed. This optical sensor 201 is provided with each groove 2
00a and the home position groove portion 200b can be identified.

Further, the rotary developing device 4 in this embodiment is rotationally driven by a revolver rotating motor (not shown) including a stepping motor as described above, and the direction of the rotational driving is shown in FIG. In a), the direction is as shown by arrow C, and its rotation speed is 0.4 for 90 degree rotation.
It is a speed that requires seconds.

In the printer constructed as described above, when the rotary developing device 4 is not performing the desired rotation operation by using the configuration described above and the control means including the microprocessor (not shown). I.e.,
When the developing device other than the developing device that should originally be in the developing position is in the developing position and the latent image formed on the photosensitive drum 1 can be developed by the developing device other than the desired developing device, the image is displayed on the apparatus. Control is performed to stop the forming operation. Figure 7
3 is a flowchart showing the control performed by the microprocessor. Hereinafter, the control will be described with reference to FIG. 7.

When the rotary developing device 4 is rotating normally, for example, after the development of the latent image formed on the photosensitive drum 1 by the black developing device is completed, the rotary developing device 4 is moved to the position shown in FIG.
By rotating 90 degrees in the direction of arrow C shown in (a), the yellow developing device is moved to the developing position. That is, if the rotation-type developing device 4 rotates normally, the rotation-type developing device 4 starts rotating 9 times from the time when the rotation-type developing device 4 starts rotating.
The optical sensor 201 should detect the yellow groove portion 200aY when 0.4 second, which is the time of 0 ° rotation, has elapsed. On the other hand, if the rotary developing device 4 does not rotate normally for some reason, the optical sensor 201 does not detect the yellow groove portion 200aY at that time. Therefore, in this printer, as shown in FIG. 7, from the time when the developing operation by the black developing device ends and the rotary developing device 4 starts rotating, that is, the optical sensor 201 does not detect the black groove portion 200a. If the sensor does not detect the yellow groove portion 200aY after 0.4 seconds from the time point, it is considered that the rotary developing device 4 is not rotating normally, and the image forming operation is stopped. Further, 0.4 seconds after that point, the optical sensor 201 causes the yellow groove portion 2 to
When 00aY is detected, the yellow developing device is made to perform the developing operation.

In this embodiment, the rotary developing device 4 is used.
After 0.4 seconds from the start of rotation, it is determined whether or not the rotary developing device 4 is rotating normally depending on whether or not the optical sensor 201 detects the yellow groove portion 200aY. The determination may be made depending on whether or not the optical sensor 201 detects the yellow groove portion 200aY during the time. For example, when the yellow groove portion 200aY is not detected within 0.35 seconds to 0.45 seconds after the start of the rotation, it may be determined that the normal rotation is not performed. That is, the predetermined timing described in the claims may be a time including a certain width.

In the above description, the case where the yellow developing device is newly moved to the developing position has been described, but the same control is performed when another developing device is newly moved to the developing position.

Further, this printer has a rotary developing device 4
Display means may be provided for displaying the occurrence of an abnormality when the rotation of the. As the display means, for example, a liquid crystal display panel or the like that displays “abnormality occurred” when an abnormality occurs can be used. In this case, the display means is operated by the control means composed of the microprocessor.

The control of the apparatus when the rotation developing device 4 has an abnormal rotation has been described above. The abnormal rotation causes, for example, a printer or a printer during a printing operation to be struck by a vibration and the vibration is caused. Therefore, the stepping motor for driving the developing device 4 may be out of step. As described above, when there is no abnormality in the printer itself and the printer can be continuously used, it is desirable that the printer in the stopped state is ready for image formation by a simple operation by the operator. Therefore, this printer has an operation unit that is operated to put the printer in an image-forming operation stopped state into a print-ready state and a revolver rotation when the operation unit is operated while the printing operation is stopped. And a control means for controlling the motor for driving to move the rotary developing device 4 to the home position.

Here, a front cover (not shown) provided in the printer main body casing is used as the operation unit, and the operation unit is operated by opening the front cover. The microprocessor is used as the control means. When the front cover is opened in the printer in which the printing operation is stopped, the microprocessor starts the stepping motor to start the rotation of the rotary developing device 4 in the direction of arrow C shown in FIG. 6A. . Then, after the optical sensor 201 detects the home position groove 200b of the rotating rotary developing device 4, the stepping motor is stopped at the time when the time required for the rotary developing device 4 to rotate 20 degrees elapses. . By such control, the rotary developing device 4 is located at the home position where the black developing device is at the developing position. That is, by opening the front cover, the printer, which has been in the state where the developing operation is stopped, is ready to form an image.

On the other hand, if the rotation of the rotary developing device 4 is abnormally rotated, for example, foreign matter is caught between the revolver output gear and the revolver input gear 79 provided in the stepping motor for rotating the rotary developing device 4. This may be due to the reason that the rotational driving force is not transmitted well. In this way, if the printer is likely to be damaged if the printer is continuously used in the state where the rotation failure occurs, the printer should not be used until there is no fear of the damage. In addition, when the rotation abnormality of the rotary developing device 4 occurs due to this kind of cause, even if the printer is in a usable state, rotation failure often occurs repeatedly unless an operation such as removing foreign matter is performed. Therefore, this printer has a control means for making the printer inoperable and displaying a serviceman call when the rotation abnormality of the rotary developing device 4 is repeated a plurality of times. The microprocessor is used as the control means.

Further, in this printer, each groove 2
00a and the optical sensor 201 may be used for identifying each developing device and detecting the developing device position when switching the developing device to be used.
That is, the result of detection of each groove portion 200a by the optical sensor 201 may be used to control the rotary developing device 4 that moves each developing device to the developing position facing the latent image carrier.

Further, in this printer, each groove 2
00a and the optical sensor 201 may be used together with the home position groove portion 200b to identify each developing device and detect the developing device position when switching the developing device to be used. For example, as shown in FIG. 6A, the angle from the home position groove portion 200b to the magenta groove portion 200a is 230.
Since the optical sensor 201 detects the home position groove portion 200b, the rotary developing device 4 is rotated by 230 degrees to move the magenta developing device to the developing position. You can

Further, in this printer, the home position groove portion 200b as the home position detected portion is provided separately from the groove portion 200a as the detected portion provided corresponding to each developing device. Either of them can also be used as the home position detected portion. For example, the black groove portion 200a can also be used as a home position detected portion.

In this printer, the groove portion 200a is used as the detected portion, but instead of this, a bar code seal or the like may be attached and read by the sensor.

[0059]

According to the inventions of claims 1 to 5,
When the detecting unit does not detect the detected portion at a predetermined timing after the developing unit starts rotating, the control unit causes the developing unit rotating unit to rotate improperly and causes the developing unit other than the developing unit to be originally used to operate. The image forming operation is stopped assuming that the image forming apparatus is ready for image development. Therefore,
By using a developing device other than the one originally used for the development, formation of a defective image is prevented.

In particular, according to the second aspect of the invention, when the detecting means does not detect the detected portion at a predetermined timing after the developing device unit starts to rotate, the developing unit rotating means malfunctions and the original Considering that a developing device other than the developing device to be used is in a state of being used for developing the latent image, the control means operates the display means for displaying the occurrence of the abnormality. Therefore, the operator can detect the malfunction of the device before the defective image is formed.

Further, according to the third aspect of the invention, since the detecting means fixed to the main body of the apparatus detects the detected portion provided in the developing device unit in a one-to-one correspondence with each developing device, each developing device is detected. The exact position of the vessel is detected. Then, since the developing device unit rotating means is controlled based on the accurate detection result, each developing device is moved accurately to a desired position, and the formed image becomes good.

According to the fourth aspect of the present invention, when the operation section for making the apparatus main body capable of forming an image is operated in a state where the image forming operation is stopped, the home provided in the developing unit is operated. The home position detecting means, which fixes the position detected portion to the main body of the apparatus, detects and the control means controls the developing device unit rotating means using the detection result to move the developing device unit to the home position. Therefore, the image forming apparatus in the stopped state can be brought into a state in which image formation is possible with a simple operation.

Further, according to the invention of claim 5, in the case where the detecting means does not detect the detected portion at a predetermined timing after the developing unit starts rotating, the image is It is considered that the device body is in a state where it may be destroyed when it is formed, and the device body is made inoperable. For this reason, it is possible to prevent the device from being destroyed by image formation in this state.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a printer according to an embodiment.

FIG. 2 is an exploded perspective view of a rotary developing device of the printer.

FIG. 3 is a sectional view of a developing unit of the rotary developing device.

FIG. 4 is an explanatory view of a connection structure between a developing device and a toner container in the rotary developing device.

FIG. 5A is an explanatory diagram of a front end portion of the revolver developing unit. (B) And (c) is explanatory drawing of the same revolver development unit.

FIG. 6A is a cross-sectional view of a tubular portion provided at the front end portion.
(B) is explanatory drawing which shows the groove part with which the said tubular part was equipped.

FIG. 7 is a flowchart showing control of the printer according to the embodiment.

[Explanation of reference numerals] 1 photoconductor drum 4 rotary developing device 40 developing device unit 41 black toner container 42 yellow toner container 43 magenta toner container 44 cyan toner container 45 toner container unit 49 supporting roller 50 front end wall 110 Toner receiving case 200 Tubular part 200a Groove 200b Home position groove 201 Optical sensor

Claims (5)

[Claims] 1. A developing device unit having a plurality of developing devices arranged around a rotation center line, and the developing device unit for moving an arbitrary developing device to a developing position facing a latent image carrier. Developing unit rotation means for rotating about the rotation center line, a detected portion provided in the developing device unit in a one-to-one correspondence with each position of the plurality of developing devices, and fixed to the apparatus main body Detecting means for detecting the detected portion, and control means for stopping the image forming operation when the detecting means does not detect the detected portion at a predetermined timing after the developing device unit starts rotating. When,
An image forming apparatus comprising: 2. A display means for displaying the occurrence of an abnormality when an abnormality occurs in the image forming operation, wherein the control means causes the detection means to operate at a predetermined timing after the developing unit starts rotating. The image forming apparatus according to claim 1, wherein the display means is operated when the detected portion is not detected. 3. The image forming apparatus according to claim 1, wherein the detected portion and the detecting means are used to identify the plurality of developing devices. 4. An operation unit operated to bring an apparatus main body in a state in which an image forming operation is stopped into an image formable state, and the developing unit are used as a reference for a rotating operation of the developing unit. A home position detected portion provided in the developing device unit for moving to the home position which is a position, home position detection means for detecting the home position detected portion fixed to the apparatus main body, and an image. Control means for controlling the developing device unit rotating means to position the developing device unit to the home position when the operating portion is operated while the forming operation is stopped. The image forming apparatus according to claim 1. 5. The apparatus main body when the control means continuously detects a plurality of times in which the detecting means does not detect the detected portion at a predetermined timing after the developing device unit starts rotating. The image forming apparatus according to claim 1, wherein the image forming apparatus is in an inoperable state.