JPH07117783B2 - Rotary developing device for image forming apparatus - Google Patents

Description

Description: TECHNICAL FIELD The present invention includes a developing unit that has a plurality of developing devices and is rotatably supported so as to face a latent image carrier. It has a developer transport member for transporting the developer in the chamber to a developing area where the electrostatic latent image on the latent image carrier is visualized, and each developer transport member causes a latent image by the rotation of the developing unit. The present invention relates to a rotary developing device of a development forming device which is positioned at a developing position facing a carrier and performs a developing operation.

2. Description of the Related Art A rotary developing device of the above type used in an image forming apparatus such as a copying machine or a printer brings a developer carrying member of a predetermined developing device to a developing position by rotating the developing unit, and the developer carrying member It is rotationally driven to perform a developing operation.

In the conventional developing device of this type, a predetermined developer conveying member is brought to the developing position, and after properly positioning it, the developing conveying member is rotated to start the developing operation. However, according to this configuration, when the developing operation is started immediately after the developer transport member is positioned at the developing position, the developer contained in the developer chamber of the developing device is still insufficient at the start of the developing operation. Because it is not charged
Toner may adhere to the background portion of the latent image carrier, and the obtained visible image may be stained to deteriorate the image quality.

To eliminate this problem, after the developer carrying member is positioned at the developing position and before the actual developing operation is started, the developer carrying member is rotated, thereby carrying the developer and Should be sufficiently charged, and then the actual developing operation should be started. By doing so, the electrostatic latent image can be visualized with the sufficiently charged toner, and therefore the occurrence of background stain can be suppressed.

However, if the above-described configuration is adopted, the developer transport member must be rotated before the actual developing operation is started, which requires a long time in order to obtain a visible image and can be shortened in a short time. It becomes impossible to obtain a visible image. Loss time is generated only for the time required to charge the developer, which impedes the speeding up of the image forming apparatus.

OBJECT It is an object of the present invention to provide a rotary developing device of the type described at the beginning which can eliminate the above-mentioned loss time or shorten it to an extremely short one, and can cope with speeding up of an image forming apparatus. .

To achieve the above object, the present invention provides a rotary developing device of the type described at the beginning, when the developing unit rotates and the developer transport member of each developing device is positioned at the developing position, A configuration is proposed in which a drive control unit that controls the rotation of each developer transport member is provided so that the developer transport member starts to rotate immediately before reaching the developing position.

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

FIG. 1 shows a rotary developing device of a copying machine, which is an example of an image forming apparatus, and this developing device has a developing unit 1 supported by a copying machine main body 2. Such developing unit 1
Is a plurality of three developing devices incorporated in the illustrated example.
It has 3,3R, 3B. As shown in FIG. 1, the developing unit 1 loaded in the main body 2 of the copying machine is rotatably supported so as to face the latent image carrier, in this example, the photosensitive drum 11. The developer chambers 4, 4R, 4B of the developing units 3, 3R, 3B are three partition walls of the casing member 5 made of a non-magnetic material such as aluminum.
6,6R, 6B and two end walls 7,8 (third end fixed to both ends)
(See FIG. 4 and FIG. 4).

A latent image carrier composed of a photosensitive belt may be used instead of the photosensitive drum 11, and a latent image carrier composed of a dielectric belt or a dielectric drum may be used depending on the model of the image forming apparatus.

Each developer chamber 4, 4R, 4B has different color developer 9, 9R, 9B
And each of these developers is black, red, and blue in this example. In each developer chamber, cyan,
The yellow and magenta toner developers may be contained to form a full-color image, or the developer chambers of the same color may be contained and selectively used. It is also possible. Although a one-component developer containing no carrier can be used as the developer, a two-component developer containing a carrier and a toner, at least a part of which is a magnetic material, is used in the example of the figure. Is used.

Although the first to third developing units 3, 3R, 3B are arranged radially with respect to the rotation center O of the developing unit 1, all of the structures are the same, and therefore, in the following description, mainly the first
The structure of the developing device 3 is clarified, and with respect to each part of the other developing devices 3R and 3B, the reference numerals assigned to the respective elements of the first developing device 3 are denoted by R and B, and the duplicate description thereof is omitted. To do.

The developing unit 1 is rotatably supported around its rotation center O, and each developing device (more accurately, a developing roller described later) rotates to a predetermined developing position to perform a developing operation.
FIG. 1 shows a state in which the first developing device 3 occupies the developing position.

In FIG. 1, a developer conveying member provided in the first developing device 3, in the example shown, the developing roller 10 is partially exposed from an opening formed by two partition walls 6 and 6R (see also FIG. 3). reference),
The developing roller 10 occupies a predetermined developing position with respect to the photosensitive drum 11 rotatably supported by the copying machine main body 2. At that time, the developing roller 10 is positioned parallel to the photosensitive drum 11 with a predetermined minute gap.

As can be seen from FIG. 2, both supporting shafts 12 and 13 of the developing roller 10 are rotatably supported by both end walls 7 and 8 of the developing unit 1, respectively, and are located on the inner side (left side in FIG. 2) of the copying machine main body 2. One spindle
Reference numeral 13 penetrates the end wall 8 and a developing gear 14 is fixed to the tip portion thereof.

An impeller 16 having a large number of blades 15 is provided inside the developer chamber 4.
And the impeller 16 is driven to rotate in the counterclockwise direction in FIG. As a result, the developer in the developer chamber 4
That is, the toner and the carrier are agitated and supplied to the developing roller 10, and the toner and the carrier are agitated to frictionally charge the toner to a predetermined polarity.

Inside the developing roller 10, a magnet 21 having a magnetic pole composed of an S pole and an N pole is fixedly arranged in the casing member 5 of the developing unit 1 as shown by S and N in FIG. As a result, when the developing roller 10 is rotationally driven in the counterclockwise direction in FIG. 1 via the above-described developing gear 14, the magnetic developer 9 supplied to the developing roller 10 is moved by the magnetic force of the magnet 21 to cause the magnetic force of the developing roller 10 to move. It is carried on the surface and conveyed counterclockwise. The conveyed developer is scraped by a doctor blade 22 fixed to the casing member 5, and a predetermined amount of the developer that has passed through the blade 22 is sent to the photosensitive drum 11 with its layer thickness regulated.

On the other hand, the photosensitive drum 11 is driven to rotate clockwise in FIG. 1, and an electrostatic latent image corresponding to an original (not shown) image is formed on its surface by a charging / exposure means (not shown). There is. When this latent image reaches the opposing developing area D between the photoconductor drum 11 and the developing roller 10, the charged toner in the developer also conveyed to this area D is electrostatically transferred to the electrostatic latent image to form the latent image. Is visualized. The visible image is transferred onto a transfer paper (not shown) by a transfer device (not shown), and the transferred visible image is fixed by a fixing device (not shown). The developer that has passed through the developing area D is returned to the inside of the developer chamber 4 again, mixed with other developers in this chamber, and used again.

As shown in FIGS. 2 to 4, a positioning pin is provided on the rotation center O of the unit 1 on the rear end wall 8 of the developing unit 1.
78 is projected, and this is a bearing on the side plate 79 on the back side of the copying machine body.
It is rotatably supported via 81, and the front end wall 7 of the unit 1 is rotatably supported by the support arm 70 of the unit carrier 62, so that the entire unit 1 is provided in the main body of the copying machine. It is positioned at the position of and is rotatably supported. By pulling out the unit carrier 62 toward the front side as shown in FIG. 3, the developing unit can be taken out of the copying machine main body while being supported by the carrier 62.

When a visible image is formed by the red or blue developer contained in the second or third developing device 3R, 3B, the developing unit 1 set at a predetermined position in the copying machine main body is used as a clock in FIG. It is rotationally driven in the direction to bring the developing roller 10R or 10B of the second or third developing device 3R, 3B to the developing position where the developing roller 10 of the first developing device 3 shown in FIG.

In this way, each of the developing units 3, 3R, 3B has a corresponding developer chamber 4, 4R, 4B.
Has developing rollers 10, 10R, 10B for conveying the developers 9, 9R, 9B of No. 1 to the developing area D for visualizing the electrostatic latent image of the photosensitive drum 11, and by the rotation of the developing unit 1. Each developing roller 10, 10R, 10B is positioned at a developing position facing the photoconductor drum 11 to perform a developing operation.

For the purpose of rotating the developing unit 1 set in the main body of the copying machine, a drive motor 88 is supported by the unit carrier 62 as clearly shown in FIG. 4 and schematically shown in FIG. The gear 89 supported by the unit carrier 62 meshes with the unit gear 90 formed on the peripheral surface of the rear end wall 8 of the developing unit 1.

When the operator selects and depresses a color conversion key switch (not shown) with the developing unit 1 pushed into the copying machine main body 2 and set, the drive motor 88 is actuated and an intermediary between the motor 88 and the gear 89 is provided. The mounted clutch is turned on, and the developing unit 1 moves around the rotation center O to the first position.
It rotates clockwise in the figures and FIG. As a result, the selected developing device, for example, the developing roller 10 of the first developing device 3 as shown in FIGS. 1 and 5, reaches the developing position, where the motor 88 stops operating or the clutch Is turned off, the developing unit 1 is stopped, and the developing operation described above is performed.

The developing roller brought to the developing position, for example, the developing roller 10 shown in FIGS. 1 and 5 rotates counterclockwise as described above, and this drive is shown in FIGS. 2 and 5. As described above, the rotation of the drive gear 111 rotatably supported by the support shaft 110 of the photosensitive drum 11 is transmitted to the gear 14 of the developing roller 10 brought to the developing position. The developing unit 1 is rotated by the drive motor 88 so that another developing device 3
Even when the R and 3B developing rollers 10R and 10B are brought to the developing position, these developing gears 14R and 14B are likewise engaged with the drive gear 111 and rotationally driven.

As shown in FIG. 5, the centers of the developing gears 14, 14R, 14B are arranged at equal intervals around the rotation center O of the developing unit 1 and at the same distance from the centers. The rotation center O ′ of the developing gear (the same applies to other developing gears) at the developing position, the rotation center O of the developing unit 1, and the rotation center O ″ of the stationary drive gear 111 are substantially on the same straight line l. When the developing rollers 14, 14R, 14B revolve around the center O due to the rotation of the developing unit 1 around the center O, these gears do not interfere with the drive gear 111, The drive gear 111 may be supported on an appropriate part other than the developing unit 1, and may be supported on the main body of the copying machine other than the support shaft of the photoconductor drum 11 or the carrier unit 62. You can also do it.

By the way, for example, until the predetermined developing roller 10 is positioned at the developing position, it is not rotated about its rotation center O ', but after the developing roller 10 reaches the developing position, it is rotated (rotated) immediately. If you start the developing operation on
As described above, the developing operation is performed in a state where the toner and the carrier of the developer housed in the developer chamber 4 of the developing device 3 are not sufficiently charged yet, and thereby the photosensitive operation is performed. The visible image formed on the body drum 11 suffers from background stain, and the image quality thereof is significantly deteriorated. Therefore, after the developing roller 10 is positioned at the developing position, the developing roller 10 is rotationally driven for a predetermined time to charge the developer,
If the developing operation is executed after that, a loss time occurs and it is impossible to cope with the speeding up of the copying machine.

Therefore, in the image forming apparatus of this example, the developing unit 1 rotates to rotate the developing roller 10, 10R, or 3B of the developing device 3, 3R, or 3B.
When the 10B is positioned at the developing position, drive control means for controlling the rotation of the developing rollers 10, 10R, 10B is provided so that the developing roller starts rotating immediately before reaching the developing position. .

In the present example, a certain developing gear 14, 14R or 14B is the drive gear 111.
The drive gear 111 has already started to rotate in the clockwise direction (the direction of arrow R) in FIG. 5 by the time immediately before the start of meshing with. That is, the developing gear is the arrow Q
By revolving in the direction, when any one of the gears engages with the drive gear 111, the gear 111 is already rotated. As a result, when the developing unit 1 rotates and the developing roller 10, 10R or 10B of each developing device 3, 3R, 3B is positioned at the developing position, the developing roller starts rotating immediately before reaching the developing position. To do. As described above, in this example, the drive gear 111 constitutes the above-mentioned drive control means.

According to the above configuration, for example, before the developing roller 10 is positioned at the developing position, the rotation of the developing roller 10 causes the developer 9 contained in the developer chamber 4 of the developing device 3 to be agitated and the toner And the carrier is charged. Therefore, even if the developing operation is started immediately after the developing roller 10 is positioned at the developing position, a visible image without background stain can be formed on the photosensitive drum 11. Suppressing loss time,
Moreover, a high-quality visible image can be obtained.

Further, when the above configuration is adopted, when the developing gear, for example, the gear 14 of the first developing device 3 starts to engage with the drive gear 111,
Even if the tooth tips of the two gears 14 and 111 abut against each other as shown in FIG. 10, the rotation of the drive gear 111 causes the two gears to release the abutment of the tooth tips into a predetermined correct meshing state. As a result, it is possible to prevent inconveniences such as the gear stopping and the gear teeth being cut off. Drive gear 111
Since the rotation start time of the above may start until any of the developing gears starts to engage with the gear 111, the operator presses a color conversion key switch (not shown) in order to change the developing device to be used. The drive gear 111 may be started to rotate at the same time when the developing unit 1 is started to rotate, and the drive gear 111 is always started when the power of the copying machine is on.
You may keep spinning 111.

Further, in the illustrated example, the direction R in which the drive gear 111 rotates when engaging with the developing gear is the clockwise direction in FIG. 5, and the direction in which the developing gear revolves around the center O, that is, the rotation of the developing unit 1. The direction is also clockwise as indicated by arrow Q. That is, when the revolving developing gear and the drive gear 111 are engaged with each other, the moving directions of the developing gear and the driving gear 111 (arrow Q direction and R direction) in the engaging area are opposite to each other, and the engaging portions of the both are in contact with each other. The rotation direction of the developing unit 1 is set so that the relative speed increases. Therefore, the abutment of the tooth tips of both gears is released more accurately and promptly, the both gears are immediately brought into the proper meshing state, and it is possible to more effectively eliminate the above-mentioned trouble.

When one of the developing gears is engaged with the drive gear 111 by its revolution, when the gear 111 is rotated in the counterclockwise direction (reverse direction of R) in FIG. It is preferable to rotate the developing unit 1 in the counterclockwise direction (opposite to Q) in FIG. 5 so that the relative speed of the gears becomes large. Further, as will be described later, it is possible to rotate the developing gear which is going to engage with the drive gear 111 while revolving, but when rotating this gear in the counterclockwise direction, the developing unit 1 should be moved as shown in FIG. If the developing unit 1 is rotated counterclockwise and the developing gear 1 is rotated clockwise,
The relative speed in the engagement region between the drive gear 111 and the developing gear can be increased.

In addition, the drive gear 111 that constitutes an example of the drive control means described above.
May be disposed inside the developing gear located at the developing position as shown in FIG. 11, and in this case as well, each of the configurations described above can be adopted. At this time, when the developing roller 14 is rotated counterclockwise during the developing operation, the drive gear 111
Rotation direction is clockwise, in this case, the developing unit 1 is rotated counterclockwise, and each developing gear is revolved in this direction.
On the other hand, if a large relative velocity is generated in the engagement area between the two, the same effect as described above can be obtained.

In this way, depending on the direction in which the revolving developing gear and the drive gear 111 rotate immediately before they are engaged, depending on the direction in which the gear 111 or the developing gear rotates, they can obtain a large relative speed in their engaging regions. It is desirable to set the rotation direction of the developing unit 1.

The developing gear to be engaged with the driving gear 111, not the driving gear 111, is rotated by an appropriate driving means other than the driving gear 111 at a suitable time until just before they are engaged with each other.
As described above, it may be configured so as to be rotationally driven (rotated) around the axis. In this case, this appropriate drive means constitutes the drive control means described above. Further, both the developing gear and the drive gear 111 are both rotated about their respective rotation centers O ′ and O ″.
The rotation of the developing roller may be started immediately before the developing roller reaches the developing position, and the relative speed at which the developing gear and the drive gear 111 are engaged may be increased. Well, in this case, drive gear 111
And appropriate drive means other than this constitute the drive control means described above.

Next, a more specific configuration example in which the above-described idea is incorporated, and each developing roller 10, 10R, 10B of the developing unit 1 is positioned at a predetermined position, and which developing roller of which developing device 3, 3A or 3B is A specific configuration example for detecting whether it has been brought to the developing position will be described.

In FIG. 5, with respect to the rotation direction of the developing unit 1 (direction of arrow Q), a portion upstream of the developing area D and in the circumferential direction around the developing unit 1 is, for example, a developing roller. The same number of sensors P1, P2, P3 are arranged side by side and fixedly arranged in the copying machine main body 2.

On the other hand, the developing unit 1 has a different circumferential length,
Light-shielding plates F1, F2, and F3 that are arranged at equal intervals in the circumferential direction are integrally provided.

The developing unit rotates in the direction of arrow Q, and the rotation center O of the developing unit, the rotation center O ′ of the developing roller 10, the rotation center of the photosensitive drum 11, that is, the rotation center O ″ of the drive gear 111.
When and match with the straight line l, the light shielding plate F2 turns off the sensors P2 and P3 of the sensors P1 to P3.

Here, for example, a well-known photocoupler is used as each of the sensors P1 to P3, and the one viewed from the direction of the arrow Y in FIG. 5 is shown in FIG. In this figure, the light receiving element 113 is turned off by blocking the light from the light emitting element 112 by the light shielding plate F2. That is, in the case of FIG. 5, only the sensors of P3 and P2 are turned off.

The developing gear 14R meshes with the drive gear 111, and the developing roller 10R
When is placed at the developing position, the light shielding plate F1 turns off only the sensor P3.

Further, when the developing gear 14B meshes with the drive gear 111 and the developing roller 10B is placed at the developing position, the light shielding plate F3 turns off all the sensors.

The above relationships are summarized in the table below.

As can be understood from Table 1, since the combination of ON / OFF is different for each developing roller, it is possible to determine which developing roller is at the developing position. That is, each developing roller 10, 10 of the developing device designated by the color conversion key switch
It can be detected that R and 10B have reached a predetermined developing position.

Light-shielding plates F1, F2, F3, etc. rotate integrally with the developing unit to turn each sensor on and off, and the combination of this on and off changes each time each developing roller is placed in the developing position. It constitutes an example of a member. Note that depending on the configuration of the detected member and the type of sensor, the ON / OFF of Table 1 shown above can be reversed. For example, as shown in Table 2 below.

By the way, in Table 1 shown above, the sensor P3 is off in any of the developing rollers.
That is, the sensor P3 is always turned off regardless of which developing roller is placed at the developing position. On the other hand, in the case of Table 2, it is always turned on.

When the sensor P3 is turned off (in the case of Table 1) or turned on (in the case of Table 2), it is possible to detect that the unspecified developing roller is placed at the developing position.

FIG. 7 is a diagram for explaining a process until the developing gear 14 meshes with the drive gear 111, and a line L is a revolution locus around O of the rotation center O ′ of each developing gear 14.

By turning on the color conversion key switch described above, the developing unit 1
When the rotation center O ′ of the developing gear 14 reaches the point S in the figure, the gear position is such that the addendum circles of the gear 14 and the drive gear 111 are in contact with each other. After that, the gear 14 usually comes on the straight line l and the teeth are regularly meshed with each other.

Here, in FIG. 7, the angle formed by O′O and SO is θ
And In this case, if the angle A formed by the line connecting the most downstream sensors P3 and O with respect to the unit rotation direction and the line connecting the most upstream sensors P1 and O is equal to the angle θ (∠O′OS), When the gear 14 reaches the point S, the shading plate F2 (Fig. 5)
When the sensor 14 reaches the sensor P1 and the gear 14 reaches the developing position, the light shielding plate F2 reaches the sensor P3. In this embodiment, the angle A is slightly smaller than the angle θ (∠O'OS). The most upstream sensor P1 was installed at a large angle (θ + α). Immediately before any of the developing gears meshes with the driving gear 111, one of the light shielding plates F1 to F3 turns on or off the sensor P1, and the driving gear 111 is rotated by this signal, and the developing roller of the selected developing device is rotated. When it reaches the developing position, it is detected by the sensors P1 to P3 as described above, and the drive motor 88 or the clutch thereof is turned off as described above by the developing device positioning signal. FIG. 9 is a flow chart showing a series of these operations. Drive gear 11 like this
By setting the rotation start timing of 1 immediately before the developing gear engages with this, the developer of the developing device to which the developing roller belongs is agitated before the predetermined developing roller is positioned at the developing position. , It can be charged. Moreover, the developing gear of the developing roller and the drive gear 111
You can skillfully engage each other.

Further, as shown in FIGS. 4 and 8, on the rear end side 8 of the developing unit 1, a positioning groove-shaped positioning cam is provided for each developing device.
114, 114R, 114B are formed, and a lever 116 urged toward the end wall 8 by a tension spring 115 is pivotally supported on the rear side support arm 71 of the carrier unit 62. The stopper is rotatably supported, and the roller 117 selectively engages the three cams 114, 114R, 114B to exert a braking force on the developing unit 1. By this engagement, each developing roller is Advantageously, 10,10R, 10 are arranged to be positioned at the development position. 116a is a stopper for the roller 117.

According to the present invention, each developing device is integrally configured by one casing member as in the illustrated rotary developing device.
Not limited to the rotary developing device that constitutes the developing unit as a whole, the rotary developing device in which each developing device has a separate casing member and these are assembled to the unit rotating body to configure the developing unit. Needless to say, the present invention can also be applied to a rotary developing device in an image forming apparatus such as a multicolor printer other than a copying machine.

When the developer transport member is composed of a developer transport belt,
Alternatively, the present invention can be applied to a case where the belt or the roller includes a magnet roller or the like rotatably installed therein, and in these cases, when the developing gear described above is provided, a gear attached to the developer transport belt, or The gear attached to the magnet roller serves as the developing gear.

Effect According to the present invention, when the developer transport member of the developing device is positioned at the developing position by the rotation of the developing unit, the developer transport member starts rotating immediately before the positioning,
This allows the developer to be charged. Therefore, it is possible to form a high-quality visible image without rotating the developer transport member for a long time in order to charge the developer after the developer transport member is positioned at the developing position. It is possible to suppress the occurrence of loss time and obtain a high quality image.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical cross-sectional view of the developing device when the developing unit is set in the copying machine main body, and FIG. 2 is III-II in FIG.
A cross-sectional view taken along the line I, FIG. 3 is a perspective view showing a state where the storage unit is pulled out from the copying machine main body, and the developing unit is removed from the storage unit. FIG. 4 is a state in which the developing unit is removed. FIG. 5 is a perspective view of the above-described element when viewed from the back side, FIG. 5 is an explanatory view for explaining the rotation operation of the developing unit, FIG. 6 is a view seen in the direction of the arrow Y in FIG. 5, and FIG. FIG. 8 is an explanatory view showing a positional relationship among gears, drive gears, sensors, etc., FIG. 8 is an explanatory view showing a cam and a stop roller as seen from the front side, and FIG. 9 is a flow showing an operation example when a developing device is selected. FIG. 10 and FIG. 10 are explanatory diagrams for explaining the abutment of the tooth tips, and FIG. 11 is an explanatory diagram showing another arrangement of the gears. 1 ... Development unit, 3,3R, 3B ... Developer 4,4R, 4B ... Developer chamber, 9,9R, 9B ... Developer D ... Development area

Claims (1)

[Claims] 1. A developing unit having a plurality of developing devices and rotatably supported so as to face a latent image carrier, each developing device containing a developer in a developer chamber and a latent image. It has a developer transport member for transporting the electrostatic latent image of the carrier to a developing area for visualizing the electrostatic latent image, and each developer transport member is moved to a developing position facing the latent image carrier by the rotation of the developing unit. In a rotary type developing device of a development forming device that is positioned and performs a developing operation, when the developing unit rotates and the developer transport member of each developing device is positioned at the developing position, the developer transport member moves to the developing position. The rotary developing device is provided with drive control means for controlling the rotation of each developer carrying member so as to start the rotation immediately before reaching.