JPH1173012A - Rotary development device of image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To cope with the high-speed operation of an image forming device by controlling the rotation of each developer carrying member so that the rotation is started immediately before the developer carrying member reaches the development position, to shorten the time loss. SOLUTION: An image forming device is provided with a drive control means to control the rotation of development rollers 10, 10R, 10B so that the rotation is started immediately before the respective development rollers reach the development position when a development unit 1 is rotated and the development rollers 10, 10R, 10B of development devices 3, 3R, 3B are positioned at the development position. Before the development roller 10, for example, is positioned to the development position, the developer 9 stored in a development chamber 4 of the development device 3 is stirred by the rotation of the development roller 10, and the toner and the carrier are charged. Thus, even when the development action is started immediately after the development roller 10 is positioned to the development position, a visible image free from any background fouling can be formed on a photoreceptor drum 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises a developing unit having a plurality of developing units and rotatably supported opposite to a latent image carrier. A developer carrying member for carrying the developer to a developing area for visualizing the electrostatic latent image on the latent image carrier, wherein each developer carrying member is moved by the rotation of the developing unit. The present invention relates to a rotary developing device of an image forming apparatus which performs a developing operation while being positioned at a developing position facing the developing device.

[0002]

2. Description of the Related Art In a rotary developing device of the above type used for an image forming apparatus such as a copying machine or a printer, a developer conveying member of a predetermined developing device is brought to a developing position by rotation of a developing unit, and the developer The developing operation is performed by rotating the transport member.

In this type of conventional developing device, a predetermined developer conveying member is brought to a developing position, and after properly positioning the developer conveying member, the developer conveying member is rotated to start a developing operation. However, according to this configuration,
When the developing operation is started immediately after the developer conveying member is positioned at the developing position, the developer contained in the developer chamber of the developing device is not sufficiently charged at the start of the developing operation. The toner adheres to the background of the image carrier,
There is a risk that the obtained visible image will be stained with the ground and its image quality will be degraded.

In order to eliminate this problem, after the developer transport member is positioned at the developing position, and before the actual developing operation is started, the developer transport member is rotated, and the developer is transported. The developer may be sufficiently charged, and then the actual developing operation may be started. With this configuration, the electrostatic latent image can be visualized by the sufficiently charged toner, so that the occurrence of background contamination can be suppressed.

However, if the above-described configuration is adopted, the developer conveying member must be rotated before the actual developing operation is started, so that it takes a long time to obtain a visible image. A visible image cannot be obtained in a short time. Loss time occurs only for the time required to charge the developer, which hinders speeding up of the image forming apparatus.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to eliminate the above-mentioned loss time, or to shorten it to an extremely short one, and to cope with a high-speed image forming apparatus. An object of the present invention is to provide a developing device.

[0007]

According to the present invention, in order to achieve the above object, in a rotary developing device of the type described at the outset, a developing unit is rotated and a developer conveying member of each developing device is moved to the developing position. A configuration is proposed in which drive control means for controlling the rotation of each developer conveying member is provided so that the developer conveying member starts rotating immediately before reaching the developing position when the developer conveying member is positioned.

[0008]

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

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

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

In each of the developer chambers 4, 4R, and 4B, developers 9, 9R, and 9B having different colors are accommodated. In this embodiment, these developers are assumed to be black, red, and blue, respectively. Each developer chamber may contain cyan, yellow, and magenta toner developers to form a full-color image, or each developer chamber may contain the same color developer and select these. It is also possible to configure so that it may be used in general. Although a one-component developer containing no carrier can be used as the developer, in the example shown in the figure, a two-component developer having a carrier and a toner, at least a part of which is a magnetic developer Shall be 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, since their structures are all the same, the following description will be made. The structure of the first developing device 3 is mainly clarified. For the other portions of the other developing devices 3R and 3B, the same reference numerals are given to the components of the first developing device 3 and R and B are added to overlap. Description is omitted.

The developing unit 1 is rotatably supported around its rotation center O, and each developing unit (more precisely, 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 unit 3, in the illustrated example, a developing roller 10 partially exposes from an opening formed by two partition walls 6, 6R (FIG. 3). ), And the developing roller 10
Occupies a predetermined developing position with respect to the photoreceptor drum 11 rotatably supported at a predetermined position. At this 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 support shafts 12 and 13 of the developing roller 10 are rotatably supported on both end walls 7 and 8 of the developing unit 1, respectively, and are located on the back side of the copying machine main body 2 (left side in FIG. 2). One of the support shafts 13 penetrates the end wall 8, and a developing gear 14 is fixed to a tip end thereof.

An impeller 16 having a number of blades 15 is arranged inside the developer chamber 4, and the impeller 16 is driven to rotate counterclockwise in FIG. Thus, the developer in the developer chamber 4, that is, the toner and the carrier are supplied to the developing roller 10 while being stirred, and the toner is frictionally charged to a predetermined polarity by the stirring of the toner and the carrier.

In FIG. 1, S, N
A magnet 21 having a magnetic pole composed of an S pole and an N pole is fixedly disposed on the casing member 5 of the developing unit 1 as indicated by the symbol. As a result, when the developing roller 10 is driven to rotate in the counterclockwise direction in FIG. 1 via the developing gear 14, the magnetic developer 9 supplied to the developing roller 10
The toner is carried on the surface of the developing roller 10 by the magnetic force of 1 and is 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 passing 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). Have been. When this latent image reaches the developing area D where the photosensitive drum 11 and the developing roller 10 are opposed to each other, the charged toner in the developer also conveyed to this area D electrostatically transfers to the electrostatic latent image, and Is visualized. This visible image is transferred to a transfer paper (not shown) by a transfer unit (not shown), and the transferred visible image is fixed by a fixing device (not shown). The developer that has passed through the development area D is returned to the inside of the developer chamber 4 again, mixed with another developer in this chamber, and used again.

As shown in FIGS. 2 to 4, the developing unit 1
A positioning pin 78 protrudes from the rear end wall 8 above the rotation center O of the unit 1 and is rotatably supported by a rear side plate 79 of the copying machine main body via a bearing 81. The end wall 7 on the front side of the unit 1 is rotatably supported by the support arm 70 of the unit carrier 62, whereby the entire unit 1 is positioned at a predetermined position in the copying machine main body and rotatably supported. . The unit carrier 62 is shown in FIG.
By pulling out the developing unit as described above, 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 with the red or blue developer stored in the second or third developing device 3R, 3B, the developing unit 1 set at a predetermined position in the main body of the copier shown in FIG. Is rotated clockwise 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. .

As described above, each of the developing devices 3, 3R, 3B
Developers 9, 9R, 9B in developer chambers 4, 4R, 4B
To the developing area D for visualizing the electrostatic latent image on the photosensitive drum 11, and each developing roller 1 is rotated by the rotation of the developing unit 1.
The developing operation is performed with the 0, 10R, and 10B positioned at the developing position facing the photosensitive drum 11.

A drive motor 88 is supported on the unit carrier 62 as shown in FIG. 4 and schematically shown in FIG. 5 for the purpose of rotating the developing unit 1 set in the copying machine main body. Driving unit carrier 62
Gear 89 meshed with a unit gear 90 formed on the peripheral surface of the rear end wall 8 of the developing unit 1.

When the operator selects and presses a color conversion key switch (not shown) in a state where the developing unit 1 is pushed into the copying machine main body 2 and set, the drive motor 88 is operated and the motor 88 and the gear 89 are operated. The clutch interposed is turned on, and the developing unit 1 rotates around its rotation center O in the clockwise direction in FIGS. As a result, the selected developing device, for example, the developing roller 10 of the first developing device 3 reaches the developing position as shown in FIGS. 1 and 5, where the motor 88 stops operating or the clutch is turned off. Then, the developing unit 1 stops 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 in the counterclockwise direction as described above, and this driving is performed as shown in FIGS. 2 and 5. The rotation of the driving gear 111 rotatably supported on 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 to rotate the developing rollers 10R, 10R of the other developing units 3R, 3B.
Also when B is brought to the developing position, these developing gears 14R and 14B are similarly driven to rotate by meshing with the drive gear 111.

As shown in FIG. 5, each developing gear 14,
The centers of R and 14B are arranged at equal intervals around the rotation center O of the developing unit 1 and at the same distance from the center. The rotation center O 'of the development gear (same for other development gears) at the development position, the rotation center O of the development unit 1, and the rotation center O ″ of the drive gear 111 that is not moved are substantially the same straight line l. When the developing rollers 14, 14 R, and 14 B revolve around the center O by the rotation of the developing unit 1 around the center O, these gears do not interfere with the drive gear 111, And the driving gear 11 can be engaged.
1 may be supported by an appropriate portion other than the developing unit 1, and may be supported by a copier main body portion other than the support shaft of the photosensitive drum 11 or a carrier unit 62.

By the way, for example, until a predetermined developing roller 10 is positioned at a developing position, the developing roller 10 is moved around its rotation center O '.
If the developing roller 10 reaches the developing position and is rotated (rotated) immediately after the developing roller 10 reaches the developing position to immediately start the developing operation, as described above, the developing device 3
The developing operation is performed in a state where the toner and the carrier of the developer housed in the developer chamber 4 have not been sufficiently charged yet, whereby the visible image formed on the photosensitive drum 11 is Background dirt is generated, and the image quality is significantly deteriorated. Therefore, if the developing roller 10 is positioned at the developing position, the developing roller 10 is driven to rotate for a predetermined time, thereby charging the developer, and then the developing operation is performed. We cannot cope with speeding up of machine.

Therefore, in the image forming apparatus of this embodiment,
When the developing unit 1 rotates, each developing unit 3, 3R, or 3B
When the developing rollers 10, 10R, and 10B are positioned at the developing position, the developing rollers 10, 10R, and 10B start rotating immediately before reaching the developing position.
Drive control means for controlling the rotation of R and 10B is provided.

In this embodiment, 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 a certain developing gear 14, 14R or 14B starts to mesh with the drive gear 111. It is configured to be. That is, when the developing gear revolves in the direction of arrow Q and any of the gears engages with the drive gear 111, the gear 111 is already rotated. As a result, the developing unit 1 rotates, and the developing units 3, 3R, 3
When the B developing roller 10, 10R or 10B is positioned at the developing position, the developing roller starts rotating immediately before reaching the developing position. Thus, in this example, the drive gear 111 constitutes the above-described drive control means.

According to the above configuration, for example, the developing roller 1
0 is positioned at the developing position before the developing roller 1
With the rotation of 0, the developer 9 contained in the developer chamber 4 of the developing device 3 is stirred, and the toner and the carrier are 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 contamination can be formed on the photosensitive drum 11. It is possible to suppress the occurrence of loss time and obtain a high-quality visible image.

When the above configuration is adopted, the developing gear,
For example, when 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, 111 abut as shown in FIG. Both gears release the abutment between the tooth tips and come into a predetermined correct meshing state. Thus, it is possible to prevent inconveniences such as the gear being stopped or the gear teeth being cut off. The timing of starting the rotation of the drive gear 111 may be until any of the developing gears starts to be engaged with the gear 111, so that the operator can change a developing device to be used by a color conversion key switch (not shown). To start rotating the developing unit 1 and at the same time
May be started, or the drive gear 111 may be kept rotating at all times when the power of the copying machine is on.

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, ie, the developing unit 1 Is also clockwise as indicated by arrow Q. That is, when the revolving developing gear and the driving gear 111 are engaged with each other, their moving directions (the directions of the arrows Q and R) in the engagement region are opposite to each other. The rotation direction of the developing unit 1 is set such that the relative speed increases. For this reason, the abutment of the tooth tips of the two gears is released more accurately and quickly, and the two gears are immediately brought into a proper meshing state, so that the above-mentioned problem can be more effectively eliminated.

When any one of the developing gears engages with the drive gear 111 due to its revolution, if this gear 111 is rotated in the counterclockwise direction (the direction opposite to R) in FIG. It is preferable to rotate the developing unit 1 in the counterclockwise direction in FIG. 5 (the direction opposite to Q) so that the relative speed between the drive gear and the driving gear increases. Further, as described later, it is also possible to rotate the developing gear that is about to engage with the drive gear 111 while revolving. However, when rotating this gear in the counterclockwise direction, the developing unit 1 is rotated in the opposite direction to FIG. If the developing unit 1 is also rotated clockwise if the developing gear is rotated clockwise and the developing gear is rotated clockwise, the relative speed in the engagement region between the driving gear 111 and the developing gear can be increased. .

The drive gear 111 which constitutes an example of the above-described drive control means may be arranged inside the developing gear located at the developing position as shown in FIG. Can be adopted. At this time, if the developing roller 14 is rotated in the counterclockwise direction during the developing operation, the rotation direction of the drive gear 111 is clockwise.
In this case, the developing unit 1 is rotated counterclockwise,
If the developing gears revolve in this direction so that a large relative speed is generated in the engagement region between the driving gear 111 and the drive gear 111 that has started to rotate, the same effect as described above can be obtained. .

As described above, according to the direction in which the revolving developing gear and the developing gear rotate by just before the revolving developing gear and the driving gear 111 are engaged, a large relative speed can be obtained in the engagement region thereof. Thus, it is desirable to set the rotation direction of the developing unit 1.

The developing gear which is to be engaged with the driving gear 111, but not the driving gear 111, is properly driven by an appropriate driving means other than the driving gear immediately before the two gears are engaged with each other. As described above, it may be configured to be driven to rotate around (self-rotation). In this case, the appropriate driving means constitutes the above-described drive control means. Further, both the developing gear and the driving gear 111 are driven to rotate around their respective rotation centers O 'and O ", and immediately before the developing roller reaches the developing position, the rotation of the developing roller is started. The relative speed when the gear and the driving gear 111 are engaged may be increased. In this case, the driving gear 111 and other appropriate driving means constitute the aforementioned driving control means. .

Next, a more specific configuration example incorporating the above-described concept and the respective developing rollers 10 and 1 of the developing unit 1 will be described.
A specific configuration example will be described in which ORR and 10B are positioned at predetermined positions and which of the developing units 3, 3A or 3B is detected to have reached the developing position.

In FIG. 5, for example, in the direction of rotation of the developing unit 1 (the direction of the arrow Q), a portion upstream of the developing region D and a circumferential direction around the developing unit 1 The same number of sensors P1, P2, P3 as rollers
Are fixedly arranged on the copying machine main body 2 side by side.

On the other hand, the developing units 1 are provided with light shielding plates F having different lengths in the circumferential direction and arranged at equal intervals in the circumferential direction.
1, F2 and F3 are provided integrally.

When the developing unit rotates in the direction of arrow Q, the rotational center O of the developing unit, the rotational center O 'of the developing roller 10, and the rotational center of the photosensitive drum 11, that is, the driving gear 1
When the rotation center O ″ of the eleventh coincides with the straight line l, the light shielding plate F2 turns off the sensors P2 and P3 among the sensors P1 to P3.

Here, for example, a well-known photocoupler is used as each of the sensors P1 to P3, and FIG. 6 shows a view seen from the direction of arrow Y in FIG. In this figure, the light from the light emitting element 112 is blocked by the light shielding plate F2, so that the light receiving element 113 is turned off. That is, in the case of FIG. 5, the sensors of only P3 and P2 are turned off.

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

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

The above relationships are summarized in the following table.

[Table 1]

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

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

[Table 2]

By the way, in Table 1 shown above, the sensor P3 is off in any of the developing rollers. That is, no matter which developing roller is placed at the developing position, the sensor P3 is always turned off. 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 can be detected that an unspecified developing roller has been placed at the developing position.

FIG. 7 is a diagram for explaining the process until the developing gear 14 meshes with the driving gear 111. The line L is the orbit of the rotation center O 'of each developing gear 14 around O. .

When the color conversion key switch is turned on, the developing unit 1 rotates and, for example, when the rotation center O 'of the developing gear 14 comes to the point S in the figure, the addendum circles of the gear 14 and the driving gear 111 contact each other. It becomes such a gear attitude. Thereafter, usually, the gear 14 comes on the straight line l, and the teeth normally mesh with each other.

Here, in FIG. 7, the angle between O'O and SO is θ. In this case, the angle A formed by the line connecting the sensors P3 and O at the most downstream in the unit rotation direction and the line connecting the sensors P1 and O at the most downstream is the angle θ (∠O ′).
OS), when gear 14 reaches point S,
When the light-shielding plate F2 (FIG. 5) reaches the sensor P1 and the gear 14 reaches the developing position, the light-shielding plate F2 reaches the position of the sensor P3. The most upstream sensor P1 was installed at an angle (θ + α) slightly larger than (∠O′OS). Immediately before any of the developing gears mesh 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. Has reached the developing position, this is detected by the sensors P1 to P3 as described above, and the drive motor 88 or the clutch is disengaged by the developing device positioning signal as described above. FIG. 9 is a flowchart showing a series of these operations. Thus, the driving gear 111
By setting the rotation start timing of the developing roller immediately before the developing gear engages with it, before the predetermined developing roller is positioned at the developing position, the developer of the developing device to which the developing roller belongs is stirred, This can be charged.
Moreover, the developing gear of the developing roller and the drive gear 111 can be meshed with each other.

As shown in FIGS. 4 and 8, on the end wall 8 on the back side of the developing unit 1, positioning cams 114, 114R, and 114B are formed for each developing device. The extension spring 11 is attached to the back side support arm 71 of 62.
5, a lever 116 urged toward the end wall 8 is pivotally supported, and a stopper including a stop roller 117 is rotatably supported by the lever 116.
7 selectively engages the three cams 114, 114R, and 114B to exert a braking force on the developing unit 1. With this engagement, the developing rollers 10, 10R, 1
Advantageously, 0 is configured to be positioned at the development position. 116a is a stopper for the roller 117.

The present invention is not limited to the rotary developing device shown in the drawing, in which each developing unit is integrally formed by one casing member, and the entire developing device constitutes a developing unit. Naturally, each developing device has a separate casing member, which can be applied to a rotary developing device in which these are assembled to a unit rotating body to form a developing unit. The present invention can be similarly applied to a rotary developing device in an image forming apparatus such as the one described above.

The present invention can also be applied to a case where the developer carrying member comprises a developer carrying belt or a magnet roller rotatably provided on a belt or a roller. When a gear is provided, a gear attached to the developer conveying belt or a gear attached to the magnet roller is the developing gear.

[0054]

According to the present invention, when the developer conveying member of the developing device is positioned at the developing position by the rotation of the developing unit, the developer conveying member starts rotating immediately before the positioning. The developer can be charged. For this reason, after positioning the developer conveying member at the developing position, a high-quality visible image can be formed without rotating the developer conveying member for a long time to charge the developer. Thus, high-quality images can be obtained by suppressing the occurrence of loss time.

[Brief description of the drawings]

FIG. 1 is a vertical cross-sectional view of a developing device when a developing unit is set in a copying machine main body.

FIG. 2 is a sectional view taken along line III-III of FIG.

FIG. 3 is a perspective view showing a state in which a storage table is pulled out from the copying machine main body, and a developing unit is removed from the storage table.

FIG. 4 is a perspective view of a storage table and related components when the developing unit is removed, as viewed from the back side.

FIG. 5 is an explanatory diagram illustrating a rotation operation of the developing unit.

FIG. 6 is a view as seen in the direction of arrow Y in FIG. 5;

FIG. 7 is an explanatory diagram illustrating a positional relationship between a developing gear, a driving gear, a sensor, and the like.

FIG. 8 is an explanatory diagram showing the cam and the stop roller as viewed from the near side.

FIG. 9 is a flowchart illustrating an operation example when a developing device is selected.

FIG. 10 is an explanatory diagram illustrating abutment between tooth tips.

FIG. 11 is an explanatory view showing another arrangement of gears.

[Description of Signs] 1 Developing unit 3 Developing unit 3R Developing unit 3B Developing unit 4 Developer room 4R Developer room 4B Developer room 9 Developer 9R Developer 9B Developer D Developing area

Claims (1)

[Claims] A developing unit having a plurality of developing units and rotatably supported opposite the latent image carrier;
Each developing device has a developer transporting member that transports the developer in the developer chamber to a developing area where the electrostatic latent image on the latent image carrier is visualized, and the developer unit is rotated by rotation of the developing unit. In a rotary developing device of an image forming apparatus in which each developer conveying member is positioned at a developing position facing a latent image carrier and performs a developing operation, a developing unit is rotated and a developer conveying member of each developing unit is used for developing. When the developer transport member is positioned at the position, drive control means for controlling the rotation of each developer transport member is provided so that the developer transport member starts rotating immediately before reaching the developing position. Mold developing device.