JPH096206A - Image forming device - Google Patents

Abstract

PURPOSE: To prevent the increases of noises and power capacity at the time except under high-speed driving conditions by changing the driving speed of drive systems not directly affecting the image forming speed in response to the image forming conditions or driving state. CONSTITUTION: A yellow developing unit 20Y, a magenta developing unit 20M, and a cyanic developing unit 20C are held on a developing rotary 23 rotated around a shaft 22. For forming an image, the developing units 20Y, 20M, 20C are rotated and moved around the shaft 22, and they are stopped at the position (development position) where the prescribed developing unit faces an image carrier 15, and a visible image is formed on the image carrier 15. The visible image is transferred to a transfer material 2 via an intermediate transfer body 9. The time for switching the developing rotary 23 to the next developing unit of another color is made the shortest for the largest transfer material A3. For the transfer material A4 requiring a short time for forming a latent image, the switching time is made longer than that for A3, and it is quietly switched with reduced power.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to an image forming apparatus for forming a visible image on an image carrier by an electrophotographic system or an electrostatic recording system and transferring the visible image onto a transfer material to obtain an image. The present invention can be suitably embodied in a color image forming apparatus such as a color copying machine or a color printer.

[0002]

2. Description of the Related Art Conventionally, a color image in which a visible image of a plurality of colors is formed on an image carrier by, for example, an electrophotographic system or an electrostatic recording system, and the visible image is transferred onto a transfer material to obtain a multicolor image. In the forming apparatus, for example, a developing device rotary holder carrying a plurality of developing devices, that is, a developing rotary for driving a developing rotary to move a predetermined developing device to a developing position and a transfer material holding position. The drive speed of the drive system such as the drive of the paper feeding unit for transporting the transfer material during the drive period from the (transfer position) to the standby position directly affects the image forming speed. Unlike the driving of the intermediate transfer member or the driving of the fixing roller, it does not directly affect the image forming speed. Nevertheless, even when the image forming conditions such as the size of the transfer material, the initial operation drive of the developing rotary, the drive for the replacement of the developing device, and the drive state such as the image forming drive are changed, they are constant. there were.

[0003]

As described above, in the conventional image forming apparatus, the drive system that does not directly affect the image forming speed is the worst condition, that is, regardless of the image forming condition and the driving state. It was driven at a constant speed at the fastest speed according to the shortest driving condition.

Therefore, a driving system that does not directly affect the image forming speed is also affected by the shortening of the driving time indirectly when the image speed increases, and the speed increases. If the speed increases, the effect will be manifested in the form of noise in the drive system and an increase in power supply capacity. The effect becomes more remarkable in a high-speed color image forming apparatus.

Therefore, an object of the present invention is to make the driving of the drive system, which has no direct influence on the image forming speed, variable depending on the image forming condition or the driving state, except for the high speed driving condition which occupies most of the actual use state. An object of the present invention is to provide an image forming apparatus capable of preventing noise and increase in power supply capacity at the time.

[0006]

The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention provides:
In an image forming apparatus that forms a visible image on an image carrier and transfers the visible image to a transfer material to obtain an image, the driving speed of a driving system that does not directly affect the image forming speed is set to an image forming condition or a driving state. The image forming apparatus is characterized in that Further, the image forming apparatus may be a color image forming apparatus that forms a visible image of a plurality of colors on the image carrier and transfers the visible images of the plurality of colors onto a transfer material to obtain a multicolor image.

More specifically, the drive system that does not directly affect the image forming speed is a developing device rotary holder that has a plurality of developing devices and moves a predetermined developing device to a developing position. The driving speed of the developing device rotary holder is variable, and the driving speed of the developing device rotary holder is set according to the size of the transfer material when the initial operation of the developing device rotary holder is driven and when the developing device is replaced. It is changed according to the driving time, the driving time of the developing device rotary holder to the developing device removal position and the driving time for replacing the developing device, or the full color mode and the mono color mode.

According to another embodiment, the drive system that does not directly affect the image forming speed is a paper feeding unit that controls the feeding of the transfer material, and the transfer material from the transfer material standby position to the transfer position. The transfer driving speed of the transfer material is variable, and the transfer driving speed of the transfer material is changed according to the first transfer material and the second and subsequent transfer materials.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A color image forming apparatus according to the present invention will be described below in more detail with reference to the drawings.

Embodiment 1 FIG. 2 shows the overall construction of a laser printer which is an embodiment of the color image forming apparatus of the present invention.

In this embodiment, the laser printer has an image forming section provided with an image carrier such as a photosensitive drum. Around the image carrier 15, a charging unit, an exposure unit, and a developing unit are provided, and a visible image is formed on the image carrier 15. The visible image on the image carrier is multiple-transferred onto the intermediate transfer member 9, and then the image on the intermediate transfer member 9 is further transferred onto the transfer material 2 fed from the feeding section to form a color image. To be done. The transfer material 2 is conveyed to the fixing means 25 to fix the color image on the transfer material 2, and is discharged to the discharging portion 37 on the upper surface of the apparatus by the discharging roller.

Next, the structure of each part of the image forming section will be described in detail.

[Image Carrier Unit] The image carrier (photosensitive drum) 15 and the container 14 of the cleaning device which also serves as a holder for the image carrier 15 are integrally formed to form a drum unit 13. The drum unit 13 is detachably supported on the printer body, and the unit can be easily replaced according to the life of the image carrier 15.

In this embodiment, the image carrier 15 has a diameter of about 60.
An organic photoconductor layer is coated on the outside of an aluminum cylinder having a diameter of 2 mm, and is rotatably supported by a container 14 of a cleaning device also serving as a holder for the image carrier 15.

A cleaner blade 16 and a primary charging means 17 are arranged on the periphery of the image carrier 15. A drive motor (not shown) is provided at one end on the rear side of the image carrier 15 in the figure.
By transmitting the driving force of, the image carrier 15 is rotated counterclockwise in accordance with the image forming operation.

[Charging Means] The charging means 17 uses a contact charging method, and a conductive roller is brought into contact with the image carrier 15 and a voltage is applied to the conductive roller to cause the image carrier 15 to move. The surface of is uniformly charged.

[Exposure Means] The exposure of the image carrier 15 is sent from the scanner section 30. That is, when the image signal is applied to the laser diode, the laser diode irradiates the polygon mirror 31 with image light corresponding to the image signal. The polygon mirror 31 is rotated at a high speed by a scanner motor, and the image light reflected by the polygon mirror 31 selectively exposes the surface of the image carrier 15 rotating at a constant speed through the imaging lens 32 and the reflection mirror 33.

[Developing Means] In this embodiment, the developing means is
In order to visualize the latent image formed on the image carrier 15, three rotary developing devices 20 mounted on the developing rotary are provided.
The rotary developing means 20 including Y, 20M, and 20C and the fixed developing means 21 including one fixed black developing device 21B are provided to enable development of each color of yellow, magenta, cyan, and black. Further, the color rotary developing device and the fixed black developing device can be individually attached to and detached from the printer body.

The black developing device 21B is a fixed developing device, and the sleeve 21BS is arranged at a position facing the image bearing member 15 and at a minute interval (about 300 μm) from the image bearing member 15, and the black developing device 21B is attached to the image bearing member 15. A visible image is formed by black toner.

In the black developing device 21B, the toner in the container is sent by a sending mechanism, and a thin layer of toner is applied to the outer circumference of the sleeve 21BS rotating clockwise in the drawing by the application blade 21BB pressed against the outer circumference of the sleeve 21BS. Charge is applied to (friction electrification). Also, by applying a developing bias to the sleeve 21BS,
The toner development is performed on the image carrier 15 according to the latent image.

Three rotary developing devices 20Y, 20M, 20C
Are detachably held by the developing rotary 23 which rotates around the shaft 22, respectively, and each of the developing devices rotates while moving around the shaft 22 while being held by the developing rotary 23 at the time of image formation. Remain at the position (developing position) facing the image carrier 15 and the developing sleeve is positioned so as to face the image carrier 15 with a minute gap (about 300 μm), and then visible to the image carrier 15. Form an image. At the time of forming a color image, the developing rotary 23 rotates for each rotation of the intermediate transfer member 9 to rotate the yellow developing device 20.
The developing process is performed in the order of Y, magenta developing device 20M, cyan developing device 20C, and then black developing device 20B.
Rotates four times to sequentially form a visible image with yellow, magenta, cyan, and black toners, respectively, and as a result, a full-color visible image is formed on the intermediate transfer member.

FIG. 2 shows a state in which the yellow rotary developing device 20Y is positioned and stationary at the developing position. The rotary developing device 20Y feeds the toner in the container to the coating roller 20YR by a feeding mechanism, and rotates the coating roller 20YR rotating clockwise in the drawing and the sleeve 20YS rotating clockwise in the drawing by a blade 20YB pressed against the outer circumference of the sleeve 20YS. A thin layer of toner is applied to the outer periphery, and an electric charge is applied to the toner (friction charging). By applying a developing bias to the sleeve 20YS facing the image carrier 15 on which the latent image is formed, the latent image formed on the image carrier 15 is developed and becomes a toner image. Magenta developer 2
The 0M and cyan developing device 20C also operate in the same manner as the yellow developing device to perform toner development.

Further, each rotary developing device 20Y, 20M, 20C
Each sleeve is connected to a high-voltage power source for each color development and a drive source provided in the printer main body when each developing device is rotationally moved to the developing position, and a voltage is selectively applied to each color development sequentially and the drive is transmitted. To be done.

[Intermediate Transfer Member] The intermediate transfer member 9 is rotated clockwise in the figure to receive multiple transfers from the image carrier 15 during the color image forming operation. The transfer material 2 is sandwiched and conveyed by the transfer roller 10 to which a voltage is applied, whereby the toner images of respective colors on the intermediate transfer member are simultaneously and multiple-transferred onto the transfer material 2.

The intermediate transfer member 9 according to this embodiment has a diameter of 18
The outer circumference of a 0 mm aluminum cylinder 12 is covered with an elastic layer 11 such as medium resistance sponge or medium resistance rubber. The intermediate transfer body 9 is rotated by the drive being transmitted to a gear (not shown) which is rotatably supported and integrally fixed. A flag 9F is arranged on the intermediate transfer member 9, and cooperates with a sensor 9S arranged on the apparatus main body to measure the timing of latent image formation.

[Cleaning Means] The cleaning means cleans the toner remaining on the image carrier 15 after the toner visualized on the image carrier 15 by the developing means is transferred to the intermediate transfer body 9. The cleaned waste toner is stored in the cleaner container 14.
The amount of waste toner stored in the container 14 does not fill the container 14 earlier than the life of the image carrier, and therefore the cleaner container 14 is simultaneously replaced when the life of the image carrier 15 is replaced.

[Paper Feeding Unit] The paper feeding unit feeds the transfer material 2 to the image forming unit, and includes a cassette 1 containing a plurality of transfer materials 2, a paper feeding roller 3, a feeding roller 4, It is mainly composed of a retard roller 5 for preventing double feeding, a paper feed guide 6, a conveyance roller 7, and a registration roller 8. At the time of image formation, the paper feed roller 3 is driven to rotate in accordance with the image forming operation to separate and feed the transfer materials 2 in the cassette 1 one by one, and the guide plate 6 guides the transfer material 2 to transfer the transfer material 2 to the registration roller 7 via the transfer roller 7. To the roller. During the image forming operation, the registration roller 8 performs a non-rotating operation of stopping the transfer material 2 in a standby state and a rotating operation of transporting the transfer material 2 toward the intermediate transfer body 9 in a predetermined sequence, which is the next step. The image and the transfer material 2 at the time of the transfer step are aligned.

[Transfer Section] The transfer section has a swingable transfer roller 10. The transfer roller 10 is formed by winding a metal shaft with a medium resistance foamed elastic body, and as shown in the drawing,
It can move up and down and is driven to rotate.

The transfer roller 10 forms the four color toner images on the intermediate transfer member 9, that is, the intermediate transfer member 9.
While it is rotated a plurality of times, it is positioned below and separated from the intermediate transfer body 9 as shown by the solid line in the figure so as not to disturb the image.
The transfer roller 10 is moved to an upper position shown by a thin line in the drawing by a cam member (not shown) at a timing when the color image is transferred to the transfer material 2 after the four color toner images are formed on the intermediate transfer member 9. Then, it is pressed against the intermediate transfer member 9 through the transfer material 2 with a predetermined pressure. At the same time, a bias voltage is applied to the transfer roller 10 and the toner image on the intermediate transfer body 9 is transferred to the transfer material 2.

In this embodiment, since the intermediate transfer member 9 and the transfer roller 10 are respectively driven, the transfer material 2 sandwiched between the two is subjected to the transfer process and at the same time, is moved to the left in the drawing by a predetermined distance. It is conveyed at a speed and fed to the fixing device which is the next step.

[Fixing Unit] The fixing unit 25 is the developing unit 2 described above.
The toner images formed by Nos. 0 and 21 are used to fix the toner image formed on the transfer material 2 through the intermediate transfer body 9, and as shown in FIG. 2, fixing for applying heat to the transfer material 2. The roller 26 and the pressure roller 27 for pressing the transfer material 2 to the fixing roller 26 are in contact with each other. Each roller is a hollow roller, and heaters 28 and 29 are provided inside.
, And is simultaneously driven to convey the transfer material 2.

That is, the transfer material 2 holding the toner image is conveyed by the fixing roller 26 and the pressure roller 27, and the toner is fixed on the transfer material 2 by applying heat and pressure.

[Image Forming Operation] Next, the operation of forming an image by the apparatus configured as described above will be described.

First, the sheet feeding roller 3 shown in FIG. 2 is rotated to separate one sheet of the transfer material 2 in the sheet feeding cassette 1, and the sheet is conveyed to the registration roller 8.

On the other hand, the image carrier 15 and the intermediate transfer member 9 rotate in the direction of the arrow in the figure, and the image carrier 1 is charged by the charging means 17.
5 The surface is uniformly charged, and the scanner unit 30 irradiates a yellow image with light to form a yellow latent image on the image carrier 15. Simultaneously with the formation of this latent image, the yellow developing device 20Y is driven to apply a voltage having substantially the same potential as the charging polarity of the image carrier 15 so that the yellow toner adheres to the latent image on the image carrier 15. Perform yellow development. A voltage having a characteristic reverse to that of the toner is applied to the intermediate transfer body 9 to transfer the yellow toner on the image carrier 15 onto the intermediate transfer body 9.

As described above, the intermediate transfer member 9 of the yellow toner
When the transfer to the end is completed, the developing rotary 23 is rotated and the next magenta developing device 20M is rotationally moved to be positioned at a position facing the image carrier 15, and magenta toner is developed in the same manner as yellow, and then cyan, Black latent image formation, development, and transfer of the toner image to the intermediate transfer body 9 are sequentially performed four times, and the surface of the intermediate transfer body 9 is colored with four types of toner images of yellow, magenta, cyan, and black. Form an image.

Then, after the color image on the surface of the intermediate transfer body 9 is formed, the transfer material 2 which has been kept waiting by the registration roller 8 is conveyed, and the transfer material 2 is pressed against the intermediate transfer body 9 by the transfer roller 10. At the same time, the color image on the intermediate transfer body 9 is transferred to the transfer material 2 by applying a bias having a characteristic reverse to that of the toner to the transfer roller 10. The transfer material 2 that has undergone the transfer process is separated from the intermediate transfer body 9 and conveyed to the fixing unit 25 to perform toner fixing, and then the discharge roller pair 34, 35,
The image is discharged onto the discharge tray 37 at the upper part of the main body through the unit 36, and the image forming operation is completed.

In FIG. 3, the developing rotary 23 has Y, M, and C
FIG. 6 is a diagram for explaining switching and taking out of the developing devices 20Y, 20M, and 20C.

Three color developing devices 20Y, 20M and 20C have 1
It is arranged at an angle of 20 degrees. The sensor 301 arranged adjacent to the developing rotary 23 detects the position of the developing rotary 23. A flag 20YF arranged on the periphery of the developing rotary 23 stops the yellow developing device 20Y at a position facing the image carrier 15, and flags 20MF and 20CF indicate a magenta developing device 20M and
The cyan developing devices 20C are stopped at positions facing the image bearing members.

A position indicated by reference numeral 300 in FIG. 3 is a position where the developing device is taken out from the developing rotary 23 in order to replace each developing device, and a flag 20YTF is a yellow position for taking out the yellow developing device 20Y. Developing device 20
Stop Y at a position facing the take-out position 300, and
At 0 MTF and 20 CTF, the magenta developing unit 20M and the cyan developing unit 20C are stopped at positions facing the take-out position 300, respectively.

FIG. 4 is a schematic system diagram of the engine section of the present color image forming apparatus. The engine unit is a Video / F400 that is an interface unit with an external controller that controls this engine; and the fixing unit 40.
6. Sensor unit 40 for temperature / humidity sensor and remaining toner amount detection
7. γ in the image data received from the interface 400
An image processing GA 409 that performs image processing such as correction, an image forming unit 408 that performs image output such as laser output and a scanner motor, and a main control CPU 401 that controls the mechanical control CPU 402 of the sub CPU. The mechanical control CPU includes a drive unit such as a motor, a clutch, and a fan, a sensor unit 403 for position detection, and a paper feed control unit 40.
4 and the high voltage controller 405 are controlled respectively.

FIG. 5 is a schematic configuration diagram of the periphery of the mechanical control CPU 402. The stepping motor 502 connected to the drive circuit 501 drives the intermediate transfer body 9. Sensor 9
S detects the flag 9F arranged on the circumference of the intermediate transfer member 9. The stepping motor 504 connected to the drive circuit 503 drives the developing rotary 23, and the motor 504 also drives the sleeves 20YS and 20M of the color developing devices.
Although the S and 20CS are driven, the clutch 505 switches the drive between the sleeve and the developing rotary. The sensor 301 detects the position of the developing rotary. The drive circuits 506 and 507 include fans 508 and 509, respectively.
Drive. Further, the main control CPU 401, the paper feed control unit 404, and the high-voltage control unit 405 are connected to each other via a serial communication SC.
0, SC1, SC2 are connected and communication is controlled.

FIGS. 1 (a) and 1 (b) show the timing of image formation and development rotary 23 for the transfer material 2 of A3 and A4 size in the apparatus of the present invention having the above construction. FIG.
The ITDTOP sensor is a signal generated by the flag 9F and the sensor 9S provided on the intermediate transfer member 9 shown in FIG. 2 for timing the image formation. The intermediate transfer member 9 makes one round at T = 5 seconds. Ts is the image start signal I
This is the timing for forming a predetermined leading edge margin after receiving the TDTOP sensor, and is Tp (A3), Tp (A4
Y) is the time for forming a latent image on the image carrier 15 of FIG. 2 for each of A3 and A4, and Td is the toner at a position that forms a latent image on the image carrier 15 and opposes the latent image on the developing sleeve. Time to adhere to Tr (A3), Tr (A4Y)
Is the time for switching and driving the developing rotary 23 to the developing device of the next color.

The timing diagram shown in FIG. 1 best represents the invention. That is, when the maximum transfer material is A3, the time for switching the developing rotary 23 is the shortest, while on the other hand, when the transfer material A4 is for a short time to form a latent image, there is time to switch the developing rotary 23. In comparison, a longer time Tr (A4Y) slowly and quietly suppresses the power, and the switching is performed.

Here, FIG. 6 is a schematic flowchart of the rotary switching process according to the conventional example executed by the mechanical control CPU 402. This switching process corresponds to FIG. 1A for explaining the present invention described above.

In the conventional switching process, in s600, it is determined at the time of calling this subroutine whether the switching process is in progress. In s601, the maximum length of transfer material A
It is determined whether the latent image formation of No. 3 is completed, and in s602, after the latent image is formed on the image carrier 15, the time Td until the toner adheres to the leading end latent image at the position opposed to the developing sleeve has elapsed. To determine. After detecting the passage of time in s601 and s602, the development rotary switching process starts.

First, the developing high voltage is stopped in s603, and s6
At 04, the rotation of the sleeve is stopped. The initial excitation timer of the stepping motor 504 is set in s605, and s60
At 6, the timer interrupt processing is enabled. In the timer processing, the excitation timer of the stepping motor 504 and the phase are updated to determine whether the desired stop position has been reached,
Is executed, and a determination process for determining whether the switching is completed is executed. When the end of the switching process is determined in s607 and the end is detected, the timer interrupt process ending process such as prohibiting the timer interrupt process is performed in s608, the ending flag of this switching process is set in s608, and this subroutine is executed in s609. Exit through.

That is, in this conventional flow chart,
For any transfer material, the switching process is executed at the timing of the A3 transfer material.

On the other hand, FIG. 7 shows the mechanical control CPU 4
12 is a schematic flowchart of a rotary switching process of one embodiment that represents the characteristics of the present invention that is executed by 02. This switching process according to the present invention corresponds to (a) and (b) of FIG.

In s700, it is determined whether or not the switching process is in progress when this subroutine is called. s701
Then, it is determined whether the transfer material is A3 or A4Y, and in s702, it is determined whether the latent image formation of the transfer material A3 having the maximum length is completed.
At 703, it is determined whether the latent image formation on the transfer material A4Y is completed. In s704, the time data T (A3) is set in the prescaler described in FIG. 8, and in s705, the time data T (A4Y) is set in the prescaler. In s706,
Time Td after the latent image is formed on the image bearing member 15 until the toner adheres to the leading edge latent image at a position facing the developing sleeve.
Is determined. After the passage of each time is detected in s701 to s706, the development rotary switching process starts.

First, the developing high pressure is stopped in s707, and s7
At 08, the rotation of the sleeve is stopped. The initial excitation timer of the stepping motor 504 is set in s709, and s71
When 0, timer interrupt processing is enabled. In the timer processing, the excitation timer of the stepping motor 504 and the phase are updated to determine whether the desired stop position has been reached,
Is executed, and a determination process for determining whether the switching is completed is executed. When it is determined in s711 that the switching process has ended and the end is detected, in s712 a timer interrupt process ending process such as prohibiting the timer interrupt process is performed. In s713, an end flag of this switching process is set and this subroutine is executed in s714. Exit through.

That is, in the flowchart according to the present invention, the switching process of the developing rotary 23 is executed at different timings depending on the transfer material. In the present embodiment, the transfer material is described as two kinds of A3 and A4Y for the sake of convenience, but the method is sufficiently effective even if the kinds of the transfer material are increased.

FIG. 8 is a mechanical control CPU for explaining the timer interrupt in the flowcharts of FIGS. 6 and 7.
It is a timer control unit inside 402.

The timer 804 has a prescaler 802, and the prescaler 802 has a prescaler latch 801. The frequency division ratio of the input system clock f _CLK is determined by the content of this data. The timer clutch 803 generates a timer interrupt request when the countdown timer 804 reaches 0, and the contents of the timer latch are reset. By changing the value set in the timer latch and changing the timer interrupt interval, the excitation timing of the motor, that is, the motor speed is controlled.

In the flow chart of the embodiment of the present invention shown in FIG. 7, the prescaler latch 8 by the transfer material 2 is used.
The value to be set to 01 is changed, and the timer interrupt processing is common, and the motor speed can be changed by the transfer material 2.

FIG. 9 is a diagram showing the concept of the motor speed (vertical axis) and the development rotary switching time (horizontal axis) when the flowchart of FIG. 7 is executed. If T
The value of (A4Y) = T (A3) × 2 is set to s704 and s705.
Set to. Since the division ratio of A4Y is double that of A3,
The motor speed of A3 is twice that of A4Y, and when compared at the top speed, V (A3) = V (A4Y) × 2, and the development rotary switching time is Tr (A4Y) =
Tr (A3) × 2.

However, in this processing in which the motor excitation time is simply changed, the excitation pattern remains unchanged. Therefore, the torque of the motor is excessive at A4Y, which may cause noise or vibration. Further, the power consumption is increased rather than reduced. Therefore, in the timer process, in the case of A3, the motor is driven by the two-phase excitation method as shown in FIG. 10A, and in the case of A4Y, it is shown in FIG. 10B. 1-phase excitation method or Fig. 1
In the 1-2 phase excitation method shown in FIG.
A process of driving the motor to reduce the torque is executed by the chopping method shown in (d).

Second Embodiment In the first embodiment, the switching speed of the developing rotary 23 is changed depending on the difference of the transfer material 2. However, in the present embodiment, the developing rotary 23 is a reference of the position of the developing rotary 23 when the power is turned on. 3 to the home position, that is, the speed of the developing rotary 23 when the flag 20MTF moves to a position facing the sensor 301 in FIG. 3, and the developing rotary 23 for replacing the developing device during normal recording. The present invention can be applied even when the moving speed is different.

Further, the developing rotary 2 for exchanging the developing device at the time of moving to the developing device take-out position 300 and at the time of normal recording.
The same applies when the moving speed of 3 is different.

Embodiment 3 In this embodiment, as shown in FIG. 11, in the full color mode (FIG. 11A) and in the mono color mode (FIG. 11).
In the case of (b)), the switching time of the developing rotary 23 is variable.

That is, in the full color mode, since the latent image formation of the next color magenta M is started by the input of the next ITDTOP sensor, the switching time Tr (Y to M) is
Next, there is no latent image formation, and it is sufficient to return to the home position HP with a time margin.
It is naturally shorter than P), and the present invention can be applied in this case as well.

Fourth Embodiment Up to now, the driving of the drive system which does not directly affect the image forming speed has been considered by switching the developing rotary, but in the present embodiment, the transfer material conveyance is controlled. Consider an example of driving from the transfer material holding position to the standby position in the paper feeding unit.

In FIG. 12, two latent image formation start flags are provided around the intermediate transfer member 9, and one A4Y rotation is made for one round of the intermediate transfer member.
FIG. 6 is a diagram for explaining the sheet feeding when two sheets of A4Y are continuously formed, which enables formation of latent images for two sheets. Tw is the time from the start of latent image formation until the transfer material waiting in the registration roller 8 starts feeding, Tp is the time from the waiting position until the feeding of the transfer roller 10 and thereafter is completed, A4Y-1 , A4
Y-2 is the latent image forming time of the first and second sheets of A4Y, T1
Represents the drive time from the first transfer material holding position to the standby position, T2 represents the drive time from the second transfer material holding position to the standby position, and timers 1 and 2 drive the paper feeding system. Indicates the value of the motor timer.

What is meant by FIG. 12 is that the first sheet with sufficient time is fed at a slower speed than the second and subsequent sheets.

FIG. 13 is an electrical block diagram of the paper feed controller 404 of FIG. In this embodiment, the paper feed controller 404 is
A CPU 1300 that controls paper feeding, a paper feeding motor 1302 that drives a paper feeding system, a drive circuit 1301 that drives the motor 1302 based on a signal from the CPU 1300, a clutch 1302 that controls transmission of power of the motor 1302 to the registration rollers 8. A sensor 1304 for detecting whether or not the transfer material 2 has reached the registration roller 8, clutches 1305 and 1307 for receiving power transmission from a motor 1302 for driving the transfer material 2 to move from the holding position, and operation of the clutch. Sensors to monitor 1306, 1308, 13
Has 09.

FIG. 14 shows the paper feeding process of FIG.
00 is a schematic flowchart of a timer switching unit for execution by 00. In s1400, it is determined whether or not it is continuous, and when it is in the continuous state, timer 2 is set in s1401, and when it is in the discontinuous state, s
At 1402, timer 1 is set. s1403 The sheet feeding process ends.

[0067]

As described above, the image forming apparatus of the present invention forms a visible image on an image carrier and transfers the visible image to a transfer material to obtain an image. The drive speed of the drive system that does not directly affect
Since the configuration is changed depending on the image forming condition or the driving state, it is possible to prevent noise and increase of the power source capacity under the conditions other than the high-speed driving condition which is almost the actual use state. Further, according to the present invention, the microcomputer can detect the state and change the driving method of the motor, so that it can be realized without substantially affecting the cost of the apparatus main body. Is.

[Brief description of drawings]

FIG. 1 is a diagram showing timings of image formation and development rotary when A3 and A4 size transfer materials are used according to the present invention.

FIG. 2 is a diagram illustrating the overall configuration of a laser printer that is an example of a color image forming apparatus according to the present invention.

FIG. 3 is a diagram illustrating switching and removal of a developing device mounted on a developing rotary.

FIG. 4 is a schematic system diagram of an engine unit of the image forming apparatus of the present invention.

FIG. 5 is a schematic configuration diagram around a mechanical control CPU.

FIG. 6 is a schematic flowchart of a conventional rotary switching process executed by a mechanical control CPU.

FIG. 7 is a schematic flowchart of a rotary switching process of an embodiment representing a feature of the present invention, which is executed by a mechanical control CPU.

8 is a diagram of a timer control unit inside the mechanical control CPU for explaining a timer interrupt in the flowcharts of FIGS. 6 and 7. FIG.

9 is a diagram showing a concept of a motor speed (vertical axis) and a development rotary switching time (horizontal axis) when the flowchart of FIG. 7 is executed.

FIG. 10 is a diagram showing an excitation method of a motor.

FIG. 11 is an explanatory diagram when the rotary switching time is variable in the full color mode of FIG. 11A and the mono color mode of FIG. 11B.

FIG. 12: Two latent image formation start flags are provided around the intermediate transfer member to enable latent image formation for two A4Y sheets per revolution of the intermediate transfer member. It is a figure explaining.

FIG. 13 is an electrical block diagram of the paper feed controller of FIG.

14 is a schematic flowchart of a timer switching unit for the CPU to execute the paper feeding process of FIG.

[Explanation of symbols]

1 Paper Feed Cassette 2 Transfer Material 9 Intermediate Transfer Body 10 Transfer Means (Transfer Roller) 15 Image Carrier (Photosensitive Drum) 16 Cleaning Means (Cleaner Blade) 17 Charging Means 20 Rotating Developing Means 21 Fixed Developing Means 23 Developer Rotating Holder (Development rotary) 25 Fixing means 30 Scanner section

Claims (6)

[Claims] 1. In an image forming apparatus for forming a visible image on an image carrier and transferring the visible image to a transfer material to obtain an image, the drive speed of a drive system that does not directly affect the image forming speed An image forming apparatus characterized by being changed according to a forming condition or a driving state. 2. An image forming apparatus is a color image forming apparatus for forming a visible image of a plurality of colors on an image carrier and transferring the visible images of the plurality of colors onto a transfer material to obtain a multicolor image. 1. The image forming apparatus of 1. 3. The drive system, which does not directly affect the image forming speed, is a developing device rotation holder that has a plurality of developing devices and moves a predetermined developing device to a developing position. The image forming apparatus according to claim 2, wherein the driving speed of the holding member is variable. 4. The rotational speed of the developing device rotary holder is set according to the size of the transfer material, depending on the initial operation driving of the developing device rotary holder and the driving time for replacing the developing device. The image forming apparatus according to claim 3, wherein the image forming apparatus is changed according to the driving time of the body to the developing device take-out position and the driving time for replacing the developing device, or according to the full color mode and the mono color mode. 5. The drive system that does not directly affect the image forming speed is a paper feeding unit that controls the feeding of the transfer material, and the transfer driving speed of the transfer material from the transfer material standby position to the transfer position is variable. The image forming apparatus according to claim 1, wherein 6. The image forming apparatus according to claim 5, wherein the transfer driving speed of the transfer material is changed according to the first transfer material and the second and subsequent transfer materials.