JPS63306477A - Developing unit control method for image forming device - Google Patents

Abstract

PURPOSE:To prevent the unequal use of developing devices and the ununiformity of toner reduction, by switching the selection among plural color developing units to equally use respective color developing units as long as color developing units of the same color are set. CONSTITUTION:Plural color developing units can be set and are selectively used to form an image. Plural attachable and detachable color developing units 5 and 6, detecting means 47 and 48 which detect colors of toner, a selecting means which selects color developing units, an operating means which designates color developing units, and a discriminating means which discriminates whether color developing units of the same color are set or not by detection results of detecting means are provided. If the discriminating means discriminates that color developing units of the same color are set, selection of the selecting means is automatically switched in accordance with such prescribed system that developing units 5 and 6 are equally used. Thus, the unequal use of developing devices is relaxed and the feeling of use of an image forming device is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image forming apparatus, such as a copying machine or a printer, which is equipped with a plurality of color developing units.

[Prior Art] For example, a copying machine is equipped with a plurality of removable developing devices each containing black, red, yellow, etc. toner, and a detection means for detecting the color of the toner in each developing device. A developing device containing colored toner is selected, and the electrostatic latent image on the surface of the photosensitive drum is visualized (developed) by the toner supplied from the developing device to the photosensitive drum, and the toner corresponding to the image of the original is developed. There are known devices that form images.

In such copying machines, even if a developer of a different color or a developer of the same color is installed, the developer selected on the operation panel is now used for image forming operations. ing.

[Problems to be Solved by the Invention] By the way, in the above-mentioned copying machine, even if a plurality of developing units contain the same color, only the developing unit set (selected) on the operation unit is used. is used for image forming operations (particularly if the priority selection order is set, because the higher priority developer is used more frequently), the toner amount of the selected developer is uneven, and the toner amount of the selected developer is uneven. The toner decreases quickly and the toner becomes empty. Therefore, the frequency of replacing the toner bottle increases.

Some copying machines switch the developer selection when the toner becomes empty when the same color developer is installed.

However, if the developing device in the toner empty state has a high priority selection order, it is cumbersome because the selection switching operation must be performed after the auto clear or main switch is pressed. In addition, if a toner replenishment operation such as toner bottle replacement is performed on a developing device that is in a toner empty state, if that developing device has a high selection priority, only that developing device will be used again. Even if there is no priority, there is a high possibility that that developing device will be selected. In such a case, the use of the developing device will be uneven. Therefore, the developing device deteriorates mechanically quickly.

Further, in a two-component type developing method, although the carrier is adjusted so as not to be consumed, in reality it is consumed little by little, which affects the toner density in the long run. In particular, a control function (hereinafter referred to as AIDC) that develops a reference latent image formed on the surface of the photoconductor, optically measures the developed density, and determines whether or not toner replenishment is necessary according to the measurement result. ), due to unbalanced usage, the amount of carrier decreases quickly in response to the increase in carrier consumption, and the T/C (mixing ratio of toner and carrier) increases, causing charging properties to increase. Problems such as the deteriorated toner scattering and spilling out of the developing device tend to occur, which tends to damage the copying machine. Furthermore, image reliability is reduced.

Such problems are also common to image forming apparatuses other than copying machines, such as printers equipped with a plurality of developing devices.

SUMMARY OF THE INVENTION An object of the present invention is to provide a developing unit control method in which a plurality of color developing units can be installed in an image forming apparatus in which the use of developing devices and the degree of toner depletion are not uneven.

[Means for Solving the Problems] A developing unit control method in an image forming apparatus according to the present invention provides an image forming apparatus that can be equipped with a plurality of color developing units and that selectively uses the color developing units to form an image. a plurality of removable color development units, a detection means for detecting the color of toner in each color development unit, and a selection means for selecting a color development unit to be used from among the plurality of color development units; An operating means for specifying a color developing unit to be used among the plurality of color developing units, a determining means for determining whether a color developing unit of the same color is installed based on the detection result of the detecting means, and a determining means. When it is determined that color development units of the same color are installed, the selection of the selection means is automatically switched in a predetermined manner in which each development unit is used on average; in other cases, the selection is specified by the operation means. The present invention is characterized by comprising a control means for switching the selection of the selection means in response to.

[Function] Only when color development units of the same color are installed, the selection of multiple color development units is switched in a predetermined manner, ignoring the designation made by the operation means (keys on the operation panel, etc.), and each color development unit is To ensure that color developing units are used evenly. The predetermined method includes, for example, switching alternately according to information such as the number of copies, or distributing multiple copies to each color developing unit, or switching according to the ON signal of the print key or the original exchange signal of the automatic document feeder. Switch accordingly.

[Example] Hereinafter, taking as an example the case where the image forming apparatus is a copying machine,
Examples will be described with reference to the accompanying drawings.

As shown in FIG. 2, a photoreceptor drum 2 is pivotally supported approximately at the center of the copying machine 1, and the photoreceptor drum 2 can be rotated counterclockwise by a main motor (not shown). ing. A charger 3, an inter-image eraser 4, first and second developing units 5, 6, a transfer charger 7, a separation charger 8, and a cleaner device are arranged around the photoconductor drum 2 at intervals in the rotation direction thereof. 9. A main eraser IO is arranged, and an optical system 0 is provided above the photosensitive drum 2 and its peripheral equipment, a paper feed system P is provided on the left side, and a fixing device II is provided on the right side. ing. Note that three or more developing devices may be provided.

The optical system O includes a scanning unit 14 which is formed by integrating a slit exposure type light source 12 and a first movable mirror 13, and second and third movable mirrors 16, which are held by a common holder I5.
17, a lens 18, and a fixed mirror 19. A document (not shown) is set between document glass 20 and document presser 21 . Note that a standard pattern for AIDC (not shown) is provided below the document scale provided on the scanning start side of the document glass. Then, on the premise that the inter-image eraser 4 removes the charges in the area between the images of the photoreceptor drum 2, that is, the area corresponding to before the edge of the original in the scanning direction and after the rear edge of the original in the scanning direction, the charger 3 The area corresponding to the original on the front side is positively charged, and the light source 12
is turned on and the scanning unit 14 is moved to the left side in the figure using a scanning motor (not shown) while scanning the standard pattern and the document, thereby creating electrostatic charges corresponding to the standard pattern and the image of the document on the photoreceptor drum 2. A latent image is formed.

During scanning, the moving speed V of the scanning unit 14 to the left in the figure is equal to the circumferential speed of the photosensitive drum 2. , if the copy magnification is m, then V = Vo / m is set, and
Second and third movable mirrors 16. l, 7 is V.

/ 2 m to the left in the diagram. In addition, when the scanning unit 14 is not scanning, it touches the fixed position switch 22 to transmit a fixed position signal (“B” when the scanning unit 14 is in the fixed position) to the first CPU 200, which will be described later. In order to synchronize the scanning unit 14 and the paper feed system P, the timing switch 23 is activated when the scanning unit 14 moves a predetermined distance to the left after starting scanning.
, and transmits a timing signal to the first CPU 200 for operating a timing roller 24 (to be described later) (when the scanning unit 14 touches the timing switch 23, the timing signal becomes "bi").

Negatively charged toner supplied from the selectively used first developer 5 or second developer 6 is attached to the surface of the photoreceptor drum 2, and this toner forms the electrostatic latent image described above. is visualized (developed) to form a toner image corresponding to the standard pattern and the original image. Subsequently, the toner image of the document image is transferred from the timing roller 24 located at the downstream end of the paper feed system P to the copy paper (not shown) that is supplied to the surface of the photosensitive drum 2 in synchronization with the above-mentioned timing signal. The transferred copy paper is further separated from the surface of the photosensitive drum 2 by a separating charger 8. The (summer photo paper) separated from the photosensitive drum 2 is conveyed to the fixing device 11 by the conveying heald 25, and the fixing device!
After the toner image is heated and fixed at 1, it is discharged onto the tray 26.

The residual toner on the surface of the photoreceptor drum 2 is removed by the cleaner device 9 and collected into the cleaner device 9, and the residual charge on the surface of the photoreceptor drum 2 is removed by the main eraser 10, which is always turned on while the main motor is driving. be done.

Note that the density of the toner image of the standard pattern is measured by an LED and a photosensor (AIDC sensor), which are not shown, before the toner image is collected by the cleaner device 9. This measurement is
It is compared with a predetermined reference value by a comparator, and a first toner replenishment motor or a second toner replenishment motor, which will be described later, is operated in accordance with the comparison result, and the amount of toner replenishment is increased or decreased. - The paper feeding system P includes a manual paper feeding section 27, a first cassette paper feeding section 28 (hereinafter simply referred to as the first paper feeding section 28), and a second cassette paper feeding section 30 (hereinafter simply referred to as the first paper feeding section 28). (referred to as 2 paper feed section 30)
The copy paper inserted from the manual paper feed section 27 is
The sheet is conveyed to the timing roller 24 via the manual feed roller 31 and the intermediate roller 32, and is also conveyed to the first and second paper feed sections 2
The copy sheets in the cassettes Z8a and 30a installed in the cassettes Z8 and 30 are conveyed to the timing roller 24 via the first and second paper feed rollers 33 and 34, and the intermediate roller 32, respectively. Each roller 24.31, 32.33.34 is detachably connected to a drive system by a main motor via a clutch (not shown), and by turning on the clutch of each roller, the roller is connected to the drive system and rotated by the main motor. Note that each cassette 28a,
Near the cassette 30a, there are size detection sensors 35, 36 for detecting the size of the copy paper stored in each cassette 28a, 30a, and a size detection sensor 35, 36 for detecting the size of copy paper stored in each cassette 28a, 30a, and a size detection sensor 35, 36 for detecting the size of the copy paper stored in each cassette 28a, 30a. Cassette empty sensors 37 and 38 are installed for detection.

As shown in FIGS. 3 and 4, a bracket 40 is attached to one end in the longitudinal direction of the first developing device 5, and a bracket 40 is provided with a bracket 40 for replenishing toner into the first developing device 5. A toner supply bottle 41 is removably attached. Toner supply port 41a of the first toner supply bottle 41
is connected to one end of the transport pipe 42 in the longitudinal direction (direction perpendicular to the paper surface of FIG. 3), and the transport pipe 42 extends into the first developing device 5 from the toner supply port 41a. and,
By rotating the first toner replenishing bottle 4N around its center line by a first replenishing motor (not shown), the toner replenishing bottle 041a is opened and closed. Toner is supplied in an amount proportional to the rotational speed, and this toner is transported into the first developing device 5 by the transport pipe 42.

The toner conveyed into the first developing device 5 is transferred to a first packet roller which is rotated clockwise in FIG. 3 by a first developing motor (not shown) attached to the other longitudinal end of the first developing device 5. 43 (having a stirring blade) is mixed with the magnetic carrier (which charges the toner to a negative polarity through frictional contact with the toner) previously filled in the first developing device 5, and this toner and carrier are mixed. The mixed developer is agitated by the first packet roller 43, and is passed from the first packet roller 43 to the first developing sleeve 44 (rotated clockwise in FIG. 3 by the first developing motor). It is supplied to the surface of the photoreceptor drum 2. The electrostatic latent image on the surface of the photoreceptor drum 2 is visualized by the toner in the developer supplied to the surface of the photoreceptor drum 2, while the carrier in the developer is transferred to the first developer 5.
be collected and used repeatedly.

Note that a bias voltage can be applied to the first developing sleeve 44 from a first developing bias power source (not shown), and when this bias voltage is not applied (first developing bias off state), Even if the first packet roller 43 and the first developing sleeve 44 are rotationally driven,
The electrostatic latent image is not developed by the first developer 5.

A bracket 4 is located near the first toner supply bottle 4I.
The first detecting whether or not the bottle 4I is attached to the
Bottle presence sensor 45 (bottle 41 on bracket 40)
If it is attached, it will be on, and if it is not, it will be off. ) is installed, while the first toner supply bottle 41
A first bottle empty sensor 46 is installed in the replenishment port 41a to detect when the toner runs out in the bottle 41.
(If there is toner in the bottle 41, it is turned on, and if there is no toner, it is turned off.) is attached.

Further, two adjacent magnet fixing parts a and b (FIG. 4) located at the upper part of the first developing device 5 are filled with toner that has been replenished into the first developing device 5 from the first toner supply bottle 41. In order to identify the colors (black, red, yellow, blue), magnets 47 and 48 can be fixed respectively,
A combination of on and off of the first and second reed switches 49 and 50 arranged opposite to each other at the magnet fixing parts a and b (the first reed switch 49 is turned on if the magnet 47 is present, is turned off if there is no magnet 47, and the second The reed switch 50 is turned on if the magnet 48 is present, and turned off if it is not.) The toner color in the first developing device 5 is determined as shown in the table below.

On the other hand, a wide bracket 52 is attached to one end of the second developing device 6 in the longitudinal direction (direction perpendicular to the paper surface of FIG. 3), and a second toner supply bottle 53 is attached to the left end of the bracket 52. is removably attached. The toner replenishment port 53a of the second toner replenishment bottle 53 is connected to the left end of a transport pipe 54 extending laterally within the bracket 52, and the right end of the transport pipe 54 is connected in a direction perpendicular to the paper plane of FIG. A second toner supply bottle 53 is connected to one longitudinal end of a transport pipe 55 that is disposed and extends into the second developing device 6 .
The toner is transported from there through transport pipes 54 and 55 into the second developing device 6. The amount of toner replenishment is controlled by a second toner replenishment motor (not shown). The toner conveyed into the second developing device 6 is mixed with the magnetic carrier' in the second developing device 6 by a second packet roller 56 rotationally driven by a second developing motor (not shown), and is negatively charged. The photosensitive drum 2 is supplied with the second developing sleeve 57 driven by the second developing motor. In addition,
The second developing sleeve 57 is connected to a second developing bias power source (not shown), and the electrostatic latent image can be developed by the second developing device 6 only when a bias voltage is applied to the second developing sleeve 57. be done.

A first bottle presence sensor 4 is provided around the second developing device 6, respectively.
5. A second bottle presence sensor 58 and a second bottle empty sensor 60 which are turned on and off under the same conditions as the first bottle empty sensor 46 are provided, and depending on the presence or absence of two magnets 61 and 62. , the third one detects the color of the toner in the second developing device 6 based on the above-mentioned table. Fourth reed switch 63,64 (the third reed switch 63 is
A reed switch 49 (the fourth reed switch 64 corresponds to the second reed switch 50) is provided.

1st. The second developing device 5.6 and the first developing device 5.6. The second toner supply bottle 41, 53 normally contains black toner, which is the main color, so that no matter which developer is selected, copies will normally be made in black. If you want to copy in a different color, you can replace one of the developing devices with a toner supply bottle attached to that developing device with one containing toner of the other color. In this embodiment, the term "developing device" refers to one unit that also includes a replenishment container such as a toner replenishment bottle attached to the developing device.

Copy machine! At the top of the is an operation panel l as shown in Figure 5.
OO is equipped, and the operation panel 100 includes a print key 102 for commanding the start of copying, and an interrupt key 103.
, stop copying immediately after copying starts or in the middle of multi-copying (successive copying of multiple sheets based on the same original), and
A clear/stop key 105 that clears the number of copies set on the copy number display section 104 consisting of a group of LEDs and returns to the standard mode "B", numeric keys 106 to 115 for setting the number of copies on the copy number display section 104, and a light source 12. an exposure up key 116 and an exposure down key 117 that increase or decrease the exposure amount; L that is selectively lit to display the exposure amount;
ED group A1 paper feed section selection key 118 for selecting the first or second paper feed section 28.30; LEDs 120 to 123 for displaying the size of copy paper fed from the selected paper feed section;
the first developing device 5 and the second developing device 6 for selecting the first developing device 5 and the second developing device 6, respectively;
A developer selection key 124, a second developer selection key 125, and an LED 126.12 for displaying the selected developer 5 or 6.
7. LEDs 28 to 131 that display the color of toner in the selected developer 5 or 6; and the selected developer 5;
or toner supply bottle 41 or 53 attached to 6
LED to indicate when is empty
l 32 is provided.

The copying machine 1 includes first and second CPUs 200 and 300 having a circuit configuration as shown in FIG. That is,
The first CPU 200 includes various keys on the operation panel 100, the first . 2nd bottle presence sensor 41.53, 1st bottle presence sensor 41.53; Second bottle empty sensor 46, 60, first to fourth reed switches 49, 50, 63, 64 for detecting toner color
A switch matrix S is connected to the main motor, various roller clutches, etc., which are arranged vertically and horizontally, and the above-mentioned main motor, various roller clutches, etc.
It is operated and controlled by U200, and various LEDs such as copy number display section 104 are turned on and off via decoder 133.

On the other hand, the second CPU 3 mainly operates and controls the optical system 0.
00 is connected to the fixed position switch 22, timing switch 23, etc. Further, the first CPU 200 and the second CPU 300 are connected to each other for mutual synchronization.

FIG. 7 shows the main flowchart. When the power is turned on, first, initial settings such as register and timer settings are performed in step Sl (hereinafter the step is abbreviated). Next, at 82, start the internal timer set in the initial settings above. This internal timer is used to keep the length of time of one routine constant regardless of the processing content in each subroutine below.

Next, at 83, processing for receiving input signals from switches on the operation panel and input signals from sensors, etc., is executed. In this embodiment, in this subroutine, the first developing device 5. Only the color determination portion of the second developing device 6 will be explained later.

Next, at 84, a subroutine for switching the developer is called and executed. The main point of this embodiment will be explained later, namely, the first part. A detailed description will be given of the portion that controls the use of the respective developing devices evenly when the second developing devices are set with the same color.

Next, in step 85, a subroutine for output processing related to copy operations and the like is called and executed. In this embodiment, since this part is well known, its explanation will be omitted.

Finally, in 86, it is determined whether or not the internal timer has expired, and after waiting for the internal timer to expire, the process returns to S2.

The flow of each subroutine will be explained below.

FIG. 8 shows the input processing subroutine (S3) in the first developing device 5. A flowchart showing a portion of determining whether the colors of the second developing devices 6 are the same is shown. The color determination of black, red, blue, and yellow shown here can be determined by inputting the aforementioned switches 49°, 50, 63, and 64.

At 5100, color determination of the first developing device 5 is performed. 5lots, 5102.510 depending on the color determined here
3,5104 processing is executed.

Since the meaning of each is the same processing, only the 5lO1 part will be explained. When the color determination of the first developing device 5 is black, it is determined whether the color of the second developing device 6 is black in 5 lots. If the second developer 6 is also black, that is, the first
．． 2 Developer 5.6 When it is determined that both are the same color, 5
Continue to 105.

8106 when it is determined that the color is unique in 5 lots.
Execute.

In step 5105, flag A is set by setting "l" to flag A. This flag A is used in a developing device switching subroutine to be described later. The fact that flag A is "bi" indicates that the 1.2 developing units 5.6 are of the same color. In 8106, "φ" is entered in flag A. This indicates that the color of the 1.2 developing units 5.6 is the same. indicates that it is a different color.This is the same for the other red, yellow, and blue.If the 1.2 developing units 5 and 6 are the same color, indicate 5105, and if the two are different colors, indicate 5105. Execute 8106.

FIG. 1 shows that in the developing device switching subroutine, when both the first and second developing devices 5.6 are set with the same color,
A flowchart showing only the part for controlling so that each developing device is used evenly is shown. 6300, the flag A (9105, 5 in FIG. 8) is set in the input processing part described above.
106) is set. When the flag A is "bi", the process of 5301-S312 is executed.On the other hand, when the flag A is "φ", the process of 531-S312 is executed.
3 is executed. When the flag A is "φ", this means that different color developing devices 5 and 6 are included, and the process advances to step 5313 to directly select the developing device 5 or 6 currently selected on the operation panel 100.

If the flag A is "1" in 5300, that is, if the developing devices of the same color are installed, the process advances to 5301, and it is determined whether a copy start signal has been input. This copy start signal, although not explained in detail in this embodiment, is normally activated and generated when the print key 102 on the operation panel 100 is pressed, and prompts the start of the copying operation. be. When copy start is determined, processes 5302 to 5308 are executed, and when it is not determined, 5309 hejump is performed.

In 5302, it is determined whether the set number of copies is divisible by 2 or not. This set number of copies and (This is the number of copies set with the number keys 106 to 115 on the input operation panel 100, and is the number of copies before the print key 102 is pressed. If the judgment in 5302 is Yes, 5303 Then, the value obtained by dividing the set number of copies by 2 is stored in addresses B1 and B2.

B I and B t each indicate the set number of sheets of the developing device 5.6.

If it is determined in step 5302 that the set number of copies is not an even number, the process advances to step 5304. In 5304, the set number of copies is “l”.
” is determined. 5304: No
If it is determined that the number of copies to be copied is an odd number greater than 1, the process advances to 5305.

5305, the value obtained by subtracting "bi" from the set number of copies is "2".
'', and the value obtained by adding ``bi'' to the obtained value is stored in the Bl address (the set number of copies of the developing unit 5). Further, the value obtained by subtracting "l" from the set copy number and dividing it by "2" is stored in the B2 address (the set copy number of the developing device 6). If the set number of copies is an odd number, the number of copies set for the developing device 5 is increased by one.

If the determination in step 5304 is Yes, that is, if the set number of copies is one, the process advances to step 8306. 8306
Then, it is determined whether the value of flag C is "φ". The value of C is single copy (number of copies set =
1) is produced, the first developing device 5. This is used for determining whether to use the second developing units 6 alternately. This 8
When C is determined to be "φ" in step 306, the first developing device 5 is selected, and when it is determined to be "bi", the second developing device 6 is selected. In other words, in step 8306, C is
When is "φ", the process advances to 5307, stores "l" in the B1 address, stores "φ" in the B2 address, and sets C to "φ". Also; when C is "l" in 5so6, the process advances to 5308, "φ" is stored in the Bl address,
"Bi" is stored in the B2 address and C is set to "φ". In this way, the value of the flag C is changed every time a single copy is made, and the developing devices are used alternately.

As described above, after steps 5303, 5305, 5307, and 5308 are executed, and when NO is determined in 6301,
Proceed to 5309. 5309, the first developing device 5 produces B.
A determination is made as to whether copy operations have been performed the number of times equal to the value of the l address. If the determination is No, the process advances to step 5310 in which the first developing device 5 is selected again.

If Yes is determined in 5309, the process advances to 5311. In step 5311, it is determined whether the second developing device 6 has performed the copying operation as many times as the value of the B2 address. If Yes, this subroutine ends.

If NO, proceed to 5312. At 5312, the second
A selection process for the developing device 6 is performed.

The selection of the developing device 5.6 in 5310.5312 above includes the process of rotating the developing motor, the process of applying a developing bias, and the process of selecting the developing device selection LED 126 on the operation panel 100.
, 127 switching processing, etc. are included.

As described above, the first developing unit 5. When the second developing device 6 also has the same color, control is performed so that each developing device is used evenly.

Note that various methods can be used for switching the developing device. Even if the developing devices of the same color are always switched alternately when the developing devices are installed, averaging can be performed in the same manner as in this embodiment. When interlocking with an automatic document feeder (ADF), the ADF switches the developing unit in response to a signal for replacing the original, thereby making it possible to even out the use of the developing unit.

When operating by pressing the print key on the main body, the use of the developing device can be balanced by switching the developing unit according to the print key-on signal.

By switching the developing unit at a predetermined number of copies based on the number of copies stored in the memory,
It can also be averaged. Furthermore, it is also possible to allocate the frequency of use of each developing unit in proportion to the toner capacity of each developing unit.

[Effect of the invention] Due to the insufficient amount of carrier due to increased carrier consumption due to frequent use, for example, in a machine with AIDC, toner concentration (T/C) increases, resulting in increased toner spillage and damage to the machine. However, in the present invention, since a developing device is used on average, this damage can be prevented.

Since the developing devices are controlled so that they are used evenly, uneven use of the developing devices is alleviated, and the usability of the image forming apparatus is improved.

[Brief explanation of the drawing]

FIG. 1 is a flowchart for switching the developing device. FIG. 2 is a sectional view of the copying machine. FIG. 3 is a diagram of the developing unit. FIG. 4 is a perspective view of the developing unit. FIG. 5 is a diagram of the operation panel. FIG. 6 is a circuit diagram of the control system of the copying machine. FIG. 7 is a diagram of the main flow of copy control. FIG. 8 is a flowchart of part of the input processing. 5.6...Developer, 41.53...Toner bottle, 47.48...Magnet for color discrimination, 100.
...Operation panel, 200...CPU. Patent applicant Minolta Camera Co., Ltd. Agent
Patent attorney Aoyama Ao and two others Figure 1] Figure 4 Figure 5 Figure 2 Figure 6

Claims (1)

[Claims] (1) In an image forming apparatus that can be equipped with a plurality of color development units and that selectively uses the color development units to form an image, the plurality of removable color development units and the color of toner in each color development unit are used. a detection means for detecting a color development unit; a selection means for selecting a color development unit to be used from among the plurality of color development units; and an operation means for specifying a color development unit to be used from among the plurality of color development units. a determining means for determining whether color developing units of the same color are installed based on the detection result of the detecting means; and when the determining means determines that color developing units of the same color are installed, each developing unit and a control means for automatically switching the selection of the selection means according to a predetermined method used for the operation, and for other cases, switching the selection of the selection means in response to a designation by the operation means. A developing unit control method in an image forming apparatus.