JP2002365944A - Imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging apparatus capable of detecting the presence or no presence of a transfer body. SOLUTION: The imaging apparatus having a detachable final transfer body which finally transfers a toner image to a recording medium is provided with a detection means for detecting the presence or no presence of the final transfer body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus such as a copying machine, a printer, a facsimile, and a multifunction peripheral thereof. More specifically, the present invention detects the presence or absence of a removable final transfer member. Related to technology.

[0002]

2. Description of the Related Art Conventionally, image forming apparatuses such as copying machines and printers using an electrophotographic system (electrostatic transfer system) are widely known. In such an image forming apparatus, a toner image formed on an image carrier such as a photoconductor by an electrophotographic process is directly transferred to a recording medium such as paper by a transfer body, or the toner image on the image carrier is temporarily transferred. After the image is transferred onto the intermediate transfer member, the image is further transferred onto the recording medium by the transfer member to obtain a toner image on the recording medium. on the other hand,
The transfer member is detachable from the image forming main body to improve the maintainability of the image forming apparatus (for example, to facilitate recovery from a jam in which the recording medium is jammed on the conveyance path in the image forming apparatus). There is something to do.

[0003]

However, if the transfer body is configured to be detachable from the main body of the image forming apparatus in this manner, for example, a general user can remove a recording medium jammed on a conveyance path in the image forming apparatus. After removing the transfer member, image formation may be performed without attaching the transfer member. Attempts to form an image in such a state may not only result in no image, but may also adversely affect other components of the image forming apparatus.

The present invention has been made in view of such a technical problem, and an object of the present invention is to provide an image forming apparatus capable of detecting the presence or absence of a transfer member.

[0005]

According to the present invention, there is provided an image forming apparatus having a removable final transfer member for finally transferring a toner image to a recording medium, and comprising a detecting means for detecting the presence or absence of the final transfer member. Things. By configuring the image forming apparatus in this way, it is possible to prevent image formation without attaching the final transfer body, to secure appropriate image formation, and to adversely affect parts of other image forming apparatuses. Can be prevented.

Here, the structure of the detecting means is an optical type detecting means, that is, a light emitting portion which emits light to the final transfer body with a predetermined light emission amount, and receives a reflected light from the surface of the final transfer body. It is possible to employ a light receiving unit having a light receiving unit and a determining unit for determining the presence or absence of the final transfer body based on the amount of light received by the light receiving unit. In addition, the determination unit includes:
The failure of the light emitting unit and / or the light receiving unit may be determined based on the amount of light received by the light receiving unit.

Further, the detecting means causes the light emitting unit to emit light at a first light emission amount, and causes the determination unit to determine the failure of the light emitting unit and / or the light receiving unit based on the received light amount at that time. If no failure has occurred, the light-emitting unit may emit light with the second light-emission light amount, and may include a detection control unit that causes the determination unit to determine the presence or absence of the final transfer body based on the received light amount at that time. Good. Here, the first light emission amount and the second light emission amount can be set independently according to each purpose. For example, the first light emission amount can be set to be lower (smaller) than the second light emission amount.

In order to improve the detection accuracy, it is preferable to measure a plurality of locations on the final transfer body and make the determination based on the plurality of measurement results. Therefore,
The detection control unit can rotate the final transfer body at the time of the determination by the determination unit. By employing such a configuration, it is possible to measure a plurality of locations in the rotation direction of the final transfer body, and to more accurately detect the presence or absence of the final transfer body based on the measurement result.

In order to maintain good image quality (density) in an image forming apparatus (particularly, a full-color image forming apparatus), a toner patch as a reference is formed immediately after power-on or after a predetermined number of images are formed. In some cases, the density of the toner patch is measured, and density control for changing image forming conditions such as a developing bias is performed based on the measurement result.
Here, if the sensor for measuring the density of the toner patch can also have the function of the detecting means for detecting the presence or absence of the final transfer body, it is advantageous in terms of cost and space.

Therefore, the present invention provides an image forming apparatus, comprising:
Image forming means for forming a toner image on a recording medium and the final transfer member based on predetermined image forming conditions, and changing the image forming condition based on a density of a toner image as a toner patch formed on the final transfer member And a density control unit for detecting the density of the toner image as the toner patch.

Further, as a more specific configuration of the image forming apparatus, the image forming means includes yellow, cyan,
Four photoconductors corresponding to each color of magenta and black,
A first primary intermediate transfer member in contact with two of these four photoconductors, a second primary intermediate transfer member in contact with the remaining two photoconductors, and the first and second primary intermediate transfer members One that includes one contacting secondary intermediate transfer member and the final transfer member that contacts the secondary intermediate transfer member.
Further, among the four photosensitive members, the first and second intermediate transfer members, the secondary intermediate transfer member, and the final transfer member, a blade cleaning device as a toner removing unit is provided only on the final transfer member. A cleaning mode in which a predetermined potential gradient is generated in the first and second intermediate transfer members, the secondary intermediate transfer member, and the final transfer member, the transfer residual toner is collected on the final transfer member, and is collectively removed by the blade cleaning device. And those comprising:

In addition to the above, the image forming apparatus has a structure in which three image bearing members corresponding to yellow, cyan and magenta, or a photosensitive member corresponding to black are added thereto as the image forming means. And a final transfer member that contacts the three or four photosensitive members and an intermediate transfer member that contacts the intermediate transfer member. Further, among the three or four photosensitive members, the intermediate transfer member, and the final transfer member, a blade cleaning device as a toner removing unit is provided only on the final transfer member, and a predetermined cleaning is performed on the photosensitive member, the intermediate transfer member, and the final transfer member. There is a device having a cleaning mode in which a potential gradient is generated, transfer residual toner is collected on a final transfer member, and is collectively removed by the blade cleaning device.

In addition to the above, the image forming apparatus may be configured such that three image forming means corresponding to yellow, cyan and magenta, or a developing means corresponding to black are added to the image forming means. One developing unit, a photoreceptor facing (fixedly or rotationally) the three or four developing units, an intermediate transfer member in contact with the photoreceptor, and a final transfer member in contact with the intermediate transfer member. And those comprising: Furthermore, a photoreceptor, an intermediate transfer member,
Of the final transfer body, only the final transfer body is provided with a blade cleaning device as a toner removing unit, and a predetermined potential gradient is generated on the photoconductor, the intermediate transfer body, and the final transfer body, and the transfer residual toner is placed on the final transfer body. One that has a cleaning mode for collecting and collectively removing with the blade cleaning device is exemplified.

In addition, the present invention can be applied to an image forming apparatus dedicated to a single color (for example, black).

[0015]

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

Embodiment FIG. 1 shows a full-color printer 100 as an image forming apparatus according to an embodiment of the present invention. FIG. 2 shows the image forming main part of the full-color printer 100 shown in FIG. 1 in more detail. In addition, the arrow in FIG. 2 has shown the rotation direction of each rotating member. Hereinafter, the basic configuration of the image forming apparatus and the operation in the image forming mode will be described.

As shown in FIG. 1, the full-color printer 100 is roughly composed of a printer main body 101 and a paper feed tray section 102. The printer body (image forming means) 101 includes an image forming unit 1, an exposing device unit 12, toner cartridges 14Y to 14K for yellow Y, magenta M, cyan C, and black K, and respective colors (not shown) from the toner cartridges 14Y to 14K. Each of the toner supply flexible pipes 15Y to 15K extending to the developing device corresponding to
A control unit 6, a power supply unit 5, and a fixing unit 4 are provided.

A pair of feed rolls 41, a pair of first transport rolls 42, a pair of registration rolls 43, from the paper feed tray 102 to the paper discharge tray 103 of the printer main body 101.
A second transport roll pair 45 (in the fixing unit 4), a third transport roll pair 46, and a discharge roll pair 47 are provided.

Further, as shown in FIG. 2, the image forming unit 1 of the printer main body 101 includes yellow Y, magenta M,
Photoconductor drums (image carriers) 10Y to 10K corresponding to the respective colors of cyan C and black K, charging rolls 11Y to K for primary charging that contact these photoconductor drums 10Y to K, and developing devices corresponding to the respective colors 13Y to 13K and the above four photosensitive drums 10
A first primary intermediate transfer drum 21a that contacts two photosensitive drums 10Y and 10M of Y to K and a second primary intermediate transfer drum 21 that contacts two other photosensitive drums 10C and 10K.
b, the first and second primary intermediate transfer drums 21a, 21
The main part is constituted by the secondary intermediate transfer drum 22 that comes into contact with 1b and the final transfer roll (final transfer body) 30 that comes into contact with the secondary intermediate transfer drum 22. The final transfer roll 30 is configured to be detachable from the printer main body 101.

The photosensitive drums 10Y to 10K have a common tangent plane M
Are arranged at regular intervals so as to have Further, the first primary intermediate transfer drum 21a and the second primary intermediate transfer drum 21b each
They are arranged so as to be parallel to the Y to K axes and have a relation of a plane object with a predetermined target plane as a boundary. Further, the secondary intermediate transfer drum 22 is arranged such that the rotation axis is parallel to each of the photosensitive drums 10Y to 10K.

A signal corresponding to image information for each color is rasterized by an image processing unit (not shown) and input to the exposure unit 12. In the exposure device unit 12, the laser beams 12Y to 12K corresponding to the respective colors of yellow Y, magenta M, cyan C, and black K are modulated and applied to the photosensitive drums 10Y to 10K of the corresponding colors.

Around each of the photosensitive drums 10Y to 10K,
An image forming process for each color is performed by a known electrophotographic method. First, as the photoconductor drums 10Y to 10K, for example, photoconductor drums using an OPC photoconductor having a diameter of 20 mm are used.
Is driven to rotate at a rotation speed of, for example, 95 mm / sec. As shown in FIG. 2, the surfaces of the photoreceptor drums 10Y to 10K have charging rolls 11Y to 11K as contact-type charging devices.
Then, by applying a DC voltage of about -840V, for example, it is charged to about -300V. The contact-type charging device includes a roll-type charging device, a film-type charging device, and a brush-type charging device, but any type may be used. In this embodiment, a charging roll generally used in an electrophotographic apparatus in recent years is employed. The photosensitive drums 10Y to 10K
In this embodiment, DC is applied to charge the surface of
Although only the charging method of application is adopted, a charging method of AC + DC application may be used.

Thereafter, the surfaces of the photosensitive drums 10Y to 10K are irradiated with laser beams 12Y to 12K corresponding to the respective colors of yellow Y, magenta M, cyan C, and black K by a laser optical unit as an exposure device (not shown). Thus, an electrostatic latent image corresponding to the input image information for each color is formed. When an electrostatic latent image is written on the photosensitive drums 10Y to 10K by the laser optical unit, the surface potential of the image exposure unit is eliminated to about -60 V or less.

Further, yellow Y, magenta M, cyan C, and black K formed on the surface of the photosensitive drums 10Y to 10K.
The electrostatic latent image corresponding to each color is developed by the developing device 1 of the corresponding color.
The image is developed by 3Y to 3K and is visualized as a toner image of each color on the photosensitive drums 10Y to 10K.

Each of the developing devices 13Y to 13K is filled with a two-component developer composed of a toner of a different color such as yellow Y, magenta M, cyan C or black K, and a carrier. As the type of toner to be used, pulverized toner or spherical toner can be considered, but in this embodiment, spherical toner is used. In addition, since the irregular shaped toner such as the pulverized toner has a large contact surface with respect to the adhesion surface, the adhesion force is large, and it is difficult to transfer the toner to the surface of the transfer destination. On the other hand, since the spherical toner has a small contact surface with respect to the adhesion surface, the adhesion force is small and the transfer efficiency is high. Further, as a method for producing a spherical toner, a method of subjecting a toner produced by an emulsion polymerization method, a suspension polymerization method, a dissolution suspension method, or a kneading and pulverizing method to a heat treatment is known. The spherical toner is defined as M1 ≦ 125, preferably M1 ≦ 120, when the shape factor M1 is represented by the following equation.
Means M1 = (π · dmax2 / 4A) × 10
0, dmax: maximum diameter of toner, A: cross-sectional area of toner

These developing devices 13Y to 13K are supplied with toners of respective colors from the respective toner cartridges 14Y to 14K shown in FIG. 1 via respective toner supply flexible pipes 15Y to 15K. The replenished toner is sufficiently stirred with the carrier by the auger 133 and triboelectrically charged to a negative polarity. Inside the developing roll 130, a magnet roll (not shown) having a plurality of magnetic poles arranged at a predetermined angle is arranged in a fixed state. The developer conveyed to the vicinity of the surface of the developing roll 130 by the paddle 132 that conveys the developer to the developing roll 130 is subjected to a developer amount regulating member 131.
The amount conveyed to the developing unit is regulated by the control. In this embodiment, the amount of the developer on the developing roll 130 is 30 to 50 g / m ² , and the charge amount of the toner on the developing roll 130 at this time is approximately 20 g / m ^2.
It is about 35 .mu.C / g.

The toner supplied onto the developing roll 130 is in the form of a magnetic brush composed of a carrier and toner by the magnetic force of the magnet roll, and this magnetic brush comes into contact with the photosensitive drums 10Y to 10K. I have. An AC + DC developing bias voltage is applied to the developing roll 130 to remove the toner on the developing roll 130 from the photosensitive drum 10Y.
To K, a toner image is formed by developing the electrostatic latent image. In this embodiment, the developing bias voltage is such that the AC component is 4 kHz, 1.5 kVpp,
The C component is about -200V.

Next, the toner images of the respective colors of yellow Y, magenta M, cyan C, and black K formed on the respective photosensitive drums 10Y to 10K are transferred to the first primary intermediate transfer drum 21a and the second primary transfer drum 21a. The primary transfer is electrostatically performed on the intermediate transfer drum 21b. That is, the yellow Y and magenta M toner images formed on the photoconductor drums 10Y and 10M are transferred onto the photoconductor drums 10C and 10K on the first primary intermediate transfer drum 21a.
The cyan C and black K toner images formed above are
The primary transfer is performed on the second primary intermediate transfer drum 21b. Therefore, on the first primary intermediate transfer drum 21a, the monochrome image transferred from either the photoconductor drum 10Y or 10M and the two-color toner image transferred from both the photoconductor drums 10Y and 10M are superimposed. A double-color image is formed. Further, on the second primary intermediate transfer drum 21b, a similar single color image and a similar double color image are formed from the photosensitive drums 10C and 10K.

The first and second primary intermediate transfer drums 2
The surface potential required for electrostatically transferring a toner image from the photosensitive drums 10Y to 10K onto the photosensitive drums 1a and 21b is +250.
About 500V. This surface potential is set to an optimum value depending on the charged state of the toner, the ambient temperature, and the humidity. The ambient temperature and the humidity can be easily known by detecting the resistance value of a member having a characteristic in which the resistance value changes depending on the ambient temperature and the humidity. As described above, when the charge amount of the toner is in the range of 20 to 35 μC / g and the environment is normal temperature and normal humidity, the first and second charge amounts are set.
The surface potential of the primary intermediate transfer drums 21a and 21b is +
About 400V is desirable.

The first and second primary intermediate transfer drums 21a and 21b used in this embodiment have, for example, an outer diameter of 42 mm.
mm, and the electric resistance value R is set to about 10 ⁸ Ω. First and second primary intermediate transfer drums 21a and 21b
Is a cylindrical rotating body having a single-layer or multiple-layer surface with flexibility or elasticity.
A low-resistance elastic rubber layer (R = 10 ² to 10 ³ Ω) typified by conductive silicone rubber or the like is formed on a metal pipe as a metal core made of e or Al to a thickness of about 0.1 to 10 mm. Is provided. Further, the outermost surfaces of the first and second primary intermediate transfer drums 21a and 21b are typically coated with a high release layer (R = 10 ⁵⁾ having a thickness of 3 to 100 μm made of fluoro rubber in which fluoro resin fine particles are dispersed. .About.10 ⁹ Ω) and bonded with a silane coupling agent-based adhesive (primer).

What is important here is the resistance value and the surface releasability.
And the resistance value of the high release layer is R = 10 ^Five ~Ten⁹ About Ω
The material is particularly limited as long as it has a high release property.
Not. The first and second primary intermediate transfer drums 21
a and b are the first and second primary cleaning rows, respectively.
23a and 23b are rotatably mounted. This
These primary cleaning rolls 23a and 23b are made of metal, respectively.
Conductive brush flocking tape is applied to the roll body
It is coated and has a predetermined cleaning bias.
Be added.

The single-color or double-color toner images formed on the first and second primary intermediate transfer drums 21a and 21b are electrostatically secondary-transferred onto the secondary intermediate transfer drum 22. You. Accordingly, on the secondary intermediate transfer drum 22, a final toner image from a single color image to a quadruple color image of yellow Y, magenta M, cyan C, and black K is formed.

The surface potential required for electrostatically transferring the toner images from the first and second primary intermediate transfer drums 21a and 21b onto the secondary intermediate transfer drum 22 is +600.
It is about 1200V. This surface potential is set to an optimum value according to the charged state of the toner, the ambient temperature, and the humidity, as in the case of the transfer from the photosensitive drums 10Y to 10K to the first primary intermediate transfer drum 21a and the second primary intermediate transfer drum 21b. Will be set. What is needed for transcription is
Since it is a potential difference between the first and second primary intermediate transfer drums 21a and 21b and the secondary intermediate transfer drum 22,
It is necessary to set a value corresponding to the surface potential of the second primary intermediate transfer drums 21a and 21b. As described above, the charge amount of the toner is in the range of 20 to 35 .mu.C / g, and the surface potential of the first and second primary intermediate transfer drums 21a and 21b is about +400 V in a normal temperature and normal humidity environment. In this case, the surface potential of the secondary intermediate transfer drum 22 is +80
0V, that is, the first and second primary intermediate transfer drums 2
It is desirable that the potential difference between 1a, 21b and the secondary intermediate transfer drum 22 be set to about + 400V.

The secondary intermediate transfer drum 22 used in this embodiment has, for example, an outer diameter of 42 mm, which is the same as the first and second primary intermediate transfer drums 21a and 21b, and a resistance value of about 10 ¹¹ Ω. Is set. Further, the secondary intermediate transfer drum 22 is also a first and a second primary intermediate transfer drum 21a,
Similar to 21b, the surface of a single layer or a plurality of layers is a cylindrical rotating body having flexibility or elasticity, and is generally placed on a metal pipe as a metal core made of Fe, Al, or the like. , A low-resistance elastic rubber layer (R = 10 ² to 10 ³ Ω) represented by a conductive silicone rubber or the like has a thickness of 0.1 to 10
mm. Further, the secondary intermediate transfer drum 2
The outermost surface of No. 2 is typically formed as a high release layer having a thickness of 3 to 100 μm made of fluororubber in which fluororesin fine particles are dispersed, and bonded with a silane coupling agent-based adhesive (primer). I have.

What is important here is the resistance value and the releasability of the surface, as in the first and second primary intermediate transfer drums 21a and 21b. However, the resistance value of the secondary intermediate transfer drum 22 depends on the first and second primary intermediate transfer drums 21a and 21a.
It must be set higher than b. Otherwise, the secondary intermediate transfer drum 22 charges the first and second primary intermediate transfer drums 21a and 21b, and it is difficult to control the surface potential of the first and second primary intermediate transfer drums 21a and 21b. Become. The material is not particularly limited as long as it satisfies such conditions. The secondary intermediate transfer drum 22
, A secondary cleaning roll 24 is attached so as to be driven and rotatable. The secondary cleaning roll 24 is configured by covering a metallic roll body with a flocking tape of a conductive brush, and a predetermined secondary cleaning bias is applied.

Next, the final toner image from the single-color image to the quadruple-color image formed on the secondary intermediate transfer drum 22 is transferred onto the sheet S passing through the sheet transport path P by the final transfer roll 30. Next is transferred. This sheet passes through a pair of registration rolls 43 through a sheet feeding process, and is sent to a nip portion between the secondary intermediate transfer drum 22 and the final transfer roll 30.
After this final transfer step, the final toner image formed on the paper is fixed by the fixing roller pair 44 in the fixing unit 4, and a series of image forming processes is completed.

The final transfer roll 30 has, for example, an outer diameter of 20.
mm, and the resistance value R is set to about 10 ⁸ Ω. As shown in FIG. 3, the final transfer roll 30 has a coating layer 3 made of urethane rubber or the like on a metal shaft 31.
2 and a coating is applied thereon as required. The optimum value of the voltage applied to the final transfer roll 30 varies depending on the ambient temperature, humidity, the type of paper (resistance value, etc.), and is generally about +1200 to 5000 V.
In this embodiment, a constant current method is employed, and a current of about +10 μA is applied under a reference environment to obtain a substantially appropriate transfer voltage (+1600 to 2000 V).

In the series of transfer steps, when the toner image passes through the transfer portion in each transfer step, a part of the positive toner in the (-) charged image is reversed by Paschen discharge or charge injection. Polar (+) charged toner may occur. The (+) charged toner flows back to the upstream side without being transferred to the next step, and thus adheres and accumulates on the charging devices 11Y to 11K having the highest negative potential. The portions of the charging devices 11Y to 11K to which the toner adheres are activated by the discharge, and the surface potential of the photoconductor drums 10Y to 10K tends to increase. Therefore, the portion where the toner adheres much, the portion where the toner adheres little, The surface potential of the photoconductor drums 10Y to 10K becomes uneven in the portion where the toner does not adhere. If the surface potentials of the photoconductor drums 10Y to 10K become uneven, even if the surface of the photoconductor drums 10Y to 10K is uniformly exposed to an image in order to form an electrostatic latent image, the nonuniformity of the latent image potential will occur. This causes a difference in the amount of development, so that the density unevenness becomes conspicuous especially when an attempt is made to develop a halftone image.

Therefore, in order to prevent the occurrence of density unevenness due to the toner attached to the charging devices 11Y to 11K, in this embodiment, there is a certain number of sheets before printing, after printing, every predetermined number of sheets during continuous printing, and the like. The following cleaning operation is performed at a predetermined timing.

Charging devices 11Y-K, photosensitive drums 10Y-
K, first and second primary intermediate transfer drums 21a, 21b
By applying voltages to the rotating bodies of the secondary intermediate transfer drum 22 and the final transfer roll 30 in order such that the final transfer roll 30 has the largest negative potential, a voltage having a potential gradient is applied to the rotating body of the charging device 11Y. To K, the (+) charged toner of the opposite polarity deposited and deposited during the printing operation is sequentially transferred and moved to the final transfer roll 30 in the cleaning operation, and a blade provided in contact with the final transfer roll 30 is provided. Is collected by the cleaning device 31 including the final cleaning member 32. This cleaning device 31
As shown in FIG. 4, each has a blade-shaped final cleaning member 32, a toner collection box 33, a support frame 34, a static eliminator 35 provided on the support frame 34, and a bias plate 36.

In this embodiment, the surface potentials of the charging devices 11Y-K are 0 V, and the surface potentials of the photosensitive drums 10Y-K are-
300V, the first and second primary intermediate transfer drums 21a,
The surface potential of the secondary intermediate transfer drum 22 is set to -1300 V, and the surface potential of the final transfer roll 30 is set to -2000 V. This potential gradient is obtained by supplying a voltage to the metal part (shaft, pipe) of each member. For example, the first and second primary intermediate transfer drums 21a and 21b or the secondary intermediate transfer drum 22 are used. If a desired surface potential can be obtained depending on the relationship between the resistance values of these members by electrically floating them, such a method may be adopted. In such a minus application cleaning mode, that is, the reverse polarity (+) charged toner collecting mode, it is possible to prevent the occurrence of density unevenness due to the toner attached to the charging devices 11Y to 11K.

An optical density sensor 7 is arranged around the cleaning device 31 at the axial center of the final transfer roll 30 so as to be located on the radial extension of the outer periphery of the final transfer roll 30. ing. The optical density sensor (detection means) 7 includes a sensor main body 70 and a holder 71 for fixing the sensor main body 70. As shown in FIG. 5A, the optical density sensor 7 is a specular reflection type sensor that detects specular reflection light, and has a predetermined incident angle φ with respect to a detection position on the surface of the final transfer roll 30. A light emitting element 70a composed of an LED or the like arranged only at an angle, and a light reflected from the light emitting element 70a to a detection position on the surface of the final transfer roll 30 to be specularly reflected from the detection position. And a light receiving element 70b, such as a phototransistor, which is arranged at an angle of reflection equal to the predetermined incident angle with respect to the detection position on the surface of the transfer roll 30.

As the optical density sensor 7, as shown in FIG. 5B, a diffuse reflection type sensor for detecting diffused light may be used. Further, both a specular reflection type sensor and a diffuse reflection type sensor may be used. In this case,
By detecting the toner density based on both the specular reflection component and the scattered light component, the detection accuracy of the toner density can be further improved.

Incidentally, in the full-color printer 100 according to the present embodiment, the optical density sensor 7 is used for detecting the presence or absence of the final transfer roll 30 and also for measuring the density of a toner patch during density control. Hereinafter, each usage method will be described in order.

FIG. 6 shows the detection of the presence or absence of the final transfer roll.
FIG. 3 is a functional block diagram illustrating a configuration for detecting the presence or absence of 0. This control system includes a detection control unit 62 and a judgment unit 6
3. Inputs to the detection control unit 62 include a power-on signal and a cover-close signal from the main control unit 61. Outputs from the detection control unit 62 include an applied voltage (input voltage) to the light emitting element 70a, Control signals to the main control unit 61 and the judgment unit 63 are mentioned. The input to the judging unit 63 includes an output voltage from the light receiving element 70b and a control signal from the detection control unit 62. The output signal from the judging unit 63 includes a signal to the main control unit 61 and the detection control unit 61. Control signals. The main control unit 6
1 displays an arbitrary message on the display panel 9 of the full-color printer 100,
It has a function to control stopping. The main control unit 61, the detection control unit 62, and the determination unit 63 are all functionally implemented in the control unit 6 of the printer main body 101.

FIG. 7 is a flowchart illustrating a procedure for detecting a failure of the optical density sensor 7 and the presence or absence of the final transfer roll 30. Hereinafter, description will be made based on this flowchart.

First, when the power is turned on to the full-color printer 100 or when the front cover of the full-color printer 100 is closed, the main control unit 61 detects a power-on signal or a cover close signal indicating them, and the detection control unit 62. Output to The detection control unit 6 to which the signal is input
2 is the sensor failure detection voltage V _lset-
chk1 is applied as an input voltage V _mon to the light emitting element 70a of the optical density sensor 7 (step S10). The light-emitting element 70a has an applied input voltage V _mon (= V _{lset- ch k1} )
The final transfer roll 30 (the part where the final transfer roll 30 originally exists) is irradiated with a light emission amount (first light emission amount) corresponding to (1).

The light receiving element 70b which receives the mirror-reflected light of the irradiated light has an output voltage V corresponding to the amount of the received light.
_out is output to the determination unit 63. The determination unit 63 determines the output voltage _Vout and the sensor abnormality threshold V stored in advance.
Compare with _snr-chk (step S11). Here, when the output voltage V _out is larger than the sensor abnormality threshold V _snr-chk , the determining unit 63 determines that the optical density sensor 7 is faulty, and outputs a sensor fault signal to the detection control unit 62 and the main control unit 62. Output to the control unit 61. The detection control unit 62 to which the sensor failure signal has been input receives the input voltage V _mon (= V
_lset-chk1 ) is set to 0 (step S12),
The main controller 61 to which the sensor failure signal has been input causes the display panel 9 to display a message indicating that "the optical density sensor 7 has failed" (step S13).

On the other hand, when the output voltage V _out is equal to the sensor abnormality threshold V
_{If the value is} equal to or _smaller than _snr-chk , the determination unit 63 determines that the optical density sensor 7 is normal, and outputs a sensor normal signal to the detection control unit 62.

Detection control unit 6 to which the sensor normal signal has been input
2 is an input voltage V _mon (= V
_lset-chk1 ) is changed to the roll presence / absence detection voltage _Vlset-chh2 (step S20). Then, the light emitting element 70a
The final transfer roll 30 has a light emission amount (second light emission amount) corresponding to the applied input voltage V _mon (= V _{lset- ch k2} ).
(A part where the final transfer roll 0 is originally present).
A light receiving element 70 for receiving the specular reflected light of the irradiated light
b outputs an output voltage V _out corresponding to the received light amount to the determination unit 63. The sensor failure detection voltage V
_lset-chk1 and the roll presence / absence detection voltage _Vlset-chh2 are set independently, and the relationship | _Vlset-chk1 | <| _Vlset-chh2 | is established. In the present embodiment, _Vlset-chk1 = 0. 38
[V], _Vlset-chh2 = 1.13 [V].

The judging section 63 compares the output voltage V _out with a roll presence / absence threshold V _{btr -chk} stored in advance (step S21). Here, if the output voltage _Vout is equal to or greater than the roll presence threshold _Vbtr-chk , the determination unit 63 determines that the final transfer roll 30 is at an appropriate position, and outputs a roll presence signal to the detection control unit 62. I do. Roll detection control unit 62 a signal is input there is an input voltage V _mon to the light emitting element 70a to (= V _{ls et-chk1)} as well as the 0 (step S22), and fault and final transfer roll of the optical density sensor 7 The detection processing of the presence / absence of 30 is ended.

On the other hand, if the output voltage V _out is equal to the roll presence threshold V
If it is smaller than _btr-chk , the determination unit 63 determines that there is a possibility that the final transfer roll 30 does not exist, and outputs a roll unknown signal to the detection control unit 62. The detection control unit 62 to which the roll unknown signal has been input outputs a signal for driving the final transfer roll 30 to rotate to the main control unit 61, and counts an elapsed time from the time when the signal is output. The main controller 61 drives the main motor based on an instruction from the detection controller 62 to rotate the final transfer roll 30. If the output voltage _Vout has become equal to or greater than the roll presence threshold _Vbtr-chk before the drive time of the main motor reaches 350 [ms] (step S27) (step S24), the determination unit 63 sets the final transfer roll. It is determined that 30 is present, and a roll presence signal is output to the detection control unit 62. The detection control unit 62 to which the roll presence signal has been input outputs a signal for stopping the final transfer roll 30 to the main control unit 61 (step S25), and the input voltage V _mon (= V _lset-chk1 ) to the light emitting element 70a. ) Is set to 0 (step S26), and the processing for detecting the failure of the optical density sensor 7 and the presence or absence of the final transfer roll 30 is completed.

On the other hand, the driving time of the main motor is 350
Until the time reaches [ms] (step S27), the output voltage V
_{If out} is not equal to or greater than the roll presence threshold V _btr-chk , the determination unit 63 determines that the final transfer roll 30 does not exist, and outputs a no-roll signal to the detection control unit 62 and the main control unit 61. The detection control unit 62, to which the no-roll signal has been input, sets the input voltage V _mon (= V
_lset-chk1 ) is set to 0 (step S29). The main control unit 61 to which the no-roll signal has been input stops the main motor to stop the rotation of the final transfer roll 30, and displays on the display panel 9 that "the final transfer roll 30 is not properly mounted". Then (step S30), the processing for detecting the failure of the optical density sensor 7 and the presence / absence of the final transfer roll 30 ends.

◎ Measurement of density of toner patch In the xerography method, etc., static electricity is used.
The image density tends to fluctuate due to environmental fluctuations and aging. For this reason, the process control mode (control mode) is provided separately from the image forming mode in response to environmental fluctuations and changes over time.
It is preferable to control the electrophotographic process while measuring the density of the toner patch by providing the image forming apparatus.

The process control mode includes a TC process control mode (toner density control mode) for controlling the toner density (ratio of toner and carrier in the developer) in each of the developing devices 13Y to 13K. Potential process control mode (image density control mode) for controlling the toner density of the toner image transferred on the paper
And exists. In any of these process control modes, a test toner patch is formed on the surface of an image density detection medium such as a photoreceptor, an intermediate transfer member, or a transfer roll or transfer belt on paper, and the density is optically measured. Various image forming processes (image forming conditions) are detected by the density sensor and controlled, but a preferable image density detecting medium differs depending on the characteristics of each process control.

That is, in the TC process control mode, an image density detection medium close to each of the developing devices 13Y to 13K is detected so that the ratio of toner and carrier in each of the developing devices 13Y to 13K can be detected more accurately. For example, it is preferable to detect toner patches on the surfaces of the photoconductor drums 10Y to 10K. On the other hand, in the potential process control mode, an image density detection medium close to the paper, for example, a toner patch on the surface of the secondary intermediate transfer drum 22 or the final transfer roll 30 is detected so that the toner density on the paper can be detected more accurately. Is preferred.

However, detecting the toner patches on the photosensitive drums 10Y to 10K requires four optical density detecting means for each of the photosensitive drums 10Y to 10K. First and second primary intermediate transfer drums 21a, 21b
If it is above, two optical density detecting means may be used. If it is on the secondary intermediate transfer drum 22 or on the final transfer roll 30, one optical density detecting means may be used.

Therefore, in this embodiment, a single optical density sensor 7 is used with emphasis on the simplicity of the configuration of the apparatus, and the toner patch on the final transfer roll 30 is detected in both process control modes. I decided that. On the other hand, in the TC process control mode, the ratio of the toner and the carrier in each of the developing devices 13Y to 13K can be detected as accurately as possible (even on the final transfer roll 30 that has undergone multiple transfers). The transfer rate in the TC process control mode is particularly high. For example, the toner amount of the test patch toner image formed on the photosensitive drums 10Y to 10K is more than 90% or 95% on the final transfer roll 30. The image forming conditions were controlled so as to transfer the image by at least%.

FIG. 8 is a block diagram illustrating an image forming condition control system of the full-color printer 100 according to the present embodiment.

As shown in the figure, this control system is mainly composed of an image forming condition control unit 60, and an input unit for inputting a signal to the image forming condition control unit 60 is a final transfer roll 30. In addition to the optical density sensor 7 for measuring the above toner density, the environmental sensor 8 for measuring the temperature and humidity in the full-color printer 100, the mode of the full-color printer 100, the printing speed, and other information of multicolor or single color are input. The main control unit 61 performs the operation. In addition,
Both the image forming condition control unit 60 and the main control unit 61 are functionally realized in the control unit 6 of the printer main body 101.

On the other hand, output units from which signals are output from the image forming condition control unit 60 include charging power supply units 110Y to 110K for applying a charging voltage to the charging rolls 11Y to 11K.
The exposure device unit 12 for irradiating the laser beams 12Y to K corresponding to each color, the developing power supply units 131Y to 131K for applying a developing bias voltage to the developing rolls 130Y to 130K, and the toner supply flexible pipes 15Y to 15K. Driving section), primary transfer power supply sections 210a, b, for applying a primary transfer voltage to the first and second primary intermediate transfer drums 21a, 21b.
A secondary transfer power supply unit 220 for applying a secondary transfer voltage to the secondary intermediate transfer drum 22, a final transfer power supply unit 300 for applying a final transfer current to the final transfer roll 30, a first and a second primary cleaning rolls 23a, b , A primary cleaning power supply unit 230a for applying a primary cleaning voltage to
b, a secondary cleaning power supply unit 240 that applies a secondary cleaning voltage to the secondary cleaning roll 24.

The image forming condition controller 60 includes a main controller 6
1 to the mode of the full color printer 100 (image forming mode, potential process control mode, TC control mode), printing speed (8 PPM or 16 PPM)
), A signal indicating a printing color (different of multicolor or single color), a signal indicating the toner density of the toner patch P from the optical density sensor 7, and a temperature and humidity in the full-color printer 100 from the environment sensor 8, respectively. Signal is input. Then, a toner image as the image I is formed on the sheet S based on these input signals and image forming conditions provided in the image forming condition control unit 60 in advance. Also,
Based on these input signals and the image forming conditions and toner patch creation conditions provided in advance in the image forming condition control unit 60, the toner patch P
A toner image as No. 1 is formed. Further, based on these input signals and the image forming conditions and toner patch creation conditions provided in the image forming condition control unit 60,
A toner image as a toner patch P2 is formed on the final transfer roll 30.

Here, the conditions for the main control section 61 to determine that the potential process control mode is necessary include:
For example, immediately after the power is turned on to the full-color printer 100, when a predetermined number of images have been formed (in the image forming mode) from the previous potential process control mode, or when there is a user's explicit instruction. Is mentioned. Similarly, the main controller 61 determines that the TC process control mode is necessary, for example, when the power is turned on to the full-color printer 100, when a predetermined number of images have been transferred from the previous TC process control mode. For example, when forming is performed (in the image forming mode), or when there is an explicit instruction from the user. Hereinafter, the operation of each control mode will be described in detail.

O Potential process control mode First, the main control unit 61 controls the mode of the full-color printer 100 (image forming mode, potential process control mode, and TC control mode). However, when the signals indicating the printing speed and the printing color are respectively input from the main control unit 61, the image forming condition control unit 60 selects the image forming condition and the toner patch creation condition stored in advance according to the situation. Choose the appropriate one.

For example, when a signal indicating that the mode is the potential process control mode, the printing speed is 16 PPM, the printing color is multicolor (color), and the temperature and humidity are the reference environment from the environment sensor 8 is input from the main control unit 61. The image forming condition control unit 60 applies the same 400 [V] as the image forming mode to the secondary intermediate transfer drum 22 as the primary transfer potential applied to the primary intermediate transfer drums 21a and 21b. 900 [V] as the secondary transfer potential to be applied, and 6 [μ] as the final transfer current applied to the final transfer roll 30.
A], 190 [V] as the primary cleaning voltage applied to the primary cleaning rolls 23a and 23b, 210 [V] as the secondary cleaning voltage, and the photosensitive drum 10
-300 [V] as the (target) charging potential and -200 [V] as the DC component of the developing bias voltage. The image forming condition control unit 60 selects the coverage input of 33.3% as the toner patch creation condition.

Based on the image forming conditions and toner patch preparation conditions selected in this way, the full-color printer 1
00 forms a toner image P1 as a toner patch on the final transfer roll 30, and performs potential process control.

FIG. 9 is a flowchart for explaining the operation of the potential process control VC. Hereinafter, based on this flowchart, the potential process control VC
Will be described in more detail.

First, in a state where the toner patch P1 is not transferred, the surface of the final transfer roll 30 is detected by the optical density sensor 7, and the output Vcl of the optical density sensor 7 at this time is detected.
n is stored (step ST101). Next, the toner patches P1 (Y) to (K) for each color of yellow, magenta, cyan, and black are determined based on the image forming conditions and the toner patch creation conditions described above, and FIG.
As shown in (2), the film is formed on the final transfer roll 30 (step ST102).

FIG. 10A illustrates the toner patch P1 formed at the center of the final transfer roll 30 in the axial direction. This toner patch P1 is
0 rotation direction, yellow P (Y), cyan P
(C), magenta P (M), and black P (K) in this order. The size of each toner patch P1 is 11 [mm] in the sub-scanning direction X and 12 [mm] in the main scanning direction Y. The interval D between the toner patches P1 is configured to be 3 [mm]. In the present embodiment, each toner patch P1
Is formed at the axial center of the final transfer roll 30,
As shown in FIG. 10B, the transfer roller 30 may be formed at an axial end of the final transfer roll 30. In that case, it is necessary to change the installation position of the optical density sensor 7.

Thereafter, the areas of the yellow, magenta, cyan, and black toner patches P1 (Y) to (K) formed on the final transfer roll 30 are optical density sensors as shown in FIG. 7 with 1 pitch of 0.5 mm
The average value Vpatch is obtained by detecting six points (step ST1).
03). Here, as shown in FIG.
Although a specular reflection type optical density sensor 7 is used, FIG.
As shown in (b), a diffuse reflection type sensor for detecting diffused light may be used, or both sensors may be used.

Then, the average value of each color is used as the final transfer roll 3
0 surface (state where toner patch P1 is not transferred)
The ratio Vpatch / Vcln divided by the value is used as a substitute value for the density (step ST104). Here, the final transfer roll 3
The ratio with the value of the elementary surface of 0 is the final transfer roll 3
This is for correcting a change in the reflectance of the zero element surface and a change in the LED light emission amount.

As a result, Vpatch / Vcln for each color
Is compared with a predetermined value (step ST105). If the obtained density of the toner patch P1 is lower than the predetermined density, the image forming condition control unit 60 determines the absolute value of the DC component _Vdc of the developing bias voltage according to the difference. more increased, at the same time (to raise the absolute value of the voltage applied to the charging roller 11 as a result) to further increase the absolute value of the charging potential V _h of the photosensitive drum 10 (step ST 106). By doing so, as shown in FIG. 12B, the electric field in the developing direction formed between the developing roll 130 and the image portion on the photosensitive drum 10 increases, and the amount of toner to be developed increases. ,
The image density increases.

On the other hand, if the determined density of the toner patch P1 is higher than the predetermined density, the image forming condition control unit 60 decreases the absolute value of the DC component _Vdc of the developing bias voltage according to the difference, At the same time (as a result lowers the absolute value of the voltage applied to the charging roller 11) smaller absolute value of the charging potential V _h of the photosensitive drum 10 (step ST10
6). By doing so, as shown in FIG. 12C, the electric field in the developing direction formed between the developing roll 130 and the image portion on the photosensitive drum 10 is reduced, and the amount of toner to be developed is reduced. , The image density decreases.

TC process control mode In toner replenishment, an image density is measured from a print image signal, and the replenishment time is controlled so as to replenish toner corresponding to the amount of toner used in accordance with the result. However, according to this method, when the development amount fluctuates, the amount of toner used fluctuates, and the balance with the amount of replenished toner deviates, so that the toner density in the developing device 13 fluctuates. Therefore, the toner patch P2 is created, the density is detected, and the toner supply amount is corrected according to the result.

First, the main control unit 61 determines the mode of the full-color printer 100 (different of image forming mode, potential process control mode, and TC control mode), the environmental sensor 8 determines the temperature and humidity in the full-color printer 100, and the main control unit. When the signals indicating the printing speed and the printing color are input from 61, respectively, the image forming condition control unit 60
Selects an appropriate one according to the situation from among the image forming conditions and toner patch creation conditions stored in advance.

For example, when a signal is input from the main controller 61 indicating that the mode is the potential process control mode, the printing speed is 16 PPM, the printing color is multi-color (color), and the temperature and humidity are the reference environment from the environment sensor 8. First, the image forming condition control unit 60 sets the image forming condition to 360 as the primary transfer potential applied to the primary intermediate transfer drums 21a and 21b.
[V] is applied as 810 [V] as a secondary transfer potential applied to the secondary intermediate transfer drum 22 and 6 [μA] as a final transfer current applied to the final transfer roll 30 to the primary cleaning rolls 23 a and 23 b. 190 V as the primary cleaning voltage, and 21 V as the secondary cleaning voltage.
0 [V] is selected as -289 [V] as the (target) charging potential of the photosensitive drum 10, and -200 [V] as the DC component of the developing bias voltage. The image forming condition control unit 60 selects 100% coverage input as the toner patch creation condition.

Based on the image forming conditions and toner patch preparation conditions selected in this way, the full-color printer 1
00 forms a toner image P2 as a toner patch on the final transfer roll 30, and performs TC process control.

FIG. 13 is a flowchart for explaining the operation of the TC process control. Hereinafter, the operation of the TC process control will be described in more detail based on this flowchart.

First, the image forming condition control section 60 detects the surface of the final transfer roll 30 with the optical density sensor 7 in a state where the toner patch P2 is not transferred, and outputs the output Vcln of the optical density sensor 7 at this time. It is stored (step ST201). Next, based on the above-described image forming conditions and toner patch creation conditions, the toner patch P2 is set for each of the colors of yellow, magenta, cyan, and black.
(Y) to (K) are formed on the final transfer roll 30 as shown in FIG. 10A (step ST202). Here, unlike the image forming mode and the potential process control mode, in this TC process control mode, the developing bias voltage is developed only with a DC component,
AC components are not superimposed.

Thereafter, the area of the yellow, magenta, cyan, and black toner patches P2 (Y) to (K) is 0.5 m by the optical density sensor 7 as shown in FIG.
The average value Vpatch is obtained by detecting 16 points at a pitch of m (step ST203). Here, FIG.
As shown in (a), a specular reflection type optical density sensor 7 is used.
However, as shown in FIG. 11B, a diffuse reflection type sensor for detecting diffused light may be used, or both sensors may be used.

Then, the average value of each color is calculated by using the final transfer roll 3
0 surface (state where toner patch P2 is not transferred)
The ratio Vpatch / Vcln divided by the value is used as a substitute value for the density (step ST204).

As a result, when the obtained toner patch density is lower than the predetermined density, the image forming condition control unit 60 measures the image density from the print image signal in advance according to the difference because the toner density is low. (Step ST210) Correction is performed so that the toner supply amount is larger than the determined toner supply amount (Step ST220) (Step ST210).
206). Conversely, when the test patch is higher than the predetermined density, the image forming condition control unit 60 measures the image density from the print image signal in advance according to the difference because the toner density is high (step ST210), and is determined. Correction is made so that the toner supply amount is smaller than the toner supply amount (step ST220) (step ST208).

Here, for example, when the density of the toner patch P2 is lower than the predetermined density, the image forming condition control unit controls the driving time of the driving unit of each of the toner supply flexible pipes 15Y to 15K so as to be longer than the specified time. Reference numeral 60 controls the driving units of the pipes 15Y to 15K (see FIG. 8).

[0084]

As described in detail above, according to the present invention, it is possible to provide an image forming apparatus capable of detecting the presence or absence of a transfer body.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a full-color printer according to an embodiment of the present invention.

FIG. 2 illustrates the image forming unit of the full-color printer shown in FIG. 1 in more detail.

FIG. 3 illustrates a cross section of a final transfer roll.

FIG. 4 is a diagram for explaining in detail a peripheral configuration of a final transfer roll.

FIG. 5 illustrates the configuration and operation of an optical density sensor main body.

FIG. 6 is a functional block diagram illustrating a final transfer roll detection control system of the full-color printer shown in FIG.

FIG. 7 is a flowchart illustrating an operation of the control system shown in FIG. 6;

FIG. 8 is a functional block diagram illustrating an image forming condition control system of the full-color printer shown in FIG. 1;

FIG. 9 is a flowchart illustrating an operation in a potential process control mode.

FIG. 10 illustrates a toner patch formed on a final transfer roll.

FIG. 11 illustrates the configuration and operation of the optical density sensor main body.

FIG. 12 illustrates adjustment of a charging potential and a developing bias potential.

FIG. 13 is a flowchart illustrating an operation in a TC process control mode.

[Explanation of symbols]

100: full-color printer (image forming apparatus), 1: image forming unit (image forming means), 6: control unit, 60: image forming condition control section (density controlling means)
61: main control unit (detection means, density control means), 62: detection control unit (detection means), 63: determination unit (detection means), 1
2 Exposure device unit (image forming means), 14 toner cartridge (image forming means), 15 toner flexible pipe (image forming means), 10 photoconductor drum (image carrier), 11 charging roll, 13 ... developing device (image forming means), 130 ... developing roll, 21 ... primary intermediate transfer drum (primary intermediate transfer body), 22 ... secondary intermediate transfer drum (secondary intermediate transfer body), 30 ... final transfer roll (final transfer) 7) Optical density sensor (detection means), 70a: Light emitting element, 70b: Light receiving element, 8: Environmental sensor, 9: Display panel (display means), P: Toner patch (image density control detection patch or toner) Detection patch for density control)

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hideaki Tanaka 3-7-1, Fuwa, Iwatsuki-shi, Saitama, F-term in the Fuji Xerox Co., Ltd. Iwatsuki office (reference) 2H027 DA01 DA09 DA13 DA14 DA21 DA41 DD05 DE02 DE07 DE09 EA06 EC06 EC10 ED24 ED27 EE02 EE07 EK09 FA28 GB08 HA01 HA13 2H030 AA03 AB02 AD16 BB23 BB36 BB38 BB42 BB46 BB54 BB63 2H200 FA12 FA17 GA23 GA34 GA45 GA47 GA53 GA57 GA60 GA61 GB25 HA03 HB12 JB12 JB12 JB02BB LB03 LB08 LB09 LB12 LB13 LB17 LB35 LB38 MA03 MA11 MA20 MB06 NA02 NA06 PB11 PB23 PB26 PB39

Claims (6)

[Claims] 1. An image forming apparatus having a removable final transfer body for finally transferring a toner image to a recording medium, comprising: a detection unit for detecting the presence or absence of the final transfer body. . 2. A light-emitting unit that emits light to the final transfer body with a predetermined light-emitting amount, a light-receiving unit that receives light reflected from the surface of the final transfer body, and a light-receiving amount of the light-receiving unit. The image forming apparatus according to claim 1, further comprising: a determination unit configured to determine the presence or absence of the final transfer body based on the determination. 3. The detecting unit causes the light emitting unit to emit light at a first light emission amount, and causes the determination unit to determine failure of the light emitting unit and / or the light receiving unit based on the light reception amount at that time. If no failure has occurred, a detection control unit that causes the light emitting unit to emit light at a second light emission amount and causes the determination unit to determine the presence or absence of the final transfer body based on the light reception amount at that time is provided. 3. The image forming apparatus according to 2. 4. The image forming apparatus according to claim 3, wherein the detection control unit rotates the final transfer body when making a determination by the determination unit. 5. An image forming apparatus, comprising: an image forming unit configured to form a toner image on a recording medium and the final transfer body based on predetermined image forming conditions; and a toner as a toner patch formed on the final transfer body. 5. The image forming apparatus according to claim 2, further comprising: a density control unit configured to change an image forming condition based on an image density, wherein the detection unit measures a density of the toner image as the toner patch. 6. 6. The image forming means includes four photoconductors corresponding to yellow, cyan, magenta, and black, a first primary intermediate transfer body that contacts two of the four photoconductors, and a remaining one. A second primary intermediate transfer member in contact with the two photoconductors, a secondary intermediate transfer member in contact with the first and second primary intermediate transfer members, and the second intermediate transfer member in contact with the secondary intermediate transfer member The image forming apparatus according to claim 5, further comprising a final transfer body.