JP2000075681A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To always obtain a stable color image even when an image forming device is compact and inexpensive the temperature in a machine is provided with a gradient by allowing a surface temperature control means for an intermediate transfer drum to control the surface temperature of a transfer drum to that the prescribed surface temperature is kept and allowing a surface temperature uniformizing means for an image carrier to uniformize the surface temperature of respective image carriers before a job is started. SOLUTION: A heater for heating Bh is arranged inside the drum for transfer B. By the surface temperature control means for an intermediate transfer drum, the heater Bh is controlled so that the prescribed surface temperature of the drum B is kept in the midst of executing the job being the image forming action that a toner image is formed at the surfaces of the image carriers Pk-Pc and transferred and fixed at a recording sheet S. By the surface temperature uniformizing means for an image carrier, the surface temperature of the respective carriers Pk-Pc are uniformized by transmitting the heat of the surface of the drum B to the plural carriers Pk-Pc by rotating the drum B and the carriers Pk-Pc in a prescribed term before the job is started.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic color image forming apparatus used for copying, a printer, a facsimile, and the like.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for colorizing documents, and in particular, a demand for high-speed output of color documents. On the other hand, a tandem color image forming apparatus having a plurality of electrophotographic image forming units is in high demand as a means for simultaneously realizing high-speed output and high image quality.

FIG. 6 is an explanatory view of a conventional tandem type color image forming apparatus having an intermediate transfer member in contact with a plurality of image carriers. In FIG. 6, the image forming apparatus U includes a main body Ua.
And an automatic document feeder Ub placed on a platen glass PG on the upper surface of the main body Ua. The image forming apparatus main body Ua has a UI (user interface) through which a user inputs an operation command signal such as a copy start signal.

[0004] Reflected light from an original (not shown) placed on the platen glass PG is transmitted through an exposure optical system A.
R (red), G (green), B with CCD (solid-state image sensor)
(Blue) electrical signal. The IPS (image processing system) uses the R input from the CCD.
The GB electrical signal is converted into K (black), Y (yellow), M (magenta), and C (cyan) image data and temporarily stored, and the image data is stored at a predetermined timing for forming a latent image. The data is output to the laser drive circuit DL as image data.

The laser driving circuit DL supplies a laser driving signal corresponding to the input image data at a predetermined timing to the latent image writing devices ROSk, ROsy, ROSm, ROSm,
Output to ROSc.

The respective image carriers Pk, Py, Pm, and Pc are uniformly charged by respective charging rolls CRk, CRy, CRm, and CRc, and then, in the image writing areas Q1k, Q1y, Q1m, and Q1c. Latent image writing devices ROSk, ROSy, ROSm,
An electrostatic latent image is formed on the surface by the laser beams Lk, Ly, Lm, Lc output from ROSc. The image carrier P
The electrostatic latent images on the surfaces of k, Py, Pm, and Pc are developed areas Q2k and Q2, respectively.
At 2y, Q2m, and Q2c, toner images are developed by developing units Dk, Dy, Dm, and Dc. The developed toner image is
The primary transfer areas Q3k, Q3y,
It is transported to Q3m and Q3c. The primary transfer areas Q3k, Q3
The primary transfer rolls T1k, T1y, T1m, and T1c arranged on the back side of the intermediate transfer belt B in y, Q3m, and Q3c include:
At a predetermined timing, a primary transfer voltage having a polarity opposite to the charging polarity of the toner is applied from a power supply circuit E controlled by the controller C. The toner images on the image carriers Pk to Pc are primarily transferred to the intermediate transfer belt B by the primary transfer rolls T1k, T1y, T1m, and T1c. The residual toner on the surface of the image carriers Pk, Py, Pm, and Pc after the primary transfer is removed by the image carrier cleaners CLk, CLy, CLm, and CLc.

Below the image carriers Pk to Pc, a pair of left and right slide rails SR, SR for the slide are used to move the slide F1.
(Indicated by a two-dot chain line) is supported so as to be slidable back and forth (in a direction perpendicular to the paper surface). A belt module (vertical moving member) F2 is supported on the movable table F1 so as to be able to move up and down. The belt module F2 includes the intermediate transfer belt B, a belt driving roll Rd, a tension roll R
t, a walking roll Rw, a belt supporting roll (Rd, Rt, Rw, Rf, T2a) including an idler roll (free roll) Rf and a backup roll T2a, and the primary transfer rolls T1k, T1y, T1m, T1c. are doing. The intermediate transfer belt B is rotatably supported by the belt support rolls (Rd, Rt, Rw, Rf, T2a).

A secondary transfer roll T2b is disposed so as to face the surface of the intermediate transfer belt B in contact with the backup roll T2a, and a secondary transfer area is provided in an area where the intermediate transfer belt B and the secondary transfer roll T2b face each other. Q4 is formed. The control roll T2c is in contact with the backup roll T2a. A secondary transfer voltage having the same polarity as the charged polarity of the toner is applied to the control T2c from the power supply circuit E controlled by the controller C at a predetermined timing. The secondary transfer unit T2 is operated by the rolls T2a to T2c.
Is configured.

The primary transfer areas Q3k, Q3y, Q3m, Q3c
The color toner images sequentially transferred and superimposed on the intermediate transfer belt B by the transfer units T1k, T1y, T1m, and T1c in the above-described manner are the same as those in the above-described 2.
The sheet is conveyed to the next transfer area Q4. The recording sheets S on the sheet feed tray TR1 disposed below the intermediate transfer belt B are taken out by a pickup roll Rp, separated one by one by a separation roll Rs, and then sent to a registration roll Rr. The registration roll Rr moves the recording sheet S from the pre-transfer sheet guide SG1 to the secondary transfer area Q4 in synchronization with the timing at which the color toner image formed on the intermediate transfer belt B is conveyed to the secondary transfer area Q4. Transport to The color toner image on the intermediate transfer belt B is transferred to the recording sheet S by the secondary transfer device T2 when passing through the secondary transfer area Q4. After the secondary transfer, the intermediate transfer belt B is cleaned by a belt cleaner CL2. The developer adhered to the surface of the secondary transfer roll T2b is removed by the secondary transfer roll cleaner CL3.

The recording sheet S on which the toner image has been secondarily transferred is transferred to a sheet guide SG2 and a sheet conveying belt BH.
After being conveyed to the fixing area Q5 through the fixing device F and fixed by the fixing device F, the sheet is discharged from the discharge roller Rh to the discharge tray TR2.

[0011]

In the tandem type image forming apparatus, a plurality of image carriers (electrophotographic photosensitive members) Pk
Since Pc is used, if there is a difference between the characteristics of the image carriers Pk to Pc, the color image will not be stable. In particular, the characteristics of the image carriers (electrophotographic photoconductors) Pk to Pc are generally temperature-sensitive. In particular, when a gradient occurs in the in-machine temperature during the operation of the image forming apparatus, each image carrier ( The characteristics of the electrophotographic photoreceptor change, causing color images to be disturbed. As a method for reducing the change in characteristics of the image carrier (electrophotographic photosensitive member) due to the temperature, controlling the temperature of the image carrier (electrophotographic photosensitive member) by a heater has been put to practical use. However, in a tandem-type color image forming apparatus, if such temperature control is performed on each image carrier (electrophotographic photosensitive member), it leads to an increase in cost and a reduction in size of the apparatus, which is particularly demanded in recent years. The obstacle is big.

In view of the above circumstances, the present invention provides the following (O01)
Is the subject of the description. (O01) To provide a small-sized and low-cost tandem-type color image forming apparatus capable of constantly obtaining a stable color image even when the temperature inside the apparatus has a gradient.

[0013]

Next, the present invention devised to solve the above-mentioned problems will be described. Elements of the present invention are used to facilitate correspondence with elements of the embodiments described later. , The reference numerals of the elements of the embodiment are enclosed in parentheses. The reason why the present invention is described in correspondence with the reference numerals of the embodiments described below is to facilitate understanding of the present invention, and not to limit the scope of the present invention to the embodiments.

(Invention) In order to solve the above problems, the image forming apparatus (U) of the invention has the following requirements (A01) to
(A01) a transfer drum (B) that rotates and has a surface on which a toner image formed on a surface of a plurality of image carriers (Pk to Pc) is transferred. ,
(A02) A plurality of image carriers (Pk to Pc) in which electrostatic latent images corresponding to images of different colors are formed on a rotating surface, and the electrostatic latent images are developed into toner images of different colors, respectively. The plurality of images arranged opposite to the surface of the transfer drum (B) in a plurality of transfer areas (Q3k to Q3c) set along a rotational movement path on the surface of the transfer drum (B). Carriers (Pk to Pc), (A03) Each of the image carriers (Pk) arranged inside the transfer drum (B) opposite to the plurality of transfer areas (Q3k to Q3c).
.About.Pc) transfer devices (T1k to T1c) for transferring the toner image on the surface to the transfer drum (B) side; (A04) a heating heater (Bh) arranged inside the transfer drum (B);
(A05) During the execution of a job which is an image forming operation of forming a toner image on the surface of the image carrier (Pk to Pc) and transferring and fixing the toner image on a recording sheet (S), the transfer drum (B) An intermediate transfer drum surface temperature control means (C2) for controlling the heating heater (Bh) so as to maintain the surface temperature at a predetermined temperature; (A06) the transfer drum (B) and the image The heat of the surface of the transfer drum (B) is transmitted to the plurality of image carriers (Pk to Pc) by rotating the carriers (Pk to Pc) for a predetermined period, and each image carrier (Pk) is rotated.
k to Pc) means for uniformizing the surface temperature of the image bearing member for uniformizing the surface temperature (C4).

(Supplementary Explanation of the Present Invention) In the present invention, the "transfer drum" can be constituted by a metal pipe such as aluminum or stainless steel and a medium resistance elastic layer formed on the surface thereof. Also, a pair of disc-shaped hubs fixed to both ends of the shaft and a tie bar (connecting plate) for connecting the outer periphery of the pair of hubs, and a film or belt stretched cylindrically outside the hub and the tie bar, etc. Can be constituted by It is preferable that the “heating heater (Bh)” is arranged at the center of the transfer drum (B). In this case, the entire surface of the transfer drum (B) can be uniformly heated by one heater (Bh). As the heating heater (Bh) disposed inside the transfer drum (B), a rod-shaped heater or a sheet-shaped heater used for a fixing device or the like can be used. However, in order to maintain temperature uniformity, Rod heaters are preferred.

The transfer drum (B) can be constituted by a transfer drum (B) on which a toner image is directly transferred to its surface, or a transfer material carrying drum that carries a transfer material such as paper and rotates. It is. When the transfer drum (B) is composed of a transfer drum, an elastic layer forming a surface layer thereof is formed of a rubber material such as silicone rubber, urethane rubber, Teflon rubber, or a conductive material such as carbon or metal oxide. Materials in which materials are dispersed can be used. The resistance value of the elastic layer is preferably 10 ⁵ (Ωcm) to 10 ¹³ (Ωcm). The elastic layer can be formed by molding or coating the above-mentioned material on a conductive substrate. The thickness of the elastic layer is preferably 5 to 50 μm, and 10 to 30 μm.
μm is particularly preferred.

When the image bearing member (electrophotographic photosensitive member) (Pk-Pc) used in the present invention is constituted by providing a photosensitive layer on a pipe-shaped conductive substrate, the conductive substrate may be a heat conductive material. Aluminum pipes with good properties are preferred. By using an aluminum pipe, the transfer drum (B) and the image carrier (Pk ~
Pc) The temperature can be kept constant in a relatively short time. At this time, if the diameter of the pipe is large, the time until the temperature becomes constant becomes long. Therefore, it is preferable to use a pipe having a diameter of 30 mm or less.

(Operation of the Present Invention) In the image forming apparatus (U) of the present invention having the above-described configuration, the image carriers (Pk to Pc) are
An electrostatic latent image corresponding to images of different colors is sequentially written on a rotating surface by a latent image writing device. The transfer drum (B) has a surface on which the toner images formed on the surfaces of the plurality of image carriers (Pk to Pc) are transferred and rotates. The plurality of image carriers (Pk to Pc) are transferred to the transfer drum (B) in a plurality of transfer areas (Q3k to Q3c) set along a rotational movement path on the surface of the transfer drum (B).
An electrostatic latent image corresponding to an image of a different color is formed on the rotating surface, and the electrostatic latent image is developed into a toner image of a different color.

The transfer units (T1k to T1c) are disposed inside the transfer drum (B) so as to face the plurality of transfer areas (Q3k to Q3c), respectively.
~ Pc) Transfer the toner image on the surface to the transfer drum (B) side. The heating heater (Bh) is arranged inside the transfer drum (B). The intermediate transfer drum surface temperature control means (C2) forms a toner image on the surface of the image carrier (Pk-Pc), and transfers the toner image to the recording sheet (S) for fixing. Medium The heating heater (Bh) is controlled so as to maintain the surface temperature of the transfer drum (B) at a predetermined temperature. Image carrier (Pk ~
Pc) Prior to the start of the job, the surface temperature equalizing device performs the transfer drum (B) and the image carrier (Pk to Pk).
c) is rotated for a predetermined period of time to transfer the heat on the surface of the transfer drum (B) to the plurality of image carriers (Pk to Pc), thereby making the surface temperatures of the respective image carriers (Pk to Pc) uniform. .

In the image forming apparatus (U) of the present invention, prior to the image forming cycle, the transfer drum (B) is heated by the heating heater (Bh) and is maintained at a temperature higher than the internal temperature. Further, prior to the job (image forming operation), the transfer drum (B) and the image carrier for each color (electrophotographic photosensitive member) (Pk to Pc) are rotated while being in contact with each other, so that the image carrier for each color is rotated. (Electrophotographic photoreceptor) (P
k to Pc) and the surfaces of the plurality of transfer drums (B) can be kept at a constant temperature.

Since the temperature inside the apparatus generally increases near the fixing device (F), the surface temperature of the image carrier (electrophotographic photosensitive member) (Pk to Pc) close to the fixing device (F) and the fixing device (F)
The surface temperature of the image bearing member (electrophotographic photosensitive member) (Pk to Pc) far from the surface tends to be different. Therefore, it is desirable that the set temperature of the surface of the transfer drum (B) be set higher than the internal temperature. On the other hand, the image bearing member (electrophotographic photosensitive member) of the present invention
(Pk to Pc) is preferably an organic photoreceptor,
If the temperature of the surface of the organic photoreceptor is too high, the surface layer is softened or the like, and in a remarkable case, the image carrier (electrophotographic photoreceptor) (Pk to Pc) is destroyed. Therefore,
In the present invention, the upper limit of the temperature of the surface of the transfer drum (B) is 5
Preferably it is 0 ° C. Within this range, there is no adverse effect on the organic photoreceptor.

Japanese Patent Application Laid-Open No. 9-106201 discloses a configuration similar to the present invention in which a plurality of image forming units are arranged around a drum-shaped intermediate transfer member to transfer paper or the like from the intermediate transfer member. Prior to transfer to a material, a technique of heating the intermediate transfer body by an heater inside or outside the intermediate transfer body to soften the toner image has been described, but here, the purpose is to soften the toner image. The point is that the content is completely different from the present invention in that the heating temperature is much higher than the range of the present invention.

[0023]

(Embodiment 1) Embodiment 1 of an image forming apparatus (U) according to the present invention is characterized by satisfying the following requirement (A07) in the present invention (A07). )
The predetermined temperature set in a range from room temperature to 50 ° C. when room temperature is 50 ° C. or lower.

(Effect of First Embodiment) In the first embodiment of the image forming apparatus (U) of the present invention having the above-mentioned configuration, the predetermined temperature is between 50 ° C. and 50 ° C.
It is set in the range below ° C. Within this range, there is no adverse effect on the organic photoreceptor.

(Embodiment 2) Embodiment 2 of the image forming apparatus (U) of the present invention is characterized in that the following requirements (A08) are provided in the present invention or Embodiment 1 of the present invention. (A08) The transfer drum (B), which is an intermediate transfer drum having an elastic layer on the surface.

(Effect of Embodiment 2) In Embodiment 2 of the image forming apparatus (U) of the present invention having the above-mentioned configuration, the transfer drum (B) is an intermediate transfer drum having an elastic layer on the surface. It is. Since the intermediate transfer drum surface can be given an appropriate elasticity by the elastic layer, the image carrier (Pk
To Pc), an appropriate nip (press-contact area) can be formed at the contact portion.

(Embodiment 3) Embodiment 3 of the image forming apparatus (U) of the present invention is the same as that of Embodiment 1 or 2 of the present invention, except for the following requirements (A09) and (A01).
(A09) The transfer drum (B) configured by a transfer material carrying drum that rotates while adsorbing a sheet-like transfer material for image recording on the surface during the job execution. (A010) When the sheet-like transfer material carried on the surface of the transfer material carrying drum passes through each of the plurality of transfer areas (Q3k to Q3c), the surface of the image carrier (Pk to Pc) The transfer device (T1k to T1c) for transferring a toner image.

(Operation of the Third Embodiment) In the third embodiment of the image forming apparatus (U) of the present invention having the above-described configuration, the transfer drum (B) is provided with an It is constituted by a transfer material carrying drum that rotates while adsorbing the transfer material of the sheet. The transfer device (T1k to T1c) is provided on the sheet surface when the sheet-shaped transfer material carried on the surface of the transfer material carrying drum passes through each of the plurality of transfer areas (Q3k to Q3c). Pk to Pc) Transfer the toner image on the surface.

(Embodiment 4) Embodiment 4 of the image forming apparatus (U) of the present invention is the same as that of the present invention or any of Embodiments 1 to 3 of the present invention, except for the following requirement (A01).
(A011) having a diameter of 30
mm or less, the image carrier (Pk to Pc).

(Operation of Embodiment 4) In Embodiment 4 of the image forming apparatus (U) of the present invention having the above-described configuration, the diameter of the image carriers (Pk to Pc) is set to 30 mm or less.
The time until the temperature becomes constant is shortened. The transfer drum (B) and the image carrier (Pk to Pk) can be formed by using an aluminum pipe having good thermal conductivity as the conductive substrate.
The surface temperature of c) can be made constant in a relatively short time.

EXAMPLES Next, specific examples (examples) of the embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following examples. (Embodiment 1) FIG. 1 is an overall perspective view of Embodiment 1 of the image forming apparatus of the present invention. FIG. 2 is a front sectional view of the first embodiment. FIG. 3 is a block diagram of a control unit according to the first embodiment.
1 and 2, an image forming apparatus U has a digital copying machine U1 as an image forming apparatus main body having a platen glass (transparent document table) PG on an upper surface, and is detachably mounted on the platen glass PG. An automatic document feeder (automatic document feeder, ADF) U2 is provided. The automatic document feeder U2 includes a document feed tray TG1 on which a plurality of documents G to be copied are placed in an overlapping manner.
have. The plurality of documents G placed on the document feed tray TG1 are configured to sequentially pass through a copy position on the platen glass PG and be discharged to a document discharge tray TG2. The automatic document feeder U2 is rotatable with respect to the copier U1 by a hinge shaft (not shown) extending in the left-right direction provided at the rear end (-X end).
When the operator places the document G on the platen glass PG by hand, the document G is rotated upward.

The copying machine U1 has a UI (user interface), an IIT (image input terminal) as an image reading unit, and an IOT as an image recording operating unit sequentially arranged below the platen glass PG.
(Image output terminal) and an IPS (image processing system) provided between the IIT and the IOT.

A document reading device II disposed below the transparent platen glass PG on the upper surface of the copier body U1.
T, and an exposure optical system A. The movement and stop of the exposure optical system A are controlled by a detection signal of the exposure system registration sensor Sp, and are always stopped at the home position. In the ADF mode in which copying is performed using the automatic document feeder (auto document feeder) U2, each document that sequentially passes through the copying position on the platen glass PG with the exposure optical system A stopped at the home position. G is exposed. In the case of the platen mode in which the operator places the original G on the platen glass PG by hand and performs copying, the exposure optical system A
Scans the original on the platen glass PG while moving. The reflected light from the document G that has been exposed passes through the exposure optical system A and is converged on a CCD (solid-state imaging device).

The CCD (solid-state image pickup device) converts the original reflected light converged on the image pickup surface into R (red), G (green), and B (blue) electric signals, and outputs the electric signals to an IPS (image processing system). input. IPS is the RG input
The B electrical signal is converted into K (black), Y (yellow), M (magenta), and C (cyan) image data, and the KYMC four-color image write data (laser drive data) at a predetermined timing. ) Is output. KY output by the IPS
The image writing data (laser driving data) of the four colors of MC is
Laser drive signal output circuits DLk, D for each color K, Y, M, C
The laser drive signal output device DL having Ly, DLm, and DLc is input. The laser drive signal output circuits DLk for each color
DLy, DLm, and DLc output a laser drive signal corresponding to the input image data to the latent image writing devices ROSk, ROSy, ROSm, and ROSc of each color at a predetermined timing.

After the respective image carriers Pk, Py, Pm, Pc are uniformly charged by the respective charging rolls CRk, CRy, CRm, CRc, the latent images in the image writing areas Q1k, Q1y, Q1m, Q1c are obtained. Image writing devices ROSk, ROSy, ROSm, R
An electrostatic latent image is formed on the surface by the laser beams Lk, Ly, Lm, and Lc output from the OSc. The image carrier P
The electrostatic latent images on the surfaces of k, Py, Pm, and Pc are developed areas Q2k and Q2, respectively.
At 2y, Q2m, and Q2c, toner images are developed by developing units Dk, Dy, Dm, and Dc. The developed toner image is
The sheet is conveyed to primary transfer areas Q3k, Q3y, Q3m, and Q3c that come into contact with the cylindrical intermediate transfer drum (transfer drum) B. In the primary transfer areas Q3k, Q3y, Q3m, and Q3c, the primary transfer rolls T1k, T1y, T1m, and T1c disposed on the back side of the intermediate transfer drum (transfer drum) B have a power supply controlled by a controller C. A primary transfer voltage having a polarity opposite to the charging polarity of the toner is applied from the circuit E at a predetermined timing. The toner images on the image carriers Pk to Pc are primarily transferred to the intermediate transfer drum B by the primary transfer rolls T1k, T1y, T1m, and T1c. The image carriers Pk, Py, after the primary transfer,
Residual toner on the surfaces of Pm and Pc is the image carrier cleaner CLk,
It is removed by CLy, CLm, and CLc.

A heating heater B is provided inside the intermediate transfer drum B rotatably supported below the image carriers Pk to Pc.
h is provided. A drum surface temperature sensor SN1, a drum rotation position sensor SN2, a drum cleaner CL2, and a secondary transfer unit (corotron) T2 are arranged along a rotation path on the surface of the intermediate transfer drum B. A secondary transfer area Q4 is formed in an area where the secondary transfer device T2 and the intermediate transfer drum B face each other. A secondary transfer voltage having the same polarity as the toner charging polarity is applied to the secondary transfer unit T2 from the power supply circuit E controlled by the controller C at a predetermined timing.

The primary transfer areas Q3k, Q3y, Q3m, Q3c
The color toner images sequentially transferred and superimposed on the intermediate transfer drum B by the transfer units T1k, T1y, T1m, and T1c in the above-described manner,
The sheet is conveyed to the next transfer area Q4. The recording sheet S on the sheet feed tray TR1 disposed below the intermediate transfer drum B is taken out by the pickup roll Rp, separated one by one by the separating roll Rs, and then sent to the registration roll Rr by the transport roll Ra. The registration roll Rr moves the recording sheet S from the pre-transfer sheet guide SG1 to the secondary transfer area Q in synchronization with the timing at which the color toner image formed on the intermediate transfer drum B is conveyed to the secondary transfer area Q4.
Transport to 4. When the color toner image on the intermediate transfer drum B passes through the secondary transfer area Q4,
The image is transferred onto the recording sheet S by the next transfer device T2. 2
After the next transfer, the intermediate transfer drum B is discharged by the discharging brush Jb.

The recording sheet S to which the toner image has been secondarily transferred is transferred to a sheet guide SG2 and a sheet conveying belt BH.
After being conveyed to the fixing area Q5 through the fixing device F and fixed by the fixing device F, the sheet is discharged from the discharge roller Rh to the discharge tray TR2.

(Intermediate Transfer Drum B) The intermediate transfer drum B was formed by mirror-finish the surface of an aluminum pipe having a diameter of 84 mm and a length of 350 mm, and then forming an elastic layer in which carbon black was dispersed in silicone rubber to 8 μm. A rod-shaped heater was mounted inside the intermediate transfer drum B.

(Image Carrier (Electrophotographic Photoconductor) Pk to Pc)
The image carriers Pk to Pc have a diameter of 20 mm and a length of 330 m.
The surface of an aluminum pipe having a thickness of m was mirror-finished, and then an undercoat layer, a charge generation layer, and a charge transport layer were sequentially laminated thereon to produce the same.

FIG. 3 is a block diagram showing functions of the image forming apparatus (tandem digital color copying machine) according to the first embodiment of the present invention. In FIG. 3, the controller C stores an I / O (input / output interface) for inputting / outputting an external signal and adjusting an input / output signal level, a program and data for performing necessary processing, and the like. ROM (read only memory), RAM for temporarily storing necessary data
(Random access memory), a CPU (Central Processing Unit) that performs processing according to the program stored in the ROM, and a computer having a clock oscillator and the like, and executes the program stored in the ROM. Thus, various functions can be realized.

The controller C receives input signals from keys such as a copy start key UI1, a copy number setting key UI2, a numeric keypad UI3, and a display unit UI4 of the UI (user interface). Further, detection signals of the drum surface temperature sensor SN1 and the drum rotation position sensor SN2 are input to the controller C.

The controller C is connected to an intermediate transfer drum rotation drive circuit D1, an intermediate transfer drum heating drive circuit D2, and other control elements. The intermediate transfer drum rotation drive circuit D1 drives the intermediate transfer drum B via an intermediate transfer drum drive motor M1. The drive circuit D2 for heating the intermediate transfer drum turns on and off the heater Bh for heating the intermediate transfer drum to adjust the surface temperature of the intermediate transfer drum B.

The controller C has a function of executing a process according to an input signal from the signal output element and outputting a control signal to each control element. That is,
The controller C has the following functions.

C1: Intermediate Transfer Drum Control Temperature Setting Means The intermediate transfer drum control temperature setting means C1 sets the control target value of the surface temperature of the intermediate transfer drum to a standby temperature (temperature when the image forming apparatus is not operating). Further, it has a function of setting any one of the operating temperatures (the temperature during execution of the operation of the image forming apparatus). C2: Intermediate transfer drum temperature control means The intermediate transfer drum temperature control means C2 is a heater for heating the intermediate transfer drum so that the surface temperature of the intermediate transfer drum becomes the temperature set by the intermediate transfer drum control temperature setting means C1.
Has a function of controlling ON and OFF of the power supply.

C3: Job possibility discrimination flag rewriting control means The job feasibility discrimination flag rewriting control means C3 sets a job feasibility discrimination flag C3F when the intermediate transfer drum makes one rotation after the surface temperature of the intermediate transfer drum reaches a predetermined temperature. "1"
When the control temperature of the intermediate transfer drum is set to the standby temperature after the job is completed, the job possibility determination flag is set to “0”. C3F: Job possible determination flag The job possible determination flag C3F stores “1” when the surface temperature of the intermediate transfer drum B reaches a temperature at which the job can be executed when the copy start key is turned on, and “0” at the end of the job. This is a flag to be stored.

(Operation of the First Embodiment) Next, the first embodiment having the above-described configuration will be described with reference to the flowcharts of FIGS.
The operation of will be described. (Explanation of Flowchart) FIG. 4 is a flowchart for setting an intermediate transfer drum control temperature and rewriting a job possible determination flag according to the first embodiment of the image forming apparatus of the present invention. The intermediate transfer drum control temperature setting and job feasibility determination flag rewriting flow shown in FIG. 4 is started when the power is turned on. The processing of each ST (step) in the flowchart of FIG. 4 is performed according to a program stored in the ROM of the controller C. In FIG. 4, when the flow for setting the intermediate transfer drum control temperature and rewriting the job possible determination flag is started,
In ST1, the control temperature of the intermediate transfer drum is set to a standby temperature. Next, in ST2, "0" is set to the job feasibility determination flag C3F. Next, in ST3, it is determined whether or not the copy start key has been turned on. If no (N), ST3 is repeatedly executed. If yes (Y), the process moves to ST4. When the copy start key UI1 is turned on, the image carrier P is activated by another program.
k to Pc and the intermediate transfer drum B rotate. However, the image recording operation (such as latent image writing) is not started until "1" is set in the job possible determination flag C3F.

Next, in ST4, the control temperature of the intermediate transfer drum B is set to the operating temperature. Next, in ST5,
It is determined whether or not the temperature of the intermediate transfer drum B is the operating temperature. If no (N), ST5 is repeatedly executed. If yes (Y), the process moves to ST6. In ST6, the timer T
Turn m on. Next, in ST7, Tm ≧ T0 (T0
Is the time required for the intermediate transfer drum B to make one rotation). If no (N), ST7 is repeatedly executed. If yes (Y), the process moves to ST8. In ST8, "1" is set to the job possible determination flag C3F. That is, when a time period for one rotation of the intermediate transfer drum elapses after the surface temperature of the intermediate transfer drum B becomes the operating temperature, C
3F becomes "1" and job execution becomes possible. This is because, in the apparatus of the embodiment, when the intermediate transfer drum B makes one rotation after the surface temperature of the intermediate transfer drum B reaches the operating temperature, the image carrier P
This is because the temperatures of k to Pc become uniform. In ST9, it is determined whether or not the job has ended. S for no (N)
Repeat T8. If yes (Y), the S
Return to T1.

FIG. 5 is a flowchart for controlling the temperature of the intermediate transfer drum in the first embodiment of the image forming apparatus of the present invention. FIG.
Is started when the power is turned on. The processing of each ST (step) in the flowchart of FIG. 5 is performed according to a program stored in the ROM of the controller C. In the flowchart of FIG. 5, the temperature of the surface of the intermediate transfer drum B is set to 37 ° C to 40 ° C.
Is controlled to be kept within the range.

In FIG. 5, when the flow of controlling the temperature of the intermediate transfer drum is started, in ST11, the surface temperature of the intermediate transfer drum B is detected using the drum temperature sensor SN1. Next, in ST12, it is determined whether the detected temperature is equal to or higher than the upper limit of the set temperature (for example, 40 ° C.). If no (N), the process moves to ST15. If yes (Y), the process moves to ST13. Next, in ST13, it is determined whether the heater is off. If no (N), the process moves to ST14. If yes (Y), the process returns to ST11. Next, in ST14, the heater for heating the intermediate transfer drum is turned off. Then, the ST
Return to 11.

Next, in ST15, it is determined whether or not the detected temperature is lower than the lower limit of the set temperature (for example, 37 ° C.). If no (N), the process proceeds to ST11. If yes (Y), the process moves to ST16. Next, in ST16, it is determined whether the heater is on. If no (N), the process moves to ST17. If yes (Y), the process returns to ST11. Next, in ST17, the heater for heating the intermediate transfer drum is turned on. Then, the process returns to ST11.

4 and 5, the temperature of the intermediate transfer drum B is controlled to about 40 ° C. prior to the print test, and then the intermediate transfer drum B and the image carrier (electrophotographic photosensitive member) are controlled. The surface of each image bearing member (electrophotographic photosensitive member) was measured while measuring the surface temperature of all the image bearing members (electrophotographic photosensitive member). Was. With this apparatus, a continuous full-color print test of 500 sheets was performed. The difference between the tint of the first print and the tint of the 500th print was very small, and good results were obtained.

(Comparative Example 1) In the apparatus of Example 1, a continuous 500 full-color print test was performed without heating the intermediate transfer drum, and the 500th print was compared with the first print. Black and cyan were darker throughout. At this time, when the surface temperature of the image bearing member (electrophotographic photosensitive member) was measured, the yellow image bearing member (electrophotographic photosensitive member) rose by about 5 ° C. from the beginning to the 500th sheet. The temperature of the black image carrier (electrophotographic photosensitive member) increased by about 25 ° C. from the beginning to the 500th sheet.

(Modifications) Although the embodiments of the present invention have been described in detail, the present invention is not limited to the above-described embodiments, but falls within the scope of the present invention described in the appended claims. Thus, various changes can be made. Modified embodiments of the present invention will be exemplified below. (H01) The present invention is applied not only to the intermediate transfer drum but also to a transfer material carrying drum that rotates while carrying a transfer material (paper or the like) on which toner images of a plurality of image carriers arranged around are transferred. be able to.

[0055]

The above-described image forming apparatus of the present invention has the following effects. (E01) It is possible to provide a small-sized and low-cost tandem-type color image forming apparatus capable of constantly obtaining a stable color image even when the temperature in the apparatus has a gradient.

[Brief description of the drawings]

FIG. 1 is an overall perspective view of an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a front sectional view of the first embodiment.

FIG. 3 is a block diagram of a control unit according to the first embodiment.

FIG. 4 is a flowchart for setting an intermediate transfer drum control temperature and rewriting a job possible determination flag according to the first embodiment of the image forming apparatus of the present invention.

FIG. 5 is a flowchart of an intermediate transfer drum temperature control in Embodiment 1 of the image forming apparatus of the present invention.

FIG. 6 is an explanatory view of a conventional example of a tandem type color image forming apparatus having an intermediate transfer belt in contact with a plurality of image carriers.

[Explanation of symbols]

U: image forming apparatus, Bh: heating heater, B: transfer drum, C2: intermediate transfer drum surface temperature control means, C4: image carrier surface temperature uniformity means, F: fixing device, Pk to Pc
Image carrier (electrophotographic photoreceptor), Qk to Qc: transfer area, S
... Recording sheet, T1k to T1c ... Transfer device.

Claims (2)

[Claims] 1. An image forming apparatus having the following requirements (A01) to (A06): (A01) a transfer rotating and having a surface on which toner images formed on a plurality of image carriers are transferred; (A02) a plurality of image carriers each having an electrostatic latent image corresponding to an image of a different color formed on a rotating surface thereof and developing the electrostatic latent image into a toner image of a different color; (A03) the plurality of image carriers disposed opposite to the transfer drum surface in a plurality of transfer regions set along a rotational movement path of the transfer drum surface; (A04) a transfer unit disposed opposite to the inside of the transfer drum to transfer the toner image on the surface of each image carrier to the transfer drum side, (A04) a heating heater disposed inside the transfer drum, (A05) A toner image is formed on the surface of the image carrier. The intermediate transfer drum controls the heating heater so that the temperature of the surface of the transfer drum is maintained at a predetermined temperature during execution of a job which is an image forming operation of transferring and fixing the toner image on a recording sheet. Surface temperature control means, (A06) rotating the transfer drum and the image carrier for a predetermined period of time prior to the start of a job and transmitting heat on the surface of the transfer drum to the plurality of image carriers; Means for equalizing the surface temperature of the image bearing member for equalizing the surface temperature. 2. The image forming apparatus according to claim 1, wherein the image forming apparatus satisfies the following requirement (A07): (A07) the predetermined temperature set in a range from room temperature to 50 ° C. when room temperature is 50 ° C. or lower.