JPH11231691A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To appropriately hold pressing force between a toner image carrier and a transfer roll regardless of the kind of transfer material by providing a position regulating member for regulating a distance between the toner image carrier and the transfer roll. SOLUTION: A pressing member 57 is supported by a transfer roll supporting frame F2. The upper surface of the member 57 abuts on the bearing 52 of an outside secondary transfer roll 30, and an eccentric cam 63 abuts on the lower surface of the lever 58 of the member 57. By adjusting the rotating position of the cam 63 through a fixing screw 64 functioning also as a cam shaft, the member 57 is lifted upward and the roll 30 is pressed toward an inside secondary transfer roll 29 by a compression spring 61 through the bearing 52 while holding an intermediate transfer belt B in between. An eccentric cam for positioning (position regulating member) 66 is fixed at the upper end of the frame F2 through a fixing screw 67. The bearing 52 abuts on the cam 66 and is positioned.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image forming apparatus using a transfer roll for transferring a toner image on a toner image carrier to another member. In the present specification, the “toner image carrier” is a “toner image carrier” that carries a toner image on the surface by developing an electrostatic latent image formed on the surface into a toner image, or another toner. It means both a "toner image carrier" such as an intermediate transfer member that carries a toner image transferred from the image carrier. The “transfer material” transfers a toner image from a “toner image carrier” that carries the toner image on the surface by developing the electrostatic latent image formed on the surface into a toner image. The term “intermediate transfer member” or “recording sheet” or “recording sheet” on which a toner image is transferred from the intermediate transfer member.

[0002]

2. Description of the Related Art When a toner image on a toner image carrier is transferred to another member using a transfer roll, the recording paper (transfer material) is moved if the pressing load of the transfer roll is insufficient. The transferred image is blurred. On the other hand, if the pressing load is too strong, an image defect called hollow is generated particularly in a line image. As described above, the pressing load of the transfer roll is an important factor for obtaining a good transfer image, and several methods for maintaining a good pressing state have been proposed in the past. For example, the following technology (J01), (J02) is known. (J01) Technology described in JP-A-5-158356. In this publication, a transfer roller 35 (outer secondary transfer roll) is fixed to a counter roll 25 (inner secondary transfer roll, that is, a toner) by a lever and a spring with a constant load. (Hereinafter, referred to as “constant load method”).

(J02) The technique described in Japanese Patent Application Laid-Open No. 5-303291 discloses that in a secondary transfer area, a belt drive roller 21 (inner secondary transfer roll, that is, a toner image support member) supports the belt drive roller 21. The paper transfer bias roller 23-1 (outer secondary transfer roll) is pressed by the cam 23-3 or the like with the recording paper (transfer material) sandwiched between the intermediate transfer belt 19 (toner image carrier) and the paper transfer. A position regulating member (taper roller 23) for keeping a constant distance between the axis of the bias roller 23-1 and the belt driving roller 21 or its axis.
-4) and a method for keeping the distance between the belt driving roller 21 and the paper transfer bias roller 23-1 constant (hereinafter, referred to as a "fixed position method"). That is, in order to keep the distance between the axis of the paper transfer bias roller 23-1 and the surface of the belt drive roller 21 or the axis thereof constant, the tapered roller 23-4 supported on the axis of the paper transfer bias roller 23-1 is used. Surface and the opposing roller 2 mounted on the surface of the belt drive roller 21 or its shaft
1-2. Therefore, this (J02)
According to the technique described above, by keeping the above-mentioned interval constant and appropriately setting the pressure contact force (the force of the spring 52) of the paper transfer bias roller 23-1 to the drive roller 21, even a thick transfer material or a thin transfer material can be appropriately used. It is possible to apply an appropriate pressing force.

[0004]

The above prior art has the following problems. (Problem of (J01)) In the technique of (J01), since the load for pressing the outer secondary transfer roll 35 against the inner secondary transfer roll 25 is kept constant, the outer secondary transfer roll 35 is kept constant.
There is no change in the press-contact load between the transfer rolls due to variations in the outer shape of the secondary transfer roll or fluctuations. However, when a strong transfer material such as a postcard or an envelope is used, the load pressing the outer secondary transfer roll against the inner secondary transfer roll is used. Was insufficient, and there was a problem that transfer failure and image bleeding occurred. In order to avoid this problem, if a sufficient pressure contact load is obtained when a postcard or an envelope is used as a transfer material, the pressure contact load becomes too strong when a thin transfer material is used, particularly in line drawings. Omission sometimes occurred.

(Problem of (J02)) In the technique of (J02), the taper roller 23-4, which is an interval maintaining member for maintaining the interval, is opposed to the driving roller 21 or an opposing shaft mounted on the shaft thereof. Since the rollers 21-2 are in rotational contact with each other, the spacing members 23-4, 21, or 21
-2, there is a problem that the rotating contact surface is worn. Due to the abrasion, there is a problem that it is difficult to keep the interval between the paper transfer bias roller 23-1 and the driving roller 21 constant over a long period of time.

In view of the above circumstances, the present invention has the following technical contents (O01) and (O02). (O01) To appropriately maintain the pressing force between the toner image carrier and the transfer roll irrespective of the outer diameter variation and deflection (eccentricity) of the transfer roll and the type of the transfer material. (O02) The interval between the toner image carrier and the transfer roll can be maintained at an appropriate value for a long period of time.

[0007]

Means for Solving the Problems Next, the present invention for solving the above-mentioned problems will be described. Elements of the present invention are described in order to facilitate correspondence with elements of the embodiments described later. The symbols of the elements in parentheses () are added. In addition,
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 of the invention has the following requirements (A01) to (A06).
(A01) a toner image carrier (B) on which a toner image is formed on a rotating surface, (A0)
2) Toner image carrier supporting members (29, 51, F1) for rotatably supporting the toner image carrier (B), (A03)
A surface pressed against the surface of the toner image carrier (B) and rotatably moved in the same direction as the surface of the toner image carrier (B) across the transfer material; A transfer roll (3) for transferring a toner image onto the transfer material
0), (A04) Transfer roll support members (52, 57, F2) for rotatably supporting the transfer roll (30), (A0)
5) The toner image carrier (B) and the transfer roll (3)
0), the toner image carrier support member (29, 51, F1) and the transfer roll support member (5).
2, 57, F2) by an elastic pressing force in a direction in which they approach each other.
1, 73, 84), (A06) the toner image carrier (B)
And regulating the positions of the non-rotating portions of the toner image carrier support members (29, 51, F1) and the transfer roll support members (52, 57, F2) to regulate the closest distance between the transfer rolls (30). By doing so, position regulating members (66, 74) for regulating the closest distance between the toner image carrier (B) and the transfer roll (30).

(Operation of the Present Invention) In the image forming apparatus of the present invention having the above configuration, the toner image support member (29,
51, F1), a toner image is formed on the rotatable surface of the toner image carrier (B) rotatably supported.
The transfer roll (30) rotatably supported by the transfer roll support members (52, 57, F2) has a surface that rotates and moves in the same direction as the surface of the toner image carrier (B). The transfer roll (30) includes a toner image carrier (B)
The toner image carrier (B) is pressed against the surface of the transfer material with the transfer material interposed therebetween, and transfers the toner image to the transfer material. Pressing means (61, 73) for pressing at least one of the toner image carrier support member (29, 51, F1) and the transfer roll support member (52, 57, F2) by an elastic pressing force in a direction in which they approach each other. , 84) press the toner image carrier (B) and the transfer roll (30) together. The position regulating member (66, 74) is provided with the image carrier supporting member and the transfer roll supporting member (52, 57, F).
By regulating the position of the non-rotating portion 2), the closest distance between the toner image carrier (B) and the transfer roll (30) is regulated.

Accordingly, the transfer material having a small thickness among the transfer materials such as recording paper passing between the surface of the toner image carrier (B) and the transfer roll (30) is the position regulating member (interval regulating member). The transfer material passing through the interval (transfer area (Q4)) regulated by (66, 74) and having a large thickness is opposed to the elastic pressing force of the pressing means (61, 73, 84). Push and pass. That is,
In the case of a transfer material such as thin paper, the transfer is performed in a state where the surface of the toner image carrier (B) and the transfer roll (30) are pressed by a predetermined bite amount, and in the case of a thick transfer material such as a postcard or an envelope. Is transferred in a state where it is pressed with a predetermined pressing load. For this reason, it is possible to obtain a good transfer image free from transfer failure and missing in a line drawing even on a thin paper postcard or an envelope. Further, according to the present invention, the toner image carrier support member (29,5) can be provided without restricting the position of the rotating toner image carrier (B) or the rotating portion of the transfer roll (30).
1, F1) and the transfer roll supporting member (52, 5).
7, F2) regulates the position of the non-rotating parts and regulates the distance between them. Therefore, unlike the case of restricting the position of the rotating parts, the non-rotating parts are not affected by the wear of the rotating contact parts.
It is possible to maintain a stable interval for a long time.

[0011]

(Embodiment 1 of the present invention) Embodiment 1 of the image forming apparatus of the present invention is characterized by satisfying the following requirement (A07) in the present invention. (A07) When the recording paper on which the toner image on the toner image carrier (B) is transferred passes between the toner image carrier (B) and the transfer roll (30), the toner image carrier (B) ) And the pressing load between the transfer roll (30) is 18 to
At 20 g / mm or more, the elastic pressing is performed so that the distance between the toner image carrier (B) and the transfer roll (30) becomes larger than the distance regulated by the position regulating members (66, 74). The pressing means (6
1, 73, 84).

(Operation of the First Embodiment of the Present Invention) In the first embodiment of the image forming apparatus of the present invention, the pressing means (6
1, 73, 84), the recording paper on which the toner image on the toner image carrier (B) is transferred passes between the toner image carrier (B) and the transfer roll (30). When the pressing load between the toner image carrier (B) and the transfer roll (30) is 18 to 20 g / mm or more, the toner image carrier (B) and the transfer roll (3)
The interval between 0) is set to be larger than the interval regulated by the position regulating members (66, 74). Therefore, it is possible to perform the transfer to the transfer material having a small thickness and also to the transfer material having a large thickness with an appropriate pressing load.

[0013]

Next, specific examples (examples) of 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 explanatory view of an image forming apparatus (color copying machine) according to an embodiment of the present invention. In FIG. 1, an image forming apparatus F has a UI (user interface) having a copy start key, a numeric keypad, and the like (not shown) at an upper part thereof.
And a transparent platen glass 2 on which a document (not shown) is placed. A document illumination unit 3 that scans the document while illuminating the document is arranged below the platen glass 2. The document illumination unit 3 includes a document illumination light source 4.
And a first mirror 5. A mirror unit 6 that moves at half the speed of the original illumination unit 3 is disposed below the platen glass 2. The mirror unit 6 includes a second mirror 7 and a third mirror 8 that reflect light emitted from the illumination light source 4 and sequentially reflected by the original and the first mirror 5 (that is, original image light). .

The original image light reflected by the third mirror 8 passes through an imaging lens 9 and is read as R, G, B analog signals by a CCD (color image reading sensor). C
The R (red), G (green), and B (blue) image signals read by the CD are input to the IPS. The IPS includes an image read data output unit 11 that converts an analog electric signal of an R, G, B read image obtained by the CCD into a digital signal and outputs the digital signal, and converts the RGB image data into a K signal.
(Black), Y (yellow), M (magenta), and C
An image data output unit 12 converts the image data into (cyan) image data, performs data processing such as density correction and enlargement / reduction correction, and outputs the image data as writing image data (laser driving data). The image data output means 12 outputs the K,
An image memory 13 for temporarily storing Y, M, and C image data is provided.

The IPS write image data output means 12
The image write data (laser drive data) of four colors of K, Y, M, and C output by the laser drive signal are input to the laser drive signal output device 14. The laser drive signal output device 14 outputs a laser drive signal of an image of each color component of K, Y, M, and C in accordance with the input image data at a predetermined timing to an ROS (optical scanning device, that is, a latent image forming device). ). The RO
S scans the electrostatic latent image writing position Q1 of the rotating image carrier 16 with the laser beam L modulated by the laser drive signal output from the laser drive signal output device 14.

A rotary developing unit (developing device) for developing the electrostatic latent image into a toner image is provided in a developing area Q2 downstream of the latent image writing position Q1 along the moving direction of the image carrier 16. (Device) 18 is disposed. The developing unit 18 has developing devices 18k, 18y, 18m, and 18c of four colors of K, Y, M, and C mounted around a rotating shaft 18a. The four color developing units 18k, 18y, 18m and 18c are sequentially arranged in the developing area Q2.
It is configured to move to. The developing unit 18k,
Reference numerals 18y, 18m, and 18c denote electrostatic latent images on the image carrier 16 as K (black), Y (yellow), M (magenta),
This is a device for developing toner images of each color (cyan). The toner image forming apparatus (14 to 18 + ROS) is constituted by the elements indicated by the reference numerals 14 to 18, ROS and the like.

In FIG. 1, the surface of the image carrier 16 is uniformly charged (−650 V in this example) with a charge of a predetermined polarity by a charger 17 and a laser beam L modulated by an image signal of a first color. An electrostatic latent image corresponding to the image of the first color (for example, K (black)) is formed on the surface of the image carrier by the writing scan, and the surface potential of the image carrier 16 is written by the laser beam L at this time. (−200 V in this example), an image is formed by the potential, that is, an electrostatic latent image is formed at the latent image writing position Q1, K, Y, M, C.
Are sequentially written in this order, and are sequentially rotated and moved to the developing area Q2.
Developed sequentially at 18m and 18c.

In a primary transfer area Q3 in which toner images of respective colors sequentially formed on the surface of the image carrier 16 are transferred onto the intermediate transfer belt B in a superimposed manner, one image is formed on the back side of the intermediate transfer belt B.
A next transfer roll (primary transfer device) T1 is provided. 1
Intermediate transfer belt B and image carrier 1 in next transfer area Q3
6 and the contact pressure was almost 0, and the nip width was 0.5.
３3 mm. To the primary transfer roll T1, a transfer bias voltage having a polarity opposite to the charging polarity of the toner image on the surface of the image carrier 16 is supplied to the power supply E1 for the primary transfer unit of the power supply E for transfer.
Is applied. The toner images of K, Y, M, and C sequentially developed on the image carrier 16 by the primary transfer roll T1 to which the transfer bias voltage is applied are transferred every time the intermediate transfer belt B rotates once. Intermediate transfer belt B for each color
The primary transfer is successively superposed on the top. On the downstream side of the primary transfer area Q3 along the surface of the image carrier 16, an image carrier cleaner 19 for collecting residual toner on the surface of the image carrier 16, and a charge on the surface of the image carrier 16 is removed. The static eliminators 20 are sequentially arranged.

The intermediate transfer belt B includes a driving roll 2
5, tension roll 26, idler roll 27, 28
And rotatably supported by belt support rolls 25 to 29 having an inner transfer roll (backup roll) 29, and driven by a drive device (not shown) at approximately the same speed as the image carrier 16 by the drive roll 25 indicated by an arrow. Rotate in direction A.

In the secondary transfer area Q4 set on the moving path of the intermediate transfer belt B, the intermediate transfer belt B
The outer secondary transfer roll 30 is disposed on the side facing the inner secondary transfer roll 29. An electrode roll 31 is in contact with the inner secondary transfer roll 29, and a toner on the intermediate transfer belt B is contacted with the electrode roll 31 by a secondary transfer unit power supply E 2 of a transfer power supply E controlled by a controller C. And a secondary transfer bias voltage having the same polarity as the charging polarity is applied, and the toner image that has been primary-transferred and superimposed on the intermediate transfer belt B is secondarily transferred onto the recording paper S at once. The elements indicated by the reference numerals 29 to 31 constitute the secondary transfer unit T2. The outer secondary transfer roll 30 is movable together with a transfer roll cleaner 33 for cleaning the surface between a separation position apart from the inner secondary transfer roll 29 and a transfer operation position pressed by the inner secondary transfer roll 29. It is. Further, in the conveying direction of the intermediate transfer belt B, a separation claw 34 for separating the recording paper S from the intermediate transfer belt B and a residual toner on the surface of the intermediate transfer belt B are provided downstream of the outer secondary transfer roll 30. The belt cleaner 35 to be removed is an intermediate transfer belt B
It is arranged so as to be able to adjust the movement between a contact position where it comes into contact with and a distant separated position.

The recording paper S taken out of the paper feed tray 41 is conveyed by a pick-up roll 42 and a separation roll 43, and once stopped by a registration roll 44, passes through a guide conveyance path 45 at a predetermined timing, and is subjected to the secondary transfer. It is transported to the area Q4. The unfixed toner image on the intermediate transfer belt B is secondarily transferred to the recording sheet S by the secondary transfer unit T2 when passing through the secondary transfer area Q4. The recording sheet S to which the unfixed toner image has been transferred moves along the upper surface of the sheet guide member 46, and is further conveyed to the fixing position Q5 through the sheet conveying belt 47. Recording paper S
When the sheet passes through the fixing area Q5, the unfixed toner image on the recording sheet S is fixed by the fixing device 48 and is discharged to the discharge tray 49.

(Primary Transfer Roll T1) The primary transfer roll T1 has a semiconductive layer formed on the surface of a metal core. The primary transfer roll T1 is pressed against the metal plate with a load of 5 kg, and a distance of 1000 mm is placed between the core of the primary transfer roll T1 and the metal plate.
A resistance value of 10 ⁵ to 10 ⁹ Ω when a voltage of V is applied is 1
The next transfer roll T1 was used. If the resistance value is lower than 10 ⁵ Ω, the electric charge given in the primary transfer area Q3 at the time of the primary transfer is injected into the image carrier 16 and a so-called charging memory phenomenon occurs. Also, 10
^{If 9} or more are used, discharge occurs in the primary transfer section,
It could not be used because transfer omission occurred.

(Intermediate Transfer Belt B) The material of the intermediate transfer belt B is PI (polyimide), PVdF (polyvinylidene fluoride) or PC (polycarbonate) mixed with a resistance control agent such as CB (carbon black) to reduce the volume resistivity. 10 ⁷
10 to 10 ¹⁴ Ωcm, but the volume resistivity is 10
If it is lower than ⁸ Ωcm, the charge applied to the back surface of the intermediate transfer belt B in the primary transfer area Q3 spreads out of the primary transfer area (primary transfer nip) Q3 through the resistance of the intermediate transfer belt B, so that the image bearing Since the toner is transferred from the image carrier 16 to the intermediate transfer belt B before the body 16 and the intermediate transfer belt B come into contact with each other, the toner is scattered so much that a good image cannot be obtained. Further, when the volume resistivity is higher than 10 ¹² [Omega] cm, since the intermediate transfer belt B is required charged to cause neutralization device, a volume resistivity of 10 ⁸ to 10 ¹² Omega
cm is desirable. Further, when the thickness of the material of the intermediate transfer belt B is 50 μm or less, the mechanical strength is insufficient and the belt is easily broken or broken.
Thickness is more preferable than m.

(Outer Secondary Transfer Roll 30) The outer secondary transfer roll 30 is provided around a metal core having an outer diameter of 15 mm.
An elastic layer having a thickness of 6.5 mm is provided by using a conductive or semiconductive material obtained by mixing a resistance control agent such as CB (carbon black) with foamed silicon or foamed urethane. Used those having an Asuka C hardness of 20 to 40 points.

(Position Control Member) FIG. 2 is an explanatory view of a position control member for controlling the distance between the inner secondary transfer roll 29 and the outer secondary transfer roll 30 of the secondary transfer device T2 of the first embodiment. Indicates that the outer secondary transfer roll 30 is the inner secondary transfer roll 2
2B is a cross-sectional view of FIG. 2A, and FIG. 2C is a view in which the outer secondary transfer roll 30 pressed by the pressing means is moved toward the inner secondary transfer roll 29 by the position regulating member. FIG. 2D is a front view of the restricted state, and FIG. 2D is a sectional view of FIG. 2C. In FIG. 2, the inner secondary transfer roll 29 has a bearing 5 by a belt supporting frame F1.
1 and rotatably supported. The inner secondary transfer roll 29 supports an intermediate transfer belt (toner image carrier) B. Therefore, in the first embodiment, the intermediate transfer belt (toner image carrier) B is supported by the toner image carrier support members (29, 51, F1) such as the inner secondary transfer roll 29, the bearing 51, and the belt support frame F1. Supported.

Both ends of the shaft 30a of the outer secondary transfer roll 30 are rotatably supported by bearings 52.
The transfer roll supporting frame F2 is connected to the outer secondary transfer roll 3
A guide groove 54 that guides the long hole 53 through which the zero shaft 30a passes and the bearing 52 that rotatably supports the shaft 30a with respect to the inner secondary transfer roll 29 so as to be able to advance and retreat.
have. The bearing 52 that rotatably supports the outer secondary transfer roll 30 is configured as the transfer roll support member of the first embodiment, and is slidable along the guide groove 54.

A pressing member 57 is supported on the transfer roll supporting frame F2 so as to be rotatable around a supporting shaft 56. The pressing member 57 has levers 58 and 59 that can rotate around the support shaft 56. The levers 58 and 59 are freely rotatable about the support shaft 56, and a compression spring (pressing means) 61 disposed therebetween.
As a result, a force such that the angle formed by the levers 58 and 59 around the support shaft 56 increases is always received. The levers 58 and 59 are provided with pins 58a and 59a, and the pins 58a and 59a are provided with the lever 5a.
The long hole 62a of the connecting member 62 for restricting the angle between 8, 59 from expanding beyond a certain value is engaged. Reference numeral 58-
The pressing member 57 is constituted by the element indicated by 62.

The upper surface of the pressing member 57 is in contact with the bearing 52, and the lever 5 of the pressing member 57
An eccentric cam 63 is in contact with the lower surface 8. The eccentric cam 63 is fixed by a fixing screw 64 also serving as a cam shaft, and the rotational position is fixed by the fixing screw 64. Therefore, by adjusting the rotational position of the eccentric cam 63, the pressing member 57 is lifted upward, and the outer secondary transfer roll 30 is directed toward the inner secondary transfer roll 29 via the bearing 52, and the pressing means is pressed. It is constituted so that it may press. An eccentric cam (position regulating member) 66 for positioning is fixed to the upper end of the transfer roll supporting frame F2 adjacent to the guide groove 54 by a fixing screw 67. The bearing 52 is positioned in contact with the positioning eccentric cam 66.

When the eccentric cam 63 rotates to the position shown in FIGS. 2A and 2B, the outer secondary transfer roll 30
Is separated from the inner secondary transfer roll 29, and FIG.
C, when rotated to the position shown in FIG.
The next transfer roll 30 is pressed by the pressing means toward the inner secondary transfer roll 29 with the intermediate transfer belt B interposed therebetween. In this case, even if the rotational position of the eccentric cam 63 is adjusted and the pressing member 57 is pushed up to press the bearing 52 and the outer secondary transfer roll 30 toward the inner secondary transfer roll 29, the bearing 52 remains Since the abutment is made on the positioning eccentric cam 66, the distance between the outer secondary transfer roll 30 and the inner secondary transfer roll 29 is maintained at a predetermined value (a value determined by the rotational position of the positioning eccentric cam 66).

Therefore, in the first embodiment, the outer secondary transfer roll 30 is supported by the transfer roll supporting members (52, 57, F2) such as the bearing 52, the pressing member 57, and the transfer roll supporting frame F2. And
When the bearing 52 has an inner race supporting the shaft 30a and an outer race mounted on the transfer roll support frame F2, the transfer roll support member (5
2, 57, F2) are rotating members such as the inner race of the bearing 52 that supports the shaft 30a of the outer secondary transfer roll 30, the outer race of the bearing 52, the pressing member 57, and the transfer roll support frame F2. And a non-rotating member. In the first embodiment, the position of the outer race of the bearing 52 which is a non-rotating member of the transfer roll supporting members (52, 57, F2) is regulated by the eccentric cam 66 for positioning.
Inner Secondary Transfer Roll 29 and Outer Secondary Transfer Roll 30
Regulates the spacing.

(Operation of the First Embodiment) Using the image forming apparatus of the first embodiment, a second original drawing (manufactured by Mitsubishi Paper Mills, trade name: Super 60), copy paper (manufactured by Fuji Xerox Office Supply, trade name: The image quality was evaluated using a J-paper), a postcard made by government, and an envelope (manufactured by Monroe brand, trade name: Monarch) as a transfer material. For comparison, the positioning eccentric cam (position regulating member) 66 was removed, that is, the range of the press-contact load for obtaining a good image for each sheet was determined so that the load was constant. FIG. 5 is a graph for explaining the results of image quality evaluation performed using the comparative example of Example 1 described above. The horizontal axis represents the type of the transfer material, and the vertical axis represents the pressure contact load, and a good image in the comparative example is obtained. It is the figure which showed the range of the pressing load by the arrow of both sides.

In the first embodiment, the positioning eccentric cam (position regulating member) is provided between the outer secondary transfer roll 30 and the inner secondary transfer roll 29 when there is no recording paper S in the secondary transfer area Q4. At the position where the bite amount is 0.3 mm, the compression spring (pressing means) 61 is adjusted, and when the pressing load becomes 18 g / mm or more, the direction in which the outer secondary transfer roll 30 separates from the inner secondary transfer roll 29 ( (The direction in which the bearing 52 moves away from the positioning eccentric cam 66)
It was configured to move to. At this time, good images were obtained for all the transfer materials shown in FIG. The bearing 52 supporting the outer secondary transfer roll 30 was in pressure contact with the positioning eccentric cam (position regulating member) 66 during the transfer of the second original drawing and the copy sheet. The bearing 52 supporting the transfer roll 30 is separated from the eccentric cam 66 for positioning. At the time of government postcard transfer, the bearing 52 supporting the outer secondary transfer roll 30 was in pressure contact with the positioning eccentric cam (position regulating member) 66, but sometimes it was slightly separated.

In the first embodiment, when thin paper such as the second original drawing is used as the transfer material, the outer secondary transfer roll 30 is moved to the inner secondary transfer roll 30 by the action of the compression spring 61 of the pressing member 57.
The shaft 30a of the outer secondary transfer roll 30 is pressed in the direction of the next transfer roll 29, and is eccentric to a positioning eccentric cam (position regulating member) 66 provided between the outer secondary transfer roll 30 and the inner secondary transfer roll 29. The outer secondary transfer roll 30 is pressed against the inner secondary transfer roll 29 until the supporting bearing 52 abuts. On the other hand, when a postcard or an envelope is used as the transfer material, the shaft 30a of the outer secondary transfer roll 30 is used.
The outer secondary transfer roll 30 is pressed against the inner secondary transfer roll 29 with a constant load (18 g / mm) because the bearing 52 that supports the roller cannot be brought into contact with the positioning eccentric cam (position regulating member) 66. Become.

That is, in the first embodiment, the transfer material of the thin paper such as the second original drawing is pressed against the inner secondary transfer roll 29 by a predetermined bite amount, and the postcard and the envelope are transferred to the inner secondary transfer roll by a predetermined pressing load. Pressed against the roll 29,
A good transfer image free from transfer failure and missing in line drawing can be obtained even with thin paper for postcards and envelopes. (Comparative Example 1) On the other hand, the eccentric cam (position regulating member) 66 for positioning is removed so that a constant load method is used, so that a good image can be obtained for each transfer material (see FIG. 5). As a result of obtaining the range of the load, as shown in FIG. 5, the range indicated by the double-sided arrow was the range of the press-contact load in which a good image was obtained.

(Comparative Example 2) Further, the eccentric positioning cam (position regulating member) 66 is attached to support the shaft 30a of the outer secondary transfer roll 30 at the time of secondary transfer for all the sheets shown in FIG. The compression spring 6 has such a strength that the bearing 52 does not separate from the eccentric cam 66 for positioning.
1 was used. The positioning eccentric cam 66 allows the outer secondary transfer roll 30 and the inner secondary transfer roll 2 to move.
The bite amount when there is no transfer material of No. 9 is 0.3 to 0.8 mm
Set to. At this time, the press-contact load on each of the transfer materials (see FIG. 5) is represented by marks ◆, ■, ▲ plotted in FIG.
Was as shown in FIG. In FIG. 5, in order to obtain a good image on the second original drawing or copy paper, the pressing load should be 10 to
Set to the range of 15 g / mm, or reduce the bite amount to 0.
It should have been 3 mm. However, the load is 10-15g
/ Mm range, postcards and envelopes suffered dropouts in line drawings.

(Embodiment 2) FIG. 3 shows the inner secondary transfer roll 29 and the outer secondary transfer roll 3 of the secondary transfer unit T2 of Embodiment 2.
FIG. 3A is an explanatory view of a position regulating member 74 that regulates the distance from the outer secondary transfer roll 30 to the inner secondary transfer roll 2.
FIG. 3B is a front view in a state away from the position 9 of FIG.
FIG. 3C is a sectional view taken along line B-IIIB, and FIG.
3D is a front view of the state in which the position of the outer secondary transfer roll 30 pressed by the pressing means is regulated by the position regulating member 74, and FIG. 3D is a sectional view taken along the line IIID-IIID in FIG. 3C. In the description of the second embodiment, components corresponding to the components of the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted. The second embodiment differs from the first embodiment in the following points, but has the same configuration as the first embodiment in other points.

In FIG. 3, the transfer roll supporting frame F
2 has a guide slot 70 for guiding the bearing 52 supporting the shaft 30 a of the outer secondary transfer roll 30 so as to be able to advance and retreat with respect to the inner secondary transfer roll 29. The bearing 52 that rotatably supports the outer secondary transfer roll 30 is configured as the transfer roll support member of the first embodiment, and is slidable along the guide slot 70. A pressing lever 72 is supported by the transfer roll supporting frame F2 so as to be rotatable around a support shaft 71. The pressing lever 72 includes the bearing 52.
Is formed with an elongated hole 72a. The pressing lever 72 is always rotated by a tension spring (pressing means) 73 to move the bearing 52 engaged with the elongated hole 72 a and the outer secondary transfer roll 30 supported by the bearing 52 to the inner It is pressed so as to push up to the next transfer roll 29.

An eccentric cam 74 (position regulating member) for regulating the rotational position of the transfer roller supporting frame F2 by contacting the pressing lever 72 is fixed to the transfer screw supporting frame F2.
5 fixed. The positioning eccentric cam 74
Abuts on the pressing lever 72 to regulate the positions of the bearing 52 and the outer secondary transfer roll 30, and the distance between the inner secondary transfer roll 29 and the outer secondary transfer roll 30 (the amount of bite). Is regulated. The inner secondary transfer roll 29 and the outer secondary transfer roll 30
Can be adjusted by adjusting the rotational position of the eccentric cam (position regulating member) 75 for positioning.

The tension spring (pressing means) 73
If the pressing load exceeds 18 g / mm when a thick transfer material is sandwiched in the secondary transfer area Q4, the outer secondary transfer roll 30
The pressing lever 72 supporting the bearing 52 supporting the shaft 30a is adjusted so as to be separated from the eccentric cam 75 for positioning.

(Operation of Embodiment 2) When thin paper or the like is used as the transfer material, the pressing lever 72 receives a clockwise rotational force around the support shaft 71 by the action of the tension spring 73,
The outer secondary transfer roll 30 is pressed in the direction of the inner secondary transfer roll 29. At this time, the pressing lever 72 and the positioning eccentric cam 75 are in contact with each other. When a postcard or an envelope is used as the transfer material, the secondary transfer area Q
4 according to the thickness of the transfer material passing therethrough.
2 is separated from the eccentric cam 75 for positioning, and the transfer material is 1
It is clamped at a linear pressure of 8 g / mm or more. Therefore, also in the second embodiment, the outer secondary transfer roll 30 is pressed against the inner secondary transfer roll 29 by a predetermined bite amount in the case of a transfer material such as thin paper, and the postcard and the envelope are pressed inside by a predetermined pressing load. It is pressed against the secondary transfer roll 29. For this reason, it is possible to obtain a good transfer image free from transfer failure and missing in a line drawing even on a thin paper postcard or an envelope.

(Embodiment 3) FIG. 4 shows the inner secondary transfer roll 29 and the outer secondary transfer roll 3 of the secondary transfer unit T2 of the third embodiment.
FIG. 4A is an explanatory view of a position regulating member that regulates an interval with zero.
FIG. 4B is a front view of the state where the outer secondary transfer roll 30 is separated from the inner secondary transfer roll 29, FIG. 4B is a cross-sectional view of FIG. 4A,
FIG. 4C is a front view of a state in which the position of the outer secondary transfer roll 30 pressed by the pressing unit toward the inner secondary transfer roll 29 is regulated by the position regulating member, and FIG.
It is sectional drawing of C. In the description of the third embodiment, components corresponding to the components of the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted. The third embodiment differs from the first embodiment in the following points.
In other respects, the configuration is the same as that of the first embodiment.

In FIG. 4, the transfer roll supporting frame F
2, a long hole 53 through which the shaft 30a of the outer secondary transfer roll 30 penetrates is formed. The shaft 3 penetrating the long hole 53
0a moves along the long hole to move the inner secondary transfer roll 2
9 can be approached and separated. The transfer roll supporting frame F2 is provided with a pair of parallel guides 81, 81. The guides 81, 81 allow the pressing slide frame 82 to approach and separate from the inner secondary transfer roll 29 in the direction of separation. It is slidably supported.
A slide member 83 slidably supported by the pressing slide frame 82 is constantly pressed upward by a compression spring 84. The slide member 83 constantly presses the bearing 52 that supports the shaft 30a of the outer secondary transfer roll 30 upward.

The same eccentric cam 63 as in the first embodiment is in contact with the lower end of the pressing slide frame 82.
The eccentric cam 63 is fixed to a cam screw fixing screw 64 similar to that of the first embodiment, and the rotation position is fixed by the fixing screw 64. Therefore, by adjusting the rotational position of the eccentric cam 63, the pressing slide frame 82 is lifted upward, and the slide member 83,
The outer secondary transfer roll 30 is configured to be pressed against the inner secondary transfer roll 29 via a bearing 52. An eccentric positioning cam (position regulating member) 66 is fixed to a lower end of the belt support frame F1 by a fixing screw 67. The positioning eccentric cam 66 is arranged at a position where it comes into contact with the bearing 52.

In the third embodiment, similarly to the first embodiment, the interval between the outer secondary transfer roll 30 and the inner secondary transfer roll 29 is regulated by adjusting the rotational position of the eccentric cam 66 for positioning. Can be. And outside 2
In the case of a transfer material such as thin paper, the next transfer roll 30 is pressed against the inner secondary transfer roll 29 by a predetermined bite amount,
Postcards and envelopes are transferred to the inner secondary transfer roll 2 with a predetermined pressing load.
Pressed to 9. For this reason, it is possible to obtain a good transfer image free from transfer failure and missing in a line drawing even on a thin paper postcard or an envelope.

(Modifications) Although the embodiments of the present invention have been described in detail, the present invention is not limited to the above-described embodiments, and does not depart from the present invention described in the claims. Various design changes can be made. Modified embodiments of the present invention will be exemplified below. (H01) The present invention can be applied to a primary transfer roll instead of the outer secondary transfer roll. (H02) The position regulating members 66 and 74 are used to position the outer race of the bearing 52 that supports the shaft 30a of the outer secondary transfer roll 30, instead of positioning the bearing 52.
It is possible to provide a member that supports position and that can adjust the position, and to restrict the position of the member whose position can be adjusted. (H03) The intermediate transfer belt (toner image carrier) of the transfer roll support member (outer race of the bearing 52)
Instead of regulating the position of the toner image carrier (intermediate transfer belt) B with the outer secondary transfer roller 30, the position of the toner image carrier support member (outer race of the bearing 51) with respect to the outer secondary transfer roll 30 is regulated. It is possible to regulate the interval with the transfer roll 30.

[0046]

The above-described image forming apparatus of the present invention has the following effects. (E01) The pressing force between the toner image carrier and the transfer roll can be appropriately maintained irrespective of the outer diameter variation and deflection (eccentricity) of the transfer roll and the type of the transfer material. (E02) The distance between the toner image carrier and the transfer roll can be maintained at an appropriate value for a long period of time.

[Brief description of the drawings]

FIG. 1 is an overall explanatory diagram of an image forming apparatus (color copier) according to an embodiment of the present invention.

FIG. 2 is an explanatory view of a position regulating member that regulates a distance between an inner secondary transfer roll 29 and an outer secondary transfer roll 30 of the secondary transfer device T2 according to the first embodiment, and FIG. FIG. 2B is a sectional view of FIG. 2A, and FIG.
FIG. 2D is a front view of a state in which the position of the outer secondary transfer roll 30 pressed by the pressing unit toward the next transfer roll 29 is regulated by the position regulating member. FIG. 2D is a cross-sectional view of FIG. 2C.

FIG. 3 is an explanatory view of a position regulating member that regulates a distance between an inner secondary transfer roll 29 and an outer secondary transfer roll 30 of the secondary transfer device T2 according to the second embodiment, and FIG. FIG. 3B is a cross-sectional view taken along the line IIIB-IIIB of FIG. 3A, in which the transfer roll 30 is separated from the inner secondary transfer roll 29.
FIG. 3C is a front view of a state in which the position of the outer secondary transfer roll 30 pressed by the pressing means toward the inner secondary transfer roll 29 is regulated by a position regulating member, and FIG.
FIG. 3C is a sectional view taken along line IIID-IIID of FIG.

FIG. 4 is an explanatory view of a position regulating member that regulates a distance between an inner secondary transfer roll 29 and an outer secondary transfer roll 30 of the secondary transfer device T2 according to the third embodiment, and FIG. FIG. 4B is a cross-sectional view of FIG. 4A, in which the transfer roll 30 is separated from the inner secondary transfer roll 29, and FIG. FIG. 4D is a cross-sectional view of FIG. 4C in a state in which the position of the transfer roll 30 is regulated by the position regulating member.

FIG. 5 is a graph for explaining the result of image quality evaluation performed using the comparative example of the first embodiment. The horizontal axis represents the type of the transfer material, and the vertical axis represents the pressure contact load. It is the figure which showed the range of the press contact load which can obtain an image with a double-sided arrow.

[Brief description of reference numerals]

 B: toner image carrier (intermediate transfer belt), 30: transfer roll (outer secondary transfer roll), 61, 84 ... pressing means (compression spring) 66, 74 ... position regulating member (spacing regulating member), 73 ... pressing Means (tensile spring), (29, 51, F1) ... toner image carrier support member, (52, 57, F2) ... transfer roll support member.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Naoto Yoshino 2274 Hongo, Ebina-shi, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd. (72) Inventor Yukio Hayashi 2274 Hongo, Ebina-shi, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd.

Claims (2)

[Claims] 1. An image forming apparatus having the following requirements (A01) to (A06): (A01) a toner image carrier on which a toner image is formed on a rotating surface; (A02)
(A03) a toner image carrier supporting member rotatably supporting the toner image carrier, pressed against the surface of the toner image carrier with a transfer material interposed therebetween, and rotated in the same direction as the surface of the toner image carrier; A transfer roll having a surface and transferring the toner image on the toner image carrier to the transfer material, (A
04) a transfer roll support member that rotatably supports the transfer roll, and (A05) at least one of the toner image support member and the transfer roll support member to press the toner image carrier and the transfer roll against each other. (A06) a pressing means for pressing the toner image carrier and the transfer roll in a direction approaching each other by elastic pressing force; A position regulating member that regulates the position of the non-rotating portion to regulate the closest distance between the toner image carrier and the transfer roll. 2. The image forming apparatus according to claim 1, further comprising the following requirement (A07): (A07) The recording sheet onto which the toner image on the toner image carrier is transferred is the toner image. When passing between the carrier and the transfer roll, the pressing load between the toner image carrier and the transfer roll is 18 to
The pressing means, wherein the elastic pressing force is set such that an interval between the toner image carrier and the transfer roll is larger than an interval regulated by the position regulating member when the toner amount is 20 g / mm or more.