JPH10228183A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of a deviation in a transfer position and to form an image of high quality by adjusting a nip width, to change with the times when an intermediate transfer body contacts with or separates from the surface of an image carrier, with a nip width adjusting means. SOLUTION: The intermediate transfer body (intermediate transfer belt) receiving the transfer of a developed image is extended on a pulley 4 facing the image carrier 1 and a tension pulley 5, rotationally driven by an intermediate transfer body driving means 6, and brought into contact with or separated from the image carrier 1 by the contact/uncontact operations of a contact/ uncontact means 7. Then, the intermediate transfer body 3 is rotated forward to come into contact with the image carrier 1 and then a toner image of the first color on the image carrier 1 is transferred onto the intermediate transfer body 3. When the nip width 1 is unsuitable because of a change in transfer conditions, etc., or fluctuated, at the time of executing the contact/uncontact operations of the intermediate transfer body 3 by the contact/uncontact means 7 for transferring the toner images of each color, the nip width 1 is adjusted to a proper value by the nip width adjusting means 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a multifunction machine using an electrophotographic system, and more particularly, to a method for forming an electrostatic latent image formed on an image carrier. The present invention relates to an improvement in an image forming apparatus of a type in which a toner image obtained by developing with a developing device is intermediately transferred onto an intermediate transfer body and then transferred to a transfer material to form an image.

[0002]

2. Description of the Related Art In a conventional image forming apparatus such as an electrophotographic copying machine using an electrophotographic system, a toner image is formed on a photosensitive drum (image carrier) and then a recording paper is formed by using a transfer roller. When a toner image is transferred to the (transfer material), a cam receiver coaxially supported by the transfer roller and a control cam are pressed against an elastic member, and the transfer belt is operated by rotating the control cam during transfer. A technique is known in which the recording paper is pressed against a photosensitive drum (image carrier) and is separated from the image carrier of the photosensitive drum during non-transfer (Japanese Patent Laid-Open No. 3-107180). No.). FIG. 16 is a configuration diagram of a part of another conventional image forming apparatus.
After the toner image obtained by developing the electrostatic latent image formed on the toner image P. 01 with the developing device 102 is transferred to the intermediate transfer member 103, the toner image is transferred to the transfer material (P) by the transfer roller 110, and then the fixing device 111 To form an image. The intermediate transfer member 103 is provided with a pulley 104 that comes into contact with and separates from the image carrier 101.
And an intermediate transfer member driving pulley 106 that is endlessly stretched by a tension pulley 105 and a driving pulley 106.
Is driven to rotate. The pulley 104 and the tension roller 105 oscillate by oscillating each of the support members 104b, 105b by the contact / separation means 107 as an eccentric cam.

That is, a pulley 10 facing an image carrier
Reference numeral 4 is supported by a rotation support portion on the swing end side of a support member 104b which is swingably supported on a support shaft 104a. The tension roller 105 is supported by a support member 105b swingably supported on a support shaft 105a.
Is supported by the rotation support portion on the swinging end side of the rotating shaft. Support member 1
The support member 104b and the support member 105b are brought into pressure contact with the contact / separation means 107 by an urging member (not shown) by the surfaces on the sides facing each other. The contact / separation means 107
The eccentric cam is a distance from the center of rotation to the opposing surface of the support member 104b and the support member 105b, that is, the support member 104b and the support member 105b maintain the same distance by half rotation of the contact / separation means 107. The intermediate transfer body 103 is configured to be able to move toward and away from the image bearing member 101 in the same direction, in other words, in the same direction. Intermediate transfer is performed. In such a conventional image forming apparatus, the image bearing member 101
A predetermined nip width to be formed when the intermediate transfer body 103 is pressed on the top is fluctuated due to a change in transfer conditions, for example, expansion and contraction of the transfer belt due to a change in environmental conditions (room temperature or the like), or It fluctuates due to a difference in the circumference of the intermediate transfer body 103 (transfer belt) due to a difference in the manufacturing lot, and this causes deterioration in image quality. In order to adjust the fluctuating nip width, it is necessary to replace the eccentric cam of the contact / separation means 107 and perform advanced adjustment work. Since the transfer is very complicated and difficult, the transfer may still be performed with the transfer position shifted even after the replacement or adjustment of the components, resulting in a problem that the quality of the formed image is deteriorated.

[0004]

The object of the present invention is to solve such problems. That is, it is possible to easily or manually adjust the predetermined nip width, which is to be formed by the operation of the intermediate transfer member on and off the image bearing member, due to the change in the transfer condition. It is another object of the present invention to provide an image forming apparatus capable of forming a high-quality image without a transfer position shift.

[0005]

To achieve the above object, according to the present invention, a toner image obtained by developing an electrostatic latent image formed on an image carrier by a developing device is formed on an intermediate transfer member. In an image forming apparatus that forms an image by transferring and fixing to a transfer material after the intermediate transfer, an image carrier that is rotatably supported and an electrostatic latent image is formed, and an image carrier that is formed on the image carrier A developing device for developing an electrostatic latent image, an intermediate transfer member on which a toner image on the image carrier developed by the developing device is intermediately transferred,
An intermediate transfer member driving unit that stretches the intermediate transfer member on a pulley and a tension pulley opposed to the image carrier and rotationally drives the intermediate transfer member; and sets an interval between the pulley opposed to the image carrier and the tension pulley to be equal. Contact / separation means for swinging the intermediate transfer member so as to contact or separate from the image carrier while holding the nip; and a nip formed by contacting the intermediate transfer member with the image carrier by the contact / separation means Nip width adjusting means for adjusting the width. According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the contact / separation means includes a pair of eccentric cams fixed to a fixed cam shaft and a swing cam shaft, respectively. According to a third aspect of the present invention, in the image forming apparatus according to the second aspect, the pair of eccentric cams each include a non-inclined side parallel to the axial direction of the fixed cam shaft and the swing cam shaft, and the fixed cam shaft. A substantially tapered roller body having an inclined side that is not parallel to the axial direction of the oscillating cam shaft, and the inclined side of one eccentric cam and the inclined side of the other eccentric cam have opposite slopes. It is characterized by having.
According to a fourth aspect of the present invention, in the image forming apparatus according to the second or third aspect, the inclined sides respectively provided on the pair of eccentric cams are:
It is characterized in that it has a shape that can be matched when the respective inclined sides come into contact with each other. The invention of claim 5 is the invention of claim 2, 3, or 4.
In the image forming apparatus described above, the pair of eccentric cams
The inclined sides are in contact with each other and the non-inclined sides are in contact with each other.

According to a sixth aspect of the present invention, in the image forming apparatus of the second, third, fourth, or fifth aspect, the eccentric cam held by at least one of the fixed cam shaft side and the swing cam shaft side. And can be moved in the axial direction. According to a seventh aspect of the present invention, in the image forming apparatus according to the first, second, third, fourth, fifth, or sixth aspect, the nip width adjusting means is configured to rotate either one of the fixed cam shaft and the oscillating cam shaft. And a pipe-shaped camshaft, and a feed screw having a screw thread on its outer periphery is arranged in a threaded state inside the pipe-shaped camshaft. According to an eighth aspect of the present invention, in the image forming apparatus according to the seventh aspect, when a plurality of eccentric cams are held on an outer periphery of the pipe-shaped fixed cam shaft or the swing cam shaft, the feed screw is moved. It is characterized in that all the eccentric cams have the same amount of movement in the axial direction when rotated. According to a ninth aspect of the present invention, in the image forming apparatus according to the second, third, fourth, fifth, sixth, or seventh aspect, the fixed camshaft and the oscillating camshaft are driven by driving force coupling means. Is transmitted. According to a tenth aspect of the present invention, in the image forming apparatus according to the ninth aspect, the driving force connecting means includes a fixed camshaft gear having an axis fixed to the fixed camshaft, and an axis centered to the swing camshaft. An oscillating camshaft gear fixed and having the same number of teeth as the fixed camshaft gear; constantly engaged with the fixed camshaft gear and the oscillating camshaft gear; and the fixed camshaft gear or the oscillating camshaft. A planetary gear that revolves around one center of the gear as a center of rotation, wherein the planetary gear meshes with the other camshaft gear to connect the driving force of the fixed camshaft and the oscillating camshaft. Features.

According to an eleventh aspect of the present invention, in the image forming apparatus according to the ninth or tenth aspect, a total dimension of a pitch circle diameter of the fixed camshaft gear or the oscillating camshaft gear and a pitch circle diameter of the planetary gear is used. Is larger than the maximum value of the inter-axis distance between the fixed cam shaft and the oscillating cam shaft. According to a twelfth aspect of the present invention, in the image forming apparatus according to the ninth, tenth or eleventh aspect, each outer diameter of the fixed camshaft gear and the oscillating camshaft gear is set between the fixed camshaft and the oscillating camshaft. The distance is smaller than the shortest value. According to a thirteenth aspect of the present invention, in the image forming apparatus according to the ninth aspect, the driving force connecting means has the same number of teeth as the fixed camshaft timing pulley provided on the fixed camshaft and the fixed camshaft timing pulley. A swing camshaft timing pulley provided on the swing camshaft; a timing belt wound around the fixed camshaft timing pulley and the swing camshaft timing pulley; and a tensioner for adjusting a tension of the timing belt. And the driving force connecting means connects the driving force of the fixed cam shaft and the driving force of the swing cam shaft. According to a fourteenth aspect of the present invention, in the image forming apparatus according to the thirteenth aspect, the circumference (L) of the timing belt is:
L> 2r (π + 2), where r is the outer radius of the fixed camshaft timing pulley and the oscillating camshaft timing pulley, and the outer radius r is the axis between the fixed camshaft and the oscillating camshaft. It is characterized in that it is smaller than 1/2 of the shortest value of the distance.

[0008]

According to the first aspect of the present invention, the toner image formed on the image carrier is
The image is transferred to an intermediate transfer member (intermediate transfer belt) which is rotated and driven by the intermediate transfer member driving means and is brought into contact with or separated from the image carrier by the contact / separation means, and is transferred from the intermediate transfer member after being transferred. It is transferred and fixed on paper, but is formed when it comes into contact with the image carrier while maintaining the same distance between the pulley and the tension pulley facing the image carrier that stretches the intermediate transfer member. The nip width can be adjusted by the nip width adjusting means, so that the nip width formed when the intermediate transfer member comes into contact with the image bearing member can be manually or automatically adjusted according to the change of the transfer condition. As a result, it is possible to prevent the occurrence of a transfer position shift, and to maintain high image quality. According to the second aspect, since the contact / separation means is constituted by a pair of eccentric cams fixed to the fixed cam shaft and the swing cam shaft, the same effect as the first aspect can be obtained. In claim 3, the pair of eccentric cams are
A substantially tapered roller body having a non-inclined side parallel to the axial direction of the fixed cam shaft and the oscillating cam shaft, and an inclined side not parallel to the axial direction of the fixed cam shaft and the oscillating cam shaft, respectively. ,
Since the inclined side of one eccentric cam and the inclined side of the other eccentric cam have opposite gradients, the same high-quality image as in the first and second aspects can be obtained. According to the fourth aspect, the inclined sides provided on the pair of eccentric cams each have a shape that can be aligned when the respective contact sides come into contact with each other, and thus are formed when the intermediate transfer member comes into contact with the image bearing member. The nip width is manually or automatically adjusted in accordance with the change of the transfer condition to prevent the transfer position from being shifted and to maintain a high image quality. In the fifth aspect, the pair of eccentric cams are configured such that the inclined sides and the non-inclined sides come into contact with each other in an aligned state, so that the same effects as those of the respective claims can be obtained. . The intermediate transfer member is in pressure contact with the image carrier when the inclined sides are in contact with each other, and is separated from the image carrier when the non-inclined sides are in contact with each other.

According to a sixth aspect of the present invention, in the image forming apparatus of the second, third, fourth, or fifth aspect, the eccentric cam held by at least one of the fixed cam shaft side and the swing cam shaft side. Can be moved in the axial direction, so that the same effects as those of the above-mentioned claims can be obtained, and the intermediate transfer body can be imaged simply by adjusting the axial positional relationship between the two eccentric cams by a simple adjustment operation. The nip width when pressed against the carrier can be finely adjusted. In claim 7, one of the camshafts is formed into a pipe having a screw thread on the inner surface, and a feed screw which is a screw rod is screwed inside the pipe-shaped camshaft.
With a simple configuration, the nip width when the intermediate transfer member is pressed against the image carrier can be finely adjusted. In claim 8, when a plurality of eccentric cams are provided on the pipe-shaped cam shaft, the moving amounts of the plurality of eccentric cams that move in the axial direction by the feed screw are all fixed to be always fixed. Since the cam shaft and the oscillating cam shaft are parallel to each other, the predetermined nip width after being formed on the image bearing member by the contact and separation operation of the intermediate transfer member,
In accordance with the change of the transfer condition, it is possible to prevent the occurrence of the transfer position shift by adjusting the position easily and always with a simple device manually or automatically. In the ninth aspect, the eccentric cams respectively held by the fixed cam shaft and the oscillating cam shaft so that the fixed cam shaft and the oscillating cam shaft are connected by the driving force by the driving force connecting means are always in the same position. Because I made contact
The nip width can always be fixed after adjusting to an appropriate value,
The occurrence of the transfer position shift can be prevented. Claim 1
0, the driving force connecting means includes a fixed cam shaft gear provided on the fixed cam shaft, an oscillating cam shaft gear having the same number of teeth as the fixed cam shaft gear, and a fixed cam shaft gear and an oscillating cam shaft gear. And a planetary gear that revolves around one center of the fixed camshaft gear or the oscillating camshaft gear, respectively, so that the planetary gear meshes with the other. Even if the distance between the shafts fluctuates, the fixed camshaft gear and the oscillating camshaft gear and the planetary gear can be securely engaged to connect the driving force of the fixed camshaft and the oscillating camshaft, and also fixed. A pair of eccentric cams respectively held by the cam shaft and the swing cam shaft are always in contact at the same position. For this reason, the nip width can always be adjusted to an appropriate value and fixed in accordance with the change of the transfer condition, and the occurrence of the transfer position shift can be prevented.

In the eleventh aspect, the pitch circle diameters of the fixed cam shaft gear and the oscillating cam shaft gear of the driving force coupling means for coupling the driving force of the fixed cam shaft and the oscillating cam shaft and the pitch circle diameter of the planetary gear are set. The sum is made larger than the value at which the distance between the fixed cam shaft and the oscillating cam shaft is the longest, so that the fixed cam shaft and the oscillating cam shaft have the longest distance between them. The shaft gear, the oscillating cam shaft gear and the planetary gear are reliably engaged. Also, since the pair of eccentric cams respectively held by the fixed cam shaft and the swing cam shaft are always in contact at the same position, after the intermediate transfer member is formed on the image bearing member by the contact / separation operation. The predetermined nip width can always be easily and surely adjusted manually or automatically according to the change of the transfer condition to prevent the occurrence of the transfer position shift. According to the twelfth aspect, the outer diameter of the fixed camshaft gear and the oscillating camshaft gear of the driving force connecting means is smaller than the shortest value of the inter-axis distance between the fixed camshaft and the oscillating camshaft. Even when the distance between the fixed camshaft and the oscillating camshaft is minimized, contact between the fixed camshaft gear and the oscillating camshaft gear can be avoided to ensure reliable meshing. Also, since the pair of eccentric cams respectively held by the fixed cam shaft and the swing cam shaft are always in contact at the same position, after the intermediate transfer member is formed on the image bearing member by the contact / separation operation. The predetermined nip width can always be easily and surely adjusted manually or automatically according to the change of the transfer condition to prevent the occurrence of the transfer position shift. In claim 13, a fixed camshaft timing pulley provided on the fixed camshaft, a swing camshaft timing pulley provided on a swinging camshaft having the same number of teeth as the fixed camshaft timing pulley, and a fixed camshaft timing pulley. Fixed by connecting the driving force of the fixed cam shaft and the oscillating cam shaft by the driving force connecting means having the timing belt wrapped around the oscillating cam shaft timing pulley, and the tensioner for adjusting the timing belt and its tension. Since a pair of eccentric cams respectively held by the cam shaft and the swing cam shaft are always in contact at the same position, a predetermined eccentric cam formed on the image bearing member after the intermediate transfer member is brought into contact with and separated from the image bearing member. The nip width can be easily and reliably adjusted manually or automatically according to the change of the transfer condition, and the occurrence of the transfer position shift can be prevented. According to a fourteenth aspect, the circumferential length (L) of the timing belt of the driving force connecting means is set to be L>
2r (π + 2) (where r is the outer radius of the fixed camshaft timing pulley and the swing camshaft timing pulley, and r is a value that minimizes the distance between the fixed camshaft and the swing camshaft).小 さ く), the pair of eccentric cams respectively held by the fixed cam shaft and the oscillating cam shaft always contact at the same position by connecting the driving force of the fixed cam shaft and the oscillating cam shaft. So that the predetermined nip width after being formed on the image bearing member by the contact and separation operation of the intermediate transfer member,
According to the present invention, it is possible to provide an image forming apparatus capable of performing high-quality image formation in which a transfer position shift is prevented by always and easily adjusting automatically or automatically in accordance with a change in a transfer condition.

[0011]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a front vertical sectional view showing the entire configuration of an image forming apparatus according to an embodiment of the present invention. A color copier as an image forming apparatus according to the present invention includes a color scanner unit 20 and a color printer unit 3.
0, a paper feed unit 40, an image processing unit (not shown), and the like. The color scanner unit 20 converts the read image of the document (O) on the contact glass 20a into an illumination lamp 20b, a mirror group 20c, and a lens 20.
The image is formed on the color sensor 20e through the line d, and the read image of the original (O) is read for each color separation light of, for example, blue (Blue), green (Green), and red (Red), and converted into an electric signal. Convert. Color change processing is performed by an image processing unit (not shown) based on the color separation image signal intensity levels of blue (Blue), green (Green), and red (Red) obtained by the color scanner unit 20 to obtain black (Black). , Cyan, magenta, and yellow color image data. This image signal is converted into an optical signal in the color printer unit 30, and optical writing corresponding to the read image of the original (O) is performed by a laser beam through the polygon mirror 30a, the f / θ lens 30b, and the reflection mirror 30c. Then, an electrostatic latent image is formed on the image carrier 1. The static colors of black (Black), cyan (Cyan), magenta (Magenta), and yellow (Yellow) color images of different colors formed on the image carrier 1 (photosensitive drum) rotating in the direction of arrow A shown in the figure. The electrostatic latent image is developed by a developing unit 2 including a plurality of developing units (black) 2a, a developing unit (cyan) 2b, a developing unit (magenta) 2c, and a developing unit (yellow) 2d arranged at predetermined intervals. The intermediate transfer body 3 (intermediate transfer belt) that receives the transfer of each developed image is stretched around a pulley 4 and a tension pulley 5 facing the image carrier 1, and is rotated and driven by an intermediate transfer body driving unit 6. The contact / separation means 7 comes into contact with / separates from the image carrier 1.

The image forming apparatus includes, for example, an intermediate transfer body 3
A switchback method is adopted to prevent the transfer positions of the Bk, C, M, and Y images from being shifted. The switchback method rotates the intermediate transfer body 3 in the forward direction,
After being brought into contact with the image carrier 1, the first color toner image on the image carrier 1 is transferred onto the intermediate transfer body 3. Next, the intermediate transfer member 3 is separated from the image carrier 1 and rotated in the return direction by an amount corresponding to the rotation in the forward direction to adjust the transfer position of the second color toner image. By repeating this operation four times, an image is formed on the intermediate transfer member 3. In this embodiment, when the contact / separation unit 7 realizes the contact / separation operation of the intermediate transfer member 3 when transferring the toner images of each color, if the nip width 1 becomes inappropriate due to a change in the transfer condition or the like, Another characteristic is that the nip width adjusting means 8 adjusts the nip width 1 to an appropriate value when the nip width changes. 4 formed on an intermediate transfer body (intermediate transfer belt) 3
The color superimposed color toner image is transferred by the transfer unit 10 onto transfer paper (P) which is fed and conveyed from the sheet feeding unit 40 and synchronously sent by the registration rollers 30e. The transfer paper (P) onto which the four-color superimposed color toner image has been transferred is conveyed to the fixing device 11 by the conveyance unit 30f, and after the toner image is fused and fixed, the paper discharge roller 30d.
And is stored on a discharge tray (not shown). Black (Blac)
k), cyan, magenta
The intermediate transfer belt 3 on which the toner images of a) and yellow (Yellow) are formed is rotated by the intermediate transfer body driving unit 6 in the forward direction of the arrow B direction shown in FIG. The first color toner image on the image carrier 1 is transferred to the intermediate transfer belt 3 after being brought into contact with the image carrier 1 by being oscillated in the illustrated arrow C direction (pressing direction).

Next, in the transfer of the second color, the contact / separation means 7 is used.
Then, the intermediate transfer belt 3 in the pressed state is separated from the image carrier 1 by swinging and driving in a direction (separation direction) opposite to the arrow C shown in the figure, and then the intermediate transfer belt 3
Is rotated in the opposite direction to the illustrated arrow B by an amount equivalent to the amount of rotation in the forward direction of the illustrated arrow B during the transfer of the first color, thereby performing the transfer position alignment for the toner image of the second color. By repeating such an operation four times for each color toner image transfer, a four-color superimposed toner image is intermediately transferred onto the intermediate transfer belt 3. FIG.
1 is a schematic view of a configuration of a main part of the image forming apparatus in FIG.
A pulley 4, a tension pulley 5, which faces the image carrier 1,
The intermediate transfer member driving unit 6 is stretched around a driving pulley 6a or the like.
Accordingly, it is rotatably supported in the forward direction in the direction of arrow B shown in the figure and the return direction in the direction opposite to the direction of arrow B in the figure. The shaft 4c of the pulley 4 facing the image carrier facing the image carrier 1 is rotated by a rotation support portion 4c 'on the swing end side of a support member 4b that is swingably supported on the support shaft 4a as a fulcrum. Supported.

A shaft 5c of the tension roller 5 is supported by a supporting member 5 swingably supported on a support shaft 5a.
b is supported by the rotation support portion 5c 'on the swing end side. The supporting member 4b and the supporting member 5b press the surfaces 4A and 5A on the sides facing each other against the pair of eccentric cams 7c. Each eccentric cam 7c is provided with a fixed cam shaft 7
a and the oscillating cam shaft 7b, and are pressed against the surfaces 5A and 4A by urging members (not shown). The pair of eccentric cams 7c maintain a constant distance from each rotation center 7a, 7b to each of the opposing surfaces 5A, 4A of the support member 4b and the support member 5b by the lift rotating half a turn, in other words, The support member 4b and the support member 5b can move toward and away from the image bearing member 1 in the same direction (advance and retreat) while maintaining the same distance.

FIG. 3 is a perspective view showing a specific example of the structure of the contacting / separating means used in the image forming apparatus of the present invention. The fixed camshaft (rotating) for holding a pair of eccentric cams 7c of the contacting / separating means 7 is shown in FIG. In this case, a half-rotation step clutch 7d is attached to the fixed camshaft 7a in either the case 7a or the oscillating camshaft (rotatable and the shaft is movable) 7b. The rotational driving force of 7e is the belt 7f
The intermediate transfer belt 3 is swingably driven in the direction of the arrow C shown in the figure or in the direction opposite to the direction of the arrow C shown in the figure by driving the pair of eccentric cams 7c by a half-rotation step by being transmitted to the clutch 7d. Then, the swinging operation is performed on the image carrier 1 in contact or separation. Of course, the toner image on the image carrier 1 is transferred to the intermediate transfer belt 3 at the time of contact with the image carrier.

FIG. 4 shows an example of the structure of the intermediate transfer member driving means. The intermediate transfer member driving means 6 rotates the driving pulley 6a by a stepping motor 6b to form an image of two or more colors. The intermediate transfer belt 3 is driven to rotate in the forward direction in the direction indicated by arrow B and in the return direction opposite to the direction indicated by arrow B. In the case of forming only one color image, the forward direction in the direction indicated by arrow B is used. Only rotate.

FIG. 5, FIG. 6 and FIG. 7 are a perspective view and a plan view showing a specific configuration of the eccentric cam, and show a fixed cam shaft 7a.
And the pair of eccentric cams 7c (7c1, 7c2) respectively held by the swing cam shaft 7b are not cylindrical,
These are generally tapered rollers in which one end in the axial direction has a small diameter and the other end has a large diameter. More specifically, as shown in the plan views of FIGS. 6 and 7, each of the cams 7c1 and 7c2 is a trapezoid having two end surfaces in parallel in the axial direction, and is a straight line parallel to each of the shafts 7a and 7b. It has a certain non-inclined side 7B and an inclined side 7A that is a straight line that is not parallel to each axis 7a, 7b. Each cam 7
Radius r1 (minimum radius) on the non-inclined side 7B side of c1 and 7c2
Are the same, and the radius r2 (maximum radius) on the inclined side 7A side is also the same. The slopes 7A have the same gradient, but the directions are opposite to each other. When the inclined sides 7A and the non-inclined sides 7B are in contact with each other (when the opposing positional relationship is reached), the alignment state (close contact state).
Becomes In this embodiment, the inclined side 7 of one cam
A and the non-inclined side 7B have a positional relationship in which the circumferential position is shifted by 180 degrees, but this is merely an example, and may be arranged so as to be shifted by 90 degrees or another angle. Therefore, in the state where the inclined sides 7A are in contact with each other as shown in FIG. 6, and in the state where the non-inclined sides 7B are in contact with each other as shown in FIG. 7, the fixed cam shaft 7a and the swing cam shaft 7b are both parallel.

In FIG. 6, a pair of eccentric cams 7c (eccentric cam 7c1 and eccentric cam 7c2) respectively held by a fixed cam shaft 7a and a swing cam shaft 7b constituting the contact / separation means 7 are in an initial position. In the state of contact, the side having the larger radius and the side having the larger radius are in opposing positional relationship as shown in this figure and are in contact with each other (when the inclined surfaces 7A are in contact with each other), the center distance , The pulley 4 is urged toward the image carrier 1 by the swing cam shaft 7b, and the intermediate transfer belt 3 (not shown) comes into contact with the image carrier 1 (not shown). As shown in FIG. 7, a pair of eccentric cams 7c (eccentric cams 7c1 and 7c2) held by a fixed cam shaft 7a and an oscillating cam shaft 7b constituting the contacting / separating means 7 are arranged on the side with the smaller radius. In the case where the pulley 4 is in contact with the side having the smaller radius (when the non-inclined surfaces 7B are in contact with each other), the pulley 4 is moved by the swing cam shaft 7b. The intermediate transfer belt 3 (not shown) is urged toward the side away from the image carrier 1 and separates from the image carrier 1 (not shown). Therefore, as is apparent from the above description, the intermediate transfer belt 3 which is moved forward and backward by the contact / separation means 7 of this embodiment.
Only one side (the pulley 4 side) swings and moves, but the other side is always constant and does not swing, so that the space in the apparatus can be omitted correspondingly, so that the design margin is widened and the whole apparatus is compact. It is possible to provide a simple image forming apparatus.

FIG. 8 is a diagram showing an example of a mechanism for finely adjusting the amount of movement of the pulley 4 advanced and retracted by the contacting / separating means (nip width adjusting means 8 will be described later with reference to FIG. 14 and the like).
The inclined sides 7A are in contact with each other. A pair of eccentric cams 7c (an eccentric cam 7c1 and an eccentric cam 7c2) constituting the contact / separation means 7
The feed screw 8a integrated with the handle is rotated by manually or automatically rotating the handle 8A of the nip width adjusting means 8, so that either the fixed cam shaft 7a side or the swing cam shaft 7b side The eccentric cam supported by the shaft is moved in the axial direction.
In the illustrated example, when the eccentric cam 7c1 on the fixed cam shaft 7a side moves in the direction of arrow D, the axial ends having the maximum radius of the eccentric cams 7c1 and 7b2 move so as to approach each other.
In this case, the center distance between the fixed cam shaft 7a and the oscillating cam shaft 7b is adjusted to be larger than that in the case of the initial position (see FIG. 6). The amount of bite into the body 1 increases, and as a result, the nip width of the intermediate transfer belt 3 (not shown) can be adjusted to a large extent. Conversely, when the eccentric cam 7c1 moves in the direction opposite to the arrow D, the axial ends having the maximum radius move so as to be separated from each other, so that the center distance between the fixed cam shaft 7a and the swing cam shaft 7b. Is adjusted to be smaller than in the case of the initial position (see FIG. 6), so that the amount of the not-shown intermediate transfer belt 3 biting into the not-shown image carrier 1 is reduced. As a result, the not-shown intermediate transfer belt 3
Nip width can be adjusted small.

FIG. 9 is a diagram showing an operation example of a mechanism for finely adjusting the amount of movement of the pulley 4 advanced and retracted by the contact / separation means. In this example, the non-inclined sides 7B are in contact with each other. The pair of eccentric cams 7c (the eccentric cams 7c
1 and the eccentric cams 7c2) rotate the handle 8A of the nip width adjusting means 8 manually or automatically to rotate the feed screw 8a so that the smallest radius side and the smallest radius side come into contact with each other. The fixed cam shaft 7 of the contact / separation means 7
The distance between the shaft a and the swing cam shaft 7b is the same as the initial position (see FIG. 7) without any change.

FIGS. 10 and 11 are diagrams showing another example of the driving force coupling mechanism. FIG. 10 shows a state in which the distance between cam shafts is maximum, and FIG. 11 shows a state in which the distance between cam shafts is minimum. The driving force connecting means 9 includes a fixed camshaft gear 9a having an axial center fixedly supported at an end of the fixed camshaft 7a, and an axial center fixedly supported and fixed at an end of the swing camshaft 7b. The oscillating camshaft gear 9b having the same number of teeth as the camshaft gear 9a, and simultaneously meshing with the fixed camshaft gear 9a and the oscillating camshaft gear 9b, respectively, and either the fixed camshaft gear 9a or the oscillating camshaft gear 9b. One end is rotatably (or fixedly) supported by one of the central shafts (in the illustrated case, the swing cam shaft 7a at the center of rotation of the fixed cam shaft gear 9a) and the other end of the arm 9c1 that rotates. A planetary gear 9c rotatably supported and revolving around the planetary gear 9c.
Meshes with the other swing camshaft gear 9b, thereby connecting the driving force of the fixed camshaft 7a and the swing camshaft 7b. The rotational driving force from a drive motor 7e (not shown) is transmitted to the fixed camshaft 7a (see FIG. 3), and is fixed via the fixed camshaft gear 9a, the planetary gear 9c, and the swing camshaft gear 9b. It is transmitted to the oscillating cam shaft 7b in the state where the distance between the shaft 7a and the shaft is farthest. Here, the sum of the pitch circle diameter of the oscillating cam shaft gear 9b (same as the fixed cam shaft gear 9a) and the pitch circle diameter of the planetary gear 9c is the distance between the fixed cam shaft 7a and the oscillating cam shaft 7b. Since the distance is set to be larger than the longest value, even if the distance between the fixed cam shaft 7a and the swing cam shaft 7b becomes maximum, the fixed cam shaft gear 9a and the swing cam Since the shaft gear 9b and the planetary gear 9c are securely engaged with each other, the eccentric cam 7c1 and the eccentric cam 7c2
Can always reliably face each other at the same position. That is, the amount of pressure contact when the pulley 4 is pressed against the image carrier 1 can be made constant.

FIG. 11 is a diagram for explaining the operation of FIG. 10. The rotational driving force of a driving motor 7e (not shown) is
(See FIG. 3), the swing camshaft 7b in a state where the distance between the fixed camshaft 7a and the shaft is closest via the fixed camshaft gear 9a, the planetary gear 9c, and the swing camshaft gear 9b. Conveyed to. Here, the outer diameter of the swing camshaft gear 9b having the same pitch circle diameter as the fixed camshaft gear 9a is larger than the value when the distance between the fixed camshaft 7a and the swing camshaft 7b is the shortest. Since the distance between the fixed cam shaft 7a and the oscillating cam shaft 7b is minimized as shown in the drawing, the fixed cam shaft gear 9a and the oscillating cam shaft gear 9b may collide with each other. Therefore, the eccentric cam 7c1 and the eccentric cam 7c2 can always always face each other at the same position. That is, the state in which the pulley 4 is separated from the image carrier 1 can be stably maintained.

FIGS. 12 and 13 are diagrams illustrating the structure and operation of another example of the driving force coupling mechanism. FIG. 12 shows a state in which the distance between cam shafts is maximum, and FIG. 13 shows a state in which the distance between cam shafts is minimum.
The driving force connecting means 9 of this embodiment includes a fixed camshaft timing pulley 9d having an axis fixed to the fixed camshaft 7a, and a shaft having the same number of teeth as the fixed camshaft timing pulley 9d and an oscillating camshaft 7b. A fixed swing camshaft timing pulley 9e, a fixed camshaft timing pulley 9d and a timing belt 9 hung on the swing camshaft timing pulley 9e.
f, and a tensioner 9g for adjusting the tension of the timing belt 9f. The timing belt 9f also connects the driving force of the fixed cam shaft 7a and the swing cam shaft 7b. The tensioner 9g is a timing belt 9
The arm 9g2, which rotatably holds the timing pulley 9g1 meshing with f, is urged to rotate in the direction of arrow E by the tension spring of the urging member 9g3 to adjust the tension of the timing belt 9f. . The arm 9g2 is supported rotatably about a fulcrum 9g4.

In FIG. 13, a drive motor 7 not shown
e is transmitted to the fixed camshaft 7a (see FIG. 3).
), The fixed camshaft timing pulley 9d, the oscillating camshaft timing pulley 9e, and the timing belt 9f. The eccentric cam 7c1 and the eccentric cam 7c2 rotate to rotate the fixed cam shaft 7a and the swing cam shaft 7b.
When the distance between the shafts becomes smaller, the arm 9g2 of the tensioner 9g rotates in the direction of arrow E shown in the figure by the force of the urging member 9g3, and the tension of the timing belt 9f is adjusted. The fixed camshaft timing pulley 9d
And the outer diameter (twice the outer radius r) of the oscillating cam shaft timing pulley 9e is smaller than the inter-axis distance between the fixed cam shaft 7a and the oscillating cam shaft 7b, which is the closest. Collisions with each other are prevented. That is,
In this embodiment, the circumference (L) of the timing belt 9f is used.
Is L> 2r (π + 2). Here, r is the outer radius of the fixed camshaft timing pulley and the oscillating camshaft timing pulley, and the outer radius r is 1/1 / the shortest value of the inter-axis distance between the fixed camshaft and the oscillating camshaft. It is preferable to configure so as to be smaller than 2.

FIG. 14 is a cross-sectional plan view showing an example of the configuration of the nip width adjusting means 8. In FIG. 14, a feed screw in which a handle 8A of the nip width adjusting means 8 is integrally fixed to the shaft center is shown. 8a has a screw thread extending in the same direction over substantially the entire length, and is provided on one of the pipe-shaped fixed cam shaft 7a side and the pipe-shaped swing cam shaft 7b side (in the illustrated case, the pipe-shaped fixed cam shaft 7a). Two sets of eccentric cam 7c1 and eccentric cam 7c3 that are fitted in a screw portion provided on the inner surface (on the side of the shaft 7a) and are fixed in the rotation direction by a rotation stopper 7a1 of the fixed cam shaft 7a.
Are screwed into the screw portions. Handle 8 of nip width adjusting means 8
By manually or automatically adjusting the rotation of A in accordance with the change of the transfer condition or the like, the feed screw 8a is rotated in the direction of the arrow F or in the direction opposite to the arrow F as shown in FIG. When the eccentric cam 7c1 and the eccentric cam 7c3 move the same distance in synchronization with each other in the direction indicated by the arrow D or in the direction opposite to the arrow D, the amount of bite of the intermediate transfer belt 3 (not shown) onto the image carrier 1 (not shown). Becomes larger or smaller,
As a result, the nip width of the intermediate transfer belt 3 (not shown) can be adjusted to be large or small.

FIG. 15 shows a modification of FIG. 14. In FIG. 15, the screw thread on the outer periphery of the feed screw 8a to which the handle 8A of the nip width adjusting means 8 is integrally fixed has the same twist direction over the entire length. It consists of a feed screw 8a1 and a feed screw 8a2 whose torsional directions are reversed from the middle, not the direction, and each of the feed screws 8a1 and 8a is a pipe-shaped fixed camshaft 7.
a and a threaded portion provided on the inner surface of one of the side of the pipe-shaped swing cam shaft 7b (in the case of the figure, the side of the fixed cam shaft 7a of the pipe shape). The two sets of eccentric cams 7c5 and the eccentric cams 7c7, which are fixed in the rotation direction by the stoppers 7a1, are fitted to the screw portions. In the above configuration, the handle 8A of the nip width adjusting means 8
When the feed screw 8a is rotated in the illustrated arrow F direction or the opposite direction of the arrow F by manually or automatically adjusting the rotation of the fixed cam shaft 7a in accordance with the variation of the transfer condition or the like, one of the fixed cam shafts 7a is rotated. The eccentric cam 7c5 moves the same distance in the direction of the arrow G or the direction opposite to the arrow G, and the other eccentric cam 7c7 moves the same distance in the direction of the arrow H or the direction opposite to the arrow H. As a result, the bite amount of the intermediate transfer belt 3 on the image carrier 1 becomes large or small, and as a result, the nip width of the intermediate transfer belt 3 (not shown) can be adjusted to be large or small.

[0027]

As described above, according to the first aspect of the present invention, the toner image formed on the image carrier is rotationally driven by the intermediate transfer member drive means, and is rotated by the contact / separation means. In an image forming apparatus in which an image is transferred onto an intermediate transfer member that is brought into contact with or separated from an intermediate transfer member and then fixed, an interval between a pulley and a tension pulley opposed to an image carrier on which the intermediate transfer member is stretched is set to the same distance. The nip width formed by holding and holding the intermediate transfer member on or away from the image carrier can be adjusted by the nip width adjustment means, so that the intermediate transfer member is pressed against the image bearing member. The nip width formed when the transfer is performed is adjusted manually or automatically so as to obtain an optimum nip width in accordance with the variation of the transfer condition, thereby preventing the occurrence of a transfer position shift and performing high quality image formation. it can. According to the second aspect of the present invention, the contact / separation means is constituted by a pair of eccentric cams respectively held by the fixed cam shaft and the swing cam shaft, and is formed when the image carrier and the intermediate transfer member are pressed against each other. The nip width can be adjusted by simply changing the center distance between the fixed cam shaft and the swing cam shaft by the nip width adjusting means, so that the nip width is formed on the image bearing member by the contact and separation operation of the intermediate transfer member. A predetermined nip width after the adjustment is easily or manually or automatically adjusted so as to have an optimum nip width in accordance with a change in the transfer condition, thereby preventing a transfer position shift from occurring and forming a high quality image. be able to.

According to the third aspect of the present invention, each eccentric cam has a substantially tapered shape, and each eccentric cam has an inclined side having a reverse slope (a side on a long radius side) and a straight non-inclined side. (The shorter radius side), the distance between the pulley facing the image carrier on which the intermediate transfer member is stretched and the tension pulley is maintained at the same distance, and the nip width is adjusted by the nip width adjustment. By adjusting the distance between the fixed cam shaft and the oscillating cam shaft by means, it is possible to adjust the nip width formed by the contact and separation operation of the intermediate transfer member on the image bearing member.
It is possible to easily and manually or automatically adjust the nip width to the optimum nip width in accordance with the fluctuation of the transfer condition, to prevent the occurrence of the transfer position shift, and to form a high quality image. Claim 4
According to the invention, each eccentric cam has a substantially tapered shape, and each eccentric cam has a sloped side (a long radius side) having a reverse slope of a shape matching each other, and a shape matching each other. Since it is configured to have straight non-inclined sides (sides on the shorter radius side), the nip width formed by the contact / separation operation of the intermediate transfer member on the image bearing member can be optimized according to the variation of the transfer condition. It is possible to easily and manually or automatically adjust the nip width so as to prevent the transfer position from being shifted and to form a high quality image.

According to the fifth aspect of the present invention, the shape of each eccentric cam is substantially tapered, and each eccentric cam has a sloped side (longer radius side) having a reverse slope of a shape that is aligned with each other. It is configured to have straight non-inclined sides (sides on the shorter radius side) of a shape that matches each other, and it is configured to contact inclined sides and non-inclined sides. The nip width to be formed can be easily or manually or automatically adjusted so as to have an optimum nip width in accordance with the fluctuation of the transfer condition to prevent the occurrence of a transfer position shift and perform high quality image formation. it can. According to the invention of claim 6, each eccentric cam held by the fixed cam shaft and the oscillating cam shaft has a substantially tapered shape, and each eccentric cam has a reverse slope of a shape in which the eccentric cams are aligned with each other. It is configured to have an inclined side (long side on the long radius side) and a straight non-inclined side (side on the short radius side) having a shape matching with each other, and further, at least one eccentric cam is connected to the other eccentric cam. In contrast, the fixed cam can be fixed at the position after moving after moving in the axial direction. Therefore, the fixed cam when the inclined side (longer radius side) of the pair of eccentric cams and the non-inclined side (longer radius side) contact each other. The distance between the shaft and the swing cam shaft can be changed, and the nip width can be finely adjusted. Further, the nip width is simply changed by changing the inter-axis distance between the fixed cam shaft and the swing cam shaft by the nip width adjusting means while maintaining the same distance between the pulley and the tension pulley as in the above claims. Since the adjustment can be adjusted, the predetermined nip width after being formed on the image bearing member by the contact and separation operation of the intermediate transfer body can be set to an optimum nip width according to the fluctuation of the transfer condition with a simple device. In addition, it is possible to easily and surely adjust the operation manually or automatically to prevent the occurrence of a transfer position shift, and to form a high quality image.

According to the seventh aspect of the present invention, as the nip width adjusting means, one of the fixed cam shaft and the oscillating cam shaft is formed in a pipe shape having a thread on the inner surface. The feed screw (engaged with the screw thread on the inner surface of the pipe) is adopted, so that a pair of eccentric cams are fixed at the time of contact between inclined sides (longer radius side) and non-inclined sides (longer radius side). The distance between the cam shaft and the swing cam shaft can be changed, and the nip width can be finely adjusted. Further, the nip width is simply changed by changing the inter-axis distance between the fixed cam shaft and the swing cam shaft by the nip width adjusting means while maintaining the same distance between the pulley and the tension pulley as in the above claims. Since the adjustment can be adjusted, the predetermined nip width after being formed on the image bearing member by the contact and separation operation of the intermediate transfer body can be set to an optimum nip width according to the fluctuation of the transfer condition with a simple device. In addition, it is possible to easily and surely adjust the operation manually or automatically to prevent the occurrence of a transfer position shift, and to form a high quality image. Claim 8
According to the seventh aspect of the present invention, in claim 7, the moving amounts of the plurality of eccentric cams that move in the axial direction by the rotation of the feed screw are all the same, so that the fixed cam shaft and the oscillating cam shaft are always parallel. The nip width after forming the intermediate transfer member on the image bearing member by the contact / separation operation can be adjusted manually or automatically so that the optimum nip width is adjusted according to the fluctuation of the transfer condition. The apparatus can be easily and always adjusted with a simple apparatus to prevent the occurrence of a transfer position shift, and to form a high-quality image.

According to the ninth aspect of the present invention, the fixed cam shaft and the oscillating cam shaft are connected to each other by the driving force connecting means so that the pair of biased cam shafts are respectively held by the fixed cam shaft and the oscillating cam shaft. Since the core cams are always in contact at the same position, the predetermined nip width after the intermediate transfer body is formed on the image bearing member by the contact / separation operation can be adjusted to the optimum nip width according to the fluctuation of the transfer condition. Thus, it is possible to easily and surely and stably perform the adjustment manually or automatically so as to prevent the transfer position shift from occurring, and to form a high-quality image. According to the tenth aspect of the present invention, the driving force connecting means includes a fixed camshaft gear having an axial center fixed to the fixed camshaft, and a fixed camshaft gear having an axial center fixed to the swing camshaft and having the same number of teeth as the fixed camshaft gear. Oscillating camshaft gear, fixed camshaft gear and oscillating camshaft gear always mesh
And a planetary gear that revolves around one center of the fixed camshaft gear or the oscillating camshaft gear as a center of rotation, and the planetary gear meshes with the other camshaft gear, so that the fixed camshaft and the oscillating camshaft By connecting the driving force, the fixed camshaft gear and the oscillating camshaft gear and the planetary gear are securely engaged even if the distance between the fixed camshaft and the oscillating camshaft fluctuates. The pair of eccentric cams respectively held by the fixed cam shaft and the oscillating cam shaft are always in contact at the same position by connecting the driving force of the shafts, so that the intermediate transfer member is placed on the image bearing member. The predetermined nip width after being formed by the contact / separation operation is manually or automatically adjusted easily and always reliably and stably so that the optimum nip width is adjusted according to the fluctuation of the transfer condition. Can be prevented and high quality image formation can be performed.

According to an eleventh aspect of the present invention, in the image forming apparatus according to the ninth or tenth aspect, the total size of the pitch circle diameter of the fixed camshaft gear or the oscillating camshaft gear and the pitch circle diameter of the planetary gear is set to be smaller. Since the maximum distance between the fixed cam shaft and the oscillating cam shaft is larger than the maximum value, even if the distance between the fixed cam shaft and the oscillating cam shaft becomes the longest, the fixed cam shaft gear and the oscillating cam The shaft gear and the planetary gear are reliably engaged with each other. Also, since the pair of eccentric cams respectively held by the fixed cam shaft and the swing cam shaft always contact at the same position, a predetermined eccentric cam formed on the image bearing member after the intermediate transfer member is brought into contact with and separated from the image bearing member. Adjusting the nip width manually or automatically so as to obtain the optimum nip width according to the fluctuation of the transfer conditions, always and surely and stably adjusting the nip width to prevent the occurrence of the transfer position shift, and achieve high quality image formation. It can be performed. According to the invention of claim 12,
The image forming apparatus according to claim 9, 10 or 11,
Since the outer diameters of the fixed cam shaft gear and the oscillating cam shaft gear are configured to be smaller than the shortest value of the inter-axis distance between the fixed cam shaft and the oscillating cam shaft, the fixed cam shaft and the oscillating cam Even when the distance between the shafts becomes the shortest, the contact between the fixed camshaft gear and the swing camshaft gear can be avoided to ensure the meshing. Also, since the pair of eccentric cams respectively held by the fixed cam shaft and the swing cam shaft are always in contact at the same position, after the intermediate transfer member is formed on the image bearing member by the contact / separation operation. The nip width can be adjusted manually or automatically so as to obtain the optimum nip width in accordance with the fluctuation of the transfer condition, always and reliably, stably, to prevent the occurrence of transfer position shift, and to achieve high quality. Can be formed.

According to a thirteenth aspect of the present invention, in the image forming apparatus according to the ninth aspect, the driving force connecting means includes a fixed camshaft timing pulley provided on the fixed camshaft, and the same number of teeth as the fixed camshaft timing pulley. A swing cam shaft timing pulley provided on the swing cam shaft, a fixed cam shaft timing pulley, a timing belt wound around the swing cam shaft timing pulley, and a tensioner for adjusting the tension of the timing belt. The driving force connecting means connects the driving force between the fixed cam shaft and the swing cam shaft so that the pair of eccentric cams respectively held by the fixed cam shaft and the swing cam shaft always contact at the same position. Therefore, the predetermined nip width formed by the contact and separation operation of the intermediate transfer member on the image bearing member can be easily or manually changed automatically or automatically so that the nip width becomes the optimum nip width according to the change of the transfer condition. Reliably and stably adjusted to prevent the occurrence of transfer positional deviation, it is possible to perform high-quality image formation. According to a fourteenth aspect of the present invention, in the image forming apparatus according to the thirteenth aspect, the circumference (L) of the timing belt is provided.
Is L> 2r (π + 2), where r is the outer radius of the fixed camshaft timing pulley and the oscillating camshaft timing pulley, and the outer radius r is between the fixed camshaft and the oscillating camshaft. And the driving force between the fixed camshaft and the oscillating camshaft is connected to each other so that the pair of biases respectively held by the fixed camshaft and the oscillating camshaft. Since the core cams are always in contact at the same position, the predetermined nip width after the intermediate transfer body is formed on the image bearing member by the contact / separation operation can be adjusted to the optimum nip width according to the fluctuation of the transfer condition. Thus, it is possible to easily and stably adjust the image stably manually or automatically so as to prevent the occurrence of a transfer position shift, and to form a high-quality image.

[Brief description of the drawings]

FIG. 1 is a diagram schematically illustrating an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a main part of the image forming apparatus according to the embodiment of the present invention.

FIG. 3 is a perspective view illustrating another main part (contact / separation means) of the image forming apparatus according to the embodiment of the present invention.

FIG. 4 is a perspective view illustrating another main part (intermediate transfer member driving unit) of the image forming apparatus according to the embodiment of the present invention.

FIG. 5 is a perspective view illustrating another main part (eccentric cam) of the image forming apparatus according to the embodiment of the present invention.

FIG. 6 is a plan view of the eccentric cam of FIG. 5;

FIG. 7 is a plan view showing another state of the eccentric cam of FIG. 5;

FIG. 8 is a plan view showing an example in which one of the eccentric cams is configured to be movable in the axial direction.

FIG. 9 is a plan view showing another state of FIG. 8;

FIG. 10 is a view for explaining the operation of another main part (driving force connecting means) of the image forming apparatus according to the embodiment of the present invention.

FIG. 11 is a view showing another state of FIG. 10;

FIG. 12 is a view for explaining the operation of a main part (driving force connecting means) of an image forming apparatus according to another embodiment of the present invention.

FIG. 13 is a view showing another state of FIG. 12;

FIG. 14 is a diagram illustrating another main part (nip width adjusting unit) of the image forming apparatus according to the embodiment of the present invention.

FIG. 15 is a view for explaining another main part (nip width adjusting means) of the image forming apparatus according to another embodiment of the present invention.

FIG. 16 is a diagram illustrating a main part of a conventional image forming apparatus.

[Explanation of symbols]

Reference Signs List 1 image carrier, 2 developing device, 2a developing device (black), 2b developing device (cyan), 2c developing device (magenta), 2d developing device (yellow), 3 intermediate transfer member, 4
Pulley, 4a support shaft, 4b support member, 5 tension pulley, 5a support shaft, 5b support member, 6 intermediate transfer member driving means, 6a drive pulley, 6
b Stepping motor, 7 contacting / separating means, 7a fixed camshaft, 7a1 rotation stop, 7b swing camshaft, 7c pair of eccentric cams, 7c1 to n eccentric cams, 7d clutch,
7e drive motor, 7f belt, 8 nip width adjusting means, 8a feed screw, 8a1 feed screw, 8a2 feed screw, 9 driving force coupling means, 9a fixed camshaft gear, 9
b Oscillating camshaft gear, 9c planetary gear, 9c1 arm, 9d fixed camshaft timing pulley, 9e oscillating camshaft timing pulley, 9f timing belt, 9g
Tensioner, 9g1 timing pulley, 9g2 arm, 9g3 biasing member, 10 transfer means, 11 fixing means, 20 color scanner unit, 20a contact glass, 20b illumination lamp, 20c mirror group, 2
0d lens, 20e color sensor, 30 color printer unit, 30a polygon mirror, 30
b f / θ lens, 30 c reflection mirror, 30 d paper discharge roller, 30 e registration roller, 30 f transport unit, 40 paper feed unit, 101 image carrier, 102
Developing device, 103 Intermediate transfer member, 104 Pulley facing image carrier, 104a Support shaft, 104b Support member, 1
05 tension pulley, 105a spindle, 105b
Support member, 106 intermediate transfer member driving pulley, 107 contacting / separating means, 110 transfer roller, 111 fixing device

Claims (14)

[Claims] 1. An image forming method, wherein an electrostatic latent image formed on an image bearing member is developed by a developing device, an intermediate transfer is performed on the intermediate transfer member, and then transferred and fixed to a transfer material to form an image. An image carrier that is rotatably supported to form an electrostatic latent image, a developing device that develops the electrostatic latent image formed on the image carrier, and an image carrier that is developed by the developing device. An intermediate transfer body on which a toner image on the body is intermediate-transferred, an intermediate transfer body driving unit that rotates the intermediate transfer body around a pulley and a tension pulley opposed to the image carrier, and drives the image carrier Contacting / separating means for oscillating the intermediate transfer body so as to contact or separate from the image carrier while maintaining the same distance between the pulley and the tension pulley opposed to each other; A nip formed when the intermediate transfer member contacts the carrier. An image forming apparatus comprising a nip width adjusting means for adjusting the width, in that it consists of. 2. The image forming apparatus according to claim 1, wherein
The image forming apparatus, wherein the contact / separation means includes a pair of eccentric cams fixed to a fixed cam shaft and a swing cam shaft, respectively. 3. The image forming apparatus according to claim 2, wherein
The pair of eccentric cams each have a non-inclined side parallel to the axial direction of the fixed cam shaft and the swing cam shaft, and an inclined side not parallel to the axial direction of the fixed cam shaft and the swing cam shaft. An image forming apparatus, comprising a substantially tapered roller body, wherein an inclined side of one eccentric cam and an inclined side of the other eccentric cam have opposite gradients. 4. The image forming apparatus according to claim 2, wherein the inclined sides provided on each of the pair of eccentric cams have a shape that can be aligned when the inclined sides come into contact with each other. Image forming device. 5. The image forming apparatus according to claim 2, wherein the pair of eccentric cams contact each other between the inclined sides and the non-inclined sides. . 6. The image forming apparatus according to claim 2, wherein at least one of the fixed cam shaft and the swing cam shaft is movable in the axial direction together with the held eccentric cam. An image forming apparatus, characterized in that: 7. An image forming apparatus according to claim 1, wherein said nip width adjusting means includes a screw provided on one of said fixed cam shaft and said swing cam shaft. An image forming apparatus comprising: a pipe having a ridge; and a feed screw having a ridge on an outer periphery thereof arranged in a threaded state inside a pipe-shaped camshaft. 8. The image forming apparatus according to claim 7, wherein
When a plurality of eccentric cams are held on the outer circumference of the pipe-shaped fixed cam shaft or swing cam shaft, when the feed screw is rotated, the amount of movement of each eccentric cam in the axial direction is all An image forming apparatus having the same configuration. 9. The image forming apparatus according to claim 2, wherein a driving force is transmitted to said fixed cam shaft and said oscillating cam shaft by driving force connecting means. An image forming apparatus, comprising: 10. The image forming apparatus according to claim 9, wherein said driving force connecting means comprises a fixed camshaft gear having an axis fixed to said fixed camshaft, and an axial center fixed to said swing camshaft. And the swinging camshaft gear having the same number of teeth as the fixed camshaft gear, the meshing of the fixed camshaft gear and the swinging camshaft gear at all times, and the fixed camshaft gear or the swinging camshaft gear. A planetary gear that revolves around one center as a center of rotation, wherein the planetary gear meshes with the other camshaft gear to connect the driving force of the fixed camshaft and the swing camshaft. Image forming apparatus. 11. A fixed camshaft according to claim 9, wherein a pitch circle diameter of said fixed camshaft gear or said oscillating camshaft gear and a pitch circle diameter of said planetary gear are fixed camshaft. An image forming apparatus wherein the distance between the shaft and the swing cam shaft is larger than the maximum value. 12. The image forming apparatus according to claim 9, 10 or 11, wherein each outer diameter of the fixed camshaft gear and the oscillating camshaft gear is equal to a distance between the fixed camshaft and the oscillating camshaft. An image forming apparatus characterized by being smaller than the shortest value. 13. The image forming apparatus according to claim 9, wherein the driving force connecting means has the same number of teeth as the fixed camshaft timing pulley provided on the fixed camshaft and the fixed camshaft timing pulley. A swing cam shaft timing pulley provided on the swing cam shaft, a fixed cam shaft timing pulley, a timing belt wound around the swing cam shaft timing pulley, and a tensioner for adjusting a tension of the timing belt. The driving force connecting means connects the driving force of the fixed cam shaft to the driving force of the swing cam shaft. 14. The image forming apparatus according to claim 13, wherein the peripheral length (L) of the timing belt is L> 2r.
(Π + 2), where r is the outer radius of the fixed cam shaft timing pulley and the oscillating cam shaft timing pulley, and the outer radius r is the distance between the fixed cam shaft and the oscillating cam shaft. The image forming apparatus is smaller than 1/2 of the shortest value of the image forming apparatus.