JP7275507B2 - Fixing device and image forming device - Google Patents

Description

The present invention relates to fixing devices and image forming apparatuses.

As a fixing device for fixing an image on a recording medium, a pressure member having an elastic surface layer is pressed against a fixing member such as a fixing belt or a fixing roller to form a fixing nip. 2. Description of the Related Art A fixing device is known in which a recording medium having a toner image electrostatically adhered thereto is introduced into a fixing nip and the toner image is fixed on the recording medium by heat and pressure in a fixing nip.

In a fixing device that applies such pressure, there is no particular problem if the recording medium is thin and constant in thickness, such as plain paper. In the case of different recording mediums, there is a problem that if the fixing nip is set to a normal nip pressure, the recording medium is wrinkled. Therefore, it is detected whether or not the recording medium is an envelope, and if the recording medium is an envelope, the nip pressure is reduced compared to the case of plain paper, and furthermore, the front and rear portions of the recording medium are controlled by other portions. A technique for further reducing the nip pressure has been proposed (see, for example, Japanese Unexamined Patent Application Publication No. 2002-100003).

In the above-described technique, if the recording medium conveyed in the conveyance orthogonal direction (the width direction of the recording medium), which is the direction perpendicular to the conveyance direction of the recording medium, has a portion with a different thickness, the thick side of the recording medium is fixed. There is a problem that the nip width is increased and the conveying speed is increased, and the recording medium is conveyed obliquely, causing a conveying jam. In addition, since the nip pressure increases on the thicker side, there is a problem that the frictional force between the recording medium and the fixing member such as a roller or belt in contact with the recording medium increases, resulting in uneven wear of the fixing member. . Therefore, when using recording media having different thicknesses, it is requested that the recording media be set in the main body of the image forming apparatus so that the thickness in the direction perpendicular to the transport direction is uniform.

However, in actual use, the recording medium must be set vertically, for example, so that the thickness is uniform, but the thickness is not uniform, for example, the recording medium is set horizontally for image formation. may occur. In this case, as described above, there are problems such as jamming of the recording medium and uneven wear of the fixing member.
The present invention solves the above-mentioned problems, and can prevent conveyance jams and uneven wear of fixing members, etc., even when recording media having different thicknesses in the direction perpendicular to conveyance are used. An object of the present invention is to provide an efficient fixing device and an image forming apparatus having the same.

According to a first aspect of the present invention, there is provided an image forming apparatus comprising a paper feeding device having a paper feeding roller and a position sensor for detecting a displacement amount of the paper feeding roller, and a fixing device, wherein the fixing device is a recording medium. a fixing member and a pressure member for fixing the toner image on the recording medium by nipping the recording medium with a predetermined nip pressure in the width direction, which is the direction perpendicular to the conveying direction, and at least two positions in the width direction; biasing means each having an ABS resin cam for pressing the pressure member against the fixing member; a control means for detecting whether the recording medium has a thick portion and a thin portion or the recording medium has a uniform thickness in the width direction, and the control means detects whether the recording medium has a uniform thickness in the width direction; When the recording medium having a thick portion and a thin portion is passed, the pressure contact force of the pressure member against the fixing member in the thick portion is set to the fixing member in the thin portion. It is characterized in that the pressure contact force of the pressure member against the member is reduced below that of the pressure contact force.

According to the present invention, when a recording medium having a thick portion and a thin portion in the width direction is passed, the pressing force of the pressure member against the fixing member at the thick portion of the recording medium is increased. , is less than the pressure contact force at the portion where the thickness is thin. As a result, the nip pressure in the fixing nip is made uniform between the thick side and the thin side of the recording medium, and the width of the fixing nip on the thick side is smaller than when normal nip pressure acts. Since the difference from the fixing nip width on the thin side is reduced, the difference in conveying speed of the recording medium between the thick side and the thin side is reduced, and the recording medium is linearly conveyed. The occurrence of jams is suppressed.
In addition, the pressure contact force of the pressure member against the fixing member is controlled in the width direction of the recording medium, and the pressure contact force at the portion where the thickness of the recording medium is thick is reduced more than the pressure contact force at the portion where the thickness is thin. , the nip pressure is suppressed from increasing on the thicker side, and the occurrence of uneven wear in the fixing member can be suppressed.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention; FIG. 1 is a schematic diagram of a fixing device used in one embodiment of the present invention; FIG. 1 is a schematic diagram illustrating a fixing roller, a pressure roller, and an urging means used in an embodiment of the invention; FIG. 1 is a schematic diagram illustrating a recording medium used in one embodiment of the present invention; FIG. It is the schematic explaining the eccentric cam used for one Embodiment of this invention. FIG. 10 is a schematic diagram illustrating a paper feed roller, a paper feed tray, and a position sensor used in a modification of one embodiment of the present invention;

First, an image forming apparatus to which an embodiment of the invention can be applied will be described.
FIG. 1 is a schematic configuration diagram showing a copier 1, which is an electrophotographic image forming apparatus. The copying apparatus 1 includes an image forming unit 2 for forming an image on a transfer sheet S which is a recording medium, a paper feeding device 3 for supplying the transfer sheet S to the image forming unit 2, an image reading unit 4 for reading an original image, and an image reading unit. The unit 4 is provided with an ADF 5 and the like for automatically feeding originals.

In the image reading unit 4, the first moving body 6 mounted with a light source, mirrors, etc. for illuminating the document and the second moving body 7 mounted with a plurality of reflecting mirrors reciprocate, and the image is placed on the contact glass 8. An original (not shown) placed is scanned for image reading. The scanning light emitted from the second traveling body 7 is condensed by the imaging lens 9 onto the imaging plane of the reading sensor 10 arranged behind it, and then taken in as an image signal by the reading sensor 10 .
On the side of the main body 11 of the copying machine 1, a manual feed tray 12 for placing a transfer sheet S for manual feeding and a discharge tray 13 for stacking the transfer sheets S discharged from the main body 11 are arranged. .

The image forming section 2 is provided with an endless intermediate transfer belt 14 as an image bearing member, and a transfer unit 15 as a transfer device having a plurality of rollers around which the intermediate transfer belt 14 is stretched. The intermediate transfer belt 14 is driven by a driving means (not shown) to rotate clockwise in the figure by a drive roller 16, a secondary transfer backup roller 17, a driven roller 18, and four primary transfer rollers 19Y, 19C, 19M and 19K. It is stretched and driven to run in the clockwise direction in the figure by the rotational driving force applied from the drive roller 16 .
The suffixes Y, C, M, and K used for the primary transfer rollers 19Y, 19C, 19M, and 19K indicate members for yellow, cyan, magenta, and black, respectively. . The same applies to the following configurations.

The intermediate transfer belt 14 is largely curved at the places where it is stretched by the drive roller 16, the secondary transfer backup roller 17, and the driven roller 18, and has an inverted triangular shape with the base facing vertically upward. there is The belt upper stretched side corresponding to the base of the inverted triangle extends in the horizontal direction, and four process units 20Y, 20C and 20M having photosensitive drums 21Y, 21C, 21M and 21K above the belt upper stretched side. , 20K are arranged horizontally in parallel.
A belt cleaning device 24 that cleans the surface of the intermediate transfer belt 14 is provided at a position facing the driven roller 18 . The intermediate transfer belt 14 , the rollers 16 , 17 , 18 , the primary transfer rollers 19 , and the belt cleaning device 24 are integrally constructed as a unit, which is detachable from the apparatus main body 11 .
In this embodiment, each process unit 20 has the same configuration except for the color of the toner used. Each process unit 20 may have a different configuration depending on the color of toner used.

An optical writing unit 22 is arranged above each process unit 20 . The optical writing unit 22 drives four semiconductor lasers (not shown) by a laser control unit (not shown) based on document image information read by the image reading unit 4, and writes four laser beams as writing light. Inject L. Each laser beam L scans each photoreceptor drum 21 in the dark and forms an electrostatic latent image on the surface of each photoreceptor drum 21 .
In this embodiment, as the optical writing unit 22, the laser beam L emitted from the semiconductor laser is deflected by a polygon mirror (not shown), reflected by a reflecting mirror (not shown), or passed through an optical lens to perform optical scanning. However, instead of this configuration, for example, an optical writing unit configured to perform optical scanning using an LED array may be used.

Each photosensitive drum 21 forms a primary transfer nip together with each primary transfer roller 19 while contacting the upper extended side of the intermediate transfer belt 14 that is driven to run. Each primary transfer roller 19 forming a primary transfer nip in contact with the back surface of the intermediate transfer belt 14 is applied with a primary transfer bias having a polarity opposite to the charging polarity of the toner from bias supply means (not shown). By this primary transfer bias, a primary transfer electric field is formed in each primary transfer nip for yellow, cyan, magenta, and black to electrostatically move each color toner from the photosensitive drum 21 side to the intermediate transfer belt 14 side.

When each color toner image formed on each photoreceptor drum 21 enters the primary transfer nip for each color due to rotation of each photoreceptor drum 21, it is superimposed on the intermediate transfer belt 14 in sequence by the action of the primary transfer electric field and nip pressure. be transcribed. As a result, a full-color toner image is formed on the front surface (outer peripheral surface of the loop) of the intermediate transfer belt 14 by superimposing toner images of four colors. As the primary transfer member, instead of the primary transfer rollers 19, other known structures such as a conductive brush to which a primary transfer bias is applied, a non-contact type corona charger, or the like may be employed.

The secondary transfer backup roller 17 has a cylindrical core metal made of metal and a conductive elastic layer coated on the outer peripheral surface of the core metal. of secondary transfer bias is applied. At a position facing the secondary transfer backup roller 17 with the intermediate transfer belt 14 interposed therebetween, a secondary transfer roller 23 is disposed to secondarily transfer the full-color toner image primarily transferred onto the intermediate transfer belt 14 onto the transfer sheet S. It is The secondary transfer roller 23 includes a cylindrical core metal made of metal, a conductive elastic layer coated on the outer peripheral surface of the core metal, and a surface layer made of conductive resin coated on the outer peripheral surface of the elastic layer. and is connected to ground. A secondary transfer nip is formed by pressing the secondary transfer roller 23 against the secondary transfer backup roller 17 via the intermediate transfer belt 14 with a predetermined pressure.
On the upstream side of the secondary transfer roller 23 in the sheet conveying direction, a registration roller pair 25 is arranged to temporarily stop the transfer sheet S and then feed it toward the secondary transfer nip.

Next, the operation of the copier 1 will be described.
When the image forming operation is started, the photosensitive drums 21 are driven to rotate counterclockwise by the operation of driving means (not shown). It is uniformly charged with polarity. The outer peripheral surface of each charged photoreceptor drum 21 is irradiated with laser light L from the optical writing unit 22 , and an electrostatic latent image of each color is formed on the outer peripheral surface of each photoreceptor drum 21 . At this time, the image information to be exposed on each photosensitive drum 21 is monochromatic image information obtained by color-separating a desired full-color image into respective color information of yellow, cyan, magenta, and black. The electrostatic latent image thus formed is visualized as a toner image by each color toner in each developing device when passing between each photosensitive drum 21 and each developing device.

When the intermediate transfer belt 14 travels clockwise by a driving force from a drive means (not shown), the yellow toner formed on the outer peripheral surface of the photoreceptor drum 21Y in the process unit 20Y occupying the most upstream position among the process units 20. The image is primarily transferred onto the intermediate transfer belt 14 by the action of the primary transfer roller 19Y. A cyan toner image, a magenta toner image, and a black toner image formed in the other process units 20C, 20M, and 20K are superimposed and transferred on the primarily-transferred yellow toner image. toner image is carried.
After the toner image is transferred, residual toner adhering to the outer peripheral surface of each photoreceptor drum 21 is removed from the outer peripheral surface of each photoreceptor drum 21 by each photoreceptor cleaning device. Each photoreceptor drum 21 that has been cleaned is subjected to a static elimination action by a static elimination device, and its surface potential is initialized to prepare for the next image formation.

On the other hand, the paper P is fed from the paper feeding device 3, and the fed paper P is sent to the paper transport path. The paper P fed into the paper transport path is temporarily stopped by the registration roller pair 25 arranged upstream of the secondary transfer roller 23 in the paper transport direction, and is sent to the secondary transfer nip at a predetermined timing. At this time, a transfer voltage having a polarity opposite to that of the toner image carried on the intermediate transfer belt 14 is applied to the secondary transfer roller 23, thereby transferring the full-color toner image on the intermediate transfer belt 14 onto the paper P. are secondary-transcribed together.

The sheet P onto which the full-color toner image has been transferred is conveyed to a fixing device 27, which is a feature of the present invention, via a conveyer 26 disposed downstream of the secondary transfer nip in the paper conveying direction. The full-color toner image on the paper P is fused and fixed on the paper P by the heat and pressure applied when passing through. The paper P on which the full-color toner image has been fixed is conveyed toward a pair of discharge rollers 28 arranged on the downstream side of the fixing device 27 in the paper conveyance direction. Discharge loaded on top.
The intermediate transfer belt 14 after the full-color toner image has been transferred to the paper P is cleaned of residual toner by the belt cleaning device 24 to prepare for the next image formation.

Here, the fixing device 27, which is a feature of the present invention, will be described.
As shown in FIG. 2, the fixing device 27 includes a fixing roller 29 as a fixing member, a heating roller 30, a fixing belt 31, a tension roller 32, a pressure roller 33 as a pressure member, an urging means 35, and the like. ing.
The fixing belt 31 is an endless belt having a multilayer structure in which an elastic layer and a release layer are sequentially laminated on a base layer made of a resin material. The elastic layer of the fixing belt 31 is made of an elastic material such as fluororubber, silicone rubber, or foamed silicone rubber. , polyetherimide, PES (polyether sulfide), or the like. By providing the release layer on the surface layer of the fixing belt 31, the releasability of the toner image adhering to the recording medium is ensured.
The fixing belt 31 is stretched and supported by the fixing roller 29, the heating roller 30, and the tension roller 32, and is driven to run clockwise in FIG. . The tension roller 32 is in contact with the outer peripheral surface of the fixing belt 31 and applies a predetermined tension to the fixing belt 31 . By using a fixing belt 31 having a low heat capacity, the temperature rise characteristic of the fixing device 27 is improved.

The fixing roller 29 is a roller member in which an elastic layer made of foamed silicone rubber having a layer thickness of about 15 mm is formed on a metal core made of SUS304. form N. By forming the elastic layer from a foam material, the nip width of the fixing nip N can be set relatively large, and heat from the fixing belt 31 is less likely to transfer to the fixing roller 29 . As the material of the elastic layer, fluororubber, silicone rubber, or the like may be used instead of the foamed silicone rubber.

The heating roller 30 is a hollow roller made of a metal material with high thermal conductivity, such as aluminum, and has a heater (not shown) installed therein. The surface of the heating roller 30 is anodized to improve corrosion resistance. The heating roller 30 is heated by radiant heat from a heater (not shown), and the surface of the fixing belt 31 heated by the heating roller 30 heats the toner image on the recording medium.
As shown in FIG. 3, the pressure roller 33 is rotatably supported at both ends of its support shaft by a back side plate 37 and a front side plate 34 of the fixing device 27 via bearings 36. The bearings 36 are attached to the respective side plates. It is vertically movably supported in elongated holes (not shown) formed in 37 and 34 . A fixing roller 29 disposed above the pressure roller 33 is also rotatably supported by the side plates 37 and 34 at both ends of its shaft via bearings 38 .

The pressure roller 33 is pressed against the fixing roller 29 via the fixing belt 31 by an urging means 35 that adjusts the nip pressure at the fixing nip N, whereby the fixing nip N is formed. The biasing means 35 includes a pressure lever 39 engaged with the bearing 36, an eccentric cam 40 as a cam that acts on the pressure lever 39 to bias the pressure roller 33 toward the fixing roller 29, and an eccentric cam 40. It has a motor 41 for rotation, a position sensor 42 for detecting the position of the eccentric cam 40, a compression spring 43 for applying a biasing force to the pressure lever 39, and the like.
The pressurizing lever 39 includes a back side plate 37 located on the back side of the apparatus, which is the left side in the width direction X, which is the direction orthogonal to the conveyance direction of the recording medium, in FIG. The support shaft 39a is rotatably supported by the front side plate 34 located on the front side of the device, which is the right side in the width direction X. As shown in FIG. An eccentric cam 40, a motor 41, a position sensor 42, and a compression spring 43, which constitute the biasing means 35 together with the pressure lever 39, are also attached to the pressure lever 39, respectively. Accordingly, the biasing means 35A and the biasing means 35B are disposed on the rear side of the fixing device 27 and the front side of the device, respectively.

The eccentric cam 40 moves the pressure lever 39 in a direction that increases or decreases the nip pressure of the fixing nip N. As shown in FIG. That is, when it is desired to set a high nip pressure, the eccentric cam 40 is rotated clockwise from the state shown in FIG. As a result, the pressure lever 39 pushes the pressure roller 33 upward via the bearing 36, and the pressure of the pressure roller 33 against the fixing roller 29 is increased.
On the other hand, when it is desired to set the nip pressure low, the eccentric cam 40 is rotated counterclockwise from the state shown in FIG. As a result, the pressure lever 39 is moved downward by the weight of the pressure roller 33, the repulsive force at the fixing nip N, and the urging force of the compression spring 43, and the pressing force of the pressure roller 33 against the fixing roller 29 is reduced.

Rotational position control of the eccentric cam 40 is recognized by control means (to be described later) by optically detecting the presence or absence of a detected member 40a attached to the eccentric cam 40 and rotating integrally with the eccentric cam 40 by means of a position sensor 42. be. Also, the shape of the eccentric cam 40, which is a feature of the present invention, will be described later.
The biasing means 35 adjusts the pressing force of the pressing roller 33 against the fixing roller 29, and adjustment of the pressing force is performed by rotating the eccentric cam 40 as described above. The eccentric cam 40 is rotated by a motor 41 as shown in FIG. 2, and the operation of the motor 41 is performed by control means 44 shown in FIG. A control means 44 comprising a well-known microcomputer having CPU, ROM, RAM, etc. controls the operation of the motor 41 based on the input from the operation panel 45 of the copier 1 as shown in FIG. Although only one biasing means 35 is shown in FIG. 2, the control means 44 controls the operation of each motor 41 in both biasing means 35 respectively.

Input from the operation panel 45 by the user of the copier 1 will now be described.
The user controls the operation of each motor 41 according to the thickness in the width direction X of the recording medium to be used. Here, there are three types of recording media that can be used in this embodiment. As shown in FIG. , a second recording medium 47 whose thickness is thicker at the front side of the apparatus as shown in FIG. There are three types of the third recording medium 48 in which the portion located on the side is thicker than the other portions. In the second recording medium 47 and the third recording medium 48, the thickness of each of the recording media 47 and 48 gradually changes from the thinner or thicker side to the thicker or thinner side. However, the recording medium to which the present invention can be applied may have a configuration in which only a portion of either the back side of the device or the front side of the device is thick.
The user selects one of the first to third types of recording media to be used on the operation panel 45 . The control means 44 controls the rotation of the eccentric cam 40 according to the recording medium selected by the user.

Next, the eccentric cam 40 will be explained. In the configuration of the present invention, the eccentric cam 40 includes an eccentric cam 40A used for the biasing means 35A and an eccentric cam 40B used for the biasing means 35B. As shown in FIG. 5, the eccentric cam 40A and the eccentric cam 40B are configured to form the eccentric cam 40B when the eccentric cam 40A is turned over. Considering manufacturing costs, the eccentric cams 40A and 40B are desirably made of ABS resin or a resin having a higher strength.
Each of the eccentric cams 40A and 40B has a spindle 40b rotated by the motor 41, and has a cam portion 40c fixed to each spindle 40b. The cam portion 40c is formed to form an arc 40d centered on the axis of the support shaft 40b only at a portion corresponding to the predetermined angle θ, and the other portions are formed to have a smaller diameter than the arc 40d. ing.

The eccentric cam 40A and the eccentric cam 40b are attached to the support shaft 40b at the positions shown in FIG. In this state, the arc 40d of both the eccentric cam 40A and the eccentric cam 40B contacts the pressure lever 39 in the range A, so that the pressure roller 33 is applied with a specified load on both the back side and the front side of the device. Range A is both prescribed load ranges suitable for fixing the first recording medium 46 .
In the range B, the arc 40d of the eccentric cam 40A contacts the pressure lever 39, but the portion other than the arc 40d of the eccentric cam 40B contacts the pressure lever 39. However, on the front side of the apparatus, a low load lower than the specified load is applied, and the range B is a low load and the other specified load area suitable for fixing the second recording medium 47 .
In range C, the arc 40d of the eccentric cam 40B contacts the pressure lever 39, but the eccentric cam 40A contacts the pressure lever 39 at the portion other than the arc 40d. However, a low load lower than the specified load is applied on the back side of the device, and range C is a low load and other specified load area suitable for fixing the third recording medium 47 .

With the above configuration, prior to the image forming operation, the user of the copier 1 can select the type of recording medium to be used from the operation panel 45 to the first recording medium 46, the second recording medium 47, or the third recording medium. Set to any of the media 48 . The control means 44 operates each motor 41 according to the set recording medium, and positions the eccentric cams 40A and 40B at predetermined positions. When the first recording medium 46 is set as the recording medium to be used, when the second recording medium 47 is set so that the range A comes into contact with each pressing lever 39, The control means 44 is arranged so that the range B comes into contact with each pressurizing lever 39, and that the above-mentioned range C comes into contact with each pressurizing lever 39 when the third recording medium 48 is set. controls the operation of each motor 41 . When it is determined from the signals of the position sensors 42 that detect the members 40a that the eccentric cams 40A and 40B are positioned at the set positions, the control means 44 controls the operation of the copying machine 1 (not shown). A signal is sent to the control means, and the copying machine 1 performs the same image forming operation as described above.

During this fixing operation, according to the present invention, when a recording medium having a thick portion and a thin portion in the width direction is passed, the control means 44 controls the positions of the eccentric cams 40A and 40B. The pressure contact force of the pressure roller 33 against the fixing roller 29 at the fixing nip N is controlled in the width direction X of the recording medium, and the pressure contact force at the portion where the thickness of the recording medium is thick is the same as the pressure contact at the portion where the thickness is thin. reduced than force. As a result, the nip pressure at the fixing nip N is made uniform between the thick side and the thin side of the recording medium, and the width of the fixing nip on the thick side is increased as compared with the case where a normal nip pressure acts. Since the difference between the fixing nip width and the fixing nip width on the thin side is reduced, the difference in conveying speed of the recording medium between the thick side and the thin side is reduced, and the recording medium is linearly conveyed. The occurrence of a conveying jam is suppressed.
Further, the pressure contact force of the pressure roller 33 against the fixing roller 29 is controlled in the width direction X of the recording medium, and the pressure contact force at a portion where the thickness of the recording medium is thick is lower than the pressure contact force at a portion where the thickness is thin. Therefore, it is possible to suppress the nip pressure from increasing on the thicker side, and to suppress the occurrence of uneven wear in the fixing member.

In the present invention, the fixing device 27 has two urging means 35A and 35B having two types of eccentric cams 40A and 40B with different cam diagrams, so that the pressing force of the pressure roller 33 against the fixing roller 29 is applied. It can be easily controlled in the width direction X of the recording medium.
Further, since the cam diagrams of the eccentric cams 40A and 40B are changed by different phases from each other, by rotating the eccentric cams 40A and 40B, the pressure roller can be easily moved to the fixing roller 29. The pressing force of 33 can be controlled, and the configuration can be simplified.
In addition, since the eccentric cams 40A and 40B have the same shape and are used upside down, there is no need to manufacture different cams one by one, and the manufacturing cost can be reduced.

In the above-described embodiment, when an image is formed on a recording medium having different thicknesses in the width direction X, the user of the copier 1 sets the type of recording medium in advance using the operation panel 45. Instead of this configuration, a configuration for automatically detecting the type of recording medium used by the copier 1 may be employed. As this configuration, for example, in the copying apparatus 1 shown in FIG. Select one of the first to third.

This configuration will be described with reference to FIG. FIG. 6 is a view of the paper feed tray 50 that accommodates the recording medium S1 in the paper feeder 3, viewed from the left side in FIG. The recording medium S1 accommodated in the paper feed tray 50 is pressed against the peripheral surface of the paper feed roller 49 with a predetermined pressure contact force by a bottom plate (not shown). Position sensors 51A and 51B for detecting the amount of displacement of the paper feed roller 40 when no load is applied are disposed above the peripheral surface of the paper feed roller 40 near the back side and near the front side of the device, respectively. Position information from each of the position sensors 51A and 51B is sent to the control means 44. FIG.

The control means 44 that has received the signal recognizes that the recording medium in the paper feed tray 50 is the first recording medium 46 when the position information of the position sensors 51A and 51B are approximately the same. Further, when the detection position of the position sensor 51B is larger than the detection position of the position sensor 51A, the recording medium in the paper feed tray 50 is thicker on the front side than on the back side in the width direction X. The control means 44 recognizes that it is the second recording medium 47 . Further, when the detection position of the position sensor 51B is smaller than the detection position of the position sensor 51A, the recording medium in the paper feed tray 50 is thicker on the back side than on the front side in the width direction X. The control means 44 recognizes that it is the third recording medium 48 .
With this configuration, there is no need to set the type of recording medium in advance, so work efficiency can be greatly improved.

In the above-described embodiment and each modified example, an example using a color printer as the liquid ejecting apparatus was shown, but the liquid ejecting apparatus is not limited to this, and the present invention can be applied to a printer, a facsimile machine, a multifunction machine, and the like. . Further, in the present embodiment and the modified example, the configuration using the first to third recording mediums 46, 47, and 48 as the recording medium on which an image is formed has been shown, but the recording medium 46, 47, and 48 It is not limited to envelopes and wrappers, and includes cardboard, postcards, envelopes, plain paper, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, OHP sheet, OHP film, resin film, etc. Any material that is sheet-like and capable of forming an image and has a structure in which the thickness is different in the width direction X may be used.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to such specific embodiments, and unless otherwise limited in the above description, the scope of the present invention set forth in the appended claims. Various modifications and changes are possible within the scope of the gist. The effects described in the embodiments of the present invention merely exemplify the most suitable effects resulting from the present invention, and the effects of the present invention are limited to those described in the embodiments of the present invention. isn't it.

1 Image forming device (copier)
27 fixing device 29 fixing member (fixing roller)
33 pressure member (pressure roller)
35, 35A, 35B biasing means 40 cam (eccentric cam)
44 control means 46, 47, 48 recording medium X width direction

Japanese Patent Publication No. 5-19713

Claims (5)

An image forming apparatus comprising: a paper feeding device having a paper feeding roller and a position sensor for detecting a displacement amount of the paper feeding roller; and a fixing device,
The fixing device includes a fixing member and a pressure member that nip the recording medium with a predetermined nip pressure to fix the toner image on the recording medium in the width direction, which is the direction perpendicular to the conveyance of the recording medium;
urging means arranged in at least two positions in the width direction, each having a cam made of ABS resin, and pressing the pressure member against the fixing member;
Based on the position information of the paper feed roller, the recording medium is a recording medium having a thick portion and a thin portion in the width direction, or the recording medium has a uniform thickness in the width direction. and a control means for detecting whether
The control means controls the pressure contact force of the pressure member against the fixing member at the thick portion when the recording medium having a thick portion and a thin portion in the width direction is passed. is reduced below the pressure contact force of the pressure member against the fixing member at the portion where the thickness is thin. The image forming apparatus according to claim 1, wherein
The image forming apparatus, wherein each of the cams has a different cam diagram. The image forming apparatus according to claim 2, wherein
An image forming apparatus according to claim 1, wherein each of said cams changes said cam diagram by making the phases of said cams different from each other. The image forming apparatus according to claim 3,
An image forming apparatus, wherein the cam diagram is changed by changing the front and back sides of the cams. The image forming apparatus according to claim 3 or 4,
An image forming apparatus, wherein each of the cams has two areas, one of which is a low load area and the other of which is a specified load area, and a both areas of specified load.

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