JP4929038B2 - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus having a dancer mechanism capable of improving preciseness of forming an image by applying a uniform tension to a whole recording medium with a simple structure. <P>SOLUTION: This inkjet printer 100 comprises a recording medium WK to be conveyed to a platen 101 and a dancer mechanism 200 for applying a tension to the recording medium WK drawn from a recording medium roll WR. The dancer mechanism 200 includes a dancer shaft 210 configured of a support shaft 211 formed in a solid-core round rod and a hollow cylinder 212. The support shaft 211 has a weight necessary for applying the tension to the recording medium WK and eliminating blocking of the recording medium roll WR. The inner diameter of the cylinder 212 is made greater than the outer diameter of the support shaft 211, and the cylinder 212 is supported by the support shaft 211 so as to be rotated such that the inner circumference thereof slides on the outer circumference of the shaft 211. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to an image forming apparatus that forms a desired image on the surface of a recording medium.

  2. Description of the Related Art Conventionally, there is an image forming apparatus that forms a desired image on a long recording medium such as roll paper by printing or cutting. Generally, an image forming apparatus prints or cuts an image by relatively displacing a recording medium held on a platen and a recording head for printing the image or a cutting head for cutting the image.

Some image forming apparatuses include a dancer mechanism that applies a predetermined tension (tension) to the recording medium in order to appropriately convey the long recording medium onto the platen without wrinkles or slack. For example, the image forming apparatus disclosed in Patent Document 1 includes a buffer roller (dancer mechanism) configured by coaxially arranging a hollow outer rotating roller outside a hollow inner fixed roller. .
Japanese Patent Laid-Open No. 2001-302063

  However, in such a dancer mechanism, since the rotation center of the outer rotating roller in contact with the recording medium is constant, the magnitude of the tension applied to the recording medium due to eccentricity or bending of the outer rotating roller, uneven outer diameter, etc. Unevenness may occur. For this reason, there is a problem in that the recording medium conveyed on the platen is shifted or distorted (wrinkles, slack, etc.), and the accuracy of image formation on the recording medium is reduced. There is also a problem that the dancer mechanism is complicated to manufacture because the number of parts constituting the dancer mechanism is large and the structure is complicated. In particular, since the outer rotating roller in contact with the recording medium is long, its manufacture and assembly are complicated.

  The present invention has been made in order to address the above-described problems, and its purpose is to uniformly apply to the entire recording medium with a simple configuration while suppressing the influence of eccentricity, bending, or non-uniform outer diameter of the roller in contact with the recording medium. An object of the present invention is to provide an image forming apparatus provided with a dancer mechanism capable of improving the accuracy of image formation on a recording medium by applying tension.

In order to achieve the above object, the present invention is characterized by a recording medium holding unit for holding a long recording medium, a platen for placing a part of the long recording medium, and a recording A recording medium conveying means for conveying the recording medium held by the medium holding unit onto the platen; a dancer mechanism provided on the conveying path of the recording medium for applying tension to the recording medium placed on the platen; In the image forming apparatus including a recording head that forms an image on a recording medium placed thereon, the dancer mechanism is formed in a cylindrical shape having a length corresponding to the width direction of the recording medium. a cylindrical body in which the recording medium to be supplied is in contact, is formed in a shaft-like outer diameter smaller than the inner diameter of the cylindrical body, the same cylindrical body rotatably with sliding contact with the inner peripheral surface of the cylindrical body And a support shaft for lifting, the cylinder body has a flexibility to flex by a tension applied to the recording medium, the outer diameter of the inner diameter and the support shaft of the cylindrical body, the rotation center relative to the cylindrical body support shaft They are formed respectively in diameter rotates while changing the in Rukoto.

According to the feature of the present invention configured as described above, a cylindrical body having an inner diameter larger than the outer diameter of the support shaft is disposed outside the support shaft, and the cylindrical body that contacts the recording medium slides on the outer peripheral surface of the support shaft. It is configured to rotate while in contact. That is, the cylinder rotates while changing the center of rotation with respect to the support shaft. Therefore, if the support shaft is arranged in parallel with the width direction of the recording medium to be conveyed, the change in the magnitude of the tension applied to the recording medium conveyed to the platen is the thickness of the rotating cylinder (thickness). It will be in response to changes in In this case, the amount of change in the position of the recording medium due to the change in the thickness of the rotating cylinder is approximately half of the amount of change in the position of the recording medium due to eccentricity, bending, or non-uniform outer diameter of the roller in the conventional example. That is, the change in the magnitude of the tension on the recording medium in the present invention is much smaller than the change in the magnitude of the tension in the conventional example.

Further, according to the feature of the present invention configured as described above, the cylindrical body is configured to be bent by a tension applied to the recording medium. For this reason, when the cylindrical body is bent, the cylindrical body is bent and is in close contact with the support shaft by the tension applied to the recording medium. That is, the bending of the cylinder is corrected. As a result, even when the cylindrical body is bent, uniform tension can be applied to the entire recording medium with high accuracy, and the accuracy of image formation on the recording medium can be improved.

Another feature of the present invention, in the image forming apparatus, the cylindrical body is in Rukoto thickness is uniformly formed.

According to another feature of the present invention configured as described above, the dancer mechanism according to the present invention is mainly composed of a support shaft and a cylinder, and the thickness of the cylinder is manufactured substantially uniformly. The manufacturing accuracy and assembly accuracy of the cylinder need not be as strict as in the conventional example. As a result, it is possible to apply a uniform tension to the entire recording medium with a simple configuration while suppressing the influence of the eccentricity of the roller in contact with the recording medium, bending or uneven outer diameter, etc. Can be improved.

  According to another aspect of the present invention, in the image forming apparatus, the recording medium holding unit holds the recording medium formed in a roll shape, and the dancer mechanism supports the support shaft in a state in which the support shaft can be displaced in the vertical direction. And a supporting shaft is formed with a weight capable of eliminating blocking generated in the roll-shaped recording medium.

  According to another feature of the present invention configured as described above, the support shaft is supported in a vertically displaceable state, and the weight of the support shaft is reduced so as to eliminate blocking that occurs in the roll-shaped recording medium. I am trying. Here, blocking is a phenomenon in which, when a recording medium wound in a roll shape is pulled out, the overlapping recording media stick together and the recording medium cannot be pulled out smoothly. That is, the weight of the support shaft is set to a weight necessary for peeling the recording medium to which the support shaft is attached. Thereby, the conveyance failure by the blocking in the recording medium formed in roll shape can be prevented, and the formation accuracy of the image with respect to a recording medium can be improved more.

  Hereinafter, an embodiment of an image forming apparatus according to the present invention will be described with reference to the drawings. 1A and 1B are perspective views schematically showing the entirety of an inkjet printer 100 including a dancer mechanism 200 according to the present invention. FIG. 1A is a perspective view of the inkjet printer 100 viewed from the front, and FIG. 1B is a perspective view of the inkjet printer 100 viewed from the rear. FIG. 2 is a schematic cross-sectional view of the inkjet printer 100 taken along line AA shown in FIG. The ink jet printer 100 is a printing apparatus that prints an image of a desired character, symbol, figure, or the like on a recording medium WK by causing ink droplets to adhere to the surface of the recording medium WK made of long paper.

  The ink jet printer 100 includes a platen 101 having a flat surface portion and a shape in which the flat surface portion is curved toward the rear side of the ink jet printer 100. The platen 101 is a mounting table on which a part of the recording medium WK is mounted on the flat portion, and is formed extending in the left-right direction in the drawing. A cylindrical grid roller 102 is provided on the flat portion of the platen 101 along the horizontal direction in the drawing with its upper surface exposed. The grid roller 102 is driven to rotate by an X-axis direction feed motor (not shown). In addition, a dryer 103 is provided on the front side of the flat plate portion of the platen 101 so as to be curved downward from the same level as the flat portion of the platen 101. The dryer 103 is a heating element for heating and drying the recording medium WK on which an image is printed, and includes an electric heater (not shown) inside.

  A long guide rail 104 is provided above the platen 101 so as to be parallel to the platen 101. Under the guide rail 104, 17 pinch rollers 105 having a cylindrical portion facing the grid roller 102 are provided at substantially equal intervals. The grid roller 102 and the pinch roller 105 convey the sheet-like recording medium WK in the front-rear direction shown in the figure while being sandwiched from the upper side in the figure. That is, the grid roller 102 and the pinch roller 105 correspond to the recording medium conveying unit according to the present invention. Here, the front-rear direction in the drawing for conveying the recording medium WK is the X-axis direction, and the left-right direction in the drawing orthogonal to the X-axis direction is the Y-axis direction.

  The guide rail 104 supports the recording head unit 105 via a linear motion rail and a linear motion block (not shown). The linear motion rail is a single rail fixed to the guide rail 104 along the Y-axis direction. The linear motion block is a moving body that slides along the linear motion rail, and is fixed to the back surface of the recording head unit 106. That is, the recording head unit 106 is guided in the Y-axis direction along the linear motion rail (guide rail 104). The recording head unit 106 includes a recording head (not shown) that introduces each ink from an ink tank (not shown) that stores six different colors of ink and emits ink droplets toward the recording medium WK. is doing.

  A part of the drive belt 107 erected along the Y-axis direction is fixed to the upper back of the recording head unit 106. The drive belt 107 is displaced in the Y-axis direction by a rotational drive of a Y-axis direction scan motor (not shown). That is, the recording head unit 106 is displaced in the Y-axis direction on the linear motion rail by the Y-axis direction scan motor via the drive belt 107. Above the recording head unit 106, a long upper cover 108 that constitutes an upper casing of the inkjet printer 100 is provided. Further, side covers 109R and 109L constituting the casings on both sides of the ink jet printer 100 are provided on both sides of the platen 101 and the upper cover 108, respectively. Among these, on the front surface of the side cover 109R, an operation panel 110 for giving an instruction to the ink jet printer 100 and displaying information from the ink jet printer 100 is provided.

  A stand 111 is provided below the platen 101 to support the inkjet printer 100 and to move the inkjet printer 100 to a position desired by the operator. The stand 111 is provided with legs 111a and 111b extending in the front-rear direction on the left and right end sides of the ink jet printer 100, and standing in a substantially central portion of the legs 111a and 111b, and the ink jet printer 100 is placed and fixed. Support pillars 111c and 111d. A pair of front and rear shafts 112 and 113 are installed along the Y-axis direction on the front side of the inkjet printer 100 in the legs 111a and 111b of the stand 111, respectively.

  Of these shafts 112 and 113, the shaft 112 arranged at the rear is a shaft body that rotatably holds the recording medium roll WR around which the recording medium WK is wound, and the recording medium holding according to the present invention. It corresponds to the part. A feed guide shaft 114 for guiding the recording medium WK pulled out from the recording medium roll WR to a dancer mechanism 200 described later is provided along the Y-axis direction above the support pillars 111c and 111d positioned behind the shaft 112. It is erected. Further, the shaft 113 disposed in front of the shaft 112 is a shaft body for winding and collecting the recording medium WK that is pulled out from the recording medium roll WR and on which an image is printed by the recording head. A collection guide shaft 115 for guiding the recording medium WK on which an image is printed by the recording head to the shaft 113 is installed in front of the shaft 113 along the Y-axis direction. Drive motors 112a and 113a for rotationally driving the shafts 112 and 113 are provided at one ends of the shafts 112 and 113, respectively.

  A dancer mechanism 200 is provided on the rear side of the ink jet printer 100 in the legs 111 a and 111 b of the stand 111. As shown in detail in FIG. 3, the dancer mechanism 200 includes a dancer shaft 210 erected along the Y-axis direction and guide support portions 220 provided in a standing state on the legs 111 a and 111 b of the stand 111. , 230. Among these, as shown in FIG. 4, the dancer shaft 210 is configured by arranging a cylindrical body 212 formed in a hollow cylindrical shape outside a support shaft 211 formed in a solid round bar shape. Yes.

  The support shaft 211 is a member made of a stainless material for applying tension (tension) to the recording medium WK guided onto the platen 101 and eliminating blocking of the recording medium roll WR, and is necessary for eliminating the blocking. It is composed of weight. In the present embodiment, the weight of the support shaft 211 is 3 kg. Here, blocking is a phenomenon in which when the recording medium WK is pulled out from the recording medium roll WR, the overlapping recording media WK are stuck together and the recording medium WK cannot be pulled out smoothly. This blocking is particularly likely to occur with a vinyl recording medium WK.

  The cylindrical body 212 is a member that is disposed outside the support shaft 211 and is hung by the recording medium WK drawn from the recording medium roll WR and led to the platen 101. More specifically, as shown in FIG. 5A, the cylindrical body 212 has an inner diameter larger than the outer diameter of the support shaft 211, and the inner peripheral surface of the cylindrical body 212 is the outer periphery of the shaft body 211. It is supported by the support shaft 211 so as to rotate while sliding on the surface. In the present embodiment, the outer diameter of the support shaft 211 is 15 mm, and the inner diameter of the cylindrical body 212 is 22 mm. Further, the cylinder 212 is made of a material that bends due to a tension applied to the recording medium WK, for example, an aluminum material.

  Both end portions of the support shaft 211 of the dancer shaft 210 are supported by guide support portions 220 and 230, respectively. The guide support portions 220 and 230 are formed in a box shape extending in the vertical direction and are configured symmetrically to each other. Guide grooves 221 (not shown) and 231 are formed on the side surfaces of the guide support portions 220 and 230 facing each other along the vertical direction, and the end portions of the support shaft 211 are formed in the guide grooves 221 and 231, respectively. Are fitted in a slidable state. That is, the dancer shaft 210 is supported in a state that it can be displaced along the guide grooves 211 and 231 along the vertical direction. Stoppers 222 (not shown) and 232 for preventing the support shaft 211 from coming off are provided above the guide grooves 221 and 231, respectively. In addition, rubber receiving portions 223 (not shown) and 233 for receiving the support shaft 211 are provided below the guide grooves 221 and 231, respectively.

  The ink jet printer 100 includes two controllers A and B (not shown) configured by a microcomputer including a CPU, a ROM, a RAM, and the like. Of these, one controller A controls various operations of the ink jet printer 100 by executing a program stored in advance in a storage device such as a ROM in accordance with an operator's instruction. Specifically, the controller A controls each operation of the X-axis direction feed motor, the Y-axis direction scan motor, the print head, and the like according to instructions from an external computer device (not shown) connected via an interface (not shown). To do. The other controller B controls the operation of the drive motor 113a using a detection signal from a sensor (not shown) that detects the position of the collection guide shaft 115 in synchronism with the controller A, and the position of the dancer shaft 210. The operation of the drive motor 112a is controlled using a detection signal from a sensor (not shown) that detects the above. The external computer device is a personal computer (so-called personal computer) including an input device including a keyboard and a mouse (not shown) and a display device including a liquid crystal display (not shown).

  Next, the operation of the ink jet printer 100 configured as described above will be described. First, the operator sets the recording medium roll WR on the shaft 112 and sets the recording medium WK on the inkjet printer 100. Specifically, the operator hangs the recording medium WK pulled out from the recording medium roll WR on the cylindrical body 212 via the feed guide shaft 114 in a substantially U shape, and then pinches the grid roller 102 on the platen 101. The recording medium WK is supported between the roller 105 and the roller 105. Then, the recording medium WK is further pulled out and wound around the shaft 113 via the collection guide shaft 115.

  In this case, the operator adjusts the pull-out amount of the recording medium WK so that the dancer shaft 210 is positioned above the displaceable lower limit position in the guide grooves 211 and 231. As a result, a tension corresponding to the weight of the dancer shaft 210 is applied to the recording medium WK placed on the platen 101 and the recording medium WK drawn from the recording medium roll WR. In this case, the cylindrical body 212 of the dancer shaft 210 is in a state where its inner peripheral surface is pressed against the bottom of the outer peripheral surface of the support shaft 211 as shown in FIG.

  Next, the operator connects the external computer device and the inkjet printer 100 via an interface, and turns on the power of the external computer device and the inkjet printer 100, respectively. As a result, the external computer device enters a standby state in which it waits for the input of a command from the operator by executing a predetermined program (not shown). The ink jet printer 100 waits for an instruction from the external computer device after returning the origin of the recording head unit 106 by executing a predetermined program (not shown) stored in the ROM in the controller A in advance. It becomes.

  Next, the operator operates the external computer device to instruct the inkjet printer 100 to output image data, and causes the inkjet printer 100 to start printing an image. Thereby, the ink jet printer 100, specifically, the controller A built in the ink jet printer 100 determines the relative positional relationship between the print head unit 105 and the print medium WK based on the image data output from the external computer device. While changing, the operation of the recording head is controlled to eject ink droplets toward the recording medium WK.

  In the image printing process on the recording medium WK, the recording medium WK placed on the platen 101 is conveyed from the rear side to the front side of the inkjet printer 100. Specifically, the controller A of the inkjet printer 100 intermittently conveys the recording medium WK from the rear side to the front side of the inkjet printer 100 by controlling the operation of the X-axis direction feed motor. Further, the controller B controls the operation of the drive motor 113a to take up the recording medium WK on which the image is printed, and also controls the operation of the drive motor 112a so that the position of the dancer shaft 210 is in the guide grooves 221 and 231. The rotation of the recording media roll WR is controlled so as to be positioned within the displaceable range.

  In this case, the dancer shaft 210 applies a tension corresponding to the weight of the dancer shaft 210 to the recording medium WK drawn from the recording medium roll WR. For this reason, the recording medium WK can be pulled out while eliminating the blocking of the recording medium WK in the recording medium roll WR. Further, the cylindrical body 212 of the dancer shaft 210 rotates while the inner peripheral surface slides on the bottom of the outer peripheral surface of the support shaft 211 to guide the recording medium WK to the platen 101. That is, the cylindrical body 212 rotates while being pressed against the support shaft 211, thereby rotating while changing the center of rotation. As a result, a change in the magnitude of the tension due to bending of the support shaft 211 and the cylindrical body 212, non-uniform outer diameter, or the like is prevented, and a uniform tension is applied to the entire recording medium WK. For this reason, the recording head can perform printing on the recording medium WK having no shift or distortion (such as wrinkles or slack).

  Further, when the cylindrical body 212 is bent, the cylindrical body 212 is bent by the tension applied to the recording medium WK, so that the cylindrical body 212 is in close contact with the support shaft 211. For this reason, even when the cylindrical body 212 is bent, uniform tension is applied to the entire recording medium WK. In this manner, the recording medium WK is transported onto the platen 101, and an image is printed on the transported recording medium WK. When printing of all images on the recording medium WK is completed, the operator removes the recording medium WK from the platen 101 and ends the processing operation.

  As can be understood from the above description of the operation, according to the above embodiment, the cylindrical body 212 having an inner diameter larger than the outer diameter of the support shaft 211 is arranged outside the support shaft 211 so that the recording medium WK comes into contact therewith. 212 is configured to rotate while contacting the outer peripheral surface of the support shaft 211. That is, the cylinder 212 rotates while changing the rotation center with respect to the support shaft 211. Therefore, the change in the magnitude of the tension applied to the recording medium WK conveyed to the platen 102 corresponds to the change in the thickness (thickness) of the rotating cylinder 212. In this case, the amount of change in the position of the recording medium WK due to the change in the thickness of the rotating cylinder 212 is approximately half of the amount of change in the position of the recording medium WK due to roller eccentricity, bending, or non-uniform outer diameter in the conventional example. It is. That is, the change in the magnitude of the tension with respect to the recording medium WK in the present invention is much smaller than the change in the magnitude of the tension in the conventional example.

The dancer mechanism 210 in the embodiment is mainly constituted by the support shaft 211 and the cylindrical body 212. In this case, if the thickness of the cylindrical body 212 is manufactured substantially uniformly, the manufacturing accuracy and the assembly accuracy of the support shaft 211 and the cylindrical body 212 do not need to be strict as in the conventional example. As a result, a uniform tension can be applied to the entire recording medium with a simple configuration, and the image forming accuracy on the recording medium can be improved.

  Further, according to the above embodiment, the cylindrical body 212 is configured to be bent by the tension applied to the recording medium WK. For this reason, when the cylindrical body 212 is bent, the cylindrical body 212 is in close contact with the bending support shaft 211 due to the tension applied to the recording medium. That is, the bending of the cylinder 212 is corrected. As a result, even when the cylindrical body 212 is bent, a uniform tension can be applied to the entire recording medium WK with high accuracy, and the image forming accuracy on the recording medium WK can be improved. .

  Further, according to the above-described embodiment, the support shaft 211 is supported in a state in which the support shaft 211 can be displaced in the vertical direction, and the weight of the support shaft 211 is set to a weight that can eliminate blocking generated in the roll-shaped recording medium WK. . That is, the weight of the support shaft 212 is set to a weight necessary for peeling the recording medium WK to which the support shaft 212 is attached. Thereby, the conveyance failure by the blocking in the recording medium WK formed in the roll shape can be prevented, and the formation accuracy of the image on the recording medium can be further improved.

  Furthermore, in carrying out the present invention, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the object of the present invention.

  In the above embodiment, the cylindrical body 212 is configured to bend by the tension applied to the recording medium WK. However, if the cylindrical body 212 is formed without bending, the cylindrical body 212 is not necessarily configured to bend. Also by this, the same effect as the above-mentioned embodiment can be expected.

  In the above-described embodiment, the recording medium WK conveyed to the platen 101 and the recording medium WK pulled out from the recording medium roll WR are configured to be tensioned by the weight of the support shaft 211. However, the present invention is not limited to this as long as the necessary tension can be applied to the recording medium WK. For example, the support shaft 211 may be configured to be pushed or pulled downward using a spring or the like. In this case, the direction in which the support shaft 211 is pushed or pulled is not limited to the downward direction, but may be any direction as long as tension can be applied to the recording medium WK. In this case, the support shaft 211 can be formed of a hollow cylinder, or the support shaft 211 can be formed of two short shaft bodies that support both end portions of the cylinder 212. Also by these, the same effect as the above-mentioned embodiment can be expected.

  In the above embodiment, the recording medium WK pulled out from the recording medium roll WR is configured to be tensioned. However, when the recording medium WK that does not cause blocking is used, it is not necessary to apply tension to the recording medium WK drawn out from the recording medium roll WR. Also by this, the same effect as the above-mentioned embodiment can be expected.

  In the above embodiment, the weight of the support shaft 211 is 3 kg in order to apply tension to the recording medium WK drawn from the recording medium roll WR. However, the weight of the support shaft 211 is appropriately set depending on the size and type of tension applied to the recording medium WK, the specification of the Y-axis direction feed motor that drives the grid roller 102, and the like. is not.

  In the above embodiment, the present invention is applied to the ink jet printer 100, but the present invention is not limited to this. For example, the present invention may be applied to a cutting apparatus that cuts out the surface of the recording medium WK to form a desired image. Further, the recording medium WK that is an image formation target is not limited to the above-described embodiment, and, for example, a vinyl sheet or a cloth can be used as the recording medium WK.

(A), (B) is the perspective view which shows roughly the whole inkjet printer provided with the dancer mechanism which concerns on one Embodiment of this invention, (A) is the perspective view which looked at the inkjet printer from the front. (B) is the perspective view which looked at the ink jet printer from back. It is sectional drawing which shows schematically the cross section of the inkjet printer in the AA line shown to FIG. 1 (A). It is a perspective view which shows the dancer mechanism provided in the inkjet printer shown to FIG. 1 (B). It is the perspective view which expanded and showed a part of dancer mechanism shown in FIG. (A) is a sectional view of the dancer shaft showing a state where the recording medium is not hung on the dancer shaft, and (B) is a cross-sectional view of the dancer shaft showing a state where the recording medium is hung on the dancer shaft.

Explanation of symbols

WK ... recording media, WR ... recording media roll, 100 ... ink jet printer, 101 ... platen, 102 ... grid roller, 103 ... dryer, 104 ... guide rail, 105 ... pinch roller, 106 ... recording head unit, 107 ... drive belt, DESCRIPTION OF SYMBOLS 110 ... Operation panel 111 ... Stand, 112, 113 ... Shaft, 114 ... Feeding guide shaft, 115 ... Collection guide shaft, 200 ... Dancer mechanism, 210 ... Dancer shaft, 211 ... Support shaft, 212 ... Cylindrical body, 220, 230 ... Guide support part.

Claims (3)

A recording medium holding unit for holding a long recording medium;
A platen for placing a part of the long recording medium;
A recording medium conveying means for conveying the recording medium held in the recording medium holding unit onto the platen;
A dancer mechanism that is provided on a conveyance path of the recording medium and applies tension to the recording medium placed on the platen;
In an image forming apparatus comprising: a recording head that forms an image on the recording medium placed on the platen;
The dancer mechanism is
A cylindrical body that is formed in a cylindrical shape having a length corresponding to the width direction of the recording medium, and that contacts the recording medium supplied from the recording medium holding unit;
A shaft having an outer diameter smaller than the inner diameter of the cylindrical body, and a support shaft that rotatably supports the cylindrical body while slidingly contacting the inner peripheral surface of the cylindrical body ,
The cylinder is
Having flexibility to bend by a tension applied to the recording medium;
The inner diameter of the cylindrical body and the outer diameter of the support shaft are as follows:
The cylindrical body An image forming apparatus comprising the Rukoto are formed respectively in diameter rotates while changing the rotation center relative to the support shaft. The image forming apparatus according to claim 1,
An image forming apparatus, wherein the cylindrical body is formed with a uniform thickness . The image forming apparatus according to claim 1, wherein:
The recording medium holding unit holds a recording medium formed in a roll shape,
The dancer mechanism is
A guide support portion for supporting the support shaft in a state displaceable in the vertical direction;
The image forming apparatus, wherein the support shaft is formed with a weight capable of eliminating blocking generated in the roll-shaped recording medium.