JP5684679B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a facsimile machine, and a printer using an endless belt stretched around a plurality of rollers.

  In a conventional image forming apparatus, after charging a photosensitive drum as an image carrier, an image is directly exposed by an exposure device, or light writing according to an image signal is performed by a laser scanning optical system or an LED light writing optical system. An electrostatic latent image is formed on the photosensitive drum, and the formed electrostatic latent image is formed into a toner image by toner adhesion of the developing device, and the toner image is transferred directly or via an intermediate transfer member to a transfer paper Or transfer to a recording medium such as film. Then, the recording medium to which the toner image is transferred is conveyed to a fixing device, and the fixing device fixes the toner image on the recording medium to obtain an image.

  In such an image forming apparatus, an endless belt is used as a transport belt for transporting a recording medium or a transfer belt for carrying a toner image, and includes a transfer belt unit disposed to face an image forming unit for forming a toner image. (See, for example, Patent Document 1). The transfer belt unit has a transfer belt that conveys a recording medium and a handle portion that is gripped when the transfer belt unit is attached to and detached from the image forming apparatus. First, the image forming unit is taken out from the inside of the image forming apparatus, and then the transfer belt unit is taken out by holding the handle portion. Thereafter, the transfer belt unit and the image forming unit are remounted in the image forming apparatus, and printing is performed.

JP 2006-78544 A (paragraph “0009” to paragraph “0011”, FIG. 1)

However, in the conventional technology described above, when the recording medium is conveyed by a belt to a contact portion (hereinafter referred to as a “nip portion”) between the image forming unit and a transfer belt unit as a transfer portion, the nip portion. When the recording medium entering the nip part is lifted, the recording medium entering the nip part may be lifted from the belt before reaching the nip part. When the leading end collides, there is a problem that the recording medium is bent or a banding line that appears as a horizontal stripe in a transfer image to the recording medium is generated, thereby deteriorating the printing quality.
An object of the present invention is to solve such a problem, and an object of the present invention is to prevent the leading edge of a recording medium to be conveyed from being lifted and to improve print quality.

Therefore, the present invention is an image forming apparatus having an image forming unit that forms an image and a transfer unit that transfers an image formed by the image forming unit to a medium, and the image forming unit includes the image forming unit. The transfer unit is detachable from the apparatus, and the transfer unit conveys a medium, and when the image forming unit is mounted, the transfer unit is pressed and moved by the image forming unit, and a facing unit adjacent to the conveying member. have a, the facing portion, the inclined surface that gradually narrows the gap between the conveying member toward the downstream side from the upstream side in the transport direction of the medium is formed, the gap becomes the smallest between the conveying member It has a closest portion, and the closest portion is a suction roller that sucks the medium onto the conveying member .

  According to the present invention as described above, it is possible to prevent the leading edge of the conveyed medium from being lifted and to improve the printing quality.

The perspective view of the transfer belt unit in the first embodiment 1 is a schematic side view illustrating a configuration of an image forming apparatus according to a first embodiment. 1 is a block diagram showing a control configuration of an image forming apparatus according to a first embodiment. Side view of transfer belt unit and image forming unit in first embodiment Sectional drawing of the transfer belt unit and the image forming unit in the first embodiment Explanatory drawing (side view) showing operations of the transfer belt unit and the image forming unit in the first embodiment. Explanatory drawing (sectional drawing) which shows operation | movement of the transfer belt unit and image forming unit in 1st Example. Explanatory drawing which shows the conveyance state of the recording medium in 1st Example Explanatory drawing of the modification of the transfer belt unit in 1st Example The perspective view of the transfer belt unit in the second embodiment Side view of transfer belt unit and image forming unit in second embodiment Sectional drawing of the transfer belt unit and the image forming unit in the second embodiment Explanatory drawing (side sectional drawing) which shows operation | movement of the transfer belt unit and image forming unit in 2nd Example.

  Embodiments of an image forming apparatus according to the present invention will be described below with reference to the drawings.

FIG. 2 is a schematic side view showing the configuration of the image forming apparatus in the first embodiment.
In FIG. 2, reference numeral 10 denotes a printer as an image forming apparatus, an image forming unit as an image forming unit for forming an image, and a transfer belt unit as a transfer unit for transferring an image formed by the image forming unit to printing paper. It is equipped with. In this embodiment, the printer 10 is described as a color printer.

The paper tray 100 has a printing paper 101 as a recording medium (medium) stacked therein and is detachably attached to the printer 10. Inside the paper tray 100 is provided a paper placement plate 102 that is rotatably supported by a support shaft (not shown), and the printing paper 101 is stacked on the paper placement plate 102.
A lift-up lever 103 is rotatably disposed on a support shaft (not shown) on the side of the paper tray 100 where the printing paper 101 is fed, and the support shaft is engaged with the motor 104 so as to be able to contact and separate.

When the paper tray 100 is inserted into the printer 10, the lift-up lever 103 and the motor 104 are engaged, and a control unit (not shown) drives the motor 104. When the lift-up lever 103 is rotated by driving the motor 104, the tip of the lift-up lever 103 lifts the bottom of the paper placing plate 102, and the printing paper 101 loaded on the paper placing plate 102 is raised.
When the printing paper 101 rises to a predetermined height, the printing paper 101 comes into contact with the pickup roller 202 and is detected by the rising detection unit 201, and the control unit controls the motor 104 based on the information detected by the rising detection unit 201. Stop.

The pickup roller 202 forms a paper feeding unit 200 together with a feed roller 203 and a retard roller 204 arranged in pairs with the peripheral surfaces in contact with each other. The pickup roller 202 and the feed roller 203 are rotationally driven in a direction indicated by an arrow in FIG. 2 by a paper feed motor 711 shown in FIG. The retard roller 204 generates torque in the direction indicated by the arrow in FIG. 2 by a torque generating means (not shown).
Accordingly, the pick-up roller 202 pulls out the printing paper 101 abutted by rotating from the paper tray 100, and the feed roller 203 and the retard roller 204 roll one by one so that a plurality of printing papers 101 are not drawn simultaneously. Transport.

  On the downstream side of the paper feeding unit 200 in the conveyance direction of the printing paper 101, a paper sensor 302, a conveyance roller pair 303 including a driving roller 304 and a driven roller 305 that regulate the skew of the printing paper 101, and a next conveyance roller pair. A paper sensor 313 for detecting the driving timing of 310, a conveyance roller pair 310 including a driving roller 311 and a driven roller 312 for feeding the printing paper 101 to the image forming unit 410, and a writing sensor for generating a writing timing in the image forming unit 410 314 is disposed. The power of the paper feed motor 711 in FIG. 3 is transmitted to the transport roller pair 303 and the transport roller pair 310 via a drive transmission unit (not shown), and the rotation is controlled by a transport control unit (not shown).

  The printer 10 includes an MPT (Multi Purpose Ray) 320 and is attached to the printer 10 so as to be opened and closed. Inside the MPT 320, there is provided a paper placing plate 321 that is rotatably supported by a support shaft (not shown), and the printing paper P is placed on the paper placing plate 321. The bottom of the paper placing plate 321 is lifted by a spring (not shown), and the printing paper P placed on the paper placing plate 321 is raised. When the printing paper P rises to a predetermined height, it comes into contact with the peripheral surface of the pickup roller 323.

The pickup roller 323 forms an MPT paper feeding portion 322 together with the MPT roller 324 and the retard roller 325 arranged in pairs with the peripheral surfaces in contact with each other. The pickup roller 323 and the MPT roller 324 are rotationally driven in a direction indicated by an arrow in FIG. 2 by a paper feed motor 711 shown in FIG. The retard roller 325 generates torque in the direction indicated by the arrow in FIG. 2 by a torque generating means (not shown).
Therefore, the pick-up roller 323 pulls out the printing paper P abutted by rotating from the MPT 320, and the MPT roller 324 and the retard roller 325 roll and convey the printing paper P one by one so as not to be drawn out simultaneously. .

  The image forming unit 410 of the printer 10 includes image forming units for each color that form four color images. The image forming unit 410 includes four image forming units 430K (black), 430Y (yellow), 430M (magenta), and 430C (cyan) that respectively form yellow, magenta, cyan, and black images. Are detachably mounted in order from the upstream side in the transport direction of the transport path of the printing paper 101 and P.

  Next, the configuration of the image forming unit 430K will be described. Since the image forming units 430Y, 430M, and 430C have the same configuration as the image forming unit 430K, the image forming unit 430K will be described as a representative.

In the image forming unit 430K, a photosensitive drum 431 is disposed so as to be rotatable in a direction indicated by an arrow in the figure. Around the photosensitive drum 431, the surface of the photosensitive drum 431 is sequentially arranged from the upstream in the rotation direction. A charging roller 432 for supplying and charging an electric charge, an exposure device 433 for selectively irradiating light onto the surface of the charged photosensitive drum 431 to form an electrostatic latent image, and a photosensitive having an electrostatic latent image formed thereon. A developing roller 434 that develops an electrostatic latent image by attaching black toner to the surface of the photosensitive drum 431, and a cleaning blade 435 that removes transfer residual toner that remains on the photosensitive drum 431 without being transferred are disposed. Has been. The toner storage unit 436 stores toner and supplies the toner to the developing roller 434.
Each drum or each roller used in the printer 10 is rotated by power transmitted from a drive source (not shown) via a gear.

  A transfer belt unit 460 serving as a transfer unit is disposed to face the image forming units 430K to 430C, and each photosensitive drum 431 of the image forming units 430K to 430C is formed of a conductive rubber or the like. The roller 464 is disposed in a state of being pressed through the transfer belt 461. The transfer roller 464 has a surface potential of each photoconductive drum 431 and a surface potential of each transfer roller 464 when a toner image formed by toner attached on the photoconductive drum 431 is transferred to the printing paper 101, P. A potential for causing a potential difference is applied between the two.

  A transfer belt 461 serving as a conveyance member for conveying the printing paper is an endless belt disposed to face the image forming units 430K to 430C, and conveys the printing paper 101 and P by electrostatic adsorption, as shown in FIG. The drive roller 462 rotated by the belt motor 609 rotates in the direction indicated by the arrow in the drawing together with the tension roller 463 that stretches the transfer belt 461 in a pair with the drive roller 462 and drives the transfer belt 461.

  The cleaning blade 465 scrapes off the transfer residual toner adhering to the transfer belt 461, and the toner box 466 stores the scraped toner. The drive roller 462 is driven to rotate by receiving power from a drive source (not shown) via drive transmission means.

  The fixing unit 500 includes a halogen lamp 503a serving as a heat source therein, an upper roller 501 whose surface is formed of an elastic body, and a lower roller 502 including a halogen lamp 503b also serving as a heat source and whose surface is formed of an elastic body. Consisting of a pair of rollers, heat and pressure are applied to the toner image transferred onto the printing paper 101, P delivered from the image forming unit 410 to melt the toner image, and this image is fixed to the printing paper 101, P. . Thereafter, the print sheets 101 and P are detected by the discharge sensor 506, conveyed by the discharge roller pairs 504 a, 504 b, and 504 c and discharged to the stacker unit 505.

Next, the configurations of the transfer belt unit and the image forming unit are shown in a perspective view of the transfer belt unit in the first embodiment of FIG. 1 and a side view of the transfer belt unit and the image forming unit in the first embodiment of FIG. The details will be described with reference to FIG.
1 and 4, a pair of conveying rollers 310 as medium conveying means for conveying the printing paper is disposed on the upstream side of the transfer belt unit 460 in the conveying direction of the printing paper indicated by the arrow A in the drawing. Reference numeral 460 receives the printing paper conveyed by the conveyance roller pair 310 and conveys the printing paper by the transfer belt 461.

  The transfer belt unit 460 includes a handle portion 467 that is gripped when the printer 10 is attached to or detached from the most upstream side in the printing paper conveyance direction indicated by an arrow A in the drawing. Further, the tension roller 463 that stretches the transfer belt 461 includes a shaft portion 463a shown in FIG. 1 and a shaft portion 463b shown in FIG.

  The handle portion 467 is formed with a slide portion 475a and a slide portion 475b that are orthogonal to a straight line connecting the shaft portion 463a and the shaft portion 463b and engage with the protruding shaft portion 463a and the shaft portion 463b, respectively. 467 is movable in a state where the slide portion 475a and the slide portion 475b are engaged with the shaft portion 463a and the shaft portion 463b. The slide portion 475a and the slide portion 475b are guide portions that bring a sheet facing surface of a handle portion 467, which will be described later, close to the transfer belt 461.

  The handle portion 467 includes the spring 469R shown in FIG. 1 and the spring 469L shown in FIG. 4 that urge the shaft portion 463a and the shaft portion 463b along the longitudinal direction of the slide portion 475a and the slide portion 475b, and the spring 469R. The spring 469L is disposed so as to bias the handle portion 467 away from the transfer belt 461 (the direction indicated by the arrow B in the figure).

  When the image forming unit 430K is attached to the printer 10, the upper portion of the handle portion 467 is moved so that the handle portion 467 is moved in a state where the slide portion 475a and the slide portion 475b are engaged with the shaft portion 463a and the shaft portion 463b. The exterior frame 440 shown in FIG.

  Further, when the transfer belt unit 460 is attached to the printer 10 at both ends of the handle portion 467 (substantially below the slide portion 475a and the slide portion 475b) and is moved by being pressed by the exterior frame 440 of the image forming unit 430K, Positioning portions 472 and 473 as recessed portions to be engaged are respectively provided on positioning posts 470 and 471 as projections formed on both sides of the frame of the printer 10. The positioning portions 472 and 473 determine and fix a position where a sheet facing surface of a handle portion 467, which will be described later, is re-approached to the transfer belt 461. In FIG. 4, the positioning post 470 is formed on the opposite side of the positioning post 471.

FIG. 5 is a sectional view of the transfer belt unit and the image forming unit in the first embodiment. It should be noted that the configuration for image formation in the image forming unit 430K is not directly related to the present invention, and is omitted.
In FIG. 5, the handle portion 467 is formed with a paper facing surface 476 as a facing portion close to the transfer belt 461, and the paper facing surface 476 is connected to the image forming unit 430 </ b> K from the transport roller pair 310 that transports the printing paper. Is formed as an inclined surface in which the gap with the belt conveyance unit 477 (transfer belt 461) gradually narrows in the direction of the photosensitive drum 431, that is, in the conveyance direction of the printing paper, and the paper conveyance path faces the transfer belt 461. And a guide member that guides the printing paper conveyed by the conveyance roller pair 310 toward the transfer belt 461. Further, the sheet facing surface 476 is also an adsorbing member that adsorbs the printing sheet to the transfer belt 461.

Further, the exterior frame 440 of the image forming unit 430K is formed with a moving part 440p that contacts the handle part 467 and moves the handle part 467, and the handle part 467 has a contact part that contacts the moving part 440p. 467p is formed.
On the sheet facing surface 476 of the handle portion 467, the moving portion 440p of the exterior frame 440 of the image forming unit 430K abuts on the abutting portion 467p on the upper portion of the handle portion 467 and the handle portion 467 moves (slide portion 475a shown in FIG. 4). And the slide portion 475b moves in a state of being engaged with the shaft portion 463a and the shaft portion 463b), moves in the direction of the transfer belt 461, comes close to the transfer belt 461, and is arranged upstream in the conveyance direction of the printing paper. It is arranged so as to come into contact with the upper surface of the printing paper conveyed by the conveying roller pair 310 and guide the printing paper toward the belt conveyance unit 477 (transfer belt 461).

Next, the control configuration of the printer will be described based on the block diagram showing the control configuration of the image forming apparatus in the first embodiment of FIG.
In FIG. 3, a control unit 600 controls the operation of the entire printer 10, and includes a main control unit 601, a paper feed motor control unit 602, an electromagnetic clutch control unit 603, and a belt motor serving as a control center. A control unit 604, an ID motor control unit 605, and a fixing motor control unit 606 are configured.

The main control unit 601 has a CPU (Central Processing Unit) composed of control means and arithmetic means, RAM and ROM of a program memory, a timer counter, etc., and a paper sensor 302, a paper sensor 313, a writing sensor inputted from an input port. Based on the detection signal from 314 and the discharge sensor 506, each unit is activated and control is switched.
Further, a paper feed motor control unit 602, an electromagnetic clutch control unit 603, a belt motor control unit 604, an ID motor control unit 605, and a fixing motor control unit 606 are connected to the main control unit 601.

  The paper feed motor control unit 602 outputs an operation signal to the paper feed motor 711 to control the paper feed motor 711, and the electromagnetic clutch control unit 603 outputs an operation signal to the electromagnetic clutch 706 to activate the electromagnetic clutch 706. The belt motor control unit 604 outputs an operation signal to the belt motor 609 to control the belt motor 609, and the ID motor control unit 605 outputs an operation signal to the ID motor 610 to control the ID motor 610. The fixing motor control unit 606 controls the fixing motor 611 by outputting an operation signal to the fixing motor 611.

  Each of these motors is a two-phase excitation stepping motor or a DC motor. The two-phase excitation stepping motor controls acceleration or deceleration of motor rotation by passing a constant current through each motor and switching the phase current direction at the rising edge of the clock signal or changing the clock frequency. The DC motor applies a voltage to the motor terminal to control the rotation speed, and controls the rotation direction of the motor according to the polarity connection direction of the motor terminal.

  As the electromagnetic clutch 706, a dry single-plate electromagnetic clutch or the like is used. The electromagnetic clutch 706 includes a field rotor assembly and an armature assembly in which a field incorporating a rotor and a coil is supported by a ball bearing. The field rotor assembly is attached to a rotating member such as a shaft, and the armature assembly takes a slight gap from the rotor. It is fixed to a member such as a pulley or a gear by a mounting bolt via a leaf spring.

  The armature is attracted to the rotor by the magnetic flux generated between the field rotor assembly and the armature assembly by the current flowing through the coil in the electromagnetic clutch 706, and the electromagnetic clutch is connected. Thereby, mechanical motion is given to the external mechanism connected to the electromagnetic clutch 706. If the energization to the coil is continued, the armature keeps the state attracted to the rotor, and if the energization is interrupted, the magnetic flux disappears, and the armature is separated from the rotor by the leaf spring and pulled back to the original position. In this way, the power from the drive source transmitted to the gear attached to the electromagnetic clutch 706 is transmitted to the drive roller.

  The printer 10 includes an operation panel 612. The operation panel 612 includes an input unit configured with a switch (not shown), a display unit configured with an LED (Light Emitting Diode), an LCD (Liquid Crystal Display), and the like. It consists of. By operating this input unit, various conditions in the printer 10 such as font selection and printing paper selection can be set. In addition, the condition set by the input unit is displayed on the display unit.

The printer 10 includes an interface unit 613. The interface unit 613 includes an interface connector (not shown), an interface IC, and the like, receives print data transmitted from a host computer (not shown), and transfers the print data to the main control unit 601.
The overall operation of the printer 10 configured as described above is controlled by a control unit 600 that executes a control program (software) stored in a storage unit such as a RAM or a ROM.

The operation of the above configuration will be described.
First, the operation of the printer will be described with reference to FIG.
When paper is fed from the paper tray 100, the print paper 101 stored in a stacked state on the paper tray 100 is fed from the top by the paper feeding unit 200 including the pickup roller 202, the feed roller 203, and the retard roller 204. The sheets are separated one by one and fed out to the sheet conveyance path.

  The fed printing paper 101 passes through the paper sensor 302 and is sent to the conveyance roller pair 303. The conveyance roller pair 303 sends out the printing paper 101 at a predetermined timing based on the passage time of the printing paper 101 through the paper sensor 302. At this time, the conveyed printing paper 101 continues to be conveyed by the paper feeding unit 200 by a predetermined amount, and the leading edge of the printing paper 101 is abutted between the two rollers of the conveying roller pair 303. Skew is corrected. Thereafter, the printing paper 101 is nipped by the conveyance roller pair 303, is sandwiched between the driving roller 304 and the driven roller 305 that rotate in the direction indicated by the arrow in FIG. 2, and is conveyed in the direction of the conveyance roller pair 310.

  The printing paper 101 sent out by the transport roller pair 303 passes through the paper sensor 313 and is sent to the transport roller pair 310. The conveyance roller pair 310 is rotationally driven from the time when the printing paper 101 reaches the paper sensor 302 and feeds the printing paper 101 without stopping. The printing paper 101 sent out by the conveying roller pair 310 passes through the writing sensor 314 and is sent to the image forming unit 410.

  The printing paper 101 sent to the image forming unit 410 by the conveying roller pair 310 is conveyed here by the transfer belt 461 and is conveyed between the photosensitive drum 431 and the transfer roller 464 of the image forming unit 430K. Thereafter, the printing paper 101 is sandwiched between the photosensitive drum 431 and the transfer roller 464, and the toner image on the photosensitive drum 431 is transferred to the recording surface.

  Similarly, the printing paper 101 passes through the image forming units 430Y, 430M, and 430C, and in the course of the passage, the electrostatic latent image formed on the photosensitive drum 431 by each exposure device 433 is developed by the developing roller 434. The toner images of the respective colors are sequentially transferred and superimposed on the recording surface.

  The printing paper 101 to which the toner image has been transferred is sent to the fixing unit 500 where the toner image transferred by the fixing unit 500 is fixed. Thereafter, the printing paper 101 on which the toner image is fixed is discharged to a printing paper stacker unit 505 outside the printer 10 by a pair of discharge rollers 504a, 504b, and 504c.

In this way, the printer 10 forms a color image on the recording paper 101.
When paper is fed from the MPT 320, the print paper P stored in a stacked state on the paper placement plate 321 is fed by the MPT paper feed unit 322 including the pickup roller 323, the MPT roller 324, and the retard roller 325. The sheets are separated from the top one by one and fed out to the paper transport path.

  The fed printing paper P passes through the paper sensor 313 and is sent to the transport roller pair 310. The conveyance roller pair 310 sends out the printing paper P at a predetermined timing based on the passage time of the printing paper P by the paper sensor 313. At this time, the conveyed printing paper P is continuously conveyed by the MPT paper feeding unit 322 by a predetermined amount, and the leading edge of the printing paper P is abutted between the two rollers of the conveying roller pair 310. , Skew is corrected. Thereafter, the printing paper P is nipped by the conveyance roller pair 310, is sandwiched by two rollers rotating in the direction indicated by the arrow in FIG. 2, passes through the writing sensor 314, and is conveyed to the image forming unit 410. .

The printing paper P sent to the image forming unit 410 by the pair of conveying rollers 310 forms a toner image through the same process as that in the case of feeding from the paper tray 100 described above, and then the printing paper outside the printer 10. It is discharged to the stacker unit 505.
In the transport mechanism for transporting the printing paper described above, the feed roller 203, the transport roller pair 303, the transport roller pair 310, and the MPT roller 324 are assembled to the respective roller shafts when power is transmitted. It is connected by an electromagnetic clutch and the drive is transmitted.

Next, the operations of the transfer belt unit and the image forming unit will be described with reference to FIG. 2 based on the explanatory views showing the operations of the transfer belt unit and the image forming unit in the first embodiment of FIGS.
FIG. 6 is a side view showing operations of the transfer belt unit 460 and the image forming unit 430K when the image forming unit 430K is inserted into the printer 10 in a state where the transfer belt unit 460 is already stacked on the printer 10. 6A shows a state before the image forming unit 430K is inserted into the printer 10, and FIG. 6B shows a state after the image forming unit 430K is inserted into the printer 10. 7 is a cross-sectional view of the transfer belt unit 460 and the image forming unit 430K in FIG. 6. FIG. 7A shows a state before the image forming unit 430K is inserted into the printer 10, and FIG. FIG. 5B shows a state after the image forming unit 430K is inserted into the printer 10.

In a state before the image forming unit 430K is inserted into the printer 10, the handle portion 467 of the transfer belt unit 460 is biased by the spring 469L and the spring 469R shown in FIG. 1, and the sheet facing surface 476 is moved to the belt conveying portion 477 ( It is separated from the transfer belt 461).
When the image forming unit 430K is inserted into the printer 10, the image forming unit 430K is guided in a direction indicated by an arrow C in FIGS. 6 and 7 along an insertion guide (not shown) provided in the printer 10. At this time, when the image forming unit 430K is guided into the printer 10 and moves a predetermined amount, the moving part 440p of the exterior frame 440 comes into contact with the contact part 467p on the upper part of the handle part 467.

  Thereafter, the handle portion 467 is pressed by the insertion of the image forming unit 430K, and is further pushed in such a direction that the sheet facing surface 476 of the handle portion 467 approaches the belt conveying portion 477 (transfer belt 461). At this time, the handle portion 467 is moved in the direction indicated by the arrow C in the figure in which the image forming unit 430K moves while being guided by a guide portion (not shown) along the slide portions 475a and 475b with the shaft portions 463a and 463b as axes. Move in parallel.

  Further, when the image forming unit 430K is inserted into the printer 10 by a predetermined amount, the positioning portions 472 and 473 of the handle portion 467 are fitted into the positioning posts 470 and 471 formed in the printer 10, respectively. The unit 460 is positioned and fixed in the printer 10. At this time, the sheet facing surface 476 of the handle portion 467 moves so as to be close to the belt conveying portion 477 (transfer belt 461).

  When the image forming unit 430K is detached from the printer 10, the image forming unit 430K is guided in a direction opposite to the direction indicated by the arrow C in the figure by being guided by a guide unit (not shown), and the image forming unit 430K and the image forming unit 430K The exterior frame 440 of the unit 430K is separated.

  For this reason, the paper facing surface 476 is moved away from the belt conveyance unit 477 (transfer belt 461) by the springs 469L and 469R that urge the handle unit 467. Thus, when the handle portion 467 moves, the positioning portions 472 and 473 are separated from the positioning posts 470 and 471, respectively, and the fixed state of the transfer belt unit 460 is released.

  As described above, in a state in which the sheet facing surface 476 is separated from the belt conveyance unit 477 (transfer belt 461), the handle unit 467 serves as a grip unit for inserting and removing the transfer belt unit 460 with respect to the printer 10. The unit 460 can be inserted into and removed from the printer 10.

  Further, since the handle portion 467 is moved away from the belt conveying portion 477 (transfer belt 461) by the springs 469L and 469R and protrudes to the upper operator side, the operator can easily grasp the handle portion 467. The operability of attaching / detaching the transfer belt unit 460 can be improved. Furthermore, when the printing paper is removed from the transfer belt 461, such as when a printing paper jam (jam) occurs, the paper facing surface 476 (particularly, the portion in contact with the printing paper) is removed when the image forming unit 430K is removed. Since it is separated from the transfer belt 461, the operation of removing the printing paper becomes easy.

  FIG. 8 is an explanatory diagram showing the conveyance state of the recording medium in the first embodiment. In FIG. 1, the transfer belt unit 460 and the image forming unit 430K are attached to the printer 10 in FIG. A state in which the printing paper 101 is nipped and conveyed and enters the image forming unit 410 is shown.

  In FIG. 8, the printing paper 101 is nipped and conveyed in the direction indicated by the arrow D in the figure by the driving roller 311 and the driven roller 312 constituting the conveying roller pair 310, and nipped and conveyed to the image forming unit 430K of the image forming unit. . In the drawing, the sheet facing surface 476 is inclined so that the distance from the belt conveyance unit 477 (transfer belt 461) is narrowed toward the image forming unit 430K of the image forming unit from the upstream side in the conveyance direction of the printing paper 101 indicated by the arrow D in the drawing. Since the image forming unit 430K is attached to the printer, the image forming unit 430K is close to the belt conveyance unit 477 (transfer belt 461), and guides the printing paper 101 to be electrostatically attracted to the transfer belt 461.

  The printing paper 101 is guided to the belt conveyance unit 477 (transfer belt 461) by the paper facing surface 476, so that the printing paper 101 is uniform and upstream of the photosensitive drum 431 in the conveyance direction of the printing paper 101 indicated by the arrow D in the drawing. Thus, it is surely electrostatically attracted to the transfer belt 461 and conveyed to the nip formed by the photosensitive drum 431 and the transfer roller 464.

  Here, the gap between the sheet facing surface 476 and the transfer belt 461 (belt conveyance unit 477) is the smallest, that is, the contact portion 476a as the closest portion closest to the transfer belt 461, and the printing sheet 101. And an opposing surface upstream portion 476k serving as an entrance. Since the contact portion 476 a is in contact with the transfer belt 461, the conveyed printing paper 101 can be adsorbed to the transfer belt 461.

  The closest contact portion is most preferably in contact with the transfer belt 461. However, a gap may be formed between the transfer belt 461 and the transfer belt 461 as long as the printing paper 101 can be adsorbed to the transfer belt 461. Preferably it is 2.0 mm or less. Here, the gap between the closest portion and the transfer belt 461 is set to 2.0 mm or less. If the gap is larger than 2.0 mm, the conveyed printing paper 101 is loosened, and the printing paper. This is because 101 cannot be sufficiently adsorbed to the transfer belt 461.

  In the present embodiment, the closest portion of the sheet facing surface 476 is described as the contact portion 476a formed by the inclined surface that contacts the transfer belt 461. However, as shown in FIG. You may make it comprise with a certain roller 476b. In this case, since the closest part is comprised with the rotary body, the effect which suppresses unnecessary wear is acquired.

  As described above, in the first embodiment, by forming the paper facing surface close to the transfer belt in the handle portion of the transfer belt unit, the leading edge of the printing paper to be conveyed is prevented from being lifted, and the printing paper is It is possible to reliably attract the transfer belt to the transfer belt, and it is possible to improve the printing quality by improving the conveyance accuracy of the printing paper.

Also, the printing paper generated when the printing paper is conveyed to the nip formed by the photosensitive drum and the transfer roller by electrostatically attracting the printing paper to the transfer belt uniformly upstream of the photosensitive drum. The effect that wrinkles can be prevented is obtained.
Further, it is possible to prevent the printing paper from being electrostatically attracted to the transfer belt and to be conveyed while the leading end is lifted from the transfer belt and collide with the photosensitive drum.

In addition, since the gripping portion of the transfer belt unit serves as the sheet facing surface for guiding the printing sheet, the apparatus can be reduced in size and the number of parts can be reduced.
Furthermore, since the handle portion also positions and fixes the transfer belt unit 460, it is possible to obtain an effect that the fixing belt can be reduced and the transfer belt unit can be easily detached from the apparatus.

The configuration of the second embodiment is different from the configuration of the first embodiment in the configuration of the transfer belt unit. The configuration of the second embodiment will be described with reference to FIGS. 10, 11 and 12. FIG. Note that parts similar to those of the first embodiment described above are denoted by the same reference numerals and description thereof is omitted.
10 is a perspective view of the transfer belt unit in the second embodiment, FIG. 11 is a side view of the transfer belt unit and the image forming unit in the second embodiment, and FIG. 12 is a transfer belt unit and an image in the second embodiment. It is sectional drawing of a formation unit. Note that a configuration for forming an image in the image forming unit is not directly related to the present invention, and thus will be omitted.

  The handle portion 480 includes a suction roller 481 that is rotatably supported in a recess formed upstream of the contact portion 476a of the paper facing surface 476 in the conveyance direction of the printing paper. The suction roller 481 is a rotating body that sucks the printing paper onto the transfer belt 461. The rotation shafts on the left and right ends are pivotally supported by suction roller bearings 482 and 483, respectively, and can move in a direction approaching / separating the transfer belt 461. It is arranged.

When the handle portion 480 is used as a grip portion, the suction roller bearings 482 and 483 are respectively separated from the transfer belt 461 by a biasing spring (not shown) so that the suction roller 481 does not protrude from the paper facing surface 476 toward the transfer belt 461. It is biased in the direction of separating. As in the first embodiment, the handle portion 480 is provided on the most upstream side of the transfer belt unit 460 in the conveyance direction of the printing paper indicated by the arrow A in the drawing.
Further, the tension roller 463 provided in the transfer belt unit 460 includes a shaft portion 463a shown in FIG. 10 and a shaft portion 463b shown in FIG.

The handle portion 480 is formed with a slide portion 475a and a slide portion 475b that are orthogonal to the straight line connecting the shaft portion 463a and the shaft portion 463b and engage with the protruding shaft portion 463a and the shaft portion 463b, respectively. 480 is movable in a state in which the slide portion 475a and the slide portion 475b are engaged with the shaft portion 463a and the shaft portion 463b.
The handle portion 480 includes a spring 469R and a spring 469L that urge the shaft portion 463a and the shaft portion 463b along the longitudinal direction of the slide portion 475a and the slide portion 475b, and the spring 469R and the spring 469L support the handle portion 480. It is disposed so as to be biased in a direction away from the transfer belt 461 (a direction indicated by an arrow B in the figure).

When the image forming unit 430K is attached to the printer 10, the upper portion of the handle portion 480 is moved so that the slide portion 475a and the slide portion 475b move the handle portion 480 with the shaft portion 463a and the shaft portion 463b engaged. The exterior frame 440 shown in FIG.
Further, the image forming unit 430K includes a lower frame 441 that contacts the upper portions of the suction roller bearings 482 and 483 and moves the suction roller bearings 482 and 483 in a direction close to the transfer belt 461 when mounted on the printer. ing.

  The transfer belt unit 460 is attached to the printer 10 at both ends of the handle portion 480 (substantially below the slide portion 475a and the slide portion 475b), and when the printer belt 10 is moved by being pressed by the exterior frame 440 of the image forming unit 430K. Positioning portions 472 and 473 as recessed portions to be engaged are respectively provided on positioning posts 470 and 471 as projections formed on both sides of the frame. In FIG. 11, the positioning post 470 is formed on the opposite side of the positioning post 471.

  The sheet facing surface 476 of the handle portion 480 and the suction roller 481 are moved when the moving portion 440p of the exterior frame 440 of the image forming unit 430K comes into contact with the abutting portion 467p on the upper portion of the handle portion 480 and the handle portion 480 moves. The printing paper is brought close to the transfer belt 461 and comes into contact with the upper surface of the printing paper conveyed by the pair of conveyance rollers 310 disposed on the upstream side in the conveyance direction of the printing paper, and the printing paper is directed to the belt conveyance unit 477 (transfer belt 461). It is arranged to guide.

Therefore, in this embodiment, the contact portion 476a of the sheet facing surface 476 and the suction roller 481 constitute the closest portion that contacts the printing paper.
Since the printer control configuration is the same as that of the first embodiment, a description thereof will be omitted.

The operation of the above configuration will be described. Note that the operation of the printer is the same as that of the first embodiment, and a description thereof will be omitted.
The operation of the transfer belt unit and the image forming unit will be described with reference to FIG. 2 based on the explanatory view showing the operation of the transfer belt unit and the image forming unit in the second embodiment of FIG.

  FIG. 13 is a side sectional view showing operations of the transfer belt unit 460 and the image forming unit 430K when the image forming unit 430K is inserted into the printer 10 in a state where the transfer belt unit 460 is already stacked on the printer 10. FIG. 13A shows a state before the image forming unit 430K is inserted into the printer 10, and FIG. 13B shows a state where the image forming unit 430K is inserted into the printer 10 and the lower frame of the image forming unit 430K. FIG. 13C shows a state in which the image forming unit 430K is inserted into the printer 10. FIG. 13C shows a state in which 441 is in contact with the upper portions of the suction roller bearings 482 and 483 of the transfer belt unit 460.

In a state before the image forming unit 430K is inserted into the printer 10, the handle portion 480 of the transfer belt unit 460 is biased by the spring 469L and the spring 469R shown in FIG. 1, and the sheet facing surface 476 is moved to the belt conveying portion 477 ( It is separated from the transfer belt 461).
Further, the suction roller 481 is housed in a recess formed in the paper facing surface 476 by the suction roller bearings 482 and 483 being biased by a biasing spring (not shown) and is prevented from protruding. Thereby, when the transfer belt unit 460 is detached from the printer 10, it is possible to prevent the operator's hand or the like from coming into contact with the suction roller 481.

When the image forming unit 430K is inserted into the printer 10, the image forming unit 430K is guided in a direction indicated by an arrow C in FIG. 13 along an insertion guide (not shown) provided in the printer 10. At this time, when the image forming unit 430K is guided into the printer 10 and moves a predetermined amount, the moving part 440p of the exterior frame 440 comes into contact with the contact part 480p on the upper part of the handle part 480.
At this time, the lower frame 441 of the image forming unit 430K contacts and presses the upper portions of the suction roller bearings 482 and 483 of the transfer belt unit 460 so that the suction roller 481 comes close to the transfer belt 461 (belt conveyance unit 477). Moving.

  Thereafter, the handle portion 480 is pressed by the insertion of the image forming unit 430K, and is further pushed in such a direction that the sheet facing surface 476 of the handle portion 480 approaches the belt conveying portion 477 (transfer belt 461). At this time, the handle portion 480 is moved in a direction indicated by an arrow C in the drawing in which the image forming unit 430K moves while being guided by a guide portion (not shown) along the slide portions 475a and 475b with the shaft portions 463a and 463b as axes. Move in parallel.

  Further, when the image forming unit 430K is inserted into the printer 10 by a predetermined amount, the positioning portions 472 and 473 of the handle portion 480 are fitted to the positioning posts 470 and 471 formed in the printer 10, respectively, and the transfer belt. The unit 460 is positioned and fixed in the printer 10. At this time, the sheet facing surface 476 of the handle unit 480 moves so as to be close to the belt conveyance unit 477 (transfer belt 461).

Further, the distance that the lower frame 441 contacts and pushes the upper portions of the suction roller bearings 482 and 483 is a predetermined amount larger than the distance that the exterior frame 440 presses the handle portion 480 so that it does not protrude from the sheet facing surface 476. The adsorbing roller 481 that has been disposed is pushed into the lower frame 441 so that when the image forming unit 430K is completely inserted into the printer 10, it protrudes a predetermined amount from the paper facing surface 476 and transports printing paper. The following roller.
The suction roller 481 is moved so as to face the tension roller 463 via the transfer belt 461, and forms a nip portion with the tension roller 463.

When the image forming unit 430K is detached from the printer 10, the image forming unit 430K is guided in a direction opposite to the direction indicated by the arrow C in the drawing by being guided by a guide unit (not shown), and the image forming unit 430K and the image forming unit 430K The exterior frame 440 of the unit 430K is separated.
For this reason, the paper facing surface 476 is moved away from the belt conveying unit 477 (transfer belt 461) by the springs 469L and 469R that urge the handle unit 480. Thus, when the handle portion 480 moves, the positioning portions 472 and 473 are separated from the positioning posts 470 and 471, respectively, and the fixed state of the transfer belt unit 460 is released.

Further, when the image forming unit 430K is removed from the printer 10, the suction roller 481 is recessed by the suction roller bearings 482 and 483 formed by a biasing spring (not shown). It is accommodated in and prevented from protruding.
As described above, in a state in which the sheet facing surface 476 is separated from the belt conveyance unit 477 (transfer belt 461), the handle unit 480 serves as a holding unit for inserting and removing the transfer belt unit 460 with respect to the printer 10. The unit 460 can be inserted into and removed from the printer 10.

  In FIG. 13C, as in the first embodiment, the printing paper is nipped and conveyed in the direction indicated by the arrow D in the drawing by the driving roller 311 and the driven roller 312 constituting the conveying roller pair 310, and image formation is performed. The image forming unit 430K is nipped and conveyed. A sheet facing surface 476 inclined so that a distance from the belt conveying unit 477 (transfer belt 461) is narrowed toward the image forming unit 430K of the image forming unit from the upstream side in the conveying direction of the printing paper indicated by the arrow D in the drawing. When the image forming unit 430K is attached to the printer, the belt is close to the belt conveyance unit 477 (transfer belt 461), and the printing paper 101 is guided to the transfer belt 461. Thereafter, the printing paper is pressed by the suction roller 481 protruding from the paper facing surface 476 and is electrostatically attracted to the transfer belt 461.

  The printing paper 101 is guided to the belt conveyance unit 477 (transfer belt 461) by the paper facing surface 476 and the suction roller 481, so that the printing paper 101 is more uniformly and indicated by the arrow D in the drawing than the photosensitive drum 431. Upstream in the transport direction, it is reliably electrostatically attracted to the transfer belt 461 and transported to the nip portion formed by the photosensitive drum 431 and the transfer roller 464.

As described above, in the second embodiment, in addition to the effects of the first embodiment, the suction roller is provided on the paper facing surface close to the transfer belt in the handle portion of the transfer belt unit. There is an effect that electrostatic adsorption to the transfer belt can be performed with higher accuracy.
Further, when electrostatically attracting the printing paper to the transfer belt, the roller is used to prevent the paper facing surface and the transfer belt from being rubbed, and the effect of enabling stable belt feeding of the printing paper can be obtained. It is done.

  In the first embodiment and the second embodiment, the handle portion of the transfer belt unit is described on the upstream side of the black image forming unit. However, the present invention is not limited to this, and the image forming portion is not limited thereto. May be arranged upstream of the yellow, magenta, or cyan image forming unit.

In the first and second embodiments, the image processing method using four colors of black, yellow, magenta, and cyan is described as the image forming unit of the image forming unit. However, the present invention is not limited to this. In addition, the corresponding color, the number of image forming units, the image processing method, the arrangement, and the like can be changed as appropriate. Further, the image forming apparatus is not limited to a printer, and a copying machine using them, automatic document reading It is good also as an apparatus.
Further, in the first and second embodiments, the image forming apparatus has been described as a color printer, but it may be a monochrome printer.

DESCRIPTION OF SYMBOLS 10 Printer 100 Paper tray 101 Printing paper 102,321 Paper mounting plate 103 Lift up lever 104 Motor 200 Paper feeding part 201 Lifting detection part 202,323 Pickup roller 203 Feed roller 204,325 Retard roller 302,313 Paper sensor 303,310 Conveying roller pair 304, 311 Drive roller 305, 312 Driven roller 314 Write sensor 320 MPT
322 MPT paper feeding unit 324 MPT roller 410 Image forming unit 430 Image forming unit 431 Photosensitive drum 432 Charging roller 433 Exposure device 434 Developing roller 440 Exterior frame 441 Lower frame 460 Transfer belt unit 461 Transfer belt 462 Drive roller 463 Tension roller 463a, 463b Shaft portion 464 Transfer roller 467, 480 Handle portion 469 Spring 470, 471 Positioning post 472, 473 Positioning portion 475 Slide portion 476 Paper facing surface 477 Belt conveying portion 481 Adsorption roller 482, 483 Adsorption roller bearing 500 Fixing portion 600 Control portion

Claims (7)

An image forming apparatus comprising: an image forming unit that forms an image; and a transfer unit that transfers an image formed by the image forming unit to a medium,
The image forming unit is detachable from the image forming apparatus,
The transfer portion is
A transport member for transporting the medium;
Wherein when the image forming unit is mounted to move by being pressed by the image forming section, have a facing portion adjacent to the conveying member,
The facing portion is formed with an inclined surface that gradually narrows the gap with the transport member from the upstream side to the downstream side in the transport direction of the medium, and has a closest portion with the smallest gap with the transport member. Have
The image forming apparatus according to claim 1, wherein the closest portion is a suction roller that sucks the medium onto the transport member . The image forming apparatus according to claim 1 .
The image forming apparatus, wherein the closest portion is in contact with the conveying member. The image forming apparatus according to claim 1 , wherein:
The image forming apparatus, wherein the suction roller is supported by a movable bearing and moves when pressed by the image forming unit when the image forming unit is mounted. The image forming apparatus according to any one of claims 1 to 3 ,
A medium conveying means is provided on the upstream side in the medium conveying direction of the transfer unit,
The image forming apparatus according to claim 1, wherein the facing unit guides the medium conveyed by the medium conveying unit to a conveying member of the transfer unit. The image forming apparatus according to any one of claims 1 to 4 , wherein:
The image forming apparatus according to claim 1, wherein the facing portion is formed in a grip portion that grips the transfer portion. The image forming apparatus according to claim 5 .
The gripping portion determines a contact portion that contacts the mounted image forming portion, a guide portion that brings the facing portion closer to the transport member, and a position where the facing portion is closest to the transport member; An image forming apparatus having a positioning portion to be fixed. The image forming apparatus according to any one of claims 1 to 6 ,
The image forming apparatus, wherein the conveying member is an endless belt disposed to face the image forming unit.

Images