Conveyance device and image forming apparatus

Abstract

To obtain a conveyance device capable of suppressing occurrence of a conveyance failure of a recording medium to a transfer part, in comparison to when a contact pressure with the recording medium of a pair of conveyance rolls provided on a conveyance direction upper stream side of the recording medium than a pair of positioning rolls is constituted to be constant without depending on a type of the recording medium.SOLUTION: A conveyance device 60 comprises: a positioning roll 54 for conveying a recording medium P to a transfer part in predetermined timing; a conveyance roll 58 provided on a conveyance direction upstream side of the recording medium P of the positioning roll 54, and for conveying the recording medium P toward the positioning roll 54 in a rotation-stopping state; a guide part 62 provided on a conveyance direction downstream side of the recording medium P of the conveyance roll 58, and for guiding the recording medium P to the positioning roll 54; a position changeable mechanism 70 for changing a position of the guide part 62 according to a type of the recording medium P; and a pressure changeable mechanism 80 for changing a contact pressure of the conveyance roll 58 by interlocking with the guide part 62 whose position is changed by the position changeable mechanism 70.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a conveying device and an image forming apparatus. [Background technology]

[0002] A sheet conveying device including a first conveying means having a rotatable first conveying member and a second conveying member, and capable of clamping a sheet between the first conveying member and the second conveying member and conveying it in the sheet conveying direction, a second conveying means arranged downstream of the first conveying means in the sheet conveying direction and capable of correcting skew of the sheet by abutting against the downstream end of the sheet in the sheet conveying direction and capable of clamping the sheet and conveying it in the sheet conveying direction, and a switching means capable of switching the first conveying means between a first state in which the first conveying member and the second conveying member abut, a second state in which the first conveying member and the second conveying member abut with a higher abutment pressure than the first state, and a third state in which the first conveying member and the second conveying member are separated, has been known for some time (see, for example, Patent Document 1).

[0003] Also, an image forming apparatus including a supply roll that pays out and supplies paper stored in a storage section, a pair of abutting rolls that send the paper supplied from the supply roll to the image forming section after abutting the leading edge of the paper, a pair of transport rolls that are disposed on a transport path connecting the storage section and the abutting rolls and transport the paper supplied from the supply roll toward the abutting rolls, and a change means for changing the contact pressure of the contacting portion of the pair of transport rolls (see, for example, Patent Document 2). The change means changes the contact pressure of the transport rolls when a specific type of paper is supplied to a contact pressure lower than the contact pressure when paper other than the specific type is supplied. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-026453 A [Patent Document 2] JP 2019-182571 A Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention aims to obtain a conveying device that can suppress the occurrence of poor conveying of the recording medium to the transfer section, compared to a case in which the contact pressure of a pair of conveying rolls, which are located upstream of a pair of alignment rolls in the conveying direction of the recording medium, on the recording medium is configured to be constant regardless of the type of recording medium. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, the transport device of the first aspect of the present invention comprises a pair of alignment rolls that transport a recording medium to a transfer section at a predetermined timing, a pair of transport rolls that are provided upstream of the pair of alignment rolls in the transport direction of the recording medium and transport the recording medium toward the pair of alignment rolls that are in a stopped state of rotation, a guide section that is provided downstream of the pair of transport rolls in the transport direction of the recording medium and guides the recording medium to the pair of alignment rolls, a position variable mechanism that changes the position of the guide section depending on the type of recording medium, and a pressure variable mechanism that changes the contact pressure of the pair of transport rolls in conjunction with the guide section whose position has been changed by the position variable mechanism.

[0007] A transport device according to a second aspect of the present invention is the transport device according to the first aspect, wherein the position variable mechanism changes a position of the guide portion in accordance with the basis weight of the recording medium.

[0008] Furthermore, a third aspect of the conveying device according to the present invention is a conveying device of the first aspect, wherein when the recording medium is paper thinner than cardboard, the position variable mechanism changes the position of the guide section so that the space downstream of the pair of conveying rolls in the conveying direction of the recording medium is wider than when the recording medium is cardboard, and the pressure variable mechanism changes the contact pressure of the pair of conveying rolls to be lower than when the recording medium is cardboard.

[0009] In addition, a fourth aspect of the conveying device according to the present invention is a conveying device of the first aspect, wherein the pressure variable mechanism has two spring members having different spring forces, and the contact pressure of the pair of conveying rolls can be changed by using one or both of the two spring members.

[0010] In addition, a fifth aspect of the conveying device according to the present invention is the conveying device of the fourth aspect, wherein the two spring members are formed in a "U" shape and are configured to press both ends protruding axially outward of the shaft portion of one of the pair of conveying rolls toward the other conveying roll.

[0011] In addition, a sixth aspect of the image forming apparatus according to the present invention includes a conveying device of any one of the first to fifth aspects, a transfer unit that transfers a toner image onto a recording medium conveyed by the conveying device, and a fixing device that fixes the toner image transferred by the transfer unit onto the recording medium. Effect of the Invention

[0012] According to the first aspect of the invention, the occurrence of transport problems of the recording medium to the transfer section can be suppressed compared to a case where the contact pressure of a pair of transport rolls located upstream of a pair of alignment rolls in the transport direction of the recording medium is configured to be constant regardless of the type of recording medium.

[0013] According to the second aspect of the invention, the occurrence of transport problems of the recording medium to the transfer section can be suppressed compared to when the contact pressure of the pair of transport rolls against the recording medium is configured to be constant regardless of the basis weight of the recording medium.

[0014] According to the third aspect of the invention, even when the recording medium is paper thinner than cardboard, the occurrence of poor transport of the paper to the transfer section can be suppressed compared to when the position of the guide section is the same as when the recording medium is cardboard and the contact pressure of the pair of transport rolls is the same as when the recording medium is cardboard.

[0015] According to the fourth aspect of the invention, the configuration of the pressure variable mechanism can be simplified compared to when the pressure variable mechanism is configured with, for example, an electric actuator.

[0016] According to the fifth aspect of the invention, the spring members are easier to assemble than when both ends of the shaft portion of one of a pair of conveying rolls that protrude axially outward are pressed toward the other conveying roll by individual springs.

[0017] According to the sixth aspect of the invention, the occurrence of poor image quality caused by poor transport of the recording medium to the transfer section can be suppressed compared to a case where the contact pressure of a pair of transport rolls, which are located upstream of a pair of alignment rolls in the transport direction of the recording medium, on the recording medium is configured to be constant regardless of the type of recording medium. [Brief description of the drawings]

[0018] [Figure 1] 1 is a schematic side view illustrating an overall configuration of an image forming apparatus according to an embodiment of the present invention. [Diagram 2] 2 is a schematic perspective view showing a guide portion and a pressure variable mechanism of the transport device according to the embodiment. FIG. [Diagram 3] 11 is a schematic side view showing an enlarged view of a position variable mechanism when the conveying device according to the embodiment conveys thick paper. FIG. [Figure 4] 11 is a schematic side view showing an enlarged view of a state of a position variable mechanism when plain paper is transported by the transport device according to the embodiment. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. For ease of explanation, the arrow UP shown in Fig. 1 indicates the upward direction of the image forming apparatus 10, the arrow LH indicates the leftward direction of the image forming apparatus 10, and the front direction of the paper surface indicates the forward direction of the image forming apparatus 10. In addition, hereinafter, the upstream side in the transport direction of a recording paper P (see Figs. 3 and 4) as an example of a recording medium may be simply referred to as the "upstream side", and the downstream side in the transport direction may be simply referred to as the "downstream side".

[0020] 1, image forming apparatus 10 is, as an example, an electrophotographic type that forms a toner image on recording paper P. This image forming apparatus 10 includes, within an apparatus body 11, an image forming section 12, a storage section 14, a conveying section 16 (including a conveying device 60), and a fixing device 18. Each section of image forming apparatus 10 (image forming section 12, conveying section 16, and fixing device 18) will be described below.

[0021] <Image forming section> The image forming unit 12 has a function of forming a toner image on recording paper P. More specifically, the image forming unit 12 has a toner image forming unit 20 and an intermediate transfer device 30. In this embodiment, examples of recording paper P include cardboard and plain paper that is thinner than cardboard. In this embodiment, "cardboard" refers to paper having a basis weight of, for example, 300 g / m 2 The above is the paper.

[0022] [Toner image forming section] 1, a plurality of toner image forming units 20 are provided to form toner images for each color. In this embodiment, toner image forming units 20Y, 20M, 20C, and 20K for a total of four colors, yellow (Y), magenta (M), cyan (C), and black (K), are provided.

[0023] Since the toner image forming units 20 of each color have the same configuration, reference numerals are mainly given to the components of the yellow toner image forming unit 20Y in Fig. 1. In addition, toner supply devices 28Y, 28M, 28C, and 28K that supply toner to each developing device 26 described later are provided inside the device body 11.

[0024] The toner image forming unit 20 for each color has a photoconductor drum 22 that rotates in one direction (for example, counterclockwise in FIG. 1) with the front-rear direction as the axial direction. The toner image forming unit 20 for each color also has, in order from the upstream side in the rotation direction of the photoconductor drum 22, a charger 24, an exposure device 25, a developing device 26, and a removal device 27.

[0025] In the toner image forming units 20 for each color, the charger 24 charges the outer peripheral surface of the photoreceptor drum 22. Then, the exposure device 25 exposes the outer peripheral surface of the photoreceptor drum 22 charged by the charger 24 to light, forming an electrostatic latent image on the outer peripheral surface of the photoreceptor drum 22. The development device 26 develops the electrostatic latent image formed on the outer peripheral surface of the photoreceptor drum 22 by the exposure device 25, forming a toner image. Then, the removal device 27 removes the toner remaining on the outer peripheral surface of the photoreceptor drum 22 after the toner image is transferred to the transfer belt 40, which will be described later.

[0026] [Intermediate transfer device] 1, the intermediate transfer device 30 includes a primary transfer roll 32 as an example of a primary transfer body whose axial direction is the front-rear direction, a transfer belt 40 as an example of an intermediate transfer body, and a secondary transfer roll 44 as an example of a secondary transfer body whose axial direction is the front-rear direction. That is, the intermediate transfer device 30 is configured to primarily transfer toner images formed on the outer circumferential surfaces of the photoconductor drums 22 of each color by superimposing the toner images onto the transfer belt 40, and then secondarily transfer the superimposed toner images onto the recording paper P.

[0027] (Primary transfer roll) 1, the primary transfer roll 32 transfers the toner images formed on the outer peripheral surfaces of the photoconductor drums 22 of each color in a multi-layered manner onto the outer peripheral surface of the transfer belt 40 at a primary transfer position between the photoconductor drums 22 and the primary transfer roll 32. In this embodiment, a primary transfer voltage is applied between the primary transfer roll 32 and the photoconductor drums 22, so that the toner images formed on the outer peripheral surfaces of the photoconductor drums 22 are transferred in a multi-layered manner onto the outer peripheral surface of the transfer belt 40 at the primary transfer position.

[0028] (Transfer belt) 1, the transfer belt 40 is annular, with a toner image transferred to its outer peripheral surface, and its posture is determined by being wound around a drive roll 34, a tension roll 36, and a backup roll 38, whose axial direction is in the front-to-rear direction. The drive roll 34 is configured to be driven to rotate by a drive unit (not shown), and rotates the transfer belt 40 in the direction of arrow A at a predetermined speed. A cleaning device 42 that cleans the outer peripheral surface of the transfer belt 40 is provided on the opposite side of the drive roll 34 with the transfer belt 40 in between.

[0029] The backup roll 38 faces the secondary transfer roll 44 with the transfer belt 40 sandwiched therebetween. The contact area where the secondary transfer roll 44 and the transfer belt 40 come into contact with each other, in other words, the area where the recording paper P is sandwiched between the secondary transfer roll 44 and the transfer belt 40, forms a nip area. This nip area forms a secondary transfer position T, which is an example of a transfer section where a toner image is transferred from the transfer belt 40 to the recording paper P.

[0030] <Fixing device> 1, the fixing device 18 has a heating roll 46 as an example of a heating member with the front-rear direction as the axial direction, and a pressure roll 47 as an example of a pressure member with the front-rear direction as the axial direction. The fixing device 18 is configured to fix the toner image transferred to the recording paper P by the secondary transfer roll 44 to the recording paper P by sandwiching and heating and pressurizing the recording paper P between the heating roll 46 and the pressure roll 47 which rotate in opposite directions to each other. In addition, downstream of the fixing device 18, a discharge roll 48 is provided with the front-rear direction as the axial direction, for discharging the recording paper P with the fixed toner image to a discharge section 50 provided at the top of the device main body 11.

[0031] <Transportation section> 1, a plurality of storage sections 14 are provided at the bottom inside the device main body 11, in which recording paper P is stored by size and type. A paper feed roll 51 is provided downstream of each storage section 14, with its axial direction extending in the front-to-rear direction, for sending out the recording paper P stored in the storage section 14 to the transport path of the transport section 16, and a plurality of pairs of transport rolls 52 are provided downstream of the paper feed roll 51, with their axial direction extending in the front-to-rear direction, for rotating in opposite directions to each other to transport the recording paper P one sheet at a time.

[0032] Downstream of the most downstream pair of transport rolls 52, a pair of alignment rolls 54 is provided with its axis extending in the front-rear direction, for transporting the recording paper P supplied from the storage unit 14 to the secondary transfer position T at a predetermined transfer timing. When the rotation of the pair of alignment rolls 54 is stopped, the recording paper P is sandwiched between the pair of transport rolls 52 and transported, forming a so-called loop of the recording paper P on the upstream side to correct the skew, and the recording paper P with the skew corrected is sent to the secondary transfer position T where the transfer belt 40 and the secondary transfer roll 44 come into contact with each other by the pair of alignment rolls 54 rotating in opposite directions, in accordance with the transfer timing.

[0033] Further, on the left side of the discharge rolls 48, a pair of transport rolls 56 and a pair of transport rolls 58 are provided with their axial direction extending in the front-rear direction in order to transport the recording paper P again to the alignment rolls 54 during double-sided printing in which an image is also formed on the back side of the recording paper P. A plurality of pairs of transport rolls 56 are provided, while a single pair of transport rolls 58 is provided.

[0034] The recording paper P is transported along a reversing path by multiple pairs of transport rolls 56 and turned over, and the recording paper P is transported again by the pair of transport rolls 58 located most downstream toward the pair of alignment rolls 54 whose rotation is stopped. Note that, by this pair of transport rolls 58 transporting the recording paper P while sandwiching it, a so-called loop is formed by the recording paper P on the upstream side of the alignment rolls 54 whose rotation is stopped, and the skew of the recording paper P is corrected.

[0035] [Transportation device] Next, the conveying device 60 in the conveying section 16 of the image forming apparatus 10 having the above-mentioned configuration will be described in more detail.

[0036] As shown in Figures 2 to 4, the conveying device 60 includes a pair of alignment rolls 54 (see Figures 3 and 4), a pair of conveying rolls 58, a guide section 62 provided downstream of the pair of conveying rolls 58 and guiding the recording paper P to the pair of alignment rolls 54, a position variable mechanism 70 (see Figures 3 and 4) that changes the position of the guide section 62 depending on the type of recording paper P, and a pressure variable mechanism 80 that changes the contact pressure of the pair of conveying rolls 58 in conjunction with the guide section 62 whose position has been changed by the position variable mechanism 70.

[0037] 2, a plurality of pairs of transport rolls 58 are arranged at predetermined intervals in the front-rear direction, and one (upper) transport roll 58A is rotatably supported at both ends 59A of a shaft portion 59 protruding axially outward by a support member 64A provided on an upper guide member 64 that constitutes a transport path for the recording paper P. The other (lower) transport roll 58B (see FIGS. 3 and 4) is rotatably supported by a support member (not shown) provided on a lower guide member 63 (see FIGS. 3 and 4) that constitutes a transport path for the recording paper P.

[0038] The pair of transport rolls 58 is configured such that one transport roll 58A is biased toward the other transport roll 58B, thereby generating contact pressure. Specifically, contact pressure is generated between the pair of transport rolls 58 by the biasing forces of two spring members 82 and 84 constituting the pressure variable mechanism 80.

[0039] The two spring members 82, 84 are formed in a substantially "U" shape with different sizes and an opening on the lower side in a plan view, and are arranged on the inside and outside. That is, the spring members 82, 84 are configured to press both ends 59A of the shaft portion 59 protruding axially outward of one transport roll 58A from above toward the other transport roll 58B, and are arranged on the inside and outside of both ends 59A in the axial direction.

[0040] The upper guide member 64 is provided with a flat beam member 65 extending in the front-rear direction with the vertical direction as the normal direction, and a pair of flat support ribs 66 with the front-rear direction as the normal direction are provided downward on the lower surface of the beam member 65. Each support rib 66 is located above both ends 59A of the shaft portion 59 of one of the transport rolls 58A, and a cylindrical locking protrusion 66A is integrally provided to protrude from the approximately vertical center of the inner surfaces of the opposing support ribs 66. A pair of flat locking ribs 67 with the front-rear direction as the normal direction are provided downward on the lower surface of the beam member 65 between the pair of support ribs 66.

[0041] Therefore, the inner spring member 82 has a bifurcated lower end 82A that contacts both ends 59A of the shaft portion 59 of one of the transport rolls 58A from above, while the bifurcated middle portion 82B contacts the locking projections 66A from below, and the upper end connecting portion 82C is locked to the pair of locking ribs 67, thereby pressing (biasing) both ends 59A of the shaft portion 59 from above toward the other transport roll 58B. Note that the pair of locking ribs 67 are formed with cutout portions 67A into which the connecting portions 82C of the inner spring member 82 fit, and are configured so that the connecting portions 82C do not come off the locking ribs 67.

[0042] On the other hand, the outer spring member 84 has a bifurcated lower end 84A that contacts both ends 59A of the shaft portion 59 of one of the transport rolls 58A from above, while the bifurcated middle portion 84B contacts the locking projection 66A from below, and the upper end connecting portion 84C is locked to the upper end portion above the notch 67A of the locking rib 67, thereby pressing (biasing) both ends 59A of the shaft portion 59 from above toward the other transport roll 58B. The lower end 84A of the outer spring member 84 extends downward further than the lower end 82A of the inner spring member 82, and contacts the upper surface of the guide portion 62.

[0043] The guide portion 62 is formed in a generally flat plate shape extending in the front-rear direction with the up-down direction as the normal direction, and its lower surface, which is shaped like an attacking angle and bulges downward in the side cross-sectional views shown in Figures 3 and 4, constitutes a part of the conveying path. That is, the lower surface of the guide portion 62 and the upper surface of a lower guide portion 78 (described later) guide the recording paper P to the pair of alignment rolls 54. The guide portion 62 is configured to be movable up and down.

[0044] 2, the outer surfaces of the lower ends of a pair of support ribs 66 adjacent in the front-rear direction are connected by a flat connecting member 68 extending in the front-rear direction with the up-down direction as the normal direction, and a substantially rectangular flat reinforcing member 69 is installed between the lower surface of the connecting member 68 and the upper surface of the guide part 62 via a hinge part 69A with the left-right direction as the rotation axis direction. In other words, the guide part 62 is configured to move rearward while rising.

[0045] 3 and 4, one end (upper end) 72A of a rod-shaped link member 72 configured to be movable along the up-down direction is attached to each of the front-rear end portions of the guide portion 62 via a conversion structure that converts up-down movement into front-rear movement. The other end (lower end) 72B of the link member 72 is configured to be constantly in contact with the circumferential surface of a flat-plate cam member 74 at least by its own weight (preferably biased downward).

[0046] The conversion structure for converting the movement in the up-down direction into the movement in the front-rear direction is not particularly limited. For example, although not shown, a conversion structure may be a structure in which a long hole extending diagonally downward and rearward in a side view from the left-right direction is formed in both front-rear direction ends of the guide part 62, and a cylindrical pin protruding from the upper end of the link member 72 is slidably fitted into the long hole.

[0047] The cam member 74 is fixed to both axial ends of a shaft 76 whose axial direction is the front-rear direction, and is configured to rotate integrally with the rotation of the shaft 76. The link member 72 and the cam member 74 provided on the shaft 76 are an example of a position variable mechanism 70. In addition, a lower guide portion 78 that guides the recording paper P to the alignment roll 54 together with the guide portion 62 is provided on the right side of the shaft 76.

[0048] 3, when the portion where the distance between the outer circumferential surface of the shaft 76 and the outer circumferential surface of the cam member 74 is the smallest is located on the upper side, the link member 72 takes the lower position, the guide portion 62 takes the lowered position, and the biasing force (pressing force) of the two spring members 82, 84 is applied to both ends 59A of the shaft portion 59 of one of the transport rolls 58A. In other words, the contact pressure between the pair of transport rolls 58 is maximized.

[0049] As shown in FIG. 4, when the part where the distance between the outer circumferential surface of the shaft 76 and the outer circumferential surface of the cam member 74 is greatest is located on the upper side, the link member 72 takes up an upper position, so that the guide portion 62 moves rearward while rising to take up an elevated position, and moves only the bifurcated lower end portion 84A of the outer spring member 84 upwardly away from both ends 59A of the shaft portion 59 of one of the conveying rolls 58A.

[0050] In other words, at this time, only the spring force (pressing force) of the inner spring member 82 is applied to both ends 59A of the shaft portion 59 of one of the conveying rolls 58A, and the pressing force (contact pressure of the pair of conveying rolls 58) applied to both ends 59A of the shaft portion 59 of the one of the conveying rolls 58A is reduced.

[0051] In this way, the contact pressure of the pair of transport rolls 58 can be changed by selecting and using one or both of the two spring members 82, 84 through the vertical movement of the guide portion 62. Note that the pair of transport rolls 58 are configured such that only the contact pressure is changed, and the pair of transport rolls 58 are always maintained in contact due to the biasing force of the inner spring member 82 that does not separate from both ends 59A of the shaft portion 59 of at least one of the transport rolls 58A.

[0052] Next, the operation of the transport device 60 according to this embodiment having the above-mentioned configuration will be described.

[0053] In general, when the recording paper P is thick paper, it is better for the contact pressure of the pair of transport rolls 58 to be high and for the space between the lower surface of the guide portion 62 and the upper surface of the lower guide portion 78 to be narrow. That is, while the thick paper is transported by the pair of transport rolls 58, the leading edge of the thick paper is abutted against the pair of alignment rolls 54 whose rotation is stopped, and a loop for skew correction is formed between the pair of transport rolls 58 and the pair of alignment rolls 54, and in the case of thick paper, it is better for the space for forming the loop to be narrow.

[0054] Therefore, when the recording paper P is thick paper, the guide section 62 takes the lowered position as shown in Fig. 3. If the thick paper (recording paper P) is transported in this state, the occurrence of transport problems of the thick paper against the pair of alignment rolls 54 is suppressed compared to a case in which the contact pressure of the pair of transport rolls 58 with respect to the recording paper P is configured to be constant regardless of the type (basis weight) of the recording paper P. Specifically, the parallelism of the thick paper is ensured, and the occurrence of wrinkles in the thick paper is suppressed or prevented. This suppresses or prevents the occurrence of transport problems of the thick paper to the secondary transfer position T, and suppresses or prevents the occurrence of poor image quality due to the transport problems.

[0055] On the other hand, when the recording paper P is plain paper which is thinner than cardboard, the contact pressure of the pair of transport rolls 58 does not need to be high, and it is preferable that the space between the lower surface of the guide portion 62 and the upper surface of the lower guide portion 78 is wide. That is, while the plain paper is transported by the pair of transport rolls 58, the leading edge of the plain paper is abutted against the pair of alignment rolls 54 whose rotation is stopped, and a loop for skew correction is formed between the pair of transport rolls 58 and the pair of alignment rolls 54, and in the case of plain paper, it is preferable that the space for forming the loop is wide.

[0056] If the recording paper P is plain paper, when its leading edge hits the pair of alignment rolls 54 that have stopped rotating, it may assume a convex upward position due to twisting or the like. If the loop-forming space described above is narrow, the paper will be relatively pushed downward by the lower surface of the guide portion 62, and will be pinched from above and below between the upper surface of the lower guide portion 78, which may cause further unnecessary twisting or the like.

[0057] Therefore, when the recording paper P is plain paper, as shown in Fig. 4, the guide portion 62 takes the raised position and separates the lower end portion 84A of the spring member 84 from both ends 59A of the shaft portion 59 of one of the transport rolls 58A. In this way, when plain paper passes through the transport path, the above-mentioned loop forming space is expanded and the contact pressure of the pair of transport rolls 58 is adjusted in a weakening direction.

[0058] In this state, when plain paper (recording paper P) is transported, poor transport of the plain paper against the pair of alignment rolls 54 is suppressed compared to when the contact pressure of the pair of transport rolls 58 against the recording paper P is configured to be constant regardless of the type (basis weight) of the recording paper P, i.e., when the position of the guide portion 62 is the same as when thick paper is used and the contact pressure of the pair of transport rolls 58 is the same as when thick paper is used.

[0059] Specifically, even if the plain paper assumes a convex upward position due to twisting or the like, the loop formation space is wide, so the paper is not relatively pushed downward by the lower surface of guide section 62, and the stiffness of the plain paper accompanying transport by transport roll 58 eliminates the twisting and ensures the parallelism of the plain paper, suppressing or preventing the occurrence of wrinkles in the plain paper. This suppresses or prevents the occurrence of poor transport of the plain paper to secondary transfer position T, and suppresses or prevents the occurrence of poor image quality due to such transport failure.

[0060] Furthermore, in this way, when the recording paper P is plain paper, the contact pressure of the pair of transport rolls 58 is adjusted to be reduced (to prevent excessive contact pressure), thereby suppressing wear on the transport rolls 58 themselves and reducing the power consumption of the motor (not shown) that drives the transport rolls 58.

[0061] In addition, since the loop formation space is expanded only when the recording paper P is thinner than cardboard (for example, regular paper), the size of the device body 11 of the image forming device 10 itself can be designed to match the loop formation space when the recording paper P is cardboard. This allows the image forming device 10 (device body 11) to be made smaller.

[0062] Also, because the pressure variable mechanism 80 is composed of two spring members 82, 84, the configuration of the pressure variable mechanism is simplified compared to a case where the pressure variable mechanism is configured to change the pressure by directly pressing both ends 59A of the shaft portion 59 with, for example, an electric actuator (not shown) etc. Moreover, since each of the spring members 82, 84 is a thin wire simply bent into a substantial "U" shape, they are inexpensive and advantageous in terms of manufacturing costs.

[0063] In addition, each spring member 82, 84 is formed in an approximately U-shape and configured to press both end portions 59A of the shaft portion 59 of one conveying roll 58A toward the other conveying roll 58B. This makes it easier to assemble each spring member 82, 84 than when both end portions 59A of the shaft portion 59 of one conveying roll 58A are pressed toward the other conveying roll 58B by individual springs (coil springs, torsion springs, etc.).

[0064] Furthermore, if one transport roll 58A is separated from the other transport roll 58B, the force of transporting the recording paper P to the alignment roll 54 when rotation is stopped (paper leading edge propulsion force) decreases, and the skew correction capability decreases. In contrast, the pair of transport rolls 58 in this embodiment always maintain a contact state, so the decrease in skew correction capability is suppressed or prevented compared to a configuration in which one transport roll 58A is separated from the other transport roll 58B.

[0065] The conveying device 60 according to the present embodiment has been described above with reference to the drawings, but the conveying device 60 according to the present embodiment is not limited to the one shown in the drawings, and can be appropriately modified in design within the scope of the present invention. For example, the recording paper P that is thinner than cardboard may be thin paper that is thinner than regular paper.

[0066] Also, the spring members 84 that are moved away from both ends 59A of the shaft portion 59 of one of the transport rolls 58A by the guide portion 62 may be arranged inside the spring members 82 that do not move away from both ends 59A of the shaft portion 59 of the one of the transport rolls 58A. Also, the guide portion 62 may be configured to rise while moving forward.

[0067] Furthermore, the pressure variable mechanism 80, which changes the contact pressure of the pair of conveying rolls 58 in conjunction with the guide section 62 whose position has been changed by the position variable mechanism 70, is not limited to being composed of two spring members 82, 84 formed in an approximately U-shape, but may be composed of spring members or actuators (not shown) of other shapes, etc., as long as the contact pressure of the pair of conveying rolls 58 is adjustable as described above.

[0068] (Additional Note) (((1))) A pair of alignment rolls that transport the recording medium to the transfer unit at a predetermined timing; a pair of conveying rolls that are provided upstream of the pair of alignment rolls in a conveying direction of the recording medium and convey the recording medium toward the pair of alignment rolls that are in a stopped state of rotation; a guide section provided downstream of the pair of transport rolls in a transport direction of the recording medium, the guide section guiding the recording medium to the pair of alignment rolls; a position varying mechanism for varying a position of the guide portion in accordance with a type of the recording medium; a pressure varying mechanism that varies a contact pressure between the pair of conveying rolls in conjunction with the guide portion whose position has been changed by the position varying mechanism; A conveying device comprising: (((2))) The conveying device according to (((1))), wherein the position variable mechanism changes the position of the guide portion depending on the basis weight of the recording medium. (((3))) When the recording medium is paper thinner than cardboard, the position variable mechanism changes a position of the guide portion so that a space on a downstream side of the pair of transport rolls in a transport direction of the recording medium is wider than that in the case of the thick paper; The conveying device according to ((1))) or (((2))), wherein the pressure variable mechanism changes the contact pressure of the pair of conveying rolls to be lower than that for the thick paper. (((4))) The pressure variable mechanism has two spring members with different biasing forces, The conveying device according to any one of (((1))) to (((3))), wherein the contact pressure of the pair of conveying rolls can be changed by using one or both of the two spring members. (((5))) The two spring members are formed in a U-shape and are configured to press both ends protruding axially outward of the shaft portion of one of the pair of transport rolls toward the other transport roll. (((4))) A conveying device as described in the above. (((6))) A conveying device according to any one of (((1))) to (((5))), a transfer unit that transfers a toner image onto the recording medium transported by the transport device; a fixing device that fixes the toner image transferred by the transfer unit onto the recording medium; An image forming apparatus comprising:

[0069] According to the conveying device of (((1))), the occurrence of poor conveying of the recording medium to the transfer section can be suppressed compared to a case in which the contact pressure of a pair of conveying rolls, which are provided upstream of a pair of alignment rolls in the conveying direction of the recording medium, on the recording medium is configured to be constant regardless of the type of recording medium. According to the conveying device of (((2))), the occurrence of poor conveying of the recording medium to the transfer section can be suppressed compared to a case in which the contact pressure of the pair of conveying rolls against the recording medium is constant regardless of the basis weight of the recording medium. According to the conveying device of (((3))), even when the recording medium is paper thinner than cardboard, the occurrence of poor conveying of the paper to the transfer section can be suppressed compared to when the position of the guide section is the same as when the recording medium is cardboard and the contact pressure of the pair of conveying rolls is the same as when the recording medium is cardboard. According to the transport device of (((4))), the configuration of the pressure variable mechanism can be simplified compared to when the pressure variable mechanism is configured with, for example, an electric actuator. According to the conveying device of (((5))), it is easier to assemble the spring members than when the device is configured so that both ends of the shaft portion of one of a pair of conveying rolls that protrude axially outward are pressed toward the other conveying roll by individual springs. According to the image forming device of (((6))), the occurrence of poor image quality due to poor transport of the recording medium to the transfer section can be suppressed, compared to a case in which the contact pressure of a pair of transport rolls, which are provided upstream of the pair of alignment rolls in the transport direction of the recording medium, with respect to the recording medium is configured to be constant regardless of the type of recording medium. [Explanation of symbols]

[0070] 10 Image forming device 18 Fixing device 54 Alignment roll 58 Transport roll 59 Shaft 59A both ends 60 Transport Equipment 62 Information Department 70 Position variable mechanism 80 Pressure variable mechanism 82 Spring material 84 Spring material P Recording paper (an example of a recording medium) T Secondary transfer position (example of transfer section)

Claims

1. A pair of alignment rolls that transport the recording medium to the transfer unit at a predetermined timing; a pair of conveying rolls that are provided upstream of the pair of alignment rolls in a conveying direction of the recording medium and convey the recording medium toward the pair of alignment rolls that are in a stopped state of rotation; a guide section provided downstream of the pair of transport rolls in a transport direction of the recording medium, the guide section guiding the recording medium to the pair of alignment rolls; a position varying mechanism for varying a position of the guide portion in accordance with a type of the recording medium; a pressure varying mechanism that varies a contact pressure between the pair of conveying rolls in conjunction with the guide portion whose position has been changed by the position varying mechanism; A conveying device comprising:

2. The conveying device according to claim 1 , wherein the position varying mechanism changes the position of the guide portion depending on the basis weight of the recording medium.

3. When the recording medium is paper thinner than cardboard, the position variable mechanism changes a position of the guide portion so that a space on a downstream side of the pair of transport rolls in a transport direction of the recording medium is wider than that in the case of the thick paper; The conveying device according to claim 1 , wherein the pressure varying mechanism changes the contact pressure between the pair of conveying rolls to be lower than that for the thick paper.

4. The pressure variable mechanism has two spring members with different biasing forces, 2. The transport device according to claim 1, wherein the contact pressure between the pair of transport rolls is changeable by using one or both of the two spring members.

5. The conveying device described in claim 4, wherein the two spring members are formed in a U-shape and configured to press both ends protruding axially outward of the shaft portion of one of the pair of conveying rolls toward the other conveying roll.

6. A conveying device according to any one of claims 1 to 5, a transfer unit that transfers a toner image onto the recording medium transported by the transport device; a fixing device that fixes the toner image transferred by the transfer unit onto the recording medium; An image forming apparatus comprising:

Images