Image forming device

Abstract

To provide an image forming device with good usability in opening a conveyance guide part.SOLUTION: An image forming device includes: a first conveyance guide part having a first roller, a first engagement part and a second engagement part; and a second conveyance guide part having a second roller that can come into contact with the first roller, a first engaged part that engages with the first engagement part, a second engaged part that engages with the second engagement part. A conveyance path along which a sheet is conveyed is formed in a state that the second conveyance guide part is positioned at a predetermined position relative to the first conveyance guide part. By moving the second conveyance guide part in a predetermined direction with respect to the first conveyance guide part, the positioning of the second conveyance guide part with respect to the first conveyance guide part is released, and the conveyance path is opened by rotating the second conveyance guide part relative to the first conveyance guide part.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to an image forming apparatus provided with a sheet conveyance guide section.

Background Art

[0002] In an image forming apparatus that forms an image on a recording material as a sheet using an image forming process such as an electrophotographic process, there is a conveyance guide section that can be opened and closed by a user in order to replace a conveyance roller or remove a jammed recording material. In such a conveyance guide section, as in Patent Document 1, there is a rotation shaft at one end on the upstream or downstream side in the recording material conveyance direction of the conveyance guide section, and a lock member for fixing the conveyance guide section is provided on the main body side or the conveyance guide section at the other end.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present invention relates to a configuration in which the conveyance guide section is opened to open the conveyance path, and an object thereof is to provide an image forming apparatus with good usability regarding opening the conveyance guide section.

Means for Solving the Problems

[0005] One of the inventions according to the present application is as follows.

[0006] An image forming apparatus for forming an image on a sheet, a first conveyance guide section having a first roller, a first engagement section, and a second engagement section, A second transport guide section having a second roller, a first engaged portion that engages with the first engaging portion, and a second engaged portion that engages with the second engaging portion, It has, With the second transport guide section positioned at a predetermined position relative to the first transport guide section, the first transport guide section and the second transport guide section form a transport path through which the sheet is transported, and the first roller and the second roller are in contact with each other in such a way that the sheet can be transported. With the first engaging portion and the first engaged portion engaged, the second transport guide portion is movable along a predetermined direction relative to the first transport guide portion such that the engagement between the second engaging portion and the second engaged portion is disengaged and the positioning of the second transport guide portion relative to the first transport guide portion is released. With the first engaging portion and the first engaged portion engaged, and the positioning of the second transport guide portion relative to the first transport guide portion released, the second transport guide portion is rotatable in an opening direction relative to the first transport guide portion so as to open the transport path. An image forming apparatus characterized by the following features. [Effects of the Invention]

[0007] According to the present invention, the positioning of the transport guide can be released by moving the transport guide itself, thus providing an image forming apparatus with good usability. [Brief explanation of the drawing]

[0008] [Figure 1] Cross-sectional view of an image forming apparatus according to the first embodiment. [Figure 2] Cross-sectional view of the double-sided transport section according to the first embodiment. [Figure 3] Side view of the double-sided transport unit according to the first embodiment. [Figure 4] Side view of the double-sided transport unit according to the first embodiment. [Figure 5] Side view of the double-sided transport unit according to the first embodiment. [Figure 6] Side view of the double-sided transport unit according to the first embodiment. [Figure 7] Side view of the duplex transport unit according to the first embodiment [Figure 8] Side view of the duplex transport unit according to the first embodiment [Figure 9] Side view of the duplex transport unit according to the first embodiment [Figure 10] Side view of the duplex transport unit according to the first embodiment [Figure 11] Side view of the duplex transport unit according to the first embodiment [Figure 12] Side view of the duplex transport unit according to the first embodiment [Figure 13] Side view of the duplex transport unit according to the first embodiment [Figure 14] Cross-sectional view of the duplex transport unit according to the first embodiment [Figure 15] External perspective view of the duplex transport unit according to the first embodiment [Figure 16] Cross-sectional view of the duplex transport unit according to the second embodiment [Figure 17] Side view of the duplex transport unit according to the second embodiment [Figure 18] Side view of the duplex transport unit according to the second embodiment [Figure 19] Side view of the duplex transport unit according to the second embodiment [Figure 20] Side view of the duplex transport unit according to the second embodiment [Figure 21] Side view of the duplex transport unit according to the second embodiment [Figure 22] Side view of the duplex transport unit according to the second embodiment [Figure 23] Detailed view of the duplex transport unit according to the second embodiment [Figure 24] Detailed view of the duplex transport unit according to the second embodiment [Figure 25] Side view of the duplex transport unit according to the third embodiment [Figure 26] Cross-sectional view of the image forming apparatus according to the fourth embodiment [Figure 27] Cross-sectional view of the transfer unit according to the fourth embodiment [Figure 28] Side view of the transfer unit according to the fourth embodiment [Figure 29] Side view of the transfer unit according to the fourth embodiment [Figure 30] Side view of the transfer section according to the fourth embodiment. [Figure 31] Side view of the transfer section according to the fourth embodiment. [Figure 32] Side view of the transfer section according to the fourth embodiment. [Modes for carrying out the invention]

[0009] The following descriptions of embodiments for carrying out the present invention will be made with reference to the drawings. It should be noted that the following embodiments are not intended to limit the scope of the claims, and not all combinations of features described in the embodiments are necessarily essential to the solution of the invention. [Examples]

[0010] The first embodiment is described below.

[0011] <Image forming apparatus> Figure 1 is a cross-sectional view showing an electrophotographic laser printer with double-sided image forming capabilities as an example of an image forming apparatus according to an embodiment. However, unless otherwise specifically stated, the dimensions, materials, shapes, and relative arrangements of the components described in this embodiment are not intended to limit the scope of this invention to those components alone. Furthermore, the image forming apparatus is not limited to laser printers, but may also be applied to other image forming apparatuses such as copiers and facsimile machines.

[0012] The image forming apparatus 101 shown in Figure 1 includes a sheet feeding unit, an image forming unit for forming an image on a sheet, a fixing unit, a paper discharge and reversing unit, and a double-sided transport unit.

[0013] The image forming apparatus 101 is equipped with a process cartridge 1 that is detachable from the main body of the apparatus. The process cartridge 1 consists of a photosensitive drum 2, a developing unit (not shown), a charging roller, and other processing means. A scanner unit 3 is positioned above the process cartridge 1 in the vertical direction, and the scanner unit 3 performs exposure on the photosensitive drum 2 based on an image signal.

[0014] After the photosensitive drum 2 is charged to a predetermined negative potential by a charging roller (not shown), an electrostatic latent image is formed on the photosensitive drum 2 by the scanner unit 3. This electrostatic latent image is inverted and developed by the developing unit in the process cartridge 1, and negatively polarized toner adheres to the electrostatic latent image, forming a toner image on the photosensitive drum 2.

[0015] The sheet feeding section includes a paper feed roller 4 mounted on the image forming apparatus 101 and a paper feed cassette 5 for storing sheets, which is detachable from the main body of the image forming apparatus 101. The sheets S stored in the paper feed cassette 5 are separated and fed one by one from the paper feed cassette 5 by the paper feed roller 4, which is rotated by the power of a paper feed drive unit (not shown). The fed sheets S are transported by a transport roller pair 6 to a registration roller pair 7, where the registration roller pair 7 performs skew correction and then transports them to the transfer section.

[0016] In the transfer section, a positive bias is applied to the transfer roller 8 by a bias application means (not shown). As a result, the toner image is transferred to the sheet S transported to the transfer section as an unfixed image.

[0017] The sheet S onto which the toner image has been transferred is transported to a fixing device 9 located downstream of the transfer section in the transport direction of the sheet S. The fixing device 9 fixes the toner image transferred to the sheet S and includes a heating roller 10, which is a fixing member heated by a heater (not shown), and a pressure roller 11, which is a pressing member that rotates in contact with the heating roller 10. The sheet S is held and transported by the fixing nip section formed by the heating roller 10 and the pressure roller 11, and the toner image is fixed to the surface of the sheet S by the application of heat and pressure to the sheet S.

[0018] The sheet S, on which the toner image has been fixed, is transported from the fuser unit 9 to the paper output reversal unit. The paper output reversal unit has a paper output roller 13, a paper output roller 14, a reversal roller 15, and a double-sided flapper 12. In the case of single-sided image formation (single-sided printing), the double-sided flapper 12 waits in a position (solid line position) that guides the sheet S to the paper output nip section formed by the paper output roller 13 and the paper output roller 14, and the sheet S is discharged onto the paper output tray 16 by the paper output roller and the paper output roller 14.

[0019] In addition, in the case of double-sided image formation (double-sided printing), the double-sided flapper 12 waits at a position (dotted line position) that guides it to the inversion nip section formed by the paper discharge roller 13 and the inversion roller 15, and the sheet S is transported to the inversion nip section by the fixing device 9. The paper discharge roller 13 rotates in the reverse direction by a rotation direction switching means (not shown) when the rear end of the sheet S reaches a predetermined position.

[0020] As a result, the sheet S passes through the double-sided transport roller pair 17 and the re-feed roller pair 18 with its trailing edge leading, and is re-feeded to the registration roller pair 7 in an inverted state. The double-sided transport roller pair 17 includes a first double-sided transport roller 17b and a second double-sided transport roller 17a, and the re-feed roller pair 18 includes a first re-feed roller 18a and a second re-feed roller 18b (Figure 2). Subsequently, the sheet S undergoes skew correction by the registration roller pair 7, transfer by the transfer roller 8, and fixing by the fuser device 9, similar to single-sided printing. Finally, the sheet S is discharged into the output tray 16 by the output roller 13 and output roller 14, completing double-sided printing.

[0021] <Double-sided transport unit> Next, the configuration of the double-sided transport unit 201 shown in Figure 1 will be explained using Figures 2 to 15. Figures 2 to 3 and Figures 7 to 9 are side views of the double-sided transport unit 201. Figures 4 to 6 and Figures 10 to 13 are enlarged views including at least one of the first engaging part, first engaged part, second engaging part, and second engaged part, which will be described later.

[0022] As shown in Figure 3, the double-sided transport unit 201 has a first transport guide unit 202 and a second transport guide unit 203, which are guide units. The first transport guide unit 202 and the second transport guide unit 203 form a transport path 21 through which the sheet S is transported. This transport path 21 is a transport path through which the sheet S is transported in order to form an image on the other side of a sheet S that has an image formed on one side.

[0023] The first transport guide section 202 is a guide section that guides the upper surface of the sheet S being transported, and is located above the second transport guide section 203 in the vertical direction. The second transport guide section 203 is a guide section that guides the lower surface of the sheet S being transported, and is located below the first transport guide section 202 in the vertical direction.

[0024] The first transport guide section 202 has a first double-sided transport roller 17b as the first roller and a first re-feed roller 18a as the third roller. The first transport guide section 202 also includes an elongated hole 202a as the first engaging part and a groove 202b as the second engaging part, with respect to a projection described later. The elongated hole 202a and groove 202b are provided on one end of the first transport guide section 202 with respect to the axial direction of the first double-sided transport roller 17b. The elongated hole 202a and groove 202b are also provided on the other end of the first transport guide section 202 with respect to the axial direction of the first double-sided transport roller 17b.

[0025] In Figures 2 and 3, the first transport guide section 202 is shown in a cross-sectional view from a direction intersecting the transport direction of the sheet S, so only one elongated hole 202a and one groove 202b are shown on one end. However, the other end of the first transport guide section 202 is also provided with one elongated hole 202a and one groove 202b.

[0026] The second transport guide section 203 includes a second double-sided transport roller 17a, which is a second roller that can move toward and away from the first double-sided transport roller 17b. Furthermore, it has a second re-feed roller 18b, which is a fourth roller. In addition, as shown in Figures 4(a) and (b), the second transport guide section 203 includes an engaging projection 203a, which is a first engaged part that engages with the first engaging part, and a positioning projection 203b, which is a second engaged part that engages with the second engaging part.

[0027] The engaging projection 203a and the positioning projection 203b are projections that protrude from the second transport guide section 203. The engaging projection 203a and the positioning projection 203b are provided on one end of the second transport guide section 203 with respect to the axial direction of the first double-sided transport roller 17b of the first transport guide section 202. The engaging projection 203a and the positioning projection 203b are also provided on the other end of the second transport guide section 203 with respect to the axial direction of the first double-sided transport roller 17b of the first transport guide section 202.

[0028] With the second transport guide section 203 positioned in a predetermined position relative to the first transport guide section 202, the first transport guide section 202 and the second transport guide section 203 form a transport path 21, and the first double-sided transport roller 17b and the second double-sided transport roller 17a come into contact with each other so that the sheet S can be transported. At this time, the first re-feed roller 18a and the second re-feed roller 18b also come into contact, and the sheet S can be transported. As shown in Figure 2, the second re-feed roller 18b is biased toward the first re-feed roller 18a by the re-feed roller spring 18c, which acts as a roller biasing section.

[0029] As shown in Figure 3, the state in which the first transport guide section 202 and the second transport guide section 203 are positioned in predetermined positions will be described in more detail. When the first transport guide section 202 and the second transport guide section 203 are positioned in predetermined positions, the engaging projection 203a is engaged with the elongated hole 202a, and the position of the engaging projection 203a is located on the right end side in the figure of the elongated hole 202a that extends in the direction of the transport path 21 of the sheet S.

[0030] When the second transport guide section 203 is positioned in a predetermined position relative to the first transport guide section 202, the positioning projection 203b engages with the groove 202b. Furthermore, the positioning projection 203b is positioned toward the back of the groove 202b. The positioning projection 203b is positioned in the groove 202b by the weight of the second transport guide section 203 and the reaction force of the second re-feed roller 18b biased by the re-feed roller spring 18c. In other words, the groove 202b receives the weight of the second transport guide section 203 and the reaction force of the second re-feed roller 18b biased by the re-feed roller spring 18c via the positioning projection 203b.

[0031] Next, we will explain how to open the double-sided transport unit 201. As shown in Figure 7, the double-sided transport unit 201 can open the transport path 21. Specifically, the engagement between the positioning projection 203b and the groove 202b is released, and the second transport guide unit 203 rotates relative to the first transport guide unit 202 around the engaging projection 203a, thereby opening the transport path 21. The direction in which the second transport guide unit 203 rotates relative to the first transport guide unit 202 at this time is called the opening direction. The direction opposite to the opening direction is called the closing direction.

[0032] At this time, the first double-sided conveying roller 17b and the second double-sided conveying roller 17a are separated by the movement of the second conveying guide section 203 in the opposite direction to the conveying path 21 (away from the conveying path 21).

[0033] If a sheet S gets jammed in the double-sided conveying section 201, the user or service technician can remove the jammed sheet S by opening the conveying path 21. Furthermore, the rollers attached to the first conveying guide section 202 and the second conveying guide section 203 can be replaced.

[0034] When the positioning projection 203b is positioned in the groove 202b, the second transport guide section 203 cannot rotate. On the other hand, when the engaging projection 203a and the elongated hole 202a of the second transport guide section 203 engage, and the positioning of the first transport guide section 202 and the second transport guide section 203 is released, the second transport guide section 203 can rotate relative to the first transport guide section 202. The opening direction is the direction in which the second transport guide section 203 rotates relative to the first transport guide section 202 by its own weight.

[0035] The positioning projection 203b can be released by removing the paper feed cassette 5 and moving the second transport guide section 203 in a predetermined direction relative to the first transport guide section 202 (translational movement). In this embodiment, the predetermined direction is the opposite direction to the transport direction (A1) of the sheet S. The transport direction of the sheet S referred to here is the transport direction of the sheet S by the first double-sided transport roller 17b and the second double-sided transport roller 17a. When the second transport guide section 203 is moved in the opposite direction, the position of the engaging projection 203a also moves to the left side (direction A2) of the elongated hole 202a in the diagram. In other words, the second transport guide section 203 can move in a predetermined direction (opposite direction) relative to the first transport guide section 202 while the engaging projection 203a and the elongated hole 202a are engaged. In other words, the second transport guide section 203 can move (translationally) so as to be displaced relative to the first transport guide section 202 in the transport direction of the sheet S and in the opposite direction, while the engaging projection 203a and the elongated hole 202a are engaged. As a result, the state in which the groove 202b and the positioning projection 203b are engaged and the state in which the engagement between the groove 202b and the positioning projection 203b is released can be switched.

[0036] Regarding the conveying direction of the sheet S, the engaging projection 203a and the elongated hole 202a are located upstream of the groove 202b and the positioning projection 203b. When moving the second conveying guide section 203, it can be moved by pushing the handle portion 203c, which is the pressed portion of the second conveying guide section 203 in Figure 2, in the direction of A2. By moving the second conveying guide section 203 along a predetermined direction (opposite direction), the engagement between the groove 202b and the positioning projection 203b is released, and the positioning of the second conveying guide section 203 relative to the first conveying guide section 202 is released. In other words, when the pressed portion is pushed, the second conveying guide section 203 moves in a direction that releases the engagement between the groove 202b and the positioning projection 203b.

[0037] Then, the engagement between the groove 202b and the positioning projection 203b is released, and the second transport guide section 203 rotates relative to the first transport guide section 202, thereby opening the transport path 21. In other words, the positioning of the second transport guide section 203 relative to the first transport guide section 202 is released, and the engagement between the groove 202b and the positioning projection 203b is released, causing the second transport guide section to rotate relative to the first transport guide section, thereby opening the transport path 21.

[0038] The engagement between the groove 202b and the positioning projection 203b when opening the transport path 21 will be explained in more detail. When the user pushes the handle portion 203c in the direction of A2, the positioning projection 203b moves up the first guide portion 202b1 of the groove 202b, as shown in Figure 4(a). At this time, as shown in Figure 4(b), the engaging projection 203a moves to the left in the elongated hole 202a. By continuing to push the handle portion 203c in the direction of A2, as shown in Figures 5(a), (b), and 6(a), (b), the positioning projection 203b moves over the tip portion 202b6 of the first guide portion with the engaging projection 203a and the elongated hole 202a engaged. Then, the positioning projection 203b moves in the direction of B in Figure 6(a), and the second transport guide portion 203 opens.

[0039] Next, the operation of closing the transport path 21 will be described. After the user lifts the second transport guide section 203 in the open state shown in Figure 7, the groove 202b and the positioning projection 203b engage, positioning the second transport guide section 203 relative to the first transport guide section 202, and the transport path 21 is closed. At this time, as shown in Figures 8 and 9, the rotational trajectories L1 and L2 of the positioning projection 203b differ depending on the position of the engaging projection 203a relative to the elongated hole 202a.

[0040] As shown in Figure 8, when the second transport guide section 203 is pulled out in the transport direction of the sheet S and lifted, the engaging projection 203a is located at one end of the elongated hole 202a, and the positioning projection 203b abuts against the fourth guide section 202b4 (Figure 10(a)). Also, as shown in Figure 9, when the second transport guide section 203 is pushed in the opposite direction and lifted, the engaging projection 203a is located at the other end of the elongated hole 202a, and the positioning projection 203b abuts against the third guide section 202b3 shown in Figure 11(a).

[0041] As shown in Figures 10(a) and (b), when the second transport guide section 203 is lifted with the engaging projection 203a positioned at one end of the elongated hole 202a and the positioning projection 203b in contact with the fourth guide section 202b4, the positioning projection 203b is lifted along the fourth guide section 202b4 in the direction of arrow A3 and comes into contact with the third guide section 202b3 shown in Figure 11(a). At this time, the second transport guide section 203 moves in the direction from the positioning position toward the release position.

[0042] As shown in Figures 11(a) and (b), with the engaging projection 203a engaged with the elongated hole 202a, the positioning projection 203b that has come into contact with the third guide portion 202b3 is lifted along the third guide portion 202b3 in the direction of arrow A4. At this time, the second transport guide portion 203 moves in the direction from the release position toward the positioning position. Subsequently, as the second transport guide portion 203 continues to be lifted, as shown in Figures 12(a) and (b), with the engaging projection 203a engaged with the elongated hole 202a, the positioning projection 203b reaches the abutment surface 202b5 of the groove 202b. At that time, the axis center 203b1 of the positioning projection 203b is configured to be located a distance L3 downstream in the transport direction from the tip of the first guide portion 202b6 of the groove 202b, as shown in Figure 13.

[0043] Furthermore, as shown in Figure 13, when the positioning projection 203b contacts the abutment surface 202b5 of the groove 202b, as shown in Figure 14, arrow A5-2, which indicates the direction of the reaction force of the refeed roller spring 18c acting on the axis center 203b1 of the positioning projection 203b, coincides with range W. Therefore, when the user releases the force while the positioning projection 203b is lifted up to the abutment surface 202b5, the positioning projection 203b is positioned in the groove 202b and the double-sided transport section 201 closes.

[0044] In this embodiment, the range W is the range between the line connecting the axis center 203b1 of the positioning projection 203b and the tip portion 202b6 of the first guide portion, and the perpendicular line of the second guide portion 202b2 of the groove 202b that passes through the axis center 203b1 of the positioning projection 203b.

[0045] When the second transport guide section 203 is positioned relative to the first transport guide section 202, the two parts (two contact points) of the positioning projection 203b contact a part of the first transport guide section 202 (the part that forms the groove 202b). The reaction force A5-2 acts to press the two contact points of the positioning projection 203b against the part of the first transport guide section 202 (the part that forms the groove 202b).

[0046] Furthermore, as shown in Figure 15, by attaching a label 203c1 with illustrations and text to prompt the user to operate the second transport guide section 203 to the handle section 203c, visibility and operability can be improved.

[0047] In this manner, with the engaging projection 203a and the elongated hole 202a engaged, the second transport guide section 203 can move between a positioning position and a release position along a predetermined direction relative to the first transport guide section 202.

[0048] As shown in Figure 3, when the second transport guide section 203 is in a position relative to the first transport guide section 202, the second transport guide section 203 is positioned relative to the first transport guide section 202. In this state, the groove 202b and the positioning projection 203b are engaged, and the rotation of the second transport guide section 203 in the opening direction relative to the first transport guide section 202 is restricted. In other words, with respect to the opening direction centered on the engaging projection 203a, a part of the first transport guide section 202 is downstream of a part of the second transport guide section 203.

[0049] Furthermore, when the second transport guide section 203 is positioned relative to the first transport guide section 202, the first double-sided transport roller 17b and the second double-sided transport roller 17a come into contact with each other so that the sheet S can be transported. In addition, the first transport guide section 202 and the second transport guide section 203 form a transport path 21.

[0050] On the other hand, as shown in Figures 6(a) and (b), when the second transport guide section 203 is in the released position relative to the first transport guide section 202, the engaging projection 203a and the elongated hole 202a engage, and the groove 202b and the positioning projection 203b are disengaged. In this state, the second transport guide section 203 is allowed to rotate in the opening direction relative to the first transport guide section. With the engaging projection 203a and the elongated hole 202a engaged, the transport path 21 is opened when the second transport guide section 203 rotates from the released position in the opening direction relative to the first transport guide section 202.

[0051] With the engaging projection 203a and the elongated hole 202a engaged, the second transport guide section 203 moves along a predetermined direction relative to the first transport guide section 202, disengaging the groove 202b from the positioning projection 203b. The positioning of the second transport guide section 203 relative to the first transport guide section 202 is also released. This predetermined direction can be called the direction from the positioning position to the release position. Furthermore, when the second transport guide section 203 moves from the positioning position to the release position, the second double-sided transport roller 17a moves relative to the first double-sided transport roller 17b. More specifically, the second double-sided transport roller 17a moves in a direction intersecting the rotation axis direction of the first double-sided transport roller 17b. Also, when the second transport guide section 203 is in the release position, the second double-sided transport roller 17a is separated from the first double-sided transport roller 17b.

[0052] In this embodiment, the second transport guide unit 203 is configured to move relative to the first transport guide unit 202 and the main body of the device, but the first transport guide unit 202 may also be configured to move relative to the second transport guide unit 203.

[0053] As described above, by moving the second transport guide section 203 itself relative to the first transport guide section 202, the positioning of the second transport guide section 203 relative to the first transport guide section 202 can be released, and the second transport guide section 203 can be rotated relative to the first transport guide section 202. By releasing the positioning of the guide section by moving the second transport guide section 203 itself relative to the first transport guide section 202, there is no need to release the lock of a separate component, resulting in improved usability. Furthermore, since there is no need to provide a separate locking component, costs can be reduced and the size can be miniaturized. In addition, by reducing the number of parts, it is less susceptible to the effects of tolerances, and the positioning accuracy of the second transport guide section 203 relative to the first transport guide section 202 is also improved. [Examples]

[0054] A second embodiment will be described using Figures 16 to 24. Figures 18 to 20 and 23 to 24 are enlarged views including at least one of the first engaging portion, the first engaged portion, the second engaging portion, and the second engaged portion.

[0055] The description of the configuration and functions, which are the same as in Example 1, will be omitted, and the characteristic features of this embodiment will be mainly described. The image forming apparatus in this embodiment has a biasing spring 304 as a biasing member that biases the second transport guide section 303 in the A1 direction, as shown in Figure 17.

[0056] <Double-sided transport unit> As shown in Figure 17, the engaging projection 303a provided on the upstream side of the second transport guide section 303 in the transport direction is held in the elongated hole 302a of the first transport guide section 302. Furthermore, a biasing spring 304 is provided between the spring holding section 303d of the second transport guide section 303 and the frame spring holding section 302c of the first transport guide section 302, acting as a biasing member that biases the second transport guide section 303 toward the transport direction of the sheet S. The direction in which the biasing spring 304 biases the second transport guide section 303 can also be described as the direction in which the positioning projection 303b is positioned by the groove 302b.

[0057] In this embodiment as well, by moving the second transport guide section 303 along a predetermined direction (opposite direction), the engagement between the groove 302b and the positioning projection 303b is released, and the positioning of the second transport guide section 303 relative to the first transport guide section 302 is released. The direction in which the biasing spring 304 biases the second transport guide section 303 can be said to be the direction opposite to the predetermined direction.

[0058] As shown in Figure 18(a), the second transport guide section 303 is subjected to a reaction force A5-3 from the refeed roller spring 18c, which applies pressure to the second refeed roller 18b that forms a nip with the first refeed roller 18a. In addition, three forces act on it: the biasing force A6 from the biasing spring 304 and gravity A7 due to the weight of the second transport guide section 303 itself. As shown in Figure 18(b), when the positioning projection 303b is held in the groove 302b, the arrow indicating the direction of the resultant force C acting on the axial center 303b1 of the positioning projection 303b coincides with the range X.

[0059] As a result, the positioning projection 303b is reliably positioned by the groove 302b. When the second transport guide section 303 is positioned relative to the first transport guide section 302 and the positioning projection 303b is engaged with the groove 302b, the positioning projection 303b contacts the contact surfaces 302b1 and 302b2 of the first transport guide section 302. Range X is the range between the line connecting the point where the positioning projection 303b and the contact surface 302b1 contact and the axis center 303b1, and the line connecting the point where the positioning projection 303b and the contact surface 302b2 contact and the axis center 303b1. When the second transport guide section 303 is positioned relative to the first transport guide section 302, the two parts (two contact parts) of the positioning projection 303b contact a part of the first transport guide section 302 (the part that forms the groove 302b). The reaction force A5-3 acts to press the two contact points of the positioning projection 303b against a part of the first transport guide section 302 (the part that forms the groove 302b). The resultant force C also acts to press the two contact points of the positioning projection 303b against a part of the first transport guide section 302 (the part that forms the groove 302b).

[0060] The operation of opening the second transport guide section 303 will now be explained. The second transport guide section 303 has a handle section 303c, and this handle section 303c allows the second transport guide section 303 to be pushed in the direction of arrow A2, as shown in Figure 16.

[0061] By pushing the second transport guide section 303 in the A2 direction, the positioning projection 303b moves upstream in the transport direction of the sheet S from the contact surface 302b2 of the groove section 302b, as shown in Figure 19(a). At this time, as shown in Figure 19(b), the engaging projection 303a moves upstream within the elongated hole 302a. Subsequently, as shown in Figure 20(a), the positioning projection 303b of the second transport guide section 303 passes the tip portion 302b4 of the first guide section.

[0062] At this time, as shown in Figures 20(a), (b), and (c), the second transport guide section 303 is subjected to the operating force A8, the biasing force A6, and the weight A7 of the second transport guide section 303 itself. Due to the resultant force D of these three forces, the second transport guide section 303 opens up as shown in Figure 21.

[0063] Next, the operation of closing the second transport guide section 303 will be described. When lifting the second transport guide section 303 in the open state shown in Figure 21, the engaging projection 303a can move relative to the elongated hole 302a, as shown in Figure 22. L4 represents the rotational trajectory of the positioning projection 303b. As shown in Figure 22, the second transport guide section 303 is lifted from a state biased toward the downstream side in the transport direction by the biasing force A6 of the biasing spring 304.

[0064] At this time, as shown in Figures 23(a) and (b), the positioning projection 303b, with its engaging projection 303a engaged with the elongated hole 302a, strikes the fifth guide portion 302b3 of the groove 302b along the rotational trajectory L4. Furthermore, as shown in Figure 23(a), an operating force A9 acts on the second transport guide portion 303, lifting it up. The second transport guide portion 303 is lifted along the fifth guide portion 302b3 in the direction of arrow A3, resisting its own weight A7.

[0065] Subsequently, as shown in Figures 24(a) and (b), with the engaging projection 303a engaged with the elongated hole 302a, the positioning projection 303b of the second transport guide section 303 passes the tip portion 302b4 of the first guide section. At this time, in addition to the operating force A9 and its own weight A7, the second transport guide section 303 is also subjected to a biasing force A6 from the biasing spring 304, and this biasing force A6 causes the positioning projection 303b to move in the direction of the resultant force E shown in Figure 24(c).

[0066] As shown in Figure 24(d), the positioning projection 303b, which has moved in the direction of the resultant force E, moves along the contact surface 302b1 by the resultant force E' of the biasing force A6 and its own weight A7, without requiring an operating force A9, and is positioned in the groove 302b by the resultant force C mentioned above.

[0067] In this manner, with the engaging projection 303a and the elongated hole 302a engaged, the second transport guide section 303 can move between a positioning position and a release position along a predetermined direction relative to the first transport guide section 302.

[0068] As shown in Figure 17, when the second transport guide section 303 is in a position relative to the first transport guide section 302, the second transport guide section 303 is positioned relative to the first transport guide section 302. In this state, the groove 302b and the positioning projection 303b are engaged, and the rotation of the second transport guide section 303 in the opening direction relative to the first transport guide section 302 is restricted. In other words, with respect to the opening direction centered on the engaging projection 303a, a part of the first transport guide section 302 is downstream of a part of the second transport guide section 303.

[0069] Furthermore, when the second transport guide section 303 is in a position relative to the first transport guide section 302, the first double-sided transport roller 17b and the second double-sided transport roller 17a come into contact with each other so that the sheet S can be transported. In addition, the first transport guide section 302 and the second transport guide section 303 form a transport path 21.

[0070] On the other hand, as shown in Figures 20(a) and (b), when the second transport guide section 303 is in the released position relative to the first transport guide section 302, the engaging projection 303a and the elongated hole 302a engage, and the groove 302b and the positioning projection 303b are disengaged. In this state, the second transport guide section 303 is allowed to rotate in the opening direction relative to the first transport guide section. With the engaging projection 303a and the elongated hole 302a engaged, the transport path 21 is opened when the second transport guide section 303 rotates from the released position relative to the first transport guide section 302 in the opening direction.

[0071] With the engaging projection 303a and the elongated hole 302a engaged, the second transport guide section 303 moves along a predetermined direction relative to the first transport guide section 302, disengaging the groove 302b from the positioning projection 303b. The positioning of the second transport guide section 303 relative to the first transport guide section 302 is also released. This predetermined direction can be called the direction from the positioning position to the release position. Furthermore, when the second transport guide section 303 moves from the positioning position to the release position, the second double-sided transport roller 17a moves relative to the first double-sided transport roller 17b. More specifically, the second double-sided transport roller 17a moves in a direction intersecting the rotation axis direction of the first double-sided transport roller 17b. Also, when the second transport guide section 303 is in the release position, the second double-sided transport roller 17a is separated from the first double-sided transport roller 17b.

[0072] Furthermore, the biasing spring 304 biases the second transport guide section 303 in the direction from the release position toward the positioning position.

[0073] As described above, when a biasing force A6 is applied by the biasing spring 304 in a direction opposite to the pressing direction, the operating force A9 after passing the tip portion 302b4 of the first guide portion can be omitted, and the positioning projection 303b can be held in the groove portion 302b. According to this embodiment, it is possible to provide an image forming apparatus having a transport guide portion that simplifies user operation and has excellent usability. [Examples]

[0074] Figure 25 is a side view showing the configuration of Embodiment 3. Figure 25(a) shows the second transport guide section 403 in a closed state, and (b) shows the second transport guide section 403 in an open state. As shown in Figure 25, the second transport guide section 403 is provided with an elongated hole 403a as the first engaged part and a groove 403b as the second engaged part, and the first transport guide section 402 is provided with an engaging projection 402a as the first engaged part and a positioning projection 402b as the second engaged part.

[0075] Furthermore, the first engaging portion may be the first projection, the first engaged portion may be the elongated hole into which the first projection engages, the second engaged portion may be the second projection, and the second engaging portion may be the groove into which the second projection engages. Alternatively, the first engaged portion may be the first projection, the first engaging portion may be the elongated hole into which the first projection engages, the second engaging portion may be the second projection, and the second engaged portion may be the groove into which the second projection engages. The groove may not be V-shaped, but may be semicircular, etc. The elongated hole may also be groove-shaped.

[0076] In other words, either the first engaging portion or the first engaged portion may be a projection, and the other may be an elongated hole into which the projection engages. Alternatively, either the second engaging portion or the second engaged portion may be a projection, and the other may be a groove into which the projection engages. This is also true for the configuration of Embodiment 2. [Examples]

[0077] Embodiment 4 will be described using Figures 26 to 32. In this embodiment, the same components as those described in Embodiment 1 will be indicated by the same reference numerals. Furthermore, the description of the same components and functions as in Embodiment 1 will be omitted, and the characteristic features of this embodiment will be mainly described.

[0078] Figure 26 is a cross-sectional view of the image forming apparatus 102 in Example 4. Figure 26 shows a configuration for opening the transfer section. Even when the transport path for re-transporting the sheet S extends in the vertical direction, the transport path can be opened as shown in Examples 1 to 3. More specifically, the transport guide can be released by moving it in the vertical direction, and the transport path can be opened by rotating the transport guide. The method for engaging the transport guide can be the same as that shown in Examples 1 to 3.

[0079] In this embodiment, the image forming apparatus 102 has a different transport path for the sheet S than the image forming apparatus 101 of the first embodiment. The image forming apparatus 102 of this embodiment has a photosensitive drum 2 as the first roller and a transfer roller 8 that can contact the photosensitive drum 2 as the second roller. The sheet S fed from the paper feed cassette 5 by the paper feed roller 4 passes through the pair of registration rollers 7 located above in the vertical direction, the transfer unit 501, and the fixing device 9, and is discharged to the paper output tray 16 by the paper output roller 13 and paper output roller 14. In such cases, the transfer unit 501 is opened and closed for jamming or replacement of the transfer roller 8.

[0080] <Transfer section> The configuration of the transfer section 501 in Figure 26 will be explained using Figures 27 and 28. Figure 27 is a schematic cross-sectional view of the transfer section 501, and Figure 28 is a schematic side view showing the fixing method of the second transport guide section 503 provided at both ends of the transport path of the second transport guide section 503. Arrow F1 in the figures indicates the transport direction of the sheet S.

[0081] As shown in Figure 28, the engaging projection 503a provided on the upstream side in the conveying direction of the second conveying guide section 503 is held in the elongated hole 502a of the first conveying guide section 502, and the positioning projection 503b provided on the downstream side is held in the groove 502b. At this time, as shown in Figure 27, the positioning projection 503b is positioned in the groove 502b by the reaction force of the transfer roller spring 8a that applies pressing force to the transfer roller 8 that forms the nip with the drum 2.

[0082] Furthermore, in the image forming apparatus 102 of this embodiment, the apparatus body 103, excluding the openable and closable second transport guide section 503, has a first transport guide section 502 and a photosensitive drum 2 as the first roller. The first transport guide section 502 is provided on the frame of the apparatus body 103 and is provided with a groove 502b and an elongated hole 502a. In other words, the apparatus body 103 has a first transport guide section 502.

[0083] The operation of opening the second transport guide section 503 will now be explained. To open the second transport guide section 503, open the door 19 shown in Figure 26 (to the state indicated by the dashed line), and apply force to the handle portion 503c of the second transport guide section 503 shown in Figure 27 in the direction of arrow F2. Then, as shown in Figure 29, the positioning projection 503b moves up the first guide portion 502b1 of the groove portion 502b and goes over the tip portion 502b6 of the first guide portion. Then, as shown in Figure 30, the positioning projection 503b moves in the direction of the dashed arrow G, and the second transport guide section 503 is opened.

[0084] Next, the operation of closing the second transport guide section 503 will be explained using Figure 31. When the second transport guide section 503 is lifted in the open state, the engaging projection 503a can move along the transport direction of the sheet S relative to the elongated hole 502a. As shown in Figure 31(a), when the second transport guide section 503 is closed with the engaging projection 503a at the lower end of the elongated hole 502a, the positioning projection 503b strikes the fourth guide section 502b4 in the rotational trajectory L5.

[0085] When the user pushes the second transport guide section 503 in the closing direction (arrow F6) from this state, the positioning projection 503b moves along the fourth guide section 502b4 in the direction of arrow F3 and hits the third guide section 502b3.

[0086] Next, as shown in Figure 31(b), when the second transport guide section 503 is closed with the engaging projection 503a at the upper end of the elongated hole 502a, the positioning projection 503b contacts the third guide section 502b3 along the rotational trajectory L6. From this state, when the second transport guide section 503 is pushed in the closing direction (arrow F6), the positioning projection 503b moves along the third guide section 502b3 in the direction of arrow F4. After that, as shown in Figure 32(a), the positioning projection 503b reaches the abutment surface 502b5 of the groove section 502b.

[0087] In this embodiment, as shown in Figure 32, the axis center 503b1 of the positioning projection 503b is configured to be located upstream in the transport direction at a distance L7 from the tip of the first guide portion 502b6. In this state, when the user releases the second transport guide portion 503, the positioning projection 503b is positioned in the groove portion 502b.

[0088] Furthermore, as shown in Figure 32(a), when the positioning projection 503b strikes the abutment surface 502b5 of the groove 502b, the arrow F5-2 indicating the direction of the reaction force of the transfer roller 8 acting on the axis center 503b1 of the positioning projection 503b coincides with range W. Range W is the range from the line connecting the axis center 503b1 of the positioning projection 503b and the tip of the first guide portion 502b6 to the perpendicular line of the second guide portion 502b2 passing through the axis center 503b1 of the positioning projection 503b.

[0089] This configuration allows the second transport guide section 503 to be directly positioned on the main body 103 of the apparatus. Furthermore, it is possible to provide an image forming apparatus that is inexpensive, compact, and has a transport guide section with excellent usability and mounting position accuracy. [Explanation of Symbols]

[0090] 1 Process Cartridge 2 Photosensitive drum 3 Scanner Unit 4 Paper feed rollers 5. Paper feed cassette 6 Conveyor roller pairs 7 Resistola vs. 8 Transfer Roller 9 Fixing device 10 Heating rollers 11 Pressure roller 11 Conveyor roller pair 12 Double-sided flappers 13 Paper output roller 14 Paper output roller 15 Reversal Roll 16 Paper output tray 101 Image forming apparatus 202a long hole 202b Groove 203a Engaging protrusion 203b Positioning projection 302a long hole 302b Groove 303b Positioning protrusion 304 biasing spring 402a Engaging protrusion 402b Positioning projection 403a long hole 403b Groove 502a long hole 502b Groove 503a Engaging protrusion 503b Positioning projection

Claims

1. An image forming apparatus for forming an image on a sheet, a first conveying guide portion having a first roller, a first engaging portion, and a second engaging portion; a second conveying guide portion including a second roller, a first engaged portion that engages with the first engaging portion, and a second engaged portion that engages with the second engaging portion; and the first engaged portion engages with the first engaging portion, and the second engaged portion engages with the second engaging portion, so that in a state in which the second conveying guide portion is positioned at a predetermined position relative to the first conveying guide portion, the first conveying guide portion and the second conveying guide portion form a conveying path along which the sheet is conveyed, and the first roller and the second roller abut against each other so as to be able to convey the sheet; When the first engaging portion and the first engaged portion are engaged with each other, the second transport guide portion is movable along a predetermined direction relative to the first transport guide portion so that the second roller moves relative to the first roller, the second engaging portion and the second engaged portion are disengaged from each other, and the second transport guide portion is released from its position relative to the first transport guide portion, When the first engaging portion and the first engaged portion are engaged with each other and the positioning of the second transport guide portion relative to the first transport guide portion is released, the second transport guide portion is rotatable in an opening direction relative to the first transport guide portion so as to open the transport path. An image forming apparatus characterized by:

2. the second transport guide portion is movable between a positioning position and a release position relative to the first transport guide portion in a state in which the first engaging portion and the first engaged portion are engaged with each other; when the second transport guide portion is at the positioning position, the second transport guide portion is positioned relative to the first transport guide portion, and the second transport guide portion is restricted from rotating in the opening direction relative to the first transport guide portion, 2. The image forming apparatus according to claim 1, wherein when the second transport guide portion is in the release position, the second transport guide portion is allowed to rotate in the opening direction relative to the first transport guide portion.

3. 3. The image forming apparatus according to claim 2, wherein the second roller moves relative to the first roller when the second transport guide portion moves from the positioning position to the release position.

4. 3. The image forming apparatus according to claim 2, further comprising a biasing member that biases the second transport guide portion in a direction from the release position toward the positioning position.

5. The image forming apparatus according to claim 1, characterized in that the second transport guide portion has a pressed portion, and when the pressed portion is pressed, the second transport guide portion moves in a direction in which the engagement between the second engaged portion and the second engaging portion is released.

6. The image forming apparatus according to claim 1 , wherein the second engaging portion is configured to receive the weight of the second conveying guide portion via the second engaged portion.

7. 2. The image forming apparatus according to claim 1, further comprising a biasing member that biases the second transport guide portion in a direction in which the second engaged portion is positioned by the second engaging portion.

8. 2. The image forming apparatus according to claim 1, wherein the first engaged portion is a protrusion, and the first engaging portion is an elongated hole with which the protrusion engages.

9. 2. The image forming apparatus according to claim 1, wherein the first engaged portion is an elongated hole, and the first engaging portion is a protrusion that engages with the elongated hole.

10. 2. The image forming apparatus according to claim 1, wherein the second engaged portion or the second engaging portion is a protrusion.

11. 2. The image forming apparatus according to claim 1, wherein the first conveying guide portion has a third roller capable of conveying a sheet, the second conveying guide has a fourth roller abutting against the third roller and capable of conveying a sheet, and a roller biasing portion biasing the fourth roller against the third roller.

12. An image forming apparatus as described in Claim 11, characterized in that when the conveying path is open, the distance between the third roller and the fourth roller is longer than the distance between the first roller and the second roller.

13. 2. The image forming apparatus according to claim 1, wherein the conveying path is a conveying path along which a sheet having an image formed on one side thereof is conveyed.

14. 2. The image forming apparatus according to claim 1, wherein the second conveying guide portion rotates in the opening direction relative to the first conveying guide portion under its own weight.

15. 2. The image forming apparatus according to claim 1, wherein the first roller and the second roller are spaced apart when the second transport guide is rotated to open the transport path.

16. 2. The image forming apparatus according to claim 1, wherein the second conveying guide portion moves along the predetermined direction, thereby separating the first roller and the second roller.

17. an apparatus body having the first conveying guide portion; 2. The image forming apparatus according to claim 1, wherein the first roller is a photosensitive drum, and the second roller is a transfer roller that can come into contact with the photosensitive drum.

18. An image forming apparatus as described in Claim 1, characterized in that when the second transport guide portion moves along the specified direction relative to the first transport guide portion so that the second engaging portion and the second engaged portion disengage, the first engaged portion moves relative to the first engagement.

19. 19. The image forming apparatus according to claim 1, wherein the predetermined direction is a direction opposite to a sheet conveying direction.

Images