Image forming apparatus

Abstract

To provide an image forming apparatus that, in order to prevent damage to a detection lever, can move the detection lever to a detection position and a retreat position when a pressure rotating body and a fixing rotating body are in a separated state.SOLUTION: A detection lever is moved by an interlock mechanism to a retreat position and a detection position while a pressure roller is maintained at a separated position. A pressure cam and a switching cam are formed therefor. When paper jam occurs during image formation (YES in S1), if the paper jam is fixing jam (YES in S3), upon detection of opening of an opening and closing door (S5), a control unit controls a motor to cause only the detection lever to operate to shift from a "state B" to a "state A" while maintaining the pressure roller at the separated position (S6). The "state B" is a state where the pressure roller is at the separated position and the detection lever is at the detection position. The "state A" is a state where the pressure roller is at the separated state and the detection lever is at the retreat position.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus such as a printer, a copier, a facsimile, or a multifunction machine. [Background technology]

[0002] The image forming apparatus includes a fixing device that fixes a toner image onto a recording material. The fixing device has a rotating fixing rotor and a pressure rotor that contacts the outer circumferential surface of the fixing rotor, and forms a fixing nip between the fixing rotor and the pressure rotor to sandwich and transport the recording material, and applies heat and pressure to the recording material that passes through the fixing nip to fix the toner image onto the recording material. The fixing device also includes a transport guide member that guides the recording material into the fixing nip, and a sheet presence / absence detection unit that detects whether the recording material is stuck inside the fixing device (Patent Document 1).

[0003] The sheet presence / absence detection unit has a detection lever that is provided so as to be movable between a detection position where it protrudes from the recording material conveying surface of the conveying guide member to detect the presence or absence of a recording material, and a retracted position where it does not protrude from the recording material conveying surface of the conveying guide member and does not detect the presence or absence of a recording material. In the case of the device described in Patent Document 1, the detection lever is moved to the detection position or the retracted position as the pressure unit moves toward or away from the recording material. That is, the detection lever is in the detection position when the pressure rotating body and the fixing rotating body are in a separated state where they do not form a fixing nip portion, and is in the retracted position when the pressure rotating body and the fixing rotating body are in a contact state where they form a fixing nip portion. The sheet presence / absence detection unit detects the retention of a recording material by pressing the detection lever in the detection position against the recording material. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2007-248790 A Summary of the Invention [Problem to be solved by the invention]

[0005] When the pressure rotating body and the fixing rotating body are in a separated state, a user can remove the recording material stuck in the fixing device or perform maintenance on the fixing device. Conventionally, when the pressure rotating body and the fixing rotating body are in a separated state, the detection lever is moved to the detection position. In this case, the detection lever gets in the way when the user removes the recording material or performs maintenance, and there is a risk that the detection lever will be damaged if the user catches the recording material on the detection lever or puts his / her hand on it.

[0006] In view of the above problems, an object of the present invention is to provide an image forming apparatus in which a detection lever can be moved between a detection position and a retracted position when the pressure rotating body and the fixing rotating body are separated from each other in order to prevent damage to the detection lever. [Means for solving the problem]

[0007] An image forming apparatus according to an embodiment of the present invention includes an apparatus main body, an image forming unit that forms a toner image on a recording material, a fixing section having a first rotating body and a second rotating body that comes into contact with the first rotating body and forms a fixing nip portion where the toner image formed by the image forming unit is fixed to the recording material, a contact and separation mechanism that can move the first rotating body between a contact position where the first rotating body comes into contact with the second rotating body and a separation position where the first rotating body is separated from the second rotating body, a detection unit that has a detection member that can be moved between a detection position where the presence of a recording material is detected in the fixing nip portion and a retracted position retracted from the detection position, and a first detection portion that detects the position of the detection member, and a detection mechanism that moves the first rotating body in response to an operation of the contact and separation mechanism. The present invention is characterized in that it comprises an interlocking mechanism that moves a detection member between the detection position and the retracted position, the interlocking mechanism being capable of moving the detection member to the retracted position when the first rotating body is in the abutment position, and moving the detection member to the retracted position and the detection position when the first rotating body is in the separation position; a door that is openably and closably provided on the device body so as to allow access to the fixing unit in an open state; a second detection unit that detects the opening and closing of the door; and a control unit that controls the contact / separation mechanism and the interlocking mechanism and detects the opening of the door using the second detection unit, wherein the control unit positions the detection member at the retracted position when opening of the door is detected. Effect of the Invention

[0008] According to the present invention, in order to prevent damage to the detection lever, the detection lever can be moved to the detection position and the retracted position when the pressure rotating body and the fixing rotating body are in the separated state. [Brief description of the drawings]

[0009] [Figure 1] 1 is a schematic diagram showing an image forming apparatus according to an embodiment of the present invention. [Diagram 2] FIG. [Diagram 3] FIG. [Figure 4] FIG. 4A is a cross-sectional view showing the pressure roller in the contact position, and FIG. 4B is a cross-sectional view showing the pressure roller in the separated position. [Diagram 5] 1A and 1B are schematic diagrams showing a detection unit with a detection lever in a detection position and a detection lever in a retracted position, respectively. [Figure 6] FIG. 4 is a control block diagram showing a control system related to removal of a fixing jam. [Figure 7] 13 is a flowchart showing a detection lever control process. [Figure 8] 5 is a graph showing the position of the pressure roller and the position of the detection lever according to the phase of the rotation shaft. [Figure 9] FIG. [Figure 10] FIG. 13 is a perspective view showing the fixing unit being pulled out with the door open. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] <Image forming device> The present embodiment will be described. First, a schematic configuration of an image forming apparatus of the present embodiment will be described with reference to FIG. 1. The image forming apparatus 100 shown in FIG. 1 is a tandem-type full-color printer of an electrophotographic system. The image forming apparatus 100 forms a toner image on a recording material P based on image data sent from a document reading device (not shown) connected to the apparatus main body or an external device (not shown) such as a personal computer connected to the apparatus main body so as to be capable of inputting and outputting data. The recording material P is, for example, a sheet such as paper or plastic film.

[0011] As shown in FIG. 1, the image forming apparatus 100 includes image forming units 120a, 120b, 120c, and 120d that form yellow, magenta, cyan, and black images, respectively. The image forming units 120a, 120b, 120c, and 120d are arranged in line along the moving direction of an intermediate transfer belt 115 in the main body of the apparatus. The intermediate transfer belt 115 is stretched around a plurality of rollers and rotates while carrying a toner image that is primarily transferred as described below. A secondary transfer outer roller 118 is arranged at a position opposite to a secondary transfer inner roller 117 that stretches the intermediate transfer belt 115 across the intermediate transfer belt 115, forming a secondary transfer portion T2 that transfers the toner image on the intermediate transfer belt 115 to a recording material P. A fixing unit 200 is arranged downstream of the secondary transfer portion T2 in the recording material conveying direction.

[0012] The image forming units 120a, 120b, 120c, and 120d have substantially the same configuration except for the different developing colors. Therefore, the yellow image forming unit 120a will be described here as a representative, and descriptions of the other image forming units 120b, 120c, and 120d will be omitted.

[0013] The image forming unit 120a is provided with a photosensitive drum 111. The photosensitive drum 111 rotates counterclockwise in Fig. 1. Around the photosensitive drum 111, a charging device 112, an exposure device 113, a developing device 114, and a primary transfer roller 116 are arranged.

[0014] A process of forming, for example, a full-color image by the image forming apparatus 100 will be described. First, the surface of a rotating photosensitive drum 111 is uniformly charged by a charging device 112. The charged photosensitive drum 111 is exposed to laser light emitted from an exposure device 113. As a result, an electrostatic latent image is formed on the surface of the photosensitive drum 111. The electrostatic latent image formed on the photosensitive drum 111 is developed into a toner image by a developing device 114 using a developer containing toner and carrier. The toner image formed on the photosensitive drum 111 is primarily transferred to the intermediate transfer belt 115 at a primary transfer section formed between the photosensitive drum 111 and a primary transfer roller 116 arranged with the intermediate transfer belt 115 sandwiched therebetween.

[0015] Thereafter, the recording material P stored in the cassette 103 is conveyed to the secondary transfer portion T2 in accordance with the timing of forming the toner image. Then, by applying a secondary transfer voltage to the secondary transfer outer roller 118, the toner image is secondarily transferred from the intermediate transfer belt 115 to the recording material P. In this embodiment, the image forming portions 120a to 120d, the intermediate transfer belt 115, the secondary transfer inner roller 117, the secondary transfer outer roller 118, etc. constitute an image forming unit 110 that forms the toner image on the recording material P.

[0016] The recording material P on which the toner image has been formed is transported to a fixing unit 200. The fixing unit 200 has a fixing belt and a pressure roller as described below, and applies heat and pressure to the recording material P on which the toner image has been formed when nipping and transporting the recording material P in a fixing nip portion formed by them, thereby fixing the toner image to the recording material P.

[0017] The image forming apparatus 100 is capable of single-sided printing, in which a toner image is formed on one side of the recording material P, and double-sided printing, in which a toner image is formed on both sides of the recording material P. In the case of single-sided printing, the recording material P, on whose one side a toner image has been fixed by the fixing unit 200, is guided by the flapper 132 to a discharge path 139 and discharged to the outside.

[0018] On the other hand, in the case of double-sided printing, the recording material P on which the toner image is fixed on the first side by the fixing unit 200 is guided by the flapper 132 to the conveying path 134 and conveyed to the reversing section 136. In the reversing section 136, the conveying direction of the recording material P is switched to the conveying path 137 by the flapper 133 in response to the detection of the rear end of the recording material P by the reversing sensor 135. The recording material P reversed in the reversing section 136 is conveyed along the conveying path 137 toward the secondary transfer section T2. ​​Then, the recording material P passes through the secondary transfer section T2 with the second side, which is opposite to the first side on which the toner image is formed, facing the intermediate transfer belt 115. In the secondary transfer section T2, the toner image formed on the intermediate transfer belt 115 is secondarily transferred to the second side of the recording material P. Thereafter, the toner image is fixed on the recording material P by the fixing unit 200, and the recording material P on which the toner image is fixed is guided by the flapper 132 to the discharge path 139 and discharged to the outside.

[0019] The image forming apparatus 100 may be configured in one housing, but in this embodiment, a first housing 100a, a second housing 100b, and a third housing 100c formed separately are connected to configure the apparatus main body. A fixing unit 200 is housed in a removable manner in the second housing 100b, which is connected between the first housing 100a and the third housing 100c so that the recording material P can be transferred between them. In the second housing 100b, a jam detection sensor 502 is provided downstream of the fixing unit 200 in the recording material transport direction. The jam detection sensor 502 is, for example, a photosensor, and detects the recording material P passing through the fixing unit 200.

[0020] The second housing 100b is provided with an openable / closable door 500 and an open / close detection sensor 501. FIG. 9 shows the openable door 500 in an open state, and FIG. 10 shows the opening and closing door 500 when the fixing unit 200 is pulled out in the open state. As shown in FIGS. 9 and 10, when the openable door 500 is in an open state, the user can access the fixing unit 200 housed in the image forming apparatus main body (specifically, the second housing 100b). By opening the openable door 500, the user can pull out the fixing unit 200 to the front side of the image forming apparatus main body. When the user pulls out the fixing unit 200 in the pull-out direction (arrow in FIG. 10), the fixing unit 200 is removed from the image forming apparatus main body. Conversely, when the user pushes in the fixing unit 200 in the direction opposite to the pull-out direction, the fixing unit 200 is attached to the image forming apparatus main body.

[0021] An opening / closing detection sensor 501 as a second detection unit detects opening / closing of the opening / closing door 500. A user can open the opening / closing door 500, pull out the fixing unit 200 from the second housing 100b, and remove the recording material P remaining in the fixing unit 200 or perform maintenance on the fixing unit 200.

[0022] <Fuser unit> Next, an overview of the fixing unit 200 of this embodiment will be described with reference to FIG. 2. In this embodiment, a fixing unit 200 of a belt heating type using an endless fixing belt is adopted. In this embodiment, the fixing unit 200 has a fixing section 210, a pressure roller contact / separation mechanism 220 (see FIG. 3), a detection unit 240, a transport guide member 250, and an interlocking mechanism 600 (see FIG. 5(a)). For convenience of illustration, the pressure roller contact / separation mechanism 220 and the interlocking mechanism 600 are omitted in FIG. 2.

[0023] 2, in fixing unit 200, recording material P is transported in a transport direction (arrow X direction) from right to left. Note that the width direction refers to a direction intersecting the transport direction of recording material P in fixing unit 200, and in this embodiment, substantially coincides with the rotation axis direction of pressure roller 202 and heating roller 204. In the following, the downstream side of fixing unit 200 in the recording material transport direction will be referred to as "downstream", and the upstream side of fixing unit 200 in the recording material transport direction will be simply referred to as "upstream".

[0024] The fixing unit 210 includes an endless fixing belt 201 , a pressure roller 202 as a first rotating body, a fixing pad 203 , a heating roller 204 , a steering roller 205 , a stay 206 , a sliding sheet 207 , and an oil supply roller 208 .

[0025] <Fixing belt> The fixing belt 201 as the second rotating body has thermal conductivity, heat resistance, etc., and is formed in a thin cylindrical shape. In this embodiment, the fixing belt 201 has a three-layer structure including a base layer, an elastic layer on the outer periphery of the base layer, and a release layer on the outer periphery of the elastic layer. For example, the base layer is made of polyimide resin (PI) with a thickness of "60 μm", the elastic layer is made of silicone rubber with a thickness of "300 μm", and the release layer is made of tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin (PFA) with a thickness of "30 μm". The fixing belt 201 is stretched by a fixing pad 203, a heating roller 204, and a steering roller 205.

[0026] <Fixing pad> The fixing pad 203 is provided to form a fixing nip N of a predetermined width in the transport direction (arrow X direction) by being pressed against the pressure roller 202 via the fixing belt 201. The recording material P is guided into the fixing nip N by a transport guide member 250 arranged upstream of the fixing nip N, with the leading end of the recording material P being guided thereto. The fixing pad 203 has a substantially rectangular cross section and extends along the width direction of the fixing belt 201. The fixing pad 203 is formed of a highly heat-resistant resin, such as liquid crystal polymer resin (LCP).

[0027] <Stay> In this embodiment, the fixing belt 201 is pressed from the inside toward the pressure roller 202 by the fixing pad 203 held by the stay 206. The stay 206 is provided inside the fixing belt 201 in a non-rotating manner. The stay 206 is a reinforcing member having high rigidity that backs up the fixing pad 203, and is formed, for example, using stainless steel (SUS304) with a thickness of "3 mm" so as to be long in the width direction and hollow with a rectangular cross section. By holding the resin fixing pad 203 on the metal stay 206 with higher rigidity, it is possible to reduce the deflection that occurs in the fixing pad 203 due to the pressure against the pressure roller 202, and thus the pressure force at the fixing nip N is ensured.

[0028] <Sliding sheet> In order to improve the sliding property between the fixing belt 201 and the fixing pad 203, the stay 206 holds a sliding sheet 207 that slides on the fixing belt 201. The sliding sheet 207 is held by the stay 206 and disposed at a position facing the pressure roller 202 with the fixing belt 201 sandwiched therebetween. The sliding sheet 207 is formed, for example, by coating the surface of a polyimide base material having a thickness of 70 μm with polytetrafluoroethylene (PTFE). Note that the method of improving the sliding property between the fixing belt 201 and the fixing pad 203 is not limited to disposing the sliding sheet 207, and a fixing pad 203 having a coating applied to its surface for improving sliding property may also be used.

[0029] <Heating roller> Heating roller 204 is disposed inside fixing belt 201, and stretches fixing belt 201 together with stay 206 and steering roller 205. Heating roller 204 is formed into a pipe shape having a thickness of "1 mm" using, for example, stainless steel, and has a halogen heater 209 disposed inside. Heating roller 204 is heated to a predetermined temperature by halogen heater 209. Fixing belt 201 is heated to a predetermined target temperature by heating roller 204 according to the type of recording material P, based on temperature detection by a thermistor (not shown).

[0030] <Steering roller> Steering roller 205 is provided to control the position of fixing belt 201 in the width direction. Steering roller 205 is supported by a steering frame (not shown) and tensions fixing belt 201. Steering roller 205 changes its alignment with heating roller 204 by rotating with respect to heating roller 204 around a rotation shaft provided on the steering frame as a fulcrum. This causes heating roller 204 to swing, generating a tension difference between one end side and the other end side of fixing belt 201 in the width direction, and thus fixing belt 201 moves in the width direction.

[0031] <Oil supply roller> The oil supply roller 208 is a roll-shaped member wound with nonwoven fabric having a thickness of, for example, 100 μm, and the nonwoven fabric is impregnated with silicone oil. The oil supply roller 208 is brought into contact with the inner circumferential surface of the fixing belt 201 by a spring (not shown) and rotates following the fixing belt 201. The oil supply roller 208 supplies silicone oil to the inner circumferential surface of the fixing belt 201. The silicone oil supplied to the inner circumferential surface of the fixing belt 201 is then supplied as a lubricant between the fixing belt 201 and the fixing pad 203 as the fixing belt 201 rotates.

[0032] <Pressure roller> The pressure roller 202 is rotatably supported by a frame (not shown) of the fixing unit 200. A gear is fixed to one end of the pressure roller 202 in the width direction, and the pressure roller 202 is rotated by a motor M1 connected via the gear. When the pressure roller 202 rotates, the frictional force generated in the fixing nip portion N transmits the rotational force of the pressure roller 202 to the fixing belt 201. In this way, the fixing belt 201 is rotated by the pressure roller 202. The pressure roller 202 has an elastic layer formed on the outer periphery of the rotating shaft, and a release layer formed on the outer periphery of the elastic layer. For example, the rotating shaft is made of stainless steel, the elastic layer is made of conductive silicone rubber with a thickness of "5 mm", and the release layer is made of perfluoroalkoxyalkane (PFA) with a thickness of "50 μm".

[0033] <Pressure roller contact / separation mechanism> In this embodiment, the pressure roller 202 can be moved to a contact position where it is in contact with the fixing belt 201 and a separation position where it is separated from the fixing belt 201. A pressure roller contact / separation mechanism 220 that moves the pressure roller 202 between the contact position and the separation position will be described with reference to FIG. 2 and with reference to FIGS. 3 to 4(b).

[0034] 3, the pressure roller contact / separation mechanism 220 has a rotating shaft 213, a pressure cam 221, an upper pressure arm 222, a lower pressure arm 223, a pressure spring 224, and a pressure cam follower 225. The pressure cam 221, the upper pressure arm 222, the lower pressure arm 223, the pressure spring 224, and the pressure cam follower 225 are disposed at both ends of the rotating shaft 213.

[0035] A motor M2 is connected to one end of the rotating shaft 213 via a gear train 229. The motor M2 as a drive unit drives the rotating shaft 213 to rotate and drive the pressure roller contact / separation mechanism 220. In the case of this embodiment, when the rotating shaft 213 is rotated in the forward direction (clockwise) in the figure in FIG. 3, the pressure roller 202 is moved to a separated position separated from the fixing belt 201 by the pressure roller contact / separation mechanism 220. On the other hand, when the rotating shaft 213 is rotated in the reverse direction (counterclockwise), the pressure roller 202 is moved to a contact position abutting against the fixing belt 201 by the pressure roller contact / separation mechanism 220. Note that, although a worm gear is used for the gear train 229 in this embodiment, this is not limiting, and the gear train 229 may be a spur gear, a helical gear, or the like.

[0036] 4(a), the pressure upper arm 222 and the pressure lower arm 223 are attached to a frame (not shown) of the fixing unit 200 so as to be rotatable about a rotation shaft 227 that communicates with the rotation hole 226. The pressure upper arm 222 is provided with a support holder 228 that supports the bearing 202a of the pressure roller 202. The pressure lower arm 223 is provided with a pressure cam follower 225. In addition, the pressure upper arm 222 and the pressure lower arm 223 are provided with a pressure spring 224 that connects them to each other on the opposite side of the rotation shaft 227 with the pressure roller 202 in between.

[0037] In this embodiment, when the rotating shaft 213 is rotated in the reverse direction (counterclockwise in FIG. 3), the pressure roller 202 moves in a direction away from the fixing belt 201. Conversely, when the rotating shaft 213 is rotated in the forward direction (clockwise in FIG. 3), the pressure roller 202 moves in a direction approaching the fixing belt 201. To achieve this, a pressure cam 221 is provided on the rotating shaft 213. The pressure cam 221 rotates in conjunction with the rotation of the rotating shaft 213.

[0038] The pressure cam 221 as the first cam portion has a bottom dead point region 221a and a top dead point region 221b, and when the bottom dead point region 221a is in contact with the pressure cam follower 225, the pressure roller 202 is separated from the fixing belt 201 as shown in Fig. 4(b). On the other hand, when the top dead point region 221b is in contact with the pressure cam follower 225, the pressure roller 202 is in contact with the fixing belt 201 as shown in Fig. 4(a). When the pressure roller 202 is in contact with the fixing belt 201, the pressure roller 202 obtains a pressure force on the fixing belt 201 by the pressure spring 224.

[0039] As shown in FIG. 2, in this embodiment, a transport guide member 250 and a detection unit 240 are disposed upstream of the fixing nip portion N. The transport guide member 250 is provided to guide the recording material P that has passed through the secondary transfer portion T2 (see FIG. 1) to the fixing nip portion N. The detection unit 240 is provided to detect retention of the recording material P in the fixing nip portion N. Note that the transport guide member 250 may be disposed downstream of the fixing nip portion N to guide the recording material P that has passed through the fixing nip portion N to the transport path 134 or the discharge path 139 (see FIG. 1). In this case, the detection unit 240 is disposed downstream of the fixing nip portion N.

[0040] <Detection unit> Next, the detection unit 240 and the interlocking mechanism 600 will be described using Figures 5(a) and 5(b) with reference to Figures 2 and 3. As shown in Figures 5(a) and 5(b), the detection unit 240 has a detection lever 241 as a detection member and a lever detection sensor 247 as a first detection section.

[0041] The detection lever 241 is provided on the transport guide member 250 so as to be rotatable about a rotation center hole 241a as a rotation center, and the lever detection sensor 247 is fixed to the transport guide member 250. The detection lever 241 is biased clockwise (in the direction of arrow C) in FIG. 5(a) by a lever biasing spring (not shown).

[0042] The lever detection sensor 247 is a photointerrupter in which a light emitting element and a light receiving element are arranged opposite each other, and the light blocking portion 241c of the detection lever 241 blocks the light between them, thereby enabling the detection sensor 247 to detect the position of the detection lever 241. In this embodiment, when the detection lever 241 is in the detection position, the lever detection sensor 247 is not blocked by the light blocking portion 241c. On the other hand, when the detection lever 241 is in the retracted position, the lever detection sensor 247 is blocked by the light blocking portion 241c.

[0043] The detection position of the detection lever 241 refers to a position in which a part of the detection lever 241 protrudes from the transport surface 250f of the transport guide member 250, as shown in Fig. 5(a). The retracted position of the detection lever 241 refers to a position in which the detection lever 241 does not protrude from the transport surface 250f of the transport guide member 250, as shown in Fig. 5(b). When the detection lever 241 is in the retracted position, it is housed in the transport guide member 250.

[0044] When recording material P is retained in the fixing nip N during image formation, the detection lever 241 at the detection position is pressed by the retained recording material P on the conveying surface 250f and moves from the detection position in a direction from the front surface to the back surface of the recording material. In other words, when the detection lever 241 moves from the detection position in a direction from the front surface to the back surface of the recording material and the lever detection sensor 247 is shielded from light, the control unit 150 described later detects that the recording material P is retained in the fixing nip N.

[0045] In this embodiment, in addition to being pressed by the recording material P staying on the conveying surface 250f, the detection lever 241 is moved to the detection position and the retracted position by the interlocking mechanism 260. As shown in Table 1, when the pressure roller 202 is moved from the separation position to the contact position, the detection lever 241 is moved from the detection position to the retracted position by the interlocking mechanism 260 (from state B to state C). This is because if the detection lever 241 is in the detection position during image formation, it will interfere with the recording material P being conveyed. On the other hand, when the pressure roller 202 is moved from the contact position to the separation position, the detection lever 241 is moved from the retracted position to the detection position by the interlocking mechanism 260 (from state C to state B). This is to enable the detection lever 241 to detect that the recording material P has stayed in the fixing nip N, as described above.

[0046] Furthermore, in this embodiment, when the pressure roller 202 is in the separated position, the detection lever 241 is moved by the interlocking mechanism 260 to the retracted position and the detection position (state B and state A) while maintaining the pressure roller 202 in the separated position. As shown in Table 1, the combinations of the positions of the pressure roller 202 and the detection lever 241 are state A, state B, and state C. The position control of the detection lever 241 will be described later. [Table 1]

[0047] <Interlocking mechanism> Next, a description will be given of the interlocking mechanism 260 capable of moving the detection lever 241 between the detection position and the retracted position. As shown in Figures 5(a) and 5(b), the interlocking mechanism 260 has a switching cam 242, a first link 243, and a second link 244.

[0048] Switching cam 242 as a second cam portion is disposed on rotating shaft 213 on which pressure cam 221 is provided, and is rotated together with rotating shaft 213 by motor M2 (see FIG. 3). First link 243 and second link 244 are each rotatably provided on a frame (not shown) of fixing unit 200. First link 243 is biased counterclockwise by a first biasing spring (not shown), and second link 244 is biased clockwise by a second biasing spring (not shown).

[0049] The switching cam 242 has a bottom dead center area 242a and a top dead center area 242b on the cam surface. As shown in FIG. 5(a), when the top dead center area 242b of the switching cam 424 abuts against the first link 243, the first link 243 presses the second link 244 while being rotated clockwise against the biasing force of the first biasing spring. When the second link 244 is pressed by the first link 243, it is rotated counterclockwise against the biasing force of the second biasing spring and moves away from the detection lever 241. The detection lever 241 rotates clockwise by a lever biasing spring (not shown) without abutting against the second link 244. In this way, the detection lever 241 moves to the detection position and is maintained at the detection position by the lever biasing spring (not shown).

[0050] 5(b), when the bottom dead center region 242a of the switching cam 424 abuts against the first link 243, the first link 243 does not press the second link 244. When the second link 244 is not pressed against the first link 243, it rotates clockwise due to the biasing force of the second biasing spring and abuts against the detection lever 241. Then, the detection lever 241 is pressed by the second link 244 and rotates counterclockwise against the biasing force of the lever biasing spring (not shown). In this way, the detection lever 241 is moved to the retracted position and maintained at the retracted position by the second link 244.

[0051] 3, in this embodiment, the switching cam 242 of the interlocking mechanism 260 is disposed in the center of the rotation shaft 213 on which the pressure cam 221 is disposed. Therefore, the detection lever 241 is moved from the retracted position to the detection position in conjunction with the movement of the pressure roller 202 from the contact position to the separation position. Also, the detection lever 241 is moved from the detection position to the retracted position in conjunction with the movement of the pressure roller 202 from the separation position to the contact position.

[0052] In this embodiment, when the pressure roller 202 is in the separated position, the detection lever 241 is moved between the retracted position and the detection position by the interlocking mechanism 260 while the pressure roller 202 is maintained in the separated position. To achieve this, a bottom dead center region 221a and a top dead center region 221b of the pressure cam 221 and a bottom dead center region 242a and a top dead center region 242b of the switching cam 242 are formed. In other words, the relationship between the phase of the cam surface of the pressure cam 221 and the phase of the cam surface of the switching cam 242 is such that the detection lever 241 can move between the detection position and the retracted position while the pressure roller 202 is in the separated position.

[0053] <Control Unit> As shown in Fig. 1, the image forming apparatus 100 includes a control unit 150. The control unit 150 will be described using Fig. 6 with reference to Figs. 1 to 3, mainly with respect to a control system for removing a recording material P (called a fixing jam) stuck in the fixing nip N. Note that in addition to those shown in the figure, various devices such as the various parts constituting the image forming apparatus 100 and drive sources (motors, power sources, etc.) for operating those parts are connected to the control unit 150. However, as this is not the main point of the invention, illustration and description of those will be omitted here.

[0054] The control unit 150 controls various operations related to image formation, and is composed of, for example, a CPU 151 (Central Processing Unit), a ROM 152 (Read Only Memory), and a RAM 153 (Random Access Memory). The CPU 151 executes various control programs stored in the ROM 152 and RAM 153 to control the image forming apparatus 100. The ROM 152 and RAM 153 store various control programs such as an image formation process (not shown) and a "detection lever control process" (see FIG. 7 described later), as well as various data such as image data for forming a toner image. The RAM 153 can also temporarily store the results of calculations associated with the execution of various programs.

[0055] An operation unit 180 is connected to the control unit 150. The operation unit 180 has a display unit such as a liquid crystal panel that displays information to a user, and an input device such as physical keys or a touch panel function unit of a liquid crystal panel that allows the user to input commands and data to the control unit 150. The control unit 150 accepts the execution of an image formation job when a command to execute an image formation job is input in response to an operation of the operation unit 180 by the user.

[0056] Further, the control unit 150 is connected to the motor M2, the lever detection sensor 247, the open / close detection sensor 501, the jam detection sensor 502, and the like. The control unit 150 receives a detection signal from the jam detection sensor 502, and determines whether the recording material P has been retained in the middle of the conveying path in the image forming apparatus 100 during image formation, that is, whether a jam of the recording material P has occurred, based on the detection signal. When a jam of the recording material P has occurred, the control unit 150 determines whether a fixing jam has occurred based on the detection result of the lever detection sensor 247. When a fixing jam has occurred, the control unit 150 displays on the liquid crystal screen of the operation unit 180 that a jam of the recording material P has occurred in the fixing nip portion N. The control unit 150 detects whether the opening / closing door 500 is open or closed based on the detection signal of the open / close detection sensor 501. Then, the control unit 150 controls the motor M2 to move the pressure roller 202 between the contact position and the separation position by the pressure roller contact / separation mechanism 220, and to move the detection lever 241 between the detection position and the retracted position by the interlocking mechanism 260.

[0057] <Detection lever control process> Next, the "detection lever control process" for controlling the position of the detection lever 241 when a fixing jam occurs will be described with reference to Figs. 7 and 8. The "detection lever control process" is started by the control unit 150 when the image forming apparatus 100 is powered on. When the image forming apparatus 100 is powered on, the pressure roller 202 is in the separated position and the detection lever 241 is in the detection position (state B in Fig. 8). The phase of the rotating shaft 213 at this time is set to phase "0" as shown in Fig. 8. In Fig. 8, the reverse rotation direction of the rotating shaft 213 is indicated as "R direction".

[0058] 7, the control unit 150 determines whether or not a jam of the recording material P has occurred based on a detection signal from the jam detection sensor 502 (S1). Generally, when the image forming apparatus 100 is powered on, no jam has occurred in the initial state. Therefore, it is determined that no jam has occurred in the initial state (NO in S1), and the control unit 150 transitions the image forming apparatus 100 from the initial state to a standby state (S7). The control unit 150 keeps the image forming apparatus 100 waiting in a "standby state" in which an image forming operation on the recording material P can be started in response to an input of an image formation job until an image formation job is accepted (S8).

[0059] When the control unit 150 accepts an image formation job, it controls the motor M2 to operate the pressure roller 202 and the detection lever 214, and transitions from "State B" to "State C" (S9). In this case, as shown in FIG. 8, the control unit 150 reverses the motor M2 to set the phase of the rotation shaft 213 to, for example, "40" or more and "60" or less. As a result, the pressure roller 202 is moved from the separated position to the abutting position, and the detection lever 214 is moved from the detection position to the retracted position. Then, in "State C", the image forming apparatus 100 forms an image on the recording material P.

[0060] The control unit 150 judges whether or not to end the image forming job (S10). For example, when image formation on the number of sheets of recording material P input from the operation unit 180 is completed, the control unit 150 judges that the image forming job is to be ended (YES in S10), and controls the motor M2 to operate the pressure roller 202 and the detection lever 214, and transitions from "state C" to "state B" (S11). In this case, as shown in FIG. 8, the control unit 150 rotates the motor M2 in the forward direction to return the phase of the rotation shaft 213 to "0". As a result, the pressure roller 202 is moved from the contact position to the separation position, and the detection lever 214 is moved from the retracted position to the detection position. On the other hand, when the image forming job is not to be ended (NO in S10), the control unit 150 returns to the process of step S1. In this case, image formation is continued in "state C". In this way, unless a jam of the recording material P occurs during image formation, transitions between "state B" and "state C" and does not transition to "state A".

[0061] If a jam occurs in the middle of the conveying path during image formation (YES in S1), the control unit 150 temporarily stops the image forming job being executed, and then controls the motor M2 to operate the pressure roller 202 and the detection lever 214, transitioning from "state C" to "state B" (S2). That is, the control unit 150 rotates the motor M2 in the forward direction to return the phase of the rotation shaft 213 to "0". After that, the control unit 150 determines whether or not a jam (fixing jam) of the recording material P has occurred in the fixing nip N based on the detection signal of the lever detection sensor 247 (S3). If no fixing jam has occurred (NO in S3), although not shown here, the control unit 150 performs control to have the user remove the jam that has occurred outside the fixing nip N. After removing the jam, the control unit 150 makes the image forming apparatus 100 wait in the "standby state" until a job resumption is instructed (S7).

[0062] If the jam that occurred during image formation is a fixing jam (YES in S3), the control unit 150 notifies the user by displaying the fact that a fixing jam has occurred on the liquid crystal panel of the operation unit 180 (S4). To remove the fixing jam, the user must open the opening / closing door 500 to access the fixing unit 200. Therefore, the control unit 150 waits until it detects that the opening / closing door 500 has been opened based on the detection signal of the opening / closing detection sensor 501 (S5). In addition, the control unit 150 controls the motor M2 to operate only the detection lever 214 while maintaining the pressure roller 202 in the separation position, and transitions from "State B" to "State A" (S6). In this case, as shown in FIG. 8, the control unit 150 rotates the motor M2 in the forward direction to change the phase of the rotation shaft 213 from "0" to, for example, "-20" or more and "-50" or less. After that, the control unit 150 returns to the process of step S3.

[0063] Thus, in the case of this embodiment, the condition for transitioning from "State B" to "State A" is when a fixing jam occurs and the user opens the opening / closing door 500 to pull out the fixing unit 200 and remove the fixing jam. That is, when the user removes the recording material P stuck in the fixing nip portion N, if the detection lever 241 remains in the detection position, there is a risk that the detection lever 241 will be damaged by catching the recording material P, particularly cardboard, on the detection lever 241 or by unintentionally touching it. Therefore, when a fixing jam occurs and the user opens the opening / closing door 500, the rotation shaft 213 is rotated to move the detection lever 241 from the detection position to the retracted position, thereby preventing damage to the detection lever 241.

[0064] In addition, when the fixing unit 200 is removed from the image forming apparatus main body (second housing 100b) as shown in FIG. 10, the detection lever 241 of the detection unit 240 is located in a retracted position housed in the transport guide member 250.

[0065] In addition, when the image forming job is not yet input and the state is “state B”, for example, if the opening and closing door 500 is opened for maintenance of the fixing unit 200, it is preferable to rotate the rotating shaft 213 to move the detection lever 241 from the detection position to the retracted position.

[0066] As described above, in this embodiment, when the pressure roller 202 is in the separated position, the detection lever 241 can be moved to the detection position and the retracted position. This prevents damage to the detection lever 241, since the detection lever 241 has already been moved to the retracted position where it is not hit by the recording material P to be removed or the user's hand when removing a fixing jam or performing maintenance on the fixing unit 200.

[0067] <Other embodiments> In the above-described embodiment, the detection lever 241 is operated by the interlocking mechanism 260, but the present invention is not limited to this. For example, the detection lever 241 may be operated by an operating mechanism including a link unit and a solenoid, according to the control of the solenoid by the control unit 150. In other words, the movement of the pressure roller 202 and the movement of the detection lever 241 may be performed by independent drive sources and mechanisms.

[0068] In addition, when the movement of the pressure roller 202 and the movement of the detection lever 241 are performed by independent driving sources and mechanisms, the detection lever 241 does not have to be configured to move based on the detection signal of the open / close detection sensor 501. For example, when the open / close door 500 is opened from the closed state with respect to the second housing 100b, the detection lever 241 may be configured to move from the detection position to the retracted position in conjunction with the movement. In other words, the detection lever 241 may be configured to move by the rotation of the switching cam 242 in conjunction with the opening / closing door 500 being opened from the closed state with respect to the second housing 100b. In this configuration, the detection lever 241 can be moved to the retracted position without using the open / close detection sensor 501.

[0069] As another alternative configuration, as shown in Fig. 10, when the fixing unit 200 is pulled out from the second housing 100b, the detection lever 241 of the detection unit 240 may be moved from the detection position to the retracted position. That is, the switching cam 242 rotates in conjunction with the pulling out operation of the fixing unit 200. In this manner, the trigger for moving the detection lever 241 to the retracted position is not limited to the opening and closing operation of the opening and closing door 500. Any configuration may be used as long as the detection lever 241 moves to the retracted position when the fixing unit 200 is removed from the second housing 100b. [Explanation of symbols]

[0070] 100a, 100b...apparatus main body (first housing, second housing), 110...image forming unit, 150...control unit, 200...fixing unit, 201...second rotating body (fixing belt), 202...first rotating body (pressure roller), 210...fixing unit, 213...rotation shaft, 220...contact and separation mechanism (pressure roller contact and separation mechanism), 221...first cam portion (pressure cam portion), 240...detection unit, 241...detection member (detection lever), 242...second cam portion (switching cam portion), 247...first detection portion (lever detection sensor), 250...conveyance guide member, 260...interlocking mechanism, 500...door (opening and closing door), 501...second detection portion (opening and closing detection sensor), M2...driving portion (motor), N...fixing nip portion, P...recording material

Claims

1. An image forming apparatus comprising: a main body; an image forming unit that forms a toner image on a recording material; and a fixing device that is detachably provided on the main body of the apparatus and fixes the toner image formed on the recording material by the image forming unit to the recording material, The first rotating body and A second rotating body that contacts the first rotating body and forms a fixing nip portion for fixing the toner image formed by the image forming unit onto the recording material, A detection unit positioned upstream of the fixing nip section with respect to the transport direction of the recording material, for detecting the recording material, having a movable detection member, the detection unit capable of detecting the recording material by the detection member contacting the back surface opposite to the front surface of the recording material on which a toner image has been formed by the image forming unit, The device comprises a cam, which, by rotating the cam, moves the detection member between a first position located within the transport path of the recording material and a second position retracted from the first position, and a moving mechanism that moves the first rotating body between a contact position in contact with the second rotating body and a separated position separated from the second rotating body, When the cam is in the first cam position, the sensing member is in the second position, and the first rotating body is in the contact position. When the cam is in the second cam position, the detection member is in the first position, and the first rotating body is in the separated position. When the cam is in the third cam position, the detection member is in the second position, and the first rotating body is in the separated position. An image forming apparatus characterized by the following:

2. Further comprising a control unit for controlling the moving mechanism, The control unit controls the movement mechanism such that when the fixing device is in the mounting position on the device body while the image forming operation is stopped, the cam is positioned at the second cam position, and when the fixing device is removed from the device body, the cam is positioned at the third cam position. The image forming apparatus according to feature 1.

3. Further comprising a control unit for controlling the moving mechanism, The control unit, With respect to the transport direction, the movement mechanism is controlled so that the cam is positioned at the first cam position from at least the time the leading edge of the recording material passes the detection unit until the trailing edge of the recording material passes the detection unit. With the fixing device mounted on the main body of the device, the movement mechanism is controlled so that the cam is positioned at the second cam position after the trailing end of the last recording material in the image forming job has passed the detection unit. When the fixing device is detached from the main body of the device, the moving mechanism is controlled so that the cam is positioned at the third cam position. The image forming apparatus according to feature 1.

4. The control unit controls the movement mechanism so that the cam is positioned at the second cam position when an error occurs due to jamming of the recording material. The image forming apparatus according to feature 3.

5. The detection unit has a rotating shaft that rotatably supports the detection member, The detection member is movable between the first position and the second position by rotating the rotation axis around the center of rotation. The image forming apparatus according to feature 1.

6. The following is a further provision of a guide member for guiding the recording material upstream of the fixing nip portion with respect to the transport direction: The rotation axis is located below the guide member in the vertical direction. The image forming apparatus according to feature 5.

7. The device body further comprises a door that can be opened and closed, The fixing device is removable from the main body of the device when the door is open. The image forming apparatus according to feature 1.

8. A control unit for controlling the moving mechanism, The system further includes a detection unit for detecting the opening and closing of the aforementioned door, The control unit controls the movement mechanism so that the cam is positioned at the third cam position when the detection unit detects that the door has been opened. The image forming apparatus according to feature 7.

9. The moving mechanism moves the detection member from the first position to the second position in conjunction with the operation of removing the fixing device from the main body of the device. The image forming apparatus according to feature 1.

10. The device body further comprises a door that can be opened and closed, The moving mechanism moves the detection member from the first position to the second position, which is retracted, in conjunction with the operation of opening the door from a closed state relative to the main body of the device. The image forming apparatus according to feature 1.

11. The cam includes a first cam portion for moving the first rotating body between the contact position and the separation position, a second cam portion for moving the detection member between the first position and the second position, and a common rotating shaft that integrally holds and rotates the first cam portion and the second cam portion. The image forming apparatus according to feature 1.

12. Further comprising a control unit for controlling the moving mechanism, The control unit, The movement mechanism is controlled so that the cam moves from the first cam position to the second cam position by rotating the cam in the first direction. The movement mechanism is controlled so that the cam moves from the second cam position to the third cam position by rotating the cam in the second direction. The image forming apparatus according to feature 1.

Images